Mercury capture by distinct fly ash carbon forms

Carbon was separated from the fly ash from a Kentucky power plant using density gradient centrifugation and a lithium heterolpolytungstate high-density media. Relative concentrations of inertinite (up to 77% vol), isotropic carbon (up to 77% vol), and anisotropic carbon (up to 76% vol) were isolated from the original fly ash. Mercury concentration was lowest in the parent fly ash (which contains non-carbon components); followed by inertinite, isotropic coke, mixed isotropic-anisotropic coke fraction, and, with the highest concentration, the anisotropic coke concentrate. The latter order corresponds to the increase in BET surface area of the fly ash carbons. Previous studies have demonstrated the capture of mercury by fly ash carbon. This study confirms prior work demonstrating the varying role of carbon types in the capture, implying that variability in the carbon forms influences the amount of mercury retained on the fly ash.