Effect of NaClO and NaOH at low agent concentration on the ageing of PVDF ultrafiltration membrane

The polyvinylidene (PVDF) ultrafiltration membrane was aged using NaClO and NaOH. The selected concentrations of the agents were 0.026mol/L and 0.025mol/L, respectively. The effect of low-concentration cleaning agents on the aging of the PVDF membrane was investigated. The virgin membrane and membranes exposed to cleaning agents were characterized using pure water flux, membrane pore size distribution, total organic carbon (TOC) rejection efficiency, tensile strength, field emission scanning electron microscopy (FESEM), contact angle and attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR). The results indicated that the average pore size of the membrane exposed to cleaning agents increased than that of the virgin membrane. After exposed to NaClO and NaOH, the total organic carbon (TOC) rejection efficiencies decreased from 36.0% to 16.2%~32.4% and13.9%~24.4%, respectively. The dehydrofluorination occurred during the aging process, which was indicated by the increased peak intensity of C=C and C=O. The chemical composition and structure of the membrane were changed by the chemical cleaning agents and this caused the reduction of membrane hydrophilicity. The tensile strength and ultimate elongation reduced along with the increased aging time. The impact of NaOH on the mechanical property of membrane was more significant than that of NaClO.