A method for extracting lithium from salt lake brine

Abstract

The application provides a method for extracting lithium from salt lake brine. The method comprises the following steps: obtaining multiple analysis solutions with different lithium-sodium molar ratios through analysis treatment, and mixing qualified analysis solutions obtained according to the lithium-sodium molar ratio, so that the lithium-sodium ratio in the obtained qualified analysis mixed solution is high. In combination with subsequent bipolar membrane electrolysis treatment and high-temperature impurity removal and pulp washing treatment, impurity elements such as sodium and / or potassium are further removed, which is beneficial to obtaining high-purity lithium carbonate products. In addition, the method for extracting lithium from salt lake brine provided by the application does not produce harmful and environmentally polluting products, and does not consume a large amount of ingredients other than salt lake brine, thereby improving environmental protection and effectively reducing production cost.

Description

Technical Field

[0001] This application relates to the field of lithium resource extraction technology, and in particular to a method for extracting lithium from salt lake brine. Background Technology

[0002] Currently, most lithium salts in China are extracted from ores. However, with the continuous depletion of high-grade lithium ores and the increasing cost of lithium extraction from ores, lithium extraction from salt lakes, rich in lithium, has significant resource and cost advantages over ores. Therefore, lithium extraction from salt lakes has become an inevitable trend in lithium resource development.

[0003] The key to lithium extraction from salt lakes lies in enriching lithium ions from the brine at a relatively low cost and precipitating them into lithium carbonate or lithium hydroxide, thereby producing value-added products. There are two main influencing factors for lithium extraction from salt lakes: first, the lithium content in the salt lake; the lower the lithium content, the longer the processing flow, the greater the evaporation rate after processing, and the higher the cost; second, the ratio of various mineral ions in the salt lake, especially the magnesium-to-lithium ratio and the boron-to-lithium ratio, generally the lower the magnesium-to-lithium and boron-to-lithium ratios, the better. Currently, the main methods for directly extracting lithium from raw salt lake brine and producing lithium carbonate include sun-drying, solar energy, solvent extraction, precipitation, calcination, adsorption, membrane extraction, and electrodialysis.

[0004] Sun-drying and solar energy methods are suitable for salt lake brines with low magnesium-to-lithium ratios, but they are inefficient and have low lithium yields. Solvent extraction uses organic solvents, and the use of large amounts of organic solvents not only severely corrodes equipment but also pollutes the surrounding environment. Electrodialysis has high energy consumption and low water yield. The calcination method uses lithium-containing brine after potassium and boron extraction as raw material, evaporates to remove water, obtains lithium-containing magnesium chloride tetrahydrate, spray-dries and calcines it to obtain lithium-containing magnesium oxide, washes and filters with water to leach lithium, removes calcium, magnesium and other impurities with lime milk, evaporates and concentrates the solution, and adds soda ash to precipitate lithium carbonate. This method has high energy consumption and pollutes the environment.

[0005] With the large-scale utilization of lithium resources, a method for extracting lithium from salt lake brine that is low in production cost, low in environmental pollution and energy consumption, and can also extract and produce other high-value-added products from salt lakes, thus achieving the comprehensive utilization of salt lake resources, has become a technical problem that researchers in this field urgently need to solve. Summary of the Invention

[0006] The purpose of this application is to provide a method for extracting lithium from salt lake brine, thereby improving the purity of lithium carbonate products and reducing the sodium content. The specific technical solution is as follows:

[0007] This application provides a method for extracting lithium from salt lake brine, which includes the following steps:

[0008] S100. The brine from the salt lake is passed through a lithium extraction resin for adsorption treatment, and then purified with pure water for desorption treatment. During the desorption treatment, N equal volumes of desorbed liquid are obtained, and they are recorded as the first desorbed liquid to the Nth desorbed liquid in the order they are obtained.

[0009] S200, Obtain the molar concentration C of lithium element in each portion of the eluent. Li With sodium molar concentration C Na , ;

[0010] S300. Obtain the sum of the lithium molar concentrations from the Nth eluent sample to the nth eluent sample, denoted as C. Li和 The sum of the molar concentrations of sodium from the Nth eluent to the nth eluent is obtained, denoted as C. Na和 ;

[0011] The molar concentration ratio C of lithium and sodium is obtained according to Equation I. Li / Na ,

[0012] C Li / Na =C Li和 / C Na和 Formula I

[0013] According to C Li / Na Based on the relationship with a0, a qualified eluent is obtained, and the qualified eluent is mixed to obtain a qualified eluent mixture;

[0014] Where a0 is a preset value for the molar ratio of lithium to sodium, 2≤a0≤5, N≥3;

[0015] n satisfies 1≤n≤N, where n is an integer and takes values ​​from N in descending order;

[0016] S400. The qualified analytical mixture is subjected to bipolar membrane electrolysis at least once to obtain a solution containing LiOH;

[0017] S500. Carbon dioxide is introduced into the solution containing LiOH for separation treatment to obtain solid phase a. The solid phase a is subjected to high-temperature impurity removal and slurry washing treatment to obtain lithium carbonate product.

[0018] In some embodiments of this application,

[0019] The step S300 described according to C Li / Na The relationship with a0, obtaining a qualified analytical solution, including,

[0020] If C Li / Na If a ≥ 0, then the Nth to nth portions of the analytical solution are all qualified analytical solutions;

[0021] If C Li / NaIf <a0, then the nth batch of analytical solution is a substandard analytical solution.

[0022] In some embodiments of this application, in step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies any one of the following conditions:

[0023] Condition 1: If 2≤a 混 If ≤50, then t≥4.5h;

[0024] Condition 2: If 50<a 混 If ≤100, then t≥3.5h;

[0025] Condition 3: If 100<a 混 Then t≥3h;

[0026] The molar ratio of lithium to sodium in the qualified analytical solution is denoted as a. 混 .

