REDUCTIVE LEACHING OF A CONCENTRATE MANGANESE-DIOXIDE ORE IN ACID-SOLUTION - STOICHIOMETRY AND PRELIMINARY KINETIC-ANALYSIS

A Pyrolusite (MnO2) Ore of industrial interest has been treated by an acid leaching process (H2SO4) With sucrose (C12H24O11) as reducing substance. The aim of the present work has been the preliminary analysis of the leaching process, considering the main factors of the process. The experimental runs have been carried out at different temperatures (50-90-degrees-C), acid concentrations (0.1-1 M), reducing substance concentrations (10-40 g/L) and mineral concentrations (5-10% w/v). In some cases, the Analysis of Variance technique (Factorial Experiments) has been used in order to determine the main effects and the cross-interactions of the above parameters. Furthermore, the possible stoichiometry of the reactions has been proposed and experimentally verified. In the experimental runs at 90-degrees-C with 10% (w/v) of mineral concentration (size distribution < 75 mum) and 20 g/L of sucrose concentration an extraction yield of 73% was obtained after 5 minutes of treatment, and 95% after 30 minutes. Experimental runs using molasse and starch were carried out in order to check the use of the agro-industrial waste material in the leaching process. The measured yield and the extraction rates show the potential application of the process for the manganese recovery from ores of industrial interest.