A method for preparing high-purity lithium carbonate from an acidic lithium-containing solution

Abstract

The present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, wherein the method is sequentially subjected to resin neutralization treatment, dropwise addition to alkali liquor depth purification and resin neutralization treatment, precipitated lithium carbonate and resin neutralization treatment to obtain lithium carbonate, lithium carbonate is sequentially subjected to carbon dioxide nano-microbubble and filler reactor enhanced carbonization, resin further purification, slurry internal circulation defoaming and additive enhanced pyrolysis, and high-purity lithium carbonate is obtained through repeated carbonization, impurity removal and pyrolysis. The high-purity lithium carbonate purity obtained by the process of the present invention can reach more than 99.9-99.999%, and the recovery rate of lithium in the process reaches more than 90%. The method of the present invention has a small amount of acid and alkali reagents, a high impurity removal efficiency, a small loss of lithium bands, a high lithium carbonate carbonization efficiency, a short carbonization time, and a safe, stable and efficient lithium bicarbonate solution pyrolysis process, with good industrial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical metallurgy and relates to a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. Background Art

[0002] Lithium is a chemically active element, found primarily in salt lake brines, seawater, lepidolite, and spodumene. Salt lake brines are the most abundant, accounting for over 69% of global lithium reserves. Among my country's identified lithium mineral reserves, the ratio of salt lake brines to ore is approximately 7:3, with salt lake brines accounting for 10.78 million tons of lithium reserves, compared to only 2.3 million tons of ore. While lithium extraction from salt lake brines is environmentally friendly, it has not been widely developed due to process and cost constraints. Lithium extraction from ore has become more mature after over a century of development, and currently 78% of my country's lithium production comes from lithium ore.

[0003] Lithium ore is often extracted by acid method, so the lithium ore extraction industry produces a large amount of acidic lithium-containing solution. Before using this solution to prepare products such as lithium carbonate, it is necessary to add alkali to neutralize and remove impurities. The alkaline lithium precipitation mother liquor obtained by lithium precipitation needs to be neutralized with acid again. CN102765734A discloses a method for extracting lithium from spodumene to prepare lithium salts, which is carried out by transformation roasting, cooling ball milling, acid roasting, adding limestone slurry for neutralization, mixing transformation, filtering and washing, deep impurity removal, adding hydrochloric acid for neutralization, cooling and sodium precipitation, concentration crystallization and separation and drying to obtain anhydrous lithium salt products. CN101736169A discloses a method for extracting lithium from lepidolite, which is subjected to defluorination-sulfuric acid pressure leaching-adding alkali to remove impurities-hot sodium precipitation-cold potassium precipitation-lithium carbonate precipitation, and the lithium precipitation mother liquor is reused after adding hydrochloric acid to neutralize carbonate. The current method for treating acidic lithium-containing solutions causes a large amount of waste of acid and alkali.

[0004] The impurity removal process of an acidic lithium-containing solution uses an alkaline substance to adjust the pH value, thereby precipitating and separating impurities such as calcium, magnesium, iron, and aluminum. CN107098365A discloses a method for extracting lithium carbonate from lepidolite ore. Calcium hydroxide is added to the acidic lithium-containing solution to adjust the pH to 11-12, thereby removing fluorine, calcium, magnesium, and aluminum ions from the solution. CN104071811A discloses a process for extracting lithium salts by sulfuric acid pressure boiling of spodumene. Lime is added to the acidic lithium-containing solution to neutralize and remove sulfate, aluminum, and iron ions, and slaked lime is added to remove magnesium ions. The impurity removal process requires a large amount of alkali, resulting in poor impurity removal effect, high cost, and low overall lithium recovery.

[0005] In order to obtain high-purity lithium carbonate, CN103539169A proposes a method for preparing battery-grade lithium carbonate or high-purity lithium carbonate using industrial-grade lithium carbonate, first carbonizing industrial-grade lithium carbonate with carbon dioxide, then removing calcium and magnesium through ion exchange, and finally obtaining battery-grade or high-purity lithium carbonate through pyrolysis. In order to improve the process reaction efficiency, CN111439761A discloses a method for preparing high-purity lithium carbonate by continuous carbonization and decomposition, which improves the carbonization efficiency by multi-stage countercurrent carbonization, and CN115893454A discloses a method for efficiently producing ultrapure lithium carbonate with uniform and stable particle size, which changes single-tube steam heating to uniform heating of steam holes evenly distributed on stirring blades, thereby improving pyrolysis efficiency. The current carbonization pyrolysis process still has the problems of high cost and low efficiency.

[0006] In summary, it is urgent to develop a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution with low reagent usage, high lithium recovery rate, low cost and low energy consumption. Summary of the Invention

[0007] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method adopts anion exchange resin acidic lithium-containing solution and impurity removal liquid, lithium precipitation mother liquor acid anions and alkaline anions technology, and carbon dioxide adsorption filler enhanced lithium carbonate carbonization technology. The method uses a small amount of acid and alkali reagents, has high impurity removal efficiency, and less lithium band loss. It also has high lithium carbonate carbonization efficiency and short carbonization time. The method is safe, stable, and efficient, and has good industrial application prospects.

[0008] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0009] To achieve the above technical effects, the present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0010] (1) using an anion exchange resin to adsorb the acidic lithium-containing solution to obtain an adsorbed anion exchange resin and an adsorbed lithium-containing solution;

[0011] (2) mixing the lithium-containing solution after adsorption in step (1) with an alkaline solution, and performing solid-liquid separation to obtain a decontamination liquid and decontamination residue;

[0012] (3) The impurity-removed liquid of step (2) is treated with the adsorbed anion exchange resin of step (1), and then a carbon source is added to precipitate lithium, and solid-liquid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0013] (4) slurrying the lithium carbonate in step (3) and introducing carbon dioxide to carry out carbonization reaction, and separating the solid and liquid to obtain carbonized liquid and carbonized slag;

[0014] (5) After the carbonized liquid in step (4) is purified, a pyrolysis reaction is performed to obtain lithium carbonate and a mother liquor, and the mother liquor is recycled to step (4) for slurrying.

[0015] As a preferred technical solution of the present invention, the pH of the lithium-containing solution after adsorption in step (1) is 3-10, such as 3, 4, 4.5, 5, 5.5, 5.9, 6, 6.2, 6.5, 7, 8, 9 or 10, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably pH=4~7.

[0016] As a preferred technical solution of the present invention, the lithium-containing solution after adsorption in step (1) is added dropwise to the alkaline solution for mixing.

[0017] Preferably, the concentration of the alkali solution is 7-75%, for example, 5%, 10%, 15%, 17%, 20%, 25%, 30%, 32.5%, 35%, 40%, 45%, 47%, 50%, 60%, 70% and 75%, but is not limited to the listed values. Other values not listed within this numerical range are also applicable, preferably 10-50%; the temperature of the alkali solution is 60-150°C, for example, 60°C, 70°C, 80°C, 85°C, 90°C, 95°C, 99°C, 100°C, 105°C, 110°C, 115°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values. Other values not listed within this numerical range are also applicable, preferably 80-120°C.

