Ongoing Research Projects

Oxidation of Contaminants by Iron Nanoparticles in the Presence of Oxygen 

Elemental iron (Fe⁰_(s)), which is also referred to as zero-valent iron, has been used to reduce halogenated solvents and other chemical contaminants that often are present in groundwater.  Zero-valent iron usually is used for contaminant removal in the absence of oxygen, because oxygen competes with the iron for reactive sites on the iron.  While the presence of oxygen slows the rate of reductive reactions, we have found that the reaction of oxygen and zero-valent iron also can result in contaminant oxidation through a complex series of reactions, such as those depicted below:

Figure 1: Oxidation of iron by oxygen and organic compounds (R) by oxygen.

The oxidation reactions are relatively fast and non-specific, which raises the possibility of using iron as a means of oxidizing recalcitrant organic compounds.   The oxidation of organic compounds is especially fast when iron nanoparticles are used.  In our initial research on this project, we found that aromatic compounds, such as benzoic acid could be oxidized by iron nanoparticles in minutes to hours (Joo et al. 2005).  The rate of oxidation of organic compounds appears to be related to properties such as the surface area of the particles, pH and solution composition.  For example, the oxidation of benzoic acid increases as the particle surface area decreases (Figure 2).  Our current research on this topic, which is being conducted in conjunction with Professor David Waite (University of New South Wales)  is examining the effects of solution pH and the surface of the iron particle on the rate of oxidation. Ultimatlely, we hope to evaluate the potential for using these reactions to remediate contaminated soil and groundwater. 

Figure 2: Effect of iron source on the conversion of benzoic acid to hydroxybenzoic acid.

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