Preparation method of multi-element co-doped lithium-aluminum layered double hydroxide and lithium extraction adsorbent

Abstract

The invention belongs to the technical field of lithium ion adsorption materials, and relates to a preparation method of a multi-element co-doped lithium-aluminum layered double hydroxide and a lithium extraction adsorbent. The invention discloses a preparation method of a multi-element co-doped lithium-aluminum layered double hydroxide. The preparation method comprises the following steps: (1) dissolving an aluminum salt, a lithium salt and a low-valence metal element salt in water to obtain a precursor solution; (2) slowly adding a bio-based precipitant to adjust the pH value, and heating and stirring for reaction to obtain a precursor colloidal solution; (3) adding a modifier containing a non-metallic element X to adjust the pH value, carrying out ultrasonic dispersion, and transferring to a microwave reaction kettle to carry out a microwave reaction; the lithium-aluminum layered double hydroxide co-doped with the low-valence metal element M and the non-metal surface modification element X is obtained. According to the method, the diffusion rate and the adsorption performance of lithium ions are remarkably improved; according to the lithium extraction adsorbent disclosed by the invention, the adsorption efficiency and selectivity of lithium ions in salt lake brine with a high magnesium-lithium ratio are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion adsorption materials and relates to a preparation method of a multi-element co-doped lithium aluminum layered double hydroxide and a lithium extraction adsorbent. Background Art

[0002] As the "white oil" of the 21st century, lithium resources have important strategic significance in the fields of new energy and new materials. However, the global lithium resources are unevenly distributed, and about 70% of lithium resources exist in salt lake brine. Therefore, efficient extraction of lithium from salt lake brine has become the key to solving the problem of lithium resource shortage. Lithium aluminum layered double hydroxide (LiAl-LDH) has become one of the main adsorbents for extracting lithium from brine due to its unique layered structure and excellent ion exchange properties. The layered structure of LiAl-LDH consists of positively charged metal hydroxide layers and exchangeable anions between layers. Lithium ions can be reversibly embedded / de-embedded in the layers, thereby realizing the adsorption and desorption of lithium.

[0003] However, traditional LiAl-LDH materials still have some limitations in practical applications: (1) Slow lithium ion diffusion rate: Although the layered structure of LiAl-LDH is conducive to the insertion / deinsertion of lithium ions, the narrow interlayer channels limit the diffusion rate of lithium ions, resulting in poor adsorption kinetics. (2) Limited adsorption capacity: The interlayer spacing of traditional LiAl-LDH is limited, and the number of lithium ions that can be accommodated is limited, resulting in its adsorption capacity being difficult to meet the needs of practical applications. (3) Poor structural stability: Li + Deep deintercalation from Li / Al-LDH may lead to lattice collapse and formation of Al(OH)3, resulting in irreversible capacity loss. In addition, anions such as SO4 2- and B(OH) 4- The co-embedding of Li / Al-LDH will change the stacking structure of Li / Al-LDH and impair reversibility. Therefore, the development of a new LiAl-LDH material that can precisely control the pore size distribution, increase the lithium ion diffusion rate, and enhance the structural stability is of great practical significance for the efficient extraction of lithium resources from salt lake brine. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and propose a method for preparing a multi-element co-doped lithium aluminum layered double hydroxide, in which metal elements are doped into the lithium aluminum layered double hydroxide to introduce defects, and non-metallic elements are also added for surface modification to introduce active site structures, thereby significantly improving the diffusion rate and adsorption performance of lithium ions inside the material.

[0005] One object of the present invention is achieved by the following technical solutions:

[0006] A preparation method of multi-element co-doped lithium-aluminum layered double hydroxide, comprising:

[0007] (1) Dissolving aluminum salt, lithium salt and low-valence metal element salt in water at a molar ratio of (1-5):1:(0.1-1) to obtain a precursor solution; the low-valence metal element X in the low-valence metal element salt is selected from Fe 2+ 、Mn 2+ 、Co 2+ 、Sn 2+ at least one of;

[0008] (2) Under stirring conditions, slowly adding a bio-based precipitant to the precursor solution in (1) to adjust the pH to 4-8, heating and stirring to react to obtain a precursor colloidal solution;

[0009] (3) Adding a modifier containing non-metal element X to the precursor colloidal solution in (2) to adjust the pH to 6-8, where X is selected from at least one of N, H, S, B; after ultrasonic dispersion, transferring to a microwave reaction kettle for microwave reaction, the microwave reaction temperature is 80-500 °C, the microwave power is 100-800 W, and the heat preservation time is 1-10 h; obtaining low-valence metal element M and non-metal surface modification element X co-doped lithium-aluminum layered double hydroxide M·X-LiAl-LDH.

