Possible mechanism of elemental mercury oxidation in the presence of sh compounds in aqueous solution

The oxidation of elemental mercury (Hg0) in the presence of sulfhydryl (SH) compounds in aqueous solution was studied. The order of potency for stimulation of Hg0 oxidation was glutathione > L-cysteine > D-penicillamine. The consumption rate of each SH residue in the reaction mixture in the presence of Hg0 showed the same order. Ethylenediaminetetraacetic acid was also found to accelerate Hg0 oxidation. These results indicated that the oxidation of Hg0 was stimulated in the presence of compounds with an affinity for the mercuric ion (Hg2+). The accelerated conversion of Hg0 to ionized Hg2+ would be the result of a shift in equilibrium between Hg0 and Hg2+ caused by the the formation of a stable RS− −Hg2+ conjugate.