Solution behavior of ZnS and ZnO in eutectic Na2CO3−NaCl molten salt used for Sb smelting

The solution behavior, including solubility, reactivity and sedimentation, of ZnO and ZnS in a Na2CO3−NaCl molten salt used for Sb smelting was investigated in the temperature range of 700-1000 ºC. The saturated amount of dissolved ZnO in the molten salt remained constant at 0.02% and was unaffected by temperature; additionally, ZnO did not react with the molten salt. In contrast, the saturated amount of dissolved ZnS in the eutectic molten salt increased with increasing temperature, and the content of ZnS was 0.53% at 1000 ºC. In addition, ZnS reacted with Na2CO3 above 900 ºC to give ZnO. The sedimentation rates of these three species in the molten salt followed the order of Sb>ZnS>ZnO. It was thus concluded that ZnO is an appropriate sulfur-fixing agent for low-temperature Sb smelting in a Na2CO3−NaCl molten medium, and that the optimal smelting temperature is below 900 ºC.