Use of Desulfovibrio and Escherichia coli Pd-nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil

Macaskie, Lynne E.; Humphries, Andrea C.; Mikheenko, Iryna P.; Baxter-Plant, Victoria S.; Deplanche, Kevin; Redwood, Mark D.; Bennett, James A. and Wood, Joe (2012). Use of Desulfovibrio and Escherichia coli Pd-nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil. Journal of Chemical Technology & Biotechnology, 87(10) pp. 1430–1435.

DOI: https://doi.org/10.1002/jctb.3763

Abstract

BACKGROUND: Desulfovibrio spp. biofabricate metallic nanoparticles (e.g. ‘Bio-Pd’) which catalyse the reduction of Cr(VI) to Cr(III) and dehalogenate polychlorinated biphenyls (PCBs). Desulfovibrio spp. are anaerobic and produce H2S, a potent catalyst poison, whereas Escherichia coli can be pre-grown aerobically to high density, has well defined molecular tools, and also makes catalytically-active ‘Bio-Pd’. The first aim was to compare ‘Bio-Pd’ catalysts made by Desulfovibrio spp. and E. coli using suspended and immobilized catalysts. The second aim was to evaluate the potential for Bio-Pd-mediated dehalogenation of PCBs in used transformer oils, which preclude recovery and re-use.

RESULTS: Catalysis via Bio-PdD.desulfuricans and Bio-PdE.coli was compared at a mass loading of Pd:biomass of 1:3 via reduction of Cr(VI) in aqueous solution (immobilized catalyst) and hydrogenolytic release of Cl from PCBs and used transformer oil (catalyst suspensions). In both cases Bio-PdD.desulfuricans outperformed Bio-PdE.coli by ∼3.5-fold, attributable to a ∼3.5-fold difference in their Pd-nanoparticle surface areas determined by magnetic measurements (Bio-PdD.desulfuricans) and by chemisorption analysis (Bio-PdE.coli). Small Pd particles were confirmed on D. desulfuricans and fewer, larger ones on E. coli via electron microscopy. Bio-PdD.desulfuricans-mediated chloride release from used transformer oil (5.6 ± 0.8 µg mL−1) was comparable with that observed using several PCB reference materials.

CONCLUSIONS: At a loading of 1:3 Pd:biomass Bio-PdD.desulfuricans is 3.5-fold more active than Bio-PdE.coli, attributable to the relative catalyst surface areas reflected in the smaller nanoparticle sizes of the former. This study also shows the potential of Bio-PdD.desulfuricans to remediate used transformer oil.

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