R1 PM Nanotechnology Environmental Remediation, Fate, and Transport|
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 1
673 (GRA-1117-829751) Nanocrystalline Zeolites: Applications in Environmental Remediation.
Start time: 1:50 PM
Grassian, V1, Larsen, S1, Song, W1, Li, G, 1 Univeristy of Iowa
Zeolites are aluminosilicate molecular sieves with pores of molecular dimensions. Zeolites, which have been commercially available in large quantities for nearly fifty years, have a number of industrial uses as shape-selective catalysts, sorbents and ion-exchangers as well as in separations through size exclusion. The crystal size of zeolites formed during conventional synthesis is typically one micron. Nanocrystalline zeolite of dimensions less than 100nm have the potential to be ideally suited for applications in environmental remediation. These materials have high internal and external surfaces area and unique functional bifunctional capabilities, such as acid/base chemistry, that can be designed into these materials. Several examples of the uses of nanocrystalline zeolites in environmental remediation will be discussed.
674 (GAN-1117-849129) Remediation of Inorganic and Organic Contaminants Using Nanoparticle Media.
Start time: 2:10 PM
Ganesh, R1, Leong, L1, Jain, M2, Bisso, S2, Skandan, G2, 1 Kennedy/Jenks Consultants, Irvine, CA, USA2 NEI Corporation, Piscattaway, NJ, USA
Nanotechnology involves the use of extremely small size (1 -100 nm) particles, synthesized by atomic or molecular level manipulation, for various applications. The smaller size provides a significantly high surface area per unit mass of the nanoparticles. In addition, as a result of the small size, there is a high density of electrons at the edge of these particles, which results in a significantly higher reactivity of the nanoparticles compared to particles of larger size prepared by conventional methods. These and other unique surface properties of nanoparticles make them an attractive media for various applications, including environmental remediation. The project team (Kennedy/Jenks Consultants and NEI Corporation) is currently involved in several projects to evaluate remediation of inorganic (arsenic, molybdenum, mercury, copper, lead and uranium) and organic (NOM) constituents of environmental concern using engineered metal oxide nanoparticles. Batch kinetic and isotherm studies were performed using synthetic as well as impacted groundwaters. The kinetic study indicated that sorption of natural organic matter to ferric oxide-based nanopowder was extremely rapid. More than 90% of the NOM (initial TOC 20 mg/l) was adsorbed within 10 minutes by 400 mg of the adsorption media. Preliminary isotherm experiments for NOM and arsenic using this media yielded specific adsorption capacities of >0.18 mg/sq m, and 16 g/sq m, respectively. These values were significantly higher than (0.1 mg/sq m and 6 g/sq m) those reported for commercially used ferric oxide media. Similar results were observed for uranium, copper, mercury adsorption using Manganese oxide based nanopowder media. The adsorption characteristics of all the contaminants, except mercury, generally followed Langmuir adsorption model. Column studies are now being performed to evaluate breakthrough characteristics.
675 (HUS-1117-838864) Applications of Nanofibers and their Fate and Transport in the Environment.
Start time: 2:30 PM
Hussain, M1, Guven, N1, Nallani, G1, Ramkumar, S1, 1 Texas Tech University, Lubbock, TX, USA
Electrospun nanofibers have created a new and rapidly growing research area due to its pronounced micro and nano characteristics such as high surface area with porous structure, fiber diameter at nano level, filtration properties, high permeability, layer thinness etc. Three different types of nanofibers have been developed in our laboratory and the first group of nanofibers is produced from a single polymeric solution (polyethylene oxide and polyurethane) by electrospinning process. These nanofibers have high filtration efficiency compared to those currently available in market. The second group of nanofibers is known as nanocompositefibers in which functional structures are incorporated in order to make them chemically active. Nanocrystalline magnesium oxide and titanium oxide have been used with polyethylene oxide and these composites can work against chemical warfare agents, organophosphorus compounds and can block ultraviolet radiation efficiently. Biodegradable polymers are the third type of nanofibers, which were made from polyepsilon-caprolactone and chitosan. These fibers can be used as cellular scaffold and in drug delivery as well. All of these nanofibers were obtained in the range of 50 nm to 300 nm and were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron dispersion spectroscopy (EDS) and X-ray diffraction method (XRD). In order to minimize the toxic effects of these nanofibers, nontoxic polymers were first selected. On the other hand, most of the polymers are not soluble in water; therefore selection of nontoxic solvent is another critical part for this fabrication process. The residual solvent in the final product is then removed by vacuum drying of these nanofibers. Since nanofibers are mostly used for filtration purposes and in chemical protective clothings, the disposal of nanofibers is always a sensitive issue. The fate and transport properties of the nanofibers are currently under investigation and the results will be reported in the presentation.
