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1

Application of Emulsified Zero-Valent Iron to Marine Environments  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

2

Application of Emulsified Zero-Valent Iron to Marine Environments  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

3

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

EPA Science Inventory

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

4

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

EPA Science Inventory

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

5

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

EPA Science Inventory

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

6

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

EPA Science Inventory

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

7

Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

8

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

9

Field demonstration of DNAPL dehalogenation using emulsified zero-valent iron  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

10

Zero-valent iron nanoparticles preparation  

SciTech Connect

Graphical abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. The synthesized nanoparticles were spherical and had diameters less than 5 nm. Highlights: ? Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}]. ? The conditions of reaction were at room temperature and a pressure of 3 atm. ? The synthesized nanoparticles were spherical and had diameters less than 5 nm. -- Abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. To monitor the reaction, a stainless steel pressure reactor lined with PTFE and mechanically stirred was designed. This design allowed the extraction of samples at different times, minimizing the perturbation in the system. In this way, the shape and the diameter of the nanoparticles produced during the reaction were also monitored. The results showed the production of zero-valent iron nanoparticles that were approximately 5 nm in diameter arranged in agglomerates. The agglomerates grew to 900 nm when the reaction time increased up to 12 h; however, the diameter of the individual nanoparticles remained almost the same. During the reaction, some byproducts constituted by amino species acted as surfactants; therefore, no other surfactants were necessary.

Oropeza, S. [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)] [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Corea, M., E-mail: mcoreat@yahoo.com.mx [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Gómez-Yáñez, C. [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)] [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Cruz-Rivera, J.J. [Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Sierra Leona 550, San Luis Potosí, C.P. 78210 (Mexico)] [Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Sierra Leona 550, San Luis Potosí, C.P. 78210 (Mexico); Navarro-Clemente, M.E., E-mail: mnavarroc@ipn.mx [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)

2012-06-15

11

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...

12

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...

13

DDT, DDD, AND DDE DECHLORINATION BY ZERO-VALENT IRON  

EPA Science Inventory

Traditionally, destruction of DDT [1,1,1-trichIoro-2,2-bis( p -chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room tempera...

14

Pressurized CO 2\\/zero valent iron system for nitrate removal  

Microsoft Academic Search

A fluidized zero valent iron (ZVI) reactor pressurized by CO2 gas for controlling pH was employed for nitrate reduction. The proposed CO2 pressurized system potentially has advantages of using less CO2 gas and reaching equilibrium pH faster than CO2-bubbled system. However, due to weak acid nature of carbonic acid, system pH gradually increased with increasing oxidation of ZVI and reduction

Chi-Wang Li; Yi-Ming Chen; Wei-Shuen Yen

2007-01-01

15

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

E-print Network

Chromate transport through columns packed with surfactant-modified zeolite/zero valent iron pellets or treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA), was studied at different flow

Li, Zhaohui

16

Electrokinetics Enhanced Delivery of Nano-scale Zero Valent Iron  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

17

Can zero-valent iron nanoparticles remove waterborne estrogens?  

PubMed

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

Jarošová, Barbora; Filip, Jan; Hilscherová, Klára; Tu?ek, Ji?í; Šimek, Zden?k; Giesy, John P; Zbo?il, Radek; Bláha, Lud?k

2015-03-01

18

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

19

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

20

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

21

Antimicrobial and Genotoxicity Effects of Zero-valent Iron Nanoparticles  

PubMed Central

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

Barzan, Elham; Mehrabian, Sedigheh; Irian, Saeed

2014-01-01

22

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

Microsoft Academic Search

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

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

1998-01-01

23

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

Microsoft Academic Search

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

R. L. Johnson; R. B. Thoms; R. O’Brien Johnson; J. T. Nurmi; Paul G. Tratnyek

2008-01-01

24

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...

25

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...

26

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...

27

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...

28

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

EPA Science Inventory

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

29

Heavy metals removal and hydraulic performance in zero-valent iron\\/pumice permeable reactive barriers  

Microsoft Academic Search

Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has

Nicola Moraci; Paolo S. Calabrò

2010-01-01

30

Field Evidence for Flow Reduction through a Zero-Valent Iron Permeable Reactive Barrier  

Microsoft Academic Search

The combination of detailed multilevel ground water geochemistry samples, a natural-gradient tracer test, minislug tests, and a numerical flow and transport model was used to examine flow through a zero-valent iron permeable reactive barrier (PRB) installed to remove explosives from ground water. After 20 months of operation, the PRB continued to completely re- move explosives from the ground water flowing

R. L. Johnson; R. B. Thoms; R. O’Brien Johnson; T. Krug

2008-01-01

31

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

Microsoft Academic Search

Permeable reactive barriers (PRBs) of zero-valent iron (Fe°) are increasingly being used to remediate contaminated ground water. Corrosion of Fe° 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

Debra Helen Phillips; Baohua Gu; David B Watson; Yul Roh

2003-01-01

32

Review of Zero Valent Iron and Apatite as reactive materials for Permeable Reactive Barrier  

Microsoft Academic Search

Permeable reactive barrier (PRB) is a technology developed recently in the last years. It has obtained promising results in the removal of several contaminants present in the groundwater. This Term paper focuses the attention on two reactive materials, Zero valent iron and Apatite, employed in the PRB system, giving an overview of the reactions and types of pollutants treated to

Luca Geranio; Evert Elzinga

33

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

EPA Science Inventory

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

34

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

SciTech Connect

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

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

2011-10-01

35

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

36

Heterogeneous reductive dehalogenation of PCB contaminated transformer oil and brominated diphenyl ethers with zero valent iron.  

PubMed

Reductive dechlorination and debromination of halogenated biphenyls (PCBs) and diphenyl ethers (PBDEs) occurs efficiently at moderately elevated temperatures (350-600 °C) with zero valent iron (iron powder) in a nitrogen atmosphere. The proton donors tested were waste transformer oil, iso-octane, and n-decane. Observation of production of biphenyl and diphenyl ether and their condensation products indicates that the reaction is not simple pyrolysis, but a reduction. No halogenated organic products are observed. PMID:22560182

Habekost, A; Aristov, N

2012-09-01

37

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

38

Olive mill wastewater degradation by Fenton oxidation with zero-valent iron and hydrogen peroxide  

Microsoft Academic Search

The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The effects of the H2O2 dose, the pH and the organic matter concentration have been studied. The optimal experimental conditions were found to have continuous presence of iron metal,

Monem Kallel; Chokri Belaid; Rachdi Boussahel; Mohamed Ksibi; Antoine Montiel; Boubaker Elleuch

2009-01-01

39

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

PubMed

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

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

2014-02-28

40

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

EPA Science Inventory

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 ...

41

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

EPA Science Inventory

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

42

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...

43

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

44

The impact of zero-valent iron nanoparticles on a river water bacterial community  

Microsoft Academic Search

Zero-valent iron (ZVI) nanoparticles are of interest because of their many potential biomedical and environmental applications. However, these particles have recently been reported to be cytotoxic to bacterial cells. The overall objective of this study was to determine the impact of 100mg\\/L ZVI nanoparticles on the diversity and structure of an indigenous river water bacterial community. Response during exposure for

Robert J. Barnes; Christopher J. van der Gast; Olga Riba; Laura E. Lehtovirta; James I. Prosser; Peter J. Dobson; Ian P. Thompson

2010-01-01

45

Polyelectrolyte multilayer film-assisted formation of zero-valent iron nanoparticles onto polymer nanofibrous mats  

Microsoft Academic Search

A facile approach that combines the electrospinning technique and layer-by-layer (LbL) assembly method has been developed to synthesize and immobilize zero-valent iron nanoparticles (ZVI NPs) onto the surface of nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning CA solution were modified with bilayers composed of positively charged poly(diallyl-dimethyl-ammoniumchloride) (PDADMAC) and negatively

Shili Xiao; Siqi Wu; Mingwu Shen; Rui Guo; Shanyuan Wang; Xiangyang Shi

2009-01-01

46

Biogeochemical dynamics in zero-valent iron columns: Implications for permeable reactive barriers  

Microsoft Academic Search

The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe°). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate

B. Gu; T. J. Phelps; L. Liang; A. V. Palumbo; G. K. Jacobs; M. J. Dickey; Y. Roh; B. L. Kinsall

1999-01-01

47

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

Microsoft Academic Search

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

Liang Chen; Fei Liu; YuLong Liu; HongZhong Dong; Patricia J. S. Colberg

2011-01-01

48

A Comparison Between Field Applications of Nano, Micro, and Millimetric Zero-Valent Iron for the Remediation of Contaminated Aquifers  

Microsoft Academic Search

In the last 10 years, the number of field applications of zero-valent iron differing from permeable reactive barrier has grown\\u000a rapidly and at present are 112. This study analyzes and compares such field applications. By using statistical analysis, especially\\u000a ANOVA and principal component analysis, this study shows that chlorinated solvent contamination can be treated efficiently\\u000a by using zero-valent iron material singly

Silvia Comba; Antonio Di Molfetta; Rajandrea Sethi

2011-01-01

49

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

Microsoft Academic Search

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

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

2009-01-01

50

Removal of organic load and phenolic compounds from olive mill wastewater by Fenton oxidation with zero-valent iron  

Microsoft Academic Search

Pre-treatment of olive mill wastewater (OMW) by Fenton Oxidation with zero-valent iron and hydrogen peroxide was investigated to improve phenolic compounds degradation and the chemical oxygen demand (COD) removal. Experimental procedure is performed with diluted OMW with COD 19g\\/L and pH 5.2. The application of zero-valent Fe\\/H2O2 procedure allows high removal efficiency of pollutants from OMW. The optimal experimental conditions

M. Kallel; C. Belaid; T. Mechichi; M. Ksibi; B. Elleuch

2009-01-01

51

Electrochemical deposition of green rust on zero-valent iron  

E-print Network

surface oxy- hydroxides of iron were removed. This was assumed to have occurred, when the washing solution contained less than 10 mg/l Fe(II). The washed ZVI was transferred into a test tube containing Endox solution to dissolve the oxy-hydroxides bound... with adequate accuracy and precision in the presence of Endox. These experiments were conducted by measuring Fe(II) in multiple samples at neutral pH in deaerated deionized water with different concentrations (0.5 mg/l, 2.5 mg/l, 5.0 mg/l, 7.5 mg/l and 10...

Kulkarni, Dhananjay Vijay

2006-08-16

52

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

53

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

NASA Astrophysics Data System (ADS)

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

Filip, Jan; Kašlík, Josef; Med?ík, Ivo; Petala, Eleni; Zbo?il, Radek; Slunský, Jan; ?erník, Miroslav; Stav?lová, Monika

2014-05-01

54

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

55

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

56

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

SciTech Connect

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

Lenly J. Weathers; Lynn E. Katz

2002-05-29

57

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

58

Applicability of nano zero valent iron (nZVI) in sono - Fenton process  

NASA Astrophysics Data System (ADS)

Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic pollutants in wastewater. In this study, instead of iron sulfate (FeSO4), nano zero valent iron (nZVI) was used as a major source of ferrous iron (Fe2+). In order to enhance the process, ultrasound was utilized in this study. Results show that, with the aid of ultrasound, nZVI produced more Fe2+ compared to FeSO4 at pH 2. Furthermore, combination of higher intensity and longer sonication time in Fenton process acceleratde the chemical oxygen demand (COD) removal from palm oil mill effluent (POME). Through the process, 80% of COD content was removed within 2 hours instead of 24 hours of silent degradation.

Taha, M. R.; Ibrahim, A. H.; Amat, R. C.; Azhari, A. W.

2014-04-01

59

Long-term performance evaluation of permeable reactive barrier using zero-valent iron  

NASA Astrophysics Data System (ADS)

Long-term performance of a permeable reactive barrier (PRB) filled with zero-valent iron (ZVI) and crushed stone as reactive media was evaluated by about ten years groundwater monitoring from its installation. After 2619 days (about 7.2 years), increase of chlorinated volatile organic carbons (CVOCs) concentrations in groundwater was observed at down-gradient wells. Reactive media was sampled from the center of PRB at 3158 days (about 8.7 years) to conduct a series of laboratory tests, which examines the dechlorination coefficient and the conditions of iron powder. Test results showed the iron powder from PRB still maintains sufficient dechlorination ability of CVOCs, and the thickness of corrosion material ranges less than 5?m and the most of the metal portion remains. Therefore, it was considered that the PRB preserves its function to reduce CVOCs concentration in groundwater met the Environmental Quality Standards for Groundwater (EQSG) of Japan.

Nakashima, Makoto; Negishi, Masanori

60

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

SciTech Connect

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

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

2013-07-01

61

Heavy metals removal and hydraulic performance in zero-valent iron/pumice permeable reactive barriers.  

PubMed

Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has recently been proposed. This paper reports the results of column tests using aqueous nickel and copper solutions of various concentrations. Three configurations of reactive material (ZVI only, granular mixture of ZVI and pumice, and pumice and ZVI in series) are discussed. The results clearly demonstrate that iron-pumice granular mixtures perform well both in terms of contaminant removal and in maintaining the long-term hydraulic conductivity. Comparison with previous reports concerning copper removal by ZVI/sand mixtures reveals higher performance in the case of ZVI/pumice. PMID:20643500

Moraci, Nicola; Calabrò, Paolo S

2010-11-01

62

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

EPA Science Inventory

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

63

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

EPA Science Inventory

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

64

Coupling Electrokinetics with Permeable Reactive Barriers of Zero-Valent Iron for Treating a Chromium Contaminated Soil  

Microsoft Academic Search

Electrokinetic (EK) remediation coupled with permeable reactive barriers (PRB) of zero-valent iron (ZVI) was applied for treating a Cr contaminated soil. Results show that loading ZVI-PRBs in different locations of soil column strongly affected the EK performance. Transport of Cr in the soil column was resulted from the balance of its electromigration and electroosmosis (EO). With increasing treatment time, the

Long Cang; Dong-Mei Zhou; Dan-Ya Wu; Akram N. Alshawabkeh

2009-01-01

65

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

SciTech Connect

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

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

2011-02-18

66

Isotopic fractionation during reductive dechlorination of trichloroethene by zero-valent iron: influence of surface treatment.  

PubMed

During reductive dechlorination of trichloroethene (TCE) by zero-valent iron, stable carbon isotopic values of residual TCE fractionate significantly and can be described by a Rayleigh model. This study investigated the effect of observed reaction rate, surface oxidation and iron type on isotopic fractionation of TCE during reductive dechlorination. Variation of observed reaction rate did not produce significant differences in isotopic fractionation in degradation experiments. However, a small influence on isotopic fractionation was observed for experiments using acid-cleaned electrolytic iron versus experiments using autoclaved electrolytic iron, acid-cleaned Peerless cast iron or autoclaved Peerless cast iron. A consistent isotopic enrichment factor of epsilon = -16.7/1000 was determined for all experiments using cast iron, and for the experiments with autoclaved electrolytic iron. Column experiments using 100% cast iron and a 28% cast iron/72% aquifer matrix mixture also resulted in an enrichment factor of -16.9/1000. The consistency in enrichment factors between batch and column systems suggests that isotopic trends observed in batch systems may be extrapolated to flowing systems such as field sites. The fact that significant isotopic fractionation was observed in all experiments implies that isotopic analysis can provide a direct qualitative indication of whether or not reductive dechlorination of TCE by Fe0 is occurring. This evidence may be useful in answering questions which arise at field sites, such as determining whether TCE observed down-gradient of an iron wall remediation scheme is the result of incomplete degradation within the wall, or of the dissolved TCE plume by passing the wall. PMID:12430646

Slater, G F; Lollar, B Sherwood; King, R Allen; O'Hannesin, S

2002-11-01

67

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

PubMed

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

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

2009-05-12

68

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

SciTech Connect

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

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

2009-06-01

69

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

70

Immobilization of Arsenic and Manganese in Contaminated Groundwater by Permeable Reactive Barriers Using Zero Valent Iron and Sheep Manure  

Microsoft Academic Search

A permeable reactive barriers (PRBs) column test was carried out to remove arsenic (As) and manganese (Mn) from groundwater using zero valent iron (ZVI), sheep manure, compost and woodchips as reactive materials. Arsenic was mainly immobilized through sorption and co-precipitation with iron-bearing minerals, and also possibly precipitation as FeAsO4. The presence of sulfate-reducing bacteria (SRB) in the inoculated column was

Wahyu Wilopo; Keiko Sasaki; Tsuyoshi Hirajima; Toshiro Yamanaka

2008-01-01

71

Bactericidal Effect of Zero-Valent Iron Nanoparticles on Escherichia coli  

PubMed Central

Zero-valent iron nanoparticles (nano-Fe0) in aqueous solution rapidly inactivated Escherichia coli (E. coli). A strong bactericidal effect of nano-Fe0 was found under deaerated conditions, with a linear correlation between log inactivation and nano-Fe0 dose (0.82 log inactivation / mg/L nano-Fe0 · hr). The inactivation of E. coli under air saturation required much higher nano-Fe0 doses due to the corrosion and surface oxidation of nano-Fe0 by dissolved oxygen. Significant physical disruption of the cell membranes was observed in E. coli exposed to nano-Fe0, which may have caused the inactivation, or enhanced the biocidal effects of dissolved iron. The reaction of Fe(II) with intracellular oxygen or hydrogen peroxide also may have induced oxidative stress by producing reactive oxygen species. The bactericidal effect of nano-Fe0 was a unique property of nano-Fe0, which was not observed in other types of iron-based compounds. PMID:18678028

Lee, Changha; Kim, Jee Yeon; Lee, Won Il; Nelson, Kara L.; Yoon, Jeyong; Sedlak, David L.

2008-01-01

72

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

73

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

SciTech Connect

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 has been building. This perception is based on the failure of some deployments to satisfy goals for treatment and operating expenses. The purpose of this report, therefore, is to suggest reasons for the problems that have been encountered and to recommend whether DOE should invest in additional research and deployments. The principal conclusion of this review is that the most significant problems have been the result of insufficient characterization, which resulted in poor engineering implementation. Although there are legitimate concerns regarding the longevity of the reactive media, the ability of zero-valent iron to reduce certain chlorinated hydrocarbons and to immobilize certain metals and radionuclides is well documented. The primary problem encountered at some DOE full-scale deployments has been an inadequate assessment of site hydrology, which resulted in misapplication of the technology. The result is PRBs with higher than expected flow velocities and/or incomplete plume capture. A review of the literature reveals that cautions regarding subsurface heterogeneity were published several years prior to the full-scale implementations. Nevertheless, design and construction have typically been undertaken as if the subsurface was homogeneous. More recently published literature has demonstrated that hydraulic heterogeneity can cause so much uncertainty in performance that use of a passive PRB is precluded. Thus, the primary conclusion of this review is that more attention must be given to site-specific issues. Indeed, the use of a passive PRB requires an unusually comprehensive hydrologic characterization so that the design can be based on a thorough understanding of subsurface heterogeneity rather than on average values for hydraulic parameters. Scientists and engineers are capable of conducting the level of investigation required. However, design costs will increase, and the pre-design field work may demonstrate that a passive PRB is not suitable for a particular site. In such cases, an option to consider is hydraulic augmentation, such as pumping (in which the system is no longer passive) or gravity flow from drains. In these circumstances, operation of the treatment media is under known hydraulic conditions. These systems typically contain the treatment media in a vault or in drums. Most of the media problems in such systems have been related to the exclusion of air and can be addressed by better engineering design or by frequent maintenance. Finally, a number of outstanding issues require resolution for further application of this technology. Of particular interest to DOE is resolving the removal mechanisms for uranium and technetium. Few data are available for the latter, and for the former, the technical literature is contradictory. Determining the mechanisms has long-term cost implications; engineers must consider whether it is appropriate to remove or simply abandon a barrier that is no longer functioning. Other issues that are unresolved include determining how hydraulic performance is affected by the emplacement method and quantifying the effects of varying groundwater types on barrier longevity.

Korte, NE

2001-06-11

74

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

75

Zero valent iron simultaneously enhances methane production and sulfate reduction in anaerobic granular sludge reactors.  

PubMed

Zero valent iron (ZVI) packed anaerobic granular sludge reactors have been developed for improved anaerobic wastewater treatment. In this work, a mathematical model is developed to describe the enhanced methane production and sulfate reduction in anaerobic granular sludge reactors with the addition of ZVI. The model is successfully calibrated and validated using long-term experimental data sets from two independent ZVI-enhanced anaerobic granular sludge reactors with different operational conditions. The model satisfactorily describes the chemical oxygen demand (COD) removal, sulfate reduction and methane production data from both systems. Results show ZVI directly promotes propionate degradation and methanogenesis to enhance methane production. Simultaneously, ZVI alleviates the inhibition of un-dissociated H2S on acetogens, methanogens and sulfate reducing bacteria (SRB) through buffering pH (Fe(0) + 2H(+) = Fe(2+) + H2) and iron sulfide precipitation, which improve the sulfate reduction capacity, especially under deterioration conditions. In addition, the enhancement of ZVI on methane production and sulfate reduction occurs mainly at relatively low COD/ [Formula: see text] ratio (e.g., 2-4.5) rather than high COD/ [Formula: see text] ratio (e.g., 16.7) compared to the reactor without ZVI addition. The model proposed in this work is expected to provide support for further development of a more efficient ZVI-based anaerobic granular system. PMID:25867207

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

2015-05-15

76

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

2012-01-01

77

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

PubMed Central

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

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

2012-01-01

78

Polyelectrolyte multilayer film-assisted formation of zero-valent iron nanoparticles onto polymer nanofibrous mats  

NASA Astrophysics Data System (ADS)

A facile approach that combines the electrospinning technique and layer-by-layer (LbL) assembly method has been developed to synthesize and immobilize zero-valent iron nanoparticles (ZVI NPs) onto the surface of nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning CA solution were modified with bilayers composed of positively charged poly(diallyl-dimethyl-ammoniumchloride) (PDADMAC) and negatively charged poly(acrylic acid) (PAA) through electrostatic LbL assembly approach to form composite nanofibrous mats. The composite nanofibrous mats were immersed into the ferrous iron solution to allow Fe(II) ions to complex with the free carboxyl groups of PAA, and then ZVI NPs were immobilized onto the composite nanofibrous mats instantly by reducing the ferrous cations. Combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and thermogravimetry analysis demonstrated that the ZVI NPs are successfully synthesized and uniformly distributed into the polyelectrolyte (PE) multilayer films assembled onto the CA nanofibers. The present approach to synthesis ZVI NPs opens a new avenue to fabricating various materials with high surface area for environmental, catalytic, and sensing applications.

Xiao, Shili; Wu, Siqi; Shen, Mingwu; Guo, Rui; Wang, Shanyuan; Shi, Xiangyang

2009-09-01

79

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

2011-04-15

80

Enhanced paramagnetic Cu²? ions removal by coupling a weak magnetic field with zero valent iron.  

PubMed

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

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

2015-02-11

81

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

PubMed

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

An, Yi; Dong, Qi; Zhang, Keqiang

2014-05-01

82

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

PubMed

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

Kim, Heonki; Yang, Haewon; Kim, Juyoung

2014-01-01

83

The use of zero-valent iron and biosand filtration to inactivate Escherichia coli O157:H7 in irrigation water  

Technology Transfer Automated Retrieval System (TEKTRAN)

Introduction: Foodborne pathogens can be disseminated to produce through contaminated irrigation water. Effective, low cost mitigation strategies, like biosand and zero-valent iron (ZVI) filtration, may be effective in decontaminating irrigation water. Purpose: To determine the effectiveness ...

84

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

EPA Science Inventory

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

85

Reduction of chromate from electroplating wastewater from pH 1 to 2 using fluidized zero valent iron process  

Microsoft Academic Search

Fluidized zero valent iron (ZVI) process was conducted to reduce hexavalent chromium (chromate, CrO42?) to trivalent chromium (Cr3+) from electroplating wastewater due to the following reasons: (1) Extremely low pH (1–2) for the electroplating wastewater favoring the ZVI reaction. (2) The ferric ion, produced from the reaction of Cr(VI) and ZVI, can act as a coagulant to assist the precipitation

Shiao-Shing Chen; Chih-Yu Cheng; Chi-Wang Li; Pao-Hsuan Chai; Yu-Min Chang

2007-01-01

86

Effect of zero-valent iron and a redox mediator on removal of selenium in agricultural drainage water  

Microsoft Academic Search

Effective and economical removal of selenium (Se) in agricultural drainage water is very important in Se bioremediation. Zero-valent iron (ZVI) and a redox mediator [anthraquinone-2,6-disulfonate (AQDS)] were assessed for their ability to enhance the removal of Se(VI) or Se(IV) (500 µg\\/L) in synthetic drainage water by Enterobacter taylorae. The results showed that E. taylorae was capable of using inexpensive sucrose to

Yiqiang Zhang; Christopher Amrhein; Andrew Chang; William T. Frankenberger

2008-01-01

87

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

PubMed

Recently, adsorption process has been introduced as a favorable and effective technique for the removal of metal ions from aqueous solutions. In the present study, bimetallic nanoparticles consisting of zero valent iron and silver were loaded on the activated carbon powder for the preparation of a new adsorbent (PAC-Fe(o)/Ag). The above adsorbent was characterized by using XRD, SEM and TEM techniqes. Experimental data were exploited for kinetic, equilibrium and thermodynamic evaluations related to the adsorption processes. The Cr(VI) adsorption process was found to be favorable at pH 3 and it reached equilibrium state within 60 min. The stirring rate did not have a significant effect on the adsorption efficiency. Furthermore, the monolayer adsorption capacity of Cr(VI) based on the Langmuir model was measured to be 100 mg/g. The experimental equilibrium data were fitted to the Freundlich adsorption and pseudo second-order models. According to the thermodynamic study, the adsorption process was spontaneous and endothermic in nature, indicating the adsorption capacity increases with increasing the temperature. The results also revealed that the synthesized composite can be potentially applied as a magnetic adsorbent to remove Cr(VI) contaminants from aqueous solutions. PMID:25184050

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

2014-01-01

88

Characteristics of two types of stabilized nano zero-valent iron and transport in porous media.  

PubMed

Nano-scale zero-valent iron (NZVI) has been shown to be suitable for remediating contaminated aquifers. However, they usually aggregate rapidly and result in a very limited migration distance that inhibits their usefulness. This study employed poly acrylic acid (PAA) and carboxymethyl cellulose (CMC) to synthesize two types of stabilized styles of NZVI with finer sizes (namely PNZVI and CNZVI). The mobility of stabilized NZVI was also demonstrated on the basis of transport in porous media. The results show that the PNZVI has a uniform particle size of 12 nm. However, tens of CNZVI particles with diameters of 1-3 nm were packed into secondary particles. Both the PNZVI and the CNZVI exhibited amorphous structures, and the stabilizer was bound to particle surfaces in the form of bidentate bridging via the carboxylic group, which could provide both electrostatic and steric repulsion to prevent particle aggregation. This study also proposes presumed stabilized configurations of PNZVI and CNZVI to reasonably illustrate their different dispersed suspension types. On the basis of the breakthrough curves and mass recovery, this study observed that the mobility of PNZVI in classic Ca(2+) concentration of groundwater was superior to CNZVI. Nonetheless, the mobility of CNZVI would be decreased less significantly than PNZVI when encountering high Ca(2+) concentrations (40 mM). Presumably, increasing the pore flow velocity would enhance the mobility of stabilized NZVI. Overall, the results of this study indicate that PNZVI has the potential to become an effective reactive material for in situ groundwater remediation. PMID:20163828

Lin, Yu-Hao; Tseng, Hui-Hsin; Wey, Ming-Yen; Lin, Min-Der

2010-04-15

89

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. PMID:16909470

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

2006-01-01

90

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

SciTech Connect

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

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

2011-06-27

91

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

PubMed

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. PMID:15949610

Bayer, Peter; Finkel, Michael

2005-06-01

92

Zero valent iron remediation of a mixed brominated ethene contaminated groundwater.  

PubMed

The suitability of a granulated zero valent iron (ZVI) permeable reactive barrier (PRB) remediation strategy was investigated for tribromoethene (TriBE), cis-1,2-dibromoethene (c-DBE), trans-1,2-dibromoethene (t-DBE) and vinyl bromide (VB), via batch and large-scale column experiments that were subsequently analysed by reactive transport modelling. The brominated ethenes in both batch and large-scale column experiments showed rapid (compared to controls and natural attenuation) degradation in the presence of ZVI. In the large-scale column experiment, degradation half-lives were 0.35 days for TriBE, 0.50 days for c-DBE, 0.31 days for t-DBE and 0.40 days for VB, under site groundwater flow conditions, resulting in removal of brominated ethenes within the first 0.2 m of a 1.0 m thick ZVI layer, indicating that a PRB groundwater remediation strategy using ZVI could be used successfully. In the model simulations of the ZVI induced brominated ethene degradation, assuming a dominant reductive beta-elimination pathway via bromoacetylene and acetylene production, simulated organic compound concentrations corresponded well with both batch and large-scale column experimental data. Changes of inorganic reactants were also well captured by the simulations. The similar ZVI induced degradation pathway of TriBE and TCE suggests that outcomes from research on ZVI induced TCE remediation could also be applied to TriBE remediation. PMID:18990465

Cohen, Elizabeth L; Patterson, Bradley M; McKinley, Allan J; Prommer, Henning

2009-01-26

93

Competition for sorption and degradation of chlorinated ethenes in batch zero-valent iron systems.  

PubMed

The sorption and degradation of the chlorinated ethenes tetrachloroethene (PCE, 5 mg L(-1)) and trichloroethene (TCE, 10 mg L(-1)) were investigated in zero-valent iron systems (ZVI, 100 g L(-1)) in the presence of compounds common to contaminated groundwater with varying physicochemical properties. The potential competitors were chlorinated ethenes, monocyclic aromatic hydrocarbons, and humic acids. The effect of a complex matrix was tested with landfill contaminated groundwater. Nonlinear Freundlich isotherms adequately described chloroethene sorption to ZVI. In the presence of the more hydrophobic PCE (5 mg L(-1)), TCE sorption and degradation decreased by 33% and 30%, respectively, while TCE (10 mg L(-1)) decreased PCE degradation by 30%. In the presence of nonreactive hydrophobic hydrocarbons (i.e., benzene, toluene, and m-xylene at 100 mg L(-1)), TCE and PCE sorption decreased by 73% and 55%, respectively. The presence of the hydrocarbons had no effect on TCE degradation and increased PCE reduction rates by 50%, suggesting that the displacement of the chloroethenes from the sorption sites by the aromatic hydrocarbons enhanced the degradation rates. Humic acids did not interfere significantly with chloroethene sorption or with TCE degradation but lowered PCE degradation kinetics by 36% when present at high concentrations (100 mg L(-1)). The landfill groundwater with an organic carbon content of 109 mg L(-1) C had no effect on chloroethene sorption but inhibited TCE and PCE degradation by 60% and 70%, respectively. PMID:15212263

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

2004-05-15

94

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

PubMed Central

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

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

2014-01-01

95

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

2013-01-15

96

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

SciTech Connect

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

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

2010-01-01

97

Filamentous sludge bulking control by nano zero-valent iron in activated sludge treatment systems.  

