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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.

MoO3-CeO2/cylindrical activated coke samples (MoCeY/AC) synthesized by an impregnation method were employed to investigate elemental mercury (Hg0) removal at 60–210 °C from simulated flue gas without HCl. MoCe0.5/AC with an optimal Mo/Ce molar ratio of 0.5 exhibited an excellent Hg0 removal efficiency (94.74%) at 120 °C, as well as good stability and prominent resistance to SO2 and H2O. The physicochemical property of the samples and the Hg0 removal mechanism were discussed by ICP-AES, SEM, EDX, BET, XRD, H2-TPR, XPS and Hg-TPD. The results of characterizations showed that MoCe0.5/AC possessed the special petal-like outer microstructure, large BET surface area, well-dispersed metal oxides and high reducibility, which was conducive for Hg0 removal. Furthermore, the synergistic effect between Mo6+ and Ce3+ was favorable to the high Hg0 removal performance by providing high valence Ce. According to the Hg-TPD tests, the chemisorption of Hg0 was a major approach for Hg0 removal, while physisorption and catalytic oxidation were just accounted for a tiny fraction. Moreover, the chemisorbed mercury could be validly distinguished into weakly-HgO, strongly-HgO, Oα-HgO and HgSO4 (when SO2 was added). Compared with raw AC, MoCe0.5/AC could enhance the Hg0 oxidation performance and produce Oα-HgO during the Hg0 removal process. In addition, the possible reason for the high SO2 tolerance of MoCe0.5/AC was examined: (i) the preferential combination between sulfate and MoO3 could protect CeO2 for Hg0 removal; (ii) SO2 could contribute to the formations of weakly-HgO and HgSO4. Finally, the regenerability of MoCe0.5/AC was also discussed.

To rationally utilize agricultural wastes and expediently simultaneous control of elemental mercury (Hg0) and NO, a series of CoOx-CeO2 loaded maize straw derived biomass activated carbon (CoCe/BAC) samples were applied for simultaneous NO and Hg0 removal. These samples’ physicochemical characteristics were characterized by BET, SEM, XRD, NH3-TPD, H2-TPR, XPS and FTIR. 15%Co0.4Ce0.6/BAC yielded prominent Hg0 removal efficiency (96.8%) and superior NO removal efficiency (84.7%) at 230 °C. The separate or synchronous deactivation effects of 400 ppm SO2 and 5%H2O were detected. The interaction between NO removal and Hg0 removal was investigated, the results demonstrated that abundant Hg0 exhibited very slightly inhibitory effect on NO removal, and NH3 negatively affected Hg0 removal, whereas NO mildly boosted Hg0 removal in presence of O2. The characterization analyses indicated the excellent performance of 15%Co0.4Ce0.6/BAC could be ascribed to its better texture properties, lower crystallinity and stronger redox ability. Besides, a synergetic effect appeared between cobalt oxide and cerium oxide, resulting in generating more Ce3+ and Co3+ to induce more anionic defects and produce more active oxygen and oxygen vacancies. The removal mechanisms of NO and Hg0 were systematically investigated, and NO reduction reactions were mainly assigned to the Langmuir-Hinshlwood mechanism while both adsorption and Hg0 oxidation contributed to Hg0 removal. Meanwhile, Hg0 oxidation corresponded to the Mars-Masson mechanism prevailed gradually with the increase of reaction time.

In this work, functional mesoporous bean dregs-based biochar electrodes were prepared by electrophoretic deposition for perchlorate (ClO4-) electro-sorption. We characterized the textural and electrochemical properties of the biochar and determined the kinetics of electro-adsorption. The results show that 15% concentration of ZnO nanoparticle modification is recommended to increase the mesoporous volume, specific surface area, hydrophilicity and conductivity of biochar materials. After betaine functionalization, the obtained biochar (BK-Z15%-N) possesses an excellent electrochemical performance with high current density, charging capacity, and low ohmic impedance. As expected, it presents an electro-adsorption capacity of 28.31 mg g-1 toward 20 mg L-1 ClO4- at 1 V, which is four times higher than that without voltage and much better than other electrodes in this study and most reported data. The electro-adsorption of ClO4- on BK-Z15%-N electrode fits the fractal model, which is a complex process controlled by the electrical force and independent of solution pH. BrO3- and Cl- are the most competitive anion to ClO4- electro-sorption. Notably, it maintains a sustainable electrochemical regeneration ability due to the reversible redox activity of quaternary amine groups. Therefore, this study offers a remarkable and reliable method for improving the electro-sorption performance of perchlorate.

To optimize simultaneous control of NO and elemental mercury (Hg0) and gain more insight into the mechanisms, nano-sized TiO2-Al2O3-CeO2 materials synthesized via sol-gel method were used for simultaneous removal of NO and Hg0 from simulated flue gas. The physicochemical characteristics of catalysts were characterized by ICP-OES, BET, XRD, SEM, TEM, XPS, H2-TPR and FT-IR. TiAl10Ce20 nanoparticle with the addition of 10 wt%Al2O3 showed superior NO removal efficiency (93.41%) and Hg0 removal efficiency (80.54%) in the presence of SCR atmosphere at 300 °C. The deactivation effects of 8% H2O and 400 ppm SO2 were also reduced by Al addition. In the presence of SCR atmosphere, the capture of Hg0 was inhibited by the existence of NH3, while the presence of Hg0 had little impact on NO removal. The characterization results showed that the excellent performance of TiAl10Ce20 nanoparticle might result from the stronger redox ability, lower crystallinity and better texture properties with highly dispersed Ce species, which were all attributed to Al addition. The mechanisms for simultaneous removal of NO and Hg0 were also proposed on the basis of above results. TiAl10Ce20 nanoparticle developed in this work was considered to be a promising catalyst for simultaneous removal of NO and Hg0.