CN115715976A - Selective Lithium Ion Adsorption Method Based on Protein/Inorganic Nanoparticle Composite Membrane - Google Patents

Abstract

The invention discloses a method for selectively adsorbing lithium ions based on a protein/inorganic nanoparticle composite membrane, which takes a composite membrane formed by protein and inorganic nanoparticles as an adsorbing material, and selectively adsorbs the lithium ions from a liquid water environment under the condition that the pH value is 5-9; the protein is soybean protein isolate or corn protein, and the inorganic nano-particles are titanium dioxide, zirconium dioxide, manganese dioxide, silicon dioxide or zinc dioxide. The preparation method of the protein/inorganic nano-particle composite membrane is simple, low in cost, good in lithium ion adsorption effect, capable of rapidly and selectively extracting lithium ions from the aqueous solution with the high magnesium-lithium ratio, economical, practical, simple and convenient to operate, and good in popularization and application prospect.

Description

Selective Lithium Ion Adsorption Method Based on Protein/Inorganic Nanoparticle Composite Membrane

technical field

The invention belongs to the technical field of adsorption and separation of lithium ions, and in particular relates to a method for selectively adsorbing lithium ions from a liquid water environment based on a protein/inorganic nanoparticle composite membrane.

Background technique

The total recoverable lithium reserves in the world are about 14 million tons (calculated as lithium metal), and more than 60% of lithium resources are in salt lake brine. Compared with minerals and ores, it is cheaper and easier to extract lithium from liquid lithium resources in terms of both economic and environmental benefits. my country's lithium resources are rich in reserves, mainly distributed in the salt lakes of Qinghai and Tibet, accounting for about 80% of my country's total lithium resources reserves, accounting for 1/3 of the world's total lithium resources reserves. Most foreign salt lakes have a low ratio of magnesium to lithium, and the large-scale production of lithium carbonate products has been realized by the precipitation method. However, salt lake brine in my country generally has a high magnesium-lithium ratio (>30). Due to the similar chemical properties of magnesium and lithium and the small difference in ion hydration radius, the difficulty of separating magnesium and lithium is greatly increased. In addition, there are many coexisting ions (such as K ⁺ , Mg ²⁺ , Ca ²⁺ , Cl ^- , SO ₄ ^{2- ,} etc.) in salt lake brine, which makes the separation of lithium ions more difficult. Therefore, there is an urgent need to develop and perfect technologies for efficient separation of Li ⁺ from low-grade brines.

Membrane technology has been considered as a promising separation method for lithium recovery due to its inherent low energy consumption and high separation efficiency. Many studies have reported that nanofiltration membranes prepared by polyelectrolyte multilayer self-assembly can extract Li ⁺ from brine, but the membrane fouling caused by salting out will greatly reduce its selectivity and permeability. Lithium ion sieves (such as manganese series, titanium series, antimonate, aluminum salt and phosphate type, etc.) have large adsorption capacity and high Li ⁺ selectivity, but the powdered lithium ion sieve adsorbent is difficult to obtain in the process of filtration and recovery. The loss is large, and the dissolution loss during acid elution and desorption is also large. In order to solve the above problems, some studies have inserted lithium ion sieves into polymer membrane matrix to prepare adsorption membranes with the function of adsorbing lithium ions. This type of adsorption membrane combines the advantages of adsorption and membrane separation, and improves the recovery efficiency of lithium ions to a certain extent. However, during the film casting process, since the organic polymer solution enters the pores of the lithium-ion sieve adsorbent, the pores of the adsorbent will be blocked, and the hydrophobicity of the organic polymer will cause the adsorption capacity of the lithium-ion sieve to decrease compared with that of the powder raw material. 20% to 50%.

Contents of the invention

The purpose of the present invention is to overcome the problems existing in the separation of lithium ions by existing adsorption membranes, and provide a method for selectively adsorbing lithium ions based on protein/inorganic nanoparticle composite membranes, which has high adsorption capacity and high adsorption selectivity for lithium ions , Good regeneration performance.

