CN117383589A - Method for preparing high-purity lithium carbonate from industrial lithium carbonate - Google Patents
Method for preparing high-purity lithium carbonate from industrial lithium carbonate Download PDFInfo
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- CN117383589A CN117383589A CN202311568648.4A CN202311568648A CN117383589A CN 117383589 A CN117383589 A CN 117383589A CN 202311568648 A CN202311568648 A CN 202311568648A CN 117383589 A CN117383589 A CN 117383589A
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- lithium chloride
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- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 title claims abstract description 132
- 229910052808 lithium carbonate Inorganic materials 0.000 title claims abstract description 132
- 238000000034 method Methods 0.000 title claims abstract description 34
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims abstract description 276
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 261
- 238000001728 nano-filtration Methods 0.000 claims abstract description 94
- 239000012528 membrane Substances 0.000 claims abstract description 91
- 239000012466 permeate Substances 0.000 claims abstract description 64
- 238000000909 electrodialysis Methods 0.000 claims abstract description 59
- 239000012535 impurity Substances 0.000 claims abstract description 48
- 238000006243 chemical reaction Methods 0.000 claims abstract description 46
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 42
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 38
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000000126 substance Substances 0.000 claims abstract description 31
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 21
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 18
- 238000001035 drying Methods 0.000 claims abstract description 14
- 239000002002 slurry Substances 0.000 claims abstract description 14
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 239000013078 crystal Substances 0.000 claims abstract description 12
- 239000000047 product Substances 0.000 claims abstract description 11
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000003456 ion exchange resin Substances 0.000 claims abstract description 10
- 229920003303 ion-exchange polymer Polymers 0.000 claims abstract description 10
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 10
- 238000005406 washing Methods 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims description 184
- 238000000108 ultra-filtration Methods 0.000 claims description 41
- 239000003513 alkali Substances 0.000 claims description 32
- 239000012141 concentrate Substances 0.000 claims description 29
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 26
- 229910052744 lithium Inorganic materials 0.000 claims description 26
- 239000012452 mother liquor Substances 0.000 claims description 22
- 239000002253 acid Substances 0.000 claims description 19
- 238000003825 pressing Methods 0.000 claims description 19
- 239000011575 calcium Substances 0.000 claims description 16
- 238000005342 ion exchange Methods 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 229920001429 chelating resin Polymers 0.000 claims description 13
- 229910052791 calcium Inorganic materials 0.000 claims description 12
- 229910052749 magnesium Inorganic materials 0.000 claims description 12
- 239000011777 magnesium Substances 0.000 claims description 12
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 10
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 10
- 229910052796 boron Inorganic materials 0.000 claims description 10
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 8
- 239000010413 mother solution Substances 0.000 claims description 7
- 238000003763 carbonization Methods 0.000 claims description 6
- 238000010000 carbonizing Methods 0.000 claims description 6
- 230000018044 dehydration Effects 0.000 claims description 6
- 238000006297 dehydration reaction Methods 0.000 claims description 6
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 6
- 238000001223 reverse osmosis Methods 0.000 claims description 6
- 238000000746 purification Methods 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 2
- 239000002699 waste material Substances 0.000 abstract description 3
- HQRPHMAXFVUBJX-UHFFFAOYSA-M lithium;hydrogen carbonate Chemical compound [Li+].OC([O-])=O HQRPHMAXFVUBJX-UHFFFAOYSA-M 0.000 description 14
- 229920005989 resin Polymers 0.000 description 11
- 239000011347 resin Substances 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 7
- 230000001276 controlling effect Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
- 239000013522 chelant Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000498 cooling water Substances 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 3
- 238000011069 regeneration method Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002642 lithium compounds Chemical class 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 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
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- -1 oxalate ions Chemical class 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/08—Carbonates; Bicarbonates
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a method for preparing high-purity lithium carbonate from industrial-grade lithium carbonate, and belongs to the technical field of chemical industry. The method of the invention comprises the following steps: reacting industrial grade lithium carbonate with a hydrochloric acid solution to generate a lithium chloride solution; heating, adding oxalic acid and lithium hydroxide solution for chemical impurity removal; sequentially ultrafiltering and nanofiltration; treating the lithium chloride nanofiltration permeate liquid by ion exchange resin to obtain a lithium chloride purifying solution; the lithium chloride purifying solution is subjected to bipolar membrane electrodialysis to respectively obtain a lithium hydroxide solution, a dilute hydrochloric acid solution and a dilute lithium chloride solution; the lithium hydroxide solution is subjected to homogeneous membrane electrodialysis to obtain lithium hydroxide concentrated solution and lithium hydroxide dilute solution, the lithium hydroxide concentrated solution is added with lithium carbonate seed crystal, carbon dioxide gas is introduced for reaction, and lithium carbonate slurry is generated; and (3) centrifugally dehydrating, washing and drying the lithium carbonate slurry to obtain a high-purity lithium carbonate finished product. The invention has high impurity removal rate, widens the limitation of raw materials, ensures the quality of lithium carbonate, has low discharge of three wastes and can recycle resources circularly and efficiently.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a method for preparing high-purity lithium carbonate from industrial-grade lithium carbonate.
Background
Lithium carbonate has a significant role in lithium compounds and is widely used in the fields of glass, ceramics, medicine, batteries and the like. In recent years, as the market demand for high-purity lithium salt expands in the fields of new energy and new materials worldwide, the demand for 4N high-purity lithium carbonate is also increasing.
