| Summary: | 碩士 === 國立高雄師範大學 === 生物科學研究所 === 93 === Groundwater contamination by gasoline and other petroleum-derived hydrocarbons released from underground or aboveground storage tanks is a serious and widespread environmental problem. Corrosion and poor sealing can cause leaks in tanks and associated piping. Contamination of petroleum products from service stations is commonly seen in Taiwan. Understanding the behavior of pollutants in the subsurface environment is important for assessing fate and transport of pollutants in site remediation. The major components of gasoline such as methyl tert butyl ether (MTBE) (a fuel oxygenate), benzene, toluene, ethylbenzene, and xylenes (BTEX), are potentially hazardous to the environments. In particular, MTBE is a volatile, flammable, and colorless liquid that dissolves rather easily in water.
The objectives of this research were to (1) evaluate concentration ranges of major components in water soluble fraction of various gasolines, (2) measure fuel-water partition coefficients (Kfw) for major aromatic components and MTBE by using gasoline, and (3) evaluate the utility of Raoult’s law to estimate aqueous-phase concentrations of MTBE and BTEX in equilibrium with various gasolines.
By use of a two-phase liquid-liquid equilibrium model, the distribution of nonpolar solutes between water (polar phase) and NAPL phase (nonpolar phase) was related to principles of equilibrium. Raoult’s law convention was employed to establish ideal relationship of six major grades of gasoline in Taiwan. The measured partition coefficients of MTBE and BTEX from gasoline-water systems were used to establish ideal-behavior models as followed:
log Kfw = -log S + 0.792 R2 = 1
log Kfw = 1.180 log Kow - 0.096 R2 = 0.994
The measured average molecular weight of gasolines range from 113 to 122 g/mL and the densities are 710 to 760 g/L. The models derived using Raoult’s law convention for activity coefficients and liquid solubility is presented. It is intended to evaluate the applicability of the ideal relationship to MTBE and BTEX of complex mixture in field scale practice of remediation and regulatory purpose. The observed inverse, log-log linear dependence of Kfw values on aqueous solubility could be well predicted by assuming gasoline to be an ideal solvent mixture.
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