In this study, high performance positively charged hyper-branched polyethyleneimine (PEI) nanofiltration (NF) layer was assembled successfully on negatively charged polyethersulfone/polyimide (PES/PI) hollow fiber ultrafiltration (UF) membranes under different conditions. In accordance with principles of green chemistry, glutaraldehyde (GA) as cross-linker and purely aqueous solutions were used as a less hazardous alternative compared to, e.g. trimesoyl chloride in an organic solvent. The effects of the surface roughness and charge of the substrate UF membranes, due to the presence of PI, and various fabrication conditions, such as pH of PEI aqueous solution, GA/PEI ratio and crosslinking reaction time, were investigated and discussed. Electron microscopy images revealed the successful assembly of the PEI NF layer at uniform coverage of the PES/PI UF membranes. It was found that the varied preparation conditions drastically affect the membrane surface hydrophilicity, surface zeta potential, permeation flux, and salt rejection. The membrane fabricated at optimum conditions had a molecular weight cut-off of ≤ 400 Da; steric hindrance and Donnan exclusion resulted to achieve salt rejections of 94.2% and 87.4% for MgCl and MgSO, respectively. Moreover, fabricated membranes were tested through three cycles of six-hour filtrations and over 95% flux recovery after the filtration of salts via the backwashing process was recorded.

中文翻译：

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通过聚乙烯亚胺层组装的绿色方法制造高性能带正电中空纤维纳滤膜


本研究在不同条件下，在带负电的聚醚砜/聚酰亚胺（PES/PI）中空纤维超滤（UF）膜上成功组装了高性能的带正电的超支化聚乙烯亚胺（PEI）纳滤（NF）层。根据绿色化学原理，与有机溶剂中的均苯三甲酰氯等相比，戊二醛（GA）作为交联剂和纯水溶液被用作危险性较小的替代品。研究并讨论了由于 PI 的存在以及各种制备条件（例如 PEI 水溶液的 pH 值、GA/PEI 比例和交联反应时间）对基底超滤膜表面粗糙度和电荷的影响。电子显微镜图像显示 PEI NF 层成功组装，均匀覆盖 PES/PI UF 膜。研究发现，不同的制备条件会极大地影响膜表面亲水性、表面zeta电位、渗透通量和脱盐率。在最佳条件下制备的膜的截留分子量≤400Da；空间位阻和唐南排斥导致 MgCl 和 MgSO 的脱盐率分别达到 94.2% 和 87.4%。此外，通过三个六小时过滤循环对制成的膜进行了测试，记录了通过反洗过程过滤盐后通量恢复超过 95%。