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WO2003104149A1 - Procede de recuperation d'oxyde de terre rare de residus liquides contenant un element de terre rare, et procede de production d'un oxyde de terre rare l'utilisant - Google Patents

Procede de recuperation d'oxyde de terre rare de residus liquides contenant un element de terre rare, et procede de production d'un oxyde de terre rare l'utilisant Download PDF

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Publication number
WO2003104149A1
WO2003104149A1 PCT/JP2003/007288 JP0307288W WO03104149A1 WO 2003104149 A1 WO2003104149 A1 WO 2003104149A1 JP 0307288 W JP0307288 W JP 0307288W WO 03104149 A1 WO03104149 A1 WO 03104149A1
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WIPO (PCT)
Prior art keywords
rare earth
earth element
abrasive
liquid
process according
Prior art date
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Ceased
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PCT/JP2003/007288
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English (en)
Inventor
Fumio Imai
Katsura Ito
Hiroshi Saegusa
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Resonac Holdings Corp
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Showa Denko KK
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Priority to AU2003238154A priority Critical patent/AU2003238154A1/en
Publication of WO2003104149A1 publication Critical patent/WO2003104149A1/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C22B7/007—Wet processes by acid leaching
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/20—Compounds containing only rare earth metals as the metal element
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1409—Abrasive particles per se
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B59/00—Obtaining rare earth metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This invention relates to a process for recovering rare earth oxides from a waste liquid containing rare earth elements. More particularly, it relates to a process for recovering rare earth oxides from an abrasive waste liquid containing rare earth elements, wherein the recovered rare earth oxides have a high quality such that they can be used as an abrasive for high-precision polishing.
  • a cerium-based abrasive is popularly used for polishing a glass material or a rock crystal material. More specifically, this abrasive is used for polishing a glass substrate for photodisc or magnetic disc, a glass plate for liquid crystal display (LCD) such as thin film transistor (TFT) LCD and twisted nematic (TN) LCD, a color filter for liquid crystal TV, a TV cathode-ray tube (CRT) , a spectacle lens, an optical lens, a glass plate LSI photomask, a wired plate glass, and a substrate for quartz oscillator.
  • LCD liquid crystal display
  • TFT thin film transistor
  • TN twisted nematic
  • TV TV cathode-ray tube
  • spectacle lens an optical lens
  • a glass plate LSI photomask a glass plate LSI photomask
  • wired plate glass a wired plate glass
  • a substrate for quartz oscillator a substrate for quartz oscillator.
  • rare earth element-containing abrasive an abrasive containing powdery oxide of cerium (Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd) or other rare earth elements.
  • the ore as a raw material of an abrasive containing rare earth elements is produced, for example, as bastnaesite or monazite in China, U.S.A. and other countries.
  • sulfuric acid is gradually added to and mixed with an ore in a rotary kiln and the ore is then dried;
  • the obtained solution is concentrated by a thickener and impurities such as BaS0 4 , CaS0 4 and Si0 2 to obtain R 2 ( S0 4 ) 3 , wherein R represents a rare earth element;
  • hydrochloric acid is added to the hydroxide of rare earth element to produce a chloride of rare earth element
  • ammonium hydrogencarbonate is added to the chloride of rare earth element to produce a rare earth carbonate
  • the rare earth chloride is baked to form a rare earth oxide .
  • the reserves of ore as a raw material for the rare earth element-containing abrasive are limited and in combination with recent increase of demand for the rare earth element-containing abrasive, the ore as a raw material is foreseen to run short. Therefore, it is eagerly desired to recover rare earth oxides from an abrasive waste liquid containing rare earth elements, for the reuse of rare earth oxides as an abrasive.
  • An abrasive particularly a cerium-rich abrasive, is prepared by mixing a rare earth oxide such as cerium oxide with water, adispersant, a surfa ⁇ tant and other ingredients to form a slurry, and is used for the polishing of glass, rock crystal or other materials.
  • a rare earth element -containing abrasive waste liquid produced upon polishing contains at least abrasive, water, dispersant, surfactant, ground powders such as glass powder, and polishing pad powder.
  • the rare earth element-containing abrasive waste liquid is different from a rare earth element-containing ore in many points in addition to the above-described difference, for example, these differ in the rare earth element content, the content ratio of each rare earth element, the kind of materials contained other than rare earth elements, and the content ratio of the materials. Therefore, it is difficult to treat these ore and abrasive waste liquid by the same method to obtain a rare earth oxide. Thus, it is very costly and of no practical utility to recover rare earth oxides having a high quality from an abrasive waste liquid, which rare earth oxides are capable of being reused as an abrasive for polishing with high precision.
  • JP-A Japanese Unexamined Patent Publication
  • a process for recovering rare earth hydroxides from an abrasive waste liquid wherein the abrasive waste liquid is diluted with sulfuric acid, oxalic acid is added to convert rare earth elements in the liquid to rare earth oxalates, the liquid is then neutralized with an alkali to covert the rare earth oxalates to rare earth hydroxides, followed by recovery thereof (for example, see JP-A 2000-87154) .
  • a method of recovering rare earth elements from an abrasive waste liquid containing the rare earth elements has been proposed, wherein ground glass powder or particles are dissolved with hydrofluoric acid to allow the rare earth element to be separated therefrom (for example, see JP- A Hll-319755) .
  • a method of recovering rare earth elements from an abrasive waste liquid containing the rare earth elements has also been proposed, wherein the abrasive waste liquid is subjected to a flocculation treatment and then to a solid-liquid separation (for example, see JP-AH10-280060) .
  • a primary object of the present invention is to provide a process for recovering rare earth oxides from a liquid containing rare earth elements , especially from an abrasive waste liquid produced upon polishing using a rare earth oxide abrasive, whereby rare earth oxides capable of being reused as an abrasive for polishing with high precision can be obtained in an industrially advantageous manner.
