Activated carbon incorporation on forward osmosis membrane surface for enhanced performance

Abstract

Cellulose triacetate (CTA) is the first-generation forward osmosis (FO) membrane used for desalination. There have been few chemical modifications of the CTA membrane surface. It has improved membrane hydrophilicity, water flux, and salt rejections compared to unmodified CTA membranes. Chitosan containing porous materials as composites resulted in increased pore characteristics. It has motivated to modify the surface of the commercial CTA forward osmosis (FO) membrane by surface coating with chitosan (CS) – powdered activated carbon (AC) mix. The membrane morphology was characterized by SEM, FTIR-ATR, contact angle measurement and AFM. Operation conditions for FO such as the orientation of the membrane active layer, feed and draw solution flow rates, type and concentration of draw salt were optimized with the original CTA membrane. The modified membrane exhibited around two-fold increase in the water flux and reduced reverse salt flux compared to the original CTA membrane. The improved water flux was attributed to the CS-AC coating enhancing water wettability of the membrane surface and the porous AC generating additional water flow channels. Overall, the water flux of the CTA-CS-AC membrane developed in this work was superior to that of CTA and cellulose acetate (CA) membranes reported in the literature.