Change in the oxidation rate of stibnite as affected by pyrite in an oxygenated flow-through system

In natural mixed-sulphide assemblages, galvanic interaction between stibnite and pyrite has been shown to increase the dissolution of stibnite, leading to enhanced antimony leaching. The objective of this study was to determine the impact of pyrite on the dissolution rate of stibnite in binary mixtures of the two minerals. Finely ground pyrite and stibnite were mixed in various ratios and the mixtures were subjected to water leaching in flow-through columns for 6 days. An increased oxidation rate of stibnite was noted in the presence of pyrite, with a greater accumulation of oxidized, solid-phase Sb in the systems containing higher pyrite inputs. This study provides evidence that galvanic interaction can enhance the oxidation of stibnite in unconsolidated mixtures of sulphides when stibnite is in close contact with pyrite. In the context of mine wastes, galvanic interaction may thus constitute a mechanism enhancing Sb release but its overall significance remains to be clarified as natural processes may occur to attenuate the aqueous transport of the released Sb.