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CN-121988168-A - Negatively charged composite nanofiltration membrane and preparation method and application thereof

CN121988168ACN 121988168 ACN121988168 ACN 121988168ACN-121988168-A

Abstract

The invention relates to the technical field of membrane separation, and discloses a negatively charged composite nanofiltration membrane and a preparation method and application thereof. The negatively charged composite nanofiltration membrane sequentially comprises a bottom layer, a porous supporting layer and a polyamide separating layer, wherein the polyamide separating layer is grafted with sulfonic acid groups and/or sulfonate groups shown in a formula I through N atoms; wherein M is H, li, na or K, R1 and R2 are each independently H, C-C6 alkyl or phenyl; Ar is derived from the residue after the reaction of the compound containing an electron withdrawing group. In the composite nanofiltration membrane, sulfonic acid groups and/or sulfonate groups with specific structures are grafted in the polyamide separation layer, so that the surface of the composite nanofiltration membrane is negatively charged, and the monovalent ion/divalent ion selectivity is improved while the high water flux is maintained.

Inventors

  • Zhao Guoke
  • ZHANG YANG
  • Liu Diequn
  • PAN GUOYUAN
  • YU HAO
  • TANG GONGQING
  • LI YU
  • ZHONG TIAN

Assignees

  • 中国石油化工股份有限公司
  • 中石化(北京)化工研究院有限公司

Dates

Publication Date
20260508
Application Date
20241108

Claims (15)

