A method for purifying a lithium-containing solution by adsorption-pressurized desorption to prepare lithium carbonate

Abstract

The application relates to the technical field of lithium extraction and resource utilization, and particularly discloses a method for preparing lithium carbonate by purifying a lithium-containing solution through an adsorption-pressurized desorption method, which comprises the following steps: step (1), preparing a granular lithium adsorbent, comprising the following steps: step a, mixing LiCl, AlCl3.6H2O, urea, deionized water, sodium oleyloxyethanesulfonate to obtain a liquid adsorbent, then performing suction filtration to remove the filtrate, and preparing a powder adsorbent; step b, mixing the powder adsorbent, DMF and ethylene-vinyl acetate copolymer, then adding water, and aging to prepare the granular lithium adsorbent; step (2), passing the lithium-containing solution into the granular lithium adsorbent, then performing pressurized desorption through flushing with a desorbent after adsorption saturation, and obtaining a lithium-rich desorption solution; and step (3), performing heating decomposition on the lithium-rich desorption solution, then performing crystallization, and obtaining lithium carbonate. The lithium extraction method has the advantages of large lithium extraction capacity, good effect and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium extraction and resource utilization, more specifically, it relates to a method for preparing lithium carbonate by purifying lithium-containing solution through adsorption and pressurized desorption. BACKGROUND

[0002] Lithium is the lightest metal element at room temperature, and is widely used in portable electronic devices, power tools, electric vehicles and power grid storage due to its extremely high redox potential and considerable specific heat capacity. With the continuous expansion of the market for rechargeable lithium batteries and consumer electronics, the consumption of lithium has increased significantly, and effective measures should be taken as soon as possible to alleviate the problem of tight supply of lithium resources.

[0003] The patent with application number CN202010279756.X provides a process for preparing lithium carbonate from oilfield underground brine, which includes purification and concentration of lithium-rich liquid, including ultrafiltration purification, nanofiltration purification, reverse osmosis concentration, and electrodialysis concentration. The adsorbent is a manganese ion sieve with a particle size of 1-4 mm. The pH of the oilfield underground brine is adjusted to 7-10 using sodium hydroxide or potassium hydroxide. The adsorption temperature is 10-60℃, and the adsorption time is 10-30h. After adsorption is complete, the adsorbent is washed with process water for 0.1-1h. The concentration of the desorption agent hydrochloric acid is 0.4-1.0mol / L, and the desorption time is 0.5-2h. After desorption, the desorption agent is washed with process water for 0.1-1h before entering the next adsorption cycle. After ultrafiltration purification, the lithium-rich liquid is neutralized by adding sodium hydroxide or potassium hydroxide, and the pH is adjusted to 2-6. It is sent to a nanofiltration membrane filter for nanofiltration. The lithium-rich liquid after nanofiltration purification is further concentrated by reverse osmosis-electrodialysis to increase the lithium ion concentration to 10-20g / L. The purified and concentrated lithium-rich liquid is reacted with sodium bicarbonate at 60-95℃ to produce lithium carbonate with a content of more than 99.5%. The amount of sodium bicarbonate used is 100-150% of the weight of lithium ions, and the reaction time is 10-100min.

[0004] Manganese ion sieve is a manganese oxide obtained by acid leaching and lithium removal of spinel-type lithium manganese oxide precursor. Since the lithium manganese spinel prepared by the existing process is a powder with a particle size of microns or even nanometers, this powder material cannot be filled into the filter bed for use due to high water head loss in actual production, and it is also impossible to separate the powder material from water. Therefore, people make this lithium manganese spinel into particles or embed it into a membrane for use. However, whether it is made into particles or a membrane, the adsorption capacity of the manganese ion sieve is greatly reduced. At the same time, the granulation process is very costly and easy to break. The cost of making a membrane is also very high, and it may fall off.

