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Poster Session Abstracts (A-M)
Acute and Chronic Toxicity of TiO2 to Freshwater Aquatic
Organisms
Scott Hall1, Tina Bradley1,
Joshua Moore2, Tunishia Kuykindall1, Lauren Minella1. (1) ENVIRON International Corporation, Nashville, Tennessee, USA; (2) Tennessee State University, USA
Four species of freshwater aquatic organisms representing three trophic levels (primary producer, invertebrate, and fish) were exposed to titanium dioxide (TiO2) with a nominal particle size of 10 nm. Powder X-ray diffraction and Scherrer’s analysis were successfully used to confirm particle sizes in aqueous media used in toxicity testing. Conventional metals analysis was shown to be inadequate to quantify aqueous Ti concentrations when Ti was present in nano forms. Acute toxicity testing indicated that invertebrates (Ceriodaphnia and Daphnia magna) were more sensitive to TiO2 than fish. Invertebrate LC50 values were in the range of 10 to 100 mg/L as compared to fish LC50 values of greater than 1,000 mg/L. Chronic toxicity values indicated the same trend of higher invertebrate sensitivity, with respective invertebrate and fish IC25 values of approximately 20 and 400 mg/L. Initial testing with the green algae Raphidocelis subcapitata (formerly Selenastrum capricornutum) indicated that this organism may be quite sensitive to TiO2, with a preliminary IC25 value of 0.99 mg/L. This paper overviews these data with respect to other data and species sensitivity trends reported in the literature on the aquatic toxicity of nanoparticles. Additionally, various aspects of experimentation with TiO2 such as solution preparation, obtaining adequate dose/response relationships, etc. in aqueous media are discussed.
Aging of Iron Nanoparticles in Water: Effects on
Structure and Reactivity
Paul G. Tratnyek1, Vaishnavi
Sarathy1, James T. Nurmi1, Donald R. Baer2, James E. Amonette2,
Chanlan Chun3, R. Lee Penn3, Eric J. Reardon4.
(1) Division of Environmental and Biomolecular Systems, Oregon Health and
Science University, USA; (2) Environmental Molecular Sciences Laboratory,
Pacific Northwest National Laboratory, USA; (3) Department
of Chemistry, University of Minnesota; USA (4) Department of Geology,
University of Waterloo, Canada
Aging (or longevity) and transport in aqueous media remain the most important and potentially limiting factors in the use of nano-Fe0 to reduce contaminants in groundwater remediation. We have investigated the short- and long-term aging of FeH2 (Toda RNIP-10DS, a nano-sized iron produced by reduction of iron oxides in a H2 atmosphere to produce a zero-valent iron core and a magnetite shell) in water and the resulting effects on the chemistry of the oxide-shell and reactivity of the particles with water (i.e., hydrogen production) and carbon tetrachloride (CT).
For short- and long-term aging effects, we used preparations of FeH2 that had not been exposed to water (FeH2(D)), and one that had been in slurry for approximately a year (FeH2(W)). We studied the aging of these materials in terms of: (i) the structure of the iron particles characterized using spectroscopy and microscopy (XPS, XRD and TEM); (ii) the Fe0-content and rate of H2 production by reaction of Fe0 with H2O, (iii) the kinetics and pathway of reaction with CT; and (iv) changes in corrosion potential of the iron-oxide particles using electrochemical experiments.
While the Fe0-content gave a monotonic decay, as has been reported previously by others, most of the other properties show more complex behavior with a period between 0 and a few days exposure to water where the FeH2(D) becomes more reactive followed by a gradual decline in reactivity of the next few hundred days. This can be seen in the kinetics of CT reduction, yield of chloroform from CT, open circuit potential, and hydrogen evolution rate. Taken together, they suggest depassivation of the oxide film on FeH2(D) soon after immersion, followed by reformation of a passivating oxide shell (but never complete passivation until the Fe0 is entirely depleted, which was not achieved for the times periods of our study ). The behavior of FeH2(W) is consistent with extrapolations from the aged FeH2(D) data.
