Method for preparing negatively charged nanofiltration membrane through grafting induced after plasma radiation

Abstract

The invention provides a method for preparing a negatively charged nanofiltration membrane. In the method, one of the polysulfone or polyvinylidene fluoride plate ultrafiltration membrane or hollow fiber membrane with molecular weight cut-off of 6,000-20,000 is grafted and modified by low temperature plasma radiation pre-activation, grafting liquid soaking and low temperature plasma radiation grafting so as to prepare the nanofiltration membrane. The preparation process is as follows: firstly, pre-activating a base membrane by a low temperature plasma so as to increase the surface energy of the base membrane and strengthen the hydrophily of the base membrane; then soaking the base membrane in solution containing a monomer and a cross-linking agent for a while; taking the base membrane out and then drying the base membrane, and radiating the base membrane in the plasma; and grafting the monomer to the surface of the base membrane through free radical graft copolymerization reaction, thus preparing the nanofiltration membrane. The method has the following beneficial effects: the prepared nanofiltration membrane has negative charges and has the advantages of big flux, good contamination resistance and long service life; the used monomer is convenient, available and cheap; the low temperature plasma just modifies the surface of the base membrane, thus the body property of the material is not influenced; and the preparation method is simple to operate and practicable, and can be completed at room temperature.

Description

technical field [0001] The invention belongs to the field of membrane material manufacturing, and in particular relates to a membrane material modification manufacturing technology, in particular to a method for preparing negatively charged nanofiltration membranes by grafting induced by plasma radiation. Background technique [0002] Nanofiltration membrane (Nanofiltration membrane, NF) is a pressure-driven membrane between reverse osmosis membrane and ultrafiltration membrane. Low rejection of monovalent salt ions and low molecular weight organics allows selective separation of species. Compared with reverse osmosis membrane technology, nanofiltration membrane technology has the advantages of low operating pressure, large permeation flux, and energy saving. areas such as recycling. [0003] According to whether the nanofiltration membrane is charged or not, it can be divided into charged nanofiltration membrane and uncharged nanofiltration membrane. Charged nanofiltrati...

AI Technical Summary

Problems solved by technology

Although the phase inversion method and the interfacial polymerization method have been widely used, there are also shortcomings. For example, the nanofiltration membrane prepared by the phase inversion method often has poor permeability. The composition of the monomer has strict requirements, the technical difficulty of the polymerization reaction is high, and the product quality is not easy to control. Moreover, the combination between the surface active layer and the base film is mainly based on physical adsorption, and the film performance may decline during long-term operation. question

There are many studies on improving the hydrophilic properties of membranes by using plasma treatment, but there is no research on the preparation of negatively charged nanofiltration membranes by using the method of low-temperature plasma pre-activation-soaking grafting solution-low-temperature plasma radiation grafting.