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1

Microbiological Characteristics in a Zero-Valent Iron Reactive Barrier  

Microsoft Academic Search

Zero-valent iron (Fe0)-based permeable reactive barriertreatment has been generating great interest for passivegroundwater remediation, yet few studies have paid particularattention to the microbial activity and characteristics withinand in the vicinity of the Fe0-barrier matrix. The presentstudy was undertaken to evaluate the microbial population andcommunity composition in the reducing zone of influence byFe0 corrosion in the barrier at the Oak Ridge

Baohua Gu; David B. Watson; Liyou Wu; Debra Helen Phillips; David C. White; Jizhong Zhou

2002-01-01

2

LONG-TERM PERFORMANCE OF PERMEABLE REACTIVE BARRIERS USING ZERO-VALENT IRON: GEOCHEMICAL AND MICROBIOLOGICAL EFFECTS  

EPA Science Inventory

Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, NC and the Denver Federal Center, CO sites. These ground water treatment systems use zero-valent iron filings (Peerless Meta...

3

GROUND WATER REMEDIATION OF CHROMIUM USING ZERO-VALENT IRON IN A PERMEABLE REACTIVE BARRIER  

EPA Science Inventory

A series of laboratory experiments were performed to elucidate the chromium transformation and precipitation reactions caused by the corrosion of zero-valent iron in water-based systems. Reaction rates were determined for chromate reduction in the presence of different types of ...

4

Mineral Precipitation Upgradient from a Zero-Valent Iron Permeable Reactive Barrier  

SciTech Connect

Core samples taken from a zero-valent iron permeable reactive barrier (ZVI PRB) at Cornhusker Army Ammunition Plant, Nebraska, were analyzed for physical and chemical characteristics. Precipitates containing iron and sulfide were present at much higher concentrations in native aquifer materials just upgradient of the PRB than in the PRB itself. Sulfur mass balance on core solids coupled with trends in ground water sulfate concentrations indicates that the average ground water flow after 20 months of PRB operation was approximately twenty fold less than the regional ground water velocity. Transport and reaction modeling of the aquifer PRB interface suggests that, at the calculated velocity, both iron and hydrogen could diffuse upgradient against ground water flow and thereby contribute to precipitation in the native aquifer materials. The initial hydraulic conductivity (K) of the native materials is less than that of the PRB and, given the observed precipitation in the upgradient native materials, it is likely that K reduction occurred upgradient to rather than within the PRB. Although not directly implicated, guar gum used during installation of the PRB is believed to have played a role in the precipitation and flow reduction processes by enhancing microbial activity.

Johnson, R. L.; Thoms, R. B.; Johnson, R. O.; Nurmi, J. T.; Tratnyek, Paul G.

2008-07-01

5

Chlorine and carbon isotope measurements can help assessing the effectivenes of a zero valent iron barrier  

NASA Astrophysics Data System (ADS)

Chlorinated aliphatic hydrocarbons (CAH's) such as trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinylchloride (VC) are extensively used in industrial applications. One of the most promising remediation techniques for CAH's in groundwater is their removal via abiotic reductive dechlorination using Zero Valent Iron (ZVI). This is applied for the treatment of contaminated sites by installing permeable reactive barriers (PRB). In this study, isotope fractionation of chlorinated ethylenes in transformation by cast iron has been investigated, because such types of iron are commonly used in PRBs. Batch experiments have been carried out in closed flasks, containing cast iron with aqueous solutions of TCE, cDCE and VC. These substrates and their respective products have been monitored by headspace samplings for their concentration (by GC-FID) and isotope fractionation of carbon and chlorine (by GC-IRMS). A decreasing reactivity trend was observed when compounds contain less chlorine atoms, with differences in rate constants of about one order of magnitude between each of the substances TCE > cDCE > VC. This resulted in the accumulation of products with fewer chlorine atoms. Therefore a similar observation can be expected if degradation in the field is incomplete, for example in the case of aged or improperly designed PRB. Pronounced carbon and chlorine isotope fractionation was measured for each of the compounds, and characteristic dual isotope plots (C, Cl) were obtained for TCE and cDCE. These results may serve as an important reference for the interpretation of isotope data from field sites, since stable isotope fractionation is widely recognized as robust indicator for such pollutant transformations. However, carbon isotope fractionation in a given parent compound may be caused by either abiotic or biotic degradation. In the field, it can therefore be difficult to delineate the contribution of abiotic transformation by PRB in the presence of ongoing biodegradation. This study investigates two different approaches to resolve these concurring modes of transformation: (i) evidence from dual (C, Cl) isotope plots; (ii) evidence from carbon isotope values of degradation products (e.g., cDCE and ethene from TCE, respectively). The comparison of dual isotope patterns for TCE degradation with cast iron and with Geobacter lovleyi exhibited similar slopes for these two types of reaction. This indicates that dual isotope plots may not be able to distinguish biotic and abiotic pathways in this case. However, the information from carbon isotope values in this study confirms earlier results (Elsner et al.), which suggest that isotope values from reaction products can be a expedient way of delineating the occurrence of abiotic transformation, even in the presence of ongoing biodegradation.

Cretnik, S.; Audi, C.; Bernstein, A.; Palau, J.; Soler, A.; Elsner, M.

2012-04-01

6

Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons  

Microsoft Academic Search

The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in

Young-Hun Kim; Elizabeth R. Carraway

2000-01-01

7

Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center  

USGS Publications Warehouse

The hydraulic and geochemical performance of a 366 m long permeable reactive barrier (PRB) at the Denver Federal Center; Denver, Colorado, was evaluated. The funnel and gate system, which was installed in 1996 to intercept and remediate ground water contaminated with chlorinated aliphatic hydrocarbons (CAHs), contained four 12.2 m wide gates filled with zero-valent iron. Ground water mounding on the upgradient side of the PRB resulted in a tenfold increase in the hydraulic gradient and ground water velocity through the gates compared to areas of the aquifer unaffected by the PRB. Water balance calculations for April 1997 indicate that about 75% of the ground water moving toward the PRB from upgradient areas moved through the gates. The rest of the water either accumulated on the upgradient side of the PRB or bypassed the PRB. Chemical data from monitoring wells screened down-gradient, beneath, and at the ends of the PRB indicate that contaminants had not bypassed the PRB, except in a few isolated areas. Greater than 99% of the CAH mass entering the gates was retained by the iron. Fifty-one percent of the CAH carbon entering one gate was accounted for in dissolved C1 and C2 hydrocarbons, primarily ethane and ethene, which indicates that CAHs may adsorb to the iron prior to being dehalogenated. Treated water exiting the gates displaced contaminated ground water at a distance of at least 3 m downgradient from the PRB by the end of 1997. Measurements of dissolved inorganic ions in one gate indicate that calcite and siderite precipitation in the gate could reduce gate porosity by about 0.35% per year. Results from this study indicate that funnel and gate systems containing zero-valent iron can effectively treat ground water contaminated with CAHs. However, the hydrologic impacts of the PRB on the flow system need to be fully understood to prevent contaminants from bypassing the PRB.

McMahon, P.B.; Dennehy, K.F.; Sandstrom, M.W.

1999-01-01

8

ENVIRONMENTAL RESEARCH BRIEF: LONG-TERM PERFORMANCE OF PERMEABLE REACTIVE BARRIERS USING ZERO-VALENT IRON: AN EVALUATION AT TWO SITES  

EPA Science Inventory

Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, NC and the Denver Federal Center, CO sites. These groundwater treatment systems use zero-valent iron filings to intercept an...

9

Electromagnetic Borehole Flowmeter Surveys at Selected In Situ Redox Manipulation Barrier Wells, Zero-Valent Iron Site, Hanford, Washington  

SciTech Connect

Ambient (i.e., static) and dynamic (i.e., pumping-induced) electromagnetic borehole flowmeter (EBF) surveys were performed in 10 selected In Situ Redox Manipulation (ISRM) barrier wells to characterize the distribution of in-well vertical flow conditions and to infer the relative hydraulic conductivity distribution in the upper-part of the unconfined aquifer. These wells are located in two areas where the aquifer is targeted for testing of zero-valent iron injection to mend a failed portion of the ISRM barrier at the 100 D Area, Hanford Site. Each of these two areas consists of a group of five wells, one group to the southwest and one group to the northeast. The upper ~15 to 20 ft (~4.6 to 6.1 m) of the unconfined aquifer was characterized for in-well vertical flow conditions and vertical profile information regarding relative hydraulic conductivity. At some well site locations, the upper ~2 to 3 ft (~0.6 to 1 m) of the well-screen interval could not be characterized under pumping (dynamic) conditions because of the presence of the pump.

Newcomer, Darrell R.

2009-02-09

10

Performance evaluation of a zero-valent iron reactive barrier: mineralogical characteristics  

Microsoft Academic Search

There is a limited amount of information about the effects of mineral precipitates and corrosion on the lifespan and long-term performance of in situ Fe reactive barriers. The objectives of this paper are (1) to investigate mineral precipitates through an in situ permeable Fe reactive barrier and (2) to examine the cementation and corrosion of Fe filings in order to

Debra Helen Phillips; Baohua Gu; David B Watson; Yul Roh; Liyuan Liang; S. Y. Lee

2000-01-01

11

Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons  

SciTech Connect

The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In their experiments, electrolytic zero valent iron with a surface area of 0.12 m{sup 2}/g resulted in an observed first-order rate constant of 3.9 x 10{sup {minus}3} h{sup {minus}1} or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (k{sub SA}) is 3.2 x 10{sup {minus}4} L m{sup {minus}2} h{sup {minus}1}. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron. Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes.

Kim, Y.H.; Carraway, E.R.

2000-05-15

12

SCANNING ELECTRON ANALYSIS OF IRON FILINGS FROM A ZERO-VALENT IRON PERMEABLE BARRIER USED FOR GROUND WATER RESTORATION  

EPA Science Inventory

Permeable iron reactive barriers have become a popular way to remediate contaminated ground water. Although this technology has been in use for about a decade, there is still little knowledge about long-term performance issues (l). One of the biggest concerns is the corrosion of ...

13

Estimate of the optimum weight ratio in zero-valent iron/pumice granular mixtures used in permeable reactive barriers for the remediation of nickel contaminated groundwater.  

PubMed

This paper presents the results of laboratory column tests aimed at defining the optimum weight ratio of zero-valent iron (ZVI)/pumice granular mixtures to be used in permeable reactive barriers (PRBs) for the removal of nickel from contaminated groundwater. The tests were carried out feeding the columns with aqueous solutions of nickel nitrate at concentrations of 5 and 50 mg/l using three ZVI/pumice granular mixtures at various weight ratios (10/90, 30/70 and 50/50), for a total of six column tests; two additional tests were carried out using ZVI alone. The most successful compromise between reactivity (higher ZVI content) and long-term hydraulic performance (higher Pumice content) seems to be given by the ZVI/pumice granular mixture with a 30/70 weight ratio. PMID:21885195

Calabr, P S; Moraci, N; Suraci, P

2012-03-15

14

THE APPLICATION OF IN SITU PERMEABLE REACTIVE (ZERO-VALENT IRON) BARRIER TECHNOLOGY FOR THE REMEDIATION OF CHROMATE-CONTAMINATED GROUNDWATER: A FIELD TEST  

EPA Science Inventory

A small-scale field test was initiated in September 1994 to evaluate the in situ remediation of groundwater contaminated with chromate using a permeable reactive barrier composed of a mixture of zero-valent Fe, sand and aquifer sediment. The site used was an old chrome-plating f...

15

Conceptual analysis of zero-valent iron fracture reactive barriers for remediating a trichloroethylene plume in a chalk aquifer  

Microsoft Academic Search

A novel concept, the Fe0 fracture reactive barrier (Fe0 FRB), is proposed to clean up chlorinated solvent pollution of groundwater in a chalk aquifer. Iron particles, suspended in a viscous biodegradable gel, can be injected into selected fractures to create an extended reactive zone of partly iron-filled fractures. To evaluate the feasibility of Fe0 FRB as a remediation strategy, we

Zuansi Cai; David N. Lerner; Robert G. McLaren; Ryan D. Wilson

2007-01-01

16

Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron  

NASA Technical Reports Server (NTRS)

Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.

Furukawa, Yoko; Kim, Jin-Wook; Watkins, Janet; Wilkin, Richard T.

2002-01-01

17

Potential artifacts in interpretation of differential breakthrough of colloids and dissolved tracers in the context of transport in a zero-valent iron permeable reactive barrier.  

PubMed

Many published studies have used visual comparison of the timing of peak breakthrough of colloids versus conservative dissolved tracers (hereafter referred to as dissolved tracers or tracers) in subsurface media to determine whether they are advected differently, and to elucidate the mechanisms of differential advection. This purely visual approach of determining differential advection may have artifacts, however, due to the attachment of colloids to subsurface media. The attachment of colloids to subsurface media may shift the colloidal peak breakthrough to earlier times, causing an apparent "faster" peak breakthrough of colloids relative to dissolve tracers even though the transport velocities for the colloids and the dissolved tracers may actually be equivalent. In this paper, a peak shift analysis was presented to illustrate the artifacts associated with the purely visual approach in determining differential advection, and to quantify the peak shift due to colloid attachment. This peak shift analysis was described within the context of microsphere and bromide transport within a zero-valent iron (ZVI) permeable reactive barrier (PRB) located in Fry Canyon, Utah. Application of the peak shift analysis to the field microsphere and bromide breakthrough data indicated that differential advection of the microspheres relative to the bromide occurred in the monitoring wells closest to the injection well in the PRB. It was hypothesized that the physical heterogeneity at the grain scale, presumably arising from differences in inter- versus intra-particle porosity, contributed to the differential advection of the microspheres versus the bromide in the PRB. The relative breakthrough (RB) of microspheres at different wells was inversely related to the ionic strength of ground water at these wells, in agreement with numerous studies showing that colloid attachment is directly related to solution ionic strength. PMID:11708449

Zhang, B P; Johnson, W P; Piana, M J; Fuller, C C; Naftz, D L

2001-01-01

18

Potential artifacts in interpretation of differential breakthrough of colloids and dissolved tracers in the context of transport in a zero-valent iron permeable reactive barrier  

USGS Publications Warehouse

Many published studies have used visual comparison of the timing of peak breakthrough of colloids versus conservative dissolved tracers (hereafter referred to as dissolved tracers or tracers) in subsurface media to determine whether they are advected differently, and to elucidate the mechanisms of differential advection. This purely visual approach of determining differential advection may have artifacts, however, due to the attachment of colloids to subsurface media. The attachment of colloids to subsurface media may shift the colloidal peak breakthrough to earlier times, causing an apparent "faster" peak breakthrough of colloids relative to dissolve tracers even though the transport velocities for the colloids and the dissolved tracers may actually be equivalent. In this paper, a peak shift analysis was presented to illustrate the artifacts associated with the purely visual approach in determining differential advection, and to quantify the peak shift due to colloid attachment. This peak shift analysis was described within the context of microsphere and bromide transport within a zero-valent iron (ZVI) permeable reactive barrier (PRB) located in Fry Canyon, Utah. Application of the peak shift analysis to the field microsphere and bromide breakthrough data indicated that differential advection of the microspheres relative to the bromide occurred in the monitoring wells closest to the injection well in the PRB. It was hypothesized that the physical heterogeneity at the grain scale, presumably arising from differences in inter- versus intra-particle porosity, contributed to the differential advection of the microspheres versus the bromide in the PRB. The relative breakthrough (RB) of microspheres at different wells was inversely related to the ionic strength of ground water at these wells, in agreement with numerous studies showing that colloid attachment is directly related to solution ionic strength.

Zhang, P.; Johnson, W.P.; Piana, M.J.; Fuller, C.C.; Naftz, D.L.

2001-01-01

19

Application of Emulsified Zero-Valent Iron to Marine Environments  

NASA Technical Reports Server (NTRS)

Contamination of marine waters and sediments with heavy metals and dense non-aqueous phase liquids (DNAPLs) including chlorinated solvents, pesticides and PCBs pose ecological and human health risks through the contaminant's potential bioaccumulation in fish, shellfish and avian populations. The contaminants enter marine environments through improper disposal techniques and storm water run-off. Current remediation technologies for application to marine environments include costly dredging and off-site treatment of the contaminated media. Emulsified zero-valent iron (EZVI) has been proven to effectively degrade dissolved-phase and DNAPL-phase contaminants in freshwater environments on both the laboratory and field-scale level. However, the application to marine environments is only just being explored. This paper discusses the potential use of EZVI in brackish and saltwater environments, with supporting laboratory data detailed. Laboratory studies were performed in 2005 to establish the effectiveness of EZVI to degrade trichloroethylene (TCE) in saltwater. Headspace vials were setup to determine the kinetic rate of TCE degradation using EZVI in seawater. The reaction vials were analyzed by Gas Chromatographic/Flame Ionization Detection (GC/FID) for ethene production after a 48 day period using a GC/FID Purge and Trap system. Analytical results showed that EZVI was very effective at degrading TCE. The reaction by-products (ethene, acetylene and ethane) were produced at 71% of the rate in seawater as in the fresh water controls. Additionally, iron within the EZVI particles was protected from oxidation of the corrosive seawater, allowing EZVI to perform in an environment where zero-valent iron alone could not compete. Laboratory studies were also performed to establish the effectiveness of emulsified zero-valent metal (EZVM) to remove dissolved-phase cadmium and lead found in seawater. EZVM is comprised of a combination of magnesium and iron metal surrounded by the same oil/surfactant membrane used in EZVI. The removal of cadmium and lead from a seawater matrix is a unique challenge. It requires a system that is resistant to the corrosive nature of seawater while removing specific ions that are in a relatively low concentration compared to naturally occurring seawater salts. Laboratory studies conducted show greater than 99% removal of lead and 96% removal of cadmium from a seawater solution spiked at 5 mg/L that was treated with an Emulsified Zero-Valent Metal (EZVM). The cadmium and lead are removed from the solution as they transport across the emulsion membrane and plate out onto the zero-valent metal surface.

Brooks, Kathleen B.; Quinn, Jacqueline W.; Clausen, Christian A.; Geiger, Cherie L.

2005-01-01

20

Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions  

Microsoft Academic Search

Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO3 and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO3 as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD

Yuxin Wu; Roelof Versteeg; Lee Slater; Douglas LaBrecque

2009-01-01

21

Applicability of Zero-Valent Iron With Lignite Additives as Geochemical In Situ Barrier for Acid Mine Water  

Microsoft Academic Search

Acid mine waters can contain high concentrations of metals like iron, aluminum, zinc, uranium and heavy metals. Research has been conducted for several years to establish the extent to which under the conditions of the former uranium mine of Knigstein (Saxony, Germany) reduction of pollutant concentrations can be positively influenced and accelerated by storage of reactive materials in open mine

Christoph Klinger; Ulf Jenk; Jochen Schreyer

22

Application of Emulsified Zero-Valent Iron to Marine Environments  

NASA Technical Reports Server (NTRS)

Contamination of marine waters and sediments with heavy metals and dense non-aqueous phase liquids (DNAPLs) including chlorinated solvents, pesticides and PCBs pose ecological and human health risks through the potential of the contaminant to bioaccumulate in fish, shellfish and avian populations. The contaminants enter marine environments through improper disposal techniques and storm water runoff. Current remediation technologies for application to marine environments include costly dredging and off-site treatment of the contaminated media. Emulsified zero-valent iron (EZVI) has been proven to effectively degrade dissolved-phase and DNAPL-phase contaminants in freshwater environments on both the laboratory and field-scale level. Emulsified Zero-Valent Metal (EZVM) using metals such as iron and/or magnesium have been shown in the laboratory and on the bench scale to be effective at removing metals contamination in freshwater environments. The application to marine environments, however, is only just being explored. This paper discusses. the potential use of EZVI or EZVM in brackish and saltwater environments, with supporting laboratory data detailing its effectiveness on trichloroethylene, lead, copper, nickel and cadmium.

Quinn, Jacqueline W.; Brooks, Kathleen B.; Geiger, Cherie L.; Clausen, Christian A.; Milum, Kristen M.

2006-01-01

23

Reduction and Immobilization of Radionuclides and Toxic Metal Ions Using Combined Zero Valent Iron and Anaerobic Bacteria  

SciTech Connect

The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. AN exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes are functional. This work evaluated the hypothesis that a system combining a mixed culture of sulfate reducing bacteria (SRB) with zero valent iron would have a greater cr(VI) removal efficiency and a greater total Cr(VI) removal capacity than a zero valent iron system without the microorganisms. Hence, the overall goal of this research was to compare the performance of these types of systems with regard to their Cr(VI) removal efficiency and total Cr(VI) removal capacity. Both batch and continuous flow reactor systems were evaluated.

Lenly J. Weathers; Lynn E. Katz

2002-05-29

24

Chromate transport through columns packed with surfactant-modified zeolite/zero valent iron pellets  

E-print Network

Chromate transport through columns packed with surfactant-modified zeolite/zero valent iron pellets Chromate transport through columns packed with zeolite/zero valent iron (Z/ZVI) pellets, either untreated of immobile water was responsible for the earlier breakthrough of chromate in columns packed with zeolite

Li, Zhaohui

25

Kinetics of RDX degradation by zero-valent iron (ZVI).  

PubMed

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a common groundwater contaminant at military facilities. The current research has been conducted to evaluate the use of zero-valent iron (ZVI) for the remediation of water contaminated with RDX. RDX was found to degrade rapidly in the presence of ZVI. The observed first-order kinetic constant for RDX reduction follows an enzymatic-like kinetic model with respect to the ZVI concentration. At low ZVI concentrations, RDX reduction follows pseudo first order kinetics with respect to ZVI concentration; while at high ZVI concentrations the RDX reduction is zero-order. Nitroso compounds (MNX, DNX, and TNX), nitrate, nitrite and nitrous oxide were identified as the main by-products for the RDX reduction by ZVI. The nitroso compounds were found to undergo reduction by ZVI. PMID:16386362

Wanaratna, Pischa; Christodoulatos, Christos; Sidhoum, Mohammed

2006-08-10

26

Kinetics of zero valent iron nanoparticle oxidation in oxygenated water.  

PubMed

Zero valent iron (ZVI) nanoparticles are versatile in their ability to remove a wide variety of water contaminants, and ZVI-based bimetallic nanoparticles show increased reactivity above that of ZVI alone. ZVI nanoparticles degrade contaminants through the reactive species (e.g., OH*, H(2(g)), H(2)O(2)) that are produced during iron oxidation. Measurement and modeling of aqueous ZVI nanoparticle oxidation kinetics are therefore necessary to optimize nanoparticle design. Stabilized ZVI and iron-nickel nanoparticles of approximately 150 nm in diameter were synthesized through solution chemistry, and nanoparticle oxidation kinetics were determined via measured mass change using a quartz crystal microbalance (QCM). Under flowing aerated water, ZVI nanoparticles had an initial exponential growth behavior indicating surface-dominated oxidation controlled by migration of species (H(2)O and O(2)) to the surface. A region of logarithmic growth followed the exponential growth which, based on the Mott-Cabrera model of thin oxide film growth, suggests a reaction dominated by movement of species (e.g., iron cations and oxygen anions) through the oxide layer. The presence of ethanol or a nickel shell on the ZVI nanoparticles delayed the onset of iron oxidation and reduced the extent of oxidation. In oxygenated water, ZVI nanoparticles oxidized primarily to the iron oxide-hydroxide lepidocrocite. PMID:23130994

Greenlee, Lauren F; Torrey, Jessica D; Amaro, Robert L; Shaw, Justin M

2012-12-01

27

USE OF PRETREATMENT ZONES AND ZERO-VALENT IRON FOR THE REMEDIATION OF CHLOROALKENES IN AN OXIC AQUIFER  

EPA Science Inventory

Pre-treatment zones (PTZs) composed of sand, 10% zero-valent iron [Fe(0)]/sand, and 10% pyrite (FeS2)/sand were examined for their ability to prolong Fe(0) reactivity in aboveground column reactors and a subsurface permeable reactive barrier (PRB). The test site had an acidic, o...

28

Electrophoresis enhanced transport of nano-scale zero valent iron  

NASA Astrophysics Data System (ADS)

Electrokinetics (EK) has been used extensively to remove heavy metals from low permeability porous media. Electrokinetics (EK) or more specifically electrophoresis (EP) has also been proposed to enhance transport of nanoscale zero valent iron (NZVI) in fine grained porous media in the subsurface. However, increased dissolved oxygen and lower pH, due to electrolysis of water at the anode oxidizes NZVI particles and thus affects the remediation potential of EP with NZVI. This study focuses on minimization of NZVI oxidation and quantification of NZVI migration enhancement through the application of EP. Application of 50 and 100 mA currents under constant current conditions with an oxygen scavenger enhanced NZVI transport from the cathode to the anode. The enhancement in transport compared to diffusion was proportional to the applied current. Predictions of a numerical model, based on traditional colloidal filtration theory (CFT), were consistent with experimental results. In developing the model, the traditional CFT based mass balance equation was modified for the case of no advection. This study suggests that EP has the potential to deliver NZVI in low permeability porous media and that the numerical simulator can be used to predict NZVI mobility with EP.

Chowdhury, Ahmed I. A.; O'Carroll, Denis M.; Xu, Yanqing; Sleep, Brent E.

2012-05-01

29

Electrokinetics Enhanced Delivery of Nano-scale Zero Valent Iron  

NASA Astrophysics Data System (ADS)

Nano-scale zero valent iron (NZVI) has shown promising results for remediation of a wide range of chlorinated hydrocarbons in the subsurface. Although rapid aggregation and subsequent sedimentation limit bare NZVI migration in subsurface systems, surface modifications have improved the colloidal stability of NZVI, enhancing NZVI migration through porous media in lab-scale experiments. However, delivery of NZVI through low permeability soil is still an unresolved challenge. Electrokinetics (EK) has been used extensively in low permeability porous media for the remediation of a variety of hazardous wastes and in particular heavy metals. Since NZVI has a net negative surface charge electrokinetics has been proposed to enhance NZVI transport in the subsurface. However, increased dissolved oxygen and lower pH, due to electrolysis of water at the anode, oxidizes Fe0 particles to Fe2+/Fe3+ and thus affects the remediation potential. This study focuses on minimization of NZVI oxidation and quantification of NZVI migration enhancement due to the EK application. Application of 50 and 100 mA currents delivered 6.0 and 4.8 times more NZVI through coarse sand, respectively, when compared to no EK application. This ratio increased to 21 and 31 at 50 and 100 mA currents when finer sand was used. In addition, a numerical model based on traditional colloidal filtration theory (CFT) fit the experimental results well.

Chowdhury, A. I.; O'Carroll, D. M.; Xu, Y.; Sleep, B. E.

2010-12-01

30

Antimicrobial and Genotoxicity Effects of Zero-valent Iron Nanoparticles  

PubMed Central

Background: In a world of nanotechnology, the first concern is the potential environmental impact of nanoparticles. An efficient way to estimate nanotoxicity is to monitor the responses of bacteria exposed to these particles. Objectives: The current study explored the antimicrobial properties of nZVI (zero-valent Iron nanoparticles) on the Gram-negative bacterial systems Erwinia amylovora, Xanthomonas oryzae and the Gram-positive bacterial systems Bacillus cereus and Streptomyces spp. The genotoxicity potential of nZVI was also assayed. Materials and Methods: The toxicity of nZVI was tested by two different methods: Growing bacteria in liquid (broth dilution) and agar media (challenge test) containing different nZVI concentrations for 24-72 hours. The genotoxicity of nZVI was assessed using the preincubation version of the Ames test. Results: The lowest concentrations of nZVI that inhibited the visible growth (MIC) of E. amylovora, X. oryzae, B. cereus and Streptomyces spp. were 625, 550, 1250 and 1280 ppm, respectively. The minimum bactericidal concentration (MBC) for E. amylovora and X. oryzae were 10,000 and 5,000 ppm of nZVI, respectively. MBC was not observed for the Gram positive bacteria. No bacteriostatic and bactericidal effects were observed for oxidized nZVI. Mutant frequency did not increase according to the vehicle control at the concentrations assayed, indicating a lack of mutagenicity associated with nZVI. Conclusions: nZVI nanoparticles are not mutagenic at low concentrations, therefore they can be used without detrimental effects on soil bacteria. PMID:25147712

Barzan, Elham; Mehrabian, Sedigheh; Irian, Saeed

2014-01-01

31

Can zero-valent iron nanoparticles remove waterborne estrogens?  

PubMed

Steroidal estrogens are one of the most challenging classes of hazardous contaminants as they can cause adverse effects to biota in extremely low concentrations. They emerge in both waste waters and surface waters serving as a source of drinking water. Environmental Quality Standards for 17?-estradiol (E2) and 17?-ethinylestradiol (EE2), promulgated within the EU Water Framework Directive, are 0.4 and 0.035ngL(-1), respectively. Because nanoscale zero-valent iron (nZVI) particles have been previously used in numerous remediation technologies and have the advantage of possible magnetic separation, interaction of nZVI with E2 and EE2 in water was investigated to assess the potential role of nZVI in removing steroidal estrogens. A mixture of E2 and EE2 dissolved in water was shaken with varying doses of nZVI for 1-5h. Concentration-dependent removal of the estrogens was observed but removal did not increase significantly with time. Concentrations of the estrogens were determined by HPLC/MS/MS and a biodetection reporter gene assay. Sorption and nonspecific oxygen-mediated oxidation of estrogens were identified as the most probable removal mechanisms. Two independent experiments confirmed that significant decrease of estrogens concentration is achieved when at least 2gL(-1) of nZVI is applied. The presented study provides insights into the mechanisms of nZVI interaction with steroidal estrogens under aerobic conditions prevailing in currently applied water treatment technologies. PMID:25567735

Jaroov, Barbora; Filip, Jan; Hilscherov, Klra; Tu?ek, Ji?; imek, Zden?k; Giesy, John P; Zbo?il, Radek; Blha, Lud?k

2015-03-01

32

Mobility and Deposition of pre-Synthesis Stabilized Nano-scale Zero Valent Iron in Long Column Experiments  

NASA Astrophysics Data System (ADS)

Reactive zero-valent iron is currently being used for remediation of contaminated groundwater. Permeable reactive barriers are the current state-of-the-art method for using zero-valent iron. Instead of an excavated trench filled with granular zero-valent iron, a relatively new and promising method is the injection of a nano -scale zero-valent iron colloid suspension (nZVI) into the subsurface using injection wells. One goal of nZVI injection can be to deposit the iron in the aquifer and form a reactive permeable zone which is no longer bound to limited depths and plume treatment, but can also be used for source zone remediation. A good understanding of the transport behavior of nZVI is necessary to design a field application. So far transport was mainly tested using commercially available nZVI, however these studies suggest that further work is required as commercial nZVI was prone to aggregation, resulting in low physical stability of the suspension and very short travel distances in the subsurface. In the presented work, nZVI is stabilized during synthesis to significantly increase the physical suspension stability. To improve our understanding of nZVI transport, the feasibility for injection into various types of porous media and controlled nZVI deposition, a suite of column experiments are conducted. The column experiments are performed using a long 1.5m column and a novel nZVI measuring technique. The measuring technique was developed to non-destructively determine the concentration of nano-scale iron during the injection. It records the magnetic susceptibility, which makes it possible to get transient nZVI retention profiles along the column. These transient nZVI retention profiles of long columns provide unique insights in the transport behavior of nZVI which cannot be obtained using short columns or effluent breakthrough curves.

de Boer, C. V.; O'Carroll, D. M.; Sleep, B. E.

2013-12-01

33

EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON  

EPA Science Inventory

The reduction rates of trichloroethylene (TCE) using zero-valent iron (ZVI) and the rates of iron hydrolysis were characterized at pH values of 5 to 10. The reduction of TCE by ZVI was carried out in batch reactors filled with pH-buffered (phosphate based) solutions under anaerob...

34

HIGH-LEVEL ARSENITE REMOVAL FROM GROUNDWATER BY ZERO-VALENT IRON  

EPA Science Inventory

The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the st...

35

FIELD EVALUATION OF THE TREATMENT OF DNAPL USING EMULSIFIED ZERO-VALENT IRON (BATTELLE PRESENTATION)  

EPA Science Inventory

A pilot scale field demonstration of dense non-aqueous phase liquids (DNAPL) treatment using emulsified zero-valent iron (EZVI) is being conducted at Parris Island Marine Corps Recruit Depot (MCRD), Parris Island SC. The EZVI technology was developed at the University of Central ...

36

FIELD EVALUATION OF THE TREATMENT OF DNAPL USING EMULSIFIED ZERO-VALENT IRON (Battelle Conference)  

EPA Science Inventory

A pilot scale field demonstration of dense non-aqueous phase liquids (DNAPL) treatment using emulsified zero-valent iron (EZVI) was conducted at Parris Island Marine Corps Recruit Depot (MCRD), Parris Island, SC. The EZVI technology was developed at the University of Central Fl...

37

FIELD EVALUATION OF THE TREATMENT OF DNAPL USING EMULSIFIED ZERO-VALENT IRON (DNAPL CONFERENCE)  

EPA Science Inventory

A pilot scale field demonstration of dense non-aqueous phase liquids (DNAPL) treatment using emulsified zero-valent iron (EZVI) is being conducted at Parris Island Marine Corps Recruit Depot (MCRD), Parris Island SC. The demonstration is being conducted by Geosyntec, the Nationa...

38

FIELD EVALUATION OF THE TREATMENT OF DNAPL USING EMULSIFIED ZERO-VALENT IRON  

EPA Science Inventory

A pilot scale field demonstration of dense non-aqueous phase liquids (DNAPL) treatment using emulsified zero-valent iron (EZVI) is being conducted at Parris Island Marine Corps Recruit Depot (MCRD), Parris Island SC. The demonstration is being conducted by Geosyntec, the Nationa...

39

LABORATORY EVALUATION OF ZERO-VALENT IRON TO TREAT WATER IMPACTED BY ACID MINE DRAINAGE  

EPA Science Inventory

This study examines the applicability and limitations of granular zero-valent iron for the treatment of water impacted by mine wastes. Rates of acid neutralization and of metal (Cu, Cd, Ni, Zn, Hg, Al, and Mn) and metalloid (As) uptake were determined in batch systems using simu...

40

Inorganic Contaminant Fate Assessment in Zero-Valent Iron Treatment Walls  

Microsoft Academic Search

This article discusses the fate assessment of several inorganic contaminants in zero-valent iron treatment walls used for the cleanup of acidic plumes and the prevention of groundwater contamination in active or abandoned mixed sulphide and coal mining sites. The fate assessment of contaminants provides useful information for potential forensics investigations carried out in affected mining and waste disposal sites. Laboratory

Kostas Komnitsas; Georgios Bartzas; Ioannis Paspaliaris

2006-01-01

41

Advanced treatment of coking wastewater by coagulation and zero-valent iron processes  

Microsoft Academic Search

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal

Peng Lai; Hua-zhang Zhao; Chao Wang; Jin-ren Ni

2007-01-01

42

ZERO VALENT IRON AND PYRITE SYSTEM USED TO DE-CHLORINATE TOXAPHENE-CONTAMINATED SOILS  

EPA Science Inventory

The project consisted of a preliminary laboratory study; an outdoor bench scale study and an in situ field Pilot Study to which the zero valent iron and pyrite system (ZVI system) was applied. Several beakers were filled with contaminated soil, the ZVI system and a solvent then...

43

Chemical Reduction of PCE by Zero Valent Iron Colloids Batch and Column Experiments  

E-print Network

of degradation potential of nZVI particles in column tests: experimental simulation of plume vs. source/l · Significant increase of pH after Ca(OH)2 injection · nZVI-reinjection induced recovery of PCE-degradation of the art for plume treatment · Injectable nano-scaled zero valent iron particles (nZVI) have potential

Cirpka, Olaf Arie

44

Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions  

SciTech Connect

Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO{sub 3} and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO{sub 3} as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD analysis. Electrical measurements revealed decreases in conductivity and polarization of both columns, suggesting that electrically insulating CaCO{sub 3} dominates the electrical response despite the presence of electrically conductive iron oxides. SEM/EDX imaging suggests that the electrical signal reflects the geometrical arrangement of the mineral phases. CaCO{sub 3} forms insulating films on ZVI/magnetite surfaces, restricting charge transfer between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions via charge transfer, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss due to CaCO{sub 3} precipitation. Comparison between laboratory and field data shows consistent changes in electrical signatures due to iron corrosion and secondary mineral precipitation.

Wu, Yuxin; Versteeg, R.; Slater, L.; LaBrecque, D.

2009-06-01

45

Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions.  

PubMed

Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO(3) and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO(3) as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD analysis. Electrical measurements revealed decreases in conductivity and polarization of both columns, suggesting that electrically insulating CaCO(3) dominates the electrical response despite the presence of electrically conductive iron oxides. SEM/EDX imaging suggests that the electrical signal reflects the geometrical arrangement of the mineral phases. CaCO(3) forms insulating films on ZVI/magnetite surfaces, restricting charge transfer between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions via charge transfer, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss due to CaCO(3) precipitation. Comparison between laboratory and field data shows consistent changes in electrical signatures due to iron corrosion and secondary mineral precipitation. PMID:19342119

Wu, Yuxin; Versteeg, Roelof; Slater, Lee; LaBrecque, Douglas

2009-05-12

46

Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions  

NASA Astrophysics Data System (ADS)

Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO 3 and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO 3 as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD analysis. Electrical measurements revealed decreases in conductivity and polarization of both columns, suggesting that electrically insulating CaCO 3 dominates the electrical response despite the presence of electrically conductive iron oxides. SEM/EDX imaging suggests that the electrical signal reflects the geometrical arrangement of the mineral phases. CaCO 3 forms insulating films on ZVI/magnetite surfaces, restricting charge transfer between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions via charge transfer, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss due to CaCO 3 precipitation. Comparison between laboratory and field data shows consistent changes in electrical signatures due to iron corrosion and secondary mineral precipitation.

Wu, Yuxin; Versteeg, Roelof; Slater, Lee; LaBrecque, Douglas

2009-05-01

47

Zero Valent Iron: Impact of Anions Present during Synthesis on Subsequent Nanoparticle Reactivity  

SciTech Connect

Zero-valent iron particles are an effective remediation technology for groundwater contaminated with halogenated organic compounds. In particular, nano-scale zero-valent iron is a promising material for remediation due to its high specific surface area, which results in faster rate constants and more effective use of the iron. An aspect of iron nanoparticle reactivity that has not been explored is the impact of anions present during iron metal nanoparticle synthesis. Solutions containing chloride, phosphate, sulfate, and nitrate anions and ferric ions were used to generate iron oxide nanoparticles. The resulting materials were dialyzed to remove dissolved byproducts and then dried and reduced by hydrogen gas at high temperature. The reactivity of the resulting zero valent iron nanoparticles was quantified by monitoring the kinetics as well as products of carbon tetrachloride reduction, and significant differences in reactivity and chloroform yield were observed. The reactivity of nanoparticles prepared in the presence of sulfate and phosphate demonstrated the highest reactivity and chloroform yield. Furthermore, substantial variations in the solid-state products of oxidation (magnetite, iron sulfide, and goethite, among others) were also observed.

Moore, Kirsten; Forsberg, Brady; Baer, Donald R.; Arnold, William A.; Penn, R. Lee

2011-10-01

48

Zero-valent iron pretreatment for enhancing the biodegradability of RDX  

Microsoft Academic Search

Hexahydro-1,3,5-trinitro-1,3,5-triazine (C3H6N3(NO2)3, royal demolition explosive or RDX) is a common nitramine explosive and one of the major constituents in wastewaters from ammunitions plants. The objective of this study is to investigate zero-valent iron (Fe(0)) pretreatment for enhancing the biodegradability of recalcitrant RDX. It was hypothesized that iron pretreatment can reductively transform RDX to products that are more amenable to biological

Seok-Young Oh; Pei C. Chiu; Byung J. Kim; Daniel K. Cha

2005-01-01

49

Reductive precipitation of uranium(VI) by zero-valent iron  

Microsoft Academic Search

This study was undertaken to determine the effectiveness of zero-valent iron (Fe°) and several adsorbent materials in removing uranium (U) from contaminated groundwater and to investigate the rates and mechanisms that are involved in the reactions. Fe° filings were used as reductants, and the adsorbents included peat materials, iron oxides, and a carbon-based sorbent (Cercona Bone-Char). Results indicate that Fe°

B. Gu; M. J. Dickey; X. Yin; S. Dai; L. Liang

1998-01-01

50

Electrochemically fabricated zero-valent iron, iron-nickel, and iron-palladium nanowires for environmental remediation applications  

Microsoft Academic Search

Monodisperse crystalline zero-valent iron, iron-nickel, iron-palladium nanowires were synthesised using template-directed electrodeposition methods. Prior to nanowire fabrication, alumina nanotemplates with controlled pore structure (e.g. pore diameter and porosity) were fabricated by anodising high purity aluminium foil in sulphuric acid. After fabrication of alumina nanotemplates, iron, iron-nickel and iron- palladium nanowires were electrodeposited within the pore structure. The dimensions of nanowires

B.-Y. Yoo; S. C. Hernandez; B. Koo; Y. Rheem; N. V. Myung

2007-01-01

51

Toxicity of Nano-Zero Valent Iron to Freshwater and Marine Organisms  

PubMed Central

We tested whether three commercial forms (uncoated, organic coating, and iron oxide coating) of nano zero-valent iron (nZVI) are toxic to freshwater and marine organisms, specifically three species of marine phytoplankton, one species of freshwater phytoplankton, and a freshwater zooplankton species (Daphnia magna), because these organisms may be exposed downstream of where nZVI is applied to remediate polluted soil. The aggregation and reactivity of the three types of nZVI varied considerably, which was reflected in their toxicity. Since levels of Fe2+ and Fe3+ increase as the nZVI react, we also evaluated their toxicity independently. All four phytoplankton species displayed decreasing population growth rates, and Daphnia magna showed increasing mortality, in response to increasing levels of nZVI, and to a lesser degree with increasing Fe2+ and Fe3+. All forms of nZVI aggregated in soil and water, especially in the presence of a high concentration of calcium ions in groundwater, thus reducing their transports through the environment. However, uncoated nZVI aggregated extremely rapidly, thus vastly reducing the probability of environmental transport and potential for toxicity. This information can be used to design a risk management strategy to arrest the transport of injected nZVI beyond the intended remediation area, by injecting inert calcium salts as a barrier to transport. PMID:22952836

Keller, Arturo A.; Garner, Kendra; Miller, Robert J.; Lenihan, Hunter S.

2012-01-01

52

The use of zero-valent iron for groundwater remediation and wastewater treatment: a review.  

PubMed

Recent industrial and urban activities have led to elevated concentrations of a wide range of contaminants in groundwater and wastewater, which affect the health of millions of people worldwide. In recent years, the use of zero-valent iron (ZVI) for the treatment of toxic contaminants in groundwater and wastewater has received wide attention and encouraging treatment efficiencies have been documented. This paper gives an overview of the recent advances of ZVI and progress obtained during the groundwater remediation and wastewater treatment utilizing ZVI (including nanoscale zero-valent iron (nZVI)) for the removal of: (a) chlorinated organic compounds, (b) nitroaromatic compounds, (c) arsenic, (d) heavy metals, (e) nitrate, (f) dyes, and (g) phenol. Reaction mechanisms and removal efficiencies were studied and evaluated. It was found that ZVI materials with wide availability have appreciable removal efficiency for several types of contaminants. Concerning ZVI for future research, some suggestions are proposed and conclusions have been drawn. PMID:24457611

Fu, Fenglian; Dionysiou, Dionysios D; Liu, Hong

2014-02-28

53

Performance of a field-scale permeable reactive barrier based on organic substrate and zero-valent iron for in situ remediation of acid mine drainage.  

PubMed

A permeable reactive barrier (PRB) was installed in Aznalcllar (Spain) in order to rehabilitate the Agrio aquifer groundwater severely contaminated with acid mine drainage after a serious mining accident. The filling material of the PRB consisted of a mixture of calcite, vegetal compost and, locally, Fe(0) and sewage sludge. Among the successes of the PRB are the continuous neutralisation of pH and the removal of metals from groundwater within the PRB (removals of >95%). Among the shortcomings are the improper PRB design due to the complexity of the internal structure of the Agrio alluvial deposits (which resulted in an inefficient capture of the contaminated plume), the poor degradability of the compost used and the short residence time within the PRB (which hindered a complete sulphate reduction), the clogging of a section of the PRB and the heterogeneities of the filling material (which resulted in preferential flows within the PRB). Undoubtedly, it is only through accumulated experience at field-scale systems that the potentials and limits of the PRB technology can be determined. PMID:23361181

Gibert, Oriol; Cortina, Jos Luis; de Pablo, Joan; Ayora, Carlos

2013-11-01

54

REDUCTION AND IMMOBILIZATION OF RADIONUCLIDES AND TOXIC METAL IONS USING COMBINED ZERO VALENT IRON AND ANAEROBIC BACTERIA  

EPA Science Inventory

Large groundwater plumes contaminated with toxic metal ions, including radionuclides, exist at several DOE facilities. Previous research indicated that both zero valent iron and sulfate reducing bacteria can yield significant decreases in concentrations of redox sensitive metals ...

55

EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON  

EPA Science Inventory

The surface normalized reaction rate constants (ksa) of trichloroethylene (TCE) and zero-valent iron (ZVI) was quantified in batch reactors at pH values between 1.7 and 10. The ksa of TCE linearly decreased from 0.044 to 0.009 L/hr-m2 between pH 3.8 and 8.0, whereas the ksa at pH...

56

Effect of Zero-Valent Iron Application on Cadmium Uptake in Rice Plants Grown in Cadmium-Contaminated Soils  

Microsoft Academic Search

Cadmium (Cd) contamination in soils is a serious problem for crop production in the world. Zero-valent iron [Fe (0)] is a reactive material with reducing power capable of stabilizing toxic elements in a solution. In the present study, we examined the effect of zero-valent iron [Fe (0)] application on Cd accumulation in rice plants growing in Cd-contaminated paddy soils. The

Toshihiro Watanabe; Yasutoshi Murata; Takashi Nakamura; Yuki Sakai; Mitsuru Osaki

2009-01-01

57

Zero-valent Iron Emplacement in Permeable Porous Media Using Polymer Additions  

SciTech Connect

At the Hanford Site in Washington, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. One possible cause for premature chromate breakthrough is associated with the presence of high-permeability zones in the aquifer. The potential emplacement of zero-valent iron (Fe0) into high-permeability Hanford sediments to enhance the barriers reductive capacity using shear-thinning fluids containing polymers was investigated in three-dimensional wedge-shaped aquifer models. Porous media were packed in the wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone between two low-permeability zones or a high-permeability channel surrounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments. The flow cell experiments indicated that iron concentration enhancements of at least 0.6% (w/w) could be obtained using moderate flow rates and injection of 30 pore volumes. The aqueous pressure increased by a maximum of 25 KPa during infiltration, but a decrease in permeability was not observed. Under optimal conditions, the 0.6% amended Fe0 concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced Fe (II) in the ISRM barrier.

Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A.; Vermeul, Vince R.

2007-02-15

58

Standardization of the reducing power of zero-valent iron using iodine.  

PubMed

Because iron-based materials that are used for the permeable reactive barrier systems come in various shapes, sizes, and with various surface properties depending on the manufacturing sources, their reductive powers vary in a wide spectrum. A new experimental procedure to evaluate the reductive power of iron material was developed in this study. Tri-iodide (I3(-)) was used as the representative oxidizing agent that reacts with zero-valent iron (ZVI). Three iron-based materials (two scraps, two powders) and four chlorinated chemicals [perchloroethene (PCE), trichloroethene (TCE), 1,1,1-trichloroethane (TCA), and pentachlorophenol (PCP)] were used in this study. Redox reactions were conducted in glass vials containing aqueous solutions of chlorinated compounds or tri-iodide with known masses of iron material. After a predetermined reaction time each vial was opened and the solution was analyzed for the concentration of reduced compound. The apparent rate contant (k(i)(obs)) of iodine reduction reaction with ZVIs was found to be proportional to that (k(c)(obs)) of chlorinated contaminant. The surface area-normalized reduction rate constants (k(c)(nor)) for contaminants and tri-iodide (k(i)(nor)) were also proportional to each other. The ratio of rate constants, K(nor) (= k(c)(nor)/k(i)(nor)) was estimated for each contaminant; 3.29 10(-7), 5.86 10(-7), 6.70 10(-7), and 7.87 10(-10) M, for PCE, TCE, TCA, and PCP, respectively. The results of this study suggest that the reductive power of ZVI materials can be standardized using tri-iodide, and thus, can provide a good reference for the quantitative assessment of the reactivity of metallic reducing agents of environmental interest including ZVIs. PMID:24410682

Kim, Heonki; Yang, Haewon; Kim, Juyoung

2014-01-01

59

ZERO-VALENT IRON PRB APPLICATION EXPANDS TO ARSENIC REMOVAL  

EPA Science Inventory

The U.S. EPA Office of Research and Development?s National Risk Management Research Laboratory (NRMRL) and Region 8 have begun evaluating performance of a pilot-scale permeable reactive barrier (PRB) to treat arsenic-contaminated ground water at the ASARCO Superfund near Helena, ...

60

Remediating RDX-contaminated water and soil using zero-valent iron  

Microsoft Academic Search

Soil and water contaminated with RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) pose a serious threat to the environment and human health. The objective was to determine the potential for using zero-valent iron (Fe°) to remediate RDX-contaminated water and soil. Mixing an aqueous solution of 32 mg RDX L⁻¹ (spiked with ¹⁴C-labeled RDX) with 10 g Fe° L⁻¹ resulted in complete RDX destruction within 72

J. Singh; S. D. Comfort; P. J. Shea

1998-01-01

61

Methods of preparation and modification of advanced zero-valent iron nanoparticles, their properties and application in water treatment technologies  

NASA Astrophysics Data System (ADS)

Zero-valent iron nanoparticles are commonly used in modern water treatment technologies. Compared to conventionally-used macroscopic iron or iron microparticles, the using of nanoparticles has the advantages given mainly by their generally large specific surface area (it drives their high reactivity and/or sorption capacity), small dimensions (it allows their migration e.g. in ground water), and particular physical and chemical properties. Following the applications of zero-valent iron particles in various pilot tests, there arose several critical suggestions for improvements of used nanomaterials and for development of new generation of reactive nanomaterials. In the presentation, the methods of zero-valent iron nanoparticles synthesis will be summarized with a special attention paid to the thermally-induced solid-state reaction allowing preparation of zero-valent iron nanoparticles in an industrial scale. Moreover, the method of thermal reduction of iron-oxide precursors enables to finely tune the critical parameters (mainly particle size and morphology, specific surface area, surface chemistry of nanoparticles etc.) of resulting zero-valet iron nanoparticles. The most important trends of advanced nanoparticles development will be discussed: (i) surface modification of nanomaterilas, (ii) development of nanocomposites and (iii) development of materials for combined reductive-sorption technologies. Laboratory testing of zero-valent iron nanoparticles reactivity and migration will be presented and compared with the field observations: the advanced zero-valent iron nanoparticles were used for groundwater treatment at the locality contaminated by chlorinated hydrocarbons (VC, DCE, TCE and PCE) and reacted nanoparticles were extracted from the sediments for their fate assessment. The authors gratefully acknowledge the support by the Technology Agency of the Czech Republic "Competence Centres" (project No. TE01020218) and the EU FP7 (project NANOREM).

