Lithium extraction system and lithium extraction method

Abstract

The invention discloses a lithium extraction system and a lithium extraction method. The lithium extraction system comprises an o-hydroxyphenyl substituted phosphine oxide extraction agent, the o-hydroxyphenyl substituted phosphine oxide extraction agent has a structure as shown in the following formula: R1, R4, R5 and R6 are independently selected from any one of H,-CnH2n + 1,-OCnH2n + 1,-X,-CF3, amino, nitryl, aryl and substituted aryl, and X is selected from F, Cl, Br or I; r1, R2 and R3 are independently selected from any one of H,-CnH2n + 1,-OCnH2n + 1 and-CnH2n-1. The key component of the lithium extraction system is the o-hydroxyphenyl substituted phosphine oxide extraction agent, so that the selectivity of extraction agent molecules to lithium ions and the relatively high extraction rate are ensured; meanwhile, the lithium extraction method is high in extraction rate and simple in step, and the practical value is improved.

Description

Technical Field

[0001] This invention belongs to the field of separation and enrichment technology, specifically relating to a lithium extraction system and a lithium extraction method. Background Technology

[0002] The main industrial sources of lithium include hard rock ores (spodumene / lepidolite), salt lake brines, clay ores (lithium clay), seawater / underground brine, and the recycling of spent lithium batteries. Lithium extraction from ores involves processes such as crushing, flotation, and roasting. Methods for extracting lithium from brine include evaporation precipitation, adsorption, membrane separation, and solvent extraction. Lithium resource recovery methods include physical sorting, hydrometallurgy, pyrometallurgy, biometallurgy, and direct recovery. Among these, solvent extraction, due to its high selectivity, fast extraction rate, modular process, and strong compatibility, has moved beyond the laboratory and gradually evolved into a key value-added process for various resources such as salt lake brines, hard rock ores, and clay ores.

[0003] The extractant is the core factor in lithium extraction using solvent extraction methods. It determines the extraction rate, selectivity, number of regeneration cycles, and the economic and environmental performance of the process. Its core lies in the performance of the extractant. Currently, the main extractants used for lithium extraction include neutral and acidic phosphorus extractants, ammonia extractants, ketone extractants, ionic liquids, and crown ether extractants.

[0004] Neutral phosphorus extractants are typically represented by tributyl phosphate (TBP), trioctylphosphine oxide (TOPO), diheptyl methylphosphonate (P350), and trialkylphosphine oxide mixtures (Cyanex 923). When used alone, they exhibit poor selectivity, low extraction rates, and significant synergistic effects, thus they are often combined with other extractants to form mixed extraction systems for lithium extraction. Acidic phosphorus extractants, represented by di(2-ethylhexyl) phosphate (D2EHPA / P204), 2-ethylhexylphosphonate mono(2-ethylhexyl) ester (PC-88A / P507), and bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272), are currently the most widely used class of extractants in industry, especially suitable for lithium extraction from brines with high magnesium-to-lithium ratios. They can effectively extract Li... + From a source containing a large amount of Mg 2+ Ca 2+ Na + K + It is extracted from complex solution systems. In particular, by controlling pH and extractant concentration, Mg can be effectively separated. 2+This system effectively solves the problem of lithium extraction from high-lithium-magnesium ratio brine in salt lakes. It can also be used for lithium extraction from ore (spodumene / lepidolite) and lithium-containing leachates obtained through acid processes in lithium battery recycling. However, the system also has significant drawbacks. The extractant formed by lithium and acidic phosphorus-based extractants in this system has high stability, and back-extraction typically requires strong acids (such as H₂SO₄) or high-concentration salt solutions, resulting in long processes, high acid consumption, and severe equipment corrosion. During long-term operation of strong acid back-extraction and alkali saponification, the organic phase undergoes degradation and loss. Therefore, developing a new extraction system is an urgent problem to be solved, addressing the low lithium extraction efficiency and Lewis acid co-extraction issues encountered when using traditional phosphorus-based extractants. Summary of the Invention

[0005] The main objective of this invention is to provide a lithium extraction system and method to overcome the shortcomings of existing technologies, such as alkali saponification, acid back-extraction, long process, and severe equipment corrosion.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: This invention provides a lithium extraction system comprising an o-hydroxyphenyl-substituted phosphine oxide extractant having a structure as shown in formula (I):

[0007] Formula (I)

[0008] Among them, R1, R4, R5, and R6 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 R1, R2, R3 are any one of -X, -CF3, amino, nitro, aryl, or substituted aryl, where X is selected from F, Cl, Br, or I; R2 and R3 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 -C n H 2n-1 Any one of them.