[0005] The above-mentioned adsorbent is manganese ion sieve, and there is only one kind of adsorbent, manganese ion sieve, which has the disadvantages of low adsorption capacity of lithium and unsatisfactory adsorption effect. SUMMARY

[0006] In order to solve the low lithium extraction capacity and the unsatisfactory lithium extraction effect of the above-mentioned lithium extraction method for preparing lithium carbonate, the application provides a method for preparing lithium carbonate by purifying a lithium-containing solution through an adsorption-pressurized desorption method.

[0007] The application provides a method for preparing lithium carbonate by purifying a lithium-containing solution through an adsorption-pressurized desorption method, which adopts the following technical scheme:

[0008] The method for preparing lithium carbonate by purifying a lithium-containing solution through an adsorption-pressurized desorption method comprises the following steps:

[0009] Step (1), preparing a granular lithium adsorbent, which comprises the following steps: step a, mixing and stirring LiCl, AlCl3·6H2O, urea, deionized water, sodium oleyloxyethanesulfonate and N-isopropyl acrylamide to obtain a liquid adsorbent, and then removing the filtrate through suction filtration to obtain a powder adsorbent; step b, mixing and stirring the powder adsorbent, DMF and ethylene-vinyl acetate copolymer to obtain a slurry, and then adding the slurry into water, aging, and obtaining the granular lithium adsorbent.

[0010] Step (2), using a desorbent to perform pressurized desorption on the granular lithium adsorbent obtained in step (1) to obtain a lithium-rich desorption solution.

[0011] Step (3), performing heating decomposition and then crystallization on the lithium-rich desorption solution obtained in step (2) to obtain lithium carbonate.

[0012] Through the above technical scheme, in step a of step (1), LiCl, AlCl3·6H2O and urea can synthesize a traditional lithium adsorbent-aluminum lithium hydrotalcite, but the traditional aluminum lithium hydrotalcite is a porous powder, which still has problems in actual production process. The application first adds an anionic surfactant sodium oleyloxyethanesulfonate and a non-ionic polymer N-isopropyl acrylamide in the process of synthesizing the aluminum lithium hydrotalcite. The sodium oleyloxyethanesulfonate and the N-isopropyl acrylamide have an associated interaction to form a poly-pseudo-anion structure, which provides morphology control for the aluminum lithium hydrotalcite, so that the aluminum lithium hydrotalcite becomes a powder adsorbent with uniform particle size. Then, in step b of step (1), the oil-soluble ethylene-vinyl acetate copolymer and the water-soluble aluminum lithium hydrotalcite are uniformly dispersed by DMF to obtain a slurry. Since the ethylene-vinyl acetate copolymer is insoluble in water, after the slurry is dropped into water, the DMF gradually dissolves in water, and the ethylene-vinyl acetate copolymer continuously precipitates to coat the powder adsorbent, forming a granular adsorbent. The granular adsorbent has uniform particle size and is porous, has a large adsorption capacity for lithium, has a good adsorption effect, and has a low production cost.

[0013] Step (2) involves desorbing lithium from the saturated particulate lithium adsorbent obtained in step (1), and finally obtaining lithium carbonate through step (3). This application improves the lithium adsorbent and lithium desorption method simultaneously, and finally forms a method with large lithium extraction capacity, good effect and low cost.

[0014] Optionally, in step (1), step a) involves mixing and stirring 10-12g LiCl, 20-26g AlCl3·6H2O, 50-60g urea, 500g-550g deionized water, 8-12g sodium oleoyloxyethanesulfonate, and 5-7g N-isopropylacrylamide to obtain a liquid adsorbent. The liquid adsorbent is then filtered to remove the filtrate, yielding a powdered adsorbent. Step b) involves mixing and stirring the powdered adsorbent, 15-20g DMF, and 0.5-2g ethylene-vinyl acetate copolymer to obtain a slurry. The slurry is then added to water and aged to obtain a granular lithium adsorbent.

