EPA 600/R-07/091 | August 2007 | www.epa.gov/ada Effects of Thermal Treatments on the Chemical Reactivity of Trichloroethylene Office of Research and Development National Risk Management Research Laboratory, Ada, Oklahoma 74820 Effects of Thermal Treatments on the Chemical Reactivity of Trichloroethylene Jed Costanza, James Mulholland, and Kurt Pennell Georgia Tech University Eva Davis Project Officer, Robert S. Kerr Environmental Research Center Office of Research and Development National Risk Management Research Laboratory, Ada, Oklahoma 74820 Notice The U.S. Environmental Protection Agency through its Office of Research and Development managed the research described here under EPA Coopera- tive agreement Contract No. R-82947401 to Georgia Institue of Technology, Atlanta, Georgia, through funds provided by the U.S. Environmental Protection Agency’s Office of Research and Development, National Risk Management Research Laboratory, Ada, Oklahoma. It has been subjected to the Agency’s peer and administrative review and has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. All research projects making conclusions or recommendations based on environmental data and funded by the U.S. Environmental Protection Agency are required to participate in the Agency Quality Assurance Program. This project was conducted under an approved Quality Assurance Plan. Information on the plan and documentation of the quality assurance activities and results are available from the lead author. ii Foreword The U.S. Environmental Protection Agency is charged by Congress with protecting the Nation’s land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and technical support for solving environmental problems today and building a science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the future. The National Risk Management Research Laboratory is the Agency’s center for investigation of technological and management approaches for preventing and reducing risks from pollution that threatens human health and the environment. The focus of the Laboratory’s research program is on methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems; remediation of contaminated sites, sediments and ground water; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies that reduce the cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions to environmental problems by: developing and promoting technologies that protect and improve the environment; advancing scientific and engineering information to support regulatory and policy decisions; and providing the technical support and information transfer to ensure implementation of environmental regulations and strategies at the national, state, and community levels. This report describes laboratory experiments conducted to determine the reactivity of trichloroethylene (TCE), a commonly-used industrial solvent and a groundwater contaminant at many Superfund sites, under the conditions used for in situ thermal remediation. It was found that at temperatures below 420°C, TCE is essentially unreactive without the presence of some type of catalyst, such as a base or mineral. Thus, during in situ thermal remediation at these temperatures, TCE is recovered by volatilization and vapor extraction. At higher temperatures, significant reaction of TCE may occur; however, the products of these reactions may include larger molecular weight chlorinated compounds as well as carbon dioxide and hydrochloric acid, which would be the expected products when TCE is completely mineralized. Stephen G. Schmelling, Director Ground Water and Ecosystems Restoration Division National Risk Management Research Laboratory iii Acknowledgment EPA would like to thank the peer reviewers, Dr. Bill Mabey, Dr. Gorm Heron, and Dr. Rick Wilken, for their insightful and useful comments. iv Contents Project Summary . 1 1.1 Introduction .......................................................................... 1 1.2 Research Objectives . 1 1.3 Experimental Systems .................................................................. 2 1.4 Conclusions and Recommendations . 2 1.4.1 Quartz Tube Reactor Experiments .................................................... 2 1.4.2 Sealed Ampule Experiments . 3 1.4.3 Implications to Field Applications .................................................... 3 1.5 Report Organization . 6 Background Information . 