[0010] Preferably, the aluminum salt in (1) is at least one of aluminum chloride, aluminum acetate, aluminum phosphate, and sodium aluminate.

[0011] Preferably, the lithium salt in (1) is at least one of lithium hydroxide, lithium sulfate, lithium chloride, and lithium nitrate.

[0012] Preferably, the low-valence metal element salt in (1) is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate, manganese sulfate, manganese chloride, manganese nitrate, cobalt sulfate, cobalt chloride, cobalt nitrate, stannous sulfate, and stannous chloride.

[0013] Preferably, the solid-liquid ratio of the aluminum salt, lithium salt, low-valence metal element salt to water in (1) is (1-10) g:100 ml.

[0014] Preferably, the bio-based precipitant in (2) includes at least one of chitosan, sodium citrate, sodium lignosulfonate, sodium lysinate, sodium arginate, and sodium carboxymethylcellulose.

[0015] More preferably, the bio-based precipitant in (2) includes at least two of chitosan, sodium citrate, sodium lignosulfonate, sodium lysinate, sodium arginate, and sodium carboxymethylcellulose.

[0016] Further preferably, the bio-based precipitating agent in (2) is chitosan and at least one of sodium citrate, sodium lignosulfonate, sodium lysinate, sodium arginate, and sodium carboxymethylcellulose with a mass ratio of 1:(1.1 - 5).

[0017] Preferably, the heating and stirring reaction temperature in (2) is 30 - 100 °C, and the reaction time is 1 - 10 hours.

[0018] Further preferably, the heating and stirring reaction temperature in (2) is 50 - 80 °C, and the reaction time is 1 - 10 hours.

[0019] Preferably, the surface modifier containing non-metallic elements in (3) includes at least one of ethylenediamine, triethanolamine, dopamine, polyethyleneimine, polyvinylpyrrolidone, and pyridine.

[0020] Preferably, the microwave reaction temperature in (3) is 100 - 300 °C, the microwave power is 200 - 600 W, and the heat preservation time is 1 - 5 h.

[0021] Preferably, the pore size distribution of the multi-element co-doped lithium aluminum layered double hydroxide is uniform, and the pore size is concentrated in the range of 2 - 6 nm.

[0022] Further preferably, the pore size of the multi-element co-doped lithium aluminum layered double hydroxide is concentrated in the range of 2 - 4 nm.

[0023] Preferably, the average pore size of the multi-element co-doped lithium aluminum layered double hydroxide is 2 - 10 nm.

[0024] Further preferably, the average pore size of the multi-element co-doped lithium aluminum layered double hydroxide is 4 - 9 nm.

[0025] Preferably, the specific surface area of the multi-element co-doped lithium aluminum layered double hydroxide is 100 - 130 m 2 / g.

[0026] Preferably, the doping amount of the low-valence metal element M in the multi-element co-doped lithium aluminum layered double hydroxide is 0.1 - 5% (based on the molar amount of Al).

[0027] Preferably, the doping amount of the non-metallic surface modification element X in the multi-element co-doped lithium aluminum layered double hydroxide is 0.05 - 0.5% (based on the molar amount of Al).

[0028] The second object of the present invention is achieved by the following technical solutions:

[0029] A lithium extraction adsorbent, which comprises a multi-element co-doped lithium aluminum layered double hydroxide.

[0030] Preferably, the application of the lithium extraction adsorbent includes: placing the lithium extraction adsorbent in (simulated) salt lake brine and adsorbing for 1 to 10 hours at room temperature. The adsorption capacity of Li + in the lithium extraction adsorbent is 8 to 20 mg / g.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. In the present invention, low-valence metal elements are doped into the lithium-aluminum layered double hydroxide, introducing defects, lattice distortion and oxygen vacancies, which accelerate the diffusion process of Li + inside the multi-element co-doped lithium-aluminum layered double hydroxide; non-metal elements are also incorporated for surface modification to introduce active site structures, enhance the conversion ability, dynamically regulate the layer spacing, form an efficient lithium ion transport channel, and significantly improve the diffusion rate and adsorption performance of lithium ions inside the multi-element co-doped lithium-aluminum layered double hydroxide.

