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CN-122006526-A - Acid-resistant composite nanofiltration membrane and preparation method thereof

CN122006526ACN 122006526 ACN122006526 ACN 122006526ACN-122006526-A

Abstract

The invention discloses an acid-resistant composite nanofiltration membrane and a preparation method thereof, and relates to the technical field of membrane separation. The method comprises washing polysulfone ultrafiltration membrane, co-depositing in Tris-HCl buffer solution containing dopamine hydrochloride and tannic acid to form polydopamine/tannic acid intermediate layer, sequentially using gamma The preparation method comprises the steps of coupling and modifying an intermediate layer by aminopropyl triethoxysilane and polyethylene glycol diglycidyl ether, preparing a coating liquid by sulfonated polyether-ether-ketone and phytic acid, scraping the coating liquid on the surface of a coupling modified film, and performing thermal crosslinking and curing. According to the method, an acid-resistant intermediate layer is constructed through codeposition, interlayer covalent bridging is realized by utilizing a silane coupling agent and a flexible epoxy compound, and then a sulfonated polyether-ether-ketone/phytic acid crosslinking system is used for forming a charge function separation layer. The obtained composite nanofiltration membrane has stable structure in a strong acid environment, high rejection rate on multivalent metal ions, strong interlayer binding force and excellent interface micro-peeling resistance, and the service life and the operation stability of the membrane are obviously improved.

Inventors

  • WANG XIAOMANG
  • GENG HAIBO
  • CHEN XI
  • LIU DONGYUE
  • WANG XUEFENG

Assignees

  • 石家庄职业技术学院(石家庄开放大学)

Dates

Publication Date
20260512
Application Date
20260403

Claims (10)

  1. 1. The preparation method of the acid-resistant composite nanofiltration membrane is characterized by comprising the following steps of: (1) Immersing the polysulfone ultrafiltration membrane in deionized water for soaking and cleaning to remove residual substances, and sucking free water on the surface of the membrane for later use; (2) Dissolving Tris (hydroxymethyl) aminomethane in deionized water, dropwise adding a hydrochloric acid solution to adjust the pH value, and fixing the volume to obtain a Tris-HCl buffer solution; (3) Sequentially adding dopamine hydrochloride and tannic acid into the Tris-HCl buffer solution, stirring and dissolving to prepare codeposition mother solution, immersing the pretreated polysulfone ultrafiltration membrane into the codeposition mother solution for oscillation reaction, sequentially immersing and washing with deionized water and absolute ethyl alcohol after the reaction is finished, and drying to obtain a PDA/TA@PSf membrane; (4) Adding gamma-aminopropyl triethoxysilane into an ethanol water solution, stirring and pre-hydrolyzing, immersing the PDA/TA@PSf membrane into the silane hydrolysate for reaction, taking out and cleaning with the ethanol water solution; (5) Slowly adding polyether-ether-ketone powder into concentrated sulfuric acid, stirring for sulfonation reaction, pouring the reaction solution into an ice-water mixture after the reaction is finished to separate out a product, repeatedly washing the product to be neutral by suction filtration and deionized water, drying, and grinding to obtain sulfonated polyether-ether-ketone powder; (6) Adding the prepared sulfonated polyether-ether-ketone powder into deionized water, heating and stirring until the sulfonated polyether-ether-ketone powder is completely dissolved, cooling, adding a phytic acid aqueous solution, stirring uniformly, and standing and defoaming to obtain SPEEK/phytic acid coating liquid; (7) Spreading and fixing the coupling modified membrane, scraping the SPEEK/phytic acid coating liquid on the surface of the coupling modified membrane to form a uniform liquid membrane, sequentially performing pre-drying and high-temperature thermal crosslinking treatment to solidify the coating, cooling, removing the membrane, immersing the membrane in deionized water, and soaking and cleaning to obtain the acid-resistant composite nanofiltration membrane.
  2. 2. The method for preparing the acid-resistant composite nanofiltration membrane according to claim 1, wherein the molecular weight cutoff of the polysulfone ultrafiltration membrane in the step (1) is 50kDa, and the soaking and cleaning conditions are that the soaking is carried out for 24 hours at room temperature, and deionized water is replaced every 8 hours during the soaking.
  3. 3. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (3), the mass ratio of dopamine hydrochloride to tannic acid is 2 (0.5-1.5).
  4. 4. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (3), the oscillation reaction temperature is 25-30 ℃, and the oscillation reaction time is 10-12 hours.
  5. 5. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (4), the mass ratio of gamma-aminopropyl triethoxysilane to polyethylene glycol diglycidyl ether is 1.5 (0.5-1).
  6. 6. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (4), the molecular weight of the polyethylene glycol diglycidyl ether is 500Da.
  7. 7. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (5), the constant-temperature reaction is performed for 3-5 hours under the stirring reaction condition of 40-50 ℃.
  8. 8. The method for preparing the acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (6), the mass ratio of the sulfonated polyether-ether-ketone powder to the phytic acid is 3 (1-2).
  9. 9. The method for preparing an acid-resistant composite nanofiltration membrane according to claim 1, wherein in the step (7), the heat crosslinking treatment temperature is 130-140 ℃ and the time is 15-20 min.
  10. 10. An acid-resistant composite nanofiltration membrane, which is characterized by being prepared by the method of any one of claims 1-9.

