Method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite

Abstract

The invention provides a method for preparing high-purity potassium sulfate from lepidolite lithium extraction waste residues, which comprises the following specific steps: (1) adding the lepidolite lithium extraction waste residues into water, carrying out microwave treatment, and filtering to obtain a purified solution; (2) adjusting the pH value of the purified liquid to 6-8, adding crown ether modified polyvinyl alcohol / glycidyl polyacrylate based magnetic microspheres, repeatedly oscillating, applying a magnetic field effect, carrying out solid-liquid separation, repeatedly adsorbing for 1-3 times, and combining the magnetic microspheres to obtain adsorption microspheres; (3) adding the adsorption microspheres into a sulfuric acid solution, stirring at a high speed, applying a magnetic field effect, and separating out the microspheres to obtain a potassium sulfate solution; and (4) carrying out vacuum concentration on the potassium sulfate solution to obtain high-purity potassium sulfate. The method is simple in preparation process and easy to industrially apply, sodium ions are not introduced in the whole process, the prepared high-purity potassium sulfate product can relieve the requirement for potassium sulfate, and the method has good economic benefits and social benefits and has practical significance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, and in particular to a method for preparing high-purity potassium sulfate from waste residues of lithium extraction from lepidolite. Background Art

[0002] Due to the increasing demand for lithium batteries in recent years and the high economic value of lithium, lepidolite has received widespread attention and has been used in large quantities to extract lithium carbonate. Currently, in the process of extracting and utilizing lepidolite raw materials, the focus is mainly on improving the grade and recovery rate of lithium, fully extracting and utilizing it, and insufficiently extracting and utilizing the resources of other elements. The content of other metal elements in lepidolite raw materials is not low, such as potassium, which is more than 6.5%. However, due to its low economic value, it is not developed and utilized, and the slag after lithium extraction is discarded in the wild as waste ore, resulting in a huge waste of resources and a safety impact on the environment.

[0003] At present, the recovery and purification process of potassium in lepidolite is generally to decarbonize the lithium precipitation mother liquor, then carry out evaporation and concentration, improve the potassium concentration in the mother liquor, then obtain potassium sulfate through flash distillation and solid-liquid separation, that is, utilize the difference of each material solubility at different temperatures, by the process of evaporation and concentration and cooling crystallization, make potassium salt precipitate from solution, add alkaline substances to lepidolite leachate to remove impurities such as magnesium and calcium, obtain lithium sulfate concentrate, then add sodium carbonate to carbonize lithium precipitation, filter and separate to obtain crude lithium carbonate and carbonization mother liquor. Add organic solvent to carbonization mother liquor, change the saturation of sodium sulfate and potassium sulfate, low temperature is conducive to the precipitation of potassium salt, filtrate is carried out evaporation and crystallization, separate and obtain sodium sulfate and sodium precipitation mother liquor, then sodium precipitation mother liquor is cooled, separate and obtain potassium precipitation mother liquor and potassium salt. It can be seen that what lepidolite mother liquor that carries out evaporation and crystallization obtains is sodium-potassium mixed salt, can only be used as waste treatment, causes waste of resources, and the recovery rate of potassium is low, the purity of potassium sulfate is low, and the potassium salt in mixed salt cannot be extracted separately, causes waste of resources.

[0004] Therefore, it is of practical significance to utilize lithium extraction waste residue from lepidolite to produce and recycle high-purity potassium sulfate products and produce high-purity potassium sulfate to alleviate the demand for potassium sulfate. Summary of the Invention

[0005] In view of this, the present invention proposes a method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite.

