A modified lithium extraction adsorbent, its preparation method and application

Abstract

This disclosure provides a modified lithium-extraction adsorbent, its preparation method, and its application. The preparation method includes the following steps: (1) mixing activated alumina with a lithium salt solution and heating to react and obtain an adsorbent precursor; (2) mixing a phenyllithium-containing solution with the adsorbent precursor, ultrasonically treating it, and then adding a triphenylchloromethane-containing solution to react and obtain a tetraphenylmethane-coated aluminum-based adsorbent; (3) subjecting the tetraphenylmethane-coated aluminum-based adsorbent to plasma hydrophilic treatment to obtain the modified lithium-extraction adsorbent. The modified outer layer of the lithium-extraction adsorbent prepared by the method of this disclosure can improve the cycle stability of the adsorbent and can physically adsorb lithium ions in brine, thus protecting the inner adsorbent without reducing the adsorption capacity.

Description

Technical Field

[0001] This disclosure belongs to the field of lithium extraction technology from salt lakes, and relates to a modified lithium extraction adsorbent, its preparation method and application. Background Technology

[0002] With the booming development of the new energy vehicle industry and the rapid development of advanced technologies such as aerospace, lithium and its compounds are receiving increasing attention, and the global demand for lithium resources is growing.

[0003] Currently, lithium resource extraction mainly relies on lithium ore and brine from salt lakes, and the reserves of lithium ore are insufficient to meet the future development needs of related industries. Lithium in liquid form accounts for approximately 70% to 80% of total lithium resources and is a crucial strategic resource for alleviating lithium scarcity. Therefore, how to effectively extract lithium from liquid form has become one of the current research hotspots.

[0004] Salt lake brines contain large amounts of Na, K, and Mg ions, exhibiting complex composition and significant regional variations, which increases the difficulty of extracting liquid lithium. Ion exchange adsorption is considered the most promising method for lithium extraction from salt lake brines, offering advantages such as simplicity, high selectivity, and low pollution. Currently, the most studied lithium-ion adsorbents include manganese-based lithium-ion sieves, titanium-based lithium-ion sieves, and aluminum salt lithium-ion adsorbents. Aluminum salt lithium-ion adsorbents are compounds formed by inserting lithium salts, such as lithium chloride, into the layered molecular structure of Al(OH)3, and partially removing Li2+ by elution with water. + The resulting vacancies can selectively adsorb Li from lithium-containing solutions. + .

[0005] CN110975795A discloses a method for synthesizing a lithium extraction adsorbent. The method involves dissolving a lithium source in a solvent containing a certain amount of additives, then adding a titanium source to the solvent to form a solid-liquid mixture. Drying is then used to assist the synthesis, resulting in rapid drying and thorough mixing of the raw materials. After calcination, a lithium-ion sieve precursor, Li2TiO3, with uniformly distributed particle size can be obtained. The precursor Li2TiO3 is then acid-washed to remove lithium, yielding a metatitanic acid type lithium-ion sieve, H2TiO3.

[0006] CN114130375A discloses a method for preparing a membrane-like lithium-ion sieve adsorbent, the method comprising the steps of: 1) preparing a composite sol; 2) preparing a lithium-ion sieve precursor slurry; 3) doping and blending, and ultrasonic homogenization; 4) casting and coating; 5) drying and peeling; 6) crosslinking; and 7) elution and displacement.

[0007] The lithium ion screening adsorbent prepared by the above method is easily corroded, and the high concentration of sulfate ions in the solution will have a great impact on the cycle stability of the aluminum salt adsorbent. Summary of the Invention

[0008] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0009] The purpose of this disclosure is to provide a modified lithium extraction adsorbent, its preparation method, and its application. The modified outer layer of the modified lithium extraction adsorbent prepared by the method described in this disclosure can improve the cycle stability of the adsorbent and can physically adsorb lithium ions in brine. Therefore, it can protect the inner layer adsorbent without reducing the adsorption capacity.

[0010] To achieve this objective, the present disclosure adopts the following technical solution:

[0011] In a first aspect, this disclosure provides a method for preparing a modified lithium extraction adsorbent, the method comprising the following steps:

[0012] (1) Mix activated alumina with lithium salt solution and heat to react to obtain adsorbent precursor;

[0013] (2) Mix the phenyl lithium solution with the adsorbent precursor, and after ultrasonic treatment, add the triphenylchloromethane solution to react and obtain the tetraphenylmethane-coated aluminum-based adsorbent.

