Adaptively Evolving Bacterial Communities for Complete and Selective Reduction of Cr(VI), Cu(II), and Cd(II) in Biocathode Bioelectrochemical Systems

Abstract

Bioelectrochemical systems (BESs) have been shown to be useful in removing individual metals from solutions, but effective treatment of electroplating and mining wastewaters requires simultaneous removal of several metals in a single system. To develop multiple-reactor BESs for metals removal, biocathodes were first individually acclimated to three different metals using microbial fuel cells with Cr(VI) or Cu(II) as these metals have relatively high redox potentials, and microbial electrolysis cells for reducing Cd(II) as this metal has a more negative redox potential. The BESs were then acclimated to low concentrations of a mixture of metals, followed by more elevated concentrations. This procedure resulted in complete and selective metal reduction at rates of 1.24 ± 0.01 mg/L-h for Cr(VI), 1.07 ± 0.01 mg/L-h for Cu(II), and 0.98 ± 0.01 mg/L-h for Cd(II). These reduction rates were larger than the no adaptive controls by factors of 2.5 for Cr(VI), 2.9 for Cu(II), and 3.6 for Cd(II). This adaptive procedure produced less diverse microbial communities and changes in the microbial communities at the phylum and genus levels. These results demonstrated that bacterial communities can adaptively evolve to utilize solutions containing mixtures of metals, providing a strategy for remediating wastewaters containing Cr(VI), Cu(II), and Cd(II).

Electricity generation and bivalent copper reduction as a function of operation time and cathode electrode material in microbial fuel cells

“…A SEM (QUANTA450, FEI company, USA) equipped with an EDS (X-MAX 20 mm 2 -50 mm 2 , Oxford Instruments, UK), and XRD (XRD-6000, Shimadzu LabX, Japan) measurements were used to examine the morphologies of the electrodes after Cu(II) reduction, as well as the crystal products. The sample preparation was strictly performed at N 2 atmosphere [22]. The cathode and anode potentials were monitored by a data logger using an automatic data acquisition system (PISO-813, Hongge Co., Taiwan).…”

“…The positive effects of the deposited copper on subsequent Cu(II) reduction and electricity generation, in the MFCs fitted with the CR, TS and SSM cathodes should be investigated in the presence of non-conductive metal deposits such as those from chromium and cadmium [22,33], to determine the most efficient cathode materials in industrial scale MFCs.…”

Impact of Fe(III) as an effective electron-shuttle mediator for enhanced Cr(VI) reduction in microbial fuel cells: Reduction of diffusional resistances and cathode overpotentials

“…However, since the Cr(VI) species (Cr 2 O 7 2-or CrO 4 2-) are electronegative and mutually exclusive against the negatively charged cathodes, the reduction of Cr(VI) and the electrochemical reaction kinetics are usually slow. The development of biocathodes based on the electrotrophic mediation between cathode electrode and Cr(VI) [12][13][15][16][17][18][19] appears to be a promising method for the reduction of Cr(VI) in…”

Continuous flow operation with appropriately adjusting composites in influent for recovery of Cr(VI), Cu(II) and Cd(II) in self-driven MFC–MEC system

“…Various HRTs of 2 h, 4 h and 6 h with different catholyte flow rates were tested for optimal system performance. Metal can be removed in the respective reactor units of MFC-MEC coupled systems [19] whereas a low influent of Cr(VI), Cu(II) and Cd(II) with each of 5 mg L -1 is completely removed in the separated biocathode MFCs or MECs [22]. Based on these considerations together with the aim of complete separation of each metals in the self-driven systems, various composites of either 5 mg L -1 Cr(VI), 1 mg L -1 Cu(II) and 5 mg L -1 Cd(II), or 1 mg L -1 Cr(VI), 5 mg L -1 Cu(II) and 5 mg L -1 Cd(II) in the influent were purposely explored.…”

“…Furthermore, the effluents studied previously still contain concentrations of metals that are too high to be discharged into the environment. Alternatively, despite the complete removal of Cr(VI), Cu(II) and Cd (II) with an mixed influent in biocathode MFCs and MECs, [22] these MFCs and MECs are individually operated, resulting in requirement of not only further collecting and utilizing electricity from the MFCs, but also external voltages to the MECs. Obviously, much effort is still needed to achieve complete removal of Cr(VI), Cu(II) and Cd(II) from mixed metals influent in the self-driven MFC-MEC systems, which is crucial for the scaling-up of this technology for remediating Cr(VI), Cu(II) and Cd(II) co-contaminated sites.…”