This research studies the adsorption of gas-phase As 2 O 3 by CaO, Fe 2 O 3 and Al 2 O 3 , using a fixed-bed reactor with an arsenic continuous generation device. The adsorption of gas-phase arsenic on CaO and Fe 2 O 3 is mainly chemical adsorption at 600−900 °C. The adsorption quantity and efficiency decreases as the temperature increases. Iron(III) oxide has the best arsenic adsorption ability, followed by calcium oxide and then aluminum oxide. The incoming arsenic concentration was varied, from 4.5 × 10 −6 v/v to 13.5 × 10 −6 v/v, to determine if this had any effect on adsorption, which revealed that the adsorbent did not become saturated under the experimental conditions used. The adsorption efficiency for each adsorbent was affected by the adsorption temperature, and the same adsorption efficiency was achieved regardless of the inlet arsenic concentration. Intrinsic reaction kinetics of CaO and Fe 2 O 3 with arsenic oxide was studied. The activation energies of CaO and Fe 2 O 3 are 12.17 kJ/mol and 25.99 kJ/mol, respectively. The reaction orders of Fe 2 O 3 and CaO are ∼1.1 and 0.8, respectively.

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The volatilization characteristics of arsenic in different coals at 600−1500 °C were studied on an isothermal reaction system. Through thermogravimetric analysis similar to that used for coal analysis, the mass loss and mass loss rate of arsenic for coal samples were determined. Sequential chemical extraction method was used to measure the mode of occurrence of arsenic in the coals. TG-MS techniques were also carried out to study the relationship between sulfur and arsenic. Results show that the volatilization proportion of arsenic increases with temperature and 53− 99% of the total arsenic in coal is vaporized in the combustion zone at PC conditions (1500 °C). Coals with higher arsenic concentrations (As > 4 μg/g) tend to have larger arsenic volatility proportions than coals with lower arsenic concentrations (As < 4 μg/g) at a given temperature. In addition, three volatility zones with two mass loss rate peaks of arsenic are observed in all coals during coal combustion. Before 600 °C, the evaporation of organic-bound arsenic dominates; then the first arsenic mass loss peak at 800−900 °C is mainly from the decomposition or oxidation of arsenic in sulfide forms. The second peak after 1000 °C is probably generated through the decomposition of arsenates. For As > 4 μg/g coals, the first peak is higher than the second peak due to the larger proportion of sulfide-bound arsenic, while the second mass loss peak of arsenic is higher in As < 4 μg/g coals due to the larger proportion of arsenates. Furthermore, thermodynamic analysis by HSC chemistry6.0 software were carried out to prove that arsenates, like Ca 3 (AsO 4 ) 2 , FeAsO 4 , and Mg 3 (AsO 4 ) 2 , are thermally stable and could only decompose at relatively high temperatures.

Poor adsorption of reactants and intermediates as well as low mineralization rate greatly restrict the application of common semiconductor photocatalyst TiO 2 for air purification. A plausible solution would be to integrate metal−organic frameworks (MOFs) materials with good gas adsorption property with traditional photocatalytic material TiO 2 with exciton generation. A core−shell structured photocatalyst with functional MOFs HKUST-1 (Cu 3 (BTC) 2 , BTC = 1,3,5 benzenetricarboxylate) as core and porous ultrathin anatase film as shell was synthesized. The composite photocatalyst was characterized in detail, and isopropanol degradation experiments were performed to evaluate the photocatalytic performances. The experimental results revealed that HKUST-1 can provide a special pathway for photogenerated electrons migration and thus restrain the recombination of electrons and holes to increase the photocatalytic efficiency. Furthermore, the capture of reactants and intermediates was also enhanced due to the unique MOFs-TiO 2 composite structure, and the mineralization rate had been markedly enhanced.

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Arsenic volatilization characteristics of SJS bituminous coal were carried out in a customized isothermal thermogravimetric experimental system at 600−1400 °C under different oxy-fuel atmospheres. The mineralogical and morphological characterization of ash samples were analyzed using XRD and SEM instruments. Different from conventional nonisothermal mass loss curves by TG analyzer, the isothermal mass loss curves of coal did not show a clear process of moisture removal and devolatilization. With the increase of combustion temperature, the isothermal mass loss curve of SJS coal shifted to the left gradually and the burnout time shortened at the same time, whereas the mass loss curves of arsenic showed different tendencies at <900 °C and >900 °C stages. At the <900 °C stage, the effect of O 2 dominated. A higher O 2 ratio led to the larger volatile proportion of arsenic, irrespective of CO 2 content. At the >900 °C stage, the volatilization of arsenic was delayed in oxyfuel condition but with a higher release rate; thus the volatility ratio of arsenic in oxy-fuel combustion was even larger than that of conventional air/flue gas combustion.

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The effects of the temperature, volatile content, and ash content on the volatilization kinetics of arsenic were discussed. Six Chinese coals were tested in an isothermal thermogravimetric reactor at 600−1300 °C. Sequential chemical extraction analysis was employed to know the speciation transformation of arsenic during coal combustion. Results show that the volatilization ratio of arsenic increases with the temperature, and most arsenic volatilizes between 700 and 1000 °C. The volatile content has a positive effect on the volatilization rate of arsenic in the initial stage of combustion. With the same level of ash content, high-volatile coals (>30%) own a larger volatilization rate of arsenic (0.55−0.6% s −1 ) than the low-volatile coals (<12%) (0.25% s −1 ). In contrast, coals with a higher ash content tend to obtain a lower volatilization rate of arsenic during the process. Despite the effect of volatile and ash contents on the volatilization rate of arsenic, the final volatilization ratio of arsenic largely depends upon its mode of occurrence of arsenic in coal, especially on sulfide-and organic-bound arsenic. A first-order reaction kinetic model can well describe the volatilization characteristics of arsenic. A calculation shows that the activation energy of arsenic volatilization is significantly affected by the volatile content, while the ash content has a tiny effect on it. High-volatile coals have lower activation energy of arsenic volatilization than low-volatile coals.