Method for separating and extracting ion-type rare earth by membrane

Abstract

The application discloses a membrane separation and extraction method for ionic rare earth, and belongs to the technical field of rare earth extraction, which is used for solving the technical problems of great environmental pollution, low extraction rate and difficult membrane direct filtration separation and extraction of ionic rare earth from rare earth minerals in the prior art. The membrane separation and extraction method for ionic rare earth comprises the following steps: loading dry ionic rare earth minerals into a leaching column, adding a wetting liquid into the leaching column, making the wetting liquid completely immerse the ionic rare earth minerals, keeping the wetting at room temperature for 2-3 hours, and then using a leaching liquid for leaching and elution. The elution process of the rare earth minerals is optimized, and the prepared adsorption filler is matched with each other, so that the extraction rate of the ionic rare earth and the adsorption capacity of the adsorption filler to the ionic rare earth are effectively improved, and the pollution of the ionic rare earth extraction to the ecological soil and the production cost are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of rare earth extraction technology, specifically to a membrane separation extraction method for ionic rare earths. Background Technology

[0002] Ionic rare earth minerals are those in which rare earth ions are adsorbed in ionic form onto minerals such as kaolin and montmorillonite. They mostly resemble soil and have a content of 0.3-0.05%, and can be extracted using electrolyte leaching. Ionic rare earth minerals are an important strategic resource for my country, and their extraction technology is directly related to resource utilization and environmental protection.

[0003] Existing technologies for extracting rare earth elements from rare earth minerals typically involve leaching with high-concentration sulfuric acid or hydrochloric acid. To improve the extraction rate of ionic rare earth elements, various ammonia nitrogen compounds are added. This results in the discharge of large amounts of acidic wastewater, and the leachate contains high levels of impurity ions such as iron and aluminum, significantly increasing subsequent separation costs. Furthermore, ammonia nitrogen compounds and other substances remain in the mineral soil for extended periods, causing severe pollution to the soil environment. Membrane separation technology uses nanofiltration to separate rare earth ions from alkaline earth elements, avoiding the need for eluent concentration and reducing production costs. However, during membrane separation for extracting ionic rare earth elements, the ionic rare earth elements often form a gel-like substance that clogs the membrane pores, making membrane separation difficult.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a membrane separation and extraction method for ionic rare earths, which solves the technical problems of high environmental pollution, low extraction rate, and difficulty in direct membrane filtration separation and extraction of ionic rare earths in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A membrane separation and extraction method for ionic rare earth elements includes the following steps:

[0008] S1. Dry ion-adsorption rare earth ore is loaded into a leaching column, and wetting solution is added to the leaching column so that the wetting solution completely covers the ion-adsorption rare earth ore. The ore is kept at room temperature for 2-3 hours, and then leaching and eluting are carried out using the leaching solution to obtain the eluent.

[0009] S2. The eluent is transferred to a pH adjustment tank to adjust the pH of the system to 5.7-5.9. After filtration, the filtrate is passed through a nanofiltration membrane module filled with adsorption packing material for nanofiltration adsorption and desorption elution to prepare nanofiltration concentrate.

[0010] S3. After alkaline precipitation, the nanofiltration concentrate is filtered and calcined to prepare ionic rare earth elements.

[0011] Furthermore, in step S1, the volume ratio of the wetting solution to the leaching solution is 1:3, the aspect ratio of the leaching column is 3:1, and a filter cloth is installed at the bottom of the leaching column. The wetting solution is obtained by adjusting the pH of a 0.3-0.5 mol / L magnesium sulfate solution composed of magnesium sulfate and purified water to 3-3.6 with sulfuric acid. The leaching solution is obtained by adjusting the pH of a 0.08-0.12 mol / L magnesium sulfate solution composed of magnesium sulfate and purified water to 5 with sulfuric acid.

[0012] Further, in step S2, the nanofiltration adsorption membrane assembly includes a dialysis membrane bag and adsorption packing material. The adsorption packing material is placed inside the dialysis membrane bag, and the molecular weight cutoff of the dialysis membrane bag is 13,000-15,000. The desorption elution method is as follows: the adsorption-saturated adsorption packing material is added to the elution column, the eluent is circulated and eluted for 30-50 minutes, and then purified water is circulated and eluted for 20-30 minutes. The eluents are combined to obtain nanofiltration concentrate. The adsorption packing material is removed from the elution column and washed with purified water until neutral to obtain regenerated adsorption packing material. The volume ratio of the adsorption-saturated adsorption packing material, the eluent, and the purified water is 1:7:3. The eluent is a 0.8-1.2 mol / L sulfuric acid aqueous solution, and the aspect ratio of the elution column is 8:1.

[0013] Furthermore, in step S3, the preparation method of ionic rare earth is as follows: sodium hydroxide is added to the nanofiltration concentrate to adjust the pH of the system to 10, the mixture is filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80℃ and dried for 4-6 hours, and then transferred to a calcination furnace at a temperature of 500-550℃ and calcined for 3-5 hours to obtain ionic rare earth.

[0014] Furthermore, the adsorption packing is obtained by the following steps:

[0015] A1. Add graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, and sodium hydroxide to deionized water and ultrasonically disperse for 40-60 min. While stirring, add emulsion to the reaction system and stir for 20-30 min. Raise the reaction temperature to 60-70℃, add epoxy resin solution to the reaction system, and keep the reaction at this temperature for 2-3 h. Post-treatment is then performed to adsorb the filler precursor.

