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, 4mol/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, 2h; and agitation speed, 500rpm. Leaching efficiency of 96.6% and 97.1% for bismuth and manganese were obtained, respectively, under the optimum experimental conditions. •Thermodynamic analysis of the Mn–H2O and Bi–S–Cl–H2O systems were conducted by use of Eh–pH diagrams.•The electrochemical experiments of bismuthinite and pyrolusite in hydrochloric acid were carried out.•Most suitable operating leach parameters of simultaneous leaching of bismuthine and pyrolusite were established.