  • rare earth oxides reusable as an abrasive for polishing with high precision can be obtained in an industrially advantageous manner from an abrasive waste liquid containing rare earth elements , by adopting a process comprising a specific combination of steps, for example, comprising the following steps (1) through (6): (1) mixing and heating a liquid containing a rare earth element with an acid, to dissolve the rare earth element contained in the liquid; (2) removing insoluble matter from a rare earth element solution obtained in step (1); (3) incorporating a soluble carbonate salt or a soluble hydrogencarbonate salt , or an oxalic acid in the rare earth element solution obtained in step (2), to convert the rare earth element in the solution to a rare earth carbonate or a rare earth oxalate; (4) separating the rare earth carbonate or rare earth oxalate from a slurry of the rare earth carbonate or rare earth oxalate, obtained in step (3); (5) baking
  • a process for recovering a rare earth oxide from a liquid containing a rare earth element which comprises the following steps (1) through (6):
  • step (3) incorporating a soluble carbonate salt or a soluble hydrogencarbonate salt, or an oxalic acid in the rare earth element solution obtained in step (2) , to convert the rare earth element in the solution to a rare earth carbonate or a rare earth oxalate;
  • step (1) the liquid containing a rare earth element and the acid are mixed and heated together with hydrogen peroxide, to dissolve the rare earth element contained in the liquid.
  • step (1) is hydrochloric acid.
  • step (1) is nitric acid.
  • step (1) a mixed liquid of the liquid containing a rare earth element with the acid is heated under reflux, and further concentrated whereby insoluble solid matter contained in the mixed liquid is allowed to float on the liquid surface.
  • step (2) the insoluble matter is removed by filtration.
  • step (3) pH value of the rare earth element solution is adjusted to a value in the range of 1 to 7, and then, the soluble carbonate salt or the soluble hydrogencarbonate salt, or oxalic acid is incorporated in the rare earth element solution to convert the rare earth element in the solution to a rare earth carbonate or a rare earth oxalate.
  • step (3) is an alkali metal salt, an alkaline earth metal salt or an ammonium salt.
  • step (4) the rare earth carbonate or the rare earth oxalate is separated by filtration.
  • a process for recovering a rare earth hydroxide from a liquid containing a rare earth element which comprises the following steps (i) through (vi) :
  • step (iv) incorporating sodium sulfate in the rare earth sulfate solution obtained in step (iii) , to produce a double salt of the rare earth element; and then, separating the double salt from the solution;
  • step (iii) the insoluble matter is removed by filtration.
  • step (v) the adjustment of pH value of the aqueous double salt suspension to a value of 8 to 13 is carried out by adding an alkali, aqueous ammonia or ammonia gas.
  • step (i) aluminum sulfate, poly- aluminum chloride or a polymeric flocculant is added to the liquid containing a rare earth element to allow a solid content containing the rare earth element to precipitate; and then the thus -produced precipitate is separated, followed by mixing the thus-separated precipitate with sulfuric acid.
  • a process for recovering a rare earth oxide which comprises recovering a rare earth hydroxide from a liquid containing a rare earth element by the process as described in any one of preceding items 13 to 17; and then, baking the recovered rare earth hydroxide to convert to a rare earth oxide, followed by recovering the thus-obtained rare earth oxide .
  • a process for recovering a rare earth oxide which comprises recovering a rare earth hydroxide from a liquid containing a rare earth element by the process as described in any one of preceding items 13 to 17; suspending the recovered rare earth hydroxide in water; and then, recovering a rare earth oxide from the thus-obtained aqueous suspension of rare earth hydroxide by the process as described in any one of preceding items 1 to 12.
  • a process for producing an abrasive containing a rare earth oxide which comprises recovering a rare earth oxide by the process as described in any one of the preceding items 1 to 20; and fabricating the recovered rare earth oxide into an abrasive.
  • a process for reusing an abrasive containing a rare earth oxide for polishing which comprises recovering a rare earth oxide from a waste liquid produced upon polishing using an abrasive, by the process as described in any one of preceding items 1 to 20; and fabricating the recovered rare earth oxide into an abrasive.
  • a method for polishing a substrate by an abrasive containing a rare earth oxide wherein said abrasive is made from a rare earth oxide, which is recovered from a waste liquid produced upon polishing using an abrasive, by the process as described in any one of preceding items 1 to 20.
  • the recovering process of the present invention comprises the following steps (1) through (6).
  • Step (1) step for dissolving rare earth element in waste liquid to prepare solution of rare earth element
  • a reaction vessel is charged with an abrasive waste liquid containing rare earth elements, and an acid or a combination of an acid with hydrogen peroxide is added to the abrasive waste liquid, and the mixture is heated.
  • the acid as used herein is not particularly limited provided that it is capable of dissolving the rare earth elements contained in the abrasive waste liquid.
  • the acid there can be mentioned hydrochloric acid, nitric acid and sulfuric acid. Of these, hydrochloric acid and nitric acid are more preferable. Hydrochloric acid is especially preferable.
  • the heating is carried out to an extent such that at least rare earth elements (which are usually in the form of rare earth oxide) contained in the waste liquid are thoroughly dissolved.
  • the heating is preferably carried out at a temperature in the range of 90°C to 120°C. More preferably, the heating is carried out at a temperature in the range of 90°C to 120°C for a period of 5 hours to 72 hours while being stirred under reflux, and then, the mixture is concentrated.
  • the concentration of hydrochloric acid used is not particularly limited, but is usually in the range of 15% to 45% by mass, preferably 20% to 35% by mass.
  • hydrochloric acid with a concentration of 35% by mass can preferably be used.
