The Future - Removing arsenic from water with rust

11.11.06

Originally posted on New Scentist Tech.

I'm going to have to add a link to these guys because they've put out articles on new water technology three times this week. This one is how arsenic can be removed from water to make it potable, arsenic contaminated water is a big problem in developing countries.

There's nothing like a new site with progressive values.

Smell that?

Its the cleaner air of the future.

19:00 09 November 2006
NewScientist.com news service
Zeeya Merali

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."

Lining up

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)


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