BATCH AND SEMICONTINUOUS TESTS IN THE BIOLEACHING OF MANGANIFEROUS MINERALS BY HETEROTROPHIC MIXED MICROORGANISMS

In the present paper a study on bioleaching of manganiferous ores by h eterotrophic mixed cultures is reported. The main goal of this work ha s been to study the bioreduction process of MnO2 in lab-scale reactor and pilot plant tests, in order to investigate the process' performanc es in a scale larger than in shaken flasks. Lab-scale reactor tests we re carried out in a batch and in a semi-continuous regime, monitoring manganese extraction yields and microbial growth. In the bioleaching t ests 95-100% of manganese extraction (in 36-48 h of treatment using a content of pulp equal to 20% (w/v) of ore having a Mn grade of 17-20%) was obtained, Final tests in a pilot plant (V = 70L) were performed u nder non-sterilised conditions, From the experimental results a flowsh eet of the process has been proposed. An approximate economical analys is of the bioleaching process has also been reported. The experimental results showed the technical feasibility of the process although seve ral problems have to be resolved to allow for a full-scale application , such as the biomass disposal, the purification of the leach liquor b efore the final manganese recovery and the too high cost of the proces s. (C) 1997 Elsevier Science B.V.