These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
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

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...

3

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...

4

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...

5

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

6

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

7

Degradation of organic and inorganic contaminants by zero valent iron  

E-print Network

DEGRADATION OF ORGANIC AND INORGANIC CONTAMINANTS BY ZERO VALENT IRON A Thesis DEEPAK BABU MALLA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1997 Major Subject: Civil Engineering DEGRADATION OF ORGANIC AND INORGANIC CONTAMINANTS BY ZERO VALENT IRON A Thesis DEEPAK BABU MALLA Submitted to Texas A&M University in partial fulfillment of the requirements for the degree...

Malla, Deepak Babu

2012-06-07

8

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...

9

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...

10

Electrochemical depassivation of zero-valent iron for trichloroethene reduction.  

PubMed

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

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

2012-11-15

11

Remediation of TNT and RDX in Groundwater Using Zero-Valent Iron Permeable Reactive Barriers.  

National Technical Information Service (NTIS)

This Cost and Performance Report documents the demonstration of a zero-valent iron (ZVI) permeable reactive barriers (PRB) for the removal of explosives from groundwater. The demonstration was conducted at the Cornhusker Army Ammunition Plant (CAAP) near ...

P. Tratnyek, R. Johnson

2008-01-01

12

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 10mM HEPES buffer was studied in aqueous, anaerobic batch systems. Orange II was reduced by cleavage of the azo linkage, as evidenced by the production of sulfanilic acid (a substituted ani...

13

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...

14

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...

15

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

Microsoft Academic Search

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 implica- tions of these processes with regard to the stability of arsenic and long-term remedial performance of the permeable reactive barrier (PRB) technology. A high concentration

Hsing-Lung Lien; Richard T. Wilkin

2004-01-01

16

Partial oxidation (?aging?) and surface modification decrease the toxicity of nano-sized zero valent iron  

EPA Science Inventory

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

17

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

Microsoft Academic Search

The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the stability of arsenic and long-term remedial performance of the permeable reactive barrier (PRB) technology. A high concentration arsenic

Hsing-Lung Lien; Richard T. Wilkin

2005-01-01

18

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

19

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

20

Enhanced dechlorination of chlorobenzene by microwave-induced zero-valent iron: particle effects and activation energy  

Microsoft Academic Search

Organic compounds such as chlorobenzene cannot be effectively decomposed with currently available biological and chemical\\u000a treatment methods. Preliminary studies show that nano-scale zero-valent iron particles irradiated by microwave is effective\\u000a in decomposing chemically refractive organic compounds such as chlorobenzene. In this study, microwave is applied to enhance\\u000a chlorobenzene removal using micron-scale iron particles and nano-scale zero-valent iron particles suspended in

Chien-Li Lee; Hsien-Yi Lee; Kuo-Hung Tseng; P. K. Andy Hong; Chih-Ju G. Jou

21

Effects of dissolved oxygen on dye removal by zero-valent iron  

Microsoft Academic Search

Effects of dissolved oxygen concentrations on dye removal by zero-valent iron (Fe0) were investigated. The Vibrio fischeri light inhibition test was employed to evaluate toxicity of decolorized solution. Three dyes, Acid Orange 7 (AO7, monoazo), Reactive Red 120 (RR120, diazo), and Acid Blue 9 (AB9, triphenylmethane), were selected as model dyes. The dye concentration and Fe0 dose used were 100mgL?1

Kai-Sung Wang; Chiou-Liang Lin; Ming-Chi Wei; Hsiu-Hao Liang; Heng-Ching Li; Chih-Hua Chang; Yung-Tai Fang; Shih-Hsien Chang

2010-01-01

22

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

Microsoft Academic Search

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

S. Kwong; J. Small; B. Tahar

2007-01-01

23

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 2.34.5; total dissolved solids 1400016000 mgl?1). Metal removal from solution and

Richard T. Wilkin; Mary S. McNeil

2003-01-01

24

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 ...

25

Assessment of Influence of Magnetic Forces on Aggregation of Zero-valent Iron Nanoparticles  

PubMed Central

Aggregation of zero-valent nanoparticles in groundwater is influenced by several physical phenomena. The article shortly introduces preceding works in modeling of aggregation of small particles including influence of sedimentation, velocity profile of water, heat fluctuations, and surface electric charge. A brief description of inclusion of magnetic forces into the model of aggregation follows. Rate of influence of the magnetic forces on the aggregation depends on the magnitude of magnetization of the particles, radius of nanoparticles, size of the aggregates, and their concentration in the solution. Presented results show that the magnetic forces have significant influence on aggregation especially of the smallest iron particles.

2011-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

27

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

28

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

29

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

30

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

31

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

32

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

33

Gas-bubbled nano zero-valent iron process for high concentration arsenate removal.  

PubMed

In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 ?g/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only. PMID:21256674

Tanboonchuy, Visanu; Hsu, Jia-Chin; Grisdanurak, Nurak; Liao, Chih-Hsiang

2011-02-28

34

Nanoscale zero valent iron and bimetallic particles for contaminated site remediation  

NASA Astrophysics Data System (ADS)

Since the late 1990s, the use of nano zero valent iron (nZVI) for groundwater remediation has been investigated for its potential to reduce subsurface contaminants such as PCBs, chlorinated solvents, and heavy metals. nZVI shows tremendous promise in the environmental sector due to its high reactivity and as such, numerous laboratory and field studies have been performed to assess its effectiveness. This paper reviews the current knowledge of nZVI/bimetallic technology as it pertains to subsurface remediation of chlorinated solvents and heavy metals. The manuscript provides background on the technology, summarizing nZVI reactions with chlorinated solvents and metals, and examines the factors affecting nZVI reactivity. Studies on subsurface transport of bare and coated nZVI particles are also reviewed and challenges with field implementation are discussed. This manuscript offers a comprehensive review of nZVI technology and highlights the work still needed to optimize it for subsurface remediation.

O'Carroll, Denis; Sleep, Brent; Krol, Magdalena; Boparai, Hardiljeet; Kocur, Christopher

2013-01-01

35

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

Microsoft Academic Search

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

Man Zhang; Feng He; Dongye Zhao; Xiaodi Hao

2011-01-01

36

Mass Transfer Effects on Kinetics of Dibromoethane Reduction by Zero- Valent Iron in Packed-Bed Reactors.  

National Technical Information Service (NTIS)

Mass transfer effects on the kinetics of 1,2-dibromoethane (EDB) reduction by zero-valent iron (ZVI) in batch reactors, a laboratory scale packed-bed reactor, and a pilot scale packed-bed reactor are described. EDB was debrominated by ZVI to ethylene and ...

G. Loraine, D. Burris, L. Li J. Schoolfield

2002-01-01

37

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...

38

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

Microsoft Academic Search

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

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

39

Multicomponent reactive transport in an in situ zero-valent iron cell  

SciTech Connect

Data collected from a field study of in situ zero-valent iron treatment for TCE were analyzed in the context of coupled transport and reaction processes. The focus of this analysis was to understand the behavior of chemical components, including contaminants, in groundwater transported through the iron cell of a pilot-scale funnel and gate treatment system. A multicomponent reactive transport simulator was used to simultaneously model mobile and nonmobile components undergoing equilibrium and kinetic reactions including TCE degradation, parallel iron dissolution reactions, precipitation of secondary minerals, and complexation reactions. The resulting mechanistic model of coupled processes reproduced solution chemistry behavior observed in the iron cell with a minimum of calibration. These observations included the destruction of TCE and cis-1,2-DCE; increases in pH and hydrocarbons; and decreases in EH, alkalinity, dissolved O2 and CO2, and major ions (i.e., Ca, Mg, Cl, sulfate, nitrate). Mineral precipitation in the iron zone was critical to correctly predicting these behaviors. The dominant precipitation products were ferrous hydroxide, siderite, aragonite, brucite, and iron sulfide. In the first few centimeters of the reactive iron cell, these precipitation products are predicted to account for a 3% increase in mineral volume per year, which could have implications for the longevity of favorable barrier hydraulics and reactivity. The inclusion of transport was key to understanding the interplay between rates of transport and rates of reaction in the field.

Yabusaki, Steven B. (BATTELLE (PACIFIC NW LAB)); Cantrell, Kirk J. (BATTELLE (PACIFIC NW LAB)); Sass, Bruce (BCO); Steefel, Carl (Lawrence Livermore National Laboratory)

2000-12-01

40

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

PubMed

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

Tkaczynska, A

2013-01-01

41

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

42

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

43

[Removal of arsenate from drinking water by activated carbon supported nano zero-valent iron].  

PubMed

A new adsorbent, activated carbon impregnated with nano zero-valent iron was prepared, which size of the needle-shaped iron particles in the pores of carbon was (30-500) nm x (1000-3000) nm and approximately 8.2% of iron was loaded onto it. The arsenate removal percentage was 99.5% by 1.5 g/L NZVI/AC in the 2 mg/L arsenic solution at pH 6.5 and (25 +/- 2) degrees C. The adsorption capacity was about 15.4 mg/g when equilibrium concentration was 1.0 mg/L. Kinetics revealed that uptake of arsenate ion by NZVI/AC was 91.4% in the first 12 h and equilibrium time was about 72 h. The intraparticle diffusion model was applied to study the mechanics of arsenate in the activated carbon. The presence of phosphate and silicate could significantly decrease arsenate removal while the effects of the other anions and cations on the arsenic removal were neglectable. NZVI/AC can be effectively regenerated when elution is done with 0.1 mol/L NaOH solution. Our results suggest that NZVI/AC is a suitable candidate for drinking water treatment due to its high reactivity. PMID:20187387

Zhu, Hui-jie; Jia, Yong-feng; Yao, Shu-hu; Wu, Xing; Wang, Shu-ying

2009-12-01

44

Debromination of decabromodiphenyl ether by organo-montmorillonite-supported nanoscale zero-valent iron: preparation, characterization and influence factors.  

PubMed

An organo-montmorillonite-supported nanoscale zero-valent iron material (M-NZVI) was synthesized to degrade decabromodiphenyl ether (BDE-209). The results showed that nanoscale zero-valent iron had good dispersion on organo-montmorillonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30-90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased. PMID:25076541

Pang, Zhihua; Yan, Mengyue; Jia, Xiaoshan; Wang, Zhenxing; Chen, Jianyu

2014-02-01

45

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

46

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

47

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

48

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

PubMed

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

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

2014-01-01

49

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

50

The impact of zero-valent iron nanoparticles upon soil microbial communities is context dependent.  

PubMed

Nanosized zero-valent iron (nZVI) is an effective land remediation tool, but there remains little information regarding its impact upon and interactions with the soil microbial community. nZVI stabilised with sodium carboxymethyl cellulose was applied to soils of three contrasting textures and organic matter contents to determine impacts on soil microbial biomass, phenotypic (phospholipid fatty acid (PLFA)), and functional (multiple substrate-induced respiration (MSIR)) profiles. The nZVI significantly reduced microbial biomass by 29 % but only where soil was amended with 5 % straw. Effects of nZVI on MSIR profiles were only evident in the clay soils and were independent of organic matter content. PLFA profiling indicated that the soil microbial community structure in sandy soils were apparently the most, and clay soils the least, vulnerable to nZVI suggesting a protective effect imparted by clays. Evidence of nZVI bactericidal effects on Gram-negative bacteria and a potential reduction of arbuscular mycorrhizal fungi are presented. Data imply that the impact of nZVI on soil microbial communities is dependent on organic matter content and soil mineral type. Thereby, evaluations of nZVI toxicity on soil microbial communities should consider context. The reduction of AM fungi following nZVI application may have implications for land remediation. PMID:23007947

Pawlett, Mark; Ritz, Karl; Dorey, Robert A; Rocks, Sophie; Ramsden, Jeremy; Harris, Jim A

2013-02-01

51

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

PubMed

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

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

2010-03-01

52

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

53

Enhanced anaerobic digestion of waste activated sludge digestion by the addition of zero valent iron.  

PubMed

Anaerobic digestion is promising technology to recover energy from waste activated sludge. However, the sludge digestion is limited by its low efficiency of hydrolysis-acidification. Zero valent iron (ZVI) as a reducing material is expected to enhance anaerobic process including the hydrolysis-acidification process. Considering that, ZVI was added into an anaerobic sludge digestion system to accelerate the sludge digestion in this study. The results indicated that ZVI effectively enhanced the decomposition of protein and cellulose, the two main components of the sludge. Compared to the control test without ZVI, the degradation of protein increased 21.9% and the volatile fatty acids production increased 37.3% with adding ZVI. More acetate and less propionate are found during the hydrolysis-acidification with ZVI. The activities of several key enzymes in the hydrolysis and acidification increased 0.6-1 time. ZVI made the methane production raise 43.5% and sludge reduction ratio increase 12.2 percent points. Fluorescence in situ hybridization analysis showed that the abundances of hydrogen-consuming microorganisms including homoacetogens and hydrogenotrophic methanogens with ZVI were higher than the control, which reduced the H2 accumulation to create a beneficial condition for the sludge digestion in thermodynamics. PMID:24275106

Feng, Yinghong; Zhang, Yaobin; Quan, Xie; Chen, Suo

2014-04-01

54

Zero-valent iron pretreatment for detoxifying iodine in liquid crystal display (LCD) manufacturing wastewater.  

PubMed

This study investigated reductive transformation of iodine by zero-valent iron (ZVI), and the subsequent detoxification of iodine-laden wastewater. ZVI completely reduced aqueous iodine to non-toxic iodide. Respirometric bioassay illustrated that the presence of iodine increase the lag phase before the onset of oxygen consumption. The length of lag phase was proportional to increasing iodine dosage. The reduction products of iodine by ZVI did not exhibit any inhibitory effect on the biodegradation. The cumulative biological oxidation associated with iodine toxicity was closely fitted to Gompertz model. When iodine-laden wastewater was continuously fed to a bench-scale activated sludge unit, chemical oxygen demand (COD) removal efficiencies decreased from above 90% to below 80% along with a marked decrease in biomass concentration. On the other hand, the COD removal efficiency and biomass concentration remained constant in the integrated ZVI-activated sludge system. Respirometric bioassay with real iodine-laden LCD manufacturing wastewater demonstrated that ZVI was effective for detoxifying iodine and consequently enhancing biodegradability of wastewater. This result suggested that ZVI pretreatment may be a feasible option for the removal of iodine in LCD processing wastewater, instead of more costly processes such as adsorption and chemical oxidation, which are commonly in the iodine-laden LCD wastewater treatment facility. PMID:18799266

Lee, J W; Cha, D K; Oh, Y K; Ko, K B; Song, J S

2009-05-15

55

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 deltoidsPopulous 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

56

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

2014-11-19

57

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

PubMed

Chromate transport through columns packed with zeolite/zero valent iron (Z/ZVI) pellets, either untreated or treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA), was studied at different flow rates. In the presence of sorbed HDTMA, the chromate retardation factor increased by a factor of five and the pseudo first-order rate constant for chromate reduction increased by 1.5-5 times. The increase in rate constant from the column studies was comparable to a six-fold increase in the rate constant determined in a batch study. At a fast flow rate, the apparent delay in chromate breakthrough from the HDTMA modified Z/ZVI columns was primarily caused by the increase in chromate reduction rate constant. In contrast, at a slower flow rate, the retardation in chromate transport from the HDTMA modified Z/ZVI columns mainly originated from chromate sorption onto the HDTMA modified Z/ZVI pellets. Due to dual porosity, the presence of immobile water was responsible for the earlier breakthrough of chromate in columns packed with zeolite and Z/ZVI pellets. The results from this study further confirm the role of HDTMA in enhancing sorption and reduction efficiency of contaminants in groundwater remediation. PMID:17448519

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

2007-08-01

58

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

PubMed

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

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

2013-12-01

59

Synergistic degradation of deca-BDE by an enrichment culture and zero-valent iron.  

PubMed

Debromination of decabromodiphenyl ether (deca-BDE) by microbe and by zero-valent iron (ZVI) has been reported previously. However, no study has indicated the presence of microorganisms and their effect on ZVI-mediated reduction of deca-BDE. Synergistic degradation of deca-BDE by an enrichment culture and ZVI was studied. It was found that synergistic effects enhanced the debromination of deca-BDE as well as promoting the reduction of lower brominated products. ZVI stimulated microbial debromination by serving as an electron donor. Correlation analysis also confirmed that ZVI was capable of enhancing microbial population in the debromination of deca-BDE. Conversely, the enrichment culture produced acid which maintained pH stability and stimulated the oxidation of ZVI. The enrichment culture supplied its energy requirements by the oxidation of ZVI and concomitant reduction of deca-BDE, but incapable of growth and reduction of BDE-209 without ZVI and vice versa. Compared to the initial culture, the microbial community of the enrichment culture became dominated by several bacterial genera based on the results of 16S rRNA-gene pyrosequencing. PMID:24643388

Chen, Xingjuan; Chen, Guilan; Qiu, Mengde; Sun, Guoping; Guo, Jun; Xu, Meiying

2014-07-01

60

Effects of nano zero-valent iron on Klebsiella oxytoca and stress response.  

PubMed

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

Sacc, Maria Ludovica; Fajardo, Carmen; Nande, Mar; Martn, Margarita

2013-11-01

61

Rapid decolorization of acid orange II aqueous solution by amorphous zero-valent iron.  

PubMed

Some problems including low treatment capacity, agglomeration and clogging phenomena, and short working life, limit the application of pre-treatment methods involving zero-valent iron (ZVI). In this article, ZVI was frozen in an amorphous state through a melt-spinning technique, and the decolorization effect of amorphous ZVI on Acid Orange II solution was investigated under varied conditions of experimental variables such as reaction temperature, ribbon dosage, and initial pH. Batch experiments suggested that the decolorization rate was enhanced with the increase of reaction temperature and ribbon dosage, but decreased with increasing initial solution pH. Kinetic analyses indicated that the decolorization process followed a first order exponential kinetic model, and the surface-normalized decolorization rate could reach 2.09 L/(m2 x min) at room temperature, which was about ten times larger than any previously reported under similar conditions. Recycling experiments also proved that the ribbons could be reused at least four times without obvious decay of decolorization rate and efficiency. This study suggests a tremendous application potential for amorphous ZVI in remediation of groundwater or wastewater contaminated with azo dyes. PMID:23505869

Zhang, Changqin; Zhu, Zhengwang; Zhang, Haifeng; Hu, Zhuangqi

2012-01-01

62

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

PubMed

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

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

2014-12-01

63

Reduction of hexavalent chromium by carboxymethyl cellulose-stabilized zero-valent iron nanoparticles  

NASA Astrophysics Data System (ADS)

The reduction of hexavalent chromium or Cr(VI) by zero-valent iron (Fe 0) nanoparticles has received increasing attention in recent years. However, Fe 0 nanoparticles prepared using conventional methods suffered several drawbacks due to their high reactivity towards surrounding media, which led to the formation of much larger flocs and significant loss in reactivity. To overcome these problems, we synthesized Fe 0 nanoparticles by applying water-soluble carboxymethyl cellulose (CMC) as a stabilizer. CMC-stabilized Fe 0 nanoparticles displayed much less agglomeration but greater Cr(VI) reduced power than those prepared without a stabilizer. At a dose of 0.15 g L -1, CMC-stabilized Fe 0 nanoparticles were able to reduce 100% of 10 mg L -1 Cr(VI) in minutes. Several factors that may affect the efficiency of Cr(VI) removal were investigated. These included the concentration of CMC, the concentration of Fe 0 nanoparticles, the initial Cr(VI) concentration, the pH value, the reaction temperature and the concentration of the calcium cation in the reaction mixture. Our study suggested that the introduction of an innocuous stabilizer such as CMC could significantly improve the performance of Fe 0 nanoparticles for environmental remediation applications.

Wang, Qian; Qian, Huijing; Yang, Yueping; Zhang, Zhen; Naman, Cissoko; Xu, Xinhua

2010-05-01

64

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

65

Reduction of hexachlorobenzene by nanoscale zero-valent iron: Kinetics, pH effect, and degradation mechanism  

Microsoft Academic Search

Nanoscale zero-valent iron (NZVI) particles were synthesized in the laboratory and used to investigate the reduction kinetics and degradation mechanisms of hexachlorobenzene (HCB) and the environmental effects. The rapid degradation of HCB by NZVI follows pseudo-first-order kinetics. Increasing the dose of NZVI particles enhanced the dechlorination rates of HCB. With an increase in temperature, the degradation rate increases. The activation

Yang-hsin Shih; Chung-yu Hsu; Yuh-fan Su

2011-01-01

66

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

Microsoft Academic Search

The degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron (US-Fe0)was investigated and an evident synergistic effect was observed. The synergetic effect is mainly due to the increase of OH radical concentration from Fentons reaction. The OH radical concentrations in sole sonication and US-Fe0 process were detected by using terephthalic acid as a fluorescent probe

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

2011-01-01

67

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...

68

Detoxification of PAX-21 ammunitions wastewater by zero-valent iron for microbial reduction of perchlorate.  

PubMed

US Army and the Department of Defense (DoD) facilities generate perchlorate (ClO(4)(-)) from munitions manufacturing and demilitarization processes. Ammonium perchlorate is one of the main constituents in Army's new main charge melt-pour energetic, PAX-21. In addition to ammonium perchlorate, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4-dinitroanisole (DNAN) are the major constituents of PAX-21. In order to evaluate microbial perchlorate reduction as a practical option for the treatment of perchlorate in PAX-21 wastewater, we conducted biodegradation experiments using glucose as the primary sources of electrons and carbon. Batch experiments showed that negligible perchlorate was removed in microbial reactors containing PAX-21 wastewater while control bottles containing seed bacteria and glucose rapidly and completely removed perchlorate. These results suggested that the constituents in PAX-21 wastewater may be toxic to perchlorate reducing bacteria. A series of batch toxicity test was conducted to identify the toxic constituents in PAX-21 and DNAN was identified as the primary toxicant responsible for inhibiting the activity of perchlorate reducing bacteria. It was hypothesized that pretreatment of PAX-21 by zero-valent iron granules will transform toxic constituents in PAX-21 wastewater to non-toxic products. We observed complete reduction of DNAN to 2,4-diaminoanisole (DAAN) and RDX to formaldehyde in abiotic iron reduction study. After a 3-day acclimation period, perchlorate in iron-treated PAX-21 wastewater was rapidly decreased to an undetectable level in 2 days. This result demonstrated that iron treatment not only removed energetic compounds but also eliminated the toxic constituents that inhibited the subsequent microbial process. PMID:21700387

Ahn, Se Chang; Cha, Daniel K; Kim, Byung J; Oh, Seok-Young

2011-08-30

69

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

PubMed

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

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

2010-10-15

70

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

SciTech Connect

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

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

2007-02-15

71

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

SciTech Connect

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{sup 0}). 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 containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe{sup 0} filings and resulted in the formation of a suite of mineral precipitates. HCO{sub 3}{sup {minus}} ions in SO{sub 4}{sup 2{minus}}-containing water were particularly corrosive to Fe{sup 0}, resulting in the formation of ferrous carbonate and enhanced H{sub 2} gas generation that stimulated the growth of microbial populations and increased SO{sub 4}{sup 2{minus}} reduction. Major mineral precipitates identified included lepidocrocite, akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO{sub 4}{sup 2{minus}} that became significant after about 2 months of column operations. This study demonstrates that biogeochemical influences on the performance and reaction of Fe{sup 0} may be minimal in the short term, necessitating longer-term operations to observe the effects of biogeochemical reactions on the performance of Fe{sup 0} barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from biogeochemical processes could reduce the reactivity and permeability of Fe{sup 0} beds, thereby decreasing treatment efficiency.

Gu, B.; Phelps, T.J.; Liang, L.; Palumbo, A.V.; Jacobs, G.K. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.] [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.; Dickey, M.J.; Roh, Y.; Kinsall, B.L. [Oak Ridge Inst. for Science and Education, TN (United States)] [Oak Ridge Inst. for Science and Education, TN (United States)

1999-07-01

72

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

73

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 m) 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 m 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

74

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

75

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-Daz, Mar; Alonso, Juan; Rodrguez-Valds, Eduardo; Pinilla, Paloma; Lobo, Maria Carmen

2014-01-01

76

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

NASA Astrophysics Data System (ADS)

This study investigated the breakthrough patterns of carboxymethyl cellulose- and polyacrylic acid-stabilized zero-valent iron (Fe 0) nanoparticles (NZVI) from packed sand columns under a range of pore water velocities of 0.02, 0.2 and 1 cm min - 1 and NZVI influent concentrations of 0.1, 0.5 and 3 g L - 1 . The NZVI effluent relative concentrations of both types of particles decreased with slower flow velocities and increasing particle concentrations. PAA-NZVI exhibited slower elution from the columns than CMC-NZVI under identical experimental conditions, and this is attributed to more rapid aggregation kinetics of PAA-NZVI. The elution patterns of PAA-NZVI showed a stronger trend of gradually increasing effluent concentrations with flushing of additional pore volumes, especially at low flushing velocities and higher influent particle concentrations and this phenomenon too can be attributed to increasing aggregate sizes with time which caused decreases in the values of the single collector efficiency and thus the deposition rate constant. A 7 nm increase in CMC-NZVI aggregate size over 60 min was observed using nanoparticle tracking analysis. The reduction in colloidal stability due to aggregation of CMC- and PAA-NZVI was verified using sedimentation tests, and it was found that PAA-NZVI were less stable than CMC-NZVI. There were also notable inherent differences in the two NZVI particles. The CMC-NZVI were monodisperse with a mean diameter of 5.7 0.9 nm, whereas PAA-NZVI had a bimodal particle size distribution with a small sub-population of particles with mean size of 30 21 nm and a more abundant population of 4.6 0.8 nm diameter particles. Furthermore, PAA-NZVI had a lower surface potential. These characteristics are also responsible for the different elution patterns CMC- and PAA-NZVI.

Raychoudhury, Trishikhi; Naja, Ghinwa; Ghoshal, Subhasis

2010-11-01

77

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

PubMed

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

Raychoudhury, Trishikhi; Tufenkji, Nathalie; Ghoshal, Subhasis

2014-03-01

78

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

PubMed

Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mssbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical warfare agents (CWAs) has been tested with three representative compounds, sulfur mustard (bis(2-chlorethyl) sulfide, HD), soman ((3,3'-imethylbutan-2-yl)-methylphosphonofluoridate, GD), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX). Zero-valent iron, even in the nanodimensional state, had a sluggish reactivity with CWAs, which was also observed in low degrees of CWAs degradation. On the contrary, ferrate(VI)/(III) composite exhibited a high reactivity and complete degradations of CWAs were accomplished. Under the studied conditions, the estimated first-order rate constants (? 10(-2)s(-1)) with the ferrate(VI)/(III) composite were several orders of magnitude higher than those of spontaneous hydrolysis of CWAs (10(-8)-10(-6)s(-1)). The results demonstrated that the oxidative technology based on application of ferrate(VI) is very promising to decontaminate CWAs. PMID:22119195

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

2012-04-15

79

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

80

Degradation of simazine from aqueous solutions by diatomite-supported nanosized zero-valent iron composite materials.  

PubMed

A novel composite material based on deposition of nanosized zero-valent iron (nZVI) particles on acid-leached diatomite was synthesised for the removal of a chlorinated contaminant in water. The nZVI/diatomite composites were characterised by X-ray diffraction, scanning electron microscopy, elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. Compared with the pure nZVI particles, better dispersion of nZVI particles on the surface or inside the pores of diatom shells was observed. The herbicide simazine was selected as the model chlorinated contaminant and the removal efficiency by nZVI/diatomite composite was compared with that of the pristine nZVI and commercial iron powder. It was found that the diatomite supported nZVI composite material prepared by centrifugation exhibits relatively better efficient activity in decomposition of simazine than commercial Fe, lab synthesised nZVI and composite material prepared via rotary evaporation, and the optimum experimental conditions were obtained based on a series of batch experiments. This study on immobilising nZVI particles onto diatomite opens a new avenue for the practical application of nZVI and the diatomite-supported nanosized zero-valent iron composite materials have potential applications in environmental remediation. PMID:24231330

Sun, Zhiming; Zheng, Shuilin; Ayoko, Godwin A; Frost, Ray L; Xi, Yunfei

2013-12-15

81

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

PubMed

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

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

2013-10-15

82

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.

83

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

84

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

85

Enhanced degradation of chlorobenzene in aqueous solution using microwave-induced zero-valent iron and copper particles.  

PubMed

Microwaves were applied to reduce the activation energy of chlorobenzene in aqueous solution and enhance its removal using nanoscale zero-valent iron (Fe0) or zero-valent copper (Cu0) particles as dielectric media. When Fe0 and Cu0 particles absorb microwave energy, the electrical potential difference causes the metal electrons to rotate faster, thus producing more heat. The microwave-irradiated metal particles reduced the chlorobenzene activation energy by 6.1 kJ/mol (13.3 kJ/mol versus 19.4 kJ/mol) for Fe0 and 5.4 kJ/mol (15.8 kJ/mol versus 21.4 kJ/mol) for Cu0 and enhanced the chlorobenzene removal 4.1 times (82.8% versus 20.4%) for Fe0 and 3.7 times (72.1% versus 19.5%) for Cu0. The Fe0 has a higher standard reduction potential than Cu0; it is capable of removing more chlorobenzene than Cu0 (82.8% versus 72.1%). Using the microwave-induced nano-scale iron or copper particle is effective in treating toxic organic substances, as demonstrated in this study. PMID:20669726

Lee, Chien-Li; Jou, Chih-Ju G; Wang, H Paul

2010-07-01

86

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

PubMed

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

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

2011-09-01

87

Nanoscale zero-valent iron/AC as heterogeneous Fenton catalysts in three-dimensional electrode system.  

