The adsorption of aqueous mercury species from chloride solutions on a number of activated
carbons has been studied. It was found that whereas the adsorption of neutral HgCl, or positive Hg’+
was very low, significant quantities of the tetrachloromercury(I1) complex, HgCI$-, were adsorbed.
Adsorption isotherms of this complex were measured at different pH values, and the results analysed by
the Langmuir equation and by a simple surface ionization and specific adsorption model in order to
obtain estimates of the adsorption stoichiometry and the mean free energy of adsorption.