Abstract
The current study investigates the characteristics of arsenic precipitation during the bioleaching of realgar. The bioleaching performance of Acidithiobacillus ferrooxidans BY-3 (A. ferrooxidans) was investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectrophotometry. SEM and XRD analyses revealed that the arsenic-adapted strain of A. ferrooxidans was more hydrophobic and showed higher attachment efficiency to realgar compared with the wild strain. The arsenic precipitation using A. ferrooxidans resulted in the precipitation of an arsenic-rich compound on the surface of the bacterial cell, as shown in the TEM images. The FT-IR spectra suggested that the −OH and −NH groups were closely involved in the biosorption process. The observations above strongly suggest that the cell surface of A. ferrooxidans plays a role in the induction of arsenic tolerance during the bioleaching of realgar.
Highlights
Realgar, which has a chemical formula of α-As4S4, is a sulfide mineral with high arsenic content and has been widely used as a traditional Chinese herbal medicine [1]
The cell adhesion caused by the interactions of minerals with A. ferrooxidans BY-3 has been shown to induce either the hydrophilicity or the hydrophobicity of the minerals and render them floatable or nonfloatable, respectively [14], which is consistent with the results of the current study
The precipitation of jarosite was visually observed in the process, and the scanning electron microscopy (SEM) and X-ray diffraction (XRD) solid residue patterns confirmed the presence of jarosites
Summary
Realgar, which has a chemical formula of α-As4S4, is a sulfide mineral with high arsenic content (over 90% As4S4) and has been widely used as a traditional Chinese herbal medicine [1]. Our group previously succeeded in developing a bio-arsenic aqueous solution from realgar particles by taking advantage of an arsenicresistant indigenous strain of A. ferrooxidans BY-3 using the bioleaching method and confirmed the anticancer activities of the developed bioarsenic aqueous solution in vitro and in vivo [3]. A high concentration of arsenic in the leaching solution could inhibit bacterial growth and activity, which have negative effects on realgar bioleaching. The decrease in arsenic concentration may be attributed to the arsenic adsorption and/or precipitation. Little is known about the arsenic adsorption and/or precipitation in the bioleaching of realgar
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