In 1990,scientists from the University of Waterloo made an important finding: certain metals, including stainless steel, “apparently transformed the [halogenated] compounds,” such as trichloroethane and tetrachloroethylene (Reynolds et al, Environ. Sci. Technol., 1990, 135-42). This discovery motivated the pursuit of finding zero-valent metals that could be injected onto the ground safely and that would remediate VOCs in groundwater. Zero Valent Iron, or ZVI, was one of choices, as it would undergoes reactions that include metal dissolution and reductions, catalytic hydrogenations, and corrosion.
Zero-valent iron is a mild reductant, and dehalogenation (the degradation of halogenated compounds) occurs at faster rates for some compounds, such as for carbon tetrachloride to chloroform, than for others, such as dichloromethane. Also, another problem is related to incomplete dehalogenation that could produce and accumulate degradation products that are far more harmful than the original parent compound. Such is the case of tetra- and trichloroethene, and formation of vinyl chloride, which is a proven carcinogen. Fortunately, research has demonstrated that in most cases that the end products of dehalogenation via ZVI are simple hydrocarbons (Tratnyek, Chemistry and Industry/July 1, 1996).
Professor Denis O’Carroll and his research group at Western University are investigating the application of nano ZVI to treat VOC contamination in groundwater. Nanomaterials are receiving widespread interest in a variety of fields due to their unique, beneficial chemical, physical, and mechanical properties. The technology application consists of pumping these nanomaterials into the ground, they flow with groundwater to a contaminated region, and then convert hazardous chemicals (ie. trichloethene) into benign daughter products (ie. ethane). Significant contribution and support during field trials have been received from CH2M Hill, one of our private sector partners.
Watch Prof Denis O’Carroll discuss Nano Revolution on The Nature of Things.