Solid-phase extraction materials for lithium extraction, their preparation methods and applications

Abstract

This invention discloses a solid-phase extraction material for lithium extraction, its preparation method, and its application. The solid-phase extraction material comprises a magnetic matrix and extraction groups connected to the magnetic matrix via a silane coupling agent. The magnetic matrix comprises an Fe3O4 core layer and a SiO2 shell layer, and the extraction groups have a structure as shown in formula (1) or formula (2). The preparation method includes: preparing a SiO2 shell layer on the surface of Fe3O4 nanoparticles to obtain a magnetic matrix; using a silane coupling agent to perform a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix; and connecting the extraction groups to the silane coupling agent through a coupling reaction or esterification reaction to obtain the solid-phase extraction material. This invention synthesizes a solid-phase extraction material with lithium-specific selectivity through organic synthesis. The synthetic substrate used is inexpensive and readily available, the synthetic route is clear, and the prepared solid-phase extraction material can be reused multiple times. It is suitable for the extraction and separation of lithium ions in salt lake brine where multiple ions coexist.

Description

Technical Field

[0001] This invention belongs to the field of salt lake chemical technology, specifically relating to a solid-phase extraction material for lithium extraction, its preparation method, and its application. Background Technology

[0002] Lithium is the lightest metal in nature and possesses extremely high electrochemical activity. Its metals and compounds are widely used in industries and fields such as glass, ceramics, aluminum smelting, organic chemicals, aerospace, and nuclear fusion. In recent years, the widespread promotion and attention given to the electric vehicle (EV) industry, which uses lithium batteries as a new energy source, has made lithium-ion batteries one of the fastest-growing fields, thus earning lithium the title of "the new energy darling of the 21st century."

[0003] Salt lake brines are an important source of lithium. my country possesses abundant lithium resources from salt lake brines, ranking among the world's largest. Salt lake brines contain various metal ions, making the separation and extraction of lithium a crucial research topic. A review of domestic and international technologies and methods for extracting lithium salts from salt lake brines reveals several key approaches, including precipitation, extraction, ion exchange adsorption, carbonization, calcination leaching, the Schereschewsky process, and electrodialysis.

[0004] Solvent extraction is an effective technique for separating and extracting various metals from solutions. It boasts advantages such as high separation efficiency, simple processes and equipment, continuous operation, and ease of automation, and is considered one of the most promising methods for extracting and separating lithium from salt lake brines. Currently, the solvent extraction method for lithium extraction from salt lake brines, also known as liquid-liquid extraction, involves first mixing a liquid extractant with an aqueous phase for extraction. After extraction, the organic phase needs to be separated, and then back-extracted using a back-extraction solution. In the liquid-liquid extraction process, the kinetics of both extraction and back-extraction are slow, and the liquid-liquid phase separation process is complex and time-consuming, resulting in low production efficiency. Furthermore, the extraction process requires large amounts of organic solvents, generating significant amounts of organic waste liquid, which is detrimental to the health of workers and the environment. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a solid-phase extraction material for lithium extraction, its preparation method and application, so as to improve the production efficiency of lithium extraction process by extraction and reduce the generation of organic waste liquid.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] A solid-phase extraction material for lithium extraction, the solid-phase extraction material comprising a magnetic matrix and extraction groups connected to the surface of the magnetic matrix by a silane coupling agent; the magnetic matrix comprising an Fe3O4 core layer and a SiO2 shell layer covering the Fe3O4 core layer, the extraction groups having a structural formula of either formula (1) or formula (2):

[0008]

[0009] In formula (1), R1 and R2 are straight-chain alkanes or branched alkanes of C2 to C14, or phenyl or benzyl, respectively; in formula (2), R3 and R4 are straight-chain alkanes or branched alkanes of C6 to C18, or straight-chain alkoxy or branched alkoxy or phenyl or benzyl, respectively.

