Method for preparing battery-grade lithium hydroxide monohydrate by using salt lake brine

Abstract

The invention relates to the technical field of lithium hydroxide extraction, and discloses a method for preparing battery-grade lithium hydroxide monohydrate by using salt lake brine. The method comprises the following steps: extracting lithium by adsorption, removing calcium and magnesium by a membrane separation method, performing electrodialysis concentration, deeply removing calcium and magnesium, removing boron by chelating resin, performing bipolar membrane dialysis, electrolyzing in an electrolytic tank, performing reduced pressure evaporation and drying. According to the method for preparing the battery-grade lithium hydroxide monohydrate by using the salt lake brine, the battery-grade lithium hydroxide monohydrate with relatively low Cl <-> content can be simply and conveniently prepared.

Description

Technical Field

[0001] The invention relates to the technical field of lithium hydroxide extraction, and in particular to a method for preparing battery-grade lithium hydroxide monohydrate by utilizing salt lake brine. Background Art

[0002] Lithium hydroxide is an important inorganic chemical product and an indispensable raw material in the production of high-nickel ternary lithium-ion battery positive electrode materials. With the rapid development of the lithium-ion battery industry, the demand for battery-grade lithium hydroxide monohydrate in the new energy industry continues to grow. At present, the preparation methods of lithium hydroxide can be divided into causticization method and bipolar membrane electrodialysis method.

[0003] The causticization method is to mix lithium carbonate and calcium hydroxide, heat them, and then evaporate, remove impurities, crystallize, wash and dry to obtain a lithium hydroxide product. The calcium ions in it are difficult to separate and do not meet battery grade standards.

[0004] The bipolar membrane electrodialysis method uses salt lake brine as raw material, removes impurities in the salt lake brine through adsorption, chemical precipitation and other methods, and then prepares battery-grade lithium hydroxide monohydrate through bipolar membrane electrodialysis. This method has the advantages of simple process, high purity and low energy consumption, but the disadvantages of this method are expensive extraction agent, easy dissolution, good selectivity and high purity. Due to the membrane itself in bipolar membrane electrodialysis, the Cl in lithium-containing solution - It cannot be removed. After passing through bipolar membrane electrodialysis, it is continuously enriched, making the Cl in the battery-grade lithium hydroxide monohydrate produced - Seriously exceeding the standard.

[0005] Patent CN106946275B discloses a method for directly preparing battery-grade lithium hydroxide monohydrate using lithium-rich brine from salt lakes. This method uses old brine from salt lakes to prepare battery-grade lithium hydroxide monohydrate. The lithium yield of the old brine during the formation process reaches 30-40%, which greatly reduces its lithium resource recovery rate. Experiments have shown that when the refined LiCl solution passes through a bipolar membrane electrodialysis system, due to the bipolar membrane itself, a large amount of Cl will exist in its alkali chamber. - . Refined LiOH solution Cl - The concentration will exceed 3g / L, resulting in Cl in the product during the subsequent crystallization process. - It is difficult to remove and the product is difficult to meet the battery-grade standard. Not only that, the product of patent CN106946275B only meets the national standard GBT26008-2010 (now abolished) for battery-grade lithium hydroxide monohydrate. The latest standard has stricter standards for the ion content in the product. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem of excessive chloride ion in the process of preparing lithium hydroxide monohydrate by conventional bipolar membrane electrodialysis in the prior art, and to provide a method for preparing battery-grade lithium hydroxide monohydrate using salt lake brine. The method of the present invention for preparing battery-grade lithium hydroxide monohydrate using salt lake brine can simply and conveniently prepare Cl - Low content of battery-grade lithium hydroxide monohydrate, while Li + The overall yield is high.

