Polyamide reverse osmosis membranes modified with graphene oxide for enhanced chlorine attack and fouling resistance

Reverse osmosis (RO) systems are an essential tool for water desalination, but their effectiveness can be hampered by membrane fouling and susceptibility to chemical degradation from free chlorine. Polyamide (PA) membranes, a staple in RO systems, are particularly susceptible to such challenges. In this study, we set out to improve the resistance of PA membranes to chlorine attack and fouling by exploring surface modification with graphene oxide (GO). A variety of deposition techniques have been investigated, including dip coating, spin coating, drop casting, and vacuum filtration. Spin coating with a GO concentration of 1 g L-1 in a 70% ethanol-water solvent was found to be the optimal method. This modification, while maintaining a high salt rejection rate (about 97%), resulted in a 16% increase in water permeability (from 3.1 to 3.6 L hm-2 bar-1) compared to the pristine membrane. In long-term tests using 100 ppm sodium hypochlorite for 21 days, the GO-coated membranes showed only a 69% increase in hydraulic permeability and a 13% decrease in salt rejection. In contrast, the reference membrane experienced a 245% increase in permeability and a 23% decrease in rejection. These improvements hold great promise for reducing energy consumption, minimizing maintenance downtime, and extending the membrane lifespan.