Clean and Efficient Removal of Copper and Sulfur from Crude Tin

Copper is a key impurity in crude tin, conventionally removed by sulfur addition, though with limited efficiency. This study investigated the interactions between Sn-S, Cu-S, and SnS-Cu within 495–673 K using Gibbs free energy, sulfur potential diagrams, and phase change analysis. The results indicate that, below 523 K, Cu and S preferentially form Cu 2 S, while Sn and S produce SnS, making this an efficient temperature range for copper removal. In crude tin experiments at 523 K, with a sulfur addition mass ratio of Cu:S = 1:0.7, copper content dropped to 0.0024 wt.%, meeting refined tin standards. At 553 K, SnS reacted with Cu to regenerate Sn and form Cu 2 S, enabling effective sulfur slag removal. By applying 30% less sulfur than conventional methods, the process achieved refined tin with copper levels below 0.0024 wt.%, complying with GB/T 728-2020. This work optimizes copper removal in tin refining, supports greener tin smelting, and enhances efficient copper recovery from crude tin.