[0014] (3) The aluminum-based adsorbent coated with tetraphenylmethane is subjected to plasma hydrophilic treatment to obtain the modified lithium-extraction adsorbent.

[0015] This disclosure uses phenyllithium and triphenylchloromethane to modify crystalline aluminum salt lithium ion adsorbents. The benzene ring in the outer modified layer can attract lithium ions, thereby improving the lithium ion adsorption efficiency and lithium extraction efficiency. The tetramethylbenzene ring is an electron-donating group, which can attract the binder required for granulation during the granulation process, which is more conducive to preparing adsorbent particles with better cycle stability.

[0016] In one embodiment, the solute in the lithium salt solution of step (1) includes lithium chloride.

[0017] In one embodiment, the solvent of the lithium salt solution includes water.

[0018] In one embodiment, the mass concentration of the lithium salt solution is 15-30%, for example: 15%, 18%, 20%, 25% or 30%, etc.

[0019] In one embodiment, the molar ratio of activated alumina to lithium salt is 1:(1 to 1.2), for example: 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2, etc.

[0020] In one embodiment, the temperature of the heating reaction in step (1) is 90 to 100°C, for example: 90°C, 92°C, 95°C, 98°C or 100°C.

[0021] In one embodiment, the heating reaction time is 8 to 12 hours, for example: 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0022] In one embodiment, the heating reaction is followed by a drying process.

[0023] In one embodiment, the drying temperature is 80–110°C, for example: 80°C, 85°C, 90°C, 100°C, or 110°C.

[0024] In one embodiment, the solvent for the phenyl lithium-containing solution in step (2) includes diethyl ether.

[0025] In one embodiment, the concentration of phenyllithium in the phenyllithium-containing solution is 0.1 to 0.3 mol / L, for example: 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, or 0.3 mol / L, etc.

[0026] In one embodiment, the solid-liquid ratio of the adsorbent precursor and the lithium phenyl solution is 1 to 2 g / mL, for example: 1 g / mL, 1.2 g / mL, 1.5 g / mL, 1.8 g / mL or 2 g / mL, etc.

[0027] In one embodiment, the ultrasonic treatment time is 20 to 30 minutes, for example: 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes.

[0028] In one embodiment, the solvent for the triphenylchloromethane solution in step (2) includes diethyl ether.

[0029] In one embodiment, the molar ratio of phenyllithium in the phenyllithium-containing solution to triphenylchloromethane in the triphenylchloromethane-containing solution is 1:(2-3), for example: 1:2, 1:2.2, 1:2.5, 1:2.8 or 1:3, etc.

[0030] In one embodiment, the reaction in step (2) includes a pre-stirred reaction followed by a reflux reaction.

[0031] In one embodiment, the temperature of the pre-stirred reaction is 20–30°C, for example: 20°C, 22°C, 25°C, 28°C, or 30°C.

[0032] In one embodiment, the pre-stirring reaction time is 1.5 to 3 hours, for example: 1.5 hours, 1.8 hours, 2 hours, 2.5 hours or 3 hours.

[0033] In one embodiment, the temperature of the heating reflux reaction is 60-80°C, for example: 60°C, 65°C, 70°C, 75°C or 80°C.

[0034] In one embodiment, the heating reflux reaction time is 0.5 to 2 hours, for example: 0.5 hours, 0.8 hours, 1 hour, 1.5 hours, or 2 hours.

[0035] In one embodiment, the reaction is followed by washing with hot water.

[0036] In one embodiment, the mass fraction of tetraphenylmethane in the aluminum-based adsorbent coated with tetraphenylmethane in step (3) is 3% to 10%, for example: 3%, 5%, 6%, 8% or 10%, etc.

[0037] In one embodiment, the gas used for plasma hydrophilic treatment in step (3) includes any one or a combination of at least two of ammonia, methane, or oxygen, with ammonia being an option.

[0038] In one embodiment, the gas flow rate for the plasma hydrophilic treatment is 80–200 sccm, for example: 80 sccm, 100 sccm, 120 sccm, 150 sccm, or 200 sccm.

[0039] In one embodiment, the power of the plasma hydrophilic treatment is 100-300W, for example: 100W, 150W, 200W, 250W or 300W.