[0010] The present invention also provides a method for preparing the solid-phase extraction material as described above. In one optional embodiment, the preparation method includes:

[0011] S11. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix;

[0012] S12. A silane coupling agent is used to perform a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix, thereby obtaining a silanized magnetic matrix.

[0013] S13. Using a compound containing the extraction group to perform a coupling reaction or esterification reaction with the silanized magnetic matrix, the extraction group is connected to the silane coupling agent to obtain the solid-phase extraction material.

[0014] In another alternative embodiment, the preparation method includes:

[0015] S21. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix;

[0016] S22. Using a silane coupling agent, a compound containing the extraction group is coupled or esterified to connect the extraction group to the silane coupling agent to obtain an intermediate compound.

[0017] S23. The intermediate compound is subjected to a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix, thereby obtaining the solid-phase extraction material.

[0018] In a preferred embodiment, the silane coupling agent has the structural formula (R'O)-Si-R; wherein R' is methyl or ethyl, and R is a straight chain with an alcohol, halogen, or amino active group at the end.

[0019] Furthermore, the present invention also provides the application of the solid-phase extraction material described above in the lithium extraction process of salt lake brine.

[0020] In a preferred embodiment, the application specifically includes: providing lithium-containing brine from a salt lake and adjusting it to H... + The concentration is 0.05 mol / L to 0.20 mol / L, and the pH is below 3.0. The solid-phase extraction material is placed in the lithium-containing brine of the salt lake for lithium extraction and then magnetically separated. The separated solid-phase extraction material is washed and back-extracted sequentially to obtain a lithium-rich solution.

[0021] In a preferred embodiment, the Fe in the lithium-containing brine of the salt lake... 3+ The mixture is adjusted to reduce the Fe content in the lithium-containing brine of the salt lake. 3+ The molar concentration of Li + 1.3 to 1.5 times that.

[0022] This invention provides a solid-phase extraction material for lithium extraction, its preparation method, and its application. Specifically, through organic synthesis, an extraction group with lithium extraction functionality, such as those in formula (1) or (2), is attached to a magnetic matrix using a silane coupling agent. This synthesizes a functionalized magnetic solid-phase extraction material with lithium-specific selectivity. The selected synthetic substrate is inexpensive and readily available, the synthesis route is clear, and the prepared solid-phase extraction material can be reused multiple times. It is suitable for the extraction and separation of lithium ions in salt lake brines where multiple ions coexist. The extraction process is a solid-liquid contact extraction, reducing the amount of organic reagents used. Furthermore, the kinetics of the extraction and back-extraction processes are relatively fast, and the phase separation process is shortened, effectively improving the production efficiency of the lithium extraction process and reducing the generation of organic waste liquid. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the synthetic process for preparing solid-phase extraction materials in Example 1 of this invention.

[0024] Figure 2 This is a TEM image of the solid-phase extraction material prepared in Example 1 of this invention;

[0025] Figure 3 This is a flowchart illustrating the synthetic process for preparing solid-phase extraction materials in Example 2 of this invention.

[0026] Figure 4 This is a TEM image of the solid-phase extraction material prepared in Example 2 of this invention;

[0027] Figure 5 This is a flowchart illustrating the synthetic process for preparing solid-phase extraction materials in Example 3 of the present invention.

[0028] Figure 6This is a TEM image of the solid-phase extraction material prepared in Example 3 of this invention;

[0029] Figure 7 This is a flowchart illustrating the synthetic process for preparing solid-phase extraction materials in Example 4 of this invention.

[0030] Figure 8 This is a TEM image of the solid-phase extraction material prepared in Example 4 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0032] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0033] The present invention first provides a solid-phase extraction material for extracting lithium, the solid-phase extraction material comprising a magnetic matrix and extraction groups connected to the surface of the magnetic matrix by a silane coupling agent.

[0034] The magnetic substrate includes an Fe3O4 core layer and a SiO2 shell layer covering the Fe3O4 core layer.

