Titanium lithium adsorbent, preparation method and application of titanium lithium adsorbent in low-salinity water treatment

Abstract

The invention belongs to the technical field of titanium-based lithium adsorbent manufacturing, and particularly relates to a titanium-based lithium adsorbent, a preparation method and application of the titanium-based lithium adsorbent in low-salinity water treatment. The method comprises the following steps: adding a complexing agent into a titanium tetrachloride solution, dropwise adding ammonia water to generate a titanium-based precursor precipitate, aging, filtering, washing, carrying out surface modification by adopting a modifier, and finally calcining to obtain the titanium-based lithium adsorbent. The titanium lithium adsorbent has excellent pore size distribution, high adsorption capacity and good regeneration performance, the adsorption capacity retention rate reaches up to 92% after 30 times of regeneration, the titanium lithium adsorbent is suitable for selective adsorption treatment of lithium ions in low-salinity water, and the problem that the performance of the adsorbent is reduced after multiple times of regeneration in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of titanium-based lithium adsorbent manufacturing technology, specifically titanium-based lithium adsorbents, their preparation methods, and their application in low-mineralization water treatment. Background Technology

[0002] Titanium-based lithium adsorbents, commonly known as titanium-based lithium ion sieve adsorbents, are inorganic ion sieves with extremely high selectivity for lithium ions. Their core principle is to utilize specific vacancies in their crystal structure, acting like a "sieve" to allow only size-matched lithium ions to enter and be firmly adsorbed, thereby achieving efficient separation of lithium from other coexisting ions (such as sodium, potassium, magnesium, calcium, etc.).

[0003] After adsorbing lithium ions, the lithium ions in titanium-based lithium adsorbents are mainly fixed in the crystal lattice or surface of the material through ion exchange or coordination. The regeneration process essentially involves replacing or washing away the adsorbed lithium ions with a high-concentration acidic or alkaline / salt solution, restoring the adsorbent to a low-lithium state so that it can be reused.

[0004] Acid washing and regeneration process: Immerse the adsorbent that has adsorbed lithium in dilute hydrochloric acid (0.2~0.5M) or dilute sulfuric acid solution and stir for 12~24h; then wash with deionized water / ethanol until neutral, centrifuge or filter to remove residue, and dry before recycling.

[0005] However, even when titanium-based lithium adsorbents are acid-washed and regenerated, their adsorption efficiency usually decreases by more than 50% after three regenerations, rendering them essentially unusable. Furthermore, the regeneration process requires a high concentration of acid, typically greater than 0.2M, which puts significant pressure on environmental protection.

[0006] Based on this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a titanium-based lithium adsorbent, its preparation method, and its application in the treatment of low-salinity water, thereby solving the aforementioned problems. This is achieved through the following technical solution: On the one hand, the preparation method of titanium-based lithium adsorbent includes the following steps: S1: Add a complexing agent to the titanium tetrachloride solution and stir until homogeneous to obtain a mixed solution; S2: Add ammonia dropwise to the mixed solution until the pH value reaches 8 to 9, forming a titanium-based precursor precipitate, then age, filter, and wash; S3: Disperse the titanium-based precursor precipitate obtained in step S2 in an alcohol solvent, add a modifier for surface modification, filter and dry after the modification reaction is complete to obtain the surface-modified titanium-based precursor. S4: The surface-modified titanium-based precursor is calcined under nitrogen protection and cooled to obtain a titanium-based lithium adsorbent.

[0008] Furthermore, in step S1, the concentration of the titanium tetrachloride solution is 0.5~2 mol / L.

[0009] Further, in step S1, the complexing agent is citric acid or ethylenediaminetetraacetic acid, and its molar ratio with titanium tetrachloride is 1:(1~3).

[0010] Furthermore, in step S2, the aging temperature is 60~80℃ and the aging time is 4~8 hours.

[0011] Further, in step S3, the modifier is prepared by mixing a phosphate coupling agent, an aluminate coupling agent, glycerol, and an alcohol solvent evenly and reacting them at 60-65°C for 2-5 hours; the mass ratio of the phosphate coupling agent, the aluminate coupling agent, and glycerol is 7:3:5.

