阅读说明：本技术 一种聚丙烯腈基复合疏松纳滤膜的制备方法 (Preparation method of polyacrylonitrile-based composite loose nanofiltration membrane ) 是由 王湛 王建涛 李平 郭洋洋 尹霜 于 2020-04-23 设计创作，主要内容包括：一种聚丙烯腈基复合疏松纳滤膜的制备方法,属于膜技术领域。具体方法如下：将聚丙烯腈超滤膜浸没在氢氧化钠水溶液中进行水解改性,水解完成后用去离子水冲洗并浸泡去除膜表面残留的碱；将水解后的基膜浸没在一定浓度的聚乙烯亚胺水溶液中,得到表面涂覆聚合物的复合膜；将涂敷后的膜置于一定浓度的肌醇六磷酸酯水溶液中进行磷酸化改性；将改性后的膜置于氯化铁水溶液中进行交联,然后将膜取出烘干,即得聚丙烯腈基复合疏松纳滤膜。本发明所制备的复合膜膜具有较高的渗透通量和截留率,在疏松纳滤膜膜制备方面具有较高的应用价值。(A preparation method of a polyacrylonitrile-based composite loose nanofiltration membrane belongs to the technical field of membranes. The specific method comprises the following steps: immersing a polyacrylonitrile ultrafiltration membrane in a sodium hydroxide aqueous solution for hydrolysis modification, washing with deionized water after hydrolysis is finished, and soaking to remove residual alkali on the surface of the membrane; immersing the hydrolyzed base membrane in a polyethyleneimine water solution with a certain concentration to obtain a composite membrane with the surface coated with a polymer; placing the coated film in a phytic acid phosphate aqueous solution with a certain concentration for phosphorylation modification; and (3) placing the modified membrane into a ferric chloride aqueous solution for crosslinking, and then taking out and drying the membrane to obtain the polyacrylonitrile-based composite loose nanofiltration membrane. The composite membrane prepared by the invention has higher permeation flux and rejection rate, and has higher application value in the aspect of preparation of loose nanofiltration membrane.)

1. A preparation method of a polyacrylonitrile-based composite loose nanofiltration membrane comprises a polyacrylonitrile-based membrane and a crosslinking modified polyethyleneimine separation layer, and is characterized by comprising the following steps:

(1) modification of base film

Immersing a Polyacrylonitrile (PAN) ultrafiltration membrane in a NaOH aqueous solution for hydrolysis modification, wherein the hydrolysis temperature is 45 +/-1 ℃, and the hydrolysis time is 30-40 min; washing with deionized water for several times after hydrolysis to remove residual alkali on the surface of the membrane until the washing water is neutral, and obtaining a basal membrane (HPAN) with carboxyl groups distributed on the surface;

(2) coating of

Immersing the base film in the step (1) in 1-3 wt% of Polyethyleneimine (PEI) water solution, placing the base film in a vacuum oven at 45 +/-1 ℃ for standing for 30-40min, taking out the base film, washing the base film with deionized water to remove unreacted PEI, and then placing the base film in the vacuum oven for drying to obtain a composite film (PEI/HPAN) with a polymer coated surface;

(3) phosphorylation modification

Soaking the PEI/HPAN composite membrane prepared in the step (2) in 0.1-0.5 wt% of phytic acid ester (IP6) aqueous solution for 3min, and taking out;

(4) chelate crosslinking

Placing the Phos-PEI/HPAN composite membrane prepared in the step (3) in ferric chloride (FeCl)₃) Soaking in water solution for 15 s; and then taking out the membrane, and placing the membrane in a vacuum oven at the temperature of 45 +/-1 ℃ for heat treatment for 30-50min to obtain the polyacrylonitrile-based composite loose nanofiltration membrane (Fe (III) -Phos-PEI/HPAN).

2. The method according to claim 1, characterized in that the base membrane in the composite loose nanofiltration membrane in step (1) is a Polyacrylonitrile (PAN) ultrafiltration membrane with a molecular weight cut-off (MWCO) of 200kDa and a total membrane thickness of 151 μm, wherein the polyacrylonitrile has a thickness of 61 μm and the nonwoven fabric has a thickness of 90 μm.

