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Solubility and Thermodynamic Investigation of Meta-Autunite Group Uranyl Arsenate Solids with Monovalent Cations Na and K
Journal article   Peer reviewed

Solubility and Thermodynamic Investigation of Meta-Autunite Group Uranyl Arsenate Solids with Monovalent Cations Na and K

Isabel Meza, Jorge Gonzalez-Estrella, Peter C Burns, Virginia Rodriguez, Carmen A Velasco, Ginger E Sigmon, Jennifer E S Szymanowski, Tori Z Forbes, Lindsey M Applegate, Abdul-Mehdi S Ali, …
Environmental science & technology, Vol.57(1), pp.255-265
01/10/2023
DOI: 10.1021/acs.est.2c06648
PMCID: PMC10039619
PMID: 36525634
url
https://pmc.ncbi.nlm.nih.gov/articles/PMC10039619/pdf/nihms-1884114.pdfView
Open Access

Abstract

We investigated the aqueous solubility and thermodynamic properties of two meta-autunite group uranyl arsenate solids (UAs). The measured solubility products (log ) obtained in dissolution and precipitation experiments at equilibrium pH 2 and 3 for NaUAs and KUAs ranged from -23.50 to -22.96 and -23.87 to -23.38, respectively. The secondary phases (UO )(H AsO ) (H O) and trögerite, (UO ) (AsO ) ·12H O , were identified by powder X-ray diffraction in the reacted solids of KUA precipitation experiments (pH 2) and NaUAs dissolution and precipitation experiments (pH 3), respectively. The identification of these secondary phases in reacted solids suggest that H O co-occurring with Na or K in the interlayer region can influence the solubilities of uranyl arsenate solids. The standard-state enthalpy of formation from the elements (Δ ) of NaUAs is -3025 ± 22 kJ mol and for KUAs is -3000 ± 28 kJ mol derived from measurements by drop solution calorimetry, consistent with values reported in other studies for uranyl phosphate solids. This work provides novel thermodynamic information for reactive transport models to interpret and predict the influence of uranyl arsenate solids on soluble concentrations of U and As in contaminated waters affected by mining legacy and other anthropogenic activities.
thermodynamic solubility interlayer cation uranyl arsenate

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