[0006] The technical solution of the present invention is achieved as follows: A method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite, comprising the following steps: (1) Adding lithium extraction waste residue from lepidolite into water, microwave treatment, and filtering to obtain a purified solution; (2) Adjusting the pH of the purified solution to 6-8, adding crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres, repeatedly shaking, applying a magnetic field, and separating the solid and liquid, and repeatedly adsorbing the purified solution after separating the microspheres with crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres for 1-3 times, and combining the magnetic microspheres to obtain adsorbed microspheres; (3) Adding the adsorbed microspheres to a sulfuric acid solution, stirring at high speed, applying a magnetic field, separating the microspheres, and obtaining a potassium sulfate solution; (4) The potassium sulfate solution is vacuum concentrated to obtain high-purity potassium sulfate.

[0007] Furthermore, in step (1), the solid-liquid ratio of the lithium-extracted lepidolite waste residue to water is 1:10-20 g / mL; and the microwave treatment is performed at 500-600 W and 60-70° C. for 10-20 min.

[0008] Furthermore, in step (2), the preparation method of the crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres is: S1. Add polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) into deionized water, stir for 30-60 min in a boiling water bath, then add liquid paraffin and Tween and continue stirring for 20-30 min, then add hydrochloric acid and dialdehyde polyethylene glycol and continue stirring in a boiling water bath for 10-20 min, centrifuge and wash the product, and dry to obtain polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres; S2. Add polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres into anhydrous ethanol, add crown ether, heat in a water bath, filter and wash, and obtain crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres.

[0009] Furthermore, in step S1, the mass ratio of the polyvinyl alcohol, ferroferric oxide nanomagnetic particles and poly(glycidyl acrylate) is 1:0.1-0.2:0.1-0.2; the solid-liquid ratio of the polyvinyl alcohol to deionized water is 1:10-20 g / mL; and the volume ratio of the deionized water to liquid paraffin, Tween, hydrochloric acid and dialdehyde polyethylene glycol is 1:0.8-1.5:0.1-0.3:0.1-0.3:0.5-0.7.

[0010] Furthermore, in step S2, the crown ether is at least one of 4-aminobenzo-12-crown-4, 4-aminobenzo-15-crown-5, 4-aminobenzo-18-crown-6 or 4-aminobisbenzo-18-crown-6.

[0011] Furthermore, in step S2, the solid-liquid ratio of the polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres to anhydrous ethanol is 1:20-30 g / mL; the water bath heating temperature is 50-70° C., and the heating time is 2-4 hours.

[0012] Furthermore, in step (2), the repeated oscillation time is 30-40 minutes; the intensity of the applied magnetic field is 0.3-0.5T, and the time is 5-10 minutes.

[0013] Furthermore, in step (3), the concentration of the sulfuric acid solution is 0.5-0.8 mol / L; and the solid-liquid ratio of the adsorption microspheres to the sulfuric acid solution is 1:10-15 g / mL.

[0014] Furthermore, in step (3), the rotation speed of the high-speed stirring is 1000-2000 rpm, and the time is 10-15 minutes.

[0015] Furthermore, in step (3), the intensity of the applied magnetic field is 0.3-0.5 T, and the time is 5-10 minutes.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The method of the present invention has a simple preparation process and is easy to industrially apply. No sodium ions are introduced during the entire process. The high-purity potassium sulfate product prepared can alleviate the demand for potassium sulfate, has good economic and social benefits, and is of practical significance.

[0017] 2. The crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres of the present invention have a cavity diameter that matches the radius of potassium ions and can be specifically complexed. By utilizing the crown ether to have high selectivity for potassium ions, the crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres of the present invention preferentially bind to potassium ions, repeatedly adsorb and enrich potassium ions, improve the recovery rate of potassium, reduce residual sodium ions, and achieve rapid separation of sodium and potassium through the action of a magnetic field, avoiding the problems of low efficiency and loss caused by traditional filtration and centrifugation. The invention has low energy consumption, simple operation, is suitable for large-scale production, and converts potassium in lithium extraction waste residue into high value-added products, thereby realizing resource utilization. DETAILED DESCRIPTION

[0018] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0019] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0020] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0021] The crown ether of the present invention is at least one of 4-aminobenzo-12-crown-4, 4-aminobenzo-15-crown-5, 4-aminobenzo-18-crown-6 or 4-aminobisbenzo-18-crown-6.

