Surface Modification of Polyethersulfon Nanofiltration Membrane for Improving Water-Ethanol Separation

Abstract

This paper reports on the surface modification of a nanofiltration polyethersulfon membrane, Microdyn Nadir NP030P, aiming at improved water-ethanol separation. To achieve this, three types of poly(vinyl alcohol) copolymers of varied hydrophilic-lipophilic balance were synthesized and tested as modifiers: double hydrophilic graft copolymer with poly(N,N-dimethyl acrylamide) side chains, amphiphilic copolymer of partially acetalized PVA, as well as amphiphilic copolymer with grafted hydrophobic poly(methyl methacrylate) chains. Copolymers’ chemical structure, composition and properties were evaluated by conventional analytical techniques. Thin film deposition via spin-coating of copolymer solution was applied as a method for membrane modification. Alteration of the hydrophilic-lipophilic balance at the membrane surface was studied by contact angle measurements whereas the surface microstructure was characterized by attenuated total reflectance Fourier-transform infrared spectroscopy as well as optical and scanning electron microscopy. The feasibility of tailoring membrane surface to specific requirements by using PVA-based copolymer was assessed and the influence of copolymer structure and composition on the membrane properties was considered.