Photocatalytic degradation of phenol by base metal-substituted orthovanadates

Base metal (Cr, Mn, Fe, Ni, Cu) substituted CeVO4 compounds were synthesized by the solution combustion technique. These compounds were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, transmission electron microscopy and BET surface area analyzer. The characterization indicated that the base metals were substituted in the ionic state in all the compounds. These compounds were used for the photocatalytic degradation of phenol and the degradation rates obtained in the presence of these compounds were compared against that obtained with the commercial Degussa P-25 TiO2 catalyst. Fe and Cr substituted CeVO4 showed photocatalytic activity that was comparable with that of Degussa P-25 TiO2. The concentration of toxic intermediates was high when the reaction was carried out in presence of Degussa P-25 TiO2 but it was found to be insignificant when the reaction was carried out in presence of base metal-substituted CeVO4. The effect of % Fe-substitution (varied from 1 to 5 at%) in CeVO4 on the photocatalytic activity was also investigated and it was observed that 1 at% Fe-substituted compound showed the highest activity. A mathematical model describing the kinetics of the photocatalytic degradation of phenol was developed on the basis of the catalyst structure and taking into account the formation of all the possible intermediates. The variation of the concentration of phenol and the intermediates was described by the model and the reaction rate constants were determined. (C) 2010 Elsevier B.V. All rights reserved.