eldavojohn writes "How do you remove arsenic from water? Well, a research team has discovered that adding and removing nanorust works well. From the article, 'The team added nanoscale iron oxide to contaminated water, where it clumped together with the arsenic. They then magnetized 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.' Big news for developing nations that are plagued with non-potable drinking water."