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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Investigating the Heterogeneous Interaction of VOCs with Natural Atmospheric Particles: Adsorption of Limonene and Toluene on Saharan Mineral Dusts
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Investigating the Heterogeneous Interaction of VOCs with Natural Atmospheric Particles: Adsorption of Limonene and Toluene on Saharan Mineral Dusts

机译：研究VOC与天然大气颗粒的异质相互作用：撒哈拉矿物粉尘上柠檬烯和甲苯的吸附

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The heterogeneous interaction of limonene and toluene with Saharan dusts was investigated under dark conditions, pressure of 1 atm, and temperature 293 K. The mineral dust samples were collected from six different regions along the Sahara desert, extending from Tunisia to the western Atlantic coastal areas of Morocco, and experiments were carried out with the smallest sieved fractions, that is, inferior to 100 mu m. N-2 sorption measurements, granulometric analysis, and X-ray fluorescence and diffraction (XRF and XRD) measurements were conducted to determine the physicochemical properties of the particles. The chemical characterization showed that dust originating from mideastern Sahara has a significantly higher SiO2 content (similar to 82%) than dust collected from the western coastal regions where the SiO2 relative abundance was similar to 50%. A novel experimental setup combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), selected-ion flow-tube mass spectrometry (SIFT-MS), and long path transmission Fourier transform infrared spectroscopy (FTIR) allowed us to follow both the adsorbed and gas phases. The kinetic adsorption/desorption measurements were performed using purified dry air as bath gas, exposing each dust surface to 10 ppm of the selective volatile organic compound (VOC). The adsorption of limonene was independent of the SiO2 content, given the experimental uncertainties, and the coverage measurements ranged between (10 and 18) x 10(13) molecules cm(-2). Experimental results suggest that other metal oxides that could possibly influence dust acidity may enhance the adsorption of limonene. On the contrary, in the case of toluene, the adsorption capacities of the Saharan samples increased with decreasing SiO2 content; however, the coverage measurements were significantly lower than those of limonene and ranged between (2 and 12) x 10(13) molecules cm(-2). Flushing the surface with purified dry air showed that VOC desorption is not a completely reversible process at room temperature. The reversibly adsorbed fraction and the rate coefficients of desorption, k(des), depended inversely on the SiO2 relative abundance for both VOCs.
机译：在黑暗条件，1 atm的压力和293 K的温度下，研究了柠檬烯和甲苯与撒哈拉尘埃的异质相互作用。从撒哈拉沙漠沿突尼斯到西大西洋沿海地区的六个不同区域收集了矿物尘埃样本。摩洛哥，并进行了最小的筛分，即小于100微米的实验。进行N-2吸附测量，粒度分析以及X射线荧光和衍射（XRF和XRD）测量，以确定颗粒的物理化学性质。化学特征表明，源自撒哈拉沙漠中部的粉尘比从西部沿海地区收集的粉尘具有更高的SiO2含量（约82％），其中SiO2相对丰度接近50％。结合了漫反射红外傅里叶变换光谱（DRIFTS），选择离子流管质谱（SIFT-MS）和长距离透射傅里叶变换红外光谱（FTIR）的新颖实验装置，使我们能够同时跟踪吸附相和气相。使用纯净的干燥空气作为浴气进行动力学吸附/解吸测量，将每个粉尘表面暴露于10 ppm的选择性挥发性有机化合物（VOC）中。给定实验的不确定性，柠檬烯的吸附与SiO2的含量无关，并且覆盖范围介于（10和18）x 10（13）分子cm（-2）之间。实验结果表明，其他可能影响粉尘酸度的金属氧化物可能会增强柠檬烯的吸附。相反，在甲苯的情况下，撒哈拉样品的吸附能力随SiO2含量的降低而增加;但是，覆盖率测量值显着低于柠檬烯，范围在（2和12）x 10（13）分子cm（-2）之间。用纯净的干燥空气冲洗表面表明，VOC解吸在室温下不是完全可逆的过程。可逆吸附的分数和解吸速率系数k（des）反过来取决于两种VOC的SiO2相对丰度。

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