  1. 1. The negatively charged composite nanofiltration membrane is characterized by sequentially comprising a bottom layer, a porous supporting layer and a polyamide separating layer; wherein the polyamide separation layer is grafted with sulfonic acid groups and/or sulfonate groups shown in the formula I through N atoms; Wherein M is H, li, na or K, R 1 and R 2 are each independently H, C C6 alkyl or phenyl; A position at which a group represented by formula I is bonded to the polyamide separation layer; Ar is derived from the residue after the reaction of a compound containing an electron withdrawing group.
  2. 2. The negatively charged composite nanofiltration membrane of claim 1, wherein R 1 and R 2 are each independently selected from H or C1-C5 alkyl; and/or the electron withdrawing group is selected from one of carbonyl, carboxyl, ester, alkynyl, cyano or phenolic hydroxyl.
  3. 3. A negatively charged composite nanofiltration membrane according to claim 1 or 2, wherein the Ar-SO 3 M is selected from at least one of the following group: Wherein R 3 、R 4 、R 5 and R 6 are each independently H, C C3 alkyl, -NH 2 or-SO 3 M, and at least one of R 3 、R 4 、R 5 and R 6 is-SO 3 M; Wherein R 7 is H, methyl or ethyl; Wherein R 8 and R 9 are each independently H or C1-C3 alkyl; Wherein R 10 is alkynyl or carboxyl, and m is an integer of 0-3; Wherein z is an integer from 1 to 3; Wherein R 11 is a C1-C3 alkylene group, and R 12 and R 13 are each independently a C1-C8 straight chain alkyl group or a branched alkyl group.
  4. 4. A negatively charged composite nanofiltration membrane according to any one of claims 1-3, wherein the content of sulfur atoms in the polyamide separation layer of the negatively charged composite nanofiltration membrane is 0.1-5 at%, preferably 0.5-3 at%.
  5. 5. A negatively charged composite nanofiltration membrane according to any one of claims 1 to 4, wherein the composite nanofiltration membrane has a surface Zeta potential of-50 mV to-30 mV, preferably-45 mV to-35 mV, at ph=7.
  6. 6. A negatively charged composite nanofiltration membrane according to any one of claims 1 to 5, wherein the composite nanofiltration membrane has an average pore size of 0.1 to 0.5nm, preferably 0.15 to 0.35nm.
  7. 7. A negatively charged composite nanofiltration membrane according to any one of claims 1 to 6, wherein the composite nanofiltration membrane has a contact angle of 20-80 °, preferably 30-50 °.
  8. 8. The preparation method of the negatively charged composite nanofiltration membrane is characterized by comprising the following steps of: S1, sequentially preparing a porous support layer and a polyamide separation layer on a bottom layer to obtain a composite membrane; S2, contacting the composite membrane with an aqueous solution containing an aldehyde compound shown in a formula 1, a sulfonate containing an electron withdrawing group and/or a sulfonic acid compound containing an electron withdrawing group and an acid catalyst, and drying to obtain the negatively charged composite nanofiltration membrane; R 1 and R 2 are each independently H, C C5 alkyl or phenyl.
  9. 9. The preparation method according to claim 8, wherein the electron withdrawing group is selected from one of carbonyl, carboxyl, ester, alkynyl, cyano or phenolic hydroxyl; and/or the acid catalyst is selected from hydrochloric acid and/or sulfuric acid.
  10. 10. The production method according to claim 8 or 9, wherein the production method of the composite film comprises: (1) Preparing a porous support layer on the bottom layer; (2) Carrying out first contact on the film layer obtained in the step (1) and a first liquid phase, wherein the first liquid phase comprises polyamine, a first organic solvent and water; (3) Performing second contact on the film layer obtained in the step (2) and a second liquid phase, and performing heat treatment to obtain the composite film, wherein the second liquid phase comprises polybasic acyl chloride and a second organic solvent; Preferably, the first organic solvent is selected from at least one of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, ethanol and methanol; preferably, the concentration of the first organic solvent in the first liquid phase is from 0.05 to 6wt%, preferably from 0.1 to 3wt%; Preferably, the concentration of polyamine in the first liquid phase is from 0.05wt% to 5wt%, preferably from 0.2wt% to 2wt%.
  11. 11. The production method according to any one of claims 8 to 10, wherein the electron-withdrawing group-containing sulfonate and/or electron-withdrawing group-containing sulfonic acid compound is selected from at least one of the following groups: Wherein R 3 、R 4 、R 5 and R 6 are each independently H, C C3 alkyl, -NH 2 or-SO 3 M, and at least one of R 3 、R 4 、R 5 and R 6 is-SO 3 M; Wherein R 7 is H, methyl or ethyl; Wherein R 8 and R 9 are each independently H or C1-C3 alkyl; Wherein R 10 is alkynyl or carboxyl, and m is an integer of 0-3; Wherein z is an integer from 1 to 3; Wherein R 11 is C1-C3 alkylene, R 12 and R 13 are each independently C1-C8 straight or branched alkyl, M is H, li, na or K; Preferably, the sulfonate containing an electron withdrawing group and/or the sulfonic acid compound containing an electron withdrawing group is selected from at least one of camphorsulfonic acid, sodium camphorsulfonate, o-hydroxybenzenesulfonic acid, m-hydroxybenzenesulfonic acid, p-hydroxybenzenesulfonic acid, sodium o-hydroxybenzenesulfonate, sodium m-hydroxybenzenesulfonate, sodium p-hydroxybenzenesulfonate, o-cresol sulfonic acid, m-cresol sulfonic acid, p-cresol sulfonic acid, sodium 2-acetylbenzenesulfonate, sodium 3-acetylbenzenesulfonate, sodium 4-acetylbenzenesulfonate, sodium 1-acetylindoline-2-sulfonate, sodium propargyl sulfonate, sulfoacetic acid, sulfopropionic acid, dioctyl sodium dibutyrate sulfonate, diisobutyl succinate and D-2-amino-4-sulfobutyric acid.
  12. 12. The production method according to any one of claims 8 to 11, wherein in step S2, the concentration of the aldehyde compound in the aqueous solution is 0.05 to 5wt%, preferably 0.1 to 4wt%, the concentration of the electron withdrawing group-containing sulfonate and/or electron withdrawing group-containing sulfonic acid compound is 0.05 to 5wt%, preferably 0.1 to 4wt%, and the concentration of the acid catalyst is 0.01 to 0.15wt%, preferably 0.03 to 0.12%; And/or in step S2, the ratio of the volume of the aqueous solution to the area of the composite film is 0.1 to 5mL/cm 2 , preferably 0.5 to 3mL/cm 2 .
  13. 13. The preparation method according to any one of claims 8-12, wherein in step S2, the contacting is for a time of 5S-240S, preferably 10S-180S; and/or in step S2, the drying temperature is 20-80 ℃, preferably 30-70 ℃, and the drying time is 0.5-120min, preferably 1-60min.
  14. 14. A negatively charged composite nanofiltration membrane produced by the process of any one of claims 8-13.
  15. 15. Use of a negatively charged composite nanofiltration membrane as claimed in any one of claims 1 to 7 and 14 in the field of water treatment.