676 (BRA-1117-722831) Transport of different nanosized aluminum particles through sand columns.
Start time: 2:50 PM
Doshi, Reeti1, Braida, Washington1, Christodoulatos, Christos1, O'Connor, Gregory2, 1 Stevens Institute of Technology, Hoboken, NJ, USA2 US Army, Environmental Technology Division, Picatinny Arsenal, NJ, USA
Nanoaluminum is used as an energetic material. The fate and transport of nanosized aluminum particles, once they are released into the environment, has not yet been addressed. As part of an ongoing research effort, the transport of two types of nanosized aluminum particles through sand columns has been studied. The Al particles are 100 nm in size and are coated with a thin layer of aluminum oxide or an organic carboxylic ligand. The transport behavior of the nanoaluminum particles was compared with the transport behavior of micron sized oxide coated-Al particles. Two experimental setups were used; i) columns fed with aqueous nanoaluminum suspension at different pHs and ii) deposit a layer of nanoaluminum particles at the top of the sand in the column and pump water at different pHs through it. The columns amended with nanoaluminum particles clogged after a few pore volumes of liquid passed through (faster clogging at pH 4 than at pH 7), suggesting the agglomeration of nanosized particles. Micron sized-Al amended sand columns clogged, but at much slower rate. Concentrations as high as 15 mg/L in the effluent were measured. Those are far larger than the World Health Organization guideline for Al in drinking water (0.2 mg/L). The total amount of aluminum leached from the columns follows the order: organic coated-pH 4>oxide coated-pH4 >> organic coated-pH 7oxide coated-pH 7. The distribution of aluminum through the column profile was measured and XRD analysis was performed to characterize the aluminum particles after exposure to the environment. The results of the research suggest that surface phenomena (i.e., changes in point of zero charge, agglomeration, etc.) play a major role in the transport of nanoaluminum particles. Furthermore, our results add to the basic knowledge necessary to predict the fate and transport of nanoparticles in the environment.
Start time: 3:10 PM
677 (GIL-1118-092655) The impact of aqueous colloid properties on the transport of metal oxide and sulfide nanoparticles.
Start time: 3:50 PM
Gilbert, B.1, 1 Lawrence Berkeley National Laboratory, Berkeley, CA, 94720
Nanoscale materials are likely to be employed in applications such as chemical catalysis, medical imaging and solar energy conversion that will carry a risk of eventual release into the environment. Furthermore, developing environmental remediation technologies either harness reactive nanoparticles or frequently lead to the precipitation of contaminants as nanoscale particles following microbial activity. The prediction of transport properties of novel nanoscale materials and of contaminants bound to or in the form of inorganic nanoparticles requires understanding of their colloid behavior. The goals of our research are (1) to determine the effects of particle size, surface adsorption and solution chemistry on the regime of colloid stability; (2) to determine the nano- and microscale structures of clusters that are formed when nanoparticles aggregate; and (3) to link aggregate structure to the kinetics of environmental transformations such as dissolution and aggregate transport properties. Metal oxide and metal sulfide nanoparticles represent two important nanomaterial classes, with distinct solution behavior. A combination of electron microscope imaging and in situ x-ray and light scattering studies has shown that iron oxyhydroxide, titanium dioxide and zinc sulfide nanoparticles exhibit a strong tendency to aggregate under environmentally relevant aqueous conditions. Thus, we predict that these nanomaterials will be transported as 20 - 1000 nm diameter pseudo-colloids with complex, and greatly varied interior structure. By using small-angle x-ray scattering to quantify the important aspects of aggregate structure we are developing models of the hydrodynamic and transport behavior of such aggregates for the interpretation of pore-scale transport experiments.
