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Crane R.A.,University of New South Wales | Pullin H.,University of Bristol | Macfarlane J.,University of Bristol | Silion M.,National Institute for Metals and Radioactive Resources | And 3 more authors.
Journal of Environmental Engineering (United States) | Year: 2015

In this work, sodium borohydride reduced nanoscale zero-valent iron (nZVI-BR), sodium borohydride reduced nanoscale zero-valent iron-nickel (nZVIN-BR), nanoscale zero-valent iron sourced from NanoIron, s.r.o. (nZVI-Star), and nanoscale zero-valent iron sourced from Toda Kogyo Corporation (nZVI-RNIP) have been tested for the ex situ removal of aqueous uranium (U) from a bicarbonate-rich mine water effluent. Laboratory scale (2 L) batch treatment systems containing the mine water and comparator uranyl solutions were tested to compare U removal efficacy and aqueous corrosion behavior of the different nanopowders. The two commercially sourced nanopowders were also tested for the removal of U from 2,500 L batch systems to determine the nature of any differential behavior exhibited by the nanopowders when deployed at commercial scale. Analysis of aqueous samples taken at periodic intervals throughout the 96 h reaction period using inductively coupled plasma mass spectroscopy recorded >95% aqueous U removal within 15 min by the sodium borohydride reduced nanopowders in all systems studied. Similar behavior was exhibited by the commercially sourced nanopowders for the uranyl-only solutions; however, a maximum of only 30.0 and 43.2% removal was recorded for the 2 L mine water effluent by nZVI-Star and nZVI-RNIP, respectively. Similar U uptake behavior was exhibited by the commercially sourced nanopowders for the 2,500 L batch treatment systems; however, a redox and U removal gradient as a function of depth was recorded, compared to a homogenous distribution recorded for the 2 L experiments. Analysis of reacted nanoparticulate solids using X-ray diffraction determined only minor aqueous corrosion of the two commercial nanopowders whereas near-total conversion to iron (hydr)oxides was recorded for the sodium borohydride reduced nanopowders. Results therefore demonstrate that in order for effective U removal from waters containing appreciable concentrations of complexing agents, highly reactive forms of iron and iron-nickel nanoparticles are required. In addition, the performance of such materials in commercial scale applications is likely to be lower than in laboratory-scale experiments due to the significant technical challenge of homogenous mixing/dispersion of the nanopowder with the aqueous phase. © 2015 American Society of Civil Engineers.

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