[0040] In one embodiment, the plasma hydrophilic treatment time is 30 to 300 seconds, for example: 30 seconds, 50 seconds, 100 seconds, 200 seconds, or 300 seconds.

[0041] In one embodiment, the pressure of the plasma hydrophilic treatment is 20 to 50 Pa, for example: 20 Pa, 25 Pa, 30 Pa, 40 Pa or 50 Pa.

[0042] In a second aspect, this disclosure provides a modified lithium extraction adsorbent, which is prepared by the method described in the first aspect.

[0043] The outer modified layer of the modified lithium-extraction adsorbent disclosed herein can protect the inner adsorbent, isolate the inner adsorbent from the adsorption-desorption solution, and improve the cycle stability of the adsorbent. The outer modified layer can also physically adsorb lithium ions in the brine, thus protecting the inner adsorbent without reducing the adsorption capacity.

[0044] Thirdly, this disclosure provides a lithium extraction method, which includes the following steps:

[0045] (1) The modified lithium-extraction adsorbent as described in the second aspect is filled into a resin column and activated by soaking in deionized water to obtain the adsorbent after desorption.

[0046] (2) After soaking the adsorbent after analysis with concentrated brine, replace the concentrated brine with ordinary brine for adsorption.

[0047] Since the inner adsorbent and the outer modified layer of the modified lithium extraction adsorbent described in this disclosure have different adsorption capacities, high-concentration brine adsorption is performed first, followed by low-concentration brine adsorption. The pore volume of the outer TPM after adsorbing lithium ions is more conducive to the passage of smaller chloride ions, which can alleviate the sulfate poisoning phenomenon of the inner aluminum-based adsorbent.

[0048] In one embodiment, the lithium ion concentration in the concentrated brine is 500–1000 mg / L, for example: 500 mg / L, 600 mg / L, 800 mg / L, 900 mg / L, or 1000 mg / L.

[0049] In one embodiment, the sulfate concentration in the concentrated brine is ≥8 g / L.

[0050] In one embodiment, the lithium ion concentration in the ordinary brine is 100–300 mg / L, for example: 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, or 300 mg / L.

[0051] In one embodiment, the sulfate concentration in the ordinary brine is 1 to 5 g / L, for example: 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L.

[0052] Compared with the prior art, this disclosure has the following beneficial effects:

[0053] (1) This disclosure prepares a surface-modified lithium adsorbent. During the adsorption process of the adsorbent, lithium ions are attracted by the benzene rings on the surface and move to the high-energy binding sites between the two benzene rings. After the benzene rings are saturated, lithium ions can diffuse into the internal adsorbent by filling the remaining pore space.

[0054] (2) The modified lithium adsorbent prepared by the method described in this disclosure has an adsorption capacity of more than 9.58 mg / g and a capacity retention rate of more than 95.83% after 100 cycles.

[0055] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0056] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0057] Example 1

[0058] This embodiment provides a modified lithium extraction adsorbent, and the preparation method of the modified lithium extraction adsorbent is as follows:

[0059] (1) Activated alumina was immersed in a 20% (w / w) lithium chloride aqueous solution, and the molar ratio of the feed was controlled to be alumina:lithium chloride = 1:1.1. The mixture was hydrothermally treated at 95°C for 10 h and then dried at 90°C to obtain a crystalline aluminum salt lithium ion adsorbent precursor.

[0060] (2) Prepare a phenyl lithium diethyl ether solution with a phenyl lithium concentration of 0.2 mol / L. Add the aluminum salt adsorbent precursor to the above solution at a solid-liquid ratio of 1.5 g / mL and sonicate for 30 min. Then add a triphenyl chloromethane diethyl ether solution with a concentration of 0.5 mol / L, so that the molar ratio of phenyl lithium to triphenyl chloromethane is 1:2.2. React at 25°C for 2 h and then heat at 70°C under reflux for 1 h. After filtration, wash the product with hot water at 50°C to obtain an aluminum-based adsorbent coated with tetraphenylmethane.

[0061] (3) The aluminum-based adsorbent coated with tetraphenylmethane was placed in a low-temperature plasma generator and the surface of the adsorbent was treated with ammonia plasma. The gas flow rate was 100 sccm, the power was 200 W, the time was 200 s, and the gas pressure was 30 Pa to obtain the modified lithium-extraction adsorbent.

