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CN-117295686-B - Method for producing high-purity lithium hydroxide monohydrate

CN117295686BCN 117295686 BCN117295686 BCN 117295686BCN-117295686-B

Abstract

A method of producing high purity lithium hydroxide monohydrate from a material comprising a lithium salt selected from Li 2 SO 4 、LiCl、Li 2 CO 3 or a mixture thereof, comprising subjecting an aqueous solution of the lithium salt to membrane electrolysis using a cation exchange membrane and nickel plated stainless steel. And extracting a catholyte from the circulating flow, evaporating to obtain lithium hydroxide monohydrate crystals, separating the lithium hydroxide monohydrate crystals from the mother liquor, washing the lithium hydroxide monohydrate crystals with water and drying the lithium hydroxide monohydrate crystals to obtain the final high-purity lithium hydroxide monohydrate. And (3) supplying part of the used washing liquid to a catholyte evaporation step. And returning part of mother liquor formed after the separation of lithium hydroxide monohydrate crystals to the evaporation process of the catholyte. The reverse flow of the anolyte was replenished with a concentrated lithium salt solution prepared from the original lithium salt. The partially used catholyte extracted from the evaporation process is directed to Li 2 CO 3 production.

Inventors

  • A. D. riabzev
  • N. M. nemkov
  • V. I. Titarenko
  • A. A. kurakov
  • A. V. Letuyev

Assignees

  • 亿科思塔诺泰克有限公司

Dates

Publication Date
20260508
Application Date
20220330
Priority Date
20210331

Claims (18)

