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

Abstract

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

Thermal-Sprayed Photocatalytic Coatings for Biocidal Applications: A Review

“…On the one hand, the decoration of Ag, CuO, or SiO 2 nanoparticles was proved to enhance the UV-induced bactericidal effect of TiO 2 photocatalysts, among which the SiO 2 nanoparticles were also able to enhance the virus adsorption and hence the photocatalytic inactivation efficiency. On the other hand, the decoration of metallic elements (e.g., Pd, Cu, Mn, Co), nonmetallic elements (e.g., N, F), or rare earth elements/oxides (e.g., Rh 4+ , SrO) were also employed to enhance the visible-induced photocatalytic inactivation effect of viruses and bacteria (Ref 23 - 28 ). Some of the recent work about modifications of TiO 2 photocatalysts are summarized as follows.…”

Pilot‐scale photocatalytic detoxification and disinfection of hazardous medical wastewater

“…As a result, these radicals attack and degrade a wide range of organic pollutants and inactivate pathogenic microorganisms. Photocatalytic processes have been thoroughly studied both in laboratory and pilot scale, in aqueous media or wastewaters of various origins 12,13 …”

“…Photocatalytic processes have been thoroughly studied both in laboratory and pilot scale, in aqueous media or wastewaters of various origins. 12,13 In this study, we report for the first time the photocatalytic treatment of hazardous laboratory healthcare wastewaters at pilot scale, aiming at the simultaneous inactivation of a wide range of potential pathogens and the mineralization of toxic organic pollutants (Fig. 1(A)).…”

The first report of covalently grafted semiconductors; n‐TiO2‐P25@ECH@WO3 as a new, efficient, robust and visible‐light‐responsive photocatalyst

“…[5][6][7] Many approaches have been presented to solve the problems mentioned, such as metal loading, doping strategies, construction of heterojunction and sensitization methods. [8][9][10][11][12][13] Among these methods, combining two semiconductors with different bandgaps and forming heterojunction structures is an effective strategy. 14 In this approach, if the band levels of semiconductors have been matched together, the photo-generated electrons slip to the low-lying conduction band, whereas the holes migrate to the higher valence band.…”

“…Many approaches have been presented to solve the problems mentioned, such as metal loading, doping strategies, construction of heterojunction and sensitization methods 8–13 . Among these methods, combining two semiconductors with different band‐gaps and forming heterojunction structures is an effective strategy 14 .…”