Crown ether polysulfone membrane for enriching lithium ions in solution and preparation method of crown ether polysulfone membrane

Abstract

The invention relates to the technical field of lithium resource extraction, in particular to a crown ether polysulfone membrane for enriching lithium ions in a solution and a preparation method of the crown ether polysulfone membrane. The crown ether polysulfone membrane is prepared from the following components by mass: 0.15 to 0.30 g of crown ether; 5 g of polysulfone; 50 mL of N, N-dimethyl acetamide; wherein the mass ratio of the crown ether to the polysulfone is 0.03: 1 to 0.06: 1, the membrane is formed by a phase inversion method, and the thickness of the membrane is 250 microns. According to the method, the 12-crown-6 ether is immobilized on the membrane, so that lithium ions can be conveniently enriched and extracted in a solution, and the operation difficulty and the operation cost are reduced. Experimental data show that after adsorption is conducted for 32 h in a lithium chloride solution with the concentration being 80 mg / L, the lithium ion adsorption capacity of the membrane is 9 mg / g, the adsorption capacity of the membrane in a lithium chloride solution with the initial concentration being 100 mg / L can reach 13.5 mg / g, lithium ions can be rapidly and simply enriched in the solution, and the membrane also has certain selective lithium ion adsorption capacity in a lithium-magnesium mixed solution; meanwhile, the problem that most crown ether is easy to lose in a liquid-liquid extraction system is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium resource extraction, and more specifically, to a crown ether polysulfone membrane for enriching lithium ions in a solution and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy industry, the demand for lithium resources at home and abroad has been continuously increasing. Most of China's lithium resources are concentrated in salt lake brines, which poses challenges to traditional salt lake lithium extraction technologies in terms of high operating costs and low separation efficiency. Crown ethers are a series of spherical cavity compounds containing ether bonds. The oxygen atoms of the ether bonds in their structures can form a very strong negative electric potential barrier. Influenced by the Pearson's hard and soft acid-base principle, they are prone to form complexes with alkali metals and alkaline earth metals (hard acids), and thus have selective recognition ability for these metal ions. When the pore diameter of the crown ether is relatively consistent with the diameter of Li+ (0.136 nm), the crown ether can achieve selective adsorption of Li+.

[0003] However, currently, crown ethers are mostly applied in liquid-liquid extraction systems, which easily lead to the loss of crown ethers, and free crown ethers are somewhat toxic. Therefore, immobilizing crown ethers is of great significance for their application in selective lithium extraction. Summary of the Invention

[0004] The purpose of the present invention is to provide a crown ether polysulfone membrane for enriching lithium ions in a solution and a preparation method thereof, which immobilize crown ethers on the membrane and solve the problem of easy loss of crown ethers in liquid-liquid extraction systems.

[0005] To achieve the above purpose, the present invention aims to provide a crown ether polysulfone membrane for enriching lithium ions in a solution, and the crown ether polysulfone membrane is prepared from the following components according to the mass ratio:

[0006] Crown ether: 0.15 - 0.30 g;

[0007] Polysulfone: 5 g;

[0008] N,N-dimethylacetamide: 50 mL;

[0009] Among them, the mass ratio of crown ether to polysulfone is 0.03:1 to 0.06:1, and the membrane is formed by the phase inversion method, and the membrane thickness is 250 μm.

[0010] As a further improvement of this technical solution, the crown ether is 12-crown-6 ether.

[0011] The present invention also provides a preparation method of a crown ether polysulfone membrane for enriching lithium ions in a solution, including the following steps:

[0012] S1. Dissolve the crown ether in N,N-dimethylacetamide, add polysulfone, and stir in an 80 °C oil bath until completely dissolved to form a homogeneous film-forming solution.

[0013] S2. Pour the film-forming solution onto a glass plate and scrape a liquid film with a scraper with a spacing of 250 μm.