[0062] Example 2

[0063] This embodiment provides a modified lithium extraction adsorbent, and the preparation method of the modified lithium extraction adsorbent is as follows:

[0064] (1) Activated alumina was immersed in a 15% (w / w) lithium chloride aqueous solution, and the molar ratio of the feed was controlled to be alumina:lithium chloride = 1:1. The mixture was hydrothermally treated at 90°C for 12 h and then dried at 80°C to obtain a crystalline aluminum salt lithium ion adsorbent precursor.

[0065] (2) Prepare a phenyl lithium diethyl ether solution with a phenyl lithium concentration of 0.1 mol / L. Add the aluminum salt adsorbent precursor to the above solution at a solid-liquid ratio of 1 g / mL and sonicate for 250 min. Then add a triphenyl chloromethane diethyl ether solution with a concentration of 0.5 mol / L, so that the molar ratio of phenyl lithium to triphenyl chloromethane is 1:2. React at 25°C for 1.5 h and then heat at 60°C under reflux for 2 h. After filtration, wash the product with hot water at 50°C to obtain an aluminum-based adsorbent coated with tetraphenylmethane.

[0066] (3) The aluminum-based adsorbent coated with tetraphenylmethane was placed in a low-temperature plasma generator and the surface of the adsorbent was treated with ammonia plasma. The gas flow rate was 80 sccm, the power was 100w, the time was 300s, and the gas pressure was 20pa to obtain the modified lithium-extraction adsorbent.

[0067] Example 3

[0068] This embodiment provides a modified lithium extraction adsorbent, and the preparation method of the modified lithium extraction adsorbent is as follows:

[0069] (1) Activated alumina was immersed in a 30% (w / w) lithium chloride aqueous solution, and the molar ratio of the feed was controlled to be alumina:lithium chloride = 1:1.2. The mixture was hydrothermally treated at 100°C for 8 hours and then dried at 110°C to obtain a crystalline aluminum salt lithium ion adsorbent precursor.

[0070] (2) Prepare a phenyl lithium diethyl ether solution with a phenyl lithium concentration of 0.3 mol / L. Add the aluminum salt adsorbent precursor to the above solution at a solid-liquid ratio of 2 g / mL and sonicate for 30 min. Then add a triphenyl chloromethane diethyl ether solution with a concentration of 0.5 mol / L, so that the molar ratio of phenyl lithium to triphenyl chloromethane is 1:3. React at 25°C for 2 h and then heat under reflux at 80°C for 0.5 h. After filtration, wash the product with hot water at 50°C to obtain an aluminum-based adsorbent coated with tetraphenylmethane.

[0071] (3) The aluminum-based adsorbent coated with tetraphenylmethane was placed in a low-temperature plasma generator and the surface of the adsorbent was treated with ammonia plasma. The gas flow rate was 200 sccm, the power was 300 W, the time was 30 s, and the pressure was 50 Pa to obtain the modified lithium-extraction adsorbent.

[0072] Example 4

[0073] The only difference between this embodiment and Example 1 is that the molar ratio of phenyllithium and triphenylchloromethane is 1:1, while the other conditions and parameters are exactly the same as in Example 1.

[0074] Example 5

[0075] The only difference between this embodiment and Example 1 is that the molar ratio of phenyllithium to triphenylchloromethane is 1:4, while the other conditions and parameters are exactly the same as in Example 1.

[0076] Example 6

[0077] The only difference between this embodiment and Embodiment 1 is that the power of the plasma hydrophilic treatment is 500W, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0078] Example 7

[0079] The only difference between this embodiment and Embodiment 1 is that the power of the plasma hydrophilic treatment is 50W, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0080] Example 8

[0081] The only difference between this embodiment and Embodiment 1 is that ammonia is replaced with oxygen; all other conditions and parameters are exactly the same as in Embodiment 1.

[0082] Example 9

[0083] The only difference between this embodiment and Embodiment 1 is that ammonia is replaced with methane; all other conditions and parameters are exactly the same as in Embodiment 1.

[0084] Comparative Example 1

[0085] The only difference between this comparative example and Example 1 is that a crystalline aluminum salt lithium ion adsorbent precursor is directly used as the adsorbent; all other conditions and parameters are exactly the same as in Example 1.

[0086] Comparative Example 2

[0087] The only difference between this comparative example and Example 1 is that a phenyl lithium-containing solution is not used; all other conditions and parameters are exactly the same as in Example 1.