[0018] Preferably, the dropping time is 60-180 min, for example, 60 min, 75 min, 90 min, 100 min, 120 min, 135 min, 150 min or 180 min; the concentration of the alkali solution at the end of the dropping is 5-30%, for example, 5%, 7%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27%, 29% and 30%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0019] As a preferred technical solution of the present invention, the pH of the solution after the impurity removal liquid treatment in step (3) is 7 to 14. For example, 7, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13 or 14, etc., but are not limited to the listed values. Other values not listed within the numerical range are also applicable. Preferably, the pH is 8 to 13.

[0020] As a preferred technical solution of the present invention, the carbon source in step (3) is sodium carbonate or carbon dioxide.

[0021] As a preferred technical solution of the present invention, the precipitation mother liquor of step (3) is treated with the anion exchange resin after adsorption in step (1) and then used in the leaching system, and the anion exchange resin is reused in step (1) for adsorption.

[0022] As a preferred technical solution of the present invention, the carbonization reaction in step (4) is carried out in a packing reactor;

[0023] Preferably, the filler is obtained by mixing porous inorganic powder, polymer plastic powder and organic amine;

[0024] Preferably, the porous inorganic powder is preferably a combination of one or at least two of activated carbon, molecular sieves, zeolites, hydrotalcite-like substances, bentonite, kaolin, montmorillonite or diatomaceous earth. Typical but non-limiting examples of the combination include: a combination of activated carbon and kaolin, a combination of molecular sieves, hydrotalcite-like substances and bentonite, a combination of activated carbon, kaolin, montmorillonite and diatomaceous earth, a combination of molecular sieves, bentonite, kaolin, montmorillonite and diatomaceous earth, a combination of activated carbon, zeolite, bentonite, kaolin, montmorillonite and diatomaceous earth, a combination of activated carbon, molecular sieves, zeolites, bentonite, kaolin, montmorillonite and diatomaceous earth, a combination of activated carbon, molecular sieves, zeolites, hydrotalcite-like substances, bentonite, kaolin, montmorillonite and diatomaceous earth, and the like.

[0025] Preferably, the polymer plastic powder is preferably a thermoplastic plastic powder, further preferably a combination of one or at least two of polyethylene, polypropylene, polybutene, polyvinyl chloride, polyvinylidene fluoride or polystyrene. Typical but non-limiting examples of the combination include: a combination of polyethylene and polyvinylidene fluoride, a combination of polyethylene, polybutene and polyvinyl chloride, a combination of polypropylene, polybutene, polyvinyl chloride and polyvinylidene fluoride, a combination of polyethylene, polypropylene, polybutene, polyvinyl chloride and polyvinylidene fluoride, a combination of polyethylene, polypropylene, polybutene, polyvinyl chloride, polyvinylidene fluoride and polystyrene, etc.

[0026] Preferably, the organic amine is preferably a combination of one or at least two of aliphatic amines, alcohol amines, amides, alicyclic amines, aromatic amines, and naphthyl amines. Typical but non-limiting examples of the combination include: a combination of aliphatic amines and amides, a combination of alcohol amines, amides and alicyclic amines, a combination of aliphatic amines, amides, alicyclic amines and aromatic amines, a combination of aliphatic amines, alcohol amines, amides, alicyclic amines and naphthyl amines, a combination of aliphatic amines, alcohol amines, amides, alicyclic amines, aromatic amines and naphthyl amines, and the like. More preferably, it is amides and / or alcoholamines, and most preferably, it is ethanolamine, propanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, formamide, acetamide, propionamide, butanamide, acrylamide, caprolactam, N,N-dimethylformamide, N,N-dimethylacetamide, or a combination of at least two thereof. Typical but non-limiting examples of the combination include: a combination of ethanolamine and propanolamine, a combination of ethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine and propionamide, a combination of ethanolamine, propanol ... , a combination of N-dimethylethanolamine, N,N-diethylethanolamine, formamide and N,N-dimethylacetamide, a combination of propanolamine, N,N-diethylethanolamine, formamide, acetamide, propionamide, butyramide, acrylamide, caprolactam and N,N-dimethylformamide, a combination of ethanolamine, propanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, formamide, acetamide, propionamide, butyramide, acrylamide, caprolactam, N,N-dimethylformamide and N,N-dimethylacetamide, etc.

[0027] Preferably, the mass ratio of the porous inorganic powder to the polymer plastic powder and the organic amine is (10-100):(10-100):(2-20), such as 10:10:2, 10:10:10, 10:10:20, 50:10:2, 50:10:10, 50:10:20, 100:10:2, 100:10:10, 100:10:20, 10:50:2, 10:50:10, 10:50:20, 50:50:2, 5 0:50:10, 50:50:20, 100:50:2, 100:50:10, 100:50:20, 10:100:2, 10:100:10, 10:100:20, 50:100:2, 50:100:10, 50:100:20, 100:100:2, 100:100:10 or 100:100:20, etc., but are not limited to the listed values, other values not listed within the numerical range are also applicable.

[0028] Preferably, the hybrid molding process is any one of injection molding, extrusion molding, thermoforming, casting molding, foaming molding, drop molding, compression molding, rotational molding or winding molding.

[0029] Preferably, the shaped filler is in any one of annular, hollow spherical, grid, corrugated, honeycomb, cotton or granular shapes.

[0030] Preferably, the filler filling rate in the packed reactor is 50-90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% and 90%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the purification treatment in step (5) is to adsorb the carbonized liquid through a cation exchange resin and / or a chelating resin.

[0032] As a preferred technical solution of the present invention, the pyrolysis reaction of the carbonized purified liquid in step (5) is carried out in a defoaming reactor, and high-purity lithium carbonate seeds are added before pyrolysis;

[0033] Preferably, the seed particle size distribution is D10: 1~3μm, D50: 3~8μm, D90: 9~15μm, such as D10: 1μm, D10: 1.02μm, D10: 1.5μm, D10: 2μm, D10: 2.5μm, D10: 3μm, D50: 3μm, D50: 4μm, D50: 5μm, D50: 6μm, D50: 7μm, D50: 8μm, D90: 9μm, D90: 10μm, D90: 11μm, D90: 12μm, D90: 13μm, D90: 14μm, D90: 15μm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0034] Preferably, the temperature of the pyrolysis reaction in step (5) is 90-120°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C; the time is 30-120 min, such as 30 min, 45 min, 60 min, 75 min, 80 min, 90 min, 100 min or 120 min, but is not limited to the listed values. Other values not listed within the above numerical ranges are also applicable.

[0035] As a preferred technical solution of the present invention, steps (4) and (5) are repeated to improve the purity of lithium carbonate.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) The present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, wherein the method adopts anion exchange resin acidic lithium-containing solution and impurity removal liquid, lithium precipitation mother liquor acid anion and alkaline anion technology, lithium solution is added dropwise to strong alkali hydrolysis to remove impurities technology, highly soluble nano carbon dioxide microbubbles and carbon dioxide adsorption fillers are used to enhance lithium carbonate carbonization technology, solution reactor internal circulation, carbon dioxide crushing and defoaming, additive-enhanced lithium bicarbonate pyrolysis technology, and high-purity lithium carbonate is obtained through multiple carbonization, impurity removal, and pyrolysis processes;

[0038] (2) The present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The purity of the high-purity lithium carbonate obtained by the method can reach 99.9-99.999% or more, and the lithium recovery rate in the process can reach more than 90%;

[0039] (3) The present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method effectively reduces the amount of acid and alkali reagents used to treat the lithium-containing acidic solution through repeated use of anion exchange resin; the deep purification and impurity removal process has high impurity removal efficiency and low lithium loss; the lithium carbonate carbonization method can greatly improve the lithium carbonate carbonization efficiency and shorten the carbonization reaction time; the lithium bicarbonate solution decomposition method can avoid the problems of bubbling, wall sticking and low decomposition efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic flow chart of a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution provided in a specific embodiment of the present invention.