[0009] The embodiments of the present invention also provide the application of the aforementioned lithium extraction system in lithium extraction.

[0010] This invention also provides a lithium extraction method, comprising: Provide the aforementioned lithium extraction system; Furthermore, the lithium extraction system is mixed with the aqueous phase to be extracted for extraction, washing, and back-extraction to achieve the separation and enrichment of lithium.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The key component of the lithium extraction system in this invention is an o-hydroxyphenyl substituted phosphine oxide extractant. This extractant has a unique structural advantage. Its molecular skeleton has phenolic hydroxyl and phosphonoyl oxygen sites that can bind to lithium ions. This characteristic ensures that the extractant molecule directly chelates with lithium without the need for a large amount of alkali to create it, thus ensuring the selectivity and extraction rate of the extraction system for lithium ions. In addition, there are many modifiable sites on the benzene ring. This structural feature gives this type of extractant excellent characteristics of tunable structure and controllable properties. (2) The present invention also provides a method for lithium extraction in an alkaline solution. This method can use a single system composed of the above-mentioned extractant or a mixed extraction system composed of the above-mentioned extractant and a co-extractant (such as TRPO). The key steps of this method include extraction, washing and impurity removal, back-extraction and recycling. This lithium extraction method has a short process flow and has significant advantages in practical applications. In the extraction and back-extraction process, the amount of acid and alkali used is small, which is low-carbon and environmentally friendly. At the same time, the organic phase recycling method is simple, efficient and energy-saving, and has greater application potential. Detailed Implementation

[0012] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0013] Specifically, as one aspect of the technical solution of this invention, a lithium extraction system includes an o-hydroxyphenyl-substituted phosphine oxide extractant, wherein the o-hydroxyphenyl-substituted phosphine oxide extractant has a structure as shown in formula (I):

[0014] Formula (I)

[0015] Among them, R1, R4, R5, and R6 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 R1, R2, R3 are any one of -X, -CF3, amino, nitro, aryl, or substituted aryl, where X is selected from F, Cl, Br, or I; R2 and R3 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 -C n H 2n-1 Any one of them.

[0016] To address the problems of low lithium extraction efficiency and Lewis acid co-extraction when using traditional phosphorus extractants, this invention discloses an o-hydroxyphenyl-substituted phosphine oxide extractant, as shown in the following formula. Its basic structural feature is the incorporation of an o-phenolic hydroxyl group onto the phosphorus atom, which, together with the phosphonoyl oxygen atom, reacts with lithium ions to form a chelate, achieving highly efficient lithium extraction. Simultaneously, the 3, 4, 5, and 6 positions of the benzene ring serve as modification sites, allowing for the adjustment of the extractant's properties through substituents, thereby improving extraction efficiency. .

[0017] Furthermore, the structural features of the o-hydroxyphenyl-substituted phosphine oxide extractant are as follows: A benzene ring is at the center, with position 1 of the benzene ring connected to the phosphorus atom of the phosphonoyl oxygen (position 7 in the structural formula) via a CP single bond, and a hydroxyl group connected to position 2 of the benzene ring, forming the basic skeleton of the o-hydroxyphenyl-substituted phosphine oxide. Positions 3, 4, 5, and 6 of the benzene ring serve as modification sites, allowing for the regulation of the extractant's properties through substituent groups.

[0018] In some preferred embodiments, the lithium extraction system further includes a co-extractant, which includes, but is not limited to, any one or more combinations of trialkylphosphine oxide (TRPO), tri-n-octylphosphine oxide (TOPO), tributylphosphine oxide (TBPO), tributyl phosphate (TBP), di(2-ethylhexyl) phosphate (P204), and phenyl-substituted phosphate diesters.

[0019] Furthermore, the co-extractant is trialkylphosphine oxide.

[0020] In some preferred embodiments, the lithium extraction system further includes a diluent, which includes, but is not limited to, any one or more combinations of sulfonated kerosene, o-dichlorobenzene, toluene, xylene, dichloromethane, 1,2-dichloroethane, chloroform, ethyl acetate, and cyclohexane.

[0021] Furthermore, the diluent is cyclohexane.

[0022] In some preferred embodiments, the molar ratio of o-hydroxyphenyl-substituted phosphine oxide extractant to co-extractant in the lithium extraction system is 100:1 to 1:100.

