Surface modification of SWRO membranes using hydroxyl poly(oxyethylene) methacrylate and zwitterionic carboxylated polyethyleneimine

Comb-like hydroxyl poly(oxyethylene) methacrylate homopolymer (HPOEM) and zwitterionic carboxylated polyethyeleneimine (carboxylated PEI) were synthesized and applied to the surface of commercially available seawater reverse osmosis (SWRO) membranes to introduce fouling resistance. The successful synthesis of the polymers and modification of the membrane surface were confirmed by X-ray photoelectron spectroscopy, zeta potential and contact angle measurements. Fouling test of the surface-modified membranes with alginate and bovine serum albumin showed opposite behavior at high salt concentrations: a salting-out effect on the HPOEM-coated membrane and a salting-in effect on the carboxylated PEI-coated membrane. HPOEM-coated SWRO membranes showed better fouling resistance under brackish conditions. However, the zwitterionic carboxylated PEI-coated membrane showed higher affinity to sodium chloride solution than deionized water, and presented an inhibitory effect to foulant adsorption under seawater conditions. This indicates that an effective fouling resistant layer specialized for seawater filtration could be prepared with zwitterionic materials.