At present, the production process of high-purity lithium carbonate generally adopts industrial grade lithium carbonate to react with water and carbon dioxide to form a soluble lithium bicarbonate solution, insoluble matters are removed through filtration, divalent metal ions are removed through chelating resin to obtain a pure lithium bicarbonate solution, the lithium bicarbonate solution is heated and decomposed to separate out battery grade lithium carbonate, the battery grade lithium carbonate is added with water and slurried, the battery grade lithium carbonate reacts with carbon dioxide again to produce soluble lithium bicarbonate, and the soluble lithium bicarbonate solution is filtered, the chelating resin is used for removing impurities, and the high-purity lithium carbonate is obtained through heating and decomposition. The method has the following defects: the quality requirement of the industrial grade lithium carbonate raw material is high; (2) The lithium bicarbonate is unstable and is easy to separate out in the process, so that a pipeline is easy to be blocked, particularly, chelating resin is seriously hardened due to the unstable precipitation of the lithium bicarbonate in the operation process of a resin impurity removal system, the consumption of acid for resin regeneration and washing is large, and the production amount of acid washing wastewater is large; (3) The solubility of the lithium bicarbonate solution is low, the amount of the lithium bicarbonate solution required for producing ton of lithium carbonate is large, the thermal decomposition process is caused, and the steam consumption is large; (4) severe reactor wall formation, affecting heat transfer efficiency; and (5) the primary yield is low, and the recovery rate is low.
Therefore, the method for producing the high-purity lithium carbonate by taking the industrial-grade lithium carbonate as the raw material has low requirements on the raw material, high yield of finished products and low discharge of three wastes, and is a problem to be solved urgently by the technicians in the field.
Disclosure of Invention
The invention aims to provide a method for preparing high-purity lithium carbonate from industrial-grade lithium carbonate, which has the advantages of high purity of the lithium carbonate product, high lithium recovery rate, few byproducts and environment-friendly process. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the invention discloses a method for preparing high-purity lithium carbonate from industrial-grade lithium carbonate, which comprises the following steps:
s1, dissolving: reacting industrial grade lithium carbonate with a hydrochloric acid solution to generate a lithium chloride solution;
s2, chemical impurity removal: heating the lithium chloride solution obtained in the step S1, sequentially adding oxalic acid and lithium hydroxide solution for reaction, and performing chemical impurity removal;
s3, ultrafiltration: ultrafiltering the lithium chloride solution subjected to the chemical impurity removal treatment in the step S2 to obtain lithium chloride ultrafiltrate and ultrafiltrate concentrate;
s4, nanofiltration: carrying out nanofiltration treatment on the lithium chloride ultrafiltration permeate obtained in the step S3 to obtain lithium chloride nanofiltration permeate and nanofiltration concentrate respectively;
s5, ion exchange: treating the lithium chloride nanofiltration permeate obtained in the step S4 by using ion exchange resin to obtain a lithium chloride purifying solution;
s6, bipolar membrane electrodialysis: carrying out bipolar membrane electrodialysis on the lithium chloride purifying solution obtained in the step S5 to respectively obtain a lithium hydroxide solution, a dilute hydrochloric acid solution and a dilute lithium chloride solution;
s7, homogeneous membrane electrodialysis: the lithium hydroxide solution obtained in the step S6 is subjected to homogeneous membrane electrodialysis to obtain lithium hydroxide concentrated solution and lithium hydroxide dilute solution,
s8, carbonizing: adding lithium hydroxide concentrated solution obtained in the step S7 into lithium carbonate seed crystal, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry;
s9, centrifugal separation and drying: carrying out centrifugal dehydration and washing on the lithium carbonate slurry prepared in the step S8 to obtain a lithium carbonate wet material and a centrifugal mother solution; and drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
In some embodiments of the present invention, the lithium concentration in the lithium chloride solution produced in S1 is 11-16g/L;
preferably, the concentration of the hydrochloric acid solution in step S1 is 1.5 to 2mol/L.
In some embodiments of the invention, in S2, the lithium chloride solution is warmed to 40-60 ℃;
preferably, C (C 2 O 4 2- )1.5～2.5g/L，c(OH - ) 1-3 g/L; preferably, in the step S2, lithium hydroxide solution produced by bipolar membrane electrodialysis is added for chemical impurity removal.
In the invention, by controlling C in the solution 2 O 4 2- And OH (OH) - The content ensures the impurity removal effect, and simultaneously gives consideration to the impurity removal cost and the influence on the subsequent use.
In some embodiments of the present invention, in S3, the pore size of the ultrafiltration membrane is 0.02 to 0.2um;
preferably, the ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank, and plate-and-frame filter pressing residues are discharged out of the system.
In some embodiments of the present invention, in S4, the nanofiltration concentrate is returned to step S2 for chemical impurity removal again;
preferably, the pH value of the lithium chloride ultrafiltration permeate is adjusted to 4-7, and then nanofiltration treatment is carried out.
The nanofiltration concentrated solution is enriched with a large amount of oxalate ions, calcium ions, magnesium ions and the like, so that the pH value of the lithium chloride ultrafiltration permeate is adjusted to 4-7, then nanofiltration treatment is carried out, the precipitation of oxalate is avoided, and the redundant oxalate can replace part of oxalic acid to be used as a impurity removing agent of S2.
In some embodiments of the invention, in S5, ca is less than or equal to 0.02ppm, mg is less than or equal to 0.01ppm, B is less than or equal to 5ppm, and Si is less than or equal to 1ppm in the lithium chloride purifying solution;
preferably, the ion exchange resin consists of a calcium and magnesium-depleted chelating resin and a boron-depleted chelating resin; the ion exchange process is to remove Ca and Mg and then B.
Preferably, the pH value of the lithium chloride nanofiltration permeate is adjusted to be 8.5-9.5, and then the lithium chloride nanofiltration permeate enters the ion exchange resin; more preferably, the ph=8.5 to 9.5 of the lithium chloride nanofiltration permeate is adjusted by using a lithium hydroxide solution produced by a bipolar membrane.
