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Final Report: In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
EPA Grant Number: R825549C022Subproject: this is subproject number 022 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
Investigators: Valentine, Richard L.
Institution: University of Iowa
EPA Project Officer: Manty, Dale
Project Period: February 22, 1990 through February 21, 1993
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989)
Research Category: Analysis/Treatment of Contaminated Soil
Description:
Objective:The overall aim of this project was to develop a better fundamental understanding of important physical-chemical processes and abiotic factors which may affect the kinetics of hydrogen peroxide decomposition as well as oxidation of organics in the subsurface environment. Specific goals were to: 1) investigate the effect of model and collected subsurface materials, especially iron oxides, on the kinetics of surface catalyzed hydrogen peroxide decomposition, 2) evaluate the effects of organic matter, pH, carbonate, and especially phosphate on hydrogen peroxide decay rates, 3) evaluate the oxidation of selected organic contaminants in subsurface and soil environments, and 4) develop mechanistic based relationships and mathematical models to provide guidance in the use of hydrogen peroxide in subsurface environments.
Summary/Accomplishments (Outputs/Outcomes):Hydrogen peroxide has been used as a source of oxygen for the bioremediation of contaminated subsurface environments and as an oxidant to degrade contaminants in solutions and soils. While a number of studies have shown that surface catalyzed decomposition of hydrogen peroxide is an important process governing its stability, little is known about the processes and factors that influence this decay or how best to control it so as not to be excessively fast. Control of this is important to ensure adequate delivery to desired regions and efficient use. Additionally, the significance of surface catalyzed contaminant oxidation in the subsurface environment, which may augment biological processes as a mechanism for contaminant loss, is unclear. A number of laboratory studies suggest its importance through the action of reactive intermediates, such as hydroxyl radical, involved in the overall hydrogen peroxide decomposition scheme. However, a poor understanding of the numerous variables makes it difficult to compare studies. Unifying principles and concepts are needed for use in exploiting this potential.
In this research, extensive work was conducted using systems containing iron oxides as model reactive soil and aquifer materials because of their central importance as components, and because evidence indicates that they are potentially important catalysts in these environments. Another focus was on modeling the effect of phosphate, which is commonly used to retard the rate of hydrogen peroxide decay. Its mode of action, however, has not been well established. Hydrogen peroxide decay kinetics was also studied in the presence of collected authentic aquifer material with and without treatment to remove oxides as a way of establishing relationships between surface chemistry and rates of hydrogen peroxide loss. Extensive studies were conducted with several organic compounds to determine the potential for surface catalyzed oxidation and to provide information upon which to develop a conceptual and a mathematical model of the reaction mechanism. Lastly, work was conducted on the use of hydrogen peroxide to treat a soil contaminated with pentachlorophenol.
This work has contributed to the funding of two additional projects, one by the Iowa State Water Resources Research Institute and one by the National Institute for Environmental Health Sciences to continue related work on the use of hydrogen peroxide to treat contaminated soils as both an oxidant and to decrease toxicity to heterotrophic organisms. Work is being done in collaboration with the Iowa Agricultural Chemical Association with the goal of applying the technology to clean up small but highly concentrated pesticide and herbicide spills.
The overall approach was to measure the change in hydrogen peroxide and organic compound concentration as a function of time in batch reactors or as a function of hydraulic residence time in column reactors. This information was used to calculate rate constants characterizing the kinetics of hydrogen peroxide decomposition and transformation of selected organic contaminants.
Three types of iron oxides were used, ferrihydrite, goethite, and a semi-amorphous iron oxide representing a fresh, "aged", and intermediate stage of genesis respectively. These oxides were produced by several different procedures in which they are precipitated from solution. Several types of granular media were also used including a sandy aquifer material (2300 mg Fe /kg and 240 mg Mn/kg) collected locally from a source also used for filter sand. Sub samples were subjected to treatment with a reductant to remove some surficial metal oxides. An iron coated sand was also prepared through deposition of iron oxides. Soil treatment studies utilized a soil containing about 4 % organic carbon.
