Membrane separation and extraction method of ionic rare earth

Abstract

The invention discloses a membrane separation and extraction method for ionic rare earth, belongs to the technical field of rare earth extraction, and aims to solve the technical problems that in the prior art, extraction of ionic rare earth from rare earth minerals causes serious environmental pollution and low extraction rate, and separation and extraction of ionic rare earth are difficult by direct filtration of a membrane. Comprising the following steps that dried ion type rare earth ore is loaded into a leaching column, an infiltration solution is added into the leaching column, the ion type rare earth ore is completely immersed in the infiltration solution, heat preservation infiltration is conducted for 2-3 h at the room temperature, and then leaching elution is conducted through a leaching solution. According to the method, by optimizing the elution process of the rare earth minerals and cooperating with the prepared adsorption filler, the extraction rate of the ion rare earth and the adsorption capacity of the adsorption filler to the ion rare earth are effectively improved, and pollution of extraction of the ion rare earth to ecological soil and the production cost are effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth extraction, and particularly relates to a method for extracting ionic rare earth by membrane separation. Background Art

[0002] Ionic rare earth is a kind of rare earth mineral in which rare earth ions are adsorbed on minerals such as kaolin and montmorillonite in ionic form. Most of them are like soil, with a content of 0.3 - 0.05%, and can be leached out with electrolytes. Ionic rare earth ore is an important strategic resource in China, and its extraction technology is directly related to resource utilization rate and environmental protection.

[0003] The existing methods for extracting rare earth from rare earth minerals usually use high-concentration sulfuric acid or hydrochloric acid for leaching. To improve the extraction rate of ionic rare earth, various ammonia-nitrogen compounds are added. On the one hand, this causes a large amount of acidic wastewater discharge, and the content of impurity ions such as iron and aluminum in the leaching solution is high, resulting in a significant increase in subsequent separation costs. On the other hand, ammonia-nitrogen compounds and the like remain in the mineral soil for a long time, causing serious pollution to the soil environment. Membrane separation technology realizes the separation of rare earth ions and alkaline earth through nanofiltration retention, avoids concentrating the eluate, and reduces production costs. However, when extracting ionic rare earth by membrane separation, ionic rare earth usually blocks the membrane pores in a colloidal state, making membrane separation difficult.

[0004] In view of the technical defects in this regard, a solution is proposed now. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for extracting ionic rare earth by membrane separation, which is used to solve the technical problems of large environmental pollution, low extraction rate, and difficult operation of directly filtering and separating ionic rare earth from rare earth minerals in the prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for extracting ionic rare earth by membrane separation includes the following steps:

[0008] S1. Load the dried ionic rare earth ore into a leaching column, add a wetting solution to the leaching column so that the wetting solution completely covers the ionic rare earth ore, keep it warm and wet for 2 - 3 h at room temperature, and then use a leaching solution for leaching and elution to obtain an eluate;

[0009] S2. Transport the eluate to a pH adjustment tank, adjust the system pH = 5.7 - 5.9, filter, and the filtrate is subjected to nanofiltration adsorption through a nanofiltration adsorption membrane group filled with adsorption filler and then desorbed and eluted to prepare a nanofiltration concentrate;

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

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

[0012] Further, in step S2, the nanofiltration adsorption membrane group includes a dialysis membrane bag and an adsorption filler. The adsorption filler is filled in the dialysis membrane bag. The retention molecular weight of the dialysis membrane bag is 13,000 - 15,000. The desorption and elution method is as follows: Add the adsorption-saturated adsorption filler into an elution column, circulate the eluent for elution for 30 - 50 min, then circulate and elute with purified water for 20 - 30 min, combine the eluents to obtain a nanofiltration concentrate, take out the adsorption filler from the elution column, wash it with purified water until it is neutral to obtain a regenerated adsorption filler. The volume ratio of the adsorption-saturated adsorption filler, the eluent, and 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] Further, 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, perform suction filtration, wash the filter cake with purified water until it is neutral and then drain it, transfer the filter cake to a drying oven at a temperature of 70 - 80 °C, dry for 4 - 6 h, and then transfer it to a roasting furnace at a temperature of 500 - 550 °C, keep it warm and roast for 3 - 5 h to obtain ionic rare earth.

[0014] Further, the adsorption filler is processed by the following steps:

[0015] A1. Add graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, and sodium hydroxide to deionized water, perform ultrasonic dispersion for 40 - 60 min. Under stirring, add an emulsion to the reaction system, stir for 20 - 30 min, raise the reaction temperature to 60 - 70 °C, add an epoxy resin solution to the reaction system, keep the temperature and react for 2 - 3 h, and perform post-treatment to obtain an adsorption filler precursor;

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

[0017] During the reaction process, graphene oxide, sulfonated cellulose, and hydroxypropyl distarch phosphate are dispersed in a sodium hydroxide solution and then emulsified. Epoxy resin is added thereto. In an alkaline environment, the epoxy groups on the epoxy resin molecules undergo ring-opening condensation with active reaction sites such as hydroxyl groups, promoting the bonding and curing of the dispersed particles to form spherical particles, and an adsorption filler precursor is prepared.