  • the amount of hydrochloric acid is preferably in the range of 200 parts to 500 parts by mass, as hydrochloric acid with a concentration of 35% by mass, based on 100 parts by mass of the solid content in the abrasive waste liquid.
  • the concentration of nitric acid used also is not particularly limited, but is preferably in the range of 62% to 98% by mass.
  • the amount of nitric acid is preferably in the range of 112 parts to 177 parts by mass based on 100 parts by mass of the solid content in the abrasive waste liquid.
  • a reducing substance such as hydrogen peroxide is preferably used in combination with the acid for suppressing oxidation of rare earth element and lowering the valency of rare earth nitrate or rare earth sulfate to a desired extent for enhancing the solubility of these rare earth salts.
  • the addition of hydrogen peroxide is advantageous also in that organic substances contained in the abrasive waste liquid are decomposed and easily removed.
  • the amount of hydrogen peroxide is preferably in the range of 9 parts to 27 parts by mass based on 100 parts by mass of nitric acid. Even when hydrochloric acid is used, hydrogen peroxide may be used so that organic substances contained in the abrasive waste liquid are decomposed and easily removed.
  • a rare earth oxide contained in the liquid is dissolved to form an aqueous acidic solution containing a rare earth element which is in the form of, for example, a rare earth chloride or a rare earth nitrate.
  • the glass powder or particles remaining in the abrasive waste liquid is converted to silica sol, which is gradually gelled into silica gel.
  • the silica gel, powdery or finely divided debris of polishing pad, and other undissolved matter can be separated by filtration of the heated mixture of the abrasive waste liquid with an acid. But, the undissolved matter contains part of the aqueous acidic solution entrapped therein which is not easily separated by filtration. Therefore, the heating is followed by concentration as described below.
  • the aqueous acidic solution containing rare earth elements When the aqueous acidic solution containing rare earth elements is heated and further concentrated, the concentration (thus, specific gravity) of the solution is enhanced, and hence, relative weight of silica gel is reduced with the results that the silica gel is floated together with the undissolved matter on the surface of liquid. Therefore, the aqueous acidic solution can easily be separated in the succeeding separation step (2).
  • the effective inner surface area may be increased, for example, by providing partition plates within the reaction vessel.
  • the temperarture of the inner wall of reaction vessel and the partition plates is preferably maintained at a temperature higher than the liquid temperature so that the shrinking of the silica gel and undissolved matter easily occurs.
  • the aqueous acidic solution is concentrated until its volume is reduced to about 25% to 75%, more preferably about 40% to 60%, of the initial volume before heating.
  • the rare earth-containing aqueous acidic solution can be separated from the silica gel and undissolved matter with an enhanced recovery ratio in the succeeding separation step (2).
  • bubbles are preferably formed. More preferably fine and uniform bubbles are formed.
  • fine and uniform bubbles rise vigorously from the boiling stones to the liquid surface in accompanied by the silica gel and undissolved matter. The formation of such bubbles enhances the separation of the aqueous acidic solution containing rare earth elements, from the silica gel and undissolved matter in step (2).
  • the boiling stone can be selected from those composed of material insoluble in the heated aqueous acidic solution, which includes, for example, ceramics such as glass, and a plastic material.
  • the boiling stone has a configuration such that small pro ections are formed on the surface thereof for promoting formation of a multiplicity of fine bubbles .
  • Step (2) step for separating rare earth element- containing aqueous acidic solution
  • the rare earth element-containing aqueous acidic solution is taken from the reaction vessel and subjected to separation for removing the silica gel and undissolved matter such as polishing pad debris.
  • separation No limitation is imposed to a separating procedure, but, filtration or centrifugal separation can be adopted. Filtration is preferable because of ease in operation.
  • a rare earth element-containing aqueous acidic solution from which silica gel and undissolved matter have been removed is obtained in step (2).
  • Step (3) step for forming rare earth carbonate or rare earth oxalate from rare earth element-containing aqueous acidic solution
  • a soluble carbonate salt or a soluble hydrogencarbonate salt, or oxalic acid is added to convert the rare earth elements in the solution to rare earth carbonates or rare earth oxalates.
  • the soluble carbonate salt and the soluble hydrogencarbonate salt include those which are soluble in the aqueous acidic solution, and are preferably selected from alkali metal salts, alkaline earth metal salts and ammonium salts.
  • alkali metal sodium, potassium and lithium are mentioned. Of these, sodium and potassium are preferable.
  • alkaline earth metal calcium, strontium and barium are mentioned.
  • carbonate salts and hydrogencarbonate salts of alkali metals, alkaline earth metals and ammonium sodium hydrogencarbonate and potassium hydrogencarbonate are preferable, and ammonium hydrogencarbonate is especially preferable .
  • the aqueous acidic solution containing rare earth elements can be diluted with water to control size of the resulting particles.
  • the pH value of the aqueous acidic solution containing rare earth elements is adjusted to 1 to 7, more preferably 1 to 3, and then, ammonium hydrogencarbonate or oxalic acid is added.
  • the pH value can be adjusted by adding an alkali such as aqueous ammonia, sodium hydroxide, potassium hydroxide or calcium hydroxide.
  • aqueous ammonia is preferable because it can be easily removed.
  • the amount of alkali is not particularly limited provided that the desired pH value is obtained. For example , in the case when aqueous ammonia is used, its amount is usually in the range of 5% to 28% by mass.
  • the carbonate salt or hydrogencarbonate salt of an alkali metal, an alkaline earth metal or ammonium can be added in the form of either solid or an aqueous solution, but an aqueous solution is preferable.
  • the concentration of these carbonate salt and hydrogencarbonate salt, and oxalic acid is not particularly limited and can be appropriately determined usually in the range of 5% to 97% by mass.
  • the amounts of the carbonate salt and hydrogencarbonate salt of an alkali metal, alkaline earth metal and ammonium, and oxalic acid are preferably in the range of 193 parts to 540 parts by mass based on 100 parts by weight of rare earth element.
