HAZARDOUS WASTE & HAZARDOUS MATERIALS Volume 13, Number 1, 1996 Mary Ann Liebert, Inc. Removal of Mercuric Chloride from Flue Gas by Sulfur Impregnated Activated Carbon DESPINA KARATZA,1 AMEDEO LANCIA,2 DIÑO MUSMARRA,1 FRANCESCO PEPE,3 and GENNARO VOLPICELLI2 'istituto di Recerche sulla Combustione C.N.R. Pie Tecchio 80 80125 Napoli, Italy ~Dipartimento di Ingegneria Chimica Université di Napoli "Federico II" Pie Tecchio 80 80125 Napoli, Italy 3FacoItà di Scienze Ambientali Seconda Università di Napoli Via Arena 22 81100 Casería, Italy ABSTRACT 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. INTRODUCTION Atmospheric emissions of mercury due to the combustion of fossil fuels or to the incineration of municipal solid wastes (MSW) have to be controlled. Anthropic mercury emissions add to the background levels of this metal both in the atmosphere and in the superficial water. Indeed, such emissions are continuously growing, and reached the value of about 3500 ton/year at the beginning of the decade [1]: such amount is greater than that originated by natural emissions, which has been estimated at about 2500 ton/year. In the last ten to fifteen years the need of keeping under control mercury emissions into the atmosphere has become the object of a great deal of attention, both for regulatory agencies worldwide and for the scientific community. The European Union has set a limit of 50 ¿ig/Nm3 (based on 11% oxygen) for mercury emissions from MSW incinerators. In the United States 95