678 (COL-1118-174688) Eco-Nano: The Impact of Engineered Nanomaterials on the Environment.
Start time: 4:10 PM
Colvin, V ,
Traditionally, nanotechnology has been motivated by the growing importance of very small (d < 50nm) computational and optical elements in diverse technologies. However, this length scale is also an important and powerful one for living systems. At Rice, we believe that the interface between the dry side of inorganic nanostructures and the wet side of biology offers enormous opportunities for medicine, environmental technologies, as well as entirely new types of nanomaterials. As part of our work on the potential biological applications, we also consider the unintended environmental implications of water soluble nanomaterials. Given the breadth of nanomaterial systems, we use a carefully selected group of model nanoparticles in our studies and focus on natural processes that occur in aqueous systems. We characterize the size and surface-dependent transport, fate and facilitated contaminant transport of these engineered nanomaterials. Models from larger colloidal particles can be extended into the nanometer size regime in some cases, while in others entirely new phenomena present themselves. We also consider biological interactions of nanoparticles and specifically address the interactions of a classic nanomaterial, C60, with cellular systems. While the water-suspendable nano-C60 nanocrystal is apparently cytotoxic to various cell lines, the closely related fully hydroxylated, C60(OH)24, is non-toxic, thus producing no cellular response. Similarly, we have also found that functionalized single-walled carbon nanotubes are non-toxic to cells in culture. More specifically, as the functionalization density of the SWNT increases, the nanotube becomes more inert to cultures.
679 (FOR-1117-852532) Reactivity of Water-Stable C60 Aggregates During Ozonation and UV Irradiation Processes.
Start time: 4:30 PM
Fortner, John1, Kim, Doo-Il1, Kim, Jae-Hong 1, Hughes, Joseph1, 1 Georgia Institute of Technology, School of Civil & Environmental Engineering, Atlanta, Georgia, USA
As industrial scale production of nanomaterials becomes a reality, little is known about the unintentional impact on natural systems, particularly with regard to water quality. Current regulation of carbon fullerenes highlights this fact as the Occupational Safety and Health Administration (OSHA, U.S. Department of Labor) guidelines for handling and disposal is to simply follow the material safety data sheet (MSDS) for carbon black. However, fullerenes do not behave in such an analogous fashion as they can form discrete aggregates on the nano-scale that remain as a stable suspension in water over time. Such behavior, coupled with recent findings that these aggregates interact with living cells, underlines the need to understand the fate and the transformation of carbon fullerenes during engineered water treatment processes, particularly with regard to potable water. Research presented herein investigates the stability, transformation kinetics and reaction products of fullerene (as C60) aggregates (termed nano-C60) during ozonation and UV irradiation, common water treatment processes. For both processes, semi-batch and batch experiments, a matrix of variables was examined including pH (5-9), temperature (5-30 C) and aggregate size. Preliminary semi-batch ozonation results suggest that the half life of nano-C60 at representative experimental conditions tested ([O3]0 = 2.8 mg/L, 5mg/L nano-C60, buffered) was approximately 24 min. UV/Vis spectral changes over time, particularly the loss of characteristic C60 absorbance peaks at 450, 340, 260 nm, indicated that the fullerene carbon cage had been altered. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) data indicate the loss of aggregate size and integrity, further suggesting soluble product(s). Ongoing product characterization using 13C-NMR and mass spectroscopy will be presented along with the results from parallel UV irradiation experiments.