  • an aqueous slurry of rare earth carbonate or an aqueous slurry of rare earth oxalate is formed from the aqueous acidic solution containing rare earth elements.
  • Step (4) (step for forming separating rare earth carbonate or rare earth oxalate)
  • An aqueous slurry of rare earth carbonate or an aqueous slurry of rare earth oxalate, formed in step (3), is subjected to separation, for example, by filtration, whereby the rare earth carbonate or rare earth oxalate is separated. If desired, the separated rare earth carbonate or rare earth oxalate is washed with water and again filtered.
  • Step (5) step for baking separated rare earth carbonate or rare earth oxalate
  • the separated rare earth carbonate or rare earth oxalate is baked into rare earth oxide.
  • the baking is carried out by maintaining the rare earth carbonate or rare earth oxalate in the air atmosphere at a temperature of 600 to 1,200°C, preferably 800 to 1,100°C for 0.5 to 3 hours, preferably 0.5 to 2 hours.
  • the baking apparatus used may be conventional baking furnaces such as a cube type furnace, a rotary furnace and a tunnel furnace.
  • Step (6) step for recovering rare earth oxides
  • the rare earth oxide obtained by baking is recovered, pulverized and classified depending upon the particle diameter and particle size distribution.
  • the rare earth oxide is reused as an abrasive for precision polishing.
  • the particle diameter may be either the same as or different from that of the abrasive as originally used.
  • the average particle diameter can be in the range of 0.1 to 2 m .
  • a pretreatment process can be carried out prior to the above-described recovering process. More specifically, a pretreatment process comprising the following steps (i) through (vi) can be carried out to obtain an aqueous slurry containing rare earth hydroxide, and subsequently, the above-described recovering process comprising the steps (1) through (6) can be carried out wherein, in step (1), the aqueous slurry containing rare earth hydroxide is used as the starting liquid containing a rare earth element.
  • the pretreatment process comprises the following steps (i) through (vi) :
  • step (iv) incorporating sodium sulfate in the rare earth sulfate solution obtained in step (iii) , to produce a double salt of the rare earth element; and then, separating the double salt from the solution;
  • Step (i) (step for converting rare earth element in waste liquid to rare earth sulfate)
  • Sulfuric acid is added to an abrasive waste liquid containing rare earth elements, and the mixture is heated.
  • the concentration of sulfuric acid is not particularly limited.
  • concentrated sulfuric acid having a concentration of 95% to 99% by mass is used.
  • the amount of sulfuric acid is preferably in the range of 80 parts to 450 parts by mass based on 100 parts by mass of the solid content in the abrasive waste liquid.
  • the heating is carried out usually at a temperature of 90 to 120°C for 10 minutes to 1 hour.
  • Hydrogen peroxide can be added to the mixture of the abrasive waste liquid and sulfuric acid to decompose organic matter such as polishing pad debris so that free carbon resulting from the decomposition can be removed as carbon dioxide gas. Then, the hydrogen peroxide-added mixed liquid is re-heated at a temperature of 200 to 600°C for 1 minute to 1 hour thereby converting rare earth element in the liquid to a rare earth sulfate.
  • the rare earth sulfate is separated from the rare earth sulfate-containing liquid, for example, by filtration or decantation.
  • Step (ii) step for adding water to rare earth sulfate to dissolve rare earth sulfate
  • the amount of water added is usually in the range of 525 parts to 1,900 parts by mass based on 100 parts by mass of the solid content of rare earth sulfate.
  • Step (ill) step for removing insoluble matter from rare earth sulfate-containing solution
  • the rare earth sulfate-containing solution is subjected to separation, for example, by filtration to remove glass particles and polishing pad debris and other insoluble matter from the solution.
  • Step ( iv) step for adding sodium sulfate to rare earth sulfate-containing solution to form double salt of rare earth element
  • step (iii) After the rare earth sulfate-containing solution is subjected to separation for removing insoluble matter therefrom in step (iii), sodium sulfate is added to the solution (e.g. , filtrate ) to form a double salt of rare earth element .
  • Sodium sulfate can be added either as solid or an aqueous solution. That is, solid sodium sulfate or its aqueous solution with a concentration of 5% to 100% by mass is added in an amount of 1.25 parts to 95 parts by mass, preferably 12.5 parts to 80 parts by mass , based on 100 parts by mass of the rare earth sulfate-containing solution .
  • a slurry of a double salt of rare earth element for example,
  • the slurry is subjected to separation, for example, by filtration, to thereby obtain the double salt of rare earth element.
  • Step (v) step for adding alkali to double salt of rare earth element to convert double salt to rare earth hydroxide
  • Step (iv) Water is added to the double salt obtained in step (iv), and then the pH value of the double salt solution is adjusted to a value in the range of 8 to 13, preferably 12 to 13, whereby the double salt is converted to a rare earth hydroxide.
  • the pH adjustment is effected by adding an alkali, aqueous ammonia or ammonia gas.
  • a rare earth hydroxide formed by the pH adjustment is highly soluble and thus it can be recovered at a high yield in the succeeding step (vi) .
  • the alkali includes, for example, sodium hydroxide and potassium hydroxide.
  • the alkali may be used either as solid or as an aqueous solution.
  • an aqueous alkali solution having a concentration of 10% to 95% by mass is added in an amount of 33 parts to 322 parts by mass based on 100 parts by mass of the double salt.
  • the amount of aqueous ammonia or ammonia gas is usually in the range of 3 parts to 30 parts by mass, as ammonia (NH 3 ), based on 100 parts by mass of the double salt.
  • Step (vi) step of recovering rare earth hydroxide
  • the rare earth hydroxide-containing solution obtained in step (v) is subje ⁇ ted to separation, for example, by filtration, whereby rare earth hydroxide is recovered.
