Iron oxide catalysts supported on MgO, Al2O3, SiO2 and ZrO2 were prepared by an impregnation method. They were characterized by BET surface analysis, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and Mossbauer spectroscopy. Fe/MgO catalyst shows the highest H2S removal capacity in wet oxidation at room temperature. Both the XRD and the TPR analyses of the catalysts indicate that H2S removal capacity correlates with the dispersion of iron oxide on Supports. Mossbauer spectroscopy shows that four kinds of Fe3+ species are present in the supported iron oxide catalysts: two highly dispersed species, Fe3+ oxide clusters, and alpha-Fe2O3 particles. Two highly dispersed species, Fe3+ cation and MgFe2O4, are present in Fe/MgO. Fe3+ oxide clusters and alpha-Fe2O3 crystals are evident in both Fe/SiO2 and Fe/ZrO2. alpha-Fe2O3 crystals are only observed in Fe/Al2O3. (c) 2004 Elsevier B.V. All rights reserved.