These observations have implications for laboratory- and field-scale applications of nano-Fe0. In particular, they suggest that the results from typical laboratory batch experiments may be more applicable to field-scale applications for source zone treatment, because both involve relatively brief periods of reaction. While FeH2 aged over longer time periods becomes much less reactive, it has the advantage of acquiring properties that are relatively stable over weeks or even months.
Bromate Reduction using Nanoscale Zero-Valent Iron:
Synthesis, Characterization, and Size Effect
Qiliang Wang, Jungwoo Kim, Heechul Choi. Department
of Environmental Science and Engineering, Gwangju Institute of Science and
Technology, Gwangju, Korea
Nanoscale Zerovalent Iron (NZVI) with different Brunauer-Emmett-Teller (BET) specific surface areas was controllably synthesized using a liquid phase reduction method for use as a solid reductant to reduce bromate, a newly emerging carcinogenic contaminant in drinking water systems. To this end, TEM, XRD, and a BET surface area and porosity analyzer were used to characterize particle size, surface morphology, surface area and corrosion layers formed onto NZVI before and after reduction of bromate. Subsequent TEM images showed that all synthesized particles had a core-shell structure and the particle sizes ranged from several nanometers to 100 nm. Capsule structures of NZVI, in which tens of particles with diameters of 2–3 nm were packed into an iron oxide layer, were synthesized using 100% ethanol as a solvent for iron salt. In addition, TEM images and XRD spectra revealed that: all synthesized NZVI particles had amorphous structures, NZVI gradually converted to Fe2O3, and Fe3O4 corrosion products mixed with iron hydroxides after a 20 min bromate reduction. The BET surface area analyzer revealed that the specific surface areas of synthesized NZVI were increased to 47.49 ± 0.24 m2/g and 67.51 ± 0.35 m2/g by using 70% and 90% ethanol aqueous solutions, respectively. When compared to bromate reduction by micro-sized ZVI using a pseudo-first-order kinetic model, it could be clearly observed that NZVI enhanced the reduction efficiency following a modified second-order kinetic model, with observed surface area normalized rate constants (KSA) of 3.93×10-5 to 3.48×10-3 l•min-1•m-2. Batch experiments were then performed to determine the feasibility of NZVI as a reductant for bromate treatment in drinking water systems in terms of initial bromate concentration, NZVI size effect, temperature, pH, and DO value. Compared to the bromate reduction by pristine NZVI, it was found that the reactivity of Fe0 toward bromate was reduced in the presence of humic acid. Moreover, the effects of sonication pretreatment showed that the bromate reduction efficiency was enhanced by increasing the real reactive surface area. Our results suggest that NZVI is a suitable candidate for drinking water treatment due to its high reactivity.
Co3O4 Nanoparticle Solubility in High-Purity Water
Lihong Su,Northwestern Polytechnical University, China
As more and more nanoparticles synthesized and applied in industry and daily life, their safety has started to become an environmental concern. In this paper, the solubility of Co3O4 particles with different morphology and sizes was investigated. We discovered that the solubility of Co3O4 nanoparticles is much lower than that of its micrometer counter-partners. A mechanism was proposed to interpret the inconsistence of this finding with the traditional soluble dynamic equilibrium theory.
Colloidal Stability of Copolymer Coated Iron
Nanoparticles: Combinatorial Synthesis and High-throughput Analysis
Harjyoti Kalita, Bret Chisholm, Achintya N. Bezbaruah.
North Dakota State University, Fargo, ND, USA
The effectiveness of zero-valent iron (ZVI) for contaminant remediation increases to a great extent with the increase in reactive surface of the particle and that is why zero-valent iron nanoparticle (nZVI) is becoming more relevant. However, nZVI is relatively unstable due to its high reactivity and less hydrolytic stability. Lack of stability of nZVI is a major concern among remediation practitioners and needs to be addressed to make the particle more effective in remediation. Several research groups are working on increasing the colloidal stability of nZVI using various surfactants and polymers as surface coatings. To achieve the high colloidal stability the authors have used copolymers having a hydrophobic backbone and hydrophilic side chain. Combinatorial synthesis and high-throughput analytical methods are used. Combinatorial chemistry involves the rapid synthesis and evaluation of large numbers of compounds in parallel using robotics, rapid analytical instrumentation, and data management software. A relatively large number of copolymers have been synthesized and analyzed. These copolymers are chemically distinct but have similar composition. The copolymers are used to coat nZVI and colloidal stability of the coated nanoparticles is determined. The batches of coated nZVI with the best colloidal stability are further characterized conducting treatability batch studies for specific contaminants of environmental concern.
