Stibnite Chloridizing with Calcium Chloride-Oxygen at Roasting Temperatures

Antimony and arsenic are impurities in copper concentrates found normally as stibnite (Sb2S3), tetrahedrite (Cu12Sb4S13) and enargite (Cu3AsS4). When copper concentrates contain appreciable amounts of As and Sb, they must be removed before smelting to avoid environmental pollution. Oxidizing volatilization roasting at 500–700 °C has been traditionally used to eliminate these impurities; however, this method allows only a fraction of Sb to volatilize. Thus, a more effective process for removing antimony from concentrates is required. This study investigates the chloridizing roasting of Sb2S3 using CaCl2–O2 to facilitate antimony removal. XRD analysis of calcines revealed that the overall reaction can be summarized as: Sb2S3 + 3CaCl2 + 6O2 → 2SbCl3 + 3CaSO4. The results show that the rate of reaction is significantly influenced by temperature and oxygen partial pressure, with an estimated conversion of around 90% achieved at 750 °C and 5.4% oxygen over a period of 20 minutes. However, high oxygen concentrations hinder the reaction's progress, leading to the formation of various antimony oxides. The findings suggest that controlling the reaction conditions is critical for optimizing the chloridization process.