Grantee Research Project Results

Transformation and Fate of Manufactured Metal Oxide and Metal Nanoparticles in Aqueous Environments

EPA Grant Number: R833891
Title: Transformation and Fate of Manufactured Metal Oxide and Metal Nanoparticles in Aqueous Environments
Investigators: Grassian, Vicki H.
Institution: University of Iowa
EPA Project Officer: Aja, Hayley
Project Period: January 15, 2009 through January 14, 2012
Project Amount: $389,303
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Fate, Transport, Transformation, and Exposure of Engineered Nanomaterials: A Joint Research Solicitation - EPA, NSF, & DOE (2007) RFA Text |  Recipients Lists
Research Category: Nanotechnology , Safer Chemicals

Description:

As commercial manufactured nanomaterials become more commonplace, we can expect that these manufactured materials have the potential to get into the environment sometime during production, distribution, use or disposal, i.e. sometime during the lifecycle of these materials. In particular, there exists the potential that nanomaterials may make their way into water systems, e.g. drinking water systems, ground water systems, estuaries, lakes etc. Nanoparticles, the primary building blocks of many nanomaterials, are of particular interest in the proposed studies as the fate of nanoparticles in aqueous environments will depend to a large extent on the physical and chemical state of the nanoparticles. A series of experiments will be done to provide the data needed to predict the environmental fate of commercially manufactured metal and metal oxide nanoparticles.

Objective:

The study will be conducted to satisfy four main objectives. These objectives are to:

1. fully characterize a variety of manufactured metal and metal oxide nanoparticles in terms of their size, shape, bulk and surface physicochemical properties;
2. determine under what environmental conditions (ionic strength, pH, ligands, organic matter, surface adsorption and nanoparticle concentration) do manufactured metal oxide and metal nanoparticles of different size and composition aggregate in aqueous solution and measure the size of the aggregates as a function of these environmentally important variables;
3. determine under what environmental conditions (ionic strength, pH, ligands, surface adsorption and solar irradiation) do manufactured metal oxide and metal nanoparticles of different size and composition dissolve in aqueous solutions and;
4. investigate fundamental aspects of the surface properties and surface chemistry of metal oxide and metal nanoparticles as surface properties and surface chemistry will control both nanoparticle aggregation and nanoparticle dissolution as well as impact nanoparticle-biological interactions.

It is clear that the fate of the nanoparticles in aqueous environments will depend on the state of the nanoparticle (i.e. whether the nanoparticle remains isolated, forms aggregates or undergoes dissolution). This is the basis of the hypotheses of the proposed studies.

The first hypothesis of the proposed project is that nanoparticles will form aggregates in solution and that the size of the aggregate will depend on nanoparticle primary size and composition as well as on environmental conditions. To test this hypothesis the following experiments will be completed:

1. Perform dynamic light scattering and sedimentation experiments on a series of metal oxide and metal nanoparticles in aqueous solution as a function of nanoparticle loading under circumneutral pH;
2. Perform a similar series of dynamic light scattering and sedimentation experiments on a series of metal oxide and metal nanoparticles in aqueous solution as a function of ionic strength and pH;
3. Perform a similar series of dynamic light scattering and sedimentation experiments on a series of metal oxide and metal nanoparticles in aqueous solution in the presence of coordinating ligands and complex organic matter;

The second hypothesis of the proposed project is that nanoparticle dissolution can occur under certain conditions that will depend on nanoparticles size and composition as well as on environmental conditions. To test this hypothesis the following experiments will be performed:

1. Perform dissolution studies on a series of metal oxide and metal nanoparticles in aqueous solution as a function of nanoparticle loading under circumneutral pH;
2. Perform dissolution studies on a series of metal oxide and metal nanoparticles in aqueous solution as a function of ionic strength and pH;
3. Perform dissolution studies on a series of metal oxide and metal nanoparticles in aqueous solution in the presence of coordinating ligands, organic matter and solar irradiation;

The third hypothesis of the proposed project is that nanoparticle aggregation and dissolution will be controlled by nanoparticle surface properties and, therefore, fundamental studies of nanoparticle surface adsorption and surface chemistry can provide further insight into nanoparticle aggregation and dissolution. To test this hypothesis the following experiments will be performed:

1. Studies using in situ surface spectroscopic probes such as ATR-FTIR spectroscopy on nanoparticle-adsorbate systems complementary to the aggregation and dissolution experiments will provide fundamental information on surface speciation and surface complexation;
2. Studies using ex situ surface spectroscopic probes such as XPS on nanoparticle-adsorbate systems complementary to the aggregation and dissolution experiments will provide fundamental information on surface speciation and surface complexation;
3. Additional studies using both in situ and ex situ surface spectroscopic investigations of probe molecule adsorption to better understand the surface chemistry and nature of surface sites and surface bonding under different environmental conditions.

Approach:

Manufactured nanoparticles will be purchased from several sources and characterized using a wide variety of techniques and analysis methods so that both bulk and surfaces properties can be understood on a molecular level. These well-characterized particles will then be used in a series of solution-phase studies to determine under what conditions metal oxide and metal nanoparticles aggregate into larger particles and under what conditions do these nanoparticles dissolve. Nanoparticle aggregation and dissolution will be probed using light scattering and elemental analysis methods, respectively. Mathematical analyses using classical kinetic and thermodynamic approaches will be applied to the data. Since nanoparticle surface processes are important in nanoparticle agglomeration and dissolution, fundamental aspects of surface properties and surface chemistry will be investigated using surface-sensitive spectroscopic and other surface-sensitive probes. These fundamental molecular level studies will be important in interpreting the more macroscopic aggregation and dissolution measurements and in determining how well classical approaches can be used to interpret macroscopic behavior of nanoscale materials.

Expected Results:

It is expected that these studies will provide important data and information to increase our understanding of the fate and transformation of manufactured metal oxide and metal nanoparticles in aqueous environments. These data can be then used as input in models that predict the environmental fate of commercial nanomaterials.

Publications and Presentations:

Publications have been submitted on this project: View all 29 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 9 journal articles for this project

Supplemental Keywords:

water, groundwater, dissolved solids, metals, heavy metals, environmental chemistry, engineering, industry, nanomaterials, nanotechnology, fate, transformation,, Health, Scientific Discipline, Health Risk Assessment, Risk Assessments, Biochemistry, Biology, biological pathways, aquatic ecosystem, bioavailability, genetic analysis, nanotechnology, carbon fullerene, human exposure, nanomaterials, toxicologic assessment, nanoparticle toxicity, carcinogenic

Progress and Final Reports:

2009 Progress Report

2010 Progress Report

Final Report