Polyacrylic acid-brushes tethered to graphene oxide membrane coating for scaling and biofouling mitigation on reverse osmosis membranes

Reverse osmosis (RO) membranes are prone to fouling, which increases the cost of operation and decreases water recovery. In this study, a commercial membrane (ESPA2) was coated with an antiscaling material, i.e. polyacrylic acid (PAA), and an antimicrobial material, i.e. graphene oxide (GO), to reduce biofouling and scaling. Bare and modified membranes with polydopamine (ESPA2-PD), as a control, GO (ESPA2-GO), GO and PAA (ESPA2-GO-PAA), and PAA (ESPA2-PAA) were tested for their antiscaling and antibiofouling properties. ESPA2-GO and ESPA2-GO-PAA had the best performance. The latter showed ~15% and 10% increase in normalized water flux compared to ESPA2 in mineral scaling and biofouling tests, respectively. This improvement can be attributed to the decrease in surface charge and the increase in hydrophilicity of membrane surface by both GO and PAA coating. Moreover, the antimicrobial characteristic of GO played a crucial role in reducing biofouling and PAA slightly enhanced antiscaling property when coated on ESPA2 but it did not improve the antibiofouling property. These results highlight the importance of antimicrobial property of the coating for biofouling prevention and show antiscaling materials can be effective not only as an additive to the feed but also as a coating on the membrane to reduce scaling.