Reductive leaching of manganiferous ores by glucose and H2SO4:: effect of alcohols

The effect of alcohols on the dissolution of manganese, calcium, and iron from manganiferous ore is reported. The extractive process was studied in sulphuric acid solution by using glucose as reducing agent. The alcohols were employed in order to evaluate their effect on the leaching performance with and without glucose as reducing agent. Three different alcohols MeOH, EtOH, and n-BuOH, were tested in order to investigate the influence of the organic chain length on the metal dissolution during the leaching process. Two different test sequences were followed. The first one was based on the leaching of manganiferous ore by using glucose as reducing agent and a mixture of alcohol/H2O/H2SO4 as reaction media. In the second one, leaching was carried out by using glucose in the H2O/H2SO4 reaction media and after leaching, the aqueous solution was separated from the solid by filtration. Successively, alcohols were added to the leach liquor. The experimental results of Mn, Ca, and Fe dissolution obtained by using the latter procedure were compared with those obtained in the former one. In both the experimental sequences, methyl alcohol gave better results as compared to ethyl and n-butyl alcohol. MeOH showed a notable negative effect on calcium dissolution, thereby decreasing its concentration with respect to manganese and iron extraction. The effect was larger in the runs performed by alcohol addition to the leach liquor than that obtained in the mixed solvent leaching tests. The decrease in calcium dissolution caused by the presence of alcohol has been analysed and modelled. (C) 2001 Elsevier Science B.V. All rights reserved.