[0014] S3. Immerse the glass plate coated with the liquid film in water for phase inversion, take it out after curing, and ventilate and dry for 2 days to obtain a crown ether-polysulfone membrane.

[0015] As a further improvement of this technical solution, the phase inversion conditions are: water temperature 25 - 30 °C, immersion time 5 - 10 seconds.

[0016] As a further improvement of this technical solution, the preparation method further includes the following modification steps: add 0.2 g of polyvinylpyrrolidone (PVP K30 or K90) to the film-forming solution.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] In the present invention, by immobilizing 12-crown-6 ether on the membrane, lithium ions can be conveniently enriched and extracted in the solution, reducing the operation difficulty and operation cost. According to the experimental data, in an 80 mg / L lithium chloride solution, after 32 hours of adsorption, the lithium ion adsorption capacity of this membrane is 9 mg / g, and in a lithium chloride solution with an initial concentration of 100 mg / L, the adsorption capacity can reach 13.5 mg / g. It can quickly and simply enrich lithium ions in the solution, and also has the ability to selectively adsorb lithium ions in a lithium-magnesium mixed solution, and at the same time solves the problem that crown ethers are easily lost in the liquid-liquid extraction system. Description of the Drawings

[0019] Figure 1 It is a graph showing the effect of contact time on the adsorption capacity in the Li+ adsorption experiment of the present invention.

[0020] Figure 2 It is a graph showing the effect of initial solution concentration on the adsorption capacity in the Li+ adsorption experiment of the present invention.

[0021] Figure 3 It is a graph showing the effect of pH value on the adsorption capacity in the Li+ adsorption experiment of the present invention.

[0022] Figure 4 It is a graph showing the effect of contact time on the adsorption capacity in the Mg2+ adsorption experiment of the present invention.

[0023] Figure 5 It is a graph showing the effect of initial solution concentration on the adsorption capacity in the Mg2+ adsorption experiment of the present invention.

[0024] Figure 6It is the influence curve of adsorption temperature on the adsorption capacity in the Mg2+ adsorption experiment of the present invention.

[0025] Figure 7 It is the schematic diagram of the lithium adsorption capacity of this membrane in the mixed solution of the present invention Figure 1 。

[0026] Figure 8 It is the schematic diagram of the lithium adsorption capacity of this membrane in the mixed solution of the present invention Figure 2 。 Specific embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0028] In a specific embodiment, as Figure 1 shown, the present invention provides a crown ether polysulfone membrane for enriching lithium ions in a solution, and the crown ether polysulfone membrane is prepared from the following components according to a mass ratio:

[0029] Crown ether: 0.15 - 0.30 g;

[0030] Polysulfone: 5 g;

[0031] N,N-dimethylacetamide: 50 mL;

[0032] Among them, the crown ether is 12-crown-6 ether, and the mass ratio of the crown ether to the polysulfone is 0.03:1 to 0.06:1. The membrane is formed by the phase inversion method, and the membrane thickness is 250 μm.

[0033] Crown ether (g) Polysulfone (g) Dimethylacetamide (ml) A 0.15 5 50 B 0.2 5 50 C 0.25 5 50 D 0.30 5 50

[0034] The present invention also provides a preparation method of a crown ether polysulfone membrane for enriching lithium ions in a solution, including the following steps:

[0035] Take a certain number of grams of 12-crown-6 ether, dissolve it in 50 ml of N,N-dimethylacetamide. After complete dissolution, take 5 g of polysulfone and oil bath it in an 80°C oil bath until the polysulfone is completely dissolved to obtain a film-forming solution.

[0036] Pour the film-forming solution after the oil bath onto a glass plate and scrape a liquid film with a scraper with a spacing of 250 μm.

[0037] And quickly place it in water for phase inversion, that is, immerse the glass plate coated with the film-forming solution in water, and collect the obtained membrane and dry it in a fume hood for 2 days until it is completely dry. The required crown ether polysulfone membrane can be obtained.

