Modification of membrane surfaces via microswelling for fouling control in drinking water treatment

Abstract

To increase membrane fouling resistance a new membrane post-treatment process, i.e. solvent induced microswelling, was used to increase membrane surface hydrophilicity and smoothness. Driven by interfacial free energy minimization, the surface of microporous membranes will reassemble when exposed to a dilute aqueous solution of a suitable solvent. To prove this concept, three commercial membranes for water treatment were used: a polysulfone ultrafiltration membrane and poly(vinylidene fluoride) ultrafiltration and microfiltration membranes. The membrane physiochemical properties were characterized by pure water permeation, contact angle, X-ray-photoelectron spectroscopy and roughness measurements. After the membranes were post-treated with dilute aqueous solutions of a suitable solvent, membrane surface hydrophilicity and smoothness were effectively increased while the permeance of pure water was maintained. After 18h of permeation using surface water, the modified poly(vinylidene fluoride) ultrafiltration membrane exhibited a 50% higher flux and the same permeate water quality compared to the unmodified membrane. The microswelling conditions (including processing time and temperature, type and amount of solvents) affected the extent of the surface reassembly and thus the surface properties and anti-fouling behavior. These results show that microswelling treatment induced by dilute solvent solutions is a promising method for altering membrane surface properties for fouling control in drinking water treatment.