Evaluation of anti-bacterial adhesion performance of polydopamine cross-linked graphene oxide RO membrane via in situ optical coherence tomography

Biofouling is a critical issue which accounts for >45% of all fouling in reverse osmosis (RO). Because fouling occurs on the surface of the membrane, surface modification has been considered an effective measure for fouling mitigation and for achieving sustainable membrane performance. Herein, we modified a RO membrane using graphene oxide (GO) crosslinked with a thin layer of polydopamine (PDA-GO) to obtain a bactericidal and antibiofouling surface. Optical coherence tomography (OCT) was used as a non-destructive, real-time, in situ monitoring tool to observe the fouling dynamics and to understand material-foulant interaction. In situ three-dimensional (3D) monitoring results showed that the modified membrane was antifouling in nature and exhibited low and fully reversible biofilm formation. In addition, the colony forming unit enumeration and results of confocal laser scanning microscopy reveal that the PDA-GO coated membrane exhibited a high bactericidal effect when compared with pristine, PDA, and GO-coated membrane surfaces. Investigation of bacterial cell morphology further validated that the presence of a GO layer and its functional groups combined with a thin PDA layer resulted in physical and chemical disruption of the bacterial cell wall. The high selectivity of the modified membrane against the monovalent salt validated its potential for desalination and wastewater reclamation.