In some embodiments of the present invention, the concentration of the lithium hydroxide solution obtained in S6 is 36-50 g/L; the concentration of the dilute hydrochloric acid solution is 1.5-2 mol/L, and the concentration of lithium in the dilute lithium chloride solution is 3-5 g/L;
preferably, the dilute hydrochloric acid solution is returned to the step S1 for use;
preferably, the dilute lithium chloride solution is subjected to acid-resistant reverse osmosis treatment to obtain a lithium chloride concentrated solution and a lithium chloride permeate, and more preferably, the lithium concentration in the lithium chloride concentrated solution is 6-10 g/L, and the lithium concentration in the lithium chloride permeate is 0.6-1 g/L; more preferably, the lithium chloride concentrate is returned to step S6 and mixed with the lithium chloride purification solution as a raw material solution for bipolar membrane electrodialysis; more preferably, the lithium chloride permeate serves as a receiver for dilute hydrochloric acid produced by bipolar membrane electrodialysis.
In some embodiments of the invention, the concentration of the lithium hydroxide concentrate obtained in S7 is 75-96 g/L;
preferably, the concentration of the lithium hydroxide dilute solution obtained in the step S7 is 10-20 g/L;
preferably, the lithium hydroxide dilute solution obtained in the step S7 is returned to the alkali circulation tank of the bipolar membrane electrodialysis in the step S6 to be used as a receiving solution of lithium hydroxide generated by the bipolar membrane electrodialysis.
In some embodiments of the present invention, in S8, the lithium hydroxide concentrate is heated to 50-60 ℃, and then high-purity lithium carbonate is added as seed crystal;
preferably, the carbon dioxide comprises carbon dioxide produced in step S1;
preferably, in the step S8, during the carbonization reaction, the reaction temperature is controlled to be 50-60 ℃;
preferably, the adding speed of lithium hydroxide and carbon dioxide is controlled, and the concentration of hydroxyl in a reaction system is maintained to be 15-30 g/L;
preferably, the seed crystal is added in an amount of 1 to 10% by mass of the lithium carbonate.
In some embodiments of the present invention, the centrifugal mother liquor obtained in S9 is subjected to nanofiltration treatment to obtain centrifugal mother liquor nanofiltration concentrate and centrifugal mother liquor nanofiltration permeate, respectively;
preferably, the concentrated water obtained by nanofiltration of the centrifugal mother liquor is returned to the step S2 to replace part or all of lithium hydroxide for removing impurities of lithium chloride;
preferably, the alkali circulation tank of bipolar membrane electrodialysis in the step S6 of nanofiltration permeate of the centrifugal mother liquor is used as a receiving solution of lithium hydroxide generated by bipolar membrane electrodialysis;
preferably, the nanofiltration membrane used for centrifuging the mother liquor is an alkali-resistant nanofiltration membrane, and the interception molecular weight of the membrane is 100-1000 daltons.
Compared with the prior art, the invention has the following beneficial effects:
the invention has scientific design and ingenious conception, combines the modes of chemical impurity removal, membrane separation impurity removal, chelating resin impurity removal and the like, has high impurity removal rate, widens the limitation of raw materials, and ensures the quality of lithium carbonate. The invention greatly reduces the load of resin impurity removal by introducing the membrane separation impurity removal, so that the resin regeneration frequency is reduced and the regeneration wastewater quantity is reduced. The lithium chloride purifying liquid for bipolar membrane electrodialysis has low impurity content, wherein Ca is less than or equal to 0.02ppm, mg is less than or equal to 0.01ppm, B is less than or equal to 5ppm, and Si is less than or equal to 1ppm; reducing the deposition of these impurities inside the film is beneficial to provide the electrical efficiency and lifetime of the film. The lithium hydroxide solution prepared by the lithium chloride solution bipolar membrane with low impurities has better quality and the produced lithium carbonate has higher quality. The invention adopts the lithium hydroxide solution to carbonize and produce the lithium carbonate, and has the advantages of high reaction speed and high productivity of single equipment. The invention has the advantages of low discharge of three wastes and high-efficiency recycling of resources in the production process link.
Compared with the traditional process for producing high-purity lithium carbonate by using industrial-grade lithium carbonate, the method is simpler and more convenient, and the industrial-grade lithium carbonate is not required to be purified into battery-grade lithium carbonate, and then the battery-grade lithium carbonate is purified into the high-purity lithium carbonate; the limitation of raw materials is widened.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a schematic diagram of a bipolar membrane electrodialysis process of the invention; wherein the names corresponding to the reference numerals are: 1-alkali circulating pump, 2-acid circulating pump and 3-brine circulating pump.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
As shown in the attached figure 1, the invention discloses a method for preparing high-purity lithium carbonate from industrial-grade lithium carbonate, which specifically comprises the following steps:
s1, dissolving: the technical grade lithium carbonate reacts with 1.5-2 mol/L dilute hydrochloric acid solution to form lithium chloride solution with the lithium concentration of 11-16 g/L.
S2, chemical impurity removal: heating the lithium chloride solution obtained in the step S1 to 40-60 ℃, sequentially adding oxalic acid and lithium hydroxide solution for reaction for 30-60 minutes, and performing chemical impurity removal; c (C) in the reaction end point control solution 2 O 4 2- )1.5～2.5g/L，c(OH - ) 1-3 g/L; preferably, in the step S2, lithium hydroxide solution produced by bipolar membrane electrodialysis is added for chemical impurity removal.
