US20140291161A1 - Method for producing metal by molten salt electrolysis and apparatus used for the production method - Google Patents

Method for producing metal by molten salt electrolysis and apparatus used for the production method Download PDF

Info

Publication number: US20140291161A1
Authority: US; United States
Prior art keywords: molten salt; metal; potential; treatment object; electrode
Prior art date: 2011-11-04
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.): Abandoned

Application number

US14/355,943

Other languages

English (en)

Inventor

Tomoyuki Awazu

Masatoshi Majima

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Sumitomo Electric Industries Ltd

Original Assignee

Sumitomo Electric Industries Ltd

Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)

2011-11-04

Filing date

2012-10-22

Publication date

2014-10-02

2012-10-22 Application filed by Sumitomo Electric Industries Ltd filed Critical Sumitomo Electric Industries Ltd

2014-05-02 Assigned to SUMITOMO ELECTRIC INDUSTRIES, LTD. reassignment SUMITOMO ELECTRIC INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MAJIMA, MASATOSHI, AWAZU, TOMOYUKI

2014-10-02 Publication of US20140291161A1 publication Critical patent/US20140291161A1/en

Status Abandoned legal-status Critical Current

Links

150000003839 salts Chemical class 0.000 title claims abstract description 728
229910052751 metal Inorganic materials 0.000 title claims abstract description 511
239000002184 metal Substances 0.000 title claims abstract description 475
238000005868 electrolysis reaction Methods 0.000 title claims abstract description 137
238000004519 manufacturing process Methods 0.000 title claims abstract description 105
238000011282 treatment Methods 0.000 claims abstract description 285
238000000151 deposition Methods 0.000 claims abstract description 134
238000000034 method Methods 0.000 claims abstract description 128
238000005275 alloying Methods 0.000 claims abstract description 28
229910052744 lithium Inorganic materials 0.000 claims description 133
WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 132
239000010937 tungsten Substances 0.000 claims description 130
229910052721 tungsten Inorganic materials 0.000 claims description 130
WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 127
239000000126 substance Substances 0.000 claims description 80
229910045601 alloy Inorganic materials 0.000 claims description 73
239000000956 alloy Substances 0.000 claims description 73
150000002739 metals Chemical class 0.000 claims description 61
239000000463 material Substances 0.000 claims description 53
229910052750 molybdenum Inorganic materials 0.000 claims description 43
239000002245 particle Substances 0.000 claims description 32
229910052761 rare earth metal Inorganic materials 0.000 claims description 32
239000000843 powder Substances 0.000 claims description 28
229910052712 strontium Inorganic materials 0.000 claims description 25
229910052720 vanadium Inorganic materials 0.000 claims description 25
150000002910 rare earth metals Chemical class 0.000 claims description 24
229910052732 germanium Inorganic materials 0.000 claims description 21
239000010405 anode material Substances 0.000 claims description 20
229910052723 transition metal Inorganic materials 0.000 claims description 20
150000003624 transition metals Chemical class 0.000 claims description 20
239000007769 metal material Substances 0.000 claims description 18
VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 17
KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 14
229910052787 antimony Inorganic materials 0.000 claims description 13
239000007772 electrode material Substances 0.000 claims description 13
229910052718 tin Inorganic materials 0.000 claims description 12
229910052797 bismuth Inorganic materials 0.000 claims description 11
229910052793 cadmium Inorganic materials 0.000 claims description 11
229910052733 gallium Inorganic materials 0.000 claims description 11
229910052738 indium Inorganic materials 0.000 claims description 11
229910052758 niobium Inorganic materials 0.000 claims description 10
229910052715 tantalum Inorganic materials 0.000 claims description 10
229910052725 zinc Inorganic materials 0.000 claims description 7
229910052745 lead Inorganic materials 0.000 claims description 6
229910052719 titanium Inorganic materials 0.000 claims description 6
229910052726 zirconium Inorganic materials 0.000 claims description 6
229910052788 barium Inorganic materials 0.000 claims description 5
239000011833 salt mixture Substances 0.000 claims description 5
229910052735 hafnium Inorganic materials 0.000 claims description 4
150000001805 chlorine compounds Chemical group 0.000 claims description 3
230000008021 deposition Effects 0.000 description 75
238000004090 dissolution Methods 0.000 description 74
230000008569 process Effects 0.000 description 42
229910021397 glassy carbon Inorganic materials 0.000 description 39
ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 33
239000011733 molybdenum Substances 0.000 description 33
239000012535 impurity Substances 0.000 description 30
239000000203 mixture Substances 0.000 description 28
PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 27
229910052799 carbon Inorganic materials 0.000 description 23
150000002500 ions Chemical class 0.000 description 23
230000008859 change Effects 0.000 description 22
230000003247 decreasing effect Effects 0.000 description 22
OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 21
229910052692 Dysprosium Inorganic materials 0.000 description 21
229910052779 Neodymium Inorganic materials 0.000 description 21
229910052777 Praseodymium Inorganic materials 0.000 description 21
LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 21
238000003723 Smelting Methods 0.000 description 20
229910001416 lithium ion Inorganic materials 0.000 description 20
CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 20
FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 18
239000010406 cathode material Substances 0.000 description 17
239000010959 steel Substances 0.000 description 17
WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 16
229910000831 Steel Inorganic materials 0.000 description 16
238000010438 heat treatment Methods 0.000 description 16
BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 16
238000004458 analytical method Methods 0.000 description 15
GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 15
238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 15
239000007774 positive electrode material Substances 0.000 description 15
238000004364 calculation method Methods 0.000 description 13
230000000694 effects Effects 0.000 description 13
238000005520 cutting process Methods 0.000 description 12
KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 12
238000000926 separation method Methods 0.000 description 12
229910000628 Ferrovanadium Inorganic materials 0.000 description 11
229910013618 LiCl—KCl Inorganic materials 0.000 description 11
PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 description 11
239000013307 optical fiber Substances 0.000 description 11
BUKHSQBUKZIMLB-UHFFFAOYSA-L potassium;sodium;dichloride Chemical compound [Na+].[Cl-].[Cl-].[K+] BUKHSQBUKZIMLB-UHFFFAOYSA-L 0.000 description 11
239000007864 aqueous solution Substances 0.000 description 10
229910001634 calcium fluoride Inorganic materials 0.000 description 10
239000010955 niobium Substances 0.000 description 10
WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 9
229910001080 W alloy Inorganic materials 0.000 description 9
230000005484 gravity Effects 0.000 description 9
230000008018 melting Effects 0.000 description 9
238000002844 melting Methods 0.000 description 9
239000011780 sodium chloride Substances 0.000 description 9
UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 8
TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 8
229910052782 aluminium Inorganic materials 0.000 description 8
XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
AIYUHDOJVYHVIT-UHFFFAOYSA-M caesium chloride Chemical compound [Cl-].[Cs+] AIYUHDOJVYHVIT-UHFFFAOYSA-M 0.000 description 8
239000001110 calcium chloride Substances 0.000 description 8
229910001628 calcium chloride Inorganic materials 0.000 description 8
238000006243 chemical reaction Methods 0.000 description 8
238000000605 extraction Methods 0.000 description 8
229910000625 lithium cobalt oxide Inorganic materials 0.000 description 8
BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 8
229910052759 nickel Inorganic materials 0.000 description 8
UXBZSSBXGPYSIL-UHFFFAOYSA-N phosphoric acid;yttrium(3+) Chemical compound [Y+3].OP(O)(O)=O UXBZSSBXGPYSIL-UHFFFAOYSA-N 0.000 description 8
239000001103 potassium chloride Substances 0.000 description 8
238000011084 recovery Methods 0.000 description 8
FGDZQCVHDSGLHJ-UHFFFAOYSA-M rubidium chloride Chemical compound [Cl-].[Rb+] FGDZQCVHDSGLHJ-UHFFFAOYSA-M 0.000 description 8
229910000164 yttrium(III) phosphate Inorganic materials 0.000 description 8
XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
229910000733 Li alloy Inorganic materials 0.000 description 7
229910017315 Mo—Cu Inorganic materials 0.000 description 7
239000002253 acid Substances 0.000 description 7
238000005137 deposition process Methods 0.000 description 7
230000005496 eutectics Effects 0.000 description 7
238000000227 grinding Methods 0.000 description 7
238000005342 ion exchange Methods 0.000 description 7
239000011572 manganese Substances 0.000 description 7
238000005259 measurement Methods 0.000 description 7
229910052697 platinum Inorganic materials 0.000 description 7
239000002344 surface layer Substances 0.000 description 7
HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
229910000990 Ni alloy Inorganic materials 0.000 description 6
ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 6
239000000654 additive Substances 0.000 description 6
230000000996 additive effect Effects 0.000 description 6
WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 6
JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 6
239000011651 chromium Substances 0.000 description 6
238000002474 experimental method Methods 0.000 description 6
238000002386 leaching Methods 0.000 description 6
229910052748 manganese Inorganic materials 0.000 description 6
VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 6
XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 5
PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 5
229910052783 alkali metal Inorganic materials 0.000 description 5
150000001340 alkali metals Chemical class 0.000 description 5
239000011324 bead Substances 0.000 description 5
BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 5
239000011575 calcium Substances 0.000 description 5
150000001768 cations Chemical class 0.000 description 5
229910052804 chromium Inorganic materials 0.000 description 5
229910017052 cobalt Inorganic materials 0.000 description 5
239000010941 cobalt Substances 0.000 description 5
GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 5
239000010949 copper Substances 0.000 description 5
APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 5
NRNCYVBFPDDJNE-UHFFFAOYSA-N pemoline Chemical compound O1C(N)=NC(=O)C1C1=CC=CC=C1 NRNCYVBFPDDJNE-UHFFFAOYSA-N 0.000 description 5
230000000737 periodic effect Effects 0.000 description 5
238000004064 recycling Methods 0.000 description 5
238000006722 reduction reaction Methods 0.000 description 5
239000011734 sodium Substances 0.000 description 5
229910052708 sodium Inorganic materials 0.000 description 5
239000007787 solid Substances 0.000 description 5
JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 5
239000002699 waste material Substances 0.000 description 5
239000011701 zinc Substances 0.000 description 5
OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 4
VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
229910001626 barium chloride Inorganic materials 0.000 description 4
