Self sustained autogenous dissolution of medium grade manganese ore of Gujarat in NH3OHCl-H2SO4-H2O medium

Abstract

Leaching studies have been carried for dissolution of manganese from medium grade manganese ore in hydroxyl ammine hydrochloride-sulphuric acid medium. Due to exothermic nature of reaction no external heat is required for quantitative extraction of manganese confirming the self sustained autogenous nature of leaching process. Initially, the effects of individual parameters including time, sulphuric acid concentration, amount of reductant, pulp density, and particle size have been studied. One parameter has been changed at a time while keeping the other parameters constant. Per cent manganese extraction is found to be dependent on acid concentration and amount of reductant. Within 20 min, manganese could be quantitatively dissolved. A comparison of FTIR spectra of synthetic solution with actual leach solution indicates the formation of ClO4- ions during leaching. The XRD pattern of the residue shows only quartz as the crystalline phase. Response surface methodology is adopted applying a central composite design for 2(4) factorial set of experiments. A statistical analysis is done to evaluate interactive effects. Using the model, optimised parameters in the range of pulp density 25 - 35 % wt /v, acid concentration 6.5-7.5% v/v, amount of reductant 15-16 g and time 10 - 30 min have been considered for maximum desirability. The experimental data is found to be fitted well with the predicted ones.