Dechlorination of Polychlorinated Biphenyls by Pd/Mg
Bimetallic Corrosion Nano-Cells
Shirish Agarwal1, Souhail R. Al-Abed2,
Dionysios D. Dionysiou1. (1) Department of Civil and Environmental
Engineering, University of Cincinnati, Cincinnati, OH, USA; (2) U.S. Environmental Protection Agency, National
Risk Management Research Laboratory, Cincinnati, OH, USA
Polychlorinated biphenyls (PCBs), manufactured until mid-1970’s for use as electrical insulators, were banned in 1979 due to their toxicity and persistence in the environment. They are recalcitrant environmental pollutants, found in numerous rivers, coastal waters and nation’s Superfund waste sites. They bioaccumulate in the ecosystem, move up the food chain and reach humans posing a possible carcinogenic hazard. We have developed an effective system for their dechlorination with magnesium (Mg) particles modified by small amounts of nano-scaled palladium (Pd) doped on its surface. Such catalytic dechlorination using bimetallic particles is a promising remediation technology for PCBs where corrosion of Mg is combined with catalytic hydrogenation properties of Pd to reduce the PCBs at the bimetallic interface. A wet-chemistry procedure involving intimate mixing of a palladium salt precursor with Mg in ethanol was used to synthesize the Pd/Mg particles. This procedure produced Mg particles with 0.11% to 1.62% Pd content and nano-scaled Pd-islands between 50-100 nm as determined by the inductively coupled plasma (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). In Pd/Mg systems, doping Pd on a nanoscale is crucial as it provides enhanced catalytic activity owing to higher fraction of available surface atoms and hence reduced requirements of expensive catalyst. Fine tuning the synthesis procedure with respect to the Pd nanoparticle precursors, the synthesis medium and nature and amount of surfactants allows tailor-made bimetallic particles having small Pd islands enabling maximized reduction performance. Also, such nano-sized islands are inherently more stable on the support compared to their micro-sized counterparts. Each bimetallic particle acted like numerous nano-scaled batteries generating an electronic current causing reduction of PCBs at the bimetallic interface. These particles, apart from producing rapid and complete PCB dechlorination (0.25 – 4 h), afforded ease of synthesis, storage and application, aspects which have been onerous in more widely researched Pd/Fe systems. The dechlorination kinetics showed linear dependence on total Pd content. A carbon mole balance showed 85-105% recoveries. A mechanism for PCB dechlorination by Pd/Mg particles is proposed integrating the self-regulating corrosion of Mg in well-established dechlorination pathway for bimetallic systems. Further, performance of the Pd/Mg particles in PCB spiked clays and sediment suggests that they may work well in such systems. These bimetallic particles which bring about reductive dechlorination may be potentially deployed in in-situ reactive barriers for highly chlorinated, recalcitrant organic contaminants occurring in the reducing environments of submarine sediments and groundwater.
Dechlorination of Polychlorinated Dibenzo-p-Dioxins
(PCDDs) by Fe0 and Pd/Fe0
Ji-Hun Kim1, Yoon-Seok Chang1,
James T. Nurmi2, Paul G. Tratnyek2. (1) School of
Environmental Science and Engineering, Pohang University of Science and
Technology, Pohang, South Korea; (2) Department of Environmental and
Biomolecular Systems, Oregon Health & Science University, Beaverton, OR,
USA
For the remediation of soil and fly ash contaminated polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), treatability tests using Fe0 and Pd/Fe0 were carried out. PCDD congeners with four or more chlorines in aqueous environment were dechlorinated by both micro- and nano sized Fe0, however the reaction is slow so application of Fe0 for PCDDs remediation is not promising. In contrast the the results with unpalladized Fe0, Pd/Fe0 shows rapid dechlorination for PCDDs, and the rate dechlorination of 1,2,3,4-tetrachloro dibenzo-p-dioxin (1,2,3,4-TeCDD) by Pd/Fe0 was about 3 orders of magnitude faster than by Fe0. Pd/Fe0 also shifts the distribution of dechlorinated products, and we hypothesized that the product difference between Pd/Fe0 and Fe0 comes from the different dechlorination mechanisms (electron dissociation and H atom transfer). The strategies for the detoxification of PCDDs by Fe0 and Pd/Fe0 will be discussed in terms of the toxic equivalent quantity (TEQ) change and the applicability for remediation technology.
