Characterization of activated carbon prepared from Aegina pistachio shells for Hg removal

Preparation of activated carbon from agricultural bio-products is a promising way to produce useful adsorbents for Hg removal. In this study Aegina pistachio shells were used as raw materials and the activation was carried out by impregnation with ZnCl2 and heating at 750oC under N2 atmosphere. Three different levels of impregnation ratios (IR) were used for the chemical activation procedure, i.e. IR 1.0, 1.5 and 2.0 grams of ZnCl2 per gram of raw material. Further sulfurization treatment of the chemically activated carbons was also examined as a means to improve the adsorption capacity of activated carbons toward Hg. Overall six different types of activated carbons were produced and characterized regarding their physicochemical properties and their capacity to adsorb mercury. The specific surface area and the pore size distribution were determined by the BET method. The morphology of produced activated carbons was observed by scanning electron microscopy (SEM). The surface chemical characteristics of activated carbons and the mechanisms of Hg retention were investigated using the FT-IR spectroscopic method. Preliminary Hg adsorption experiments indicated that the sulfur modified carbons were much more efficient for the removal of Hg from aqueous streams compared to simple chemically activated carbons.