Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups
Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups
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DOI：
10.1021/es303673p
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发表时间：
2012-12-18
影响因子：
11.4
通讯作者：
Elimelech, Menachem
中科院分区：
文献类型：
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作者：
Mo, Yinghui;Tiraferri, Alberto;Elimelech, Menachem
羧基是聚酰胺纳滤膜的固有官能团，对膜的性能和污染有一定的影响。它们的表面存在是由于酰氯单体在界面聚合合成膜活性层过程中反应不完全所致。为了揭示羧基密度对有机污染的影响，通过将哌嗪(PIP)与间苯二甲酰氯(IPC)或更常用的三甲酰氯(TMC)反应，制备了纳滤膜。以海藻酸盐为模型亲水性有机污泥剂，模拟城市二级出水的组成，进行了溶液结垢实验。与TMC膜(通量下降51%，清洗效率40%)相比，IPC膜具有更好的抗污染性能，表现出更低的通量下降(40%)和更高的污染可逆性或清洗效率(74%)。表面表征表明，IPC膜和TMC膜的表面羧基密度有很大差异，而其他表面性质是相似的。通过原子力显微镜测量表面分子间作用力来阐明羧基的作用，结果表明，在溶液中有钙离子存在的情况下，IPC膜的粘附力和断裂距离低于TMC膜。结果表明，降低IPC单体聚酰胺膜的表面羧基密度可以阻止钙桥接海藻酸盐，从而改善膜的抗污染性能。
Carboxyls are inherent functional groups of thin-film composite polyamide nanofiltration (NF) membranes, which may play a role in membrane performance and fouling. Their surface presence is attributed to incomplete reaction of acyl chloride monomers during the membrane active layer synthesis by interfacial polymerization. In order to unravel the effect of carboxyl group density on organic fouling, NF membranes were fabricated by reacting piperazine (PIP) with either isophthaloyl chloride (IPC) or the more commonly used trimesoyl chloride (TMC). Fouling experiments were conducted with alginate as a model hydrophilic organic foulant in a solution, simulating the composition of municipal secondary effluent. Improved antifouling properties were observed for the IPC membrane, which exhibited lower flux decline (40%) and significantly greater fouling reversibility or cleaning efficiency (74%) than the TMC membrane (51% flux decline and 40% cleaning efficiency). Surface characterization revealed that there was a substantial difference in the density of surface carboxyl groups between the IPC and TMC membranes, while other surface properties were comparable. The role of carboxyl groups was elucidated by measurements of foulant-surface intermolecular forces by atomic force microscopy, which showed lower adhesion forces and rupture distances for the IPC membrane compared to TMC membranes in the presence of calcium ions in solution. Our results demonstrated that a decrease in surface carboxyl group density of polyamide membranes fabricated with IPC monomers can prevent calcium bridging with alginate and, thus, improve membrane antifouling properties.