SORPTION OF ELEMENTAL MERCURY BY ACTIVATED CARBONS

The mechanisms and rate of elemental mercury (He-0) capture by activated carbons have been studied using a bench-scale apparatus. Three types of activated carbons, two of which are thermally activated (PC-100 and FGD) and one with elemental sulfur (S) impregnated in it (HGR), were chosen to study the effects of surface area (approximately 550-1000 m2/g), sorption temperature (23-140-degrees-C), and Hg0 concentration (30 and 60 ppb of Hein nitrogen). Investigations revealed that sorption occurs in active sites in PC-100 and FGD which are either depleted or deactivated upon heat treatment at 140-degrees-C. For HGR, sorption at 23-degrees-C occurred in non-S sites residing in the external surface, and sorption of 140-degrees-C primarily occurred through the reaction of Hg0 and S. Desorption studies for PC-100 and HGR revealed the sorption mechanism to be a combination of physisorption and chemisorption at 23-degrees-C, whereas chemisorption is the primary route at 140-degrees-C.