A high-adsorption salt lake lithium extraction adsorbent and a preparation method thereof

Abstract

This invention belongs to the field of materials technology, specifically relating to a high-adsorption-capacity lithium extraction adsorbent from salt lakes and its preparation method. The method involves first preparing a packing support, then dissolving AlCl3 and NaAlO2 in a mixed solution of boric acid and sodium hexametaphosphate, respectively. The packing support is added to the AlCl3-containing mixed solution, allowed to stand, and then a mixed solution containing NaAlO2 and a LiCl solution are added. Ammonia solution is then slowly added, controlling the pH at 4-5 and the temperature at 50-60℃. After centrifugation, the precipitate is dried. After elution for 5-8 hours, a high-adsorption-capacity lithium extraction adsorbent from salt lakes is obtained. In this invention, the adsorbent is LiAl-LDHs, a type of adsorbent composed of monovalent Li... + and trivalent Al 3+ The unique layered material composed of Li + By selectively entering the solid phase to form LiAl-LDHs, the adsorbent of this invention exhibits excellent performance in the field of lithium extraction from salt lakes.

Description

Technical Field

[0001] This invention belongs to the field of materials technology and relates to a lithium extraction adsorbent from salt lakes and its preparation method, specifically a high-adsorption-capacity lithium extraction adsorbent from salt lakes and its preparation method. Background Technology

[0002] With the increasing global demand for renewable energy, lithium batteries have become one of the core components of modern energy storage solutions. Lithium resources exist primarily in three forms: brine lithium deposits in closed basins, pegmatite-type hard rock lithium deposits, and sedimentary clay lithium deposits. These are mainly distributed in Bolivia, Argentina, the United States, Chile, and Australia. Brine lithium resources are highly concentrated in the arid zones of the Northern and Southern Hemispheres. Only five salt lakes possess more than 1 million tons of metallic lithium resources, and only 16 possess more than 100,000 tons, located in Bolivia, Chile, China, Argentina, the United States, and Canada, with China accounting for five of them.

[0003] In terms of reserves, my country has proven lithium resources of 6.8 million tons, including salt lakes and hard-rock lithium deposits. Salt lake brine is the main form of lithium resources in my country, primarily located in the inland plateau salt lakes of Qinghai and Tibet. In terms of mineral grade, my country's hard-rock lithium deposits are mainly composed of lower-quality lepidolite, while salt lake brine deposits generally have low lithium content, such as K... + Na + Ca 2+ Mg 2+ Due to the high content of impurities and the difficulty of extraction, some high-quality salt lake lithium resources are distributed in ecologically fragile or harsh natural conditions such as Tibet and Sichuan, resulting in slow development and utilization. This has led to high extraction costs for lithium resources in my country and mining profitability that is far lower than international levels.

[0004] It is evident that my country's lithium resources primarily originate from ores and brine from salt lakes, with the latter accounting for approximately 60% of the total. Compared to ores, extracting lithium from brine has lower production costs and is less challenging, with a smaller environmental impact beyond a slight water footprint. Therefore, a crucial approach to achieving a sustainable lithium supply is to develop a promising method for extracting lithium from brine. However, lithium in brine is typically accompanied by high concentrations of cations such as Mg2+. 2+ Na + K + and Ca 2+ These cations, especially Mg 2+ Mg has properties similar to Li+, which makes lithium recovery from brine challenging. Traditionally, when Mg... 2+ / Li + When the MgO ratio is below 6, lithium can be economically extracted using the soda ash precipitation method. However, when MgO... 2+ / Li +At relatively high concentrations, the cost of the sedimentation process increases significantly. It is noteworthy that large quantities of brine have high magnesium content. 2+ / Li + The ratio, especially in China. In this case, people have proposed using high Mg ratios. 2+ / Li + Alternative technologies for lithium extraction from saline solutions include adsorption, nanofiltration, electrodialysis, reverse osmosis, and evaporation concentration.