3. The process according to claim 1, characterized in that the Polyethyleneimine (PEI) in step (2) has a molecular weight of 750,000 g/mol; the concentration of Polyethyleneimine (PEI) is 1 to 3 wt.%, preferably 1.5 wt.%.

4. A process according to claim 1, characterized in that the phytate (IP6) in step (3) has a molecular weight of 660 g/mol; the concentration of phytate (IP6) is between 0.1 and 0.5 wt%, preferably 0.3 wt%.

5. The polyacrylonitrile-based composite loose nanofiltration membrane prepared by the method of any one of claims 1 to 4.

6. The application of the polyacrylonitrile-based composite loose nanofiltration membrane prepared by the method according to any one of claims 1 to 4 in dye desalination and wastewater treatment in the printing and dyeing industry.

Technical Field

The invention relates to the field of membrane separation, in particular to a preparation method of a composite loose nanofiltration membrane taking polyacrylonitrile as a base membrane.

Technical Field

With the development of urbanization and industrialization, water pollution and resource shortage become problems to be solved urgently. Especially, the printing and dyeing wastewater contains dye molecules, inorganic salts and additives with high concentration, has high chroma and high biological toxicity, and can cause serious damage to the ecological environment if directly discharged. Meanwhile, the dye molecules have stable chemical structure and poor biodegradability, a large amount of chemical reagents are used in the traditional water treatment methods such as adsorption, oxidation, flocculation or precipitation, the effluent quality is poor, and the efficiency is low. Therefore, more efficient and environmentally friendly water treatment technologies need to be developed to solve this problem.

The nanofiltration membrane (L oose-NFMs) has higher flux, lower operating pressure, higher retention rate on dye molecules and higher permeability on salt in the filtering process, and is suitable for wastewater treatment in the printing and dyeing industry compared with the traditional nanofiltration membrane.

The invention provides a preparation method of a novel polyacrylonitrile-based composite loose nanofiltration membrane, which adopts hydrolyzed polyacrylonitrile-based composite loose nanofiltration membraneCoating polyethylene imine (PEI) on the surface of polyacrylonitrile (HPAN) microfiltration membrane as base membrane, performing phosphorylation modification with inositol hexaphosphate chelate (IP6), and adding ferric chloride (FeCl)₃) And (3) crosslinking the phosphorylated polyethyleneimine (Phos-PEI) to obtain the high-performance loose nanofiltration composite membrane.

Disclosure of Invention

Aiming at the problems of low permeation flux, poor hydrophilicity, instability, serious pollution and the like existing in the existing nanofiltration membrane, the invention uses a simple process to prepare the composite loose nanofiltration membrane with high rejection rate and high permeation flux.

In order to solve the problems, the invention provides a preparation method of a polyacrylonitrile-based composite loose nanofiltration membrane. The cross-linked modified Polyethyleneimine (PEI) has higher charge property, good acid and alkali resistance, chlorine resistance and other properties as a selective separation layer of the composite membrane, and the membrane prepared by using the PEI has better hydrophilicity and stable properties. The invention adopts a dip coating method to prepare the composite membrane, and particularly, the method comprises the steps of coating Polyethyleneimine (PEI) on a Hydrolyzed Polyacrylonitrile (HPAN) ultrafiltration membrane, carrying out phosphorylation modification by using phytic acid ester chelate (IP6), and then using ferric chloride (FeCl)₃) Cross-linking the phosphorylated polyethyleneimine (Phos-PEI). The prepared composite loose nanofiltration membrane consists of a thin separation layer and a porous support layer, and has good interception performance and pollution resistance.