[0033] 2. The preparation method of the multi-element co-doped lithium-aluminum layered double hydroxide of the present invention significantly changes the pore structure of M·X-LiAl-LDH, making its pore size distribution uniform, and the pore size concentrated in the range of 2-4 nm.

[0034] 3. The preparation method of the multi-element co-doped lithium-aluminum layered double hydroxide of the present invention inhibits the phenomenon of particle agglomeration and reduces the large pores of about 10 nm generated by the agglomeration of LiAl-LDH.

[0035] 4. The present invention uses a bio-based precipitant, reducing the dosage of NaOH, meeting the requirements of green chemistry.

[0036] 5. The lithium extraction adsorbent of the present invention significantly improves the adsorption efficiency and selectivity of lithium ions in salt lake brine with a high magnesium-lithium ratio, and has good stability in cyclic use. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the specific surface area diagram (a) and pore size distribution diagram (b) of Mn·N-LiAl-LDH in Example 1, Co·N-LiAl-LDH in Example 2, Fe·N-LiAl-LDH in Example 3, and LiAl-LDH in Comparative Example 1 of the present invention.

[0038] Figure 2 It is the scanning electron microscope image of Mn·N-LiAl-LDH in Example 1 of the present invention.

[0039] Figure 3 It is the scanning electron microscope image of Co·N-LiAl-LDH in Example 2 of the present invention.

[0040] Figure 4This is the scanning electron microscope image of Fe·N-LiAl-LDH in Example 3 of the present invention.

[0041] Figure 5 This is the scanning electron microscope image of LiAl-LDH in Comparative Example 1 of the present invention. Detailed implementation manners

[0042] The technical solutions of the present invention will be further described and illustrated below through specific examples. It should be understood that the specific examples described herein are only for helping to understand the present invention and are not used for specific limitations of the present invention.

[0043] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0044] Example 1

[0045] The preparation method of Mn·N-LiAl-LDH in this example includes:

[0046] (1) Dissolve aluminum chloride (1.5 mol), lithium acetate (1.0 mol) and manganese chloride (0.2 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0047] (2) Under stirring conditions, slowly add a sodium citrate-chitosan composite biobased precipitant (mass ratio 2:1) to the precursor solution in (1) to adjust the pH to 5, heat and stir the reaction at 60 °C for 2 h, and the stirring rate is 300 rpm to obtain a precursor colloidal solution;

[0048] (3) Add ethyleneimine (PEI) to the precursor colloidal solution in (2) to adjust the pH to 7, disperse by ultrasonic wave (frequency 40 kHz, time 30 min), transfer to a microwave reaction kettle, set the temperature at 120 °C and the microwave power at 500 W, and keep warm for 2 h for microwave reaction; after the reaction is completed, cool, centrifuge, wash and dry to obtain a lithium aluminum layered double hydroxide with adjustable pore size and co-doped with Mn and N, denoted as Mn·N-LiAl-LDH.

[0049] Characterize Mn·N-LiAl-LDH. Figure 1 For the nitrogen adsorption-desorption (BET) test to analyze the specific surface area and pore size distribution diagram of the material, it can be known that the specific surface area of Mn·N-LiAl-LDH is 108.99 m 2 / g, the average pore size is 5.42 nm, and the pore size is concentrated in the range of 2-4 nm.

[0050] Figure 2 For the scanning electron microscope image, it can be seen that the particle agglomeration phenomenon is not obvious, and the surface of the material presents a uniformly distributed small pore structure.

