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Mechanisms affecting the dissolution of nonaqueous phase liquids into the aqueous phase in slow‐stirring batch systems
Author(s) -
Schluep Mathias,
Imboden Dieter M.,
Gälli René,
Zeyer Josef
Publication year - 2001
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.5620200301
Subject(s) - ethylbenzene , partition coefficient , chemistry , toluene , aqueous solution , dissolution , benzene , aqueous two phase system , btex , diffusion , phase (matter) , hydrocarbon , kinetics , thermal diffusivity , xylene , thermodynamics , organic chemistry , physics , quantum mechanics
Understanding the kinetics of the exchange processes between nonaqueous phase liquids (NALs) and water is important in predicting the fate of anthropogenic compounds such as petroleum hydrocarbons, i.e., benzene, toluene, ethylbenzene, and xylene (BTEX) as well as polynuclear aromatic hydrocarbons (PAHs). Exchange processes occurring in the environment resemble the experimental setup of the slow‐stirring method (SSM) designed to determine solubilities and octanol‐water partition coefficients. Data obtained from SSM experiments for diesel fuel compounds are interpreted by a linear transfer model that is characterized by an aqueous molecular boundary layer and the water/NAPL equilibrium partition coefficient. For the chosen experimental setup, the boundary layer thickness is 2.42 × 10 −2 cm. Typical equilibration times lie between 1 and 2 d. Due to the temperature dependence of the aqueous diffusivity, this time increases with decreasing temperature. Transport within the NAPL phase can slow down the exchange process for the more water‐soluble compounds (e.g., benzene) provided that the stirring rate exceeds a critical value.