Chemical Composition and Structure of Oxidation Product Layer on the Carrollite Surface during Bioleaching

Abstract

The chemical composition and structure variation law of the oxidation product layer, which formed on the surface of carrollite during bioleaching, were studied by the means of SEM, XPS and EDS in this paper. It was demonstrated that an oxidation product layer formed on the mineral surface when the oxidation product adhered gradually increased. Initially, the layer mainly was composed by jarosite and sulfite, and the layer thickness was less than 2 μm. Additionally, the structure of layer was loose and pocket, and covered the partial mineral surface. In the middle stage, the layer was composed of elemental sulfur, jarosite and sulfite. Moreover, the structure of the layer became compact, and the surface of carrollite was completely coated by the layer. Lastly, the element sulfur containing in the layer was totally oxidized, thus the layer was mainly composed of jarosite. Meanwhile, the layer thickness had a tendency to continue to increase, and the layer thicknesses can reach over 6 μm.