[0007] In order to achieve the above object, the present invention provides a method for preparing battery-grade potassium hydroxide monohydrate using salt lake brine, the method comprising the following steps:

[0008] (1) extracting lithium from salt lake brine by adsorbing it through an aluminum-based lithium adsorbent to obtain a LiCl solution;

[0009] (2) subjecting the LiCl solution to membrane separation treatment and concentrating it by electrodialysis to obtain a LiCl concentrated solution;

[0010] (3) The LiCl concentrate is subjected to nanofiltration treatment, and then subjected to adsorption and desorption treatment using an ion exchange resin to obtain Mg 2+ Concentration ≤5mg / L and Ca 2+ Low calcium and magnesium LiCl solution with a concentration of ≤2mg / L;

[0011] (4) removing boron from the low calcium and magnesium LiCl solution through a chelating resin to obtain B 3+ Refined LiCl solution with a concentration of ≤10mg / L;

[0012] (5) passing the refined LiCl solution through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl, and then electrolyzing it through an electrolysis device to obtain a refined lithium hydroxide solution;

[0013] (6) The lithium hydroxide solution is evaporated under reduced pressure and dried.

[0014] Preferably, in step (1), the salt lake brine contains the following components: Li + ≥0.1g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B 3+ ≤0.6g / L, and pH≥7.2, and the pH value of the salt lake brine is ≥7.2.

[0015] Preferably, in step (1), the LiCl solution contains the following components: Li + ≥0.5g / L, Mg 2+ ≤0.5g / L, Na+ ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.5g / L.

[0016] Preferably, in step (2), the membrane separation treatment is carried out using at least one of a nanofiltration membrane, a reverse osmosis membrane and an electrodialysis membrane.

[0017] Preferably, in step (2), the LiCl concentrate contains the following components: Li + ≥12g / L, Mg 2+ ≤0.6g / L, Na + ≤1.6g / L, K + ≤0.51g / L, B 3+ ≤1g / L, Ca 2+ ≤0.02g / L.

[0018] Preferably, in step (3), the ion exchange resin is a phenoxyacetic acid resin, and the functional group of the phenoxyacetic acid resin is at least one of a halogen, a hydroxyl, an amino, a thiol, a carboxyl, an ester, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl and a substituted or unsubstituted aryl.

[0019] Preferably, in step (3), the low calcium and magnesium LiCl solution contains the following components: Li + ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.52g / L, B 3+ ≤0.41g / L, Ca 2+ ≤2mg / L.

[0020] Preferably, in step (4), the functional group of the chelating resin is at least one of N-methylglucamine, halogen, hydroxyl, amino, thiol, carboxyl, ester, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl and substituted or unsubstituted aromatic.

[0021] Preferably, in step (4), the refined LiCl solution contains the following components: Li + ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.5g / L, B 3+ ≤10mg / L, Ca 2+ ≤2mg / L.

[0022] Preferably, in step (5), the working conditions of the bipolar membrane electrodialysis system include: a DC voltage of 220-400 V, a current of 200-400 A, and a current density of 700-800 A / m 2 .

[0023] Preferably, in step (5), the mixed solution of LiOH and NaCl contains the following components: Li + ≥13g / L, Mg 2 + ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - 3~7g / L.

[0024] Preferably, in step (5), the refined LiOH solution contains the following components: Li + ≥14g / L, Mg 2+ ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - ≤7g / L.

[0025] Preferably, in step (6), the conditions for reduced pressure evaporation include: temperature of 85-87° C., time of 1-3 h, and vacuum degree of 380-480 mbar.

[0026] According to the method for preparing battery-grade lithium hydroxide monohydrate using salt lake brine of the present invention, the process of extracting lithium by adsorption, removing calcium and magnesium by membrane separation, electrodialysis concentration, deep calcium and magnesium removal, boron removal by chelating resin, bipolar membrane dialysis, electrolysis in electrolytic cell, reduced pressure evaporation and drying is adopted. By using salt lake brine as raw material to prepare battery-grade lithium hydroxide monohydrate, the Cl - The problem of excessive content can be solved by simply and conveniently preparing Cl - The content of battery-grade lithium hydroxide monohydrate is low, while reducing operating costs and ensuring product yield. + The comprehensive yield can reach 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A working principle diagram of electrolysis performed by an electrolysis device in the method for preparing battery-grade lithium hydroxide monohydrate using salt lake brine provided by the present invention. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] The method for preparing battery-grade lithium hydroxide monohydrate based on salt lake brine of the present invention comprises the following steps:

[0031] (1) extracting lithium from salt lake brine by adsorbing it through an aluminum-based lithium adsorbent to obtain a LiCl solution;

[0032] (2) subjecting the LiCl solution to membrane separation treatment and concentrating it by electrodialysis to obtain a LiCl concentrated solution;