For the above-mentioned purpose, the technical solution adopted in the present invention is to use the protein/inorganic nanoparticle composite membrane as the adsorption material to selectively adsorb lithium ions from liquid water under the condition of pH 5-9; wherein, the protein is soybean protein isolate Or zein, the inorganic nanoparticles are any one of titanium dioxide, zirconium dioxide, manganese dioxide, silicon dioxide, zinc dioxide; preferably the protein is soybean protein isolate, and the inorganic nanoparticles are titanium dioxide. The liquid water is any one of salt lake brine, seawater, and electronic waste (such as lithium ion battery) leaching solution.

The preparation method of the above-mentioned protein/inorganic nanoparticle composite film is as follows: completely dissolve the protein in 0.05-1mol/L NaOH aqueous solution to form a protein solution; then add sodium alginate and inorganic nanoparticles to the protein solution, ultrasonically disperse evenly, and then add Glycerin is used as a plasticizer, after stirring for 6-12 hours, pour the mixture into a mold to dry to form a film, then place the mold in CaCl ₂ aqueous solution, and cross-link at room temperature for 12-24 hours. The membrane was peeled off from the mold, washed with deionized water and dried to obtain a protein/inorganic nanoparticle composite membrane.

In the preparation method of the above-mentioned protein/inorganic nanoparticle composite film, the mass ratio of the protein to sodium alginate and the inorganic nanoparticle is 20-100:1:1-6; the ratio of the added amount of the glycerol to the protein is 1mL : 20～400mg; Described CaCl The concentration of _aqueous solution is 0.5～4mg/mL.

The specific method for the selective adsorption of lithium ions based on the protein/inorganic nanoparticle composite film of the present invention is as follows: adding the protein/inorganic nanoparticle into liquid water, adjusting the pH to 5-9, placing it in an oscillator for 1-2 hours, and performing lithium ion ion adsorption. Further, the protein/inorganic nanoparticle composite membrane can be placed in 0.5-1mol/L HCl aqueous solution after adsorbing lithium ions, and shaken for 10-12 hours. After desorbing the adsorbed lithium ions, the protein/inorganic nanoparticle composite membrane can be reused to adsorb lithium ion. Wherein, the solid-to-liquid ratio of the protein/inorganic nanoparticle composite membrane to liquid water is 0.5-5 g/L.

The beneficial effects of the present invention are as follows:

1) Compared with the powdered lithium ion adsorbent, the present invention loads the inorganic nanoparticles into the protein film, can better disperse the inorganic nanoparticles in the film, and facilitates recycling after adsorption.

2) Compared with the organic polymer membrane-based separation material, the protein membrane material of the present invention has no pollution to the environment, is acid-resistant, does not affect the adsorption capacity of inorganic nanoparticles to lithium ions, and contains a large number of active groups in the protein, which is renewable and reproducible. advantages of biodegradability.

3) The preparation method of the protein membrane material of the present invention is simple and low in cost, and can quickly and selectively extract lithium ions from an aqueous solution with a high magnesium-to-lithium ratio.

Description of drawings

Fig. 1 is the scanning electron micrograph of SPI/TiO ₂ composite film in embodiment 1.

Figure 2 shows the effect of pH on the adsorption performance of SPI/TiO ₂ composite membranes.

Figure 3 is the effect of lithium ion concentration on the adsorption performance of SPI/TiO ₂ composite film.

Figure 4 is the effect of adsorption time on the adsorption performance of SPI/TiO ₂ composite membranes.

Figure 5 shows the adsorption of lithium by the SPI/ _TiO2 composite film in the mixed metal ion solution.

Figure 6 shows the adsorption of lithium ions in simulated seawater by the SPI/TiO ₂ composite membrane.

