Kinetic modelling of TOC removal in the photocatalytic ozonation of diclofenac aqueous solutions

A kinetic model for aqueous diclofenac photocatalytic ozonation is proposed and experimentally tested. The kinetic model, based on mol balance equations of main species present in water, gives total organic carbon (TOC), ozone and hydrogen peroxide concentrations with time as output variables. The model relies on both, experimental data obtained in this work (i.e. rate constant of reactions and quantum yield values) and published data on the nature of intermediate formation, free radicals and hydrogen peroxide yield and rate constants of the reactions between intermediates, ozone and hydroxyl radicals. Intermediates of different structure and reactivity towards ozone and hydroxyl radical have been classified into groups. Accordingly, the remaining TOC in water, at each time, is considered as the sum of the contributing TOC values of these groups. The kinetic model is applied to buffered systems and acceptably reproduces the experimental results for the reaction period investigated. (C) 2010 Elsevier B.V. All rights reserved.