A study of the electrolytic oxidation of cinnabar ore for the recovery of mercury

Abstract

A study of the United States Bureau of Mines newly developed electrooxidation process for the recovery of mercury from cinnabar ores was performed. The investigation included testing of both synthetic and naturally occurring cinnabar ores. A preliminary mechanism for the dissolution reaction has been developed. Generation of hypochlorite was found to be the rate controlling step in the dissolution sequence for synthetic ores. The study showed that essentially all of the cinnabar is reacted under normal test conditions and that an optimum of from 50-70% of the mercury contained in the ore as cinnabar in present in the aqueous phase at any given time. The remainder is present on the cathode or in the cell residue as elemental mercury. The chemical effects of the addition of pyrite and sulfur to synthetic ore samples were also studied. The addition of these oxidizable impurities to unbuffered ores was found to adversely affect electrooxidation results.