Innovative Methodology for Sulfur Release from Copper Tailings by the Oxidation Roasting Process

Abstract

To effectively prevent the accumulation of copper tailings from producing acid mine drainage (AMD) and maximize the comprehensive utilization of copper tailings, the process of oxidation roasting was adopted to release sulfur in the form of SO2 to achieve the purpose of sulfur recovery later. Based on the AMD risk assessment, thermogravimetric (TG) analysis, and differential scanning calorimeter (DSC) analysis, the influences of roasting temperature, residence time, and air flow in the roasting process were investigated. The thermal stability, reaction equilibrium, mineral transformation, and residual S content were characterized by TG-DSC, HSC chemical software 6.0, X-ray diffraction (XRD), and combustion neutralization, respectively. The optimum conditions for sulfur release in the roasting process were shown with a temperature of 1200°C, a residence time of 60 min, and an air flow of 0.8 L/min. Under these conditions, the sulfur release rate was 99.82%, and the residual S content was 0.05%. Subsequently, the process of sulfur release was proposed as four steps: oxidative decomposition of pyrrhotite, formation of ferric sulfate, decomposition of ferric sulfate, and formation of hematite. All of the findings could propose a theoretical and experimental reference for the recovery of the sulfur component from tailings rich in sulfide minerals.