US3725221A - Recovery of niobium and tantalum - Google Patents
Recovery of niobium and tantalum Download PDFInfo
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- US3725221A US3725221A US00221092A US3725221DA US3725221A US 3725221 A US3725221 A US 3725221A US 00221092 A US00221092 A US 00221092A US 3725221D A US3725221D A US 3725221DA US 3725221 A US3725221 A US 3725221A
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- tantalum
- niobium
- alkali metal
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- 239000010955 niobium Substances 0.000 title abstract description 17
- 229910052758 niobium Inorganic materials 0.000 title abstract description 13
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 title abstract description 13
- 229910052715 tantalum Inorganic materials 0.000 title abstract description 12
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 title abstract description 10
- 238000011084 recovery Methods 0.000 title description 7
- 239000000463 material Substances 0.000 abstract description 11
- 229910052500 inorganic mineral Inorganic materials 0.000 abstract description 10
- 239000011707 mineral Substances 0.000 abstract description 10
- 238000000151 deposition Methods 0.000 abstract description 8
- 230000008021 deposition Effects 0.000 abstract description 8
- 238000005868 electrolysis reaction Methods 0.000 abstract description 8
- 229910011255 B2O3 Inorganic materials 0.000 abstract description 6
- 229910001508 alkali metal halide Inorganic materials 0.000 abstract description 6
- 229910000318 alkali metal phosphate Inorganic materials 0.000 abstract description 6
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 abstract description 6
- 229910052783 alkali metal Inorganic materials 0.000 abstract description 5
- 150000008045 alkali metal halides Chemical class 0.000 abstract description 5
- OATFOCVSPXTLNR-UHFFFAOYSA-N phosphanylidyneniobium Chemical group [Nb]#P OATFOCVSPXTLNR-UHFFFAOYSA-N 0.000 abstract description 5
- AUOAQYMBESBNJR-UHFFFAOYSA-N phosphanylidynetantalum Chemical group [Ta]#P AUOAQYMBESBNJR-UHFFFAOYSA-N 0.000 abstract description 4
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 abstract description 2
- 238000004070 electrodeposition Methods 0.000 abstract description 2
- 150000003839 salts Chemical class 0.000 abstract description 2
- 150000001340 alkali metals Chemical class 0.000 abstract 1
- 238000000034 method Methods 0.000 description 13
- 239000003792 electrolyte Substances 0.000 description 11
- 235000010755 mineral Nutrition 0.000 description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- -1 tantalum metals Chemical class 0.000 description 7
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 6
- 239000012141 concentrate Substances 0.000 description 5
- 235000002639 sodium chloride Nutrition 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910001610 cryolite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 229910000027 potassium carbonate Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 239000011780 sodium chloride Substances 0.000 description 4
- 239000011775 sodium fluoride Substances 0.000 description 4
- 235000013024 sodium fluoride Nutrition 0.000 description 4
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- 150000002739 metals Chemical group 0.000 description 2
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 2
- 239000003870 refractory metal Substances 0.000 description 2
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 description 2
- 229940048086 sodium pyrophosphate Drugs 0.000 description 2
- 235000019818 tetrasodium diphosphate Nutrition 0.000 description 2
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 2
- MOMKYJPSVWEWPM-UHFFFAOYSA-N 4-(chloromethyl)-2-(4-methylphenyl)-1,3-thiazole Chemical compound C1=CC(C)=CC=C1C1=NC(CCl)=CS1 MOMKYJPSVWEWPM-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 235000010678 Paulownia tomentosa Nutrition 0.000 description 1
- 240000002834 Paulownia tomentosa Species 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- FZQSLXQPHPOTHG-UHFFFAOYSA-N [K+].[K+].O1B([O-])OB2OB([O-])OB1O2 Chemical compound [K+].[K+].O1B([O-])OB2OB([O-])OB1O2 FZQSLXQPHPOTHG-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- PSHMSSXLYVAENJ-UHFFFAOYSA-N dilithium;[oxido(oxoboranyloxy)boranyl]oxy-oxoboranyloxyborinate Chemical compound [Li+].[Li+].O=BOB([O-])OB([O-])OB=O PSHMSSXLYVAENJ-UHFFFAOYSA-N 0.000 description 1
- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000000622 liquid--liquid extraction Methods 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- MRVHOJHOBHYHQL-UHFFFAOYSA-M lithium metaphosphate Chemical compound [Li+].[O-]P(=O)=O MRVHOJHOBHYHQL-UHFFFAOYSA-M 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- RHDUVDHGVHBHCL-UHFFFAOYSA-N niobium tantalum Chemical compound [Nb].[Ta] RHDUVDHGVHBHCL-UHFFFAOYSA-N 0.000 description 1
- VUWVDWMFBFJOCE-UHFFFAOYSA-N niobium(5+);oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Ta+5] VUWVDWMFBFJOCE-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 239000011698 potassium fluoride Substances 0.000 description 1
- 235000003270 potassium fluoride Nutrition 0.000 description 1
- OQZCJRJRGMMSGK-UHFFFAOYSA-M potassium metaphosphate Chemical compound [K+].[O-]P(=O)=O OQZCJRJRGMMSGK-UHFFFAOYSA-M 0.000 description 1
- 229940099402 potassium metaphosphate Drugs 0.000 description 1
- SKFYTVYMYJCRET-UHFFFAOYSA-J potassium;tetrafluoroalumanuide Chemical compound [F-].[F-].[F-].[F-].[Al+3].[K+] SKFYTVYMYJCRET-UHFFFAOYSA-J 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- MEFOUWRMVYJCQC-UHFFFAOYSA-N rimsulfuron Chemical compound CCS(=O)(=O)C1=CC=CN=C1S(=O)(=O)NC(=O)NC1=NC(OC)=CC(OC)=N1 MEFOUWRMVYJCQC-UHFFFAOYSA-N 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 235000019983 sodium metaphosphate Nutrition 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- MVGWWCXDTHXKTR-UHFFFAOYSA-J tetralithium;phosphonato phosphate Chemical compound [Li+].[Li+].[Li+].[Li+].[O-]P([O-])(=O)OP([O-])([O-])=O MVGWWCXDTHXKTR-UHFFFAOYSA-J 0.000 description 1
- RYCLIXPGLDDLTM-UHFFFAOYSA-J tetrapotassium;phosphonato phosphate Chemical compound [K+].[K+].[K+].[K+].[O-]P([O-])(=O)OP([O-])([O-])=O RYCLIXPGLDDLTM-UHFFFAOYSA-J 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G33/00—Compounds of niobium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G35/00—Compounds of tantalum
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Definitions
- Niobium and tantalum metals have excellent high temperature properties and are resistant to attack by liquid metals and acids. Both metals form important alloys with ferrous metals and other refractory metals, the alloys having numerous space, electronic and defense applications. In addition, the phosphides find utility as corrosion resistant coatings, semi-conductors and hard metal compounds.
- niobium and tantalum may be recovered from their minerals by means of a much simpler and more eflicient process in which the two metals are selectively electrolytically deposited as monophosphides from a fused salt bath comprising alkali metal phosphate, halide and borate or boric oxide.
- Selective electrodeposition is achieved by initial deposition of NbP at a potential of 2.5 volts or less, followed by deposition of TaP at a potential of 3.0 volts or greater.
- the feed material in the process of the invention is essentially a mixed oxide of niobium and tantalum, but it may also contain oxides of other elements such as iron, manganese, sodium, titanium, silicon, etc., depending on the composition of the mineral from which it is derived. It may be derived from suitable minerals by the conventional alkali fusion and acid leaching described above, or it may consist of a concentrate obtained by bcneficiating a niobium and tantalum-containing mineral. Examples of such minerals are columbite, pyrochlor and euxenite.
- the preferred feed material consists of a columbite concentrate containing about 50 to 60 wt. percent Nb 0 5 to 25 wt. percent Ta O to wt. percent Fe O and 2 to 10' wt. percent MnO.
- the feed material is initially dissolved in a molten electrolyte comprising (1) an alkali metal phosphate, (2) an alkali metal halide and (3) an alkali metal borate or boric oxide.
- suitable alkali metal phosphates are sodium pyrophosphate, sodium metaphosphate, potassium pyrophosphate, potassium metaphosphate, lithium pyrophosphate and lithium metaphosphate.
- Suitable alkali metal halides comprise sodium chloride, sodium fluoride, cryolite (Na AlF potassium chloride, potassium fluoride, potassium aluminum tetrafluoride (KAIF lithium chloride and lithium fluoride. A combination of sodium chloride and sodium fluoride has been found to give particularly good results.