Filip, Jan; Kalk, Josef; Med?k, Ivo; Petala, Eleni; Zbo?il, Radek; Slunsk, Jan; ?ernk, Miroslav; Stav?lov, Monika

2014-05-01

62

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs  

NASA Technical Reports Server (NTRS)

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2006-01-01

63

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS  

NASA Technical Reports Server (NTRS)

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water. The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Geiger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2003-01-01

64

Sulfur-Modified Zero-Valent Iron for Remediation Applications at DOE Sites - 13600  

SciTech Connect

Many DOE remediation sites have chemicals of concern that are compounds in higher oxidation states, which make them both more mobile and more toxic. The chemical reduction of these compounds both prevents the migration of these chemicals and in some cases reduces the toxicity. It has also been shown that zero-valent iron is a very effective substance to use in reducing oxygenated compounds in various treatment processes. These have included the treatment of halogenated hydrocarbons in the form volatile organic compounds used as solvents and pesticides. Zero-valent iron has also been used to reduce various oxidized metals such as chromium, arsenic, and mercury in order to immobilize them, decrease their toxicity, and prevent further transport. In addition, it has been used to immobilize or break down other non-metallic species such as selenium compounds and nitrates. Of particular interest at several DOE remediation sites is the fact that zero-valent iron is very effective in immobilizing several radioactive metals which are mobile in their oxidized states. These include both technetium and uranium. The main difficulty in using zero-valent iron has been its tendency to become inactive after relatively short periods of time. While it is advantageous to have the zero-valent iron particles as porous as possible in order to provide maximum surface area for reactions to take place, these pores can become clogged when the iron is oxidized. This is due to the fact that ferric oxide has a greater volume for a given mass than metallic iron. When the surfaces of the iron particles oxidize to ferric oxide, the pores become narrower and will eventually shut. In order to minimize the degradation of the chemical activity of the iron due to this process, a modification of zero-valent iron has been developed which prevents or slows this process, which decreases its effectiveness. It is called sulfur-modified iron, and it has been produced in high purity for applications in municipal water treatment applications. Sulfur-modified iron has been found to not only be an extremely economical treatment technology for municipal water supplies, where very large quantities of water must be treated economically, but it has also been demonstrated to immobilize technetium. It has the added benefit of eliminating several other harmful chemicals in water supplies. These include arsenic and selenium. In one large-scale evaluation study an integrated system implemented chemical reduction of nitrate with sulfur-modified iron followed by filtration for arsenic removal. The sulfur-modified iron that was used was an iron-based granular medium that has been commercially developed for the removal of nitrate, co-contaminants including uranium, vanadium and chromium, and other compounds from water. The independent study concluded that 'It is foreseen that the greatest benefit of this technology (sulfur-modified iron) is that it does not produce a costly brine stream as do the currently accepted nitrate removal technologies of ion exchange and reverse osmosis. This investigation confirmed that nitrate reduction via sulfur-modified iron is independent of the hydraulic loading rate. Future sulfur-modified iron treatment systems can be designed without restriction of the reactor vessel dimensions. Future vessels can be adapted to existing site constraints without being limited to height-to-width ratios that would exist if nitrate reduction were to depend on hydraulic loading rate'. Sulfur-modified iron was studied by the Pacific Northwest National Laboratory (PNNL) for its effectiveness in the reduction and permanent sequestration of technetium. The testing was done using Hanford Site groundwater together with sediment. The report stated, 'Under reducing conditions, TcO{sub 4} is readily reduced to TcIV, which forms highly insoluble oxides such at TcO{sub 2}.nH{sub 2}O. However, (re)oxidation of TcIV oxides can lead to remobilization. Under sulfidogenic conditions, most TcIV will be reduced and immobilized as Tc{sub 2}S{sub 7}, which is less readily re-mobilized, ev

Fogwell, Thomas W. [Fogwell Consulting, P.O. Box 20221, Piedmont, CA 94620 (United States)] [Fogwell Consulting, P.O. Box 20221, Piedmont, CA 94620 (United States); Santina, Pete [SMI-PS, Inc., 2073 Prado Vista, Lincoln, CA 95648 (United States)] [SMI-PS, Inc., 2073 Prado Vista, Lincoln, CA 95648 (United States)

2013-07-01

65

Remediating RDX-contaminated water and soil using zero-valent iron  

SciTech Connect

Soil and water contaminated with RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) pose a serious threat to the environment and human health. The objective was to determine the potential for using zero-valent iron (Fe{sup 0}) to remediate RDX-contaminated water and soil. Mixing an aqueous solution of 32 mg RDX L{sup {minus}1} (spiked with {sup 14}C-labeled RDX) with 10 g Fe{sup 0} L{sup {minus}1} resulted in complete RDX destruction within 72 h. Nitroso derivatives of RDX accounted for approximately 26% of the RDX transformed during the first 24 h; these intermediates disappeared within 96 h ad the remaining {sup 14}C products were water soluble and not strongly sorbed by iron surfaces. When RDX-contaminated soil was treated with a single amendment of Fe{sup 0} in a static soil microcosm, more than 60% of the initial {sup 14}C-RDX was recovered as {sup 14}CO{sub 2} after 112 d. Treating surface and subsurface soils containing 3,600 mg RDX kg{sup {minus}1} with 50 g Fe{sup 0} kg{sup {minus}1} at a constant soil water content resulted in a 52% reduction in extractable RDX following 12 mo of static incubation. A second Fe{sup 0} addition at 12 mo further reduced the initial extractable RDX by 71% after 15 mo. These results support the use of zero-valent iron for in situ remediation of RDX-contaminated soil.

Singh, J.; Comfort, S.D.; Shea, P.J. [Univ. of Nebraska, Lincoln, NE (United States)

1998-09-01

66

Demonstration of combined zero-valent iron and electrical resistance heating for in situ trichloroethene remediation.  

PubMed

The effectiveness of in situ treatment using zero-valent iron (ZVI) for nonaqueous phase or significant sediment-associated contaminant mass can be limited by relatively low rates of mass transfer to bring contaminants in contact with the reactive media. For a field test in a trichloroethene (TCE) source area, combining moderate-temperature subsurface electrical resistance heating with in situ ZVI treatment was shown to accelerate TCE treatment by a factor of about 4 based on organic daughter products and a factor about 8 based on chloride concentrations. A mass-discharge-based analysis was used to evaluate reaction, dissolution, and volatilization processes at ambient groundwater temperature (~10 C) and as temperature was increased up to about 50 C. Increased reaction and contaminant dissolution were observed with increased temperature, but vapor- or aqueous-phase migration of TCE out of the treatment zone was minimal during the test because reactions maintained low aqueous-phase TCE concentrations. PMID:21591672

Truex, M J; Macbeth, T W; Vermeul, V R; Fritz, B G; Mendoza, D P; Mackley, R D; Wietsma, T W; Sandberg, G; Powell, T; Powers, J; Pitre, E; Michalsen, M; Ballock-Dixon, S J; Zhong, L; Oostrom, M

2011-06-15

67

Remediation of a nonachloro biphenyl congener with zero-valent iron in subcritical water.  

PubMed

Dechlorination of a nonachloro biphenyl congener with zero-valent iron in water under high temperature and pressure was investigated over time. Temperature has the main influence on the speed of dechlorination. Determination of polychlorinated biphenyls (PCBs) according to the grade of chlorination was performed by gas chromatography with mass selective detection in single ion monitoring mode. Dechlorination results in a variety of lower chlorinated biphenyls. The level of chlorination decreases with time. The amount of PCB molecules decreases to one-third within 90 min at 250 degrees C and 100 atm. However, no increase of biphenyl could be detected over time. A first-order kinetic model fitted the data obtained. PMID:11256641

Hinz, D C; Wai, C M; Wenclawiak, B W

2000-02-01

68

Injection of Zero Valent Iron into an Unconfined Aquifer Using Shear-Thinning Fluids  

SciTech Connect

Approximately 190 kg of two micron-diameter zero-valent iron (ZVI) particles were injected into a test zone in the top two meters of an unconfined aquifer within a trichloroethene (TCE) source area. A shear-thinning fluid was used to enhance ZVI delivery in the subsurface to a radial distance of up to four meters from a single injection well. The ZVI particles were mixed in-line with the injection water, shear-thinning fluid, and a low concentration of surfactant. ZVI was observed at each of the seven monitoring wells within the targeted radius of influence during injection. Additionally, all wells within the targeted zone showed low TCE concentrations and primarily dechlorination products present 44 days after injection. These results suggest that ZVI can be directly injected into an aquifer with shear-thinning fluids and extends the applicability of ZVI to situations where other emplacement methods may not be viable.

Truex, Michael J.; Vermeul, Vincent R.; Mendoza, Donaldo P.; Fritz, Brad G.; Mackley, Rob D.; Oostrom, Martinus; Wietsma, Thomas W.; Macbeth, Tamzen

2011-02-18

69

Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron  

NASA Technical Reports Server (NTRS)

This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nano-scale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, non-aqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (V005) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.

Quinn, Jacqueline; Geiger, Cherie; Clausen, Chris; Brooks, Kathleen; Coon, Christina; O'Hara, Suzanne; Krug, Thomas; Major, David; Yoon, Sam; Gavaskar, Arun; Holdsworth, Thomas

2004-01-01

70

Field demonstration of DNAPL dehalogenation using emulsified zero-valent iron  

NASA Technical Reports Server (NTRS)

This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.

Quinn, Jacqueline; Geiger, Cherie; Clausen, Chris; Brooks, Kathleen; Coon, Christina; O'Hara, Suzanne; Krug, Thomas; Major, David; Yoon, Woong-Sang; Gavaskar, Arun; Holdsworth, Thomas

2005-01-01

71

Field demonstration of DNAPL dehalogenation using emulsified zero-valent iron.  

PubMed

This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion. PMID:15787371

Quinn, Jacqueline; Geiger, Cherie; Clausen, Chris; Brooks, Kathleen; Coon, Christina; O'Hara, Suzanne; Krug, Thomas; Major, David; Yoon, Woong-Sang; Gavaskar, Arun; Holdsworth, Thomas

2005-03-01

72

Removal of As from groundwater by in situ bioprecipitation and zero-valent iron.  

PubMed

The aim of this study was to evaluate the in situ bioprecipitation (ISBP) and zero-valent iron (ZVI) for removal of arsenic from groundwater. Batch experiments were set up to test the metal/oxyanion removal efficiency using the processes induced by ZVI, by ISBP and by combining both technologies. For the construction of microcosms in anaerobic condition, aquifer material was mixed with synthetic groundwater in serum bottles. Solutions that contained commercial iron (powder, filings), iron from foundry (chips) and lactate with the carbon concentration of 0.02% (w/v) were amended. After 57 days the pH increased to 7.9 in the microcosm with lactate + iron chips. In the microcosms amended with lactate + commercial iron (powder and filings), pH was between 6.9 and 7.5 The highest decrease in sulfate concentrations was observed in the microcosm supplied with lactate (from 1,976 to 630 mg/L), and with lactate + iron filings (from 1,985 to 1,280 mg/L). The results showed that ISBP and ZVI can be efficient in the removal of As from groundwater; however, it strongly depends on the type and particle size of ZVI. The most effective was commercial ZVI. The highest decrease in As concentration was observed in the microcosm supplied with ethanol and iron powder (from 4,832 to 131 ?g/L). PMID:24225108

Tkaczynska, A

2013-01-01

73

Bioinhibitory effect of hydrogenotrophic bacteria on nitrate reduction by nanoscale zero-valent iron.  

PubMed

Hydrogenotrophic bacteria (HTB) were introduced into a nitrate removal system, which used nanoscale zero-valent iron (nZVI) as reductant, to investigate its bioinhibitory effect. Based on the results, it was noted that addition of HTB culture (10-50 mL) led to 58.9-91.4% decrease in the first observed rate constant (kobs1), which represented the nitrate removal rate by nZVI, and a reduction in the generated poisonous by-products from 94.9% to 38.5%. In other words, HTB had a significant inhibitory effect on nitrate reduction by nZVI. However, the pathway of this bioinhibition only prevented the occurrence of chemical reduction, but not competition for nitrate. Furthermore, FeOOH coating was observed on the surface of nZVI, instead of Fe3O4 or Fe2O3, which could prevent electron transmission from nZVI to nitrate. Considering that FeOOH was the product of iron corrosion, the result indicated that HTB could inhibit chemical reduction by enhancing the reaction between nZVI and water. PMID:24331034

An, Yi; Dong, Qi; Zhang, Keqiang

2014-05-01

74

Enhanced paramagnetic Cu(2+) ions removal by coupling a weak magnetic field with zero valent iron.  

PubMed

A weak magnetic field (WMF) was proposed to enhance paramagnetic Cu(2+) ions removal by zero valent iron (ZVI). The rate constants of Cu(2+) removal by ZVI with WMF at pH 3.0-6.0 were -10.8 to -383.7 fold greater than those without WMF. XRD and XPS analyses revealed that applying a WMF enhanced both the Cu(2+) adsorption to the ZVI surface and the transformation of Cu(2+) to Cu(0) by ZVI. The enhanced Cu(2+) sequestration by ZVI with WMF was accompanied with expedited ZVI corrosion and solution ORP drop. The uneven distribution of paramagnetic Cu(2+) along an iron wire in an inhomogeneous MF verified that the magnetic field gradient force would accelerate the paramagnetic Cu(2+) transportation toward the ZVI surface due to the WMF-induced sharp decay of magnetic flux intensity from ZVI surface to bulk Cu(2+) solution. The paramagnetic Fe(2+) ions generated by ZVI corrosion would also accumulate at the position with the highest magnetic flux intensity on the ZVI surface, causing uneven distribution of Fe(2+), and facilitate the local galvanic corrosion of ZVI, and thus, Cu(2+) reduction by ZVI. The electrochemical analysis verified that the accelerated ZVI corrosion in the presence of WMF partly arose from the Lorentz force-enhanced mass transfer. PMID:25464332

Jiang, Xiao; Qiao, Junlian; Lo, Irene M C; Wang, Lei; Guan, Xiaohong; Lu, Zhanpeng; Zhou, Gongming; Xu, Chunhua

2015-02-11

75

Continuous phosphorus removal from water by physicochemical method using zero valent iron packed column.  

PubMed

Excessive phosphorus in aquatic systems causes algal bloom resulting in eutrophication. To treat wastewater including effluent of wastewater treatment plant containing various amounts of phosphorus, a series of continuous experiments on removal of phosphorus from water were performed by using an electrochemical method. The spherical type of zero valent iron (ZVI) and silica sand were packed at appropriate volume ratio of 1:2 in a cylindrical column. An electric potential was applied externally, which can be changed as per the operational requirement. The results indicate that optimum hydraulic retention time of 36 min was required to meet the effluent standards with our laboratory-scale experimental setup. Lower amounts of phosphorus were removed by precipitation due to contact with iron, and additional electric potential was not required. In order to remove high amounts of phosphorus (around 150 mg/L as phosphate), external electric potential of 600 V was applied to the reactor. As the precipitation of phosphate mainly occurs at neutral pH, it is likely that FeHPO4 will be the main phosphorus-containing compound. Through the results of the large-scale experiments, the ZVI packed reactor can be used as a filter for removal of phosphorus of less than 10 mg/L as phosphate concentration. PMID:25225938

Jeong, Joo-Young; Ahn, Byoung-Min; Kim, Yu-Jin; Park, Joo-Yang

2014-01-01

76

ARSENATE AND ARSENITE REMOVAL BY ZERO-VALENT IRON: EFFECTS OF PHOSPHATE, SILICATE, CARBONATE, BORATE, SULFATE, CHROMATE, MOLYBDATE, AND NITRATE, RELATIVE TO CHLORIDE: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-ADA-01667 Su, C., and Puls*, R.W. Arsenate and Arsenite Removal by Zero-Valent Iron: Effects of Phosphate, Silicate, Carbonate, Borate, Sulfate, Chromate, Molybdate, and Nitrate, Relative to C...

77

Enhancement of electrokinetic remediation of hyper-Cr(VI) contaminated clay by zero-valent iron.  

PubMed

This paper investigated the effectiveness of incorporating zero-valent iron (ZVI) into electrokinetic (EK) to remediate hyper-Cr(VI) contaminated clay (2497 mg/kg). A ZVI wall was installed in the center of the soil specimen and was filled with 1:1 (w/w) ratio of granular ZVI and sand. Results show that transport of H(+) is greatly retarded by the strong opposite migration of anionic chromate ions, whereupon a revered electroosmosis flow (EO) was resulted and alkaline zone across the specimen was developed promoting the release of Cr(VI) from the clay. Chromium removal was characterized by high Cr(VI) concentration occurred in the anolyte and the presence of Cr(III) precipitates in the catholyte. The Cr(VI) reduction efficiencies for the process without ZVI wall were 68.1 and 79.2% for 1 and 2V/cm, respectively. As ZVI wall was installed, the corresponding reduction efficiencies increased to 85.8 and 92.5%. The costs for energy and ZVI utilized in this process are US$ 41.0 and 57.5 per cubic meter for the system with electric gradient of 1 and 2V/cm, respectively. The role of ZVI wall effectively reducing Cr(VI) contamination and the operation simultaneous collection of Cr(VI) from the electrode reservoirs are two major advantages of this process. PMID:17485164

Weng, Chih-Huang; Lin, Yao-Tung; Lin, T Y; Kao, C M

2007-10-22

78

Degradation of carbon tetrachloride in the presence of zero-valent iron.  

SciTech Connect

Efforts to achieve the decomposition of carbon tetrachloride through anaerobic and aerobic bioremediation and chemical transformation have met with limited success because of the conditions required and the formation of hazardous intermediates. Recently, particles of zero-valent iron (ZVI) have been used with limited success for in situ remediation of carbon tetrachloride. We studied a modified microparticulate product that combines controlled-release carbon with ZVI for stimulation of in situ chemical reduction of persistent organic compounds in groundwater. With this product, a number of physical, chemical, and microbiological processes were combined to create very strongly reducing conditions that stimulate rapid, complete dechlorination of organic solvents. In principle, the organic component of ZVI microparticles is nutrient rich and hydrophilic and has high surface area capable of supporting the growth of bacteria in the groundwater environment. In our experiments, we found that as the bacteria grew, oxygen was consumed, and the redox potential decreased to values reaching -600 mV. The small modified ZVI particles provide substantial reactive surface area that, in these conditions, directly stimulates chemical dechlorination and cleanup of the contaminated area without accumulation of undesirable breakdown products. The objective of this work was to evaluate the effectiveness of ZVI microparticles in reducing carbon tetrachloride under laboratory and field conditions. Changes in concentrations and in chemical and physical parameters were monitored to determine the role of the organic products in the reductive dechlorination reaction. Laboratory and field studies are presented.

Alvarado, J. S.; Rose, C.; LaFreniere, L.; Environmental Science Division

2010-01-01

79

Zero-valent iron mediated degradation of ciprofloxacin - assessment of adsorption, operational parameters and degradation products.  

PubMed

The zero-valent iron (ZVI) mediated degradation of the antibiotic ciprofloxacin (CIP) was studied under oxic condition. Operational parameters such as ZVI concentration and initial pH value were evaluated. Increase of the ZVI concentration from 1 to 5gL(-1) resulted in a sharp increase of the observed pseudo-first order rate constant of CIP degradation, reaching a plateau at around 10 g L(-1). The contribution of adsorption to the overall removal of CIP and dissolved organic carbon (DOC) was evaluated after a procedure of acidification to pH 2.5 with sulfuric acid and sonication for 2 min. Adsorption increased as pH increased, while degradation decreased, showing that adsorption is not important for degradation. Contribution of adsorption was much more important for DOC removal than for CIP. Degradation of CIP resulted in partial defluorination since the fluoride measured corresponded to 34% of the theoretical value after 120 min of reaction. Analysis by liquid chromatography coupled to mass spectrometry showed the presence of products of hydroxylation on both piperazine and quinolonic rings generating fluorinated and defluorinated compounds as well as a product of the piperazine ring cleavage. PMID:25150686

Perini, Joo Angelo de Lima; Silva, Bianca Ferreira; Nogueira, Raquel F Pupo

2014-12-01

80

-encapsulated zero-valent iron nanoparticles for degradation of organic dyes  

NASA Astrophysics Data System (ADS)

A series of nanocomposites consisting of zero-valent iron nanoparticles (ZVI NPs) encapsulated in SiO2 microspheres were successfully synthesized through a successive two-step method, i.e., the wet chemical reduction by borohydride followed by a modified Stber method. The as-synthesized nanocomposites were characterized using X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer, and inductively coupled plasma-atomic emission spectrometer. The catalytic performance of SiO2-encapsulated ZVI nanocomposites for the degradation of organic dyes was investigated using methylene blue (MB) as the model dye in the presence of H2O2. The results showed that the degradation efficiency and apparent rate constant of the degradation reaction were significantly enhanced with increased ZVI NPs encapsulated in SiO2 microspheres, whereas the dosage of H2O2 remarkably promoted degradation rate without affecting degradation efficiency. The content-dependent magnetic property ensured the excellent magnetic separation of degradation products under an external magnet. This strategy for the synthesis of SiO2-encapsulated ZVI NPs nanocomposites was low cost and easy to scale-up for industrial production, thereby enabling promising applications in environmental remediation.

Mao, Zhou; Wu, Qingzhi; Wang, Min; Yang, Yushi; Long, Jia; Chen, Xiaohui

2014-09-01

81

Potential environmental implications of nanoscale zero-valent iron particles for environmental remediation  

PubMed Central

Objectives Nanoscale zero-valent iron (nZVI) particles are widely used in the field of various environmental contaminant remediation. Although the potential benefits of nZVI are considerable, there is a distinct need to identify any potential risks after environmental exposure. In this respect, we review recent studies on the environmental applications and implications of nZVI, highlighting research gaps and suggesting future research directions. Methods Environmental application of nZVI is briefly summarized, focusing on its unique properties. Ecotoxicity of nZVI is reviewed according to type of organism, including bacteria, terrestrial organisms, and aquatic organisms. The environmental fate and transport of nZVI are also summarized with regards to exposure scenarios. Finally, the current limitations of risk determination are thoroughly provided. Results The ecotoxicity of nZVI depends on the composition, concentration, size and surface properties of the nanoparticles and the experimental method used, including the species investigated. In addition, the environmental fate and transport of nZVI appear to be complex and depend on the exposure duration and the exposure conditions. To date, field-scale data are limited and only short-term studies using simple exposure methods have been conducted. Conclusions In this regard, the primary focus of future study should be on 1) the development of an appropriate and valid testing method of the environmental fate and ecotoxicity of reactive nanoparticles used in environmental applications and 2) assessing their potential environmental risks using in situ field scale applications. PMID:25518840

Jang, Min-Hee; Lim, Myunghee; Hwang, Yu Sik

2014-01-01

82

Demonstration of Combined Zero-Valent Iron and Electrical Resistance Heating for In Situ Trichloroethene Remediation  

SciTech Connect

The effectiveness of in situ treatment using zero-valent iron to remediate sites with non-aqueous phase or significant sediment-associated contaminant mass can be limited by relatively low rates of mass transfer to bring contaminants in contact with the reactive media. For a field test in a trichloroethene source area, combining moderate-temperature (maximum 50oC) subsurface electrical resistance heating with in situ ZVI treatment was shown to accelerate dechlorination and dissolution rates by a factor of 4 to 6 based on organic daughter products and a factor 8-16 using a chloride concentrations. A mass-discharge-based analysis was used to evaluate reaction, dissolution, and volatilization at ambient groundwater temperature (~10oC) and as temperature was increased up to about 50oC. Increased reaction and contaminant dissolution were observed with increased temperature, but volatilization was minimal during the test because in situ reactions maintained low aqueous-phase TCE concentrations.

Truex, Michael J.; Macbeth, Tamzen; Vermeul, Vincent R.; Fritz, Brad G.; Mendoza, Donaldo P.; Mackley, Rob D.; Wietsma, Thomas W.; Sandberg, Greg; Powell, Thomas; Powers, Jeff; Pitre, Emile; Michalsen, Mandy M.; Ballock-Dixon, Sage; Zhong, Lirong; Oostrom, Martinus

2011-06-27

83

Reduction and immobilization of chromate in chromite ore processing residue with nanoscale zero-valent iron.  

PubMed

Chromite ore processing residue (COPR) poses a great environmental and health risk with persistent Cr(VI) leaching. To reduce Cr(VI) and subsequently immobilize in the solid matrix, COPR was incubated with nanoscale zero-valent iron (nZVI) and the Cr(VI) speciation and leachability were studied. Multiple complementary analysis methods including leaching tests, X-ray powder diffraction, X-ray absorption near edge structure (XANES) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to investigate the immobilization mechanism. Geochemical PHREEQC model calculation agreed well with our acid neutralizing capacity experimental results and confirmed that when pH was lowered from 11.7 to 7.0, leachate Cr(VI) concentrations were in the range 358-445mgL(-1) which contributed over 90% of dissolved Cr from COPR. Results of alkaline digestion, XANES, and XPS demonstrated that incubation COPR with nZVI under water content higher than 27% could result in a nearly complete Cr(VI) reduction in solids and less than 0.1mgL(-1) Cr(VI) in the TCLP leachate. The results indicated that remediation approaches using nZVI to reduce Cr(VI) in COPR should be successful with sufficient water content to facilitate electron transfer from nZVI to COPR. PMID:22417394

Du, Jingjing; Lu, Jinsuo; Wu, Qiong; Jing, Chuanyong

2012-05-15

84

Immobilization of chromate in hyperalkaline waste streams by green rusts and zero-valent iron.  

PubMed

Zero-valent iron (ZVI) and green rusts can be used as reductants to convert chromium from soluble, highly toxic Cr(VI) to insoluble Cr(III). This study compared the reduction rates of Cr(VI) by ZVI and two carbonate green rust phases in alkaline/hyperalkaline solutions. Batch experiments were carried out with synthetic chromate solutions at pH 7.7-12.3 and a chromite ore processing residue (COPR) leachate (pH approximately 12.2). Green rust removes chromate from high pH solutions (pH 10-12.5) very rapidly (<400 s). Chromate reduction rates for both green rust phases were consistently higher than for ZVI throughout the pH range studied; the surface area normalized rate constants were two orders of magnitude higher in the COPR leachate solution at pH 12.2. The performances of both green rusts were unaffected by changes in pH. In contrast, ZVI exhibited a marked decline in reduction rate with increasing pH to become almost ineffective above pH12. PMID:24600891

Rogers, Christine M; Burke, Ian T; Ahmed, Imad A M; Shaw, Samuel

2014-01-01

85

Enhanced chromium (VI) removal using activated carbon modified by zero valent iron and silver bimetallic nanoparticles.  

PubMed

Recently, adsorption process has been introduced as a favorable and effective technique for the removal of metal ions from aqueous solutions. In the present study, bimetallic nanoparticles consisting of zero valent iron and silver were loaded on the activated carbon powder for the preparation of a new adsorbent (PAC-Fe(o)/Ag). The above adsorbent was characterized by using XRD, SEM and TEM techniqes. Experimental data were exploited for kinetic, equilibrium and thermodynamic evaluations related to the adsorption processes. The Cr(VI) adsorption process was found to be favorable at pH3 and it reached equilibrium state within 60min. The stirring rate did not have a significant effect on the adsorption efficiency. Furthermore, the monolayer adsorption capacity of Cr(VI) based on the Langmuir model was measured to be 100mg/g. The experimental equilibrium data were fitted to the Freundlich adsorption and pseudo second-order models. According to the thermodynamic study, the adsorption process was spontaneous and endothermic in nature, indicating the adsorption capacity increases with increasing the temperature. The results also revealed that the synthesized composite can be potentially applied as a magnetic adsorbent to remove Cr(VI) contaminants from aqueous solutions. PMID:25184050

Kakavandi, Babak; Kalantary, Roshanak Rezaei; Farzadkia, Mahdi; Mahvi, Amir Hossein; Esrafili, Ali; Azari, Ali; Yari, Ahmad Reza; Javid, Allah Bakhsh

2014-01-01

86

Zero valent iron reduces toxicity and concentrations of organophosphate pesticides in contaminated groundwater.  

PubMed

The potential of zero valent iron (ZVI) for remediation of contaminated groundwater from an abandoned chemical disposal site was examined through batch and column experiments. The key contaminants were organophosphate pesticides but the chemical analysis also comprised additional 22 compounds including synthesis intermediates and degradation products of organophosphates. The ZVI treatment showed that all the contaminants were degraded with the exception of two diesters (phosphorothioates). The most rapid reduction was found for methyl parathion, ethyl parathion and malathion, which had first-order degradation rate constants on the order of 10(-3) min(-1). In the study, acute toxicity towards freshwater crustaceans (Daphnia magna) was included to evaluate the overall efficiency of ZVI treatment of the complex mixture. The acute toxicity tests with D. magna showed that the untreated groundwater was highly toxic. Thus, 50% of the daphnids were unable to swim upon 24h exposure to groundwater diluted 770 times. ZVI facilitated degradation resulted in a complete toxicity removal for the first four pore volumes, where after a three times dilution caused 50% inhibition of the mobility of the daphnids. The rapid degradation of the highly toxic organophosphates combined with the significant decrease in the ecotoxicological potential shows a promising potential for site remediation of organophosphates with ZVI technologies. PMID:23021613

Fjordbge, Annika S; Baun, Anders; Vastrup, Troels; Kjeldsen, Peter

2013-01-01

87

Weak magnetic field significantly enhances selenite removal kinetics by zero valent iron.  

PubMed

The effect of weak magnetic field (WMF) on Se(IV) removal by zero valent iron (ZVI) was investigated as functions of pH and initial Se(IV) concentrations. The presence of WMF significantly accelerated Se(IV) removal and extended the working pH range of ZVI from 4.0-6.0 to 4.0-7.2. The WMF induced greater enhancement in Se(IV) removal by ZVI at lower initial Se(IV) concentrations. The influence of WMF on Se(IV) removal by ZVI was associated with a more dramatic drop in ORP and a more rapid release of Fe(2+) compared to the case without WMF. SEM and XRD analysis revealed that WMF accelerated the corrosion of ZVI and the transformation of amorphous iron (hdyr)oxides to lepidocrocite. XANES analyses showed that WMF expedited the reduction of Se(IV) to Se(0) by ZVI at pH 6.0 when its initial concentration was ?20.0mgL(-1). Se(IV) dosed at 40.0mgL(-1) was removed by ZVI via adsorption followed by reduction to Se(0) at pH 7.0 but via adsorption at 7.2 in the presence of WMF. Regardless of WMF, Se(IV) applied at 40.0mgL(-1) was removed by reduction at pH 4.0-6.0. The WMF-induced improvement in Se(IV) removal by ZVI may be mainly attributable to the Lorentz force and magnetic field gradient force. Employing WMF to enhance Se(IV) removal by ZVI is a promising and environmental-friendly method since it does not need extra energy and costly reagents. PMID:24199999

Liang, Liping; Sun, Wu; Guan, Xiaohong; Huang, Yuying; Choi, Wonyong; Bao, Hongliang; Li, Lina; Jiang, Zheng

2014-02-01

88

Influence of zero-valent iron nanoparticles on nitrate removal by Paracoccus sp.  

PubMed

Nitrate contamination in drinking water is a major threat to public health. This study investigated the efficiency of denitrification of aqueous solutions in the co-presence of synthesized nanoscale zero-valent iron (nZVI; diameter: 20-80 nm) and a previously isolated Paracoccus sp. strain YF1. Various influencing factors were studied, such as oxygen, pH, temperature, and anaerobic corrosion products (Fe(2+), Fe(3+) and Fe3O4). With slight toxicity to the strain, nZVI promoted denitrification efficiency by providing additional electron sources under aerobic conditions. For example, 50 mg L(-1) nZVI increased the nitrate removal efficiency from 66.9% to 85.2%. However, a high concentration of nZVI could lead to increased production of Fe(2+), a toxic ion which could compromise the removal efficiency. Kinetic studies suggest that denitrification by both free cells, and nZVI-amended cells fitted well to the zero-order model. Temperature and pH are the major factors affecting nitrate removal and cell growth, with or without the presence of nZVI. In this study, nitrate removal and cell growth increased in the pH range of 6.5-8.0, and temperature range of 25-35 C. These conditions favor the growth of the strain, which dominated denitrification in all scenarios involved. As for anaerobic corrosion products, compared with Fe(2+) and Fe(3+), Fe3O4 promoted denitrification by serving as an electron donor. Finally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed attachments of nZVI on the surface of the cell, and the formation of iron oxides. This study indicated that, as an electron donor source with minimal cellular toxicity, nZVI could be used to promote denitrification efficiency under biotic conditions. PMID:24630453

Liu, Yan; Li, Shibin; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

2014-08-01

89

Foam-assisted delivery of nanoscale zero valent iron in porous media  

SciTech Connect

Foam is potentially a promising vehicle to deliver nanoparticles for vadose zone remediation as foam can overcome the intrinsic problems associated with solution-based delivery, such as preferential flow and contaminant mobilization. In this work, the feasibility of using foam to deliver nanoscale zero valent iron (nZVI) in unsaturated porous media was investigated. Foams generated using surfactant sodium lauryl ether sulfate (SLES) showed excellent ability to carry nZVI. SLES and nZVI concentrations in the foaming solutions did not affect the percentages of nZVI concentrations in foams relative to nZVI concentrations in the solutions. When foams carrying nZVI were injected through the unsaturated columns, the fractions of nZVI exiting the column were much higher than those when nZVI was injected in liquid. The enhanced nZVI transport implies that foam delivery could significantly increase the radius of influence of injected nZVI. The type and concentrations of surfactants and the influent nZVI concentrations did not noticeably affect nZVI transport during foam delivery. In contrast, nZVI retention increased considerably as the grain size of porous media decreased. Oxidation of foam-delivered nZVI due to oxygen diffusion into unsaturated porous media was visually examined using a flow cell. It was demonstrated that if foams are injected to cover a deep vadose zone layer, oxidation would only cause a small fraction of foam-delivered nZVI to be oxidized before it reacts with contaminants.

Ding, Yuanzhao; Liu, Bo; Shen, Xin; Zhong, Lirong; Li, Xiqing

2013-09-01

90

Degradation of decabromodiphenyl ether by nano zero-valent iron immobilized in mesoporous silica microspheres.  

PubMed

The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO(2)@FeOOH@Fe). The characteristics of SiO(2)@FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy, and Brunnaer-Emmett-Teller surface area analysis. The mean particle size of the reactive mesoporous silica microspheres was 450 nm, and its specific surface area was 383.477 m(2) g(-1). The degradation of dcabromodiphenyl ether (BDE209) was followed pseudo-first-order kinetics, and the observed reaction rate constant could be improved by increasing the SiO(2)@FeOOH@Fe dosage and by decreasing the initial BDE209 concentration. The stability and longevity of the immobilized Fe nanoparticles were evaluated by repeatedly renewing the BDE209 solution in the reactor. The stable degradation of BDE209 by SiO(2)@FeOOH@Fe was observed within 10 cycles. Agglomeration-resistance and magnetic separation of SiO(2)@FeOOH@Fe were also performed. The improved dispersion of SiO(2)@FeOOH@Fe in solution after one-month storage and its good performance in magnetic separation indicated that SiO(2)@FeOOH@Fe has the potential to be efficiently applied to environmental remediation. PMID:21802203

Qiu, Xinhong; Fang, Zhanqiang; Liang, Bin; Gu, Fenglong; Xu, Zhencheng

2011-10-15

91

Straining of polyelectrolyte-stabilized nanoscale zero valent iron particles during transport through granular porous media.  

PubMed

In this study, the relevance of straining of nano-sized particles of zero valent iron coated with carboxymethyl cellulose (CMC-NZVI) during transport in model subsurface porous media is assessed. Although deposition of polyelectrolyte stabilized-NZVI on granular subsurface media due to physicochemical attachment processes has been reported previously, there is limited knowledge on the significance of the collector (sand) diameter on the deposition and spatial distribution of the retention of such nanoparticles. Experiments were conducted to assess the transport of CMC-NZVI in columns packed with four different-sized sands of mean diameter of 775?m, 510?m, 250?m and 150?m and at three different particle concentrations of 0.085gL(-1), 0.35gL(-1) and 1.70gL(-1). CMC-NZVI effluent concentrations decreased with smaller sand diameters. High CMC-NZVI particle retention near the inlet, particularly for the finer sands was observed, even with a low ionic strength of 0.1mM for the electrolyte medium. These observations are consistent with particle retention in porous media due to straining and/or wedging. Two colloid transport models, one considering particle retention by physicochemical deposition and detachment of those deposited particles, and the other considering particle retention by straining along with particle deposition and detachment, were fitted to the experimental data. The model accounting for straining shows a better fit, especially to the CMC-NZVI retention data along the length of the column. The straining rate coefficients decreased with larger sand diameters. This study demonstrates that CMC-NZVI particles, despite of their small size (hydrodynamic diameters of 167-185nm and transmission electron microscopy imaged diameters of approximately 85nm), may be removed by straining during transport, especially through fine granular subsurface media. The tailing effect, observed in the particle breakthrough curves, is attributed to detachment of deposited particles. PMID:24361705

Raychoudhury, Trishikhi; Tufenkji, Nathalie; Ghoshal, Subhasis

2014-03-01

92

Mechanisms of NOx removal from flue gas by zero valent iron  

SciTech Connect

Chemical reaction between nitric oxide (NO) and zero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523- 773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contact time, NO was completely removed for temperature of 573-773 K but not for 523 K. Breakthrough curves were conducted for the five working temperatures, and the results indicated that NO reductions by ZVI were varied from 2 to 26.7 mg NO/g ZVI. Higher temperature and longer EBCT achieved better NO removal efficiency. X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Three layers of iron species were detected by XRD: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. ZVI was the most prevalent species, and Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} were less from the XRD analysis. By ESCA, the oxidation state on the reacted ZVI surface was determined, and the species was identified as Fe{sub 2}O{sub 3}, which is the most oxidizing species for iron. Therefore, three layers from the ZVI core to the ZVI surface can be identified: ZVI, Fe{sub 3}O{sub 4}, and Fe{sub 2}O{sub 3}. Combining the results from XRD and ESCA, the mechanisms for ZVI and NO can be proposed as two consecutive reactions from lower oxidation state (ZVI) in the core to higher oxidation state on the iron surface (Fe{sub 2}O{sub 3}). Because there was only {lt}5% ZVI used to remove NO comparing to theoretical ZVI used based on the proposed stoichiometry, it can be concluded that the heterogeneous reaction only occurred on the ZVI surface instead of on bulk of the ZVI. 11 refs., 8 figs., 3 tabs.

Shiao-Shing Chen; Chih-Yu Cheng; Jung-Chun Chang; Chih-Hui Tang [National Taipei University of Technology, Taipei (Taiwan). Institute of Environment Planning and Management

2006-06-15

93

Remediation of TCE-contaminated groundwater using zero valent iron and direct current: experimental results and electron competition model  

NASA Astrophysics Data System (ADS)

The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted to evaluate the effect of different arrangements of electrodes and ZVI barriers in the column on the TCE removal capacity (RC). In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved up to six times with simultaneous application of ZVI and DC compared to that using ZVI only. The most effective arrangement of electrode and ZVI for TCE removal was the column set with ZVI and a cathode installed at the down gradient. Based on the electrokinetic study for the column systems with only DC input, single acid front movement could explain different RCs. An enhanced dechlorination rate of TCE using E2PRB systems, compared to a conventional PRB system, was observed, and is considered to be attributed to more electron sources: (1) external DC, (2) electrolysis of water, (3) oxidation of ZVI, (4) oxidation of dissolved Fe2+, (5) oxidation of molecular hydrogen at the cathode, and (6) oxidation of Fe2+ in mineral precipitates. Each of these electron sources was evaluated for their potential influencing the TCE RC through the electron competition model and energy consumption. A strong correlation between the quantity of electrons generated, RC, and the energy-effectiveness was found.

Moon, Ji-Won; Moon, Hi-Soo; Kim, Heonki; Roh, Yul

2005-09-01

94

An Experimental Study of Micron-Size Zero-Valent Iron Emplacement in Permeable Porous Media Using Polymer-Enhanced Fluids  

SciTech Connect

At the Hanford Site, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. One possible cause for premature chromate breakthrough is associated with the presence of high-permeability zones in the aquifer. In these zones, groundwater moves relatively fast and is able to oxidize iron more rapidly. There is also a possibility that the high-permeability flow paths are deficient in reducing equivalents (e.g. reactive iron), required for barrier performance. One way enhancement of the current barrier reductive capacity can be achieved is by the addition of micron-scale zero-valent iron to the high-permeability zones within the aquifer. The potential emplacement of zero-valent iron (Fe0) into high-permeability Hanford sediments (Ringold Unit E gravels) using shear-thinning fluids containing polymers was investigated in three-dimensional wedge-shaped aquifer models. Polymers were used to create a suspension viscous enough to keep the Fe0 in solution for extended time periods to improve colloid movement into the porous media without causing a permanent detrimental decrease in hydraulic conductivity. Porous media were packed in the wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone in between two low-permeability zones or a high-permeability channel surrounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments.

Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A.; Vermeul, Vince R.

2005-12-22

95

Degradation of Perchloroethene by zero-valent iron evaluated by carbon isotope fractionation  

NASA Astrophysics Data System (ADS)

Perchloroethene (PCE) is a widely spread groundwater contaminant in formally used industrial sites. Zero valent iron (ZVI) is used for in situ chemical reduction (ISCR) of PCE contaminants in the groundwater. A key factor in the application of in situ remediation technologies is a proper monitoring of contaminant reduction. The measurement of the stable isotope ratio is a promising method that is already used for quantifying microbial degradation of chlorinated contaminants. The carbon isotope ratio of PCE, measured by - isotope ratio mass spectrometry coupled to a gas chromatograph via a combustion interface (GC-C-IRMS), increases during degradation of PCE and can be directly related to the degree of degradation. It can be used to directly quantify chemical degradation and thus serves as a useful monitoring tool for groundwater remediation. An experiment to determine the carbon isotopic fractionation factor was performed as a lab experiment using Nanofer Star (NANOIRON). Two different PCE concentrations (c1: 220mgL-1, c2: 110mgL-1) mixed with 0.5 g of ZVI were sealed under deoxygenated conditions in 250 ml glas bottles locked with mininert caps. The bottles were incubated on a shaker for 865 h. Samples were taken weekly to measure the change in the carbon isotopic ratio of PCE as well as its concentration. Results showed a strong increase in the carbon isotope ratio (?-value) of PCE (start: -27 o end: -4 ), which indicates a significant dechlorination process of PCE. Beside PCE also one degradation product (Trichloroethylene - TCE) was measured. TCE was further dechlorinated as indicated by the ?-value change of TCE from -26 o to -4 oȦn unexpected intermediate value of -45 o for TCE was observed in the experiment. This fluctuation could be induced by the time depending concentration due to degradation and conversation processes. Furthermore, it seems that the progress of the ?-value is affected by the starting concentration of PCE (?-value of c1 < c2) as there is a higher ratio of PCE to ZVI.

Leitner, Simon; Watzinger, Andrea; Reichenauer, Thomas G.

2014-05-01

96

Effectiveness of nanoscale zero-valent iron for treatment of a PCE-DNAPL source zone.  

PubMed

Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20-30 mesh Ottawa sand and PCE-DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3mM CaCl(2) at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200mg/L) and production of dissolved-phase ethene (10-30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE-DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE-DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE-DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.421/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE-DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products. PMID:20888664

Taghavy, Amir; Costanza, Jed; Pennell, Kurt D; Abriola, Linda M

2010-11-25

97

Conjunctive effect of CMC-zero-valent iron nanoparticles and FYM in the remediation of chromium-contaminated soils  

NASA Astrophysics Data System (ADS)

Chromium is an important industrial metal used in various products and processes but at the same time causing lethal environmental hazards. Remediation of Cr-contaminated soils poses both technological and economic challenges, as conventional methods are often too expensive and difficult to operate. Zero-valent iron particles at nanoscale are proposed to be one of the important reductants of Cr(VI), transforming the same into nontoxic Cr(III). In the present investigation, soils contaminated with Cr(VI) are allowed to react with the various loadings of zero-valent iron nanoparticles (Fe0) for a reaction period of 24 h. Fe0 nanoparticles were synthesized by the reduction of ferrous sulfate in the presence of sodium borohydride and stabilized with carboxy methyl cellulose and were characterized by scanning electron microscopy, energy dispersion spectroscopy, X-ray diffraction, UV-vis spectrophotometer, Fourier transform-infra red spectrophotometer, Raman spectroscopy, dynamic light scattering technique and zeta potential. Further, this work demonstrates the potential utilization of farm yard manure (FYM) and Fe0 nanoparticles in combination and individually for the effective remediation of Cr(VI)-contaminated soils. An increase in the reduction of Cr(VI) from 60 to 80 % was recorded with the increase in the loading of Fe0 nanoparticles from 0.1 to 0.3 mg/100 g individually and in combination with FYM ranging from 50 to 100 mg/100 g soil.

Madhavi, Vemula; Prasad, Tollamadugu Naga Venkata Krishna Vara; Reddy, Balam Ravindra; Reddy, Ambavaram Vijay Bhaskar; Gajulapalle, Madhavi

2013-04-01

98

Removal of heavy metals and dyes by supported nano zero-valent iron on barium ferrite microfibers.  

PubMed

The binary nano zero-valent iron/barium ferrite (NZVI/BFO) microfibers with uniform diameters and high porosity were prepared by the organic gel-thermal selective reduction process. The composite microfibers are fabricated from nano zero-valent iron and nano BaFe12O19 grains. The effects of pH, adsorbent dosage, and contact time on the adsorption of heavy metals and dyes have been investigated. The adsorption isotherms of heavy metals and dyes on the microfibers are well described by the Langmuir model, in which the estimated adsorption capacities are 14.5, 29.9, 68.3 and 110.4 mg/g for Pb(II), As(V), Congo red and methylene blue, respectively. After five cycles, these microfibers still exhibit a high removal efficiency for As(V), Pb(II), Congo red and methylene blue. The enhanced adsorption characteristics can be attributed to the porous structure, strong surface activity and electronic hopping. Therefore, the magnetic NZVI/BFO microfibers can be used as an efficient, fast and high capacity adsorbent for heavy metals and dyes removal. PMID:24758012

Yang, Xinchun; Shen, Xiangqian; Jing, Maoxiang; Liu, Ruijiang; Lu, Yi; Xiang, Jun

2014-07-01

99

Degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron.  

PubMed

The degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron (US-Fe(0))was investigated and an evident synergistic effect was observed. The synergetic effect is mainly due to the increase of ()OH radical concentration from Fenton's reaction. The ()OH radical concentrations in sole sonication and US-Fe(0) process were detected by using terephthalic acid as a fluorescent probe and found that ()OH radicals were generated continuously during sonication and the production of ()OH radicals in US-Fe(0) process was much higher than that in sole sonication. The degradation of direct sky blue 5B followed a pseudo-first-order kinetics and the degradation rate constants were found to be 0.0206 and 0.169 min(-1) with sole sonication and US-Fe(0) process respectively. It was also found that the degradation ratio of direct sky blue 5B increased with the increase of zero-valent iron dosage and decrease of pH value of the dye aqueous solution. The degradation mechanism of direct sky blue 5B with US-Fe(0) process was discussed by the changes of UV-Vis spectrogram of the dye during degradation. The dramatic changes of UV spectra showed a disappearance of both azo and aromatic groups during the degradation. PMID:21514206

Chen, Bing; Wang, Xikui; Wang, Chen; Jiang, Wenqiang; Li, Shuping

2011-09-01

100

Conjunctive effect of CMC-zero-valent iron nanoparticles and FYM in the remediation of chromium-contaminated soils  

NASA Astrophysics Data System (ADS)

Chromium is an important industrial metal used in various products and processes but at the same time causing lethal environmental hazards. Remediation of Cr-contaminated soils poses both technological and economic challenges, as conventional methods are often too expensive and difficult to operate. Zero-valent iron particles at nanoscale are proposed to be one of the important reductants of Cr(VI), transforming the same into nontoxic Cr(III). In the present investigation, soils contaminated with Cr(VI) are allowed to react with the various loadings of zero-valent iron nanoparticles (Fe0) for a reaction period of 24 h. Fe0 nanoparticles were synthesized by the reduction of ferrous sulfate in the presence of sodium borohydride and stabilized with carboxy methyl cellulose and were characterized by scanning electron microscopy, energy dispersion spectroscopy, X-ray diffraction, UV-vis spectrophotometer, Fourier transform-infra red spectrophotometer, Raman spectroscopy, dynamic light scattering technique and zeta potential. Further, this work demonstrates the potential utilization of farm yard manure (FYM) and Fe0 nanoparticles in combination and individually for the effective remediation of Cr(VI)-contaminated soils. An increase in the reduction of Cr(VI) from 60 to 80 % was recorded with the increase in the loading of Fe0 nanoparticles from 0.1 to 0.3 mg/100 g individually and in combination with FYM ranging from 50 to 100 mg/100 g soil.

Madhavi, Vemula; Prasad, Tollamadugu Naga Venkata Krishna Vara; Reddy, Balam Ravindra; Reddy, Ambavaram Vijay Bhaskar; Gajulapalle, Madhavi

2014-04-01

101

EFFECTS OF NATURAL ORGANIC MATTER, ANTHROPOGENIC SURFACTANTS, AND MODEL QUINONES ON THE REDUCTION OF CONTAMINANTS BY ZERO-VALENT IRON. (R827117)  

EPA Science Inventory

Recent studies of contaminant reduction by zero-valent iron metal (Fe0) have highlighted the role of iron oxides at the metalwater interface and the effect that sorption has at the oxidewater interface on contaminant reduction kinetics. The results s...

102

Micron-Size Zero-Valent Iron Emplacement in Porous Media Using Polymer Additives: Column and Flow Cell Ex-periments  

SciTech Connect

At the Hanford Site, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. Laboratory experiments have been conducted to investigate whether barrier reductive capacity can be enhanced by adding micron-scale zero-valent iron to the high-permeability zones within the aquifer using shear-thinning fluids containing polymers. Porous media were packed in a wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone between two low-permeability zones or a high-permeability channel sur-rounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments. The flow cell experiments indicated that iron concentration enhancements of at least 0.6% (w/w) could be obtained using moderate flow rates and injection of 30 pore volumes. The 0.6% amended Fe0 concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced iron in the ISRM barrier. Calculations show that a 1-m-long Fe0 amended zone with an average concentration of 0.6% w/w iron subject to a groundwater velocity of 1 m/day will have an estimated longevity of 7.2 years.

Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A.; Vermeul, Vince R.

2006-03-20

103

Capture and storage of hydrogen gas by zero-valent iron.  

PubMed

Granular Fe(o), used to reductively degrade a variety of contaminants in groundwater, corrodes in water to produce H2(g). A portion enters the Fe(o) lattice where it is stored in trapping sites such as lattice defects and microcracks. The balance is dissolved by the groundwater where it may exsolve as a gas if its solubility is exceeded. Gas exsolution can reduce the effectiveness of the Fe(o) treatment zone by reducing contact of the contaminant with iron surfaces or by diverting groundwater flow. It also represents a lost electron resource that otherwise could be involved in reductive degradation of contaminants. It is advantageous to select an iron for remediation purposes that captures a large proportion of the H2(g) it generates. This study examines various aspects of the H2(g) uptake process and has found 1) H2(g) does not have to be generated at the water/iron interface to enter the lattice. It can enter directly from the gas/water phases, 2) exposure of granular sponge iron to H2(g) reduces the dormant period for the onset of iron corrosion, 3) the large quantities of H2(g) generated by nano-Fe(o) injected into a reactive barrier of an appropriate granular iron can be captured in the lattice of that iron, and 4) lattice-bound hydrogen represents an additional electron resource to Fe(o) for remediation purposes and may be accessible using physical or chemical means. PMID:24389351

Reardon, Eric J

2014-02-01

104

Treatment of dissolved perchlorate, nitrate, and sulfate using zero-valent iron and organic carbon.  