[0027] In some embodiments of this application, the time t of the high-temperature impurity removal and washing treatment satisfies any one of the following conditions:

[0028] Condition 1: If 2≤a 混 If ≤50, then 4.5h≤t≤5.5h;

[0029] Condition 2: If 50<a 混 If ≤100, then 3.5h≤t≤4.5h;

[0030] Condition 3: If 100<a 混 Therefore, 3h≤t≤3.5h.

[0031] In some embodiments of this application, step S100, which involves passing the brine from the salt lake into the lithium extraction resin for adsorption treatment, includes: adjusting the pH of the brine from the salt lake to 5-6, and then passing it into the lithium extraction resin for the adsorption treatment.

[0032] In some embodiments of this application, in step S100, N satisfies 3≤N≤50.

[0033] In some embodiments of this application, in step S100, at least one of the following conditions is met:

[0034] Condition a: The temperature of the adsorption treatment is 15℃~35℃, and the flow rate V1 of the adsorption treatment is 1BV / h~3BVh;

[0035] Condition b: The temperature of the analytical processing is 15℃~35℃, and the flow rate V2 of the analytical processing is 4BV / h~6BV / h.

[0036] In some embodiments of this application, step S400 includes sequentially performing concentration treatment, impurity removal treatment and bipolar membrane electrolysis treatment on the qualified analytical mixture to obtain the solution containing LiOH.

[0037] In some embodiments of this application, in step S400, at least one of the following conditions is met:

[0038] Condition c: The concentration process is carried out to obtain lithium chloride solution 1, wherein the mass concentration C1 of LiCl in lithium chloride solution 1 is 50 g / L to 100 g / L;

[0039] Condition d: The impurity removal process is performed to obtain lithium chloride solution 2, wherein the mass concentration C2 of calcium and / or magnesium in lithium chloride solution 2 is less than 5 ppm;

[0040] Condition e: In the bipolar membrane electrolysis treatment, the electrolysis voltage is 27V~29V, the electrolysis current is 8A~9A, and the electrolysis temperature is 10℃~40℃;

[0041] Condition f, the termination condition of the bipolar membrane electrolysis treatment includes: H generated during electrolysis + or OH - The electrolysis process is terminated when the concentration reaches 1 mol / L to 3 mol / L.

[0042] The beneficial effects of this application are:

[0043] This application provides a method for extracting lithium from salt lake brine. The method involves obtaining multiple eluents with different molar ratios of lithium to sodium through analytical treatment. After mixing these eluents to obtain a suitable eluent with the correct lithium-to-sodium molar ratio, the resulting suitable eluent mixture has a high lithium-to-sodium ratio. Subsequent bipolar membrane electrolysis and high-temperature slurry washing further remove impurities such as sodium and / or potassium, resulting in a high-purity lithium carbonate product. For example, the purity of the lithium carbonate product can reach over 99.5%, with a sodium content of less than 150 ppm. Furthermore, the lithium extraction method provided in this application does not produce harmful or environmentally polluting byproducts and does not consume large amounts of ingredients other than the salt lake brine, thus improving environmental friendliness and effectively reducing production costs, making it commercially valuable.

[0044] Furthermore, the qualified analytical mixture obtained by the method of this application has an impurity element to lithium / sodium molar concentration ratio a 混 The linear relationship between them is high, therefore it can be achieved by utilizing different a 混 The value is used to determine the time for high-temperature impurity removal and slurry washing treatment, thereby obtaining low-energy-consumption, high-purity lithium carbonate products.

[0045] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0047] Figure 1 This is a flowchart illustrating a method for extracting lithium from salt lake brine according to one embodiment of this application. Detailed Implementation

[0048] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0049] This application provides a method for extracting lithium from salt lake brine, exemplarily, such as... Figure 1 As shown, it includes the following steps:

[0050] S100. The brine from the salt lake is passed through a lithium extraction resin for adsorption treatment, and then purified water is used for desorption treatment. During the desorption treatment, N equal volumes of desorbed liquid are obtained, and they are recorded as the first desorbed liquid to the Nth desorbed liquid in the order they are obtained.

[0051] S200, Obtain the molar concentration of lithium in each eluent sample C Li With sodium molar concentration C Na ;

[0052] S300. Obtain the sum of the lithium molar concentrations from the Nth eluent sample to the nth eluent sample, denoted as C. Li和 The sum of the molar concentrations of sodium from the Nth eluent to the nth eluent is obtained, denoted as C. Na和 ;

[0053] The molar concentration ratio C of lithium and sodium is obtained according to Equation I. Li / Na ,

[0054] C Li / Na =C Li和 / C Na和 Formula I

[0055] According to C Li / Na The relationship with a0 is used to obtain a qualified eluent, and the qualified eluent is mixed to obtain a qualified eluent mixture;

[0056] Where a0 is a preset value for the molar ratio of lithium to sodium, 2≤a0≤5, N≥3;

[0057] n satisfies 1≤n≤N, where n is an integer and takes values ​​from N in descending order;

[0058] S400. The qualified analytical mixture shall be subjected to bipolar membrane electrolysis at least once to obtain a solution containing LiOH.

[0059] S500: Carbon dioxide is introduced into a solution containing LiOH, and the solution is separated to obtain solid phase a. Solid phase a is then subjected to high-temperature impurity removal and slurry washing to obtain lithium carbonate product.

