Surface modification of commercial cellulose acetate membranes using surface-initiated polymerization of 2-hydroxyethyl methacrylate to improve membrane surface biofouling resistance

To improve biofouling resistance, cellulose acetate (CA) reverse osmosis membranes were modified by reacting surface hydroxyl groups with an atom transfer radical polymerization (ATRP) initiator, 2-bromoisobutyryl bromide, followed by polymeric grafting of 2-hydroxyethyl methacrylate (pHEMA) using activators regenerated by electron transfer (ARGET) ATRP. Thermogravimetric analysis (TGA), atomic force microscopy (AFM) and water contact angle (WCA) measurements of pristine and modified membranes were performed to measure and compare the amount of polymer deposited, the surface morphology and the hydrophilicity of the surfaces, respectively. Roughness and hydrophilicity increased with graft density. The biofouling resistance of pHEMA-modified membranes immersed in seawater aquarium tanks was compared to pristine membranes and the effect of pHEMA coating on water flux and NaCl rejection was measured. Based on stirred-cell and aquaria experiments, pHEMA-modified membranes with low graft density showed just a 6% decrease in salt rejection and water flux relative to pristine CA membranes, and a 24% improvement in resistance to seawater microbial biofouling.

► Cellulose acetate reverse osmosis membranes surface-modified with polyHEMA.
► Modified membranes showed a greater resistance to biofouling than pristine membranes.
► Membranes with low graft density showed no major loss of filtration properties.