Brussels, 09 Sep 2003
Researchers report that an ultrafine powder made from iron, one of the most abundant metals on Earth, can be used to clean up contaminated soil and groundwater at thousands of landfills, abandoned mines and industrial sites in the United States.
A National Science Foundation press release says the so-called "nanoscale" iron particles -- which are 10 to 1,000 times smaller than most bacteria -- 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.
This is a vastly cheaper proposition than digging out the soil and treating it shovelful by shovelful, which is how contamination problems are typically handled today. There are more than a thousand still-untreated sites in the nation where hazardous waste is uncontrolled or abandoned, referred to as Superfund sites.
A report on eight years of pioneering work on nanoscale iron and how it can be used to clean up the environment appears in the September 3 issue of the Journal of Nanoparticle Research. The research project has been funded by the National Science Foundation as part of the federal government's 16-agency National Nanotechnology Initiative.
According to Lehigh University environmental engineer Wei-xian Zhang, who headed the research project, iron's cleansing power stems from the simple fact that it rusts, or oxidizes. Contaminants such as trichloroethene, carbon tetrachloride, dioxins or PCBs are caught up in the oxidizing reaction and break down into simple carbon compounds that are far less toxic. The oxidizing iron also reduces dangerous heavy metals such as lead, nickel, mercury or even uranium into an insoluble form that tends to stay locked in the soil, rather than spreading through the food chain.
Nanoscale iron treatments currently cost about $50 per kilogram, far less than the $500 per kilogram cost of such treatments in 1995, when Zhang and his colleagues first developed a chemical route for making the particles. Zhang is currently forming a company to mass-produce the ultrafine iron particles.
The Journal of Nanoparticle Research can be found at http://www.wkap.nl/journals/nano