[0033] (3) The LiCl concentrate is subjected to nanofiltration treatment, and then subjected to adsorption and desorption treatment using an ion exchange resin to obtain Mg 2+ Concentration ≤5mg / L and Ca 2+ Low calcium and magnesium LiCl solution with a concentration of ≤2mg / L;

[0034] (4) removing boron from the low calcium and magnesium LiCl solution through a chelating resin to obtain B 3+ Refined LiCl solution with a concentration of ≤10mg / L;

[0035] (5) passing the refined LiCl solution through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl, and then electrolyzing it through an electrolysis device to obtain a refined lithium hydroxide solution;

[0036] (6) The lithium hydroxide solution is evaporated under reduced pressure and dried.

[0037] In step (1), preferably, the salt lake brine contains the following components: Li + ≥0.1g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B3+ ≤0.6g / L, and pH≥7.2, and the pH value of the salt lake brine is ≥7.2. The lithium ion concentration is greatly increased and the impurity content is greatly reduced by adsorbing and extracting lithium with aluminum-based lithium adsorbents.

[0038] In step (1), preferably, the LiCl solution contains the following components: Li + ≥0.5g / L, Mg 2+ ≤0.5g / L, Na + ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.5g / L.

[0039] In step (1), the process of adsorption and extraction of lithium can be carried out in various conventional ion exchange devices. In one embodiment, the ion exchange device can be composed of an adsorption zone, a water washing zone, a desorption zone and a qualified liquid top water zone, and the salt lake brine is processed in the adsorption zone, the water washing zone, the desorption zone and the qualified liquid top water zone in sequence to obtain a LiCl solution. In the adsorption zone, the salt lake brine can be fed into the ion exchange device by an upper feeding method for adsorption. In the water washing zone, pure water can be used to wash the ion exchange device by an upper feeding method.

[0040] In the present invention, the aluminum-based lithium adsorbent used can be a common commercial product, as long as it can remove most of the impurities such as calcium, magnesium, sodium, boron, etc. in the salt lake brine, and the obtained solution meets the requirements of the LiCl solution. In one embodiment, the active ingredient of the aluminum-based lithium adsorbent is aluminum hydroxide.

[0041] In the present invention, the membrane separation treatment in step (2) is a pretreatment operation, the purpose of which is to remove most of the Ca 2+ and / or Mg 2+ . In step (2), the membrane separation treatment process can be implemented in various conventional separation equipment in the art. In some embodiments, the membrane separation treatment can be implemented using at least one of a nanofiltration membrane, a reverse osmosis membrane, and an electrodialysis membrane. In the most preferred case, the membrane separation treatment process is implemented using a nanofiltration membrane, a reverse osmosis membrane, and an electrodialysis membrane at the same time, that is, the membrane separation treatment process includes: the LiCl solution is treated sequentially through a nanofiltration membrane, a reverse osmosis membrane, and an electrodialysis membrane; wherein the nanofiltration membrane treatment process can include a primary nanofiltration, a secondary nanofiltration, an RO membrane concentration, a tertiary nanofiltration, and a quaternary nanofiltration performed sequentially.

[0042] In step (2), the electrodialysis concentration conditions may include: a DC voltage of 100-140 V, a current of 50-60 A, and a current density of 50-60 A / m2 The electrodialysis concentration process can be implemented in various conventional electrodialysis equipment in the art.

[0043] In step (2), preferably, the LiCl concentrate contains the following components: Li + ≥12g / L, Mg 2+ ≤0.6g / L, Na + ≤1.6g / L, K + ≤0.51g / L, B 3+ ≤1g / L, Ca 2+ ≤0.02g / L.

[0044] In the present invention, the purpose of step (3) is to perform deep calcium and magnesium removal to reduce the Ca 2+ and Mg 2+ , a low calcium and magnesium LiCl solution is obtained. The present invention uses "nanofiltration and ion exchange resin" to deeply remove calcium and magnesium.

[0045] In the method of the present invention, the nanofiltration treatment in step (3) can be carried out in a two-stage nanofiltration manner, that is, the LiCl concentrate is subjected to primary nanofiltration and secondary nanofiltration in sequence.

