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Microscopic and spectroscopic investigation of the calcite surface interacted with Hg(II) in aqueous solutions

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Godelitsas, Athanasios and Astilleros García-Monge, José Manuel and Hallam, K.R. and Löns, J. and Putnis, Andrew (2003) Microscopic and spectroscopic investigation of the calcite surface interacted with Hg(II) in aqueous solutions. Mineralogical magazine, 67 (6). pp. 1193-1204. ISSN 0026-461X

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Abstract

The interaction of the {101¯4} cleavage surface of calcite with Hg(CH3COO)2 aqueous solutions with
concentration of 5 mM Hg(II) (pH ≈3.5), was investigated using microscopic and spectroscopic
techniques. In situ atomic force microscopy experiments showed that surface microtopography changes
significantly as a result of the interaction, and that the initial rhombic etch pits induced by H2O
dissolution are rapidly transformed to deeper etch pits exhibiting an unusual triangular shape. The
growth of these etch pits is strongly anisotropic, moving faster along the [22¯1] direction than along the
[010] direction (with step-retreat velocities of ~12 nm s –1 and ~4 nm s–1, respectively). The modified
etch pits are due to Hg(II) sorption in the surface, rather than due to the effect of the acetate anion. The
sorption (adsorption and probably absorption also) of Hg(II), in the first minutes of the interaction, is
shown by X-ray photoelectron spectroscopy. After ~2 h, the triangular etch pits are interconnected to
form larger hexagonal etch pits, while Hg(II)-bearing phases (confirmed later by SEM-EDS) grow onto
the surface through a heterogeneous nucleation process. The crystal growth of orthorhombic
(montroydite-type) hydrated Hg(II) oxide (HgO·nH2O) on the surface of calcite was confirmed by
XRD patterns and FT-IR spectra from samples exposed for longer times to Hg(CH3COO)2 solution.


Item Type:Article
Uncontrolled Keywords:Calcite, Cleavage surfaces, Dissolution, Sorption, Crystal growth, Mercury
Subjects:Sciences > Geology > Crystallography
ID Code:19899
Deposited On:11 Feb 2013 12:43
Last Modified:11 Dec 2018 08:46

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