Science.gov

Sample records for emulsified zero-valent iron

  1. Application of Emulsified Zero-Valent Iron to Marine Environments

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  2. Application of Emulsified Zero-Valent Iron to Marine Environments

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  3. 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...

  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 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...

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

    EPA Science Inventory

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

  7. Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  9. Zero-valent iron nanoparticles preparation

    SciTech Connect

    Oropeza, S.; Corea, M.; Gmez-Yez, C.; Cruz-Rivera, J.J.; Navarro-Clemente, M.E.

    2012-06-15

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

  10. 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...

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

    EPA Science Inventory

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

  12. Laser-induced transformations of zero-valent iron particles

    NASA Astrophysics Data System (ADS)

    Petr, M.; Šišková, K.; Machala, L.; Kašlík, J.; Šafářová, K.; Zbořil, R.

    2012-10-01

    This paper deals with laser-induced transformations of zero-valent iron particles performed under ambient conditions. The excitation wavelength of 633 nm and several values of laser power, from 0.1 to 4.0 mW, have been used for the samples irradiation. Changes in phase composition and particle morphology, occurring during the transformations have been monitored by in-situ Raman spectroscopy, ex-situ Mössbauer spectroscopy, X-ray diffraction, and scanning electron microscopy. The results revealed that laser-induced oxidation is more pronounced in the sample with smaller particles. Furthermore, by this work, we also wanted to stress the fact that Raman spectroscopic technique has to be performed with caution when investigating zero-valent metal samples.

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

    PubMed

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

    2012-10-15

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

  14. Magnetic memory effect in chelated zero valent iron nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghosh, N.; Mandal, B. K.; Mohan Kumar, K.

    2012-11-01

    We report the study of nonequilibrium magnetic behavior of air stable zero valent iron nanoparticles synthesized in presence of N-cetyl-N,N,N-trimethyl ammonium bromide chelating agent. X-ray photoelectron spectroscopy study has suggested the presence of iron oxides on nZVI surfaces. Zero-field-cooled and field-cooled magnetization measurements have been carried out at 20-300 K and 100 Oe. For field-cooled measurements with 1 h stops at 200, 100 and 50 K when compared with the warming cycle, we found the signature of magnetic memory effect. A study of magnetic relaxation at the same temperatures shows the existence of two relaxation times.

  15. Removal of arsenic from water by zero-valent iron.

    PubMed

    Bang, Sunbaek; Korfiatis, George P; Meng, Xiaoguang

    2005-05-20

    Batch and column experiments were conducted to investigate the effect of dissolved oxygen (DO) and pH on arsenic removal with zero-valent iron [Fe(0)]. Arsenic removal was dramatically affected by the DO content and the pH of the solution. Under oxic conditions, arsenate [As(V)] removal by Fe(0) filings was faster than arsenite [As(III)]. Greater than 99.8% of the As(V) was removed whereas 82.6% of the As(III) was removed at pH 6 after 9h of mixing. When the solution was purged with nitrogen gas to remove DO, less than 10% of the As(III) and As(V) was removed. High DO content and low solution pH also increased the rate of iron corrosion. The removal of arsenic by Fe(0) was attributed to adsorption by iron hydroxides generated from the oxic corrosion of Fe(0). The column results indicated that a filtration system consisting of an iron column and a sand filter could be used for treatment of arsenic in drinking water. PMID:15885407

  16. [Dechlorination of HCB by bimetals based on zero valent iron].

    PubMed

    Zeng, Xian-Wei; Liu, Jian-Guo; Nie, Xiao-Qin

    2013-01-01

    Based on the reducing capacity of zero valent iron, the study investigated the behavior of dechlorination of hexachlorobenzene by bimetals synthetized using Fe with Ag, Pb or Cu as catalysts, respectively. The results showed that bimetals could dechlorinate HCB faster than Fe(0) did, the optimal ratios of Ag/Fe, Pb/Fe and Cu/Fe were 0.2%, 0.5% and 1%. After reacting 2 hours, the dechlorination rates of HCB by Ag/Fe, Pb/Fe and Cu/Fe were 93.5%, 88.5% and 49.6% respectively. The catalyst metal distribution had a great effect on the reductive dechlorination capacity of the bimetal systems, due to more galvanic cells produced by well-distributed catalyst metal and iron. Increasing the amount of bimetal was an effective way to promote HCB dechlorination rate, 88.6% HCB was degraded in 2 h by 0.8 g Pb/Fe while only 38.3% HCB was degraded by 0.1 g Pb/Fe. Besides, HCB dechlorination could be enhanced a little with increasing ionic strength, the HCB dechlorination rates were 93.5%, 98.0% and 98.9% respectively with Na2SO4 concentration at 0, 0.05 and 0.5 mol x L(-1). PMID:23487936

  17. Electrokinetics Enhanced Delivery of Nano-scale Zero Valent Iron

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  18. Mechanism study of nitrate reduction by nano zero valent iron.

    PubMed

    Hwang, Yu-Hoon; Kim, Do-Gun; Shin, Hang-Sik

    2011-01-30

    This study investigates the fate of nitrogen species during nitrate reduction by nano-scale zero valent iron (NZVI) and related reaction mechanisms. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. NZVI has great ability to reduce nitrate. However, the question of what end-product results from nitrate reduction by NZVI has sparked controversy. Establishing nitrogen mass balance by quantitative analysis of aqueous phase and gas-phase nitrogen species, this study clearly determines that nitrate was converted to ammonium ion followed by ammonia stripping under a strong alkaline condition, which leads to a decrease in the total aqueous nitrogen amount. Moreover, some of the major reactions, which consisted of nitrate reduction, ammonia production, and ammonia stripping were modelled by pseudo first-order kinetics. According to the model estimation results, additional reaction mechanisms would exist in an early stage of reaction. This might be due to the adsorption and desorption reaction which could be explained by the core-shell structure model. PMID:21093984

  19. Microbiological characteristics in a zero-valent iron reactive barrier

    SciTech Connect

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

    2002-01-01

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

  20. Textile dye degradation using nano zero valent iron: A review.

    PubMed

    Raman, Chandra Devi; Kanmani, S

    2016-07-15

    Water soluble unfixed dyes and inorganic salts are the major pollutants in textile dyeing industry wastewater. Existing treatment methods fail to degrade textile dyes and have limitations too. The inadequate treatment of textile dyeing wastewater is a major concern when effluent is directly discharged into the nearby environment. Long term disposal threatens the environment, which needs reclamation. This article reviews the current knowledge of nano zero valent iron (nZVI) technique in the degradation of textile dyes. The application of nZVI on textile dye degradation is receiving great attention in the recent years because nZVI particles are highly reactive towards the pollutant, less toxic, and economical. The nZVI particles aggregate quickly with respect to time and the addition of supports such as resin, nickel, zinc, bentonite, biopolymer, kaolin, rectorite, nickel-montmorillonite, bamboo, cellulose, biochar, graphene, and clinoptilolite enhanced the stability of iron nanoparticles. Inclusion of supports may in turn introduce additional toxic pollutants, hence green supports are recommended. The majority of investigations concluded dye color removal as textile dye compound removal, which is not factual. Very few studies monitored the removal of total organic carbon and observed the products formed. The results revealed that partial mineralization of the textile dye compound was achieved. Instead of stand alone technique, nZVI can be integrated with other suitable technique to achieve complete degradation of textile dye and also to treat multiple pollutants in the real textile dyeing wastewater. It is highly recommended to perform more bench-scale and pilot-scale studies to apply this technique to the textile effluent contaminated sites. PMID:27115482

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

    SciTech Connect

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

    2004-03-31

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

  2. Can zero-valent iron nanoparticles remove waterborne estrogens?

    PubMed

    Jarošová, Barbora; Filip, Jan; Hilscherová, Klára; Tuček, Jiří; Šimek, Zdeněk; Giesy, John P; Zbořil, Radek; Bláha, Luděk

    2015-03-01

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

  3. Antimicrobial and Genotoxicity Effects of Zero-valent Iron Nanoparticles

    PubMed Central

    Barzan, Elham; Mehrabian, Sedigheh; Irian, Saeed

    2014-01-01

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

  4. Effect of Zero-Valent Iron on Removal of Escherichia coli O157:H7 from Agricultural Waters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel water filtration system using zero-valent iron (ZVI) is being investigated as a simple and inexpensive approach to reducing E. coli O157:H7 in water for both pre- and post-harvest processes. Purpose: This study was initiated to determine the effectiveness of zero-valent iron in the removal ...

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

  9. Analytical Characterisation of Nanoscale Zero-Valent Iron: A Methodological Review

    EPA Science Inventory

    Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their te...

  10. 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...

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

    EPA Science Inventory

    Nanosize zero-valent iron (nZVI) is used as a redox-active catalyst for in situ remediation of contaminated ground waters. In aqueous environments, nZVI oxidizes over time (i.e., ages) to magnetite and other oxides. For remediation, hi...

  12. 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...

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

    SciTech Connect

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

    2011-10-01

    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.

  15. Comparison of characteristics of montmorillonite supported nano zero valent iron (M-nZVI) and nano zero valent iron (nZVI)

    NASA Astrophysics Data System (ADS)

    How, Ho Kuok; Wan Zuhairi W., Y.

    2015-09-01

    In this study, synthesized montmorillonite supported nano zero valent iron (M-nZVI) and nano zero valent iron (nZVI) are compared physically and chemically. The samples were prepared using chemical reduction method that includes sodium borohydride and ethanol. Due to the tendency of nZVI to aggregate, montmorillonite is used as a supporting material. TEM and FESEM images show that the M-nZVI has decreased the aggregation by dispersing the particles on the surface of montmorillonite whereas images of nZVI show chain-like particle due to aggregation. Both images also show particles synthesized are nanoparticles. With less aggregation, the surface area of the M-nZVI is greater than nZVI which is 45.46 m2/g and 10.49 m2/g respectively. XRD patterns have shown Fe0 are synthesized and small amount of iron oxides are produced. M-nZVI has the capability in reducing aggregation which might lead to the increase in reactivity of the particles thus enhancing the performance of nZVI.

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

    EPA Science Inventory

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

  17. Electrochemical and spectroscopic study of arsenate removal from water using zero-valent iron media.

    PubMed

    Farrell, J; Wang, J; O'Day, P; Conklin, M

    2001-05-15

    This study investigated the mechanisms involved in removing arsenate from drinking water supplies using zero-valent iron media. Batch experiments utilizing iron wires suspended in anaerobic arsenate solutions were performed to determine arsenate removal rates as a function of the arsenate solution concentration. Corrosion rates of the iron wires were determined as a function of elapsed time using Tafel analysis. The removal kinetics in the batch reactors were best described by a dual-rate model in which arsenate removal was pseudo-first-order at low concentrations and approached zero-order in the limit of high arsenate concentrations. The presence of arsenate decreased iron corrosion rates as compared to those in blank 3 mM CaSO4 background electrolyte solutions. However, constant corrosion rates were attained after approximately 10 days elapsed, indicating that the passivation processes had reached steady state. The cathodic Tafel slopes were the same in the arsenate and the blank electrolyte solutions. This indicates that water was the primary oxidant for iron corrosion and that arsenate did not directly oxidize the iron wires. The anodic Tafel slopes were greater in the arsenate solutions, indicating that arsenate formed complexes with iron corrosion products released at anodic sites on the iron surfaces. Ion chromatography analyses indicated that there was no measurable reduction of As(V) to As(III). X-ray absorption spectroscopy analyses indicated that all arsenic associated with the zero-valent iron surfaces was in the oxidation state. Interatomic arsenic-iron distances determined from EXAFS analyses were consistent with bidentate corner-sharing among arsenate tetrahedra and iron octahedra. Results from this study show that under conditions applicable to drinking water treatment, arsenate removal by zero-valent iron media involves surface complexation only and does not involve reduction to metallic arsenic. PMID:11393984

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

    NASA Astrophysics Data System (ADS)

    Filip, Jan; Kašlík, Josef; Medřík, Ivo; Petala, Eleni; Zbořil, Radek; Slunský, Jan; Černík, Miroslav; Stavělová, Monika

    2014-05-01

    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).

  19. Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  20. Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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

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

    SciTech Connect

    Lenly J. Weathers; Lynn E. Katz

    2002-05-29

    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.

  2. Hybrid biological, electron beam and zero-valent nano iron treatment of recalcitrant metalworking fluids.

    PubMed

    Thill, Patrick G; Ager, Duane K; Vojnovic, Borivoj; Tesh, Sarah J; Scott, Thomas B; Thompson, Ian P

    2016-04-15

    Hybrid approaches for the remediation and detoxification of toxic recalcitrant industrial wastewater were investigated. The focus was waste metalworking fluid, which was selected as a representative model of other waste streams that are toxic, recalcitrant and that require more sustainable routes of safe disposal. The hybrid approaches included biodegradation, electron beam irradiation and zero-valent nano iron advanced oxidation processes that were employed individually and in sequence employing a factorial design. To compare process performance operationally exhausted and pristine metalworking fluid were compared. Sequential hybrid electron beam irradiation, biological, nanoscale zero-valent iron and biological treatment lead to synergistic detoxification and degradation of both recalcitrant streams, as determined by complementary surrogates and lead to overall improved COD removal of 92.8 ± 1.4% up from 85.9 ± 3.4% for the pristine metalworking fluid. Electron beam pre-treatment enabled more effective biotreatment, achieving 69.5 ± 8% (p = 0.005) and 24.6 ± 4.8% (p = 0.044) COD reductions. PMID:26905800

  3. Utilization of food industry wastes for the production of zero-valent iron nanoparticles.

    PubMed

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

    2014-10-15

    The proper disposal of the several types of wastes produced in industrial activities increases production costs. As a consequence, it is common to develop strategies to reuse these wastes in the same process and in different processes or to transform them for use in other processes. This work combines the needs for new synthesis methods of nanomaterials and the reduction of production cost using wastes from citrine juice (orange, lime, lemon and mandarin) to produce a new added value product, green zero-valent iron nanoparticles that can be used in several applications, including environmental remediation. The results indicate that extracts of the tested fruit wastes (peel, albedo and pulp fractions) can be used to produce zero-valent iron nanoparticles (nZVIs). This shows that these wastes can be an added value product. The resulting nZVIs had sizes ranging from 3 up to 300 nm and distinct reactivities (pulp>peel>albedo extracts). All the studied nanoparticles did not present a significant agglomeration/settling tendency when compared to similar nanoparticles, which indicates that they remain in suspension and retain their reactivity. PMID:25089685

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

    SciTech Connect

    Fogwell, Thomas W.; Santina, Pete

    2013-07-01

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

  5. Removal of chromium from synthetic plating waste by zero-valent iron and sulfate-reducing bacteria.

    PubMed

    Guha, Saumyen; Bhargava, Puja

    2005-01-01

    Experiments were conducted to evaluate the potential of zero-valent iron and sulfate-reducing bacteria (SRB) for reduction and removal of chromium from synthetic electroplating waste. The zero-valent iron shows promising results as a reductant of hexavalent chromium (Cr+6) to trivalent chromium (Cr+3), capable of 100% reduction. The required iron concentration was a function of chromium concentration in the waste stream. Removal of Cr+3 by adsorption or precipitation on iron leads to complete removal of chromium from the waste and was a slower process than the reduction of Cr+6. Presence SRB in a completely mixed batch reactor inhibited the reduction of Cr+6. In a fixed-bed column reactor, SRB enhanced chromium removal and showed promising results for the treatment of wastes with low chromium concentrations. It is proposed that, for waste with high chromium concentration, zero-valent iron is an efficient reductant and can be used for reduction of Cr+6. For low chromium concentrations, a SRB augmented zero-valent iron and sand column is capable of removing chromium completely. PMID:16121509

  6. 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...

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

    EPA Science Inventory

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

  8. Partial oxidation (“aging”) and surface modification decrease the toxicity of nano-sized zero valent iron.

    EPA Science Inventory

    Nanosize zero-valent iron (nZVI) is used as a redox-active catalyst for in situ remediation of contaminated ground waters. In aqueous environments, nZVI oxidizes over time (i.e., “ages”) to magnetite and other oxides. For remediation, hi...

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

    PubMed

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

    2011-06-15

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

  10. Enhancement of aerobic granulation by zero-valent iron in sequencing batch airlift reactor.

    PubMed

    Kong, Qiang; Ngo, Huu Hao; Shu, Li; Fu, Rong-Shu; Jiang, Chun-Hui; Miao, Ming-sheng

    2014-08-30

    This study elucidates the enhancement of aerobic granulation by zero-valent iron (ZVI). A reactor augmented with ZVI had a start-up time of aerobic granulation (43 days) that was notably less than that for a reactor without augmentation (64 days). The former reactor also had better removal efficiencies for chemical oxygen demand and ammonium. Moreover, the mature granules augmented with ZVI had better physical characteristics and produced more extracellular polymeric substances (especially of protein). Three-dimensional-excitation emission matrix fluorescence showed that ZVI enhanced organic material diversity. Additionally, ZVI enhanced the diversity of the microbial community. Fe(2+) dissolution from ZVI helped reduce the start-up time of aerobic granulation and increased the extracellular polymeric substance content. Conclusively, the use of ZVI effectively enhanced aerobic granulation. PMID:25108827

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

    NASA Astrophysics Data System (ADS)

    Busch, Jan; Meißner, Tobias; Potthoff, Annegret; Oswald, Sascha E.

    2014-08-01

    Injection of nanoscale zero-valent iron (nZVI) has recently gained great interest as emerging technology for in-situ remediation of chlorinated organic compounds from groundwater systems. Zero-valent iron (ZVI) is able to reduce organic compounds and to render it to less harmful substances. The use of nanoscale particles instead of granular or microscale particles can increase dechlorination rates by orders of magnitude due to its high surface area. However, classical nZVI appears to be hampered in its environmental application by its limited mobility. One approach is colloid supported transport of nZVI, where the nZVI gets transported by a mobile colloid. In this study transport properties of activated carbon colloid supported nZVI (c-nZVI; d50 = 2.4 μm) are investigated in column tests using columns of 40 cm length, which were filled with porous media. A suspension was pumped through the column under different physicochemical conditions (addition of a polyanionic stabilizer and changes in pH and ionic strength). Highest observed breakthrough was 62% of the injected concentration in glass beads with addition of stabilizer. Addition of mono- and bivalent salt, e.g. more than 0.5 mM/L CaCl2, can decrease mobility and changes in pH to values below six can inhibit mobility at all. Measurements of colloid sizes and zeta potentials show changes in the mean particle size by a factor of ten and an increase of zeta potential from - 62 mV to - 80 mV during the transport experiment. However, results suggest potential applicability of c-nZVI under field conditions.

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

    SciTech Connect

    Yabusaki, Steven B. ); Cantrell, Kirk J. ); Sass, Bruce; Steefel, Carl

    2000-12-01

    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.

  13. Effects of Precipitation and Particle Size on Low Frequency Electrical Properties of Zero Valent Iron

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Slater, L.