[0060] The method for extracting lithium from salt lake brine provided in this application involves obtaining multiple eluents with different molar ratios of lithium to sodium through analytical processing. The lithium-to-sodium ratio of these eluents generally shows an increasing trend over time; however, this application does not rule out the possibility of some data showing a decrease, but this does not affect the overall increasing trend. Furthermore, according to C... Li / Na After mixing with the qualified eluent obtained from a0, the resulting qualified eluent mixture has a high lithium-sodium ratio. Combined with subsequent bipolar membrane electrolysis and high-temperature impurity removal washing, further impurities such as sodium and / or potassium are removed, which is beneficial for obtaining high-purity lithium carbonate products. For example, the purity of the lithium carbonate product can reach 99.5% with a sodium content of less than 150 ppm, meeting the standards for battery-grade lithium carbonate products specified in industry standard YS / T 582-2023 "Battery-Grade Lithium Carbonate". Furthermore, the lithium extraction method from salt lake brine provided in this application does not produce harmful or environmentally polluting products, nor does it consume large amounts of ingredients other than salt lake brine. This improves environmental friendliness while effectively reducing production costs, giving it high commercial value.

[0061] a0 is a preset value for the molar ratio of lithium to sodium, where 2 ≤ a0 ≤ 5. For example, a0 can be any value among 2, 2.5, 3, 3.5, 4, and 5, or a range of any two values ​​in between. The number of eluent fractions N ≥ 3. For example, N can be any value among 3, 4, 5, 10, 15, 20, 25, 30, 50, 100, and 150, or a range of any two values ​​in between. In this application, the number of eluent fractions can be determined based on the volume of the brine in the salt lake and the equivalence of the lithium extraction resin.

[0062] In some embodiments, the lithium extraction resin may include, but is not limited to, at least one of aluminum-based lithium adsorbents, manganese-based lithium adsorbents, etc. The lithium extraction resin in this invention is commercially available.

[0063] In some embodiments of this application, step S300 is performed according to C Li / NaThe relationship with a0, obtaining a qualified analytical solution, includes, if C Li / Na If a ≥ 0, then the Nth to nth portions of the eluent are all qualified eluents; if C Li / Na If a < a0, then the nth analytical solution is a substandard analytical solution. Exemplarily, in some embodiments, for example, when N is 20, the 20th analytical solution C is obtained first. Li / Na Compare with a0, if C Li / Na If a ≥ 0, then the 20th eluent sample is a qualified eluent; then obtain the C saturation values ​​of eluent samples 20 to 19. Li / Na Compare with a0, if C Li / Na If a ≥ 0, then the 20th to 19th eluent samples are qualified eluent samples; then obtain the C saturation of the 20th to 18th eluent samples. Li / Na Compare with a0, if C Li / Na If a ≥ 0, then the 20th to 18th analytical solutions are qualified analytical solutions... Following the steps described above, calculate the corresponding C for each additional analytical solution in descending order of its serial number. Li / Na Then compare it with a0, until C. Li / Na <a0, let C be the value at this time. Li / Na C for the Nth to xth eluent samples Li / Na If the Nth to x+1th portions of the eluent are considered qualified eluents, and the xth to 1st portions are considered unqualified eluents, where 1 ≤ x < n. The qualified eluent mixture obtained by mixing the qualified eluents obtained using the above method has a high lithium-to-sodium ratio and relatively controllable impurity content. This is beneficial for obtaining high-purity lithium carbonate products through subsequent bipolar membrane electrolysis and high-temperature impurity removal washing, thus improving the purity of the lithium carbonate product and reducing its sodium content.

[0064] In some embodiments of this application, in step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies any one of the following conditions: Condition 1: If 2 ≤ a 混 If ≤50, then t≥4.5h; Condition 2: If 50<a 混 If ≤100, then t≥3.5h; Condition 3: If 100<a 混 If t ≥ 3h, then t ≥ 3h; where, the molar ratio of lithium to sodium in the qualified analytical solution is denoted as a. 混 In some embodiments of this application, the high-temperature impurity removal and washing time t satisfies any one of the following conditions: Condition 1: If 2 ≤ a 混 If ≤50, then 4.5h≤t≤5.5h; Condition 2: If 50<a 混 If ≤100, then 3.5h≤t≤4.5h; Condition 3: If 100<a 混Then 3h ≤ t ≤ 3.5h. For example, T can be 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, or a range of any two values ​​within this range. For example, a 混 It can be a range of 2, 10, 15, 20, 25, 30, 35, 40, 45, 50, or any two values ​​within that range; t can be 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, or any two values ​​within that range. For example, a 混 The range can be 51, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, or any two values ​​within this range. t can be 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, or any two values ​​within this range. For example, a 混 The time interval can be 101, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, or any range of two values ​​within this range. For example, t can be 3h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, or any range of two values ​​within this range. By controlling the temperature of the high-temperature impurity removal slurry washing process within the above range, lithium carbonate is basically insoluble in water, but sodium carbonate and potassium carbonate have high solubility. Therefore, the high-temperature impurity removal slurry washing process can remove impurity elements sodium and / or potassium, thereby obtaining a high-purity lithium carbonate product. In addition, the high-temperature impurity removal slurry washing process has high temperature and high energy consumption. Since the correlation between impurity ions and the lithium-sodium ratio in the qualified eluent obtained in this application is good, the molar concentration ratio α of lithium to sodium in the qualified eluent can be used as a reference. 混 Determine the time t, a for high-temperature impurity removal and washing treatment. 混 Matching with t, when achieving the required purity of lithium carbonate products, excessive washing can be minimized. On the one hand, this helps reduce energy consumption in high-temperature impurity removal washing processes; on the other hand, it reduces lithium loss caused by excessive washing and improves the recovery rate of lithium elements.