[0018] A2. Mix and stir the adsorption filler precursor, triethoxysilane-modified PAN, and absolute ethanol. Raise the temperature of the reaction system to 50 - 60 °C. Add a catalyst to the reaction system, keep the temperature for reaction for 80 - 90 min, and perform post-treatment to obtain the adsorption filler.

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

[0020] During the reaction process, the siloxane bonds on the triethoxysilane-modified PAN molecules are hydrolyzed to form silanol groups, and the silanol groups combine with the active reaction sites on the adsorption filler precursor particles to form PAN modification, and the adsorption filler is prepared.

[0021] Furthermore, in step A1, the dosage ratios of graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, sodium hydroxide, deionized water, emulsifying liquid, and epoxy resin solution are 1 g:3 g:5 g:0.5 g:30 mL:20 mL:10 mL. The emulsifying liquid is composed of N,N-dimethylformamide, Tween-80, and sodium dodecyl sulfate in a ratio of 10 mL:0.5 g:0.3 g. The epoxy resin solution is composed of epoxy resin and N,N-dimethylformamide in a ratio of 1 g:3 mL. The post-treatment includes: after the reaction is completed, lower the temperature of the reaction system to room temperature, perform suction filtration, wash the filter cake with purified water 3 times and then drain it, transfer the filter cake to a drying oven at 60 - 70 °C, and vacuum dry it to constant weight to obtain the adsorption filler precursor.

[0022] Furthermore, in step A2, the dosage ratios of the adsorption filler precursor, triethoxysilane-modified PAN, absolute ethanol, and catalyst are 5 g:1 g:30 mL:7 mL. The catalyst is 0.5 mol / L sodium hydroxide solution. The post-treatment includes: after the reaction is completed, lower the temperature of the reaction system to room temperature, perform suction filtration, wash the filter cake with purified water until it is neutral and then drain it, transfer the filter cake to a drying oven at 60 - 70 °C, and vacuum dry it to constant weight to obtain the adsorption filler.

[0023] Furthermore, the preparation method of triethoxysilane-modified PAN is as follows: under the protection of an inert gas, stir and mix 1-(2-pyridylazo)-2-naphthol and tetrahydrofuran. Raise the temperature of the reaction system to 40 - 50 °C. Add isocyanatopropyltriethoxysilane to the reaction system, and keep the temperature for reaction for 40 - 60 min to obtain triethoxysilane-modified PAN.

[0024] The synthesis reaction equation of triethoxysilane-modified PAN is as follows:

[0025]

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

[0027] During the reaction, the hydroxyl group on the 1-(2-pyridylazo)-2-naphthol molecule undergoes a condensation reaction with the isocyanate group on the isocyanatopropyltriethoxysilane molecule, and triethoxysilane is modified on the 1-(2-pyridylazo)-2-naphthol molecule to prepare triethoxysilane-modified PAN.

[0028] The mass spectrometry analysis data of triethoxysilane-modified PAN are: 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 dosage ratio of 1-(2-pyridylazo)-2-naphthol to isocyanatopropyltriethoxysilane is 1 mol:1 mol, the dosage ratio of 1-(2-pyridylazo)-2-naphthol to tetrahydrofuran is 1 g:7 mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is raised to 55 °C, and the low-boiling substances are removed by reduced pressure 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 °C, a chlorosulfonic acid solution is added dropwise to the reaction system, after the addition is completed, the reaction system is naturally heated to 25 - 35 °C, and the reaction is carried out for 3 - 4 h, followed by post-treatment to obtain sulfonated cellulose.

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

[0032]

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

[0034] During the reaction, chlorosulfonic acid is used as a sulfonating agent. Due to the high electrophilicity of its sulfur atom, in the reaction system, chlorosulfonic acid dissociates into H +With the electrophilic reagent SO3, the oxygen atom of the hydroxyl group in the hydroxypropyl cellulose molecule has lone pair electrons and exhibits nucleophilicity. The electrophilic SO3 attacks the oxygen atom of the hydroxyl group to form an unstable intermediate structure, followed by rearrangement of chemical bonds. The sulfonic acid group -SO3 replaces the hydrogen atom on the hydroxyl group to generate sulfonated cellulose, and hydrogen chloride is generated simultaneously.

[0035] Furthermore, the dosage ratio of the hydroxypropyl cellulose, N,N-dimethylformamide and chlorosulfonic acid solution is 10 g:70 mL:7 mL. The chlorosulfonic acid solution is composed of chlorosulfonic acid and N,N-dimethylformamide at a ratio of 1 g:3 mL. The post-treatment includes: after the reaction is completed, add a 0.1 mol / L sodium hydroxide solution at a temperature of 5 - 8 °C to the reaction system, stir and disperse for 20 - 30 min, put the reaction solution into a dialysis bag with a molecular weight cut-off of 1000, dialyze in a purified water environment for 3 days, change the purified water every 6 h, and then transfer the solution in the dialysis bag to a freeze dryer at a temperature of -30 °C for freeze-drying to obtain sulfonated cellulose.

