Carnegie Mellon University
Department of Chemical Engineering
Department of Biomedical Engineering
Center for Complex Fluids Engineering
Center for Environmental Implications of Nanotechnology
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Environmental Application of Nanotechnologies: Transport and Targeted Delivery of Nanoscale Zero Valent Iron for in situ Remediation of Contaminated Groundwater

Organic contamination of subsurface soil and groundwater is an extensive and vexing environmental problem that stands to benefit from nanotechnology. The Environmental Protection Agency reports that contamination by organic pollutants, especially chlorinated volatile organic compounds (CVOCs), are primary concerns at over half of the Superfund National Priorities List sites. (See Common Chemicals Found at Superfund Sites, update January 11, 2005; http://www.epa.gov/superfund/resources/chemicals.htm).  As concluded by the National Research Council of the National Academy of Sciences, the prevailing “pump-and-treat” technologies cannot meet cleanup targets in a reasonable amount of time in most cases. (Water Science Technology Board. Contaminants in the subsurface:  Source zone assessment and remediation; Division of Earth and Life Sciences, National Research Council of the National Academies, The National Academies Press: Washington, DC, 2004.)  This is because they address primarily the solvent plume, not the source, in the groundwater.

In collaboration with Professors Gregory Lowry (Dept. of Civil & Environmental Engineering), Krzysztof Matyjaszewski (Dept. of Chemistry) and Sara Majetich (Dept. of Physics), we have developed the concept of targeted delivery of remediation agents to the contamination source – underground residuals of dense nonaqueous phase liquids (DNAPL) trapped in microporous aquifers.  We have synthesized amphiphilic poly(methacrylic acid)-b-poly(methylmethacrylate)-b-poly(styrenesulfonate) triblock copolymers that adsorb to reactive nanoparticulate Fe(0). See Liu et al. “TCE Dechlorination Rates, Pathways, and Efficiency of Nanoscale Iron Particles with Different Properties,” Environmental Science and Technology, 39, 1338-1335 (2005). The adsorbed polymers stably disperse the particles in water, maximize their transportability through saturated sand columns and other soil surface models, and cause the particles to adsorb to the DNAPL/water interface.

NZVT transport

Residual DNAPL (shown in gray) is trapped in and between soil grains (shown in black) in pores that range from micrometers to as small as 2 – 50 nm in diameter.  Targeted iron nanoparticles, by virtue of their size and surface functionalization, gain access to the trapped DNAPL in micropores and adsorb with high affinity to the DNAPL/water interface.  There, the accumulated iron can reduce DNAPL to nontoxic products.

Representative Publications

Y.Liu, S. Majetich, K. Matyjaszewski, R.D. Tilton, D. Sholl, and G.V. Lowry, “TCE dechlorination rates, pathways, and efficiency of nanoscale iron particles with different properties,” Environmental Science and Technology, 39, 1338-1345 (2005). DOI: 10.1021/es049195r

N. Saleh, T. Phenrat, K. Sirk, B.  Dufour, J. Ok, T.  Sarbu, K. Matyjaszewski, R.D. Tilton, G.V. Lowry, “Adsorbed triblock copolymers deliver reactive iron nanoparticles to the oil/water interface,” Nano Letters 5, 2489-2494 (2005). DOI: 10.1021/nl0518268

T. Phenrat, N. Saleh, K. Sirk, R.D. Tilton, G.V. Lowry, “Aggregation and sedimentation of aqueous nanoscale zerovalent iron dispersions,” Environmental Science and Technology 41, 284-290 (2007). DOI: 10.1021/es061349a

N. Saleh, H.-J. Kim, T. Phenrat, K. Matyjaszewski, R.D. Tilton, G.V. Lowry, “Ionic strength and composition affect the mobility of surface-modified Fe0 nanoparticles in water-saturated sand columns,” Environmental Science and Technology, 42, 3349-3355 (2008). DOI: 10.1021/es071936b

K.M. Sirk, N.B. Saleh, T. Phenrat, H.-J. Kim, B. Dufour, J. Ok, P.L. Golas, K. Matyjaszewski, G.V. Lowry, R.D. Tilton, “Effect of adsorbed polyelectrolytes on nanoscale zero valent iron particle attachment to soil surface models,” Environmental  Science and Technology 43, 3803-3808 (2009).  DOI: 10.1021/es803589t

T. Phenrat, J.E. Song, C. Cisneros, D. Schoenfelder, R.D. Tilton, G.V. Lowry, “Estimating attachment of nano- and submicrometer-particles coated with organic macromolecules in porous media: development of an empirical model,” Environmental Science and Technology 44, 4531–4538 (2010). DOI: 10.1021/es903959c

T. Phenrat, F. Fagerlund, T. Illangasekare, G.V. Lowry, R.D. Tilton,Polymer-modified Fe0 nanoparticles target entrapped NAPL in two dimensional porous media: effect of particle concentration, NAPL saturation, and injection strategy" Environmental Science and Technology 45, 6102-6109 (2011). DOI: 10.1021/es200577n