The present study reports a series-parallel kinetic model, based on the experimentally observed evolution of liquid-phase species. The model is adequate to describe the conversion of phenolic compounds in slurry units. The reported model can be applied under a wide range of operating conditions and this includes different pHs, two catalysts (Degussa P25 and Hombikat UV100) and several initial phenol concentrations. Furthermore, it is proven that the parameters resulting from this model, can be estimated with reduced spans and adequate reliability. Finally, PTEF and quantum efficiencies based on the initial phenol photodegradation remain, for the various operating conditions of this study, at 0.43-0.77% and 0.94-1.67% levels, respectively. (C) 2003 Elsevier Ltd. All rights reserved.