Effect of hypochlorite concentration on properties of posttreated outer‐skin ultrafiltration membranes spun from cellulose acetate/poly(vinyl pyrrolidone) blends

Abstract

AbstractAn outer‐skin hollow‐fiber ultrafiltration (UF) membrane was spun from a new dope solution containing cellulose acetate (CA)/poly(vinyl pyrrolidone) (PVP 360K)/N‐methyl‐2‐pyrrolidone (NMP)/water using a wet‐spinning technique. The as‐spun fibers were posttreated with a hypochlorite solution over a range of concentrations for a fixed period of 24 h. The experimental results showed that the pure water flux of the treated membrane increased with increasing hypochlorite concentration. The treated membrane experienced an increased fouling tendency with increasing hypochlorite concentration because the hydrophilicity of the treated membrane decreased as a result of the removal of PVP contents in the membrane matrix after hypochlorite treatment. SEM images revealed that the membrane had an outer dense skin, a porous inner surface, and a spongelike structure, which confirmed that addition of PVP favored the suppression of macrovoids in the membrane. The membrane pore size could be significantly increased when the hypochlorite concentration reached 200 mg/L. It was concluded that hypochlorite treatment provided an additional option to easily alter the pore size of UF membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 227–231, 2005