Synthesis, Characterization and Performance Evaluation of TiO.sub.2-SnO.sub.2 photocatalyst for Removal of Toxic Hexavalent Chromium

Heavy metal pollution bears a substantial threat to flora, fauna, humans, and milieu. The elimination of hexavalent chromium [Cr(VI)] from polluted water is of considerable research interest from a health and environmental viewpoint. This work aims for photocatalytic reduction of Cr(VI) to Cr(III) using TiO.sub.2 and SnO.sub.2 as catalysts. The process parameters varied are catalyst dosage, pH, initial concentration of model pollutant with citric acid (CA) as a scavenger. TiO.sub.2-SnO.sub.2 (in the molar ratios 10:1, 20:1, 30:1, and 40:1)-based catalysts were synthesized using the hydrothermal method. The 40:1 catalyst showed higher photoactivity than other catalysts and could extend the optical activity in the visible light region. The complete reduction of Cr(VI) with a concentration of 15 mg/L and pH 3.0 was achieved when catalyst concentration was 0.6 g/L over a period of 30 min. The XRD (X-Ray Diffraction Spectroscopy) and ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy) results confirm the Ti-Sn heterojunction formation, and XPS (X-ray Photoelectron Spectroscopy) analysis corroborate the presence of trivalent chromium [Cr(III)] on TiO.sub.2-SnO.sub.2 catalyst after reduction.