WDIHJSXYQDMJHN-UHFFFAOYSA-L barium chloride Chemical compound [Cl-].[Cl-].[Ba+2] WDIHJSXYQDMJHN-UHFFFAOYSA-L 0.000 description 4
229910001632 barium fluoride Inorganic materials 0.000 description 4
XJHCXCQVJFPJIK-UHFFFAOYSA-M caesium fluoride Inorganic materials [F-].[Cs+] XJHCXCQVJFPJIK-UHFFFAOYSA-M 0.000 description 4
229910052791 calcium Inorganic materials 0.000 description 4
WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 4
KEOQXONTSMDHSC-UHFFFAOYSA-K calcium;potassium;trichloride Chemical compound [Cl-].[Cl-].[Cl-].[K+].[Ca+2] KEOQXONTSMDHSC-UHFFFAOYSA-K 0.000 description 4
239000003054 catalyst Substances 0.000 description 4
239000004020 conductor Substances 0.000 description 4
229910052802 copper Inorganic materials 0.000 description 4
238000011049 filling Methods 0.000 description 4
229910001629 magnesium chloride Inorganic materials 0.000 description 4
229910001635 magnesium fluoride Inorganic materials 0.000 description 4
230000004048 modification Effects 0.000 description 4
238000012986 modification Methods 0.000 description 4
GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 4
238000000746 purification Methods 0.000 description 4
230000009467 reduction Effects 0.000 description 4
AHLATJUETSFVIM-UHFFFAOYSA-M rubidium fluoride Inorganic materials [F-].[Rb+] AHLATJUETSFVIM-UHFFFAOYSA-M 0.000 description 4
239000002893 slag Substances 0.000 description 4
XMVONEAAOPAGAO-UHFFFAOYSA-N sodium tungstate Chemical compound [Na+].[Na+].[O-][W]([O-])(=O)=O XMVONEAAOPAGAO-UHFFFAOYSA-N 0.000 description 4
229910001631 strontium chloride Inorganic materials 0.000 description 4
AHBGXTDRMVNFER-UHFFFAOYSA-L strontium dichloride Chemical compound [Cl-].[Cl-].[Sr+2] AHBGXTDRMVNFER-UHFFFAOYSA-L 0.000 description 4
229910001637 strontium fluoride Inorganic materials 0.000 description 4
FVRNDBHWWSPNOM-UHFFFAOYSA-L strontium fluoride Chemical compound [F-].[F-].[Sr+2] FVRNDBHWWSPNOM-UHFFFAOYSA-L 0.000 description 4
GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 4
239000010936 titanium Substances 0.000 description 4
229910000838 Al alloy Inorganic materials 0.000 description 3
KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 3
229910001182 Mo alloy Inorganic materials 0.000 description 3
HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
XAYGUHUYDMLJJV-UHFFFAOYSA-Z decaazanium;dioxido(dioxo)tungsten;hydron;trioxotungsten Chemical compound [H+].[H+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O XAYGUHUYDMLJJV-UHFFFAOYSA-Z 0.000 description 3
238000009826 distribution Methods 0.000 description 3
239000008151 electrolyte solution Substances 0.000 description 3
239000000284 extract Substances 0.000 description 3
229910052742 iron Inorganic materials 0.000 description 3
239000001989 lithium alloy Substances 0.000 description 3
XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 3
229910052808 lithium carbonate Inorganic materials 0.000 description 3
FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 3
229910001947 lithium oxide Inorganic materials 0.000 description 3
-1 metal oxide ions Chemical class 0.000 description 3
239000003921 oil Substances 0.000 description 3
PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 3
235000010344 sodium nitrate Nutrition 0.000 description 3
239000004317 sodium nitrate Substances 0.000 description 3
239000000243 solution Substances 0.000 description 3
238000000638 solvent extraction Methods 0.000 description 3
UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 3
239000002351 wastewater Substances 0.000 description 3
NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 2
229910020549 KCl—NaCl Inorganic materials 0.000 description 2
PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
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238000010306 acid treatment Methods 0.000 description 2
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239000002585 base Substances 0.000 description 2
239000003990 capacitor Substances 0.000 description 2
IKNAJTLCCWPIQD-UHFFFAOYSA-K cerium(3+);lanthanum(3+);neodymium(3+);oxygen(2-);phosphate Chemical compound [O-2].[La+3].[Ce+3].[Nd+3].[O-]P([O-])([O-])=O IKNAJTLCCWPIQD-UHFFFAOYSA-K 0.000 description 2
150000001875 compounds Chemical class 0.000 description 2
238000006477 desulfuration reaction Methods 0.000 description 2
230000023556 desulfurization Effects 0.000 description 2
GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 2
239000000428 dust Substances 0.000 description 2
KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 2
229910000248 eudialyte Inorganic materials 0.000 description 2
238000009854 hydrometallurgy Methods 0.000 description 2
239000003456 ion exchange resin Substances 0.000 description 2
229920003303 ion-exchange polymer Polymers 0.000 description 2
239000010410 layer Substances 0.000 description 2
229910002102 lithium manganese oxide Inorganic materials 0.000 description 2
VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 2
238000001000 micrograph Methods 0.000 description 2
229910052590 monazite Inorganic materials 0.000 description 2
QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 2
230000003647 oxidation Effects 0.000 description 2
238000007254 oxidation reaction Methods 0.000 description 2
230000001590 oxidative effect Effects 0.000 description 2
VSIIXMUUUJUKCM-UHFFFAOYSA-D pentacalcium;fluoride;triphosphate Chemical compound [F-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O VSIIXMUUUJUKCM-UHFFFAOYSA-D 0.000 description 2
238000002360 preparation method Methods 0.000 description 2
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238000007670 refining Methods 0.000 description 2
238000001878 scanning electron micrograph Methods 0.000 description 2
238000012216 screening Methods 0.000 description 2
229910052938 sodium sulfate Inorganic materials 0.000 description 2
235000011152 sodium sulphate Nutrition 0.000 description 2
238000001179 sorption measurement Methods 0.000 description 2
239000010935 stainless steel Substances 0.000 description 2
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239000011593 sulfur Substances 0.000 description 2
229910052717 sulfur Inorganic materials 0.000 description 2
229910000601 superalloy Inorganic materials 0.000 description 2
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229910000722 Didymium Inorganic materials 0.000 description 1
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229910013574 LiCo0.3Ni0.7O2 Inorganic materials 0.000 description 1
229910013104 LiMyMn2-yO4 Inorganic materials 0.000 description 1
FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
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229910000756 V alloy Inorganic materials 0.000 description 1
238000002441 X-ray diffraction Methods 0.000 description 1
HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
TUEGREKNWIPDRA-UHFFFAOYSA-N [Ca].[Mn] Chemical compound [Ca].[Mn] TUEGREKNWIPDRA-UHFFFAOYSA-N 0.000 description 1
QTHKJEYUQSLYTH-UHFFFAOYSA-N [Co]=O.[Ni].[Li] Chemical compound [Co]=O.[Ni].[Li] QTHKJEYUQSLYTH-UHFFFAOYSA-N 0.000 description 1
FDLZQPXZHIFURF-UHFFFAOYSA-N [O-2].[Ti+4].[Li+] Chemical compound [O-2].[Ti+4].[Li+] FDLZQPXZHIFURF-UHFFFAOYSA-N 0.000 description 1
239000003929 acidic solution Substances 0.000 description 1
239000003513 alkali Substances 0.000 description 1
239000012670 alkaline solution Substances 0.000 description 1
HEHRHMRHPUNLIR-UHFFFAOYSA-N aluminum;hydroxy-[hydroxy(oxo)silyl]oxy-oxosilane;lithium Chemical compound [Li].[Al].O[Si](=O)O[Si](O)=O.O[Si](=O)O[Si](O)=O HEHRHMRHPUNLIR-UHFFFAOYSA-N 0.000 description 1
CNLWCVNCHLKFHK-UHFFFAOYSA-N aluminum;lithium;dioxido(oxo)silane Chemical compound [Li+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O CNLWCVNCHLKFHK-UHFFFAOYSA-N 0.000 description 1
229910052822 amblygonite Inorganic materials 0.000 description 1
229910052785 arsenic Inorganic materials 0.000 description 1
RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
238000010923 batch production Methods 0.000 description 1
229910052790 beryllium Inorganic materials 0.000 description 1
ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
239000011230 binding agent Substances 0.000 description 1
239000012267 brine Substances 0.000 description 1
239000000378 calcium silicate Substances 0.000 description 1
229910052918 calcium silicate Inorganic materials 0.000 description 1
229910002090 carbon oxide Inorganic materials 0.000 description 1
229910000428 cobalt oxide Inorganic materials 0.000 description 1
IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
239000012141 concentrate Substances 0.000 description 1
230000018044 dehydration Effects 0.000 description 1
238000006297 dehydration reaction Methods 0.000 description 1
238000011161 development Methods 0.000 description 1
238000010494 dissociation reaction Methods 0.000 description 1
230000005593 dissociations Effects 0.000 description 1
238000005265 energy consumption Methods 0.000 description 1
230000007613 environmental effect Effects 0.000 description 1
239000003337 fertilizer Substances 0.000 description 1
238000001914 filtration Methods 0.000 description 1
150000002222 fluorine compounds Chemical class 0.000 description 1
PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
229910052737 gold Inorganic materials 0.000 description 1
239000010931 gold Substances 0.000 description 1
229910002804 graphite Inorganic materials 0.000 description 1
239000010439 graphite Substances 0.000 description 1
229910001385 heavy metal Inorganic materials 0.000 description 1
230000008676 import Effects 0.000 description 1
229910052747 lanthanoid Inorganic materials 0.000 description 1
150000002602 lanthanoids Chemical class 0.000 description 1
229910052629 lepidolite Inorganic materials 0.000 description 1
239000007788 liquid Substances 0.000 description 1
QEXMICRJPVUPSN-UHFFFAOYSA-N lithium manganese(2+) oxygen(2-) Chemical class [O-2].[Mn+2].[Li+] QEXMICRJPVUPSN-UHFFFAOYSA-N 0.000 description 1
CJYZTOPVWURGAI-UHFFFAOYSA-N lithium;manganese;manganese(3+);oxygen(2-) Chemical compound [Li+].[O-2].[O-2].[O-2].[O-2].[Mn].[Mn+3] CJYZTOPVWURGAI-UHFFFAOYSA-N 0.000 description 1
VROAXDSNYPAOBJ-UHFFFAOYSA-N lithium;oxido(oxo)nickel Chemical compound [Li+].[O-][Ni]=O VROAXDSNYPAOBJ-UHFFFAOYSA-N 0.000 description 1
229910052749 magnesium Inorganic materials 0.000 description 1
239000011777 magnesium Substances 0.000 description 1
238000007885 magnetic separation Methods 0.000 description 1
QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
229910052753 mercury Inorganic materials 0.000 description 1
229910044991 metal oxide Inorganic materials 0.000 description 1
238000005272 metallurgy Methods 0.000 description 1
239000007773 negative electrode material Substances 0.000 description 1
239000007800 oxidant agent Substances 0.000 description 1
229910052670 petalite Inorganic materials 0.000 description 1
229910052698 phosphorus Inorganic materials 0.000 description 1
239000011574 phosphorus Substances 0.000 description 1
238000001556 precipitation Methods 0.000 description 1
238000012545 processing Methods 0.000 description 1
230000003252 repetitive effect Effects 0.000 description 1
230000002441 reversible effect Effects 0.000 description 1
230000000630 rising effect Effects 0.000 description 1
229910052706 scandium Inorganic materials 0.000 description 1
SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
229910052709 silver Inorganic materials 0.000 description 1
239000004332 silver Substances 0.000 description 1
HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
239000002904 solvent Substances 0.000 description 1
229910052642 spodumene Inorganic materials 0.000 description 1
239000013077 target material Substances 0.000 description 1
238000005979 thermal decomposition reaction Methods 0.000 description 1
238000013519 translation Methods 0.000 description 1
229910052727 yttrium Inorganic materials 0.000 description 1
VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1

