Mineral-Phase Reconstruction for Efficient Recovery of Tin from High-Barium Copper Anode Slime

The recovery of tin from high-barium copper anode slime by Kaldor furnace smelting remains challenging because barium sulfate hinders the conversion of tin (Sn) from SnO2 into acid-soluble phases. In this study, the smelting behavior of high-barium copper anode slime in a Kaldor furnace was simulated under optimal smelting conditions: SnO2 was effectively converted into BaSnO3, while SiO2 was transformed into Na2Ba6Si4O15, achieving a high Sn conversion efficiency of 92.18%. Phase and microstructure analyses indicated that the preferential reaction of SiO2 with Na2CO3 and BaSO4 governs the early-stage phase reconstruction, whereas the subsequent reaction between SnO2 and BaCO3 promotes the formation of BaSnO3. Kinetic analysis showed that the Sn conversion process was well described by the Avrami–Erofeev model, with an apparent activation energy of 43.75 kJ/mol and an Avrami index of 1.13, suggesting mixed control by diffusion and chemical reaction. Thermodynamic analysis further confirmed that stannates and silicates are the dominant equilibrium phases under the optimized conditions. This work provides a promising route for the efficient recovery of tin from high-barium, tin-bearing smelting slag.