Thermochemical studies of X(NpO2)(PO4)(H2O)3 (X = K+, Rb+), neptunium analogs of the autunite/meta-autunite group

Lei Zhang; Samuel N. Perry; Jennifer E.S. Szymanowski; Ginger E. Sigmon; Peter C. Burns

doi:10.1016/j.jssc.2020.121373

Thermochemical studies of X(NpO₂)(PO₄)(H₂O)₃ (X = K⁺, Rb⁺), neptunium analogs of the autunite/meta-autunite group

Lei Zhang
, Samuel N. Perry
, Jennifer E.S. Szymanowski
, Ginger E. Sigmon
, Peter C. Burns

Research output: Contribution to journal › Article › peer-review

1 Scopus citations

Abstract

Actinide phosphate materials with autunite or meta-autunite type sheets consisting of vertex-sharing actinyl square bipyramids and phosphate tetrahedra have low aqueous solubility and potential applications for actinide immobilization in the environment. Neptunyl phosphates, X(NpO₂)(PO₄)(H₂O)₃, X = K⁺ and Rb⁺, have been synthesized by hydrothermal reactions and characterized for their structures and purities. Direct thermochemical studies were performed using high temperature oxide melt drop solution calorimetry. After correcting for the presence of residual fluorapatite from the synthesis, the formation enthalpies of K(NpO₂)(PO₄)(H₂O)₃ and Rb(NpO₂)(PO₄)(H₂O)₃ are determined to be −3235 ± 21 kJ/mol and −3270 ± 11 kJ/mol, respectively. The thermodynamic data presented here may be important for understanding neptunium mobility after disposal of nuclear waste in a geological repository.

Original language	English
Article number	121373
Journal	Journal of Solid State Chemistry
Volume	287
DOIs	https://doi.org/10.1016/j.jssc.2020.121373
State	Published - Jul 2020
Externally published	Yes

Funding

This work is supported by the Department of Energy, Basic Energy Sciences, Heavy Elements Program under grant number: DE-FG02-07ER15880 . High-temperature calorimetry data were collected at the Materials Characterization Facility supported by the Center for Sustainable Energy at the University of Notre Dame (ND Energy) .

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@article{e292b3baca4a4c03829ae1e95d852edc,

title = "Thermochemical studies of X(NpO2)(PO4)(H2O)3 (X = K+, Rb+), neptunium analogs of the autunite/meta-autunite group",

abstract = "Actinide phosphate materials with autunite or meta-autunite type sheets consisting of vertex-sharing actinyl square bipyramids and phosphate tetrahedra have low aqueous solubility and potential applications for actinide immobilization in the environment. Neptunyl phosphates, X(NpO2)(PO4)(H2O)3, X = K+ and Rb+, have been synthesized by hydrothermal reactions and characterized for their structures and purities. Direct thermochemical studies were performed using high temperature oxide melt drop solution calorimetry. After correcting for the presence of residual fluorapatite from the synthesis, the formation enthalpies of K(NpO2)(PO4)(H2O)3 and Rb(NpO2)(PO4)(H2O)3 are determined to be −3235 ± 21 kJ/mol and −3270 ± 11 kJ/mol, respectively. The thermodynamic data presented here may be important for understanding neptunium mobility after disposal of nuclear waste in a geological repository.",

author = "Lei Zhang and Perry, \{Samuel N.\} and Szymanowski, \{Jennifer E.S.\} and Sigmon, \{Ginger E.\} and Burns, \{Peter C.\}",

note = "Publisher Copyright: {\textcopyright} 2020 Elsevier Inc.",

year = "2020",

month = jul,

doi = "10.1016/j.jssc.2020.121373",

language = "English",

volume = "287",

journal = "Journal of Solid State Chemistry",

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T1 - Thermochemical studies of X(NpO2)(PO4)(H2O)3 (X = K+, Rb+), neptunium analogs of the autunite/meta-autunite group

AU - Zhang, Lei

AU - Perry, Samuel N.

AU - Szymanowski, Jennifer E.S.

AU - Sigmon, Ginger E.

AU - Burns, Peter C.

PY - 2020/7

Y1 - 2020/7

N2 - Actinide phosphate materials with autunite or meta-autunite type sheets consisting of vertex-sharing actinyl square bipyramids and phosphate tetrahedra have low aqueous solubility and potential applications for actinide immobilization in the environment. Neptunyl phosphates, X(NpO2)(PO4)(H2O)3, X = K+ and Rb+, have been synthesized by hydrothermal reactions and characterized for their structures and purities. Direct thermochemical studies were performed using high temperature oxide melt drop solution calorimetry. After correcting for the presence of residual fluorapatite from the synthesis, the formation enthalpies of K(NpO2)(PO4)(H2O)3 and Rb(NpO2)(PO4)(H2O)3 are determined to be −3235 ± 21 kJ/mol and −3270 ± 11 kJ/mol, respectively. The thermodynamic data presented here may be important for understanding neptunium mobility after disposal of nuclear waste in a geological repository.

AB - Actinide phosphate materials with autunite or meta-autunite type sheets consisting of vertex-sharing actinyl square bipyramids and phosphate tetrahedra have low aqueous solubility and potential applications for actinide immobilization in the environment. Neptunyl phosphates, X(NpO2)(PO4)(H2O)3, X = K+ and Rb+, have been synthesized by hydrothermal reactions and characterized for their structures and purities. Direct thermochemical studies were performed using high temperature oxide melt drop solution calorimetry. After correcting for the presence of residual fluorapatite from the synthesis, the formation enthalpies of K(NpO2)(PO4)(H2O)3 and Rb(NpO2)(PO4)(H2O)3 are determined to be −3235 ± 21 kJ/mol and −3270 ± 11 kJ/mol, respectively. The thermodynamic data presented here may be important for understanding neptunium mobility after disposal of nuclear waste in a geological repository.

UR - https://www.scopus.com/pages/publications/85083075573

U2 - 10.1016/j.jssc.2020.121373

DO - 10.1016/j.jssc.2020.121373

M3 - Article

AN - SCOPUS:85083075573

SN - 0022-4596

VL - 287

JO - Journal of Solid State Chemistry

JF - Journal of Solid State Chemistry

M1 - 121373

ER -

Thermochemical studies of X(NpO₂)(PO₄)(H₂O)₃ (X = K⁺, Rb⁺), neptunium analogs of the autunite/meta-autunite group

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