[0016] The synthesis reaction mechanism of the adsorption filler precursor is as follows:

[0017] During the reaction, graphene oxide, sulfonated cellulose, and hydroxypropyl distarch phosphate were dispersed in a sodium hydroxide solution and then emulsified. Epoxy resin was added to the solution. Under alkaline conditions, the epoxy groups and hydroxyl groups on the epoxy resin molecules underwent ring-opening condensation, promoting the adhesion and solidification of the dispersed particles to form spherical particles, thus preparing the adsorption filler precursor.

[0018] A2. Mix and stir the adsorption packing precursor, triethoxysilane-modified PAN and anhydrous ethanol. Raise the temperature of the reaction system to 50-60℃, add the catalyst to the reaction system, keep the reaction at this temperature for 80-90 min, and then perform post-treatment to obtain the adsorption packing.

[0019] The synthesis reaction mechanism of the adsorption filler is as follows:

[0020] During the reaction, the siloxane bonds on the PAN molecule modified by triethoxysilane hydrolyze to form silanol groups. The silanol groups combine with the active reaction sites on the precursor particles of the adsorption filler to form PAN modification, thus preparing the adsorption filler.

[0021] Further, in step A1, the ratio of graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, sodium hydroxide, deionized water, emulsion, and epoxy resin solution is 1g:3g:5g:0.5g:30mL:20mL:10mL. The emulsion is composed of N,N-dimethylformamide, Tween-80, and sodium dodecyl sulfate in a ratio of 10mL:0.5g:0.3g. The epoxy resin solution is composed of epoxy resin and N,N-dimethylformamide in a ratio of 1g:3mL. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed three times with purified water and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70℃ and vacuum dried to constant weight to obtain the adsorption filler precursor.

[0022] Further, in step A2, the ratio of the adsorption packing precursor, triethoxysilane-modified PAN, anhydrous ethanol, and catalyst is 5g:1g:30mL:7mL, the catalyst is a 0.5mol / L sodium hydroxide solution, and the post-treatment includes: after the reaction is complete, the reaction system temperature is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70℃ and vacuum dried to constant weight to obtain the adsorption packing.

[0023] Furthermore, the preparation method of triethoxysilane-modified PAN is as follows: under the protection of an inert gas, 1-(2-pyridiniazo)-2-naphthol and tetrahydrofuran are stirred and mixed, the temperature of the reaction system is raised to 40-50℃, propyltriethoxysilane isocyanate is added to the reaction system, and the reaction is kept at the temperature for 40-60 min to obtain triethoxysilane-modified PAN.

[0024] The synthesis reaction equation for triethoxysilane-modified PAN is:

[0025]

[0026] The synthesis reaction mechanism of triethoxysilane-modified PAN is as follows:

[0027] During the reaction, the hydroxyl group on the 1-(2-pyridiniazo)-2-naphthol molecule undergoes a condensation reaction with the isocyanate group on the propyltriethoxysilane molecule, thereby modifying the 1-(2-pyridiniazo)-2-naphthol molecule with triethoxysilane to prepare triethoxysilane-modified PAN.

[0028] The mass spectrometry analysis data of triethoxysilane-modified PAN were as follows: m / z: 495.21895 (100.0%), 496.22230 (28.1%), 496.21852 (5.1%), 497.22566 (3.8%), 497.21579 (3.3%), 497.22187 (1.4%), 496.21598 (1.1%), 497.22319 (1.0%).

[0029] Furthermore, the ratio of 1-(2-pyridiniazo)-2-naphthol to propyltriethoxysilane is 1 mol: 1 mol, and the ratio of 1-(2-pyridiniazo)-2-naphthol to tetrahydrofuran is 1 g: 7 mL. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is raised to 55°C, and low-boiling substances are removed by vacuum distillation to obtain triethoxysilane-modified PAN.

[0030] Furthermore, the preparation method of sulfonated cellulose is as follows: under the protection of an inert gas, hydroxypropyl cellulose and N,N-dimethylformamide are stirred and mixed, the reaction temperature is lowered to 0-5℃, chlorosulfonic acid solution is added dropwise to the reaction system, after the addition is completed, the reaction system is naturally heated to 25-35℃, and the reaction is kept at this temperature for 3-4 hours. After post-treatment, sulfonated cellulose is obtained.

[0031] The synthesis reaction equation for sulfonated cellulose is as follows:

[0032]

[0033] The synthesis mechanism of sulfonated cellulose is as follows:

[0034] During the reaction, chlorosulfonic acid acts as a sulfonating agent. Due to the high electrophilicity of its sulfur atoms, chlorosulfonic acid dissociates into H+ in the reaction system. +With the electrophilic reagent SO3, the hydroxyl oxygen atom in the hydroxyl group of hydroxypropyl cellulose has a lone pair of electrons, exhibiting nucleophilicity. Electrophilic SO3 attacks the oxygen atom of the hydroxyl group, forming an unstable intermediate structure. Subsequently, a rearrangement of chemical bonds occurs, and the sulfonic acid group -SO3 replaces the hydrogen atom on the hydroxyl group, generating sulfonated cellulose and hydrogen chloride.

