不同超滤膜过滤天然有机物的膜污染特性研究

超滤膜的截留分子量、天然有机物的分子量分布以及两者之间的相对关系对于膜污染以及过滤阻力的组成有很大的影响。MWCO140kDa、70kDa、30kDa、10kDa、4kDa和1kDa的超滤膜过滤10mg/L腐殖酸溶液和未名湖湖水的试验结果表明,在过滤初始时刻就发生了膜污染,膜的截留分子量越大,膜污染越显著。在长期过滤的过程中,截留分子量>10kDa的超滤膜的过滤阻力受到膜污染的控制,膜孔堵塞和膜面形成凝胶层是造成膜污染的主要原因;当膜的截留分子量≤10kDa时,过滤阻力主要由膜本身固有的阻力决定,膜污染影响较小。不同浓度、类型的腐殖酸溶液和不同种类的超滤膜过滤试验数据分析表明,当膜对腐殖酸分子的截留率超过40%时,膜污染的程度会逐渐减小,过滤阻力将由膜本身固有的阻力控制。

Study on characteristics of membrane fouling during the ultrafiltration of natural organic matters

The molecular weight cut-off (MWCO) of UF membrane, the distribution of molecular weight of natural organic matter or humic acid, and their relative relationship can take great effects on the membrane fouling and the filtration resistance. According to the experiments on the filtration of 10 mg/L humic acid and the water samples from Weiming Lake by using MWCO 140 kDa, 70 kDa, 30 kDa, 10 kDa, 4 kDa, and 1 kDa UF membrane, respectively, it showed that fouling could occur at the beginning of filtration.The larger MWCO of UF membrane the more severe fouling will happen.During the long-term operation,the filtration resistances would be determined by fouling mainly composed of pore blocking and gel layer formation, when MWCO of membrane was larger than 10 kDa.On the contrary,the intrinsic resistance of membrane would dominate the filtration process when MWCO of membrane was less than 10 kDa.The data analysis on the different humic acids and UF membranes showed that fouling could decrease and the intrinsic resistance would determine the total resistance only when the UF membrane could reject more than 40% of the total natural organic matters.