In the method, oxalic acid and lithium hydroxide are added to precipitate metal impurities such as calcium, magnesium, iron, manganese, barium and the like;
s3, ultrafiltration: ultrafiltering the lithium chloride solution subjected to the chemical impurity removal treatment in the step S2 to obtain lithium chloride ultrafiltrate and ultrafiltrate concentrate; wherein, the aperture of the ultrafiltration membrane is 0.02-0.2 um; the ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank, and plate-and-frame filter pressing residues are discharged out of the system;
s4, nanofiltration: regulating the pH value of the lithium chloride ultrafiltration permeate obtained in the step S3 to 4-7 by adopting hydrochloric acid, and then carrying out nanofiltration treatment to obtain lithium chloride nanofiltration permeate and nanofiltration concentrate respectively; the nanofiltration concentrated solution returns to the step S2 to perform chemical impurity removal again; the nanofiltration membrane in the step S4 is an acid-resistant nanofiltration membrane, and the interception molecular weight of the membrane is 100-1000 daltons;
in the step S4, the pH value of the lithium chloride ultrafiltration permeate is adjusted to be 4-7, so that the reaction of divalent ions on the concentrate side and oxalic acid radicals after enrichment in the nanofiltration process is avoided to form an oxalate precipitation blocking film; at the same time pass through nanofiltration treatment C 2 O 4 2- 、SO 4 2- And a trace amount of Si, al, ca, mg, B plasma is intercepted in the nanofiltration concentrated solution, and the nanofiltration concentrated solution returns to the step S2 for impurity removal reaction.
S5, ion exchange: treating the lithium chloride nanofiltration permeate obtained in the step S4 by using ion exchange resin to obtain a lithium chloride purifying solution; ca is less than or equal to 0.02ppm, mg is less than or equal to 0.01ppm, B is less than or equal to 5ppm and Si is less than or equal to 1ppm in the lithium chloride purifying solution;
the ion exchange resin consists of chelate resin for removing calcium and magnesium and chelate resin for removing boron; the ion exchange process is to make the lithium chloride nanofiltration permeate pass through calcium and magnesium removal chelating resin and boron removal resin in sequence for ion exchange treatment, and then remove calcium and magnesium and boron.
Preferably, the pH value of the lithium chloride nanofiltration permeate is adjusted to be 8.5-9.5, and then the lithium chloride nanofiltration permeate enters the ion exchange resin; more preferably, the ph=8.5 to 9.5 of the lithium chloride nanofiltration permeate is adjusted by using a lithium hydroxide solution produced by a bipolar membrane.
S6, bipolar membrane electrodialysis: and (3) carrying out bipolar membrane electrodialysis on the lithium chloride purifying solution obtained in the step (S5) to respectively obtain a lithium hydroxide solution with the concentration of 36-50 g/L, a dilute hydrochloric acid solution with the concentration of 1.5-2 mol/L and a dilute lithium chloride solution with the concentration of 3-5 g/L.
As shown in figure 2, the bipolar membrane electrodialysis device is a three-compartment electrodialysis device which is respectively an alkali chamber, a salt chamber and an acid chamber, wherein the alkali chamber is connected with an alkali circulation tank through an alkali circulation pump, the salt chamber is connected with the salt circulation tank through a brine circulation pump, and the acid chamber is connected with the acid circulation tank through an acid circulation pump.
The dilute hydrochloric acid solution with the concentration of 1.5-2 mol/L is extracted from the acid circulation tank, the lithium hydroxide solution with the concentration of 36-50 g/L is extracted from the alkali circulation tank, and the dilute lithium chloride solution with the concentration of 3-5 g/L is extracted from the salt circulation tank.
Returning the dilute hydrochloric acid solution to the step S1 for use;
the dilute lithium chloride solution with the lithium concentration of 3-5 g/L is subjected to acid-resistant reverse osmosis treatment to obtain a lithium chloride concentrated solution with the lithium concentration of 6-10 g/L and a lithium chloride permeate with the lithium concentration of 0.6-1 g/L; returning the lithium chloride concentrated solution with the lithium concentration of 6-10 g/L to the step S6, and mixing the concentrated solution with the lithium chloride purifying solution to be used as the raw material solution of bipolar membrane electrodialysis; the lithium chloride permeate with the lithium concentration of 0.6-1 g/L enters an acid circulation tank and is used as a receiving liquid of dilute hydrochloric acid. The alkali circulation tank is supplemented with pure water as a receiving liquid.
S7, homogeneous membrane electrodialysis: the lithium hydroxide solution with the concentration of 36-50 g/L obtained in the step S6 is subjected to homogeneous membrane electrodialysis to obtain lithium hydroxide concentrated solution with the concentration of 75-96 g/L and lithium hydroxide light solution with the concentration of 10-20 g/L,
returning the lithium hydroxide dilute solution to the alkali circulation tank of the bipolar membrane electrodialysis in the step S6 to be mixed with pure water, and taking the mixed solution as a receiving solution of lithium hydroxide generated by the bipolar membrane electrodialysis;
s8, carbonizing: adding the lithium hydroxide concentrated solution obtained in the step S7 into a reaction kettle, heating to 50-60 ℃, adding high-purity lithium carbonate as seed crystal, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry; the carbon dioxide gas comprises carbon dioxide produced in the step S1; in the carbonization reaction process, the reaction temperature is controlled to be 50-60 ℃; controlling the adding speed of lithium hydroxide and carbon dioxide, and maintaining the concentration of hydroxyl in a reaction system to be 15-30 g/L; the adding amount of the seed crystal is 1-10% of the mass of the generated lithium carbonate.
