A series of experiments was completed to investigate abiotic degradation and reaction product formation of trichloroethylene (TCE) when heated. A quartz-tube apparatus was used to study short residence time and high temperature conditions that are thought to occur during thermal conductive heating and during the recovery of contaminants by vapor phase extraction. Glass ampules were used to study longer residence time conditions and moderate temperatures that are thought to occur during steam flushing and electrical resistive heating
The quartz tube experiments were conducted at the temperatures of 120, 240 and 420°C. Free chloride ions were detected at all three temperatures considered, which was interpreted as evidence of gas-phase TCE degradation. However, the amounts of TCE degraded were very small at the lower temperatures (0.01 % and 6.5%, respectively). At 420C, as much as 20 percent of the TCE was converted to carbon dioxide and carbon monoxide, depending on vapor phase composition.
In the glass ampule experiments the concentration of TCE decreased in ampules that were incubated at 120°C. The decrease in TCE content was matched with a decrease in pH, an increase in the chloride, formate, and glycolate content, and an increase in the carbon monoxide and carbon dioxide. Dichloroacetylene (DCA) was detected in ampules and may represent an intermediate formed during TCE degradation.
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