DEHALOGENATION OF CHLORINATED ORGANIC-COMPOUNDS BY STRONG ALKALIS

Chlorinated organic compounds such as trichloroethylene (TCE) are the most prevalent contaminants found in soil and ground water, and pose s erious health risks even at trace concentrations. This research report s a new chemical treatment technique for rapid degradation of TCE in s trong 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-f irst-order rate kinetics with an estimated activation energy of simila r to 85 kJ/mol. The half-lives for TCE degradation in 2M NaOH at 40, 6 0, 80, and 100 degrees C were approximately 347, 48.8, 4.0, and 2.4 mi n, respectively. The reaction end-products are primarily Cl- anions an d Na-glycollate, both of which are nonhazardous. This treatment techni que is applicable for degrading other halogenated organic compounds wh erein a nucleophilic substitution or elimination is the major reaction mechanism or pathway. Potential applications of this technology inclu des the removal and destruction of vapor-phase chlorinated volatile or ganic compounds (VOCs) in off-gases when soil vapor extraction or air- stripping techniques are used for remediating VOC-contaminated soils a nd ground water. A bench-scale alkaline destruction module was tested, and results indicated that similar to 90% of TCE was destroyed when T CE vapor (10 mg/L) was passed through a destruction column with a rete ntion time of similar to 1 min at 95 degrees C.