Enhancing the Permeability and Antifouling Properties of Polyamide Composite Reverse Osmosis Membrane by Surface Modification with Zwitterionic Amino Acid l-Arginine

The increase of the permeability and antifouling properties of reverse osmosis (RO) membranes is always significant in desalination. In this study, zwitterionic amino acid l-Arginine (Arg) is grafted onto the self-made RO membrane by one-step method to construct the zwitterionic surface for enhancing the performances of the membranes. X-ray photoelectron spectroscopy verifies the successful covalent attachment of Arg onto the membrane surface. Atomic force microscopy, contact angle, and zeta potential measurements manifest that the modified membrane surface becomes smoother, more hydrophilic, and less negatively charged. The contact angles decrease from 72.6 degrees to 43.7 degrees after Arg-modification. For the optimized modified membrane, its water flux increases from original 45.46 to 63.51 L m(-2) h(-1) (improved by 39.7%); while the salt rejection ascends from 96.42% to 98.08%. Using bovine serum albumin and dodecyltrimethyl ammonium bromide as model foulants, fouling-resistant properties of the modified membranes are estimated by three-time cycle filtration tests. The experimental results show that the modified membranes have superior fouling-resistant and easy-cleaning properties. Mechanism concerning the roles of grafting Arg in the enhancement of the performances of the resulting membranes is proposed.