[0035] The extracting group has the following structural formula (1) or (2):

[0036]

[0037] In formula (1), R1 and R2 are C2-C14 straight-chain alkanes or branched alkanes or phenyl or benzyl, respectively; in formula (2), R3 and R4 are C6-C18 straight-chain alkanes or branched alkanes or C6-C18 straight-chain alkoxy or branched alkoxy or phenyl or benzyl, respectively.

[0038] The present invention also provides a method for preparing the solid-phase extraction material as described above.

[0039] In the first alternative approach (which may be simply referred to as the lateral grafting method), the preparation method includes the following steps:

[0040] S11. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix.

[0041] S12. A silane coupling agent is used to perform a silanization reaction with the magnetic matrix, thereby connecting the silane coupling agent to the magnetic matrix to obtain a silanized magnetic matrix.

[0042] S13. Using a compound containing the extraction group to perform a coupling reaction or esterification reaction with the silanized magnetic matrix, the extraction group is connected to the silane coupling agent to obtain the solid-phase extraction material.

[0043] In the second alternative (which may be simply referred to as the reverse grafting method), the preparation method includes the following steps:

[0044] S21. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix.

[0045] S22. Using a silane coupling agent, a compound containing the extraction group is coupled or esterified to connect the extraction group to the silane coupling agent to obtain an intermediate compound.

[0046] S23. The intermediate compound is subjected to a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix, thereby obtaining the solid-phase extraction material.

[0047] In the preparation method described above, the preferred structural formula of the silane coupling agent is (R'O)-Si-R; wherein R' is methyl or ethyl, and R is a straight chain with an alcohol, halogen, or amino active group at the end.

[0048] In the preparation method described above, the specific process for preparing a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix can be referred to existing reported technical solutions, such as through... The method prepares a SiO2 coating layer on the surface of Fe3O4 nanoparticles.

[0049] This invention further provides the application of the solid-phase extraction material described above in the lithium extraction process from salt lake brine. In one specific embodiment, the application includes the following steps: (1) providing lithium-containing salt lake brine and adjusting it to H... + The concentration is 0.05 mol / L to 0.20 mol / L, and the pH is below 3.0; (2) The solid phase extraction material is placed in the lithium-containing salt lake brine for lithium extraction and then magnetically separated; (3) The separated solid phase extraction material is washed and back-extracted in sequence to obtain a lithium-rich solution.

[0050] As a preferred option, in step (1), the Fe in the lithium-containing salt lake brine is... 3+ The mixture is adjusted to reduce the Fe content in the lithium-containing brine of the salt lake. 3+ The molar concentration of Li +1.3 to 1.5 times that.

[0051] Among them, magnetic separation mainly uses magnetic materials (such as strong magnets) to enrich and separate lithium-loaded solid-phase extraction materials through magnetic force.

[0052] The washing process can use a hydrochloric acid solution with a concentration of 0.1 mol / L to 0.5 mol / L as the washing liquid to wash the lithium-loaded solid-phase extraction material.

[0053] The back-extraction process can use a hydrochloric acid solution with a concentration of 1 mol / L to 3 mol / L as the back-extraction solution to back-extract the lithium-loaded solid-phase extraction material.

[0054] Example 1

[0055] I. Preparation of solid phase extraction materials

[0056] See Figure 1 Synthetic process route: The raw material 4-carboxyphenylboronic acid pinacol ester S11 (CAS No. 180516-87-4) is reacted with thionyl chloride (CAS No. 7719-09-7) to obtain the corresponding acyl chloride S12. Then, it is reacted with di-n-hexylamine (CAS No. 143-16-8) in the presence of triethylamine to obtain the corresponding amide compound S13. Then, tetrakis(triphenylphosphine) palladium and cesium carbonate are added to N,N-dimethylformamide solvent and 3-chloropropyltriethoxysilane (CAS No. 5089-70-3) in a reverse coupling reaction to obtain the intermediate product S14. Finally, S14 is silanized with a magnetic matrix (Fe3O4@SiO2) to obtain the solid phase extraction material S15.