[0023] In some preferred embodiments, the total concentration of the o-hydroxyphenyl-substituted phosphine oxide extractant and co-extractant in the lithium extraction system is 0.01 mol / L to 2.5 mol / L.

[0024] Another aspect of the present invention provides the application of the aforementioned lithium extraction system in lithium extraction.

[0025] For example, the lithium extraction system is used in the extraction of lithium from alkaline solutions.

[0026] Another aspect of the present invention provides a lithium extraction method, comprising: Provide the aforementioned lithium extraction system; Furthermore, the lithium extraction system is mixed with the aqueous phase to be extracted for extraction, washing, and back-extraction to achieve the separation and enrichment of lithium.

[0027] In some preferred embodiments, the lithium extraction method specifically includes: mixing the extractable organic phase with the aqueous phase to be extracted and extracting at 5~70°C, and after reaching extraction equilibrium, allowing the mixture to stand and separate phases to obtain the loaded organic phase and the raffinate.

[0028] Furthermore, the extraction time is 2 to 20 minutes.

[0029] Furthermore, the Li in the extracted aqueous phase + The concentration is 0.001~0.6 mol / L.

[0030] Furthermore, the OH in the extracted aqueous phase - The concentration ranges from 0.001 to 4.0 mol / L.

[0031] Furthermore, the aqueous phase being extracted also includes Na. + and / or K + .

[0032] Furthermore, the volume ratio V of the lithium extraction system to the aqueous phase being extracted is... O / V A The ratio is 1:10 to 10:1.

[0033] Furthermore, extraction can be performed using any one of the following methods: single-stage oscillating extraction, multi-stage countercurrent extraction, or multi-stage cross-current extraction.

[0034] Furthermore, the mass transfer process of the extraction is carried out using any one of the following devices: a shaker, a centrifugal extractor, a tower extractor, or a mixing and clarifying tank.

[0035] In some preferred embodiments, the lithium extraction method specifically includes: washing and removing impurities from the supported organic phase with water.

[0036] Furthermore, the volume ratio V of the supported organic phase to the aqueous phase... O / V A The ratio is 10:1 to 1:10.

[0037] Furthermore, the aqueous phase includes any one or more combinations of water, dilute acid solution, lithium carbonate solution, and lithium chloride solution, and is not limited thereto.

[0038] In some preferred embodiments, the lithium extraction method specifically includes: mixing the loaded organic phase obtained from washing and impurity removal treatment with acid for back-extraction to obtain a lithium-rich aqueous solution and an empty organic phase.

[0039] Furthermore, the acid includes any one or more combinations of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, carbonic acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and oxalic acid, and is not limited thereto.

[0040] Furthermore, the acid contains H + The concentration ranges from 0.01 mol / L to 6.0 mol / L.

[0041] Furthermore, the volume ratio V of the supported organic phase to the acid is... O / V A The ratio is 2:1 to 1:20.

[0042] In some preferred embodiments, the lithium extraction method specifically includes: mixing the loaded organic phase obtained from washing and impurity removal treatment with water and then back-extracting it by introducing CO2 under conditions of pressure of 0.1~1 MPa and temperature of 5~70°C to obtain lithium carbonate and an empty organic phase.

[0043] Furthermore, the flow rate of the introduced CO2 is 0.001 ~ 10 L / min, and the duration is 0.1 ~ 100 min.

[0044] Furthermore, the lithium carbonate exists in the form of Li2CO3 solution, Li2CO3 solid, or a mixture of both; wherein the Li2CO3 solid is cleaned and purified using an organic solvent, the organic solvent including any one or more combinations of ethanol, methanol, ethyl acetate, dichloromethane, n-hexane, and petroleum ether, and is not limited thereto.

[0045] Furthermore, the mass transfer process of the back-extraction is carried out using any one of the following devices: a stirrer, a centrifugal extractor, a tower extractor, or a mixing and clarifying tank.

[0046] Furthermore, the empty organic phase can be directly used in the extraction cycle, or the empty organic phase can be mixed with water and an alkaline solution to obtain a regenerated organic phase.

[0047] In some more specific embodiments, the lithium extraction method includes extraction, washing and impurity removal, back-extraction, and recycling stages, as detailed below: Extraction stage The corresponding organic phase is prepared according to a certain composition ratio. The prepared organic phase is mixed with the aqueous phase to be extracted in a certain proportion, shaken for a certain time to reach equilibrium, and then allowed to stand to separate phases, so as to obtain the loaded organic phase and the raffinate.

