Impact of sodium hypochlorite cleaning on the surface properties and performance of PVDF membranes

The adverse effect of sodium hypochlorite (NaClO) cleaning has raised concerns regarding their potential impacts on the membrane materials and activated sludge. In this study, the effect of NaClO cleaning on the physicochemical properties, surface free energy, and fouling propensity of polyvinylidene fluoride (PVDF) membranes was systematically investigated. The Analysis of Variance showed that the variation of NaClO soaking time had a significant effect on the permeability and hydrophilicity of PVDF membranes, while effects of NaClO concentration were insignificant. Results showed that the chemical cleaning with NaClO led to a reduction of membrane mechanical strength, which meant the potential harmful impact on the mechanical stability of membranes. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory analysis results showed that the electron donor components (γ−) of membrane surfaces decreased and the electron acceptor components (γ+) relatively increased with the extension of NaClO exposure time, which facilitated membrane fouling propensity.