Aqueous mercury precipitation with the synthetic dithiolate, BDTH₂

BDTH₂, 1,3-benzenediamidoethanethiol (common name) and closely related derivatives were specifically designed to become insoluble after the formation of linear, covalent bonds to aqueous mercury(II). BDTH₂ (IUPAC nomenclature, N,N′-bis(2-mercaptoethyl)isophthalamide) emerged as the preeminent reagent for the complete precipitation of mercury from water after several years of studies with a wide range of compounds having one, two, three, and four thiol groups. BDTH₂ does not become inactive through oxidation to disulfide and can be applied to mercury-containing water as acidic, basic, and ethanolic solutions. The BDT-Hg precipitate is extremely stable and leaches low-ppm levels of mercury only under extremely acidic and basic conditions. BDTH₂ is also effective in the aqueous precipitation of other soft, divalent metals, such as copper, cadmium, lead, and the main group elements, arsenic and selenium. The insolubility of the BDT-M compounds can be attributed to the presence of strong, non-polar, covalent M-S bonding within a water-insoluble organic framework. BDTH₂ has no known biological toxicity and is being sold as a nutritional supplement under the trade name OSR-1. This review describes the chemistry, precipitation, and leaching studies of BDTH₂ with mercury.