State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing100190, China.
State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin300387, China.
Environ Sci Technol. 2022 Dec 20;56(24):18018-18029. doi: 10.1021/acs.est.2c06582. Epub 2022 Nov 29.
A nanofiltration (NF) membrane with high salt permeation and high retention of small organics is appealing for the treatment of high-salinity organic wastewater. However, the conventional negatively charged NF membranes commonly show high retention of divalent anions (e.g., SO), and the reported positively charged NF membranes normally suffer super low selectivity for small organics/NaSO and high fouling potential. In this work, we propose a novel "etching-swelling-planting" strategy assisted by interfacial polymerization and mussel-inspired catecholamine chemistry to prepare a mix-charged NF membrane. By X-ray photoelectron spectroscopy depth profiling and pore size distribution analysis, it was found that such a strategy could not only deepen the positive charge distribution but also narrow the pore size. Molecular dynamics confirm that the planted polyethyleneimine chains play an important role to relay SO ions to facilitate their transport across the membrane, thus reversing the retention of NaSO and glucose (43 vs 71%). Meanwhile, due to the high surface hydrophilicity and smoothness as well as the preservation of abundant negatively charged groups (-OH and -COOH) inside the separation layer, the obtained membrane exhibited excellent antifouling performance, even for the coking wastewater. This study advances the importance of vertical charge distribution of NF membranes in separation selectivity and antifouling performance.
一种具有高盐渗透和高保留小分子有机物能力的纳滤（NF）膜，对于处理高盐有机废水具有吸引力。然而，传统的带负电荷的 NF 膜通常对二价阴离子（如 SO ）具有高保留率，而报道的带正电荷的 NF 膜通常对小分子有机物/NaSO 的选择性极低，且易堵塞。在这项工作中，我们提出了一种新的“刻蚀-溶胀-种植”策略，通过界面聚合和贻贝启发的儿茶酚化学辅助，制备了一种混合带电 NF 膜。通过 X 射线光电子能谱深度剖析和孔径分布分析，发现这种策略不仅可以加深正电荷分布，还可以缩小孔径。分子动力学证实，种植的聚乙烯亚胺链在传递 SO 离子方面发挥了重要作用，从而促进了它们在膜中的传输，因此逆转了 NaSO 和葡萄糖的保留率（43 对 71%）。同时，由于分离层内表面具有高亲水性和光滑性以及丰富的带负电荷的基团（-OH 和-COOH）得以保留，所得到的膜表现出优异的抗污染性能，即使是对于焦化废水也是如此。本研究推进了 NF 膜在分离选择性和抗污染性能方面垂直电荷分布的重要性。
