In order to facilitate the removal of elemental mercury (Hg-0) in flue gas, iodine was used as the oxidant to convert He-0 to the oxidized or particulate-bound form. The removal of He-0 by the homogenous gas phase reaction and the heterogeneous particle-involved reactions was investigated under various conditions, and a method to test the particle-involved reaction kinetics was developed. Iodine was found to be efficient in He-0 oxidation, with a 2nd-order rate constant of about 7.4(+/- 0.2) x 10(-17) cm(3) molecules(-1) s(-1) at 393 K. Nitric oxide showed significant inhibition in the homogenous gas reaction of He-0 oxidation. The oxidation of He-0 with iodine can be greatly accelerated in the presence of fly-ash or powder activated carbon. SO2 slightly reduced He removal efficiency in the particle-involved reaction. It was estimated that He-0 removal efficiency was as high as 70% by adding 0.3 ppmv iodine into the flue gas with 20 g/m(3) of fly-ash. In addition, the predicted removal efficiency of He-0 was as high as 90% if 10 mg/m(3) of activated carbon and 0.3 ppmv iodine were injected into the flue gas with fly-ash. The results suggest that the combination of iodine with fly-ash and/or activated carbon can efficiently enhance the removal of He-0 in coal-fired flue gas. (C) 2009 Elsevier B.V. All rights reserved.