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Complexation of carboxylate on smectites surfaces

Abstract

We report a first principles molecular dynamics (FPMD) study of carboxylate complexation on clay surfaces. By taking acetate as a model carboxylate, we investigate its inner-sphere complexes adsorbed on clay edges (including (010) and (110) surfaces) and in interlayer space. The simulations show that acetate forms stable monodentate complexes on edge surfaces and bidentate complex with Ca2+ in interlayer region. The free energy calculations indicate that the complexation on edge surfaces is slightly more stable than in interlayer space. By integrating the pKas and desorption free energies of Al coordinated water calculated previously (Liu et al., 2014; Liu et al., 2012a), the pH dependence of acetate complexation has been revealed. It shows that acetate forms inner-sphere complexes on (110) in a very limited mildly acidic pH range while it can complex on (010) in the whole common pH range. The results in this study form a physical basis for understanding the geochemical processes involving clay-organics interactions.

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Publication details

The article was received on 08 May 2017, accepted on 16 Jun 2017 and first published on 16 Jun 2017


Article type: Paper
DOI: 10.1039/C7CP03019C
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Complexation of carboxylate on smectites surfaces

    X. Liu, X. Lu, Y. Zhang, C. Zhang and R. Wang, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP03019C

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