The removal of Hg-0 by the homogenous gas-phase reaction and particle-induced reaction was investigated under various conditions. Iodine monochloride was found to be efficient for Hg-0 oxidation, with the apparent 2nd-order rate constant of about 10.5(+/-0.3) x 10(-17) cm(3) molecules(-1) s(-1) and 5.7(+/-0.3) x 10(-17) cm(3) molecules(-1) s(-1) at 273 K and 373 K, respectively. The pilot-scale tests showed that the removal of Hg-0 by ICl increased significantly in presence of flyash. It was predicted that over 90% of Hg-0 removal efficiency can be obtained with 0.2 ppmv ICl and 20 g/m(3) flyash in flue gas. Though the reaction between Hg-0 and ICl was by far faster than that of Hg-0/Cl-2, the major product was found to be HgCl2 rather than HgI2, which implicated that iodine might partly act as the accelerant in Hg-0 oxidation by facilitating the formation of certain intermediates. The results indicated that using ICl to oxidize elemental mercury in coal-fired flue gas can save the consumption of iodine, and it appeared to be a promising oxidant to enhance the removal of Hg-0. (C) 2010 Elsevier B.V. All rights reserved.