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Conference Abstracts (N-R)
Nanofiber Sensor Platform for
Environmental Pollutant Monitoring and Detection
Li Han, Anthony Andrady, Kim Guzan, David
Ensor, RTI International, USA
Electrospun polymer nanofiber materials have attracted tremendous interest in sensor applications as their effective sensing surface area dramatically increases with decreasing fiber diameter. The highly tunable polymer composite chemistry and surface functionality of the nanofiber material provides a wide platform for exploring different applications, such as filtration media, sound isolation materials, and as components within sensors. This paper presents for the first time a Nanofiber Sensor Platform composed of electrospun polymer/carbon composite nanofibers combined with printed electrodes to form an integrated sensor system for detecting various chemical vapors, including volatile organic compounds and oxidative gases. In this platform, composite polymer nanofibers form the chemo-resistor sensing material since the conductivity of these composite sensing materials varies with chemical vapor exposure, including volatile organic compounds (VOCs) and oxidative gases. The novel custom printed metal electrode can be directly deposited onto the surface of the electrospun fiber mat to enhance the contact between the electrode and the fiber mat. The sensor performance exhibits very stable baselines with dramatically reduced noise levels compared to conventional interdigitated electrodes. Furthermore, the sensor response to different vapors shows a linear relationship between conductivity change and vapor concentration in the range of ppb – ppm for some analytes, including methanol at 200ppb, chloroform at 3.3 ppm and ozone at 250 ppb level. The sensitivity and selectivity of these sensors to different vapor analytes, including VOCs such as methanol, chloroform, and oxidative gases such as ozone, will be discussed.
Nanoscale Zero Valent Iron Phase II Injection Field Pilot
Study, Phoenix-Goodyear Airport North Superfund Site, Goodyear, Arizona
Robert J. Ellis, Harry
S. Brenton, David S. Liles, Chase McLaughlin, Nick Wood, ARCADIS-US, Inc., USA
Bench scale kinetics testing and a Phase II field injection test were completed to evaluate using Polyflon Company PolyMetallixTM nanoscale zero velent iron (nZVI) to treat trichloroethene (TCE) at the Phoenix-Goodyear Airport North Superfund Site in Goodyear, Arizona. Pre-injection dissolved-phase TCE concentrations in source area groundwater ranged from approximately 3,000 micrograms per liter (g/L) in injection well IRZ-IW-05, to 7,000 g/L in monitoring well IRZ-IW-03. Based on recent characterization efforts, TCE concentrations are present from 110 to 120 feet below ground surface (bgs), approximately 25 to 35 feet below the top of the water table.
During bench-scale testing conducted in 2007, technical and quality protocols for nZVI production were defined. Results of the bench scale testing indicated:
- nZVI, with and without the dispersing agent sodium hexametaphosphate (SHMP), remains very reactive up to 30 days after production, indicating good product shelf-life;
- nZVI remains very reactive in the presence of site groundwater, despite elevated ionic strength;
- Degradation rate constants for destruction of TCE in the presence of the nZVI with and without SHMP are similar and significantly higher than degradation rate constants under natural attenuation conditions;
- Post-production nZVI processing via high-speed shearing forces produced by colloid milling minimizes agglomeration, with minimal impact on reactivity.
During Phase II Field testing conducted in June 2008, 10,400 liters (2,750 gallons) of a 2.1 grams per liter (g/l) nZVI suspension with SHMP totaling 22 kilograms (49 pounds) of nZVI were injected into the aquifer through injection well IRZ-IW-05 over a three day period utilizing an onsite colloid mill. Significant changes in groundwater chemistry were observed during the injection at monitoring well IRZ-IW-01, located 1.5 meters (m) (5 feet) from the injection well, including a 400 millivolt (mV) decrease in oxidation reduction potential (ORP) and decrease in dissolved oxygen to below detection. The average injection rate was 6.3 liters per minute (l/m) (1.6 gallons per minute [gpm]). A decrease in injection rate over the duration test was observed, indicating an apparent decrease in permeability within the aquifer. The apparent loss of permeability may be temporary due to geochemical reactions, such as hydrogen gas production and amorphous mineral precipitation, or semi-permanent, due to emplacement of nZVI particles within the aquifer. Post-injection hydraulic testing will evaluate the nature and duration of the permeability loss. Available laboratory results from the post-injection hydraulic testing and two months of periodic groundwater monitoring at three monitoring wells will be discussed.
Nanostructured Metal Oxides for Removing Heavy Metal Ions
from Water
Weiguo Song, Liangshu Zhong, Lijun Wan, Institute of Chemistry, Chinese Academy of Sciences, CHINA
Nanostructured metal oxides with hierarchical structures may satisfy our requirements for desired materials. We developed several general synthesis routes to synthesize metal oxides with desired morphologies and hierarchical structures. These methods include poly-ol mediated route, surfactant assisted aqueous route, hydrothermal route. These routes provide general, reliable and environmental friendly method to prepare a series of transitional metal oxides and rare earth metal oxides, including iron oxide, titania and ceria. These materials are overall micron sized particles that are consisted of assembled or self assembled nano building blocks. The nano building blocks provide high surface area, high surface to bulk ratio as well as surface functional groups that can interact with heavy metal ions; while the overall micron structures provide desired mechanical properties, such as robustness, facile specie transportation, easy recovery and regeneration. These features are suited for environmental applications including removing heavy metal ions from water.
References:
- Liang-Shu Zhong, Jin-Song Hu, Li-Jun Wan, Wei-Guo Song “Facile synthesis of nanoporous anatase spheres and their environmental applications” Chem. Comm. 2008, ASAP.
- Qiang Liu, Zhi-Min Cui, Zhuo Ma, Shao-Wei-Bian, Wei-Guo Song, Li-Jun Wan* “The morphology control of Fe2O3 nanocrystals and their application in catalysis”, Nanotechnology 2007, 18，385605
- Liang-Shu Zhong, Jin-Song Hu, Zhi-Min Cui, Li-Jun Wan, Wei-Guo Song “In-Situ Loading of Noble Metal Nanoparticles on Hydroxyl-Group-Rich Titania Precursor and Their Catalytic Applications ” Chemistry of Materials 2007, 19, 4557-4562.