[0035] Furthermore, the ratio of hydroxypropyl cellulose, N,N-dimethylformamide, and chlorosulfonic acid solution is 10g:70mL:7mL, wherein the chlorosulfonic acid solution is composed of chlorosulfonic acid and N,N-dimethylformamide at a ratio of 1g:3mL. The post-treatment includes: after the reaction is complete, adding 0.1mol / L sodium hydroxide solution at a temperature of 5-8℃ to the reaction system, stirring and dispersing for 20-30min, placing the reaction solution into a dialysis bag with a molecular weight cutoff of 1000, dialyzing in purified water for 3 days, changing the purified water every 6h, and then transferring the solution in the dialysis bag to a freeze dryer at a temperature of -30℃ for freeze drying to obtain sulfonated cellulose.

[0036] The present invention has the following beneficial effects:

[0037] 1. The membrane separation and extraction method for ionic rare earths proposed in this invention involves eluting ionic rare earths from rare earth ores using a magnesium sulfate solution, and optimizing the pH of the wetting solution and the leachate. The strong acidity and high concentration of the wetting solution can disrupt the mineral structure and promote the desorption of rare earth ions, while the weak acidity and low concentration of the leachate can maintain the dissolved state of rare earths, avoid premature precipitation, and reduce the risk of co-dissolution of impurities. Furthermore, ammonia nitrogen compounds are not used when eluting rare earth minerals, which can effectively reduce pollution to the mineral soil. Then, by adjusting the pH of the leachate, impurities such as aluminum in the leachate are promoted to settle. The ionic rare earths in the leachate are then adsorbed and filtered by a nanofiltration adsorption module, and the concentration of rare earth ions in the nanofiltration solution is detected to reduce the loss of ionic rare earths. This method avoids the large amount of energy loss caused by the traditional method of treating the leachate by vacuum concentration, thus reducing production costs.

[0038] 2. The membrane separation and extraction method for ionic rare earth minerals proposed in this invention involves the protonation reaction of the layered silicate structure in ionic rare earth minerals such as kaolinite and montmorillonite under strongly acidic conditions during elution. This causes the interlayer hydrogen bonds to break, leading to mineral expansion and disintegration, which promotes the release of adsorbed rare earth ions from the minerals. Meanwhile, in the acidic environment, H+... + Competition with rare earth ions for adsorption sites on the mineral surface weakens the binding energy between rare earth ions and the mineral. During wetting, according to Donnan's film equilibrium theory, the ion exchange rate between the mineral surface and the solution is directly proportional to the cation concentration gradient. High concentrations of Mg... 2+It can significantly improve the exchange reaction rate, thereby rapidly displacing adsorbed rare earth ions from rare earth minerals. Then, after adjusting the pH of the leachate, it promotes the precipitation of iron and aluminum ions in the eluent. Filtration removes most of the precipitated impurities, reducing competitive adsorption and improving the selectivity of rare earth elements. Simultaneously, the increased pH promotes the coordination of water molecules (H3O) in the hydration layer. + As the hydrolysis concentration decreases, the exposure of ionic rare earth elements increases, leading to an increase in apparent charge density. This increased charge density enhances the electrostatic attraction between the ionic rare earth elements and the negatively charged surface of the adsorption packing material, thereby increasing the adsorption loading capacity of the adsorption packing material for ionic rare earth elements. This prevents ionic rare earth elements from clogging the membrane pores during membrane separation, thus improving the membrane separation effect.

[0039] 3. The membrane separation and extraction method for ionic rare earth elements proposed in this invention utilizes epoxy resin as a curing agent to promote the bonding of graphene oxide, sulfonated cellulose, and hydroxypropyl distarch phosphate to form an adsorption filler precursor. Sulfonic acid groups are introduced onto the hydroxypropyl cellulose molecules through chlorosulfonic acid modification, resulting in complete ionization to -SO3 in an acidic aqueous environment. - Graphene oxide forms strong electrostatic adsorption with rare earth elements. While increasing the specific surface area of ​​the adsorption filler, the carboxyl and hydroxyl groups on its surface can chelate with the phosphate groups on hydroxypropyl distarch phosphate molecules, enhancing adsorption capacity. Furthermore, hydroxypropyl distarch phosphate is a cross-linked modified starch; its molecular chains form a three-dimensional network structure through phosphate bonds, inhibiting particle expansion, preventing excessive swelling of the filler in acidic or high-salt environments, maintaining pore structure stability, and reducing filler breakage under stirring or flowing conditions, thus maintaining filler stability. The high degree of cross-linking and resistance to hydrolysis in strong acids give hydroxypropyl distarch phosphate excellent stability in eluents, improving its regeneration performance. Triethoxysilane modification of PAN introduces a rigid framework of siloxane network into the adsorption filler to support its structure, while the pyridine azo groups of PAN undergo π-π stacking with the rare earth elements, further enhancing its selectivity for rare earth elements. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In this invention, the CAS number of hydroxypropyl cellulose is 9004-64-2, the viscosity is 10-20 mPa·s, and the pH is 5.0-8.5 (1% aqueous solution);

[0042] In this invention, hydroxypropyl distarch phosphate is selected from Wuhan Xinzhongxin Chemical Technology Co., Ltd., CAS No. 53124-00-8, and the content of active ingredient is 99%.