[0048] Washing and cleaning stage

[0049] The supported organic phase was washed with distilled water, dilute hydrochloric acid, lithium carbonate solution, and lithium chloride solution at a certain ratio to remove sodium impurities.

[0050] Back-extraction stage

[0051] The loaded organic phase obtained in the washing and impurity removal stage is back-extracted with a certain concentration of acid at a certain ratio, or by introducing a certain amount of CO2, to obtain a lithium-rich aqueous solution and an empty mixed organic phase, respectively.

[0052] Recycling Phase

[0053] The organic phase obtained in the back-extraction stage can be directly entered into the next stage of the extraction cycle, or it can be regenerated by water or a certain concentration of alkaline solution before entering the next stage of the extraction cycle.

[0054] Furthermore, the mixing ratio V between the organic phase and the aqueous phase being extracted during the extraction process is... O / V A It ranges from 1 / 10 to 10 / 1.

[0055] Furthermore, the extraction process includes single-stage oscillating extraction, multi-stage countercurrent extraction, and multi-stage cross-current extraction.

[0056] Furthermore, the extraction time is 2 min to 20 min, and the equilibrium is reached by shaking at 25 ℃, with a preferred time of 10 min.

[0057] Furthermore, the extraction temperature is 5 ℃ ~ 70 ℃.

[0058] Furthermore, the extraction process can achieve mass transfer through a shaker, or it can also be achieved through a centrifugal extractor, a tower extractor, or a mixing and clarification tank.

[0059] Furthermore, in the washing and impurity removal stage, the aqueous phase used for washing the organic phase is pure water, dilute acid solution, lithium carbonate solution, or lithium chloride solution. The washing ratio of the organic phase to the aqueous phase is V. O / V A : 10 / 1 ~ 1 / 10.

[0060] Furthermore, the acid used in the back-extraction stage is one or more of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, carbonic acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and oxalic acid.

[0061] Furthermore, the acid H in the back-extraction stage + The concentration ranges from 0.01 mol / L to 6.0 mol / L.

[0062] Furthermore, in the acid back-extraction process, the organic phase is V compared to the aqueous phase. O / VA It ranges from 2 / 1 to 1 / 20.

[0063] Furthermore, the back-extraction stage can also be carried out under certain conditions by introducing CO2 gas into a mixed solution of the loaded organic phase and water.

[0064] Furthermore, the mixing ratio V of the loaded organic solution with water O / V A It ranges from 1 / 100 to 100 / 1.

[0065] Furthermore, the aforementioned conditions refer to a pressure of 0.1 ~ 1 MPa and a temperature of 5 ~ 70 ℃.

[0066] Furthermore, the CO2 flow rate is 0.001 ~ 10 L / min, and the duration is 0.1 ~ 100 min.

[0067] Furthermore, the mass transfer process of the back-extraction can be achieved by a stirrer, and also includes centrifugal extractors, tower extractors, mixing and clarifying tanks, etc. Furthermore, the Li2CO3 obtained from back-extraction may exist in three states: Li2CO3 solution, Li2CO3 solid, or a mixture of both.

[0068] Furthermore, the obtained Li2CO3 solid can be cleaned and purified using organic solvents such as ethanol, methanol, ethyl acetate, dichloromethane, n-hexane, and petroleum ether.

[0069] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. These embodiments are implemented on the premise of the technical solution of the invention, and provide detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0070] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0071] Examples 1-7

[0072] Preparation of the organic phase: The extractant 5-bromo-2-hydroxyphenyl diisobutyl phosphate (structure shown below) and the co-extractant trialkylphosphine oxide (TRPO) were mixed in a certain molar ratio (Examples 1-7), and cyclohexane was used as a diluent to prepare an organic phase with a total concentration of 0.2 mol / L.

[0073]

[0074] Extracted aqueous phase: Li + Concentration: 0.1 mol / L, Na +Concentration: 0.2 mol / L, OH - Concentration: 0.2 mol / L, Cl - The concentration is 0.1 mol / L.

[0075] Table 1 Extraction efficiency of different extraction systems in Examples 1-7

[0076] The organic phase and the aqueous phase to be extracted are separated by V O / V A The extractant and co-extractant were mixed in a 1:1 ratio and shaken at 25 °C for 10 min to reach equilibrium. After standing, the mixture was allowed to separate into two phases: the loaded organic phase and the raffinate. The lithium-ion extraction rate was calculated from the raffinate. The molar ratio of extractant to co-extractant significantly affected the extraction efficiency of the extraction system. The extraction system with a molar ratio of 5 / 3 achieved the highest single-stage extraction rate, reaching 87.43% (see Table 1 for details).

