Synthesis and characterization of Mn-doped g-C3N4/ZnO nanocomposite for photocatalytic degradation and antibacterial activity applications

Abstract

The current study involves the investigation of photocatalytic degradation of malachite green dye and antibacterial activity by Mn-doped g-C3N4/ZnO nanocomposite. The molten salt method was used to synthesize g-C3N4 and Mn-doped g-C3N4. The co-precipitation method was used to synthesize ZnO, g-C3N4/ZnO, and Mn-doped g-C3N4/ZnO. The nanocomposite was effectively synthesized and analyzed by XRD, FT-IR, UV–Vis DRS, PL, SEM with EDAX, HR-TEM, BET, EIS and lifetime analysis. Photocatalytic degradation activity was tested under different conditions, namely initial concentration of malachite green, solution pH, catalyst dosage, and time. When Mn is doped with g-C3N4, it improves the ability of g-C3N4/ZnO composite to remove and degrade 10 ppm of malachite green by about 13 % in 90 min under simulated sunlight exposure. The synthesized photocatalyst degrades 10 ppm of malachite green with a degradation efficiency of 95.6 % at 90 min and also 100 ppm of the same dye was degraded by 80.8 % in 90 min. The study of photocatalytic mechanism showed that reactive oxygen species, such as holes and superoxide radicals, are very important in breaking down dyes. Under dark condition, the Mn-doped g-C3N4/ZnO nanocomposite has adsorption and desorption efficiencies of ∼70 % and ∼50 %, respectively in 10 ppm dye. The reusability and stability of the nanocomposite was retained for up to five consecutive photocatalytic degradation processes. The antibacterial property of the synthesized nanocomposite was also investigated. The composite has shown activity against S. aureus and E. coli. This research shows that the synthesized catalyst has good photocatalytic as well as antibacterial activities.