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CN-122006522-A - High-flux high-salt polyamide nanofiltration membrane and preparation method thereof

CN122006522ACN 122006522 ACN122006522 ACN 122006522ACN-122006522-A

Abstract

The invention belongs to the technical field of membrane separation, and particularly relates to a high-flux high-salt polyamide nanofiltration membrane and a preparation method thereof. The preparation method comprises the steps of sequentially carrying out S1, providing aqueous phase solution and oil phase solution, wherein polyamine, a surfactant and carboxylate containing hydroxyl are dissolved in the aqueous phase solution, the oil phase solution is dissolved with polybasic acyl chloride, S2, soaking a porous support base film in the aqueous phase solution, removing the surplus aqueous phase solution on the surface of the porous support base film, then contacting the oil phase solution with the porous support base film, enabling the oil phase solution and the aqueous phase solution to carry out interfacial polymerization reaction, and obtaining a nascent composite film, S3, carrying out heat treatment, and S4, sequentially soaking in an acid solution, pure water, an alkali solution and pure water, and carrying out post treatment, thus obtaining the high-flux high-salinity polyamide nanofiltration membrane. The invention can improve the water permeation flux of the polyamide nanofiltration membrane and the selectivity thereof, and solves the problems that the water flux and the retention rate of the traditional nanofiltration membrane are difficult to cooperatively promote and the high-requirement separation application scene is difficult to meet.

Inventors

  • HUANG MI
  • WANG MING
  • YAO ZHIKAN
  • MAO YUNCHEN
  • CHEN KEKE
  • LIU WENCHAO
  • YU YANPING
  • HAO ZIXIN
  • Cui Shuaichuan

Assignees

  • 杭州水处理技术研究开发中心有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (10)

  1. 1. The preparation method of the high-flux high-salt polyamide nanofiltration membrane is characterized by comprising the following steps of: s1, providing an aqueous phase solution and an oil phase solution, wherein polyamine, a surfactant and carboxylate containing hydroxyl are dissolved in the aqueous phase solution, and the oil phase solution is dissolved with polybasic acyl chloride; S2, soaking the porous support base film in aqueous phase solution, removing surplus aqueous phase solution on the surface of the porous support base film, and then contacting the oil phase solution with the porous support base film to enable the oil phase solution and the aqueous phase solution to undergo interfacial polymerization reaction to obtain a nascent state composite film; S3, heat treatment is carried out to obtain a heat-strengthened composite film; S4, sequentially soaking in acid solution, pure water, alkali solution and pure water for post-treatment to obtain the high-flux high-salinity polyamide nanofiltration membrane.
  2. 2. The method according to claim 1, wherein in S1, the carboxylate containing hydroxyl group is at least one of sodium lactate, sodium glycolate, sodium hydroxyethylenediamine triacetate, sodium salicylate, and sodium citrate, and the concentration thereof in the aqueous phase solution is 0.01% to 5% by weight.
  3. 3. The method according to claim 1, wherein in S1, the surfactant is an anionic surfactant, a nonionic surfactant or a cationic surfactant, and the concentration of the surfactant in the aqueous phase solution is 0.01-2 wt%.
  4. 4. The method according to claim 3, wherein in S1, the anionic surfactant is at least one selected from the group consisting of sodium dodecylbenzenesulfonate, sodium dodecylsulfonate and sodium dodecylsulfate, the nonionic surfactant is Tween 20, and the cationic surfactant is at least one selected from the group consisting of octamethyltrimethylammonium chloride, octamethyltrimethylammonium bromide, dodecyl trimethylammonium chloride, dodecyl trimethylammonium bromide, hexadecyltrimethylammonium chloride and hexadecyltrimethylammonium bromide.
  5. 5. The process according to claim 1, wherein in S1, the polyamine is at least one selected from the group consisting of piperazine, 2-methylpiperazine, 2, 5-dimethylpiperazine, 2, 6-dimethylpiperazine, 1, 2-diaminocyclohexane, 1, 4-diaminocyclohexane, ethylenediamine, N-bis (2-aminoethyl) ethylenediamine, diethylenetriamine and polyethyleneimine, and the concentration thereof in the aqueous solution is 0.01 to 2wt%.
  6. 6. The preparation method according to claim 1, wherein in S1, the polybasic acyl chloride in the oil phase solution is selected from at least one of trimesoyl chloride, terephthaloyl chloride, phthaloyl chloride, pyromellitic chloride, malonyl chloride, glutaryl chloride and fumaroyl chloride, and the concentration of the polybasic acyl chloride in the oil phase solution is 0.01-2wt%; The organic solvent of the oil phase solution is one or more of n-hexane, cyclohexane, n-heptane, toluene, benzene, isopar G, isopar E, isopar H, isopar L and isopar M.
  7. 7. The preparation method of claim 1, wherein in S2, the porous support base membrane is an ultrafiltration membrane with a molecular weight cut-off of 1kDa to 50kDa, and the membrane material is at least one of polysulfone, polyethersulfone, polyvinylidene fluoride, polypropylene, polyacrylonitrile, polyethylene, polystyrene, polyvinyl chloride, polyphenylene oxide, polyetheretherketone and polyimide.
  8. 8. The preparation method of the composite membrane according to claim 1, wherein the operation in S2 is that the porous support base membrane is soaked in the aqueous phase solution for 10S-10min, the surplus aqueous phase solution on the surface of the porous support base membrane is removed to obtain the soaked porous support base membrane, and then the oil phase solution is contacted with the soaked porous support base membrane for 10S-10min to perform interfacial polymerization reaction to obtain the nascent composite membrane; and S3, treating in an oven at 20-120 ℃ for 1-30min.
  9. 9. The preparation method of claim 1, wherein in S4, the acid solution is one of dilute sulfuric acid, dilute hydrochloric acid and dilute nitric acid, the concentration of the acid solution is 0.05-0.5 wt%, the alkali solution is one of sodium hydroxide, potassium hydroxide and lithium hydroxide, and the concentration of the alkali solution is 0.05-0.5 wt%; and S4, soaking time of the heat-strengthening composite film in the acid solution, the pure water, the alkali solution and the pure water is respectively 30S-15min, and soaking temperature is respectively 20-80 ℃.
  10. 10. Nanofiltration membranes prepared by the preparation method of any one of claims 1 to 9 and application of the nanofiltration membranes in removal of divalent salts in water or salt separation treatment of mono/divalent salts in water.

