Chemistry and stability of precipitates from aqueous solutions of 2,4,6-trimercaptotriazine, trisodium salt, nonahydrate (TMT-55) and mercury (II) chloride

2,4,6-trimercaptotriazine, trisodium salt, nonahydrate (TMT-55) is a planar C3 symmetric compound that is used commercially to precipitate mercury and other heavy metals from waste waters and contaminated natural waters. A series of laboratory experiments and analyses were performed to evaluate the chemistry and stability of mercury trimercaptotriazine “Hg-TMT” precipitates that result from the addition of aqueous solutions of TMT-55 to aqueous solutions of mercury(II) chloride (HgCl2). Several Hg-TMT species exist, most of which were previously unrecognized. The leaching properties, chemistry and long-term stability of the solids are very diverse. As examples, the white and yellow varieties of Hg-TMT are often unstable in both water and air, and may release more than 6000 μg/l of mercury into distilled and deionized water leachates. Although waste waters and contaminated ground waters are likely to contain less mercury than the HgCl2 solutions used in this study, individuals should recognize that any Hg-TMT compounds are likely to be chemically complex and perhaps unstable under aqueous or atmospheric conditions.