[0022] Example 1 A method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite, comprising the following steps: (1) Add lithium mica waste residue to water at a solid-liquid ratio of 1:15 g / mL, microwave-treat at 550 W, 65 ° C for 15 min, and filter to obtain a purified solution; (2) The pH of the purified solution was adjusted to 7.5 ± 0.5, and crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres were added. The solution was repeatedly shaken for 35 min, and a 0.4 T magnetic field was applied for 8 min to separate the solid and liquid. The purified solution after separation of the microspheres was repeatedly adsorbed twice with crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres, and the magnetic microspheres were combined to obtain adsorbed microspheres. (3) According to the solid-liquid ratio of 1:13 g / mL, the adsorbed microspheres were added to a 0.7 mol / L sulfuric acid solution, stirred at 1500 rpm for 13 min, and a 0.4 T magnetic field was applied for 8 min to separate the microspheres to obtain a potassium sulfate solution; (4) The potassium sulfate solution is vacuum concentrated to obtain high-purity potassium sulfate.

[0023] Preparation of crown ether modified polyvinyl alcohol / polyglycidyl acrylate based magnetic microspheres: S1, polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) in a mass ratio of 1:0.15:0.15 were added to deionized water, the solid-liquid ratio of polyvinyl alcohol to deionized water was 1:15 g / mL, and the mixture was stirred for 45 min under boiling water bath conditions, and then liquid paraffin and Tween were added, the volume ratio of liquid paraffin, Tween and deionized water was 1:0.2:1, and stirring was continued for 25 min, followed by the addition of hydrochloric acid and dialdehyde polyethylene glycol, the volume ratio of hydrochloric acid, dialdehyde polyethylene glycol and deionized water was 0.2:0.6:1, and stirring was continued in boiling water bath for 15 min. The product was centrifuged and washed, and dried to obtain polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres; S2. Add polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres to anhydrous ethanol at a solid-liquid ratio of 1:25 g / mL, add 4-aminobenzo-18-crown-6, heat in a 60°C water bath for 3 h, filter and wash to obtain crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres.

[0024] Example 2 A method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite, comprising the following steps: (1) Add lithium mica waste residue to water at a solid-liquid ratio of 1:10 g / mL, microwave-treat at 500 W, 60 ° C for 10 min, and filter to obtain a purified solution; (2) The pH of the purified solution was adjusted to 7.5±0.5, and crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres were added. The solution was repeatedly shaken for 30 min, and a 0.3 T magnetic field was applied for 5 min to separate the solid and liquid. The purified solution after separation of the microspheres was repeatedly adsorbed once with crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres, and the magnetic microspheres were combined to obtain adsorbed microspheres. (3) According to the solid-liquid ratio of 1:10 g / mL, the adsorbed microspheres were added to a 0.5 mol / L sulfuric acid solution, stirred at 1000 rpm for 10 min, and a 0.3 T magnetic field was applied for 5 min to separate the microspheres to obtain a potassium sulfate solution; (4) The potassium sulfate solution is vacuum concentrated to obtain high-purity potassium sulfate.

[0025] Preparation of crown ether modified polyvinyl alcohol / polyglycidyl acrylate based magnetic microspheres: S1, polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) in a mass ratio of 1:0.1:0.1 were added to deionized water, the solid-liquid ratio of polyvinyl alcohol to deionized water was 1:10 g / mL, and the mixture was stirred for 30 min under boiling water bath conditions, and then liquid paraffin and Tween were added, the volume ratio of liquid paraffin, Tween and deionized water was 0.8:0.1:1, and stirring was continued for 20 min, followed by the addition of hydrochloric acid and dialdehyde polyethylene glycol, the volume ratio of hydrochloric acid, dialdehyde polyethylene glycol and deionized water was 0.1:0.5:1, and stirring was continued in boiling water bath for 10 min. The product was centrifuged and washed, and dried to obtain polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres; S2. Add polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres to anhydrous ethanol at a solid-liquid ratio of 1:20 g / mL, add 4-aminobenzo-18-crown-6, heat in a 50°C water bath for 2 h, filter and wash to obtain crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres.

