Preparation of cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis

Cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis (FO) were prepared by immersion precipitation. Casting composition and preparation conditions — 1,4-dioxane/acetone ratio, CTA/CA ratio, substrate type, casting thickness, evaporation time and annealing temperature — were tested for their effects on formation and subsequent performance of membranes. Membranes were characterized by various methods, and their performances were tested against commercially available membranes. The FO membrane prepared under optimized composition and conditions had a smooth surface and showed higher water flux and salt resistance than the commercial membranes. Annealing improved the membrane performance by removing residual additives and solvents. The computerized image processing of optical microscopy images was shown to be useful for assessing the membrane substrates.