[0041] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0043] A specific embodiment of the present invention provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0044] (1) using an anion exchange resin to adsorb the acidic lithium-containing solution to obtain an adsorbed anion exchange resin and an adsorbed lithium-containing solution;

[0045] (2) mixing the lithium-containing solution after adsorption in step (1) with an alkaline solution, and performing solid-liquid separation to obtain a decontamination liquid and decontamination residue;

[0046] (3) The impurity-removed liquid of step (2) is treated with the adsorbed anion exchange resin of step (1), and then a carbon source is added to precipitate lithium, and solid-liquid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0047] (4) slurrying the lithium carbonate in step (3) and introducing carbon dioxide to carry out carbonization reaction, and separating the solid and liquid to obtain carbonized liquid and carbonized slag;

[0048] (5) After the carbonized liquid in step (4) is purified, a pyrolysis reaction is performed to obtain lithium carbonate and a mother liquor, and the mother liquor is recycled to step (4) for slurrying.

[0049] In the present invention, anion exchange resin is used to repeatedly exchange alkaline anions with acid radical anions between an acidic lithium-containing solution and an alkaline solution such as a deep impurity removal solution or a lithium precipitation mother liquor. The alkaline anions in the alkaline solution are used to neutralize the acidic lithium-containing solution, while the acid radical ions in the acid solution replace the alkaline anions (equivalent to neutralizing the impurity removal solution and the lithium precipitation mother liquor). The repeated use of the anion exchange resin effectively reduces the amount of acid and base reagents used to treat the lithium-containing acidic solution. The lithium carbonate carbonization method can significantly improve the lithium carbonate carbonization efficiency and shorten the carbonization reaction time.

[0050] In the present invention, anion exchange resin is used to adsorb alkaline anions such as hydroxide and carbonate in the impurity removal liquid and lithium carbonate precipitation mother liquor onto the resin, and then the resin is used to treat the acidic lithium-containing solution, so that acid anions such as sulfate, chloride and nitrate are ion-exchanged with the alkaline anions on the resin, and the alkaline anions enter the acidic lithium-containing solution, thereby realizing the use of alkaline anions in the impurity removal liquid and lithium carbonate precipitation mother liquor to neutralize the acidic lithium-containing solution, thereby reducing or avoiding the problem of consuming additional alkaline reagents in conventional acidic lithium-containing solutions; at the same time, sulfate, chloride and nitrate anions are used to neutralize the acidic lithium-containing solution. Ions and acid anions such as nitrates are exchanged with alkaline anions such as hydroxide and carbonate in the impurity removal liquid and lithium carbonate precipitation mother liquor, and the acid anions enter the impurity removal liquid and lithium carbonate precipitation mother liquor, thereby achieving the effect of neutralizing the impurity removal liquid and lithium carbonate precipitation mother liquor, thereby reducing or avoiding the problem of acid reagent consumption in conventional lithium carbonate precipitation mother liquor; in this process, the resin repeatedly exchanges alkaline anions such as hydroxide and carbonate with acid anions such as sulfate, chloride and nitrate, greatly reducing the amount of acid and alkali reagents used in treating lithium-containing acidic solutions.

[0051] In a specific embodiment of the present invention, the lithium concentration in the acidic lithium-containing solution is 1 to 45 g / L, for example, 1 g / L, 3 g / L, 5 g / L, 7 g / L, 9 g / L, 10 g / L, 12.5 g / L, 15 g / L, 17 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L or 45 g / L, but is not limited to the listed values. Other values not listed within this numerical range are also applicable, preferably 3 to 20 g / L.

[0052] In the present invention, the acidic lithium-containing solution can be an acidic lithium extraction solution or lithium-containing acidic wastewater in the lithium salt production industry. When the lithium concentration in the acidic lithium-containing solution is lower than 1 g / L, the acidic lithium-containing solution can be concentrated to reach the target lithium concentration range.

[0053] In a specific embodiment of the present invention, if the salt concentration of the impurity removal liquid is high after being treated with anion exchange resin, the present invention also includes recovering the salt by any one of the existing evaporation crystallization, cooling crystallization and evaporation-cooling crystallization processes.

[0054] In a specific embodiment of the present invention, the alkali solution in step (2) is an alkaline inorganic solution, and the alkaline inorganic substance is any one or a combination of at least two of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia water, calcium oxide and calcium hydroxide. Typical but non-limiting examples of the combination include: a combination of lithium hydroxide and sodium hydroxide, a combination of potassium hydroxide and calcium oxide, a combination of sodium hydroxide, potassium hydroxide and ammonia water, a combination of lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, a combination of lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia water, calcium oxide and calcium hydroxide, etc., more preferably sodium hydroxide and / or potassium hydroxide.

[0055] In the present invention, a lithium-containing solution is added dropwise to an alkaline solution, and the temperature, addition time, and concentration of the alkaline solution at the end of the addition are controlled. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to remove common divalent and higher metal impurities in the acidic lithium-containing solution, such as common calcium, magnesium, aluminum, iron, etc. Under conditions of a higher alkaline solution temperature and a higher alkaline solution concentration at the end of the addition, liquid-solid separation is immediately performed after the addition is completed within a certain period of time. Under synergistic effects, the rapid hydrolysis of divalent and higher metals can be promoted, and the hydrolysis precipitation rate is extremely high. Surprisingly, the hydrolysis product has a poor adsorption effect on alkali metals, and the alkali metals, including lithium, are less damaged. Therefore, the impurity removal method of the present invention has high impurity removal efficiency and low lithium damage.

[0056] In the present invention, the anion exchange resin is cleverly repeatedly used to interchange alkaline anions and acid radical anions in the acid leaching solution, the impurity removal solution, and the lithium precipitation mother liquor alkali solution. The present invention can use a higher alkali solution concentration for impurity removal, thereby solving the problem of increased acid usage.

[0057] In a specific embodiment of the present invention, when the carbon source in step (3) is sodium carbonate, the molar ratio of sodium carbonate to lithium in the treated solution is (1-5):1, for example, 1:1, 1.1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.75:1, 3:1, 3.5:1, 4:1, 4.25:1, 4.5:1 or 5:1, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0058] In one embodiment of the present invention, when the carbon source in step (3) is carbon dioxide, the endpoint pH of the carbon dioxide solution is 10-12, for example, 10, 10.05, 10.3, 10.5, 10.7, 11, 11.2, 11.4, 11.5, 11.7, 11.9 or 12, etc., but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0059] In a specific embodiment of the present invention, the temperature of the lithium precipitation in step (3) is 60-100°C, such as 60°C, 65°C, 68°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 98°C, 99°C or 100°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0060] In a specific embodiment of the present invention, the lithium precipitation time in step (3) is 30 to 300 min, such as 30 min, 60 min, 90 min, 100 min, 120 min, 150 min, 180 min, 200 min, 240 min or 300 min, but is not limited to the listed values. Other values not listed within the above numerical ranges are also applicable.