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

[0037] 1. The membrane separation and extraction method of ionic rare earths proposed by the present invention infiltrates and elutes the ionic rare earths in the rare earth ore by selecting magnesium sulfate solution, and optimizes the pH of the infiltration solution and the leaching solution. The strong acidity and high concentration of the infiltration solution can destroy the mineral structure and promote the desorption of rare earth ions, while the weak acidity and low concentration of the leaching solution can maintain the dissolved state of rare earths, avoid premature precipitation, and reduce the risk of co-dissolution of impurities. Moreover, when eluting the rare earth ore, ammonia-nitrogen compounds are not used, which can effectively reduce the pollution to the mineral soil. Then, by adjusting the pH of the leaching solution, impurities such as aluminum in the leaching solution are promoted to settle, and then the ionic rare earths in the leaching solution are adsorbed and nanofiltrated by the nanofiltration adsorption module, and the concentration of rare earth ions in the nanofiltrate is detected to reduce the loss of ionic rare earths, avoiding the large amount of energy consumption caused by treating the leaching solution in the form of vacuum concentration in the traditional process and reducing the production cost.

[0038] 2. The membrane separation and extraction method of ionic rare earths proposed by the present invention, when eluting the rare earth ore, the layered silicate structures such as kaolin and montmorillonite in the ionic rare earth ore undergo protonation reactions under strong acidic conditions, the intermolecular hydrogen bonds are broken, and the minerals expand and disintegrate, promoting the release of the adsorbed rare earth ions in the minerals. And in the acidic environment, H + competes with rare earth ions for the adsorption sites on the mineral surface, weakening the binding energy between rare earth ions and the minerals. During infiltration, according to the Donnan membrane equilibrium theory, the ion exchange rate between the mineral surface and the solution is proportional to the cation concentration gradient. The high-concentration Mg 2+It can significantly improve the exchange reaction rate, thereby quickly displacing the adsorbed rare earth ions in rare earth minerals. Then, after adjusting the pH of the leaching solution, it promotes the precipitation of iron ions and aluminum ions in the eluent. By filtering, most of the precipitated impurities are removed, reducing competitive adsorption and improving the selectivity of rare earth. At the same time, as the pH increases, the coordination water molecules H3O in the hydration layer + have a reduced hydrolysis concentration, the exposure degree of ionic rare earth increases, the apparent charge density rises, the charge density of ionic rare earth becomes larger, increasing the electrostatic attraction between it and the negatively charged surface of the adsorption filler, increasing the adsorption loading capacity of the adsorption filler for ionic rare earth, avoiding the blockage of the membrane pores by ionic rare earth during membrane separation, and improving the membrane separation effect.

[0039] 3. The membrane separation and extraction method of ionic rare earth proposed by the present invention promotes the combination of graphene oxide, sulfonated cellulose, and hydroxypropyl distarch phosphate by using epoxy resin as a curing agent to form an adsorption filler precursor. Sulfonic acid groups are introduced onto the hydroxypropyl cellulose molecules through chlorosulfonic acid modification, and it is completely ionized into -SO3 in an acidic aqueous environment - , forming a strong electrostatic adsorption with ionic rare earth. While graphene oxide can increase the specific surface area of the adsorption filler, the carboxyl and hydroxyl groups on its surface and the phosphate groups on the hydroxypropyl distarch phosphate molecules can form chelation with ionic rare earth, enhancing the adsorption capacity. At the same time, hydroxypropyl distarch phosphate is a crosslinked modified starch, and its molecular chains form a three-dimensional network structure through phosphate ester bonds, inhibiting particle swelling, preventing the filler from swelling excessively in an acidic or high-salt environment, maintaining the stability of the pore structure, reducing the breakage of the filler under stirring or flowing conditions, and maintaining the stability of the filler. The high crosslinking degree and the resistance to hydrolysis in strong acids of hydroxypropyl distarch phosphate make it show excellent stability in the eluent, improving its recycling performance. The modification of triethoxysilane-modified PAN introduces a rigid skeleton of a siloxane network into the adsorption filler to support the filler structure, and the pyridine azo group of PAN undergoes π-π stacking interaction with ionic rare earth, further enhancing its selectivity for ionic rare earth. Specific Embodiments

[0040] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0041] In the present 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 the present invention, hydroxypropyl distarch phosphate is selected from Wuhan Xinzhongxin Chemical Technology Co., Ltd., with a CAS number of 53124-00-8 and an active ingredient content of 99%;

[0043] In the present invention, the epoxy resin is bisphenol A epoxy resin, with the model number of E-42;

