Bioremediation process and bioremoval mechanism of heavy metal ions in acidic mine drainage

Acidic mine drainage(AMD) containing acidity and a broad range of heavy metal ions is classified as hazardous, and must be properly treated. The removal mechanism of heavy metal ions in acidic mine drainage containing Cu2+, Fe2+, and Zn2+ with biological method was studied here. Using 20 mmol/L ethanol as carbon source, Desulfovibrio marrakechensis, one of sulfate reducing bacteria(SRB) species, grew best at 35 °C and pH=6.72 with concentrations of 10, 55 and 32 mg/L for Cu2+, Fe2+ and Zn2+, respectively. The removal efficiency for each ion mentioned above was 99.99%, 87.64% and 99.88%, respectively. The mineralogy and surface chemistry of precipitates were studied by means of energy dispersive spectrometer(EDS), X-ray photoelectron spectroscopy(XPS), X-ray diffraction(XRD) combined with control tests. The experimental results demonstrate that the removal mechanism of heavy metal ions by Desulfovibrio marrakechensis is comprehensive function of chemical precipitation, adsorption and bioprecipitation. The biogenic iron sulfide solid was characterized as greigite(Fe3S4), while the zinc sulfide solid was characterized as sphalerite(ZnS).