Bioloužení těžce rozpustných sulfidických rud

Abstract

Within the scope of my master's research, the conditions of the direct interaction process between bacterial cells of Acidithiobacillus ferrooxidans and dispersed particles in suspension were optimized. Subsequent studies expanded the application to new microorganisms. The cooperative action of a mixed bacterial culture comprising Acidithiobacillus ferrooxidans (AF), Acidithiobacillus thiooxidans (AT), and Leptospirillum ferrooxidans (LF) was investigated at a constant temperature of 30 ºC. Fixed parameters for bioleaching were determined: particle size of 71−100 µm, agitation at 150 rpm, suspension density of 10% (w/v), and pH value of 1.8. The effect of enzymatic activity of the thermophilic culture Sulfobacillus thermosulfidooxidans (ST) was examined, with temperature as a differentiating factor, maintained at 50 ºC. System modification involved the addition of AgNO3 at a concentration of 5 mg∙l-1 Ag+ ions. Comparative tests on the enzymatic effects of microorganisms on the kinetics of extraction mechanisms were conducted under purely chemical conditions in H2SO4 medium. Waste materials from adjacent heaps, namely Jezírko ore body, Staré Ransko (SR), Leopoldina adit, Mikulov (LE), and a sample from the Rožná mine, Dolní Rožínka (RO), were used as input components. The solubility of four elements, Cu, Zn, Fe, Pb, and As, was investigated. Significant intensification of the process was demonstrated in coherence with the use of ST microorganisms and the presence of Ag+ ions in liquid phases. In laboratory tests labeled ST/Ag+, the maximum final solubility expressed as a percentage was determined for the SR/Cu (91.93%), SR/Zn (85.67%), SR/As (69.16%), RO/Zn (79.64%), and LE/As (75.19%) experiments. The addition of the additive primarily increased extraction for Cu (SR/AF, AT, LF/Ag+ by 40.33%; SR/ST/Ag+ by 44.39%) and As (SR/AF, AT, LF/Ag+ by 23.79%; SR/ST/Ag+ by 26.08%; LE/AF, AT, LF/Ag+ by 19.48%; LE/ST/Ag+ by 21.90%). Application of thermophilic bacteria ST and maintaining a fixed temperature of 50 ºC enhanced the kinetics of reaction systems, especially for Zn (SR/ST by 18.36%; SR/ST/Ag+ by 14.24%; RO/ST by 22.56%; RO/ST/Ag+ by 25.05%) compared to the suspension with mesophilic species. The crucial enzymatic effect of bacterial cells on the course of extraction mechanisms was demonstrated, as significant metal solubilities were not achieved in an abiotic environment. After completing the experiments, the synthesis of new products, CaSO4·2H2O and KFe3(SO4)2(OH)6, was detected using XRD. The formation of jarosite-type compounds led to maximum Fe solubilities between the 14th and 18th day (SR/ST/Ag+ 86.21%; RO/ST/Ag+ 76.48%), followed by a decline in final extractions. The presence of LF microorganisms, capable of enzymatically transforming Fe3+ ions into lower valence states (Fe2+ ions), was explicitly modeled [1]. Lead was identified as the least extractable metal, with its major concentrations analyzed in solid waste phases after bioleaching.