Grantee Research Project Results
2006 Progress Report: Fate and Transformation of C60 Nanoparticles in Water Treatment Processes
EPA Grant Number: R832526Title: Fate and Transformation of C60 Nanoparticles in Water Treatment Processes
Investigators: Kim, Jae Hyung , Hughes, Joseph
Institution: Georgia Institute of Technology
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through December 31, 2008
Project Period Covered by this Report: September 1, 2005 through December 31, 2006
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: A Joint Research Solicitation - EPA, NSF, NIOSH (2005) RFA Text | Recipients Lists
Research Category: Nanotechnology , Human Health , Safer Chemicals
Objective:
The environmental impact of carbon fullerenes is of great concern because of projections for bulk production in the near future and the recent discovery that they form nano-scale water-stable aggregates upon release to water. Understanding the fate and transformation of carbon fullerenes during water treatment, currently our first line of defense against ingestion pathways, is of particular importance. Human exposure to these materials via water ingestion will be strongly influenced by the behavior of these aggregates in potable water treatment processes. The objective of this research is to examine the response of water-stable fullerene aggregates to processes that are used in water treatment, using C60 and its stable aggregate, nano-C60, as a model compound.
Progress Summary:
In Year 1 of the project, we focused on chemical and photochemical responses of aqueous stable forms of C60. Chemical and photochemical reactivity are responsible for the fundamental mechanisms behind C60’s fate during oxidant and UV application in water treatment. First, a specific reaction between dissolved ozone, a common disinfectant reagent, and nano-C60 was studied, detailing the reaction kinetics as a function of pH observed by spectral changes, dynamic light scattering (DLS), and transmission electron microscopy (TEM) analyses over time. Molecular soluble products were characterized by a battery of spectral analyses including nuclear magnetic resonance (NMR) imaging, X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR), UV-visible spectroscopy (UV-Vis), and time-of-flight mass spectrometry (laser desorption/ionization [LDI]) and determined to be a highly oxidized fullerene (fullerol) with approximately 28-30 oxygen additions. To our knowledge, this is the first report describing the chemical transformation of C60 as a suspended aggregation in water. This finding is significant as the material reactivity, which leads to molecularly soluble products, must now be considered in aqueous fate and transport models. Second, the photochemical production of singlet oxygen (1O2) and superoxide radical anion (O2·ˉ) by C60 in water was examined. Our study demonstrated that photoexcited C60 in the aqueous phase efficiently mediated transfer of absorbed energy to oxygen and produced singlet oxygen when associated with surfactant or polymer, which is consistent with its behavior in organic solvents. However, when C60 was present as colloidal aggregate suspension, prepared through solvent exchange or sonication, this intrinsic characteristic was lost. Similarly, C60 associated with surfactant-mediated electron transfer from electron donor to oxygen, producing superoxide radicals, while C60 aggregates and C60 associated with polymer did not. These results suggest that the ability of C60 to mediate energy and electron transfer may be affected by the degree of C60 aggregation in the aqueous phase as well as characteristics of associated stabilizing molecules. Dependence of photochemical reactivity of C60 on its dispersion status in the aqueous phase is critical in assessing environmental impact and cytotoxicity of this material. For example, as C60 was associated with model natural organic matter (NOM), it was found to exist in aggregate form and did not produce reactive oxygen species under UV illumination. Third, we also studied the aqueous stability of multi-walled carbon nanotubes (MWNTs) in the presence of NOM. MWNTs were readily dispersed as an aqueous suspension in both model NOM (Suwannee River NOM [SR-NOM]) solutions and natural surface water NOM (actual Suwannee River water with unaltered NOM background), and suspended MWNTs remained stable for over 1 month. These findings suggest that dispersal of carbon-based nano-materials in the natural, aqueous environment might occur to an unexpected extent following a mechanism (i.e., enhanced dispersion) that has not been previously considered in environmental fate and transport studies. Although extending the study to carbon nanotubes (CNT) was not originally proposed, it was recognized as critical to include this class of carbon nanomaterials and examine their behaviors in natural aqueous environment, as C60 was found to behave very differently from CNT.
Future Activities:
In Year 2, we will continue to study the response of aqueous stable C60 to UV irradiation, especially at lower wavelengths, to verify the potential for direct photolysis of C60. Reaction of C60 with radical species (such as hydroxyl radical) as well as other common oxidants such as chlorine will be examined.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 20 publications | 10 publications in selected types | All 10 journal articles |
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Hyung H, Fortner JD, Hughes JB, Kim J-H. Natural organic matter stabilizes carbon nanotubes in the aqueous phase. Environmental Science & Technology 2007;41(1):179-184. |
R832526 (2006) R832526 (2007) R832526 (Final) |
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Supplemental Keywords:
fullerene, nano-C60, water treatment, coagulation, ozonation, UV irradiation, chlorination, chloramination, membrane, activated carbon adsorption, kinetics, product identity,, Health, RFA, Scientific Discipline, PHYSICAL ASPECTS, Water, Health Risk Assessment, Physical Processes, Risk Assessments, Environmental Chemistry, Engineering, Chemistry, & Physics, Biochemistry, Drinking Water, community water system, health effects, toxicity, toxicokinetics, epidemelogy, nanomaterials, water quality, human exposure, engineered nanomaterials, drinking water system, drinking water contaminants, exposure, fate and transport, ambient particle health effects, nanotechnology, other - risk assessment, cellular responses, human health effects, human health risk, particle exposure, biochemical researchRelevant Websites:
http://www.ce.gatech.edu/~jkim Exit
Progress and Final Reports:
Original AbstractThe 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.