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CN-121972018-A - Acid-resistant nanofiltration membrane and preparation method thereof

CN121972018ACN 121972018 ACN121972018 ACN 121972018ACN-121972018-A

Abstract

The invention relates to the technical field of filter media, in particular to an acid-resistant nanofiltration membrane and a preparation method thereof, and the acid-resistant nanofiltration membrane comprises the following steps of S1, providing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution is an aqueous solution in which polyamine monomers are dissolved, the oil phase solution is an organic solution in which isocyanate monomers and alkyl phosphate salt compounds serving as reaction promoters are dispersed, S2, enabling the aqueous phase solution and the oil phase solution to contact on a support base membrane to generate an interfacial polymerization reaction so as to form a polyurea active separation layer on the surface of the support base membrane, and S3, carrying out heat treatment to obtain the strong acid-resistant nanofiltration membrane. According to the invention, a small amount of alkyl phosphate compound is added into the oil phase solution as a reaction promoter, so that a polyurea active separation layer with a better structure can be promoted to be formed, and the synchronous promotion of the water flux, the acid permeability and the metal ion retention rate of the nanofiltration membrane is realized.

Inventors

  • CHENG XIN
  • PAN QIAOMING
  • SHI YINGYING
  • XIAO LUQI
  • ZHANG ZHEHUA
  • QU ZHOU
  • YANG SHUAI
  • SONG YIMING

Assignees

  • 杭州水处理技术研究开发中心有限公司

Dates

Publication Date
20260505
Application Date
20260408

Claims (10)

  1. 1. The preparation method of the acid-resistant nanofiltration membrane is characterized by comprising the following steps of: s1, providing an aqueous phase solution and an oil phase solution; The aqueous phase solution is an aqueous solution in which polyamine monomers are dissolved; the oil phase solution is an organic solution in which isocyanate monomers and alkyl phosphate salt compounds serving as reaction promoters are dispersed; s2, enabling the aqueous phase solution and the oil phase solution to contact on the support base film so as to carry out interfacial polymerization reaction, so that a polyurea active separation layer is formed on the surface of the support base film; S3, heat treatment is carried out, and the strong acid resistant nanofiltration membrane is obtained.
  2. 2. The preparation method according to claim 1, wherein in S1, the alkyl phosphate compound in the oil phase solution is mono-or dialkyl-substituted phosphate containing C 8 -C 18 , and the addition concentration of the alkyl phosphate compound in the oil phase solution is 0.001-0.1wt%.
  3. 3. The method according to claim 1, wherein in S1, the alkyl phosphate salt compound is sodium dodecyl phosphate.
  4. 4. The process according to claim 1, wherein in S1, the isocyanate monomer of the oil phase solution is aliphatic or alicyclic diisocyanate, the concentration of the isocyanate monomer is 0.01 to 1.0wt%, and the organic solvent of the oil phase solution is an aprotic organic solvent which is not miscible with water.
  5. 5. The method according to claim 4, wherein in S1, the organic solvent is n-hexane, cyclohexane, isoparaffin, or a mixed solvent of n-hexane and cyclohexane in a mass ratio of 1:1-3:1.
  6. 6. The process according to claim 4, wherein in S1, the isocyanate monomer of the oil phase solution is at least one selected from the group consisting of benzene diisocyanate, 1, 4-diisocyanatobutane, toluene diisocyanate and isophorone diisocyanate.
  7. 7. The method according to claim 1, wherein in S1, the amine monomer in the aqueous solution is at least one selected from the group consisting of polyethylene polyamine, hyperbranched polyethylene imine and linear diamine, and the concentration of the amine monomer is 0.1 to 2.0wt%.
  8. 8. The method according to claim 1, wherein the aqueous phase solution and the oil phase solution are contacted for 10 to 300 seconds in S2.
  9. 9. The method according to claim 1, wherein in S3, heat treatment is performed at 60 to 120 ℃ for 3 to 15 minutes to consolidate and strengthen the polyurea active separation layer.
  10. 10. An acid-resistant nanofiltration membrane produced by the production process according to any one of claims 1 to 9.