- Liang-Shu Zhong, Jin-Song Hu, An-Min Cao, Qiang Liu, Wei-Guo Song, and Li-Jun Wan “3D Flowerlike Ceria Micro/Nanocomposite Structure and Its Application for Water Treatment and CO Removal” Chemistry of Materials 2007, 19, 1648-1655.
- Qiang Liu, Wei-Min Zhang, Zhi-Min Cui, Wei-Guo Song, Li-Jun Wan “Aqueous Route for Mesoporous Metal Oxides Using Inorganic Metal Source and Their Applications” Microporous and Mesoporous Materials 2007, 100, 233-240.
- An-Min Cao, Jin-Song Hu, Han-Pu Liang, Wei-Guo Song, Li-Jun Wan, Xiu-Li He, Xiao-Guang Gao, Shan-Hong Xia “Hierarchically structured cobalt oxide (Co3O4): The morphology control and its potential in sensors” J. Phys. Chem. B 2006, 110, (32), 15858-15863
- Liang-Shu Zhong, Jin-Song Hu, Han-Pu Liang, An-Min Cao, Wei-Guo Song, Li-Jun Wan “Self-assembled 3D flowerlike iron oxide nanostructures and their application in water treatment” Adv. Mater. 2006, 18, (18), 2426-2430
Nanotechnology for Suppressing Mercury Release from Fluorescent
Lamps
Love Sarin, Natalie Johnson, Indrek Kulaots, Brian
Lee, Steven Hamburg, Robert Hurt, Division of Engineering and Institute for
Molecular and Nanoscale Innovation, Brown University, USA
Fluorescent lighting technologies are undergoing rapid market growth as part of a resurgent societal interest in energy efficiency. Much of the current and projected growth is in the domestic use of compact fluorescent lamps (CFLs), which offer consumers approximately 75% reduction in energy usage and ten-fold increase in lifetime relative to incandescent bulbs. CFLs, however, contain 3-5 mg of mercury, which is a well-known human toxicant that is of special concern for neural development in the fetus and in young children. The OSHA occupational exposure limit is 100 µg/m3, while the Agency for Toxic Substances and Disease Registry recommends 0.2 µg/m3 level for continual habitation by children, a level that can easily be exceeded by a single CFL break. The present work is motivated by two specific issues in the management of Hg from CFLs: (i) direct exposure of consumers or workers to Hg vapor from fractured lamps, and (ii) release of Hg to the environment at end of lamp life.
This paper describes the development of a nanomaterial-based technology for suppressing the release of mercury from broken CFLs. Experiments were first conducted to characterize the dynamic release of mercury vapor as a function of bulb type, age, substrate (carpet and hard surface) and flow environment. A wide range of nanomaterials and reference materials were then evaluated for mercury vapor capture under conditions relevant to these release profiles (time, temperature, mercury vapor concentration, and gas environment). Several nanomaterials were found to offer higher capacity than conventional sorbents and one nanomaterial (a particular formulation of nano-selenium) was found to have a 50-fold higher activity than any sorbent commercially available today.
Finally, the most promising sorbent materials were used to fabricate prototypes of a CFL spill kit, a new retail packaging concept, and a new disposal concept that avoid the release of mercury vapor at various stages of the lamp lifecycle. The prototypes were tested for in situ capture under scenarios relevant to domestic breakage and disposal. The outlook for widespread implementation of this new nanotechnology will be discussed.
Nanotechnology-Based
Membrane Systems for Detoxification for Chlorinated Organics from Water
D.
Bhattacharyya, J. Xu, D. Meyer, Y. Tee, L.
Bachas, Department of Chemical and Materials Engineering, University of
Kentucky, USA
The development of nano-sized materials has brought important and promising techniques into the field of environmental remediation of chlorinated organics. Nanostructured metals have become an important class of materials in the field of catalysis, optical, electronic, magnetic and biological devices due to the unique physical and chemical properties. Extensive studies have been reported on the degradation of toxic chlorinated organics (such as, TCE, PCB) with nonimmobilized Fe0 based bulk/nano particles. Work involving reductive dechlorination involved the use of bimetallic (Fe/Ni, and Fe/Pd) nanoparticle systems, both membrane-supported and direct aqueous-phase synthesis. The nanosized metals precipitated from solutions are extremely reactive due to the high surface energy, and they usually form aggregates without the protection of their surface. Therefore, immobilization of metal nanoparticles in polymer membrane (such as, cellulose acetate, PVDF, polysulfone, chitosan, etc,) media is important from the point of view of reactivity, organic partitioning, preventing loss of nanoparticles, and reduction of surface passivation. Another major advantage of having a polymer domain is that nanoparticles (without causing agglomeration) can be directly synthesized in the matrix.
We report a novel in-situ synthesis method of bimetallic nanoparticles (< 40 nm) embedded in polyacrylic acid (PAA) functionalized microfiltration type membranes by chemical reduction of metal ions bound to the carboxylic acid groups. Polymer immobilization eliminates worker exposure issues relating to nanoparticles. We demonstrated complete (with product and intermediates analysis) dechlorination of trichloroethylene (TCE) and selected PCBs by nanosized metals. The 2nd dopant metal (such as, Ni, Pd) plays a very important role in terms of catalytic property (hydrodechlorination) and the significant minimization of intermediates formation. In addition to the rapid degradation (by Fe/Ni) of TCE (trichloroethylene) to ethane,
we were also able to achieve complete dechlorination of selected chloro-biphenyls (PCBs) using milligram quantities immobilized Fe/Pd nanoparticles in membrane domain. In order to predict detoxification reactions at different conditions, a two-dimensional steady state model was developed to correlate and simulate mass transfer and reaction in the membrane pores under convective flow mode. The 2-D equations were solved by COMSOL (Femlab). The influence of changing parameters such as, membrane pore size and Pd coating composition were evaluated by the model and compared well with the experimental data. The role of hydrogen generation by the
Fe corrosion reaction and the surface reactivity will also be discussed. This research has been supported by the NIEHS – SBRP program and by the U.S. EPA STAR Grant.