PubMed

In the present work, nanoscale zero-valent iron/activated carbon (NZVI/AC) was investigated as heterogeneous Fenton catalyst in three-dimensional (3D) electrode system for methyl orange (MO) degradation. Some important operating parameters such as cathodic potential, pH, and O? flow rate were investigated, exhibiting good decolorization. The mineralization of MO was significantly improved by 20-35% compared to two-dimensional (2D) AC system at the optimum conditions. Although the TOC removal of AC was higher than NZVI/AC due to its good adsorption capacity initially, heterogeneous Fenton catalysis played a more and more important roles in the following test. After eight runs, NZVI/AC still exhibited excellent catalytic properties with low iron leaching. Further, a relatively comprehensive mechanism of NZVI/AC as particle electrodes in 3D system was proposed. PMID:24677061

Zhang, Chao; Zhou, Lei; Yang, Jie; Yu, Xinmin; Jiang, Yonghai; Zhou, Minghua

2014-07-01

88

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

89

Enhanced removal of soluble Cr(VI) by using zero-valent iron composite supported by surfactant-modified zeolites.  

PubMed

Zero-valent iron (ZVI) was immobilized onto surfactant-modified zeolites (SMZ) using calcium alginate. Scanning electron microscopy showed that ZVI powder was uniformly immobilized on the surface of the SMZ. The added ZVI powder resulted in enhanced dichromate removal efficiency and the heterogeneous surface of the composite. The adsorption of dichromate onto the ZVI-SMZ composites fitted well to a pseudo-second-order model and the Langmuir adsorption isotherm. The maximum dichromate adsorption capacity of the composite was 2.49 mg/g at the temperature of 293 K. Higher removal efficiency was obtained at pH lower than 7. X-ray photoelectron spectrometry revealed that the composites combined the strong reductive quality of ZVI and superior adsorption of SMZ. PMID:25353946

Dang, Hongyu; Zhang, Yongxiang; Du, Peiwen

2014-10-01

90

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...

91

Application of zero-valent iron nanoparticles for the removal of aqueous zinc ions under various experimental conditions.  

PubMed

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

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

2014-01-01

92

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

PubMed Central

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

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

2014-01-01

93

Effects of dissolved oxygen on formation of corrosion products and concomitant oxygen and nitrate reduction in zero-valent iron systems with or without aqueous Fe 2+  

Microsoft Academic Search

Batch tests were conducted in zero-valent iron (ZVI or Fe0) systems to investigate oxygen consumption and the effect of dissolved oxygen (DO) on formation of iron corrosion products, nitrate reduction, the reactivity of Fe0, the role Fe2+ (aq) played, and the fate of Fe2+. The study indicates that without augmenting Fe2+ (aq), neither nitrate nor DO could be removed efficiently

Yong H. Huang; Tian C. Zhang

2005-01-01

94

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

95

Simultaneous removal of perchlorate and energetic compounds in munitions wastewater by zero-valent iron and perchlorate-respiring bacteria.  

PubMed

Ammonium perchlorate is one of the main constituents in Army's insensitive melt-pour explosive, PAX-21 in addition to RDX and 2,4-dinitroanisole (DNAN). The objective of this study is to develop an innovative treatment process to remove both perchlorate and energetic compounds simultaneously from PAX-21 production wastewater. It was hypothesized that the pretreatment of PAX-21 wastewater with zero-valent iron (ZVI) would convert energetic compounds to products that are more amenable for biological oxidation and that these products serve as electron donors for perchlorate-reducing bacteria. Results of batch ZVI reduction experiments showed that DNAN was completely reduced to 2,4-diaminoanisole and RDX was completely reduced to formaldehyde. Anaerobic batch biodegradation experiments showed that perchlorate (30 mg L(-1)) in ZVI-treated PAX-21 wastewater was decreased to an undetectable level after 5 days. Batch biodegradation experiments also confirmed that formaldehyde in ZVI-treated wastewater was the primary electron donor for perchlorate-respiring bacteria. The integrated iron-anaerobic bioreactor system was effective in completely removing energetic compounds and perchlorate from the PAX-21 wastewater without adding an exogenous electron donor. This study demonstrated that ZVI pretreatment not only removed energetic compounds, but also transformed energetic compounds to products that can serve as the source of electrons for perchlorate-respiring bacteria. PMID:24410688

Ahn, Se Chang; Hubbard, Brian; Cha, Daniel K; Kim, Byung J

2014-01-01

96

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

97

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

98

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

PubMed

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

El-Temsah, Yehia S; Joner, Erik J

2012-09-01

99

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

PubMed

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

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

2014-01-01

100

Remediation of DDTs contaminated soil in a novel Fenton-like system with zero-valent iron.  

PubMed

Application of a novel Fenton-like system with zero-valent iron, EDTA and Air (ZVI/EDTA/Air) was investigated to degrade dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane, and dichlorodiphenyldichloroethylene (DDE) in the actual contaminated soil from an organochlorine pesticide site. It was found DDTs in the soil were effectively degraded by the system at room temperature, ambient atmosphere pressure and near neutral pH. The dosages of EDTA and ZVI were the dominant factors influencing the removal of contaminants. An increase of EDTA from 0.05 to 0.2 mM and ZVI from 1 to 5 g L(-1) improved the removal of the contaminants significantly. However, excessive amount of EDTA led to a negative effect on the degradation process. Meanwhile, EDTA was simultaneously degraded so as to avoid the secondary pollution risk on soil remediation. Only a small amount of 4,4'-DDE and 2,2-bis(4-chlorophenyl)-1-chloroethylene (4,4'-DDMU) generated as the intermediates of DDT degradation during the process. Our investigation suggests that the Fenton-like system is a promising alternative for remediation of organochlorine pesticides contaminated soils. PMID:23102698

Cao, Menghua; Wang, Linling; Wang, Li; Chen, Jing; Lu, Xiaohua

2013-02-01

101

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

PubMed

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

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

2014-10-01

102

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

PubMed

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

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

2013-04-01

103

Decolourization of direct blue 15 by Fenton/ultrasonic process using a zero-valent iron aggregate catalyst.  

PubMed

Decolourization of direct azo dye, direct blue 15 (DB15), by an advanced Fenton process coupled with ultrasonic irradiation (Fenton/US) was investigated. Zero-valent iron (ZVI) aggregates were used as the catalyst. A positive synergistic effect occurred when Fenton's reagent was combined with ultrasonic irradiation. Experimental results showed that the optimum conditions for decolourization were pH 3.0, Fe(0) 1g/L, H(2)O(2) 5.1510(-3)mol/L with ultrasound density of 120W/L at 60kHz. These conditions yielded 99% decolouration of 4.710(-5) M DB15 (4130 ADMI) solution within 10min. DB15 decolouration follows the first-order decolouration kinetics. Although the solutions containing H(2)CO(3), Cl(-), ClO(4)(-), NO(3)(-) and SO(4)(2-) ions did not have a significant effect on the decolouration, the H(2)PO(4)(-) ion did decrease the decolouration rate. High ultrasonic input power accelerated the reaction and increased decolourization efficiency. The cost effectiveness of this process at high ultrasound density could be controlled despite the high electricity costs incurred by the process. ZVI aggregates were reusable; however, an increase in the number of times ZVI was recycled decreased the decolourization rate. This study demonstrates that a Fenton/US process can effectively decolour the direct azo dye DB15 in wastewater. PMID:23187066

Weng, Chih-Huang; Lin, Yao-Tung; Chang, Cheng-Kuan; Liu, Na

2013-05-01

104

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 45months. 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 6months, it was possible to achieve water production with an As content from 20?gL(-1) to below 5?gL(-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; Sgaard, Erik G

2014-12-01

105

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

106

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

2014-01-01

107

Influences of humic acid, bicarbonate and calcium on Cr(VI) reductive removal by zero-valent iron.  

PubMed

The influences of various geochemical constituents, such as humic acid, HCO(3)(-), and Ca(2+), on Cr(VI) removal by zero-valent iron (Fe(0)) were investigated in a batch setting. The collective impacts of humic acid, HCO(3)(-), and Ca(2+) on the Cr(VI) reduction process by Fe(0) appeared to significantly differ from their individual impacts. Humic acid introduced a marginal influence on Fe(0) reactivity toward Cr(VI) reduction, whereas HCO(3)(-) greatly enhanced Cr(VI) removal by maintaining the solution pH near neutral. The Cr(VI) reduction rate constants (k(obs)) were increased by 37.8% and 78.3%, respectively, with 2 mM and 6 mM HCO(3)(-) in solutions where humic acid and Ca(2+) were absent. Singly present Ca(2+) did not show a significant impact to Cr(VI) reduction. However, probably due to the formation of passivating CaCO(3), further addition of Ca(2+) to HCO(3)(-) containing solutions resulted in a decrease of k(obs) compared to solutions containing HCO(3)(-) alone. Ca(2+) enhanced humic acid adsorption led to a minor decrease of Cr(VI) reduction rates. In Ca(2+)-free solutions, humic acid increased the amount of total dissolved iron to 25 mg/l due to the formation of soluble Fe-humate complexes and stably dispersed fine Fe (oxy)hydroxide colloids, which appeared to suppress iron precipitation. In contrast, the coexistence of humic acid and Ca(2+) significantly promoted the aggregation of Fe (oxy)hydroxides, with which humic acid co-aggregated and co-precipitated. These aggregates would progressively be deposited on Fe(0) surfaces and impose long-term impacts on the permeability of PRBs. PMID:19232679

Liu, Tongzhou; Rao, Pinhua; Lo, Irene M C

2009-05-01

108

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

109

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

NASA Astrophysics Data System (ADS)

The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation and possible reaction pathway in a very complex adsorption and redox reaction process. Experimentally, ZVIN of this study was prepared by sodium borohydride reduction method at room temperature and ambient pressure. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20-50 nm were observed with FE-SEM or TEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65-83% and 51-68%, respectively, based on three different initial concentrations. Based on the XRD pattern analyses, it is found that the quantitative relationship between nitrite and Fe(III) or Fe(II) is similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is due to the faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The extended x-ray absorption fine structure (EXAFS) or x-ray absorption near edge structure (XANES) spectra show that the nitrites or nitrates reduce to N2 or NH3 while oxidizing the ZVIN to Fe2O3 or Fe3O4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.

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

2008-04-01

110

Capture and storage of hydrogen gas by zero-valent iron  

NASA Astrophysics Data System (ADS)

Granular Feo, used to reductively degrade a variety of contaminants in groundwater, corrodes in water to produce H2(g). A portion enters the Feo 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 Feo 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-Feo 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 Feo for remediation purposes and may be accessible using physical or chemical means.

Reardon, Eric J.

2014-02-01

111

2.2 Zero-valent Iron Nanoparticles 2.2.1 Background  

E-print Network

meters wide, contained by gravel supporting beds. The chemistry is well understood as the corrosion) + 2H2O(l) 2Fe3+ (aq) + H2(g) + 2OH- (aq) As ZVI is oxidized to ferrous and/or ferric iron, pH created are favorable for the pathways (oxide-mediated electron transfer from the metal to the chlorinated

112

Enhanced degradation of trichloroethylene in nano-scale zero-valent iron Fenton system with Cu(II).  

PubMed

Degradation of trichloroethylene (TCE) in nano-scale zero-valent iron (nZVI) Fenton system with Cu(II) was investigated in a closed batch system. TCE was significantly degraded (95%) in 10 min in nZVI Fenton system with 20mM Cu(II) at initial pH 3, while slight degradation (25%) was observed in nZVI Fenton system without Cu(II) at the same experimental condition. Aqueous Fe(II) concentration proportionally increased (1.2-19.6mM) with increasing Cu(II) concentration (1-20mM). Surface analyses using X-ray spectroscopy showed that metallic Cu was formed on the nZVI surface and surface Fe(0) decreased by 1.4 times after the addition of Cu(II) to nZVI suspension. Kinetic rate constant for TCE degradation at 15.3mM nZVI (4.1989 min(-1)) increased by 1.8 times till the increase of nZVI concentration by 5 times and then showed a saturation pattern at higher nZVI concentration. As Cu(II) concentrations increased in the Cu/nZVI Fenton system, the rate constant increased linearly (R(2)=0.979). No significant difference has been observed in the degradation kinetics of TCE by Cu/nZVI Fenton at pH 3 and pH 6 (4.8720 min(-1) vs. 4.9858 min(-1)), whereas the kinetics by nZVI Fenton at pH 6 were 1.6 times faster (0.0318 min(-1)) than at pH 3 (0.0194 min(-1)). PMID:22079185

Choi, Kyunghoon; Lee, Woojin

2012-04-15

113

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

114

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; Lhotsk, Ond?ej; Cajthaml, Tom

2014-07-01

115

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

116

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

PubMed

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

Jia, Hanzhong; Wang, Chuanyi

2013-01-01

117

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

SciTech Connect

Calcium carbonate is a major secondary mineral precipitate that influences PRB reactivity and hydraulic performance. In this study, we conducted column experiments to investigate electrical signatures resulting from concurrent CaCO3 and iron oxides precipitation in two simulated PRB media. Solid phase analysis identified CaCO3 (calcite and aragonite) as a major mineral phase throughout the columns, with magnetite being another major phase present close to the influent. Electrical measurements revealed a consistent decrease in conductivity and polarization magnitude of both columns, suggesting that the electrically insulating CaCO3 dominates the electrical response despite the presence of both electrically conductive iron oxides and CaCO3 precipitates. SEM/EDX imaging suggests that the electrical properties result from the geometrical arrangement of the mineral phases. The CaCO3 forms an insulating film on ZVI/magnetite surfaces, which we assume restricts redox-driven transfer of electric charge 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, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss.

Yuxin Wu; Roelof Versteeg; Lee Slater; Doug Labrecque

2009-05-01

118

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

119

Challenges in the Theoretical Description of Nanoparticle Reactivity: Nano Zero-Valent Iron  

E-print Network

The reactivity of iron atoms, clusters and nanoparticles (nZVI) is of increasing interest owing to their important practical applications, ranging from the steel industry to water remediation technologies. Here, we provide an overview of computational methods and models that can be applied to study nZVI reactions and discuss their benefits and limitations. We also report current progress in calculations through recent examples treating the reactivity of nZVI particles. Finally, we consider the potential use of highly accurate methods with favorable scaling (such as quantum Monte Carlo or random phase approximation), which are currently considered too computationally expensive but are expected to become more amenable in the future as computer power increases.

Karlick, Frantiek

2014-01-01

120

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

Microsoft Academic Search

The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2\\/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compared. DBCP reacted with iron powder (100200 mesh, 36 g\\/l) in HEPES-buffered water (pH = 7.0) with a t12 of 2.5 min and in different groundwaters (pH = 8.28.7) with a

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

1996-01-01

121

Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling  

NASA Astrophysics Data System (ADS)

Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe 3O 4), calcite (CaCO 3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH) 2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO 2, V 2O 3), sulfides (As 2S 3, ZnS), iron minerals (FeSe 2, FeMoO 4) and carbonate (MnCO 3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell.

Morrison, Stan J.; Metzler, Donald R.; Dwyer, Brian P.

2002-05-01

122

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

123

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

124

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

125

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

126

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...

127

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

PubMed

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

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

2009-09-01

128

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

SciTech Connect

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

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

2006-03-20

129

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

130

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

131

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

PubMed

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

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

2012-01-30

132

Nanoscale zero-valent iron (nZVI): aspects of the core-shell structure and reactions with inorganic species in water.  

PubMed

Aspects of the core-shell model of nanoscale zero-valent iron (nZVI) and their environmental implications were examined in this work. The structure and elemental distribution of nZVI were characterized by X-ray energy-dispersive spectroscopy (XEDS) with nanometer-scale spatial resolution in an aberration-corrected scanning transmission electron microscope (STEM). The analysis provides unequivocal evidence of a layered structure of nZVI consisting of a metallic iron core encapsulated by a thin amorphous oxide shell. Three aqueous environmental contaminants, namely Hg(II), Zn(II) and hydrogen sulfide, were studied to probe the reactive properties and the surface chemistry of nZVI. High-resolution X-ray photoelectron spectroscopy (HR-XPS) analysis of the reacted particles indicated that Hg(II) was sequestrated via chemical reduction to elemental mercury. On the other hand, Zn(II) removal was achieved via sorption to the iron oxide shell followed by zinc hydroxide precipitation. Hydrogen sulfide was immobilized on the nZVI surface as disulfide (S(2)(2-)) and monosulfide (S(2-)) species. Their relative abundance in the final products suggests that the retention of hydrogen sulfide occurs via reactions with the oxide shell to form iron sulfide (FeS) and subsequent conversion to iron disulfide (FeS(2)). The results presented herein highlight the multiple reactive pathways permissible with nZVI owing to its two functional constituents. The core-shell structure imparts nZVI with manifold functional properties previously unexamined and grants the material with potentially new applications. PMID:20889228

Yan, Weile; Herzing, Andrew A; Kiely, Christopher J; Zhang, Wei-Xian

2010-11-25

133

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

PubMed

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

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

2013-10-01

134

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

135

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 (160mgL(-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

136

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

PubMed

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

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

2013-01-01

137

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

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

2014-01-01

138

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

PubMed

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

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

2013-09-15

139

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

140

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) ...

141

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

PubMed

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

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

2013-01-01

142

The effects of operational parameters and common anions on the reactivity of zero-valent iron in bromate reduction.  

PubMed

Bromate reduction by Fe(0) was investigated under various conditions in batch tests. The bromate was primarily reduced to bromide ions with possible adsorption onto iron. Bromate reduction by Fe(0) can be described by pseudo-first-order kinetics. The differences in surface areas, numbers of reactive sites, impurities, pretreatment methods and numbers of repeated uses of iron affected the rates of bromate reduction through reducing or accumulating a passive oxide film on the iron surface. The reduction of bromate was significantly affected by only the dissolved oxygen content at supersaturated concentrations or by decreasing the pH from 6 to 5. Increasing the temperature increased the bromate reduction rate, which followed the Arrhenius relationship with activation energy of 52.6 kJmol(-1) and the reduction rate increased with increased mixing rates. These observations indicate that bromate reduction by iron is a surface-mediated process and diffusion to the surface is essential. Under the test conditions, modest inhibitory effects on bromate reduction by Fe(0) from nitrite, chlorate and bicarbonate were observed and the inhibitory effect from phosphate was relatively larger. Enhanced reactivity of Fe(0) to bromate was observed in the presence of nitrate or sulfate. These findings suggest that bromate reduction by Fe(0) can be an effective method for bromate control. PMID:16942788

Xie, Li; Shang, Chii

2007-01-01

143

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

144

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

PubMed

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

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

2013-01-01

145

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

146

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...

147

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

148

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

PubMed

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

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

2014-01-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

150

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

151

[Reductive debromination of polybrominated diphenyl ethers in aquifier by nano zero-valent iron: debromination kinetics and pathway].  

PubMed

Nano-zerovalent iron (nZVI) approach is effective in the debromination of polybrominated biphenyl ethers (PBDEs). The kinetics and degradation pathway are the key issues to understand the PBDEs degradation mechanisms. In this study, nZVI, synthesized through liquid phase reduction method, coupled with Triton X-100, could completely debrominate the highly brominated congeners of a commercial octa-BDEs mixture within 46 h. The debromination of octa-BDEs could be described by means of pseudo-first-order kinetics with the reaction constant (k) of 0.106 h(-1). In case of lacking the PBDE standards, an effective approach has been developed to determine the unknown PBDE congeners using the quantitative-structure retention relationship (QSRR) model. The retention time of all 39 PBDE congeners in a standard mixture was firstly analyzed with gas chromatography coupled with an electron capture detector (GC-ECD), and the relative retention time (RRT) for each standard was obtained after normalizing the RT by the average RT of BDE47 and BDE183. Then a QSRR model was developed by fitting the RRT of each PBDE congener and its specific RRT index. The debromination products of octa-BDEs were identified using this QSRR model and the degradation pathway of octa-BDEs was elucidated. The results showed that in the stepwise reductive debromination process of PBDEs by nZVI, meta-debromin was facile to be degraded. PMID:24881384

Yang, Yu-Han; Xu, Wei-Wei; Peng, Si-Kan; Lu, Shan-Fu; Xiang, Yan; Liang, Da-Wei

2014-03-01

152

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

153

Photo degradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron: influence of various reaction parameters and its degradation mechanism.  

PubMed

Advanced Fenton process (AFP) using zero valent metallic iron (ZVMI) is studied as a potential technique to degrade the azo dye in the aqueous medium. The influence of various reaction parameters like effect of iron dosage, concentration of H(2)O(2)/ammonium per sulfate (APS), initial dye concentration, effect of pH and the influence of radical scavenger are studied and optimum conditions are reported. The degradation rate decreased at higher iron dosages and also at higher oxidant concentrations due to the surface precipitation which deactivates the iron surface. The rate constant for the processes Fe(0)/UV and Fe(0)/APS/UV is twice compared to their respective Fe(0)/dark and Fe(0)/APS/dark processes. The rate constant for Fe(0)/H(2)O(2)/UV process is four times higher than Fe(0)/H(2)O(2)/dark process. The increase in the efficiency of Fe(0)/UV process is attributed to the cleavage of stable iron complexes which produces Fe(2+) ions that participates in cyclic Fenton mechanism for the generation of hydroxyl radicals. The increase in the efficiency of Fe(0)/APS/UV or H(2)O(2) compared to dark process is due to continuous generation of hydroxyl radicals and also due to the frequent photo reduction of Fe(3+) ions to Fe(2+) ions. Though H(2)O(2) is a better oxidant than APS in all respects, but it is more susceptible to deactivation by hydroxyl radical scavengers. The decrease in the rate constant in the presence of hydroxyl radical scavenger is more for H(2)O(2) than APS. Iron powder retains its recycling efficiency better in the presence of H(2)O(2) than APS. The decrease in the degradation rate in the presence of APS as an oxidant is due to the fact that generation of free radicals on iron surface is slower compared to H(2)O(2). Also, the excess acidity provided by APS retards the degradation rate as excess H(+) ions acts as hydroxyl radical scavenger. The degradation of Methyl Orange (MO) using Fe(0) is an acid driven process shows higher efficiency at pH 3. The efficiency of various processes for the de colorization of MO dye is of the following order: Fe(0)/H(2)O(2)/UV>Fe(0)/H(2)O(2)/dark>Fe(0)/APS/UV>Fe(0)/UV>Fe(0)/APS/dark>H(2)O(2)/UV approximately Fe(0)/dark>APS/UV. Dye resisted to degradation in the presence of oxidizing agent in dark. The degradation process was followed by UV-vis and GC-MS spectroscopic techniques. Based on the intermediates obtained probable degradation mechanism has been proposed. The result suggests that complete degradation of the dye was achieved in the presence of oxidizing agent when the system was amended with iron powder under UV light illumination. The concentration of Fe(2+) ions leached at the end of the optimized degradation experiment is found to be 2.78 x 10(-3)M. With optimization, the degradation using Fe(0) can be effective way to treat azo dyes in aqueous solution. PMID:18805635

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

2009-05-30

154

[Influence of inorganic ions and humic acid on the removal of Pb(II) and Hg(II) in water by zero-valent iron].  

PubMed

The effects of Ca2+, Cl- and humic acid (HA) on the removal rates of Pb(II) and Hg(II) in water by zero-valent (ZVI) and the kinetic characteristics were studied, and the removal mechanism of Pb(II) and Hg(II) by ZVI were preliminarily investigated using X-ray diffraction (XRD). The results indicated that the removal mechanism of Pb(II) might mainly be attributed to the adsorption and co-precipitation of ZVI, while that of Hg(II) might mainly be attributed to the oxidation-reduction of ZVI. With the increase of Ca2+ concentration, the removal rates of Hg(II) and Pb(II) showed the trends of gradual increase and slight decrease, respectively. The Hg(II) removal increased with increasing Cl- concentration, whereas no obvious increase in Pb(II) removal was observed. The removal rates of Hg(II) and Pb(II) showed the trends of slow increase and slow decrease with increasing HA concentration, respectively. When Ca2+, Cl- and HA coexisted, the removal rates of Hg(II) and Pb(II) reached 99.71% and 97.95%, respectively. The removal processes of Pb(II) and Hg(II) could be described by pseudo first-order reaction kinetic equations when Ca2+, Cl- and HA existed alone and in combination. The removal rate constant of Pb(II) was the maxinum (0.024 0 min(-1)) when 5 mg x L(-1) HA existed alone, whereas that of Hg(II) was the maximum (0.0169 min(-1)) when 0.80 mmol x L(-1) Ca2+ existed alone. PMID:25338370

Shi, Qiu-Ling; Zhou, Xin; Zhang, Jin-Zhong; Qiu, Xin-Kai

2014-08-01

155

Chromium(VI) reduction kinetics by zero-valent iron in moderately hard water with humic acid: iron dissolution and humic acid adsorption.  

PubMed

In zerovalent iron treatment systems, the presence of multiple solution components may impose combined effects that differ from corresponding individual effects. The copresence of humic acid and hardness (Ca2+/Mg2+) was found to influence Cr(VI) reduction by Feo and iron dissolution in a way different from their respective presence in batch kinetics experiments with synthetic groundwater at initial pH 6 and 9.5. Cr(VI) reduction rate constants (k(obs)) were slightly inhibited by humic acid adsorption on iron filings (decreases of 7-9% and 10-12% in the presence of humic acid alone and together with hardness, respectively). The total amount of dissolved Fe steadily increased to 25 mg L(-1) in the presence of humic acid alone because the formation of soluble Fe-humate complexes appeared to suppress iron precipitation. Substantial amounts of soluble and colloidal Fe-humate complexes in groundwater may arouse aesthetic and safety concerns in groundwater use. In contrast, the coexistence of humic acid and Ca2+/Mg2+ significantly promoted aggregation of humic acid and metal hydrolyzed species, as indicated by XPS and TEM analyses, which remained nondissolved (>0.45 microm) in solution. These metal-humate aggregates may impose long-term impacts on PRBs in subsurface settings. PMID:18409642

Liu, Tongzhou; Tsang, Daniel C W; Lo, Irene M C

2008-03-15

156

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

157

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...

158

Influences of Humic Acid on Cr(VI) Removal by Zero-Valent Iron From Groundwater with Various Constituents: Implication for Long-Term PRB Performance  

Microsoft Academic Search

A 9-month-long continuous flow column study was carried out to investigate Cr(VI) removal by Fe0 with the presence of humic acid. The study focused on the influences of humic acid promoted dissolved iron release and humic\\u000a acid aggregation in Fe0 columns receiving synthetic Cr(VI) contaminated groundwater containing various components such as bicarbonate and Ca. The\\u000a effects of humic acid varied

Tongzhou Liu; Irene M. C. Lo

2011-01-01

159

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

160

Nanoscale Zero-Valent Iron (NZVI) supported on sineguelas waste for Pb(II) removal from aqueous solution: kinetics, thermodynamic and mechanism.  

PubMed

In this study, the synthesis and characterization of a new adsorbent containing nanoscale zerovalent iron particles (NZVI) decorated sineguelas waste (S-NaOH-NZVI) from agriculture biomass was investigated for the adsorption/reduction of inorganic pollution such as Pb(II) ions. The combination of ZVI particles on the surface of sineguelas waste can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. The synthesized materials were characterized with different methods such as FT-IR, BET, XRD, TEM and pHPZC. Good dispersion of NZVI particles (ca. 10-70nm) on the sineguelas waste was observed. The effects of various parameters, such as contact time, pH, concentration, adsorbent dosage and temperature were studied. The adsorption of Pb(II) ions has been studied in terms of pseudo-first- and second-order kinetics, and the Freundlich, Langmuir and Langmuir-Freundlich isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (?G, ?H and ?S) indicated that the adsorption of Pb(II) ions were feasible, spontaneous and endothermic at 25-80C. XRD analysis indicated the presence of Pb(0) on the S-NaOH-NZVI surface. This study suggests that the modified sineguelas waste by NZVI particles can be prepared at low cost and the materials are environmentally benign for the removal of Pb(II) ions, and likely many other heavy metal ions, from water. PMID:24863789

Arshadi, M; Soleymanzadeh, M; Salvacion, J W L; SalimiVahid, F

2014-07-15

161

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...

162

Fundamental Studies of The Removal of Contaminants from Ground and Waste Waters Via Reduction By Zero-Valent metals  

SciTech Connect

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 are performing fundamental investigations of the interactions of the relevant compounds with Fe filings and single- and poly-crystalline surfaces. The aim of this work is to develop the physical and chemical understanding that is necessary for the development of cleanup techniques and procedures.

