Recipe for pure water

时间:2019-03-07 03:07:00166网络整理admin

By Jens Thomas 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’s 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 °C for several hours. As the researchers will report in the Journal of the American Chemical Society, the reaction leaves no detectable trace of organic contaminants. “At the end of the process you only need to filter off the metal,” says Sen. “There’s nothing organic left.” The researchers discovered the method when they noticed that dissolved organic compounds in contact with the metal palladium tend to oxidise—the 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’s 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. “We didn’t actually use nerve gas, my students would kill me,” he says. The imitation nerve gas vanished without a trace. Experts have reacted enthusiastically. “It’s one of the goals of the people who clean up industry,” says Robert Lyndsay Smith, who researches oxidative catalysts at York University. “You’d have thought someone would have tried it before,” he says. “They have put it together quite nicely.” 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,