Composite hydrogel lithium ion sieve and preparation method thereof

Abstract

The application provides a composite hydrogel lithium ion sieve and a preparation method thereof, and belongs to the technical field of lithium ion sieve adsorption.The active component of the ion sieve is H2TiO3, the binder is polyacrylamide PAM, and the ion sieve is uniformly dispersed in the polyacrylamide.The composite lithium ion sieve is used for selective adsorption extraction of lithium ions in low-concentration geothermal water, oil and gas field water, salt lake brine and seawater.The H2TiO3@PAM composite lithium ion sieve provided by the application has the advantages of high adsorption capacity, good ion sieve structure stability, high selectivity for salt lake brine with a high magnesium-lithium ratio, easy separation of the composite ion sieve from a liquid solution, good regeneration repeatability, and good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ion sieve adsorption, and particularly relates to a composite hydrogel lithium ion sieve and a preparation method thereof, and application of the composite hydrogel lithium ion sieve in adsorption extraction of liquid lithium resources. BACKGROUND

[0002] Metallic lithium and its compounds are of great interest as strategic resources in the fields of national defense, energy, batteries, and metallurgy due to their outstanding physical and chemical properties. In recent years, due to technological advances and increasing demand for renewable clean energy, consumption of lithium, especially for batteries, has been on the rise. However, the supply of lithium resources lags behind the growing demand.

[0003] Titanium-based lithium ion sieves (Ti-LIS) as a widely studied adsorbent show high selectivity and cyclic performance for lithium, and these sieves are increasingly attracting the attention of researchers. Compared with manganese-based ion sieves, titanium-based ion sieves have higher chemical stability, which is mainly due to their strong Ti-O bonds. Although the theoretical adsorption capacity of H2TiO3 reaches 126.9 mg·g -1 , the actual lithium adsorption capacity of Ti-LIS is much lower, mainly because the exposure of active adsorption sites is limited due to particle agglomeration. This gap between the actual adsorption capacity and the theoretical adsorption capacity of titanium-based ion sieves requires optimization of H2TiO3 adsorbents to improve their adsorption capacity.

[0004] Hydrogels are attracting more and more attention in the fields of biomedical engineering and environmental research due to their three-dimensional network structure, softness, and water-rich characteristics (Chemical reviews, 2020, 120, 7642-7707). For lithium ion sieves, these characteristics allow liquid to fully diffuse in the hydrogel and contact active sites, thereby promoting Li + desorption and improving adsorption rate and performance. Polyacrylamide (PAM) has good hydrophilicity, mainly due to the polar amide groups (-CONH2) in its molecular structure that interact with water molecules through hydrogen bonds (Journal of Central South University of Technology, 2008, 15, 443-446.). H2TiO3 with good hydrophilicity is more likely to form hydrogen bonds with water molecules, thereby promoting the diffusion of lithium ions from water into the sieve pores and enhancing the adsorption effect. The hydrophilic surface can effectively reduce the resistance of water molecules during the adsorption process and improve the capture rate of lithium ions.

[0005] In summary, the existing technology, titanium ion sieve exists adsorption rate is slow, too fine particles can not be fully recycled and reused, not conducive to industrial production. For the use of polyacrylamide as a support prepared hydrogel lithium ion sieve, design and development of high hydrophilicity and can be fully recycled lithium ion sieve, has industrial significance and social value. SUMMARY

[0006] The purpose of the present application is to improve the prior art and provide a H2TiO3@PAM composite hydrogel lithium ion sieve; another purpose of the present application is to provide a preparation method of the above ion sieve.

[0007] The technical scheme adopted by the present application is: a H2TiO3@PAM composite hydrogel lithium ion sieve, characterized in that the composite hydrogel lithium ion sieve is prepared by embedding the powdered active component H2TiO3 into PAM with polyacrylamide PAM as a binder, solving the problem of loss of the powdered particles and difficulty in recycling; wherein the mass fraction of H2TiO3 in H2TiO3@PAM is 13.8%-24%.

