Summary: | The molten salt metallurgy of Sb, which involves the smelting of stibnite in a binary NaCl-Na<sub>2</sub>CO<sub>3</sub> salt with sulfur-fixing and the addition of a reductant, has been proposed as a clean method for Sb extraction. However, the reacting behaviors of the minerals associated with stibnite (Sb<sub>2</sub>S<sub>3</sub>) during the smelting are still unclear, and industrial tests have not been conducted. This study investigated the behaviors of PbS, FeS<sub>2</sub>, SiO<sub>2</sub>, and CaCO<sub>3</sub>, which are the main minerals associated with stibnite, during reducing smelting by using the NaCl-Na<sub>2</sub>CO<sub>3</sub> molten salt. The results showed that PbS could react with Na<sub>2</sub>CO<sub>3</sub> to generate metallic Pb at 950 °C. FeS<sub>2</sub> and SiO<sub>2</sub> formed stable NaFeS<sub>2</sub> and Na<sub>2</sub>SiO<sub>3</sub> with the molten salt at a high temperature, respectively. CaCO<sub>3</sub> formed an unstable intermediate product of Na<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub> at 675 °C and decomposed with increasing temperature. Kilogram-class trials were also performed using 50 kg of concentrate and more than 300 kg of mixture material, and the results showed that the direct recovery rate of Sb and Au reached maximum values of 93.22% and 92.06% at temperature 920 °C in eutectic Na<sub>2</sub>CO<sub>3</sub>-NaCl molten salt, respectively, while the total sulfur-fixing ratio reached 99.49%. Thus, the associated minerals consumed the molten salt, and the feasibility of molten salt smelting was verified by this kilogram-class pilot experiment.
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