[0046] In step (3), preferably, the ion exchange resin is a phenoxyacetic acid resin, and the functional groups of the phenoxyacetic acid resin can be at least one of halogen, hydroxyl, amino, thiol, carboxyl, ester, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl and substituted or unsubstituted aryl.

[0047] In step (3), preferably, the low calcium and magnesium LiCl solution contains the following components: Li + ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.52g / L, B 3+ ≤0.41g / L, Ca 2+ ≤2mg / L.

[0048] In some embodiments, the functional group of the chelating resin in step (4) can be at least one of N-methylglucamine, halogen, hydroxyl, amino, thiol, carboxyl, ester, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl and substituted or unsubstituted aromatic.

[0049] In step (4), preferably, the refined LiCl solution contains the following components: Li+ ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.5g / L, B 3+ ≤10mg / L, Ca 2+ ≤2mg / L.

[0050] In step (5), the operating conditions of the bipolar membrane electrodialysis system may include: a DC voltage of 220-400 V, a current of 200-400 A, and a current density of 700-800 A / m 2 .

[0051] In step (5), the alkali chamber of the bipolar membrane electrodialysis system forms a mixed solution of LiOH and NaCl. The acid chamber of the bipolar membrane electrodialysis system forms an HCl solution, and the concentration of the HCl solution is 6-7 wt%.

[0052] In step (5), preferably, the mixed solution of LiOH and NaCl contains the following components: Li + ≥13g / L, Mg 2+ ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - 3~7g / L.

[0053] In step (5), by Figure 1 The electrolysis device shown in the figure can be used to obtain a refined LiOH solution in the cathode chamber. Preferably, the refined LiOH solution contains the following components: Li + ≥14g / L, Mg 2+ ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - ≤7g / L.

[0054] In step (5), the working conditions of the electrolysis device may include: DC voltage of 220-380V, current of 200A-400A, current density of 700-800A / m 2 .

[0055] In step (6), the conditions for the reduced pressure evaporation may include: temperature of 85-90°C, time of 1-3h, vacuum degree of 350-500mbar. In a more preferred case, the conditions for the reduced pressure evaporation may include: temperature of 85-87°C, time of 1.5-2h, vacuum degree of 380-480mbar.

[0056] In step (6), the drying conditions may include: a temperature of 80-110° C. and a time of 1-2 hours. In a more preferred case, the drying conditions may include: a temperature of 90-110° C. and a time of 1.5-1.6 hours.

[0057] The following examples further illustrate the method for preparing battery-grade lithium hydroxide monohydrate based on salt lake brine of the present invention. The examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0058] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0059] In the following examples and comparative examples, the concentrations of various ions in various solutions and the contents of various components in the prepared battery-grade lithium hydroxide monohydrate were tested in accordance with the national standard GB / T 11064.1-2013.

[0060] In the following examples and comparative examples, Li + The comprehensive yield is calculated as follows: the amount of lithium in the lithium hydroxide monohydrate product in step (6) ÷ the amount of lithium in the salt lake brine in step (1) × 100%.

[0061] In the following examples and comparative examples, in the salt lake brine used in step (1), Li + The concentration is 0.15g / L, Mg 2+ The concentration is 29.53 g / L, Na + The concentration of K is 78.29 g / L. + The concentration of B is 12.88 g / L. 3+ The concentration is 0.53 g / L, and the pH value of the salt lake brine is 7.3.

[0062] Example 1

[0063] (1) The brine of a salt lake in a certain place is subjected to adsorption and lithium extraction in an adsorption treatment device through an aluminum-based adsorbent (the main component of which is 40-60% aluminum hydroxide) to obtain a LiCl solution, wherein Li + The concentration is 0.620g / L, Mg2+ The concentration is 0.254 g / L, Na + The concentration of K is 0.304 g / L. + The concentration of B is 0.021 g / L. 3+ The concentration is 0.492g / L.

[0064] (2) The LiCl solution is subjected to membrane separation treatment using a nanofiltration membrane, a reverse osmosis membrane and an electrodialysis membrane in sequence, wherein the nanofiltration membrane treatment process includes sequentially performing primary nanofiltration, secondary nanofiltration, RO membrane concentration, tertiary nanofiltration and quaternary nanofiltration, and then concentrating by electrodialysis, and the working conditions of the electrodialysis include a DC voltage of 120 V, a current of 60 A, and a current density of 60 A / m 2 , obtaining a LiCl concentrated solution, wherein in the LiCl concentrated solution, Li + The concentration is 13.12 g / L, Mg 2+ The concentration is 0.574 g / L, Na + The concentration of K is 1.412 g / L. + The concentration of B is 0.478 g / L. 3+ The concentration of Ca is 0.996 g / L, 2+ The concentration is 0.02g / L.