  1. 1. A method of producing high purity lithium hydroxide monohydrate from a material comprising a lithium salt selected from the group consisting of lithium sulfate, lithium chloride monohydrate, lithium carbonate, or mixtures thereof, the method comprising: subjecting an aqueous solution of lithium salt to membrane electrolysis in a mode in which a catholyte in the form of a lithium hydroxide solution and an anolyte in the form of a lithium salt solution circulate, using a cation exchange membrane as a membrane separating the cathode circuit and the anode circuit of an electrolysis unit, wherein a cathode for the membrane electrolysis is made of nickel-plated stainless steel and the cation exchange membrane is selected from alkali-and acid-resistant membranes, and wherein the anolyte has a current density of 2 kA/m 2 to 4 kA/m 2 and a concentration of lithium in the anolyte is maintained in the range of 20 kg/m 3 to 25 kg/m 3 ; Extracting a volume of catholyte from the circulating catholyte stream and evaporating the extracted volume of catholyte to obtain crystals of lithium hydroxide monohydrate; Separating the formed crystals from the mother liquor, washing with water and drying to obtain the final lithium hydroxide monohydrate with high purity; Wherein the method is further characterized by the steps of: removing cathode gas and anode gas formed during electrolysis; supplying a portion of the generated spent wash solution stream to the catholyte evaporation process, and using a portion of the spent wash solution supplied to the catholyte evaporation process to recover the extracted spent anolyte stream; A step of returning a part of the mother liquor formed after separation of lithium hydroxide monohydrate crystals to the step of evaporating the catholyte; Recovering a portion of the used catholyte stream withdrawn from the evaporation process and representing a concentrated lithium hydroxide solution mixed with sodium hydroxide and potassium hydroxide to obtain lithium carbonate; wherein the spent catholyte stream is recovered by mixing the spent catholyte stream with an aqueous solution stream comprising sodium bicarbonate, potassium bicarbonate and lithium bicarbonate, concentrating the resulting slurry representing a mixture of a solid phase of lithium carbonate and a carbonate solution comprising Na 2 CO 3 、K 2 CO 3 and Li 2 CO 3 by removing water, separating the solid phase of lithium carbonate from the liquid phase, carbonizing the liquid phase by direct contact with carbon dioxide to convert the carbonate solution into a bicarbonate suspension representing a mixture of the solid phases of sodium bicarbonate and potassium bicarbonate in a solution of sodium bicarbonate, potassium bicarbonate and lithium bicarbonate, filtering the resulting suspension to separate the solid phases of sodium bicarbonate and potassium bicarbonate from the solution comprising sodium bicarbonate, potassium bicarbonate and lithium bicarbonate, which solution is directed to be mixed with the spent catholyte stream comprising lithium hydroxide, sodium hydroxide and potassium hydroxide extracted from the evaporation process, and The circulating anolyte stream is replenished with a concentrated solution of lithium salt prepared from the original source of lithium salt and a solution of lithium salt obtained by recovering the withdrawn used anolyte stream.
  2. 2. The method of claim 1, wherein using a portion of the used wash solution supplied to the catholyte evaporation process for recovering the withdrawn used anolyte stream comprises using the used wash solution as an alkaline reagent in a step of chemically purifying a lithium salt solution to remove impurities and/or using the used wash solution as a regeneration solution for converting an ion exchanger from H to Li form in an ion exchange purification step.
  3. 3. The method according to claim 2, wherein the cation exchange membrane used for membrane electrolysis is a Nafion-438, CTIEM-3, MF-4SK-100 type membrane or an equivalent thereof, and a Lewatit 208-TP ion exchanger is used in the ion exchange purification step.
  4. 4. The method according to claim 3, wherein when lithium sulfate is used as the lithium salt-containing material, titanium coated with a noble metal selected from the group consisting of platinum, iridium, ruthenium and tantalum is used as an anode in the membrane electrolysis process, and the anolyte stream is continuously withdrawn from the circulating anolyte stream subjected to Li 2 SO 4 depletion and H 2 SO 4 enrichment Or with Ca (OH) 2 , Or with CaCO 3 until H 2 SO 4 is completely neutralized, separating the resulting CaSO 4 ·2H 2 O solid phase from the Li 2 SO 4 solution, contacting the Li 2 SO 4 solution with an initial lithium sulfate salt to dissolve it to obtain a lithium sulfate solution, adding a spent scrubbing solution to the resulting solution, then carbonizing the solution with carbon dioxide from the neutralization of the withdrawn anolyte stream until calcium and magnesium contained in the solution are converted to the insoluble compounds CaCO 3 and Mg (OH) 2 ·3MgCO 3 ·3H 2 O, filtering the resulting suspension, separating the precipitate from the Li 2 SO 4 solution, subjecting the chemically purified Li 2 SO 4 solution to ion exchange purification by means of a layer of Li type Lewatit-208-TP ion exchanger or equivalent Li type ion exchanger, using the Li 2 SO 4 solution that has undergone ion exchange purification as a make-up solution for the circulating anolyte in the membrane electrolysis process, subjecting the spent ion exchanger to two-step regeneration by a first step consisting of 2.0N sulfuric acid solution treatment, a second step consisting of 2.0N solution, subjecting the LiOH solution to a second step consisting of 2.0N solution to a second step of a gas stream to a co-purification by-current of hydrogen gas to be heated by-produced in a gas stream from the resulting cathode-gas stream to a gas-phase separator, and a co-produced by-product of the chemically purified solution to a cathode-produced by a gas stream from the cathode-gas-separator, in particular, the catholyte is used as a heat carrier in the evaporation process.
