| Summary: | 碩士 === 國立中央大學 === 環境工程研究所 === 95 === The sorption phenomena of organic compound in dry or water- unsaturated soil are dominated by mineral/inorganic adsorption due to the relatively low soil organic matter contents. However, in water- saturated system, the partioning of organic compounds into soil organic matter as the major process because the adsorption of organic compounds by minerals is suppressed by water.
The sorption of organic compounds by natural soil in dry/water- saturated system has been studied extensively. However there are still some controversies in purification of soil inorganic phase. To overcome the purification shortcomings of soil inorganic phase, three highly pure synthetic mineral oxides with no detectable organic carbon：Boiling chips、Aluminum oxide and Silica gell were selected as adsorbents; In addition, n-hexane、cyclohexane、benzene and toluene were selected as adsorbates for all experiments to evaluate the sorption phenomena between soil mineral phase and organic compounds in dry/water- saturated systems. In dry system，all isotherms are in the form of BET type II，total adsorption capacity was related to adsorbent surface area. Most notably, as stated, the extent of uptake for given compounds is affected by molecular steric structure、polarity as well as polar-group of adsorbate. The heat of first layer on adsorbent surface of all adsorbates and water was calculated by BET adsorption theory. The sorption data in aqueous system show that water molecule must be preferentially adsorbed by soil mineral phase and offer a theoretical basis for linear solute adsorption, low exothermic heats, and no adsorptive competition and hence organic solutes are separated by water showing a partition flake. Adsorption occurs presumably by dispersion forces and polar-group interactions onto a water film above the mineral surface. This study not only proved the role of water in linear adsorption, but also revealed the negative relationship between Kd and water solubility of organic compounds.
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