The Effect of Relative Humidity to Sorption Kinetics of VOC in Soil

• Main Authors: Young, Di-kwung, 楊迪光
• Other Authors: Wu Shian-chee
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/34069251392363868647

碩士 === 國立臺灣大學 === 環境工程學研究所 === 86 === Abstract Soil contamination by organic pollutants happened frequently in th e recent year in Taiwan. It is necessary to estabilish practical models to pre dict the fates of these organic pollutants and to choose a suitable remediatio n approach. Recent researches showed that the fates of volatile organic chemic als (VOCs) in the unsaturated zone were significantly influenced by the sorpti on of VOCs in soils. Furthermoe, the sorption behavior is affected by the wate r in soils and the relative humidity in soil pores. The objectives of this res earch are to elucidate the mechanisms for water influeced adsorption of VOCs b y soil, and to predict the rate of sorption/desorption in soil. Toluene wa s chosen as a model of VOC, Chung-Li soil and Tai-Chung soil were used as sorb ents in the experiments. Fourier transform infrared absorption spectrumeter(FT IR) was used to monitor the adsorption processes. In addition to the original soil, soil with low organic matters, and clay from the same soil were used. Ex periments was controlled under of low(0~2%), medium(35~50%), and high(90~100%) relative humidity. The effects of different relative humidity ranges on the m echanism of VOC sorption by soils were investigated. According to the exp erimental results, the rate constant under medium relative humidity was the hi ghest. That is the moisture enhances the sorptive process under medium relativ e humidity conditions. In other words, moisture provides a better path which r educes the activated energy when toluene is being adsorbed. The sorptive IR s pectrums at equilibrium show that clay has the most strong interactive force w ith VOC. From the change of the configuration of toluene adsorbed, it could fi nd some informations about how toluene is sorbed by soils. The results fro m this research showed that FTIR not only provided direct evidences of the con figuration while VOCs were sorbed by soil, but also recorded the time courses of the sorption processes. The results were used to calculate the rate constan ts of adsorption and desorption. It is new to make FTIR a powerful tool that monitors the adsorptive/desorptive processes under relative humidity.