STABILIZATION AND LEACHABILITY TESTS OF MERCURY-CONTAINING WASTES

This paper summarizes the findings of our studies on mercury stabilization by sulfide treatment. Primary stabilization variables such as stabilization pH and sulfide/mercury molar ratio were investigated. Mercury stabilization effectiveness was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) and constant pH leaching tests. The influence of interfering ions on Hg immobilization was also tested. The experimental results indicate that the most effective mercury stabilization occurs at pH 6 combined with a sulfide/mercury molar ratio of 1. The mercury stabilization efficiency reached 99%, even in the presence of interferents. The constant pH leaching results indicate that sulfide- treated mercury wastes produce significantly higher mercury concentrations in high pH (pH >10) leachants relative to others. Nevertheless, the mercury stabilization efficiency was still as high as 99%, even with exposure of the wastes to high pH leachants. Therefore, it is concluded that sulfide-induced stabilization is an effective way to stabilize mercury-containing wastes.