Inside Iowa State
Sept. 6, 1996
An electrifying experiment
by Skip Derra
The fear of electrocution keeps most of us from crossing electricity with water, but it hasn't deterred Dennis Johnson.
The professor of chemistry and senior chemist at Ames Laboratory routinely runs electrical current through water solutions in his lab and he would like to do it in farm fields some day.
By applying electricity to water and toxic chemicals, Johnson has been able to render the chemicals into harmless compounds. His research, based on the fundamental chemical process of electrolysis, some day could have a dramatic impact on the way toxic chemicals are handled.
Johnson wants to use the process to transform some nasty wastes -- especially the carcinogen benzene, which is used to make herbicides, pesticides and a variety of industrial compounds -- into pure water. By passing an electrical current through a solution that includes the benzene, Johnson incinerates the chemical.
The idea is the same as burning the compound, said Johnson, who leads one of two groups in the world working on electrochemical incineration. "But we use a voltage to totally destroy the molecules and we do it under water."
In the process, Johnson sets up an electrolytic cell, which contains water, the toxic compound and two electrodes (metal conductors) connected to an electrical source. With the correct water mixture, the bonds of the toxic compound are broken as it passes between the electrodes, leaving benign substances in its wake.
With this process, Johnson has taken a vile mixture of polluted water, almost black in color, and changed it into clear, drinkable tap water and carbon dioxide.
He said electrochemical processes have been used in industry for years to make several useful chemical compounds, such as chlorine gas and rocket propellants.
"The technology is there. Now it's a matter of getting the best electrode material to work in it," said Johnson, a 1991 recipient of the Governor's Medal for Science Application.
The breaking of the chemical bonds in compounds happens on the surface of the electrodes, making electrode design critical.
Johnson said that if fully developed, electrochemical incineration could have effects both large and small. For example, it could be used to handle a rural chemical spill in which thousands of gallons of pollutants seep into an underground aquifer.
"Instead of taking the toxic material to the incinerator, you take the incinerator to the toxic material," he said.
At the other end of the spectrum, a small commercial reactor based on this method could greatly simplify how every day lab waste is dealt with.
"Rather than having to dispose of a small amount of toxic waste and dealing with the ensuing paper work, lab technicians can simply dump all of the waste in our device, close the lid, flip a switch, and when they come into work the next day it's clear water," Johnson said. "End of problem."
But much work still needs to be done. Johnson admits he has a long way to go from 50-milliliter experiments in his lab to actual field tests. He's looking at new electrode designs and possible collaboration to scale up the process and possibly take it on the road.
Johnson has a wide range of nasty compounds to test out in his "incinerator." But with each new compound he successfully renders harmless, his confidence builds.
"We're working our way up to the big animals, like pesticides and herbicides," said Johnson who, in addition to his research, is teaching general chemistry to 500 freshmen this semester. "With every week and month, I get braver and braver and think, 'Yeah, we will be able to chew up all of these pesticides and toxic chemicals.'"
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