Handbook of Solvents - George Wypych - ChemTech - Ventech!

17.1 The environmental fate and movement of organic solvents 1155
805
535
472
175
170
161
156
150
130
120
Solubility, mg/L Solvent (reference)
Carbon tetrachloride (4)
Toluene (20)
Chlorobenzene (17)
o-Xylene (4)
F-113 (4)
Ethylbenzene (17)
o-Dichlorobenzene (17)
Tetrachloroethylene (4)
F-114 (4)
F-112 (4)
Relatively hydrophobic
9.5 Hexane (21)
0.05 Decane (22) “Insoluble”
17.1.5.2 Volatilization from water
Henry�s Law constants were compiled for each of the solvents in Table 17.1.1. The numerical
values ranged over 7 orders of magnitude (Table 17.1.3). Based on these values, it can be
expected that volatilization from water will be a significant fate mechanism for decane, hexane,
the chlorinated fluorocarbons, carbon tetrachloride, tetrachloroethylene and trichloroethylene.
Many of the solvents in Table 17.1.1 are characterized by KH values of 10 -3 to 10 -2
atm-m 3 /mole; volatilization from water can be an important pathway for these solvents, depending
on the specific situation. Volatilization may be a relatively slow process for the remaining
solvents. The actual rate of volatilization of some solvents from water has been
experimentally measured. 4,17 However, experimental data are lacking for some compounds,
and the diversity of experimental conditions makes generalizations difficult. Thomas 8 described
a two-layer model of the liquid-gas interface that is based on a Henry�s Law constant
and mass-transfer coefficients. To illustrate the relative volatilities of the solvents in water,
the half-lives of each solvent in a shallow stream were compiled (Table 17.1.4). The stream
was assumed to be 1 meter deep and flowing at a rate of 1 meter per second. With the exception
of hexane, it was also assumed that there was a breeze blowing across the stream at a
rate of 3 meters per second. Under these conditions, the predicted half-lives of many of the
solvents in Table 16.1.1 are less than 10 hours, indicating that volatilization into the atmosphere
can be a relatively rapid pathway for solvents released to surface water. The volatilization
of pyridine, isobutyl alcohol, and cyclohexanone may be a slow process, and other
fate processes may be more important in water.
17.1.5.3 Degradation in water
As mentioned in 17.1.3.3, Howard et al. 14 compiled ranges of half-life values for most of
the organic solvents given in Table 17.1.1. If a “rapid” half-life is defined as in the range of
1 to 10 days, then about 12 of the solvents in Table 17.1.1 may degrade rapidly in surface
water by primarily biodegradation (Figures 17.1.1 and 17.1.2). Abiotic mechanisms such as
photo-oxidation, photolysis, and hydrolysis appear to be either slow or not significant. If
“slow degradation” is defined as that taking longer than 100 days, then it appears that F-11
and most of the chlorinated hydrocarbons may be relatively persistent in surface water. The
available data suggest that the half-life of nitrobenzene and isobutyl alcohol may be variable.
Note that data were not available for all of the solvents listed in Table 17.1.1. In