Model study of initial adsorption of SO2 on calcite and dolomite
| Autor: | Itai Panas, Oliver Lindqvist, Katarina Malaga-Starzec |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Calcite
Gypsum Diffusion Dolomite Inorganic chemistry Nucleation General Physics and Astronomy Surfaces and Interfaces General Chemistry engineering.material Condensed Matter Physics Surfaces Coatings and Films Matrix (geology) chemistry.chemical_compound Adsorption chemistry engineering Grain boundary |
| Zdroj: | Applied Surface Science. 222:82-88 |
| ISSN: | 0169-4332 |
| DOI: | 10.1016/j.apsusc.2003.08.019 |
| Popis: | The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO2. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO2 catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO3 (s) and dolomite CaxMg1-xCO3 (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic microcrystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO2 diffusion. The subsequent formation of gypsum under such conditions will not require SO42+ (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO2 Coverage. Rather, upon oxidation, SO42+ (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals. |
| Databáze: | OpenAIRE |
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