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

[0045] Example 1

[0046] This example provides a preparation method of a metal ion adsorption filler, which includes the following steps:

[0047] Step I. Prepare sulfonated cellulose

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

[0049] Weigh: 100 g of hydroxypropyl cellulose and 700 mL of N,N-dimethylformamide, add them to a reaction flask under nitrogen protection and stir. Lower the temperature of the reaction flask to 0 °C, dropwise add 70 mL of the chlorosulfonic acid solution to the reaction flask. After the addition is completed, let the temperature of the reaction flask rise to 25 °C naturally, keep the reaction for 3 h, add 100 mL of 0.1 mol / L sodium hydroxide solution at 5 °C to the reaction flask, stir and disperse for 20 min. Put the reaction solution into a dialysis bag with a cut-off molecular weight of 1000, dialyze in a purified water environment for 3 days, change the purified water every 6 h, and then transfer the solution in the dialysis bag to a freeze dryer at -30 °C for freeze-drying to obtain sulfonated cellulose.

[0050] Step II. Prepare the precursor of the adsorption filler

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

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

[0053] Weigh: 20 g of graphene oxide, 30 g of sulfonated cellulose, 100 g of hydroxypropyl distarch phosphate, 10 g of sodium hydroxide and 600 mL of deionized water and add them to a reaction flask. Ultrasonically disperse for 40 min. Fix the reaction flask in a water bath equipped with mechanical stirring and stir. Set the stirring speed to 800 r / min. Add 400 mL of emulsion to the reaction flask and stir for 20 min. Raise the reaction temperature to 60 °C. Add 200 mL of epoxy resin solution to the reaction flask and keep the reaction at this temperature for 2 h. Lower the temperature of the reaction flask to room temperature, filter by suction. Wash the filter cake with purified water 3 times and then drain it by suction. Transfer the filter cake to a drying oven at 60 °C and vacuum dry to constant weight to obtain the precursor of the adsorption filler.

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

[0055] Weigh: 24.9 g of 1-(2-pyridylazo)-2-naphthol and 174.3 mL of tetrahydrofuran and add them to a reaction flask under argon protection and stir. Raise the temperature of the reaction flask to 40 °C. Add 24.7 g of isocyanatopropyltriethoxysilane to the reaction flask and keep the reaction at this temperature for 40 min. Raise the temperature of the reaction flask to 55 °C and distill off the low-boiling substances under reduced pressure to obtain triethoxysilane-modified PAN.

[0056] Step IV. Preparation of the adsorption filler

[0057] Weigh: 500 g of the precursor of the adsorption filler, 100 g of triethoxysilane-modified PAN and 3 L of absolute ethanol and add them to a reaction flask and stir. Raise the temperature of the reaction flask to 50 °C. Add 700 mL of 0.5 mol / L sodium hydroxide solution to the reaction system and keep the reaction at this temperature for 80 min. Lower the temperature of the reaction flask to room temperature, filter by suction. Wash the filter cake with purified water until neutral and then drain it by suction. Transfer the filter cake to a drying oven at 60 °C and vacuum dry to constant weight to obtain the adsorption filler.

[0058] Example 2

[0059] This example provides a method for preparing a metal ion adsorption filler, which includes the following steps:

[0060] Step I. Preparation of sulfonated cellulose

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

[0062] Weigh: Add 100 g of hydroxypropyl cellulose and 700 mL of N,N-dimethylformamide into a reaction flask under nitrogen protection and stir. Lower the temperature of the reaction flask to 3 °C, and add 70 mL of chlorosulfonic acid solution dropwise into the reaction flask. After the addition is complete, let the temperature of the reaction flask rise to 30 °C naturally and keep the reaction for 3.5 h. Add 100 mL of 0.1 mol / L sodium hydroxide solution at 7 °C into the reaction flask and stir for 25 min. Put the reaction solution into a dialysis bag with a molecular weight cut-off of 1000 and dialyze it in a purified water environment for 3 days, changing the purified water every 6 h. Then transfer the solution in the dialysis bag to a freeze dryer at -30 °C and freeze-dry it to obtain sulfonated cellulose.

[0063] Step II: Prepare the precursor of the adsorption filler

[0064] Mix 10 mL of N,N-dimethylformamide, 0.5 g of Tween-80, and 0.3 g of sodium dodecyl sulfate evenly to obtain an emulsion.

[0065] Mix 1 g of epoxy resin and 3 mL of N,N-dimethylformamide evenly to obtain an epoxy resin solution.

[0066] Weigh: Add 20 g of graphene oxide, 30 g of sulfonated cellulose, 100 g of hydroxypropyl distarch phosphate, 10 g of sodium hydroxide, and 600 mL of deionized water into a reaction flask, disperse them ultrasonically for 50 min, fix the reaction flask in a water bath with mechanical stirring, set the stirring speed to 800 r / min, add 400 mL of the emulsion into the reaction flask, stir for 25 min, raise the reaction temperature to 65 °C, add 200 mL of the epoxy resin solution into the reaction flask, keep the reaction for 2.5 h, lower the temperature of the reaction flask to room temperature, filter by suction, wash the filter cake with purified water 3 times and then drain it by suction, transfer the filter cake to a drying oven at 65 °C, and dry it under vacuum to constant weight to obtain the precursor of the adsorption filler.

