Model study of initial adsorption of SO2 on calcite and dolomite
Artikel i vetenskaplig tidskrift, 2004

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.

sulphation

sulphite stability

sulphate distribution

calcite

dolomite

Författare

Katarina Malaga-Starzec

Itai Panas

Chalmers, Institutionen för oorganisk miljökemi

Oliver Lindqvist

Chalmers, Institutionen för oorganisk miljökemi

Applied Surface Science

0169-4332 (ISSN)

Vol. 222 82-88

Ämneskategorier

Materialteknik

Annan naturresursteknik

Kemi

DOI

10.1016/j.apsusc.2003.08.019