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RISS 인기검색어
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- 저자 : Saslow, Sarah (검색결과 2 건)
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Saslow, Sarah A.,Um, Wooyong,Pearce, Carolyn I.,Engelhard, Mark H.,Bowden, Mark E.,Lukens, Wayne,Leavy, Ian I.,Riley, Brian J.,Kim, Dong-Sang,Schweiger, Michael J.,Kruger, Albert A. American Chemical Society 2017 Environmental science & technology Vol.51 No.15
<P>Technetium (Tc) remains a priority remediation concern due to persistent challenges, including mobilization due to rapid reoxidation of immobilized Tc, and competing comingled contaminants, e.g., Cr(VI), that inhibit Tc(VII) reduction and incorporation into stable mineral phases. Here Fe(OH)(2)(s) is investigated as a comprehensive solution for overcoming these challenges, by serving as both the reductant, (Fe(II)), and the immobilization agent to form Tc-incorporated magnetite (Fe3O4). Trace metal analysis suggests removal of Tc(VII) and Cr(VI) from solution occurs simultaneously; however, complete removal and reduction of Cr(VI) is achieved earlier than the removal/reduction of comingled Tc(VII). Bulk oxidation state analysis of the final magnetite solid phase by XANES shows that the majority of Tc is Tc(IV), which is corroborated by XPS measurements. Furthermore, EXAFS results show successful, albeit partial, Tc(IV) incorporation into magnetite octahedral sites. Cr XPS analysis indicates reduction to Cr(III) and the formation of a Cr-incorporated spinel, Cr2O3, and Cr(OH)(3) phases. Spinel (modeled as Fe3O4), goethite (alpha-FeOOH), and feroxyhyte (delta-FeOOH) are detected in all reacted final solid phase samples analyzed by XRD. Incorporation of Tc(IV) has little effect on the spinel lattice structure. Reaction of Fe(OH)(2)(s) in the presence of Cr(III) results in the formation of a spinel phase that is a solid solution between magnetite (Fe3O4) and chromite (FeCr2O4).</P>
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Enhanced <sup>99</sup>Tc retention in glass waste form using Tc(IV)-incorporated Fe minerals
Um, Wooyong,Luksic, Steven A.,Wang, Guohui,Saslow, Sarah,Kim, Dong-Sang,Schweiger, Michael J.,Soderquist, Chuck Z.,Bowden, Mark E.,Lukens, Wayne W.,Kruger, Albert A. Elsevier 2017 JOURNAL OF NUCLEAR MATERIALS Vol.495 No.-
<P><B>Abstract</B></P> <P>Technetium (<SUP>99</SUP>Tc) immobilization by doping into iron oxide mineral phases may alleviate the problems with Tc volatility during vitrification of nuclear waste. Because reduced Tc, Tc(IV), substitutes for Fe(III) in the crystal structure by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation of Fe oxide minerals, two Tc-incorporated Fe minerals (Tc-goethite and Tc-magnetite/maghemite) were prepared and tested for Tc retention in glass melt samples at temperatures between 600 and 1000 °C. After being cooled, the solid glass specimens prepared at different temperatures at 600, 800, and 1000 °C were analyzed for Tc oxidation state using Tc K-edge XANES. In most samples, Tc was partially (<60%) oxidized from Tc(IV) to Tc(VII) as the melt temperature increased up to 600 °C. However, most of Tc(IV) was completely (>95%) oxidized to Tc(VII) at temperature above 800 °C. Tc retention in glass melt samples prepared using Tc-incorporated Fe minerals were slightly higher (∼10%) than in glass prepared using KTcO<SUB>4</SUB> because of limited and delayed Tc volatilization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Reduced Tc(IV) can be incorporated within an Fe oxide mineral structure. </LI> <LI> Tc-incorporated Fe minerals can increase Tc retention in glass waste forms. </LI> <LI> Increased Tc retention in glass can reduce the cost of waste treatment. </LI> </UL> </P>
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