[0008] Preferably, the active component is the delithiated product H2TiO3 of Li2TiO3 lithium ion sieve precursor, and the support is polyacrylamide PAM; preferably, the Li2TiO3 is a typical monoclinic β-Li2TiO3.

[0009] The present application also provides a method for preparing the above-mentioned composite hydrogel lithium ion sieve, which comprises the following specific steps:

[0010] H2TiO3 and deionized water are added to a beaker and stirred uniformly to obtain a suspension; then, a viscosity modifier is added to the suspension, and acrylamide and N,N'-methylenebisacrylamide are simultaneously added after sufficient stirring, and a catalyst and an initiator are added after sufficient stirring, and the mixture is then placed in an oven for heating and polymerization to obtain a composite hydrogel; then the hydrogel is cultured in distilled water, and the water is changed every day, and finally H2TiO3@PAM is obtained.

[0011] Preferably, the mass fraction of H2TiO3 in the suspension is 16-30%. Preferably, the viscosity modifier is polyvinyl alcohol, chitosan or sodium alginate; and the mass ratio of the viscosity modifier to the suspension is (0.002-0.010):1.

[0012] Preferably, the mass ratio of acrylamide to the suspension is (0.14-0.18):1. Preferably, the molar ratio of N,N'-methylenebisacrylamide to acrylamide is (0.0005-0.0040):1.

[0013] Preferably, the initiator is potassium persulfate, sodium persulfate, ammonium persulfate; the molar ratio of the initiator to acrylamide is (0.015-0.051):1.

[0014] Preferably, the catalyst is triethanolamine, tetramethyl ethylenediamine; the molar ratio of the catalyst to acrylamide is (0.005-0.007):1.

[0015] Preferably, the polymerization reaction temperature is (20-70) DEG C, and the reaction time is 3-5h.

[0016] The polyacrylamide PAM reaction equation is:

[0017]

[0018] Beneficial effects:

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. The present application first uses polyacrylamide PAM as a binder for H2TiO3 powder forming, fully utilizes the rich amide groups on the surface of polyacrylamide PAM and the high porosity of the network structure, improves the hydrophilicity of β-H2TiO3, and thus increases the adsorption capacity and adsorption efficiency.

[0021] 2. The present application embeds H2TiO3 in polyacrylamide PAM by in-situ polymerization reaction, has the advantages of simple operation and low cost, and compared with other forming methods, the hydrogel forming method has the advantages of low mass transfer resistance and high adsorption capacity, and thus has a wide application prospect as a composite ion sieve adsorbent in the field of continuous lithium extraction from salt lake brine.

[0022] 3. Compared with granulation forming, the hydrogel lithium ion sieve prepared by combining polyacrylamide PAM and H2TiO3 has rich network structure and high hydrophilicity, reduces the mass transfer resistance of lithium ion sieve adsorption, and thus improves the adsorption efficiency.

[0023] 4. The H2TiO3@PAM composite hydrogel lithium ion sieve prepared by the present application is rich in hydroxyl groups and amide groups and the like functional groups, which is beneficial to fully contact with the solution. For salt lake brine with high magnesium-lithium ratio, it has high adsorption selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the XRD pattern of polyacrylamide PAM, H2TiO3 particles, Li2TiO3 particles, H2TiO3@PAM-1 and Li2TiO3@PAM-1 prepared in Example 1 of the present application;

[0025] Figure 2is the infrared spectrum of polyacrylamide PAM, H2TiO3 particles and H2TiO3@PAM-1 prepared in Example 1 of the present application;

[0026] Figure 3 is the SEM morphology diagram of H2TiO3 particles prepared in Example 1 of the present application;

[0027] Figure 4 is the SEM morphology diagram of H2TiO3@PAM prepared in Example 1 of the present application;

[0028] Figure 5 is the stress-strain curve of H2TiO3@PAM-x prepared in Examples 1, 2, 3 of the present application;

[0029] Figure 6 is the stress-strain curve of H2TiO3@PAM-x prepared in Examples 1, 6, 7, 8 of the present application. DETAILED DESCRIPTION

[0030] The following examples are only used to illustrate the description of the best mode of the present application, and the protection scope of the present application is not limited by the specific embodiments.

