Geological Society of America

T234 Geologic Energy Research (Posters)

Tuesday, 27 September 2016
9:00 AM - 6:30 PM
Exhibit Hall E/F

STRUCTURAL STABILITY AND THERMODYNAMICS OF URANYL VANADATE MINERALS

Paper number: T234-23
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Tyler L. Spano Presenting Author
University of Notre Dame, Notre Dame, IN
Ewa Dzik
University of Notre Dame, Notre Dame, IN
Melika Sharifironizi
Uni of Notre Dame, Notre Dame, IN
Megan K. Dustin
Stanford University, Stanford, CA
Madison Turner
University of Maryland, College Park, MD
Peter C. Burns
University of Notre Dame, Notre Dame, IN

Abstract

Uranyl vanadate minerals are highly insoluble and are widely disseminated in uranium ore deposits and mine and mill tailings in which primary uranium and vanadium minerals are undergoing oxidation. Understanding the crystal chemistry, materials properties, and thermodynamics of uranyl vanadate minerals is an essential step for predicting and controlling the long term environmental behavior of uranium. Delineating crystal chemical changes as related to thermodynamic properties enables prediction of stable structural arrangements. Uranyl vanadate mineral analogues have been synthesized using mild hydrothermal methods. Synthetic uranyl vanadate mineral analogues were investigated using high-temperature drop solution calorimetry. Calculated standard-state enthalpies of formation were found to be -5233.97 ± 14.594, -6028.41 ± 9.36, and -4908.78 ± 12.59 kJ•mol^-1for carnotite (K₂[(UO₂)₂(V₂O₈)]•3H₂O), francevillite (Ba[(UO₂)₂(V₂O₈)]•5H₂O), and curienite (Pb[(UO₂)₂(V₂O₈)]•5H₂O), respectively. Enthalpies of formation from oxides for uranyl vanadate minerals exhibit a positive linear correlation as a function of the acidity of oxides. Overall charge deficiency (OCD) is presented as a quantification of the balance of bond strengths between structural units and interstitial complexes. A negative exponential correlation was observed between OCD and structural stability (enthalpy of formation from oxides) for the studied minerals. Additionally, OCD and oxide acidity exhibit a positive exponential correlation where decreasing oxide acidity results in an exponential decrease in OCD. The number of occurrences of uranyl vanadate mineral species is found to correlate with both enthalpy of formation from oxides and OCD.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-279636

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