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Structure and Stability of Uranium Containing Garnets

Structure and Stability of Uranium Containing Garnets. X. Guo 1,2 , A. Navrotsky 1 , R. K. Kukkadapu 3 , M. H. Engelhard 3 , A. Lanzirotti 4 , M. Newville 4 , E. S. Ilton 3 , S. R. Sutton 4,5 , and H. Xu 2

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Structure and Stability of Uranium Containing Garnets

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  1. Structure and Stability of Uranium Containing Garnets X. Guo1,2, A. Navrotsky1, R. K. Kukkadapu3, M. H. Engelhard3, A. Lanzirotti4, M. Newville4, E. S. Ilton3, S. R. Sutton4,5, and H. Xu2 1Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California, Davis, 2Earth & Environmental Sciences Division, Los Alamos National Laboratory, 3Pacific Northwest National Laboratory, 4Center for Advanced Radiation Sources, University of Chicago, 5Department of Geophysical Sciences, University of Chicago LA-UR-15-28481

  2. Incorporate actinides of various valences Physical, chemical, and thermodynamic stability Leaching resistance in aqueous environments Integrity under radiation damage Mineral Prototypes and Nuclear Waste Form Criteria Pyrochlore, St Lawrence Columbium Mine, Oka Complex, Oka, Deux-Montagnes RCM, Laurentides, Quebec, Canada – Collected 2007, Donald Doell Monazite: Shinkolobwe Mine, Shinkolobwe, Katanga Copper Crescent, Katanga, Democratic Republic of Congo – Paaul De Bondt Zircon: Poudrette quarry, Mont Saint-Hilaire, La Vallee-du-Richelieu RCM, monteregie, Quebec, Canada Brannerite: El’konskoe U deposit, El’konskii Gorst, Aldan, Aldan Shield, Sakha Republic, Eastern-Siberian Region, Russia – Pavel M. Kartashov Garnet, Elbrusite-(Zr): Lakargi Mt., Verkhnechegemskaya caldera, Kabardino-Balkarian Republic, Northern Caucasus Region, Russia – Evgeny Galuskin

  3. YIG, Ce/Th incorporated3-5 U:YIG synthesis Garnet Structure XdIV Advantages: • Sites A and B have high affinity for lanthanides or actinides • Irradiation response irrelevant to chemical composition, and comparable to zircon1 • Natural radioactive garnet: Elbursite-(Zr)2, Ca3(U6+Zr)(Fe3+2Fe2+)O12 Previous work at UC Davis: BaVI AcVIII • J. M. Zhang, T. S. Livshits, A. A. Lizin, Q. N. Hu and R. C. Ewing, J Nucl Mater, 2010, 407, 137-142 • I. O. Galuskina, E. V. Galuskin, T. Armbruster, B. Lazic, J. Kusz, P. Dzierzanowski, V. M. Gazeev, N. N. Pertsev, K. Prusik, A. E. Zadov, A. Winiarski, R. Wrzalik and A. G. Gurbanov, Am. Mineral., 2010, 95, 1172-1181. • X. Guo, A. H. Tavakoli, S. Sutton, R. K. Kukkadapu, L. Qi, A. Lanzirotti, M. Newville, M. Asta and A. Navrotsky, Chem Mater, 2014, 26, 1133-1143. • X. Guo, Z. Rak, A. H. Tavakoli, U. Becker, R. C. Ewing and A. Navrotsky, Journal of Materials Chemistry A, 2014, 2, 16945-16954. • X. Guo, R. K. Kukkadapu, A. Lanzirotti, M. Newville, M. H. Engelhard, S. R. Sutton and A. Navrotsky, Inorg Chem, 2015, 54, 4156-4166.

  4. Design of Uranium Containing Garnets (Ca3)Zr2(Fe2Si)O12 (Ca3)(Zr2-xUx)Fe3O12 XdIV: [FeO4] X0 (kerimasit) X5, X6, and X7 BaVI: [UO6] [ZrO6] AcVIII: [CaO8]

  5. Synthesis (Ca3)Zr2(Fe2Si)O12 (Ca3)(Zr2-xUx)Fe3O12 Solid state synthesis Citrate-nitrate combustion method Ca(NO3)3·4H2O + ZrO(NO3)2·yH2O + UO2(NO3)2·6H2O + Fe(NO3)3·9H2O CaCO3 + ZrO2 + SiO2 + Fe2O3 Citric acid monohydrate Mixed in agate mortar for 1 hr Stirred and dried at ~90 C Gels burnt at 350 C, 2hrs pelletized pelletized Calcined at 1250 C, 24 hrs Calcined at 1250 C, 24 hrs

  6. X-ray Diffraction Zr4+ and U6+↔ U5+/6+ Fe3+ ↔ Fe2+ (Ca3)(Zr2-xUx)Fe3O12 Zr4+ ↔ U6+ Si4+ ↔ Fe3+ (Ca3)Zr2(Fe2Si)O12

  7. X-ray Photoelectron Spectroscopy x 102 U(VI)2 381.3 eV Sample x = 0.5 U(VI)2 381.4 eV U(VI)2 381.4 eV 55 45 50 U 4f7/2 U 4f7/2 U 4f7/2 U 4f5/2 U 4f5/2 50 U 4f5/2 45 40 45 40 35 40 Counts per second 35 35 30 U(V) 379.9 eV U(V) 380.0 eV U(VI)1 382.3 eV U(VI)1 382.3 eV 30 U(VI)1 382.5 eV 30 U(V) 379.9 eV 25 25 25 20 20 20 400 396 392 388 384 380 376 400 396 392 388 384 380 376 400 396 392 388 384 380 376 Binding Energy (eV) x 102 x 102 Sample x = 0.7 Sample x = 0.6 Counts per second Counts per second Binding Energy (eV) Binding Energy (eV)

