Influence of l-arginine on performances of polyamide thin-film composite reverse osmosis membranes

To prepare polyamide thin-film composite reverse osmosis (PA-TFC-RO) membranes with high performance, l-arginine (Arg) was used as an additive in m-phenylenediamine (MPD) aqueous solution. Arg with active amine groups can react with 1,3,5-benzenetricarboxylic chloride (TMC) to be incorporated into the polyamide selective layer during interfacial polymerization. X-ray photoelectron spectroscopy verified the successful introduction of Arg into the polyamide selective layer. Scanning electron microscopy, atomic force microscopy, contact angle and zeta potential measurements manifested that the polyamide selective layer was thinner, smoother, more hydrophilic and less negatively charged after the incorporation of Arg. The thinner and more hydrophilic polyamide selective layers favor the boosting of the permeability of the RO membrane by decreasing the hydraulic resistance to water permeation. Consequently, when the content of Arg was 0.5 wt%, the water flux and salt rejection of the resulting membranes increased from the original 46.46 L m^-2 h^-1 and 96.34% to 54.13 L m^-2 h^-1 and 98.36%. Besides, the modified membranes showed excellent fouling-resistance and easy-cleaning properties when tested by using bovine serum albumin (BSA) and dodecyltrimethyl ammonium bromide (DTAB) as model foulants.