[0015] By adopting the above technical solution and using the appropriate amount of raw materials, it is possible to ensure that the required granular lithium adsorbent is obtained in the end, without wasting raw materials.

[0016] Optionally, in step (1), step a, while mixing and stirring LiCl, AlCl3·6H2O, urea, deionized water, sodium oleoyloxyethanesulfonate and N-isopropylacrylamide, also includes a step of condensation and reflux.

[0017] By adopting the above technical solution, the condensation and reflux step enables the liquid adsorbent prepared from LiCl, AlCl3·6H2O, urea, deionized water, sodium oleoyloxyethanesulfonate, and N-isopropylacrylamide to be rapidly condensed in a short time, which shortens the preparation time, improves the safety of the preparation, leaves impurities in the raw material bottle, and improves the purity of the liquid adsorbent.

[0018] Optionally, in step (1), step a, the temperature range of condensation reflux is 80-100℃, and the time range is 20-28h.

[0019] By adopting the above technical solution, within the above temperature and time range, a condensed liquid adsorbent can be obtained quickly, and the obtained liquid adsorbent has high purity, resulting in high purity of the final lithium carbonate.

[0020] Optionally, in step (1), step a, the mixing speed range is 40-60 r / min.

[0021] By adopting the above technical scheme, under the above speed range, LiCl, AlCl3·6H2O, urea and deionized water can be uniformly controlled in morphology by oil acyloxy ethanesulfonic acid sodium and N-isopropyl acrylamide, so as to facilitate the subsequent formation of granular lithium adsorbent with uniform particle size.

[0022] Optionally, in step b of step (1), the powder adsorbent, DMF and ethylene-vinyl acetate copolymer are mixed and stirred to prepare a slurry, then the slurry is added to water, cooled to room temperature, aged for 20-30 h and filtered to prepare a granular lithium adsorbent.

[0023] By adopting the above technical scheme, the appropriate aging time makes the natural connection of ethylene-vinyl acetate copolymer and powder adsorbent in water more closely and firmly, and finally the granular lithium adsorbent prepared has good stability and good adsorption stability, and good lithium adsorption effect.

[0024] Optionally, the pressure of the pressurized desorption in step (2) is 0.5-3 MPa.

[0025] By adopting the above technical scheme, under the pressure of 0.5-3 MPa, the lithium in the saturated granular lithium adsorbent can be quickly desorbed, the solubility of the acid gas in the bicarbonate solution is improved, the desorption process is strengthened, the desorption rate of lithium ions is improved, and the cyclic adsorption performance of the lithium adsorbent is improved, and at the same time, the lithium adsorbent can be realized without solution loss, and the number of cycles of the lithium adsorbent is improved.

[0026] Optionally, the desorbent includes an acid gas and a sodium bicarbonate solution, and the acid gas is CO2 or SO2.

[0027] By adopting the above technical scheme, the desorbent used does not react with other elements in the saturated granular lithium adsorbent, which is beneficial to improving the stability of the granular lithium adsorbent; lithium ions can form a stable lithium salt solution with bicarbonate ions in the desorbent to realize the desorption of lithium ions; in combination with pressurized desorption, the desorption process is strengthened, the desorption rate of lithium ions is improved, and the cost of lithium adsorption process is reduced.

[0028] Optionally, the pH value of the desorbent is 6-8.

[0029] By adopting the above technical scheme, compared with the traditional strong acid desorbent, the weak acid and neutral desorbent of the present application does not cause the dissolution of metal elements in the lithium adsorbent, protects other elements in the lithium adsorbent from being lost, maintains the structure of the lithium adsorbent for a long time, and maintains the stability and cyclic lithium adsorption performance of the lithium adsorbent.

[0030] Optionally, the sodium oleyl oxyethyl sulfonate is an anionic surfactant, which can uniformly disperse LiCl, AlCl3·6H2O, urea and deionized water in water, so that the particle size of the finally formed liquid lithium adsorbent is uniform, and the finally prepared granular lithium adsorbent has uniform particle size and good adsorption effect.