Images

Classifications

- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/02—Electrolytic production, recovery or refining of metals by electrolysis of melts of alkali or alkaline earth metals
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/26—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/26—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium
- C25C3/28—Electrolytic production, recovery or refining of metals by electrolysis of melts of titanium, zirconium, hafnium, tantalum or vanadium of titanium
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/34—Electrolytic production, recovery or refining of metals by electrolysis of melts of metals not provided for in groups C25C3/02 - C25C3/32
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/36—Alloys obtained by cathodic reduction of all their ions
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
- C25C7/06—Operating or servicing

Definitions

the present invention relates to a method for producing a metal by molten salt electrolysis; and an apparatus used for the production method.
the pyrometallurgical smelting is a method of melting an ore in a high temperature furnace to separate a target metal. For example, a concentrate, a roasted ore, or a sintered ore is melted in a high temperature furnace, concentrated into a crude metal ingot while gangue, impurities, and the like are separated as slag (Non Patent Literature (NPL) 1, p. 46).
NPL Non Patent Literature
the hydrometallurgy is a method of dissolving an ore in, for example, an alkaline or acidic solution and separating and extracting a target metal from the solution.
a method for separating and extracting the target metal from this aqueous solution is, for example, a method using ion exchange, a method using solvent extraction, or a method using aqueous solution electrolysis.
a solid substance that partially has a group of ions allowing ion exchange and is referred to as an ion exchanger is used to perform reversible ion exchange (NPL 1, p. 194).
Ion exchange which uses the adsorption capability and exchange capability of an ion-exchange resin, is an excellent treatment. However, since this treatment is performed by repeating of adsorption and dissociation of ions, ion exchange is not suitable for economically and efficiently treating a large amount of substance, which is problematic.
the method using solvent extraction is a separation method using the difference in the distributions of different solutes in two solvents that are immiscible with each other (NPL 1, p. 199).
metal elements that can be separated and deposited by purification using aqueous solution electrolysis are limited.
deposition of rare earth materials cannot be theoretically achieved, which is problematic.
electrolytic smelting utilizing molten salt electrolysis is also known.
the target metal of this method is Al.
the potential of an impurity present with the purification target metal is close to the potential of the purification target metal, entry of the impurity into the deposited target metal occurs, which is problematic.
NPL 2 a method for recovering tungsten is described in, for example, NPL 2 as follows.
Hard scrap or soft scrap of cemented carbide tools is made to react with sodium nitrate molten salt and then dissolved in water to produce an aqueous solution of sodium tungstate.
the aqueous solution of sodium tungstate is treated by an ion-exchange method using an ion-exchange resin to produce an aqueous solution of ammonium tungstate.
ammonium paratungstate is crystallized. After that, the thus-crystallized ammonium paratungstate is calcined, reduced, and carbonized to provide tungsten carbide.
the hard scrap collectively denotes pieces of scrap still having the shapes of products.
the soft scrap denotes powder-form scrap such as powder dust and cutting dust generated during processing for producing cemented carbide tools.
Patent Literature (PTL) 1 proposes, in the production of sodium tungstate by oxidizing hard alloy scrap and/or heavy metal scrap in a molten salt bath, use of a molten salt containing 60 to 90 wt % of sodium hydroxide and 10 to 40 wt % of sodium sulfate. PTL 1 also proposes that the reaction between such scrap and the molten salt is performed in a rotary kiln that is operated as batch processes and can be directly heated.
sodium sulfate molten salt serving as an oxidizing agent has a high melting point of 884° C. Accordingly, the temperature during reaction needs to be set to a high temperature of 884° C. or more. As a result, metal materials are corroded, which is problematic. In addition, the reaction proceeds slowly and hence the reaction is time-consuming and involves a large energy loss, which is problematic.
lithium is mainly extracted from lithium-containing ores (such as spodumene, amblygonite, petalite, and lepidolite), and salt lakes and underground brine that have high lithium concentrations.
lithium-containing ores such as spodumene, amblygonite, petalite, and lepidolite
salt lakes and underground brine that have high lithium concentrations.
Japan does not have lithium-containing ores or salt lakes. Accordingly, almost the whole amount of lithium is actually supplied by imports.
lithium cobalt oxide serving as the positive electrode material of lithium secondary batteries, together with metallic lithium is subjected to a reduction reaction in lithium chloride molten salt, so that lithium oxide is generated and cobalt or cobalt oxide is separated by precipitation; after that, lithium oxide is electrolyzed in the lithium chloride molten salt, so that metallic lithium is deposited on the cathode and recovered (PTL 2: Japanese Unexamined Patent Application Publication No. 2005-011698).
a method for recovering lithium has been proposed in which a mixture of carbon and lithium manganese oxide serving as the positive electrode material of lithium secondary batteries is roasted in any one of the air atmosphere, an oxidizing atmosphere, an inert atmosphere, and a reducing atmosphere, to turn the lithium into lithium oxide; and this roasted substance is immersed in water so that lithium is leached in the form of lithium hydroxide and lithium carbonate (PTL 3).
tantalum is mainly used in tantalum capacitors and can be recovered from tantalum capacitor scrap. Specifically, tantalum is recovered by processes of oxidation treatment, magnetic separation, screening, separation with running water, grinding, screening, leaching, oxidation treatment, reduction treatment, and leaching (refer to NPL 3, pages 319 to 326).
Vanadium (V) is used as an additive to steel or a desulfurization catalyst in oil refining. Vanadium used as an additive to steel is collected in the form of steel scrap and recycled as steel. Spent catalysts can be sequentially subjected to steps of classification, roasting, grinding, leaching, filtration, leaching solution, dehydration, thermal decomposition, and melting, so that vanadium pentoxide can be obtained (NPL 3, pages 391 to 396).
Molybdenum (Mo) is also used as an additive to steel, alloy, or a desulfurization catalyst in oil refining. Molybdenum used as an additive to steel or an alloy element is collected in the form of steel or alloy and used, without being extracted, in the form of steel or alloy. Spent catalysts can be sequentially subjected to steps of roasting, removal of oil, water, and sulfur, leaching in basic condition, and recovery, so that Mo can be obtained (NPL 3, pages 301 to 303).
Niobium (Nb) is mainly used as an additive to steel. Niobium used as an additive to steel is collected in the form of steel scrap. However, the niobium content of high-tensile steel, stainless steel, and the like is very low and niobium itself is not recycled (NPL 3, page 339).
Manganese (Mn) is mostly used for steel and aluminum alloy and collected in the form of steel scrap and aluminum alloy scrap, respectively. In the case of recycling of steel, a high proportion of manganese is left in various slags and such manganese forming slags is not suitable for recycling. Manganese in slag is partially used in, for example, a manganese-calcium silicate fertilizer.
Aluminum cans containing such aluminum alloy are collected and then recycled (NPL 3, pages 343 to 344).
Chromium (Cr) used for steel (stainless steel) and superalloy is collected in the form of steel scrap and superalloy scrap, respectively, and then recycled; and extraction and recovery of elemental chromium is not performed (NPL 3, pages 219 to 221).
recovery involves a large number of processes such as roasting (heating), grinding, leaching, and reduction. And the processes are complicated and hence the treatment is time-consuming and costly, which is problematic.
the treatment requires roasting and, in the treatment, substances that are not the extraction target are also treated, resulting in unnecessary energy consumption. Furthermore, by subjecting substances that are not the treatment target to the roasting treatment, unnecessary oxides are generated, resulting in a large amount of waste. In addition, since acid treatment or base treatment is performed, the treatment produces acid or base wastewater, which exerts a load on the environment.
an object of the present invention is to provide a method for producing a metal, the method being applicable to any ore and providing high purity metal at low cost; and an apparatus used for the production method.
An object of the present invention is to provide a method for producing a metal, the method providing a particular metal at high purity, with safety, and at low cost, from a treatment object containing two or more metal elements; and an apparatus used for the production method.
An embodiment of the present invention is a method for producing a metal by molten salt electrolysis, the method including a step of dissolving, in a molten salt, a metal element contained in a treatment object containing two or more metal elements; and a step of depositing or alloying a particular metal present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing the dissolved metal element, by controlling a potential of the electrode members to a predetermined value.
the treatment object is an ore or a crude metal ingot obtained from the ore.
Another embodiment of the present invention is a method for producing tungsten, wherein a metal element contained in the treatment object is tungsten, in the step of dissolving, in a molten salt, a metal element from a treatment object, tungsten is dissolved from the treatment object, and in the step of depositing or alloying a particular metal, tungsten present in the molten salt is deposited on one of a pair of electrode members disposed in the molten salt containing dissolved tungsten, by controlling a potential of the electrode members to a predetermined value.
the treatment object is a metal material containing the tungsten.
the treatment object is a metal material containing tungsten and a transition metal.
the treatment object is a cemented carbide product.
Another embodiment of the present invention is a method for producing lithium, wherein a metal element contained in the treatment object is lithium, in the step of dissolving, in a molten salt, a metal element from a treatment object, lithium is dissolved from the treatment object, and in the step of depositing or alloying a particular metal, lithium present in the molten salt is deposited on one of a pair of electrode members disposed in the molten salt containing dissolved lithium, by controlling a potential of the electrode members to a predetermined value.
the treatment object is a material containing lithium and a transition metal.
the treatment object is a battery electrode material containing lithium.
the treatment object contains a transition metal or a rare earth metal.
the treatment object contains one or more metals selected from the group consisting of V, Nb, Mo, Ti, Ta, Zr, and Hf.
the treatment object contains Sr and/or Ba.
the treatment object contains one or more metals selected from the group consisting of Zn, Cd, Ga, In, Ge, Sn, Pb, Sb, and Bi.
the molten salt is selected such that, in the step of depositing or alloying a particular metal, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the potential of the electrode members is controlled to the predetermined value so that the particular metal element in the molten salt is selectively deposited or alloyed.
the metal in the step of dissolving, in a molten salt, a metal element contained in a treatment object, the metal is dissolved in the molten salt by a chemical procedure.
a cathode and an anode that is formed of an anode material containing the treatment object are disposed in the molten salt, and a potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential is dissolved in the molten salt from the treatment object.
the molten salt is selected such that, in the step of dissolving, in a molten salt, a metal element contained in a treatment object, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the potential at the anode is controlled to a predetermined value so that the particular metal element is selectively dissolved in the molten salt.
the particular metal deposited or alloyed is a transition metal.
the particular metal deposited or alloyed is a rare earth metal.
the particular metal deposited or alloyed is V, Nb, Mo, Ti, Ta, Zr, or Hf.
the particular metal deposited or alloyed is Sr or Ba.
the particular metal deposited or alloyed is Zn, Cd, Ga, In, Ge, Sn, Pb, Sb, or Bi.
the molten salt is a chloride or fluoride molten salt.
the molten salt is a molten salt mixture containing a chloride molten salt and a fluoride molten salt.
the treatment object has a form of particles or powder.
the treatment object having the form of particles or powder is compacted to form the anode.
Another embodiment of the present invention is a method for producing a metal by molten salt electrolysis, the method being a method for producing a particular metal by molten salt electrolysis from a treatment object containing two or more metal elements, wherein a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and a potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential is dissolved in the molten salt from the treatment object and a particular metal is left in the anode.
the treatment object is an ore or a crude metal ingot obtained from the ore.
Another embodiment of the present invention is a method for producing tungsten by molten salt electrolysis from a treatment object containing tungsten, wherein a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and a potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential is dissolved in the molten salt from the treatment object and tungsten is left in the anode.
the molten salt is selected such that, in the step of dissolving a metal element in the molten salt from the treatment object, a difference between a standard electrode potential of a simple substance or alloy of the particular metal and a standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
Another embodiment of the present invention is an apparatus used for a method for producing a metal by molten salt electrolysis, the apparatus including a container containing a molten salt; a cathode immersed in the molten salt contained within the container; and an anode that is immersed in the molten salt contained within the container and that contains a treatment object containing two or more metal elements, wherein the molten salt is movable into and out of the anode, the apparatus further includes a control unit configured to control a potential of the cathode and the anode to a predetermined value, and a value of the potential is changeable in the control unit.
Another embodiment of the present invention is an apparatus used for a method for producing a metal by molten salt electrolysis, the apparatus including a container containing a molten salt containing two or more dissolved metal elements; a cathode and an anode that are immersed in the molten salt contained within the container; and a control unit configured to control a potential of the cathode and the anode to a predetermined value, wherein a value of the potential is changeable in the control unit.
the two or more metal elements include at least one of tungsten and lithium.
a method for producing a metal and an apparatus used for the production method according to the present invention are applicable to any ore.
Use of a production method or an apparatus used for the production method according to the present invention can provide a particular metal at high purity, with safety, and at low cost, from a treatment object containing two or more metal elements.
FIG. 1 is a flow chart for explaining an embodiment of the present invention.
FIG. 2 is a schematic view describing examples of deposition potentials of rare earth metals in a molten salt.
FIG. 3 is a graph illustrating examples of a relationship between treatment time and concentration of ions of a rare earth metal in a molten salt in an embodiment of the present invention.
FIG. 4 is a schematic sectional view for explaining the configuration of an apparatus according to an embodiment of the present invention.
FIG. 5 is a schematic sectional view for explaining the configuration of an apparatus according to an embodiment of the present invention.
FIG. 6 is a flow chart for explaining another embodiment of the present invention.
FIG. 7 is a schematic sectional view for explaining another embodiment of the present invention.
FIG. 8 is a schematic sectional view for explaining another embodiment of the present invention.
FIG. 9 is a schematic sectional view for explaining another embodiment of the present invention.
FIG. 10 is a schematic sectional view for explaining another embodiment of the present invention.
FIG. 11 is a schematic sectional view for explaining a modification of another embodiment of the present invention.
FIG. 12 is a schematic sectional view for explaining a modification of another embodiment of the present invention.
FIG. 13 is a schematic sectional view for explaining a modification of another embodiment of the present invention.
FIG. 14 is a photograph for explaining an anode electrode used in examples according to the present invention.
FIG. 15 is a graph illustrating the relationship between the value of anode current and time in an example according to the present invention.
FIG. 16 is a scanning electron micrograph of a surface portion of a cathode electrode used in an electrolysis step in an example according to the present invention.
the scale in the lower right of the micrograph indicates a length of 8 ⁇ m.
FIG. 17 is a scanning electron micrograph illustrating Dy distribution status in the regions of the micrograph illustrated in FIG. 16 .
FIG. 18 is a schematic sectional view for explaining an example of the configuration of an apparatus according to an embodiment of the present invention.
FIG. 19 is a schematic sectional view for explaining an example of the configuration of an apparatus according to an embodiment of the present invention.