[0088] Comparative Example 3

[0089] The only difference between this comparative example and Example 1 is that a solution containing triphenylchloromethane is not used; all other conditions and parameters are exactly the same as in Example 1.

[0090] Comparative Example 4

[0091] The only difference between this comparative example and Example 1 is that plasma hydrophilic treatment is not performed; all other conditions and parameters are exactly the same as in Example 1.

[0092] Performance testing:

[0093] The adsorption performance test method is static adsorption. This adsorbent was used for Li + Lithium was extracted from brine with a concentration of 500 ppm. 20 g of deionized water and 2 g of lithium adsorbent were mixed and extracted at room temperature for 10 h. The concentration of brine before and after adsorption was measured, and the adsorption capacity was calculated according to the following formula.

[0094] The adsorption capacity of the adsorbent is: Q = V(C0 - C) / m;

[0095] Q is the adsorption capacity, mg / g; V is the adsorption liquid volume, L; m is the adsorbent mass, g; C0 and C are the lithium ion concentrations in the brine before and after adsorption, mg / L, respectively.

[0096] The capacity retention rate after 100 cycles is obtained by comparing the adsorption capacity after 100 cycles with the initial adsorption capacity. The test results are shown in Table 1.

[0097] Table 1

[0098] Adsorption capacity (mg / g) Capacity retention rate (%) after 100 cycles Example 1 9.84 95.87 Example 2 9.64 95.84 Example 3 9.58 95.83 Example 4 9.13 93.79 Example 5 9.08 94.01 Example 6 9.21 92.87 Example 7 9.07 93.75 Example 8 7.88 94.61 Example 9 6.49 94.73 Comparative Example 1 7.35 88.25 Comparative Example 2 7.58 88.64 Comparative Example 3 7.53 88.52 Comparative Example 4 6.51 90.52

[0099] As can be seen from Table 1, as obtained from Examples 1-3, the modified lithium adsorbent prepared by the method described in this disclosure has an adsorption capacity of more than 9.58 mg / g, and the capacity retention rate after 100 cycles can reach more than 95.83%.

[0100] A comparison of Examples 1 and 4-5 shows that the molar ratio of phenyllithium to triphenylchloromethane affects the performance of the modified lithium-extraction adsorbent described in this disclosure. Controlling the molar ratio of phenyllithium to triphenylchloromethane to 1:2-3 results in a modified lithium-extraction adsorbent with better performance. If the proportion of phenyllithium is too high or too low, it is difficult to form tetraphenylmethane, thereby affecting the performance of the adsorbent.

[0101] A comparison of Examples 1 and 6-7 shows that the power of plasma hydrophilic treatment affects the performance of the modified lithium extraction adsorbent described in this disclosure. Controlling the power of plasma hydrophilic treatment to 100-300W results in a better performance of the modified lithium extraction adsorbent. If the power of plasma hydrophilic treatment is too high, the improvement in hydrophilicity is limited and energy is wasted. If the power of plasma hydrophilic treatment is too low, the improvement in hydrophilicity is poor and it affects the brine wetting of the adsorbent.

[0102] A comparison of Examples 1 and 8-9 shows that using ammonia as the atmosphere for plasma hydrophilic treatment during the preparation of the modified lithium-extraction adsorbent disclosed in this invention results in a better effect on the hydrophilic modification of the adsorbent.

[0103] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, the present disclosure uses phenyl lithium and triphenylchloromethane to modify the crystalline aluminum salt lithium ion adsorbent. The benzene ring of the outer modified layer can attract lithium ions, improve the lithium ion adsorption efficiency, and improve the lithium extraction efficiency. The tetramethylbenzene ring is an electron-donating group, which can attract the binder required for granulation during the granulation process, which is more conducive to preparing adsorbent particles with better cycle stability.

[0104] As can be seen from the comparison between Example 1 and Comparative Example 4, plasma hydrophilic treatment can promote the wetting of the adsorbent by brine and improve the adsorption capacity.

Claims

1. A method for preparing a modified lithium extraction adsorbent, comprising the following steps: (1) Mix activated alumina with lithium salt solution and heat to react to obtain adsorbent precursor; (2) Mix the lithium phenyl solution with the adsorbent precursor, and after ultrasonic treatment, add the triphenylchloromethane solution to react and obtain the aluminum-based adsorbent coated with tetraphenylmethane. (3) The aluminum-based adsorbent coated with tetraphenylmethane is subjected to plasma hydrophilic treatment to obtain the modified lithium-extraction adsorbent.