- Suitable alkali metal borates include sodium tetraborate, potassium tetraborate and lithium tetraborate.
- feed material 4 to 12 percent
- alkali metal phosphate 9 to 25 percent
- alkali metal halides 60 to percent
- alkali metal borate or boric oxide 8 to 15 percent.
- cryolite and potassium carbonate are suitably about 15 to 20 weight percent and 2 to 5 weight percent, respectively.
- the operating temperature i.e., the temperature during deposition of the NbP and TaP, should be between about 900 and 1150 C., preferably about 1100" C.
- Niobium in the form of dendritic crystals of niobium monophosphide, is first deposited at a potential of about 1.0 to 2.5 volts and a cathode current density of about 30 to 75 amp/dmF. The cathode is removed from the electrolyte and the NbP crystals are scraped off. The cathode is replaced and electrolysis continued at a potential of about 3.0 to 5.0 volts and a cathode current density of about to 200 amp/dm. to deposit tantatum, also in the form of phosphide. Time required for substantially complete deposition of each metal is about 1 to 2 hours.
- the cell employed for the electrolysis is conventional and preferably consists of a graphite crucible serving as container and anode.
- the cathode is a centrally positioned graphite or refractory metal rod.
- the cell is desirably heated in an electric resistance furnace, but an oil or gas-fired furnace may also be used. A protective atmosphere is not required.
- Niobium and tantalum metals may be readily recovered from their phosphides by means of conventional processes such as (1) dissolution in nitric or sulfuric acid to prepare oxides which are reduced to metal by metallothermic reactions or (2) chlorination at high temperatures to yield chlorides which are reduced to metal by metallothermic reactions.
- EXAMPLE 1 Weight Mole Electrolyte composition percent percent (Nb, T9205 4 1 NmPzOy 21 6 B20; 11 11 NaCl 56 68 NaF. 9 14 1 50 wt. percent each 01 Nb O; and Tarot.
- Electrode 3'' ID. x 7" high graphite crucible
- Cathode 1" diameter graphite rod
- Electrode spacing Cathode 1" from side walls and 1%" from cell bottom
- Operating temperature 1,1 i10 C.
- Electrolyte weight 1,000 grams
- Cell feed Congo columbite concentrate Analysis, wt. pct.:
- a method for recovery of niobium and tantalum, in the form of phosphide, from crude oxide or mineral feed material comprising dissolving the feed material in a molten electrolyte comprising an alkali metal phosphate, an alkali metal halide and an alkali metal borate or boric oxide, electrolyzing the molten mixture at a potential of about 1.0 to 2.5 volts to selectively deposit niobium phosphide at the cathode, removing the deposited niobium phosphide from the cathode, and subsequently electrolyzing the molten mixture at a potential of about 3.0 to 5.0 volts to deposit tantalum phosphide at the cathode.
- electrolyte consists essentially of sodium pyrophosphate, sodium chloride, sodium fluoride and boric oxide.
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
NIOBIUM AND TANTALUM ARE RECOVERED AS PHOSPHIDES FROM A CRUDE OXIDE OR MINERAL FEED MATERIAL BY SELECTIVE ELECTRODEPOSITION FROM A FSED SALT BATH COMPRISING THE FEED MATERIAL, AN ALKALI METAL PHOSPHATE, AN ALKALI METAL HALIDE AND AN ALKALI METAL BORATE OR BORIC OXIDE, ELECTROLYSIS AT A POTENTIAL OF 2.5 VOLTS OR LESS RESULTS IN DEPOSITION OF NIOBIUM PHOSPHIDE ESSENTIALLY FREE OF TANTALUM, WITH SUBSEQUENT ELECTROLYSIS AT 4.0 VOLTS OR GREATER RESULTING IN DESPOSITION OF TANTALUM PHOSPHIDE.
Description
United States Patent 3,725,221 RECOVERY OF NIOBIUM AND TAN TALUM John M. Games, 1650 Rayburn Drive 89503; Kenji Uchida, 1341 Hillside Drive 89502; and Morton M. Wong, 2281 Riviera St. 89502, all of Reno, Nev. No Drawing. Filed Jan. 26, 1972, Ser. No. 221,092
Int. Cl. B01k 1/00 US. Cl. 204-61 Claims ABSTRACT OF THE DISCLOSURE Niobium and tantalum metals have excellent high temperature properties and are resistant to attack by liquid metals and acids. Both metals form important alloys with ferrous metals and other refractory metals, the alloys having numerous space, electronic and defense applications. In addition, the phosphides find utility as corrosion resistant coatings, semi-conductors and hard metal compounds.
