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 C-3 symmetric compound that is used commercially to precipitate mercury an d other heavy metals from waste waters and contaminated natural waters. A s eries of laboratory experiments and analyses were performed to evaluate the chemistry and stability of mercury trimercaptotriazine "Hg-TMT" precipitat es that result from the addition of aqueous solutions of TMT-55 to aqueous solutions of mercury(II) chloride (HgCl2). Several Hg-TMT species exist, mo st of which were previously unrecognized. The leaching properties, chemistr y 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 a ir, and may release more than 6000 mu g/l of mercury into distilled and dei onized water leachates. Although waste waters and contaminated ground water s 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 co nditions. (C) 2000 Elsevier Science Ltd. All rights reserved.