PubMed

Waters containing ClO and dissolved NO, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO. Four column experiments, containing mixtures of silica sand, zero-valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO, SO and ClO. Initially, the flow rate was maintained at 0.5 pore volumes (PV) d and then decreased to 0.1 PV d after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L (NO-N) to trace levels through NO reduction to NH using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO reduction and denitrification. Up to 71% of input SO (24.5 3.5 mg L) was removed in the column containing OC, and >99.7% of the input ClO (857 63 ?g L) was removed by the OC- and (ZVI + OC)-containing columns as the flow rate was maintained at 0.1 PV d. Nitrate and ClO removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L (NO-N) inhibited ClO removal in the OC-containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO degradation within any of the columns. PMID:25602813

Liu, YingYing; Ptacek, Carol J; Blowes, David W

2014-05-01

105

Generation of Oxidants From the Reaction of Nanoparticulate Zero-Valent Iron and Oxygen for the use in Contaminant Remediation  

NASA Astrophysics Data System (ADS)

The reaction of zero-valent iron (ZVI) with oxygen can lead to the formation of oxidants, which may be used to transform recalcitrant contaminants including non-polar organics and certain metals. Nanoparticulate iron might provide a practical mechanism of remediating oxygen-containing groundwater and contaminated soil. To gain insight into the reaction mechanism and to quantify the yield of oxidants, experiments were performed with model organic compounds in the presence of nanoparticulate zero-valent iron and oxygen. At pH values below 5, ZVI nanoparticles were oxidized within 30 minutes with a stoichiometry of approximately two Fe0 oxidized per O2 consumed. Using the oxidation of methanol and ethanol to formaldehyde and acetaldehyde, respectively, we found that less than 2% of the consumed oxygen was converted to reactive oxidants under acidic conditions. The yield of aldehydes increased with pH up to pH 7, with maximum oxidant yields of around 5% relative to the mass of ZVI added. The increase of aldehyde yield with pH was attributable to changes in the processes responsible for oxidant production. At pH values below 5, the corrosion of ZVI by oxygen produces hydrogen peroxide, which subsequently reacts with ferrous iron [Fe(II)] via the Fenton reaction. At higher pH values, the aldehydes are produced when Fe(II), the initial product of ZVI oxidation, reacts with oxygen. The decrease in oxidant yield at pH values above 7 may be attributable to precipitation of Fe(II). The oxidation of benzoic acid and 2-propanol to para-hydroxybenzoic acid and acetone, respectively, followed a very different trend compared to the primary alcohols. In both cases, the highest product yields (approximately 2% with respect to ZVI added) were observed at pH 3. Yields decreased with increasing pH, with no oxidized product detected at neutral pH. These results suggest that two different oxidants may be produced by the system: hydroxyl radical (OH-) at acidic pH and a more selective oxidant such as the ferryl ion [Fe(IV)] at neutral pH. This provides insight into the type of compounds that may be oxidized using the zero-valent iron and oxygen system. The addition of certain compounds such as oxalate and polyoxometalate (POM) may improve contaminant remediation efficiencies by enhancing oxidant yields. The introduction of 1 mM oxalate improved the formaldehyde yield by approximately 20% at neutral pH. Oxalate accelerates the Fenton reaction and limits the passivation of the ZVI surface by increasing iron solubility. The presence of excess POM greatly enhanced the yield of formaldehyde, with maximum yields of 60 and 35% with respect to ZVI added at pH 2 and 7, respectively. The mechanism of POM enhancement is a function of solution pH. At acidic pH, POM acts an electron shuttle by directly transferring electrons from ZVI to oxygen to increase the hydrogen peroxide production. At neutral pH, POM may act by forming soluble iron-complexes and preventing the build-up of an iron oxide layer on the ZVI surface.

Keenan, C. R.; Lee, C.; Sedlak, D. L.

2007-12-01

106

Zero Valent Iron Significantly Enhances Methane Production from Waste Activated Sludge by Improving Biochemical Methane Potential Rather Than Hydrolysis Rate  

PubMed Central

Anaerobic digestion has been widely applied for waste activated sludge (WAS) treatment. However, methane production from anaerobic digestion of WAS is usually limited by the slow hydrolysis rate and/or poor biochemical methane potential of WAS. This work systematically studied the effects of three different types of zero valent iron (i.e., iron powder, clean scrap and rusty scrap) on methane production from WAS in anaerobic digestion, by using both experimental and mathematical approaches. The results demonstrated that both the clean and the rusty iron scrap were more effective than the iron powder for improving methane production from WAS. Model-based analysis showed that ZVI addition significantly enhanced methane production from WAS through improving the biochemical methane potential of WAS rather than its hydrolysis rate. Economic analysis indicated that the ZVI-based technology for enhancing methane production from WAS is economically attractive, particularly considering that iron scrap can be freely acquired from industrial waste. Based on these results, the ZVI-based anaerobic digestion process of this work could be easily integrated with the conventional chemical phosphorus removal process in wastewater treatment plant to form a cost-effective and environment-friendly approach, enabling maximum resource recovery/reuse while achieving enhanced methane production in wastewater treatment system. PMID:25652244

Liu, Yiwen; Wang, Qilin; Zhang, Yaobin; Ni, Bing-Jie

2015-01-01

107

Zero valent iron significantly enhances methane production from waste activated sludge by improving biochemical methane potential rather than hydrolysis rate.  

PubMed

Anaerobic digestion has been widely applied for waste activated sludge (WAS) treatment. However, methane production from anaerobic digestion of WAS is usually limited by the slow hydrolysis rate and/or poor biochemical methane potential of WAS. This work systematically studied the effects of three different types of zero valent iron (i.e., iron powder, clean scrap and rusty scrap) on methane production from WAS in anaerobic digestion, by using both experimental and mathematical approaches. The results demonstrated that both the clean and the rusty iron scrap were more effective than the iron powder for improving methane production from WAS. Model-based analysis showed that ZVI addition significantly enhanced methane production from WAS through improving the biochemical methane potential of WAS rather than its hydrolysis rate. Economic analysis indicated that the ZVI-based technology for enhancing methane production from WAS is economically attractive, particularly considering that iron scrap can be freely acquired from industrial waste. Based on these results, the ZVI-based anaerobic digestion process of this work could be easily integrated with the conventional chemical phosphorus removal process in wastewater treatment plant to form a cost-effective and environment-friendly approach, enabling maximum resource recovery/reuse while achieving enhanced methane production in wastewater treatment system. PMID:25652244

Liu, Yiwen; Wang, Qilin; Zhang, Yaobin; Ni, Bing-Jie

2015-01-01

108

Comparisons of the reactivity, reusability and stability of four different zero-valent iron-based nanoparticles.  

PubMed

Our previous reports showed that nano zero-valent iron (nZVI), steel pickle liquor for the synthesis of nZVI (S-nZVI), nZVI immobilised in mesoporous silica microspheres (SiO2@FeOOH@Fe) and nano Ni/Fe bimetallic particles (Ni/Fe) have been proved to show good property for elimination of polybrominated diphenyl ethers (PBDEs). However, it is necessary to compare their reactivity, reusability and stability when applied to in situ remediation. In this study, the performances of different iron-based nanoparticles were compared through reusability, sedimentation and iron dissolution experiments. The SiO2@FeOOH@Fe and Ni/Fe nanoparticles were shown to have higher reusability and stability, as they could be reused more than seven times, and that the SiO2@FeOOH@Fe can effectively avoid leaching iron ions into the solution and causing secondary pollution in the reaction. This study may serve as a reference for PBDE remediation in the future. PMID:24582360

Xie, Yingying; Fang, Zhanqiang; Qiu, Xinhong; Tsang, Eric Pokeung; Liang, Bin

2014-08-01

109

Application of Zero-Valent Iron Nanoparticles for the Removal of Aqueous Zinc Ions under Various Experimental Conditions  

PubMed Central

Application of zero-valent iron nanoparticles (nZVI) for Zn2+ removal and its mechanism were discussed. It demonstrated that the uptake of Zn2+ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn2+ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn2+ removal by nZVI. The DO enhanced the removal efficiency of Zn2+. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn2+ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn2+ by nZVI because the existing H+ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn2+ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn2+ were higher than Cd2+. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn2+. PMID:24416439

Liang, Wen; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei

2014-01-01

110

Hexavalent chromium reduction in contaminated soil: A comparison between ferrous sulphate and nanoscale zero-valent iron.  

PubMed

Iron sulphate (FeSO4) and colloidal nano zero-valent iron (nZVI) as reducing agents were compared, with the aim of assessing their effectiveness in hexavalent chromium [Cr(VI)] removal from a contaminated industrial soil. Experiments were performed on soil samples collected from an industrial site where a nickel contamination, caused by a long-term productive activity, was also verified. The influence of reducing agents amount with respect to chromium content and the effectiveness of deoxygenation of the slurry were discussed. The soil was fully characterized before and after each test, and sequential extractions were performed to assess chemico-physical modifications and evaluate metals mobility induced by washing. Results show that both the reducing agents successfully lowered the amount of Cr(VI) in the soil below the threshold allowed by Italian Environmental Regulation for industrial reuse. Cr(VI) reduction by colloidal nZVI proved to be faster and more effective: the civil reuse of soil [Cr(VI)<2mg/kg] was only achieved using colloidal nZVI within 60min adopting a nZVI/Cr(VI) molar ratio of 30. The reducing treatment resulted in an increase in the amount of chromium in the oxide-hydroxide fraction, thus confirming a mechanism of chromium-iron hydroxides precipitation. In addition, a decrease of nickel (Ni) and lead (Pb) content in soil was also observed when acidic conditions were established. PMID:25139286

Di Palma, L; Gueye, M T; Petrucci, E

2015-01-01

111

Transformation and composition evolution of nanoscale zero valent iron (nZVI) synthesized by borohydride reduction in static water.  

PubMed

The reactivity of nanoscale zero valent iron (nZVI) toward targeted contaminants is affected by the initial nZVI composition and the iron oxides formed during the aging process in aquatic systems. In this paper, the aging effects of nZVI, prepared using a borohydride reduction method in static water over a period of 90days (d), are investigated. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy are used to characterize the corrosion products of nZVI. Results show that both the structures and the compositions of the corrosion products change with the process of aging. The products of nZVI aged for 5d in static water media are mainly magnetite (Fe3O4) and maghemite (?-Fe2O3), accompanied by lepidocrocite (?-FeOOH). For products aged 10d, XRD data show the formation of ferrihydrite and lepidocrocite. When aged up to 90d, the products are mainly ?-FeOOH mixed with small amounts of Fe3O4 and ?-Fe2O3. Transmission electronic microscopy (TEM) images show that the core-shell structure forms into a hollow spherical shape after 30d of aging in aquatic media. The results indicate first that iron ions in the Fe(0) core diffuse outwardly toward the shell, and hollowed-out iron oxide shells emerge. Then, the iron oxide shell collapses and becomes a flaky, acicular-shaped structure. The type and the crystal phase of second iron oxide minerals are vastly different at various aging times. This study helps to explain the patterns of occurrence of specific iron oxides in different natural conditions. PMID:25317915

Liu, Airong; Liu, Jing; Zhang, Wei-Xian

2015-01-01

112

Mechanism insights into enhanced trichloroethylene removal using xanthan gum-modified microscale zero-valent iron particles.  

PubMed

This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe(2+) concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the in-situ remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity. PMID:25556871

Xin, Jia; Han, Jun; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf

2015-03-01

113

Influences of nanoscale zero valent iron loadings and bicarbonate and calcium concentrations on hydrogen evolution in anaerobic column experiments.  

PubMed

The estimation of nanoscale zero-valent iron (nZVI) reactivity after its injection into the subsurface is essential for its application in groundwater remediation. In the present study H2 generation of commercially available nZVI and novel milled nZVI flakes were investigated in column experiments with varying nZVI loads (ranging from 8 to 43g nZVI per kg sand). H2 evolution rates were determined for column experiments without and with hydrogen carbonate and/or calcium. On average 0.29mmol H2/L per g Fe(0) evolved within the first 30 days in column experiments with spherical, commercial nZVI particles. The H2 evolution developed almost independently of the water matrices applied. The application of nZVI flakes resulted in lower H2 generation rates. In general corrosion rates accelerated linearly with increasing initial amounts of iron. This was evident in experiments with both particle types. Concentration profiles of carbonate and calcium in influent and effluent were used to estimate corrosion products and precipitates. Despite the presence of high concentrations of inorganic carbon, Fe(2+) reacted preferably with hydroxide ions to form ferrous hydroxide which is the precursor of magnetite. As a result only minor passivation of the reactive nZVI was observed. PMID:25462777

Paar, Hendrik; Ruhl, Aki Sebastian; Jekel, Martin

2014-11-01

114

Biodegradable surfactant stabilized nanoscale zero-valent iron for in situ treatment of vinyl chloride and 1,2-dichloroethane.  

PubMed

Nanoscale zero-valent iron (NZVI) stabilized with dispersants is a promising technology for the remediation of contaminated groundwater. In this study, we demonstrated the use of biodegradable surfactant stabilized NZVI slurry for successful treatment of vinyl chloride (VC) and 1,2-dichloroethane (1,2-DCA) in a contaminated site in Taiwan. The biodegradable surfactant stabilized NZVI was coated with palladium and synthesized on-site. From monitoring the iron concentration breakthrough and distribution, it was found that the stabilized NZVI is capable of transporting in the aquifer at the test plot (200 m(2)). VC was effectively degraded by NZVI while the 1,2-DCA degradation was relatively sluggish during the 3-month field test. Nevertheless, as 1,2-DCA is known to resist abiotic reduction by NZVI, the observation of 1,2-DCA degradation and hydrocarbon production suggested a bioremediation took place. ORP and pH results revealed that a reducing condition was achieved at the testing area facilitating the biodegradation of chlorinated organic hydrocarbons. The bioremediation may be attributed to the production of hydrogen gas as electron donor from the corrosion of NZVI in the presence of water or the added biodegradable surfactant serving as the carbon source as well as electron donor to stimulate microbial growth. PMID:22118849

Wei, Yu-Ting; Wu, Shian-chee; Yang, Shi-wei; Che, Choi-Hong; Lien, Hsing-Lung; Huang, De-Huang

2012-04-15

115

Oxidation of Orange G by persulfate activated by Fe(II), Fe(III) and zero valent iron (ZVI).  

PubMed

Persulfate (PS) was employed in the oxidation of Orange G (OG), an azo dye commonly found in textile wastewaters. Activation of PS was conducted with iron to generate sulfate free radicals (SO4(-)) with high redox potential capable to oxidize most of the organics in water. Identification of oxidation intermediates was carried out by analyzing at different times organic by-products generated from treatment of a concentrate dye solution (11.6 mM) with 153 mM of PS and 20 mM of Fe(II) at 20 C. Intermediate reaction products (mainly phenol (PH) and benzoquinone (BQ), and in less extent aniline, phenolic compounds and naphthalene type compounds with quinone groups) were identified by GC/MS and HPLC, and an oxidation pathway was proposed for the oxidation of OG with iron activated PS. The effect of iron valence (0, II and III) in the oxidation of an aqueous solution of OG (containing 0.1 mM) was studied in a 0.5 L batch reactor at 20 C. Initial activator and PS concentrations employed were both 1 mM. Complete pollutant removal was achieved within the first 30 min when iron II or III were employed as activators. Quinone intermediates generated during pollutant oxidation may act as electron shuttles, allowing the reduction of Fe(III) into Fe(II) in the redox cycling of iron. Therefore, activation of PS by Fe(III) allowed complete OG removal. When zero valent iron (ZVI) was employed (particle diameter size 0.74 mm) the limiting step in SO4(-) generation was the surface reaction between ZVI and the oxidant yielding a lower oxidation rate of the dye. An increase in the oxidant dosage (0.2 mM OG, 2 mM Fe(III) and 6 mM PS) allowed complete pollutant and ecotoxicity removal, as well as mineralization close to 75%. PMID:24439838

Rodriguez, S; Vasquez, L; Costa, D; Romero, A; Santos, A

2014-04-01

116

Effect of anions and humic acid on the performance of nanoscale zero-valent iron particles coated with polyacrylic acid.  

PubMed

Effects of anions (NO3(-), HCO3(-), Cl(-), SO4(2-)) and humic acid on the reactivity and core/shell chemistries of polyacrylic acid-coated nanoscale zero-valent iron (PAA-NZVI) and inorganically modified NZVI (INORG-NZVI) particles were investigated. The reactivity tests under various ion concentrations (0.2-30mN) revealed the existence of a favorable molar ratio of anion/NZVI that increased the reactivity of NZVI particles. The presence of a relatively small amount of humic acid (0.5mgL(-1)) substantially decreased the INORG-NZVI reactivity by 76%, whereas the reactivity of PAA-NZVI decreased only by 12%. The XRD and TEM results supported the role of the PAA coating of PAA-NZVI in impeding the oxidation of the Fe(0) core by groundwater solutes. This protective role provided by the organic coating also resulted in a 2.3-fold increase in the trichloroethylene (TCE) reduction capacity of PAA-NZVI compared to that of INORG-NZVI in the presence of anions/humic acid. Ethylene and ethane were simultaneously produced as the major reduction products of TCE in both NZVI systems, suggesting that a hydrodechlorination occurred without the aid of metallic catalysts. The PAA coating, originally designed to improve the mobility of NZVI, enhanced TCE degradation performances of NZVI in the presence of anions and humic acid. PMID:25065795

Kim, Hong-Seok; Ahn, Jun-Young; Kim, Cheolyong; Lee, Seockheon; Hwang, Inseong

2014-10-01

117

Evaluation of the effects of nanoscale zero-valent iron (nZVI) dispersants on intrinsic biodegradation of trichloroethylene (TCE).  

PubMed

In this study, the biodegradability of nanoscale zero-valent iron (nZVI) dispersants and their effects on the intrinsic biodegradation of trichloroethylene (TCE) were evaluated. Results of a microcosm study show that the biodegradability of three dispersants followed the sequence of: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A) > polyoxyethylene (20) sorbitan monolaurate (Tween 20) > polyacrylic acid (PAA) under aerobic conditions, and PV3A > Tween 20 > PAA under anaerobic conditions. Natural biodegradation of TCE was observed under both aerobic and anaerobic conditions. No significant effects were observed on the intrinsic biodegradation of TCE under aerobic conditions with the presence of the dispersants. The addition of PAA seemed to have a slightly adverse impact on anaerobic TCE biodegradation. Higher accumulation of the byproducts of anaerobic TCE biodegradation was detected with the addition of PV3A and Tween 20. The diversity of the microbial community was enhanced under aerobic conditions with the presence of more biodegradable PV3A and Tween 20. The results of this study indicate that it is necessary to select an appropriate dispersant for nZVI to prevent a residual of the dispersant in the subsurface. Additionally, the effects of the dispersant on TCE biodegradation and the accumulation of TCE biodegrading byproducts should also be considered. PMID:24901632

Chang, Y C; Huang, S C; Chen, K F

2014-01-01

118

Nonionic surfactant greatly enhances the reductive debromination of polybrominated diphenyl ethers by nanoscale zero-valent iron: mechanism and kinetics.  

PubMed

Nanoscale zero-valent iron (nZVI) has been considered as an effective agent for reductive debromination of polybrominated diphenyl ethers (PBDEs). But the high lipophilicity of PBDEs will hinder their debromination owing to the inefficient contact of PBDEs with nZVI. In this study, different ionic forms of surfactants were investigated aiming to promote PBDE debromination, and the beneficial effects of surfactant were found to be: nonionic polyethylene glycol octylphenol ether (Triton X-100, TX)>cationic cetylpyridinium chloride (CPC)>anionic sodium dodecyl benzenesulfonate (SDDBS). Except for with SDDBS, the promotion effect for PBDE debromination was positively related to the surfactant concentrations until a critical micelle concentration (CMC). The debromination process of octa-BDE and its intermediates could be described as a consecutive reaction. The corresponding rate constants (k) for the debromination of parent octa-BDE (including nona- to hepta-BDEs), the intermediates hexa-, penta-, and tetra-BDEs are 1.24 10(-1) h(-1), 8.97 10(-2) h(-1), 6.50 10(-2) h(-1) and 2.37 10(-3) h(-1), respectively. PMID:25019577

Liang, Da-wei; Yang, Yu-han; Xu, Wei-wei; Peng, Si-kan; Lu, Shan-fu; Xiang, Yan

2014-08-15

119

Effect of zero-valent iron on the start-up performance of anaerobic ammonium oxidation (anammox) process.  

PubMed

The long start-up time of anaerobic ammonium oxidation (anammox) process hinders the widespread application of anammox technology in practical wastewater treatment when anammox seed sludge is not available. Meanwhile, the production of nitrate cannot meet the increasingly more strict discharge standards. To combine the chemical nitrate reduction to ammonium with biological nitrogen removal, two anammox upflow anaerobic sludge blanket reactors packed with different types of zero-valent iron (ZVI), microscale ZVI (mZVI) and nanoscale ZVI (nZVI), were developed to accelerate the start-up of anammox process. The results revealed that anammox start-up time shortened from 126 to 105 and 84days with the addition of mZVI and nZVI. The nitrogen removal performance was also improved remarkably by adding ZVI, especially in the start-up stage. The value of dissolved oxygen showed that ZVI could be regarded as a useful deoxidant to create anaerobic condition for the proliferation of anammox bacteria. ZVI was favorable for the secretion of EPS, which would represent the activity of anammox bacteria. The result of real-time quantitative PCR (qPCR) further confirmed that the proliferation of anammox bacteria was enhanced by ZVI. PMID:25226835

Ren, Long-Fei; Ni, Shou-Qing; Liu, Cui; Liang, Shuang; Zhang, Bo; Kong, Qiang; Guo, Ning

2015-02-01

120

Enhanced colloidal stability of nanoscale zero valent iron particles in the presence of sodium silicate water glass.  

PubMed

A method for the stabilization of nanoscale zero valent iron (nZVI) particles using silica was developed. Stabilization can significantly improve the performance characteristics of currently available nZVI products containing agglomerated particles. In the first step of the method, the agglomerates were broken using a sonication. A subsequent stabilizing effect was brought about by the deposition of silica onto the surface of the nZVI particles. The method was tested on three commercially available nZVI suspensions which formed agglomerates with mean sizes ranging from 1000 to 5000?nm. The application of the method resulted in a significant reduction of the mean size of the agglomerates to the values from 100 to 200?nm. The stabilizing effect of silica was also evidenced using scanning electron microscopy, zeta potential measurements and sedimentation analysis. The introduction of typical groundwater ions did not significantly affect the colloidal stability of the treated nZVI suspensions. The results of this study indicate that the silica coating have the potential to protect nZVI against agglomeration. PMID:25323113

Honetschlgerov, Lenka; Janoukovcov, Petra; Kubal, Martin; Sofer, Zden?k

2015-02-01

121

Synthesis and characterization of porous zero-valent iron nanoparticles for remediation of chromium-contaminated wastewater.  

PubMed

The physical and chemical properties of porous zero-valent iron nanoparticles (ZVINs) have highly been acknowledged in the decontamination of heavy metal containing wastes and groundwater. In the present work, the treatment of Cr-contaminant through adsorption onto the ZVINs has been studied. The morphology, crystal structure, and surface composition of Fe(O) nanoparticles were investigated by field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. X-ray absorption near edge structure (XANES) revealed that the Cr(VI) species reduce to Cr(III) while oxidizing the ZVINs to Fe2O3, Fe3O4 or FeO electrochemically. Furthermore, the nitrogen adsorption-desorption isotherm of the porous nanoparticles was similar to a type IV curve with an obvious mesopore-characteristic H3 hysteresis loop, whereas the sizes of mesopores were in the range of 30-50 nm. Experimentally, the efficiency for Cr(VI) removal in the range of 150-300 ppm was found to be > 99.9%. Remarkably, the reduction reaction was completed within 10 min in the absence of additional pH controls. This work also highlights the utility of X-ray absorption spectroscopy (XAS) coupled with conventional characterization methods to comprehensively study the speciation and possible reaction pathway in adsorption process. PMID:23763143

Lin, Kuen-Song; Dehvari, Khalilalrahman; Liu, Yeu-Jye; Kuo, Hua; Hsu, Pei-Ju

2013-04-01

122

Removal of para-nitrochlorobenzene from aqueous solution on surfactant-modified nanoscale zero-valent iron/graphene nanocomposites.  

PubMed

This study demonstrated a remarkably simple and efficient method for the synthesis of nanoscale zero-valent iron (NZVI)/graphene (GN) nanocomposites. In order to prevent the agglomeration and restack of nanocomposites, chemical functionalization of nanocomposites with cetyltrimethylammonium bromide was proposed. The adsorption performance of surfactant-modified NZVI/GN nanocomposites was evaluated for the removal of para-nitrochlorobenzene (p-NCB) from aqueous solutions. The characteristics of nanocomposites were characterized by X-ray diffraction, BET surface area, Fourier transform infrared spectrum, thermogravimetric analysis and scanning electron microscopy. The effect factors including initial solution pH, contact time, reaction temperature, dosage, initial concentration of humic acid (HA) on the adsorption property of p-NCB onto surfactant-modified nanocomposites were investigated. The adsorption kinetics fitted well with pseudo-second-order model. The adsorption capacity of p-NCB on surfactant-modified nanocomposites inferred from the Langmuir model was 105.15 mg/g at 293 K. The thermodynamic parameters indicated that the adsorption of p-NCB onto surfactant-modified nanocomposites was an exothermic and spontaneous process. HA had a strong suppression effect on p-NCB uptake in the adsorption experiment. PMID:25176304

Wu, Yan; Luo, Hanjin; Wang, Hou

2014-01-01

123

Mobility enhancement of nanoscale zero-valent iron in carbonate porous media through co-injection of polyelectrolytes.  

PubMed

The mobility of nanoscale zero-valent iron (nZVI), which is used for in situ groundwater remediation, is affected by chemical and physical heterogeneities within aquifers. Carbonate minerals in porous aquifers and the presence of divalent cations reduce nZVI mobility. This study assesses the potential for enhancing the mobility of polyacrylic acid coated nZVI (PAA-nZVI) in such aquifers through the co-injection of polyelectrolytes (natural organic matter, humic acid, carboxymethyl cellulose, and lignin sulfonate). When applied at the same concentration, all of the polyelectrolytes produced similar enhancement of PAA-nZVI mobility in carbonate porous media. This increase in mobility was a result of increased repulsion between PAA-nZVI and the carbonate matrix. Lignin sulfonate, an environmentally friendly and inexpensive agent, was identified as the most suitable polyelectrolyte for field applications. The greatest increase in PAA-nZVI mobility was achieved with co-injection of lignin sulfonate at concentrations ?50mgL(-1); at these concentrations the maximum PAA-nZVI travel distance in carbonate porous media was twice of that in the absence of lignin sulfonate. PMID:24361704

Laumann, Susanne; Mici?, Vesna; Hofmann, Thilo

2014-03-01

124

Temperature programmed reduction for measurement of oxygen content in nanoscale zero-valent iron.  

PubMed

Nanoscale zerovalent iron (nZVI) has increasingly been used for environmental remediation and in toxic waste treatment. Most applications exploit its large surface area and high reactivity, the latter being a function of zerovalent iron content. In this work, temperature programmed reduction was applied to measure oxygen in nZVI. Iron oxides in nZVI were reduced by hydrogen to form metallic iron and water, which was then measured with an online mass spectrometer to determine oxygen content of the sample. For fresh nZVI prepared by sodium borohydride reduction of iron salts, average oxygen content was 8.21%. Total iron content was approximately 90.35% by the method of acid digestion; Fe(III) content was estimated at 14.37%, and that of zerovalent iron [Fe(0)] at 75.98%. The oxygen content quickly increased to 26.14% after purging with oxygen for four hours. Several other techniques were also used to characterize the iron nanoparticles. High resolution TEM provided direct evidence of the oxide shell structure and indicated that the shell thickness was predominantly in the range of 2-4 nm. The surface elemental composition was determined from high-resolution X-ray photoelectron spectroscopy. The nZVI oxygen content results fill a knowledge gap on nZVI composition. PMID:18546722

Cao, Jiasheng; Li, Xiaoqin; Tavakoli, Javad; Zhang, Wei-Xian

2008-05-15

125

Oxidation of nanoscale zero-valent iron under sufficient and limited dissolved oxygen: Influences on aggregation behaviors.  

PubMed

Oxidations of nanoscale zero-valent iron (nZVI) under aerobic (dissolved oxygen?8mgL(-1)) and anaerobic (dissolved oxygen <3mgL(-1)) conditions were simulated, and their influences on aggregation behaviors of nZVI were investigated. The two oxidation products were noted as HO-nZVI (nZVI oxidized in highly oxygenated water) and LO-nZVI (nZVI oxidized in lowly oxygenated water) respectively. The metallic iron of the oxidized nZVI was almost exhausted (Fe(0)?85%), thus magnetization mainly depended on magnetite content. Since sufficient dissolved oxygen led to the much less magnetite (?15%) in HO-nZVI than that in LO-nZVI (>90%), HO-nZVI was far less magnetic (Ms=88kAm(-1)) than LO-nZVI (Ms=365kAm(-1)). Consequently, HO-nZVI formed small agglomerates (22810nm), while LO-nZVI tended to form chain-like aggregations (>1?m) which precipitated rapidly. Based on the EDLVO theory, we suggested that dissolved oxygen level determined aggregation morphologies by controlling the degree of oxidation and the magnitude of magnetization. Then the chain-like alignment of LO-nZVI would promote further aggregation, but the agglomerate morphology of HO-nZVI would eliminate magnetic forces and inhibit the aggregation while HO-nZVI remained magnetic. Our results indicated the fine colloidal stability of HO-nZVI, which might lead to the great mobility in the environment. PMID:25441925

Jiang, Danlie; Hu, Xialin; Wang, Rui; Yin, Daqiang

2015-03-01

126

Enhancing Fenton oxidation of TNT and RDX through pretreatment with zero-valent iron  

Microsoft Academic Search

The effect of reductive treatment with elemental iron on the rate and extent of TOC removal by Fenton oxidation was studied for the explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using a completely stirred tank reactor (CSTR). The results support the hypothesis that TNT and RDX are reduced with elemental iron to products that are oxidized more rapidly and completely by

Seok-Young Oh; Pei C. Chiu; Byung J. Kim; Daniel K. Cha

2003-01-01

127

Deployment of an innovative thermally enhanced soil mixing process augmented with zero-valent iron.  

SciTech Connect

An innovative in-situ soil treatment process, referred to as soil mixing/thermally enhanced soil vapor extraction (SM/TESVE), was used to remediate the 317 Area of Argonne National Laboratory-East (i.e., Argonne), which is contaminated with volatile organic compounds (VOCs). Following the initial soil treatment, polishing was required to reduce residual concentrations of contaminants. A study of polishing methods was conducted. It determined that injecting metallic iron particles into the soil, in conjunction with soil mixing, would reduce residual VOC concentrations more effectively than the original conventional soil ventilation approach. After the effectiveness of iron injection was verified, it replaced the soil ventilation step. The modified process involved mixing the soil while hot air and steam were injected into it. Off-gases were captured in a hood over the treatment area. During this process, an iron slurry, consisting of up to 50% iron particles in water with guar gum added as a thickening agent, was injected and mixed into the soil by the mixing equipment. Approximately 6,246 m{sup 3} (8, 170 yd{sup 3}) of soil was treated during this project. Confirmatory samples were then collected. In these samples, VOC concentrations were usually reduced by more than 80%.

Lynch, P. L.

1999-01-15

128

Arsenic stabilization by zero-valent iron, bauxite residue, and zeolite at a contaminated site planting Panax notoginseng.  

PubMed

Panax notoginseng (Burk.) F.H. Chen, a rare traditional Chinese medicinal herb, is a widely used phytomedicine used all over the world. In recent years, the arsenic contamination of the herb and its relative products becomes a serious problem due to elevated soil As concentration. This study aimed to evaluate the effects of different types and dosages of amendments on As stabilization in soil and its uptake by P. notoginseng. Results showed that comparing to control treatment, the As concentrations of P. notoginseng declined by 49-63%, 43-61% and 52-66% in 0.25% zero-valent iron (Fe(0)), 0.5% bauxite residue, and 1% zeolite treatment, respectively; whereas the biomasses were elevated by 62-116%, 45-152% and 114-265%, respectively. The As(III) proportions of P. notoginseng increased by 8%, 9%, and 8%, and the transfer factors of As from root to shoot increased by 37%, 42% and 84% in the optimal treatments of Fe(0), bauxite residue, and zeolite. For soil As, all the three amendments could transform the non-specifically adsorbed As fraction to hydrous oxides Fe/Al fractions (by Fe(0) and red mud) or specifically adsorbed As fraction (by zeolite), therefore reduced the bioavailability of soil As. With a comprehensive consideration of stabilization efficiency, plant growth, environmental influence, and cost, Fe(0) appeared to be the best amendment, and zeolite could also be a good choice. In conclusion, this study was of significance in developing As contamination control in P. notoginseng planting areas, and even other areas for medicinal herb growing. PMID:23871591

Yan, X L; Lin, L Y; Liao, X Y; Zhang, W B; Wen, Y

2013-10-01

129

Transformation of chlorinated hydrocarbons using aquocobalamin or coenzyme F{sub 430} in combination with zero-valent iron  

SciTech Connect

More effective methods are necessary for the remediation of soils, sediments, and ground waters contaminated with halogenated organic compounds. The authors objective was to determine the feasibility and utility of using a tetrapyrrole-Fe(0) mixture for reductive dehalogenation of synthetic organic contaminants. Aquocobalamin or coenzyme F{sub 430} was combined with Fe(0) in aqueous systems containing either a single chlorinated compound or mixtures of chlorinated compounds, and substrate disappearance was monitored using gas chromatography-mass spectrometry (GC-MS). Zero-valent iron effectively dehalogenated CCl{sub 4} at low to neutral pH values, while increases in CCl{sub 4} dehalogenation resulting from inclusion of tetrapyrrole catalysts along with Fe(0) occurred only at basic pH values. Rates of CCl{sub 4} disappearance increased with additional aquocobalamin, but reached a maximum and decreased at higher aquocobalamin concentrations. overall dehalogenation rates may thus be a function of Fe(0)'s limited reactive surface area. There was a trend for both tetrapyrrole catalysts to promote the disappearance of halogenated compounds in a mixed substrate containing 20 compounds. Studies with five individual substrates likewise showed trends for increased substrate removal with F{sub 430} beyond that for Fe(0) alone. This increase is most important for compounds such as 1,2-dichloroethane and 1,4-dichlorobenzene that are not readily dehalogenated by Fe(0). Chloride concentrations in the reaction mixtures indicated that reductive dehalogenation was the dominant process responsible for substrate disappearance. Use of a combination of aquocobalamin or coenzyme F{sub 430} and Fe(0) may effectively promote dehalogenation, thus producing fewer products and more complete dehalogenation of the target substrates than can be achieved using only one of the abiotic reductants alone.

Morra, M.J.; Borek, V.; Koolpe, J.

2000-06-01

130

Graphene-supported nanoscale zero-valent iron: removal of phosphorus from aqueous solution and mechanistic study.  

PubMed

Excess phosphorus from non-point pollution sources is one of the key factors causing eutrophication in many lakes in China, so finding a cost-effective method to remove phosphorus from non-point pollution sources is very important for the health of the aqueous environment. Graphene was selected to support nanoscale zero-valent iron (nZVI) for phosphorus removal from synthetic rainwater runoff in this article. Compared with nZVI supported on other porous materials, graphene-supported nZVI (G-nZVI) could remove phosphorus more efficiently. The amount of nZVI in G-nZVI was an important factor in the removal of phosphorus by G-nZVI, and G-nZVI with 20 wt.% nZVI (20% G-nZVI) could remove phosphorus most efficiently. The nZVI was very stable and could disperse very well on graphene, as characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FT-IR) and Raman spectroscopy were used to elucidate the reaction process, and the results indicated that Fe-O-P was formed after phosphorus was adsorbed by G-nZVI. The results obtained from X-ray diffraction (XRD) indicated that the reaction product between nZVI supported on graphene and phosphorus was Fe?(PO?)?8H?O (Vivianite). It was confirmed that the specific reaction mechanism for the removal of phosphorus with nZVI or G-nZVI was mainly due to chemical reaction between nZVI and phosphorus. PMID:25108732

Liu, Fenglin; Yang, JingHe; Zuo, Jiane; Ma, Ding; Gan, Lili; Xie, Bangmi; Wang, Pei; Yang, Bo

2014-08-01

131

Reduced transport potential of a palladium-doped zero valent iron nanoparticle in a water saturated loamy sand.  

PubMed

Direct in situ injection of palladium-doped nanosized zero valent iron (Pd-NZVI) particles can contribute to remediation of various environmental contaminants. A major challenge encountered is rapid aggregation of Pd-NZVI and hence very limited mobility. To reduce aggregation and concurrently improve particle mobility, the surface of bare Pd-NZVI can be modified with stabilizing surface modifiers. Selected surface-modified Pd-NZVI has shown dramatically improved stability and transport. However, little is known regarding the effects of aquifer grain geochemical heterogeneity on the transport and deposition behavior of surface-modified Pd-NZVI. Herein, the mobility of surface stabilized Pd-NZVI in two granular matrices representative of model ground water environments (quartz sand and loamy sand) was assessed over a wide range of environmentally relevant ionic strengths (IS). Carboxymethyl cellulose (CMC), soybean flour and rhamnolipid biosurfactant were used as Pd-NZVI surface modifiers. Our results show that, both in quartz sand and loamy sand, an increase in solution IS results in reduced Pd-NZVI transport. Moreover, at a given water chemistry, Pd-NZVI transport is notably attenuated in loamy sand implying that geochemical heterogeneity associated with loamy sand is a key factor influencing Pd-NZVI transport potential. Experiments conducted at a higher Pd-NZVI particle concentration, to be more representative of field conditions, show that rhamnolipid and CMC are effective stabilizing agents even when 1g/L Pd-NZVI is injected into quartz sand. Overall, this study emphasizes the extent to which variation in groundwater chemistry, coupled with changes in aquifer geochemistry, could dramatically alter the transport potential of Pd-NZVI in the subsurface environment. PMID:25462742

Basnet, Mohan; Tommaso, Caroline Di; Ghoshal, Subhasis; Tufenkji, Nathalie

2014-10-01

132

Abiotic aspects of zero-valent iron induced degradation of pentachlorophenol in water  

SciTech Connect

Investigations of dehalogenation of aqueous pentachlorophenol (PCP) were performed under aerobic conditions using laboratory batch systems containing granular electrolytic iron. It was observed that the kinetics of degradation of PCP were strongly dependent on a number of factors including substrate concentration, temperature, pH of solution and the presence of certain inorganic substances. Experiments on the mechanisms of the reaction have been carried out as well.

Ravary, C.; Lipczynska-Kochany, E. [Univ. of Waterloo, Ontario (Canada)

1995-12-01

133

A comparison of the low frequency electrical signatures of iron oxide versus calcite precipitation in granular zero valent iron columns.  

PubMed

Geophysical methods have been proposed as technologies for non-invasively monitoring geochemical alteration in permeable reactive barriers (PRBs). We conducted column experiments to investigate the effect of mineralogy on the electrical signatures resulting from iron corrosion and mineral precipitation in Fe0 columns using (a) Na2SO4, and (b) NaHCO3 plus CaCl2 mixture, solutions. At the influent interface where the reactions were most severe, a contrasting time-lapse electrical response was observed between the two columns. Solid phase analysis confirmed the formation of corrosion halos and increased mineralogical complexity in the corroded sections of the columns compared to the minimal/non-corroded sections. We attribute the contrasting time-lapse signatures to the differences in the electrical properties of the mineral phases formed within the two columns. While newly precipitated/transformed polarizable and semi-conductive iron oxides (mostly magnetite and green rust) increase the polarization and conductivity of the sulfate column, the decrease of both parameters in the bicarbonate column is attributed to the precipitation of non-polarizable and non-conductive calcite. Our results show that precipitate mineralogy is an important factor influencing the electrical properties of the corroded iron cores and must be considered if electrical geophysical methods are to be developed to monitor PRB barrier corrosion processes in situ. PMID:17996979

Wu, Yuxin; Slater, Lee; Versteeg, Roelof; LaBrecque, Douglas

2008-01-28

134

Carboxymethyl Cellulose Stabilized Nano-scale Zero Valent Iron Transport in Porous Media: An Experimental and Modeling Study  

NASA Astrophysics Data System (ADS)

An experimental and modeling study is being conducted to evaluate carboxymethyl cellulose (CMC) stabilized nano-scale zero valent iron (nZVI) transport in porous media. A two-dimensional water-saturated glass-walled sandbox (55 cm x 45 cm x 1.3 cm in size) is being used for the study. The sandbox was packed uniformly with silica sand (600 ?m to 425 ?m grain diameter) under water-saturated conditions. From a series of hydraulic tests permeability of the system was calculated to be 1.0 x 10-12 m2. The transport tests are being conducted at pore-water velocities of 3, 5, and 10 m.d-1 to identify any shear-thinning effects associated with the CMC (MW = 90,000) solution, and effects of velocity on nZVI attachment to the porous media. A set of transport tests is being carried out using LissamineTM Green B (LGB) dye and CMC mixtures to characterize the CMC transport without nZVI. The transport tests are being conducted at various CMC concentrations ranging from 0.2% to 0.8% (w/v) to determine the effect of CMC concentration on nZVI transport under flowing conditions. For the CMC stabilized nZVI transport tests, nZVI is synthesized freshly in CMC solution before each experiment using sodium borohydride and ferrous sulfate. The synthesized nZVI concentrations range from 0.1 to 2.5 g.L-1. While higher nZVI concentration is desired for higher contaminant degradation, the higher nZVI concentration may cause greater aggregation and attachment to the porous media limiting the delivery distance for nZVI. In each transport experiment, the LGB-CMC solution or nZVI-CMC solution is injected into the sandbox as a pulse of 0.25 pore volume (PV). For LGB, the mass recovery was calculated to be ~ 96.5% indicating non-reactive transport in silica sand. The preliminary results also show that increased concentration of CMC (from 0.2% to 0.4 %) causes higher pressure drop across the sandbox, indicating that use of high CMC concentrations will limit injection rates with a corresponding effect on velocity and nZVI attachment. The transport experiments are being modeled using a two-dimensional multiphase flow and transport model. The sandbox is being discretized into 55 by 45 grid blocks (1 cm x 1 cm x 1.3 cm in size). LGB and CMC are modeled as soluble components, while nZVI is being considered as a colloid. In case of nZVI transport, attachment coefficients are being fitted to match the experimental breakthrough curves. The estimated attachment coefficients can be used to predict the CMC stabilized nZVI transport in field scale applications.

Mondal, P.; Rrokaj, E.; Sleep, B. E.

2013-12-01

135

Injection of polyelectrolytes enhances mobility of zero-valent iron nanoparticles in carbonate-rich porous media  

NASA Astrophysics Data System (ADS)

The application of nanoscale zero-valent iron (nZVI) for in situ groundwater remediation has received increased attention as a beneficial and novel remediation technique. A precondition for effective nZVI field applications is its delivery to the contaminated source zones. This has proved to be difficult due to the limited mobility of nZVI, which remains one major obstacle to widespread utilization of this remediation approach (O'CAROLL ET AL., 2012). One important factor that controls mobility of nZVI is physical and chemical heterogeneity within the subsurface, such as mineralogical variations (KIM ET AL., 2012). In our previous study we showed that the nZVI transport in carbonate-rich porous media is significantly reduced compared to that in quartz porous media (LAUMANN ET AL., 2012). This is caused by favorable nZVI deposition onto carbonate sand and is attributed to the less negative surface charge of carbonate compared to that of quartz sand under the range of water chemical conditions typically encountered in aquifers. New strategies are therefore required to improve nZVI mobility in carbonate-rich porous media. One approach can be the injection of polyelectrolytes in the subsurface, which are expected to adsorb onto aquifer grains and provide greater repulsion between nZVI and the porous media. In this study the effect of co-injected polyelectrolytes on the transport of polyacrylic acid (PAA) coated nZVI in two model porous media, quartz and carbonate sands was evaluated. Column experiments were carried out aiming to evaluate mobility of PAA-nZVI co-injected with four polyelectrolytes, including natural organic matter (NOM), humic acid, carboxymethyl cellulose (CMC), and lignin sulfonate. The results demonstrated that the co-injection of the chosen polyelectrolytes does not influence mobility of PAA-nZVI in quartz sand; the breakthrough with co-injected polyelectrolytes was similar to that of the pure PAA-nZVI dispersion. This observation can be explained by the strong negative surface charge of the quartz sand, which was apparently not changed in the presence of polyelectrolytes. Conversely, the co-injected polyelectrolytes affected the breakthrough in carbonate sand, increasing nZVI mobility for approximately 15%. This can be explained by the attachment of the polyelectrolytes to the less negatively charged carbonate sand, which then promoted the PAA-nZVI mobility. Even though there are structural differences among the polyelectrolytes applied in this study, our results showed no significant variations in the PAA-nZVI mobility when these polyelectrolytes are present at concentration of 50 mg L-1. Lignin sulfonate was furthermore selected to investigate the effect of different polyelectrolyte concentrations (0, 10, 25, 50, 250, and 500 mg L-1) on the PAA-nZVI mobility. The results showed that higher lignin sulfonate concentrations (250 and 500 mg L-1) do not affect the transport of PAA-nZVI in quartz sand. In carbonate sand, on contrary, increasing mobility due to co-injected lignin sulfonate was observed at concentrations above 25 mg L-1, having the highest value with 500 mg L-1 co-injected with the PAA-nZVI dispersion. Overall, the results demonstrated that lignin sulfonate adsorption onto the carbonate sand reduce PAA-nZVI deposition onto aquifer grains and promote its mobility, the effect which is more pronounced at higher polyelectrolyte concentrations co-injected with the PAA-nZVI dispersion. The project is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). Management by Kommunalkredit Public Consulting GmbH. Literature O'CAROLL, D. ET AL., (2012): Advances in Water Resources, in press. KIM, H.-J. ET AL., (2012): Journal of Colloid and Interface Science 370, 1-10. LAUMANN, S. ET AL., (2012): Environmental Pollution, submitted.

Laumann, Susanne; Mici?, Vesna; Schmid, Doris; Hofmann, Thilo

2013-04-01

136

Application of ultrasound to enhance the zero-valent iron-initiated abiotic degradation of halogenated aliphatic compounds  

NASA Astrophysics Data System (ADS)

Permeable iron barriers, while effective as a near-passive in situ remediation technology for halogenated organic solvents, are susceptible to the loss of reactivity over time, most probably due to a build up of corrosion products or other precipitates on the iron surface. If such material can be removed, a barrier's lifetime can be significantly extended. This proof-of-concept project employed ultrasonic energy to rejuvenate an iron surface. Through batch studies, iron's capacity to degrade dissolved chlorinated solvents under various conditions before and after sonication was examined. The impact of iron pretreatment, groundwater quality, and sonication and the nature of the deposits formed on iron during solvent degradation were determined in order to evaluate the physical mechanism of ultrasonic enhancement of iron and to develop guidelines for barrier design and an ultrasound delivery system for a future field study. Iron (coarse filings, 100-mesh powder, or foamed pellets) placed in deoxygenated natural groundwater was exposed to 330 W-hr of ultrasonic energy prior to the introduction of trichloroethylene (TCE). The iron was also subjected to various pretreatments to create surface conditions with differing rates of activity for chlorinated solvent degradation. Aqueous concentrations of TCE and any degradation products were monitored over time. Geochemical modeling indicated that an iron barrier in this water would be subject to heavy precipitation of carbonates and hydroxides. Sonication positively impacted iron's degradation of chlorinated solvents, probably most directly linked to an increase in active specific surface area, achieved by removing deposits and/or etching the surface, as suggested by scanning electron micrographs. X-Ray photoelectron spectroscopy (XPS) analysis indicated that sonication also changes the chemical composition of the outermost 40 Angstroms of an iron surface. For some degraded irons, activity was restored to near initial rates after sonication. The nonchlorinated fraction of degradation products increased after sonication, suggesting more complete, as well as more rapid, degradation. The application of ultrasound to restore an iron barrier holds great promise. Sonication removes obstructive material from an iron surface, improves its activity for the degradation of chlorinated solvents, and is effective even in water environments with a great tendency to form precipitates.

Ruiz, Nancy Elaine

137

Iron Nanoparticles in Reactive Environmental Barriers  

SciTech Connect

Zero-valent iron is cheap, environmentally innocuous, and effective at reducing chlorinated organics. It has, as a result, become a popular candidate for remediating aquifers contaminated with trichloroethylene and other halogenated pollutants. In this paper, we discuss one such system, where iron nanoparticles are synthesized and incorporated into polyvinyl alcohol membranes, forming water-permeable barriers to these pollutants. These barriers are tested against a variety of contaminants, including carbon tetrachloride, copper, and chromate.

Nuxoll, Eric E.; Shimotori, Tsutomu; Arnold, William A.; Cussler, Edward L.

2003-09-23

138

Effects of hardness and alkalinity on the removal of arsenic(V) from humic acid-deficient and humic acid-rich groundwater by zero-valent iron.  

PubMed

The effects of hardness (Ca(2+)) and alkalinity (HCO(3)(-)) on arsenic(V) removal from humic acid (HA)-deficient and HA-rich groundwater by zero-valent iron (Fe(0)) were investigated using batch experiments. Arsenic, in general, is removed from groundwater possibly by adsorption and co-precipitation with the iron corrosion products. However, in the co-presence of HCO(3)(-) and Ca(2+), the removal rate of arsenic increased with increasing concentrations of either Ca(2+) or HCO(3)(-). It was observed that the removal of arsenic was significantly enhanced by the formation of CaCO(3) as a nucleation seed for the growth of large iron (hydr)oxide particles. In the co-existence of Ca(2+), HCO(3)(-) and HA, the presence of HA diminished the positive role of Ca(2+) due to the formation of Fe-humate complexes in solution and delaying of the formation of CaCO(3). As a result, the formation of the large iron (hydr)oxide particles was inhibited in the earlier stage which, in turn, affected the removal of arsenic. However, after the formation of CaCO(3) and the subsequent growth of such particles, the presence of large iron (hydr)oxide particles resulted in the rapid removing of arsenic and Fe-humate by adsorption and/or co-precipitation. PMID:19580986

Mak, Mark S H; Rao, Pinhua; Lo, Irene M C

2009-09-01

139

Inhibition of nitrate reduction by NaCl adsorption on a nano-zero-valent iron surface during a concentrate treatment for water reuse.  

PubMed

Nanoscale zero-valent iron (NZVI) has been considered as a possible material to treat water and wastewater. However, it is necessary to verify the effect of the matrix components in different types of target water. In this study, different effects depending on the sodium chloride (NaCl) concentration on reductions of nitrates and on the characteristics of NZVI were investigated. Although NaCl is known as a promoter of iron corrosion, a high concentration of NaCl (>3?g/L) has a significant inhibition effect on the degree of NZVI reactivity towards nitrate. The experimental results were interpreted by a Langmuir-Hinshelwood-Hougen-Watson reaction in terms of inhibition, and the decreased NZVI reactivity could be explained by the increase in the inhibition constant. As a result of a chloride concentration analysis, it was verified that 7.7-26.5% of chloride was adsorbed onto the surface of NZVI. Moreover, the change of the iron corrosion product under different NaCl concentrations was investigated by a surface analysis of spent NZVI. Magnetite was the main product, with a low NaCl concentration (0.5?g/L), whereas amorphous iron hydroxide was observed at a high concentration (12?g/L). Though the surface was changed to permeable iron hydroxide, the Fe(0) in the core was not completely oxidized. Therefore, the inhibition effect of NaCl could be explained as the competitive adsorption of chloride and nitrate. PMID:25358487

Hwang, Yuhoon; Kim, Dogun; Shin, Hang-Sik

2014-12-01

140

Enhanced degradation of ortho-nitrochlorobenzene by the combined system of zero-valent iron reduction and persulfate oxidation in soils.  

