Aluminum-based lithium adsorbent and preparation method thereof

Abstract

The invention belongs to the technical field of inorganic synthetic adsorption, and particularly relates to a preparation method of a novel hollow nano honeycomb aluminum-based lithium adsorbent. The method comprises the following steps: by taking nano bubbles generated by a black wine effect as a soft template, adding a specific alcohol solvent into a mixed aqueous solution of a lithium source and an aluminum source, generating supersaturated gas in a solvent exchange process by utilizing solubility difference between alcohol and water, and forming stable nano bubbles as the soft template. Then, under the alkaline condition, an aluminum source and a lithium source are subjected to a polymerization reaction on a liquid / gas interface, and the honeycomb-shaped aluminum-based lithium adsorption precursor which is clear in hollow morphology and stable is generated. The precursor material prepared by the method has high specific surface area and high adsorption capacity. The method is simple to operate, green and environment-friendly, does not need to use a high-corrosivity etching agent, avoids damage to a material structure, is suitable for large-scale production, and has a wide application prospect in the field of lithium resource extraction.

Description

Technical Field

[0001] The present invention relates to an aluminum-based lithium adsorbent and a preparation method thereof, and particularly to a preparation method of a hollow nano-honeycomb aluminum-based lithium adsorbent, belonging to the technical field of inorganic synthetic adsorbents. Background Art

[0002] Lithium, as a key strategic resource, plays an important role in modern science and technology and the energy field. Global lithium resources are mainly distributed in ores and salt lakes. Among them, the lithium extraction process from ores is relatively mature. However, due to the limited nature of ore resources and the high energy consumption and high cost of mining, salt lake brines have gradually become the main direction of lithium resource development. Lithium resources in salt lake brines account for more than 60% of the total global lithium resources. Using aluminum salt adsorbents for lithium extraction from salt lakes fully meets the requirements of green production both in terms of the preparation of aluminum salt adsorbents and the lithium extraction process. Aluminum salt adsorbents have the characteristics of simple preparation and good stability. However, the adsorption capacity of aluminum salt adsorbents is relatively low. How to efficiently improve the adsorption capacity is a hot issue in current research.

[0003] Hollow nano materials refer to solid materials with internal cavities and clear boundaries, and their sizes are in the nanometer range. Compared with solid particle materials, hollow nano materials have advantages such as high specific surface area, low density, fast ion transfer rate, and good stability. Such materials have always been a research hotspot in the fields of basic science and engineering technology applications, and there have been many applications in fields such as catalysis, sensing, drug delivery, and adsorption separation. Given the structural advantages of hollow nano materials, hollow nano adsorbents are considered to be an adsorption functional material with great application potential. On the one hand, the adjustable cavity structure provides a pathway for mass diffusion during the adsorption process, reduces the diffusion resistance, and endows the adsorbent with the characteristic of fast adsorption rate. On the other hand, the cavity structure greatly reduces the mass of the adsorbent, increases the number of specific binding sites contained in the adsorbent per unit mass, and endows the adsorbent with good adsorption performance of high adsorption capacity.

[0004] Since hollow nano adsorbents have certain adsorption advantages, researchers have been committed to optimizing the methods for designing and synthesizing hollow nano-structured materials. So far, many technologies for synthesizing hollow nano-structures have been developed, which can be divided into two types: hard template method and soft template method according to different preparation principles. Among them, the soft template method is a commonly used method for preparing hollow nano adsorbents. Since the formation and coating processes of the soft template occur simultaneously, the soft template method is usually a one-step method and does not require the removal of the template. Compared with hard templates, soft templates are easier to remove, avoiding the damage of the material structure caused by removing the template, and at the same time avoiding the use of highly corrosive etching agents. The preparation process is more green and safe. Generally, common soft templates include emulsions, vesicles, and bubbles, etc.

[0005] Nanobubbles are defined as cavities in an aqueous solution with a diameter less than 200 nm. Due to their small size, they have a high specific surface area and a long residence time, which greatly increases the mass transfer efficiency, physical absorption, and the chemical reaction rate at the gas-liquid interface. Nanobubbles have been applied in many industries, such as the manufacture of functional materials, soil and sediment purification, drug delivery, and food disinfection.

