Nanofiltration of nonionic surfactants: Effect of the molecular weight cutoff and contact angle on flux behavior
Nanofiltration of nonionic surfactants: Effect of the molecular weight cutoff and contact angle on flux behavior
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DOI：
10.1021/ie0501226
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发表时间：
2005-09-28
影响因子：
4.2
通讯作者：
Vandecasteele, C
中科院分区：
文献类型：
--
作者：
Cornelis, G;Boussu, K;Vandecasteele, C
非离子表面活性剂在工业上应用广泛，每年产生大量含非离子表面活性剂的废水。纳滤是净化这些水的一种可能的选择，减少了总的用水量并增强了生物净化。然而，在含非离子表面活性剂的废水净化过程中，纳滤膜的通量行为还不是很清楚。对合成溶液和含有非离子表面活性剂的地毯漂洗废水进行了纳滤试验。当选择截留相对分子质量(MWCO)较高的膜时，膜通量下降到低于大多数超滤膜的水平。当选择较低的MWCO时，当选择相对疏水的膜时，通量增加到高于纯水的通量，或者当选择相对亲水的膜时，通量降低。因此，当选择合适的膜时，纳滤膜似乎可以减少涉及非离子表面活性剂的工业过程中的用水量。研究表明，膜通量受三种机制控制：第一，当截留分子量相当或大于单体尺寸时，通过吸附单体使膜孔变窄，导致通量下降；第二，通过单体在疏水基团上的吸附，改善膜表面的润湿性，导致通量增加到纯水通量以上；第三，通过单体在亲水基团上的吸附，使润湿性降低，导致通量下降。非离子表面活性剂的浓度、截留分子量和膜的亲水性决定了哪种机理起主导作用。
Nonionic surfactants are widely used in industry, and large amounts of wastewater containing nonionic surfactants are produced each year. Nanofiltration (NF) is a possible option to purify these waters, reducing the overall water consumption and enhancing biological purification. However, the flux behavior of NF during purification of wastewaters containing nonionic surfactants is not well understood. NF tests were performed with both synthetic solutions and real wastewaters containing nonionic surfactants from carpet rinsing. When a membrane with a relatively high molecular weight cutoff (MWCO) was chosen, flux decreased to a level lower than that with most ultrafiltration membranes. When a low MWCO was chosen, flux either increased above pure water flux when a relatively hydrophobic membrane was chosen or decreased when a relatively hydrophilic membrane was chosen. NF thus seems feasible to reduce water usage in industrial processes involving nonionic surfactants when a proper membrane is selected. It appeared that flux is controlled by three mechanisms: first, the narrowing of membrane pores through adsorption of monomers when the MWCO is comparable or larger than the monomer size, causing flux decline; second, an improved wettability of the membrane surface through adsorption of monomers on hydrophobic groups, causing flux to increase above pure water flux; third, a decreased wettability through adsorption of monomers on hydrophilic groups, causing flux decline. The nonionic surfactant concentration, MWCO, and membrane's hydrophilicity determine which mechanism is dominant.