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Two samples of well and poorly ordered kaolinite were inoculated with mixture of Bacillus cereus and Bacillus purilus, isolated from the kaolin deposits in Luceneckci Kotlina, Slovakia. The results obtained after 100 days showed that, although the samples had almost the same contents of Al and Si, only the extraction rates of Al were comparable. Extraction of Si and Fe from the poorly ordered sample was higher than from the well ordered one, indicating that the higher disorder facilitates the role of bacteria in the selective dissolution of kaolinite. The dissolution of impurities from the poorly ordered sample resulted in the creation of more pores which are accessible for nitrogen molecules., Two samples of well and poorly ordered kaolinite were inoculated with mixture of Bacillus cereus and Bacillus purilus, isolated from the kaolin deposits in Luceneckci Kotlina, Slovakia. The results obtained after 100 days showed that, although the samples had almost the same contents of Al and Si, only the extraction rates of Al were comparable. Extraction of Si and Fe from the poorly ordered sample was higher than from the well ordered one, indicating that the higher disorder facilitates the role of bacteria in the selective dissolution of kaolinite. The dissolution of impurities from the poorly ordered sample resulted in the creation of more pores which are accessible for nitrogen molecules.

The removal is discussed of oxidic Fe-phases from industrial silicates by bioleaching. Results are presented which show that small additions of the chelators AQDS or NTA resulted in enhanced Fe (III) reduction or the stimulation of Fe dissolution under non-controlled anaerobic conditions. The bacteria enhanced Fe dissolution indirectly through microbially promoted pH changes and production of organic acids. AQDS stimulated bacterial iron reduction, and Fe2+ concentration in solution was higher than Fe3+. NTA did not stimulate iron reduction but increased bacterial iron dissolution in the form of Fe3+. The concentration of carbon source in the medium was crucial for Fe dissolution and metabolite production. Cheap alternatives such as molasses and food-sugar were used to optimise costs on an industrial scale. The low toxicity of the chelators and bacterial metabolites (pH 4) makes bioleaching an attractive alternative compared with chemical leaching., The removal is discussed of oxidic Fe-phases from industrial silicates by bioleaching. Results are presented which show that small additions of the chelators AQDS or NTA resulted in enhanced Fe (III) reduction or the stimulation of Fe dissolution under non-controlled anaerobic conditions. The bacteria enhanced Fe dissolution indirectly through microbially promoted pH changes and production of organic acids. AQDS stimulated bacterial iron reduction, and Fe2+ concentration in solution was higher than Fe3+. NTA did not stimulate iron reduction but increased bacterial iron dissolution in the form of Fe3+. The concentration of carbon source in the medium was crucial for Fe dissolution and metabolite production. Cheap alternatives such as molasses and food-sugar were used to optimise costs on an industrial scale. The low toxicity of the chelators and bacterial metabolites (pH 4) makes bioleaching an attractive alternative compared with chemical leaching.

A summary is presented of results from research into the possibilities of using biotechnological procedures for the treatment of Slovak sulphide ores. Microbial cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans were isolated from the mining waters of sulphide deposits. Leaching experiments were carried out with the separated minerals. Results on environmental biogenic processes in selected waste dumps confirmed the assumption that the waste deposits are not stable from the element point of view. The consequences of environmental biogenic processes in sulphide deposits in the field were compared with those of laboratory tests., A summary is presented of results from research into the possibilities of using biotechnological procedures for the treatment of Slovak sulphide ores. Microbial cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans were isolated from the mining waters of sulphide deposits. Leaching experiments were carried out with the separated minerals. Results on environmental biogenic processes in selected waste dumps confirmed the assumption that the waste deposits are not stable from the element point of view. The consequences of environmental biogenic processes in sulphide deposits in the field were compared with those of laboratory tests.

Quartz sand containing mineral impurities, from Vysny Petrovec in Slovakia, was biologically leached for 3 months by strains of Bacillus bacteria to determine the reduction of Fe(III)-oxyhydroxides and the effect of particle size on the extent of Fe removal. Bioleaching removed visible Fe-bearing minerals that coated the quartz grains. Elements were dissolved from silicate minerals and poorly crystalline Fe-oxides that sealed siderite nodules were released from intergranular spaces to form a fine-grained fraction whose voltammetry indicated reductive dissolution of Fe3+. Chemical analysis showed a slight increase in Fe2O3 content and a decrease in FeO content. X-ray diffraction analysis showed a loss of Fe-bearing minerals and mica while transmission electron microscopy and energy-dispersive X-ray analysis showed nucleation of fine-grained Fe,Al silicates on the surfaces of bacteria., Quartz sand containing mineral impurities, from Vysny Petrovec in Slovakia, was biologically leached for 3 months by strains of Bacillus bacteria to determine the reduction of Fe(III)-oxyhydroxides and the effect of particle size on the extent of Fe removal. Bioleaching removed visible Fe-bearing minerals that coated the quartz grains. Elements were dissolved from silicate minerals and poorly crystalline Fe-oxides that sealed siderite nodules were released from intergranular spaces to form a fine-grained fraction whose voltammetry indicated reductive dissolution of Fe3+. Chemical analysis showed a slight increase in Fe2O3 content and a decrease in FeO content. X-ray diffraction analysis showed a loss of Fe-bearing minerals and mica while transmission electron microscopy and energy-dispersive X-ray analysis showed nucleation of fine-grained Fe,Al silicates on the surfaces of bacteria.

