High-boron system lithium ion targeted adsorbent and preparation method thereof

Abstract

The invention discloses a high-boron system lithium ion targeted adsorbent and a preparation method thereof, and relates to the technical field of lithium ion adsorption materials. In order to solve the problems that the adsorption capacity of an existing adsorbent in a high-boron system is reduced and the impurity concentration of qualified liquid boron is high, the invention provides a method for modifying lithium adsorbent powder, firstly preparing the adsorbent powder modified by a silane coupling agent, then preparing the adsorbent powder modified by a fluorinating agent, and finally obtaining the boron-resistant adsorbent powder. The adsorption / desorption path of boric acid molecules is blocked through a powder chemical modification-competitor pre-loading synergistic strategy, and efficient separation of lithium / boron is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion adsorption materials, and particularly relates to an adsorbent suitable for selectively adsorbing lithium ions in a high boron system and a preparation method thereof. Background Art

[0002] Lithium is a core strategic resource in fields such as new energy batteries and aerospace. The global demand for lithium is increasing year by year, and the compound annual growth rate from 2020 to 2030 is expected to be 20%-25% (from IEA's "Global EV Outlook 2023"). At present, salt lake brine accounts for more than 60% of the lithium resource reserves (such as CN106882816B), but most salt lakes (such as the Uyuni Salt Lake in South America) are associated with high concentrations of boron (the concentration can reach 500-5000 mg / L), resulting in low separation efficiency of lithium ions (Li + ). During the process of extracting lithium from salt lakes, the hydroxyl groups (Al-OH) on the surface of the adsorbent are easily combined with boric acid (B(OH)3) through hydrogen bonds or coordination, resulting in problems such as a decrease in lithium adsorption capacity and a high concentration of boron impurities in the qualified liquid. Therefore, it is urgent to develop a new type of adsorption material resistant to boron interference.

[0003] Currently, in the field of extracting lithium from salt lake brine, aluminum-based adsorbents (such as LiAl-LDHs) are widely used due to their high selectivity. However, they still face the following technical bottlenecks: (1) The physicochemical properties of boric acid (H3BO3) molecules and lithium ions are similar (such as charge density, hydration radius, etc.), resulting in competitive adsorption problems. The adsorption capacity of boric acid by typical industrial adsorbents can reach 8-15 mg / g, resulting in a reduction in lithium adsorption capacity of more than 30%. (2) Existing boron-resistant modification technologies mostly use pre-removing boron at the front end of the feed liquid, resulting in problems such as complex processes, high costs, and lithium ion losses. Therefore, it is of great significance to develop an adsorbent that can selectively adsorb lithium ions and resist boron interference. Summary of the Invention

[0004] In order to overcome the problems of attenuation of adsorption capacity and high concentration of boron impurities in the qualified liquid of existing adsorbents in a high boron system, the present invention provides a lithium ion targeted adsorbent in a high boron system and a preparation method thereof. Through a synergistic strategy of powder chemical modification - preloading of a competitive agent, the adsorption / desorption path of boric acid molecules is blocked, and efficient separation of lithium / boron is achieved.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] A preparation method of a lithium ion targeted adsorbent in a high boron system, comprising the following steps:

[0007] (1) Disperse the lithium adsorbent powder in an ethanol solution of a silane coupling agent, and carry out a heating and stirring reaction; after the reaction is completed, wash to remove the unreacted silane coupling agent and by-products, and obtain the adsorbent powder modified with the silane coupling agent;

[0008] (2) Disperse the adsorbent powder modified with the silane coupling agent in an ethanol solution of a fluorination modifier, introduce an inert atmosphere, and carry out a heating and stirring reaction; after the reaction is completed, wash to remove the unreacted fluorination modifier and by-products, and obtain the adsorbent powder modified with the fluorinating agent;

[0009] (3) Immerse the adsorbent powder modified with the fluorinating agent in an ethanol solution of a polyol, where the polyol is a competitive agent, carry out stirring at room temperature, and then carry out heating and drying; after the reaction is completed, wash to remove the unreacted competitive agent and by-products, and obtain the anti-boron adsorbent powder.

[0010] Further, in step (1), the lithium adsorbent is but not limited to an aluminum-based lithium ion adsorbent (LiAl-LDHs).

[0011] Further, in step (1), the silane coupling agent is one or more of trimethylchlorosilane (TMCS), hexamethyldisilazane, triethylchlorosilane, tert-butyldimethylchlorosilane, and trimethylmethoxysilane.

