低浓度NaClO和NaOH对聚偏氟乙烯超滤膜老化的影响

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

利用质量分数分别为0.2%的NaClO和0.1%的NaOH溶液老化聚偏氟乙烯(PVDF)超滤膜,研究低浓度化学清洗剂对PVDF超滤膜老化的影响.通过纯水通量、膜孔径分布、扫描电镜、拉伸性能、接触角、红外光谱和有机物截留效果,对老化后超滤膜的特征和性能进行评估.结果表明,经过NaClO和NaOH处理后,超滤膜孔径增大,对总有机碳(TOC)的截留率甶36.0%分别降低至16.2%~32.4%和13.9%~24.4%.老化使PVDF膜表面发生了脱氟化氢反应,生成了C=C和C=O等新基团,改变了膜的化学组成和结构,增强了膜的疏水性.老化后膜的机械性能变差,拉断力和断裂伸长率均随老化时间的延长而降低.NaOH对PVDF膜机械性能的影响高于NaClO.

The polyvinylidene(PVDF)ultrafiltration membrane was aged using NaClO and NaOH.The selectedconcentrations of the agents were0.026mol/L and0.025mol/L,respectively.The effect of low-concentration cleaningagents on the aging of the PVDF membrane was investigated.The virgin membrane and membranes exposed to cleaningagents were characterized using pure water flux,membrane pore size distribution,total organic carbon(TOC)rejectionefficiency,tensile strength,field emission scanning electron microscopy(FESEM),contact angle and attenuated totalreflectance fourier transform infrared spectroscopy(ATR-FTIR).The results indicated that the average pore size of themembrane exposed to cleaning agents increased than that of the virgin membrane.After exposed to NaClO and NaOH,thetotal organic carbon(TOC)rejection efficiencies decreased from36.0%to16.2%~32.4%and13.9%~24.4%,respectively.The dehydrofluorination occurred during the aging process,which was indicated by the increased peak intensity of C Cand C O.The chemical composition and structure of the membrane were changed by the chemical cleaning agents andthis caused the reduction of membrane hydrophilicity.The tensile strength and ultimate elongation reduced along with theincreased aging time.The impact of NaOH on the mechanical property of membrane was more significant than that ofNaClO.