Slag Chemistry and Behavior of Nickel and Tin in Black Copper Smelting with Alumina and Magnesia-Containing Slags

The global amount of waste electrical and electronic equipment (WEEE) is growing fast. Non-ferrous metals represent a large portion of this waste, and they can be potentially recovered via black copper smelting. Alumina and magnesia, originating from the e-waste or fluxes, can be present in the feed of a secondary copper smelter in varying concentrations. Our study focuses on the impact of MgO on the slag chemistry of high-alumina iron silicate slags. The distributions of tin and nickel as minor elements were also investigated and compared with literature data. The equilibrium study was performed at 1300 °C in reducing conditions. Three different slag mixtures with 0, 3, and 6 wt% MgO were used in the study. The MgO addition significantly reduced the solubility of alumina in the slag and changed the primary spinel phase composition. The combined effects of increasing MgO and decreasing Al₂O₃ concentration in the slag regarding the distribution of tin were noticeable, i.e., its deportment to metal phase increased, but for nickel the effect was negligible. Theoretical calculations were performed for estimating the isolated effect of MgO on the distributions and they confirmed the beneficial effect on the behavior of tin but showed no impact for nickel. Graphical Abstract: [Figure not available: see fulltext.]