Transition Metal Recovery Using Manganese-Oxidizing Microbes and Recycled Carpet Fiber

Mining metals for the advancement of society requires innovative and cost-effective remediation strategies that protect the environment and, ideally, allow for concentration and recovery of metals from waste streams. Microbially mediated strategies that remove metals from aqueous waste streams via sorption and/or oxidation-reduction reactions show promise as eco-friendly, cost-effective solutions. Our objective was to use Mn-oxidizing fungi, isolated from the Soudan Underground Mine State Park, MN, a high-salinity, mine-impacted environment, to sequester transition metals Mn, Co, Cu, and Ni. Additionally, we demonstrate the use of recycled carpet fibers to support dense biomass growth and promote rapid Mn(II) oxidation rates, resulting in the formation of Mn(III/IV) oxides. The addition of fibers promoted increases in metal uptake in the presence of 500 μM Mn(II) along with 20 μM Co(II), 20 μM Cu(II), <i>or</i> 20 μM Ni(II) as well as with all metals combined where sequestration increased by as much as 6-fold for Mn and 3-fold for Co, following 10 days of incubation. The system was most effective in removing Co from solution with carpet fibers and Co and Cu without fibers. Recycled carpet fibers enhance the effectiveness of this bioremediation strategy while providing a use for spent carpet fibers or similar waste manufactured fiber materials.