Jory A. Yarmoff; Christopher Amrhein

2002-04-23

163

Electrochemical deposition of green rust on zero-valent iron  

E-print Network

the capability to degrade PCE faster and to a greater extent than either reductant alone (2). An electrochemical cell consists of a source of electrical potential connected to two electrodes (anode and cathode) that are immersed in an electrolyte. Several... hydrogen gas at the cathode. Fe 0 ? Fe 3+ + 3 e - possible Oxidation half reaction (4) Fe 2+ + 2 e - ? Fe 0 possible...

Kulkarni, Dhananjay Vijay

2006-08-16

164

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

165

Perchlorate reduction during electrochemically induced pitting corrosion of zero-valent titanium (ZVT).  

PubMed

Zero-valent metals and ionic metal species are a popular reagent for the abatement of contaminants in drinking water and groundwater and perchlorate is a contaminant of increasing concern. However, perchlorate degradation using commonly used reductants such as zero-valent metals and soluble reduced metal species is kinetically limited. Titanium in the zero-valent and soluble states has a high thermodynamic potential to reduce perchlorate. Here we show that perchlorate is effectively reduced to chloride by soluble titanium species in a system where the surface oxide film is removed from ZVT and ZVT is oxidized during electrochemically induced pitting corrosion to produce reactive soluble species. The pitting potential of ZVT was measured as 12.770.04 V (SHE) for a 100 mM solution of perchlorate. The rate of perchlorate reduction was independent of the imposed potential as long as the potential was maintained above the pitting potential, but it was proportional to the applied current. Solution pH and surface area of ZVT electrodes showed negligible effects on rates of perchlorate reduction. Although perchlorate is effectively reduced during electrochemically induced corrosion of ZVT, this process may not be immediately applicable to perchlorate treatment due to the high potentials needed to produce active reductants, the amount of titanium consumed, the inhibition of perchlorate removal by chloride, and oxidation of chloride to chlorine. PMID:21993148

Lee, Chunwoo; Batchelor, Bill; Park, Sung Hyuk; Han, Dong Suk; Abdel-Wahab, Ahmed; Kramer, Timothy A

2011-12-15

166

Degradation of Acid Orange 7 in aqueous solution by zero-valent aluminum under ultrasonic irradiation.  

PubMed

Degradation of azo dye Acid Orange 7 (AO7) by zero-valent aluminum (ZVAl) in combination with ultrasonic irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with sole ultrasonic, sole ZVAl/air system, ultrasonication + ZVAl/air system (US-ZVAl). In ZVAl/air system, the degradation of AO7 could almost not be observed within 30 min. The degradation of AO7 by ZVAl/air system was obviously enhanced under ultrasound irradiation, and the enhancement is mainly attributed to that the production of hydroxyl radicals in ultrasound-ZVAl process was much higher than that in sole ultrasonic or in sole ZVAl/air system. The variables considered for the effect of degradation were the power of ultrasound, the initial concentration of AO7, as well as the initial pH value and the dosage of zero-valent aluminum. The results showed that the decolorization rate increased with the increase of power density and the dosage of ZVAl, but decreased with the increase of initial pH value and initial concentration of AO7. More than 96% of AO7 removal was achieved within 30 min under optimum operational conditions (AO7: 20 mg/L, ZVAl: 2 g/L, pH: 2.5, ultrasound: 20 kHz, 300 W). This study demonstrates that ultrasound-ZVAl process can effectively decolorize the azo dye AO7 in wastewater. PMID:24201009

Wang, Anqi; Guo, Weilin; Hao, Feifei; Yue, Xinxin; Leng, Yanqiu

2014-03-01

167

Perchlorate removal by acidified zero-valent aluminum and aluminum hydroxide.  

PubMed

Removal of perchlorate using either acid-washed zero-valent aluminum or aluminum hydroxide was studied in batch reactors under ambient temperature and pressure. Approximately 90-95% of perchlorate was removed within 24h in the presence of 35 g L(-1) aluminum at acidic pH (4.5+/-0.2). Although aluminum is a strong reductant, this study indicated no explicit evidence to support perchlorate reduction while it was found that an adsorption process is involved in the perchlorate removal. The adsorbed perchlorate ions were desorbed effectively using a 1.0 N MgSO(4) solution. The effective composition for the perchlorate adsorption is confirmed as aluminum hydroxide (bayerite), which is a product of the aluminum corrosion. Rapid adsorption of perchlorate was observed in the presence of aluminum hydroxide. The perchlorate adsorption by aluminum hydroxide is dependent on the solution pH. The removal mechanism can be attributed to the ion-pair formation at the aluminum hydroxide surface. PMID:20627355

Lien, Hsing-Lung; Yu, Chia Ching; Lee, Ya-Ching

2010-08-01

168

Stabilization of engineered zero-valent nanoiron with Na-acrylic copolymer enhances spermiotoxicity.  

PubMed

Studies were carried out to assess the effects of stabilized (i.e., coated with organic polyacrylic stabilizer) and nonstabilized forms of zero-valent nanoiron (nZVI) on the development of Mytilus galloprovincialis embryos following 2 h exposure of the sperm prior to in vitro fertilization. Both forms of nZVI caused serious disruption of development, consisting of 30% mortality among spermatozoa with subsequent 20% decline in fertilization success, and delay in development, i.e., over 50% of the larvae were suspended in the trochophore stage. Significant DNA damage was also detected in sperm exposed to the highest exposure concentrations (10 mg L(-1)). Distinct dose response to the two different types of nZVI observed are linked to aggregation behavior that is controlled by the surface stabilizers. This work reports on conventional biomarkers (for membrane integrity, genotoxicity, and developmental toxicity) applied for the rapid assessment of toxicity of nZVI, which are able to detect surface property-related effects to meet the requirements of risk assessments for nanotechnology. The study highlights the potential ecotoxicological impact of an environmentally relevant engineered nanoparticle. Implications of the NOM-nZVI interactions regarding soil and groundwater remediation and wastewater treatment are discussed. PMID:21291273

Kadar, Eniko; Tarran, Glenn A; Jha, Awadhesh N; Al-Subiai, Sherain N

2011-04-15

169

Reduction of perchlorate using zero-valent titanium (ZVT) anode: kinetic models.  

PubMed

The kinetics of perchlorate reduction by zero-valent titanium (ZVT) undergoing electrical pitting corrosion was described by interactions of two domains (pit and solution). Two kinetic models were developed based on two possible inhibition mechanisms. A competitive adsorption model was developed based on surface coverage of perchlorate and chloride on bare ZVT, and a Ti(II) consumption model was developed based on Ti(II) oxidation by electrochemically developed chlorine. Both models well predicted perchlorate concentration changes in the solution. The competitive adsorption model showed that chloride has a higher adsorption affinity on both sites where oxidative dissolution of ZVT occurs and where chloride oxidation occurs. Also, the rates of perchlorate removal and chloride oxidation were directly proportional to current applied. For the Ti(II) consumption model, the rate constant of Ti(II) production was dependent on current. The rate of chloride oxidation is also believed to be proportional to current, but this conclusion cannot be made with confidence. Both kinetic models described changes in perchlorate concentration well. However, the Ti(II) consumption model was limited in its ability to predict chloride concentration. This limitation was probably caused by a lack of available information like electrochemical oxidation of chloride on bare ZVT and Ti(II) oxidation by chlorine. PMID:22878003

Lee, Chunwoo; Batchelor, Bill; Park, Sung Hyuk; Han, Dong Suk; Abdel-Wahab, Ahmed; Kramer, Timothy A

2012-11-01

170

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

Microsoft Academic Search

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

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

2000-01-01

171

Degradation of Polymers Coating Nano-scale Zero Valent Iron Particles used in Groundwater Remediation  

E-print Network

. The information will be essential to determine how long they can persist in the groundwater, and to determine if the polymers can enable growth of sulphate reducing bacteria (SRB). SRB causes sulfide formation which has been Experiments Starkey's mineral media was prepared to produce favorable growth conditions for the sulphate

Barthelat, Francois

172

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

E-print Network

to electrostatic attraction between nZVI and aminoclay nanoparticles. This silica-coated nZVI composite (ratio 1.0) exhibited a highly positively charged surface ($+40 mV) and a ferromagnetic property ($30 emu g?1 ). On the basis of these characteristics, oleaginous Chlorella sp. KR-1 was harvested within 3 min at a > 20 g L?1

Mosegaard, Klaus

173

Reductive dehalogenation of chlorinated organic compounds using zero-valent iron  

Microsoft Academic Search

Because of the widespread occurrence of halogenated organic compounds, and commonly low drinking water limits, remediation of ground water contaminated by these chemicals has become an important technical challenge. Difficulties associated with conventional remediation methods have stimulated great interest in the development of passive in situ technologies. Studies in progress at the Waterloo Centre for Groundwater Research at the University

Gillham

2008-01-01

174

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

E-print Network

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

Marchal, Fabienne

2012-06-07

175

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

Microsoft Academic Search

The Publisher regrets that this article was an accidental duplication of an article that has already been published in J. Contam. Hydrol. 78 (2005) 291 312, doi:10.1016\\/j.jconhyd.2005.05.006. The duplicate article has therefore been withdrawn from J. Contam. Hydrol. 80 (2005) 71 91.

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

2005-01-01

176

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...

177

Preparation of spherical iron nanoclusters in ethanolwater solution for nitrate removal  

Microsoft Academic Search

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

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

2006-01-01

178

Reductive Dechlorination of Chlorinated Biphenyls by Palladized Zero-Valent Metals  

Microsoft Academic Search

Laboratory-scale reductive dechlorination studies using bimetals were conducted to detoxify chlorinated biphenyls, which are known as one of the most recalcitrant organic compounds. Palladized iron and palladized zinc readily dechlorinated mono- and di-chlorinated biphenyls while plain metals were not active. Biphenyl and less chlorinated biphenyls were detected as the major products and calculated mass balance was around 100%, indicating that

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

2004-01-01

179

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

180

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...

181

Cysteine-induced modifications of zero-valent silver nanomaterials: implications for particle surface chemistry, aggregation, dissolution, and silver speciation.  

PubMed

The persistence of silver nanoparticles in aquatic environments and their subsequent impact on organisms depends on key transformation processes, which include aggregation, dissolution, and surface modifications by metal-complexing ligands. Here, we studied how cysteine, an amino acid representative of thiol ligands that bind monovalent silver, can alter the surface chemistry, aggregation, and dissolution of zero-valent silver nanoparticles. We compared nanoparticles synthesized with two coatings, citrate and polyvinylpirrolidone (PVP), and prepared nanoparticle suspensions (approximately 8 ?M total Ag) containing an excess of cysteine (400 ?M). Within 48 h, up to 47% of the silver had dissolved, as indicated by filtration of the samples with a 0.025-?m filter. Initial dissolution rates were calculated from the increase of dissolved silver concentration when particles were exposed to cysteine and normalized to the available surface area of nanoparticles in solution. In general, the rates of dissolution were almost 3 times faster for citrate-coated nanoparticles relative to PVP-coated nanoparticles. Rates tended to be slower in solutions with higher ionic strength in which the nanoparticles were aggregating. X-ray absorption spectroscopy analysis of the particles suggested that cysteine adsorbed to silver nanoparticles surfaces through the formation of Ag(+I)--sulfhydryl bonds. Overall, the results of this study highlight the importance of modifications by sulfhydryl-containing ligands that can drastically influence the long-term reactivity of silver nanoparticles in the aquatic environment and their bioavailability to exposed organisms. Our findings demonstrate the need to consider multiple interlinked transformation processes when assessing the bioavailability, environmental risks, and safety of nanoparticles, particularly in the presence of metal-binding ligands. PMID:22448900

Gondikas, Andreas P; Morris, Amanda; Reinsch, Brian C; Marinakos, Stella M; Lowry, Gregory V; Hsu-Kim, Heileen

2012-07-01

182

Mineral precipitation and porosity losses in granular iron columns  

Microsoft Academic Search

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

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

1999-01-01

183

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 ...

184

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

SciTech Connect

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

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

2007-08-17

185

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

E-print Network

is expensive and its solutions rather unstable. By using hydrazine as an alternate reductant under solvothermal been obtained. This is a significant result in that hydrazine is more stable and much less expensive reduction (right, bar: 5 nm) and, solvothermal reduction using hydrazine (bottom, bar: 5 nm). References: 1

Azad, Abdul-Majeed

186

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

Microsoft Academic Search

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

Qian Wang; Naman Cissoko; Mi Zhou; Xinhua Xu

2011-01-01

187

Hydrocarbon Formation in Metallic Iron/Water Systems  

E-print Network

Hydrocarbon Formation in Metallic Iron/Water Systems B A O L I N D E N G , , § T I M O T H Y J . C, Florida 32403-5323 Chlorinated ethenes can be reduced in metallic (zero- valent) iron/water systems of aqueous CO2 was not a major source of carbon for the background hydrocarbons. Acid dissolution of gray

Deng, Baolin

188

Determination of sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry.  

PubMed

In this study, oil-in-water formulations were optimized to determine sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry (FAAS). This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures and allows the calibration to be carried out using aqueous standards. Different oily phases such as corn oil, decyl oleate and octyl stearate were tested, as well as Tween 80, Triton X-100 and Triton 114 were analyzed as surfactants. The optimum type and proportion of formulations were determined and their use depended on the element studied. The emulsion preparation was performed by a conventional method that involves mixing both phases at 60 degrees C by magnetic stirring and phase inversion to change the water-to-oil ratio by increasing the volume of the surfactant-water external phase and correspondingly decreasing the volume of internal phase. The accuracy of the method was further confirmed by determining the metals in a whole egg powder CRM and recoveries ranged from 97.5% for Mg to 102.2% for Na, with relative standard deviations lower than 2.3%. The precision of the procedures was determined through repeatability (intra-day precision) and intermediate precision (inter-day). The repeatability presented RSD values lower than 4.2%. The intermediate precision was evaluated using the RSD and F-test. The RSD values to intermediate precision was lower than 5.3% and the computed F-values were lower than tabulated F-values, indicating no significant difference between the results obtained on different days. The proposed method including, sample emulsification for subsequent metal determination for FAAS, has proved to be sensitive, reproducible, simple and economical. PMID:20006088

Ieggli, C V S; Bohrer, D; do Nascimento, P C; de Carvalho, L M; Garcia, S C

2010-01-15

189

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...

190

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 120 nm and specific surface area of 25.4m2\\/g. The

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

2004-01-01

191

Reduction of Contaminant Mobility at the TNX Outfall Delta Through the Use of Apatite and Zero-Valent Iron as Soil Amendments.  

National Technical Information Service (NTIS)

The TNX pilot-scale research facility released processed waste, containing high concentrations of several metals and radionuclides into an unlined seepage basin between 1958 and 1980. The contents of this basin have entered the nearby swamp, the TNX Outfa...

D. Kaplan, A. Knox, C. Coffey

2002-01-01

192

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

SciTech Connect

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

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

2007-03-25

193

Treatment of mature landfill leachate by internal micro-electrolysis integrated with coagulation: a comparative study on a novel sequencing batch reactor based on zero valent iron.  

PubMed

A comparative study of treating mature landfill leachate with various treatment processes was conducted to investigate whether the method of combined processes of internal micro-electrolysis (IME) without aeration and IME with full aeration in one reactor was an efficient treatment for mature landfill leachate. A specifically designed novel sequencing batch internal micro-electrolysis reactor (SIME) with the latest automation technology was employed in the experiment. Experimental data showed that combined processes obtained a high COD removal efficiency of 73.7 1.3%, which was 15.2% and 24.8% higher than that of the IME with and without aeration, respectively. The SIME reactor also exhibited a COD removal efficiency of 86.1 3.8% to mature landfill leachate in the continuous operation, which is much higher (p<0.05) than that of conventional treatments of electrolysis (22.8-47.0%), coagulation-sedimentation (18.5-22.2%), and the Fenton process (19.9-40.2%), respectively. The innovative concept behind this excellent performance is a combination effect of reductive and oxidative processes of the IME, and the integration electro-coagulation. Optimal operating parameters, including the initial pH, Fe/C mass ratio, air flow rate, and addition of H(2)O(2), were optimized. All results show that the SIME reactor is a promising and efficient technology in treating mature landfill leachate. PMID:22771343

Ying, Diwen; Peng, Juan; Xu, Xinyan; Li, Kan; Wang, Yalin; Jia, Jinping

2012-08-30

194

Reductive dechlorination of carbon tetrachloride with elemental iron  

Microsoft Academic Search

Carbon tetrachloride (CCl4) was abiotically dechlorinated to chloroform (CHCl3) and methylene chloride (CH2Cl2) by zero valent iron (Fe0). Dechlorination of CCl4 was rapid, and approximately followed first-order kinetics in the range of concentrations tested (CCl4: 1.55.5 ?M; Fe0 powder: 110 g per 265 ml distilled water). Initial dechlorination rate coefficients for anoxic batch reactors (0.290 0.009 h?1 for 1

Bradley R. Helland; Pedro J. J. Alvarez; Jerald L. Schnoor

1995-01-01

195

Emulsifiers in bread making  

Microsoft Academic Search

The literature on the application of emulsifiers for baking as dough conditioners and anti-staling agents, is reviewed. The first part of the paper is devoted to reviewing the various studies on dough handling and bread quality improvement due to emulsifiers. In the second part, emphasis is given to the presentation of the phenomenon of staling in bread. Considerable work has

L. Stampfli; B. Nersten

1995-01-01

196

Channel flow and trichloroethylene treatment in a partly iron-filled fracture: Experimental and model results  

Microsoft Academic Search

Technical developments have now made it possible to emplace granular zero-valent iron (Fe0) in fractured media to create a Fe0 fracture reactive barrier (Fe0 FRB) for the treatment of contaminated groundwater. To evaluate this concept, we conducted a laboratory experiment in which trichloroethylene (TCE) contaminated water was flushed through a single uniform fracture created between two sandstone blocks. This fracture

Zuansi Cai; Corrine Merly; Neil R. Thomson; Ryan D. Wilson; David N. Lerner

2007-01-01

197

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

Microsoft Academic Search

There are reports that nano-sized zero-valent iron (Fe?) exhibits greater reactivity than micro-sized particles of Fe?, which may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. To better understand the reactivity of

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

2005-01-01

198

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

Microsoft Academic Search

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

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

2007-01-01

199

7 CFR 58.722 - Emulsifying agents.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 false Emulsifying agents. 58.722 Section 58.722 Agriculture Regulations of the Department of Agriculture...1 Quality Specifications for Raw Material 58.722 Emulsifying agents. Emulsifying agents...

2010-01-01

200

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) ...

201

[Emulsified intermediate moisture foods].  

PubMed

A water-in-oil emulsion with IMF behavior has been studied within DGRST Grant Nr. 75-7-0406. The dispersion of a sirupy aqueous phase of known aw into a more or less hardened fatty continuous phase was looked into through its effects, particularly how the fatty phase would modify the water behaviour of the dispersed aqueous phase. The emulsion was conventionally prepared by a preemulsion of the syrup into the lecithinated fat, an homogeneisation till enough dispersion and a centrifugation to get rid of free fat. Lecithin has to promote sufficient fat incorporation, correct dispersion and a final viscosity allowing pumpability. To get a cold centrifugate of enough consistency implies an efficient dispersion but before all a judicious choice of the continuous fatty phase, making allowance of organoleptic properties and shelf-life stability. The water behaviour has been worked at on two model systems, of initial phase volume phi = 0,36, with an internal phase made of partially inverted sucrose syrup (aw = 0,79) and an external fatty phase of either refined soybean oil or hydrogenated palm oil (m.p. 42 degrees C). These models respectively retained after centrifugation 12,5 p. 100 oil and 19,5 p. 100 fat; sorption-desorption isotherms were determined by the saturated salt solution method both at 37 degrees C and room temperature, exhibiting that the solid fat content of the continuous fatty phase positively reduces the water transfer velocity from-and-into the syrup. Such a W/O emulsified structure with a prevalent internal aqueous behaves like a pasty IMF, inherently protected against outside relative humidity variations; it also leads the system to a better consistency. PMID:707936

Fribourg, J L

1978-01-01

202

Iron  

MedlinePLUS

... shows that giving iron intravenously can improve some symptoms of heart failure. It is not yet known if taking an iron supplement by mouth would help.Attention deficit-hyperactivity disorder (ADHD). Developing research shows that taking iron sulfate ( ...

203

Implementation of fluidized granulated iron reactors in a chromate remediation process.  

PubMed

A new approach concerning in-situ remediation on source ('hot-spot') decontamination of a chromate damage in connection with an innovative pump-and-treat-technique has been developed. Iron granulates show significant higher reduction rates, using fluidized bed conditions, than a literature study with a fixed bed installation of small-sized iron granules. First results from an abandoned tannery site concerning injections of sodium dithionite as a chromate reductant for the vadose zone in combination with a pump-and-treat-method, allying the advantages of granulated zero valent iron (ZVI), are reported. Reduction amounts of chromate have been found up to 88% compared with initial values in the soil after a soil water exchange of 8 pore volumes within 2.5 months. Chromate concentrations in the pumped effluent have been reduced to under the detection limit of 0.005 mg/L by treatment with ZVI in the pilot plant. PMID:24530188

Mller, P; Lorber, K E; Mischitz, R; Weiss, C

2014-07-01

204

Oil emulsifier said to prevent carbon buildup  

SciTech Connect

A Philadelphia hospital trimmed 40% off its fuel oil bills after designing and installing a fuel oil emulsifier that increased combustion efficiency and prevented carbon buildup in the boilers. Carbon byproducts of combustion had been accumulating on heat exchange surfaces, reducing heating efficiency. The ultrasonic emulsifier burns oil 4% more efficiently than conventional burners alone by creating turbulence in a 7% solution of water and preheated oil. The magnitude of the improvement reflects the poor condition of the boilers before installation of the emulsifier.

Ladd, C.

1985-10-21

205

Emulsifier system for tertiary oil recovery  

SciTech Connect

A new emulsifier system for use in the tertiary recovery of oil comprises a mixture of an alcohol having no more than 12 carbon atoms and a surfactant comprising a neutralized, oxidized solvent extracted oil.

Alford, H.E.; Frazier, D.

1982-02-02

206

Functions of emulsifiers in food systems  

Microsoft Academic Search

and SummaryThe function of food grade emulsifiers in various food products (emulsions, starch based food, yeast raised bakery products,\\u000a etc.) are reviewed. The stability of emulsions against coalescence of dispersed droplets is among other factors dependent\\u000a on monoor multimolecular interfacial films with viscoelastic properties formed by adsorbed emulsifier molecules. Agglomeration\\u000a of fat globules in whippable emulsion is needed to obtain

N. Krog; Edwin Rahrs Vej

1977-01-01

207

Iron  

MedlinePLUS

... several factors [ 1 , 3 , 8 , 11-15 ]. Storage levels of iron have the greatest influence on iron ... RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily intake ...

208

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

209

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

210

Interfacial rheology of food emulsifiers and proteins  

Microsoft Academic Search

The scientific literature from 1997 (inclusive) to the present on the interfacial rheology of emulsifiers and proteins of relevance to food has been reviewed. Both shear and dilatational rheology of oilwater and airwater interfaces have been covered and the main factors affecting interfacial rheology have been tabulated. Special attention is paid to: the sensitivity of interfacial rheology to film composition

Brent S Murray

2002-01-01

211

Nucleation kinetics of emulsified triglyceride mixtures  

Microsoft Academic Search

The purpose of this study is to determine character istic nucleation parameters such as the surface free energy for nucleus\\u000a formation in mixtures of fully hydrogenated palm oil (HP) in sunflower oil (SF). These parameters will be used to model the\\u000a bulk crystallization kinetics of the same mixtures. This was achieved by determining the crystallization kinetics in emulsified\\u000a triglyceride mixtures

William Kloek; Pieter Walstra; Ton van Vliet

2000-01-01

212

Food emulsifiers: Surface activity, edibility, manufacture, composition, and application  

Microsoft Academic Search

Food emulsifiers are indispensable ingredients in most processed foods containing fats and oils. Terms like surface activity\\u000a and edibility have a special relevance to emulsifiers and are described. Food emulsifiers may be grouped according to different\\u000a aspects. In this paper they are described from the viewpoint of their origin, and special attention is given to monoglyceride\\u000a derivatives, such as lactylated

Jens Birk Lauridsen

1976-01-01

213

Formulation design for target delivery of iron nanoparticles to TCE zones.  

PubMed

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. PMID:24096200

Wang, Ziheng; Acosta, Edgar

2013-12-01

214

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

215

Emulsified coal oils as flotation reagents  

SciTech Connect

Investigations were conducted with the goal of preparing coal oils for use in coal flotation by preliminary emulsification. When added to the slurry, this oil is rapidly and uniformly distributed over the surface of the coal particles. The emulsification was conducted by mechanical dispersion in a laboratory agitator. (Under industrial conditions this process may be conducted in a centrifugal pump). A neutralized solution of acid tar (a waste from the sulfuric acid purification of crude benzol) was used as the emulsifier and emulsion stabilizer. The concentration of sulfonic acids was about 48%. Stable homogeneous emulsions were obtained at a concentration of oil up to 20% and neutralized tar of 0.2%. The size of the oil droplets in the emulsions was 2-10 microns. Experimental testing was conducted on a Mekhanobr laboratory flotation machine with a chamber 1 litter in volume. Unemulsified and emulsified coal oils from the tar refining division of the Makeevka Coke Works were investigated; screenings from the charge of the Yasinovka Coke Works (the below-0.5-mm size class) were floated. As a comparison experiments with the traditional kerosene reagent were conducted. In the experiments with anthracene oil, pitch distillates and kerosene, T-66 frothing agent was added at 140 g/ton of sludge; during the work with wash oil and naphthalene exudates T-66 was not added, assuming that the water-soluble phenols and bases contained in these oils have adequate frothing capacity. 5 references, 2 figures.

Selyanko, I.T.; Belov, K.A.; Karnozhitskii, P.V.; Ivashchenko, V.A.

1983-01-01

216

Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System  

E-print Network

The scope of work can be divided into; the measurement of the rheological properties of a new emulsified acid system that can be suitable for high temperature applications, a study of the performance of the new emulsified acid in stimulating both...

Sayed, Mohammed Ali Ibrahim

2013-05-15

217

Neural network model for resilient modulus of emulsified asphalt mixtures  

Microsoft Academic Search

This paper explores the potential use of neural networks (NNs) in the field of emulsified asphalt mixtures. A neural network model is developed for predicting, with sufficient approximation, relationship between the factors affecting resilient modulus (inputs: curing time, cement addition level, and residual asphalt content) and the resilient modulus (output) of emulsified asphalt mixture. A backpropagation neural network of three

Talat Sukru Ozsahin; Seref Oruc

2008-01-01

218

New emulsifiers are finding use in oil-based muds  

SciTech Connect

Oil mud component chemistry has always been proprietary in nature with new types of products described only superficially by suppliers. This article, however, brings to light many important aspects of primary and secondary emulsifiers for both diesel and low-toxicity oil mud systems. Topics discussed include pertinent oil mud background, emulsifier chemistry, performance evaluation and field testing results.

Clapper, D.K.; Salisbury, D.

1984-11-01

219

Water-in-oil emulsifier and oil-burner boiler system incorporating such emulsifier  

SciTech Connect

An oil-water emulsifier comprises a venturi member having an inlet for receiving oil, an oil-water emulsion outlet and an opening extending therethrough from the inlet to the outlet. The opening of the venturi member comprises a diameter-reducing portion which connects to a throat portion having a substantially smaller diameter than the inlet, the throat portion being connected to an expanding portion extending from the throat to the outlet, the diameter of the outlet of the opening being substantially greater than that of the throat portion. A plurality of water injection holes extend from the outer periphery of the venturi member to the throat portion so as to be in communication with the oil flowing through the throat portion, the injection holes being preferably substantially perpendicular to the direction of oil flow through the throat portion. Also disposed is an oil-burner boiler system incorporating the abovedescribed oil-water emulsifier.

Gallagher, J.P.

1982-08-17

220

Effects of antioxidants and additional emulsifiers on the stability of emulsified milk fat in the photo/radical oxidation system.  

PubMed

The effects of antioxidants on the oxidative deterioration of emulsified oils and fats differ depending on the oxidation conditions, oils and fats used, and type of emulsifier. In this study, milk fat was emulsified to obtain water-oil (O/W) emulsion using Tween20 as emulsifier. The antioxidative effects of several antioxidants with various lipophilic properties, such as ?-tocopherol (Toc), epigallocatechin gallate (EGCg), quercetin (Qu), green tea extract (GTE), and rooibos tea extract (RTE) were investigated, the effects of additional emulsifiers such as polyglycerol and sucrose esters of fatty acids on the oxidation stability of the emulsion were also investigated. Under oxidative conditions of 30C in 650 lx, Toc was more effective than GTE in suppressing the increase of the peroxide value (PV, meq/kg) of the emulsified milk fat. Under these oxidative conditions, the antioxidative effect of GTE was enhanced by the addition of polyglycerol and sucrose esters of fatty acids. Under the oxidative conditions at 40C in dark with 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) or 2,2'-azobis (2,4-dimethylvaleronitrile) (AMVN), Toc showed the most antioxidative effect on suppression of the increase of PV and anisidine value (AnV) of the emulsified milk fat. Furthermore, additional emulsifiers also showed suppressive effects on the increase of the PV and AnV of the emulsified milk fat even without any antioxidants. The effects of additional emulsifiers on the oxidative stability of O/W emulsions were enhanced with antioxidants such as Toc, EGCg, and Qu. PMID:25174675

Yamamoto, Yukihiro; Hiyama, Shinichiro; Takase, Yoshihiko; Kadowaki, Akio; Hara, Setsuko

2014-01-01

221

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

222

Occupational asthma due to an emulsified oil mist.  