[0012] Furthermore, the amount of the modifier is 1% to 5% of the amount of titanium-based precursor precipitate.

[0013] Furthermore, in step S4, the calcination temperature is 500~700℃, and the calcination time is 2~4 hours.

[0014] Furthermore, the alcohol solvent is one or more of methanol, ethanol, propanol, and butanol.

[0015] Secondly, a titanium-based lithium adsorbent was prepared according to the above preparation method.

[0016] Thirdly, the application of the titanium-based lithium adsorbent in the treatment of low-mineralized water.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This titanium-based lithium adsorbent is prepared through complexation precipitation, surface modification, and calcination processes, exhibiting excellent pore size distribution, high adsorption capacity, and good regeneration performance. The preparation method involves dissolving titanium tetrachloride, adding a complexing agent to form a mixed solution, followed by precipitation, aging, washing, surface modification, and calcination to obtain the target adsorbent.

[0018] 2. Experiments show that the titanium-based lithium adsorbent retains up to 92% of its adsorption capacity after 30 regenerations, making it suitable for the selective adsorption treatment of lithium ions in low-mineralized water, thus solving the problem of performance degradation of adsorbents after multiple regenerations in existing technologies.

[0019] 3. In the process of 30 regenerations, the concentration of hydrochloric acid used by this titanium-based lithium adsorbent can be as low as 0.03 mol / L, which is extremely low compared to the 0.2 mol / L commonly used in existing technologies, and has a relatively small impact on the environment.

[0020] 4. This titanium-based lithium adsorbent still has a certain regeneration capacity after it has become saturated with lithium ions in water with moderate mineralization. Detailed Implementation

[0021] The present invention will be further described in detail below through specific embodiments.

[0022] Example 1 S1: Dissolve titanium tetrachloride in deionized water to form a titanium tetrachloride solution with a concentration of 1 mol / L; add citric acid as a complexing agent to the titanium tetrachloride solution, stir well to obtain a mixed solution; the molar ratio of citric acid to titanium tetrachloride is 1:2; S2: Add ammonia to the mixed solution until the pH reaches 8.5 to generate a titanium-based precursor precipitate; age the titanium-based precursor precipitate at 70 degrees Celsius for 6 hours, then filter and wash with deionized water until no chloride ions remain in the filtrate. S3: Disperse the titanium-based precursor precipitate obtained in step S2 in ethanol, add a modifier for surface modification, the amount of which is 3% of the mass of the titanium-based precursor precipitate; stir the reaction for 4 hours, then filter and dry to obtain the surface-modified titanium-based precursor. The modifier is prepared by mixing a phosphate coupling agent, an aluminate coupling agent, glycerol, and ethanol evenly and reacting them at 63 degrees Celsius for 2 hours; the mass ratio of the phosphate coupling agent, the aluminate coupling agent, glycerol, and ethanol is 7:3:5:25. S4: The surface-modified titanium-based precursor was calcined under nitrogen protection at a heating rate of 4 degrees Celsius per minute, a calcination temperature of 600 degrees Celsius, and a holding time of 3 hours. After cooling, a titanium-based lithium adsorbent was obtained.

[0023] Example 2 S1: Dissolve titanium tetrachloride in deionized water to form a titanium tetrachloride solution with a concentration of 1.5 mol / L; add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the titanium tetrachloride solution, and stir until homogeneous to obtain a mixed solution; the molar ratio of EDTA to titanium tetrachloride is 1:3. S2: Add ammonia to the mixed solution until the pH reaches 8 to generate a titanium-based precursor precipitate; age the titanium-based precursor precipitate at 80 degrees Celsius for 4 hours, then filter and wash with deionized water until no chloride ions remain in the filtrate. S3: The titanium-based precursor precipitate was dispersed in ethanol, and a modifier was added for surface modification at an amount of 5% of the titanium-based precursor mass. The reaction was stirred for 6 hours, and then filtered and dried to obtain the surface-modified titanium-based precursor. The modifier is prepared by mixing a phosphate coupling agent, an aluminate coupling agent, glycerol, and ethanol evenly and reacting them at 63 degrees Celsius for 2 hours; the mass ratio of the phosphate coupling agent, the aluminate coupling agent, glycerol, and ethanol is 7:3:5:25. S4: The surface-modified titanium-based precursor was calcined under nitrogen protection at a heating rate of 5 degrees Celsius per minute, a calcination temperature of 700 degrees Celsius, and a holding time of 2 hours. After cooling, a titanium-based lithium adsorbent was obtained.