PubMed

Sludge bulking causes loss of biomass in the effluent and deterioration of effluent water quality. This study explored the use of nano zero-valent iron (NZVI with an average particle size of 55 ± 11 nm) for sludge bulking control. In two Modified Ludzack-Ettinger (MLE) activated sludge treatment systems, a single dose of NZVI at the final concentration of 100 mg Fe per L in the mixed liquor reduced the number of filamentous bacteria Type 021N by 2-3?log units (a reduction of 99.9 and 96.7% in MLE tank #1 and #2, respectively). The side effect of the use of NZVI depended on sludge bulking conditions and biomass concentration. In the system with sludge bulking and significant sludge loss (average biomass concentration of 1022 ± 159 COD mg per L or at the ratio of 0.098 g Fe per g biomass COD), the use of NZVI increased effluent COD, NH4(+)-N and NO2(-)-N concentrations, as also evident with the loss of nitrifying populations and nitrifying activities resulting in more than 40 days to have the full recovery of the activated sludge system. In contrast, in the system with the early stages of bulking and the biomass concentration of 1799 ± 113 COD mg per L (at the ratio of 0.056 g Fe per g biomass COD), the effluent water quality and overall bioreactor performance were only slightly affected for a few days. PMID:25386669

Xu, Shengnan; Sun, Minghao; Zhang, Chiqian; Surampalli, Rao; Hu, Zhiqiang

2014-12-01

98

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

PubMed

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

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

2012-05-15

99

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

2012-09-15

100

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

101

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

102

In situ removal of arsenic from groundwater by using permeable reactive barriers of organic matter\\/limestone\\/zero-valent iron mixtures  

Microsoft Academic Search

In this study, two mixtures of municipal compost, limestone and, optionally, zero-valent iron were assessed in two column\\u000a experiments on acid mine treatment. The effluent solution was systematically analysed throughout the experiment and precipitates\\u000a from both columns were withdrawn for scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry\\u000a analysis and, from the column containing zero-valent iron, solid digestion and sequential

O. Gibert; J. de Pablo; J.-L. Cortina; C. Ayora

2010-01-01

103

A novel conditioning process for enhancing dewaterability of waste activated sludge by combination of zero-valent iron and persulfate.  

PubMed

Improvement of sludge dewaterability is crucial for reducing the costs of sludge disposal in wastewater treatment plants. This study presents a novel conditioning method for improving waste activated sludge dewaterability by combination of persulfate and zero-valent iron. The combination of zero-valent iron (0-30g/L) and persulfate (0-6g/L) under neutral pH substantially enhanced the sludge dewaterability due to the advanced oxidization reactions. The highest enhancement of sludge dewaterability was achieved at 4g persulfate/L and 15g zero-valent iron/L, with which the capillary suction time was reduced by over 50%. The release of soluble chemical oxygen demand during the conditioning process implied the decomposition of sludge structure and microorganisms, which facilitated the improvement of dewaterability due to the release of bound water that was included in sludge structure and microorganism. Economic analysis showed that the proposed conditioning process with persulfate and ZVI is more economically favorable for improving WAS dewaterability than classical Fenton reagent. PMID:25804531

Zhou, Xu; Wang, Qilin; Jiang, Guangming; Liu, Peng; Yuan, Zhiguo

2015-06-01

104

Synthesis of Highly Reactive Subnano-sized Zero-valent Iron using Smectite Clay Templates  

PubMed Central

A novel method was developed for synthesizing subnano-sized zero-valent iron (ZVI) using smectite clay layers as templates. Exchangeable Fe(III) cations compensating the structural negative charges of smectites were reduced with NaBH4, resulting in the formation of ZVI. The unique structure of smectite clay, in which isolated exchangeable Fe(III) cations reside near the sites of structural negative charges, inhibited the agglomeration of ZVI resulting in the formation of discrete regions of subnanoscale ZVI particles in the smectite interlayer regions. X-ray diffraction revealed an interlayer spacing of ~ 5 Å. The non-structural iron content of this clay yields a calculated ratio of two atoms of ZVI per three cation exchange sites, in full agreement with the XRD results since the diameter of elemental Fe is 2.5 Å. The clay-templated ZVI showed superior reactivity and efficiency compared to other previously reported forms of ZVI as indicated by the reduction of nitrobenzene; structural Fe within the aluminosilicate layers was nonreactive. At a 1:3 molar ratio of nitrobenzene:non-structural Fe, a reaction efficiency of 83% was achieved, and over 80% of the nitrobenzene was reduced within one minute. These results confirm that non-structural Fe from Fe(III)-smectite was reduced predominantly to ZVI which was responsible for the reduction of nitrobenzene to aniline. This new form of subnano-scale ZVI may find utility in the development of remediation technologies for persistent environmental contaminants, e.g. as components of constructed reactive domains such as reactive caps for contaminated sediments. PMID:20446730

Gu, Cheng; Jia, Hanzhang; Li, Hui; Teppen, Brian J.; Boyd, Stephen A.

2010-01-01

105

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

106

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

107

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

PubMed

Permeable reactive barriers (PRBs) of zero-valent iron (Fe(0)) are increasingly being used to remediate contaminated ground water. Corrosion of Fe(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(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(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(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 degrees C. We conclude that care must be taken during sample preparation of Fe(0) PRB material, especially for detection of green rusts, to ensure accurate identification of minerals present within the barrier system. PMID:12931885

Phillips, D H; Gu, B; Watson, D B; Roh, Y

2003-01-01

108

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

PubMed

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

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

2014-08-01

109

Transport of carbon colloid supported nanoscale zero-valent iron in porous media  

NASA Astrophysics Data System (ADS)

The use of nano zero-valent iron (nZVI) for environmental remediation is an emerging technology for in situ remediation of contaminated groundwater. Due to its high surface area and high reactivity nZVI is able to dechlorinate organic contaminants and render them to less harmful substances. Carbo-Iron is a newly developed material consisting of activated carbon particles (d50 = 0.6 - 2.4 µm) that are doted with nZVI particles. These particles combine the sorption capacity of activated carbon and the reactivity of nZVI. Additionally the main limitation for nZVI delivery, a limited mobility due to fast aggregation and sedimentation of nZVI in dispersions and soils, might be solved. According to transport theory, particles with a diameter of approximately 1 µm are more mobile than unsupported nZVI particles in sandy aquifer systems. Results from column tests and a two dimensional laboratory aquifer test system are presented: Column tests using columns of 40 cm length were filled with sand. A particle suspension was pumped against gravity through the system. Results show, addition of a polyanionic stabilizer such as Carboxymethylcellulouse (CMC) is required to enhancing mobility. Ionic strength and pH concentrations in an environmental relevant range do not interfere significantly with transport, but particle size was found to be crucial. Another experiment was performed in a two dimensional aquifer test system. The test system contains a sand filled container with a inner size of 40 x 5 x 110 cm and seven ports on each side. A constant flow of water was applied from the left to the right side through all ports and the middle port was fed with a Carbo-Iron suspension. Results show a transport through the laboratory aquifer within few exchanged pore volumes, and breakthrough of Carbo-Iron at the outlet. Deposits of immobile Carbo-Iron were found to be decreasing with distance from the injection port. No gravity effects were observed. Results suggest high mobility of carbon supported nZVI under environmental relevant conditions. Carbo-Iron might be helpful to deliver nZVI into contaminated aquifers. There 1D and 2D results support the design of a field test and application of Carbo-Iron for nZVI delivery.

Busch, Jan; Oswald, Sascha

2013-04-01

110

Reducing the mobility of arsenic in brownfield soil using stabilised zero-valent iron nanoparticles.  

PubMed

The use of nanoscale zero-valent iron (nZVI) as a new tool for the treatment of polluted soils and groundwater has received considerable attention in recent years due to its high reactivity, in situ application and cost-effectiveness. The objectives of this study were to investigate the effectiveness of using a commercial stabilised suspension of nZVI to immobilise As in brownfield soil and to investigate its impact on Fe availability in the treated soil. The phytotoxicities of the soil samples were also evaluated using a germination test with two plant species: barley (Hordeum vulgare L) and common vetch (Vicia sativa L). Two doses of the commercial nZVI suspension were studied, 1% and 10%, and two soil-nanoparticle interaction times, 72 h and 3 mo, were used to compare the stabilities of the soils treated with nZVI. The As availability was evaluated using a sequential extraction procedure and the toxicity characteristics leaching procedure (TCLP) test. The application of nZVI significantly decreased the availability of As in the soil. The immobilisation of As was more effective and more stable over time with the 10% dose than with the 1% dose of the commercial nZVI suspension. The application of nZVI did not induce an important increase in Fe mobility because the Fe leachability was less than 2 mg L(-1) over the time period studied. The lower availability of As in the soil led to a decrease in the phytotoxicity of the soil to barley and vetch germination. Thus, the proposed nanotechnology could be a potential alternative for the in situ remediation of As-polluted soils and could be combined with remediation processes where plants are involved. PMID:25072767

Gil-Díaz, Mar; Alonso, Juan; Rodríguez-Valdés, Eduardo; Pinilla, Paloma; Lobo, Maria Carmen

2014-01-01

111

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

SciTech Connect

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

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

2013-09-01

112

Quantification of changes in zero valent iron morphology using X-ray computed tomography.  

PubMed

Morphological changes within the porous architecture of laboratory scale zero valent iron (ZVI) permeable reactive barriers (PRBs), after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios (10%, 50% and 100%, W/W) with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised (DI) water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography (CT). CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI (W/W) columns had a higher frequency of small pores (0.6 mm) was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity (44%) and larger average pore size (2.8 mm). 10% ZVI PRB barrier material had the highest mean porosity (56%) after exposure to any water chemistry whilst 100% ZVI (W/W) columns always had the lowest (34%) with the 50% ZVI (W/W) in between (40%). These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs. PMID:24552065

Luo, Ping; Bailey, Elizabeth H; Mooney, Sacha J

2013-11-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

114

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

NASA Astrophysics Data System (ADS)

Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20-30 mesh Ottawa sand and PCE-DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3 mM CaCl 2 at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200 mg/L) and production of dissolved-phase ethene (10-30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE-DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE-DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE-DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.42 1/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE-DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products.

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

2010-11-01

115

[Treatment of Cr( VI) in deoxygenated simulated groundwater using nanoscale zero-valent iron].  

PubMed

Laboratory experiments and theoretical modeling studies were performed to investigate the mechanisms of Cr( VI) removal from deoxygenated simulated groundwater using nanoscale zero-valent iron, and to evaluate influencing factors and kinetics based on zeta potential, redox potential, ferrous concentrations, and the pe-pH diagram of Fe-Cr-H2O system. Experimental results demonstrate that the removal efficiency of Cr(VI) decreases with the increasing Cr( VI)/Fe mass ratio. When the Cr(VI)/Fe mass ratios are 0.025, 0.050, 0.075, and 0.100, the corresponding Cr(VI) removal rates are 100.0%, 85.6%, 72.7% and 39.6%, respectively. The Cr( VI) removal is favorable at acidic pH with fixed Cr(VI)/Fe mass ratio of 0.100. When pH are 3.0, 5.0, 7.0, 9.0 and 11.0, the Cr(VI) removal rates are 73.4%, 57.6%, 39.6%, 44.1%, and 41.2%, accordingly. The Cr(VI) removal follows the pseudo second-order kinetics. When pH is 7.0 and Cr(VI)/nZVI mass ratio is 0.025, the rate of Cr(VI) removal is the highest with rate constant at 9.76 x 10(-3) g x (mg x min)(-1). The conversion from Cr2O7(2-) to Cr3+ should be instantaneous when Cr2O7(2-) is absorbed on the surface of Fe. The Cr(VI) was reduced to Cr(III), which was subsequently incorporated into the FeOOH shell and formed a Cr-Fe film. The film once formed could further inhibit the electron transfer between Cr2O7(2-) and Fe. Then Cr(V) removal was primary controlled by the adsorption process. PMID:20358821

Wu, Jia; Tian, Xiu-jun; Wang, Jin; Jing, Chuan-yong

2010-03-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

Removal of selenium from water with nanoscale zero-valent iron: Mechanisms of intraparticle reduction of Se(IV).  

PubMed

Increasing evidences suggest that nanoscale zero-valent iron (nZVI) is an effective agent for treatment and removal of selenium from water. For example, 1.3 mM selenite was quickly removed from water within 3 min with 5 g/L nZVI. In this work, reaction mechanisms of selenite [Se(IV)] in a single core-shell structured nanoscale zero-valent iron (nZVI) particle were studied with the method of spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) integrated with X-ray energy dispersive spectroscopy (XEDS). This method was utilized to visualize solid phase translocation and transformation of Se(IV) such as diffusion, reduction, deposition and the effect of surface defects in a single nanoparticle. Se(IV) was reduced to Se(-II) and Se(0), which then formed a 0.5 nm layer of selenium at the iron oxide-Fe(0) interface at a depth of 6 nm from the surface. The results provided near atomic-resolution proof on the intraparticle diffusion-reduction of Se(IV) induced by nZVI. The STEM mapping also discovered that defects on the surface layer accelerate the diffusion of selenium and increase the capacity of nZVI for selenium sequestration. PMID:25622004

Ling, Lan; Pan, Bingcai; Zhang, Wei-Xian

2015-03-15

118

Investigation into the potential toxicity of zero-valent iron nanoparticles to a trichloroethylene-degrading groundwater microbial community  

NASA Astrophysics Data System (ADS)

The microbiological impact of zero-valent iron remediation of groundwater was investigated by exposing a trichloroethylene-degrading anaerobic microbial community to bare and coated iron nanoparticles. Changes in population numbers and metabolic activity were analyzed using qPCR and were compared to those of a blank, negative, and positive control to assess for microbial toxicity. Additionally, these results were compared to those of samples exposed to an equal concentration of iron filings in an attempt to discern the source of toxicity. Statistical analysis revealed that the three iron treatments were equally toxic to total Bacteria and Archaea populations, as compared with the controls. Therefore, toxicity appears to result either from the release of iron ions and the generation of reactive oxygen species, or from alteration of the redox system and the disruption of microbial metabolisms. There does not appear to be a unique nanoparticle-based toxicity.

Zabetakis, Kara M.

119

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

120

Advantages of low pH and limited oxygenation in arsenite removal from water by zero-valent iron.  

PubMed

The removal of toxic arsenic species from contaminated waters by zero-valent iron (ZVI) has drawn considerable attention in recent years. In this approach, arsenic ions are mainly removed by adsorption to the iron corrosion products. Reduction to zero-valent arsenic on the ZVI surface is possible in the absence of competing oxidants and can reduce arsenic mobility and sludge formation. However, associated removal rates are relatively low. In the current study, simultaneous high reduction and removal rates of arsenite (H3AsO3), the more toxic and mobile environmentally occurring arsenic species, was demonstrated by reacting it with ZVI under limited aeration and relatively low pH. 90% of the removed arsenic was attached to the ZVI particles and 60% of which was in the elemental state. Under the same non-acidic conditions, only 40-60% of the removed arsenic was attached to the ZVI with no change in arsenic oxidation state. Under anaerobic conditions, reduction occurred but total arsenic removal rate was significantly lower and ZVI demand was higher. The effective arsenite removal under acidic oxygen-limited conditions was explained by formation of Fe(II)-solid intermediate on the ZVI surface that provided high surface area and reducing power. PMID:23500792

Klas, Sivan; Kirk, Donald W

2013-05-15

121

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

122

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

PubMed

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

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

2014-07-01

123

Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite  

NASA Astrophysics Data System (ADS)

The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (<9) but not at higher pH. Acid-treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by XANES/EXAFS, which could result in reduced mobility and toxicity of arsenic. Fourth, magnetite is a good adsorbent for both As(V) and As(III). As(V) was not reduced by stoichiometric magnetite even under a strictly anoxic condition. Addition of dissolved Fe(II) to magnetite did not reduce As(V) either. Under oxic conditions, the homogeneous oxidation of As(III) by dissolved oxygen was negligible. As(III) was rapidly oxidized in the presence of magnetite. The extent of the oxidation was promoted with addition of As(V). The effect is more significant at low As(III) concentrations. The effect could be important at field sites where total arsenic concentrations are low. This research is contributes to the understanding of the behavior of arsenic in sulfidic natural systems and in sites treated with GAC, ZVI-based permeable reactive barriers or injected with nano-ZVI particles. The optimum conditions and kinetic data for arsenic removal are applicable in field situations and engineered systems.

Sun, Fenglong

124

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

EPA Science Inventory

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

125

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

126

Modelling the long-term performance of zero-valent iron using a spatio-temporal approach for iron aging.  

PubMed

Zero-valent iron (ZVI) permeable reactive barriers (PRBs) have become popular for the degradation of chlorinated ethenes (CEs) in groundwater. However, a knowledge gap exists pertaining to the longevity of ZVI. The present investigation addresses this situation by suggesting a numerical simulation model that is intended to be used in conjunction with field or column tests in order to describe long-term ZVI performance at individual sites. As ZVI aging processes are not yet completely understood and are still subject to research, we propose a phenomenological modelling technique instead of a common process-based approach. We describe ZVI aging by parameters that characterise the extent and rate of ZVI reactivity change depending on the propagation of the precipitation front through ZVI. We approximate degradation of CEs by pseudo-first order kinetics accounting for the formation of partially dechlorinated products, and describe ZVI reactivity change by scaling the degradation rate constants. Three independent modelling studies were carried out to test the suitability of the conceptual and numerical model to describe the observations of accelerated column tests. All three tests indicated that ZVI reactivity declined with an increasing number of exchanged pore volumes. Measured and modelled concentrations showed good agreement, thereby proving that resolving spatial as well as temporal changes in ZVI reactivity is reasonable. PMID:17113680

Kouznetsova, Irina; Bayer, Peter; Ebert, Markus; Finkel, Michael

2007-02-20

127

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

EPA Science Inventory

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

128

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

Microsoft Academic Search

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

Yunho Lee; Jeyong Yoon

2009-01-01

129

Removal of water contaminants by nanoscale zero-valent iron immobilized in PAN-based oxidized membrane  

NASA Astrophysics Data System (ADS)

The functionalizing nanoporous polyacrylonitrile-based oxidized membrane (PAN-OM) firmly immobilized with highly reactive nanoscale zero-valent iron (NZVI) are successfully prepared via an innovative in situ synthesis method. Due to the formation of ladder structure, the PAN-OM present excellent thermal and chemical stabilities as a new carrier for the in-situ growth of NZVI via firm chelation and reduction action, respectively, which prevent the aggregation and release of NZVI. The developed NZVI-immobilized membrane present effective decolorizing efficiency to both anionic methyl blue and cationic methylene blue with a pseudo-first-order decay and degrading efficiency to trichloroethylene (TCE). The regeneration and stability results show that NZVI-immobilized membrane system can be regenerated without obvious performance reduction, which remain the reactivity after half a year storage period. These results suggest that PAN-based oxidized membrane immobilized with NZVI exhibit significant potential for environmental applications.

Liu, Chunyi; Li, Xiang; Ma, Bomou; Qin, Aiwen; He, Chunju

2014-12-01

130

Reductive dechlorination of activated carbon-adsorbed trichloroethylene by zero-valent iron: carbon as electron shuttle.  

PubMed

Sequestration of organic contaminants in carbonaceous materials can significantly affect contaminant fate and transport. We investigated the reductive dechlorination of granular-activated carbon (GAC)-adsorbed trichloroethylene (TCE) by nanoscale zero-valent iron (nZVI) to understand the effect of sequestration on abiotic reactivity of organic contaminants. Significant reduction of TCE sequestered in GAC micropores was observed, even though direct contact with nZVI was unlikely. Reduction of sequestered TCE by reactive Fe(II) species or molecular hydrogen was ruled out as the reaction mechanisms. We propose that GAC served as the conductor for the transfer of electrons or atomic hydrogen from nZVI to the micropores, wherein adsorbed TCE molecules were reduced. An important implication for environmental remediation is that carbonaceous adsorbents not only function as a superb sink for organic contaminants but also allow them to be slowly degraded while being trapped. PMID:22031571

Tang, Hao; Zhu, Dongqiang; Li, Tielong; Kong, Haonan; Chen, Wei

2011-01-01

131

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

2003-01-01

132

Arsenic(V) removal from groundwater using nano scale zero-valent iron as a colloidal reactive barrier material.  

PubMed

The removal of As(V), one of the most poisonous groundwater pollutants, by synthetic nanoscale zero-valent iron (NZVI) was studied. Batch experiments were performed to investigate the influence of pH, adsorption kinetics, sorption mechanism, and anionic effects. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Mossbauer spectroscopy were used to characterize the particle size, surface morphology, and corrosion layer formation on pristine NZVI and As(V)-treated NZVI. The HR-TEM study of pristine NZVI showed a core-shell-like structure, where more than 90% of the nanoparticles were under 30 nm in diameter. Mössbauer spectroscopy further confirmed its structure in which 19% were in zero-valent state with a coat of 81% iron oxides. The XRD results showed that As(V)-treated NZVI was gradually converted into magnetite/maghemite corrosion products over 90 days. The XPS study confirmed that 25% As(V) was reduced to As(III) by NZVI after 90 days. As(V) adsorption kinetics were rapid and occurred within minutes following a pseudo-first-order rate expression with observed reaction rate constants (Kobs) of 0.02-0.71 min(-1) at various NZVI concentrations. Laser light scattering analysis confirmed that NZVI-As(V) forms an inner-sphere surface complexation. The effects of competing anions revealed that HCO3-, H4SiO4(0), and H2PO4(2-) are potential interfering agents in the As(V) adsorption reaction. Our results suggest that NZVI is a suitable candidate for As(V) remediation. PMID:16570634

Kanel, Sushil Raj; Greneche, Jean-Mark; Choi, Heechul

2006-03-15

133

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

134

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

PubMed

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

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

2015-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

136

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

PubMed Central

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

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

2015-01-01

137

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

NASA Astrophysics Data System (ADS)

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 trichloroethylene (TCE), cis-dichloroethylene (DCE) and mixtures of both was measured in order to investigate interspecies competition. Although a decreasing rate of dechlorination is to be expected, when several degradable substances compete for the reactive sites on the iron surface, TCE degradation is nearly unaffected by the presence of cis-DCE. In contrast, cis-DCE degradation rates decrease significantly when TCE is added. A new modelling approach is developed in order to identify and quantify the observed competitive effects. The numerical model TBC (Transport, Biochemistry and Chemistry, Schäfer et al., 1998a) is used to describe adsorption, desorption and dechlorination in a mechanistic way. Adsorption and degradation of a contaminant based on a limited number of reactive sites leads to a combined zero- and first-order degradation kinetics for high and low concentrations, respectively. The adsorption of several contaminants with different sorption parameters to a limited reactive surface causes interspecies competition. The reaction scheme and the parameters required are successfully transferred from Arnold and Roberts (2000b) to the model TBC. The degradation behaviour of the mixed contamination observed in the column experiments can be related to the adsorption properties of TCE and cis-DCE. By predicting the degradation of the single substances TCE and cis-DCE as well as mixtures of both, the calibrated model is used to investigate the effects of interspecies competition on the design of permeable reactive iron barriers. Even if TCE is present in only small concentrations (>3% of molar cis-DCE concentration) it is the contaminant limiting the residence time and the required thickness of the iron barrier.

Schäfer, Dirk; Köber, Ralf; Dahmke, Andreas

2003-09-01

138

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

PubMed

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

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

2014-08-01

139

Removal of hexavalent chromium from aqueous solutions using micro zero-valent iron supported by bentonite layer.  

PubMed

Hexavalent chromium Cr(VI) is of particular environmental concern due to its toxicity, mobility, and challenging removal from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. Moreover, it does not form insoluble compounds in aqueous solutions; therefore, separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are the opposite and, like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI)-Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. Permeable reactive barriers (PRBs) with zero-valent iron (ZVI) have been used to remediate contaminated groundwater with metals, but using ZVI in remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation, and difficulty in separation of iron from the treated solution. Thus, the technology used in the present study is developed to address these problems by placing a layer of bentonite after the PRB layer to remove iron from the treated water. The removal rates of Cr(VI) under different values of pH were investigated, and the results indicated the highest adsorption capacity at low pH. PMID:25768212

Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

2015-03-01

140

Efficient removal of uranium from aqueous solution by zero-valent iron nanoparticle and its graphene composite.  

PubMed

Zero-valent iron nanoparticle (ZVI-np) and its graphene composites were prepared and applied in the removal of uranium under anoxic conditions. It was found that solutions containing 24ppm U(VI) could be completely cleaned up by ZVI-nps, regardless of the presence of NaHCO3, humic acid, mimic groundwater constituents or the change of solution pH from 5 to 9, manifesting the promising potential of this reactive material in permeable reactive barrier (PRB) to remediate uranium-contaminated groundwater. In the measurement of maximum sorption capacity, removal efficiency of uranium kept at 100% until C0(U)=643ppm, and the saturation sorption of 8173mgU/g ZVI-nps was achieved at C0(U)=714ppm. In addition, reaction mechanisms were clarified based on the results of SEM, XRD, XANES, and chemical leaching in (NH4)2CO3 solution. Partially reductive precipitation of U(VI) as U3O7 was prevalent when sufficient iron was available; nevertheless, hydrolysis precipitation of U(VI) on surface would be predominant as iron got insufficient, characterized by releases of Fe(2+) ions. The dissolution of Fe(0) cores was assigned to be the driving force of continuous formation of U(VI) (hydr)oxide. The incorporation of graphene supporting matrix was found to facilitate faster removal rate and higher U(VI) reduction ratio, thus benefitting the long-term immobilization of uranium in geochemical environment. PMID:25734531

Li, Zi-Jie; Wang, Lin; Yuan, Li-Yong; Xiao, Cheng-Liang; Mei, Lei; Zheng, Li-Rong; Zhang, Jing; Yang, Ju-Hua; Zhao, Yu-Liang; Zhu, Zhen-Tai; Chai, Zhi-Fang; Shi, Wei-Qun

2015-06-15

141

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

PubMed

A 200m(2) 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 in groundwater. The degradation efficiency of vinyl chloride (VC) determined at most of monitoring wells was 50-99%. It was found that the injection of NZVI caused a significant change in total iron, total solid (TS) and suspended solid (SS) concentrations in groundwater. Total iron concentration showed a moderate and weak correlation with SS and TS, respectively, suggesting that SS may be used to indicate the NZVI distribution in groundwater. A decrease in oxidation-reduction potential (ORP) values from about -100 to -400mV after NZVI injection was observed. This revealed that NZVI is an effective means of achieving highly reducing conditions in the subsurface environment. Both VC degradation efficiency and ORP showed a correlative tendency as an increase in VC degradation efficiency corresponded to a decrease of ORP. This is in agreement with the previous studies suggesting that ORP can serve as an indicator for the NZVI reactivity. PMID:19800096

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

2010-01-01

142

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

PubMed

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

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

2015-01-01

143

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

NASA Astrophysics Data System (ADS)

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 conditions, recommending the use of FeS in PRB systems. For both ZVI and FeS PRB systems, the interaction of the reactive porous media with groundwater species, and calcium and carbonate in particular, is key to maintaining the permeability and reactivity of the PRB, both of which are necessary for continued treatment. If geochemical conditions are favorable, CaCO3(s) may precipitate, thus reducing permeability and passivating the reactive surface, preventing further remediation. In a statistical review of field PRB performance (Henderson and Demond, Env. Eng. Sci., 2007), it was found that alkalinity, as an indicator of the potential for precipitation of carbonate solids, was correlated to increased risk of PRB failure. A combination of experimental and geochemical modeling approaches is being used to investigate the quantity of calcium carbonate formation in anaerobic FeS and ZVI systems. Column tests with FeS to date have resulted in behavior unlike that observed with ZVI. In the ZVI columns, a pH increase has allowed the precipitation of CaCO3(s), which led to a reduction in permeability. In the FeS columns, the effluent pH and aqueous calcium concentrations were essentially the same as the influent, suggesting that the buffer capacity of carbonate prevented a pH increase, thus precluding the precipitation of CaCO3(s). Geochemical modeling suggests that the interaction of carbonate and FeS may self-regulate in PRB systems: at high carbonate concentrations, when the precipitation of CaCO3(s) could reduce permeability, the buffer capacity provided by the carbonate precludes the pH rise necessary for precipitation. Based on this work, it appears that FeS has additional attributes that recommend it as a reactive medium for in situ removal of arsenic from groundwater.

Henderson, A. D.; Demond, A. H.

2007-12-01

144

Degradation of organic dye using zero-valent iron prepared from by-product of pickling line.  

PubMed

In this study, zero-valent iron (ZVI) was produced using iron oxide that is a by-product of a pickling line at a steel works. The reaction activity of the produced ZVI was evaluated through a series of decomposition experiments of Orange II aqueous solution. The size of ZVI particles increased with reduction temperature due to coalescence. Correspondingly, the specific surface area of ZVI decreased with increasing reduction temperature. The decomposition efficiency of synthesized ZVI particles was higher at a lower pH. In particular, no significant decomposition reaction was observed at pH of 4 and higher. The rate of the ZVI-assisted decomposition of Orange II was increased by addition of H2O2 at pH of 3, whereas it was reduced by addition of H2O2 at a higher pH of 6. Nevertheless, simultaneous use of ZVI, UV and H2O2 led to a considerable increase in the decomposition rate even at a high pH condition (pH = 6). PMID:22097085

Jung, S C; Cho, H C; Ra, D G; Park, S H; Yoon, H S; Kim, S C; Kim, S J

2011-01-01

145

Mechanism of enhanced nitrate reduction via micro-electrolysis at the powdered zero-valent iron/activated carbon interface.  

PubMed

Nitrate reduction by zero-valent iron (Fe(0)) powder always works well only at controlled pH lower than 4 due to the formation of iron (hydr)oxides on its surface. Fe(0) powder combined with activated carbon (AC), i.e., Fe(0)/AC micro-electrolysis system, was first introduced to enhance nitrate reduction in aqueous solution. Comparative study was carried out to investigate nitrate reduction by Fe(0)/AC system and Fe(0) under near-neutral conditions, showing that the Fe(0)/AC system successfully reduced nitrate even at initial pH 6 with the reduction efficiency of up to 73%, whereas for Fe(0) only ?10%. The effect of Fe(0) to AC mass ratio on nitrate reduction efficiency was examined. Easier nitrate reduction was achieved with more contact between Fe(0) and AC as the result of decreasing Fe(0) to AC mass ratio. Ferrous ion and oxidation-reduction potential were measured to understand the mechanism of enhanced nitrate reduction by Fe(0)/AC micro-electrolysis. The results suggest that a relative potential difference drives much more electrons from Fe(0) to AC, thus generating adsorbed atomic hydrogen which makes it possible for nitrate to be reduced at near-neural pH. Fe(0)/AC micro-electrolysis thus presents a great potential for practical application in nitrate wastewater treatment without excessive pH adjustment. PMID:25217726

Luo, Jinghuan; Song, Guangyu; Liu, Jianyong; Qian, Guangren; Xu, Zhi Ping

2014-12-01

146

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

PubMed

The estimation of nanoscale zero-valent iron (nZVI) reactivity after its injection into the subsurface is essential for its application in groundwater remediation. In the present study H? generation of commercially available nZVI and novel milled nZVI flakes were investigated in column experiments with varying nZVI loads (ranging from 8 to 43 g nZVI per kg sand). H? evolution rates were determined for column experiments without and with hydrogen carbonate and/or calcium. On average 0.29 mmol H?/L per g Fe? evolved within the first 30 days in column experiments with spherical, commercial nZVI particles. The H? evolution developed almost independently of the water matrices applied. The application of nZVI flakes resulted in lower H? generation rates. In general corrosion rates accelerated linearly with increasing initial amounts of iron. This was evident in experiments with both particle types. Concentration profiles of carbonate and calcium in influent and effluent were used to estimate corrosion products and precipitates. Despite the presence of high concentrations of inorganic carbon, Fe²? reacted preferably with hydroxide ions to form ferrous hydroxide which is the precursor of magnetite. As a result only minor passivation of the reactive nZVI was observed. PMID:25462777

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

2015-01-01

147

Reduction of chromate from electroplating wastewater from pH 1 to 2 using fluidized zero valent iron process.  

