Note: This page contains sample records for the topic zero-valent iron barrier from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Microbiological characteristics in a zero-valent iron reactive barrier  

SciTech Connect

Zero-valent iron (Fe{sup 0})-based permeable reactive barrier treatment has been generating great interest for passive groundwater remediation, yet few studies have paid particular attention to the microbial activity and characteristics within and in the vicinity of the Fe{sup 0}-barrier matrix. The present study was undertaken to evaluate the microbial population and community composition in the reducing zone of influence by Fe{sup 0} corrosion in the barrier at the Oak Ridge Y-12 Plant site. Both phospholipid fatty acids and DNA analyses were used to determine the total microbial population and microbial functional groups, including sulfate-reducing bacteria, denitrifying bacteria, and methanogens, in groundwater and soil/iron core samples. A diverse microbial community was identified in the strongly reducing Fe{sup 0} environment despite a relatively high pH condition within the Fe{sup 0} barrier (up to pH {approx} 10). In comparison with those found in the background soil/groundwater samples, the enhanced microbial population ranged from {approx} 1 to 3 orders of magnitude and appeared to increase from upgradient of the barrier to downgradient soil. In addition, microbial community composition appeared to change overtime, and the bacterial types of microorganisms increased consistently as the barrier aged. DNA analysis indicated the presence of sulfate-reducing and denitrifying bacteria in the barrier and its surrounding soil. However, the activity of methanogens was found to be relatively low, presumably as a result of the competition by sulfate/metal-reducing bacteria and denitrifying bacteria because of the unlimited availability of sulfate and nitrate in the site groundwater. Results of this study provide evidence of a diverse microbial population within and in the vicinity of the iron barrier, although the important roles of microbial activity, either beneficially or detrimentally, on the longevity and enduring efficiency of the Fe{sup 0} barriers are yet to be evaluated.

Gu, Baohua [ORNL; Watson, David B [ORNL; Wu, Liyou [University of Oklahoma, Norman; Phillips, Debra Helen [ORNL; White, David C. [University of Tennessee; Zhou, Jizhong [ORNL

2002-01-01

2

Zero-Valent Iron Permeable Reactive Barriers: A Review of Performance  

Microsoft Academic Search

This report briefly reviews issues regarding the implementation of the zero-valent iron permeable reactive barrier (PRB) technology at sites managed by the U.S. Department of Energy (DOE). Initially, the PRB technology, using zero-valent iron for the reactive media, was received with great enthusiasm, and DOE invested millions of dollars testing and implementing PRBs. Recently, a negative perception of the technology

Korte

2001-01-01

3

Ground water remediation of chromium using zero-valent iron in a permeable reactive barrier  

SciTech Connect

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 iron and in systems with iron mixed with aquifer materials. Various geochemical parameters were measured to confirm the proposed reactions. Laboratory experiments were scaled up to pilot and full-scale field demonstrations. Intensive geochemical sampling in the field tests corroborate laboratory results and successfully demonstrate the effectiveness of this innovative in situ approach to remediate chromate-contaminated ground water using a permeable reactive barrier composed of zero-valent iron.

Puls, R.W.; Powell, R.M.; Paul, C.J.; Blowes, D.

1998-09-01

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

Benzene and toluene biodegradation down gradient of a zero-valent iron permeable reactive barrier.  

PubMed

This study simulated benzene and toluene biodegradation down gradient of a zero-valent iron permeable reactive barrier (ZVI PRB) that reduces trichloroethylene (TCE). The effects of elevated pH (10.5) and the presence of a common TCE dechlorination by product [cis-1,2-dichloroethene (cis-1,2-DCE)] on benzene and toluene biodegradation were evaluated in batch experiments. The data suggest that alkaline pH (pH 10.5), often observed down gradient of ZVI PRBs, inhibits Fe(III)-mediated biotransformation of both benzene and toluene. Removal was reduced by 43% for benzene and 26% for toluene as compared to the controls. The effect of the addition of cis-1,2-DCE on benzene and toluene biodegradation was positive and resulted in removal that was greater than or equal to the controls. These results suggest that, at least for cis-1,2-DCE, its formation may not be toxic to iron-reducing benzene and toluene degrading bacteria; however, for microbial benzene and toluene removal down gradient of a ZVI PRB, it may be necessary to provide pH control, especially in the case of a biological PRB that is downstream from a ZVI PRB. PMID:21316847

Chen, Liang; Liu, Fei; Liu, Yulong; Dong, Hongzhong; Colberg, Patricia J S

2011-01-26

6

Impact of sample preparation on mineralogical analysis of zero-valent iron reactive barrier materials  

SciTech Connect

Permeable reactive barriers (PRBs) of zero-valent iron (Fe{sup 0}) are increasingly being used to remediate contaminated ground water. Corrosion of Fe{sup 0} filings and the formation of precipitates can occur when the PRB material comes in contact with ground water and may reduce the lifespan and effectiveness of the barrier. At present, there are no routine procedures for preparing and analyzing the mineral precipitates from Fe{sup 0} PRB material. These procedures are needed because mineralogical composition of corrosion products used to interpret the barrier processes can change with iron oxidation and sample preparation. The objectives of this study were (i) to investigate a method of preparing Fe{sup 0} reactive barrier material for mineralogical analysis by X-ray diffraction (XRD), and (ii) to identify Fe mineral phases and rates of transformations induced by different mineralogical preparation techniques. Materials from an in situ Fe{sup 0} PRB were collected by undisturbed coring and processed for XRD analysis after different times since sampling for three size fractions and by various drying treatments. We found that whole-sample preparation for analysis was necessary because mineral precipitates occurred within the PRB material in different size fractions of the samples. Green rusts quickly disappeared from acetone-dried samples and were not present in air-dried and oven-dried samples. Maghemite/magnetite content increased over time and in oven-dried samples, especially after heating to 105 C. We conclude that care must be taken during sample preparation of Fe{sup 0} PRB material, especially for detection of green rusts, to ensure accurate identification of minerals present within the barrier system.

Phillips, Debra Helen [ORNL; Gu, Baohua [ORNL; Watson, David B [ORNL; Roh, Yul [ORNL

2003-03-01

7

Modelling the remediation of contaminated groundwater using zero-valent iron barrier  

SciTech Connect

This paper presents results of modelling studies on remediation of groundwater contaminated with uranium using a zero-valent iron permeable reactive barrier (ZVI PRB) at the U.S. Oak Ridge Y-12 site that are used to establish modelling techniques that are of value to other sites such as in the UK. A systematic modelling methodology has been developed to study the problem by using a suite of modelling tools. Firstly a conceptual basis of the main chemical processes representing the remediation of uranium by the ZVI PRB is developed. Two main effects involving reduction and corrosion have been identified as being relevant for the remediation processes. These are then formulated and implemented using the reactive chemical model PHREEQC to provide underpinning chemical input parameters for subsequent reactive solute transport modelling using the TRAFFIC and PHAST codes. Initial results shows that modelling can be a very cost-effective means to study the hydrogeological and geochemical processes involved and to aid understanding of the remediation concept. The modelling approaches presented and lessons learnt are thought to be relevant to other cases of contaminated land study and are likely to be of value to site management concepts which consider on-site disposal of contaminated soils and materials. (authors)

Kwong, S.; Small, J.; Tahar, B. [Nexia Solutions Ltd., Hinton House, Risley, Warrington, WA (United Kingdom)

2007-07-01

8

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

9

Long-term performance of permeable reactive barriers using zero-valent iron: geochemical and microbiological effects.  

PubMed

Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, North Carolina, and the Denver Federal Center, Colorado, sites. These ground water treatment systems use zero-valent iron filings (Peerless Metal Powders Inc.) to intercept and remediate chlorinated hydrocarbon compounds at the Denver Federal Center (funnel-and-gate system) and overlapping plumes of hexavalent chromium and chlorinated hydrocarbons at Elizabeth City (continuous wall system). Zero-valent iron at both sites is a long-term sink for carbon, sulfur, calcium, silicon, nitrogen, and magnesium. After about four years of operation, the average rates of inorganic carbon (IC) and sulfur (S) accumulation are 0.09 and 0.02 kg/m2/year, respectively, at Elizabeth City where upgradient waters contain <400 mg/L of total dissolved solids (TDS). At the Denver Federal Center site, upgradient ground water contains 1000 to 1200 mg/L TDS and rates of IC and S accumulation are as high as 2.16 and 0.80 kg/m2/year, respectively. At both sites, consistent patterns of spatially variable mineral precipitation and microbial activity are observed. Mineral precipitates and microbial biomass accumulate the fastest near the upgradient aquifer-Fe0 interface. Maximum net reductions in porosity due to the accumulation of sulfur and inorganic carbon precipitates range from 0.032 at Elizabeth City to 0.062 at the Denver Federal Center (gate 2) after about four years. Although pore space has been lost due the accumulation of authigenic components, neither site shows evidence of pervasive pore clogging after four years of operation. PMID:12873012

Wilkin, Richard T; Puls, Robert W; Sewell, Guy W

10

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

SciTech Connect

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{sup 0} reactive barriers. The objectives of this paper are (1) to investigate mineral precipitates through an in situ permeable Fe{sup 0} reactive barrier and (2) to examine the cementation and corrosion of Fe{sup 0} filings in order to estimate the lifespan of this barrier. This field scale barrier (225-ft long x 2-ft wide x 31-ft deep) has been installed in order to remove uranium from contaminated groundwater at the Y-12 plant site, Oak Ridge, TN. According to XRD and SEM-EDX analysis of core samples recovered from the Fe{sup 0} portion of the barrier, iron oxyhydroxides were found throughout, while aragonite, siderite, and FeS occurred predominantly in the shallow portion. Additionally, aragonite and FeS were present in up-gradient deeper zone where groundwater first enters the Fe{sup 0} section of the barrier. After 15 months in the barrier, most of the Fe{sup 0} filings in the core samples were loose, and a little corrosion of Fe{sup 0} filings was observed in most of the barrier. However, larger amounts of corrosion (10-150 {micro}m thick corrosion rinds) occurred on cemented iron particles where groundwater first enters the barrier. Bicarbonate/carbonate concentrations were high in this section of the barrier. Byproducts of this corrosion, iron oxyhydroxides, were the primary binding material in the cementation. Also, aragonite acted as a binding material to a lesser extent, while amorphous FeS occurred as coatings and infilings. Thin corrosion rinds (2-50 {micro}m thick) were also found on the uncemented individual Fe{sup 0} filings in the same area of the cementation. If corrosion continues, the estimated lifespan of Fe{sup 0} filings in the more corroded sections is 5 to 10 years, while the Fe{sup 0} filings in the rest of the barrier perhaps would last longer than 15 years. The mineral precipitates on the Fe{sup 0} filing surfaces may hinder this corrosion but they may also decrease reactive surfaces. This research shows that precipitation will vary across a single reactive barrier and that greater corrosion and subsequent cementation of the filings may occur where groundwater first enters the Fe{sup 0} section of the barrier.

Phillips, Debra Helen [ORNL; Gu, Baohua [ORNL; Watson, David B [ORNL; Roh, Yul [ORNL; Liang, Liyuan [ORNL; Lee, S. Y. [University of Tennessee, Knoxville (UTK)

2000-08-01

11

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

12

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

Microsoft Academic Search

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

Lenly J. Weathers; Lynn E. Katz

2002-01-01

13

Reduction of Aromatic Hydrocarbons by Zero-Valent Iron and Palladium Catalyst  

SciTech Connect

Permeable reactive barrier (PRB) is an alternative technology for soil and groundwater remediation. Zero valent iron, which is the most popular PRB material, is only applicable to halogenated aliphatic organics and some heavy metals. The objective of this study was to investigate reductive dechlorination of halogenated compounds and reduction of non-halogenated aromatic hydrocarbons using zero valent metals (ZVMs) and catalysts as reactive materials for PRBs. A group of small aromatic hydrocarbons such as monochlorophenols, phenol and benzene were readily reduced with palladium catalyst and zero valent iron. Poly-aromatic hydrocarbons (PAHs) were also tested with the catalysts and zero valent metal combinations. The aromatic rings were reduced and partly reduced PAHs were found as the daughter compounds. The current study demonstrates reduction of aromatic compounds by ZVMs and modified catalysts and implicates that PRB is applicable not only for halogenated organic compounds but nonhalogenated aromatic compounds such as PAHs.

Kim, Young-Hun; Shin, Won Sik; Ko, Seok-Oh; Kim, Myung-Chul

2004-03-31

14

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

Calabrň, P S; Moraci, N; Suraci, P

2011-08-10

15

Dechlorination of ?-hexachlorocyclohexane by zero-valent metallic iron  

Microsoft Academic Search

This study investigated the rates and pathways of ?-hexachlorocyclohexane (?-HCH) dechlorination by granular zero-valent iron under different pH, iron dosage and temperature conditions. It was found that ?-HCH was rapidly reduced to benzene and chlorobenzene (CB) with benzene as the major product and that the dechlorination likely follows three steps of dichloroelimination to benzene, or two steps of dichloroeliminations and

Zhiyuan Wang; Ping’an Peng; Weilin Huang

2009-01-01

16

TREATMENT OF GROUND WATER WITH ZERO VALENT IRON (ZVI)  

EPA Science Inventory

A presentation on the use of zero valent iron (ZVI) for groundwater remediation at the Memphis Defense Depot Site in Memphis, TN, will be given at a public meeting in Memphis on February 24. The presentation is being given in response to a request by a citizen's group associated...

17

ZERO-VALENT IRON FOR HIGH-LEVEL ARSENITE REMOVAL  

EPA Science Inventory

This study conducted by flow through column systems was aimed at investigating the feasibility of using zero-valent iron for arsenic remediation in groundwater. A high concentration arsenic solution (50 mg l-1) was prepared by using sodium arsenite (arsenic (III)) to simulate gr...

18

Electrokinetics Enhanced Delivery of Nano-scale Zero Valent Iron  

Microsoft Academic Search

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

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

2010-01-01

19

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

20

Feasibility of amending slurry walls with zero-valent iron  

SciTech Connect

Rapid degradation of aqueous trichloroethylene (TCE) was observed in batch experiments conducted with soil/bentonite slurry wall materials amended with the addition of zero-valent iron. The first-order TCE decay constants for soil/bentonite/iron mixtures, when normalized to the available iron surface area, were approximately 1--2 orders of magnitude higher than observed in batch experiments with pure iron systems. Permeability tests indicated an increase in SB hydraulic conductivity roughly proportional to the amount of iron added. Based on the observed reaction rates and the assumption of sustained long-term performance, significantly less than one percent added iron would be required to reduce the diffusive flux of TCE across an installed slurry wall by over 10 orders of magnitude. However, the release of hydrogen gas was noted as a potential problem for low permeability systems containing zero-valent iron.

Rabideau, A.J. [State Univ. of New York, Buffalo, NY (United States). Dept. of Civil, Structural, and Environmental Engineering; Shen, P. [Chopra Lee, Inc., Grand Island, NY (United States); Khandelwal, A. [S.S. Papadopulos and Associates, Bethesda, MD (United States)

1999-04-01

21

The application of in situ permeable reactive (zero-valent iron) barrier technology for the remediation of chromate-contaminated groundwater: a field test  

Microsoft Academic Search

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 facility located on a U.S. Coast Guard air base near Elizabeth City, North Carolina. Dissolved chromate concentrations

Robert W Puls; Cynthia J Paul; Robert M Powell

1999-01-01

22

Sustained and complete hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) degradation in zero-valent iron simulated barriers under different microbial conditions.  

PubMed

Flow-through columns packed with "aged" zero-valent iron (ZVI) between layers of soil and sand were constructed to mimic a one-dimensional permeable reactive iron barrier (PRB). The columns were continuously fed RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine, ca. 18 mg l(-1)) for over one year. Two columns were bioaugmented with dissimilatory iron reducing bacteria (DIRB) Shewanella algae BrY or Geobacter metallireducens GS-15 to investigate their potential to enhance the reactivity of aged iron by reductive dissolution of passivating iron oxides or via production of biogenic reactive minerals. A third column was not bioaugmented to evaluate colonization by indigenous soil microorganisms. [14C]-RDX was completely removed in all columns at the start of the iron layer, and concentration profiles showed rapid and sustainable RDX removal over one year; however, a phylogenetic profile conducted after one year using DGGE analysis of recovered DNA did not detect S. algae BrY or G. metallireducens in their respective columns. Bacterial DNA was recovered from within the ZVI. Several unidentified 14C-labeled byproducts were present in the effluent of all columns. Dissolved 14C removal and the detection of dissolved inorganic 14C in these columns (but not in the sterile control) suggest microbial-mediated mineralization of RDX and sorption/precipitation of degradation products. Enhanced RDX mineralization in bioaugmented columns was temporary relative to the indigenously colonized column. However, shorter acclimation periods associated with bioaugmented PRBs may be desirable for rapid RDX mineralization, thereby preventing breakthrough of potentially undesirable byproducts. Overall, these results show that high RDX removal efficiency by ZVI-PRBs is achievable and sustainable and that the efficacy and start-up of ZVI-PRBs might be enhanced by bioaugmentation. PMID:16342534

Shrout, J D; Larese-Casanova, P; Scherer, M M; Alvarez, P J

2005-10-01

23

Reduction of trichloroethylene and nitrate by zero-valent iron with peat  

Microsoft Academic Search

The feasibility of using zero-valent iron (ZVI) and peat mixture as in situ barriers for contaminated sediments and groundwater was investigated. Trichloroethylene (TCE) and nitrate (NO3 ), redox sensitive contaminants were reduced by ZVI and peat soil mixture under anaerobic condition. Peat was used to support the sorption of TCE, microbial activity for biodegradation of TCE and denitrification while TCE

Jee-Eun Min; Meejeong Kim; John H. Pardue; Jae-Woo Park

2008-01-01

24

Polarographic studies of zero valent iron as a reductant for remediation of nitroaromatics in the environment  

Microsoft Academic Search

Zero valent iron as a reactive barrier material has garnered considerable attention over the past few years because it is relatively inexpensive, abundant, harmless to the environment and effective in reducing organic contaminants. The redox process requires adsorption of the organic contaminant onto the Fe surface, where protonation and electron transfer occur. In this study, nitrobenzene reduction by Fe was

Barry K. Lavine; Glenn Auslander; Jason Ritter

2001-01-01

25

Assessment of zero-valent iron as a permeable reactive barrier for long-term removal of arsenic compounds from synthetic water.  

PubMed

Zero-valent iron (ZVI) has great potential to be used as a remediation material for the removal of a wide range of pollutants from groundwater. The present study assessed the potential of ZVI for arsenic remediation by investigating (i) the removal kinetics of arsenic by ZVI in a batch reactor and (ii) the longevity of ZVI to remove arsenic in a flow-through column system which mimics the permeable reactive barrier (PRB) technology. Results of the batch experiments showed an effective removal (99.5%) of arsenic compounds from the synthetic water samples. Based on our kinetic study, the arsenic removals are expected to occur in a timescale of less than a few hours in typical PRB treatment conditions using ZVI (e.g. [ZVI] > 20 g/L and [As] < 1 mg/L). The flow-through columns were continuously operated for 360 days at a flow rate of 2 mL/h. Samples were taken at regular intervals (90, 150, 230 and 360 days) and analysed for total arsenic concentration. The removal rates decreased by (45% in aerobic and 39% in anoxic) after 360 days of operation indicate that the regular replacement of the reactive material would be required for efficient removal of arsenic. PMID:20088207

Lee, Kui-Jae; Lee, Yunho; Yoon, Jeyong; Kamala-Kannan, Seralathan; Park, Seung-Moon; Oh, Byung-Taek

2009-12-01

26

Reduction of azo dyes with zero-valent iron  

Microsoft Academic Search

The reduction of azo dyes by zero-valent iron metal (Fe0) at pH 7.0 in 10mM HEPES buffer was studied in aqueous, anaerobic batch systems. Orange II was reduced by cleavage of the azo linkage, as evidenced by the production of sulfanilic acid (a substituted aniline). Adsorption of the dyes on iron particles was less than 4% of the initial concentration,

Sangkil Nam; Paul G. Tratnyek

2000-01-01

27

Nitrate removal in zero-valent iron packed columns  

Microsoft Academic Search

Nitrate removal by laboratory and field continuous-flow zero-valent iron (Fe0) packed bed columns was evaluated for different influent water qualities (pH, dissolved oxygen (DO), nitrate concentration) and several months of operation (600–1500 bed volumes (BVs)). In contrast to previous batch experiments with Fe0 where nitrate was stoichiometrically converted to ammonium, only 70% of the applied nitrogen was recovered as nitrate,

Paul Westerhoff; Jennifer James

2003-01-01

28

Electrochemical depassivation of zero-valent iron for trichloroethene reduction.  

PubMed

Permeable reactive barriers (PRBs) composed of zero-valent iron (ZVI) are susceptible to passivation, resulting in substantially decreased rates of chlorinated solvent removal over time. In this study, the application of low electrical direct current (DC) to restore the reductive capacity of passivated ZVI was examined. Electrical current was applied to a laboratory column reactor filled with a mixture of pre-passivated ZVI and sand. Variable voltage settings (0-12 V) were applied through two stainless steel electrodes placed at the ends of the reactor. While only partial restoration of the reductive capacity of the passivated ZVI was observed, higher rates of trichloroethene (TCE) removal were always obtained when current was applied, and the rates of TCE removal were roughly proportional to the voltage level. Although differences were observed between the rates and extent of TCE removal within the column, it is noteworthy that TCE removal was not restricted to that region of the column where the electrons entered (i.e., at the cathode). While complete "depassivation" of ZVI may be difficult to achieve in practice, the application of DC demonstrated observable restoration of reactivity of the passivated ZVI. This study provides evidence that this approach may significantly extend the life of a ZVI PRB. PMID:23009798

Chen, Liang; Jin, Song; Fallgren, Paul H; Swoboda-Colberg, Norbert G; Liu, Fei; Colberg, Patricia J S

2012-09-05

29

High-level arsenite removal from groundwater by zero-valent iron.  

PubMed

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 stability of arsenic and long-term remedial performance of the permeable reactive barrier (PRB) technology. A high concentration arsenic solution (50 mg l(-1)) was prepared by using sodium arsenite (arsenic (III)) to simulate groundwater at a heavily contaminated Superfund site in the USA. Batch studies indicate that the removal of arsenic is a two-step reaction with fast initial disappearance of arsenite followed by a slow subsequent removal process. Flow-through columns were conducted at a flow rate of 17 ml h(-1) under reducing conditions for 6.6 mo. Kinetic analysis suggested that arsenic removal behaves as a zero-order reaction at high arsenic concentrations. Arsenic removal rate constants decreased with time and arsenic breakthrough was observed in the column study. Arsenic removal capacity of zero-valent iron was determined to be approximately 7.5 mg As/g Fe. Carbonate green rust was identified from the analysis of surface precipitates; arsenite uptake by green rust may be a major mechanism responsible for arsenic remediation by zero-valent iron. Analysis of HCl-extractable arsenic from iron samples indicated that approximately 28% of arsenic was in the form of arsenate suggesting that a surface oxidation process was involved in the arsenic removal with zero-valent iron. PMID:15763090

Lien, Hsing-Lung; Wilkin, Richard T

2004-12-13

30

Comparison of Iron Sulfide and Zero-Valent Iron as Reactive Materials for the Removal of Arsenic From Groundwater  

Microsoft Academic Search

Zero-valent iron (ZVI) installed in permeable reactive barriers (PRBs) has been shown to be an effective remediation agent for several contaminants, including arsenic (As), a redox-active oxyanion present in reduced form as arsenite, AsO3(3-), and in oxidized form as arsenate, AsO4(3-). Work performed has shown greater removal of arsenic by iron sulfide (FeS), as mackinawite, than by ZVI under anaerobic

A. D. Henderson; A. H. Demond

2007-01-01

31

Cost and Performance Report Nanoscale Zero-Valent Iron Technologies for Source Remediation.  

National Technical Information Service (NTIS)

This cost and performance report is a compilation of technical and performance data from three recent Navy demonstration projects involving the use of microscale or nanoscale zero-valent iron (NZVI) for treatment of dense, nonaqueous-phase liquid (DNAPL) ...

A. Gavaskar L. Tatar W. Condit

2005-01-01

32

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

33

Chromium removal using resin supported nanoscale zero-valent iron.  

PubMed

Resin supported nanoscale zero-valent iron (R-nZVI) was synthesized by the borohydride reduction method. Batch experiments were conducted to evaluate the factors affecting Cr(VI) removal. It was found that nZVI loads, resin dose, pH value and initial concentration of Cr(VI) were all important factors. Scanning electron microscopy showed that the nZVI particles in R-nZVI became sphere after reacting with Cr(VI). This phenomenon was attributed to the co-precipitation of Cr(III) and Fe(III) on the surface of resin. X-ray diffraction pattern confirmed that Fe(0) diminished after the reaction. At optimum conditions, the Cr(VI) removal efficiency was 84.4% when the initial concentration of Cr(VI) was 20.0 mg/L. Regeneration of R-nZVI and resin was possible. R-nZVI can also remove Cr(III) efficiently. However, the removal mechanisms of Cr(VI) (anion) and Cr(III) (cation) are different. The former is chemical reduction, while the latter is ion exchange at pH below 6.3 and precipitation at pH above 6.3. This study demonstrates that R-nZVI has the potential to become an effective agent for treating wastewater containing Cr(VI) and Cr(III). PMID:23867839

Fu, Fenglian; Ma, Jun; Xie, Liping; Tang, Bing; Han, Weijiang; Lin, Suya

2013-07-15

34

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

Microsoft Academic Search

The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation\\u000a of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the\\u000a mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted\\u000a to evaluate the effect of different arrangements of

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

2005-01-01

35

Reducing degradation of azo dye by zero-valent iron in aqueous solution  

Microsoft Academic Search

The reducing degradation kinetics of five azo dyes, Acid orange II , Acid orange IV, Acid orange GG, Acid red 3B and Orange I , by zero-valent iron powder in aqueous solution were studied. It showed that the degradation is a two-step reaction, with the first step being reversible. Solution acidity and iron surface area are the factors greatly influencing

Jiasheng Cao; Liping Wei; Qingguo Huang; Liansheng Wang; Shuokui Han

1999-01-01

36

Competing TCE and cis-DCE degradation kinetics by zero-valent iron—experimental results and numerical simulation  

Microsoft Academic Search

The successful dechlorination of mixtures of chlorinated hydrocarbons with zero-valent metals requires information concerning the kinetics of simultaneous degradation of different contaminants. This includes intraspecies competitive effects (loading of the reactive iron surface by a single contaminant) as well as interspecies competition of several contaminants for the reactive sites available. In columns packed with zero-valent iron, the degradation behaviour of

Dirk Schäfer; Ralf Köber; Andreas Dahmke

2003-01-01

37

REDUCTION OF AZO DYES WITH ZERO-VALENT IRON. (R827117)  

EPA Science Inventory

The reduction of azo dyes by zero-valent iron metal (Fe0) at pH 7.0 in 10 mM HEPES buffer was studied in aqueous, anaerobic batch systems. Orange II was reduced by cleavage of the azo linkage, as evidenced by the production of sulfanilic acid (a substituted ani...

38

Effects of Nano Zero-Valent Iron on the Performance of Denitrification of Alcaligenes eutrophus  

Microsoft Academic Search

Being a strong redox agent, when nano zero-valent iron (NZVI) is much applied in the environmental remediation, it is important to understand if the functions of indigenous microorganisms have been affected. For this purpose, in this paper, effects of NZVI on the performance of denitrification of autotrophic denitrifying bacteria especially Alcaligenes eutrophus and possible toxicity mechanism were studied. The results

Meiying Dong; Fang Huang; Tielong Li; Meiting Ju

2011-01-01

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

REMOVAL OF HIGH-LEVEL ARSENIC 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...

41

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...

42

Zero-valent iron on Mars: An alternative energy source for methanogens  

NASA Astrophysics Data System (ADS)

Zero-valent iron, montmorillonite-like smectites, and CO 2 gas are known to exist on Mars, and work was performed to investigate the ability of methanogens to subsist on these materials. After 71 days of incubation at 55 °C, mean methane concentration as percent of headspace volume was 19.80 ± 1.76% (mean ± SE) for replicates containing elemental iron and 0.50 ± 0.15% for those lacking elemental iron.

Chastain, Brendon K.; Kral, Timothy A.

2010-07-01

43

Perchloroethene and Chromium Removal from Humic AcidContaining Groundwater by Zero-Valent Iron Systems  

Microsoft Academic Search

In zero-valent iron (Fe0) treatment systems, the co-presence of humic acid and divalent cations was found to impose combined effects that differ from corresponding individual effects. This study investigated the reactions of Fe0 with humic acid-containing solutions in batch experiments using HPSEC, TEM, FTIR, and XPS analyses. The formation of soluble iron-humate complexes in monovalent cation solution suppressed iron precipitation

Daniel C. W. Tsang; Irene M. C. Lo; Nigel J. D. Graham

2009-01-01

44

Arsenic removal by zero-valent iron: field, laboratory and modeling studies  

Microsoft Academic Search

Field and laboratory studies were conducted to elucidate the design factors and mechanisms of arsenic removal from contaminated ground water using zero-valent iron. Large scale, field pilot experiments demonstrated for more than 8 months that iron filing filters can efficiently remove arsenite from aqueous solutions to levels less than 10?g\\/L. The maximum arsenic accumulation measured was 4.4mg As\\/g of media.

Nikolaos P Nikolaidis; Gregory M Dobbs; Jeffrey A Lackovic

2003-01-01

45

Remediation of pyrene-contaminated soil by synthesized nanoscale zero-valent iron particles  

Microsoft Academic Search

Laboratory experiments were conducted to assess pyrene removal from soil using synthesized nanoscale zero-valent iron (nZVI) particles. Batch experiments indicated that nZVI particles were more efficient in removing pyrene than commercially available microscale ZVI (mZVI, < 10 ?m) particles. Reaction kinetics of pyrene removal were dominated by the iron dosage and approximated by a pseudo–first-order model. The reaction rate constants

Ming C. Chang; Hung Y. Kang

2009-01-01

46

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

47

Phenol degradation using hydroxyl radicals generated from zero-valent iron and hydrogen peroxide  

Microsoft Academic Search

The degradation of the model pollutant phenol with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of HPLC analysis of the intermediates. The optimum conditions for degradation utilise the continuous presence of iron metal, acidic pH and relatively concentrated hydrogen peroxide (9.5M). When less stringent conditions were used, the products obtained from the decomposition

David H. Bremner; Arthur E. Burgess; Didier Houllemare; Kyu-Cheol Namkung

2006-01-01

48

INFLUENCE OF GROUNDWATER GEOCHEMISTRY ON THE LONG-TERM PERFORMANCE OF IN-SITU PERMEABLE REACTIVE BARRIERS CONTAINING ZERO-VALENT IRON  

EPA Science Inventory

Reactive barriers that couple subsurface fluid flow with a passive chemical treatment zone are emerging, cost effective approaches for in-situ remediation of contaminated groundwater. Factors such as the build-up of surface precipitates, bio-fouling, and changes in subsurface tr...

49

Toxicity of nano-zero valent iron to freshwater and marine organisms.  

PubMed

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 Fe(2+) and Fe(3+) 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 Fe(2+) and Fe(3+). 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

2012-08-30

50

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.

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

2012-01-01

51

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...

52

Laboratory evaluation of zero-valent iron to treat water impacted by acid mine drainage  

Microsoft Academic Search

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 simulated mine drainage (initial pH 2.3–4.5; total dissolved solids 14000–16000 mgl?1). Metal removal from solution and

Richard T. Wilkin; Mary S. McNeil

2003-01-01

53

Effect of pH on Reduction of Nitrobenzene in Groundwater by Zero-Valent Iron  

Microsoft Academic Search

The effects of different pH values on the reduction of nitrobenzene (NB or ArNO2) by zero-valent iron (ZVI) were studied in groundwater through batch experiments. The concentrations of NB and its reduction product aniline were determined during the process of reaction. The changes in the reduction rates for nitrobenzene, the quantities of aniline formed, and the reaction kinetics during the

Lei Liu; Jun Yin; Liguo Zhang; Guoxiao Lu

2009-01-01

54

A field comparison of two reductive dechlorination (zero-valent iron and lactate) methods  

Microsoft Academic Search

Two parallel pilot experiments were performed at Kurivody (Czech Republic) in order to compare two reductive remedial technologies for chlorinated ethenes – microbial dehalogenation assisted by lactate and chemical dehalogenation with zero-valent iron (nZVI) nanoparticles. The methods were applied at a site contaminated by tetrachlorethylene (PCE) and trichlorethylene (TCE), with total concentrations from 10 to 50 mg\\/l. Concentrations of chlorinated ethenes,

Lenka Lacinova; Petr Kvapil; Miroslav Cernik

2012-01-01

55

A field comparison of two reductive dechlorination (zero-valent iron and lactate) methods  

Microsoft Academic Search

Two parallel pilot experiments were performed at Kurivody (Czech Republic) in order to compare two reductive remedial technologies for chlorinated ethenes – microbial dehalogenation assisted by lactate and chemical dehalogenation with zero-valent iron (nZVI) nanoparticles. The methods were applied at a site contaminated by tetrachlorethylene (PCE) and trichlorethylene (TCE), with total concentrations from 10 to 50 mg\\/l. Concentrations of chlorinated ethenes,

Lenka Lacinova; Petr Kvapil; Miroslav Cernik

2011-01-01

56

Effect of phosphate and sediment bacteria on trichloroethylene dechlorination with zero valent iron  

Microsoft Academic Search

The effects of sediment-isolated bacteria and phosphate on the efficacy of zero valent iron (ZVI) for the dechlorination of trichloroethylene (TCE) were examined in batch experiments. TCE (0.3 mM) and a constant concentration of sediment bacteria were simultaneously exposed to ZVI in the presence of 0 mmol, 15 mmol, and 30 mmol of phosphate. TCE profiles, starting from 0.3 mM

Jee-Eun Min; In Sun Park; Seokoh Ko; Won Sik Shin; Jae-Woo Park

2009-01-01

57

Enhanced degradation of carbon tetrachloride by surfactant-modified zero-valent iron  

Microsoft Academic Search

Sorption of carbon tetrachloride (CT) by zero-valent iron (ZVI) is the rate-limiting step in the degradation of CT, so the\\u000a sorption capacity of ZVI is of great importance. This experiment was aimed at enhancing the sorption of CT by ZVI and the\\u000a degradation rate of CT by modification of surfactants. This study showed that ZVI modified by cationic surfactants has

Ya-feng Meng; Bao-hong Guan; Zhong-biao Wu; Da-hui Wang

2006-01-01

58

Removal of hexavalent chromium from contaminated ground water using zero-valent iron nanoparticles  

Microsoft Academic Search

Batch experiments were conducted on ground water samples collected from a site contaminated with Cr(VI) to evaluate the redox\\u000a potential of zero-valent iron (Fe0) nanoparticles for remediation of Cr(VI)-contaminated ground water. For this, various samples of contaminated ground water\\u000a were allowed to react with various loadings of Fe0 nanoparticles for a reaction period of 60 min. Data showed 100% reduction of

Ritu Singh; Virendra Misra; Rana Pratap Singh

59

Application of nanoscale zero valent iron (NZVI) for groundwater remediation in Europe  

Microsoft Academic Search

Purpose  Nanoscale zero valent iron (NZVI) is emerging as a new option for the treatment of contaminated soil and groundwater targeting\\u000a mainly chlorinated organic contaminants (e.g., solvents, pesticides) and inorganic anions or metals. The purpose of this article\\u000a is to give a short overview of the practical experience with NZVI applications in Europe and to present a comparison to the\\u000a situation

Nicole C. Mueller; Jürgen Braun; Johannes Bruns; Miroslav ?erník; Peter Rissing; David Rickerby; Bernd Nowack

60

Zero-Valent Iron Removal Rates of Aqueous Cr(VI) Measured Under Flow Conditions  

Microsoft Academic Search

The rates of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), was measured under flow conditions. The intent\\u000a of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater\\u000a remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as

Daniel I. Kaplan; Tyler J. Gilmore

2004-01-01

61

Zero-valent iron nanoparticles in treatment of acid mine water from in situ uranium leaching  

Microsoft Academic Search

Acid mine water from in situ chemical leaching of uranium (Straz pod Ralskem, Czech Republic) was treated in laboratory scale experiments by zero-valent iron nanoparticles (nZVI). For the first time, nZVI were applied for the treatment of the real acid water system containing the miscellaneous mixture of pollutants, where the various removal mechanisms occur simultaneously. Toxicity of the treated saline

Stepanka Klimkova; Miroslav Cernik; Lenka Lacinova; Jan Filip; Dalibor Jancik; Radek Zboril

2011-01-01

62

Removal Rates of Aqueous Cr(VI) by Zero-Valent Iron Measured Under Flow Conditions  

Microsoft Academic Search

Studies were undertaken to measure the rate of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive

2002-01-01

63

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

Microsoft Academic Search

Chromate transport through columns packed with zeolite\\/zero valent iron (Z\\/ZVI) pellets, either untreated or treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA), was studied at different flow rates. In the presence of sorbed HDTMA, the chromate retardation factor increased by a factor of five and the pseudo first-order rate constant for chromate reduction increased by 1.5–5 times. The increase in rate

Zhaohui Li; H. Kirk Jones; Pengfei Zhang; Robert S. Bowman

2007-01-01

64

Assessment of transport of two polyelectrolyte-stabilized zero-valent iron nanoparticles in porous media  

Microsoft Academic Search

This study investigated the breakthrough patterns of carboxymethyl cellulose- and polyacrylic acid-stabilized zero-valent iron (Fe0) nanoparticles (NZVI) from packed sand columns under a range of pore water velocities of 0.02, 0.2 and 1cmmin?1 and NZVI influent concentrations of 0.1, 0.5 and 3gL?1. The NZVI effluent relative concentrations of both types of particles decreased with slower flow velocities and increasing particle

Trishikhi Raychoudhury; Ghinwa Naja; Subhasis Ghoshal

2010-01-01

65

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 Aznalcóllar (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, José Luis; de Pablo, Joan; Ayora, Carlos

2013-01-30

66

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 barrier’s 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

67

Effect of common ions on nitrate removal by zero-valent iron from alkaline soil.  

