Photocatalytic disinfection and purification of water employing reduced graphene oxide/TiO2 composites

BACKGROUND Recombination of photogenerated carriers in titanium dioxide (TiO2)-mediated semiconducting photocatalysis is considered to be the principal obstacle in its unlimited exploitation in practical applications. Hybridization of TiO2 with graphene-based materials appears to be a highly promising alternative. In this context, reduced graphene oxide (rGO)/TiO2 composites were prepared using a simple ultrasonically assisted route under mild reaction conditions. RESULTS The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Fourier-transform infrared spectroscopy (FTIR) and nitrogen adsorption-desorption isotherms. Photocatalytic efficiencies of the as-prepared composites were evaluated employing the pesticide clopyralid as a model pollutant. Initial degradation and mineralization rates obtained in the presence of the as-prepared composites were, in all cases, higher than the one obtained in the presence of the bare TiO2, with 5% rGO/TiO2 achieving the highest r(0) and r(DOC) values. The as-prepared composites also were evaluated based on their potential to inactivate bacterial endospores of the Bacillus stearothermophilus species, well-known for their extraordinary resistance to most inactivation processes. Prevalence of 5% rGO/TiO2 in the inactivation of B. stearothermophilus among all as-prepared materials was evident, accomplished within 120 min of UV-A illumination. Real-time PCR experiments enabled the detection of genomic DNA released during photocatalytic oxidation, in the presence of 5% rGO/TiO2 and UV-A, suggesting lysis of the outer and inner spore coat caused by the generated ROS. CONCLUSIONS These findings demonstrate the potential of rGO, a low-cost, nontoxic material to serve as a reliable alternative in the enhancement of TiO2 photocatalytic efficiency in water processing applications. (c) 2019 Society of Chemical Industry