TiO2–Fe2O3 nanocomposite heterojunction for superior charge separation and the photocatalytic inactivation of pathogenic bacteria in water under direct sunlight irradiation

Abstract

Photocatalysis is considered as one of the diverse advanced oxidation processes widely applicable in energy and environment sectors. TiO2 is vastly recognized as a photocatalyst having high oxidative and reductive power. Herein, TiO2–Fe2O3 nanocomposite in three different ratios of TiO2 and Fe2O3 are successfully synthesized by an ex-situ process. The synthesized nanocomposites were characterized by different analytical techniques. The TiO2–Fe2O3 nanocomposites are utilized as an efficient photocatalyst towards the inactivation of harmful pathogenic bacteria Escherichia coli (E.coli) in water under direct natural sunlight irradiation. The inactivation of E. coli was found to be 99.28% in 120min. Further, we have established the mechanism for the generation of photogenerated reactive species (OH and O2−) from the TiO2–Fe2O3 nanocomposite. The strong oxidizing species OH and O2− readily attacks the bacterial cell membrane resulting in the oxidation of polyunsaturated phospholipids leading to the destruction of the bacterial cell membrane and the exposure of the inner cellular components. These inner cellular components further undergo oxidation ultimately resulting in bacterial cell death. The photogenerated OH radical trapping experiment indicates the active role of OH radical in the photocatalytic inactivation process. The final photogenerated products like aldehyde, ketone and carboxylic acid were analysed by FTIR (DRIFT) analysis. Moreover, the reusability of the photocatalyst was studied and the morphology of the photocatalyst was analysed at different time intervals during the photoinactivation.