Thermodynamic analysis of decomposing Bi2S3 in acidic system and its application in treatment of molybdenite-bismuthinite mixed ore

Through thermodynamic calculations, the E-pH diagrams of the Bi-S-H2O and Bi-S-Cl-H2O systems at 298 K were plotted, the dominant regions of the components in the system and their changes with pH were clarified, and the mechanism and thermodynamic conditions for the decomposition of Bi2S3 in acidic systems were clarified. The key to the decomposition of Bi2S3 in acidic systems was based on the coordination of Cl− and Bi3+. The formation of BiCl4− can promote the decomposition of Bi2S3 in acidic systems, based on this characteristic, HCl was used to achieve efficient leaching of bismuth in molybdenite-bismuthinite mixed ore. Under the optimized conditions of hydrochloric acid concentration of 6 mol/L, liquid-to-solid ratio of 5:1, temperature of 95 °C, stirring speed of 400 rpm, and time of 300 min, the leaching efficiency of bismuth reached 97.64 %, and the bismuth content in the leaching residue was 0.93 %, while molybdenum remained in the form of MoS2 in the residue, The efficient separation of molybdenum and bismuth has been achieved, providing a new process to solve the traditional separation of molybdenite-bismuthinite mixed ores.