[0065] In some embodiments, the high-temperature impurity removal slurry washing process involves soaking and stirring solid phase a in pure water to remove sodium and / or potassium elements. This application does not limit the content of solid phase a in pure water, as long as it achieves the purpose of this application. For example, the content of solid phase a in pure water can be from 500 g / L to 1500 g / L.

[0066] In some embodiments of this application, in step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies condition 1: if 2 ≤ a 混 If ≤50, then t≥4.5h; preferably, if 2≤a 混 ≤50, then 4.5h≤t≤5.5h. a 混 Within the above range, it indicates that the lithium and sodium content in the qualified analytical solution is relatively low, while the impurity elements are relatively high. Matching the high-temperature impurity removal slurry washing treatment time t within the above range can effectively remove the impurity elements and obtain a high-purity lithium carbonate product.

[0067] In some embodiments of this application, in step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies condition 2: if 50 < a 混 If ≤100, then t≥3.5h; preferably, if 50<a 混 ≤100, then 3.5h≤t≤4.5h. a 混 Within the above range, the lithium-to-sodium ratio in the qualified analytical solution increases compared to condition 1, the content of impurity elements decreases, and the time t for high-temperature impurity removal slurry washing within the above range can be shortened compared to condition 1, which can also effectively remove impurity elements and obtain high-purity lithium carbonate products.

[0068] In some embodiments of this application, in step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies condition 3: if 100 < a 混 If t ≥ 3h; preferably, if 100 < a 混 , then 3h≤t≤3.5h. a 混 Within the above range, the lithium-to-sodium ratio in the qualified analytical solution increases compared to condition 2, and the content of impurity elements is further reduced. The time t for high-temperature impurity removal slurry washing within the above range can be shortened compared to condition 2, and impurity elements can be effectively removed to obtain high-purity lithium carbonate products.

[0069] In some embodiments of this application, step S100, which involves passing the brine into the lithium extraction resin for adsorption treatment, includes adjusting the pH of the brine to 5-6, and then passing it into the lithium extraction resin for adsorption treatment. For example, the pH of the brine can be adjusted to 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, or any range of two values ​​within this range. Adjusting the pH of the brine to this range allows the lithium extraction resin to more fully exert its adsorption effect.

[0070] In some implementation schemes, the pH of the salt lake brine can be adjusted to 5-6 by adding at least one of hydrochloric acid and sulfuric acid.

[0071] In some embodiments of this application, in step S100, N satisfies 3 ≤ N ≤ 50. For example, N can be 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a range of any two values ​​within this range. By adjusting N within the above range, the proportion of the eluent obtained is reasonable, and while screening for qualified eluent, the proportion of unqualified eluent is minimized, which is beneficial to improving the overall lithium recovery rate.

[0072] In some embodiments of this application, step S100 satisfies at least one of the following conditions: condition a, the adsorption treatment temperature is 15℃~35℃, and the adsorption treatment flow rate V1 is 1BV / h~3BV / h; condition b, the desorption treatment temperature is 15℃~35℃, and the desorption treatment flow rate V2 is 4BV / h~6BV / h. For example, the desorption treatment temperature can be 15℃, 18℃, 20℃, 23℃, 25℃, 28℃, 30℃, 33℃, 35℃, or a range of any two values ​​therein. For example, the adsorption treatment temperature can be 15℃, 18℃, 20℃, 23℃, 25℃, 28℃, 30℃, 33℃, 35℃, or a range of any two values ​​therein. For example, V1 can be 1 BV / h, 1.3 BV / h, 1.5 BV / h, 1.8 BV / h, 2 BV / h, 2.3 BV / h, 2.5 BV / h, 2.8 BV / h, 3 BV / h, or a range of any two values ​​within this range. For example, the flow rate for the analytical treatment can be 4 BV / h, 4.3 BV / h, 4.5 BV / h, 4.8 BV / h, 5 BV / h, 5.3 BV / h, 5.5 BV / h, 5.8 BV / h, 6 BV / h, or a range of any two values ​​within this range. Step S100 satisfying at least one of the above conditions is beneficial for achieving lithium recovery and improving the lithium recovery rate. In this application, the flow rates of the adsorption treatment and the desorption treatment are calculated in terms of the equivalent volume of lithium extraction resin. For example, the flow rate V1 of the adsorption treatment is 2 BV / h, which means that 2 times the volume of lithium extraction resin flows through the brine of the salt lake per hour. The same logic applies when the flow rate V1 is other values. Similarly, the flow rate V2 of the desorption treatment is 4 BV / h, which means that 4 times the volume of lithium extraction resin flows through the pure water per hour. The same logic applies when the flow rate V2 is other values.

[0073] In some embodiments of this application, in step S100, condition a is met: the adsorption treatment temperature is 15℃~35℃, and the adsorption treatment flow rate V1 is 1BV / h~3BV / h. By controlling the adsorption treatment temperature and flow rate within the above range, it is beneficial for lithium elements in the salt lake brine to be fully adsorbed into the lithium extraction resin, and for lithium elements to be recovered in combination with subsequent treatment.

[0074] In some embodiments of this application, in step S100, condition b is met, the temperature of the elution treatment is 15℃~35℃, and the flow rate V2 of the elution treatment is 4BV / h~6BV / h. By controlling the temperature and flow rate of the elution treatment within the above range, it is beneficial to fully elute the lithium element in the lithium extraction resin into pure water, thereby improving the lithium recovery rate.

[0075] In some embodiments of this application, exemplarily, such as Figure 1 As shown, step S400 includes sequentially concentrating the qualified eluent mixture, removing impurities, and performing bipolar membrane electrolysis to obtain a solution containing LiOH. The qualified eluent mixture is first concentrated to increase the concentration of lithium ions in the liquid phase, then removed to primarily remove impurity elements such as calcium and / or magnesium, and finally subjected to bipolar membrane electrolysis. The resulting LiOH-containing solution has a low content of impurity elements, yielding a high-purity lithium carbonate product.