PubMed

Zero-valent iron (Fe(0))-based permeable reactive barrier (PRB) technology has been proved to be effective for soil and groundwater nitrate remediation under acidic or near neutral conditions. But few studies have been reported about it and the effects of coexistent ions under alkaline conditions. In this study, nitrate reduction by Fe(0) was evaluated via batch tests in the presence of alkaline soil and common cation (Fe(2+), Fe(3+) and Cu(2+)) and anion (citrate, oxalate, acetate, SO(4)(2-), PO(4)(3-), Cl(-) and HCO(3)(-)). The results showed that cation significantly enhanced nitrate reduction with an order of Fe(3+)>Fe(2+)>Cu(2+) due to providing Fe(2+) directly or indirectly. Most anions enhanced nitrate reduction, but PO(4)(3-) behaved inhibition. The promotion decreased in the order of citrate>acetate>SO(4)(2-)>Cl(-)?HCO(3)(-)?oxalate?PO(4)(3-). Ammonium was the major final product from nitrate reduction by Fe(0), while a little nitrite accumulated in the beginning of reaction. The nitrogen recovery in liquid and gas phase was only 56-78% after reaction due to ammonium adsorption onto soil. The solution pH and electric conductivity (EC) varied depending on the specific ion added. The results implied that PRB based Fe(0) is a potential approach for in situ remediation of soil and groundwater nitrate contamination in the alkaline conditions. PMID:22795587

Tang, Cilai; Zhang, Zengqiang; Sun, Xining

2012-06-29

68

ZERO-VALENT IRON PRB APPLICATION EXPANDS TO ARSENIC REMOVAL  

EPA Science Inventory

The U.S. EPA Office of Research and Developmentâ??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, ...

69

Rapid removal of flutriafol in water by zero-valent iron powder  

Microsoft Academic Search

A study of the effect of zero-valent iron (ZVI) powder is carried out for the first time on the degradation of flutriafol ((RS)-2,4?-difluoro-?-(1H-1,2,4-triazol-1-ylmethyl)-benzhydryl alcohol, C16H13F2N3O), a bifluorinated soil and water persistent triazole pesticide using a laboratory scale device consisting of a 20ml pyrex serum vials fixed to a Vortex agitator. Different amounts of ZVI powder (10–50gl?1) at pH 6.6 and

Antoine Ghauch

2008-01-01

70

Laboratory evaluation of zero-valent iron to treat water impacted by acid mine drainage.  

PubMed

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 simulated mine drainage (initial pH 2.3-4.5; total dissolved solids 14000-16000 mgl(-1)). Metal removal from solution and acid-neutralization occurred simultaneously and were most rapid during the initial 24 h of reaction. Reaction half-lives ranged from 1.50+/-0.09 h for Al to 8.15+/-0.36 h for Zn. Geochemical model results indicate that metal removal is most effective in solutions that are highly undersaturated with respect to pure-metal hydroxides suggesting that adsorption is the initial and most rapid metal uptake mechanism. Continued adsorption onto or co-precipitation with iron corrosion products are secondary metal uptake processes. Sulfate green rust was identified as the primary iron corrosion product, which is shown to be the result of elevated [SO(4)(2-)]/[HCO(3)(-)] ratios in solution. Reversibility studies indicate that zero-valent iron will retain metals after shifts in redox states are imposed, but that remobilization of metals may occur after the acid-neutralization capacity of the material is exhausted. PMID:13129511

Wilkin, Richard T; McNeil, Mary S

2003-11-01

71

Reduction and immobilization of radionuclides and toxic metal ions using combined zero valent iron and anaerobic bacteria. 1998 annual progress report  

Microsoft Academic Search

'Previous research findings indicate that both zero valent iron and sulfate reducing bacteria (SRB) can yield significant decreases in Cr(VI) or U(VI) concentrations due to abiotic and microbial reduction, respectively. The major hypothesis associated with this research project is that a combined abiotic-biological system can synergistically combine both processes to maximize metal ion reduction in an engineered permeable reactive barrier.

Weathers

1998-01-01

72

Remediation of chromate-contaminated groundwater using zero-valent iron: Field test at USCG Support Center, Elizabeth City, North Carolina  

Microsoft Academic Search

A field test was conducted near an old hard-chrome plating facility on the USCG Support Center near Elizabeth City, North Carolina to evaluate the in situ remediation of ground water contaminated by hexavalent chromium using a passive permeable reactive barrier composed of a zero-valent iron-sand-aquifer material mixture. The remedial effectiveness of this innovative in situ technology was in situ technology

R. W. Puls; C. J. Paul; R. M. Powell

1996-01-01

73

Remediation of chromate-contaminated groundwater using zero-valent iron: Field test at USCG Support Center, Elizabeth City, North Carolina  

SciTech Connect

A field test was conducted near an old hard-chrome plating facility on the USCG Support Center near Elizabeth City, North Carolina to evaluate the in situ remediation of ground water contaminated by hexavalent chromium using a passive permeable reactive barrier composed of a zero-valent iron-sand-aquifer material mixture. The remedial effectiveness of this innovative in situ technology was in situ technology was monitored over a one year period.

Puls, R.W.; Paul, C.J.; Powell, R.M.

1996-12-31

74

TREATABILITY STUDY BY NEW JERSEY INSTITUTE OF TECHNOLOGY (NJIT) USING ZERO-VALENT IRON TO TREAT SOILS CONTAMINATED BY PCBS AND LEAD  

EPA Science Inventory

Contaminated wetlands soils from the Burnt Fly Bog Superfund site will be treated with a newly developed variety of zero-valent iron. Although zero-valent iron has been shown effective for treating chlorinated solvents, its ability to effectively treat PCBs is unproven. The tre...

75

Generation of free radicals, analytical methods, bacterial disinfections, and oxidative destruction of organic chemicals using zero valent iron and other metals  

US Patent & Trademark Office Database

Disclosed are methods for chemical analysis, bacterial disinfection, oxidative destruction and/or mineralization of organic compounds comprising using zero-valent iron and/or zero-valent iron-containing bimetallic compounds, preferably in acidic solution and/or in the presence of oxygen.

Rima; Jamil (Beirut, LB); Li; Qing X. (Honolulu, HI); Aouezova; Lizette (Beirut, LB)

2011-11-01

76

Dechlorination of short chain chlorinated paraffins by nanoscale zero-valent iron.  

PubMed

In this study, nanoscale zero-valent iron (NZVI) particles were synthesized and used for the reductive dehalogenation of short chain chlorinated paraffins (SCCPs) in the laboratory. The results show that the dechlorination rate of chlorinated n-decane (CP(10)) by NZVI increased with decreased solution pH. Increasing the loading of NZVI enhanced the dechlorination rate of CP(10). With an increase in temperature, the degradation rate increased. The reduction of CP(10) by NZVI was accelerated with increasing the concentration of humic acid up to 15 mg/L but then was inhibited. The dechlorination of CP(10) within the initial 18 h followed pseudo-first order rate model. The formation of intermediate products indicates a stepwise dechlorination pathway of SCCPs by NZVI. The carbon chain length and chlorination degree of SCCPs have a polynominal impact on dechlorination reactions. PMID:23107289

Zhang, Zhi-Yong; Lu, Mang; Zhang, Zhong-Zhi; Xiao, Meng; Zhang, Min

2012-10-11

77

Effects of various ions on the dechlorination kinetics of hexachlorobenzene by nanoscale zero-valent iron.  

PubMed

The effect of several anions and cations normally co-present in soil and groundwater contamination sites on the degradation kinetics and removal efficiency of hexachlorobenzene (HCB) by nanoscale zero-valent iron (NZVI) particles was examined. The degradation kinetics was not influenced by the HCO(3)(-), Mg(2+), and Na(+) ions. It was enhanced in the presence of the Cl(-) and SO(4)(2-) ions due to their corrosion promotion. The NO(3)(-) competes with HCB so it inhibits the degradation reaction. The Fe(2+) ions would inhibit the degradation reaction due to passivation layer formed, while it was enhanced in the presence of Cu(2+) ions resulted from the reduced form of copper on NZVI surfaces. These observations lead to a better understanding of HCB dechlorination with NZVI particles and can facilitate the remediation design and prediction of treatment efficiency of HCB at remediation sites. PMID:22704216

Su, Yuh-fan; Hsu, Chung-Yu; Shih, Yang-hsin

2012-06-15

78

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

2011-05-17

79

Micro-electrolysis of Cr (VI) in the nanoscale zero-valent iron loaded activated carbon.  

PubMed

In this paper we prepared a novel material of activated carbon/nanoscale zero-valent iron (C-Fe(0)) composite. The C-Fe(0) was proved to possess large specific surface area and outstanding reducibility that result in the rapid and stable reaction with Cr (VI). The prepared composite has been examined in detail in terms of the influence of solution pH, concentration and reaction time in the Cr (VI) removal experiments. The results showed that the C-Fe(0) formed a micro-electrolysis which dominated the reaction rate. The Micro-electrolysis reaches equilibrium is ten minutes. Its reaction rate is ten times higher than that of traditional adsorption reaction, and the removal rate of Cr reaches up to 99.5%. By analyzing the obtained profiles from the cyclic voltammetry, PXRD and XPS, we demonstrate that the Cr (VI) is reduced to insoluble Cr (III) compound in the reaction. PMID:23632041

Wu, Limei; Liao, Libing; Lv, Guocheng; Qin, Faxiang; He, Yujuan; Wang, Xiaoyu

2013-03-14

80

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

81

Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate(VI)\\/(III) composite  

Microsoft Academic Search

Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mössbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical

Radek Zboril; Marek Andrle; Frantisek Oplustil; Libor Machala; Jiri Tucek; Jan Filip; Zdenek Marusak; Virender K. Sharma

82

Reduction of 1,2-dibromoethane in the presence of zero-valent iron  

SciTech Connect

The degradation reaction of 1,2-dibromoethane (ethylene dibromide or EDB) in water was studied in the presence of zero-valent iron (acid-cleaned, cast iron) in well-mixed batch aqueous systems. The observed products were ethylene and bromide ions. Carbon and bromine mass recoveries of >95% were obtained. Bromoethane and vinyl bromide were not observed. The reduction rates of bromoethane and vinyl bromide with iron indicate that they should have been observed if they were significant reaction intermediates for EDB. The results indicate that reductive {beta}-elimination may be the dominant reaction pathway. Reaction kinetics are rapid and pseudo-first order. The activation energy was determined to be 50 kJ/mol, indicating that the reaction rate may not be aqueous phase diffusion controlled but rather controlled by the chemical reaction rate on the iron surface. Metallic iron may be a suitable treatment approach for EDB-contaminated groundwater in above-ground, as well as in situ applications, due to rapid kinetics and nontoxic products.

Rajagopal, V.K.; Burris, D.R.

1999-08-01

83

Effects of alcohols, anionic and nonionic surfactants on the reduction of pce and tce by zero-valent iron  

Microsoft Academic Search

The effects of surfactants, sodium dodecyl sulfate (SDS) and Triton X-a00 (TX), and alcohols (methanol, ethanol, and propanol) on the dehalogenation of TCE and PCE by zero-valent iron were examined. Surface concentrations of PCE and TCE on the iron were dependent on aqueous surfactant concentrations. At concentrations above the CMC, sorbed halocarbon concentrations declined and concentrations associated with solution phase

Gregory A Loraine

2001-01-01

84

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

Microsoft Academic Search

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

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

2007-01-01

85

Using resin supported nano zero-valent iron particles for decoloration of Acid Blue 113 azo dye solution  

Microsoft Academic Search

In this study, a synthesized cation exchange resin supported nano zero-valent iron (NZVI) complex forming NZVI–resin was proposed for the decoloration of an azo dye Acid Blue 113 (AB 113), taking into account reaction time, initial dye concentration, NZVI dose and pH. From results, the successful decoloration of the AB 113 solution was observed using a NZVI–resin. Increasing the iron

Hung-Yee Shu; Ming-Chin Chang; Chi-Chun Chen; Po-En Chen

2010-01-01

86

Investigation of the long-term performance of zero-valent iron for reductive dechlorination of trichloroethylene  

Microsoft Academic Search

This research investigated the long-term performance of zero-valent iron for mediating the reductive dechlorination of trichloroethylene (TCE). Over a 2-year period, rates of TCE dechlorination in columns packed with iron filings were measured in simulated groundwaters containing either 3 mM CaSOâ, 5 mM CaClâ, or 5 mM Ca(NOâ)â. At early elapsed times, TCE reaction rates were pseudo-first-order in TCE concentration

James Farrell; Mark Kason; Nicos Melitas; Tie Li

2000-01-01

87

Remediation of soil contaminated with pyrene using ground nanoscale zero-valent iron  

SciTech Connect

The sites contaminated with recalcitrant polycyclic aromatic hydrocarbons (PAHs) are serious environmental problems ubiquitously. Some PAHs have proven to be carcinogenic and hazardous. Therefore, the innovative PAH in situ remediation technologies have to be developed instantaneously. Recently, the nanoscale zero-valent iron (ZVI) particles have been successfully applied for dechlorination of organic pollutants in water, yet little research has investigated for the soil remediation so far. The objective in this work was to take advantage of nanoscale ZVI particles to remove PAHs in soil. The experimental factors such as reaction time, particle diameter and iron dosage and surface area were considered and optimized. From the results, both microscale and nanoscale ZVI were capable to remove the target compound. The higher removal efficiencies of nanoscale ZVI particles were obtained because the specific surface areas were about several dozens larger than that of commercially microscale ZVI particles. The optimal parameters were observed as 0.2 g iron/2 mL water in 60 min and 150 rpm by nanoscale ZVI. Additionally, the results proved that nanoscale ZVI particles are a promising technology for soil remediation and are encouraged in the near future environmental applications. Additionally, the empirical equation developed for pyrene removal efficiency provided the good explanation of reaction behavior. Ultimately, the calculated values by this equation were in a good agreement with the experimental data. 19 refs., 9 figs., 2 tabs.

Ming-Chin Chang; Hung-Yee Shu; Wen-Pin Hsieh; Min-Chao Wang [Hungkuang University, Taichung (China). Department of Environmental Engineering

2007-02-15

88

A built-in zero valent iron anaerobic reactor to enhance treatment of azo dye wastewater.  

PubMed

Waste scrap iron was packed into an upflow anaerobic sludge blanket (UASB) reactor to form a zero valent iron (ZVI) - UASB reactor system for treatment of azo dye wastewater. The ZVI acted as a reductant to decrease ORP in the reactor by more than 40 mv and functioned as an acid buffer to increase the pH in the reactor from 5.44 to 6.29, both of which improved the performance of the anaerobic reactor. As a result, the removal of color and COD in this reactor was 91.7% and 53%, respectively, which was significantly higher than that of a reference UASB reactor without ZVI. The UV-visible spectrum demonstrated that absorption bands of the azo dye from the ZVI-UASB reactor were substantially reduced. The ZVI promoted methanogenesis, which was confirmed by an increase in CH(4) content in the biogas from 47.9% to 64.8%. The ZVI bed was protected well from rusting, which allowed it to function stably. The effluent could be further purified only by pH adjustment because the Fe(2+) released from ZVI served as a flocculent. PMID:21330722

Zhang, Yaobin; Jing, Yanwen; Quan, Xie; Liu, Yiwen; Onu, Pascal

2011-01-01

89

Degradation of chloropicrin in the presence of zero-valent iron.  

PubMed

Halonitromethanes (HNMs) are a class of halogenated disinfection byproducts formed upon the addition of chlorine to water containing organic matter. Batch experiments were performed to investigate the reaction pathways and kinetics of three HNMs (chloropicrin or trichloronitromethane [TCNM], dichloronitromethane [DCNM], and chloronitromethane [CNM]) with zero-valent iron (Fe0). All three compounds reacted rapidly in the presence of Fe0 (1.8-4.4 g/L) with methylamine (MA) as the final product. The geometric surface area-normalized rate constants decreased with decreasing halogenation: TCNM (301 L/[h-m2]) > DCNM (153 L/(h-m2)) > CNM (45.9 L/[h-m2]). Nitromethane, an intermediate species, rapidly reacted to form MA (302 L/[h-m2]). These reactions all experienced some degree of mass transfer limitation (9-73%). The average carbon and chlorine mass balances for TCNM were >85%, indicating that the major reaction products were recovered. The degradation of TCNM and DCNM proceeded via the parallel reaction pathways of hydrogenolysis and alpha-elimination. For TCNM, 60.7 +/- 8.7% of reaction proceeded via hydrogenolysis and 39.3 +/- 6.4% via alpha-elimination. Knowledge of HNM reaction pathways and kinetics in the presence of Fe0 may be useful for predicting the fate of these compounds in drinking water distribution systems containing cast or ductile iron pipe and for developing treatment systems for HNM removal from water. PMID:16445082

Pearson, Carrie R; Hozalski, Raymond M; Arnold, William A

2005-12-01

90

Green production of zero-valent iron nanoparticles using tree leaf extracts.  

PubMed

The interest in zero-valent iron nanoparticles has been increasing significantly since the development of a green production method in which extracts from natural products or wastes are used. However, this field of application is yet poorly studied and lacks knowledge that allows the full understanding of the production and application processes. The aim of the present work was to evaluate the viability of the utilization of several tree leaves to produce extracts which are capable of reducing iron(III) in aqueous solution to form nZVIs. The quality of the extracts was evaluated concerning their antioxidant capacity. The results show that: i) dried leaves produce extracts with higher antioxidant capacities than non-dried leaves, ii) the most favorable extraction conditions (temperature, contact time, and volume:mass ratio) were identified for each leaf, iii) with the aim of developing a green, but also low-cost, method water was chosen as solvent, iv) the extracts can be classified in three categories according to their antioxidant capacity (expressed as Fe(II) concentration): >40 mmol L(-1); 20-40 mmol L(-1); and 2-10 mmol L(-1); with oak, pomegranate and green tea leaves producing the richest extracts, and v) TEM analysis proves that nZVIs (d=10-20 nm) can be produced using the tree leaf extracts. PMID:23298788

Machado, S; Pinto, S L; Grosso, J P; Nouws, H P A; Albergaria, J T; Delerue-Matos, C

2013-01-07

91

Effect of humic acids on heavy metal removal by zero-valent iron in batch and continuous flow column systems.  

PubMed

The effects of Aldrich humic acids (HA) on the removal of Zero-valent iron (ZVI) was investigated in laboratory systems. In batch, the removal rate of Zn and Ni (5 mg l(-1)) was, respectively, 2.8 and 2.4 times lower in the presence of HA (20 mg l(-1)) than in the absence of HA, presumably due to the formation of HA-heavy metal complexes which prevented the removal reactions at the ZVI surface. Chromate removal was not affected. In a column test, two parallel systems were supplemented with a continuous input of simulated groundwater containing a mixture of the heavy metals Zn, Ni and Cr(VI) (5 mg l(-1) each), with or without HA (at 20 mg l(-1)). Initially, the two column systems efficiently (>90%) removed the heavy metals from the simulated groundwater. When the input heavy metal concentration was increased to 8-10 mg l(-1), a significant breakthrough of Ni and Zn, up to 80%, occurred in the column system fed with HA. Chromate and HA did not significantly break through. After 60 weeks, the effect of HA on leaching of the accumulated metals (approx. 2 mg g(-1)) was investigated. No significant leaching was observed. The results of this study suggest that the impact of dissolved organic matter on the efficiency and lifetime of a ZVI barrier for in situ removal of heavy metals should be considered in the design of the barrier. PMID:16095659

Dries, Jan; Bastiaens, Leen; Springael, Dirk; Kuypers, Stefaan; Agathos, Spiros N; Diels, Ludo

2005-09-01

92

Fine structure characterization of zero-valent iron nanoparticles for decontamination of nitrites and nitrates in wastewater and groundwater  

Microsoft Academic Search

The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation

Kuen-Song Lin; Ni-Bin Chang; Tien-Deng Chuang

2008-01-01

93

Injection of Nano Zero-Valent Iron for Subsurface Remediation: Evaluation of Methods for Assessment of Nanoparticle Delivery (Invited)  

Microsoft Academic Search

Among emerging technologies for in situ remediation of subsurface contamination, injection of nano-sized zero-valent iron (nZVI) stands out for the sudden growth in interest it has attracted. Field scale applications of this technology exist for a variety of types of sites, and most of these projects have been described as being successful. None of these sites have been extensively characterized,

P. G. Tratnyek; Z. Shi; J. T. Nurmi; R. L. Johnson

2010-01-01

94

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

Microsoft Academic Search

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

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

95

Effect of pH and Dissolved Oxygen on the Cr(VI) Removal by Zero-Valent Iron  

Microsoft Academic Search

Chromate (Cr(VI)) is an industrial contaminant in groundwater and soil, and known as a carcinogen material. In this study, the effect of pH and dissolved oxygen (DO) for Cr(VI) removal by Zero-Valent Iron (ZVI) was investigated using batch and column experiments. Under oxic condition, 5 mg\\/L Cr(VI) in batch experiments was completely removed by 1 g ZVI at pH 4,

In-Ho Yoon; Kyoung-Woong Kim

96

Effect of humic acids on heavy metal removal by zero-valent iron in batch and continuous flow column systems  

Microsoft Academic Search

The effects of Aldrich humic acids (HA) on the removal of Zero-valent iron (ZVI) was investigated in laboratory systems. In batch, the removal rate of Zn and Ni (5mgl?1) was, respectively, 2.8 and 2.4 times lower in the presence of HA (20mgl?1) than in the absence of HA, presumably due to the formation of HA–heavy metal complexes which prevented the

Jan Dries; Leen Bastiaens; Dirk Springael; Stefaan Kuypers; Spiros N. Agathos; Ludo Diels

2005-01-01

97

Influence of nanoscale zero-valent iron on geochemical properties of groundwater and vinyl chloride degradation: A field case study  

Microsoft Academic Search

A 200m2 pilot-scale field test successfully demonstrated the use of nanoscale zero-valent iron (NZVI) for effective remediation of groundwater contaminated with chlorinated organic compounds in Taiwan within six months. Both commercially available and on-site synthesized NZVI were used. A well-defined monitoring program allowing to collect three-dimensional spatial data from 13 nested multi-level monitoring wells was conducted to monitor geochemical parameters

Yu-Ting Wei; Shian-Chee Wu; Chih-Ming Chou; Choi-Hong Che; Shin-Mu Tsai; Hsing-Lung Lien

2010-01-01

98

Enhanced treatment of wastewater from the vitamin C biosynthesis industry using a UASB reactor supplemented with zero-valent iron  

Microsoft Academic Search

The effects of zero-valent iron (Fe) on the performance of a mesophilic upflow anaerobic sludge blanket (UASB) reactor treating high-strength wastewater from the vitamin C biosynthesis industry (VCW) was investigated during a 200-day period. The results showed that the chemical oxygen demand (COD) removal efficiency, CH4 content in biogas, specific methanogenic activity of sludge, and phosphate removal efficiency were significantly

Rongjiu Shi; Hui Xu; Ying Zhang

2011-01-01

99

Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability  

Microsoft Academic Search

To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template

Hanzhong Jia; Chuanyi Wang

2012-01-01

100

Atmospherically stable nanoscale zero-valent iron particles formed under controlled air contact: characteristics and reactivity.  

PubMed

Atmospherically stable NZVI (nanoscale zero-valent iron) particles were produced by modifying shell layers of Fe(H2) NZVI particles (RNIP-10DS) by using a controlled air contact method. Shell-modified NZVI particles were resistant to rapid aerial oxidation and were shown to have TCE degradation rate constants that were equivalent to 78% of those of pristine NZVI particles. Fe(H2) NZVI particles that were vigorously contacted with air (rapidly oxidized) showed a substantially compromised reactivity. Aging of shell-modified particles in water for one day resulted in a rate increase of 54%, implying that depassivation of the shell would play an important role in enhancing reactivity. Aging of shell-modified particles in air led to rate decreases by 14% and 46% in cases of one week and two months of aging, respectively. A series of instrumental analyses using transmission electron microscopy, X-ray diffractography, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure showed that the shells of modified NZVI particles primarily consisted of magnetite (Fe(3)O(4)). Analyses also implied that the new magnetite layer produced during shell modification was protective against shell passivation. Aging of shell-modified particles in water yielded another major mineral phase, goethite (alpha-FeOOH), whereas aging in air produced additional shell phases such as wustite (FeO), hematite (alpha-Fe(2)O(3)), and maghemite (gamma-Fe(2)O(3)). PMID:20136088

Kim, Hong-Seok; Ahn, Jun-Young; Hwang, Kyung-Yup; Kim, Il-Kyu; Hwang, Inseong

2010-03-01

101

Synergetic decolorization of reactive blue 13 by zero-valent iron and anaerobic sludge.  

PubMed

Efficient decolorization of reactive blue 13 was achieved by a combined use of anaerobic sludge and zero-valent iron (ZVI), and the underlying mechanism of this process was elucidated, Addition of 1.0g/L ZVI into sludge accelerated the decolorization, with the decoloration ratio after 1-h treatment increased by 29.4% compared with the sum of the individual systems, indicating a synergy between the sludge and ZVI. Meanwhile, substantial changes in sludge morphology and microbial community were observed. The increased dye removal by ZVI was mainly attributed to: (1) a directly chemical reduction and aggregation; and (2) creation of a more favorable pH and anaerobic environment for microorganisms. The acid production by acidogens also partially offset the pH rise in ZVI corrosion and would alleviate ZVI deactivation. This work might offer valuable implications for the optimization and practical application of ZVI-anaerobic sludge processes for treatment of azo dyes or other recalcitrant pollutants. PMID:24084202

Li, Wen-Wei; Zhang, Yang; Zhao, Jin-Bao; Yang, Ya-Li; Zeng, Raymond J; Liu, Hou-Qi; Feng, Yu-Jie

2013-09-17

102

Phytotoxicity and uptake of nanoscale zero-valent iron (nZVI) by two plant species.  

PubMed

Use of nano-scale zero valent iron (nZVI) for the treatment of various environmental pollutants has been proven successful. However, large scale introduction of engineered nanomaterials such as nZVI into the environment has recently attracted serious concerns. There is an urgent need to investigate the environmental fate and impact of nZVI due to the scope of its application. The goal of this study was to evaluate the toxicity and accumulation of bare nZVI by two commonly encountered plant species: cattail (Typha latifolia) and hybrid poplars (Populous deltoids×Populous nigra). Plant seedlings were grown hydroponically in a greenhouse and dosed with different concentrations of nZVI (0-1000 mg/L) for four weeks. The nZVI exhibited strong toxic effect on Typha at higher concentrations (>200 mg/L) but enhanced plant growth at lower concentrations. nZVI also significantly reduced the transpiration and growth of hybrid poplars at higher concentrations. Microscopic images indicated that large amount of nZVI coated on plant root surface as irregular aggregates and some nZVI penetrated into several layers of epidermal cells. Transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) confirmed the internalization of nZVI by poplar root cells but similar internalization was not observed for Typha root cells. The upward transport to shoots was minimal for both plant species. PMID:23247287

Ma, Xingmao; Gurung, Arun; Deng, Yang

2012-12-17

103

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

2007-03-30

104

Reductive degradation of carbaryl in water by zero-valent iron.  

PubMed

Reduction of carbaryl solution by zero-valent iron powder (ZVIP) was studied in a rotator batch system (70 rpm) in order to evaluate the utility of this reaction in remediation of carbamate contaminated water. Degradation with different amount of ZVIP: 0.01, 0.02, 0.03, 0.04 g/ml at pH 6.6 and at ambient temperature was investigated. The results show that the process exhibits a degradation rate appearing to be directly proportional to the surface contact area of ZVIP (325-mesh) with the carbaryl molecules. Three analytical techniques were used to monitor carbaryl degradation: (1) A UV-Vis diode array spectrophotometer was used to record all spectra. (2) A high performance liquid chromatography was used to separate by-products and examine the evolution of breakdown products. (3) A home-built spectrophosphorimeter that uses the solid surface room temperature phosphorescence (SSRTP) was employed to observe selectively the decline of the carbaryl concentration at different amount of ZVIP on Whatman no. 1 filter paper. Results show that the reducing degradation of carbaryl with ZVIP as the source of electrons is effective with a half-life close to several minutes. PMID:11100794

Ghauch, A; Gallet, C; Charef, A; Rima, J; Martin-Bouyer, M

2001-02-01

105

Mobility of Nano-scale Zero Valent Iron in Porous Media with Residual NAPL  

NASA Astrophysics Data System (ADS)

Nano-scale Zero Valent Iron (nZVI) has been the focus of many studies in recent years aimed to remediate priority source zone pollutants. Existing technologies are frequently unable to achieve clean up goals in contaminated aquifers at the completion of remedial activities. The problem relates to the inability of existing remedial technologies to remove sufficient free phase NAPL mass in the subsurface to significantly reduce dissolved aqueous phase NAPL concentrations. The reactivity of nanoparticles and the ability to precisely design and synthesize nanoparticles make them particularly attractive for the remediation of free phase chlorinated solvents in the subsurface. This remediation technology involves a series of steps: the transport of the nanoparticles, with the bulk aqueous phase (or some delivery fluid), to the NAPL contaminated zone, nanoparticle partitioning to the NAPL/aqueous phase interface, and nanoparticle reaction with the chlorinated solvents to form less toxic daughter products. In this study the ability of stabilized nZVI particles to achieve the first two processes was assessed. A series of column experiments were conducted utilizing a variety of NAPLs at residual saturations. Experimental conditions were representative of those that would be found at contaminated sites (eg: pore water velocity). The mobility and partitioning of the stabilized nZVI particles in these systems will be presented. In addition the potential of stabilized nZVI particles for chlorinated solvent source zone remediation will be discussed.

Kocur, C. M.; O'Carroll, D. M.; Sakulchaicharoen, N.

2008-12-01

106

Enhanced degradation of carbon tetrachloride by surfactant-modified zero-valent iron*  

PubMed Central

Sorption of carbon tetrachloride (CT) by zero-valent iron (ZVI) is the rate-limiting step in the degradation of CT, so the sorption capacity of ZVI is of great importance. This experiment was aimed at enhancing the sorption of CT by ZVI and the degradation rate of CT by modification of surfactants. This study showed that ZVI modified by cationic surfactants has favorable synergistic effect on the degradation of CT. The CT degradation rate of ZVI modified by cetyl pyridinium bromide (CPB) was higher than that of the unmodified ZVI by 130%, and the CT degradation rate of ZVI modified by cetyl trimethyl ammonium bromide (CTAB) was higher than that of the unmodified ZVI by 81%. This study also showed that the best degradation effect is obtained at the near critical micelle concentrations (CMC) and that high loaded cationic surfactant does not have good synergistic effect on the degradation due to its hydrophilicity and the block in surface reduction sites. Furthermore degradation of CT by ZVI modified by nonionic surfactant has not positive effect on the degradation as the ionic surfactant and the ZVI modified by anionic surfactant has hardly any obvious effects on the degradation.

Meng, Ya-feng; Guan, Bao-hong; Wu, Zhong-biao; Wang, Da-hui

2006-01-01

107

Modelling of sequential groundwater treatment with zero valent iron and granular activated carbon  

NASA Astrophysics Data System (ADS)

Multiple contaminant mixtures in groundwater may not efficiently be treated by a single technology if contaminants possess rather different properties with respect to sorptivity, solubility, and degradation potential. An obvious choice is to use sequenced units of the generally accepted treatment materials zero valent iron (ZVI) and granular activated carbon (GAC). However, as the results of this modelling study suggest, the required dimensions of both reactor units may strongly differ from those expected on the grounds of a contaminant-specific design. This is revealed by performing an analysis for a broad spectrum of design alternatives through numerical experiments for selected patterns of contaminant mixtures consisting of monochlorobenzene, tetrachloroethylene, trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), and vinyl chloride (VC). It is shown that efficient treatment can be achieved only if competitive sorption effects in the GAC unit as well as the formation of intermediate products in the ZVI unit are carefully taken into account. Cost-optimal designs turned out to vary extremely depending on the prevailing conditions concerning contaminant concentrations, branching ratios, and unit costs of both reactor materials. Where VC is the critical contaminant, due to high initial concentration or extensive production as an intermediate, two options are cost-effective: an oversized ZVI unit with an oversized GAC unit or a pure GAC reactor.

Bayer, Peter; Finkel, Michael

2005-06-01

108

Effects of Nano Zero-Valent Iron on Klebsiella oxytoca and Stress Response.  

PubMed

Nano zero-valent iron (NZVI) is a new option for contaminated soil and groundwater treatment, despite little is known on their impact on environmental microorganisms. Klebsiella oxytoca K5 strain, isolated from the NZVI-treated soil, was used to investigate the bacterial, phenotypical and molecular response to commercial NZVI exposure. Cytotoxicity assays at three NZVI concentrations (1, 5 and 10 mg mL(-1)) suggested a negligible bacteriostatic effect and the lack of bactericidal effect. Structural changes were analysed by electronic microscopy. Scanning electron microscopy revealed the presence of NZVI around some bacterial cells, but no apparent morphological changes were seen. NZVI attachment to the cell surface was confirmed by transmission electron microscopy, although most of them were not affected. A proteomic approach (two-dimensional electrophoresis, matrix-assisted laser desorption ionization time-of-flight mass spectrometry) was used to investigate NZVI impact. For the first time to our knowledge, results revealed that exposure of a soil bacterium to NZVI resulted in the overproduction of tryptophanase, associated with oxidative stress response. K5 may set up an adaptative stress response involving indole as a signal molecule to inform the bacterial population about environmental changes. These findings would improve knowledge on the molecular mechanisms underlying bacterial response to NZVI exposure. PMID:23893265

Saccŕ, Maria Ludovica; Fajardo, Carmen; Nande, Mar; Martín, Margarita

2013-07-28

109

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

Microsoft Academic Search

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

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

2010-01-01

110

Conceptual comparison of pink water treatment technologies: granular activated carbon, anaerobic fluidized bed, and zero-valent iron-Fenton process  

Microsoft Academic Search

Pink water, explosive-laden wastewater produced in army ammunition plants is often treated using expensive and non-destructive granular activated carbon (GAC) adsorption. This paper compares GAC adsorption and two alternative treatment technologies, anaerobic GAC fluidized bed reactor and zero- valent iron-Fenton process. The bench-scale demonstration of the zero-valent iron-Fenton process with real pink water is reported. The features of three technologies

S.-Y. Oh; D. K. Cha; P. C. Chiu; B. J. Kim

111

Kinetics and mechanisms of pH-dependent selenite removal by zero valent iron.  

