Project Summary (2006-2011)

The main objective of this project is to assess the potential for using oxidants produced during the corrosion of granular and nanoparticulate zero-valent iron (ZVI) by oxygen to remediate contaminated groundwater and soil. These objectives are being realized by studying the reaction mechanisms involved in oxidant production and contaminant transformation and the efficiency of potential treatment methods under conditions similar to those that are likely to be employed in treatment systems. The overall hypothesis is that the oxidative ZVI system offers a practical, cost-effective means of remediating contaminants that have the greatest impact on human health at Superfund sites. This investigation of the reaction mechanisms focuses on the role of solution chemistry and surface structure on the rate of contaminant transformation. To gain insight into the processes occurring on or near ZVI surfaces, chemical processes occurring in the solution phase are being measured in conjunction with studies conducted using techniques designed to probe the surface, such as potentiometry, surface enhanced Raman spectroscopy and electrochemical quartz microbalance methods. This investigation of the potential applications of the oxidative ZVI system to contaminant remediation focuses on permeable reactive barriers and water infiltration systems used to treat organic contaminants and drinking water treatment systems used to remove arsenic. These studies extend the research in oxidant formation mechanisms to account for the effect of oxide coatings on the ZVI surfaces on contaminant oxidation rates and transport of contaminants to and from the corroding iron surfaces. This research has the potential to provide innovative and cost-effective ways of removing contaminants from groundwater and drinking water that are difficult or expensive to treat by conventional methods. The development of these technologies could reduce human exposure to organic and inorganic contaminants of concern.