680 (FER-1117-829068) Fate of single-walled carbon nanotubes in the estuarine environment.
Start time: 4:50 PM
Ferguson, P.1, DeMarco, A.1, Templeton, R.1, Chandler, G.1, 1 University of South Carolina, Columbia, SC, USA
Single-walled carbon nanotubes (SWNTs) are filamentous manifestations of a repeating aromatic carbon structure formed into an open cylinder. These nanomaterials exhibit novel physical and chemical properties and much attention has been devoted to their commercialization in such applications as structural composites and microelectronics. Because of their unique physicochemical properties and potential for large-scale commercialization, recent concerns have emerged over the potential of nanomaterials such as SWNTs to elicit adverse effects in the aquatic environment. However, little information exists on the environmental fate of these materials in aquatic systems. In order to address the potential for SWNTs to enter, persist, and be transported within estuaries, we have systematically investigated the physicochemical behavior of these materials under simulated estuarine conditions. Specifically, we have utilized dynamic light-scattering analysis to examine the agglomeration of colloidal SWNT suspensions over a range of salinities. Results indicate that SWNTs exist as stable colloidal suspensions (average particle size 200 - 250 nm) in buffered (pH 7) solutions of low ionic strength (10 mM) but that relatively large (average particle size > 2 m) SWNT flocs formed over rapid (minute) timescales as salinity increased over 5 ppt. These results indicate that SWNTs are highly sensitive to changes in solution ionic strength, and that estuarine mixing may play an important role in determining the fate of SWNTs after entry into the aquatic environment (e.g. settling or association with suspended particulates). We will discuss the results of more comprehensive, multivariate experiments designed to test the combined effects of salinity, pH, SWNT concentration, and dissolved organic matter concentration on SWNT aggregation behavior as well as the use of 14C-labeled SWNTs for quantifying the association of these nanomaterials with estuarine sediments. Finally, we will report on progress in utilizing confocal Raman microspectroscopy to analyze distributions of SWNTs in estuarine sediments and in sediment-ingesting benthic invertebrates (copepods and polychaetes) exposed to SWNTs in a laboratory setting.
681 (MAD-1117-842672) Hazard assessment and sensitivity analysis for buckminsterfullerene in the environment.
Start time: 5:10 PM
Maddalena, R1, MacLeod, M2, McKone, T1, 3, Sohn, M1, 1 Lawrence Berkeley National Laboratory, Berkeley, CA, USA2 Swiss Federal Institute of Technology, Zürich, Switzerland3 University of California, Berkeley, Berkeley, CA, USA
A prospective assessment of ecological and human health hazards associated with nanomaterials is timely given the increasing commercialization of nanotechnology. Because relevant data for the environmental behavior of nanomaterials is lacking, the goal of this paper is to provide an initial assessment of hazard for an archetypal nano-molecule (Buckminsterfullerene) in the context of current fate and exposure models. We extend the traditional approach to hazard assessment, which focuses primarily on toxicity, to include properties of the chemical that are indicative of environmental hazard such as persistence, bioaccumulation, long-range transport potential and exposure potential, where the latter is characterized using the intake fraction metric. The prospective analysis is developed using a series of representative polycyclic aromatic hydrocarbons increasing in size from naphthalene to Buckminsterfullerene. The approach illustrates how experience with "conventional" organic pollutants can provide insight about plausible, or at least bounding environmental fate and exposure outcomes. As part of the illustrative analysis, we apply non-traditional Monte Carlo-based sensitivity analyses techniques to identify (i) influential input/output relationships and (ii) internal constituents of the fate and exposure model (e.g, modules, algorithms and imbedded assumptions) that influence the hazard estimates for fullerene. The analysis provides an opportunity to identify potentially important exposure scenarios for organic nanomolecules given our current modeling framework, and explore the relevance of these scenarios for engineered nanomaterials dispersed in the environment.