| Summary: | 碩士 === 國立中興大學 === 土壤環境科學系所 === 96 === The volatile organic compound (VOCs) can cause great damage to the environment by emission into the atmosphere. By the exchange of organic cations for inorganic cations in the surfaces, the clay minerals can be converted into organo-clays. The mineral surfaces of resulting orgno-clays become hydrophobe, capable of effectively removing organic pollutants. Because of their natural and unique sorption powers, the organo-clays have been investigated for a wide variety of environmental applications. The VOCs sorption behaviors of organobentonites are much more complex than those of common adsorbents. Therefore, there would be practically useful to explain the relative contributions of the sorption mechanisms, between adsorbents and VOCs, via linear solvation energy relationships (LSER).
The aims of the study is to establish a LSER predictive equation , and also to discuss the sorption mechanisms of VOCs with organobentonites. The reactivity descriptors calculated by molecular model, and were based on the density functional theory (DFT) combined with the hard-soft acid-base (HSAB) principle. Calculated parameters will carry on the multi-regression analysis with sorption constant (log Kc). The chemical reaction of organic molecule divided into non-specific effect and specific effect two major parts. Non-specific effect is solvation interaction. Specific effect divided into global and local two parts, and both they subdivided into charge controlled and orbital controlled two parts.
The result of multi-regression analysis indicated that the sorption reactions of organobentonites with VOCs are mainly effected by several parameters. these parameters include the polar surface area (PSA) in salvation interaction, the hardness (η) in molecular global interaction, the maximum positive charge (ρ+max(H)) and maximum electrostatic potential (Vmax(H)) in the local charge controlled interaction, and the maximum nucleophilic condensed local softness (s+max) in the local frontier controlled interaction.
The sorption mechanism of organobentonite (HDTMA-bentonite) with the volatile organic compounds mainly are partition (hydrophobe), the Van der Waals force, and the hydrogen bond. Negative charges in the mineral interlayer would infect the sorption of organic compounds. Finally the optimum prediction equation was obtained. Although the square of correlation coefficient (R2) is lower, the equation can analyse the reaction mechanism by electrons redistribution in molecule structure.
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