The specific technical scheme of the invention is as follows:

a preparation method of a polyacrylonitrile-based composite loose nanofiltration membrane comprises a polyacrylonitrile-based membrane and a crosslinking modified polyethyleneimine separation layer, and is characterized by comprising the following steps:

(1) modification of base film

Immersing a Polyacrylonitrile (PAN) ultrafiltration membrane in a NaOH aqueous solution such as a 2 mol/L NaOH aqueous solution for hydrolysis modification, wherein the hydrolysis temperature is 65 +/-1 ℃, the hydrolysis time is 50-60min, and washing with deionized water for multiple times after the hydrolysis is finished to remove residual alkali on the surface of the membrane until the washing water is neutral, thereby obtaining a base membrane (HPAN) with carboxyl groups distributed on the surface;

(2) coating of

Immersing the base film in the step (1) in 1-3 wt% of Polyethyleneimine (PEI) water solution, placing the base film in a vacuum oven at 45 +/-1 ℃ for standing for 30-40min, taking out the base film, washing the base film with deionized water to remove unreacted PEI, and then placing the base film in the vacuum oven for drying to obtain a composite film (PEI/HPAN) with a polymer coated surface;

(3) phosphorylation modification

Soaking the PEI/HPAN composite membrane prepared in the step (2) in 0.1-0.5 wt% of phytic acid ester (IP6) aqueous solution for 3min, and taking out;

(4) chelate crosslinking

And (3) placing the Phos-PEI/HPAN composite membrane prepared in the step (3) into an iron chloride (FeCl3) aqueous solution for soaking for 15s, then taking out the membrane, and placing the membrane into a vacuum oven at the temperature of 45 +/-1 ℃ for heat treatment for 30-50min to obtain the polyacrylonitrile-based composite loose nanofiltration membrane (Fe (III) -Phos-PEI/HPAN).

Further preferably, the basement membrane in the composite loose nanofiltration membrane in the step (1) is a Polyacrylonitrile (PAN) ultrafiltration membrane, and the molecular weight cut-off (MWCO) of the basement membrane is 200 kDa; the total thickness of the membrane is 151 mu m, wherein the thickness of polyacrylonitrile is 61 mu m, and the thickness of non-woven fabric is 90 mu m;

further preferably, the molecular weight of Polyethyleneimine (PEI) in step (2) is preferably 750,000 g/mol; the Polyethyleneimine (PEI) concentration is 1 to 3 wt%, preferably 1.5 wt%;

further preferably, the phytate (IP6) in step (3) preferably has a molecular weight of 660 g/mol; the concentration of phytate (IP6) is between 0.1 and 0.5 wt%, preferably 0.3 wt%.

The core of the method is that primary amine groups and secondary amine groups with positive electricity on long chains of polyethyleneimine are adsorbed on a hydrolyzed polyacrylonitrile base membrane, phosphate groups with negative electricity in phytate molecules are adsorbed on the polyethyleneimine to carry out phosphorylation modification on the polyethyleneimine, and ferric chloride is used for crosslinking the phosphorylated polyethyleneimine to prepare the composite loose nanofiltration membrane with high stability. The membrane prepared by the method has higher retention rate on dye molecules, higher permeability on salt and better pollution resistance, and can be applied to dye desalination and wastewater treatment in the printing and dyeing industry. And the membrane preparation method is simple and easy to implement, has low cost, and has important significance for the development of the composite loose nanofiltration membrane.

Drawings

FIG. 1 is a schematic diagram of a process for preparing a polyacrylonitrile-based composite loose nanofiltration membrane by a dip-coating method;

FIG. 2 is an electron scanning electron microscope image of the surface (a) and the section (b) of the polyacrylonitrile-based composite loose nanofiltration membrane of the invention;

FIG. 3 is a graph of the dye wastewater treatment performance of example 1;

FIG. 4 is a graph showing the desalting separation performance in example 1.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. However, the present invention is not limited to the following examples.

Wherein the polyacrylonitrile ultrafiltration membrane (PAN-UF) is purchased from Andec Membrane separation technology engineering (Beijing) Co., Ltd; sodium hydroxide (NaOH), ferric chloride (FeCl)₃) Purchased from Fochen chemical reagent works, Tianjin; polyethyleneimine (PEI) was purchased from tokyo chemical industries, japan; phytate (phytic acid, IP6) was purchased from shanghai mclin biochemistry science and technology limited. Crystal Violet (CV) was purchased from beijing chemical plant.