Environmental Engineering Reference
In-Depth Information
TABLE 3.10
Effective Solubilities of Components in a Waste Mixture of Methyl Chloroform Degreasing
Solvent from a 1970s-Era Aerospace Industry Degreaser
Single-
Component
Aqueous
Solubility
c
(mg/L)
Mass in
1 mol of
Mixture
(g/mol)
S
eff
(Effective
Solubility)
d
(mg/L)
Molecular
Weight
(g/mol)
Specifi c
Gravity
(g/cm
3
)
Initial Mass
Fraction
a
(%)
Final Mass
Fraction
b
(%)
X
i
(Mole
Fraction)
Component
Methyl chloroform
113.40
1.35
93.25
53.62
62.71
0.55
1334
740
1,4-Dioxane
88.12
1.03
3.00
15.00
17.54
0.20
10,000,000
1,991,600
sec
-Butyl alcohol
74.10
0.80
1.50
7.06
8.25
0.11
10,000,000
1,114,000
1,3-Dioxolane
74.09
1.06
1.00
1.27
1.48
0.02
10,000,000
200,000
1,2-Butylene oxide
72.12
0.83
0.70
0.31
0.36
0.01
95,000
480
Nitromethane
61.04
1.14
0.55
2.75
3.22
0.05
11,100
590
Cutting oil
e
400.00
0.95
0.00
20.00
23.39
0.06
50
3
Overall mixture
f
116.96
1.13
100
100
116.96
1.00
a
Initial mass fraction represents the composition of methyl chloroform-containing spent-solvent waste listed in Archer
(1984).
b
Final mass fraction represents the roughly estimated composition of spent-solvent waste after 6 weeks of intensive vapor
degreasing during which volatile vapors are lost to the atmosphere, “high-boilers” are concentrated in the still bottoms, and
cutting oil accumulates. The assumed oil composition and hypothetical aerospace industry setting are based on Jackson
and Dwarakanath (1999).
c
Miscible compounds assigned a solubility of 10
6
mg/L for calculation; values are from frequently cited solubilities in
Table 3.9
.
d
The effective solubility is calculated by using the adaptation of Raoult's law explained in
Section 3.3.1
and in Jackson and
Mariner (1995) (values are rounded).
e
Molecular weight, specii c gravity, and solubility of cutting oil are assumed values.
f
Properties of overall mixture are for i nal composition of the degreasing waste at the point it was removed from the
degreaser and replaced with new solvent.
3.3.2 A
DSORPTION
Adsorption is the attachment of a compound in the aqueous or vapor phase onto a solid surface. A
related process,
ab
sorption, involves the transfer of a compound from the aqueous phase
into
a vol-
ume of solid material. Because adsorption and absorption are usually not distinguishable in natural
systems, the term
sorption
is used to indicate that the specii c mechanism of attachment to or move-
ment into a solid surface or volume is not known (Schwarzenbach et al., 1993).
Adsorption of molecules, while technically a partitioning phenomenon, can be represented as a
chemical reaction:
A
+
B
↔
A
⋅
B,
(3.27)
where A represents the adsorbate, B the adsorbent, and A·B the adsorbed compounds. The “adsorption
reaction” involves a variety of intermolecular forces and is often reversible: molecules continue to
accumulate onto the soil particle surface until equilibrium is reached and the rate of forward reac-
tion (adsorption) equals the rate of reverse reaction (desorption) (Snoeyink, 1999).
*
*
The technical term “soil” is typically reserved for the root-zone material; the geologic material comprising aquifers is
referred to as “aquifer solids.” For convenience, this chapter uses the less precise practice of calling all subsurface solids
by the term “soils.”
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