Studies were conducted in shaken batch reactors and a well mixed thermostatted batch pH stat to allow for pH control. Studies were also conducted using the granular media in continuous flow column reactors.; Data collection involved sampling to determine hydrogen peroxide and organic contaminant as a function of time or hydraulic residence time. Most detailed modeling work involved the contaminant, quinoline, a representative PAH associated with ground water contamination by old coal gas disposal facilities. Studies were also conducted using the pesticide atrazine, naphthalene, and several chlorinated phenols. The use of hydrogen peroxide and Fenton's reagent to oxidize soil contaminated with pentachlorophenol was also compared.
Hydrogen Peroxide Decomposition Kinetics. The decomposition rate of hydrogen peroxide determined in batch and continuous flow column studies followed a simple first order relationship for all granular and oxide media. Among the three iron oxides, ferrihydrite which has a much higher surface area per unit mass, showed the greatest catalytic ability, approximately 14 times greater than goethite on either a mass or iron content basis. However, on a surface area basis, the catalytic activity of ferrihydrite was only about 3 times higher than goethite. As might be expected the intermediate semi-amorphous iron oxide exhibited intermediate properties.
The rate of hydrogen peroxide decomposition was only weakly pH dependent increasing only about 30% from pH 6 to 8. Aldrich humic acid was significantly sorbed to both ferrihydrite and aquifer material but its presence only moderately decreased the rate of hydrogen peroxide decay by about 2.5 % per mg C/L up to 20 mg C/L for ferrihydrite. The effect leveled off suggesting that some catalytic sites are not available for humic sorption. The decomposition rate also decreased with increasing carbonate concentration and the effect was significant over environmentally important concentrations.
Treatment of the granular aquifer material to remove surficial metal oxides resulted in a 90 % reduction in decomposition rate showing that most activity is due to metal oxides. However, the treatment was ineffective at significantly reducing the total iron concentrations, but did effectively reduce the manganese concentration by 80%. Manganese oxides have been shown to be effective catalysts for the decomposition of hydrogen peroxide.
The results indicate that as ferrihydrite ages and is transformed to goethite, its reactivity should decrease substantially on a mass basis. However, the nature of the iron oxide is not as important as its specific surface area, a fact which should be of use in predicting hydrogen peroxide decay in a subsurface environment where particle surface is dominated by iron oxide coatings. In addition, differences in alkalinity appear to be more important than variations in pH or humic acid content. Our work on authentic material however, suggests that manganese and not iron may govern the rate of hydrogen peroxide decomposition rate even if it is greatly exceeded in amount by iron. Based on the rates seen for the granular media, the decay of hydrogen peroxide would be rapid if applied to an aquifer containing it. For example at a high Darcy flow rate of 0.67 ft/min, 62 % of the hydrogen peroxide would be gone in 2 ft of travel or in about 3 minutes contact time. Clearly some strategy such as adding phosphate, is needed to reduce this rate if further dispersal is needed.
Modeling the Effect of Phosphate. A model has been successfully developed which describes the reduction in hydrogen peroxide decomposition rate in the presence of phosphate and iron oxides. The model assumes that the total catalytic site concentration is linearly related to the maximum sorptive capacity for phosphate and that the effect of phosphate is to reduce the availability of catalytic sites in proportion to the amount of phosphate adsorbed, which could be described by a simple Langmuir isotherm. While almost total reduction in activity of the iron oxides could be achieved with sufficient phosphate addition, at most only about an 80 % reduction could be achieved with any of the granular media. This suggests that not all catalytic sites bind with phosphate and that some sites are more catalytically active. The application of an inhibitor that was selective only for them might be advantageous over phosphate for which subsurface media has a very large sorptive capacity.
