Conversion of novel tannery sludge-derived biochar/TiO2 nanocomposite for efficient removal of Cr (VI) under UV light: photocatalytic performance and mechanism insight

An investigation on the reduction of Cr (VI) pollutant from tannery effluents using TiO2, SB/TiO2, and c-SB/TiO2 nano photocatalysts was presented in this study. For the preparation of Biochar-based TiO2 photocatalyst (SB/TiO2), tannery sludge was utilized as a precursor. Hydrothermal pre-treatment was adopted to prepare chemically activated SB/TiO2 and SB/TiO2 nanocomposites. The morphology, crystal structure, optical properties, and elemental composition of the prepared catalysts were analyzed by XRD, FT-IR, SEM-EDX, BET analysis, ZPC, PL, TGA, and Raman spectroscopy. The band gap analysis of Photocatalyst was measured using a DRS instrument, and band gap energy of 3.39 eV was obtained for c-SB/TiO2 photocatalyst. The developed c-SB/TiO2 catalyst exhibits a larger specific surface area of 646.85 m(2)/g than TiO2 and SB/TiO2 (74.58 m(2)/g and 573.74 m(2)/g), respectively. The enhanced photocatalytic activity for the pollutant removal was achieved by the photocatalyst due to their wide band gap and effective charge separation. The kinetic rate constant was achieved in the pseudo-first-order model, which fits well for the reduction of Cr (VI). Furthermore, at the optimal conditions of 10 mg/L contaminant concentration, pH 2, and 0.5 g/L catalyst dosage, 98.56% reduction was observed after 180 min of reaction. The OH acts as a major removal pathway for Cr (VI) contaminants with more than 50% reduction in COD. This study proves that c-SB/TiO2 photocatalysts can remove toxic contaminants under UV light irradiation with good recycling performance up to 5 times.