Simultaneous leaching of low grade bismuthinite and pyrolusite ores in hydrochloric acid medium

A simultaneous leaching process to extract both bismuth and manganese by one-step leaching in hydrochloric acid solution is proposed in this paper. Thermodynamic investigations of the Eh-pH diagram of both Mn-H2O and Bi-S-Cl-H2O systems showed that the equilibrium potentials of MnO2/Mn2 + couple were much higher than that of Bi2S3/Bi(III) couple. The electrochemical experiments presented the electrochemical reactions of bismuthinite and pyrolusite. Most suitable operating leach parameters were established as follows: liquid-to-solid ratio (mL/g), 5:1; initial hydrochloric acid concentration, 4 mol/L; leaching temperature, 70 °C; ore ratio (measured by the mole ratio of manganese and sulfur, n(Mn)/n(S)), 1.4/1; leaching time, 2 h; and agitation speed, 500 rpm. Leaching efficiency of 96.6% and 97.1% for bismuth and manganese were obtained, respectively, under the optimum experimental conditions.