The deportment of mercury during thiosulfate leaching and resin-in-pulp recovery of gold from ores

Minerals & Metallurgical Processing , 2010, Vol. 27, No. 4, pp. 184-189

Oraby, E.A.; Jeffrey, M.I.; Browner, R.E.

ABSTRACT:

This paper reports on the behavior of mercury and its compounds during the thiosulfate leaching and recovery of gold. Thiosulfate solutions are shown to dissolve Hg⁰ and Hg₂Cl₂ to a similar extent as cyanide, but the leaching of HgS is significantly slower in thiosulfate solutions compared to cyanide. Hence, the use of thiosulfate may be an option for treating ores containing high levels of cinnabar, especially since the legislation concerning the discharge or sale of mercury is becoming more restrictive. The deportment of mercury during gold thiosulfate loading and recovery using a strongly basic anion-exchange resin was also studied. Although the mercury thiosulfate complex loads on the resin, the adsorption is weaker than for gold, with an equilibrium constant between gold and mercury of 51. Resin loaded with gold, mercury and copper was pre-eluted with thiosulfate (to remove copper) and eluted with a chloride and sulfite eluant. The majority of the mercury is eluted by the eluant and, hence, its deportment closely follows gold and the eluate would need to be treated to remove either mercury during or prior to gold electrowinning.