Tunning active oxygen species for boosting Hg removal and SO-resistance of Mn-Fe oxides supported on (NH)SO doping activated coke.

Active oxygen species (AOS) play an essential role in modulating the activity of activated coke (AC) based samples. In this paper, AC was endowed with abundant AOS by modifying with (NH)SO and MnO-FeO for Hg removal. (NH)SO treatment induced abundant micropores and oxygen-containing functional groups, and thus provided more anchoring sites for the dispersion of MnO-FeO. The synergy of MnO-FeO and interaction between MnO-FeO and NAC support contributed to a larger surface area, highly-dispersed active components, stronger reducibility, and more metal ions with high valence of MnFe/NAC. The optimal MnFe/NAC exhibited superior Hg removal efficiency above 90% at 120∼180 ℃, as well as excellent performance for simultaneous removal of Hg and NO, and 600 ppm SO and 8 vol.% HO addition led to a slight deterioration. XPS and Hg-TPD revealed that mercury adsorbed on MnFe/NAC included phy-Hg, C=O-Hg, COO-Hg, and O-HgO. Besides, the priority of AOS for Hg chemisorption was C=O > COO- > O, and Hg was also detected in the outlet. Moreover, the SO-poisoning effect was ascribed to the sulfation of MnO and the occupation of COO- and C=O, and FeO incorporation enhanced the SO-resistance through weakening SO adsorption on C=O and COO-. The motivation of O mainly contributed to the regeneration of AOS, especially O. The excellent regeneration performance and stability further affirmed the application potential of MnFe/NAC for Hg capture from coal-fired flue gas.