Structure, dynamics and stability of water/scCO₂/mineral interfaces from ab initio molecular dynamics simulations

Journal Article · Mon Oct 12 00:00:00 EDT 2015 · Scientific Reports

DOI:https://doi.org/10.1038/srep14857· OSTI ID:1225145

Lee, Mal -Soon ^[1]; Peter McGrail, B. ^[1]; Rousseau, Roger ^[1]; Glezakou, Vassiliki -Alexandra ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Here, the interface between a solid and a complex multi-component liquid forms a unique reaction environment whose structure and composition can significantly deviate from either bulk or liquid phase and is poorly understood due the innate difficulty to obtain molecular level information. Feldspar minerals, as typified by the Ca-end member Anorthite, serve as prototypical model systems to assess the reactivity and ion mobility at solid/water-bearing supercritical fluid (WBSF) interfaces due to recent X-ray based measurements that provide information on water-film formation, and cation vacancies at these surfaces. Using density functional theory based molecular dynamics, which allows the evaluation of reactivity and condensed phase dynamics on equal footing, we report on the structure and dynamics of water nucleation and surface aggregation, carbonation and Ca mobilization under geologic carbon sequestration scenarios (T = 323 K and P = 90 bar). We find that water has a strong enthalpic preference for aggregation on a Ca-rich, O-terminated anorthite (001) surface, but entropy strongly hinders the film formation at very low water concentrations. Carbonation reactions readily occur at electron-rich terminal Oxygen sites adjacent to cation vacancies, when in contact with supercritical CO₂. Cation vacancies of this type can form readily in the presence of a water layer that allows for facile and enthalpicly favorable Ca²⁺ extraction and solvation. Apart from providing unprecedented molecular level detail of a complex three component (mineral, water and scCO₂) system), this work highlights the ability of modern capabilities of AIMD methods to begin to qualitatively and quantitatively address structure and reactivity at solid-liquid interfaces of high chemical complexity. This work was supported by the US Department of Energy, Office of Fossil Energy (M.-S. L., B. P. M. and V.-A. G.) and the Office of Basic Energy Science, Division of Chemical Sciences, Geosciences and Biosciences (R.R.), and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle. Computational resources were provided by PNNL’s Platform for Institutional Computing (PIC), the W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL and the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1225145
• Report Number(s): PNNL-SA-105852; srep14857
• Journal Information: Scientific Reports, Vol. 5; ISSN 2045-2322
• Publisher: Nature Publishing Group
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
plagioclase
anorthite
AIMD
solid-liquid interface
liquid-liquid interface supercritical CO2