CN-121972019-A - Polyacid conductive nanofiltration membrane for rare earth purification and preparation method and application thereof

CN121972019ACN 121972019 ACN121972019 ACN 121972019ACN-121972019-A

Abstract

The invention discloses a polyacid conductive nanofiltration membrane for rare earth purification and a preparation method and application thereof. The nanofiltration membrane comprises a porous base membrane and a selective separation layer attached to the porous base membrane, wherein the selective layer consists of polyamine polymers, polyoxometallates (POMs) and polyfunctional acyl chloride. The preparation method adopts a layer-by-layer self-assembly cooperative interfacial polymerization strategy, firstly builds an intermediate layer through the electrostatic action of polyamine and POMs, and then forms a crosslinked network through interfacial polymerization. The membrane has excellent conductivity and electrical responsiveness, and in the purification process of the rare earth leaching solution, by applying an external electric field and utilizing the specific interaction of POMs and rare earth ions, the high-efficiency separation of the rare earth ions from high-valence impurity ions such as calcium, magnesium and the like is realized, the separation factor is obviously improved, and the problem that the separation precision of the traditional nanofiltration membrane on similar high-valence ions is insufficient is solved.

Inventors

SUN SHIPENG
CAO XUELI
YU DAN
SUN YUXUAN
SUN MENGLIN
Nan Zaixu
LI MINGSHU

Assignees

南京工业大学
蔚华膜科技(昆山)有限公司
南京工业大学苏州未来膜技术创新中心

Dates

Publication Date: 20260505
Application Date: 20260206

Claims (10)

1. A polyacid conductive nanofiltration membrane for purification of rare earth leaching solution is characterized by comprising a porous base membrane and a selective separation layer attached to the surface of the porous base membrane, wherein the selective separation layer comprises polyamine polymers, polyoxometallate and polyfunctional acyl chloride, electrostatic interaction exists between the polyamine polymers and the polyoxometallate, interfacial polymerization reaction occurs between the polyamine polymers and the polyfunctional acyl chloride to form a crosslinked network structure, and the polyoxometallate is distributed in the crosslinked network structure.
2. The polyacid conductive nanofiltration membrane according to claim 1, wherein the porous base membrane is made of at least one material selected from polyethersulfone, polysulfone, polyvinylidene fluoride and polyacrylonitrile, the polyamine polymer is polyethyleneimine, the polyoxometalate is Keggin-type polyoxometalate, preferably sodium dodecyl tungsten phosphate, and the polyfunctional acyl chloride is aromatic acyl chloride, preferably 1,3, 5-trimesic acyl chloride.
3. The polyacid conductive nanofiltration membrane according to claim 1, wherein the selective separation layer has a hierarchical structure formed by alternate deposition of polyamine-based polymer layers, polyoxometallate layers, and polyamine-based polymer layers, followed by interfacial polymerization curing.
4. The polyacid conductive nanofiltration membrane according to claim 1, wherein the nanofiltration membrane has conductivity and electrical responsiveness, and the nanofiltration membrane has a higher rejection rate of rare earth ions than divalent impurity ions under the condition of applying an external electric field.
5. A method for preparing a polyacid conductive nanofiltration membrane according to any one of claims 1 to 4, comprising the steps of S1 providing a porous base membrane, S2 immersing the porous base membrane in a first aqueous phase solution for adsorption, taking out the porous base membrane, cleaning and removing surface residual liquid, wherein the first aqueous phase solution contains polyamine polymer, S3 immersing the membrane treated in the step S2 in an intermediate layer solution for reaction, taking out the membrane, cleaning and removing surface residual liquid, wherein the intermediate layer solution contains polyoxometalate, S4 immersing the membrane treated in the step S3 in a second aqueous phase solution for adsorption, taking out the membrane, cleaning and removing surface residual liquid, wherein the second aqueous phase solution contains polyamine polymer, S5 contacting the membrane treated in the step S4 with an oil phase solution for interfacial polymerization reaction, and removing solvent after the reaction is finished to obtain the polyacid conductive nanofiltration membrane, wherein the oil phase solution contains polyfunctional acyl chloride.
6. The method according to claim 5, wherein the polyamine-based polymer concentration in the steps S2 and S4 is independently 0.5 to 5.0wt%, preferably 2.0wt%, the immersion time is independently 1 to 10min, preferably 5min, the polyoxometallate concentration in the step S3 is 0.5 to 4.0wt%, preferably 1.0 to 2.5wt%, and the immersion reaction time is 1 to 10min, preferably 5min.
7. The method according to claim 5, wherein in the step S5, the concentration of the polyfunctional acyl chloride is 0.05-0.5wt%, preferably 0.1wt%, the solvent of the oil phase solution is C5-C8 alkane, preferably n-hexane, and the interfacial polymerization reaction time is 0.5-5min, preferably 1min.
8. Use of a polyacid conductive nanofiltration membrane as defined in any one of claims 1-4 in the field of rare earth leachate purification or high valence ion separation.
9. The application according to claim 8, wherein the application comprises the steps of placing the polyacid conductive nanofiltration membrane in a mixed salt solution to be separated, taking the polyacid conductive nanofiltration membrane as a working electrode, taking the membrane as a cathode, applying an applied voltage to carry out filtration separation, wherein the mixed salt solution contains rare earth ions and high-valence impurity ions, the rare earth ions are at least one of lanthanum ions, cerium ions, neodymium ions, dysprosium ions or lutetium ions, and the high-valence impurity ions are at least one of calcium ions or magnesium ions.
10. The use according to claim 9, wherein the polyacid conductive nanofiltration membrane is used as a cathode, the applied voltage is in the range of-15V to-1V, preferably-11V to-5V, and the separation factor of the rare earth ions and the high-valence impurity ions increases with the increase of the negative voltage absolute value.

