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Cleaning the Environment with Iron Nanoparticles
Roland Piquepaille writes "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. "Iron's cleansing power stems from the simple fact that it rusts. When metallic iron oxidizes in the presence of contaminants, these organic molecules get caught up in the reactions and broken down into simple carbon compounds that are far less toxic." Using this technology, cleaning landfills or industrial sites would cost about $5 per square meter. More details are available in this summary, including other links and a diagram showing how the method works."
Iron oxide occurs naturally. People have been cooking with iron frying pans for years, and studies show it's actually good for you in trace amounts. Eating an entire frying pan in one sitting, however, is most likely bad for you.
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the size is part of the issue (smaller particles have more surface area). the more important point is that iron in the evironment is already in an oxidized state, e.g., Fe(OH)2. And it is the oxidation/reduction reaction that is driving the detoxification of the compounds. Specifically, Fe0 goes to Fe2+ or Fe3+, giving up 2 electrons which then are used to reduce the compound. (reduction also has the benefit that it usually makes the compound more amenable for microorganisms to chew up naturally).
This site has some diagrams of chemical pathways. Also try googling "zero valent iron".
That article is talking about children overdosing on iron pills. You'd have to eat a lot of dirt to get that kind of iron into your system from the ground.
Rusting iron consumes free oxygen. When used in water sources, this can be a very Bad Thing for most closed-system watersheds.
Powdered iron has been suggested as a means of controlling greenhouse buildup by scattering hundreds of tons of it across the surface of the pacific ocean; it creates dramatic blooms of algae in the water that suck up carbon dioxide and other pollutants.
The problem to this, of course, is that the ocean is a closed-system as well, albeit a far larger one. The iron rusts, consumes oxygen, leaving fish in oxygen-deprived waters and with little place else to go. (Fish aren't immune to pressure, quite the opposite, so no, going down isn't much of an option.)
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LTFD (Look at The F* Diagram). They are injecting it into the ground using special wells.