[0031] Example 1

[0032] (1) Preparation of H2TiO3@PAM

[0033] 50 g of H2TiO3 suspension with a mass fraction of 30% was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, and the water was changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-1, the mass fraction of H2TiO3 in the total mass of the composite hydrogel was 24%, and the tensile strength was 0.190 MPa.

[0034] (2) Adsorption test

[0035] 1 g of H2TiO3@PAM-1 was placed in a solution containing Li + , Na + , Ca 2+ , K + and Mg 2+The adsorption selectivity and saturated adsorption capacity of the ion on lithium ion in 1 L salt lake brine were determined. The initial concentration of ions in the salt lake brine was C Li+ = 116.78 mg·L -1 Na+ = 99.45 mg·L -1 Ca2+ = 98.65 mg·L -1 K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0036] Figure 1 XRD images of Li2TiO3, H2TiO3, H2TiO3@PAM, Li2TiO3@PAM and PAM hydrogel are shown. The characteristic peaks of Li2TiO3 are consistent with the standard XRD pattern of monoclinic β-Li2TiO3 (PDF #33-0831). Compared with H2TiO3, new peaks and some peak shifts of Li2TiO3 appear, especially the (-133) peak, which indicates that ion exchange reaction occurs between hydrogen ions and lithium ions. The PAM pattern shows a broad scattering peak from 20° to 28°, which indicates an amorphous structure. After introducing PAM hydrogel, the characteristic peaks of H2TiO3@PAM are consistent with those of H2TiO3. The peak intensity decreases due to the embedding of H2TiO3 or Li2TiO3 particles in PAM.

[0037] Figure 2 Infrared images of H2TiO3 particles, PAM hydrogel and H2TiO3@PAM hydrogel are shown. In PAM and H2TiO3@PAM, characteristic peaks corresponding to N-H stretching vibration, C=O stretching vibration, N-H bending vibration and C-N stretching vibration are observed at 3184 cm -1 , 1648 cm -1 , 1607 cm -1 and 1448 cm -1 , indicating the presence of amide groups (-CONH2) in H2TiO3@PAM. Amide groups contain polar groups such as carbonyl (C=O) and amino (-NH2). In addition, O-H stretching vibration characteristic peaks at 3478 cm -1 are observed in both H2TiO3 particles and H2TiO3@PAM hydrogel. This proves the presence of hydroxyl groups (-OH) in H2TiO3@PAM, which have polarity and can form hydrogen bonds with water molecules, increasing the surface free energy and thus enhancing the hydrophilicity of the material.

[0038] Figure 3 and Figure 4 ​​​The images show SEM images of H2TiO3 and H2TiO3@PAM-4 composite hydrogel lithium ion sieves, respectively. The morphology of the H2TiO3@PAM-4 composite ion sieve is a honeycomb cross-linked structure.

[0039] Figure 5 The stress-strain curves of the material are shown. The tensile strength of the PAM hydrogel is 0.009 MPa, while the tensile strength increases significantly after adding H2TiO3 to the PAM hydrogel. The maximum elongation at break of H2TiO3@PAM-1 is 267.6%, and the peak tensile strength is 0.19 MPa.

[0040] Figure 6 The effect of MBA dosage on the mechanical properties of H2TiO3@PAM was shown. When the MBA dosage was 0.03 g, the tensile strength reached its maximum value of 0.19 MPa. However, with increasing MBA dosage, both tensile strength and elongation at break decreased significantly. This is because excessively high crosslinking density makes the material too hard and brittle, leading to a decrease in tensile strength and a reduction in the material's ability to deform before fracture.