An embodiment of the present invention is a method for producing a metal by molten salt electrolysis, the method including a step of dissolving, in a molten salt, a metal element contained in a treatment object containing two or more metal elements; and a step of depositing or alloying a particular metal present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing the dissolved metal element, by controlling a potential of the electrode members to a predetermined value.
the treatment object is an ore containing two or more metal elements or a crude metal ingot obtained from the ore (hereafter sometimes simply referred to as a crude metal ingot).
this embodiment includes a process of dissolving, in a molten salt, a metal contained in an object (the ore or crude metal ingot), and a process of depositing a metal or an alloy of a separation-extraction target element on one of electrodes (cathode) from a molten salt containing the dissolved metal by molten salt electrolysis.
a feature of this embodiment is that, by controlling the potential of the electrodes, a particular target element is selectively dissolved or deposited to achieve separation and smelting.
a procedure for dissolving, in a molten salt, a metal element contained in an ore or a crude metal ingot is, for example, a chemical procedure for dissolution. Specifically, an ore or a crude metal ingot is ground into particles or powder, mixed with a salt, and heated. As a result, two or more metal elements contained in the ore or the crude metal ingot can be dissolved in the molten salt. Alternatively, the treatment object may be placed in a molten salt and dissolved.
Another procedure is an electrochemical procedure. Specifically, an object is disposed as an anode in a molten salt and the value of the potential at the object is controlled to selectively dissolve an element contained in the object: molten salt electrolysis is characterized in that different elements are dissolved at different potentials; and such characteristics are utilized to selectively separate metals corresponding to potentials. In this way, by using an object as an anode and controlling the potential during dissolution, a metal element that is a smelting target can be selectively dissolved in a molten salt.
the potential is preferably controlled such that impurities contained in the object remain undissolved. As a result, entry of impurities in the subsequent deposition process can be reduced.
the molten salt is preferably selected such that, in the step of dissolving, in the molten salt, a metal element contained in an ore or a crude metal ingot, the difference between the standard potential of a simple substance or alloy of a particular metal (metal element to be dissolved) and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the metal element that is dissolved in the molten salt can be sufficiently separated from the metal element that is left in the anode.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation described below.
the potential may be controlled such that respective metals are dissolved in a molten salt.
the ore or crude metal ingot (anode) containing the remainder of the metals may be moved to another molten salt and the potential may be similarly controlled to a predetermined value so that the remainder of the particular metals is dissolved in the molten salt.
Some metals are more easily separated by deposition described below. In such cases, the entire treatment object may be dissolved or only a particular metal and some other metals may be dissolved.
the potential at the anode is preferably controlled to a predetermined value so that the particular metal element is selectively dissolved in the molten salt.
the molten salt can be selected from chlorides and fluorides.
chloride molten salts include KCl, NaCl, CaCl 2 , LiCl, RbCl, CsCl, SrCl 2 , BaCl 2 , and MgCl 2 .
fluoride molten salts include LiF, NaF, KF, RbF, CsF, MgF 2 , CaF 2 , SrF 2 , and BaF 2 .
chloride molten salts are preferably used in view of efficiency; in particular, KCl, NaCl, and CaCl 2 are preferably used because they are inexpensive and easily available.
a plurality of molten salts can be combined and used as a molten salt having a desirable composition.
a molten salt having a composition such as KCl—CaCl 2 , LiCl—KCl, or NaCl—KCl may be used.
the cathode is formed of carbon or a material that tends to form an alloy with an alkali metal such as Li or Na constituting cations in the molten salt.
an alkali metal such as Li or Na constituting cations in the molten salt.
aluminum (Al), zinc (Zn), gallium (Ga), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), lead (Pb), or bismuth (Bi) may be used.
the ore or crude metal ingot contained in a conductive basket formed of a metal or the like may be disposed in the molten salt.
An opening may be formed in an upper portion of the basket so that the ore or crude metal ingot serving as the treatment object can be inserted through the opening into the basket; and a large number of holes may be formed in the side and bottom walls of the basket so that the molten salt can flow into the basket.
the basket may be constituted by a desired material such as a mesh member knitted from metal wires or a sheet member that is a sheet-shaped metal plate having a large number of holes. In particular, it is effective that the material is formed of C, Pt, Mo, or the like.
the contact area between the object and the conductive material is preferably increased.
the object is effectively used as an electrode by, for example, wrapping the object with a metal mesh member or filling the object into spaces within a metal porous member.
a target metal can be dissolved in the molten salt from the ore or crude metal ingot.
molten salt electrolysis is performed with a pair of electrode members disposed in the molten salt so that a metal element dissolved in the molten salt is deposited on one of the electrode members (cathode).
a particular metal element can be selectively deposited as metal or alloy on the cathode.
molten salt electrolysis is characterized in that different elements are deposited at different potentials as metal or alloy on the cathode; and such characteristics are utilized to separate the metals.
the metals can be individually deposited on cathodes one by one.
the electrode members may be formed of, for example, nickel (Ni), molybdenum (Mo), or glassy carbon (C).
the above-described two processes are used to separate and extract from an object a particular metal element that is a smelting target.
the system since a molten salt is used, the system needs to be heated such that the temperature of the system in the processes is equal to or more than the melting point of the molten salt.
a feature of the two processes is use of a molten salt.
the processes can be designed by selecting a molten salt such that the dissolution-deposition potentials of a particular metal element that is a target element and the other impurity metal elements are values that allow easy performance of the processes.
the molten salt is preferably selected such that, in the step of depositing or alloying the particular metal, the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the potential of the electrode members is preferably controlled to a predetermined value so that the particular metal element in the molten salt is selectively deposited or alloyed.
the deposition potential of a simple substance or alloy of a metal to be deposited on the cathode can be determined by electrochemical calculation. Specifically, the calculation is performed with Nernst equation.
Pr(III) trivalent Pr ions
E 0 Pr represents the standard potential
R represents the gas constant
T represents absolute temperature
F represents the Faraday constant
a Pr(III) represents the activity of Pr(III) ions
a Pr(0) represents the activity of Pr simple substance.
E Pr E Pr 0 ′ + RT / 3 ⁇ ⁇ F ⁇ ln ⁇ ⁇ C Pr ⁇ ( III ) Equation ⁇ ⁇ ( 3 )
C Pr(III) represents the concentration of trivalent Pr ions
E 0′ Pr represents formal electrode potential (here, equal to E 0 Pr +RT/3F ⁇ ln ⁇ Pr(III) ).
the potential at which PrNi alloy is deposited on the electrode surface (deposition potential: E Pr.Ni ) can be determined with the following equation.
E 0′ Pr.Ni represents formal electrode potential (here, equal to E 0 Pr.Ni +RT/3F ⁇ ln ⁇ Pr(III) ).
deposition potentials of all deposits corresponding to different molten salts can be determined.
a deposit that provides a potential difference with respect to another metal or an alloy thereof is selected or the order of depositions is determined.
Voltage and current during operation vary depending on the size or positional relationship of electrodes. Accordingly, reference values of voltage and current are determined on the basis of conditions and subsequently voltage and current are determined in each step on the basis of the potential value and order determined by the above-described method.
the potential value is controlled to thereby electrochemically dissolve and deposit a target metal. Accordingly, the steps can be simplified, compared with, for example, the existing wet treatment involving repeating of processes of dissolution and extraction using acid or the like; and a particular element can be selectively separated and recovered.
adjustment of the specific gravity of the molten salt is not necessary; and, by selecting a low-temperature molten salt in which an object can be treated in the solid state, a simple apparatus configuration can be employed.
the operation pattern can also be simplified. As a result, the steps can be performed efficiently at low cost.
a particular metal can be smelted on the basis of an idea that is totally contrary to the above-described idea of depositing or alloying a particular metal on the cathode.
a method for producing a metal is a method for producing a particular metal by molten salt electrolysis from an ore containing two or more metal elements or a crude metal ingot obtained from the ore, wherein a cathode and an anode that is formed of an anode material containing the ore or crude metal ingot are disposed in a molten salt, and the potential at the anode is controlled to a predetermined value so that a metal element corresponding to the potential is dissolved in the molten salt from the ore or crude metal ingot and a particular metal is left in the anode.
the object (the ore or crude metal ingot) is used as the anode and metal elements other than a particular metal element, that is, only metal elements serving as impurities are dissolved in the molten salt, so that the particular metal is left in the anode.
metal elements other than a particular metal element that is, only metal elements serving as impurities are dissolved in the molten salt, so that the particular metal is left in the anode.
the molten salt is also preferably selected such that, in the step of dissolving, in the molten salt, a metal element from the ore or crude metal ingot, the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the particular metal can be sufficiently separated from the other metal and the particular metal alone can be left in the anode.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation as described above.
Ores usable in the method for producing a metal by molten salt electrolysis are ores containing target particular metals.
the ores include gold ore, silver ore, copper ore, iron ore, aluminum ore, lead ore, zinc ore, tin ore, mercury ore, sulfur ore, phosphorus ore, nickel ore, cobalt ore, manganese ore, chromium ore, molybdenum ore, tungsten ore, antimony ore, arsenic ore, bismuth ore, strontium ore, beryllium ore, magnesium ore, barium ore, and calcium ore.
rare earth metals can be obtained from bastnaesite, monazite, loparite, apatite, xenotime, fergusonite, and eudialyte.
the crude metal ingot obtained from the ore denotes a metal containing a target particular metal at a low purity, such as a metal obtained by smelting the ore.
the method for producing a metal by molten salt electrolysis according to this embodiment is suitably applied to an ore or crude metal ingot obtained from the ore that is used as the anode and contains a transition metal or a rare earth metal.
the transition metal is not particularly limited and may be any element among from group 3 (group IIIA) to group 11 (group IB) of the periodic table.
the rare earth metal is also not particularly limited and may be any element among scandium (Sc), yttrium (Y), and 15 lanthanoid elements in group 3 (group IIIA) of the periodic table.
the method for producing a metal by molten salt electrolysis is also suitably applicable to the cases where particular metals deposited or alloyed on cathodes are rare earth metals.
appropriate selection of the composition of the molten salt allows even deposition of rare earth metals that cannot be deposited by aqueous solution electrolysis. Thus, rare earth metals that are difficult to mine as resources can be easily obtained.
the ore or crude metal ingot obtained from the ore preferably has the form of particles or powder.
the ore or crude metal ingot to be treated is prepared so as to have the form of particles or powder, the surface area is increased and the treatment efficiency can be increased.
the maximum particle size of the ore or crude metal ingot is preferably 0.01 mm to 2 mm, more preferably 0.01 mm to 1 mm, still more preferably 0.01 mm to 0.2 mm.
the ore or crude metal ingot in the form of particles or powder is preferably compacted to form the anode.
the ore or crude metal ingot in the form of powder can be compacted and, as a result, can be used as the anode. In this case, between the particles, there are desirably spaces that the molten salt can easily enter.
Nd neodymium
Dy dysprosium
Pr praseodymium
Examples of the ore include monazite, apatite, xenotime, fergusonite, and eudialyte.
a preparation step (S 10 ) is first performed.
an ore that is a treatment object, a molten salt to be used, and an apparatus including, for example, electrodes and a container for containing the molten salt are prepared.
the treatment object may be finely ground for the purpose of increasing the contact area between the treatment object and the molten salt.
the ore containing Nd, Dy, and Pr may be, for example, xenotime ore.
a xenotime ore has a composition of 3.0% Nd, 7.9% Dy, and 0.5% Pr.
the ore and (another) electrode member are immersed in the prepared molten salt; the ore and the electrode member are connected via a power supply so that the potential of the ore and the electrode member is controlled.
rare earth elements (Nd, Dy, and Pr) in the ore are selectively dissolved in the molten salt.
the molten salt used may be a molten salt having a desired composition.
the molten salt may be LiF—NaF—KF; the other electrode member may be an electrode formed of glassy carbon; and the above-described ore may be used as the treatment object.
Nd, Dy, and Pr can be selectively dissolved in the molten salt from the ore.
the potential is controlled to a value at which elements other than Nd, Dy, and Pr are scarcely dissolved in the molten salt but Nd, Dy, and Pr are dissolved in the molten salt.
a separation extraction step (S 30 ) is performed.
a pair of electrodes are inserted and the potential of the electrode members is controlled to a predetermined value.
the potential value is controlled to potentials corresponding to deposition potentials determined for respective rare earth metals.
the rare earth metal deposited on the electrode can be selected.
the rare earth metals can be selectively recovered element by element.
rare earth elements such as Nd, Dy, and Pr have different deposition potential values for respective elements.
the deposition potential of Nd is about 0.40 V (vs. Li + /Li); the deposition potentials of Pr and Dy are about 0.47 V (vs. Li + /Li); and the deposition potential of DyNi 2 , which is a Dy compound, is about 0.77 V (vs. Li + /Li).
deposition potentials in FIG. 2 are described with reference to Li.
the ordinate axis indicates deposition potential (unit: V).
Such deposition potentials are values in the case where the molten salt is LiCl—KCl and the temperature of the molten salt is set at 450° C.
elements and compounds have different deposition potentials. Accordingly, by immersing a pair of electrodes in a molten salt in which particular metals are dissolved and by controlling the potential at the cathode so as to correspond to the above-described deposition potentials, particular rare earth elements can be selectively deposited on the cathode. By changing the potential value at the cathode (for example, sequential potential changes), particular metals to be deposited can be selected.
Nd, Dy, and Pr are dissolved in the molten salt in which Nd, Dy, and Pr are dissolved.
concentrations (ion concentrations) of Nd, Dy, and Pr in the molten salt are each 0.5 mol %.
LiCl—KCl is used as the molten salt and the temperature of the molten salt is set at 450° C.
the abscissa axis indicates treatment time and the ordinate axis indicates the ion concentrations of rare earth elements in the molten salt.
the unit in the ordinate axis is mol %.
the electrode used in STEP 2 is different from the electrode on which DyNi 2 has been deposited in STEP 1 .
the electrode on which DyNi 2 has been deposited in STEP 1 may be removed from the molten salt before STEP 2 is started, and another electrode may be immersed in the molten salt; alternatively, the electrode on which DyNi 2 has been deposited may be left unremoved and, in STEP 2 , the potential at another electrode may be controlled.
the electrode on which Pr has been deposited in STEP 2 may be removed from the molten salt before STEP 3 is started, and another electrode may be immersed in the molten salt; alternatively, the electrode on which Pr has been deposited in STEP 2 may be left immersed in the molten salt and, in STEP 3 , another electrode may be used.
DyNi 2 recovered in STEP 1 is treated in STEP 4 : the electrode on the surface of which DyNi 2 has been deposited and another electrode (for example, a Mo electrode) are immersed in a molten salt; and the potential at the DyNi 2 electrode is set to be in a potential range in which Dy is dissolved but Ni is not dissolved (0.77 or more and 2.6 or less V (vs. Li + /Li)), so that Dy can be dissolved in the molten salt and Dy alone can be deposited on the surface of the other electrode.
another electrode for example, a Mo electrode
the target particular metals can be individually recovered from the molten salt.
a recovery apparatus illustrated in FIG. 4 includes a container 1 containing a molten salt, a molten salt 2 contained within the container 1 , a basket 4 containing a treatment object (the ore or crude metal ingot) 3 , electrodes 6 to 8 , a heater 10 for heating the molten salt 2 , and a control unit 9 electrically connected to the basket 4 and the electrodes 6 to 8 via conductive wires 5 .
the control unit 9 is configured to control the potential (change the potential) of one electrode that is the basket 4 and the other electrode that is one of the electrodes 6 to 8 .
the heater 10 is disposed so as to circularly surround the container 1 .
the electrodes 6 to 8 may be formed of desired materials.
the electrode 6 may be formed of nickel (Ni).
the electrodes 7 and 8 may be formed of carbon (C).
the container 1 may have a bottom surface that has a circular shape or a polygonal shape.
the basket 4 may be the above-described basket.
the basket 4 and the electrodes 6 to 8 are controlled by the control unit 9 to predetermined potential values.