The ability of Bacillus bacteria to destroy aluminosilicate minerals such as feldspar and quartz suggests that interesting biochemical processes occur in the hypergenic zone. Several kinds of bacteria contribute to the weathering process and accelerate the leaching of elements from rock-forming minerals. Samples from the Horna Prievrana kaolin pit in Slovakia are characterised by a large number of Bacillus and Pseudomonas bacteria, including B. pumilus, B. megaterium, B. cereus and B. mycoides, which coexist together under aerobic and anaerobic conditions in moist environments. Their activity and release of organic compounds into circulating solutions are displayed in the deposit's zonal formation, with kaolin and Fe oxide zones and the remains of graphitic phyllites. Higher extraction of iron, the main contaminant in ceramic and glass raw materials, has been observed under laboratory conditions and suggests a possible new means of processing non-metallic ores., The ability of Bacillus bacteria to destroy aluminosilicate minerals such as feldspar and quartz suggests that interesting biochemical processes occur in the hypergenic zone. Several kinds of bacteria contribute to the weathering process and accelerate the leaching of elements from rock-forming minerals. Samples from the Horna Prievrana kaolin pit in Slovakia are characterised by a large number of Bacillus and Pseudomonas bacteria, including B. pumilus, B. megaterium, B. cereus and B. mycoides, which coexist together under aerobic and anaerobic conditions in moist environments. Their activity and release of organic compounds into circulating solutions are displayed in the deposit's zonal formation, with kaolin and Fe oxide zones and the remains of graphitic phyllites. Higher extraction of iron, the main contaminant in ceramic and glass raw materials, has been observed under laboratory conditions and suggests a possible new means of processing non-metallic ores.

Bioleaching experiments were carried out on iron-contaminated raw materials from Strazov, Cierny and Poproc, Slovakia. A new mineral, weddellite (calcium oxalate dihydrate), was identified in the fine-grained fraction after bioleaching. The formation of weddellite by the destruction of Ca-plagioclase indicated that oxalic acid was one of the metabolites involved in the bioleaching process. Bioleaching resulted in a 35-41% decrease in the Fe content of the Strazov raw material, and subsequent electromagnetic separation reduced the Fe content by up to 69-74%. Bioleaching of the Poproc material, which had a high Fe2O3 content, removed 60% of the Fe, the removal rate increasing to 75% in combination with electromagnetic separation. The removal of Fe resulted in a high-quality, white-coloured product., Bioleaching experiments were carried out on iron-contaminated raw materials from Strazov, Cierny and Poproc, Slovakia. A new mineral, weddellite (calcium oxalate dihydrate), was identified in the fine-grained fraction after bioleaching. The formation of weddellite by the destruction of Ca-plagioclase indicated that oxalic acid was one of the metabolites involved in the bioleaching process. Bioleaching resulted in a 35-41% decrease in the Fe content of the Strazov raw material, and subsequent electromagnetic separation reduced the Fe content by up to 69-74%. Bioleaching of the Poproc material, which had a high Fe2O3 content, removed 60% of the Fe, the removal rate increasing to 75% in combination with electromagnetic separation. The removal of Fe resulted in a high-quality, white-coloured product.

The content of iron oxides in glass of various grades is strictly regulated, but ultra-fine iron particles and clay minerals which coat quartz grains or are impregnated in silicate matrix are difficult to treat using conventional mineral processing methods. Laboratory tests and in situ experiments were carried out to investigate the use of basin water bioleaching with Bacillus spp. followed by dry electromagnetic separation to improve the quality of quartz sands from the Sastin region of Slovakia. The effect of chelators including EDTA, Na2EDTA, Na4EDTA and NTA on the bacterial dissolution of iron impurities was also studied. The rate of iron dissolution varied with environmental conditions and with the addition of chelators and organic feedstock in the form of glucose. Iron removal was higher in the presence of the chelators. Bacterial removal of clay and iron minerals exposed the white surfaces of the quartz grains. In situ treatment of 13 t of quartz sand in a fixed-basin container resulted in the bacterial solubilisation of 22 kg of Fe2O3 after 83 days. The products were suitable for use in the glass industry., The content of iron oxides in glass of various grades is strictly regulated, but ultra-fine iron particles and clay minerals which coat quartz grains or are impregnated in silicate matrix are difficult to treat using conventional mineral processing methods. Laboratory tests and in situ experiments were carried out to investigate the use of basin water bioleaching with Bacillus spp. followed by dry electromagnetic separation to improve the quality of quartz sands from the Sastin region of Slovakia. The effect of chelators including EDTA, Na2EDTA, Na4EDTA and NTA on the bacterial dissolution of iron impurities was also studied. The rate of iron dissolution varied with environmental conditions and with the addition of chelators and organic feedstock in the form of glucose. Iron removal was higher in the presence of the chelators. Bacterial removal of clay and iron minerals exposed the white surfaces of the quartz grains. In situ treatment of 13 t of quartz sand in a fixed-basin container resulted in the bacterial solubilisation of 22 kg of Fe2O3 after 83 days. The products were suitable for use in the glass industry.