Handbook of Solvents - George Wypych - ChemTech - Ventech!

1000 An Li
Trade Name Cosolvent vol% Manufacturer Type
Tylenol Propylene glycol McNeil Consumer Oral
Valium
Ethanol
Propylene glycol
10
40
Roche Parenteral
Vepesid Ethanol 30.5 Bristol-Myers Parenteral
(Data are from reference 21)
14.21.2.3 Applications of cosolvency in environmental sciences and
engineering
The significance of cosolvency research in environmental sciences stems from the need for
accurately modeling the distribution and movement of organic pollutants, and cleaning up
polluted soils and sediments. Since the late 1970s, environmental research on the effect of
cosolvents has grown steadily.
Most published research papers have focused on the effects of adding cosolvents on
the aqueous solubility 18,22-31 and soil sorption 28,32-44 of pollutants of interest. A few researchers
have also examined cosolvent effects on liquid phase partitioning. 45,46 In the cases of industrial
waste discharges, liquid fuel and paint spills, storage tank leakage, landfill leaching,
and illegal dumping, various organic solvents may find their way into the natural environment.
These solvents may not only act as pollutants themselves, but also bring substantial
changes on the distribution, movement, and fate of other environmental pollutants with high
concern. In environmental cosolvency studies, the majority of the solutes are hydrophobic
organic compounds (HOCs), including benzene and its derivatives, polycyclic aromatic hydrocarbons
(PAHs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins
and furans (PCDDs and PCDFs), and various pesticides. These chemicals are toxic, and
many of them are mutagenic and carcinogenic. The 1990 Clean Air Act Amendment has
stimulated research on gasoline additives such as methyl t-butyl ether (MTBE) and formulated
fuels like gasohol. Their cosolvent effects on the solubility and sorption of a few pollutant
groups have also been examined. 25,47
Meanwhile, environmental engineers have put cosolvents to work in cleaning up contaminated
sites. As a consequence of the failure of using traditional pump-and-treat
remediation for soils contaminated with organic pollutants, a few new approaches have
been experimented since the late 1980s. Among those involving cosolvents, Ex situ solvent
extraction was developed to treat excavated soils, sediment, or sludge. A typical one is the
basic extractive sludge treatment (B.E.S.T.) process certified by USEPA. 48,49 Triethylamine
was selected as the extracting solvent due mainly to its inverse miscibility property - it is
completely miscible with water below 60 o F but separates from water above 90 o F. This property
makes it easier to recycle the solvents after separating the treated solids from liquids
containing the solvent, pollutants, and water. For PCBs in various soils, it is typical to
achieve an extraction efficiency higher than 99% using the B.E.S.T technique.
More attractive are in situ remediation approaches, which often cost less. Cosolvents
promote the mobilization of organic chemicals in soils, thus accelerating the cleanup of
contaminated site. Cosolvent flushing has been developed using the same principles as
those used in solvent flooding, a technique to enhance petroleum recovery in oil fields. It involves
injecting a solvent mixture, mostly water plus a miscible cosolvent, into the vadose