Self-oxidation among iron-bearing minerals promoting magnetite formation from pyrite in Bayer liquor

The effects of siderite, hematite, and goethite on pyrite reactions in sodium aluminate solution at high temperatures, based on the coexistence of pyrite and iron-bearing minerals in bauxite, were studied. The addition of siderite, goethite, and hematite increases the concentrations of S 2 O 3 2− , SO 3 2− and SO 4 2− , enhancing sulfur removal during desilication. Siderite and hematite facilitate nearly 100% magnetite formation from pyrite, whereas goethite leads to the formation of both hematite and magnetite from pyrite through a multiphase transformation process. Iron-bearing minerals significantly increase the iron content in residues and enhance iron recovery from the red mud. Siderite, goethite, and hematite produce a porous surface in the form of erosive holes due to electrochemical corrosion, improving reaction efficiency of pyrite. Additionally, electrochemical corrosion promotes the pyrite reaction in accordance with the Kröger and Ziegler models, controlled by interfacial diffusion and chemical reactions in the presence of siderite, hematite and magnetite.