1-Alkyl-3-methylimidazolium chloride ionic liquids ([C(n)mim] Cl, n=4, 6,8) were prepared. The ionic liquid was then mixed with hydrogen peroxide (H2O2) to form an absorbent. The Hg-0 removal performance of the absorbent was investigated in a gas/liquid scrubber using simulated flue gas. It was found that the ionic liquid/H2O2 mixture was an excellent absorbent and could be used to remove Hg-0 from flue gas. When the mass ratio of H2O2 to ionic liquid was 0.5, the absorbent showed high Hg-0 removal efficiency (up to 98%). The Hg-0 removal efficiency usually increased with the absorption temperature, while decreased with the increase of alkyl chain length in ionic liquid molecule. The Hg-0 removal mechanism involved with Hg-0 oxidation by H2O2 and Hg2+ transfer from aqueous phase to ionic liquid phase. (C) 2014 Elsevier B.V. All rights reserved.