Adsorption of volatile hydrophobic organic compounds at the vapor/water interface
AuthorBruant, Robert Gilbert.
Organic compounds -- Absorption and adsorption.
Interfaces (Physical sciences)
Committee ChairConklin, Martha H.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractAqueous solution surface tension as a function of vapor-phase solute pressure isotheims were measured at atmospheric pressure for single and binary component benzene, methyl-substituted benzene (i.e., methylbenzene, 1,2-dimethylbenzene, 1,3- dimethylbenzene, 1,4-dimethylbenzene, 1,3,5-trimethylbenzene), and trichloroethene adsorption. Solute-induced surface tension variations were quantified using a dynamic adsorption protocol in conjunction with Axisymmetric Drop Shape Analysis-Profile (ADSA-P) applied to pendant drop tensiometry. For single component adsorption, isotherms were measured at temperatures of 285.2K, 291.2 K, 297.2 K, 298.2 K, 303.2 K, and 315.2 K, for vapor-phase solute pressures ranging from zero to near/at saturated vapor pressure. For binary solute experiments, three intermediate constant vapor-phase mole ratio isotherms were developed for each solute pair (i.e., benzene and each of the five methyl-substituted benzenes) at temperatures of 285.2 K, 291.2 K, 298.2 K. Results for single component adsorption studies indicate that for a given vapor-phase solute pressure, interface-phase solute activity increases with molecular size (mass) among the benzene homologues. Similarly, compounds are more strongly adsorbed at the vapor/water interface as the system temperature decreases. Ideal standard free energy, enthalpy, and entropy changes of adsorption, calculated from limiting isotherm data, suggest specific solute-water interactions and a perturbation of the interface-phase water structure on adsorption. Further analysis of binary solute isotherms indicates that interface-mixing is well described by a two-dimensional application of Raoult's law, implying ideal interface-phase solute-solute interactions. Consideration of the twodimensional second virial coefficients suggests that interface-phase solute molecules engage in attractive interactions, with greater interactions for larger molecular sizes.
Degree NamePh. D.
Degree ProgramHydrology and Water Resources