Comparative study of pyrite and chalcopyrite bioleaching by mesophilic strains of mine Tizapa (Mexico)

摘要

In recent years the hydrobiotechological processes are being preferred to pyrometallurgical and hydrometallurgical processes, which are expensive and polluting too. Bioleaching processes have now turned out to be environmentally friendly and promising lowcost processes and better extraction in the mining industry. This work identified the bioleaching capacity of four mixed bacterial strains; PYT06, AMT06, DT06 JT06 in the presence of two high purity sulfide minerals; pyrite and chalcopyrite. These strains were obtained from environmental mineral samples in the Tizapa Mine ( Mexico). Strains were adapted to a mixed substrate of elemental sulfur and ferrous sulfate, (FeSO4 ? 7H2O) , in MKM nutrient medium (medium Kelly modified) by the technique of successive steps during 30 days, 35°C and 150 rpm on an orbital incubator shaker. Once adapted, mineral cultures using pyrite and chalcopyrite were prepared, also by the technique of successive steps during 30 days, inoculating a mineral pulp prepared with MKM medium with 0. 5% solids. The results show that for pyrite the PyT06 - Py strain produced lower iron extraction, 57. 37% and the strain JT06 - Py higher iron extraction, 65 %. For the chalcopyrite ore the results were similar: the best strain for the copper extraction was JT06 - Cp, 40% iron extraction and 40. 33% copper extraction and the best strain for iron extraction was AMT06 - CP with a 38. 39% Fe extraction. Studies of scanning electronic microscopy, show that the attack of minerals occured preferentially by a direct mechanism in the pyrite dissolution and an indirect mechanism for the chalcopyrite.