In Situ Chemical Reduction of Aquifer Sediments: Enhancement of Reactive Iron Phases and TCE Dechlorination
In situ chemical reduction of aquifer sediments is currently being used for chromate and TCE remediation by forming a permeable reactive barrier. The chemical and physical processes that occur during abiotic reduction of natural sediments by sodium dithionite were investigated. In different aquifer sediments, 15 to 25% of Fe{sup III} -oxides were dissolved/reduced, which produces primarily adsorbed Fe{sup II}, and some siderite. The sediment reduction rate ({approx} 5h) was the chemically controlled (58 kJ/mole) reduction of a minor phase (<20%). It was necessary to maintain neutral to high pH to maintain reduction efficiency and prevent iron mobilization, as reduction generated H{sup +}. Sequential extractions on reduced sediment showed that adsorbed ferrous iron and iron oxides on the clay size fraction controlled TCE reactivity, and not structural ferrous iron in clay. The mass and rate of field-scale reduction of aquifer sediments were generally predicted with laboratory data using a single reduction reaction.
- Research Organization:
- Pacific Northwest National Lab., Richland, WA (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15011105
- Report Number(s):
- PNNL-SA-39253; ESTHAG; 400403209; TRN: US200503%%674
- Journal Information:
- Environmental Science and Technology, Vol. 38, Issue 17; Other Information: PBD: 29 Jul 2004; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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