Detoxification of hexavalent chromium in wastewater containing organic substances using simonkolleite-TiO2 photocatalyst

• Innovative preparation of visible-light sensitive simonkolleite-TiO2 photocatalyst.
• Detoxification of Cr(VI) using simonkolleite-TiO2 photocatalyst in wastewater.
• Presence of organic compounds improve the photoreduction of Cr(VI).

Innovative simple method for the preparation of simonkolleite-TiO2 photocatalyst with different Zn contents was achieved. The prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, Raman and diffuse reflectance spectroscopy techniques. The photocatalytic activities of the materials were evaluated for the simultaneous detoxification of hexavalent chromium (Cr(VI)) and oxidation of organic compounds commonly present in wastewater under simulated solar light. The best photoreduction efficiency of Cr(VI) has been achieved at 1000 ppm simonkolleite-TiO2 photocatalyst of 5% Zn/TiO2 weight ratio, and pH value of 2.5 to enhance the adsorption onto catalyst surface. Photoreduction was significantly improved by using formic acid as holes scavenger owing to its chemical adsorption on the catalyst surface. Finally, 100% photoreduction of Cr(VI) could be achieved using formic/simonkolleite-TiO2 systems under sunlight.