Partitioning behavior of ethanol-blended gasoline and biodiesel into groundwater

• Main Authors: Yun-Wei Lai, 賴允偉
• Other Authors: Colin S. Chen
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/74614386595491382326

碩士 === 國立高雄師範大學 === 生物科技系 === 96 === The dwindling fossil fuel sources and the increasing dependency on imported crude oil have led to a major interest in expanding the use of alternative fuels in many countries. Groundwater contamination by gasoline and other petroleum-derived hydrocarbons released from underground or aboveground storage tanks is a serious and widespread environmental problem. 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 chemistry. The objectives of this research were to (1) evaluate concentration ranges of major components in water soluble fraction of regular gasolines, ethanol-blended gasolines, diesels, and biodiesels. (2) measure fuel-water partition coefficients (Kfw) for major components. (3) evaluate the utility of Raoult’s law to estimate aqueous-phase concentrations of methyl tert-butyl ether (MTBE), benzene, toluene, ethylbenzene, xylenes (BTEX), and polycyclic aromatic hydrocarbons (PAHs) in equilibrium with various fuel products. and (4) investigates the cosolvency effect of MTBE and ethanol on the aqueous solubility of ethanol-blended gasoline. Raoult’s law convention was employed to establish ideal relationship of 67 fuel samples. The measured fuel-water partition coefficients of MTBE, BTEX, and PAHs from various fuel product were used to establish ideal-behavior models as following: log Kfw = - logS + 0.699 log Kfw= 1.0242 log Kow + 0.3138　　R2 = 0.9679 The models derived using Raoult’s law convention for activity coefficients and liquid solubility is presented. The Raoult’s law is applicable to complex mixture in field scale practice of remediation and regulatory purpose. Oxygenated additives (i.e., ethanol and MTBE), in the high percent range, were shown to have evidence cosolvent effects on hydrocarbon partitioning. Cosolvency experiments were carried out in batch reactors under equilibrium conditions for ethanol-blended gasoline. A linear relationship between cosolvency power and Kow was established, which allows predictions of the increase of aromatic hydrocarbon solubility due to the presence of ethanol in gasoline. σ = 1.3883 logKow + 0.2286　　R2=0.9753 Results indicated that cosolvency would be significant only for high aqueous ethanol concentrations (higher than 20%). In the case of high fuel-to-water ratio (e.g., 1:1) or near contaminant source zone, the cosolvent effect of oxygenated gasoline with high content of ethanol (e.g., E85) will be environmentally significant.