[0012] Further, in step (1), the mass concentration of the ethanol solution of the silane coupling agent is 1% to 3%, preferably 2%.

[0013] Further, in step (1), the solid-liquid ratio of the lithium adsorbent powder dispersed in the ethanol solution of the silane coupling agent is 1:4 to 1:6.

[0014] Further, in step (1), the conditions for heating and stirring are: stirring reaction at 60 to 80 °C for 4 to 6 hours.

[0015] Further, in step (1), centrifuge and wash with absolute ethanol several times, for example, 3 times.

[0016] Further, in step (2), the fluorination modifier is one or more of perfluorooctyltriethoxysilane, perfluorohexyltriethoxysilane, and perfluorobutyltrimethoxysilane.

[0017] Further, in step (2), the mass concentration of the ethanol solution of the fluorination modifier is 1% to 3%, preferably 2%.

[0018] Further, in step (2), the solid-liquid ratio of the adsorbent powder modified with the silane coupling agent dispersed in the ethanol solution of the fluorination modifier is 1:4 to 1:6.

[0019] Further, in step (2), the inert atmosphere is nitrogen or argon, and the introduction duration is 20 to 50 minutes.

[0020] Further, the conditions for heating and stirring in step (2) are: stirring reaction at 50 - 80 °C for 2 - 5 hours.

[0021] Further, in step (2), it is centrifugally washed with anhydrous ethanol for several times, for example, 3 times.

[0022] Further, in step (3), the polyol is one or more of xylitol, arabinitol, ribitol, mannitol, sorbitol, dulcitol.

[0023] Further, in step (3), the mass concentration of the ethanol solution of the polyol is 5% - 10%, preferably 7%.

[0024] Further, in step (3), the solid - liquid ratio of the adsorbent powder modified by the fluorinating agent impregnated in the ethanol solution of the polyol is 1:2 - 1:4.

[0025] Further, in step (3), the stirring duration at room temperature is 3 - 5 hours, and the heating and drying conditions are drying at 60 - 80 °C for 8 - 12 hours.

[0026] Further, in step (3), it is centrifugally washed with anhydrous ethanol for several times, for example, 3 times.

[0027] A high - boron - system lithium - ion targeted adsorbent is prepared by the above - mentioned preparation method.

[0028] The high - boron - system lithium - ion targeted adsorbent prepared by the present invention has high mechanical strength, and the reasons are as follows:

[0029] 1. Surface hydroxyl group blocking: Using a silane coupling agent to modify the powder surface, covering the hydroxyl active sites, blocking the surface hydroxyl groups, and inhibiting or blocking the binding of boric acid molecules to the hydroxyl groups on the powder surface through hydrogen bonds;

[0030] 2. Hydrophobic barrier construction: Enhancing the surface hydrophobicity through fluorination modification to form a physical barrier, inhibiting boric acid from approaching the adsorption sites, while keeping the lithium - ion channels open;

[0031] 3. Competitive agent pre - loading: Pre - loading polyol on the powder surface, enabling boric acid molecules to form a stable six - membered ring complex with the polyol (B(OH)3 + 2 polyol → B(O - R)3 -3 ), occupying the adsorption sites, and the binding energy is much higher than the hydrogen - bond interaction between boric acid and the hydroxyl groups on the adsorbent surface. Therefore, it can reduce the precipitation of boric acid during the desorption stage, thus realizing the targeted adsorption of lithium ions in the high - boron system.

[0032] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0033] 1. The present invention realizes high-selectivity adsorption of lithium ions by regulating the surface chemical properties and interfacial structure of the adsorbent, and can solve the problem of high boron impurity content in the qualified liquid during the lithium extraction process from high-boron systems with traditional lithium adsorbents.

[0034] 2. Through surface chemical modification of the adsorbent powder, the present invention effectively inhibits the adsorption and desorption of boric acid molecules, significantly improves the quality of the qualified liquid, and improves the problem of attenuation of adsorption capacity during the operation of traditional lithium adsorbents.

[0035] 3. The adsorbent of the present invention is prepared under mild conditions, with low-cost raw materials and is easy to produce on a large scale. Brief Description of the Drawings

[0036] Figure 1 is a brief flow chart for preparing a lithium-ion targeted adsorbent for high-boron systems in the present invention.

[0037] Figure 2 is a graph of lithium adsorption capacity of the adsorbent prepared in Example 2 and a traditional adsorbent in high-boron brine.

[0038] Figure 3 is a graph of the boron impurity concentration in the desorbed liquid after the adsorbent prepared in Example 2 and a traditional adsorbent treat high-boron brine. Detailed Embodiments

[0039] To make the technical features, advantages or technical effects in the above technical solutions of the present invention more obvious and understandable, the following is a detailed description through examples.

