| dc.description.abstract | The central focus of this paper revolves around volatile organic compounds (VOCs), which are significant air pollutants in the environment. These compounds are further categorized into hazardous air pollutants (HAPs) and photochemical ozone precursors (PAMS) based on their characteristics. The first section of the paper concentrates on monitoring hazardous air pollutants at sensitive receptor sites in the vicinity of industrial areas. Thermal desorption gas chromatography-mass spectrometry (TD-GC/MS) is employed to conduct online continuous monitoring of 86 toxic organic substances. The monitoring results reveal that toxic organics such as vinyl chloride, 1,2-dichloroethane, butadiene, acrylonitrile, n-hexane, vinyl acetate, etc., are prominent in the Renda Industrial Zone. A comparison of the current and previous year′s monitoring data indicates a decrease for most target compounds, except for vinyl acetate, which displays increased concentrations. When compared with data from the PAMS stations, there is a strong correlation observed among common compounds (r >0.92), validating the robustness of the online continuous monitoring method.
The second part of my research explores the gas adsorption characteristics of metal-organic-framework (MOF) materials. Specifically, the relatively hydrophobic UiO-66, heat-resistant UiO-66, and UiO-67 among MOF materials are chosen as adsorbents to evaluate their adsorption capacity for the 54 PAMS species and to compare with commercial carbon adsorbents. Our findings demonstrate that these three materials can effectively adsorb hydrocarbon species ranging from C3 to C11. The calibration curve exhibits good linearity (R2 > 0.995), and the adsorption capacity of these MOF materials is comparable to that of the multi-bed carbon adsorbents. Additionally, the per-carbon response results indicate that the adsorption capacity of UiO-66 and heat-resistant UiO-66 is similar to that of the multi-bed carbon adsorbents, while UiO-67 exhibits slightly higher adsorption capacity for medium and heavy carbon species but lower adsorption capacity for smaller and extremely heavy carbon species. The study further investigates the structural differences between heat-resistant UiO-66 and UiO-67 after repeated cryogenic adsorption and thermal desorption using X-ray diffractometry. The results reveal that heat-resistant UiO-66 maintains its crystallinity under heating conditions, while the crystallinity of UiO-67 collapses to some degree, accompanied by poor peak shape as shown by the X-ray result.
Finally, the heat-resistant UiO-66 and UiO-67 are subjected to continuous heating cycles (>100) of thermal desorption and analysis along with calibration and blank tests. The recovery rate falls within 81%-111%, and the relative standard deviation (RSD) is less than 3%, complying with the NIEA A505.12B standard method acceptance criteria (recovery≦±25%). This demonstrates that adsorbents incorporating heat-resistant UiO-66 and UiO-67 are ideal for the application of thermal desorption of ambient-level VOCs. | en_US |