[0043] In this invention, the epoxy resin is a bisphenol A type epoxy resin, model E-42;

[0044] In this invention, the ionic rare earth ore contains, by weight percentage, 0.073% ionic rare earth, 16.85% Al2O3, 4.35% Fe2O3, 4.68% K2O, 0.11% Na2O, 0.62% CaO, and 2.53% MgO, with the balance being SiO2 and mineral impurities.

[0045] Example 1

[0046] This embodiment provides a method for preparing metal ion adsorption packing material, including the following steps:

[0047] Step I: Preparation of sulfonated cellulose

[0048] Chlorosulfonic acid and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain a chlorosulfonic acid solution;

[0049] Weigh 100g of hydroxypropyl cellulose and 700mL of N,N-dimethylformamide and add them to a reaction flask under nitrogen protection. Stir the mixture and lower the temperature of the reaction flask to 0℃. Add 70mL of chlorosulfonic acid solution dropwise to the reaction flask. After the addition is complete, allow the reaction flask to naturally heat up to 25℃ and maintain the temperature for 3 hours. Add 100mL of 0.1mol / L sodium hydroxide solution at 5℃ to the reaction flask and stir to disperse for 20 minutes. Place the reaction solution into a dialysis bag with a molecular weight cutoff of 1000 and dialyze it in purified water for 3 days, changing the purified water every 6 hours. Then transfer the solution in the dialysis bag to a freeze dryer at -30℃ and freeze dry it to obtain sulfonated cellulose.

[0050] Step II: Preparation of Adsorption Packing Material Precursor

[0051] N,N-dimethylformamide, Tween-80, and sodium dodecyl sulfate were mixed evenly at a ratio of 10 mL: 0.5 g: 0.3 g to obtain an emulsion.

[0052] Epoxy resin and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain an epoxy resin solution;

[0053] Weigh out 20g of graphene oxide, 30g of sulfonated cellulose, 100g of hydroxypropyl distarch phosphate, 10g of sodium hydroxide, and 600mL of deionized water and add them to a reaction flask. Sonicate the mixture for 40min. Fix the reaction flask in a water bath with a mechanical stirrer and set the stirring speed to 800r / min. Add 400mL of emulsion to the reaction flask and stir for 20min. Raise the reaction temperature to 60℃ and add 200mL of epoxy resin solution to the reaction flask. Keep the reaction at this temperature for 2h. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake three times with purified water and dry it under vacuum. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to constant weight to obtain the adsorption filler precursor.

[0054] Step III: Preparation of triethoxysilane-modified PAN

[0055] Weigh out 24.9 g of 1-(2-pyridiniazo)-2-naphthol and 174.3 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and raise the temperature of the reaction flask to 40 °C. Add 24.7 g of propyltriethoxysilane isocyanate to the reaction flask and keep the mixture at this temperature for 40 min. Raise the temperature of the reaction flask to 55 °C and remove the low-boiling-point substances by vacuum distillation to obtain triethoxysilane-modified PAN.

[0056] Step IV: Preparation of adsorption packing material

[0057] Weigh out 500g of the adsorption packing precursor, 100g of triethoxysilane-modified PAN, and 3L of anhydrous ethanol and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 50℃. Add 700mL of 0.5mol / L sodium hydroxide solution to the reaction system and keep the mixture at this temperature for 80min. Then, lower the temperature of the reaction flask to room temperature, filter the mixture, wash the filter cake with purified water until neutral, and then dry it under vacuum. Transfer the filter cake to a drying oven at 60℃ and vacuum dry it to constant weight to obtain the adsorption packing.

[0058] Example 2

[0059] This embodiment provides a method for preparing metal ion adsorption packing material, including the following steps:

[0060] Step I: Preparation of sulfonated cellulose

[0061] Chlorosulfonic acid and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain a chlorosulfonic acid solution;

[0062] Weigh 100g of hydroxypropyl cellulose and 700mL of N,N-dimethylformamide and add them to a reaction flask under nitrogen protection. Stir the mixture and lower the temperature of the reaction flask to 3℃. Add 70mL of chlorosulfonic acid solution dropwise to the reaction flask. After the addition is complete, allow the reaction flask to naturally heat up to 30℃ and maintain the temperature for 3.5h. Add 100mL of 0.1mol / L sodium hydroxide solution at 7℃ to the reaction flask and stir to disperse for 25min. Place the reaction solution into a dialysis bag with a molecular weight cutoff of 1000 and dialyze it in purified water for 3 days, changing the purified water every 6h. Then transfer the solution in the dialysis bag to a freeze dryer at -30℃ and freeze dry it to obtain sulfonated cellulose.

[0063] Step II: Preparation of Adsorption Packing Material Precursor

[0064] N,N-dimethylformamide, Tween-80, and sodium dodecyl sulfate were mixed evenly at a ratio of 10 mL: 0.5 g: 0.3 g to obtain an emulsion.

[0065] Epoxy resin and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain an epoxy resin solution;

[0066] Weigh out 20g of graphene oxide, 30g of sulfonated cellulose, 100g of hydroxypropyl distarch phosphate, 10g of sodium hydroxide, and 600mL of deionized water and add them to a reaction flask. Sonicate the mixture for 50min. Fix the reaction flask in a water bath with a mechanical stirrer and set the stirring speed to 800r / min. Add 400mL of emulsion to the reaction flask and stir for 25min. Raise the reaction temperature to 65℃ and add 200mL of epoxy resin solution. Keep the reaction at this temperature for 2.5h. Lower the temperature of the reaction flask to room temperature, filter the mixture, wash the filter cake three times with purified water, and then dry it under vacuum. Transfer the filter cake to a drying oven at 65℃ and vacuum dry it to constant weight to obtain the adsorption filler precursor.