PubMed

The kinetics of Se(IV) removal by zero valent iron (ZVI) open to the air as a function of pH and the involved mechanisms were investigated in this study. The specific rate constants of Se(IV) removal by ZVI decreased from 92.87 to 6.87 L h(-1) m(-2) as pH increased from 4.0 to 7.0. The positive correlation between the removal rate of Se(IV) and the generation rate of Fe(II) and the depression of Se(IV) removal in the presence of 1,10-phenanthroline indicated that both ZVI and adsorbed Fe(II) on ZVI surface contributed to the reductive removal of Se(IV). The soft X-ray STXM measurement confirmed the adsorption of Fe(II) on the surface of ZVI and freshly formed ferric (hydr)oxides. Se(IV) was removed by adsorption followed by reduction to Se(0) on ZVI surface at pH 4.0-7.0, as revealed by XANES spectra. A core-shell structure was observed when ZVI reacted with Se(IV)-containing solution for 3 h at pH 6.0. Se(IV) was reduced to Se(0) and co-precipitated with the freshly formed Fe(III), forming the shell surrounding the iron core. After reaction for 24 h, the generated Se(0) was surrounded by multiple layers of Fe(III) oxides/hydroxides. SEM images and XRD patterns revealed that the corrosion products of ZVI at pH 6.0 transformed from amorphous iron hydroxides to lepidocrocite (?-FeOOH) as reaction proceeded. The final corrosion products of ZVI contained both lepidocrocite and goethite at pH 5.0 while they were X-ray amorphous at pH 4.0 and 7.0. PMID:23899877

Liang, Liping; Yang, Wenjun; Guan, Xiaohong; Li, Jialing; Xu, Zijian; Wu, Jiang; Huang, Yuying; Zhang, Xiangzi

2013-07-16

112

Effects of pH and particle size on kinetics of nitrobenzene reduction by zero-valent iron.  

PubMed

Nitrobenzene has been considered as a significant groundwater contaminant due to its wide usage in explosives, insecticides, herbicides, pharmaceuticals and dyes. Nitrobenzene is of environmental concern because of its toxicity. In the presence of zero-valent iron (ZVI), reduction of the nitro group is the dominant transformation process for nitrobenzene. A series of experiments were carried out to investigate the kinetics of nitrobenzene reduction by ZVI and the effects of pH and ZVI particle size on nitrobenzene removal in groundwater. The results indicated that nitrobenzene could be reduced to aniline by ZVI; the reduction of nitrobenzene by ZVI followed a pseudo first-order kinetics; the observed nitrobenzene reduction rate constant (k(obs)) was 0.0006 min(-1) and the half-life of nitrobenzene (t1/2) was 115.5 min; the mass balance achieved 87.5% for nitrobenzene reduction by the 1 mm ZVI particle and the final removal efficiency was 80.98%. In addition, the pH and ZVI particle size were found to exhibit significant influences on the nitrobenzene reduction. The observed nitrobenzene reduction rate constant linearly decreased with increase pH and the data fitted on polynomial regression equation for the observed nitrobenzene reduction rate constant and ZVI particle size. Therefore, use of ZVI based permeable reactive barrier technology to remedy nitrobenzene contaminated groundwater was feasible. PMID:21235162

Dong, Jun; Zhao, Yongsheng; Zhao, Ran; Zhou, Rui

2010-01-01

113

Arsenate removal from water by zero-valent iron/activated carbon galvanic couples.  

PubMed

Galvanic couples composed of zero-valent iron and activated carbon (Fe(0)/AC) were investigated for As(V) removal from water. The effects of Fe(0) to AC mass ratio (FCR), solution pH, ionic strength and co-existing anions (phosphate, carbonate, silicate, nitrate, chloride and sulfate) and humic acid (HA) on As(V) removal were evaluated. The results showed that the optimum mass ratio was 1:1, and Fe(0)/AC with this ratio was more effective for As(V) removal than Fe(0) and AC alone at pH of 7 and ion strength of 0.03 M NaCl. The enhanced performance for As(V) removal was fulfilled through an accelerated corrosion process of Fe(0), which meant more corrosion products for efficient As(V) removal. The As(V) removal followed a pseudo-first order reaction. The rate constants (k) for 1:1 Fe(0)/AC and Fe(0) alone were 0.802 and 0.330 h(-1), respectively. Potentiodynamic polarization scans further confirmed that Fe(0) corrosion was promoted when Fe(0) was coupled with AC. Except silicates, other co-existing anions promoted As(V) removal. No reduction form of As (As(III) or As(0)) could be detected on iron corrosion products (ICPs) and in solutions. Identified ICPs included poorly crystallized lepidocrocite (gamma-FeOOH) and magnetite/maghemite (Fe(3)O(4)/gamma-Fe(2)O(3)) for both of Fe(0)/AC and Fe(0) systems. In conclusion, the Fe(0)/AC couple exhibited higher As removal performance than that of Fe(0) alone from water. PMID:20599323

Dou, Xiaomin; Li, Rui; Zhao, Bei; Liang, Wenyan

2010-06-08

114

Rapid removal of flutriafol in water by zero-valent iron powder.  

PubMed

A study of the effect of zero-valent iron (ZVI) powder is carried out for the first time on the degradation of flutriafol ((RS)-2,4'-difluoro-alpha-(1H-1,2,4-triazol-1-ylmethyl)-benzhydryl alcohol, C(16)H(13)F(2)N(3)O), a bifluorinated soil and water persistent triazole pesticide using a laboratory scale device consisting of a 20 ml pyrex serum vials fixed to a Vortex agitator. Different amounts of ZVI powder (10-50 g l(-1)) at pH 6.6 and room temperature were investigated. Experiments showed an observed degradation rate k(obs) directly proportional to the surface of contact of flutriafol with ZVI. Flutriafol degradation reactions demonstrated first order kinetic with a half-live of about 10.8+/-0.5 min and 3.6+/-0.2 min when experiments were conducted at [ZVI]=10 g l(-1) into oxygenated and anoxic solutions, respectively. Three analytical techniques were employed to monitor flutriafol degradation and to understand solution and by-products behaviors: (1) A UV-Vis spectrophotometer; (2) a high performance liquid chromatography (HPLC) coupled with a photo diode array (PDA) and fluorescence detectors; (3) a similar HPLC coupled with a PDA and a mass spectrometer detectors equipped with an atmospheric pressure photoionization source. Results showed a complete disappearance of flutriafol after 20 min of contact with ZVI, the loss of fluorescence properties of the final by-products, the defluorination of the triazole pesticide via hydroxylation reaction and finally the hydrogenation of the triazole ring. PMID:18178235

Ghauch, Antoine

2008-02-21

115

Impact of nano zero valent iron (NZVI) on methanogenic activity and population dynamics in anaerobic digestion.  

PubMed

Nano zero valent iron (NZVI), although being increasingly used for environmental remediation, has potential negative impact on methanogenesis in anaerobic digestion. In this study, NZVI (average size = 55 ± 11 nm) showed inhibition of methanogenesis due to its disruption of cell integrity. The inhibition was coincident with the fast hydrogen production and accumulation due to NZVI dissolution under anaerobic conditions. At the concentrations of 1 mM and above, NZVI reduced methane production by more than 20%. At the concentration of 30 mM, NZVI led to a significant increase in soluble COD (an indication of cell disruption) and volatile fatty acids in the mixed liquor along with an accumulation of H2, resulting in a reduction of methane production by 69% (±4% [standard deviation]). By adding a specific methanogenesis inhibitor-sodium 2-bromoethanesulfonate (BES) to the anaerobic sludge containing 30 mM NZVI, the amount of H2 produced was only 79% (±1%) of that with heat-killed sludge, indicating the occurrence of bacterially controlled hydrogen utilization processes. Quantitative PCR data was in accordance with the result of methanogenesis inhibition, as the level of methanogenic population (dominated by Methanosaeta) in the presence of 30 mM NZVI decreased significantly compared to that of the control. On the contrary, ZVI powder (average size <212 ?m) at the same concentration (30 mM) increased methane production presumably due to hydrogenotrophic methanogenesis of hydrogen gas that was slowly released from the NZVI powder. While it is a known fact that NZVI disrupts cell membranes, which inhibited methanogenesis described herein, the results suggest that the rapid hydrogen production due to NZVI dissolution also contribute to methanogenesis inhibition and lead to bacterially controlled hydrogenotrophic processes. PMID:24112628

Yang, Yu; Guo, Jialiang; Hu, Zhiqiang

2013-09-27

116

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

117

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

118

More on sonolytic and sonocatalytic decomposition of Diclofenac using zero-valent iron.  

PubMed

The study is an extension of our previous work on sonolytic and sonocatalytic decomposition of Diclofenac-Na (DCF) to depict and highlight further operation parameters of significance, and to assess the effect of a novel home-made catalyst made of magnetic nanoparticles of zero-valent iron (ZVI). It was found that high-frequency was more effective than power ultrasound (20 kHz), and the efficiency was a maximum at 861 kHz, acetate-buffered pH 3.0 and air bubbling provided that samples were prepared from a pre-heated stock solution to enhance solubility of the compound. As such, 40-min sonication rendered nearly complete transformation of DCF to intermediate products that were more biodegradable than itself, but with little mineralization of organic carbon. Catalytic sono-treatment showed that the effect of the catalyst was largest in a non-buffered acidic solution and the rate of DCF elimination increased with increasing concentrations of solids up to a "critical" mass, above which it declined via the coalescence of particles and bubbles. Sonocatalysis using the "effective" solid mass also enhanced the overall degradation or mineralization of the compound as portrayed by the accumulation of chloride and nitrate ions in solution after prolonged contact. The production of excess H(2)O(2) during catalysis with ZVI was attributed to the presence of additional and major routes of (·)OH and/or H(2)O(2) formation (other than water pyrolysis). The initial rate of DCF degradation in the presence of nanoparticles was found highly sensitive to the mass of solids in solution, declining sharply as the mass exceeded a "critical" effective level. A catalyst efficacy factor was defined as a function of the initial mass ratio of Fe(0) to DCF and found to be one order of magnitude larger than that obtained by using commercial microparticles with a threefold larger Fe content. The result signifies that the role of aqueous Advanced Fenton reactions (Fe(0)/H(2)O(2)) was less significant in the presence of nanoparticles relative to that of heterogeneous reactions with reactive Fe and oxygen species on the massive surface areas with enriched reaction/adsorption and nucleation sites. PMID:22738831

Ziylan, Asu; Koltypin, Yuri; Gedanken, Aharon; Ince, Nilsun H

2012-06-01

119

Removal of Arsenic(III) from Groundwater with Nano Scale Zero-Valent Iron  

NASA Astrophysics Data System (ADS)

Arsenite (As(III)) is a highly toxic, soluble species that is a naturally occurring groundwater contaminant of environmental concern. There is a need for detailed information about the natural geochemical cycling of As(III), including the fundamental chemical mechanisms of the reactions of As(III) with a variety of surfaces, both natural and engineered. In this paper we focus on the development of ultra-fine, synthetic nanoscale zero-valent iron (nano-Fe(0)) material as both a potential candidate for As(III) remediation and a high surface area model compound to study the remediation of groundwater containing As(III) with larger Fe(0) particles. A variety of techniques were used including SEM, AFM, XRD, and X-ray absorption spectroscopy (XAS) to characterize particle size, surface morphology, corrosion layers formed, and As(III)-nano-Fe(0) surface complexation chemistry. Results from AFM showed particle size ranged from 1-120 nm. XRD and SEM results revealed that nano-Fe(0) gradually converted to magnetite/maghemite corrosion products mixed with lepidocrocite over 60 d. Arsenic(III) batch adsorption kinetics were rapid following a pseudo-first-order rate expression with observed reaction rate constants (kobs) of up to 1.3 per min (at varying Fe(0) densities). These values are about 1000 times higher than kobs literature values for As(III) adsorption on micron size Fe(0). Results from laser light scattering (electrophoretic mobility) and XAS confirmed that inner-sphere surface complexation occurred on nano-Fe(0) corrosion products. In addition, oxidation of As(III) to As(V) was evident in batch experiments. Addition of 10 mM anions (bicarbonate, sulfate, nitrate, and arsenate) had no effect on the uptake of As(III) whereas 10 mM silicic acid and phosphate reduced the uptake of As(III) from 99.9% to 44.9 and 66.3%, respectively. Our results suggest that nano-Fe(0) is an appropriate material for further investigation of the feasibility of using Fe(0) for As(III) remediation.

Manning, B. A.; Kiser, J.; Kanel, S. R.; Choi, H.

2004-12-01

120

Effects of alcohols, anionic and nonionic surfactants on the reduction of PCE and TCE by zero-valent iron.  

PubMed

The effects of surfactants, sodium dodecyl sulfate (SDS) and Triton X-a00 (TX), and alcohols (methanol, ethanol, and propanol) on the dehalogenation of TCE and PCE by zero-valent iron were examined. Surface concentrations of PCE and TCE on the iron were dependent on aqueous surfactant concentrations. At concentrations above the CMC, sorbed halocarbon concentrations declined and concentrations associated with solution phase micelles increased. The anionic surfactant SDS ([SDS] < CMC) did not affect reduction rates, until the CMC was exceeded after which reactivity decreased, possibly due to sequestering of the TCE and PCE in mobile micelles. The nonionic TX showed a mixed effect on reactivity, increasing the PCE reduction rate, but not affecting TCE removal. Production of TCE from PCE increased in the presence of TX. Similar experiments showed that methanol, ethanol, and propanol inhibited reduction of TCE and PCE by metallic iron. Zero-valent iron may be useful in recycling soil washing effluents contaminated with TCE and PCE. PMID:11317892

Loraine, G A

2001-04-01

121

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

122

Nanoscale zero-valent iron supported on mesoporous silica: Characterization and reactivity for Cr(VI) removal from aqueous solution.  

PubMed

MCM-41-supported nanoscale zero-valent iron (nZVI) was sytnhesized by impregnating the mesoporous silica martix with ferric chloride, followed by chemical reduction with NaHB4. The samples were studied with a combination of characterization techniques such as powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Mössbauer spectroscopy, N2 adsorption measurements, transmission electron microscopy (TEM), magnetization measurements, and thermal analysis methods. The experimental data revealed development of nanoscale zero-valent iron particles with an elliptical shape and a maximum size of ?80nm, which were randomly distributed and immobilized on the mesoporous silica surface. Surface area measurements showed that the porous MCM-41 host matrix maintains its hexagonal mesoporous order structure and exhibits a considerable high surface area (609m(2)/g). Mössbauer and magnetization measurements confirmed the presence of core-shell iron nanoparticles composed of a ferromagnetic metallic core and an oxide/hydroxide shell. The kinetic studies demonstrated a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these stabilized nZVI particles on MCM-41, and a considerably increased reduction capacity per unit mass of material in comparison to that of unsupported nZVI. The results also indicate a highly pH-dependent reduction efficiency of the material, whereas their kinetics was described by a pseudo-first order kinetic model. PMID:23959249

Petala, Eleni; Dimos, Konstantinos; Douvalis, Alexios; Bakas, Thomas; Tucek, Jiri; Zbo?il, Radek; Karakassides, Michael A

2013-07-30

123

Transport of zero-valent iron nanoparticles in carbonate-rich porous aquifers  

NASA Astrophysics Data System (ADS)

Use of nanoscale zero-valent iron (nZVI) for in situ dechlorination of chlorinated solvents in groundwater is a promising remediation technology, due to a high dechlorination efficiency of nZVI and possible applications in e.g., great depth or under above-ground infrastructure. The success of the in situ nZVI dechlorination strongly depends on the particle delivery to the contaminants. Previous studies reported a limited transport of nZVI through porous media (cm- to dm-range) and this has been recognized as one of the major obstacles in a widespread utilization of this technology (TRATNYEK & JOHNSON, 2006). Factors that limit the transport are particle aggregation and deposition onto the aquifer solids. Both depend on particle properties (e.g., size, shape, iron content, surface coating, surface charge), on concentrations of suspensions, and on site-specific parameters, such as the groundwater chemistry and the properties and inhomogeneity of the aquifer material. Adsorbed anionic polyelectrolyte coatings provide electrostatic double layer repulsions between negatively charged nZVI particles (SALEH ET AL., 2007), hindering their aggregation and also deposition on the negatively charged quartz surfaces (usually prevailing in aquifers). However, it is shown that the presence of surface charge heterogeneities in the aquifer effects the particle transport (JOHNSON ET AL., 1996). Carbonates, iron oxides, and the edges of clay minerals, for instance, carry a positive surface charge at neutral pH (often encountered in groundwater). This leads to a favorable deposition of negatively charged nZVI particles onto carbonates, metal oxide impurities or clay edges, and finally to a decreased particle transport. Considering the high proportion of carbonates commonly encountered in Alpine porous aquifers, in this study we aimed to evaluate the transport of commercially available polyelectrolyte coated nZVI (polyacrylic acid coated-nZVI, NANOIRON s.r.o., CZ) in both quartz and carbonate-rich porous media and to quantify alteration in travel distances with the increasing proportion of carbonate sands. Transport studies using Nanofer 25S are carried out in 1 D columns filled with different proportions of quartz and carbonate sands at a pH typically encountered in groundwater. Column experiments demonstrated that the travel distance of coated-nZVI systematically decreases with increasing portion of carbonate sand. The transportability of Nanofer 25S was reduced by ~45% in pure carbonate sand, compared to that in pure quartz sand. These results demonstrated different attachment affinities of coated-nZVI for the investigated solids. Current experiments are carried out in order to provide a mechanistic understanding of the observed nanoparticle-solid matrix interactions. Furthermore, the effects of varying groundwater chemistry, size and shape of the packing material, as well as the presence of metal oxides and natural organic matter on the nZVI transport will be investigated. The project is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). Management by Kommunalkredit Public Consulting GmbH. Literature TRATNYEK, P.G., JOHNSON, R.L., (2006): Nano Today 1, 44-48. SALEH, N. ET AL., (2007): Environmental Engineering Science24, 45-57. JOHNSON, P.R. ET AL., (1996): Environmental Science & Technology 30, 3284-3293.

Laumann, S.; Micic, V.; Hofmann, T.

2012-04-01

124

Degradation of model olive mill contaminants of OMW catalysed by zero-valent iron enhanced with a chelant.  

PubMed

The aim of this study was to investigate the effect of a chelated zero valent iron as catalyst on the oxidation of six organic acids that are generally found in olive mill wastewater. The reaction was carried out in a stirred tank reactor under extremely mild conditions, a temperature of 30°C and atmospheric pressure. Solutions of 350 mg/L of the six organic compounds were treated individually using zero valent iron particles (15 g), nitrilotriacetic acid disodium salt (NTA, 100mg/L) and air. The efficiency of the process was evaluated to determine the organic compound conversion, the chemical oxygen demand (COD) reduction and the total organic carbon (TOC) reduction. The caffeic, 4-hydroxyphenylacetic and vanillic acids showed a total conversion after 180, 240 and 300 min of reaction, respectively. In turn, coumaric acid, tyrosol and cinnamic acid only reached conversions of 90, 87 and 68%, respectively, after 360 min of reaction. Four mixtures of the six acids with an initial total concentration of 1000 mg/L were also tested and gave an overall conversion of the organic compounds of 92-99% after 360 min of reaction. The COD conversions of the mixtures were always above 84%, but the TOC conversions values were lower, indicating a poorer mineralization. PMID:22118846

Sanchez, Irama; Stüber, Frank; Fabregat, Azael; Font, Josep; Fortuny, Agustí; Bengoa, Christophe

2011-11-11

125

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

126

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid  

Microsoft Academic Search

The combination of zero-valent iron (Fe0) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe0 or IOCS alone, the

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

2011-01-01

127

Coupling of zero valent iron and biobarriers for remediation of trichloroethylene in groundwater.  

PubMed

This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene (TCE; 500 mg/L) in synthetic groundwater. The system consisted of three reactive barriers using iron fillings as an iron-based barrier in the first column, sugarcane bagasse mixed with anaerobic sludge as an anaerobic barrier in the second column, and a biofilm coated on oxygen carbon inducer releasing material as an aerobic barrier in the third column. In order to evaluate the extent of removal of TCE and its metabolites in the aquifer down gradient of the barrier system, a fourth column filled with sand was applied. Residence time of the system was investigated by a bromide tracer test. The results showed that residence time in the column system of the control set and experimental set were 23.62 and 29.99 days, respectively. The efficiency of the three series barrier system in removing TCE was approximately 84% in which the removal efficiency of TCE by the iron filling barrier, anaerobic barrier and aerobic barrier were 42%, 16% and 25%, respectively, cis-Dichloroethylene (cis-DCE), vinyl chloride (VC), ethylene and chloride ions were observed as metabolites following TCE degradation. The presence of chloride ions in the effluent from the column system indicated the degradation of TCE. However, cis-DCE and VC were not fully degraded by the proposed barrier system which suggested that another remediation technology after the barrier treatment such as air sparging and adsorption by activated carbon should be conducted. PMID:21793396

Teerakun, Mullika; Reungsang, Alissara; Lin, Chien-Jung; Liao, Chih-Hsiang

2011-01-01

128

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

129

The use of Zero-valent iron biosand filters to reduce E. coli O157:H12 in irrigation water applied to spinach plants in a field setting  

Technology Transfer Automated Retrieval System (TEKTRAN)

Contaminated irrigation water is a potential source for the introduction of foodborne pathogens on to produce commodities. Zero-valent iron (ZVI) may provide a simple cheap method to mitigate the contamination of produce groups through irrigation water. A small field scale system was utilized to e...

130

Systematic comparison of the size, surface characteristics and colloidal stability of zero valent iron nanoparticles pre- and post-grafted with common polymers  

Microsoft Academic Search

This study systematically examines the effect of four common polymers on the size, surface chemistry, colloidal stability, and sedimentation behaviour of nanoparticles of zero valent iron (NZVI). The mean diameters of NZVI ranged from 5 to 189nm, depending on the synthesis conditions. The influence of the pre- or post-grafting of the polymers on the above parameters was also investigated. The

Ciprian M. Cirtiu; Trishikhi Raychoudhury; Subhasis Ghoshal; Audrey Moores

2011-01-01

131

Carbonate minerals in porous media decrease mobility of polyacrylic acid modified zero-valent iron nanoparticles used for groundwater remediation.  

PubMed

The limited transport of nanoscale zero-valent iron (nZVI) in porous media is a major obstacle to its widespread application for in situ groundwater remediation. Previous studies on nZVI transport have mainly been carried out in quartz porous media. The effect of carbonate minerals, which often predominate in aquifers, has not been evaluated to date. This study assessed the influence of the carbonate minerals in porous media on the transport of polyacrylic acid modified nZVI (PAA-nZVI). Increasing the proportion of carbonate sand in the porous media resulted in less transport of PAA-nZVI. Predicted travel distances were reduced to a few centimeters in pure carbonate sand compared to approximately 1.6 m in quartz sand. Transport modeling showed that the attachment efficiency and deposition rate coefficient increased linearly with increasing proportion of carbonate sand. PMID:23644276

Laumann, Susanne; Mici?, Vesna; Lowry, Gregory V; Hofmann, Thilo

2013-05-03

132

Reduction of aqueous Crvi using nanoscale zero-valent iron dispersed by high energy electron beam irradiation.  

PubMed

High energy electron beam (HEEB) irradiation was used to disperse nanoscale zero-valent iron (NZVI) for reduction of Crvi to Criii in aqueous solution. Pore size distribution, scanning electron microscopy and X-ray diffraction characterizations demonstrated that HEEB irradiation could effectively increase the dispersion of NZVI resulting in more active reduction sites of Crvi on NZVI. Batch reduction experiments indicated that the reductive capacity of HEEB irradiation-modified NZVI (IMNZVI) was significantly improved, as the reductive efficiency reached 99.79% under the optimal conditions (electron beam dose of 30 kGy at 10 MeV, pH 2.0 and 313 K) compared with that of raw NZVI (72.14%). Additionally, the NZVI was stable for at least two months after irradiation. The modification mechanism of NZVI by HEEB irradiation was investigated and the results indicated that charge and thermal effects might play key roles in dispersing the NZVI particles. PMID:23982295

Zhang, Jing; Zhang, Guilong; Wang, Min; Zheng, Kang; Cai, Dongqing; Wu, Zhengyan

2013-09-26

133

Reduction of aqueous Crvi using nanoscale zero-valent iron dispersed by high energy electron beam irradiation  

NASA Astrophysics Data System (ADS)

High energy electron beam (HEEB) irradiation was used to disperse nanoscale zero-valent iron (NZVI) for reduction of Crvi to Criii in aqueous solution. Pore size distribution, scanning electron microscopy and X-ray diffraction characterizations demonstrated that HEEB irradiation could effectively increase the dispersion of NZVI resulting in more active reduction sites of Crvi on NZVI. Batch reduction experiments indicated that the reductive capacity of HEEB irradiation-modified NZVI (IMNZVI) was significantly improved, as the reductive efficiency reached 99.79% under the optimal conditions (electron beam dose of 30 kGy at 10 MeV, pH 2.0 and 313 K) compared with that of raw NZVI (72.14%). Additionally, the NZVI was stable for at least two months after irradiation. The modification mechanism of NZVI by HEEB irradiation was investigated and the results indicated that charge and thermal effects might play key roles in dispersing the NZVI particles.

Zhang, Jing; Zhang, Guilong; Wang, Min; Zheng, Kang; Cai, Dongqing; Wu, Zhengyan

2013-09-01

134

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

135

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

2011-11-10

136

Decolorization of anthraquinone dye Reactive Blue 19 by the combination of persulfate and zero-valent iron.  

PubMed

Decolorization of anthraquinone dye Reactive Blue 19 (RB19) with sulfate radicals generated in situ from persulfate and zero-valent iron (ZVI) was investigated. The effects of initial solution pH, initial concentration of RB19, ZVI and persulfate, reaction temperature and common dissolved anions were studied. 100% color removal efficiency and 54% TOC removal efficiency were achieved in 45 min with an initial RB19 concentration of 0.1 mM under typical conditions (pH 7.0, 0.8 g L(-1) ZVI, 10 mM persulfate and 30 C). The decolorization efficiency of RB19 increased with higher iron dosage, higher initial persulfate concentration, and higher reaction temperature. It is also an acid driven process. The decolorization process followed pseudo-first order kinetics and the activation energy was 98.1 kJ mol-1. RB19 decolorization was inhibited by common dissolved anions such as CL-, NO3-, H2PO4- and HCO3- since they reacted with sulfate radicals that retarded the oxidation process. The experiment demonstrated that the combination of persulfate and ZVI was a promising technology for the decolorization of dye wastewater. PMID:22097057

Le, Chen; Wu, Jin-Hua; Li, Ping; Wang, Xiangde; Zhu, Neng-Wu; Wu, Ping-Xiao; Yang, Bo

2011-01-01

137

Preparation of stabilized nano zero-valent iron particles via a rheological phase reaction method and their use in dye decolourization  

Microsoft Academic Search

In this study, sodium carboxymethyl cellulose (NaCMC)-stabilized nano zero-valent iron (C-nZVI) was synthesized using a rheological phase reaction method. The orthogonal method was used to evaluate the factors influencing C-nZVI properties and this showed that the reaction time, solid–liquid ratio (w\\/v), grinding time and NaCMC concentration were all important factors. Characterization with scanning electron microscopy validated the hypothesis that the

Yue Cheng; Mang Lu; Chuang Jiao; Hai-Jiang Liu

2012-01-01

138

The improvement of boron-doped diamond anode system in electrochemical degradation of p-nitrophenol by zero-valent iron  

Microsoft Academic Search

Boron-doped diamond (BDD) electrodes are promising anode materials in electrochemical treatment of wastewaters containing bio-refractory organic compounds due to their strong oxidation capability and remarkable corrosion stability. In order to further improve the performance of BDD anode system, electrochemical degradation of p-nitrophenol were initially investigated at the BDD anode in the presence of zero-valent iron (ZVI). The results showed that

Xiuping Zhu; Jinren Ni

139

Treatment of phenol-containing wastewater by photoelectro-Fenton method using supported nanoscale zero-valent iron.  

PubMed

This study presents the degradation of phenol by the photoelectro-Fenton method using nano zero-valent iron (nZVI) immobilized in polyvinyl alcohol-alginate beads. The effect of nZVI loading, H(2)O(2) concentration, pH, and initial phenol concentration on phenol degradation and chemical oxygen demand reduction was studied. The scanning electron microscope images of the nZVI beads were used to analyze their morphology, and their diameters were in the range of 500-600 ?m. The concentration of nZVI in the beads was varied from 0.1 to 0.6 g/L. Fe(2+) leakage of 1 and 3 % was observed with 0.5 and 0.6 g/L of nZVI, respectively, and the observed beads' fracture frequency was 2 %, which confirmed the stability of the beads. The optimum operating conditions that arrived for better degradation were 0.5 g/L of nZVI, pH 6.2, and 400 mg H(2)O(2)/L. The treatment of effluent by this method increased the biodegradability index of the effluent, and the degradation data were found to follow pseudo first-order kinetics. PMID:22711016

Babuponnusami, Arjunan; Muthukumar, Karuppan

2012-06-19

140

Assessing the impact of zero-valent iron (ZVI) nanotechnology on soil microbial structure and functionality: a molecular approach.  

PubMed

In this work, nanoscale zero-valent iron (NZVI) particles have been used as an immobilisation strategy to reduce Pb and Zn availability and mobility in polluted soils. The application of NZVI to two soil microcosms (MPb and MZn) at a dose of 34 mg g(-1) soil efficiently immobilised Pb (25%) and zinc (20%). Exposure to NZVI had little impact on the microbial cellular viability and biological activity in the soils. Three bacterial genes (narG, nirS and gyrA) were used as treatment-related biomarkers. These biomarkers ruled out a broad bactericidal effect on the bulk soil microbial community. A transcriptome analysis of the genes did not reveal any changes in their expression ratios after the NZVI treatment: 1.6 (narG), 0.8 (nirS) and 0.7 (gyrA) in the MPb microcosm and 0.6 (narG), 1.2 (nirS) and 0.5 (gyrA) in the MZn microcosm. However, significant changes in the structure and composition of the soil bacteria population were detected by fluorescence in situ hybridisation. Thus, our results showed that NZVI toxicity could be highly dose and species dependent, and the effective applicability of the proposed molecular approach in assessing the impact of this immobilisation strategy on soil microbial population. PMID:22169206

Fajardo, C; Ortíz, L T; Rodríguez-Membibre, M L; Nande, M; Lobo, M C; Martin, M

2011-12-12

141

Remediation of s-triazines contaminated water in a laboratory scale apparatus using zero-valent iron powder.  

PubMed

Atrazine, propazine and simazine were tested separately and in mixture by batch procedure in a laboratory-constructed apparatus. 3.75 l of a buffered s-triazines pesticide solution was treated at room temperature by 325-mesh zero-valent iron powder (ZVIP) (20 g/l). High performance liquid chromatography was used to separate by-products and study the decline in the pesticide's concentrations. Results obtained show that the order of degradation was simazine, atrazine and then propazine. The half-lives (t1/2) of the s-triazines pesticides are, respectively, 7.4, 9.0 and 10.6 min when they are treated separately, and 9.8, 11.2 and 13.7 min when they are treated together under the same conditions. The final by-product obtained after 50 min of contact of simazine with ZVIP shows a shift to longer wavelength in its UV spectrum. A similar phenomenon is shown for atrazine and propazine. Identical primary by-products are produced and subsequently degraded to 4,6-(diamino)-s-triazine, which seems to be the major by-product of the reductive treatment process. Pathways for the degradation of the studied s-triazines by ZVIP are proposed. PMID:11061305

Ghauch, A; Suptil, J

2000-12-01

142

Ecotoxicological effects on earthworms of fresh and aged nano-sized zero-valent iron (nZVI) in soil.  

PubMed

Although nano-sized zero-valent iron (nZVI) has been used for several years for remediation of contaminated soils and aquifers, only a limited number of studies have investigated secondary environmental effects and ecotoxicity of nZVI to soil organisms. In this study we therefore measured the ecotoxicological effects of nZVI coated with carboxymethyl cellulose on two species of earthworms, Eisenia fetida and Lumbricus rubellus, using standard OECD methods with sandy loam and artificial OECD soil. Earthworms were exposed to nZVI concentrations ranging from 0 to 2000 mg nZVI kg soil(-1) added freshly to soil or aged in non-saturated soil for 30 d prior to exposure. Regarding avoidance, weight changes and mortality, both earthworm species were significantly affected by nZVI concentrations ?500 mg kg(-1)soil. Reproduction was affected also at 100 mg nZVI kg(-1). Toxicity effects of nZVI were reduced after aging with larger differences between soils compared to non-aged soils. We conclude that doses ?500 mg nZVI kg(-1) are likely to give acute adverse effects on soil organisms, and that effects on reproduction may occur at significantly lower concentrations. PMID:22595530

El-Temsah, Yehia S; Joner, Erik J

2012-05-15

143

The role of clay minerals in the reduction of nitrate in groundwater by zero-valent iron.  

PubMed

Bench-scale batch experiments were performed to investigate the feasibility of using different types of clay minerals (bentonite, fuller's earth, and biotite) with zero-valent iron for their potential utility in enhancing nitrate reduction and ammonium control. Kinetics experiments performed with deionized water (DW) and groundwater (GW) revealed nitrate reduction by Fe(0) proceeded at significantly faster rate in GW than in DW, and such a difference was attributed to the formation of green rust in GW. The amendment of the minerals at the dose of 25 g L(-1) in Fe(0) reaction in GW resulted in approximately 41%, 43%, and 33% more removal of nitrate in 64 h reaction for bentonite, fuller's earth, and biotite, respectively, compared to Fe(0) alone reaction. The presumed role of the minerals in the rate enhancement was to provide sites for the formation of surface bound green rust. Bentonite and fuller's earth also effectively removed ammonium produced from nitrate reduction by adsorption, with the removal efficiencies significantly increased with the increase in mineral dose above 5:1 Fe(0) to mineral mass ratio. Such a removal of ammonium was not observed for biotite, presumably due to its lack of swelling property. Equilibrium adsorption experiments indicated bentonite and fuller's earth had maximum ammonium adsorption capacity of 5.6 and 2.1 mg g(-1), respectively. PMID:20797759

Cho, Dong-Wan; Chon, Chul-Min; Jeon, Byong-Hun; Kim, Yongje; Khan, Moonis Ali; Song, Hocheol

2010-08-24

144

Effects of an electric field and zero valent iron on anaerobic treatment of azo dye wastewater and microbial community structures.  

PubMed

A zero valent iron (ZVI) bed with a pair of electrodes was packed in an anaerobic reactor aiming at enhancing treatment of azo dye wastewater. The experiments were carried out in three reactors operated in parallel: an electric field enhanced ZVI-anaerobic reactor (R1), a ZVI-anaerobic reactor (R2) and a common anaerobic reactor (R3). R1 presented the highest performance in removal of COD and color. Raising voltage in R1 further improved its performance. Scanning electron microscopy images displayed that the structure of granular sludge from R1 was intact after being fed with the high dye concentration, while that of R3 was broken. Fluorescence in situ hybridization analysis indicated that the abundance of methanogens in R1 was significantly greater than that in the other two reactors. Denaturing gradient gel electrophoresis showed that the coupling of electric field and ZVI increased the diversity of microbial community and especially enhanced bacterial strains responsible for decolorization. PMID:21167707

Liu, Yiwen; Zhang, Yaobin; Quan, Xie; Zhang, Jingxin; Zhao, Huimin; Chen, Shuo

2010-11-28

145

Investigation of the long-term performance of zero-valent iron for reductive dechlorination of trichloroethylene  

SciTech Connect

This research investigated the long-term performance of zero-valent iron for mediating the reductive dechlorination of trichloroethylene (TCE). Over a 2-year period, rates of TCE dechlorination in columns packed with iron filings were measured in simulated groundwaters containing either 3 mM CaSO{sub 4}, 5 mM CaCl{sub 2}, or 5 mM Ca(NO{sub 3}){sub 2}. At early elapsed times, TCE reaction rates were pseudo-first-order in TCE concentration and were independent of the solution pH. With increasing elapsed time, reaction rates deviated from pseudo-first-order behavior due to reactive site saturation and increased iron surface passivation toward the influent end of each column. The extent of passivation was dependent on both the TCE concentration and the background electrolyte solution. For most of the investigation, TCE reaction rates in 3 mM CaSO{sub 4} and 5 mM CaCl{sub 2} solutions were statistically identical at the 0.05 confidence level. However, TCE reaction rates in 5 mM Ca(NO{sub 3}){sub 2} were slower. In columns operated using chloride- and sulfate-containing waters, the effective half-life for TCE dechlorination increased from approximately 400 min after 10 days elapsed to approximately 2,500 min after 667 days. The effective TCE half-life in the nitrate-containing water increased from approximately 1,500 min after 10 days to approximately 3,500 min after 667 days. Measurements of iron corrosion rates in nitrate and chloride solutions showed that nitrate contributed to increased iron surface passivation and decreased rates of iron corrosion. Corrosion current measurements indicated that halocarbon reduction on fresh iron surfaces was cathodically controlled, whereas on aged iron surfaces, iron corrosion was anodically controlled. Anodic control of iron corrosion contributed to the development of reactive site saturation with time and to similar reaction rates for TCE and perchloroethylene. Passivation of the iron surfaces was found to be dependent on the adhering tendency of the corrosion products and not on the overall mass of corrosion products in the columns. The decrease in TCE reaction rates over time can be attributed to anodic control of iron corrosion and not to increasing reactant mass transfer limitations associated with diffusion through porous corrosion products.

