Graphene oxide surface modification of polyamide reverse osmosis membranes for improved N-nitrosodimethylamine (NDMA) removal

In the growing area of wastewater reuse, the performance of reverse osmosis (RO) is limited by poor membrane selectivity towards nitrosamines and other low-molecular weight, neutral contaminants. This study aimed to increase RO membrane rejection of N-nitrosodimethylamine (NDMA), a carcinogenic nitrosamine that is produced during chlorination and chloramination of secondary wastewater effluent. Toward this goal, we modified commercial polyamide RO membranes with graphene oxide (GO) nanosheets, and demonstrated that GO functionalization can decrease the NDMA permeability coefficient by 31%, while only decreasing water permeability by 13%. The improved selectivity is likely due to additional steric exclusion derived from the GO nanosheet coating. Moreover, membrane characterization indicated that the GO modification does not change the hydrophilicity or roughness of the interface. The latter interfacial characteristics, combined with the well-established biocidal properties of graphenic nanomaterials, render GO functionalization a promising strategy for the development of highly selective membranes for wastewater reclamation.