[0067] Step III: Preparation of triethoxysilane-modified PAN

[0068] Weigh out 24.9 g of 1-(2-pyridiniazo)-2-naphthol and 174.3 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and raise the temperature of the reaction flask to 45 °C. Add 24.7 g of propyltriethoxysilane isocyanate to the reaction flask and keep the mixture at this temperature for 50 min. Raise the temperature of the reaction flask to 55 °C and remove the low-boiling-point substances by vacuum distillation to obtain triethoxysilane-modified PAN.

[0069] Step IV: Preparation of adsorption packing material

[0070] Weigh out 500g of the adsorption packing precursor, 100g of triethoxysilane-modified PAN, and 3L of anhydrous ethanol and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 55℃. Add 700mL of 0.5mol / L sodium hydroxide solution to the reaction system and keep the mixture at this temperature for 85min. Then, lower the temperature of the reaction flask to room temperature, filter the mixture, wash the filter cake with purified water until neutral, and then dry it under vacuum. Transfer the filter cake to a drying oven at 65℃ and vacuum dry it to constant weight to obtain the adsorption packing.

[0071] Example 3

[0072] This embodiment provides a method for preparing metal ion adsorption packing material, including the following steps:

[0073] Step I: Preparation of sulfonated cellulose

[0074] Chlorosulfonic acid and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain a chlorosulfonic acid solution;

[0075] Weigh 100g of hydroxypropyl cellulose and 700mL of N,N-dimethylformamide and add them to a reaction flask under nitrogen protection. Stir the mixture and lower the temperature of the reaction flask to 5℃. Add 70mL of chlorosulfonic acid solution dropwise to the reaction flask. After the addition is complete, allow the reaction flask to naturally heat up to 35℃ and maintain the temperature for 4 hours. Add 100mL of 0.1mol / L sodium hydroxide solution at 8℃ to the reaction flask and stir to disperse for 30 minutes. Place the reaction solution into a dialysis bag with a molecular weight cutoff of 1000 and dialyze it in purified water for 3 days, changing the purified water every 6 hours. Then transfer the solution in the dialysis bag to a freeze dryer at -30℃ and freeze dry it to obtain sulfonated cellulose.

[0076] Step II: Preparation of Adsorption Packing Material Precursor

[0077] N,N-dimethylformamide, Tween-80, and sodium dodecyl sulfate were mixed evenly at a ratio of 10 mL: 0.5 g: 0.3 g to obtain an emulsion.

[0078] Epoxy resin and N,N-dimethylformamide were mixed evenly at a ratio of 1g:3mL to obtain an epoxy resin solution;

[0079] Weigh out 20g of graphene oxide, 30g of sulfonated cellulose, 100g of hydroxypropyl distarch phosphate, 10g of sodium hydroxide, and 600mL of deionized water and add them to a reaction flask. Disperse the mixture by sonication for 60min. Fix the reaction flask in a water bath with a mechanical stirrer and set the stirring speed to 800r / min. Add 400mL of emulsion to the reaction flask and stir for 30min. Raise the reaction temperature to 70℃ and add 200mL of epoxy resin solution to the reaction flask. Keep the reaction at this temperature for 3h. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake three times with purified water and dry it under vacuum. Transfer the filter cake to a drying oven at 70℃ and dry it under vacuum to constant weight to obtain the adsorption filler precursor.

[0080] Step III: Preparation of triethoxysilane-modified PAN

[0081] Weigh out 24.9 g of 1-(2-pyridiniazo)-2-naphthol and 174.3 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir the mixture and raise the temperature of the reaction flask to 50 °C. Add 24.7 g of propyltriethoxysilane isocyanate to the reaction flask and keep the mixture at this temperature for 60 min. Raise the temperature of the reaction flask to 55 °C and remove the low-boiling-point substances by vacuum distillation to obtain triethoxysilane-modified PAN.

[0082] Step IV: Preparation of adsorption packing material

[0083] Weigh out 500g of the adsorption packing precursor, 100g of triethoxysilane-modified PAN, and 3L of anhydrous ethanol and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 60℃. Add 700mL of 0.5mol / L sodium hydroxide solution to the reaction system and keep the mixture at this temperature for 90min. Then, lower the temperature of the reaction flask to room temperature, filter the mixture, wash the filter cake with purified water until neutral, and then dry it under vacuum. Transfer the filter cake to a drying oven at 70℃ and vacuum dry it to constant weight to obtain the adsorption packing.

[0084] Example 4

[0085] This embodiment provides a membrane separation and extraction method for ionic rare earth elements, including the following steps:

[0086] Step 1: Preparation and elution of rare earth ore

[0087] Magnesium sulfate and purified water were mixed and stirred until the system was clear, resulting in a 0.3 mol / L magnesium sulfate solution. Sulfuric acid was added to adjust the pH to 3.0 to obtain the wetting solution.

[0088] Magnesium sulfate and purified water were stirred and mixed until the system was clear, resulting in a magnesium sulfate solution with a concentration of 0.08 mol / L. Sulfuric acid was added to adjust the pH to 5 to obtain the leachate.

