Formation of HgS—mixing HgO or elemental Hg with S, FeS or FeS2

The aim of this study is to assess the feasibility for generation of the sparingly soluble solid HgS from HgO or elemental Hg by mixing with a suitable sulphur source under various conditions (dry, wet at different pH, and room temperature). The formation of mercury sulphide was confirmed in 14 of the 36 combinations of Hg and S sources. Mercury sulphide was generally formed under alkaline conditions. Almost 100% HgS was obtained in anaerobic systems at high pH in the presence of elemental sulphur after about two years. Thus, it is feasible to create an environment at room temperature that, with time, leads to the generation of HgS from elemental Hg or HgO. This is relevant for the design of a repository for permanent geologic disposal of mercury. Choosing wrong components and conditions can however lead to a reduction of Hg(II) to elemental mercury.