S9, centrifugal separation and drying: carrying out centrifugal dehydration and washing on the lithium carbonate slurry prepared in the step S8 to obtain a lithium carbonate wet material and a centrifugal mother solution; and drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
S10, carrying out nanofiltration treatment on the centrifugal mother liquor obtained in the step S9 to respectively obtain concentrated nanofiltration water of the centrifugal mother liquor and nanofiltration permeate of the centrifugal mother liquor;
the centrifugal mother liquor nanofiltration concentrated water is returned to the step S2 to replace part or all of lithium hydroxide for removing impurities of lithium chloride, and a small amount of carbonate is intercepted in the nanofiltration concentrated water after alkali-resistant nanofiltration treatment, so that the carbonate is prevented from entering bipolar membrane electrodialysis to form a lithium carbonate precipitation blocking membrane;
returning the nanofiltration permeate of the centrifugal mother liquor to an alkali circulation tank of the bipolar membrane electrodialysis in the step S6, and taking the nanofiltration permeate of the centrifugal mother liquor as a receiving solution of lithium hydroxide generated by a bipolar membrane;
the nanofiltration membrane used for the centrifugal mother solution is an alkali-resistant nanofiltration membrane, and the interception molecular weight of the membrane is 100-1000 daltons.
Example 1
The embodiment discloses a method for preparing high-purity lithium carbonate from industrial grade lithium carbonate, which specifically comprises the following steps:
s1, dissolving: 200kg of technical grade lithium carbonate with a main content of 99.2wt.% is added into a 3000L reaction kettle, and 1.5mol/L dilute hydrochloric acid is slowly added into the reaction kettle to react to form a lithium chloride solution with a lithium concentration of 15.5g/L.
S2, chemical impurity removal: heating the lithium chloride solution to 42 ℃, sequentially adding oxalic acid and lithium hydroxide solution for reaction for 30 minutes, and controlling the reaction end point to control C (C) 2 O 4 2- )1.5g/L，c(OH - )1g/L。
S3, ultrafiltration: ultrafiltering the lithium chloride solution with the chemical impurity removed by an ultrafiltration membrane with the aperture of 0.05um to obtain lithium chloride ultrafiltration permeate and lithium chloride ultrafiltration concentrate, wherein the lithium chloride ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, and clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank and filter pressing residues are discharged out of the system.
S4, nanofiltration: the pH value of the ultrafiltration permeate is adjusted to 4.5 by dilute hydrochloric acid generated by bipolar membrane electrodialysis, and nanofiltration is carried out by an alkali-resistant nanofiltration membrane of 100 daltons, so that lithium chloride nanofiltration permeate and nanofiltration concentrate are respectively obtained; the nanofiltration concentrated solution returns to the chemical impurity removal reaction kettle in the step S2, and the lithium chloride nanofiltration permeate enters an ion exchange system;
s5, ion exchange: after the pH value of lithium hydroxide solution produced by a bipolar membrane is regulated to be 8.8, ion exchange treatment is sequentially carried out on the lithium chloride nanofiltration permeate through calcium and magnesium removal chelating resin and boron removal resin, and finally lithium chloride purifying solution with Ca less than or equal to 0.02ppm, mg less than or equal to 0.01ppm, B less than or equal to 5ppm and Si less than or equal to 1ppm is obtained;
s6, the lithium chloride purifying solution enters bipolar membrane electrodialysis treatment to respectively obtain a lithium hydroxide solution with the concentration of 36g/L, a dilute hydrochloric acid solution with the concentration of 1.5mol/L and a dilute lithium chloride solution with the concentration of 4.5 g/L.
Returning the dilute hydrochloric acid solution to the step S1 to dissolve the industrial lithium carbonate;
the dilute lithium chloride solution is subjected to acid-resistant reverse osmosis treatment to obtain lithium chloride concentrated solution with the lithium concentration of 9.0g/L and lithium chloride penetrating fluid with the lithium concentration of 0.8g/L, and the lithium chloride concentrated solution and the lithium chloride purifying solution are mixed to be used as raw material liquid of bipolar membrane electrodialysis to enter a salt circulation tank; the lithium chloride permeate enters an acid circulation tank;
s7, homogeneous membrane electrodialysis: concentrating the lithium hydroxide solution obtained in the step S6 through homogeneous membrane electrodialysis to obtain lithium hydroxide concentrated solution with the concentration of 76g/L and lithium hydroxide dilute solution with the concentration of 15.8g/L, and returning the lithium hydroxide dilute solution to the alkali circulation tank of the bipolar membrane electrodialysis in the step S6 to serve as receiving solution of lithium hydroxide generated by the bipolar membrane;
s8, carbonizing: adding the lithium hydroxide concentrated solution with the concentration of 76g/L obtained in the step S7 into a carbonization reaction kettle, heating to 52 ℃, adding lithium carbonate seed crystals with the mass of 1wt.% of generated lithium carbonate, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry; the reaction temperature was controlled at 52℃by cooling water, and the hydroxyl concentration in the reaction system was maintained at 15.5g/L.
S9, centrifugal separation and drying: and (3) carrying out centrifugal dehydration and washing on the lithium carbonate slurry to obtain a lithium carbonate wet material and a centrifugal mother solution. And drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
S10, after the centrifugal mother liquor is subjected to alkali-resistant nanofiltration treatment with the interception molecular weight of 100 daltons, the obtained lithium hydroxide concentrated water is returned to the chemical impurity removal step S2, and the alkali-resistant nanofiltration permeate is returned to an alkali circulation tank of bipolar membrane electrodialysis for recycling.
Example 2
The embodiment discloses a method for preparing high-purity lithium carbonate from industrial grade lithium carbonate, which specifically comprises the following steps:
s1, dissolving: 180kg of technical grade lithium carbonate with a main content of 99.0wt.% is added into a 3000L reaction kettle, and 1.8mol/L dilute hydrochloric acid is slowly added into the reaction kettle to react to form a lithium chloride solution with a lithium concentration of 13.5 g/L.