[0006] Currently, there are many methods for preparing nanobubbles. The "Ouzo" effect for preparing nanobubbles is a newly proposed chemical method for preparing nanobubbles. The "Ouzo" effect is also known as the suspension emulsion effect, which refers to the phenomenon of producing a milky white suspension when water is added to certain anise-flavored liqueurs or spirits. "Ouzo" is a saturated solution of spirits and essential oils. When this saturated solution is mixed with an aqueous solution, the anise oil will precipitate due to reduced solubility, and the originally clear liquor will turn milky white. This process can spontaneously initiate liquid-liquid nucleation to form stable and uniform emulsion droplets without operations such as stirring or adding surfactants, and this suspension emulsion is very stable and will not show stratification in the short term. Therefore, the problem to be solved urgently is whether an aluminum-based lithium adsorbent with the characteristics of high adsorption capacity and high specific surface area can be prepared based on the above principle. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the present invention uses nanobubbles generated by the "Ouzo" effect as a soft template, and polymerizes and grows aluminum sources and lithium sources at the liquid / gas interface under alkaline conditions to prepare a honeycomb-shaped aluminum-based lithium adsorption precursor with a clear hollow morphology and stability, which has a higher specific surface area and adsorption capacity.

[0008] First, the present invention provides a hollow nano-honeycomb-shaped aluminum-based lithium adsorption precursor. The aluminum-based lithium adsorption precursor is in a hollow nano-honeycomb shape, and the specific surface area of the aluminum-based lithium adsorption precursor is greater than 320 m² / g, and the adsorption capacity is greater than 12 mg / g.

[0009] Second, the present invention also provides a preparation method for the above-mentioned hollow nano-honeycomb-shaped aluminum-based lithium adsorption precursor, which includes the following steps: (1) Add an alcohol solvent to a mixed aqueous solution including a lithium source and an aluminum source to prepare a micro-nano bubble soft template; (2) Stabilize the pH value of the aqueous solution to 5.0 - 9.0 through an alkali source for reaction; (3) After the reaction is completed, obtain the hollow nano-honeycomb-shaped aluminum-based lithium adsorption precursor through aging, filtration, washing with water, and drying.

[0010] Preferably, the lithium source is selected from one or a mixture of lithium hydroxide, lithium chloride, lithium carbonate, lithium citrate, lithium acetate, and lithium formate.

[0011] Preferably, the aluminum source is selected from one or a mixture of several of pseudoboehmite, aluminum chloride, aluminum hydroxide, sodium metaaluminate, hydroxyaluminum oxide, and boehmite.

[0012] Preferably, after the lithium source and the aluminum source are added, the molar ratio of aluminum to lithium elements is ensured to be 2-2.2:1.

[0013] Preferably, the alcohol solvent includes one or more of methanol, ethanol, propanol, and butanol.

[0014] Preferably, the methods used for preparing the aluminum-based adsorption precursor include the co-precipitation method, the one-pot method, and the hydrothermal method.

[0015] Preferably, the base source includes one or more of sodium hydroxide, ammonia water, sodium carbonate, and sodium bicarbonate, and the pH of the aqueous solution is adjusted to 5.0-7.5.

[0016] Preferably, the base source includes one or a mixture of urea and ammonium bicarbonate, the pH of the aqueous solution is adjusted to 6.0-9.0, and the reaction temperature is controlled at 70°C-150°C. The beneficial effects of the present invention are as follows: Compared with the prior art, the present invention innovatively utilizes the significant difference in the solubility of air in different solvents (water and alcohols). By mixing alcohols and water in a specific ratio, during the solvent exchange process, the excess air originally dissolved in the alcohol will precipitate in the form of nano-bubbles due to the decrease in solubility. These nano-bubbles then serve as soft templates, and polymerization and growth reactions occur at the liquid / gas interface between the aluminum source and the lithium source under alkaline conditions, ultimately forming a honeycomb-like aluminum-based lithium adsorbent with a clear hollow structure and excellent stability.

[0017] The precursor material prepared by the present invention exhibits two core advantages: First, its specific surface area is increased by 2.5 times compared with the traditional method, significantly enhancing the contact area between the material and lithium ions; second, the adsorption capacity reaches 15 mg / g, which is 1.7 times higher than that of the control sample, demonstrating excellent lithium adsorption performance. In addition, the preparation process of the present invention is simple to operate and environmentally friendly, without the use of highly corrosive etching agents throughout the process, effectively avoiding the destruction of the material structure, and providing the possibility for large-scale industrial production. Given its significant advantages and broad application prospects in the field of lithium resource extraction, the present invention is expected to become one of the key technologies to promote the efficient recovery and utilization of lithium resources.

