Oxidative fusion and alkaline leaching for manganese extraction from low grade silicate ore

Abstract

Manganese silicate is one of manganese mineral which is barely exploited for mineral processing and extraction compared to other manganese minerals such as pyrolusite, psilomelane and rhodochrosite. Manganese silicate ore could not directly be leached out in the hydrometallurgical extraction process due to strong bonding between silicon and manganese. At the same time, traditional high-temperature treatment (pyrometallurgy) was unfavorable in terms of high consumption of energy and additives (flux). Therefore, in this research fusion pre-treatment would be proposed to break Mn-silicate bonding using NaOH, in a relatively lower temperature than the traditional pyrometallurgical process for common manganese ore. Fusion pre-treatment of manganese silicate would produce intermediate compound sodium manganate (Na2MnO4), which is easily leached using a mildly alkaline solution. The effect of manganese silicate ore/NaOH mass ratio, fusion temperature, fusion time, leaching pulp density, and leaching time on the Mn recovery would be investigated and discussed. Optimum parameters for Mn recovery (94 %) obtained were manganese silicate ore/NaOH ratio 1, fusion temperature 500 °C, fusion time 1 h, leaching pulp density 7 %, and leaching time 5 min.