Farrell, J.; Kason, M.; Melitas, N.; Li, T.

2000-02-01

146

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

147

Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability.  

PubMed

To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template in preparation via heterogeneous nucleation process. However, the particle sizes spanned from 0.62 nm (perpendicular to the clay layers) for the ZV1 intercalated in montmorillonite interlayers to 1-50 nm for the ZVI residing on an external surface when using montmorillonite as a dispersion agent in the preparation via homogeneous nucleation. Furthermore, parallel batch experiments have been conducted with nZVIs synthesized by the two different methods in solutions of nitrobenzene and their reactivity is evaluated via response of nZVI to nitrobenzene remediation. As a result, the reactivity of ZVI synthesized by heterogeneous nucleation is greater than that by homogeneous nucleation, which is inversely correlated to the size of ZVI supported by montmorillonite clay. Evaluation of the stability of montmorillonite-supported ZVI showed that ZVI intercalated in the interlayers of montmorillonite is more stable than that located on the external surface, which can be attributed to the protective effect of montmorillonite layers on ZVI from oxidation. These results suggest that the great reactivity and high stability of montmorillonite-intercalated ZVI synthesized through heterogeneous nucleation process warrants its significant potential in developing in situ remediation and treatment technologies for organic contaminants. PMID:23530312

Jia, Hanzhong; Wang, Chuanyi

148

High Precision Measurements of 235U/238U Isotopic Fractionations Resulting From Uranium Reduction Induced by Zero Valent Iron  

NASA Astrophysics Data System (ADS)

Uranium is a widespread natural and anthropogenic contaminant in surface and subsurface waters. Like several other inorganic contaminants, uranium is mobile under oxidizing conditions but may be immobilized by chemical reduction. U(VI) moves with groundwater as (UO2)2+ and as soluble complexes with carbonate, phosphate, and fluoride. In many groundwater systems, uranium undergoes chemical reduction to U(IV), which is insoluble and immobile. Therefore, understanding the extent of reduction is essential for predicting the mobility of uranium in groundwater. Mass dependent isotopic fractionations of redox sensitive contaminants frequently found in groundwater (including chromate, selenate, and nitrate) have proven exceptionally useful for estimating the rate and extent of reduction and immobilization. Until recently, however, analytical limitations have prevented these techniques from being applied to heavier redox sensitive elements, such as uranium. The advent of highly sensitive multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) enables high precision measurements of previously undetected variations in many elements. Laboratory reduction experiments with zero valent iron (ZVI) were performed in a controlled environment to test the hypothesis that uranium isotopes, specifically 235U/238U, behave similarly to other redox sensitive contaminants and produce a mass dependent fractionation during the transformation between valence states. Because of the large abundance differences between 235U and 238U, initial experiments used U500, an enriched uranium standard with approximately equal parts 235U and 238U. Results suggest that the highly sensitive MC-ICP-MS distinguishes 235U/238Uvariations to approximately + 0.02per mil. Measured isotopic fractionations between the 235U/238U of the initial and final experimental solutions (~70% reduced) are approximately 1.1 per mil, and increase with decreasing concentration. Measured variations in 235U/238U suggest that uranium isotopic ratios could also prove to be valuable indicators of contaminant immobilization and paleoenvironmental conditions.

Rademacher, L.; Lundstrom, C.; Johnson, T.

2003-12-01

149

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

150

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

2013-07-18

151

Applying an electric field in a built-in zero valent iron--anaerobic reactor for enhancement of sludge granulation.  

PubMed

A zero valent iron (ZVI) bed with a pair of electrodes was installed in an upflow anaerobic sludge blanket (UASB) reactor to create an enhanced condition to increase the rate of anaerobic granulation. The effects of an electric field and ZVI on granulation were investigated in three UASB reactors operated in parallel: an electric field enhanced ZVI-UASB reactor (reactor R1), a ZVI-UASB reactor (reactor R2) and a common UASB reactor (reactor R3). When a voltage of 1.4 V was supplied to reactor R1, COD removal dramatically increased from 60.3% to 90.7% over the following four days, while the mean granule size rapidly grew from 151.4 ?m to 695.1 ?m over the following 38 days. Comparatively, COD removal was lower and the increase in granule size was slower in the other two reactors (in the order: R1 > R2 > R3). The electric field caused the ZVI to more effectively buffer acidity and maintain a relatively low oxidation-reduction potential in the reactor. In addition, the electric field resulted in a significant increase in ferrous ion leaching and extracellular polymeric substances (EPS) production. These changes benefited methanogenesis and granulation. Scanning electron microscopy (SEM) images showed that different microorganisms were dominant in the external and internal layers of the reactor R1 granules. Additionally, fluorescence in situ hybridization (FISH) analysis indicated that the relative abundance of methanogens in reactor R1 was significantly greater than in the other two reactors. Taken together, these results suggested that the use of ZVI combined with an electric field in an UASB reactor could effectively enhance the sludge granulation. PMID:20965541

Liu, Yiwen; Zhang, Yaobin; Quan, Xie; Chen, Shuo; Zhao, Huimin

2010-10-19

152

Degradation of Organochlorine Compounds Using Zero Valent Iron (ZVI) Nano Particles Impregnated in Hydrophobic Modified Bentonite  

Microsoft Academic Search

\\u000a The degradation of perchloroethylene (PCE) adsorbed on hydrophobic modified bentonite was investigated. The degradation occurred\\u000a via reduction of iron particles with zero valence (ZVI) incorporated in hydrophobic surface of bentonite. We compared two\\u000a different systems, one containing ZVI and another without ZVI. The degradation of PCE was accompanied by decreasing concentrations\\u000a of PCE and the increase of resulting compounds such

Sandro Froehner; M. Maceno; E. C. Luz; K. S. Machado; F. Falcăo

153

Reduction and immobilization of radionuclides and toxic metal ions using combined zero valent iron and anaerobic bacteria. 1998 annual progress report  

SciTech Connect

'Previous research findings indicate that both zero valent iron and sulfate reducing bacteria (SRB) can yield significant decreases in Cr(VI) or U(VI) concentrations due to abiotic and microbial reduction, respectively. The major hypothesis associated with this research project is that a combined abiotic-biological system can synergistically combine both processes to maximize metal ion reduction in an engineered permeable reactive barrier. The overall goal 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. Successful completion of this goal requires testing of the two hypotheses listed above by evaluating: (1) the rates of abiotic metal ion reduction, and (2) the rates of microbial metal ion reduction in microbial and combined abiotic/microbial reduction systems under a range of environmental conditions. This report summarizes work after one and one-half years of a three year project. Abiotic studies: The thrust of the abiotic research conducted to date has been to determine the rates of Cr(VI) reduction in batch reactors and to evaluate the role of aquifer materials on those rates. Experiments have been conducted to determine the rates of reduction by Fe(II) and Fe(O). The parameters that have been evaluated are the effect of pH and the presence of sulfide and aquifer material.'

Weathers, L.

1998-06-01

154

Field-scale transport and transformation of carboxymethylcellulose-stabilized nano zero-valent iron.  

PubMed

The fate of nano zerovalent iron (nZVI) during subsurface injection was examined using carboxymethylcellulose (CMC) stabilized nZVI in a very large three-dimensional physical model aquifer with detailed monitoring using multiple, complementary detection methods. A fluorescein tracer test in the aquifer plus laboratory column data suggested that the very-aggressive flow conditions necessary to achieve 2.5 m of nZVI transport could be obtained using a hydraulically constrained flow path between injection and extraction wells. However, total unoxidized nZVI was transported only about 1 m and <2% of the injected nZVI concentration reached that distance. The experimental data also indicated that groundwater flow changed during injection, likely due to hydrogen bubble formation, which diverted the nZVI away from the targeted flow path. The leading edge of the iron plume became fully oxidized during transport. However, within the plume, oxidation of nZVI decreased in a fashion consistent with progressive depletion of aquifer "reductant demand". To directly quantify the extent of nZVI transport, a spectrophotometric method was developed, and the results indicated that deployment of unoxidized nZVI for groundwater remediation will likely be difficult. PMID:23311327

Johnson, Richard L; Nurmi, James T; O'Brien Johnson, Graham S; Fan, Dimin; O'Brien Johnson, Reid L; Shi, Zhenqing; Salter-Blanc, Alexandra J; Tratnyek, Paul G; Lowry, Gregory V

2013-01-23

155

Effects of nano zero-valent iron on oxidation-reduction potential.  

PubMed

Oxidation-reduction potential (ORP) measurements have been widely used to assess the results of injection of nano zerovalent iron (nZVI) for groundwater remediation, but the significance of these measurements has never been established. Using rotating disk electrodes (RDE) in suspensions of nZVI, we found the electrode response to be highly complex but also a very sensitive probe for a range of fundamentally significant processes. The time dependence of the electrode response reflects both a primary effect (attachment of nZVI onto the electrode surface) and several secondary effects (esp., oxidation of iron and variations in dissolved H2 concentration). At nZVI concentrations above ?200 mg/L, attachment of nZVI to the electrode is sufficient to give it the electrochemical characteristics of an Fe(0) electrode, making the electrode relatively insensitive to changes in solution chemistry. Lower nZVI concentrations give a proportional response in ORP, but much of this effect is mediated by the secondary effects noted above. Coating the nZVI with natural organic matter (NOM), or the organic polymers used to make stabile suspensions of nZVI, moderates its effect on ORP measurments. Our results provide the basis for interpretating ORP measurements used to characterize the results of injecting nZVI into groundwater. PMID:21204580

Shi, Zhenqing; Nurmi, James T; Tratnyek, Paul G

2011-01-04

156

Treatment of 1,2-dibromo-3-chloropropane and nitrate-contaminated water with zero-valent iron or hydrogen\\/palladium catalysts  

Microsoft Academic Search

The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2\\/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compared. DBCP reacted with iron powder (100–200 mesh, 36 g\\/l) in HEPES-buffered water (pH = 7.0) with a t12 of 2.5 min and in different groundwaters (pH = 8.2–8.7) with a

Darsa P. Siantar; Cindy G. Schreier; Chi-Su Chou; Martin Reinhard

1996-01-01

157

Impact of nanoscale zero valent iron on geochemistry and microbial populations in trichloroethylene contaminated aquifer materials.  

PubMed

Nanoscale zerovalent iron (NZVI) particles are a promising technology for reducing trichloroethylene (TCE) contamination in the subsurface. Prior to injecting large quantities of nanoparticles into the groundwater it is important to understand what impact the particles will have on the geochemistry and indigenous microbial communities. Microbial populations are important not only for nutrient cycling, but also for contaminant remediation and heavy metal immobilization. Microcosms were used to determine the effects of NZVI addition on three different aquifer materials from TCE contaminated sites in Alameda Point, CA, Mancelona, MI, and Parris Island, SC. The oxidation and reduction potential of the microcosms consistently decreased by more than 400 mV when NZVI was added at 1.5 g/L concentrations. Sulfate concentrations decreased in the two coastal aquifer materials, and methane was observed in the presence of NZVI in Alameda Point microcosms, but not in the other two materials. Denaturing gradient gel electrophoresis (DGGE) showed significant shifts in Eubacterial diversity just after the Fe(0) was exhausted, and quantitative polymerase chain reaction (qPCR) analyses showed increases of the dissimilatory sulfite reductase gene (dsrA) and Archaeal 16s rRNA genes, indicating that reducing conditions and hydrogen created by NZVI stimulate both sulfate reducer and methanogen populations. Adding NZVI had no deleterious effect on total bacterial abundance in the microcosms. NZVI with a biodegradable polyaspartate coating increased bacterial populations by an order of magnitude relative to controls. The lack of broad bactericidal effect, combined with the stimulatory effect of polyaspartate coatings, has positive implications for NZVI field applications. PMID:20350000

Kirschling, Teresa L; Gregory, Kelvin B; Minkley, Edwin G; Lowry, Gregory V; Tilton, Robert D

2010-05-01

158

Effects of zero-valent iron (Fe 0) and temperature on the transformation of DDT and its metabolites in lake sediment  

Microsoft Academic Search

Zero-valent iron improves the transformation of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its metabolites in aged and highly contaminated lake sediment under biotic conditions. The addition of Fe0 has a strong effect on transformation rates at 22°C and 9°C, the most enhanced degradation being obtained for DDT and DDOH [2,2-bis(p-chlorophenyl)ethanol]. At 22°C and 10 weeks’ incubation, the DDT concentration is reduced from 2.75?molg?1

Trine Eggen; Andrzej Majcherczyk

2006-01-01

159

Nano zero-valent iron impregnated on titanium dioxide nanotube array film for both oxidation and reduction of methyl orange.  

PubMed

Here, we demonstrated that nano zero-valent iron (nZVI) impregnated onto self-organized TiO(2) nanotube thin films exhibits both oxidation and reduction capacities in addition to the possible electron transfer from TiO(2) to nZVI. The TiO(2) nanotubes were synthesized by anodization of titanium foil in a two-electrode system. Amorphous TiO(2) (amTiO(2)) nanotubes were annealed at 450 °C for 1 h to produce crystalline TiO(2) (crTiO(2)) nanotubes. The nZVI particles were immobilized on the TiO(2) array film by direct borohydride reduction. Field emission scanning electron microscopy (FE-SEM) analysis of the crystalline TiO(2) nanotube with nZVI (nZVI/crTiO(2)) indicated that the nZVI particles with a mean particle diameter of 28.38 ± 11.81 nm were uniformly distributed onto entire crTiO(2) nanotube surface with a mean pore diameter of 75.24 ± 17.66 nm and a mean length of 40.07 ?m. Environmental applicability of our proposed nZVI/TiO(2) nanotube thin films was tested for methyl orange (MO) degradation in the aqueous system with and without oxygen. Since oxygen could facilitate the nZVI oxidation and inhibit electron transfer from crTiO(2) to nZVI surface, MO degradation by nZVI/crTiO(2) in the presence of oxygen was significantly suppressed whereas nZVI/crTiO(2) in the absence of oxygen enhanced MO degradation. MO degradation rate by each sample without oxygen were in following order: nZVI/crTiO(2) (k(obs) = 0.311 min(-1)) > nZVI/amTiO(2) (k(obs) = 0.164 min(-1)) > crTiO(2) (k(obs) = 0.068 min(-1)). This result can be explained with a synergistic effect of the significant reduction by highly-dispersed nZVI particles on TiO(2) nanotubes as well as the electron transfer from the conduction band of crTiO(2) to the nZVI on the crTiO(2) for the degradation of MO. PMID:23375600

Yun, Dong-Min; Cho, Hyun-Hee; Jang, Jun-Won; Park, Jae-Woo

2013-01-17

160

Injection of Nano Zero-Valent Iron for Subsurface Remediation: Evaluation of Methods for Assessment of Nanoparticle Delivery (Invited)  

NASA Astrophysics Data System (ADS)

Among emerging technologies for in situ remediation of subsurface contamination, injection of nano-sized zero-valent iron (nZVI) stands out for the sudden growth in interest it has attracted. Field scale applications of this technology exist for a variety of types of sites, and most of these projects have been described as being successful. None of these sites have been extensively characterized, however, and there is not yet a critical mass of field data on which to make generalizations about the performance of nZVI-based remediation technologies. Furthermore, some aspects of the reported field results are not easily reconciled with results of laboratory and modeling studies of nZVI properties and behavior. Clearly, a more thorough and rigorous understanding of this system is needed to ensure that applications of this technology are successful. Among the critical issues to be addressed, detection of iron nanoparticles remains a challenge, and there is no established protocol for detecting iron nanoparticles in the field upon nZVI injection. Oxidation-reduction potential (ORP) measurements have been widely used to assess the results of injection of nZVI for groundwater remediation. However, the significance of such measurements is unclear because the complex interaction between the target materials (e.g. suspensions of highly reactive and variably aggregated nanoparticles) and the electrode has never been characterized. In recent work, we have investigated the effect of nZVI on ORP measurements under various reaction conditions. The electrochemical techniques used include chronopotentiometry and linear-sweep voltammetry with traditional stationary disc electrodes (SDEs), rotating disc electrodes (RDEs), and flow-through cell disc electrodes (FDEs). From ORP measurements in suspensions of nZVI, we found the electrode response to be highly complex, but also a very sensitive probe for a range of fundamentally significant processes. The ORP measurements of nZVI suspensions with both SDEs and RDEs indicate that the interaction of iron nanoparticles with the working electrode significantly contributed to the working electrode response, which is complicated by the solution chemistry and particle properties. The time dependence of the electrode response reflects both a primary effect (sorption of nZVI on the electrode surface) and secondary effects (via Fe oxidation and dissolved H2) of nZVI on ORP. Organic coatings on nZVI particles reduced the primary effect of nZVI by protecting the particle and electrode surfaces. Oxidation of nZVI resulted in rebound of the ORP, as indicated by a progressive shift of the corrosion potential (Ecorr) to more positive values obtained from LSV measurements. Combinations of electrochemical and other methods will be needed to differentiate particle concentration, composition, and reactivity after nZVI injection into the subsurface environment.

Tratnyek, P. G.; Shi, Z.; Nurmi, J. T.; Johnson, R. L.

2010-12-01

161

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

Microsoft Academic Search

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

Yuxin Wu; Lee Slater; Roelof Versteeg; Douglas LaBrecque

2008-01-01

162

Multifunctional kaolinite-supported nanoscale zero-valent iron used for the adsorption and degradation of crystal violet in aqueous solution.  

PubMed

Kaolinite-supported nanoscale zero-valent iron (K-nZVI) was successfully synthesized as a multifunctional composite and used for the degradation of crystal violet (CV). The presence of kaolinite not only decreased the aggregation of zero-valent iron nanoparticles (nZVI) with maintenance of reactivity, but also facilitated reaction by increasing the local concentration of CV in the vicinity of nZVI as an adsorbent. This was confirmed by scanning electron microscopy (SEM) and batch experiments, which showed that 97.23% of CV was removed using K-nZVI, while only 78.72% and 39.22% of CV were removed using nZVI and kaolinite after 30 min, respectively. Different factors impacting on degradation of CV were investigated as well. On the basis of these results, a removal mechanism was proposed including: (i) prompt adsorption of CV to the K-nZVI phase, and (ii) reduction of CV by Fe(0) on K-nZVI. Furthermore, different adsorption and reduction kinetics were employed to examine the removal process of CV, where a better fit with the pseudo-second-order model for adsorption and pseudo-first-order model for reduction process was observed, and reduction was the rate limiting step. In addition, isotherm and thermodynamic parameters were evaluated for a specific study of the important adsorption step. Finally, the application of K-nZVI to treat wastewater showed the removal efficiency higher than 99.9%. PMID:23489613

Chen, Zhengxian; Wang, Ting; Jin, Xiaoyin; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

2013-02-21

163

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid.  

PubMed

The combination of zero-valent iron (Fe(0)) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe(0) or IOCS alone, the Fe(0)-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe(0) and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage. PMID:21130550

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

2010-12-04

164

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

165

Synergistic effect of coupling zero-valent iron with iron oxide-coated sand in columns for chromate and arsenate removal from groundwater: Influences of humic acid and the reactive media configuration  

Microsoft Academic Search

A column study was conducted using a combination of zero-valent iron (Fe0) and iron oxide-coated sand (IOCS) for removing Cr(VI) and As(V) from groundwater. The removal efficiency and mechanism of Cr(VI) and As(V), the effects of humic acid (HA), and the various configurations of Fe0 and IOCS were investigated. The results showed that the use of an Fe0 and IOCS

Mark S. H. Mak; Irene M. C. Lo; Tongzhou Liu

2011-01-01

166

TREATMENT OF 1,2-DIBROMO-3-CHLOROPROPANE AND NITRATE-CONTAMINATED WATER WITH ZERO-VALENT IRON OR HYDROGEN/PALLADIUM CATALYSTS. (R825689C054,R825689C078)  

EPA Science Inventory

Abstract The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compa...

167

Preparation of stabilized nano zero-valent iron particles via a rheological phase reaction method and their use in dye decolourization.  

PubMed

In this study, sodium carboxymethyl cellulose (NaCMC)-stabilized nano zero-valent iron (C-nZVI) was synthesized using a rheological phase reaction method. The orthogonal method was used to evaluate the factors influencing C-nZVI properties and this showed that the reaction time, solid-liquid ratio (w/v), grinding time and NaCMC concentration were all important factors. Characterization with scanning electron microscopy validated the hypothesis that the introduction of CMC led to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirmed the existence of Fe(0) and the strong antioxidant activity of the iron particles. Batch decolourization experiments exhibited that solution pH, C-nZVI dosage and reaction time have significant effects on dye decolourization. A high decolourization efficiency (94.5%) was obtained within 30 min for 100 mg/L of reactive blue-19 at the optimal pH value of 5 and C-nZVI loading of 6 g/L at room temperature. The decolourization rates followed modified pseudo-first-order kinetic equations with respect to dye concentration. The observed removal rate constant was 0.0447 min(-1) for the C-nZVI loading of 6 g/L. PMID:23530358

Cheng, Yue; Lu, Mang; Jiao, Chuang; Liu, Hai-Jiang

168

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

169

Degradation of 4-Chloro-3,5-Dimethylphenol by a Heterogeneous Fenton-Like Reaction Using Nanoscale Zero-Valent Iron Catalysts.  

PubMed

Degradation of 4-chloro-3,5-dimethylphenol (PCMX) by a heterogeneous Fenton-like process using nanoparticulate zero-valent iron (nZVI) and hydrogen peroxide (H2O2) at pH 6.3 was investigated. Interactive effects of three factors-initial PCMX concentration, nZVI dosage, and H2O2 concentration-were investigated using the response surface method based on the Box-Behnken design. Experimental results showed that complete decomposition of PCMX and 65% of total organic carbon removal were observed after 30?min of reaction at neutral pH under recommended reaction conditions: nZVI, 1.0?g/L; H2O2, 18?mM; and initial PCMX concentration, 0.15?g/L. Based on the effects of scavengers n-butanol and KI, removal of PCMX was mainly attributed to the attack of •OH, especially the surface-bonded •OH. A possible degradation pathway of PCMX was proposed. PMID:23781127

Xu, Lejin; Wang, Jianlong

2013-06-01

170

Pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater using a combined zero-valent iron (ZVI) reduction and Fenton oxidation process.  

PubMed

A combined zero-valent iron (ZVI) reduction and Fenton oxidation process was tested for the pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater. Operating conditions were optimized and overall performance of the combined process was evaluated. For ZVI process, almost complete reduction of nitroaromatic compounds was observed at empty bed contact time (EBCT) of 8h. For Fenton process, the optimal pH, H?O? to Fe(II) molar ratio, H?O? dosage and hydraulic retention time (HRT) were found to be 3.0, 15, 0.216 mol/L and 5h, respectively. After pretreatment by the combined ZVI-Fenton process under the optimal conditions, aromatic organic compound removal was as high as 77.2%, while the majority of COD remained to be further treated by sequent biological process. The combined anaerobic-aerobic process consisted of an anaerobic baffled reactor (ABR) and a moving-bed biofilm reactor (MBBR) was operated for 3 months, fed with ZVI-Fenton effluent. The results revealed that the coupled ZVI-Fenton-ABR-MBBR system was significantly efficient in terms of correcting the effluent's main parameters of relevance, mainly aromatic compounds concentration, COD concentration, color and acute toxicity. These results indicate that the combined ZVI-Fenton process offers bright prospects for the pretreatment of wastewater containing nitroaromatic compounds. PMID:23892166

Shen, Jinyou; Ou, Changjin; Zhou, Zongyuan; Chen, Jun; Fang, Kexiong; Sun, Xiuyun; Li, Jiansheng; Zhou, Lin; Wang, Lianjun

2013-07-10

171

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; Saccŕ, M L; Martinez-Gomariz, M; Costa, G; Nande, M; Martin, M

2013-06-28

172

Zero-valent iron/iron oxide-oxyhydroxide/graphene as a magnetic sorbent for the enrichment of polychlorinated biphenyls, polyaromatic hydrocarbons and phthalates prior to gas chromatography-mass spectrometry.  

PubMed

A composite magnetic material consisting of zero-valent iron, iron oxide-oxyhydroxide and graphene was synthesized and used successfully as a sorbent for the micro solid-phase extraction of PAHs, PCBs and phthalic acid esters. The components endow the composite with multiple characteristics such as adsorption capability and facile removal due to its magnetic properties. Due to the ?-? electrostatic stacking property of graphene, the high specific surface area and the adsorption capability of both components, the resulting black flaky Fe(0)/iron oxide-oxyhydroxide/graphene composite showed high extraction efficiency for the target analytes from water samples. Compared with the neat graphene, the composite material has improved properties in terms of microextraction capabilities as both the hydrophobic graphene and zero-valent iron participate in the adsorption of the hydrophobic molecules. The precision from the extraction of all three groups of compounds was lower than 7% and the recoveries were from 90 to 93% from a spiked lake water sample. The high recoveries in relation to the low final volume of the desorption solvent ensure high preconcentration efficiency and a promising sorbent for analytical applications. PMID:23228921

Karamani, Anna A; Douvalis, Alexios P; Stalikas, Constantine D

2012-11-19

173

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

Microsoft Academic Search

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

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

2006-01-01

174

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

175

Simultaneous adsorption and degradation of Zn(2+) and Cu (2+) from wastewaters using nanoscale zero-valent iron impregnated with clays.  

PubMed

Clays such as kaolin, bentonite and zeolite were evaluated as support material for nanoscale zero-valent iron (nZVI) to simultaneously remove Cu(2+) and Zn(2+) from aqueous solution. Of the three supported nZVIs, bentonite-supported nZVI (B-nZVI) was most effective in the simultaneous removal of Cu(2+) and Zn(2+) from a aqueous solution containing a 100 mg/l of Cu(2+) and Zn(2+), where 92.9 % Cu(2+) and 58.3 % Zn(2+) were removed. Scanning electronic microscope (SEM) revealed that the aggregation of nZVI decreased as the proportion of bentonite increased due to the good dispersion of nZVI, while energy dispersive spectroscopy (EDS) demonstrated the deposition of copper and zinc on B-nZVI after B-nZVI reacted with Cu(2+) and Zn(2+). A kinetics study indicated that removing Cu(2+) and Zn(2+) with B-nZVI accorded with the pseudo first-order model. These suggest that simultaneous adsorption of Cu(2+)and Zn(2+) on bentonite and the degradation of Cu(2+)and Zn(2+) by nZVI on the bentonite. However, Cu(2+) removal by B-nZVI was reduced rather than adsorption, while Zn(2+) removal was main adsorption. Finally, Cu(2+), Zn(2+), Ni(2+), Pb(2+) and total Cr from various wastewaters were removed by B-nZVI, and reusability of B-nZVI with different treatment was tested, which demonstrates that B-nZVI is a potential material for the removal of heavy metals from wastewaters. PMID:23114838

Shi, Li-Na; Zhou, Yan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

2012-11-01

176

Effects of physicochemical factors on Cr(VI) removal from leachate by zero-valent iron and alpha-Fe(2)O(3) nanoparticles.  

PubMed

The effects of nanoparticle dosage, initial hexavalent chromium concentration, pH value, reaction temperature, and initial concentration of humic acid (HA) on chromate (CrO(4)(2-)) removal from landfill leachate by nanoscale zero-valent iron (NZVI) and hematite (alpha-Fe(2)O(3)) nanoparticles were examined in the present investigations. The Cr(VI) removal rate decreased as the initial Cr(VI) concentration and the reaction temperature increased, whereas corresponding removal rate by NZVI was higher than that of alpha-Fe(2)O(3). The optimum pH for the removal of Cr(VI) by NZVI was found to be 5.0 and more than 99.0% of Cr(VI) was removed within 5 h. However, the removal rate by alpha-Fe(2)O(3) decreased as pH increased. Presence of HA resulted in substantial reduction in the rate and extent of Cr(VI) removal by NZVI, whereas Cr(VI) removal rate by alpha-Fe(2)O(3) did not significantly decrease as HA concentration increased from 0.5 g/L to 3.0 g/L. Increasing the dosage of nanoparticles enhanced the rate constant and the removal of Cr(VI) by NZVI and alpha-Fe(2)O(3) followed pseudo-first-order reaction kinetics. The information should be very useful for the successful application of NZVI and alpha-Fe(2)O(3) for the treatment of groundwater or raw wastewater. PMID:20489248

Liu, T Y; Zhao, L; Tan, X; Liu, S J; Li, J J; Qi, Y; Mao, G Z

2010-01-01

177

Integration of nanosized zero-valent iron particles addition with UV/H2O2 process for purification of azo dye Acid Black 24 solution.  

PubMed

The challenging national effluent standards for color and organic concentration enforce the industrial concern most the techniques providing fast and efficient solution for the strenuous dye wastewater treatment before outflow. The best remediation technique pursuit is urgently demand for the industrial, government, academia and community. In this study, a di-azo dye, C.I. Acid Black 24, synthesized wastewater was successfully removed synchronously its total color and total organic carbon (TOC) using an integrated innovation technology by coupling the zero-valent iron (ZVI) nanoparticles with UV/H(2)O(2) oxidation process. The nanosized ZVI (NZVI) primarily reduced color successfully following coupling UV/H(2)O(2) oxidation process for the residual organic mineralization resulting reduction with oxidation process (Re-Ox) for total color removal and organic mineralization. From the experimental data, the Re-Ox process consumed shorter time than UV/H(2)O(2) oxidation process alone to obtain total color removal of dye wastewater. Moreover, the residual TOC of dye wastewater after NZVI reduction from 45 to 100% was effectively mineralized by UV/H(2)O(2) process. By using proposed processes integration with NZVI dosage of 0.3348 g l(-1) and hydrogen peroxide concentration of 23.2 mM, in only 10 min the AB24 color was complete eliminated and in 90 min the TOC was 93.9% removed. Thus, the coupling Re-Ox process was developed to provide a superior solution for dye wastewater treatment. PMID:19250743

Shu, Hung-Yee; Chang, Ming-Chin; Chang, Chi-Chen

2009-02-06

178

Changes in Ground-Water Quality near Two Granular-Iron Permeable Reactive Barriers in a Sand and Gravel Aquifer, Cape Cod, Massachusetts, 1997-2000.  

National Technical Information Service (NTIS)

Two experimental permeable reactive barriers (PRBs) of granular zero-valent iron were emplaced in the path of a tetrachloroethene plume (the Chemical Spill-10 plume) at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in June 1998. The goa...

J. G. Savoie D. B. Kent R. L. Smith D. R. LeBlanc D. W. Hubble

2004-01-01

179

Removal of co-present chromate and arsenate by zero-valent iron in groundwater with humic acid and bicarbonate.  

PubMed

The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe(0) were investigated in a batch setting using simulated groundwater with 5 mM NaCl, 1 mM Na(2)SO(4), and 0.8 mM CaCl(2) as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject to different impacts induced by co-existing As(V) or Cr(VI), humic acid and bicarbonate, originating from their distinct removal mechanisms by Fe(0). Cr(VI) removal is a reduction-dominated process, whereas As(V) removal principally involves adsorption onto iron corrosion products. Experimental results showed that Cr(VI) removal was not affected by the presence of As(V) and humic acid. However, As(V) removal appeared to be inhibited by co-present Cr(VI). When the Cr(VI) concentration was 2, 5, and 10 mg/L, in the absence of humic acid and bicarbonate, As(V) removal rate constants were decreased by 27.9%, 49.0%, and 61.2%, respectively, which probably resulted from competition between Cr(VI) and As(V) for adsorption sites of the iron corrosion products. Furthermore, the presence of humic acid significantly varied As(V) removal kinetics by delaying the formation and aggregation of iron hydroxides due to the formation of soluble Fe-humate complexes and stably dispersed fine iron hydroxides colloids. In the presence of bicarbonate, both Cr(VI) and As(V) removal was increased and the inhibitory effect of Cr(VI) on As(V) removal was suppressed, resulting from the buffering effects and the promoted iron corrosion induced by bicarbonate, and the formation of CaCO(3) in solution, which enhanced As(V) adsorption. PMID:19321187

Liu, Tongzhou; Rao, Pinhua; Mak, Mark S H; Wang, Peng; Lo, Irene M C

2009-03-12

180

Zero-valent iron reduction of nitrate in the presence of ultraviolet light, organic matter and hydrogen peroxide  

Microsoft Academic Search

This paper describes the use of metallic iron (Fe0) powder for nitrate removal in a well-mixed batch reactor. Important variables explored include Fe0 dosage (1–3g\\/L), UV light intensity (64–128W), and the presence of propanol (20mg\\/L as DOC) and H2O2 (100–200mg\\/L). Accumulation of ferrous ions released from the Fe0 surface can be expressed by an S-curve, which involves lag growth phase,

Chih-Hsiang Liao; Shyh-Fang Kang; Yu-Wei Hsu

2003-01-01

181

Rapid and extensive debromination of decabromodiphenyl ether by smectite clay-templated subnanoscale zero-valent iron.  

PubMed

Subnanoscale zerovalent iron (ZVI) synthesized using smectite clay as a template was utilized to investigate reduction of decabromodiphenyl ether (DBDE). The results revealed that DBDE was rapidly debrominated by the prepared smectite-templated ZVI with a reaction rate 10 times greater than that by conventionally prepared nanoscale ZVI. This enhanced reduction is plausibly attributed to the smaller-sized smectite-templated ZVI clusters (?0.5 nm) vs that of the conventional nanoscale ZVI (?40 nm). The degradation of DBDE occurred in a stepwise debromination manner. Pentabromodiphenyl ethers were the terminal products in an alkaline suspension (pH 9.6) of smectite-templated ZVI, whereas di-, tri-, and tetrabromodiphenyl ethers formed at the neutral pH. The presence of tetrahydrofuran (THF) as a cosolvent at large volume fractions (e.g., >70%) in water reduced the debromination rates due to enhanced aggregation of clay particles and/or diminished adsorption of DBDE to smectite surfaces. Modification of clay surfaces with tetramethylammonium (TMA) attenuated the colsovent effect on the aggregation of clay particles, resulting in enhanced debromination rates. Smectite clay provides an ideal template to form subnanoscale ZVI, which demonstrated superior debromination reactivity with DBDE compared with other known forms of ZVIs. The ability to modify the nature of smectite clay surface by cation exchange reaction utilizing organic cations can be harnessed to create surface properties compatible with various contaminated sites. PMID:22846063

Yu, Kai; Gu, Cheng; Boyd, Stephen A; Liu, Cun; Sun, Cheng; Teppen, Brian J; Li, Hui

2012-07-31

182

Influence of various organic molecules on the reduction of hexavalent chromium mediated by zero-valent iron.  

PubMed

Hexavalent chromium is a priority pollutant in many countries. Reduction of Cr(VI) to Cr(III) is desirable as the latter specie is an essential nutrient for maintaining normal physiological function and also has a low mobility and bioavailability. A variety of naturally-occurring organic molecules (containing alpha-hydroxyl carbonyl, alpha-hydroxyl carboxylate, alpha-carbonyl carboxylate, phenolate, carboxylates and/or thiol groups, siderophore, ascorbic acid); chelating agents (ethylenediaminetetraacetic acid derivates, acetyacetone) and others were examined their reducing activity towards a surfactant preparation (Tween 20) containing Cr(VI) and Fe(0) under a variety of reaction conditions. An appreciable enhancement (up to 50-fold) of the pseudo-first-order rate constant was achieved at acidic and circum neutral pH values for those compounds capable of reducing Cr(VI) (alpha-hydroxyl carboxylate, ascorbic acid, cysteine). Comparable enhancements were obtained for certain chelating agents (ethylenediaminetetraacetic acid derivates and siderophores) which is attributed to the formation of complexes with reaction products, such as Cr(III) and Fe(III), which impede the precipitation of Cr(III) and Fe(III) hydroxides and Cr(x)Fe(1-)(x)(OH)(3) and thus reduce passivation of the Fe(0) surface. The results suggest that these molecules might be used in effective remediation mediated by Fe(0) of Cr(VI)-contaminated soils or groundwater in a wide range of pH, thus increasing reaction rates and long-term performance of permeable reductive barriers. PMID:19559460

Rivero-Huguet, Mario; Marshall, William D

2009-06-25

183

Carbon isotope fractionation during reductive dechlorination of TCE in batch experiments with iron samples from reactive barriers  

Microsoft Academic Search

Reductive dechlorination of trichloroethene (TCE) by zero-valent iron produces a systematic enrichment of 13C in the remaining substrate that can be described using a Rayleigh model. In this study, fractionation factors for TCE dechlorination with iron samples from two permeable reactive barriers (PRBs) were established in batch experiments. Samples included original unused iron as well as material from a barrier

Christoph Schüth; Markus Bill; Johannes A. C. Barth; Gregory F. Slater; Robert M. Kalin

2003-01-01

184

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

NASA Astrophysics Data System (ADS)

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 SO42- 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.

