The adsorption of Hg(II) by natural rubber chips was investigated. First, the effect of chip size (5 mm x 5 mm and 10 mm x 10 mm) on the adsorption kinetics was studied. The pseudo-second-order modeling was found to explain the kinetics well. The smaller chips had higher adsorption rate so they were used for the rest of the research. Next the effects of sulfur, zinc oxide and carbon black on the adsorption capacity of Hg(II) at equilibrium conditions were investigated. The effect of sulfur was studied through different standard vulcanizing systems. The amount of zinc oxide was varied to be 3, 4 and 5 part per hundred parts of rubber (phr) while the carbon black (N-330) loading was varied to be 0, 30 and 50 phr, respectively. It was found that adsorption capacity increased with the degree of crosslink density, generated by sulfur reacting with rubber molecules. In addition, the adsorption capacities of various amounts of zinc oxide corresponded with their crosslink densities while the addition of carbon black seemed to obstruct Hg(II) adsorption. (c) 2007 Elsevier B.V. All rights reserved.