Nanotoxicology: Developing a Responsible Technology
Christie M. Sayes, Department of
Veterinary Physiology & Pharmacology, College of Veterinary Medicine, Texas A&M University, USA
Nanotechnology is not only an emerging field of study, it is now an industry. Because of this, we now see an abundance of nanomaterials in numerous consumer goods. Still further, well established industries, such as food packaging, forestry and paper, plastics and paints, and electronics are beginning to use nanotechnology’s scientific and engineering-based advances to better their products, profit, and marketability.
The research presented here describes basic concepts of nanotechnology and its potential health and safety risks, the current status of nanomaterial-containing consumer products in the marketplace, and nanomaterial synthesis and physico-chemical properties important to toxicological and ecotoxicological evaluations. This material aims to prepare chemists, toxicologists, risk assessors, and policy-makers to meet the rapidly growing need to understand and evaluate the risks that engineered nanomaterials may pose to human health and the environment.
A toxicological and risk assessment of nanomaterials requires an understanding of the unique differences between these “new” materials and their previously studied chemicals or larger-particle predecessors. For example, studies on the biocompatibility of various metal oxide nanoparticles (such as titanium dioxide, aluminum oxide, and iron oxide) in various crystalline forms exposed to whole animal and cultured cells are compared and contrasted to the more commonly used micro-sized particles. Results show that, depending on chemical composition, crystalline structure, and type (and degree of) surface modifaction, nano-scale metal oxide particles may induce elevated levels of alkaline or acid phosphatase and increase levels of lactate dehydrogenase (an indicator for “leaky” membranes). However, larger metal oxide particles remain relatively inert in cultured cells, the lungs of rats, and algae test systems.
Current methods for, and challenges to, toxicological and ecotoxicological testing of nanomaterials will be covered. Most importantly, this work identifies strategies in the material design process that minimize potential human health and safety risks when working with nano-scale materials.
Natural Organic Matter (NOM) -Mediated
Phase Transfer of Quantum Dots in the Aquatic Environment
Divina Angela Navarro, Sarbajit Banerjee, Diana Aga, Department of Chemistry, University at
Buffalo, USA
The increasing interest in quantum dots (QDs) raises a concern with regard to their environmental impact. With the eventual commercialization of these materials for applications such as in solar energy conversion and as fluorophores in biomedicine, the release of QDs in the environment is inevitable. One way by which the fate and transport of QDs will be influenced is through their interactions with Natural Organic Matter (NOM). This study examined the NOM-mediated phase transfer of TOPO-capped CdSe quantum dots in water. Results from our study indicates that humic and fulvic acids (HA and FA) could facilitate the solubilization of the organic QDs in water with kinetics that is measurable in less than 24 hours. Phase transfer of the QD to the aqueous phase was observed for CdSe particles of different sizes. Solution pH and Ca2+ ion concentration also influenced the rate of phase transfer, favoring lower pH and absence of Ca2+. HA and FA interacts with the surface capping groups of QDs instead of metal coordination, as revealed by dynamic light scattering, transmission electron microscopy and infrared spectroscopy studies. Whether HA or FA forms aggregates with random coil conformations or as micelles when they facilitate the transfer of QDs remains inconclusive and needs further investigation. The results observed with the Suwannee River HAs and FAs translated to the natural surface water samples collected from local creeks. This study presents the first evidence of stabilization of QDs in water by humic substances in real environmental samples, illustrating that NOM will have a significant role in the fate and transport of QDs in the aquatic systems.
Natural Organic Matter Enhanced C60 Fullerene Dispersion in the Aqueous Phase
Qilin Li 1, Bin Xie 1, Steven
Xu 2. (1) Department of Civil and Environmental
Engineering, Rice University, Houston TX, USA; (2) Department of Chemical and
Biomolecular Engineering, Rice University, Houston, TX, USA
Assessing exposure and risk of engineered nanomaterials requires accurate prediction of their concentrations and physicochemical properties in the natural environment. Although C60 fullerene is virtually insoluble in water, stable aqueous suspension of C60 nanoparticles (nC60) can form when C60 powder is mixed with water for an extended period of time. In this study, we investigate the effect of natural organic matter (NOM) on the dispersion of C60 in water as well as the properties of nC60 particles formed. Suwannee River humic acid (SRHA) and fulvic acid (SRFA) standards were used as model NOM compounds and a range of solution conditions (i.e., pH, total ionic strength and ionic composition) were tested to simulate realistic natural aqueous environment. The amount of C60 that can be dispersed in synthetic waters containing different concentrations of NOM was assessed, and the physicochemical properties of the nC60 nanoparticles were thoroughly characterized. Experiments were performed under dark, room light and sunlight conditions to investigate the potential photochemical transformation of C60.
In dark or fluorescent light conditions, NOM was found to only slightly increase dispersion of C60 in the aqueous phase. C60 concentration of the suspension after an extended period of mixing (29 days) was relatively low, < 5 mg/L. In contrast, the presence of NOM was found to significantly increase the kinetics of C60 dispersion under sunlight, and the dispersed C60 concentration in the suspension increased with increasing NOM concentration. Up to 20 mg/L of C60 was dispersed in the aqueous phase after 10 days of mixing under sunlight in waters containing 10 mg/L SRHA. Electrophoretic mobility analysis revealed that negative particle surface charges developed over time. In consistence with this observation, the size of the nC60 particles formed was found to decrease with increasing mixing time and increase with ionic strength and calcium concentration, suggesting that electrostatic interaction plays an important role. Accordingly, kinetics of C60 dispersion was also found to increase with decreasing ionic strength. Interestingly, the presence of calcium ions was found to accelerate C60 dispersion, possibly due to the increased adsorption of NOM on nC60 particle surface through intermolecular bridging by calcium ions. UV/Vis spectra of the nC60 suspensions formed in the presence of NOM under sunlight indicate photochemical transformation of C60, as evidenced by the loss of C60 signature absorbance peak at ~340 nm. Further investigation is necessary to reveal the reaction mechanisms and to identify the products.
