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 r0 and rDOC 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. © 2019 Society of Chemical Industry