[0077] Examples 8-12

[0078] Preparation of the organic phase: The extractant 5-bromo-2-hydroxyphenyl diisobutyl phosphate was mixed with the co-extractants trialkylphosphine oxide (TRPO), tributylphosphine oxide (TBPO), tributyl phosphate (TBP), phenyl substituted phosphine diester compound (DTPO), and tri-n-octylphosphine oxide (TOPO) at a 1 / 1 molar ratio (Examples 8 to 12), and cyclohexane was used as a diluent to prepare an organic phase with a total concentration of 0.2 mol / L.

[0079] Extracted aqueous phase: Li + Concentration: 0.1 mol / L, Na + Concentration: 0.2 mol / L, OH - Concentration: 0.2 mol / L, Cl - The concentration is 0.1 mol / L.

[0080] Table 2 Extraction efficiency of different extraction system components in Examples 8-12

[0081] The organic phase and the aqueous phase to be extracted are separated by V O / V AThe mixtures were prepared in a 1:1 ratio and shaken for 10 min at 25 °C until equilibrium was reached. After standing, the mixtures were allowed to separate into two phases: the loaded organic phase and the raffinate. The lithium-ion extraction rate was calculated using the raffinate. The mixed extraction system consisting of 5-bromo-2-hydroxyphenyl phosphate diisobutyl ester and the co-extractant TRPO showed the best extraction effect, with an extraction rate of 83.11%. The single-stage extraction rates of the extraction systems consisting of 5-bromo-2-hydroxyphenyl phosphate diisobutyl ester and the other co-extractants also all reached over 75% (see Table 2 for details).

[0082] Examples 13-18

[0083] Preparation of the organic phase: The extractants 6-methyl-2-hydroxyphenyl phosphate dibutyl ester, 5-methyl-2-hydroxyphenyl phosphate dibutyl ester, 4-methoxy-2-hydroxyphenyl phosphate dibutyl ester, 5-chloro-2-hydroxyphenyl phosphate diisobutyl ester, 5-fluoro-2-hydroxyphenyl phosphate diisobutyl ester, and 2-hydroxyphenyl phosphate diisooctyl ester were mixed with the co-extractant trialkylphosphine oxide (TRPO) at a 1 / 1 molar ratio (Examples 13-18), and cyclohexane was used as a diluent to prepare an organic phase with a total concentration of 0.2 mol / L.

[0084] Extracted aqueous phase: Li + Concentration: 0.1 mol / L, Na + Concentration: 0.2 mol / L, OH - Concentration: 0.2 mol / L, Cl - The concentration is 0.1 mol / L.

[0085] The organic phase and the aqueous phase to be extracted are separated by V O / V A The mixtures were prepared in a 1:1 ratio and shaken at 25 °C for 10 min to reach equilibrium. After standing, the mixtures were allowed to separate into two phases: the loaded organic phase and the raffinate. The lithium-ion extraction rate was calculated using the raffinate. The extractant structure significantly affected the extraction efficiency of the extraction system. The mixed extraction system consisting of diisobutyl 5-chloro-2-hydroxyphenylphosphonate and the co-extractant TRPO achieved the highest extraction rate, reaching 72.35% (see Table 3).

[0086] Table 3 Extraction efficiency of different extractant structures in Examples 13-18

[0087] Example 19

[0088] Preparation of the organic phase: The extractant 5-bromo-2-hydroxyphenylphosphonic acid diisobutyl ester and the co-extractant trialkylphosphine oxide (TRPO) were mixed in a 5 / 3 molar ratio, and cyclohexane was used as a diluent to prepare an organic phase with a total organic phase concentration of 0.6 mol / L.

[0089] Extracted aqueous phase: Li + Concentration: 0.39 mol / L, Na + Concentration: 1.73 mol / L, K + Concentration: 0.017 mol / L, OH - Concentration: 0.1 mol / L, Cl - The concentration was 1.82 mol / L, CO3 2- The concentration is 0.21 mol / L.

[0090] Extraction stage

[0091] The organic phase and the aqueous phase to be extracted are separated by V O / V A The mixture was mixed in a 1:1 ratio and subjected to three-stage cascade extraction at 25 °C. After reaching equilibrium, the mixture was allowed to stand and separate into two phases: the loaded organic phase and the raffinate. The lithium-ion extraction rate was calculated to be 95.66% based on the raffinate.