    2004-12-01

    Observational methods are required to monitor the long-term efficiency of permeable reactive barrier (PRB) installations used to remediate hydrocarbon and heavy metal contaminated groundwater. Our previous studies investigated the relationship between induced polarization (IP) and zero valent iron (Fe0) surface area and electrolyte activity. In this continuous research, we performed experiments on mixtures of Fe0 and Ottawa sand to study (1) the relationship between IP and zero valent iron particle size, and (2) the impact of precipitation induced on the Fe0 surface. The latter experiment addresses the issue of whether reduction in PRB performance can be inferred from electrical measurements. The effect of iron particle size on IP was studied by running background solutions (0.01 ¡C 0.1M NaCl) through samples of the mixture of sand with 5% of different sizes of iron (diameter 1-0.2 mm). Precipitation experiments were conducted by running samples with different solutions to induce precipitation on the iron surface. This involved: (1) long term execution (about 1 year) of four identical samples (5% Fe0 mixture with sand) continuously flushed with four different solutions (0.1 M NaHCO3, 0.1 M Na2SO4, 0.1 M Na2HPO4 and pure water); (2) a short term experiment (in days) with high percentage of Fe0 (30%, 70%) run with high highly basic solutions (0.1M NaOH and 0.1 M Na2CO3). The results show that the IP response is correlated with iron particle size: First, the IP magnitude is inversely proportional to iron particle diameter principally due to the inverse relation between particle diameter and specific surface area. Second, the dominant relaxation time of the polarization is inversely proportional to the particle diameter. The short term precipitation experiment revealed two significant observations: (1) the IP magnitude increased after induced precipitation on Fe0 surface which we tentatively attribute to an increase in the surface area due to an irregular coating of metallic precipitants (FeCO3, Fe(OH)2, FeOOH, Fe(OH)3) on the Fe0 (2) a clear increase in the time constant, which we attribute to an increase in the effective particle size due to the precipitation. Our results to date suggest that IP may be a viable method for long-term monitoring of reactive iron barriers.

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

    SciTech Connect

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

    2009-06-01

    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.

  15. Restoration of Porous Media Reductive Capacity Through Zero-valent Iron Emplacement with Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Vermeul, V. R.; Oostrom, M.; Wietsma, T. W.; Covert, M. A.

    2006-12-01

    At the Hanford Site in Washington, an extensive In Situ Redox Manipulation permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. After the installation, 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 into high-permeability Hanford Site sediments to enhance the barrier's reductive capacity using polymer solutions was investigated in various size columns and 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. Under optimal conditions, the 0.6% amended iron concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced iron in the Hanford Site barrier.

  16. Use of agar agar stabilized milled zero-valent iron particles for in situ groundwater remediation

    NASA Astrophysics Data System (ADS)

    Schmid, Doris; Velimirović, Milica; Wagner, Stephan; Micić Batka, Vesna; von der Kammer, Frank; Hofmann, Thilo

    2015-04-01

    A major obstacle for use of nanoscale zero-valent iron (nZVI) particles as a nontoxic material for effective in situ degradation of chlorinated aliphatic hydrocarbons (CAHs) is the high production cost. For that reason, submicro-scale milled zero-valent iron particles were recently developed (milled ZVI, UVR-FIA, Germany) by grinding macroscopic raw materials of elementary iron as a cheaper alternative to products produced by solid-state reduction. However, milled ZVI particles tend to aggregate and due to the rather large particle size (d50= 11.9 µm) also rapidly sediment. To prevent aggregation and consequently sedimentation of milled ZVI particles and therefore improve the mobility after in situ application, the use of a stabilizer is considered in literature as a most promising option. In this study, milled ZVI particles (1 g L-1 of particle concentration) were stabilized by environmentally friendly polymer agar agar (>0.5 g L-1), which had a positive impact on the milled ZVI stability. Sedimentation rate was significantly decreased by increasing the suspension viscosity. Column transport experiments were performed for bare and agar agar stabilized milled ZVI particles in commercially available fine grained quartz sand (DORSILIT® Nr.8, Gebrüder Dorfner GmbH Co, Germany) and different porous media collected from brownfields. The experiments were carried out under field relevant injection conditions of 100 m d-1. The maximal travel distance (LT) of less than 10 cm was determined for non-stabilized suspension in fine grained quartz sand, while agar agar (1 g L-1) stabilized milled ZVI suspension revealed LT of 12 m. Similar results were observed for porous media from brownfields showing that mobility of agar agar stabilized particle suspensions was significantly improved compared to bare particles. Based on the mobility data, agar agar stabilized milled zero-valent iron particles could be used for in situ application. Finally, lab-scale batch degradation experiments were performed to determine the impact of agar agar on the reactivity of milled ZVI and investigate the apparent corrosion rate of particles by quantifying the hydrogen gas generated by anaerobic corrosion of milled ZVI. The results indicate that agar agar had a positive impact on the milled ZVI stability and mobility, however adverse impact on the reactivity towards trichloroethene (TCE) was observed compared to the non-stabilized material. On the other hand, this study shows that the apparent corrosion rate of non-stabilized and agar agar stabilized milled ZVI particles is in the same order of magnitude. These data indicate that the dechlorination pathway of TCE by agar agar stabilized milled ZVI particles is possibly impacted by blocking of the reactive sites and not hydrogen revealed during particles corrosion. Finally, calculated longevity of the particles based on the apparent corrosion rate is significantly prolonged compared to the longevity of the nZVI particles reported in previous studies. This research receives funding from the European Union's Seventh Framework Programme FP7/2007-2013 under grant agreement n°309517.

  17. Enhancing zero valent iron based natural organic matter removal by mixing with dispersed carbon cathodes.

    PubMed

    Liu, Peng; Keller, Jurg; Gernjak, Wolfgang

    2016-04-15

    Former studies have shown that adding granular activated carbon (GAC) cathodes could enhance the overall performance of the zero valent iron (ZVI) process for organics removal. The present study evaluates for the first time the performance of such an enhanced ZVI process to remove natural organic matter (NOM), an important water quality parameter in drinking water. Lab-scale batch tests were conducted with surface reservoir feed water from a drinking water plant. In the GAC enhanced ZVI process dissolved organic carbon (DOC) and UV254 were reduced by 61±3% and 70±2%, respectively, during 24h treatment corresponding to 1.8min empty bed contact time. The process was superior to ZVI alone, particularly during the earlier stages of the process due to the synergistically increased iron dissolution rate. Besides GAC, graphite and anthracite also prove to be suitable and potentially more cost-effective options as cathode materials for the enhanced ZVI process, whereby electrically conductive graphite clearly outperformed anthracite. The dominant mechanisms in terms of NOM removal from surface water were found to be coagulation following iron dissolution and adsorption in the case of employing GAC. Oxidation was also occurring to a lesser degree, converting some non-biodegradable into biodegradable DOC. PMID:26808400

  18. Bactericidal Effect of Zero-Valent Iron Nanoparticles on Escherichia coli

    PubMed Central

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

    2008-01-01

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

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

    SciTech Connect

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

    2008-07-01

    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.

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

    SciTech Connect

    Korte, NE

    2001-06-11

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

  1. Recent advances and future perspectives of nanosized zero- valent iron for extraction of heavy elements from metallurgical sludges

    NASA Astrophysics Data System (ADS)

    Mikhailov, I. Yu; Levina, V. V.; Kolesnikov, E. A.; Chuprunov, K. O.; Gusev, A. A.; Godymchuk, A. Yu; Kuznetsov, D. V.

    2016-01-01

    Advanced oxidation processes with nanosized zero-valent iron have presented great potential in wastewater treatment technology and now experience both increasing popularity and reliable technical improvements. Besides wastewater treatment, there is another promising application for an emerging technology of iron nanoparticles - as Fenton-like catalyst for extraction of valuable elements from poor and secondary raw materials such as metallurgical sludges. In present research, we carried out a set of experiments with emphasis on the physicochemical mechanisms and their relationship to the performance. In particular, we examined complex acidic - hydrogen peroxide leaching of zinc from blast furnace sludge with nanosized zero-valent iron as Fenton-like catalyst. Results of the experiments showed promising potential for subsequent application in extraction of heavy and rare-earth elements.

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

    PubMed

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

    2014-02-01

    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

  3. Enhanced degradation performances of plate-like micro/nanostructured zero valent iron to DDT.

    PubMed

    Kang, Shenghong; Liu, Shengwen; Wang, Huimin; Cai, Weiping

    2016-04-15

    Micro/nanostructured zero valent iron (MNZVI) is successfully mass-synthesized by ball-milling the industrially-reduced iron powders. The as-prepared MNZVI is plate-like in morphology with about 2-5μm in planar size and 35-55nm in thickness, and ∼16m(2)/g in specific surface area. Such plate-like MNZVI has demonstrated much higher degradation performances to DDT [or 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane] in the aqueous solution than the commercial ZVI powders under acidic conditions. The MNZVI-induced DDT degradation is also much faster than the previously reported results. The time-dependent DDT removal amount can be described by the pseudo first-order kinetic model. Further experiments have shown that more than 50% of DDT can be mineralized in 20min and the rest is dechlorinated to DDX (the products with less chlorine). It has been revealed that the DDT degradation could be attributed to the acid assisted ZVI-induced mineralization and dechlorination. The mineralization process is dominant during the initial stage within 20min, and the dechlorination is the main reaction in the anaphase of the degradation. This work not only deepens understanding of DDT degradation but also could provide a highly efficient material for the practical treatment of the DDT in a real environment. PMID:26780701

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

    PubMed

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

    2015-05-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    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.

  6. Treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron.

    PubMed

    Ayala-Parra, Pedro; Sierra-Alvarez, Reyes; Field, James A

    2016-05-01

    This study assessed the bioremediation of acid rock drainage (ARD) in flow-through columns testing zero-valent iron (ZVI) for the first time as the sole exogenous electron donor to drive sulfate-reducing bacteria in permeable reactive barriers. Columns containing ZVI, limestone or a mixture of both materials were inoculated with an anaerobic mixed culture and fed a synthetic ARD containing sulfuric acid and heavy metals (initially copper, and later also cadmium and lead). ZVI significantly enhanced sulfate reduction and the heavy metals were extensively removed (>99.7%). Solid-phase analyses showed that heavy metals were precipitated with biogenic sulfide in the columns packed with ZVI. Excess sulfide was sequestered by iron, preventing the discharge of dissolved sulfide. In the absence of ZVI, heavy metals were also significantly removed (>99.8%) due to precipitation with hydroxide and carbonate ions released from the limestone. Vertical-profiles of heavy metals in the columns packing, at the end of the experiment, demonstrated that the ZVI columns still had excess capacity to remove heavy metals, while the capacity of the limestone control column was approaching saturation. The ZVI provided conditions that enhanced sulfate reduction and generated alkalinity. Collectively, the results demonstrate an innovative passive ARD remediation process using ZVI as sole electron-donor. PMID:26808248

  7. Reduction of nitrate by resin-supported nanoscale zero-valent iron.

    PubMed

    Park, Heesu; Park, Yong-Min; Yoo, Kyoung-Min; Lee, Sang-Hyup

    2009-01-01

    For environmental remediation of a contaminated groundwater, the use of nanosized zero-valent iron (nZVI) represents one of the latest innovative technologies. However, nZVI gets easily agglomerated due to its colloidal characteristics and has limited applications. To overcome this drawback, nZVI was immobilized on a supporting material. In this study, nZVI was formed and bound to ion-exchange resin spheres at the same time through the borohydride reduction of an iron salt. The pore structures and physical characteristics of the supported nZVI were investigated and its reactivity was measured using nitrate. The degradation of nitrate appeared to be a pseudo first-order reaction with the observed reaction rate constant of 0.425 h(-1) without pH control. The reduction process continued but at a much lower rate with a rate constant of 0.044 h(-1). When the simulated groundwater was used to assess the effects of coexisting ions, the rate constant was 0.078 h(-1) and it also reduced to 0.0021 h(-1) in later phase. The major limitation of ZVI use for nitrate reduction is ammonium production. By using a support material with ion-exchange capacity, this problem can be solved. The ammonium was not detected in our batch tests. PMID:19494454

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    SciTech Connect

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

    2010-01-01

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

  10. Effective removal of nemacide fosthiazate from an aqueous solution using zero-valent iron.

    PubMed

    Wu, Junxue; Shen, Chongyang; Zhang, Hongyan; Lu, Weilan; Zhang, Yun; Wang, Chengju

    2015-09-15

    In this study, the removal of fosthiazate in an aqueous solution using zero valent iron (ZVI) and the related removal reaction mechanism were investigated. The results indicate that the dissipation of fosthiazate adheres to a pseudo-first order reaction law. The apparent rate constant of fosthiazate removal could be improved by increasing the ZVI dosage, control temperature and initial pH. The observed pseudo-first-order degradation rate constants (Kobs) of fosthiazate removal using ZVI were varied in the different electrolyte solutions, and were determined as follows: Kobs (MgSO4) < Kobs (KCl) < Kobs (Control)

  11. Analytical characterisation of nanoscale zero-valent iron: A methodological review.

    PubMed

    Chekli, L; Bayatsarmadi, B; Sekine, R; Sarkar, B; Shen, A Maoz; Scheckel, K G; Skinner, W; Naidu, R; Shon, H K; Lombi, E; Donner, E

    2016-01-15

    Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Both the mobility and reactivity of nZVI mainly depends on properties such as particle size, surface chemistry and bulk composition. In order to ensure efficient remediation, it is crucial to accurately assess and understand the implications of these properties before deploying these materials into contaminated environments. Many analytical techniques are now available to determine these parameters and this paper provides a critical review of their usefulness and limitations for nZVI characterisation. These analytical techniques include microscopy and light scattering techniques for the determination of particle size, size distribution and aggregation state, and X-ray techniques for the characterisation of surface chemistry and bulk composition. Example characterisation data derived from commercial nZVI materials is used to further illustrate method strengths and limitations. Finally, some important challenges with respect to the characterisation of nZVI in groundwater samples are discussed. PMID:26709296

  12. Oxidation of polyvinyl alcohol by persulfate activated with heat, Fe2+, and zero-valent iron.

    PubMed

    Oh, Seok-Young; Kim, Hyeong-Woo; Park, Jun-Mo; Park, Hung-Suck; Yoon, Chohee

    2009-08-30

    The oxidation of polyvinyl alcohol (PVA) by persulfate (S(2)O(8)(2-)) activated with heat, Fe(2+), and zero-valent iron (Fe(0)) was investigated via batch experiments. It was hypothesized that elevated temperature and the addition of Fe(2+) or Fe(0) into a persulfate-water system could enhance the oxidation of PVA by activated persulfate. Increasing the temperature from 20 to 60 degrees C or 80 degrees C accelerated the oxidation rate of PVA, which achieved complete oxidation in 30 and 10 min, respectively. At 20 degrees C, the addition of Fe(2+) or Fe(0) to the persulfate-water system significantly enhanced the oxidation of PVA. The optimal persulfate-to-Fe(2+) or Fe(0) molar ratio was found to be 1:1. Complete oxidation of PVA was obtained by Fe(0)-activated persulfate in 2h. Synergistic activation of persulfate by heat and Fe(2+) or Fe(0) was also shown to enhance the oxidation of PVA in the persulfate-water system. By using GC-MS analysis, an oxidation product of PVA was identified as vinyl acetic acid (C(4)H(6)O(2)), which is readily biodegradable. Our results suggest that the oxidative treatment of PVA by activated persulfate is a viable option for the pretreatment of PVA-laden wastewater to enhance its biodegradability. PMID:19285795

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

    SciTech Connect

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

    2011-06-27

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

  14. Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts.

    PubMed

    Machado, S; Pacheco, J G; Nouws, H P A; Albergaria, J T; Delerue-Matos, C

    2015-11-15

    In the last decades nanotechnology has become increasingly important because it offers indisputable advantages to almost every area of expertise, including environmental remediation. In this area the synthesis of highly reactive nanomaterials (e.g. zero-valent iron nanoparticles, nZVI) is gaining the attention of the scientific community, service providers and other stakeholders. The synthesis of nZVI by the recently developed green bottom-up method is extremely promising. However, the lack of information about the characteristics of the synthetized particles hinders a wider and more extensive application. This work aims to evaluate the characteristics of nZVI synthesized through the green method using leaves from different trees. Considering the requirements of a product for environmental remediation the following characteristics were studied: size, shape, reactivity and agglomeration tendency. The mulberry and pomegranate leaf extracts produced the smallest nZVIs (5-10 nm), the peach, pear and vine leaf extracts produced the most reactive nZVIs while the ones produced with passion fruit, medlar and cherry extracts did not settle at high nZVI concentrations (931 and 266 ppm). Considering all tests, the nZVIs obtained from medlar and vine leaf extracts are the ones that could present better performances in the environmental remediation. The information gathered in this paper will be useful to choose the most appropriate leaf extracts and operational conditions for the application of the green nZVIs in environmental remediation. PMID:26151651

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

    PubMed

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

    2010-04-15

    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

  16. Impact of nanoscale zero valent iron on bacteria is growth phase dependent.

    PubMed

    Chaithawiwat, Krittanut; Vangnai, Alisa; McEvoy, John M; Pruess, Birgit; Krajangpan, Sita; Khan, Eakalak

    2016-02-01

    The toxic effect of nanoscale zero valent iron (nZVI) particles on bacteria from different growth phases was studied. Four bacterial strains namely Escherichia coli strains JM109 and BW25113, and Pseudomonas putida strains KT2440 and F1 were experimented. The growth curves of these strains were determined. Bacterial cells were harvested based on the predetermined time points, and exposed to nZVI. Cell viability was determined by the plate count method. Bacterial cells in lag and stationary phases showed higher resistance to nZVI for all four bacterial strains, whereas cells in exponential and decline phases were less resistant to nZVI and were rapidly inactivated when exposed to nZVI. Bacterial inactivation increased with the concentration of nZVI. Furthermore, less than 14% bacterial inactivation was observed when bacterial cells were exposed to the filtrate of nZVI suspension suggesting that the physical interaction between nZVI and cell is necessary for bacterial inactivation. PMID:26378872

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

    PubMed

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

    2014-01-01

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

  18. Mechanisms for removal of p-nitrophenol from aqueous solution using zero-valent iron.

    PubMed

    Nakatsuji, Yusuke; Salehi, Zeinab; Kawase, Yoshinori

    2015-04-01

    Batch experiments were conducted to examine mechanisms for removal of p-nitrophenol (PNP) from aqueous solution using zero-valent iron (ZVI). Removal of PNP using ZVI was mainly attributed to three mechanisms: degradation, precipitation and adsorption. A complete removal of 30 mg L(-1) PNP with ZVI dosage of 1000 mg L(-1) achieved within 30 min at pH 3. The PNP removal rate in the acidic solutions was significantly suppressed at higher pH. The modified Langmuir-Hinshelwood kinetic model could successfully describe the PNP removal process using ZVI at different pH conditions. Total organic carbon (TOC) removal efficiencies were found to be almost independent of pH. While the TOC removal at lower pH was profoundly affected by the reductive and/or oxidative degradation, the adsorption was favorable at higher pH. The effect of dissolved oxygen on PNP removal was investigated at pH 3 where a maximum contribution of oxidative degradation could be expected. The PNP removal in the anoxic system purged with nitrogen gas was quick as well as that in the system being open to the air. However, the TOC removal under the anoxic condition was negligible as compared with that in the oxic system. The profiles of the intermediates formed during the PNP degradation indicated that the reductive degradation was predominant in the initial phase of the removal and subsequently the oxidative degradation occurred. PMID:25662484

  19. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater.

    PubMed

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-01-01

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3-6 mmol/L in temperature range of 30-40 °C, 6-10 mmol/L in temperature range of 15-30 °C and 10-14 mmol/L in temperature range of 5-15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency. PMID:26199053

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

    PubMed

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

    2012-05-15

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

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

    SciTech Connect

    Kwong, S.; Small, J.; Tahar, B.

    2007-07-01

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

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

    PubMed Central

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

    2014-01-01

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

  3. [Simultaneous Biotransformation of Ammonium and Nitrate via Zero-Valent Iron on Anaerobic Conditions].