2. The preparation method according to claim 1, wherein, The solute in the lithium salt solution in step (1) includes lithium chloride.

3. The preparation method according to claim 1, wherein, The solvent for the lithium salt solution includes water.

4. The preparation method according to claim 1, wherein, The mass concentration of the lithium salt solution is 15-30%.

5. The preparation method according to claim 1, wherein, The molar ratio of activated alumina to lithium salt is 1:(1~1.2).

6. The preparation method according to claim 1, wherein, The heating reaction in step (1) is carried out at a temperature of 90~100℃.

7. The preparation method according to claim 1, wherein, The heating reaction takes 8 to 12 hours.

8. The preparation method according to claim 1, wherein, The heating reaction is followed by drying.

9. The preparation method according to claim 8, wherein, The drying process is carried out at a temperature of 80~110℃.

10. The preparation method according to claim 1, wherein, The solvent for the phenyl lithium solution in step (2) includes diethyl ether.

11. The preparation method according to claim 1, wherein, The concentration of phenyllithium in the phenyllithium-containing solution is 0.1~0.3 mol / L.

12. The preparation method according to claim 1, wherein, The solid-liquid ratio of the adsorbent precursor and the phenyl lithium-containing solution is 1~2 g / mL.

13. The preparation method according to claim 1, wherein, The ultrasonic treatment time is 20-30 minutes.

14. The preparation method according to claim 1, wherein, The solvent for the triphenylchloromethane solution in step (2) includes diethyl ether.

15. The preparation method according to claim 1, wherein, The molar ratio of phenyllithium in the phenyllithium-containing solution to triphenylchloromethane in the triphenylchloromethane-containing solution is 1:(2~3).

16. The preparation method according to claim 1, wherein, The reaction in step (2) includes a pre-stirred reaction followed by a reflux reaction.

17. The preparation method according to claim 16, wherein, The temperature of the pre-stirred reaction is 20~30℃.

18. The preparation method according to claim 16, wherein, The pre-stirring reaction time is 1.5~3h.

19. The preparation method according to claim 16, wherein, The temperature of the heating reflux reaction is 60~80℃.

20. The preparation method according to claim 16, wherein, The heating and reflux reaction time is 0.5 to 2 hours.

21. The preparation method according to claim 16, wherein, The reaction is followed by washing with hot water.

22. The preparation method according to claim 1, wherein, In step (3), the mass fraction of tetraphenylmethane in the aluminum-based adsorbent coated with tetraphenylmethane is 3-10%.

23. The preparation method according to claim 1, wherein, The gas used in step (3) for plasma hydrophilic treatment includes any one or a combination of at least two of ammonia, methane, or oxygen.

24. The preparation method according to claim 1, wherein, The gas flow rate for the plasma hydrophilic treatment is 80~200 sccm.

25. The preparation method according to claim 1, wherein, The power of the plasma hydrophilic treatment is 100~300W.

26. The preparation method according to claim 1, wherein, The plasma hydrophilic treatment time is 30~300s.

27. The preparation method according to claim 1, wherein, The pressure of the plasma hydrophilic treatment is 20~50 Pa.

28. The preparation method according to claim 23, wherein, The gas used in the plasma hydrophilic treatment in step (3) is ammonia.

29. A modified lithium extraction adsorbent prepared by the method according to any one of claims 1-28.

30. A method for lithium extraction, comprising the following steps: (1) The modified lithium-extraction adsorbent as described in claim 29 is filled into a resin column and activated by soaking in deionized water to obtain the adsorbent after desorption; (2) After soaking the adsorbent after analysis with concentrated brine, replace the concentrated brine with ordinary brine for adsorption.

31. The lithium extraction method as described in claim 30, wherein, The lithium ion concentration in the concentrated brine is 500~1000 mg / L.

32. The lithium extraction method as described in claim 30, wherein, The sulfate concentration in the concentrated brine is ≥8 g / L.

33. The lithium extraction method as described in claim 30, wherein, The lithium ion concentration in the ordinary brine is 100~300 mg / L.

34. The lithium extraction method as described in claim 30, wherein, The sulfate concentration in the ordinary brine is 1~5 g / L.