Extraction of manganese through baking-leaching technique from high iron containing manganese sludge

Abstract

The growing demand for manganese and environmental regulations had made it increasingly important to develop a process for the recovery of manganese from manganese sludge before dumping. This article explores the possibility of extracting manganese from manganese sludge containing 10% manganese and 15.5% iron. Detailed physico-chemical characterization was carried out by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray fluorescence (XRF), Atomic absorption spectrometer (AAS) and conventional analytical tools. The manganese present in the form of Mn+4 is stable in acid or alkaline oxidizing condition. So the recovery of manganese must be carried out under reducing condition. Sulfation roasting in the presence of proper reductant followed by water leaching process was developed to recover manganese. Different processes parameters such as roasting temperature, reductant mass, sulfuric acid concentration were studied and optimized to give more than 98% dissolution of manganese. The leached sulphate solution is purified further and precipitated as manganese carbonate (>95%) in the presence of ammonium carbonate. The precipitate was dried and calcined at 350 °C to produce chemical manganese dioxide (CMD). The products were characterized by using XRD and SEM.