Biotreatment of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ with Sulfate-Reducing Bacterium Desulfuromonas alkenivorans S-7

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.