[0051] Example 2

[0052] In this example, the preparation method of Co·N-LiAl-LDH includes:

[0053] (1) Dissolve aluminum chloride (1.5 mol), lithium acetate (1.0 mol) and cobalt nitrate ((0.2 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0054] (2) Under stirring conditions, slowly add a sodium citrate-chitosan composite biobased precipitant (mass ratio 2:1) to the precursor solution in (1) to adjust the pH to 5, heat and stir the reaction at 60 °C for 2 h, and the stirring rate is 300 rpm to obtain a precursor colloidal solution;

[0055] (3) Add ethylenediamine to the precursor colloidal solution in (2) to adjust the pH to 7, disperse by ultrasonic wave (frequency 40 kHz, time 30 min), transfer to a microwave reaction kettle, set the temperature at 150 °C and the microwave power at 500 W, and keep warm for 2 h for microwave reaction; after the reaction is completed, cool, centrifuge, wash, and dry to obtain a lithium aluminum layered double hydroxide with adjustable pore size co-doped with Co and N, denoted as Co·N-LiAl-LDH.

[0056] Characterize Co·N-LiAl-LDH. According to Figure 1 、 3 it can be known that the specific surface area of Co·N-LiAl-LDH is 117.36 m 2 / g, the average pore size is 7.58 nm, and the pore size is concentrated in the range of 2 - 3 nm; the phenomenon of particle agglomeration is not obvious, and the surface of the material shows a uniformly distributed small pore structure.

[0057] Example 3

[0058] In this example, the preparation method of Fe·N-LiAl-LDH includes:

[0059] (1) Dissolve aluminum chloride (1.5 mol), lithium acetate (1.0 mol) and ferrous sulfate (0.2 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0060] (2) Under stirring conditions, slowly add a sodium citrate-chitosan composite biobased precipitant (mass ratio 2:1) to the precursor solution in (1) to adjust the pH to 5, heat and stir the reaction at 60 °C for 2 h, and the stirring rate is 300 rpm to obtain a precursor colloidal solution;

[0061] (3) Ethylenediamine was added to the precursor colloidal solution in (2) to adjust the pH to 7. After ultrasonic dispersion (frequency 40 kHz, time 30 min), it was transferred to a microwave reactor. The temperature was set at 100 °C and the microwave power was 500 W, and it was kept warm for 2 h for microwave reaction; after the reaction, it was cooled, centrifuged, washed, and dried to obtain pore-size adjustable Fe and N co-doped lithium aluminum layered double hydroxide, denoted as Fe·N-LiAl-LDH.

[0062] The Fe·N-LiAl-LDH was characterized. According to Figure 1 、 4 it can be known that the specific surface area of Fe·N-LiAl-LDH is 98.13 m 2 / g, the average pore size is 7.116 nm, and the pore size is concentrated in the range of 2 - 4 nm; the phenomenon of particle aggregation is not obvious, and the surface of the material presents a uniformly distributed small pore structure.

[0063] Example 4

[0064] The preparation method of Mn·N-LiAl-LDH-2 in this example includes:

[0065] (1) Aluminum chloride (1.5 mol), lithium acetate (1.0 mol) and manganese chloride (0.2 mol) were dissolved in 100 mL of water, and stirred to obtain a precursor solution;

[0066] (2) Under stirring conditions, sodium arginate-chitosan composite biobased precipitant (mass ratio 2:1) was slowly added to the precursor solution in (1) to adjust the pH to 5, and heated and stirred at 60 °C for 2 h, with a stirring rate of 300 rpm, to obtain a precursor colloidal solution;

[0067] (3) Ethylenimine (PEI) was added to the precursor colloidal solution in (2) to adjust the pH to 7. After ultrasonic dispersion (frequency 40 kHz, time 30 min), it was transferred to a microwave reactor. The temperature was set at 120 °C and the microwave power was 500 W, and it was kept warm for 2 h for microwave reaction; after the reaction, it was cooled, centrifuged, washed, and dried to obtain pore-size adjustable Mn and N co-doped lithium aluminum layered double hydroxide, denoted as Mn·N-LiAl-LDH-2.