  • the recovered rare earth hydroxide is suspended in water to prepare a slurry.
  • the thus-obtained rare earth hydroxide-containing slurry can be subjected to the above-mentioned process comprising steps (1) through (6) wherein, in step (1), the rare earth hydroxide-containing slurry is used as the starting liquid containing a rare earth element.
  • the rare earth hydroxide recovered in step (vi) can be baked at a temperature of 600 to 1,400°C in the air atmosphere to obtain rare earth oxide.
  • This rare earth oxide can be re-used as an abrasive, but its quality is somewhat inferior to the rare earth oxide obtained by further treating the rare earth hydroxide by the process comprising steps (1) through (6).
  • step (i) prior to mixing the liquid containing a rare earth element with sulfuric acid, aluminum sulfate, poly-aluminum chloride or a polymeric flo ⁇ culant can be added to the liquid containing a rare earth element to allow the solid content containing the rare earth element to precipitate; and then the thus-produced precipitate is separated, followed by mixing the thus-separated precipitate with sulfuric acid.
  • the aluminum sulfate and poly-aluminum chloride can be used either as solid or an aqueous solution.
  • the polymeric flo ⁇ culant used is commercially available and includes, for example, Kurifloc TM (Kurita Water Industries Ltd.) and Orfloc (Organo Corporation).
  • the rare earth oxides recovered by the process comprising the steps (1) through (6) are pulverized and classified into particles having desired particle size and particle size distribution, and re-used as an abrasive used for polishing with high precision.
  • Example 1 Recovery of rare earth oxides from abrasive waste liquid
  • Rare earth oxides were recovered by the following procedures from an abrasive waste liquid having a solid composition shown in Table 1 , which liquid was produced when a glass disc was polished.
  • the beaker was again heated at 300°C to produce rare earth sulfate as a yellow solid.
  • This rare earth sulfate was dissolved in cold water at 5°C to obtain a brown transparent acidic aqueous sulfate solution.
  • This acidic aqueous sulfate solution containing rare earth sulfate was filtered to remove undissolved matter such as glass debris. By this treatment, carbide and the like were also removed as undissolved matter.
  • the recovered solid and 1,500 g of pure water were mixed together to form a slurry, the slurry was heated to
  • the composition of the recovered material obtained as rare earth oxide is shown in Table 1.
  • Powdery rare earth oxides were recovered by the following procedures from an abrasive waste liquid having a solid composition shown in Table 1, which liquid was produced when a glass filter was polished.
  • the obtained yellow solid (rare earth sulfate) was placed in a mortar and cracked with a pestle. Separately, 1 liter of cold water was charged in a beaker surrounded by ice water, and stirred. To this ice water, the cracked material obtained above was gradually added and mixed to obtain an aqueous acidic sulfate solution (brown transparent solution) containing rare earth sulfate. This aqueous acidic sulfate solution containing rare earth sulfate was filtered using a filter paper (No. 5C, available from Toyo Roshi Kaisha , Ltd. ) and the filtrate was recovered .
  • a filter paper No. 5C, available from Toyo Roshi Kaisha , Ltd.
  • This solution was filtered through a filter paper (No. 5C, available from Toyo Roshi Kaisha, Ltd. ) and the filtrate was recovered in a beaker. While the recovered filtrate was stirred, aqueous ammonia having a concentration of 5% by mass was added dropwise to adjust the pH to 1 to 2. To this solution, 833 g of an aqueous ammonium hydrogencarbonate solution having a concentration of 20% by mass was added and stirred to give a rare earth carbonate slurry.
  • the obtained rare earth carbonate slurry was filtered through a filter paper (No. 5C, available from Toyo Roshi Kaisha, Ltd. ) and about 197 g of a solid content was recovered. To the recovered solid content, 1.5 liter of pure water was added, and stirred. Then, the resulting solution was filtered through a filter paper (No. 5C, available from Toyo Roshi Kaisha, Ltd.), and the solid content was recovered. This operation was repeated until a neutral slurry having a pH value of 6 to 8 was obtained.
  • the recovered solid content was baked at 1,000°C for 1 hour in the air atmosphere to obtain about 95 g of rare earth oxides .
  • the composition of the recovered material obtained as rare earth oxide is shown in Table 1.
  • Example 3 (Recovery of rare earth oxides from abrasive waste liquid) Rare earth oxides were recovered by the following procedures from an abrasive waste liquid having a solid composition shown in Table 1, which liquid was produced when a glass substrate for hard disc was polished.
  • a abrasive waste liquid having a solid content of 100 g and 250 g of aqueous hydrochloric acid having a concentration of 35% by mass were placed in a flask provided with a water-cooling tube.
  • the content was heated and maintained at a temperature of 103°C.
  • the vapor emitted by heating was cooled by the water-cooling tube, and returned to the flask so that the liquid surface is not lowered.
  • the abrasive waste liquid became a mixed liquid composed of a green aqueous acidic solution containing rare earth chloride, a white silica gel, and undissolved matter such as polishing pad debris.
  • the water-cooling tube was removed from the flask, and the mixed liquid was heated and concentrated to about a half in volume. By the heating, the silica gel and undissolved matter were floated on the liquid surface. Thereafter, the concentrated mixed liquid was taken from the flask, and filtered through a filter paper (No. 5C, available from Advantec Toyo Kaisha, Ltd. ) , whereby undissolved matter was separated and removed from the rare earth chloride-containing aqueous acidic solution.
  • a filter paper No. 5C, available from Advantec Toyo Kaisha, Ltd.