Figure 7 shows the desorption-adsorption of lithium ions by the SPI/TiO ₂ composite film.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

Add 200 mg of soybean protein isolate (SPI) into 5 mL of 0.1 mol/L NaOH aqueous solution, and stir until the protein is completely dissolved to form a soybean protein isolate solution. Then add 10mg sodium alginate (SA) and 20mg titanium dioxide to the soybean protein isolate solution, and disperse it evenly by ultrasonication for 30 minutes, then add 0.5mL glycerin as a plasticizer, stir and disperse for 6 hours, and pour the mixture into Put it into a polytetrafluoroethylene mold and dry it in an oven at 80°C to form a film. Finally, the membrane was placed in 5 mL of 2 mg/mL _CaCl2 aqueous solution and crosslinked at room temperature for 12 h. After the reaction, the membrane was peeled off from the mold with ethanol, washed with deionized water for 5 times and then dried to obtain the SPI/ _TiO2 composite membrane. It can be seen from the SEM image of Fig. 1 that the _TiO2 nanoparticles are coated in the SPI film.

The above-mentioned SPI/TiO ₂ composite film was used to adsorb lithium ions under different conditions, and the specific experiments were as follows:

1. The effect of pH on the adsorption performance of the composite membrane

Adjust the pH value of 10mL 20mg/L Li ⁺ aqueous solution to 2.3, 3.9, 5.1, 6.7, 8.4, 9.8 respectively, then add SPI/TiO2 _composite membrane (1cm×1cm, 13mg) and shake in a shaker for 2 hours Finally, the content of lithium ions contained in the solution was measured with an atomic absorption spectrophotometer. The results shown in Fig. 2 show that the adsorption rate of the adsorption material to lithium reaches more than 85% in the pH range of 5-9.

2. The effect of lithium ion concentration on the adsorption performance of the composite membrane

Adjust the pH value of 10mL 2～100mg/L Li ⁺ aqueous solution to 7, then add SPI/TiO ₂ composite membrane (1cm×1cm, 13mg) to investigate the adsorption of lithium ions at room temperature, and place it in a shaker After 2 hours, the content of lithium ions contained in the solution was measured with an atomic absorption spectrophotometer. The results in Figure 3 show that the adsorption capacity of lithium increases as the concentration increases, and the maximum saturated adsorption capacity of the film for lithium is 24.4 mg/g.

3. Effect of adsorption time on adsorption performance of composite membrane

The pH value of 10mL 50mg/L Li ⁺ aqueous solution was adjusted to 7, and then SPI/ _TiO2 composite membrane (1cm×1cm, 13mg) was added to investigate the adsorption of lithium ions by the composite membrane at different times, using an atomic absorption spectrophotometer The content of lithium ions contained in the solution. The results shown in Figure 4 show that the adsorption capacity of the membrane for lithium ions rose sharply to 22.3 mg/g in the first 1 hour, then rose slowly and reached equilibrium within 2 hours.

4. Adsorption of Lithium by SPI/TiO ₂ Composite Membrane in Mixed Metal Ion Solution

Prepare a mixed solution of metal ions containing Mg ²⁺ , Ca ²⁺ , Na ⁺ , K ⁺ and Li ⁺ , in which the concentrations of Mg ²⁺ , Ca ²⁺ , Na ⁺ , and K ⁺ ions are all 1ppm or 10ppm or all 50ppm, the concentration of Li ⁺ ions is 1ppm, and adjust the pH value to 7, add SPI/TiO ₂ composite film (1cm × 1cm, 13mg), place it in an oscillator for 2 hours, and use an atomic absorption spectrophotometer Measure the content of lithium ions in the solution. The results in Fig. 5 show that when the Mg/Li ratio is 10 and 50, the obtained separation factor values α are as high as 600 and 1000, respectively, which indicates that when Li ⁺ coexists with other cations, the cations (Mg ²⁺ , Ca ²⁺ , Na ⁺ and K ⁺ ) had no significant effect on Li ⁺ adsorption, indicating that the SPI/TiO ₂ composite membrane had a high selectivity for Li ⁺ at a relatively high Mg ²⁺ /Li ⁺ ratio.