[0038] Take 0.2 g of the crown ether polysulfone membrane and place it in lithium ion and magnesium ion solutions respectively. By controlling the temperature, solution concentration, solution pH, and adsorption time, the ion adsorption effect of the crown ether polysulfone membrane is explored. Dilute the experimental samples under different experimental conditions and measure their solution concentrations with an atomic absorption spectrometer to obtain experimental data. In the experiment, lithium ion solution is prepared with anhydrous lithium chloride, and magnesium ion solution is prepared with magnesium chloride hexahydrate.

[0039] Example 1: Li+ adsorption experiment.

[0040] Effect of contact time on adsorption capacity (as Figure 1 shown).

[0041] Based on the optimal pH value for adsorption, take 0.2 g of membranes A - D and place them in 100 mL conical flasks containing 80 mL of 80 mg / L Li+ ion solution with the adjusted pH value. Control the adsorption time within 0 - 32 h, measure the adsorption capacity at each selected time segment, and explore the effect of this factor on the performance of the polysulfone crown ether membrane in adsorbing metal ions with this data. The time segments are 2 h, 4 h, 8 h, 16 h, and 32 h. And perform fitting of the pseudo - first - order and pseudo - second - order adsorption kinetic models.

[0042] Effect of initial solution concentration on adsorption capacity (as Figure 2 shown).

[0043] Based on the optimal pH value for adsorption and the adsorption equilibrium time, adjust the initial ion concentration gradient of the solution to 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L. Take 0.2 g of membranes A - D and place them in the pre - prepared lithium ion solutions respectively, and explore the adsorption performance of the membrane in different systems of initial ion concentrations. Similarly, fit the Langmuir adsorption isotherm model and the Freundlich adsorption isotherm model, and judge whether it is surface adsorption or multi - layer adsorption based on this.

[0044] Effect of pH value on adsorption capacity (as Figure 3 shown).

[0045] Take 0.2 g of membranes A - D and place them in 100 mL conical flasks containing 80 mL of Li+ ion solution with different pH values of 80 mg / L. Adjust the pH of the initial ion solution to 2, 3, 4, and 5. Conduct static adsorption at room temperature for 72 h to explore the effect of the pH value of the initial solution on the adsorption performance.

[0046] Effect of adsorption temperature on adsorption capacity.

[0047] Based on the optimal pH value and time in the experiment, 0.2 g of membranes A - D were respectively placed in 80 mL of 80 mg / L lithium ion solution, and the temperature during the adsorption process was changed by an oven to explore the relationship between the adsorption temperature and the membrane adsorption performance. The temperature gradient was set as 25 °C, 35 °C, 45 °C, and 55 °C.

[0048] Example 2. Mg2+ adsorption experiment.

[0049] Effect of contact time on the adsorption capacity (as Figure 4 shown).

[0050] Based on the optimal pH value for adsorption, 0.2 g of membranes A - D were respectively placed in 100 mL conical flasks containing 80 mL of 80 mg / L Mg2+ ion solution with the adjusted pH value. The adsorption time was controlled within 0 - 32 h, and the adsorption capacity at each selected time period was measured. Based on this data, the effect of this factor on the performance of polysulfone crown ether membrane in adsorbing metal ions was explored. The time periods were 2 h, 4 h, 8 h, 16 h, and 32 h. And the pseudo - first - order and pseudo - second - order adsorption kinetic models were fitted.

[0051] Effect of initial solution concentration on the adsorption capacity (as Figure 5 shown).

[0052] Based on the optimal pH value for adsorption and the adsorption equilibrium time, the initial ion concentration gradient of the solution was adjusted to 40 mg / L, 60 mg / L, 80 mg / L, and 100 mg / L. 0.2 g of membranes A - D were respectively placed in the pre - prepared magnesium ion solutions, and the adsorption performance of the membranes was explored in different systems of initial ion concentrations. Similarly, the Langmuir adsorption isotherm model and the Freundlich adsorption isotherm model were fitted, and based on this, it was judged whether it was surface adsorption or multi - layer adsorption.