[0089] A circular column with an aspect ratio of 3:1 was selected as the leaching column. A filter cloth with a pore size of 50 μm was placed at the bottom of the leaching column. Ion-adsorption rare earth ore with a moisture content of 1% was loaded into the leaching column. Wetting solution was added to the leaching column so that the wetting solution completely submerged the ion-adsorption rare earth ore. The leaching was kept at room temperature for 2 hours. Then, leaching solution was added to the leaching column for leaching and elution to obtain the eluent. The volume ratio of wetting solution to leaching solution was 1:3.

[0090] Step 2: Nanofiltration Adsorption

[0091] A dialysis membrane bag with a molecular weight cutoff of 13,000 was placed in a filter bag with a pore size of 50 μm, and then the adsorption packing material prepared in Example 1 was placed in the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0092] The eluent is transferred to a pH adjustment tank to adjust the system pH to 5.7. After filtration through a filter cloth with a pore size of 1 μm, the filtrate enters the dialysis membrane bag of the nanofiltration adsorption membrane module for nanofiltration adsorption. The rare earth metal content in the filtrate is detected. When the rare earth metal content in the filtrate reaches 5 ppm, the adsorption packing is saturated and needs to be replaced.

[0093] Step 3: Preparation of nanofiltration concentrate

[0094] The adsorption-saturated packing material was added to an elution column with an aspect ratio of 8:1. The column was eluted for 30 minutes using 0.8 mol / L sulfuric acid aqueous solution as the eluent, followed by 20 minutes of elution using purified water. The eluents were combined to obtain a nanofiltration concentrate. The adsorption packing material was then removed from the elution column and washed with purified water until neutral to obtain regenerated adsorption packing material. The volume ratio of the adsorption-saturated packing material, eluent, and purified water was 1:7:3.

[0095] Step 4: Preparation of Ionic Rare Earth

[0096] Sodium hydroxide was added to the nanofiltration concentrate to adjust the pH of the system to 10. The mixture was then filtered, and the filter cake was washed with purified water until neutral and then dried. The filter cake was transferred to a drying oven at 70°C and dried for 4 hours. Then it was transferred to a calcining furnace at 500°C and calcined for 3 hours to obtain ionic rare earth elements.

[0097] Example 5

[0098] This embodiment provides a membrane separation and extraction method for ionic rare earth elements, including the following steps:

[0099] Step 1: Preparation and elution of rare earth ore

[0100] Magnesium sulfate and purified water were mixed and stirred until the system was clear, resulting in a magnesium sulfate solution with a concentration of 0.4 mol / L. Sulfuric acid was added to adjust the pH to 3.3 to obtain the impregnation solution.

[0101] Magnesium sulfate and purified water were stirred and mixed until the system was clear, resulting in a magnesium sulfate solution with a concentration of 0.10 mol / L. Sulfuric acid was added to adjust the pH to 5 to obtain the leachate.

[0102] A circular column with an aspect ratio of 3:1 was selected as the leaching column. A filter cloth with a pore size of 75 μm was placed at the bottom of the leaching column. Ion-adsorption rare earth ore with a moisture content of 3% was loaded into the leaching column. Wetting solution was added to the leaching column so that the wetting solution completely submerged the ion-adsorption rare earth ore. The leaching was carried out at room temperature for 2.5 hours. Then, leaching solution was added to the leaching column for leaching and elution to obtain the eluent. The volume ratio of wetting solution to leaching solution was 1:3.

[0103] Step 2: Nanofiltration Adsorption

[0104] A dialysis membrane bag with a molecular weight cutoff of 14,000 was placed in a filter bag with a pore size of 75 μm, and then the adsorption packing material prepared in Example 2 was placed in the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0105] The eluent is transferred to a pH adjustment tank to adjust the system pH to 5.8. After filtration through a filter cloth with a pore size of 3 μm, the filtrate enters the dialysis membrane bag of the nanofiltration adsorption membrane module for nanofiltration adsorption. The rare earth metal content in the filtrate is detected. When the rare earth metal content in the filtrate reaches 5 ppm, the adsorption packing is saturated and needs to be replaced.

[0106] Step 3: Preparation of nanofiltration concentrate

[0107] The adsorption-saturated packing material was added to an elution column with an aspect ratio of 8:1. The column was eluted with 1.0 mol / L sulfuric acid aqueous solution for 40 min, followed by elution with purified water for 25 min. The eluents were combined to obtain a nanofiltration concentrate. The packing material was removed from the elution column and washed with purified water until neutral to obtain regenerated packing material. The volume ratio of the adsorption-saturated packing material, eluent, and purified water was 1:7:3.

[0108] Step 4: Preparation of Ionic Rare Earth

[0109] Sodium hydroxide was added to the nanofiltration concentrate to adjust the pH of the system to 10. The mixture was then filtered, and the filter cake was washed with purified water until neutral and then dried. The filter cake was transferred to a drying oven at 75°C and dried for 5 hours. Then it was transferred to a calcining furnace at 525°C and calcined for 4 hours to obtain ionic rare earth elements.

