Thermodynamic Parameters for the Adsorption of Aromatic Hydrocarbon Vapors at the Gas-Water Interface

摘要

Experimental data on the adsorption of polycyclic aromatic hydrocarbons (PAHs) at the gas-water interface is lacking. The inverse gas chromatography (IGC) technique with Chromosorb P NAW as the packing support was used to obtain the thermodynamic parameters for the adsorption of three aromatic compounds (benzene, naphthalene, and phenanthrene) at the gas-water interface. The partition constants at different temperatures were measured and used to compute the free energy, enthalpy, and entropy of adsorption using the Gibbs-Helmholtz equation. The enthalpy of adsorption at the gas-water interface for all three compounds was larger than the enthalpy of condensation and the enthalpy of aqueous solvation. This supports the prevailing "critical cluster" model for the dynamics of the transfer of compounds to the gas-water interface. The thermodynamics of adsorption at the was-solid interface was more fabvorable than that at the gas-water interface. The partition constant at the gas-water interface was correlated with the subcooled liquid vapor pressure of the PAHs. The possible effect of gas-water partitioning of PAHs upon their wet deposition from the atmosphere is explored theoretically.