  • the heating and concentration By the heating and concentration, most of the silica gel was removed from the rare earth chloride-containing aqueous acidic solution, and hence, as compared with the case where the heating and concentration were not carried out, the time required for filtration using a filter paper was drastically reduced from about 1 hour to about 10 minutes . Further, a rare earth element-containing aqueous acidic solution entrapped in the silica gel was removed by the heating and concentration, and hence, the yield of the rare earth chloride-containing aqueous acidic solution was increased from 82% to 98%, as expressed by the amount of final rare earth oxides, as compared with the case where the heating and concentration were not carried out.
  • hydrochloric acid can be re-used as a raw material.
  • the above-mentioned rare earth chloride-containing aqueous acidic solution recovered by filtration was diluted with water into a volume of 1 liter .
  • 1,653 g of an aqueous ammonium hydrogencarbonate solution having a concentration of 10% by mass was added, and the mixture was stirred to give a white precipitate of rare earth carbonate .
  • the aqueous solution containing the rare earth carbonate precipitate was filtered through a filter paper (No. 5C, available from Advantec Toyo Kaisha, Ltd.), and the thus-separated precipitate was washed with water.
  • the obtained precipitate was placed in a porcelain container and baked at 1,000°C for 1 hour in the air atmosphere to obtain 98 g of rare earth oxides.
  • composition of the recovered material obtained as rare earth oxides is shown in Table 1.
  • Rare earth oxides were recovered by the following procedures from an abrasive waste liquid having a solid composition shown in Table 1, which liquid was produced when a glass substrate for liquid crystal display (LCD) was polished.
  • a abrasive waste liquid having a solid content of 100 g and 250 g of aqueous hydrochloric acid having a concentration of 35% by mass were placed in a flask provided with a water-cooling tube.
  • the content was heated and maintained at a temperature of 103°C.
  • the abrasive waste liquid became a mixed liquid composed of a green aqueous acidic solution containing rare earth chloride, a white silica gel, and undissolved matter such as polishing pad debris.
  • the water-cooling tube was removed from the flask.
  • a boiling stone was placed in the mixed liquid, and the mixed liquid was heated and concentrated to about a half in volume .
  • fine and uniform bubbles were formed from the boiling stone and floated on the liquid surface, in accompanied by the silica gel and undissolved matter.
  • the silica gel and undissolved matter were transferred to the inner wall of flask, and deposited on the inner wall by the lowering of the liquid surface due to evaporation.
  • the silica gel deposited on the inner wall was further heated by the hot inner wall, and hence, was shrunk in volume whereby the rare earth chloride-containing aqueous acidic solution entrapped in the silica gel was released therefrom.
  • the yield of the rare earth chloride-containing aqueous acidic solution was 73%, as expressed by the amount of final rare earth oxides.
  • the yield of the rare earth chloride-containing aqueous acidic solution was increased to 95% by the heating.
  • the concentrated mixed liquid was filtered through a filter paper (No. 5C, available from Advantec Toyo Kaisha, Ltd. ) , whereby undissolved matter was separated and removed from the rare earth chloride- containing aqueous acidic solution.
  • a filter paper No. 5C, available from Advantec Toyo Kaisha, Ltd.
  • the above-mentioned rare earth chloride-containing aqueous acidic solution was diluted with water into a volume of 2 liters. To this solution, 450 g of an aqueous oxalic acid solution having a concentration of 10% by mass was added, and the mixture was stirred to give a white precipitate of rare earth carbonate.
  • the aqueous solution containing the rare earth carbonate precipitate was filtered through a filter paper (No. 5C, available from Advantec Toyo Kaisha, Ltd.), and the thus-separated precipitate was washed with water.
  • the thus-obtained precipitate was placed in a porcelain container and baked at 1,000°C for 1 hour in the air atmosphere to obtain 95 g of rare earth oxides.
  • composition of the recovered material obtained as rare earth oxides is shown in Table 1.
  • Example 3 The procedures for recovering rare earth oxides described in Example 3 were repeated wherein the rare earth chloride-containing aqueous acidic solution was treated with an aqueous sodium hydrogencarbonate solution instead of an aqueous ammonium hydrogencarbonate solution as follows .
  • the rare earth chloride-containing aqueous acidic solution prepared in the same manner as in Example 3, was diluted with water into a volume of 1 liter. To this solution, 1,098 g of an aqueous sodium hydrogencarbonate solution having a concentration of 10% by mass was added, and the mixture was stirred to give a white precipitate of rare earth carbonate.
  • the aqueous solution containing the rare earth carbonate precipitate was filtered through a filter paper (No. 5C, available from Advantec Toyo Kaisha, Ltd.), and the thus-separated precipitate was washed with water.
  • the obtained precipitate was placed in a porcelain container and baked at 1,000°C for 1 hour in the air atmosphere to obtain 92 g of rare earth oxides.
  • Example 6 Re-use of recovered rare earth oxide abrasive
  • Example 5 Using the material obtained as rare earth oxides in Example 5, an abrasive was made and its polishing performance was evaluated as follows.
  • a fraction of slurry containing coarse particles and a fraction of slurry containing fine particles were obtained each in a small amount by the classification.
  • the former slurry fraction was again subjected to wet grinding, and the latter slurry fraction was mixed with an abrasive waste liquid for re-use as an abrasive.
  • the separable flask was fitted with a three-necked separable flask cover provided with a water-cooling tube, a rod thermometer and a two-way cock, and then, placed in a mantle heater to be thereby heated. The vapor emitted was condensed in the water-cooling tube and returned to the separable flask.
  • Raw material Solid content in abrasive waste liquid used
  • Example 3 an abrasive in Comparative Example 1 in Table 1 was used for polishing a glass substrate for hard disc to produce an abrasive waste liquid, from which rare earth oxide was recovered in Example 3.
  • Example 5 Using each of the abrasives prepared in Example 5 and Example 6, and the abrasive used for polishing a glass substrate for hard disc in Example 3, an abrasive slurry was prepared by the same procedures as described in Example 6, paragraphs (i) and (ii).