[0018] Figure 1 : is the scanning electron microscope (SEM) image of the hollow nano-honeycomb-like aluminum-based lithium adsorbent prepared in Example 1 of the present invention; Figure 2 : Comparative chart of the specific surface area test results of the aluminum-based lithium adsorbents prepared in the examples and comparative examples of the present invention; Figure 3 :Comparison chart of the adsorption capacity test results of the adsorbents prepared in the examples and comparative examples of the present invention. Detailed implementation manners

[0019] The present invention uses the nanobubbles generated by the "ouzo effect" as a soft template, and polymerizes and grows aluminum sources and lithium sources at the liquid / gas interface under alkaline conditions to prepare a honeycomb-shaped aluminum-based lithium adsorbent with a definite hollow morphology and stability, which has a higher specific surface area and adsorption capacity.

[0020] First, the present invention provides a hollow nano-honeycomb-shaped aluminum-based lithium adsorbent, the aluminum-based lithium adsorbent is in a hollow nano-honeycomb shape, and the specific surface area of the aluminum-based lithium adsorbent is greater than 320 m² / g, and the adsorption capacity is greater than 12 mg / g.

[0021] Second, the present invention also provides a preparation method of the above-mentioned hollow nano-honeycomb-shaped aluminum-based lithium adsorbent, which includes the following steps: Adding an alcohol solvent to a mixed aqueous solution including a lithium source and an aluminum source to prepare a micro-nano bubble soft template; Stabilizing the pH value of the aqueous solution to 5.0 - 9.0 through an alkali source for reaction; After the reaction is completed, the hollow nano-honeycomb-shaped aluminum-based lithium adsorbent is obtained through aging, filtration, washing with water, and drying.

[0022] Preferably, the lithium source is selected from one or several mixtures of lithium hydroxide, lithium chloride, lithium carbonate, lithium citrate, lithium acetate, and lithium formate.

[0023] Preferably, the aluminum source is selected from one or several mixtures of pseudo-boehmite, aluminum chloride, aluminum hydroxide, sodium meta-aluminate, hydroxyaluminum oxide, and boehmite.

[0024] Preferably, after the lithium source and the aluminum source are added, the molar ratio of aluminum to lithium elements is ensured to be 2 - 2.2﹕1.

[0025] Preferably, the alcohol solvent includes one or more of methanol, ethanol, propanol, and butanol.

[0026] Preferably, the methods used for preparing the aluminum-based adsorbent include coprecipitation method, one-pot method, and hydrothermal method.

[0027] Preferably, the alkali source includes one or more of sodium hydroxide, ammonia water, sodium carbonate, and sodium bicarbonate, and the pH of the aqueous solution is adjusted to 5.0 - 7.5.

[0028] Preferably, the alkali source includes one or a mixture of urea and ammonium bicarbonate, the pH of the aqueous solution is adjusted to 6.0 - 9.0, and the reaction temperature is controlled at 70℃ - 150℃.

[0029] The test method for the adsorption capacity of the adsorbent in the present invention is as follows: Weigh approximately 10.00 g of the prepared aluminum-based lithium adsorbent sample and place it in a 250 mL mixed solution of LiCl - NaCl (where the mass concentrations of LiCl and NaCl are 5 g / L and 150 g / L respectively). Transfer the mixed system to a constant temperature water bath shaker and conduct the adsorption reaction at a set temperature for a fixed time. After the reaction, centrifuge to separate the solid and liquid phases, and collect the supernatant. Use an inductively coupled plasma optical emission spectrometer (ICP-OES) to measure the residual lithium ion concentration in the supernatant.

[0030] The adsorption capacity (Q t , in mg / g) is calculated by the following formula:

[0031] In the formula: ρ 0 is the initial mass concentration of lithium ions in the solution before adsorption (mg / L); ρ t is the equilibrium mass concentration of lithium ions in the solution after adsorption (mg / L); V is the volume of the adsorption solution (L); m is the mass of the adsorbent (g).

[0032] Example 1: Preparation of a hollow nano honeycomb - shaped aluminum - based lithium adsorbent by coprecipitation method In this example, a hollow nano honeycomb - shaped aluminum - based lithium adsorbent is prepared by coprecipitation method. First, use lithium hydroxide (LiOH) as the lithium source and pseudo - boehmite (AlOOH) as the aluminum source, mix them in a molar ratio of aluminum to lithium of 2:1, add them to deionized water and stir evenly. Subsequently, add ethanol to the mixed solution, with a volume ratio of ethanol to water of 1:3, and use the "Ouzo effect" to generate nano - bubbles as a soft template. Then, adjust the pH of the solution to 6.5 with sodium hydroxide (NaOH) and stir - react at room temperature for 2 hours. After the reaction, age the reaction solution for 12 hours, filter to obtain a filter cake, wash it twice with deionized water, filter again and dry it at 80 °C to finally obtain a hollow nano honeycomb - shaped aluminum - based lithium adsorbent. Its SEM image is as shown in Figure 1 , which shows its honeycomb - shaped structure and hollow morphology. The test results show that the specific surface area of this material is 350 m² / g and the adsorption capacity is 15 mg / g.