[0068] Example 5

[0069] The preparation method of Mn·N-LiAl-LDH-3 in this example includes:

[0070] (1) Aluminum chloride (1.5 mol), lithium acetate (1.0 mol) and manganese chloride (0.2 mol) were dissolved in 100 mL of water, and stirred to obtain a precursor solution;

[0071] (2) Under stirring conditions, sodium citrate bio-based precipitant was slowly added to the precursor solution in (1) to adjust the pH to 5, and the mixture was heated and stirred at 60 °C for 2 h with a stirring rate of 300 rpm to obtain a precursor colloidal solution;

[0072] (3) Ethyleneimine (PEI) was added to the precursor colloidal solution in (2) to adjust the pH to 7. After ultrasonic dispersion (frequency 40 kHz, time 30 min), it was transferred to a microwave reactor, and the temperature was set at 120 °C and the microwave power was 500 W, and it was kept warm for 2 h for microwave reaction; after the reaction, it was cooled, centrifuged, washed, and dried to obtain Mn and N co-doped lithium aluminum layered double hydroxide with adjustable pore size, denoted as Mn·N-LiAl-LDH-3.

[0073] Comparative Example 1

[0074] The preparation method of LiAl-LDH in this comparative example includes:

[0075] (1) Aluminum chloride (1.5 mol) and lithium chloride (1.0 mol) were dissolved in 100 mL of water and stirred to obtain a precursor solution;

[0076] (2) Under stirring conditions, sodium hydroxide solution was slowly added to the precursor solution in (1) to adjust the pH to 7.5 and stirred for 2 h with a stirring rate of 300 rpm. After the reaction, it was cooled, centrifuged, washed, and dried to obtain LiAl-LDH.

[0077] LiAl-LDH was characterized. According to Figure 1 、 5 it can be known that the specific surface area of LiAl-LDH is 127.36 m 2 / g, the average pore size is 10.09 nm, and the pore size shows a bimodal distribution of 2 - 5 nm and 10 nm; there is a macroporous structure formed by particle aggregation on the material surface.

[0078] Comparative Example 2

[0079] The preparation method of Fe-LiAl-LDH in this comparative example includes:

[0080] (1) Aluminum chloride (1.5 mol), lithium chloride (1.0 mol) and ferrous chloride (0.2 mol) were dissolved in 100 mL of water and stirred to obtain a precursor solution;

[0081] (2) Under stirring conditions, sodium hydroxide solution was added to the precursor solution in (1) to adjust the pH to 7.5, and stirred for 2 h with a stirring rate of 300 rpm. After the reaction, it was cooled, centrifuged, washed, and dried to obtain Fe-doped lithium aluminum layered double hydroxide, denoted as Fe-LiAl-LDH.

[0082] Comparative Example 3

[0083] The preparation method of N-LiAl-LDH in this comparative example includes:

[0084] (1) Dissolve aluminum chloride (1.5 mol) and lithium chloride (1.0 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0085] (2) Under stirring conditions, slowly add sodium hydroxide solution to the precursor solution in (1) to adjust the pH to 5, and stir and react for 2 h to obtain a precursor colloidal solution;

[0086] (3) Add ethylenediamine to the precursor colloidal solution in (2) to adjust the pH to 7. After ultrasonic dispersion (frequency 40 kHz, time 30 min), transfer it to a microwave reaction kettle, set the temperature at 100 °C and the microwave power at 500 W, and keep warm for 2 h for microwave reaction; after the reaction is completed, cool, centrifuge, wash, and dry to obtain N-doped lithium aluminum layered double hydroxide, denoted as N-LiAl-LDH.

[0087] Comparative Example 4

[0088] The preparation method of Mn-LiAl-LDH in this comparative example includes:

[0089] (1) Dissolve aluminum chloride (1.5 mol), lithium chloride (1.0 mol) and manganese chloride (0.2 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0090] (2) Under stirring conditions, slowly add sodium citrate biobased precipitant to the precursor solution in (1) to adjust the pH to 5, stir and react for 2 h, and the stirring rate is 300 rpm; after the reaction is completed, cool, centrifuge, wash, and dry to obtain Mn-doped lithium aluminum layered double hydroxide, denoted as Mn-LiAl-LDH.

[0091] Comparative Example 5

[0092] The preparation method of LiAl-LDH-2 in this comparative example includes:

[0093] (1) Dissolve aluminum chloride (1.5 mol) and lithium chloride (1.0 mol) in 100 mL of water, and stir to obtain a precursor solution;

[0094] (2) Under stirring conditions, slowly add sodium citrate biobased precipitant to the precursor solution in (1) to adjust the pH to 5, stir and react for 2 h, and the stirring rate is 300 rpm; after the reaction is completed, cool, centrifuge, wash, and dry to obtain lithium aluminum layered double hydroxide, denoted as LiAl-LDH-2.

