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. 2023 Nov 3;11(11):2702.
doi: 10.3390/microorganisms11112702.

Bioleaching Mercury from Coal with Aspergillus flavus M-3

Wenqing Mao  1 , Juan Mei  1 , Huan He  1 , Cheng Liu  1 , Xiuxiang Tao  1 , Zaixing Huang  2   3
Affiliations

Bioleaching Mercury from Coal with Aspergillus flavus M-3

Wenqing Mao et al. Microorganisms. .

Abstract

This study focuses on the utilization of Aspergillus flavus(M-3) for the bioleaching mercury from coal, offering an alternative and environmentally to its clean utilization. The fungus was isolated from the soil near a high mercury coal mine in Lao Ying Shan (LYS), Guizhou. Utilizing direct mercury analysis, X-ray diffraction (XRD), and Fourier Transform-Infrared (FT-IR) analysis techniques, the transformation of mercury speciation, mineral components, and organic groups in the coal were analyzed before and after the bioleaching process. The findings of the study illustrated that the fungus M-3 exhibited a remarkable capacity for coal bioliquefaction and mercury leaching from LYS coal. Following a 15-day bioleaching process, a remarkable mercury leaching rate of 83.79% was achieved. Various forms of mercury speciation, including residue, organic matter, sulfide-bound, oxide-bound, exchangeable, and carbonate-bound forms, were released from the coal, with leaching rates ranging from 80.41% to 92.60%. XRD analysis indicated that the M-3 strain facilitated the dissolution of coal pyrite and the degradation of macromolecules, effectively loosening the coal structure. FT-IR analysis of raw and residual coal demonstrated the breakdown of the aromatic ring structure and introduced oxygen-containing functional groups by M-3. Overall, this study highlights the efficacy of bioliquefying coal using Aspergillus flavus (M-3) as a method for clean coal utilization while simultaneously bioleaching mercury.

Keywords: bioleaching; bioliquefaction; fungi; mercury; mercury speciation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Bioliquefaction test of raw coal by the isolated strains. (a): M-1, (b): M-2, (c): M-3 (10×), (d): M-4, (e): M-5, (f): M-6, (g): HN-1, (h): HN-2 (10×), (i): HN-3, (j): HN-4, (k): HN-5, (l): HN-6.
Figure 2
Figure 2
Bioleaching rate of mercury by Isolated strains on solid media. Note: Error bars indicate standard deviation, the same below.
Figure 3
Figure 3
Changes in pH (a), ORP (b), Ec (c), and Hg (d) of the culture solution during coal bioliquefaction.
Figure 4
Figure 4
Mercury speciation in coal samples of microbial group (a,c) and control group (b,d).
Figure 5
Figure 5
XRD spectra of raw coal and residual coal before and after bioleaching.
Figure 6
Figure 6
FT-IR spectra of raw and residual coal before and after bioleaching.
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