[0031] By adopting the technical scheme,

[0032] In summary, the present application has the following beneficial effects:

[0033] 1. In the present application, sodium oleyl oxyethyl sulfonate and N-isopropyl acrylamide are added in the process of synthesizing aluminum-lithium hydrotalcite to provide morphology control for the aluminum-lithium hydrotalcite, so that the aluminum-lithium hydrotalcite becomes a powder-shaped adsorbent with uniform particle size. Then in step b of step (1), the oil-soluble ethylene-vinyl acetate copolymer and the water-soluble aluminum-lithium hydrotalcite are uniformly dispersed by DMF to prepare a slurry. DMF gradually dissolves in water, and the ethylene-vinyl acetate copolymer continuously precipitates to coat the powder-shaped adsorbent, forming a granular adsorbent. The granular adsorbent has large adsorption capacity for lithium and good adsorption effect, and the production cost is relatively low.

[0034] 2. The desorption agent used in the present application does not react with other elements except lithium ions in the saturated granular lithium adsorbent, which is conducive to improving the stability of the granular lithium adsorbent. Lithium ions can react with bicarbonate ions in the desorption agent to form a stable lithium salt solution, realizing the desorption of lithium ions. In combination with pressurized desorption, the desorption process is strengthened, the desorption rate of lithium ions is improved, and the cost of lithium adsorption process is reduced.

[0035] 3. The sodium oleyl oxyethyl sulfonate of the present application can uniformly disperse LiCl, AlCl3·6H2O, urea and deionized water in water, so that the particle size of the finally formed liquid lithium adsorbent is uniform, and the finally prepared granular lithium adsorbent has uniform particle size and good adsorption effect. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flow chart of the method for preparing lithium carbonate provided by the present application. DETAILED DESCRIPTION

[0037] The raw materials of the examples and comparative examples of the present application can be commercially purchased.

[0038] The present application will be further described in detail below in combination with examples and comparative examples.

[0039] Examples

[0040] Example 1

[0041] A method for purifying a lithium-containing solution to prepare lithium carbonate by an adsorption-pressurized desorption method, characterized in that the method comprises the following steps:

[0042] Step (1), preparing a granular lithium adsorbent, which is prepared by the following steps: step a, mixing and stirring 10 g of LiCl, 26 g of AlCl3·6H2O, 50 g of urea, 550 g of deionized water, 8 g of sodium oleyloxyethanesulfonate and 7 g of N-isopropyl acrylamide at a speed of 40 r / min, condensing and refluxing at 100℃ for 20 h to obtain a liquid adsorbent, and then removing the filtrate by suction filtration to obtain a powdered adsorbent; step b, mixing and stirring the powdered adsorbent, 20 g of DMF and 0.5 g of ethylene-vinyl acetate copolymer to obtain a slurry, then adding the slurry into water, and aging for 30 h after cooling to room temperature and then suction filtering to obtain the granular lithium adsorbent;

[0043] Step (2), passing the lithium-containing solution into the granular lithium adsorbent obtained in step (1) at a flow rate of 30 BV / h at 80℃, and obtaining a saturated lithium adsorbent after the granular lithium adsorbent is saturated, and obtaining a lithium-lean solution as the effluent solution; then washing and pressurizing the saturated lithium adsorbent by using deionized water at a pressure of 0.5 MPa, a flow rate of 10 BV / h and a temperature of 0℃ to obtain a lithium-rich desorption solution;

[0044] Step (3), adding the lithium-rich desorption solution obtained in step (2) into 1 mol / L sodium bicarbonate aqueous solution according to a volume ratio of 1:1, and then performing heating decomposition, wherein the heating decomposition temperature is 95℃, water is evaporated during the heating decomposition process, and lithium carbonate is crystallized and precipitated to obtain a lithium carbonate product.

