14. Solar Energy Driven-Photocatalysis: Kinetics and Sorption Studies of Cr(VI) Reduction in Paint Effluent

by Osarumwense J. O and Chris-Abey O. F.
Department of Science Laboratory Technology, Faculty of Life Sciences,
University of Benin, Benin City.

Abstract
Solar energy driven-photocatalysis is a clean and relatively new technology adopted to assuage the environmental problems caused by industrial effluent discharge. Chromium is widely used for the production of pigments for the paint and textile industries. The hexavalent form of chromium, Cr(VI) is highly toxic to human if ingested, and it is capable of causing oxidative damages to the blood cells at low concentration which may lead to hemolysis. In this study, a mixture of titanium oxide (TiO2) and chromium contaminated effluent was irradiated under the sunlight for three hours in batch system. Some operational conditions such as catalyst dosage and exposure time were investigated during the photocatalytic process. Atomic absorption spectrophotometer (AAS) was used to determine the residual Cr(VI) ion in the mixture. The data obtained was subjected to a variety of kinetics models and adsorption equilibrium isotherms; the process was well modeled by pseudo-first kinetics order with a reaction rate constant of 0.0141 min-1.The intra-particle diffusivity model revealed that the uptake of Cr(VI) ion was more of the film diffusion than the intra-particle diffusion. The data obtained from adsorption fitted well into the Langmuir adsorption isotherm with coefficient of determination (R2) of 0.9387; while the Temkin isotherm indicates that the process was exothermic.

Keywords: Solar energy, Photocatalysis, Chromium (VI), Adsorption equilibrium, Intra-particle diffusion.