    PubMed

    Zhou, Jian; Huang, Yong; Yuan, Yi; Liu, Xin; Li, Xiang; Shen, Jie; Yang, Peng-bing

    2015-12-01

    Zero-valent iron (ZVI) was used to improve the biological autotrophic denitrification process between nitrate and ammonia by anaerobic ammonia oxidation ( ANAMMOX) bacteria. With the addition of ZVI, the biological autotrophic denitrification process could be reacted in the influent condition of pH was 7-8, at 35°C ±0.5°C, the concentration of ammonia was 50-100 mg · L⁻¹ and the concentration of nitrate was 50-100 mg · L⁻¹. The highest conversion rate could be reached to 17.2 mg · (L·h) ⁻¹. With the change of reaction time and the molar ratio of nitrate and ammonia in influent, the final molar conversion ratio of nitrate and ammonia in effluent fluctuated between 1.2-3. 5. The result showed that this autotrophic denitrification process was not belonged to elementary reaction. The mechanism of this autotrophic denitrification process could be summarized that with the reduction of ZVI, the nitrate could be reduced to nitrite. Hereafter, the ANAMMOX process reacted between the nitrite and ammonia. PMID:27011992

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

    PubMed

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

    2014-01-01

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

  5. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater

    PubMed Central

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-01-01

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3–6 mmol/L in temperature range of 30–40 °C, 6–10 mmol/L in temperature range of 15–30 °C and 10–14 mmol/L in temperature range of 5–15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency. PMID:26199053

  6. [Zero-valent iron-enhanced azoreduction by the Shewanella decolorationis S12].

    PubMed

    Zhou, Qing; Chen, Xing-Juan; Guo, Jun; Sun, Guo-Ping; Xu, Mei-Ying

    2013-07-01

    Characteristics and optimal reaction conditions of anaerobic azoreduction by the Shewanella decolorationis S12 in the presence of zero-valent iron (ZVI) were evaluated in this study. The results showed that the presence of ZVI significantly enhanced the decolorization rate of azo dye. In the presence of 20 mmol x L(-1) ZVI, the decolorization rate of 1 mmol x L(-1) amaranth reached up to 100% by the Shewanella decolorationis S12 after 30 h incubation, which was significantly higher than 23.16% and 94.66% in the pure strain S12 and pure ZVI treatment systems, respectively. When 20 mmol x L(-1) of sodium formate was added in the medium, ZVI still improved the decolorization rate of amaranth by 20.54%. In addition, the presence of ZVI significantly increased the azo dye treatment amount in the ZVI plus S12 system. In the system with ZVI, 1 mmol x L(-1) amaranth was completely reduced 11 times in fed-batch process within 276 h, while the dye could only be completely reduced 3 times in the system without ZVI. The optimal pH and the Fe(0) dose for the ZVI plus S12 system was 9.0 and 60 mmol c L(-1), respectively. The microscale ZVI was more suitable for the decolorization than those with larger size and the nanoscale ZVI. This study may provide some useful information for improving the biodegradation of azo dye in the treatment system with ZVI. PMID:24028023

  7. Mercury remediation in wetland sediment using zero-valent iron and granular activated carbon

    USGS Publications Warehouse

    Lewis, Ariel S.; Huntington, Thomas G.; Marvin-DiPasquale, Mark C.; Amirbahman, Aria

    2016-01-01

    Wetlands are hotspots for production of toxic methylmercury (MeHg) that can bioaccumulate in the food web. The objective of this study was to determine whether the application of zero-valent iron (ZVI) or granular activated carbon (GAC) to wetland sediment could reduce MeHg production and bioavailability to benthic organisms. Field mesocosms were installed in a wetland fringing Hodgdon Pond (Maine, USA), and ZVI and GAC were applied. Pore-water MeHg concentrations were lower in treated compared with untreated mesocosms; however, sediment MeHg, as well as total Hg (THg), concentrations were not significantly different between treated and untreated mesocosms, suggesting that smaller pore-water MeHg concentrations in treated sediment were likely due to adsorption to ZVI and GAC, rather than inhibition of MeHg production. In laboratory experiments with intact vegetated sediment clumps, amendments did not significantly change sediment THg and MeHg concentrations; however, the mean pore-water MeHg and MeHg:THg ratios were lower in the amended sediment than the control. In the laboratory microcosms, snails (Lymnaea stagnalis) accumulated less MeHg in sediment treated with ZVI or GAC. The study results suggest that both GAC and ZVI have potential for reducing MeHg bioaccumulation in wetland sediment.

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

    PubMed

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

    2013-02-01

    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

  9. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater

    NASA Astrophysics Data System (ADS)

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-07-01

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3-6 mmol/L in temperature range of 30-40 °C, 6-10 mmol/L in temperature range of 15-30 °C and 10-14 mmol/L in temperature range of 5-15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency.

  10. Zero-valent iron-activated persulfate oxidation of a commercial alkyl phenol polyethoxylate.

    PubMed

    Temiz, Kubra; Olmez-Hanci, Tugba; Arslan-Alaton, Idil

    2016-07-01

    Aqueous Triton X-45 (TX-45; 20 mg/L; original total organic carbon (TOC) = 14 mg/L), a representative, commercially important alkylphenol polyethoxylate, was subjected to persulfate (PS) oxidation activated with zero-valent iron (ZVI) nanoparticles. After optimization of the ZVI/PS treatment combination (1 g/L ZVI; 2.5 mM PS at pH5) in terms of pH (3-9), ZVI (0.5-5 g/L) and PS (0.5-5.0 mM) concentrations, TX-45 could be efficiently (>90%) degraded within short treatment periods (<60 min) accompanied with significant (>40%) TOC removals. The degree of PS consumption and Fe release was also followed during the experiments and a positive correlation existed between enhanced TX-45 removals and ZVI-activated PS consumption rates accompanied with a parallel Fe release. Acute toxicity tests were conducted using two different bioassays to examine the toxicological safety of the ZVI/PS oxidation system. Acute toxicity profiles significantly decreased from an original value of 66% relative inhibition to 21% and from 16% relative inhibition to non-toxic values according to Vibrio fischeri and Pseudokirchneriella subcapitata bioassays, respectively. The photobacterium V. fischeri appeared to be more sensitive to TX-45 and its degradation products than the microalgae P. subcapitata. PMID:26797469

  11. Mercury remediation in wetland sediment using zero-valent iron and granular activated carbon.

    PubMed

    Lewis, Ariel S; Huntington, Thomas G; Marvin-DiPasquale, Mark C; Amirbahman, Aria

    2016-05-01

    Wetlands are hotspots for production of toxic methylmercury (MeHg) that can bioaccumulate in the food web. The objective of this study was to determine whether the application of zero-valent iron (ZVI) or granular activated carbon (GAC) to wetland sediment could reduce MeHg production and bioavailability to benthic organisms. Field mesocosms were installed in a wetland fringing Hodgdon Pond (Maine, USA), and ZVI and GAC were applied. Pore-water MeHg concentrations were lower in treated compared with untreated mesocosms; however, sediment MeHg, as well as total Hg (THg), concentrations were not significantly different between treated and untreated mesocosms, suggesting that smaller pore-water MeHg concentrations in treated sediment were likely due to adsorption to ZVI and GAC, rather than inhibition of MeHg production. In laboratory experiments with intact vegetated sediment clumps, amendments did not significantly change sediment THg and MeHg concentrations; however, the mean pore-water MeHg and MeHg:THg ratios were lower in the amended sediment than the control. In the laboratory microcosms, snails (Lymnaea stagnalis) accumulated less MeHg in sediment treated with ZVI or GAC. The study results suggest that both GAC and ZVI have potential for reducing MeHg bioaccumulation in wetland sediment. PMID:26874318

  12. Enhanced transport of Si-coated nanoscale zero-valent iron particles in porous media.

    PubMed

    HonetschlÄgerová, Lenka; Janouškovcová, Petra; Kubal, Martin

    2016-06-01

    Laboratory column experiments were conducted to evaluate the effect of previously described silica coating method on the transport of nanoscale zero-valent iron (nZVI) in porous media. The silica coating method showed the potential to prevent the agglomeration of nZVI. Transport experiments were conducted using laboratory-scale sand-packed columns at conditions that were very similar of natural groundwater. Transport properties of non-coated and silica-coated nZVI are investigated in columns of 40 cm length, which were filled with porous media. A suspension was injected in three different Fe particle concentrations (100, 500, and 1000 mg/L) at flow 5  mL/min. Experimental results were compared using nanoparticle attachment efficiency and travel distances which were calculated by classical particle filtration theory. It was found that non-coated particles were essentially immobile in porous media. In contrast, silica-coated particles showed significant transport distances at the tested conditions. Results of this study suggest that silica can increase nZVI mobility in the subsurface. PMID:26582314

  13. Kinetics of Nutrient Removal by Nano Zero-Valent Iron under Different Biochemical Environments.

    PubMed

    Xu, Shengnan; Hu, Zhiqiang

    2015-06-01

    The effectiveness of nano zero-valent iron (NZVI; an average size of 55 nm at a concentration of 200 mg Fe/L) in nutrient removal was determined under anaerobic, anoxic, and aerobic conditions. Compared to the rate of reduction of nitrate nitrogen (NO3--N) to ammoniacal nitrogen (NH4+-N) by NZVI alone, the presence of activated sludge increased the rate of complete reduction by 300%. About 31% of NO3--N was converted to NH4+-N through NZVI-facilitated dissimilatory nitrate reduction to ammonium, while 56% of NO3--N was removed by heterotrophic denitrification. The presence of sludge reduced the rates of phosphorus removal by NZVI, with the first-order reaction rate constants of 0.06/hour, 0.42/hour, and 0.18/hour under anaerobic, anoxic, and aerobic conditions, respectively. The highest phosphorus removal efficiency (95%) by NZVI was observed under anoxic abiotic conditions, whereas the efficiency dropped to 31% under anaerobic biotic conditions, which was attributed to significant sludge-facilitated NZVI agglomeration. PMID:26459816

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

    PubMed

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

    2013-11-01

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

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

    PubMed

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

    2011-08-30

    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

  16. Ultrasound-assisted synthesis of nanosized zero-valent iron for metal cations extraction and wastewater treatment applications

    NASA Astrophysics Data System (ADS)

    Mikhailov, I. Yu; Lysov, D. V.; Levina, V. V.; Mazov, I. N.; Gusev, A. A.; Yudintseva, T. I.; Kuznetsov, D. V.

    2016-01-01

    Nanosized zero-valent iron has shown good results in wastewater treatment and activation of physicochemical processes. Its applications in modern industry are complicated by high production costs of nanomaterials produced via existing synthesis routes. Therefore there is a need of cheap and high-productive methods of nanosized zero-valent iron with advanced functional properties. Improvement of oxidative conditions with additions may find its place in extraction of rare-earth metals, where high cost of nanomaterials could be viable. In this paper we studied an effect of ultrasonic irradiation on specific surface area and particle size of nanosized zero-valent iron synthesized by methods of chemical precipitation with high- temperature reduction in hydrogen flow and sodium borohydride reduction. Obtained results showed significant decrease of particle size and differences in particles morphology depending on presence of ultrasonication during synthesis and on chosen method. For ultrasonic-assisted synthesis with 100% amplitude, particle size calculated from specific surface area was 70 nm for sample synthesized by chemical precipitation with high-temperature reduction and 35 nm for borohydide reduction method compared to 63 nm for reference sample without ultrasonication.

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

    PubMed

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Reactive zero-valent iron is currently being used for remediation of contaminated groundwater. Permeable reactive barriers are the current state-of-the-practice 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 zero valent 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 directly at the source. It is very important to have a good understanding of the transport behavior of nZVI during injection as well as the fate of nZVI after injection due to changes in the flow regime or water chemistry changes. 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 porous media materials and controlled 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.

  19. Impact of the morphology and reactivity of nanoscale zero-valent iron (NZVI) on dechlorinating bacteria.

    PubMed

    Rónavári, Andrea; Balázs, Margit; Tolmacsov, Péter; Molnár, Csaba; Kiss, István; Kukovecz, Ákos; Kónya, Zoltán

    2016-05-15

    Nanoscale zero-valent iron (NZVI) is increasingly used for reducing chlorinated organic contaminants in soil or groundwater. However, little is known about what impact the particles will have on the biochemical processes and the indigenous microbial communities. Nanoiron reactivity is affected by the structure and morphology of nanoparticles that complicates the applicability in bioremediation. In this study, the effect of precursors (ferrous sulfate and ferric chloride) and reducing agents (sodium dithionite and sodium borohydride) on the morphology and the reactivity of NZVIs was investigated. We also studied the impact of differently synthesized NZVIs on microbial community, which take part in reductive dechlorination. We demonstrated that both the applied iron precursor and the reducing agent had influence on the structure of the nanoparticles. Spherical nanoparticles with higher Fe(0) content (>90%) was observed by using sodium borohydride as reducing agent, while application of sodium dithionite as reducing agent resulted nanostructures with lower Fe(0) content (between 68,7 and 85,5%). To determine the influence of differently synthesized NZVIs on cell viability anaerobic enriched microcosm were used. NVZI was used in 0.1 g/L concentration in all batch experiments. Relative amount of Dehalococcoides, sulfate reducers (SRBs) and methanogens were measured by quantitative PCR. We found that the relative amount of Dehalococcoides slowly decreased in all experiments independently from the precursor and reducing agent, whereas the total amount of microbes increased. The only clear distinction was in relative amount of sulfate reducers which were higher in the presence of NZVIs synthesized from sodium dithionite. PMID:26994337

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

    PubMed Central

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

    2010-01-01

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

  1. Mechanism of Co(II) adsorption by zero valent iron/graphene nanocomposite.

    PubMed

    Xing, Min; Xu, Lejin; Wang, Jianlong

    2016-01-15

    Nanoscale zero valent iron (ZVI)/graphene (GF) composite was prepared and characterized by Brunauer-Emmett-Teller (BET) surface area measurement and zeta potential determination. The adsorption isotherm of Co(II) in aqueous solution, as well as the influence of pH values and ionic strengths was studied. The mechanism of Co(II) adsorption by GF was investigated through analyzing the sorption products at initial pH of 3.0, 6.0 and 9.0 using high-resolution transmission electron microscope with energy dispersive X-ray detector (HRTEM-EDX), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), Raman spectra, X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) measurement. The results indicated that Langmuir isotherm model fitted well and the adsorption capacity was 131.58 mg g(-1) at 30°C. Adsorption capacity was not significantly influenced by ionic strength and kept high at pH 4.0∼9.0. The detail information of GF-Co interaction at different initial pH values was obtained using XAFS analysis combined with other characterization methods. Coordination numbers (CN) and interatomic distances (R) of both Fe and Co were given. At pH 3.0 and pH 6.0, the Co-substituted iron oxides transformed to CoFe2O4-like structure, while at pH 9.0 they changed to green rust-like phases. Co occupied preferentially in the octahedral sites in acid solution. The adsorption mechanism of Co(II) was attributed to inner-sphere complexation and dissolution/re-precipitation of the substituted metal oxides. PMID:26368802

  2. Synthesis of highly reactive subnano-sized zero-valent iron using smectite clay templates.

    PubMed

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

    2010-06-01

    A novel method was developed for synthesizing subnano-sized zero-valent iron (ZVI) using smectite clay layers as templates. Exchangeable Fe(III) cations compensating the structural negative charges of smectites were reduced with NaBH(4), resulting in the formation of ZVI. The unique structure of smectite clay, in which isolated exchangeable Fe(III) cations reside near the sites of structural negative charges, inhibited the agglomeration of ZVI resulting in the formation of subnanoscale ZVI particles in the smectite interlayer regions. X-ray diffraction revealed an interlayer spacing of approximately 5 A. The non-structural iron content of this clay yields a calculated ratio of two atoms of ZVI per three cation exchange sites, in full agreement with the X-ray diffraction (XRD) results since the diameter of elemental Fe is 2.5 A. The clay-templated ZVI showed superior reactivity and efficiency compared to other previously reported forms of ZVI as indicated by the reduction of nitrobenzene; structural Fe within the aluminosilicate layers was nonreactive. At a 1:3 molar ratio of nitrobenzene/non-structural Fe, a reaction efficiency of 83% was achieved, and over 80% of the nitrobenzene was reduced within one minute. These results confirm that non-structural Fe from Fe(III)-smectite was reduced predominantly to ZVI which was responsible for the reduction of nitrobenzene to aniline. This new form of subnanoscale ZVI may find utility in the development of remediation technologies for persistent environmental contaminants, for example, as components of constructed reactive domains such as reactive caps for contaminated sediments. PMID:20446730

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

    PubMed

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

    2010-10-15

    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

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

    NASA Astrophysics Data System (ADS)

    Busch, Jan; Oswald, Sascha

    2013-04-01

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

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

    SciTech Connect

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

    2013-09-01

    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.

  6. Weak magnetic field accelerates chromate removal by zero-valent iron.

    PubMed

    Feng, Pian; Guan, Xiaohong; Sun, Yuankui; Choi, Wonyong; Qin, Hejie; Wang, Jianmin; Qiao, Junlian; Li, Lina

    2015-05-01

    Weak magnetic field (WMF) was employed to improve the removal of Cr(VI) by zero-valent iron (ZVI) for the first time. The removal rate of Cr(VI) was elevated by a factor of 1.12-5.89 due to the application of a WMF, and the WMF-induced improvement was more remarkable at higher Cr(VI) concentration and higher pH. Fe2+ was not detected until Cr(VI) was exhausted, and there was a positive correlation between the WMF-induced promotion factor of Cr(VI) removal rate and that of Fe2+ release rate in the absence of Cr(VI) at pH4.0-5.5. These phenomena imply that ZVI corrosion with Fe2+ release was the limiting step in the process of Cr(VI) removal. The superimposed WMF had negligible influence on the apparent activation energy of Cr(VI) removal by ZVI, indicating that WMF accelerated Cr(VI) removal by ZVI but did not change the mechanism. The passive layer formed with WMF was much more porous than without WMF, thereby facilitating mass transport. Therefore, WMF could accelerate ZVI corrosion and alleviate the detrimental effects of the passive layer, resulting in more rapid removal of Cr(VI) by ZVI. Exploiting the magnetic memory of ZVI, a two-stage process consisting of a small reactor with WMF for ZVI magnetization and a large reactor for removing contaminants by magnetized ZVI can be employed as a new method of ZVI-mediated remediation. PMID:25968271

  7. Removal of arsenic(III) from groundwater by nanoscale zero-valent iron.

    PubMed

    Kanel, Sushil Raj; Manning, Bruce; Charlet, Laurent; Choi, Heechul

    2005-03-01

    Nanoscale zero-valent iron (NZVI) was synthesized and tested for the removal of As(III), which is a highly toxic, mobile, and predominant arsenic species in anoxic groundwater. We used SEM-EDX, AFM, and XRD to characterize particle size, surface morphology, and corrosion layers formed on pristine NZVI and As(III)-treated NZVI. AFM results showed that particle size ranged from 1 to 120 nm. XRD and SEM results revealed that NZVI gradually converted to magnetite/maghemite corrosion products mixed with lepidocrocite over 60 d. Arsenic(III) adsorption kinetics were rapid and occurred on a scale of minutes following a pseudo-first-order rate expression with observed reaction rate constants (K(obs)) of 0.07-1.3 min(-1) (at varied NZVI concentration). These values are about 1000x higher than K(obs) literature values for As(III) adsorption on micron size ZVI. Batch experiments were performed to determine the feasibility of NZVI as an adsorbent for As(III) treatment in groundwater as affected by initial As(III) concentration and pH (pH 3-12). The maximum As(III) adsorption capacity in batch experiments calculated by Freundlich adsorption isotherm was 3.5 mg of As(III)/g of NZVI. Laser light scattering (electrophoretic mobility measurement) confirmed NZVI-As(III) inner-sphere surface complexation. The effects of competing anions showed HCO3-, H4SiO4(0), and H2P04(2-) are potential interferences in the As(III) adsorption reaction. Our results suggest that NZVI is a suitable candidate for both in-situ and ex-situ groundwater treatment due to its high reactivity. PMID:15787369

  8. Hydrogen production from the dissolution of nano zero valent iron and its effect on anaerobic digestion.

    PubMed

    Huang, Yu-Xi; Guo, Jialiang; Zhang, Chunyang; Hu, Zhiqiang

    2016-01-01

    Nano zero valent iron (NZVI) has shown inhibition on methanogenesis in anaerobic digestion due to its reductive decomposition of cell membrane. The inhibition was accompanied by the accumulation of hydrogen gas due to rapid NZVI dissolution. It is not clear whether and how rapid hydrogen release from NZVI dissolution directly affects anaerobic digestion. In this study, the hydrogen release kinetics from NZVI (average size = 55 ± 11 nm) dissolution in deionized water under anaerobic conditions was first evaluated. The first-order NZVI dissolution rate constant was 2.62 ± 0.26 h(-1) with its half-life of 0.26 ± 0.03 h. Two sets of anaerobic digestion experiments (i.e., in the presence of glucose or without any substrate but at different anaerobic sludge concentrations) were performed to study the impact of H2 release from rapid NZVI dissolution, in which H2 was generated in a separate water bottle containing NZVI (i.e., ex situ H2 or externally supplied from NZVI dissolution) before hydrogen gas was introduced to anaerobic digestion. The results showed that the H2 partial pressure in the headspace of the digestion bottle reached as high as 0.27 atm due to rapid NZVI dissolution, resulting in temporary inhibition of methane production. Nevertheless, the 5-d cumulative methane volume in the group with ex situ H2 production due to NZVI dissolution was actually higher than that of control, suggesting NZVI inhibition on methanogenesis is solely due to the reductive decomposition of cell membrane after direct contact with NZVI. PMID:26521217

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

    PubMed

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

    2014-01-01

    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

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

    PubMed

    Yang, Yu; Guo, Jialiang; Hu, Zhiqiang

    2013-11-01

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

  11. A Case Study of Using Zero-Valent Iron Nanoparticles for Groundwater Remediation

    NASA Astrophysics Data System (ADS)

    Xiong, Z.; Kaback, D.; Bennett, P. J.