S2, chemical impurity removal: heating the lithium chloride solution to 55 ℃, sequentially adding oxalic acid and lithium hydroxide solution for reacting for 43 minutes, and controlling the reaction end point to control C (C) 2 O 4 2- )2.1g/L，c(OH - )1.9g/L。
S3, ultrafiltration: ultrafiltering the lithium chloride solution with the chemical impurity removed by an ultrafiltration membrane with the aperture of 0.1um to obtain lithium chloride ultrafiltration permeate and lithium chloride ultrafiltration concentrate, wherein the lithium chloride ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, and clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank and filter pressing residues are discharged out of the system.
S4, nanofiltration: the pH value of the ultrafiltration permeate is adjusted to 5.3 by dilute hydrochloric acid generated by bipolar membrane electrodialysis, and nanofiltration is carried out by an alkali-resistant nanofiltration membrane of 400 daltons, so that lithium chloride nanofiltration permeate and nanofiltration concentrate are respectively obtained; returning the lithium chloride nanofiltration concentrated solution to the chemical impurity removal reaction kettle in the step S2, and enabling nanofiltration permeate to enter an ion exchange system;
s5, ion exchange: the lithium chloride nanofiltration permeate liquid is subjected to ion exchange treatment sequentially through calcium and magnesium removal chelating resin and boron removal resin after the pH value of the lithium hydroxide permeate liquid is regulated to be 9.0, and finally lithium chloride purifying solution with Ca less than or equal to 0.02ppm, mg less than or equal to 0.01ppm, B less than or equal to 5ppm and Si less than or equal to 1ppm is obtained;
s6, the lithium chloride purifying solution enters bipolar membrane electrodialysis treatment to respectively obtain a lithium hydroxide solution with the concentration of 43.2g/L, a dilute hydrochloric acid solution with the concentration of 1.8mol/L and a dilute lithium chloride solution with the concentration of 3.5 g/L.
Returning the dilute hydrochloric acid solution to the step S1 to dissolve the industrial lithium carbonate;
the dilute lithium chloride solution is subjected to acid-resistant reverse osmosis treatment to obtain lithium chloride concentrated solution with the lithium concentration of 8.4g/L and lithium chloride permeate with the lithium concentration of 0.8g/L, and the lithium chloride concentrated solution and the lithium chloride purifying solution are mixed to serve as raw material liquid of bipolar membrane electrodialysis to enter a salt circulation tank; the lithium chloride permeate enters an acid circulation tank;
s7, homogeneous membrane electrodialysis: concentrating the lithium hydroxide solution obtained in the step S6 through homogeneous membrane electrodialysis to obtain a lithium hydroxide concentrated solution with the concentration of 84g/L and a lithium hydroxide dilute solution with the concentration of 18.3g/L, wherein the lithium hydroxide dilute solution returns to the alkali circulation tank of the bipolar membrane electrodialysis in the step S6 and is used as a receiving solution of lithium hydroxide generated by the bipolar membrane;
s8, carbonizing: adding the lithium hydroxide concentrated solution with the concentration of 84g/L obtained in the step S7 into a carbonization reaction kettle, heating to 58 ℃, adding lithium carbonate seed crystals with the mass of 5wt.% of generated lithium carbonate, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry; the reaction temperature was controlled at 58℃by cooling water, and the hydroxyl concentration in the reaction system was maintained at 23g/L.
S9, centrifugal separation and drying: and (3) carrying out centrifugal dehydration and washing on the lithium carbonate slurry to obtain a lithium carbonate wet material and a centrifugal mother solution. And drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
S10, after the centrifugal mother liquor is subjected to alkali-resistant nanofiltration treatment with the interception molecular weight of 200 daltons, the obtained lithium hydroxide concentrated water is returned to the chemical impurity removal step S2, and the alkali-resistant nanofiltration permeate is returned to an alkali circulation tank of bipolar membrane electrodialysis for recycling.
Example 3
The embodiment discloses a method for preparing high-purity lithium carbonate from industrial grade lithium carbonate, which specifically comprises the following steps:
s1, dissolving: 160kg of technical grade lithium carbonate with a main content of 98.0wt.% was added to a 3000L reactor, and 1.5mol/L dilute hydrochloric acid was slowly added to the reactor to react to form a lithium chloride solution with a lithium concentration of 12 g/L.
S2, chemical impurity removal: heating the lithium chloride solution to 50 ℃, sequentially adding oxalic acid and lithium hydroxide solution for reaction for 60 minutes, and controlling the reaction end point to control C (C) 2 O 4 2- )2.4g/L，c(OH - )2.8g/L。
S3, ultrafiltration: ultrafiltering the lithium chloride solution with the chemical impurity removed by an ultrafiltration membrane with the aperture of 0.2um to obtain lithium chloride ultrafiltration permeate and lithium chloride ultrafiltration concentrate, wherein the lithium chloride ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, and clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank and filter pressing residues are discharged out of the system.
S4, nanofiltration: the pH value of the ultrafiltration permeate is adjusted to 6.5 by dilute hydrochloric acid generated by bipolar membrane electrodialysis, and nanofiltration is carried out by an alkali-resistant nanofiltration membrane of 1000 daltons, so that lithium chloride nanofiltration permeate and nanofiltration concentrate are respectively obtained; the nanofiltration concentrated solution returns to the chemical impurity removal reaction kettle in the step S2, and the lithium chloride nanofiltration permeate enters an ion exchange system;
s5, ion exchange: the lithium chloride nanofiltration permeate liquid adopts lithium hydroxide solution to adjust pH=9.3, and then sequentially passes through calcium and magnesium removing chelating resin and boron removing resin to carry out ion exchange treatment, and finally lithium chloride purifying solution with Ca less than or equal to 0.02ppm, mg less than or equal to 0.01ppm, B less than or equal to 5ppm and Si less than or equal to 1ppm is obtained;
s6, the lithium chloride purifying solution enters bipolar membrane electrodialysis treatment to respectively obtain a lithium hydroxide solution with the concentration of 50g/L, a dilute hydrochloric acid solution with the concentration of 2mol/L and a dilute lithium chloride solution with the concentration of 3.0 g/L.