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

2005-08-01

185

MINERAL PARAGENESIS OF FINE-GRAINED PRECIPITATES IN PERMEABLE REACTIVE BARRIERS OF ZERO-VALENT IRON  

EPA Science Inventory

U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a Geopr...

186

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

187

Reductive dechlorination of TCE by zero valent bimetals.  

PubMed

Six zero valent bimetal combinations were tested for trichloroethene (TCE) dechlorination. Palladium, nickel, and copper were coated at 500 mg kg(-1) or less onto zero valent iron, producing Pd/Fe, Ni/Fe, and Cu/Fe bimetals, and zinc, producing Pd/Zn, Ni/Zn, and Cu/Zn bimetals. The order of reactivity of the six bimetals and two metals based on surface area normalized pseudo first order rate constants was observed to be: Pd/Fe > Pd/Zn > Ni/Fe > Cu/Fe > Ni/Zn > Cu/Zn > Fe > Zn. Thus, in general, 1) iron metal and bimetals exhibit faster reaction rates than the corresponding zinc reductants, 2) bimetals exhibit faster reaction rates than pure metals, and 3) metal coating enhance reactivity in the order of Pd > Ni > Cu. Chlorinated intermediate products were observed in small amounts for Fe only. In all cases, the chloride balance, calculated from TCE and chloride concentrations, ranged from 90 to 111%. The results are discussed in terms of the effects of bimetal combinations on catalytic dechlorination, prevention of nonreactive film and metal corrosion. PMID:12641254

Kim, Y H; Carraway, E R

2003-01-01

188

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

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

2009-01-01

189

A two and half-year-performance evaluation of a field test on treatment of source zone tetrachloroethene and its chlorinated daughter products using emulsified zero valent iron nanoparticles.  

PubMed

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) and its chlorinated daughter products. Two EZVI delivery methods were used: pneumatic injection and direct injection. In the pneumatic injection plot, 2180 L of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of CVOCs. In the direct injection plot, 572 L of EZVI were injected to treat an estimated 0.155 kg of CVOCs. After injection of the EZVI, significant reductions in PCE and trichloroethene (TCE) concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for PCE (>85%) and TCE (>85%) and a significant increase in the mass flux of ethene. There were significant reductions in total CVOC mass (86%); an estimated reduction of 63% in the sorbed and dissolved phases and 93% reduction in the PCE DNAPL mass. There are uncertainties in these estimates because DNAPL may have been mobilized during and after injection. Following injection, significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed. In contrast, dissolved sulfate and pH decreased in many wells. The apparent effective remediation seems to have been accomplished by direct abiotic dechlorination by nanoiron followed by biological reductive dechlorination stimulated by the corn oil in the emulsion. PMID:22868086

Su, Chunming; Puls, Robert W; Krug, Thomas A; Watling, Mark T; O'Hara, Suzanne K; Quinn, Jacqueline W; Ruiz, Nancy E

2012-07-07

190

Degradation of Toxic Chemicals by Zero-Valent Metal Nanoparticles - A Literature Review  

Microsoft Academic Search

The ultimate aim of researchers in the area of decontamination is to develop the perfect decontaminant - a substance that will degrade all contaminants but will leave surfaces and environments unharmed. Published research into zero-valent metal particles (ZVMs), in particular iron, shows that these particles, particularly those whose size is on the nanoscale, have the potential to be used as

Lyndal McDowall

191

Effect of pH on the dissolution kinetics of zero-valent iron in the presence of EDDHA and EDTA  

SciTech Connect

The effect of environmental factors (e.g., pH, solution composition, and temperature) that affect the longevity of Fe(0) barriers in the subsurface are difficult to quantify independently from changes that occur to the passivating layer. Therefore, to quantify the rate of Fe(0) dissolution under conditions which maintain the pO2 at a relatively constant level and minimize the formation of a passivating layer on the metal surface, a series of experiments have been conducted with the single-pass flow-through (SPFT) apparatus. These experiments were conducted over the pH range from 7.0 to 12.0 at 90°C in the presence of 5 mM EDDHA or 5 mM EDTA. The organic acids, EDDHA and EDTA, helped to maintain the aqueous Fe concentration below saturation with respect to Fe-bearing alteration phases and minimize the formation of a partially oxidized surface film. Results suggest the corrosion of Fe(0) is relatively insensitive to pH and the forward or maximum dissolution rate is 3 to 4 orders of magnitude higher than when a passive film and corrosion products are present.

Lodge, Alexander M.; Pierce, Eric M.; Wellman, Dawn M.; Cordova, Elsa A.

2007-03-25

192

Impact of peroxydisulfate in the presence of zero valent iron on the oxidation of cyclohexanoic acid and naphthenic acids from oil sands process-affected water.  

PubMed

Large volumes of oil sands process-affected water (OSPW) are produced during the extraction of bitumen from oil sands in Alberta, Canada. The degradation of a model naphthenic acid, cyclohexanoic acid (CHA), and real naphthenic acids (NAs) from OSPW were investigated in the presence of peroxydisulfate (S(2)O(8)(2-)) and zerovalent iron (ZVI). For the model compound CHA (50 mg/L), in the presence of ZVI and 500 mg/L S(2)O(8)(2-), the concentration decreased by 45% after 6 days of treatment at 20 °C, whereas at 40, 60, and 80 °C the concentration decreased by 20, 45 and 90%, respectively, after 2 h of treatment. The formation of chloro-CHA was observed during ZVI/S(2)O(8)(2-) treatment of CHA in the presence of chloride. For OSPW NAs, in the presence of ZVI alone, a 50% removal of NAs was observed after 6 days of exposure at 20 °C. The addition of 100 mg/L S(2)O(8)(2-) to the solution increased the removal of OSPW NAs from 50 to 90%. In absence of ZVI, a complete NAs removal from OSPW was observed in presence of 2000 mg/L S(2)O(8)(2-) at 80 °C. The addition of ZVI increased the efficiency of NAs oxidation by S(2)O(8)(2-) near room temperature. Thus, ZVI/S(2)O(8)(2-) process was found to be a viable option for accelerating the degradation of NAs present in OSPW. PMID:22799739

Drzewicz, Przemys?aw; Perez-Estrada, Leonidas; Alpatova, Alla; Martin, Jonathan W; Gamal El-Din, Mohamed

2012-08-08

193

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 ...

194

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...

195

Study of different methods for enhancing the nitrate removal efficiency of a zero-valent metal process.  

PubMed

This study explores the effect of several enhancing methods, namely acid wash pretreatment, ultrasound treatment and addition of nickel catalyst on the nitrate removal efficiency of three zero-valent metals--iron, aluminium and zinc. It is hoped that by learning about the major reaction pathways of nitrate removal with zero-valent metals and the main factors influencing the reactivity of those zero-valent metals, optimum process conditions may be identified. The study results show that direct transfer of electrons is the major reaction pathway. Thus increasing a clean, fresh metal surface and decreasing the thickness of the diffusion layer to accelerate mass transfer are the main determinants of reaction rate. In the absence of a clean, fresh metal surface, the catalytic reaction of nickel becomes the primary removal pathway. PMID:16862777

Cheng, S F; Huang, C Y; Liu, J Y

2006-01-01

196

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

197

Field Studies of the Electrical Properties of Permeable Reactive Barriers for Monitoring Barrier Aging  

Microsoft Academic Search

Permeable reactive barriers (PRB) are a promising technology for the remediation of groundwater containing a range of organic and inorganic contaminants. Although there are number of different types of reactive barriers, some of the most important are constructed from granular zero valent iron (ZVI). One challenge in the large- scale, long-term implementation of PRBs is to monitor the change in

R. Sharpe; D. J. Labrecque; L. Slater

2006-01-01

198

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...

199

Partial oxidation (â??agingâ?ť) and surface modification decrease the toxicity of nano-sized zero valent ironâ??â??â??â??â??  

EPA Science Inventory

Zero-valent iron (nZVI) is a redox-active nanomaterial used for in situ remediation of contaminated groundwater. To assess the effect of â??agingâ?ť and surface modification on its potential neurotoxicity, cultured rodent microglia and neurons were exposed to fresh nZVI, â??agedâ?ť (>11...

200

Fundamental Studies of the Removal of Contaminants from Ground and Waste Waters via Reduction by Zero-Valent Metals  

SciTech Connect

Contaminated groundwater and surface waters are a problem throughout the United States and the world. In many instances, the types of contamination can be directly attributed to man's actions. For instance, the burial of chemical wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater and surface water contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements (including radioisotopes) that are soluble and mobile in soils and aquifers. Oxyanions of uranium, selenium, chromium, arsenic, technetium, and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. Uranium is a particularly widespread contaminant at most DOE sites including Oak Ridge, Rocky Flats, Hanford, Idaho (INEEL), and Fernald. The uranium contamination is associated with mining and milling of uranium ore (UMTRA sites), isotope separation and enrichment, and mixed waste and TRU waste burial. In addition, the careless disposal of halogenated solvents, such as carbon tetrachloride and trichloroethylene, has further contaminated many groundwaters at these sites. 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 at many DOE sites. 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. We are performing fundamental investigations of the interactions of the relevant chlorinated solvents and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop th e fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures.

Yarmoff, Jory A.; Amrhein, Christopher

1999-06-01

201

Accumulation Rate of Microbial Biomass at Two Permeable Reactive Barrier Sites  

Microsoft Academic Search

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 and permeability. Results are presented from solid phase and groundwater monitoring studies conducted at two Permeable Reactive Barrier sites, U.S. Coast Guard

R. Wilkin; G. Sewell; R. Puls

2001-01-01

202

Oxidation of sulfoxides and arsenic(III) in corrosion of nanoscale zero valent iron by oxygen: evidence against ferryl ions (Fe(IV)) as active intermediates in Fenton reaction.  

PubMed

Previous studies have shown that the corrosion of zerovalent iron (ZVI) by oxygen (O(2)) via the Fenton reaction can lead to the oxidation of various organic and inorganic compounds. However, the nature of the oxidants involved (i.e., ferryl ion (Fe(IV)) versus hydroxyl radical (HO(•))) is still a controversial issue. In this work, we reevaluated the relative importance of these oxidants and their role in As(III) oxidation during the corrosion of nanoscale ZVI (nZVI) in air-saturated water. It was shown that Fe(IV) species could react with sulfoxides (e.g., dimethyl sulfoxide, methyl phenyl sulfoxide, and methyl p-tolyl sulfoxide) through a 2-electron transfer step producing corresponding sulfones, which markedly differed from their HO(•)-involved products. When using these sulfoxides as probe compounds, the formation of oxidation products indicative of HO(•) but no generation of sulfone products supporting Fe(IV) participation were observed in the nZVI/O(2) system over a wide pH range. As(III) could be completely or partially oxidized by nZVI in air-saturated water. Addition of scavengers for solution-phase HO(•) and/or Fe(IV) quenched As(III) oxidation at acidic pH but had little effect as solution pH increased, highlighting the importance of the heterogeneous iron surface reactions for As(III) oxidation at circumneutral pH. PMID:21133375

Pang, Su-Yan; Jiang, Jin; Ma, Jun

2010-12-06

203

USE OF ZERO-VALENT IRON FOR WASTEWATER TREATMENT  

Microsoft Academic Search

Nowadays many water resources are polluted by anthropogenic sources including household and agricultural waste and industrial processes. Public concern over the environmental impact of wastewater pollution has increased. Several conventional wastewater treatment techniques, i.e. chemical coagulation, adsorption, activated sludge, have been applied to remove the pollution, however there are still some limitations, especially that of high operation costs. The use

Suwannee Junyapoon

2005-01-01

204

Degradation of Toxic Chemicals by Zero-Valent Metal Nanoparticles - A Literature Review.  

National Technical Information Service (NTIS)

The ultimate aim of researchers in the area of decontamination is to develop the perfect decontaminant - a substance that will degrade all contaminants but will leave surfaces and environments unharmed. Published research into zero-valent metal particles ...

L. McDowall

2005-01-01

205

Linkage of Mineral Precipitation to the Development of Heterogeneity in Permeable Reactive Barrier: a Field Column Study  

Microsoft Academic Search

A column study was conducted on site at Y-12, Oak Ridge, TN, to investigate the rate of mineral accumulation in relation to the hydraulic change as a result of heterogeneity development in a Fe(0) permeable reactive barrier (PRB). To better simulate the fluctuation in groundwater characteristics and the least disturbance to gas-water equilibrium, two columns filled with zero valent iron

W. Kamolpornwijit; L. Liang; G. R. Moline; A. B. Sullivan; O. R. West

2001-01-01

206

Reduction of N-nitrosodimethylamine with zero-valent zinc.  

PubMed

N-Nitrosodimethylamine (NDMA) is known as the disinfection by-product and the pollutant in the source water. Reduction with zero-valent zinc (Zn(0)) was investigated as a potential technology to treat NDMA. The results showed that Zn(0) was effective for NDMA reduction at initial pH 7.0. There were lag period and rapid period during the process, the corresponding zero-order rate constant (k(zero)) was 2.968 ± 0.245 ?g L(-1) h(-1) ([Zn(0)](0) = 10g L(-1)),the mass normalized pseudo-first-order rate (k(M)) was 0.1215 ± 0.0171 L g(-1) h(-1). The reactivity of zinc on NDMA removal was consistent with the zinc corrosion rate. NDMA had little effect on the corrosion of zinc. Lower solution pH benefited the reduction of NDMA with Zn(0). The consumption of the oxygen and the localized acidification should be the cause of the shift from lag to rapid reaction period in the aerobic experiments. 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH), dimethylamine (DMA) were detected as the products of NDMA degradation. The nitrogen mass balance at 24 h was 56%, the loss can be due to the formation of ammonium, the degradation of UDMH and other unmeasured products. DMA formed during the degradation of UDMH with Zn(0), the nitrogen loss could be caused by the formation of unmeasured products. Catalytic hydrogenation is proposed to be the mechanism based on the results and the redox properties of zinc and NDMA. One reduction process is: the active hydrogen atoms initially cleave and reduce the N=O bond in NDMA, generating UDMH. Then the N-N bond in UDMH is cleaved to form DMA and ammonium. PMID:23084118

Han, Ying; Chen, Zhong-lin; Tong, Li-na; Yang, Lei; Shen, Ji-min; Wang, Bin-yuan; Liu, Yue; Liu, Yu; Chen, Qian

2012-10-04

207

Catalytic transformation of persistent contaminants using a new composite material based on nanosized zero-valent metal - field experiment results  

NASA Astrophysics Data System (ADS)

A new composite material based on deposition of nanosized zero valent iron (ZVI) particles and cyanocobalamine (vitamin B12) on a diatomite matrix is presented. Cyanocobalamine is known to be an effective electron mediator, having strong synergistic effects with ZVI for reductive dehalogenation reactions. This composite material also improves the reducing capacity of nanosized ZVI by preventing agglomeration of iron particles, thus increasing their active surface area. The porous structure of the diatomite matrix allows high hydraulic conductivity, which favors channeling of contaminated water to the reactive surface of the composite material and in turn faster rates of remediation. The ability of the material to degrade or transform rapidly and completely a large spectrum of water pollutants will be demonstrated, based on results from two field site experiments where polluted groundwater containing a mixture of industrial and agricultural persistent pollutants was treated. In addition a set of laboratory experiments using individual contaminant solutions to analyze chemical transformations under controlled conditions will be presented.

Dror, I.; Merom Jacov, O.; Berkowitz, B.

2010-12-01

208

Reductive Dehalogenation of Chlorinated Ethenes with Elemental Iron: The Role of Microorganisms  

Microsoft Academic Search

Trichloroethne (TCE) transformation and the product distribution in an aqueous medium containing zero-valent iron (Fe(0)) was investigated in the presence of an anaerobic mixed culture to assess the potential role of microorganisms in permeable iron barriers. The presence of the culture increased the rate of TCE disappearance and changed the product distribution. Rapid formation and degradation of cis-dichloroethene (cis-DCE) was

K. J Lampron; P. C Chiu; D. K Cha

2001-01-01

209

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

Microsoft Academic Search

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

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

2002-01-01

210

Reactive transport modeling of an in situ reactive barrier for the treatment of hexavalent chromium and trichloroethylene in groundwater  

Microsoft Academic Search

Multicomponent reactive transport modeling was conducted for the permeable reactive barrier at the Coast Guard Support Center near Elizabeth City, North Carolina. The zero-valent iron barrier was installed to treat groundwater contaminated by hexavalent chromium and chlorinated solvents. The simulations were performed using the reactive transport model MIN3P, applied to an existing site-specific conceptual model. Reaction processes controlling the geochemical

K. Ulrich Mayer; David W. Blowes; Emil O. Frind

2001-01-01

211

Fundamental studies of the removal of contaminants from ground and waste waters via reduction by zero-valent metals. 1998 annual progress report  

SciTech Connect

'Contaminated groundwater and surface waters are a problem throughout the US and the world. In many instances, the types 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 and surface water 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. Oxyanions of selenium, nitrogen, arsenic, vanadium, uranium, chromium, and molybdenum are contaminants in agricultural areas of the Western US. 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. 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. 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, 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. As of May 1998, they have performed both bulk chemical measurements of the reduction reactions and surface science studies of model chemical systems. During these first two years of funding, the authors have made significant progress in both areas. Initially, they focused primarily on the reduction of selenate by elemental iron. They also performed some work with chromate, perchlorate, uranyl, and carbon tetrachloride. In the following sections some of the progress is described.'

Yarmoff, J.A.; Amrhein, C.

1998-06-01

212

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

213

Long-term efficiency and kinetic evaluation of ZVI barriers during clean-up of copper containing solutions  

Microsoft Academic Search

Sixteen continuous column experiments were carried out under dynamic flow conditions in order to study the efficiency of zero-valent iron (ZVI) permeable reactive barriers (PRBs) to remove copper from solutions. The effect of various operational parameters, such as pH of the feed solution (2.5 and 4.5), initial copper concentration (5 and 50mg\\/L), pore water velocity (30.48 and 152.40cm\\/day) and residence

K. Komnitsas; G. Bartzas; K. Fytas; I. Paspaliaris

2007-01-01

214

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

215

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

216

Reaction of zero-valent magnesium with water: Potential applications in environmental remediation  

NASA Astrophysics Data System (ADS)

This study examined the dissolution kinetics of granular zero-valent Mg (ZVMg) at pH 7 in water that was open to the atmosphere and buffered with 50 mM Na–MOPS. The oxidative dissolution of ZVMg was rapid; the initial amount of ZVMg (10–50 mg/L) dissolved completely within 200 min. The rate and extent of ZVMg dissolution was not affected by atmospheric oxygen. Although the oxidation of ZVMg is thermodynamically more feasible by dissolved oxygen or proton ions (H+), the primary oxidants are water molecules. The initial rate of ZVMg dissolution obeys first order kinetics with respect to ZVMg concentration with an observed rate constant, kMg,7 = 1.05 ± 0.06 × 10?2 min?1. Model calculations using the rate constant perfectly predict the extent of ZVMg dissolution for an extended time period at lower [Mg0]0 but underestimate at 50 mg/L [Mg0]0. The offset is likely attributed to the rapid dissolution of ZVMg particles, which could cause a substantial increase in the specific surface area. As to the reactivity of Mg–water system, we suggest that the hydrated electron (eaq-), the most powerful reducing agent, would probably be the major reactive entity under neutral and alkaline conditions. In addition, we discuss briefly the factors affecting the rate and extent of the Mg–water reaction such as background electrolytes, ZVMg impurities, surface passivation, solution pH and temperature based on literature review.

Lee, Giehyeon; Park, Jaeseon

2013-02-01

217

Aerosol synthesis of nano and micro-scale zero valent metal particles from oxide precursors  

SciTech Connect

In this work a novel aerosol method, derived form the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aerosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current work is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.

Phillips, Jonathan [Los Alamos National Laboratory; Luhrs, Claudia [UNM; Lesman, Zayd [UNM; Soliman, Haytham [UNM; Zea, Hugo [UNM

2010-01-01

218

Transformation of chlorinated hydrocarbons using aquocobalamin or coenzyme Fâââ in combination with zero-valent iron  

Microsoft Academic Search

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 Fâââ was combined with Fe(0) in aqueous systems containing either a single chlorinated compound or mixtures

Matthew J. Morra; Vladimir Borek; Jonathan Koolpe

2000-01-01

219

FIELD TESTING OF NANOSCALE ZERO-VALENT IRON PARTICLE TECHNOLOGY FOR IN-SITU GROUNDWATER TREATMENT  

Microsoft Academic Search

This pilot test has been carried out as part of a RCRA Corrective Measure Study (CMS) at a facility located in Research Triangle Park, North Carolina. The study area is located in the Durham subbasin of the Deep River Triassic Basin and is underlain by interbedded siltstone and sandstone sequences. Groundwater underlying portions of the site has been impacted by

Robert Glazier; Florin Gheorghiu; Lindsey Walata; Ramesh Venkatakrishnan

220

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...

221

Emulsified Zero-Valent Nano-Scale Iron Treatment of Chlorinated Solvent DNAPL Source Areas.  

National Technical Information Service (NTIS)

Chlorinated solvents are present in groundwater at an overwhelming number of Department of Defense (DoD), Department of Energy (DOE), and related contractor sites. A significant number of these sites have volatile organic compounds (VOC) present as free-p...

M. Watling S. O'Hara T. Krug

2010-01-01

222

Biogeochemical Reactions and Mineralogical Characteristics in an Iron Reactive Barrier at the Oak Ridge Y-12 Site  

NASA Astrophysics Data System (ADS)

A permeable iron reactive barrier was installed in late November, 1997 at the U.S. Department of Energy's Y-12 National Security Complex in Oak Ridge, Tennessee. The biogeochemical reactions and mineralogical and hydrological characteristics in the barrier were investigated over an extended field operation ( ~3 years). Results indicated that zero-valent iron (Fe0) reacts with a number of groundwater constituents such as bicarbonates, nitrate, and sulfate in addition to its effectiveness in removing contaminant metals or radionuclides such as uranium and technetium. Both nitrate and sulfate were reduced within or in the influence zone of the Fe0 with a low redox potential (i.e., low Eh). An increased anaerobic microbial population was also observed within and in the vicinity of the Fe0 barrier, and these microorganisms were at least partially responsible for the reduction of nitrate and sulfate in groundwater. Decreased concentrations of Ca2+ and bicarbonate in groundwater occurred as a result of the formation of minerals such as aragonite (CaCO3) and siderite (FeCO3), which coincided with the Fe0 corrosion and an increased groundwater pH. A suite of mineral precipitates was identified in the Fe0 barrier system, including amorphous iron oxyhydroxides, goethite, ferrous carbonates and sulfides, aragonite, and green rusts. These minerals were found to be responsible for the cementation and possibly clogging of Fe0 filings observed in a number of core samples from the barrier. Significant increases in cementation of the Fe0 occurred between two coring events conducted at ~1 year apart and appeared to correspond to the changes in an apparent decrease in hydraulic connectivity. The present study concludes that, while Fe0 may be used as an effective reactive medium for the retention or degradation of many redox-sensitive contaminants, its long-term reactivity and performance could be severely hindered by its reactions with other groundwater constituents; and groundwater flow may be restricted because of the build up of mineral precipitates at the soil/Fe0 interface. Depending on the site biogeochemical conditions, the rate of Fe0 corrosion may increase; therefore, the life span of the Fe0 barrier could be shorter than predicted in previous studies (i.e., <15 years instead of ~15-30 years).

Gu, B.; Watson, D.; Phillips, D.

2001-12-01

223

Changes in Ground-Water Quality near Two Granular-Iron Permeable Reactive Barriers in a Sand and Gravel Aquifer, Cape Cod, Massachusetts, 1997-2000  

USGS Publications Warehouse

Two experimental permeable reactive barriers (PRBs) of granular zero-valent iron were emplaced in the path of a tetrachloroethene plume (the Chemical Spill-10 plume) at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in June 1998. The goal of the field experiment was to achieve emplacement of a granular-iron PRB deeper than attempted before. The PRBs were expected to create a reducing environment and degrade the tetrachloroethene by reductive dechlorination. The goal of the work presented in this report was to observe temporary and sustained changes to the ground-water chemistry downgradient from the PRBs. A hydraulic-fracturing method involving injection of the granular iron with a guar-biopolymer and enzyme slurry was used to install the parallel 30- to 33-foot-wide wall-shaped barriers at a depth of 82 to 113 feet below land surface. An acetic acid and enzyme mixture was subsequently injected in wells near the barriers to degrade the guar biopolymer. Prior to the emplacement, tetrachloroethene concentrations in the Chemical Spill-10 plume at the study area were as high as 250 micrograms per liter. Other water properties in the plume generally were similar to the properties of uncontaminated ground water in the area, which typically has dissolved oxygen concentrations of 250 to 375 micromoles per liter, pH of 5.5 to 6.0, and specific conductance of 60 to 90 microsiemens per centimeter. Water-quality samples were collected periodically from monitoring wells near the PRBs to determine how the emplacement of the granular-iron walls altered the ground-water quality. In addition, an automated well-sampling device measured temperature, specific conductance, pH, and dissolved oxygen every 1?4 days for 16 months in a well downgradient from the two parallel PRBs. Temporary increases (lasting about 5 to 6 months) in specific conductance were observed downgradient from the PRBs as a result of the sodium chloride, potassium carbonate, and other salts included in the slurry and the acetic acid and enzyme mixture that was subsequently injected to degrade the guar biopolymer. Temporary increases in the concentrations of major cations (sodium, potassium, magnesium, and calcium) were observed downgradient from the PRBs, as were temporary but substantial increases in the dissolved and total organic carbon concentrations. Methane was detected, sulfate concentrations decreased temporarily, and concentrations of dissolved inorganic carbon increased in samples from wells downgradient from the PRBs. A sustained (longer than 12 months) reducing environment, in which dissolved oxygen concentrations decreased to zero, the pH increased to about 6.8, and dissolved iron concentrations increased substantially, developed as a result of the oxidation (corrosion) of the granular iron; this zone persisted at least 65 feet downgradient from the PRBs. The pH and dissolved iron concentrations increased with distance from the granular-iron walls. Concentrations of arsenic, cobalt, manganese, and phosphorus increased, and nitrate concentrations were reduced to below the detection limit downgradient from the walls. A sustained decrease of tetrachloroethene concentrations was not observed; however, reductive dechlorination products were observed at wells downgradient from the PRBs during several rounds of sampling. The emplacement of zero-valent iron in the aquifer to remove tetrachloroethene from the ground water caused changes in the water chemistry that persisted farther downgradient from the PRBs than has been observed at other sites because of the low chemical reactivity of the quartz-dominated aquifer sediments and the low ambient dissolved chemical concentrations in the ground water. The small transverse dispersion in the aquifer and the probable long-term persistence of the iron indicate that the chemically altered zone probably will extend a substantial distance downgradient from the PRBs for a substantial period of time (years); fur

Savoie, Jennifer G.; Kent, Douglas B.; Smith, Richard L.; LeBlanc, Denis R.; Hubble, David W.

2004-01-01

224

Development and Optimization of Targeted Nanoscale Iron Delivery Methods for Treatment of NAPL Source Zones.  

National Technical Information Service (NTIS)

This project was designed to develop and evaluate innovative nanoscale zero valent iron (nZVI) technologies for application to the treatment of dense nonaqueous phase liquid (DNAPL) source zones. An integrated research program, that combined multi-scale l...

A. Ramsburg K. Pennell L. Abriola

2011-01-01

225

Preparation of spherical iron nanoclusters in ethanol–water 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 ethanol–water 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

226

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

227

C-C coupling reactions of superstrong CF3 groups with C(sp2)-H bonds: reactivity and synthetic utility of zero-valent niobium catalyst.  

PubMed

It was found that zero-valent niobium is an efficient catalyst for the intramolecular C-C coupling reactions of o-aryl and o-alkenyl alpha,alpha,alpha-trifluorotoluene derivatives. The superstrong C-F bonds of CF3 groups and neighboring C(sp2)-H bonds were doubly activated, and fluorenes and indenes were obtained in good yields. The niobium fluorocarbenoid species is proposed to be the key intermediate. PMID:18175305

Fuchibe, Kohei; Mitomi, Ken; Suzuki, Ryo; Akiyama, Takahiko

2008-02-01

228

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

2009-05-22

229

Reductive dechlorination of chlorinated biphenyls by palladized zero-valent metals.  

PubMed

Laboratory-scale reductive dechlorination studies using bimetals were conducted to detoxify chlorinated biphenyls, which are known as one of the most recalcitrant organic compounds. Palladized iron and palladized zinc readily dechlorinated mono- and di-chlorinated biphenyls while plain metals were not active. Biphenyl and less chlorinated biphenyls were detected as the major products and calculated mass balance was around 100%, indicating that predominant degradation reaction was dechlorination. For Pd/Fe, degradation rates of mono-chlorobiphenyls were higher than those of di-chlorobiphenyls. Pd/Zn showed higher reactivity than Pd/Fe for the degradation of chlorobiphenyls. Degradation rates of three mono-chlorobiphenyls were in order of 4-CBP > 3-CBP > 2-CBP and this order was matched with the selectivity and dechlorination rate of dichlorobiphenyls. Based on the detected daughter products, it was considered that degradation reaction of dichlorobiphenyls was mainly governed by stepwise dechlorination. However, sequential reaction model fittings indicated that concerted dechlorination was also partly involved in the dichlorobiphenyl degradation. This study demonstrated that catalytically modified ZVM could be successfully applied for the detoxification of chlorinated aromatic compounds including PCBs. PMID:15137691

Kim, Young-Hun; Shin, Won Sik; Ko, Seok-Oh

2004-01-01

230

Biogeochemical mineralogical, and hydrological characteristics of an iron reactive barrier used for treatment of uranium and other contaminants  

SciTech Connect

A permeable iron reactive barrier was installed in late November, 1997 at the U.S. Department of Energy's Y-12 National Security Complex in Oak Ridge, Tennessee. The overall goal of this research was to determine the effectiveness of the use of zero-valent iron (Fe{sup 0}) to retain or remove uranium and other contaminants such as technetium and nitrate in groundwater. The long-term performance issues were investigated by studying the biogeochemical interactions between Fe{sup 0} and groundwater constituents and the mineralogical and biological characteristics over an extended field operation. Results from nearly 3 years of monitoring indicated that the Fe{sup 0} barrier was performing effectively in removing contaminant radionuclides such as uranium and technetium. In addition, a number of groundwater constituents such as bicarbonates, nitrate, and sulfate were found to react with the Fe{sup 0}. Both nitrate and sulfate were reduced within or in the influence zone of the Fe{sup 0} with a low redox potential (i.e., low Eh). An increased anaerobic microbial population was also observed within and in the vicinity of the Fe{sup 0} barrier, and these microorganisms were at least partially responsible for the reduction of nitrate and sulfate in groundwater. Decreased concentrations of Ca{sup 2+} and bicarbonate in groundwater occurred as a result of the formation of minerals such as aragonite (CaCO{sub 3}) and siderite (FeCO{sub 3}), which coincided with the Fe{sup 0} corrosion and an increased groundwater pH. A suite of mineral precipitates was identified in the Fe{sup 0} barrier system, including amorphous iron oxyhydroxides, goethite, ferrous carbonates and sulfides, aragonite, and green rusts. These minerals were found to be responsible for the cementation and possibly clogging of Fe{sup 0} filings observed in a number of core samples from the barrier. Significant increases in cementation of the Fe{sup 0} occurred between two coring events conducted at {approx}1 year apart and appeared to correspond to the changes in an apparent decrease in hydraulic gradient and connectivity. The present study concludes that, while Fe{sup 0} may be used as an effective reactive medium for the retention or degradation of many redox-sensitive contaminants, its long-term reactivity and performance could be severely hindered by its reactions with other groundwater constituents; and groundwater flow may be restricted because of the build up of mineral precipitates at the soil/Fe{sup 0} interface. Depending on the site biogeochemical conditions, the rate of Fe{sup 0} corrosion may increase; therefore, the life span of the Fe{sup 0} barrier could be shorter than predicted in previous studies ({approx}15-30 years).

Gu, Baohua [ORNL; Watson, David B [ORNL; Phillips, Debra H. [Queen's University, Belfast; Liang, Liyuan [ORNL

2002-05-01

231

Reduction of Chromium(VI) mediated by zero-valent magnesium under neutral pH conditions.  

PubMed

In an effort to assess the potential use of ZVMg in contaminant treatments, we examined Cr(VI) reduction mediated by ZVMg particles under neutral pH conditions. The reduction of Cr(VI) was tested with batch experiments by varying [Cr(VI)](0) (4.9, 9.6, 49.9 or 96.9 ?M) in the presence of 50 mg/L ZVMg particles ([Mg(0)](0) = 2.06 mM) at pH 7 buffered with 50 mM Na-MOPS. When [Cr(VI)](0) = 4.9 or 9.6 ?M, Cr(VI) was completely reduced within 60 min. At higher [Cr(VI)](0) (49.9 or 96.9 ?M), by contrast, the reduction became retarded at >120 min likely due to rapid ZVMg dissolution in water and surface precipitation of Cr(III) on ZVMg particles. Surface precipitation was observed only when [Cr(VI)](0) = 49.9 or 96.9 ?M and increased with increasing [Cr(VI)](0). The effect of dissolved oxygen was negligible on the rate and extent of Cr(VI) reduction. Experimental results indicated that Cr(VI) was reduced not directly by ZVMg but by reactive intermediates produced from ZVMg-water reaction under the experimental conditions employed in this study. In addition, the observed rates of Cr(VI) reduction appeared to follow an order below unity (0.19) with respect to [Cr(VI)](0). These results imply that ZVMg-mediated Cr(VI) reduction likely occurred via an alternative mechanism to the direct surface-mediated reduction typically observed for other zero-valent metals. Rapid and complete Cr(VI) reduction was achieved when a mass ratio of [ZVMg](0):[Cr(VI)](0) ? 100 at neutral pH under both oxic and anoxic conditions. Our results highlights the potential for ZVMg to be used in Cr(VI) treatments especially under neutral pH conditions in the presence of dissolved oxygen. PMID:23253471

Lee, Giehyeon; Park, Jaeseon; Harvey, Omar R

2012-11-29

232

Electron paramagnetic resonance spectroscopic studies on the zero-valent rhodium complex [Rh(P(OPr i) 3) 4] at X-and Q-band frequencies  

NASA Astrophysics Data System (ADS)

The EPR spectroscopic properties of the zero-valent rhodium complex [Rh(P(OPr i) 3) 4] have been examined at both X- and Q-band frequencies. The spectra show a large, essentially axial anisotropy and ligand hyperfine coupling to four equivalent 31P phosphorous nuclei. No resolved coupling to 103Rh was detected. The data indicate a tetragonally compressed tetrahedral structure (D 2d) rather than the alternative C 3v geometry provisionally proposed for the related [Co(P(OMe) 3) 4] complex.

George, G. N.; Klein, S. I.; Nixon, J. F.

1984-07-01

233

Experimental Determination of the Dissolution Kinetics of Zero-Valent Iron in the Presence of Organic Complexants  

SciTech Connect

Single-pass flow-through tests were conducted under conditions of relatively constant dissolved O2 [O2 (aq)] over the pH(23°C) range (from 7 to 12) and temperature (23° to 90°C) in the presence of EDTA and EDDHA to maintain dilute conditions and minimize the formation of a partially oxidized surface film and Fe-bearing secondary phase(s) during testing. These results indicate that the corrosion of Fe(0) is relatively insensitive to pH and temperature and the forward rate is 3 to 4 orders of magnitude higher than when a passive film and corrosion products are present. Tests conducted with Amasteel (a low carbon steel) and 99Tc-bearing Fe(0) metal indicated that the forward dissolution rates for both metals were similar, if not identical. In other words, under these test conditions the presence of P and 99Tc in the 99Tc-bearing Fe(0) metal appeared to have little effect on the forward dissolution rate and subsequent release of 99Tc.