[0057] Figure 2 This is a TEM image of the solid-phase extraction material S15 prepared in this embodiment.

[0058] II. Application of solid-phase extractants in the extraction and separation of lithium from salt lake brine

[0059] 1.0 g of solid-phase extraction material S15 was added to a beaker containing 5.0 L of high magnesium-to-lithium ratio brine (simulating the brine of Qinghai Chaka Salt Lake, with ionic composition as shown in Table 1). Ferric chloride hexahydrate was then added to the brine to increase the Fe content. 3+ The concentration is 3.0 g / L, and the pH is adjusted to 2-3.

[0060] After stirring for 5 minutes, the extraction reached a basic equilibrium. The solid-phase extractant was then attracted to the outer wall of the beaker using a magnet, and the aqueous phase was poured off. 95% of the lithium-loaded solid-phase extractant was recoverable, with a lithium loading of 400 mg / g. -1 .

[0061] Table 1: Composition of Brine Content

[0062] Types of ions Li Na K Ca Mg B Cl <![CDATA[SO4 2- ]]> <![CDATA[(g·L -1 )]]> 0.279 2.281 0.763 0.107 108.04 0.275 103.04 6.39

[0063] Subsequently, impurities in the lithium-loaded solid-phase extractant after magnetic separation were washed with 0.2M dilute hydrochloric acid. At this point, based on the usual extraction order of cations by amide extractants, it is considered that: H... + >Li + >Ca 2+ Na + >K + >Mg 2+ Other impurity ions were basically completely washed away, Li + The loss rate is less than 5%.

[0064] Finally, the lithium-loaded solid-phase extraction material, after washing with dilute hydrochloric acid, was back-extracted with 2.0 M hydrochloric acid. The Li on the solid-phase extraction material was largely washed off. + Washing rate > 95%. The unloaded magnetic solid phase extractant after back-extraction can be recycled.

[0065] Example 2

[0066] I. Preparation of solid phase extraction materials

[0067] See Figure 3 Synthetic process route: The raw material 4-carboxyphenylboronic acid pinacol ester S21 (CAS No. 180516-87-4) is reacted with thionyl chloride (CAS No. 7719-09-7) to obtain the corresponding acyl chloride S22. Then, it is reacted with di-sec-butylamine (CAS No. 626-23-3) in the presence of triethylamine to obtain the corresponding amide compound S23. Then, tetrakis(triphenylphosphine) palladium and cesium carbonate are added to N,N-dimethylformamide solvent and 3-chloropropyltriethoxysilane (CAS No. 5089-70-3) to obtain intermediate product S24. Finally, S24 is silanized with a magnetic matrix (Fe3O4@SiO2) to obtain solid phase extraction material S25.

[0068] Figure 4 This is a TEM image of the solid-phase extraction material S25 prepared in this embodiment.

[0069] II. Application of solid-phase extractants in the extraction and separation of lithium from salt lake brine

[0070] 1.0 g of solid-phase extraction material S25 was added to a beaker containing 5.0 L of high magnesium-to-lithium ratio brine from a salt lake (the same brine as in Example 1). Ferric chloride hexahydrate was then added to the brine to increase the Fe content. 3+ The concentration is 3.0 g / L, and the pH is adjusted to 2-3.

[0071] After stirring for 5 minutes, the extraction reached a basic equilibrium. The solid-phase extractant was then attracted to the outer wall of the beaker using a magnet, and the aqueous phase was poured off. 96% of the lithium-loaded solid-phase extractant was recoverable, with a lithium loading of 345 mg / g. -1 .

[0072] Subsequently, the impurities in the lithium-loaded solid-phase extractant after magnetic separation were washed with 0.15M dilute hydrochloric acid, and the impurity ions were basically completely washed away. + The loss rate is less than 5%.