[0045] Example 2

[0046] The difference from Example 1 is that the raw material usage in step (1) is different, and step (1) is as follows:

[0047] Step (1), preparing a granular lithium adsorbent, which is prepared by the following steps: step a, mixing and stirring 10 g of LiCl, 26 g of AlCl3·6H2O, 50 g of urea, 550 g of deionized water, 8 g of sodium oleyloxyethanesulfonate and 7 g of N-isopropyl acrylamide at a speed of 40 r / min, condensing and refluxing at 100℃ for 20 h to obtain a liquid adsorbent, and then removing the filtrate by suction filtration to obtain a powdered adsorbent; step b, mixing and stirring the powdered adsorbent, 20 g of DMF and 0.5 g of ethylene-vinyl acetate copolymer to obtain a slurry, then adding the slurry into water, and aging for 30 h after cooling to room temperature and then suction filtering to obtain the granular lithium adsorbent;

[0048] Example 3

[0049] The difference between the example 1 is that the step (1) raw material is different, the step (1) is as follows:

[0050] Step (1), the preparation of granular lithium adsorbent, the granular lithium adsorbent is prepared by the following steps: step a, 11g LiCl, 23g AlCl3·6H2O, 55g urea, 520g deionized water, 10g sodium oleyloxyethanesulfonate and 6g N-isopropyl acrylamide are mixed and stirred at a speed of 50r / min, and then condensed refluxing at 90℃ for 25h to obtain a liquid adsorbent; the liquid adsorbent is filtered to remove the filtrate to obtain a powder adsorbent; step b, the powder adsorbent, 18g DMF and 1g ethylene-vinyl acetate copolymer are mixed and stirred to obtain a slurry, then the slurry is added into water, and after cooling to room temperature, the slurry is aged for 25h and filtered to obtain a granular lithium adsorbent.

[0051] Example 4

[0052] The difference between the example 3 is that the step (2) desorption agent is different, the step (3) treatment method is different, the step (2) and the step (3) are as follows:

[0053] Step (2), the lithium-containing solution is passed into the granular lithium adsorbent obtained in step (1) at a flow rate of 30BV / h at 80℃, and the granular lithium adsorbent is saturated to obtain a saturated lithium adsorbent, and the effluent solution is a lithium-poor solution; then the saturated lithium adsorbent is washed and pressurized desorbed by using 1mol / L sodium bicarbonate aqueous solution with pH of 7 at a pressure of 0.5MPa, a flow rate of 10BV / h and a temperature of 0℃ to obtain a lithium-rich desorption solution;

[0054] Step (3), the lithium-rich desorption solution obtained in step (2) is heated and decomposed, the temperature of the heating and decomposition is 95℃, and during the heating and decomposition process, water evaporates and lithium carbonate is crystallized and precipitated to obtain a lithium carbonate product.

[0055] Example 5

[0056] The difference between the example 3 is that the step (2) desorption agent is different, the step (3) treatment method is different, the step (2) and the step (3) are as follows:

[0057] Step (2), the lithium-containing solution is passed into the granular lithium adsorbent obtained in step (1) at a flow rate of 30BV / h at 80℃, and the granular lithium adsorbent is saturated to obtain a saturated lithium adsorbent, and the effluent solution is a lithium-poor solution; the desorption agent is a mixture of CO2 gas and 1mol / L sodium bicarbonate aqueous solution, wherein the volume fraction of air is 30%, and the pH of the desorption agent is 7; the saturated lithium adsorbent is washed and pressurized desorbed by using the desorption agent at a pressure of 0.5MPa, a flow rate of 10BV / h and a temperature of 0℃ to obtain a lithium-rich desorption solution;

[0058] Step (3), the lithium-rich desorption solution obtained in step (2) is subjected to gas-liquid separation, the temperature of the gas-liquid separation is 0℃, the pressure is 0MPa, the gas phase obtained in the gas-liquid separation is returned to step (2) to be used as a component of the desorption agent again, the liquid phase obtained is heated and decomposed, the temperature of the heating and decomposition is 95℃, in the process of the heating and decomposition, water is evaporated, lithium carbonate is crystallized and precipitated, and lithium carbonate product is obtained.

