A modification method for titanium-based lithium ion sieve

Abstract

The present invention discloses a modification method of a titanium-based lithium ion sieve, using a titanium source and a lithium source as basic raw materials, doping a modifier, wherein the modifier is selected from any one of sulfur powder, thiourea, urea, ammonium sulfide, hexamethylenetetramine, and selenium powder; a modified lithium metatitanate precursor is prepared by solid phase synthesis, sol-gel synthesis, or hydrothermal synthesis. The titanium source is selected from any one of titanium dioxide, industrial metatitanic acid, tetrabutyl titanate, titanium tetrachloride, isopropyl titanate, titanium sulfate, and titanium nitrate. The lithium source is selected from any one of lithium hydroxide, lithium chloride, lithium carbonate, lithium acetate dihydrate, lithium oxalate, lithium fluoride, lithium bromide, lithium nitrate, and lithium sulfate. The modification method of the present invention further improves the adsorption capacity and adsorption rate of the titanium-based lithium ion sieve by doping with non-metallic ions nitrogen, sulfur, or selenium.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction from salt lakes, in particular to a method for modifying a titanium-based lithium ion sieve. Background Art

[0002] Lithium is the lightest metallic element. With its increasing application in new energy materials, lithium resource extraction has garnered widespread attention. my country boasts abundant lithium reserves, with salt lake brines accounting for up to 70% of lithium reserves. Therefore, the comprehensive development and utilization of lithium resources in salt lake brines has become a key development direction for the lithium industry. Ion sieve adsorption, based on an ion exchange mechanism, offers high lithium recovery, excellent selectivity, and a short process, making it ideal for extracting lithium from low-concentration salt lake brines. Using lithium ion sieves for lithium extraction is a promising green method, characterized by its simple process and high adsorption capacity, making it one of the most promising lithium extraction methods for industrialization. The key to ion adsorption is the development of high-performance adsorbents with excellent lithium selectivity to eliminate interference from the abundant alkali and alkaline earth metal ions present in the brine. The adsorbents must also exhibit stable adsorption and elution properties, making them suitable for large-scale operations.

[0003] At present, the lithium ion sieve adsorbent of metatitanate (H2TiO3) obtained by acid washing of lithium metatitanate (Li2TiO3) has attracted much attention due to its high theoretical capacity and stable material structure. However, existing studies have found that after acid washing of Li2TiO3, due to H + Radius smaller than Li + , which will cause the interplanar spacing of Li2TiO3 to shrink, and the hydrogen bonds formed by the interlayer OH also cause the interplanar spacing to shrink, further hindering the Li + Entering the interlayer, thereby reducing the adsorption rate and actual adsorption capacity. Summary of the Invention

[0004] Aiming at the problem that the adsorption rate and actual adsorption capacity of current titanium-based lithium ion sieve adsorbents are reduced after acid washing, the present invention provides a modification method for titanium-based lithium ion sieves.

[0005] The present invention provides a method for modifying a titanium-based lithium ion sieve, which uses a titanium source and a lithium source as basic raw materials, and dopes a modifier selected from any one of sulfur powder, thiourea, urea, ammonium sulfide, hexamethylenetetramine, and selenium powder; and prepares a modified lithium metatitanate precursor by a solid-phase synthesis method, a sol-gel synthesis method, or a hydrothermal synthesis method.

[0006] The titanium source is selected from any one of titanium dioxide, industrial metatitanic acid, tetrabutyl titanate, titanium tetrachloride, isopropyl titanate, titanium sulfate, and titanium nitrate.

[0007] The lithium source is selected from any one of lithium hydroxide, lithium chloride, lithium carbonate, lithium acetate dihydrate, lithium oxalate, lithium fluoride, lithium bromide, lithium nitrate, and lithium sulfate.

[0008] Different modification methods are adopted according to the different types of titanium sources used.

[0009] When the titanium source used is titanium dioxide, industrial metatitanic acid, or titanium dioxide obtained by hydrolyzing any one of titanium tetrachloride, titanium sulfate, and titanium nitrate, a modified lithium metatitanate precursor is prepared by a solid phase synthesis method.

[0010] The steps of the solid phase synthesis method are as follows:

[0011] The titanium source, lithium source and modifier are mixed evenly, and calcined at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen.

[0012] Alternatively, the titanium source and the modifier are mixed evenly, calcined at a constant temperature of 300-600°C for 2-10 hours, and then the calcined product is mixed evenly with the lithium source, and calcined at a constant temperature of 600-900°C for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen, and the heating rate is 3-10°C / min.

[0013] When the titanium source used is tetrabutyl titanate or isopropyl titanate, a modified lithium metatitanate precursor is prepared by a sol-gel synthesis method.

