A new recipe for "nanorust" could give developing nations a cheap tool for removing arsenic from drinking water.
Arsenic contamination is linked to bladder cancer and is a big problem in many places, especially in Bangladesh and the neighbouring Indian state of West Bengal.
Chemists know that arsenic binds particularly well to iron oxides, including rust, but practical techniques for doing this have been slow and laborious.
Vicki Colvin and colleagues at Rice University in Houston, Texas, realised that the efficiency of this process could be improved by reducing the size of the iron oxide particles employed. This is because a given weight of smaller particles has more surface area available for binding than the same weight of larger particles.
"One kilogram of nanorust has the same surface area as a football field," says Colvin. "Basically, you can treat a whole lot more arsenic with less material."
The team added nanoscale iron oxide to contaminated water, where it clumped together with the arsenic. They then magnetised the nanoparticles with an electromagnet and pulled them out. "We only needed a surprisingly weak magnetic field," says Colvin. "In fact, we could pull then out with just a hand-held magnet, making this a very practical method."
They believe that only a small field was needed because the magnetised nanoparticles line up to form a single giant magnet and drag each other along.
At the moment, the high cost of making nanoparticles means the trick is too expensive to be used widely. In principle, however, the nanoparticles are easy to make: the team created them by dissolving large pieces of rust in heated oleic acid, which can be found in ordinary olive oil.
"The temperatures needed are accessible in a frying pan," Colvin adds. "So we are now trying to develop a production method using ingredients and equipment that are available in poorer nations."
Journal reference: Science (vol 314, p 964)
Today's lecture was about this. It's horrible. It's a situation of pick your poison. The surface pond water is gross, filled with bacteria. When they switched to ground water (wells), infant mortality was reduced by 500%. But now those healthy babies are doomed toan early grave. 125 million people are drinking aresenic contaminated waters. They get black bubbly lesions all over their bodies and die of horrible cancers.
It's a difficult problem too. The arsenic isn't very predicatble. You might have deadly 400 ppb levels, while your neighbour has drinkable <10ppb levels. The sediments have normal 1-15 ppm levels, lower by a factor of 10-100 than the yukon or baffin island sediments.
To top it off, these people are dirt poor. Drilling operations for instance, cost 17 cents a foot, while here the same function (better equipment) is $35 a foot.
Be grateful for clean water.