Tunning active oxygen species for boosting Hg0 removal and SO2-resistance of Mn-Fe oxides supported on (NH4)2S2O8 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 (NH4)(2)S2O8 and MnOx-FeOx for Hg-0 removal. (NH4)(2)S2O8 treatment induced abundant micropores and oxygen-containing functional groups, and thus provided more anchoring sites for the dispersion of MnOx-FeOx. The synergy of MnOx-FeOx and interaction between MnOx-FeOx 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-0 removal efficiency above 90% at 120 similar to 180 degrees C, as well as excellent performance for simultaneous removal of Hg-0 and NO, and 600 ppm SO2 and 8 vol.% H2O 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-L-HgO. Besides, the priority of AOS for Hg-0 chemisorption was C=O > COO- > O-L, and Hg2+ was also detected in the outlet. Moreover, the SO2-poisoning effect was ascribed to the sulfation of MnOx and the occupation of COO- and C=O, and FeOx incorporation enhanced the SO2-resistance through weakening SO2 adsorption on C=O and COO-. The motivation of O-2 mainly contributed to the regeneration of AOS, especially O-L. The excellent regeneration performance and stability further affirmed the application potential of MnFe/NAC for Hg-0 capture from coal-fired flue gas.

Automated summary

In this paper, the authors investigated the removal of Hg-0 using modified AC samples with abundant active oxygen species (AOS). The results showed that the treatment with (NH4)2S2O8 increased the microporosity and oxygen-containing functional groups, providing more anchoring sites for the dispersion of MnOx-FeOx. The optimized MnFe/NAC exhibited excellent efficiency for Hg-0 removal, as well as simultaneous removal of Hg-0 and NO.