Adsorbed Triblock Copolymers Deliver Reactive Iron Nanoparticles to the Oil/Water Interface

Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Nano Letters (Impact Factor: 13.59). 01/2006; 5(12):2489-94. DOI: 10.1021/nl0518268
Source: PubMed


Reactive zero valent iron nanoparticles can degrade toxic nonaqueous phase liquids (NAPL) rapidly in contaminated groundwater to nontoxic products in situ, provided they can be delivered preferentially to the NAPL/water (oil/water) interface. This study demonstrates the ability of novel triblock copolymers to modify the nanoiron surface chemistry in a way that both promotes their colloidal stability in aqueous suspension and drives their adsorption to the oil/water interface. The ability of the copolymers to drive adsorption is demonstrated by the ability of copolymer-modified iron nanoparticles, but not the unmodified iron nanoparticles, to stabilize oil-in-water emulsions.

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    • "Nanoscale zerovalent iron particles (NZVIs) have rapidly received much attention as a novel, in situ subsurface remediation agent to treat various kinds of vexing environmental contaminants , including chlorinated organics such as trichloroethylene (TCE) (Lowry 2007; Tratnyek and Johnson 2006; Zhang 2003). Various organic macromolecule surface modifiers, such as xanthane, guar gum, poly(aspartate) (PAP), poly(styrene sulfonate ), carboxymethyl cellulose (CMC), poly(methyl methacrylate ), poly(acrylic acid), and tri-block copolymers, are used to engineer NZVIs to inhibit their aggregation (Golas et al. 2010; Phenrat et al. 2008; Sakulchaicharoen et al. 2010; Saleh et al. 2005; Wang et al. 2010), increase their mobility in the subsurface (Kim et al. 2009; Phenrat et al. 2009a, 2010; Saleh et al. 2008; Vecchia et al. 2009), and provide pollutant selectivity (Bishop et al. 2010; Phenrat et al. 2011; Saleh et al. 2005; Wang and Zhou 2010), all of which are necessary for effective in situ remediation. "
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    ABSTRACT: For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.
    Environmental Science and Pollution Research 08/2015; DOI:10.1007/s11356-015-5092-4 · 2.83 Impact Factor
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    • "Third, NZVI has a short lifetime in the subsurface due to its high reactivity with water [2]. Finally, the intrinsic hydrophilic properties of NZVI make the particles non-specific for treating hydrophobic contaminants in source zones [15]. Significant efforts have been made to address these challenges. "
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    ABSTRACT: Nanoscale zero-valent iron (NZVI) is effective in reductively degrading dense non-aqueous phase liquids (DNAPLs), such as trichloroethene (TCE), in groundwater (i.e., dechlorination) although the NZVI technology itself still suffers from high material costs and inability to target hydrophobic contaminants in source zones. To address these problems, we developed a novel, inexpensive iron-carbon (Fe-C) nanocomposite material by simultaneously milling micron-size iron and activated carbon powder. Microscopic and X-ray diffraction (XRD) characterization of the composite material revealed that nanoparticles of Fe were dispersed in activated carbon and a new iron carbide phase was formed. Bench-scale studies showed that this material instantaneously sorbed >90% of TCE from aqueous solutions and subsequently decomposed TCE into non-chlorinated products. Compared to milled Fe, Fe-C nanocomposite dechlorinated TCE at a slightly slower rate and favored the production of ethene over other TCE degradation products such as C3C6 compounds. When placed in hexane-water mixture, the Fe-C nanocomposite materials are preferentially partitioned into the organic phase, indicating the ability of the composite materials to target DNAPL during remediation. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of hazardous materials 07/2015; 300:443-450. DOI:10.1016/j.jhazmat.2015.07.038 · 4.53 Impact Factor
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    • "Modification of surface properties has been adopted as the main approach to pursue an enhanced colloidal stability of nZVI aqueous dispersions, and consequent enhanced mobility in porous media. Natural and engineered polymers, anionic surfactants as well as other organic coatings have been studied and identified as promising materials for improving colloidal stability and mobility of nZVI (Saleh et al., 2005). Alternative approaches explored to date for stabilizing nZVI suspensions include oil-in-water emulsions for a targeted delivery of nZVI to NAPL source zones using environmental friendly, easily degradable oils, eg. "
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    ABSTRACT: Nanoscale zero-valent iron particles (nZVI) have been studied in recent years as a promising technology for the remediation of contaminated aquifers. Specific positive features of nZVI are the high reactivity towards a broad range of contaminants and the possibility of injecting in aqueous slurries for a targeted remediation of contaminated areas. However, crucial points to be addressed are stability against aggregation, mobility in subsurface environments, and longevity. In this work a review is presented on the current knowledge on the properties, reactivity and mobility in porous media of nZVI and their application to groundwater remediation. A specific focus is devoted to the methodologies to the colloidal stability of the nZVI slurries and to the available numerical tools for the simulation of laboratory and field scale mobility of the particles when injected in porous media.
    Journal of Cleaner Production 08/2014; 77:10–21. DOI:10.1016/j.jclepro.2013.12.026 · 3.84 Impact Factor
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