[0095] Application Example 1

[0096] Prepare a simulated salt lake brine with a Li⁺ concentration of 500 mg / L and a pH of 6.5.

[0097] Add 1 g of Mn·N-LiAl-LDH from Example 1 to 50 mL of the simulated salt lake brine and adsorb at 25 °C with a rotation speed of 450 rpm for 24 hours. After adsorption, filter using a 0.22 μm microporous membrane filter and measure the Li⁺ concentration in the solution using an inductively coupled plasma mass spectrometer (ICP-MS) to calculate the adsorption capacity. The adsorption capacity of Mn·N-LiAl-LDH is 10.98 mg / g.

[0098] Application Example 2

[0099] Test the product from Example 2 according to the method of Application Example 1. The adsorption capacity of Co·N-LiAl-LDH is 9.62 mg / g.

[0100] Application Example 3

[0101] Test the product from Example 3 according to the method of Application Example 1. The adsorption capacity of Fe·N-LiAl-LDH is 10.01 mg / g.

[0102] Application Example 4

[0103] Test the product from Example 4 according to the method of Application Example 1. The adsorption capacity of Mn·N-LiAl-LDH-2 is 10.21 mg / g.

[0104] Application Example 5

[0105] Test the product from Example 5 according to the method of Application Example 1. The adsorption capacity of Mn·N-LiAl-LDH-3 is 9.98 mg / g.

[0106] Application Comparative Example 1

[0107] Test the product from Comparative Example 1 according to the method of Application Example 1.

[0108] The adsorption capacity of LiAl-LDH is 6.81 mg / g.

[0109] Application Comparative Example 2

[0110] Test the product from Comparative Example 2 according to the method of Application Example 1.

[0111] The adsorption capacity of Fe-LiAl-LDH is 7.64 mg / g.

[0112] Application Comparative Example 3

[0113] Test the product from Comparative Example 3 according to the method of Application Example 1.

[0114] The adsorption capacity of N-LiAl-LDH is 7.99 mg / g.

[0115] Application Comparative Example 4

[0116] The product in Comparative Example 4 was tested according to the method of Application Example 1.

[0117] The adsorption capacity of Mn-LiAl-LDH is 8.64 mg / g.

[0118] Application Comparative Example 5

[0119] The product in Comparative Example 5 was tested according to the method of Application Example 1.

[0120] The adsorption capacity of LiAl-LDH-2 is 7.11 mg / g. Application Example 5

[0121] Prepare simulated salt lake brine with a Li+ concentration of 0.5 mmol / L.

[0122] 5 g of Co·N-LiAl-LDH in Example 2 was placed in 300 ml of simulated salt lake brine, and continuous 5 adsorption-desorption cycle experiments were carried out at 25 °C. The adsorption time for each time was 2 h, and desorption was carried out with 50 ppm LiCl solution for elution.

[0123] The experimental results show that after 5 cycles, the retention rate of the adsorption capacity of Co·N-LiAl-LDH for Li+ > 92%, showing excellent cycle stability.

[0124] Application Example 6

[0125] Prepare simulated salt lake brine with a Li+ concentration of 0.5 mmol / L, and the concentrations of Na+, K+, and Mg 2 + are all 25 mmol / L.

[0126] 5 g of Co·N-LiAl-LDH in Example 2 was placed in 300 ml of simulated salt lake brine, and continuous 5 adsorption-desorption cycle experiments were carried out at 25 °C. The adsorption time for each time was 2 h, and desorption was carried out with 50 ppm LiCl solution for elution.

[0127] The experimental results show that the adsorption capacity of Co·N-LiAl-LDH for Li+ reaches 9.21 mg / g. By calculation, the selectivity coefficients of Co·N-LiAl-LDH for Li+ are: K(Li / Na) = 332, K(Li / K) = 112, K(Li / Mg) = 285, fully proving that Co·N-LiAl-LDH still maintains excellent anti-ion interference ability and lithium ion selectivity in the presence of high-concentration impurity ions.

