Column leaching of a manganese dioxide ore: a study by using fractional factorial design

Reductive acid leaching of a manganese dioxide ore has been carried out in a fixed bed column in order to monitor and evaluate the effect of some proc ess parameters on the manganese, iron and calcium extraction yields: althou gh manganese is the metal of interest, iron and calcium were selected as re presentative of the moat significant contaminants of the leach liquor. A two-level fractional factorial design was planned to study the effect of five process factors: temperature, reagent concentration, ore particle size , solid/liquid ratio and flow rate of leaching solution were taken in consi deration in the experimental tests. The main effects and the interaction among the factors investigated were ob tained by ANOVA, carried out for each selected leaching time, taking into c onsideration manganese, iron and calcium extraction yields as response of t he process. This analysis permitted to establish temperature and reagent co ncentration exerting the most important positive effect on the manganese ex traction yield: 93% of manganese dissolution was obtained after 4 h of leac hing in the following experimental conditions: temperature 70 degreesC, S/L ratio 1/2, specific flow rate 1223 L/m(2) h, +50% of reagent excess (H2SO4 and glucose) and 208-252 mum as ore size fraction. Each statistically significant main and interaction effects, evaluated in t he selected leaching time, were correlated by empirical models in order to build a general model to perform simulation studies valid in the investigat ed range of experimental conditions but helpful for further modelling studi es. Besides these experimental and simulation studies, the potential applicatio n of column leaching conditions in the extraction of manganiferous ores has been shown, although further work should be carried out in order to invest igate a much more wide range of process conditions. (C) 2001 Elsevier Scien ce B.V. All rights reserved.