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Dynamic equilibrium dissolution of complex nonaqueous phase liquid mixtures into the aqueous phase
Author(s) -
Schluep Mathias,
Gälli René,
Imboden Dieter M.,
Zeyer Josef
Publication year - 2002
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620210704
Subject(s) - dissolution , chemistry , ethylbenzene , aqueous solution , btex , mass transfer , molar mass , diesel fuel , phase (matter) , henry's law , aqueous two phase system , xylene , toluene , chromatography , organic chemistry , polymer
Human health risks posed by hazardous substances seeping from a pool of nonaqueous phase liquids (NAPLs) into groundwater change over time because the more soluble compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX) dissolve faster into the aqueous phase than less soluble compounds such as polycyclic aromatic hydrocarbons (PAH). Long‐term dissolution from diesel fuel into the aqueous phase was determined experimentally in a continuous flow‐through system using the slow‐stirring method. The data obtained are interpreted using a dynamic equilibrium dissolution model based on Raoult's law. The predicted temporal development of aqueous concentrations are in good agreement with the experimental results. When a compound in the NAPL approaches complete depletion, a tailing behavior is observed, which is assigned to nonequilibrium effects, such as mass transfer limitations in the NAPL phase. The model predicted an increase of the mean molar mass of the diesel fuel of 1.5% over the entire experimental period. It should be noted that, if the dissolution process were to proceed further, the change in the mean molar mass could become significant and render the simple model inaccurate. Yet the simple model supports the assessment of initial action after a contamination event as well as the planning of long‐term remedial strategies.