PubMed

ortho-Nitrochlorobenzene (o-NCB) in soil poses significant health risks to human because of its persistence and high toxicity. The removal of o-NCB by both zero-valent iron (ZVI) and chemical oxidation (persulfate) was investigated by batch experiments. The o-NCB removal rate increases significantly from 15.1 to 97.3 % with an increase of iron dosage from 0.1 to 1.0 mmol g(-1). The o-NCB removal rate increases with the decrease of the initial solution pH, and a removal efficiency of 90.3 % is obtained at an initial pH value of 6.8 in this combined system. It is found that temperature and soil moisture could also increase the o-NCB removal rate. The o-NCB degradation rate increases from 83.9 to 96.2 % and from 41.5 to 82.4 % with an increase of temperature (15 to 35 C) and soil moisture (0.25 to 1.50 mL g(-1)), respectively. Compared to the persulfate oxidation system and ZVI system, the persulfate-iron system shows high o-NCB removal capacity. o-NCB removal rates of 41.5 and 62.4 % are obtained in both the persulfate oxidation system and the ZVI system, while the removal rate of o-NCB is 90.3 % in the persulfate-iron system. PMID:24385185

Xu, Hai-bo; Zhao, Dao-yuan; Li, Yu-jiao; Liu, Pei-ya; Dong, Chang-xun

2014-04-01

141

Synthesis and characterization of pentaphosphino zero-valent iron complexes and their corresponding iron(II)-chloride and -hydride complexes.  

PubMed

A pentaphosphino iron(II)-chloride species [(t)SiP(3)(dmpm)FeCl][Cl] (1-Cl) ((t)SiP(3) = (t)BuSi(CH(2)PMe(2))(3), dmpm = Me(2)PCH(2)PMe(2)) was prepared from [((t)SiP(3)Fe)(2)(mu-Cl)(3)][Cl] and dmpm. This species was reduced to give the corresponding iron(0) complex, (t)SiP(3)(dmpm)Fe (3), in near quantitative yield. Analogous complexes [SiP(3)(dmpe)FeCl][Cl] (2-Cl) and SiP(3)(dmpe)Fe (4) (SiP(3) = MeSi(CH(2)PMe(2))(3), dmpe = Me(2)PCH(2)CH(2)PMe(2)) were prepared in the same manner as 1 and 3 but with lower yields because of competitive ligand rearrangement reactions that gave byproduct of trans-(dmpe)(2)FeCl(2) and (dmpe)(5)Fe(2) (5). [(t)SiP(3)(dmpm)FeH][A] (6) was prepared from the reaction of 3 with weak acids (HA), and the pK(a) of 6 was established to be approximately 25. Attempts to prepare pentaphosphino-iron(0) complexes of the form SiP(3)(PR(3))(2)Fe using PPh(3) and PMe(3) resulted in cyclometalated products, SiP(3)FeH((o-C(6)H(4))PPh(2)) (7) and SiP(3)FeH(CH(2)PMe(2)) (8). Synthesis and characterization of these complexes, including crystal structures of 1-5, are reported. PMID:20230063

Thoreson, Kristen A; Follett, Angela D; McNeill, Kristopher

2010-04-19

142

Fine structural features of nanoscale zero-valent iron characterized by spherical aberration corrected scanning transmission electron microscopy (Cs-STEM).  

PubMed

An angstrom-resolution physical model of nanoscale zero-valent iron (nZVI) is generated with a combination of spherical aberration corrected scanning transmission electron microscopy (Cs-STEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) on the Fe L-edge. Bright-field (BF), high-angle annular dark-field (HAADF) and secondary electron (SE) imaging of nZVI acquired by a Hitachi HD-2700 STEM show near atomic resolution images and detailed morphological and structural information of nZVI. The STEM-EDS technique confirms that the fresh nZVI comprises of a metallic iron core encapsulated with a thin layer of iron oxides or oxyhydroxides. SAED patterns of the Fe core suggest the polycrystalline structure in the metallic core and amorphous nature of the oxide layer. Furthermore, Fe L-edge of EELS shows varied structural features from the innermost Fe core to the outer oxide shell. A qualitative analysis of the Fe L(2,3) edge fine structures reveals that the shell of nZVI consists of a mixed Fe(II)/Fe(III) phase close to the Fe (0) interface and a predominantly Fe(III) at the outer surface of nZVI. PMID:25050411

Liu, Airong; Zhang, Wei-xian

2014-09-21

143

Environmental benefits and risks of zero-valent iron nanoparticles (nZVI) for in situ remediation: Risk mitigation or trade-off?  

NASA Astrophysics Data System (ADS)

The use of nanoscaled zero-valent iron particles (nZVI) to remediate contaminated soil and groundwater has received increasing amounts of attention within the last decade, primarily due to its potential for broader application, higher reactivity, and cost-effectiveness compared to conventional zero-valent iron applications and other in situ methods. However, the potential environmental risks of nZVI in in situ field scale applications are largely unknown at the present and traditional environmental risk assessment approaches are not yet able to be completed. Therefore, it may not yet be fully clear how to consider the environmental benefits and risks of nZVI for in situ applications. This analysis therefore addresses the challenges of comprehensively considering and weighing the expected environmental benefits and potential risks of this emerging environmentally-beneficial nanotechnology, particularly relevant for environmental engineers, scientists, and decision makers. We find that most of the benefits of using nZVI are based on near-term considerations, and large data gaps currently exist within almost all aspects of environmental exposure and effect assessments. We also find that while a wide range of decision support tools and frameworks alternative to risk assessment are currently available, a thorough evaluation of these should be undertaken in the near future to assess their full relevancy for nZVI at specific sites. Due to the absence of data in environmental risk evaluations, we apply a 'best' and 'worst' case scenario evaluation as a first step to qualitatively evaluate the current state-of-knowledge regarding the potential environmental risks of nZVI. The result of this preliminary qualitative evaluation indicates that at present, there are no significant grounds on which to form the basis that nZVI currently poses a significant, apparent risk to the environment, although the majority of the most serious criteria (i.e. potential for persistency, bioaccumulation, toxicity) are generally unknown. We recommend that in cases where nZVI may be chosen as the 'best' treatment option, short and long-term environmental monitoring is actively employed at these sites. We furthermore recommend the continued development of responsible nZVI innovation and better facilitated information exchange between nZVI developers, nano-risk researchers, remediation industry, and decision makers.

Grieger, Khara D.; Fjordbge, Annika; Hartmann, Nanna B.; Eriksson, Eva; Bjerg, Poul L.; Baun, Anders

2010-11-01

144

A comparative evaluation of hexavalent chromium treatment in contaminated soil by calcium polysulfide and green-tea nanoscale zero-valent iron.  

PubMed

A column study for hexavalent chromium (Cr(VI)) removal from contaminated soil was performed using calcium polysulfide (CPS) and nanoscale zero-valent iron stabilized with green tea extract (GT-nZVI). Injection of CPS at 12 times the stoichiometric requirement (12) resulted in quantitative Cr(VI) removal for up to 195 days of equivalent groundwater flow. Solid-bound Cr(VI) was reduced up to >99% (<2mg/kg). Treatment with CPS resulted in a short-term release of high sulfur concentrations. Injections of 12 and 24 stoichiometric GT-nZVI resulted in decrease in leachate pH from 6 to 2.5, which rebounded to 4.5 after the equivalent of 45 days and remained stable for the next equivalent 3 years. Metals concentrations in the effluent (Pb, Cr and Fe) increased following injection and quickly decreased, such that the mass flux was low with respect to the total amounts in the solid. Aqueous Cr(VI) was non-detect for the majority of the monitoring time, but concentrations eventually increased with respect to the control sample. Solid-bound Cr(VI) concentrations decreased by 30% and 66% in the 12 and 24 treatments, respectively. The low efficiency was attributed to increased sorption to iron surfaces at pH 2.5 and slow dissolution of PbCrO4, both of which were identified by micro-X-ray fluorescence and absorption analyses. PMID:22169240

Chrysochoou, Maria; Johnston, Chad P; Dahal, Geeta

2012-01-30

145

Effects of washing solution and drying condition on reactivity of nano-scale zero valent irons (nZVIs) synthesized by borohydride reduction.  

PubMed

Washing and drying processes are essential when synthesizing nano-scale zero valent irons (nZVIs) by borohydride reduction of iron salts in aqueous phase. However, effects of these processes on nZVI reactivity have not been investigated in detail, although different washing and drying conditions might alter surface characteristics of nZVIs and thus vary their reactivity towards reducible contaminants. In this study, effects of three washing solutions and drying conditions on the reactivity of nZVIs for nitrate were investigated. Washing with volatile solvents and drying under anaerobic condition decreased thickness of Fe-oxide layer on nZVIs and increased content of Fe(2+)-containing oxides in the layer, which enhanced nZVI reactivity toward nitrate. Volatile solvent washing could minimize the decrease in nZVI reactivity according to changing anaerobic drying condition to aerobic. Findings from this study suggest that application of washing with volatile solvents and drying under aerobic condition should be recommended as effective processes to obtain nZVIs with maximum reactivity at reasonable costs and efforts. PMID:24290304

Woo, Heesoo; Park, Junboum; Lee, Seockheon; Lee, Seunghak

2014-02-01

146

Conversion of mill-scale waste to nanoscale zero valent iron (nZVI) for 'green' hydrogen generation via metal-steam reforming  

NASA Astrophysics Data System (ADS)

The Proton Exchange Membrane Fuel Cells (PEMFCs) are the most preferred and efficient energy conversion devices for automotive applications but demand high purity hydrogen which comes at a premium price. The currently pursued hydrogen generation methods suffer from issues such as, low efficiency, high cost, environmental non-benignity, and, in some cases, commercial non-viability. Many of these drawbacks including the CO contamination and, storage and delivery can be overcome by resorting to metal-steam reforming (MSR) using iron from steel industry's mill-scale waste. A novel solution-based room temperature technique using sodium borohydride (NaBH4) as the reducing agent has been developed that produces highly active nanoscale (30-40 nm) iron particles. A slightly modified version of this technique using a surfactant and water oil microemulsion resulted in the formation of 5 nm Fe particles. By using hydrazine (N2H4) as an inexpensive and more stable (compared to NaBH4) reductant, body centered cubic iron particles with edge dimensions 5 nm were obtained under mild solvothermal conditions in ethanol. The nanoscale zero valent iron (nZVI) powder showed improved kinetics and greater propensity for hydrogen generation than the coarser microscale iron obtained through traditional reduction techniques. To initiate and sustain the somewhat endothermic MSR process, a solar concentrator consisting of a convex polyacrylic sheet with aluminum reflective coating was fabricated. This unique combination of mill-scale waste as iron source, hydrazine as the reductant, mild process conditions for nZVI generation and solar energy as the impetus for actuating MSR, obviates several drawbacks plaguing the grand scheme of producing, storing and delivering pure and humidified H2 to a PEMFC stack.

Kesavan, Sathees Kumar

147

Bio-beads with immobilized anaerobic bacteria, zero-valent iron, and active carbon for the removal of trichloroethane from groundwater.  

PubMed

Chlorinated hydrocarbons are the most common organic pollutants in groundwater systems worldwide. In this study, we developed bio-beads with immobilized anaerobic bacteria, zero-valent iron (ZVI), and activated carbon (AC) powder and evaluated their efficacy in removing 1,1,1-trichloroethane (TCA) from groundwater. Bio-beads were produced by polyvinyl alcohol, alginate, and AC powder. We found that the concentration of AC powder used significantly affected the mechanical properties of immobilized bio-beads and that 1.0 % (w/v) was the optimal concentration. The bio-beads effectively degraded TCA (160 mg L(-1)) in the anaerobic medium and could be reused up to six times. The TCA degradation rate of bio-beads was 1.5 and 2.3 times greater, respectively, than ZVI + AC treatment or microbes + AC treatment. Measuring FeS produced by microbial reactions indicated that TCA removal occurred via FeS-catalyzed dechlorination. Analysis of clonal libraries derived from bio-beads demonstrated that the dominant species in the community were Betaproteobacteria and Gammaproteobacteria, which may contribute to the long-term stability of ZVI reactivity during TCA dechlorination. This study shows that the combined use of immobilized anaerobic bacteria, ZVI, and AC in bio-beads is effective and practical for TCA dechlorination and suggests they may be applicable towards developing a groundwater treatment system for the removal of TCA. PMID:24906831

Zhou, Ya-Zhen; Yang, Jie; Wang, Xiao-Li; Pan, Yue-Qing; Li, Hui; Zhou, Dong; Liu, Yong-Di; Wang, Ping; Gu, Ji-Dong; Lu, Qiang; Qiu, Yue-Feng; Lin, Kuang-Fei

2014-10-01

148

Examination of Cr(VI) treatment by zero-valent iron using in situ, real-time X-ray absorption spectroscopy and Cr isotope measurements  

NASA Astrophysics Data System (ADS)

A series of replicate flow-through cell experiments was conducted to characterize Cr isotope fractionation during Cr(VI) treatment by granular zero-valent iron (ZVI). Synthetic groundwater containing 50 mg L-1 Cr(VI) was pumped upward through a custom-made cell packed with ZVI under anaerobic conditions. The geochemical evolution of the system was monitored using pH and redox measurements, while aqueous effluent samples were retained for analysis of cations and Cr isotopes. Real-time, in situ X-ray absorption near edge structure (XANES) spectroscopy collected via a Kapton window in the cell provided additional information on the speciation of the reaction products. Increases in ?53Cr values corresponding to decreases in Cr(VI) concentration suggested the occurrence of redox processes. Spectroscopic results correlated well with the isotope data, indicating reduction of Cr(VI) to Cr(III). The isotope data did not appear to follow a single trend. A two-stage system was proposed to explain the complex isotope trend, where the rapid Cr removal was associated with very little fractionation (? = -0.2), whereas slower removal was associated with a greater degree of fractionation (? = -1.2 to -1.5). Reactive transport modeling was used to quantify distinct isotope fractionation values (?), differentiated by a significant change in the Cr removal rate.

Jamieson-Hanes, Julia H.; Lentz, Adam M.; Amos, Richard T.; Ptacek, Carol J.; Blowes, David W.

2014-10-01

149

Surface coating with Ca(OH)2 for improvement of the transport of nanoscale zero-valent iron (nZVI) in porous media.  

PubMed

A novel thermal deposition method was developed to coat Ca(OH)2 on the surface of nanoscale zero-valent iron (nZVI). The nZVI particles with the Ca(OH)2 coating layer, nZVI/Ca(OH)2, had a clear core-shell structure based on the transmission electron microscopy observations, and the Ca(OH)2 shell was identified as an amorphous phase. The Ca(OH)2 coating shell would not only function as an effective protection layer for nZVI but also improve the mobility of nZVI in porous media for its use in environmental decontamination. A 10% Ca/Fe mass ratio was found to result in a proper thickness of the Ca(OH)2 shell on the nZVI surface. Based on the filtration tests in sand columns, the Ca(OH)2-based surface coating could greatly improve the mobility and transport of nZVI particles in porous media. In addition, batch experiments were conducted to evaluate the reactivity of Ca(OH)2-coated nZVI particles for the reduction of Cr(VI) and its removal from water. PMID:24292480

Wei, Cai-jie; Li, Xiao-yan

2013-01-01

150

Degradation pathway and kinetics of 1-alkyl-3-methylimidazolium bromides oxidation in an ultrasonic nanoscale zero-valent iron/hydrogen peroxide system.  

PubMed

Fenton and Fenton-like oxidation has been already demonstrated to be efficient for the degradation of imidazolium ionic liquids (ILs), but little is known for their degradation pathway and kinetics in such systems. In this work, degradation pathway and kinetics of 1-alkyl-3-methylimidazolium bromides ([Cnmim]Br, n=2, 4, 6, 8, and 10) were investigated in an ultrasound nanoscale zero-valent iron/hydrogen peroxide (US-nZVI/H2O2) system. For this purpose, 1-butyl-3-methylimidazolium bromide ([C4mim]Br) was used as a representative ionic liquid to optimize pH value, nZVI dose, and H2O2 concentration for the degradation reaction. Then, the degradation kinetics of [Cnmim]Br was investigated under optimal conditions, and their degradation intermediates were monitored by gas chromatography-mass spectrometry (GC-MS). It was shown that the degradation of [Cnmim]Br in such a heterogeneous Fenton-like system could be described by a second order kinetic model, and a number of intermediate products were detected. Based on these intermediate products, detailed pathways were proposed for the degradation of [Cnmim]Br in the ultrasound-assisted nZVI/H2O2 system. These findings may be useful for the better understanding of degradation mechanism of the imidazolium ILs in aqueous solutions. PMID:25463239

Zhou, Haimei; Shen, Yuanyuan; Lv, Ping; Wang, Jianji; Li, Pu

2015-03-01

151

Pilot-scale demonstration of the hybrid zero-valent iron process for treating flue-gas-desulfurization wastewater: part I.  

PubMed

The hybrid zero-valent-iron (hZVI) process is a novel chemical treatment process that has shown great potential in previous laboratory and field bench-top scale tests for removing selenium, mercury and nutrients from various industrial wastewaters. In this study, a pilot-scale demonstration was conducted to continuously treat 3.8-7.6 L/min (1-2 gpm) of the flue-gas-desulfurization (FGD) wastewater at a coal-fired power plant for five months. Results show that the hZVI process could simultaneously reduce selenate-Se from 1 to 3 mg/L to below 10 ?g/L and mercury from over 100 ?g/L to below 10 ng/L in compliance with the new stringent effluent discharge limits planned by the U.S. EPA for Se and Hg. A three-stage hZVI system with a combined hydraulic retention time of 12 h is sufficient for Se treatment, while a single-stage system can meet Hg treatment requirement. The successful pilot study demonstrated that the hZVI process is scalable and could be a reliable, low-cost, high-performance treatment platform with many application potentials, particularly, for solving some of the toughest heavy metal water problems. PMID:23128616

Huang, Yong H; Peddi, Phani K; Zeng, Hui; Tang, Ci-Lai; Teng, Xinjun

2013-01-01

152

SBA-15-incorporated nanoscale zero-valent iron particles for chromium(VI) removal from groundwater: mechanism, effect of pH, humic acid and sustained reactivity.  

PubMed

Nanoscale zero-valent iron particles (NZVIs) were incorporated inside the channels of SBA-15 rods by a "two solvents" reduction technique and used to remove Cr(VI) from groundwater. The resulting NZVIs/SBA-15 composites before and after reaction were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results helped to propose the mechanism of Cr(VI) removal by NZVIs/SBA-15, where Cr(VI) in aqueous was firstly impregnated into the channels of the silica, then adsorbed on the surfaces of the incorporated NZVIs and reduced to Cr(III) directly in the inner pores of the silica. Corrosion products included Fe2O3, FeO(OH), Fe3O4 and Cr2FeO4. Batch experiments revealed that Cr(VI) removal decreased from 99.7% to 92.8% when the initial solution pH increased from 5.5 to 9.0, accompanied by the decrease of the kobs from 0.600 to 0.024 min(-1). Humic acid (HA) had a little effect on the removal efficiency of Cr(VI) by NZVIs/SBA-15 but could decrease the reduction rate. The stable reduction of NZVIs/SBA-15 was observed within six cycles. NZVIs/SBA-15 composites offer a promising alternative material to remove heavy metals from groundwater. PMID:24374562

Sun, Xia; Yan, Yubo; Li, Jiansheng; Han, Weiqing; Wang, Lianjun

2014-02-15

153

Molecular stress responses to nano-sized zero-valent iron (nZVI) particles in the soil bacterium Pseudomonas stutzeri.  

PubMed

Nanotoxicological studies were performed in vitro using the common soil bacterium Pseudomonas stutzeri to assess the potentially toxic impact of commercial nano-sized zero-valent iron (nZVI) particles, which are currently used for environmental remediation projects. The phenotypic response of P. stutzeri to nZVI toxicity includes an initial insult to the cell wall, as evidenced by TEM micrographs. Transcriptional analyses using genes of particular relevance in cellular activity revealed that no significant changes occurred among the relative expression ratios of narG, nirS, pykA or gyrA following nZVI exposure; however, a significant increase in katB expression was indicative of nZVI-induced oxidative stress in P. stutzeri. A proteomic approach identified two major defence mechanisms that occurred in response to nZVI exposure: a downregulation of membrane proteins and an upregulation of proteins involved in reducing intracellular oxidative stress. These biomarkers served as early indicators of nZVI response in this soil bacterium, and may provide relevant information for environmental hazard assessment. PMID:24586957

Sacc, Maria Ludovica; Fajardo, Carmen; Martinez-Gomariz, Montserrat; Costa, Gonzalo; Nande, Mar; Martin, Margarita

2014-01-01

154

Transcriptional and proteomic stress responses of a soil bacterium Bacillus cereus to nanosized zero-valent iron (nZVI) particles.  

PubMed

Nanosized zero valent iron (nZVI) is emerging as an option for treating contaminated soil and groundwater even though the potentially toxic impact exerted by nZVI on soil microorganisms remains uncertain. In this work, we focus on nanotoxicological studies performed in vitro using commercial nZVI and one common soil bacterium (Bacillus cereus). Results showed a negative impact of nZVI on B. cereus growth capability, consistent with the entrance of cells in an early sporulation stage, observed by TEM. Despite no changes at the transcriptional level are detected in genes of particular relevance in cellular activity (narG, nirS, pykA, gyrA and katB), the proteomic approach used highlights differentially expressed proteins in B. cereus under nZVI exposure. We demonstrate that proteins involved in oxidative stress-response and tricarboxilic acid cycle (TCA) modulation are overexpressed; moreover proteins involved in motility and wall biosynthesis are repressed. Our results enable to detect a molecular-level response as early warning signal, providing new insight into first line defense response of a soil bacterium after nZVI exposure. PMID:23816452

Fajardo, C; Sacc, M L; Martinez-Gomariz, M; Costa, G; Nande, M; Martin, M

2013-10-01

155

[Effects of particle size of zero-valent iron on the reactivity of activating persulfate and kinetics for the degradation of acid orange 7].  

PubMed

This research described the heterogeneous reactions of persulfate with different particle sizes of zero-valent iron (including 1 mm-ZVI,150 ?m-ZVI,50 nm-ZVI) for degradation of acid orange 7(AO7) , and studied the kinetics and intermediate products of AO7 under these systems. The results demonstrated that these three types of ZVI were efficient in promoting the degradation of AO7, the degradation efficiencies of AO7 were 43% , 97% , and 100% within 90 min respectively, in the 1 mm-ZVI,150 ?m-ZVI and 50 nm- ZVI systems, respectively. With the results of kinetic fitting models, the pseudo first-order kinetics exhibited better fitting results in the 1 mm-ZVI,150 ?m-ZVI systems, while the second-order kinetics exhibited better fitting results in the 50 nm-ZVI system. And the different ZVI types exhibited difference on the AO7 degradation rate constant, which ranged as 50 nm-ZVI > 150 ?m-ZVI > 1 mm-ZVI. The iron corrosion products coating on the ZVI after reaction were composed of ?-Fe2 O3 and some Fe3O4 in the 1 mm-ZVI system while that consisted of Fe3O4 and ?-Fe2O3, FeOOH respectively, in thel50 ?m-ZVI and 50 nm-ZVI systems,. Which were identified by scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and Raman spectroscopy. Some intermediate products, including 2-naphthalenol, 2-methylphenol, 4-ethyl- 3-methyl-phenol, isoindole- 1,3-dione and phthalic acid et al. were identified by GC/MS measurement. Both UV-vis absorbance spectra and GC/MS determination indicated that there was difference in degradation paths of AO7 between the three systems. PMID:25518660

Li, Huan-xuan; Wan, Jin-quan; Ma, Yong-wen; Huang, Ming-zhiz; Wang, Yan; Chen Yang, Mei

2014-09-01

156

Degradation of bromothymol blue by 'greener' nano-scale zero-valent iron synthesized using tea polyphenols  

EPA Science Inventory

A green single-step synthesis of iron nanoparticles using tea (Camellia sinensis) polyphenols is described that uses no added surfactants/polymers as a capping or reducing agents. The expeditious reaction between polyphenols and ferric nitrate occurs within few minutes at room te...

157

Exploring the Role of Nanoscale Zero Valent Iron and Bacteria on the Degradation of a Multi-component Chlorinated Solvent at the Field Scale  

NASA Astrophysics Data System (ADS)

Nanoscale zero valent iron (nZVI) has advanced as a technology for the remediation of priority source zone contaminants in response to early laboratory studies that showed rapid rates of compound degradation. The challenges associated with the delivery of nZVI particles (eg. rapid aggregation and settling) were partially resolved with the addition of a polyelectrolyte polymers, like Carboxymethyl cellulose, that significantly improves the colloidal stability of particles allowing for more controlled injection and transport in the subsurface. Following nZVI application and abiotic contaminant degradation nZVI oxidizes and yields reducing conditions. These reducing conditions are ideal for many dechlorinating bacteria. Given this, application of nZVI for abiotic contaminant degradation followed by bioremediation has become an area of active research interest. In this study nZVI was injected into a contaminated sandy subsurface area. Concentrations of a range of chlorinated compounds, including chlorinated ethenes, ethanes, and methanes were monitored in detail following nano-particle injection in order to access short term abiotic degradation. Monitoring continued over a 2 year period to evaluate the long term effects of nZVI injection on the bacterial communities and the biotic degradation of targeted chlorinated compounds. The study focusses on the degradation and evolution of intermediate compounds from reaction with targeted contaminant compounds along the nZVI flow path. Bacterial populations were quantified before injection to confirm that beneficial chloride reducing bacteria were present on site. The microbiological response to the injection of nZVI was studied and the performance of bacteria along the nZVI flow path and outside the nZVI affected area will be compared.

Kocur, C. M.; Lomheim, L.; Boparai, H.; Chowdhury, A. I.; Weber, K.; Austrins, L. M.; Sleep, B. E.; Edwards, E.; O'Carroll, D. M.

2013-12-01

158

Pilot-scale demonstration of the hybrid zero-valent iron process for treating flue-gas-desulfurization wastewater: part II.  

PubMed

The hybrid zero-valent-iron (hZVI) process is a novel chemical treatment process that has shown promise for removing heavy metals and nutrients from industrial wastewaters. In this study, a pilot-scale demonstration was conducted to continuously treat 3.8-7.6 L/min (1-2 gpm) of the flue-gas-desulfurization (FGD) wastewater at a coal-fired power plant for 5 months. In this paper, a spike test was conducted to evaluate performance of the hZVI process for removing selected toxic metals at artificially elevated concentrations. The results showed that a multiple-stage hZVI process could decrease selenate-Se from 22 mg/L to ~10 ?g/L and dissolved Hg(2+) from 1.15 mg/L to ~10 ng/L. In addition, the process simultaneously removed a broad spectrum of heavy metals such as As(III), As(V), Cr(VI), Cd(II), Pb(II) and Cu(II) from mg/L to near or sub-ppb (?g/L) level after a single-stage treatment. The process consumed about 0.3 kg ZVI per 1 m(3) FGD wastewater treated at a cost of about US$0.6/m(3). Solid waste production and energy consumption were reasonably low. The successful pilot study demonstrated that the hZVI technology can be a low-cost, high-performance treatment platform for solving some of the toughest heavy metal water problems. PMID:23168619

Huang, Yong H; Peddi, Phani K; Zeng, Hui; Tang, Ci-Lai; Teng, Xinjun

2013-01-01

159

Removal of organic compounds and trace metals from oil sands process-affected water using zero valent iron enhanced by petroleum coke.  

PubMed

The oil production generates large volumes of oil sands process-affected water (OSPW), referring to the water that has been in contact with oil sands or released from tailings deposits. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. Zero valent iron alone (ZVI) and in combination with petroleum coke (CZVI) were investigated as environmentally friendly treatment processes for the removal of naphthenic acids (NAs), acid-extractable fraction (AEF), fluorophore organic compounds, and trace metals from OSPW. While the application of 25g/L ZVI to OSPW resulted in 58.4% removal of NAs in the presence of oxygen, the addition of 25g petroleum coke (PC) as an electron conductor enhanced the NAs removal up to 90.9%. The increase in ZVI concentration enhanced the removals of NAs, AEF, and fluorophore compounds from OSPW. It was suggested that the electrons generated from the oxidation of ZVI were transferred to oxygen, resulting in the production of hydroxyl radicals and oxidation of NAs. When OSPW was de-oxygenated, the NAs removal decreased to 17.5% and 65.4% during treatment with ZVI and CZVI, respectively. The removal of metals in ZVI samples was similar to that obtained during CZVI treatment. Although an increase in ZVI concentration did not enhance the removal of metals, their concentrations effectively decreased at all ZVI loadings. The Microtox() bioassay with Vibrio fischeri showed a decrease in the toxicity of ZVI- and CZVI-treated OSPW. The results obtained in this study showed that the application of ZVI in combination with PC is a promising technology for OSPW treatment. PMID:24681364

Pourrezaei, Parastoo; Alpatova, Alla; Khosravi, Kambiz; Drzewicz, Przemys?aw; Chen, Yuan; Chelme-Ayala, Pamela; Gamal El-Din, Mohamed

2014-06-15

160

ARSENATE AND ARSENITE REMOVAL BY ZERO-VALENT IRON: KINETICS, REDOX TRANSFORMATION, AND IMPLICATIONS FOR IN SITU GROUNDWATER REMEDIATION  

EPA Science Inventory

Batch tests were performed utilizing four zerovalent iron (Fe0) filings (Fisher, Peerless, Master Builders, and Aldrich) to remove As(V) and As(III) from water. One gram of metal was reacted headspace-free at 23 C for up to 5 days in the dark with 41.5 mL of 2 mg L-1 As(V), or A...

161

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose.  

PubMed

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500?g/L) was achieved in just 5min when the S-nZVI mass concentration was 0.3g/L and initial solution pH of 7??0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5??0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14mg/g for arsenic (V), and 12.2mg/g for arsenic (III). It could be concluded that starch stabilized Fe(0) nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Mosaferi, Mohammad; Nemati, Sepideh; Khataee, Alireza; Nasseri, Simin; Hashemi, Ahmad Asl

2014-01-01

162

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose  

PubMed Central

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500?g/L) was achieved in just 5min when the S-nZVI mass concentration was 0.3g/L and initial solution pH of 7??0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5??0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14mg/g for arsenic (V), and 12.2mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

2014-01-01

163

Removal of uranium (VI) from aqueous systems by nanoscale zero-valent iron particles suspended in carboxy-methyl cellulose  

NASA Astrophysics Data System (ADS)

Carboxy-methyl-cellulose (CMC), a common "delivery vehicle" for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxy-methyl-cellulose with and without iron nanoparticles (CMC-INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Qmax, of 185.18 mg/g and 322.58 mg/g for CMC and CMC-INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.

Popescu (Ho?tuc), Ioana-Carmen; Filip, Petru; Humelnicu, Doina; Humelnicu, Ionel; Scott, Thomas Bligh; Crane, Richard Andrew

2013-11-01

164

Reduction of chlorinated ethanes by nanosized zero-valent iron: kinetics, pathways, and effects of reaction conditions.  

PubMed

Nanosized iron (< 100 nm in diameter) was synthesized in the laboratory and applied to the reduction of eight chlorinated ethanes (hexachloroethane (HCA), pentachloroethane (PCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA), 1,1,2-trichloroethane (1,1,2-TCA), 1,1,1-trichloroethane (1,1,1-TCA), 1,2-dichloroethane (1,2-DCA), and 1,1-dichloroethane (1,1-DCA)) in batch reactors. Reduction of 1,1,1-TCA increased linearly with increasing iron loading between 0.01 and 0.05 g per 124 mL solution (0.08-0.4 g/L). Varying initial concentrations of PCA between 0.025 and 0.125 mM resulted in relatively constant pseudo-first-order rate constants, indicating PCA removal conforms to pseudo-first-order kinetics. The reduction of 1,1,2,2-TeCA decreased with increasing pH; however, dehydrohalogenation of 1,1,2,2-TeCA became important at high pH. All chlorinated ethanes except 1,2-DCA were transformed to less chlorinated ethanes or ethenes. The surface-area-normalized rate constants from first-order kinetics analysis ranged from < 4 x 10(-6) to 0.80 L m(-2) h(-1). In general, the reactivity increased with increasing chlorination. Among tri- and tetrasubstituted compounds, the reactivity was higher for compounds with chlorine atoms more localized on a single carbon (e.g., 1,1,1-TCA > 1,1,2-TCA). Reductive beta-elimination was the major pathway for the chlorinated ethanes possessing alpha,beta-pairs of chlorine atoms to form chlorinated ethenes, which subsequently reacted with nanosized iron. Reductive alpha-elimination and hydrogenolysis were concurrent pathways for compounds possessing chlorine substitution on one carbon only, forming less chlorinated ethanes. PMID:16173587

Song, Hocheol; Carraway, Elizabeth R

2005-08-15

165

Field Application of Nanoscale Zero-Valent Iron Particles to In-Situ Treatment of Trichloroethylene in an Aquifer with an Oxic Condition  

NASA Astrophysics Data System (ADS)

Nanoscale zero-valent iron (NZVI) is a promising reactive medium for rapid in situ remediation of various contaminants including chlorinated solvents, in the groundwater and soil. However, once NZVI particles are injected into an aquifer, they can have poor mobility and reactivity due to their aggregation tendency and to interactions with groundwater solutes such as anions, dissolved organic matter (NOM), and oxygen. Therefore, key technical challenges in the field application are to distribute NZVI particles effectively within the contaminated area, and to maintain the reactivity of NZVI particles while they are delivered. Field studies were conducted to evaluate: (i) mobility of a polymer-coated NZVI in an aquifer with a strong oxic condition, (ii) effect of dissolved oxygen on the degradation of TCE, and (iii) effects of dissolved anions and oxygen on the sustainability of injected NZVI. Initially, natural gradient and forced gradient tracer tests were carried out to investigate the hydrogeological characteristics of the site before injecting NZVI. Preferential flow paths of the groundwater identified by the tracer tests were towards northeast and northwest. The NZVI slurry was then prepared on site and injected at a concentration of up to 10 g/L into the subsurface having area of 140 ft2. A total of approximately 66 pounds of the coated NZVI were successfully injected. During the field injections, NZVI particles were observed in a monitoring well located 13 feet downgradient from the injection well. Iron monitoring data showed that the NZVI could reasonably be delivered under the oxic condition that could enhance the formation of iron oxides, which could be deleterious for the NZVI transport. TCE degradation was more active at the wells with high DO concentrations, based on the correlation between TCE concentrations and DO or NZVI concentrations. It was suspected that solid or liquid form of ferrous ion from the oxidation of NZVI caused a Fenton reaction in presence of oxygen. The TCE monitoring data showed that 99% of the TCE at the site was removed by the NZVI injection. The concentrations of degradation products such as ethane and ethene increased in the monitoring wells following the NZVI injections. A lab evaluation showed that TCE degradation capacity of the injected NZVI (collected after 5 months) remained up to 30% compared with the initial capacity. Groundwater monitoring was conducted for approximately eight months to evaluate the long-term performance of the NZVI particles.

Ahn, J.; Kim, C.; Huynh, T. N.; Hwang, I.

2013-12-01

166

Effects of carbonate species on the kinetics of dechlorination of 1,1,1-trichloroethane by zero-valent iron.  

PubMed

The effect of precipitates on the reactivity of iron metal (Fe0) with 1,1,1-trichloroethane (TCA) was studied in batch systems designed to model groundwaters that contain dissolved carbonate species (i.e., C(IV)). At representative concentrations for high-C(IV) groundwaters (approximately 10(-2) M), the pH in batch reactors containing Fe0 was effectively buffered until most of the aqueous C(IV) precipitated. The precipitate was mainly FeCO3 (siderite) but may also have included some carbonate green rust. Exposure of the Fe0 to dissolved C(IV) accelerated reduction of TCA, and the products formed under these conditions consisted mainly of ethane and ethene, with minor amounts of several butenes. The kinetics of TCA reduction were first-order when C(IV)-enhanced corrosion predominated but showed mixed-order kinetics (zero- and first-order) in experiments performed with passivated Fe0 (i.e., before the onset of pitting corrosion and after repassivation by precipitation of FeCO3). All these data were described by fitting a Michaelis-Menten-type kinetic model and approximating the first-order rate constant as the ratio of the maximum reaction rate (Vm) and the concentration of TCA at half of the maximum rate (K(1/2)). The decrease in Vm/K(1/2) with increasing C(IV) exposure time was fit to a heuristic model assuming proportionality between changes in TCA reduction rate and changes in surface coverage with FeCO3. PMID:12387405

Agrawal, Abinash; Ferguson, William J; Gardner, Bruce O; Christ, John A; Bandstra, Joel Z; Tratnyek, Paul G

2002-10-15

167

Influence of hydrogeochemical processes on zero-valent iron reactive barrier performance: a field investigation.  

PubMed

Geochemical and mineralogical changes were evaluated at a field Fe0-PRB at the Oak Ridge Y-12 site concerning operation performance during the treatment of U in high NO3- groundwater. In the 5-year study period, the Fe0 remained reactive as shown in pore-water monitoring data, where increases in pH and the removal of certain ionic species persisted. However, coring revealed varying degrees of cementation. After 3.8-year treatment, porosity reduction of up to 41.7% was obtained from mineralogical analysis on core samples collected at the upgradient gravel-Fe0 interface. Elsewhere, Fe0 filings were loose with some cementation. Fe0 corrosion and pore volume reduction at this site are more severe due to the presence of NO3- at a high level. Tracer tests indicate that hydraulic performance deteriorated: the flow distribution was heterogeneous and under the influence of interfacial cementation a large portion of water was diverted around the Fe0 and transported outside the PRB. Based on the equilibrium reductions of NO3- and SO4(2-) by Fe0 and mineral precipitation, geochemical modeling predicted a maximum of 49% porosity loss for 5 years of operation. Additionally, modeling showed a spatial distribution of mineral precipitate volumes, with the maximum advancing from the interface toward downgradient with time. This study suggests that water quality monitoring, coupled with hydraulic monitoring and geochemical modeling, can provide a low-cost method for assessing PRB performance. PMID:16051393

Liang, Liyuan; Moline, Gerilynn R; Kamolpornwijit, Wiwat; West, Olivia R

2005-08-01

168

Influence of hydrogeochemical processes on zero-valent iron reactive barrier performance: a field investigation.  

PubMed

Geochemical and mineralogical changes were evaluated at a field Fe0-PRB at the Oak Ridge Y-12 site concerning operation performance during the treatment of U in high NO3- groundwater. In the 5-yr study period, the Fe0 remained reactive as shown in pore water monitoring data, where increases in pH and the removal of certain ionic species persisted. However, coring revealed varying degrees of cementation. After 3.8-yr treatment, porosity reduction of up to 41.7% was obtained from mineralogical analysis on core samples collected at the upgradient gravel-Fe0 interface. Elsewhere, Fe0 filings were loose with some cementation. Fe0 corrosion and pore volume reduction at this site are more severe due to the presence of NO3- at a high level. Tracer tests indicate that hydraulic performance deteriorated: the flow distribution was heterogeneous and under the influence of interfacial cementation a large portion of water was diverted around the Fe0 and transported outside the PRB. Based on the equilibrium reductions of NO3- and SO4(2-) by Fe0 and mineral precipitation, geochemical modeling predicted a maximum of 49% porosity loss for 5 yr of operation. Additionally, modeling showed a spatial distribution of mineral precipitate volumes, with the maximum advancing from the interface toward downgradient with time. This study suggests that water quality monitoring, coupled with hydraulic monitoring and geochemical modeling, can provide a low-cost method for assessing PRB performance. PMID:16126304

Liang, Liyuan; Moline, Gerilynn R; Kamolpornwijit, Wiwat; West, Olivia R

2005-11-01

169

Reduction and immobilization of radionuclides and toxic metal ions using combined zero valent iron and anaerobic bacteria. Year one technical progress report  

SciTech Connect

'The objective of this project is to design a combined abiotic/microbial, reactive, permeable, in-situ barrier with sufficient reductive potential to prevent downgradient migration of toxic metal ions. The field-scale application of this technology would utilize anaerobic digester sludge, Fe(O) particles for supporting anaerobic biofilms, and suitable aquifer material for construction of the barrier. The major goals for Year 1 were to establish the sulfate reducing mixed culture, to obtain sources of iron metal, and to conduct background experiments which will establish baseline rates for abiotic chromium reduction rates. Research completed to date is described.'

Weathers, L.J.; Katz, L.E.

1997-10-01

170

Reduction of Hexavalent Chromium in Soil and Ground Water Using Zero-Valent Iron Under Batch and Semi-Batch Conditions  

Microsoft Academic Search

Chemical remediation of soil and groundwater containing hexavalent chromium (Cr(VI)) was carried out under batch and semi-batch\\u000a conditions using different iron species: (Fe(II) (sulphate solution); Fe0\\u000a G (granulated elemental iron); ZVIne (non-stabilized zerovalent iron) and ZVIcol (colloidal zerovalent iron). ZVIcol was synthesized\\u000a using different experimental conditions with carboxymethyl cellulose (CMC) and ultra-sound. Chemical analysis revealed that\\u000a the contaminated soil (frank

Dbora V. Franco; Leonardo M. Da Silva; Wilson F. Jardim

2009-01-01

171

ARSENATE AND ARSENITE REMOVAL BY ZERO-VALENT IRON: EFFECTS OF PHOSPHATE, SILICATE, CARBONATE, BORATE, SULFATE, CHROMATE, MOLYBDATE, AND NITRATE, RELATIVE TO CHLORIDE  

EPA Science Inventory

Batch tests were performed to evaluate the effects of inorganic anion competition on the kinetics of arsenate (As(V)) and arsenite (As(III)) removal by zerovalent iron (Peerless Fe0) in aqueous solution. The oxyanions underwent either sorption-dominated reactions (phosphate, sil...

172

DIRECT PUSH METHODS FOR LOCATING AND COLLECTING CORES OF AQUIFER SEDIMENT AND ZERO-VALENT IRON FROM PERMEABLE REACYTIVE BARRIERS  

EPA Science Inventory

It is often necessary to collect core samples that do not fit the normal sampling protocol. This Field Innovation Forum submission describes new methodology that enables researchers to collect soil samples in situations where the normal vertical sampling techniques will deliver ...

173

USING ZERO-VALENT METAL NANOPARTICLES TO REMEDIATE ORGANIC CONTAMINANTS  

EPA Science Inventory

The transport of organic contaminants down the soil profile constitutes a serious threat to the quality of ground water. Zero-valent metals are considered innocuous abiotic agents capable of mediating decontamination processes in terrestrial systems. In this investigation, ze...

174

Oxidative degradation of organic pollutants in aqueous solution using zero valent copper under aerobic atmosphere condition.  

PubMed

Oxidative degradation of organic pollutants and its mechanism were investigated in aqueous solution using zero valent copper (ZVC) under aerobic atmosphere condition. Diethyl phthalate (DEP) was completely oxidized after 120 min reaction by ZVC at initial pH 2.5 open to the air. DEP degradation followed the pseudo-first-order kinetics after the lag period, and the degradation rate of DEP increased gradually with the increase of ZVC dosage, and the decrease of initial pH from 5.8 to 2.0. ZVC required a shorter induction time and exhibited persistent oxidation capacity compared to that of zero valent iron and zero valent aluminium. The mechanism investigation showed that remarkable amount of Cu(+)/Cu(2+) and H2O2 were formed in ZVC acidic system, which was due to the corrosive dissolution of ZVC and the concurrent reduction of oxygen. The addition of tert-butanol completely inhibited the degradation of DEP and the addition of Fe(2+) greatly enhanced the degradation rate, which demonstrated that hydroxyl radical was mainly responsible for the degradation of DEP in ZVC acidic system under aerobic atmosphere condition, and the formation of hydroxyl radical was attributed to the Fenton-like reaction of in situ formed Cu(+) with H2O2. PMID:24857902

Wen, Gang; Wang, Sheng-Jun; Ma, Jun; Huang, Ting-Lin; Liu, Zheng-Qian; Zhao, Lei; Xu, Jin-Lan

2014-06-30

175

Mineral precipitation and porosity losses in granular iron columns  

Microsoft Academic Search

As permeable reactive barriers containing zero-valent iron are becoming more widely used to remediate contaminated groundwaters, there remains much uncertainty in predicting their long-term performance. This study focuses on two factors affecting performance and lifetime of the granular iron media: plugging at the treatment zone entrance and precipitation in the bulk iron media. Plugging at the system entrance is due

Patricia D. Mackenzie; David P. Horney; Timothy M. Sivavec

1999-01-01

176

Reductive elimination of chlorinated ethylenes by zero-valent metals  

Microsoft Academic Search

To date it does not appear to have been demonstrated in the literature that halogenated ethylenes can undergo reductive β-elimination to alkynes under environmental conditions. The purpose of this paper is to provide experimental evidence that such pathways may be involved in the reaction of chloroethylenes with zero-valent metals as well as to speculate on the significance of the products

A. Lynn Roberts; Lisa A. Totten; William A. Arnold; David R. Burris; Timothy J. Campbell

1996-01-01

177

[Zero valent seleniume nanoparticles bioavailability estimation in rats].  

PubMed

Bioavailability of zero valent selenium (Se) nanoparticles with average size 60 nm was measured in rats receiving selenium deficient diet. There was demonstrated that intragastric administration of Se nanoparticles resulted in dose-dependent increase of serum Se level, normalization of tissue thiol pools, immune status and hepatocytes apoptosis. Possibilities are discussed of Se nanoparticles use in nutrition as a source of this trace element. PMID:22232881

Raspopov, R V; Arianova, E A; Trushina, N; Mal'tsev, G Iu; Kuz'min, P G; Shafeev, G A; Prodvorova, S M; Gmoshinski?, I V; Khotimchenko, S A

2011-01-01

178

AMELIORATION OF ACID MINE DRAINAGE USING REACTIVE MIXTURES IN PERMEABLE REACTIVE BARRIERS  

EPA Science Inventory

The generation and release of acidic drainage from mine wastes is an environmental problem of international scale. The use of zero-valent iron and/or iron mixtures in subsurface Permeable Reactive Barriers (PRB) presents a possible passive alternative for remediating acidic grou...

179

FINAL REPORT. FUNDAMENTAL STUDIES OF THE REMOVAL OF CONTAMINANTS FROM GROUND AND WASTE WATER VIA REDUCTION BY ZERO-VALENT METALS  

EPA Science Inventory

Oxyanions of uranium, selenium, chromium, arsenic, technetium, and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites, and in other areas of the U.S. A potential remediation method is to react the contaminated water with zero-valent iron (ZVI). We ar...

180

Reactive iron barriers: a niche enabling microbial dehalorespiration of 1,2-dichloroethane.  

PubMed

A reactive iron barrier in a contaminated aquifer with low pH was found to dechlorinate 1,2-dichloroethane (1,2-DCA) in situ. This chlorinated ethane is known to resist abiotic reduction by zero valent iron. Samples taken up-gradient and within the barrier were used to inoculate anaerobic batch cultures amended with various electron donors. Cultures inoculated with groundwater from within the reactive iron barrier reduced 1,2-DCA to ethene. The same effect could be achieved by simultaneously supplying hydrogen while neutralising pH. The presence of iron or hydrogen at neutral pH had negligible effects on 1,2-DCA reduction in cultures inoculated with groundwater sampled up-gradient of the barrier. Molecular microbial community characterisation revealed that Dehalobacter species were more abundant in groundwater sampled from within the barrier. These findings suggest reactive iron barriers represent a remediation technology for 1,2-DCA degradation acting through in situ recruitment of 1,2-DCA reducing bacteria such as Dehalobacter. PMID:20607230

Zemb, Olivier; Lee, Matthew; Low, Adrian; Manefield, Mike

2010-09-01

181

ACCUMULATION RATE OF MICROBIAL BIOMASS AT TWO PERMEABLE REACTIVE BARRIER SITES  

EPA Science Inventory

Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of in-situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero-valent iron reactivity...

182

Electrochemical deposition of green rust on zero-valent iron  

E-print Network

Chair of Advisory Committee: Dr. Bill Batchelor Perchloroethylene (PCE) is a toxic contaminant that has been introduced into the environment over many years through industrial and agricultural wastes. Research has been done in the past...ble Vijay D. Kulkarni) whose toil in the barren soil of my mind bore this fruit, finally! vi ACKNOWLEDGEMENTS I hereby wholeheartedly acknowledge the help provided by my lab-mates, especially Jin- Kun Song and Choi; and my advisor Dr. Batchelor...

Kulkarni, Dhananjay Vijay

2006-08-16

183

Perchlorate reduction using electrochemically induced pitting corrosion of zero-valent titanium  

E-print Network

effective technologies, especially chemical treatments, to completely destroy trace levels of perchlorate present in drinking and groundwater. The research on perchlorate reduction by zero-valent titanium (Ti(0)) showed that perchlorate was effectively...

Lee, Chun Woo

2009-05-15

184

Performance Evaluation of In-Situ Iron Reactive Barriers at the Oak Ridge Y-12 Site  

SciTech Connect

In November 1997, a permeable iron reactive barrier trench was installed at the S-3 Ponds Pathway 2 Site located at the Y-12 Plant, Oak Ridge, Tennessee. The overall goal of the project is to evaluate the ability of permeable reactive barrier technology to remove uranium, nitrate, and other inorganic contaminants in groundwater and to assess impacts of biogeochemical interactions on long-term performance of the treatment system. Zero-valent iron (Fe0) was used as the reactive medium, which creates a localized zone of reduction or low oxidation reduction potential (ORP), elevated pH, and dissolved H{sub 2} as Fe{sup 0} corrodes in groundwater. These conditions favor the removal of metals and radionuclides (such as uranium and technetium) through redox-driven precipitation and/or sorption to iron corrosion byproducts, such as iron oxyhydroxides. The technology is anticipated to be economical and low in maintenance as compared with conventional pump-and-treat technology. Groundwater monitoring results indicate that the iron barrier is effectively removing uranium and technetium, the primary contaminants of concern, as anticipated from our previous laboratory studies. In addition to uranium and technetium, nitrate, sulfate, bicarbonate, calcium, and magnesium are also found to be removed, either partially or completely by the iron barrier. Elevated concentrations of ferrous ions and sulfide, and pH were observed within the iron barrier. Although ferrous iron concentrations were initially very high after barrier installation, ferrous ion concentrations have decreased to low to non-detectable levels as the pH within the iron has increased over time (as high as 9 or 10). Iron and soil core samples were taken in February 1999 and May 2000 in order to evaluate the iron surface passivation, morphology, mineral precipitation and cementation, and microbial activity within and in the vicinity of the iron barrier. Results indicate that most of the iron filings collected in cores were still loose and not clogged after approximately 2.5 years of barrier installation. However, significant amounts of cemented iron filings were observed in the upgradient portion of the iron. In particular, the cementation appeared to have increased significantly over time from the 1999 to 2000 coring events in both the upgradient and downgradient portions of the iron. Minerals identified by scanning electron microscope (SEM), energy dispersive x-ray (EDX), and x-ray diffraction (XRD) that have precipitated in the iron include iron sulfide, calcium carbonate (aragonite), iron oxyhydroxides (goethite, akagneite, amorphous), siderite (iron carbonate), makinawite, and green rusts. These mineral precipitants are responsible for the cementation observed within the iron barrier. Elevated microbial activity and increased diversity within and in the vicinity of the iron barrier were also observed, particularly denitrifiers and sulfate-reducers, which may have been responsible or partially responsible for the removal of nitrate and sulfate in groundwater and the formation of ferrous sulfide minerals within the iron barrier. Hydraulic gradients across the Pathway 2 site have remained relatively stable and consistent from east to west. Increases and decreases in the gradients across the site observed over the past 2.5 years appear to be primarily related to recharge during precipitation events and seasonal fluctuations. However, closer inspection of gradient fluctuations within the iron appear to indicate that cementation within the iron may be starting to impact groundwater flow through the iron. Since the spring of 1999, recharge events have had a more pronounced impact on hydraulic gradients observed between wells located upgradient, within, and downgradient of the iron. This data suggests that the connectivity of the iron and gravel in the upgradient portion of the trench to the iron and gravel in the downgradient portion of the trench may be decreasing over time due to cementation in the iron.

Watson, D.B.

2003-12-30

185

Zero-Valent Metallic Treatment System and Its Application for Removal and Remediation of Polychlorinated Biphenyls (Pcbs)  

NASA Technical Reports Server (NTRS)

PCBs are removed from contaminated media using a treatment system including zero-valent metal particles and an organic hydrogen donating solvent. The treatment system may include a weak acid in order to eliminate the need for a coating of catalytic noble metal on the zero-valent metal particles. If catalyzed zero-valent metal particles are used, the treatment system may include an organic hydrogen donating solvent that is a non-water solvent. The treatment system may be provided as a "paste-like" system that is preferably applied to natural media and ex-situ structures to eliminate PCBs.

