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To reduce the mercury content in flue gas from coal-fired power plants and to obtain high-performance, low-cost mercury adsorbents, a novel composite material was prepared by structural design through the in situ growth method. Functionalization treatments such as the modification of functional groups and multilayer loading of polymetallic were conducted. These materials include the MOF material UiO-66 and modified biochar doped with Fe/Ce polymetallic, both of which contain unsaturated metal centrals and oxygen-containing functional groups. On the basis of obtaining the effects of adsorption temperature and composite ratio on the Hg0 removal characteristics, coupling and synergistic mechanisms between the various types of active centers included were investigated by using a variety of characterization and analysis tools. The active adsorption sites and oxidation sites were identified during this process, and the constitutive relationship between the physicochemical properties and the performance of Hg0 removal was established. The temperature-programmed desorption technique, Grand Canonical Monte Carlo simulation, and adsorption kinetic model were employed to reveal the mechanism of Hg0 removal. The results showed that the UiO-66-Br@MBC composite adsorbent possessed an excellent Hg0 removal performance at adsorption temperatures ranging from 50 to 250 °C, and targeted construction of adsorption and oxidation sites while maintaining thermal stability. The Hg0 removal by the composites is the result of both adsorption and oxidation. The micropores and small pore mesopores in the samples provide physical adsorption sites. The modified biochar acts as a carrier to facilitate the full exposure of the central metal zirconium ions, the formation of more active sites, and the process of electron transfer. The doping modification of the Br element can enhance the overall redox ability of the sample, and the introduced Fe and Ce polymetallic ions can work in concert to promote the oxidation process of Hg0. The excellent regulation of the ratio between adsorption and oxidation sites on the surface of the composite material finally led to a significant boost in the samples' capacity to remove Hg0. [ABSTRACT FROM AUTHOR]

The problem of As pollution emission from sludge during combustion has received widespread attention. The impact of flue gas components on the interaction with CaO and As during sludge combustion was analyzed using a series of experimental characterization methods. The strength of the activity of As2O3 on the CaO(001) surface as well as on the CO2/SO2/H2O+CaO(001) surface with different O adsorption sites was revealed by combining with Density Functional Theory (DFT). According to the results, CO2 in the flue gas reacted with CaO in a reversible carbonation reaction, which optimized the pore structure of the solid phase products and promoted the capture of As by CaO. SO2 in the flue gas reacted with CaO in a sulfation reaction reaction to block the pores, which was not conducive to the capture of As by CaO. The presence of moisture led to poor pore structure collapse of the solid phase products as well as the formation of gehlenite, which reduced the enrichment of As by CaO. DFT calculations showed that the adsorption of As2O3 molecules on the CO2+CaO(001) surface was affected by the position of the O active site, and the adsorption energy at the OC1 top site was higher than that on the clean surface, which was favorable for the stable adsorption of As2O3 molecules. The existence of SO2 decreased As2O3 molecules' adsorption energy on the CaO(001) surface, which was unfavorable for the adsorption of As2O3 molecules. There were two main effects of H2O molecules on the adsorption of As2O3 on the CaO(001) surface. One was the H2O molecules weakened the interaction between the As atoms and Osurf atoms, which was unfavorable to the adsorption of As2O3 molecules; the other was the existence of stronger adsorption of O atoms in H2O molecules on As atoms in As2O3 molecules, which made As2O3 molecules adsorbed at the top of OH0 adsorbed with adsorption energies much larger than that of clean surface, and the adsorption was more stable. [ABSTRACT FROM AUTHOR]