Portal de Periódicos da CAPES

Kinetics of Na- and K- uranyl arsenate dissolution

2023; Elsevier BV; Volume: 636; Linguagem: Inglês

10.1016/j.chemgeo.2023.121642

1872-6836

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

Groundwater flow and contamination studies

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, Na0.48H0.52(UO2)(AsO4)(H2O)2.5(s) (NaUAs(s)) and K0.9H0.1(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.