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Grantee Research Project Results

Grantee Research Project Results

“Effects of Surface Oxides on the Behavior of Carbon Nanotubes and their influence on the Mobility of Contaminants in Aquatic Environments”

EPA Grant Number: R833857
Title: “Effects of Surface Oxides on the Behavior of Carbon Nanotubes and their influence on the Mobility of Contaminants in Aquatic Environments”
Investigators: Ball, William P. , Fairbrother, D. Howard
Institution: Johns Hopkins University
EPA Project Officer: Shapiro, Paul
Project Period: July 1, 2008 through June 30, 2011
Project Amount: $399,467
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Fate, Transport, Transformation, and Exposure of Engineered Nanomaterials: A Joint Research Solicitation - EPA, NSF, & DOE (2007)
Research Category: Nanotechnology

Description:

Objective:

The proposed project will investigate the influence that oxygen-containing functional groups (surface oxides) exert on the aggregation, transport, and sorption properties of carbon nanotubes (CNTs) in aquatic environments. These studies will also include experiments designed to understand the effect of CNTs on the mobility of organic and inorganic toxins. To accomplish our objectives, we will test specific hypotheses on the relationships that exist between CNT surface properties and their behavior. Such testing will include (1) elucidating the effect that different oxidizing conditions exert on the surface chemistry and aquatic behavior of CNTs, (2) examining the suitability of new and existing mathematical models to describe the behavior of CNTs in aqueous environments, (3) evaluating the potential for CNTs to facilitate or hinder the transport of toxic organic and inorganic chemicals through porous media, and (4) developing structure-activity relationships that can help predict the environmental fate and impact of CNTs.

Approach:

We will prepare a range of surface-modified CNTs from the commercially available pristine nanomaterials using different combinations of oxidizing agents and reaction conditions. Oxidized CNTs will be characterized using a suite of complementary analytical techniques including Atomic Force Microscopy, Transmission Electron Microscopy, Electropheresis and X-ray Photoelectron Spectroscopy in conjunction with chemical derivatization. For each surface modified CNT, aggregation kinetics will be measured using Dynamic Light Scattering and transport properties through porous media will be studied in column studies with and without the co-elution of toxic pollutants. Sorption/desorption kinetics and equilibria of selected organic and inorganic contaminants with CNTs will be obtained using batch reactors and recently developed analytical methods for solid-water separation. Aggregation, transport, and sorption studies will be conducted over a range of solution conditions (defined by pH, ionic strength, electrolyte composition and concentration of dissolved organic matter) designed to explore mechanistic hypotheses while also being representative of aquatic environments.

Expected Results:

By identifying conditions where CNTs could influence the transport of organic or inorganic contaminants, the proposed studies will have far reaching and broad implications for the health and safety risks associated with CNTs. Moreover, the experimental database generated in these studies will enable us to test the suitability of existing theories to describe the behavior of CNTs while providing a foundation for new and improved modeling approaches. Such information is urgently needed in response to the increasing quantities of colloidally stable, surface modified CNTs that will be entering the environment.

References:

* Department of Geography and Environmental Engineering, Johns Hopkins University; † Department of Chemistry, Johns Hopkins University.

Supplemental Keywords:

Health, Scientific Discipline, Health Risk Assessment, Risk Assessments, Biochemistry, aquatic ecosystem, biological pathways, CNT, bioavailability, nanotechnology, carbon fullerene, human exposure, nanomaterials, toxicologic assessment, nanoparticle toxicity, human health risk

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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