State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology , Harbin 150090, China.
Environ Sci Technol. 2015 Feb 3;49(3):1436-44. doi: 10.1021/es5044062. Epub 2015 Jan 22.
In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes.
在这项研究中，我们研究了表面结构对薄膜复合（TFC）正向渗透（FO）膜结垢倾向的影响。具体来说，我们比较了通过相同程序制造的膜，只是在相分离过程中使用了不同的溶剂（二甲基甲酰胺，DMF 和 N-甲基-2-吡咯烷酮，NMP）。FO 结垢实验使用含有模型有机污染物的进料溶液进行。与使用 DMF 制造的 TFC 膜（DMF-TFC，通量下降 12.70±2.62%）相比，使用 NMP 制造的 TFC 膜（NMP-TFC）的通量下降明显较少（7.47±0.15%）。通过物理清洗，NMP-TFC 膜的水通量也更容易恢复。为了确定结垢倾向差异的根本原因，对膜的活性层和支撑层进行了广泛的物理和化学特性表征，这些特性与结垢行为有关。聚酰胺表面粗糙度被发现是决定我们的膜彼此之间结垢倾向的所有其他研究因素的主导因素。DMF-TFC 膜的高粗糙度聚酰胺表面还富含较大的叶状结构，而 NMP-TFC 膜的低粗糙度聚酰胺层则包含更多的结节和较小的特征。两种膜类型的支撑层也进行了形态特性的表征，并讨论了支撑层表面结构与聚酰胺活性层形成之间的关系。总的来说，我们的研究结果表明，支撑层结构对活性层的结垢倾向有重大影响，在设计 TFC 膜的支撑层结构时应考虑这一影响。
