HZSM-5-supported Fe was synthesized through an impregnation method, and its efficiency during mercury oxidation in a simulated flue gas was determined. The Fe/HZSM-5 was highly active for Hg-0 oxidation. In this study, 3% Fe/HZSM-5 was the optimal catalyst within the temperature range of a selective catalytic reduction reaction. Two Hg-containing products are produced in the presence of HCl and O-2. Below 200 degrees C, the products are probably adsorbed HgCl2. When above 200 degrees C, the products might be both adsorbed and gaseous HgCl2. No Hg2+ was observed in the gas state in the presence of SO2 and NO. The competitive adsorption and formation of Fe-2(SO4)(3), which might be the intermediate product, are the primary reasons that SO2 inhibits Hg-0 oxidation. The formation of the N-containing active species generated on the catalyst surface facilitated the oxidation of Hg-0 in the presence of NO and O-2 to probably produce Hg(NO3)(2). The Fe/HZSM-5 catalysts remain highly active toward Hg-0 oxidation in the presence of SO2 and O-2.