Manganese metallurgy review. Part 1: Leaching of ores/secondary materials and recovery of electrolytic/chemical manganese dioxide

The world rapidly growing demand for manganese has made it increasingly important to develop processes for economical recovery of manganese from low grade manganese ores and other secondary sources. Part I of this review outlines metallurgical processes for manganese production from various resources, particularly focusing on recent developments in direct hydrometallurgical leaching and recovery processes to identify potential sources of manganese and products which can be economically produced. High grade manganese ores (> 40%) are typically processed into suitable metallic alloy forms by pyrometallurgical processes. Low grade manganese ores (< 40%) are conventionally processed by pyrometallurgical reductive roasting or melting followed by hydrometallurgical processing for production of chemical manganese dioxide (CMD), electrolytic manganese (EM) or electrolytic manganese dioxide (EMD). Various direct reductive leaching processes have been studied and developed for processing low manganese ores and ocean manganese nodules, including leaching with ferrous iron, sulfur dioxide, cuprous copper, hydrogen peroxide, nitrous acid, organic reductants, and bio- and electro-reductions. Among these processes, the leaching with cheap sulfur dioxide or ferrous ion is most promising and has been operated in a pilot scale, The crucial issue is the purification of leach liquors and the selective recovery of copper, nickel and cobalt is often difficult from solutions containing soluble iron and manganese. For treatment of manganese bearing materials including waste batteries, spent electrodes, sludges, slags and spent catalysts, a leaching or reductive leaching step is generally needed followed by various purification steps, which makes the processes less economically viable. It is concluded that the recovery of manganese from nickel laterite process effluents which contain 1-5 g/L Mn offers a growing low cost resource of manganese. Part II of this review considers the application of various solvent extraction reagents and precipitation methods for treating such manganese liquors. (C) 2007 Elsevier B.V. All rights reserved.