[0073] Finally, the lithium-loaded solid-phase extraction material, after washing with dilute hydrochloric acid, was back-extracted with 2.0 M hydrochloric acid. The Li on the solid-phase extraction material was largely washed off. + Washing rate > 98%. The unused magnetic solid-phase extractant after back-extraction can be recycled.

[0074] Example 3

[0075] I. Preparation of solid phase extraction materials

[0076] See Figure 5 Synthesis process route diagram: The raw material S31 is esterified with dibutyl phosphate S32 to remove one molecule of water to obtain the corresponding intermediate product S33. Then, S33 is silanized with a magnetic matrix (Fe3O4@SiO2) to obtain solid phase extraction material S34.

[0077] Figure 6 This is a TEM image of the solid-phase extraction material S34 prepared in this embodiment.

[0078] II. Application of solid-phase extractants in the extraction and separation of lithium from salt lake brine

[0079] 1.0 g of solid-phase extraction material S34 was added to a beaker containing 5.0 L of high magnesium-to-lithium ratio brine from a salt lake (the same brine as in Example 1). Ferric chloride hexahydrate was then added to the brine to increase the Fe content. 3+ The concentration is 3.0 g / L, and the pH is adjusted to 2-3.

[0080] After stirring for 5 minutes, the extraction reached a basic equilibrium. The solid-phase extractant was then attracted to the outer wall of the beaker using a magnet, and the aqueous phase was poured off. 95% of the lithium-loaded solid-phase extractant was recoverable, with a lithium loading of 355 mg / g. -1 .

[0081] Subsequently, the impurities in the lithium-loaded solid-phase extractant after magnetic separation were washed with 0.20M dilute hydrochloric acid, and the impurity ions were basically completely washed away. + The loss rate is less than 5%.

[0082] Finally, the lithium-loaded solid-phase extraction material, after washing with dilute hydrochloric acid, was back-extracted with 2.5M hydrochloric acid. The Li on the solid-phase extraction material was largely washed off. + Washing rate > 95%. The unloaded magnetic solid phase extractant after back-extraction can be recycled.

[0083] Example 4

[0084] I. Preparation of solid phase extraction materials

[0085] See Figure 7 Synthesis process route diagram: The raw material S41 (CAS No. 67812-17-3) undergoes a silanization reaction with the magnetic matrix (Fe3O4@SiO2) to obtain the solid phase extraction material S42.

[0086] Figure 8 This is a TEM image of the solid-phase extraction material S42 prepared in this embodiment.

[0087] II. Application of solid-phase extractants in the extraction and separation of lithium from salt lake brine

[0088] 1.0 g of solid-phase extraction material S34 was added to a beaker containing 5.0 L of high magnesium-to-lithium ratio brine from a salt lake (the same brine as in Example 1). Ferric chloride hexahydrate was then added to the brine to increase the Fe content. 3+ The concentration is 3.0 g / L, and the pH is adjusted to 2-3.

[0089] After stirring for 5 minutes, the extraction reached a basic equilibrium. The solid-phase extractant was then attracted to the outer wall of the beaker using a magnet, and the aqueous phase was poured off. 92% of the lithium-loaded solid-phase extractant was recoverable, with a lithium loading of 205 mg / g. -1 .

[0090] Subsequently, the impurities in the lithium-loaded solid-phase extractant after magnetic separation were washed with 0.10M dilute hydrochloric acid, and the impurity ions were basically completely washed away. + The loss rate is less than 5%.

[0091] Finally, the lithium-loaded solid-phase extraction material, after washing with dilute hydrochloric acid, was back-extracted with 2.0 M hydrochloric acid. The Li on the solid-phase extraction material was largely washed off. + Washing rate > 95%. The unloaded magnetic solid phase extractant after back-extraction can be recycled.