Novel Zerovalent Iron/Silica Composites for Targeted Remediation of TCE Contaminated Water and Soil
Vijay John, Jingjing Zhan, Tonghua Zheng, Gerhard Piringer, Yunfeng Lu, Gary McPherson, Department of Chemical and Biomolecular Engineering, Tulane University, USA
Nanoscale zero-valent iron (ZVI) particles are a preferred option for the reductive dehalogenation of trichloroethylene (TCE). However, it is difficult to transport these particles to the source of contamination due to aggregation. This study describes a novel approach to the preparation of ZVI nanoparticles that are efficiently and effectively transported to contaminant sites. The technology developed involves the encapsulation of ZVI nanoparticles in porous sub-micron silica spheres which are easily functionalized with alkyl groups. These composite particles have the following characteristics (1) They are in the optimal size range for transport through sediments (2) dissolved TCE adsorbs to the organic groups thereby bringing tremendously increasing contaminant concentration near the ZVI sites (3) they are reactive as access to the ZVI particles is possible (4) when they reach bulk TCE sites, the alkly groups extend out to stabilize the particles in the TCE bulk phase or at the water-TCE interface (5) the materials are environmentally benign. We have extensively demonstrated these concepts through reactivity studies, and transport studies using column transport, capillary and microcapillary transport studies. These iron/silica aerosol particles with controlled surface properties also have the potential to be efficiently applied for in situ remediation and permeable reactive barriers construction.
In extensions of the work, we have shown that these particles function effectively as reactive adsorbents for TCE. Our work will describe the synthesis of such composite nanoscale materials through an aerosol-assisted method and through solution methods, to illustrate the versatility and ease of materials synthesis, scale up and application.
This research has been funded by the Environmental Protection Agency through Grant EPA – GR832374.
One Step Flame Synthesis of TiO2/CeO2 Nanocomposite with Controlled Properties for VOC Photo Oxidation
V. Tiwari1, V. Sethi1, P. Biswas2. (1) Centre for Environmental Science and Engineering, Indian Institute of Technology Bombay, Mumbai, India; (2) Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, USA
Cerium oxide is being used in several industrial catalytic processes, as a key component in the formulation of catalysts for the control of some emissions from mobile sources (Boaro et al., 2003; Kasper and Fornasiero, 2003) and also in fuel cells (Park et al., 2000). Under alternating lean and rich fuel conditions, ceria stores and releases oxygen thereby enabling the oxidation of CO and volatile organics, and the reduction of NOx (Kasper and Fornasiero, 2003; Bunleusin et al., 1997). Mixed oxide catalyst has been found to be helpful in overcoming the poor thermal stability of CeO2 by substitution of another metal or metal oxide into the ceria lattice (Reddy et al., 2003). TiO2 is well known for its photocatalytic activity because of its special properties, such as high dielectric constant, excellent optical transmittance, high refractive index, high chemical stability and suitable band gap.
There are several studies on the wet chemical synthesis of CeO2-TiO2 nanocomposite reported in the literature. Rynkowski et al. (2000) studied the redox properties of CeO2–TiO2 composites. Nakagawa et al. (2007) synthesized cubic-shaped CeO2 nanoparticles with a length of 2.7–3.8 nm and also showed that catalyst activity enhances when the sample is calcinated at higher temperature. Periyat et al. (2007) synthesized CeO2 doped TiO2 powder via sol-gel route to enhance the high temperature stability of the anatase phase TiO2. Compared to conventional wet chemical method flame synthesis offers good control on catalyst properties, less post-processing steps (viz., filtration, drying or calcination) and produces less waste material. In the present study TiO2 / CeO2 mixed oxide was synthesized using a flame reactor with controlled Ti/Ce ratio and quenching system (Jiang et al., 2007). Surface area can be controlled by quenching the flame at various heights. Ti/Ce ratio is controlled by varying the ratio of precursor feed rates (TTIP: Cerium Nitrate).
In the present work, pristine TiO2, pristine CeO2 and TiO2/CeO2 nanocomposite (10 and 15% Ce:Ti ratio) were synthesized successfully in one step using a flame aerosol reactor. Experimental conditions and catalyst characterization results are summarized in Table 1. Precursors namely TTIP and Cerium Acetate, were fed in the flame as a vapour and cerium acetate aerosol respectively. Pristine TiO2 was synthesized at two different methane flow rate to see the effect of fuel to oxygen ratio on the TiO2 crystal phase. Catalyst morphology was analyzed using TEM. Geometric mean diameter of pristine TiO2 and pristine CeO2 was in range of 45~60 nm. XRD patterns of the synthesized powders are shown in Figure 1. UV-vis spectra indicates that absorption of light in UV range on the CeO2 / TiO2 nanocomposite was more when compared with that for the pristine TiO2.
Further work includes synthesis of catalyst with different size and surface by quenching the flame at different heights. Catalyst activity are to be tested using a photocatalytic reactor for the gas phase photo-oxidation of a volatile organic compound (VOC). The influence of Ti:Ce ratio, temperature and surface area on the catalytic activity will be studied.
Acknowledgement
Financial support from Department of Science and Technology
(DST), India for the study is gratefully acknowledged.
