Grantee Research Project Results

2002 Progress Report: Chemical, Physical, and Biological Processes at the Surface of Palladium Catalysts Under Groundwater Treatment Conditions

EPA Grant Number: R828772C004
Subproject: this is subproject number 004 , established and managed by the Center Director under grant R828772
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Solutions for Energy, AiR, Climate and Health Center (SEARCH)
Center Director: Bell, Michelle L.
Title: Chemical, Physical, and Biological Processes at the Surface of Palladium Catalysts Under Groundwater Treatment Conditions
Investigators: Reinhard, Martin , Westall, John C.
Institution: Oregon State University
EPA Project Officer: Aja, Hayley
Project Period: January 1, 2002 through December 31, 2003
Project Period Covered by this Report: January 1, 2002 through December 31, 2003
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

The objectives of this research project are to: (1) evaluate the impacts of groundwater on catalyst activity; (2) elucidate the chemical and physical mechanisms responsible for changes in catalyst activity; (3) investigate potential biofouling issues that may result from biological activity expected in long-term treatment applications; and (4) develop convenient and economical methods to regenerate catalysts in situ.

Batch studies with supported palladium catalysts have demonstrated the potential of the palladium/hydrogen process for treating groundwaters or effluent streams that are contaminated by halogenated compounds. These studies yielded virtually complete reductive dehalogenation of chlorinated ethylenes to ethane at room temperature in short contact times, with reaction rates that are orders of magnitude higher than zero-valent iron. Other batch studies have shown the ability of palladium to catalyze the reaction of a range of compounds: all six species of chlorinated ethylenes, carbon tetrachloride, chloroform, Freon 113, chlorobenzene, naphthalene, lindane, and 1,2-dibromo-3-chloropropane. However, laboratory column studies and field tests have indicated that catalyst activity may decline over time, thereby potentially affecting the economic competitiveness of this process. Research is needed to optimize the catalyst and operating parameters for the field. This will be accomplished by determining the causes of activity loss and the means for preventing or minimizing such effects.

Progress Summary:

This research project approaches optimization of the Pd process through understanding changes in the catalyst surface during treatment and correlating these to changes in catalytic activity. Laboratory reactors will be constructed and used to remove the model substrate trichloroethylene (TCE) from water sources of varying quality (e.g., deionized water or groundwater). Samples will be removed from the reactor periodically during the course of treatment for spectroscopic characterization. The experiments will use both dispersed catalysts and model catalysts. Dispersed catalysts typically are used in field applications. Model catalysts are more amenable to spectroscopic analyses, and therefore, may yield more insight into surface phenomena. The research will be undertaken in collaboration with a field study at Edwards Air Force Base (EAFB) near Lancaster, CA.

The model catalyst has been developed and tested for catalytic activity. The reactor for the model catalyst has been designed and constructed, but has not yet been tested in flow-through mode. The reactor system for the dispersed catalyst has been constructed, tested, and modified based on results.

The reactor system with the dispersed Pd catalyst successfully removed TCE from EAFB groundwater. Observed deactivation was consistent with sulfide poisoning and was attributed to the growth of sulfate-reducing bacteria. In response, the reactor system was modified so that feed water for the reactor is no longer stored under hydrogen (i.e., conditions are now less favorable for the growth of sulfate-reducing bacteria). During the experiment, sodium hypochlorite fully regenerated a deactivated catalyst; it is expected to maintain catalyst activity in the field as well, through periodic regeneration.

Future Activities:

Future work will complete testing of the laboratory catalyst systems and will compare the data with kinetic results from the field study. In addition, the model and field catalysts will be analyzed with x-ray photoelectron spectroscopy, to identify chemical changes on the catalyst surface. Finally, we will make a comparison of the effectiveness of regeneration using sodium hypochlorite, hydrogen peroxide, and ammonium chloride.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this subproject

Supplemental Keywords:

palladium catalyst, groundwater, trichloroethylene, TCE, surface science, environmental chemistry., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Hazardous, Environmental Chemistry, Groundwater remediation, Hazardous Waste, Environmental Engineering, chlorinated ethylenes, catalysts, groundwater contamination, hazardous waste treatment, contaminated groundwater, carbon tetrachloride, napthalene, palladium catalysts, palladium catalysis, TCE

Progress and Final Reports:

Original Abstract

Final

Main Center Abstract and Reports:

R828772    Solutions for Energy, AiR, Climate and Health Center (SEARCH)

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828772C001 Developing and Optimizing Biotransformation Kinetics for the Bio- remediation of Trichloroethylene at NAPL Source Zone Concentrations
R828772C002 Strategies for Cost-Effective In-situ Mixing of Contaminants and Additives in Bioremediation
R828772C003 Aerobic Cometabolism of Chlorinated Aliphatic Hydrocarbon Compounds with Butane-Grown Microorganisms
R828772C004 Chemical, Physical, and Biological Processes at the Surface of Palladium Catalysts Under Groundwater Treatment Conditions
R828772C006 Development of the Push-Pull Test to Monitor Bioaugmentation with Dehalogenating Cultures
R828772C007 Development and Evaluation of Field Sensors for Monitoring Bioaugmentation with Anaerobic Dehalogenating Cultures for In-Situ Treatment of TCE
R828772C008 Training and Technology Transfer
R828772C009 Technical Outreach Services for Communities (TOSC) and Technical Assistance to Brownfields Communities (TAB) Programs
R828772C010 Aerobic Cometabolism of Chlorinated Ethenes by Microorganisms that Grow on Organic Acids and Alcohols
R828772C011 Development and Evaluation of Field Sensors for Monitoring Anaerobic Dehalogenation after Bioaugmentation for In Situ Treatment of PCE and TCE
R828772C012 Continuous-Flow Column Studies of Reductive Dehalogenation with Two Different Enriched Cultures: Kinetics, Inhibition, and Monitoring of Microbial Activity
R828772C013 Novel Methods for Laboratory Measurement of Transverse Dispersion in Porous Media
R828772C014 The Role of Micropore Structure in Contaminant Sorption and Desorption