Oxidation of Contaminants. Significant losses of contaminants occurred in batch studies using granular media but required relatively high peroxide concentrations of several hundred to several thousand milligrams per liter. The process is clearly surface catalyzed and involves the formation of some reactive intermediate. It is not a very efficient process under these test conditions. The efficiency of hydrogen peroxide utilization varied with granular material and increased with decreasing normalized decay constants. No evidence could be found that contaminant sorption to surfaces enhanced degradation. Most interestingly, degradation of contaminants in column studies was much less than expected based on comparable batch results. This suggested that the amount of contaminant degraded was not a simple function of the amount of peroxide applied or decomposed.
A key finding based on extensive experimentation with quinoline, was that the percentage of quinoline degraded in batch studies depended both on the amount of hydrogen peroxide decomposed, and the media to water ratio (M in g/ml). While rates of hydrogen peroxide decomposition increased linearly with increasing M ratio as previously described, the efficiency of quinoline degradation decreased. Specifically, the amount of quinoline degraded per unit of hydrogen peroxide loss decreases with increasing M ratio. This behavior is consistent with the reaction scheme whose central elements include: 1) a rate limiting surface catalyzed reaction initiating hydrogen peroxide decomposition with the formation of a reactive intermediate (such as hydroxyl radical, OH
k1
H2O2 + =M ------> 0H
k2
OH
H202
k3
OH
Efficiency of removal is therefore expected to be the least under continuous flow column operation where the M ratio is the highest value (approximately 4 for our granular media) and increase in batch systems which typically have a lower M ratio.
A model was developed which was capable of predicting quinoline loss as a function of M ratio. The model should provide a basis for comparing data in the literature and may help explain some conflicting observations about the ability of hydrogen peroxide to oxidize a number of contaminants. It may also be of use in understanding and optimizing the use of traditional Fenton's reagent or other oxidant systems which rely on the formation of hydroxyl radicals or other reactive intermediates. Our results also suggest several strategies for improving the oxidation of organic contaminants in the subsurface environment. Additional studies showed that quinoline is not degraded in systems containing ferrihydrite but is degraded in those containing goethite. This difference may be due to differences in free radical scavenging rates or hydrogen peroxide decomposition mechanisms.
Work done with soils, also showed that hydrogen peroxide alone can be as effective as Fenton's reagent (a mixture of ferrous iron and hydrogen peroxide) in treatment to remove pentachlorophenol. Efficiency is greatest at low pH values in the range of 2-3 where greater than 90% removals could be achieved if sufficient hydrogen peroxide is added. The cost to do so would likely limit the applicability to relatively small localized problems.
The research has been presented at professional meetings and to other interested
professionals.
No journal articles submitted with this report: View all 9 publications for this subproject
Supplemental Keywords:carbon tetrachloride, cometabolism, bioremediation, anaerobic , Ecosystem Protection/Environmental Exposure & Risk, Water, Geographic Area, Scientific Discipline, Waste, RFA, Remediation, Analytical Chemistry, Chemistry, Hazardous Waste, EPA Region, Fate & Transport, Environmental Chemistry, Contaminated Sediments, Hazardous, Ecology and Ecosystems, Geochemistry, Fenton-like reductions, fate and transport, fate and transport , soil and groundwater remediation, groundwater, chemical kinetics, contaminated sediment, hazardous wate, contaminant transport, Region 8, contaminated soil, contaminated groundwater, groundwater remediation, Pentachlorophenol, sediment treatment, Region 7, hydrogen peroxide, in situ remediation
Relevant Websites:
http://www.engg.ksu.edu/HSRC
Progress and Final Reports:
Original Abstract
Main Center Abstract and Reports:
R825549 HSRC (1989) - Great Plains/Rocky Mountain HSRC
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
R825549C009 Vadose Zone Decontamination by Air Venting
R825549C010 Thermochemical Treatment of Hazardous Wastes
R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
R825549C019 Development of In-situ Biodegradation Technology
R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
R825549C039 Remediation of Soil Contaminated with an Organic Phase
R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
R825549C041 Heavy Metals Removal from Contaminated Water Solutions
R825549C042 Metals Soil Pollution and Vegetative Remediation
R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
R825549C061 Biofilm Barriers for Waste Containment
R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals