Study by sulphidizing-cyanidation of jarosite-beudantite solid solutions reactivity

Abstract

The jarositic materials occurs as ores (such as gossan) or as residues from some hydrometallurgical processes. To recover silver contained in these materials, processes of alkaline decompositioncyanidation at room or high temperatures or under pressure have been proposed. A sulphidizingcyanidation study of jarosite-beudantite solid solutions from gossan ores is presented. The solid transformations have been determined using X-ray diffraction, optical and electron microscopy (SEM-EDS) and electron microprobe. During the first step of the process the jarosite phases are decomposed with the formation of lead and silver sulphides and amorphous iron hydroxide. The decomposition of potassium jarosite-beudantite and beudantite-plumbojarosite are carried out at pH ≥ 12 and pH = 14, respectively. An oxidation, to remove the excess of sulphide, followed by the conventional cyanidation process leads to the recovery of the silver.