In "Nanoscale Iron Could Help Cleanse the Environment," the National Science Foundation (NSF) reports that "nanoscale" powder made from iron could be used to clean contaminated soil and water.
The case for nanoscale iron is laid out in the September 3 issue of the Journal of Nanoparticle Research, where Lehigh University environmental engineer Wei-xian Zhang reviews his eight years of pioneering work with the material.
You can read the abstract, "Nanoscale Iron Particles for Environmental Remediation: An Overview" and download a PDF paper from the same page.
Iron's cleansing power stems from the simple fact that it rusts, or oxidizes, explains 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 such as lead, nickel, mercury, or even uranium, says Zhang: The oxidizing iron will reduce these metals to an insoluble form that tends to stay locked in the soil, rather than spreading through the food chain. And, iron itself has no known toxic effect.
Here is how a site can be cleaned by using these iron nanoparticles (Credit: Lehigh University).
What about the cost of this method?
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.)
This amounts to about $5 per square meter.
Source: National Science Foundation, September 3, 2003
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