[0061] In one embodiment of the present invention, the pH value of the solution of the precipitated mother liquor in step (3) after being treated with the post-adsorption anion exchange resin in step (1) is 7 to 13, for example, 7, 7.5, 7.9, 8, 8.5, 9, 9.5, 10, 10.5, 11, 12, 12.5 or 13, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably pH = 8 to 10.

[0062] In the present invention, if the salt concentration of the precipitation mother liquor is high after being treated with anion exchange resin, the present invention also includes recovering the salt by any one of the existing evaporative crystallization, cooling crystallization and evaporative-cooling crystallization processes.

[0063] In a specific embodiment of the present invention, the liquid-to-solid ratio of the lithium carbonate slurry prepared in step (4) is (15-40):1, for example, 15:1, 17:1, 20:1, 22.5:1, 25:1, 30:1, 32.5:1, 35:1 or 40:1, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0064] In one embodiment of the present invention, the carbon dioxide in step (4) is introduced from the bottom of the slurry in the form of nanoporous aeration.

[0065] In a specific embodiment of the present invention, the carbon dioxide gas pressure in step (4) is 0.01-1 MPa, for example, 0.01 MPa, 0.05 MPa, 0.075:1 MPa, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.5 MPa, 0.75 MPa, 0.9 MPa or 1 MPa, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 0.05-0.5 MPa.

[0066] In a specific embodiment of the present invention, the carbonization reaction temperature in step (4) is 20-35°C, for example, 20°C, 22°C, 25°C, 27.5°C, 29°C, 30°C, 32.5°C or 35°C, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0067] In a specific embodiment of the present invention, the carbonization reaction time in step (4) is 10-100 min, for example, 10 min, 15 min, 20 min, 25 min, 28 min, 30 min, 45 min, 50 min, 60 min, 70 min, 80 min, 90 min or 100 min, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 15-45 min.

[0068] In one embodiment of the present invention, the carbon dioxide overflowed from the carbonization reaction in step (4) is pressurized and then recycled to step (4).

[0069] In the present invention, in a homemade porous inorganic powder and polymer plastic powder, organic amine mixed molding filler reactor, carbon dioxide is introduced from the bottom of the lithium carbonate slurry to carbonize, and by controlling carbon dioxide partial pressure and carbonization temperature, liquid-solid ratio, the carbonization reaction time can be significantly reduced. The reason for reducing the carbonization reaction time: first, the filler of the mixed molding of porous inorganic powder and polymer plastic powder, organic amine has the function of adsorbing nano-micro bubble carbon dioxide under the effects of suitable proportioning, mixed molding process, filler shape and filler filling rate in the reactor, which can extend the reaction residence time of carbon dioxide and lithium carbonate slurry. Secondly, the nano carbon dioxide bubbles produced by nano-micropore aeration increase in solubility in water, further extending the reaction residence time of carbon dioxide and lithium carbonate slurry. The lithium carbonate carbonization method of the present invention can significantly improve lithium carbonate carbonization efficiency and shorten the carbonization reaction time.

[0070] In the present invention, cation exchange resin and / or chelating resin are used to further purify divalent and higher metal ions in the carbonized liquid.

[0071] In a specific embodiment of the present invention, the amount of seed crystal added in step (5) is 0.1-2% of the mass of the carbonization purification liquid, for example, 0.1%, 0.125%, 0.3%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75% and 2%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0072] In one embodiment of the present invention, the pyrolysis in step (5) is heated by introducing steam into the bottom of the reactor, and a demister is installed on the top of the reactor.

[0073] In one embodiment of the present invention, when the carbonized purified liquid is heated to a temperature lower than 70°C in step (5), the purified liquid in the lower portion of the reactor is circulated from the top of the reactor into the reactor via a pump. When the carbonized purified liquid is heated to a temperature higher than 70°C, the purified liquid in the lower portion of the reactor is circulated from the middle portion of the reactor into the reactor via a pump.

[0074] In one embodiment of the present invention, the carbon dioxide overflowed from the pyrolysis in step (5) is pressurized and then recycled to step (4).

[0075] In the present invention, the pyrolysis process first introduces steam into the bottom of the reactor for heating. When the temperature of the carbonized purified liquid is less than 70°C, the carbonized purified liquid at the bottom of the reactor is circulated from the top of the reactor to the reactor via a pump. The circulated solution causes the carbonized purified liquid to heat up quickly and evenly. When the carbonized purified liquid flows downward from the top of the reactor and passes through the demister on the upper part of the reactor, large bubbles of carbon dioxide are broken, which can promote the rapid overflow of carbon dioxide from the reactor, thereby accelerating the decomposition of lithium bicarbonate in the solution. Then, when the temperature of the carbonized purified liquid reaches above 70°C, the lithium bicarbonate in the solution is decomposed. Due to the temperature rising decomposition speed is accelerated, carbon dioxide production increases rapidly, along with the reactor bottom slurry is transferred to the reactor by the reactor middle part circulation through pump, a large amount of carbon dioxide bubbles can be broken and quickly overflowed from the reactor middle part upwards through the upper part demister of the reactor, now due to the addition of small particle crystal seeds, lithium bicarbonate is quickly and evenly decomposed to generate high-purity lithium carbonate in the crystal seed surface induction slurry, due to the slurry being transferred to by the reactor middle part circulation so that the slurry heating process is uniform, there is no explosive generation of high-purity lithium carbonate, whole decomposition process is controllable, and lithium bicarbonate decomposition efficiency is high. Adopting the decomposition method of lithium bicarbonate of the present invention, the risk of lithium bicarbonate bursting out and decomposing and causing venting groove can be avoided, while solving the problem of lithium carbonate sticking to the wall and decomposition efficiency being low caused by uneven heating.

[0076] In the present invention, the carbon dioxide overflowed from the carbonization process and the decomposition process can be recycled and used in the carbonization process after being pressurized, thereby increasing the utilization rate of the carbon dioxide in the present invention.

[0077] In one embodiment of the present invention, steps (4) and (5) are repeated to improve the purity of lithium carbonate, preferably 1-5 times, for example 1 time, 2 times, 3 times, 4 times, 5 times, more preferably 2-4 times.

[0078] In the present invention, the carbonization, impurity removal and pyrolysis operations are repeated multiple times in order to obtain high-purity lithium carbonate of different purities, such as 99.9%, 99.95%, 99.99%, 99.999% and the like.

[0079] In the present invention, the lithium carbonate, impurity-removing residues, resin and other solids all include a washing operation with pure water, and the washing liquid is combined with the filtrate or effluent. The final lithium carbonate product also includes a drying operation.

[0080] In the present invention, a lithium-containing solution is added dropwise to an alkaline solution, and the temperature of the alkaline solution, the addition time, and the concentration of the alkaline solution at the end of the addition are controlled. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to deeply remove divalent and higher metal impurities commonly found in the acidic lithium-containing solution. In a self-made porous inorganic powder, polymer plastic powder, and organic amine mixed molded filler reactor, carbon dioxide is introduced from the bottom of the lithium carbonate slurry using nano-microporous aeration to carbonize it. During the pyrolysis process, steam is introduced into the bottom of the reactor for heating. Depending on the heating conditions, the carbonized purified liquid in the lower part of the reactor is circulated into the reactor from the top or middle of the reactor via a pump. The carbon dioxide overflows the reactor through the demister, and high-purity lithium carbonate is added to promote the decomposition of lithium bicarbonate. The lithium carbonate undergoes multiple carbonization, resin adsorption, and pyrolysis to obtain high-purity lithium carbonate. The present invention can significantly improve the carbonization efficiency of lithium carbonate and shorten the carbonization reaction time through the acid lithium carbonization method; the lithium bicarbonate solution decomposition method can avoid the problems of bubbling, wall adhesion, and low decomposition efficiency.

