Recovery of manganese from iron containing sulfate solutions by precipitation

Worldwide consumption of manganese is increasing, nevertheless huge amounts of manganese from hydrometallurgical processes still end up as waste since the recovery of manganese from multi-metal solutions at low concentrations is not considered feasible. Poor iron control typically prevents the production of high purity manganese. This work studies a number of precipitants in manganese recovery and iron separation from sulfate solutions. The precipitation reagents were compared from the point of view of selectivity and economy. Carbonate precipitation is a fast and effective method for the recovery of manganese from bulk solutions. Subsequent leaching of metal carbonate is also easier and consumes less acid than, for example, hydroxide or sulfide precipitates. In order to avoid gypsum formation, soda ash should be used instead of limestone. It was found that efficient selective iron removal from MnSO4 solutions is achieved with combined O2 or air oxidation and CaCO3 precipitation at pH >5.8 and at a redox potential of >200 mV. Effective mixing and sufficient retention time are essential to make the method technically efficient and economically feasible.

The paper covers the recovery of manganese from sulfate leach solution after base metal removal. The process steps studied in this work are shown in the diagram with solid lines.Figure optionsDownload as PowerPoint slideHighlights
► Mn recovery by precipitation from sulfate solutions.
► Effective Fe separation from Mn with combined air oxidation and carbonate precipitation.
► Precipitation with O2 (air)/SO2 is also effective and economical.
► Method suffers from sensitive feed control and toxic SO2 gas.
► A rather long residence time needed for hydroxide and sulfide precipitations.