  8. Synchrotron X-ray Absorption Spectroscopy U LIII XANES spectra U5+ and U6+ standard (~ 0.8 ~ 2.0 eV)* 17196.7 eV 17170.4 eV 17169.5 eV 17169.5 eV Coordination number 5.8 ~ 5.9 ± 0.2 * Soldatov, A. V.; Lamoen, D.; Konstantinovic, M. J.; Van, d. B. S.; Scheinost, A. C.; Verwerft, M. J. Solid State Chem.2007, 180, 54. Kelly, S. D.; Kemner, K. M.; Carley, J.; Criddle, C.; Jardine, P. M.; Marsh, T. L.; Phillips, D.; Watson, D.; Wu, W. M. Environ. Sci. Technol.2008, 42, 1558. Belai, N.; Frisch, M.; Ilton, E. S.; Ravel, B.; Cahill, C. L. Inorg. Chem.2008, 47, 10135. Kosog, B.; La Pierre, H. S.; Denecke, M. A.; Heinemann, F. W.; Meyert, K. Inorg. Chem.2012, 51, 7940

  9. No Fe2+ presence Distorted tetrahedral Fe sub-lattice in U substituted garnets Mössbauer Spectroscopy x = 0.5, Ca3(U6+0.5Zr1.5)VI(Fe3+3)IVO12 x = 0.6, Ca3(U6+0.4U5+0.2Zr1.4)VI(Fe3+3)IVO12 x = 0.7,Ca3(U6+0.3U5+0.4Zr1.3)VI(Fe3+3)IVO12

  10. High-T Oxide-Melt Calorimeter lead borate Pt-PtRh Drop solution calorimetry (enthalpy of drop solution): Hds = HC + Hs Navrotsky 1997

  11. Derivation of enthalpies of formation from binary oxides RT, solid 700 C, solution 3 CaO(s,25 C) → (2-x) ZrO2(s,25 C)→ xg-UO3(s,25 C)→ 3/2 Fe2O3(s,25 C)→ S solution Final state 1 (Ca3)(Zr2-xUx)Fe3O12(s,25°C) → S solution Final state 2 3 CaO(s,25 C) +(2-x) ZrO2(s,25 C) + xg-UO3(s,25 C) + 3/2 Fe2O3(s,25 C) → Ca3(UxZr2-x)Fe3O12(s,25C) Navrotsky 1997

  12. Phase Stability Oxidative reaction (RT): Ca3Zr2SiFe2O12(s,25 C) + xg-UO3(s,25 C) + 1/2 Fe2O3(s,25 C) → Ca3(UxZr2-x)Fe3O12(s,25 C) + x ZrO2(s,25 C) + SiO2(s,25 C) + (2x – 1)/4 O2(g, 25 C) 45.6 ~ 82.0 kJ/mol NOT stable Reducing associated-mineral environment (RT): Ca3Zr2SiFe2O12(s,25 C) + xg-UO3(s,25 C) + FeO(s,25 C) + (1 - x)/2 O2(g, 25 C) → Ca3(UxZr2-x)Fe3O12(s,25 C) + x ZrO2(s,25 C) + SiO2(s,25 C) -99.2 ~ -65.3 kJ/mol Very stable Phase formation condition (T ~ 800 – 1000 C): Ca3Zr2SiFe2O12(s, T) + x/3 U3O8(s,T) + 1/2 Fe2O3(s,T) + (1/4 – x/3) O2(g, T) → Ca3(UxZr2-x)Fe3O12(s,T) + x ZrO2(s,T) + SiO2(s,T) x = 0.5, 32.0 ± 5.3 kJ/mol x = 0.6, 11.5 ± 5.2 kJ/mol x = 0.7, -19.7 ± 5.3 kJ/mol DG800 Csub = -28.4 ± 5.3 kJ/mol

  13. Implications for Waste Form Applications Substitution reaction: Ca3(UxZr2-x)Fe3O12(s,25 C) + (x’ – x) g-UO3(s,25 C) → Ca3(Ux’Zr2-x’)Fe3O12(s,25 C) + (x’ – x) ZrO2(s,25 C) + (x’ – x)/2 O2(g, 25 C) Implications: Once Ca3(UxZr2-x)Fe3O12 with a higher U content forms, the phase will remain stable and will unlikely decompose into U(VI) oxide phases, which are soluble in aqueous environments. Credit: U.S. Geological Survey Hawaii Volcano Observatory

  14. Conclusions • Structure: • The garnet structure can incorporate U up to 70 mol % (22 wt. %) • U5+ emerges when U content increases in garnet • Stability: • All garnet phases are stable with respect to their binary constituent oxides • U can be stably accommodated in garnet structure under certain geological conditions • Garnets with high U contents tend to be more robust in the long term in nature

  15. Acknowledgments Dr. Alexandra Navrotsky Dr. Amir H. Tavakoli All of my graduate research group members Dr. Hongwu Xu at LANL This work is supported by the Office of Basic Energy Sciences of the U.S. Dept of Energy as part of the Materials Science of Actinides Energy Frontier Research Center (DE-SC0001089).

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  17. Blank Page 2: Previous research on YIG garnet (Y3-xCe/Thx)Fe2Fe3O12 XdIV: [FeO4] (Y3-xCa0.5xCe/Th0.5x)Fe2Fe3O12 AcVIII: [YO8] [CeO8] [ThO8] [CaO8] BaVI: [FeO6]

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