Enhance SO2 adsorption performance of biochar modified by CO2 activation and amine impregnation

To enhance the SO 2 adsorption of biochar, CO 2 activation and impregnation with methyldiethanolamine (MDEA) was simultaneously employed to improve its physicochemical characteristics. Furthermore, the effects of the pore structure and nitrogen functionality on SO 2 adsorption were also explored. The results show that after CO 2 activation, the specific surface area of biochar increased from 56.91 m 2 /g to 755.35 m 2 /g, while this figure dropped to 25.54 m 2 /g or even lower after impregnation with MDEA. Although the pore structure of activated biochar was destroyed, the surface nitrogen content of the nitrogen-enriched biochar (with 10% MDEA impregnation) increased from 1.46% to its highest level (7.20%); moreover, as indicated by Fourier Transform Infrared (FTIR) spectroscopy, the nitrogen functional groups introduced on the surface of the nitrogen-enriched biochar were mainly C-N. After 10% MDEA impregnation, the maximum SO 2 adsorption capacity increased from 57.8 mg/g to 156.2 mg/g. Changes to physical and chemical properties in the nitrogen-enriched biochar indicate that the nitrogen functional groups on the surface are more important than the pore structure for SO 2 adsorption at 393 K, and that the dominant nitrogen species are quaternary nitrogen.