Quinn, Jacqueline W. (Inventor); Clausen, Christian A. (Inventor); Geiger, Cherie L. (Inventor); Brooks, Kathleen B. (Inventor)

2012-01-01

186

Chemistry and Microbiology of Permeable Reactive Barriers for In Situ Groundwater Clean up  

Microsoft Academic Search

Permeable reactive barriers (PRBs) are receiving a great deal of attention as an innovative, cost-effective technology for in situ clean up of groundwater contamination. A wide variety of materials are being proposed for use in PRBs, including zero-valent metals (e.g., iron metal), humic materials, oxides, surfactant-modified zeolites (SMZs), and oxygen- and nitrate-releasing compounds. PRB materials remove dissolved groundwater contaminants by

Michelle M. Scherer; Sascha Richter; Richard L. Valentine; Pedro J. J. Alvarez

2000-01-01

187

Hydrogeochemical and biological processes affecting the long-term performance of an iron-based permeable reactive barrier.  

PubMed

Despite the wide diffusion of zero-valent iron (Fe(0)) permeable reactive barriers (PRBs), there is still a great uncertainty about their longevity and long-term performance. The aim of this study is to investigate the biological and the hydrogeochemical processes that take place at a Fe(0) installation located in Avigliana, Italy, and to derive some general considerations about long-term performance of PRBs.The examined PRB was installed in November 2004 to remediate a chlorinated solvents plume (mainly trichloroethene and 1,2-dichloroethene). The investigation was performed during the third year of operation and included: (1) groundwater sampling and analysis for chlorinated solvents, dissolved CH(4), dissolved H(2) and major inorganic constituents; (2) Fe(0) core sampling and analysis by SEM-EDS, XRD, and FTIR spectroscopy for the organic fraction; (3) in situ permeability tests and flow field monitoring by water level measurements.The study revealed that iron passivation is negligible, as the PRB is still able to effectively treat the contaminants and to reduce their concentrations below target values. Precipitation of several inorganic compounds inside the PRB was evidenced by SEM-EDS and XRD analysis conducted on iron samples. Groundwater sampling evidenced heavy sulfate depletion and the highest reported CH(4) concentration (>5,000 microg/L) at zero-valent iron PRB sites. These are due to the intense microbial activity of sulfate-reducers and methanogens, whose proliferation was most likely stimulated by the use of a biopolymer (i.e. guar gum) as shoring fluid during the excavation of the barrier. Slug tests within the barrier evidenced an apparent hydraulic conductivity two orders of magnitude lower than the predicted value. This occurrence can be ascribed to biofouling and/or accumulation of CH(4)(g) inside the iron filings.This experience suggests that when biopolymer shoring is planned to be used, long-term column tests should be performed beforehand with initial bacterial inoculation and organic substrate dosing, in order to predict the effects of bacterial overgrowth and gas generation. During construction particular care should be taken in order to minimize the amount of used biopolymer so that complete breakdown can be achieved. PMID:19329678

Zolla, Valerio; Freyria, Francesca Stefania; Sethi, Rajandrea; Di Molfetta, Antonio

2009-01-01

188

EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment  

SciTech Connect

This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

NONE

1999-11-01

189

EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment  

SciTech Connect

This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

Not Available

1999-01-01

190

Low-Frequency Electrical Properties of Zero Vvalent Iron-Sand Columns: Implications for Monitoring the Performance of Reactive Iron Wall Barriers  

NASA Astrophysics Data System (ADS)

The reactive iron barrier is an in-situ technology for passive remediation of chlorinated solvents and heavy metals. Redox reactions occurring on the iron surface effectively remove these contaminants from groundwater. The effectiveness of this redox reaction diminishes with time due to oxidation and precipitation occurring on the metal surface, such that the long-term performance of reactive barriers is uncertain. Non-invasive measurement methods for evaluating reactive barrier performance are thus required to support remedial strategies at reactive barrier installations. Low-frequency (0.1-1000 Hz) electrical measurements are sensitive to the electrochemistry of the metal surface-pore fluid interface. We are conducting a series of laboratory experiments to assess the sensitivity of electrical methods (induced polarization and resistivity) to changes in the physicochemical properties of the metal-fluid interface that occur over time. In this paper we present the results of baseline studies on zero-valent iron-sand columns as a function of (a) reactive iron concentration (b) saturating fluid chemistry, and (c) degree of surface oxidation. The sensitivity of low-frequency electrical parameters to total zero-valent iron (Fe0) surface area was investigated by synthesizing Fe-Ottawa sand samples with varying Fe0 concentration from 0-10 percent. The dependence on ionic strength and electrolyte activity was investigated by making measurements on samples saturated with 0.001-1.0 for NaNO3, NaCl and CaCl2 solutions. The effect of pH was evaluated at constant electrolyte activity. As a first step towards evaluating the sensitivity of electrical measurements to reduction in reactive iron performance, measurements were made over a three month period of ageing and correlated with geochemical indicators (pH, Eh, electrical conductivity, iron concentrations) of Fe surface oxidation and precipitation. We find that induced polarization (IP) parameters are highly sensitive to Fe0 surface area whereas conduction parameters measured with the resistivity method are insensitive to Fe0 concentration over the investigated range. Polarization at the iron-electrolyte interface shows a power law relationship with electrolyte activity for all solutions and is consistent with Warburg impedance theory. Power-law exponents are slightly higher than that predicted for the active ion species based on Warburg impedance theory. Polarization magnitude depends on ionic composition of the electrolyte with the magnitude following the order CaCl2: NaCl: NaNO3. Conduction parameters are insensitive to ionic composition at constant electrolyte activity. Electrolyte activity exerts a strong control on the polarization relaxation length-scale, with time constant of the relaxation decreasing with increasing electrolyte activity. Polarization parameters measured during three months of ageing are clearly correlated with time and suggest that electrical measurements are sensitive to reduction in reactive iron performance.

Choi, J.; Slater, L. D.; Wu, Y.

2003-12-01

191

Fundamental studies of the removal of contaminants from ground and waste waters via reduction by zero-valent metals. Annual progress report, September 1, 1996--August 31, 1997  

SciTech Connect

'Contaminated groundwater is a problem throughout the US and the world. In many instances the tvpes of contamination can be directly attributed to man''s actions. For instance, the burial of wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements that are soluble and mobile in soils and aquifers. Oxyanions of selenium. chromium. uranium. arsenic. and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. In addition. the careless disposal of cleaning solvents. such as carbon tetrachloride and trichloroethylene. has further contaminated many groundwaters at these sites. In agricultural areas of the western US, shallow groundwaters have become contaminated with high levels of selenate, chromate, and uranyl. The management of these waters requires treatment to remove the contaminants before reuse or surface water disposal. In one instance in the Central Valley of California. the discharge of selenate-contaminated shallow groundwater to a wildlife refuge caused catastrophic bird deaths and deformities of embryos. At sites where solid-propellant rocket motors were tested or disposed of, high concentrations of perchlorate and trichloroethylene are being found in the groundwater. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used, on an experimental basis, for the reductive dechlorination of solvents and the removal of toxic trace elements. Both in situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. Only limited success has been achieved in the field, partly because the basic surface chemical reactions are not well understood. The authors are performing fundamental investigations of the interactions of the relevant chlorinated solvents, trace elements, and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop the fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures. The authors are perforrming both bulk chemical measurements of the reduction reactions and surface science studies of model chemical systems. During this first year of funding, the authors have already made significant progress in both areas. Initially, they have focused primarily on the reduction of selenate by elemental iron. They have also performed some work with chromate, perchlorate, uranyl, and carbon tetrachloride, as well. In the following sections, some of the progress is described.'

Yarmoff, J.A.; Amrhein, C.

1997-01-01

192

Rapid degradation of endosulfan by zero-valent zinc in water and soil.  

PubMed

Endosulfan has been included in the list of persistent organic pollutants (POPs) in 2011. The degradation of endosulfan by zero-valent zinc in water and soil was first investigated. The results showed that >90% endosulfan could be degraded in 180min. The degradation was accelerated under acidic conditions with the absence of dissolved oxygen, while the nature of the soil only exhibited a negligible effect. The half-life was decreased from 130.75min to 41.75min with the increment of Zn(0) from 0.1g to 1g in soil. The use of Zn(0) was more effective than Fe(0) for the degradation of endosulfan with a half-life of 110min and 330min. The cationic surfactant was more effective at enhancing the degradation of endosulfan than anionic and nonionic surfactant. The degradation pathway was speculated, and four chlorine of endosulfan were proposed to be reduced. The method exhibited obvious advantages over traditional endosulfan treatments, and the research results will lay a foundation for practical application of the method. PMID:25556870

Cong, Lujing; Guo, Jing; Liu, Jisong; Shi, Haiyan; Wang, Minghua

2015-03-01

193

In situ synthesis of zero-valent silver nanoparticles in polymethylmethacrylate under high temperature  

NASA Astrophysics Data System (ADS)

In this work, the silver nanoparticles were synthesized in polymethylmethacrylate (PMMA) matrix under high temperature with polyvinylpyrrolidone (PVP) as additional stabilizer and N,N-dimethylformamide (DMF) as reaction medium. The UV-vis spectroscopy and transmission electron microscopy (TEM) were adopted to investigate the growth and shape conversion of Ag nanoparticles with the lacking of additional Ag source. The results showed that the stable zero-valent Ag in PMMA was obtained successfully. Two types of Ag nanoparticles, single-crystal and twinned ones, could form in the initial period. While the twinned ones will gradually disappear along with the reaction processed, the single-crystal ones could survive and slowly grow by consuming the Ag atoms which were etched form twinned ones. The single-crystal ones will take shape conversion from sphere to nanocube with nearly the same particle size after the total disappearance of twinned ones. The size and shape of Ag nanoparticles can be well controlled by reaction time. The high viscosity PMMA matrix plays the important role of controlling the growth of the Ag nanoparticles, and the PVP takes the responsibility of the shape conversion.

Xiong, Yuanlu; Luo, Guoqiang; Chen, Cheng; Yuan, Huan; Shen, Qiang; Li, Meijuan

2012-05-01

194

REMEDIATING RDX-CONTAMINATED WATER AND SOIL USING ZERO-VALENT IRON. (R825549C043)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

195

Dechlorination of PCE by mixtures of green rust and zero-valent iron  

E-print Network

such as pH (8, 9, and 10), ZVI pretreatment, and preparation method of the mixtures (GR[S]?? synthesized in the presence of ZVI; GR[S]?? and ZVI mixed after preparation). For all the experimental conditions evaluated, the activities of these reductants...

Marchal, Fabienne

2012-06-07

196

LABORATORY EVALUATION OF ZERO-VALENT IRON TO TREAT GROUNDWATER IMPACTED BY ACID MINE DRAINAGE  

EPA Science Inventory

The generation and release of acidic, metal-rich water from mine wastes continues to be an intractable environmental problem. Although the effects of acid mine drainage (AMD) are most evident in surface waters, there is an obvious need for developing cost-effective approaches fo...

197

Effects of zero-valent metals together with quartz sand on the mechanochemical destruction of dechlorane plus coground in a planetary ball mill.  

PubMed

Mechanochemical destruction by grinding with additives in high energy ball milling has been identified as a good alternative to traditional incineration for the disposal of wastes containing halogenated organic pollutants. Despite CaO normally used as an additive, recently Fe+SiO2 has been used to replace CaO for a faster destruction. In the present study, zero-valent metals (Al, Zn, besides Fe) together with SiO2 were investigated for their efficiencies of prompting the destruction of dechlorane plus (DP). Aluminum was found of be the best with a destruction percentage of nearly 99% for either syn- or anti-DP after 2.5h milling. In comparison, only 88/85% and 37/32% of syn-/anti-DP were destroyed when using zinc and iron after the same time, respectively. The detected water soluble chloride was lower than the stoichiometric amount containing in the original DP samples, due to the Si-Cl bond formed during the process. The potential fate of C and Cl present in DP is in the form of inorganic carbon, inorganic Cl and formation of Si-Cl bonds, respectively. The results suggested that Al+SiO2 is promising in the mechanochemical destruction of chlorinated organic pollutants like DP. PMID:24295775

Wang, Haizhu; Huang, Jun; Zhang, Kunlun; Yu, Yunfei; Liu, Kai; Yu, Gang; Deng, Shubo; Wang, Bin

2014-01-15

198

BIFUNCTIONAL ALUMINUN: A PERMEABLE BARRIER MATERIAL FOR THE DEGRADATION OF MTBE  

EPA Science Inventory

Bifunctional aluminum is an innovative remedial material for the treatment of gasoline oxygenates in permeable reactive barriers (PRBs). PRBs represent a promising environmental technology for remediation of groundwater contamination. Although zero-valent metals (ZVM) have been...

199

THE EFFECT OF SMECTITE ON THE CORROSION OF IRON METAL  

SciTech Connect

The combination of zero-valent iron and a clay-type amendment is often observed to have a synergistic effect on the rate of reduction reactions. In this paper, electrochemical techniques are used to determine the mechanism of interaction between the iron and smectite clay minerals. Iron electrodes coated with an evaporated smectite suspension (clay-modified iron electrodes, CMIEs) were prepared using five different smectites: SAz-1, SWa-1, STx-1, SWy-1, and SHCa-1. All the smectites were exchanged with Na+ and one sample of SWy-1 was also exchanged with Mg2+. Potentiodynamic potential scans and cyclic voltammograms were taken using the CMIEs and uncoated but passivated iron electrodes. These electrochemical experiments, along with measurements of the amount of Fe2+ and Fe3+ sorbed in the smectite coating, suggested that the smectite removed the passive layer of the underlying iron electrode during the evaporation process. Cyclic voltammograms taken after the CMIEs were biased at the active-passive transition potential for varying amounts of time suggested that the smectite limited growth of a passive layer, preventing passivation. These results are attributed to the Broensted acidity of the smectite as well as to its ability to sorb iron cations. Oxides that did form on the surface of the iron in the presence of the smectite when it was biased anodically seemed to be different than those that form on the surface of an uncoated iron electrode under otherwise similar conditions; this difference suggested that the smectite reacted with the Fe2+ formed from the oxidation of the underlying iron. No significant correlation could be found between the ability of the smectite to remove the iron passive film and the smectite type. The results have implications for the mixing of sediments and iron particles in permeable reactive barriers, underground storage of radioactive waste in steel canisters, and the use of smectite supports in preventing aggregation of nano-sized zero-valent iron.

Balko, Barbara A.; Bosse, Stephanie A.; Cade, Anne E.; Jones-Landry, Elise F.; Amonette, James E.; Daschbach, John L.

2012-04-24

200

Preparation of spherical iron nanoclusters in ethanolwater solution for nitrate removal  

Microsoft Academic Search

In this study, a higher surface area spherical nanoscale zero valent iron (HNZVI) cluster (80nm, 54.25m2g?1) was synthesized in ethanolwater mixed solvent in the presence of dispersion agent of polyglycol (PEG). At the same time, a lower surface area nanoscale zero valent iron (LNZVI) particle (80nm, 8.08m2g?1) was also prepared with only de-ioned water as reaction media. Their structures, compositions

Wei Wang; Zhao-hui Jin; Tie-long Li; Huan Zhang; Si Gao

2006-01-01

201

FUNDAMENTAL STUDIES OF THE REMOVAL OF CONTAMINANTS FROM GROUND AND WASTE WATERS VIA REDUCTION BY ZERO-VALENT METALS  

EPA Science Inventory

In an effort to remove trace contaminants from wastewaters and groundwaters, elemental iron is being used for the reductive dechlorination of solvents and the removal of toxic trace elements, such as Se, Cr, and U. Both in situ reactive barriers and above-ground reactors are bein...

202

Laboratory evaluation of zero valent iron and sulfur modified iron filter materials for agricultural drainage water treatment  

Technology Transfer Automated Retrieval System (TEKTRAN)

On site filter treatment systems have the potential to remove nutrients and pesticides from agricultural subsurface drainage waters. The effectiveness and efficiency of this type of drainage water treatment will depend on the actual filter materials utilized. Two promising filter materials that coul...

203

Assessment of solid reactive mixtures for the development of biological permeable reactive barriers.  

PubMed

Solid reactive mixtures were tested as filling material for the development of biological permeable reactive barriers for the treatment of heavy metals contaminated waters. Mixture selection was performed by taking into account the different mechanisms operating in sulphate and cadmium removal with particular attention to bioprecipitation and sorption onto the organic matrices in the mixtures. Suspensions of eight reactive mixtures were tested for sulphate removal (initial concentration 3 g L(-1)). Each mixture was made up of four main functional components: a mix of organic sources for bacterial growth, a neutralizing agent, a porous medium and zero-valent iron. The best mixture among the tested ones (M8: 6% leaves, 9% compost, 3% zero-valent iron, 30% silica sand, 30% perlite, 22% limestone) presented optimal conditions for SRB growth (pH 7.8 +/- 0.1; E(h)= -410 +/- 5 mV) and 83% sulphate removal in 22 days (25% due to bioreduction, 32% due to sorption onto compost and 20% onto leaves). M8 mixture allowed the complete abatement of cadmium with a significant contribution of sorption over bioprecipitation (6% Cd removal due to SRB activity). Sorption properties, characterised by potentiometric titrations and related modelling, were mainly due to carboxylic sites of organic components used in reactive mixtures. PMID:19505754

Pagnanelli, Francesca; Viggi, Carolina Cruz; Mainelli, Sara; Toro, Luigi

2009-10-30

204

Enhanced ozonation degradation of di-n-butyl phthalate by zero-valent zinc in aqueous solution: performance and mechanism.  

PubMed

Enhanced ozonation degradation of di-n-butyl phthalate (DBP) by zero-valent zinc (ZVZ) has been investigated using a semi-continuous reactor in aqueous solution. The results indicated that the combination of ozone (O3) and ZVZ showed an obvious synergetic effect, i.e. an improvement of 54.8% on DBP degradation was obtained by the O3/ZVZ process after 10min reaction compared to the cumulative effect of O3 alone and O2/ZVZ. The degradation efficiency of DBP increased gradually with the increase of ZVZ dosage, enhanced as solution pH increasing from 2.0 to 10.0, and more amount of DBP was degraded with the initial concentration of DBP arising from 0.5 to 2.0mgL(-1). Recycling use of ZVZ resulted in the enhancement of DBP degradation, because the newly formed zinc oxide took part in the reaction. The mechanism investigation demonstrated that the enhancement effect was attributed to the introduction of ZVZ, which could promote the utilization of O3, enhance the formation of superoxide radical by reducing O2 via one-electron transfer, accelerate the production of hydrogen peroxide and the generation of hydroxyl radical. Additionally, the newly formed zinc oxide on ZVZ surface also contributed to the enhancement of DBP degradation in the recycling use of ZVZ. Most importantly, the O3/ZVZ process was also effective in enhanced ozonation degradation of DBP under the background of actual waters. PMID:24333716

Wen, Gang; Wang, Sheng-Jun; Ma, Jun; Huang, Ting-Lin; Liu, Zheng-Qian; Zhao, Lei; Su, Jun-Feng

2014-01-30

205

Selected hydrologic data for the field demonstration of three permeable reactive barriers near Fry Canyon, Utah, 1996-2000  

USGS Publications Warehouse

Three permeable reactive barriers (PRBs) were installed near Fry Canyon, Utah, in August 1997 to demonstrate the use of PRBs to control the migration of uranium in ground water. Reactive material included (1) bone-char phosphate, (2) zero-valent iron pellets, and (3) amorphous ferric oxyhydroxide coated gravel. An extensive monitoring network was installed in and around each PRB for collection of water samples, analysis of selected water-quality parameters, and monitoring of water levels. Water temperature, specific conductance, pH, Eh (oxidation-reduction potential), and dissolved oxygen were measured continuously within three different barrier materials, and in two monitoring wells. Water temperature and water level below land surface were electronically recorded every hour with pressure transducers. Data were collected from ground-water monitoring wells installed in and around the PRBs during 1996-98 and from surface-water sites in Fry Creek.

Wilkowske, Chris D.; Rowland, Ryan C.; Naftz, David L.

2001-01-01

206

Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability  

EPA Science Inventory

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...

207

Integrated evaluation of the performance of a more than seven year old permeable reactive barrier at a site contaminated with chlorinated aliphatic hydrocarbons (CAHs)  

NASA Astrophysics Data System (ADS)

An important issue of concern for permeable reactive iron barriers is the long-term efficiency of the barriers due to the long operational periods required. Mineral precipitation resulting from the anaerobic corrosion of the iron filings and bacteria present in the barrier may play an important role in the long-term performance. An integrated study was performed on the Vapokon permeable reactive barrier (PRB) in Denmark by groundwater and iron core sample characterization. The detailed field groundwater sampling carried out from more than 75 well screens up and downstream the barrier showed a very efficient removal (> 99%) for the most important CAHs (PCE, TCE and 1,1,1-TCA). However, significant formation of cis-DCE within the PRB resulted in an overall insufficient efficiency for cis-DCE removal. The detailed analysis of the upstream groundwater revealed a very heterogeneous spatial distribution of contaminant loading into the PRB, which resulted in that only about a quarter of the barrier system is treating significant loads of CAHs. Laboratory batch experiments using contaminated groundwater from the site and iron material from the core samples revealed that the aged iron material performed equally well as virgin granular iron of the same type based on determined degradation rates despite that parts of the cored iron material were covered by mineral precipitates (especially iron sulfides, carbonate green rust and aragonite). The PCR analysis performed on the iron core samples indicated the presence of a microbial consortium in the barrier. A wide range of species were identified including sulfate and iron reducing bacteria, together with Dehalococcoides and Desulfuromonas species indicating microbial reductive dehalogenation potential. The microbes had a profound effect on the performance of the barrier, as indicated by significant degradation of dichloromethane (which is typically unaffected by zero valent iron) within the barrier.

Muchitsch, Nanna; Van Nooten, Thomas; Bastiaens, Leen; Kjeldsen, Peter

2011-11-01

208

Monitoring Performance of a Dual Wall Permeable Reactive Barrier for Treating Perchlorate and TCE  

Microsoft Academic Search

AMEC Geomatrix, through collaboration with Aerojet General Corporation and the University of California, Davis (UCD), has performed work leading to the installation of a dual wall permeable reactive barrier (PRB) system capable of treating perchlorate and chlorinated aliphatic hydrocarbon compounds (CAHs), including trichloroethylene (TCE), at Aerojet's Area 40 site in Sacramento, California. This unique system consisted of an upgradient zero-valent

C. E. Dowman; Y. Hashimoto; S. Warner; P. Bennett; D. Gandhi; F. Szerdy; S. Neville; C. Fennessy; K. M. Scow

2008-01-01

209

Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier  

USGS Publications Warehouse

Installation of a permeable reactive barrier to intercept a phosphate (PO4) plume where it discharges to a pond provided an opportunity to develop and test methods for monitoring the barrier's performance in the shallow pond-bottom sediments. The barrier is composed of zero-valent-iron mixed with the native sediments to a 0.6-m depth over a 1100-m2 area. Permanent suction, diffusion, and seepage samplers were installed to monitor PO 4 and other chemical species along vertical transects through the barrier and horizontal transects below and near the top of the barrier. Analysis of pore water sampled at about 3-cm vertical intervals by using multilevel diffusion and suction samplers indicated steep decreases in PO4 concentrations in ground water flowing upward through the barrier. Samples from vertically aligned pairs of horizontal multiport suction samplers also indicated substantial decreases in PO4 concentrations and lateral shifts in the plume's discharge area as a result of varying pond stage. Measurements from Lee-style seepage meters indicated substantially decreased PO4 concentrations in discharging ground water in the treated area; temporal trends in water flux were related to pond stage. The advantages and limitations of each sampling device are described. Preliminary analysis of the first 2 years of data indicates that the barrier reduced PO4 flux by as much as 95%. ?? 2009 National Ground Water Association.

McCobb, T.D.; LeBlanc, D.R.; Massey, A.J.

2009-01-01

210

Iron(II,III)-polyphenol complex nanoparticles derived from green tea with remarkable ecotoxicological impact  

EPA Science Inventory

There are several greener methods exist to synthesize zero?valent iron nanoparticles (nZVI) using different bio-based reducing agents. Although their useful properties in degradation of organic dyes, chlorinated organics, or arsenic have been described earlier, their characteriza...

211

SPATIAL AND TEMPORAL TRENDS IN GROUNDWATER CHEMISTRY AND PRECIPITATE FORMATION AT THE ELIZABETH CITY PERMEABLE REACTIVE BARRIER  

EPA Science Inventory

Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of PRBs. Both processes can impact remedial performance by affecting zero-valent iron reactivity and permeability. Results will be presented from solid-phase and gro...

212

Reductive denitrification of nitrate by scrap iron filings.  

PubMed

Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed. PMID:15682502

Hao, Zhi-Wei; Xu, Xin-Hua; Wang, Da-Hui

2005-03-01

213

Reductive denitrification of nitrate by scrap iron filings*  

PubMed Central

Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed. PMID:15682502

Hao, Zhi-wei; Xu, Xin-hua; Wang, Da-hui

2005-01-01

214

APPLICATIONS OF SURFACE ANALYSIS IN THE ENVIRONMENTAL SCIENCES: DEHALOGENATION OF CHLOROCARBONS WITH ZERO-VALENT IRON AND IRON-CONTAINING MINERAL SURFACES. (R828771C006)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

215

APPLICATIONS OF SURFACE ANALYSIS IN THE ENVIRONMENTAL SCIENCES: DEHALOGENATION OF CHLOROCARBONS WITH ZERO-VALENT IRON AND IRON-CONTAINING MINERAL SURFACES. (R828164)  

EPA Science Inventory

Halogenated organic compounds are common pollutants in groundwater. Consequently, there is widespread interest in understanding the reactions of these compounds in the environment and developing remediation strategies. One area of ongoing research involves the reductive dechlo...

216

Phosphate Barriers for Immobilization of Uranium Plumes  

SciTech Connect

Uranium contamination of the subsurface remains a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB?s) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, may be a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorus amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain sodium polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is paramount to preventing fouling of wells at the point of injection.

Burns, Peter C.

2004-12-01

217

Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability  

SciTech Connect

Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation ({Delta}{sub f}G{sup o}) for chukanovite is - 1174.4 {+-} 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.

Wilkin, Richard T.; Lee, T.R. (U.S. EPA)

2010-10-22

218

DEMONSTRATION OF IN SITU DEHALOGENATION OF DNAPL THROUGH INJECTION OF EMULSIFIED ZERO-VALIENT IRON AT LAUNCH COMPLEX 34 IN CAPE CANAVERAL AIR FORCE STATION, FLORIDA  

EPA Science Inventory

The purpose of this project was to evaluate the technical and cost performance of emulsified zero-valent iron (EZVI) technology when applied to DNAPL contaminants in the saturated zone. This demonstration was conducted at Launch Complex 34, Cape Canaveral Air Force Station, FL, w...

219

Predicting longevity of iron permeable reactive barriers using multiple iron deactivation models  

NASA Astrophysics Data System (ADS)

In this study we investigate the model uncertainties involved in predicting long-term permeable reactive barrier (PRB) remediation efficiency based on a lab-scale column experiment under accelerated flow conditions. A PRB consisting of 20% iron and 80% sand was simulated in a laboratory-scale column and contaminated groundwater was pumped into the column for approximately 1 year at an average groundwater velocity of 3.7E - 1 m d- 1. Dissolved contaminants (PCE, TCE, cis-DCE, trans-DCE and VC) and inorganic (Ca2 +, Fe2 +, TIC and pH) concentrations were measured in groundwater sampled at different times and at eight different distances along the column. These measurements were used to calibrate a multi-component reactive transport model, which subsequently provided predictions of long-term PRB efficiency under reduced flow conditions (i.e., groundwater velocity of 1.4E - 3 m d- 1), representative of a field site of interest in this study. Iron reactive surface reduction due to mineral precipitation and iron dissolution was simulated using four different models. All models were able to reasonably well reproduce the column experiment measurements, whereas the extrapolated long-term efficiency under different flow rates was significantly different between the different models. These results highlight significant model uncertainties associated with extrapolating long-term PRB performance based on lab-scale column experiments. These uncertainties should be accounted for at the PRB design phase, and may be reduced by independent experiments and field observations aimed at a better understanding of reactive surface deactivation mechanisms in iron PRBs.

Carniato, L.; Schoups, G.; Seuntjens, P.; Van Nooten, T.; Simons, Q.; Bastiaens, L.

2012-11-01

220

Iron transport across the blood-brain barrier: development, neurovascular regulation and cerebral amyloid angiopathy.  

PubMed

There are two barriers for iron entry into the brain: (1) the brain-cerebrospinal fluid (CSF) barrier and (2) the blood-brain barrier (BBB). Here, we review the literature on developmental iron accumulation by the brain, focusing on the transport of iron through the brain microvascular endothelial cells (BMVEC) of the BBB. We review the iron trafficking proteins which may be involved in the iron flux across BMVEC and discuss the plausible mechanisms of BMVEC iron uptake and efflux. We suggest a model for how BMVEC iron uptake and efflux are regulated and a mechanism by which the majority of iron is trafficked across the developing BBB under the direct guidance of neighboring astrocytes. Thus, we place brain iron uptake in the context of the neurovascular unit of the adult brain. Last, we propose that BMVEC iron is involved in the aggregation of amyloid-? peptides leading to the progression of cerebral amyloid angiopathy which often occurs prior to dementia and the onset of Alzheimer's disease. PMID:25355056

McCarthy, Ryan C; Kosman, Daniel J

2015-02-01

221

A Two and Half-Year-Performance Evaluation of a Field Test on Treatment of Source Zone Tetrachloroethene and Its Chlorinated Daughter Products Using Emulsified Zaro Valent Iron Nanoparticles  

EPA Science Inventory

A field test of emulsified zero valent iron (EZVI) nanoparticles was conducted at Parris Island, SC, USA and was monitored for two and half years to assess the treatment of subsurface-source zone chlorinated volatile organic compounds (CVOCs) dominated by tetrachloroethene (PCE) ...

222

Intrinsic Barriers for Electron and Hydrogen Atom Transfer Reactions of Biomimetic Iron Complexes  

E-print Network

Intrinsic Barriers for Electron and Hydrogen Atom Transfer Reactions of Biomimetic Iron Complexes: Self-exchange reactions between high-spin iron complexes of 2,2-bi-imidazoline (H2bim) have been.3 ( 0.3 at 324 K, whereas no such effect is detected in the electron exchange reaction. Proton self

Roth, Justine P.

223

Ferritin polarization and iron transport across monolayer epithelial barriers in mammals  

PubMed Central

Epithelial barriers are found in many tissues such as the intestine, kidney and brain where they separate the external environment from the body or a specific compartment from its periphery. Due to the tight junctions that connect epithelial barrier-cells (EBCs), the transport of compounds takes place nearly exclusively across the apical or basolateral membrane, the cell-body and the opposite membrane of the polarized EBC, and is regulated on numerous levels including barrier-specific adapted trafficking-machineries. Iron is an essential element but toxic at excess. Therefore, all iron-requiring organisms tightly regulate iron concentrations on systemic and cellular levels. In contrast to most cell types that control just their own iron homeostasis, EBCs also regulate homeostasis of the compartment they enclose or the body as a whole. Iron is transported across EBCs by specialized transporters such as the transferrin receptor and ferroportin. Recently, the iron storage protein ferritin was also attributed a role in the regulation of systemic iron homeostasis and we gathered evidence from the literature and original data that ferritin is polarized in EBC, suggesting also a role for ferritin in iron trafficking across EBCs. PMID:25202274

Meyron-Holtz, Esther G.; Cohen, Lyora A.; Fahoum, Lulu; Haimovich, Yael; Lifshitz, Lena; Magid-Gold, Inbar; Stuemler, Tanja; Truman-Rosentsvit, Marianna

2014-01-01

224

Permeability of iron sulfide (FeS)-based materials for groundwater remediation.  

PubMed

Iron sulfide (FeS) has been extensively assessed as a reactive medium to remove both metals and halogenated organics from groundwater. However, to address its suitability as a material for permeable reactive barriers (PRBs), its propensity for solids and gas production, which result in reduced permeability, must be evaluated. The reduction in permeability for sands coated with FeS (as mackinawite), under the anoxic conditions often encountered at contaminated groundwater sites, was examined through column experiments and geochemical modeling under conditions of high calcium and nitrate, which have been previously shown to cause significant permeability reduction in zero-valent iron (ZVI) systems. The column experiments showed negligible production of both solids and gases. The geochemical modeling predicted a maximum reduction in permeability of 1% due to solids and about 30% due to gas formation under conditions for which a complete loss of permeability was predicted for ZVI systems. This difference in permeability reduction is driven by the differences in thermodynamic stability of ZVI and FeS in aqueous solutions. The results suggest that geochemical conditions that result in high permeability losses for ZVI systems will likely not be problematic for FeS-based reactive materials. PMID:23246668

Henderson, Andrew D; Demond, Avery H

2013-03-01

225

Removal of TNT and RDX from water and soil using iron metal  

Microsoft Academic Search

Contaminated water and soil at active or abandoned munitions plants is a serious problem since these compounds pose risks to human health and can be toxic to aquatic and terrestrial life. Our objective was to determine if zero-valent iron (Fe0) could be used to promote remediation of water and soil contaminated with 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). As little as

L. S. Hundal; J. Singh; E. L. Bier; P. J. Shea; S. D. Comfort; W. L. Powers

1997-01-01

226

Pyrite formation by reactions of iron monosulfides with dissolved inorganic and organic sulfur species  

Microsoft Academic Search

Pyrite formation has been investigated at 70C and pH 68 by aging precipitated, disordered mackinawite, Fe9S8, and greigite, Fe3S4, in solutions containing aqueous H2S, HS?, Sx2?, S2O32?, SO32?, colloidal elemental sulfur, and the organic sulfur species thiol, disulfide, and sulfonate. Pyrite formed in all experiments where unoxidized iron monosulfides were aged with species containing zero-valent sulfur, i.e., polysulfides and colloidal

R. T. Wilkin; H. L. Barnes

1996-01-01

227

Use of iron-based technologies in contaminated land and groundwater remediation: a review.  

PubMed

Reactions involving iron play a major role in the environmental cycling of a wide range of important organic, inorganic and radioactive contaminants. Consequently, a range of environmental clean-up technologies have been proposed or developed which utilise iron chemistry to remediate contaminated land and surface and subsurface waters, e.g. the use of injected zero zero-valent iron nanoparticles to remediate organic contaminant plumes; the generation of iron oxyhydroxide-based substrates for arsenic removal from contaminated waters; etc. This paper reviews some of the latest iron-based technologies in contaminated land and groundwater remediation, their current state of development, and their potential applications and limitations. PMID:18692221

Cundy, Andrew B; Hopkinson, Laurence; Whitby, Raymond L D

2008-08-01

228

CHROMIUM REMOVAL PROCESSES DURING GROUNDWATER REMEDIATION BY A ZEROVALENT IRON PERMEABLE REACTIVE BARRIER  

EPA Science Inventory

Solid-phase associations of chromium were examined in core materials collected from a full-scale, zerovalent iron, permeable reactive barrier (PRB) at the U.S. Coast Guard Support Center located near Elizabeth City (NC). The PRB was installed in 1996 to treat groundwater contami...

229

Phosphate Barriers for Immobilization of Uranium Plumes  

SciTech Connect

Uranium contamination of the subsurface has remained a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of fissile uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB?s) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, are a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorous amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is key to preventing fouling of wells at the point of injection. Our other fundamental objective is to synthesize and correctly characterize the uranyl phosphate phases that form in the geochemical conditions under consideration. This report summarizes work conducted at the University of Notre Dame through November of 2003 under DOE grant DE-FG07-02ER63489, which has been funded since September, 2002. The objectives at Notre Dame are development of synthesis techniques for uranyl phosphate phases, together with detailed structural and chemical characterization of the myriad of uranyl phosphate phases that may form under geochemical conditions under consideration.

Burns, Peter C.

2005-06-01

230

Regulation of brain iron and copper homeostasis by brain barrier systems: implication in neurodegenerative diseases.  

PubMed

Iron (Fe) and copper (Cu) are essential to neuronal function; excess or deficiency of either is known to underlie the pathoetiology of several commonly known neurodegenerative disorders. This delicate balance of Fe and Cu in the central milieu is maintained by the brain barrier systems, i.e., the blood-brain barrier (BBB) between the blood and brain interstitial fluid and the blood-cerebrospinal fluid barrier (BCB) between the blood and cerebrospinal fluid (CSF). This review provides a concise description on the structural and functional characteristics of the brain barrier systems. Current understanding of Fe and Cu transport across the brain barriers is thoroughly examined, with major focuses on whether the BBB and BCB coordinate the direction of Fe and Cu fluxes between the blood and brain/CSF. In particular, the mechanism by which pertinent metal transporters in the barriers, such as the transferrin receptor (TfR), divalent metal transporter (DMT1), copper transporter (CTR1), ATP7A/B, and ferroportin (FPN), regulate metal movement across the barriers is explored. Finally, the detrimental consequences of dysfunctional metal transport by brain barriers, as a result of endogenous disorders or exogenous insults, are discussed. Understanding the regulation of Fe and Cu homeostasis in the central nervous system aids in the design of new drugs targeted on the regulatory proteins at the brain barriers for the treatment of metal's deficiency or overload-related neurological diseases. PMID:22115751

Zheng, Wei; Monnot, Andrew D

2012-02-01

231

Transformation of Reactive Iron Minerals in a Permeable Reactive Barrier (Biowall) Used to Treat TCE in Groundwater  

EPA Science Inventory

Abstract: Iron and sulfur reducing conditions are generally created in permeable reactive barrier (PRB) systems constructed for groundwater treatment, which usually leads to formation of iron sulfide phases. Iron sulfides have been shown to play an important role in degrading ch...

232

Chemical stabilization of metals in mine wastes by transformed red mud and other iron compounds: laboratory tests.  

PubMed

A series of static and kinetic laboratory-scale tests were designed in order to evaluate the efficacy of transformed red mud (TRM) from bauxite refining residues, commercial zero-valent iron, and synthetic iron (III) hydroxides as sorbents/reagents to minimize the generation of acid drainage and the release of toxic elements from multi-contaminant-laden mine wastes. In particular, in some column experiments the percolation of meteoric water through a waste pile, alternated with periods of dryness, was simulated. Wastes were placed in columns together with sorbents/reagents in three different set-ups: as blended amendment (mixing method), as a bed at the bottom of the column (filtration method), or as a combination of the two previous methods. The filtration methods, which simulate the creation of a permeable reactive barrier downstream of a waste pile, are the most effective, while the use of sorbents/reagents as amendments leads to unsatisfactory results, because of the selective removal of only some contaminants. The efficacy of the filtration method is not significantly affected by the periods of dryness, except for a temporary rise of metal contents in the leachates due to dissolution of soluble salts formed upon evaporation in the dry periods. These results offer original information on advantages/limits in the use of TRM for the treatment of multi-contaminant-laden mine wastes, and represent the starting point for experimentation at larger scale. PMID:25244134

Ardau, C; Lattanzi, P; Peretti, R; Zucca, A

2014-01-01

233

Effect of Geochemical and Physical Heterogeneity on the Hanford 100D Area In Situ Redox Manipulation Barrier Longevity  

SciTech Connect

The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: i) high hydraulic conductivity zones; ii) zones of low reducible iron; and iii) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations.Results of this laboratory study did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity / low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes.Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity.The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.

Szecsody, Jim E.; Fruchter, Jonathan S.; Phillips, Jerry L.; Rockhold, Mark L.; Vermeul, Vince R.; Williams, Mark D.; Devary, Brooks J.; Liu, Ying

2005-12-22

234

Effect of Geochemical and Physical Heterogeneity on the Hanford 100D Area In Situ Redox Manipulation Barrier Longevity  

SciTech Connect

The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: (1) high hydraulic conductivity zones; (2) zones of low reducible iron; and (3) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations. Results of this laboratory study did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity/low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes. Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity. The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.

Szecsody, Jim E.; Vermeul, Vince R.; Fruchter, Jonathan S.; Williams, Mark D.; Phillips, Jerry L.; Devary, Brooks J.; Rockhold, Mark L.; Liu, Ying

2005-11-30

235

Solid lipid nanoparticles loaded with iron to overcome barriers for treatment of iron deficiency anemia  

PubMed Central

According to the World Health Organization, 46% of the worlds children suffer from anemia, which is usually treated with iron supplements such as ferrous sulfate. The aim of this study was to prepare iron as solid lipid nanoparticles, in order to find an innovative way for alleviating the disadvantages associated with commercially available tablets. These limitations include adverse effects on the digestive system resulting in constipation and blood in the stool. The second drawback is the high variability in the absorption of iron and thus in its bioavailability. Iron solid lipid nanoparticles (Fe-SLNs) were prepared by hot homogenization/ultrasonication. Solubility of ferrous sulfate in different solid lipids was measured, and effects of process variables such as the surfactant type and concentration, homogenization and ultrasonication times, and charge-inducing agent on the particle size, zeta potential, and encapsulation efficiency were determined. Furthermore, in vitro drug release and in vivo pharmacokinetics were studied in rabbits. Results indicated that Fe-SLNs consisted of 3% Compritol 888 ATO, 1% Lecithin, 3% Poloxamer 188, and 0.2% dicetylphosphate, with an average particle size of 25 nm with 92.3% entrapment efficiency. In vivo pharmacokinetic study revealed more than fourfold enhanced bioavailability. In conclusion, Fe-SLNs could be a promising carrier for iron with enhanced oral bioavailability. PMID:25609917

Hosny, Khaled Mohamed; Banjar, Zainy Mohammed; Hariri, Amani H; Hassan, Ali Habiballah

2015-01-01

236

Solid lipid nanoparticles loaded with iron to overcome barriers for treatment of iron deficiency anemia.  

PubMed

According to the World Health Organization, 46% of the world's children suffer from anemia, which is usually treated with iron supplements such as ferrous sulfate. The aim of this study was to prepare iron as solid lipid nanoparticles, in order to find an innovative way for alleviating the disadvantages associated with commercially available tablets. These limitations include adverse effects on the digestive system resulting in constipation and blood in the stool. The second drawback is the high variability in the absorption of iron and thus in its bioavailability. Iron solid lipid nanoparticles (Fe-SLNs) were prepared by hot homogenization/ultrasonication. Solubility of ferrous sulfate in different solid lipids was measured, and effects of process variables such as the surfactant type and concentration, homogenization and ultrasonication times, and charge-inducing agent on the particle size, zeta potential, and encapsulation efficiency were determined. Furthermore, in vitro drug release and in vivo pharmacokinetics were studied in rabbits. Results indicated that Fe-SLNs consisted of 3% Compritol 888 ATO, 1% Lecithin, 3% Poloxamer 188, and 0.2% dicetylphosphate, with an average particle size of 25 nm with 92.3% entrapment efficiency. In vivo pharmacokinetic study revealed more than fourfold enhanced bioavailability. In conclusion, Fe-SLNs could be a promising carrier for iron with enhanced oral bioavailability. PMID:25609917

Hosny, Khaled Mohamed; Banjar, Zainy Mohammed; Hariri, Amani H; Hassan, Ali Habiballah

2015-01-01

237

Chromium-Removal Processes during Groundwater Remediation by a Zerovalent Iron Permeable Reactive Barrier  

SciTech Connect

Solid-phase associations of chromium were examined in core materials collected from a full-scale, zerovalent iron permeable reactive barrier (PRB) at the U.S. Coast Guard Support Center located near Elizabeth City, NC. The PRB was installed in 1996 to treat groundwater contaminated with hexavalent chromium. After eight years of operation, the PRB remains effective at reducing concentrations of Cr from average values >1500 {micro}g L{sup -1} in groundwater hydraulically upgradient of the PRB to values <1 {micro}g L{sup -1} in groundwater within and hydraulically downgradient of the PRB. Chromium removal from groundwater occurs at the leading edge of the PRB and also within the aquifer immediately upgradient of the PRB. These regions also witness the greatest amount of secondary mineral formation due to steep geochemical gradients that result from the corrosion of zerovalent iron. X-ray absorption near-edge structure (XANES) spectroscopy indicated that chromium is predominantly in the trivalent oxidation state, confirming that reductive processes are responsible for Cr sequestration. XANES spectra and microscopy results suggest that Cr is, in part, associated with iron sulfide grains formed as a consequence of microbially mediated sulfate reduction in and around the PRB. Results of this study provide evidence that secondary iron-bearing mineral products may enhance the capacity of zerovalent iron systems to remediate Cr in groundwater, either through redox reactions at the mineral-water interface or by the release of Fe(II) to solution via mineral dissolution and/or metal corrosion.

Wilkin, Richard T.; Su, Chunming; Ford, Robert G.; Paul, Cynthia J. (US EPA)

2008-06-09

238

Environmental application of millimetre-scale sponge iron (s-Fe?) particles (I): pretreatment of cationic triphenylmethane dyes.  

PubMed

To investigate the removal capability of millimetric zero valent iron (mmZVI), sponge iron (s-Fe(0)) particles were characterized with XRD, XPS, TEM, HRSEM and EDS techniques. Moreover, the roles of particle size, catalyst dosage, dye concentration, mixing conditions (e.g. ultrasound (US), stirring or shaking), and regeneration treatment were studied with the removal of cationic triphenylmethane dyes. Notably, the reduction process was also revealed as compared to nanoscale zero valent iron (nZVI), microscale iron power, and iron scurf. Furthermore, the reductive mechanism was exemplified with brilliant green. The results demonstrated that (1) the synergetic effect between US and s-Fe(0) greatly enhanced the removal of dyes, (2) the dosage of preferred s-Fe(0) (1-3mm) particles was optimized as 30.0g/L; (3) reuse cycles of s-Fe(0) catalyst were enhanced with the assistance of diluted HCl solution; (4) the main degradation routes included the cleavage of conjugated structure reactions, N-de-ethylation reactions, hydroxylation reactions, the removal of benzene ring reactions, and opening ring reactions. Accordingly, the pretreatment of aqueous solution over s-Fe(0) was hypothesized to achieve mainly through direct reduction reaction by electron transfer and indirect reductive reactions by the highly activated hydrogen atom. Additionally, decoration with noble metals was utilized to reveal the reaction mechanism. PMID:25464285

Ju, Yongming; Liu, Xiaowen; Li, Zhaoyong; Kang, Juan; Wang, Xiaoyan; Zhang, Yukui; Fang, Jiande; Dionysiou, Dionysios D

2015-02-11

239

Enhanced chitosan beads-supported Fe(0)-nanoparticles for removal of heavy metals from electroplating wastewater in permeable reactive barriers.  

PubMed

The removal of heavy metals from electroplating wastewater is a matter of paramount importance due to their high toxicity causing major environmental pollution problems. Nanoscale zero-valent iron (NZVI) became more effective to remove heavy metals from electroplating wastewater when enhanced chitosan (CS) beads were introduced as a support material in permeable reactive barriers (PRBs). The removal rate of Cr (VI) decreased with an increase of pH and initial Cr (VI) concentration. However, the removal rates of Cu (II), Cd (II) and Pb (II) increased with an increase of pH while decreased with an increase of their initial concentrations. The initial concentrations of heavy metals showed an effect on their removal sequence. Scanning electron microscope images showed that CS-NZVI beads enhanced by ethylene glycol diglycidyl ether (EGDE) had a loose and porous surface with a nucleus-shell structure. The pore size of the nucleus ranged from 19.2 to 138.6 ?m with an average aperture size of around 58.6 ?m. The shell showed a tube structure and electroplating wastewaters may reach NZVI through these tubes. X-ray photoelectron spectroscope (XPS) demonstrated that the reduction of Cr (VI) to Cr (III) was complete in less than 2 h. Cu (II) and Pb (II) were removed via predominant reduction and auxiliary adsorption. However, main adsorption and auxiliary reduction worked for the removal of Cd (II). The removal rate of total Cr, Cu (II), Cd (II) and Pb (II) from actual electroplating wastewater was 89.4%, 98.9%, 94.9% and 99.4%, respectively. The findings revealed that EGDE-CS-NZVI-beads PRBs had the capacity to remediate actual electroplating wastewater and may become an effective and promising technology for in situ remediation of heavy metals. PMID:24075723

Liu, Tingyi; Yang, Xi; Wang, Zhong-Liang; Yan, Xiaoxing

2013-11-01

240

Studies of the slow bidirectional transport of iron and transferrin across the blood-brain barrier.  

PubMed

Although iron is involved in brain function, very little is known about the regulation of its concentrations in the central nervous system. We quantitatively measured the entry and exit rates of iron, transferrin (its major transport protein), and albumin in mice. The blood to brain transport of iron greater than transferrin greater than albumin and the brain to blood transport of transferrin greater than albumin greater than iron. The results suggest that iron and transferrin have slow, bidirectional, probably saturable, and to some degree independent transport systems, although iron introduced directly into the brain is not readily available for brain to blood transport. PMID:3224280

Banks, W A; Kastin, A J; Fasold, M B; Barrera, C M; Augereau, G

1988-12-01

241

Iron-mediated remediation of RDX-contaminated water and soil under controlled Eh\\/pH  

Microsoft Academic Search

Soil and water contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a serious environmental problem at several active and abandoned munitions production facilities. Zero-valent iron (Fe°) can effectively remediate RDX-contaminated soil and water. The objective of this study was to manipulate Eh and pH for enhanced Fe°-mediated destruction of RDX. This was accomplished by monitoring RDX destruction under controlled Eh-pH conditions (Eh: -300

J. Singh; S. D. Comfort; P. J. Shea

1999-01-01

242

Verification and monitoring of deep granular iron permeable reactive barriers emplaced by vertical hydraulic fracturing and injection for groundwater remediation  

NASA Astrophysics Data System (ADS)

This study evaluated the use of vertical hydraulic fracturing and injection (VHFI) to emplace granular iron as a deep passive treatment system to remove organic contaminants from groundwater at the Massachusetts Military Reservation on Cape Cod, Massachusetts. It was the first permeable reactive barrier (PRB) constructed at a depth greater than 15 m below the ground surface. VHFI propagates a vertical fracture from a slot cut through the injection-well casing at a selected depth and orientation. Granular iron is suspended in a viscous fluid using a biodegradable guar polymer and pumped through the slot to form a thin vertical sheet. Two PRBs were emplaced 6 m apart and perpendicular to the groundwater flow direction with mid-depths of about 30 m below the ground surface. Due to the depth, all of the emplacement and verification methods used down-hole tools. Resistivity imaging used salt added to the guar as an electrical tracer to map the spread of the VHFI fluid for propagation control and to estimate the extent of the completed PRB. Radar tomography before and after emplacement also provided images of the PRBs and hydraulic pulse testing and electromagnetic logging provided additional data. One PRB consisted of 40 tonnes of granular iron and was estimated to be an average of 80 mm thick. Based on geophysical imaging, the 100% iron PRB was 15 m long and extended from about 24.5 to 35.5 m depth. The second PRB consisted of a mixture of 5.6 tonnes of well sand and 4.4 tonnes of iron, but was only partially completed. Based on imaging, the sand/iron PRB comprised an area 9 m long extending from about 27 to 34.5 m below the ground surface. The proximity of screened wells, which deviated significantly from vertical toward the PRB alignment, resulted in loss of VHFI control. A sub-horizontal layer of iron formed between the 100% iron PRB and several of the wells. Similarly, piping failure zones formed between the sand/iron PRB and two geophysical wells. Selected groundwater constituents were monitored up- and down-gradient of the two PRBs for 11 months before the PRB emplacement and for 48 months afterwards. Temporary elevated levels of sodium, chloride, and conductance (from the salt tracer), total organic carbon (from the guar) and lowered DO were observed down-gradient of the PRBs. Although the various verification methods confirmed the presence of the 100% iron PRB and its overall continuity, the groundwater data showed no evidence of flow through the granular iron (PCE degradation, elevated pH, dissolved oxygen removal and reducing conditions). This suggests that the groundwater flows around the 100% iron PRB. It is possible that the guar used for the VHFI remained cross-linked, creating a low-permeability barrier. In contrast, the partially completed sand/iron wall did affect the groundwater chemistry in several down-gradient wells. Reducing conditions, zero DO, high pH, and high levels of dissolved iron were noted. A reduction in PCE concentrations and formation of degradation products were observed. (Abstract shortened by UMI.)

