摘要 本研究選用四種已知結構之高分子聚合物模擬土壤有機質，利用Cahn D200型電子微量天平，摒除水分的干擾，以重量法對氣態有機污染物吸附行為之影響進行探討，並著重於低相對壓力下，吸附等溫線非線性吸附程度與有機質特定官能基及吸附質之物化特性間之相關性。 實驗結果顯示，於相對壓力P/Po=0.1~0.8之範圍內，各吸附組合之氣態吸附等溫線均為線性，說明以高分子聚合物模擬土壤有機質吸持有機污染物，符合分佈作用吸附等溫線為線性之特徵。低相對壓力P/Po=0~0.1之範圍內，各組合之氣態吸附等溫線均出現凹口向下且彎曲程度不一之非線性吸附，彎曲程度與吸附質之極性大小明顯相關，當吸附質極性程度愈大，則非線性吸附程度愈大；極性程度愈小，則非線性程度愈小。吸附劑之特定官能基與非線性彎曲程度亦有高度相關性，實驗結果顯示，如羧酸基，氰基等極性官能基對非線性吸附程度有顯著的影響，主要是此類官能基與吸附質間產生氫鍵、偶極-偶極力等吸附作用力，使吸附劑吸附位址在低相對壓力下即達飽和。整體而言，本研究實驗結果說明分佈作用吸附等溫線於低相對壓力下之非線性彎曲程度與土壤有機質官能基及吸附質極性程度有明顯相關性。 Abstract In researches of the sorption nonionic organic compounds by soil, the soil organic matters (SOM) has been recognized to behave as a partition medium. The unique isotherm shape which means the isotherms show nonlinear at low Ce/Sw but virtually linear at other Ce/Sw in soil/water system, implies that more than one mechanism is in effect over the entire range Ce/Sw. In order to evaluate the effect of specific functional groups in SOM on the adsorption of organic compounds, especially at low pressure, we chose polymers with known functional groups as the adsorbents in this experiment to simplify the complex characteristics of soil organic phase. To deliberate on the cause of such nonlinear sorption for organic contaminants at low pressure, several polar organic compounds were used to be the adsorbates. The surface area and adsorption/desorption characteristics isotherms were analyzed to realize the adsorbent structure and the surface images display the microcosmic appearances of the adsorbent. Vapor-phase adsorption isotherms of cyclohexane, benzene, acetonitrile, and methanol on polymers, such as Poly(acrylic-acid)、Poly(benzyl-methacrylate)、Poly(acrylonitrile)、and Carbowax, were gravimerically measured under 25℃.In all experimental data, the adsorption isotherms show nonlinearity with concave-downward curvatures at low relative pressure but exhibit a linear shape at higher pressure. The nonlinearity of isotherms coincides with solute polarity. The sorption capacities are greater for polar solutes than for nonpolar solutes. The nonlinear capacity increases progressively with increasing solute polarity for other solutes. In addition to the polarity, the functional groups of the adsorbents affect on the nonlinear sorption as well. There are the specific interaction, like H-bond and Van der Waal’s force adsorbent, between organic compounds and adsorbents with functional group of OH bond、COOH bond. In summary, the final results are fit with the specific-interaction model.
