Effluent particle size and permeability of polyvinylchloride membranes after sodium hypochlorite exposure

摘要

Sodium hypochlorite (NaOCl) is a common cleaning agent for treating ultrafiltration (UF) membranes. Although it efficiently removes fouling, NaOCl accelerates membrane degradation and reduces membrane integrity. In this paper, new and polluted polyvinylchloride hollow fiber membranes were treated with NaOCl solutions. The effects on the membrane were evaluated by using transmembrane pressure, bovine serum albumin permeability, particle-size distribution of the effluent (PSDE), attenuated total reflectance-Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The membrane pore size increased after exposure to solutions with a NaOCl mass fraction of <1%. The membrane surface wrinkled after exposure to solutions with a NaOCl mass fraction of >1%. The PSDE was successfully used to test membrane integrity. When the NaOCl mass fraction was <1%, the PSDE increased; otherwise, the PSDE decreased. The main reason for pore-size enlargement was the breaking of C-C and C-H bonds, which caused C=C bond formation and chain scission. Polluted membranes were affected more than new membranes by NaOCl cleaning.