Silica-based adsorbent was prepared by gamma-radiation induced grafting of vinyl imidazole (VIM) onto the silanized silica, which was silanized by chlorotrimethylsilane (TMCS). The effects of monomer concentration and absorbed dose on the grafting yield were investigated to optimize the reaction conditions. Thermodynamic analysis, FTIR analysis and XPS spectra manifested that VIM was successfully grafted onto the silica surface. The SS-g-VIM adsorbent had excellent selectivity for Hg(II) adsorption in mixture divalent cationic metal solution and a high adsorption capacity of Hg(II). The theoretical maximum adsorption capacity was calculated to be 355.9 mgg(-1) (1.774 mmol g(-1)) in HgCl2/HNO3 solution at pH 5 at room temperature. The adsorption kinetics and adsorption isotherm were investigated. It was found that the Langmuir isotherm model fitted well with the adsorption process and the adsorption of Hg(II) onto SS-g-VIM adsorbent could be considered as a spontaneous, endothermic and chemical sorption process. The comprehensive results suggested that SS-g-VIM adsorbent has potential application for the removal of Hg(II) from wastewater. (C) 2012 Elsevier B.V. All rights reserved.