Removal of mercuric chloride from flue gas by sulfur impregnated activated carbon

In this work the attention was focused on the adsorption of mercuric chloride on activated carbon and on Na2S impregnated activated carbon. The study was performed in an apparatus at laboratory scale in which simulated flue gas at a given temperature and HgCl2 concentration flowed through a fixed bed of adsorbent material. The experiments showed that the impregnation process definitely enhances the adsorption capacity of the carbon, and that the higher the temperature the lower the adsorption capacity, with an effect almost independent of the presence of Na2S. A possible interpretation of the experimental results is that impregnation with Na2S facilitates HgCl2 capture by activated carbon, possibly by increasing the concentration of sites available for adsorption. However the heat of adsorption, which was found to be about 25 kJ/mol both for raw and impregnated activated carbon, indicates that the process taking place can be defined as a physical adsorption. The gas-solid equilibrium data were used to evaluate the Langmuir's parameters for the three different materials under investigation, The differential equations modeling the adsorption phenomenon were integrated, leading to the evaluation of a kinetic parameter describing the experimentally determined breakthrough curves.