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					                                            NSF Nanoscale Science and Engineering Grantees Conference, Dec 3-6, 2007
                                                                                                    Grant # : 068646

                           NANO HIGHLIGHT
   Targeted Delivery and Microbial Interactions of Polymer-Functionalized
         Nanoparticles for Groundwater Source-Zone Remediation
                                 NSF NIRT Grant 068646
   Robert D. Tilton, Gregory V. Lowry, Krzysztof Matyjaszewski and Edwin G. Minkley
                                Carnegie Mellon University

Organic contamination of subsurface soil and groundwater is an extensive and vexing problem
that stands to benefit from nanotechnology. Contamination by organic pollutants, especially
chlorinated organic compounds (COC) are primary concerns at over half of the Superfund
National Priorities List sites. Associated health risks have led to an extensive remediation effort
for the past 30 years. Past remediation efforts have had limited success primarily because most
organic pollutants are only weakly water-soluble and tend to remain as a separate non-aqueous
phase liquid in the subsurface. Most COC of concern are denser than water and migrate
downward in the aquifer where they collect as saturated pools and ganglia in the microporous
soil. These pools slowly leach their contents, resulting in large contaminant plumes and decades-
long remediation times. Prevailing cleanup technologies are inefficient because they address
only the plumes. New technologies that directly remediate the contaminant source zone could
significantly reduce cleanup times. A promising technology for source zone remediation is the
introduction of zero valent iron nanoparticles into the contaminated groundwater. These react
with chlorinated contaminants and convert them to non-toxic products. The main obstacle
against the use of such reactive nanoparticles is that they are immobile in groundwater – they
tend to aggregate and be filtered out by soil grains before they reach the contaminant. This
research team is developing polymer coatings for zero valent iron nanoparticles that prevent
aggregation and adhesion to soil surfaces in the groundwater. When adsorbed to nanoparticles,
these polymers form highly charged “brushes” that repel other particles, including soil grains that
would cause undesired particle filtration. This allows the nanoparticles to travel the large
distances required to react with chlorinated organic contaminant source zones.
                                                               Figure 1. Whereas unmodified iron
                                                               nanoparticles aggregate and adhere to
                                                               soil surfaces, nanoparticles with
                                                               newly synthesized poly(methacrylic
                                                               acid)-poly(methyl       methacrylate)-
                                                               poly(styrene      sulfonate)     block
                                      water             water
                                                               copolymer coatings resist aggregation
                                     solvent
                                                               and transport effectively through
                                                       solvent
                                                               model soils in laboratory tests.
References
[1] For further information about this project send email to tilton@andrew.cmu.edu or glowry@cmu.edu
                                                       water

[2] T. Phenrat, N. Saleh, K. Sirk, H.-J. Kim, R.D. Tilton, G.V. Lowry, “Stabilization of aqueous nanoscale
                                                      solvent
    zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and
    their effect on aggregation and sedimentation,” Journal of Nanoparticle Research, in press (2007).
[3] N. Saleh, H.-J. Kim, K. Matyjaszewski, R.D. Tilton, G.V. Lowry “Ionic Strength and Composition affect the
    mobility of surface-modified NZVI in water-saturated sand columns,” Environmental Science and Technology
    submitted (2007).
[4] K.M. Sirk, N.B. Saleh, T. Phenrat, H.-J. Kim, B. Dufour, J. Ok, P.L. Golas, K.M. Matyjaszewski, G.V. Lowry,
    R.D. Tilton, “Effect of Adsorbed Polyelectrolytes on Nanoscale Zero Valent Iron Particle Attachment to Silica
    and Humic Acid-Coated Surfaces” in preparation (2007)

				
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