Title: Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite

Abstract

Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO₂²⁺) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO₂Cl₂ , 0.1 M NaCl). We find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si₄Al₂ rings near aluminum substitution sites.

Authors:

Teich-McGoldrick, Stephanie L. ^[1]; Greathouse, Jeffery A. ^[1]; Cygan, Randall T. ^[1]

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+ Show Author Affiliations

1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geochemistry Department

Publication Date:

Wed Feb 05 00:00:00 EST 2014

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1082222

Report Number(s):

SAND2013-4522J
Journal ID: ISSN 0892-7022; 456021

Grant/Contract Number:  

AC04-94AL85000

Resource Type:

Accepted Manuscript

Journal Name:

Molecular Simulation

Additional Journal Information:

Journal Volume: 40; Journal Issue: 7-9; Related Information: Proposed for publication in Molecular Simulation.; Journal ID: ISSN 0892-7022

Publisher:

Taylor & Francis

Country of Publication:

United States

Language:

English

Subject:

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; mica; uranium; surface charge; electrolyte