[0081] In one embodiment of the present invention, the method for preparing high-purity lithium carbonate from the acidic lithium-containing solution comprises the following steps:

[0082] (1) using an anion exchange resin to adsorb lithium-containing acidic leachate and / or lithium-containing acidic wastewater having a lithium concentration of 1-45 g / L, to obtain an adsorbed anion exchange resin and an adsorbed lithium-containing solution having a pH of 3-10;

[0083] (2) adding the lithium-containing solution after adsorption in step (1) dropwise into an alkaline solution with a concentration of 7-75% and an alkaline solution temperature of 60-150°C for 60-180 min to obtain a slurry with an alkaline solution concentration of 5-30%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0084] (3) The impurity removal liquid of step (2) is treated with an anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 7-14, and sodium carbonate or carbon dioxide is added to precipitate lithium at a temperature of 60-100°C and a precipitation time of 30-300 min, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1); when the carbon source is sodium carbonate, the molar ratio of sodium carbonate to lithium in the treated solution is (1-5):1; when the carbon source is carbon dioxide, the end point pH of the carbon dioxide solution is 10-12;

[0085] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 7-13, the treated precipitation mother liquor is reused in the leaching system, and the treated anion exchange resin is reused in step (1);

[0086] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of (15-40):1 and 0.01-1 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized at a reaction temperature of 20-35°C and a reaction time of 10-100 min in a 50-90% filling rate filling reactor formed by mixing porous inorganic powder, polymer plastic powder and organic amine in a mass ratio of (10-100):(10-100):(2-20). The carbonized liquid and solid are separated to obtain carbonized liquid and carbonized slag, which is then recycled to the leaching system; the carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (5);

[0087] (5) The carbonized liquid of step (4) is purified by a cation exchange resin and / or a chelating resin to obtain a carbonized purified liquid; 0.1-2% by weight of the obtained carbonized purified liquid and high-purity lithium carbonate seeds with a particle size distribution of D10: 1-3 μm, D50: 3-8 μm, and D90: 9-15 μm are added, steam is introduced into the bottom of the reactor for heating at a temperature of 90-120° C. and a holding time of 30-120 min to perform pyrolysis to obtain lithium carbonate and mother liquor, which is recycled for carbonization in step (5); a demister is provided at the top of the reactor; when the heating temperature of the carbonized purified liquid is less than 70° C., the purified liquid at the bottom of the reactor is circulated from the top of the reactor into the reactor via a pump; when the heating temperature of the carbonized purified liquid reaches above 70° C., the purified liquid at the bottom of the reactor is circulated from the middle of the reactor into the reactor via a pump; the carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (5);

[0088] Repeat steps (4) and (5) 1-5 times to obtain high-purity lithium carbonate.

[0089] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0090] Example 1:

[0091] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The process flow chart of the method is as follows: Figure 1 As shown, the following steps are included:

[0092] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution having a lithium concentration of 8.85 g / L, thereby obtaining an anion exchange resin after adsorption and a lithium-containing solution after adsorption having a pH of 4;

[0093] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 60% sodium hydroxide alkaline solution at 100° C. for 120 minutes to obtain a slurry with an alkaline concentration of 20%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0094] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to a pH of 8, sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 2:1, lithium is precipitated at a temperature of 70°C and a time of 60 minutes, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0095] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 8, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0096] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 30:1 and 0.1 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is mixed and injection-molded in an 80% filling rate annular packing reactor with porous inorganic powder (activated carbon, zeolite and diatomaceous earth) and polymer plastic powder (polyvinyl chloride, polyvinylidene chloride and polystyrene) and organic amine (amides and aromatic amines) in a mass ratio of 50:100:10, and carbonized at a reaction temperature of 30°C and a reaction time of 45 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0097] (5) The carbonized liquid of step (4) is purified by a cation exchange resin and a chelating resin to obtain a carbonized purified liquid; 0.4% by weight of the obtained carbonized purified liquid and high-purity lithium carbonate seed crystals with a particle size distribution of D10: 2.54 μm, D50: 4.82 μm, and D90: 10.98 μm are added to the obtained carbonized purified liquid, steam is introduced into the bottom of the reactor for heating, and a defoamer is installed on the upper part of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid at the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid at the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 100°C for 45 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0098] Repeat steps (4) and (5) 4 times to obtain high-purity lithium carbonate.

[0099] Example 2:

[0100] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0101] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution having a lithium concentration of 7.53 g / L, thereby obtaining an anion exchange resin after adsorption and a lithium-containing solution after adsorption having a pH of 7;

[0102] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 75% alkaline solution (lithium hydroxide, potassium hydroxide, ammonia water, calcium oxide and calcium hydroxide) at 120° C. for 180 minutes to obtain a slurry with an alkaline concentration of 30%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0103] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to a pH of 7, sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 4:1, lithium is precipitated at a temperature of 60°C and a precipitation time of 150 min, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0104] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 13, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0105] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 15:1 and 0.01 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized in a 50% filling rate hollow spherical filler reactor which is formed by rotating a mixture of porous inorganic powder (zeolite), polymeric plastic powder (thermoplastic plastic powder) and organic amine (N,N-dimethylacetamide) in a mass ratio of 100:50:5 at a reaction temperature of 35°C and a reaction time of 100 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system.

[0106] (5) The carbonized liquid in step (4) is purified by a cation exchange resin to obtain a carbonized purified liquid; the obtained carbonized purified liquid is added with 2% by weight of high-purity lithium carbonate seeds with a particle size distribution of D10: 2.93 μm, D50: 7.18 μm, and D90: 14.53 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 120°C for 120 min to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0107] Repeat steps (4) and (5) three times to obtain high-purity lithium carbonate.

[0108] Example 3:

[0109] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0110] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution with a lithium concentration of 1.29 g / L, to obtain an anion exchange resin after adsorption and a lithium-containing solution after adsorption with a pH of 5;

[0111] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to an 80°C, 50% (lithium hydroxide and sodium hydroxide) alkaline solution for 60 minutes to obtain a slurry with an alkaline concentration of 15%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0112] (3) The impurity-removed liquid from step (2) is treated with an anion exchange resin after adsorption in step (1) to a pH of 9, sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 5:1, lithium is precipitated at a lithium precipitation temperature of 100°C and a lithium precipitation time of 300 min, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0113] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 7, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0114] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 40:1 and 1 MPa of carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The carbonization is carried out in a 90% filling rate grid-shaped filler reactor with a mass ratio of 80:60:8 of porous inorganic powder (activated carbon, molecular sieve, bentonite and kaolin) to polymer plastic powder (polyvinyl chloride) and organic amine (formamide, acetamide, propionamide, butanamide, N,N-diethylmethanolamine, propionamide and acrylamide) at a reaction temperature of 25°C and a reaction time of 10 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0115] (5) The carbonized liquid in step (4) is purified by a cation exchange resin to obtain a carbonized purified liquid; the obtained carbonized purified liquid is added with 1% by weight of high-purity lithium carbonate seeds with a particle size distribution of D10: 1.71 μm, D50: 4.63 μm, and D90: 12.57 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 90°C for 30 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0116] Repeat steps (4) and (5) 5 times to obtain high-purity lithium carbonate.

