Method for preparing nanofiltration membrane with high desalination selectivity and high flux

Abstract

The invention provides a method for preparing a nanofiltration membrane with high desalination selectivity and high flux. The method comprises the following steps: S10, preparation of an aqueous phase solution and an organic phase solution, wherein the aqueous phase solution containing multifunctional polyamines, reactive hydroxyl polymer and hydrophilic polymer salt, and the organic phase solution of polyfunctional acyl chloride with at least two reactive acyl halide groups are prepared; S20, interfacial polymerization reaction, wherein an ultrafiltration diaphragm is fixed on a glass plate, then the aqueous phase solution is poured onto the surface of the ultrafiltration diaphragm, and is poured away after placed for 10-30s, the organic phase solution is poured onto the surface of the ultrafiltration diaphragm after the aqueous phase solution on the surface of the diaphragm is dry, and poured away after placed for 10-30s, the ultrafiltration diaphragm is then placed in an oven at a temperature of 40-120 DEG C for thermal treatment, and a finished product is obtained. The method for preparing the nanofiltration membrane has the advantages that while the water flux of the nanofiltration membrane is improved, the desalination selectivity of the nanofiltration membrane is expanded to a relatively large extent.

Description

technical field [0001] The invention relates to membrane treatment technology, in particular to a preparation method of a nanofiltration membrane with high desalination selectivity and high flux. Background technique [0002] Nanofiltration is a new membrane separation technology between ultrafiltration and reverse osmosis, its operating pressure range is 0.2-1.0MPa, and the molecular weight cut-off is in the range of 200-2000. Compared with ultrafiltration membranes and reverse osmosis membranes, nanofiltration membranes have the advantages of high water flux and high rejection at lower operating pressures, especially for divalent ions and low molecular weight organic small molecules. It has a high rejection rate (greater than 98%), so it is widely used in water treatment, medicine, food and biological industries. The preparation process of nanofiltration membrane mainly includes phase inversion method, dilute solution coating method, interfacial polymerization method, hea...

AI Technical Summary

Problems solved by technology

However, this treatment method has a limited range to increase the flux. At the same time, due to the side reactions of other small molecules introduced in the reaction, a looser desalination layer is formed. The decrease in the density of the desalination layer makes the molecular interception of the membrane drop significantly, thus bringing The membrane performance improvement effect is not significant

[0005] Still aiming at the problem of low performance, some researchers improved its performance by "coating the hydrophilic polymer first, drying it in the shade, then adding the aqueous phase solution and continuing the interfacial polymerization reaction with the oil phase on the basis", but This method often causes the desalination layer to fall off after long-term operation due to poor adhesion between the base film and the first desalination layer; in addition, many researchers obtain a polyamide desalination layer through the "acyl chloride reaction, and then continue to coat the desalination layer on the basis of the desalination layer." However, this method often reduces the flux of the membrane significantly, so it is impossible to achieve both high flux and high desalination options.

Moreover, the properties of the nanofiltration membrane membranes prepared by these methods are seriously attenuated, which cannot meet the actual long-term production, that is, the long-term stability of the nanofiltration membranes cannot be guaranteed.