Facile surface coating of nanofiltration membranes with graphene oxide for controlling membrane fouling

Membrane fouling is a critical issue in nanofiltration (NF) membranes used for water treatment. This study systematically evaluated a surface coating technique using three commercial graphene oxide (GO) materials to enhance fouling resistance of commercial NF membranes. The GO coating minimally affected salt separation but slightly reduced water permeance. The membrane coated with GO having the largest lateral size and highest oxidation degree exhibited a 19% lower flux decline during humic acid filtration compared to the pristine membrane. Surface analysis showed that GO deposition increased membrane hydrophilicity, lowering the contact angle from 38° to 16°, and enhanced the negative surface charge from −8 to −32 mV. GO patches remained stable after 6 days of filtration and 24 hours of simulated chemical cleaning. In the subsequent filtration test using pre-filtered lake water, the selected GO-coated membrane demonstrated approximately 26% less fouling than the pristine membrane without compromising permeate quality. These findings provide useful insights into the selection of commercially available GO materials for NF membrane surface coatings in surface water treatment applications.