[0014] The steps of the sol-gel synthesis method are as follows:

[0015] (1) Tetrabutyl titanate or isopropyl titanate is added to ethanol to form solution A; a modifier is dissolved in another portion of ethanol, and hydrochloric acid and deionized water are added to form solution B; solution B is added dropwise to solution A and stirred at high speed for 12-48 hours, and allowed to stand at room temperature for 12-48 hours to obtain a gel; the gel is dried at 60-100°C for 6-24 hours to obtain a powder;

[0016] (2) Mixing the powder with a lithium source, calcining at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen; and the heating rate is 3-10° C. / min.

[0017] The step (2) may also be: first calcining the powder at 300-600° C. for 2-5 hours, then mixing with a lithium source, and calcining at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor.

[0018] When the titanium source used is any one of titanium tetrachloride, titanium sulfate and titanium nitrate, a modified lithium metatitanate precursor is prepared by a hydrothermal synthesis method.

[0019] The steps of the hydrothermal synthesis method are as follows:

[0020] (1) adding a titanium source, phenol or resorcinol to deionized water, stirring and dissolving, adding formaldehyde, continuing to stir and dissolve, then adding a modifier, continuing to stir and dissolve, adding the resulting solution to a reactor, hydrothermally reacting at 60-120° C. for 4-24 hours, collecting the generated solid after cooling, and washing and drying; the titanium source is any one of titanium tetrachloride, titanium sulfate, and titanium nitrate;

[0021] (2) The dried solid product is mixed evenly with a lithium source, and calcined at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; wherein the calcination atmosphere is air, argon, or nitrogen.

[0022] Compared with the prior art, the present invention is beneficial in that:

[0023] (1) The present invention replaces a small amount of O in lithium metatitanate by doping with non-metallic ions such as nitrogen (N), sulfur (S) or selenium (Se), which can reduce interlayer hydrogen bonds, open up some interlayer spacing, and improve adsorption rate and adsorption capacity. The inventor's research shows that the interface modification of introducing N active sites can effectively accelerate the adsorption of Li + Extraction, and the hydrogen bond energy formed by N is smaller than that formed by O, so N is selected as the doping source. S and Se, as elements of the same group as O, have similar properties and do not form hydrogen bonds, which can reduce the crystal surface shrinkage after pickling and promote Li + extraction process, thereby improving the adsorption rate and adsorption capacity.

[0024] (2) The modification method of the present invention avoids the problem that the existing Li2TiO3 is washed by acid due to H + Radius smaller than Li + The resulting H2TiO3 interplanar spacing contraction and the hydrogen bonds formed between the OH layers also lead to a contraction of the interplanar spacing, hindering the Li + The technical defect is that the adsorption agent enters the interlayer, thereby reducing the adsorption rate and actual adsorption capacity.

[0025] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a diagram of the adsorption capacity of the Se-doped H2TiO3 ion sieve of Example 1 at different times.

[0027] Figure 2 This is a diagram of the adsorption capacity of the S-doped H2TiO3 ion sieve of Example 2 at different times.

[0028] Figure 3 This is a diagram of the adsorption capacity of the N-doped H2TiO3 ion sieve of Example 3 at different times.

[0029] Figure 4 This is a diagram of the adsorption capacity of the Se-doped H2TiO3 ion sieve of Example 4 at different times. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] Example 1

[0032] A modification method for titanium-based lithium ion sieve:

[0033] 10g of Ti(SO4)2 was added to 250mL of deionized water and stirred for 20 minutes. The mixture was then hydrothermally reacted at 85°C for 12 hours. The resulting solid, titanium dioxide (TiO2), was collected, washed several times, and then dried at 60°C for 12 hours. 1.25g of the dried TiO2 was mixed with 0.098g of selenium powder and calcined at 300°C for 6 hours under argon, followed by calcination at 500°C for 2 hours at a heating rate of 5°C / min to obtain Se-doped TiO2. 1g of Se-doped TiO2 was mixed with 0.934g of Li2CO3 and calcined at 700°C for 4 hours under argon at a heating rate of 5°C / min. After cooling to room temperature, Se-doped Li2TiO3 powder was obtained. The resulting powder was eluted in 0.25mol / L HCl solution for 24 hours, washed several times, and dried at 60°C for 24 hours to obtain Se-doped H2TiO3 ion sieve, designated HTO-Se-1.

[0034] According to the same method as above, the amount of selenium powder added was changed to 0.2964 g and 0.4941 g respectively. The Se-doped H2TiO3 ion sieves were finally prepared and recorded as HTO-Se-2 and HTO-Se-3 respectively.

[0035] An ion sieve without selenium powder was prepared under the same conditions and was labeled as HTO.