PubMed

Fluidized zero valent iron (ZVI) process was conducted to reduce hexavalent chromium (chromate, CrO(4)(2-)) to trivalent chromium (Cr(3+)) from electroplating wastewater due to the following reasons: (1) Extremely low pH (1-2) for the electroplating wastewater favoring the ZVI reaction. (2) The ferric ion, produced from the reaction of Cr(VI) and ZVI, can act as a coagulant to assist the precipitation of Cr(OH)(3(s)) to save the coagulant cost. (3) Higher ZVI utilization for fluidized process due to abrasive motion of the ZVI. For influent chromate concentration of 418 mg/L as Cr(6+), pH 2 and ZVI dosage of 3g (41 g/L), chromate removal was only 29% with hydraulic detention time (HRT) of 1.2 min, but was increased to 99.9% by either increasing HRT to 5.6 min or adjusting pH to 1.5. For iron species at pH 2 and HRT of 1.2 min, Fe(3+) was more thermodynamically stable since oxidizing agent chromate was present. However, if pH was adjusted to 1.5 or 1, where chromate was completely removed, high Fe(2+) but very low Fe(3+) was present. It can be explained that ZVI reacted with chromate to produce Fe(2+) first and the presence of chromate would keep converting Fe(2+) to Fe(3+). Therefore, Fe(2+) is an indicator for complete reduction from Cr(VI) to Cr(III). X-ray diffraction (XRD) was conducted to exam the remained species at pH 2. ZVI, iron oxide and iron sulfide were observed, indicating the formation of iron oxide or iron sulfide could stop the chromate reduction reaction. PMID:16987595

Chen, Shiao-Shing; Cheng, Chih-Yu; Li, Chi-Wang; Chai, Pao-Hsuan; Chang, Yu-Min

2007-04-01

148

Dechlorination of PCBs in the simulative transformer oil by microwave-hydrothermal reaction with zero-valent iron involved.  

PubMed

The conventional hydrothermal reaction with iron powder, NaOH and H(2)O as reactants was reported to occur at temperature above 423K, and iron oxides (Fe(3)O(4) and NaFeO(2)) and hydrogen were produced. In this study, microwave heating was adopted to take the place of conventional heating to induce the hydrothermal reaction. Under microwave irradiation, NaOH and H(2)O absorbed microwave energy by space charge polarization and dipolar polarization and instantly converted it into thermal energy, which initiated the hydrothermal reaction that involved with zero-valent iron. X-ray diffraction (XRD) analysis found Fe(3)O(4)/NaFeO(2) and confirmed the occurrence of microwave-induced hydrothermal reaction. The developed microwave-hydrothermal reaction was employed for the dechlorination of PCBs. Hexadecane containing 100mgL(-1) of Aroclor1254 was used as simulative transformer oil, and the dechlorination of PCBs was evaluated by GC/ECD, GC/MS and ion chromatography. For PCBs in 10mL simulative transformer oil, almost complete dechlorination was achieved by 750W microwave irradiation for 10min, with 0.3g iron powder, 0.3g NaOH and 0.6mL H(2)O added. The effects of important factors including microwave power and the amounts of reactants added, on the dechlorination degree were investigated, moreover, the dechlorination mechanism was suggested. Microwave irradiation combined with the common and cheap materials, iron powder, NaOH and H(2)O, might provide a fast and cost-effective method for the treatment of PCBs-containing wastes. PMID:21074824

Liu, Xitao; Zhao, Wei; Sun, Ke; Zhang, Guixiang; Zhao, Ye

2011-01-01

149

Kinetics of Solvent Blue and Reactive Yellow removal using microwave radiation in combination with nanoscale zero-valent iron.  

PubMed

We investigated the efficiency and kinetics of the degradation of soluble dyes over the pH range 5.0-9.0 using a method employing microwave radiation in combination with nanoscale zero-valent iron (MW-nZVI). The nZVI particles (40-70nm in diameter) were prepared by a liquid-phase chemical reduction method employing starch as a dispersant. Compared to the removal of Solvent Blue 36 and Reactive Yellow K-RN using only nZVI, more rapid and efficient dye removal and total organic carbon removal were achieved using MW-nZVI. The dye removal efficiency increased significantly with decreasing pH, but was negligibly affected by variation in the microwave power. The kinetics of dye removal by MW-nZVI followed both an empirical equation and the pseudo first-order model, while the kinetics of dye removal using nZVI could only be described by an empirical equation. It was also concluded that microwave heating of the dye solutions as well as acceleration of corrosion of nZVI and consumption of Fe(II) were possible reasons behind the enhanced dye degradation. PMID:25872723

Mao, Yanpeng; Xi, Zhenqian; Wang, Wenlong; Ma, Chunyuan; Yue, Qinyan

2015-04-01

150

Improving dewaterability of waste activated sludge by combined conditioning with zero-valent iron and hydrogen peroxide.  

PubMed

Improvement of sludge dewaterability is crucial for reducing the costs of sludge disposal in wastewater treatment plants. This study presents a novel method based on combined conditioning with zero-valent iron (ZVI) and hydrogen peroxide (HP) at pH 2.0 to improve dewaterability of a full-scale waste activated sludge (WAS). The combination of ZVI (0-750mg/L) and HP (0-750mg/L) at pH 2.0 substantially improved the WAS dewaterability due to Fenton-like reactions. The highest improvement in WAS dewaterability was attained at 500mg ZVI/L and 250mg HP/L, when the capillary suction time of the WAS was reduced by approximately 50%. Particle size distribution indicated that the sludge flocs were decomposed after conditioning. Economic analysis showed that combined conditioning with ZVI and HP was a more economically favorable method for improving WAS dewaterability than the classical Fenton reaction based method initiated by ferrous salts and HP. PMID:25463788

Zhou, Xu; Wang, Qilin; Jiang, Guangming; Zhang, Xiwang; Yuan, Zhiguo

2014-12-01

151

Efficiency of nanoscale zero-valent iron on the enhanced low molecular weight organic acid removal Pb from contaminated soil.  

PubMed

The Pb removal efficiencies from contaminated soils by low molecular weight organic acid (LMWOA) and nanoscale zero-valent iron (nZVI) were investigated through batch soil washing experiments. Results showed that significant promotion on Pb-removal with the mixed solutions of LMWOA and nZVI (p < 0.05). The Pb removal efficiencies reached 64% and 83% for mine and farmland soil by addition of 0.2 M citric acid and 2.0 g L?1 nZVI, respectively. They decreased with increasing pH from 3 to 9. The mixed solutions of LMWOA and nZVI induced Pb(II) releases processes including a rapid desorption within 4 h and a slow desorption in the following hours. The second-order model was the most appropriate for describing the kinetic processes of Pb(II) desorption. The main fractions of Pb removal were exchangeable and reducible. Compared with LMWOA, the loss rates of nitrogen, phosphorus and potassium decreased after washing with the mixed solutions. Our study suggests that combining of LMWOA and nZVI would be a promising alternative approach for remediation Pb-contaminated soils. PMID:25461926

Wang, Guiyin; Zhang, Shirong; Xu, Xiaoxun; Li, Ting; Li, Yun; Deng, Ouping; Gong, Guoshu

2014-12-01

152

Implementation of zero-valent iron (ZVI) into drinking water supply - role of the ZVI and biological processes.  

PubMed

Arsenic in drinking water is concerning millions of people around the world, even though many solutions to the problem have come up in recent years. One of the promising solutions for removing arsenic from water is by implementation of a zero-valent iron (ZVI) in the drinking water production. The purpose of this work was to study a treatment of As pollution based on the ZVI, aeration and sand filtration that was monitored for period of 45 months. In applied configuration and conditions ZVI was not able to remove arsenic alone, but it worked as a source of ferrous ions that during its oxidation enabled to co-precipitate arsenic compounds in the sand filter. The results show that after a lag phase of about 6 months, it was possible to achieve water production with an As content from 20 ?g L(-1) to below 5 ?g L(-1). The treatment also enabled to remove phosphates that were present in groundwater and affected As uptake by hindering its co-precipitation with Fe compounds. Determination of colony forming units on As amended agar helped to find arsenic resistant bacteria at each stage of treatment and also in the sand filter backwash sludge. Bacterial communities found in groundwater, containing low concentration of As, were found to have high As resistance. The results also indicate that the lag phase might have been also needed to initiate Fe ions release by corrosion from elemental Fe by help of microbial activity. PMID:24996201

Kowalski, Krzysztof P; Søgaard, Erik G

2014-12-01

153

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

PubMed

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

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

2015-02-01

154

Modelling of geochemical and isotopic changes in a column experiment for degradation of TCE by zero-valent iron.  

PubMed

Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter ((12)C) and heavier ((13)C) isotopes. The simulation of a column experiment involving the parallel degradation of TCE by hydrogenolysis and beta-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products. PMID:18267347

Prommer, Henning; Aziz, Lidia H; Bolaño, Nerea; Taubald, Heinrich; Schüth, Christoph

2008-04-01

155

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

PubMed

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

Wu, Yan; Luo, Hanjin; Wang, Hou

2014-01-01

156

Complete debromination of decabromodiphenyl ether using the integration of Dehalococcoides sp. strain CBDB1 and zero-valent iron.  

PubMed

This study investigated the effects of nano- and micro-scale zero-valent iron (nZVI and mZVI) particles on Dehalococcoides sp. strain CBDB1 participating in anaerobic reduction of polybrominated diphenyl ethers. nZVI (>0.25 g L(-)(1)) had an inhibitory effect upon this strain, whereas 1.0 g L(-1) mZVI showed no negative impact on bacterial growth. Strain CBDB1 could only utilize lower brominated congeners (<7 bromines) as electron acceptor. In the bio-ZVI system, decabromodiphenyl ether (BDE-209) was first reduced by ZVI to lower brominated congeners, which were then dehalogenated to diphenyl ether by CBDB1. Within 30 d, a BDE-209 debromination efficiency of 16% and 24% was obtained in the bio-nZVI (0.25 g L(-1)) and bio-mZVI (1.0 g L(-1)) systems with a corresponding diphenyl ether yield efficiency of 14% and 19%, respectively. The debromination efficiency increased significantly from 8% to 24% with an increase of mZVI dosage from 0.25 to 1.0 g L(-1) in the bio-mZVI system. PMID:25217713

Xu, Guiying; Wang, Jiangbo; Lu, Mang

2014-12-01

157

The role of magnetite nanoparticles in the reduction of nitrate in groundwater by zero-valent iron.  

PubMed

Magnetite nanoparticles were used as an additive material in a zero-valent iron (Fe(0)) reaction to reduce nitrate in groundwater and its effects on nitrate removal were investigated. The addition of nano-sized magnetite (NMT) to Fe(0) reactor markedly increased nitrate reduction, with the rate proportionally increasing with NMT loading. Field emission scanning electron microscopy analysis revealed that NMT aggregates were evenly distributed and attached on the Fe(0) surface due to their magnetic properties. The rate enhancement effect of NMT is presumed to arise from its role as a corrosion promoter for Fe(0) corrosion as well as an electron mediator that facilitated electron transport from Fe(0) to adsorbed nitrate. Nitrate reduction by Fe(0) in the presence of NMT proceeded much faster in groundwater (GW) than in de-ionized water. The enhanced reduction of nitrate in GW was attributed to the adsorption or formation of surface complex by the cationic components in GW, i.e., Ca(2+) and Mg(2+), in the Fe(0)-H2O interface that promoted electrostatic attraction of nitrate to the reaction sites. Moreover, the addition of NMT imparted superior longevity to Fe(0), enabling completion of four nitrate reduction cycles, which otherwise would have been inactivated during the first cycle without an addition of NMT. The results demonstrate the potential applicability of a Fe(0)/NMT system in the treatment of nitrate-contaminated GW. PMID:25665757

Cho, Dong-Wan; Song, Hocheol; Schwartz, Franklin W; Kim, Bokseong; Jeon, Byong-Hun

2015-04-01

158

Tunable synthesis of SiO2-encapsulated zero-valent iron nanoparticles for degradation of organic dyes  

PubMed Central

A series of nanocomposites consisting of zero-valent iron nanoparticles (ZVI NPs) encapsulated in SiO2 microspheres were successfully synthesized through a successive two-step method, i.e., the wet chemical reduction by borohydride followed by a modified Stöber method. The as-synthesized nanocomposites were characterized using X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer, and inductively coupled plasma-atomic emission spectrometer. The catalytic performance of SiO2-encapsulated ZVI nanocomposites for the degradation of organic dyes was investigated using methylene blue (MB) as the model dye in the presence of H2O2. The results showed that the degradation efficiency and apparent rate constant of the degradation reaction were significantly enhanced with increased ZVI NPs encapsulated in SiO2 microspheres, whereas the dosage of H2O2 remarkably promoted degradation rate without affecting degradation efficiency. The content-dependent magnetic property ensured the excellent magnetic separation of degradation products under an external magnet. This strategy for the synthesis of SiO2-encapsulated ZVI NPs nanocomposites was low cost and easy to scale-up for industrial production, thereby enabling promising applications in environmental remediation. PMID:25258615

2014-01-01

159

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

PubMed

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

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

2014-08-15

160

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

SciTech Connect

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

Newcomer, Darrell R.

2009-02-09

161

Modelling of geochemical and isotopic changes in a column experiment for degradation of TCE by zero-valent iron  

NASA Astrophysics Data System (ADS)

Zero-valent iron (ZVI) permeable-reactive barriers have become an increasingly used remediation option for the in situ removal of various organic and inorganic chemicals from contaminated groundwater. In the present study a process-based numerical model for the transport and reactions of chlorinated hydrocarbon in the presence of ZVI has been developed and applied to analyse a comprehensive data set from laboratory-scale flow-through experiments. The model formulation includes a reaction network for the individual sequential and/or parallel transformation of chlorinated hydrocarbons by ZVI, for the resulting geochemical changes such as mineral precipitation, and for the carbon isotope fractionation that occurs during each of the transformation reactions of the organic compounds. The isotopic fractionation was modelled by formulating separate reaction networks for lighter ( 12C) and heavier ( 13C) isotopes. The simulation of a column experiment involving the parallel degradation of TCE by hydrogenolysis and ?-elimination can conclusively reproduce the observed concentration profiles of all collected organic and inorganic data as well as the observed carbon isotope ratios of TCE and its daughter products.

Prommer, Henning; Aziz, Lidia H.; Bolaño, Nerea; Taubald, Heinrich; Schüth, Christoph

2008-04-01

162

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

2010-10-01

163

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

164

Coupled effects of aging and weak magnetic fields on sequestration of selenite by zero-valent iron.  

PubMed

The sequestration of Se(IV) by zero-valent iron (ZVI) is strongly influenced by the coupled effects of aging ZVI and the presence of a weak magnetic field (WMF). ZVI aged at pH 6.0 with MES as buffer between 6 and 60 h gave nearly constant rates of Se(IV) removal with WMF but with rate constants that are 10- to 100-fold greater than without. XANES analysis showed that applying WMF changes the mechanism of Se(IV) removal by ZVI aged for 6-60 h from adsorption followed by reduction to direct reduction. The strong correlation between Se(IV) removal and Fe2+ release suggests direct reduction of Se(IV) to Se(0) by Fe0, in agreement with the XANES analysis. The numerical simulation of ZVI magnetization revealed that the WMF influence on Se(IV) sequestration is associated mainly with the ferromagnetism of ZVI and the paramagnetism of Fe2+. In the presence of the WMF, the Lorentz force gives rise to convection in the solution, which narrows the diffusion layer, and the field gradient force, which tends to move paramagnetic ions (esp. Fe2+) along the higher field gradient at the ZVI particle surface, thereby inducing nonuniform depassivation and eventually localized corrosion of the ZVI surface. PMID:24804570

Liang, Liping; Guan, Xiaohong; Shi, Zhong; Li, Jialing; Wu, Yinan; Tratnyek, Paul G

2014-06-01

165

Degradation of trinitroglycerin (TNG) using zero-valent iron nanoparticles/nanosilica SBA-15 composite (ZVINs/SBA-15).  

PubMed

Trinitroglycerin (TNG) is an industrial chemical mostly known for its clinical use in treating angina and manufacturing dynamite. The wide manufacture and application of TNG has led to contamination of vast areas of soil and water. The present study describes degradation of TNG with zero-valent iron nanoparticles (ZVINs) in water either present alone or stabilized on nanostructured silica SBA-15 (Santa Barbara Amorphous No. 15). The BET surface areas of ZVINs/SBA-15 (275.1 m2 g(-1)), as determined by nitrogen adsorption-desorption isotherms, was much larger than the non-stabilized ZVINs (82.0 m2 g(-1)). X-ray diffraction (XRD) showed that iron in both ZVINs and ZVINs/SBA-15 was present mostly in the ?-Fe0 crystalline form considered responsible for TNG degradation. Transmission Electron Microscopy (TEM) showed that iron nanoparticles were well dispersed on the surface of the nanosilica support. Both ZVINs and ZVINs/SBA-15 degraded TNG (100%) in water to eventually produce glycerol and ammonium. The reaction followed pseudo-first-order kinetics and was faster with ZVINs/SBA-15 (k1 0.83 min(-1)) than with ZVINs (k1 0.228 min(-1)). The corresponding surface-area normalized rate constants, knorm, were 0.36 and 0.33 L h(-1) m(-2) for ZVINs/SBA-15 and ZVINs, respectively. The ZVINs/SBA-15 retained its original degradation efficiency of TNG after repeatedly reacting with fresh nitrate ester for five successive cycles. The rapid and efficient transformation of TNG with ZVINs/SBA-15, combined with excellent sustained reactivity, makes the nanometal an ideal choice for the clean up of water contaminated with TNG. PMID:20801482

Saad, Rabih; Thiboutot, Sonia; Ampleman, Guy; Dashan, Wang; Hawari, Jalal

2010-11-01

166

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

PubMed

Oxidations of nanoscale zero-valent iron (nZVI) under aerobic (dissolved oxygen?8mgL(-1)) and anaerobic (dissolved oxygen <3mgL(-1)) conditions were simulated, and their influences on aggregation behaviors of nZVI were investigated. The two oxidation products were noted as HO-nZVI (nZVI oxidized in highly oxygenated water) and LO-nZVI (nZVI oxidized in lowly oxygenated water) respectively. The metallic iron of the oxidized nZVI was almost exhausted (Fe(0)?8±5%), thus magnetization mainly depended on magnetite content. Since sufficient dissolved oxygen led to the much less magnetite (?15%) in HO-nZVI than that in LO-nZVI (>90%), HO-nZVI was far less magnetic (Ms=88kAm(-1)) than LO-nZVI (Ms=365kAm(-1)). Consequently, HO-nZVI formed small agglomerates (228±10nm), while LO-nZVI tended to form chain-like aggregations (>1?m) which precipitated rapidly. Based on the EDLVO theory, we suggested that dissolved oxygen level determined aggregation morphologies by controlling the degree of oxidation and the magnitude of magnetization. Then the chain-like alignment of LO-nZVI would promote further aggregation, but the agglomerate morphology of HO-nZVI would eliminate magnetic forces and inhibit the aggregation while HO-nZVI remained magnetic. Our results indicated the fine colloidal stability of HO-nZVI, which might lead to the great mobility in the environment. PMID:25441925

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

2015-03-01

167

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

PubMed

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

Reardon, Eric J

2014-02-01

168

Microbial community response of nitrifying sequencing batch reactors to silver, zero-valent iron, titanium dioxide and cerium dioxide nanomaterials.  

PubMed

As nanomaterials in consumer products increasingly enter wastewater treatment plants, there is concern that they may have adverse effects on biological wastewater treatment. Effects of silver (nanoAg), zero-valent iron (NZVI), titanium dioxide (nanoTiO?) and cerium dioxide (nanoCeO?) nanomaterials on nitrification and microbial community structure were examined in duplicate lab-scale nitrifying sequencing batch reactors (SBRs) relative to control SBRs that received no nanomaterials or ionic/bulk analogs. Nitrification function was not measurably inhibited in the SBRs by any of the materials as dosing was initiated at 0.1 mg/L and sequentially increased every 14 days to 1, 10, and 20 mg/L. However, SBRs rapidly lost nitrification function when the Ag? experiment was repeated at a continuous high load of 20 mg/L. Shifts in microbial community structure and decreased microbial diversity were associated with both sequential and high loading of nanoAg and Ag?, with more pronounced effects for Ag?. Bacteroidetes became more dominant in SBRs dosed with Ag?, while Proteobacteria became more dominant in SBRs dosed with nanoAg. The two forms of silver also had distinct effects on specific bacterial genera. A decrease in nitrification gene markers (amoA) was observed in SBRs dosed with nanoAg and Ag?. In contrast, impacts of NZVI, nanoTiO?, nanoCeO? and their analogs on microbial community structure and nitrification gene markers were limited. TEM-EDS analysis indicated that a large portion of nanoAg remained dispersed in the activated sludge and formed Ag–S complexes, while NZVI, nanoTiO? and nanoCeO? were mostly aggregated and chemically unmodified. Overall, this study suggests a high threshold of the four nanomaterials in terms of exerting adverse effects on nitrification function. However, distinct microbial community responses to nanoAg indicate potential long-term effects. PMID:25462719

Ma, Yanjun; Metch, Jacob W; Vejerano, Eric P; Miller, Ian J; Leon, Elena C; Marr, Linsey C; Vikesland, Peter J; Pruden, Amy

2015-01-01

169

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

PubMed

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

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

2014-08-01

170

Nanoscale zero-valent iron application for in situ reduction of hexavalent chromium and its effects on indigenous microorganism populations.  

PubMed

Because of its high toxicity and mobility, hexavalent chromium is considered to be a high priority pollutant. This study was performed to carry out a pilot-scale in-situ remediation test in the saturated zone of a historically Cr(VI)-contaminated site using commercially available nanoscale zero-valent iron (nZVI). The site was monitored before and after the nZVI application by means of microbial cultivation tests, phospholipid fatty acid analysis (PLFA) and toxicological tests with Vibrio fischeri. Injection of nZVI resulted in a rapid decrease in the Cr(VI) and total Cr concentrations in the groundwater without any substantial effect on its chemical properties. The ecotoxicological test with V. fischeri did not indicate any negative changes in the toxicity of the groundwater following the application of nZVI and no significant changes were observed in cultivable psychrophilic bacteria densities and PLFA concentrations in the groundwater samples during the course of the remediation test. However, PLFA of soil samples revealed that the application of nZVI significantly stimulated the growth of Gram-positive bacteria. Principle component analysis (PCA) was applied to the PLFA results for the soil samples from the site in order to explain how Cr(VI) reduction and the presence of Fe influence the indigenous populations. The PCA results clearly indicated a negative correlation between the Cr concentrations and the biota before the application of nZVI and a significant positive correlation between bacteria and the concentration of Fe after the application of nZVI. PMID:24369106

N?me?ek, Jan; Lhotský, Ond?ej; Cajthaml, Tomáš

2014-07-01

171

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

172

Oxidant production from corrosion of nano- and microparticulate zero-valent iron in the presence of oxygen: a comparative study.  

PubMed

In aqueous solution, zero-valent iron (ZVI, Fe(0)) is known to activate oxygen (O2) into reactive oxidants such as hydroxyl radical and ferryl ion capable of oxidizing contaminants. However, little is known about the effect of the particle size of ZVI on the yield of reactive oxidants. In this study, the production of reactive oxidants from nanoparticulate and microparticulate ZVIs (denoted as nZVI and mZVI, respectively) was comparatively investigated in the presence of O2 and EDTA. To quantify the oxidant yield, excess amount of methanol was employed, and the formation of its oxidation product, formaldehyde (HCHO), was monitored. The concentration of HCHO in the nZVI/O2 system rapidly reached the saturation value, whereas that in the mZVI/O2 system gradually increased throughout the entire reaction time. The mZVI/O2 system exhibited higher yields of HCHO than the nZVI/O2 system under both acidic and neutral pH conditions. The higher oxidant yields in the mZVI/O2 system are mainly attributed to the less reactivity of the mZVI surface with hydrogen peroxide (H2O2) relative to the surface of nZVI, which minimize the loss of H2O2 by ZVI (i.e., the two-electron reduction of H2O2 into water). In addition, the slow dissolution of Fe(II) from mZVI was found to be partially responsible for the higher oxidant yields at neutral pH. PMID:24361799

Lee, Hongshin; Lee, Hye-Jin; Kim, Hyung-Eun; Kweon, Jihyang; Lee, Byeong-Dae; Lee, Changha

2014-01-30

173

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

174

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

175

Polyoxometalate-Enhanced Oxidation of Organic Compounds by Nanoparticulate Zero-Valent Iron and Ferrous Ion in the Presence of Oxygen  

PubMed Central

In the presence of oxygen, organic compounds can be oxidized by zero-valent iron or dissolved Fe(II). However, this process is not a very effective means of degrading contaminants because the yields of oxidants are usually low (i.e., typically less than 5% of the iron added is converted into oxidants capable of transforming organic compounds). The addition of polyoxometalate (POM) greatly increases the yield of oxidants in both systems. The mechanism of POM enhancement depends on solution pH. Under acidic conditions, POM-mediates the electron transfer from nanoparticulate zero-valent iron (nZVI) or Fe(II) to oxygen, increasing the production of hydrogen peroxide, which is subsequently converted to hydroxyl radical through the Fenton reaction. At neutral pH values, iron forms a complex with POM, preventing iron precipitation on the nZVI surface and in bulk solution. At pH 7, the yield of oxidant approaches the theoretical maximum in the nZVI/O2 and the Fe(II)/O2 systems when POM is present, suggesting that coordination of iron by POM alters the mechanism of the Fenton reaction by converting the active oxidant from ferryl ion to hydroxyl radical. Comparable enhancements in oxidant yields are also observed when nZVI or Fe(II) are exposed to oxygen in the presence of silica-immobilized POM. PMID:18678027

Lee, Changha; Keenan, Christina R.; Sedlak, David L.

2008-01-01

176

Performance of a zero valent iron-based anaerobic system in swine wastewater treatment.  

PubMed

In this paper, short-term exposure experiments with different ZVI concentrations were conducted to research the effects of ZVI adding on the anaerobic system for treating swine wastewater. Increasing the ZVI dose had a stimulatory effect on COD removal and CH4 production possibly due to a higher corrosion-induced H2 and dissolved ferrous ions, which could stimulate the methanogenesis and thus the biodegradation. In addition, the abiotic corrosion reactions such as flocculation, adsorption and precipitation were inevitable to removal some suspended COD. However, high ZVI doses had a potential risk on microorganism due to the present of large numbers of solid iron species in sludge, which likely encapsulated the cells and even damaged the cellular structure. Taken as a whole, the most enhancing effect induced by ZVI was observed at the rZVI/VSS of 2.63, and the maximum efficiency of per ZVI adding occurred at the rZVI/VSS of 0.74. But the ZVI concentration of 50g/L (the rZVI/VSS was 5.26) was proved too high to facilitate microorganism activity, considering the higher LDH leakage and lower intracellular ATP level than the only sludge system. PMID:25543891

Wu, Donglei; Zheng, Shuangshuang; Ding, Aqiang; Sun, Guodong; Yang, Meiqing

2015-04-01

177

Experimentally determined uranium isotope fractionation during reduction of hexavalent U by bacteria and zero valent iron.  

PubMed

Variations in stable isotope ratios of redox sensitive elements are often used to understand redox processes occurring near the Earth's surface. Presented here are measurements of mass-dependent U isotope fractionation induced by U(VI) reduction by zerovalent iron (Fe0) and bacteria under controlled pH and HCO3- conditions. In abiotic experiments, Fe0 reduced U(VI), but the reaction failed to induce an analytically significant isotopic fractionation. Bacterial reduction experiments using Geobacter sulfurreducens and Anaeromyxobacter dehalogenans reduced dissolved U(VI) and caused enrichment of 238U relative to 235U in the remaining U(VI). Enrichmentfactors (epsilon) calculated using a Rayleigh distillation model are -0.31% per hundred and -0.34% per hundred for G. sulfurreducens and A. dehalogenans, respectively, under identical experimental conditions. Further studies are required to determine the range of possible values for 238U/235U fractionation factors under a variety of experimental conditions before broad application of these results is possible. However, the measurable variations in delta(5238)U show promise as indicators of reduction for future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemical cycling. PMID:17153999

Rademacher, Laura K; Lundstrom, Craig C; Johnson, Thomas M; Sanford, Robert A; Zhao, Juanzho; Zhang, Zhaofeng

2006-11-15

178

Monitoring of Zero-Valent Iron Permeable Reactive Barriers: Electrical Properties and Barrier Aging  

NASA Astrophysics Data System (ADS)

An innovative method of groundwater remediation invented in the 1990"s, Permeable Reactive Barriers, use sand-sized grains of scrap iron placed in trenches or injected under pressure to remediate a number of organic and inorganic contaminants. Monitoring the aging of these barriers becomes increasingly important as many of these barriers approach their predicted life spans. In-situ resistivity and induced polarization studies have been conducted at six barriers at four different sites: Monticello, Utah; the Denver Federal Center; Kansas City, Missouri; and East Helena, Montana. As some barriers tend to age dramatically faster than others, for this study we consider low permeability barriers as of greater age, as "old" barriers tend to loose permeability rather than exhaust reactive materials. One complicating factor is that two of the barriers studied appear to have issues related to installation. One site, the former Asarco Smelter Site near East Helena, Montana, has been instrumented with an autonomous monitoring system allowing continuous monitoring of the evolution of a relatively new (less than three years old) barrier. The barrier showed surprisingly rapid evolution over the first year of monitoring with changes in both resistivity and chargeability of tens of percent per month. 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.

Labrecque, D. J.; Adkins, P. L.; Slater, L. D.; Versteeg, R.; Sharpe, R.

2007-12-01

179

Iron-mediated oxidation of arsenic(III) by oxygen and hydrogen peroxide: dispersed versus resin-supported zero-valent iron.  

