Unburned Carbon from Fly Ash for Mercury Adsorption: II. Adsorption Isotherms and Mechanisms

Adsorption behavior of unburned carbons from fly ash has been investigated in this study. Batch tests and column test were carried out for several unburned carbon samples from various ash sources and processing schemes. Adsorption isotherms have been obtained from these tests. Results show that the unburned carbons have equal or better adsorption capacity for elemental mercury comparing with some general purpose commercial activated carbons at low gas phase mercury concentration that is in the range of power plant emissions. Also it has been found that heat treatment of unburned carbon in the presence of air at 400 C enhanced the adsorption capacity, and the adsorption capacity decreased with the increase of the adsorption temperature. The mechanism of mercury adsorption on the unburned carbon was explained by the physical and chemical interaction between mercury and primary sites on the carbon surface. 80 Z. Li, X. Sun, J. Luo, J. Y. Hwang, and J. C. Crittenden Vol. 1, No.2