References
Boaro, M.,Vicario, M., Leitenburg, C., Dolcetti, G., and Trovarelli, A., (2003), Catalysis Today, 77, 407–417
Bunluesin, T., Gottea, R. J, and Grahamb, G.W., (1997), Applied Catalysis B: Environmental, 14, 105-l 15
Jiang, J., Chen, D.R., Biswas, P, (2007), Nanotechnology, 18, 285-303
Kaspar, J., and Fornasiero, P., (2003), Journal of Solid State Chemistry, 171, 19–29
Nakagawa, K., Murata, Y., Kishida, M., Adachi, M., Hiro, M. and Susa, K., (2007), Materials Chemistry and Physics, 104, 30-39.
Park, S., Gorte, R. J. and Vohs, J. M., (2000), Applied Catalysis a-General, 200, 55-61.
Periyat, P., Baiju, K. V., Mukundan, P., Pillai, P. K. and Warrier, K. G. K., (2007), Journal of Sol-Gel Science and Technology, 43, 299-304.
Reddy, B. M., Khan, A., Yamada, Y., Kobayashi, T., Loridant, S. and Volta, J. C., (2003), Journal of Physical Chemistry B, 107, 5162-5167.
Rynkowski J., Farbotko J., Touroude, R., and Hilaire, L., (2000), Applied Catalysis A: General , 203, 335–348
Table 1: Experimental conditions for synthesis of TiO2/CeO2 nanocomposite using Flame Aerosol Reactor (FLAR)
| Sample No. | Powder | CH4 (lpm) | O2 (lpm) | CeO2 content | SMPS Diameter (nm) | Crystallinity |
|---|---|---|---|---|---|---|
1 |
TiO2 |
1.5 |
5 |
0 |
52.6 |
Anatase |
2 |
TiO2 |
1.0 |
5 |
0 |
61.5 |
Anatase+Rutile |
3 |
TiO2/CeO2 |
1.0 |
5 |
10% |
- |
Anatase+Rutile |
4 |
TiO2/CeO2 |
1.0 |
5 |
15% |
- |
Anatase+Rutile |
5 |
CeO2 |
1.0 |
5 |
100% |
46.5 |
Cubic fluorite |
Figure 1: XRD patterns of pristine TiO2, pristine CeO2 and TiO2/CeO2 powder.
A = Anatase, R = Rutile, C = Ceria (Cubic)
Oxidative Transformations Mediated by Nanoparticulate Zero Valent Iron
T. David Waite1,Quan Sun1,
Steven E. Mylon2; (1) School of Civil and Environmental Engineering, The University of New South Wales, Sydney, Australia; (2), Lafayette College, PA, USA
While there has been extensive investigation of the ability of zero valent iron (ZVI) to induce reductive transformations of contaminants, there has been much less study of oxidative transformations induced by nanosized ZVI (nZVI). In this presentation, current understanding of the mechanism by which nZVI-mediated oxidative transformations occur will be presented as will information on the chemical and biological impacts of these oxidative processes. Current state of knowledge concerning the factors controlling the rate and extent of nZVI-mediated oxidation will be described and recent studies of approaches to enhancing the oxidative ability of nZVI will be reviewed.
Ozone Sensors for Real-time Passive Wireless Application
Ryan S. Westafer, Michael Bergin, Dennis Hess, William D. Hunt, Desmond D. Stubbs [affiliation?]
There is an existing need to develop compact, robust, low-powered real-time sensors for air pollutants, such as ozone and particulate matter (PM), for both personal exposure assessment and remote monitoring [1]. For this reason we have developed surface acoustic wave (SAW) sensors that are radio frequency identification (RFID) adaptable. It has been shown that resonant acoustic mass sensors, such as the quartz crystal microbalance (QCM), can perform near real-time ozone detection [2]. Our approach [3] employs surface acoustic waves (SAWs) which offer several immediate advantages over QCMs: higher frequency and thus mass sensitivity, signal encoding capability, and passive (no battery) operation; see US Patent 7005964. In this paper, we give our first results for detection of both aerosols and ozone at ambient level concentrations.
Through mass adhesion and/or modification of surface physical and chemical properties, SAW and QCM sensors are suitable for detection of submicron aerosols. Our first experiments targeted aerosol detection. This helped establish dose/response curves for mass adsorption. For ozone detection we coated SAW surfaces with a polybutadiene film and collected data at environmentally relevant concentration and flow rate. Through a finite element model, we have demonstrated a corresponding SAW frequency shift of 20 Hz pg-1. Previous quartz crystal microbalance (QCM) work demonstrates ozone detection in both laboratory and ambient conditions [2]. However, those relatively fragile thin-plate quartz sensors are less sensitive than high frequency surface acoustic wave (SAW) devices.
Our results also demonstrated the utility of these devices as temperature sensors, giving approximately 20 kilohertz/°C sensor response for waves on Y-cut Z-propagating lithium niobate. All devices exhibited this response. With just two acoustic paths we can differentially detect ozone and also determine the temperature to fractions of a degree.
While the devices themselves are mechanically robust and approximately 500 microns thick (compare to ~100 microns for QCMs), several nanoscale attributes are evident. For proper device operation, the sensing film must be much thinner than the acoustic wavelength. To this end, we developed a polybutadiene coating process which yields 200 nanometer films over the active device area. Another miniature aspect of these devices is set by frequency requirements. Electron beam lithography has allowed us to fabricate test devices with standing acoustic potentials separated by as few as 648 nanometers. This enables operation in the GHz frequency range, further increasing sensitivity and affording operation in the industrial, scientific, and machinery (ISM) band as high as 2.4 GHz.
References
[1] RFA-ES-06-011
[2] Black, Harley, Hering, and Stolzenburg, “A New, Portable, Real-Time Ozone Monitor,” Environmental Science & Technology, vol. 34, no. 14, 2000.
[3] D. D. Stubbs, S. H. Lee, and W. D. Hunt, "Investigation of cocaine plumes using surface acoustic wave immunoassay sensors," Anal Chem, vol. 75, pp. 6231-5, 2003.
