Roasting and self-leaching process research of gold-bearing sulfides

In view of serious environmental pollution in the traditional roasting-cyanide leaching process,a roasting and selfleaching process was adopted to treat gold-bearing sulfides. The transformation rate of elemental sulfur and the gold leaching rate were tested at different roasting temperatures,roasting times and sample masses. The phase transformation of sulfur in the sulfides was analyzed by X-ray diffraction analysis,scanning electron microscopy and energy dispersive spectrometry. It is found that pyrite in the sulfides transforms to elemental sulfur and pyrrhotite because of a thermal decomposition reaction. Along with the increasing of roasting temperature and roasting time,the characteristic diffraction peaks of pyrite gradually weaken and finally disappear. Meanwhile,the characteristic diffraction peaks of pyrrhotite generate and heighten. The initial dense pyrite particles become porous. Under the conditions of the roasting temperature of 800℃,roasting time of 60 min,nitrogen flow of 1 L·min^-1 and sample mass of 50 g,the transformation rate of elemental sulfur and the gold leaching rate reach 42.53% and 88.7%,respectively. Gold from the sulfides is effectively extracted by this non-cyanide leaching.