Final Report: Development of Mechanisms and Kinetic Models on Formation of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans from Aromatic Precursors

EPA Grant Number: R825511C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R825511
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - Northeast HSRC
Center Director: Sidhu, Sukh S.
Title: Development of Mechanisms and Kinetic Models on Formation of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans from Aromatic Precursors
Investigators: Bozzelli, Joseph W. , Sidhu, Sukh S. , Taylor, Philip H.
Institution: University of Dayton
EPA Project Officer: Hahn, Intaek
Project Period: January 15, 1999 through January 14, 2001
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Hazardous Substance Research Centers , Land and Waste Management

Objective:

The objective of this collaborative study is to develop a thorough understanding on the formation and destruction pathways on Poly Chlorinated Dibenzo - Dioxins and Furans (PCDD/F) by combination of controlled experiments and detailed reaction models that follow fundamental principles of thermochemistry and kinetics. The data and models developed can be used to improve methods for reducing the formation and emission of these PCDD/F's from combustion sources by modification of reaction conditions and parameters in the Combustion.

Summary/Accomplishments (Outputs/Outcomes):

Rationale: Incineration is one of the few technologies proven to be an effective bulk destroyer of wastes; it is not a transformation of one waste stream into another. Present regulations demand 99.99% to 99.9999% destruction efficiency for hazardous pollutants, which is seldom achieved by other technologies. In spite of the proven bulk effectiveness and cost advantages of combustion; it is being used less and less because of concerns about products of incomplete combustion (PICs) including PCDD/Fs. Combustion is, however, the only practical technology for solids, which are highly contaminated with semi-volatile toxic wastes. The fundamental research conducted in this project is resulting in an increased understanding into the origin of PCDD/F and related endocrine disrupter chemical (EDC) pollutants. This improved knowledge on the fundamental reaction pathways will result in more efficient destruction and cost effective control techniques. The mechanistic and kinetic models developed in this study will also improve risk assessment techniques that currently struggle to even approximate the emissions and exposure to PCDD/F and related chemicals.

Approach: Experimental: Benzene and related aromatic species are readily formed via molecular weight growth processes in combustors and their attached air pollution control systems under mild oxidizing and fuel rich (partial oxidizing) conditions. This is a result of the high stability in the aromatic molecules. These aromatics readily form phenols via reaction with OH radical or O2. Molecular weight growth of these phenols leads to formation of closed dimers, usually dibenzo-p-dioxin or -furans. We therefore choose to study the elementary paths to formation of these dibenzo -dioxin and -furans in a well-characterized reactor system. We further select chlorinated phenol precursors because of the obvious relation to chlorinated dibenzo-dioxins and -furans. Selection of target aromatic's as precursors allows us to simplify our data interpretation and permits initial modeling efforts to focus on known intermediates in the formation mechanisms. This study complements our previous and on-going studies of formation of chlorinated aromatic species from chlorinated hydrocarbons. Previously developed mechanism, kinetic data and models can then be combined with the results of this study to yield a unified view and model of PCDD/F formation. A second experimental component is a study on catalytic surfaces, which is relative to formation in the air pollution control component of a combustor.

Theoretical: Elementary pathways for both homogeneous and metal catalyzed PCCD /PCCF's formation (simulation of catalytic surfaces) will be investigated using ab initio calculations on the several paths for formation of the dioxin or furan linkages. ab initio and density-functional molecular orbital, calculation methods will be utilized. Thermodynamic properties of stable molecules, radical intermediates and transition states will be determined. Fundamental principles of thermochemical kinetics and statistical mechanics will be utilized to convert the microscopic data from the calculations (Electronic Energies, Structures, Internal Rotation Barriers, and Vibration Frequencies) into enthalpies, entropy (298), heat capacity (T) and reaction barriers. Proposals to NSF super-computer sites (Ohio State, Illinois and San Diego) for Cray and Origin computer times are submitted for additional computer time.