PubMed Central

A toolsetter developed occupational asthma due to the oil mist generated by his lathe on which it was used as a coolant. The diagnosis was confirmed by serial measurements of peak expiratory flow at home and work, including a prolonged period away from work. Occupational type bronchial provocation tests were performed using the whole emulsified oil and its components separately. He reacted specifically to the whole emulsified oil and to the reodorant, a pine oil preparation. He also reacted to colophony, a constituent of the emulsifier. PMID:3965015

Hendy, M S; Beattie, B E; Burge, P S

1985-01-01

223

Fast liquid-liquid reactions: Role of emulsifiers  

SciTech Connect

The effect of emulsifiers such as sodium dioctyl sulfosuccinate, sorbitan monooleate, etc., on the rate of alkaline hydrolysis of higher formate esters was studied. The extraction of these formate esters is accompanied by a fast pseudo-first-order reaction in the diffusion film. Values of effective interfacial area were measured in a mechanically agitated contactor; the specific rate of extraction was measured in a stirred cell of known interfacial area. The effects of speed of agitation and the emulsifier concentration on the effective interfacial area were studied. Emulsifiers can increase the effective interfacial area markedly; the highest increase was by a factor of 14.

Smita, S.L.; Bhave, R.R.; Sharma, M.M.

1983-01-01

224

Effects of concentration, degree of deacetylation and molecular weight on emulsifying properties of chitosan.  

PubMed

Chitosan has excellent emulsifying properties. Emulsifying activity and stability of chitosan were determined by integrated light scattering technique and turbidimetric method. The effects of concentration, degree of deacetylation and molecular weight on emulsifying properties of chitosan were systematically studied in the paper. Emulsifying activity of chitosan initially increased, arrived at the peak at 0.75% and then declined, while emulsifying stability continuously increased with a rise of chitosan concentration from 0.25% to 1.25%. Emulsifying activity and stability of chitosan initially decreased and reached the minimum, then increased with the rise of degree of deacetylation. Chitosan with DD 60.5% and 86.1% showed superior emulsifying activity and stability. Chitosan with low Mw exhibited better emulsifying activity than those with high Mw. Chitosan with Mw 410 kDa and 600 kDa showed superior emulsifying activity in the test range. Emulsifying stability of chitosan increased with a rise of Mw. PMID:21382402

Li, Xingke; Xia, Wenshui

2011-06-01

225

Emulsifier system for the tertiary recovery of oil  

SciTech Connect

In an emulsifier system for the tertiary recovery of oil comprising a surfactant and an alcohol cosurfactant, improved results are achieved if the alcohol cosurfactant is composed of a mixture of alcohols having no more than 12 carbon atoms.

Alford, H.E.; Hardman, H.F.

1984-01-03

226

Proteins as emulsifiers: Methods for assessing the role  

Microsoft Academic Search

The objective of this review is to present a variety of surface and colloid chemical methodologies, in brief, with which one\\u000a may study the role of proteins as emulsifiers and co-emulsifiers. The techniques range from microtechniques aimed at single\\u000a interfaces (film balance) and double interfaces (tensiolaminometry) to macrotechniques aimed at the gross emulsion (microcalorimetry,\\u000a electrophoresis, pulsed, nuclear magnetic resonance, microwaves).

Charles J. Cante; Roger W. Franzen; Fouad Z. Saleeb

1979-01-01

227

Vitrification of emulsified dilute aqueous sucrose solutions at high pressures  

NASA Astrophysics Data System (ADS)

The supercooling and glass-forming behavior of aqueous sucrose solution was investigated using emulsified sucrose solutions at high pressures. It is shown that emulsified aqueous sucrose solution with the sucrose concentration being as low as 1 m (m: molality) is glass-forming at high pressures above 190 MPa. This finding may form the basis of a useful vitrification method for cryo-preservation of living cells and tissues at high pressures.

Kanno, H.; Miyata, K.; Hayakawa, S.; Kajiwara, K.

2008-12-01

228

Vitrification of emulsified dilute aqueous sucrose solutions at high pressures  

Microsoft Academic Search

The supercooling and glass-forming behavior of aqueous sucrose solution was investigated using emulsified sucrose solutions at high pressures. It is shown that emulsified aqueous sucrose solution with the sucrose concentration being as low as 1m (m: molality) is glass-forming at high pressures above 190MPa. This finding may form the basis of a useful vitrification method for cryo-preservation of living cells

H. Kanno; K. Miyata; S. Hayakawa; K. Kajiwara

2008-01-01

229

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 380L of commercially available emulsion (EOS) containing emulsified soybean oil, food-grade surfactants, lactate, and yeast extract through ten

Robert C. Borden

2007-01-01

230

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

231

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

232

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

233

Oral solid self-emulsifying formulations: a patent review.  

PubMed

Self-emulsifying compositions are lipidic drug delivery systems that provide a number of delivery advantages. A variety of excipients are available for designing of these drug delivery systems. These systems can be classified as Type I, II, III, and IV, and alternatively as solid, semi-solid, and liquid. Till date many patents have been published on self-emulsifying compositions, and a few commercial products have also been launched. The purpose of this review is to have insights into the patent literature capturing the developments in the area of oral solid self-emulsifying formulations. Though the main emphasis is on developments in solid self-emulsifying formulations, an overview of different manufacturing techniques has also been provided. These formulations can be grouped as conventional, granules, pellets, tablets, supersaturable, controlled release, eutectic-based, and positively charged. The components of self-emulsifying formulations described in this review are not limited only to oils, surfactants, and cosurfactants but also include binders, polymers, diluents, alkalinizing agents, stabilizing agents, preservatives, and viscosity adjusting agents. The inventions highlighted in this article provide useful guidelines for enhancement of oral bioavailability of drugs through this drug delivery platform. PMID:24628371

Tarate, Bapurao; Chavan, Rahul; Bansal, Arvind K

2014-01-01

234

Nonionic emulsifier and substituted succinic anhydride compositions therewith  

SciTech Connect

This patent describes an emulsifier prepared by the process which comprises heating the reaction product of: a hydrocarbyl-substituted succinic anhydride having from 12 to 25 carbon atoms in the substituent; and a nonionic water-soluble compound having from 1 to 3 groups reactive to anhydrides, wherein the water-soluble compound has sufficient hydrophilic strength to give a balanced oil-in-water emulsifier; and wherein the reaction product contains a free carboxyl group and a substituted carboxyl group per each reacted anhydride molecule; under conditions sufficient to remove the free carboxyl group. A stable hydrocarbyl-substituted succinic anhydride/nonionic emulsifier composition comprising: 70 to 99.5% of a normally liquid hydrocarbyl-substituted succinic anhydride having from 12 to 25 carbon atoms in the substituent; and 0.5 to 30% of an emulsifier prepared by the process which comprises heating the reaction product of a hydrocarbyl-substituted succinic anhydride having from 12 to 25 carbon atoms in the substituent and a nonionic water-soluble compound having 1 to 3 groups reactive to anhydrides, wherein the water-soluble compound has sufficient hydrophilic strength to give as balanced oil-in-water emulsifier; and wherein the reaction product contains a free carboxyl group and a substituent carboxyl group per each reacted anhydride molecule; under conditions sufficient to remove the free carboxyl group.

Sweeney, W.A.

1989-07-18

235

Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction.  

PubMed

Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1M Na2SO4 containing 0.5wt% NH4F electrolyte, holding the potential at 20, 40, and 60V for 20min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40V for 20min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H2O2). In case of INT-40V in the presence of H2O2 3%, the first-order rate constant was found to be 1.710(-2)min(-1), and 1.210(-2)min(-1) with commercial hematite powder. Degradation of cyanide was much less with only H2O2. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction. PMID:24704548

Jang, Jun-Won; Park, Jae-Woo

2014-05-30

236

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

237

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

238

Effects of processing factors on qualities of emulsified meatball  

Microsoft Academic Search

A four-factor central composite design was adopted for studying the effects of fat, salt, sugar and cooking temperature on qualities of an emulsified meatball or Chinese meatball. Results indicated that texture is the most important characteristic of this type of meat product. Consumers prefer a harder texture. Panel preferences significantly increased with the amount of salt added and significantly decreased

S. Y. Hsu; H.-Y. Chung

1998-01-01

239

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

240

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

2014-12-01

241

Formulation of emulsifiable cutting fluids and extreme pressure behaviour  

Microsoft Academic Search

Extreme pressure tests following the ASTM D 2783 standard were carried out to evaluate the performance of several oil-in-water (O\\/W) emulsions used as lubricating and cooling fluids in machining operations. The effect of concentration of three different emulsifiers (anionic, non-ionic, and cationic surfactants) on the extreme pressure properties of the O\\/W emulsions was studied in more detail. The base oil

A. Cambiella; J. M. Benito; C. Pazos; J. Coca; A. Hernndez; J. E. Fernndez

2007-01-01

242

Effect of high pressure on the emulsifying behaviour of ?-lactoglobulin  

Microsoft Academic Search

The influence of high pressure (up to 800 MPa) on the emulsifying behaviour of ?-lactoglobulin has been investigated at neutral pH. Fine oil-in-water emulsions (0.4% w\\/w ?-lactoglobulin, 20% v\\/v oil) made with the pressure-treated protein were found to give substantially larger droplets than those made with the native protein. Visual creaming behaviour and changes in average droplet size have been

Vanda B. Galazka; Eric Dickinson; Dave A. Ledward

1996-01-01

243

HYDROCOLLOIDS AS EMULSIFYING AGENTS FOR OIL-IN-WATER EMULSIONS  

Microsoft Academic Search

Hydrocolloids are water-soluble biopolymers consisting of high molecular weight polysaccharides. For generations, these biopolymers were also termed gums or stabilizers imparting viscosity, gelification and long-term stability to food systems.Some hydrocolloids were also considered as emulsifying agents, since they help to form and stabilize oil-in-water emulsions. Only in the last two decades questions have been raised as to the mode of

Nissim Garti

1999-01-01

244

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

245

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

246

The influence of food emulsifiers on fat and sugar dispersions in oils. II. Rheology, colloidal forces  

Microsoft Academic Search

The influence of food emulsifiers on the viscoelastic properties (storage modulus and yield value) of fat and sugar dispersions\\u000a in vegetable oils has been investigated. It was found that almost all of the emulsifiers tested influence the rheology of\\u000a the dispersions. The magnitude and the direction of the rheological changes depend on both the type and the amount of emulsifier.

Dorota Johansson; Bjm Bergensthl

1992-01-01

247

The influence of food emulsifiers on fat and sugar dispersions in oils. I. Adsorption, sedimentation  

Microsoft Academic Search

The adsorption isotherms of several emulsifiers to fat and sugar crystals dispersed in oils have been determined. Further,\\u000a the influence of the emulsifiers on the interactions between the crystals has been estimated in sedimentation experiments,\\u000a where an increased sediment volume due to adsorption corresponds to an increased adhesion between the crystals andvice versa. Most of the emulsifiers examined adsorb weakly

Dorota Johansson; Bjm Bergensthl

1992-01-01

248

Influence of Composition of Emulsifier Blends on the Rheological Properties of Salad Dressing-Type Emulsions  

Microsoft Academic Search

This paper deals with the influence that composition of emulsifier blends exerts on the rheological properties of low-in-fat salad dressing-type emulsions. Binary blends of egg yolk and different types of amphiphilic molecules (low-molecular weight and macromolecules) were used in several proportions to stabilize emulsions by keeping constant the total amount of emulsifier. The different emulsifiers added to egg yolk were

M. A. Riscardo; J. M. Franco; C. Gallegos

2003-01-01

249

Impact of emulsifiers on the quality and rheological properties of gluten-free breads and batters  

Microsoft Academic Search

The effects of the emulsifiers lecithin (LC), di-acetyl tartaric ester of monoglycerides (DATEM), distilled monoglycerides\\u000a (DM) or sodium stearoyl lactylate (SSL) were studied in a gluten-free (GF) batter and bread formulation. Three different levels,\\u000a i.e. low, medium, and high, were evaluated and compared to a control bread with no emulsifier. The rheological properties\\u000a of the emulsifiers at their optimum level

Maria Helena B. Nunes; Michelle M. Moore; Liam A. M. Ryan; Elke K. Arendt

2009-01-01

250

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

251

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

E-print Network

reduced to chloride using electrochemically developed pitting corrosion on Ti(0). Perchlorate reduction was believed to be caused by an active reductant (dissolved Ti(II)) during the pitting corrosion of Ti(0). The rate of perchlorate reduction...

Lee, Chun Woo

2009-05-15

252

Emulsifiers and thickeners on extrusion-cooked instant rice product.  

PubMed

Extrusion-cooked instant rice was prepared by optimizing the formulation with emulsifiers, glycerol monostearate (GMS), soybean lecithin (LC), and sodiumstearoyl lactylate (SSL), and thickeners, gum Arabic (GA), sodium alginate (SA), and sticky rice (SR). The emulsifiers addition caused increase of degree of gelatinization (DG), and decrease of water soluble carbohydrate (WSC), ?-amylase sensitivity, water soluble index (WAI) and adhesive for extrudates, while the thickeners addition increased extrudates DG, bulk density (BD), WSC, ?-amylase sensitivity, WAI, hydration rate (HR) and adhesiveness. Based on the data generated by a single additive at various levels, optimum formulation was obtained employing orthogonal matrix system with combination of the selected additives for extrusion cooking. Extrudates were evaluated for optimum hydration time followed by drying to prepare the finished product. Texture profile analysis and sensory evaluation indicate that quality of the finished product is equivalent to that of the round shaped rice and superior to a commercial instant rice product. This study also demonstrates possibility of value-added and versatile instant rice product development using broken rice. PMID:24425967

Wang, Jin Peng; An, Hong Zhou; Jin, Zheng Yu; Xie, Zheng Jun; Zhuang, Hai Ning; Kim, Jin Moon

2013-08-01

253

Dispersion and Sorption of Oil Spills by Emulsifier-Modified Expanded Perlite  

Microsoft Academic Search

Three grain sizes of expanded perlite were modified with emulsifiers and their potential usefulness in combating oil spills was studied. The tests in the laboratory show that when this perlite is added to a wateroil mixture, the light perlite particles move on the surface spreading over it very quickly (in fractions of a second). It seems that the emulsifier disperses

M Roulia; K Chassapis; Ch Fotinopoulos; Th Savvidis; D Katakis

2003-01-01

254

Emulsifying agents from bacteria isolated during screening for cells with hydrophobic surfaces  

Microsoft Academic Search

Summary The culture supernatants of 126 bacterial strains isolated during screening for hydrophobic cell surfaces, were tested for the production of emulsifying agents. Forty-eight strains were found to produce effective emulsion-stabilizing substances during growth on glucose. The most effective emulsifying agents were isolated and could be divided into two chemical groups. The first group was separated from the isolated extracts

Thomas R. Neu; Karl Poralla

1990-01-01

255

Interfacial, foaming and emulsifying characteristics of sodium caseinate as influenced by protein concentration in solution  

Microsoft Academic Search

The foaming and emulsifying characteristics of proteins are important attributes during the production stage, storage, transport, and consumer perception of quality (appearance) of food dispersions (emulsions and foams). In this contribution, we are concerned with the analysis of interfacial, foaming, and emulsifying characteristics of a typical milk protein (sodium caseinate) as a function of protein concentration in aqueous solution (C,

Cecilio Carrera Snchez; Juan M. Rodrguez Patino

2005-01-01

256

Surface phase behavior and microstructure of lipid\\/PEG-emulsifier monolayer-coated microbubbles  

Microsoft Academic Search

Langmuir trough methods and fluorescence microscopy were combined to investigate the phase behavior and microstructure of monolayer shells coating micron-scale bubbles (microbubbles) typically used in biomedical applications. The monolayer shell consisted of a homologous series of saturated acyl chain phospholipids and an emulsifier containing a single hydrophobic stearate chain and polyethylene glycol (PEG) head group. PEG-emulsifier was fully miscible with

Mark A. Borden; Gang Pu; Gabriel J. Runner; Marjorie L. Longo

2004-01-01

257

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

258

ISAP 2012 Goyer et al: Environmental data of cold mix using emulsified bitumen for a better selection of road materials  

E-print Network

ISAP 2012 Goyer et al: Environmental data of cold mix using emulsified bitumen for a better selection of road materials 1/12 Environmental data of cold mix using emulsified bitumen for a better of cold mix using emulsified bitumen for a better selection of road materials, France (2012)" #12;ISAP

Paris-Sud XI, Université de

259

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

NASA Astrophysics Data System (ADS)

Biological and abiotic approaches for treating co-mingled perchlorate, nitrate, and nitramine explosives in groundwater were compared in microcosm and column studies. In microcosms, microscale zero-valent iron (mZVI), nanoscale zero-valent iron (nZVI), and nickel catalyzed the reduction of RDX and HMX from initial concentrations of 9 and 1 mg/L, respectively, to below detection (0.02 mg/L), within 2 h. The mZVI and nZVI also degraded nitrate (3 mg/L) to below 0.4 mg/L, but none of the metal catalysts were observed to appreciably reduce perchlorate ( 5 mg/L) in microcosms. Perchlorate losses were observed after approximately 2 months in columns of aquifer solids treated with mZVI, but this decline appears to be the result of biodegradation rather than abiotic reduction. An emulsified vegetable oil substrate was observed to effectively promote the biological reduction of nitrate, RDX and perchlorate in microcosms, and all four target contaminants in the flow-through columns. Nitrate and perchlorate were biodegraded most rapidly, followed by RDX and then HMX, although the rates of biological reduction for the nitramine explosives were appreciably slower than observed for mZVI or nickel. A model was developed to compare contaminant degradation mechanisms and rates between the biotic and abiotic treatments.

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

2007-01-01

260

Preparation of nanocapsules via emulsifier-free miniemulsion polymerization.  

PubMed

Nanocapsules containing hexadecane or paraffin as core materials and polystyrene as a shell were produced in a new method through emulsifier-free miniemulsion polymerization using 2,2' azobis (2-amidinopropane) dihydrochloride (V-50) as a cationic ionizable water-soluble initiator. The effect of some parameters such as hexadecane or paraffin amounts and polymerization duration on morphology and thermal properties of resulting nanocapsule particles was studied. Transmission electron microscopy (TEM) showed that the products had latex particles having a size range of about 200-700 nanometer and both nanocapsules with core-shell morphology and solid particles. The phase change temperature and phase transition heat of the produced nanocapsules were determined by differential scanning calorimetric (DSC) analyses. Thermogravimetric analysis (TGA) was also used to prove the capsulation and to determine the amount of hexadecane or paraffin in the nanocapsules. PMID:19916455

Barari, Mohammad; Faridi-Majidi, Reza; Madani, Mohammad; Sharifi-Sanjani, Naser; Oghabian, Mohammad Ali

2009-07-01

261

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

262

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

263

Iron and Iron Deficiency  

MedlinePLUS

... other types of foods eaten at the same meal. Foods containing heme iron (meat, poultry, and fish) ... heme iron absorption when eaten at the same meal. Substances (such as polyphenols, phytates, or calcium) that ...

264

Effects of emulsifier on particle size of a phase change material in a mixture with water  

SciTech Connect

The use of a phase-change material (PCM) in a district cooling system was studied in order to increase the heat transfer performance of the system. One of the major technical obstacles to its use is the clogging of the piping system. The present study attempts to minimize the clogging problem by using an emulsifier. Effects of the emulsifier on the mixture of water and hexadecane (a PCM) were studied. A small amount (60 to 2775 ppm) of emulsifier caused remarkable effects resulting in the production of fine PCM particles. As the amount of the emulsifier was increased in the 25% hexadecane mixture with water, the size of the solid particles of hexadecane became smaller. When the size of the hexadecane particles was small enough, they did not stick together or stick to the surface of the cold wall of a heat exchanger.

Choi, E.; Cho, Y.I.; Lorsch, H.G.

1991-06-30

265

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

266

Identification and characterization of a soil bacterium with extracellular emulsifying activity  

Microsoft Academic Search

A gram?negative bacterial strain (designated UG2) isolated from oil?contaminated soil was identified as Pseudomonas aeruginosa based on biochemical characterization, total cellular fatty acid analysis, and serotyping. The strain produced high extracellular emulsifying activity when grown on various aromatic and straight chain hydrocarbons such as naphthalene, stearic acid, hexadecane and sunflower oil. The emulsifying activity in crude culture filtrates of UG2

Gary Berg; Alan G. Seech; Hung Lee; Jack T. Trevors

1990-01-01

267

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

Microsoft Academic Search

The influence of high pressure (HP) treatment (200600MPa) 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 (0.250.75%) 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

268

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

269

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

270

Effects of selected polysorbate and sucrose ester emulsifiers on the physicochemical properties of astaxanthin nanodispersions.  

PubMed

The effects of selected nonionic emulsifiers on the physicochemical characteristics of astaxanthin nanodispersions produced by an emulsification/evaporation technique were studied. The emulsifiers used were polysorbates (Polysorbate 20, Polysorbate 40, Polysorbate 60 and Polysorbate 80) and sucrose esters of fatty acids (sucrose laurate, palmitate, stearate and oleate). The mean particle diameters of the nanodispersions ranged from 70 nm to 150 nm, depending on the emulsifier used. In the prepared nanodispersions, the astaxanthin particle diameter decreased with increasing emulsifier hydrophilicity and decreasing carbon number of the fatty acid in the emulsifier structure. Astaxanthin nanodispersions with the smallest particle diameters were produced with Polysorbate 20 and sucrose laurate among the polysorbates and the sucrose esters, respectively. We also found that the Polysorbate 80- and sucrose oleate-stabilized nanodispersions had the highest astaxanthin losses (i.e., the lowest astaxanthin contents in the final products) among the nanodispersions. This work demonstrated the importance of emulsifier type in determining the physicochemical characteristics of astaxanthin nano-dispersions. PMID:23303336

Anarjan, Navideh; Tan, Chin Ping

2013-01-01

271

Graduate Student Seminar Series, Fall 2010 Department of Civil and Environmental Engineering  

E-print Network

. Monday November 22 Yun-ta Yeh Electrochemical Reduction of Carbon Dioxide into Oxy-Hydrocarbons #12 Inactivation by Nano Zero-Valent Iron (nZVI) Amended Cation Exchange Resin (CER) Monday December 6 Yue Wang

Kirby, James T.

272

Changes in secondary structure of gluten proteins due to emulsifiers  

NASA Astrophysics Data System (ADS)

Changes in the secondary structure of gluten proteins due to emulsifiers were analyzed by Raman Spectroscopy. The protein folding induced by 0.25% SSL (Sodium Stearoyl Lactylate) (GS0.25, Gluten + 0.25% SSL) included an increase in ?-helix conformation and a decrease in ?-sheet, turns and random coil. The same behavior, although in a less degree, was observed for 0.5% gluten-DATEM (Diacetyl Tartaric Acid Esters of Monoglycerides) system. The low burial of Tryptophan residues to a more hydrophobic environment and the low percentage area of the C-H stretching band for GS0.25 (Gluten + 0.25% SSL), could be related to the increased in ?-helix conformation. This behavior was also confirmed by changes in stretching vibrational modes of disulfide bridges (S-S) and the low exposure of Tyrosine residues. High levels of SSL (0.5% and 1.0%) and DATEM (1.0%) led to more disordered protein structures, with different gluten networks. SSL (1.0%) formed a more disordered and opened gluten matrix than DATEM, the last one being laminar and homogeneous.

Gmez, Anala V.; Ferrer, Evelina G.; An, Mara C.; Puppo, Mara C.

2013-02-01

273

Diesel cogeneration plant using oxygen enriched air and emulsified fuels  

SciTech Connect

The investigation of oxygen-enriched combustion of alternative fuels in diesel engines at Argonne National Laboratory (ANL) is based on information gathered from two previous Department of Energy programs. The first was the slow-speed diesel engine program which used fuels such as coal-water slurry and coal derived liquid fuels in a slow speed diesel engine. The second was the development of membrane oxygen separation equipment. The results of these programs indicated that using the new membrane oxygen enrichment technology with medium- and high-speed diesel engines would do two things. First, oxygen enrichment could reduce some emissions from stationary diesel engines, particularly smoke, particulates and hydrocarbons while significantly increasing power output. The second, was that it might be possible to use less expensive liquid fuels such as No. 4, No. 6 and residual oil emulsified with water in medium- to high-speed diesel engines. The water would (1) help to eliminate the undesirable increase in nitrogen oxide production when enriched oxygen is used, and (2) by reducing the viscosity of the heavier liquid fuels, make them easier to use in smaller industrial cogeneration applications. This program consists of four steps: preliminary feasibility study, exploratory experiments, system development, and demonstration and commercialization of an industrial cogeneration system. 3 refs., 13 figs.

Marciniak, T.J.; Cole, R.L.; Sekar, R.R.; Stodolsky, F. (Argonne National Lab., IL (USA)); Eustis, J.N. (USDOE, Washington, DC (USA))

1990-01-01

274

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

275

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

SciTech Connect

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

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

2013-04-24

276

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

277

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

278

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

NASA Astrophysics Data System (ADS)

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 ?g/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.

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

2010-07-01

279

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

280

Effects of supplemental exogenous emulsifier on performance, nutrient metabolism, and serum lipid profile in broiler chickens.  

PubMed

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

281

Recent patents survey on self emulsifying drug delivery system.  

PubMed

Self-Emulsifying Drug Delivery System is a unique feasible approach to overcome low oral bioavailability problem which is associated with the hydrophobic drugs due to their unparalleled potential as a drug delivery with the broad range of application. The estimated 40% of active pharmaceuticals are poorly water soluble. Now recently, formulation containing oral SEDDS has received much interest as it solve problems related to oral bioavailability, intra and inter-subject variability and lack of dose proportionality of hydrophobic drugs. Now a days, it is the first way to investigate the development of any kind of innovative dosage forms. Many important in-vitro characteristics such as surfactant concentration, oil/surfactant ratio, emulsion polarity, droplet size and zeta potential play an important role in oral absorption of drug from SEEDS. It can be orally administered in the form of SGC or HGC and also enhances bioavailability of drugs to increase solubility and minimizes the gastric irritation. After administration the drug remains entrapped in the oily droplets (inside the droplet or in the surfactant`s film at the interface) of the emulsion that are formed in the GIT upon self-emulsification process. It is also a bit problematic to say that the drug is being released from SMEDDS, it would be more precise to say that it diffuses out of oily droplets into the GIT media resulting in the formation of an equilibrium between the drug dissolved in oily droplets and the outer dispersed media (e.g. GIT fluids). Many of the application and preparation methods of SEDDS are reported by research articles and patents in different countries. We present an exhaustive and updated account of numerous literature reports and more than 150 patents published on SEDDS in the recent period. This current patent review is useful in knowledge of SEDDS for its preparations and patents in different countries with emphasis on their formulation, characterization and systematic optimization strategies, thus paving the way for accelerated progress into the SEDDS application in pharmaceutical research as well as patents on SEDDS methods. PMID:25146965

Jethara, Sahilhusen I; Patel, Alpesh D; Patel, Mukesh R

2014-01-01

282

Influences of Fat, Thickener and Emulsifier Contents on Salad Dressing: Static and Dynamic Sensory and Rheological Analyses  

Microsoft Academic Search

The effects of contents of fat, thickener and emulsifier in salad dressing were investigated. Twelve types of dressings were produced according to a full factorial design, whereby the fat content was set at three levels, the thickener and the emulsifier contents at two levels. The dressings were analysed by a sensory panel, using both quantitative descriptive profiling and time-intensity (TI)

Karin Wendin; Gunnar Hall

2001-01-01

283

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...

284

Design of nanoemulsion-based delivery systems of natural antimicrobials: Effect of the emulsifier  

Microsoft Academic Search

This work aims at investigating the effect of the nanoemulsion delivery systems on the antimicrobial activity of different essential oil components.Carvacrol, limonene and cinnamaldehyde were encapsulated in the sunflower oil droplets of nanoemulsions prepared by high pressure homogenization and stabilized by different emulsifiers: (a) lecithin, (b) pea proteins, (c) sugar ester and (d) a combination of Tween 20 and glycerol

Francesco Dons; Marianna Annunziata; Mariarosaria Vincensi; Giovanna Ferrari

285

Evaluation of soy based heavy fuel oil emulsifiers for energy efficiency and environmental improvement  

SciTech Connect

It is known that the emulsification of water into heavy fuel oil (No. 6) can result in improved atomization of the fuel in a combustion chamber, which results in several benefits. In this study, two soybean lecithin based emulsifiers were evaluated. The emulsifiers were added to the No. 6 fuel at 0.5% and 1 % levels and emulsions of 10% and 15% water were prepared and burned in a pilot scale combustion chamber. The results showed a significant decrease in NO{sub x} emissions, and a reduction in carbon particulates, as well as a decrease in the excess oxygen requirement when the emulsions were burned when compared to fuel oil alone and a fuel oil/water mixture without the emulsifier. It was concluded that the use of a soybean lecithin based emulsifier may be used to increase the burning efficiency of heavy fuel oils, reduce emissions and particulates, and reduce down time for cleaning. This can be very important in utility plants which burn large volumes of heavy fuel oil and are located near urban areas.

Lee, P.K.; Szuhaj, B.F. [Central Soya Company, Inc., Fort Wayne, IN (United States); Diego, A. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1996-12-31

286

Effects of emulsifiers on the controlled release of paclitaxel (Taxol ) from nanospheres of biodegradable polymers  

Microsoft Academic Search

Paclitaxel (Taxol) is an antineoplastic drug effective for various cancers especially ovarian and breast cancer. Due to its high hydrophobicity, however, an adjuvant such as Cremophor EL has to be used in its clinical administration, which causes serious side-effects. Nanospheres of biodegradable polymers could be an ideal solution. This study investigates the effects of various emulsifiers on the physical\\/chemical properties

Si-shen Feng; Guofeng Huang

2001-01-01

287

Isolation and functional characterization of hydrocarbon emulsifying and solubilizing factors produced by a Pseudomonas species  

Microsoft Academic Search

Pseudomonas PG-1 cultivated on pristane produced in good amount a heat-stable polymeric substance which showed strong hydrocarbon emulsifying and solubilizing properties. The substance was isolated in crude form and was found to contain 34% protein, 16% carbohydrate, and 40% lipid. The hydrocarbon solubilizing activity of the isolate was strongly inhibited by EDTA but the chelating agent had no effect on

P. G. Reddy; J. N. Banuah; S. D. Bhagat; M. G. Pathak; H. D. Singh

1983-01-01

288

Effect of Emulsifier Salts on Textural and Flavor Properties of Processed Cheeses1  

Microsoft Academic Search

Commercial processed cheeses, cheese foods, and cheese spreads were char- acterized for meltability, sliceability, composition, theological properties (In- stron), and descriptive sensory attributes. Samples varied within each grouping. Seventeen emulsifier salts were evaluated for performance in experimental processed cheese by the same criteria for the commercial samples. Tripotassium citrate, dipotassium phosphate, and tetrapotas- sium pyrophosphate each contributed properties to processed

S. K. Gupta; C. Karahadian; R. C. Lindsay

1984-01-01

289

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

290

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...

291

Emulsifying and foaming capacity and emulsion and foam stability of sesame protein concentrates  

Microsoft Academic Search

This study examined the effects of oil concentration and pH on the emulsifying and foaming characteristics of sesame protein concentrate (SESPC). SESPC was obtained through a simplified process, and its properties were compared with those of a commercial soybean concentrate (SOYPC). The simplified process did not affect the functional characteristics of SESPC, which were often similar or superior to those

Alicia Cano-Medina; Hugo Jimnez-Islas; Luc Dendooven; Rosalba Patio Herrera; Guillermo Gonzlez-Alatorre; Eleazar M. Escamilla-Silva

2011-01-01

292

Role of conformational flexibility in the emulsifying properties of bovine serum albumin.  

PubMed

Although it is well recognized that the conformation state of a protein affects its surface properties, the importance of conformation flexibility to its functionality is still not well understood. This study systemically investigated the influence of protein concentration (c) and disulfide bond (S-S) cleavage with a reducing agent, ?-mercaptoethanol (2-ME), on the conformation and emulsifying properties of an ideal globular protein, bovine serum albumin (BSA), with the aim to unravel the role of conformational flexibility in the functionality. The conformations were evaluated using size exclusion chromatography, dynamic light scattering (DLS), extrinsic fluorescence, and derivative UV spectroscopy. The emulsifying properties, including emulsifying ability, extent of droplet flocculation at a specific period of storage, and stability against flocculation and/or coalescence as well as creaming, were characterized using droplet size and creaming index analyses. The results indicated that the tertiary conformation of native BSA was closely dependent on its c (in the range of 0.05-1.0%), and increasing c resulted in a more compacted and rigid conformation. The c dependence largely determined the susceptibility of S-S bridges to reduction and even refolding of reduced BSA molecules. Interestingly, there was approximately a critical c (e.g., 0.25-0.5%) below which the S-S cleavage resulted in a gradual structural unfolding of the molecules and above which the situation was the reverse. On the other hand, the alteration with protein and 2-ME concentrations led to a variety of changes in emulsion size (d4,3; in water or 1% SDS) at 4 and 24 h and creaming index (up to 2 weeks). In general, at a low c value (e.g., 0.25%) increasing the S-S cleavage progressively improved the emulsifying ability and emulsion stability (especially against coalescence and creaming), whereas at c = 0.5 or 0.75%, the S-S cleavage, on the contrary, impaired the emulsifying properties, especially emulsion stability against flocculation and/or coalescence. These results suggest that the conformational flexibility of the protein (in solution) plays a vital role in different aspects of its emulsifying properties, for example, ease of structural unfolding at the interface, lateral interactions between adsorbed proteins, and formation of a viscoelastic interfacial layer (or multilayers). This knowledge could provide an in-depth understanding of the relationships between tertiary conformational flexibility and emulsifying properties of globular proteins. PMID:23470054

Tang, Chuan-He; Shen, Lan

2013-03-27

293

Emulsifying Activities of Purified Alasan Proteins from Acinetobacter radioresistens KA53  

PubMed Central

The bioemulsifier of Acinetobacter radioresistens KA53, referred to as alasan, is a high-molecular-weight complex of polysaccharide and protein. The emulsifying activity of the purified polysaccharide (apo-alasan) is very low. Three of the alasan proteins were purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had apparent molecular masses of 16, 31, and 45 kDa. Emulsification assays using the isolated alasan proteins demonstrated that the active components of the alasan complex are the proteins. The 45-kDa protein had the highest specific emulsifying activity, 11% higher than the intact alasan complex. The 16- and 31-kDa proteins gave relatively low emulsifying activities, but they were significantly higher than that of apo-alasan. The addition of the purified 16- and 31-kDa proteins to the 45-kDa protein resulted in a 1.8-fold increase in the specific emulsifying activity and increased stability of the oil-in-water emulsion. Fast-performance liquid chromatography analysis indicated that the 45-kDa protein forms a dimer in nondenaturing conditions and interacts with the 16- and 31-kDa proteins to form a high-molecular-mass complex. The 45-kDa protein and the three-protein complex had substrate specificities for emulsification and a range of pH activities similar to that of alasan. The fact that the purified proteins are active emulsifiers should simplify structure-function studies and advance our understanding of their biological roles. PMID:11229898

Toren, Amir; Navon-Venezia, Shiri; Ron, Eliora Z.; Rosenberg, Eugene

2001-01-01

294

Experimental Study of Using Emulsified Diesel Fuel on the Performance and Pollutants Emitted from Four Stroke Water Cooled Diesel Engine  

NASA Astrophysics Data System (ADS)

A water-cooled, four stroke, four cylinder, direct injection diesel engine was used to study the effect of emulsified diesel fuel on the engine performance and on the main pollutant emissions. Emulsified diesel fuels of 0%, 5%, 10%, 15%, 20%, 25% and 30% water by volume were used. The experiments were conducted in the speed range from 1000 to 3000 rpm. It was found that, in general, using emulsified fuel improves the engine performance and reduces emissions. While the BSFC has a minimum value at 5% water and 2000 rpm, the torque, the BMEP and efficiency are found to have maximum values under these conditions. CO2 was found to increase with engine speed and to decrease with water content. NOx produced from emulsified fuel is significantly less than that produced from pure diesel under the same conditions.

Sakhrieh, A.; Fouad, R. H.; Yamin, J. A.

2009-08-01

295

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

PubMed

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

Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

2014-10-01

296

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

NASA Astrophysics Data System (ADS)

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

Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

2014-10-01

297

Influence of emulsifier type and content on functional properties of polysaccharide lipid-based edible films.  

PubMed

This study investigates the effect of different types of surfactant (glycerol monostearate, Tween 60, and Tween 80) on water vapor permeability (WVP), tensile strength (TS), percentage elongation at breaking (E), and structure of an emulsified edible film composed of cornstarch, methylcellulose, and cocoa butter or soybean oil. Factorial designs at two levels were used to analyze the effect of emulsifier (EM) and lipid content on the functional properties of film. Results showed that the effects of independent variables on WVP, TS, and E depend on surfactant and lipid type. The presence of EM significantly decreased the WVP of cocoa butter films but did not improve the barrier or mechanical properties of soybean oil-based film. PMID:15479005

Bravin, Barbara; Peressini, Donatella; Sensidoni, Alessandro

2004-10-20

298

Experimental evaluation of oxygen-enriched air and emulsified fuels in a six-cylinder diesel engine  

Microsoft Academic Search

The objectives of this investigation are to (1) determine the technical feasibility of using oxygen-enriched air to increase the efficiency of and reduce emissions from diesel engines, (2) examine the effects of water-emulsified fuel on the formation of nitrogen oxides in oxygen-enriched combustion, and (3) investigate the use of lower-grade fuels in high-speed diesel engines by emulsifying the fuel with

R. R. Sekar; W. W. Marr; R. L. Cole; T. J. Marciniak; D. E. Longman

1993-01-01

299

Improvement of emulsifying properties of soybean protein isolate by conjugation with carboxymethyl cellulose  

Microsoft Academic Search

Soybean protein isolate (SBPI) was mixed with sodium carboxymethyl cellulose (NaCMC) and dry-heated at 60C for a time period of up to 5 weeks. An improvement in emulsifying properties of the mixture, especially in oil droplet size reduction and emulsion stabilization against creaming was observed, depending on polysaccharide molecular weight, SBPI\\/NaCMC weight ratio and time of incubation. This is attributed

N. Diftis; V. Kiosseoglou

2003-01-01

300

Controlled release of oral tetrahydrocurcumin from a novel self-emulsifying floating drug delivery system (SEFDDS).  

PubMed

The objectives of this study were to develop and evaluate a novel self-emulsifying floating drug delivery system (SEFDDS) that resulted in improved solubility, dissolution, and controlled release of the poorly water-soluble tetrahydrocurcumin (THC). The formulations of liquid self-emulsifying drug delivery system (SEDDS; mixtures of Labrasol, Cremophor EL, Capryol 90, Labrafac PG) were optimized by solubility assay and pseudo-ternary phase diagram analysis. The liquid SEDDS was mixed with adsorbent (silicon dioxide), glyceryl behenate, pregelatinized starch, sodium starch glycolate, and microcrystalline cellulose and transformed into pellets by the extrusion/spheronization technique. The resulting pellets with 22% liquid SEDDS had a uniform size and good self-emulsification property. The microemulsions in aqueous media of different self-emulsifying floating pellet formulations were in a particle size range of 25.9-32.5 nm. Use of different weight proportions of glyceryl behenate and sodium starch glycolate in pellet formulations had different effects on the floating abilities and in vitro drug release. The optimum formulation (F2) had a floating efficiency of 93% at 6 h and provided a controlled release of THC over an 8-h period. The release rate and extent of release of THC liquid SEDDS (80% within 2 h) and self-emulsifying floating pellet formulation (80% within 8 h) were significantly higher than that of unformulated THC (only 30% within 8 h). The pellet formulation was stable under intermediate and accelerated storage conditions for up to 6 months. Controlled release from this novel SEFDDS can be a useful alternative for the strategic development of oral solid lipid-based formulations. PMID:21181511

Setthacheewakul, Saipin; Kedjinda, Wichan; Maneenuan, Duangkhae; Wiwattanapatapee, Ruedeekorn

2011-03-01

301

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.

302

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 245-265C 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

303

Influence of astaxanthin, emulsifier and organic phase concentration on physicochemical properties of astaxanthin nanodispersions  

PubMed Central

Background The emulsification-evaporation method was used to prepare astaxanthin nanodispersions using a three-component emulsifier system composed of Tween 20, sodium caseinate and gum Arabic. Using Response-surface methodology (RSM), we studied the main and interaction effects of the major emulsion components, namely, astaxanthin concentration (0.020.38 wt %, x1), emulsifier concentration (0.23.8 wt %, x2) and organic phase (dichloromethane) concentration (238 wt %, x3) on nanodispersion characteristics. The physicochemical properties considered as response variables were: average particle size (Y1), PDI (Y2) and astaxanthin loss (Y3). Results The results indicated that the response-surface models were significantly (p??0.930) for all responses. The overall optimum region resulted in a desirable astaxanthin nanodispersions obtained with the concentrations of 0.08 wt % astaxanthin, 2.5 wt % emulsifier and 11.5 wt % organic phase. Conclusion No significant differences were found between the experimental and predicted values, thus certifying the adequacy of the Response-surface models developed for describing the changes in physicochemical properties as a function of main emulsion component concentrations. PMID:23875816

2013-01-01

304

Eat Iron?!!  

NSDL National Science Digital Library

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

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

305

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

NASA Astrophysics Data System (ADS)

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

Tosco, Tiziana; Gastone, Francesca; Sethi, Rajandrea

2014-10-01

306

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

PubMed

In the present work column transport tests were performed in order to study the mobility of guar-gum suspensions of microscale zero-valent iron particles (MZVI) in porous media. The results were analyzed with the purpose of implementing a radial model for the design of full scale interventions. The transport tests were performed using several concentrations of shear thinning guar gum solutions as stabilizer (1.5, 3 and 4g/l) and applying different flow rates (Darcy velocity in the range 110(-4) to 210(-3)m/s), representative of different distances from the injection point in the radial domain. Empirical relationships, expressing the dependence of the deposition and release parameters on the flow velocity, were derived by inverse fitting of the column transport tests using a modified version of E-MNM1D (Tosco and Sethi, 2010) and the user interface MNMs (www.polito.it/groundwater/software). They were used to develop a comprehensive transport model of MZVI suspensions in radial coordinates, called E-MNM1R, which takes into account the non Newtonian (shear thinning) rheological properties of the dispersant fluid and the porous medium clogging associated with filtration and sedimentation in the porous medium of both MZVI and guar gum residual undissolved particles. The radial model was run in forward mode to simulate the injection of MZVI dispersed in guar gum in conditions similar to those applied in the column transport tests. In a second stage, we demonstrated how the model can be used as a valid tool for the design and the optimization of a full scale intervention. The simulation results indicated that several concurrent aspects are to be taken into account for the design of a successful delivery of MZVI/guar gum slurries via permeation injection, and a compromise is necessary between maximizing the radius of influence of the injection and minimizing the injection pressure, to guarantee a sufficiently homogeneous distribution of the particles around the injection point and to prevent preferential flow paths. PMID:25063698

Tosco, Tiziana; Gastone, Francesca; Sethi, Rajandrea

2014-10-01

307

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

308

Formulation strategies to improve the bioavailability of poorly absorbed drugs with special emphasis on self-emulsifying systems.  

PubMed

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; Omri, Abdelwahab

2013-12-26

309

Numerical simulation of emulsified fuel spray combustion with puffing and micro-explosion  

SciTech Connect

The purpose of this study was to develop numerical simulation of spray combustion of emulsified fuel with considering puffing and micro-explosion. First, a mathematical model for puffing was proposed. In the proposed puffing model, the rate of mass change of a droplet during puffing was expressed by the evaporation rate of dispersed water and the mass change rate due to fine droplets spouted from the droplet surface. The mass change rate due to fine droplets was related to the evaporation rate of the dispersed water and each liquid content. This model had only one experimental parameter. The essential feature of this model was that it was simple to apply to numerical simulation of spray combustion. First, the validity of the proposed puffing model was investigated with the experimental results for a single droplet. The calculated results for a single droplet with the experimental parameter varying from 5.0 to 10 were in good agreement with the experimental results. Moreover, numerical simulation of spray combustion of emulsified fuel was carried out. The occurrence of puffing and micro-explosion was determined by the inner droplet temperature. When micro-explosion occurred, a droplet changed to vapor rapidly. When the proposed puffing model was used in numerical simulation of spray combustion, the experimental parameter in the puffing model was determined for each droplet by random numbers within the range 5.0-10. The calculated results of spray combustion of emulsified fuel without considering puffing or micro-explosions were different from the experimental results even where combustion reactions were almost terminated. Meanwhile, the calculated results when considering puffing and micro-explosions were in good agreement with experimental results at the same location. (author)

Watanabe, Hirotatsu [JSPS Research Fellow, Graduate School of Engineering, Tohoku University 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Matsushita, Yohsuke; Aoki, Hideyuki; Miura, Takatoshi [Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2010-05-15

310

Improved atomization of residual fuels for marine boilers. Volume III: cold flow characterization of emulsified fuels  

SciTech Connect

The objectives of this research are to study the physical properties of water/oil emulsions and determine how these properties affect atomization in a non-combustion environment. A literature survey was performed to establish a technical base. An emulsifier was obtained and tests run to establish a correlation between Bunker 'C' fuel oil emulsions and model test fluid emulsions. Droplet size distribution and droplet ballistics tests were performed in the Atomizer Test Facility to demonstrate the effect that water concentration has on atomization quality.

Smith, D.A.; LaFlesh, R.C.; Solomon, J.; Lachowicz, Y.

1982-02-01

311

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

312

Iron refractory iron deficiency anemia  

PubMed Central

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

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

2013-01-01

313

Determination of food emulsifiers in commercial additives and food products by liquid chromatography/atmospheric-pressure chemical ionisation mass spectrometry.  

PubMed

A new, reliable liquid chromatography/atmospheric-pressure chemical ionisation mass spectrometry (LC-APCI-MS) method was developed for the quantitative determination of food emulsifiers composed of mono- and diacylglycerols of fatty acids (E471 series) in complex food matrices. These additives are extremely interesting for the food industry because of their useful properties. Indeed, they improve the manufacture of products by acting as foams and creams stabilisers, crumb-softeners, or antistaling agents. The proposed method also allows us to qualitatively characterise new food emulsifiers composed of other acid esters of mono- and diacylglycerols (E472 series). The validation of the method was performed on blank minicake spiked samples for detection limits (reaching ppm levels), linearity, recovery, precision, and accuracy. The method was then successfully applied to commercial additives containing mixtures of emulsifiers, as well as to food products such as margarines and minicakes. PMID:19286189

Suman, M; Silva, G; Catellani, D; Bersellini, U; Caffarra, V; Careri, M

2009-05-01

314

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

USGS Publications Warehouse

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

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

2001-01-01

315

Emulsifying agents  

SciTech Connect

Surfactant compositions suitable for the emulsification of methanol or ethanol in hydrocarbon liquids, especially diesel oil, consist of a blend of from 10% to 90% by weight of block or graft copolymer in which one polymeric component is the residue of an oil-soluble complex monocarboxylic acid and another polymeric component is the residue of a water-soluble polyalkylene glycol or polyalkylenoxy polyol and from 90% to 10% by weight of a polyester obtained by condensation of a poly(isobutenyl) succinic acid or anhydride with a water-soluble poly(alkylene glycol).

Baker, A. S.

1985-04-09

316

Influence of aqueous phase emulsifiers on lipid oxidation in water-in-walnut oil emulsions.  

PubMed

Effects of selected aqueous phase emulsifiers on lipid oxidative stability of water-in-walnut oil (W/O) emulsions stabilized by polyglycerol polyricinoleate (PGPR) were evaluated. The formation of primary oxidation products (lipid hydroperoxides) and secondary oxidation products (headspace hexanal) increased with increasing dodecyltrimethylammonium bromide (DTAB) concentration (0.1-0.2 wt % of emulsions). In contrast, the addition of sodium dodecyl sulfate (SDS) in the aqueous phase reduced lipid hydroperoxide and hexanal formation. In addition, the presence of Tween 20 in the aqueous phase did not significantly influence lipid oxidation rates in W/O emulsions compared to the control (without Tween 20). Whey protein isolate (WPI) was observed to inhibit lipid oxidation in the W/O emulsions (0.05-0.2 wt % of emulsions). Aqueous phase pH had an important impact on the antioxidant capability of WPI, with higher pH improving its ability to inhibit lipid oxidation. The combination of WPI and DTAB in the aqueous phase suppressed the prooxidant effect of DTAB. The combination of WPI and SDS resulted in improved antioxidant activity, with inhibition being greater at pH 7.0 than at pH 3.0. These results suggest that the oxidative stability of W/O emulsions could be improved by the use of suitable emulsifiers in the aqueous phase. PMID:24446832

Yi, Jianhua; Zhu, Zhenbao; McClements, D Julian; Decker, Eric A

2014-03-01

317

Effects of emulsifier addition on the crystallization and melting behavior of palm olein and coconut oil.  

PubMed

Two commercial emulsifiers (EM1 and EM2), containing predominantly monoacylglycerols (MAGs), were added in proportiond of 1.0 and 3.0% (w/w) to coconut oil and palm olein. EM1 consisted of approximately 90% MAGs, whereas EM2 consisted of approximately 50% MAGs. The crystallization behavior of these systems was evaluated by differential scanning calorimetry (DSC) and microscopy under polarized light. On the basis of DSC results, it was clear that the addition of EM2 accelerated the crystallization of coconut oil and delayed the crystallization of palm olein. In both oils EM2 addition led to the formation of smaller spherulites, and these effects improved the possibilities for using these fats as ingredients. In coconut oil the spherulites were maintained even at higher temperatures (20 C). The addition of EM1 to coconut oil changed the crystallization pattern. In palm olein, the addition of 3.0% (w/w) of this emulsifier altered the pattern of crystallization of this fat. PMID:24547939

Maruyama, Jessica Mayumi; Soares, Fabiana Andreia Schafer De Martini; D'Agostinho, Natalia Roque; Gonalves, Maria Ins Almeida; Gioielli, Luiz Antonio; da Silva, Roberta Claro

2014-03-12

318

Effect of emulsifiers on oil separation problem and quality characteristics of Tahin Helva during storage.  

PubMed

Tahin helva is one of Turkish traditional confectionary foods. Sesame paste, sugar syrup and soapwort extract were used for tahin helva's production. The purpose of this study was to solve the oil separation problem occurred in tahin helva by using food additives permitted as an emulsifier for tahin helva in the Turkish and EU Codex. Sorbitan tristearate (STS), sorbitan monopalmitate (SMP) and their combinations (STS:SMP, 1:1) were added to tahin helva, then helva samples were stored at the storage temperatures of 20C, 30C, and 40C. The emulsifiers did not have any effect on physical, chemical and sensory properties of tahin helva except on its oil content, whereas storage temperature and storage time had effects on those properties of helva. STS:SMP combination was found to be statistically more effective than SMP and STS formulations in preventing oil separation. Penetration force of tahin helva has increased by increasing the storage temperature and storage time. It was found that there was a decrease in -a colour value of helva through the storage time at 20C and 30C, while there was an increase in that value at 40C. The highest change in the moisture content of all helva samples through storage was observed at the storage temperature of 20C. Sensory scores for appearance, texture and flavour characteristics of helva have decreased significantly during the storage period. PMID:24876640

Guneser, Onur; Zorba, Murat

2014-06-01

319

Some emulsifying and suspending properties of the mucilage extracted from kernels of Irvingia gabonensis.  

PubMed

The mucilage extracted from the kernels of Irvingia gabonensis was evaluated for use as suspending and emulsifying agent. The rheological behaviour of the mucilage was studied and compared to that of tragacanth. As a suspending agent, Irvingia mucilage was compared to tragacanth at various concentrations (0.5, 1.0, 1.5 and 2.0% w/v) in the formulation of sulphanilamide suspensions. At all concentrations the formulated suspensions with Irvingia mucilage gave higher Hu (final sedimentation height) and F (sedimentation volume) values. As an emulsifying agent, the properties of Irvingia mucilage was compared to tragacanth and acacia gum. The emulsions prepared with 0.6, 1.0, and 1.5% tragacanth and Irvingia 'cracked' within six days while that with 12.5% w/v acacia started showing signs of creaming at the tenth day. The emulsion prepared with 2.0% w/v Irvingia mucilage was however stable throughout the six weeks of study. The results indicate that Irvingia mucilage performed better than acacia and tragacanth even at lower concentrations in the formulation of emulsions and suspensions. PMID:11213437

Isimi, C Y; Kunle, O O; Bangudu, A B

2000-01-01

320

Emulsifying and interfacial properties of vicilins: role of conformational flexibility at quaternary and/or tertiary levels.  

PubMed

Although the functionality of plant proteins (and soy proteins in particular) has been widely investigated in the last decades, the importance of conformational characteristics to their functionalities is still far away from being understood. The aim of the present work was to unravel the role of conformational flexibility at the quaternary and/or tertiary levels in the emulsifying and interfacial properties of phaseolin, an ideal vicilin (or 7S globulin) from red kidney bean. The conformational flexibility at quaternary and tertiary levels of phaseolin was modulated by urea with increasing concentrations from 0 to 8 M, as characterized by using dynamic light scattering (DLS), intrinsic fluorescence and derivative UV spectroscopy, and differential scanning calorimetry (DSC). The emulsifying and interfacial properties, including emulsifying ability, flocculated state of oil droplets (in fresh emulsions), emulsion stability against creaming, and adsorption dynamics at the oil-water interface, were characterized at a specific protein concentration of 0.5% (w/v). The results indicated that increasing the urea concentration resulted in a progressive dissociation of trimeric phaseolin molecules into monomeric subunits, and even a structural unfolding of dissociated subunits; the urea-induced conformational changes at quaternary and/or tertiary levels were reversible, and the molecules at high urea concentrations shared similar structural features to the "molten globule state". On the other hand, increasing the urea concentration progressively improved the emulsifying ability of the protein, and flocculated extent of oil droplets in the fresh emulsions, but led to a progressive decrease in interfacial protein concentration. The improvement of the emulsifying ability was not related to diffusion (during initial adsorption) and penetration at the interface, but highly dependent on ease of structural rearrangement of the adsorbed proteins. These observations clearly confirmed that the flexibility of phaseolin at quaternary and/or tertiary levels plays a vital role in its emulsifying ability, mainly through the way of affecting the ease of structural rearrangement of adsorbed proteins at the interface. The findings could provide an in-depth understanding of the importance of conformational flexibility for the emulsifying properties of oligomeric storage globulins, and thus are of great help to guide the modifications of the proteins for better emulsifying properties. PMID:24151988

Liang, Han-Ni; Tang, Chuan-He

2013-11-20

321

EPA evaluation of the Tries Emulsifier device under Section 511 of the Motor Vehicle Information and Cost Savings Act  

SciTech Connect

This document announces the conclusions of the EPA evaluation of the Treis Emulsifier device under provisions of Section 511 of the Motor Vehicle Information and Cost Savings Act. On February 17 1981 the EPA received a request from Treis International for evaluation of a fuel saving device termed Treis Emulsifier. This device is designed to generate a gasoline, water-alcohol emulsion. The water is in finite droplet form, evenly dispersed throughout the gasoline and is claimed to prevent premature ignition or knock, and allow a more complete combustion. This is claimed to result in improved fuel economy, torque, and engine life.

Penninga, T.J.

1981-07-01

322

Iron deficiency  

Microsoft Academic Search

Iron deficiency remains one of the worlds greatest public health problems. Globally it is the greatest contributor to anaemia, affecting 47% of pre-school age children and 25% of school age children worldwide, and is a major contributor to both physical and neuro-developmental morbidity.Iron deficiency results from inadequate intake, excess turnover or excessive loss. Whilst inadequate intake is the commonest cause

Katrina Pettit; Jennifer Rowley; Nick Brown

2011-01-01

323

Adsorption at the biocompatible ?-pinene-water interface and emulsifying properties of two eco-friendly surfactants.  

PubMed

In this contribution, we provide an accurate characterization at the ?-pinene/water interface of two commercial polyoxytheylene glycerol ester surfactants which differ in the number of ethylene oxide (EO) groups, comprising a systematic analysis of interfacial pressure isotherms, dynamic curves, interfacial rheology and emulsifying properties. Polyoxyethylene glycerol esters derived from cocoa oil are non-ionic surfactants obtained from a renewable source which fulfill the environmental and toxicological requirements to be used as eco-friendly emulsifying agents. ?-Pinene is a renewable biosolvent completely insoluble in water, which could find numerous applications. Interfacial rheology and equilibrium interfacial pressure data fitted a rigorous reorientation model that assumes that the surfactant molecules, when adsorbed at the interface, can acquire two orientations. The surfactant with the highest number of EO groups (Levenol C201) turned out to be more surface active at the ?-pinene/water interface. In addition, the surfactant with the lowest number of EO groups (Levenol H&B) is solubilized into the adjacent oil phase. Slightly concentrated ?-pinene emulsions were obtained using both surfactants. Nevertheless, more stable ?-pinene emulsions with smaller droplet sizes and lower polidispersity were obtained when Levenol C201 was used as emulsifier instead of Levenol H&B. The systematic characterization presented in this work provides important new findings on the interfacial and emulsifying properties of polyoxytheylene glycerol ester surfactants, which can be applied in the rational development of new biocompatible products. PMID:25129697

Trujillo-Cayado, Luis Alfonso; Ramrez, Pablo; Alfaro, Mara Carmen; Ruz, Manuela; Muoz, Jos

2014-10-01

324

Influence of emulsifiable concentrate formulations on the physical properties of the fluid, spray characteristics, and insecticide deposits on stored grains  

Microsoft Academic Search

The influence of emulsifiable concentrate formulations on the physical properties of the spraying fluid (viscosity and surface tension), volumetric distribution, droplet spectrum, and insecticide depositions on stored grains was studied. In order to determine its physical properties, the applied mix was prepared at a concentration of 0.4 % of commercial product (Sumigranplus EC). Volumetric distribution was used as an evaluation

J. A. Vsquez-Castro; G. C. de Baptista; C. D. Gadanha Jr; L. R. P. Trevizan

325

Preparation of magnetic latexes functionalized with chloromethyl groups via emulsifier-free miniemulsion polymerization  

NASA Astrophysics Data System (ADS)

Functionalized crosslinked polystyrene-co-divinylbenzene-co-chloromethylstyrene magnetic latex particles were prepared via emulsifier-free miniemulsion polymerization using 2, 2' azobis (2-amidinopropane) dihydrochloride (V-50) as an initiator and in the presence of magnetite nanoparticles in the monomers. Transmission electron microscopy (TEM) proved the presence of magnetite nanoparticles in polymer particles. Differential scanning calorimetery (DSC) analysis of the product showed an exothermic signal due to crosslinking of chains through electrophilic aromatic substitution of phenyl groups with chloromethyl groups in the presence of the dispersed Fe 3O 4 as Lewis acid. This was proven by thermogravimetric analysis (TGA) via the loss of gaseous HCl. The results were also compared with those of magnetite-free miniemulsion polymerization using V-50.

Faridi-Majidi, Reza; Sharifi-Sanjani, Naser

2007-04-01

326

[Mechanisms of hydroxypropyl methylcellulose for the precipitation inhibitor of supersaturatable self-emulsifying drug delivery systems].  

PubMed

Hydroxypropyl methylcellulose (HPMC) propels self-emulsifying drug delivery systems (SEDDS) to achieve the supersaturated state in gastrointestinal tract, which possesses important significance to enhance oral absorption for poorly water-soluble drugs. This study investigated capacities and mechanisms of HPMC with different viscosities (K4M, K15M and K100M) to inhibit drug precipitation of SEDDS in the simulated gastrointestinal tract environment in vitro. The results showed that HPMC inhibited drug precipitation during the dispersion of SEDDS under gastric conditions by inhibiting the formation of crystal nucleus and the growth of crystals. HPMC had evident effects on the rate of SEDDS lipolysis and benefited the distribution of drug molecules across into the aqueous phase and the decrease of drug sediment. The mechanisms were related to the formed network of HPMC and its viscosities and molecular weight. These results offered a reference for selecting appropriate type of HPMC as the precipitation inhibitor of supersaturatable SEDDS. PMID:23888703

Xiao, Lu; Yi, Tao

2013-05-01

327

Integrated process for the removal of emulsified oils from effluents in the steel industry  

SciTech Connect

Emulsified oils contained in aqueous effluents from cold-rolling mills of the steel industry can be effectively removed via an integrated process consisting of a coagulation/flocculation stage followed by ultrafiltration of the resulting aqueous phase. The effects of CaCl{sub 2}, NaOH, and lime on the stability of different industrial effluents were studied in the coagulation experiments. The flocculants tested were inorganic prehydrolyzed aluminum salts and quaternary polyamines. Ultrafiltration of the aqueous phase from the coagulation/flocculation stage was carried out in a stirred cell using Amicon PM30 and XM300 organic membranes. Permeate fluxes were measured for industrial effluents to which the indicated coagulants and flocculants had been added. Oil concentrations in the permeate were 75% lower than the limits established by all European Union countries. Complete regeneration of the membrane was accomplished with an aqueous solution of a commercial detergent.

Benito, J.M.; Rios, G.; Gutierrez, B.; Pazos, C.; Coca, J.

1999-11-01

328

Self-emulsifying drug delivery systems for improving oral absorption of ginkgo biloba extracts.  

PubMed

Self-emulsifying drug delivery systems (SEDDS) are mixtures of oils, surfactants, and cosurfactants, which are emulsified in aqueous media under conditions of gentle stirring and digestive motility that would be encountered in the gastrointestinal tract. We found that SEDDS could efficiently improve oral absorption of the sparingly soluble drugs by rapid self-emulsification and subsequently dispersion in the absorption sites. Ginkgo biloba extract (GBE) has become a widely used herbal remedy for increasing cognitive function in elderly people. The main purpose of our work is to prepare SEDDS for improving oral absorption of GBE. Pseudoternary phase diagrams were constructed to identify the efficient self-emulsification region, and particle size distributions of resultant emulsions were determined. The optimized formulation for bioavailability assessment consisted of 45% Tween 80-Cremophor EL35 (1:1, w/w), 10% 1, 2-propanediol, and 45% ethyl oleate. The mean droplet size distribution of the optimized SEDDS was approximately 100 nm when diluted with 500-fold volume of the distilled water. The in vitro dissolution rates of the active components of GBE SEDDS form were significantly faster than those of the GBE tablets. After single oral administration of 800 mg GBE as SEDDS or tablets to fasted dogs, the relative bioavailability of SEDDS for bilabolide and ginkgolide A and B was 162.1, 154.6, and 155.8% compared with the reference tablets, respectively. Our results suggested the potential and promising use of SEDDS for the efficient delivery of the sparingly soluble drugs or traditional Chinese medicines, such as GBE by oral administration. PMID:18720135

Tang, Jingling; Sun, Jin; Cui, Fude; Zhang, Tianhong; Liu, Xiaohong; He, Zhonggui

2008-11-01

329

Are block copolymer worms more effective Pickering emulsifiers than block copolymer spheres?  

PubMed

RAFT-mediated polymerisation-induced self-assembly (PISA) is used to prepare six types of amphiphilic block copolymer nanoparticles which were subsequently evaluated as putative Pickering emulsifiers for the stabilisation of n-dodecane-in-water emulsions. It was found that linear poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer spheres and worms do not survive the high shear homogenisation conditions used for emulsification. Stable emulsions are obtained, but the copolymer acts as a polymeric surfactant; individual chains rather than particles are adsorbed at the oil-water interface. Particle dissociation during emulsification is attributed to the weakly hydrophobic character of the PHPMA block. Covalent stabilisation of these copolymer spheres or worms can be readily achieved by addition of ethylene glycol dimethacrylate (EGDMA) during the PISA synthesis. TEM studies confirm that the resulting cross-linked spherical or worm-like nanoparticles survive emulsification and produce genuine Pickering emulsions. Alternatively, stabilisation can be achieved by either replacing or supplementing the PHPMA block with the more hydrophobic poly(benzyl methacrylate) (PBzMA). The resulting linear spheres or worms also survive emulsification and produce stable n-dodecane-in-water Pickering emulsions. The intrinsic advantages of anisotropic worms over isotropic spheres for the preparation of Pickering emulsions are highlighted. The former particles are more strongly adsorbed at similar efficiencies compared to spheres and also enable smaller oil droplets to be produced for a given copolymer concentration. The scalable nature of PISA formulations augurs well for potential applications of anisotropic block copolymer nanoparticles as Pickering emulsifiers. PMID:25254485

Thompson, K L; Mable, C J; Cockram, A; Warren, N J; Cunningham, V J; Jones, E R; Verber, R; Armes, S P

2014-10-15

330

Solid self-emulsifying phospholipid suspension (SSEPS) with diatom as a drug carrier.  

PubMed

We report the application of diatom as a solid carrier for water insoluble drugs applied in oral drug delivery system based on the self-emulsifying drug delivery system (SEDDS) caprylocaproyl macrogol-8 glycerides/lecithin/propylene glycol/caprylic/capric triglyceride. Diatoms are fossilized skeletons of photosynthetic algae with complex 3-dimensional (3D), porous structure consisting of amorphous silica, obtained by purification of diatomaceous earth. Different solid samples of carbamazepine (CBZ) suspension in SEDDS, called solid self-emulsifying phospholipid suspension (SSEPS), were prepared using two methods: adsorption of CBZ dispersion in SEDDS by gentle mixing with diatoms in mortar with pestle (Method A) or dispersion of diatoms in ethanol solution of CBZ and SEDDS components, followed by ethanol evaporation (Method B). Release rate of CBZ from SSEPS was significantly higher in comparison to pure drug, physical mixture of diatoms and CBZ as well as solid dispersion of pure CBZ and diatoms obtained by ethanol evaporation. The dissolution of CBZ from SSEPS sample prepared using method B was faster than from the sample prepared by the method A. Higher dissolution for sample prepared by the method B can be attributed to the partial adsorption (deeper localization) of liquid material inside the pores of diatoms. Upon storage of the samples under accelerated conditions (40C and 70% RH) for 10 weeks no significant changes in CBZ crystallinity and dissolution was in case of SSEPS, contrary to solid dispersion with increased crystallinity, indicating that diatoms with adsorbed liquid CBZ-loaded SEPS can maintain initial CBZ characteristics. PMID:25125211

Milovi?, Mladen; Simovi?, Spomenka; Loi?, Duan; Dashevskiy, Andriy; Ibri?, Svetlana

2014-10-15

331

Self-emulsifying bifendate pellets: preparation, characterization and oral bioavailability in rats.  

PubMed

In this study, a self-emulsifying pellet (SEP) was prepared in order to improve the bioavailability of bifendate (DDB). First, a liquid self-emulsifying drug delivery system (SEDDS) was formulated, and then further developed into the SEP by extrusion/spheronization technology using the reconstituted emulsion as the adhesive. The optimized liquid SEDDS consisted of Miglycol() 840, a mixture of Cremorphor() EL and Solutol HS() 15 (1:2, w/w), and Transcutol HP as the oil phase, the surfactant and the co-surfactant at a weight ratio of 40:45:15 (w/w/w), respectively. The SEP were prepared using a mixture of MCC, lactose, and mannitol (45:45:10, w/w/w) as solid adsorbents. The SEP with 40% (w/w) of the liquid SEDDS was round-shaped with a uniform size (800-1000 m). There was no difference in droplet size between the emulsions obtained from the liquid SEDDS or the SEP (169.8 6.3 nm and 163.7 3.8 nm). Compared with that of DDB pills (less than 20%), in vitro release of DDB from the SEP (over 80% within 60 min) was significantly enhanced in 0.1N HCl, although slower than that of the liquid SEDDS (over 80% within 5 min). AUC of DDB of the SEP after oral administration in rats exhibited 2.36-fold greater than that of DDB pills and no significant difference compared with that of the liquid SEDDS. In conclusion, our studies illustrated that extrusion/spheronization technique could be a useful method to prepare this SEP and it could be a promising way for enhancing oral bioavailability of poorly water-soluble drugs. PMID:22630165

Xiao, Yanyu; Wang, Shan; Chen, Yinan; Ping, Qineng

2013-05-01

332

Taking iron supplements  

MedlinePLUS

... levels. You may also need to take iron supplements as well to rebuild iron stores in your ... ABOUT IRON SUPPLEMENTS Iron supplements may be taken as capsules, tablets, chewable tablets, and liquids. The most common tablet size is ...

333

TRANSFORMATION OF HALOGENATED PBTS WITH NANOSCALE BIMETALLIC PARTICLES  

EPA Science Inventory

Zero-valent iron nanoparticle technology is becoming a popular option for treatment of a variety of hazardous and toxic wastes, and for remediation of contaminated sites. As a matter of fact, nano iron has quickly become the most widely used nanomaterial in environmental ...

334

Long Term Effect of Biotic Reductive Dechlorination on Permeable Treatment Walls  

Microsoft Academic Search

Increased, reactivity is a potentially important phenomena with respect to the cost effectiveness of zero-valent iron permeable barriers. A column study followed by batch experiments using microcosms was performed to analyze biotic reactions and their impact on kinetic reaction rates. In the biotic iron column study ethylene formation as a by-product of the TCE degradation was decreasing gradually after 200

Hala A. Sfeir; A. Randall; D. Reinhart; C. Clausen; C. Geiger

335

PLANT MULCH TO TREAT TCE IN GROUND WATER IN A PRB  

EPA Science Inventory

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

336

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

EPA Science Inventory

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

337

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

EPA Science Inventory

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

338

Iron and infection  

Microsoft Academic Search

Iron and infection. Intravenous iron therapy maintains iron stores and decreases erythropoietin demand in patients undergoing regular dialysis therapy. Microbiology studies show a close relationship between the availability of iron and bacterial virulence. Iron is also an essential requirement of bacteria for multiplication in the host. Therefore, clinical conditions associated with iron excess in the host may increase the risk

SANDA I. PATRUTA; WALTER H. HORL

1999-01-01

339

Effects of emulsifier on particle size of a phase change material in a mixture with water. Progress report, March 31, 1991--June 30, 1991  

SciTech Connect

The use of a phase-change material (PCM) in a district cooling system was studied in order to increase the heat transfer performance of the system. One of the major technical obstacles to its use is the clogging of the piping system. The present study attempts to minimize the clogging problem by using an emulsifier. Effects of the emulsifier on the mixture of water and hexadecane (a PCM) were studied. A small amount (60 to 2775 ppm) of emulsifier caused remarkable effects resulting in the production of fine PCM particles. As the amount of the emulsifier was increased in the 25% hexadecane mixture with water, the size of the solid particles of hexadecane became smaller. When the size of the hexadecane particles was small enough, they did not stick together or stick to the surface of the cold wall of a heat exchanger.

Choi, E.; Cho, Y.I.; Lorsch, H.G.

1991-06-30

340

Genetics Home Reference: Iron-refractory iron deficiency anemia  

MedlinePLUS

... Genetic disorder catalog Conditions > Iron-refractory iron deficiency anemia On this page: Description Genetic changes Inheritance Diagnosis ... July 2014 What is iron-refractory iron deficiency anemia? Iron-refractory iron deficiency anemia is one of ...

341

Effect of emulsifier content of sizing agent on the surface of carbon fibres and interface of its composites  

NASA Astrophysics Data System (ADS)

In this work, carbon fibres were sized with different emulsifier content sizing agent in order to improve the performances of carbon fibres and the interface of carbon fibres composites. The surface characteristic changing after modification was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM). Wetting and surface energy along with contact angles were determined by the dynamic contact angle analysis test (DCAT). At the same time, the single fibre strengths and weibull distributions were also studied in order to understand the effect of the emulsifier content of sizing agent on the carbon fibres. The interfacial shear strength and hygrothermal ageing of the composites were measured which showed a different enhancement, respectively. The results revealed that sizing agent E-3 showed better interface adhesion between fibres and matrix and sizing agent E-2 sized carbon fibre has better ageing resistant properties.

Zhang, R. L.; Huang, Y. D.; Liu, L.; Tang, Y. R.; Su, D.; Xu, L. W.

2011-02-01

342

A new route of emulsifier-free emulsion polymerization for the preparation of polymer coated magnetite nanoparticles  

NASA Astrophysics Data System (ADS)

A new route of emulsifier-free emulsion polymerization based on the homogenous mechanism was investigated to prepare magnetic nanoparticles coated by poly (methyl methacrylate) (PMMA). The experimental results confirm the formation of PMMA thin and unique layers covering magnetite cores. The polymer layer thickness, determined from transmission electron microscopy (TEM) images, increases from 4.3 nm to 6.8 nm with increasing mass ratio of MMA to magnetite from 3:1 to 11:1. The increase of the polymer thickness results in the decrease in magnetization saturation of polymeric coated magnetic particles. However, this reduction, no more than 13 emu g-1, is much lower compared to that in other studies with the presence of surfactants or emulsifiers. Besides, the dispersion stability of the prepared particles is significantly improved.

Nguyen, Q. H.; Quyen, D. H.; Hoang, T. K. N.

2014-06-01

343

Effects of high hydrostatic pressure on emulsifying properties of sweet potato protein in model protein-hydrocolloids system.  

PubMed

The effects of high hydrostatic pressure (HHP) on emulsifying properties of sweet potato protein (SPP) in presence of 0.1%, 0.3% and 0.5% (w/v) of guar gum (GG) and glycerol monostearate (GMS) were investigated. Emulsifying stability index (ESI) of the SPP with GG revealed significant increase (P<0.05) in ESI value at 600MPa treatment, while the stability of SPP-GMS emulsions significantly decreased with increase in GMS concentrations and HHP treatments (200-600MPa). HHP treatment considerably reduced the creaming rate for SPP-GG model while such case was not observed for SPP-GMS model. The flow index for SPP-GG emulsion model was found to decrease with increase in HHP treatment and had non-Newtonian behaviour. The SPP-GMS emulsion models with HHP treatments showed comparatively lower viscosities but had more Newtonian flow character. PMID:25236250

Khan, Nasir Mehmood; Mu, Tai-Hua; Ali, Farman; Arogundade, Lawrence A; Khan, Zia Ullah; Zhang, Maio; Ahmad, Shujaat; Sun, Hong-Nan

2015-02-15

344

Bi-layered self-emulsifying pellets prepared by co-extrusion and spheronization: Influence of formulation variables and preliminary study on the in vivo absorption  

Microsoft Academic Search

The aim of this work was to produce by co-extrusionspheronization pellets with two cohesive layers, one of them containing a self-emulsifying system for vinpocetine, a poorly water soluble model drug. Two layers were prepared: an inert layer of microcrystalline cellulose, lactose and water and a second one wetted with the self-emulsifying system. Different formulations of both layers were tested, evaluating

Tamara Iosio; Dario Voinovich; Mario Grassi; Joo F. Pinto; Beatrice Perissutti; Marina Zacchigna; Ugo Quintavalle; Francesca Serdoz

2008-01-01

345

Influence of emulsifier type on freeze-thaw stability of hydrogenated palm oil-in-water emulsions  

Microsoft Academic Search

The influence of emulsifier type (Tween 20, whey protein isolate, casein) on the physical properties of 20wt% hydrogenated palm oil-in-water emulsions after crystallization of (i) the oil phase only or (ii) both the oil and water phases has been examined. Emulsion stability was assessed by differential scanning calorimetry measurements of fat destabilization after coolheat cycles, and by measurements of mean

P Thanasukarn; R Pongsawatmanit; D. J McClements

2004-01-01

346

Effect of the initial concentration of emulsifying agents on the ultracentrifugal stability of oil-in-water emulsions  

Microsoft Academic Search

The rate of loss of oil from 50% Nujol-50% water emulsions stabilized with varying concentrations of Tween 20 or Triton X-100,\\u000a and from 50% olive oil-50% water emulsions stabilized with sodium dodecyl sulfate (SDS), was determined by ultracentrifugation\\u000a at 39,460 rpm. In all cases the ultracentrifugal stability increased with increasing initial concentration of emulsifier,\\u000a although, unlike the behavior of Nujol-water-SDS

Kashmiri L. Mittal; Robert D. Vold

1972-01-01

347

Emulsifying properties of three African food hydrocolloids: okra (Hibiscus esculentus), dika nut (Irvingia gabonensis), and khan (Belschmiedia sp.)  

Microsoft Academic Search

This study investigated the emulsifying properties of okra (Hibiscus esculentus), dika nut (Irvingia gabonensis) and khan\\u000a (Belschmiedia sp.), three African food hydrocolloids used to thicken and flavor soups. Results showed that khan has an emulsion\\u000a potential approximately 20 and 100 times higher than the second and the first, respectively. A kinetic study indicated that\\u000a the mechanism involved formation of thick

R. Ndjouenkeu; J. O. Akingbala; G. B. Oguntimein

1997-01-01

348

Effect of salt content on the rheological properties of salad dressing-type emulsions stabilized by emulsifier blends  

Microsoft Academic Search

The effects that salt content and composition of emulsifier blends exert on the rheological properties of salad dressing-type emulsions were studied. Binary blends of egg yolk and different types of amphiphilic molecules (Tween 20, sucrose laurate and pea protein), in several proportions, were used to stabilize emulsions. Salt concentration was ranged from 0 to 2.3% w\\/w. Steady-state flow tests and

Inmaculada Martnez; M Angustias Riscardo; Jose M Franco

2007-01-01

349

Determination of food emulsifiers in commercial additives and food products by liquid chromatography\\/atmospheric-pressure chemical ionisation mass spectrometry  

Microsoft Academic Search

A new, reliable liquid chromatography\\/atmospheric-pressure chemical ionisation mass spectrometry (LCAPCI-MS) method was developed for the quantitative determination of food emulsifiers composed of mono- and diacylglycerols of fatty acids (E471 series) in complex food matrices. These additives are extremely interesting for the food industry because of their useful properties. Indeed, they improve the manufacture of products by acting as foams and

M. Suman; G. Silva; D. Catellani; U. Bersellini; V. Caffarra; M. Careri

2009-01-01

350

Topical (+)-catechin emulsified gel prevents DMBA/TPA-induced squamous cell carcinoma of the skin by modulating antioxidants and inflammatory biomarkers in BALB/c mice.  

PubMed

An emulsified gel of (+)-catechin was developed and evaluated topically against 7,12-dimethylbenz(a)anthracene-induced and 12-O-tetradecanoylphorbol-13-acetate-promoted (DMBA-induced and TPA-promoted) squamous cell carcinoma of the skin in BALB/c mice. The biological evaluation outcome indicated that the (+)-catechin emulsified gel increased the activity of oxidative stress biomarkers glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPx), whereas it decreased the level of malondialdehyde (MDA). The mechanistic study showed that genes implicated in the inflammation and cancer, such as cyclooxygenase-2 (COX-2), nuclear factor-kappa B (NF-?B), and inducible nitric-oxide synthase (iNOS), were down-regulated by (+)-catechin emulsified gel while inhibiting an inflammatory mediator prostaglandin E2 (PGE2). The (+)-catechin emulsified gel further suppressed the activity of pro-inflammatory cytokines, viz. tumor necrosis factor-alpha (TNF-?), interleukin-1 beta (IL-1?), and interleukin-6 (IL-6). The in vitro permeation study revealed that release of (+)-catechin from an emulsified gel base reached a steady state after 6 h, while pH of the entire emulsified gel was found to be between 6.2 and 6.5 that falls well within the normal pH range of the skin. PMID:25310126

Monga, Jitender; Aggarwal, Vaibhav; Suthar, Sharad Kumar; Monika; Nongalleima, Khumukcham; Sharma, Manu

2014-11-19

351

One-Step Synthesis of W/O and O/W Emulsifiers in the Presence of Surface Active Agents.  

PubMed

The main goal of this study was to describe the method of the synthesis of the dodecyl-, tetradecyl-, hexadecyl- and octadecyl-propylene glycol emulsifiers in the presence of selected anionic and nonionic surfactants. Acyl propylene glycol emulsifiers were produced by esterification of propane-1,2-diol (propylene glycol, PG) with C12:0-C18:0 fatty acids in the presence of anionic sodium dodecyl sulfate (SDS) and nonionic-poly(ethylene glycol) monolaurate (PEGML). The presence of SDS and PEGML in the reaction system caused microemulsion formation. Depending on the structure and amount of the surfactant in the system reactions proceeded at different rates and with different efficiency levels. The esterification of propylene glycol carried out under applied conditions causes products with the desired contents of propylene glycol monoesters (MAPG) to be obtained in a one-step reaction. Knowledge of the reaction kinetics creates the possibility to program the composition and properties of the synthesized emulsifiers. The interaction of nonionic, lipophilic MAPG with anionic, hydrophilic SDS or nonionic, hydrophilic PEGML influences the hydrophile-lipophile balance (HLB) values of the products which may be used to stabilize water-in-oil (W/O) and oil-in-water (O/W) emulsions. Use of the synthesized compounds allows stable emulsions to be prepared which include the following vegetable fats in the oil phase: mango oil, palm oil, shorea butter and hydrogenated soybean oil. PMID:23606803

Sadecka, Elwira; Szel?g, Halina

2013-05-01

352

Highly permeable double-skinned forward osmosis membranes for anti-fouling in the emulsified oil-water separation process.  

PubMed

Forward osmosis (FO) has attracted wide attention in recent years. However, the FO performance may be restricted due to internal concentration polarization (ICP) and fast fouling propensity that occurs in the membrane sublayer. Particularly, these problems significantly affect the membrane performance when treating highly contaminated oily wastewater. Recently, double-skinned flat sheet cellulose acetate (CA) membranes consisting of two selective skins via the phase inversion method have demonstrated less ICP and fouling propensity over typical single-skinned membranes. However, these membranes exhibit low water fluxes of <12 LMH under 2 M NaCl draw solution. Therefore, a novel double-skinned FO membrane with a high water flux has been aimed for in this study for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between (i) a truly dense skin for salt rejection and (ii) a fairly loose dense skin for emulsified oil particle rejection. The former dense skin is a polyamide synthesized via interfacial polymerization, while the latter one is a self-assembled sulfonated pentablock copolymer (Nexar copolymer) layer. The resultant double-skinned membrane exhibits a high water flux of 17.2 LMH and a low reverse salt transport of 4.85 gMH using 0.5 M NaCl as the draw solution and DI water as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation. PMID:24621207

Duong, Phuoc H H; Chung, Tai-Shung; Wei, Shawn; Irish, Lana

2014-04-15

353

Iron-refractory iron deficiency anemia (IRIDA).  

PubMed

Iron deficiency anemia is a common global problem whose etiology is typically attributed to acquired inadequate dietary intake and/or chronic blood loss. However, in several kindreds multiple family members are affected with iron deficiency anemia that is unresponsive to oral iron supplementation and only partially responsive to parenteral iron therapy. The discovery that many of these cases harbor mutations in the TMPRSS6 gene led to the recognition that they represent a single clinical entity: iron-refractory iron deficiency anemia (IRIDA). This article reviews clinical features of IRIDA, recent genetic studies, and insights this disorder provides into the regulation of systemic iron homeostasis. PMID:25064705

Heeney, Matthew M; Finberg, Karin E

2014-08-01

354

Characterization of edible emulsified films with low affinity to water based on kefiran and oleic acid.  

PubMed

New edible composite films based on kefiran and oleic acid (OA) at the ratio of 15, 25, and 35% (w/w) were prepared using emulsification with the aim of improving their water vapour barrier and mechanical properties. Film-forming solutions were characterized in terms of rheological properties and particle-size distribution. The impact of the incorporation of OA into the film matrix was studied by investigating the physical, mechanical, and thermal properties of the films. The water vapour permeability (WVP) of the emulsified films was reduced by approximately 33% by adding OA. The mechanical properties of kefiran films were also affected by adding OA: tensile strength was diminished, and elongation increased considerably. Differential scanning calorimetry showed that the glass transition temperature (T(g)) of the kefiran film was -16C and was not considerably affected by adding OA. Therefore, OA could be incorporated into these films for some food-technology applications that need a low affinity toward water. PMID:21640752

Ghasemlou, Mehran; Khodaiyan, Faramarz; Oromiehie, Abdulrasoul; Yarmand, Mohammad Saeid

2011-10-01

355

Voluntary Ingestion of Antiparasitic Drugs Emulsified in Honey Represents an Alternative to Gavage in Mice  

PubMed Central

The oral route is the most frequently used method of drug intake in humans. Oral administration of drugs to laboratory animals such as mice typically is achieved through gavage, in which a feeding needle is introduced into the esophagus and the drug is delivered directly into the stomach. This method requires technical skill, is stressful for animals, and introduces risk of injury, pain and morbidity. Here we investigated another method of drug administration. The benzimidazole derivative albendazole was emulsified in commercially available honey and administered to mice by voluntary feeding or gavage. Mice that received albendazole by either gavage or honey ingestion had virtually identical levels of serum albendazole sulfoxide, indicating that uptake and metabolism of albendazole was similar for both administration techniques. In addition, dosing mice with the albendazolehoney mixture for 8 wk had antiparasitic activity comparable to earlier studies using gavage for drug administration. Compared with gavage, voluntary ingestion of a drug in honey is more rapid, less stressful to the animal, and less technically demanding for the administrator. Because of its low cost and ready availability, honey presents a viable vehicle for drug delivery. PMID:22776122

Kuster, Tatiana; Zumkehr, Beatrice; Hermann, Corina; Theurillat, Regula; Thormann, Wolfgang; Gottstein, Bruno; Hemphill, Andrew

2012-01-01

356

Simultaneous Determination of Benzene and Toluene in Pesticide Emulsifiable Concentrate by Headspace GC-MS  

PubMed Central

The toxic inert ingredients in pesticide formulations are strictly regulated in many countries. In this paper, a simple and efficient headspace-gas chromatography-mass spectrometry (HSGC-MS) method using fluorobenzene as an internal standard (IS) for rapid simultaneous determination of benzene and toluene in pesticide emulsifiable concentrate (EC) was established. The headspace and GC-MS conditions were investigated and developed. A nonpolar fused silica Rtx-5 capillary column (30?m 0.20?mm i.d. and 0.25??m film thickness) with temperature programming was used. Under optimized headspace conditions, equilibration temperature of 120C, equilibration time of 5?min, and sample size of 50??L, the regression of the peak area ratios of benzene and toluene to IS on the concentrations of analytes fitted a linear relationship well at the concentration levels ranging from 3.2?g/L to 16.0?g/L. Standard additions of benzene and toluene to blank different matrix solutions 1ead to recoveries of 100.1%109.5% with a relative standard deviation (RSD) of 0.3%8.1%. The method presented here stands out as simple and easily applicable, which provides a way for the determination of toxic volatile adjuvant in liquid pesticide formulations. PMID:23607048

Jiang, Hua; Yang, Jing; Fan, Li; Li, Fengmin; Huang, Qiliang

2013-01-01

357

Emulsifying, flocculating, and physicochemical properties of exopolysaccharide produced by cyanobacterium Nostoc flagelliforme.  

PubMed

The emulsifying, flocculating, and physicochemical properties of purified exopolysaccharide (EPS) of terrestrial cyanobacterium Nostoc flagelliforme cultured in liquid media were investigated. The EPS was defined as heteropolysaccharide composed by 41.2 % glucose, 21.1 % galactose, 21.0 % mannose, 2.5 % fructose, 3.6 % ribose, 1.7 % xylose, 0.6 % arabinose, 3.0 % rhamnose, 0.9 % fucose, and 4.3 % glucuronic acid. The EPS possessed higher intrinsic viscosity than other cyanobacterial strains as reported and displayed pseudoplastic behavior in aqueous solution. The EPS produced more stable emulsions with tested hydrocarbons and oils than xanthan gum, and the emulsification indexes with n-hexadecane, liquid paraffin, and peanut oil were higher than 50 %, indicating the strong emulsion-stabilizing capacity. The EPS showed peak flocculating rates of 93.5 and 86.1 % in kaolin and MgO suspension, respectively, and exhibited a better flocculation performance than Al2(SO4)3 and xanthan gum. These results demonstrated that the EPS of N. flagelliforme was a very promising candidate for numerous industrial applications, as it had higher intrinsic viscosity, good emulsification activity, and excellent flocculation capability. PMID:24043454

Han, Pei-pei; Sun, Ying; Wu, Xiao-ying; Yuan, Ying-jin; Dai, Yu-jie; Jia, Shi-ru

2014-01-01

358

Systematic Development of Self-Emulsifying Drug Delivery Systems of Atorvastatin with Improved Bioavailability Potential  

PubMed Central

The aim of this study was to prepare and characterize a self-emulsifying drug delivery system (SEDDS) with a high drug load of poorly water-soluble atorvastatin for the enhancement of dissolution and oral bioavailability. Solubility of atorvastatin in oil, surfactant, and cosurfactant was determined. Pseudo-ternary phase diagrams were constructed by the aqueous titration method, and formulations were developed based on the optimum excipient combinations. A high drug load (10% w/w) was achieved with a combination of oleic acid, Tween 80, and polyethylene glycol 400, ensuring the maximum dissolution property (in the case of SES6). Effects of lipids and surfactants on physical properties of SEDDS such as in vitro emulsification efficiency in terms of self-emulsification time, emulsion droplet size, and percent transmittance were measured. Multiple regression analysis revealed that a higher amount of surfactants significantly increased dissolution of ATV while decreasing emulsion droplet size and emulsification time. About a four-fold increase in dissolution was achieved by SEDDS compared to pure ATV powder. Overall, this study suggests that dissolution and oral bioavailability of ATV could be improved by SEDDS technology. PMID:23264948

Khan, Fariba; Islam, Md. Saiful; Roni, Monzurul Amin; Jalil, Reza-Ul

2012-01-01

359

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

SciTech Connect

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 and analysis of previous work in this area led to the following conclusions about expected engine performance and emissions: the power density of the engine is significantly increased by oxygen enrichment. Ignition delay and particulate emissions are reduced. Combustion temperatures and No{sub x} emissions are increased with oxygen enrichment but could be brought back to the base levels by introducing water in the fuel. The peak cylinder pressure which increases with the power output level might result in mechanical problems with engine components. Oxygen enrichment also provides an opportunity to use cheaper fuel such as No. 6 diesel fuel. Overall, the adverse effects of oxygen enrichment could be countered by the addition of water and it appears that an optimum combination of water content, oxygen level, and base diesel fuel quality may exist. This could yield improved performance and emissions characteristics compared to a state-of-the-art diesel engine. 9 refs., 8 figs.

Assanis, D.N.; Baker, D. (Illinois Univ., Urbana, IL (USA)); Sekar, R.R.; Siambekos, C.T.; Cole, R.L.; Marciniak, T.J. (Argonne National Lab., IL (USA))

1990-01-01

360

Enhanced dissolution of celecoxib by supersaturating self-emulsifying drug delivery system (S-SEDDS) formulation.  

PubMed

A supersaturating self-emulsifying drug delivery system (S-SEDDS) was prepared and evaluated for enhanced dissolution of celecoxib (CXB), a poorly water-soluble drug. The selected CXB-dissolved SEDDS formulation consisting 10% Capryol 90 (oil), 45% Tween 20 (surfactant), and 45% Tetraglycol (cosurfactant) had the characteristics of small droplet size and great solubility as 208nm and 556.7mg/mL in average, respectively. CXB dissolution from SEDDS in simulated gastric fluid was increased to about 20% for the initial period of 5min, but decreased to a half level as time elapsed. Thus, precipitation inhibitors were screened to stabilize the supersaturation. The stabilizing effect of Soluplus, an amphiphilic copolymer, was concentration-dependent, revealing the greatest dissolution of approximately 90% level with delayed drug crystallization by the addition of the copolymer. CXB dissolution from S-SEDDS was pH-independent. We concluded that S-SEDDS formulation would be very useful in the future for developing oral delivery product of poorly water-soluble drugs. PMID:23325487

Song, Woo Heon; Park, Jong Hyeok; Yeom, Dong Woo; Ahn, Byeong Kil; Lee, Kyung Min; Lee, Sang Gon; Woo, Hye Seung; Choi, Young Wook

2013-01-01

361

Pharmacology of Iron Transport  

PubMed Central

Elucidating the molecular basis for the regulation of iron uptake, storage, and distribution is necessary to understand iron homeostasis. Pharmacological tools are emerging to identify and distinguish among different iron transport pathways. Stimulatory or inhibitory small molecules with effects on iron uptake can help characterize the mechanistic elements of iron transport and the roles of the transporters involved in these processes. In particular, iron chelators can serve as potential pharmacological tools to alleviate diseases of iron overload. This review focuses on the pharmacology of iron transport, introducing iron transport membrane proteins and known inhibitors. PMID:23020294

Byrne, Shaina L.; Krishnamurthy, Divya; Wessling-Resnick, Marianne

2013-01-01

362

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

Microsoft Academic Search

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

Manuel Muoz; Jos Antonio Garca-Erce; ngel Francisco Remacha

2010-01-01

363

Saving energy and reducing emissions of both polycyclic aromatic hydrocarbons and particulate matter by adding bio-solution to emulsified diesel.  

PubMed

Development of emulsified diesel has been driven by the need to reduce emissions from diesel engines and to save energy. Emulsification technology and bio-solution (NOE-7F) were used to produce emulsified diesel in this study. The experimental results indicated that there were no significant separation layers in W13 (13 wt % water + 87 wt % PDF), W16 (16 wt % water + 84 wt % PDF), W19 (19 wt % water + 81 wt % PDF), E13 (13 wt % NOE-7F water + 87 wt % PDF), E16 (16 wt % NOE-7F water + 83 wt % PDF), and E19 (19 wt % NOE-7F water + 81 wt % PDF) after premium diesel fuel (PDF) was emulsified for more than 30 days. In addition, there was no significant increase in damage from using these six emulsified fuels after the operation of the diesel generator for more than one year. The energy saving and reduction of particulate matter (PM) and total polycyclic aromatic hydrocarbons (PAHs) for W13, W16, W19, E13, E16 and E19, respectively, were 3.90%, 30.9%, 27.6%; 3.38%, 37.0%, 34.9%; 2.17%, 22.2%, 15.4%; 5.87%, 38.6%, 49.3%; 5.88%, 57.8%, 58.0%; and 4.75%, 31.1%, 47.3%, compared with PDF. The above results revealed that the bio-solution (NOE-7F) had a catalytic effect which elevated the combustion efficiency and decreased pollutant emissions during the combustion process. Furthermore, bio-solution (NOE-7F) can stabilize the emulsified fuels and enhance energy saving. Thus, emulsified fuels are highly suitable for use as alternative fuels. Due to the increasing price of diesel, emulsified diesel containing NOE-7F has potential for commercial application. PMID:16999139

Lin, Yuan-Chung; Lee, Wen-Jhy; Chen, Chun-Chi; Chen, Chung-Bang

2006-09-01

364

Iron deficiency anemia  

MedlinePLUS

... You get iron deficiency anemia when your body's iron stores run low. This can occur because: You lose ... ferrous sulfate) are needed to build up the iron stores in your body. Most of the time, your ...

365

Iron and Prochlorococcus/  

E-print Network

Iron availability and primary productivity in the oceans are intricately linked through photosynthesis. At the global scale we understand how iron addition induces phytoplankton blooms through meso-scale iron-addition ...

Thompson, Anne Williford

2009-01-01

366

Double emulsions and colloidosomes-in-colloidosomes using silica-based Pickering emulsifiers.  

PubMed

Poly(ethylene imine) (PEI) has been adsorbed onto the surface of fumed silica particles at pH 10 in order to produce an effective "hybrid" Pickering emulsifier. Systematically increasing the PEI/silica mass ratio at a fixed silica concentration of 1.0% w/w modifies the silica particle surface and hence allows the formation of oil-in-water (o/w) Pickering emulsions prepared via homogenization of an aldehyde-rich multi-component fragrance oil (at 12,000 rpm for 2 min at 20 C). Further increasing the PEI/silica mass ratio leads to phase inversion, producing water-in-oil (w/o) Pickering emulsions. Thus this approach allows formation of stable water-in-oil-in-water (w/o/w) double emulsions using two batches of hydrophilic and hydrophobic PEI/silica hybrid particles that differ only in their PEI/silica mass ratios prior to homogenization. Stable w/o/w double emulsions can be prepared with oil volume fractions ranging from 5 to 42%. Moreover, controlling the volume fraction of the w/o Pickering emulsion homogenized in the presence of an aqueous dispersion of the hydrophilic PEI/silica particles allows the mean diameter of the resulting oil droplets to be conveniently controlled between 20 and 160 ?m. Fluorescence microscopy studies confirm that controlling the mean diameter of these oil droplets allows encapsulation of either single or multiple droplets within them. Although these double emulsions do not require cross-linking at either interface to withstand an alcohol challenge, epoxy-amine cross-linking between the physically-adsorbed PEI chains and either an oil-soluble or a water-soluble bisepoxy-based polymeric cross-linker can be achieved to produce novel colloidosomes-in-colloidosomes, which may offer payload retention benefits over conventional colloidosomes. PMID:24559174

Williams, Mark; Armes, Steven P; Verstraete, Pierre; Smets, Johan

2014-03-18

367

Formulation and in vitro evaluation of self-emulsifying formulations of Cinnarizine.  

PubMed

The main objectives of this study were to improve the aqueous solubility and to modify in vitro dissolution profile of hydrophobic drug using self-emulsifying drug delivery systems (SEDDS). SEDDS were formulated using Capmul PG-12, Cremophor RH 40 and Tween 20 at different weight ratios and incorporated with Cinnarizine. The drug incorporation into pre-concentrate and drug solubility in phosphate buffer (pH 7.2) were investigated. In addition, the mean droplet size and drug release profile of the SEDDS were also determined. The drug incorporation was over 120?mg per 0.5?g pre-concentrate regardless of the composition of the formulations. The solubility of Cinnarizine in phosphate buffer (pH 7.2) was at least 1500 ?M in the SEDDS. Formulations with only 10% w/w Capmul PG-12 were less than 20?nm in mean diameter while those produced with at least 20% w/w Capmul PG-12 were more than 100?nm regardless of the ratios of Cremophor RH 40 to Tween 20. SEDDS showed a significant increase of the mean percentage drug release than pure drug (p?

Vithlani, Shyam; Sarraf, Shruthi; Chaw, Cheng Shu

2012-10-01

368

Use of emulsified vegetable oil to support bioremediation of TCE DNAPL in soil columns  

NASA Astrophysics Data System (ADS)

The interaction between emulsified vegetable oil (EVO) and trichloroethylene (TCE) dense non-aqueous phase liquid (DNAPL) was observed using two soil columns and subsequent reductive dechlorination of TCE was monitored over a three year period. Dyed TCE DNAPL (~ 75 g) was emplaced in one column (DNAPL column), while the second was DNAPL-free (plume column). EVO was added to both columns and partitioning of the EVO into the TCE DNAPL was measured and quantified. TCE (1.9 mM) was added to the influent of the plume column to simulate conditions down gradient of a DNAPL source area and the columns were operated independently for more than one year, after which they were connected in series. Initially limited dechlorination of TCE to cDCE was observed in the DNAPL column, while the plume column supported complete reductive dechlorination of TCE to ethene. Upon connection and reamendment of the plume column with EVO, near saturation levels of TCE from the effluent of the DNAPL column were rapidly dechlorinated to c-DCE and VC in the plume column; however, this high rate dechlorination produced hydrochloric acid which overwhelmed the buffering capacity of the system and caused the pH to drop below 6.0. Dechlorination efficiency in the columns subsequently deteriorated, as measured by the chloride production and Dehalococcoides counts, but was restored by adding sodium bicarbonate buffer to the influent groundwater. Robust dechlorination was eventually observed in the DNAPL column, such that the TCE DNAPL was largely removed by the end of the study. Partitioning of the EVO into the DNAPL provided significant operational benefits to the remediation system both in terms of electron donor placement and longevity.

Harkness, Mark; Fisher, Angela

2013-08-01

369

Intravenous pretreatment with emulsified isoflurane preconditioning protects kidneys against ischemia/reperfusion injury in rats  

PubMed Central

Background Emulsified isoflurane (EIso) is a novel intravenous general anesthetic, which can provide rapid anesthetic induction and recovery. EIso preconditioning could attenuate heart, lung and liver ischemia/reperfusion (I/R) injury. We tested the hypothesis that intravenous pretreatment with EIso would protect kidneys against I/R injury by inhibiting systemic inflammatory responses and improving renal antioxidative ability. Methods Rats were randomly divided into these six groups: sham, I/R, intralipid, 1, 2 or 4ml/kg EIso. Rats were subjected to 45min left renal pedicle occlusion followed by 3h reperfusion after right nephrectomy. Rat were treated with intravenous 8% EIso with 1, 2 or 4ml/kg, or 30% intralipid with 2ml/kg for 30min before ischemia, respectively. After reperfusion, renal functional parameters, serum mediator concentrations and markers of oxidative stress in kidney tissues were determined, and renal histopathological analysis were performed. Results Serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-?, interleukin-6, and interleukin-10 concentrations were significantly increased after renal I/R as compared to the sham group. So was renal tissue MDA content and histological scores, but renal tissue SOD activity was decreased. Additionally, severe morphological damages were observed in these study groups. In contrast, 2 or 4ml/kg EIso reduced serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-?, and interleukin-6 levels, decreased renal tissue MDA content and histological scores, increased serum interleukin-10 level and tissue SOD activity as compared to the I/R, intralipid and 1ml/kg EIso groups. Renal morphological damages were alleviated after pretreatment of 2 or 4ml/kg EIso. Conclusions Intravenous EIso produces preconditioning against renal I/R injury in rats, which might be mediated by attenuating inflammation and increasing antioxidation ability. PMID:24739487

2014-01-01

370

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

SciTech Connect

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

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

2002-05-01

371

Iron and Stony-iron Meteorites  

Microsoft Academic Search

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

H. Haack; T. J. McCoy

2003-01-01

372

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

EPA Science Inventory

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

373

Geoecology PhD Seminar WS 2013/14 Institute of Earth and Environmental Sciences, University of Potsdam  

E-print Network

flood of 2013 on depositional processes within Lake Mondsee Climate change shifts environmental space supported nanoscale zero-valent iron 04.12.13 Abbas Dara (UP) Christian Lehr (ZALF) Mapping Compensating Water Uptake in Heterogeneous Soils via Neutron Radiography Effects of a restored stream channel

Potsdam, Universität

374

NZVI modified magnetic filter paper with high redox and catalytic activities for advanced water treatment technologies.  

PubMed

The in situ synthesis of air-stable zero-valent iron nanoparticles (NZVI) embedded in cellulose fibers leads to the assembly of highly reactive magnetic filter papers. These engineered materials display a wide range of applications in the treatment of wastewater and drinking water, including chromium removal, phenol degradation, environmental bioremediation, and catalysis. PMID:25299729

Datta, K K R; Petala, E; Datta, K J; Perman, J A; Tucek, J; Bartak, P; Otyepka, M; Zoppellaro, G; Zboril, R

2014-12-25

375

PRB STRATEGIES AND PERFORMANCE MONITORING FOR REMEDIATION OF INORGANIC CONTAMINANTS  

EPA Science Inventory

A combination of experimental and field investigations will be conducted to evaluate the effectiveness and long-term performance of zero-valent iron mixtures for treating inorganic contaminants. Long-term performance research will explore the geochemical and microbiological proce...

376

Perchlorate Reduction by Autotrophic Bacteria in the  

E-print Network

Perchlorate Reduction by Autotrophic Bacteria in the Presence of Zero-Valent Iron X U E Y U A N Y U because ClO4 - is completely transformed into chlorideandothernontoxicendproducts(2).Microbiological-limiting step with complete conversion to chloride (7). Perchlorate reducing microorganisms (PRMs) are ubiq

377

Bioremediation of Uranium Plumes with Nano-scale  

E-print Network

Reservation Land MCL for Uranium = 30 g/L MCL for Alpha particles = 15 pCi/L Arizona Well Water energy.cr.usgs.gov/other/uraniumBioremediation of Uranium Plumes with Nano-scale Zero-valent Iron Angela Athey Advisers: Dr. Reyes Undergraduate Student Fellowship Program April 15, 2011 #12;Main Sources of Uranium Natural · Leaching from

Fay, Noah

378

DEMONSTRATION BULLETIN: METAL-ENHANCED ABIOTIC DEGRADATION TECHNOLOGY - ENVIROMETAL TECHNOLOGIES, INC.  

EPA Science Inventory

EnviroMetal Technologies, Inc. (ETI), of Guelph, ON, Canada, has developed the metal-enhanced abiotic degradation technology to treat halogenated volatile organic compounds (VOC) in water. A reactive, zero-valent, granular iron medium causes reductive dehalogenation of VOCs yield...

379

Environmental Aspects of Two Volatile Organic Compound Groundwater Treatment Designs at the Rocky Flats Site - 13135  

SciTech Connect

DOE's Rocky Flats Site in Colorado is a former nuclear weapons production facility that began operations in the early 1950's. Because of releases of hazardous substances to the environment, the federally owned property and adjacent offsite areas were placed on the CERCLA National Priorities List in 1989. The final remedy was selected in 2006. Engineered components of the remedy include four groundwater treatment systems that were installed before closure as CERCLA-accelerated actions. Two of the systems, the Mound Site Plume Treatment System and the East Trenches Plume Treatment System, remove low levels of volatile organic compounds using zero-valent iron media, thereby reducing the loading of volatile organic compounds in surface water resulting from the groundwater pathway. However, the zero-valent iron treatment does not reliably reduce all volatile organic compounds to consistently meet water quality goals. While adding additional zero-valent iron media capacity could improve volatile organic compound removal capability, installation of a solar powered air-stripper has proven an effective treatment optimization in further reducing volatile organic compound concentrations. A comparison of the air stripper to the alternative of adding additional zero-valent iron capacity to improve Mound Site Plume Treatment System and East Trenches Plume Treatment System treatment based on several key sustainable remediation aspects indicates the air stripper is also more 'environmentally friendly'. These key aspects include air pollutant emissions, water quality, waste management, transportation, and costs. (authors)

Michalski, Casey C.; DiSalvo, Rick; Boylan, John [Stoller LMS Team, 11025 Dover Street, Suite 1000, Westminster, CO 80021 (United States)] [Stoller LMS Team, 11025 Dover Street, Suite 1000, Westminster, CO 80021 (United States)

2013-07-01

380

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

EPA Science Inventory

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

381

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

EPA Science Inventory

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

382

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

Microsoft Academic Search

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

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

383

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

1987-03-31

384

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

Sachtler, Wolfgang M. H. (Evanston, IL); Tzou, Ming-Shin (Evanston, IL); Jiang, Hui-Jong (Evanston, IL)

1987-01-01

385

GROUND WATER ARSENIC AND METALS TREATMENT USING A COMBINATION COMPOST-ZVI PRB  

EPA Science Inventory

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

386

TREATMENT OF METALS IN GROUND WATER USING AN ORGANIC-BASED SULFATE-REDUCING PERMEABLE REACTIVE BARRIER  

EPA Science Inventory

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

387

ACCUMULATION RATE OF MICROBIAL BIOMASS AT TWO PERMEABLE REACTIVE BARRIER SITES  

EPA Science Inventory

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

388

Translocation of Crohn's disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers  

PubMed Central

Background Crohn's disease is common in developed nations where the typical diet is low in fibre and high in processed food. Primary lesions overlie Peyer's patches and colonic lymphoid follicles where bacterial invasion through M-cells occurs. We have assessed the effect of soluble non-starch polysaccharide (NSP) and food emulsifiers on translocation of Escherichia coli across M-cells. Methods To assess effects of soluble plant fibres and food emulsifiers on translocation of mucosa-associated E coli isolates from Crohn's disease patients and from non-Crohn's controls, we used M-cell monolayers, generated by co-culture of Caco2-cl1 and Raji B cells, and human Peyer's patches mounted in Ussing chambers. Results E coli translocation increased across M-cells compared to parent Caco2-cl1 monocultures; 15.8-fold (IQR 6.232.0) for Crohn's disease E coli (N=8) and 6.7-fold (IQR 3.721.0) for control isolates (N=5). Electron microscopy confirmed E coli within M-cells. Plantain and broccoli NSP markedly reduced E coli translocation across M-cells at 5?mg/ml (range 45.382.6% inhibition, p<0.01); apple and leek NSP had no significant effect. Polysorbate-80, 0.01% vol/vol, increased E coli translocation through Caco2-cl1 monolayers 59-fold (p<0.05) and, at higher concentrations, increased translocation across M-cells. Similarly, E coli translocation across human Peyer's patches was reduced 457% by soluble plantain NSP (5?mg/ml) and increased 2-fold by polysorbate-80 (0.1% vol/vol). Conclusions Translocation of E coli across M-cells is reduced by soluble plant fibres, particularly plantain and broccoli, but increased by the emulsifier Polysorbate-80. These effects occur at relevant concentrations and may contribute to the impact of dietary factors on Crohn's disease pathogenesis. PMID:20813719

Roberts, Carol L; Keita, Asa V; Duncan, Sylvia H; O'Kennedy, Niamh; Soderholm, Johan D; Rhodes, Jonathan M

2010-01-01

389

Effects of Hydrophile-Lypophile Balance of Emulsifier on Electrooptical Properties and Morphology of Poly(vinylalcohol)/Liquid Crystal Composite  

NASA Astrophysics Data System (ADS)

We clarified the relationship between the morphology of a poly(vinyl alcohol) (PVA)/liquid crystal (LC) composite film fabricated by an emulsification method and a hydrophile-lypophile balance (HLB) of an emulsifier. The LC domain size was affected by the surface tension of the PVA aqueous solution and of the LC. The surface tension of the PVA aqueous solution and the LC was varied by changing the HLB value. The electrooptical properties, such as threshold voltage and response time, were strongly dependent on the LC droplet size, in good qualitative agreement with results obtained using the equations of Doane et al. [Mol. Cryst. Liq. Cryst. 5 (1989) 1453].

Ono, Hiroshi; Kawatsuki, Nobuhiro

1995-12-01

390

HEPCIDIN AND IRON HOMEOSTASIS  

PubMed Central

Despite fluctuations in dietary iron intake and intermittent losses through bleeding, the plasma iron concentrations in humans remain stable at 1030 ?M. While most of the iron entering blood plasma comes from recycling, appropriate amount of iron is absorbed from the diet to compensate for losses and maintain nontoxic amounts in stores. Plasma iron concentration and iron distribution are similarly regulated in laboratory rodents. The hepatic peptide hepcidin was identified as the systemic iron-regulatory hormone. In the efferent arc, hepcidin regulates intestinal iron absorption, plasma iron concentrations, and tissue iron distribution by inducing degradation of its receptor, the cellular iron exporter ferroportin. Ferroportin exports iron into plasma from absorptive enterocytes, from macrophages that recycle the iron of senescent erythrocytes, and from hepatocytes that store iron. In the more complex and less well understood afferent arc, hepatic hepcidin synthesis is transcriptionally regulated by extracellular and intracellular iron concentrations through a molecular complex of bone morphogenetic protein receptors and their iron-specific ligands, modulators and iron sensors. Through as yet undefined pathways, hepcidin is also homeostatically regulated by the iron requirements of erythroid precursors for hemoglobin synthesis. In accordance with the role of hepcidin-mediated iron redistribution in host defense, hepcidin production is regulated by inflammation as well. Increased hepcidin concentrations in plasma are pathogenic in iron-restrictive anemias including anemias associated with inflammation, chronic kidney disease and some cancers. Hepcidin deficiency causes iron overload in hereditary hemochromatosis and ineffective erythropoiesis. Hepcidin, ferroportin and their regulators represent potential targets for the diagnosis and treatment of iron disorders and anemias. PMID:22306005

Ganz, Tomas; Nemeth, Elizabeta

2014-01-01

391

Novel Pickering emulsifiers based on pH-responsive poly(2-(diethylamino)ethyl methacrylate) latexes.  

PubMed

The emulsion copolymerization of 2-(diethylamino)ethyl methacrylate (DEA) with a divinylbenzene cross-linker in the presence of monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA) at 70 C afforded near-monodisperse, sterically stabilized PEGMA-PDEA latexes at 10% solids. Dynamic light scattering studies indicated intensity-average diameters of 190 to 240 nm for these latexes at pH 9. A latex-to-microgel transition occurred on lowering the solution pH to below the latex pKa of 6.9. When dilute HCl/KOH was used to adjust the aqueous pH, a systematic reduction in the cationic microgel hydrodynamic diameter of 80 nm was observed over ten pH cycles as a result of the gradual buildup of background salt. However, no such size reduction was observed when using CO2/N2 gases to regulate the aqueous pH because this protocol does not generate background salt. Thus, the latter approach offers better reversibility, albeit at the cost of slower response times. PEGMA-PDEA microgel does not stabilize Pickering emulsions when homogenized at pH 3 with n-dodecane, sunflower oil, isononyl isononanoate, or isopropyl myristate. In contrast, PEGMA-PDEA latex proved to be a ubiquitous Pickering emulsifier at pH 10, forming stable oil-in-water emulsions with each of these four model oils. Lowering the solution pH from 10 to 3 resulted in demulsification within seconds. This is because these pH-responsive particles undergo a latex-to-microgel transition, which leads to their interfacial desorption. Six successive demulsification/emulsification cycles were performed on these Pickering emulsions using HCl/KOH to adjust the solution pH. Demulsification could also be achieved by purging the emulsion solution with CO2 gas to lower the aqueous pH to 4.8. However, complete phase separation required CO2 purging for 4 h at 20 C. A subsequent N2 purge raised the aqueous pH sufficiently to induce a microgel-to-latex transition, but rehomogenization did not produce a stable Pickering emulsion. Presumably, a higher pH is required, which cannot be achieved by a N2 purge alone. PMID:23570375

Morse, A J; Armes, S P; Thompson, K L; Dupin, D; Fielding, L A; Mills, P; Swart, R

2013-05-01

392

Interfacial Tension in Binary Polymer Blends and the Effects of Copolymers as Emulsifying Agents  

NASA Astrophysics Data System (ADS)

The structure and the thermodynamic state of polymeric interfaces are important features in many materials of technological interest. This is especially true for multiconstituent systems such as blends of immiscible polymers, where the interface structure can affect greatly their morphology and, thus, their mechanical properties. In this article, we first present a review of the experimental and theoretical investigations of the interfacial tension in phase-separated homopolymer blends. We emphasize the effects of temperature and molecular weight on the behavior: interfacial tension ? decreases with increasing temperature (for polymer systems exhibiting upper critical solution temperature behavior) with a temperature coefficient of the order of 10-2 dyn/(cm C), whereas it increases with increasing molecular weight. The increase follows a ? = ? _infty ( {1 - k_{operatorname{int} } M_{n}}^{ - z} } ) dependence (with z ? 1 for high molecular weights), where ? ? is the limiting interfacial tension at infinite molecular weight and M n the number average molecular weight. Suitably chosen block or graft copolymers are widely used in blends of immiscible polymers as compatibilizers for controlling the morphology (phase structure) and the interfacial adhesion between the phases. The compatabilitizing effect is due to their interfacial activity, i.e., to their affinity to selectively segregate to the interface between the phase-separated homopolymers, thus reducing the interfacial tension between the two macrophases. The experimental and theoretical works in this area are reviewed herein. The effects of concentration, molecular weight, composition, and macromolecular architecture of the copolymeric additives are discussed. An issue that can influence the efficient utilization of a copolymeric additive as an emulsifier is the possibility of micelle formation within the homopolymer matrices when the additive is mixed with one of the components. These micelles will compete with the interfacial region for copolymer chains. A second issue relates to the possible trapping of copolymer chains at the interface, which can lead to stationary states of partial equilibrium. The in-situ formation of copolymers by the interfacial reaction of functionalized homopolymers is also discussed.

