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CN-122006533-A - High-flux acid-resistant nanofiltration membrane and preparation method thereof

CN122006533ACN 122006533 ACN122006533 ACN 122006533ACN-122006533-A

Abstract

The invention belongs to the technical field of membrane materials, and discloses a high-flux acid-resistant nanofiltration membrane and a preparation method thereof. The method comprises the steps of (1) coating a nitrogen-containing heterocyclic quaternary ammonium salt aqueous solution on a porous support bottom film, soaking, then, pouring excessive liquid, and then, coating an n-hexane solution dissolved with cyanuric chloride on the surface of the film prepared in the step (1), soaking to enable the nitrogen-containing hybridized quaternary ammonium salt to undergo a substitution reaction with cyanuric chloride, and drying after the reaction is finished to obtain the nanofiltration film, wherein the nitrogen-containing heterocyclic quaternary ammonium salt has a structure of nitrogen-containing heterocyclic quaternary ammonium salt containing two or more amino groups, the quaternary ammonium groups are positioned on the nitrogen heterocycle, the amino groups are positioned on the nitrogen heterocycle or are directly connected with carbon atoms forming the nitrogen heterocycle, and the counter ions are Cl ‑ 、Br ‑ or I ‑ . According to the invention, the specific nitrogen-containing heterocyclic quaternary ammonium salt is designed to be used as a water phase monomer, so that the cyanuric chloride is subjected to trisubstituted reaction at room temperature to form a compact separation layer.

Inventors

  • ZHAO QIANG
  • PENG HUAWEN
  • LIU XUFEI

Assignees

  • 华中科技大学

Dates

Publication Date
20260512
Application Date
20260331

Claims (10)

  1. 1. The preparation method of the high-flux acid-resistant nanofiltration membrane is characterized by comprising the following steps of: (1) Coating a nitrogen-containing heterocyclic quaternary ammonium salt aqueous solution on a porous support base film, and removing redundant liquid after infiltration; (2) Then, coating n-hexane solution dissolved with cyanuric chloride on the surface of the substance obtained in the step (1), and soaking to enable the nitrogen-containing hybridized quaternary ammonium salt to undergo substitution reaction with cyanuric chloride; The structure of the nitrogen-containing heterocyclic quaternary ammonium salt is nitrogen-containing heterocyclic quaternary ammonium salt containing two or more amino groups, the quaternary ammonium group is positioned on the nitrogen heterocycle, the amino groups are positioned on the nitrogen heterocycle or are directly connected with carbon atoms forming the nitrogen heterocycle, and the counter ion is Cl - 、Br - or I - .
  2. 2. The method of preparing a high flux acid resistant nanofiltration membrane according to claim 1, wherein the nitrogen heterocycle is a monocyclic, bicyclic or spiro ring structure containing at least one quaternary ammonium group.
  3. 3. The method for preparing the high-flux acid-resistant nanofiltration membrane according to claim 1, wherein the nitrogen-containing heterocyclic quaternary ammonium salt is selected from any one of the following structures, and the counter ion is Cl - 、Br - or I - : Formula (1); Formula (2); formula (3); Formula (4); Formula (5); formula (6); Formula (7).
  4. 4. The method for preparing the high-flux acid-resistant nanofiltration membrane according to claim 1, wherein in the step (1), the mass concentration of the nitrogen-containing heterocyclic quaternary ammonium salt in the nitrogen-containing heterocyclic quaternary ammonium salt aqueous solution is 0.5-3 wt%, the pH is 9-12, the infiltration time is 0.5-3 min, and the pH is preferably 12.
  5. 5. The method for preparing a high-flux acid-resistant nanofiltration membrane according to claim 1, wherein in the step (2), the mass concentration of cyanuric chloride in the n-hexane solution dissolved with cyanuric chloride is 0.1-0.5 wt%.
  6. 6. The method for preparing the high-flux acid-resistant nanofiltration membrane according to claim 1, wherein in the step (2), the infiltration time is 0.5-3 min.
  7. 7. The method for preparing the high-flux acid-resistant nanofiltration membrane according to claim 1, wherein in the step (2), the drying and film-forming conditions are that the drying temperature is 50-70 ℃ and the time is 10-20 min.
  8. 8. The preparation method of the high-flux acid-resistant nanofiltration membrane according to claim 1 is characterized by comprising the steps of dissolving a primary nitrogen-containing heterocyclic amine and a halogenated reagent in ethanol according to a molar ratio, stirring for reaction, and carrying out suction filtration and vacuum drying on reaction liquid after the reaction is finished to obtain the nitrogen-containing heterocyclic quaternary ammonium salt.
  9. 9. The method for preparing a high-flux acid-resistant nanofiltration membrane according to claim 1, wherein the porous support base membrane is a polysulfone membrane, a polyethersulfone membrane or a polyacrylonitrile membrane.
  10. 10. The high-flux acid-resistant nanofiltration membrane prepared by the method according to any one of claims 1 to 9.