[0024] Comparative Example 1 In this example, no modifying agent is used, and step S3 of Example 1 is omitted. The titanium-based precursor precipitate is directly calcined under nitrogen protection, and the remaining steps are the same as in Example 1.

[0025] Comparative Example 2 In this example, a silane coupling agent is used as the modifier, and the remaining steps are the same as in Example 1.

[0026] Comparative Example 3 In this example, a silane coupling agent is used as the modifier, and the remaining steps are the same as in Example 1.

[0027] Comparative Example 4 In this example, the modifier used is a phosphate ester coupling agent, and the remaining steps are the same as in Example 1.

[0028] Comparative Example 5 In this example, the modifier used is an aluminate coupling agent, and the remaining steps are the same as in Example 1.

[0029] Comparative Example 6 The modifier in this example is prepared by reacting phosphate ester coupling agent, aluminate coupling agent and ethanol in a mass ratio of 7:3:30 at 63 degrees Celsius. The reactants do not contain glycerol. The remaining steps are the same as in Example 1.

[0030] Comparative Example 7 The modifier in this example was prepared by reacting silane coupling agent, aluminate coupling agent, glycerol and ethanol in a mass ratio of 7:3:5:25 at 63 degrees Celsius. The remaining steps were the same as in Example 1.

[0031] Comparative Example 8 The modifier in this example was prepared by reacting a phosphate ester coupling agent, a silane coupling agent, glycerol and ethanol in a mass ratio of 7:3:5:25 at 63 degrees Celsius. The remaining steps were the same as in Example 1.

[0032] The experimental characterization data include pore volume, average pore size, adsorption capacity, and adsorption capacity retention rate after multiple regenerations. The specific test methods are as follows: 1. Pore volume and average pore size: determined by nitrogen adsorption method, specific surface area calculated by BET model, and pore size distribution calculated by BJH model.

[0033] 2. Adsorption capacity: The adsorbent was placed in simulated low-mineralization water with an initial lithium ion concentration of 10 mg / L and a total dissolved solids of 100 mg / L. The adsorption time was 24 hours. The change in lithium ion concentration before and after adsorption was measured by ICP-OES (inductively coupled plasma optical emission spectrometry) to calculate the adsorption capacity.

[0034] 3. Regeneration performance: The acid washing regeneration process is adopted: the titanium-based lithium adsorbent that has been saturated with lithium is immersed in 0.03 mol / L ultra-dilute hydrochloric acid and stirred for 17 hours; then it is washed with deionized water until neutral, filtered to remove residue, and dried to complete one regeneration. The process is repeated as required (e.g., 30 times), and the adsorption capacity after each regeneration is measured to calculate the adsorption capacity retention rate.

[0035] The experimental results are shown in Table 1: Table 1

[0036] The adsorption capacity of Comparative Example 1 was significantly lower than that of Example 1, and the adsorption capacity retention rate was less than 50% after 4 regenerations and less than 20% after 10 regenerations.

[0037] The adsorption capacity of Comparative Example 2 was basically the same as that of Example 1, but the adsorption capacity retention rate was less than 50% after 10 regenerations.

[0038] The test results of Comparative Example 3 were basically the same as those of Comparative Example 2.

[0039] The test results of Comparative Examples 4, 5, 6, 7, and 8 are basically the same as those of Comparative Example 3.

[0040] Comparative Example 9 In this example, referring to the process of Example 1, the ratio of the modifiers was adjusted so that the mass ratio of phosphate coupling agent, aluminate coupling agent and glycerol was 3:7:5 (Group 1), and the rest were the same.

[0041] In this example, referring to the process of Example 1, the ratio of the modifiers was adjusted so that the mass ratio of phosphate coupling agent, aluminate coupling agent and glycerol was 5:5:5 (Group 2), and the rest were the same.

