Nanoscale iron as environmental cleanser: "An ultrafine, "nanoscale" powder made from iron, one of the most abundant metals on Earth, is turning out to be a remarkably effective tool for cleaning up contaminated soil and groundwater--a trillion-dollar problem that encompasses more than 1000 still-untreated Superfund sites in the United States, some 150,000 underground storage tank releases, and a staggering number of landfills, abandoned mines, and industrial sites.
Iron's cleansing power stems from the simple fact that it rusts, or oxidizes, explains [Lehigh University environmental engineer Wei-xian]Zhang. Ordinarily, of course, the only result is the familiar patina of brick-red iron oxide. But when metallic iron oxidizes in the presence of contaminants such as trichloroethene, carbon tetrachloride, dioxins, or PCBs, he says, these organic molecules get caught up in the reactions and broken down into simple carbon compounds that are far less toxic. Likewise with dangerous heavy metals..
[N]anoscale iron particles are some 10 to 1000 times more reactive than conventional iron powders, because their smaller size collectively gives them a much larger surface area, and they can be suspended in a slurry and pumped straight into the heart of a contaminated site like an industrial-scale hypodermic injection. Once there, the particles will flow along with the groundwater to work their decontamination magic in place--a vastly cheaper proposition than digging out the soil..
Laboratory and field tests have confirmed that treatment with nanoscale iron particles can drastically lower contaminant levels around the injection well within a day or two, and will all but eliminate them within a few weeks--reducing them so far that the formerly polluted site will now meet federal groundwater quality standards. The tests also show that the nanoscale iron will remain active in the soil for 6 to 8 weeks, says Zhang, or until what's left of it dissolves in the groundwater. And after that, of course, it will be essentially undetectable against the much higher background of naturally occurring iron.
Finally, says Zhang, the cost of the nanoscale iron treatments is not nearly as big a barrier as it was in 1995, when he and his colleagues first developed a chemical route for making the particles. Then the nanoscale iron cost about $500 a kilogram; now, it's more like $40 to $50 per kilogram. (Decontaminating an area of about 100 square meters using a single injection well requires 11.2 kilograms.) Zhang is currently forming a company to mass-produce the nanoscale iron particles. " Contact: (610)-758-5318, email@example.com. 11:28:47 AM