[0041] Example 2

[0042] (1) Preparation of H2TiO3@PAM

[0043] 50 g of a 16% (w / w) H₂TiO₃ suspension was placed in a beaker (solution A). Sodium alginate (0.15 g, 0.68 mmol) was then added to solution A and stirred for 15 min. Acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added simultaneously, and the mixture was stirred for another 10 min to obtain solution B. Tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were then added to solution B and stirred for 2 min. The mixture was then placed in an oven and dried. 50℃ Polymerization was carried out for 3 hours to obtain a hydrogel. The hydrogel was then cultured in distilled water for 7 days, with the water changed daily, to finally obtain H2TiO3@PAM, labeled as HTO@PAM-2. The mass fraction of H2TiO3 was 13.8% of the total mass of the composite hydrogel, and its tensile strength was 0.051 MPa.

[0044] (2) Adsorption test

[0045] 1g of H2TiO3@PAM-2 was placed at 25℃ in a solution containing Li at pH 8. + Na + Ca 2+ K + and Mg 2+The adsorption selectivity and saturated adsorption capacity of lithium ions were determined in 1 L of salt lake brine containing Li Li+ = 116.78 mg·L -1 ,C Na+ = 99.45 mg·L -1 ,C Ca2+ = 98.65 mg·L -1 ,C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0046] Figure 5 The stress-strain curve of the material is shown. The maximum elongation at break of H2TiO3@PAM-2 was 190.4%, and the peak tensile strength was 0.051 MPa.

[0047] Example 3

[0048] (1) Preparation of H2TiO3@PAM

[0049] A 50 g mass fraction of 25% H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and 10% potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, labeled as HTO@PAM-3, with a mass fraction of H2TiO3 of 19% of the total mass of the composite hydrogel, and a tensile strength of 0.075 MPa.

[0050] (2) Adsorption test

[0051] 1 g of H2TiO3@PAM-3 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity of lithium ions were determined. The initial concentrations of ions in the salt lake brine were C Li+ = 116.78 mg·L-1 ,C Na+ = 99.45 mg·L -1 ,C Ca2+ = 98.65 mg·L -1 ,C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0052] Figure 5 The stress-strain curve of the material is shown in FIG. 6. The maximum elongation at break of H2Ti03@PAM-3 was 248.6%, and the peak tensile strength was 0.075 MPa.

[0053] Example 4

[0054] (1) Preparation of H2Ti03@PAM

[0055] A 50 g mass fraction of 30% H2Ti03 suspension was placed in a beaker (solution A). Then sodium alginate (0.1 g, 0.45 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2Ti03@PAM was obtained, labeled as HTO@PAM-4, with a mass fraction of H2Ti03 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.138 MPa.

[0056] (2) Adsorption test

[0057] 1 g of H2Ti03@PAM-4 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 ,C Na+ = 99.45 mg·L -1 ,C Ca2+ = 98.65 mg·L -1C K+ = 99.73 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0058] Example 5

[0059] (1) Preparation of H2TiO3@PAM

[0060] A 50 g mass fraction of 30% H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.5 g, 2.27 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, labeled as HTO@PAM-5, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.129 MPa.

[0061] (2) Adsorption test

[0062] 1 g of H2TiO3@PAM-5 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 99.45 mg·L -1 , C Na+ = 98.65 mg·L -1 , C Ca2+ = 100.72 mg·L -1 , C K+ = 99.73 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0063] Example 6

[0064] (1) Preparation of H2TiO3@PAM

[0065] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.01 g, 0.06 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-6, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.121 MPa.

[0066] (2) Adsorption test

[0067] 1 g of H2TiO3@PAM-6 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0068] Figure 6 The stress-strain curve of the material is shown. The maximum elongation at break of H2TiO3@PAM-6 was 337.3%, and the peak tensile strength was 0.121 MPa.

[0069] Example 7

[0070] (1) Preparation of H2TiO3@PAM

[0071] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.05 g, 0.30 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-7, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.076 MPa.

[0072] (2) Adsorption test

[0073] 1 g of H2TiO3@PAM-7 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0074] Figure 6 The stress-strain curve of the material is shown. The maximum elongation at break of H2TiO3@PAM-7 was 81.2%, and the peak tensile strength was 0.076 MPa.

[0075] Example 8

[0076] (1) Preparation of H2TiO3@PAM

[0077] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.07 g, 0.45 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-8, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.052 MPa.