PubMed

The goal of this study is to assess the differences in As(III) removal kinetics and mechanisms between dispersed zero-valent iron (d-ZVI) and resin-supported zero-valent iron (D201-ZVI) in the presence of dissolved oxygen and hydrogen peroxide. Experimental results show that As(III) could be removed by all the studied systems (d-ZVI/O2, d-ZVI/H2O2, D201-ZVI/O2, D201-ZVI/H2O2). The d-ZVI/H2O2 system was more efficient than D201-ZVI/H2O2 for the oxidation of As(III). Similar trends were observed in O2 system for both solids. The kinetic behaviors as well as the influence of a hydroxyl radical scavenger (2-propanol) on the oxidation of As(III) at different pH suggest that the oxidation of As(III) in the d-ZVI/O2 and d-ZVI/H2O2 systems occurred mainly through Fenton-like reactions. The oxidation of As(III) in the D201-ZVI/O2 and D201-ZVI/H2O2 systems might be expected as follows: As(III) was firstly adsorbed onto the surface of the D201-ZVI, and then oxidation may proceed mainly through a non-Fenton mechanism that directly converts H2O2 into O2 and H2O. In addition, certain iron oxides in the D201-ZVI could also serve as oxidants for As(III) oxidation. The significant differences between the dispersed and supported ZVIs suggest that the supporting matrix interfered in the removal process, which deserves a further investigation. PMID:24910051

Du, Qiong; Zhou, Lixia; Zhang, Shujuan; Pan, Bingcai; Lv, Lu; Zhang, Weiming; Zhang, Quanxing

2014-08-15

180

Nitrate reduction using nanosized zero-valent iron supported by polystyrene resins: role of surface functional groups.  

PubMed

To probe the role of host chemistry in formation and properties of the inside nano-zero valent iron (nZVI), we encapsulated nZVI within porous polystyrene resins functionalized with -CH(2)Cl and -CH(2)N(+)(CH(3))(3) respectively and obtained two hybrid nZVIs denoted Cl-S-ZVI and N-S-ZVI. 14.5% (in Fe mass) of nZVI particles were distributed in N-S within a ring-like region (about 0.10 mm in thickness) of size around ? 5 nm, whereas only 4.0% of nZVI particles were entrapped near the outer surface of Cl-S of size > 20 nm. -CH(2)N(+)(CH(3))(3) is more favorable than -CH(2)Cl to inhibit nZVI dissolution into Fe(2+) ions under acidic pH (3.0-5.5). 97.2% of nitrate was converted into ammonium when introducing 0.12 g N-S-ZVI into 50 mL 50 mg N/L nitrate solution, while that for Cl-S-ZVI was 79.8% under identical Fe/N molar ratio. Under pH = 2 of the effectiveness of nZVI was 88.8% for nitrate reduction, whereas that for Cl-S-ZVI was only 14.6% under similar conditions. Nitrate reduction by N-S-ZVI exhibits relatively slower kinetics than Cl-S-ZVI, which may be related to different nZVI distribution of both composites. The coexisting chloride and sulfate co-ions are favorable for the reactivity enhancement of N-S-ZVI whereas slightly unfavorable for Cl-S-ZVI. The results demonstrated that support chemistry plays a significant role in formation and reactivity of the encapsulated nZVI, and may shed new light on design and fabrication of hybrid nZVIs for environmental remediation. PMID:21316071

Jiang, Zhenmao; Lv, Lu; Zhang, Weiming; Du, Qiong; Pan, Bingcai; Yang, Lei; Zhang, Quanxing

2011-03-01

181

Degradation of soil-sorbed trichloroethylene by stabilized zero valent iron nanoparticles: Effects of sorption, surfactants, and natural organic matter  

SciTech Connect

Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited by desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, {approx}44% of TCE sorbed in the potting soil was degraded in 30 h, compared to {approx}82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1 x cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith Farm soil, the presence of SDS at sub-cmc increased TCE degraded by {approx}10%. However, effect of SDS on degradation of TCE in the potting soil was more complex. The presence of SDS at sub-cmc decreased TCE degradation by 5%, but increased degradation by 5% when SDS dosage was raised to 5 x cmc. The opposing effects were attributed to combined effects of SDS on TCE desorption and degradation, release of soil organic matter and nanoparticle aggregation. The findings strongly suggest that effect of soil sorption on the effectiveness of Fe-Pd nanoparticles must be taken into account in process design, and soil organic content plays an important role in the overall degradation rate and in the effectiveness of surfactant uses.

Zhang, Man [Auburn University, Auburn, Alabama; He, Feng [ORNL; Zhao, Dongye [Auburn University, Auburn, Alabama; Hao, Xiaodi [Beijing University of Civil Engineering and Architecture

2011-01-01

182

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

EPA Science Inventory

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

183

Incorporation of nanoscale zero-valent iron particles inside the channels of SBA-15 silica rods by a “two solvents” reduction technique  

NASA Astrophysics Data System (ADS)

A new reduction method named a “two solvents” reduction technique was developed for incorporation of nanoscale zero-valent iron particles (NZVIs) inside the channels of SBA-15 silica rods under mild conditions. The resulting NZVIs/SBA-15 composites were compared with the ones prepared by the conventional liquid phase reduction method in structure, morphology and reactivity. All the samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM) and all-direct-reading plasma atomic emission spectrometry (ICP-AES). Results showed that abundant ultrasmall zero-valent iron particles were synthesized and well dispersed in the mesopores of SBA-15 silica rods by the new reduction technique, whereas larger iron particles were supported and aggregated on the surface of the silica rods by conventional reduction method. Batch experiment demonstrated that NZVIs incorporated inside the silica channels had higher reactivity for the removal of Cr(VI) in aqueous solution than those supported on the surface.

Sun, Xia; Yu, Hongxia; Zheng, Da; Wang, Xuesong; Li, Jiansheng; Wang, Lianjun

2013-08-01

184

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

185

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

186

Effects on nano zero-valent iron reactivity of interactions between hardness, alkalinity, and natural organic matter in reverse osmosis concentrate.  

PubMed

Nanoscale zero-valent iron (NZVI) is considered to have potential to reduce nitrate in the concentrate generated by high pressure membrane processes aimed at water reuse. However, it is necessary to verify the effect of the matrix components in the concentrates on NZVI reactivity. In this study, the influence of hardness, alkalinity, and organic matter on NZVI reactivity was evaluated by the response surface method (RSM). Hardness (Ca2+) had a positive effect on NZVI reactivity by accelerating iron corrosion. In contrast, alkalinity (bicarbonate; HCO-3) and organic matter (humic acid; HA) had negative effects on NZVI reactivity due to morphological change to carbonate green rust, and to competitive adsorption of HA, respectively. The validity of the statistical prediction model derived from RSM was confirmed by an additional confirmation experiment, and the experimental result was within the 95% confidential interval. Therefore, it can be indicated that the RSM model produced results that were statistically significant. PMID:24552045

Hwang, Yuhoon; Shin, Hang-Sik

2013-11-01

187

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

188

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...

189

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

Calabrò, P S; Moraci, N; Suraci, P

2012-03-15

190

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

PubMed

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

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

2015-05-01

191

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

EPA Science Inventory

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

192

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

EPA Science Inventory

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

193

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

194

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

195

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

NASA Astrophysics Data System (ADS)

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 Fe 0 columns using (a) Na 2SO 4, and (b) NaHCO 3 plus CaCl 2 mixture, solutions. At the influent interface where the reactions were most severe, a contrasting time-lapse electrical response was observed between the two columns. Solid phase analysis confirmed the formation of corrosion halos and increased mineralogical complexity in the corroded sections of the columns compared to the minimal/non-corroded sections. We attribute the contrasting time-lapse signatures to the differences in the electrical properties of the mineral phases formed within the two columns. While newly precipitated/transformed polarizable and semi-conductive iron oxides (mostly magnetite and green rust) increase the polarization and conductivity of the sulfate column, the decrease of both parameters in the bicarbonate column is attributed to the precipitation of non-polarizable and non-conductive calcite. Our results show that precipitate mineralogy is an important factor influencing the electrical properties of the corroded iron cores and must be considered if electrical geophysical methods are to be developed to monitor PRB barrier corrosion processes in situ.

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

2008-01-01

196

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

PubMed

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

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

2008-01-28

197

Effects of humic acid on arsenic(V) removal by zero-valent iron from groundwater with special references to corrosion products analyses.  

PubMed

The effects of humic acid (HA) on As(V) removal by zero-valent iron (Fe(0)) from groundwater, associated with corrosion products analyses, were investigated using batch experiments. It was found that arsenic was rapidly removed from groundwater possibly due to its adsorption and co-precipitation with the corrosion products of Fe(0). The removal rate of arsenic by Fe(0) was inhibited in the presence of HA probably because of the formation of soluble Fe-humate in groundwater which hindered the production of iron precipitates. A longer reaction time was then required for arsenic removal. Such an influence of HA on arsenic removal increased with increasing HA concentration from 5 to 25mgL(-1). The binding capacity of HA for dissolved Fe was estimated to be about 0.75mg Femg(-1) HA. When the complexation of HA with dissolved Fe was saturated, further corrosion of Fe(0) would produce precipitates, which significantly accelerated the removal of arsenic from groundwater via adsorption and co-precipitation with the corrosion products. Iron (hydr)oxides such as maghemite, lepidocrocite, and magnetite were characterized by XRD analyses as the corrosion products, while As(V) was found on the surface of these corrosion products as detected by fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. PMID:19157491

Rao, Pinhua; Mak, Mark S H; Liu, Tongzhou; Lai, Keith C K; Lo, Irene M C

2009-04-01

198

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

2013-01-01

199

Reductive removal of selenate by zero-valent iron: The roles of aqueous Fe(2+) and corrosion products, and selenate removal mechanisms.  

PubMed

Batch tests were conducted to investigate the roles of dissolved Fe(2+) and corrosion products, and the involved mechanisms in selenate (Se(VI)) removal by zero-valent iron (ZVI). The results showed that insignificant Se(VI) removal (4-7.5%) was observed in the presence of ZVI or Fe(2+) alone. However, external supply of dissolved ferrous ion dramatically enhanced Se(VI) removal in the presence of ZVI. Selenate removal efficiency increased with increasing Fe(2+) concentration. Selenate removal sustained only if Fe(2+) was supplied continuously. Both sequential extraction experiments and XPS analysis showed that selenate was reduced step by step, with elemental selenium and adsorbed selenite as the dominant reductive products. Selenite and elemental selenium could be further reduced to selenide, with continuous Fe(2+) supply and sufficient reaction time. In the ZVI-Se(VI)-Fe(2+) system, ZVI was the major electron donor for selenate reduction. Fe(2+) functioned as electron donor as well and was consumed with a Fe(2+):Se stoichiometry of ?1:1. It also facilitated the transformation of the passive layer of iron coatings to a medium (e.g., magnetite) favoring electron transfer and thus enhanced selenate reduction. Iron corrosion products were media for electron transfer and reactive interfaces for selenium adsorption and reduction. These findings provided a new approach to overcome ZVI surface passivation for long-term application. PMID:25269108

Tang, Cilai; Huang, Yong H; Zeng, Hui; Zhang, Zengqiang

2014-12-15

200

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

PubMed

The use of nanoscaled zero-valent iron particles (nZVI) to remediate contaminated soil and groundwater has received increasing amounts of attention within the last decade, primarily due to its potential for broader application, higher reactivity, and cost-effectiveness compared to conventional zero-valent iron applications and other in situ methods. However, the potential environmental risks of nZVI in in situ field scale applications are largely unknown at the present and traditional environmental risk assessment approaches are not yet able to be completed. Therefore, it may not yet be fully clear how to consider the environmental benefits and risks of nZVI for in situ applications. This analysis therefore addresses the challenges of comprehensively considering and weighing the expected environmental benefits and potential risks of this emerging environmentally-beneficial nanotechnology, particularly relevant for environmental engineers, scientists, and decision makers. We find that most of the benefits of using nZVI are based on near-term considerations, and large data gaps currently exist within almost all aspects of environmental exposure and effect assessments. We also find that while a wide range of decision support tools and frameworks alternative to risk assessment are currently available, a thorough evaluation of these should be undertaken in the near future to assess their full relevancy for nZVI at specific sites. Due to the absence of data in environmental risk evaluations, we apply a 'best' and 'worst' case scenario evaluation as a first step to qualitatively evaluate the current state-of-knowledge regarding the potential environmental risks of nZVI. The result of this preliminary qualitative evaluation indicates that at present, there are no significant grounds on which to form the basis that nZVI currently poses a significant, apparent risk to the environment, although the majority of the most serious criteria (i.e. potential for persistency, bioaccumulation, toxicity) are generally unknown. We recommend that in cases where nZVI may be chosen as the 'best' treatment option, short and long-term environmental monitoring is actively employed at these sites. We furthermore recommend the continued development of responsible nZVI innovation and better facilitated information exchange between nZVI developers, nano-risk researchers, remediation industry, and decision makers. PMID:20813426

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

2010-11-25

201

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

NASA Astrophysics Data System (ADS)

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

Kesavan, Sathees Kumar

202

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

PubMed Central

Abstract 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

2013-01-01

203

Molecular Stress Responses to Nano-Sized Zero-Valent Iron (nZVI) Particles in the Soil Bacterium Pseudomonas stutzeri  

PubMed Central

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

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

2014-01-01

204

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

PubMed

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

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

2014-10-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

206

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

PubMed

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

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

2015-03-01

207

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

208

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

PubMed

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

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

2014-02-15

209

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

NASA Astrophysics Data System (ADS)

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

Ruiz, Nancy Elaine

210

Low frequency electrical properties of zero valent iron: Implications for performance monitoring of permeable reactive barriers (PRBs)  

Microsoft Academic Search

The permeable reactive barrier is an in-situ remediation technology for groundwater contaminants. Long term performance monitoring of PRB is critical to the estimation of barrier efficiency. Iron corrosion and mineral precipitation are recognized as the primary causes of barrier performance reduction and can serve as a proper indicator of barrier efficiency. Electrical signature is sensitive to iron corrosion processes. This

Yuxin Wu

2007-01-01

211

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

PubMed

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

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

2014-09-01

212

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

213

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

PubMed

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

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

2001-01-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

215

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

USGS Publications Warehouse

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

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

2001-01-01

216

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

2013-06-01

217

Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate.  

PubMed

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process. PMID:24535668

Wijesekara, S S R M D H R; Basnayake, B F A; Vithanage, Meththika

2014-06-01

218

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

219

Ten year performance evaluation of a field-scale zero-valent iron permeable reactive barrier installed to remediate trichloroethene contaminated groundwater.  

PubMed

The Monkstown zero-valent iron permeable reactive barrier (ZVI PRB), Europe's oldest commercially-installed ZVI PRB, had been treating trichloroethene (TCE) contaminated groundwater for about 10 years on the Nortel Network site in Northern Ireland when cores from the reactive zone were collected in December, 2006. Groundwater data from 2001-2006 indicated that TCE is still being remediated to below detection limits as the contaminated groundwater flows through the PRB. Ca and Fe carbonates, crystalline and amorphous Fe sulfides, and Fe (hydr)oxides have precipitated in the granular ZVI material in the PRB. The greatest variety of minerals is associated with a approximately 1-2 cm thick, slightly cemented crust on top (up-gradient influent entrance) of the ZVI section of the PRB and also with the discontinuous cemented ZVI material ( approximately 23 cm thick) directly below it. The greatest presence of microbial communities also occurred in the up-gradient influent portion of the PRB compared to its down-gradient effluent section, with the latter possibly due to less favorable conditions (i.e., high pH, low oxygen) for microbial growth. The ZVI filings in the down-gradient effluent section of the PRB have a projected life span of >10 years compared with ZVI filings from the continuous to discontinuous cemented up-gradient ZVI section (upper approximately 25 cm) of the PRB, which may have a life span of only approximately 2-5 more years. Supporting Information from applied, multi-tracer testing indicated that restricted groundwater flow is occurring in the upper approximately 25 cm of the ZVI section and preferential pathways have also formed in this PRB over its 10 years of operation. PMID:20420442

Phillips, D H; Van Nooten, T; Bastiaens, L; Russell, M I; Dickson, K; Plant, S; Ahad, J M E; Newton, T; Elliot, T; Kalin, R M

2010-05-15

220

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

221

Mg(OH)2 Supported Nanoscale Zero Valent Iron Enhancing the Removal of Pb(II) from Aqueous Solution.  

PubMed

In this article, a novel composite (Mg(OH)2 supported nanoscale zerovalent iron (denoted as nZVI@Mg(OH)2) was prepared and characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy method. The morphology analysis revealed that Mg(OH)2 appeared as self-supported flower-like spheres, and nano Fe(0) particles were uniformly immobilized on the surface of their "flower petals", thus aggregation of Fe(0) particles was minimized. Then the Pb(II) removal performance was tested by batch experiments. The composite presented exceptional removal capacity (1986.6 mg/g) compared with Mg(OH)2 and nanoscale zerovalent iron due to the synergistic effect. Mechanisms were also explored by a comparative study of the phase, morphology, and surface valence state of composite before and after reaction, indicating that at least three paths are involved in the synergistic removal process: (1) Pb(II) adsorption by Mg(OH)2 (companied with ion exchange reaction); (2) Pb(II) reduction to Pb(0) by nanoscale zerovalent iron; and (3) Pb(II) precipitation as Pb(OH)2. The hydroxies provided by Mg(OH)2 can dramatically promote the role of nanoscale zerovalent iron as reducer, thus greatly enhancing the whole Pb(II) sequestration process. The excellent performance shown in our research potentially provides an alternative technique for Pb(II) pollution treatment. PMID:25826707

Liu, Minghui; Wang, Yonghao; Chen, Luntai; Zhang, Yan; Lin, Zhang

2015-04-22

222

Degradation of chlorobenzene by Fenton?like processes using zero?valent iron in the presence of Fe and Cu  

Microsoft Academic Search

Batch and column tests were conducted to compare the efficiencies of three Fenton?like systems in the degradation of chlorobenzene. In the investigated systems, iron powder was the source of Fe ions, and either Fe or Cu were added in order to enhance the degradation process. Optimum pH and concentrations of Fe, Cu and hydrogen peroxide were assessed by treating synthetic

Michele Pagano; Angela Volpe; Antonio Lopez; Giuseppe Mascolo; Ruggiero Ciannarella

2011-01-01

223

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

EPA Science Inventory

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

224

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

EPA Science Inventory

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

225

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

EPA Science Inventory

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

226

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

2009-05-01

227

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

228

Catalytic transformation of persistent contaminants using a new composite material based on nanosized zero-valent iron.  

PubMed

A new composite material based on deposition of nanosized zerovalent iron (nZVI) particles and cyanocobalamine (vitamin B12) on a diatomite matrix is presented, for catalytic transformation of organic contaminants in water. Cyanocobalamine is known to be an effective electron mediator, having strong synergistic effects with nZVI for reductive dehalogenation reactions. This composite material also improves the reducing capacity of nZVI by preventing agglomeration of iron nanoparticles, 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 resulting in faster rates of remediation. The composite material rapidly degrades or transforms completely a large spectrum of water contaminants, including halogenated solvents like TCE, PCE, and cis-DCE, pesticides like alachlor, atrazine and bromacyl, and common ions like nitrate, within minutes to hours. A field experiment where contaminated groundwater containing a mixture of industrial and agricultural persistent pollutants was conducted together with a set of laboratory experiments using individual contaminant solutions to analyze chemical transformations under controlled conditions. PMID:22680618

Dror, Ishai; Jacov, Osnat Merom; Cortis, Andrea; Berkowitz, Brian

2012-07-25

229

Removal of chromium (VI) by acid-washed zero-valent iron under various groundwater geochemistry conditions.  

PubMed

The hexavalent chromium (Cr(VI)) removal capacity of acid-washed zerovalent iron (AW-Fe0) was evaluated under different groundwater geochemistry conditions through column experiments. It was found that each gram of the AW-Fe0 could remove 0.65-1.76 mg of Cr(VI) from synthetic groundwater in the absence of bicarbonate (HCO3-), magnesium and/or calcium ions. Groundwater geochemistry was found to exert various degrees of impact on Cr(VI) removal by the AW-Fe0, in which HCO3- alone gave the mildest impact whereas the copresence of calcium and HCO3- exerted the greatest impact In comparison with the unwashed Fe0, the AW-Fe0 showed a poorer Cr(VI) removal capacity and was also more susceptible to the influence of the dissolved groundwater constituents on Cr(VI) removal,thereby indicating the unsuitability of using AW-Fe0 in permeable reactive barriers for remediation of Cr(VI)-contaminated groundwater. On the AW-Fe0 surface, where the indigenous iron precipitates were almost erased, trivalent chromium including chromium (III) oxides, hydroxides, and oxyhydroxides in irregular strip, chick footmark-liked or boulder-liked forms as well as Cr(III)-Cr(VI) mixed oxides were detected. PMID:18351099

Lai, Keith C K; Lo, Irene M C

2008-02-15

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

231

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

PubMed

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

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

2002-10-15

232

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

233

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

234

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

EPA Science Inventory

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

235

Reductive dechlorination of octachlorodibenzo-p-dioxin by nanosized zero-valent zinc: modeling of rate kinetics and congener profile.  

PubMed

Polychlorinated dibenzo-p-dioxins (PCDDs), a group of recalcitrant toxic compounds, are ubiquitous in nature. Amongst them, octachlorodibenzo-p-dioxin (OCDD) is not only prevalent in soil and sediment due to its high lipophilicity and hydrophobicity, but also detected in ground water and surface water. The present study examined the degradation of OCDD in aqueous solutions using four different zero-valent metal nanoparticles; zero-valent aluminum (nZVAL), zero-valent zinc (nZVZ), zero-valent iron (nZVI) and zero-valent nickel (nZVN). Only nZVZ was found to efficiently degrade OCDD into lower chlorinated congeners [OCDD ? 1,2,3,4,6,7,9-HxCDD (63%)? 1,2,3,6,8,9-HpCDD (21%) ? 1,2,4,7,8-PeCDD (46%) ? 1,2,4,7-TeCDD (19%)] under ambient conditions. Simulations were also performed to predict the OCDD dechlorination pathway using a linear free energy relationship (LFER) model. Additionally, toxic equivalent quantity (TEQ) and homologue patterns were calculated by LFER modeling. The experimentally observed congener profiles were in excellent agreement with the model-predicted results, especially considering the complexity of the OCDD dechlorination pathway (256 theoretically possible reactions). This study proposes nZVZ as a suitable candidate for OCDD dechlorination and constitutes the first report on OCDD degradation using zero-valent metal nanoparticles under ambient conditions. PMID:23500419

Bokare, Varima; Jung, Ju-Lim; Chang, Yoon-Young; Chang, Yoon-Seok

2013-04-15

236

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

PubMed

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

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

2014-06-30

237

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...

238

Effect of various inorganic anions on the degradation of Congo Red, a di azo dye, by the photo-assisted Fenton process using zero-valent metallic iron as a catalyst  

Microsoft Academic Search

The present research focuses on the heterogeneous advanced photo-Fenton processes of the type Fe\\/H2O2\\/UV and Fe\\/ammonium persulfate (APS)\\/UV as a potential technique to degrade Congo Red (di azo dye). Both the oxidants H2O2 and APS showed comparable efficiencies on the iron surface for the mineralization of Congo Red (CR) under UV light. The influence of various reaction parameters like pH

L. Gomathi Devi; S. Girish Kumar; K. Mohan Reddy; C. Munikrishnappa

2009-01-01

239

Mitigation of Irrigation Water Using Zero-Valent Iron Treatment  

Technology Transfer Automated Retrieval System (TEKTRAN)

Significant problems have occurred in the U.S. with regard to the contamination of produce by pathogenic bacteria. Minimally processed produce lacks the processing and preparation hurdles, such as cooking, to aid in reduction or elimination of the occasional and incidental contamination that can le...

240

ZERO-VALENT IRON PRB APPLICATION EXPANDS TO ARSENIC REMOVAL  

EPA Science Inventory

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

241

Degradation of organic and inorganic contaminants by zero valent iron  

E-print Network

/Feo. The only product observed in the reduction of 2,4-DNT was 2,4-diaminotoluene (2,4-DAT). The 2,4-DAT produced accounted for 83-100% and only 42-54% of the initial mass of 2@4.DNT under anaerobic and aerobic conditions respectively. Since no degradation of 2...

Malla, Deepak Babu

1997-01-01

242

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

243

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

244

High-density chemical intercalation of zero-valent copper into Bi2Se3 nanoribbons.  

PubMed

A major goal of intercalation chemistry is to intercalate high densities of guest species without disrupting the host lattice. Many intercalant concentrations, however, are limited by the charge of the guest species. Here we have developed a general solution-based chemical method for intercalating extraordinarily high densities of zero-valent copper metal into layered Bi(2)Se(3) nanoribbons. Up to 60 atom % copper (Cu(7.5)Bi(2)Se(3)) can be intercalated with no disruption to the host lattice using a solution disproportionation redox reaction. PMID:22524598

Koski, Kristie J; Cha, Judy J; Reed, Bryan W; Wessells, Colin D; Kong, Desheng; Cui, Yi

2012-05-01

245

Enhanced decolorization of methyl orange using zero-valent copper nanoparticles under assistance of hydrodynamic cavitation.  

PubMed

The rate of reduction reactions of zero-valent metal nanoparticles is restricted by their agglomeration. Hydrodynamic cavitation was used to overcome the disadvantage in this study. Experiments for decolorization of methyl orange azo dye by zero-valent copper nanoparticles were carried out in aqueous solution with and without hydrodynamic cavitation. The results showed that hydrodynamic cavitation greatly accelerated the decolorization rate of methyl orange. The size of nanoparticles was decreased after hydrodynamic cavitation treatment. The effects of important operating parameters such as discharge pressure, initial solution pH, and copper nanoparticle concentration on the degradation rates were studied. It was observed that there was an optimum discharge pressure to get best decolorization performance. Lower solution pH were favorable for the decolorization. The pseudo-first-order kinetic constant for the degradation of methyl orange increased linearly with the copper dose. UV-vis spectroscopic and Fourier transform infrared (FT-IR) analyses confirmed that many degradation intermediates were formed. The results indicated hydroxyl radicals played a key role in the decolorization process. Therefore, the enhancement of decolorization by hydrodynamic cavitation could due to the deagglomeration of nanoparticles as well as the oxidation by the in situ generated hydroxyl radicals. These findings greatly increase the potential of the Cu(0)/hydrodynamic cavitation technique for use in the field of treatment of wastewater containing hazardous materials. PMID:24948487

Li, Pan; Song, Yuan; Wang, Shuai; Tao, Zheng; Yu, Shuili; Liu, Yanan

2015-01-01

246

Interactions between iron, phenolic compounds, emulsifiers, and pH in omega-3-enriched oil-in-water emulsions.  

PubMed

The behavior of antioxidants in emulsions is influenced by several factors such as pH and emulsifier type. This study aimed to evaluate the interaction between selected food emulsifiers, phenolic compounds, iron, and pH and their effect on the oxidative stability of n-3 polyunsaturated lipids in a 10% oil-in-water emulsion. The emulsifiers tested were Tween 80 and Citrem, and the phenolic compounds were naringenin, rutin, caffeic acid, and coumaric acid. Lipid oxidation was evaluated at all levels, that is, formation of radicals (ESR), hydroperoxides (PV), and secondary volatile oxidation products. When iron was present, the pH was crucial for the formation of lipid oxidation products. At pH 3 some phenolic compounds, especially caffeic acid, reduced Fe(3+) to Fe(2+), and Fe(2+) increased lipid oxidation at this pH compared to pH 6. Among the evaluated phenols, caffeic acid had the most significant effects, as caffeic acid was found to be prooxidative irrespective of pH, emulsifier type, and presence of iron, although the degrees of lipid oxidation were different at the different experimental conditions. The other evaluated phenols were prooxidative at pH 3 in Citrem-stabilized emulsions and had no significant effect at pH 6 in Citrem- or Tween-stabilized emulsions on the basis of the formation of volatiles. The results indicated that phenol-iron complexes/nanoparticles were formed at pH 6. PMID:18271542

Sørensen, Ann-Dorit Moltke; Haahr, Anne-Mette; Becker, Eleonora Miquel; Skibsted, Leif H; Bergenståhl, Björn; Nilsson, Lars; Jacobsen, Charlotte

2008-03-12

247

Zero-valent sulphur is a key intermediate in marine methane oxidation.  

PubMed

Emissions of methane, a potent greenhouse gas, from marine sediments are controlled by anaerobic oxidation of methane coupled primarily to sulphate reduction (AOM). Sulphate-coupled AOM is believed to be mediated by a consortium of methanotrophic archaea (ANME) and sulphate-reducing Deltaproteobacteria but the underlying mechanism has not yet been resolved. Here we show that zero-valent sulphur compounds (S(0)) are formed during AOM through a new pathway for dissimilatory sulphate reduction performed by the methanotrophic archaea. Hence, AOM might not be an obligate syntrophic process but may be carried out by the ANME alone. Furthermore, we show that the produced S(0)--in the form of disulphide--is disproportionated by the Deltaproteobacteria associated with the ANME. Our observations expand the diversity of known microbially mediated sulphur transformations and have significant implications for our understanding of the biogeochemical carbon and sulphur cycles. PMID:23135396

Milucka, Jana; Ferdelman, Timothy G; Polerecky, Lubos; Franzke, Daniela; Wegener, Gunter; Schmid, Markus; Lieberwirth, Ingo; Wagner, Michael; Widdel, Friedrich; Kuypers, Marcel M M

2012-11-22

248

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

249

Oxidative removal of bisphenol A using zero valent aluminum-acid system.  

PubMed

Bisphenol A (BPA), a controversial endocrine disruptor, is ubiquitous in the aquatic environment. In this study, the oxidative degradation of BPA and its mechanism using zero valent aluminum (ZVAl)-acid system under air-equilibrated conditions was investigated. Under pH <3.5 acidic conditions, ZVAl demonstrated an excellent capacity to remove BPA. More than 75% of BPA was eliminated within 12 h in pH 1.5 reaction solutions initially containing 4.0 g/L aluminum and 2.0 mg/L BPA at 25 ± 1 °C. The removal of BPA was further accelerated with increasing aluminum loadings. Higher temperature and lower initial pH also facilitated BPA removal. The addition of Fe(2+) into the ZVAl-acid system significantly accelerated the reaction likely due to the enhancing transformation of H(2)O(2) to HO via Fenton reaction. Furthermore, the primary products or intermediates including monohydroxylated BPA, hydroquinone, 2-(4-hydroxyphenyl)propane and 4-isopropenylphenol, were identified and a possible reaction scheme was proposed. The remarkable capacity of the ZVAl-acid system in removing BPA displays its potential application in the treatment of organic compound-contaminated water. PMID:21185583

Liu, Wanpeng; Zhang, Honghua; Cao, Beipei; Lin, Kunde; Gan, Jay

2011-02-01

250

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

251

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...