Hubble, David Wallace

243

Electro-enhanced Permeable Reactive Barrier : Optimal Design of PRB System With External Current for Effective TCE Removal From Groundwater  

NASA Astrophysics Data System (ADS)

The objective of this study was to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC). A series of column experiments were conducted to evaluate the location of Fe0 permeable reactive barrier (PRB) and the effects of electrode arrangement in the column on the TCE removal efficiency and iron corrosion processes. In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved with simultaneous application of both ZVI and DC compared to that used ZVI only to evaluate the synergistic effect (SE). The most effective arrangement of electrode and ZVI for TCE removal from simulated groundwater was a column set with ZVI and cathode installed at the down gradient (outlet side). Based on the electrochemical study in the E2PRB system, application of direct current provided external electrons to the system so that the system did not depend entirely on the oxidation of the medium for the reductive dechlorination of TCE. The enhanced dechlorination rate of TCE in ZVI-DC systems is considered to attributed to more generation and fast formation kinetic of electron by following reactions: (1) direct supply of electrons from external DC source (2) the electrolysis of water generating additional electrons at the vicinity of the anode (3) the electro-reduction of the compound by released electrons on the ZVI surfaces by oxidation (4) released electron through oxidation of dissolved ferrous iron, and (5) oxidation of atomic hydrogen at the cathode. The competition between five different electron sources generated from five sources evidently influenced on the TCE removal efficiency, valid lifetime of E2PRB system, and reduction of energy expenditure in both of electrochemical and electrokinetic aspects. The results from a series of experiments with twelve columns showed a trend that removal efficiency was more related to the electrode arrangement, but longevity of ZVI PRB and reduction of energy expenditure to location of ZVI installation.

Moon, J.; Moon, H.; Roh, Y.; Kim, H.; Song, Y.

2002-12-01

244

X-231A demonstration of in-situ remediation of DNAPL compounds in low permeability media by soil fracturing with thermally enhanced mass recovery or reactive barrier destruction  

SciTech Connect

The overall goal of the program of activities is to demonstrate robust and cost-effective technologies for in situ remediation of DNAPL compounds in low permeability media (LPM), including adaptations and enhancements of conventional technologies to achieve improved performance for DNAPLs in LPM. The technologies sought should be potential for application at simple, small sites (e.g., gasoline underground storage tanks) as well as at complex, larger sites (e.g., DOE land treatment units). The technologies involved in the X-231A demonstration at Portsmouth Gaseous Diffusion Plant (PORTS) utilized subsurface manipulation of the LPM through soil fracturing with thermally enhanced mass recovery or horizontal barrier in place destruction. To enable field evaluation of these approaches, a set of four test cells was established at the X-231A land treatment unit at the DOE PORTS plant in August 1996 and a series of demonstration field activities occurred through December 1997. The principal objectives of the PORTS X-231A demonstration were to: determine and compare the operational features of hydraulic fractures as an enabling technology for steam and hot air enhanced soil vapor extraction and mass recovery, in situ interception and reductive destruction by zero valent iron, and in situ interception and oxidative destruction by potassium permanganate; determine the interaction of the delivered agents with the LPM matrix adjacent to the fracture and within the fractured zone and assess the beneficial modifications to the transport and/or reaction properties of the LPM deposit; and determine the remediation efficiency achieved by each of the technology strategies.

Siegrist, R.L. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); [Colorado School of Mines, Golden, CO (United States). Environmental Science and Engineering Div.; Lowe, K.S. [Oak Ridge National Lab., Grand Junction, CO (United States). Life Sciences Div.] [Oak Ridge National Lab., Grand Junction, CO (United States). Life Sciences Div.; Murdoch, L.D. [FRx, Inc., Cincinnati, OH (United States)] [FRx, Inc., Cincinnati, OH (United States); [Clemson Univ., SC (United States); Slack, W.W. [FRx, Inc., Cincinnati, OH (United States)] [FRx, Inc., Cincinnati, OH (United States); Houk, T.C. [Lockheed Martin Energy Systems, Piketon, OH (United States)] [Lockheed Martin Energy Systems, Piketon, OH (United States)

1998-03-01

245

Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 1. Hydrogeochemical studies.  

PubMed

Developments and improvements of remedial technologies are needed to effectively manage arsenic contamination in groundwater at hazardous waste sites. In June 2005, a 9.1 m long, 14 m deep, and 1.8 to 2.4 m wide (in the direction of groundwater flow) pilot-scale permeable reactive barrier (PRB) was installed at a former lead smelting facility, located near Helena, Montana (USA). The reactive barrier was designed to treat groundwater contaminated with moderately high concentrations of both As(III) and As(V). The reactive barrier was installed over a 3-day period using bio-polymer slurry methods and modified excavating equipment for deep trenching. The reactive medium was composed entirely of granular iron which was selected based on long-term laboratory column experiments. A monitoring network of approximately 40 groundwater sampling points was installed in July 2005. Monitoring results indicate arsenic concentrations >25 mg L(-1) in wells located hydraulically upgradient of the PRB. Of 80 groundwater samples collected from the pilot-PRB, 11 samples exceeded 0.50 mg As L(-1); 62 samples had concentrations of arsenic at or below 0.50 mg L(-1); and, 24 samples were at or below the maximum contaminant level (MCL) for arsenic of 0.01 mg L(-1). After 2 years of operation, monitoring points located within 1 m of the downgradient edge of the PRB showed significant decreases in arsenic concentrations at depth intervals impacted by the emplaced zerovalent iron. This study indicates that zerovalent iron can be effectively used to treat groundwater contaminated with arsenic given appropriate groundwater geochemistry and hydrology. The study also further demonstrates the shortcomings of hanging-wall designs. Detailed subsurface characterization data that capture geochemical and hydrogeologic variability, including a flux-based analysis, are needed for successful applications of PRB technology for arsenic remediation. PMID:19167133

Wilkin, Richard T; Acree, Steven D; Ross, Randall R; Beak, Douglas G; Lee, Tony R

2009-04-15

246

Iron  

MedlinePLUS

Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

247

Transformation of reactive iron minerals in a permeable reactive barrier (biowall) used to treat TCE in groundwater.  

PubMed

Iron and sulfur reducing conditions generally develop in permeable reactive barrier systems (PRB) constructed to treat contaminated groundwater. These conditions allow formation of FeS mineral phases. FeS readily degrades TCE, but a transformation of FeS to FeS2 could dramatically slow the rate of TCE degradation in the PRB. This study uses acid volatile sulfide (AVS) and chromium reducible sulfur (CRS) as probes for FeS and FeS2 to investigate iron sulfide formation and transformation in a column study and PRB field study dealing with TCE degradation. Solid phase iron speciation shows that most of the iron is reduced and sulfur partitioning measurements show that AVS and CRS coexist in all samples, with the conversion of AVS to CRS being most significant in locations with potential oxidants available. In the column study, 54% of FeS was transformed to FeS2 after 2.4 years. In the field scale PRB, 43% was transformed after 5.2 years. Microscopy reveals FeS, Fe3S4 and FeS2 formation in the column system; however, only pyrite formation was confirmed byX-ray diffraction. The polysulfide pathway is most likely the primary mechanism of FeS transformation in the system, with S0 as an intermediate species formed through H2S oxidation. PMID:18800550

He, Y Thomas; Wilson, John T; Wilkin, Richard T

2008-09-01

248

Iron mediates endothelial cell damage and blood-brain barrier opening in the hippocampus after transient forebrain ischemia in rats  

PubMed Central

Blood cells are transported into the brain and are thought to participate in neurodegenerative processes following hypoxic ischemic injury. We examined the possibility that transient forebrain ischemia (TFI) causes the blood-brain barrier (BBB) to become permeable to blood cells, possibly via dysfunction and degeneration of endothelial cells in rats. Extravasation of Evans blue and immunoglobulin G (IgG) was observed in the hippocampal CA1-2 areas within 8 h after TFI, and peaked at 48 h. This extravasation was accompanied by loss of tight junction proteins, occludin, and zonula occludens-1, and degeneration of endothelial cells in the CA1-2 areas. Iron overload and mitochondrial free radical production were evident in the microvessel endothelium of the hippocampus before endothelial cell damage occurred. Administration of deferoxamine (DFO), an iron chelator, or Neu2000, an antioxidant, blocked free radical production and endothelial cell degeneration. Our findings suggest that iron overload and iron-mediated free radical production cause loss of tight junction proteins and degeneration of endothelial cells, opening of the BBB after TFI. PMID:21278483

Won, Sun Mi; Lee, Jin Hwan; Park, Ui Jin; Gwag, Jina

2011-01-01

249

Impact of microbial activities on the mineralogy and performance of column-scale permeable reactive iron barriers operated under two different redox conditions.  

PubMed

The present study focuses on the impact of microbial activities on the performance of various long-term operated laboratory-scale permeable reactive barriers. The barriers contained both aquifer and Fe0 compartments and had received either sulfate or iron(III)-EDTA to promote sulfate-reducing and iron(III)-reducing bacteria, respectively. After dismantlement of the compartments after almost 3 years of operation, DNA-based PCR-DGGE analysis revealed the presence of methanogenic, sulfate-reducing, metal-reducing, and denitrifying bacteria within as well as up- and downgradient of the Fe0 matrix. Under all imposed conditions, the main secondary phases were vivianite, siderite, ferrous hydroxy carbonate, and carbonate green rust as found by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). Under sulfate-reduction promoting conditions, iron sulfides were formed in addition, resulting in 7 and 10 times higher degradation rates for PCE and TCE, respectively, compared to unreacted iron. These results indicate that the presence of sulfate-reducing bacteria in or around iron barriers and the subsequent formation of iron sulfides might increase the barrier reactivity. PMID:17874779

Van Nooten, Thomas; Lieben, Franois; Dries, Jan; Pirard, Eric; Springael, Dirk; Bastiaens, Leen

2007-08-15

250

Geophysical Monitoring of Two types of Subsurface Injection  

EPA Science Inventory

Nano-scale particles of zero-valent iron (ZVI) were injected into the subsurface at the 100-D area of the DOE Hanford facility. The intent of this iron injection was to repair a gap in the existing in-situ redox manipulation barrier located at the site. A number of geophysical me...

251

Positive impact of microorganisms on the performance of laboratory-scale permeable reactive iron barriers.  

PubMed

Degradation efficiencies of zerovalent iron (Fe0) containing different bacterial inocula, i.e., an iron(III)-reducing Geobacter sulfurreducens strain and/or a bacterial consortium, were compared to degradation efficiencies of noninoculated Fe0 in a laboratory-scale column experiment. Contaminant removal efficiencies and hydrogen production rates indicated an increasing reactivity in time for all inoculated iron columns, while reactivity of the noninoculated columns remained the same. The main mineral precipitates, including carbonate green rust, ferrous hydroxy carbonate, aragonite, and to a lesser extent goethite, were observed under all imposed conditions. The higher reactivity of the inoculated column material is explicable by the reduction of ferric iron species by iron(III)-reducing bacteria, resulting in the observed higher amounts of highly reactive carbonate green rust. However, contributions of other bacteria could not be excluded. Although different groups of hydrogen-consuming bacteria were detected in the columns, no indication was found that hydrogen consumption was sufficiently high to affect reactivity or permeability of the iron matrix, as the abiotic generation of H2 was substantially exceeding its potential consumption. PMID:18441820

van Nooten, Thomas; Springael, Dirk; Bastiaens, Leen

2008-03-01

252

Evaluation of Geochemical Processes Affecting Uranium Sequestration and Longevity of Permeable Reactive Barriers for Groundwater Remediation  

NASA Astrophysics Data System (ADS)

Development of effective remediation techniques for protecting existing drinking water supplies and for mitigating existing contamination problems requires evaluating both the contaminant sequestration processes and the secondary reactions affecting the long term stability of contaminant attenuation. Permeable reactive barriers (PRB) provide a means for passive remediation of dissolved groundwater contaminants and may be an effective strategy for remediation of uranium (U) groundwater contamination provided that long term stability of the sequestered U can be achieved for the geochemical conditions of the aquifer expected subsequent to remediation. Understanding the chemical reaction mechanisms resulting in U uptake and PRB performance are critical to evaluating the potential for release of sequestered U and for improved design of remediation devices. We are using synchrotron X-ray techniques to investigate U sequestration reaction mechanisms and biogeochemical processes in PRB materials recovered from a 9-year field demonstration of zero-valent iron (ZVI) and bone char apatite PRBs in a U contaminated aquifer near Fry Canyon, Utah. X-ray microprobe mapping of iron phases shows that extensive secondary precipitation of mackinawite, siderite and aragonite in the ZVI PRB has resulted from ZVI corrosion coupled with microbial sulfate reduction. Bulk U-EXAFS measurements and micron-scale U-oxidation state mapping indicates that U removal occurs largely by reduction and precipitation of a UO2-like U(IV) phase on the ZVI surfaces, and that the sequestered U is often buried by the secondary Fe precipitates. These findings are significant to the efficacy of ZVI PRBs for remediation of U and other contaminants in that the ongoing secondary phase precipitation cements grains and fills internal porosity resulting in the observed decreased PRB permeability and limits subsequent U removal, but likely limits oxidative remobilization of U. In the bone char apatite PRB, elevated levels of U uptake were observed at up to 20-times above the maximum for U(VI) sorption by surface complexation expected for this material. XAS measurements show that the sequestered U is predominantly in the +4 oxidation state, instead of +6, indicating a reduction process. Bulk U-EXAFS is consistent with the reduced U(IV) occurring as a sorbed species instead of forming biogenic urananite, and thus may be more likely to undergo re-oxidation and mobilization.

Fuller, C. C.; Webb, S.; Bargar, J.; Naftz, D. L.

2009-12-01

253

Monitoring Performance of a Dual Wall Permeable Reactive Barrier for Treating Perchlorate and TCE  

NASA Astrophysics Data System (ADS)

AMEC Geomatrix, through collaboration with Aerojet General Corporation and the University of California, Davis (UCD), has performed work leading to the installation of a dual wall permeable reactive barrier (PRB) system capable of treating perchlorate and chlorinated aliphatic hydrocarbon compounds (CAHs), including trichloroethylene (TCE), at Aerojet's Area 40 site in Sacramento, California. This unique system consisted of an upgradient zero-valent iron (ZVI) permeable reactive barrier (PRB) that is intended to not only degrade CAHs, but also, provide hydrogen generated from the ZVI corrosion process, to a downgradient bio-effective PRB (carbohydrate solution circulated through a gravel-packed trench) for destroying perchlorate. The subsurface was characterized during a site investigation, and numerous logistical and site-specific challenges of installation were addressed. The site-specific challenges included installation of a passive remediation system in a remote location with no access to electricity. The selected remediation system was keyed into the undulating bedrock 20 to 25 feet below the ground surface without the use of shoring. Under a collaborative effort, UCD provided initial bench testing. AMEC Geomatrix designed and installed the dual wall system consisting of two approximately parallel 50-foot long by 2-foot thick by 25-foot deep PRB segments which are separated by about 8 feet perpendicular to the approximate direction of groundwater flow. AMEC Geomatrix performed the installation of performance monitoring network, which consisted of 21 wells, and monitored these points for a 6-month period. Monitoring and sampling techniques were designed to measure water levels and water quality parameters in the subsurface during sampling events, to better assess the hydrologic and chemical processes. The monitoring results indicate that the upgradient ZVI PRB effectively treats groundwater with TCE concentrations approaching 60 mg/L, and in addition, may reduce concentrations of perchlorate from approximately 25 mg/L to less than 1 mg/L. A database was maintained to manage analytical results, water quality parameters, and water levels from each sampling event, and geographic information system (GIS) was used to generate plan diagrams of the treatment and performance. The small footprint of the monitoring network allowed for visualizations of the sample results in vertical segments, cross-gradient, within the PRBs, and upgradient or downgradient of the treatment zone. This method of monitoring treatment performance allowed for rapid assessment of the effectiveness of the dual walled PRB as new data became available. The initial time and cost to set up the data management structure (database to GIS) would allow for the ability to monitor the remediation performance more efficiently and to make more effective decisions, including assessment of the carbohydrate depletion within the bio-effective PRB.

Dowman, C. E.; Hashimoto, Y.; Warner, S.; Bennett, P.; Gandhi, D.; Szerdy, F.; Neville, S.; Fennessy, C.; Scow, K. M.

2008-12-01

254

Iron  

MedlinePLUS

... mealtime or when you take iron supplements.RiboflavinTaking riboflavin supplements may improve the way iron supplements work ... significant only in people with low levels of riboflavin.SoySoy protein seems to reduce the body's ability ...

255

IRON  

EPA Science Inventory

The document surveys the effects of organic and inorganic iron that are relevant to humans and their environment. The biology and chemistry of iron are complex and only partially understood. Iron participates in oxidation reduction processes that not only affect its geochemical m...

256

Thermally Evaporated Iron (Oxide) on an Alumina Barrier Layer, by XPS  

SciTech Connect

We report the XPS characterization of a thermally evaporated iron thin film (6 nm) deposited on an Si/SiO_2/Al_2O_3 substrate using Al Ka X-rays. An XPS survey spectrum, narrow Fe 2p scan, narrow O 1s, and valence band scan are shown.

Madaan, Nitesh; Kanyal, Supriya S.; Jensen, David S.; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.

2013-09-06

257

Magnetic resonance imaging of post-ischemic blood-brain barrier damage with PEGylated iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Blood-brain barrier (BBB) damage during ischemia may induce devastating consequences like cerebral edema and hemorrhagic transformation. This study presents a novel strategy for dynamically imaging of BBB damage with PEGylated supermagnetic iron oxide nanoparticles (SPIONs) as contrast agents. The employment of SPIONs as contrast agents made it possible to dynamically image the BBB permeability alterations and ischemic lesions simultaneously with T2-weighted MRI, and the monitoring could last up to 24 h with a single administration of PEGylated SPIONs in vivo. The ability of the PEGylated SPIONs to highlight BBB damage by MRI was demonstrated by the colocalization of PEGylated SPIONs with Gd-DTPA after intravenous injection of SPION-PEG/Gd-DTPA into a mouse. The immunohistochemical staining also confirmed the leakage of SPION-PEG from cerebral vessels into parenchyma. This study provides a novel and convenient route for imaging BBB alteration in the experimental ischemic stroke model.

Liu, Dong-Fang; Qian, Cheng; An, Yan-Li; Chang, Di; Ju, Sheng-Hong; Teng, Gao-Jun

2014-11-01

258

Performance of a Zerovalent Iron Reactive Barrier for the Treatment of Arsenic in Groundwater: Part 2. Geochemical Modeling and Solid Phase Studies  

EPA Science Inventory

Arsenic uptake processes were evaluated in a zerovalent iron reactive barrier installed at a lead smelting facility using geochemical modeling, solid-phase analysis, and X-ray absorption spectroscopy techniques. Aqueous speciation of arsenic plays a key role in directing arsenic...

259

REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS  

EPA Science Inventory

Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

260

Laboratory Evaluation of Sulfur Modified Iron for Use as a Filter Material to Treat Agricultural Drainage Waters  

NASA Astrophysics Data System (ADS)

Where subsurface drainage practices are employed, fertilizer nutrients and pesticides applied on farm fields and municipal locations are commonly intercepted by the buried drainage pipes and then discharged into local streams and lakes, oftentimes producing adverse environmental impacts on these surface water bodies. On-site water filter treatment systems can be employed to prevent the release of agricultural nutrients/pesticides into adjacent waterways. Sulfur modified iron is a relatively unknown industrial product that may have promise for use as a filter material to remove contaminants from subsurface drainage waters. Sulfur modified iron (SMI) is a high surface area iron powder (zero valent iron) that has been altered via chemical reaction with pure sulfur to produce a sulfur/iron surface coating on the iron particles. A laboratory investigation was conducted with contaminant removal batch tests, saturated falling-head hydraulic conductivity tests, and saturated solute transport column experiments to evaluate the feasibility for using SMI to treat subsurface drainage waters. Contaminant removal batch tests showed that three SMI samples were much more effective removing nitrate (> 94% nitrate removed) than three zero valent iron samples (< 10% nitrate removed). Batch test results additionally showed that SMI removed greater that 94% of dissolved phosphate, but was not particularly effective removing the pesticide, atrazine (< 37% atrazine removed). Hydraulic conductivity tests indicated that all three SMI samples that were evaluated had sufficient hydraulic conductivity, much greater than the 1 x 10-3 cm/s standard used for stormwater sand filters. The saturated solute transport tests confirmed that SMI can be effective removing nitrate and phosphate from drainage waters. Analysis of column effluent also showed that the large majority of nitrate removed by SMI was converted to ammonium. Consequently, these laboratory findings support the use of SMI in agricultural drainage water filter treatment systems, particularly when nitrate and phosphate pollution are major environmental concerns.

Allred, B. J.

2009-12-01

261

Mechanism of copper transport at the blood-cerebrospinal fluid barrier: influence of iron deficiency in an in vitro model.  

PubMed

Copper (Cu) is an essential trace element that requires tight homeostatic regulation to ensure appropriate supply while not causing cytotoxicity due to its strong redox potential. Our previous in vivo study has shown that iron deficiency (FeD) increases Cu levels in brain tissues, particularly in the choroid plexus, where the blood-cerebrospinal fluid (CSF) barrier resides. This study was designed to elucidate the mechanism by which FeD results in excess Cu accumulation at the blood-CSF barrier. The effect of FeD on cellular Cu retention and transporters Cu transporter-1 (Ctr1), divalent metal transporter 1 (DMT1), antioxidant protein-1 (ATOX1) and ATP7A was examined in choroidal epithelial Z310 cells. The results revealed that deferoximine treatment (FeD) resulted in 70% increase in cellular Cu retention (P < 0.05). A significant increase in the mRNA levels of DMT1, but not Ctr1, was also observed after FeD treatment, suggesting a critical role of DMT1 in cellular Cu regulation during FeD. Knocking down Ctr1 or DMT1 resulted in significantly lower Cu uptake by Z310 cells, whereas the knocking down of ATOX1 or ATP7A led to substantial increases of cellular retention of Cu. Taken together, these results suggest that Ctr1, DMT1, ATOX1 and ATP7A contribute to Cu transport at the blood-CSF barrier, and that the accumulation of intracellular Cu found in the Z310 cells during FeD appears to be mediated, at least in part, via the upregulation of DMT1 after FeD treatment. PMID:22442359

Monnot, Andrew D; Zheng, Gang; Zheng, Wei

2012-03-01

262

Iron monosulfide as a scavenger for dissolved hexavalent chromium and cadmium.  

PubMed

Iron sulfide minerals are common components of soil/sedimentary environments. Reactions near the surfaces of iron sulfides play important roles in metal retention, mobility, and bioavailability. A series of batch experiments was conducted to study the removal of aqueous chromium and cadmium by iron monosulfide. Hexavalent chromium was reduced to Cr(III) by iron monosulfide with simultaneous precipitation of chromium and iron oxyhydroxide. In contrast to chromium, the primary retention mechanism of cadmium by iron monosulfide was lattice exchange. Surface adsorption to iron monosulfide and precipitation with sulfide on the iron monosulfide surface also contributed to the removal of aqueous cadmium. New phases of both chromium and cadmium were confirmed with transmission electron microscopy. The solution pH was an important factor in this research; it can change particle surface charge and metal species, hence affecting the removal of chromium, but not cadmium. Ferrous ions without FeS exhibited less Cr(VI) removal than with FeS, which might be owing to sulfides from FeS and the existence of the solid phase. Iron monosulfide exhibited higher removal efficiency for chromium and cadmium than zero valent iron and other iron oxide minerals, and the synergistic effect of ferrous iron and sulfide appeared to cause this result. PMID:18844124

Jo, S; Lee, J Y; Kong, S H; Choi, J; Park, J W

2008-09-01

263

GROUND WATER ARSENIC AND METALS TREATMENT USING A COMBINATION COMPOST-ZVI PRB (ABSTRACT ONLY)  

EPA Science Inventory

A pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI), limestone and pea gravel was installed at a former phosphate fertilizer manufacturing facility in Charleston, S.C. in September 2002. The PRB is designed to treat arsenic an...

264

THE APPLICATION OF PRB TECHNOLOGY AT TWO SITES: LESSONS LEARNED AFTER 7 YEARS OF PERFORMANCE MONITORING  

EPA Science Inventory

In June of 1996, a 46 m long, 7.3 m deep, and 0.6 m wide permeable reactive barrier (continuous wall configuration) of zero-valent iron was installed at the USCG-SC site. The reactive wall was designed to remediate hexavalent chromium-contaminated groundwater, in addition to tre...

265

Treatment of Arsenic, Heavy Metals, and Acidity Using a Mixed ZVI-Compost PRB  

EPA Science Inventory

A 30-month performance evaluation of a pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI), limestone and pea gravel installed at a former phosphate fertilizer manufacturing facility was conducted. The PRB is designed to remove ...

266

Dehalogenation of Polybrominated Diphenyl Ethers and Polychlorinated Biphenyl by Bimetallic, Impregnated, and Nanoscale Zerovalent Iron  

PubMed Central

Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zero-valent, which shows the difficulty with in-situ synthesis of a significant fraction of zero-valent iron in the micro-porous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogenous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI. PMID:21557574

Zhuang, Yuan; Ahn, Sungwoo; Seyfferth, Angelia L.; Masue-Slowey, Yoko; Fendorf, Scott; Luthy, Richard G.

2011-01-01

267

Dielectric barrier formation and tunneling magnetoresistance effect in strontium iron molybdate  

NASA Astrophysics Data System (ADS)

A comparative X-ray diffraction study of the initial single-phase metal-oxide compound-strontium iron molybdate Sr2FeMoO6 - ? (SFMO)-and that subjected to additional isothermal annealing shows that this heat treatment leads to the appearance of a SrMoO4 (SMO) phase. Small-angle neutron scattering measurements indicate that the SMO phase forms a dielectric shell surrounding SFMO grains, which has a characteristic thickness of 2-4 nm and extends above 120 nm. The character of the temperature dependence of the electric resistance corresponds to the metal-type conduction in single-phase SFMO and changes to a semiconductor type in the material with SMO dielectric shells, which is evidence of a tunneling mechanism of charge transfer. This conclusion is confirmed by an increase in the absolute value of the negative magnetoresistance of SFMO due to the appearance of a tunneling magnetoresistance component of the same sign.

Dem'yanov, S. E.; Kalanda, N. A.; Kovalev, L. V.; Avdeev, M. V.; Zheludkevich, M. L.; Garamus, V. M.; Willumeit, R.

2013-06-01

268

Pulsed Magnetic Field Improves the Transport of Iron Oxide Nanoparticles through Cell Barriers  

PubMed Central

Understanding how a magnetic field affects the interaction of magnetic nanoparticles (MNPs) with cells is fundamental to any potential downstream applications of MNPs as gene and drug delivery vehicles. Here, we present a quantitative analysis of how a pulsed magnetic field influences the manner in which MNPs interact with, and penetrate across a cell monolayer. Relative to a constant magnetic field, the rate of MNP uptake and transport across cell monolayers was enhanced by a pulsed magnetic field. MNP transport across cells was significantly inhibited at low temperature under both constant and pulsed magnetic field conditions, consistent with an active mechanism (i.e. endocytosis) mediating MNP transport. Microscopic observations and biochemical analysis indicated that, in a constant magnetic field, transport of MNPs across the cells was inhibited due to the formation of large (>2 ?m) magnetically-induced MNP aggregates, which exceeded the size of endocytic vesicles. Thus, a pulsed magnetic field enhances the cellular uptake and transport of MNPs across cell barriers relative to a constant magnetic field by promoting accumulation while minimizing magnetically-induced MNP aggregates at the cell surface. PMID:23373613

Min, Kyoung Ah; Shin, Meong Cheol; Yu, Faquan; Yang, Meizhu; David, Allan E.; Yang, Victor C.; Rosania, Gus R.

2013-01-01

269

Corrosion resistance of cast irons and titanium alloys as reference engineered metal barriers for use in basalt geologic storage: a literature assessment  

SciTech Connect

A survey and assessment of the literature on the corrosion resistance of cast irons and low-alloy titanium are presented. Selected engineering properties of cast iron and titanium are briefly described; however, the corrosion resistance of cast iron and titanium in aqueous solutions or in soils and their use in a basalt repository are emphasized. In evaluating the potential use of cast iron and titanium as structural barrier materials for long-lived nuclear waste packages, it is assumed that titanium has the general corrosion resistance to be used in relatively thin cross sections whereas the cost and availability of cast iron allows its use even in very thick cross sections. Based on this assumption, the survey showed that: The uniform corrosion of low-alloy titanium in a basalt environment is expected to be extremely low. A linear extrapolation of general corrosion rates with an added corrosion allowance suggests that a 3.2- to 6.4-mm-thick wall may have a life of 1000 yr. Pitting and crevice corrosion are not likely corrosion modes in basalt ground waters. It is also unlikely that stress corrosion cracking (SCC) will occur in the commercially pure (CP) titanium alloy or in palladiumor molybdenum-alloyed titanium materials. Low-alloy cast irons may be used as barrier metals if the environment surrounding the metal keeps the alloy in the passive range. The solubility of the corrosion product and the semipermeable nature of the oxide film allow significant uniform corrosion over long time periods. A linear extrapolation of high-temperature corrosion rates on carbon steels and corrosion rates of cast irons in soils gives an estimated metal penetration of 51 to 64 mm after 1000 yr. A corrosion allowance of 3 to 5 times that suggests that an acceptable cast iron wall may be from 178 to 305 mm thick. Although they cannot be fully assessed, pitting and crevice corrosion should not affect cast iron due to the ground-water chemistry of basalt.

Charlot, L.A.; Westerman, R.E.

1981-07-01

270

Valiant 'Zero-Valent' Effort Restores Contaminated Grounds  

NASA Technical Reports Server (NTRS)

Dense non-aqueous phase liquids (DNAPLs) are chemical compounds that can contaminate soil and groundwater to the point of irreparability. These substances are only slightly soluble in water, and are much denser than water. Because of their solubility, DNAPLs form separate liquid phases in groundwater, and because of their density, DNAPLs sink in aquifers instead of floating at the water table, making it extremely difficult to detect their presence. If left untreated in the ground, they can taint fresh water sources. Common DNAPLs include chlorinated hydrocarbon compounds such as carbon tetrachloride, chloroform, tetrachloroethylene, and trichloroethylene. Trichloroethylene was used during the early days of the Space Program, as a solvent for flushing rocket engines, and for metal cleaning and degreasing of equipment, electronics, and heavy machinery. As a result, areas of Cape Canaveral s Launch Complex 34, the site of several historic Saturn rocket launches occurring from 1959 to 1968, were polluted with chlorinated DNAPLs. Through the direction and guidance of Dr. Jacqueline Quinn, an environmental engineer in the Spaceport Engineering and Technology Directorate at NASA s Kennedy Space Center, a biodegradable environmental cleanup technology was developed to reductively dechlorinate DNAPL sources in polluted water at Launch Complex 34. It was important for Kennedy to nip this problem in the bud, in light of the fact that the Space Center is also a National Wildlife Refuge, home to thousands of shorebirds, endangered sea turtles and eagles, manatees, alligators, and diverse habitats that include brackish marshes and salt water estuaries. The success in remediating this historic launch site has led to numerous commercial applications that are restoring the health of our environmental surroundings.

2005-01-01

271

Evaluating Trichloroethylene Degradation Using Differing Nano- and Micro-Scale Iron Particles  

NASA Technical Reports Server (NTRS)

Trichioroethylene, or TCE, is a central nervous system depressant and possible carcinogen, as well as a persistent groundwater pollutant. TCE exists in the aquifer either as free product in the form of a dense non-aqueous phase liquid (DNAPL) or as a dissolved-phase constituent. It is only slightly soluble in water, so dissolution of the contaminant is a long-term process and in-situ remediation is difficult. To remedy this, NASA and the University of Central Florida developed Emulsified Zero-Valent Iron, or EZVI. The emulsion droplet contains ZVI particles and water encapsulated by an oil/surfactant membrane, and effectively penetrates to degrade DNAPL-phase TCE. To maximize the efficiency of this process, several commercially available ZVIs of radically different particle sizes and morphologies both in emulsion and as neat (unemulsified) metal were evaluated for relative effectiveness at TCE degradation.

Berger, Cristina M.; Geiger, Cherie L.; Clausen, Christian A.; Billow, Alexa M.; Quinn, Jacqueline W.; Brooks, Kathleen B.

2006-01-01

272

Remediation of the Highland Drive South Ravine, Port Hope, Ontario: Contaminated Groundwater Discharge Management Using Permeable Reactive Barriers and Contaminated Sediment Removal - 13447  

SciTech Connect

The Highland Drive South Ravine (HDSR) is the discharge area for groundwater originating from the Highland Drive Landfill, the Pine Street North Extension (PSNE) roadbed parts of the Highland Drive roadbed and the PSNE Consolidation Site that contain historical low-level radioactive waste (LLRW). The contaminant plume from these LLRW sites contains elevated concentrations of uranium and arsenic and discharges with groundwater to shallow soils in a wet discharge area within the ravine, and directly to Hunt's Pond and Highland Drive South Creek, which are immediately to the south of the wet discharge area. Remediation and environmental management plans for HDSR have been developed within the framework of the Port Hope Project and the Port Hope Area Initiative. The LLRW sites will be fully remediated by excavation and relocation to a new Long-Term Waste Management Facility (LTWMF) as part of the Port Hope Project. It is projected, however, that the groundwater contaminant plume between the remediated LLRW sites and HDSR will persist for several hundreds of years. At the HDSR, sediment remediation within Hunt's Ponds and Highland Drive South Creek, excavation of the existing and placement of clean fill will be undertaken to remove current accumulations of solid-phase uranium and arsenic associated with the upper 0.75 m of soil in the wet discharge area, and permeable reactive barriers (PRBs) will be used for in situ treatment of contaminated groundwater to prevent the ongoing discharge of uranium and arsenic to the area in HDSR where shallow soil excavation and replacement has been undertaken. Bench-scale testing using groundwater from HDSR has confirmed excellent treatment characteristics for both uranium and arsenic using permeable reactive mixtures containing granular zero-valent iron (ZVI). A sequence of three PRBs containing ZVI and sand in backfilled trenches has been designed to intercept the groundwater flow system prior to its discharge to the ground surface and the creek and ponds in the HDSR. The first of the PRBs will be installed immediately up-gradient of the wet discharge area approximately 50 m from the creek, the other two will be installed across the area of shallow soil replacement, and all will extend from ground surface to the base of the water table aquifer through which the impacted groundwater flows. The PRBs have been designed to provide the removal of uranium and arsenic for decades, although the capacity of the treatment mixture for contaminant removal suggests that a longer period of treatment may be feasible. The environmental management plan includes an allowance for on-going monitoring, and replacement of a PRB(s) as might be required. (authors)

Smyth, David; Roos, Gillian [Golder Associates Ltd., 2390 Argentia Road, Mississauga, ON L5N 5Z7 (Canada)] [Golder Associates Ltd., 2390 Argentia Road, Mississauga, ON L5N 5Z7 (Canada); Ferguson Jones, Andrea [MMM Group Ltd., 100 Commerce Valley Drive West, Thornhill, ON L3T 0A1 (Canada)] [MMM Group Ltd., 100 Commerce Valley Drive West, Thornhill, ON L3T 0A1 (Canada); Case, Glenn [AECL Port Hope Area Initiative Management Office, 115 Toronto Road, Port Hope, ON L1A 3S4 (Canada)] [AECL Port Hope Area Initiative Management Office, 115 Toronto Road, Port Hope, ON L1A 3S4 (Canada); Yule, Adam [Public Works and Government Services Canada, 4900 Yonge Street, 11th Floor, Toronto, ON, M2N 6A6 (Canada)] [Public Works and Government Services Canada, 4900 Yonge Street, 11th Floor, Toronto, ON, M2N 6A6 (Canada)

2013-07-01

273

Formulation design for target delivery of iron nanoparticles to TCE zones  

NASA Astrophysics Data System (ADS)

Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones. To this end, iron oxide nanoparticles coated with oleate (OL) ions were used as stable analogs for NZVI. The OL-coated iron oxide nanoparticles are rendered lipophilic via (a) the addition of CaCl2, (b) acidification, or (c) the addition of a cationic surfactant, benzethonium chloride (BC). Mixtures of OL and BC show promise as a target delivery strategy due to the high stability of the nanoparticles in water, and their preferential partition into TCE in batch experiments. Column tests show that while the OL-BC coated iron oxide nanoparticles remain largely mobile in TCE-free columns, a large fraction of these particles are retained in TCE-contaminated columns, confirming the effectiveness of this target delivery strategy.

Wang, Ziheng; Acosta, Edgar

2013-12-01

274

Removal of mixed contaminants by Fe 0 -based biobarrier in flow-through columns using recycled waste materials  

Microsoft Academic Search

The present study investigated the reactivity and ability of permeable reactive barriers [zero-valent iron (ZVI)-barrier plus\\u000a biobarrier) to remove various contaminants (Cd, As, Zn, Cu, Mn, Cr, NO3\\u000a ?, NH4\\u000a +, and CODcr) from synthetic leachate. Two different reactive materials were used in this study, namely ZVI and autoclaved lightweight\\u000a concrete (ALC). After 90 days of column operation, the contaminant

Jai-Young Lee; Sun Young Youm; Sang-Il Choi; Byung-Taek Oh

2009-01-01

275

In-situ method to remove iron and other metals from solution in groundwater down gradient from permeable reactive barrier  

DOEpatents

This invention is directed to a process for treating the flow of anaerobic groundwater through an aquifer with a primary treatment media, preferably iron, and then passing the treated groundwater through a second porous media though which an oxygenated gas is passed in order to oxygenate the dissolved primary treatment material and convert it into an insoluble material thereby removing the dissolved primary treatment material from the groundwater.

Carpenter, Clay E. (Grand Junction, CO); Morrison, Stanley J. (Grand Junction, CO)

2001-07-03

276

In-situ method to remove iron and other metals from Solution in Groundwater down Gradient from Permeable Reactive Barrier  

SciTech Connect

This invention is directed to a process for treating the flow of anaerobic groundwater through an aquifer with a primary treatment media, preferably iron, and then passing the treated groundwater through a second porous media though which an oxygenated gas is passed in order to oxygenate the dissolved primary treatment material and convert it into an insoluble material thereby removing the dissolved primary treatment material from the groundwater.

Carpenter, Clay E.; Morrison, Stanley J.

1999-09-22

277

Ammonium-nitrogen-contaminated groundwater remediation by a sequential three-zone permeable reactive barrier (multibarrier) with oxygen-releasing compound (ORC)/clinoptilolite/spongy iron: column studies.  

PubMed

A novel sequential permeable reactive barrier (multibarrier), composed of oxygen-releasing compound (ORC)/clinoptilolite/spongy iron zones in series, was proposed for ammonium-nitrogen-contaminated groundwater remediation. Column experiments were performed to: (1) evaluate the overall NH4 (+)-N removal performance of the proposed multibarrier, (2) investigate nitrogen transformation in the three zones, (3) determine the reaction front progress, and (4) explore cleanup mechanisms for inorganic nitrogens. The results showed that NH4 (+)-N percent removal by the multibarrier increased up to 90.43% after 21 pore volumes (PVs) at the influent dissolved oxygen of 0.68?2.45mg/L and pH of 6.76?7.42. NH4 (+)-N of 4.06?10.49mg/L was depleted and NO x (-)-N (i.e., NO3 (-)-N?+?NO2 (-)-N) of 4.26?9.63mg/L was formed before 98 PVs in the ORC zone. NH4 (+)-N of ?4.76mg/L was eliminated in the clinoptilolite zone. NO x (-)-N of 10.44?12.80mg/L was lost before 21 PVs in the spongy iron zone. The clinoptilolite zone length should be reduced to 30cm. Microbial nitrification played a dominant role in NH4 (+)-N removal in the ORC zone. Ion exchange was majorly responsible for NH4 (+)-N elimination in the clinoptilolite zone. Chemical reduction and hydrogenotrophic denitrification both contributed to NO x (-)-N transformation, but the chemical reduction capacity decreased after 21 PVs in the spongy iron. PMID:25256584

Huang, Guoxin; Liu, Fei; Yang, Yingzhao; Kong, Xiangke; Li, Shengpin; Zhang, Ying; Cao, Dejun

2014-09-27

278

Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis  

PubMed Central

The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L?1 in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe15Cr5(OH)60 precipitate. PMID:23284182

Sarahney, Hussam; Mao, Xuhui; Alshawabkeh, Akram N.

2012-01-01

279

Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis.  

PubMed

The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L(-1) in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe(15)Cr(5)(OH)(60) precipitate. PMID:23284182

Sarahney, Hussam; Mao, Xuhui; Alshawabkeh, Akram N

2012-12-30

280

Optimization of soil mixing technology through metallic iron addition.  

SciTech Connect

Enhanced soil mixing is a process used to remove volatile organic compounds (VOCs) from soil. In this process, also known as soil mixing with thermally enhanced soil vapor extraction, or SM/TESVE, a soil mixing apparatus breaks up and mixes a column of soil up to 9 m (30 ft) deep; simultaneously, hot air is blown through the soil. The hot air carries the VOCs to the surface where they are collected and safely disposed of. This technology is cost effective at high VOC concentrations, but it becomes cost prohibitive at low concentrations. Argonne National Laboratory-East conducted a project to evaluate ways of improving the effectiveness of this system. The project investigated the feasibility of integrating the SM/TESVE process with three soil treatment processes--soil vapor extraction, augmented indigenous biodegradation, and zero-valent iron addition. Each of these technologies was considered a polishing treatment designed to remove the contaminants left behind by enhanced soil mixing. The experiment was designed to determine if the overall VOC removal effectiveness and cost-effectiveness of the SM/TESVE process could be improved by integrating this approach with one of the polishing treatment systems.

Moos, L. P.

1999-01-15

281

Ambient iron-mediated aeration (IMA) for water reuse.  

PubMed

Global water shortages caused by rapidly expanding population, escalating water consumption, and dwindling water reserves have rendered water reuse a strategically significant approach to meet current and future water demand. This study is the first to our knowledge to evaluate the technical feasibility of iron-mediated aeration (IMA), an innovative, potentially economical, holistic, oxidizing co-precipitation process operating at room temperature, atmospheric pressure, and neutral pH, for water reuse. In the IMA process, dissolved oxygen (O?) was continuously activated by zero-valent iron (Fe?) to produce reactive oxygen species (ROS) at ambient pH, temperature, and pressure. Concurrently, iron sludge was generated as a result of iron corrosion. Bench-scale tests were conducted to study the performance of IMA for treatment of secondary effluent, natural surface water, and simulated contaminated water. The following removal efficiencies were achieved: 82.2% glyoxylic acid, ~100% formaldehyde as an oxidation product of glyoxylic acid, 94% of Ca? and associated alkalinity, 44% of chemical oxygen demand (COD), 26% of electrical conductivity (EC), 98% of di-n-butyl phthalate (DBP), 80% of 17?-estradiol (E2), 45% of total nitrogen (TN), 96% of total phosphorus (TP), 99.8% of total Cr, >90% of total Ni, 99% of color, 3.2 log removal of total coliform, and 2.4 log removal of E. Coli. Removal was attributed principally to chemical oxidation, precipitation, co-precipitation, coagulation, adsorption, and air stripping concurrently occurring during the IMA treatment. Results suggest that IMA is a promising treatment technology for water reuse. PMID:23232032

Deng, Yang; Englehardt, James D; Abdul-Aziz, Samer; Bataille, Tristan; Cueto, Josenrique; De Leon, Omar; Wright, Mary E; Gardinali, Piero; Narayanan, Aarthi; Polar, Jose; Tomoyuki, Shibata

2013-02-01

282

Epirubicin-loaded superparamagnetic iron-oxide nanoparticles for transdermal delivery: cancer therapy by circumventing the skin barrier.  

PubMed

The transdermal administration of chemotherapeutic agents is a persistent challenge for tumor treatments. A model anticancer agent, epirubicin (EPI), is attached to functionalized superparamagnetic iron-oxide nanoparticles (SPION). The covalent modification of the SPION results in EPI-SPION, a potential drug delivery vector that uses magnetism for the targeted transdermal chemotherapy of skin tumors. The spherical EPI-SPION composite exhibits excellent magnetic responsiveness with a saturation magnetization intensity of 77.8 emu g(-1) . They feature specific pH-sensitive drug release, targeting the acidic microenvironment typical in common tumor tissues or endosomes/lysosomes. Cellular uptake studies using human keratinocyte HaCaT cells and melanoma WM266 cells demonstrate that SPION have good biocompatibility. After conjugation with EPI, the nanoparticles can inhibit WM266 cell proliferation; its inhibitory effect on tumor proliferation is determined to be dose-dependent. In vitro transdermal studies demonstrate that the EPI-SPION composites can penetrate deep inside the skin driven by an external magnetic field. The magnetic-field-assisted SPION transdermal vector can circumvent the stratum corneum via follicular pathways. The study indicates the potential of a SPION-based vector for feasible transdermal therapy of skin cancer. PMID:24925046

Rao, Yue-Feng; Chen, Wei; Liang, Xing-Guang; Huang, Yong-Zhuo; Miao, Jing; Liu, Lin; Lou, Yan; Zhang, Xing-Guo; Wang, Ben; Tang, Rui-Kang; Chen, Zhong; Lu, Xiao-Yang

2015-01-01

283

Laboratory comparison of four iron-based filter materials for water treatment of trace element contaminants.  

PubMed

A laboratory investigation provided preliminary comparison of trace element contaminant water treatment capabilities for four iron-based filter materials. The iron-based filter materials tested were zero-valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and iron oxide/hydroxide (IOH). Two types of trace element contaminant solutions were tested, one combined As, Cr, and Se (added as AsO4(3-), CrO4(2-), and SeO4(2-), respectively), while the second combined Cd2+, Cu2+, and Pb2+. The laboratory investigation included saturated falling-head hydraulic conductivity tests, contaminant removal-desorption/dissolution batch tests, and low-to-high flow rate saturated solute transport column tests. Hydraulic conductivity test results indicate that all four iron-based filter materials have sufficient water flow capacity as indicated by saturated hydraulic conductivity values greater than 1 x 10(-2) cm/s. Essentially, 100% of each trace element (As, Cd, Cr, Cu, Pb, and Se) was removed by SMI during the contaminant removal portion of the batch tests and during the column tests, while IOH exhibited good removal of each trace element except Se. Results from the contaminant removal portion of the batch tests and from the column tests showed ZVI and PIC were effective in treating Cd, Cr, Cu, and Pb. With the exception of Se adsorption/precipitation onto IOH, the desorption/dissolution portion of the batch tests showed that once As, Cd, Cr, Cu, Pb, or Se are adsorbed/precipitated onto ZVI, PIC, SMI, or IOH particle surfaces, these trace elements are then not readily desorbed or dissolved back into solution. PMID:25509527

Allred, Barry J; Tost, Brian C

2014-11-01

284

Iron and Iron Deficiency  

MedlinePLUS

... iron. (NIH) back to top Iron Overload and Hemochromatosis Iron overload is the accumulation of excess iron in body tissues. Hemochromatosis is the disease resulting from significant iron overload. ...

285

Treatment of oilfield produced water using Fe/C micro-electrolysis assisted by zero-valent copper and zero-valent aluminium.  

PubMed

In this study, the Fe/Cu/C and Fe/Al/C inner micro-electrolysis systems were used to treat actual oilfield produced water to evaluate the feasibility of the technology. Effects of reaction time, pH value, the dosage of metals and activated carbon, and Fe:C mass ratio on the treatment efficiency of wastewater were studied. The results showed that the optimum conditions were reaction time 120?min, initial solution pH 4.0, Fe dosage 13.3?g/L, activated carbon dosage 6.7?g/L, Cu dosage 2.0?g/L or Al dosage 1.0?g/L. Under the optimum conditions, the removal efficiencies of chemical oxygen demand (COD) were 39.3%, 49.7% and 52.6% in the Fe/C, Fe/Cu/C and Fe/Al/C processes, respectively. Meanwhile, the ratio of five-day biochemical oxygen demand to COD was raised from 0.18 to above 0.35, which created favourable conditions for the subsequent biological treatment. All these led to an easy maintenance and low operational cost. PMID:25182172

Zhang, Qi

2015-02-01

286

Electrodialytic remediation of polychlorinated biphenyls contaminated soil with iron nanoparticles and two different surfactants.  

PubMed

Polychlorinated biphenyls (PCB) are persistent organic pollutants (POP) that strongly adsorb in soils and sediments. There is a need to develop new and cost-effective solutions for the remediation of PCB contaminated soils. The suspended electrodialytic remediation combined with zero valent iron nanoparticles (nZVI) could be a competitive alternative to the commonly adapted solutions of incineration or landfilling. Surfactants can enhance the PCB desorption, dechlorination, and the contaminated soil cleanup. In this work, two different surfactants (saponin and Tween 80) were tested to enhance PCB desorption and removal from a soil sampled at a polluted site, in a two-compartment cell where the soil was stirred in a slurry with 1% surfactant, 10mL of nZVI commercial suspension, and a voltage gradient of 1Vcm(-1). The highest PCB removal was obtained with saponin. Higher chlorinated PCB congeners (penta, hexa, hepta and octachlorobiphenyl) showed removal percentages between 9% and 96%, and the congeners with highest removal were PCB138, PCB153 and PCB180. The use of low level direct current enhanced PCB removal, especially with saponin. Electrodechlorination of PCB with surfactants and nZVI showed encouraging tendencies and a base is thus formed for further optimization towards a new method for remediation of PCB polluted soils. PMID:25129337

Gomes, Helena I; Dias-Ferreira, Celia; Ottosen, Lisbeth M; Ribeiro, Alexandra B

2014-11-01

287

Laboratory comparison of four iron-based filter materials for drainage water phosphate treatment.  

PubMed

A laboratory investigation evaluated phosphate (PO4(3-)) drainage water treatment capabilities of four iron-based filter materials. The iron-based filter materials tested were zero-valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and iron oxide/ hydroxide (IOH). Only filter material retained on a 60-mesh sieve (> 0.25 mm) was used for evaluation. The laboratory investigation included saturated falling-head hydraulic conductivity tests, contaminant removal or desorption/dissolution batch tests, and low-to-high flow rate saturated solute transport column tests. Each of the four iron-based filter materials have sufficient water flow capacity as indicated by saturated hydraulic conductivity values that in most cases were greater than 1 x 10(-2) cm/s. For the 1, 10, and 100 ppm PO4(3-)-P contaminant removal batch tests, each of the four iron-based filter materials removed at least 95% of the PO4(3-)-P originally present. However, for the 1000 ppm PO4(3-)-P contaminant removal batch tests, IOH by far exhibited the greatest removal effectiveness (99% PO4(3-)-P removal), followed by SMI (72% PO4(3-)-P removal), then ZVI (62% PO4(3-)-P removal), and finally PIC (15% PO4(3-)-P removal). The desorption/dissolution batch test results, especially with respect to SMI and IOH, indicate that once PO4(3-) is adsorbed/precipitated onto surfaces of iron-based filter material particles, this PO4(3-) becomes fixed and is then not readily desorbed/dissolved back into solution. The results from the column tests showed that regardless of low or high flow rate (contact time ranged from a few hours to a few minutes) and PO4(3-) concentration (1 ppm or 10 ppm PO4(3-)-P), PIC, SMI, and IOH reduced PO4(3-)-P concentrations to below detection limits, while ZVI removed at least 90% of the influent PO4(3-)-P. Consequently, these laboratory results indicate that the ZVI, PIC, SMI, and IOH filter materials all exhibit promise for phosphate drainage water treatment. PMID:25327026

Allred, Barry J; Racharaks, Ratanachat

2014-09-01

288

High-Density Chemical Intercalation of Zero-Valent Copper into Bi2Se3 Nanoribbons  

E-print Network

disproportionation redox reaction. Layered 2D nanomaterials have attracted much recent research interest because disproportionation redox reaction. Previous strategies for intercalating copper into Bi2Se3 have employed either, 0 x 1.25).21-26 In this type of reaction, mercury is typically intercalated into a dichalcogenide

Cui, Yi

289

Lead exposure results in hearing loss and disruption of the cochlear blood-labyrinth barrier and the protective role of iron supplement.  