[0076] In some embodiments, the concentration process includes concentration using a filter membrane, or concentration using evaporation. In some embodiments, the filter membrane may include, but is not limited to, a seawater desalination membrane. In this application, evaporation refers to removing part of the solvent from the qualified eluent mixture by raising the temperature. This application does not limit the temperature and time of the evaporation process, as long as the purpose of this application is achieved.

[0077] In some embodiments, the impurity removal process includes preliminary impurity removal using a nanofiltration membrane, followed by deep impurity removal using a purification resin. In some embodiments, the purification resin is selected from at least one commercially available cation exchange resin such as CH90-Na, CH93-Na, Amberlite™ IRC748, DOWEX™ M4195, and Purolite® S930, for Cu... 2+ Fe 3+ Al 3+ Ca 2+ Mg 2+ The target impurity ions exhibit excellent selective adsorption capacity.

[0078] In some embodiments of this application, step S400 satisfies at least one of the following conditions: condition c, a concentration treatment is performed to obtain lithium chloride solution 1, wherein the mass concentration C1 of LiCl in lithium chloride solution 1 is 50 g / L to 100 g / L; condition d, a purification treatment is performed to obtain lithium chloride solution 2, wherein the mass concentration C2 of calcium and / or magnesium in lithium chloride solution 2 is less than 5 ppm; condition e, in the bipolar membrane electrolysis treatment, the electrolysis voltage is 27 V to 29 V, the electrolysis current is 8 A to 9 A, and the electrolysis temperature is 10 ° C to 40 ° C; condition f, the termination conditions of the bipolar membrane electrolysis treatment include: the H generated by electrolysis + or OH - Electrolysis is terminated when the concentration C3 reaches 1 mol / L to 3 mol / L. For example, C1 can be 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, or any two values ​​within this range. For example, C2 can be 0.1 ppm, 0.5 ppm, 1 ppm, 1.5 ppm, 2 ppm, 2.5 ppm, 3 ppm, 3.5 ppm, 4 ppm, 4.5 ppm, 5 ppm, or any two values ​​within this range. For example, the electrolysis voltage can be 27 V, 27.3 V, 27.5 V, 27.8 V, 28 V, 28.3 V, 28.5 V, 28.8 V, 29 V, or any two values ​​within this range. For example, the electrolysis current can be 8A, 8.1A, 8.3A, 8.4A, 8.5A, 8.6A, 8.8A, 8.9A, 9A, or any combination of two values ​​within this range. For example, the electrolysis temperature can be 10℃, 13℃, 15℃, 18℃, 20℃, 23℃, 25℃, 28℃, 30℃, 33℃, 35℃, 38℃, 40℃, or any combination of two values ​​within this range. For example, C3 can be 1mol / L, 1.3mol / L, 1.5mol / L, 1.8mol / L, 2mol / L, 2.3mol / L, 2.5mol / L, 2.8mol / L, 3mol / L, or any combination of two values ​​within this range. Step S400 satisfying at least one of the above conditions is beneficial for improving the purity of the lithium carbonate product.

[0079] In some embodiments of this application, in step S400, condition c is met, and a concentration process is performed to obtain lithium chloride solution 1, wherein the mass concentration C1 of LiCl in lithium chloride solution 1 is 50 g / L to 100 g / L. By adjusting C1 within the above range, it is beneficial to carry out subsequent impurity removal and bipolar membrane electrolysis processes smoothly, so as to achieve the extraction of lithium source.

[0080] In some embodiments of this application, in step S400, after satisfying condition d, a lithium chloride solution 2 is obtained by impurity removal treatment, wherein the mass concentration C2 of calcium and / or magnesium in the lithium chloride solution 2 is less than 5 ppm. By controlling C2 within the above range, that is, the content of impurity elements in the lithium chloride solution 2 is low, which, combined with the subsequent high-temperature impurity removal and washing treatment, is beneficial to improving the purity of the lithium carbonate product.

[0081] In some embodiments of this application, in step S400, condition e is met: in the bipolar membrane electrolysis treatment, the electrolysis voltage is 27V~29V, the electrolysis current is 8A~9A, and the electrolysis temperature is 10℃~40℃. In the bipolar membrane electrolysis treatment, the lithium chloride solution 2 is electrolyzed using a bipolar membrane electrodialysis device. During the electrolysis process, LiCl in the lithium chloride solution 2 will ionize into Li in the solution. + and Cl - Simultaneously, water in lithium chloride solution 2 is electrolyzed to obtain H. + and OH - OH - With ionized Li + The reaction produces LiOH, i.e., a solution containing LiOH. Additionally, H... + With ionized Cl - The reaction produces HCl, which also yields a solution containing HCl. By controlling the electrolysis voltage, current, and temperature within the aforementioned ranges, it is beneficial to promote the full progress of the bipolar membrane electrolysis reaction and increase the reaction rate to obtain a solution containing LiOH, thus providing a foundation for the subsequent production of lithium carbonate products.