different particular metals corresponding to the controlled potential values are deposited on the surfaces of the electrodes 6 to 8 as described below.
the potential value set for the electrode 6 can be adjusted so that a DyNi 2 film 11 is deposited on the surface of the electrode 6 .
a Pr film 12 can be deposited on the surface of the electrode 7 .
a Nd film 13 can be deposited on the surface of the electrode 8 .
the electrode 6 on which the DyNi 2 film 11 is deposited is then placed in a container 1 containing a molten salt 2 as illustrated in FIG. 5 . Furthermore, another electrode is placed in the molten salt 2 so as to face the electrode 6 on the surface of which the DyNi 2 film 11 is deposited.
the electrodes 6 and 15 are connected to a control unit 9 via conductive wires 5 . While the molten salt 2 is heated with a heater 10 disposed so as to surround the container 1 , the control unit 9 is used to control the potential of the electrodes 6 and 15 to a predetermined value. At this time, the potential is controlled such that the potential at the cathode (electrode 15 ) is the deposition potential of Dy.
the heating temperature for the molten salt 2 with the heater 10 may be, for example, 800° C. in both of the treatments using the apparatuses illustrated in FIGS. 4 and 5 . In this way, particular metals can be deposited as simple substances on the surfaces of the electrodes 7 , 8 , and 15 .
the method of this embodiment is performed with the apparatuses illustrated in FIGS. 4 and 5 , for example, the method may be performed in the following manner.
the ore (9 kg) is first prepared as the treatment object 3 and LiF—NaF—KF is prepared as the molten salt 2 .
the ore may contain 3.0 wt % of Nd, 0.5 wt % of Pr, and 7.9 wt % of Dy.
the ore is ground and placed within the basket 4 .
the size of the ore serving as the treatment object 3 is preferably minimized by grinding.
the ore is ground into particles having a maximum particle size of 2 mm or less, preferably 1 mm or less, more preferably 0.2 mm or less.
the amount of the molten salt 2 is about 16 liters (mass: 25 kg).
the treatment object 3 contained in the basket 4 and one of the electrodes 6 to 8 are used as a pair of electrodes and STEP 1 to STEP 3 of the method of this embodiment described with reference to FIGS. 2 and 3 are performed.
the treatment object 3 contained in the basket 4 and the electrode 6 are used as a pair of electrodes and the potential of the electrodes is controlled to a predetermined value.
DyNi 2 is deposited on the surface of the electrode 6 .
the treatment object 3 contained in the basket 4 and the electrode 7 are used as a pair of electrodes and the potential of the electrodes is controlled to a predetermined value.
Pr is deposited on the surface of the electrode 7 .
the mass of a Pr film deposited on the surface of the electrode 7 in FIG. 4 is, for example, about 30 g to about 50 g.
the treatment object 3 contained in the basket 4 and the electrode 8 are used as a pair of electrodes and the potential of the electrodes is controlled to a predetermined value.
Nd is deposited on the surface of the electrode 8 .
the mass of a Nd film deposited on the surface of the electrode 8 is, for example, about 200 g to about 300 g.
the electrode 6 and the electrode 15 are placed in the apparatus illustrated in FIG. 5 and the potential of the electrodes in the molten salt is controlled to a predetermined value.
Dy is deposited on the surface of the electrode 15 .
the mass of a Dy film 16 deposited on the surface of the electrode 15 is, for example, 600 g to 800 g.
the step of dissolving target metals in the molten salt 2 and the step of depositing particular metals as simple substances on the surfaces of the electrodes 7 , 8 , and the like can be performed within the same apparatus (with the same molten salt 2 ).
the step of separating and extracting Dy from DyNi 2 described above in STEP 4 is preferably performed in an apparatus (apparatus illustrated in FIG. 5 ) other than the apparatus (apparatus illustrated in FIG. 4 ) used for the step of dissolving metals in the molten salt 2 described with reference to FIG. 4 .
particular metals for example, Dy, Pr, and Nd can be recovered from an ore or crude metal ingot serving as the treatment object 3 .
Nd neodymium
Dy dysprosium
Pr praseodymium
the crude metal ingot containing Nd, Dy, and Pr may be, for example, mixed rare earth metal (didymium).
a smelting method for obtaining the mixed rare earth metal is not particularly limited and may be selected from publicly known methods.
a step (S 11 ) of preparing a crude metal ingot serving as a treatment object is first performed. Specifically, as illustrated in FIG. 7 , a crude metal ingot serving as a treatment object 3 is immersed in a molten salt 2 contained within a container 1 ; and a conductive wire 5 is connected to the treatment object 3 , the conductive wire 5 being used for connection to a power supply in a control unit 9 .
the salt used was LiCl—KCl.
an electrode material 25 contained within a basket 24 and serving as the other electrode is immersed together with the basket 24 .
the electrode material 25 is a material that tends to form an alloy with an alkali metal such as Li and Na constituting cations in the molten salt.
Examples of the electrode material 25 include aluminum (Al), zinc (Zn), gallium (Ga), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), lead (Pb), and bismuth (Bi).
a step (S 21 ) of dissolving Nd, Dy, and Pr in a molten salt is performed.
the potential of the treatment object 3 and the electrode material 25 contained within the basket 24 is controlled with the control unit 9 , so that the potential at the treatment object 3 is adjusted to a predetermined value.
rare earth elements such as Nd, Dy, and Pr are dissolved in the molten salt 2 from the crude metal ingot serving as the treatment object 3 .
a step (S 31 ) of depositing DyNi 2 by electrolysis is performed. Specifically, instead of the electrode material 25 contained in the basket 24 in FIG. 7 , as illustrated in FIG. 8 , an electrode 6 formed of nickel is immersed in the molten salt 2 . This electrode 6 is connected to the control unit 9 via a conductive wire 5 . In this state, the control unit 9 is used to control the potential of the treatment object 3 serving as one electrode and the electrode 6 serving as the other electrode, to a predetermined value.
rare earth elements such as Dy are dissolved in the molten salt 2 from the treatment object 3 and DyNi 2 is deposited on the surface of the electrode 6 from the molten salt 2 .
a step (S 32 ) of recovering Pr by electrolysis is performed.
an electrode 27 formed of carbon is immersed as one electrode in the molten salt 2 .
an electrode 7 formed of carbon is placed at a position so as to face the electrode 27 and be immersed in the molten salt 2 .
the electrode 27 and the electrode 7 are electrically connected to the control unit 9 via conductive wires 5 . In this state, the potential of one electrode 27 and the other electrode 7 is controlled to a predetermined value.
a step (S 33 ) of recovering Nd by electrolysis is performed.
an electrode 8 formed of carbon is placed so as to face the electrode 27 and be immersed in the molten salt 2 .
This electrode 8 is electrically connected to the control unit 9 via a conductive wire 5 .
the control unit 9 is used to control the potential of the electrode 8 and the electrode 27 to a predetermined value.
Nd is deposited on the surface of the electrode 8 .
chlorine gas is released from the region around the electrode 27 .
a step (S 34 ) of recovering Dy by electrolysis from DyNi 2 recovered in the step (S 31 ) is performed.
the electrode 6 on the surface of which DyNi 2 is deposited (refer to FIG. 8 ) is immersed in the molten salt 2 ; the other electrode 15 is disposed so as to be immersed in the molten salt 2 ; and the control unit 9 is used to control the potential of the electrodes 6 and 15 to a predetermined value.
Dy is temporarily dissolved in the molten salt 2 from DyNi 2 deposited on the surface of the electrode 6 and then a Dy film 16 is deposited on the surface of the electrode 15 .
Nd, Dy, and Pr which are rare earth metals, can be individually recovered.
the above-described steps (S 21 to S 32 ) may be performed with the following apparatus configurations.
the above-described step (S 31 ) may be performed with an apparatus configuration illustrated in FIG. 11 .
the basket 24 containing a material 26 alloyed by the step illustrated in FIG. 7 is immersed in the molten salt 2 .
this basket 24 is electrically connected to the control unit 9 via a conductive wire 5 .
the potential of the electrode 6 and the material 26 contained within the basket 24 and alloyed by the step illustrated in FIG. 7 is controlled to a predetermined value.
Dy dissolved in the molten salt 2 is deposited as DyNi 2 on the surface of the electrode 6 .
Dy can be recovered as a simple substance from DyNi 2 deposited on the surface of the electrode 6 , by the same step as the step (S 34 ) in FIG. 6 .
the above-described step (S 32 ) may be performed by a treatment with an apparatus configuration illustrated in FIG. 12 .
an electrode 7 formed of carbon is placed at a position so as to face the basket 24 and be immersed in the molten salt 2 .
This electrode 7 is electrically connected to the control unit 9 via a conductive wire 5 .
the control unit is used to control the potential of the electrode 7 and the alloy 26 contained within the basket 24 , to a predetermined value. As a result, Pr dissolved in the molten salt 2 is deposited on the surface of the electrode 7 .
the above-described step (S 33 ) may be performed by a treatment with an apparatus configuration illustrated in FIG. 13 .
an electrode 8 formed of carbon is placed at a position so as to face the basket 24 and be immersed in the molten salt 2 .
the electrode 8 is electrically connected to the control unit 9 via a conductive wire 5 .
the control unit 9 is used to control the potential of the electrode 8 and the alloy 26 disposed within the basket 24 , to a predetermined value. As a result, Nd is deposited on the surface of the electrode 8 .
a method for producing tungsten by molten salt electrolysis is a method for producing tungsten by molten salt electrolysis from a treatment object containing tungsten, the method including a step of dissolving, in a molten salt, tungsten from the treatment object, and a step of depositing tungsten present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing dissolved tungsten, by controlling a potential of the electrode members to a predetermined value.
this embodiment includes a process of dissolving, in a molten salt, tungsten contained in the treatment object, and a process of depositing tungsten on one of electrodes (cathode) from the molten salt containing dissolved tungsten by molten salt electrolysis.
a feature of this embodiment is that, by controlling the potential of the electrodes, tungsten is selectively deposited from a treatment object to provide high purity tungsten.
a procedure for dissolving, in a molten salt, tungsten contained in a treatment object is, for example, a chemical procedure for dissolution. Specifically, a treatment object is ground into particles or powder, mixed with a salt, and heated. As a result, tungsten contained in the treatment object can be dissolved in the molten salt. Alternatively, a treatment object may be placed in a molten salt and dissolved.
Another procedure is an electrochemical procedure. Specifically, an anode formed of an anode material containing a treatment object is placed in a molten salt and the value of the potential at the treatment object placed as the anode is controlled to selectively dissolve tungsten contained in the treatment object.
Molten salt electrolysis is characterized in that different elements are dissolved at different potentials. Such characteristics can be utilized to separate tungsten form other metals. In this way, by using a treatment object as an anode and controlling the potential during dissolution, tungsten can be selectively dissolved in a molten salt.
the entire treatment object may be dissolved, or a tungsten-containing portion of the treatment object or tungsten alone may be dissolved.
Conditions under which non-tungsten metals contained in the treatment object are dissolved may be employed; however, if possible, the potential is preferably controlled so that tungsten alone is dissolved. That is, in the step of dissolving tungsten in a molten salt, the potential of the anode and the cathode is preferably controlled to a predetermined value so that tungsten is selectively dissolved in the molten salt. As a result, entry of impurities in the subsequent deposition step can be reduced.
the molten salt is preferably selected such that, in the step of dissolving, in the molten salt, tungsten from the treatment object, the difference between the standard electrode potential of a simple substance or alloy of tungsten and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation described below.
the cathode used in the dissolution step is formed of carbon or a material that tends to form an alloy with an alkali metal such as Li or Na constituting cations in the molten salt.
an alkali metal such as Li or Na constituting cations in the molten salt.
aluminum (Al), zinc (Zn), gallium (Ga), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), lead (Pb), or bismuth (Bi) may be used.
the treatment object contained within a conductive basket (anode material) formed of metal or the like may be disposed in the molten salt.
An opening may be formed in an upper portion of the basket so that the treatment object can be inserted through the opening into the basket; and a large number of holes may be formed in the side and bottom walls of the basket so that the molten salt can flow into the basket.
the basket may be constituted by a desired material such as a mesh member knitted from metal wires or a sheet member that is a sheet-shaped metal plate having a large number of holes.
the material is formed of C, Pt, Mo, or the like.
the contact area between the object and the conductive material is preferably increased.
the object is effectively used as an electrode by, for example, wrapping the object with a metal mesh member or filling the object into spaces within a metal porous member.
the cathode and an anode formed of an anode material containing the treatment object are disposed in the molten salt; a control unit configured to control the potential of the electrodes from the outside is connected; and the potential is controlled as described above.
tungsten can be dissolved in the molten salt from the treatment object.
molten salt electrolysis is performed with a pair of electrode members disposed in the molten salt containing dissolved tungsten so that tungsten is deposited on one of the electrode members (cathode).
tungsten can be selectively deposited as metal or alloy on the cathode.
tungsten is separated from other metals by utilizing the following characteristics: in molten salt electrolysis, different elements are deposited at different potentials as metal or alloy on the cathode. Thus, even when metals other than tungsten are contained in the molten salt, by controlling the potential, tungsten alone can be deposited on the cathode. As a result, high purity tungsten can be obtained.
the cathode material may be selected and the potential may be controlled such that an alloy of the cathode material and tungsten is deposited.
tungsten in the molten salt can be separated as a tungsten alloy from the other impurity metal; and, after that, for example, a dissolution step and a deposition step in another molten salt can be performed with the cathode material alloyed with tungsten to thereby provide high purity tungsten.
the electrode members used in the deposition step may be formed of, for example, nickel (Ni), molybdenum (Mo), or glassy carbon (C).
the above-described two processes are used to separate and extract tungsten from a treatment object.
the system since a molten salt is used, the system needs to be heated such that the temperature of the system in the processes is equal to or more than the melting point of the molten salt.
smelting in the processes can be performed on the basis of a totally contrary idea. That is, a treatment object is used as the anode and only metal elements serving as impurities are dissolved in a molten salt. In this case, by also controlling the potential at the anode to a predetermined value, such a phenomenon is caused in which tungsten is left in the anode and impurity elements are dissolved. As a result, tungsten is provided in the anode.
a feature of the two processes is use of a molten salt.
the characteristics of molten salt electrolysis in which different molten salts have different dissolution-deposition potentials for elements are utilized; and the processes can be designed by selecting a molten salt such that the dissolution-deposition potential of tungsten and the dissolution-deposition potential of a non-tungsten impurity metal are sufficiently different values that allow easy performance of the processes.
the molten salt is preferably selected such that, in the step of depositing or alloying tungsten, the difference between the standard electrode potential of a simple substance or alloy of tungsten and the standard electrode potential of a simple substance or alloy of another impurity metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potential of a simple substance or alloy of tungsten and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the potential of the electrode members is preferably controlled to a predetermined value so that the tungsten in the molten salt is selectively deposited or alloyed.
the deposition potential of tungsten to be deposited on the cathode can be determined by electrochemical calculation. Specifically, the calculation is performed with Nernst equation.
W(II) tungsten
E 0 W represents the standard potential
R represents the gas constant
T represents absolute temperature
F represents the Faraday constant
a W(II) represents the activity of W(II) ions
a W(0) represents the activity of W simple substance.
E W E W 0 ′ + RT / 3 ⁇ ⁇ F ⁇ ln ⁇ ⁇ C W ⁇ ( II ) Equation ⁇ ⁇ ( 3 )
C W(II) represents the concentration of divalent W ions
E 0′ W represents formal electrode potential (here, equal to E 0 W +RT/3F ⁇ ln ⁇ W(II) ).
deposition potentials of all deposits corresponding to different molten salts can be determined. Similar calculations can also be performed in the case of depositing tungsten as an alloy.
the molten salt and the cathode material are selected such that a sufficiently high potential difference is achieved with respect to the deposition potential of a simple substance or alloy of another metal, and whether tungsten is deposited or a tungsten alloy is deposited is decided.
Voltage and current during operation vary depending on the size or positional relationship of electrodes. Accordingly, reference values of voltage and current are determined on the basis of conditions and subsequently voltage and current are determined in each step on the basis of the potential value and order determined by the above-described method.