5. Selective extraction of lithium by SPI/TiO ₂ composite membrane in simulated seawater

Prepare simulated seawater containing 1144ppm Mg ²⁺ , 457ppm Ca ²⁺ , 10770ppm Na ⁺ , 332ppm K ⁺ and 0.21ppm Li ⁺ , and adjust the pH value to 7, add SPI/TiO ₂ composite membrane (1cm×1cm, 13mg), After shaking in an oscillator for 2 hours, use an atomic absorption spectrophotometer to measure the content of lithium ions contained in the solution. The results in Figure 6 show that the composite membrane has a good adsorption effect on low-concentration lithium ions at high ion concentrations (1144ppm Mg ²⁺ , 457ppm Ca ²⁺ , 10770ppm Na ⁺ , 332ppmK ⁺ ), and the adsorption of lithium ions The rate can reach 85%.

6. Desorption-adsorption experiment of SPI/TiO ₂ composite film for lithium ions

Add the SPI/ _TiO2 composite membrane (1cm×1cm, 13mg) into 10mL of 20mg/L Li ⁺ aqueous solution with a pH value of 7, place it in a shaker for 2 hours, and add the composite membrane after absorbing lithium ions to the In 50mL 0.5mol/L HCl aqueous solution, shake slowly for 12 hours, and use an atomic absorption spectrophotometer to measure the content of lithium ions contained in the solution. The adsorption experiment was carried out again on the desorbed composite membrane, and the desorption-adsorption was repeated four times. The results show that after four adsorption-desorption, the adsorption rate of lithium can still reach 90% (see Figure 7).

Example 2

In this embodiment, the soybean protein isolate of Example 1 was replaced with equal mass zein, and other steps were the same as in Example ₁ to obtain zein/TiO Composite film.

The pH value of 10mL 2, 10, 20, 50, 100mg/L Li ⁺ aqueous solution was adjusted to 7, and then the zein/ _TiO2 composite film (1cm×1cm, 16mg) was added to investigate the adsorption of lithium ions at room temperature , placed in a shaker and vibrated for 2 hours, the content of lithium ions contained in the solution was measured with an atomic absorption spectrophotometer. The results show that the adsorption capacity of lithium increases with the increase of the concentration, and the maximum saturated adsorption capacity of the membrane for lithium is 27.2 mg/g.

Example 3

In this example, the titanium dioxide in Example 1 was replaced with zirconium dioxide of equal mass, and the other steps were the same as in Example 1 to obtain the SPI/ZrO ₂ composite film.

The pH value of the 10mL 2, 10, 20, 50, 100mg/L Li ⁺ aqueous solution was adjusted to 7 respectively, and then SPI/ZrO in Example 3 was added Composite membrane (1cm × 1cm, 14.5mg) was investigated at _room temperature for For the adsorption of lithium ions, place in an oscillator and vibrate for 2 hours, then use an atomic absorption spectrophotometer to measure the content of lithium ions contained in the solution. The results show that the adsorption capacity of lithium increases with the increase of the concentration, and the maximum saturated adsorption capacity of the film for lithium is 20.1 mg/g.

Example 4

In this example, manganese dioxide, silicon dioxide, and zinc dioxide were used to replace the titanium dioxide in Example 1, and the other steps were the same as in Example 1 to obtain SPI/MnO ₂ , SPI/SiO ₂ , and SPI/ZnO _{2 .} Composite film.

SPI/MnO ₂ (1cm×1cm, 12mg), SPI/SiO ₂ (1cm×1cm, 12mg) and SPI/ZnO ₂ (1cm×1cm, 12mg) composite membranes were added to 10mL of 5mg/L In the Li ⁺ aqueous solution, after being placed in a shaker to vibrate for 2 hours, the content of lithium ions contained in the solution was measured with an atomic absorption spectrophotometer. The results showed that the adsorption rates of lithium ions for SPI/MnO ₂ , SPI/SiO ₂ and SPI/ZnO ₂ composite films were 79.3%, 68.1%, and 61.2%, respectively.

