Polyaniline-graphitic carbon nitride nanosheets incorporated polyamide thin film nanocomposite membranes for enhanced desalination and antibiofouling properties

The current study was designed to enhance the desalination potential of the polyamide reverse osmosis membranes coupled with improved antifouling properties for extending the life of membranes during desalination experiments. This was achieved by initially synthesizing the polyaniline-decorated graphitic carbon nitride nanosheets (Pani@g-CN) via thermal polymerization using a melamine precursor, followed by their incorporation into the polyamide (PA) active layer of thin-film nanocomposite (TFN) membranes at varying concentrations. Pani@g-CN nanosheets were investigated for their chemical and internal structure using different characterization techniques such as FTIR, HRTEM, XRD, and SAED to confirm the incorporation and interaction between Pani and g-CN. The performance of the Pani@g-CN incorporated reverse osmosis (RO) TFN membranes was evaluated and compared to a control MPD-TMC membrane, where the 50-PANI@g-CN/MPD-TMC membrane possessed a permeate flux of 17.2 L m⁻² h⁻¹ at 30 bar with a NaCl rejection of 97.7 % and Na₂SO₄ rejection of 98.8 %. In contrast, the control MPD-TMC membrane possessed a permeate flux of 11.6 L m⁻² h⁻¹ at 30 bar and NaCl rejection of 97.5 %. The stability tests demonstrated that among different Pani@g-CN decorated membranes, 50-PANI@g-CN/MPD-TMC membranes showed better fouling resistance by maintaining a normalized flux of nearly 0.90. In contrast, the control MPD-TMC membrane showed a normalized flux of almost 0.85 after 16 h of operation. The anti-biofouling studies revealed that the 50-PANI@g-CN/MPD-TMC showed a bacteriostasis rate of 96.7 % and 86.8 % for the E. coli ATCC 25922 and S. aureus ATCC 25923, respectively. While the control MPD-TMC membrane showed a bacteriostasis rate of 40.4 % and 31.1 % against E. coli and S. aureus, respectively. Hence, the current approach of incorporating the Pani@g-CN sheets in the active layer enhanced the permeate flux significantly and overcame the challenge of low permeability, and conferred antifouling properties to the membranes.