[0117] Example 4:

[0118] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0119] (1) Anion exchange resin is used to adsorb an acidic lithium-containing solution with a lithium concentration of 2.82 g / L to obtain an adsorbed anion exchange resin and an adsorbed lithium-containing solution with a pH of 3;

[0120] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 10% (potassium hydroxide) alkaline solution at 60° C. for 180 minutes to obtain a slurry with an alkaline concentration of 7%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0121] (3) The impurity removal liquid from step (2) is treated with anion exchange resin after adsorption in step (1) until the pH value of the solution is 14, and carbon dioxide solution is introduced until the end point pH value is 11. Lithium is precipitated at a temperature of 90°C and a precipitation time of 100 min, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is then reused in step (1);

[0122] The mother liquor of the precipitation in step (3) is treated with an anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 8.5. The treated mother liquor of the precipitation is reused in the leaching system, and the treated anion exchange resin is reused in step (1);

[0123] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 30:1 and 0.05 MPa of carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized in a 70% filling rate granular filler reactor which is formed by foaming a mixture of porous inorganic powder (bentonite), polymer plastic powder (polypropylene), and organic amine (propionamide and N,N-dimethylformamide) in a mass ratio of 20:100:2 at a reaction temperature of 20°C and a reaction time of 30 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system.

[0124] (5) The carbonized liquid in step (4) is purified by chelating resin to obtain a carbonized purified liquid; 1.5% by weight of the obtained carbonized purified liquid and high-purity lithium carbonate seed crystals with a particle size distribution of D10: 1.89 μm, D50: 3.91 μm, and D90: 9.73 μm are added to the obtained carbonized purified liquid, steam is introduced into the bottom of the reactor for heating, and a defoamer is installed on the upper part of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 110°C for 60 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0125] Repeat steps (4) and (5) 4 times to obtain high-purity lithium carbonate.

[0126] Example 5:

[0127] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0128] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution having a lithium concentration of 20.26 g / L, thereby obtaining an anion exchange resin after adsorption and a lithium-containing solution after adsorption having a pH of 6;

[0129] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 7% (sodium hydroxide and potassium hydroxide) alkaline solution at 150° C. for 90 minutes to obtain a slurry with an alkaline concentration of 5%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0130] (3) The impurity removal liquid from step (2) is treated with anion exchange resin after adsorption in step (1) until the pH value of the solution is 13, and a carbon dioxide solution is introduced to the solution until the pH value of the solution is 10. Lithium is precipitated at a temperature of 95° C. and a precipitation time of 120 min. Liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is then reused in step (1);

[0131] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 9, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0132] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 35:1 and 0.1 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized in a cotton-like filler reactor with an 80% filling rate, which is formed by mixing and casting porous inorganic powder (kaolin and montmorillonite) with polymer plastic powder (polyethylene and polyvinyl chloride) and organic amine (propanolamine, butyramide, caprolactam and N,N-dimethylformamide) in a mass ratio of 60:80:10 at a reaction temperature of 30°C and a reaction time of 25 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled for step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system.

[0133] (5) The carbonized liquid in step (4) is purified by chelating resin to obtain a carbonized purified liquid; the obtained carbonized purified liquid is added with 1.25% by weight of high-purity lithium carbonate seeds with a particle size distribution of D10: 2.14 μm, D50: 3.57 μm, and D90: 9.08 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the upper part of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 120°C for 45 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0134] Repeat steps (4) and (5) twice to obtain high-purity lithium carbonate.

[0135] Example 6:

[0136] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0137] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution having a lithium concentration of 42.85 g / L, thereby obtaining an anion exchange resin after adsorption and a lithium-containing solution after adsorption having a pH of 6.5;

[0138] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 40% (sodium hydroxide) alkaline solution at 135° C. for 75 minutes to obtain a slurry with an alkaline concentration of 25%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0139] (3) The impurity-removed liquid from step (2) is treated with anion exchange resin after adsorption in step (1) until the pH value of the solution is 12, and a carbon dioxide solution is introduced to the solution until the pH value of the solution is 10. Lithium is precipitated at a temperature of 85°C and a precipitation time of 30 minutes, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is then reused in step (1);

[0140] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 8, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0141] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 28:1 and 0.3 MPa of carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized in a 60% filling rate honeycomb filler reactor formed by mixing and extruding porous inorganic powder (molecular sieve, zeolite and montmorillonite) with polymer plastic powder (polypropylene, polybutene and polyvinylidene fluoride) and organic amine (ethanolamine, propanolamine, N,N-diethylethanolamine and N,N-dimethylacetamide) in a mass ratio of 100:20:5 at a reaction temperature of 27°C and a reaction time of 15 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled for step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system.

[0142] (5) The carbonized liquid in step (4) is purified by a cation exchange resin to obtain a carbonized purified liquid; 0.25% by weight of the obtained carbonized purified liquid is added to high-purity lithium carbonate seeds with a particle size distribution of D10: 1.86 μm, D50: 5.81 μm, and D90: 13.38 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 115°C for 100 min to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0143] Repeat steps (4) and (5) once to obtain high-purity lithium carbonate.

[0144] Example 7:

[0145] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0146] (1) Anion exchange resin is used to adsorb an acidic lithium-containing solution with a lithium concentration of 13.27 g / L to obtain an anion exchange resin after adsorption and a lithium-containing solution after adsorption with a pH of 4.5;

[0147] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 125° C., 65% (lithium hydroxide and potassium hydroxide) alkaline solution for 135 minutes to obtain a slurry with an alkaline concentration of 20%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0148] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to a pH of 11, sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 1:1, lithium is precipitated at a temperature of 105°C and a precipitation time of 240 min, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0149] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 9, the treated precipitation mother liquor is reused in the leaching system, and the treated anion exchange resin is reused in step (1);

[0150] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 22:1 and 0.25 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The carbonization is carried out in an 85% filling rate annular packing reactor thermoformed with porous inorganic powder (hydrotalcite-like, bentonite and kaolin) and polymer plastic powder (polyethylene and polystyrene) and organic amine (acrylamide, N,N-diethylformamide and N,N-dimethylacetamide) in a mass ratio of 75:75:15 at a reaction temperature of 22°C and a reaction time of 40 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled for step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0151] (5) The carbonized liquid in step (4) is purified by a cation exchange resin to obtain a carbonized purified liquid; the obtained carbonized purified liquid is added with 0.95% by weight of high-purity lithium carbonate seeds with a particle size distribution of D10: 2.02 μm, D50: 4.84 μm, and D90: 12.77 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 110°C for 110 min to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0152] Repeat steps (4) and (5) 5 times to obtain high-purity lithium carbonate.

