Developing Functional Fe(0)-based Nanoparticles for In Situ Degradation of DNAPL Chlorinated Organic SolventsEPA Grant Number: R830898
Title: Developing Functional Fe(0)-based Nanoparticles for In Situ Degradation of DNAPL Chlorinated Organic Solvents
Investigators: Lowry, Gregory V. , Majetich, Sara A. , Matyjaszewski, Krzysztof , Tilton, Robert D.
Institution: Carnegie Mellon University
EPA Project Officer: Lasat, Mitch
Project Period: May 1, 2003 through October 31, 2007
Project Amount: $358,000
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Groundwater contamination by chlorinated organic solvents poses a significant health hazard. Dense Non-Aqueous Phase Liquid (DNAPL) present at these sites acts as a long-term source, making cleanup difficult and costly. Nanotechnology has the potential to reduce the health risk and financial burden of these sites, as recently demonstrated by the use of Pd-Fe(0) nanoparticles to degrade dissolved phase TCE in situ. This project will develop and test “smart” nanoparticle assemblies that are transportable in water-saturated porous media and capable of targeting and degrading DNAPL in the subsurface. Delivering reactive nanoparticles directly to the DNAPL-water interface can significantly improve the efficiency of in situ groundwater remediation.
The hypothesis being tested is that the surfaces of Fe(0)-based reactive nanoparticles can be modified to be transportable in water through a porous matrix, to preferentially partition at a DNAPL-water interface, and to degrade DNAPL to non-toxic products. The broad project objective is to demonstrate that engineered nanoparticles (i.e. supramolecular assemblies) have the potential to significantly improve the efficiency of in situ groundwater remediation technologies. Specific project objectives are to i) demonstrate the ability to provide targeted delivery of reactive nanoparticles to the DNAPL-water interface in saturated porous media, ii) increase the DNAPL degradation efficiency relative to unmodified particles, and iii) retain reactive particles at the DNAPL-water interface long enough to be fully utilized.
The approach is directly inspired by biomedical targeted drug delivery technologies that efficiently concentrate drug molecules in diseased tissue sites without wasting drugs (or introducing toxicity) in healthy tissue. Remediation agents introduced into the subsurface would concentrate at the DNAPL-water interface in response to designed thermodynamic affinity for the contaminant.
The particular materials proposed are hybrid nano-structures (<100nm) consisting of Fe(0)-based nanoparticles and tailored polymers to provide targeting. Fe(0) and Pd/Fe(0) nanoparticles will be synthesized and tested for their ability to degrade TCE. The nanoparticle surfaces will be modified with amphiphilic block copolymers such that they maintain a stable suspension in water for transport in a porous matrix, and create an affinity for the water-DNAPL interface. The physical and chemical properties of particle suspensions will be determined including composite morphology, colloid stability, polymer layer thickness, and DNAPL/water partitioning behavior. The mobility of these hybrid nano-structures, and their ability to target and degrade DNAPL present in saturated porous media will be tested in model flow cells representative of subsurface properties at contaminated sites. Feedback from characterization and transport/targeting experiments will help develop polymer combinations optimal for their intended function. Trichloroethylene (TCE) will serve as the model DNAPL.
A new class of affinity-targeted nanoscale remediation agents will be developed for efficient in situ remediation of DNAPL source areas in aquifers. By locating and maintaining reactive nanoparticles at the DANPL-water interface, fewer particles will be required and more efficient DNAPL remediation is possible relative to other methods. Moreover, the time to site closure can be accelerated, significantly lowering the risk to human health and remediation costs. New methods to investigate the transport and trapping of nanoparticles in saturated porous media will result from this project. This research will also produce novel polymer and block copolymer combinations with unique properties that may benefit other technologies. Lastly, the optimal properties of Fe(0)-based nanoparticles (e.g. diameter and composition) for TCE dechlorination will be determined.
The strategy emphasized in this project, manipulating the surface properties of nanoparticles to deliver them to specific subsurface regions, pertains to a variety of equally important applications to other environmental problems such as: creating subsurface barriers to flow; improving bioremediation through selective delivery of nutrients; encapsulating contaminants; selectively mobilizing or sequestering toxic compounds; and developing “smart tracers” for in situ subsurface characterization. Results from this project will improve our understanding of the movement of suspended particles in the subsurface, including particles with engineered functions.