Effect of membrane fouling on transport of organic contaminants in NF/RO membrane applications
Effect of membrane fouling on transport of organic contaminants in NF/RO membrane applications
复制标题
DOI：
10.1016/j.memsci.2005.12.001
复制
发表时间：
2006-08
影响因子：
9.5
通讯作者：
P. Xu;J. Drewes;Tae-Uk Kim;C. Bellona;G. Amy
中科院分区：
文献类型：
--
作者：
P. Xu;J. Drewes;Tae-Uk Kim;C. Bellona;G. Amy
采用商用聚酰胺纳滤(NF)、反渗透(RO)和超低压反渗透(ULPRO)膜(NF-90、NF-200、TFC-HR和XLE)以及三醋酸酯纤维素膜(CTA)研究了污染对有机微污染物迁移的影响。由于污染物的沉淀和滤饼层的形成，膜的表面特性在接触角(疏水性的一个指数)、Zeta电位、官能度和表面形态方面都发生了很大的变化，与未受污染的(原始)膜相比，这可能会影响污染物的传输。离子有机微污染物的迁移由于改进的Donnan排斥(静电斥力)而受到阻碍，这可能是由于表面电荷更负，通过Zeta电位测量来量化的。膜污染还通过溶质在膜上的分配和扩散，增加了吸附容量，减少了传质。这些影响导致受污染的膜对疏水性非离子溶质(例如消毒副产品和氯化溶剂)的截留率增加。然而，由于膜的溶胀，表面电荷的增加有可能导致受污染的膜具有更大的截留分子量，这会降低对亲水性非离子溶质的截留率，特别是在使用截留分子量较大的纳滤膜的情况下。膜污染促进了疏水性和亲水性有机污染物通过CTA膜的传输，导致渗透液中目标溶质浓度的增加。研究结果表明，膜污染对CTA膜、纳滤膜和ULPRO膜对有机溶质的截留有显著影响，而对薄膜复合反渗透膜的影响较小。
Commercial polyamide nanofiltration (NF), reverse osmosis (RO), and ultra-low pressure RO (ULPRO) membranes (NF-90, NF-200, TFC-HR, and XLE) as well as a cellulose triacetate RO membrane (CTA) were employed to investigate the effect of fouling on transport of organic micropollutants. Due to foulant precipitation and cake-layer formation, membrane surface characteristics changed considerably in terms of contact angle (an index of hydrophobicity), zeta-potential, functionality, and surface morphology, which potentially affected transport of contaminants as compared to unfouled (virgin) membranes. The transport of ionic organic micropollutants was hindered as a result of improved Donnan exclusion (electrostatic repulsion) likely due to a more negative surface charge as quantified by zeta-potential measurements. Membrane fouling also resulted in an increased adsorption capacity and reduced mass transport through partitioning and diffusion of solutes across the membrane. These effects led to an increase in rejection of hydrophobic non-ionic solutes (e.g., disinfection byproducts and chlorinated solvents) by fouled membranes. However, the increasing surface charge has the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling, which can lead to lower rejection for hydrophilic non-ionic solutes, especially where nanofiltration membranes with a larger molecular weight cut-off are employed. Membrane fouling facilitated the transport of hydrophobic and hydrophilic organic contaminants through CTA membranes resulting in elevated concentrations of target solutes in the permeate. Findings of the study indicate that membrane fouling significantly affects the rejection of organic solute by CTA, NF, and ULPRO membranes while it is less important for thin film composite RO membranes.