In the current work, the degradation of Acid Orange 7 (also called Orange II - OII) by a heterogeneous catalytic wet hydrogen peroxide process has been described by a simple semi-empirical kinetic model, based on the Fermi's equation, which captures simultaneously the influence of all the reaction conditions with few adjustable parameters. Complete decolorization was reached in less than 4h, using as catalyst a pillared saponite clay impregnated with Fe(II) acetylacetonate (16 wt.% of iron) in a slurry batch reactor. The model was fitted to the dye concentration histories, being the kinetic parameters determined by non-linear regression. The adherence of the model to the data was remarkable, and the effect of the operating conditions (temperature, catalyst dose and both pollutant and hydrogen peroxide concentration) on the fitting parameters - apparent rate constant and transition time - was analyzed. (c) 2010 Elsevier B.V. All rights reserved.