the potential value is controlled to thereby electrochemically dissolve and deposit tungsten. Accordingly, the steps can be simplified, compared with, for example, the existing wet treatment involving repeating of processes of dissolution and extraction using acid or the like; and the particular element can be selectively separated and recovered.
adjustment of the specific gravity of molten salt is not necessary; and, by selecting a low-temperature molten salt in which tungsten can be treated in the solid state, a simple apparatus configuration can be employed.
the operation pattern can also be simplified. As a result, the steps can be performed efficiently at low cost.
tungsten can be smelted on the basis of an idea that is totally contrary to the idea of depositing or alloying tungsten on the cathode.
a method for producing a metal is a method for producing tungsten by molten salt electrolysis from a treatment object containing tungsten, wherein a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and the potential at the anode is controlled so that a metal element corresponding to the potential value is dissolved in the molten salt from the treatment object and tungsten is left in the anode.
the anode material containing the treatment object is used as the anode and metal elements other than tungsten, that is, only metal elements serving as impurities are dissolved in the molten salt, so that tungsten is left in the anode.
metal elements other than tungsten that is, only metal elements serving as impurities are dissolved in the molten salt, so that tungsten is left in the anode.
the molten salt is also preferably selected such that, in the step of dissolving, in the molten salt, a metal element from the treatment object, the difference between the standard electrode potential of a simple substance or alloy of tungsten and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation as described above.
the treatment object containing tungsten is preferably, for example, a metal material containing tungsten.
the metal material containing tungsten include tungsten heaters.
This embodiment is also suitably applicable to cases where the treatment object is a metal material containing tungsten and a transition metal.
a transition metal is not particularly limited and may be any element among from group 3 (group IIIA) to group 11 (group IB) of the periodic table.
Examples of the metal material containing tungsten and a transition metal include cemented carbide.
the treatment object may be, for example, cemented carbide products.
cemented carbide products collectively denote products including cemented carbide materials, such as cutting tools, jigs, dies, and molds including cemented carbide materials.
the molten salt can be selected from chloride molten salts and fluoride molten salts.
a molten salt mixture containing a chloride molten salt and a fluoride molten salt may be used.
chloride molten salts include KCl, NaCl, CaCl 2 , LiCl, RbCl, CsCl, SrCl 2 , BaCl 2 , and MgCl 2 .
fluoride molten salts include LiF, NaF, KF, RbF, CsF, MgF 2 , CaF 2 , SrF 2 , and BaF 2 .
Chloride molten salts are preferably used in view of efficiency; in particular, KCl, NaCl, and CaCl 2 are preferably used because they are inexpensive and easily available.
a plurality of molten salts can be combined and used as a molten salt having a desirable composition.
a molten salt having a composition such as KCl—CaCl 2 , LiCl—KCl, or NaCl—KCl may be used.
an apparatus used for a method for producing tungsten by molten salt electrolysis according to this embodiment includes a container containing a molten salt; a cathode immersed in the molten salt contained within the container; and an anode that is immersed in the molten salt contained within the container and that contains a conductive treatment object containing tungsten, wherein the molten salt is movable into and out of the anode, the apparatus further includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus used for a method for producing tungsten by molten salt electrolysis includes a container containing a molten salt containing dissolved tungsten; and a cathode and an anode that are immersed in the molten salt contained within the container, wherein the apparatus includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus illustrated in FIG. 18 includes a container 1 containing a molten salt, a molten salt 2 contained within the container 1 , a basket 4 containing a treatment object 3 containing tungsten, an electrode 6 , a heater 10 for heating the molten salt 2 , and a control unit 9 electrically connected to the basket 4 and the electrode 6 via conductive wires 5 .
the control unit 9 is configured to control the potential of one electrode (anode) that is the basket 4 and the other electrode (cathode) that is the electrode 6 , to a predetermined value. In the control unit 9 , the value to which the potential is controlled is changeable.
the heater 10 is disposed so as to circularly surround the container 1 .
the electrode 6 may be formed of a desired material, for example, carbon.
the container 1 may have a bottom surface that has a circular shape or a polygonal shape.
the basket 4 may be the above-described basket.
the potential of the basket 4 and the electrode 6 is controlled by the control unit 9 to a predetermined potential value. As a result, tungsten is dissolved in the molten salt 2 from the treatment object 3 .
the basket 4 and the electrode 6 are removed and another electrode 7 (cathode) and another electrode 8 (anode) are placed in the molten salt 2 .
These electrodes 7 and 8 are connected to the control unit 9 via conductive wires 5 .
the control unit 9 is used to control the potential of the electrodes 7 and 8 to a predetermined value. At this time, the potential is controlled such that the potential at the electrode 7 is the deposition potential of tungsten. As a result, tungsten dissolved in the molten salt 2 is deposited on the surface of the electrode 7 (cathode).
the electrodes 7 and 8 may be formed of a material such as glassy carbon (C).
the heating temperature for the molten salt 2 with the heater 10 may be, for example, 800° C. in both of the treatments using the apparatuses illustrated in FIGS. 18 and 19 . In this way, tungsten can be deposited as a simple substance on the surface of the electrode 7 .
the potential of the electrodes 7 and 8 may be controlled such that an alloy of tungsten and the cathode material is deposited on the surface of the electrode 7 (cathode).
the above-described dissolution step and deposition step may be performed with the alloyed electrode 7 . That is, the apparatus illustrated in FIG. 18 is newly prepared and the electrode 7 alloyed with tungsten is used instead of the above-described treatment object 3 .
the method for producing tungsten of this embodiment is performed with the apparatuses illustrated in FIGS. 18 and 19 , for example, the method may be performed in the following manner.
Cemented carbide cutting tools (9 kg) are first prepared as the treatment object 3 and KCl—NaCl is prepared as the molten salt 2 .
the cemented carbide cutting tools may contain 90 wt % of tungsten carbide (WC) and 10 wt % of cobalt (Co).
the cemented carbide cutting tools are ground and placed within the basket 4 .
the size of the cemented carbide cutting tools serving as the treatment object 3 is preferably minimized by grinding.
the cemented carbide cutting tools are ground into particles having a maximum particle size of 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less.
the amount of the molten salt 2 is about 16 liters (mass: 25 kg).
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
tungsten can be recovered from cemented carbide cutting tools serving as the treatment object 3 .
the apparatus configuration can be simplified and the treatment time can also be decreased, compared with the existing wet separation method and the like. Thus, the cost incurred can be reduced.
tungsten can be deposited as a simple substance on the electrode surface and hence high purity tungsten can be obtained.
the potentials for depositing tungsten and a tungsten alloy can be determined by the above-described calculation.
a method for producing lithium by molten salt electrolysis is a method for producing lithium by molten salt electrolysis from a treatment object containing lithium, the method including a step of dissolving, in a molten salt, lithium from the treatment object, and a step of depositing lithium present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing dissolved lithium, by controlling a potential of the electrode members to a predetermined value.
the lithium production method of this embodiment includes a process of dissolving, in a molten salt, lithium contained in the treatment object, and a step of depositing lithium on one of electrodes (cathode) from the molten salt containing dissolved lithium by molten salt electrolysis.
a feature of this embodiment is that, by controlling the potential of the electrodes in the step of dissolving lithium, lithium is selectively dissolved from the treatment object; and, by controlling the potential of the electrodes to a predetermined value in the step of depositing lithium, lithium is selectively deposited on the cathode from the molten salt to thereby provide high purity lithium.
a procedure for dissolving, in a molten salt, lithium contained in a treatment object is, for example, a chemical procedure for dissolution. Specifically, a treatment object is ground into particles or powder, mixed with a salt, and heated. As a result, lithium contained in the treatment object can be dissolved in the molten salt. Alternatively, a treatment object may be placed in a molten salt and dissolved.
Another procedure is an electrochemical procedure. Specifically, an anode formed of an anode material containing a treatment object is placed in a molten salt and the value of the potential at the treatment object placed as the anode is controlled to selectively dissolve lithium contained in the treatment object.
Molten salt electrolysis is characterized in that different elements are dissolved at different potentials. Accordingly, in this way, by using a treatment object as an anode and controlling the potential during dissolution, lithium can be selectively dissolved in a molten salt to separate lithium from the other metals.
the entire treatment object may be dissolved, or a lithium-containing portion of the treatment object or lithium alone may be dissolved.
Non-lithium metals contained in the treatment object may also be dissolved; however, if possible, the potential value is preferably controlled so that lithium alone is dissolved. That is, in the step of dissolving lithium in a molten salt, the potential of the anode and the cathode is preferably controlled to a predetermined value so that lithium is selectively dissolved in the molten salt. As a result, entry of impurities in the subsequent deposition step can be reduced.
the molten salt is preferably selected such that, in the step of dissolving, in the molten salt, lithium from the treatment object, the difference between the standard electrode potential of a simple substance or alloy of lithium and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation described below.
the cathode used in the dissolution step is formed of carbon or a material that tends to form an alloy with an alkali metal such as Li or Na constituting cations in the molten salt.
an alkali metal such as Li or Na constituting cations in the molten salt.
aluminum (Al), zinc (Zn), gallium (Ga), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), lead (Pb), or bismuth (Bi) may be used.
the treatment object contained within a conductive basket (anode material) formed of metal or the like may be disposed in the molten salt.
An opening may be formed in an upper portion of the basket so that the treatment object can be inserted through the opening into the basket; and a large number of holes may be formed in the side and bottom walls of the basket so that the molten salt can flow into the basket.
the basket may be constituted by a desired material such as a mesh member knitted from metal wires or a sheet member that is a sheet-shaped metal plate having a large number of holes.
the material is formed of C, Pt, Mo, or the like.
the contact area between the object and the conductive material is preferably increased.
the object is effectively used as an electrode by, for example, wrapping the object with a metal mesh member or filling the object into spaces within a metal porous member.
the cathode and an anode formed of an anode material containing the treatment object are disposed in the molten salt; a control unit configured to control the potential of the electrodes from the outside to a predetermined value is connected; and the potential is controlled as described above.
a control unit configured to control the potential of the electrodes from the outside to a predetermined value is connected; and the potential is controlled as described above.
molten salt electrolysis is performed with a pair of electrode members disposed in the molten salt containing dissolved lithium so that lithium is deposited on one of the electrode members (cathode).
cathode the electrode members
lithium is separated from other metals by utilizing the following characteristics: in molten salt electrolysis, different elements are deposited at different potentials as metal or alloy on the cathode. Thus, even when metals other than lithium are contained in the molten salt, by controlling the potential, lithium alone can be deposited on the cathode. As a result, high purity lithium can be obtained.
the cathode material may be selected and the potential may be controlled such that an alloy of the cathode material and lithium is deposited.
the cathode material can be separated as a lithium alloy from the other impurity metal; and, after that, a dissolution step and a deposition step in another molten salt are performed with the cathode material alloyed with lithium to thereby provide high purity lithium.
the electrode members used in the deposition step may be formed of, for example, nickel (Ni), molybdenum (Mo), or glassy carbon (C).
the above-described two steps are used to separate and recover lithium from a treatment object.
the system since a molten salt is used, the system needs to be heated such that the temperature of the system in the steps is equal to or more than the melting point of the molten salt.
a feature of the two steps is use of a molten salt as the electrolytic solution.
a molten salt as the electrolytic solution.
the characteristics of molten salt electrolysis in which different molten salts have different dissolution-deposition potentials for elements are utilized; and the steps can be designed by selecting a molten salt such that the dissolution-deposition potential of lithium and the dissolution-deposition potential of a non-lithium impurity metal are sufficiently different values that allow easy performance of the steps.
the molten salt is preferably selected such that, in the step of depositing or alloying lithium, the difference between the standard electrode potential of a simple substance or alloy of lithium and the standard electrode potential of a simple substance or alloy of another impurity metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potential of a simple substance or alloy of lithium and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the potential of the electrode members is preferably controlled to a predetermined value so that the lithium in the molten salt is selectively deposited or alloyed.
the deposition potential of lithium to be deposited on the cathode can be determined by electrochemical calculation. Specifically, the calculation is performed with Nernst equation.
Li + lithium ions
E 0 Li represents the standard potential
R represents the gas constant
T represents absolute temperature
F represents the Faraday constant
a Li(I) represents the activity of Li ions
a Li(0) represents the activity of Li simple substance.
E Li E Li 0 ′ + RT / 3 ⁇ ⁇ F ⁇ ln ⁇ ⁇ C Li ⁇ ( I ) Equation ⁇ ⁇ ( 3 )
C Li(I) represents the concentration of Li ions
E 0′ Li represents formal electrode potential (here, equal to E 0 Li +RT/3F ⁇ ln ⁇ Li(I) ).
the potential (deposition potential: E LiM ) can be determined with the following equation.
E 0′ Li.M represents formal electrode potential (here, equal to E 0 Li.M +RT/3F ⁇ ln ⁇ Li(I) ).
deposition potentials of all deposits corresponding to different molten salts can be determined.
the molten salt and the cathode material are selected such that a sufficiently high potential difference is achieved with respect to the deposition potential of a simple substance or alloy of another metal, and whether lithium is deposited or a lithium alloy is deposited is decided.
Voltage and current during operation vary depending on the size or positional relationship of electrodes. Accordingly, reference values of voltage and current are determined on the basis of conditions and subsequently voltage and current are determined in each step on the basis of the potential value and order determined by the above-described method.
the potential value is controlled to thereby electrochemically dissolve and deposit lithium. Accordingly, the steps can be simplified, compared with, for example, the existing wet treatment involving repeating of steps of dissolution and extraction using acid or the like; and the particular element can be selectively separated and recovered.
adjustment of the specific gravity of molten salt is not necessary; and, by selecting a low-temperature molten salt in which lithium can be treated in the solid state, a simple apparatus configuration can be employed.
the operation pattern can also be simplified. As a result, the steps can be performed efficiently at low cost.
the treatment object is not limited as long as it is a material containing lithium.
Preferred examples of the treatment object include negative electrode materials of lithium primary batteries and positive electrode materials of lithium-ion secondary batteries.
the molten salt can be selected from chloride molten salts and fluoride molten salts.
a molten salt mixture containing a chloride molten salt and a fluoride molten salt may be used.
chloride molten salts include KCl, NaCl, CaCl 2 , LiCl, RbCl, CsCl, SrCl 2 , BaCl 2 , and MgCl 2 .
fluoride molten salts include LiF, NaF, KF, RbF, CsF, MgF 2 , CaF 2 , SrF 2 , and BaF 2 .
Chloride molten salts are preferably used in view of efficiency; in particular, KCl, NaCl, and CaCl 2 are preferably used because they are inexpensive and easily available.
a plurality of molten salts can be combined and used as a molten salt having a desirable composition.
a molten salt having a composition such as KCl—CaCl 2 , LiCl—KCl, or NaCl—KCl may be used.
