An environmentally friendly method for efficient atmospheric oxidation of pyrrhotite in arsenopyrite/pyrite calcine

• Published in: Chemical engineering journal advances Vol. 7; p. 100122
• Main Authors: Li, Lin, Wang, Jingxiu, Wu, Chengqian, Ghahreman, Ahmad
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2021; Elsevier
• Subjects: Calcine; Oxidation; Pyrolysis; Pyrrhotite; Sulfur balance; Thermal phase transformation; Pyrolysis; Oxidation; Thermal phase transformation; Calcine; Pyrrhotite; Sulfur balance
• ISSN: 2666-8211; 2666-8211
• DOI: 10.1016/j.ceja.2021.100122

•The atmospheric oxidation of an iron sulfide calcine was studied for the first time.•The sulfide oxidation rate was determined by the iron sulfide thermal phase transition.•More than 95% of the calcine can be oxidized at optimal conditions without ultrafine grinding.•Elemental sulfur was the major oxidation product.•This study indicates an efficient and green process to deal with gold-bearing concentrates. Pyrite and arsenopyrite are the most common hosts for invisible gold, but pyrite and arsenic are refractory during conventional sulfide oxidation, which significantly challenges subsequent gold extraction. One option is high-temperature pretreatment of arsenical materials to sequester > 90% of the arsenic as a gas, then convert it to a stable form. This process produces a calcine similar in composition to pyrrhotite (Fe1-xS) but with higher porosity. In this study, the calcine product is oxidized with an efficient, cost-effective atmospheric process using acidic and near-neutral solutions. A sulfur mass balance analysis method based on iron sulfide thermal transformation in nitrogen atmosphere was developed to quantify the oxidation efficiency of pyrrhotite leaching. The optimization confirmed that > 90% of the calcine was oxidized by Fe3+ (5 and 10 g/L) and O2 (0.5 L/min) at pH 1 after 48 h and at 95 °C even without ultrafine grinding. Elemental sulfur was the main oxidation product when the oxidation pH was 1,2. This study provides the foundation for the development of a low-cost and environmentally friendly process option for pretreatment of arsenical sulfide refractory gold materials. [Display omitted]