This work focused on the development and the validation of a mathematical model for the UV-C photo-Fenton degradation of acetic acid using a LaFeO3 heterogeneous structured catalyst with a monolithic structure. A combined study of the evolved gases and the liquid phase was conducted. The experimental results led to the identification of the main reactions that occur in the system: the complete mineralisation of acetic acid by H2O2 due to the presence of the catalyst and the decomposition of H2O2 to water and O-2 in the homogeneous phase. A mathematical model was then developed using Eley-Rideal-type kinetics for the acetic acid consumption and first-order kinetics for the photolysis of hydrogen peroxide. The apparent kinetic constants were estimated, and the accuracy of the model was tested under different experimental conditions to evidence the predictive capability of the model. A very good agreement between the mathematical model calculations and the experimental data obtained in the presence of various H2O2 dosages was achieved. The results demonstrate that the continuous addition of H2O2 during the photo-Fenton reaction ensures the fruitful utilisation of the produced hydroxyl radicals in the acetic acid oxidation reaction to minimise the oxidant consumption and maximise the TOC removal in a shorter irradiation time. (C) 2013 Elsevier B.V. All rights reserved.