Simultaneous leaching of manganese and silver from manganese–silver ores at room temperature

Abstract

Manganese–silver ores are typical refractory ores and are not amenable to conventional silver extraction methods. A simultaneous leaching process to extract manganese and silver by one-step leaching in sulfuric acid solution in the presence of hydrogen peroxide is proposed in this paper. Thermodynamic investigations of the Mn–H 2O and Ag–H 2O systems show that there is a predominance area in the Eh–pH diagram where Mn 2+ and Ag + coexist in solution. Hydrogen peroxide was used in the leaching process in order to simultaneously extract manganese and silver. A recovery of 98% for manganese and 85% for silver was attained for an ore analyzing 12.2% Mn and 1850 g/t Ag under the conditions of 0.8 mol/L H 2O 2, 0.8 mol/L H 2SO 4, 25 °C, 2 h of leaching time. Investigations show that hydrogen peroxide is critical to the simultaneous leaching of manganese and silver at room temperature, and it plays a dual role as an oxidizing agent for native silver and a reducing agent for manganese dioxide.