Description

High-flux high-salt polyamide nanofiltration membrane and preparation method thereof Technical Field The invention belongs to the technical field of membrane separation, and particularly relates to a high-flux high-salt polyamide nanofiltration membrane and a preparation method thereof. Background The membrane separation technology has the remarkable advantages of high separation efficiency, simple and convenient operation, low energy consumption, environmental friendliness and the like, and has been widely applied to the key fields of industrial wastewater recycling, domestic sewage regeneration, deep purification of drinking water, seawater desalination and the like. In the pressure-driven membrane separation process, there are four types of Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and Reverse Osmosis (RO) according to the difference between membrane pore size and molecular weight cut-off. The nanofiltration membrane has a special aperture range of 0.5-2.0 nm and unique surface charge characteristics, has higher interception accuracy on single/multivalent ions compared with an ultrafiltration membrane, can operate at lower operating pressure compared with a reverse osmosis membrane, can selectively permeate monovalent salt, has obvious energy consumption advantages and process economy, and therefore, the development of the high-performance nanofiltration membrane becomes a research hotspot in the field of membrane material science. Currently commercialized nanofiltration membranes are mainly of a thin layer composite (TFC) structure, and generally consist of a polyester nonwoven fabric substrate, a polysulfone/polyethersulfone porous support layer and a polyamide separation layer, wherein the polyamide separation layer is a core structure determining membrane separation performance (permeability and selectivity). The separation layer is mainly prepared by an Interfacial Polymerization (IP) technology, namely, an aqueous phase polyamine monomer (such as piperazine) and an organic phase polybasic acyl chloride monomer (such as trimesic chloride) are formed by polycondensation reaction at mutually-insoluble two-phase interfaces. However, during this reaction, the polymerization reaction of the acid chloride monomer and the amine monomer competes with the hydrolysis reaction of the acid chloride itself, which makes it difficult to achieve both high water flux and high rejection rate of the prepared polyamide separation layer, with a significant "permeability-selectivity" Trade-off effect. This effect fundamentally limits further improvement of polyamide nanofiltration membrane performance, and is a core technical bottleneck which is long-term to be solved in the field. In order to break through the bottleneck, researchers have conducted a great deal of research around the directions of interfacial polymerization process regulation, membrane layer structure optimization and the like, including introducing functional additives into an aqueous phase or organic phase solution of interfacial polymerization, regulating and controlling monomer diffusion and reaction kinetics in situ by means of physicochemical effects of the additives, and optimizing the microstructure of a polyamide separation layer. For example, chinese patent application CN112007525A discloses a method for preparing a high-performance salt-separating nanofiltration membrane by using synergistic regulation of complexing agent and inorganic salt, although the separation performance of the membrane is improved to a certain extent, the improvement effect is still limited. The water flux of the nanofiltration membrane prepared in the example of the patent application is 166LMH (test condition 15.5 bar) at most, the water flux is only 10.7LMH/bar, and the performance of the nanofiltration membrane is still required to be further improved in the separation application scene with higher requirements. Therefore, the existing additive regulation technology still has limitation on the improvement effect of the membrane performance, the cooperative improvement degree of the water flux and the retention rate of the prepared nanofiltration membrane is insufficient, the requirement of a high-requirement separation application scene is difficult to meet, and a more efficient regulation strategy still needs to be developed. Therefore, the preparation regulation and control method for the polyamide nanofiltration membrane with the process simplicity and the performance high efficiency is developed, the accurate regulation and control of the polyamide separation layer structure is realized, the permeability-selectivity trade-off effect is fundamentally relieved and even broken through, and the method has important practical significance for promoting the industrialized application of the high-performance nanofiltration membrane. Disclosure of Invention First, the technical problem to be solved In view of the above-mentioned shortcomings and d