[0059] Example 6

[0060] The difference from Example 5 is that the pH of the desorption agent in step (2) is 6.

[0061] Example 7

[0062] The difference from Example 5 is that the pH of the desorption agent in step (2) is 8.

[0063] Comparative Example

[0064] Comparative Example 1

[0065] The difference from Example 5 is that no sodium oleyloxyethanesulfonate is added in step (1), and 15g of N-isopropylacrylamide is added.

[0066] Comparative Example 2

[0067] The difference from Example 5 is that no N-isopropylacrylamide is added in step (1), and 15g of sodium oleyloxyethanesulfonate is added.

[0068] Comparative Example 3

[0069] The difference from Example 5 is that DMF is replaced by water of the same weight in step (1).

[0070] Comparative Example 4

[0071] The difference from Example 5 is that no ethylene-vinyl acetate copolymer is added in step (1).

[0072] Comparative Example 5

[0073] The difference from Example 5 is that the pH of the desorption agent in step (2) is 10.

[0074] Comparative Example 6

[0075] The difference from Example 5 is that no pressure is added in the desorption process in step (2).

[0076] Comparative Example 7

[0077] The difference from Example 5 is that step b is not performed in step (1).

[0078] Performance detection test

[0079] Detection method

[0080] The concentration of lithium element in the solution is determined by using an inductively coupled plasma emission spectrometer. The adsorption capacity mg / g of the lithium adsorbent is calculated by subtracting the initial concentration of lithium element in the lithium-containing solution, the volume of the solution, and the initial concentration of lithium element in the lithium-lean solution, the volume of the solution. The desorption capacity of lithium is calculated by subtracting the concentration of lithium element in the lithium-rich desorption solution, the volume of the solution, and the concentration of lithium element in the desorption solution, the volume of the solution. Thus, the desorption rate of lithium is obtained.

[0081] Table 1

[0082]

[0083]

[0084] According to the data of Examples 1, 2 and 3, it can be seen that the only difference between Examples 1, 2 and 3 is the different proportion of raw materials. The adsorption capacity of the granular lithium adsorbent of Example 3 is larger than that of the granular lithium adsorbents of Examples 1 and 2, and the desorption rates are similar. Therefore, the raw material composition of Example 3 is the best ratio for preparing the granular lithium adsorbent.

[0085] The difference between Examples 4 and 5 and Example 3 is that the desorption agent of Example 4 is sodium bicarbonate aqueous solution, and the desorption agent of Example 5 is a composite desorption agent of CO2 and sodium bicarbonate aqueous solution. The results show that the desorption rate of Example 5 is higher than that of Examples 3 and 4. Therefore, the best desorption agent of the present application is the composite desorption agent of CO2 and sodium bicarbonate aqueous solution.

[0086] The pH of the desorption agents of Examples 6 and 7 is 6 and 8, respectively, which is lower than the pH of the desorption agent of Example 5, which is 7. Therefore, the desorption rate of the desorption agent of Examples 6 and 7 is slightly lower than that of the desorption agent of Example 5. Therefore, the pH of the best desorption agent of the present application is 7.

[0087] In Comparative Examples 1 and 2, no sodium oleyl oxyethyl sulfonate or N-isopropyl acrylamide is added, and in Comparative Example 1, N-isopropyl acrylamide is used to replace all sodium oleyl oxyethyl sulfonate; in Comparative Example 2, sodium oleyl oxyethyl sulfonate is used to replace all N-isopropyl acrylamide. The adsorption capacity of the granular adsorbent finally prepared is less than that of the granular adsorbent prepared in Example 5, which proves that sodium oleyl oxyethyl sulfonate and N-isopropyl acrylamide are indispensable in the preparation of the granular adsorbent.

