| Summary: | Bacteria of Bacillus genus from Banská Hodrua ore deposit and from Horná Prievrana kaolin deposit caused a more intensive destruction of silicate minerals by their activity, especially by the metabolites production. Their activity resulted to the development of corrosive and enantiomorphic holes on silicate minerals surface when sulphidic minerals were released and the metals were extracted into solution.The monitoring of Bacillus spp. occurrence in various deposits with silicate minerals composition suggested that these bacteria can be found in several deposits and waste dumps with silicate minerals at Slovakia. The widest species representation was detected in samples from the Horná Prievrana kaolin deposit.The experiments with primary silicates showed either a more intensive destruction of silicate minerals accompanied by sulphides releasing from these minerals or a more intensive metals extraction from sulphidic minerals after ore dressing. The important percentage of precious metals extraction (30% of gold and 30% of argentine) from silicate minerals can suggest a possibility of the regulation of cyanides use in precious metals winning. A process for biological removal of elements from the samples was the result of the cultivation of organic acids - producing strains of the genus Bacillus. Hovewer, these bacteria synthesized also polysaccharides during bioleaching. Extensive acidic mucopolysaccharide films, which entrapped mineral particles, were identified by the ruthenium red staining. Ore bioleaching can not compete with physical and chemical methods in the rapidity of metal extraction from rich ores without ecological criterion. However, biotechnology becomes an alternative way in metals extraction from poor ores or wastes from the economical as well as the ecological view.The laboratory experiments with secondary silicates confirmed various forms of iron binding in kaolins and an important influence of the iron binding form on the Fe releasing during the bacterial leaching of kaolin. The release of the structural element, dissolved Fe from mica, and Fe from oxyhydroxides were used as indicators of the mineral dissolution and beneficiation of kaolin quality in this study report. They confirmed that bacteria of Bacillus genus are capable of a significant (52%) iron removal in different times from kaolin either found as oxyhydroxides or also when it is bound in the mica structure. The significant enrichment by fine-grained fraction as a result of bacterial leaching is important also for the quality improvement of kaolins. These experimental results are important also for a possible development of a new industrial technology of kaolin raw material treatment.Bacteria and fungi interact with clay minerals and synthesize an array of organic compounds that have been shown to affect the mobility of metal ions.
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