Anastasiadis, Spiros H.

393

Microbial Dynamics During a Temporal Sequence of Bioreduction Stimulated by Emulsified Vegetable Oil  

NASA Astrophysics Data System (ADS)

Amendments of slow-release substrates (e.g. emulsified vegetable oil; EVO) are potentially pragmatic alternatives to short-lived labile substrates for sustained uranium bioimmobilization within groundwater systems. The spatial and temporal dynamics of geochemical and microbial community changes during EVO amendment are likely to differ significantly from populations stimulated by readily utilizable soluble substrates (e.g. ethanol or acetate). We tracked dynamic changes in geochemistry and microbial communities for 270 days following a one-time EVO injection at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site that resulted in decreased groundwater U concentrations for ~4 months. Pyrosequencing and quantitative PCR of 16S rRNA and dissimilatory sulfite reductase (dsrA) genes from monitoring well samples revealed a rapid decline in bacterial community richness and evenness after EVO injection, concurrent with increased 16S rRNA copy levels, indicating the selection of a narrow group consisting of 10-15 dominant OTUs, rather than a broad community stimulation. By association of the known physiology of close relatives identified in the pyrosequencing analysis, it is possible to infer a hypothesized sequence of microbial functions leading the major changes in electron donors and acceptors in the system. Members of the Firmicutes family Veillonellaceae dominated after injection and most likely catalyzed the initial oil decomposition and utilized the glycerol associated with the oils. Sulfate-reducing bacteria from the genus Desulforegula, known for LCFA oxidation to acetate, also dominated shortly after EVO amendment and are thought to catalyze this process. Acetate and H2 production during LCFA degradation appeared to stimulate NO3-, Fe(III), U(VI), and SO42- reduction by members of the Comamonadaceae, Geobacteriaceae, and Desulfobacterales. Methanogenic archaea flourished late in the experiment and in some samples constituted over 25 % of the total microbial community. Bacterial richness rebounded after nine months, although community composition remained distinct from the pre-amendment conditions. Subsequent to the experiment we have isolated several of these organisms into pure culture including representatives of probable new species of Geobacter, Desulforegula and Desulfovibrio. A hypothesized model for the functioning of these limited communities will be verified in the laboratory using defined combinations of isolates from the field where possible. These results demonstrated EVO serves as an effective electron donor source for in situ U(VI) bioreduction, and subsurface EVO degradation and metal reduction was likely mediated by successive identifiable guilds of organisms.

Schadt, C. W.; Gihring, T. M.; Yang, Z.; Wu, W.; Green, S.; Overholt, W.; Zhang, G.; Brandt, C. C.; Campbell, J. H.; Carroll, S. C.; Criddle, C.; Jardine, P. M.; Lowe, K.; Mehlhorn, T.; Kostka, J. E.; Watson, D. B.; Brooks, S. C.

2011-12-01

394

Amino Acid Complexes of Metal Carbonyls: Mechanistic Aspects of the CO-Labilizing Ability of Glycinate Ligands in Zero-Valent Chromium and Tungsten Derivatives.  

PubMed

The amino and phosphino acid derivatives of chromium(0) and tungsten(0), [Et(4)N][Cr(CO)(4)(O(2)CCH(2)NH(2))] (1), [Et(4)N][Cr(CO)(4)(O(2)CCH(2)NHMe)] (2), [Et(4)N][Cr(CO)(4)(O(2)CCH(2)NMe(2))] (3), [Et(4)N][W(CO)(4)(O(2)CCH(C(CH(3))(3))NH(2))] (4), [Et(4)N][W(CO)(4)(O(2)CCH(C(6)H(5))NH(2))], [Et(4)N][W(CO)(4)(O(2)CCH(2)PPh(2))] (5), and [Et(4)N][Cr(CO)(4)(O(2)CCH(2)PPh(2))] have been synthesized from the reaction of the M(CO)(5)THF adduct with the tetraethylammonium salt of the corresponding amino or phosphino acid in THF solution. The complexes have been characterized in solution by (13)C NMR and infrared spectroscopies and in the solid state by X-ray crystallography. The geometry of the metal anion is, in each case, that of a distorted octahedron consisting of four carbonyl ligands and a puckered five-membered glycinate chelate ring, bound through the nitrogen atom and one of its oxygen atoms. Notable about complex 1 is that the crystal obtained exhibited both a different morphology and a different space group than its tungsten analogue. Examination of the packing diagram reveals that this change is due to the different orientation of the chelate ring in 1 relative to the corresponding orientation in the W(CO)(4)(O(2)CCH(2)NH(2))(-) anion. Complexes 1 and 2 exhibit intermolecular hydrogen-bonding interactions between the amine N-H group and the distal oxygen on an adjacent molecule, with N.O distances of 2.828 and 2.821 , respectively. Investigations of the lability of the carbonyl ligands have been carried out. The lability is proposed to be due to base-assisted removal of a proton from the amine ligand leading to a substitutionally labile amide transient species. The tungsten analogue of complex 1 was used to obtain evidence in support of this mechanism. The isotope effect (k(H)/k(D)) was measured for W(CO)(4)(O(2)CCH(2)NH(2))(-) using d(5)-glycine and was found to be 2.34. The activation parameters for the intermolecular exchange of CO in the [Et(4)N][W(CO)(4)(O(2)CCH(2)NH(2))] salt were determined and found to be DeltaH() = 15.4 +/- 1.0 kcal/mol and DeltaS() = -23.2 +/- 3.2 eu, values consistent with the proposed mechanism. In addition, the effect of substitution of electron-donating (C(CH(3))(3)) and electron-withdrawing (C(6)H(5)) substituents on the methylene carbon was evaluated. There was little change in the rate of CO exchange observed for W(CO)(4)(O(2)CCH(C(CH(3))(3))NH(2))(-) (5) and W(CO)(4)(O(2)CCH(C(6)H(5))NH(2))(-) vs W(CO)(4)(O(2)CCH(2)NH(2))(-), showing that steric or electronic effects away from the N center are not responsible for the observed CO lability. As anticipated on the basis of the proposed substitutional pathway, the phosphino acid metal carbonyl derivatives did not exhibit facile intermolecular CO exchange. PMID:11670056

Darensbourg, Donald J.; Draper, Jennifer D.; Reibenspies, Joseph H.

1997-08-13

395

Delayed formation of zero-valent selenium nanoparticles by Bacillus mycoides SeITE01 as a consequence of selenite reduction under aerobic conditions  

PubMed Central

Background Selenite (SeO32?) oxyanion shows severe toxicity to biota. Different bacterial strains exist that are capable of reducing SeO32? to non-toxic elemental selenium (Se0), with the formation of Se nanoparticles (SeNPs). These SeNPs might be exploited for technological applications due to their physico-chemical and biological characteristics. The present paper discusses the reduction of selenite to SeNPs by a strain of Bacillus sp., SeITE01, isolated from the rhizosphere of the Se-hyperaccumulator legume Astragalus bisulcatus. Results Use of 16S rRNA and GyrB gene sequence analysis positioned SeITE01 phylogenetically close to B. mycoides. On agarized medium, this strain showed rhizoid growth whilst, in liquid cultures, it was capable of reducing 0.5 and 2.0 mM SeO32? within 12 and 24 hours, respectively. The resultant Se0 aggregated to form nanoparticles and the amount of Se0 measured was equivalent to the amount of selenium originally added as selenite to the growth medium. A delay of more than 24 hours was observed between the depletion of SeO32 and the detection of SeNPs. Nearly spherical-shaped SeNPs were mostly found in the extracellular environment whilst rarely in the cytoplasmic compartment. Size of SeNPs ranged from 50 to 400 nm in diameter, with dimensions greatly influenced by the incubation times. Different SeITE01 protein fractions were assayed for SeO32? reductase capability, revealing that enzymatic activity was mainly associated with the membrane fraction. Reduction of SeO32? was also detected in the supernatant of bacterial cultures upon NADH addition. Conclusions The selenite reducing bacterial strain SeITE01 was attributed to the species Bacillus mycoides on the basis of phenotypic and molecular traits. Under aerobic conditions, the formation of SeNPs were observed both extracellularly or intracellullarly. Possible mechanisms of Se0 precipitation and SeNPs assembly are suggested. SeO32? is proposed to be enzimatically reduced to Se0 through redox reactions by proteins released from bacterial cells. Sulfhydryl groups on peptides excreted outside the cells may also react directly with selenite. Furthermore, membrane reductases and the intracellular synthesis of low molecular weight thiols such as bacillithiols may also play a role in SeO32? reduction. Formation of SeNPs seems to be the result of an Ostwald ripening mechanism. PMID:24606965

2014-01-01

396

Pathways of iron absorption.  

PubMed

Iron is vital for all living organisms but excess iron can be lethal because it facilitates free radical formation. Thus iron absorption is carefully regulated to maintain an equilibrium between absorption and body loss of iron. In countries where meat is a significant part of the diet, most body iron is derived from dietary heme because heme binds few of the dietary chelators that bind inorganic iron. Uptake of heme into enterocytes occurs as a metalloporphyrin in an endosomal process. Intracellular iron is released from heme by heme oxygenase to enter plasma as inorganic iron. Ferric iron is absorbed via a beta(3) integrin and mobilferrin pathway (IMP) which is unshared with other nutritional metals. Ferrous iron uptake is facilitated by a DMT-1 pathway which is shared with manganese. In the iron deficient gut, large quantities of both mobilferrin and DMT-1 are found in goblet cells and intraluminal mucins suggesting that they are secreted with mucin into the intestinal lumen to bind iron to facilitate uptake by the cells. In the cytoplasm, IMP and DMT associate in a large protein complex called paraferritin which serves as a ferrireductase. Paraferritin solublizes iron binding proteins and reduces iron to make iron available for production of iron containing proteins such as heme. Iron uptake by intestinal absorptive cells is regulated by the iron concentration within the cell. Except in hemochromatosis it remains in equilibrium with total body stores via transferrin receptors on the basolateral membrane of absorptive cells. Increased intracellular iron either up-regulates or satiates iron binding proteins on regulatory proteins to alter their location in the intestinal mucosa. PMID:12547224

Conrad, Marcel E; Umbreit, Jay N

2002-01-01

397

Interfacial, stability and rheological study of microbubbles coated with a monostearin/monopalmitin-rich food emulsifier and PEG40 stearate  

NASA Astrophysics Data System (ADS)

Micron-scale bubbles (microbubbles) are of considerable interest in environmental, biomedical, and food sciences. The low cost food emulsifiers, which are used to stabilize the gas core of the microbubble, consist of a mixture of monoglycerides, diglycerides and sodium steroyl lactylate in combination with polyethylene glycol (PEG) 40 sterate. Langmuir trough methods and fluorescence microscopy were combined to investigate the surface tension, interfacial elastic modulus, phase behavior and microstructure of monolayer shells coating these microbubbles. Polydisperse coated microbubbles can be generated using a probe sonication technique. The dissolution behavior of a microbubble in different unsaturated media was studied using a fluorescence microscope. These dissolution behaviors, involving the buckling and rupture of the coated monolayer, can be explained by the phase behavior of emulsifiers and their roles in the stabilization of microbubbles in aqueous systems. Nearly monodispersed populations of microbubbles ranged in 120--200mum were produced using flow focusing Technique. Sufficient short-term stability in size allows the rheological properties of microbubble suspension to be obtained by rheometer. The effect of shearing on the bubble sizes is investigated. There results show that the microbubble suspensions are viscoelastic and exhibit power law behavior. The relationship between the air fraction of the suspension and fluid rheology is determined.

Shen, Yuyi

398

Comparison of emulsifying properties of milk fat globule membrane materials isolated from different dairy by-products.  

PubMed

Emulsifying properties of milk fat globule membrane (MFGM) materials isolated from reconstituted buttermilk (BM; i.e., BM-MFGM) and BM whey (i.e., whey-MFGM), individually or in mixtures with BM powder (BMP) were compared with those of a commercial dairy ingredient (Lacprodan PL-20; Arla Foods Ingredients Group P/S, Viby, Denmark), a material rich in milk polar lipids and proteins. The particle size distribution, viscosity, interfacial protein, and polar lipids load of oil-in-water emulsions prepared using soybean oil were examined. Pronounced droplet aggregation was observed with emulsions stabilized with whey-MFGM or with a mixture of whey-MFGM and BMP. No aggregation was observed for emulsions stabilized with BM-MFGM, Lacprodan PL-20, or a mixture of BM-MFGM and BMP. The surface protein load and polar lipids load were lowest in emulsions with BM-MFGM. The highest protein load and polar lipids load were observed for emulsions made with a mixture of whey-MFGM and BMP. The differences in composition of MFGM materials, such as in whey proteins, caseins, MFGM-specific proteins, polar lipids, minerals, and especially their possible interactions determine their emulsifying properties. PMID:24913653

Phan, T T Q; Le, T T; Van der Meeren, P; Dewettinck, K

2014-08-01

399

The utility of self-emulsifying oil formulation to improve the poor solubility of the anti HIV drug CSIC  

PubMed Central

Background CSIC (5-chloro-3-phenylsulfonylindole-2-carboxamide), a non-nucleoside reverse transcriptase inhibitor (NNRTI) has not been advanced as a therapeutic anti-HIV candidate drug due to its low aqueous solubility and poor bioavailability. Objective The objective of this work was to formulate CSIC into self-emulsifying oil formulations for the purpose of improving its aqueous solubility and evaluating in vitro antiretroviral activity. Methods CSIC self-emulsifying oil formulations (SEFs) were formulated and evaluated for droplet size, zeta potential, polydispersity index (PDI), viscosity, emulsification time, stability and bioactivity. Results Results showed significantly improved solubility of CSIC in the SEFs.The concentration of co-surfactant affected the droplet size, zeta potential and polydispersity index. In vitro bioactivity studies showed that the CSIC SEFs retained full anti-HIV activity. Conclusion The in vitro data from this first attempt to formulate CSIC SEFs suggest that improvement on the aqueous solubility of CSIC through this delivery system may accentuate its antiretroviral effectiveness in vivo via bioavailability enhancement. The formulation is therefore intended as an oral anti-HIV agent for prophylactic and therapeutic uses. PMID:23721408

2013-01-01

400

Hazardous air pollutants from the combustion of an emulsified heavy fuel oil in a firetube boiler. Final report, May-November 1995  

SciTech Connect

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 determining the impacts of the emulsifier on HAP emissions. The boiler flue gases were sampled and analyzed for both metal and organic HAPs, and the effects of the emulsification on criteria emissions such as carbon dioxide (CO), nitrogen oxides (NOx), and particulate matter (PM) were also measured.

Miller, C.A.

1996-02-01

401

Iron metabolism in transplantation.  

PubMed

Recipient's iron status is an important determinant of clinical outcome in transplantation medicine. This review addresses iron metabolism in solid organ transplantation, where the role of iron as a mediator of ischemia-reperfusion injury, as an immune-modulatory element, and as a determinant of organ and graft function is discussed. Although iron chelators reduce ischemia-reperfusion injury in cell and animal models, these benefits have not yet been implemented into clinical practice. Iron deficiency and iron overload are associated with reduced immune activation, whose molecular mechanisms are reviewed in detail. Furthermore, iron overload and hyperferritinemia are associated with poor prognosis in end-stage organ failure in patients awaiting kidney, or liver transplantation. This negative prognostic impact of iron overload appears to persist after transplantation, which highlights the need for optimizing iron management before and after solid organ transplantation. In contrast, iron deficiency and anemia are also associated with poor prognosis in patients with end-stage heart failure. Intravenous iron supplementation should be managed carefully because parenterally induced iron overload could persist after successful transplantation. In conclusion, current evidence shows that iron overload and iron deficiency are important risk factors before and after solid organ transplantation. Iron status should therefore be actively managed in patients on the waiting list and after transplantation. PMID:24964028

Schaefer, Benedikt; Effenberger, Maria; Zoller, Heinz

2014-11-01

402

Iron deficiency in Europe.  

PubMed

In Europe, iron deficiency is considered to be one of the main nutritional deficiency disorders affecting large fractions of the population, particularly such physiological groups as children, menstruating women and pregnant women. Some factors such as type of contraception in women, blood donation or minor pathological blood loss (haemorrhoids, gynaecological bleeding...) considerably increase the difficulty of covering iron needs. Moreover, women, especially adolescents consuming low-energy diets, vegetarians and vegans are at high risk of iron deficiency. Although there is no evidence that an absence of iron stores has any adverse consequences, it does indicate that iron nutrition is borderline, since any further reduction in body iron is associated with a decrease in the level of functional compounds such as haemoglobin. The prevalence of iron-deficient anaemia has slightly decreased in infants and menstruating women. Some positive factors may have contributed to reducing the prevalence of iron-deficiency anaemia in some groups of population: the use of iron-fortified formulas and iron-fortified cereals; the use of oral contraceptives and increased enrichment of iron in several countries; and the use of iron supplements during pregnancy in some European countries. It is possible to prevent and control iron deficiency by counseling individuals and families about sound iron nutrition during infancy and beyond, and about iron supplementation during pregnancy, by screening persons on the basis of their risk for iron deficiency, and by treating and following up persons with presumptive iron deficiency. This may help to reduce manifestations of iron deficiency and thus improve public health. Evidence linking iron status with risk of cardiovascular disease or cancer is unconvincing and does not justify changes in food fortification or medical practice, particularly because the benefits of assuring adequate iron intake during growth and development are well established. But stronger evidence is needed before rejecting the hypothesis that greater iron stores increase the incidence of CVD or cancer. At present, currently available data do not support radical changes in dietary recommendations. They include all means for increasing the content of dietary factors enhancing iron absorption or reducing the content of factors inhibiting iron absorption. Increased knowledge and increased information about factors may be important tools in the prevention of iron deficiency in Europe. PMID:11683548

Hercberg, S; Preziosi, P; Galan, P

2001-04-01

403

Iron and Diabetes Risk  

PubMed Central

Iron overload is a risk factor for diabetes. The link between iron and diabetes was first recognized in pathologic conditionshereditary hemochromatosis and thalassemiabut high levels of dietary iron also impart diabetes risk. Iron plays a direct and causal role in diabetes pathogenesis mediated both by ?-cell failure and insulin resistance. Iron is also a factor in the regulation of metabolism in most tissues involved in fuel homeostasis, with the adipocyte in particular serving an iron-sensing role. The underlying molecular mechanisms mediating these effects are numerous and incompletely understood, but include oxidant stress and modulation of adipokines and intracellular signal transduction pathways. PMID:23473030

Simcox, Judith A.; McClain, Donald A.

2013-01-01

404

Availability of Food Iron  

PubMed Central

Iron has been extracted from 25 common foods under conditions resembling those prevailing in the stomach under physiological conditions. In most cases less than half the iron in the foods is released into solution. The soluble iron is mainly in ionizable form, except in the case of meat products and black pudding. The amount of food iron released is influenced by cooking and the presence of iron-binding substances in some foods. The total dietary iron probably does not represent the amount available for absorption. PMID:5774316

Jacobs, A.; Greenman, D. A.

1969-01-01

405

Development and Assessment of Oil-in-Water Emulsions for Encapsulation of Reactive Iron Particles for Subsurface Delivery  

NASA Astrophysics Data System (ADS)

Reactive iron particles hold promise for use in the destruction of contaminants in the subsurface environment. Application of these nano- to submicron-scale particles, however, may be limited by poor subsurface transport and non-uniform distribution of the reactive material. Delivery issues are particularly important when evaluating the efficacy of iron-based technologies for treatment of dense non-aqueous phase liquid (DNAPL) source zones. Current approaches for the delivery of reactive iron particles within DNAPL source zones are hindered by particle agglomeration, flow bypassing, and presence of non-target reactions. Encapsulation of the reactive particles within an oil-in-water emulsion is a novel approach that may overcome these limitations. Development of kinetically-stable, iron-laden, oil-in-water emulsions commenced by identifying surfactant-based coatings to increase the stability of commercially-available iron particles within non-polar organic phases (e.g., soy oil). A phase inversion technique was employed to disperse approximately 10% wt of the iron-laden, organic phase within a continuous aqueous phase containing nonionic emulsifiers. Emulsions were designed to ensure emulsifier proportions yielded hydrophilic-lipophilic balances affiliated with oil-in-water emulsions. Micrographs of the oil-in-water emulsions suggest that the average diameter of the oil droplets is approximately one micrometer. The presence of iron within oil droplets was confirmed in the micrographs and supported by an absence of iron agglomeration within the continuous phase. Bulk characteristics of each emulsion (density and viscosity) were used in conjunction with interfacial tension measurements in total trapping number analyses to assess the propensity of these emulsions to mobilize an entrapped trichloroethene (TCE)-DNAPL. Results suggest that the emulsions described herein should not cause significant mobilization of entrapped TCE-DNAPL in fine-to-medium grain sandy media. Column experiments are being conducted to evaluate the transport of these emulsions through sandy media. Preliminary results from experiments with iron-free emulsions suggest conductivity reductions occurring during emulsion flushing are not the result of extensive pore-clogging but rather are due to viscosity changes (emulsion viscosities range from 2 to 10 cP). Current efforts are focused on assessing and comparing both transport and reaction of commercially available iron particles and iron-laden emulsions within sandy porous media.

Berge, N. D.; Taghavy, A.; Ramsburg, A.

2007-12-01

406

Ocean iron cycle  

NASA Astrophysics Data System (ADS)

Interest in the biogeochemical cycle of iron has grown rapidly over the last two decades, due to the potential role of this element in modulating global climate in the geological past and ocean productivity in the present day. This trace metal has a disproportionately large effect (1 105 C:Fe) on photosynthetic carbon fixation by phytoplankton. In around one third of the open ocean, so-called high-nitrate low-chlorophyll (HNLC) regions, the resident phytoplankton have low growth rates despite an abundance of plant nutrients. This is due to the low supply of iron. Iron is present in the ocean in three phases, dissolved, colloidal, and particulate (biogenic and lithogenic). However, iron chemistry is complex with interactions between chemistry and biology such as the production of iron-binding siderophores by oceanic bacteria. This results in the interplay of inorganic chemistry, photochemistry, and organic complexation. Sources of new iron include dust deposition, upwelling of iron-rich deep waters, and the resuspension and lateral transport of sediments. Sinks for iron are mainly biological as evidenced by the vertical nutrient-like profile for dissolved iron in the ocean. Iron is rapidly recycled by the upper ocean biota within a so-called "ferrous wheel." The fe ratio [(new iron)/(new + regenerated iron)] provides an index of the relative supply of iron to the biota by new versus recycled iron. Over the last 15 years, interest in the potential role of iron in shaping climate in the geological past resulted in some of the most ambitious experiments in oceanography: large-scale (i.e., 50-1000 km2) iron enrichment of HNLC waters. They have provided valuable insights into how iron supply influences the biogeochemical cycles of elements such as carbon, sulfur, silicon, nitrogen, and phosphate.

Boyd, Philip W.

407

Stability of w\\/o type emulsions as a function of temperature and of the hydrophilic chain length of the emulsifier  

Microsoft Academic Search

The stability of W\\/O type emulsions of the cyclohexane-water system stabilized with polyoxyethylene nonylphenylether was studied as a function of temperature and of the hydrophilic chain length of the emulsifier. The interfacial tension of the same system was also studied as a function of temperature. It was found that: (1) the interfacial tension between the water and the oil phases

H. Saito; K. Shinoda

1970-01-01

408

Molecular control of vertebrate iron homeostasis by iron regulatory proteins  

Microsoft Academic Search

Both deficiencies and excesses of iron represent major public health problems throughout the world. Understanding the cellular and organismal processes controlling iron homeostasis is critical for identifying iron-related diseases and in advancing the clinical treatments for such disorders of iron metabolism. Iron regulatory proteins (IRPs) 1 and 2 are key regulators of vertebrate iron metabolism. These RNA binding proteins post-transcriptionally

Michelle L. Wallander; Elizabeth A. Leibold; Richard S. Eisenstein

2006-01-01

409

Iron and Your Child  

MedlinePLUS

... they lose monthly when they begin menstruating.) Young athletes who regularly engage in intense exercise tend to ... iron-containing RBCs during menstrual bleeding. Also, teen athletes lose iron through sweating and other routes during ...

410

Iron Chelation Therapy  

MedlinePLUS

... also in other organs that don't normally store iron, such as the: pancreas joints (especially in the ... Ferritin is a protein inside of cells that stores iron for later use by your body. For unknown ...

411

Hemochromatosis: Iron Storage Disease  

MedlinePLUS

... What's this? Submit Button CDC Features Hemochromatosis: Iron Storage Disease Language: English Espaol (Spanish) Share Compartir Excessive ... Learn more about hemochromatosis, a type of iron storage disease, and stay healthy. What Is Hemochromatosis? Hemochromatosis ...

412

Emulsifying properties of three African food hydrocolloids: okra (Hibiscus esculentus), dika nut (Irvingia gabonensis), and khan (Belschmiedia sp.).  

PubMed

This study investigated the emulsifying properties of okra (Hibiscus esculentus), dika nut (Irvingia gabonensis) and khan (Belschmiedia sp.), three African food hydrocolloids used to thicken and flavor soups. Results showed that khan has an emulsion potential approximately 20 and 100 times higher than the second and the first, respectively. A kinetic study indicated that the mechanism involved formation of thick and strong interfacial gum films around the oil globules, in addition to a high Water Absorption Capacity and weak gelling behavior of khan gum in solution. These results indicated that, when used in soups, which are typical oil/water emulsions, khan contribute both to thickening and stabilizing of the emulsion, whereas okra and dika nut functioned more as thickeners than as emulsion stabilizers. PMID:9629864

Ndjouenkeu, R; Akingbala, J O; Oguntimein, G B

1997-01-01

413

Novel solid self-emulsifying drug delivery system of coenzyme Q?? with improved photochemical and pharmacokinetic behaviors.  

PubMed

The present study was undertaken to develop a solid self-emulsifying drug delivery system of coenzyme Q(10) (CoQ(10)/s-SEDDS) with high photostability and oral bioavailability. The CoQ(10)/s-SEDDS was prepared by spray-drying an emulsion preconcentrate containing CoQ(10), medium-chain triglyceride, sucrose ester of fatty acid, and hydroxypropyl cellulose, and its physicochemical, photochemical, and pharmacokinetic properties were evaluated. The CoQ(10)/s-SEDDS powder with a diameter of ca. 15 ?m was obtained by spray-drying, in which the CoQ(10) was mostly amorphized. The CoQ(10)/s-SEDDS exhibited immediate self-emulsification when introduced to aqueous media under gentle agitation, forming uniform fine droplets with a mean diameter of ca. 280 nm. There was marked generation of reactive oxygen species, in particular superoxide, from CoQ(10) exposed to simulated sunlight (250W/m(2)), suggesting potent photoreactivity. Nano-emulsified solution of CoQ(10) under light exposure underwent photodegradation with 22-fold higher degradation kinetics than crystalline CoQ(10), although the CoQ(10)/s-SEDDS was less photoreactive. After the oral administration of CoQ(10)/s-SEDDS (100 mg-CoQ(10)/kg) in rats, enhanced exposure of CoQ(10) was observed with increases in both C(max) and AUC of ca. 5-fold in comparison with those of orally administered crystalline CoQ(10). From the improved physicochemical and pharmacokinetic data, the s-SEDDS approach upon spray-drying might be a suitable dosage option for enhancing nutraceutical and pharmaceutical values of CoQ(10). PMID:22498005

Onoue, Satomi; Uchida, Atushi; Kuriyama, Kazuki; Nakamura, Tatsuya; Seto, Yoshiki; Kato, Masashi; Hatanaka, Junya; Tanaka, Toshiyuki; Miyoshi, Hiroyuki; Yamada, Shizuo

2012-08-15

414

A comparison of composition and emulsifying properties of MFGM materials prepared from different dairy sources by microfiltration.  

PubMed

Milk fat globule membrane (MFGM), due to its specific nature and composition, is known as material possessing advantageous nutritional as well as technological properties. In this study MFGM materials were produced from several dairy sources such as buttermilk (BM), butter serum (BS) and buttermilk whey (BMW) by microfiltration (MF). The obtained materials, depending on the sources, were called BM-MFGM, BS-MFGM and BMW-MFGM, respectively. The compositions of starting materials and the isolated MFGM materials as well as their emulsifying properties were analyzed and compared. As expected, the MF resulted in enrichment of polar lipids (PLs), major components of MFGM. On dry matter basis, BM-MFGM and BS-MFGM were about 2.5 times higher in PLs compared to their beginning materials while BMW-MFGM was about 8.3 times compared to buttermilk powder (BMP). Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the microfiltered products still contained a high amount of non-MFGM proteins such as caseins, ?-lactoglobulin, and ?-lactalbumin. Emulsions of 35% soya oil in water were prepared with the mentioned materials using a homogenizer at various pressures. Generally, emulsions prepared with BMP and butter serum powder had significantly higher particle sizes than those prepared with the MFGM materials. This result along with microscopy observation and viscosity measurement indicated the presence of aggregated particles in the former emulsions, probably as a result of lack of surface-active componen