[0065] (3) subjecting the LiCl concentrate to primary and secondary nanofiltration treatments, and then using phenoxyacetic acid resin (the functional group of the phenoxyacetic acid resin is styrene) for adsorption and desorption treatment to obtain a low-calcium and magnesium LiCl solution, wherein the low-calcium and magnesium LiCl solution has Li + The concentration of Mg is 8.338 g / L, 2+ The concentration is 0.0003g / L, Na + The concentration of K is 1.439 g / L. + The concentration of B is 0.458 g / L. 3+ The concentration of Ca is 0.366 g / L, 2+ The concentration is 0.0002g / L.

[0066] (4) treating the low calcium and magnesium LiCl solution with a chelating resin (the functional group of the chelating resin is polyhydroxy) to obtain a refined LiCl solution, wherein Li + The concentration of Mg is 8.276 g / L, 2+ The concentration is 0.0003g / L, Na + The concentration of K is 1.458 g / L. + The concentration of B is 0.469 g / L. 3+ The concentration of Ca is 0.0015 g / L, 2+The concentration is 0.0002g / L.

[0067] (5) The refined LiCl solution is passed through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl. The working conditions of the bipolar membrane electrodialysis system include: a DC voltage of 220 V, a current of 400 A, and a current density of 750 A / m 2 , wherein in the mixed solution of LiOH and NaCl, Li + The concentration of Mg is 13.586 g / L, 2+ The concentration is 0.0003g / L, Na + The concentration of K is 2.453 g / L. + The concentration of B is 0.588 g / L. 3+ The concentration of Ca is 0.016 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration is 32g / L, Cl - The concentration is 6.6g / L, and then electrolyzed by an electrolysis device. The working conditions of the electrolysis device include: DC voltage of 220V, current of 200A, and current density of 700A / m 2 , a refined lithium hydroxide solution is obtained, wherein the refined lithium hydroxide solution, Li + The concentration is 14.32 g / L, Mg 2+ The concentration is 0.0003g / L, Na + The concentration of K is 2.251 g / L. + The concentration of B is 0.533 g / L. 3+ The concentration of Ca is 0.018 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration is 32g / L, Cl - The concentration is 0.97g / L.

[0068] (6) The refined lithium hydroxide solution is subjected to reduced pressure evaporation treatment at a temperature of 85° C., a time of 1.5 h, and a vacuum degree of 450 mbar; and then subjected to drying treatment at a temperature of 110° C., a time of 1.5, to obtain lithium hydroxide monohydrate product A1.

[0069] After calculation, Li in this embodiment + The comprehensive yield is 99%.

[0070] After testing, the main components and contents of the lithium hydroxide monohydrate product obtained in this embodiment and the standards that the battery-grade lithium hydroxide monohydrate product needs to meet are shown in Table 1.

[0071] Table 1

[0072]

[0073] Example 2

[0074] (1) The brine of a salt lake in a certain place is subjected to adsorption and lithium extraction in an adsorption treatment device through an aluminum-based adsorbent (the main component of which is 40-60% aluminum hydroxide) to obtain a LiCl solution, wherein Li + The concentration is 0.698g / L, Mg 2+ The concentration is 0.211g / L, Na + The concentration of K is 0.565 g / L. + The concentration of B is 0.029 g / L. 3+ The concentration is 0.088g / L.

[0075] (2) The LiCl solution is subjected to membrane separation treatment using a nanofiltration membrane, a reverse osmosis membrane and an electrodialysis membrane in sequence, wherein the nanofiltration membrane treatment process includes sequentially performing primary nanofiltration, secondary nanofiltration, RO membrane concentration, tertiary nanofiltration and quaternary nanofiltration, and then concentrating by electrodialysis, and the working conditions of the electrodialysis include a DC voltage of 100 V, a current of 50 A, and a current density of 50 A / m 2 , obtaining a LiCl concentrated solution, wherein in the LiCl concentrated solution, Li + The concentration is 14.25 g / L, Mg 2+ The concentration is 0.468g / L, Na + The concentration of K is 1.196 g / L. + The concentration of B is 0.478 g / L. 3+ The concentration of Ca is 0.996 g / L, 2+ The concentration is 0.02g / L.

