These scavengers of water pollutants have a magnetic attraction

A process that uses magnetic nanoparticles, coated with a reactive material, to clean up contaminated water for human use is being developed at Stanford University (Stanford, Calif.; www.stanford.edu). The nanoscavengers, as they are called, are distributed in the water to kill pollutants, then are recovered magnetically for re-use. Stanford’s particles are discs that consist of a layer of titanium, sandwiched between layers of pure iron, with an outer coating of reactive material. The discs, measuring about 150-nm dia. by 60-nm thick, are fabricated by thermal evaporation. The novel feature is that the direction of the magnetic force in the top and bottom layers point in opposite directions, thereby canceling the magnetic properties of the material, says Mingliang Zhang, of the Stanford School of Engineering. However, when a strong electromagnetic field is activated the opposing magnetic forces are aligned, making the particles strongly magnetic. So far the researchers have used silver-coated nanoparticles to achieve 99.9% destruction of E.coli and E. hirae bacteria, and are now testing titanium dioxide-coated particles for photocatalytic degradation of trichloroethylene (TCE) and N-nitrosodimethylamine (NDMA). The researchers’…