[0026] Example 3 A method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite, comprising the following steps: (1) Add lithium mica waste residue to water at a solid-liquid ratio of 1:20 g / mL, microwave-treat at 600 W, 70 °C for 20 min, and filter to obtain a purified solution; (2) The pH of the purified solution was adjusted to 7.5±0.5, and crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres were added. The solution was repeatedly shaken for 40 min, and a 0.5 T magnetic field was applied for 10 min to separate the solid and liquid. The purified solution after separation of the microspheres was repeatedly adsorbed 3 times with crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres, and the magnetic microspheres were combined to obtain adsorbed microspheres. (3) According to the solid-liquid ratio of 1:15 g / mL, the adsorbed microspheres were added to a 0.8 mol / L sulfuric acid solution, stirred at 2000 rpm for 15 min, and a 0.5 T magnetic field was applied for 10 min to separate the microspheres and obtain a potassium sulfate solution; (4) The potassium sulfate solution is vacuum concentrated to obtain high-purity potassium sulfate.

[0027] Preparation of crown ether modified polyvinyl alcohol / polyglycidyl acrylate based magnetic microspheres: S1, polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) in a mass ratio of 1:0.2:0.2 were added to deionized water, the solid-liquid ratio of polyvinyl alcohol to deionized water was 1:20 g / mL, and the mixture was stirred for 60 min under boiling water bath conditions, and then liquid paraffin and Tween were added, the volume ratio of liquid paraffin, Tween and deionized water was 1.5:0.3:1, and stirring was continued for 30 min, followed by the addition of hydrochloric acid and dialdehyde polyethylene glycol, the volume ratio of hydrochloric acid, dialdehyde polyethylene glycol and deionized water was 0.3:0.7:1, and stirring was continued in boiling water bath for 20 min. The product was centrifuged and washed, and dried to obtain polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres; S2. Add polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres to anhydrous ethanol at a solid-liquid ratio of 1:30 g / mL, add 4-aminobenzo-18-crown-6, heat in a 70°C water bath for 4 h, filter and wash to obtain crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres.

[0028] Comparative Example 1 The difference from Example 1 is that: crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres are not used, that is, traditional evaporation crystallization is used, and the rest is the same as Example 1.

[0029] The invention relates to a method for preparing high-purity potassium sulfate from lithium extraction waste residue of lepidolite, which specifically comprises the following steps: using the lepidolite waste residue as raw material, performing dissolution, neutralization reaction, impurity removal and filtration, concentration, crystallization, centrifugation and drying to obtain potassium sulfate.

[0030] Test Case The high-purity potassium sulfate prepared in Examples 1-3 and Comparative Example 1 was tested, and the results are shown in Table 1.

[0031] The calculation formula for the yield of potassium sulfate is: Potassium sulfate yield W = (actual production capacity / theoretical production capacity) × 100% Actual production capacity refers to the potassium sulfate equivalent (including process quantity) produced by process equipment in production (laboratory), and theoretical production capacity refers to the equivalent calculated through theoretical data.

[0032] Potassium sulfate purity is determined by measuring the difference between the mass of the sample to be tested and the mass of the product after the chemical reaction to calculate the potassium sulfate content. Specifically, the sample to be tested reacts with a specific reagent to generate a precipitate or a weighable product, and the potassium sulfate content is calculated by weighing it.