[0042] In this example, the adsorption capacity test was conducted in water with moderate mineralization, an initial lithium ion concentration of 10 mg / L, and a total dissolved solids concentration of 600 mg / L (a 6-fold increase), with all other parameters remaining the same.

[0043] In Example 1, the titanium-based lithium adsorbent retained 83.7% of its adsorption capacity after 22 regenerations in the medium-mineralized water test. Group 1 retained 16.6% of its adsorption capacity after 2 regenerations. Group 2 retained 25.3% of its adsorption capacity after 1 regeneration.

[0044] In the above embodiments, no modifier was added in Comparative Example 1, and the adsorption capacity and regeneration performance were significantly inferior to those of the Examples; in Comparative Examples 2 to 8, although different types of modifiers were used, the effects of the Examples were not achieved.

[0045] In particular, in Comparative Example 9, although the modifier components were the same, the ratio was different, resulting in limited effectiveness in treating moderately mineralized water with a 6-fold increase in total dissolved solids. It could only be regenerated 1-2 times before becoming unregenerable, leading to poor regeneration.

[0046] In this invention, the modifier is prepared by reacting a phosphate ester coupling agent, an aluminate coupling agent, and glycerol in an alcohol solvent. The mixture is uniformly distributed on the surface of the titanium-based precursor precipitate. After subsequent calcination, most of the organic groups disappear, leaving the remaining silicon-oxygen bond network structure to account for the majority of the mass. At this point, the coupling agent material no longer possesses its original coupling agent function, but the resulting framework, combined with the original microporous structure, significantly improves adsorption and regeneration performance. Experiments revealed that, possibly due to the inherent structure of the titanium-based lithium adsorbent, only a specific ratio of phosphate ester coupling agent, aluminate coupling agent, and glycerol can be used for the reaction. Changing the type and ratio of coupling agents allows for better integration of the final framework with the original microporous structure, achieving the desired adsorption effect.

[0047] According to China's "Standards for Drinking Water Quality" (GB5749-2022) and industry practice, low-mineralized water is defined as TDS (Total Dissolved Solids) <100mg / L.

[0048] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

Claims

1. A method for preparing a titanium-based lithium adsorbent, characterized in that, Includes the following steps: S1: Add a complexing agent to the titanium tetrachloride solution and stir until homogeneous to obtain a mixed solution; S2: Add ammonia dropwise to the mixed solution until the pH value reaches 8 to 9, forming a titanium-based precursor precipitate, then age, filter, and wash; S3: Disperse the titanium-based precursor precipitate obtained in step S2 in an alcohol solvent, add a modifier for surface modification, filter and dry after the modification reaction is complete to obtain the surface-modified titanium-based precursor. S4: The surface-modified titanium-based precursor is calcined under nitrogen protection and cooled to obtain a titanium-based lithium adsorbent.

2. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the titanium tetrachloride solution is 0.5~2 mol / L.

3. The preparation method according to claim 1, characterized in that, In step S1, the complexing agent is citric acid or ethylenediaminetetraacetic acid, and its molar ratio with titanium tetrachloride is 1:(1~3).

4. The preparation method according to claim 1, characterized in that, In step S2, the aging temperature is 60~80℃ and the aging time is 4~8 hours.

5. The preparation method according to claim 1, characterized in that, In step S3, the modifier is prepared by mixing a phosphate coupling agent, an aluminate coupling agent, glycerol, and an alcohol solvent evenly and reacting them at 60-65°C for 2-5 hours; the mass ratio of the phosphate coupling agent, the aluminate coupling agent, and glycerol is 7:3:

5.

6. The preparation method according to claim 1, characterized in that, The amount of the modifier used is 1% to 5% of the amount of titanium-based precursor precipitate.

7. The preparation method according to claim 1, characterized in that, In step S4, the calcination temperature is 500~700℃ and the calcination time is 2~4 hours.

8. The preparation method according to claim 1 or 5, characterized in that, The alcohol solvent is one or more of methanol, ethanol, propanol, and butanol.

9. A titanium-based lithium adsorbent, characterized in that, Prepared by the method according to any one of claims 1 to 8.

10. The application of the titanium-based lithium adsorbent as described in claim 9 in the treatment of low-mineralized water.

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