One-step extraction of antimony from low-grade stibnite in Sodium Carbonate - Sodium Chloride binary molten salt

The extraction of antimony from low-grade stibnite in eutectic Na2CO3-NaCl molten salt using ZnO as a sulphur-fixed agent was studied. The results of the experiments on the reaction mechanism indicate that the reaction courses of antimony and sulphur were Sb2S3 -> Sb2O3 -> Sb and Sb2S3 -> ZnS. Sulphur was fixed in the form of ZnS, while molten salt did not react with other components, serving only as the reaction medium. The influencing factors, including the smelting temperature, reaction time, and dosage of ZnO, salt and carbon, were investigated in detail by single factor experiments. The optimum conditions were determined as follows: temperature 1123 K, time 1 h, W-salt/W-ore = 51, W-ZnO/W-theory = 1.0, and W-carbon = 10%W-ore, where W represents weight. Under those optimum conditions, the average direct recovery ratio of antimony reached 92.88%. It is suggested that an increase in the temperature and the dosage of salt and carbon powder is beneficial for the improved direct recovery rate of antimony. (C) 2015 Elsevier Ltd. All rights reserved.