Conventional procedures for recovery of pure niobium and tantalum from their minerals require a complex sequence of processing operations. This sequence involves alkali fusion to decompose the mineral concentrate, followed by hydrofluoric acid leaching. A11 intermediate impure niobium-tantalum oxide or fluoride is obtained, which is then purified by wet chemical methods to obtain a pure niobium-tantalum compound. Separation of niobium and tantalum is achieved by a liquid-liquid extraction technique with an SO-percent recovery of pure oxides of the two elements being obtained. The oxides are then reduced to metal by metallothermic or electrolytic techniques.
It has now been found, according to the process of the invention, that niobium and tantalum may be recovered from their minerals by means of a much simpler and more eflicient process in which the two metals are selectively electrolytically deposited as monophosphides from a fused salt bath comprising alkali metal phosphate, halide and borate or boric oxide. Selective electrodeposition is achieved by initial deposition of NbP at a potential of 2.5 volts or less, followed by deposition of TaP at a potential of 3.0 volts or greater.
The feed material in the process of the invention is essentially a mixed oxide of niobium and tantalum, but it may also contain oxides of other elements such as iron, manganese, sodium, titanium, silicon, etc., depending on the composition of the mineral from which it is derived. It may be derived from suitable minerals by the conventional alkali fusion and acid leaching described above, or it may consist of a concentrate obtained by bcneficiating a niobium and tantalum-containing mineral. Examples of such minerals are columbite, pyrochlor and euxenite. The preferred feed material consists of a columbite concentrate containing about 50 to 60 wt. percent Nb 0 5 to 25 wt. percent Ta O to wt. percent Fe O and 2 to 10' wt. percent MnO.
The feed material is initially dissolved in a molten electrolyte comprising (1) an alkali metal phosphate, (2) an alkali metal halide and (3) an alkali metal borate or boric oxide. Examples of suitable alkali metal phosphates are sodium pyrophosphate, sodium metaphosphate, potassium pyrophosphate, potassium metaphosphate, lithium pyrophosphate and lithium metaphosphate. Suitable alkali metal halides comprise sodium chloride, sodium fluoride, cryolite (Na AlF potassium chloride, potassium fluoride, potassium aluminum tetrafluoride (KAIF lithium chloride and lithium fluoride. A combination of sodium chloride and sodium fluoride has been found to give particularly good results. Suitable alkali metal borates include sodium tetraborate, potassium tetraborate and lithium tetraborate.
Optimum proportions of feed material and components of the electrolyte will vary considerably, depending on the specific materials employed, and are best determined experimentally. However, the following proportions, in percent by weight of the molten bath, including the feed, are generally satisfactory: feed material, 4 to 12 percent; alkali metal phosphate, 9 to 25 percent; alkali metal halides, 60 to percent; and alkali metal borate or boric oxide, 8 to 15 percent. It has also been found that further addition of cryolite and potassium carbonate to the electrolyte after deposition of NbP improve the subsequent recovery of TaP. Amounts of cryolite and potassium carbonate for this purpose are suitably about 15 to 20 weight percent and 2 to 5 weight percent, respectively.
The operating temperature, i.e., the temperature during deposition of the NbP and TaP, should be between about 900 and 1150 C., preferably about 1100" C. Niobium, in the form of dendritic crystals of niobium monophosphide, is first deposited at a potential of about 1.0 to 2.5 volts and a cathode current density of about 30 to 75 amp/dmF. The cathode is removed from the electrolyte and the NbP crystals are scraped off. The cathode is replaced and electrolysis continued at a potential of about 3.0 to 5.0 volts and a cathode current density of about to 200 amp/dm. to deposit tantatum, also in the form of phosphide. Time required for substantially complete deposition of each metal is about 1 to 2 hours.
The cell employed for the electrolysis is conventional and preferably consists of a graphite crucible serving as container and anode. The cathode is a centrally positioned graphite or refractory metal rod. The cell is desirably heated in an electric resistance furnace, but an oil or gas-fired furnace may also be used. A protective atmosphere is not required.
Niobium and tantalum metals may be readily recovered from their phosphides by means of conventional processes such as (1) dissolution in nitric or sulfuric acid to prepare oxides which are reduced to metal by metallothermic reactions or (2) chlorination at high temperatures to yield chlorides which are reduced to metal by metallothermic reactions.