[0005] Adsorption is not only a key step in the lithium extraction process, but is also considered the most direct technique for extracting lithium from brine, especially in brines with low grade and high Mg content. 2+ / Li + Compared to brine, brine offers advantages such as lower pretreatment requirements, higher lithium selectivity and recovery rate, higher concentration efficiency, cost-effectiveness, and environmental friendliness. It is worth noting that lithium recovery efficiency significantly depends on the lithium adsorbent. The selection of a lithium adsorbent typically depends on its performance (including adsorption capacity, selectivity, stability, and recyclability), its structure (including macroscopic and microscopic structures), and the characteristics of the brine (including pH, lithium concentration, temperature, and Mg content). 2+ / Li + (Ratios, etc.). Currently, lithium adsorbents in the industry are in powder form, which is greatly affected by the preparation and molding process, resulting in poor flowability and permeability, and easy loss of adsorbent during production. In addition, due to the poor flowability of powder, it is prone to problems such as dissolution damage, large pressure difference, equipment blockage, and dust explosion, which reduces its sustainability and efficiency of recycling.

[0006] Fly ash is the fine ash collected from the flue gas after coal combustion, and it is a major solid waste discharged from coal-fired power plants. The main oxide components of fly ash from my country's thermal power plants are: SiO2, Al2O3, FeO, Fe2O3, CaO, and TiO2. The alumina content in fly ash is generally around 40%, but can reach as high as 50% in some areas. With the development of the power industry, the amount of fly ash emitted by coal-fired power plants has been increasing year by year, becoming one of the largest industrial waste emissions in my country. Summary of the Invention

[0007] This invention overcomes the above-mentioned shortcomings and provides a high-adsorption-capacity lithium extraction adsorbent from salt lakes and its preparation method. This invention features low-cost and environmentally friendly lithium recovery.

[0008] The technical solution of this invention is as follows: A method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes includes the following steps: (1) Mix fly ash, kaolin, attapulgite and pore-forming agent, mix the material with water, grind, centrifuge, take the precipitate and squeeze, and then calcine at 500~600℃ for 2~3h to obtain the treated filler carrier; (2) Dissolve AlCl3 and NaAlO2 in a mixed solution of boric acid and sodium hexametaphosphate respectively. Add filler carrier to the mixed solution of AlCl3, let it stand for 3-6 hours, then add NaAlO2 mixed solution and LiCl solution, and then slowly add ammonia solution, controlling the pH value at 4-5 and the temperature at 50-60℃. (3) After centrifugation, the precipitate is dried; (4) Elute in deionized water for 5-8 hours to obtain a high-adsorption-capacity lithium-extraction adsorbent from salt lakes.

[0009] In the above method, in step (1), the pressing is to press the precipitate into a spherical state.

[0010] In the above method, in step (1), the material and water are added at a mass ratio of 1 to 2:1.

[0011] In the above method, in step (1), the mass ratio of fly ash, kaolin, attapulgite and pore-forming agent is 5~10:15~20:5~10:8~10; the pore-forming agent is starch.

[0012] In the above method, in step (2), the molar ratio of boric acid to sodium hexametaphosphate in the mixed solution of boric acid and sodium hexametaphosphate is 1~2:1; the concentration of boric acid in the mixed solution is 1~2g / L.

[0013] In the above method, in step (2), the concentration of AlCl3 in the mixed solution is 10-30 g / L, and the concentration of NaAlO2 in the mixed solution is 5-20 g / L.

[0014] In the above method, in step (2), the concentration of the LiCl solution in the mixed solution is 1.5~10 g / L.

[0015] In the above method, the adsorption capacity of the adsorbent is 2.0-4.0 mg / g.

[0016] The adsorbent described in this invention is used for lithium extraction from salt lakes.