Detection and Characterization of Inorganic Nanoparticles
Using Inductively Coupled Plasma-Mass Spectrometry in Hyphenated and Real Time
Single Particle Modes
Emily K. Lesher1, Sungyun Lee2,
James F. Ranville3. (1) Environmental Science and Engineering
Division, Colorado School of Mines, Golden, CO, USA; (2) Gwangju Institute of
Science and Technology, Gwangju, Korea; (3) Department of Chemistry and
Geochemistry, Colorado School of Mines, Golden, CO, USA
In the last twenty years, we have witnessed an explosion in the manufacture of nanoparticles (diameters smaller than 10-7 meter) for medical and engineering applications. Some of the characteristics most prized in these applications, such as catalytic capability, are the very same that make engineered nanoparticles a potential environmental hazard. While the impact of nanotechnology has increased, successful efforts at efficiently characterizing the output of this nascent industry for environmental, toxicological, and hydrological studies have not kept up. Application of traditional methods, such as electron microscopy and UV spectroscopy, are not feasible for environmental samples due to the significant dilution and the complex matrices that can be encountered. These matrices may include an abundance of natural nanoparticles.
Inductively coupled plasma-mass spectrometry (ICP-MS) is a powerful detector for inorganic nanoparticles that might overcome these detection and discrimination obstacles.
In hyphenated mode, where particles are first separated by hydrodynamic diameter using flow field flow fractionation (Fl FFF), ICP-MS can be used to measure the size distribution, metal concentrations, and stability of some inorganic nanoparticles. In real team single particle mode, ICP-MS can detect the presence of some nanoparticles at environmentally relevant concentrations, and also has potential for use in sizing. We will present characterizations of CdSe/ZnS quantum dots and polydisperse silver nanoparticles using these techniques.
Effects of Ingested Engineered Carbon Nanomaterials on
Zooplankton
A.P. Roberts1, L.M. Taylor1, A.
Edgington2, S.J. Klaine2. (1) Department of Biology,
University of North Texas, Denton, TX, USA; (2) Institute of Environmental
Toxicology, Clemson University, Pendleton, SC, USA
Nanotechnology is a rapidly growing industry, and increased manufacturing and use of engineered nanoparticles will likely increase their deposition into aquatic ecosystems. However, relatively little is known about the potential impacts of engineered nanoparticles on aquatic biota. Particularly relevant to aquatic ecosystems are those particles which display increased solubility either through specialized coatings or through an ability to interact with water column constituents such as natural organic matter. Previous research indicated that grazing zooplankton (Daphnia magna) were able to ingest lipid-coated single walled carbon nanotubes (SWNTs) from the water column during their normal feeding behavior. While SWNTs were observed to fill the gut of the zooplankton, they were easily egested, and acute mortality was observed only at high concentrations (>5mg/L). The purpose of this research was to examine the potential for sublethal effects to occur at lower concentrations following ingestion of solubilized engineered carbon nanomaterials. D. magna and C. dubia were exposed to a range of concentrations of multiwalled carbon nanotubes (0.1 -1mg/L) suspended in water using natural organic matter. Survival was monitored in each species for the duration of the test period (7 days for C. dubia and 4 days for D. magna). In order to assess sublethal effects, reproduction was monitored in C. dubia. We hypothesized that the accumulation of nanotubes in the gut tract of zooplankton would decrease their ability to take up normal food (algae) and, thus, growth (dry mass per individual) was measured in both species using an electromicrobalance. No significant effect on survival of either species was observed at any of the concentrations tested. However, C. dubia reproduction was significantly decreased by 50% at concentrations > 0.25mg/L. Growth in both species was inhibited in a concentration dependent manner. Although we observed no evidence that the MWNTs were taken up across the gut membrane, we have shown that simply ingesting the materials can lead to significant toxic effects in zooplankton through the inhibition of normal feeding activity.
