Development of one-step process method to separate tin from tin-refining sulfur slag via vacuum sulfuration and volatilization

Abstract

Sulfur slag is a dangerous solid waste generated during tin refining. To ensure environmental safety, sulfur slag must be treated. As a result, a novel one-step process method was proposed and developed for clean and efficient recovery of tin and copper from sulfur slag. The method was based on the thermal stability of pyrite to simultaneously sulfurize and volatilize tin, which greatly improved the reaction efficiency. The feasibility of the one-step separation of tin and copper was confirmed by theoretical calculations such as Gibbs free energy and saturated vapor pressure. The effects of temperature, pyrite dosage, system pressure, and holding time were experimentally studied. Finally, the volatile was stannous sulfide, and the residue was cuprous and ferrous sulfides. The optimal experimental conditions were as follows: the reaction temperature was 1273 K, the pyrite addition ratio was 40%, the system pressure was 10 Pa, and the holding time was 3 h. The direct recovery rates of tin, copper, and iron were 99.95, 99.77, and 99.57%, respectively. The removal rates of tin, copper, and iron were all above 99.8%. The vacuum sulfuration and volatilization method provides a novel process for the clean and effective cyclic treatment of tin-refining sulfur slag.