Effects of membrane fouling on the nanofiltration of trace organic contaminants
Effects of membrane fouling on the nanofiltration of trace organic contaminants
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DOI：
10.1016/j.desal.2007.10.077
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发表时间：
2009-01
期刊：
影响因子：
9.9
通讯作者：
L. Nghiem;S. Hawkes
中科院分区：
文献类型：
--
作者：
L. Nghiem;S. Hawkes
研究了三种纳滤膜对有机污染物的截留效果。加速结垢的条件下，实现了污垢鸡尾酒含有腐殖酸在背景电解质溶液。通过比较清洁和污染膜的截留值，并将其与膜孔径以及痕量有机物的理化特性相关联，来描述膜污染对分离过程的影响。与更紧密的NF-90膜相比，更开放的孔径尺寸的TFC-SR 2和NF-270膜的结垢更严重。本文报道的结果表明，纳滤膜对痕量有机物的截留受空间位阻、静电和疏水相互作用的影响。然而，空间位阻（或尺寸排阻）似乎是最普遍的机制，不仅控制痕量有机物的保留，但也膜污染的过程，以及污染对保留的影响。与NF-270和NF-90膜相比，孔堵塞是松散纳滤TFC-SR 2膜污染更严重的主要原因，NF-270和NF-90膜具有较小的膜孔径。TFC-SR 2膜在污染条件下对痕量有机物的截留率显著增加可能是由于孔堵塞，这是这种松散NF膜的主要污染机制。虽然由于孔堵塞的保留增加可能仅限于TFC-SR 2膜，但在所有三种膜的污染条件下，疏水性痕量有机物的保留得到增强。这种增强的疏水性痕量有机物的保留可以解释为形成的污垢层，减少疏水性痕量有机物和膜表面之间的疏水相互作用，从而减少跨膜的扩散传输。
Organic fouling and its effects on trace organic retention by three nanofiltration (NF) membranes were investigated in this study. Accelerated fouling conditions were achieved with foulant cocktails containing humic acids in a background electrolyte solution. The effects of membrane fouling on the separation process were delineated by comparing the retention values of clean and fouled membranes and relate them to the membrane pore size as well as physicochemical characteristics of the trace organics. Fouling was more severe for the more open pore size TFC-SR2 and NF-270 membranes as compared to the tighter NF-90 membrane. Results reported here indicate that retention of trace organics by NF membranes was governed by steric hindrance, electrostatic, and hydrophobic interactions. However, steric hindrance (or size exclusion) appears to be the most prevalent mechanism controlling not only trace organic retention but also the membrane fouling process as well as the effects of fouling on retention. Pore blocking was a major reason for the more severe fouling by the loose nanofiltration TFC-SR2 membrane as compared to the NF-270 and NF-90 membranes which had smaller membrane pore size. Considerable increase in retention of trace organics by the TFC-SR2 membrane under fouled conditions was probably attributed to pore blocking, which was a dominating fouling mechanism for this loose NF membrane. While retention increase due to pore blocking was probably limited to only the TFC-SR2 membrane, retention of hydrophobic trace organics was enhanced under fouled conditions by all three membranes. This enhancement in retention of the hydrophobic trace organics could be explained by the formation of a fouling layer which reduced hydrophobic interaction between the hydrophobic trace organics and the membrane surface, hence reducing diffusional transport across the membrane.