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Vanadium-based catalysts have been extensively applied for the synergistic control of NO x and chlorinated organics. However, how the vanadia species affect the reaction activity and products distribution, and what are the dominant reaction sites of these vanadia species are still unknown. Herein, we investigated the reaction characteristics of monomeric and polymeric vanadate domains for the catalytically synergistic elimination of NO x and chlorobenzene (CB). Density functional theory (DFT) calculations and experimental investigations have been combined to clarify the effects of different vanadyl species on the synergistic reaction. It was noted that the main adsorption site of CB on the monomeric domain was V−OH bond, and that on the polymeric one was VO bond. The monomeric vanadyl was favorable for converting the Lewis VO into Brønsted V−OH, which provided sufficient H protons for HCl formation, whereas the polymeric species could effectively retain the V 4+ /V 5+ redox cycle, and yielded superior activity in CB catalytic oxidation (CBCO) reaction. However, the abundant oxygen vacancies and the inclined accumulation of Cl by forming the V−Cl bands led to significant polychlorinated byproducts on the polymeric vanadyl catalysts. Our work gives the first insight into different vanadate domain effects on the synergistic reaction, and is expected to provide theoretical basis for efficient design of the vanadium-based catalysts toward multipollutants elimination.

Zeolites have been recognized as one type of the most promising adsorbents for capturing volatile organic compounds (VOCs, e.g., toluene), but their performance suffers severely from water vapor under wet conditions. In this contribution, we demonstrated that the hydrophobicity of microporous zeolites can be significantly improved by coating vertically aligned LDH nanoplatelets when the contact angle is increased from 16.5−20.1°to 44.4−64.2°. The toluene adsorption capacity of such synthesized zeolite@ LDH core@shell composites in wet conditions can thus be largely enhanced when the breakthrough time is increased from 6.4−10.8 to 20.1−27.5 min.

To estimate the deposition effect of PM2.5 (particle matter with aerodynamic diameter <2.5 µm) in forests in northern China, we used the gradient method to measure the deposition velocity of PM2.5 during the winter and spring above a deciduous forest in Olympic Forest Park and above a coniferous forest in Jiufeng National Forest Park. Six aerosol samplers were placed on two towers at each site at heights of 9, 12 and 15 m above the ground surface. The sample filters were exchanged every four hours at 6∶00 AM, 10∶00 AM, 2∶00 PM, 6∶00 PM, 10∶00 PM, and 2∶00 AM. The daytime and nighttime deposition velocities in Jiufeng Park and Olympic Park were compared in this study. The February deposition velocities in Jiufeng Park were 1.2±1.3 and 0.7±0.7 cm s−1 during the day and night, respectively. The May deposition velocities in Olympic Park were 0.9±0.8 and 0.4±0.5 cm s−1 during the day and night, respectively. The May deposition velocities in Jiufeng Park were 1.1±1.2 and 0.6±0.5 cm s−1 during the day and night, respectively. The deposition velocities above Jiufeng National Forest Park were higher than those above Olympic Forest Park. The measured values were smaller than the simulated values obtained by the Ruijgrok et al. (1997) and Wesely et al. (1985) models. However, the reproducibility of the Ruijgrok et al. (1997) model was better than that of the Wesely et al. (1985) model. The Hicks et al. (1977) model was used to analyze additional forest parameters to calculate the PM2.5 deposition, which could better reflect the role of the forest in PM2.5 deposition.

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