Characterization and leaching of ferromanganese slag

Abstract

Ferromanganese slag, a product of the manganese industry, was characterized mineralogically. The slag, which contains high Mn values, was characterized using optical microscopy, XRD analysis and electron microscopy. No separate Mn-bearing oxide mineral phase was found. The slag is amorphous, and no crystalline phase was identified in the bulk sample by XRD. However, in fine fractions, quartz was identified. Scanning electron microscopy (SEM) revealed the presence of Mn, Si, Al and Ca in the matrix without the development of a mineral phase. Leaching experiments using H₂SO₄ were carried out to determine if Mn could be extracted from the slag. At room temperature, almost 100% of the manganese could be dissolved at a solid-liquid ratio of 1:10 by leaching with dilute sulfuric acid. The impurities could be precipitated by pH adjustment to produce a manganese sulfate solution suitable for the production of MnO₂ or electrolytic Mn metal. Based on the laboratory-scale experiments, a suitable process is proposed to recover manganese values from the ferromanganese slag.