High rate copper and energy recovery in microbial fuel cells

Abstract

Bioelectrochemical systems (BESs) are a novel, promising technology for the recovery of metals. The prerequisite for upscaling from laboratory to industrial size is that high current and high power densities can be produced. In this study we report the recovery of copper from a copper sulfate stream (2 g L(-1) Cu(2+)) using a laboratory scale BES at high rate. To achieve this, we used a novel cell configuration to reduce the internal voltage losses of the system. At the anode, electroactive microorganisms produce electrons at the surface of an electrode, which generates a stable cell voltage of 485 mV when combined with a cathode where copper is reduced. In this system, a maximum current density of 23 A m(-2) in combination with a power density of 5.5 W m(-2) was produced. XRD analysis confirmed 99% purity in copper of copper deposited onto cathode surface. Analysis of voltage losses showed that at the highest current, most voltage losses occurred at the cathode, and membrane, while anode losses had the lowest contribution to the total voltage loss. These results encourage further development of BESs for bioelectrochemical metal recovery.

Keywords: bioelectrochemical systems; copper; metal recovery; microbial fuel cells.

FIGURE 1

Cell design 3D view with copper electrode (brown), membrane (yellow), spacer (clear blue patterned), graphite felt (black with white dots), and framework (transparent).

FIGURE 2

Evolution of current density (black) and the power density (grey) shown vs. time during the entire range of the experiment. The arrows indicate when resistances were changed.

FIGURE 3

Polarization curve of the copper reducing microbial fuel cell (MFC). The potential is represented vs. current density (black) and the power is shown versus current density (grey).

FIGURE 4

Contribution of the cell components (anode, cathode, and membrane) to the total voltage loss in the system at different external resistors. Also the cell voltage is shown for each external resistor.

FIGURE 5

(A) SEM image of crystalline scaling from cathode side on anion exchange membrane (AEM), (B) SEM image of biofilm on anode side of AEM. (C) SEM image of smooth copper deposited on flat copper surface (D) SEM image of the dendrites formed on cathode surface.