7 2.1 Trichloroethylene Properties ............................................................. 7 2.2 TCE-Water Phase Behavior.............................................................. 8 2.3 Selected Experiments on the Stability of TCE . 8 2.3.1 TCE-NAPL Degradation by Oxygen .................................................. 8 2.3.2 Hydrolysis of TCE-NAPL Degradation Products . 10 2.3.3 Degradation of TCE Dissolved in Water at Elevated Temperatures . 11 2.3.4 Thermal Degradation of TCE in a Water-Filled Reactor . 12 2.3.5 Degradation of Gas-Phase TCE within Heated Quartz Tubes ............................... 15 2.3.6 TCE Degradation Products as a Function of the Cl:H Ratio . 19 2.4 Operational Conditions of In Situ Thermal Treatment Technologies . 21 2.4.1 Steam Flushing................................................................... 21 2.4.2 Thermal Conductive Heating ........................................................ 22 2.4.3 Electrical Resistive Heating ......................................................... 23 2.4.4 Hybrid Thermal Technologies . 24 TCE Degradation in Flow-Through Quartz Tube Reactors............................................. 25 3.1 Introduction .......................................................................... 25 3.2 Experimental Materials and Methods . 26 3.2.1 Materials........................................................................ 26 3.2.2 Quartz Tube Apparatus............................................................. 26 3.2.3 Experimental Procedures . 27 3.2.3.1 Experimental Series 1........................................................ 27 3.2.3.2 Experimental Series 2........................................................ 27 3.2.3.3 Experimental Series 3........................................................ 27 3.2.3.4 Experimental Series 4........................................................ 28 3.2.3.5 Experimental Series 5........................................................ 28 3.2.4 Analytical Methods . 29 3.3 Experimental Results................................................................... 29 3.3.1 Results of Experimental Series 1-4 . 29 3.3.2 Results of Experimental Series 5 . 31 3.3.2.1 TCE Recovery . 32 3.3.2.2 Compounds in the DCM Trap . 33 3.3.2.3 Compounds Detected in Tedlar® Bags . 35 3.3.2.4 Compounds Detected in the Water Rinse......................................... 36 3.3.2.5 Compounds Detected in the Iso-Octane Rinse..................................... 37 3.3.2.6 Mass Balance . 39 3.4 Discussion . 40 3.4.1 Nitrogen as the Carrier Gas at 420°C.................................................. 40 3.4.2 Air as the Carrier Gas at 420°C ...................................................... 42 3.4.3 Experiments Conducted at 120 and 240°C . 43 3.5 Summary . 45 v 3.6 Quality Assurance Summary for the Flow-Through Experiments . 45 TCE Degradation in Heated Ampules . 47 4.1 Introduction .......................................................................... 47 4.2 Experimental Materials and Methods . 47 4.2.1 Preparation of Solids . 47 4.2.2 Preparation of Aqueous Solutions . 48 4.2.3 Preparation of Ampules . 48 4.2.4 Description of Ampule Experiments . 49 4.2.4.1 Ampule Experiment 1 . 49 4.2.4.2 Ampule Experiment 2 . 49 4.2.4.3 Ampule Experiment 3 . 50 4.2.3.4 Ampule Experiment 4 . 50 4.2.4 Ampule Sampling Methods . 54 4.2.5 Analytical Methods . 55 4.3 Experimental Results................................................................... 56 4.3.1 Results of Ampule Experiment 1 . 56 4.3.2 Results of Ampule Experiment 2 . 56 4.3.3 Results of Ampule Experiment 3 . 58 4.3.2 Results of Ampule Experiment 4 . 61 4.3.2.1 Change in TCE Content ...................................................... 61 4.3.2.2 Change in pH . 64 4.3.2.3 CO and CO2 in the Gas Phase . 67 4.3.2.4 Other Gas Phase Compounds.................................................. 69 4.3.2.5 Aqueous Phase Compounds................................................... 69 4.3.2.6 Mass Balance . 74 4.4 Discussion . 76 4.4.1 Oxygen Initiated TCE Degradation . 76 4.4.2 Hydrogen Elimination Initiated TCE Degradation . 77 4.4.3 Oven Explosion . 78 4.4.4 Comparison to Knauss et al. (1999) Results . 78 4.5 Summary . 79 4.6 Quality Assurance Summary for the Ampule Experiments...................................... 80 References . 81 APPENDIX A . 87 Detailed Experimental Methods for Flow-Through Quartz Tube Reactors................................. 87 A.1 Quartz