Ch. Fan et Ct. Jafvert, MARGULES EQUATIONS APPLIED TO PAH SOLUBILITIES IN ALCOHOL-WATER MIXTURES, Environmental science & technology, 31(12), 1997, pp. 3516-3522
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 1, at 25 degrees
C and atmospheric pressure. These data, and data from the literature o
n naphthalene were compared to various forms of two- and three-suffix
Margules equations and UNIFAC predictions. For each solute-solvent-cos
olvent (i.e., PAH-water-alcohol) system examined, the solubility (S) o
f each PAH increased with increasing alcohol volume fraction (v(3)). T
he UNIFAC model poorly estimated solubilities at cosolvent volume frac
tions near 0.5. Analysis of the data with various forms of the Margule
s equations shows that, in addition to solute-solvent and solute-cosol
vent interaction terms, inclusion of solvent-cosolvent (i.e., water-al
cohol) and solute-solvent-cosolvent interaction forms in the model imp
roves predictions, particularly 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 experim
ental data with a consistent set of interaction parameters. All sets o
f interaction parameters involving solute molecules were regressed aga
inst each solute's respective log octanol-water partition coefficient,
K-aw. Solubilities of other PAH compounds in similar alcohol-water mi
xtures, obtained from the literature, were estimated accurately with t
hese relationships and knowledge of each solute's K-aw value and entha
lpy of fusion.