Improvement in performance of g-C3N4 nanosheets blended PES ultrafiltration membranes including biological properties

Abstract

This study aims to investigate the modification of polyethersulphone (PES) membrane with graphitic carbon nitride (g-C3N4) nanosheets for improving the antifouling and separation performance. The nanocomposite membranes were fabricated with blending of different g-C3N4 nanosheets (0.50, 1.00, and 2.00 wt%) into PES and they were synthesized by the phase inversion method. The fabricated g-C3N4 nanosheets and composite membranes were analyzed for their morphology. Scanning electron microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) mapping were used to detect the distribution of g-C3N4 nanosheets on membrane surface, whereas surface roughness of membrane was evaluated by atomic force microscopy (AFM). The composite membrane surface was found to be hydrophilic (67.54°), while the water flux of the composite membrane was found to be 254.8 L/m2/h for 2.00 wt% g-C3N4/PES membrane. The bovine serum albumin (BSA) separation tests indicated that the composite membrane supplied 98.5% BSA rejection ratio. Moreover, a significant improvement in antifouling characteristics were verified from BSA filtration experiments. g-C3N4 was also investigated for some of its biological properties such as antioxidant, antimicrobial, DNA cleavage, biofilm inhibition, and bacterial viability effect. g-C3N4 showed good free radical scavenging activity and moderate chelating activity at 500 mg/L. It was also determined that single-strand DNA cleavage activities occurred at all tested concentrations. g-C3N4 exhibited significant antibiofilm activity and inhibitory effects on E. coli vitality as 90.9%, 97.1%, and 98.9% at 250, 500, and 1000 mg/L, respectively. This study provides a simple and useful guideline to create a UF membrane resistant against organic fouling and expand its practical applications for wastewater treatment.