High flux and highly fouling-resistant polyamide reverse osmosis membrane having inner and outer zwitterion-like layers

The development of high flux and highly fouling-resistant reverse osmosis (RO) membranes is crucial for addressing water crisis. However, it is still challenged to enhance the antifouling performance of the membrane against organic foulants, particularly charged small organic foulants. We herein reported the fabrication of antifouling thin-film composite (TFC) polyamide (PA) RO membranes having inner and outer zwitterion-like layers by a scalable layer-by-layer interfacial polymerization process. The inner zwitterion-like layer is constituted by the positive charges from the incorporated cationic surfactant of benzalkonium chloride (BAC) and the negative charges from carboxylic acid groups in the PA. Then, the outer zwitterion layer is the L-arginine molecules grafted on the PA. The modified RO membranes have a high water permeance of 3.92 L m-2 h-1 bar- 1, while maintaining a NaCl rejection rate of 99.18 %. In addition, the obtained membranes exhibit excellent antifouling properties with the flux decline rate (FDR) of below 40 % and the flux recovery rate (FRR) of above 98 % against 200 ppm of positively and negatively charged surfactants as small organic foulant models, surpassing most of the reported membranes. Our work provides insights to engineer the polyamide RO membrane surface with superior separation performance and efficient anti-fouling properties.