Grantee Research Project Results
2003 Progress Report: Developing Functional Fe(0)-based Nanoparticles for In Situ Degradation of DNAPL Chlorinated Organic Solvents
EPA Grant Number: R830898Title: Developing Functional Fe(0)-based Nanoparticles for In Situ Degradation of DNAPL Chlorinated Organic Solvents
Investigators: Lowry, Gregory V. , Matyjaszewski, Krzysztof , Majetich, Sara A. , Tilton, Robert D.
Institution: Carnegie Mellon University
EPA Project Officer: Aja, Hayley
Project Period: May 1, 2003 through October 31, 2007
Project Period Covered by this Report: May 1, 2003 through October 31, 2004
Project Amount: $358,000
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
The premise of this research project is that the surfaces of zero-valent iron (Fe0) reactive nanoparticles can be modified to be transportable in water through a porous matrix, to partition preferentially at a dense nonaqueous phase liquid (DNAPL)-water interface, and to degrade DNAPL to nontoxic products. The specific objectives of the research project are to: (1) demonstrate the ability to provide targeted delivery of reactive nanoparticles to the DNAPL-water interface in saturated porous media; (2) increase the DNAPL degradation efficiency relative to unmodified particles; and (3) retain reactive particles at the DNAPL-water interface long enough to be utilized fully.
Progress Summary:
Nanoparticle Synthesis
Two Fe nanoparticles were investigated: reactive nanoscale iron particles (RNIPs, Toda American, Inc.) and Fe0 nanoparticles (Fe/B) synthesized in our laboratory using aqueous sodium borohydride reduction of dissolved Fe. RNIPs are synthesized commercially by reduction of Fe-oxides in H2 gas. Transmission electron microscopy and N2-BET indicate that particle sizes and specific surface areas of each particle type are similar. A method to determine the Fe0 content of Fe nanoparticles was developed. Using this method, the Fe0 content (wt %) of fresh particles (determined from H2 evolution upon digestion in concentrated HCl) is 97 percent for Fe/B and 27 percent for RNIPs.
Implications. Because of their similar properties, both Fe0 types should degrade trichloro? ethylene (TCE) at similar rates and with similar efficiency. The presence of B and the morphology of the particles may, however, affect the ability of each particle type to dechlorinate TCE. Understanding the properties affecting particle reactivity and lifetime will allow the synthesis of particles optimal for subsurface remediation.
Polymer Synthesis and Surface Modification
Polymer and Nanoparticle-Polymer Synthesis. Polystyrene and poly(methyl methacrylate) (PMMA) are good candidates for the hydrophobic blocks. Sulfonated polystyrene was selected as the hydrophilic block because of its excellent water solubility. Methacrylate macromonomers with poly(ethylene oxide) side chains adhered strongly to silica because of the polyether blocks. Nanoparticles with a hydrophobic-hydrophilic shell were synthesized by atom transfer radical polymerization. The hybrid nanoparticles consist of an inorganic core (SiO2 or Fe0) surrounded by a hydrophobic inner shell and a hydrophilic outer shell. A ratio of 1/5 - 1/10 between hydrophobic and hydrophilic blocks is sufficient to provide water solubility of the hybrid nanoparticles.
Surface Modifications. Sorption of the synthesized triblock copolymers to Fe0 nanoparticles was measured by the solution depletion technique. The synthesized polymers sorb to two types of Fe nanoparticles (RNIPs and Fe2O3). The coverage of 2900(PMA)2000(MMA)6300(SS) onto RNIPs was approximately 7 mg/m2. Sorption to Fe2O3 (hematite) nanoparticles was similar.
Implications. Polymers adsorb to the Fe surfaces in sufficient quantity to stabilize nanoparticle suspensions in water and fairly strongly (steep isotherm). Therefore, it is possible to modify the Fe particle surfaces to provide them with NAPL-water targeting ability.
Nanoparticle Characterization
DNAPL-Water Partitioning. The TCE/water interfacial tension decreased as the polymer (PMAA42-b-PMMA26-b-PSS466) concentration increased, indicating that the polymers target the interface. Polymer-coated SiO2 particles caused surface tension lowering in excess of approximately 23 dyne/cm, also indicating interfacial partitioning.
Implications. The PMAA42-b-PMMA26-b-PSS466 triblock polymer and polystyrenesulfonate (PSS)-grafted particles target the TCE-water interface and demonstrate that an inexpensive PSS polymer can provide targeting of the NAPL-water interface.
Nanoparticle Reactivity
Fe/B is highly reactive and transformed TCE into ethane (80%) and C3-C6 coupling products with a surface area normalized rate constant that is approximately fourfold higher than RNIPs. All Fe0 in the Fe/B particles was accessible for TCE dechlorination, and 92 wt percent of the Fe0 was used to reduce TCE. RNIPs yielded acetylene using limited Fe and ethylene using excess Fe. Approximately 44 wt percent of Fe0 in the RNIPs was unavailable for TCE dechlorination and remained in the particles.
Implications. Although more reactive, Fe/B particles generate H2 quickly in water and have a limited lifetime. Polymer coatings may protect the particles and maintain the reactivity until targeting DNAPL TCE. RNIPs are more stable in water and have a longer lifetime. The efficiency of RNIPs is comparable with that of Fe/B particles in terms of TCE degraded by unit mass of Fe0 because of the formation of less saturated reaction products.
Future Activities:
p>We will: (1) continue to explore the role of B in Fe/B particles and determine how changes in the particle properties during reaction affect their reactivity; (2) quantify the mass of polymer required to stabilize the particles and measure the desorption rate; and (3) begin transport studies on Fe0 and polymer-coated particles.Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 75 publications | 13 publications in selected types | All 11 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Liu Y, Majetich SA, Tilton RD, Sholl DS, Lowry GV. TCE dechlorination rates, pathways, and efficiency of nanoscale iron particles with different properties. Environmental Science & Technology 2005;39(5):1338-1345. |
R830898 (2003) R830898 (2004) R830898 (2005) R830898 (Final) |
Exit |
Supplemental Keywords:
groundwater, volatile organic compound, VOC, trichloroethylene, TCE, nonaqueous phase liquid, NAPL, subsurface remediation, catalysis, zero valent iron, palladium, block copolymers, environmental chemistry, environmental engineering, source zone remediation, nanotechnology, reductive dechlorination, bimetallic particles, interdisciplinary research,, RFA, Scientific Discipline, Waste, Water, TREATMENT/CONTROL, Ecosystem Protection/Environmental Exposure & Risk, Sustainable Industry/Business, Remediation, Environmental Chemistry, Sustainable Environment, Restoration, Technology, Technology for Sustainable Environment, New/Innovative technologies, Chemistry and Materials Science, Aquatic Ecosystem Restoration, Engineering, Chemistry, & Physics, Environmental Engineering, waste reduction, in situ remediation, DNAPL, remediation technologies, nanotechnology, environmental sustainability, reductive degradation of hazardous organics, environmentally applicable nanoparticles, aquifer remediation design, groundwater remediation, acuatic ecosystems, degradation rates, sustainability, reductive dechlorination, hazardous organics, groundwater contamination, innovative technologies, pollution prevention, contaminated aquifers, reductive detoxification, recycleRelevant Websites:
http://www.ce.cmu.edu/~glowry/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.