In comparison to the adsorption of hydrocarbons, the adsorption of mercury on activated carbons reveals many unexpected results. Both physisorptive and chemisorptive mechanisms play a role even in the adsorption on nonimpregnated activated carbons. In this work, the adsorption of Hg-0 from a N-2 carrier gas stream is studied on three commercial adsorbents. Single and cumulative breakthrough curves are measured in a fixed bed at temperatures of 25-100 degrees C and mercury concentrations of 50-1000 mu g m(-3). Isosteric heats of adsorption are calculated from the measured adsorption isotherms. Here, adsorption enthalpies in the range of 50% of the vaporization enthalpy are determined. In addition, desorption experiments are conducted to distinguish the contributions of physisorption and chemisorption. A dynamic simulation of experimental breakthrough curves yields diffusion coefficients, which are discussed with respect to the concentration and temperature dependence of diffusion mechanisms in mercury physisorption.