[0128] In summary, the present invention dopes low-valence metal elements into lithium aluminum layered double hydroxides, introducing defects, lattice distortion and oxygen vacancies, and accelerating the diffusion process of Li + inside the multi-element co-doped lithium aluminum layered double hydroxides; non-metallic elements are also doped for surface modification to introduce active site structures, enhance the conversion ability, dynamically regulate the layer spacing, form efficient lithium ion transport channels, and significantly improve the diffusion rate and adsorption performance of multi-element co-doped lithium ions inside the lithium aluminum layered double hydroxides.

[0129] All aspects, embodiments and features of the present invention should be considered illustrative in all respects and do not limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications and uses.

[0130] In the preparation method of the present invention, the order of each step is not limited to the listed order. For those of ordinary skill in the art, without creative efforts, the sequential changes of each step are also within the protection scope of the present invention. In addition, two or more steps or actions can be carried out simultaneously.

[0131] Finally, it should be noted that the specific embodiments described herein are only illustrative of the present invention and do not limit the implementation mode of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. It is not necessary and impossible to list all implementation modes here. And these obvious changes or variations derived from the essence of the present invention still fall within the protection scope of the present invention. Interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A preparation method of multi-element co-doped lithium aluminum layered double hydroxide, characterized in that, The preparation method includes: (1) Dissolve an aluminum salt, a lithium salt, and a salt of a low-valence metal element in water at a molar ratio of (1 to 5):1:(0.1 to 1) to obtain a precursor solution; the low-valence metal element X in the salt of the low-valence metal element is selected from Fe 2+ , Mn 2+ , Co 2+ , Sn 2+ ; at least one of them; (2) Under stirring conditions, slowly add a bio-based precipitating agent to the precursor solution in (1) to adjust the pH to 4-8, heat and stir for reaction to obtain a precursor colloidal solution; (3) Add a modifier containing a non-metal element X to the precursor colloidal solution in (2) to adjust the pH to 6-8, where X is selected from at least one of N, H, S, and B; after ultrasonic dispersion, transfer it to a microwave reaction kettle for microwave reaction, the microwave reaction temperature is 80-500 °C, the microwave power is 100-800 W, and the heat preservation time is 1-10 h; obtain a lithium-aluminum layered double hydroxide M·X-LiAl-LDH co-doped with a low-valence metal element M and a non-metal surface modification element X.

2. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, wherein The aluminum salt in (1) is at least one of aluminum chloride, aluminum acetate, aluminum phosphate, and sodium aluminate.

3. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The lithium salt in (1) is at least one of lithium hydroxide, lithium sulfate, lithium chloride, and lithium nitrate.

4. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The low-valence metal element salt in (1) is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate, manganese sulfate, manganese chloride, manganese nitrate, cobalt sulfate, cobalt chloride, cobalt nitrate, stannous sulfate, and stannous chloride.

5. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The bio-based precipitating agent in (2) includes at least one of chitosan, sodium citrate, sodium lignosulfonate, sodium lysinate, sodium arginate, and sodium carboxymethylcellulose.

6. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The bio-based precipitating agent in (2) is chitosan and at least one of sodium citrate, sodium lignosulfonate, sodium lysinate, sodium arginate, and sodium carboxymethylcellulose with a mass ratio of 1:(1.1-5).

7. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The surface modifier containing a non-metal element in (3) includes at least one of ethylenediamine, triethanolamine, dopamine, polyethyleneimine, polyvinylpyrrolidone, and pyridine.

8. The preparation method of the multi-element co-doped lithium aluminum layered double hydroxide according to claim 1, characterized in that, The pore size distribution of the multi-element co-doped lithium-aluminum layered double hydroxide is uniform, and the pore size is concentrated in the range of 2-6 nm.

9. A lithium extraction adsorbent, characterized in that, It includes a multi-element co-doped lithium-aluminum layered double hydroxide prepared by the preparation method of the multi-element co-doped lithium-aluminum layered double hydroxide according to any one of claims 1-8.

10. The lithium extraction adsorbent according to claim 9, characterized in that, The applications of the lithium extraction adsorbent include: placing the lithium extraction adsorbent in simulated salt lake brine and adsorbing for 1 to 10 hours at room temperature. The adsorption capacity of the lithium extraction adsorbent for Li + is 8 to 20 mg / g.

Images