Mineralization process of ferrous ions from ZnSO4-FeSO4 solution at a temperature range of 368.15–423.15 K

Abstract

The abiotic mineralization of ferrous ions for ZnSO4-FeSO4 solution at temperatures of 368.15–423.15 K was investigated. The effect of kinetic factors including oxygen partial pressure, temperature, agitation speed, with presence of a neutralizer or not, and seeding on the ferrous oxidation process was evaluated in detail. Also, the rate constants for the ferrous oxidation process were calculated by a second-order kinetic curve of the partial concentration of [Fe2+] with time to realize the effect of the different kinetic factors as variables. Furthermore, the morphology of the minerals was identified using scanning electron microscopy electron dispersive spectroscopy measurements (SEM-EDS), and the phase composition was characterized by the X-ray diffraction (XRD), the thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The research indicated that the ferrous oxidation process was accelerated by elevating temperature, increasing agitation speed, and adding a neutralizer. Conversely, increasing oxygen partial and seeding both decrease the rate constant of the oxidation process. The iron-rich precipitates produced comprise a wide range of chemical compositions, structures, sizes, and morphologies. They consisted primarily of goethite and hematite, with goethite being dominant below 403.15 K, and hematite above 403.15 K. Moreover, the iron-rich products were successfully obtained by abiotic mineralization of industrial ZnSO4 solution at 423.15 K, containing 59% of Fe and 1% of Zn, while the resultant ZnSO4 solution after removal of iron contained less than 1 g/L of iron ions. Thus, abiotic mineralization of ferrous ions for ZnSO4 is clean and energy-saving, and the iron-rich products can be used as raw materials for ironmaking.