[0078] (2) Adsorption test

[0079] 1 g of H2TiO3@PAM-8 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0080] Figure 6 The stress-strain curve of the material is shown in FIG. 6. The maximum elongation at break of H2TiO3@PAM-8 was 47.68%, and the peak tensile strength was 0.052 MPa.

[0081] Example 9

[0082] (1) Preparation of H2TiO3@PAM

[0083] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (1.5 g, 5.7 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-9, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.051 MPa.

[0084] (2) Adsorption test

[0085] 1 g of H2TiO3@PAM-9 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0086] Example 10

[0087] (1) Preparation of H2TiO3@PAM

[0088] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 20°C for 5 h to obtain a hydrogel. The hydrogel was then cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, labeled as HTO@PAM-10, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.182 MPa.

[0089] (2) Adsorption test

[0090] 1 g of H2TiO3@PAM-10 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0091] Example 11

[0092] (1) Preparation of H2TiO3@PAM

[0093] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 70°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-11, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.143 MPa.

[0094] (2) Adsorption test

[0095] 1 g of H2TiO3@PAM-11 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0096] Example 12

[0097] (1) Preparation of H2TiO3@PAM

[0098] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, triethanolamine (0.09 mL, 0.67 mmol) and sodium persulfate (0.44 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-12, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.171 MPa.

[0099] (2) Adsorption test

[0100] 1 g of H2TiO3@PAM-12 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0101] Example 13

[0102] (1) Preparation of H2TiO3@PAM

[0103] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then polyvinyl alcohol (0.25 g, 5.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and ammonium persulfate (0.43 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 3 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-13, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.165 MPa.

[0104] (2) Adsorption test

[0105] 1 g of H2TiO3@PAM-13 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0106] Example 14

[0107] (1) Preparation of H2TiO3@PAM

[0108] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then chitosan (0.25 g, 1.55 mmol) was added to solution A and stirred for 15 min, and then acrylamide (8 g, 112.55 mmol) and N,N'-methylene bisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 5 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 7 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-14, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.183 MPa.

[0109] (2) Adsorption test

[0110] 1 g of H2TiO3@PAM-14 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0111] Example 15

[0112] (1) Preparation of H2TiO3@PAM

[0113] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (7 g, 98.49 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B, stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 5 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 6 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-15, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.174 MPa.

[0114] (2) Adsorption test

[0115] 1 g of H2TiO3@PAM-15 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 , respectively.

[0116] Example 16

[0117] (1) Preparation of H2TiO3@PAM

[0118] A 50 g 30% mass fraction H2TiO3 suspension was placed in a beaker (solution A). Then sodium alginate (0.15 g, 0.68 mmol) was added to solution A and stirred for 15 min, and then acrylamide (9 g, 126.64 mmol) and N,N'-methylenebisacrylamide (0.03 g, 0.19 mmol) were added at the same time, and stirred for 10 min to obtain solution B. Subsequently, tetramethylethylenediamine (0.1 mL, 0.67 mmol) and potassium persulfate (0.5 g, 1.9 mmol) were added to solution B and stirred for 2 min, and then the mixture was placed in an oven and polymerized at 50°C for 5 h to obtain a hydrogel. Then the hydrogel was cultured in distilled water for 8 days, with water changed every day, and finally H2TiO3@PAM was obtained, marked as HTO@PAM-16, with a mass fraction of H2TiO3 of 24% of the total mass of the composite hydrogel, and a tensile strength of 0.186 MPa.

[0119] (2) Adsorption test

[0120] 1 g of H2TiO3@PAM-16 was placed in 1 L of salt lake brine containing Li + , Na + , Ca 2+ , K + and Mg 2+ ions at pH = 8 at 25°C, and the adsorption selectivity and saturated adsorption capacity for lithium ions were determined. The initial concentrations of the ions in the salt lake brine were C Li+ = 116.78 mg·L -1 , C Na+ = 99.45 mg·L -1 , C Ca2+ = 98.65 mg·L -1 , C K+ = 100.72 mg·L -1 and C Mg2+ = 99.73 mg·L -1 .