[0092] Washing and cleaning stage

[0093] The organic load obtained in the previous step and distilled water were mixed in V O / V A Mix in a 1 / 1 ratio, perform three-stage cascade washing, and after reaching equilibrium, allow to stand and separate phases to obtain a lithium-loaded organic phase. The lithium ion elution rate is 8.7%, and the sodium ion elution rate is 92.0%.

[0094] Back-extraction stage

[0095] The lithium-loaded organic phase obtained in the previous step was dissolved in 6.0 mol / L hydrochloric acid at V O / V A = 10 / 1 mixing, two-stage back-extraction, after reaching equilibrium, allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 97.4%, and the total lithium yield was 85.1%.

[0096] Example 20

[0097] Compared to Example 19, the extractant in Example 20 is changed to dibutyl 2-hydroxyphenylphosphonate (as shown in the formula below), while the other conditions remain unchanged: .

[0098] Extraction stage

[0099] The lithium-ion extraction rate was 90.4% with three-stage cascade extraction.

[0100] Washing and cleaning stage

[0101] The three-stage cascade washing was performed using 0.1 mol / L hydrochloric acid. After reaching equilibrium, the phases were separated by standing to obtain a lithium-loaded organic phase. The lithium ion elution rate was 27.1%, and the sodium ion elution rate was 97.8%.

[0102] Back-extraction stage

[0103] The lithium-loaded organic phase obtained in the previous step was dissolved in 6.0 mol / L hydrochloric acid at V O / V A = 10 / 1 mixing, two-stage back-extraction, after reaching equilibrium, allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 98.3% and the total lithium yield was 64.78%.

[0104] Example 21

[0105] Compared to Example 19, the extractant in Example 21 was changed to methyl 3-(dibutoxyphosphoryl)-4-hydroxybenzoate (structure shown below), while all other conditions remained unchanged: .

[0106] Extraction stage

[0107] The lithium-ion extraction rate was 97.39% with three-stage cascade extraction.

[0108] Washing and cleaning stage

[0109] A three-stage cascade washing process was performed using 0.1 mol / L lithium carbonate. After reaching equilibrium, the mixture was allowed to stand and separate to obtain a lithium-loaded organic phase. The lithium ion elution rate was -6% (some lithium ions from the lithium carbonate solution entered the organic phase), and the sodium ion elution rate was 94.55%.

[0110] Back-extraction stage

[0111] Acid back-extraction: The lithium-loaded organic phase obtained in the previous step is subjected to 6.0 mol / L hydrochloric acid with V O / V A = 10 / 1 mixing, two-stage back-extraction, after reaching equilibrium, let stand for phase separation to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate is 96.61%, and the total lithium yield is 99.7% (while the water washing and impurity removal step removes most of the sodium ions, some lithium ions in the lithium carbonate solution enter the organic phase, resulting in a higher total lithium ion yield).

[0112] CO2 back-extraction: If the lithium-loaded organic phase obtained from washing and impurity removal is mixed with distilled water at a V... O / V A = 4 / 1 mixture, under normal pressure and 23℃, CO2 gas at a flow rate of 0.1 L / min was introduced into it for 10 min, and then allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 75.92% and the total lithium yield was 78.37%.

[0113] Example 22

[0114] Compared to Example 19, the extractant in Example 22 was changed to diisobutyl 4-fluoro-2-hydroxyphenylphosphonate (structure shown below), while all other conditions remained unchanged: .

[0115] Extraction stage

[0116] The lithium-ion extraction rate was 97.88% with three-stage cascade extraction.

[0117] Washing and cleaning stage

[0118] The lithium-loaded organic phase was obtained by three-stage cascade washing with distilled water. After reaching equilibrium, the phases were separated by standing. The lithium ion elution rate was 11.1%, and the sodium ion elution rate was 95.76%.

[0119] Back-extraction stage

[0120] Acid back-extraction: The lithium-loaded organic phase obtained in the previous step is subjected to 6.0 mol / L hydrochloric acid with V O / V A = 10 / 1 mixing, two-stage back-extraction, after reaching equilibrium, allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 97.84%, and the total lithium yield was 89.36%.