an apparatus used for a method for producing lithium by molten salt electrolysis includes a container containing a molten salt; a cathode immersed in the molten salt contained within the container; and an anode that is immersed in the molten salt contained within the container and that contains a conductive treatment object containing lithium, wherein the molten salt is movable into and out of the anode, the apparatus further includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus used for a method for producing lithium by molten salt electrolysis includes a container containing a molten salt containing dissolved lithium; and a cathode and an anode that are immersed in the molten salt contained within the container, wherein the apparatus includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus illustrated in FIG. 18 includes a container 1 containing a molten salt, a molten salt 2 contained within the container 1 , a basket 4 containing a treatment object 3 containing lithium, an electrode 6 , a heater 10 for heating the molten salt 2 , and a control unit 9 electrically connected to the basket 4 and the electrode 6 via conductive wires 5 .
the control unit 9 is configured to control the potential of one electrode (anode) that is the basket 4 and the other electrode (cathode) that is the electrode 6 , to a predetermined value. In the control unit 9 , the value to which the potential is controlled is changeable.
the heater 10 is disposed so as to circularly surround the container 1 .
the electrode 6 may be formed of a desired material, for example, aluminum.
the container 1 may have a bottom surface that has a circular shape or a polygonal shape.
the basket 4 may be the above-described basket.
the potential of the basket 4 and the electrode 6 is controlled by the control unit 9 to a predetermined potential value. As a result, lithium is dissolved in the molten salt 2 from the treatment object 3 .
the basket 4 and the electrode 6 are removed and, as illustrated in FIG. 19 , another electrode 7 (cathode) and another electrode 8 (anode) are placed in the molten salt 2 .
These electrodes 7 and 8 are connected to the control unit 9 via conductive wires 5 .
the control unit 9 is used to control the potential of the electrodes 7 and 8 to a predetermined value. At this time, the potential is controlled such that the potential at the electrode 7 is the deposition potential of lithium. As a result, lithium dissolved in the molten salt 2 is deposited on the surface of the electrode 7 (cathode).
the electrodes 7 and 8 may be formed of a material such as glassy carbon (C).
the heating temperature for the molten salt 2 with the heater 10 may be, for example, 800° C. in both of the treatments using the apparatuses illustrated in FIGS. 18 and 19 . In this way, lithium can be deposited as a simple substance on the surface of the electrode 7 .
the potential of the electrodes 7 and 8 may be controlled to a value such that an alloy of lithium and the cathode material is deposited on the surface of the electrode 7 (cathode).
the above-described dissolution step and deposition step may be performed with the alloyed electrode 7 . That is, the apparatus illustrated in FIG. 18 is newly prepared and the electrode 7 alloyed with lithium is used instead of the above-described treatment object 3 .
the method for producing lithium of this embodiment is performed with the apparatuses illustrated in FIGS. 18 and 19 , for example, the method may be performed in the following manner.
a lithium-containing positive electrode material of lithium-ion batteries is first prepared as the treatment object 3 and KCl—NaCl is prepared as the molten salt 2 .
the positive electrode material is a powder containing lithium cobalt oxide (LiCoO 2 ) or lithium manganese oxide.
the positive electrode material is ground and placed within the basket 4 .
the size of the positive electrode material serving as the treatment object 3 is preferably minimized by grinding.
the positive electrode material is ground into particles having a maximum particle size of 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less.
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
lithium can be recovered from the positive electrode material serving as the treatment object 3 .
the apparatus configuration can be simplified and the treatment time can also be decreased, compared with the existing wet separation method and the like.
the cost incurred can be reduced.
lithium can be deposited as a simple substance on the electrode surface and hence high purity lithium can be obtained.
This embodiment is a method for producing a metal by molten salt electrolysis, the method including a step of dissolving, in a molten salt, a metal element contained in a treatment object containing two or more metal elements; and a step of depositing or alloying a particular metal present in the molten salt, on one of a pair of electrode members disposed in the molten salt containing the dissolved metal element, by controlling a potential of the electrode members to a predetermined value.
this embodiment includes a process of dissolving, in a molten salt, a particular metal contained in the treatment object, and a process of depositing the particular metal on one of electrodes (cathode) from the molten salt containing the dissolved particular metal by molten salt electrolysis.
a feature of this embodiment is that, by controlling the potential of the electrodes to a predetermined value, the particular metal is selectively deposited from the treatment object to provide the particular metal at high purity.
a procedure for dissolving, in a molten salt, a particular metal contained in a treatment object is, for example, a chemical procedure for dissolution.
a treatment object is ground into particles or powder, mixed with a salt, and heated.
the particular metal contained in the treatment object can be dissolved in the molten salt.
the treatment object may be placed in a molten salt and dissolved.
Another procedure is an electrochemical procedure. Specifically, a cathode and an anode that is formed of an anode material containing the treatment object are disposed in the molten salt; and the potential at the anode is controlled to a predetermined value so that a metal element corresponding to the controlled potential value is dissolved in the molten salt from the treatment object.
Molten salt electrolysis is characterized in that different elements are dissolved at different potentials; and such characteristics are utilized to thereby separate a particular metal from other metals. In this way, by using a treatment object as an anode and controlling the potential during dissolution, a particular metal can be selectively dissolved in a molten salt.
all the metals contained in the treatment object may be dissolved.
a particular metal and another metal contained in the treatment object may be dissolved.
Conditions under which a particular metal and another metal contained in the treatment object are dissolved may be employed; however, if possible, the potential is preferably controlled so that the particular metal alone is dissolved. That is, in the step of dissolving a particular metal in a molten salt, the potential at the anode is preferably controlled to a predetermined value so that the particular metal element is selectively dissolved in the molten salt. As a result, entry of impurities in the subsequent deposition step can be reduced.
the molten salt is preferably selected such that, in the step of dissolving, in the molten salt, a particular metal from the treatment object, the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the particular metal that is dissolved in the molten salt can be sufficiently separated from the other metal element that is left in the anode.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation described below.
one or more target particular metals are contained in the treatment object, in the dissolution step, one or more particular metals are dissolved in the molten salt.
the treatment object contains only one particular metal, as described above, this particular metal is dissolved and then the deposition step is performed to provide the target metal.
the treatment object contains two or more target particular metals, only one of the metals may be dissolved in a molten salt; a deposition step may be subsequently performed; and, after that, another dissolution step may be performed so that the remainder of the particular metals is dissolved in the molten salt.
the treatment object having been used in the initial dissolution step may be moved from the molten salt used in this dissolution step to another molten salt and subjected to a dissolution step to thereby dissolve the remainder of the particular metals.
the subsequent deposition step may be performed such that the particular metals present in the molten salt are deposited or alloyed one by one on electrode materials, so that desired particular metals can be produced.
this electrode material may be replaced by another electrode material and another particular metal dissolved in the molten salt may be deposited or alloyed on this electrode material.
the cathode used in the dissolution step is formed of carbon or a material that tends to form an alloy with an alkali metal such as Li or Na constituting cations in the molten salt.
an alkali metal such as Li or Na constituting cations in the molten salt.
aluminum (Al), zinc (Zn), gallium (Ga), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), lead (Pb), or bismuth (Bi) may be used.
the treatment object contained within a conductive basket (anode material) formed of metal or the like may be disposed in the molten salt.
An opening may be formed in an upper portion of the basket so that the treatment object can be inserted through the opening into the basket; and a large number of holes may be formed in the side and bottom walls of the basket so that the molten salt can flow into the basket.
the basket may be constituted by a desired material such as a mesh member knitted from metal wires or a sheet member that is a sheet-shaped metal plate having a large number of holes.
the material is formed of C, Pt, Mo, or the like.
the contact area between the object and the conductive material is preferably increased.
the object is effectively used as an electrode by, for example, wrapping the object with a metal mesh member or filling the object into spaces within a metal porous member.
the cathode and an anode formed of an anode material containing the treatment object are disposed in the molten salt; and the potential at the anode is controlled to a predetermined value.
an anode material containing the treatment object for example, a metal basket containing the treatment object
molten salt electrolysis is performed with a pair of electrode members disposed in the molten salt containing the dissolved particular metal so that the particular metal is deposited on one of the electrode members (cathode).
the particular metal can be selectively deposited as metal or alloy on the cathode.
the particular metal is separated from other metals by utilizing the following characteristics: in molten salt electrolysis, different elements are deposited at different potentials as metal or alloy on the cathode.
the particular metal element can be selectively deposited or alloyed on the cathode. That is, the particular metal at high purity can be obtained.
the cathode material may be selected and the potential may be controlled such that an alloy of the cathode material and the particular metal is deposited.
the particular metal in the molten salt can be deposited as an alloy and separated from the other impurity metal; and, after that, for example, a dissolution step and a deposition step in another molten salt can be performed with the cathode material alloyed with the particular metal to thereby provide the particular metal at high purity.
the electrode members used in the deposition step may be formed of, for example, nickel (Ni), molybdenum (Mo), or glassy carbon (C).
the above-described two processes are used to separate and extract a particular metal from a treatment object.
the system since a molten salt is used, the system needs to be heated such that the temperature of the system in the processes is equal to or more than the melting point of the molten salt.
smelting can be performed on the basis of an idea that is totally contrary to that of the processes. That is, a treatment object is used as the anode and only metal elements serving as impurities are dissolved in a molten salt. In this case, by also controlling the potential at the anode, such a phenomenon is caused in which a particular metal is left in the anode and impurity elements are dissolved. As a result, the particular metal is provided in the anode.
a feature of the two processes is use of a molten salt.
the characteristics of molten salt electrolysis in which different molten salts have different dissolution-deposition potentials for elements are utilized; and the processes can be designed by selecting a molten salt such that the dissolution-deposition potential of a particular metal and the dissolution-deposition potential of an impurity metal other than the particular metal are sufficiently different values that allow easy performance of the processes.
the molten salt is preferably selected such that, in the step of depositing or alloying a particular metal, the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the potential of the electrode members is preferably controlled to a predetermined value so that the particular metal element in the molten salt is selectively deposited or alloyed.
the deposition potential of a particular metal to be deposited on the cathode can be determined by electrochemical calculation. Specifically, the calculation is performed with Nernst equation.
Mo(IV) tetravalent Mo ions
E 0 Mo represents the standard potential
R represents the gas constant
T represents absolute temperature
F represents the Faraday constant
a Mo(IV) represents the activity of Mo(IV) ions
a Mo(0) represents the activity of Mo simple substance.
E Mo E Mo 0 ′ + RT / 3 ⁇ ⁇ F ⁇ ln ⁇ ⁇ C Mo ⁇ ( IV ) Equation ⁇ ⁇ ( 3 )
C Mo(IV) represents the concentration of tetravalent Mo ions
E 0′ Mo represents formal electrode potential (here, equal to E 0 Mo +RT/3F ⁇ ln ⁇ Mo(IV) ).
the molten salt and the cathode material are selected such that a sufficiently high potential difference is achieved with respect to the deposition potential of a simple substance or alloy of another metal, and whether molybdenum simple substance is deposited or a molybdenum alloy is deposited is decided.
Voltage and current during operation vary depending on the size or positional relationship of electrodes. Accordingly, reference values of voltage and current are determined on the basis of conditions and subsequently voltage and current are determined in each step on the basis of the potential value and order determined by the above-described method.
the potential value is controlled to thereby electrochemically dissolve and deposit the particular metal. Accordingly, the steps can be simplified, compared with, for example, the existing wet treatment involving repeating of processes of dissolution and extraction using acid or the like; and a particular metal can be selectively separated and recovered.
adjustment of the specific gravity of molten salt is not necessary; and, by selecting a low-temperature molten salt in which the particular metal can be treated in the solid state, a simple apparatus configuration can be employed.
the operation pattern can also be simplified. As a result, the steps can be performed efficiently at low cost.
a particular metal can be smelted on the basis of an idea that is totally contrary to the idea of depositing or alloying a particular metal on the cathode.
a method for producing a metal by molten salt electrolysis is a method for producing a particular metal by molten salt electrolysis from a treatment object containing two or more metal elements, wherein a cathode and an anode that is formed of an anode material containing the treatment object are disposed in a molten salt, and the potential at the anode is controlled to a predetermined value so that a metal element corresponding to the potential is dissolved in the molten salt from the treatment object and the particular metal is left in the anode.
the anode material containing the treatment object is used as the anode and metal elements other than the particular metal, that is, only metal elements serving as impurities are dissolved in the molten salt, so that the particular metal is left in the anode.
metal elements other than the particular metal that is, only metal elements serving as impurities are dissolved in the molten salt, so that the particular metal is left in the anode.
the molten salt is also preferably selected such that, in the step of dissolving, in the molten salt, a metal element from the treatment object, the difference between the standard electrode potential of a simple substance or alloy of the particular metal and the standard electrode potential of a simple substance or alloy of another metal in the molten salt is 0.05 V or more.
the particular metal can be sufficiently separated from the other metal and the particular metal alone can be left in the anode.
the difference between the standard electrode potentials is more preferably 0.1 V or more, still more preferably 0.25 V or more.
the value of the potential controlled at the anode can be calculated by Nernst equation as described above.
the treatment object containing two or more metal elements is not limited at all as long as it is a metal material containing a target particular metal.
Mn, Co, Sb, and the like can be obtained from collected battery materials; Nb and the like can be obtained from metal superconducting materials; Bi, Sr, and the like can be obtained from oxide superconducting materials; V can be obtained from ferrovanadium; Mo and the like can be obtained from Mo—Cu heat spreaders; and Ge and the like can be obtained from optical fiber materials.
This embodiment is also suitably applicable to cases where the treatment object is a metal material containing a transition metal or a rare earth metal.
a transition metal is not particularly limited and may be any element among from group 3 (group IIIA) to group 11 (group IB) of the periodic table.
This embodiment is also suitably applicable to cases where the treatment object contains, as a transition metal, one or more metals selected from the group consisting of V, Nb, Mo, Ti, Ta, Zr, and Hf.
this embodiment is also suitably applicable to cases where the treatment object contains a metal that is one or both of Sr and Ba. Furthermore, this embodiment is also suitably applicable to cases where the treatment object contains one or more metals selected from the group consisting of Zn, Cd, Ga, In, Ge, Sn, Pb, Sb, and Bi.
a transition metal or a rare earth metal as the particular metal to be deposited or alloyed, the transition metal or the rare earth metal can be obtained.
a transition metal is not particularly limited and may be any element among from group 3 (group IIIA) to group 11 (group IB) of the periodic table.
one or more of these metals contained in the treatment object can be dissolved in a molten salt and particular metals can be sequentially deposited or alloyed on electrode members from the molten salt.
the treatment object preferably has the form of particles or powder.
the treatment object is prepared so as to have the form of particles or powder, the surface area is increased and the treatment efficiency can be increased.