[0121] The H2TiO3@PAM was evaluated as a composite lithium ion sieve for its adsorption capacity Q t , equilibrium adsorption time and adsorption selectivity in salt lake brine

[0122] Application Example 1

[0123] (1) Adsorption capacity Q t and adsorption equilibrium time test:

[0124] 1 g of H2TiO3@PAM was added to 1 L of LiOH solution (100 mg·L-1 The stirring time was then measured. Subsequently, ICP (inductively coupled plasma) was used to measure the Li in the solution. + The initial and instantaneous concentrations of (C0) t ), C t The concentration remained relatively stable over time. The adsorption capacity Q of H2TiO3@PAM was determined. t It is calculated using formula (1).

[0125]

[0126] (2) Adsorption cycle test (calculated based on an 80% decrease in adsorption capacity):

[0127] 1g of H2TiO3@PAM was placed in LiOH solution (100mg·L⁻¹). -1 The cycling performance of Li₂TiO₃@PAM after adsorption and acid washing with 0.2 mol mg·L⁻¹ was assessed. -1 Then, an adsorption experiment was conducted to observe the decrease in adsorption capacity. The calculation formula for the test conditions is the same as formula (1).

[0128] (3) Adsorption selectivity test (using Li) + For Mg 2+ The separating factor is the subject of this study:

[0129] 1 g of H2TiO3@PAM was placed at 25°C in a solution containing Li at pH 8. + Na + Ca 2+ K + and Mg 2+ The adsorption selectivity of ions in salt lake brine for 24 h was investigated (the corresponding ion concentrations were 113.48, 99.24, 100.55, 99.63, and 101.69 mg·L⁻¹). -1 ). Measurement of Li in solution using ICP. + The initial and instantaneous concentrations (C0) of the hetero ions and their associated concentrations (C20) t Allocation coefficient (K) d and separation factor The results are obtained by formulas (2) and (3) respectively.

[0130]

[0131] The experimental results of the application example are shown in Table 1.

[0132] Table 1. Experimental Results of Application Examples

[0133]

[0134]

Claims

1. A method for preparing a composite hydrogel lithium ion sieve, comprising the following specific steps: H2TiO3 and deionized water are added into a beaker and stirred to obtain a suspension; then, a viscosity modifier is added into the suspension and stirred, and acrylamide and N,N'-methylenebisacrylamide are simultaneously added into the suspension and stirred, and a catalyst and an initiator are added into the suspension and stirred, and the mixture is placed into an oven and heated to polymerize to obtain a composite hydrogel; and the hydrogel is cultured in distilled water to obtain H2TiO3@PAM; the prepared composite hydrogel lithium ion sieve is prepared by embedding a powdered active component H2TiO3 into polyacrylamide PAM as a binder, and the mass fraction of H2TiO3 in H2TiO3@PAM is 13.8%-24%.

2. The method of claim 1, wherein, The mass fraction of H2TiO3 in the suspension is 16%-30%.

3. The method of claim 1, wherein, The viscosity modifier is polyvinyl alcohol, chitosan or sodium alginate; and the mass ratio of the viscosity modifier to the suspension is (0.002-0.010) :

1.

4. The method of claim 1, wherein, The mass ratio of acrylamide to the suspension is (0.14-0.18) :

1.

5. The method of claim 1, wherein, The molar ratio of N,N'-methylenebisacrylamide to acrylamide is (0.0005-0.0040) :

1.

6. The method of claim 1, wherein, The initiator is potassium persulfate, sodium persulfate or ammonium persulfate; and the molar ratio of the initiator to acrylamide is (0.015-0.051) :

1.

7. The method of claim 1, wherein, The catalyst is triethanolamine or tetramethylethylenediamine; and the molar ratio of the catalyst to acrylamide is (0.005-0.007) :

1.

8. The method of claim 1, wherein, The polymerization temperature is (20-70) ℃, and the reaction time is 3-5 h.

9. The method of claim 1, wherein, The culture in distilled water is performed for 6-8 days.

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