Aging of PVDF and PES ultrafiltration membranes by sodium hypochlorite:Effect of solution pH

• 作者: Kai Li Qian Su Shu Li Gang Wen Tinglin Huang
• 来源期刊: 环境科学学报（英文版）
• 年，卷（期）: 2021,（6）
• 页码范围: 444-455
• 页数: 12页
• 语种: 英文

摘要

Sodium hypochlorite(NaClO)is a commonly applied cleaning agent for ultrafiltration mem-branes in water and wastewater treatment.Long-term exposure to NaClO might change the properties and performance of polymeric membranes,and ultimately shorten membrane lifespan.Active species in NaClO solution vary with solution pH,and the aging effects can change depending on the membrane material.In this study,the aging of polyvinylidene flu-oride(PVDF)and polyethersulfone(PES)membranes by NaClO at pH 3-11 was investigated by examining variations in chemical composition,surface charge,surface morphology,me-chanical strength,permeability,and retention ability.Polyvinyl pyrrolidone(PVP),which was blended in both membranes,was oxidized and dislodged due to NaClO aging at all inves-tigated pH values,but the oxidation products and dislodgement ratio of PVP varied with solution pH.For the PVDF membrane,NaClO aging at pH 3-11 caused a moderate increase in permeability and decreased retention due to the oxidation and release of PVP.The ten-sile strength decreased only at pH 11 because of the defluorination of PVDF molecules.For the PES membrane,NaClO aging at all investigated pH resulted in chain scission of PES molecules,which was favored at pH 7 and 9,potentially due to the formation of free radi-cals.Therefore,a decrease in tensile strength and retention ability,as well as an increase in permeability,occurred in the PES membrane for NaClO aging at pH 3-11.Overall,the results can provide a basis for selecting chemical cleaning conditions for PVDF and PES membranes.