[0033] Table 1

[0034] As can be seen from Table 1, the potassium sulfate prepared in Examples 1-3 of the present invention has a high yield and high purity. This is because crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres are used. The cavity diameter of the crown ether matches the radius of potassium ions, which can be specifically complexed. The crown ether has high selectivity for potassium ions, and potassium ions are repeatedly adsorbed and enriched, thereby improving the recovery rate and purity of potassium. Comparative Example 1 uses traditional evaporative crystallization, and the product obtained is actually a sodium-potassium mixed salt, with a low potassium recovery rate and a low purity of potassium sulfate.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite, characterized in that: The specific steps include: (1) Adding lithium extraction waste residue from lepidolite into water, microwave treatment, and filtering to obtain a purified solution; (2) Adjusting the pH of the purified solution to 6-8, adding crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres, repeatedly shaking, applying a magnetic field, and separating the solid and liquid, and repeatedly adsorbing the purified solution after separating the microspheres with crown ether-modified polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres for 1-3 times, and combining the magnetic microspheres to obtain adsorbed microspheres; (3) Adding the adsorbed microspheres to a sulfuric acid solution, stirring at high speed, applying a magnetic field, separating the microspheres, and obtaining a potassium sulfate solution; (4) The potassium sulfate solution is vacuum concentrated to obtain high-purity potassium sulfate.

2. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 1, wherein: In step (1), the solid-liquid ratio of the lithium-extracted lepidolite waste residue to water is 1:10-20 g / mL; and the microwave treatment is performed at 500-600 W and 60-70° C. for 10-20 min.

3. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 1, wherein: In step (2), the preparation method of the crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres is: S1. Add polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) into deionized water, stir for 30-60 min in a boiling water bath, then add liquid paraffin and Tween and continue stirring for 20-30 min, then add hydrochloric acid and dialdehyde polyethylene glycol and continue stirring in a boiling water bath for 10-20 min, centrifuge and wash the product, and dry to obtain polyvinyl alcohol / poly(glycidyl acrylate)-based magnetic microspheres; S2. Add polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres into anhydrous ethanol, add crown ether, heat in a water bath, filter and wash, and obtain crown ether-modified polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres.

4. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 3, wherein: In step S1, the mass ratio of the polyvinyl alcohol, ferroferric oxide nanoparticles and poly(glycidyl acrylate) is 1:0.1-0.2:0.1-0.2; the solid-liquid ratio of the polyvinyl alcohol to deionized water is 1:10-20 g / mL; and the volume ratio of the deionized water to liquid paraffin, Tween, hydrochloric acid and dialdehyde polyethylene glycol is 1:0.8-1.5:0.1-0.3:0.1-0.3:0.5-0.

7.

5. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 3, wherein: In step S2, the crown ether is at least one of 4-aminobenzo-12-crown-4, 4-aminobenzo-15-crown-5, 4-aminobenzo-18-crown-6 or 4-aminobisbenzo-18-crown-6.

6. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 3, wherein: In step S2, the solid-liquid ratio of the polyvinyl alcohol / polyglycidyl acrylate-based magnetic microspheres to anhydrous ethanol is 1:20-30 g / mL; the water bath heating temperature is 50-70° C., and the heating time is 2-4 hours.

7. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 1, wherein: In step (2), the repeated oscillation time is 30-40 minutes; the intensity of the applied magnetic field is 0.3-0.5T, and the time is 5-10 minutes.

8. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 1, wherein: In step (3), the concentration of the sulfuric acid solution is 0.5-0.8 mol / L; the solid-liquid ratio of the adsorption microspheres to the sulfuric acid solution is 1:10-15 g / mL.

9. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite as claimed in claim 1, wherein: In step (3), the rotation speed of the high-speed stirring is 1000-2000 rpm, and the time is 10-15 minutes.

10. The method for preparing high-purity potassium sulfate from lithium-extracting waste residue of lepidolite according to claim 1, wherein: In step (3), the intensity of the applied magnetic field is 0.3-0.5 T, and the time is 5-10 minutes.

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