Dehalogenation of Chlorinated Organic Compounds by Strong Alkalis

by Baohua Gu, Envir. Sci. Div., Oak Ridge Nat. Lab., P.O. Box 2008, MS-6036, Oak Ridge, TN 37831,
Robert L. Siegrist, Oak Ridge Nat. Lab./Colorado School of Mines, Envir Sci. and Engrg. Div., Golden, CO 80401-1887,

Serial Information: Issue 10, Pg. 982-987

Document Type: Journal Paper

Abstract: Chlorinated organic compounds such as trichloroethylene (TCE) are the most prevalent contaminants found in soil and ground water, and poses serious health risks even at trace concentrations. This research reports a new chemical treatment technique for rapid degradation of TCE in strong alkaline solutions. Batch kinetic reactions between TCE and NaOH indicate that TCE can be rapidly and completely dechlorinated in NaOH at elevated temperatures. The reaction can be described by a pseudo-first-order rate kinetics with an estimated activation energy of ∼85 kJ/mol. The half-lives for TCE degradation in 2M NaOH at 40, 60, 80, and 100°C were approximately 347, 48.8, 4.0, and 2.4 min, respectively. The reaction end-products are primarily Cl anions and Na-glycollate, both of which are nonhazardous. This treatment technique is applicable for degrading other halogenated organic compounds wherein a nucleophilic substitution or elimination is the major reaction mechanism or pathway. Potential applications of this technology includes the removal and destruction of vapor-phase chlorinated volatile organic compounds (VOCs) in off-gases when soil vapor extraction or air-stripping techniques are used for remediating VOC-contaminated soils and ground water. A bench-scale alkaline destruction module was tested, and results indicated that ∼90% of TCE was destroyed when TCE vapor (10 mg/L) was passed through a destruction column with a retention time of ∼1 min at 95°C.

Subject Headings: TCE | Chlorine | Organic compounds | Alkalinity | Chemical degradation | Soil water | Health hazards | Chemical treatment | Groundwater |

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