Description

Negatively charged composite nanofiltration membrane and preparation method and application thereof Technical Field The invention relates to the technical field of membrane separation, in particular to a negatively charged composite nanofiltration membrane and a preparation method and application thereof. Background Nanofiltration membranes are separation membrane materials with pore diameters of 0.1 to 1 nanometer, have an average molecular weight cut-off (MWCO) of 200-1000Da, and can effectively separate divalent/monovalent inorganic salts. Due to the advantages of low operating pressure, high separation precision and the like, the nanofiltration technology is widely applied to the fields of sea water desalination, industrial wastewater zero emission, resource recovery and the like. In the zero emission and recycling process of industrial wastewater, sodium sulfate and sodium chloride are required to be separated so as to obtain a sodium sulfate product with higher purity. The nanofiltration membrane reported in the literature and patents is required to further improve the separation efficiency of sodium sulfate and sodium chloride. The introduction of negatively charged groups on the membrane surface is an effective means of achieving high sodium sulfate rejection. The separation principle of the negatively charged nanofiltration membrane is based on physical screening of pore size, and electrostatic adsorption and rejection based on the southwest effect. In addition, by introducing a charged group, hydrophilicity of the membrane is enhanced, and the membrane is advantageous in terms of reduction in operating pressure, contamination resistance, and selective permeability. Most charge modification means cause a significant decrease in membrane water flux, while improving mono/divalent salt separation efficiency, overall water treatment efficiency is not an advantage. Accordingly, there is a need to provide negatively charged nanofiltration membranes with high water flux and high efficiency of mono/divalent salt separation. Disclosure of Invention The invention aims to overcome the defect that the composite nanofiltration membrane in the prior art can not simultaneously keep high monovalent/divalent anion selectivity and high water flux, and provides a negatively charged composite nanofiltration membrane, a preparation method and application thereof, the negatively charged composite nanofiltration membrane is grafted with sulfonic acid groups and/or sulfonate groups with specific structures in the polyamide separation layer, so that the surface of the composite nanofiltration membrane is negatively charged, and the monovalent/divalent anion selectivity is improved while the high water flux is maintained. The first aspect of the invention provides a negatively charged composite nanofiltration membrane, wherein the negatively charged composite nanofiltration membrane sequentially comprises a bottom layer, a porous support layer and a polyamide separation layer; wherein the polyamide separation layer is grafted with sulfonic acid groups and/or sulfonate groups shown in the formula I through N atoms; wherein M is H, li, na or K, R1 and R2 are each independently H, C-C6 alkyl or phenyl; A position at which a group represented by formula I is bonded to the polyamide separation layer; Ar is derived from the residue after the reaction of a compound containing an electron withdrawing group. The second aspect of the invention provides a preparation method of a negatively charged composite nanofiltration membrane, wherein the preparation method comprises the following steps: s1, preparing a porous support layer and a polyamide separation layer on a bottom layer to obtain a composite membrane; S2, contacting the composite membrane with an aqueous solution containing an aldehyde compound shown in a formula 1, a sulfonate containing an electron withdrawing group and/or a sulfonic acid compound containing an electron withdrawing group and an acid catalyst, and drying to obtain the negatively charged composite nanofiltration membrane; r1 and R2 are each independently H, C-C6 alkyl or phenyl. The third aspect of the invention provides a negatively charged composite nanofiltration membrane prepared by the preparation method. The fourth aspect of the invention provides an application of the negatively charged composite nanofiltration membrane in water treatment. Through the technical scheme, the negatively charged composite nanofiltration membrane provided by the invention and the preparation method and application thereof have the following beneficial effects: The negatively charged composite nanofiltration provided by the invention grafts sulfonic acid groups and/or sulfonate groups with specific structures in the polyamide separation layer, so that the composite nanofiltration membrane is negatively charged, and the monovalent/divalent anion selectivity is improved while the high water flux is maintained. According to the