Abstract— The soil and sediment samples with different content of metals and clay minerals were investigated during bioleaching. The increasing of clay and metal concentrations with decreasing particle size were found both in contaminated soil and sediment. Heterotrophic bioleaching of the iron rich clay fractions from the soil and the sediment were evaluated for his effectiveness in the cycling of iron bound As by consuming organic nutrients. The treatment involved the use of the indigenous bacteria, whose activity was combined with the chelating strength of EDDS, SDS, Na4P2O7 and fertilizers. Heterotrophic bacteria caused decomposition of iron binding deposition as is adsorption on clay with followed dissolving of Fe mainly by the sediment bioleaching. The concentration of iron decreased by precipitation with As sorption after 19 days of sediment bioleaching. The Cu and Zn extraction was inhibited by bioleaching during the iron and arsenic dissolution and precipitation. By contrast, the additives 3mM Cu and 3mM Zn were applied into medium and thus affected the activity of soil resistant heterotrophic bacteria with followed increasing of the iron and arsenic extraction by the soil clay bioleaching. Therefore, this study confirmed the soil and sediment bioleaching in Fe or As releasing efficiency under different conditions regulated by indigenous bacteria. The bioleaching can be a suitable technology for As removal from the untreated soil and sediment by stimulation of the resistant bacteria activity. The separation of clays from the soil and sediment samples did not decreased of toxic element limits because clay and iron minerals coated on coarse silicate particles and the clay fraction is bearers of metals which contaminate the soil and sediment environment.
Keywords— soil, sediment, clay minerals, heavy metals, bioleaching.
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