Partial Oxidation (aging) and Surface Modification Decrease the Toxicity of Nano-sized ZeroValent Iron
Gregory Lowry1, Tanapon Phenrat1, Thomas Long2, Bellina Veronesi3. (1) Carnegie Mellon University, USA; (2) U.S. EPA National Center for Environmental Assessment, USA; (3) U.S. EPA National Health and Environmental Effects Research Laboratory, USA
Nanosize zero-valent iron (nZVI) is used as a redox-active catalyst for in situ remediation of contaminated ground waters. In aqueous environments, nZVI oxidizes over time (i.e., “ages”) to magnetite and other oxides. For remediation, high concentration slurries are injected directly into the ground near the source of contamination. However, nZVI particles do not readily disperse in aqueous or organic environments, rather they form large aggregates with limited mobility. To remedy this, “second generation” nZVI materials have been developed that are surface-modified (SM) with polymers or surfactants that facilitate their migration and proximity to the pollutant materials. This added mobility and nZVI’s direct application to ground waters increase the likelihood that nZVI materials will distribute through the environment and raises the possibility that at low concentrations, nZVI could enter the ecosystem and food chain and impact biological systems. Since nZVI can generate reactive oxygen species (though Fenton chemistry, toxicity experiments were conducted on nerve cells which are especially sensitive to oxidative stress. Immortalized rodent microglia (BV2) and dopaminergic neurons (N27) were exposed (1, 2, 5,10, 20 ppm) to fresh nZVI, “aged” (>11 mo) nZVI, magnetite, and two polymer surface-modified (SM) products (i.e., poly AA-nZVI, MRNIP). Increases in the oxidative burst, caspase 3/7 activity and inflammatory cytokine release and reductions in the mitochondrial membrane potential and intracellular ATP levels occurred in the BV2 microglia in following rank order: nZVI > “aged” nZVI > magnetite = SM nZVI = MRNIP. In addition, BV2 microglia showed morphological evidence of mitochondrial swelling and apoptosis after 3 h and 18 h exposure to fresh nZVI (5 ppm). Significant reductions of intracellular ATP levels occurred in N27 neurons in the following rank order: nZVI>“aged” nZVI>magnetite> SM nZVI=MRNIP. Ultrastructurally, nZVI exposure (1 ppm) produced a perinuclear flocular material and cytoplasmic granularity in N27 neurons. In contrast, the cytoplasm of SM-nZVI treated neurons appeared normal although ultrastructural evidence of intranuclear SM-ZVI particles was noted. The physicochemical properties (i.e., aggregation, size, zeta potential) of each material were measured under exposure conditions (time, exposure media). All materials showed an electronegative zeta potentials in the different exposure media. Sedimentation and aggregation occurred in the following rank order: nZVI>”aged” nZVI>magnetite>>SM-nZVI=MRNIP in each of the vehicles. Together, these data indicate that fresh, “aged”, oxidized and surface modified nZVI are differentially neurotoxic in culture. Such differences may relate not only to their redox chemistry but also to their sedimentation rates.
Pentachlorophenol Reduction in Soils by Reactive Nanoscale Iron Particles
Amid P. Khodadoust1, Krishna R. Reddy2, Kenneth Darko-Kagya3.(1)Associate Professor; (2) Professor; (3) Graduate Research Assistant, University of Illinois at Chicago, Department of Civil and Materials Engineering, Chicago, IL, USA
Pentachlorophenol (PCP) has been used extensively as a general biocide for a variety of purposes such as agriculture and timber preservation. Worldwide use of PCP has led to severe contamination problems particularly around former timber treatment plant sites. Various methods employed to remediate PCP from contaminated soils include soil washing, chemical oxidation, and bioremediation; however, these methods are either ineffective or expensive in subsurface soils. Reactive nanoscale iron particles (RNIP) have been recently investigated for the effective treatment of various aquifer systems. The objective of this study was to investigate the efficiency of RNIP to promote the reductive degradation of PCP in subsurface soils with low permeability and high permeability using clayey and sandy soils, respectively. Typically, RNIP cannot be applied in the subsurface effectively without surface modification. The effect of surface modification of RNIP on degradation of PCP in soils was evaluated using RNIP slurries with and without aluminum lactate. A series of batch experiments were conducted using kaolin and natural sandy soils spiked with PCP at 100 mg/kg and RNIP at two concentrations of 1 and 4 g/L. RNIP was modified with 10% aluminum lactate (w/w). To determine the reactivity of RNIP with PCP in soil, the spiked soils were mixed with a simulated groundwater solution containing bare RNIP or modified RNIP using a soil:solution mixing ratio of 1:5 (g:mL) on a rotating shaker for 2, 4 and 7 days. After separation of soil and solution using centrifugation, the residual soil and solution were analyzed for unreacted PCP. For both soils, the degradation (reduction) of PCP in soil increased with reaction time for all systems, while degradation of PCP in soil was greater for systems without lactate and for systems with the higher concentration of RNIP (4 g/L). Higher RNIP concentrations would likely result in greater degradation of PCP in soil based on the observed trends for degradation of PCP, while longer reaction periods would lead to greater degradation of PCP in soil (1 and 4 g/L RNIP, with or without lactate). The results show that the greatest degradation after 7 days occurred for the systems with 4 g/L of bare RNIP in both soils. PCP degradation of 35 and 41 percent in natural sand was obtained for RNIP with and without lactate, respectively. PCP degradation of 34 and 63 percent in kaolin was obtained for RNIP with and without lactate, respectively. PCP degradation was greater for kaolin than for natural sand using 4 g/L bare RNIP, while PCP degradation in both soils was comparable using 4 g/L modified RNIP.
