Highly antifouling and chlorine resistance polyamide reverse osmosis membranes with g-C3N4 nanosheets as nanofiller

Improvement of antifouling and chlorine resistance properties of polyamide (PA) reverse osmosis (RO) membranes have been major challenges for desalination of seawater. In this work, graphitic carbon nitride nanosheets (g-C3N4 NS) were incorporated into PA membranes (PA/CN) through an in-situ interfacial polymerization process. With the optimized g-C3N4 NS loading within the PA-RO membranes (PA/CN100), the water permeability was improved by about 30% with a high salt rejection ratio of 99.23%. More importantly, due to the attractive features of g-C3N4 NS, including NH bonds to provide more chlorine attack sites, rich oxygen-containing functional groups to capture and react with chlorine radicals, negatively charged membrane surface to repel and isolate active chlorine and pollutants, the chlorine resistance and antifouling performance of PA RO membranes were greatly enhanced. After being immersed in an active chlorine solution of 1000 ppm for 24 h, the PA/CN100 membranes show a higher chlorine resistance compared to that of pure PA RO membranes, with salt rejection decreased by 1.08% and 2.95%, respectively. Moreover, after 200 ppm bovine serum albumin (BSA) treatment, the total fouling rate was 31.2% for PA membrane and 18.3% for PA/CN100 membrane. This work provides a promising approach to improve the comprehensive performance for desalination and the trend of industrialization.