CHEMISTRY OF HEAVY-METAL PRECIPITATES RESULTING FROM REACTIONS WITH THIO-RED(R)

Thio-Red(R) is a commercial product that is widely used to precipitate divalent heavy metal contaminants from water. To gain a better unders tanding of how Thio-Red(R) reacts with dissolved divalent metals, the product was added to laboratory aqueous solutions, each of which conta ined one of several dissolved copper, lead, mercury, and zinc compound s. In all of the solutions, precipitates rapidly formed after adding T hio-Red(R). X-ray diffraction analyses of the precipitates detected or dinary metal sulfides rather than metal thiocarbonates. Further invest igations identified reactions that may be responsible for the formatio n of the precipitates.