  • Polishing of a glass substrate was conducted by using the abrasive slurry.
  • a four-way type double side polishing machine ( 5B Type available from Fujikoshi Machinery Corp. ) , and a suede-type polishing pad (Politex DG, available from Rodel, Inc.) were used.
  • the feed rate of slurry was 60 ml/min
  • the revolution speed of under surface plate was 90 rpm
  • the polishing pressure was 75 g/cm 2
  • the polishing time was 10 minutes.
  • the glass substrate to be polished was an aluminosili ⁇ ate-based glass substrate for magnetic disc having a diameter of 2.5 inches.
  • the glass substrate was pre-polished by a commercially available cerium oxide-based abrasive ( " SHOROX H-l” available from Tohoku Kinzoku Kagaku K.K.).
  • the surface roughness Ra of the pre-polished substrate was 9 angstrom.
  • the polished glass substrate was taken from the polishing apparatus, and subjected to ultrasonic washing with pure water .
  • the washed glass substrate was dried and then the following characteristics were evaluated. The evaluation results are shown in Table 2.
  • the rate of removal of a glass substrate was determined by the change in mass as measured before and after the polishing.
  • a polished surface of the glass substrate was observed by a differential difference microscope.
  • the state of adhesion, and occurrence of scratches and pits were examined.
  • the examination results of scratches were expressed by the number of scratches as observed on the surface.
  • the surface defect was expressed according to the following three ratings .
  • rare earth oxides of high purity which is capable of being re-used as an abrasive for precision polishing can be easily recovered with enhanced efficiency.
  • an abrasive made of the recovered rare earth oxides is similar to that made initially from an ore containing rare earth elements, for example, cerium (Ce) , lanthanum (La) , praseodymium (Pr) and neodymium (Nd) .
  • rare earth elements for example, cerium (Ce) , lanthanum (La) , praseodymium (Pr) and neodymium (Nd) .
  • the abrasive is used for polishing, for example, a glass substrate for photodisc or magnetic disc, a glass plate for liquid crystal such as thin film transistor (TFT) LCD and twisted nematic (TN) LCD, a color filter for liquid crystal TV, a TV cathode-ray tube (CRT), a spectacle lens , an optical lens, a glass plate LSI photomask, a wired plate glass, a substrate for quartz oscillator, and the like.
  • TFT thin film transistor
  • TN twisted nematic
  • TV TV cathode-ray tube
  • spectacle lens an optical lens
  • a glass plate LSI photomask a wired plate glass
  • a substrate for quartz oscillator and the like.

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Abstract

L'invention concerne des oxydes de terre rare pouvant être réutilisés comme abrasifs, que l'on récupère de résidus liquides abrasifs suivant un procédé qui consiste (1) à mélanger et chauffer le résidu liquide contenant des éléments de terre rare avec un acide, pour dissoudre les éléments de terre rare que ledit liquide renferme; (2) à débarrasser la solution d'éléments de terre rare des matières insolubles; (3) à incorporer un sel de carbonate soluble ou un sel d'hydrogène carbonate soluble, ou un acide oxalique dans la solution d'éléments de terre rare, pour transformer lesdits éléments en carbonates ou en oxalates de terre rare; (4) à séparer les carbonates ou les oxalates de terre rare d'une suspension épaisse des carbonates ou des oxalates de terre rare; (5) à cuire le carbonate ou l'oxalate de terre rare ainsi séparé de façon à produire des oxydes de terre rare; et (6) à récupérer les oxydes de terre rare.
PCT/JP2003/007288 2002-06-07 2003-06-09 Procede de recuperation d'oxyde de terre rare de residus liquides contenant un element de terre rare, et procede de production d'un oxyde de terre rare l'utilisant Ceased WO2003104149A1 (fr)

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EP2444507A1 (fr) * 2010-10-20 2012-04-25 Montanuniversität Leoben Récupération de métaux de terres rares à partir de déchets par lessivage dans un acide non oxydant et par précipitation avec des sulfates
CN102530971A (zh) * 2011-12-31 2012-07-04 云南云天化国际化工股份有限公司 含氟硅胶的洗涤方法
CN102703682A (zh) * 2012-06-29 2012-10-03 广州有色金属研究院 一种稀有金属矿综合回收的方法
CN102703697A (zh) * 2012-06-29 2012-10-03 广州有色金属研究院 一种稀土-铌-铁共生矿的回收方法
WO2013090817A1 (fr) * 2011-12-15 2013-06-20 Reenewal Corporation Récupération de terres rares à partir d'un luminophore
CN103570158A (zh) * 2013-11-06 2014-02-12 中国地质大学（武汉） 一种从稀土生产废水中回收稀土且氨氮达标排放的方法
CN104357670A (zh) * 2014-11-04 2015-02-18 江西理工大学 一种稀土草酸废水中和渣综合回收利用的方法
