A unified kinetic model for phenol photocatalytic degradation over TiO2 photocatalysts

This study reports the kinetics of the photocatalytic degradation of phenol using four different TiO2 catalysts. It is shown that phenol yields hydroquinone, catechol, benzoquinone and acetic and formic acids as main intermediate species. A phenomenological unified kinetic model (UKM) based in a series-parallel reaction network is proposed. The UKM follows a Langmuir-Hinshelwood kinetics with this being applicable to the various TiO2 photocatalysts studied. The UKM requires a number of significant assumptions in order to be used effectively avoiding overparametization. This approach also requires that the adsorption constants be obtained independently. As a result, the UKM is adapted for each specific TiO2 photocatalyst to describe the experimental photoconversion data. It is concluded that this approach provides good and objective parameter estimates with low to moderate cross-correlation among kinetic parameters and acceptable 95% CIs. (C) 2012 Elsevier Ltd. All rights reserved.