Sn recovery from a tin-bearing middling with a high iron content and the transformation behaviours of the associated As, Pb, and Zn

Abstract A tin-bearing middling with high Fe and low SiO2 contents is generated from the beneficiation of tin-bearing tailings. The middling is composed of valuable Sn and Fe metals and harmful Pb, Zn, and As elements, which can cause severe economic and environmental issues if left on land for extended periods. This study proposed a new two-step process for the treatment of the middling, which includes oxidising roasting followed by sulfurization roasting. The results demonstrate that Sn, Pb, Zn, and As were volatilised efficiently and concentrated in the collected dust while concentrated Fe remained in the roasted residue. During the sulfurization roasting process, CaSO4 that originated from the middling played a major role in Sn sulfurization and volatilisation through its transformation to SO2 (g). Furthermore, CO2 (g) positively affected separation of Sn and As from Fe Sn and Fe As alloys, respectively, via the selective oxidation of the Fe component in the alloy phases. Under optimal conditions, the Sn recovery reached 97.5%, and the residual contents of As, Pb, and Zn decreased to 0.055, 0.013, and 0.13 wt%, respectively. This study aids in the resource utilisation of tin-bearing middling and is of substantial significance for the quantitative reduction of tin-bearing tailings.