252

2.2 Zero-valent Iron Nanoparticles 2.2.1 Background  

E-print Network

nanoparticles for the treatment of organic contaminants in groundwater. There are, however, few examples groundwater for almost 20 years (Senzaki and Kumagai 1988) and has been demonstrated in the field, and the removal of arsenic, lead, uranium, mercury, and hexavalent chromium (Nuxoll et al. 2003, Arnold

253

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

E-print Network

in the model is as follows. C~c =CRc ? B (13) where, B is the cumulative aqueous PCE concentration removed by GRsp4. The concentration of PCE removed by GRsp4 at any time was calculated by solving the following equation. dB (k/P)C pcE (CRc B) dt 1/K+ CUE...

Marchal, Fabienne

2002-01-01

254

Aminoclay-templated nanoscale zero-valent iron (nZVI) synthesis for efficient harvesting of  

E-print Network

, micro- algae were successfully collected by attachment to the magnetic rods or by precipitation as a feedstock.6,7 Microalgae-based biorenement entails several downstream processes including cultivation

Mosegaard, Klaus

255

Assessment of polyphenol coated nano zero valent iron for hexavalent chromium removal from contaminated waters.  

PubMed

Alternative plant extracts were examined as raw materials for the synthesis of nZVI from ferric solutions. Four plants were selected for evaluation, i.e. Camellia sinensis (green tea, GT), Syzygium aromaticum (clove, CL), Mentha spicata (spearmint, SM) and Punica granatum (pomegranate, PG). Based on the results obtained, it was concluded that the reduction of Fe(III) with the herb extracts is not complete. Using the GT extract, approximately 28 mM of the initial 66 mM of Fe (42.4 %) are reduced to the elemental state Fe(0). The highest reduction of Fe(III), about 53 %, was achieved with PG and the lowest, only 15.6 %, with the SM extract. Additional batch experiments have been carried out to evaluate the effectiveness of nZVI, synthesized with GT, CL, SM and PG, for the removal of hexavalent chromium from a 0.96 mM solution. The highest reduction of Cr(VI) (96 %) was obtained using the nZVI suspension produced with PG juice. The other three nZVI suspensions, i.e. CL-nZVI, GT-nZVI, and SM-nZVI, had a comparable effectiveness corresponding to 70 % reduction of chromate. PMID:25512186

Mystrioti, C; Sparis, D; Papasiopi, N; Xenidis, A; Dermatas, D; Chrysochoou, M

2015-03-01

256

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...

257

Characteristics and Mobility of Zero-Valent Nano-Iron in Porous Media  

E-print Network

of Earth Sciences Environmental Hydrogeology Group Supervisor: Dr. Ruud Schotting, schotting@geo.9.1 Transport in a Horizontal Capillary Tube . . . . . . . . . . . . . . . . . . . . . 27 #12;Contents iii 2

Cirpka, Olaf Arie

258

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

Microsoft Academic Search

Permeable reactive barriers (PRBs) have shown great promise as an alternative to pump and treat for the remediation of groundwater containing a wide array of contaminants including organics, metals, and ra- dionuclides. Analyses to date have focused on individual case studies, rather than considering broad per- formance issues. In response to this need, this study analyzed data from field installations

Andrew D. Henderson; Avery H. Demond

2007-01-01

259

Trichloroethene (TCE) Degradation using Granular Activated Carbon and Zero Valent Iron Particles  

E-print Network

methods of TCE removal include Permeable Reactive Barriers (PRB), Bioremediation and Solvent Extraction, and Dionysios D. Dionysiou, Synthesis of Reactive Nano- Fe/Pd Bimetallic System-Impregnated Activated Carbon

Barthelat, Francois

260

Field test on the treatment of source zone chloroethenes using emulsified zerovalent iron  

EPA Science Inventory

This talk summarizes the research activities currently underway at the Solid Waste Management Unit 45 (Site 45), Marine Corps Recruit Depot, Parris Island, South Carolina. A pilot field test was initiated in 2005 at this site to evaluate the effectiveness of nanoscale emulsified...

261

Ultrasound-assisted activation of zero-valent magnesium for nitrate denitrification: Identification of reaction by-products and pathways.  

PubMed

Zero-valent magnesium (Mg(0)) was activated by ultrasound (US) in an aim to promote its potential use in water treatment without pH control. In this context, nitrate reduction was studied at batch conditions using various doses of magnesium powder and ultrasound power. While neither ultrasound nor zero-valent magnesium alone was effective for reducing nitrate in water, their combination removed up to 90% of 50mg/L NO3-N within 60min. The rate of nitrate reduction by US/Mg(0) enhanced with increasing ultrasonic power and magnesium dose. Nitrogen gas (N2) and nitrite (NO2(-)) were detected as the major reduction by-products, while magnesium hydroxide Mg(OH)2 and hydroxide ions (OH(-)) were identified as the main oxidation products. The results from SEM-EDS measurements revealed that the surface oxide level decreased significantly when the samples of Mg(0) particles were exposed to ultrasonic treatment. The surface passivation of magnesium particles was successfully minimized by mechanical forces of ultrasound, which in turn paved the way to sustain the catalyst activity toward nitrate reduction. PMID:25781370

Ileri, Burcu; Ayyildiz, Onder; Apaydin, Omer

2015-07-15

262

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

263

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

PubMed

Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation. PMID:12521177

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

2002-12-15

264

CARBON AND SULFUR ACCUMULATION AND IRON MINERAL TRANSFORMATION IN PERMEABLE REACTIVE BARRIERS CONTAINING ZERO-VALENT IRON  

EPA Science Inventory

Permeable reactive barrier technology is an in-situ approach for remediating groundwater contamination that combines subsurface fluid flow management with passive chemical treatment. Factors such as the buildup of mineral precipitates, buildup of microbial biomass (bio-fouling...

265

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

266

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

PubMed

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

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

2014-01-30

267

Removal of Nitrate and Ammonium ions from Livestock Wastewater by Hybrid Systems Composed of Zero-Valent Iron and Adsorbents  

Microsoft Academic Search

The feasibility of hybrid systems for simultaneous removal of nitrate (NO) and ammonium ions (NH) from livestock wastewater was examined in batch experiments. As a part of efforts to remove nitrate and ammonium simultaneously, Fe and adsorbents including coconut-based granular activated carbon (GAC), sepiolite and filtralite were used. Various parameters such as adsorbent dosages and temperature were studied. Removal of

Min-Kyu Ji; Yong-Tae Ahn; Moonis Ali Khan; Reda A. I. Abou-Shanab; Yunchul Cho; Jae-Young Choi; Yong Je Kim; Hocheol Song; Byong-Hun Jeon

2011-01-01

268

A MD Simulation and Analysis for Aggregation Behaviors of Nanoscale Zero-Valent Iron Particles in Water via MS  

PubMed Central

With the development of nanotechnology, more nanomaterials will enter into water environment system. Studying the existing form of nanomaterials in water environment will help people benefit from the correct use of them and to reduce the harm to human caused by them for some nanomaterials can bring polluting effect. Aggregation is a main behavior for nanoparticle in water environment. NZVI are used widely in many fields resulting in more NZVI in water environment. Molecular dynamics simulations and Materials Studio software are used to investigate the microaggregation behaviors of NZVI particles. Two scenes are involved: (1) particle size of NZVI in each simulation system is the same, but initial distance of two NZVI particles is different; (2) initial distance of two NZVI particles in each simulation system is the same, but particle size of NZVI is different. Atomistic trajectory, NP activity, total energy, and adsorption of H2O are analyzed with MS. The method provides new quantitative insight into the structure, energy, and dynamics of the aggregation behaviors of NZVI particles in water. It is necessary to understand microchange of NPs in water because it can provide theoretical research that is used to reduce polluting effect of NPs on water environment. PMID:25250388

Liu, Dongmei; Tang, Huan; Lu, Jing; Cui, Fuyi

2014-01-01

269

Conversion of Steel Mill's Surface Waste into Zero Valent Iron (ZVI) Nanoparticles for Hydrogen Generation for PEMFCs  

E-print Network

, photocatalysis and high temperature electrocatalysis of water and, sulfur-iodine cycle in a nuclear reactor by CO/CO2 emission. Recently, a novel, solution-based room temperature technique using an aqueous

Azad, Abdul-Majeed

270

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 ...

271

Effects of precipitation on the low-frequency electrical properties of zero valent iron: implications for monitoring PRBs  

NASA Astrophysics Data System (ADS)

The relatively recent development of permeable reactive barrier (PRB) has provided a potentially viable alternative to established pump-and-treat systems for remediation of chlorinated solvent contaminated groundwater. Non-invasive methods for the assessment and monitoring of PRB have been required for evaluating long-term PRB performance and allowing effective management decisions regarding in situ site cleanup. The presence of metal in the subsurface results in the following additional charge transfer mechanisms (a) electronic conduction in the metal (b) polarization of charges at the interface between a metal and the pore-filling electrolyte. Both these mechanisms profoundly modify the measured electrical properties of the subsurface and support the utilization of electrical measurements for investigating PRB. Low frequency (0.1-1000 Hz) electrical properties are sensitive to the surface chemistry of metals in subsurface environment. In this range, electrical properties are controlled by ionic conduction through the electrolyte, surface electronic or ionic conduction, as well as diffusion mechanisms that occur at the mineral surface-pore fluid interface. Oxidation-reduction reactions may transfer electrons between mineral and fluid. The magnitude of polarization is directly related to the amount of metallic mineral surface available for charge transfer. The frequency dependence of the low frequency electrical response is indicative of the nature of electrochemical reactions occurring at the grain-fluid interface. Numerous experimental studies confirm that the frequency at which imaginary conductivity peaks inversely correlates with the grain size of the metallic particles. It is thus possible that the numerous complex surface chemical reactions involved in chlorinated solvent degradation may have distinct frequency dependent electrical signatures. In addition to the polarization term, the conduction term may also contain valuable information on PRB performance.

Choi, Jaeyoung; Ji, Won-Hyun; Yang, Jung-Seok; Um, Jeong-Gi; Woo, Ik; Lee, Ju-Young; Park, Young-Tae

2010-05-01

272

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

2009-08-01

273

Total aerobic destruction of azo contaminants with nanoscale zero-valent copper at neutral pH: promotion effect of in-situ generated carbon center radicals.  

PubMed

In this study, nanoscale zero-valent copper (nZVC) was synthesized with a facile solvothermal method and used for the aerobic removal of azo contaminants at neutral pH for the first time. We found that both Cu(I) and OH generated during the nZVC induced molecular oxygen activation process accounted for the rapid total destruction of azo contaminants in the nZVC/Air system, where nZVC could activate molecular oxygen to produce H2O2, and also release Cu(I) to break the -NN- bond of azo contaminants via the sandmeyer reaction for the generation of carbon center radicals. The in-situ generated carbon center radicals would then react with OH produced by the Cu(I) catalyzed decomposition of H2O2, resulting in the generation of low molecular weight organic acids and their subsequent mineralization. The indispensible role of Cu(I) catalyzed sandmeyer reaction and the promotion effect of in-situ generated carbon center radicals on the rapid total destruction of azo contaminants in the nZVC/Air system were confirmed by gas chromatography-mass spectrometry analysis. This study can deepen our understanding on the degradation of organic pollutant with molecular oxygen activated by zero valent metal, and also provide a new method to remove azo contaminants at neutral pH. PMID:25181614

Dong, Guohui; Ai, Zhihui; Zhang, Lizhi

2014-12-01

274

The Use of Ultrasound to Restore the Dehalogenation Activity of Iron in Permeable Reactive Barriers  

Microsoft Academic Search

In situ permeable reactive barriers (PRBs) containing iron as the reactive agent have gained popularity in the past decade as a near-passive, in situ groundwater remediation technology for halogenated solvents. Although zero-valent iron has been shown to be effective for this purpose, a continuing problem is the loss of system reactivity over time. This loss is due, at least in

Cherie L. Geiger; Christian A. Clausen; Debra R. Reinhart; Nancy Ruiz

275

Emulsifiers in Confectionery  

Microsoft Academic Search

Emulsifiers are used in both chocolate and sugar confectionery products as functional additives that provide significant advantages\\u000a during both processing and storage. Emulsifiers serve several different functions in confectionery products. In products containing\\u000a a dispersed fat phase (caramel, toffee, etc.), emulsifiers help to promote breakdown into small fat globules. Emulsifiers\\u000a also provide lubrication, in part through dispersion of the fat

Mark Weyland; Richard W. Hartel

276

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

EPA Science Inventory

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

277

Travel Distance and Transformation of Injected Emulsified Zerovalent Iron Nanoparticles in the Subsurface During Two and Half Years  

EPA Science Inventory

Nanoscale zerovalent iron (NZVI) such as Toda Kogyo RNIP-10DS has been used for site remediation, yet information is lacking regarding how far injected NZVI can travel, how long it lasts, and how it transforms to other minerals in a groundwater system. Previously we reported effe...

278

I. Hole-transporting dendrimers and their use in organic light-emitting devices (OLEDs) and II. Novel layered catalysts containing bipyridinium and zero-valent metal species  

NASA Astrophysics Data System (ADS)

A series of polyaromatic ether/ester dendrimers containing a hole transporting naphthylphenylbenzyl amine at the periphery and a variety of fluorescent dyes at the core has been studied in an effort to observe energy transfer in these species. The dyes incorporated in these dendrimers include 1,4-dihydroxyanthraquinone (quinizarin), Coumarin 343, and a benzopentathiophene. These dendrimers have been incorporated into both single layer and heterostructure organic light emitting devices (OLEDs). In the case of first generation dendrimer OLEDs, excimer/exciplex formation was predominant. In third generation dendrimers, complete energy transfer from the periphery to the dye at the core was observed both in photoluminescence spectra and electroluminescence in OLEDs. Dendrimers containing different dye cores can be combined to achieve color mixing/tuning. In addition, layered catalysts were prepared via both covalent and electrostatic means to achieve the catalytic production of hydrogen peroxide from hydrogen and oxygen. Covalent catalysts were prepared by first growing layers of zirconium and a bipyridinium containing bisphosphonate onto silica particles. Palladium and/or platinum was ion-exchanged into the structure and reduced to the zero valent metal by hydrogen gas. A second set of catalysts was prepared by electrostatically depositing polycations/polyanions onto carboxylate or amine functionalized polystyrene microspheres. Anionic colloidal particles were adsorbed to the polycationic surface. An octacationic viologen oligomer was used in an attempt to increase the affinity of adsorption of the Pd particles to the surface of the microspheres. Catalytic studies of both types of catalysts are herein reported.

Koene, Shannon Carol

279

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

EPA Science Inventory

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

280

Reduction of TNT and RDX by Core Material from an Iron Permeable Reactive Barrier  

Microsoft Academic Search

We recently completed a pilot-scale permeable reactive barrier (PRB) with zero-valent iron (ZVI) to treat groundwater contaminated with explosives (TNT and RDX) at the Cornhusker Army Ammunition Plant (CAAP) near Grand Island, Nebraska. While the PRB at CAAP continues to be effective at removing explosives from the groundwater, the hydraulic performance is significantly reduced. This may be due to the

James T. Nurmi; Paul G. Tratnyek; Richard L. Johnson; R. Brad Thoms; Reid O'Brien Johnson

281

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

EPA Science Inventory

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

282

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

EPA Science Inventory

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

283

HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX) DEGRADATION IN BIOLOGICALLY-ACTIVE IRON COLUMNS  

E-print Network

, permeable reactive barrier, RDX, zero-valent iron 1. Introduction RDX (hexahydro-1,3,5-trinitro-1: 319/335-5660) Abstract. Flow-through columns were used to evaluate the efficacy of permeable reactive, there has been an explosion of activity directed at the development and implementation of permeable reactive

Alvarez, Pedro J.

284

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

285

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...

286

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

2013-11-01

287

Coupled acidification and ultrasound with iron enhances nitrate reduction  

Microsoft Academic Search

Contaminated soils, especially when pollutant concentrations are high, pose potentially serious threats to surface and groundwater quality, when there are spills, discharges, or leaking storage tanks. For in situ remediation of nitrate in groundwater, the use of zero-valent iron (Fe0) is suggested. The formation of passivating scales on Fe0 over time may limit the long-term reduction potential of Fe0. The

Yih-Jin Tsai; Feng-Chih Chou; Tsung-Chieh Cheng

2009-01-01

288

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

Microsoft Academic Search

Pyrite formation has been investigated at 70°C and pH 6–8 by aging precipitated, disordered mackinawite, Fe9S8, and greigite, Fe3S4, in solutions containing aqueous H2S, HS?, Sx2?, S2O32?, SO32?, colloidal elemental sulfur, and the organic sulfur species thiol, disulfide, and sulfonate. Pyrite formed in all experiments where unoxidized iron monosulfides were aged with species containing zero-valent sulfur, i.e., polysulfides and colloidal

R. T. Wilkin; H. L. Barnes

1996-01-01

289

EZVI Injection Field Test Leads to Pilot-Scale Application  

EPA Science Inventory

Testing and monitoring of emulsified zero-valent ironTM (EZVI) injections was conducted at Cape Canaveral Air Force Station?s Launch Complex 34, FL, in 2002 to 2005 to evaluate the technology?s efficacy in enhancing in situ dehalogenation of dense nonaqueous-phase liquid (DNAPL) ...

290

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

291

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

PubMed

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 in Belfast after almost 4 years of operation. Despite the variety of samples, carbon isotope fractionations of TCE were remarkably similar and seemed to be independent of iron origin, reaction rate, and formation of precipitates on the iron surfaces. The average enrichment factor for all experiments was -10.1 per thousand (+/- 0.4 per thousand). These results indicate that the enrichment factor provides a powerful tool to monitor the reaction progress, and thus the performance, of an iron-reactive barrier over time. The strong fractionation observed may also serve as a tool to distinguish between insufficient residence time in the wall and a possible bypassing of the wall by the plume, which should result in an unchanged isotopic signature of the TCE. Although further work is necessary to apply this stable isotope method in the field, it has potential to serve as a unique monitoring tool for PRBs based on zero-valent iron. PMID:14516939

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

2003-10-01

292

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

293

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

PubMed

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

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

2015-02-11

294

Review of iron-free Fenton-like systems for activating H2O2 in advanced oxidation processes.  

PubMed

Iron-catalyzed hydrogen peroxide decomposition for in situ generation of hydroxyl radicals (HO(•)) has been extensively developed as advanced oxidation processes (AOPs) for environmental applications. A variety of catalytic iron species constituting metal salts (in Fe(2+) or Fe(3+) form), metal oxides (e.g., Fe2O3, Fe3O4), and zero-valent metal (Fe(0)) have been exploited for chemical (classical Fenton), photochemical (photo-Fenton) and electrochemical (electro-Fenton) degradation pathways. However, the requirement of strict acidic conditions to prevent iron precipitation still remains the bottleneck for iron-based AOPs. In this article, we present a thorough review of alternative non-iron Fenton catalysts and their reactivity towards hydrogen peroxide activation. Elements with multiple redox states (like chromium, cerium, copper, cobalt, manganese and ruthenium) all directly decompose H2O2 into HO(•) through conventional Fenton-like pathways. The in situ formation of H2O2 and decomposition into HO(•) can be also achieved using electron transfer mechanism in zero-valent aluminum/O2 system. Although these Fenton systems (except aluminum) work efficiently even at neutral pH, the H2O2 activation mechanism is very specific to the nature of the catalyst and critically depends on its composition. This review describes in detail the complex mechanisms and emphasizes on practical limitations influencing their environmental applications. PMID:24857896

Bokare, Alok D; Choi, Wonyong

2014-06-30

295

Enrichment and encapsulation of uranium with iron nanoparticle.  

PubMed

The ability to recover uranium from water is significant because of its potential applications on nuclear fuel capture and mitigation of nuclear wastes. In this work, a unique nanostructure is presented by which trace level (2.32-882.68 ?g/L) uranium can be quickly separated from water and encapsulated at the center of zero-valent iron nanoparticles. Over 90% of the uranium is recovered with 1 g/L nanoparticles in less than 2 min. Near atomic-resolution elemental mapping on the U(VI) intraparticle reactions in a single iron nanoparticle is obtained with aberration corrected scanning transmission electron microscopy, which provides direct evidence on U(VI) diffusion, reduction to U(IV), and deposition in the core area. PMID:25689272

Ling, Lan; Zhang, Wei-Xian

2015-03-01

296

Iron  

MedlinePLUS

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

297

Effect of Cement on Emulsified Asphalt Mixtures  

NASA Astrophysics Data System (ADS)

Emulsified asphalt mixtures have environmental, economical, and logistical advantages over hot mixtures. However, they have attracted little attention as structural layers due to their inadequate performance and susceptibility to early life damage by rainfall. The objective of this article is to provide an improved insight into how the mechanical properties of emulsion mixtures may be improved and to determine the influence of cement on emulsified asphalt mixtures. Laboratory tests on strength, temperature susceptibility, water damage, creep and permanent deformation were implemented to evaluate the mechanical properties of emulsified asphalt mixtures. The test results showed that mechanical properties of emulsified asphalt mixtures have significantly improved with Portland cement addition. This experimental study suggested that cement modified asphalt emulsion mixtures might be an alternate way of a structural layer material in pavement.

Oruc, Seref; Celik, Fazil; Akpinar, M. Vefa

2007-10-01

298

Study of formulation and stability of emulsions with polymeric emulsifiers  

Microsoft Academic Search

Polymeric emulsifiers have appeared recently and have got emulsifying and thickness properties. These emulsifiers provide exceptional stability to oil-in-water-emulsions. This study shows formulations of new emulsifiers. The polymeric emulsifiers used were acrylate C10–C30 alkyl–acrylate cross polymer (Tr1–Tr2). They provide exceptional stability to oil-in-water emulsions at very low usage levels (0.1,0.3%), they can be used with any oil phase, easily prepared

Marie-France Bobin; Valérie Michel; Marie-Claude Martini

1999-01-01

299

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

300

Application of a montmorillonite clay modified with iron in photo-Fenton process. Comparison with goethite and nZVI.  

PubMed

Iron pillared clay (Fe-PILC) was prepared from a montmorillonite and was characterized by scanning electron microscopy and X-ray fluorescence. Fe-PILC catalytic activity was evaluated in photo-Fenton processes applied to the degradation of 2-clorophenol. Different catalyst loads were assayed. The Fe-PILC allowed almost complete degradation of the contaminant. An increase in the contaminant degradation rate was observed, following leaching of iron during catalytic assays, which suggest the existence of a homogeneous photo-Fenton mechanism. The catalytic performance of the Fe-PILC was compared with that for goethite and zero valent iron nanoparticles. Differences were found regarding the achieved degradation levels, the efficiency in oxidant consumption, and the extension of iron leaching. PMID:24604272

De León, María A; Sergio, Marta; Bussi, Juan; Ortiz de la Plata, Guadalupe B; Cassano, Alberto E; Alfano, Orlando M

2015-01-01

301

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...

302

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

303

Oxidation of water emulsified olive oils  

Microsoft Academic Search

The susceptibility to oxidation of water emulsified olive oils was monitored by preparing emulsions with different amounts of water.The oxidative and kinetic stability of the emulsions were studied by performing simultaneous measurements of sedimentation and oxidation. The results reveal that the greater the region of emulsion stability, the longer the resistance of oil to oxidation. The micrographs of Video-Enhanced Microscopy

L. Ambrosone; M. Mosca; A. Ceglie

2006-01-01

304

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

PubMed Central

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

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

2011-01-01

305

The removal of nitrate by nanoscale iron particles produced using the sodium borohydride method.  

PubMed

This study was conducted to investigate removal of nitrate by nanoscale zero-valent iron (ZVI) particles in aqueous solution. ZVI particles was produced from wasted acid that is by-products of a pickling line at a steel work. The reaction activity of ZVI particles was evaluated through decomposition experiments of NO3-N aqueous solution. Addition of a larger amount of ZVI particles resulted in a higher decomposition rate. ZVI particles showed higher decomposition efficiencies than commercially purchased ZVI particles at all pH values. Both ZVIs showed a higher decomposition rate at a lower pH. Virtually no decomposition reaction was observed at pH of 4 or higher for purchased ZVI. The ZVI particles produced directly from wasted acid by the sodium borohydride method were not easy to handle because they were very small (10-200 nm) and were oxidized easily in the air. PMID:21456267

Cho, Hyoung-Chan; Park, Sung Hoon; Ahn, Ho-Geun; Chung, Minchul; Kim, Byungwhan; Kim, Sun-Jae; Seo, Seong-Gyu; Jung, Sang-Chul

2011-02-01

306

Domain Shape Transitions in Emulsified Polyolefin Blends  

NASA Astrophysics Data System (ADS)

The shape of dispersed domains in emulsified polyolefin blends was studied by transmission electron microscopy. Model polyolefins - polyethylene (PE), head-to-head polypropylene (PP), and PE-PP diblock copolymers - were synthesized via anionic polymerization. We find that increasing block copolymer concentration leads to an abrupt transition from spherical domains to cell-like domains with faceted walls. The cell-like domains were aggregated and formed large macrophases. The characteristic size of the domain-rich phase was larger than the size of the PE droplets formed in the absence of the block copolymer. This indicates strong adhesive interactions between the domains.

Lee, Joon; Jeon, Hyun; Balsara, Nitash

1997-03-01

307

Valiant 'Zero-Valent' Effort Restores Contaminated Grounds  

NASA Technical Reports Server (NTRS)

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

2005-01-01

308

Sensory characteristics and iron dialyzability of gluten-free bread fortified with iron  

Microsoft Academic Search

The objectives of the present study were (a) to produce gluten-free bread, fortified with iron (GFB-Fe), using selected iron compounds (ferric pyrophosphate, ferric pyrophosphate with emulsifiers, NaFeEDTA, electrolytic iron, ferrous gluconate, ferrous lactate and ferrous sulphate) (b) to test sensory characteristics of the GFB-Fe (feel-mouth texture, crumb colour, aroma and taste) (c) to compare iron dialyzability of various iron compounds

Alexandra Kiskini; Konstantina Argiri; Michael Kalogeropoulos; Michael Komaitis; Athanasios Kostaropoulos; Ioanna Mandala; Maria Kapsokefalou

2007-01-01

309

MICROENCAPSULATION OF EMULSIFIED HYDROPHOBIC FLAVORS BY SPRAY DRYING  

Microsoft Academic Search

The retention of emulsified flavor during spray drying was investigated under various compositions of feed liquid. Drying of the emulsion solution was carried out in a spray dryer, equipped with a centrifugal atomizer. The retention of d-limonene during spray dying was nearly hundred percent independent of the composition of the feed liquid, whereas the retention of ethyl butyrate emulsified by

Xiang-Dong Liu; Takuroh Atarashi; Takeshi Furuta; Hidefumi Yoshii; Shizuo Aishima; Masaaki Ohkawara; Pekka Linko

2001-01-01

310

Reductive denitrification of nitrate by scrap iron filings*  

PubMed Central

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

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

2005-01-01

311

Ferritin as a bionano-particulate emulsifier.  

PubMed

Stable 'Pickering-type' emulsions were prepared using ferritin, a spherical protein, as a bionano-particulate emulsifier and n-dodecane, toluene, castor oil, olive oil or vegetable oil as an oil phase, in the absence of any surfactant molecules. All the emulsions prepared were of the oil-in-water type and an increase of ferritin concentration decreased the volume average droplet diameters. Transmission electron microscopy studies of the ferritin residues remaining after evaporation of oil and water from the emulsion revealed a broken capsule morphology, which is strong evidence for the attachment of ferritin at the oil-water interface thereby stabilizing the emulsion. The emulsion droplets could be elongated and made to pass through a glass capillary. PMID:19604513

Fujii, Syuji; Aichi, Atsushi; Muraoka, Masahiro; Kishimoto, Naoko; Iwahori, Kenji; Nakamura, Yoshinobu; Yamashita, Ichiro

2009-10-01

312

Influence of emulsifier concentration on nanoemulsion gelation.  

PubMed

Nanoemulsion gels are a new class of soft materials that manifest stronger elasticity even at lower dispersed phase volume fraction. In this work, gelation in 40 wt % canola oil-in-water nanoemulsions was investigated as a function of emulsifier type (anionic sodium dodecyl sulfate (SDS) or nonionic Tween 20) and concentration. It was observed that the liquid nanoemulsions transformed into viscoelastic gels at a specific concentration range of SDS, whereas no gelation was observed for Tween 20. The apparent viscosity, yield stress, and storage modulus of the nanogels increased with SDS concentration until 15 times critical micelle concentration (CMC), thereafter decreased steadily as the gelation weakened beginning 20 CMC. Three regimes of colloidal interactions in the presence of emulsifier were proposed. (1) Repulsive gelation: at low SDS concentration (0.5-2 times CMC) the repulsive charge cloud around the nanodroplets acted as interfacial shell layer that significantly increased the effective volume fraction of the dispersed phase (?(eff)). When ?(eff) became comparable to the volume fraction required for maximal random jamming, nanoemulsions formed elastic gels. (2) Attractive gelation: as the SDS concentration increased to 5-15 times CMC, ?(eff) dropped due to charge screening by more counterions from SDS, but depletion attractions generated by micelles in the continuous phase led to extensive droplet aggregation which immobilized the continuous phase leading to stronger gel formation. (3) Decline in gelation due to oscillatory structural forces (OSF): at very high SDS concentration (20-30 time CMC), structural forces were manifested due to the layered-structuring of excess micelles in the interdroplet regions resulting in loss of droplet aggregation. Tween 20 nanoemulsions, on the other hand, did not show repulsive gelation due to lack of charge cloud, while weak depletion attraction and early commencement of OSF regime leading to liquid-like behavior at all concentrations. The nanogels possess great potential for use in low-fat foods, pharmaceuticals and cosmetic products. PMID:25137632

Erramreddy, Vivek Vardhan; Ghosh, Supratim

2014-09-23

313

Formulation design for target delivery of iron nanoparticles to TCE zones  

NASA Astrophysics Data System (ADS)

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

Wang, Ziheng; Acosta, Edgar

2013-12-01

314

Removal of hexavalent chromium from aqueous solution by iron nanoparticles*  

PubMed Central

Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe0) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contaminated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe0 type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe0 nanoparticles>Fe0 nanoparticles>Fe0 powder>Fe0 filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)3 should be the final product of Cr(VI). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater. PMID:16187417

Niu, Shao-feng; Liu, Yong; Xu, Xin-hua; Lou, Zhang-hua

2005-01-01

315

Effective distribution of emulsified edible oil for enhanced anaerobic bioremediation  

Microsoft Academic Search

Recent laboratory and field studies have shown that injection of emulsified edible oils can provide an effective, low-cost alternative for stimulating anaerobic biodegradation processes. A pilot-scale permeable reactive bio-barrier (PRBB) was installed at a perchlorate and chlorinated solvent impacted site by injecting 380 L of commercially available emulsion (EOS®) containing emulsified soybean oil, food-grade surfactants, lactate, and yeast extract through ten

Robert C. Borden

2007-01-01

316

Remediation of Ni(2+)-contaminated water using iron powder and steel manufacturing byproducts.  

