PARTITIONING OF AROMATIC CONSTITUENTS INTO WATER FROM GASOLINE AND OTHER COMPLEX SOLVENT MIXTURES

Variations in gasoline composition (source variations) as well as complexity in composition (nonideal behavior, cosolvent effects) contributing to variability in gasoline-water partitioning of aromatic hydrocarbon constituents were examined. Aromatic hydrocarbon concentrations in water extracts of 31 gasoline samples varied over 1 order of magnitude, reflecting the diversity in gasoline composition. However, the gasoline-water partition coefficients (K(fw)) varied by less than 30% among these samples. Partitioning between water and known mixtures of aromatic and aliphatic solvents was measured and used to estimate the upper and lower bounds of K(fw) values for more complex solvent mixtures such as gasoline and diesel fuel. Oxygenated additives, such as methanol and methyl tert-butyl ether (MTBE), were shown to have minimal cosolvent effects on hydrocarbon partitioning. The observed inverse, log-log linear dependence of K(fw) values on aqueous solubility could be well predicted by assuming gasoline to be an ideal solvent mixture (i.e., Raoult's law is valid).