Returning the dilute hydrochloric acid solution to the step S1 to dissolve the industrial lithium carbonate;
the dilute lithium chloride solution is subjected to acid-resistant reverse osmosis treatment to obtain lithium chloride concentrated solution with the lithium concentration of 7.0g/L and lithium chloride permeate with the lithium concentration of 0.6g/L, and the lithium chloride concentrated solution and the lithium chloride purifying solution are mixed to serve as raw material liquid of bipolar membrane electrodialysis to enter a salt circulation tank; the lithium chloride permeate enters an acid circulation tank;
s7, homogeneous membrane electrodialysis: concentrating the lithium hydroxide solution obtained in the step S6 through homogeneous membrane electrodialysis to obtain a lithium hydroxide concentrated solution with the concentration of 96g/L and a lithium hydroxide dilute solution with the concentration of 20g/L, wherein the lithium hydroxide dilute solution returns to an alkali circulation tank of the bipolar membrane electrodialysis S6 and is used as a receiving solution of lithium hydroxide generated by the bipolar membrane;
s8, carbonizing: adding the lithium hydroxide concentrated solution with the concentration of 96g/L obtained in the step S7 into a carbonization reaction kettle, heating to 58 ℃, adding lithium carbonate seed crystals with the mass of 5wt.% of generated lithium carbonate, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry; the reaction temperature was controlled at 60℃by cooling water, and the hydroxyl concentration in the reaction system was maintained at 28g/L.
S9, centrifugal separation and drying: and (3) carrying out centrifugal dehydration and washing on the lithium carbonate slurry to obtain a lithium carbonate wet material and a centrifugal mother solution. And drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
S10, after the centrifugal mother liquor is subjected to alkali-resistant nanofiltration treatment with the interception molecular weight of 100 daltons, the obtained lithium hydroxide concentrated water is returned to the chemical impurity removal step S2, and the alkali-resistant nanofiltration permeate is returned to an alkali circulation tank of bipolar membrane electrodialysis for recycling.
Test example 1
Sample detection analysis was performed on the high-purity lithium carbonate obtained in examples 1 to 3, respectively, and the detection results were as follows:
TABLE 1 Table of the results of the detection of high purity lithium carbonate prepared in examples 1-3
The percentages in the above tables represent mass percentages.
As is clear from the above table, lithium carbonate with a purity of more than 99.99% can be obtained by the method of the present invention.
Comparative example 1
The comparative example is that industrial grade lithium carbonate reacts with water and carbon dioxide to form a soluble lithium bicarbonate solution, insoluble matters are removed through filtration, and divalent metal ions are removed by adopting chelate resin to obtain a pure lithium bicarbonate solution, and the lithium bicarbonate solution is heated to decompose and separate out lithium carbonate. The method comprises the following specific steps:
105kg of industrial grade lithium carbonate with the main content of 98.0wt.% and 2500L of pure water are added into a 3000L reaction kettle, carbon dioxide is introduced to react for 2 hours to make the solution clear, the solution is subjected to plate-frame filter pressing in sequence, precise filtration with the filter precision of 0.2um is carried out, and then the solution enters a chelating resin tower to remove calcium, magnesium and boron to obtain 2500L lithium bicarbonate purifying liquid with the lithium content of 7.5 g/L.
Transferring the lithium bicarbonate purifying liquid into a stainless steel reaction kettle, starting stirring, heating to 90-95 ℃ to thermally decompose and separate out lithium carbonate, and releasing carbon dioxide.
And (3) centrifugally separating, washing to obtain a wet lithium carbonate material, and drying to obtain a lithium carbonate product. A pyrolysis mother liquor having a lithium content of 2.3g/L was obtained.
The content of lithium carbonate obtained in this comparative example is shown in table 2.
TABLE 2
The foregoing description of the preferred embodiment of the invention is merely illustrative of the invention and is not intended to limit the scope of the invention. Various modifications and improvements of the technical scheme of the present invention will fall within the protection scope of the present invention as defined in the claims without departing from the design spirit of the present invention.
Claims (10)
1. The method for preparing the high-purity lithium carbonate from the industrial-grade lithium carbonate is characterized by comprising the following steps of:
s1, dissolving: reacting industrial grade lithium carbonate with a hydrochloric acid solution to generate a lithium chloride solution;
s2, chemical impurity removal: heating the lithium chloride solution obtained in the step S1, sequentially adding oxalic acid and lithium hydroxide solution for reaction, and performing chemical impurity removal;
s3, ultrafiltration: ultrafiltering the lithium chloride solution subjected to the chemical impurity removal treatment in the step S2 to obtain lithium chloride ultrafiltrate and ultrafiltrate concentrate;
s4, nanofiltration: carrying out nanofiltration treatment on the ultrafiltration permeate obtained in the step S3 to obtain lithium chloride nanofiltration permeate and nanofiltration concentrate respectively;
s5, ion exchange: treating the lithium chloride nanofiltration permeate obtained in the step S4 by using ion exchange resin to obtain a lithium chloride purifying solution;
s6, bipolar membrane electrodialysis: carrying out bipolar membrane electrodialysis on the lithium chloride purifying solution obtained in the step S5 to respectively obtain a lithium hydroxide solution, a dilute hydrochloric acid solution and a dilute lithium chloride solution;
s7, homogeneous membrane electrodialysis: the lithium hydroxide solution obtained in the step S6 is subjected to homogeneous membrane electrodialysis to obtain lithium hydroxide concentrated solution and lithium hydroxide dilute solution,
s8, carbonizing: adding lithium hydroxide concentrated solution obtained in the step S7 into lithium carbonate seed crystal, and introducing carbon dioxide gas for reaction to generate lithium carbonate slurry;
s9, centrifugal separation and drying: carrying out centrifugal dehydration and washing on the lithium carbonate slurry prepared in the step S8 to obtain a lithium carbonate wet material and a centrifugal mother solution; and drying the wet lithium carbonate material to obtain a high-purity lithium carbonate finished product.
