Effects of surface modification on antifouling and performance properties of reverse osmosis membranes

The effects of surface modification of commercial reverse osmosis (RO) polyamide membranes were studied in terms of flux/rejection and surface properties. Selected RO membranes, spanning ultra-low pressure to seawater membranes, were modified by in-situ graft polymerization using redox generation of monomer radicals. Modification of the membrane significantly reduced both receding and advancing contact angles of some of the membranes as measured by a modified Wilhelmy plate method. Lower contact angles indicate more hydrophilic membranes and such membranes will potentially show better resistance to fouling by hydrophobic foulants. This was confirmed by adsorption measurements carried out on modified and unmodified membranes with a highly fouling surface water. Modified membranes adsorbed less organic material and were more easily cleaned than unmodified membranes. Specific fluxes were not changed by more than 0-25% and NaCl rejection was unchanged or increased slightly.