[0036] The adsorption experiment was carried out by dissolving 0.3 g of ion sieve in 100 mL of 1000 mg / L Li solution. Samples were taken at different times. The concentration of the solution was tested by flame photometer and the adsorption capacity was calculated. The change of adsorption capacity with time is shown in Fig. Figure 1It can be seen that compared with the ion sieve HTO not doped with selenium powder, the Se-doped H2TiO3 ion sieve of the present invention significantly improves the adsorption rate and adsorption capacity, and the adsorption capacity of HTO-Se-2 is the highest.

[0037] Example 2

[0038] A modification method for titanium-based lithium ion sieve:

[0039] 10 ml of tetrabutyl titanate was added to 20 ml of ethanol to form solution A. 2.2052 g of thiourea was added to 20 ml of ethanol, followed by 1 ml of 12 M HCl and 3 ml of deionized water to form solution B. Solution B was added dropwise to solution A with high-speed stirring for 24 hours, and then allowed to stand at room temperature for 24 hours to obtain a gel. The gel was dried at 100°C for 12 hours, and the resulting powder was calcined in air at 500°C for 2 hours at a heating rate of 5°C / min to obtain S-doped TiO2. 1 g of S-doped TiO2 was mixed with 0.934 g of Li2CO3 in a uniform ratio and calcined at 700°C for 4 hours under argon at a heating rate of 5°C / min. After cooling to room temperature, S-doped Li2TiO3 powder was obtained. The resulting S-doped Li2TiO3 was eluted in 0.25 mol / L HCl solution for 24 hours, washed, and dried to obtain S-doped H2TiO3 ion sieve, designated HTO-S-1.

[0040] According to the same preparation method as above, the amount of thiourea was changed to 4.4103 g and 6.6155 g to prepare S-doped H2TiO3 ion sieves, which were recorded as HTO-S-2 and HTO-S-3, respectively.

[0041] The undoped ion sieve was prepared under the same conditions and was labeled as HTO-sol.

[0042] 0.3 g of ion sieve was adsorbed in 100 mL of 1000 mg / L Li solution, and samples were taken at different times. The adsorption capacity was tested using a flame photometer. The change of adsorption capacity over time is shown in Figure 2 It can be seen that the doped ion sieve significantly improved the adsorption capacity and adsorption rate, and HTO-S-2 had the highest adsorption capacity.

[0043] Example 3

[0044] A modification method for titanium-based lithium ion sieve:

[0045] 5g of titanium sulfate and 0.8g of resorcinol were dissolved in 50mL of deionized water and stirred for 20 minutes. 2mL of formaldehyde was added and stirred for another 30 minutes. Subsequently, 0.6256g of urea was added and stirred until dissolved. The mixture was hydrothermally reacted at 85°C for 12 hours, cooled naturally to room temperature, and the resulting solid was collected, washed several times, and then dried at 60°C for 12 hours to obtain a hydrothermal solid product. The hydrothermally fixed product was mixed with Li2CO3 at a Li:Ti molar ratio of 2.02:1. The mixture was then calcined at 700°C under argon for 4 hours, followed by calcination at 500°C in air for 2 hours at a heating rate of 5°C / min. After cooling to room temperature, N-doped Li2TiO3 powder was obtained.

[0046] The method for determining the mixing ratio of the hydrothermal solid product and Li2CO3 is to quantitatively sample a portion of the hydrothermal solid product and calcine it in air at 500°C for 2 hours at a heating rate of 5°C / min to obtain the product titanium dioxide, and then calculate the titanium dioxide yield. The calculated yield can be used to estimate the amount of hydrothermal solid product to be mixed with Li2CO3 in subsequent steps.

[0047] The obtained N-doped Li2TiO3 was eluted in 0.25mol / L HCl solution for 24h, washed and dried to obtain N-doped H2TiO3 ion sieve, which was recorded as HTO-N-1.

[0048] According to the same preparation method as above, the amount of urea was changed to 1.2512g and 1.8768g respectively, and the N-doped H2TiO3 ion sieves were prepared, which were recorded as HTO-N-2 and HTO-N-3 respectively.

[0049] The undoped ion sieve was prepared under the same conditions and was labeled as HTO-h.

[0050] 0.3 g of ion sieve was adsorbed in 100 mL of 1000 mg / L Li solution, and samples were taken at different times. The adsorption capacity was tested using a flame photometer. The results are shown in Table 2. Figure 3 The N-doped ion sieve significantly improved the adsorption capacity and adsorption rate. HTO-N-2 had the highest adsorption capacity. Although the equilibrium capacity of HTO-N-3 decreased, the adsorption rate was faster in the first 2 hours.