PubMed

Steel manufacturing byproducts and commercial iron powders were tested in the treatment of Ni(2+)-contaminated water. Ni2+ is a priority pollutant of some soils and groundwater. The use of zero-valent iron, which can reduce Ni2+ to its neural form appears to be an alternative approach for the remediation of Ni(2+)-contaminated sites. Our experimental data show that the removal efficiencies of Ni2+ were 95.15% and 94.68% at a metal to solution ratio of 20 g/L for commercial iron powders and the steel manufacturing byproducts in 60 min at room temperature, respectively. The removal efficiency reached 98.20% when the metal to solution ratio was 40 g/L for commercial iron powders. Furthermore, we found that the removal efficiency was also largely affected by other factors such as the pHs of the treated water, the length of time for the metal to be in contact with the Ni(2+)-contaminated water, initial concentrations of metal solutions, particle sizes and the amount of iron powders. Surprisingly, the reaction temperature appeared to have little effect on the removal efficiency. Our study opens the way to further optimize the reaction conditions of in situ remediation of Ni2+ or other heavy metals on contaminated sites. PMID:17294641

Jin, Jian; Zhao, Wei-Rong; Xu, Xin-Hua; Hao, Zhi-Wei; Liu, Yong; He, Ping; Zhou, Mi

2006-01-01

317

Effect of droplet size on the behavior and characteristics of emulsified acid  

E-print Network

Emulsified acids have been extensively used in the oil industry since 1933. Most of the available research and publications discussed mainly the application of emulsified acid in the field. A fair number of the published work also discussed in depth...

Almutairi, Saleh Haif

2008-10-10

318

Solutions Remediate Contaminated Groundwater  

NASA Technical Reports Server (NTRS)

During the Apollo Program, NASA workers used chlorinated solvents to clean rocket engine components at launch sites. These solvents, known as dense non-aqueous phase liquids, had contaminated launch facilities to the point of near-irreparability. Dr. Jacqueline Quinn and Dr. Kathleen Brooks Loftin of Kennedy Space Center partnered with researchers from the University of Central Florida's chemistry and engineering programs to develop technology capable of remediating the area without great cost or further environmental damage. They called the new invention Emulsified Zero-Valent Iron (EZVI). The groundwater remediation compound is cleaning up polluted areas all around the world and is, to date, NASA's most licensed technology.

2010-01-01

319

Oxidative stability of polyunsaturated fatty acids and soybean oil in an aqueous solution with emulsifiers  

Microsoft Academic Search

The oxidative stability of polyunsaturated fatty acids (PUFA) and soybean oil homogenized with emulsifiers was investigated.\\u000a Model emulsions were prepared from PUFA, including linoleic acid (LA), arachidonic acid (AA), eicosapentaenoic acid (EPA),\\u000a and docosahexaenoic acid (DHA), and from soybean oil emulsified with different emulsifiers: three Tween emulsifiers (Tween\\u000a 20, Tween 60, Tween 80) and two sucrose esters (S-1170 and S-1570)

Pin-Der Duh; Wen Jye Yen; Gow-Chin Yen

1999-01-01

320

Wormhole initiation and propagation of emulsified acid in carbonate cores using computerized tomography  

Microsoft Academic Search

Emulsified acids are widely used for stimulating carbonate reservoirs. This study examines alternate ways to evaluate the performance of emulsified acids by using a non-destructive visual-based technique. Using advanced image processing software and techniques, it was possible to examine the dissolution patterns created by emulsified acids at different operating conditions. Computerized Tomography (CT) was successful in monitoring wormhole initiation and

Shameem Siddiqui; Hisham A. Nasr-El-Din; Aon A. Khamees

2006-01-01

321

Reduction of nitrobenzene in groundwater by iron nanoparticles immobilized in PEG/nylon membrane.  

PubMed

The highly reactive iron nanoparticles (NPs) immobilized in nylon membrane were synthesized and characterized, and the reduction of nitrobenzene (NB) in groundwater by the NPs was investigated. Environmental scanning electron microscopy (ESEM) images showed that the NPs distributed homogeneously on the membrane surface without agglomeration. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the NPs immobilized in membrane were mainly composed of Fe-oxides rather than zero-valent iron. Thermogravimetric (TG) analysis suggested that the weight percentage of the immobilized NPs and the oxygen introduced to the reacted sample after 80min reaction were about 18.5% and 13%, respectively. Moreover, Fourier transform infrared (FTIR) analysis further demonstrated the changes on the membrane surface after thermal grafting, NPs immobilizing and reacting for 80min. Using the reactive NPs immobilized in nylon membrane, NB in groundwater was rapidly and quantitatively decreased by 68.9% just in the first 20min, the Fe(2+) associated with the iron NPs immobilized in PEG/nylon66 membrane was mainly responsible for this reduction. The reaction appeared to follow pseudo-first-order kinetics and the rate constants increased upon decreasing the pH value. The samples we prepared exhibited good corrosion resistance for humic acid (HA) but had a short-term performance for NB degradation. More so, the groundwater chemistry had a negative influence on the reactivity of membrane immobilized NPs. PMID:21081255

Tong, Man; Yuan, Songhu; Long, Huayun; Zheng, Mingming; Wang, Linling; Chen, Jing

2011-03-25

322

Reduction of nitrobenzene in groundwater by iron nanoparticles immobilized in PEG/nylon membrane  

NASA Astrophysics Data System (ADS)

The highly reactive iron nanoparticles (NPs) immobilized in nylon membrane were synthesized and characterized, and the reduction of nitrobenzene (NB) in groundwater by the NPs was investigated. Environmental scanning electron microscopy (ESEM) images showed that the NPs distributed homogeneously on the membrane surface without agglomeration. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the NPs immobilized in membrane were mainly composed of Fe-oxides rather than zero-valent iron. Thermogravimetric (TG) analysis suggested that the weight percentage of the immobilized NPs and the oxygen introduced to the reacted sample after 80 min reaction were about 18.5% and 13%, respectively. Moreover, Fourier transform infrared (FTIR) analysis further demonstrated the changes on the membrane surface after thermal grafting, NPs immobilizing and reacting for 80 min. Using the reactive NPs immobilized in nylon membrane, NB in groundwater was rapidly and quantitatively decreased by 68.9% just in the first 20 min, the Fe 2+ associated with the iron NPs immobilized in PEG/nylon66 membrane was mainly responsible for this reduction. The reaction appeared to follow pseudo-first-order kinetics and the rate constants increased upon decreasing the pH value. The samples we prepared exhibited good corrosion resistance for humic acid (HA) but had a short-term performance for NB degradation. More so, the groundwater chemistry had a negative influence on the reactivity of membrane immobilized NPs.

Tong, Man; Yuan, Songhu; Long, Huayun; Zheng, Mingming; Wang, Linling; Chen, Jing

2011-03-01

323

Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis  

PubMed Central

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

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

2012-01-01

324

Hexavalent chromium removal from near natural water by copper-iron bimetallic particles.  

PubMed

The reduction of hexavalent chromium (Cr(VI)) by zero-valent iron (ZVI) is self-inhibiting in near natural groundwater because insulating Fe(III)-Cr(III) (oxy)hydroxide film forms on the ZVI surface during the reaction. This study tries to overcome this deficiency by coating the surface of ZVI with copper to form copper-iron bimetallic particles. The Cr(VI) removal rate by ZVI rose significantly after the copper coating was applied. The copper loading needed for enhancing Cr(VI) removal was much higher than that needed for enhancing removal of chlorinated organic compounds or other oxidative contaminants, because of the higher oxidation potential of Cr(VI). The results of X-ray photoelectron spectroscopy (XPS) indicate that coating copper onto the surface of ZVI can not only increase the deepness of the oxidation film but also increase the oxidation state of iron in the film. This phenomenon means higher Cr(VI) removal capacity per unit weight of ZVI. PMID:20350740

Hu, Ching-Yao; Lo, Shang-Lien; Liou, Ya-Hsuan; Hsu, Ya-Wen; Shih, Kaimin; Lin, Chin-Jung

2010-05-01

325

Design of Hard Water Stable Emulsifier Systems for Petroleum-  

E-print Network

Design of Hard Water Stable Emulsifier Systems for Petroleum- and Bio-based Semi for petroleum and bio-based MWFs that improve fluid lifetime by providing emulsion stability under hard water. The newly developed petroleum and bio-based formulations with improved hard water stability are competitive

Clarens, Andres

326

Evaluation of emulsified asphalt for use in Saudi Arabia  

SciTech Connect

Saudi Arabia currently contains 31,000 km (18,600 mi) of paved roads and 42,000 km (25,200 mi) of agricultural roads, with the prospect of more roads to be constructed. The low population (6 million) compared to the large area of the country (2,253,300 kmS, 900,000 miS) coupled with the high cost of crushed aggregate makes maintenance and road building costs very high. Local emulsified-asphalt economics, plants, and uses were investigated in this study. Emulsified asphalt proved to be attractive when used for local road maintenance and road bases and low-volume road construction, especially when used with dune sand and marl. Emulsified asphalts were evaluated for use with dune sand and marl and at two portland cement contents. Three types of emulsified asphalts were used which included locally produced, laboratory prepared, and Chevron USA emulsions. Emulsion treated mixes were tested for tensile strength, Poisson's ratio, resilient modulus, fatigue life, and rutting characteristics. Both diametral and beam fatigue tests were used and tests were conducted at 10, 25, 40, and 55C (50, 77, 104, and 131F). The open-graded mix was tested for fatigue characteristics using beam flexure with a confining membrane.

Al-Abdulwahhab, H.I.

1985-01-01

327

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

328

Research of inverted emulsions properties on the base of new emulsifiers  

NASA Astrophysics Data System (ADS)

Emulsifiers on the base of tallol and ethanolamines derived acids have been researched in the paper. Electrical stability of emulsions drilling muds has been investigated. It is proved that synthesized emulsifiers according to emulsion stability can be divided into two groups. The first group is emulsifiers with high initial electrical stability but low emulsion stability under long-term storing, and the second group is emulsifiers with low electrical stability but with high emulsion stability. Emulsions flow characteristics have been researched. It is established that emulsifier on the base of ethanolamine provides better emulsion characteristics for drilling muds emulsions.

Minaev, K.; Epikhin, A.; Novoseltsev, D.; Andropov, M.; Yanovsky, V.; Ulyanova, O.

2014-08-01

329

Grape seed and apple tannins: Emulsifying and antioxidant properties.  

PubMed

Tannins are natural antioxidants found in plant-based foods and beverages, whose amphiphilic nature could be useful to both stabilize emulsions and protect unsaturated lipids from oxidation. In this paper, the use of tannins as antioxidant emulsifiers was studied. The main parameters influencing the stability of emulsions (i.e. tannins structure and concentration, aqueous phase pH, and ionic strength) were identified and optimized. Oil in water emulsions stabilized with tannins were compared with those stabilized with two commercial emulsifying agents, poly(vinyl alcohol) (PVA) and polyoxyethylene hydrogenated castor oil. In optimized conditions, the condensed tannins allowed to obtain a stability equivalent to that of PVA. Tannins presented good antioxidant activity in oil in water emulsion, as measured by the conjugated autoxidizable triene (CAT) assay. PMID:25704681

Figueroa-Espinoza, Maria Cruz; Zafimahova, Andrea; Alvarado, Pedro G Maldonado; Dubreucq, Eric; Poncet-Legrand, Céline

2015-07-01

330

Emulsifying property of a viscous exopolysaccharide from Sphingomonas paucimobilis  

Microsoft Academic Search

A viscous exopolysaccharide fromSphingomonas paucimobilis-GS1, emulsified xylene, benzene, 2-methylnaphthalene, hexadecane, hexane, kerosene and paraffin oil as well as castor, coconut and olive oils when used at 1 mg\\/ml. It stabilized the emulsions more efficiently than commercial gums such as arabic, tragacanth, karaya and xanthan. Emulsions were stable for 6 months, from 4 to 40°C and pH 4 to 10 and

A. A. Ashtaputre; A. K. Shah

1995-01-01

331

Influence of electrolyte and voltage on the direct current enhanced transport of iron nanoparticles in clay.  

PubMed

Zero valent iron nanoparticles (nZVI) transport for soil and groundwater remediation is slowed down or halted by aggregation or fast depletion in the soil pores. Direct electric current can enhance the transport of nZVI in low permeability soils. However operational factors, including pH, oxidation-reduction potential (ORP), voltage and ionic strength of the electrolyte can play an important role in the treatment effectiveness. Experiments were conducted to enhance polymer coated nZVI mobility in a model low permeability soil medium (kaolin clay) using low direct current. Different electrolytes of varying ionic strengths and initial pH and high nZVI concentrations were applied. Results showed that the nZVI transport is enhanced by direct current, even considering concentrations typical of field application that favor nanoparticle aggregation. However, the factors considered (pH, ORP, voltage and electrolyte) failed to explain the iron concentration variation. The electrolyte and its ionic strength proved to be significant for pH and ORP measured during the experiments, and therefore will affect aggregation and fast oxidation of the particles. PMID:24252496

Gomes, Helena I; Dias-Ferreira, Celia; Ribeiro, Alexandra B; Pamukcu, Sibel

2014-03-01

332

Effective distribution of emulsified edible oil for enhanced anaerobic bioremediation.  

PubMed

Recent laboratory and field studies have shown that injection of emulsified edible oils can provide an effective, low-cost alternative for stimulating anaerobic biodegradation processes. A pilot-scale permeable reactive bio-barrier (PRBB) was installed at a perchlorate and chlorinated solvent impacted site by injecting 380 L of commercially available emulsion (EOS) containing emulsified soybean oil, food-grade surfactants, lactate, and yeast extract through ten direct push injection wells over a two day period. Soil cores collected six months after emulsion injection indicate the oil was distributed up to 5 m downgradient of the injection wells. A previously developed emulsion transport model was used to simulate emulsion transport and retention using independently estimated model parameters. While there was considerable variability in the soil sampling results, the model simulations generally agreed with the observed oil distribution at the field site. Model sensitivity analyses indicate that increasing the injection flow rate or diluting the oil with more water will have little effect on final oil distribution in the aquifer. The only effective approach for enhancing the spread of emulsified oil away from the injection well appears to be injecting a greater mass of oil. PMID:17673332

Borden, Robert C

2007-10-30

333

Role of food emulsifiers in milk coffee beverages.  

PubMed

To emphasize the coffee flavor, many milk coffee beverages contain coffee extracts; these are the so-called "rich milk coffee" beverages. When the content of the coffee extracts increases, milk coffee beverages become unstable. The milk ring formation, or oiling off, is accelerated in these kinds of drinks. We prepared a "rich milk coffee" beverage and studied the stability of the emulsion. We also investigated the influence of the food emulsifiers on the stability of the emulsion. We tried to test the emulsifier system in order to improve the emulsion stability. When the milk coffee beverage with a low light value for the roasted coffee beans sterilized by UHT was stored at a low temperature, the milk component strongly separated. We found that the sucrose monoester with a high HLB and diglycerol monoester accelerated the milk separation, and the decaglycerol monoester controlled the milk separation. We discussed the milk separation mechanism and showed that maintaining the hydration of the hydrophilic group in the rich milk coffee beverage was related to the combination of emulsifiers that control the milk separation. PMID:25680691

Ogawa, A; Cho, H

2015-07-01

334

Studies on gum of Moringa oleifera for its emulsifying properties  

PubMed Central

Background: Emulsion has been a form of presenting water insoluble substances for a long period of time. Now a day, it has been a way of presenting various intravenous additives and diagnostic agents in X-ray examinations. Various substances can be used as emulsifying agent, which can be operationally defined as a stabilizer of the droplets formed of the internal phase. Materials and Methods: Gum from Moringa oleifera was evaluated for its emulsifying properties. Castor oil emulsions 30 percent (o/w), containing 2 to 4% Moringa oleifera gum was prepared. Emulsions containing equivalent concentration of acacia were also prepared for comparison. All the emulsions prepared were stored at room temperature and studied for stability at various time intervals for 8 weeks. The prepared emulsions were evaluated for creaming rate, globule size and rate of coalescence. 23 factorial design was chosen to investigate the effects of centrifugation, pH, temperature changes and electrolytes on the creaming rate and globule size. Results: The results of the investigations show that the gum of Moringa oleifera possesses better emulsifying properties as compared to gum acacia. Conclusion: Gum of Moringa oleifera could be used in pharmaceutical and non-pharmaceutical preparation. PMID:24741276

Panda, Dibya Sundar

2014-01-01

335

Evaluating the Mobility of Arsenic in Synthetic Iron-containing Solids Using a Modified Sequential Extraction Method  

PubMed Central

Many water treatment technologies for arsenic removal that are used today produce arsenic-bearing residuals which are disposed in non-hazardous landfills. Previous works have established that many of these residuals will release arsenic to a much greater extent than predicted by standard regulatory leaching tests (e.g. the toxicity characteristic leaching procedure, TCLP) and, consequently, require stabilization to ensure benign behavior after disposal. In this work, a four-step sequential extraction method was developed in an effort to determine the proportion of arsenic in various phases in untreated as well as stabilized iron-based solid matrices. The solids synthesized using various potential stabilization techniques included: amorphous arsenic-iron sludge (ASL), reduced ASL via reaction with zero valent iron (RASL), amorphous ferrous arsenate (PFA), a mixture of PFA and SL (M1), crystalline ferrous arsenate (HPFA), and a mixture of HPFA and SL (M2). The overall arsenic mobility of the tested samples increased in the following order: ASL > RASL > PFA > M1 > HPFA > M2. PMID:23459695

Shan, Jilei; Sáez, A. Eduardo; Ela, Wendell P.

2013-01-01

336

Emulsified microemulsions and oil-containing liquid crystalline phases.  

PubMed

Self-assembled nanostructures, such as inverted type mesophases of the cubic or hexagonal geometry or reverse microemulsion phases, can be dispersed using a polymeric stabilizer, such as the PEO-PPO-PEO triblock copolymer Pluronic F127. The particles, which are described in the present study, are based on monolinolein (MLO)-water mixtures. When adding tetradecane (TC) to the MLO-water-F127 system at constant temperature, the internal nanostructure of the kinetically stabilized particles transforms from a Pn3m (cubosomes) to a H2 (hexosomes) and to a water-in-oil (W/O, L2) microemulsion phase (emulsified microemulsion (EME)). To our knowledge, this is the first time that the formation of stable emulsified microemulsion (EME) systems has been described and proven to exist even at room temperature. The same structural transitions can also be induced by increasing temperature at constant tetradecane content. The internal nanostructure of the emulsified particles is probed using small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM). At each investigated composition and temperature, the internal structure of the dispersions is observed to be identical to the corresponding structure of the nondispersed, fully hydrated bulk phase. This is clear evidence for the fact that the self-assembled inner particle nanostructure is preserved during the dispersion procedure. In addition, the internal structure of the particles is in thermodynamic equilibrium with the surrounding water phase. The internal structure of the dispersed, kinetically stabilized particles is a "real" and stable self-assembled nanostructure. To emphasize this fact, we denoted this new family of colloidal particles (cubosomes, hexosomes, and EMEs) as "ISASOMES" (internally self-assembled particles or "somes"). PMID:15641825

Yaghmur, Anan; de Campo, Liliana; Sagalowicz, Laurent; Leser, Martin E; Glatter, Otto

2005-01-18

337

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

PubMed

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

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

2014-01-01

338

EFFECT OF EMULSIFIERS ON TEXTURAL PROPERTIES OF WHOLE WHEAT TORTILLAS DURING STORAGE  

Technology Transfer Automated Retrieval System (TEKTRAN)

All three emulsifiers tested (SSL, GMS, de-oiled lecithin) impacted the textural quality of 100% WW tortillas during storage. However, the amount of emulsifier incorporated into the formulation was crucial. SSL was more effective at its lowest usage level (0.125%), unlike the de-oiled lecithin, whi...

339

Preparation and properties of methanol–diesel oil emulsified fuel under high-gravity environment  

Microsoft Academic Search

A new process for preparation of methanol–diesel emulsified fuel with a rotating packed bed is proposed. The influence of additive amount, methanol content, rotational speed, liquid flow rate of diesel on the rheological characteristics, surface tension and stabilization was discussed. The result showed that the emulsified fuel appeared as proximately Newtonian behavior. The rheological characteristics of the emulsions were significantly

Youzhi Liu; Weizhou Jiao; Guisheng Qi

2011-01-01

340

Influence of emulsifiers on ice cream produced by conventional freezing and low-temperature extrusion processing  

Microsoft Academic Search

Ice cream at six different levels of emulsification was produced by freezing in a conventional scraped surface freezer and with a serial configuration of a conventional freezer followed by a low-temperature extruder. The aim was to examine the influence of emulsifiers on the process, since both emulsifier addition and low-temperature extrusion may have similar effects on promotion of colloidal structure

S. Bolliger; B. Kornbrust; H. D. Goff; B. W. Tharp; E. J. Windhab

2000-01-01

341

A modified ice cream processing routine that promotes fat destabilization in the absence of added emulsifier  

Microsoft Academic Search

The quality of ice cream made without added emulsifier using a modified processing routine was compared to ice cream made conventionally with and without added emulsifier. “Two-phase process” ice cream was created by preparing two separate phases; emulsion (fat, some protein, water) and solution (remaining protein, sugar, corn syrup solids, stabilizer, water) and combining them just before freezing. Quality indicators

K. I. Segall; H. D. Goff

2002-01-01

342

The preparation of magnetically guided lipid based nanoemulsions using self-emulsifying technology  

NASA Astrophysics Data System (ADS)

This paper reports an easy and highly reproducible preparation route, using self-emulsifying technology, for an orally administered high quality magnetically responsive drug delivery system. Hydrophobic iron oxide nanoparticles of about 5 nm in diameter were prepared and incorporated into the lipid core of the produced oil droplets of a self-nanoemulsifying drug delivery system (MagC18/SNEDDS). The produced nanoemulsion exhibits colloidal stability at high ionic strengths and temperatures. The observed value of the saturation magnetization at 2 K is ?4.1 emu g-1. The nanoemulsion displayed the magnetic properties of a non-interacting assembly of superparamagnetic particles and a low blocking temperature. Moreover the effect of MagC18/SNEDDS on biological systems in vitro was investigated in rodent fibroblasts (3T3 cells). The cytotoxicity studies show that none of the formulations tested affected cell activity significantly over the 24 h incubation. Such systems might have a potential use for oral delivery of poorly soluble compounds by extending the residence time of the formulation in the small intestine resulting in increased drug absorption values.

Bakandritsos, Aristides; Zboril, Radek; Bouropoulos, Nikolaos; Kallinteri, Paraskevi; Favretto, Marco E.; Parker, Terry L.; Mullertz, Anette; Fatouros, Dimitrios G.

2010-02-01

343

The preparation of magnetically guided lipid based nanoemulsions using self-emulsifying technology.  

PubMed

This paper reports an easy and highly reproducible preparation route, using self-emulsifying technology, for an orally administered high quality magnetically responsive drug delivery system. Hydrophobic iron oxide nanoparticles of about 5 nm in diameter were prepared and incorporated into the lipid core of the produced oil droplets of a self-nanoemulsifying drug delivery system (MagC(18)/SNEDDS). The produced nanoemulsion exhibits colloidal stability at high ionic strengths and temperatures. The observed value of the saturation magnetization at 2 K is approximately 4.1 emu g(-1). The nanoemulsion displayed the magnetic properties of a non-interacting assembly of superparamagnetic particles and a low blocking temperature. Moreover the effect of MagC(18)/SNEDDS on biological systems in vitro was investigated in rodent fibroblasts (3T3 cells). The cytotoxicity studies show that none of the formulations tested affected cell activity significantly over the 24 h incubation. Such systems might have a potential use for oral delivery of poorly soluble compounds by extending the residence time of the formulation in the small intestine resulting in increased drug absorption values. PMID:20032554

Bakandritsos, Aristides; Zboril, Radek; Bouropoulos, Nikolaos; Kallinteri, Paraskevi; Favretto, Marco E; Parker, Terry L; Mullertz, Anette; Fatouros, Dimitrios G

2010-02-01

344

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

PubMed

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

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

2014-11-01

345

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

PubMed

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

Zhang, Qi

2015-02-01

346

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

347

Reconstitution of emulsifying activity of Acinetobacter calcoaceticus BD4 emulsan by using pure polysaccharide and protein.  

PubMed Central

Acinetobacter calcoaceticus BD4 and BD413 produce extracellular emulsifying agents when grown on 2% ethanol medium. For emulsifying activity, both polysaccharide and protein fractions were required, as demonstrated by selective digestion of the polysaccharide with a specific bacteriophage-borne polysaccharide depolymerase, deproteinization of the extracellular emulsifying complex with hot phenol, and reconstitution of emulsifier activity with pure polysaccharide and a polysaccharide-free protein fraction. Chemical modification of the carboxyl groups in the polysaccharide resulted in a loss of activity. The protein required for reconstitution of emulsifying activity was purified sevenfold. The BD4 emulsan apparently derives its amphipathic properties from the association of an anionic hydrophilic polysaccharide with proteins. PMID:3566271

Kaplan, N; Zosim, Z; Rosenberg, E

1987-01-01

348

Performance Optimization of Metallic Iron and Iron Oxide Nanomaterials for Treatment of Impaired Water Supplies  

NASA Astrophysics Data System (ADS)

Iron nanomaterials including nanoscale zero valent iron (NZVI), NZVI-based bimetallic reductants (e.g., Pd/NZVI) and naturally occurring nanoscale iron mineral phases represent promising treatment tools for impaired water supplies. However, questions pertaining to fundamental and practical aspects of their reactivity may limit their performance during applications. For NZVI treatment of pollutant source zones, a major hurdle is its limited reactive lifetime. In Chapter 2, we report the longevity of NZVI towards 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and hexavalent chromium [Cr(VI)] in oxygen-free systems with various anionic co-solutes (e.g., Cl-, SO4 2-, ClO4-, HCO3 -, NO3-). Trends in longevity provide evidence that surface-associated Fe(II) species are responsible for Cr(VI) reduction, whereas 1,1,1,2-TeCA reduction depends on the accessibility of Fe(0) at the NZVI particle surface. In Chapter 3, we show that dithionite, previously utilized for in situ redox manipulation, can restore the reducing capacity of passivated NZVI treatment systems. Air oxidation of NZVI at pH ? 8 quickly exhausted reactivity despite a significant fraction of Fe(0) persisting in the particle core. Reduction of this passive layer by low dithionite concentrations restored suspension reactivity to levels of unaged NZVI, with multiple dithionite additions further improving pollutant removal. In Chapter 4, measurements of solvent kinetic isotope effects reveals that optimal Pd/NZVI reactivity results from accumulation of atomic hydrogen, which only occurs in NZVI-based systems due to their higher rates of corrosion. However, atomic hydrogen formation only occurs in aged Pd/NZVI suspensions for ˜2 weeks, after which any reactivity enhancement likely results from galvanic corrosion of Fe(0). Finally, the activity of hybrid nanostructures consisting of multi-walled carbon nanotubes decorated with of hematite nanoparticles (alphaFe 2O3/MWCNT) is explored in Chapter 5. Sorption of Cu(II) and Cr(VI) is enhanced in hybrid nanostructure systems beyond what would be expected from simple additive sorption capacities of their building blocks. The enhanced sorption capacity is in part derived from the greater surface area of hematite nanoparticles immobilized on MWCNTs relative to aggregated hematite suspensions. The hybrid alphaFe2O3/MWCNT may also exhibit unique surface chemistry, as supported by the tunable values of zeta potential measured as a function of the mass of alphaFe2O 3 deposited on the MWCNTs.

Xie, Yang

349

Environmental application of millimeter-scale sponge iron (s-Fe(0)) particles (II): The effect of surface copper.  

PubMed

To enhance the catalytic reactivity of millimeter-scale particles of sponge iron (s-Fe(0)), Cu(2+) ions were deposited on the surface of s-Fe(0) using a simple direct reduction reaction, and the catalytic properties of the bimetallic system was tested for removal of rhodamine B (RhB) from an aqueous solution. The influence of Cu(0) loading, catalyst dosage, particle size, initial RhB concentration, and initial pH were investigated, and the recyclability of the catalyst was also assessed. The results demonstrate that the 3?5 millimeter s-Fe(0) particles (s-Fe(0)(3?5mm)) with 5wt% Cu loading gave the best results. The removal of RhB followed two-step, pseudo-first-order reaction kinetics. Cu(0)-s-Fe(0) showed excellent stability after five reuse cycles. Cu(0)-s-Fe(0) possesses great advantages compared to nanoscale zero-valent iron, iron power, and iron flakes as well as its bimetals. The surface Cu(0) apparently catalyzes the production of reactive hydrogen atoms for indirect reaction and generates Fe-Cu galvanic cells that enhance electron transfer for direct reaction. This bimetallic catalyst shows great potential for the pre-treatment of recalcitrant wastewaters. Additionally, some oxides containing iron element are selected to simulate the adsorption process. The results prove that the adsorption process of FeOOH, Fe2O3 and Fe3O4 played minor role for the removal of RhB. PMID:25668301

Ju, Yongming; Liu, Xiaowen; Liu, Runlong; Li, Guohua; Wang, Xiaoyan; Yang, Yanyan; Wei, Dongyang; Fang, Jiande; Dionysiou, Dionysios D

2015-04-28

350

Efficiency of the EPS emulsifier produced by Ochrobactrum anthropi in different hydrocarbon bioremediation assays.  

PubMed

Ochrobactrum anthropi strain AD2 was isolated from the waste water treatment plant of an oil refinery and was identified by analysis of the sequence of the gene encoding 16S rDNA. This bacterium produced exopolysaccharides in glucose nutrient broth media supplemented with various hydrocarbons (n-octane, mineral light and heavy oils and crude oils). The exopolysaccharide AD2 (EPS emulsifier) synthesized showed a wide range of emulsifying activity but none of them had surfactant activity. Yield production varied from 0.47 to 0.94 g of EPS l(-1) depending on the hydrocarbon added. In the same way, chemical composition and emulsification activity of EPS emulsifier varied with the culture conditions. Efficiency of the EPS emulsifier as biostimulating agent was assayed in soil microcosms and experimental biopiles. The AD2 biopolymer was added alone or combined with commercial products frequently used in oil bioremediation such as inorganic NPK fertilizer and oleophilic fertilizer (S200 C). Also, its efficiency was tested in mixture with activated sludge from an oil refinery. In soil microcosms supplemented with S200 C+EPS emulsifier as combined treatment, indigenous microbial populations as well as hydrocarbon degradation was enhanced when compared with microcosms treated with NPK fertilizer or EPS emulsifier alone. In the same way EPS emulsifier stimulated the bioremediation effect of S200 C product, increasing the number of bacteria and decreasing the amount of hydrocarbon remained. Finally, similar effects were obtained in biopile assays amended with EPS emulsifier plus activated sludge. Our results suggest that the bioemulsifier EPS emulsifier has interesting properties for its application in environment polluted with oil hydrocarbon compounds and may be useful for bioremediation purposes. PMID:18784947

Calvo, C; Silva-Castro, G A; Uad, I; García Fandiño, C; Laguna, J; González-López, J

2008-11-01

351

Biogeochemistry of two types of permeable reactive barriers, organic carbon and iron-bearing organic carbon for mine drainage treatment: column experiments.  