[0153] Example 8:

[0154] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0155] (1) Anion exchange resin is used to adsorb an acidic lithium-containing solution with a lithium concentration of 2.97 g / L to obtain an anion exchange resin after adsorption and a lithium-containing solution after adsorption with a pH of 5.5;

[0156] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 45% (sodium hydroxide) alkaline solution at 85°C for 120 minutes to obtain a slurry with an alkaline concentration of 10%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0157] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to a pH of 10, sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 2.5:1, lithium is precipitated at a temperature of 80°C and a precipitation time of 45 minutes, and liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0158] The precipitation mother liquor of step (3) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 13, the treated precipitation mother liquor is returned to the leaching system, and the treated anion exchange resin is returned to step (1);

[0159] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 20:1 and 0.2 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The lithium carbonate is carbonized in a 65% filling rate granular filler reactor formed by winding porous inorganic powder (molecular sieve), polymer plastic powder (polyethylene), and organic amine (N,N-dimethylethanolamine and N,N-dimethylformamide) in a mass ratio of 100:10:20 at a reaction temperature of 32°C and a reaction time of 35 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0160] (5) The carbonized liquid of step (4) is purified by chelating resin to obtain a carbonized purified liquid; 0.7% by weight of the obtained carbonized purified liquid and high-purity lithium carbonate seed crystals with a particle size distribution of D10: 2.37 μm, D50: 6.93 μm, and D90: 11.73 μm are added to the obtained carbonized purified liquid, steam is introduced into the bottom of the reactor for heating, and a defoamer is installed on the upper part of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump, and the carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4), and pyrolysis is carried out at 105°C for 90 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0161] Repeat steps (4) and (5) three times to obtain high-purity lithium carbonate.

[0162] Example 9:

[0163] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0164] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution with a lithium concentration of 2.88 g / L, to obtain an anion exchange resin after adsorption and a lithium-containing solution after adsorption with a pH of 10;

[0165] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 45% (potassium hydroxide) alkaline solution at 115° C. for 75 minutes to obtain a slurry with an alkaline concentration of 12%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0166] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to a pH of 11.5, and sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 3:1, and lithium precipitation is carried out at a lithium precipitation temperature of 75°C and a lithium precipitation time of 180 min. Liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate, and the treated anion exchange resin is reused in step (1);

[0167] The mother liquor of the precipitation in step (3) is treated with an anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 8.5. The treated mother liquor of the precipitation is reused in the leaching system, and the treated anion exchange resin is reused in step (1);

[0168] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 25:1 and 0.5 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The carbonization is carried out in a 75% filling rate corrugated packing reactor formed by drop molding with a mass ratio of porous inorganic powder (kaolin, bentonite and hydrotalcite) to polymer plastic powder (polypropylene and polyvinyl chloride) and organic amine (N,N-diethylethanolamine) of 10:50:10 at a reaction temperature of 25°C and a reaction time of 20 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled for step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0169] (5) The carbonized liquid in step (4) is purified by chelating resin to obtain a carbonized purified liquid; 0.5% by weight of the obtained carbonized purified liquid and high-purity lithium carbonate seed crystals with a particle size distribution of D10: 1.83 μm, D50: 7.42 μm, and D90: 14.26 μm are added to the obtained carbonized purified liquid, steam is introduced into the bottom of the reactor for heating, and a defoamer is installed on the upper part of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump, and the carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4), and pyrolysis is carried out at 95°C for 60 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0170] Repeat steps (4) and (5) three times to obtain high-purity lithium carbonate.

[0171] Example 10:

[0172] This embodiment provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, the method comprising the following steps:

[0173] (1) using an anion exchange resin to adsorb an acidic lithium-containing solution having a lithium concentration of 18.94 g / L, thereby obtaining an anion exchange resin after adsorption and a lithium-containing solution after adsorption having a pH of 7;

[0174] (2) adding the lithium-containing solution after adsorption in step (1) dropwise to a 40% (sodium hydroxide) alkaline solution at 120° C. for 120 minutes to obtain a slurry with an alkaline concentration of 20%. After the addition is completed, the slurry is immediately subjected to liquid-solid separation to obtain a decontamination liquid and decontamination residue;

[0175] (3) The impurity removal liquid of step (2) is treated with anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 10, and sodium carbonate is added according to a molar ratio of sodium carbonate to lithium element in the treated solution of 2.5:1. Lithium is precipitated at a temperature of 100°C and a precipitation time of 120 min. Liquid-solid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1);

[0176] The mother liquor of the precipitation in step (3) is treated with an anion exchange resin after adsorption in step (1) to obtain a solution with a pH of 11, the mother liquor of the precipitation after treatment is returned to the leaching system, and the anion exchange resin after treatment is returned to step (1);

[0177] (4) The lithium carbonate obtained in step (3) is made into a slurry with a liquid-solid ratio of 25:1 and 0.4 MPa carbon dioxide is introduced from the bottom of the slurry in the form of nano-microporous aeration. The mixture is carbonized in a granular filler reactor with an 82% filling rate, which is formed by extruding porous inorganic powder (zeolite and bentonite), polymer plastic powder (polyethylene), and organic amine (N,N-dimethylacetamide) in a mass ratio of 20:80:20 at a reaction temperature of 30°C and a reaction time of 35 min. The carbon dioxide overflowed from the carbonization reaction is pressurized and recycled to step (4). The liquid and solid are separated to obtain carbonized liquid and carbonized slag, and the carbonized slag is reused in the leaching system;

[0178] (5) The carbonized liquid in step (4) is purified by a cation exchange resin to obtain a carbonized purified liquid; the obtained carbonized purified liquid is added with 0.95% by weight of high-purity lithium carbonate seeds with a particle size distribution of D10: 1.23 μm, D50: 5.36 μm, and D90: 12.19 μm, and steam is introduced into the bottom of the reactor for heating. A defoamer is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid in the lower part of the reactor is circulated from the top of the reactor to the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid in the lower part of the reactor is circulated from the middle of the reactor to the reactor through a pump. The carbon dioxide overflowed from the pyrolysis is pressurized and circulated for step (4). The pyrolysis is carried out at 110°C for 90 minutes to obtain lithium carbonate and mother liquor, and the mother liquor is reused for carbonization in step (4);

[0179] Repeat steps (4) and (5) three times to obtain high-purity lithium carbonate.

[0180] Comparative Example 1:

[0181] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 1, except that steps (1) and (3) do not include anion exchange resin and related operations.

[0182] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0183] Comparative Example 2:

[0184] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is based on Example 2, with the only difference being that in step (2), "adding the lithium solution dropwise to the alkaline solution" is adjusted to "adding the alkaline solution dropwise to the lithium solution."

[0185] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0186] Comparative Example 3:

[0187] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 3, except that the temperature of the alkaline solution in step (2) is 20°C.

[0188] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0189] Comparative Example 4:

[0190] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 3, except that: in step (2), "liquid-solid separation of the slurry is immediately performed after the dropwise addition is completed" is adjusted to "liquid-solid separation of the slurry is performed 2 hours after the dropwise addition is completed."

[0191] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0192] Comparative Example 5:

[0193] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 3, the only difference is that the concentration of the alkali added dropwise in step (2) is pH=13.

[0194] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0195] Comparative Example 6:

[0196] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 4, except that step (4) does not include a filler.

[0197] The lithium recovery rate of this comparative example was reduced after analysis and detection.

[0198] Comparative Example 7:

[0199] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that of Example 4, with the only difference being that the filler in step (4) does not include porous inorganic powder.

[0200] The lithium recovery rate of this comparative example was reduced after analysis and detection.

[0201] Comparative Example 8:

[0202] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 4, except that the filler in step (4) does not include polymeric plastic powder.

[0203] This comparative example failed to obtain filler, and the lithium recovery rate was reduced after analysis and detection.

[0204] Comparative Example 9:

[0205] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 4, except that the filler in step (4) does not include an organic amine.

[0206] The lithium recovery rate of this comparative example was reduced after analysis and detection.