PubMed

This study was designed to investigate the impact of lead (Pb(2+)) on the auditory system and its molecular mechanisms. Pb(AC)2 was administrated to male SD rats aged 21-22 d for 8 weeks at a dose of 300ppm. Male guinea pigs were also administrated with 50mg/kg Pb(AC)2 two times a week for 8 weeks. The auditory nerve-brainstem evoked responses (ABR) was recorded and the morphological changes of the outer hair cells (OHCs) were observed with Phallodin-FITC staining. In addition, the integrity of the blood-labyrinth barrier was observed by TEM and the expression of tight junction proteins (TJPs) in the cochlear stria vascularis was determined by immunofluorescence. Our results showed that Pb(2+) exposure resulted in increased ABR threshold in both rats and guinea pigs. Abnormal shapes and loss of OHCs were found in the cochlear basilar membrane following the Pb(2+) exposure. TEM study showed that the tight junctions between the endothelial cells and the border cells were lost and disrupted. Down-regulation of the occludin, ZO-1 and claudin-5 in the stria vascularis suggested that the increased permeability of the blood-labyrinth barrier may attribute to the Pb(2+)-induced decrease of TJPs' expression. Additionally, Fe(2+) supplement partly reversed the Pb(2+)-induced hearing loss and down-regulation of TJPs. Taken together, these data indicate that the disruption of blood-labyrinth barrier by down-regulating the expression of TJPs plays a role in the Pb(2+)-induced hearing loss, and Fe(2+) supplement protects the auditory system against Pb(2+)-induced toxicity and may have significant clinical implications. PMID:24144481

Liu, Xinqin; Zheng, Gang; Wu, Yongxiang; Shen, Xuefeng; Jing, Jinfei; Yu, Tao; Song, Han; Chen, Jingyuan; Luo, Wenjing

2013-12-01

290

Modeling the injection of non-Newtonian shear-thinning dispersions of iron particles in porous media  

NASA Astrophysics Data System (ADS)

In the context of groundwater remediation, an increasing interest has been devoted to the use of nanoscale and microscale zero-valent iron particles (NZVI and MZVI, respectively). MZVI and NZVI are not stable when dispersed in water, due to the occurrence of fast aggregation and sedimentation. Consequently, the use of shear thinning solutions of green biopolymers has been recently studied as kinetic stabilizers and viscous carrier for the delivery of MZVI and NZVI in the subsurface. Shear thinning fluids exhibit high viscosity in static conditions, improving the colloidal stability, and lower viscosity at high flow rates enabling the injection at limited pressures. In this work, co-funded by European Union project AQUAREHAB (FP7 - Grant Agreement Nr. 226565), a modeling approach is described, and implemented in E-MNM1D software (www.polito.it/groundwater/software), to simulate the transport in porous media of nanoscale iron slurries. Colloid transport mechanisms are controlled by particle-collector and particle-particle interactions, usually modeled using a non equilibrium kinetic model accounting for deposition and release processes. The key aspects included in the E-MNM1D are clogging phenomena (i.e. reduction of porosity and permeability due to particles deposition), and the rheological properties of the carrier fluid (in this project, guar gum solution). The influence of colloid transport on porosity, permeability, and fluid viscosity is explicitly lumped into the model and the shear-thinning nature of the iron slurries is described by a modified Darcy law generalized for non Newtonian fluids. Since during the injection in wells the velocity field is not constant over the distance, E-MNM1D was modified in order to account for variable colloidal transport coefficients, thus allowing the estimation of the radius of influence during a full scale intervention.

sethi, R.; Tosco, T.; Gastone, F.

2013-12-01

291

Thermal barrier coating system  

NASA Technical Reports Server (NTRS)

A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.

Stecura, S. (inventor)

1984-01-01

292

Characterization and Properties of Metallic Iron and Iron-Oxide Nanoparticles: Spectroscopy, Electrochemistry, and Kinetics  

SciTech Connect

There are reports that nano-sized zero-valent iron (Fe0) exhibits greater reactivity than micro-sized particles of Fe0, and it has been suggested that the higher reactivity of nano-Fe0 may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In an effort to better understand the reactivity of nano-Fe0, we have used a variety of complementary techniques to characterize two widely studied nano-Fe0 preparations:?¢???? one synthesized by reduction of goethite with heat and H2 (FeH2) and the other by reductive precipitation with borohydride (FeBH). FeH2 is a two-phase material consisting of 40 nm ???±-Fe0 (made up of crystals approximately the size of the particles) and Fe3O4 particles of similar size or larger containing reduced sulfur; whereas FeBH is mostly 20?¢????80 nm metallic Fe particles (aggregates of <1.5 nm grains) with an oxide shell/coating that is high in oxidized boron. The FeBH particles further aggregate into chains. Both materials exhibit corrosion potentials that are more negative than nano-sized Fe2O3, Fe3O4, micro-sized Fe0, or a solid Fe0 disk, which is consistent with their rapid reduction of oxygen, benzoquinone, and carbon tetrachloride. Benzoquinonewhich presumably probes inner-sphere surface reactionsreacts more rapidly with FeBH than FeH2, whereas carbon tetrachloride reacts at similar rates with FeBH and FeH2, presumably by outer-sphere electron transfer. Both types of nano-Fe0 react more rapidly than micro-sized Fe0 based on mass-normalized rate constants, but surface area-normalized rate constants do not show a significant nano-size effect. The distribution of products from reduction of carbon tetrachloride is more favorable with FeH2, which produces less chloroform than reaction with FeBH.

JT Nurmi; PG Tratnyek; V Sarathy; DR Baer; JE Amonette; K Pecher; CM Wang; JC Linehan; DW Matson; RL Penn; MD Driessen

2005-12-01

293

ARSENIC INTERACTION WITH IRON (II, III) HYDROXYCARBONATE GREEN RUST: IMPLICATIONS FOR ARSENIC REMEDIATION  

EPA Science Inventory

Zerovalent iron is being used in permeable reactive barriers (PRBs) to remediate groundwater arsenic contamination. Iron(II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron under anaerobic conditions. The interaction between arsenic and this green...

294

Reductive Sequestration Of Pertechnetate (99TcO4) By Nano Zerovalent Iron (nZVI) Transformed By Abiotic Sulfide  

SciTech Connect

Under anoxic conditions, soluble 99TcO4 can be reduced to less soluble TcO2nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zero-valent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 hrs to mimic the stages of aquifer sulfate reduction and onset of biotic sulfidogenesis. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between S/Fe = 00.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO4 for FeS (over iron oxides), and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS. X-ray absorption spectroscopy revealed that as S/Fe increased, Tc speciation shifted from TcO2nH2O to TcS2. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase of Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.

Fan, Dimin; Anitori, Roberto; Tebo, Bradley M.; Tratnyek, Paul G.; Lezama Pacheco, Juan S.; Kukkadapu, Ravi K.; Engelhard, Mark H.; Bowden, Mark E.; Kovarik, Libor; Arey, Bruce W.

2013-04-24

295

In situ testing of metallic iron nanoparticle mobility and reactivity in a shallow granular aquifer.  

PubMed

This paper describes the results of a series of single well push-pull tests conducted to evaluate the in situ transport of carboxymethyl cellulose (CMC) stabilized nanoscale zero-valent iron (ZVI) particles in saturated sediments and their reactivity toward chlorinated ethenes. CMC-stabilized nanoscale ZVI particles were synthesized on site by reducing ferrous ions with borohydride in water in the presence of CMC. Nanoscale ZVI and bimetallic ZVI-Pd nanoparticle suspensions were prepared and injected into depth-discrete aquifer zones during three push-pull tests. The injected nanoparticle suspensions contained a conservative tracer (Br(-)) and were allowed to reside in the aquifer pore space for various time periods prior to recovery by groundwater extraction. The comparison between Br(-) and Fe concentrations in extracted groundwater samples indicated that the CMC-stabilized nanoscale ZVI particles were mobile in the aquifer but appeared to lose mobility with time, likely due to the interactions between particles and aquifer sediments. After 13 h in the aquifer, the nanoscale ZVI particles became essentially immobilized. During the push-pull test with injection of Fe-Pd nanoparticles, ethane concentrations increased from non-detectable to 65 microg/L in extracted groundwater within less than 2 h of reaction time, indicating the rapid abiotic degradation of chlorinated ethenes. The amount of total chlorinated ethene mass destroyed was low presumably because the injected solutions "pushed" the dissolved chlorinated ethenes away from the injection well, without substantial mixing, and because stationary (sorbed) chlorinated ethene mass on the aquifer sediments was low. In situ remediation programs using highly reactive metallic nanoparticles should incorporate delivery methods that maintain high groundwater pore velocities during injection to increase advective transport distances (e.g. groundwater circulation wells). Also, source zones with abundant stationary contaminant mass that is accessible by advective transport should be targeted for remediation with the nanoparticles, as opposed to portions of dissolved plumes, in order to maximize the in situ destruction of contaminants. PMID:20542350

Bennett, Peter; He, Feng; Zhao, Dongye; Aiken, Brian; Feldman, Lester

2010-07-30

296

Inhibition of sulfate reducing bacteria in aquifer sediment by iron nanoparticles.  

PubMed

Batch microcosms were setup to determine the impact of different sized zero valent iron (Fe(0)) particles on microbial sulfate reduction during the in situ bio-precipitation of metals. The microcosms were constructed with aquifer sediment and groundwater from a low pH (3.1), heavy-metal contaminated aquifer. Nano (nFe(0)), micro (mFe(0)) and granular (gFe(0)) sized Fe(0) particles were added to separate microcosms. Additionally, selected microcosms were also amended with glycerol as a C-source for sulfate-reducing bacteria. In addition to metal removal, Fe(0) in microcosms also raised the pH from 3.1 to 6.5, and decreased the oxidation redox potential from initial values of 249 to -226mV, providing more favorable conditions for microbial sulfate reduction. mFe(0) and gFe(0) in combination with glycerol were found to enhance microbial sulfate reduction. However, no sulfate reduction occurred in the controls without Fe(0) or in the microcosm amended with nFe(0). A separate dose test confirmed the inhibition for sulfate reduction in presence of nFe(0). Hydrogen produced by Fe(0) was not capable of supporting microbial sulfate reduction as a lone electron donor in this study. Microbial analysis revealed that the addition of Fe(0) and glycerol shifted the microbial community towards Desulfosporosinus sp. from a population initially dominated by low pH and metal-resisting Acidithiobacillus ferrooxidans. PMID:24388832

Kumar, Naresh; Omoregie, Enoma O; Rose, Jerome; Masion, Armand; Lloyd, Jonathan R; Diels, Ludo; Bastiaens, Leen

2014-03-15

297

Nanomaterialien in der Boden-und Grundwassersanierung: Status quo quo vadis?  

E-print Network

Bisherige Anwendung der Nano-Sanierungstechnologie in Europa ....................3 4 Reaktion der EU auf .................................................4 5.1 Nullwertige Eisen Nanopartikel ­ ,,Nano Zero Valent Iron, n Quo vadis - das EU-Projekt NanoRem...................................................................5

Cirpka, Olaf Arie

298

Characterization of corrosion products in the permeable reactive barriers  

Microsoft Academic Search

The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive\\u000a iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease\\u000a the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well\\u000a as evaluates the effect of the

Y. Roh; S. Y. Lee; M. P. Elless

2000-01-01

299

Vehicle barrier  

DOEpatents

A vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate member and lateral, security fixed vertical pipe posts. The security barrier of the present invention provides for the use of cable restraints across gate openings to provide necessary security while at the same time allowing for quick opening and closing of the gate areas without compromising security.

Hirsh, Robert A. (Bethel Park, PA)

1991-01-01

300

Synthetic and field based electrical tomography of a permeable reactive barrier: implications for monitoring barrier performance  

Microsoft Academic Search

We performed a study of the sensitivity of electrical imaging to geochemical alteration of a zerovalent iron permeable reactive barrier (PRB) over time. Complex resistivity measurements on laboratory cores from an operational PRB defined the electrical properties of both unreacted and geochemically altered (reacted) iron as well as the growth rate of the reacted front on the up-gradient edge of

L. D. Slater; A. Binley; Y. Wu

2005-01-01

301

Iron-mediated remediation of RDX-contaminated water and soil under controlled Eh/pH  

SciTech Connect

Soil and water contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a serious environmental problem at several active and abandoned munitions production facilities. Zero-valent iron (Fe{sup 0}) can effectively remediate RDX-contaminated soil and water. The objective of this study was to manipulate Eh and pH for enhanced Fe{sup 0}-mediated destruction of RDX. This was accomplished by monitoring RDX destruction under controlled Eh-pH conditions (Eh: {minus}300 to +150 mV; pH: 2--10). Decreasing Eh and pH increased RDX destruction in aqueous solution. Treating 20 mg of RDX L{sup {minus}1} (90 {micro}M) under a static Eh of {minus}150 mV and pH 7 with 20 g of Fe{sup 0} L{sup {minus}1} removed 95% of the RDX within 4 h; no RDX was detected after 8 h. Treating a soil slurry (20% solids; 510 mg RDX kg{sup {minus}1} soil) with 20 g of Fe{sup 0} L{sup {minus}1} at an Eh of {minus}150 mV and pH 7 increased RDX destruction by 24% over the unbuffered control and resulted in 99% RDX destruction within 24 h. Adding 4.2 mM sodium sulfide (in lieu of a static Eh) under similar conditions resulted in 93% RDX loss within 24 h. Results indicated that lowering Eh and maintaining neutral pH during Fe{sup 0} treatment can increase RDX destruction in contaminated soil and water.

Singh, J.; Comfort, S.D.; Shea, P.J. [Univ. of Nebraska, Lincoln, NE (United States). School of Natural Resource Sciences] [Univ. of Nebraska, Lincoln, NE (United States). School of Natural Resource Sciences

1999-05-01

302

ARSENATE AND ARSENITE SORPTION AND ARSENITE OXIDATION BY IRON (II, III) HYDROXYCARBONATE GREEN RUST  

EPA Science Inventory

Iron (II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron that is being used in permeable reactive barriers to remediate groundwater arsenic contamination. To optimize the design of iron barriers, it is important to evaluate the influence of geoch...

303

Development of metal based thermal barrier coatings  

Microsoft Academic Search

In this work, metal-based thermal barrier coatings (MBTBCs) have been produced, using high frequency induction plasma spraying (IPS) of iron-based nanostructured alloy powders. Important advances have been made over recent years to the development of ceramic-based thermal barrier coatings (TBCs) for internal combustion engines application, but they are not yet applied in mass production situations. Besides the important economic considerations,

Dong-Il Shin

2005-01-01

304

Eat Iron?!!  

NSDL National Science Digital Library

To gain an understanding of mixtures and the concept of separation of mixtures, students use strong magnets to find the element of iron in iron-fortified breakfast cereal flakes. Through this activity, they see how the iron component of this heterogeneous mixture (cereal) retains its properties and can thus be separated by physical means.

NSF GK-12 and Research Experience for Teachers (RET) Programs,

305

Overcoming Barriers to the Remediation of Carbon Tetrachloride through Manipulation of Competing Reaction Mechanisms--Final Technical Report  

SciTech Connect

The premise of this project was that if we understood the fundamental chemistry that controls the branching among product formation pathways for the degradation of CCl4, we could design remediation strategies that minimize the formation of CHCl3 and thereby provide badly needed alternatives for remediation of the large plumes of CCl4 that contaminate several DOE sites. To this end, we performed a series of coordinated batch, spectroscopic, and modeling experiments, to study the effect of a variety of factors on the yield of CHCl3 from CCl4 during reduction with zero-valent iron (Fe0). The factors studied include those with direct implications for field performance (e.g., the concentration of CCl4 relative to the amount of iron surface area) and others chosen for diagnosis of the reaction mechanism (e.g., incorporation of deuterium into CCl4 reduction products in the presence of D2O). The key mechanistic findings of this study are (i) that CCl3 probably is not an intermediate in the formation of CF, but CCl3? probably is, (ii) the high reductive capacity of the Fe0 core favors the concerted 2e? reduction, and (iii) magnetite on Fe0 favors the benign product formation pathway. The latter conclusion is based on the observation that one type of nano-sized Fe0 that is coated with magnetite shell produces low yields of chloroform (0-40%), whereas others produce the higher yields of chloroform (60-100%) that are typical of most methods for reducing CCl4 (including biodegradation). Since nano-Fe0 can, in principle, be introduced into the deep subsurface by injection, our results would suggest that the right type of nano-Fe0 introduced in the right way might be highly effective at dechlorinating CCl4 with minimal formation of CHCl3 or other undesirable by-products. This conclusion may offer a breakthrough in the search for remediation technologies that are suitable for the deep CCl4-contamination at DOE sites such as the 200-W area of Hanford.

Paul G. Tratnyek; James E. Amonette; Eric J. Bylaska

2007-03-07

306

Guar gum solutions for improved delivery of iron particles in porous media (Part 1): Porous medium rheology and guar gum-induced clogging  

NASA Astrophysics Data System (ADS)

The present work is the first part of a comprehensive study on the use of guar gum to improve delivery of microscale zero-valent iron particles in contaminated aquifers. Guar gum solutions exhibit peculiar shear thinning properties, with high viscosity in static conditions and lower viscosity in dynamic conditions: this is beneficial both for the storage of MZVI dispersions, and also for the injection in porous media. In the present paper, the processes associated with guar gum injection in porous media are studied performing single-step and multi-step filtration tests in sand-packed columns. The experimental results of single-step tests performed by injecting guar gum solutions prepared at several concentrations and applying different dissolution procedures evidenced that the presence of residual undissolved polymeric particles in the guar gum solution may have a relevant negative impact on the permeability of the porous medium, resulting in evident clogging. The most effective preparation procedure which minimizes the presence of residual particles is dissolution in warm water (60 C) followed by centrifugation (procedure T60C). The multi-step tests (i.e. injection of guar gum at constant concentration with a step increase of flow velocity), performed at three polymer concentrations (1.5, 3 and 4 g/l) provided information on the rheological properties of guar gum solutions when flowing through a porous medium at variable discharge rates, which mimic the injection in radial geometry. An experimental protocol was defined for the rheological characterization of the fluids in porous media, and empirical relationships were derived for the quantification of rheological properties and clogging with variable injection rate. These relationships will be implemented in the second companion paper (Part II) in a radial transport model for the simulation of large-scale injection of MZVI-guar gum slurries.

Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

2014-10-01

307

Guar gum solutions for improved delivery of iron particles in porous media (part 1): porous medium rheology and guar gum-induced clogging.  

PubMed

The present work is the first part of a comprehensive study on the use of guar gum to improve delivery of microscale zero-valent iron particles in contaminated aquifers. Guar gum solutions exhibit peculiar shear thinning properties, with high viscosity in static conditions and lower viscosity in dynamic conditions: this is beneficial both for the storage of MZVI dispersions, and also for the injection in porous media. In the present paper, the processes associated with guar gum injection in porous media are studied performing single-step and multi-step filtration tests in sand-packed columns. The experimental results of single-step tests performed by injecting guar gum solutions prepared at several concentrations and applying different dissolution procedures evidenced that the presence of residual undissolved polymeric particles in the guar gum solution may have a relevant negative impact on the permeability of the porous medium, resulting in evident clogging. The most effective preparation procedure which minimizes the presence of residual particles is dissolution in warm water (60C) followed by centrifugation (procedure T60C). The multi-step tests (i.e. injection of guar gum at constant concentration with a step increase of flow velocity), performed at three polymer concentrations (1.5, 3 and 4g/l) provided information on the rheological properties of guar gum solutions when flowing through a porous medium at variable discharge rates, which mimic the injection in radial geometry. An experimental protocol was defined for the rheological characterization of the fluids in porous media, and empirical relationships were derived for the quantification of rheological properties and clogging with variable injection rate. These relationships will be implemented in the second companion paper (Part II) in a radial transport model for the simulation of large-scale injection of MZVI-guar gum slurries. PMID:25065767

Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

2014-10-01

308

Guar gum solutions for improved delivery of iron particles in porous media (Part 2): Iron transport tests and modeling in radial geometry  

NASA Astrophysics Data System (ADS)

In the present work column transport tests were performed in order to study the mobility of guar-gum suspensions of microscale zero-valent iron particles (MZVI) in porous media. The results were analyzed with the purpose of implementing a radial model for the design of full scale interventions. The transport tests were performed using several concentrations of shear thinning guar gum solutions as stabilizer (1.5, 3 and 4 g/l) and applying different flow rates (Darcy velocity in the range 1 10- 4 to 2 10- 3 m/s), representative of different distances from the injection point in the radial domain. Empirical relationships, expressing the dependence of the deposition and release parameters on the flow velocity, were derived by inverse fitting of the column transport tests using a modified version of E-MNM1D (Tosco and Sethi, 2010) and the user interface MNMs (www.polito.it/groundwater/software). They were used to develop a comprehensive transport model of MZVI suspensions in radial coordinates, called E-MNM1R, which takes into account the non Newtonian (shear thinning) rheological properties of the dispersant fluid and the porous medium clogging associated with filtration and sedimentation in the porous medium of both MZVI and guar gum residual undissolved particles. The radial model was run in forward mode to simulate the injection of MZVI dispersed in guar gum in conditions similar to those applied in the column transport tests. In a second stage, we demonstrated how the model can be used as a valid tool for the design and the optimization of a full scale intervention. The simulation results indicated that several concurrent aspects are to be taken into account for the design of a successful delivery of MZVI/guar gum slurries via permeation injection, and a compromise is necessary between maximizing the radius of influence of the injection and minimizing the injection pressure, to guarantee a sufficiently homogeneous distribution of the particles around the injection point and to prevent preferential flow paths.

Tosco, Tiziana; Gastone, Francesca; Sethi, Rajandrea

2014-10-01

309

Environmental Management Science Program (EMSP) Annual Report  

SciTech Connect

The treatment or remediation of contaminants at some sites is neither technically nor economically feasible. Containment or stabilization of these subsurface contaminants, therefore, may be the only viable alternative for the protection of human and ecological health. The overall goal of the proposed research is the development of reactive membrane barriers which dramatically enhance containment. Reactive particles in these barriers serve to either immobilize or transform contaminants within the membrane, and thus increase the time to breakthrough. These membranes are a powerful, novel, and versatile technique to contain and stabilize subsurface contaminants. This work focuses on reactive membrane barriers containing either zero-valent iron (Fe0) particles (which can reduce metals and chlorinated solvents) or crystalline silicotitanate (CST, a selective ion exchanger of cesium and strontium) particles.

Arnold, William A.; Cussler, Edward L.

2003-06-01

310

Barrier Formation  

PubMed Central

Enamel fluorosis is an irreversible structural enamel defect following exposure to supraoptimal levels of fluoride during amelogenesis. We hypothesized that fluorosis is associated with excess release of protons during formation of hypermineralized lines in the mineralizing enamel matrix. We tested this concept by analyzing fluorotic enamel defects in wild-type mice and mice deficient in anion exchanger-2a,b (Ae2a,b), a transmembrane protein in maturation ameloblasts that exchanges extracellular Cl? for bicarbonate. Defects were more pronounced in fluorotic Ae2a,b ?/? mice than in fluorotic heterozygous or wild-type mice. Phenotypes included a hypermineralized surface, extensive subsurface hypomineralization, and multiple hypermineralized lines in deeper enamel. Mineral content decreased in all fluoride-exposed and Ae2a,b?/? mice and was strongly correlated with Cl?. Exposure of enamel surfaces underlying maturation-stage ameloblasts to pH indicator dyes suggested the presence of diffusion barriers in fluorotic enamel. These results support the concept that fluoride stimulates hypermineralization at the mineralization front. This causes increased release of protons, which ameloblasts respond to by secreting more bicarbonates at the expense of Cl? levels in enamel. The fluoride-induced hypermineralized lines may form barriers that impede diffusion of proteins and mineral ions into the subsurface layers, thereby delaying biomineralization and causing retention of enamel matrix proteins. PMID:24170372

Lyaruu, D.M.; Medina, J.F.; Sarvide, S.; Bervoets, T.J.M.; Everts, V.; DenBesten, P.; Smith, C.E.; Bronckers, A.L.J.J.

2014-01-01

311

Effects of Solution Chemistry on the Dechlorination of 1,2,3-Trichloropropane by Zero-Valent Zinc  

SciTech Connect

The reactivity of zerovalent zinc (ZVZ) toward 1,2,3-trichloropropane (TCP) was evaluated under a variety of solution conditions, including deionized water, groundwater, and artificial groundwater, over a pH range of about 6.5-12. In deionized water, first-order rate constants for TCP disappearance (kobs) exhibit a broad minimum between pH 8 and 10, with increasing kobs observed at lower and higher pH. The similarity between this trend and zinc oxide (ZnO) solubility behavior suggests pH related changes to the ZnO surface layer strongly influence ZVZ reactivity. Values of kobs measured in acidic groundwater are similar to those measured in DI water, whereas values measured in alkaline groundwater are much smaller (>1 order of magnitude at pH values >10). Characterization of the surfaces of ZVZ exposed to deionized water, acidic groundwater, and alkaline groundwater suggests that the slower rates obtained in alkaline groundwater are related to the presence of a morphologically distinct surface film that passivates the ZVZ surface. TCP degradation rates in artificial groundwater containing individual solutes present in groundwater suggest that silicate anions contribute to the formation of this passivating film.

Salter-Blanc, Alexandra; Tratnyek, Paul G.

2011-04-12

312

Combined Therapy of Iron Chelator and Antioxidant Completely Restores Brain Dysfunction Induced by Iron Toxicity  

PubMed Central

Background Excessive iron accumulation leads to iron toxicity in the brain; however the underlying mechanism is unclear. We investigated the effects of iron overload induced by high iron-diet consumption on brain mitochondrial function, brain synaptic plasticity and learning and memory. Iron chelator (deferiprone) and antioxidant (n-acetyl cysteine) effects on iron-overload brains were also studied. Methodology Male Wistar rats were fed either normal diet or high iron-diet consumption for 12 weeks, after which rats in each diet group were treated with vehicle or deferiprone (50 mg/kg) or n-acetyl cysteine (100 mg/kg) or both for another 4 weeks. High iron-diet consumption caused brain iron accumulation, brain mitochondrial dysfunction, impaired brain synaptic plasticity and cognition, blood-brain-barrier breakdown, and brain apoptosis. Although both iron chelator and antioxidant attenuated these deleterious effects, combined therapy provided more robust results. Conclusion In conclusion, this is the first study demonstrating that combined iron chelator and anti-oxidant therapy completely restored brain function impaired by iron overload. PMID:24400127

Sripetchwandee, Jirapas; Pipatpiboon, Noppamas; Chattipakorn, Nipon; Chattipakorn, Siriporn

2014-01-01

313

Cross-hole radar scanning of two vertical, permeable, reactive-iron walls at the Massachusetts Military Reservation, Cape Cod, Massachusetts  

USGS Publications Warehouse

A pilot-scale study was conducted by the U.S. Army National Guard (USANG) at the Massachusetts Military Reservation (MMR) on Cape Cod, Massachusetts, to assess the use of a hydraulic-fracturing method to create vertical, permeable walls of zero-valent iron to passively remediate ground water contaminated with chlorinated solvents. The study was conducted near the source area of the Chemical Spill-10 (CS-10) plume, a plume containing chlorinated solvents that underlies the MMR. Ground-water contamination near the source area extends from about 24 m (meters) to 35 m below land surface. The USANG designed two reactive-iron walls to be 12 m long and positioned 24 to 37 m below land surface to intersect and remediate part of the CS-10 plume.Because iron, as an electrical conductor, absorbs electromagnetic energy, the US Geological Survey used a cross-hole common-depth, radar scanning method to assess the continuity and to estimate the lateral and vertical extent of the two reactive-iron walls. The cross-hole radar surveys were conducted in boreholes on opposite sides of the iron injection zones using electric-dipole antennas with dominant center frequencies of 100 and 250 MHz. Significant decreases in the radar-pulse amplitudes observed in scans that traversed the injection zones were interpreted by comparing field data to results of two-dimensional finite-difference time-domain numerical models and laboratory-scale physical models.The numerical and physical models simulate a wall of perfectly conducting material embedded in saturated sand. Results from the numerical and physical models show that the amplitude of the radar pulse transmitted across the edge of a conductive wall is about 43 percent of the amplitude of a radar pulse transmitted across background material. The amplitude of a radar pulse transmitted through a hole in a conductive wall increases as the aperture of the hole increases. The modeling results indicate that holes with an aperture of less than 40 percent of the dominant wavelength of the radar pulse are not likely to be detected.Based on the results of the numerical and physical modeling, the decreases in radar-pulse amplitudes observed in scans traversing the injection zones are interpreted as electrically conductive zones that outline the distribution of iron. The area interpreted as iron in the northern A-wall contains two zones -- an upper zone about 10 m wide, extending from about 25 to 31 m below land surface, and a lower zone about 8 m wide, extending from 31.5 to 34.5 m below land surface. The area interpreted as iron in the southern B-wall is about 9 m wide, extending from about 27 to 34.5 m below land surface. No discrete holes were interpreted in either the A- or B-wall zones.The interpretation of the field data suggests that (1) the hydraulic-fracturing method introduced iron into the subsurface, but not in the dimensions originally proposed; (2) the iron within the treatment zones is distributed in a generally continuous manner; and (3) excluding the discontinuity in the A-wall, holes within the iron treatment zone, if any, exist at scales smaller than about 10 cm, the resolution limit of the radar antennas and acquisition geometry used for this study. The cross-hole radar method appears to have been an effective method for delineating the distribution of iron in the two walls; however, the veracity of the results cannot be ascertained without excavation or drilling into the treatment zone.

Lane, J.W., Jr.; Joesten, P.K.; Savoie, J.G.

2001-01-01

314

Bacterial iron homeostasis  

Microsoft Academic Search

Iron is essential to virtually all organisms, but poses problems of toxicity and poor solubility. Bacteria have evolved various mechanisms to counter the problems imposed by their iron dependence, allowing them to achieve effective iron homeostasis under a range of iron regimes. Highly efficient iron acquisition systems are used to scavenge iron from the environment under iron-restricted conditions. In many

Simon C Andrews; Andrea K Robinson; Francisco Rodr??guez-Quiones

2003-01-01

315

Barriers to Environmental Education  

Microsoft Academic Search

Personal interviews with elementary teachers were conducted to identify and determine the relative importance of barriers to environmental education (EE) in Palouse-region public schools. Results indicated that lack of time (both in the school day and for preparation) was the most important barrier. Other important logistical barriers were lack of instructional materials and lack of funding. Conceptual barriers included a

Sam H. Ham; Daphne R. Sewing

1988-01-01

316

Brain iron metabolism and its perturbation in neurological diseases  

Microsoft Academic Search

Metal ions are of particular importance in brain function, notably iron. A broad overview of iron metabolism and its homeostasis\\u000a both at the cellular level (involving regulation at the level of mRNA translation) and the systemic level (involving the peptide\\u000a hormone hepcidin) is presented. The mechanisms of iron transport both across the bloodbrain barrier and within the brain\\u000a are then

Robert R. CrichtonDavid; David T. Dexter; Roberta J. Ward

2011-01-01

317

ENVIRONMENTAL ENGINEERING SCIENCE Volume 21, Number 2, 2004  

E-print Network

reduction by iron metal (Fe0), nitrate and nitrite reduction rates were measured over a range of mixing in some studies and not in others. Key words: iron metal; zero-valent iron; nutrients; rotating disk was the compound most frequently detected at concentrations exceeding a regulatory standard [such as U.S. EPA

Alvarez, Pedro J.

318

CHEMICAL INTERACTIONS OF ARSENATE, ARSENITE, PHOSPHATE, AND SILICATE WITH IRON (II, III) HYDROXYCARBONATE GREEN RUST  

EPA Science Inventory

Granular zerovalent iron has been proposed to be used as a medium in permeable reactive barriers (PRBs) to remove arsenic from contaminated groundwater. Iron(II, III) hydroxycarbonate green rust (carbonate green rust, or CGR) is a major corrosion product of zerovalent iron under ...

319

CHEMICAL INTERACTIONS OF ARSENATE, ARSENITE, PHOSPHATE, AND SILICATE WITH IRON (II,III) HYDROXYCARBONATE GREEN RUST  

EPA Science Inventory

Granular zerovalent iron has been proposed to be used as a medium in permeable reactive barriers (PRBs) to remove arsenic from contaminated groundwater. Iron(II, III) hydroxycarbonate green rust (carbonate green rust, or CGR) is a major corrosion product of zerovalent iron under ...

320

Expression and Function of Iron-Regulatory Proteins in Retina  

PubMed Central

Summary Iron is essential for cell survival and function; yet excess iron is toxic to cells. Therefore, the cellular and whole-body levels of iron are regulated exquisitely. At least a dozen proteins participate in the regulation of iron homeostasis. Hemochromatosis, a genetic disorder of iron overload, is caused by mutations in at least five genes, namely HFE, hemojuvelin, Transferrin receptor 2, ferroportin, and hepcidin. Retina is separated from systemic circulation by inner and outer blood-retinal barriers; therefore it is widely believed that this tissue is immune to changes in systemic circulation. Even though hemochromatosis is associated with iron overload and dysfunction of a variety of systemic organs, little is known on the effects of this disease on the retina. Recent studies have shown that all five genes that are associated with hemochromatosis are expressed in the retina in a cell type-specific manner. The retinal pigment epithelium, which forms the outer blood-retinal barrier, expresses all of these five genes. It is therefore clearly evident that iron homeostasis in the retina is maintained locally by active participation of various iron-regulatory proteins. Excess iron is detrimental to the retina as evidenced from human studies and from mouse models of iron overload. Retinal iron homeostasis is disrupted in various clinical conditions such as hemochromatosis, aceruloplasminemia, age-related macular degeneration, and bacterial and viral infections. PMID:20408179

Gnana-Prakasam, Jaya P.; Martin, Pamela M.; Smith, Sylvia B.; Ganapathy, Vadivel

2013-01-01

321

Geochemical barriers for environment protection and recovery of nonferrous metals.  

PubMed

A study of natural minerals, ore tailings and their products as materials for artificial geochemical barriers is presented. In particular, it focuses on interaction between calcite and dolomite and sulfate solutions containing nickel, copper and iron under static conditions. Calcite of -0.1 mm fraction has been shown to perform well as a barrier when added to water phases of tailing dumps and natural reservoirs. Experiments under dynamic conditions have revealed a high potential of thermally activated copper-nickel tailings as barriers. After a 500-day precipitating period on a geochemical barrier, the contents of nickel and copper in ore dressing tailings were found to increase 12- and 28-fold, respectively. An effective sorbent of copper, iron and nickel ions is a brucite-based product of hydrochloric acid treatment of vermiculite ore tailings. Its sorption capacity can be essentially increased through thermal activation. PMID:25072773

Chanturiya, Valentine; Masloboev, Vladimir; Makarov, Dmitriy; Nesterov, Dmitriy; Bajurova, Julia; Svetlov, Anton; Men'shikov, Yuriy

2014-01-01

322

Iron and alloys of iron. [lunar resources  

NASA Technical Reports Server (NTRS)

All lunar soil contains iron in the metallic form, mostly as an iron-nickel alloy in concentrations of a few tenths of 1 percent. Some of this free iron can be easily separated by magnetic means. It is estimated that the magnetic separation of 100,000 tons of lunar soil would yield 150-200 tons of iron. Agglutinates contain metallic iron which could be extracted by melting and made into powder metallurgy products. The characteristics and potential uses of the pure-iron and iron-alloy lunar products are discussed. Processes for working iron that might be used in a nonterrestrial facility are also addressed.

Sastri, Sankar

1992-01-01

323

Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method  

SciTech Connect

We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of FischerTropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

2012-06-01

324

Quantification and modelling of 2,4-dinitrotoluene reduction with high-purity and cast iron  

Microsoft Academic Search

Cast iron has been used as a reactive material in permeable reactive barriers (PRBs) for site remediation. While reactions are generally believed to occur on the iron (oxide) surface, a recent study by [Oh, S.Y., Cha, D.K., Chiu, P.C., 2002a. Graphite-mediated reduction of 2,4-dinitrotoluene with elemental iron. Environ. Sci. Technol. 36 (10), 21782184] showed that graphite inclusions in cast iron

Benham Jafarpour; Paul T. Imhoff; Pei C. Chiu

2005-01-01

325

Injection of colloidal Fe{sup 0} particles in sand with shear-thinning fluids  

SciTech Connect

A novel approach to emplacing chemically reactive barriers is the injection of zero-valent iron (Fe{sup 0}) colloids into the subsurface. A difficulty encountered in this approach is that the dense Fe{sup 0} colloids settle out of solution with time, decreasing the distance the colloids can be injected into the subsurface. Studies were conducted to evaluate if several viscous shear-thinning fluids could enhance Fe{sup 0} colloid emplacement in porous media. Aqueous solutions of three nontoxic polymers at different concentrations were investigated: a synthetic high molecular weight polymer [vinyl polymer, (VP)], a biopolymer (gum xanthan, GX), and a cellulose-type polymer (carboxymethyl cellulose, CMC). The use of shear-thinning fluids greatly increases the mobility of the colloidal Fe{sup 0} suspensions in porous media. VP was superior to GX and GMC because the VP suspensions produced the lowest back pressures, resulting in the highest hydraulic conductivities.

Cantrell, K.J.; Kaplan, D.I.; Gilmore, T.J. [Battelle Memorial Inst., Richland, WA (United States). Pacific Northwest National Lab.

1997-08-01

326

Comparing barrier algorithms  

NASA Technical Reports Server (NTRS)

A barrier is a method for synchronizing a large number of concurrent computer processes. After considering some basic synchronization mechanisms, a collection of barrier algorithms with either linear or logarithmic depth are presented. A graphical model is described that profiles the execution of the barriers and other parallel programming constructs. This model shows how the interaction between the barrier algorithms and the work that they synchronize can impact their performance. One result is that logarithmic tree structured barriers show good performance when synchronizing fixed length work, while linear self-scheduled barriers show better performance when synchronizing fixed length work with an imbedded critical section. The linear barriers are better able to exploit the process skew associated with critical sections. Timing experiments, performed on an eighteen processor Flex/32 shared memory multiprocessor, that support these conclusions are detailed.

Arenstorf, Norbert S.; Jordan, Harry F.

1987-01-01

327

TRANSFORMATION OF HALOGENATED PBTS WITH NANOSCALE BIMETALLIC PARTICLES  

EPA Science Inventory

Zero-valent iron nanoparticle technology is becoming a popular option for treatment of a variety of hazardous and toxic wastes, and for remediation of contaminated sites. As a matter of fact, nano iron has quickly become the most widely used nanomaterial in environmental ...

328

Iron chelation and multiple sclerosis.  

PubMed

Histochemical and MRI studies have demonstrated that MS (multiple sclerosis) patients have abnormal deposition of iron in both gray and white matter structures. Data is emerging indicating that this iron could partake in pathogenesis by various mechanisms, e.g., promoting the production of reactive oxygen species and enhancing the production of proinflammatory cytokines. Iron chelation therapy could be a viable strategy to block iron-related pathological events or it can confer cellular protection by stabilizing hypoxia inducible factor 1?, a transcription factor that normally responds to hypoxic conditions. Iron chelation has been shown to protect against disease progression and/or limit iron accumulation in some neurological disorders or their experimental models. Data from studies that administered a chelator to animals with experimental autoimmune encephalomyelitis, a model of MS, support the rationale for examining this treatment approach in MS. Preliminary clinical studies have been performed in MS patients using deferoxamine. Although some side effects were observed, the large majority of patients were able to tolerate the arduous administration regimen, i.e., 6-8h of subcutaneous infusion, and all side effects resolved upon discontinuation of treatment. Importantly, these preliminary studies did not identify a disqualifying event for this experimental approach. More recently developed chelators, deferasirox and deferiprone, are more desirable for possible use in MS given their oral administration, and importantly, deferiprone can cross the blood-brain barrier. However, experiences from other conditions indicate that the potential for adverse events during chelation therapy necessitates close patient monitoring and a carefully considered administration regimen. PMID:24397846

Weigel, Kelsey J; Lynch, Sharon G; LeVine, Steven M

2014-01-01

329

Pharmacology of Iron Transport  

PubMed Central

Elucidating the molecular basis for the regulation of iron uptake, storage, and distribution is necessary to understand iron homeostasis. Pharmacological tools are emerging to identify and distinguish among different iron transport pathways. Stimulatory or inhibitory small molecules with effects on iron uptake can help characterize the mechanistic elements of iron transport and the roles of the transporters involved in these processes. In particular, iron chelators can serve as potential pharmacological tools to alleviate diseases of iron overload. This review focuses on the pharmacology of iron transport, introducing iron transport membrane proteins and known inhibitors. PMID:23020294

Byrne, Shaina L.; Krishnamurthy, Divya; Wessling-Resnick, Marianne

2013-01-01

330

HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX) DEGRADATION IN BIOLOGICALLY-ACTIVE IRON COLUMNS  

E-print Network

HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX) DEGRADATION IN BIOLOGICALLY-ACTIVE IRON COLUMNS BYUNG iron barriers to treat groundwater contamination by RDX. Three columns were packed with iron filings (Fe0) between soil and sand layers, and were fed continuously with unlabeled plus 14C-labeled RDX

Alvarez, Pedro J.

331

Iron metabolism and toxicity  

SciTech Connect

Iron is an essential nutrient with limited bioavailability. When present in excess, iron poses a threat to cells and tissues, and therefore iron homeostasis has to be tightly controlled. Iron's toxicity is largely based on its ability to catalyze the generation of radicals, which attack and damage cellular macromolecules and promote cell death and tissue injury. This is lucidly illustrated in diseases of iron overload, such as hereditary hemochromatosis or transfusional siderosis, where excessive iron accumulation results in tissue damage and organ failure. Pathological iron accumulation in the liver has also been linked to the development of hepatocellular cancer. Here we provide a background on the biology and toxicity of iron and the basic concepts of iron homeostasis at the cellular and systemic level. In addition, we provide an overview of the various disorders of iron overload, which are directly linked to iron's toxicity. Finally, we discuss the potential role of iron in malignant transformation and cancer.

Papanikolaou, G. [First Department of Internal Medicine, National and Kapodistrian University of Athens, School of Medicine, Laikon General Hospital, Athens 11527 (Greece); Pantopoulos, K. [Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, H3T 1E2 (Canada) and Department of Medicine, McGill University (Canada)]. E-mail: kostas.pantopoulos@mcgill.ca

2005-01-15

332

Iron deficiency anemia  

MedlinePLUS

Anemia - iron deficiency ... Iron deficiency anemia is the most common form of anemia. Red blood cells bring oxygen to the ... such as your spleen, remove old blood cells. Iron is a key part of red blood cells. ...

333

Iron Sucrose Injection  

MedlinePLUS

... any other iron injection such as ferumoxytol (Feraheme), iron dextran (Dexferrum, Infed, Proferdex), or sodium ferric gluconate (Ferrlecit); any other medications; or any of the ingredients in iron sucrose injection. Ask your pharmacist for a list ...

334

Saugus Iron Works Forge  

USGS Multimedia Gallery

The Saugus Iron Works forge, which used a large hammer to compress the iron. Forging strenghened the iron, which, right out of the blast furnace, was brittle. The Saugus River, which powered the forge, can be seen in the background....

335

Iron and vegetarian diets.  

PubMed

Vegetarians who eat a varied and well balanced diet are not at any greater risk of iron deficiency anaemia than non-vegetarians. A diet rich in wholegrains, legumes, nuts, seeds, dried fruits, iron-fortified cereals and green leafy vegetables provides an adequate iron intake. Vitamin C and other organic acids enhance non-haem iron absorption, a process that is carefully regulated by the gut. People with low iron stores or higher physiological need for iron will tend to absorb more iron and excrete less. Research to date on iron absorption has not been designed to accurately measure absorption rates in typical Western vegetarians with low ferritin levels. PMID:25369923

Saunders, Angela V; Craig, Winston J; Baines, Surinder K; Posen, Jennifer S

2013-08-19

336

Lipidoid-Coated Iron Oxide Nanoparticles for Efficient DNA and siRNA delivery  

E-print Network

The safe, targeted and effective delivery of gene therapeutics remains a significant barrier to their broad clinical application. Here we develop a magnetic nucleic acid delivery system composed of iron oxide nanoparticles ...

Jiang, Shan

337

Specular graphene transport barrier  

NASA Astrophysics Data System (ADS)

We present a flexible model for a generic straight transport barrier in graphene in the specular limit. The specular limit applies for scattering of carriers sufficiently close to the Fermi level in three quarters of the transport barriers. Using the Lippmann-Schwinger equation, we obtain the wave function, from which we derive the reflection and transmission probabilities as a function of the angle of incidence. The results, which are compared to those from exact multichannel tight-binding quantum transport calculations, show that some barriers exhibit a broader absence of reflection across a wide range of incident angles, whereas other barriers are highly reflective. The power of our model is that it could be used even when the precise atomistic detail of the transport barriers is unknown.

Gunlycke, Daniel; White, Carter T.

2014-07-01

338

Iron fluorophosphates.  

PubMed

18 new iron fluorophosphates and a chlorofluorophosphate have been synthesised hydrothermally in a fluoride-rich medium, using FeF2, FeF3, Fe, HPF6. HCl, monovalent metal fluorides as reactants and amines as templating agents. Products have been fully structurally characterised using single crystal X-ray diffraction, and the stability of some compounds investigated using thermogravimetric analysis. Reaction in fluoride-rich conditions produce ribbon-like, layer and framework structures containing new and unusual structural motifs based on the linking of Fe(O,F)6, PO3F, and PO2(OH,F)2 polyhedra. Structures exhibiting inter-layer spaces and channels are frequently lined by terminal fluoride anions of the PO3F, PO2(OH,F)2 and Fe(O,F)6 polyhedra. PMID:23770666

Keates, Adam C; Armstrong, Jennifer A; Weller, Mark T

2013-08-14

339

Complementary Barrier Infrared Detector  

NASA Technical Reports Server (NTRS)

The complementary barrier infrared detector (CBIRD) is designed to eliminate the major dark current sources in the superlattice infrared detector. The concept can also be applied to bulk semiconductor- based infrared detectors. CBIRD uses two different types of specially designed barriers: an electron barrier that blocks electrons but not holes, and a hole barrier that blocks holes but not electrons. The CBIRD structure consists of an n-contact, a hole barrier, an absorber, an electron barrier, and a p-contact. The barriers are placed at the contact-absorber junctions where, in a conventional p-i-n detector structure, there normally are depletion regions that produce generation-recombination (GR) dark currents due to Shockley-Read- Hall (SRH) processes. The wider-bandgap complementary barriers suppress G-R dark current. The barriers also block diffusion dark currents generated in the diffusion wings in the neutral regions. In addition, the wider gap barriers serve to reduce tunneling dark currents. In the case of a superlattice-based absorber, the superlattice itself can be designed to suppress dark currents due to Auger processes. At the same time, the barriers actually help to enhance the collection of photo-generated carriers by deflecting the photo-carriers that are diffusing in the wrong direction (i.e., away from collectors) and redirecting them toward the collecting contacts. The contact layers are made from materials with narrower bandgaps than the barriers. This allows good ohmic contacts to be made, resulting in lower contact resistances. Previously, THALES Research and Technology (France) demonstrated detectors with bulk InAsSb (specifically InAs0.91Sb0.09) absorber lattice-matched to GaSb substrates. The absorber is surrounded by two wider bandgap layers designed to minimize impedance to photocurrent flow. The wide bandgap materials also serve as contacts. The cutoff wavelength of the InAsSb absorber is fixed. CBIRD may be considered as a modified version of the THALES double heterostructure (DH) p-i-n device, but with even wider bandgap barriers inserted at the contact layer/absorber layer interfaces. It is designed to work with either bulk semiconductors or superlattices as the absorber material. The superlattice bandgap can be adjusted to match the desired absorption cutoff wavelength. This infrared detector has the potential of high-sensitivity operation at higher operating temperatures. This would reduce cooling requirements, thereby reducing the power, mass, and volume of the equipment and allowing an increased mission science return.

Ting, David Z.; Bandara, Sumith V.; Hill, Cory J.; Gunapala, Sarath D.

2009-01-01

340

Complementary barrier infrared detector (CBIRD)  

NASA Technical Reports Server (NTRS)

An infrared detector having a hole barrier region adjacent to one side of an absorber region, an electron barrier region adjacent to the other side of the absorber region, and a semiconductor adjacent to the electron barrier.

Ting, David Z. (Inventor); Bandara, Sumith V. (Inventor); Hill, Cory J. (Inventor); Gunapala, Sarath D. (Inventor)

2013-01-01

341

Vehicle barrier systems  

SciTech Connect

The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper. 2 tabs.

Sena, P.A.

1986-01-01

342

Vehicle barrier systems  

SciTech Connect

The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment, and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper.

Sena, P.A.

1986-01-01

343

Vehicle barrier systems  

SciTech Connect

The ground vehicle is one of the most effective tools available to an adversary force. Vehicles can be used to penetrate many types of perimeter barriers, transport equipment and personnel rapidly over long distances, and deliver large amounts of explosives directly to facilities in suicide missions. The function of a vehicle barrier system is to detain or disable a defined threat vehicle at a selected distance from a protected facility. Numerous facilities are installing, or planning to install, vehicle barrier systems and many of these facilities are requesting guidance to do so adequately. Therefore, vehicle barriers are being evaluated to determine their stopping capabilities so that systems can be designed that are both balanced and capable of providing a desired degree of protection. Equally important, many of the considerations that should be taken into account when establishing a vehicle barrier system have been identified. These considerations which pertain to site preparation, barrier selection, system integration and operation, and vehicle/barrier interaction, are discussed in this paper.

Sena, P.A.

1986-01-01

344

Retractable barrier strip  

DOEpatents

A portable barrier strip having retractable tire-puncture spikes for puncturing a vehicle tire. The tire-puncture spikes have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture spikes removably disposed in a shaft that is rotatably disposed in each barrier block. The plurality of barrier blocks hare hingedly interconnected by complementary hinges integrally formed into the side of each barrier block which allow the strip to be rolled for easy storage and retrieval, but which prevent irregular or back bending of the strip. The shafts of adjacent barrier blocks are pivotally interconnected via a double hinged universal joint to accommodate irregularities in a roadway surface and to transmit torsional motion of the shaft from block to block. A single flexshaft cable is connected to the shaft of an end block to allow a user to selectively cause the shafts of a plurality of adjacently connected barrier blocks to rotate the tire-puncture spikes to the armed position for puncturing a vehicle tire, and to the retracted position for not puncturing the tire. The flexshaft is provided with a resiliently biased retracting mechanism, and a release latch for allowing the spikes to be quickly retracted after the intended vehicle tire is punctured.

Marts, Donna J. (Idaho Falls, ID); Barker, Stacey G. (Idaho Falls, ID); Wowczuk, Andrew (Wheeling, WV); Vellenoweth, Thomas E. (Wheeling, WV)

2002-01-01

345

[Experimental study on the remediation of chromium contaminated groundwater with PRB media].  