Pierce, Eric M.; Wellman, Dawn M.; Lodge, Alex M.; Rodriguez, Elsa A.

2007-08-17

234

Removal of high concentration p-nitrophenol in aqueous solution by zero valent iron with ultrasonic irradiation (US-ZVI).  

PubMed

In this study, the US-ZVI system was used to produce the strong reductants including H and nascent Fe(2+) ions to eliminate the toxicity of the high concentration p-nitrophenol (PNP) wastewater. The effect of the reactor structure, initial pH, ZVI dosage, ultrasonic power and initial PNP concentration on the removal efficiency of PNP from water was investigated intensively. The results show that a higher removal rate can be obtained by using a conical structure reactor, and the lower initial pH can aid the acceleration of PNP removal rate by using US-ZVI system. Furthermore, the removal efficiencies of PNP increased obviously with the increase of initial ZVI concentration from 0 to 15 gL(-1). Also, the treatment capacity of ZVI was enhanced remarkably by the ultrasonic irradiation, and the US-ZVI system can maintain high treatment efficiency for the high concentration PNP wastewater (500-10,000 mgL(-1)). Meanwhile, the high removal efficiency of PNP was mainly resulted from the synergistic reaction of ZVI and US. At last, the main degradation product (i.e., p-aminophenol) was detected by gas chromatography-mass spectrum (GC-MS). Thus, the reaction pathway of PNP in the US-ZVI system is proposed as a reducing process by the H and nascent Fe(2+) ions. PMID:23454461

Lai, Bo; Chen, Zhaoyu; Zhou, Yuexi; Yang, Ping; Wang, Juling; Chen, Zhiqiang

2013-02-10

235

Removal of co-present chromate and arsenate by zero-valent iron in groundwater with humic acid and bicarbonate  

Microsoft Academic Search

The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe0 were investigated in a batch setting using simulated groundwater with 5mM NaCl, 1mM Na2SO4, and 0.8mM CaCl2 as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject

Tongzhou Liu; Pinhua Rao; Mark S. H. Mak; Peng Wang; Irene M. C. Lo

2009-01-01

236

Effects and mechanism of humic acid on chromium(VI) removal by zero-valent iron (Fe 0) nanoparticles  

Microsoft Academic Search

The present study dealt with the performance evaluation of the nanoscale Fe0 systems for the remediation of chromium contaminated groundwater in the ambient environment. The role of humic acid (HA) in the Cr(VI) removal and the reduction mechanism were investigated. HA was found to exert an obvious inhibitory effect on Cr(VI) removal by Fe0 nanoparticles, and the Cr(VI) removal efficiencies

Qian Wang; Naman Cissoko; Mi Zhou; Xinhua Xu

2011-01-01

237

Investigating the potential for long-term permeable reactive barrier (PRB) monitoring from the electrical signatures associated with the reduction in reactive iron performance  

SciTech Connect

The objective of this work was to conduct laboratory and field experiments to determine the sensitivity of low frequency electrical measurements (resistivity and induced polarization) to the processes of corrosion and precipitation that are believed to limit permeable reactive barrier (PRB) performance. The research was divided into four sets of experiments that were each written up and submitted to a peer-reviewed journal: [1] A laboratory experiment to define the controls of aqueous chemistry (electrolyte activity; pH; valence) and total zero valent iron (Fe0) available surface area on the electrical properties of Fe0 columns. [2] A laboratory experiment to determine the impact of corrosion and precipitation on the electrical response of synthetic Fe0 columns as a result of geochemical reactions with NaSO4 and NaCO3 electrolytes. [3] Laboratory experiments on a sequence of cores retrieved from the Kansas City PRB to determine the magnitude of electrical and geochemical changes within a field active PRB after eight years of operation [4] Field-scale cross borehole resistivity and induced polarization monitoring of the Kansas City PRB to evaluate the potential of electrical imaging as a technology for non-invasive, long-term monitoring of indicators of reduced PRB performance This report first summarizes the findings of the four major experiments conducted under this research. The reader is referred to the four papers in Appendices 1-4 for a full description of each experiment, including motivation and significance, technical details, findings and implications. The deliverables of the project, including the publications, conference papers and new collaborative arrangements that have resulted are then described. Appendices 5-6 contain two technical reports written by co-PI Korte describing (1) supporting geochemical measurements, and (2) the coring procedure, conducted at the Kansas City PRB as part of this project.

Slater, Lee D.; Korte, N.; Baker, J.

2005-12-14

238

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

239

Processes Affecting Nitro Reduction by Iron Metal: Mineralogical Consequences of Precipitation in Aqueous Carbonate Environments.  

National Technical Information Service (NTIS)

In aqueous systems, zero-valent iron metal is readily oxidized by many substances to ferrous iron. These reactions may be considered as corrosion processes in which oxidation of Fe(0) to Fe(2+) is the anodic half-reaction. In anoxic pure aqueous media the...

A. Agrawal P. G. Tratnyek P. Stoffyn-Egli L. Liang

1995-01-01

240

Formation Processes and Impacts of Reactive and Nonreactive Minerals in Permeable Reactive Barriers  

EPA Science Inventory

Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., changes in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction,...

241

PERMEABLE REACTIVE BARRIER STRATEGIES FOR REMEDIATION OF ARSENIC-CONTAMINATED GROUNDWATER  

EPA Science Inventory

Results are presented from laboratory batch tests using zero-valent iron to treat arsenic-contaminated groundwater. The laboratory tests were conducted using near- neutral pH groundwater from a contaminated aquifer located adjacent to a custom smelting facility. Experiments we...

242

Iron Barrier Walls for Chlorinated Solvent Remediation  

Microsoft Academic Search

\\u000a Over the past decade, permeable reactive barrier (PRB) technology has progressed through the conceptual, experimental and\\u000a innovative stages to its current status as accepted standard practice for groundwater remediation. As represented in the schematic\\u000a of Figure 16.1, a PRB can be defined as an in situ treatment zone positioned such that it passively captures a contaminant plume and removes or

Robert W. Gillham; John Vogan; Lai Gui; Michael Duchene; Jennifer Son

243

Accumulation Rate of Microbial Biomass at Two Permeable Reactive Barrier Sites  

NASA Astrophysics Data System (ADS)

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 and permeability. Results are presented from solid phase and groundwater monitoring studies conducted at two Permeable Reactive Barrier sites, U.S. Coast Guard Support Center (Elizabeth City, North Carolina) and the Denver Federal Center (Lakewood, Colorado). At both sites barrier installations have been in place for approximately five years. Over this period, consistent patterns of spatially heterogeneous microbial biomass accumulation are observed at these sites. The iron-aquifer interface witnesses the greatest accumulation of microbial biomass and mineral precipitates. There accumulation rates are a factor of 3 to 10 times greater than midwall or downgradient regions. Estimates of porosity loss due to mineral and biomass buildup range from about 1 to 5 percent per year of the initial available volume. Phospholipid fatty acid profiles indicate that the PRB biomass is dominated by biomarkers indicative of anaerobic sulfate reducing or iron reducing bacteria. This result is in agreement with acid volatile sulfide concentrations that strongly correlate with biomass concentrations. Upgradient groundwater chemistry and flow rate appear to be the main factors that control the rate (and type) of mineral precipitate formation as well as the rate of biomass accumulation. Notice, this is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

Wilkin, R.; Sewell, G.; Puls, R.

2001-12-01

244

Carbon isotopic fractionation during reductive dehalogenation of chlorinated ethenes by metallic iron  

Microsoft Academic Search

Highly chlorinated ethenes are resilient under aerobic conditions, but are known to degrade in reducing systems through biotic and abiotic reductive dehalogenation. Reductive dehalogenation of chlorinated ethenes by zero valent iron was recently shown to occur in both natural and engineered systems. The study reported in this paper was aimed at determining the magnitude and direction of the carbon isotopic

H. Dayan; T. Abrajano; N. C. Sturchio; L. Winsor

1999-01-01

245

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...

246

Investigating dominant processes in ZVI permeable reactive barriers using reactive transport modeling.  

PubMed

The reactive and hydraulic efficacy of zero valent iron permeable reactive barriers (ZVI PRBs) is strongly affected by geochemical composition of the groundwater treated. An enhanced version of the geochemical simulation code MIN3P was applied to simulate dominating processes in chlorinated hydrocarbons (CHCs) treating ZVI PRBs including geochemical dependency of ZVI reactivity, gas phase formation and a basic formulation of degassing. Results of target oriented column experiments with distinct chemical conditions (carbonate, calcium, sulfate, CHCs) were simulated to parameterize the model. The simulations demonstrate the initial enhancement of anaerobic iron corrosion due to carbonate and long term inhibition by precipitates (chukanovite, siderite, iron sulfide). Calcium was shown to enhance long term corrosion due to competition for carbonate between siderite, chukanovite, and aragonite, with less inhibition of iron corrosion by the needle like aragonite crystals. Application of the parameterized model to a field site (Bernau, Germany) demonstrated that temporarily enhanced groundwater carbonate concentrations caused an increase in gas phase formation due to the acceleration of anaerobic iron corrosion. PMID:23743511

Weber, Anne; Ruhl, Aki S; Amos, Richard T

2013-05-21

247

Oxidative removal of arsenite by Fe(II)- and polyoxometalate (POM)-amended zero-valent aluminum (ZVAl) under oxic conditions.  

PubMed

Abiotic transformation of As(III) to As(V) is possible which would decrease As toxicity. This study investigated the potential applications of zero-valent Al (ZVAl) or Al wastes, such as Al beverage cans, for converting As(III) to As(V) in an acidic solution under aerobic conditions. Results showed that As(III) could not be oxidized by ZVAl within 150 min reaction at pH 1 because of the presence of an oxide layer on ZVAl. However, 85 ?M As(III) could be completely oxidized with the addition of Fe(II) or POM due to the generation of a Fenton reaction or the enhancement of H2O2 production, respectively, on the ZVAl surfaces. Because Fe(II) or polyoxometalate (POM) exhibited more stable at low pH and scavenged rapidly the H2O2 produced on the aerated ZVAl surfaces, OH radical productions were more efficient and As(III) was rapidly oxidized in the ZVAl/O2 system with theses two catalysts. The catalytic oxidation kinetics of As(III) in the presence of Fe(II) or POM were best described by zero-order reaction, and the rate constants increased with a decrease of pH from 2 to 1. Following the oxidative conversion of As(III) to As(V) in the ZVAl/Fe/O2 system, As(V) was removed by the newly formed hydrous Al/Fe precipitates by increasing the solution pH to 6. Nonetheless, the As(V) removal was incomplete in the ZVAl/POM/O2 system because the hydrolyzed products of POM, e.g., PO4(3-), inhibited As(V) removal due to the competitive adsorption of the oxyanion on Al precipitates. Discarded Al-based beverage cans exhibit a higher efficiency for As(III) oxidation and final As removal compared with that of ZVAl, and thus, the potential application of Al beverage cans to scavenge As in solutions is feasible. PMID:23497977

Wu, C C; Hus, L C; Chiang, P N; Liu, J C; Kuan, W H; Chen, C C; Tzou, Y M; Wang, M K; Hwang, C E

2013-02-26

248

A new method to produce nanoscale iron for nitrate removal  

Microsoft Academic Search

This article proposes a novel technology combining electrochemical and ultrasonic methods to produce nanoscale zero valent iron (NZVI). With platinum placed in the cathode and the presence of the dispersion agent, 0.2g\\/l cetylpyridinium chloride (CPC), a cation surfactant, in the solution, the nanoscale iron particle was successfully produced with diameter of 1–20 nm and specific surface area of 25.4m2\\/g. The

Shiao-Shing Chen; Hong-Der Hsu; Chi-Wang Li

2004-01-01

249

Batch-Mixed Iron Treatment of High Arsenic Waters  

Microsoft Academic Search

This paper develops batch-mixed treatment with zero-valent iron as a point-of-use technology, appropriate for arsenic removal from water stored within rural homes in Bangladesh and West Bengal, India, where arsenic poisoning has affected an estimated 20 million people. Batch tests with iron yielded the following results: (1) High arsenic removal (>93%) was achieved from highly arsenated waters (2000?g\\/L) over short

Anuradha Ramaswami; Santhiti Tawachsupa; Mehmet Isleyen

2001-01-01

250

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

251

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 phosphorous 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.

Icenhower, Jonathan P.; Burns, Peter C.

2005-06-01

252

Influence of Groundwater Constituents on Longevity of Iron-Based Permeable Barriers.  

National Technical Information Service (NTIS)

Recent work has demonstrated the utility of iron permeable reactive barriers (PRBs) for the in situ treatment of chlorinated hydrocarbons. In these systems, the surface of the granular iron acts as an electron donor with the reducible contaminant acting a...

A. L. Roberts H. Fairbrother P. Searson P. J. Vikesland W. P. Ball

2002-01-01

253

Reactive Barriers and Pollutant Attenuation: The Iron(ii) Case  

NASA Astrophysics Data System (ADS)

The concept of iron reactive barriers exploits the capability of Fe(0) to act as an electron donor to organic or inorganic pollutants. The organic pollutants are then transformed (e.g. dechlorinated) and become less toxic, whereas some inorganic pollutants are reduced and can sorb on mineral phase or precipitate. This lost of mobility participates to the natural attenuation but the redox reactions will also lead to the launch of a great amount of Fe2+ in the aquifers. It is possible that this ion becomes the major cation in the system around the reactive barrier. What will be its influence on the major sink for pollutant, i.e.on clay minerals ? In the present study, we show that Fe2+ can sorb strongly onto the smectite particles. This adsorption can be explained and modeled by cation exchange on the basal planes of the particles and by specific adsorption on the edges, as previously described for other cations (Zn2+, Co2+, Ni2+). Calculation of the thermodynamic exchange constants shows that Fe2+ behaves like Ca2+ for cation exchangewhereas, for sorption on the clay edges sites, specific complexation constants are much higher than those published for Zn 2+ and Ni2+. Sorption of Fe(II) on the downstream aquifer clay particles may potentially have a strong impact on clay immobilization capacity towards both, organic and inorganic pollutants. In order to predict the evolution of pollutants downstream from a barrier, it is necessary to assess the behavior of Fe(II) which acts as a waste of this reactive barrier. This project is part of a Ph.D. study carried out in the framework of nuclear engineered barriers, sponsored by the french agency for the management of nuclear wastes (ANDRA), during the period 2000-2003.

Tournassat, C.; Charlet, L.

254

Integration of nanosized zero-valent iron particles addition with UV\\/H 2O 2 process for purification of azo dye Acid Black 24 solution  

Microsoft Academic Search

The challenging national effluent standards for color and organic concentration enforce the industrial concern most the techniques providing fast and efficient solution for the strenuous dye wastewater treatment before outflow. The best remediation technique pursuit is urgently demand for the industrial, government, academia and community. In this study, a di-azo dye, C.I. Acid Black 24, synthesized wastewater was successfully removed

Hung-Yee Shu; Ming-Chin Chang; Chi-Chen Chang

2009-01-01

255

Remediation of Chromate-Contaminated Groundwater Using Zero-Valent Iron: Field Test at USCG Support Center, Elizabeth City, North Carolina.  

National Technical Information Service (NTIS)

A field test was conducted near an old hard-chrome plating facility on the USCG Support Center near Elizabeth City, North Carolina to evaluate the in situ remediation of ground water contaminated by hexavalent chromium using a passive permeable reactive b...

R. W. Puls C. J. Paul R. M. Powell

1996-01-01

256

Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface  

Microsoft Academic Search

Dehalogenation of chlorinated aliphatic contaminants at the surface of zero-valent iron metal (Fe0) is mediated by the thin film of iron (hydr)oxides found on Fe0 under environmental conditions. To evaluate the role this oxide film plays in the reduction of chlorinated methanes, carbon tetrachloride (CCl4) degradation by Fe0 was studied under the influence of various anions, ligands, and initial CCl4

Timothy L. Johnson; William Fish; Yuri A. Gorby; Paul G. Tratnyek

1998-01-01

257

Reduction of selenite on iron surfaces: Amicro-spectroscopic study  

Microsoft Academic Search

Under anoxie conditions zero-valent iron can react with water to produce hydrogen gas and magnetite or green rust, a highly reactive mineral phase that can induce reduction processes and thus control the speciation, the solubility, toxicity and the mobility of redox sensitive elements in (nuclear) waste repositories. In this study micro X-ray fluorescence (micro-XRF) and micro X-ray absorption spectroscopy (micro-XAS)

A. M. Scheidegger; D. Grolimund; D. Cui; J. Devoy; K. Spahiu; P. Wersin; I. Bonhoure; M. Janousch

2003-01-01

258

Synthetic and field-based electrical imaging of a zerovalent iron barrier: Implications for monitoring long-term barrier performance  

Microsoft Academic Search

We performed a study of electrical imaging sensitivity to geochemical alteration of a zerovalent iron permeable reactive barrier PRB over time. Complex-resistivity measurements of laboratory cores from an operational PRB defined the electrical propertiesofbothunreactedandgeochemicallyalteredreacted iron, as well as the growth rate of the reacted front on the up gradientedgeofthebarrier.Laboratoryresultswereusedtogen- eratemodelsoftheelectricalstructureofthePRBat0,15,and30 years of operation. Synthetic cross-borehole resistivity and in- duced-polarization data

Lee Slater; Andrew Binley

2006-01-01

259

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

Microsoft Academic Search

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

2003-01-01

260

Rapid and controlled transformation of nitrate in water and brine by stabilized iron nanoparticles  

Microsoft Academic Search

Highly reactive zero-valent iron (ZVI) nanoparticles stabilized with carboxymethyl cellulose (CMC) were tested for reduction\\u000a of nitrate in fresh water and brine. Batch kinetic tests showed that the pseudo first-order rate constant (k\\u000a obs) with the stabilized nanoparticles was five times greater than that for non-stabilized counterparts. The stabilizer not only\\u000a increased the specific surface area of the nanoparticles, but

Zhong Xiong; Dongye Zhao; Gang Pan

2009-01-01

261

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

Microsoft Academic Search

There are reports that nano-sized zero-valent iron (Fe?) exhibits greater reactivity than micro-sized particles of Fe?, which 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. To better understand the reactivity of

James T. Nurmi; Paul G. Tratnyek; Vaishnavi Sarathy; Donald R. Baer; James E. Amonette; Klaus H. Pecher; Chongmin Wang; John C. Linehan; Dean W. Matson; R. Lee Penn; Michelle D. Driessen

2005-01-01

262

Reductive immobilization of chromate in water and soil using stabilized iron nanoparticles  

Microsoft Academic Search

Laboratory batch and column experiments were conducted to investigate the feasibility of using a new class of stabilized zero-valent iron (ZVI) nanoparticles for in situ reductive immobilization of Cr(VI) in water and in a sandy loam soil. Batch kinetic tests indicated that 0.08g\\/L of the ZVI nanoparticles were able to rapidly reduce 34mg\\/L of Cr(VI) in water at an initial

Yinhui Xu; Dongye Zhao

2007-01-01

263

Laboratory study on sequenced permeable reactive barrier remediation for landfill leachate-contaminated groundwater.  

PubMed

Permeable reactive barrier (PRB) was a promising technology for groundwater remediation. Landfill leachate-polluted groundwater riches in various hazardous contaminants. Two lab-scale reactors (reactors A and B) were designed for studying the feasibility of PRB to remedy the landfill leachate-polluted groundwater. Zero valent iron (ZVI) and the mixture of ZVI and zeolites constitute the first section of the reactors A and B, respectively; the second section of two reactors consists of oxygen releasing compounds (ORCs). Experimental results indicated that BOD5/COD increased from initial 0.32 up to average 0.61 and 0.6 through reactors A and B, respectively. Removal efficiency of mixed media for pollutants was higher than that of single media (ZVI only). Zeolites exhibited selective removal of Zn, Mn, Mg, Cd, Sr, and NH4+, and removal efficiency was 97.2%, 99.6%, 95.9%, 90.5% and 97.4%, respectively. The maximum DO concentration of reactors A and B were 7.64 and 6.78mg/L, respectively, while the water flowed through the ORC. Therefore, sequenced PRB system was effective and was proposed as an alternative method to remedy polluted groundwater by landfill leachate. PMID:18479811

Jun, Dong; Yongsheng, Zhao; Weihong, Zhang; Mei, Hong

2008-03-26

264

Tracer method to determine residence time in a permeable reactive barrier.  

PubMed

A method is presented to evaluate ground water residence time in a zero-valent iron (ZVI) permeable reactive barrier (PRB) using radon-222 ((222)Rn) as a radioactive tracer. Residence time is a useful indicator of PRB hydraulic performance, with application to estimating the volumetric rate of ground water flow through a PRB, identifying flow heterogeneity, and characterizing flow conditions over time as a PRB matures. The tracer method relies on monitoring the decay of naturally occurring aqueous (222)Rn as ground water flows through a PRB. Application of the method at a PRB site near Monticello, Utah, shows that after 8 years of operation, residence times in the ZVI range from 80 to 486 h and correlate well with chemical parameters (pH, Ca, SO(4), and Fe) that indicate the relative residence time. Residence times in this case study are determined directly from the first-order decay equation because we show no significant emanation of (222)Rn within the PRB and no measurable loss of (222)Rn other than by radioactive decay. PMID:19245377

Bartlett, T R; Morrison, S J

2009-02-25

265

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

266

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 phosphorus 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

267

Field assessment of carboxymethyl cellulose stabilized iron nanoparticles for in situ destruction of chlorinated solvents in source zones  

Microsoft Academic Search

This study pilot-tested carboxymethyl cellulose (CMC) stabilized zero-valent iron (ZVI) nanoparticles (with a trace amount of Pd catalyst) for in situ destruction of chlorinated ethenes such as perchloroethylene (PCE) and trichloroethylene (TCE) and polychlorinated biphenyls (PCBs) that had been in groundwater for decades. The test site was located in a well-characterized secondary source zone of PCBs and chlorinated ethenes. Four

Feng He; Dongye Zhao; Chris Paul

2010-01-01

268

Performance evaluation of a pilot-scale permeable reactive barrier at former Naval Air Station Moffett Field, Mountain View, California: Volume 1. Final report, April 1996--November 1998  

SciTech Connect

A pilot scale permeable reactive barrier (PRB) or treatment wall demonstration project was initiated by the US Navy EFA West at the former Naval Air Station Moffett Field site in Mountain View, California about 3 years ago. Performance evaluations and cost-benefit analyses were performed by the US Naval Facilities Engineering Service Center (NFESC) and were sponsored by the Department of Defense (DoD) Environmental Security Technology Certification Program (ESTCP). The Moffett Field PRB uses a funnel-and-gate design, where the funnel is made of interlocking steel sheet piles and the gate consists of a reactive cell filled with zero-valent granular iron. Since its construction in April 1996, groundwater monitoring was conducted on a quarterly basis to demonstrate the effectiveness of the barrier technology in capturing and remediating groundwater that contained dissolved chlorinated hydrocarbon compounds. The primary contaminants of concern at Moffett Field in the vicinity of the PRB are trichloroethene, cis-1,2 dichloroethene, and perchloroethene at upgradient concentrations of about 2900 micrograms per liter, 280 micrograms/L, and 26 microgram/L, respectively. Quarterly monitoring events included water level measurements, field parameter testing, and groundwater sampling at about 75 monitoring points. Two tracer tests using bromide solutions and flow meter testing were also completed in April and August 1997 at the site. Iron cell coring samples were collected and analyzed in December 1997 for use as indicators of reactivity and longevity. Data from the quarterly monitoring, tracer testing, and iron cell coring have been used to determine the overall barrier performance. Since the first sampling event in June 1996, concentrations of all chlorinated compounds were either reduced to non-detect or to below the drinking water maximum contaminant levels within the first 2-3 feet of the permeable iron cell.

Reeter, C.; Gavaskar, A.; Sass, B.; Gupta, N.; Hicks, J.

1998-11-01

269

High intrinsic barriers against spin-state relaxation in iron(II)-complex solutions.  

PubMed

Slow relaxation: Exergonic high-spin?low-spin relaxation after photoexcitation has been found to be exceedingly slow in a class of iron(II) complexes with hexadentate imine ligands. The thermal activation barriers that arise between the quintet- and singlet-spin manifolds are the highest ever recorded for spin crossover of isolated molecules in free solution (see figure). PMID:23229415

Stock, Philipp; P?dzi?ski, Tomasz; Spintig, Nicole; Grohmann, Andreas; Hörner, Gerald

2012-12-11

270

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...

271

Removal of dinitrotoluenes from water via reduction with iron and peroxidase-catalyzed oxidative polymerization: A comparison between Arthromyces ramosus peroxidase and soybean peroxidase  

Microsoft Academic Search

A two-step process for the removal of dinitrotoluene from water is presented: zero-valent iron reduction is coupled with peroxidase-catalyzed polymerization of the resulting diaminotoluenes (DAT). The effect of pH was examined in the reduction step: at pH 6 the reaction occurred much more rapidly than at pH 8. In the second step, optimal pH and substrate ratio, minimal enzyme concentration

Joey Patapas; Mohammad Mousa Al-Ansari; K. E. Taylor; J. K. Bewtra; N. Biswas

2007-01-01

272

Regulation of Brain Iron and Copper Homeostasis by Brain Barrier Systems: Implication in Neurodegenerative Diseases  

PubMed Central

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.

Zheng, Wei; Monnot, Andrew D.

2011-01-01

273

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

2011-11-13

274

Effect of water chemistry and aging on iron-mica interaction forces: implications for iron particle transport.  

PubMed

The transport of particles through groundwater systems is governed by a complex interplay of mechanical and chemical forces that are ultimately responsible for binding to geological substrates. To understand these forces in the context of zero valent iron particles used in the remediation of groundwater, atomic force microscopy (AFM)-based force spectroscopy was employed to characterize the interactions between AFM tips modified with either carbonyl iron particles (CIP) or electrodeposited Fe as a function of counterion valency, temperature, particle morphology, and age. The measured interaction forces were always attractive for both fresh and aged CIP and electrodeposited iron, except in 100 mM NaCl, as a consequence of electrostatic attraction between the negatively charged mica and positively charged iron. In 100 mM NaCl, repulsive hydration forces appeared to dominate. Good agreement was found between the experimental data and predictions based on the extended DLVO (XDLVO) theory. The effect of aging on iron particle composition and morphology was assessed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) revealing that the aged particles comprising a zero valent iron core passivated by a mixture of iron oxides and hydroxides. Force spectroscopy showed that aging caused variations in the adhesive force due to the changes in particle morphology and contact area. PMID:22716956

Pensini, Erica; Yip, Christopher M; O'Carroll, Denis M; Sleep, Brent E

2012-07-09

275

Reactive Membrane Barriers for Containment of Subsurface Contamination  

SciTech Connect

The overall goal of this project was to develop reactive membrane barriers--a new and flexible technique to contain and stabilize subsurface contaminants. Polymer membranes will leak once a contaminant is able to diffuse through the membrane. By incorporating a reactive material in the polymer, however, the contaminant is degraded or immobilized within the membrane. These processes increase the time for contaminants to breakthrough the barrier (i.e. the lag time) and can dramatically extend barrier lifetimes. In this work, reactive barrier membranes containing zero-valent iron (Fe{sup 0}) or crystalline silicotitanate (CST) were developed to prevent the migration of chlorinated solvents and cesium-137, respectively. These studies were complemented by the development of models quantifying the leakage/kill time of reactive membranes and describing the behavior of products produced via the reactions within the membranes. First, poly(vinyl alcohol) (PVA) membranes containing Fe{sup 0} and CST were prepared and tested. Although PVA is not useful in practical applications, it allows experiments to be performed rapidly and the results to be compared to theory. For copper ions (Cu{sup 2+}) and carbon tetrachloride, the barrier was effective, increasing the time to breakthrough over 300 times. Even better performance was expected, and the percentage of the iron used in the reaction with the contaminants was determined. For cesium, the CST laden membranes increased lag times more than 30 times, and performed better than theoretical predictions. A modified theory was developed for ion exchangers in reactive membranes to explain this result. With the PVA membranes, the effect of a groundwater matrix on barrier performance was tested. Using Hanford groundwater, the performance of Fe{sup 0} barriers decreased compared to solutions containing a pH buffer and high levels of chloride (both of which promote iron reactivity). For the CST bearing membrane, performance improved by a factor of three when groundwater was used in place of deionized water. The performance of high density polyethylene (HDPE) membranes containing Fe{sup 0} was then evaluating using carbon tetrachloride as the target contaminant. Only with a hydrophilic additive (glycerol), was the iron able to extend lag times. Lag times were increased by a factor of 15, but only 2-3% of the iron was used, likely due to formation of oxide precipitates on the iron surface, which slowed the reaction. With thicker membranes and lower carbon tetrachloride concentrations, it is expected that performance will improve. Previous models for reactive membranes were also extended. The lag time is a measurement of when the barrier is breached, but contaminants do slowly leak through prior to the lag time. Thus, two parameters, the leakage and the kill time, were developed to determine when a certain amount of pollutant has escaped (the kill time) or when a given exposure (concentration x time) occurs (the leakage). Finally, a model was developed to explain the behavior of mobile reaction products in reactive barrier membranes. Although the goal of the technology is to avoid such products, it is important to be able to predict how these products will behave. Interestingly, calculations show that for any mobile reaction products, one half of the mass will diffuse into the containment area and one half will escape, assuming that the volumes of the containment area and the surrounding environment are much larger than the barrier membrane. These parameters/models will aid in the effective design of barrier membranes.

William A. Arnold; Edward L. Cussler

2007-02-26

276

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

Microsoft Academic Search

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

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

2003-01-01

277

Automated Impedance Tomography for Monitoring Permeable Reactive Barrier Health  

SciTech Connect

The objective of this research was the development of an autonomous, automated electrical geophysical monitoring system which allows for near real-time assessment of Permeable Reactive Barrier (PRB) health and aging and which provides this assessment through a web-based interface to site operators, owners and regulatory agencies. Field studies were performed at four existing PRB sites; (1) a uranium tailing site near Monticello, Utah, (2) the DOE complex at Kansas City, Missouri, (3) the Denver Federal Center in Denver, Colorado and (4) the Asarco Smelter site in East Helena, Montana. Preliminary surface data over the PRB sites were collected (in December, 2005). After the initial round of data collection, the plan was modified to include studies inside the barriers in order to better understand barrier aging processes. In September 2006 an autonomous data collection system was designed and installed at the EPA PRB and the electrode setups in the barrier were revised and three new vertical electrode arrays were placed in dedicated boreholes which were in direct contact with the PRB material. Final data were collected at the Kansas City, Denver and Monticello, Utah PRB sites in the fall of 2007. At the Asarco Smelter site in East Helena, Montana, nearly continuous data was collected by the autonomous monitoring system from June 2006 to November 2007. This data provided us with a picture of the evolution of the barrier, enabling us to examine barrier changes more precisely and determine whether these changes are due to installation issues or are normal barrier aging. Two rounds of laboratory experiments were carried out during the project. We conducted column experiments to investigate the effect of mineralogy on the electrical signatures resulting from iron corrosion and mineral precipitation in zero valent iron (ZVI) columns. In the second round of laboratory experiments we observed the electrical response from simulation of actual field PRBs at two sites: the Kansas City barrier and the East Helena barrier. As these sites are also used for our field monitoring efforts, this allowed for a comparison between field and laboratory. In column studies with high concentrations of calcium and carbonate/bicarbonate, we observed that the increase of electrical resistivity and decrease of polarization magnitude is significant and is mainly controlled by the precipitation of calcium carbonates. In general, the electrical properties of all of the barriers studied follow a pattern. New barriers are fairly resistive with in-situ conductivity only a few times background (outside the barrier) values. Older barriers get increasingly conductive, with failed barriers showing values of over 100 S/m. The induced polarization response is more complicated. Chargeability values increase over time for young barriers, are largest for healthy barriers in the middle of their lifespan, and decrease as the barrier ages These results suggest that normalized IP appears promising as a measure of barrier age.

LaBrecque, D J; Adkins, P L

2009-07-02

278

Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers.  

PubMed

A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO3, FeCO3, and Fe(OH)2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO3-, Ca2+, CO3(2-), and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO3 and FeCO3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant. PMID:16386821

Li, Lin; Benson, Craig H; Lawson, Elizabeth M

2005-12-28

279

Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers  

NASA Astrophysics Data System (ADS)

A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO3, FeCO3, and Fe(OH)2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO3-, Ca2+, CO32-, and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO3 and FeCO3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant.

Li, Lin; Benson, Craig H.; Lawson, Elizabeth M.

2006-02-01

280

Carbo-Iron - An Fe/AC composite - As alternative to nano-iron for groundwater treatment.  

PubMed

Carbo-Iron(®)(1) is a novel colloidal composite consisting of activated carbon colloids (ACC) with a d(50) particle size of 0.8 ?m and anchored deposits of zero-valent iron clusters. This study discusses the principal material properties of Carbo-Iron colloids (CIC) relevant for groundwater treatment in comparison to commercially available nano-sized zero-valent iron (nZVI). CIC with 10-25 wt% Fe(0) have been developed and tested in laboratory studies for their suitability as dehalogenation reagent and are especially designed to overcome some limitations known from the utilization of nZVI: CIC combine the sorption properties of ACC and the chemical reactivity of nZVI. In column tests, flushed-in CIC showed an enhanced mobility in sediment material compared to nZVI, without the need for colloid stabilizers. However, adding 1-3 wt-% of carboxymethyl cellulose (CMC) related to CIC as colloid stabilizer was found to assure long-lived stable suspensions under laboratory conditions which may additionally support the already improved mobility of the CIC and the homogeneity of particle deposition on the sediment matrix. The hydrophobic character of the ACC carrier provides a high affinity of CIC to non-aqueous phase liquids (NAPL). In undisturbed flow, the reactive particles are collected at the water-NAPL interface. The reagent accumulation at the organic phase is necessary for a successful source attack. PMID:22591820

Mackenzie, Katrin; Bleyl, Steffen; Georgi, Anett; Kopinke, Frank-Dieter

2012-04-26

281

Reduction of selenite on iron surfaces: Amicro-spectroscopic study  

NASA Astrophysics Data System (ADS)

Under anoxie conditions zero-valent iron can react with water to produce hydrogen gas and magnetite or green rust, a highly reactive mineral phase that can induce reduction processes and thus control the speciation, the solubility, toxicity and the mobility of redox sensitive elements in (nuclear) waste repositories. In this study micro X-ray fluorescence (micro-XRF) and micro X-ray absorption spectroscopy (micro-XAS) were used to investigate the speciation of selenium that immobilized in the presence of Fe(0) and an anoxie synthetic groundwater solution. The selenium immobilization was accompanied by the formation of a green rust corrosion layer. Micro-XRF revealed that a Se-rich layer is present along the iron surfaces that were exposed to the Se(IV) solution. Micro-XAS experiments at the Se K-edge showed that Se(IV) was reduced to elemental Se(0). Thus, the reactivity of zero-valent and green rust should to be considered in assessing the long-term fate of selenium in nuclear waste repositories.

Scheidegger, A. M.; Grolimund, D.; Cui, D.; Devoy, J.; Spahiu, K.; Wersin, P.; Bonhoure, I.; Janousch, M.

2003-03-01

282

Relating Empirically Derived and Mechanistic Kinetic Models for Solute Reduction and Formation of Precipitates in Reactive Barriers of Iron Metal  

Microsoft Academic Search

To further our understanding of contaminant degradation rates and particle surface aging in iron metal permeable reactive barriers, we have developed an expanded reaction scheme and a set of accompanying rate laws. In this analysis, the particle surface is parceled into surface sites where reactions occur via sorption of an aqueous species, transformation of the sorbed species (and possibly the

J. Z. Bandstra; P. G. Tratnyek

2001-01-01

283

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

2013-09-14

284

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

285

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

286

Transient growth and thinning of the barrier oxide layer on iron measured by real-time spectroscopic ellipsometry  

Microsoft Academic Search

The transient growth and thinning of the passive film on iron was investigated in ethylenediaminetetraacetic acid, disodium salt (EDTA) containing borate buffer solutions of pH 8.4 using real-time spectroscopic ellipsometry under potentiostatic control. EDTA effectively suppressed the formation of the outer layer of the passive film, thereby rendering the barrier layer amenable to direct examination. It was shown that the

Zijie Lu; Digby D. Macdonald

2008-01-01

287

PLANT MULCH TO TREAT TCE IN GROUND WATER IN A PRB  

EPA Science Inventory

In the past ten years, passive reactive barriers (PRBs) have found widespread application to treat chlorinated solvent contamination in ground water. The traditional PRB commonly uses granular zero-valent iron and/or iron alloys as filling materials for treatment of chlorinated ...