  5. 5. The method of claim 4, wherein a volume of anolyte continuously withdrawn from the circulating anolyte stream that has undergone depletion of Li 2 SO 4 and enrichment of H 2 SO 4 is contacted with an air-ammonia mixture to neutralize H 2 SO 4 and produce a mixed solution of Li 2 SO 4 and (NH 4 ) 2 SO 4 ) which is evaporated to salt out (NH 4 ) 2 SO 4 and raise the concentration of Li 2 SO 4 in the evaporated solution, the evaporated solution containing the remainder (NH 4 ) 2 SO 4 ) is mixed with a volume of spent alkaline scrubbing solution, the mixed solution and the air stream from the process of contacting the spent anolyte stream with the ammonia-air mixture are contacted to remove residual ammonia from the Li 2 SO 4 solution, the air stream containing gaseous ammonia is enriched with ammonia from the ammonia source and directed to the neutralization process of the spent anolyte stream, and the Li 2 SO 4 solution without ammonia after strengthening and purification of impurities with Li 2 SO 4 by dissolution of the initial Li 2 SO 4 salt therein is used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process.
  6. 6. A method according to claim 3, characterized in that when lithium chloride or lithium chloride monohydrate is used as the lithium salt-containing material, a titanium anode coated with ruthenium oxide is used in the membrane electrolysis process and a volume of anolyte is continuously withdrawn from the circulating anolyte stream subjected to LiCl depletion, the withdrawn anolyte stream is contacted with the initial lithium chloride salt so that the concentration of LiCl in the withdrawn anolyte stream reaches a predetermined value, the withdrawn LiCl-enriched anolyte stream is converted into insoluble BaSO 4 precipitate by adding barium chloride in addition to remove metal cation impurities by chemical purification to purify the sulfate ions, the liquid phase is separated from the precipitate, after ion exchange purification, used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process, the cathodic hydrogen gas withdrawn from the gas separator and the anodic chlorine gas are mixed and flame combusted, and the resulting hydrogen chloride is absorbed by demineralised water to produce 36% concentrated hydrochloric acid.
  7. 7. The process of claim 6, wherein the anode chlorine gas withdrawn from the gas separator is absorbed by ammonia, NH 4 Cl solution is produced at a molar ratio of NH 3 : Cl 2 =8:3, 6N HCl solution is produced at a molar ratio of NH 3 : Cl 2 =2:3, the resulting NH 4 Cl solution is evaporated, NH 4 Cl is crystallized and dried, and the cathode hydrogen gas withdrawn from the gas separator is used as a heat carrier for generating heated steam.
  8. 8. The method of claim 6, wherein the anode chlorine extracted from the gas separator is completely absorbed by NaOH solution to produce a disinfectant solution of sodium hypochlorite, or the extracted chlorine of 0.5 volume flow is absorbed by NaOH solution to produce a saturated solution of sodium hypochlorite, and the extracted anode chlorine of another 0.5 volume flow is absorbed by Ca (OH) 2 suspension to produce a saturated solution of calcium hypochlorite, the produced solution is mixed to salt out neutral calcium hypochlorite, the calcium hypochlorite is separated from the mother liquor and dried, calcium is precipitated from the resulting mother liquor by adding a predetermined amount of NaOH followed by Na 2 CO 3 , the Ca (OH) 2 -containing precipitate mixed with CaCO 3 is separated from the solution and directed to the preparation of a Ca (OH) 2 suspension containing active chlorine in the form of hypochlorite ions, the solution is divided into two equal parts, one part is mixed with NaOH and directed to the chlorination process to obtain a sodium hypochlorite solution, and the other part is mixed with Ca (OH) 2 and directed to the chlorination process to obtain a calcium hypochlorite solution.
  9. 9. A method according to claim 3, characterized in that when lithium carbonate is used as the lithium salt-containing material, the lithium carbonate is used for the regeneration of the anolyte by conversion of Li 2 CO 3 into the highly soluble lithium salt lithium chloride or lithium sulfate, which is circulated in the anode circuit of the electrolysis cell as anolyte and undergoes exhaustion of LiCl or Li 2 SO 4 during membrane electrolysis.
  10. 10. The method according to claim 3, wherein when an aqueous lithium chloride solution is used as the anolyte, a titanium anode coated with ruthenium oxide is used in the membrane electrolysis process, wherein after mixing, cathodic hydrogen and anodic chlorine are combusted to produce high temperature hydrogen chloride vapor, which is cooled and absorbed by demineralized water in a stepwise countercurrent pattern to obtain a 36% concentrated hydrochloric acid stream withdrawn from the first absorption step along the path of HCl vapor, the resulting concentrated hydrochloric acid stream is mixed with a stream withdrawn from the circulating anolyte stream in the membrane electrolysis process for purification of sulfate ions and purification of sulfate ions using BaCl 2 as a reagent, the mixed stream of concentrated hydrochloric acid and the purified sulfate ion-removed anolyte is contacted with initial lithium carbonate and demineralized water to obtain a LiCl solution stream, which is used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process after purification of calcium and magnesium impurities.