[0207] Comparative Example 10:

[0208] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 5, except that in step (4), the mass ratio of the porous inorganic powder to the polymeric plastic powder and the organic amine is 1:1:20.

[0209] The lithium recovery rate of this comparative example was reduced after analysis and detection.

[0210] Comparative Example 11:

[0211] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to that in Example 5, except that in step (4), the mass ratio of the porous inorganic powder to the polymeric plastic powder and the organic amine is 120:120:2.

[0212] The lithium recovery rate of this comparative example was reduced after analysis and detection.

[0213] Comparative Example 12:

[0214] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is similar to Example 6, with the only difference being that in step (5), the particle size distribution of the high-purity lithium carbonate seeds is D10: 10.69 μm, D50: 58.83 μm, and D90: 98.37 μm.

[0215] The comparative example was analyzed and tested to have a lower purity of lithium carbonate and a lower lithium recovery rate.

[0216] Comparative Example 13:

[0217] This comparative example provides a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. The method is described with reference to Example 7, with the only difference being that: in step (5), "steam is introduced into the bottom of the reactor for heating, a demister is installed at the top of the reactor, when the heating temperature of the carbonized purified liquid is less than 70°C, the purified liquid at the bottom of the reactor is circulated from the top of the reactor into the reactor via a pump, and when the heating temperature of the carbonized purified liquid reaches above 70°C, the purified liquid at the bottom of the reactor is circulated from the middle of the reactor into the reactor via a pump" is adjusted to "jacket or coil heating".

[0218] The comparative example was analyzed and tested to determine the final purity of lithium carbonate and the lithium recovery rate. (The lithium carbonate was severely sticky and the thermal decomposition efficiency of lithium bicarbonate was low.)

[0219] The solution and solid lithium contents in Examples 1-10 and Comparative Examples 1-13 were measured, and the impurities in the lithium carbonate products were analyzed to calculate the lithium carbonate purity and the single-pass lithium recovery rate of the entire process. The test results are shown in Table 1.

[0220] Table 1

[0221]

[0222] From the above embodiments and comparative examples, it can be seen that the repeated use of anion exchange resins effectively reduces the amount of acid and alkali reagents used to treat lithium-containing acidic solutions; the deep purification and impurity removal process has high impurity removal efficiency and less lithium band loss; the lithium carbonate carbonization method can greatly improve the lithium carbonate carbonization efficiency; the lithium bicarbonate solution decomposition method can avoid the problems of bubbling, wall sticking and low decomposition efficiency. The purity of the high-purity lithium carbonate obtained by the process of the present invention can reach more than 99.9-99.999%, and the lithium recovery rate of the process reaches more than 90%. The method of the present invention uses less acid and alkali reagents, has high impurity removal efficiency, less lithium band loss, high carbonization efficiency, short carbonization time, safe, stable and efficient pyrolysis process, green and environmentally friendly process, low production cost, and has good industrial application prospects.

[0223] The applicant declares that the present invention is intended to illustrate the detailed structural features of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed structural features. This does not mean that the present invention must rely on the above-described detailed structural features in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0224] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0225] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0226] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing high-purity lithium carbonate from an acidic lithium-containing solution, characterized in that: The method comprises the following steps: (1) using an anion exchange resin to adsorb the acidic lithium-containing solution to obtain an adsorbed anion exchange resin and an adsorbed lithium-containing solution; (2) adding the adsorbed lithium-containing solution of step (1) dropwise to an alkali solution for mixing, wherein the alkali solution concentration is 7-75%, the alkali solution temperature is 60-150° C., the adding time is 60-180 min, and the alkali solution concentration is 5-30% after the adding is completed. Immediately after the adding is completed, solid-liquid separation is performed to obtain a decontamination liquid and decontamination residue; (3) The impurity-removed liquid of step (2) is treated with the adsorbed anion exchange resin of step (1), and then a carbon source is added to precipitate lithium, and solid-liquid separation is performed to obtain a precipitated mother liquor and lithium carbonate. The treated anion exchange resin is reused in step (1); (4) slurrying the lithium carbonate in step (3) and introducing carbon dioxide to carry out carbonization reaction, and separating the solid and liquid to obtain carbonized liquid and carbonized slag; The carbonization reaction is carried out in a filler reactor, wherein the filler is a mixture of porous inorganic powder, polymeric plastic powder, and organic amine; the mass ratio of the porous inorganic powder to the polymeric plastic powder and the organic amine is (10-100):(10-100):(2-20); (5) Purifying the carbonized liquid obtained in step (4) to obtain a purified carbonized liquid, subjecting the purified carbonized liquid to a pyrolysis reaction to obtain lithium carbonate and a mother liquor, and reusing the mother liquor to slurry in step (4); In step (5), the carbonized purified liquid is pyrolyzed in a defoaming reactor, and high-purity lithium carbonate seeds are added before pyrolysis; the seed crystal particle size distribution is D10: 1-3 μm, D50: 3-8 μm, and D90: 9-15 μm; Steam is introduced into the bottom of the reactor for heating. A demister is installed on the top of the reactor. When the heating temperature of the carbonized purified liquid is lower than 70°C, the carbonized purified liquid in the lower part of the reactor is circulated from the top of the reactor into the reactor through a pump. When the heating temperature of the carbonized purified liquid reaches above 70°C, the carbonized purified liquid in the lower part of the reactor is circulated from the middle part of the reactor into the reactor through a pump.

2. The method according to claim 1, characterized in that The pH of the lithium-containing solution after the adsorption in step (1) is 3-10.

3. The method according to claim 1, characterized in that The pH of the solution after the impurity removal liquid treatment in step (3) is 7-14.

4. The method according to claim 1, wherein The carbon source in step (3) is sodium carbonate or carbon dioxide.

5. The method according to claim 1, wherein The mother liquor of the precipitation in step (3) is treated with the anion exchange resin after adsorption in step (1) and then used in the leaching system, and the anion exchange resin is reused in step (1) for adsorption.

6. The method according to claim 1, characterized in that The porous inorganic powder is one or a combination of at least two of activated carbon, molecular sieve, zeolite, hydrotalcite, bentonite, kaolin, montmorillonite or diatomaceous earth.

7. The method according to claim 1, characterized in that The polymer plastic powder is thermoplastic plastic powder.

8. The method according to claim 1, characterized in that The polymer plastic powder is one or a combination of at least two of polyethylene, polypropylene, polybutylene, polyvinyl chloride, polyvinylidene fluoride or polystyrene.

9. The method according to claim 1, characterized in that The organic amine is one or a combination of at least two of aliphatic amines, alcohol amines, amides, alicyclic amines, aromatic amines, and naphthyl amines.

10. The method according to claim 9, characterized in that The organic amines are amides and / or alcoholamines.

11. The method according to claim 10, characterized in that The organic amine is one or a combination of at least two of ethanolamine, propanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, formamide, acetamide, propionamide, butyramide, acrylamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide.

12. The method according to claim 1, characterized in that The packing rate of the packing reactor is 50-90%.

13. The method according to claim 1, wherein The purification treatment in step (5) is to adsorb the carbonized liquid through a cation exchange resin and / or a chelating resin.

14. The method according to claim 1, wherein The temperature of the pyrolysis reaction in step (5) is 90-120°C and the time is 30-120 minutes.

15. The method according to claim 1, wherein Repeat steps (4) and (5) to improve the purity of lithium carbonate.

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