[0033] Comparative Example 1: Under the condition of not using ethanol and the nano - bubble soft template, prepare an aluminum - based lithium adsorbent according to the same raw material ratio and reaction conditions. As shown in Figure 2 and Figure 3The test results show that the specific surface area of the control sample is 140 m² / g and the adsorption capacity is 8.8 mg / g. Compared with Example 1, the specific surface area of Example 1 is increased by 2.5 times and the adsorption capacity is increased by 1.7 times.

[0034] Example 2: One-pot preparation of hollow nano-honeycomb aluminum-based lithium adsorbent In this example, a hollow nano-honeycomb aluminum-based lithium adsorbent was prepared by a one-pot method. First, lithium carbonate (Li 2 CO 3 ) was used as the lithium source and aluminum chloride (AlCl 3 ) was used as the aluminum source. They were mixed in a molar ratio of aluminum to lithium of 2.2:1, added to deionized water and stirred evenly. Subsequently, methanol was added to the mixed solution, and the volume ratio of methanol to water was 1:4. The "Ouzo effect" was used to generate nano-bubbles as a soft template. Then, urea was added as the base source to adjust the pH of the solution to 7.0, and the reaction was carried out at 80 °C for 4 hours. After the reaction was completed, the reaction solution was aged for 10 hours, filtered to obtain a filter cake, washed twice with deionized water, filtered again and dried at 90 °C to finally obtain a hollow nano-honeycomb aluminum-based lithium adsorbent. The test results show that the specific surface area of this material is 380 m² / g and the adsorption capacity is 16 mg / g.

[0035] Comparative Example 2: Under the condition of not using methanol and the nano-bubble soft template, an aluminum-based lithium adsorbent was prepared according to the same raw material ratio and reaction conditions. As Figure 2 and Figure 3 the test results show that the specific surface area of the control sample is 150 m² / g and the adsorption capacity is 9.2 mg / g. Compared with Example 2, the specific surface area of Example 2 is increased by 2.5 times and the adsorption capacity is increased by 1.7 times.

Claims

1. A method for preparing an aluminum-based lithium adsorbent, characterized in that The steps include: adding an alcohol solvent into a mixed aqueous solution including a lithium source and an aluminum source to prepare a micro-nano bubble soft template; The pH value of the aqueous solution is stabilized to 5.0-9.0 by an alkali source to carry out the reaction; After the reaction is completed, the hollow nano honeycomb aluminum-based lithium adsorbent is obtained through aging, filtering, washing and drying.

2. The preparation method according to claim 1, characterized in that The aluminum-based lithium adsorbent is in the shape of a hollow nano honeycomb, and has a specific surface area greater than 320 m² / g and an adsorption capacity greater than 12 mg / g.

3. The lithium source is selected from one of lithium hydroxide, lithium chloride, lithium carbonate, lithium citrate, lithium acetate, and lithium formate, or a mixture of several of them.

4. The preparation method according to claim 1, characterized in that: The aluminum source is selected from pseudo-boehmite, aluminum chloride, aluminum hydroxide, sodium aluminate, aluminum oxyhydroxide and boehmite, one of them or a mixture of several thereof.

5. The preparation method according to claim 1, characterized in that: After the lithium source and the aluminum source are added, the molar ratio of aluminum to lithium is ensured to be 2-2.2:

1.

6. The preparation method according to claim 1, characterized in that: The alcohol solvent includes one or more of methanol, ethanol, propanol and butanol; the methods used to prepare the aluminum-based adsorbent include coprecipitation method, one-pot method and hydrothermal method.

7. The preparation method according to claim 1, characterized in that: The alkali source includes one or more of sodium hydroxide, ammonia water, sodium carbonate, and sodium bicarbonate, and the pH of the aqueous solution is adjusted to 5.0-7.

5.

8. The preparation method according to claim 1, characterized in that: The alkaline source includes urea, ammonium bicarbonate or a mixture of the two. The pH of the aqueous solution is adjusted to 6.0-9.0, and the reaction temperature is controlled at 70°C-150°C.

9. An aluminum-based lithium adsorbent, characterized in that The method is prepared by any one of claims 1 to 8.

10. Use of the aluminum-based adsorbent according to claim 9 in lithium extraction by adsorption.

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