[0040] Example 1

[0041] (1) Weigh 1 kg of lithium adsorbent powder and 4 kg of a 1% mass concentration hexamethyldisilazane (HMDS) ethanol solution, and mix the two. Stir and react at 60 °C for 4 hours. After the reaction, centrifuge and wash with anhydrous ethanol 3 times to remove the unreacted silane coupling agent and by-products, obtaining a silane coupling agent-modified adsorbent powder.

[0042] (2) Weigh 1 kg of the silane coupling agent-modified adsorbent powder and 4 kg of a 1% mass concentration perfluorohexyltriethoxysilane (F6-TES) ethanol solution, and mix the two. Pass N2 gas for 20 minutes. Stir and react at 50 °C for 2 hours. After the reaction, centrifuge and wash with anhydrous ethanol 3 times to remove the unreacted fluorination modifier and by-products, obtaining a fluorinated-modified adsorbent powder.

[0043] (3) Weigh 1 kg of the fluorinated-modified adsorbent powder and 2 kg of a 5% mass concentration sorbitol ethanol solution, and mix the two. Stir at room temperature for 3 hours. Dry at 60 °C for 8 hours. After the reaction, centrifuge and wash with anhydrous ethanol 3 times to remove the unreacted competitive agent and by-products, obtaining an anti-boron adsorbent powder.

[0044] Example 2

[0045] (1) Weigh 1.5 kg of lithium adsorbent powder and 7.5 kg of a 2% mass concentration solution of tert-butyldimethylchlorosilane (TBDMCS), and mix the two. Stir and react at 70 °C for 5 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted silane coupling agent and by-products, obtaining the silane coupling agent-modified adsorbent powder.

[0046] (2) Weigh 1.5 kg of the silane coupling agent-modified adsorbent powder and 7.5 kg of perfluorooctyltriethoxysilane (PFOTS) with a 2% mass concentration, and mix the two. Pass in Ar gas for 35 minutes. Stir and react at 65 °C for 3.5 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted fluorination modifier and by-products, obtaining the fluorination-modified adsorbent powder.

[0047] (3) Weigh 1.5 kg of the fluorination-modified adsorbent powder and 4.5 kg of a 7% mass concentration mannitol solution, and mix the two. Stir at room temperature for 4 hours. Dry at 70 °C for 10 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted competitor and by-products, obtaining the boron-resistant adsorbent powder.

[0048] Example 3

[0049] (1) Weigh 2 kg of lithium adsorbent powder and 12 kg of a 3% mass concentration trimethylmethoxysilane (TMMS), and mix the two. Stir and react at 80 °C for 6 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted silane coupling agent and by-products, obtaining the silane coupling agent-modified adsorbent powder.

[0050] (2) Weigh 2 kg of the silane coupling agent-modified adsorbent powder and 12 kg of perfluorobutyltrimethoxysilane (F4-TMS) with a 3% mass concentration, and mix the two. Pass in N2 gas for 50 minutes. Stir and react at 80 °C for 5 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted fluorination modifier and by-products, obtaining the fluorination-modified adsorbent powder.

[0051] (3) Weigh 2 kg of the fluorination-modified adsorbent powder and 8 kg of a 10% mass concentration dulcitol solution, and mix the two. Stir at room temperature for 5 hours. Dry at 80 °C for 12 hours. After the reaction, centrifuge and wash with absolute ethanol 3 times to remove the unreacted competitor and by-products, obtaining the boron-resistant adsorbent powder.

[0052] Adsorbent adsorption experiment:

[0053] Weigh 200 g of the adsorbent powder of the present invention prepared in Example 2 and add it to a conical flask. Prepare 3 L of high-boron brine (composition shown in Table 1) and 5 L of deionized water. Adjust the pH of both to 5.0, and then add them to the conical flask containing the adsorbent. Conduct the adsorption-desorption experiment using a constant temperature and constant oscillator. The adsorption stage lasts for 2 h and the desorption stage lasts for 1 h. Repeat the above operations for 15 cycle experiments.

[0054] Conduct the same above-mentioned experiment on the traditional adsorbent as a control group. After the adsorption and desorption are completed, test each component of the tail brine. The test results are shown in Table 2.

[0055] The lithium adsorption capacity data of the adsorbent of the present invention and the traditional adsorbent are as Figure 2 shown, and the boron impurity concentration data in the desorbing solution are as Figure 3 shown.