[0053] Effect of pH value on the adsorption capacity.

[0054] 0.2 g of membranes A - D were respectively placed in 100 mL conical flasks containing ion solutions with different pH values of 80 mL of 80 mg / L magnesium ions. The initial pH of the ion solution was adjusted to 2, 3, 4, and 5. Static adsorption was carried out at room temperature for 72 h to explore the effect of the initial solution pH value on the adsorption performance.

[0055] Effect of adsorption temperature on the adsorption capacity (as Figure 6 shown).

[0056] Based on the optimal pH value and time in the experiment, 0.2 g of membranes A - D were respectively placed in the treated magnesium ion solutions, and the temperature during the adsorption process was changed by an oven to explore the relationship between the adsorption temperature and the membrane adsorption performance. The temperature gradient was set as 25 °C, 35 °C, 45 °C, and 55 °C.

[0057] Example 3: Competitive adsorption of lithium and magnesium.

[0058] Take 0.2 g of polyvinylpyrrolidone K30 and K90 respectively in two beakers containing 50 ml of N,N-dimethylacetamide. Then add 0.2 g of 12-crown-6 ether to each of the two beakers. After stirring until completely dissolved, add 5 g of polysulfone to each. Heat in an oil bath at 80 °C until the polysulfone is completely dissolved to obtain a film-forming solution. Pour the film-forming solution after the oil bath onto a glass plate, and use a scraper with a spacing of 250 μm to scrape a liquid film, and quickly place it in water for phase inversion, that is, immerse the glass plate coated with the film-forming solution in water, and collect the obtained film and dry it in a fume hood for 2 days until completely dry. The required modified crown ether polysulfone membrane can be obtained.

[0059]

[0060] The influence of different lithium-magnesium mass ratios on the adsorption effect (as Figure 7 and Figure 8 shown).

[0061] Take an equal volume mixture of a 40 mg / L lithium ion solution and magnesium ion solutions with concentrations of 20 mg / L, 40 mg / L, 60 mg / L, and 80 mg / L respectively to obtain four groups of mixed solutions with a volume of 80 ml each.

[0062] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A crown ether polysulfone membrane for enriching lithium ions in a solution, characterized in that: The crown ether polysulfone membrane is prepared from the following components in proportion by mass: Crown ether: 0.15-0.30 g; Polysulfone: 5g; N,N-dimethylacetamide: 50mL; The mass ratio of crown ether to polysulfone is 0.03:1 to 0.06:1, and the membrane is formed by a phase inversion method with a membrane thickness of 250 μm.

2. The crown ether polysulfone membrane for enriching lithium ions in a solution according to claim 1, characterized in that: The crown ether is 12-crown-6 ether.

3. The method for preparing a crown ether polysulfone membrane for enriching lithium ions in a solution according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Dissolve the crown ether in N,N-dimethylacetamide, add polysulfone, and stir in an 80°C oil bath until completely dissolved to form a uniform film-forming solution; S2, pour the film-forming liquid onto a glass plate and scrape the liquid film with a scraper with a spacing of 250 μm; S3. Immerse the glass plate coated with the liquid film in water for phase inversion, take it out after solidification, and dry it in ventilation for 2 days to obtain a crown ether polysulfone membrane.

4. The method for preparing a crown ether polysulfone membrane for enriching lithium ions in a solution according to claim 1, characterized in that: The phase transformation conditions are: water temperature 25-30° C., immersion time 5-10 seconds.

5. The method for preparing a crown ether polysulfone membrane for enriching lithium ions in a solution according to claim 1, characterized in that: The preparation method further comprises the following modification step: adding 0.2 g of polyvinyl pyrrolidone (PVP K30 or K90) into the film-forming solution.

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