[0051] Example 4

[0052] A modification method for titanium-based lithium ion sieve:

[0053] 1g of TiO2 was mixed with 0.934g of Li2CO3 and then with 0.0988g of selenium powder. The mixture was calcined at 700°C under argon for 4 hours at a heating rate of 5°C / min. After cooling to room temperature, Se-doped Li2TiO3 powder was obtained. The resulting powder was eluted in 0.25mol / L HCl solution for 24 hours, washed several times, and dried at 60°C for 24 hours to obtain Se-doped H2TiO3 ion sieve, designated HTO-Se-1-step.

[0054] Se-doped H2TiO3 ion sieves were prepared using the same preparation method as above, but with different amounts of selenium powder used, 0.2964g and 0.4941g, respectively. These were designated HTO-Se-2-one-step and HTO-Se-3-one-step, respectively.

[0055] Undoped ion sieves were prepared under the same conditions, denoted as HTO-one-step.

[0056] 0.3 g of ion sieve was adsorbed in 100 mL of 1000 mg / L Li solution, and samples were taken at different times. The concentration of the solution was tested using a flame photometer and the adsorption capacity was calculated. The results are shown in Figure 4 The figure shows that Se-doped H2TiO3 ion sieve significantly improves the adsorption rate and adsorption capacity. The adsorption capacity of HTO-Se-2-step is the highest, but the overall change is small.

[0057] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for modifying a titanium-based lithium ion sieve, characterized in that: A modified lithium metatitanate precursor is prepared by using a titanium source and a lithium source as basic raw materials, doping a modifier, and using a solid phase synthesis method, a sol-gel synthesis method, or a hydrothermal synthesis method; the modifier is selected from any one of sulfur powder, thiourea, ammonium sulfide, and selenium powder; The titanium source is selected from any one of titanium dioxide, industrial metatitanic acid, tetrabutyl titanate, titanium tetrachloride, isopropyl titanate, titanium sulfate, and titanium nitrate; different modification methods are used according to the type of titanium source used: When the titanium source used is titanium dioxide or industrial metatitanic acid, a modified lithium metatitanate precursor is prepared by a solid phase synthesis method; When the titanium source used is tetrabutyl titanate or isopropyl titanate, a modified lithium metatitanate precursor is prepared by a sol-gel synthesis method; When the titanium source used is any one of titanium tetrachloride, titanium sulfate and titanium nitrate, a modified lithium metatitanate precursor is prepared by a hydrothermal synthesis method.

2. The method for modifying the titanium-based lithium ion sieve according to claim 1, wherein: The lithium source is selected from any one of lithium hydroxide, lithium chloride, lithium carbonate, lithium acetate dihydrate, lithium oxalate, lithium fluoride, lithium bromide, lithium nitrate, and lithium sulfate.

3. The method for modifying the titanium-based lithium ion sieve according to claim 1, wherein: The steps of the solid phase synthesis method are as follows: The titanium source, lithium source and modifier are mixed evenly, and calcined at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen.

4. The method for modifying a titanium-based lithium ion sieve according to claim 1, wherein: The steps of the solid phase synthesis method are as follows: The titanium source and the modifier are mixed evenly, and calcined at a constant temperature of 300-600°C for 2-10 hours. Then, the calcined product is mixed evenly with the lithium source, and calcined at a constant temperature of 600-900°C for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen.

5. The method for modifying the titanium-based lithium ion sieve according to claim 1, wherein: The steps of the sol-gel synthesis method are as follows: (1) Tetrabutyl titanate or isopropyl titanate is added to ethanol to form solution A; a modifier is dissolved in another portion of ethanol, and hydrochloric acid and deionized water are added to form solution B; solution B is added dropwise to solution A and stirred at high speed for 12-48 hours, and allowed to stand at room temperature for 12-48 hours to obtain a gel; the gel is dried at 60-100°C for 6-24 hours to obtain a powder; (2) Mixing the powder with a lithium source, and calcining at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; the calcination atmosphere is air, argon, or nitrogen.

6. The method for modifying the titanium-based lithium ion sieve according to claim 5, wherein: In the step (2), the powder is first calcined at 300-600° C. for 2-5 hours, then mixed with a lithium source, and calcined at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor.

7. The method for modifying a titanium-based lithium ion sieve according to claim 1, wherein: The steps of the hydrothermal synthesis method are as follows: (1) adding a titanium source, phenol or resorcinol to deionized water, stirring and dissolving, adding formaldehyde, continuing to stir and dissolve, then adding a modifier, continuing to stir and dissolve, adding the resulting solution to a reactor, hydrothermally reacting at 60-120° C. for 4-24 hours, collecting the generated solid after cooling, and washing and drying; the titanium source is any one of titanium tetrachloride, titanium sulfate, and titanium nitrate; (2) The solid product is mixed evenly with a lithium source, and calcined at 600-900° C. for 4-12 hours to obtain a modified lithium metatitanate precursor; wherein the calcination atmosphere is air, argon, or nitrogen.

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