[0082] The bipolar membrane electrodialysis device of this application includes a bipolar membrane (cation exchange membrane and anion exchange membrane), an acid chamber, and an alkali chamber. The electrolysis of water occurs separately inside the bipolar membrane. Under the action of reverse bias, the generated OH-... - Migrating to the alkaline chamber, the generated H + Migration to the acid chamber, Li + Attracted by the cathode, it migrates towards the cathode, passes through the cation exchange membrane (CEM) and enters the alkaline chamber, where it reacts with the OH- produced by the bipolar membrane. - Combined, forming a solution containing LiOH; Cl - Attracted by the anode, it migrates towards the anode, passes through the anion exchange membrane (AEM) and enters the acid chamber, where it reacts with H+ generated by the bipolar membrane. +The HCl and LiOH are combined to form HCl, thus physically separating the generated HCl and LiOH into different chambers, facilitating the subsequent preparation of a LiOH-containing solution. Therefore, in this application, the use of a bipolar membrane electrodialysis device to electrolyze lithium chloride solution 2 directly converts LiCl into lithium hydroxide and hydrochloric acid, facilitating the collection of the LiOH-containing solution, being environmentally friendly, and producing a high-purity LiOH-containing solution. Simultaneously, due to the bipolar membrane setup, the cation exchange membrane effectively separates LiCl from LiOH. + It has high selectivity and can remove most of the Li in lithium chloride solution 2. + The lithium is drawn into the alkali chamber, which helps to increase the yield of the LiOH-containing solution and improve the overall lithium recovery rate. This application does not specifically limit the source of the aforementioned bipolar membrane electrodialysis equipment, as long as it can achieve the purpose of this application. For example, the aforementioned bipolar membrane electrodialysis equipment can be obtained by purchase.

[0083] In some embodiments of this application, in step S300, the conditions for terminating the bipolar membrane electrolysis process, including satisfying condition f, include: the H generated during electrolysis. + or OH - Electrolysis was terminated when the concentration of C3 reached 1 mol / L to 3 mol / L. The H2 produced during electrolysis... + or OH - Reaching the above concentration range not only yields a higher concentration of LiOH-containing solution, but also helps extend the service life of the bipolar membrane in the bipolar membrane electrodialysis equipment, thereby reducing the cost of lithium extraction from salt lake brine.

[0084] Example

[0085] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0086] Example 1

[0087] In this embodiment, a solution was prepared using lithium chloride, sodium chloride, magnesium chloride, calcium chloride, and water to simulate salt lake brine, wherein the concentration of Li ions was 600 ppm, the concentration of Na ions was 93500 ppm, the concentration of Ca ions was 360 ppm, and the concentration of Mg ions was 4260 ppm.

[0088] (1) Adsorption treatment and desorption treatment: take 100L of salt lake brine, adjust its pH value to about 5.4 with hydrochloric acid, then pass through 10L of lithium extraction resin (manufacturer: Lanxiao Technology New Materials Co., Ltd., model: LSV-Li-1) at a flow rate of 2BV / h for adsorption treatment, and the temperature of the adsorption treatment is 25°C. Then perform desorption treatment with 200L of pure water at a flow rate of 5BV / h, the temperature of the desorption treatment is 25°C, to obtain 20 portions of desorption solution, each portion has a volume of 10L.

[0089] The Li ion concentration and Na ion concentration (both in mol / L) of each desorption solution were tested by inductively coupled plasma (ICP), the results are shown in Table 1, the 20 portions of desorption solution are screened, and a0=3.

[0090] Calculation starts from the 20th desorption solution, C of the 20th desorption solution Li / Na is ∞, C Li / Na ≥a0, the 20th desorption solution is qualified;

[0091] The sum of Na element concentrations from the 20th desorption solution to the 19th desorption solution is 0, C Li / Na is ∞, C Li / Na ≥a0, the 20th desorption solution and the 19th desorption solution are qualified desorption solutions;

[0092] By calculation in sequence, all desorption solutions from the 20th to the 6th are qualified;

[0093] The sum of Na element concentrations from the 20th desorption solution to the 5th desorption solution is 0.001, the sum of Li element concentrations is 0.358, C Li / Na is 358≥3, the desorption solutions from the 20th to the 5th are qualified desorption solutions;

[0094] The sum of Na element concentrations from the 20th desorption solution to the 4th desorption solution is 0.003, the sum of Li element concentrations is 0.405, C Li / Na is 135≥3, the desorption solutions from the 20th to the 4th are qualified desorption solutions;

[0095] The sum of Na element concentrations from the 20th desorption solution to the 3rd desorption solution is 0.004, the sum of Li element concentrations is 0.484, C Li / Na is 121≥3, the desorption solutions from the 20th to the 3rd are qualified desorption solutions;

[0096] The sum of Na element concentrations from the 20th desorption solution to the 2nd desorption solution is 0.325, the sum of Li element concentrations is 0.597, C Li / Na is 1.84<3, the 2nd desorption solution is an unqualified desorption solution; similarly, the 1st desorption solution is also calculated to be an unqualified desorption solution;

[0097] Therefore, the 20th to 3rd eluent samples are qualified eluents, while the 2nd and 1st eluents are unqualified eluents. Mixing the 18 qualified eluents yields a qualified eluent mixture. 混 The value is 121.

[0098] Table 1

[0099] (2) Concentration treatment: The qualified analytical mixture was concentrated using a seawater desalination membrane (manufacturer: Hefei Woteng Membrane Separation Equipment Co., Ltd., model: 102177) to obtain lithium chloride solution 1, in which the mass concentration of LiCl C1 in lithium chloride solution 1 was 75 g / L.

[0100] (3) Impurity removal treatment: The lithium chloride solution 1 is first subjected to a large amount of calcium and magnesium removal using a nanofiltration membrane (manufacturer: Hefei Woteng Membrane Separation Equipment Co., Ltd., model: 2506280165). Then, it is further subjected to a deep impurity removal resin (manufacturer: Lanxiao Technology New Materials Co., Ltd., model: LSC-850) for deep impurity removal to obtain lithium chloride solution 2. The mass concentrations of calcium and magnesium elements C2 in lithium chloride solution 2 are less than 1 ppm.

