Removal of pertechnetate from simulated nuclear waste streams using supported zerovalent iron

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The application of nanoparticles of predominantly zerovalent iron (nanoiron), either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO4-) from complex waste mixtures was investigated as an alternative approach to current waste-processing schemes. Although applicable to pertechnetate-containing waste streams in general, the research discussed here was directed at two specific potential applications at the U.S. Department of Energy's Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste, and (2) the removal of dilute pertechnetate from near-neutral solutions, typical of the eluate streams from commercial organic ion-exchange ... continued below

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Darab, John; Amonette, Alexandra; Burke, Deborah; Orr, Robert; Ponder, Sherman; Schrick, Bettina et al. July 11, 2007.

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The application of nanoparticles of predominantly zerovalent iron (nanoiron), either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO4-) from complex waste mixtures was investigated as an alternative approach to current waste-processing schemes. Although applicable to pertechnetate-containing waste streams in general, the research discussed here was directed at two specific potential applications at the U.S. Department of Energy's Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste, and (2) the removal of dilute pertechnetate from near-neutral solutions, typical of the eluate streams from commercial organic ion-exchange resins that may be used to remediate Hanford tank wastes. It was envisioned that both applications would involve the subsequent encapsulation of the loaded sorbent material into a separate waste form. A high surface area (>200 M2/g) base-stable, nanocrystalline zirconia was used as a support for nanoiron for tests with highly alkaline solutions, while a silica gel support was used for tests with near-neutral solutions. It was shown that after 24 h of contact time, the high surface area zirconia supported nanoiron sorbent removed about 50percent (K-d = 370 L/kg) of the pertechnetate from a pH 14 tank waste simulant containing 0.51 mM TCO4- and large concentrations of Na+, OH-, NO3-, and CO32- for a phase ratio of 360 L simulant per kg of sorbent. It was also shown that after 18 h of contact time, the silica-supported nanoiron removed>95percent pertechnetate from a neutral pH eluate simulant containing 0.076 mM TcO4_ for a phase ratio of 290 L/kg. It was determined that in all cases, nanoiron reduced the Tc(VII) to Tc(IV), or possibly to Tc(V), through a redox reaction. Finally, it was demonstrated that a mixture of 20 mass percent of the solid reaction products obtained from contacting zirconia- supported nanoiron with an alkaline waste solution containing Re(VII), a surrogate for Tc(VII), with 80 mass percent alkali borosilicate based frit heat-treated at 700 degrees C for 4 h sintered into an easily handled glass composite waste form.

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  • Journal Name: Chemistry of Materials; Journal Volume: 19; Journal Issue: 23

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  • Report No.: LBNL-624E
  • Grant Number: DE-AC02-05CH11231
  • DOI: 10.1021/cm0607379 | External Link
  • Office of Scientific & Technical Information Report Number: 941056
  • Archival Resource Key: ark:/67531/metadc897083

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  • July 11, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Sept. 30, 2016, 6:56 p.m.

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Darab, John; Amonette, Alexandra; Burke, Deborah; Orr, Robert; Ponder, Sherman; Schrick, Bettina et al. Removal of pertechnetate from simulated nuclear waste streams using supported zerovalent iron, article, July 11, 2007; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc897083/: accessed August 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.