    2011-12-01

    Zero-valent iron nanoparticle (nZVI) is a promising technology for rapid in situ remediation of numerous contaminants, including chlorinated solvents, in groundwater and soil. Because of the high specific surface area of nZVI particles, this technology achieves treatment rates that are significantly faster than micron-scale and granular ZVI. However, a key technical challenge facing this technology involves agglomeration of nZVI particles. To improve nZVI mobility/deliverability and reactivity, an innovative method was recently developed using a low-cost and bio-degradable organic polymer as a stabilizer. This nZVI stabilization strategy offers unique advantages including: (1) the organic polymer is cost-effective and "green" (completely bio-compatible), (2) the organic polymer is highly effective in stabilizing nZVI particles; and (3) the stabilizer is applied during particle preparation, making nZVI particles more stable. Through a funding from the U.S. Air Force Center for Engineering and the Environment (AFCEE), AMEC performed a field study to test the effectiveness of this innovative technology for degradation of chlorinated solvents in groundwater at a military site. Laboratory treatability tests were conducted using groundwater samples collected from the test site and results indicated that trichloroethene (main groundwater contaminant at the site) was completely degraded within four hours by nZVI particles. In March and May 2011, two rounds of nZVI injection were performed at the test site. Approximately 700 gallons of nZVI suspension with palladium as a catalyst were successfully prepared in the field and injected into the subsurface. Before injection, membrane filters with a pore size of 450 nm were used to check the nZVI particle size and it was observed that >85% of nZVI particles were passed through the filter based on total iron measurement, indicating particle size of <450 nm. During field injections, nZVI particles were observed in a monitoring well located 5 feet downgradient from the injection well. Chlorinated solvent degradation products, e.g. ethane and ethene, increased significantly in monitoring wells following nZVI injections. Groundwater monitoring will be continued for approximately eight months following the last sampling event in July 2011 to demonstrate the performance of nZVI particles.

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

    PubMed

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

    2012-04-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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 (δ-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 δ-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 δ-value is affected by the starting concentration of PCE (δ-value of c1 < c2) as there is a higher ratio of PCE to ZVI.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  15. Influence of fulvic acid on the colloidal stability and reactivity of nanoscale zero-valent iron.

    PubMed

    Dong, Haoran; Ahmad, Kito; Zeng, Guangming; Li, Zhongwu; Chen, Guiqiu; He, Qi; Xie, Yankai; Wu, Yanan; Zhao, Feng; Zeng, Yalan

    2016-04-01

    This study investigated the effect of fulvic acid (FA) on the colloidal stability and reactivity of nano zero-valent iron (nZVI) at pH 5, 7 and 9. The sedimentation behavior of nZVI differed at different pH. A biphasic model was used to describe the two time-dependent settling processes (i.e., a rapid settling followed by a slower settling) and the settling rates were calculated. Generally, the settling of nZVI was more significant at the point of zero charge (pHpzc), which could be varied in the presence of FA due to the adsorption of FA on the nZVI surface. More FA was adsorbed on the nZVI surface at pH 5-7 than pH 9, resulting in the varying sedimentation behavior of nZVI via influencing the electrostatic repulsion among particles. Moreover, it was found that there was a tradeoff between the stabilization and the reactivity of nZVI as affected by the presence of FA. When FA concentration was at a low level, the adsorption of FA on the nZVI surface could enhance the particle stabilization, and thus facilitating the Cr(VI) reduction by providing more available surface sites. However, when the FA concentrations were too high to occupy the active surface sites of nZVI, the Cr(VI) reduction could be decreased even though the FA enhanced the dispersion of nZVI particles. At pH 9, the FA improved the Cr(VI) reduction by nZVI. Given the adsorption of FA on the nZVI surface was insignificant and its effect on the settling behavior of nZVI particles was minimal, it was proposed that the FA formed soluble complexes with the produced Fe(III)/Cr(III) ions, and thus reducing the degree of passivation on the nZVI surface and facilitating the Cr(VI) reduction. PMID:26796746

  16. Effect of accelerated carbonation and zero valent iron on metal leaching from bottom ash.

    PubMed

    Nilsson, M; Andreas, L; Lagerkvist, A

    2016-05-01

    About 85% of the ashes produced in Sweden originated from the incineration of municipal solid waste and biofuel. The rest comes from the thermal treatment of recycled wood, peat, charcoal and others. About 68% of all ashes annually produced in Sweden are used for constructions on landfills, mainly slopes, roads and embankments, and only 3% for construction of roads and working surfaces outside the landfills (SCB, 2013). Since waste bottom ash (BA) often has similar properties to crushed bedrock or gravel, it could be used for road constructions to a larger extent. However, the leaching of e.g. Cr, Cu, Mo, Pb and Zn can cause a threat to the surrounding environment if the material is used as it is. Carbonation is a commonly used pre-treatment method, yet it is not always sufficient. As leaching from aged ash is often controlled by adsorption to iron oxides, increasing the number of Fe oxide sorption sites can be a way to control the leaching of several critical elements. The importance of iron oxides as sorption sites for metals is known from both mineralogical studies of bottom ash and from the remediation of contaminated soil, where iron is used as an amendment. In this study, zero valent iron (Fe(0)) was added prior to accelerated carbonation in order to increase the number of adsorption sites for metals and thereby reduce leaching. Batch, column and pHstat leaching tests were performed and the leaching behaviour was evaluated with multivariate data analysis. It showed that leaching changed distinctly after the tested treatments, in particular after the combined treatment. Especially, the leaching of Cr and Cu clearly decreased as a result of accelerated carbonation. The combination of accelerated carbonation with Fe(0) addition reduced the leaching of Cr and Cu even further and reduced also the leaching of Mo, Zn, Pb and Cd compared to untreated BA. Compared with only accelerated carbonation, the Fe(0) addition significantly reduced the leaching of Cr, Cu and Mo. The effects of Fe(0) addition can be related to binding of the studied elements to newly formed iron oxides. The effects of Fe(0) addition were often more distinct at pH values between 7 and 9, which indicates that a single treatment with only Fe addition would be less effective and a combined treatment is recommended. The pHstat results showed that accelerated carbonation in combination with Fe(0)(0) addition widens the pH range for low solubility of about one unit for several of the studied elements. This indicates that pre-treating the bottom ash with a combination of accelerated carbonation and Fe(0) addition makes the leaching properties of the ash less sensitive to pH changes that may occur during reuse. All in all, the addition of Fe(0) in combination with carbonation could be an effective pre-treatment method for decreasing the mobility of potentially harmful components in bottom ash. PMID:26786400

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

    PubMed

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

    2015-03-15

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

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

    PubMed

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

    2013-12-15

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  1. Removing pentachlorophenol from water using a nanoscale zero-valent iron/H2O2 system.

    PubMed

    Cheng, Rong; Cheng, Can; Liu, Guo-Hua; Zheng, Xiang; Li, Guanqing; Li, Jie

    2015-12-01

    Nanoscale zero-valent iron (nZVI) is an environmentally benign material that has been widely used as a reducing agent to treat environmental pollutants. In this study, nZVI was used as a heterogeneous Fenton catalyst in an nZVI/H2O2 system to remove pentachlorophenol (PCP) from water. The PCP degradation process in the nZVI/H2O2 system was completed within 1h. The relative Cl(-) concentration increased throughout the test period (6h), indicating that the performance of the oxidative system in terms of dechlorination was excellent. The initial H2O2 concentration significantly influenced the PCP removal rate, and nZVI performed better than commercial zero-valent iron as a catalyst. Moreover, magnetite (Fe3O4), which was the main product of the corrosion of nZVI, was found to perform well as an adsorbent and catalyst, so it allowed the nZVI to be effectively reused. PMID:26184790

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

    PubMed

    Klas, Sivan; Kirk, Donald W

    2013-05-15

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

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

    PubMed

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

    2012-01-15

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

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

    NASA Astrophysics Data System (ADS)

    Sun, Fenglong

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

  5. Transport characteristics of nanoscale zero-valent iron carried by three different "vehicles" in porous media.

    PubMed

    Su, Yan; Zhao, Yong S; Li, Lu L; Qin, Chuan Y; Wu, Fan; Geng, Nan N; Lei, Jian S

    2014-01-01

    This study investigated the transport properties of nanoscale zero-valent iron (Fe(0)) (nZVI) carried by three vehicles: water, sodium dodecyl sulfate (SDS) solution, and SDS foam. Batch experiments were conducted to assess the sedimentation capability of nZVI particles in these three vehicles. Column experiments were conducted to investigate the transport properties of nZVI in porous media formed with different sizes of sand (0.25 mm to 0.5 mm, 0.5 mm to 0.9 mm, and 0.9 mm to 1.4 mm). Three main results were obtained. First, the batch experiments revealed that the stabilities of nZVI particles in SDS solution and SDS foam were improved, compared with that of nZVI particles in water. Moreover, the sedimentation of nZVI in foam was closely associated with the foam drainage volume. The nZVI content in foam was similar to that in the original foaming suspension, and the nZVI particle distribution in foam became significantly more uniform at a stirring speed of 3000 r/min. Second, the transport of nZVI was enhanced by foam compared with water and SDS solution for 0.25 mm to 0.5 mm diameter sand. For sand with diameters of 0.5 mm to 0.9 mm and 0.9 mm to 1.4 mm, the mobility of nZVI carried by SDS solution was optimal, followed by that of nZVI carried by foam and water. Thus, the mobility of nZVI in finer sand was significantly enhanced by foam, compared with that in coarse sand. In contrast, compared with the bare nZVI suspension and nZVI-laden foam, the spatial distribution of nZVI particles carried by SDS solution was significantly uniform along the column length. Third, the SDS concentration significantly influenced the migration of nZVI in porous media. The enhancement in the migration of nZVI carried by SDS solution was greater at an SDS dose of 0.25% compared with that at the other three doses (0.2%, 0.5%, and 1%) for sand with a 0.25 mm to 0.5 mm diameter. Increased SDS concentrations positively affected the transport of nZVI by foam for sand with a 0.25 mm to 0.5 mm diameter, and the SDS concentrations for enhancing the mobility of nZVI carried by SDS foam satisfied the following order: 1% > 0.5% > 0.25% > 0.2%. Thus, SDS solution and SDS foam were better vehicles than water for delivering nZVI particles to porous media for contamination remediation. PMID:25320851

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

    EPA Science Inventory

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

  7. A field investigation on transport of carbon-supported nanoscale zero-valent iron (nZVI) in groundwater.

    PubMed

    Busch, J; Meißner, T; Potthoff, A; Bleyl, S; Georgi, A; Mackenzie, K; Trabitzsch, R; Werban, U; Oswald, S E

    2015-10-01

    The application of nanoscale zero-valent iron (nZVI) for subsurface remediation of groundwater contaminants is a promising new technology, which can be understood as alternative to the permeable reactive barrier technique using granular iron. Dechlorination of organic contaminants by zero-valent iron seems promising. Currently, one limitation to widespread deployment is the fast agglomeration and sedimentation of nZVI in colloidal suspensions, even more so when in soils and sediments, which limits the applicability for the treatment of sources and plumes of contamination. Colloid-supported nZVI shows promising characteristics to overcome these limitations. Mobility of Carbo-Iron Colloids (CIC) - a newly developed composite material based on finely ground activated carbon as a carrier for nZVI - was tested in a field application: In this study, a horizontal dipole flow field was established between two wells separated by 5.3m in a confined, natural aquifer. The injection/extraction rate was 500L/h. Approximately 1.2kg of CIC was suspended with the polyanionic stabilizer carboxymethyl cellulose. The suspension was introduced into the aquifer at the injection well. Breakthrough of CIC was observed visually and based on total particle and iron concentrations detected in samples from the extraction well. Filtration of water samples revealed a particle breakthrough of about 12% of the amount introduced. This demonstrates high mobility of CIC particles and we suggest that nZVI carried on CIC can be used for contaminant plume remediation by in-situ formation of reactive barriers. PMID:25864966

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

    USGS Publications Warehouse

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

    1999-01-01

    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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  10. Zero-valent iron/biotic treatment system for perchlorate-contaminated water: lab-scale performance, modeling, and full-scale implications

    EPA Science Inventory

    The computer program AQUASIM was used to model biological treatment of perchlorate-contaminated water using zero-valent iron corrosion as the hydrogen gas source. The laboratory-scale column was seeded with an autohydrogenotrophic microbial consortium previously shown to degrade ...

  11. 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...

  12. Use of zero-valent iron biosand filters to reduce E. coli O157:H12 in irrigation water applied to spinach plants in a field setting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction: Zero-valent iron (ZVI) filters may provide an efficient method to mitigate the contamination of produce crops through irrigation water. Purpose: To evaluate the use of ZVI-filtration in decontaminating E. coli O157:H12 in irrigation water and on spinach plants in a small, field-scale...

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

    PubMed

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

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

    2013-08-01

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

  16. Enhanced reductive dechlorination of polychlorinated biphenyl-contaminated soil by in-vessel anaerobic composting with zero-valent iron.

    PubMed

    Long, Yu-Yang; Zhang, Chi; Du, Yao; Tao, Xiao-Qing; Shen, Dong-Sheng

    2014-03-01

    Anaerobic dechlorination is an effective degradation pathway for higher chlorinated polychlorinated biphenyls (PCBs). The enhanced reductive dechlorination of PCB-contaminated soil by anaerobic composting with zero-valent iron (ZVI) was studied, and preliminary reasons for the enhanced reductive dechlorination with ZVI were investigated. The results show that the addition of nanoscale ZVI can enhance dechlorination during in-vessel anaerobic composting. After 140 days, the average number of removed Cl per biphenyl with 10 mg g(-1) of added nanoscale ZVI was 0.63, enhancing the dechlorination by 34 % and improving the initial dechlorination speed. The ZVI enhances dechlorination by providing a suitable acid base environment, reducing volatile fatty acid inhibition and stimulating the microorganisms. The C/N ratios for treatments with the highest rate of ZVI addition were smaller than for the control, indicating that ZVI addition can promote compost maturity. PMID:24363050

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

    PubMed

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

    2003-01-01

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

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

    PubMed

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

    2006-03-15

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

  19. AsIII oxidation by Thiomonas arsenivorans in up-flow fixed-bed reactors coupled to As sequestration onto zero-valent iron-coated sand.

    PubMed

    Wan, Junfeng; Klein, Jonathan; Simon, Stephane; Joulian, Catherine; Dictor, Marie-Christine; Deluchat, Véronique; Dagot, Christophe

    2010-09-01

    The combined processes of biological As(III) oxidation and removal of As(III) and As(V) by zero-valent iron were investigated with synthetic water containing high As(III) concentration (10 mg L(-1)). Two up-flow fixed-bed reactors (R1 and R2) were filled with 2 L of sieved sand (d = 3 ± 1 mm) while zero-valent iron powder (d = 76 μm; 1% (w/w) of sand) was mixed evenly with sand in R2. Thiomonas arsenivorans was inoculated in the two reactors. The pilot unit was studied for 33 days, with HRT of 4 and 1 h. The maximal As(III) oxidation rate was 8.36 mg h(-1) L(-1) in R1 and about 45% of total As was removed in R2 for an HRT of 1 h. A first order model fitted well with the As(III) concentration evolution at the different levels in R1. At the end of the pilot monitoring, batch tests were conducted with support collected at different levels in R1. They showed that bacterial As(III) oxidation rate was correlated with the axial length of reactor, which could be explained by biomass distribution in reactor or by bacterial activity. In opposition, As(III) oxidation rate was not stable in R2 due to the simultaneous bacterial As(III) oxidation and chemical removal by zero-valent iron and its oxidant products. However, a durable removal of total As was realized and zero-valent iron was not saturated by As over 33 days in R2. Furthermore, the influence of zero-valent iron and its oxidant corrosion products on the evolution of As(III)-oxidizing bacteria diversity was highlighted by the molecular fingerprinting method of PCR-DGGE using aoxB gene as a functional marker of aerobic As(III) oxidizers. PMID:20850864

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2014-08-01

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

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed

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

    2015-06-15

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2014-12-01

    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

  8. Aging study on carboxymethyl cellulose-coated zero-valent iron nanoparticles in water: Chemical transformation and structural evolution.

    PubMed

    Dong, Haoran; Zhao, Feng; Zeng, Guangming; Tang, Lin; Fan, Changzheng; Zhang, Lihua; Zeng, Yalan; He, Qi; Xie, Yankai; Wu, Yanan

    2016-07-15

    To assess the long-term fate and the associated risks of nanoscale zero-valent iron (nZVI) used in the water remediation, it is essential to understand the chemical transformations during aging of nZVI in water. This study investigated the compositional and structural evolution of bare nZVI and carboxymethyl cellulose (CMC) coated nZVI in static water over a period of 90 days. Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the corrosion products of nZVI and CMC-nZVI. Results show that both the structures and the compositions of the corrosion products change with the process of aging, but the coating of CMC could slow down the aging rate of nZVI (as indicated by the slower drop in Fe(0) intensity in XRD pattern). For the bare nZVI, magnetite (Fe3O4) and/or maghemite (γ-Fe2O3) are the dominant corrosion products after 90 days of aging. However, for the CMC-nZVI, the core-shell spheres collapses to acicular-shaped structures after aging with crystalline lepidocrocite (γ-FeOOH) as the primary end product. Moreover, more lepidocrocite present in the corrosion products of CMC-nZVI with higher loading of CMC, which reveals that the CMC coating could influence the transformation of iron oxides. PMID:27037478

  9. Arsenic removal from geothermal waters with zero-valent iron--effect of temperature, phosphate and nitrate.

    PubMed

    Tyruvola, Konstantina; Nikolaidis, Nikolaus P; Veranis, Nikolaus; Kallithrakas-Kontos, Nikolaso; Koulouridakis, Pavlos E

    2006-07-01

    Field column studies and laboratory batch experiments were conducted in order to assess the performance of zero-valent iron in removing arsenic from geothermal waters in agricultural regions where phosphates and nitrates were present. A field pilot study demonstrated that iron filings could remove arsenic, phosphate and nitrate from water. In addition, batch studies were performed to evaluate the effect of temperature, phosphate and nitrate on As(III) and As(V) removal rates. All batch experiments were conducted at three temperatures (20, 30 and 40 degrees C). Pseudo-first-order reaction rate constants were calculated for As(III), As(V), phosphate, nitrate and ammonia for all temperatures. As(V) exhibited greater removal rates than As(III). The presence of phosphate and nitrate decreased the rates of arsenic removal. The temperature of the water played a dominant role on the kinetics of arsenic, phosphate and nitrate removal. Nitrate reduction resulted in the formation of nitrite and ammonia. In addition, the activation energy, Eact, and the constant temperature coefficient, theta were determined for each removal process. PMID:16769102

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

    PubMed

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

    2014-01-01

    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

  11. Facile synthesis of graphene nano zero-valent iron composites and their efficient removal of trichloronitromethane from drinking water.