The gas phase kinetic model includes the NJIT Chlorocarbon Oxidation Mechanism, ca 600 reactions, 180 species, developed under current EPA Center funding. Reaction pathways, thermodynamics and kinetic parameters are derived or updated for elementary reaction sequences leading to experimentally observed products. The thermochemical data is utilized in conjunction with: principles of thermochemical kinetics, Transition State Theory and evaluated literature data for high pressure limit rate parameters. Quantum Rice Ramsperger Kassel (QRRK) theory is used to determine k(E) and Master Eqn analysis is used for pressure effects. Reactions and corresponding rate constants are assembled into detailed mechanisms, which describe the overall reaction process as function of time and temperature. Models will be validated against the experimental data.

Status: Interactions of phenoxy radicals with other radicals (phenyl, methyl, hydroxyl, etc.) and with 2-chlorophenol, 2-chloro-anisole, and mono-chlorobenzene molecules were examined under simulated incinerator conditions. Temperatures represent the high temperature post combustion zone, where gas-phase precursor chemistry is known to take place. The precursor concentration is low (4 PPM), and typical residence times for effluent gases are maintained to mirror incinerator conditions. The 2-chlorophenol, 2-chloroanisole, and monochlorobenzene experiments show, along with the variable concentration experiments, that the concentration of radicals present in the oxidation system has a significant effect on the PCDD/F product distribution and ultimately the PCDD: PCDF ratio. Observation of intermediate compounds in this study suggests that the radical-radical pathways are dominant in the mechanism to PCDF and PCDD formation under the experiment conditions of this study. Results show that mono-chlorobenzene produced a significant amount of phenols; but produced PCDD/F in lower yields than 2-chlorophenol. This suggests that most PCDD/F's formed from chlorobenzenes reacts through a phenol intermediate. Thermochemical and kinetic modeling on this data (below) has been useful in clarifying aspects of the various pathways to PCDD/F formation from precursors.

Thermodynamic and transition state parameters for species involved in these reaction systems are developed, (ii) analysis of important elementary reaction paths has been performed and. (iii) fundamentally based reaction model has been assembled and used to model the experimental data. The model fits the data in most regimes and has been used to correct the qualitative identification of one experimental observed species. Equilibrium conditions and Steady State (SS) levels of intermediates of important species can be determined with detailed kinetic model. Improvement in the model and thermochemical properties is continuing.

Journal Articles:

No journal articles submitted with this report: View all 9 publications for this subproject

Supplemental Keywords:

kinetic modeling, dioxin, furan, incineration, incinerator., RFA, Scientific Discipline, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Remediation, Environmental Chemistry, Fate & Transport, Hazardous Waste, Environmental Monitoring, Ecological Risk Assessment, Hazardous, Environmental Engineering, EPA Region, hazardous waste management, hazardous waste treatment, fate and transport, advanced treatment technologies, industrial waste, cleanup, remediation technologies, kinetics, polychlorinated dibenzo-p-dioxins, Dibenzofurans, treatment, hazadous waste streams, technology transfer, Region 2

Progress and Final Reports:

Original Abstract
  • 1999

  • Main Center Abstract and Reports:

    R825511    HSRC (1989) - Northeast HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825511C001 Development of Mechanisms and Kinetic Models on Formation of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans from Aromatic Precursors
    R825511C002 Real-Time Monitoring and Control of Emissions from Stationary Combustors and Incinerators
    R825511C003 Development of Sampling Systems for Continuous Monitoring of Volatile Organic Compounds (VOCs)
    R825511C004 Investigation into the Effectiveness of DNAPL Remediation Strategies in Fractured Media
    R825511C005 Advanced Leak Detection and Location Research: Extending the SERDP-funded Technical Base
    R825511C006 Three-Dimensional Geostatistical Site Characterization with Updating
    R825511C007 Anaerobic Biodegradation of PAHs in Soils and Dredged Sediments: Characterizing, Monitoring and Promoting Remediation
    R825511C008 Substrate Accelerated Death and Extended Lag Phases as Causes of the Recalcitrance of Halogenated Compounds in Anoxic Environments
    R825511C009 Fate and Transport of Nonionic Surfactants
    R825511C010 In Situ Degradation of Petroleum Hydrocarbons and PAHs in Contaminated Salt Marsh Sediments
    R825511C011 Design and Operation of Surfactant-Enhanced Bioslurry Reactors
    R825511C012 Experimental Study of Overland Transport of Cryptosporidium parvum Oocysts
    R825511C013 Development of a Framework for Evaluation of Leaching from Solid Waste
    R825511C014 Use of a New Leaching Test Framework for Evaluating Alternative Treatment Processes for Mercury Contaminated Mixed Waste (Hazardous and Radioactive)
    R825511C015 Field Pilot Test of In Situ Ultrasonic Enhancement Coupled With Soil Fracturing to Detoxify Contaminated Soil
    R825511C016 Development of Sampling Systems for Continuous Monitoring of Volatile Organic Compounds (VOCs)
    R825511C017 Field Demonstration of the Use of Reactive Zero-Valence Iron Powder to Treat Source Zone Sites Impacted by Halogenated Volatile Organic Chemicals
    R825511C018 Technology Transfer of Continuous Non-Methane Organic Carbon (C-NMOC) Analyzer
    R825511C019 Field Sampling and Treatability Study for In-Situ Remediation of PCB's and Leachable Lead with Iron Powder
    R825511C020 Experimental and Modeling Studies of Chlorocarbon Incineration, PIC Formation, and Emissions Control
    R825511C021 Experimental Studies and Numerical Modeling of Turbulent Combustion During Thermal Treatment of Hazardous Wastes: Applied Research for the Generation of Design and Diagnostic Tools
    R825511C022 Electrochemical Sensor for Heavy Metals in Groundwater - Phase IV
    R825511C023 Novel Molecular Tools for Monitoring In-Situ Bioremediation
    R825511C024 Surfactant-Enhanced Bioremediation of Soils in the Presence of an Organic Phase
    R825511C025 Enhanced Microbial Dechlorination of PCBs and Dioxins in Contaminated Dredge Spoils
    R825511C026 Toward A Risk-Based Model for Bioremediation of Multicomponent NAPL Contaminants
    R825511C027 Removal and Recovery of VOCs and Oils from Surfactant-Flushed Recovered Water by Membrane Permeation
    R825511C029 Field Pilot Test of In-Situ Ultrasonic Enhancement Coupled With Soil Fracturing to Detoxify Contaminated Soil in Cooperation with McLaren/Hart Environmental Engineers at the Hillsborough, NJ Site
    R825511C030 In-Situ Field Test of Electroremediation of a Chromate-Contaminated Site in Hudson County, New Jersey
    R825511C031 Electrokinetic Removal of Heavy Metals and Mixed Hazardous Wastes from Partially and Fully Saturated Soils
    R825511C032 Effects of Clay Charge and Confining Stresses on Soil Remediation by Electroosmosis
    R825511C033 Assessment of Surfactant Enhanced Bioremediation for Soils/Aquifers Containing Polycyclic Aromatic Hydrocarbons (PAHs)
    R825511C034 In-Situ Bioremediation of Organic Compounds: Coupling of Mass Transfer and Biodegradation
    R825511C035 Investigation into the Effectiveness of DNAPL Remediation Strategies in Fractured Media