Endotoxin Contamination of Engineered Nanomaterials
R. Keith Esch, David Ensor, Karin Foarde, Li Han.
Research Triangle Institute, International, NC, USA
Relatively little is known about the potentially novel risks inherent in nanotechnology applications. Of particular concern is how contamination of engineered nanomaterials (ENM) might impact human health and toxicity assessments. Endotoxins are bacterial cell wall components that may be released upon cell death as well as during growth and division. Endotoxins occur naturally in soil, water and air and because they are widely produced, highly stable, water soluble and amphiphilic, they routinely contaminate other materials. Endotoxin levels are regulated in clinical procedures as exposure is associated with respiratory symptoms as well as fever, septic shock, impaired organ function and death. The decreased size and exponentially increased surface area of ENM indicates the potential for much greater endotoxin adsorption, for a given mass, compared to larger particles of the same chemical composition.
Endotoxin is a potential confounding factor in ENM toxicity studies. Generally, induction of inflammatory response and oxidative stress are observed for both endotoxin and ENM. Furthermore, intratracheal administration using carbon-based ENMs and endotoxin show a common series of physiological events.
The established method for quantifying endotoxin relies on its activity in a complex biochemical assay system. Because of their physical and chemical properties, examination of many ENM under these conditions presents nontrivial technical challenges. We have made progress in identifying and implementing methods for analysis of ENM with respect to endotoxin contamination. An examination of a series of carbon-based ENM reveals widely varying levels of endotoxin. The physical association of ENM and endotoxin and their shared physiological effects suggest the possibility that contaminating endotoxin may represent a health risk and contribute to the toxicity that is ascribed to ENMs.
Exploring a Framework of Nanotechnology Research and
Applications in Addressing Global Climate Change Issues
David LePoire, Argonne National Laboratory, Illinois, USA
Nobel Laureate Richard Smalley had suggested in the early part of this decade that nanotechnology be internationally researched and applied in solving the world's energy issue and thereby relieving many other related problems, such as the challenge of global climate change. While the scale and international collaboration towards this goal were not realized, many independent research activities are being pursued to address this air quality issue with the application and understanding of nanotechnologies. The recent U.S. science and technology strategic research plans concerning global climate change constitute a classification framework. Major components of this framework include aspects such as (1) system understanding, (2) mitigation efforts through non-energy sources, energy sources, efficient energy use, and direct CO2 capture, (3) adaptation, (4) assessing potential impacts, and (5) evaluating policy responses. Various international reports and activities are placed in the context of this framework to identify progress, gaps and uncertainties in areas such as application of nanotechnology to understanding aerosols, better measures of the system dynamics, direct use in energy storage, transmission, efficiency, conversion, and how reduction of environmental emissions.
This project is an initial step in an effort to try to determine whether decision techniques such as a real options analysis approach might be suitable for this large public investment. On a smaller scale, commercial organizations have applied real options analysis to gain better understanding of research investments under large uncertainties. Options analysis includes accounting for future options such as deployment, abandonment, or continued research. As such it views research as an insurance policy against potential uncertain conditions such as the impacts of global climate change. Such an analysis could lead to better understanding and decision making concerning the public role of governments to speed learning curves, develop shared basic information, and correct environmental externalities.
Geochemical Laboratory Testing of Nano-Size ZVI for
Mending an Existing Permeable Reactive Barrier in the 100-D Area at the Hanford Site
Gary Wyss1, Adam Logar1,
Martin Foote1, Nick Jaynes1, Marek H. Zaluski1, Michael Hogan1, Scott Petersen2. (1)
MSE Technology Applications, Butte, Montana, USA; (2) Fluor Hanford, Washington, USA
MSE Technology Applications, Inc, has conducted investigations associated with 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, 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 and installed to intercept a hexavalent chromium plume moving towards the Columbia River. The investigation included geochemical column tests to evaluate the potential for nZVI impregnated soil to reduce hexavalent chromium.