[0110] Example 6

[0111] This embodiment provides a membrane separation and extraction method for ionic rare earth elements, including the following steps:

[0112] Step 1: Preparation and elution of rare earth ore

[0113] Magnesium sulfate and purified water were mixed and stirred until the system was clear, resulting in a 0.5 mol / L magnesium sulfate solution. Sulfuric acid was added to adjust the pH to 3.6 to obtain the wetting solution.

[0114] Magnesium sulfate and purified water were stirred and mixed until the system was clear, resulting in a magnesium sulfate solution with a concentration of 0.12 mol / L. Sulfuric acid was added to adjust the pH to 5 to obtain the leachate.

[0115] A circular column with an aspect ratio of 3:1 was selected as the leaching column. A filter cloth with a pore size of 100 μm was placed at the bottom of the leaching column. Ion-adsorption rare earth ore with a moisture content of 5% was loaded into the leaching column. Wetting solution was added to the leaching column so that the wetting solution completely submerged the ion-adsorption rare earth ore. The leaching was kept at room temperature for 3 hours. Then, leaching solution was added to the leaching column for leaching and elution to obtain the eluent. The volume ratio of wetting solution to leaching solution was 1:3.

[0116] Step 2: Nanofiltration Adsorption

[0117] A dialysis membrane bag with a molecular weight cutoff of 15,000 was placed in a filter bag with a pore size of 100 μm, and then the adsorption packing material prepared in Example 3 was placed in the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0118] The eluent is transferred to a pH adjustment tank to adjust the system pH to 5.9. After filtration through a filter cloth with a pore size of 5 μm, the filtrate enters the dialysis membrane bag of the nanofiltration adsorption membrane module for nanofiltration adsorption. The rare earth metal content in the filtrate is detected. When the rare earth metal content in the filtrate reaches 5 ppm, the adsorption packing is saturated and needs to be replaced.

[0119] Step 3: Preparation of nanofiltration concentrate

[0120] The saturated adsorption packing material was added to an elution column with an aspect ratio of 8:1. The column was eluted with 1.2 mol / L sulfuric acid aqueous solution for 50 min, followed by elution with purified water for 30 min. The eluents were combined to obtain a nanofiltration concentrate. The adsorption packing material was removed from the elution column and washed with purified water until neutral to obtain regenerated adsorption packing material. The volume ratio of the saturated adsorption packing material, eluent, and purified water was 1:7:3.

[0121] Step 4: Preparation of Ionic Rare Earth

[0122] Sodium hydroxide was added to the nanofiltration concentrate to adjust the pH of the system to 10. The mixture was then filtered, and the filter cake was washed with purified water until neutral and then dried. The filter cake was transferred to a drying oven at 80°C and dried for 6 hours. Then it was transferred to a calcining furnace at 550°C and calcined for 5 hours to obtain ionic rare earth elements.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 6 is that in step one, the wetting solution is replaced by the leachate.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 6 is that in step two, the pH adjustment of the eluent is omitted, and the eluent is directly introduced into the dialysis membrane bag.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 6 is that hydroxypropyl distarch phosphate was not added in step II during the preparation of the adsorption packing material.

[0129] Comparative Example 4

[0130] The difference between this comparative example and Example 6 is that, in the preparation of the adsorption packing material, steps III and IV are omitted, and the adsorption packing material precursor is used as the adsorption packing material.

[0131] Performance testing:

[0132] Reference formula The extraction rates of rare earth ions in Examples 4-6 and Comparative Examples 1-4 were determined, where m 稀土 The quality of the ore is that of rare earth ore, w 稀土矿-稀土 m represents the rare earth content in rare earth ore. 稀土 For the mass of ionic rare earth elements, w 稀土 This refers to the content of ionic rare earth elements;

[0133] The adsorption capacity of the adsorption packing materials used in Examples 4-6 and Comparative Examples 1-4 for ionic rare earth elements was determined in an aqueous environment with pH = 5.7-5.9, according to standard JC / T 2021-2010 "Test Method for Adsorption Capacity of Mesoporous Materials". The regenerated adsorption packing materials were recycled 50 times, and the adsorption capacity was determined according to the formula. The adsorption capacity retention rate was determined, where Q1 is the initial adsorption capacity of the adsorption packing material, and Q... 100 The adsorption capacity of the adsorption packing material after 100 cycles of use;

[0134] The specific test results are shown in Table 1 below.

[0135] Table 1 - Performance Test Data of Samples

[0136]

[0137] Data Analysis:

[0138] Comparative analysis of the data in Table 1 shows that the extraction rate of ionic rare earth elements from rare earth minerals in this invention reaches 89.2%, and the adsorption capacity of the adsorption packing material for ionic rare earth elements reaches 392.5 mg / g. After 100 cycles, the adsorption capacity retention rate of the adsorption packing material reaches 88.4%. Although the extraction rate of Comparative Example 2 is not much different from that of Example 3, the amount of adsorption required to adsorb the same eluent is greatly increased. All performance test data are better than those of the comparative example. This indicates that by optimizing the elution process of rare earth minerals and cooperating with the adsorption packing material prepared in this application, this invention not only effectively improves the extraction rate of ionic rare earth elements and the adsorption capacity of the adsorption packing material for ionic rare earth elements, but also effectively reduces the pollution of ecological soil and production costs caused by the extraction of ionic rare earth elements.

