不同相对分子质量的有机物对膜通量的影响

采用截留分子量分别为10、30kDa的聚醚砜膜和100kDa的聚偏氟乙烯膜对原水进行分级处理,并采用截留分子量分别为150kDa的聚偏氟乙烯膜和0.1μm的醋酸纤维素膜对出水进行膜过滤试验,研究不同相对分子质量的有机物对膜通量的影响.结果表明,虽然相对分子质量>30kDa的大分子有机物仅为总有机物的15%,但它分别引起微滤膜的通量下降86%和超滤膜通量下降54%.混凝处理可以去除相对分子质量>100kDa的有机物,这部分有机物导致通量下降40%以上.因此,尽管混凝处理仅去除10%的有机物,但改善通量的效果显著.粉末活性炭可以去除相对分子量<30kDa的小分子有机物,这部分有机物对通量下降的贡献程度甚低.因此,尽管粉末活性炭去除76%的有机物,但改善通量的效果甚微.预处理改善通量的效果并不取决于去除有机物的多少,而是取决于所去除的有机物对通量的影响大小.

Influence of different molecular weight of nature organic matter on membrane flux

Water samples were fractionated by PES UF membranes with molecular weight cutoffs (MWCOs) of 10、30kDa and PVDF UF membrane with MWCOs of 100kDa, and these permeates were filtrated by PVDF UF membrane with MWCOs of 150kDa and CA MF membrane with a 0.1μm pore size, as to investigate influence of nature organic matter (NOM) with different MWCOs on flux. The NOM larger than 30kDa accounting for 15% of total organic matter resulted in 86% of flux decline for MF and 54% for UF, respectively. It was shown that coagulation removed the NOM larger than 100kDa that result in over 40% of flux decline. As a result, in spite of removing 10% of NOM only, coagulation enhanced flux substantially. Powdered active carbon (PAC) removed NOM smaller than 30kDa that showed little contribution to flux decline. Therefore, PAC removed 76% of NOM but showed little contribution to enhance flux. It can be concluded that the effect of pretreatment on enhancing flux depended on contribution of NOM to flux decline rather than its amounts removed.