Arginine- and lysine-modified forward osmosis membranes with simultaneous enhancement of water flux and antibacterial properties: Performance and mechanisms

Forward osmosis (FO) technology has been employed extensively in a multitude of fields. The primary impediment to the development of this technology is the phenomenon of bio-fouling. This study presented an innovative and straightforward approach to mitigating bio-fouling and simultaneously improving water drawing performance through the incorporation of arginine (Arg) and lysine (Lys) into the active layer of FO membranes. This was contributed from the hydrophilic groups (i.e. guanidine and amino groups) derived from Arg and Lys. The highest water fluxes were observed of 23.3 ± 0.4 and 20.7 ± 0.7 LMH, with Arg and Lys loading concentrations of 6 and 7 wt%, respectively (Arg-FO-6 and Lys-FO-7 membrane). The E. coli fouling test demonstrated that the modified FO membranes exhibited excellent and stable antibacterial activity. The normalized water fluxes of the Arg-FO-6 and Lys-FO-7 membranes remained at 0.50 and 0.59, respectively, after 120-hour dynamic fouling, whereas the flux of the pristine membrane declined to 0.32. The Arg-FO-6 and Lys-FO-7 membranes exhibited total membrane resistance ( R t ) of 3.6 × 10 8 and 4.9 × 10 8 m −1 , respectively, significantly lower than the pristine membrane (11.4 × 10 8 m −1 ). These findings demonstrate that the modification of FO membranes with Arg and Lys is an effective approach with significant potential for alleviating bio-fouling.