[0139] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0140] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0141] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A membrane separation and extraction method for ionic rare earth elements, characterized in that, Includes the following steps: S1. Dry ion-adsorption rare earth ore is loaded into a leaching column, and wetting solution is added to the leaching column so that the wetting solution completely covers the ion-adsorption rare earth ore. The ore is kept at room temperature for 2-3 hours, and then leaching and eluting are carried out using the leaching solution to obtain the eluent. S2. The eluent is transferred to a pH adjustment tank to adjust the pH of the system to 5.7-5.

9. After filtration, the filtrate is passed through a nanofiltration membrane packed with adsorption packing material for nanofiltration adsorption and desorption elution to prepare nanofiltration concentrate. S3. After alkaline precipitation, the nanofiltration concentrate is filtered and calcined to prepare ionic rare earth elements. The adsorption packing material is obtained by the following steps: A1. Add graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, and sodium hydroxide to deionized water and ultrasonically disperse for 40-60 min. While stirring, add emulsion to the reaction system and stir for 20-30 min. Raise the reaction temperature to 60-70℃, add epoxy resin solution to the reaction system, and keep the reaction at this temperature for 2-3 h. Post-treatment is then performed to adsorb the filler precursor. A2. Mix and stir the adsorption packing precursor, triethoxysilane-modified PAN and anhydrous ethanol. Raise the temperature of the reaction system to 50-60℃, add the catalyst to the reaction system, keep the reaction at this temperature for 80-90 min, and then perform post-treatment to obtain the adsorption packing. The triethoxysilane-modified PAN is obtained by the condensation reaction between the hydroxyl group on the 1-(2-pyridinium azo)-2-naphthol molecule and the isocyanate group on the propyltriethoxysilane molecule.

2. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, In step S1, the volume ratio of the wetting solution to the leachate is 1:

3. The wetting solution is obtained by adjusting the pH of a 0.3-0.5 mol / L magnesium sulfate solution composed of magnesium sulfate and purified water to 3-3.6 with sulfuric acid. The leachate is obtained by adjusting the pH of a 0.08-0.12 mol / L magnesium sulfate solution composed of magnesium sulfate and purified water to 5 with sulfuric acid.

3. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, In step S2, the nanofiltration adsorption membrane assembly includes a dialysis membrane bag and adsorption packing material. The adsorption packing material is placed inside the dialysis membrane bag, and the molecular weight cutoff of the dialysis membrane bag is 13,000-15,000. The desorption elution method is as follows: the adsorption-saturated adsorption packing material is added to the elution column, the eluent is circulated and eluted for 30-50 minutes, and then purified water is circulated and eluted for 20-30 minutes. The eluents are combined to obtain nanofiltration concentrate. The adsorption packing material is removed from the elution column and washed with purified water until neutral to obtain regenerated adsorption packing material. The volume ratio of the adsorption-saturated adsorption packing material, the eluent, and the purified water is 1:7:3, and the eluent is a 0.8-1.2 mol / L sulfuric acid aqueous solution.

4. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, In step S3, the preparation method of ionic rare earth is as follows: add sodium hydroxide to the nanofiltration concentrate, adjust the pH of the system to 10, filter, wash the filter cake with purified water until neutral, dry it, transfer the filter cake to a drying oven at 70-80℃, dry it for 4-6 hours, and then transfer it to a calcination furnace at 500-550℃, keep it heated and calcined for 3-5 hours to obtain ionic rare earth.

5. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, In step A1, the ratio of graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, sodium hydroxide, deionized water, emulsion, and epoxy resin solution is 1g:3g:5g:0.5g:30mL:20mL:10mL; in step A2, the ratio of the adsorption filler precursor, triethoxysilane-modified PAN, anhydrous ethanol, and catalyst is 5g:1g:30mL:7mL, and the catalyst is a 0.5mol / L sodium hydroxide solution.

6. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, The preparation method of triethoxysilane modified PAN is as follows: under the protection of inert gas, 1-(2-pyridiniazo)-2-naphthol and tetrahydrofuran are stirred and mixed, the temperature of the reaction system is raised to 40-50℃, propyltriethoxysilane isocyanate is added to the reaction system, and the reaction is kept at the temperature for 40-60 min to obtain triethoxysilane modified PAN.

7. The membrane separation and extraction method for ionic rare earth elements according to claim 6, characterized in that, The ratio of 1-(2-pyridiniazo)-2-naphthol to propyltriethoxysilane is 1 mol: 1 mol, and the ratio of 1-(2-pyridiniazo)-2-naphthol to tetrahydrofuran is 1 g: 7 mL.

8. The membrane separation and extraction method for ionic rare earth elements according to claim 1, characterized in that, The preparation method of sulfonated cellulose is as follows: under the protection of inert gas, hydroxypropyl cellulose and N,N-dimethylformamide are stirred and mixed. The reaction temperature is lowered to 0-5℃, and chlorosulfonic acid solution is added dropwise to the reaction system. After the addition is completed, the reaction system is naturally heated to 25-35℃ and kept at this temperature for 3-4 hours. After post-treatment, sulfonated cellulose is obtained.

9. The membrane separation and extraction method for ionic rare earth elements according to claim 8, characterized in that, The ratio of hydroxypropyl cellulose, N,N-dimethylformamide, and chlorosulfonic acid solution is 10g:70mL:7mL, and the chlorosulfonic acid solution is composed of chlorosulfonic acid and N,N-dimethylformamide at a ratio of 1g:3mL.

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