[0101] (4) Bipolar membrane electrolysis treatment: Lithium chloride solution 2 was added to a bipolar membrane electrodialysis device for bipolar membrane electrolysis treatment to obtain a solution containing LiOH. The electrolysis voltage was 28V, the electrolysis current was 8.96A, and the electrolysis temperature was 25℃. + Electrolysis was terminated when the concentration reached 2 mol / L.

[0102] (5) Introduce CO2: Introduce CO2 into the solution containing LiOH until the solution is clear, converting LiOH into Li2CO3. Filter and separate to obtain solid phase a.

[0103] (6) High-temperature impurity removal and slurry washing treatment: Solid phase a is subjected to high-temperature impurity removal and slurry washing treatment with pure water. The temperature of the high-temperature impurity removal and slurry washing treatment is T=90℃, the content of solid phase a in pure water is 1000g / L, and the high-temperature impurity removal and slurry washing treatment time is 3h. The lithium carbonate product is obtained. The purity is 99.6% and the Na content is 150ppm by ICP test, which meets the standard of battery grade lithium carbonate products specified in the industry standard YS / T 582-2023 "Battery Grade Lithium Carbonate".

[0104] Example 2

[0105] Except for adjusting the high-temperature impurity removal slurry washing time t in step (6) to 2 hours, the rest was the same as in Example 1. The purity of the obtained lithium carbonate product was 99.1%.

[0106] Compared with Example 1, it can be seen that the high-temperature impurity removal and washing process takes 2 hours, which is insufficient to remove impurities and results in a decrease in the purity of the lithium carbonate product.

[0107] Example 3

[0108] Except for adjusting the high-temperature impurity removal slurry washing time t in step (6) to 4 hours, the rest was the same as in Example 1. The purity of the obtained lithium carbonate product was 99.5%.

[0109] Compared with Example 1, it can be seen that although battery-grade Li2CO3 can be obtained after high-temperature impurity removal and washing treatment for 4 hours, the time consumption is long, resulting in low efficiency, and extending the high-temperature washing process will also consume energy.

[0110] Example 4

[0111] In this embodiment, the brine from the salt lake is the same as in Embodiment 1.

[0112] (1) Adsorption and desorption treatment: 50L of salt lake brine was taken and its pH value was adjusted to about 5.6 with hydrochloric acid. Then, it was adsorbed at a rate of 3BV / h through 2L of lithium extraction resin at a temperature of 25℃. Then, 100L of pure water was used for desorption treatment at a rate of 6BV / h at a temperature of 25℃, resulting in 10 desorption solutions, each with a volume of 10L.

[0113] The Li ion concentration and Na ion concentration of each eluent sample were tested by inductively coupled plasma (ICP) (both in mol / L). The results are shown in Table 2. Ten eluent samples were screened, with a0=3.

[0114] Calculations show that samples 10 through 3 are all qualified analytical solutions, as detailed below;

[0115] The sum of Na concentrations in the 10th to 3rd eluent samples was 0.005, the sum of Li concentrations was 0.213, and the sum of C concentrations was... Li / Na The value is 42.6 ≥ 3, and the 10th to 3rd portions of the analytical solution are qualified analytical solutions;

[0116] The sum of Na concentrations in the 10th eluent sample to the 2nd eluent sample was 0.239, the sum of Li concentrations was 0.291, and the sum of C concentrations was... Li / Na Since 1.22 < 3, the second analytical solution is a substandard analytical solution; similarly, the first analytical solution is also calculated to be a substandard analytical solution.

[0117] Therefore, fractions 10 through 3 are considered qualified eluents, while fractions 2 and 1 are considered unqualified eluents. The eight qualified eluents from fractions 10 through 3 are mixed to obtain a qualified eluent mixture.混 It is 42.6.

[0118] Table 2

[0119] In steps (2) to (6), except for the time t of the high-temperature impurity removal slurry washing treatment in step (6) being 5h, the rest are the same as in Example 1. The purity of the obtained lithium carbonate product is 99.5%, and the Na content is 130ppm, which meets the standard of battery-grade lithium carbonate products specified in the industry standard YS / T582-2023 "Battery-grade Lithium Carbonate".

[0120] Example 5

[0121] In this embodiment, a solution was prepared using lithium chloride, sodium chloride, magnesium chloride, calcium chloride, and water to simulate salt lake brine, wherein the concentration of Li ions was 810 ppm, the concentration of Na ions was 93200 ppm, the concentration of Ca ions was 340 ppm, and the concentration of Mg ions was 4100 ppm.

[0122] (1) Adsorption and desorption treatment: 100L of salt lake brine was taken and its pH value was adjusted to about 5.2 with hydrochloric acid. Then, it was adsorbed at a rate of 1BV / h through 10L of lithium extraction resin at a temperature of 25℃. Then, 100L of pure water was used for desorption treatment at a rate of 4BV / H at a temperature of 25℃, resulting in 10 desorption solutions, each with a volume of 10L.

[0123] The concentrations of Li and Na ions in each eluent sample were measured by inductively coupled plasma (ICP) (both in mol / L), and the results are shown in Table 3. Ten eluent samples were screened, with a0=3.

[0124] Calculations show that samples 10 through 3 are all qualified analytical solutions, as detailed below;

[0125] The sum of Na concentrations in the 10th to 3rd eluent samples was 0.007, the sum of Li concentrations was 0.599, and the sum of C concentrations was... Li / Na The value is 85.6 ≥ 3, and the 10th to 3rd portions of the analytical solution are considered qualified analytical solutions;

[0126] The sum of Na concentrations in the 10th eluent sample to the 2nd eluent sample was 0.452, the sum of Li concentrations was 0.762, and the sum of C concentrations was... Li / Na Since 1.69 < 3, the second analytical solution is a substandard analytical solution; similarly, the first analytical solution is also a substandard analytical solution after calculation.