[0067] Step III: Prepare triethoxysilane-modified PAN

[0068] Weigh: Add 24.9 g of 1-(2-pyridylazo)-2-naphthol and 174.3 mL of tetrahydrofuran into a reaction flask under argon protection and stir. Raise the temperature of the reaction flask to 45 °C, add 24.7 g of isocyanatopropyltriethoxysilane into the reaction flask, keep the reaction for 50 min, raise the temperature of the reaction flask to 55 °C, and distill off the low-boiling substances under reduced pressure to obtain triethoxysilane-modified PAN.

[0069] Step IV: Prepare the adsorption filler

[0070] Weigh: Add 500 g of the adsorbent filler precursor, 100 g of triethoxysilane-modified PAN, and 3 L of absolute ethanol into a reaction flask and stir. Raise the temperature of the reaction flask to 55 °C. Add 700 mL of 0.5 mol / L sodium hydroxide solution to the reaction system, keep the temperature for reaction for 85 min, lower the temperature of the reaction flask to room temperature, perform suction filtration, wash the filter cake with purified water until it is neutral and then dry it by suction. Transfer the filter cake to a drying oven at 65 °C and vacuum dry it to a constant weight to obtain the adsorbent filler.

[0071] Example 3

[0072] This example provides a method for preparing a metal ion adsorbent filler, which includes the following steps:

[0073] Step I: Prepare sulfonated cellulose

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

[0075] Weigh: Add 100 g of hydroxypropyl cellulose and 700 mL of N,N-dimethylformamide into a reaction flask protected by nitrogen and stir. Lower the temperature of the reaction flask to 5 °C. Dropwise add 70 mL of the chlorosulfonic acid solution to the reaction flask. After the addition is complete, let the temperature of the reaction flask rise to 35 °C naturally and keep the temperature for reaction for 4 h. Add 100 mL of 0.1 mol / L sodium hydroxide solution at 8 °C to the reaction flask and stir for dispersion for 30 min. Put the reaction solution into a dialysis bag with a molecular weight cut-off of 1000 and dialyze it in a purified water environment for 3 days, changing the purified water every 6 h. Then transfer the solution in the dialysis bag to a freeze dryer at -30 °C for freeze drying to obtain sulfonated cellulose.

[0076] Step II: Prepare the adsorbent filler precursor

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

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

[0079] Weigh: 20 g of graphene oxide, 30 g of sulfonated cellulose, 100 g of hydroxypropyl distarch phosphate, 10 g of sodium hydroxide and 600 mL of deionized water and add them to a reaction flask. Sonicate for 60 min, fix the reaction flask in a water bath equipped with mechanical stirring and stir, set the stirring speed to 800 r / min, add 400 mL of emulsion to the reaction flask, stir for 30 min, raise the reaction temperature to 70 °C, add 200 mL of epoxy resin solution to the reaction flask, keep the temperature for reaction for 3 h, lower the temperature of the reaction flask to room temperature, perform suction filtration, wash the filter cake with purified water 3 times and then drain it, transfer the filter cake to a drying oven at 70 °C, and vacuum dry to constant weight to obtain the precursor of the adsorption filler.

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

[0081] Weigh: 24.9 g of 1-(2-pyridylazo)-2-naphthol and 174.3 mL of tetrahydrofuran and add them to a reaction flask protected by argon and stir. Raise the temperature of the reaction flask to 50 °C, add 24.7 g of isocyanatopropyltriethoxysilane to the reaction flask, keep the temperature for reaction for 60 min, raise the temperature of the reaction flask to 55 °C, and distill off the low-boiling substances under reduced pressure to obtain triethoxysilane-modified PAN.

[0082] Step IV. Preparation of the adsorption filler

[0083] Weigh: 500 g of the precursor of the adsorption filler, 100 g of triethoxysilane-modified PAN and 3 L of absolute ethanol and add them to a reaction flask and stir. Raise the temperature of the reaction flask to 60 °C, add 700 mL of 0.5 mol / L sodium hydroxide solution to the reaction system, keep the temperature for reaction for 90 min, lower the temperature of the reaction flask to room temperature, perform suction filtration, wash the filter cake with purified water until neutral and then drain it, transfer the filter cake to a drying oven at 70 °C, and vacuum dry to constant weight to obtain the adsorption filler.