[0092] In summary, the solid-phase extraction material for lithium extraction, its preparation method, and its application provided in this embodiment of the invention utilize an organic synthesis method. Specifically, it uses a silane coupling agent to connect extraction groups with lithium extraction functions, such as those in formula (1) or (2), to a magnetic matrix, thus synthesizing a functionalized magnetic solid-phase extraction material with lithium-specific selectivity. The selected synthetic substrate is inexpensive and readily available, the synthesis route is clear, and the prepared solid-phase extraction material can be reused multiple times. It is suitable for the extraction and separation of lithium ions in salt lake brines where multiple ions coexist. The extraction process is a solid-liquid contact extraction, which reduces the amount of organic reagents used. Furthermore, the kinetics of the extraction and back-extraction processes are relatively fast, and the phase separation process is shortened, effectively improving the production efficiency of the lithium extraction process and reducing the generation of organic waste liquid.

[0093] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A solid-phase extraction material for lithium extraction, characterized in that, The solid-phase extraction material comprises a magnetic matrix and extraction groups connected to the surface of the magnetic matrix via a silane coupling agent; the magnetic matrix comprises an Fe3O4 core layer and a SiO2 shell layer covering the Fe3O4 core layer, and the extraction groups have the following structural formula (1) or (2): ， ， In formula (1), R1 is one of a straight-chain or branched alkane, phenyl, or benzyl from C2 to C14, and R2 is one of a straight-chain or branched alkane, phenyl, or benzyl from C2 to C14; in formula (2), R3 is one of a straight-chain or branched alkane, a straight-chain or branched alkoxy from C6 to C18, phenyl, or benzyl from C6 to C18, and R4 is one of a straight-chain or branched alkane, a straight-chain or branched alkoxy from C6 to C18, phenyl, or benzyl from C6 to C18.

2. A method for preparing the solid-phase extraction material as described in claim 1, characterized in that, include: S11. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix; S12. A silane coupling agent is used to perform a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix, thereby obtaining a silanized magnetic matrix. S13. Using a compound containing the extraction group to perform a coupling reaction or esterification reaction with the silanized magnetic matrix, the extraction group is connected to the silane coupling agent to obtain the solid-phase extraction material.

3. The preparation method according to claim 2, characterized in that, The silane coupling agent has the structural formula (R'O)-Si-R; wherein R' is methyl or ethyl, and R is a straight chain with an alcohol, halogen, or amino active group at the end.

4. A method for preparing the solid-phase extraction material as described in claim 1, characterized in that, include: S21. Prepare a SiO2 shell on the surface of Fe3O4 nanoparticles to obtain the magnetic matrix; S22. Using a silane coupling agent, a compound containing the extraction group is coupled or esterified to connect the extraction group to the silane coupling agent to obtain an intermediate compound. S23. The intermediate compound is subjected to a silanization reaction with the magnetic matrix to connect the silane coupling agent to the magnetic matrix, thereby obtaining the solid-phase extraction material.

5. The preparation method according to claim 4, characterized in that, The silane coupling agent has the structural formula (R'O)-Si-R; wherein R' is methyl or ethyl, and R is a straight chain with an alcohol, halogen, or amino active group at the end.

6. The application of the solid-phase extraction material as described in claim 1 in the lithium extraction process of salt lake brine.

7. The application according to claim 6, characterized in that, include: Provide lithium-containing brine from salt lakes and adjust it to H + The concentration is 0.05 mol / L to 0.20 mol / L, and the pH is below 3.0; The solid-phase extraction material was placed in the lithium-containing brine of the lithium-bearing salt lake to extract lithium, followed by magnetic separation. The separated solid-phase extraction material was washed and back-extracted sequentially to obtain a lithium-rich solution.

8. The application according to claim 7, characterized in that, Fe in the lithium-containing brine of the brine 3+ The mixture is adjusted to reduce the Fe content in the lithium-containing brine. 3+ The molar concentration of Li + 1.3 to 1.5 times that.

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