[0076] (3) subjecting the LiCl concentrate to primary and secondary nanofiltration treatments, and then using phenoxyacetic acid resin (the functional group of the phenoxyacetic acid resin is styrene) for adsorption and desorption treatment to obtain a low-calcium and magnesium LiCl solution, wherein the low-calcium and magnesium LiCl solution has Li + The concentration is 8.437 g / L, Mg 2+ The concentration is 0.0003g / L, Na + The concentration of K is 0.946 g / L. + The concentration of B is 0.358 g / L. 3+ The concentration of Ca is 0.366 g / L, 2+ The concentration is 0.0002g / L.

[0077] (4) treating the low calcium and magnesium LiCl solution with a chelating resin (the functional group of the chelating resin is polyhydroxy) to obtain a refined LiCl solution, wherein Li + The concentration of Mg is 8.387 g / L, 2+ The concentration is 0.0003g / L, Na + The concentration of K is 0.946 g / L. + The concentration of B is 0.372 g / L. 3+ The concentration of Ca is 0.0015 g / L, 2+ The concentration is 0.0002g / L.

[0078] (5) The refined LiCl solution is passed through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl. The working conditions of the bipolar membrane electrodialysis system include: a DC voltage of 400 V, a current of 400 A, and a current density of 700 A / m 2 , wherein in the mixed solution of LiOH and NaCl, Li + The concentration is 14.537 g / L, Mg 2+ The concentration is 0.0003g / L, Na + The concentration of K is 2.193 g / L. + The concentration of B is 0.498 g / L. 3+ The concentration of Ca is 0.016 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration is 34.45 g / L, Cl - The concentration is 6.53g / L, and then electrolyzed by an electrolysis device. The working conditions of the electrolysis device include: DC voltage of 200V, current of 200A, and current density of 800A / m 2 , a refined lithium hydroxide solution is obtained, wherein in the refined lithium hydroxide solution, Li + The concentration is 14.68 g / L, Mg 2+ The concentration is 0.0003g / L, Na + The concentration of K is 2.213 g / L, + The concentration of B is 0.433 g / L. 3+ The concentration of Ca is 0.017 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration of Cl is 35.29 g / L. - The concentration is 0.88g / L.

[0079] (6) The refined lithium hydroxide solution was subjected to reduced pressure evaporation treatment at a temperature of 86° C., a time of 1.8 h, and a vacuum degree of 380 mbar; and then subjected to drying treatment at a temperature of 110° C., a time of 1.5 h, to obtain lithium hydroxide monohydrate product A2.

[0080] After calculation, Li in this embodiment + The comprehensive yield is 99%.

[0081] After testing, the main components and contents of the lithium hydroxide monohydrate product obtained in this embodiment and the standards that the battery-grade lithium hydroxide monohydrate product needs to meet are shown in Table 2.

[0082] Table 2

[0083]

[0084] Example 3

[0085] (1) The brine of a salt lake in a certain place is subjected to adsorption and lithium extraction in an adsorption treatment device through an aluminum-based adsorbent (the main component of which is 40-60% aluminum hydroxide) to obtain a LiCl solution, wherein Li + The concentration is 0.751 g / L, Mg 2+ The concentration is 0.277 g / L, Na + The concentration of K is 0.436 g / L. + The concentration of B is 0.033 g / L. 3+ The concentration is 0.102g / L.

[0086] (2) The LiCl solution is subjected to membrane separation treatment using a nanofiltration membrane, a reverse osmosis membrane and an electrodialysis membrane in sequence, wherein the nanofiltration membrane treatment process includes sequentially performing primary nanofiltration, secondary nanofiltration, RO membrane concentration, tertiary nanofiltration and quaternary nanofiltration, and then concentrating by electrodialysis, and the working conditions of the electrodialysis include a DC voltage of 140 V, a current of 60 A, and a current density of 60 A / m 2 , obtaining a LiCl concentrated solution, wherein in the LiCl concentrated solution, Li + The concentration is 14.42 g / L, Mg 2+ The concentration is 0.552g / L, Na + The concentration of K is 1.257 g / L. + The concentration of B is 0.502 g / L. 3+ The concentration of Ca is 0.815 g / L, 2+ The concentration is 0.02g / L.

