"Ionic liquid" may sound like a new brand of dish detergent.
But it's really an unexplored class of chemical compound with
the potential to help clean the nation's air while saving industry
millions of dollars. At least that's the hope. Whether it's any
more than that an interdisciplinary team of Notre Dame researchers
intends to find out.
The novel compounds, which can dissolve petroleum-based and
water-based liquids, have huge potential as "green" alternatives
to conventional industrial solvents used in manufacturing everything
from plastics to drugs. Since their tight chemical bonds inhibit
evaporation, they won't contribute to air pollution, and they
can be recycled and reused at considerable savings. An estimated
20 million tons of conventional solvents annually float out of
industrial smokestacks into American skies.
There is a hitch, however. Since ionic liquids are water soluble,
inevitably they will work their way into the environment through
accidents or inappropriate disposal. And since so little is known
about them, what if they're toxic? "It does no good to replace
something that is air polluting with something that is water polluting,"
points out Gary Lamberti, professor of biology.
To head off any future eco-problem, Lamberti and fellow biology
professors David Lodge and Charles Kulpa, along with chemical
engineering professors Edward Maginn, Joan Brenneke and Mark Stadtherr
and several student assistants, are attempting to identify some
of the most eco-friendly ionic liquid solvents from an estimated
1 trillion possible compounds.
Maginn and Stadtherr are using mathematical models to design
ionic liquids with the proper characteristics, while Brenneke
is using her lab to synthesize the compounds and then test and
measure such properties as solubility and thermodynamic characteristics.
Meanwhile, Lamberti and Lodge are examining the ecological toxicity
of the compounds, exposing various organisms from bacteria to
fish and measuring their reaction. Finally, Kulpa's lab is measuring
the compounds' biodegradability, ascertaining which microbes break
down the ionic liquids.
So far, not so good. Initial results have shown that some of
these compounds are pretty toxic to aquatic animals. "But," Lamberti
insists, "this is exactly the information we need to design safe
chemicals. In the past, things were only dealt with after they
became a problem. Eventually the plan is to test the most benign
candidates in an artificial stream, lake and pond to determine
their effect on an entire ecosystem."
The promise is still there, but for now the biologists are telling
the chemical engineers "back to the drawing board."
* * *
(April 2004)
