Theoretical study of different speciation of mercury adsorption on CaO (001) surface

Adsorption Of Mercury and Mercury chloride oil the surface of CaO surface has been investigated by means of density functional theory (DFT) Cluster model calculations. Different embedding clusters (shell models. point charges Cluster and bare cluster) have been compared. The calculation functions and basis used for mercury were optimized to provide the reliable fundamental understanding of gas-solid adsorption system. A small binding energy of -21.47 kJ/mol was found when the elemental mercury molecule is coordinated to the O2- anion, which inferred mercury was weakly physisorbed at the surface of the CaO. HgCl, adsorption is more complex. When the mercury chloride Molecular axis was parallel to the Surface, the Hg atom oriented to the O2- anion and had a large binding energy, which meant that mercury chloride adsorbed on surface of CaO is mainly chemisorption. The present calculations indicated that CaO injection could substantially reducing gaseous mercury chloride, but have 110 apparent effect oil the mercury, which was compatible with the available experimental results. Besides obtaining structures and energies, the temperature effect on adsorption were also studied. The results Suggested that the high temperature has adverse effect on the adsorption when the temperature is above 280 degrees C because of the nature of adsorption. (c) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.