[0084] Example 4

[0085] This example provides a method for membrane separation and extraction of ionic rare earths, including the following steps:

[0086] Step 1. Preparation of rare earth ore eluate

[0087] Mix magnesium sulfate and purified water and stir until the system becomes clear to obtain a magnesium sulfate solution with a concentration of 0.3 mol / L, add sulfuric acid to adjust the pH to 3.0 to obtain the infiltration liquid;

[0088] Stir and mix magnesium sulfate and purified water until the system becomes clear to obtain a magnesium sulfate solution with a concentration of 0.08 mol / L, add sulfuric acid to adjust the pH to 5 to obtain the leaching liquid;

[0089] Select a circular column with an aspect ratio of 3:1 as the leaching column. Set a filter cloth with a pore size of 50 μm at the bottom of the leaching column. Load the ionic rare earth ore with 1% moisture into the leaching column. Add the wetting solution to the leaching column so that the wetting solution completely covers the ionic rare earth ore. At room temperature, keep it warm and wet for 2 h. Then add the leaching solution to the leaching column for leaching and elution to obtain the eluate. The volume ratio of the wetting solution to the leaching solution is 1:3.

[0090] Step 2: Nanofiltration adsorption

[0091] Place a dialysis membrane bag with a molecular weight cut-off of 13,000 in a filter bag with a pore size of 50 μm. Then place the adsorption packing prepared in Example 1 into the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0092] Transport the eluate to a pH adjustment tank, adjust the system pH = 5.7, filter through a filter cloth with a pore size of 1 μm. The filtrate enters the inside of the dialysis membrane bag of the nanofiltration adsorption membrane group for nanofiltration adsorption. Detect the rare earth metal content in the filtrate. When the rare earth metal content in the filtrate reaches 5 ppm, obtain the adsorption packing saturated with adsorption. At this time, the adsorption packing needs to be replaced.

[0093] Step 3: Prepare nanofiltration concentrate

[0094] Add the adsorption packing saturated with adsorption to an elution column with an aspect ratio of 8:1. Use a 0.8 mol / L sulfuric acid aqueous solution as the eluent for cyclic elution for 30 min, and then use purified water for cyclic elution for 20 min. Combine the eluates to obtain the nanofiltration concentrate. Take out the adsorption packing from the elution column and wash it with purified water until it is neutral to obtain the regenerated adsorption packing. Among them, the volume ratio of the adsorption packing saturated with adsorption, the eluent, and purified water is 1:7:3.

[0095] Step 4: Prepare ionic rare earth

[0096] Add sodium hydroxide to the nanofiltration concentrate, adjust the system pH = 10, filter by suction. Wash the filter cake with purified water until it is neutral and then drain it by suction. Transfer the filter cake to a drying oven at 70 °C and dry for 4 h. Then transfer it to a roasting furnace at 500 °C and keep it warm and roast for 3 h to obtain ionic rare earth.

[0097] Example 5

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

[0099] Step 1: Prepare rare earth ore elution

[0100] Mix magnesium sulfate and purified water and stir until the system is clear to obtain a 0.4 mol / L magnesium sulfate solution. Add sulfuric acid to adjust the pH = 3.3 to obtain the wetting solution.

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

[0102] A circular column with a length-to-diameter ratio of 3:1 was selected as the leaching column. A filter cloth with a pore size of 75 μm was set at the bottom of the leaching column. The ionic rare earth ore with 3% water content was loaded into the leaching column. An infiltration solution was added to the leaching column to completely submerge the ionic rare earth ore. At room temperature, it was kept infiltrated for 2.5 h. Then, the leaching solution was added to the leaching column for leaching and elution to obtain an eluate. The volume ratio of the infiltration solution to the leaching solution was 1:3.

[0103] Step 2: Nanofiltration adsorption

[0104] A dialysis membrane bag with a cut-off molecular weight of 14,000 was placed in a filter bag with a pore size of 75 μm. Then, the adsorption packing prepared in Example 2 was placed into the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0105] The eluate was transported to a pH adjustment tank to adjust the system pH to 5.8. It was filtered through a filter cloth with a pore size of 3 μm. The filtrate entered the inside of the dialysis membrane bag of the nanofiltration adsorption membrane group for nanofiltration adsorption. The rare earth metal content in the filtrate was detected. When the rare earth metal content in the filtrate reached 5 ppm, the adsorption packing with saturated adsorption was obtained. At this time, the adsorption packing needed to be replaced.

[0106] Step 3: Preparation of nanofiltration concentrate

[0107] The adsorption packing with saturated adsorption was added to an elution column with a length-to-diameter ratio of 8:1. A 1.0 mol / L sulfuric acid aqueous solution was used as the eluent for cyclic elution for 40 min, and then purified water was used for cyclic elution for 25 min. The eluents were combined to obtain a nanofiltration concentrate. The adsorption packing was taken out of the elution column and washed with purified water until neutral to obtain a regenerated adsorption packing. Among them, the volume ratio of the adsorption packing with saturated adsorption, the 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 system pH to 10. It was suction-filtered. The filter cake was washed with purified water until neutral and then dried by suction. The filter cake was transferred to a drying oven at 75 °C and dried for 5 h. Then, it was transferred to a roasting furnace at 525 °C and kept roasted for 4 h to obtain ionic rare earth.

