Thermodynamic properties of autunite, uranyl hydrogen phosphate, and uranyl orthophosphate from solubility and calorimetric measurements.
In this study, we use solubility and drop-solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite, uranyl hydrogen phosphate, and uranyl orthophosphate. Conducting the solubility measurements from both supersaturated and undersaturated conditions and under different pH conditions rigorously demonstrates attainment of equilibrium and yields well-constrained solubility product values. We use the solubility data and the calorimetry data, respectively, to calculate standard-state Gibbs free energies of formation and standard-state enthalpies of formation for these uranyl phosphate phases. Combining these results allows us also to calculate the standard-state entropy of formation for each mineral phase. The results from this study are part of a combined effort to develop reliable and internally consistent thermodynamic data for environmentally relevant uranyl minerals. Data such as these are required to optimize and quantitatively assess the effect of phosphate amendment remediation technologies for uranium contaminated systems.
Department of Civil Engineering and Geological Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, Indiana 46556, USA. dgormanl@u.washington.edu
Drew
D
Gorman-Lewis
Tatiana
T
Shvareva
Karrie-Ann
KA
Kubatko
Peter C
PC
Burns
Dawn M
DM
Wellman
Bruce
B
Mcnamara
Jennifer E S
JE
Szymanowski
Alexandra
A
Navrotsky
Jeremy B
JB
Fein
D002151:Calorimetry; D006358:Hot Temperature; D010710:Phosphates / Q000737:chemistry*; D012995:Solubility; D013816:Thermodynamics; D017974:Uranium Compounds / Q000737:chemistry*; D014875:Water Pollutants, Radioactive / Q000737:chemistry*
D010710:Phosphates; D017974:Uranium Compounds; D014875:Water Pollutants, Radioactive; C075963:hydrogen uranyl phosphate