Development of O2 and NO Co-Doped Porous Carbon as a High-Capacity Mercury Sorbent

Abstract

In this study, a novel Hg0 adsorption strategy based on nonthermal plasma and porous carbon was proposed and tested. The O2 and NO in flue gas were used to activate porous carbon with auxiliary plasma. The plasma significantly increased the functionalities on the carbon surface, and it has a negligible effect on the textural properties of porous carbon. The O2/NO co-doped porous carbon was used to remove elemental mercury (Hg0). The sample functionalized by plasma in 4% O2 and 200 ppm NO (balanced with N2) for 3 min exhibited superior Hg0 adsorption ability, which could be assigned to the formation of a large amount of C═O, C-NO, and C-NO2. O2, NO, and HCl have a positive effect on Hg0 adsorption, whereas SO2 and H2O have an inhibitory effect on Hg0 removal. The equilibrium Hg0 adsorption capacity of optimal O2/NO co-doped porous carbon was found to be 12315 μg/g, which was far greater than that of brominated activated carbon (1061 μg/g). Density functional theory was used to investigate the mechanism responsible for Hg0 adsorption. C═O and C-NO improved the interaction of Hg0 with neighboring carbon sites. C-NO2 could react with Hg0 by forming HgO.