Construction of RGO@N-ZnO nanocomposite photocatalyst for disinfection of microbes and dye degradation under visible light irradiation

Background: Globally, water resources are becoming scarce, and there is an urgent need to develop sustainable and energy efficient methods of water and wastewater treatment, where photocatalysis is emerging as a promising method for water purification. Thus, the design of photocatalysts that is easy to recover, eco-friendly, cost-effective and reduce the environmental footprint. Methods: Present investigation, the RGO@N-ZnO nanocomposite photocatalyst was fabricated through the solvothermal method and it was characterized by various physio-chemical methods such as FE-SEM, RAMAN, HRTEM, BET, EPR, EIS, PL and XPS etc., analyses. The photocatalytic activity of the photocatalyst was examined against Escherichia coli (E. coli), tannery wastewater and Methylene Blue (MB) dye degradation under visible light irradiation in a slurry photoreactor. Significant findings: The RGO@N-ZnO nanocomposite has a high specific surface area of 141.2 m2g-1. The results of electron spin resonance (ESR) spectra and free radicals trapping experimental studies confirmed that e- , center dot OH and center dot O2 - radicals serve as the primary active species in photocatalytic disinfection. It has been observed that, after 30 min and 45 min of visible light irradiation, 100 mg/100 mL RGO@N-ZnO nanocomposite destroyed more than 99 % of E. coli present in the tannery wastewater and more than 95 % of Methylene Blue (MB) dye molecules were degraded. Reusability tests showed that, after four cycles of use RGO@N-ZnO retained more than 90 % of its photocatalytic activity with minimal loss. Thus, these findings manifest the RGO@N-ZnO nanocomposite is a potential photocatalyst due to its high photocatalytic efficiency, low-cost and is suitable for environmental remedial applications.