One Pollution Solution?

Author: John Monczunski

“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.”