Photocatalytic treatment of industrial wastewater containing chromium as a model pollutant-effect on process parameters and kinetically studies

This study has focused on treatment of the metal ions, which have infinite lifetimes and build up their concentrations in food chains to toxic levels. Many researches have been performed about use of photocatalysis processes in treatment of industrial wastewater. The additional advantage is coming from sensitivity of the Cr(VI) photo reduction to the surface catalytic effects or to the presence of an additional electron donor and acceptors; then, a synergistic effect was observed in two- or multi-component systems. The efficiency of total chromium reduction by photo catalytic treatment under UV-light in different degradation systems, UV, TiO2/UV, H2O2/UV, TiO2/citric acid/UV, and TiO2/H2O2/UV, was studied and compared. Even when the TiO2/citric acid/H2O2/UV reaction happened to be the most efficient process, both homogeneous and heterogeneous photocatalysis can be considered as suitable methods to reach the complete mineralization of the solutions. Maximum treatment efficiency of total chromium reduction with increasing citric acid concentration from 20 to 80 mg/l was reduced to 62%, 76.7%, 77.91%, and 100%, and with increasing H2O2 concentration from 20 to 100 ml/l was reduced to 40.57%, 41.84%, 50.77%, 61.03%, and 100%, which is more efficient than the H2O2/UV process. Finally, the combination of TiO2/citric acid/H2O2/UV result was observed more efficient than the TiO2/citric acid and TiO2/H2O2/UV processes in the solutions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757629]