[0056] The results show that within the 15 cycles of the cyclic test, the adsorption capacity of the adsorbent of the present invention always remains at about 12.7 mg / g, and the boron-lithium ratio is only 0.3:1. While the adsorption capacity of the traditional adsorbent in high-boron brine is generally about 8.6 mg / g, and the boron-lithium ratio is as high as about 1.5:1. This experiment strongly demonstrates the excellent boron resistance of the adsorbent of the present invention.

[0057] Table 1. Composition of high-boron brine from a salt lake enterprise in Qinghai

[0058] Item Li (mg / L) B (mg / L) B / Li Concentration (mg / L) 546.8 5120.3 9.4:1

[0059] Table 2. Composition of the desorbing solution after the high-boron brine is treated with the adsorbent of the present invention

[0060] Item Li (mg / L) B (mg / L) B / Li Traditional adsorbent 511.4 767.1 1.5:1 Adsorbent of the present invention 768.2 240.6 0.3:1

[0061] Although the present invention has been disclosed above with examples, it is not intended to limit the present invention. Any appropriate modification or equivalent replacement of the technical solutions of the present invention by those of ordinary skill in the art shall be covered within the protection scope of the present invention. The protection scope of the present invention shall be defined by the claims.

Claims

1. A preparation method of a high-boron system lithium ion target adsorbent, characterized in that, It includes the following steps: (1) Disperse the lithium adsorbent powder in an ethanol solution of a silane coupling agent, and carry out a heating and stirring reaction; after the reaction ends, wash to remove the unreacted silane coupling agent and by-products, and obtain the adsorbent powder modified with the silane coupling agent; (2) Disperse the adsorbent powder modified with the silane coupling agent in an ethanol solution of a fluorination modifier, introduce an inert atmosphere, and carry out a heating and stirring reaction; after the reaction ends, wash to remove the unreacted fluorination modifier and by-products, and obtain the adsorbent powder modified with the fluorinating agent; (3) Immerse the adsorbent powder modified with the fluorinating agent in an ethanol solution of a polyol, where the polyol is a competitive agent, carry out stirring at room temperature, and then carry out heating and drying; after the reaction ends, wash several times to remove the unreacted competitive agent and by-products, and obtain the anti-boron adsorption agent powder.

2. The preparation method according to claim 1, characterized in that, In step (1), the silane coupling agent is one or more of trimethylchlorosilane, hexamethyldisilazane, triethylchlorosilane, tert-butyldimethylchlorosilane, trimethylmethoxysilane; the mass concentration of the ethanol solution of the silane coupling agent is 1% - 3%.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the solid-liquid ratio of the lithium adsorbent powder dispersed in the ethanol solution of the silane coupling agent is 1:4 - 1:

6.

4. The preparation method according to claim 1, characterized in that, In step (2), the fluorination modifier is one or more of perfluorooctyltriethoxysilane, perfluorohexyltriethoxysilane, perfluorobutyltrimethoxysilane; the mass concentration of the ethanol solution of the fluorination modifier is 1% - 3%.

5. The preparation method according to claim 1 or 4, characterized in that, In step (2), the solid-liquid ratio of the adsorbent powder modified with the silane coupling agent dispersed in the ethanol solution of the fluorination modifier is 1:4 - 1:

6.

6. The preparation method according to claim 1, characterized in that, In step (3), the polyol is one or more of xylitol, arabinitol, ribitol, mannitol, sorbitol, dulcitol; the mass concentration of the ethanol solution of the polyol is 5% - 10%.

7. The preparation method according to claim 1 or 6, characterized in that, In step (3), the solid-liquid ratio of the adsorbent powder modified with the fluorinating agent immersed in the ethanol solution of the polyol is 1:2 - 1:

4.

8. The preparation method according to claim 1, characterized in that, In step (1), the conditions for heating and stirring are: stirring reaction at 60 - 80 °C for 4 - 6 hours; In step (2), the inert atmosphere is nitrogen or argon, and the introduction time is 20 - 50 minutes; the conditions for heating and stirring are: stirring reaction at 50 - 80 °C for 2 - 5 hours; In step (3), the stirring time at room temperature is 3 - 5 hours, and the heating and drying conditions are drying at 60 - 80 °C for 8 - 12 hours.

9. The preparation method according to claim 1, wherein, In steps (1), (2) and (3), after the reaction ends, centrifuge and wash several times with anhydrous ethanol.

10. A high-boron system lithium ion targeted adsorbent, characterized in that, Prepared by the preparation method described in any one of claims 1 - 9.

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