PubMed

Permeable reactive barriers (PRBs) are an alternative technology to treat mine drainage containing sulfate and heavy metals. Two column experiments were conducted to assess the suitability of an organic carbon (OC) based reactive mixture and an Fe(0)-bearing organic carbon (FeOC) based reactive mixture, under controlled groundwater flow conditions. The organic carbon mixture contains about 30% (volume) organic carbon (composted leaf mulch) and 70% (volume) sand and gravel. The Fe(0)-bearing organic carbon mixture contains 10% (volume) zero-valent iron, 20% (volume) organic carbon, 10% (volume) limestone, and 60% (volume) sand and gravel. Simulated groundwater containing 380 ppm sulfate, 5 ppm As, and 0.5 ppm Sb was passed through the columns at flow rates of 64 (the OC column) and 62 (the FeOC column) ml d(-1), which are equivalent to 0.79 (the OC column) and 0.78 (the FeOC column) pore volumes (PVs) per week or 0.046 m d(-1) for both columns. The OC column showed an initial sulfate reduction rate of 0.4 micromol g (OC)(-1) d(-1) and exhausted its capacity to promote sulfate reduction after 30 PVs, or 9 months of flow. The FeOC column sustained a relatively constant sulfate reduction rate of 0.9 micromol g (OC)(-1) d(-1) for at least 65 PVs (17 months). In the FeOC column, the delta34S values increase with the decreasing sulfate concentration. The delta34S fractionation follows a Rayleigh fractionation model with an enrichment factor of 21.6 per thousand. The performance decline of the OC column was caused by the depletion of substrate or electron donor. The cathodic production of H2 by anaerobic corrosion of Fe probably sustained a higher level of SRB activity in the FeOC column. These results suggest that zero-valent iron can be used to provide an electron donor in sulfate reducing PRBs. A sharp increase in the delta(13)C value of the dissolved inorganic carbon and a decrease in the concentration of HCO3- indicate that hydrogenotrophic methanogenesis is occurring in the first 15 cm of the FeOC column. PMID:19467564

Guo, Qiang; Blowes, David W

2009-07-21

352

Biogeochemistry of two types of permeable reactive barriers, organic carbon and iron-bearing organic carbon for mine drainage treatment: Column experiments  

NASA Astrophysics Data System (ADS)

Permeable reactive barriers (PRBs) are an alternative technology to treat mine drainage containing sulfate and heavy metals. Two column experiments were conducted to assess the suitability of an organic carbon (OC) based reactive mixture and an Fe 0-bearing organic carbon (FeOC) based reactive mixture, under controlled groundwater flow conditions. The organic carbon mixture contains about 30% (volume) organic carbon (composted leaf mulch) and 70% (volume) sand and gravel. The Fe 0-bearing organic carbon mixture contains 10% (volume) zero-valent iron, 20% (volume) organic carbon, 10% (volume) limestone, and 60% (volume) sand and gravel. Simulated groundwater containing 380 ppm sulfate, 5 ppm As, and 0.5 ppm Sb was passed through the columns at flow rates of 64 (the OC column) and 62 (the FeOC column) ml d - 1 , which are equivalent to 0.79 (the OC column) and 0.78 (the FeOC column) pore volumes (PVs) per week or 0.046 m d - 1 for both columns. The OC column showed an initial sulfate reduction rate of 0.4 µmol g (OC) - 1 d - 1 and exhausted its capacity to promote sulfate reduction after 30 PVs, or 9 months of flow. The FeOC column sustained a relatively constant sulfate reduction rate of 0.9 µmol g (OC) - 1 d - 1 for at least 65 PVs (17 months). In the FeOC column, the ?34S values increase with the decreasing sulfate concentration. The ?34S fractionation follows a Rayleigh fractionation model with an enrichment factor of 21.6‰. The performance decline of the OC column was caused by the depletion of substrate or electron donor. The cathodic production of H 2 by anaerobic corrosion of Fe probably sustained a higher level of SRB activity in the FeOC column. These results suggest that zero-valent iron can be used to provide an electron donor in sulfate reducing PRBs. A sharp increase in the ?13C value of the dissolved inorganic carbon and a decrease in the concentration of HCO 3- indicate that hydrogenotrophic methanogenesis is occurring in the first 15 cm of the FeOC column.

Guo, Qiang; Blowes, David W.

2009-07-01

353

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. PMID:19068843

Lee, Changha; Sedlak, David L.

2009-01-01

354

Enhanced absorption of n-3 fatty acids from emulsified compared with encapsulated fish oil  

Technology Transfer Automated Retrieval System (TEKTRAN)

The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have important nutrition and disease management properties. Presently fish oil (FO) supplementation relies on capsular triglyceride. Flavored emulsified lipid preparations may provide an improved approach to FO del...

355

Relationship between the chemical components of taro rhizome mucilage and its emulsifying property.  

PubMed

The objective of this study was to determine the chemical composition of taro mucilage (TM) and explain its emulsification properties using different commercial emulsifiers and gums as benchmarks. The following analyses were performed: moisture, ether extract, protein, fiber, ash, sugar fraction, starch content, infrared spectroscopy and determination of monosaccharides and amino acids using HPLC. The analyses showed that TM has a high carbohydrate content and small protein fraction, similar to commercial gums. Commercial emulsifiers have a high content of lipids compared to TM. Therefore, it can be concluded that the emulsifying power of the studied mucilage is primarily caused by the protein content along with weakly polar amino acids, which occur in gums. The methyl group (CH3), which was observed in the infrared spectrum, and the lipid content may also contribute to the emulsifying activity by providing a hydrophobic moiety. PMID:25704720

Andrade, Luan Alberto; Nunes, Cleiton Antônio; Pereira, Joelma

2015-07-01

356

Emulsifying properties of high pressure treated soy protein isolate and 7S and 11S globulins  

Microsoft Academic Search

The influence of high pressure (HP) treatment (200–600MPa) on the emulsifying activity index (EAI) and emulsifying stability index (ESI) on the 7S and 11S globulins and soya protein isolate (SPI) at pHs 7.5 and 6.5, at different concentrations (0.25–0.75%) was studied. Solubility and surface hydrophobicity were used as indices of the degree of denaturation caused by HP. 7S showed the

E Molina; A Papadopoulou; D. A Ledward

2001-01-01

357

Emulsifier content and side effects of oil-based adjuvant vaccine in swine  

Microsoft Academic Search

Side effects caused by the excessive emulsifier in oil-based adjuvant vaccine were examined practically in swine using one oil-in-water type adjuvant vaccine against swine pleuropneumonia. The vaccine was prepared from cell-free-antigen of Actinobacillus pleuropneumoniae, liquid paraffin, and several polyoxyethylenesorbitan and sorbitan oleates. Based on findings about safety in mice and emulsion stability, 2 vaccines containing either 11.25% or 6.25% emulsifier

Kenji Oda; Fusayo Tsukahara; Sei Kubota; Kayoko Kida; Takashi Kitajima; Satoru Hashimoto

2006-01-01

358

Emulsifying Agent Production During PAHs Degradation by the White Rot Fungus Pleurotus Ostreatus D1  

Microsoft Academic Search

For the first time the production of an emulsifying agent during phthalic, 2,2?-diphenic and ?-hydroxy-?-naphthoic acids,\\u000a phenanthrene, anthracene, fluorene, pyrene, fluoranthene, and chrysene degradation by white rot fungus Pleurotus ostreatus was found. The emulsifying activity of the cultivation medium after degradation of these compounds was assessed. Maximal\\u000a activities were found in the presence of chrysene (48.4%) and ?-hydroxy-?-naphthoic acid (52.2%).

Svetlana V. Nikiforova; Natalia N. Pozdnyakova; Olga V. Turkovskaya

2009-01-01

359

Effect of single and integrated emulsifier-stabiliser on soy-ice confection  

Microsoft Academic Search

Soy-ice confections were prepared incorporating locust bean gum (LBG), guar gum (GG), sodium carboxymethylcellulose (CMC) and alginate as single stabilisers with glyceromonostearate (GMS) as an emulsifier. The integrated emulsifier-stabiliser (IBS) used was Sherex (mixture of mono-di glycerides, LBG, GG and carrageenan). All confections were analysed for viscosity, foam and texture properties, meltdown and shape factor, glass transition temperature (Tg), melting

K. Kailasapathy; C. D. Sellepan

1998-01-01

360

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

361

Cardiocerebral protection by emulsified isoflurane during cardiopulmonary resuscitation.  

PubMed

Although improvement in cardiopulmonary resuscitation (CPR) performance and the increasing success at achieving return of spontaneous circulation (ROSC) have been possible in recent years, the survival and discharge rates of post-cardiac arrest (CA) patients remain disappointing. The high mortality rate is attributed to whole-body ischemia/reperfusion (I/R) induced multi-organ dysfunction that is well known as post-cardiac arrest syndrome. Post-cardiac arrest myocardial dysfunction and brain injury are the main clinical features of this complex pathophysiological process. Previous evidences have shown that volatile anesthetics, such as isoflurane, trigger a powerful and highly integrated cell survival response during I/R period in multiple organs, including heart and brain, which reduces I/R injury. This effect that called anesthetic-induced postconditioning can be shown when volatile anesthetics are administered after the onset of ischemia and at the time of reperfusion. Emulsified isoflurane (EIso) is a new anesthetic for intravenous administration, which is conveniently feasible outside operating room. Therefore, we hypothesize that EIso postconditioning could provide the cardiocerebral protection, and combined with therapeutic hypothermia as sedative agent could produce enhanced cardiocerebral protection, which can result in significant improvement of neurologically intact post-cardiac arrest survival. We consider that it would become a feasible, safe and efficient cardiocerebral protective intervention in the prevention and alleviation of post-cardiac arrest syndrome, which would also improve the outcomes after CA. PMID:25466299

Zhang, Ya-Jie; Wu, Meng-Jun; Li, Yi; Yu, Hai

2015-01-01

362

Nanoscale and Microscale Iron Emulsions for Treating DNAPL  

NASA Technical Reports Server (NTRS)

This study demonstrated the feasibility of using emulsified nanoscale and microscale iron particles to enhance dehalogenation of (Dense Non-Aqueous Phase Liquid) DNAPL free-phase. The emulsified system consisted of a surfactant-stabilized, biodegradable oil-in-water emulsion with nanoscale or microscale iron particles contained within the emulsion droplets. It was demonstrated that DNAPLs, such as trichloroethene (TCE), diffuse through the oil membrane of the emulsion particle whereupon they reach an aqueous interior and the surface of an iron particle where dehalogenation takes place. The hydrocarbon reaction by-products of the dehalogenation reaction, primarily ethene (no chlorinated products detected), diffuse out of the emulsion droplet. This study also demonstrated that an iron-emulsion system could be delivered in-situ to the DNAPL pool in a soil matrix by using a simulated push well technique. Iron emulsions degraded pure TCE at a rate comparable to the degradation of dissolved phase TCE by iron particles, while pure iron had a very low degradation rate for free-phase TCE. The iron-emulsion systems can be injected into a sand matrix where they become immobilized and are not moved by flowing water. It has been documented that surfactant micelles possess the ability to pull pooled TCE into emulsion droplets where degradation of TCE takes place.

Geiger, Cherie L.

2002-01-01

363

Fate and Transport of Superparamagentic Iron Oxide Nanoparticles in Porous Media  

NASA Astrophysics Data System (ADS)

The increased use of engineered nanoparticles in various applications such as electronics and biomedical engineering has raised concerns about their impact on human health and the environment. In this study we investigate the fate and transport in porous media of super paramagnetic iron oxide (SPIO) nanoparticles surface coated with poly acrylic acid for size stabilization. The nanoparticle size distribution was first analyzed to assess the effect of dilution on the particle size. It was found that the poly acrylic acid is generally effective in stabilizing the size of the nanoparticles, except for highly diluted solutions. Sorption batch experiments performed at different pH values showed that the SPIO nanoparticles did not adsorb significantly on sand. Transport experiments were conducted in a sand-packed column for different SPIO injection concentrations and for upwards and downwards flow conditions. Comparison of the nanoparticle breakthrough curves to that of a conservative tracer showed that while advection and dispersion are the two main mechanisms responsible for the tracer transport, nanoparticle transport is also strongly influenced by the nanoparticle concentration in the solution. At low concentrations (in the range of 1 mg/L) the high levels of dilution mean that only a small portion of the nanoparticles get transported due to their larger effective size. Another consequence of the concentration-dependent mobility of the nanoparticles is sharper breakthrough curves compared to that of the tracer. Overall, the results demonstrate the significance of concentration on nanoparticle size and, consequently, transport. These results also point to the need for effective nanoparticle size control for the efficient deliverability of reactive nanoparticles (such as zero-valent iron) in in-situ groundwater remediation applications.

Aksoy, D.; Ziylan, A.; Ince, N. H.; Yagci Acar, F.; Copty, N. K.

2008-12-01

364

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

E-print Network

of chloride and bromide. Inhibition mechanism of perchlorate reduction inhibition was believed to be caused either by competitive adsorption of aggressive anions on bare Ti(0) surface or Ti(II) consumption by electrochemically produced chlorine. Kinetic models...

Lee, Chun Woo

2009-05-15

365

Iron and Iron Deficiency  

MedlinePLUS

... from these substances is usually not of concern. Vegetarian diets are low in heme iron, but careful meal ... heme iron sources in the diet (e.g., vegetarian diets) Low absorption Taking antacids beyond the recommended dose ...

366

Safe, in situ methodologies for the destruction of triacetone triperoxide and other explosive peroxides  

NASA Technical Reports Server (NTRS)

Triacetone triperoxide (TATP) and other explosives of the peroxide family are safely degraded in situ. Nano and micron size metal particles in an elemental state include pure iron and magnesium or iron and magnesium particles that are mechanically alloyed with palladium and nickel. The metal particles are used in both the elemental state and in emulsions that are made from water, a hydrophobic solvent, such as corn oil, and a food-grade nonionic surfactant. The neat metals and emulsified zero valent metals (EZVM) safely degrade TATP with the major degradation product being acetone. The EZVM system absorbs and dissolves the TATP into the emulsion droplets where TATP degradation occurs. EZVM systems are ideal for degrading dry TATP crystals that may be present on a carpet or door entrance. Both the neat metal system and the emulsion system (EZVM) degrade TATP in an aqueous slurry.

Clausen, III, Christian (Inventor); Geiger, Cherie L. (Inventor); Sigman, Michael (Inventor); Fidler, Rebecca (Inventor)

2011-01-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

368

Iron Sulfide as a Sustainable Reactive Material for Permeable Reactive Barriers  

NASA Astrophysics Data System (ADS)

Permeable reactive barriers (PRBs) are gaining acceptance for groundwater remediation, as they operate in situ and do not require continuous energy input. The majority of PRBs use zero-valent iron (ZVI). However, some ZVI PRBs have hydraulically failed [1,2], due to the fact that ZVI may reduce not only contaminants but also water and non-contaminant solutes. These reactions may form precipitates or gas phases that reduce permeability. Therefore, there is a need to assess the hydraulic suitability of possible alternatives, such as iron sulfide (FeS). The capability of FeS to remove both metals and halogenated organics from aqueous systems has been demonstrated previously [3,4], and FeS formed in situ within a ZVI PRB has been linked to contaminant removal [5]. These results suggest possible applications in groundwater remediation as a permeable reactive barrier (PRB) material. However, the propensity of FeS for permeability loss, due to solids and gas production, must be evaluated in order to address its suitability for PRBs. The reduction in permeability for FeS-coated sands under the anoxic conditions often encountered at contaminated groundwater sites was examined through column experiments and geochemical modeling under conditions of high calcium and nitrate, which have been previously shown to cause significant permeability reduction in zero-valent iron (ZVI) systems [6]. The column experiments showed negligible production of both solids and gases. The geochemical model was used to estimate solid and gas volumes generated under conditions of varying FeS concentration. Then, the Kozeny-Carman equation and a power-law relationship was used to predict permeability reduction, with a maximum reduction in permeability of 1% due to solids and about 30% due to gas formation under conditions for which a complete loss of permeability was predicted for ZVI systems. This difference in permeability reduction is driven by the differences in thermodynamic stability of ZVI and FeS in aqueous solutions. The results suggest that geochemical conditions that result in high permeability losses for ZVI systems will necessarily not be problematic, from a permeability perspective, for FeS-based reactive materials. Therefore, this research represents an important advance for sustainable groundwater remediation. References: [1] Mushovic, P., Bartlett, T. R., Morrison, S. (2006) Tech. News & Trends 23, 1-3. [2] Kiilerich, O., Larsen, J. W., Nielsen, C., Deigaard, L. D. (2000) In: Wickramanayake, G.B., et al. (Eds.), Chemical Oxidation and Reactive Barriers: Remediation of Chlorinated and Recalcitrant Compounds, Battelle Press, Columbus, OH, 377-384. [3] Han, Y., Gallegos, T. J., Demond, A. H., Hayes, K. F. (2011) Water Res. 45(2), 593-604. [4] Jeong, H. Y. and Hayes, K. F. (2007) Environ. Sci. Technol. 41(18), 6390-6396. [5] Beak, D. G. and Wilkin, R. T. (2009) J. Contam. Hydrol. 106(1-2), 15-28. [6] Henderson, A. D. and Demond, A. H. (2007) Environ. Eng. Sci. 24(4), 401-423.

Henderson, A. D.; Demond, A. H.

2012-12-01

369

Effects of Supplemental Exogenous Emulsifier on Performance, Nutrient Metabolism, and Serum Lipid Profile in Broiler Chickens  

PubMed Central

The effects of an exogenous emulsifier, glyceryl polyethylene glycol ricinoleate, on performance and carcass traits of broiler chickens were assessed. The emulsifier was added to the diet at dose rates of 0 (control), 1 (E1) and 2 (E2) % of added fat (saturated palm oil). Live weight gain (P < .07) and feed conversion ratio (P < .05) in 39 days were higher in the E1 dietary group. Gain: ME intake and gain: protein intake during the grower phase improved quadratically (P < .05). Gross carcass traits were not affected. Body fat content and fat accretion increased (P < .05) and liver fat content decreased (P < .05) linearly with the level of emulsifier in diet. Fat excretion decreased (P < .001) leading to increased ileal fat digestibility (P < .06) in the E1 group (quadratic response). Metabolizable intake of N (P < .1) and fat (P < .05) increased quadratically due to supplementation of emulsifier in diet. Metabolism of trace elements and serum lipid profiles were not affected. The study revealed that supplementation of exogenous emulsifiers in diets containing moderate quantities of added vegetable fats may substantially improve broiler performance. PMID:20671938

Roy, Amitava; Haldar, Sudipto; Mondal, Souvik; Ghosh, Tapan Kumar

2010-01-01

370

Quantification of unadsorbed protein and surfactant emulsifiers in oil-in-water emulsions.  

PubMed

Unadsorbed emulsifiers affect the physical and chemical behaviour of oil-in-water (O/W) emulsions. A simple methodology to quantify unadsorbed emulsifiers in the aqueous phase of O/W emulsions has been developed. Emulsions were centrifuged and filtered to separate the aqueous phase from the oil droplets and the concentration of unadsorbed emulsifiers in the aqueous phase determined. The quantification of unadsorbed surfactants based on the direct transesterification of their fatty acids was validated for Tween 20, Tween 80, citric acid ester (Citrem), Span 20 and monolauroyl glycerol. To determine unadsorbed proteins, results obtained with Folin-Ciocalteu reagent or UV-spectrophotometry were compared on emulsions stabilized by ?-lactoglobulin (BLG), ?-casein (BCN) or bovine serum albumin (BSA). The first method gave more accurate results especially during aging of emulsions in oxidative conditions. The whole methodology was applied to emulsions stabilized with single or mixed emulsifiers. This approach enables optimization of emulsion formulations and could be useful to follow changes in the levels of unadsorbed emulsifiers during physical or chemical aging processes. PMID:21167495

Berton, Claire; Genot, Claude; Ropers, Marie-Hélène

2011-02-15

371

Emulsifier content and side effects of oil-based adjuvant vaccine in swine.  

PubMed

Side effects caused by the excessive emulsifier in oil-based adjuvant vaccine were examined practically in swine using one oil-in-water type adjuvant vaccine against swine pleuropneumonia. The vaccine was prepared from cell-free-antigen of Actinobacillus pleuropneumoniae, liquid paraffin, and several polyoxyethylenesorbitan and sorbitan oleates. Based on findings about safety in mice and emulsion stability, 2 vaccines containing either 11.25% or 6.25% emulsifier content were injected intramuscularly twice in swine, as the highest and lowest limits, respectively, within the practical range. All pigs showed temporary fever and malaise with anorexia for several days after each injection. The fever of the higher emulsifier content group took significantly longer to recover than the lower. Malaise also showed a similar tendency. On the other hand, antibody response was sufficiently induced with no significant difference between the 2 groups. Lowering the emulsifier content is a very simple but effective solution for mitigation of side effects without the reduction of adjuvanticity. For safe and high-quality oil-based adjuvant vaccines, not only antigen and base-oil, but emulsifier content must be optimized. PMID:16337664

Oda, Kenji; Tsukahara, Fusayo; Kubota, Sei; Kida, Kayoko; Kitajima, Takashi; Hashimoto, Satoru

2006-08-01

372

The influence of humic acid and clay content on the transport of polymer-coated iron nanoparticles through sand.  

PubMed

The introduction of nanoscale zero valent iron (nZVI) into the subsurface has recently received significant attention as a potentially effective method for remediation of source zones of chlorinated solvents present as dense nonaqueous phase liquids (DNAPL). One of the challenges in the deployment of nZVI is to achieve good subsurface nZVI mobility to permit delivery of the nZVI to the target treatment zone. Stabilization of nZVI with various polymers has shown promise for enhancing nZVI subsurface mobility, but the impact of subsurface conditions on nZVI mobility has not been fully explored. In this study, the effect of humic acid and kaolinite on the transport of polymer-stabilized nZVI (carboxylmethyl cellulose-surface modified nZVI, CMC90K-RNIP) in sand was investigated using column experiments. In addition, effects of electrolytes on the stability of CMC90K-RNIP in the presence of humic acid, and the stability of humic acid-coated reactive nanoscale iron particles (HA-RNIP) at various humic acid concentrations were investigated. Humic acid enhanced the mobility of bare RNIP, whereas the transport of CMC90K-RNIP was not significantly affected by humic acid injected as a background solution, except at the highest concentration of 500mg/L. At lower pore water velocity, the effect of humic acid on the transport of CMC90K-RNIP was greater than that at high water velocity. Adding kaolinite up to 2% by weight to the sand column reduced the retention of CMC90K-RNIP, but further increases in kaolinite content (to 5%) did not significantly affect nZVI retention. The impact of kaolinite on nZVI retention was more pronounced at lower pore water velocities. PMID:25079234

Jung, Bahngmi; O'Carroll, Denis; Sleep, Brent

2014-10-15

373

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

SciTech Connect

Under anoxic conditions, soluble 99TcO4– can be reduced to less soluble TcO2•nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zero-valent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 hrs to mimic the stages of aquifer sulfate reduction and onset of biotic sulfidogenesis. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between S/Fe = 0–0.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO4– for FeS (over iron oxides), and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS–. X-ray absorption spectroscopy revealed that as S/Fe increased, Tc speciation shifted from TcO2•nH2O to TcS2. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase of Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.

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

2013-04-24

374

Simultaneous adsorption and reduction of U(VI) on reduced graphene oxide-supported nanoscale zerovalent iron.  

PubMed

The reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized by chemical deposition method and were characterized by SEM, high resolution TEM, Raman and potentiometric acid-base titrations. The characteristic results showed that the nZVI nanoparticles can be uniformly dispersed on the surface of rGO. The removal of U(VI) on nZVI/rGO composites as a function of contact time, pH and U(VI) initial concentration was investigated by batch technique. The removal kinetics of U(VI) on nZVI and nZVI/rGO were well simulated by a pseudo-first-order kinetic model and pseudo-second-order kinetic model, respectively. The presence of rGO on nZVI nanoparticles increased the reaction rate and removal capacity of U(VI) significantly, which was attributed to the chemisorbed OH(-) groups of rGO and the massive enrichment of Fe(2+) on rGO surface by XPS analysis. The XRD analysis revealed that the presence of rGO retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite. According to the fitting of EXAFS spectra, the UC (at ?2.9?) and UFe (at ?3.2?) shells were observed, indicating the formation of inner-sphere surface complexes on nZVI/rGO composites. Therefore, the nZVI/rGO composites can be suitable as efficient materials for the in-situ remediation of uranium-contaminated groundwater in the environmental pollution management. PMID:25194557

Sun, Yubing; Ding, Congcong; Cheng, Wencai; Wang, Xiangke

2014-09-15

375

Pilot-Scale Demonstration of hZVI Process for Treating Flue Gas Desulfurization Wastewater at Plant Wansley, Carrollton, GA  

E-print Network

The hybrid Zero Valent Iron (hZVI) process is a novel chemical treatment platform that has shown great potential in our previous bench-scale tests for removing selenium, mercury and other pollutants from Flue Gas Desulfurization (FGD) wastewater...

Peddi, Phani 1987-

2011-12-06

376

Bioremediation of Uranium Plumes with Nano-scale  

E-print Network

Bioremediation of Uranium Plumes with Nano-scale Zero-valent Iron Angela Athey Advisers: Dr. Reyes and economically feasible e-donor for uranium bioremediation 15 #12;Future Work · Determine uranium solubility

Fay, Noah

377

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

PubMed

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

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

2014-03-15

378

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

PubMed

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

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

2010-07-30

379

X-ray Spectroscopic Tools for Structural Determination of Cr(VI)-Treated Iron Nanoparticles  

NASA Astrophysics Data System (ADS)

Chromate (Cr(VI)) is a highly soluble groundwater contaminant of environmental concern. We are developing and investigating zero-valent iron nanoparticles (nano-Fe) for possible use in remediation of Cr(VI). In this paper we focus on the application of X-ray techniques to determine the electronic environment and solid phase chemistry of Cr and Fe in Cr(VI)-and Cr(III)-treated nano-Fe. Results from X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES) confirmed that Cr(VI) was quantitatively reduced to Cr(III) by nano- Fe. Parallel experiments with 100-mesh Fe filings as a model system show similar Cr(VI) reduction properties but with a somewhat different Fe(III) corrosion product. Detailed analysis of XPS O 1s line spectra revealed that both Cr(III)- and Cr(VI)-treated nano-Fe yielded a predominantly Cr(III) hydroxide product. The Cr local atomic structure in Cr(III)- and Cr(VI)-treated nano-Fe was determined using extended x-ray absorption fine structure spectroscopy (EXAFS) and revealed octahedral Cr(III) with Cr-O interatomic distances between 1.97-1.98 angstroms for both Cr(III) and Cr(VI) treatments. A pronounced second Cr-Cr (and/or Cr-Fe) interatomic shell at 3.01 angstroms was also detected. Our results suggest that the reaction product of Cr(VI)-treated nano-Fe is an insoluble, poorly ordered Cr(III) precipitate and/or a mixed-phase Cr(III)/Fe(III) hydroxide.

Manning, B. A.; Kiser, J.; Ruiz, A.

2007-12-01

380

In situ SERS detection of emulsifiers at lipid interfaces using label-free amphiphilic gold nanoparticles.  

PubMed

Herein, we fabricated amphiphilic gold nanoparticles (GNPs) that can self-assemble at oil-water interfaces. We applied those GNPs for in situ SERS detection of emulsifier molecules within the interfacial region of oil in water (O/W) emulsion systems. PMID:25134491

Li, Yue; Driver, Michael; Winuprasith, Thunnalin; Zheng, Jinkai; McClements, David Julian; He, Lili

2014-10-21

381

Effect of emulsifying salts on the physicochemical properties of processed cheese made from Mozzarella.  

PubMed

The aim of this study was to investigate the effect of different types and concentrations of emulsifying salts (trisodium citrate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, and disodium orthophosphate) on the physicochemical properties of processed cheese. The physicochemical composition, texture profile, degree of casein dissociation, fat particle size, color, and nuclear magnetic resonance profile (NMR) of processed cheese were determined. Hardness, degree of casein dissociation, and pH increased as the concentration of emulsifying salts increased. The fat particle size of processed cheese was significantly influenced by the type of emulsifying salts, with processed cheese made with sodium hexametaphosphate having larger particles (4.68 µm) than cheeses made with the other salts (from 2.71 to 3.30 µm). The processed cheese prepared with trisodium citrate was whiter than those prepared with the other emulsifying salts. The NMR analysis showed that the relaxation time of processed cheese of 10 to 100 ms accounted for a major proportion, indicating that the moisture in processed cheese was mainly bound water combined with the fat globule and hydrated casein. PMID:22916886

Chen, L; Liu, H

2012-09-01

382

Factors affecting the emulsifying and rheological properties of gum acacia in beverage emulsions  

Microsoft Academic Search

Gum acacia, a natural hydrocolloid, is extensively used as an emulsifier\\/stabilizer in beverage emulsions. Factors that may affect emulsion formation, emulsion stability and viscosity of the emulsion concentrate were studied to assess their significance, including proximal composition of the gum (protein content and mineral content), gum processing prior to emulsion preparation (pasteurization and demineralization), and pH of the dilute emulsion.

R. A Buffo; G. A Reineccius; G. W Oehlert

2001-01-01

383

Influence of emulsified olive oil stabilizing system used for pork backfat replacement in frankfurters  

Microsoft Academic Search

The purpose of this study was to evaluate the influence of emulsified olive oil stabilizing systems used for pork backfat replacement on frankfurter characteristics. The oil-in-water emulsions were stabilized with various protein systems formulated using sodium caseinate, soy protein isolate, meat protein and microbial transglutaminase. These emulsions presented excellent fat and water binding properties, with no noticeable release of exudate

F. Jiménez-Colmenero; A. Herrero; T. Pintado; M. T. Solas; C. Ruiz-Capillas

2010-01-01

384

Simulation studies of diesel engine performance with oxygen enriched air and water emulsified fuels  

Microsoft Academic Search

A computer simulation code of a turbocharged, turbocompound diesel engine was modified to study the effects of using oxygen-enriched combustion air and water-emulsified diesel fuels. Oxygen levels of 21 percent to 40 percent by volume in the combustion air were studied. Water content in the fuel was varied from 0 percent to 50 percent mass. Simulation studies and a review

D. N. Assanis; D. Baker; R. R. Sekar; C. T. Siambekos; R. L. Cole; T. J. Marciniak

1990-01-01

385

An Experimental Investigation of Microexplosion in Emulsified Vegetable-Methanol Blend  

E-print Network

in emulsions causes a high probability of microexplosion event due to the sudden expansion of the emulsified fluid. Also, the effect of size on microexplosion was evident in the greater probability of explosion. Methanol-in-canola oil emulsion with 15...