[0017] This invention maximizes the utilization of porous fly ash to provide a carrier for the subsequent synthesis of LiAl-LDHs, thus achieving a certain degree of waste utilization, turning waste into treasure, and reducing environmental pressure. The use of a crystallization method to directly generate aluminum hydroxide crystals on the surface of the packing material effectively improves the strength and adsorption capacity of the aluminum-based adsorbent. This method provides that the fly ash particles used in this invention have a porous honeycomb structure, a large specific surface area, and high adsorption activity, with a particle size range of 300~600μm. They possess a porous structure with a porosity as high as 50%-80%, exhibiting strong water absorption.

[0018] In step 1 of this invention, a porous filler carrier is synthesized. A pore-forming agent ensures uniform pore distribution within the filler carrier. Simultaneously, kaolin and attapulgite also shape the internal porous filler channels, with the attapulgite acting as a binder for fly ash. In step 2, a mixed solution of boric acid and sodium hexametaphosphate, along with precise pH control, results in the final synthesis of spherical structures loaded with LiAl-LDHs. In this application, pH and the synthesis temperature of 50-60°C are key parameters. The applicant has verified that these conditions play a crucial role in the formation of layered crystals. Exceeding these temperatures and pH values ​​will cause the generated LiAl-LDHs to dissolve, forming powder after drying.

[0019] The adsorption principle of this invention is: The adsorbent of this invention can be used as Li in various cationic saline solutions. + Selective capture materials, namely Li + Li+ selectively enters the solid phase to form LiAl-LDHs, while other ions remain in the liquid phase. This is because Li+ can bind to the structural vacancies of LiAl-LDHs. Due to the memory effect and steric hindrance effect, highly selective adsorption of Li+ from the brine is achieved, while other impurity ions cannot enter. LiAl-LDHs are a type of brine composed of monovalent Li+. + and trivalent Al 3+ A unique layered material. Li + They are embedded in the lattice vacancies in the octahedral framework of Al(OH)3, resulting in a positively charged structure.

[0020] Compared with the prior art, the advantages of the present invention are: The adsorbent in this invention is a spherical lithium adsorbent, which has the characteristics of high strength, low solubility, strong adsorption capacity and good regeneration performance. The adsorbent of this invention has excellent performance in lithium extraction from salt lakes. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the high-adsorption-capacity lithium extraction adsorbent from salt lakes obtained in Example 1.

[0022] Figure 2This is a scanning electron microscope (SEM) image of the high-adsorption-capacity lithium extraction adsorbent from salt lakes obtained in Example 1.

[0023] Figure 3 This is a schematic diagram of the device structure in Example 3. Detailed Implementation Example 1

[0024] (1) Mix 5kg fly ash, 20kg kaolin, 7kg attapulgite and 8kg starch, mix the materials with 25kg water, grind, centrifuge, take the precipitate, squeeze into a spherical state, and then calcine at 5℃ for 3h to obtain the treated filler carrier. (2) First, take 100g of boric acid and 100g of sodium hexametaphosphate and add them to 100L of water to prepare a mixed solution of boric acid and sodium hexametaphosphate; take 1500g of AlCl3 and 700g of NaAlO2 and dissolve them in the mixed solution of boric acid and sodium hexametaphosphate (50L each); add 15kg of filler carrier to the mixed solution of AlCl3 and let it stand for 5h; then place the solution in a water bath and control the water bath temperature at 55℃; add the mixed solution of NaAlO2 and 50L of LiCl solution (15g / L), and then slowly add ammonia solution to control the pH value at 4~5; (3) Centrifuge at 150 r / min for 20 min and dry the precipitate; (4) Elute in deionized water for 5 hours to obtain a high-adsorption-capacity lithium-extraction adsorbent from salt lakes.