[0110] Example 6

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

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

[0113] Mix magnesium sulfate and purified water and stir until the system becomes clear to obtain a magnesium sulfate solution with a concentration of 0.5 mol / L. Add sulfuric acid to adjust the pH to 3.6 to obtain an infiltration solution.

[0114] Stir and mix magnesium sulfate and purified water until the system becomes clear to obtain a magnesium sulfate solution with a concentration of 0.12 mol / L. Add sulfuric acid to adjust the pH to 5 to obtain a leaching solution.

[0115] Select a circular column with a length-to-diameter ratio of 3:1 as the leaching column. Set a filter cloth with a pore size of 100 μm at the bottom of the leaching column. Load the ionic rare earth ore with 5% moisture into the leaching column. Add the infiltration solution to the leaching column so that the infiltration solution completely covers the ionic rare earth ore. Keep it warm and infiltrate for 3 h at room temperature. Then add the leaching solution to the leaching column for leaching and elution to obtain an eluate. The volume ratio of the infiltration solution to the leaching solution is 1:3.

[0116] Step 2: Nanofiltration adsorption

[0117] Place a dialysis membrane bag with a cut-off molecular weight of 15000 in a filter bag with a pore size of 100 μm. Then place the adsorption packing prepared in Example 3 into the dialysis membrane bag to obtain a nanofiltration adsorption module.

[0118] Transport the eluate to a pH adjustment tank, adjust the system pH to 5.9, filter through a filter cloth with a pore size of 5 μm. The filtrate enters the inside of the dialysis membrane bag of the nanofiltration adsorption membrane group for nanofiltration adsorption. Detect the rare earth metal content in the filtrate. When the rare earth metal content in the filtrate reaches 5 ppm, obtain the adsorption packing saturated with adsorption. At this time, it is necessary to replace the adsorption packing.

[0119] Step 3: Prepare nanofiltration concentrate

[0120] Add the adsorption packing saturated with adsorption to an elution column with a length-to-diameter ratio of 8:1. Use a 1.2 mol / L sulfuric acid aqueous solution as the eluent for cyclic elution for 50 min, and then use purified water for cyclic elution for 30 min. Combine the eluents to obtain a nanofiltration concentrate. Take out the adsorption packing from the elution column and wash it with purified water until it is neutral to obtain a regenerated adsorption packing. Among them, the volume ratio of the adsorption packing saturated with adsorption, the eluent, and purified water is 1:7:3.

[0121] Step 4: Prepare ionic rare earth

[0122] Add sodium hydroxide to the nanofiltration concentrate to adjust the system pH to 10. Perform suction filtration. Wash the filter cake with purified water until it is neutral and then drain it. Transfer the filter cake to a drying oven at 80 °C and dry for 6 h. Then transfer it to a roasting furnace at 550 °C and keep it warm and roast for 5 h to obtain ionic rare earth.

[0123] Comparative Example 1

[0124] The difference between this comparative example and Example 6 is that in Step 1, the leaching solution is used instead of the infiltration solution.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 6 is that in Step 2, the pH adjustment of the eluent is cancelled, and the eluent directly enters the dialysis membrane bag.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 6 is that when the adsorption packing used is prepared, hydroxypropyl distarch phosphate is not added in Step II.

[0129] Comparative Example 4

[0130] The difference between this comparative example and Example 6 is that when the adsorption packing used is prepared, Steps III and IV are cancelled, and the adsorption packing precursor is used as the adsorption packing.

[0131] Performance test:

[0132] Refer to the formula Determine the extraction rate of rare earth ions in Examples 4 - 6 and Comparative Examples 1 - 4. In the formula, m 稀土 ore is the mass of the rare earth ore, w 稀土矿-稀土 is the content of rare earth in the rare earth ore, m 稀土 is the mass of ionic rare earth, w 稀土 is the content of ionic rare earth;

[0133] Refer to the standard JC / T 2021 - 2010 "Test Method for Adsorption Capacity of Mesoporous Materials" to determine the adsorption capacity of the adsorption packing used in Examples 4 - 6 and Comparative Examples 1 - 4 for ionic rare earth in an aqueous environment with pH = 5.7 - 5.9, and recycle the regenerated adsorption packing 50 times. Calculate the adsorption capacity retention rate according to the formula where Q1 is the adsorption capacity of the adsorption packing for the first time, and Q 100 is the adsorption capacity of the adsorption packing for the 100th cycle;

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

[0135] Table 1 - Data Sheet of Performance Detection of Samples

[0136]

[0137] Data analysis:

[0138] By comparing and analyzing the data in Table 1 above, the extraction rate of ionic rare earth in rare earth minerals by the present invention reaches 89.2%. The adsorption capacity of the adsorption packing used for ionic rare earth reaches 392.5 mg / g. After 100 cycles, the retention rate of the adsorption capacity of the adsorption packing reaches 88.4%. Although the extraction rate of Comparative Example 2 is not much different from that of Example 3, the amount of adsorption packing required for adsorbing the same eluent increases greatly. All the performance measurement data are superior to those of the comparative examples. This shows that by optimizing the elution process of rare earth minerals and cooperating with the adsorption packing prepared in this application, the present invention not only effectively improves the extraction rate of ionic rare earth and the adsorption capacity of the adsorption packing for ionic rare earth, but also effectively reduces the pollution of ionic rare earth extraction to ecological soil and the production cost.