The invention will be more specifically illustrated by the following examples.
EXAMPLE 1 Weight Mole Electrolyte composition percent percent (Nb, T9205 4 1 NmPzOy 21 6 B20; 11 11 NaCl 56 68 NaF. 9 14 1 50 wt. percent each 01 Nb O; and Tarot.
Cell potential, cycle A: 2.5 volts Cell potential, cycle B: 4.0 volts Cell current, cycle A: 40-70 amps Cell current, cycle B: 110-140 amps Addition between cycles A and B: 210 g. Na AlF and 30 g. K2C03 Duration of electrolysis and results are given in Table 1.
TABLE 1 Analysis of Recovery, Electrolysis Product product percent duration, weight, Cycle amp-hrs. gms. NbP TaP Nb Ta A 75 19.4 94.0 5.6 98 7 B 168 8.0 7.9 91.0 2 as Total 100 45 EXAMPLE 2 In this example, a columbite mineral concentrate was used as feed material. The following operating data and electrolyte composition were employed:
Cell configuration:
Anode: 3'' ID. x 7" high graphite crucible Cathode: 1" diameter graphite rod Electrode spacing: Cathode 1" from side walls and 1%" from cell bottom Operating temperature: 1,1 i10 C. Electrolyte weight: 1,000 grams Cell feed: Congo columbite concentrate Analysis, wt. pct.:
Nb O 52 T3205 F6203 MnO Weight Mole Electrolyte composition percent percent Cell potential, cycle A: 2.5 volts Cell potential, cycle B: 4.0 volts Cell current, cycle A: 55-70 ampercs Cell current, cycle '13: 120-130 amperes '4 Electrolysis duration, cycle A: 2 hours Electrolysis duration, cycle B: 1 hour Addition between cycles A and B: 200 g. Na AlF and 20 g. K 'CO Results are given in Table 2.
1. A method for recovery of niobium and tantalum, in the form of phosphide, from crude oxide or mineral feed material comprising dissolving the feed material in a molten electrolyte comprising an alkali metal phosphate, an alkali metal halide and an alkali metal borate or boric oxide, electrolyzing the molten mixture at a potential of about 1.0 to 2.5 volts to selectively deposit niobium phosphide at the cathode, removing the deposited niobium phosphide from the cathode, and subsequently electrolyzing the molten mixture at a potential of about 3.0 to 5.0 volts to deposit tantalum phosphide at the cathode.
2. The method of claim 1 in which the electrolyte consists essentially of sodium pyrophosphate, sodium chloride, sodium fluoride and boric oxide.
3. The method of claim 1 in which a mixture of cryolite and potassium carbonate are added to the molten electrolyte after deposition of the niobium phosphide and prior to deposition of the tantalum phosphide.
4. The method of claim 1 in which the niobium phosphide is deposited at a potential of about 2.5 volts.
5. The method of claim 1 in which the tantalum phosphide is deposited at a potential of about 4.0 volts.
References Cited UNITED STATES PATENTS 3,498,894 3/ 1970 Cuomo et al. 204-61 TUNG TA-HSUNG, Primary Examiner D. R. VALENTINE, Assistant Examiner
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22109272A | 1972-01-26 | 1972-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3725221A true US3725221A (en) | 1973-04-03 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US00221092A Expired - Lifetime US3725221A (en) | 1972-01-26 | 1972-01-26 | Recovery of niobium and tantalum |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3725221A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4637864A (en) * | 1986-03-28 | 1987-01-20 | The United States Of America As Represented By The Secretary Of The Navy | Electrochemical synthesis of ternary phosphides |
| US5009751A (en) * | 1988-01-12 | 1991-04-23 | Mitsubishi Nuclear Fuel Company, Ltd. | Process for separation of hafnium tetrachloride from zirconium tetrachloride |
-
1972
- 1972-01-26 US US00221092A patent/US3725221A/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4637864A (en) * | 1986-03-28 | 1987-01-20 | The United States Of America As Represented By The Secretary Of The Navy | Electrochemical synthesis of ternary phosphides |
| US5009751A (en) * | 1988-01-12 | 1991-04-23 | Mitsubishi Nuclear Fuel Company, Ltd. | Process for separation of hafnium tetrachloride from zirconium tetrachloride |
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