Independent and simultaneous photocatalytic decontamination and disinfection of water over In2O3/TiO2 heterojunctions

Abstract

We have explored the application of In2O3/TiO2 heterojunctions to the photocatalytic removal of a substance classified as a pollutant of emerging concern, such as the anti-inflammatory drug sodium diclofenac (DCF), from aqueous solutions. In addition, the study of water disinfection by means of photocatalysis, simultaneously with the elimination of DCF, has been carried out with the same catalysts, by using bacterial populations of the genus Enterococcus faecalis. The In2O3/TiO2 catalysts with different indium amounts consist of bi-phasic samples with anatase TiO2 and In2O3 phases, without evidence in In doping into the titania structure, and show, according to UV–vis and time-resolved fluorescence spectra, light absorption into the visible range and interfacial charge transfer from the conduction band of In2O3 to that of TiO2. Complete photocatalytic removal of DCF was achieved by using all catalysts after 120 min of irradiation, being the most active the catalyst with 5% of In2O3, in agreement with its highest efficiency of interfacial charge transfer revealed by fluorescence lifetime. In contrast, in terms of DCF mineralization, the 5In2O3/TiO2 catalyst did not outperform the pristine TiO2, the higher mineralization percentage being achieved with 1% In. Simultaneous decontamination and disinfection experiments show that the 5% In2O3/TiO2 heterojunction outperforms the activity of titania for DFC removal in the presence of Enterococcus faecalis, but not for the inactivation of bacteria.