288

EFFECTIVE REMOVAL OF TCE IN A LABORATORY MODEL OF A PRB CONSTRUCTED WITH PLANT MULCH  

EPA Science Inventory

In the past ten years, passive reactive barriers (PRBs) have found widespread application to treat chlorinated solvent contamination in ground water. The traditional PRB commonly uses granular zero-valent iron and/or iron alloys as filling materials for treatment of chlorinated ...

289

PLANT MULCH TO TREAT TCE IN GROUND WATER IN A PRB (ABSTRACT ONLY)  

EPA Science Inventory

In the past ten years, passive reactive barriers (PRBs) have found widespread application to treat chlorinated solvent contamination in ground water. The traditional PRB commonly uses granular zero-valent iron and/or iron alloys as filling materials for treatment of chlorinated ...

290

Advanced hydraulic fracturing methods to create in situ reactive barriers  

SciTech Connect

This article describes the use of hydraulic fracturing to increase permeability in geologic formations where in-situ remedial action of contaminant plumes will be performed. Several in-situ treatment strategies are discussed including the use of hydraulic fracturing to create in situ redox zones for treatment of organics and inorganics. Hydraulic fracturing methods offer a mechanism for the in-situ treatment of gently dipping layers of reactive compounds. Specialized methods using real-time monitoring and a high-energy jet during fracturing allow the form of the fracture to be influenced, such as creation of assymmetric fractures beneath potential sources (i.e. tanks, pits, buildings) that should not be penetrated by boring. Some examples of field applications of this technique such as creating fractures filled with zero-valent iron to reductively dechlorinate halogenated hydrocarbons, and the use of granular activated carbon to adsorb compounds are discussed.

Murdoch, L. [FRX Inc., Cincinnati, OH (United States)]|[Clemson Univ., SC (United States). Dept. of Geological Sciences; Siegrist, B.; Meiggs, T. [Oak Ridge National Lab., TN (United States)] [and others

1997-12-31

291

Investigations of Arsenic and Iron Interactions in Environmental Systems Using Synchrotron Radiation Techniques  

NASA Astrophysics Data System (ADS)

Understanding the reactions of arsenic with iron oxide is of critical importance to predicting the environmental cycling and bioavailability of this toxic element. Arsenic is strongly adsorbed on most of the common iron oxide surfaces such as hydrous iron oxide (ferrihydrite), goethite, and lepidocrocite. In addition to surface binding reactions, co-precipitation of arsenic with iron oxide also removes dissolved arsenic from solution. We investigated arsenic binding to iron oxide in a variety of different environmentally relevant systems including batch reactions with synthetic Fe(III) oxides, flow-through column experiments with corroding zero-valent iron as a groundwater remediation material, and sequestration during formation of an Fe(III) precipitate (plaque) on the root surfaces of two aquatic plants (Phalaris arundinacea (reed canarygrass) and Typha latifolia (cattail)). The mechanisms of arsenic binding were investigated using X-ray absorption spectroscopy and X-ray fluorescence microtomography. Arsenate (As(V)) and arsenite (As(III)) form inner-sphere surfaces complexes on ferrihydrite, goethite, and lepidocrocite with As-Fe inter-atomic distances indicative of predominantly bidentate binuclear complexes. Zero-valent iron corrosion causes in-situ Fe(III) oxide formation and both As(V) and As(III) are strongly adsorbed and occluded by the mixed Fe(III) oxide products. Iron plaque of both P. arundinacea and T. latifolia consisted predominantly of ferrihydrite with lesser amounts of goethite and minor levels of siderite. X-ray fluorescence microtomography results suggested that root surface arsenic generally corresponded to regions of enhanced Fe levels.

Manning, B. A.; Hansel, C. M.; Fendorf, S. E.

2002-12-01

292

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

293

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

2008-12-24

294

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.

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

2011-01-01

295

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

296

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, François; Dries, Jan; Pirard, Eric; Springael, Dirk; Bastiaens, Leen

2007-08-15

297

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

298

IRON  

Technology Transfer Automated Retrieval System (TEKTRAN)

Iron is an essential mineral. Although abundant in nature, it is mostly insoluble and biological absorbable forms are limited to most organisms. Iron is of fundamental importance to a variety of iron-containing proteins, especially the oxygen-carrying molecules hemoglobin and myoglobin. Iron may als...

299

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...

300

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...

301

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.

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

2011-01-01

302

Iron  

MedlinePLUS

... high in calories but low in vitamins and minerals. Sugar sweetened sodas and most desserts are examples ... higher doses of iron supplementation [ 86 ]. Iron and mineral interactions Some researchers have raised concerns about interactions ...

303

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...

304

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 ...

305

Surface Reactivity of Core Shell Iron-Iron Oxide Nanoclusters towards Breakdown of Carbon Tetrachloride  

NASA Astrophysics Data System (ADS)

Zero-valent iron (ZVI) is one of the technologies for groundwater remediation to reduce contaminants by removal of mobile chlorinated hydrocarbons. Iron-Iron oxide (Fe/Fe3O4) nanoclusters (NCs) made in our laboratory using cluster deposition technique have enhanced reactivity towards targeted contaminants due to the presence of ZVI protected by a passivated oxide shell. Here, we investigate the effectiveness of the Fe/Fe3O4 NCs in reducing carbon tetrachloride (CT) under laboratory conditions. The reactivity of the NCs was investigated by conducting unbuffered aqueous batch experiments to reduce CT at room temperature. Initial results show that 80% of the degradation of CT resulted in the formation of dichloromethane (DCM) and chloroform (CF); the remainder likely followed a competing pathway to yield nonhazardous products such as CO. The production of undesirable hydrogenated products such as DCM and CF suggests that the dominant reaction pathway occurs through hydrogen (H) atom transfer via H atoms generated by corrosion of the iron. Comparative experiments with ZVI NCs prepared by other methods are underway and the results will be reported. Future work is to analyze and understand factors that control the reaction pathways between desirable and undesirable products.

Tarsem S., Maninder K.; Qiang, You; Kim, Hongseok; Amonette, James E.; Baer, Donald R.

2012-02-01

306

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

307

Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 2. Geochemical modeling and solid phase studies.  

PubMed

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 is expected to play a key role in directing arsenic uptake processes. Geochemical modeling reveals contrasting pH-dependencies for As(III) and As(V) precipitation. At the moderately alkaline pH conditions typically encountered in zerovalent iron reactive barriers, As(III) is unlikely to precipitate as an oxide or a sulfide phase. Conversely, increasing pH is expected to drive precipitation of metal arsenates including ferrous arsenate. Bacterially mediated sulfate reduction plays an important role in field installations of granular iron. Neoformed iron sulfides provide surfaces for adsorption of oxyanion and thioarsenic species of As(III) and As(V) and are expected to provide enhanced arsenic removal capacity. X-ray absorption near edge structure (XANES) spectra indicate that arsenic is sequestered in the solid phase as both As(III) and As(V) in coordination environments with O and S. Arsenic removal in the PRB probably results from several pathways, including adsorption to iron oxide and iron sulfide surfaces, and possible precipitation of ferrous arsenate. Corrosion of granular iron appears to result in some As(III) oxidation to As(V) as the proportion of As(V) to As(III) in the solid phase is greater compared to influent groundwater. As(0) was not detected in the PRB materials. These results are broadly comparable to laboratory based studies of arsenic removal by zerovalent iron, but additional complexity is revealed in the field environment, which is largely due to the influence of subsurface microbiota. PMID:19167132

Beak, Douglas G; Wilkin, Richard T

2008-12-24

308

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

309

Corrosion and environmental-mechanical characterization of iron-base nuclear waste package structural barrier materials. Annual report, FY 1984  

SciTech Connect

Disposal of high-level nuclear waste in deep underground repositories may require the development of waste packages that will keep the radioisotopes contained for up to 1000 y. A number of iron-base materials are being considered for the structural barrier members of waste packages. Their uniform and nonuniform (pitting and intergranular) corrosion behavior and their resistance to stress-corrosion cracking in aqueous environments relevant to salt media are under study at Pacific Northwest Laboratory. The purpose of the work is to provide data for a materials degradation model that can ultimately be used to predict the effective lifetime of a waste package overpack in the actual repository environment. The corrosion behavior of the candidate materials was investigated in simulated intrusion brine (essentially NaCl) in flowing autoclave tests at 150/sup 0/C, and in combinations of intrusion/inclusion (high-Mg) brine environments in moist salt tests, also at 150/sup 0/C. Studies utilizing a /sup 60/Co irradiation facility were performed to determine the corrosion resistance of the candidate materials to products of brine radiolysis at dose rates of 2 x 10/sup 3/ and 1 x 10/sup 5/ rad/h and a temperature of 150/sup 0/C. These irradiation-corrosion tests were ''overtests,'' as the irradiation intensities employed were 10 to 1000 times as high as those expected at the surface of a thick-walled waste package. With the exception of the high general corrosion rates found in the tests using moist salt containing high-Mg brines, the ferrous materials exhibited a degree of corrosion resistance that indicates a potentially satisfactory application to waste package structural barrier members in a salt repository environment.

Westerman, R.E.; Haberman, J.H.; Pitman, S.G.; Pulsipher, B.A.; Sigalla, L.A.

1986-03-01

310

Pulsed magnetic field improves the transport of iron oxide nanoparticles through cell barriers.  

PubMed

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 aggregation 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

2013-02-13

311

Investigating the potential for long-term permeable reactive barrier (PRB) monitoring from the electrical signatures associated with the reduction in reactive iron performance  

SciTech Connect

The objective of this project is to quantify the ability of the electrical induced polarization (IP) method to noninvasively monitor the reduction in reactive iron performance that is known to reduce the effectiveness of the permeable reactive barrier (PRB) with time. The primary scientific goals include: (A) fundamental laboratory studies to evaluate the sensitivity of the IP method to: Fe0 total surface area Fe0 surface chemistry physical/chemical changes to the Fe0 surface resulting from oxidation and precipitation; (B) monitoring of the electrical tomographic response of the Kansas City PRB over a three-year period and assessment, via correlation with aqueous geochemical data and extracted iron cores, of whether electrical signatures associated with reduced PRB performance are resolvable in field studies; (C) optimization of a three-dimensional tomographic imaging algorithm for application to highly conductive, high electrical contrast environments as represented by a PRB.

Slater, Lee

2004-06-15

312

Permeable reactive barrier of surface hydrophobic granular activated carbon coupled with elemental iron for the removal of 2,4-dichlorophenol in water.  

PubMed

Granular activated carbon was modified with dimethyl dichlorosilane to improve its surface hydrophobicity, and therefore to improve the performance of permeable reactive barrier constructed with the modified granular activated carbon and elemental iron. X-ray photoelectron spectroscopy shows that the surface silicon concentration of the modified granular activated carbon is higher than that of the original one, leading to the increased surface hydrophobicity. Although the specific surface area decreased from 895 to 835 m(2)g(-1), the modified granular activated carbon could adsorb 20% more 2,4-dichlorophenol than the original one did in water. It is also proven that the permeable reactive barrier with the modified granular activated carbon is more efficient at 2,4-dichlorophenol dechlorination, in which process 2,4-dichlorophenol is transformed to 2-chlorophenol or 4-chlorophenol then to phenol, or to phenol directly. PMID:20864257

Yang, Ji; Cao, Limei; Guo, Rui; Jia, Jinping

2010-09-22

313

LONG-TERM GEOCHEMICAL BEHAVIOR OF A ZEROVALENT IRON PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM IN GROUNDWATER  

EPA Science Inventory

Passive, in-situ reactive barriers have proven to be viable, cost-effective systems for the remediation of Cr-contaminated groundwater at some sites. Permeable reactive barriers (PRBs) are installed in the flow-path of groundwater, most typically as vertical treatment walls. Re...

314

Removal of contaminants from aqueous solution by reaction with iron surfaces  

SciTech Connect

Irrigation drainage and industrial wastewaters often contain elevated levels of toxic oxyanions and oxycations such as selenate, chromate, and uranyl. A potential remediation method is to react contaminated water with zero-valent iron, which transforms the mobile contaminants into immobile forms. In this work, iron foil was exposed to aqueous solutions containing the relevant ions, and the reacted surfaces were characterized by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM images collected in situ show that the protrusions on the foil surface associated with iron oxides are smoothed out by the reaction. XPS indicates that partially reduced Se(IV) and Cr(III) are adsorbed on the surface, while uranium is deposited as U(VI), i.e., without reduction. More Se and Cr are deposited when the atmospheric gases are removed from solution because of the elimination of a competing process in which dissolved O{sub 2} increases the thickness of the iron oxide overlayer to the point where the reduction reaction is quenched. The amount of U deposited is greatly increased when the atmospheric gases are removed because of the elimination of dissolved CO{sub 2}, which can form carbonate complexes with uranium.

Qiu, S.R.; Lai, H.F.; Roberson, M.J.; Hunt, M.L.; Amrhein, C.; Giancarlo, L.C.; Flynn, G.W.; Yarmoff, J.A.

2000-03-07

315

Column studies on transport of deicing additive benzotriazole in a sandy aquifer and a zerovalent iron barrier.  

PubMed

Benzotriazole (BTA), a chemical with wide industrial applications, is a typical additive in deicer/anti-icer used at airport. To achieve a better understanding of the transport behaviour and environmental fate of BTA, laboratory column studies have been performed on subsoil samples from Oslo Airport, Gardermoen. To explore possibilities for aquifer remediation, BTA behaviour was also studied in a column of granular zerovalent iron (Fe(0)). The subsoil column study demonstrates a very limited retardation of BTA. Consecutive loadings of BTA of the subsoil column showed no change of the break-through curve (BTC) and complete desorption was observed. The sorption behaviour of BTA to metallic iron (Fe(0)) was rather complex. Considerable retardation was observed in the Fe(0) column and repeated BTA loading resulted in an earlier break-through. Between 20% and 50% of the input concentration was retained permanently in the iron (Fe(0)) column. The BTA sorption to metallic iron was found to be enhanced by chloride which lowered the break-through concentration (i.e the C/C(0) plateau). The fraction of BTA remaining in the iron column was found to vary with the flow rate, indicating a time dependant multilayer sorption mechanism. The steady increase in the amount of adsorbed BTA to the iron column during loading corresponds to a rather strong bonding of 4-15 BTA layers to the iron surface. A very slow desorption of BTA was observed; even after flushing with 753 pore volumes of BTA free water, 7.5% of the BTA remained in the column. A geochemical model was developed based on PHREEQC-2 to simulate the sorption and transport of BTA in the tested materials. The BTA sorption was modelled with Freundlich sorption isotherms, as earlier determined in batch experiments. A slight adjustment of the Freundlich parameters was required to fit the observed column break-through. However, our model was not able to simulate the long-term retainment of BTA in the granular iron columns. The simulations confirm the high mobility of BTA in groundwater aquifers and suggest that zerovalent iron could be used to retain a BTA plume, although oxidation of the sorbent might reduce the long-term performance of such a remediation scheme and slow desorption has been observed. PMID:17588639

Jia, Yu; Breedveld, Gijs D; Aagaard, Per

2007-06-22

316

Green rust nanoparticle formation, stability and oxidation, and its role in natural and engineered systems  

Microsoft Academic Search

Highly reactive green rust (GR) nanoparticles are believed to play an important role in the geochemistry of water saturated sediments (e.g. hydromorphic soils) and engineered systems where zero-valent iron is used for decontaminating polluted sites (e.g. permeable reactive barriers). The presence of structural Fe2+ within GR and its high specific surface area make it an effective reductant for many inorganic

S. Shaw; L. Benning; I. Ahmed; G. Kakonyi; A. Sumoondur; N. Terrill

2009-01-01

317

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

318

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

319

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

2012-11-21

320

Simultaneous Cr(VI) reduction and non-ionic surfactant oxidation by peroxymonosulphate and iron powder.  

PubMed

Some industrial wastewaters contain both hexavalent chromium and surfactants. In this work, their removal from aqueous solution by zero-valent iron (ZVI) and peroxymonosulphate (PMS) was studied using Brij 35 as a representative non-ionic surfactant. The performance of the ZVI/PMS system in the simultaneous removal of both pollutants was compared to that achieved with control solutions containing either Cr(VI) or Brij 35 separately. Reactions were carried out over 24h at initial pH=2.3 with variable initial amounts of Cr(VI) and Brij 35. The results showed that surfactant removal was enhanced in the system also containing Cr(VI). Surfactant degradation followed zero-order kinetics and produced formic acid as the main by-product, together with hydroxylated aldehydes, formates and alcohols that were identified by LC/MS. The presence of surfactant similarly enhanced Cr(VI) reduction, which also followed zero-order kinetics. Chromium removal was quantitative only when the initial chromium concentration was lower than 140 mg L(-1). Reduced chromium was mainly in the solution phase together with dissolved iron. Precipitation with NaOH was therefore required to definitively remove dissolved metals from the investigated system. PMID:23499224

Volpe, Angela; Pagano, Michele; Mascolo, Giuseppe; Lopez, Antonio; Ciannarella, Ruggiero; Locaputo, Vito

2013-03-15

321

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

Microsoft Academic Search

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

L. A. Charlot; R. E. Westerman

1981-01-01

322

Nano-scale metallic iron for the treatment of solutions containing multiple inorganic contaminants.  

PubMed

Although contaminant removal from water using zero-valent iron nanoparticles (INP) has been investigated for a wide array of chemical pollutants, the majority of studies to date have only examined the reaction of INP in simple single-contaminant systems. Such systems fail to reproduce the complexity of environmental waters and consequently fail as environmental analogues due to numerous competitive reactions not being considered. Consequently there is a high demand for multi-elemental and site-specific studies to advance the design of INP treatment infrastructure. Here INP are investigated using batch reactor systems over a range of pH for the treatment of water containing multi-element contaminants specifically U, Cu, Cr and Mo, selected to provide site-specific analogues for leachants collected from the Li?ava mine, near Oravi?a in South West Romania. Concurrently, a U-only solution was also analysed as a single-system for comparison. Results confirmed the suitability of nano-Fe(0) as a highly efficient reactive material for the aqueous removal of Cr(IV), Cu(II) and U(VI) over a range of pH applicable to environmental waters. Insufficient Mo(VI) removal was observed at pH >5.7, suggesting that further studies were necessary to successfully deploy INP for the treatment of geochemically complex mine water effluents. Results also indicated that uranium removal in the multi-element system was less than for the comparator containing only uranium. PMID:21115222

Scott, T B; Popescu, I C; Crane, R A; Noubactep, C

2010-11-09

323

Cellular management of iron in the brain  

Microsoft Academic Search

All organs including the brain contain iron, and the proteins involved in iron uptake (transferrin and transferrin receptor) and intracellular storage (ferritin). However, because the brain resides behind a barrier and has a heterogeneous population of cells, there are aspects of its iron management that are unique. Iron management, the timely delivery of appropriate amounts of iron, is crucial to

James R. Connor; Sharon L. Menzies

1995-01-01

324

Reduction of 2,4,6-trichlorophenol with zero-valent zinc and catalyzed zinc.  

PubMed

Reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was conducted with Zn and Zn bimetals, Pd/Zn, Ni/Zn, Cu/Zn, Pt/Zn. Zn showed relatively low reaction rate toward 2,4,6-TCP, while Pd/Zn had dramatically increased reactivity and other bimetals had higher reaction rates than that of plain zinc. Phenol and less chlorinated phenols were found as dechlorination products. Pd/Zn produced cyclohexanone which is a product of aromatic ring reduced. Surface area normalized kinetic constants and second metal contents normalized kinetic constants were calculated and compared. Two mechanisms, mainly catalytic activation and enhanced corrosion, were proposed for the reactivity enhancement. PMID:19171423

Choi, Jeong-Hak; Kim, Young-Hun

2008-12-06

325

The enhancement methods for the degradation of TCE by zero-valent metals  

Microsoft Academic Search

Batch tests were performed to compare the degradation rates of TCE on Fe0 and Zn0. Our results indicated that the degradating capability of Zn0 to TCE was nearly 10 times higher than that of Fe0. On the other hand, the degradation rates of Fe0 or Zn0 in conjunction with other metals for reduction of TCE was investigated. The selected metals

Shu-Fen Cheng; Shian-Chee Wu

2000-01-01

326

Enhanced formation of oxidants from bimetallic nickel-iron nanoparticles in the presence of oxygen.  

PubMed

Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants capable of transforming organic contaminants in water. However,the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not increase the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4-9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values. PMID:19068843

Lee, Changha; Sedlak, David L

2008-11-15

327

Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen  

PubMed Central

Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not enhance the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4 – 9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values.

Lee, Changha; Sedlak, David L.

2009-01-01

328

Effect of approximating the scattering indicatrix and representation of the constants on the results of calculating the field characteristics beyond an iron barrier  

Microsoft Academic Search

Calculations were carried out for barriers of thickness H = 5, 10, 20, 40, and 60 em and for R = 2.5, 10, and 100 cm. The neutrons passing through the barrier were distributed over the nine energy intervals (10.5-6.5; 6.5-4.0; 4.0-3.0; 3.0-2.0; 2.0-1.5; 1.5-1.0; 1.0-0.5; 0.5-0.25; 0.25-0.1 MeV). Absorption and escape of neutrons beyond the barrier were taken into

G. Sh. Pekarskii; Yu. Ya. Katsman; G. A. Kucher

1977-01-01

329

2,4-Dichlorophenoxyacetic acid (2,4-D) degradation promoted by nanoparticulate zerovalent iron (nZVI) in aerobic suspensions.  

PubMed

Reactive species generated by Fe(0) oxidation promoted by O2 (catalyzed or not by ligands) are able to degrade contaminant compounds like the herbicide 2,4-dichlorophenoxyacetic acid. The degradation of 2,4-D was influenced by the concentrations of zero valent iron (ZVI) and different ligands, as well as by pH. In the absence of ligands, the highest 2,4-D degradation rate was obtained at pH 3, while the highest percentage degradation (50%) was achieved at pH 5 after 120 min of reaction. Among the ligands studied (DTPA, EDTA, glycine, oxalate, and citrate), only ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) significantly enhanced oxidation of 2,4-D. This increase in oxidation was observed at all pH values tested (including neutral to alkaline conditions), indicating the feasibility of the technique for treatment of contaminated water. In the presence of EDTA, the oxidation rate was greater at pH 3 than at pH 5 or 7. Increasing the EDTA concentration increased the rate and percentage of 2,4-D degradation, however increasing the Fe(0) concentration resulted in the opposite behavior. It was found that degradation of EDTA and 2,4-D occurred simultaneously, and that the new methodology avoided any 2,4-D removal by adsorption/coprecipitation. PMID:23524398

Correia de Velosa, Adriana; Pupo Nogueira, Raquel F

2013-03-20

330

Iron and Iron Deficiency  

MedlinePLUS

... them to get enough iron from their normal diet. Women who are pregnant have higher iron needs. To ... iron sources in the diet (e.g., vegetarian diets) Low absorption Taking antacids beyond ... Young children and pregnant women are at higher risk of iron deficiency because ...

331

Investigating the potential for long-term permeable reactive barrier (PRB) monitoring from the electrical signatures associated with the reduction in reactive iron performance  

Microsoft Academic Search

The objective of this work was to conduct laboratory and field experiments to determine the sensitivity of low frequency electrical measurements (resistivity and induced polarization) to the processes of corrosion and precipitation that are believed to limit permeable reactive barrier (PRB) performance. The research was divided into four sets of experiments that were each written up and submitted to a

Lee D. Slater; N. Korte; J. Baker

2005-01-01

332

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

333

Comparison of biotic and abiotic treatment approaches for co-mingled perchlorate, nitrate, and nitramine explosives in groundwater  

Microsoft Academic Search

Biological and abiotic approaches for treating co-mingled perchlorate, nitrate, and nitramine explosives in groundwater were compared in microcosm and column studies. In microcosms, microscale zero-valent iron (mZVI), nanoscale zero-valent iron (nZVI), and nickel catalyzed the reduction of RDX and HMX from initial concentrations of 9 and 1 mg\\/L, respectively, to below detection (0.02 mg\\/L), within 2 h. The mZVI and nZVI also degraded

C. E. Schaefer; M. E. Fuller; C. W. Condee; J. M. Lowey; P. B. Hatzinger

2007-01-01

334

Comparison of biotic and abiotic treatment approaches for co-mingled perchlorate, nitrate, and nitramine explosives in groundwater  

Microsoft Academic Search

Biological and abiotic approaches for treating co-mingled perchlorate, nitrate, and nitramine explosives in groundwater were compared in microcosm and column studies. In microcosms, microscale zero-valent iron (mZVI), nanoscale zero-valent iron (nZVI), and nickel catalyzed the reduction of RDX and HMX from initial concentrations of 9 and 1 mg\\/L, respectively, to below detection (0.02 mg\\/L), within 2 h. The mZVI and

C. E. Schaefer; M. E. Fuller; C. W. Condee; J. M. Lowey; P. B. Hatzinger

2007-01-01

335

Brain iron homeostasis.  

PubMed

Iron is essential for virtually all types of cells and organisms. The significance of the iron for brain function is reflected by the presence of receptors for transferrin on brain capillary endothelial cells. The transport of iron into the brain from the circulation is regulated so that the extraction of iron by brain capillary endothelial cells is low in iron-replete conditions and the reverse when the iron need of the brain is high as in conditions with iron deficiency and during development of the brain. Whereas there is good agreement that iron is taken up by means of receptor-mediated uptake of iron-transferrin at the brain barriers, there are contradictory views on how iron is transported further on from the brain barriers and into the brain extracellular space. The prevailing hypothesis for transport of iron across the BBB suggests a mechanism that involves detachment of iron from transferrin within barrier cells followed by recycling of apo-transferrin to blood plasma and release of iron as non-transferrin-bound iron into the brain interstitium from where the iron is taken up by neurons and glial cells. Another hypothesis claims that iron-transferrin is transported into the brain by means of transcytosis through the BBB. This thesis deals with the topic "brain iron homeostasis" defined as the attempts to maintain constant concentrations of iron in the brain internal environment via regulation of iron transport through brain barriers, cellular iron uptake by neurons and glia, and export of iron from brain to blood. The first part deals with transport of iron-transferrin complexes from blood to brain either by transport across the brain barriers or by uptake and retrograde axonal transport in motor neurons projecting beyond the blood-brain barrier. The transport of iron and transport into the brain was examined using radiolabeled iron-transferrin. Intravenous injection of [59Fe-125]transferrin led to an almost two-fold higher accumulation of 59Fe than of [125I]transferrin in the brain. Some of the 59Fe was detected in CSF in a fraction less than 30 kDa (III). It was estimated that the iron-binding capacity of transferrin in CSF was exceeded, suggesting that iron is transported into the brain in a quantity that exceeds that of transferrin. Accordingly, it was concluded that the paramount iron transport across the BBB is the result of receptor-mediated endocytosis of iron-containing transferrin by capillary endothelial cells, followed by recycling of transferrin to the blood and transport of non-transferrin-bound iron into the brain. It was found that retrograde axonal transport in a cranial motor nerve is age-dependent, varying from almost negligible in the neonatal brain to high in the adult brain. The principle sources of extracellular transferrin in the brain are hepatocytes, oligodendrocytes, and the choroid plexus. As the passage of liver-derived transferrin into the brain is restricted due to the BBB, other candidates for binding iron in the interstitium should be considered. In vitro studies have revealed secretion of transferrin from the choroid plexus and oligodendrocytes. The second part of the thesis encompasses the circulation of iron in the extracellular fluids of the brain, i.e. the brain interstitial fluid and the CSF. As the latter receives drainage from the interstitial fluid, the CSF of the ventricles can be considered a mixture of these fluids, which may allow for analysis of CSF in matters that relate to the brain interstitial fluid. As the choroid plexus is known to synthesize transferrin, a key question is whether transferrin of the CSF might play a role for iron homeostasis by diffusing from the ventricles and subarachnoid space to the brain interstitium. Intracerebroventricular injection of [59Fe125I]transferrin led to a higher accumulation of 59Fe than of [125I]transferrin in the brain. Except for uptake and axonal transport by certain neurons with access to the ventricular CSF, both iron and transferrin were, however, restricted to areas situated in close proximity to the ventric

Moos, Torben

2002-11-01

336

The effect of engineered iron nanoparticles on growth and metabolic status of marine microalgae cultures.  

PubMed

Synthetic zero-valent nano-iron (nZVI) compounds are finding numerous applications in environmental remediation owing to their high chemical reactivity and versatile catalytic properties. Studies were carried out to assess the effects of three types of industrially relevant engineered nZVI on phytoplankton growth, cellular micromorphology and metabolic status. Three marine microalgae (Pavlova lutheri, Isochrysis galbana and Tetraselmis suecica) were grown on culture medium fortified with the nano-Fe compounds for 23 days and subsequent alterations in their growth rate, size distribution, lipid profiles and cellular ultrastructure were assessed. The added nano Fe concentrations were either equimolar with the EDTA-Fe conventionally added to the generic f/2 medium (i.e. 1.17 × 10(-5)M), or factor 10 lower and higher, respectively. We provide evidence for the: (1) broad size distribution of nZVI particles when added to the nutrient rich f/2 media with the higher relative percentage of the smallest particles with the coated forms; (2) normal algal growth in the presence of all three types of nZVIs with standard growth rates, cellular morphology and lipid content comparable or improved when compared to algae grown on f/2 with EDTA-Fe; (3) sustained algal growth and normal physiology at nZVI levels 10 fold below that in f/2, indicating preference to nanoparticles over EDTA-Fe; (4) increased total cellular lipid content in T. suecica grown on media enriched with uncoated nZVI25, and in P. lutheri with inorganically coated nZVI(powder), when compared at equimolar exposures; (5) significant change in fatty acid composition complementing the nZVI(powder)-mediated increase in lipid content of P. lutheri; (6) a putative NP uptake mechanism is proposed for I. galbana via secretion of an extracellular matrix that binds nZVIs which then become bioavailable via phagocytotic membrane processes. PMID:23059967

Kadar, Eniko; Rooks, Paul; Lakey, Cara; White, Daniel A

2012-10-09

337

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

338

Geotechnical techniques for the construction of reactive barriers  

Microsoft Academic Search

One of the newest and most promising remediation techniques for the treatment of contaminated groundwater and soil is the reactive barrier wall (commonly known as PRB for permeable reactive barrier or reactive barrier). Although a variety of treatment media and strategies are available, the most common technique is to bury granular iron in a trench so that contaminated groundwater passes

Steven R Day; Stephanie F O'Hannesin; Lloyd Marsden

1999-01-01

339

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

340

Fundamental Studies of the Removal of Contaminants from Ground and Waste Waters Via Reduction by Zero-Valent Metals.  

National Technical Information Service (NTIS)

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 zer...

J. A. Yarmoff C. Amrhein

2000-01-01

341

Electrical Resistivity Modeling of a Permeable Reactive Barrier for Vista Engineering Technologies: Summary  

Microsoft Academic Search

We have performed a numerical modeling study that evaluated the capacity of electrical resistance tomography (ERT) to detect flaws in a passive reactive barrier (PRB). The model barrier is based on a real barrier described in the literature Slater and Binley (2003). It consists of highly conducting, granular iron emplaced within a trench. We assumed that the barrier was filled

A L Ramirez; W D Daily

2003-01-01

342

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

343

Barrier fence  

US Patent & Trademark Office Database

The movement of small vertebrates, e.g. endangered or threatened species, into and/or out of defined areas, e.g. construction sites, is controlled by use of a barrier fence which includes an apertured polymeric sheet. The polymeric sheet includes an upper portion which extends upwards from the ground and a lower portion which is buried in the ground. The polymeric sheet is formed by first and second sets of polymeric strands which are bonded to each other and are spaced apart from each other, thus providing apertures. The height and depth of the barrier fence and the size of the apertures prevent the small vertebrates from crossing the fence, and the apertures permit wind and water flow through the barrier fence.

2013-03-26

344

Radiant barriers  

SciTech Connect

This article discusses the effectiveness of radiant barriers in houses. Used in conjunction with mineral insulation and proper ventilation, they keep houses cooler in summer and warmer in winter. In addition, they save energy. Problems with installation, lack of reliable guidelines and cost are drawbacks.

Henkenius, M.

1989-09-01

345

Transport of Iron Particles in the Silica Aquifers: Effect of Water Chemistry and Carboxy-Methyl Cellulose Polymer Coatings  

NASA Astrophysics Data System (ADS)

Zero-valent iron particles are employed to remediate subsurface areas contaminated by chlorinated compounds, degrading them into less harmful substances. An aspect of major importance when assessing the viability of the technology is the ability of the particles to migrate in the subsurface reaching the contaminant source zone. Particle transport is influenced by particle adhesion onto geological substrates, since in the presence of strong adhesion particles are retained and their transport is hindered. Iron particles are generally coated with polymeric materials to prevent their rapid aggregation, and such coatings are expected to affect the surface properties and thus iron particle transport. This study investigates the forces of interaction between bare and carboxy-methyl cellulose CMC coated iron particles and silica (SiO2), to assess the influence of CMC coatings on iron particle adhesion. Atomic force spectroscopy experiments were conducted to measure the interactions between uncoated iron particles and silica in ultra pure water, NaCl and CaCl2 solutions at concentrations of 100 mM, as well as in solutions buffered with acetate and NaHCO3 (pH= 4 and 8 respectively). At pH values below 8 attractive interactions were observed, suggesting that silica could effectively retain the particles due to electrostatic attraction between negatively charged silica and positively charged iron particles. In contrast, at pH values of 8 the forces of interactions were repulsive, possibly because at this pH the positive charge on the iron surface is neutralized and repulsive hydration forces dominate. The interactions between SiO2 and CMC coated iron particles were repulsive in ultra pure water, as well as in solutions buffered with acetate or NaHCO3, and neutral in 100 mM NaCl solutions. In 100 mM CaCl2 solutions the forces of interaction were either neutral or attractive, suggesting that the presence of Ca2+ ions favors attachment of CMC to SiO2. Similar observations were previously reported with regard to the sorption of CMC onto talc in the presence of Ca2+ ions (1). CMC adhesion onto SiO2 was further investigated with the aid of a quartz-crystal microbalance with dissipation monitoring. Under the conditions studied CMC sorption onto SiO2 was reversible, as can be explained due to the electrostatic repulsion between silica and CMC. The point of zero charge for silica is about 3, while CMC completely dissociates, becoming negatively charged at pH values greater than 5.5, and partly dissociated bearing a smaller negative charge at lower pH values. The lack and/or the weakness of CMC adhesion in SiO2 indicates that CMC coatings promote iron particle migration, while uncoated iron particles would be more strongly retained at pH values below 8. (1) Khraisheh M., Holland C., Creany C., Harris P., Parolis L.. Effect of molecular weight and concentration on the adsorption of CMC onto talc at different ionic strengths. Int. J. Miner. Process. (2005) 75.

Pensini, E.; Sleep, B. E.; Yip, C.

2011-12-01

346

Iron overdose  

MedlinePLUS

Ferrous sulfate overdose; Ferrous gluconate overdose; Ferrous fumarate overdose ... Iron is an ingredient in many mineral and vitamin supplements. Iron ... (Femiron, Feostat) Note: This list may not be all-inclusive.

347

Performance evaluation of intermediate cover soil barrier for removal of heavy metals in landfill leachate  

Microsoft Academic Search

This pilot-scale study evaluated the use of intermediate cover soil barriers for removing heavy metals in leachate generated from test cells for co-disposed fly ash from municipal solid waste incinerators, ash melting plants, and shredder residue. Cover soil barriers were mixtures of Andisol (volcanic ash soil), waste iron powder, (grinder dust waste from iron foundries), and slag fragments. The cover

Kazuyuki Suzuki; Aya Anegawa; Kazuto Endo; Masato Yamada; Yusaku Ono; Yoshiro Ono

2008-01-01

348

Iron chelators and iron toxicity  

Microsoft Academic Search

Iron chelation may offer new approaches to the treatment and prevention of alcoholic liver disease. With chronic excess, either iron or alcohol alone may individually injure the liver and other organs. In combination, each exaggerates the adverse effects of the other. In alcoholic liver disease, both iron and alcohol contribute to the production of hepatic fibrosis through their effects on

Gary M. Brittenham

2003-01-01

349

Placental iron transfer in the cat  

PubMed Central

1. The transfer of iron from maternal plasma to the foetus was studied in the cat using cat transferrin labelled with 59Fe and radioiodine. 2. Pregnancy was accompanied by a fall in maternal haematocrit, a rise in serum total iron-binding capacity and iron stores, but no change in serum iron concentration or plasma iron turnover. 3. Near-term foetal haematocrit and serum iron concentration were higher and iron binding capacity lower than in the pregnant animals. 4. The uptake of 59Fe from maternal plasma by the placenta and transfer to the foetuses were slow and small in amount. The daily transfer of iron to the foetuses calculated from these data was only 5 ?g. 5. There was a small, transient uptake of 59Fe from the plasma by the foetal membranes. 6. Small amounts of plasma transferrin and albumin were slowly taken up by the placenta. 7. It was concluded that the maternal endothelium of the placenta of the cat acts as a barrier for the uptake of plasma transferrin-bound iron. As a result the rate of iron transfer to the foetuses from maternal plasma is inadequate to account for their rate of iron accumulation, and another source, such as maternal erythrocytes, must supply most of the iron to the foetuses.