Description

High-flux acid-resistant nanofiltration membrane and preparation method thereof Technical Field The invention belongs to the technical field of membrane materials, and particularly relates to a high-flux acid-resistant nanofiltration membrane and a preparation method thereof. Background With the acceleration of the industrialization process, the problem of industrial waste acid faced by China is increasingly serious. According to statistics, the annual production of waste acid in China reaches the order of hundred million tons, and the waste acid contains valuable metal ions such as iron, cobalt, nickel, copper and the like, thereby not only causing environmental pollution, but also causing huge waste of resources. Nanofiltration is used as a pressure-driven membrane separation technology, is widely applied to the fields of salt lake lithium extraction, heavy metal removal, hard water softening, chlor-alkali industry and the like, and has an application prospect in the aspect of recovering metal ions in waste acid. However, most commercial nanofiltration membranes are made of polyamide, and amide bonds in the molecular structure of the nanofiltration membranes are easily degraded in a strong acid environment, so that the membranes lose separation performance. Cyanuric chloride contains three chlorine atoms with high reactivity, and can undergo nucleophilic substitution reaction with amine monomers to form strong acid-resistant C-N bonds, so that cyanuric chloride is considered to be an ideal monomer for constructing acid-resistant nanofiltration membranes. However, when two chlorine atoms of cyanuric chloride are replaced by amine monomers, the electron cloud density of the triazine ring increases significantly, and the electrophilicity of the remaining carbon atoms decreases, resulting in a substantial decrease in the leaving activity of the third chlorine atom. This makes it difficult for cyanuric chloride to undergo a sufficient trisubstituted reaction with small-molecule amine monomers at room temperature, so that a highly crosslinked polymer network structure necessary for the separation layer cannot be formed. To overcome this difficulty, researchers have attempted to use amino-rich high molecular polymers (e.g., polyethyleneimine) as aqueous monomers to undergo interfacial polymerization with cyanuric chloride to prepare acid-resistant membranes （Sep. Purif. Technol., 2023, 320, 124108; Sep. Purif. Technol., 2020, 250, 117245; J. Membr. Sci., 2021, 640, 119833）., however, high molecular chains such as polyethyleneimine are highly entangled, and a separation layer with a dense structure is easily formed, resulting in a significant increase in mass transfer resistance and a generally low membrane permeation flux (< 5L m -2h-1bar-1). In addition, studies have been made on the preparation of acid-resistant membranes (j. Membrane. Sci., 2018, 546, 225-233) by synthesis of trifunctional triazine ring derivatives and interfacial polymerization with 1,3, 5-benzoyl chloride, but the surfaces of such membranes are usually negatively charged, have a low rejection rate for metal ions, and their permeation flux is still not ideal (< 10 5L m-2h-1bar-1). In view of the above, the prior art still lacks a small molecule amine monomer which can rapidly undergo a trisubstituted reaction with cyanuric chloride at room temperature and form a high permeability separation layer. Disclosure of Invention Aiming at the defects or improvement demands of the prior art, the invention provides a high-flux acid-resistant nanofiltration membrane and a preparation method thereof, and the specific nitrogen-containing heterocyclic quaternary ammonium salt is designed as a water phase monomer, so that the cyanuric chloride is subjected to trisubstituted reaction at room temperature to form a compact separation layer, thereby solving the problems that the cyanuric chloride is difficult to be subjected to trisubstituted reaction with small molecular amine at room temperature and the permeation flux of the existing acid-resistant nanofiltration membrane is low. In order to achieve the above object, in one aspect of the present invention, there is provided a method for preparing a high flux acid-resistant nanofiltration membrane, comprising the steps of: (1) Coating a nitrogen-containing heterocyclic quaternary ammonium salt aqueous solution on a porous support base film, and splashing excessive liquid after infiltration; (2) Then, coating n-hexane solution dissolved with cyanuric chloride on the surface of the substance obtained in the step (1), and soaking to enable the nitrogen-containing hybridized quaternary ammonium salt to undergo substitution reaction with cyanuric chloride; The structure of the nitrogen-containing heterocyclic quaternary ammonium salt is nitrogen-containing heterocyclic quaternary ammonium salt containing two or more amino groups, the quaternary ammonium group is positioned on the nitrogen heterocycle, the amino g