    PubMed

    Chen, Haifeng; Cao, Yu; Wei, Enze; Gong, Tingting; Xian, Qiming

    2016-03-01

    Halonitromethanes (HNMs), as an emerging class of disinfection by-products containing nitrogen (N-DBPs) in drinking water, have possessed public health concerns. Two most studied materials, graphene and nanometer-sized zero-valent iron, have been successfully combined into binary nanocomposites (G-nZVI) via facile carbonization and calcinations of glucose and ferric chloride, which was used in the removal of HNMs from drinking water in this study. When the Fe/C mass ratio was 1:5, the as-prepared G-nZVI hybrids comprised numerous dispersed Fe(0) nanoparticles with a range of 5-10 nm in diameter. Batch experimental results indicated that the as-prepared G-nZVI could effectively remove trichloronitromethane (TCNM), a dominant in the group of HNMs from drinking water. About 99% of initial TCNM could be adsorbed and degraded under 60 mg/L G-nZVI dosage within 120 min. Kinetic studies indicated that the removal of TCNM by G-nZVI followed a pseudo first order rate (R(2) > 0.9). The degradation pathways of TCNM by G-nZVI nanocomposites might include dechlorination and denitration of TCNM. The Fe was in the form of iron oxides in the graphene material shape which was then restored to Fe(0) again via calcinations. These results indicated that the synthesized G-nZVI nanocomposites could be a powerful material to remove HNMs from drinking water. PMID:26706929

  12. The specific reactive surface area of granular zero-valent iron in metal contaminant removal: Column experiments and modelling.

    PubMed

    Statham, Tom M; Mason, Lachlan R; Mumford, Kathryn A; Stevens, Geoffrey W

    2015-06-15

    A series of dynamic-flow kinetic experiments were conducted to assess the removal rates of aqueous Cu(2+) and Zn(2+) ions by zero-valent iron (ZVI), a promising material for inclusion in cold-climate remediation applications. The influence of experimental parameters on contaminant removal rates, including aqueous flow rate, operating temperature, and the concentrations of ZVI, salt and dissolved oxygen, was investigated. A mass transport model has been developed that accounts (i) aqueous-phase dispersion processes, (ii) film diffusion of contaminant ions to the reactive ZVI surface and (iii) the reactive removal mechanism itself. Regression to the experimental data indicated that when oxygen is present in the solution feed Cu(2+) and Zn(2+) removal processes were limited by film diffusion. In de-aerated solutions film diffusion still controls Cu(2+) removal but a first-order surface reaction provides a better model for Zn(2+) kinetics. Using air as the equilibrium feed gas, the reactive proportion of the total surface area for contaminant removal was calculated to be 97% and 64% of the active spherically-assumed geometric area associated with ZVI media for Cu(2+) and Zn(2+), respectively. Relative to a gas absorption area, determined in previous studies, the reactive proportion is less than 0.41% of the unreacted ZVI total surface area. These findings suggest that only part of the iron oxyhydroxide surface is reacting during ZVI based metal contaminant removal. PMID:25839833

  13. Simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewater by zero-valent iron.

    PubMed

    Yoshino, Hiroyuki; Tokumura, Masahiro; Kawase, Yoshinori

    2014-01-01

    The zero-valent iron (ZVI) wastewater treatment has been applied to simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewaters. The simultaneous removal occurs by the reactions performed due to the sequential transformation of ZVI under the acidic condition. Fortunately the solution pH of semiconductor acidic wastewaters is low which is effective for the sequential transformation of ZVI. Firstly the reduction of nitrate is taken place by electrons generated by the corrosion of ZVI under acidic conditions. Secondly the ferrous ion generated by the corrosion of ZVI reacts with hydrogen peroxide and generates ·OH radical (Fenton reaction). The Fenton reaction consists of the degradation of hydrogen peroxide and the generation of ferric ion. Finally phosphate precipitates out with iron ions. In the simultaneous removal process, 1.6 mM nitrate, 9.0 mM hydrogen peroxide and 1.0 mM phosphate were completely removed by ZVI within 100, 15 and 15 min, respectively. The synergy among the reactions for the removal of nitrate, hydrogen peroxide and phosphate was found. In the individual pollutant removal experiment, the removal of phosphate by ZVI was limited to 80% after 300 min. Its removal rate was considerably improved in the presence of hydrogen peroxide and the complete removal of phosphate was achieved after 15 min. PMID:24798898

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

    PubMed Central

    2014-01-01

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

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

    SciTech Connect

    Newcomer, Darrell R.

    2009-02-09

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

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

    PubMed

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

    2014-01-01

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

  17. Microbial and mineral evolution in zero valent iron-based permeable reactive barriers during long-term operations.

    PubMed

    Kumar, Naresh; Millot, Romain; Battaglia-Brunet, Fabienne; Omoregie, Enoma; Chaurand, Perrine; Borschneck, Daniel; Bastiaens, Leen; Rose, Jérôme

    2016-03-01

    Impacts of subsurface biogeochemical processes over time have always been a concern for the long-term performance of zero valent iron (Fe(0))-based permeable reactive barriers (PRBs). To evaluate the biogeochemical impacts, laboratory experiments were performed using flow-through glass columns for 210 days at controlled temperature (20 °C). Two different particle sizes of Fe(0) were used in the columns, and to simulate indigenous microbial activity, extra carbon source was provided in the two columns (biotic columns) and the remaining two columns were kept abiotic using gamma radiations. Heavy metals (Zn, As) were removed efficiently in all the columns, and no exhaustion of treatment capability or clogging was observed during our experimental duration. Newly formed Fe mineral phases and precipitates were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and micro-XRF techniques in solid phase at the end of the experiment. In addition, 16S rRNA gene extraction was used for microbial community identification in biotic columns. During the incubation, microbial population shifted in favor of Desulfosporosinus species (sulfate-reducing bacteria) from initial dominance of Acidithiobacillus ferrooxidans in sediments. Dominant mineral phases detected in biotic columns were mackinawite (FeS) and sulfate green rust, while in abiotic columns, magnetite/maghemite phases were more prevalent. PMID:26604198

  18. Targeted removal of trichlorophenol in water by oleic acid-coated nanoscale palladium/zero-valent iron alginate beads.

    PubMed

    Chang, Jaewon; Woo, Heesoo; Ko, Myoung-Soo; Lee, Jaesang; Lee, Seockheon; Yun, Seong-Taek; Lee, Seunghak

    2015-08-15

    A new material was developed and evaluated for the targeted removal of trichlorophenol (TCP) from among potential interferents which are known to degrade removal activity. To achieve TCP-targeted activity, an alginate bead containing nanoscale palladium/zero-valent iron (Pd/nZVI) was coated with a highly hydrophobic oleic acid layer. The new material (Pd/nZVI-A-O) preferentially sorbed TCP from a mixture of chlorinated phenols into the oleic acid cover layer and subsequently dechlorinated it to phenol. The removal efficacy of TCP by Pd/nZVI-A-O was not affected by co-existing organic substances such as Suwannee River humic acid (SRHA), whereas the material without the oleic acid layer (Pd/nZVI-A) became less effective with increasing SRHA concentration. The inorganic substances nitrate and phosphate significantly reduced the reactivity of Pd/nZVI-A, however, Pd/nZVI-A-O showed similar TCP removal efficacies regardless of the initial inorganic ion concentrations. The influence of bicarbonate on the TCP removal efficacies of both Pd/nZVI-A and Pd/nZVI-A-O was not significant. The findings from this study suggest that Pd/nZVI-A-O, with its targeted, constant reactivity for TCP, would be effective for treating this contaminant in surface water or groundwater containing various competitive substrates. PMID:25819991

  19. Influence of humic acid on the colloidal stability of surface-modified nano zero-valent iron.

    PubMed

    Dong, Haoran; Lo, Irene M C

    2013-01-01

    To enhance colloidal stability of nano zero-valent iron (NZVI) used for groundwater remediation, the surfaces of such NZVI can be modified via coating with organic stabilizers. These surface stabilizers can electrostatically, sterically, or electrosterically stabilize NZVI suspensions in water, but their efficacy is affected by the presence of humic acid (HA) in groundwater. In this study, the effect of HA on the colloidal stability of NZVI coated with three types of stabilizers (i.e., polyacrylic acid (PAA), Tween-20 and starch) was evaluated. Differing stability behaviors were observed for different surface-modified NZVIs (SM-NZVI) in the presence of HA. Fluorescence spectroscopic analysis probed the possible interactions at the SM-NZVI-HA interface, providing a better understanding of the effect of HA on SM-NZVI stability. The adsorption of HA on the surface of PAA-modified NZVI via complexation with NZVI (rather than the PAA stabilizer) enhanced the electrosteric repulsion effect, increasing the stability of the particles. However, for NZVI modified with Tween-20 or starch, HA could interact with the surface stabilizer and apparently play a "bridge" role among the particles, which might induce aggregation of the particles. Therefore, the stability behavior of NZVI modified with Tween-20 or starch might have resulted from the combined effect of "bridging" and "electrosteric" exerted by HA. PMID:23123051

  20. Chromate removal by surface-modified nanoscale zero-valent iron: Effect of different surface coatings and water chemistry.

    PubMed

    Dong, Haoran; He, Qi; Zeng, Guangming; Tang, Lin; Zhang, Chang; Xie, Yankai; Zeng, Yalan; Zhao, Feng; Wu, Yanan

    2016-06-01

    This study investigated the correlation between the colloidal stability and reactivity of surface-modified nano zero-valent iron (SM-nZVI) as affected by the surface coating (i.e., polyacrylic acid [PAA] and starch) under various geochemical conditions. Generally, the colloidal stability of nZVI was enhanced with increasing loading of surface coating, while there is an optimum loading for the most efficient Cr(VI) removal by SM-nZVI. At lower loadings than the optimum loading, the surface coating could enhance the particle stabilization, facilitating the Cr(VI) reduction by providing more available surface sites. However, the over-loaded surface coating on the surface of nZVI particles decreased the Cr(VI) reduction due to the occupation of the reactive sites and the inhibition of the mass transfer of Cr(VI) ions from water to the particle surface by providing the electrostatic or steric repulsion. The effects of Ca(2+) ions or humic acid (HA) on the colloidal stability and reactivity of PAA-modified nZVI (P-nZVI) and starch-modified nZVI (S-nZVI) were examined. Differing stability behavior and reactivity were observed for different SM-nZVI. It was found that the presence of Ca(2+) or HA altered surface chemistry of SM-nZVI, the particle-particle interaction and the particle-contaminant interaction, and hence influencing the stability behavior and reactivity of the particles. PMID:26970032

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

    PubMed

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

    2014-08-15

    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

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

    PubMed

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

    2015-04-01

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

  3. Zero-valent iron enhanced methanogenic activity in anaerobic digestion of waste activated sludge after heat and alkali pretreatment.

    PubMed

    Zhang, Yaobin; Feng, Yinghong; Quan, Xie

    2015-04-01

    Heat or alkali pretreatment is the effective method to improve hydrolysis of waste sludge and then enhance anaerobic sludge digestion. However the pretreatment may inactivate the methanogens in the sludge. In the present work, zero-valent iron (ZVI) was used to enhance the methanogenic activity in anaerobic sludge digester under two methanogens-suppressing conditions, i.e. heat-pretreatment and alkali condition respectively. With the addition of ZVI, the lag time of methane production was shortened, and the methane yield increased by 91.5% compared to the control group. The consumption of VFA was accelerated by ZVI, especially for acetate, indicating that the acetoclastic methanogenesis was enhanced. In the alkali-condition experiment, the hydrogen produced decreased from 27.6 to 18.8 mL when increasing the ZVI dosage from 0 to 10 g/L. Correspondingly, the methane yield increased from 1.9 to 32.2 mL, which meant that the H2-utilizing methanogenes was enriched. These results suggested that the addition of ZVI into anaerobic digestion of sludge after pretreated by the heat or alkali process could efficiently recover the methanogenic activity and increase the methane production and sludge reduction. PMID:25681947

  4. Remediation and phytotoxicity of decabromodiphenyl ether contaminated soil by zero valent iron nanoparticles immobilized in mesoporous silica microspheres.

    PubMed

    Xie, Yingying; Cheng, Wen; Tsang, Pokeung Eric; Fang, Zhanqiang

    2016-01-15

    Polybrominated diphenyl ethers (PBDEs) are a new class of environmental pollutants which easily accumulated in the soil, especially at e-waste sites. However, knowledge about their phytotoxicity after degradation is not well understood. Nano zero valent iron (nZVI) immobilized in mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) synthesized in this study was utilized to remove decabromodiphenyl ether (BDE209) from soil. Results revealed that the removal efficiency of BDE209 can be achieved 78% within 120 h using a dosage of 0.165 g g(-1) and a pH of 5.42. Furthermore, the removal efficiency enhanced with increasing soil moisture content and the decreasing of initial BDE209 concentration. Phytotoxicity assays (biomass and germination rate, shoots and roots elongation of Chinese cabbage) were carried out to provide a preliminary risk assessment of treated soil for the application of SiO2@FeOOH@Fe. PMID:26560640

  5. Structural Evolution of Nanoscale Zero-Valent Iron (nZVI) in Anoxic Co(2+) Solution: Interactional Performance and Mechanism.

    PubMed

    Zhang, Yalei; Chen, Wen; Dai, Chaomeng; Zhou, Chuanlong; Zhou, Xuefei

    2015-01-01

    The structures of nanoscale zero-valent iron (nZVI) particles evolving during reactions, and the reactions are influenced by the evolved structures. To understand the removal process in detail, it is important to investigate the relationships between the reactions and structural evolution. Using high resolution-transmission electron microscopy (HR-TEM), typical evolved structures (sheet coprecipitation and cavity corrosion) of nZVI in anoxic Co(2+) solutions were revealed. The system pH (pH measured in mixture), which controls the stability of coprecipitation and the nZVI corrosion rate, were found to be the determining factors of structural evolutions. X-ray photoelectron spectroscopy (XPS) results indicated that the formation and dissolution of sheet structure impacts on the ratio of Fe(0) on the nZVI surface and the surface Co(2+) reduction. The cavity structure provides the possibility of Co migration from the surface to the bulk of nZVI, leading to continuous removal. Subacidity conditions could accelerate the evolution and improve the removal; the results of structurally controlled reactions further indicated that the removal was suspended by the sheet structure and enhanced by cavity structure. The results and discussion in this paper revealed the "structural influence" crucial for the full and dynamical understanding of nZVI reactions. PMID:26355955

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

    PubMed

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

    2015-04-01

    Magnetite nanoparticles were used as an additive material in a zero-valent iron (Fe0) reaction to reduce nitrate in groundwater and its effects on nitrate removal were investigated. The addition of nano-sized magnetite (NMT) to Fe0 reactor markedly increased nitrate reduction, with the rate proportionally increasing with NMT loading. Field emission scanning electron microscopy analysis revealed that NMT aggregates were evenly distributed and attached on the Fe0 surface due to their magnetic properties. The rate enhancement effect of NMT is presumed to arise from its role as a corrosion promoter for Fe0 corrosion as well as an electron mediator that facilitated electron transport from Fe0 to adsorbed nitrate. Nitrate reduction by Fe0 in the presence of NMT proceeded much faster in groundwater (GW) than in de-ionized water. The enhanced reduction of nitrate in GW was attributed to the adsorption or formation of surface complex by the cationic components in GW, i.e., Ca2+ and Mg2+, in the Fe0-H2O interface that promoted electrostatic attraction of nitrate to the reaction sites. Moreover, the addition of NMT imparted superior longevity to Fe0, enabling completion of four nitrate reduction cycles, which otherwise would have been inactivated during the first cycle without an addition of NMT. The results demonstrate the potential applicability of a Fe0/NMT system in the treatment of nitrate-contaminated GW. PMID:25665757

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

    PubMed

    Kowalski, Krzysztof P; Søgaard, Erik G

    2014-12-01

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

  8. Inhibition or promotion of biodegradation of nitrate by Paracoccus sp. in the presence of nanoscale zero-valent iron.

    PubMed

    Jiang, Chenghong; Xu, Xuping; Megharaj, Mallavarapu; Naidu, Ravendra; Chen, Zuliang

    2015-10-15

    To investigate the effect of nanoscale zero-valent iron (nZVI) on the growth of Paracoccus sp. strain and biodenitrification under aerobic conditions, specific factors were studied, pH, concentration of nitrate, Fe (II) and carbon dioxide. Low concentration of nZVI (50mg/L) promoted both cell growth and biodegradation of nitrate which rose from 69.91% to 76.16%, while nitrate removal fell to 67.10% in the presence of high nZVI concentration (1000 mg/L). This may be attributed to the ions produced in nZVI corrosion being used as an electron source for the biodegradation of nitrate. However, the excess uptake of Fe (II) causes oxidative damage to the cells. To confirm this, nitrate was completely removed after 20 h when 100mg/L Fe (II) was added to the solution, which is much faster than the control (86.05%, without adding Fe (II)). However, nitrate removal reached only 45.64% after 20 h, with low cell density (OD 600=0.62) in the presence of 300 mg/L Fe (II). Characterization techniques indicated that nZVI adhered to microorganism cell membranes. These findings confirmed that nZVI could affect the activity of the strain and consequently change the biodenitrification. PMID:26047857

  9. Structural Evolution of Nanoscale Zero-Valent Iron (nZVI) in Anoxic Co2+ Solution: Interactional Performance and Mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Yalei; Chen, Wen; Dai, Chaomeng; Zhou, Chuanlong; Zhou, Xuefei

    2015-09-01

    The structures of nanoscale zero-valent iron (nZVI) particles evolving during reactions, and the reactions are influenced by the evolved structures. To understand the removal process in detail, it is important to investigate the relationships between the reactions and structural evolution. Using high resolution-transmission electron microscopy (HR-TEM), typical evolved structures (sheet coprecipitation and cavity corrosion) of nZVI in anoxic Co2+ solutions were revealed. The system pH (pH measured in mixture), which controls the stability of coprecipitation and the nZVI corrosion rate, were found to be the determining factors of structural evolutions. X-ray photoelectron spectroscopy (XPS) results indicated that the formation and dissolution of sheet structure impacts on the ratio of Fe(0) on the nZVI surface and the surface Co2+ reduction. The cavity structure provides the possibility of Co migration from the surface to the bulk of nZVI, leading to continuous removal. Subacidity conditions could accelerate the evolution and improve the removal; the results of structurally controlled reactions further indicated that the removal was suspended by the sheet structure and enhanced by cavity structure. The results and discussion in this paper revealed the “structural influence” crucial for the full and dynamical understanding of nZVI reactions.

