TY - JOUR
T1 - Structure and thermochemistry of perrhenate sodalite and mixed guest perrhenate/pertechnetate sodalite
AU - Pierce, Eric M.
AU - Lilova, Kristina
AU - Missimer, David M.
AU - Lukens, Wayne W.
AU - Wu, Lili
AU - Fitts, Jeffrey
AU - Rawn, Claudia
AU - Huq, Ashfia
AU - Leonard, Donovan N.
AU - Eskelsen, Jeremy R.
AU - Woodfield, Brian F.
AU - Jantzen, Carol M.
AU - Navrotsky, Alexandra
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/17
Y1 - 2017/1/17
N2 - Treatment and immobilization of technetium-99 (99Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na8[AlSiO4]6(ReO4)2, and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na8[AlSiO4]6(ReO4)2 x(TcO4)x. Perrhenate was used as a chemical analogue for pertechnetate. Bulk analyses of each solid confirm a cubic sodalite-type structure (P43n, No. 218 space group) with rhenium and technetium in the 7+ oxidation state. High-resolution nanometer scale characterization measurements provide first-of-a-kind evidence that the ReO4− anions are distributed in a periodic array in the sample, nanoscale clustering is not observed, and the ReO4− anion occupies the center of the sodalite β-cage in Na8[AlSiO4]6(ReO4)2. We also demonstrate, for the first time, that the TcO4− anion can be incorporated into the sodalite structure. Lastly, thermochemistry measurements for the perrhenate sodalite were used to estimate the thermochemistry of pertechnetate sodalite based on a relationship between ionic potential and the enthalpy and Gibbs free energy of formation for previously measured oxyanion-bearing feldspathoid phases. The results collected in this study suggest that micro- and mesoporous crystalline solids maybe viable candidates for the treatment and immobilization of 99Tc present in reprocessed nuclear waste streams and contaminated subsurface environments.
AB - Treatment and immobilization of technetium-99 (99Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na8[AlSiO4]6(ReO4)2, and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na8[AlSiO4]6(ReO4)2 x(TcO4)x. Perrhenate was used as a chemical analogue for pertechnetate. Bulk analyses of each solid confirm a cubic sodalite-type structure (P43n, No. 218 space group) with rhenium and technetium in the 7+ oxidation state. High-resolution nanometer scale characterization measurements provide first-of-a-kind evidence that the ReO4− anions are distributed in a periodic array in the sample, nanoscale clustering is not observed, and the ReO4− anion occupies the center of the sodalite β-cage in Na8[AlSiO4]6(ReO4)2. We also demonstrate, for the first time, that the TcO4− anion can be incorporated into the sodalite structure. Lastly, thermochemistry measurements for the perrhenate sodalite were used to estimate the thermochemistry of pertechnetate sodalite based on a relationship between ionic potential and the enthalpy and Gibbs free energy of formation for previously measured oxyanion-bearing feldspathoid phases. The results collected in this study suggest that micro- and mesoporous crystalline solids maybe viable candidates for the treatment and immobilization of 99Tc present in reprocessed nuclear waste streams and contaminated subsurface environments.
UR - http://www.scopus.com/inward/record.url?scp=85026904510&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85026904510&partnerID=8YFLogxK
U2 - 10.1021/acs.est.6b01879
DO - 10.1021/acs.est.6b01879
M3 - Article
C2 - 28026187
AN - SCOPUS:85026904510
SN - 0013-936X
VL - 51
SP - 997
EP - 1006
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 2
ER -