[0121] CO2 back-extraction: If the lithium-loaded organic phase obtained from washing and impurity removal is mixed with distilled water at a V... O / V A = 1 / 1 mixture, under normal pressure and 23℃, CO2 gas at a flow rate of 0.08 L / min was introduced into it for 10 min, and then allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 82.63% and the total lithium yield was 71.90%.

[0122] Example 23

[0123] Compared to Example 19, the total concentration of the organic phase in Example 23 is 0.4 mol / L. The phase change of the extracted water is: Li + Concentration: 0.17 mol / L, Na + Concentration: 1.41 mol / L, K + Concentration: 0.02 mol / L, OH - Concentration: 0.15 mol / L, Cl - The concentration was 1.31 mol / L, CO3 2- The concentration was 0.13 mol / L. All other conditions remained unchanged.

[0124] Extraction stage

[0125] The lithium-ion extraction rate was 98.50% with three-stage cascade extraction.

[0126] Washing and cleaning stage

[0127] A 0.1 mol / L lithium carbonate solution was used compared to V O / V A = 2 / 1 undergoes three-stage cascade washing. After reaching equilibrium, it is allowed to stand and separate phases to obtain a lithium-loaded organic phase. The lithium ion elution rate is -23.9% (some lithium ions in the lithium carbonate solution enter the organic phase), and the sodium ion elution rate is 99.02%.

[0128] Back-extraction stage

[0129] Acid back-extraction: The lithium-loaded organic phase obtained in the previous step is subjected to 6.0 mol / L hydrochloric acid with V O / V A = 20 / 1 mixing, two-stage back-extraction, after reaching equilibrium, allowed to stand and separate phases to obtain a lithium-rich solution (28.04 g / L) and an empty organic phase. The back-extraction rate was 97.39%, and the total lithium yield was 118.86% (while most of the sodium ions were washed away in the water washing and impurity removal step, some lithium ions entered the organic phase, resulting in a total lithium ion yield greater than 100%).

[0130] CO2 back-extraction: If the lithium-loaded organic phase obtained from washing and impurity removal is mixed with distilled water at a V... O / V A = 2 / 1 mixture, under normal pressure and 23℃, CO2 gas at a flow rate of 0.05 L / min was introduced into it for 10 min, and then allowed to stand and separate phases to obtain a lithium-rich solution and an empty organic phase. The back-extraction rate was 78.34% and the total lithium yield was 95.61%.

[0131] Recycling Phase

[0132] The organic phase obtained from the acid back-extraction was directly fed into the extraction-back-extraction cycle experiment. After 11 cycles, the single-stage extraction rate was still above 70% (see Table 4 for details).

[0133] Table 4. Number of cycles and extraction efficiency

[0134] Comparative Examples 1-2

[0135] The method is the same as in Example 1, except for the extractant, as detailed in Table 5: Table 5 Extraction efficiency of different extractant structures in Comparative Examples 1-2

[0136] Preparation of organic phase: In Comparative Examples 1 and 2, the extractants o-propoxyphenol and 2-isopropoxyphenol were mixed with the co-extractant TRPO at a 1 / 1 molar ratio, and cyclohexane was used as a diluent to prepare an organic phase with a concentration of 0.2 mol / L.

[0137] Extracted aqueous phase: Li + Concentration: 0.1 mol / L, Na + Concentration: 0.2 mol / L, OH - Concentration: 0.2 mol / L, Cl - The concentration is 0.1 mol / L.

[0138] The organic phase and the aqueous phase to be extracted are separated by V O / V A Mix the components in a 1:1 ratio, shake at 25 °C for 10 min to reach equilibrium, and then allow them to stand to separate into two phases: the loaded organic phase and the raffinate. The lithium-ion extraction rate is then calculated from the raffinate.

[0139] The results showed that comparative examples 1 and 2 extracted almost no lithium (see Table 5 for details). In addition, the inventors of this invention also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned examples, and obtained relatively ideal results in all cases.

[0140] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A lithium extraction system, characterized in that: The lithium extraction system includes an o-hydroxyphenyl-substituted phosphine oxide extractant, which has a structure as shown in formula (I): ； Formula (I); Among them, R1, R4, R5, and R6 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 R1, R2, R3 are any one of -X, -CF3, amino, nitro, aryl, or substituted aryl, where X is selected from F, Cl, Br, or I; R2 and R3 are independently selected from H and -C. n H 2n+1 -OC n H 2n+1 -C n H 2n-1 Any one of them.

