CLEANING up water contaminated with deadly chemicals is a piece of cake, say
chemists who have discovered a cheap and easy way to break down organic poisons.
With some improvements, they say, the method could even be used to dispose of
nerve gas and other chemical weapons.
Organic chemicals are among the world鈥檚 most worrisome pollutants. They
include PCBs and dioxin, and military wastes from expired explosives to VX, a
lethal nerve gas. Since organic compounds consist almost entirely of carbon,
hydrogen and oxygen, they can theoretically be broken down into water and carbon
dioxide, along with trace quantities of relatively harmless ions such as
nitrates, sulphates and chloride.
But up to now, this process has required either very harsh and expensive
conditions, or equally toxic chemicals. Now chemists led by Ayusman Sen at the
Pennsylvania State University have come up with a simple recipe: dissolve a
small amount of oxygen and carbon monoxide in the water containing any organic
chemical, add a pinch of a cheap metal catalyst and cook at 85 掳C for
several hours.
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As the researchers will report in the Journal of the American Chemical
Society, the reaction leaves no detectable trace of organic contaminants.
鈥淎t the end of the process you only need to filter off the metal,鈥� says Sen.
鈥淭here鈥檚 nothing organic left.鈥�
The researchers discovered the method when they noticed that dissolved
organic compounds in contact with the metal palladium tend to oxidise鈥攖he
process in which a molecule loses electrons and combines with oxygen. How
compounds become sufficiently oxidised to break down completely is still poorly
understood. Sen believes the metal catalyses the compound鈥檚 oxidation both
directly and indirectly, by converting water and oxygen into hydrogen peroxide,
a powerful oxidising agent.
Having tested the process with simple molecules such as methane, Sen moved on
to try more complex compounds which are chemically similar to nerve gases but
safe. 鈥淲e didn鈥檛 actually use nerve gas, my students would kill me,鈥� he says.
The imitation nerve gas vanished without a trace.
Experts have reacted enthusiastically. 鈥淚t鈥檚 one of the goals of the people
who clean up industry,鈥� says Robert Lyndsay Smith, who researches oxidative
catalysts at York University. 鈥淵ou鈥檇 have thought someone would have tried it
before,鈥� he says. 鈥淭hey have put it together quite nicely.鈥�
Sen says the method might eventually be useful as an alternative to
incineration for destroying chemical weapons stockpiles. However, in its
existing form, the technique would require too much water to be practical, so
Sen is trying to improve the process.