[0139] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claims, they should fall within the protection scope of the present invention.

[0140] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0141] The above disclosed preferred embodiments of the present invention are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific implementation manners. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art of this technology can understand and utilize the present invention well. The present invention is only limited by the claims and its full scope and equivalents.

Claims

1. A method for membrane separation and extraction of ionic rare earths, characterized in that, It includes the following steps: S1. Load the dry ionic rare earth ore into the leaching column, add the wetting solution to the leaching column so that the wetting solution completely covers the ionic rare earth ore, keep it warm and wet for 2 - 3 h at room temperature, and then carry out leaching and elution with the leaching solution to obtain the eluate; S2. Transport the eluate to the pH adjustment tank, adjust the system pH = 5.7 - 5.9, filter, and the filtrate is subjected to nanofiltration adsorption through a nanofiltration adsorption membrane module filled with adsorption packing and then desorbed and eluted to prepare a nanofiltration concentrate; S3. After the nanofiltration concentrate is precipitated with alkali, it is filtered and calcined to prepare ionic rare earth.

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

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

3. The membrane separation and extraction method of an ionic rare earth according to claim 1, characterized in that, In step S2, the nanofiltration adsorption membrane module includes a dialysis membrane bag and adsorption packing. The adsorption packing is filled in the dialysis membrane bag. The cut-off molecular weight of the dialysis membrane bag is 13000 - 15000. The desorption and elution method is as follows: Add the adsorption-saturated adsorption packing to the elution column, elute with the eluate for 30 - 50 min, then elute with purified water for 20 - 30 min, combine the eluates to obtain the nanofiltration concentrate, take out the adsorption packing from the elution column, wash it with purified water until neutral to obtain the regenerated adsorption packing. The volume ratio of the adsorption-saturated adsorption packing, the eluate, and purified water is 1:7:

3. The eluate is a sulfuric acid aqueous solution with a concentration of 0.8 - 1.2 mol / L.

4. A membrane separation and extraction method for ionic rare earths 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 system pH = 10, carry out suction filtration, wash the filter cake with purified water until neutral and then drain it, transfer the filter cake to a drying oven at a temperature of 70 - 80 °C and dry for 4 - 6 h, then transfer it to a roasting furnace at a temperature of 500 - 550 °C and keep it roasted for 3 - 5 h to obtain ionic rare earth.

5. A membrane separation and extraction method for ionic rare earths according to claim 1, characterized in that The adsorption packing is obtained by the following steps: A1. Add graphene oxide, sulfonated cellulose, hydroxypropyl distarch phosphate, and sodium hydroxide to deionized water, ultrasonically disperse for 40 - 60 min, under stirring, add the emulsion to the reaction system, stir for 20 - 30 min, raise the reaction temperature to 60 - 70 °C, add the epoxy resin solution to the reaction system, keep the reaction for 2 - 3 h, and carry out post-treatment to obtain the adsorption packing precursor; A2. Mix and stir the adsorption packing precursor, triethoxysilane-modified PAN, and absolute ethanol, raise the temperature of the reaction system to 50 - 60 °C, add the catalyst to the reaction system, keep the reaction for 80 - 90 min, and carry out post-treatment to obtain the adsorption packing.

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

7. A membrane separation and extraction method for ionic rare earths according to claim 5, characterized in that, The preparation method of triethoxysilane-modified PAN is as follows: under the protection of inert gas, 1-(2-pyridylazo)-2-naphthol and tetrahydrofuran are stirred and mixed, the temperature of the reaction system is raised to 40-50 °C, and propyl isocyanatotriethoxysilane is added to the reaction system, and the reaction is carried out at a constant temperature for 40-60 min to obtain triethoxysilane-modified PAN.

8. A membrane separation and extraction method for ionic rare earths according to claim 7, characterized in that, The dosage ratio of 1-(2-pyridylazo)-2-naphthol and propyl isocyanatotriethoxysilane is 1 mol: 1 mol, and the dosage ratio of 1-(2-pyridylazo)-2-naphthol and tetrahydrofuran is 1 g: 7 mL.

9. A membrane separation and extraction method for ionic rare earths according to claim 5, 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 °C, 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 °C, and the reaction is carried out at a constant temperature for 3-4 h, followed by post-treatment to obtain sulfonated cellulose.

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

Images