I&EC 280 |
| Gregory V. Lowry1, Sara Majetich2, David Sholl3, Robert D Tilton3, and Krzysztof Matyjaszewski4. (1) Department of Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, (2) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213-3890, (3) Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, (4) Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave, Pittsburgh, PA 15213 |
| Over the past decade, laboratory and field studies have demonstrated that zero-valent iron and bimetallic colloids combined with noble metal catalysts can rapidly transform dissolved chlorinated organic solvents into non-toxic compounds. This emerging technology also has the potential to address Dense Non-Aqueous Phase Liquid (DNAPL) contamination, a vexing contamination problem. The objective of this research is to develop and test reactive nanoscale catalysts for in situ delivery and remediation of chlorinated solvents that are present as DNAPLs in the subsurface. The hypothesis under consideration is that the surfaces of reactive Fe0-based nanoparticles can be modified with amphiphilic block copolymers to maintain a stable suspension of the particles in water for transport in a porous matrix, as well as create an affinity for the water-DNAPL interface. Initial research has focused on developing suitable polymer blocks, attaching these blocks to SiO2 particle surfaces, and evaluating the properties (hydrodynamic radius, stability, TCE-water partitioning behavior, mobility in a porous matrix) of the resulting polymer-modified functional nanoparticles. Atom Transfer Radical Polymerization (ATRP) was used to design tailored block copolymers for hybrid nanoparticles. Particles have an inorganic core (Fe0 or SiO2) with a block copolymer shell (hydrophobic inner shell surrounded with a hydrophilic outer shell). The hydrophobic inner shell protects the zero-valent iron from the contact with water before reaching the DNAPL, and the hydrophilic shell enables transport of the particle in water to the contaminated areas. Polystyrene and poly(methyl methacrylate) have been identified as good candidates for the hydrophobic blocks. Sulfonated polystyrene has excellent water solubility and makes a good hydrophilic block. Poly(ethylene oxide) methacrylate segments strongly adhered to silica due to the poly(ethylene oxide) side chains. This is undesired because it will limit the transportability of the hybrid nanoparticles in the subsurface. Polymerizing styrene using the silica-immobilized initiators provided nanoparticles with attached polystyrene chains (dp~100 nm). After sulfonation the particles were completely soluble in water, formed stable suspensions, and partition to the TCE (DNAPL)-water interface. Bench scale transport studies indicate that these nanoparticles are readily transported through a saturated porous matrix suggesting that they will be transportable in the subsurface. |
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Nanotechnology and the Environment
1:30 PM-4:30 PM, Thursday, April 1, 2004 Marriott -- Grand Ballroom F, Oral
Division of Industrial and Engineering Chemistry |