在商业膜的表面正电改性研究中采用两步接枝法依次将PEI和23-环氧丙基三甲基氯化铵EPTAC接枝到膜表面提高改性膜表面的正电荷密度。实验结果表明与EDCNHS活化剂相比2-氯-1-甲基吡啶碘化物CMPI活化操作更简便水通量衰减更小。随着接枝PEI分子量的减小膜表面平均有效孔径变小采用PEI 600 Da改性膜的平均有效孔径由原始膜的04393 nm降低为04052 nm同时膜表面正电性增加分离效果

In the study of positive modification on commercial membranes, a two-step grafting method was employed to sequentially graft PEI and 2,3-epoxypropyltrimethylammonium chloride (EPTAC) onto the membrane surface, increasing the positive charge density of the modified membrane surface. Experimental results showed that compared with EDC/NHS activators, the activation operation with 2-chloro-1-methylpyridinium iodide (CMPI) was simpler and had less water flux decline. As the molecular weight of grafted PEI decreased, the average effective pore size on the membrane surface decreased. The modified membrane using PEI with a molecular weight of 600 Da had an average effective pore size of 0.4052 nm, which was smaller than that of the original membrane (0.4393 nm), and the surface positive charge increased, resulting in the best separation performance. Through optimization, the optimal grafting conditions for surface modification were determined to be 0.05 wt% CMPI, 2 wt% PEI, and 1 wt% EPTAC. The modified membrane had a Mg2+ retention rate of 94.93%, which was higher than that of the original membrane (57.65%). Anti-fouling and long-term operation tests showed that the two-step modified nanofiltration membrane with PEI and EPTAC had better separation performance for mono- and divalent cations, anti-fouling performance, and alkali resistance compared to the original membrane.