Evaluating hexavalent chromium reduction and electricity production in microbial fuel cells with alkaline cathodes

Abstract

The work investigated the efficiency of microbial fuel cells (MFCs) for the treatment of alkaline hexavalent chromium containing wastewater. When lactate was used as the metal chelator in alkaline (pH 8) abiotic cathodes, hexavalent chromium concentration dropped from 10 mg l -1 to undetectable levels within the first 45 h of operation. Power density produced in the pH 8 abiotic cathodes was up to 21.4 mW m -2 , and in the pH 9 cathodes up to 2.4 mW m -2 ; these values were well comparable with other values found in the literature for biologically catalysed cathodes, even at lower pH values. When Shewanella oneidensis MR-1 was present in a hexavalent chromium reducing cathode at pH 8, current production contributed by 26 % to the total hexavalent chromium reduced during the 36 days of operation. On the other hand, when hexavalent chromium (10 mg l -1 ) was controllably added in the anode where S. oneidensis MR-1 was present, up to 73 % of current decreased immediately after every hexavalent chromium addition; this toxic effect remained even after hexavalent chromium was depleted in the anode and strongly indicates that the presence of hexavalent chromium in the anodes of MFCs must be avoided. Overall, our results indicate that alkaline hexavalent chromium wastewater can be effectively remediated in the cathodes of MFCs, provided that a metal chelator is present in the cathodes and that hexavalent chromium is not present in the anodes.

Recent bioreduction of hexavalent chromium in wastewater treatment: A review

“…fuel cells (MFC) are an emerging technology combining microbiologically-catalyzed reduction reaction with a biocathode. AMFC was recently shown to reduce Cr(VI) in an autotrophic environment and simultaneously harvest electricity during the treatment process [171,172]. Biocathode MFCs using electrochemically active microorganisms as catalytic centers at both the anode and cathode show great promise in Cr(VI) bioremediation.…”

Critical review on microbial fuel cells for concomitant reduction of hexavalent chromium and bioelectricity generation

“…However, dissolution of the conductive polymer in repeated batch experiments and precipitation or adsorption of Cr(III) on the electrode surface affected the durability of the system and restricted its application for real time treatment of wastewater. 39 Remediation of alkaline Cr(VI) wastewater was later studied by Xafenias et al 40 because Cr ore processing residues typically have high pH. 41 Cr(VI) reduction took place within 45 h in an alkaline (pH 8) abiotic cathode using lactate as metal chelator, and a power density of 21.4 mW m −2 was produced.…”

Progress Towards Bioelectrochemical Remediation of Hexavalent Chromium

“…Tests with potentiostatically controlled cathodes pointed out an optimal potential range that typically exists for enhancing Cr(VI) reduction performances in biocathodes [95,107]. Theoretically, from Nernst's law, in MFC with a chromium-reducing cathode and acetate-oxidizing bioanode, the open-circuit voltage at pH 7.0 and 25 • C is about 0.68 V, which results in about 0.4 V theoretical cathode potential [90].…”