Kinetics of Na- and K- uranyl arsenate dissolution

Isabel Meza; Noah Jemison; Jorge Gonzalez-Estrella; Peter C Burns; Virginia Rodriguez; Ginger E Sigmon; Jennifer E S Szymanowski; Abdul-Mehdi S Ali; Kaelin Gagnon; José M Cerrato; Peter Lichtner

doi:10.1016/j.chemgeo.2023.121642

Kinetics of Na- and K- uranyl arsenate dissolution

Chem Geol. 2023 Oct 5:636:121642. doi: 10.1016/j.chemgeo.2023.121642. Epub 2023 Jul 26.

Authors

Isabel Meza^{1

2}, Noah Jemison^{1

2}, Jorge Gonzalez-Estrella³, Peter C Burns⁴, Virginia Rodriguez⁴, Ginger E Sigmon⁴, Jennifer E S Szymanowski⁴, Abdul-Mehdi S Ali⁵, Kaelin Gagnon^{1

2}, José M Cerrato^{1

2}, Peter Lichtner²

Affiliations

¹ Department of Civil, Construction & Environmental Engineering, MSC01 1070, University of New Mexico, Albuquerque, New Mexico 87131, USA.
² Center for Water and the Environment, UNM, Albuquerque, NM, USA.
³ School of Civil and Environmental Engineering, College of Engineering, Architecture, and Technology, Oklahoma State University, Stillwater, Oklahoma, USA.
⁴ Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
⁵ Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, New Mexico 87131, USA.

Abstract

We integrated aqueous chemistry analyses with geochemical modeling to determine the kinetics of the dissolution of Na and K uranyl arsenate solids (UAs_(s)) at acidic pH. Improving our understanding of how UAs_(s) dissolve is essential to predict transport of U and As, such as in acid mine drainage. At pH 2, Na_0.48H_0.52(UO₂)(AsO₄)(H₂O)_2.5(s) (NaUAs_(s)) and K_0.9H_0.1(UO₂)(AsO₄)(H₂O)_2.5(s) (KUAs_(s)) both dissolve with a rate constant of 3.2 × 10^-7 mol m^-2 s^-1, which is faster than analogous uranyl phosphate solids. At pH 3, NaUAs_(s) (6.3 × 10^-8 mol m^-2 s^-1) and KUAs_(s) (2.0 × 10^-8 mol m^-2 s^-1) have smaller rate constants. Steady-state aqueous concentrations of U and As are similarly reached within the first several hours of reaction progress. This study provides dissolution rate constants for UAs_(s), which may be integrated into reactive transport models for risk assessment and remediation of U and As contaminated waters.

Keywords: geochemical modeling; rate constants; reaction kinetics; solubility; uranyl arsenate.

Grants and funding

P42 ES025589/ES/NIEHS NIH HHS/United States