The shuttling effects and associated mechanisms of different types of iron oxide nanoparticles for Cu(II) reduction by Geobacter sulfurreducens

Publication date: Available online 24 February 2020Source: Journal of Hazardous MaterialsAuthor(s): Hao Qiu, Hang Xu, Zibo Xu, Bing Xia, Willie J.G.M. Peijnenburg, Xinde Cao, Huihui Du, Ling Zhao, Rongliang Qiu, Erkai HeABSTRACTIron oxide nanoparticles (IONPs), commonly occurring in soils, aquifers and subsurface sediments, may serve as important electron shuttles for the biotransformation of coexisting toxic metals. Here, we explored the impact of different IONPs (low-crystallinity goethite and ferrihydrite, high-crystallinity magnetite and hematite) on the reduction of Cu(II) by Geobacter sulfurreducens and the associated electron shuttle mechanisms. All four IONPs tested can function as electron shuttles to enhance long distance electron transfer from bacteria to Cu(II). Upon IONPs addition, the rate of Cu(II) reduction increased from 14.9 to 65.0-83.8% in solution after 7 days of incubation. Formation of both Cu(I) and Cu(0) on the iron oxide nanoparticles was revealed by the X-ray absorption near-edge spectroscopy. The IONPs can be utilized as conduits by bacteria to directly transfer electrons and they can also reversibly accept and donate electrons as batteries through a charging-discharging cycle to transfer electron. The latter mechanism (geo-battery) played an important role in all four types of IONPs while the former one (geo-conductor) can only be found in the magnetite and hematite treatments due to the higher crystallinity. Our results shed new light on the biog...
Source: Journal of Hazardous Materials - Category: Environmental Health Source Type: research