Preparation and properties of acrylonitrile-DMAEMA copolymer based crosslinked and positively-charged nanofiltration membranes

A fabrication strategy for positively charged nanofiltration (NF) membranes is proposed based on the blending system of amphiphilic copolymer poly(acrylonitrile-co-dimethylaminoethyl methacrylate) (AN-DMAEMA) and homopolymer poly(dimethylaminoethyl methacrylate) (PDMAEMA). The membrane is first cast by non-solvent induced phase separation (NIPS), followed by a 5 min annealing-crosslinking post-treatment to synergistically tailor its charge density and pore structure. This system enables the synergistic regulation of positive charge density and pore size of the separation membrane by tuning the blending ratio of PDMAEMA. Experimental results show that the optimized NADBPD-20 % membrane possesses a mean pore size (μp) of 0.84 nm and an isoelectric point (IEP) of 9.07, exhibiting a water flux of 9.56 L/(m 2  h bar) at 0.4 MPa, with rejection rates of 94.2 % and 95.1 % for MgCl 2 and CaCl 2 , respectively. At pH = 5, the rejection rates for poly(hexamethylene biguanide) hydrochloride (PHMB), chlorhexidine (CHX), and hexamidine diisethionate (HDI) reach 99.3 %, 98.4 %, and 93.0 %, respectively. The membrane shows excellent static antifouling performance against Bovine Serum Albumin (BSA) solution, with a flux recovery rate of 89.5 % after dynamic filtration fouling with BSA. Simulated wastewater treatment experiments validate its capability for simultaneous hard water softening and cationic disinfectants removal. Additionally, it maintains continuous filtration stability for 36 h during the filtration of a mixed solution of MgCl 2 and CHX. This study provides a feasible solution for the efficient removal of Ca 2+ /Mg 2+ and cationic pollutants in water bodies.