  11. 11. The method according to claim 10, characterized in that anodic chlorine is absorbed by demineralized water in the presence of ammonia gas in a molar ratio NH 3 : Cl 2 = 2:3, a 6N hydrochloric acid solution is obtained, which is mixed with a chemically purified anolyte stream, which is a stream extracted from the circulating anolyte stream in a membrane electrolysis process, from which sulfate ions are purified, the mixed stream of hydrochloric acid solution and the anolyte purified from sulfate ions is contacted with initial lithium carbonate to obtain a LiCl solution stream, which after purification of calcium and magnesium impurities is used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process, and cathodic hydrogen is used as fuel for generating heated steam.
  12. 12. The method according to claim 10, characterized in that anode chlorine is absorbed from an aqueous slurry of lithium carbonate in the presence of an elemental chlorine reducing agent, the elemental chlorine reducing agent having a material composition that prevents contamination of the absorbent by extraneous cations and anions during chlorine absorption, as an absorption product, the lithium chloride solution being used as a make-up solution for a circulating anolyte stream in a membrane electrolysis process after purification of calcium and magnesium impurities, wherein the aqueous slurry for absorbing anode chlorine is prepared from demineralized water, lithium carbonate obtained from a used catholyte, lithium carbonate in the form of an initial salt, a reducing agent, and an anolyte stream after extraction from the circulating anolyte stream in a membrane electrolysis process for purification of sulfate ions removal using a reagent purification, and cathode hydrogen is used as a fuel for generating heated steam.
  13. 13. A method according to claim 3, characterized in that when an aqueous lithium sulfate solution is used as the anolyte, titanium coated with a noble metal selected from platinum, iridium, tantalum or ruthenium is used as the anode in the electrolysis process, and the stream of spent lithium sulfate and enriched sulfuric acid anolyte extracted from the anolyte circulation loop is contacted with initial lithium carbonate to obtain a lithium sulfate solution, which is used as a make-up solution for the anolyte circulation loop after purification to remove impurities.
  14. 14. The method of claim 3, wherein when a mixture of lithium salt lithium sulfate and lithium carbonate is used as the lithium salt-containing material, a predetermined volume of anolyte stream is continuously withdrawn from the circulating anolyte stream that has undergone depletion of Li 2 SO 4 and enrichment of H 2 SO 4 , the withdrawn anolyte stream is contacted with an initial mixture of Li 2 SO 4 and Li 2 CO 3 salts to obtain a lithium sulfate solution containing residual amounts of H 2 SO 4 , and the resulting solution is recovered as a Li 2 SO 4 solution suitable for replenishing the circulating anolyte stream in the membrane electrolysis process.
  15. 15. The method according to claim 3, wherein when a mixture of lithium chloride and lithium carbonate is used as the lithium salt-containing material, the initial mixture of lithium chloride and lithium carbonate is contacted with a hydrochloric acid solution and an anolyte stream extracted from a circulating anolyte stream that has undergone LiCl depletion during membrane electrolysis to produce a lithium chloride solution of a predetermined concentration, and the resulting lithium chloride solution is used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process after purification to remove impurities.
  16. 16. A process according to claim 3, wherein when a mixture of lithium sulfate and lithium chloride is used as the lithium salt-containing material, titanium coated with a noble metal selected from the group consisting of platinum, iridium, tantalum and ruthenium is used as the anode in the membrane electrolysis process, and an anolyte stream is withdrawn from the circulating anolyte stream subjected to depletion of lithium sulfate and lithium chloride and enrichment of H 2 SO 4 , and is contacted with a predetermined amount of CaO, or Ca (OH) 2 , or CaCO 3 until H 2 SO 4 is completely neutralized, the resulting mixed solution of Li 2 SO 4 and LiCl is separated from the CaSO 4 ·2H 2 O precipitate, and is contacted with the initial mixture of Li 2 SO 4 and LiCl salts to dissolve it, to give a Li 2 SO 4 and LiCl mixed solution having a predetermined lithium concentration, which is used as a make-up solution for the circulating anolyte stream in the membrane electrolysis process after purification of impurities, and the cathode hydrogen is used as heating steam.
  17. 17. The method of claim 16, wherein the amount of anolyte stream continuously withdrawn from the recycled anolyte stream that has undergone Li 2 SO 4 and LiCl depletion is used as a Li 2 SO 4 and LiCl make-up mixed solution for the recycled anolyte stream after recovery, and the anode chlorine withdrawn from the gas separator is recovered as 36% hydrochloric acid, or NH 4 Cl, or sodium hypochlorite solution, or calcium hypochlorite neutral.
  18. 18. The method of claim 3, wherein when a mixture of lithium sulfate, lithium chloride and lithium carbonate is used as the lithium salt-containing material, a volume of anolyte is continuously withdrawn from the circulating anolyte stream that is subjected to Li 2 SO 4 and LiCl depletion and H 2 SO 4 enrichment, which is first contacted with an initial mixture of Li 2 SO 4 , liCl and Li 2 CO 3 salts to produce a mixed solution having a predetermined lithium concentration, and the resulting mixed solution is recovered as a mixed solution of Li 2 SO 4 and LiCl that is used as a make-up solution for the anolyte recycle stream in the membrane electrolysis process.

