原水中有机物特性对纳滤膜污染的影响

EFFECT OF ORGANIC MATTER CHARACTERISTICS IN RAW WATER ON NANOFILTRATION MEMBRANE FOULING

通过XDLVO理论分析了赣江原水中亲疏水性有机污染物对纳滤(NF)膜的污染状况,对选取的不同分子量区间(<100 kDa、<50 kDa、<3 kDa)的6种亲、疏水性有机物及NF膜的界面自由能进行定量分析,分析了膜污染性能,并通过纳滤试验验证通量衰减与界面自由能的对应关系。结果表明:6种不同分子量的亲/疏水性有机污染物对膜造成污染严重程度与XDLVO理论分析结果相符。不同分子量的有机污染物对NF膜污染程度由大到小顺序为小于100 kDa(疏水性)>小于50 kDa(疏水性)>小于3 kDa(疏水性)>小于3 kDa(亲水性)>小于50 kDa(亲水性)>小于100 kDa(亲水性)。分子量<100 kDa的疏水性有机物与膜之间排斥作用最小,污染最为严重。膜表面的污染物主要是多糖、蛋白质和苯环烯烃类,且在过滤初期有机物堵塞膜孔,膜比通量下降速度较快,而在过滤后期滤饼层形成,膜比通量下降速度减缓。

In this research,the XDLVO(extended Derjaguin-Landau-Verwey-Overbeek)theory was employed to analyze the fouling status of nanofiltration(NF)membrane caused by hydrophilic and hydrophobic organic matters.Quantitative analysis was conducted on six types of hydrophilic and hydrophobic organic matters with different molecular weight ranges(less than 100 kDa,less than 50 kDa,and less than 3 kDa,respectively)and the interfacial free energy of NF membrane was analyzed,in a bid to figure out the performance of the membrane fouling.Furthermore,the corresponding relationship between flux decay and interfacial free energy was verified by the NF experiment.The results showed that the degree of membrane fouling caused by the above-mentioned six hydrophilic or hydrophobic organic matters with different molecular weights in this study was consistent with the XDLVO theoretical analysis,in which the hydrophobic ones with a molecular weight less than 100 kDa showed the slightest repulsive interaction against the membrane and led to the most serious fouling.Besides,the degree of NF membrane fouling by different organic matters was ordered in a descending way as follows:(hydrophobic,molecular weight less than 100 kDa)>(hydrophobic,molecular weight less than 50 kDa)>(hydrophobic,molecular weight less than 3 kDa)>(hydrophilic,molecular weight less than 3 kDa)>(hydrophilic,molecular weight less than 50 kDa)>(hydrophilic,molecular weight less than 100 kDa).The main contaminants on the membrane surface were polysaccharides,proteins and phencyclic olefins,the organic matter clogged the membrane pores in the early stages of filtration,resulting in a rapid decrease in the specific flux of the membrane,while the formation of a cake layer in the later stages of filtration slowed the decrease in the specific flux of the membrane.