Volatilization of solid phase organic mixtures in soil

This dissertation presents data pertaining to the volatilization of solid polycyclic aromatic (PAH) mixtures from dry soils. The partial pressures of each constituent in synthetically formed binary solid PAHs were measured in batch systems to determine if ideal solid solutions were formed. The same binary solid PAHs were applied to soil to conduct column studies. Borden 40–60 sand was contaminated at two levels and subjected to dry air at interstitial velocities that are typically encountered in the field. Mass transfer coefficients were calculated from steady-state column data taken at the column exit and were compared to mass transfer coefficients predicted by correlations found in the literature. Lastly, a bench-scale thermal desorption experiment was performed to investigate the viability of using soil vapor thermal desorption at moderate temperatures to remove PAHs from a lampblack-contaminated field sample to acceptable levels.; Naphthalene, fluorene, and anthracene were chosen as model PAHs because of their crystal structures and quantifiable vapor pressures at the experimental conditions. Naphthalene and anthracene represented PAHs with similar crystal structures and naphthalene and fluorene represented PAHs with dissimilar crystal structures. Batch vapor pressure experiments indicated that each individual PAH achieved its pure component vapor pressure, implying that ideal solid solutions were not formed. Results from the column studies corroborated the findings in the batch experiments and shed light onto the mass transfer mechanisms in solid/air systems. Wall-channeling of air flow resulting from the existence of non-uniform porosity lowered observed average mass transfer coefficients 2–4 orders of magnitude below those mass transfer coefficients predicted for packed beds with uniform porosity. Mass transfer coefficients for the bulk region or core section of the packed bed were extracted from the data and were close to those predicted by theory.; Acceptable total PAH concentrations in lampblack-contaminated field samples were achieved at temperatures close to 250°C using a bench-scale soil vapor thermal desorption process. A screening-level model indicated that the desorption process was thermodynamically controlled.