Carbon dioxide, bicarbonate and carbonate ions in aqueous solutions under deep Earth conditions.

Author(s) Dettori, R.; Donadio, D.
Journal Phys Chem Chem Phys
Date Published 2020 Feb 27
Abstract

We investigate the effect of pressure, temperature and acidity on the composition of water-rich carbon-bearing fluids under thermodynamic conditions that correspond to the Earth's deep crust and upper mantle. Our first-principles molecular dynamics simulations provide mechanistic insight into the hydration shell of carbon dioxide, bicarbonate and carbonate ions, and into the pathways of the acid/base reactions that convert these carbon species into one another in aqueous solutions. At temperatures of 1000 K and higher, our simulations can sample the chemical equilibrium of these acid/base reactions, thus allowing us to estimate the chemical composition of diluted carbon dioxide and (bi)carbonate ions as a function of acidity and thermodynamic conditions. We find that, especially at the highest temperature, the acidity of the solution is essential to determine the stability domain of CO2 vs. HCO3- vs. CO32-.

DOI 10.1039/c9cp06904f
ISSN 1463-9084
Citation Phys Chem Chem Phys. 2020.

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