[0087] (3) subjecting the LiCl concentrate to primary and secondary nanofiltration treatments, and then subjecting the LiCl concentrate to adsorption and desorption treatment using a phenoxyacetic acid resin (the functional group of the phenoxyacetic acid resin is styrene) to obtain a low-calcium and magnesium LiCl solution, wherein the Li + The concentration is 8.762g / L, Mg 2+ The concentration is 0.0002g / L, Na + The concentration of K is 1.397 g / L. + The concentration of B is 0.511 g / L. 3+ The concentration of Ca is 0.409 g / L, 2+ The concentration is 0.0002g / L.

[0088] (4) treating the low calcium and magnesium LiCl solution with a chelating resin (the functional group of the chelating resin is polyhydroxy) to obtain a refined LiCl solution, wherein Li + The concentration is 8.665g / L, Mg 2+ The concentration is 0.0002g / L, Na + The concentration of K is 1.482 g / L. + The concentration of B is 0.494 g / L. 3+ The concentration of Ca is 0.0019 g / L, 2+ The concentration is 0.0002g / L.

[0089] (5) The refined LiCl solution is passed through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl. The working conditions of the bipolar membrane electrodialysis system include: a DC voltage of 400 V, a current of 400 A, and a current density of 800 A / m 2 , wherein in the mixed solution of LiOH and NaCl, Li + The concentration is 14.45 g / L, Mg 2+ The concentration is 0.0002g / L, Na + The concentration of K is 1.661 g / L. + The concentration of B is 0.549 g / L. 3+ The concentration of Ca is 0.323 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration is 30.24 g / L, Cl - The concentration is 6.88g / L, and then electrolyzed by an electrolysis device. The working conditions of the electrolysis device include: DC voltage of 200V, current of 180A, and current density of 180A / m 2 , to obtain a refined lithium hydroxide solution, wherein the refined lithium hydroxide solution, Li +The concentration is 14.98 g / L, Mg 2+ The concentration is 0.0002g / L, Na + The concentration of K is 1.721 g / L. + The concentration of B is 0.552 g / L. 3+ The concentration of Ca is 0.339 g / L, 2+ The concentration is 0.0003g / L, OH - The concentration of Cl is 30.66 g / L. - The concentration is 6.83g / L.

[0090] (6) The refined lithium hydroxide solution is subjected to reduced pressure evaporation treatment at a temperature of 87° C., a time of 2 h, and a vacuum degree of 480 mbar; and then subjected to drying treatment at a temperature of 100° C., a time of 1.6 h, to obtain lithium hydroxide monohydrate.

[0091] After calculation, Li in this embodiment + The comprehensive yield is 99%.

[0092] After testing, the main components and contents of the lithium hydroxide monohydrate product obtained in this embodiment and the standards that the battery-grade lithium hydroxide monohydrate product needs to meet are shown in Table 3.

[0093] Table 3

[0094]

[0095] Comparative Example 1

[0096] Lithium hydroxide monohydrate is prepared using salt lake brine according to the method of Example 1, except that in step (5), electrolysis is not performed by an electrolysis device, and lithium hydroxide product D1 is finally prepared.

[0097] After calculation, Li + The comprehensive yield is 99%.

[0098] After testing, the main components and contents of the lithium hydroxide product D1 obtained in this comparative example and the standards that the battery-grade lithium hydroxide monohydrate product needs to meet are shown in Table 4.

[0099] Table 4

[0100]

[0101]

[0102] From the data comparison of Examples 1-3 and Comparative Example 1, it can be seen that the lithium hydroxide obtained by the method for preparing single-water lithium hydroxide using salt lake brine according to the present invention has a lower Cl - content.

