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

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-H2O and Ag-H2O systems show that there is a predominance area in the Eh-pH diagram where Mn2+ and Ag+ coexist in solution. Hydrogen peroxide was used in the leaching process in order to simultaneously extract manganese and silver. A recovery of98% 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 H2O2, 0.8 mol/L H2SO4, 25degreesC, 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. (C) 2003 Elsevier Science B.V. All rights reserved.