WO2015095303A1 (fr) * 2013-12-20 2015-06-25 General Electric Company Systèmes et procédés destinés à récupérer des constituants de terres rares à partir de revêtements de barrières environnementales
JP2015123385A (ja) * 2013-12-25 2015-07-06 太平洋セメント株式会社 焼成物及びその製造方法
CN105200250A (zh) * 2015-09-30 2015-12-30 中铝广西国盛稀土开发有限公司 一种从草酸沉淀稀土母液中回收稀土元素的方法
CN107162120A (zh) * 2017-06-27 2017-09-15 包头稀土研究院 碳酸稀土沉淀废水的净化利用方法
WO2018022129A1 (fr) * 2016-07-27 2018-02-01 Iowa State University Research Foundation, Inc. Séparation d'oxalates de métaux des terres rares
CN109534472A (zh) * 2019-01-24 2019-03-29 湖南科技大学 一种稀土抛光粉废料的回收和再利用方法
US10533239B2 (en) 2016-11-01 2020-01-14 Battelle Energy Alliance, Llc Methods of recovering rare earth elements from a material
US10570480B2 (en) 2015-03-24 2020-02-25 Sumitomo Metal Mining Co., Ltd. Method for recovering scandium
WO2020181381A1 (fr) * 2019-03-12 2020-09-17 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of Natural Resources Canada Procédé et système de récupération d'éléments des terres rares
CN112505007A (zh) * 2020-11-09 2021-03-16 安徽大学 利用氧化石墨烯同时富集和检测稀土元素的方法
CN115010165A (zh) * 2022-05-20 2022-09-06 全南县新资源稀土有限责任公司 一种稀土碳酸盐的制备方法、一种稀土氧化物的制备方法
CN115094238A (zh) * 2022-05-09 2022-09-23 中南大学 一种从硫化锌基荧光粉中回收稀土元素的装置和方法
US20230010128A1 (en) * 2021-07-09 2023-01-12 Anita See Method of collecting rare earth elements

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Cited By (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2444507A1 (fr) * 2010-10-20 2012-04-25 Montanuniversität Leoben Récupération de métaux de terres rares à partir de déchets par lessivage dans un acide non oxydant et par précipitation avec des sulfates
US8821817B2 (en) 2011-12-15 2014-09-02 Reenewal Corporation Rare earth recovery from phosphor
WO2013090817A1 (fr) * 2011-12-15 2013-06-20 Reenewal Corporation Récupération de terres rares à partir d'un luminophore
US8524176B2 (en) 2011-12-15 2013-09-03 Reenewal Corporation Rare earth recovery from phosphor
CN102530971A (zh) * 2011-12-31 2012-07-04 云南云天化国际化工股份有限公司 含氟硅胶的洗涤方法
CN102703682A (zh) * 2012-06-29 2012-10-03 广州有色金属研究院 一种稀有金属矿综合回收的方法
CN102703697A (zh) * 2012-06-29 2012-10-03 广州有色金属研究院 一种稀土-铌-铁共生矿的回收方法
CN102703697B (zh) * 2012-06-29 2014-01-01 广州有色金属研究院 一种稀土-铌-铁共生矿的回收方法
CN102703682B (zh) * 2012-06-29 2014-01-01 广州有色金属研究院 一种稀有金属矿综合回收的方法
CN103570158A (zh) * 2013-11-06 2014-02-12 中国地质大学（武汉） 一种从稀土生产废水中回收稀土且氨氮达标排放的方法
CN103570158B (zh) * 2013-11-06 2015-10-14 中国地质大学（武汉） 一种从稀土生产废水中回收稀土且氨氮达标排放的方法
WO2015095303A1 (fr) * 2013-12-20 2015-06-25 General Electric Company Systèmes et procédés destinés à récupérer des constituants de terres rares à partir de revêtements de barrières environnementales
US9334549B2 (en) 2013-12-20 2016-05-10 General Electric Company Systems and methods for recovery of rare-earth constituents from environmental barrier coatings
JP2015123385A (ja) * 2013-12-25 2015-07-06 太平洋セメント株式会社 焼成物及びその製造方法
CN104357670A (zh) * 2014-11-04 2015-02-18 江西理工大学 一种稀土草酸废水中和渣综合回收利用的方法
CN104357670B (zh) * 2014-11-04 2016-05-18 江西理工大学 一种稀土草酸废水中和渣综合回收利用的方法
US10570480B2 (en) 2015-03-24 2020-02-25 Sumitomo Metal Mining Co., Ltd. Method for recovering scandium
CN105200250A (zh) * 2015-09-30 2015-12-30 中铝广西国盛稀土开发有限公司 一种从草酸沉淀稀土母液中回收稀土元素的方法
WO2018022129A1 (fr) * 2016-07-27 2018-02-01 Iowa State University Research Foundation, Inc. Séparation d'oxalates de métaux des terres rares
US11090579B2 (en) 2016-07-27 2021-08-17 Iowa State University Research Foundation, Inc. Separating rare earth metal oxalates
US10533239B2 (en) 2016-11-01 2020-01-14 Battelle Energy Alliance, Llc Methods of recovering rare earth elements from a material
CN107162120A (zh) * 2017-06-27 2017-09-15 包头稀土研究院 碳酸稀土沉淀废水的净化利用方法
CN109534472A (zh) * 2019-01-24 2019-03-29 湖南科技大学 一种稀土抛光粉废料的回收和再利用方法
CN109534472B (zh) * 2019-01-24 2021-09-10 湖南科技大学 一种稀土抛光粉废料的回收和再利用方法
US12319982B2 (en) 2019-03-12 2025-06-03 His Majesty The King In Right Of Canada As Represented By The Minister Of Natural Resources Process and system for recovering rare earth elements
WO2020181381A1 (fr) * 2019-03-12 2020-09-17 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of Natural Resources Canada Procédé et système de récupération d'éléments des terres rares
CN112505007A (zh) * 2020-11-09 2021-03-16 安徽大学 利用氧化石墨烯同时富集和检测稀土元素的方法
US20230010128A1 (en) * 2021-07-09 2023-01-12 Anita See Method of collecting rare earth elements
CN115094238A (zh) * 2022-05-09 2022-09-23 中南大学 一种从硫化锌基荧光粉中回收稀土元素的装置和方法
CN115094238B (zh) * 2022-05-09 2023-10-20 中南大学 一种从硫化锌基荧光粉中回收稀土元素的装置和方法
CN115010165A (zh) * 2022-05-20 2022-09-06 全南县新资源稀土有限责任公司 一种稀土碳酸盐的制备方法、一种稀土氧化物的制备方法

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