Geochemical column tests were performed to simulate geochemical conditions found in the highly permeable zones within the Ringold formation at Hanford. Changes in the physical parameters and chemical constituents were monitored as 40 to 50 pore volumes of surrogate groundwater containing 0.55 mg/L hexavalent chromium were flushed through columns packed with nZVI impregnated Ringold E soil. Two nZVI materials were investigated in the geochemical column tests, RNIP-M2, which is manufactured by Toda Japan and Polymetallix, which is manufactured by Crane-Polyflon. The columns were packed with the nZVI at three concentrations, 0.015%, 0.15%, and 1.5% and run in triplicate with one control column.
The geochemical column effluents were collected and analyzed for physical and chemical parameters at six sampling events throughout the three-week test. Effluent samples were analyzed during the test for pH, oxidation-reduction potential (ORP), specific conductance (SC), dissolved oxygen (DO), temperature, hexavalent chromium, nitrate, nitrite, ammonia, iron(II), iron(III), alkalinity, and sulfate.
RNIP-M2 consistently showed greater reduction of hexavalent chromium and ORP, and increase pH, than the Polymetallix.
This work was conducted through the support of Fluor Hanford under Contract Number 30994.
Impact of Single-Walled Carbon Nanotubes on the Soil
Microbial Community Composition and Function
Zhonghua Tong, Marianne Bischoff, Loring F. Nies,
Natalie Carroll, Ronald F. Turco. Purdue University, West Lafayette, IN, USA
Nanomaterials, especially carbon nanotubes are finding their way into many product applications. With increased use, the release of nanotubes in the environment is inevitable. This potential is of concern as recent work has shown that single-walled nanotubes (SWNTs) can be cytotoxic and can cause pulmonary and developmental toxicity. Moreover, it has been demonstrated that under specific test conditions SWNTs have strong antimicrobial tendency. However, no studies have investigated the effects of carbon nanotubes when released directly to soil. In this study, two soils, a silty clay loam (high organic matter) and a sandy loam (low organic matter) were initially treated with either dry SWNTs at 1000 μg g-1 soil or SWNTs functionalized with either polyethyleneglycol (PEG) or m-polyaminobenzene sulfonic acid (PABS) at 10 μg g-1 and 50 μg g-1, and a control containing water. The samples were incubated for 6 weeks. During this time, SWNTs or SWNTs functionalized were reapplied weekly at initial rate. Microbial activity was evaluated by measuring total microbial biomass (indicated by phospholipid derived phosphate), basal soil respiration, and glucose-induced respiration. Community structure was evaluated using DGGE after PCR amplification of genomic DNA using universal bacterial 16S rDNA primers or eukaryote 18S rDNA. This work shows that SWNTs, as-produced or functionalized, had little impact on soil microbial activity. DGGE banding patterns showed that although there were enhancement and some inhibition in a number of bands, the overall structures of both bacteria and eukaryote patterns was not changed.
Increased Efficacy of Zero-Valent Iron Nanoparticles in
Groundwater Remediation: Development of a Polymeric Delivery Vehicle
Sita Krajangpan, Achintya N. Bezbaruah, Bret J.
Chisholm. North Dakota State University, Fargo, ND, USA
Chlorinated solvents such as trichloroethylene (TCE) present in the subsurface as non-aqueous phase liquids (NAPL) are continuous long-term sources of halogenated organic contaminants in groundwater. In the recent years zero-valent iron nanoparticles (nZVI) have been increasingly used for environmental cleanup. Being a strong reducing agent nZVI can reductively transform relatively oxidized pollutants including chlorinated solvents, metals, nitrates, and explosives. However, to be effective for groundwater remediation, the iron nanoparticles not only must be protected from the oxidation by non-target compounds (e.g. water and dissolve oxygen in the aquifer) but also must be dispersible and transportable through the aquifer into the target area (i.e., contaminant plume). An amphiphilic polysiloxane graft copolymer is synthesized as the delivery vehicle for the nZVI. The hydrophobicity of the polysiloxane polymer backbone protects the nZVI from oxidation by water by creating a barrier to water while also creating an affinity of the coated nanoparticles for the water/organic interface. The polymer also promotes colloidal stability of the iron nanoparticles in aqueous suspension. Stable colloidal dispersion of the nanoparticles makes more particle surface available for reaction. Batch studies for TCE degradation using modified nZVI show a 9% increase in percent degradation as compare to bare nZVI. The reaction rate constant, k, using modified nZVI (k= 0.027 h-1) is 40% higher than bare nZVI (k=0.016 h-1). Results from batch studies using nitrate and arsenic also show similar trends. Provisional patent rights have been awarded for this polymer and the authors are planning pilot studies using the polymer coated nZVI.
