Disposal of elemental mercury via sulphur reaction by milling

Abstract

The formation of HgS (metacinnabar) from elemental mercury and pure sulphur, in non stoichiometric conditions, by means of the mechanical energy provided by a ball mill was studied. The effect of milling time in the completeness of the reaction was also studied. The formation of metacinnabar (HgS black) was observed even at short milling time (15 min), but several drops of un-reacted liquid mercury could be seen at that time. Liquid mercury was not detected for milling time of 90 min. The mechanism of the reaction was observed by SEM. This indicated that the reaction of formation of metacinnabar by mechanical dispersion starts with the diminishing of the size of the mercury drops; as reaction time increases the sulphur molecules form an interface with the microspheres of Hg and yield the formation of metacinnabar. The mercuric sulphide obtained passed the TCLP tests, yielded 2.0 x10-3 mg/l of Hg in the leachate.