Biomass-derived active carbon (AC) modified TiO2 photocatalyst for efficient photocatalytic reduction of chromium (VI) under visible light

Abstract

Creation of novel visible light efficient photocatalyst requires great effort and it is always a challenging task for scientific community. The present report demonstrates the designing of highly effective biomass derived active carbon (AC) modified TiO 2 photocatalyst and its utilization towards the photocatalytic reduction of chromium (VI) to chromium (III) in presence of citric acid under visible light. The photocatalyst comprising of various wt% of AC doped m-TiO 2 has been fabricated by straightforward sol–gel approach followed by a sonication technique. The fabricated photocatalysts composed of TiO 2 nanoparticles (particles size in the range of 8–20 nm) are entangled with biomass derived AC nanosheets. FTIR analysis further confirmed the successful creation of hetro-structures between AC and TiO 2 . All hybrid nanostructures showed lower band gap value i.e. in the visible absorption spectral region. The developed photocatalysts were found to be significantly boosted towards the photo-reduction of chromium (VI) to chromium (III) with a photo‐reduction efficiency of 94.7% after 25 min of irradiation, compared to pure TiO 2 which gave a conversion rate of 72.10%. The enhanced photocatalytic reduction efficiencies were related to the effectual separation of charge carriers i.e. electron and holes pairs as confirmed by the photoluminescence (PL) analysis. Besides this, the presence of citric acid in dichromate solution enhances the transformation rate due to its involvement in oxidation reaction, which helps in retardation of unacceptable re‐oxidation process of Cr (III) to Cr (VI). Furthermore, the newly designed photocatalyst showed excellent recyclability and reusability. Achieved results and involved reaction mechanism have been thoroughly addressed and elucidated.