Synthetic zeolites as potential sorbents of mercury from wastewater occurring during wet FGD processes of flue gas

Abstract

This paper evaluates the suitability of fly ash-derived zeolites as sorbents of mercury in water and wastewater. The tested materials were type X and type A synthetic zeolites obtained by hydrothermal synthesis of Class F fly ash. Silver-modified type X fly ash-derived zeolites were also used to check the need for structural modification. The commercial products 4A and 13X zeolites were used as reference materials. Mercury sorption experiments were carried out under static conditions in an artificial solution with an Hg concentration in the range of 13.20–575 mg dm−3. In each case, the sorption efficiency was achieved at a level of above 90%. A second experiment involved the removal of mercury from real wastewater using the wet desulphurization process for flue gas. The results for the tested samples show extremely high sorption efficiency at a level of 99%. Based on these results, it can be stated that fly ash-derived zeolites have similar sorption properties to commercial products in terms of their used as mercury sorbents for liquid waste and are therefore a cost-effective substitute for commercially available products. The X and A types of the zeolite structure were found to remove mercury at a similar level.