Graphite-phase carbon nitrides (g-C 3 N 4 ), composed of only C, N, and some impurity H, have been synthesized by direct thermal polymerization of urea in air and employed to capture elemental mercury (Hg 0 ) from simulated flue gas. The performance and kinetic behavior of g-C 3 N 4 toward Hg 0 adsorption are investigated. Its optimal polymerization temperature and ramping rate are 550 °C and 5 K/min, respectively. It shows extraordinary affinity with elemental mercury associated with an Hg 0 removal efficiency >77% at 40−240 °C under a nitrogen atmosphere, which is probably attributed to its unique electronic structure property and fluffy tremella-like morphology with ample exposed adsorption sites. The Hg 0 may be captured on the sp 2 -bonded carbon atoms in g-C 3 N 4 by producing carbon−mercury (C−Hg) covalent bonds via Lewis acid−base interaction. The presence of O 2 slightly reduces the mercury capture efficiency, while the Hg 0 removal efficiency greatly decreases by nearly a half in the presence of H 2 O, NO, and SO 2 , which is plausibly owing to the competitive adsorption or deletion of active sites on the g-C 3 N 4 surface. The process of Hg 0 adsorption on g-C 3 N 4 is controlled by both intraparticle diffusion and chemisorption processes.

No abstract

No abstract

No abstract