[0025] The electron micrograph of the adsorbent obtained in this embodiment is shown below. Figure 1 and Figure 2 As shown in the scanning electron microscope image, the lithium adsorbent exhibits good stability, is spherical with uniform size, and possesses excellent adsorption properties and mechanical strength. Example 2

[0026] (1) Mix 8kg fly ash, 15kg kaolin, 5kg attapulgite and 8kg starch, mix the materials with 18kg water, grind, centrifuge, take the precipitate, squeeze into a spherical state, and then calcine at 500℃ for 3h to obtain the treated filler carrier. (2) First, take 100g of boric acid and 100g of sodium hexametaphosphate and add them to 100L of water to prepare a mixed solution of boric acid and sodium hexametaphosphate; take 1500g of AlCl3 and 700g of NaAlO2 and dissolve them in the mixed solution of boric acid and sodium hexametaphosphate (50L each); add 15kg of filler carrier to the mixed solution of AlCl3 and let it stand for 5h; then place the solution in a water bath and control the water bath temperature at 55℃; add the mixed solution of NaAlO2 and 50L of LiCl solution (15g / L), and then slowly add ammonia solution to control the pH value at 4~5; (3) Centrifuge at 150 r / min for 20 min and dry the precipitate; (4) Elute in deionized water for 5 hours to obtain a high-adsorption-capacity lithium-extraction adsorbent from salt lakes. Example 3

[0027] Method A: Take the adsorbent obtained in Example 1, take 80g of lithium adsorbent, clean it thoroughly, and then pack it into a column using a wet method (e.g., Figure 3 The apparatus simulates industrial operating conditions, passing brine from a salt lake in Qinghai downstream through a resin column for treatment, with samples taken at intervals for analysis. The test results showed that the lithium ion content in the brine from this Qinghai salt lake was 0.533 mg / g.

[0028] Method B: Reload the adsorbent from Method A into a new resin column and use... Figure 3 The apparatus was used to elute with deionized water, and the eluent was collected in stages (every 2 hours) for analysis.

[0029] Detailed parameters are shown in Table 1 Table 1

[0030] Adsorption capacity = Cumulative adsorption amount / Mass of lithium adsorbent Desorption capacity = Desorption amount / Lithium adsorbent mass Desorption rate = Desorption capacity / Adsorption capacity × Adsorption mass.

Claims

1. A method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes, characterized in that, Includes the following steps: (1) Mix fly ash, kaolin, attapulgite and pore-forming agent, mix fly ash, kaolin, attapulgite and pore-forming agent with water, grind, centrifuge, take the precipitate and squeeze, and then calcine at 500~600℃ for 2~3h to obtain the treated filler carrier; (2) Dissolve AlCl3 and NaAlO2 in a mixed solution of boric acid and sodium hexametaphosphate respectively. Add a filler carrier to the mixed solution containing AlCl3, let it stand for 3-6 hours, then add a mixed solution containing NaAlO2 and LiCl solution, and then slowly add ammonia solution, controlling the pH value at 4-5 and the temperature at 50-60℃. (3) After centrifugation, the precipitate is dried; (4) Elute in deionized water for 5-8 hours to obtain a high-adsorption-capacity lithium-extraction adsorbent from salt lakes.

2. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (1), the extrusion is to compress the precipitate into a spherical shape.

3. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (1), the mixture of fly ash, kaolin, attapulgite and pore-forming agent is added to water at a mass ratio of 1 to 2:

1.

4. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (1), the mass ratio of fly ash, kaolin, attapulgite and pore-forming agent is 5~10:15~20:5~10:8~10; the pore-forming agent is starch.

5. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (2), the molar ratio of boric acid to sodium hexametaphosphate in the mixed solution of boric acid and sodium hexametaphosphate is 1~2:1; the concentration of boric acid in the mixed solution is 1~2 g / L.

6. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (2), the concentration of AlCl3 in the mixed solution is 10~30 g / L, and the concentration of NaAlO2 in the mixed solution is 5~20 g / L.

7. The method for preparing a high-adsorption-capacity lithium extraction adsorbent from salt lakes according to claim 1, characterized in that, In step (2), the concentration of the LiCl solution in the mixed solution is 1.5~10 g / L.

8. A high-adsorption-capacity lithium extraction adsorbent from salt lakes prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The adsorption capacity of the adsorbent is 2.0-4.0 mg / g.

9. The adsorbent of claim 8 is used in lithium extraction from salt lakes.

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