Hybrid nanofiltration membranes prepared by a simultaneous synthesis method for precise molecular separation

Incorporation of nanofillers is an option to break through the trade-off of nanofiltration membranes. In the present work, a simultaneous synthesis method, ZIF and selective layer formed in one step, was proposed to prepare hybrid nanofiltration membrane. Co2+ ions pre-assembled on hydrolyzed polyacrylonitrile (PANH) support provided nucleation sites for ZIF-67 formation. The growth of ZIF-67 and the formation of polyethyleneimine (PEI) selective layer on the support completed in one step through co-depositing of a solution of PEI and Hmim (2-methylimidazole). The feasibility of the simultaneous synthesis method was verified by using different supports, PEIs, and the precursor concentrations. All results show that ZIF-67 incorporation improved the water permenace, without significant compromising of membrane rejection. At an optimized condition, the obtained hybrid composite membrane showed high permeance of 35 L/(m2*h*bar) and rejection of 93% toward PEG 200. The permeance increased by about 150%–200% compared with the membrane without ZIF-67. Meanwile, the rejections of salts of the hybrid membrane were very low, exhibiting outstanding organic selectivity.