the treatment object prepared in the form of particles or powder can be compacted and used as the anode.
the particles there are desirably spaces that the molten salt can easily enter.
the molten salt can be selected from chloride molten salts and fluoride molten salts.
a molten salt mixture containing a chloride molten salt and a fluoride molten salt may be used.
chloride molten salts include KCl, NaCl, CaCl 2 , LiCl, RbCl, CsCl, SrCl 2 , BaCl 2 , and MgCl 2 .
fluoride molten salts include LiF, NaF, KF, RbF, CsF, MgF 2 , CaF 2 , SrF 2 , and BaF 2 .
Chloride molten salts are preferably used in view of efficiency; in particular, KCl, NaCl, and CaCl 2 are preferably used because they are inexpensive and easily available.
a plurality of molten salts can be combined and used as a molten salt having a desirable composition.
a molten salt having a composition such as KCl—CaCl 2 , LiCl—KCl, or NaCl—KCl may be used.
the apparatus includes a container containing a molten salt; a cathode immersed in the molten salt contained within the container; and an anode that is immersed in the molten salt contained within the container and that contains a conductive treatment object containing two or more metal elements, wherein the molten salt is movable into and out of the anode, the apparatus further includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus used for a method for producing a metal by molten salt electrolysis is preferably an apparatus that includes a container containing a molten salt containing a dissolved particular metal; and a cathode and an anode that are immersed in the molten salt contained within the container, wherein the apparatus includes a control unit configured to control the potential of the cathode and the anode to a predetermined value, and the value of the potential is changeable in the control unit.
An apparatus illustrated in FIG. 18 includes a container 1 containing a molten salt, a molten salt 2 contained within the container 1 , a basket 4 containing a treatment object 3 containing two or more metal elements, an electrode 6 , a heater 10 for heating the molten salt 2 , and a control unit 9 electrically connected to the basket 4 and the electrode 6 via conductive wires 5 .
the control unit 9 is configured to control the potential of one electrode (anode) that is the basket 4 and the other electrode (cathode) that is the electrode 6 , to a predetermined value. In the control unit 9 , the value to which the potential is controlled is changeable.
the heater 10 is disposed so as to circularly surround the container 1 .
the electrode 6 may be formed of a desired material, for example, carbon.
the container 1 may have a bottom surface that has a circular shape or a polygonal shape.
the basket 4 may be the above-described basket.
the potential of the basket 4 and the electrode 6 is controlled by the control unit 9 to a predetermined potential value. As a result, a particular metal is dissolved in the molten salt 2 from the treatment object 3 .
the basket 4 and the electrode 6 are removed and another electrode 7 (cathode) and another electrode 8 (anode) are placed in the molten salt 2 .
These electrodes 7 and 8 are connected to the control unit 9 via conductive wires 5 .
the control unit 9 is used to control the potential of the electrodes 7 and 8 to a predetermined value. At this time, the potential is controlled such that the potential at the electrode 7 is the deposition potential of the particular metal. As a result, the particular metal dissolved in the molten salt 2 is deposited on the surface of the electrode 7 (cathode).
the electrodes 7 and 8 may be formed of a material such as glassy carbon (C).
the heating temperature for the molten salt 2 with the heater 10 may be, for example, 800° C. in both of the treatments using the apparatuses illustrated in FIGS. 18 and 19 .
the particular metal can be deposited as a simple substance on the surface of the electrode 7 .
the potential of the electrodes 7 and 8 may be controlled such that an alloy of the particular metal and the cathode material is deposited on the surface of the electrode 7 (cathode).
the above-described dissolution step and deposition step may be performed with the alloyed electrode 7 . That is, the apparatus illustrated in FIG. 18 is newly prepared and the electrode 7 alloyed with the particular metal is used instead of the above-described treatment object 3 .
the method for producing a metal of this embodiment may be performed in the following manner.
examples relating to vanadium, molybdenum, strontium, and germanium will be described.
the method for producing a metal of this embodiment is used to obtain vanadium.
Ferrovanadium (1 kg) is first prepared as the treatment object 3 and NaCl—KCl is prepared as the molten salt 2 .
the ferrovanadium contains 75 wt % of vanadium (V) and 25 wt % of iron (Fe).
the ferrovanadium is ground and placed within the basket 4 .
the amount of the molten salt 2 is about 15 liters.
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
Mo—Cu heat spreaders (1 kg) are first prepared as the treatment object 3 and LiCl—KCl is prepared as the molten salt 2 .
the Mo—Cu heat spreaders contain 50 wt % of molybdenum (Mo) and 50 wt % of copper (Cu).
the heat spreaders are ground and placed within the basket 4 .
the amount of the molten salt 2 is about 5 liters.
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
the method for producing a metal of this embodiment is used to obtain molybdenum.
An oxide superconducting material (1 kg) is first prepared as the treatment object 3 and LiF—CaF 2 is prepared as the molten salt 2 .
the oxide superconducting material contains 17 wt % of strontium (Sr) and 8 wt % of calcium (Ca).
the oxide superconducting material is ground and placed within the basket 4 .
the amount of the molten salt 2 is about 4 liters.
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
the method for producing a metal of this embodiment is used to obtain germanium.
An optical fiber material (1 kg) is first prepared as the treatment object 3 and LiF—CaF 2 is prepared as the molten salt 2 .
the optical fiber material contains 3 wt % of germanium (Ge).
the optical fiber material is ground and placed within the basket 4 .
the amount of the molten salt 2 is about 4 liters.
the above-described dissolution step may be performed with a carbon electrode serving as the electrode 6 .
the deposition step may be performed with electrodes formed of glassy carbon and serving as the electrodes 7 and 8 .
the size of ferrovanadium, Mo—Cu heat spreaders, oxide superconducting material, and optical fiber material serving as the treatment object 3 is preferably minimized by grinding: for example, the treatment object 3 is preferably ground into particles having a maximum particle size of 5 mm or less, more preferably 3 mm or less, still more preferably 1 mm or less.
the apparatus configuration can be simplified and the treatment time can also be decreased, compared with the existing recovery methods and the like.
the cost incurred can be reduced.
a particular metal can be deposited as a simple substance on the electrode surface and hence high purity metal can be obtained.
the potentials for depositing vanadium, a vanadium alloy, molybdenum, a molybdenum alloy, strontium, a strontium alloy, germanium, and a germanium alloy can be determined by the above-described calculation.
First to Fourth embodiments have been individually described so far. However, for example, in order to obtain tungsten, lithium, transition metals, and rare earth metals in Second to Fourth embodiments, methods in other embodiments may be entirely or partially employed.
Nd, Dy, and Pr were produced by molten salt electrolysis from an ore containing rare earth metals.
the ore serving as a treatment object was xenotime ore.
the xenotime ore was ground with a crusher or a ball mill so as to have a particle size of about 2 mm.
the ground sample (xenotime ore) was wrapped with a molybdenum (Mo) mesh (50 mesh).
the sample powder contained within the mesh was used as an anode (anode electrode).
a molten LiF—NaF—KF eutectic salt was employed as the molten salt. This salt was completely melted by heating at 700° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. After about 4 hours lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by inductively coupled plasma-atomic emission spectroscopy (ICP-AES).
ICP-AES inductively coupled plasma-atomic emission spectroscopy
a cathode electrode formed of Ni and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that Dy—Ni alloy was formed in the LiF—NaF—KF molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the anode current observed in the dissolution step varied with time as illustrated in FIG. 15 .
the abscissa axis indicates time (unit: min), and the ordinate axis indicates the value of anode current (unit: mA).
the current value decreased with time.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of Nd and Dy in the molten salt was confirmed.
FIGS. 16 and 17 illustrate results of observation of a section of the surface layer of the cathode electrode with a scanning electron microscope (SEM).
SEM scanning electron microscope
FIG. 16 illustrates a back-scattered electron image observed with the SEM.
FIG. 17 illustrates the distribution of Dy atoms in the regions illustrated in FIG. 16 and subjected to X-ray analysis. As illustrated in FIG. 17 , Dy was scarcely detected in a region 33 corresponding to the electrode body part 31 ; however, Dy was detected in a region 34 corresponding to the Dy—Ni alloy 32 .
Cemented carbide tools were used as the metal material containing tungsten and tungsten was produced by molten salt electrolysis.
the cemented carbide tools serving as a treatment object were cutting tools containing 90 wt % of tungsten carbide and 10 wt % of cobalt serving as a binder.
the cutting tools were ground with a bead mill or an attritor so as to have a particle size of about 2 mm.
the ground sample (cutting tools) was wrapped with a molybdenum (Mo) mesh (50 mesh). As illustrated in FIG. 14 , the sample powder (treatment object) contained within the Mo mesh was used as an anode (anode electrode).
a molten NaCl—KCl eutectic salt was employed as the molten salt. This salt was completely melted by heating at 700° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that tungsten was deposited in the NaCl—KCl molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the anode current observed in the dissolution step varied with time as in First embodiment (example) ( FIG. 15 ).
the abscissa axis indicates time (unit: min), and the ordinate axis indicates the value of anode current (unit: mA).
the current value decreased with time.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of tungsten in the molten salt was confirmed.
lithium-ion secondary batteries were used as the treatment object containing lithium and lithium was produced by molten salt electrolysis.
the positive electrode was formed of lithium cobalt oxide and the negative electrode was formed of graphite, lithium cobalt oxide content: mass %)
the lithium-ion secondary batteries were immersed in an electrolytic solution (5% NaCl) and discharged until the voltage became 0.1 mV. After that, the positive electrode material was taken out by manual disassembly, and ground with a cutter mill to provide a positive electrode material powder having an average particle size of 0.1 mm.
the composition of the powder is described in Table I. As a result of analysis, it was confirmed that the powder obtained by the separation was lithium cobalt oxide.
the powder was wrapped with a molybdenum (Mo) mesh (200 mesh). As illustrated in FIG. 14 , the sample powder contained within the Mo mesh was used as an anode (anode electrode).
Mo molybdenum
a molten NaCl—KCl eutectic salt was employed as the molten salt. This salt was completely melted by heating at 700° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode (cathode electrode) was formed of carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
the anode current observed in the dissolution step varied with time as in First embodiment (example) ( FIG. 15 ).
the abscissa axis indicates time (unit: min), and the ordinate axis indicates the value of anode current (unit: mA).
the current value decreased with time.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of lithium in the molten salt was confirmed.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that lithium was deposited in the NaCl—KCl molten salt. After a predetermined time lapsed, a section of the surface layer of the cathode electrode was observed with a scanning electron microscope (SEM).
Ferrovanadium was used as the metal material containing vanadium and vanadium was produced by molten salt electrolysis.
the ferrovanadium serving as a treatment object contained 75 wt % of vanadium and 25 wt % of iron.
the ferrovanadium was ground with a bead mill or an attritor so as to have a particle size of about 2 mm.
the ground sample (ferrovanadium) was wrapped with a molybdenum (Mo) mesh (50 mesh). As illustrated in FIG. 14 , the sample powder (treatment object) contained within the Mo mesh was used as an anode (anode electrode).
a molten NaCl—KCl eutectic salt was employed as the molten salt. This salt was completely melted by heating at 700° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. At this time, the potential was set such that iron was not dissolved but vanadium alone was selectively dissolved. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that vanadium was deposited in the NaCl—KCl molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the anode current observed in the dissolution step varied with time as in First embodiment (example) ( FIG. 15 ).
the abscissa axis indicates time (unit: min), and the ordinate axis indicates the value of anode current.
the current value decreased with time.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of vanadium in the molten salt was confirmed.
Mo—Cu heat spreaders were used as the metal material containing molybdenum and molybdenum was produced by molten salt electrolysis.
the Mo—Cu heat spreaders serving as a treatment object contained 50 wt % of molybdenum and 50 wt % of copper.
the heat spreaders were ground with a bead mill or an attritor so as to have a particle size of about 2 mm.
the ground sample (heat spreaders) was wrapped with a platinum (Pt) mesh (50 mesh).
the sample powder (treatment object) contained within the Pt mesh was used as an anode (anode electrode).
a molten LiCl—KCl eutectic salt was employed as the molten salt. This salt was completely melted by heating at 450° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. At this time, the potential was set such that copper was not dissolved but molybdenum alone was selectively dissolved. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that molybdenum was deposited in the LiCl—KCl molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the value of anode current observed in the dissolution step decreased with time as in the above-described case relating to vanadium.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of molybdenum in the molten salt was confirmed.
An oxide superconducting material was used as the metal material containing strontium and strontium was produced by molten salt electrolysis.
the oxide superconducting material serving as a treatment object contained 17 wt % of strontium and 8 wt % of calcium.
the oxide superconducting material was ground with a bead mill or an attritor so as to have a particle size of about 2 mm.
the ground sample (oxide superconducting material) was wrapped with a platinum (Pt) mesh (50 mesh).
the sample powder (treatment object) contained within the Pt mesh was used as an anode (anode electrode).
a molten LiF—CaF 2 eutectic salt was employed as the molten salt. This salt was completely melted by heating at 850° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. At this time, the potential was set such that strontium and calcium alone were selectively dissolved and the other elements contained were not dissolved. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that strontium was deposited in the LiF—CaF 2 molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the value of anode current observed in the dissolution step decreased with time as in the above-described case relating to vanadium.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of strontium in the molten salt was confirmed.
An optical fiber material was used as the metal material containing germanium and germanium was produced by molten salt electrolysis.
the optical fiber material serving as a treatment object contained 3 wt % of germanium.
the optical fiber material was ground with a bead mill or an attritor so as to have a particle size of about 2 mm.
the ground sample (optical fiber material) was wrapped with a platinum (Pt) mesh (50 mesh).
the sample powder (treatment object) contained within the Pt mesh was used as an anode (anode electrode).
a molten LiF—CaF 2 eutectic salt was employed as the molten salt. This salt was completely melted by heating at 850° C. In this molten salt, the above-described anode electrode and a cathode electrode were wired and immersed. The cathode electrode was formed of glassy carbon.
the anode electrode and the cathode electrode were thus immersed in the molten salt, the anode electrode was maintained at a predetermined potential. At this time, the potential was set such that germanium alone was selectively dissolved and the other elements contained were not dissolved. After a predetermined time lapsed, a sample was taken from the molten salt and the sample was subjected to composition analysis by ICP-AES.
a cathode electrode formed of glassy carbon and an anode electrode formed of glassy carbon were immersed in the molten salt.
the potential at the cathode electrode was maintained at a predetermined potential. Specifically, the potential was maintained such that germanium was deposited in the LiF—CaF 2 molten salt. After a predetermined time lapsed, the surface status of the cathode electrode was observed.
the anode current observed in the dissolution step decreased with time as in the above-described case relating to vanadium.
the change rate of current value with respect to time had the following tendency: the change rate was the highest at the beginning of the measurement (at the beginning of application of current) and, after that, the change rate gradually decreased.
the sample taken from the molten salt was subjected to composition analysis by ICP-AES. As a result, dissolution of germanium in the molten salt was confirmed.
the present invention is suitably applicable to a method for obtaining a particular metal at high purity from a treatment object containing two or more metal elements.
the present invention is also suitably applicable to a method for obtaining a desirable metal from an ore or a crude metal ingot.
the present invention is also suitably applicable to a method for obtaining tungsten at high purity from a treatment object containing at least one of tungsten and lithium.

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WO2013065511A1 (ja)	2013-05-10
CN103906861A (zh)	2014-07-02

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