2. The lithium extraction system according to claim 1, characterized in that: The lithium extraction system further includes a co-extractant, which includes any one or more combinations of trialkylphosphine oxide, tri-n-octylphosphine oxide, tributylphosphine oxide, tributyl phosphate, di(2-ethylhexyl) phosphate, and phenyl-substituted phosphate diesters, preferably trialkylphosphine oxide; And / or, the lithium extraction system further includes a diluent, which includes any one or more combinations of sulfonated kerosene, o-dichlorobenzene, toluene, xylene, dichloromethane, 1,2-dichloroethane, chloroform, ethyl acetate, and cyclohexane, preferably cyclohexane.

3. The lithium extraction system according to claim 2, characterized in that: In the lithium extraction system, the molar ratio of o-hydroxyphenyl substituted phosphine oxide extractant to co-extractant is 100:1 to 1:100; And / or, the total concentration of o-hydroxyphenyl substituted phosphine oxide extractant and co-extractant in the lithium extraction system is 0.01 mol / L to 2.5 mol / L.

4. The application of the lithium extraction system according to any one of claims 1-3 in lithium extraction, preferably in lithium extraction using alkaline solutions.

5. A method for lithium extraction, characterized in that, include: Provide a lithium extraction system according to any one of claims 1-3; Furthermore, the lithium extraction system is mixed with the aqueous phase to be extracted for extraction, washing, and back-extraction to achieve the separation and enrichment of lithium.

6. The lithium extraction method according to claim 5, characterized in that, Specifically, it includes: The organic phase to be extracted is mixed with the aqueous phase to be extracted and extracted at 5~70℃. After reaching extraction equilibrium, the mixture is allowed to stand and separate to obtain the loaded organic phase and the raffinate. Preferably, the extraction time is 2 to 20 minutes; Preferably, the Li in the extracted aqueous phase + The concentration is 0.001~0.6 mol / L; Preferably, the OH in the extracted aqueous phase - The concentration ranges from 0.001 to 4.0 mol / L; Preferably, the aqueous phase being extracted also includes Na. + and / or K + ; Preferably, the volume ratio V of the lithium extraction system to the aqueous phase being extracted is... O / V A The ratio is 1:10 to 10:1; Preferably, extraction is performed using any one of the following methods: single-stage oscillating extraction, multi-stage countercurrent extraction, or multi-stage cross-current extraction. Preferably, the mass transfer process of the extraction is carried out using any one of the following devices: a shaker, a centrifugal extractor, a tower extractor, or a mixing and clarifying tank.

7. The lithium extraction method according to claim 6, characterized in that, Specifically, it includes: The loaded organic phase was washed and purified with water. Preferably, the volume ratio V of the supported organic phase to the aqueous phase is... O / V A The ratio is 10:1 to 1:10; Preferably, the aqueous phase includes any one or more combinations of water, dilute acid solution, lithium carbonate solution, and lithium chloride solution.

8. The lithium extraction method according to claim 7, characterized in that, Specifically, it includes: The loaded organic phase obtained from the washing and impurity removal process was mixed with acid and back-extracted to obtain a lithium-rich aqueous solution and an empty organic phase. Preferably, the acid includes any one or more combinations of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, carbonic acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, and oxalic acid; Preferably, the acid contains H + The concentration ranges from 0.01 mol / L to 6.0 mol / L. Preferably, the volume ratio V of the supported organic phase to the acid is... O / V A The ratio is 2:1 to 1:

20.

9. The lithium extraction method according to claim 7, characterized in that, Specifically, it includes: The loaded organic phase obtained from the washing and impurity removal process is mixed with water and back-extracted by passing CO2 through it under conditions of 0.1~1 MPa and 5~70℃ to obtain lithium carbonate and an empty organic phase. Preferably, the flow rate of the introduced CO2 is 0.001 ~ 10 L / min, and the duration is 0.1 ~ 100 min; Preferably, the lithium carbonate exists in the form of Li2CO3 solution, Li2CO3 solid, or a mixture of both; wherein the Li2CO3 solid is cleaned and purified using an organic solvent, the organic solvent including any one or more combinations of ethanol, methanol, ethyl acetate, dichloromethane, n-hexane, and petroleum ether.

10. The lithium extraction method according to claim 8 or 9, characterized in that: The mass transfer process of the back-extraction is carried out using any one of the following devices: a stirrer, a centrifugal extractor, a tower extractor, or a mixing and clarifying tank. And / or, the empty organic phase is used directly in the extraction cycle, or the empty organic phase is mixed with water and an alkaline solution to obtain a regenerated organic phase.

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