Solubilities of PAHs in alcohol-water mixtures
Abstract
Solubilities of phenanthrene, pyrene, and perylene were determined in aqueous solutions containing either methanol, ethanol, or propanol at alcohol volume fractions ranging from zero to nearly one, at 25$\sp\circ$C under atmospheric pressure. These data, and data from the literature on naphthalene, were compared to 2, 3, and 4 interaction-parameter Margules equations and UNIFAC predictions. For each solute-solvent-cosolvent (i.e., PAH-water-alcohol) system examined, the solubility of each PAH increased with increasing alcohol volume fraction. The UNIFAC model poorly estimated solubilities at cosolvent volume fractions near 0.5. Analysis of the data with various forms of the Margules equations suggests that, in addition to solute-solvent and solute-cosolvent interactions, solvent-cosolvent (i.e., water-alcohol) and solute-solvent-cosolvent interactions are important at cosolvent volume fractions near 0.5. A simplified three-suffix Margules model is proposed, which includes terms for all these interactions and accurately estimates the experimental data with a consistent set of interaction parameters. All interaction parameters involving solute molecules may be estimated from the octanol-water partition coefficient, $K\sb{ow},$ of the respective solute. This empirical result suggests that the solubility of other PAHs in similar alcohol-water mixtures may be estimated from $K\sb{ow},$ and enthalpy of fusion. Additionally, extension of Margules equations to quaternery systems were conducted and evaluated. Generally, the two-suffix model is able to calculate the PAHs solubilities in ternary solvent systems studied. The deviation of calculated PAH's solubilities from experimental measurements for systems containing phenol as cosolvent results from the complex molecular interactions of phenol. Similar solubility data for phenanthrene and pyrene were determined at 4$\sp\circ$ and 43$\sp\circ$C. Combined the data at 25$\sp\circ$C, these data were analyzed with van't Hoff's equation. At each temperature, solubility increases as alcohol volume fraction concentration increases. The data suggests that excess enthalpies of the solute are close to zero. Assuming excess enthalpies as zero, excess entropy was calculated to be nearly independent of temperature.
Degree
Ph.D.
Advisors
Jafvert, Purdue University.
Subject Area
Chemistry|Civil engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.