    R825511C036 Field Pilot Scale Demonstration of Trench Bio-Sparge: An In-Situ Groundwater Treatment Technology
    R825511C037 In-Situ Reductive Dehalogenation of Aliphatic Compounds by Fermentative Heterotrophic Bacteria
    R825511C038 The Effect of Carbon-Nitrogen Ratios on Bacterial Transport and Biodegradation Rates In Soils
    R825511C039 Ultrasonic Enhancement of Soil Fracturing Technologies for In-Situ Detoxification of Contaminated Soil
    R825511C040 Full Field Demonstration of Integrated Pneumatic Fracturing and In-Situ Bioremediation
    R825511C041 Determination of Adsorption and Desorption Behavior of Petroleum Products on Soils
    R825511C042 Evaluation of the Potential for Complete Bioremediation of NAPL-Contaminated Soils Containing Polycyclic Aromatic Hydrocarbons (PAHs)
    R825511C043 Characterization of Subsurface NAPL Distributions at Heterogeneous Field Sites
    R825511C044 Development of a Thermal Desorption Gas Chromatograph/Microwave Induced Plasma/Mass Spectrometer (TDGC/MIP/MS) for On-site Analysis of Organic and Metal Contaminants
    R825511C045 Using Trainable Networks for a Three-dimensional Characterization of Subsurface Contamination
    R825511C046 Application of Advanced Waste Characterization to Soil Washing and Treatment
    R825511C047 Electrochemical Sensor for Heavy Metals in Groundwater Phase III
    R825511C048 Improved Luminescence Sensors for Oxygen Measurement
    R825511C049 Preconcentration, Speciation and Determination of Dissolved Heavy Metals in Natural Waters, using Ion Exchange and Graphite Furnace Atomic Absorption Spectrometry
    R825511C050 Experimental and Modeling Studies of Chlorocarbon Incineration and PIC Formation
    R825511C051 PIC Emission Minimization: Fundamentals and Applications
    R825511C052 Project Title: Development of a Two Stage, Pulse Combustion, VOC Destruction Technology
    R825511C053 Development of Sampling Systems for Continuous Monitoring of Volatile Organic Compounds (VOCs)
    R825511C054 FTIR Analysis of Gaseous Products from Hazardous Waste Combustion
    R825511C055 Toxic Metals Volatilization for Waste Separation and Real-time Metals Analyses
    R825511C056 Mixed Metal Removal and Recovery by Hollow Fiber Membrane-Based Extractive Adsorber
    R825511C057 Removal of Volatile Organic Compounds (VOCs) from Contaminated Groundwater and Soils by Pervaporation
    R825511C058 Simultaneous SO2/NO Removal/Recovery by Hollow Fiber Membrane
    R825511C059 Superfund Sites and Mineral Industries Method
    R825511C060 Soil Washing of Mixed Organics/Metal Contamination
    R825511C061 Removal of Cesium, Strontium, Americium, Technetium and Plutonium from Radioactive Wastewater
    R825511C062 Development of a Method for Removal of Nonvolatile Organic Materials from Soil using Flotation
    R825511C063 Recovery of Evaporative Fuel Losses by Vapor Permeation Membranes
    R825511C064 Surfactant Selection Protocol for Ex Situ Soil Washing
    R825511C065 Biofiltration for the Control of Toxic Industrial VOCs Emissions
    R825511C066 Catalytic Oxidation of Volatile Organic Compounds in Water
    R825511C067 Soil Washing for Remediating Metal Contaminated Soils
    R825511C068 Aqueous Absorption and Kinetics of NO by Strong Oxidizing Agents
    R825511C069 Remediation of Dredging Spoils
    R825511C070 Freeze Concentration for Zero-Effluent Processes
    R825511C071 Life Cycle/Pollution Prevention Response to Executive Order 12856
    R825511C072 Faster Better, Cheaper Hazardous Waste Site Characterization and Cleanup: an Adaptive Sampling and Analysis Strategy Employing Dynamic Workplans
    R825511C073 Development of a Comprehensive Computer Model for the Pneumatic Fracturing Process
    R825511C074 Technology Demonstration and Validation of CFAST Field Analytical Instrumentation for Use in Hazardous Waste Site Characterization, Clean-up and Monitoring
    R825511C075 XFLOW: Training Software Simulating Contaminant Site Characterization and Remediation