BACKGROUND: Heterogeneous Fenton catalysts have been used to treat various organic pollutants in an aqueous environment. The present study has investigated the degradation of 2,4-dinitrophenol (2,4-DNP), a priority pollutant generated by such industries as pharmaceuticals, pesticides, pigments and dyes. Degradation of 2,4-DNP (100 mg L-1) was studied using Fe3+ loaded on Al2O3 as a heterogeneous catalyst in the presence of H2O2, and the efficiency compared with the homogeneous Fe3+/H2O2 based Fenton-like process. The effect of different parameters for both processes, such as catalyst loading, H2O2 concentration, initial solution pH, initial substrate concentration and temperature were investigated and the optimum operating conditions determined. RESULTS: Under optimal operating conditions of the homogeneous system ([Fe3+] 125 mg L-1; [H2O2] 250 mg L-1; pH 3; room temperature), 92.5% degradation was achieved in 35 min for an initial 2,4-DNP concentration of 100 mg L-1. In the case of immobilized Fe (Fe3+Al2O3 catalyst), degradation improved to 98.7% under the condition 10 wt% [Fe3+Al2O3] 1 g L-1 catalyst loading; [H2O2] 250 mg L-1; pH 3; at room temperature for the same duration. CONCLUSIONS: This study demonstrated the stability and reusability of the prepared heterogeneous catalyst. This process is a viable technique for treatment of aqueous solutions containing contaminants. Copyright (c) 2012 Society of Chemical Industry