[0088] In Comparative Example 3, DMF is replaced by water, and the ethylene-vinyl acetate copolymer is insoluble in water, so the ethylene-vinyl acetate copolymer precipitates in DMF to coat the powdered adsorbent, and the uniform granular adsorbent is difficult to form, and the data shows that the adsorption capacity of the granular adsorbent of Comparative Example 3 is much smaller than that of the granular adsorbent of Example 5, so DMF cannot be replaced by water.

[0089] In Comparative Example 4, no ethylene-vinyl acetate copolymer is added, and the adsorption capacity of the granular adsorbent prepared in Comparative Example 4 is much smaller than that of the granular adsorbent prepared in Example 5, so the ethylene-vinyl acetate copolymer is indispensable in the preparation of the granular adsorbent.

[0090] The desorption agent of Comparative Example 5 has a pH of 10, and the desorption rate is much smaller than that of Example 5, so the optimal range of the acidity and alkalinity of the desorption agent is 6-8.

[0091] In Comparative Example 6, no pressure is added in step (2), and the desorption rate of Comparative Example 6 is much smaller than that of Example 5, so the pressure step in step (2) is indispensable.

[0092] In Comparative Example 7, step b of step (1) is not performed, so the granular adsorbent prepared in Comparative Example 7 is not obviously granular, and the adsorption capacity is much smaller than that of Example 5, so step b of step (1) is indispensable.

[0093] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the Patent Law.

Claims

1. A method for purifying lithium-containing solutions and preparing lithium carbonate using an adsorption-pressure desorption process, characterized in that, The method includes the following steps: Step (1) Preparation of granular lithium adsorbent, wherein the granular lithium adsorbent is prepared by the following steps: Step a, mixing and stirring LiCl, AlCl3·6H2O, urea, deionized water, sodium oleoyloxyethanesulfonate and poly(N-isopropylacrylamide) while refluxing to obtain a liquid adsorbent, filtering the liquid adsorbent to remove the filtrate, and obtaining a powdered adsorbent; Step b, mixing and stirring the powdered adsorbent, DMF and ethylene-vinyl acetate copolymer to obtain a slurry, then adding the slurry to water, cooling to room temperature and aging for 20-30 h and filtering to obtain the granular lithium adsorbent; In step a, the mixing and stirring speed range is 40-60 r / min, the reflux temperature range is 80-100℃, and the time range is 20-28 h; Step (2): The lithium-containing solution is passed into the granular lithium adsorbent obtained in step (1). After the granular lithium adsorbent is saturated, a saturated lithium adsorbent is obtained. Then, the saturated lithium adsorbent is rinsed and desorbed under pressure using a desorbent to obtain a lithium-rich desorbent solution. The pressure of the desorption is 0.5-3 MPa. The desorbent is a CO2 and sodium bicarbonate solution with a pH of 6-8. Step (3) involves heating and decomposing the lithium-rich desorption solution obtained in step (2) to crystallize it, thereby obtaining lithium carbonate.

2. The method for purifying lithium-containing solutions and preparing lithium carbonate using an adsorption-pressure desorption method according to claim 1, characterized in that: In step (1), step a) 10-12g LiCl, 20-26g AlCl3·6H2O, 50-60g urea, 500g-550g deionized water, 8-12g sodium oleoyloxyethanesulfonate and 5-7g poly(N-isopropylacrylamide) are mixed and stirred to obtain a liquid adsorbent. The liquid adsorbent is filtered to remove the filtrate and obtain a powdered adsorbent. Step b) The powdered adsorbent, 15-20g DMF and 0.5-2g ethylene-vinyl acetate copolymer are mixed and stirred to obtain a slurry. The slurry is then added to water and aged to obtain a granular lithium adsorbent.

Images