Nam, Hyungseok

2012-07-16

386

Self-Emulsifying Drug Delivery Systems: Strategy for Improving Oral Delivery of Poorly Soluble Drugs  

Microsoft Academic Search

Drugs are most often administered by the oral route. However, more than 40% of new chemical entities exhibit poor aqueous solubility, resulting in unsatisfactory oral drug delivery. Recently, much attention has been focused on self- emulsifying drug delivery systems (SEDDS) to improve the oral bioavailability of poorly aqueous soluble drugs. SEDDS are isotropic mixtures of oil, surfactants, solvents and co-solvents\\/surfactants.

Jing-ling Tang; Jin Sun; Zhong-Gui He

2007-01-01

387

21 CFR 178.3400 - Emulsifiers and/or surface-active agents.  

Code of Federal Regulations, 2012 CFR

...acetoxyhydroxystearic acids) meeting the following specifications: Acid number 160-180, saponification number 210-235, iodine number 2-15, and epoxy groups 0-0.4 percent For use only:1. As a polymerization emulsifier at levels not to...

2012-04-01

388

HAZARDOUS AIR POLLUTANTS FROM THE COMBUSTION OF AN EMULSIFIED HEAVY FUEL OIL IN A FIRETUBE BOILER  

EPA Science Inventory

The report gives results of measuring emissions of hazardous air pollutants (HAPs) from the combustion flue gases of a No. 6 fuel oil, both with and without an emulsifying agent, in a 2.5 million Btu/hr (732 kW) firetube boiler with the purpose of determining the impacts of the e...

389

THE INFLUENCE OF CARBON BURNOUT ON SUBMICRON PARTICLE FORMATION FROM EMULSIFIED FUEL OIL COMBUSTION  

EPA Science Inventory

The paper gives results of an examination of particle behavior and particle size distributions from the combustion of different fuel oils and emulsified fuels in three experimental combusators. Results indicate that improved carbon (C) burnout from fule oil combustion, either by...

390

Peroxidase mediated conjugation of corn fibeer gum and bovine serum albumin to improve emulsifying properties  

Technology Transfer Automated Retrieval System (TEKTRAN)

The emulsifying properties of corn fiber gum (CFG), a naturally-occurring polysaccharide protein complex, were improved by kinetically controlled formation of hetero-covalent linkages with bovine serum albumin (BSA), using horseradish peroxidase. The formation of hetero-crosslinked CFG-BSA conjugate...

391

Effects of water-emulsified fuel on a diesel engine generator's thermal efficiency and exhaust.  

PubMed

Water-emulsified diesel has proven itself as a technically sufficient improvement fuel to improve diesel engine fuel combustion emissions and engine performance. However, it has seldom been used in light-duty diesel engines. Therefore, this paper focuses on an investigation into the thermal efficiency and pollution emission analysis of a light-duty diesel engine generator fueled with different water content emulsified diesel fuels (WD, including WD-0, WD-5, WD-10, and WD-15). In this study, nitric oxide, carbon monoxide, hydrocarbons, and carbon dioxide were analyzed by a vehicle emission gas analyzer and the particle size and number concentration were measured by an electrical low-pressure impactor. In addition, engine loading and fuel consumption were also measured to calculate the thermal efficiency. Measurement results suggested that water-emulsified diesel was useful to improve the thermal efficiency and the exhaust emission of a diesel engine. Obviously, the thermal efficiency was increased about 1.2 to 19.9%. In addition, water-emulsified diesel leads to a significant reduction of nitric oxide emission (less by about 18.3 to 45.4%). However the particle number concentration emission might be increased if the loading of the generator becomes lower than or equal to 1800 W. In addition, exhaust particle size distributions were shifted toward larger particles at high loading. The consequence of this research proposed that the water-emulsified diesel was useful to improve the engine performance and some of exhaust emissions, especially the NO emission reduction. Implications: The accumulated test results provide a good basis to resolve the corresponding pollutants emitted from a light-duty diesel engine generator. By measuring and analyzing transforms of exhaust pollutant from this engine generator, the effects of water-emulsified diesel fuel and loading on emission characteristics might be more clear. Understanding reduction of pollutant emissions during the use of water-emulsified diesel helps improve the effectiveness of the testing program. The analyzed consequences provide useful information to the government for setting policies to curb pollutant emissions from a light-duty diesel engine generator more effectively. PMID:25185398

Syu, Jin-Yuan; Chang, Yuan-Yi; Tseng, Chao-Heng; Yan, Yeou-Lih; Chang, Yu-Min; Chen, Chih-Chieh; Lin, Wen-Yinn

2014-08-01

392

In vivo Evaluation of Self Emulsifying Drug Delivery System for Oral Delivery of Nevirapine  

PubMed Central

Nevirapine is a highly lipophilic and water insoluble non-nucleoside reverse transcriptase inhibitor used for the treatment of HIV-1 infection. Lymphoid tissue constitutes the major reservoir of HIV virus and infected cells in HIV-infected patients. Self-emulsifying drug delivery system, using long chain triglycerides, is a popular carrier of drugs due to their ability to transport lipophilic drugs into the lymphatic circulation. However, HIV/AIDS patients experience a variety of functional and anatomical abnormalities in gastrointestinal tract that result in diarrhoea and nutrient malabsorption. Medium chain triglycerides are readily absorbed from the small bowel under conditions in which the absorption of long chain triglycerides is impaired. Therefore, nevirapine self-emulsifying drug delivery system containing medium chain fatty acid, caprylic acid and a solubilizer, Soluphor® P (2-pyrrolidone) was developed and found to be superior to the marketed conventional suspension with respect to in vitro diffusion and ex vivo intestinal permeability. This self-emulsifying drug delivery system has now been further investigated for in vivo absorption in an animal model. The contribution of caprylic acid and Soluphor® P on in vivo absorption of nevirapine was also studied in the present study. The bioavailability of nevirapine from self-emulsifying drug delivery system, after oral administration, was 2.69 times higher than that of the marketed suspension. The improved bioavailability could be due to absorption of nevirapine via both portal and intestinal lymphatic routes. The study indicates that medium chain or structured triglycerides can be a better option to develop self-emulsifying drug delivery system for lipophilic and extensively metabolised drugs like nevirapine for patients with AIDS-associated malabsorption. PMID:25035533

Chudasama, A. S.; Patel, V. V.; Nivsarkar, M.; Vasu, Kamala K.; Shishoo, C. J.

2014-01-01

393

Enhanced antitumor efficacy of vitamin E TPGS-emulsified PLGA nanoparticles for delivery of paclitaxel.  

PubMed

Nanoparticles are efficient delivery vehicles for cancer therapy such as paclitaxel (PTX). In this study, we formulated PTX into PLGA polymeric nanoparticles. Vitamin E TPGS was used as an emulsifier to stabilize the nanoparticle formulation. PTX was encapsulated in TPGS-emulsified polymeric nanoparticles (TENPs) by a nanoprecipitation method in ethanol-water system. The resultant PTX-TENPs showed a very uniform particle size (?100 nm) and high drug encapsulation (>80%). The cytotoxicity of PTX-TENPs was examined in A549 lung cancer cell line. Preferential tumor accumulation of TENPs was observed in the A549 lung cancer xenograft model. Tumor growth was significantly inhibited by intravenous injection of PTX-TENPs. Our results suggested that the modified nanoprecipitation method holds great potential for the fabrication of the PTX loaded polymeric nanoparticles. TPGS can be used in the manufacture of polymeric nanoparticles for the controlled release of PTX and other anti-cancer drugs. PMID:25456995

Sun, Yanbin; Yu, Bo; Wang, Guoying; Wu, Yongsheng; Zhang, Xiaomin; Chen, Yanmin; Tang, Suoqing; Yuan, Yuan; Lee, Robert J; Teng, Lesheng; Xu, Shun

2014-11-01

394

Comparison of structures of gas atomized and of emulsified highly undercooled Ni-Sn alloy droplets  

NASA Technical Reports Server (NTRS)

A comparison is made of microstructures of droplets of Ni-Sn alloys rapidly solidified by gas atomization and in a glass emulsifying medium. Cooling rate of the gas atomized particles ranged from 10 to the 3rd to 10 to the 6th K/s depending on droplet diameter (20-230 microns). In the hypoeutectic alloy studied, /Ni-(25 wt pct Sn)/, most particles showed a dendritic structure. These same particles, melted and resolidified in a glass medium using DTA (Differential Thermal Analysis), showed undercoolings up to 280 K: the structures were dendritic at low undercoolings and nondendritic at undercoolings above 220 K. It is concluded that the gas atomized particles exhibited little or no undercooling before nucleation; the solidification time of the undercooled emulsified droplets is substantially less than that of gas atomized droplets, and the undercooling required to achieve nondendritic structure depends on sample size.

Yamamoto, M.; Wu, Y.; Shiohara, Y.; Flemings, M. C.

1986-01-01

395

Identification of an emulsifier and conditions for preparing stable nanoemulsions containing the antioxidant astaxanthin.  

PubMed

In this study, oil-in-water nanoemulsions of astaxanthin were prepared by high-pressure homogenization. The influence of emulsifying conditions including emulsifier type, concentration, passing time, astaxanthin concentration and coantioxidants were optimized. The stabilities of nanoemulsions were measured using zetasizer, FF-SEM, TEM, colorimeter and particle size analyzer. The mean diameter of the dispersed particles containing astaxanthin ranged from 160 to 190 nm. The size distribution was unimodal and extended from 100 to 200 nm. The nanoemulsions prepared with glyceryl citrate/lactate/linoleate/oleate (glyceryl ester) had smaller particle size and narrower size distribution than the emulsion prepared with hydrogenated lecithin. Stable incorporation of astaxanthin in nanoemulsion was performed and checked using HPLC, FF-SEM and TEM. The nanoemulsion was not significantly affected during storage under light and thermal condition for one month indicating that the nanoemulsion had a zeta potential of less than -41 mV, indicating a stable colloid. PMID:21883294

Kim, D-M; Hyun, S-S; Yun, P; Lee, C-H; Byun, S-Y

2012-02-01

396

Effect of emulsifiers and fat crystals on shear induced droplet break-up, coalescence and phase inversion  

Microsoft Academic Search

We have investigated the breakup and coalescence of food grade emulsions under dynamic conditions with a range of emulsifiers. Not unexpectedly, breakup of the emulsions varied with applied shear. The coalescence rate for an emulsifier free system with purified sunflower oil after the imposed shear was reduced, was measured at 1.2×10?2s?1, which is similar to reported values for non-food systems

Ian T. Norton; Fotis Spyropoulos; Phil W. Cox

2009-01-01

397

Toxicity studies on the components of an oil-spill emulsifier using Lichina pygmaea and Xanthoria parietina  

Microsoft Academic Search

Previous work on lichens suggested that the toxic component of the oil-spill emulsifier BP 1002 might be the surfactant rather than the solvent, to which toxicity is usually attributed. The effect of the emulsifier on both Lichina pygmaea and Xanthoria parietina (measured by reduced total photosynthetic 14C-fixation and enhanced loss of labelled material from the lichen) was shown to be

D. H. Brown

1973-01-01

398

Preparation of spherical, submicrometer oxide particles by hydrolysis of emulsified alkoxide droplets  

SciTech Connect

A new method for forming spherical, submicrometer ceramic oxide particles by the hydrolysis of emulsified alkoxide droplets is reported. Emulsions are formed of alkoxide droplets dispersed in an inert, polar solvent. The alkoxide droplets are hydrolyzed to form oxide particles by adding water to the emulsion. It was shown that individual droplets acted as microreactors and controlled the powder size, shape, and composition. Both single-oxide and mixed-oxide powders were formed by this technique.

Hardy, A.B.; Rhine, W.E.; Bowen, H.K. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Ceramics Processing Research Lab.)

1993-01-01

399

Effect of some emulsifiers on the structure of extrudates with high content of fat  

Microsoft Academic Search

A study on extruded foods with wheat flour, almond flour, water and four kinds of emulsifiers (soy lecithin (SL), sucrose esters (SE), mono-glycerides (MG) and mono- and di-glycerides (MDG) of fatty acids) was carried out. In particular, the effects of these additives on the oil loss, which occurs during extrusion processing, and the structural characteristics of extrudates were evaluated.Results showed

Teresa De Pilli; Barbara F. Carbone; Anna G. Fiore; Carla Severini

2007-01-01

400

Study on Different Emulsifiers to Retain Fatty Fraction During Extrusion of Fatty Flours  

Microsoft Academic Search

Cereal Chem. 82(5):494-498 Doughs made from wheat and almond flours, water, and five types of emulsifiers commonly used in confectionary and bakery products (soy lecithin, sucrose esters, mono-glycerides, mono- and di-glycerides of fatty acids, and diacetyl tartaric acid esters of monoglycerides (DATEM)) were studied. To evaluate the additive ability to retain the fatty fraction during the extrusion process, electrical conductivity

Teresa De Pilli; Roma Giuliani; Barbara F. Carbone; Antonio Derossi; Carla Severini

2005-01-01

401

Evaluation of emulsifier stability of biosurfactant produced by Saccharomyces lipolytica CCT0913  

Microsoft Academic Search

Surface-active compounds of biological origin are w idely used for many industries (cosmetic, food, pet rochemical). The Saccharomyces lipolytica CCT-0913 was able to grow and produce a biosurfact ant on 5% (v\\/v) diesel-oil at pH 5.0 and 32 o C. The cell-free broth emulsified and stabilized th e oil-in-water emulsion through a first order kinet ics. The results showed that

Álvaro Silva Lima; Ranulfo Monte Alegre

2009-01-01

402

Effects of Emulsifying Salts on the Turbidity and Calcium-Phosphate–Protein Interactions in Casein Micelles  

Microsoft Academic Search

Influence of emulsifying salts (ES) on some physical properties of casein micelles was investigated. A recon- stituted milk protein concentrate (MPC) solution (5% wt\\/wt) was used as the protein source and the effects of ES (0 to 2.0% (wt\\/wt)) were estimated by measuring turbidity, acid-base titration curves and amount of ca- sein-bound Ca and inorganic P (Pi). Various ES, triso-

R. Mizuno; J. A. Lucey

2005-01-01

403

Preparation and emulsifying properties of polyethylene glycol (15OO) diesters of fatty acids  

Microsoft Academic Search

Oil soluble polyethylene glycol (PEG-1500) diesters of stearic, 12-hydroxystearic, oleic and 12-hydroxy oleic (ricinoleic)\\u000a acids were prepared by standard condensation reaction procedure. The surface active\\/emulsifying properties of the products\\u000a were evaluated by determining interfacial tension and through performance test in making water-in-oil emulsion. The presence\\u000a of double bond or hydroxyl group in the C18 acids, PEG content of reacting mixture,

D. N. Bhattacharyya; S. Krishnan; R. Y. Kelkar; S. V. Chikale

1984-01-01

404

Emulsifying effect of dimethyldioctadecylammonium-hectorite in polystyrene\\/poly(ethyl methacrylate) blends  

Microsoft Academic Search

An organically modified clay, dimethyldioctadecylammonium-hectorite (DMDO-Hect.), was used as an emulsifier for the immiscible polystyrene\\/poly(ethyl methacrylate) (PS\\/PEMA) pair of polymers. The organoclay in this blend adsorbs selectively the PEMA chains and creates PEMA\\/DMDO-Hect. intercalated structures within which the PS chains are shaped into separate domains. The size of these domains decreases as the concentration of the inorganic DMDO-Hect. partner increases

D Voulgaris; D Petridis

2002-01-01

405

The Effects of Protein Content of Flour and Emulsifiers on Tanoor Bread Quality  

Microsoft Academic Search

Emulsifiers (SSL, GMS-90, DATEM, S-570, S-1170, S-1670, P-1670) with three concentrations (0·25%, 0·50%, 0·75%) and three flour types (soft red winter wheat flour with 9·7% protein, hard red winter wheat flour with 11·2% protein, and hard red spring wheat flour with 14·2% protein) were used to evaluate their effects on tanoor bread quality. For baking breads, an air impingement oven

N. Farvili; C. E. Walker; J. Qarooni

1997-01-01

406

Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome.  

PubMed

The intestinal tract is inhabited by a large and diverse community of microbes collectively referred to as the gut microbiota. While the gut microbiota provides important benefits to its host, especially in metabolism and immune development, disturbance of the microbiota-host relationship is associated with numerous chronic inflammatory diseases, including inflammatory bowel disease and the group of obesity-associated diseases collectively referred to as metabolic syndrome. A primary means by which the intestine is protected from its microbiota is via multi-layered mucus structures that cover the intestinal surface, thereby allowing the vast majority of gut bacteria to be kept at a safe distance from epithelial cells that line the intestine. Thus, agents that disrupt mucus-bacterial interactions might have the potential to promote diseases associated with gut inflammation. Consequently, it has been hypothesized that emulsifiers, detergent-like molecules that are a ubiquitous component of processed foods and that can increase bacterial translocation across epithelia in vitro, might be promoting the increase in inflammatory bowel disease observed since the mid-twentieth century. Here we report that, in mice, relatively low concentrations of two commonly used emulsifiers, namely carboxymethylcellulose and polysorbate-80, induced low-grade inflammation and obesity/metabolic syndrome in wild-type hosts and promoted robust colitis in mice predisposed to this disorder. Emulsifier-induced metabolic syndrome was associated with microbiota encroachment, altered species composition and increased pro-inflammatory potential. Use of germ-free mice and faecal transplants indicated that such changes in microbiota were necessary and sufficient for both low-grade inflammation and metabolic syndrome. These results support the emerging concept that perturbed host-microbiota interactions resulting in low-grade inflammation can promote adiposity and its associated metabolic effects. Moreover, they suggest that the broad use of emulsifying agents might be contributing to an increased societal incidence of obesity/metabolic syndrome and other chronic inflammatory diseases. PMID:25731162

Chassaing, Benoit; Koren, Omry; Goodrich, Julia K; Poole, Angela C; Srinivasan, Shanthi; Ley, Ruth E; Gewirtz, Andrew T

2015-03-01

407

Effect of homogenization pressure, lipid content, and emulsifier content on the rheological properties of yogurt  

E-print Network

this effect. One theory suggests that fat globules act as "fillers" in the protein structure, thus making the gel structure stronger (Aguilera and Kessler, 1989; Aguilera and Kinsella, 1991; Xiong et al. 1991). Emulsifiers added to the yogurt mixture adsorb... of gels which contain no fat was small and large void spaces were present which reduced the strength of the gel (Xiong et al. , 1991). Gel strength decreased with increasing fat content when gels were made using washed natural milk fat globules which...

Jaar Sansur, Patricia Mary

1998-01-01

408

Acacia gum as modifier of thermal stability, solubility and emulsifying properties of ?-lactalbumin.  

PubMed

Protein-polysaccharide conjugates often display improved techno-functional properties when compared to their individual involved biomolecules. ?-Lactalbumin:acacia gum (?-la:AG) conjugates were prepared via Maillard reaction by the dry-heating method. Conjugate formation was confirmed using results of absorbance, o-phthalaldehyde test, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography. Techno-functional properties (emulsifying characteristics, solubility, and thermal stability) were evaluated for ?-la, ?-la/AG mixtures and ?-la:AG conjugates. Conjugate thermal stability was improved compared to pure ?-la treated at the same conditions of conjugate formation. Response surface methodology was used to establish models to predict solubility and emulsifying activity as functions of the salt concentration, pH and reaction time. ?-la:AG conjugate solubility is affected in a complex manner by the three factors analyzed. Emulsifying activity index (EAI) of ?-la is significantly affected by pH, while the ?-la:AG EAI is affected by the three analyzed factors. Both solubility and EAI are maximized with pH 8.0, NaCl concentration of 0.3 mol L(-1) and two days of Maillard reaction. PMID:25563962

de Oliveira, Fabíola Cristina; Dos Reis Coimbra, Jane Sélia; de Oliveira, Eduardo Basílio; Rodrigues, Marina Quadrio Raposo Branco; Sabioni, Rachel Campos; de Souza, Bartolomeu Warlene Silva; Santos, Igor José Boggione

2015-03-30

409

Emulsification by high frequency ultrasound using piezoelectric transducer: formation and stability of emulsifier free emulsion.  

PubMed

Emulsifier free emulsion was developed with a new patented technique for food and cosmetic applications. This emulsification process dispersed oil droplets in water without any emulsifier. Emulsions were prepared with different vegetable oil ratios 5%, 10% and 15% (v/v) using high frequency ultrasounds generated by piezoelectric ceramic transducer vibrating at 1.7 MHz. The emulsion was prepared with various emulsification times between 0 and 10h. Oil droplets size was measured by laser granulometry. The pH variation was monitored; electrophoretic mobility and conductivity variation were measured using Zêtasizer equipment during emulsification process. The results revealed that oil droplets average size decreased significantly (p<0.05) during the first 6h of emulsification process and that from 160 to 1 ?m for emulsions with 5%, 10% and from 400 to 29 ?m for emulsion with 15% of initial oil ratio. For all tested oil ratios, pH measurement showed significant decrease and negative electrophoretic mobility showed the accumulation of OH(-) at oil/water interface leading to droplets stability in the emulsion. The conductivity of emulsions showed a decrease of the ions quantity in solution, which indicated formation of positive charge layer around OH(-) structure. They constitute a double ionic layer around oil particles providing emulsion stability. This study showed a strong correlation between turbidity measurement and proportion of emulsified oil. PMID:24315670

Kaci, Messaouda; Meziani, Smail; Arab-Tehrany, Elmira; Gillet, Guillaume; Desjardins-Lavisse, Isabelle; Desobry, Stephane

2014-05-01

410

Interfacial and emulsifying properties of soybean peptides with different degrees of hydrolysis.  

PubMed

In this study, the effects of the degree of hydrolysis on the interfacial and emulsifying properties of soybean peptides were evaluated based on surface and interfacial tension, dynamic light scattering (DLS), and freeze-fracture transmission electron microscopy (FF-TEM) analyses. Of the five evaluated soybean peptides (SP95, SP87, SP75, SP49, and SP23), those with higher degrees of hydrolysis (SP95 and SP87) did not exhibit noticeable surface-active properties in water, whereas those with relatively low degrees of hydrolysis (SP75, SP49, and SP23) exhibited remarkable surface tension-lowering activity. The latter set (SP75, SP49, and SP23) also formed giant associates with average sizes ranging from 64.5 nm to 82.6 nm above their critical association concentration (CAC). Moreover, SP23 with the lowest degree of hydrolysis exhibited excellent emulsifying activity for soybean oil, and FF-TEM analysis demonstrated that the emulsions were stabilized by a lamella-like multilayer peptide structure on the oil droplets that prevented coagulation. The peptide with the lowest degree of hydrolysis (SP23) was effective not only for soybean oil emulsification, but also for the emulsification of liquid paraffin and silicon oil that are generally difficult to emulsify. PMID:25476545

Imura, Tomohiro; Nakayama, Mio; Taira, Toshiaki; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

2015-02-01

411

Influence of emulsifiers on the characteristics of polyurethane structures used as drug carrier  

PubMed Central

Background Emulsifiers have a significant role in the emulsion polymerization by reducing the interfacial tension thus increasing the stability of colloidal dispersions of polymer nanostructures. This study evaluates the impact of four emulsifiers on the characteristics of polyurethane hollow structures used as drug delivery system. Results Polyurethane (PU) structures with high stability and sizes ranging from nano- to micro-scale were obtained by interfacial polyaddition combined with spontaneous emulsification. The pH of PU aqueous solutions (0.1% w/w) was slightly acidic, which is acceptable for products intended to be used on human skin. Agglomerated structures with irregular shapes were observed by scanning electron microscopy. The synthesized structures have melting points between 245-265°C and reveal promising results in different evaluations (TEWL, mexametry) on murine skin. Conclusions In this study hollow PU structures of reduced noxiousness were synthesized, their size and stability being influenced by emulsifiers. Such structures could be used in the pharmaceutical field as future drug delivery systems. PMID:23575277

2013-01-01

412

Removal of Emulsified Oil from Water by Fruiting Bodies of Macro-Fungus (Auricularia polytricha)  

PubMed Central

The aim of this study was to investigate the feasibility of utilizing the fruiting bodies of a jelly macro-fungus Auricularia polytricha as adsorbents to remove emulsified oil from water. The effects of several factors, including temperature, initial pH, agitation speed, and adsorbent dosage, were taken into account. Results showed that the optimized conditions for adsorption of A. polytricha were a temperature of 35°C, pH of 7.5, and agitation speed of 100 rpm. The adsorption kinetics were characterized by the pseudo-first order model, which showed the adsorption to be a fast physical process. The Langmuir-Freundlich isotherm described the adsorption very well and predicted the maximum adsorption capacity of 398 mg g?1, under optimized conditions. As illustrated by scanning electron micrographs, the oil particles were adsorbed onto the hairs covering the bottom surface and could be desorbed by normal temperature volatilization. The material could be used as an emulsified oil adsorbent at least three times, retaining more than 95% of the maximum adsorption capacity. The results demonstrated that the fruiting bodies of A. polytricha can be a useful adsorbent to remove emulsified oil from water. PMID:24743498

Yang, Xunan; Guo, Mengting; Wu, Yinghai; Wu, Qunhe; Zhang, Renduo

2014-01-01

413

Peroxidase-mediated conjugation of corn fiber gum and bovine serum albumin to improve emulsifying properties.  

PubMed

The emulsifying properties of corn fiber gum (CFG), a naturally occurring polysaccharide-protein complex, was improved by kinetically controlled formation of hetero-covalent linkages with bovine serum albumin (BSA), using horseradish peroxidase (HRP). The formation of hetero-crosslinked CFG-BSA conjugates was confirmed using ultraviolet-visible and Fourier-transform infrared analyses. The optimum CFG-BSA conjugates were prepared at a CFG:BSA weight ratio of 10:1, and peroxidase:BSA weight ratio of 1:4000. Selected CFG-BSA conjugates were used to prepare oil-in-water emulsions; the emulsifying properties were better than those of emulsions stabilized with only CFG or BSA. Measurements of mean droplet sizes and zeta potentials showed that CFG-BSA-conjugate-stabilized emulsions were less susceptible to environmental stresses, such as pH changes, high K ionic strengths, and freeze-thaw treatments than CFG- or BSA-stabilized emulsions. These conjugates have potential applications as novel emulsifiers in food industry. PMID:25542109

Liu, Yan; Qiu, Shuang; Li, Jinlong; Chen, Hao; Tatsumi, Eizo; Yadav, Madhav; Yin, Lijun

2015-03-15

414

New emulsifying and cryoprotective exopolysaccharide from Antarctic Pseudomonas sp. ID1.  

PubMed

Pseudomonas sp. ID1 is a cold-adapted bacterium isolated from a marine sediment sample collected from South Shetland Islands (Antarctica) that is noted for the highly mucous appearance of its colonies. In this work, we have characterized an exopolysaccharide (EPS) produced by this strain, which is mainly composed of glucose, galactose and fucose, and has a molecular mass higher than 2×10(6) Da. We have also studied its potential biotechnological applications as an emulsifier and cryoprotectant agent. The EPS emulsifying activity against different food and cosmetic oils was much higher than commercial gums such as xanthan gum and arabic gum, and surfarctants such as Span 20. It formed highly stable emulsions against the cosmetic oil cetiol V, exhibiting pseudoplastic flow behavior, low thixotrophy and yield stress. The EPS of Pseudomonas sp. ID1 conferred significant cryoprotection for the strain itself as well as for other bacteria, including Escherichia coli, suggesting a universal cryoprotectant role. The cryoprotective activity of the EPS showed a clear dose-response relation at -20 °C and -80 °C and was significantly higher than that observed for the membrane stabilizer fetal bovine serum (FBS). These properties make the EPS of Pseudomonas sp. ID1 a promising alternative to commercial polysaccharides as an emulsifier and cryoprotectant agent for food, pharmaceutical and cosmetic industries. PMID:25498731

Carrión, Ornella; Delgado, Lidia; Mercade, Elena

2015-03-01

415

Iron overdose  

MedlinePLUS

Iron is an ingredient in many mineral and vitamin supplements. Iron supplements are also sold by themselves. Types include: Ferrous sulfate (Feosol, Slow Fe) Ferrous gluconate (Fergon) Ferrous fumarate (Femiron, Feostat) Note: This list may not be all-inclusive.

416

Eat Iron?!!  

NSDL National Science Digital Library

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

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

417

Formulation Strategies to Improve the Bioavailability of Poorly Absorbed Drugs with Special Emphasis on Self-Emulsifying Systems  

PubMed Central

Poorly water-soluble drug candidates are becoming more prevalent. It has been estimated that approximately 60–70% of the drug molecules are insufficiently soluble in aqueous media and/or have very low permeability to allow for their adequate and reproducible absorption from the gastrointestinal tract (GIT) following oral administration. Formulation scientists have to adopt various strategies to enhance their absorption. Lipidic formulations are found to be a promising approach to combat the challenges. In this review article, potential advantages and drawbacks of various conventional techniques and the newer approaches specifically the self-emulsifying systems are discussed. Various components of the self-emulsifying systems and their selection criteria are critically reviewed. The attempts of various scientists to transform the liquid self-emulsifying drug delivery systems (SEDDS) to solid-SEDDS by adsorption, spray drying, lyophilization, melt granulation, extrusion, and so forth to formulate various dosage forms like self emulsifying capsules, tablets, controlled release pellets, beads, microspheres, nanoparticles, suppositories, implants, and so forth have also been included. Formulation of SEDDS is a potential strategy to deliver new drug molecules with enhanced bioavailability mostly exhibiting poor aqueous solubility. The self-emulsifying system offers various advantages over other drug delivery systems having potential to solve various problems associated with drugs of all the classes of biopharmaceutical classification system (BCS). PMID:24459591

Gupta, Shweta; Kesarla, Rajesh

2013-01-01

418

Preparation of polystyrene latex particles by ?-rays-induced emulsifier-free emulsion polymerization  

NASA Astrophysics Data System (ADS)

Monodisperse polystyrene latex particles were prepared by 60Co- ?-ray radiation-induced emulsifier-free emulsion polymerization with the use of surfactant monomer at room temperature. The surfactant monomer 10(9)-hydroxyl-9(10)-allyl ether octadecanoic acid (HAEOA) was synthesized and characterized by FT-IR and 1H-NMR spectra. TEM was used to characterize the polystyrene latex particles. HAEOA acted as not only a comonomer but also a stabilizer to copolymerize with styrene and stabilize the polystyrene latex particles. Kinetics analysis shows that there is no constant rate stage which seems to indicate a droplet nucleation mechanism.

Wang, Xinbo; Zhang, Zhicheng

2006-09-01

419

Effect of high-pressure treatment on emulsifying properties of soybean proteins  

Microsoft Academic Search

Modifications of emulsifying properties of soybean protein isolates (SPI) by high-pressure processing have been studied. SPI solutions at 10g\\/l in two pH conditions: alkaline (pH 8: SPI8) and acidic (pH 3: SPI3) were treated by high-pressure at various pressure levels (200, 400 and 600MPa for 10min at 10°C). Oil-in-water emulsions (30\\/70) were prepared with untreated and high-pressure treated SPI3 and

M. C. Puppo; F. Speroni; N. Chapleau; M. de Lamballerie; M. C. Añón; M. Anton

2005-01-01