Recovery of flakey cobalt from aqueous Co(II) with simultaneous hydrogen production in microbial electrolysis cells

Metals removal and recovery in bioelectrochemical systems: A review

“…Co(II) ions leached from LiCoO 2 particles on the cathode of a MFC were reduced to Co(0) on the cathode of a MEC. Operation of the Co(II) reducing MEC was powered by the Co(II) leaching MFC.Therefore, a sequential MFC-MEC (MFC Co(III) -MEC Co(II) ) system was proposed for leaching and recovery of cobalt from spent lithium ion batteries(Huang et al, 2014). A cobalt leaching rate of 46 mg l -1 h -1 was observed in the MFC, while a Co(II) to Co(0) reduction rate of 7 mg l -1 h -1 was achieved in the MEC.…”

“…A rapid removal of cobalt with an efficiency of 92% from 847 µM of Co(II) solution was observed within the first 6 h. Cobalt was removed from the aqueous solution via reductive deposition and formation of flakes of metallic Co crystals on the cathode surface.However, adsorption and diffusion of Co(II) from the cathode chamber to the anode chamber accounted for about 27% Co(II) removal. The microbial community of the anode biofilm in the Co(II) reducing MEC was completely different from that present in the start-up period.Co(II) ingress into the anode chamber could have exerted a selection pressure for the development of a cobalt resistance microbial community(Jiang et al, 2014). This again highlights the importance of ingress of metal ions to the anode compartment and there is a need to link metal ion ingress, structure and function of the microbial community to the fate of metal ions.5.2 Cadmium(II)The standard redox potential of the Cd(II)/Cd(0)couple is -0.40 V. For the reduction of the Cd(II) at the cathode, external voltage was supplied.…”

Microbial electrolysis cells with biocathodes and driven by microbial fuel cells for simultaneous enhanced Co(II) and Cu(II) removal

“…5.0-7.0) is appreciably required to achieve a complete Cu (II) reduction on the cathodes of MFCs and thus avoids the adverse effects of Cu(II) and more acidic pHs on the electrotrophic activities in the connected MECs. In addition and in terms of product purity, the formation of pure copper on the cathodes of MFCs is heavily dependent on an anaerobic environment [2,31,32] whereas cobalt deposited on the biocathodes of MECs may have somewhat been chelating with the cellular surface and thus heavily depends on the characteristics of specific bacteria [3]. Relationship between the bacterial community and the specific mechanism cannot be concluded based on the species level results reported here.…”

“…Moreover, Cu(II) removal rate here was 3.4-38 times of individual MFCs at a similar Cu(II) concentration of 800-1000 mg•L -1 but with various reactor architectures [2,34] whereas the Co(II) Fig. 4 Theoretical cathode potentials for half-reactions of (a) Cu (II) to Cu(I), Cu(II) to Cu and Cu(I) to Cu, and (b) Co(III) to Co(II), Co(III) to Co 3 O 4 and Co(II) to Co, at different pH values removal rate was 2.2 times of individual MECs with biocathodes at similar solution conditions with requirement of an additional energy consumption of 1.6 kWh•kg -1 Co [3]. Compared to the MECs with abiotic cathodes and driven by MFCs under similar solution and reactor conditions [9], Co(II) and Cu(II) removal rates here were 3.3 times and 1.7 times as high as those in the former, demonstrating the more efficiency of the present systems for Cu(II) and Co(II) removals.…”

“…The newly developed bioelectrochemical systems (BESs) show promising for this recovery, where Cu(II) can be spontaneously reduced to Cu(0) on the cathodes of microbial fuel cells (MFCs) due to a favorable half cell redox potential of 0.34 (vs. standard hydrogen electrode, SHE) relative to that of organic matter (ca. -0.30 V for acetate, standard conditions), and Co(II) can be reduced in microbial electrolysis cells (MECs) at a more negative potential of -0.23 V (vs. SHE, standard conditions) [2,3]. Multiple factors including but are not limited to, initial Cu (II) and Co(II) concentrations, temperature, solution conductivity, pH and operation time affect system performance for Cu(II) and Co(II) removal.…”