Description

Method for producing high-purity lithium hydroxide monohydrate Technical Field The invention belongs to the technical field of inorganic chemistry, and in particular relates to a method for producing high-purity lithium hydroxide monohydrate from a material containing lithium salt. Background It is known to produce lithium hydroxide solutions by contacting lithium waste material containing solid carbonate with water, precipitating the resulting slurry, decanting the clarified liquid phase, then filtering and recirculating the resulting lithium-containing solution through the central compartment of an electrodialysis unit, thereby obtaining lithium hydroxide solution in the cathode compartment, mixed acid solution in the anode compartment, and desalinated liquid in the central compartment, which is returned to the process of leaching lithium from lithium waste material containing solid carbonate [1]. The disadvantage of this process is that the LiOH solution produced has a low concentration (up to 25kg/m 3) and, owing to the operation at a current density of up to 2A/dm 2(0.2kA/m2, the process production efficiency is low, and owing to the low concentration of Li 2CO3 (up to 10kg/m 3), the resistance of the recovered Li 2CO3 solution is high and, therefore, the specific energy consumption per unit of the product produced is high. Another known method [2] of producing lithium hydroxide solutions from lithium compound containing materials, in particular from waste lithium ion batteries, involves extracting lithium in the form of highly soluble lithium sulfate from the waste material and subjecting the lithium sulfate solution to membrane electrolysis using a Nafion 350 cation exchange membrane separating the cathode and anode. Electrolysis was carried out at a direct current density of 20A/dm 2 and a voltage of 5.3V, with a continuous withdrawal of LiOH solution (catholyte (catholyte) stream) from the cathode chamber and a continuous withdrawal of Li 2SO4 depleted anolyte (anolyte) stream containing sulfuric acid formed at the anode from the anode chamber. The extracted anolyte stream is directed to a lithium leaching process to neutralize sulfuric acid while strengthening the electrolyte stream with lithium sulfate. The anolyte reinforced with Li 2SO4 is returned to the electrolysis process. The disadvantage of this anolyte is that only LiOH solutions contaminated with impurities can be produced. This process does not produce a product in the form of LiOH H 2 O of high purity. It is known to produce lithium hydroxide of high purity by subjecting an aqueous solution containing lithium chloride and lithium carbonate recovered from natural brine to membrane electrolysis in the presence of a reducing agent [3]. The extracted catholyte was evaporated to crystallize lioh·h 2 O. After separation from the mother liquor, liOH H 2 O was washed with demineralized water (demineralized) and dried to obtain high purity LiOH H 2 O. Here, the cathodic hydrogen is used to produce a heat carrier for generating heated steam in the catholyte evaporation process, and the anodic chlorine oxidizes bromide ions to elemental bromine by contact with natural brine rich in bromide ions. Disadvantages of this method include the use of low concentration LiCl solution, which is first recovered from lithium-containing natural brine by means of LiCl selective adsorbents, as feed for electrochemical conversion and the need to use reducing agents to eliminate the risk of formation of oxychlorides in the anode compartment during electrolysis of the low concentration LiCl solution. A process [4] for producing high purity lithium monohydrate from lithium carbonate-containing materials overcomes most of the disadvantages of the above-described processes. The method is based on the reproduction of highly soluble aqueous lithium sulphate solutions subjected to Li 2SO4 depletion and H 2SO4 enrichment for replenishing the anolyte circulated in the anolyte loop of the electrolysis unit. For this purpose, a portion of the lithium depleted anolyte is continuously withdrawn from the anolyte loop and contacted with an equal amount of lithium carbonate to convert anodic sulfuric acid to lithium sulfate. The method also provides for chemical purification of the regenerated Li 2SO4 solution to remove Ca, mg impurities and heavy metals by a carbonate-alkali process using LiOH solution and CO 2 released when neutralizing the carbonate in the anolyte. The method has the disadvantage that the cation exchange membrane M-40 with lower mechanical stability and chemical stability is used in the membrane electrolysis process. Further, disadvantages of this method include contamination of water by liquid waste, contamination of lithium carbonate solution by sodium carbonate and potassium carbonate, and unsatisfactory chemical purification of the Li 2SO4 solution supplied to replenish the anolyte loop, which means that membranes contaminated with calcium cations and mag