"Friendly" chemical has its mean side
By Associate Professor Allan Blackman
This article was orignally published in the Otago Daily Times on Tuesday 3 October 2006.
It’s funny what you see sometimes when you’re out for a drive.
The weirdest thing I’ve ever seen on a road came on a trip up to the Cardrona skifield a couple of years ago. Near the top, I came upon a guy in drag (and believe me, it wasn’t flattering drag) in the middle of the road, “cleaning” it with a vacuum cleaner — and bizarrely, he was still there at the end of the day as everyone headed home.
The truck in the accompanying photo also gave me a chuckle. I came across this on a motorway recently, thereby getting the inspiration for today’s column. The caption reads “Hydrogen peroxide — a friendly chemical” and surrounds what looks to be either a dolphin or a killer whale, apparently cavorting joyously in said chemical.
So is hydrogen peroxide in fact a “friendly chemical”? The answer to this question is, as we’ll see, yes and no.
Hydrogen peroxide has the chemical formula H2O2, seemingly not too different from that of water, H2O. However, the extra hydrogen atom ensures that hydrogen peroxide behaves very differently from water.
For starters, pure H2O2 is highly explosive, and for this reason, it is usually diluted with water to give a 30% solution. H2O2 is also a strong oxidising agent; meaning it is very reactive towards many molecules, indiscriminately ripping electrons off them. These properties, I would say, render H2O2 distinctly unfriendly. If you manage to get 30% H2O2 on your skin, it leaves painful white burns (yes, I am speaking from experience) and I doubt that any self-respecting marine creature would venture anywhere near the stuff, let alone cavort in it.
Having said this, H2O2 does indeed have a friendly side. Of the hundreds of thousands of tonnes produced annually worldwide, more than half is used to bleach wood pulp.
In years gone by, chlorine and chlorine dioxide were commonly used to carry out this process, but use of these reagents has been shown to produce dioxins. The beauty of using H2O2 as a bleach is that the final product of this reaction is water, and you can hardly get more environmentally friendly than that. However, a problem associated with the use of H2O2 is that, despite the fact it is an excellent oxidising agent, it usually reacts quite slowly, and so it often needs a bit of a “helping hand” in the form of a catalyst in order to get it going.
New Zealand chemists have been instrumental in making such catalysts.
Professor Terry Collins, an ex-pat Kiwi at Carnegie Mellon University in the United States, has overseen the development of TAML (Tetra Amido Macrocyclic Ligand) catalysts during the past 20 years.
These are environmentally benign compounds which catalyse reactions of H2O2, and can be used for, among other things, mitigation of pulp and paper effluent colour and smell, destruction of biological and chemical warfare agents, and degradation of a wide variety of pollutants.
His work has been recognised in the US through the Presidential Green Chemistry Challenge Academic Award in 1999, and he is now collaborating with scientists at Auckland University and the New Zealand Forest Research Institute to further develop these catalysts, with particular emphasis on their use in the pulp and paper field.
What began as an “academic” exercise in the synthesis of unusual molecules has led to the production of catalysts which can truly improve the environment — a nice reminder that all research, no matter how apparently abstruse, can have unexpected beneficial applications.
So you can see that hydrogen peroxide has both a friendly and an unfriendly side.
Perhaps a more accurate motto for the trucking company might be:
“Hydrogen peroxide — a mostly friendly chemical”.
Welcome sight? . . . A truck carries hydrogen peroxide on a European motorway.
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