Description

Acid-resistant composite nanofiltration membrane and preparation method thereof Technical Field The invention relates to the technical field of membrane separation, in particular to an acid-resistant composite nanofiltration membrane and a preparation method thereof. Background Nanofiltration membrane is used as a pressure driving membrane between ultrafiltration and reverse osmosis, and is widely applied to the fields of water treatment, chemical separation, food processing and the like by virtue of a unique molecular sieving and charge rejection mechanism. In recent years, with the continuous expansion of application scenes such as hydrometallurgy, waste battery recovery, acid mine drainage treatment and the like, urgent demands are put on the long-term operation stability of nanofiltration membranes under the condition of strong acid (pH < 2). At present, most commercial nanofiltration membranes use polyamide as a separation functional layer, and the preparation of the nanofiltration membranes generally adopts an interfacial polymerization method of piperazine or m-phenylenediamine and trimesoyl chloride. However, the amide bond in the polyamide structure is easy to be hydrolyzed and broken in a strong acid medium, so that the membrane layer structure is damaged, the interception performance is drastically reduced, and the industrial application of the polyamide in an acidic environment is severely limited. In the prior art, researchers try to crosslink acyl chloride monomers with steric hindrance effect with polyamine compounds, and regulate the density and flux of the membrane through subsequent acid dissociation treatment. For example, chinese patent publication No. CN114950135B discloses an acid-resistant nanofiltration membrane and a preparation method thereof, which uses cyanuric chloride and polyethylenimine to perform interfacial polymerization, uses glutaraldehyde to perform secondary crosslinking, and finally, is soaked in acid liquor to dissociate cyanuric chloride components to obtain the acid-resistant membrane. Although the acid resistance of the membrane is improved to a certain extent, the method has the following defects that the acid dissociation step is extremely sensitive to operation conditions (acid concentration and soaking time), the process controllability is poor, the batch-to-batch performance fluctuation is easy to cause, the dissociated membrane layer structure is loose, the compaction deformation is easy to occur under high-pressure operation, the long-term operation stability is insufficient, the toxicity of cyanuric chloride used in the preparation process is high, and high requirements are put on the operation environment and waste liquid treatment. Therefore, the nanofiltration membrane preparation method which is simple and convenient in process, environment-friendly, stable in membrane layer structure and excellent in acid resistance is developed, and has important significance for promoting the large-scale application of the nanofiltration technology in an acid system. Disclosure of Invention The invention aims to provide an acid-resistant composite nanofiltration membrane and a preparation method thereof, so as to solve the technical problems of the background technology. In order to achieve the above purpose, the present invention provides the following technical solutions: the preparation method of the acid-resistant composite nanofiltration membrane comprises the following steps: (1) Immersing the polysulfone ultrafiltration membrane in deionized water for soaking and cleaning to remove residual substances, and sucking free water on the surface of the membrane for later use. (2) Dissolving Tris (hydroxymethyl) aminomethane in deionized water, dropwise adding a hydrochloric acid solution to adjust the pH value, and fixing the volume to obtain a Tris-HCl buffer solution. (3) Adding dopamine hydrochloride and tannic acid into the Tris-HCl buffer solution in turn, stirring and dissolving to prepare codeposition mother solution, immersing the pretreated polysulfone ultrafiltration membrane into the codeposition mother solution for oscillation reaction, sequentially immersing and washing with deionized water and absolute ethyl alcohol after the reaction is finished, and drying to obtain the PDA/TA@PSf membrane. (4) Adding gamma-aminopropyl triethoxy silane into ethanol water solution, stirring for prehydrolysis, immersing the PDA/TA@PSf membrane into the silane hydrolysis solution for reaction, taking out, washing with ethanol water solution, adding polyethylene glycol diglycidyl ether into ethanol water solution, stirring for dissolution, and immersing the washed membrane to obtain the coupling modified membrane. (5) Slowly adding polyether-ether-ketone powder into concentrated sulfuric acid, stirring for sulfonation reaction, pouring the reaction solution into an ice-water mixture after the reaction is finished to separate out a product, filtering, repeatedly washing