Surface modification of FO membrane by plasma-grafting polymerization to minimize protein fouling

Abstract

The aim of this study was to compared the effect of two plasma gases, Argon (Ar) and carbon dioxide (CO2), in the acrylic acid (AAc) grafting modification of a commercial cellulose triacetate (CTA) membrane to improve water flux and anti-protein fouling properties in forward osmosis (FO) for protein recovery application. The successful grafting polymerization was evaluated by measuring the grafting yield and water contact angle, X-ray photoelectron spectroscopy (XPS) analysis, Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) analysis. The contact angle of the CTA membrane was decreased from 64.0° to 37.1° and 36.4° by CO2 and Ar plasma gas treatment, respectively, which indicated an increase in hydrophilicity. The FO experiments were carried out in a lab-scale filtration apparatus. The effects of interfacial characteristics between membrane surfaces and model protein and polysaccharide foulants on flux decline and reversibility of foulants were compared. Ar gas was able to provide more free radicals and plasma electrons on the membrane surfaces, thus it was more effective than CO2 in increasing water flux and also decreased reverse salt flux and fouling tendency. The modified membranes had excellent anti-protein fouling properties, which makes them suitable for protein recovery applications. Using the Ar plasma modified membranes, tuna protein was concentrated from 4.5 % to 10.7 %, and excellent maintenance of water flux was achieved.