Comparative example 1

In Example 1, titanium dioxide was not added, and other steps were the same as in Example 1 to obtain an SPI/SA composite film.

Add 10 mg of SPI/TiO ₂ composite film, SPI/SA composite film and TiO ₂ powder into 10 mL of 2 mg/L Li ⁺ aqueous solution with a pH value of 7, place them in a shaker for 2 hours, and use atomic absorption spectrophotometry The content of lithium ions contained in the solution was measured. The results showed that the adsorption rates of SPI/TiO ₂ composite film, SPI/SA composite film and TiO ₂ powder to lithium ions were 92.3%, 2.1%, and 78.4%, respectively.

Claims (8)

1. A method for selectively adsorbing lithium ions based on protein/inorganic nanoparticle composite membranes, characterized in that, the method is based on protein/inorganic nanoparticle composite membranes as adsorption material, and the pH is from 5 to 9 under the condition of Selective adsorption of lithium ions in liquid water; The protein is soybean protein isolate or zein, and the inorganic nanoparticles are any one of titanium dioxide, zirconium dioxide, manganese dioxide, silicon dioxide, and zinc dioxide; The preparation method of the protein/inorganic nanoparticle composite film is as follows: the protein is completely dissolved in 0.05-1mol/L NaOH aqueous solution to form a protein solution; then sodium alginate and inorganic nanoparticles are added to the protein solution, and the ultrasonic dispersion is uniform, and then Add glycerin as a plasticizer, stir for 6 to 12 hours, pour the mixture into a mold to dry to form a film, then place the mold in an aqueous CaCl ₂ solution, and cross-link at room temperature for 12 to 24 hours. After the reaction, wash with ethanol The film is peeled off from the mold, washed with deionized water and dried to obtain a protein/inorganic nanoparticle composite film; The liquid water is any one of salt lake brine, sea water, and leach solution of electronic waste. 2. The method for selectively adsorbing lithium ions based on a protein/inorganic nanoparticle composite membrane according to claim 1, wherein the protein is isolated soybean protein, and the inorganic nanoparticle is titanium dioxide. 3. the method based on protein/inorganic nanoparticle composite membrane selective adsorption lithium ion according to claim 1, is characterized in that, in the preparation method of described protein/inorganic nanoparticle composite membrane, protein and sodium alginate, inorganic The mass ratio of the nanoparticles is 20-100:1:1-6. 4. the method based on protein/inorganic nanoparticle composite membrane selective adsorption lithium ion according to claim 1, is characterized in that, in the preparation method of described protein/inorganic nanoparticle composite membrane, the add-on of described glycerol and The ratio of protein 1mL: 20～400mg. 5. the method for selectively adsorbing lithium ions based on protein/inorganic nanoparticle composite film according to claim 1, is characterized in that, in the preparation method of described protein/inorganic nanoparticle composite film, _CaCl The concentration of aqueous solution is 0.5 ~4mg/mL. 6. The method for selectively adsorbing lithium ions based on a protein/inorganic nanoparticle composite membrane according to claim 1, wherein the protein/inorganic nanoparticle is added to liquid water, the pH is adjusted to be 5 to 9, and placed in a shaker Shake in medium for 1-2 hours to carry out lithium ion adsorption. 7. The method for selectively adsorbing lithium ions based on a protein/inorganic nanoparticle composite membrane according to claim 6, wherein the protein/inorganic nanoparticle composite membrane is placed in a 0.5-1mol/L HCl aqueous solution after absorbing lithium ions In the process, shaking for 10-12 hours, after desorbing the adsorbed lithium ions, the protein/inorganic nanoparticle composite film is repeatedly used to adsorb lithium ions. 8. The method for selectively adsorbing lithium ions based on a protein/inorganic nanoparticle composite membrane according to claim 6, wherein the solid-to-liquid ratio of the protein/inorganic nanoparticle composite membrane to liquid water is 0.5 to 5 g/ L.

Images