Highly chlorine resistance polyamide reverse osmosis membranes with oxidized graphitic carbon nitride by ontology doping method

Poor chlorine resistance is one of the main challenges of polyamide (PA) reverse osmosis membranes. In this work, PA hybrid membranes modified with oxidized graphitic carbon nitride (CNO), graphitic carbon nitride (g-C 3 N 4 ), or graphene oxide (GO) are prepared by interfacial polymerization. The results show that CNO can be used as antioxidant to improve chlorine resistance of the PA membrane, and PA-CNO hybrid membranes demonstrate better chlorine resistance than PA-GO membranes. For instance, after 40 h active chlorine treatment, salt rejection of PA-CNO decreases by 15%, while the salt rejection of PA-GO, PA-g-C 3 N 4 , and pristine membrane declines by 22%, 30%, and 27%, respectively. X-ray photoelectron spectroscopy is used to analyze antioxidant performance of CNO. The number of C-N bond of PA-CNO membrane and pristine membrane respectively decreases by 1.2% and 7.6% after chlorine treatment, which indicates CNO has ability to capture and react with chlorine free radicals.