Pilot Field Test of the Treatment of Source Zone Chlorinated Solvents Using Emulsified Zero-Valent Iron
Chunming Su1, Robert Puls1, Susan O’Hara2, Thomas Krug2, Mark Watling2, Jacqueline Quinn3, Nancy Ruiz4. (1) U.S. EPA National Risk Management Research Laboratory, Ada, Oklahoma, USA; (2) Geosyntec Consultants, Guelph, Ontario, Canada; (3) NASA, Kennedy Space Center, Florida, USA; (4) Naval Facilities Engineering Service Center, Port Hueneme, California, USA
A previous field test shows that the emulsified zero-valent iron (EZVI) technology, developed at the University of Central Florida and the National Aeronautics and Space Administration (NASA), was successfully used to treat dense non-aqueous phase liquids (DNAPL) at a Florida field site. The technology is being further tested at a pilot scale at Parris Island Marine Corps Recruit Depot (MCRD), Parris Island, SC. The essence of the technology is creation of surfactant-stabilized, biodegradable emulsion droplets composed of oil-liquid membrane surrounding nanoscale zero-valent iron (nZVI) particles in water. The corn oil in the membrane combines with the DNAPL so as to enhance contact between the ZVI and the DNAPL. The ZVI provides rapid abiotic degradation of the DNAPL and the corn oil also serves as a long-term electron donor source to enhance microbial degradation.
The DNAPL source area at a former dry cleaning facility is the site of the field demonstration at Parris Island MCRD. The objectives of the field test are to (1) examine two injection technologies for EZVI delivery, pneumatic injection and direct injection using a direct push rig in two side-by-side treatment areas; (2) evaluate the performance of nanoscale EZVI to remediate a shallow (<20 ft) tetrachloroethene (PCE) DNAPL source area; and (3) investigate the fate and transport of nanoscale EZVI. Soil and groundwater samples were collected from the site in June 2005 to assess contaminant distribution within the treatment areas, and a network of performance monitoring wells was installed at the site in June 2006. Groundwater samples were collected prior to EZVI injection to establish baseline conditions for the demonstration. EZVI was injected into the treatment areas in October 2006 and performance monitoring is ongoing and expected to be completed by October 2008. Preliminary results show a decrease in PCE and trichloroethene (TCE) downgradient of the treatment areas following EZVI injection, with an increase in degradation products including significant increases in ethene. Compound-specific carbon-13 isotope results suggest that degradation of PCE and its daughter products are occurring. X-ray diffraction results of suspended solids from monitoring wells show rapid transformation of element iron to magnetite (Fe3O4) and lepidocrocite (γ-FeOOH).
The demonstration work is collaboration among the United States Environmental Protection Agency (USEPA), Geosyntec, NASA, and the Naval Facilities Engineering Service Center. Funding was provided by the Department of Defense’s Environmental Securities Technology Certification Program and the USEPA.
This is an abstract for presentation and it does not reflect EPA’s policy.
Predictive Numerical Model of Post-Injection Distribution of Nano-Size ZVI in the Ringold Aquifer for Mending an Existing Permeable Reactive Barrier in the 100-D Area at the Hanford Site
Marek H. Zaluski1, Gilbert M. Zemansky1, Adam Logar1, Kenneth R. Manchester1, David Reichhardt2, Scott Petersen3. (1) MSE Technology Applications, Butte, Montana, USA; (2) Montana Tech, Butte, Montana, USA; (3) Fluor Hanford, Washington, USA
MSE Technology Applications, Inc. has conducted investigations associated with the injection of nano-size zero-valent iron (nZVI) into the subsurface at the 100-D Area at the U.S. Department of Energy (DOE) Hanford Site in Washington State. The purpose of this work was to demonstrate the feasibility of using nZVI to repair portions of the In Situ Redox Manipulation (ISRM) barrier located in the 100-D Area of the Hanford Site that was installed to intercept a hexavalent chromium plume moving towards the Columbia River. The investigation included predictive computer modeling of post-injection distribution of nZVI material in the Ringold aquifer.
The modeling effort used PORFLOW™ and focused on simulation of the groundwater flow field and emplacement of nZVI into the aquifer by injection of nZVI fluid through an injection well. Therefore, the model domain encompassed a cylindrical “block” of the unconfined aquifer around the injection well discretized in the manner that reflects geological and hydrogeologic stratification.
Presence and gradual separation (deposition) of nZVI particles that are originally suspended in the fluid were addressed using a pseudo-solute-transport approach. This approach was used because nZVI particles behave in the fluid more like solids than dissolved constituents. Consequently, a pseudo-isotherm was used to quantify the rate that iron particles fall out of the fluid. The pseudo-isotherm equation was developed through laboratory experiments that involved a number of 3-meter-long flow cells injected with nZVI fluid at different flow rates. The result of the experiment was a multivariable regression that describes nZVI deposition as a function of distance, time of injection, and nZVI-fluid velocity. The latter being especially important considering the radial flow pattern around the injection well and the decreasing flow velocity with increased distance. This functional relationship was incorporated in the PORFLOW™ simulation algorithm utilizing its unique ability to accommodate user-defined functions.
This work was conducted through the support of Fluor Hanford under Contract Number 30994.
Rapid Assessment of Engineered Nanomaterial Toxicity using a Suspended Lipid Bilayer Assay
Steven A. Klein1, Trevor J. Thornton2, Jonathan D. Posner1. (1) Mechanical Engineering, Arizona State University, Tempe, AZ, USA; (2) Electrical Engineering, Arizona State University, Tempe, AZ, USA
Over the past five years there has been a growing interest in the toxicity of engineered nanomaterials. Quantitative measures of nanomaterial bioavailability and toxicity must be made so that the impact of nanotechnology on human health and the environment can be addressed. Recent research focuses on either collection of empirical epidemiological data (e.g. uptake of nanoparticles (NP) by cells, toxicity to organisms such as rats or fish, mutation of SNP) or precise NP characterization (e.g. size, shape, degree of aggregation, charge, and surface chemistry). However, it is difficult to transition from these measurements to a rapid assessment of emerging nanomaterials toxicity or to understand the fundamental interactions of NM with biomolecules or biological interfaces (e.g. cellular uptake, infusion in tissue, etc.) In this talk, a novel nanoparticle toxicity assay is presented which can rapidly provide information about the interaction of nanomaterials at the lipid bilayer-fluid interface. Lipid bilayers are arguably the most important interface between life and its environment. The platform uses lipid bilayers suspended over apertures, low-noise electronic measurement tools and high speed, spinning disk epi-fluorescence microscopy for real-time measurements of NP-bilayer interactions. The system is used to quantify the unmediated transport of NP through lipid membranes, aggregation of NP in solution and on the lipid bilayer, as well as monitor degradation of the membrane due to NP influence. This system operates over a wide range of conditions (NP composition, charge, shape and size) and physicochemical conditions (e.g. EDL thickness, aggregation, etc.). Here, results of quantum dot, polystyrene, and carbon nanotube NP interactions DOPC suspended membranes will be presented. Optical images and low noise current signatures are correlated to provide insight into the physical mechanisms of lipid bilayer-NP interactions.
