The release of sulphidic minerals from aluminosilicates by Bacillus strains

The influence of bacterial strains mixtures of Bacillus species on the structure of mineral samples in the form of polished sections and granulated products subsequently to ore dressing at the Banskfa Hodrusa deposit was investigated. These bacterial strains were isolated from a mining dump near Banska Stiavnica and from a kaolin pit near Horna Prievrana. The ability of our bacteria to destroy some silicates and to produce the release of several metal cations from their structure was confirmed by morphological changes of the mineral surface in comparison with the control samples after 20 days of bioleaching. In the polished sections quartz and silicates were the predominant minerals, whereas sphalerite, galena, rhodonite, pyrite and finely disseminated gold were present in traces. The main metabolites of our bacterial strains detected by the capillary isotachophoresis methodwere acetic acid, butyric acid, pyruvic acid, lactic acid and formic acid. The biodegradation ability of our strains was also confirmed by X- Ray analysis and by the removal of individual metal cations from the samples determined by atomic absorption spectrometry. These methods showed the different activity of these strains on mineral samples. The mixture of Bacillus strains extracted 39% Si, 60% Pb, 43% Zn and 32% Cu from flotation concentrate, 33% Si, 75% Pb, 76% Zn, 76% Cu and 82% Mn from post-flotation waste, 30% Si, 59% Pb, 35% Zn, 56% Cu, 78% Mn, 37% A1 and even 30 % Au from gravitational concentrate.