  10. Nanosilver and Nano Zero-Valent Iron Exposure Affects Nutrient Exchange Across the Sediment-Water Interface.

    PubMed

    Buchkowski, Robert W; Williams, Clayton J; Kelly, Joel; Veinot, Jonathan G C; Xenopoulos, Marguerite A

    2016-01-01

    To examine how nanoparticles influence biogeochemical cycles in streams, we studied the acute impact of nanosilver (nAg) and nanoparticulate zero-valent iron (nZVI) exposure on nutrient and oxygen exchange across the sediment-water interface of two streams (agricultural canal and wetland) that differed in their water quality and sediment characteristics. At the agricultural site, nAg increased oxygen consumption and decreased N2 flux rates from that observed in control incubations. nZVI caused sediment-water systems from both streams to go hypoxic within 1.5 h of exposure. N2 flux rates were at least an order of magnitude higher in nZVI treatments as compared to control. Water column nitrate and nitrite concentrations were not impacted by nZVI exposure but total dissolved phosphorus concentrations were higher in cores treated with nZVI. nAg and nZVI exposure to surface water ecosystems can disrupt ecological function across the sediment-water interface. PMID:26611367

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

    PubMed

    Babuponnusami, Arjunan; Muthukumar, Karuppan

    2013-03-01

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

  12. Functional chitosan-stabilized nanoscale zero-valent iron used to remove acid fuchsine with the assistance of ultrasound.

    PubMed

    Jin, Xiaoying; Zhuang, Zechao; Yu, Bing; Chen, Zhengxian; Chen, Zuliang

    2016-01-20

    Chitosan-stabilized nanoscale zero-valent iron (CS-nZVI) was prepared and used for the removal of acid fuchsine (AF) from aqueous solution with the assistance of ultrasound. More than 98.9% of AF was removed using CS-nZVI, aged CS-nZVI (exposed to air for 2 months), while only 14.6% removal efficiency was achieved after 15 min by chitosan alone with the assistance of ultrasound. Scanning electron microscopy (SEM) confirmed that chitosan polymers were arranged in a homocentric layered structure. Thus, the polymer can prevent the aggregation of nZVI and increase their anti-oxidation capacity. X-ray diffraction (XRD) also suggested that the chitosan used in synthesis may protect nZVI nanoparticles from air oxidation. Different factors impacting on the removal of AF using CS-nZVI showed that the reduction increased when dosage and temperature increased, but decreased when pH and initial concentration rose. Kinetic studies revealed that the removal of AF fitted well to the pseudo-first-order model. The apparent activation energy was 55.34 kJ/mol, indicating a chemically controlled reaction. Finally, the application of CS-nZVI in dyeing wastewater led to a removal efficiency of 99% of AF, while the reuse test confirmed that AF's removal efficiency declined from 99.6 to 39.3% after seven cycles. PMID:26572450

  13. Fate of nitrogen species in nitrate reduction by nanoscale zero valent iron and characterization of the reaction kinetics.

    PubMed

    Hwang, Y H; Kim, D G; Ahn, Y T; Moon, C M; Shin, H S

    2010-01-01

    This study investigates the fate of nitrogen species during nitrate reduction by nanoscale zero valent iron (NZVI) as well as the related kinetics. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The pseudo first order kinetic constant of nitrate reduction at 30 degrees C with an NZVI/nitrate ratio of 1.25:1, which were the reference conditions of this study, was 4.08 h(-1) (R(2)=0.955). A nitrogen mass balance was established by quantitative analysis of aqueous-phase and gas-phase nitrogen species. The results confirm that the nitrate was converted to ammonium ion, that ammonia stripping subsequently occurred under a strong alkaline condition, and that the total amount of aqueous nitrogen was consequently reduced. The nitrate reduction rate also increased with a lower pH and a higher temperature when microscale ZVI was used. However, in contrast to the reaction by microscale ZVI, the nitrate reduction rate by NZVI was higher for an unbuffered condition, possibly due to the abundance of surface atoms and the smaller size. PMID:20150707

  14. Decreasing ammonium generation using hydrogenotrophic bacteria in the process of nitrate reduction by nanoscale zero-valent iron.

    PubMed

    An, Yi; Li, Tielong; Jin, Zhaohui; Dong, Meiying; Li, Qianqian; Wang, Shuaima

    2009-10-15

    An integrated nitrate treatment using nanoscale zero-valent iron (NZVI) and Alcaligenes eutrophus, which is a kind of hydrogenotrophic denitrifying bacteria, was conducted to remove nitrate and decrease ammonium generation. Within 8 days, nitrate was removed completely in the reactors containing NZVI particles plus bacteria while the proportion of ammonium generated was only 33%. That is a lower reduction rate but a smaller proportion of ammonium relative to that in abiotic reactors. It was also found that ammonium generation experienced a biphasic process, involving an increasing period and a stable period. After domestication of the bacteria, the combined NZVI-cell system could remove all nitrate without ammonium released when the refreshed nitrate was introduced. Nitrate reduction and the final product distribution were also studied in batch reactors amended with different initial NZVI contents and biomass concentrations, respectively. Both the nitrate removal rate and the ammonium yield decreased when the initial content of NZVI reduced and the initial biomass concentration increased. However, about 27% of the nitrate was converted to ammonium when excess bacteria (OD(422)=0.026) were used, which was higher than that with appropriate amount of bacteria. PMID:19665759

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

    PubMed

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

    2015-02-01

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

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

    PubMed

    Xu, Guiying; Wang, Jiangbo; Lu, Mang

    2014-12-01

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

  17. Structural Evolution of Nanoscale Zero-Valent Iron (nZVI) in Anoxic Co2+ Solution: Interactional Performance and Mechanism

    PubMed Central

    Zhang, Yalei; Chen, Wen; Dai, Chaomeng; Zhou, Chuanlong; Zhou, Xuefei

    2015-01-01

    The structures of nanoscale zero-valent iron (nZVI) particles evolving during reactions, and the reactions are influenced by the evolved structures. To understand the removal process in detail, it is important to investigate the relationships between the reactions and structural evolution. Using high resolution-transmission electron microscopy (HR-TEM), typical evolved structures (sheet coprecipitation and cavity corrosion) of nZVI in anoxic Co2+ solutions were revealed. The system pH (pH measured in mixture), which controls the stability of coprecipitation and the nZVI corrosion rate, were found to be the determining factors of structural evolutions. X-ray photoelectron spectroscopy (XPS) results indicated that the formation and dissolution of sheet structure impacts on the ratio of Fe(0) on the nZVI surface and the surface Co2+ reduction. The cavity structure provides the possibility of Co migration from the surface to the bulk of nZVI, leading to continuous removal. Subacidity conditions could accelerate the evolution and improve the removal; the results of structurally controlled reactions further indicated that the removal was suspended by the sheet structure and enhanced by cavity structure. The results and discussion in this paper revealed the “structural influence” crucial for the full and dynamical understanding of nZVI reactions. PMID:26355955

  18. Removal of EDTA from low pH printed-circuit board wastewater in a fluidized zero valent iron reactor.

    PubMed

    Chen, Shiao-Shing; Hsu, Hong-Der; Lin, Yi-Jiun; Chin, Pei-Ying

    2008-01-01

    Fluidized zero valent iron (ZVI) process was adopted to reduce ethylenediaminetetraacetic acid (EDTA) from low pH printed-circuit board (PCB) wastewater for two reasons: (1) low pH of the wastewater favoring the ZVI reaction; (2) higher ZVI utilization for fluidized process due to abrasive motion of the ZVI. The results showed that the degradation of EDTA was greatly enhanced under acidic pH, longer hydraulic detention time (HRT) and presence of dissolved oxygen (DO). Without addition of oxygen, 65% of EDTA was removed with capacity of 7.33 mg EDTA/g ZVI at pH 2, ZVI dosage of 424 g/L and HRT 10 min. With 6.8 mg/L of DO, 83% of EDTA was reduced with capacity of 19.01 mg EDTA/g ZVI for the same experimental condition. The presence of oxygen/ZVI initiated a Fenton type reaction to reduce EDTA. The end product after EDTA degradation was analyzed by high performance liquid chromoagraphy (HPLC), where propionic acid (C(2)H(5)COOH) was observed, indicating EDTA (oxidation number for carbon is 2) was oxidized to propionic acid (oxidation number for carbon is 3). Nitrogen species was also measured and the nitrogen in EDTA was converted to ammonium instead of nitrate and nitrite. PMID:18725736

  19. Inhibiting excessive acidification using zero-valent iron in anaerobic digestion of food waste at high organic load rates.

    PubMed

    Kong, Xin; Wei, Yonghong; Xu, Shuang; Liu, Jianguo; Li, Huan; Liu, Yili; Yu, Shuyao

    2016-07-01

    Excessive acidification occurs frequently in food waste (FW) anaerobic digestion (AD) due to the high carbon-to-nitrogen ratio of FW. In this study, zero-valent iron (ZVI) was applied to prevent the excessive acidification. All of the control groups, without ZVI addition (pH∼5.3), produced little methane (CH4) and had high volatile fatty acids/bicarbonate alkalinity (VFA/ALK). By contrast, at OLR of 42.32gVS/Lreactor, the pH of effluent from the reactors with 0.4g/gVSFWadded of ZVI increased to 7.8-8.2, VFA/ALK decreased to <0.1, and the final CH4 yield was ∼380mL/gVSFWadded, suggesting inhibition of excessive acidification. After adding powdered or scrap metal ZVI to the acidogenic reactors, the fractional content of butyric acid changed from 30-40% to 0%, while, that of acetic acid increased. These results indicate that adding ZVI to FW digestion at high OLRs could eliminate excessive acidification by promoting butyric acid conversion and enhancing methanogen activity. PMID:26998799

  20. Nanoscaled zero valent iron/graphene composite as an efficient adsorbent for Co(II) removal from aqueous solution.

    PubMed

    Xing, Min; Wang, Jianlong

    2016-07-15

    A magnetic graphene, i.e., nanoscaled zero valent iron/graphene (0FG) composite, was prepared, characterized and applied for the removal of Co(II) from aqueous solution. The magnetic graphene (0FG) was synthesized through reduction of graphene oxide (GO) and ferrous ions by potassium borohydride. The kinetics and isotherms of Co(II) adsorption onto 0FG were investigated. The mechanism for Co(II) removal was proposed based on the Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and the X-ray absorption fine structure (XAFS) analysis. The results showed that pseudo second-order models and the Freundlich isotherm model fitted well with the data obtained. The adsorption capacity of 0FG was calculated from the Langmuir isotherm, which was 65.58, 101.60 and 134.27mg/g at 10, 20 and 30°C, respectively. Thermodynamic parameters suggested that the adsorption process was endothermic and spontaneous. Co(2+) was stabilized by γ-FeOOH/γ-Fe2O3/Fe3O4 on the surface of graphene sheets, forming CoFe2O4-like nanocrystals. The coordination numbers and interatomic distances indicated that Co(2+) mainly occupied the octahedral site, while pseudo-tetrahedral coordination may occur by dehydroxylation of Co(O,OH)6. Magnetic graphene is a potential adsorbent for Co(2+) removal. PMID:27115333

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

    PubMed

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

    2014-10-01

    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

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

    PubMed

    Laumann, Susanne; Micić, Vesna; Hofmann, Thilo

    2014-03-01

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

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

    PubMed

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

    2014-01-01

    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

  4. Identifying abiotic chlorinated ethene degradation: characteristic isotope patterns in reaction products with nanoscale zero-valent iron.

    PubMed

    Elsner, Martin; Chartrand, Michelle; Vanstone, Nancy; Couloume, Georges Lacrampe; Lollar, Barbara Sherwood

    2008-08-15

    Carbon isotope fractionation is of great interest in assessing chlorinated ethene transformation by nanoscale zero-valent iron at contaminated sites, particularly in distinguishing the effectiveness of an implemented abiotic degradation remediation scheme from intrinsic biotic degradation. Transformation of trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), and vinyl chloride (VC) with two types of nanoscale iron materials showed different reactivity trends, but relatively consistent carbon isotope enrichment factors (epsilon) of -19.4 per thousand +/- 1.8 per thousand (VC), -21.7 per thousand +/- 1.8 per thousand (cis-DCE), and -23.5 per thousand +/- 2.8 per thousand (TCE) with one type of iron (FeBH), and from -20.9 per thousand +/- 1.1 per thousand to -26.5 per thousand +/- 1.5 per thousand (TCE) with the other (FeH2). Products of the dichloroelimination pathway (ethene, ethane, and acetylene) were consistently 10 per thousand more isotopically depleted than those of the hydrogenolysis pathway (cis-DCE from TCE, VC from cis-DCE), displaying a characteristic pattern that may serve as an indicator of abiotic dehalogenation reactions and as a diagnostic parameter for differentiating the effects of abiotic versus biotic degradation. In contrast, the product-related enrichment factors of each respective pathway varied significantly in different experiments. Because such variation would not be expected for independent pathways with constant kinetic isotope effects, our data give preliminary evidence that the two pathways may share an irreversible first reaction step with subsequent isotopically sensitive branching. PMID:18767652

  5. The limitations of applying zero-valent iron technology in contaminants sequestration and the corresponding countermeasures: the development in zero-valent iron technology in the last two decades (1994-2014).

    PubMed

    Guan, Xiaohong; Sun, Yuankui; Qin, Hejie; Li, Jinxiang; Lo, Irene M C; He, Di; Dong, Haoran

    2015-05-15

    Over the past 20 years, zero-valent iron (ZVI) has been extensively applied for the remediation/treatment of groundwater and wastewater contaminated with various organic and inorganic pollutants. Based on the intrinsic properties of ZVI and the reactions that occur in the process of contaminants sequestration by ZVI, this review summarizes the limitations of ZVI technology and the countermeasures developed in the past two decades (1994-2014). The major limitations of ZVI include low reactivity due to its intrinsic passive layer, narrow working pH, reactivity loss with time due to the precipitation of metal hydroxides and metal carbonates, low selectivity for the target contaminant especially under oxic conditions, limited efficacy for treatment of some refractory contaminants and passivity of ZVI arising from certain contaminants. The countermeasures can be divided into seven categories: pretreatment of pristine ZVI to remove passive layer, fabrication of nano-sized ZVI to increase the surface area, synthesis of ZVI-based bimetals taking advantage of the catalytic ability of the noble metal, employing physical methods to enhance the performance of ZVI, coupling ZVI with other adsorptive materials and chemically enhanced ZVI technology, as well as methods to recover the reactivity of aged ZVI. The key to improving the rate of contaminants removal by ZVI and broadening the applicable pH range is to enhance ZVI corrosion and to enhance the mass transfer of the reactants including oxygen and H(+) to the ZVI surface. The characteristics of the ideal technology are proposed and the future research needs for ZVI technology are suggested accordingly. PMID:25770444

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    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.

  7. Removal of nitrobenzene by immobilized nanoscale zero-valent iron: Effect of clay support and efficiency optimization

    NASA Astrophysics Data System (ADS)

    Li, Xiaoguang; Zhao, Ying; Xi, Beidou; Mao, Xuhui; Gong, Bin; Li, Rui; Peng, Xing; Liu, Hongliang

    2016-05-01

    In this study, natural clays were used as the support for nanoscale zero-valent iron (nZVI) to fulfill affordable and efficient decontamination materials. In comparison with the kaolinite (K) and montmorillonite (M) supported nZVI materials (K-nZVI and M-nZVI), Hangjin clay supported nZVI (HJ-nZVI) exhibited the best performance for nitrobenzene (NB) removal because of its favorable characteristics, such as higher specific surface area (SSA, 82.0 m2 g-1), larger pore volume (0.1198 cm3 g-1) and bigger average pore diameter (6.2 nm). The NB removal efficiency achieved by HJ-nZVI (93.2 ± 2.8%) was much higher than these achieved by HJ clay alone (38.2 ± 2.3%), nZVI alone (52.3 ± 2.5%) and by the combined use of nZVI and HJ clay (70.2 ± 1.3%). The superior performance of HJ-nZVI was associated with three aspects: the even distribution of nZVIs onto HJ clay, higher payload efficiency of nZVIs and the stronger adsorption capability of HJ clay support. Higher SSA, larger pore volume, favorable cation exchange capacity and structural negative charges all facilitated the payload of iron onto HJ clay. The adsorption process accelerated the reduction via increasing the local concentration of aqueous NB. The high efficiency of HJ-nZVI for decontamination warranted its promising prospect in remediation applications.

  8. The dual effects of carboxymethyl cellulose on the colloidal stability and toxicity of nanoscale zero-valent iron.

    PubMed

    Dong, Haoran; Xie, Yankai; Zeng, Guangming; Tang, Lin; Liang, Jie; He, Qi; Zhao, Feng; Zeng, Yalan; Wu, Yanan

    2016-02-01

    Nanoscale zero-valent iron (NZVI) particles are usually modified with surface coating to mitigate the particle stability in water during the environmental application. However, the surface coating may not only influence the particle stabilization but also the particle cytotoxicity. In this study, we investigated the dual effects of carboxymethyl cellulose (CMC) on the colloidal stability and cytotoxicity of NZVI towards gram-negative Escherichia coli (E. coli) and discussed the interrelation between particle stability and cytotoxicity. The effect of CMC concentration, ionic strength (Ca(2+)) and aging treatment on the particle cytotoxicity were also examined. Specifically, the aqueous stability of NZVI suspensions with CMC ratio dose-dependently strengthened within 1 h. The inactivation of E. coli by bare NZVI was significant and concentration- and time-dependent. On the contrary, an increasing reduction in cytotoxicity of NZVI with CMC ratio increasing was observed, even though the particles became more dispersed. TEM analysis demonstrates the membrane disruption and the cellular internalization of nanoparticles after exposure of E. coli to NZVI. However, in the case of CMC-modified NZVI (CNZVI), the bacterial cell wall displays an outer shell of a layer of nanoparticles attached around the outer membrane, but the cell membrane was kept intact. The presence of Ca(2+) can either increase or decrease the cytotoxicity of NZVI and CNZVI, depending on the concentration. The aged NZVI and CNZVI particles did not seem to present obvious bactericidal effect due to the transformation of Fe(0) to the less toxic or non-toxic iron oxides, as indicated by the XRD analysis. PMID:26519799

  9. Novel sequential process for enhanced dye synergistic degradation based on nano zero-valent iron and potassium permanganate.

    PubMed

    Wang, Xiangyu; Liu, Peng; Fu, Minglai; Ma, Jun; Ning, Ping

    2016-07-01

    A novel synergistic technology based on nano zero-valent iron (NZVI) and potassium permanganate (KMnO4) was developed for treatment of dye wastewater. The synergistic technology was significantly superior, where above 99% of methylene blue (MB) was removed, comparatively, removal efficiencies of MB with the sole technology of NZVI and KMnO4 at pH 6.39 being 52.9% and 63.1%, respectively. The advantages of this technology include (1) the in situ formed materials (manganese (hydr)oxides, iron hydroxides and MnFe oxide), resulting in the stable and high removal efficiency of MB and (2) high removal capacity in a wide range of pH value. Compared with simultaneous addition system of NZVI and KMnO4, MB removal was remarkably improved by sequential addition system, especially when KMnO4 addition time was optimized at 20 min. Analyses of crystal structure (XRD), morphological difference (FE-SEM), element valence and chemical groups (XPS) of NZVI before and after reaction had confirmed the formation of in situ materials, which obviously enhanced removal of MB by oxidation and adsorption. More importantly, the roles of in situ formed materials and degradation mechanism were innovatively investigated, and the results suggested that NCH3 bond of MB molecule was attacked by oxidants (KMnO4 and in situ manganese (hydr)oxides) at position C1 and C9, resulting in cleavage of chromophore. This study provides new insights about an applicable technology for treatment of dye wastewater. PMID:27105151

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

    SciTech Connect

    Lynch, P. L.