Reactive Oxygen Species Related Microbial Growth Inhibition By Silver Nanoparticles
Okkyoung Choi1, Rao Y. Surampalli2, Zhiqiang Hu1. (1) Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO, USA; (2) U.S. EPA, Region 7 Office, Kansas City, Kansas, USA
Silver nanoparticles are used in many consumer products because of their strong antimicrobial activity. Although the mode of antimicrobial activity is still not clear, it is believed that silver species could induce to generate intracellular reactive oxygen species (ROS) that can damage protein, DNA and membrane. We recently showed that at 1mg/L Ag, silver nanoparticles (average size, 14 ± 6 nm) significantly inhibited nitrifying bacterial growth without compromise of cell membrane integrity. To help elucidate the inhibition mechanism, we measured the degrees of nitrification inhibition by various forms of silver including silver nanoparticles, silver ions, and silver chloride colloids to evaluate the relationship between silver concentrations and intracellular ROS concentrations.
Autotrophic nitrifying bacteria were cultivated in a continuously stirred tank reactor (14L) operated at solids retention time (SRT) of 20d and hydraulic retention time (HRT) of 1d. Aliquots of biomass were collected from the bioreactor for maximum specific oxygen uptake rate and ROS measurements, respectively. The resulting ROS generation was quantified in the presence and absence of the bacteria while the degree of inhibition was inferred from specific oxygen uptake rate measurements, determined by extant respirometry. To determine intracellular ROS concentrations, aliquots of nitrifying biomass suspensions were removed from the bioreactor, centrifuged and resuspended in a loading buffer solution containing 10 μM H2DCFDA (Eugene, OR, USA) and plated into 96-well plates. The fluorescence of the cells from each well was measured with 485 nm excitation and 535 nm emission filter using a microreader (VICTOR3, PerkinElmer, Shelton, USA).
Of all the forms of silver tested, silver nanoparticles presented the highest degree of inhibition. The inhibition appeared to follow a saturation curve with R2 range from 0.91 to 0.97. The concentration of silver nanoparticle, silver chloride, silver ion causing 50% inhibition was 0.14 mg/L, 0.25 mg/L, and 0.27 mg/L. The concentrations of intracellular reactive oxygen species increased when the biomass suspensions were exposed to silver nanoparticles. Inhibition by Ag nanoparticles as well as other forms of silver (AgCl colloid and Ag+ ion) correlated well with the intracellular ROS concentrations, but not with the photocatalytic ROS fractions. Although there was correlation between nitrification inhibition and intracellular ROS concentrations, the ROS correlations were different for the different forms of silver, indicating that factors other than ROS are also important in determining nanosilver toxicity.
Removal and Degradation of Subsurface Pollutants by Nanoscale Bimetallic Pd/Fe Slurry under an Electric Field
Gordon C. C. Yang. Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan
In this work a novel, hybrid technology combining the injection of nanoscale bimetallic Pd/Fe slurry (hereinafter referred to as the “Slurry”) and electrokinetic remediation process was used to mimic the removal and degradation of trichloroethylene (TCE) and nitrate in the subsurface. Laboratory-prepared palladized nanoiron was characterized to be in the range 50-80 nm with a specific surface area of 101 m2/g. The nanoscale Pd/Fe bimetal was further stabilized using 1 vol% polyacrylic acid to form the Slurry so that it can be easily stored and pumped. To evaluate the treatment efficiency of combined technologies of the injection of the Slurry and electrokinetic remediation process in treating subsurface pollutants, a bench-scale electrokinetic system consisting of the anode compartment, horizontal soil compartment, and cathode compartment was employed. To mimic the horizontal flow of groundwater, both electrode compartments were filled with a simulated groundwater and the horizontal soil compartment was packed with loamy sand soil polluted by a selected target contaminant (e.g., TCE or nitrate). In this work the initial TCE concentration in test soil specimen ranged from 160 to 181 mg/kg, while nitrate concentration was 7316 mg/kg. At the beginning of each remediation test, a desired dose of the Slurry was injected to selected position(s) at electrode compartment(s) and/or soil compartment to determine the best spot for Slurry injection. Upon the application of an external electric field, various electrokinetic phenomena would occur and play significant roles in such a simulated in situ remediation system. Test conditions used were: (1) electric potential gradient: 1 V/cm; (2) daily addition of 20 mL of the Slurry (2.5 g/L and 4.0 g/L for the cases of TCE and nitrate, respectively) to the electrode reservoir(s); and (3) reaction time: 6 days. The addition of the Slurry to the anode reservoir yielded the lowest residual TCE concentration in soil, namely about 92.5% removal of TCE from soil. The residual TCE concentration in the cathode reservoir was about 8 mg/L. Although the addition of the Slurry to the cathode reservoir could completely degrade TCE therein, its residual TCE in soil was up to 29.0%. In the case of nitrate contamination, an efficiency of over 99% removal and degradation for the entire system was achieved by injecting the Slurry into the anode reservoir. The cathode reservoir, however, was found to be the worst injection position. Chemical reduction of nitrate would occur mostly in the anode reservoir where nanoscale Pd/Fe bimetal existed.