Au-TiO2 Catalysts for Enhanced Visible Light Photocatalysis for Sustainable Treatment of Textile Effluents

Abstract

The present study investigates the need to improve photocatalytic processes for the treatment of textile effluents, which are traditionally reliant on ultraviolet radiation, which is impractical on an industrial scale. Therefore, enhancing efficiency in the visible spectrum is crucial. This study emphasizes the importance of the synthesis methodology in the creation of gold nanoparticles (Au-NPs) to boost their photocatalytic activity via electron transfer and surface plasmon resonance. This study explores the synthesis of modified Au-NPs on TiO₂ using precipitation deposition (PD) and modified wet impregnation (MWI) techniques. Results showed that MWI synthesis yields catalysts with greater surface area and smaller particle sizes than PD, enhancing the photocatalytic efficiency, and achieving 100% dye removal in less than 90 min, and a reduction in total organic carbon (TOC) of more than 70%. Photocatalytic degradation tests under solar and visible light reveal that MWI-derived catalysts outperform PD-derived ones in reducing RB5 dye. The analysis of active species involved in the redox reactions identified h⁺, ^{− •}O₂, e⁻, and ^•OH radicals as contributors to the degradation of the organic pollutant RB5, with photogenerated holes being the primary active species in the photocatalytic process, followed by hydroxyl radicals. Thus, it was possible to confirm the important role of gold nanoparticles in the enhancement of the photocatalytic activity.