Biotreatment of heavy metals in acid mine drainage (AMD) with sulfate-reducing bacteria (SRB) is considered the most promising technique in the ecological restoration of mines. In the present work, the authors evaluated the ability of bioprocessing acidic water ($\mathrm{pH}=6.0$ ) containing different concentrations of ${\mathrm{Mn}}^{2+}$ (ranging from 1.0 to $\sim 102.28\mathrm{mg}/\mathrm{L}$ ) and ${\mathrm{Pb}}^{2+}$ (ranging from 1.0 to $\sim 11.6\mathrm{mg}/\mathrm{L}$ ) and coexisting with sulfate ($0.8–1.1\mathrm{g}/\mathrm{L}$ ) with a native SRB Desulfuromonas alkenivorans S-7 obtained from a coal gangue dump. Furthermore, the organic functional groups and sulfur components involved in the bioprocess mediated with SRB were investigated with Fourier transform infrared spectroscopy (FT-IR) and detailed in a Peakfit analysis. The results showed that the S-7 strain could remove 93.1% ${\mathrm{Mn}}^{2+}$ and 90.0% ${\mathrm{Pb}}^{2+}$ from acid mine drainage after 7 days’ culture, respectively. Three clear stages of biotreatment of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ were identified as initial rapid precipitation, subsequent absorption, and a final equilibrium state. The removal of heavy metals included chemical precipitation and biosorption. FT-IR spectroscopy results showed that the OH, ${\mathrm{NH}}_2$ , $\mathrm{C}═\mathrm{O}$ , and amide group might play an important role in the absorption of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ by extracellular polymeric substances. Furthermore, the intermediate sulfite products of the sulfate-reducing process were also identified in the cell samples. The present study proves that biotreatment of heavy metals with a native SRB S-7 is possible, and thus provides potential information for its future application in the ecological restoration of coal gangue dumps.

A mixed culture of A. ferrooxidans and A. thiooxidans isolated from a coal gangue dump was used to bioleach coal gangue in a column reactor to investigate the leaching of elements. The changes of metal ions (Fe, Mn and Cr) and sulfate in the leaching solution, elemental composition, mineral components and sulfur speciation of the coal gangue before and after bioleaching were analyzed by atomic absorption, anion chromatography, XRF, XRD and XPS. The results show that the mixed culture could promote the release of metal ions in coal gangue, with a leaching concentration of Fe > Mn > Cr. EC and Eh have significantly increased with the increase of metal ion concentrations in the leaching solution. XRF analyses show that the contents of Fe, Mn and S decreased in coal gangue after bioleaching. XRD results suggest that the bioleaching has impacts on minerals in coal gangue, particularly the Fe-containing components. XPS analyses show that sulfur speciation in the raw gangue samples was associated with sulfate, dibenzothiophene and pyrite sulfur. After continuous leaching by the mixed culture, the total sulfur, pyrite sulfur and sulfate sulfur in coal gangue decreased from 2.06% to 1.18%, 0.66% to 0.14% and 1.02% to 0.52%. The desulfurization rates of the pyrite and sulfate were 78.79% and 49.02 %. It is concluded that the mixed culture of these two microorganisms could effectively leach metals from coal gangue coupling with the oxidation of sulfide to sulfate. This study has provided fundamental information as a potential application in the recovery of valuable metals from coal gangue or environmental remediation related to gangue in the future.