[0103] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing battery-grade lithium hydroxide monohydrate using salt lake brine, characterized in that: The method comprises the following steps: (1) extracting lithium from salt lake brine by adsorbing it through an aluminum-based lithium adsorbent to obtain a LiCl solution; (2) subjecting the LiCl solution to membrane separation treatment and concentrating it by electrodialysis to obtain a LiCl concentrated solution; (3) The LiCl concentrate is subjected to nanofiltration treatment, and then subjected to adsorption and desorption treatment using an ion exchange resin to obtain Mg 2 + Concentration ≤5mg / L and Ca 2+ Low calcium and magnesium LiCl solution with a concentration of ≤2mg / L; (4) removing boron from the low calcium and magnesium LiCl solution through a chelating resin to obtain B 3+ Refined LiCl solution with a concentration of ≤10mg / L; (5) passing the refined LiCl solution through a bipolar membrane electrodialysis system to obtain a mixed solution of LiOH and NaCl, and then electrolyzing it through an electrolysis device to obtain a refined lithium hydroxide solution; (6) The lithium hydroxide solution is evaporated under reduced pressure and dried.

2. The method according to claim 1, characterized in that In step (1), the salt lake brine contains the following components: Li + ≥0.1g / L, Mg 2+ ≤85g / L, Na + ≤85g / L, K + ≤15g / L, B 3+ ≤0.6g / L, and pH≥7.2, and the pH value of the salt lake brine is ≥7.

2.

3. The method according to claim 1 or 2, characterized in that: In step (1), the LiCl solution contains the following components: Li + ≥0.5g / L, Mg 2+ ≤0.5g / L, Na + ≤0.6g / L, K + ≤0.15g / L, B 3+ ≤0.5g / L.

4. The method according to claim 1, characterized in that In step (2), the membrane separation treatment is carried out using at least one of a nanofiltration membrane, a reverse osmosis membrane and an electrodialysis membrane.

5. The method according to claim 1 or 4, characterized in that: In step (2), the LiCl concentrate contains the following components: Li + ≥12g / L, Mg 2+ ≤0.6g / L, Na + ≤1.6g / L, K + ≤0.51g / L, B 3+ ≤1g / L, Ca 2+ ≤0.02g / L.

6. The method according to claim 1, characterized in that In step (3), the nanofiltration treatment is carried out in a two-stage nanofiltration manner.

7. The method according to claim 1 or 6, characterized in that: In step (3), the ion exchange resin is a phenoxyacetic acid resin, and the functional group of the phenoxyacetic acid resin is at least one of a halogen, a hydroxyl, an amino, a thiol, a carboxyl, an ester, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted alkenyl, a substituted or unsubstituted alkynyl and a substituted or unsubstituted aryl.

8. The method according to claim 1, characterized in that In step (3), the low calcium and magnesium LiCl solution contains the following components: Li + ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.52g / L, B 3+ ≤0.41g / L, Ca 2+ ≤2mg / L.

9. The method according to claim 1, characterized in that: In step (4), the functional group of the chelating resin is at least one of N-methylglucosamine, halogen, hydroxyl, amino, thiol, carboxyl, ester, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl and substituted or unsubstituted aromatic.

10. The method according to claim 1, characterized in that: In step (4), the refined LiCl solution contains the following components: Li + ≥8g / L, Mg 2+ ≤5mg / L, Na + ≤1.6g / L, K + ≤0.5g / L, B 3+ ≤10mg / L, Ca 2+ ≤2mg / L.

11. The method according to claim 1, characterized in that: In step (5), the working conditions of the bipolar membrane electrodialysis system include: DC voltage of 220-400V, current of 200-400A, current density of 700-800A / m 2 .

12. The method according to claim 1 or 11, characterized in that: In step (5), the mixed solution of LiOH and NaCl contains the following components: Li + ≥13g / L, Mg 2+ ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - 3~7g / L.

13. The method according to any one of claims 1, 11 and 12, characterized in that: In step (5), the refined LiOH solution contains the following components: Li + ≥14g / L, Mg 2+ ≤20mg / L, Na + ≤2.5g / L, K + ≤0.6g / L, B 3+ ≤0.35g / L, Ca 2+ ≤15mg / L, OH — ≥30g / L, Cl - ≤7g / L.

14. The method according to claim 1, characterized in that In step (6), the conditions for the reduced pressure evaporation include: temperature of 85-87° C., time of 1-3 h, and vacuum degree of 380-480 mbar.

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