Volatilization of monoaromatic compounds (benzene, toluene, and xylenes; BTX) from gasoline: effect of the ethanol.

The main objective of present study was to assess the evaporation profile of monoaromatic compounds, namely, benzene, toluene, and xylenes (BTX) from gasoline-ethanol-blend fuels. The vapors from two river sand columns contaminated with gasoline and gasoline-ethanol were monitored for 77 d. Standards mixtures (batch tests) of benzene, toluene, and xylenes with different ethanol contents were also analyzed for evaporation rates studies. The instrumental analysis was performed via gas chromatography. The concentration of benzene in the vapor phase of the gasoline-ethanol column was decreased by 89.09%, considering the entire experimental period, whereas the toluene and xylenes concentrations were increased by 239.34 and 251.78%, respectively. In the batch tests, the benzene concentration in the vapor phase varied from 0.4 to 0.9 mg/L for ethanol concentrations (v/v) of 5 and 10%, respectively. For ethanol concentrations higher than 10%, no important changes in the benzene concentration were observed. The toluene exponentially increases between 20 and 30% ethanol concentration. and the maximum concentration of xylenes was observed when the ethanol concentration was 20% (v/v). These results suggest that the benzene evaporation behavior is preferentially affected by the interactions among ethanol and other aromatic compounds rather than the ethanol concentration itself. The evaporation behaviors of toluene and xylenes are directly dependent on the ethanol content. (c) 2009 SETAC.