Studies on Mercury Adsorption Species and Equilibrium on Activated Carbon Surface

Mercury adsorption capability of raw activated carbon (R-AC) and NH 4 Br modified activated carbon (NH 4 Br-AC) was evaluated in a fixed-bed reactor. The effect of inlet Hg 0 concentration and flue gas components on mercury adsorption was investigated. The mercury adsorption species on the sorbent surface was analyzed by the Temperature Programmed Desorption (TPD) method. Finally, the mercury adsorption equilibrium of R-AC and NH 4 Br-AC was explored. Mercury adsorption results show that the mercury adsorption capability of NH 4 Br-AC is significantly larger than that of R-AC and increased with higher inlet Hg 0 concentration. O 2 and NO promote mercury adsorption on NH 4 Br-AC, but SO 2 inhibits the mercury adsorption. The TPD result shows that mercury adsorption on R-AC is mainly physical in nature, enhanced by chemisorption with the product of HgO. Mercury adsorption on NH 4 Br-AC is in the major form of chemisorption with the product of HgBr 2 . O 2 has little effect on the mercury adsorption mechanism. SO 2 reduces the generation of HgBr 2, but promotes little of HgS generation on NH 4 Br-AC. NO significantly improves the generation of Hg 2 (NO 3 ) 2 on NH 4 Br-AC. Adsorption equilibrium analysis shows that Langmuir and Temkin equations are more suitable to describe the mercury adsorption on R-AC, indicating the uniformity of the R-AC surface. Mercury adsorption on the NH 4 Br-AC surface can be described well by the Freundlich equation, illustrating the nonuniformity of the NH 4 Br-AC surface.