    1999-01-15

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

  11. Effect of natural organic matter on toxicity and reactivity of nano-scale zero-valent iron.

    PubMed

    Chen, Jiawei; Xiu, Zongming; Lowry, Gregory V; Alvarez, Pedro J J

    2011-02-01

    Nano-scale zero-valent iron (NZVI) particles are increasingly used to remediate aquifers contaminated with hazardous oxidized pollutants such as trichloroethylene (TCE). However, the high reduction potential of NZVI can result in toxicity to indigenous bacteria and hinder their participation in the cleanup process. Here, we report on the mitigation of the bactericidal activity of NZVI towards gram-negative Escherichia coli and gram-positive Bacillus subtilis in the presence of Suwannee River humic acids (SRHA), which were used as a model for natural organic matter (NOM). B. subtilis was more tolerant to NZVI (1 g/L) than E. coli in aerobic bicarbonate-buffered medium. SRHA (10 mg/L) significantly mitigated toxicity, and survival rates after 4 h exposure increased to similar levels observed for controls not exposed to NZVI. TEM images showed that the surface of NZVI and E. coli was surrounded by a visible floccus. This decreased the zeta potential of NZVI from -30 to -45 mV and apparently exerted electrosteric hindrance to minimize direct contact with bacteria, which mitigated toxicity. H(2) production during anaerobic NZVI corrosion was not significantly hindered by SRHA (p > 0.05), However, NZVI reactivity towards TCE (20 mg/L), assessed by the first-order dechlorination rate coefficient, decreased by 23%. Overall, these results suggest that the presence of NOM offers a tradeoff for NZVI-based remediation, with higher potential for concurrent or sequential bioremediation at the expense of partially inhibited abiotic reactivity with the target contaminant (TCE). PMID:21232782

  12. PCE dissolution and simultaneous dechlorination by nanoscale zero-valent iron particles in a DNAPL source zone.

    PubMed

    Fagerlund, F; Illangasekare, T H; Phenrat, T; Kim, H-J; Lowry, G V

    2012-04-01

    While the capability of nanoscale zero-valent iron (NZVI) to dechlorinate organic compounds in aqueous solutions has been demonstrated, the ability of NZVI to remove dense non-aqueous phase liquid (DNAPL) from source zones under flow-through conditions similar to a field scale application has not yet been thoroughly investigated. To gain insight on simultaneous DNAPL dissolution and NZVI-mediated dechlorination reactions after direct placement of NZVI into a DNAPL source zone, a combined experimental and modeling study was performed. First, a DNAPL tetrachloroethene (PCE) source zone with emplaced NZVI was built inside a small custom-made flow cell and the effluent PCE and dechlorination byproducts were monitored over time. Second, a model for rate-limited DNAPL dissolution and NZVI-mediated dechlorination of PCE to its three main reaction byproducts with a possibility for partitioning of these byproducts back into the DNAPL was formulated. The coupled processes occurring in the flow cell were simulated and analyzed using a detailed three-dimensional numerical model. It was found that subsurface emplacement of NZVI did not markedly accelerate DNAPL dissolution or the DNAPL mass-depletion rate, when NZVI at a particle concentration of 10g/L was directly emplaced in the DNAPL source zone. To react with NZVI the DNAPL PCE must first dissolve into the groundwater and the rate of dissolution controls the longevity of the DNAPL source. The modeling study further indicated that faster reacting particles would decrease aqueous contaminant concentrations but there is a limit to how much the mass removal rate can be increased by increasing the dechlorination reaction rate. To ensure reduction of aqueous contaminant concentrations, remediation of DNAPL contaminants with NZVI should include emplacement in a capture zone down-gradient of the DNAPL source. PMID:22326687

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

    PubMed

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

    2014-01-30

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

  14. Nano-scale zero valent iron transport in a variable aperture dolomite fracture and a glass fracture

    NASA Astrophysics Data System (ADS)

    Mondal, P.; Sleep, B. E.; Cui, Z.; Zhou, Z.

    2014-12-01

    Experiments and numerical simulations are being performed to understand the transport behavior of carboxymethyl cellulose polymer stabilized nano-scale zero valent iron (nZVI) in a variable aperture dolomite rock fracture and a variable aperture glass replica of a fractured slate. The rock fracture was prepared by artificially inducing a fracture in a dolomite block along a stylolite, and the glass fracture was prepared by creating molds with melted glass on two opposing sides of a fractured slate rock block. Both of the fractures were 0.28 m in length and 0.21 m in width. Equivalent hydraulic apertures are about 110 microns for the rock fracture and 250 microns for the glass replica fracture. Sodium bromide and lissamine green B (LGB) serve as conservative tracers in the rock fracture and glass replica fracture, respectively. A dark box set-up with a light source and digital camera is being used to visualize the LGB and CMC-nZVI movement in the glass fracture. Experiments are being performed to determine the effects of water specific discharge and CMC concentration on nZVI transport in the fractures. Transmission electron microscopy, dynamic light scattering, and UV-visual spectrophotometry were performed to determine the stability and characteristics of the CMC-nZVI mixture. The transport of bromide, LGB, CMC, and CMC-nZVI in both fractures is being evaluated through analysis of the effluent concentrations. Time-lapse images are also being captured for the glass fracture. Bromide, LGB, and CMC recoveries have exceeded 95% in both fractures. Significant channeling has been observed in the fractures for CMC transport due to viscous effects.

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

    PubMed

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

    2013-10-01

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

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

    SciTech Connect

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

    2000-06-01

    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.

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

    PubMed

    Choi, Kyunghoon; Lee, Woojin

    2012-04-15

    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

  18. Polyelectrolyte multilayer-assisted immobilization of zero-valent iron nanoparticles onto polymer nanofibers for potential environmental applications.

    PubMed

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

    2009-12-01

    We report a facile approach to synthesizing and immobilizing zero-valent iron nanoparticles (ZVI NPs) onto polyelectrolyte (PE) multilayer-assembled electrospun polymer nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning were assembled with multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and polyacrylic acid (PAA) through electrostatic layer-by-layer assembly. The formed PAA/PDADMAC multilayers onto CA nanofibers were then used as a nanoreactor to complex Fe(II) ions through the binding with the free carboxyl groups of PAA for subsequent reductive formation of ZVI NPs. Combined scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetry analysis studies demonstrate that the ZVI NPs are successfully synthesized and uniformly distributed into the PE multilayers assembled onto the CA nanofibers. The produced hybrid nanofibrous mats containing ZVI NPs were found to exhibit superior capability to decolorize acid fuchsin, an organic dye in dyeing wastewater. We show that the loading capacity of ZVI NPs can be tuned by changing the number of PE layers and the cycles of binding/reduction process. Increasing the number of the binding/reduction cycles leads to a slight bigger size of the ZVI NPs, which is not beneficial for improving the reactivity of ZVI NPs. The present approach to synthesizing and immobilizing ZVI NPs onto polymer nanofibers opens a new avenue to fabricating various fiber-based composite materials with a high surface area to volume ratio for environmental, catalytic, and sensing applications. PMID:20356166

  19. Particles and enzymes: Combining nanoscale zero valent iron and organochlorine respiring bacteria for the detoxification of chloroethane mixtures.

    PubMed

    Koenig, Joanna C; Boparai, Hardiljeet K; Lee, Matthew J; O'Carroll, Denis M; Barnes, Robert J; Manefield, Michael J

    2016-05-01

    Nanoscale zero valent iron (nZVI) and organochlorine respiring bacteria (ORB) are two technologies used to detoxify chlorinated aliphatic hydrocarbons (CAHs). nZVI can rapidly detoxify high CAH concentrations, but is quickly oxidised and unable to degrade certain CAHs (e.g., 1,2-dichlorothane). In contrast, ORB can dechlorinate CAHs resistant to nZVI (e.g., 1,2-dichlorothane) but are inhibited by other CAHs of concern degradable by nZVI (e.g., chloroform and carbon tetrachloride). Combining the two was proposed as a unique treatment train to overcome each technology's shortcomings. In this study, this combined remedy was investigated using a mixture of 1,2-dichloroethane, degradable by ORB but not nZVI, and 1,1,2-trichloroethane, susceptible to both. Results indicated that nZVI rapidly dechlorinated 1,1,2-trichloroethane when supplied above 0.5g/L, however ORB were inhibited and unable to dechlorinate 1,2-dichloroethane. pH increase and ionic species associated with nZVI did not significantly impact ORB, pinpointing Fe(0) particles as responsible for ORB inhibition. Below 0.05g/L nZVI, ORB activity was stimulated. Results suggest that combining ORB and nZVI at appropriate doses can potentially treat a wider range of CAHs than each individual remedy. At field sites where nZVI was applied, it is likely that in situ nZVI concentrations were below the threshold of negative consequences. PMID:26808236

  20. Stimulation of Peanut Seedling Development and Growth by Zero-Valent Iron Nanoparticles at Low Concentrations

    PubMed Central

    Li, Xuan; Yang, Yuechao; Gao, Bin; Zhang, Min

    2015-01-01

    Because of its strong pollutant degradation ability, nanoscale zerovalent iron (NZVI) has been introduced to soils and groundwater for remediation purposes, but its impacts on plants are still not very clear. In this work, the effects of low concentration (10–320 μmol/L) NZVI particles on seed germination and growth of peanut plants were evaluated. The exposure of peanut seeds to NZVI at all the tested concentrations altered the seed germination activity, especially the development of seedlings. In comparison with the deionized water treated controls (CK), all of the NZVI treatments had significantly larger average lengths. Further investigations with transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) suggested that NZVI particles may penetrate the peanut seed coats to increase the water uptake to stimulate seed germination. The growth experiments showed that although NZVI at a relatively high concentration (320μmol/L) showed phytotoxicity to the peanut plants, the lower concentrations of NZVI particles stimulated the growth and root development of the plants. At certain concentrations (e.g., 40 and 80 μmol/L), the NZVI treated samples were even better than the ethylenediaminetetraacetate-iron (EDTA-Fe) solution, a commonly used iron nutrient solution, in stimulating the plant growth. This positive effect was probably due to the uptake of NZVI by the plants, as indicated in the TEM analyses. Because low concentrations of NZVI particles stimulated both the seedling development and growth of peanut, they might be used to benefit the growth of peanuts in large-scale agricultural settings. PMID:25901959

  1. Stimulation of peanut seedling development and growth by zero-valent iron nanoparticles at low concentrations.

    PubMed

    Li, Xuan; Yang, Yuechao; Gao, Bin; Zhang, Min

    2015-01-01

    Because of its strong pollutant degradation ability, nanoscale zerovalent iron (NZVI) has been introduced to soils and groundwater for remediation purposes, but its impacts on plants are still not very clear. In this work, the effects of low concentration (10-320 μmol/L) NZVI particles on seed germination and growth of peanut plants were evaluated. The exposure of peanut seeds to NZVI at all the tested concentrations altered the seed germination activity, especially the development of seedlings. In comparison with the deionized water treated controls (CK), all of the NZVI treatments had significantly larger average lengths. Further investigations with transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) suggested that NZVI particles may penetrate the peanut seed coats to increase the water uptake to stimulate seed germination. The growth experiments showed that although NZVI at a relatively high concentration (320 μmol/L) showed phytotoxicity to the peanut plants, the lower concentrations of NZVI particles stimulated the growth and root development of the plants. At certain concentrations (e.g., 40 and 80 μmol/L), the NZVI treated samples were even better than the ethylenediaminetetraacetate-iron (EDTA-Fe) solution, a commonly used iron nutrient solution, in stimulating the plant growth. This positive effect was probably due to the uptake of NZVI by the plants, as indicated in the TEM analyses. Because low concentrations of NZVI particles stimulated both the seedling development and growth of peanut, they might be used to benefit the growth of peanuts in large-scale agricultural settings. PMID:25901959

  2. Effect of Structural Transformation of Nanoparticulate Zero-Valent Iron on Generation of Reactive Oxygen Species.

    PubMed

    He, Di; Ma, Jinxing; Collins, Richard N; Waite, T David

    2016-04-01

    While it has been recognized for some time that addition of nanoparticlate zerovalent iron (nZVI) to oxygen-containing water results in both corrosion of Fe(0) and oxidation of contaminants, there is limited understanding of either the relationship between transformation of nZVI and oxidant formation or the factors controlling the lifetime and extent of oxidant production. Using Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, we show that while nZVI particles are transformed to ferrihydrite then lepidocrocite in less than 2 h, oxidant generation continues for up to 10 h. The major products (Fe(II) and H2O2) of the reaction of nZVI with oxygenated water are associated, for the most part, with the surface of particles present with these surface-associated Fenton reagents inducing oxidation of a target compound (in this study, (14)C-labeled formate). Effective oxidation of formate only occurred after formation of iron oxides on the nZVI surface with the initial formation of high surface area ferrihydrite facilitating rapid and extensive adsorption of formate with colocation of this target compound and surface-associated Fe(II) and H2O2 apparently critical to formate oxidation. Ongoing formate oxidation long after nZVI is consumed combined with the relatively slow consumption of Fe(II) and H2O2 suggest that these reactants are regenerated during the nZVI-initiated heterogeneous Fenton process. PMID:26958862

  3. Selenate removal by zero-valent iron in oxic condition: the role of Fe(II) and selenate removal mechanism.

    PubMed

    Yoon, In-Ho; Bang, Sunbaek; Kim, Kyoung-Woong; Kim, Min Gyu; Park, Sang Yoon; Choi, Wang-Kyu

    2016-01-01

    In this study, batch experiments were conducted to investigate the effect of the concentration of ferrous [Fe(II)] ions on selenate [Se(VI)] removal using zero-valent iron (ZVI). The mechanism of removal was investigated using spectroscopic and image analyses of the ZVI-Fe(II)-Se(VI) system. The test to remove 50 mg/L of Se(VI) by 1 g/L of ZVI resulted in about 60 % removal of Se(VI) in the case with absence of Fe(II), but other tests with the addition of 50 and 100 mg/L of the Fe(II) had increased the removal efficiencies about 93 and 100 % of the Se(VI), respectively. In other batch tests with the absence of ZVI, there were little changes on the Se(VI) removal by the varied concentration of the Fe(II). From these results, we found that Fe(II) ion plays an accelerator for the reduction of Se(VI) by ZVI with the stoichiometric balance of 1.4 (=nFe(2+)/nSe(6+)). Under anoxic conditions, the batch test revealed about 10 % removal of the Se(VI), indicating that the presence of dissolved oxygen increased the kinetics of Se(VI) removal due to the Fe(II)-containing oxides on the ZVI, as analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) spectra also showed that the reductive process of Se(VI) to Se(0)/Se(-II) occurred in the presence of the both ZVI and Fe(II). The final product of iron corrosion was lepidocrocite (γ-FeOOH), which acts as an electron transfer barrier from Fe(0) core to Se(VI). Therefore, the addition of Fe(II) enhanced the reactivity of ZVI through the formation of iron oxides (magnetite) favoring electron transfer during the removal of Se(VI), which was through the exhaustion of the Fe(0) core reacted with Se(VI). PMID:25943509

  4. Nanoscale zero-valent iron: future prospects for an emerging water treatment technology.

    PubMed

    Crane, R A; Scott, T B

    2012-04-15

    For the past 15 years, nanoscale metallic iron (nZVI) has been investigated as a new tool for the treatment of contaminated water and soil. The technology has reached commercial status in many countries worldwide, however is yet to gain universal acceptance. This review summarises our contemporary knowledge of nZVI aqueous corrosion, manufacture and deployment, along with methods to enhance particle reactivity, stability and subsurface mobility. Reasons for a lack of universal acceptance are also explored. Key factors include: concerns over the long-term fate, transformation and ecotoxicity of nZVI in environmental systems and, a lack of comparable studies for different nZVI materials and deployment strategies. It is highlighted that few investigations to date have examined systems directly analogous to the chemistry, biology and architecture of the terrestrial environment. Such emerging studies have highlighted new concerns, including the prospect for remobilisation of heavy metals and radionuclides over extended periods. The fundamental importance of being able to accurately predict the long-term physical, chemical and biological fate of contaminated sites following nZVI treatment is emphasised and, as part of this, a universal empirical testing framework for nZVI is suggested. PMID:22305041

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

    PubMed

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

    2015-04-01

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

  6. Contributions of Abiotic and Biotic Dechlorination Following Carboxymethyl Cellulose Stabilized Nanoscale Zero Valent Iron Injection.

    PubMed

    Kocur, Chris M D; Lomheim, Line; Boparai, Hardiljeet K; Chowdhury, Ahmed I A; Weber, Kela P; Austrins, Leanne M; Edwards, Elizabeth A; Sleep, Brent E; O'Carroll, Denis M

    2015-07-21

    A pilot scale injection of nanoscale zerovalent iron (nZVI) stabilized with carboxymethyl cellulose (CMC) was performed at an active field site contaminated with a range of chlorinated volatile organic compounds (cVOC). The cVOC concentrations and microbial populations were monitored at the site before and after nZVI injection. The remedial injection successfully reduced parent compound concentrations on site. A period of abiotic degradation was followed by a period of enhanced biotic degradation. Results suggest that the nZVI/CMC injection created conditions that stimulated the native populations of organohalide-respiring microorganisms. The abundance of Dehalococcoides spp. immediately following the nZVI/CMC injection increased by 1 order of magnitude throughout the nZVI/CMC affected area relative to preinjection abundance. Distinctly higher cVOC degradation occurred as a result of the nZVI/CMC injection over a 3 week evaluation period when compared to control wells. This suggests that both abiotic and biotic degradation occurred following injection. PMID:26090687

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    An innovative method of groundwater remediation invented in the 1990"s, Permeable Reactive Barriers, use sand-sized grains of scrap iron placed in trenches or injected under pressure to remediate a number of organic and inorganic contaminants. Monitoring the aging of these barriers becomes increasingly important as many of these barriers approach their predicted life spans. In-situ resistivity and induced polarization studies have been conducted at six barriers at four different sites: Monticello, Utah; the Denver Federal Center; Kansas City, Missouri; and East Helena, Montana. As some barriers tend to age dramatically faster than others, for this study we consider low permeability barriers as of greater age, as "old" barriers tend to loose permeability rather than exhaust reactive materials. One complicating factor is that two of the barriers studied appear to have issues related to installation. One site, the former Asarco Smelter Site near East Helena, Montana, has been instrumented with an autonomous monitoring system allowing continuous monitoring of the evolution of a relatively new (less than three years old) barrier. The barrier showed surprisingly rapid evolution over the first year of monitoring with changes in both resistivity and chargeability of tens of percent per month. In general, the electrical properties of all of the barriers studied follow a pattern. New barriers are fairly resistive with in-situ conductivity only a few times background (outside the barrier) values. Older barriers get increasingly conductive, with failed barriers showing values of over 100 S/m. The induced polarization response is more complicated. Chargeability values increase over time for young barriers, are largest for healthy barriers in the middle of their lifespan, and decrease as the barrier ages.

  8. Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

    PubMed

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

    2006-01-01

    The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation. PMID:17165447

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

    PubMed Central

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

    2008-01-01

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

  10. Rapid magnetic removal of aqueous heavy metals and their relevant mechanisms using nanoscale zero valent iron (nZVI) particles.

