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Environmental Engineering Research 2011;16(4): 187-203. DOI: https://doi.org/10.4491/eer.2011.16.4.187
Degradation of Chlorinated Phenols by Zero Valent Iron and Bimetals of Iron: A Review
Buddhika Gunawardana1, Naresh Singhal1, and Peter Swedlund2
1Department of Civil and Environmental Engineering, University of Auckland, Private Bag 92019, Auckland, New Zealand
2Department of Chemistry, University of Auckland, Private Bag 92019, Auckland, New Zealand
Corresponding Author: Naresh Singhal ,Tel: +64-9-373-7599, Fax: +64-9-373-7462, Email: n.singhal@auckland.ac.nz
Received: September 10, 2011;  Accepted: November 20, 2011.
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Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.
Keywords: Chlorophenols | Bimetals | Dechlorination | Iron oxides | Passivation | Sorption | Zero valent iron
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