Stabilizing conditions of metal mercury in mercury sulfurization using a planetary ball mill

Abstract

This study used a non-heating process to stabilize mercury by mercury sulfurization. Elemental mercury and sulfur were mixed using planetary ball milling under various experimental conditions and the optimal conditions were determined. The labile intermediate, mercury sulfide, was observed in the early stages of milling, and the intermediates were then pulverized into mercury sulfide powder. These phenomena were significantly influenced by the diameter of the planetary ball. A larger diameter enhanced mercury stabilization. For a ball with a 19.04-mm diameter, the toxicity characteristic leaching procedure (TCLP) and the Japanese leaching test (JLT) values were 0.263μg/L and 0.0586μg/L, respectively, suggesting that mercury leachability was strictly controlled. When the molar ratio of sulfur to mercury was 1.05, the mercury concentration in the headspace was <1μg/Nm3 at 20°C, which was equivalent to the level in pure reagent. The stability of the planetary ball milling product at optimum conditions was either comparable or superior to that in other stabilization techniques. The running cost of this technology was estimated to be 15,360Yen (154USD)/ton-Hg. This stabilization technology is cost-effective and environmentally sound for the long-term and safe management of mercury.