Baker, Erica; Morgan, E. H.

1973-01-01

350

Iron toxicity  

PubMed Central

During the past half century, excessive/misplaced iron has been observed to be a risk factor for an increasing number and diversity of disease conditions. An extensive list of conditions and of the types of iron association were published in early 2008. Within the subsequent year, four additional disorders have been recognized to be enhanced by iron: aging muscle atrophy, viral replication, rosacea and pulmonary alveolar proteinosis. This paper adds new data and emphasis on these disorders as entities associated with increased iron load and toxicity.

2009-01-01

351

Iron refractory iron deficiency anemia.  

PubMed

Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in adulthood. The disease is refractory to oral iron treatment but shows a slow response to intravenous iron injections and partial correction of the anemia. To date, 40 different Matriptase-2 mutations have been reported, affecting all the functional domains of the large ectodomain of the protein. In vitro experiments on transfected cells suggest that Matriptase-2 cleaves Hemojuvelin, a major regulator of hepcidin expression and that this function is altered in this genetic form of anemia. In contrast to the low/undetectable hepcidin levels observed in acquired iron deficiency, in patients with Matriptase-2 deficiency, serum hepcidin is inappropriately high for the low iron status and accounts for the absent/delayed response to oral iron treatment. A challenge for the clinicians and pediatricians is the recognition of the disorder among iron deficiency and other microcytic anemias commonly found in pediatric patients. The current treatment of iron refractory iron deficiency anemia is based on parenteral iron administration; in the future, manipulation of the hepcidin pathway with the aim of suppressing it might become an alternative therapeutic approach. PMID:23729726

De Falco, Luigia; Sanchez, Mayka; Silvestri, Laura; Kannengiesser, Caroline; Muckenthaler, Martina U; Iolascon, Achille; Gouya, Laurent; Camaschella, Clara; Beaumont, Carole

2013-06-01

352

Traffic Barrier Performance.  

National Technical Information Service (NTIS)

The report summarizes research on traffic barrier performance conducted by New York from 1983 through 1987, which concentrated on (1) development of height standards and tolerances for light-post barriers, (2) barrier performance related to vehicle charac...

J. G. F. Hiss J. E. Bryden

1992-01-01

353

Iron chelators and iron toxicity.  

PubMed

Iron chelation may offer new approaches to the treatment and prevention of alcoholic liver disease. With chronic excess, either iron or alcohol alone may individually injure the liver and other organs. In combination, each exaggerates the adverse effects of the other. In alcoholic liver disease, both iron and alcohol contribute to the production of hepatic fibrosis through their effects on damaged hepatocytes, hepatic macrophages, hepatic stellate cells, and the extracellular matrix. The pivotal role of iron in these processes suggests that chelating iron may offer a new approach to arresting or ameliorating liver injury. For the past four decades, deferoxamine B mesylate has been the only iron-chelating agent generally available for clinical use. Clinical experience with deferoxamine has demonstrated the safety and effectiveness of iron chelation for the prevention and treatment of iron overload. Determined efforts to develop alternative agents have at last resulted in the development of a variety of candidate iron chelators that are now in or near clinical trial, including (a) the hexadentate phenolic aminocarboxylate HBED [N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid], (b) the tridentate desferrithiocin derivative 4'-OH-dadmDFT [4'-hydroxy-(S)-desazadesmethyl-desferrithiocin; (S)-4,5-dihydro-2-(2,4-dihydroxyphenyl)-4-thiazolecarboxylic acid], (c) the tridentate triazole ICL670A [CGP72 670A; 4-[3,5-bis-(hydroxyphenyl)-1,2,4-triazol-1-yl]-benzoic acid], and (d) the bidentate hydroxypyridin-4-one deferiprone [L1, CP20; 1,2-dimethyl-3-hydroxypyridin-4-one]. These agents may provide new pharmacological means of averting or ameliorating liver damage in alcoholic liver disease by binding, inactivating, and eliminating the reactive forms of iron that contribute to oxidative injury of cellular components, are involved in signal transduction, or both. PMID:12957300

Brittenham, Gary M

2003-06-01

354

Studies of catalytic aerobic oxidation with nanostructured amorphous metals, alloys and metal oxides  

Microsoft Academic Search

The oxidation of cyclohexane with molecular oxygen in the presence of isobutyraldehyde catalyzed by nanostructured iron and cobalt oxides and iron oxide supported on titania has been studied. It was found that highly dispersed transi- tion metal oxide is more effective for oxidation than the corresponding zero-valent metal powders. Nanostructured cobalt oxide on MCM-41 is found to be efficient for

J. Indian; V. K ESAVANa; D. DHAR; Y. KOLTYPIN; N. PERKAS; A. GEDANKEN; S. CHANDRASEKARAN

355

Supported metal nanoparticles for the remediation of chlorinated hydrocarbons  

Microsoft Academic Search

Zero valent iron filings are currently being used in pilot scale field studies to dehalogenate toxic chlorinated hydrocarbons from contaminated surface- and groundwater. Iron filings reduce trichloroethylene (TCE), a model contaminant, via two interconnected degradation pathways: (a) reductive beta-elimination and (b) sequential hydrogenolysis, in which each chlorine atom is sequentially replaced by hydrogen. For the latter pathway, problems arise because

Bettina Schrick

2002-01-01

356

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

357

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

358

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 blood–brain barrier and within the brain\\u000a are then

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

2011-01-01

359

Dimensioning metallic iron beds for efficient contaminant removal  

Microsoft Academic Search

Remediation of contaminated groundwater is an expensive and lengthy process. Permeable reactive barrier of metallic iron (Fe0 PRB) is one of the leading technologies for groundwater remediation. One of the primary challenges for the Fe0 PRB technology is to appropriately size the reactive barrier (length, width, Fe0 proportion and nature of additive materials) to enable sufficient residence time for effective

C. Noubactep; S. Caré

2010-01-01

360

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 ...

361

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 ...

362

The Influence of Silica on the Reactivity of Iron Towards Chlorinated Hydrocarbons  

Microsoft Academic Search

Previous work has illustrated that dissolved silica present in groundwater can adsorb onto the iron media of a permeable reactive barrier. To date, little is known about the effect of adsorbed silica on the reactivity of iron towards chlorinated contaminants. Silica is a known corrosion inhibitor, and therefore silica sorption may affect the reactivity of cast iron towards redox-active species

T. Kohn; D. W. Himmelheber; P. J. Vikesland; D. Fairbrother; A. Roberts

2001-01-01

363

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.

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

2013-01-01

364

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 Fischer–Tropsch (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

365

The effects of iron fortification on the gut microbiota in African children: a randomized controlled trial in Côte d'Ivoire  

Microsoft Academic Search

Background: Iron is essential for the growth and virulence of many pathogenic enterobacteria, whereas beneficial barrier bacteria, such as lactobacilli, do not require iron. Thus, increasing colonic iron could select gut microbiota for humans that are unfavorable to the host. Objective: The objective was to determine the effect of iron fortification on gut microbiota and gut inflammation in African children.

M. B. Zimmermann; C. Chassard; F. Rohner; E. K. N'goran; C. Nindjin; A. Dostal; J. Utzinger; H. Ghattas; C. Lacroix; R. F. Hurrell

2010-01-01

366

California Highway Barrier Aesthetics.  

National Technical Information Service (NTIS)

This report will familiarize designers with current barrier design options, and encourage appropriate aesthetic considerations to develop visually pleasing context sensitive solutions for highway projects. The development of alternative barriers that are ...

2002-01-01

367

Barrier Ring Injector.  

National Technical Information Service (NTIS)

The patent application relates to a rocket engine injector device including three flanged concentric annular members and a manifold ring assembled to provide the high injection density required for barrier cooling. The barrier ring assembly includes an in...

K. Y. Wong

1972-01-01

368

Bacterial iron homeostasis.  

PubMed

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 cases, this involves the secretion and internalisation of extracellular ferric chelators called siderophores. Ferrous iron can also be directly imported by the G protein-like transporter, FeoB. For pathogens, host-iron complexes (transferrin, lactoferrin, haem, haemoglobin) are directly used as iron sources. Bacterial iron storage proteins (ferritin, bacterioferritin) provide intracellular iron reserves for use when external supplies are restricted, and iron detoxification proteins (Dps) are employed to protect the chromosome from iron-induced free radical damage. There is evidence that bacteria control their iron requirements in response to iron availability by down-regulating the expression of iron proteins during iron-restricted growth. And finally, the expression of the iron homeostatic machinery is subject to iron-dependent global control ensuring that iron acquisition, storage and consumption are geared to iron availability and that intracellular levels of free iron do not reach toxic levels. PMID:12829269

Andrews, Simon C; Robinson, Andrea K; Rodríguez-Quińones, Francisco

2003-06-01

369

Puncture detecting barrier materials  

DOEpatents

A method and apparatus for continuous real-time monitoring of the integrity of protective barrier materials, particularly protective barriers against toxic, radioactive and biologically hazardous materials has been developed. Conductivity, resistivity or capacitance between conductive layers in the multilayer protective materials is measured by using leads connected to electrically conductive layers in the protective barrier material. The measured conductivity, resistivity or capacitance significantly changes upon a physical breach of the protective barrier material.

Hermes, Robert E. (Los Alamos, NM); Ramsey, David R. (Bothel, WA); Stampfer, Joseph F. (Santa Fe, NM); Macdonald, John M. (Santa Fe, NM)

1998-01-01

370

Iron and iron derived radicals  

SciTech Connect

We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fastexclamation Think smallexclamation In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab.

Borg, D.C.; Schaich, K.M.

1987-04-01

371

Barriers to Enterprise Interoperability  

NASA Astrophysics Data System (ADS)

Interoperability is a key feature for enterprises in today’s competitive environment. Fundamental interoperability problems are however still not well understood. Within the scope of the Framework for Enterprise Interoperability (FEI) originally proposed by INTEROP NoE and now moved to ISO standardization process, this paper tentatively identifies and categorizes a set of interoperability barriers. Barriers to interoperability are defined as incompatibility between two enterprise systems. A list of interoperability barriers is presented and these barriers are then mapped to the FEI and illustrated with examples. The most significant dependencies between barriers are also tentatively defined and presented.

Ullberg, Johan; Chen, David; Johnson, Pontus

372

A Physiological Barrier Distal to the Anatomic Blood Brain Barrier in a Model of Transvascular Delivery  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Osmotic disruption of the blood-brain barrier (BBB) pro- vides a method for transvascular delivery of therapeutic agents to the brain. The apparent global delivery of viral-sized iron oxide particles to the rat brain after BBB opening as seen on MR images was compared with the cellular and subcellular location and distribution of the particles. METHODS: Two dextran-coated

Leslie L. Muldoon; Michael A. Pagel; Robert A. Kroll; Simon Roman-Goldstein; Russell S. Jones; Edward A. Neuwelt

1999-01-01

373

The role of iron in the fixation of heavy metals and metalloids in soils: a review of publications  

NASA Astrophysics Data System (ADS)

Iron’s contribution to fixing heavy metals and metalloids in soils is very important. Iron compounds participating in redox processes control the behavior of siderophilic elements with variable oxidation degrees (Cr, As, and Sb). The behavior of heavy elements with permanent oxidation (Zn, Co, and Ni) indirectly depends on iron compounds. In organic soils, iron competes with heavy metals for active places in the functional groups of organic substances. Organic pollutants intensify the reduction of iron (hydr)oxides in an anaerobic environment, which influences the release of arsenic. Iron compounds are used as ameliorating agents and geochemical barriers for fixing heavy elements.

Vodyanitskii, Yu. N.

2010-05-01

374

Systemic iron homeostasis.  

PubMed

The iron hormone hepcidin and its receptor and cellular iron exporter ferroportin control the major fluxes of iron into blood plasma: intestinal iron absorption, the delivery of recycled iron from macrophages, and the release of stored iron from hepatocytes. Because iron losses are comparatively very small, iron absorption and its regulation by hepcidin and ferroportin determine total body iron content. Hepcidin is in turn feedback-regulated by plasma iron concentration and iron stores, and negatively regulated by the activity of erythrocyte precursors, the dominant consumers of iron. Hepcidin and ferroportin also play a role in host defense and inflammation, and hepcidin synthesis is induced by inflammatory signals including interleukin-6 and activin B. This review summarizes and discusses recent progress in molecular characterization of systemic iron homeostasis and its disorders, and identifies areas for further investigation. PMID:24137020

Ganz, Tomas

2013-10-01

375

Disorders of iron metabolism. Part II: iron deficiency and iron overload  

Microsoft Academic Search

Main disorders of iron metabolismIncreased iron requirements, limited external supply, and increased blood loss may lead to iron deficiency (ID) and iron deficiency anaemia. In chronic inflammation, the excess of hepcidin decreases iron absorption and prevents iron recycling, resulting in hypoferraemia and iron restricted erythropoiesis, despite normal iron stores (functional iron deficiency), and finally anaemia of chronic disease (ACD), which

Manuel Muńoz; José Antonio García-Erce; Ángel Francisco Remacha

2010-01-01

376

Controversies in iron management  

Microsoft Academic Search

Controversies in iron management.BackgroundIron therapy is required in hemodialysis patients receiving erythropoietic stimulators in order to achieve the target hemoglobin in the most efficient way. While oral iron has been disappointing in this regard, parenteral iron has been widely used, despite a significant incidence of severe side effects when iron dextran is used. The recent availability of a more effective

Allen R. Nissenson; Chaim Charytan

2003-01-01

377

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...

378

Enhanced Bioremediation Field Experience: Using Observed Half Lives in Design and Prediction  

Microsoft Academic Search

A priori assessment of the effectiveness of amendments for enhanced bioremediation of chlorinated hydrocarbons is complicated by the varying geologic settings, groundwater flow rates, and background geochemistry encountered. Amendments employing a combination of carbon, nutrients, and micro-scale zero-valent iron result in multiple biotic and abiotic treatment mechanisms at various length and timescales which makes direct physical and chemical prediction of

Joanna Moreno; Jim Mueller; Fayaz Lakhwala; John Valkenburg; Alan Seech; Kerry Bolanos-Shaw

379

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...

380

Removal of technetium, carbon tetrachloride, and metals from DOE properties. 1998 annual progress report  

Microsoft Academic Search

'The objective of the project is to develop and characterize supported reducing agents, and solid waste forms derived from them, which will be effective in the removal of transition metal ions, chlorinated organic molecules, and technetium from aqueous mixed wastes. This work follows the discovery that a nanoscale form of zero-valent iron, dispersed on high surface area supports, reduces metal

T. E. Mallouk; J. G. Darab; S. M. Ponder

1998-01-01

381

Experimental Study on Restoration of Polluted Groundwater from in Situ Leaching Uranium Mining with Sulfate Reducing Bacteria and ZVI-SRB  

Microsoft Academic Search

In the case of in situ leaching of uranium, the primitive geochemical environment for groundwater is changed since leachant is injected into the water beaving uranium deposit. This increases the concentration of uranium and results in the groundwater contamination.Microbial reduction technology by Sulfate reducing bacteria and Zero Valent Iron were employed to treat uranium wastewater. The experiments were conducted to

Kaiguang Hu; Qingliang Wang; Ganqiang Tao; Aihe Wang; Dexin Ding

2011-01-01

382

Use of an Intermediate-Scale Tank to Study Strategies for Modified NZVI Emplacement for Effective Treatment of DNAPL Source Zones  

Microsoft Academic Search

Dense non-aqueous phase liquid (DNAPL) sources act as long term sources of ground water contamination. Emplacing modified nano-scale zero valent iron (NZVI) particles in the source zone and area immediately downstream of the source zone may serve the dual purpose of reducing the mass transfer from entrapped DNAPL and reductive dechlorination of the dissolved mass, thus reducing the total mass

T. H. Illangasekare; M. Mittal; T. Phenrat; F. Fagerlund; H. Kim; A. Cihan; G. V. Lowry

2009-01-01

383

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

384

[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

385

Iron metabolism in man.  

PubMed

Iron metabolism in man is a highly regulated process designed to provide iron for erythropoiesis, mitochondrial energy production, electron transport, and cell proliferation. The mechanisms of iron handling also protect cells from the deleterious effects of free iron, which can produce oxidative damage of membranes, proteins, and lipids. Over the past decade, several important molecules involved in iron homeostasis have been discovered, and their function has expanded our understanding of iron trafficking under normal and pathological conditions. Physiologic iron metabolism is strongly influenced by inflammation, which clinically leads to anemia. Although hepcidin, a small circulating peptide produced by the liver, has been found to be the key regulator of iron trafficking, molecular pathways of iron sensing that control iron metabolism and hepcidin production are still incompletely understood. With this review, we provide an overview of the current understanding of iron metabolism, the recently discovered regulators of iron trafficking, and a focus on the effects of inflammation on the process. PMID:22968710

von Drygalski, Annette; Adamson, John W

2012-09-11

386

Iron Absorption by Infants.  

National Technical Information Service (NTIS)

The research team studied absorption of iron from carefully selected iron-fortified foods that are now commercially available or are attractive candidates for future iron fortification. Because of possible adverse interactions with zinc and copper when in...

S. J. Fomon

1995-01-01

387

Taking iron supplements  

MedlinePLUS

... care provider immediately. Liquid forms of iron may stain your teeth. Try mixing the iron with water ... and drinking the medicine with a straw. Iron stains can be removed by brushing your teeth with ...

388

Hemochromatosis: Iron Storage Disease  

MedlinePLUS

... en... Favorites Delicious Digg Google Bookmarks Hemochromatosis: Iron Storage Disease Excessive iron buildup in the body's tissues ... Learn more about hemochromatosis, a type of iron storage disease, and stay healthy. What Is Hemochromatosis? Hemochromatosis ...

389

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

390

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

Microsoft Academic Search

'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

J. A. Yarmoff; C. Amrhein

1997-01-01

391

Comparison of removing NO3? in the polluted groundwater of in-situ leaching of uranium mine with DNB and Fe0  

Microsoft Academic Search

Removing NO3 - in polluted groundwater of in-situ leaching uranium mine with iron powder (zero-valent iron, Fe 0 ), DNB, iron powder and DNB are studied. The condition of tests include different pH of solution, dosage of iron powder, and treating time. The experimental results show that over 93% of NO3 - in unneutralized polluted groundwater (pH value about 1.46)

Eming Hu; Qingliang Wang; Guoqi Zhang; Wang Wu; Dexin Ding

2011-01-01

392

Hanford Protective Barriers Program asphalt barrier studies -- FY 1988  

Microsoft Academic Search

The Hanford Protective Barrier (HPB) Program is evaluating alternative barriers to provide a means of meeting stringent water infiltration requirements. One type of alternative barrier being considered is an asphalt-based layer, 1.3 to 15 cm thick, which has been shown to be very effective as a barrier for radon gas and, hence, should be equally effective as a barrier for

H. D. Freeman; G. W. Gee

1989-01-01

393

Iron and Stony-iron Meteorites  

Microsoft Academic Search

Without iron and stony-iron meteorites, our chances of ever sampling the deep interior of a differentiated planetary object would be next to nil. Although we live on a planet with a very substantial core, we will never be able to sample it. Fortunately, asteroid collisions provide us with a rich sampling of the deep interiors of differentiated asteroids.Iron and stony-iron

H. Haack; T. J. McCoy

2003-01-01

394

Penetration resistant barrier  

DOEpatents

The disclosure relates to a barrier for resisting penetration by such as hand tools and oxy-acetylene cutting torches. The barrier comprises a layer of firebrick, which is preferably epoxy impregnated sandwiched between inner and outer layers of steel. Between the firebrick and steel are layers of resilient rubber-like filler.

Hoover, William R. (Albuquerque, NM); Mead, Keith E. (Albuquerque, NM); Street, Henry K. (Albuquerque, NM)

1977-01-01

395

Informationally Ecient Trade Barriers  

Microsoft Academic Search

Why are trade barriers often used to protect home producers, even at the cost of introducing deadweight losses from higher commodity prices? We add an informational friction to the standard textbook argument in favor of free trade, and show that trade restrictions may be a more ecient policy than a lump sum transfer to the displaced producers. Trade barriers, while

Matthew F. Mitchell; Andrea Moro

396

Barriers: friend or foe?  

Microsoft Academic Search

Modern garbage collectors rely on read and write barriers imposed on heap accesses by the mutator, to keep track of references between different regions of the garbage collected heap, and to synchronize actions of the mutator with those of the collector. It has been a long-standing untested assumption that barriers impose significant overhead to garbage-collected applications. As a result, researchers

Stephen M. Blackburn; Antony L. Hosking

2004-01-01

397

Catalytic thermal barrier coatings  

DOEpatents

A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

Kulkarni, Anand A. (Orlando, FL); Campbell, Christian X. (Orlando, FL); Subramanian, Ramesh (Oviedo, FL)

2009-06-02

398

Irontophoresis: transdermal delivery of iron by iontophoresis.  

PubMed

Transdermal delivery of iron can overcome the GI side effects and the discomfort associated with parenteral administration. Slow and prolonged transdermal delivery of iron would also avoid potential oversaturation of transferrin and overcome accumulation of free iron in the systemic circulation. Ferric pyrophosphate (FPP) has been demonstrated to be safe for systemic administration. Passive transdermal delivery of FPP is poor due to the impermeable skin barrier. Irontophoresis was developed for transdermal delivery of FPP. The predictability and programmability of the technique was assessed in vitro across the hairless rat skin. Following Irontophoresis for 6 h in hairless rats, the total serum iron concentration increased from 182.36 +/- 39.93 microg/dL to 317.56 +/- 28.33 microg/dL and the transferrin saturation increased from 44.6% +/- 2.2% to 60.8% +/- 6.7%. Irontophoresis based iron therapy could be relatively more patient compliant, safe and effective treatment for iron deficiency anemia condition. PMID:19117049

Murthy, S Narasimha; Vaka, Siva Ram Kiran

2009-08-01

399

Pathways of Iron Absorption  

Microsoft Academic Search

ABSTRACTIron is vital for all living organisms but excess iron can be lethal because it facilitates free radical formation. Thus iron absorption is carefully regulated to maintain an equilibrium between absorption and body loss of iron. In countries where meat is a significant part of the diet, most body iron is derived from dietary heme because heme binds few of

Marcel E. Conrad; Jay N. Umbreit

2002-01-01

400

Highway noise barrier perceived benefit  

NASA Astrophysics Data System (ADS)

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 experiment. Prediction equations were developed for barrier benefit in terms of these sound levels, their purpose being to provide a model for barrier benefit that can be used in barrier site selection and design. An unexpected finding was that barrier benefit was highest when before-barrier sound levels were lowest: i.e., subjects preferred a noise barrier that solved a moderate noise problem over an equally-attenuating barrier that only partially solved a more severe noise problem.

May, D. N.; Osman, M. M.

1980-05-01

401

Modelling Iron-Bentonite Interactions  

NASA Astrophysics Data System (ADS)

The presence of both iron canisters and bentonitic clay in some engineered barrier system (EBS) designs for the geological disposal of high-level radioactive wastes creates the potential for chemical interactions which may impact upon the long-term performance of the clay as a barrier to radionuclide migration. Flooding of potential radionuclide sorption sites on the clay by ferrous ions and conversion of clay to non-swelling sheet silicates (e.g. berthierine) are two possible outcomes deleterious to long-term performance. Laboratory experimental studies of the corrosion of iron in clay show that corrosion product layers are generally thin (< 1 µm) with magnetite, siderite, or ‘green rust' occurring depending upon temperature and ambient partial pressure of carbon dioxide. In theory, incorporation of iron into clay alteration products could act as a ‘pump' to accelerate corrosion. However, the results of laboratory experiments to characterise the products of iron-bentonite interaction are less than unequivocal. The type and amounts of solid products appear to be strong functions of time, temperature, water/clay ratio, and clay and pore fluid compositions. For example, the products of high temperature experiments (> 250 °C) are dominated by chlorite, whereas lower temperatures produce berthierine, odinite, cronstedtite, or Fe-rich smectite. Unfortunately, the inevitable short-term nature of laboratory experimental studies introduces issues of metastability and kinetics. The sequential formation in time of minerals in natural systems often produces the formation of phases not predicted by equilibrium thermodynamics. Evidence from analogous natural systems suggests that the sequence of alteration of clay by Fe-rich fluids will proceed via an Ostwald step sequence. The computer code, QPAC, has been modified to incorporate processes of nucleation, growth, precursor cannibalisation, and Ostwald ripening to address the issues of the slow growth of bentonite alteration products. This, together with inclusion of processes of iron corrosion and diffusion, has enabled investigation of a representative model of the alteration of bentonite in a typical EBS environment. Simulations with fixed mineral surface areas show that berthierine dominates the solid product assemblage, with siderite replacing it at simulation times greater than 10 000 years. Simulations with time-dependent mineral surface areas show a sequence of solid alteration products, described by: magnetite -> cronstedtite -> berthierine -> chlorite. Using plausible estimates of mineral-fluid interfacial free energies, chlorite growth is not achieved until 5 000 years of simulation time. The results of this modelling work suggest that greater emphasis should be placed upon methods to up-scale the results of laboratory experiments to timescales of relevance to performance assessment.

Watson, C.; Savage, D.; Benbow, S.; Wilson, J.

2009-04-01

402

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

403

Aesthetic Concrete Barrier Design.  

National Technical Information Service (NTIS)

This report contains guidelines for aesthetic treatment of concrete safety shape barriers. The report will be of particular interest to design and safety practitioners with responsibility for roadside safety improvements. The increasing application of con...

D. L. Bullard N. M. Sheikh R. R. Haug J. R. Schutt B. J. Storey

2005-01-01

404

Barrier-Free Design.  

National Technical Information Service (NTIS)

Consisting primarily of planning and design materials, this annotated bibliography provides information on making buildings accessible to the physically handicapped. One of a series of 6 documents on the subject of barrier - free design for the physically...

1979-01-01

405

Barriers to Financial Reform.  

National Technical Information Service (NTIS)

Despite widespread agreement that rural financial reforms are needed in LDCs, arguments against the possibility of implementing such reforms are often heard. Four common arguments, all illustrative of existing barriers to financial reform are analyzed her...

R. C. Vogel

1979-01-01

406

Barrier Surfaces of Skin.  

National Technical Information Service (NTIS)

Stratum corneum, the nonliving layer of skin, is refractory as a substrate for chemical reactions, but it has a strong physical affinity for water. The chemical stability of stratum corneum is evident in its mechanical barriers which include insoluble cel...

M. M. Mershon

1974-01-01

407

MENDING THE IN SITU MANIPULATION BARRIER  

SciTech Connect

In early 2004, the U.S. Department of Energy (DOE) Richland and Fluor Hanford requested technical assistance from the DOE Headquarters EM-23 Technical Assistance Program to provide a team of technical experts to develop recommendations for mending the In Situ Redox Manipulation (ISRM) Barrier in the 100-D Area of the Hanford Site in Washington State. To accommodate this request, EM-23 provided support to convene a group of technical experts from industry, a national laboratory, and a DOE site to participate in a 2 1/2-day workshop with the objective of identifying and recommending options to enhance the performance of the 100-D Area reactive barrier and of a planned extension to the northeast. This report provides written documentation of the team's findings and recommendations. In 1995, a plume of dissolved hexavalent chromium [Cr(VI)], which resulted from operation of the D/DR Reactors at the Hanford site, was discovered along the Columbia River shoreline and in the 100-D Area. Between 1999 and 2003, a reactive barrier using the In Situ Redox Manipulation (ISRM) technology, was installed a distance of 680 meters along the river to reduce the Cr(VI) in the groundwater. The ISRM technology creates a treatment zone within the aquifer by injection of sodium dithionite, a strong reducing agent that scavenges dissolved oxygen (DO) from the aquifer and reduces ferric iron [Fe(III)], related metals, and oxy-ions. The reduction of Fe(III) to ferrous [Fe(II)] iron provides the primary reduction capacity to reduce Cr(VI) to the +3 state, which is less mobile and less toxic. Bench-scale and field-scale treatability tests were initially conducted to demonstrate proof-of principle and to provide data for estimation of barrier longevity. These calculations estimated barrier longevity in excess of twenty years. However, several years after initial and secondary treatment, groundwater in a number of wells has been found to contain elevated chromium (Cr) concentrations, indicating some loss of reductive capacity within the aquifer. The Technical Assistance Team (TAT) was requested to perform the following activities: (1) evaluate the most probable condition(s) that has led to the presence of Cr(VI) in 12 different barrier wells (i.e. premature loss of reductive capacity), (2) recommend methods for determining the cause of the problem, (3) recommend methods for evaluating the magnitude of the problem, (4) recommend practicable method(s) for mending the barrier that involves a long-term solution, and (5) recommend methods for extending the barrier to the northeast (e.g., changing injection procedure, changing or augmenting the injected material). Since the March 2004 workshop, a decision has been made to place a hold on the barrier extension until more is known about the cause of the problem. However, the report complies with the original request for information on all of the above activities, but focuses on determining the cause of the problem and mending of the existing barrier.

PETERSEN, S.W.

2006-02-06

408

Retractable barrier strip  

SciTech Connect

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

409

Preparation and Characterization of Nanocrystalline Fe\\/N Co-Doped Titania  

Microsoft Academic Search

Doping nitrogen in TiO2 enhances photoresponse in visible light region while doping iron reduces the recombination of photo-induced electrons and holes. In this work, a simple procedure for preparing nitrogen and iron co-doped titanium dioxide nanocrystalline (Fe\\/N-TiO2) by calcinating the mixture of Degussa P-25 TiO2, zero-valent iron (ZVI), and NH4Cl at the temperature of 400°C under airtight condition. Characterization of

Bao-Chrung Hsu; Shiao-Shing Chen; Chaochin Su; Yan-Chan Li

2009-01-01

410

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

411

Monitoring Permeable Reactive Barriers using Electrical Resistance Tomography  

SciTech Connect

An electrical resistivity tomography (ERT) method is being evaluated as a measurement tool to determine the integrity of permeable reactive barriers (PRBs) during and after construction of the barrier and as a monitoring tool to determine the long-term operational health of the barrier. The method is novel because it inserts the electrodes directly into the barrier itself. Numerical modeling calculations indicate that the ERT method can detect flaws (voids) in the barrier as small as 0.11 m{sup 2} (0.33 m x 0.33 m) when the aspect ratio of the electrodes are 2:1. Laboratory measurements indicate that the change in resistance over time of the iron-filling mixture used to create the PRB is sufficient for ERT to monitor the long-term health of the barrier. The use of this ERT method allows for the cost-effective installation of the barrier, especially when the vadose zone is large, because borehole installation methods, rather than trenching methods, can be used.

Ramirez, A; Bratton, W; Maresca, J; Daily, W; Dickerson, W

2003-12-08

412

Neonatal iron nutrition.  

PubMed

Preterm infants are prone to iron deficiency. Their total body iron content at birth is low and gets further depleted by clinical practices such as uncompensated phlebotomy losses and exogenous erythropoietin administration during the neonatal period. Early iron deficiency appears to adversely affect cognitive development in human infants. To maintain iron sufficiency and meet the iron demands of catch-up postnatal growth, iron supplementation is prudent in preterm infants. A dose of 2-4 mg/kg/day is recommended for preterm infants who are fed exclusively human milk. A dose of 6 mg/kg/day or more is needed with the use of exogenous erythropoietin or to correct preexisting iron deficiency. However, due to the poor antioxidant capabilities of preterm infants and the potential role of iron in several oxidant-related perinatal disorders, indiscriminate iron supplementation should be avoided. PMID:11988032

Rao, R; Georgieff, M K

2001-10-01

413

Geophysical characterization of subsurface barriers  

Microsoft Academic Search

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

1995-01-01

414

Tritium\\/hydrogen barrier development  

Microsoft Academic Search

A review of hydrogen permeation barriers that can be applied to structural metals used in fusion power plants is presented. Both implanted and chemically available hydrogen isotopes must be controlled in fusion plants. The need for permeation barriers appears strongest in Li17-Pb blanket designs, although barriers also appear necessary for other blanket and coolant systems. Barriers that provide greater than

G. W. Hollenberg; E. P. Simonen; G. Kalinen; A. Terlain

1994-01-01

415

Tritium\\/hydrogen barrier development  

Microsoft Academic Search

A review of the hydrogen permeation barriers which can be applied to the structural metals used in fusion power plants is presented. Both implanted and chemically available hydrogen isotopes must be controlled in fusion plants. The need for permeation barriers appears strongest in Pb-17Li blanket designs, although barriers are also necessary for other blanket and coolant systems. Barriers which provide

G. W Hollenberg; E. P Simonen; G Kalinin; A Terlain

1995-01-01

416

Quantum Tunneling of the Magnetization in an Iron Cluster Nanomagnet  

Microsoft Academic Search

We have investigated the magnetic relaxation of clusters of eight iron ions characterized by a spin ground state of ten and an Ising anisotropy. Below 400 mK the relaxation rate is temperature independent suggesting that tunneling of the magnetic moment across its anisotropy energy barrier occurs. Using the anisotropy constants derived from EPR data, we can calculate both the crossover

C. Sangregorio; T. Ohm; C. Paulsen; R. Sessoli; D. Gatteschi

1997-01-01

417

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

418

Iron Fractionation During Microbial Reduction of Iron  

NASA Astrophysics Data System (ADS)

The isotopic fractionation of iron during the biological reduction of iron by microbes has received much attention due to the possible use of iron isotopes as an indicator of biological activity in ancient and extraterrestrial environments. However the mechanisms of dissimilatory iron reduction have not been fully characterized. We are investigating the mechanisms by which Shewanella putrefaciens strain CN32 reduces ferric iron in the form of goethite, as well as, the resulting iron isotopic fractionation. In the experiments a PIPES buffered minimal media was used in an effort to eliminate or control the formation of secondary ferrous-iron solids. S. putrefaciens is thought to also produce an electron shuttle, which carries electrons from the cell to the iron solid. In one set of experiments, S. putrefaciens was cultured in minimal media containing goethite both with and without anthraquinone-2,6-disulfonate (AQDS, an artificial electron shuttle). Preliminary data indicates that the fractionation of iron in solution in the AQDS amended cultures is -1.57 per mil lighter than the starting goethite. This fractionation corresponds well with previously reported fractionations in similar systems. However, other researchers have shown that, in these systems, much of the reduced Fe(II) sorbs to the goethite. An acid extraction is often used to remove this sorbed Fe(II) and determine the total amount of reduced iron. This extraction was used to extract sorbed Fe(II) for isotopic analysis. Although the extraction itself may cause a fractionation effect, less than 1% of the total iron in the extraction can be attributed to this effect. Therefore, the observed fractionation should be primarily a function of the microbially reduced iron and not an artifact of the extraction. The isotope fractionation in the extraction, which includes both soluble and sorbed Fe(II), is -2.42 per mil relative to the starting goethite. We are currently combining parts of the cell involved in iron reduction (cell wall components) with an electron shuttle and goethite to accomplish in vitro Fe reduction. We will compare the in vitro iron isotope fractionations that occur without live cells to those with live cultures in an effort to elucidate iron reducing mechanisms and pathways.

Icopini, G. A.; Brantley, S. L.; Ruebush, S.; Tien, M.; Bullen, T. D.

2002-12-01

419

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.

Rao, Raghavendra; Georgieff, Michael K.

2009-01-01

420

Iron-Deficiency Anemia  

MedlinePLUS Videos and Cool Tools

... NHLBI Entire Site NHLBI Entire Site 1 Health Topics 2 News & Resources 3 Intramural Research 4 Home » Health Information for the Public » Health Topics » Iron-Deficiency Anemia » What Is ... Iron-Deficiency Anemia ...

421

Ferrous Sulfate (Iron)  

MedlinePLUS

... the iron needed by the body to produce red blood cells. It is used to treat or prevent iron- ... that occurs when the body has too few red blood cells because of pregnancy, poor diet, excess bleeding, or ...

422