PubMed

Due to the surface reaction between zero-valent iron and Cr(VI), iron cannot be fully utilized in the Fe(0)-Permeable Reactive Barrier(PRB), and the PRB is prone to compaction and blockage. In order to resolve these problems, iron powder coated with different polymer was tested in the treatment of chromium-polluted groundwater. Experimental results demonstrated that sodium alginate (SA) was the best package materials. According to analysis with FEI and EDX, pore structures were created by cross-linking of SA with Ca2+, in which a lot of attaching points exist, and through which Cr(VI) could react with interior iron powder. SA coating cast iron (SAC) and reduced iron (SAR) were tested in the treatment of chromium-polluted groundwater individually; the results showed that the removal efficiency of Cr( VI) by SAC was double that by SAR. After optimization of technology parameters of SAC, the Cr(VI) removal process follows the pseudo first-order kinetics. Based on dynamic experiments with SAC, Cr(VI)/Fe(0) was up to 32.25 mg x g(-1) and the PRB maintained high permeability coefficient (2.38 cm x s(-1)) after complete reaction. Compared with cast iron media is feasible in the remediation of chromium contaminated groundwater. PMID:24028003

Zhu, Wen-Hui; Dong, Liang-Fei; Wang, Xing-Run; Zhai, Ya-Li

2013-07-01

346

Iron metabolism in bifidobacteria  

Microsoft Academic Search

Bifidobacteria are Gram-positive, anaerobic microaerophilic rods that are capable of internalizing ferrous iron at pH 5.0 and 6.5 when assayed in a post-logarithmic growth phase. Dependent upon iron concentration, iron uptake is most efficient in cells grown in a metal-depleted medium. There are two iron-uptake systems: one operating at low outside iron concentrations (1 to 20 ?M); and one operating

Anatoly Bezkorovainy; Eva Kot; Robin Miller-Catchpole; George Haloftis; Sergey Furmanov

1996-01-01

347

Recycler barrier RF buckets  

SciTech Connect

The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

Bhat, C.M.; /Fermilab

2011-03-01

348

Minocycline-induced attenuation of iron overload and brain injury following experimental intracerebral hemorrhage  

PubMed Central

Background and Purpose Brain iron overload plays a detrimental role in brain injury after intracerebral hemorrhage (ICH). A recent study found that minocycline acts as an iron chelator and reduces iron-induced neuronal death in vitro. The present study investigated if minocycline reduces iron overload after ICH and iron-induced brain injury in vivo. Methods This study was divided into four parts. (1) Rats with different sizes of ICH were euthanized 3 days later for serum total iron and brain edema determination. (2) Rats had an ICH treated with minocycline or vehicle. Serum iron, brain iron, and brain iron handling proteins were measured. (3) Rats had an intracaudate injection of either saline, iron, iron+minocycline or iron+macrophage/microglia inhibitory factor and were used for brain edema and neuronal death measurements. (4) Rats had an intracaudate injection of iron and were treated with minocycline. The brains were used for edema measurement. Results After ICH, serum total iron and brain non-heme iron increased and these changes were reduced by minocycline treatment. Minocycline also reduced ICH-induced upregulation of brain iron handling proteins and neuronal death. Intracaudate injection of iron caused brain edema, blood-brain barrier leakage and brain cell death, all of which were significantly reduced by co-injection with minocycline. Conclusions The current study found that minocycline reduces iron overload after ICH and iron-induced brain injury. It is also well known minocycline is an inhibitor of microglial activation. Minocycline may be very useful for ICH patients because both iron accumulation and microglia activation contribute to brain damage following ICH. PMID:21998050

Zhao, Fan; Hua, Ya; He, Yangdong; Keep, Richard F; Xi, Guohua

2011-01-01

349

A Polymer Membrane Containing Fe0 as a Contaminant Barrier  

SciTech Connect

A polyvinyl alcohol (PVA) membrane containing iron (Fe0) particles was developed and tested as a model barrier for contaminant containment. Carbon tetrachloride, copper (Cu2+), nitrobenzene, 4-nitroacetophenone, and chromate (CrO4 2-) were selected as model contaminants. Compared with a pure PVA membrane, the Fe0/PVA membrane can increase the breakthrough lag time for Cu2+ and carbon tetrachloride by more than 100 fold. The increase in the lag time was smaller for nitrobenzene and 4-nitroacetophenone which stoichiometrically require more iron and for which the PVA membrane has a higher permeability. The effect of Fe0 was even smaller for CrO4 2- because of its slow reaction. Forty-five percent of the iron, based on the content in the dry membrane prior to hydration, was consumed by reaction with Cu2+ and 19% by reaction with carbon tetrachloride. Similarly, 25%, 17%, and 6% of the iron was consumed by nitrobenzene, 4-nitroacetophenone, and CrO4 2-, respectively. These percentages approximately double when the loss of iron during membrane hydration is considered. The permeability of the Fe0/PVA membrane after breakthrough was within a factor of three for that of pure PVA, consistent with theory. These results suggest that polymer membranes with embedded Fe0 have potential as practical contaminant barriers.

Shimotori, Tsutomu; Nuxoll, Eric E.; Cussler, Edward L.; Arnold, William A.

2003-11-03

350

Quantification and modelling of 2,4-dinitrotoluene reduction with high-purity and cast iron  

Microsoft Academic Search

Cast iron has been used as a reactive material in permeable reactive barriers (PRBs) for site remediation. While reactions are generally believed to occur on the iron (oxide) surface, a recent study by [Oh, S.Y., Cha, D.K., Chiu, P.C., 2002a. Graphite-mediated reduction of 2,4-dinitrotoluene with elemental iron. Environ. Sci. Technol. 36 (10), 2178 2184] showed that graphite inclusions in cast

Benham Jafarpour; Paul T. Imhoff; Pei C. Chiu

2005-01-01

351

Barriers to Interpersonal Communication  

E-print Network

or her own background of experiences. People sometimes have trouble communi- cating because of differences in age, experience or background. We can eliminate this barrier by realizing that we can learn valuable lessons from people whose experi- ences...

Warren, Judith L.

2000-03-02

352

Great Barrier Reef  

Atmospheric Science Data Center

article title: Australia's Great Barrier Reef View Larger Image ... not a single reef, but a vast maze of reefs, passages, and coral cays (islands that are part of the reef). This nadir true-color image was ...

2013-04-16

353

Iron accumulation and neurotoxicity in cortical cultures treated with holotransferrin.  

PubMed

Nonheme iron accumulates in CNS tissue after ischemic and hemorrhagic insults and may contribute to cell loss. The source of this iron has not been precisely defined. After blood-brain barrier disruption, CNS cells may be exposed to plasma concentrations of transferrin-bound iron (TBI), which exceed that in the CSF by over 50-fold. In this study, the hypothesis that these concentrations of TBI produce cell iron accumulation and neurotoxicity was tested in primary cortical cultures. Treatment with 0.5-3mg/ml holotransferrin for 24h resulted in the loss of 20-40% of neurons, associated with increases in malondialdehyde, ferritin, heme oxygenase-1, and iron; transferrin receptor-1 expression was reduced by about 50%. Deferoxamine, 2,2'-bipyridyl, Trolox, and ascorbate prevented all injury, but apotransferrin was ineffective. Cell TBI accumulation was significantly reduced by deferoxamine, 2,2'-bipyridyl, and apotransferrin, but not by ascorbate or Trolox. After treatment with (55)Fe-transferrin, approximately 40% of cell iron was exported within 16h. Net export was increased by deferoxamine and 2,2'-bipyridyl, but not by apotransferrin. These results suggest that downregulation of transferrin receptor-1 expression is insufficient to prevent iron-mediated death when neurons are exposed to plasma concentrations of TBI. Chelator therapy may be beneficial for acute CNS injuries associated with loss of blood-brain barrier integrity. PMID:21939754

Chen-Roetling, Jing; Liu, Wenpei; Regan, Raymond F

2011-12-01

354

TRICHLOROETHYLENE REMOVAL FROM GROUNDWATER IN FLOW-THROUGH COLUMNS SIMULATING A PERMEABLE REACTIVE BARRIER CONSTRUCTED WITH PLANT MULCH  

EPA Science Inventory

Ground water contaminated with TCE is commonly treated with a passive reactive barrier (PRB) constructed with zero-valence iron. The cost of iron as the reactive matrix has driven a search for less costly alternatives, and composted plant mulch has been used as an alternative re...

355

Laboratory tests for reactive barrier design.  

PubMed

Owing to limitations of pump-and-treat, several technologies are being investigated for groundwater treatment. One of the most promising is the treatment of contaminants through the use of reactive barriers installed in situ, especially in the case of aquifers contaminated with chlorinated solvents. This work presents results of batch and column tests with metallic iron and some chlorinated solvents (1,2-DCA, 1,1,2-TCA and TCE). Such tests provided means to evaluate the degradation rates of these compounds and their byproducts. It is concluded that the reductive dechlorination with metallic iron can have different results, depending on the type of contaminant. Some contaminants may not present any degradation, or they have a half-life time so high that the use of the reactive barrier technology may not be practical. Furthermore, the formation of chlorinated byproducts, eventually more toxic than the original contaminant and that are not degradable using this same technology, emphasises that the treatment of aquifers should be sequential. PMID:15177731

Gusmo, Alexandre Duarte; de Campos, Tcio Mauro Pereira; Nobre, Manoel de Melo Maia; Vargas, Eurpedes do Amaral

2004-07-01

356

Step Barrier Scattering Model  

NSDL National Science Digital Library

The Step Barrier Scattering model shows a quantum mechanical experiment in which an incident wave (particle) traveling from the left is transmitted and reflected from a potential step at x=0.  Although the analytic solution to this standard problem is well known, its visualization shows how the incident and reflected waves form an interference pattern and how the incident wave penetrates the classically forbidden region when its energy is less than the barrier height V

Christian, Wolfgang

2008-10-09

357

Effects of maternal iron nutrition during lactation on milk iron and rat neonatal iron status?3  

Microsoft Academic Search

We studied the milk iron content and iron status of lactating rats and their pups to investigatethe relationshipsbetween the iron concentrations of maternal diet and the iron content of milk, and that between the milk iron content and neonatal iron status. Three days after parturition lactating rats were divided into three groups and fed a control (250 ppm iron), a

Sunil G. Anaokar; Philip J. Garry

358

Clamshell excavation of a permeable reactive barrier  

NASA Astrophysics Data System (ADS)

Nowadays, permeable reactive barriers (PRB) are one of the most widespread techniques for the remediation of contaminated aquifers. Over the past 10 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC in: Permeable reactive barriers: lessons learned/new directions. The Interstate Technology and Regulatory Council, Permeable Reactive Barriers Team 2005). Although, a variety of excavation methods have been developed, backhoe excavators are often used for the construction of PRBs. The aim of this study is to describe the emplacement of a full-scale PRB and the benefits deriving from the use of a crawler crane equipped with a hydraulic grab (also known as clamshell excavator) in the excavation phases. The studied PRB was designed to remediate a chlorinated hydrocarbons plume at an old industrial landfill site, in Avigliana, near the city of Torino, in Italy. The continuous reactive barrier was designed to be 120 m long, 13 m deep, and 0.6 m thick. The installation of the barrier was accomplished using a clamshell for the excavation of the trench and a guar-gum slurry to support the walls. The performance of this technique was outstanding and allowed the installation of the PRB in 7 days. The degree of precision of the excavation was very high because of the intrinsic characteristics of this excavation tool and of the use of a concrete curb to guide the hydraulic grab. Moreover, the adopted technique permitted a saving of bioslurry thus minimizing the amount of biocide required.

Molfetta, Antonio Di; Sethi, Rajandrea

2006-06-01

359

Retractable barrier strip  

DOEpatents

A portable barrier strip having retractable tire-puncture means for puncturing a vehicle tire. The tire-puncture means, such as spikes, have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture means removably disposed in a shaft that is rotatably disposed in each barrier block. The shaft removably and pivotally interconnects the plurality of barrier blocks. Actuation cables cause the shaft to rotate the tire-puncture means to the armed position for puncturing a vehicle tire and to the retracted position for not puncturing the tire. Each tire-puncture means is received in a hollow-bed portion of its respective barrier block when in the retracted position. The barrier strip rests stable in its deployed position and substantially motionless as a tire rolls thereon and over. The strip is rolled up for retrieval, portability, and storage purposes, and extended and unrolled in its deployed position for use.

Marts, Donna J. (Idaho Falls, ID); Barker, Stacey G. (Idaho Falls, ID); McQueen, Miles A. (Idaho Falls, ID)

1996-01-01

360

Retractable barrier strip  

DOEpatents

A portable barrier strip is described having retractable tire-puncture means for puncturing a vehicle tire. The tire-puncture means, such as spikes, have an armed position for puncturing a tire and a retracted position for not puncturing a tire. The strip comprises a plurality of barrier blocks having the tire-puncture means removably disposed in a shaft that is rotatably disposed in each barrier block. The shaft removably and pivotally interconnects the plurality of barrier blocks. Actuation cables cause the shaft to rotate the tire-puncture means to the armed position for puncturing a vehicle tire and to the retracted position for not puncturing the tire. Each tire-puncture means is received in a hollow-bed portion of its respective barrier block when in the retracted position. The barrier strip rests in its deployed position and substantially motionless as a tire rolls thereon and over. The strip is rolled up for retrieval, portability, and storage purposes, and extended and unrolled in its deployed position for use. 13 figs.

Marts, D.J.; Barker, S.G.; McQueen, M.A.

1996-04-16

361

Technical Assistance to Ohio Closure Sites Technologies to Address Excavated VOC Contaminated Soil  

E-print Network

disposal, passive soil venting, enhanced soil venting, zero-valent iron, anaerobic bioremediation, aerobic technology ­ enhanced soil venting ­ stood out as best at meeting all of the requirements at FEMP. Enhanced soil venting is a simple process of removing the VOCs during the storage period using air extraction

Hazen, Terry

362

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, Wolfgang M. H. (Evanston, IL); Tzou, Ming-Shin (Evanston, IL); Jiang, Hui-Jong (Evanston, IL)

1987-01-01

363

Evaluation of simple methods of arsenic removal from domestic water supplies in rural communities  

Microsoft Academic Search

This study looked at two arsenic removal technologies, method Bucket Treatment Unit and removal using citrus lime, lemon and filter. The method Bucket Treatment Unit used zero-valent iron and removal using citrus lime, lemon and filter used photochemical oxidation of arsenic. The citrus lime, lemon and filter setup was found to be ineffective with its current design. The results reviewed

E. Awuah; R. T. Morris; P. A. Owusu; R. Sundell; J. Lindstrom

2009-01-01

364

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

1987-03-31

365

EZVI Injection Field Test Leads to Pilot-Scale Application  

EPA Science Inventory

Testing and monitoring of emulsified zero-valent ironTM (EZVI) injections was conducted at Cape Canaveral Air Force Station?s Launch Complex 34, FL, in 2002 to 2005 to evaluate the technology?s efficacy in enhancing in situ dehalogenation of dense nonaqueous-phase liquid (DNAPL) ...

366

NZVI modified magnetic filter paper with high redox and catalytic activities for advanced water treatment technologies.  

PubMed

The in situ synthesis of air-stable zero-valent iron nanoparticles (NZVI) embedded in cellulose fibers leads to the assembly of highly reactive magnetic filter papers. These engineered materials display a wide range of applications in the treatment of wastewater and drinking water, including chromium removal, phenol degradation, environmental bioremediation, and catalysis. PMID:25299729

Datta, K K R; Petala, E; Datta, K J; Perman, J A; Tucek, J; Bartak, P; Otyepka, M; Zoppellaro, G; Zboril, R

2014-12-25

367

Green synthesis of Fe0 and bimetallic Fe0 for oxidative catalysis and reduction applications  

EPA Science Inventory

A single-step green approach to the synthesis of nanoscale zero valent iron (nZVI) and nanoscale bimetallic (Fe0/Pd) particles using tea (Camellia sinensis) polyphenols is described. The expedient reaction between polyphenols and ferric chloride (FeCl3) occurs within a minute at ...

368

DEMONSTRATION BULLETIN: METAL-ENHANCED ABIOTIC DEGRADATION TECHNOLOGY - ENVIROMETAL TECHNOLOGIES, INC.  

EPA Science Inventory

EnviroMetal Technologies, Inc. (ETI), of Guelph, ON, Canada, has developed the metal-enhanced abiotic degradation technology to treat halogenated volatile organic compounds (VOC) in water. A reactive, zero-valent, granular iron medium causes reductive dehalogenation of VOCs yield...

369

Perchlorate Reduction by Autotrophic Bacteria in the  

E-print Network

to study the combination of zero-valent iron (ZVI) with perchlorate- reducing microorganisms (PRMs by water is used by PRMs as an electron donor to reduce perchlorate to chloride. Perchlorate degradation-limiting step with complete conversion to chloride (7). Perchlorate reducing microorganisms (PRMs) are ubiq

370

PRB STRATEGIES AND PERFORMANCE MONITORING FOR REMEDIATION OF INORGANIC CONTAMINANTS  

EPA Science Inventory

A combination of experimental and field investigations will be conducted to evaluate the effectiveness and long-term performance of zero-valent iron mixtures for treating inorganic contaminants. Long-term performance research will explore the geochemical and microbiological proce...

371

ZVI-CLAY SOIL MIXING TREATS DNAPL SOURCE AREA AT 35-FOOT DEPTH  

EPA Science Inventory

The DuPont Company and Colorado State University (CSU) are collaborating in development and refinement of a technology that involves in-situ admixing of contaminated soil, granular zero valent iron (ZVI), and clay using conventional soil mixing equipment. A full-scale application...

372

Environmental Aspects of Two Volatile Organic Compound Groundwater Treatment Designs at the Rocky Flats Site - 13135  

SciTech Connect

DOE's Rocky Flats Site in Colorado is a former nuclear weapons production facility that began operations in the early 1950's. Because of releases of hazardous substances to the environment, the federally owned property and adjacent offsite areas were placed on the CERCLA National Priorities List in 1989. The final remedy was selected in 2006. Engineered components of the remedy include four groundwater treatment systems that were installed before closure as CERCLA-accelerated actions. Two of the systems, the Mound Site Plume Treatment System and the East Trenches Plume Treatment System, remove low levels of volatile organic compounds using zero-valent iron media, thereby reducing the loading of volatile organic compounds in surface water resulting from the groundwater pathway. However, the zero-valent iron treatment does not reliably reduce all volatile organic compounds to consistently meet water quality goals. While adding additional zero-valent iron media capacity could improve volatile organic compound removal capability, installation of a solar powered air-stripper has proven an effective treatment optimization in further reducing volatile organic compound concentrations. A comparison of the air stripper to the alternative of adding additional zero-valent iron capacity to improve Mound Site Plume Treatment System and East Trenches Plume Treatment System treatment based on several key sustainable remediation aspects indicates the air stripper is also more 'environmentally friendly'. These key aspects include air pollutant emissions, water quality, waste management, transportation, and costs. (authors)

Michalski, Casey C.; DiSalvo, Rick; Boylan, John [Stoller LMS Team, 11025 Dover Street, Suite 1000, Westminster, CO 80021 (United States)] [Stoller LMS Team, 11025 Dover Street, Suite 1000, Westminster, CO 80021 (United States)

2013-07-01

373

Bioremediation of Uranium Plumes with Nano-scale  

E-print Network

Bioremediation of Uranium Plumes with Nano-scale Zero-valent Iron Angela Athey Advisers: Dr. Reyes Undergraduate Student Fellowship Program April 15, 2011 #12;Main Sources of Uranium Natural · Leaching from(IV) (UO2[s], uraninite) Anthropogenic · Release of mill tailings during uranium mining - Mobilization

Fay, Noah

374

Vacuum barrier for excimer lasers  

DOEpatents

A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

Shurter, R.P.

1992-09-15

375

Vacuum barrier for excimer lasers  

DOEpatents

A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

Shurter, Roger P. (Jemez Springs, NM)

1992-01-01

376

Mercury Removal from Aqueous Systems Using Commercial and Laboratory Prepared Metal Oxide Nanoparticles  

E-print Network

of arsenic. The other oxides which have shown promising results for arsenic removal include the nanoparticles of copper ox- ide [23], titanium dioxide [24],[25],[26],iron-titanium binary mixed oxide [27], humic acid coated iron oxide [28] and cerium doped... iron oxide [29]. Successful attempts have been also made to remove chromium (using nanoscale surface modi ed jacobsite [30], maghemite [31], akaganeite [32]), lead (using nanoscale titanium dioxide [33], zero-valent iron [34] and nanoscale chitosan [35...

Desai, Ishan

2010-10-12

377

Method of installing subsurface barrier  

DOEpatents

Systems, components, and methods relating to subterranean containment barriers. Laterally adjacent tubular casings having male interlock structures and multiple female interlock structures defining recesses for receiving a male interlock structure are used to create subterranean barriers for containing and treating buried waste and its effluents. The multiple female interlock structures enable the barriers to be varied around subsurface objects and to form barrier sidewalls. The barrier may be used for treating and monitoring a zone of interest.

Nickelson, Reva A. (Shelley, ID); Richardson, John G. (Idaho Falls, ID); Kostelnik, Kevin M. (Idaho Falls, ID); Sloan, Paul A. (Rigby, ID)

2007-10-09

378

Highway noise barrier perceived benefit  

Microsoft Academic Search

A laboratory experiment was performed in which 82 subjects judged the benefit of a noise barrier by listening to tape recordings of before-barrier and after-barrier traffic noise. These perceived benefit judgments were related by regression analysis to the barrier attenuation, the before-barrier traffic sound level, and a music background level, all of which were varied over the course of the

D. N. May; M. M. Osman

1980-01-01

379

Genetics Home Reference: Iron-refractory iron deficiency anemia  

MedlinePLUS

... PubMed Recent literature OMIM Genetic disorder catalog Conditions > Iron-refractory iron deficiency anemia On this page: Description Genetic changes ... names Glossary definitions Reviewed July 2014 What is iron-refractory iron deficiency anemia? Iron-refractory iron deficiency ...

380

Iron Therapy for Preterm Infants  

PubMed Central

SYNOPSIS Preterm infants are at risk for both iron deficiency and iron overload. The role of iron in multiple organ functions suggests that iron supplementation is essential for the preterm infant. Conversely, the potential for iron overload and the poorly developed anti-oxidant measures in the preterm infant argues against indiscriminate iron supplementation in this population. The purpose of this article is to review the predisposing factors and consequences of iron deficiency and iron overload in the preterm infant, the current recommendation for iron supplementation and its appropriateness, and describe potential management strategies that strike a balance between iron deficiency and iron toxicity. PMID:19161863

Rao, Raghavendra; Georgieff, Michael K.

2009-01-01

381

Barriers to effective teaching.  

PubMed

Medical school faculty members are charged with the critical responsibility of preparing the future physician and medical scientist workforce. Recent reports suggest that medical school curricula have not kept pace with societal needs and that medical schools are graduating students who lack the knowledge and skills needed to practice effectively in the 21st century. The majority of faculty members want to be effective teachers and graduate well-prepared medical students, but multiple and complex factors-curricular, cultural, environmental, and financial-impede their efforts. Curricular impediments to effective teaching include unclear definitions of and disagreement on learning needs, misunderstood or unstated goals and objectives, and curriculum sequencing challenges. Student and faculty attitudes, too few faculty development opportunities, and the lack of an award system for teaching all are major culture-based barriers. Environmental barriers, such as time limitations, the setting, and the physical space in which medical education takes place, and financial barriers, such as limited education budgets, also pose serious challenges to even the most committed teachers. This article delineates the barriers to effective teaching as noted in the literature and recommends action items, some of which are incremental whereas others represent major change. Physicians-in-training, medical faculty, and society are depending on medical education leaders to address these barriers to effect the changes needed to enhance teaching and learning. PMID:21346500

DaRosa, Debra A; Skeff, Kelley; Friedland, Joan A; Coburn, Michael; Cox, Susan; Pollart, Susan; O'connell, Mark; Smith, Sandy

2011-04-01

382

Synthetic and field based electrical tomography of a permeable reactive barrier: implications for monitoring barrier performance  

NASA Astrophysics Data System (ADS)

We performed a study of the sensitivity of electrical imaging to geochemical alteration of a zerovalent iron permeable reactive barrier (PRB) over time. Complex resistivity measurements on laboratory cores from an operational PRB defined the electrical properties of both unreacted and geochemically altered (reacted) iron as well as the growth rate of the reacted front on the up-gradient edge of the barrier. Laboratory results were used to generate models of the electrical structure of the PRB at 0, 15 and 30 years of operation. Synthetic cross-borehole resistivity and induced polarization data were generated and perturbed with errors representative of noise at the site. In order to generate reliable images of the engineered structure, a complex resistivity inversion was employed with a 'disconnect' in the regularization between the part of the finite element mesh (FEM) representing the internal structure of the barrier and the remainder of the FEM mesh. Synthetic results show that, although the internal structure of inverted images at 15 and 30 years does not accurately reflect the width of the reacted front modeled along the up-gradient edge of the barrier, perturbations to the internal structure of the imaged PRB are diagnostic of the growth of the reacted front. Cross-borehole electrical data obtained at the field site over a 15 month period demonstrate that the complex resistivity algorithm can reliably resolve the PRB target. Both resistivity and induced polarization reciprocal errors are low and the induced polarization data highly repeatable over this period. Changes in the electrical properties of the PRB over time were small, but consistent with growth of a reacted front based on the synthetic study.

Slater, L. D.; Binley, A.; Wu, Y.

2005-12-01

383

Hemochromatosis: Iron Storage Disease  

MedlinePLUS

... this? Submit What's this? Submit Button CDC Features Hemochromatosis: Iron Storage Disease Language: English Espaol (Spanish) Share ... iron storage disease, and stay healthy. What Is Hemochromatosis? Hemochromatosis occurs when the body absorbs too much ...

384

Iron Chelation Therapy  

MedlinePLUS

... This is caused by a hereditary condition called hemochromatosis . Hereditary hemochromatosis is most common in people whose ancestors came ... supplements or multivitamins with iron. Patients with hereditary hemochromatosis may develop iron overload after a very small ...

385

Iron supplements (image)  

MedlinePLUS

The mineral iron is an essential nutrient for humans because it is part of blood cells, which carry oxygen to all body cells. There is no conclusive evidence that iron supplements contribute to heart attacks.

386

KINETICS OF SOLUBLE CHROMIUM REMOVAL FROM CONTAMINATED WATER BY ZEROVALENT IRON MEDIA: CORROSION INHIBITION AND PASSIVE OXIDE EFFECTS. (R825223)  

EPA Science Inventory

Permeable reactive barriers containing zerovalent iron are being increasingly employed for in situ remediation of groundwater contaminated with redox active metals and chlorinated organic compounds. This research investigated the effect of chromate concentration on...

387

Iron and hepatitis C  

Microsoft Academic Search

Serum iron markers are often elevated in hepatitis C virus infection, particularly in African-American persons, although the\\u000a clinical significance of this finding remains unclear. Although hepatic iron is usually only mildly elevated in hepatitis\\u000a C virus, iron overload is associated with more advanced disease, nonresponse to interferon monotherapy, and increased risk\\u000a of hepatocellular carcinoma. Iron status does not predict response

James E. Nelson; Kris V. Kowdley

2004-01-01

388

[Barriers to hypertension treatment].  

PubMed

The objective was to describe the barriers faced by people with hypertension for non compliance to treatment and control the levels of blood pressure. This is a transversal and descriptive study which was carried out in 6 basic health units in Fortaleza-Cear, Brazil. The population consisted of 246 people enrolled in the program to Control Hypertension for at least a year. Data were collected using a structured interview and electronic chart. Of them, 69 showed normal blood pressure levels. The main barriers discovered were: poor financial condition, continuous treatment with many medicines and practice physical activity. It was concluded that barriers to the anti-hypertensive treatment include the sick people, their environment and their access to health care. PMID:22664601

Guedes, Maria Vilani Cavalcante; de Araujo, Thelma Leite; Lopes, Marcos Vencios de Oliveira; da Silva, Lucia de Fatima; de Freitas, Maria Clia; de Almeida, Paulo Csar

2011-01-01

389

Segmented Thermal Barrier Coating  

NASA Technical Reports Server (NTRS)

The article has a macro-segmented thermal barrier coating due to the presence of a pattern of three-dimensional features. The features may be a series of raised ribs formed on the substrate surface and being spaced from 0.05 inches to 0.30 apart. The ribs have a width ranging from 0.005 inches to 0.02 inches, and a height ranging from 25% to 100% of the thickness of the barrier coating. Alternately, the features may be a similar pattern of grooves formed in the surface of the substrate. Other embodiments provide segmentation by grooves or ribs in the bond coat or alternately grooves formed in the thermal barrier layer.

Smialek, James L. (Inventor)

2001-01-01

390

Iron in diet  

MedlinePLUS

Diet - iron ... the body. Treatment consists of a low-iron diet, no iron supplements, and phlebotomy (blood removal) on ... The Food and Nutrition Board at the Institute of Medicine recommends the following: Infants and children Younger than 6 months: 0.27 milligrams ...

391

Thermal barrier coating system  

NASA Technical Reports Server (NTRS)

A coating system which contains a bond coating and a thermal barrier coating is applied to metal surfaces such as turbine blades and provides both low thermal conductivity and improved adherence when exposed to high temperature gases or liquids. The bond coating contains NiCrAlY and the thermal barrier coating contains a reflective oxide. The reflective oxides ZrO2-Y2O3 and ZrO2-MgO have demonstrated significant utility in high temperature turbine applications.

Stecura, S.; Leibert, C. H. (inventors)

1977-01-01

392

Thermal Barrier Coating Workshop  

NASA Technical Reports Server (NTRS)

This document contains the agenda and presentation abstracts for the Thermal Barrier Coating Workshop, sponsored by NASA, DOE, and NIST. The workshop covered thermal barrier coating (TBC) issues related to applications, processing, properties, and modeling. The intent of the workshop was to highlight the state of knowledge on TBC's and to identify critical gaps in knowledge that may hinder TBC use in advanced applications. The workshop goals were achieved through presentations by 22 speakers representing industry, academia, and government as well as through extensive discussion periods.

Brindley, W. J. (compiler); Lee, W. Y. (compiler); Goedjen, J. G. (compiler); Dapkunas, S. J. (compiler)

1995-01-01

393

Barrier RF stacking  

SciTech Connect

This paper introduces a new method for stacking beams in the longitudinal phase space. It uses RF barriers to confine and compress beams in an accelerator, provided that the machine momentum acceptance is a few times larger than the momentum spread of the injected beam. This is the case for the Fermilab Main Injector. A barrier RF system employing Finemet cores and high-voltage solid-state switches is under construction. The goal is to double the number of protons per cycle on the production target for Run2 and NuMI experiments.

Weiren Chou and Akira Takagi

2003-02-24

394

Ice barrier construction  

SciTech Connect

A method is provided for constructing spray ice barriers to protect offshore structures in a frigid body of water from mobile ice, waves and currents. Water is withdrawn from the body of water and is sprayed through ambient air which is below the freezing temperature of the water so that a substantial amount of the water freezes as it passes through the air. The sprayed water is directed to build up a mass of ice having a size and shape adapted to protect the offshore structure. Spray ice barriers can also be constructed for the containment of pollutant spills.

Finucane, R. G.; Jahns, H. O.

1985-06-18

395

Iron chelating strategies in systemic metal overload, neurodegeneration and cancer.  

PubMed

Iron is a trace element required for normal performance of cellular processes. Because both the deficiency and excess of this metal are dangerous, its absorption, distribution and accumulation must be tightly regulated. Disturbances of iron homeostasis and an increase in its level may lead to overload and neurodegenerative diseases. Phlebotomy was for a long time the only way of removing excess iron. But since there are many possible disadvantages of this method, chelation therapy seems to be a logical approach to remove toxic levels of iron. In clinical use, there are three drugs: desferrioxamine, deferiprone and deferasirox. FBS0701, a novel oral iron chelator, is under clinical trials with very promising results. Developing novel iron-binding chelators is an urgent matter, not only for systemic iron overload, but also for neurodegenerative disorders, such as Parkinson's disease. Deferiprone is also used in clinical trials in Parkinson's disease. In neurodegenerative disorders the main goal is not only to remove iron from brain tissues, but also its redistribution in system. Few chelators are tested for their potential use in neurodegeneration, such as nonhalogeneted derivatives of clioquinol. Such compounds gave promising results in animal models of neurodegenerative diseases. Drugs of possible use in neurodegeneration must meet certain criteria. Their development includes the improvement in blood brain barrier permeability, low toxicity and the ability to prevent lipid peroxidation. One of the compounds satisfying these requirements is VK28. In rat models it was able to protect neurons in very low doses without significantly changing the iron level in liver or serum. Also iron chelators able to regulate activity of monoamine oxidase were tested. Polyphenols and flavonoids are able to prevent lipid peroxidation and demonstrate neuroprotective activity. While cancer does not involve true iron overload, neoplastic cells have a higher iron requirement and are especially prone to its depletion. It was shown, that desferrioxamine and deferasirox are antiproliferative agents active in several types of cancer. Very potent compounds with possible use as anticancer drugs are thiosemicarbazones. They are able to inhibit ribonucleotide reductase, an enzyme involved in DNA synthesis. Because the relationship between the development of overload / neurodegenerative disorders, or cancer, and iron are very complex, comprehension of the mechanisms involved in the regulation of iron homeostasis is a crucial factor in the development of new pharmacological strategies based on iron chelation. In view of various factors closely involved in pathogenesis of such diseases, designing multifunctional metal-chelators seems to be the most promising approach, but it requires a lot of effort. In this perspective, the review summarizes systemic iron homeostasis, and in brain and cancer cells, iron dysregulation in neurodegenerative disease and possible chelation strategies in the treatment of metal systemic overload, neurodegeneration and cancer. PMID:25005181

Gumienna-Kontecka, Elzbieta; Pyrkosz-Bulska, Monika; Szebesczyk, Agnieszka; Ostrowska, Malgorzata

2014-01-01

396

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions  

PubMed Central

Background Selenite (SeO32?) oxyanion shows severe toxicity to biota. Different bacterial strains exist that are capable of reducing SeO32? to non-toxic elemental selenium (Se0), with the formation of Se nanoparticles (SeNPs). These SeNPs might be exploited for technological applications due to their physico-chemical and biological characteristics. The present paper discusses the reduction of selenite to SeNPs by a strain of Bacillus sp., SeITE01, isolated from the rhizosphere of the Se-hyperaccumulator legume Astragalus bisulcatus. Results Use of 16S rRNA and GyrB gene sequence analysis positioned SeITE01 phylogenetically close to B. mycoides. On agarized medium, this strain showed rhizoid growth whilst, in liquid cultures, it was capable of reducing 0.5 and 2.0 mM SeO32? within 12 and 24 hours, respectively. The resultant Se0 aggregated to form nanoparticles and the amount of Se0 measured was equivalent to the amount of selenium originally added as selenite to the growth medium. A delay of more than 24 hours was observed between the depletion of SeO32 and the detection of SeNPs. Nearly spherical-shaped SeNPs were mostly found in the extracellular environment whilst rarely in the cytoplasmic compartment. Size of SeNPs ranged from 50 to 400 nm in diameter, with dimensions greatly influenced by the incubation times. Different SeITE01 protein fractions were assayed for SeO32? reductase capability, revealing that enzymatic activity was mainly associated with the membrane fraction. Reduction of SeO32? was also detected in the supernatant of bacterial cultures upon NADH addition. Conclusions The selenite reducing bacterial strain SeITE01 was attributed to the species Bacillus mycoides on the basis of phenotypic and molecular traits. Under aerobic conditions, the formation of SeNPs were observed both extracellularly or intracellullarly. Possible mechanisms of Se0 precipitation and SeNPs assembly are suggested. SeO32? is proposed to be enzimatically reduced to Se0 through redox reactions by proteins released from bacterial cells. Sulfhydryl groups on peptides excreted outside the cells may also react directly with selenite. Furthermore, membrane reductases and the intracellular synthesis of low molecular weight thiols such as bacillithiols may also play a role in SeO32? reduction. Formation of SeNPs seems to be the result of an Ostwald ripening mechanism. PMID:24606965

2014-01-01

397

Iron, radiation, and cancer.  

PubMed Central

Increased iron content of cells and tissue may increase the risk of cancer. In particular, high available iron status may increase the risk of a radiation-induced cancer. There are two possible mechanisms for this effect: iron can catalyze the production of oxygen radicals, and it may be a limiting nutrient to the growth and development of a transformed cell in vivo. Given the high available iron content of the western diet and the fact that the world is changing to the western model, it is important to determine if high iron increases the risk of cancer. PMID:2269234

Stevens, R G; Kalkwarf, D R

1990-01-01

398

The Fission Barrier Landscape  

SciTech Connect

Fission excitation functions have been measured for a chain of neighboring compound nuclei from {sup 207}Po to {sup 212}Po. We present a new analysis which provides a determination of the fission barriers and ground state shell effects with nearly spectroscopic accuracy. The accuracy achieved in this analysis may lead to a future detailed exploration of the saddle mass surface and its spectroscopy.

Phair, L.; Moretto, L. G. [Nuclear Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

2008-04-17

399

Great Barrier Reef  

NSDL National Science Digital Library

This lesson addresses the environmental importance of coral reefs and the threats to the conservation of reefs. Through the process of gathering geographic information about a place (in this case, the Great Barrier Reef), students will learn how a geographic focus can sharpen their insights about a conservation issue.

400

Great Barrier Reef  

NASA Technical Reports Server (NTRS)

A better than average view of the Great Barrier Reef was captured by SeaWiFS on a recent overpass. There is sunglint northeast of the reef and there appears to be some sort of filamentous bloom in the Capricorn Channel.

2002-01-01

401

Thermal barrier coating  

DOEpatents

A thermal barrier coating for hot gas path components of a combustion turbine based on a zirconia-scandia system. A layer of zirconium scandate having the hexagonal Zr.sub.3 Sc.sub.4 O.sub.12 structure is formed directly on a superalloy substrate or on a bond coat formed on the substrate.

Bowker, Jeffrey Charles (Gibsonia, PA); Sabol, Stephen M. (Orlando, FL); Goedjen, John G. (Oviedo, FL)

2001-01-01

402

Barriers to Afterschool Programs.  

ERIC Educational Resources Information Center

Describes successful strategies used by school superintendents in Sauk City, Wisconsin; Beaverton, Oregon; and Vancouver, Washington to overcome barriers to implementing after-school programs. Provides brief summary of Mott Foundation-funded study of after-school programs conducted by the American Association of School Administrators (AASA). (PKP)

Lockwood, Anne Turnbaugh

2003-01-01

403

Geophysical characterization of subsurface barriers  

SciTech Connect

An option for controlling contaminant migration from plumes and buried waste sites is to construct a subsurface barrier of a low-permeability material. The successful application of subsurface barriers requires processes to verify the emplacement and effectiveness of barrier and to monitor the performance of a barrier after emplacement. Non destructive and remote sensing techniques, such as geophysical methods, are possible technologies to address these needs. The changes in mechanical, hydrologic and chemical properties associated with the emplacement of an engineered barrier will affect geophysical properties such a seismic velocity, electrical conductivity, and dielectric constant. Also, the barrier, once emplaced and interacting with the in situ geologic system, may affect the paths along which electrical current flows in the subsurface. These changes in properties and processes facilitate the detection and monitoring of the barrier. The approaches to characterizing and monitoring engineered barriers can be divided between (1) methods that directly image the barrier using the contrasts in physical properties between the barrier and the host soil or rock and (2) methods that reflect flow processes around or through the barrier. For example, seismic methods that delineate the changes in density and stiffness associated with the barrier represents a direct imaging method. Electrical self potential methods and flow probes based on heat flow methods represent techniques that can delineate the flow path or flow processes around and through a barrier.

Borns, D.J.

1995-08-01

404

Chaotic correlations in barrier billiards with arbitrary barriers  

NASA Astrophysics Data System (ADS)

We study autocorrelation functions in symmetric barrier billiards for golden mean trajectories with arbitrary barriers. Renormalization analysis reveals the presence of a chaotic invariant set and thus that, for a typical barrier, there are chaotic correlations. The chaotic renormalization set is the analogue of the so-called orchid that arises in a generalized Harper equation.

Osbaldestin, A. H.; Adamson, L. N. C.

2013-06-01

405

Systems study on engineered barriers: barrier performance analysis  

Microsoft Academic Search

A performance assessment model for multiple barrier packages containing unreprocessed spent fuel has been modified and applied to several package designs. The objective of the study was to develop information to be used in programmatic decision making concerning engineered barrier package design and development. The assessment model, BARIER, was developed in previous tasks of the System Study on Engineered Barriers

R. T. Stula; T. E. Albert; B. E. Kirstein; D. H. Lester

1980-01-01

406

Apoplastic Diffusion Barriers in Arabidopsis  

PubMed Central

During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, Jos J.; Kunst, Ljerka

2013-01-01

407

Iron traps terrestrially derived dissolved organic matter at redox interfaces  

PubMed Central

Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 7% (mean SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten

2013-01-01

408

Multilayer thermal barrier coating systems  

DOEpatents

The present invention generally describes multilayer thermal barrier coating systems and methods of making the multilayer thermal barrier coating systems. The thermal barrier coating systems comprise a first ceramic layer, a second ceramic layer, a thermally grown oxide layer, a metallic bond coating layer and a substrate. The thermal barrier coating systems have improved high temperature thermal and chemical stability for use in gas turbine applications.

Vance, Steven J. (Orlando, FL); Goedjen, John G. (Oviedo, FL); Sabol, Stephen M. (Orlando, FL); Sloan, Kelly M. (Longwood, FL)

2000-01-01

409

Modeling Catastrophic Barrier Island Dynamics  

NASA Astrophysics Data System (ADS)

Barrier islands, thin strips of sand lying parallel to the mainland coastline, along the U.S. Atlantic and Gulf Coasts appear to have maintained their form for thousands of years in the face of rising sea level. The mechanisms that allow barrier islands to remain robust are transport of sediment from the ocean side of barriers to the top and backside during storms, termed island overwash, and the growth and alongshore propagation of tidal deltas near barrier island inlets. Dynamically these processes provide the necessary feedbacks to maintain a barrier island in an attractor that withstands rising sea level within a phase space of barrier island geometrical characteristics. Current barrier island configurations along the Atlantic and Gulf coasts exist among a wide range of storm climate and underlying geologic conditions and therefore the environment that forces overwash and tidal delta dynamics varies considerably. It has been suggested that barrier islands in certain locations such as those between Avon and Buxton (losing 76% of island width since 1852) and Chandeleur islands (losing 85% of its surface area since 2005) along the Atlantic and Gulf coasts, respectively, may be subject to a catastrophic shift in barrier island attractor states - more numerous inlets cutting barriers in some locations and the complete disappearance of barrier islands in other locations. In contrast to common models for barrier islands that neglect storm dynamics and often only consider cross-shore response, we use an alongshore extended model for barrier island dynamics including beach erosion, island overwash and inlet cutting during storms, and beach accretion, tidal delta growth and dune and vegetation growth between storms to explore the response of barrier islands to a wide range of environmental forcing. Results will be presented that show how barrier island attractor states are altered with variations in the rate of sea level rise, storminess, and underlying geology. We will also investigate the conditions necessary for a barrier island attractor similar to those found along the Atlantic and Gulf coasts to become unstable.

Whitley, J. W.; McNamara, D.

2012-12-01

410

Microsoft Word - barriers.doc  

Cancer.gov

Description and Theoretical Background Definition The concept of perceived barriers has been used in behavioral medicine for a long time in one form or another. The earliest widespread use of the barriers concept was associated with the Health Belief Model, as described in the following section. Websters dictionary defines a barrier as something that impedes or separates.

411

Can-Filled Crash Barrier  

NASA Technical Reports Server (NTRS)

Crash barrier composed largely of used aluminum beverage cans protects occupants of cars in collisions with poles or trees. Lightweight, can-filled barrier very effective in softening impact of an automobile in head-on and off-angle collisions. Preliminary results indicate barrier is effective in collisions up to 40 mi/h (64 km/h).

Wilson, A. H.

1983-01-01

412

Impairment of interrelated iron- and copper homeostatic mechanisms in brain contributes to the pathogenesis of neurodegenerative disorders.  

PubMed

Iron and copper are important co-factors for a number of enzymes in the brain, including enzymes involved in neurotransmitter synthesis and myelin formation. Both shortage and an excess of iron or copper will affect the brain. The transport of iron and copper into the brain from the circulation is strictly regulated, and concordantly protective barriers, i.e., the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier (BCB) have evolved to separate the brain environment from the circulation. The uptake mechanisms of the two metals interact. Both iron deficiency and overload lead to altered copper homeostasis in the brain. Similarly, changes in dietary copper affect the brain iron homeostasis. Moreover, the uptake routes of iron and copper overlap each other which affect the interplay between the concentrations of the two metals in the brain. The divalent metal transporter-1 (DMT1) is involved in the uptake of both iron and copper. Furthermore, copper is an essential co-factor in numerous proteins that are vital for iron homeostasis and affects the binding of iron-response proteins to iron-response elements in the mRNA of the transferrin receptor, DMT1, and ferroportin, all highly involved in iron transport. Iron and copper are mainly taken up at the BBB, but the BCB also plays a vital role in the homeostasis of the two metals, in terms of sequestering, uptake, and efflux of iron and copper from the brain. Inside the brain, iron and copper are taken up by neurons and glia cells that express various transporters. PMID:23055972

Skjrringe, Tina; Mller, Lisbeth Birk; Moos, Torben

2012-01-01

413

Impairment of Interrelated Iron- and Copper Homeostatic Mechanisms in Brain Contributes to the Pathogenesis of Neurodegenerative Disorders  

PubMed Central

Iron and copper are important co-factors for a number of enzymes in the brain, including enzymes involved in neurotransmitter synthesis and myelin formation. Both shortage and an excess of iron or copper will affect the brain. The transport of iron and copper into the brain from the circulation is strictly regulated, and concordantly protective barriers, i.e., the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier (BCB) have evolved to separate the brain environment from the circulation. The uptake mechanisms of the two metals interact. Both iron deficiency and overload lead to altered copper homeostasis in the brain. Similarly, changes in dietary copper affect the brain iron homeostasis. Moreover, the uptake routes of iron and copper overlap each other which affect the interplay between the concentrations of the two metals in the brain. The divalent metal transporter-1 (DMT1) is involved in the uptake of both iron and copper. Furthermore, copper is an essential co-factor in numerous proteins that are vital for iron homeostasis and affects the binding of iron-response proteins to iron-response elements in the mRNA of the transferrin receptor, DMT1, and ferroportin, all highly involved in iron transport. Iron and copper are mainly taken up at the BBB, but the BCB also plays a vital role in the homeostasis of the two metals, in terms of sequestering, uptake, and efflux of iron and copper from the brain. Inside the brain, iron and copper are taken up by neurons and glia cells that express various transporters. PMID:23055972

Skjrringe, Tina; Mller, Lisbeth Birk; Moos, Torben

2012-01-01

414

System and method for producing metallic iron  

DOEpatents

A hearth furnace for producing metallic iron material has a furnace housing having a drying/preheat zone, a conversion zone, a fusion zone, and optionally a cooling zone, the conversion zone is between the drying/preheat zone and the fusion zone. A moving hearth is positioned within the furnace housing. A hood or separation barrier within at least a portion of the conversion zone, fusion zone or both separates the fusion zone into an upper region and a lower region with the lower region adjacent the hearth and the upper region adjacent the lower region and spaced from the hearth. An injector introduces a gaseous reductant into the lower region adjacent the hearth. A combustion region may be formed above the hood or separation barrier.

Bleifuss, Rodney L; Englund, David J; Iwasaki, Iwao; Fosnacht, Donald R; Brandon, Mark M; True, Bradford G

2013-09-17

415

System and method for producing metallic iron  

DOEpatents

A hearth furnace 10 for producing metallic iron material has a furnace housing 11 having a drying/preheat zone 12, a conversion zone 13, a fusion zone 14, and optionally a cooling zone 15, the conversion zone 13 is between the drying/preheat zone 12 and the fusion zone 14. A moving hearth 20 is positioned within the furnace housing 11. A hood or separation barrier 30 within at least a portion of the conversion zone 13, fusion zone 14 or both separates the fusion zone 14 into an upper region and a lower region with the lower region adjacent the hearth 20 and the upper region adjacent the lower region and spaced from the hearth 20. An injector introduces a gaseous reductant into the lower region adjacent the hearth 20. A combustion region may be formed above the hood or separation barrier.

Bleifuss, Rodney L. (Grand Rapids, MN); Englund, David J. (Bovey, MN); Iwasaki, Iwao (Grand Rapids, MN); Fosnacht, Donald R. (Hermantown, MN); Brandon, Mark M. (Charlotte, NC); True, Bradford G. (Charlotte, NC)

2012-01-17

416

Mechanisms of mammalian iron homeostasis  

PubMed Central

Iron is vital for almost all organisms because of its ability to donate and accept electrons with relative ease. It serves as a cofactor for many proteins and enzymes necessary for oxygen and energy metabolism, as well as for several other essential processes. Mammalian cells utilize multiple mechanisms to acquire iron. Disruption of iron homeostasis is associated with various human diseases: iron deficiency resulting from defects in acquisition or distribution of the metal causes anemia; whereas iron surfeit resulting from excessive iron absorption or defective utilization causes abnormal tissue iron deposition, leading to oxidative damage. Mammals utilize distinct mechanisms to regulate iron homeostasis at the systemic and cellular levels. These involve the hormone hepcidin and iron regulatory proteins, which collectively ensure iron balance. This review outlines recent advances in iron regulatory pathways, as well as in mechanisms underlying intracellular iron trafficking, an important but less-studied area of mammalian iron homeostasis. PMID:22703180

Pantopoulos, Kostas; Porwal, Suheel Kumar; Tartakoff, Alan; Devireddy, L.

2012-01-01

417

Barrier RF stacking  

SciTech Connect

A novel wideband RF system, nicknamed the barrier RF, has been designed, fabricated and installed in the Fermilab Main Injector. The cavity is made of seven Finemet cores, and the modulator made of two bipolar high-voltage fast solid-state switches. The system can deliver {+-}7 kV square pulses at 90 kHz. The main application is to stack two proton batches injected from the Booster and squeeze them into the size of one so that the bunch intensity can be doubled. High intensity beams have been successfully stacked and accelerated to 120 GeV with small losses. The problem of large longitudinal emittance growth is the focus of the present study. An upgraded system with two barrier RF cavities for continuous stacking is under construction. This work is part of the US-Japan collaborative agreement.

Chou, W.; Wildman, D.; /Fermilab; Zheng, H.; /Caltech; Takagi, A.; /KEK, Tsukuba

2004-12-01

418

The butterfly barrier  

Microsoft Academic Search

We describe and algorithm for barrier synchronization that requires only read and write to shared store. The algorithm is faster than the traditionallocked counter approach for two processors and has an attractive log2N time scaling for largerN. The algorithm is free of hot spots and critical regions and requires a shared memory bandwidth which grows linearly withN, the number of

Eugene D. Brooks

1986-01-01

419

Barrier breaching device  

DOEpatents

A barrier breaching device that is designed primarily for opening holes in interior walls of buildings uses detonating fuse for explosive force. The fuse acts as the ribs or spokes of an umbrella-like device that may be opened up to form a cone. The cone is placed against the wall so that detonating fuse that rings the base of the device and which is ignited by the spoke-like fuses serves to cut a circular hole in the wall.

Honodel, Charles A. (Tracy, CA)

1985-01-01

420

Barrier breaching device  

DOEpatents

A barrier breaching device that is designed primarily for opening holes in interior walls of buildings uses detonating fuse for explosive force. The fuse acts as the ribs or spokes of an umbrella-like device that may be opened up to form a cone. The cone is placed against the wall so that detonating fuse that rings the base of the device and which is ignited by the spoke-like fuses serves to cut a circular hole in the wall.

Honodel, C.A.

1983-06-01

421

40 CFR 194.44 - Engineered barriers.  

Code of Federal Regulations, 2013 CFR

...selecting any engineered barrier(s) for the disposal...Department shall evaluate the benefit and detriment of engineered barrier alternatives...accessible environment, the benefit and detriment of engineered barriers for existing waste...

2013-07-01

422

40 CFR 194.44 - Engineered barriers.  

Code of Federal Regulations, 2012 CFR

...selecting any engineered barrier(s) for the disposal...Department shall evaluate the benefit and detriment of engineered barrier alternatives...accessible environment, the benefit and detriment of engineered barriers for existing waste...

2012-07-01