Interactions Between Engineered Iron Oxide Nanoparticles
and Microorganisms
Maria Casado, Department of Environmental Health, University of Birmingham, United Kingdom
The development of materials and products at the nanoscale has become a major investment area on a global scale and there are many products already on the market which use materials in this size range. Applications in medicine, cosmetics and personal care products, materials science, energy production and storage and electronics are just a few examples where benefits to society, human health and the environment are predicted. The anticipated increase in nanoparticle production makes exposure of the environment to these materials more and more likely. Their biological effects, environmental fate and behaviour of engineered nanoparticles, are relatively unknown. Assessing the benefits and risks of nanomaterials requires a better understanding of their chemistry, mobility, bioavailability, and ecotoxicity in the environment.
Iron is an essential growth factor for most bacteria while bioavailability of iron will depend on its physico-chemical form. Gram-negative bacteria Pseudomonas Fluorescens have been exposed to well-characterised manufactured iron oxide nanoparticles at different pH values, iron concentrations and in presence and absence of humic substances. Parallel experiments were performed with dissolved iron and latex beads. Results showed after 24h higher iron uptake when this was dissolved than when the case of nanoparticles. Although iron oxide nanoparticles are less accessible than the dissolved iron, bacteria are still able to uptake a proportion of the nanoparticles. This knowledge will help understanding the bioavailability of nanoparticles and the role of microorganisms on the behavior, fate, and segregation of particles in contaminated environments.
Laboratory Investigations on Injectibility of Nano-Size
ZVI into Saturated Sand for Mending an Existing Permeable Reactive Barrier in the
100-D Area at the Hanford Site
Gilbert M. Zemansky1, Adam Logar1,
Kenneth R. Manchester1, Marek H. Zaluski1, Michael Hogan1, Nick Jaynes1, Scott
Petersen2. (1) MSE Technology Applications, Butte, Montana, USA; (2) Fluor Hanford, Washington, USA
MSE Technology Applications. Inc., has conducted investigations associated with 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, 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 and installed to intercept a hexavalent chromium plume moving towards the Columbia River. The investigation included laboratory testing of injectibility of nZVI into saturated sand.
A tank injection experiment was conducted to simulate an actual field injection in a Hanford well at a scale intermediate between laboratory flow cell and field conditions. A 6" diameter injection well was installed in the center of a 5-foot diameter and 5-foot high cylindrical tank. Sand was loaded into the tank to form three layers with a very coarse sand layer 1 foot thick sandwiched between two layers of medium sand. This simulated conditions at Hanford where there is a thin, highly permeable zone of material.
nZVI fluid (RNIP-M2 at a concentration of 9,030 mg/L total iron was injected through the injection well and flowed outward through the sand to the tank walls outfitted with drainage fabric. Two monitoring wells each were installed at radial distances of 1 and 2 feet from the injection well in the center of the very coarse and underlying medium sand layers. The injection took place at a flow rate of 3 gpm for 100 minutes. This corresponded to five pore volumes injected to the very coarse sand layer.
All wells were hydraulically tested before and after the injection and fluid samples were taken from the injection line, monitoring wells, and tank effluent lines during the injection. After the injection, the sand was methodically removed from the tank and samples taken for total iron analysis during the process. Visual observations during excavation were recorded with a camera.
The tank test confirmed that iron deposition occurred primarily in the very coarse sand layer and provided both quantitative and qualitative data indicating deposition patterns. In addition, long flow column tests were conducted that facilitated the development of a functional relationship of nZVI distribution necessary for predictive computer modeling.
Major portion of this work was conducted through the DOE Environmental Management Consolidated Business Center at the Western Environmental Technology Office under DOE Contract Number DE-AC09-96EW96405.