2. The method for preparing high-purity lithium carbonate from technical grade lithium carbonate according to claim 1, wherein the lithium concentration in the lithium chloride solution generated in S1 is 11-16g/L;
preferably, the concentration of the hydrochloric acid solution in step S1 is 1.5 to 2mol/L.
3. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein in S2, the lithium chloride solution is heated to 40-60 ℃;
preferably, C (C 2 O 4 2- )1.5～2.5g/L，c(OH - )1～3g/L；
Preferably, in the step S2, lithium hydroxide solution produced by bipolar membrane electrodialysis is added for chemical impurity removal.
4. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein in S3, the pore diameter of the ultrafiltration membrane is 0.02-0.2 um;
preferably, the ultrafiltration concentrate enters a plate-and-frame filter press for filter pressing, clear liquid obtained by filter pressing returns to an ultrafiltration raw material tank, and plate-and-frame filter pressing residues are discharged out of the system.
5. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein in S4, the nanofiltration concentrate is returned to step S2 for chemical impurity removal again;
preferably, the ultrafiltration permeate is subjected to nanofiltration after the pH value of the ultrafiltration permeate is adjusted to 4 to 7.
6. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein in S5, ca is less than or equal to 0.02ppm, mg is less than or equal to 0.01ppm, B is less than or equal to 5ppm and Si is less than or equal to 1ppm in the lithium chloride purification solution;
preferably, the ion exchange resin consists of a calcium and magnesium-depleted chelating resin and a boron-depleted chelating resin; the ion exchange process is to remove Ca and Mg and then B.
Preferably, the pH value of the lithium chloride nanofiltration permeate is adjusted to be 8.5-9.5, and then the lithium chloride nanofiltration permeate enters the ion exchange resin; more preferably, the ph=8.5 to 9.5 of the lithium chloride nanofiltration permeate is adjusted by using a lithium hydroxide solution produced by a bipolar membrane.
7. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein the concentration of the lithium hydroxide solution obtained in S6 is 36-50 g/L; the concentration of the dilute hydrochloric acid solution is 1.5-2 mol/L, and the concentration of lithium in the dilute lithium chloride solution is 3-5 g/L;
preferably, the dilute hydrochloric acid solution is returned to the step S1 for use;
preferably, the dilute lithium chloride solution is subjected to acid-resistant reverse osmosis treatment to obtain a lithium chloride concentrated solution and a lithium chloride permeate, and more preferably, the lithium concentration in the lithium chloride concentrated solution is 6-10 g/L, and the lithium concentration in the lithium chloride permeate is 0.6-1 g/L; more preferably, the lithium chloride concentrate is returned to step S6 and mixed with the lithium chloride purification solution as a raw material solution for bipolar membrane electrodialysis; more preferably, the lithium chloride permeate serves as a receiver for dilute hydrochloric acid produced by bipolar membrane electrodialysis.
8. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein the concentration of the lithium hydroxide concentrate obtained in S7 is 75-96 g/L;
preferably, the concentration of the lithium hydroxide dilute solution obtained in the step S7 is 10-20 g/L;
preferably, the lithium hydroxide dilute solution obtained in the step S7 is returned to the alkali circulation tank of the bipolar membrane electrodialysis in the step S6 to be used as a receiving solution of lithium hydroxide generated by the bipolar membrane electrodialysis.
9. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein in S8, the lithium hydroxide concentrate is heated to 50-60 ℃, and then high-purity lithium carbonate is added as seed crystal;
preferably, the carbon dioxide comprises carbon dioxide produced in step S1;
preferably, in the step S8, during the carbonization reaction, the reaction temperature is controlled to be 50-60 ℃;
preferably, the adding speed of lithium hydroxide and carbon dioxide is controlled, and the concentration of hydroxyl in a reaction system is maintained to be 15-30 g/L;
preferably, the seed crystal is added in an amount of 1 to 10% by mass of the lithium carbonate.
10. The method for preparing high-purity lithium carbonate from industrial grade lithium carbonate according to claim 1 or 2, wherein the centrifugal mother liquor obtained in step S9 is subjected to nanofiltration treatment to obtain centrifugal mother liquor nanofiltration concentrate and centrifugal mother liquor nanofiltration permeate respectively;
preferably, the concentrated water obtained by nanofiltration of the centrifugal mother liquor is returned to the step S2 to replace part or all of lithium hydroxide for removing impurities of lithium chloride;
preferably, the alkali circulation tank of bipolar membrane electrodialysis in the step S6 of nanofiltration permeate of the centrifugal mother liquor is used as a receiving solution of lithium hydroxide generated by bipolar membrane electrodialysis;
preferably, the nanofiltration membrane used for centrifuging the mother liquor is an alkali-resistant nanofiltration membrane, and the interception molecular weight of the membrane is 100-1000 daltons.
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