Description

Acid-resistant nanofiltration membrane and preparation method thereof Technical Field The invention relates to the technical field of filter media, in particular to an acid-resistant nanofiltration membrane and a preparation method thereof. Background Nanofiltration membranes have become core materials for a plurality of industrial separation processes such as mining, metallurgy, printing and dyeing wastewater reclamation and the like by virtue of the high-efficiency interception characteristic of multivalent ions and small organic molecules. However, the active layer of the traditional polyamide nanofiltration membrane takes an amide bond as a core structure, and is easy to hydrolyze in a strong acid environment with pH of less than 2, so that the membrane structure is damaged and the separation performance is rapidly attenuated, and the defect severely limits the industrial application of the polyamide nanofiltration membrane in a strong acid system. In order to solve the acid-resistant short plates of polyamide nanofiltration membranes, the prior art mainly forms two types of improvement strategies, namely, firstly, developing a novel acid-resistant monomer, for example, adopting a multi-functional piperazine derivative to react with trimesoyl chloride to construct a poly-piperazine amide structure with higher crosslinking degree so as to improve the chemical stability of a molecular skeleton, and secondly, carrying out post-treatment or surface modification on the membrane, and optimizing the acid resistance of the surface of the membrane through means of sulfonation, grafting and the like. However, the above strategies have obvious limitations, namely the problems of high cost and difficult accurate regulation and control of the reactivity of the novel acid-resistant monomer are common, the post-treatment and surface modification processes are complex, the compatibility with the existing mature interfacial polymerization film-making production line is poor, and the industrial popularization is difficult to realize. Interfacial polymerization is a mainstream process for preparing a high-performance composite nanofiltration membrane, and in the preparation of an acid-resistant nanofiltration membrane, published researches are carried out by adopting aliphatic or alicyclic isocyanate to replace traditional acyl chloride and reacting with amine monomers to form a polyurea active layer. The hydrolytic resistance of the polyurea structure is obviously superior to that of polyamide, and the problem of chemical stability of the film is effectively solved. However, the reactivity of isocyanate and amine is far lower than that of the traditional acyl chloride-amine system, and the defects of insufficient reactivity can be overcome only by means of improving the monomer concentration, prolonging the reaction time and the like in the prior art, so that a compact separation layer meeting the requirement of high ion rejection rate is obtained. This remedial measure can lead to excessive thickening of the polyurea active layer, while maintaining certain rejection performance, severely sacrifices the acid permeation flux of the membrane, making the membrane performance a classical trade-off between "high flux and low rejection and high rejection and low flux". The core root of the method is that the prior art does not solve the problem of insufficient reactivity of an isocyanate-amine system from the aspect of reaction dynamics, and negative changes of a film structure are caused only by macroscopic process parameter adjustment. Some of the prior art approaches have attempted to improve membrane performance by introducing conventional surfactants or pore formers (e.g., nonionic surfactants) during interfacial polymerization. The mechanism of action of such additives is mainly to physically hinder monomer diffusion, or to introduce more free volume in the polymer network (i.e. irregularly distributed voids or interstitial spaces not occupied by molecular chain atoms/groups in the condensed structure formed by polymer molecular chain stacking), the technical direction being to construct a porous membrane structure to promote water flux. However, the guiding and the requirement of a 'high-integrity compact active layer' required by separation in a strong acid environment have fundamental conflict, and the adoption of the method can possibly improve the medium transmission rate, but the method is necessary to be at the cost of sacrificing the high interception rate of multivalent ions, and cannot meet the core requirement of high-selectivity separation in a strong acid system. In recent years, related domestic patents have developed various technical researches around acid-resistant nanofiltration membranes, for example, china patent application CN113509839A discloses an acid/alkali-resistant composite nanofiltration membrane, a polyurea separation layer is formed by interfacial polymerization of polyamine and polyisocyan