Description

Polyacid conductive nanofiltration membrane for rare earth purification and preparation method and application thereof Technical Field The invention relates to a polyacid conductive nanofiltration membrane for rare earth purification and a preparation method and application thereof, belonging to the technical field of nanofiltration membranes and applications. Background Rare earth elements (RARE EARTH ELEMENTS, REEs), which are "vitamins" of the modern industry, have become key strategic resources for supporting the development of the high and new technology industry by virtue of unique magnetic, optical and electrical properties. However, the current rare earth purification faces significant technical challenges in that ion-adsorbing deposits, which are the primary sources of rare earth, inevitably incorporate high-valence metal impurity ions, such as calcium, magnesium, etc., during leaching. These impurities have similar ionic radii and coordination chemistry to rare earth ions, resulting in severe co-extraction during solvent extraction. This not only increases the extraction stages and acid-base consumption, but also significantly reduces the purity of the final product. Although emerging membrane separation technologies, such as ion-imprinted membranes, polymer inclusion membranes, liquid membranes, and the like, exhibit good ion selectivity and ease of operation, they are limited by key problems such as insufficient stability and mechanical strength. Therefore, the development of a novel purification technology with high-efficiency separation performance and environmental-friendly characteristics becomes a key research direction for promoting the high-quality development of the rare earth industry. Nanofiltration (nanofiltration, NF) membranes can achieve high-selectivity separation of ions by virtue of the synergistic effect of the Dainan effect and pore size sieving, and are of great interest in the fields of material purification and resource recovery. The traditional nanofiltration membrane has realized the high-efficiency separation of ions with different valence states such as SO 4²⁻/Cl⁻、Cl⁻/CO3 & lt 2 & gt-, mg2+ & lt/Li & gt and the like, and can distinguish monovalent ions such as CH 3 COO- & lt/Cl & lt- & gt and the like. However, separation between high valence ions remains challenging. The method is mainly characterized in that the hydration radius of the high valence ions is similar, the pore size screening effect is limited, and the difference of the daonan repulsive force between the high valence ions is insufficient. In conclusion, the nanofiltration membrane has insufficient separation precision for high-valence ions due to the unobvious difference between the aperture screening effect and the southward effect. The conductive nanofiltration membrane is prepared from advanced materials such as conductive polymers, and the charge density of the membrane, electrostatic interaction on the surface of the membrane and hydration state of ions can be effectively regulated by combining an electric field with the conductive nanofiltration membrane. This finding shows that by fine-tuning the voltage, the separation selectivity of the membrane can be precisely controlled, thereby achieving efficient screening of specific ions. Disclosure of Invention According to the invention, the polyoxometallate is introduced into the nanofiltration membrane to prepare the conductive membrane with excellent electrical response, and the separation performance of the membrane is regulated and controlled by utilizing an external electric field, so that the efficient separation of rare earth ions and impurity ions is successfully realized, and the separation efficiency of rare earth elements is remarkably improved. The polyacid conductive nanofiltration membrane for purification of rare earth leaching solution comprises a porous base membrane and a selective separation layer attached to the surface of the porous base membrane, wherein the selective separation layer comprises a polyamine polymer, polyoxometalate and polyfunctional acyl chloride, electrostatic interaction exists between the polyamine polymer and the polyoxometalate, interfacial polymerization reaction occurs between the polyamine polymer and the polyfunctional acyl chloride to form a crosslinked network structure, and the polyoxometalate is distributed in the crosslinked network structure. The porous base membrane is made of at least one of polyethersulfone, polysulfone, polyvinylidene fluoride or polyacrylonitrile, the polyamine polymer is polyethyleneimine, the polyoxometallate is Keggin polyoxometallate, preferably sodium dodecyl tungsten phosphate, and the polyfunctional acyl chloride is aromatic acyl chloride, preferably 1,3, 5-trimesic acyl chloride. The selective separation layer has a hierarchical structure, and the hierarchical structure is formed by alternately depositing a polyamine polymer layer, a polyoxometallate layer and a polyamin