[0127] Therefore, the 10th to 3rd portions of the eluent are qualified eluents, while the 2nd and 1st portions are unqualified eluents. The 8 qualified eluents from the 10th to 3rd portions are mixed to obtain a qualified eluent mixture. 混 It is 85.6.

[0128] Table 3

[0129] In steps (2) to (6), except for the time t of the high-temperature impurity removal slurry washing treatment in step (6) being 4h, the rest are the same as in Example 1. The purity of the obtained lithium carbonate product is 99.6% and the Na content is 165ppm, which meets the standard for battery-grade lithium carbonate products specified in the industry standard YS / T582-2023 "Battery-grade Lithium Carbonate".

[0130] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0131] The element connected by the terms "one of," "among," "a kind of," or other similar terms refers to any one of the listed elements. For example, "one of A or B" means only A or only B; similarly, "one of A, B, and C" means only A, only B, or only C. The element connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms refers to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B; similarly, "at least one of A, B, or C" means only A, only B, only C, only A and B, only A and C, only B and C, A and B and C.

[0132] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for extracting lithium from salt lake brine, comprising the following steps: S100. The brine from the salt lake is passed through a lithium extraction resin for adsorption treatment, and then purified with pure water for desorption treatment. During the desorption treatment, N equal volumes of desorbed liquid are obtained, and they are recorded as the first desorbed liquid to the Nth desorbed liquid in the order they are obtained. S200, Obtain the molar concentration C of lithium element in each portion of the eluent. Li With sodium molar concentration C Na ; S300. Obtain the sum of the lithium molar concentrations from the Nth eluent to the nth eluent, denoted as C. Li和 The sum of the molar concentrations of sodium from the Nth eluent to the nth eluent is obtained, denoted as C. Na和 ; The molar concentration ratio C of lithium and sodium is obtained according to Equation I. Li / Na , C Li / Na =C Li和 / C Na和 Formula I According to C Li / Na Based on the relationship with a0, a qualified eluent is obtained, and the qualified eluent is mixed to obtain a qualified eluent mixture; Where a0 is a preset value for the molar ratio of lithium to sodium, 2≤a0≤5, N≥3; n satisfies 1≤n≤N, where n is an integer and takes values ​​from N in descending order; S400. The qualified analytical mixture is subjected to bipolar membrane electrolysis at least once to obtain a solution containing LiOH; S500. Carbon dioxide is introduced into the solution containing LiOH for separation treatment to obtain solid phase a. The solid phase a is subjected to high-temperature impurity removal and slurry washing treatment to obtain lithium carbonate product.

2. The method according to claim 1, wherein, The step S300 described according to C Li / Na The relationship with a0, obtaining a qualified analytical solution, includes, If C Li / Na If a ≥ 0, then the Nth to nth portions of the analytical solution are all qualified analytical solutions; If C Li / Na If <a0, then the nth batch of analytical solution is a substandard analytical solution.

3. The method according to claim 1, wherein, In step S500, the temperature T of the high-temperature impurity removal and washing treatment is 85°C to 95°C, and the time t of the high-temperature impurity removal and washing treatment satisfies any one of the following conditions: Condition 1: If 2≤a 混 If ≤50, then t≥4.5h; Condition 2: If 50<a 混 If ≤100, then t≥3.5h; Condition 3: If 100<a 混 Then t≥3h; The molar ratio of lithium to sodium in the qualified analytical solution is denoted as a. 混 .

4. The method according to claim 3, wherein, The time t of the high-temperature impurity removal and washing treatment satisfies any one of the following conditions: Condition 1: If 2≤a 混 If ≤50, then 4.5h≤t≤5.5h; Condition 2: If 50<a 混 If ≤100, then 3.5h≤t≤4.5h; Condition 3: If 100<a 混 Therefore, 3h≤t≤3.5h.

5. The method according to claim 1, wherein, In step S100, the step of passing the salt lake brine into the lithium extraction resin for adsorption treatment includes: adjusting the pH of the salt lake brine to 5-6, and then passing it into the lithium extraction resin for the adsorption treatment.

6. The method according to claim 1, wherein, In step S100, N satisfies 3≤N≤50.

7. The method according to claim 1, wherein, In step S100, at least one of the following conditions must be met: Condition a: The temperature of the adsorption treatment is 15℃~35℃, and the flow rate V1 of the adsorption treatment is 1BV / h~3BV / h; Condition b: The temperature of the analytical processing is 15℃~35℃, and the flow rate V2 of the analytical processing is 4BV / h~6BV / h.

8. The method according to claim 1, wherein, Step S400 includes sequentially performing concentration treatment, impurity removal treatment and bipolar membrane electrolysis treatment on the qualified analytical mixture to obtain the solution containing LiOH.

9. The method according to claim 8, wherein, In step S400, at least one of the following conditions is met: Condition c: The concentration process is carried out to obtain lithium chloride solution 1, wherein the mass concentration C1 of LiCl in lithium chloride solution 1 is 50 g / L to 100 g / L; Condition d: The impurity removal process is performed to obtain lithium chloride solution 2, wherein the mass concentration C2 of calcium and / or magnesium in lithium chloride solution 2 is less than 5 ppm; Condition e: In the bipolar membrane electrolysis treatment, the electrolysis voltage is 27V~29V, the electrolysis current is 8A~9A, and the electrolysis temperature is 10℃~40℃; Condition f, the termination condition of the bipolar membrane electrolysis treatment includes: H generated during electrolysis + or OH - The electrolysis process is terminated when the concentration reaches 1 mol / L to 3 mol / L.

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