A Detailed Investigation of Adsorption Isotherms, Enthalpies, and Kinetics of Mercury Adsorption on Nonimpregnated Activated Carbon

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 non-impregnated activated carbons. In this work the adsorption of Hg0 from a N2 carrier gas stream is studied on three commercial adsorbents. Single and cumulative breakthrough curves are measured in a fixed bed at temperatures of 25 °C to 100 °C and mercury concentrations of 50 to 1000 μg∙m-3. From the measured adsorption isotherms isosteric heats of adsorption are calculated. 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.