Superior performance and resistance to SO2 and H2O over CoOx-modified MnOx/biomass activated carbons for simultaneous Hg0 and NO removal

Abstract

A series of CoOx modified MnOx/biomass activated carbons (CoMn/BACs) prepared by the ultrasound-assisted impregnation method were employed for the simultaneous removal of NO and Hg0 from simulated coal-fired flue gas for the first time. The physicochemical properties of such samples were characterized by XRD, BET, SEM, TEM, NH3-TPD, H2-TPR, FTIR, TG and XPS. 15%CoMn/BAC exhibited preferable performance for NO and Hg0 removal in a wide temperature range from 160 to 280 °C, and it yielded prominent NO removal efficiency (86.5%) and superior Hg0 removal efficiency (98.5%) at 240 °C. The interaction between NO removal and Hg0 removal lessened corresponding separate efficiency, the adverse effect of NH3 on Hg0 removal could not be offset by promotional influences of NO and O2. Compared with 15%Mn/BAC, the addition of CoOx with suitable amount into 15%CoMn/BAC could contribute to the synergistic effect between MnOx and CoOx, resulting in the increase of BET surface area and surface active oxygen species as well as Mn4+ concentration, the enhancement of redox ability and the strength or amount of surface acid sites, restraining the crystallization of MnOx, which might be responsible for the improvement of catalytic performance and resistance to SO2 and H2O. Additionally, the hydrophobic property of BAC further strengthened H2O tolerance. The results of stability and recyclability tests indicated that 15%CoMn/BAC possessed a promising application potential for NO and Hg0 simultaneous removal at low temperature.