    PubMed

    Huang, Pengpeng; Ye, Zhengfang; Xie, Wuming; Chen, Qi; Li, Jing; Xu, Zhencheng; Yao, Maosheng

    2013-08-01

    Much work is devoted to heavy metal sorption, reduction and relevant mechanisms by nanoscale zero valent iron (nZVI) particle, but fewer studies utilize its magnetic properties in aqueous metal removals. Here, we have investigated the use of nZVI particles both electrosprayed (E-nZVI) and non-electrosprayed (NE-nZVI) with different concentration levels (0.186-1.86 mg/mL) in removing aqueous Cd(II), Cr(IV), and Pb(II) through the magnetic separation means. The effects of the reaction time (5-20 min) and magnetic treatment time (1-30 min) on relevant magnetic removal efficiencies were studied. Metal ion concentration was analyzed using inductively coupled plasma (ICP), and the magnetically obtained metal-nZVI mixtures were further analyzed using X-ray photoelectron spectroscopy (XPS). Results showed that the magnetic removal efficiencies of heavy metals varied with the metal species, nZVI loading, reaction and magnetic separation time. In most cases, use of 1.5 mg/mL E-nZVI or NE-nZVI resulted in removal efficiencies of more than 80% for Pb(II), Cd(II), and Cr(IV). Increasing the magnetic treatment time from 1 to 20 min was shown to lead to ≈ 20% increase in Pb(II) removal efficiency, but no improvements for Cd(II) and Cr(IV). In contrast, increasing the reaction time decreased the Pb(II) removal efficiency, yet no effects observed for Cd(II) and Cr(IV). In general, 1 min reaction and 5 min magnetic treatment were found sufficient to achieve considerable heavy metal removals. For comparable efficiencies, use of magnetic method could significantly reduce nZVI loading. XPS analysis results indicated that atomic percentages of O 1s, Fe 2p, Cd 3d, Pb 4f and Cr 2p varied with metal exposures. Different from Cd(II) and Cr(IV), aqueous iron ions might be possibly present when treating Pb(II). This study demonstrated a rapid heavy metal removal method using the magnetic property of nZVI particles, while contributing to understanding of the relevant removal mechanisms. PMID:23566331

  11. Environmental benefits and risks of zero-valent iron nanoparticles (nZVI): risk mitigation or trade-off?

    NASA Astrophysics Data System (ADS)

    Grieger, K.; Fjordbge, A.; Hartmann, N.; Eriksson, E.; Baun, A.

    2009-12-01

    The use of nanoscaled particles in environmental remediation is gaining increasing amounts of attention in recent years, including the use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation. The main advantages of its use include high degrees of reactivity towards a wide range of contaminants, enhanced mobility of the often coated particles, and its cost-effective in situ applications. Numerous studies have shown that compared to larger sized iron particles nZVI may have some superior properties, due to high surface areas and small sizes associated with nanoscale dimensions. While the use and further development of nZVI is understandably heralded as an environmentally-beneficial technology, the potentials risks of introducing these nanoparticles into the environment also needs to be considered. To date most research has focused on the potential benefits of nZVI and very little research has investigated its potential health and environmental risks. Nonetheless, some recent studies have documented adverse effects from its exposure including the generation of reactive oxygen species (ROS), oxidative stress, bactericidal effects, DNA damage, and inflammatory responses. Moreover, field site injections often involve the use of large quantities of nZVI (10-50 g/L) which may be directly injected into groundwater flow. Combined with the pursuit of designing more mobile and reactive particles, this may potentially lead to risks related to environmental exposures of substantial concentrations. In this study, we provide a brief synopsis of the expected environmental benefits and potential risks of nZVI, particularly focusing on its environmental fate and behavior and potential role as contaminant carrier. These are some areas of primary concern for risk assessors. Furthermore, we estimate and compare the span between probable environmental concentrations from its use in the field and concentrations which have been shown to cause adverse effects in laboratory settings. This is in light of the challenges that quantitative risk assessments face for nZVI and other nanoparticles, in part due to extensive and fundamental uncertainties. These data may provide a starting point to more thoroughly investigate the potential risks of nZVI and ultimately help scientists, engineers, and decision makers make better informed decisions regarding the use of nZVI for environmental remediation.

  12. Transport and retention of xanthan gum-stabilized microscale zero-valent iron particles in saturated porous media.

    PubMed

    Xin, Jia; Tang, Fenglin; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf

    2016-01-01

    Microscale zero valent iron (mZVI) is a promising material for in-situ contaminated groundwater remediation. However, its usefulness has been usually inhibited by mZVI particles' low mobility in saturated porous media for sedimentation and deposition. In our study, laboratory experiments, including sedimentation studies, rheological measurements and transport tests, were conducted to investigate the feasibility of xanthan gum (XG) being used as a coating agent for mZVI particle stabilization. In addition, the effects of XG concentration, flow rate, grain diameter and water chemistry on XG-coated mZVI (XG-mZVI) particle mobility were explored by analyzing its breakthrough curves and retention profiles. It was demonstrated that XG worked efficiently to enhance the suspension stability and mobility of mZVI particles through the porous media as a shear thinning fluid, especially at a higher concentration level (3g/L). The results of the column study showed that the mobility of XG-mZVI particles increased with an increasing flow rate and larger grain diameter. At the highest flow rate (2.30נ10(-3)m/s) within the coarsest porous media (0.8-1.2mm), 86.52% of the XG-mZVI flowed through the column. At the lowest flow rate (0.97נ10(-4)m/s) within the finest porous media (0.3-0.6mm), the retention was dramatically strengthened, with only 48.22% of the particles flowing through the column. The XG-mZVI particles appeared to be easily trapped at the beginning of the column especially at a low flow rate. In terms of two representative water chemistry parameters (ion strength and pH value), no significant influence on XG-mZVI particle mobility was observed. The experimental results suggested that straining was the primary mechanism of XG-mZVI retention under saturated condition. Given the above results, the specific site-related conditions should be taken into consideration for the design of a successful delivery system to achieve a compromise between maximizing the radius of influence of the injection and minimizing the injection pressure. PMID:26497937

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

    SciTech Connect

    Zhang, Man; He, Feng; Zhao, Dongye; Hao, Xiaodi

    2011-01-01

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

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

    PubMed

    Zhang, Man; He, Feng; Zhao, Dongye; Hao, Xiaodi

    2011-03-01

    Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited by desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, ∼ 44% of TCE sorbed in the potting soil was degraded in 30 h, compared to ∼ 82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1 × cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith Farm soil, the presence of SDS at sub-cmc increased TCE degraded by ∼ 10%. However, effect of SDS on degradation of TCE in the potting soil was more complex. The presence of SDS at sub-cmc decreased TCE degradation by 5%, but increased degradation by 5% when SDS dosage was raised to 5 × cmc. The opposing effects were attributed to combined effects of SDS on TCE desorption and degradation, release of soil organic matter and nanoparticle aggregation. The findings strongly suggest that effect of soil sorption on the effectiveness of Fe-Pd nanoparticles must be taken into account in process design, and soil organic content plays an important role in the overall degradation rate and in the effectiveness of surfactant uses. PMID:21376362

  15. Measuring the reactivity of commercially available zero-valent iron nanoparticles used for environmental remediation with iopromide.

    PubMed

    Schmid, Doris; Micić, Vesna; Laumann, Susanne; Hofmann, Thilo

    2015-10-01

    The high specific surface area and high reactivity of nanoscale zero-valent iron (nZVI) particles have led to much research on their application to environmental remediation. The reactivity of nZVI is affected by both the water chemistry and the properties of the particular type of nZVI particle used. We have investigated the reactivity of three types of commercially available Nanofer particles (from Nanoiron, s.r.o., Czech Republic) that are currently either used in, or proposed for use in full scale environmental remediation projects. The performance of one of these, the air-stable and thus easy-to-handle Nanofer Star particle, has not previously been reported. Experiments were carried out first in batch shaking reactors in order to derive maximum reactivity rates and provide a rapid estimate of the Nanofer particle's reactivity. The experiments were performed under near-natural environmental conditions with respect to the pH value of water and solute concentrations, and results were compared with those obtained using synthetic water. Thereafter, the polyelectrolyte-coated Nanofer 25S particles (having the highest potential for transport within porous media) were chosen for the experiments in column reactors, in order to elucidate nanoparticle reactivity under a more field-site realistic setting. Iopromide was rapidly dehalogenated by the investigated nZVI particles, following pseudo-first-order reaction kinetics that was independent of the experimental conditions. The specific surface area normalized reaction rate constant (kSA) value in the batch reactors ranged between 0.12 and 0.53Lm(-2)h(-1); it was highest for the uncoated Nanofer 25 particles, followed by the polyacrylic acid-coated Nanofer 25S and air-stable Nanofer Star particles. In the batch reactors all particles were less reactive in natural water than in synthetic water. The kSA values derived from the column reactor experiments were about 1000 times lower than those from the batch reactors, ranging between 2.6×10(-4) and 5.7×10(-4)Lm(-2)h(-1). Our results revealed that the easy-to-handle and air-stable Nanofer Star particles are the least reactive of all the Nanofer products tested. The reaction kinetics predicted by column experiments were more realistic than those predicted by batch experiments and these should therefore be used when designing a full-scale field application of nanomaterials for environmental remediation. PMID:25708601

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

    PubMed

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

    2011-03-01

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

  17. The effects of flow rate and concentration on nitrobenzene removal in abiotic and biotic zero-valent iron columns.

    PubMed

    Yin, Weizhao; Wu, Jinhua; Huang, Weilin; Li, Yongtao; Jiang, Gangbiao

    2016-08-01

    This study investigated the effects of varying nitrobenzene (NB) loadings via increasing flow rate or influent NB concentration mode on the removal efficiency in zero-valent iron (ZVI) columns sterilized (abiotic) or preloaded with acclimated microorganisms (biotic). It was shown that physical sequestration via adsorption/co-precipitation and reductive transformation of NB to aniline (AN) were the two major mechanisms for the NB removal in both abiotic and biotic ZVI columns. The NB removal efficiency decreased in both columns as the flow rate increased from 0.25 to 1.0mLmin(-1) whereas the AN recovery increased accordingly, with relatively high AN recovery observed at the flow rate of 1.0mLmin(-1). At the constant flow rate of 0.5mLmin(-1), increasing influent NB concentration from 80 to 400μmolL(-1) resulted in decreasing of the overall NB removal efficiency from 79.5 to 48.6% in the abiotic column and from 85.6 to 62.5% in the biotic column. The results also showed that the sequestration capacity and chemical reduction capacity were respectively 72% and 157.6% higher in the biotic column than in the abiotic column at the same tested hydraulic conditions and NB loadings. The optimal flow rates and influent NB concentrations were at 0.5mLmin(-1) and 80μmolL(-1) for the abiotic column and 2.0mLmin-1 and 240μmolL(-1) for the biotic column, respectively. This study indicated that microorganisms not only enhanced overall reduction of NB, but also facilitated NB sequestration within the porous media and that the optimal loading conditions for overall removal, sequestration, and reduction of NB may be different. Optimal operation conditions should be found for preferred sequestration or transformation (or both) of the target contaminants to meet different goals of groundwater remediation with the ZVI-PRB systems. PMID:27093118

  18. Variability in carbon isotope fractionation of trichloroethene during degradation by persulfate activated with zero-valent iron: Effects of inorganic anions.

    PubMed

    Liu, Yunde; Zhou, Aiguo; Gan, Yiqun; Li, Xiaoqian

    2016-04-01

    Stable carbon isotope analysis has the potential to be used for assessing the performance of in situ remediation of organic contaminants. Successful application of this isotope technique requires understanding the magnitude and variability in carbon isotope fractionation associated with the reactions under consideration. This study investigated the influence of inorganic anions (sulfate, bicarbonate, and chloride) on carbon isotope fractionation of trichloroethene (TCE) during its degradation by persulfate activated with zero-valent iron. The results demonstrated that the significant carbon isotope fractionation (enrichment factors ε ranging from -3.4±0.3 to -4.3±0.3‰) was independent on the zero-iron dosage, sulfate concentration, and bicarbonate concentration. However, the ε values (ranging from -7.0±0.4 to -13.6±1.2‰) were dependent on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during TCE degradation by persulfate activated with zero-valent iron. The dependence of ε values on chloride concentration, indicated that TCE degradation mechanisms may be different from the degradation mechanism caused by sulfate radical (SO4(-)). Ignoring the effect of chloride on ε value may cause numerous uncertainties in quantitative assessment of the performance of the in situ chemical oxidation (ISCO). PMID:26784392

  19. [Preparation of nano zero-valent iron/Sargassum horneri based activated carbon for removal of Cr (VI) from aqueous solution].

    PubMed

    Zeng, Gan-Ning; Wu, Xiao; Zheng, Lin; Wu, Xi; Tu, Mei-Ling; Wang, Tie-Gan; Ai, Ning

    2015-02-01

    Nanoscale zero-valent iron supported on Sargassum horneri activated carbon (NZVI/SAC) was synthesized by zinc chloride activation and incipient wetness method, and characterized with X-ray diffraction (XRD), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). XRD confirmed the existence of nano zero-valent iron, and SEM revealed that the material consisted of mainly 30-150 nm spherical particles aggregated into chains of individual units. The valence state of iron conformed with the nuclear-shell model. The effects of NZVI loading on AC, pH and the initial concentration of Cr(VI) on the removal of Cr(VI) were investigated. The final Cr(VI) removal percentage was up to 100% under the following conditions: 30 degrees C, pH = 2, NZVI/SAC dosage of 2 g x L(-1) and the amounts of NZVI loaded on SAC of 30%. And the equilibrium time was 10 minutes. These results showed that NZVI/SAC could be potentially applied for removal of high concentration Cr(VI). By analyzing the chemical change of NZVI/ SAC, we demonstrated that Cr(VI) was mainly reduced to insoluble Cr (III) compound in the reaction when pH was less than 4, and adsorbed by NZVI and SAC when pH was over 4. PMID:26031079

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  1. Rapid reductive degradation of aqueous p-nitrophenol using nanoscale zero-valent iron particles immobilized on mesoporous silica with enhanced antioxidation effect

    NASA Astrophysics Data System (ADS)

    Tang, Lin; Tang, Jing; Zeng, Guangming; Yang, Guide; Xie, Xia; Zhou, Yaoyu; Pang, Ya; Fang, Yan; Wang, Jiajia; Xiong, Weiping

    2015-04-01

    In this study, nanoscale zero-valent iron particles immobilized on mesoporous silica (nZVI/SBA-15) were successfully prepared for effective degradation of p-nitrophenol (PNP). The nZVI/SBA-15 composites were characterized by N2 adsorption/desorption, transmission electron microscopy (TEM), UV-vis spectrum and X-ray photoelectron spectroscopy (XPS). Results showed that abundant ultrasmall nanoscale zero-valent iron particles were formed and well dispersed on mesoporous silica (SBA-15). Batch experiments revealed that PNP removal declined from 96.70% to 16.14% as solution pH increased from 3.0 to 9.0. Besides, degradation equilibrium was reached within 5 min, which was independent of initial PNP concentration. Furthermore, only a little PNP elimination on SBA-15 indicated that nZVI immobilized on mesoporous silica was mainly responsible for the target contaminant removal. The UV-vis spectrum and XPS measurement confirmed that the PNP removal was a reductive degradation process, which was further proved by the detected intermediates using gas chromatography-mass spectrometry (GC/MS). The excellent antioxidation ability had been discovered with more than 80% of PNP being removed by nZVI/SBA-15 treated with 30 days' exposure to air. These results demonstrated the feasible and potential application of nZVI/SBA-15 composites in organic wastewater treatment.

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

    EPA Science Inventory

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

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

    PubMed

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

    2011-02-01

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

  4. Higher concentrations of nanoscale zero-valent iron (nZVI) in soil induced rice chlorosis due to inhibited active iron transportation.

    PubMed

    Wang, Jie; Fang, Zhanqiang; Cheng, Wen; Yan, Xiaomin; Tsang, Pokeung Eric; Zhao, Dongye

    2016-03-01

    In this study, the effects of concentrations 0, 100, 250, 500, 750 and 1000 mg kg(-1) of nanoscale zero-valent iron (nZVI) on germination, seedlings growth, physiology and toxicity mechanisms were investigated. The results showed that nZVI had no effect on germination, but inhibited the rice seedlings growth in higher concentrations (>500 mg kg(-1) nZVI). The highest suppression rate of the length of roots and shoots reached 46.9% and 57.5%, respectively. The 1000mg kg(-1) nZVI caused the highest suppression rates for chlorophyll and carotenoids, at 91.6% and 85.2%, respectively. In addition, the activity of antioxidant enzymes was altered by the translocation of nanoparticles and changes in active iron content. Visible symptoms of iron deficiency were observed at higher concentrations, at which the active iron content decreased 61.02% in the shoots, but the active iron content not decreased in roots. Interestingly, the total and available amounts of iron in the soil were not less than those in the control. Therefore, the plants iron deficiency was not caused by (i) deficiency of available iron in the soil and (ii) restraint of the absorption that plant takes in the available iron, while induced by (ⅲ) the transport of active iron from the root to the shoot was blocked. The cortex tissues were seriously damaged by nZVI which was transported from soil to the root, these were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). This current study shows that the mechanism of iron deficiency in rice seedling was due to transport of active iron from the root to the shoot blocked, which was caused by the uptake of nZVI. PMID:26803790

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Laumann, Susanne; Micić, Vesna; Schmid, Doris; Hofmann, Thilo

    2013-04-01

    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.

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

    SciTech Connect

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

    2005-12-22

    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.

  8. Synthesis of zeolite-supported microscale zero-valent iron for the removal of Cr(6+) and Cd(2+) from aqueous solution.

    PubMed

    Kong, Xiangke; Han, Zhantao; Zhang, Wei; Song, Le; Li, Hui

    2016-03-15

    Zeolite-supported microscale zero-valent iron (Z-mZVI) was synthesized and used to remove heavy metal cation (Cd(2+)) and anion (Cr(6+)) from aqueous solution. Transmission electron microscope (TEM) confirmed that mZVI (100-200 nm) has been successfully loaded and efficiently dispersed on zeolite. Atomic absorption Spectroscopy (AAS) revealed the amount of stabilized mZVI was about 1.3 wt.%. The synthesized Z-mZVI has much higher reduction ability and adsorption capacity for Cr(6+) and Cd(2+) compared to bare nanoscale zero-valent iron (nZVI) and zeolite. Above 77% Cr(6+) and 99% Cd(2+) were removed by Z-mZVI, while only 45% Cr(6+) and 9% Cd(2+) were removed by the same amount iron of nZVI, and 1% Cr(6+) and 39% Cd(2+) were removed by zeolite alone with an initial concentration of 20 mg/L Cr(6+) and 200 mg/L Cd(2+). The removal of Cr(6+) by Z-mZVI follows the pseudo first-order kinetics model, and X-ray photoelectron spectroscopy (XPS) analysis confirmed that Cr(6+) was reduced to Cr(3+) and immobilized on the surface of Z-mZVI. The removal mechanisms for Cr(6+) include reduction, adsorption of Cr(3+) hydroxides and/or mixed Fe(3+)/Cr(3+) (oxy)hydroxides. The pseudo-second-order kinetic model indicated that chemical sorption might be rate-limiting in the sorption of Cd(2+) by Z-mZVI. This synthesized Z-mZVI has shown the potential as an efficient and promising reactive material for removing various heavy metals from wastewater or polluted groundwater. PMID:26731307

  9. 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...

  10. Permeable reactive barrier of coarse sand-supported zero valent iron for the removal of 2,4-dichlorophenol in groundwater.

    PubMed

    Gao, Weichun; Zhang, Yongxiang; Zhang, Xiaoye; Duan, Zhilong; Wang, Youhao; Qin, Can; Hu, Xiao; Wang, Hao; Chang, Shan

    2015-11-01

    In this study, coarse sand-supported zero valent iron (ZVI) composite was synthesized by adding sodium alginate to immobilize. Composite was detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). SEM results showed that composite had core-shell structure and a wide porous distribution pattern. The synthesized composite was used for degradation of 2,4-dichlorophenol (2,4-DCP) contamination in groundwater. Experimental results demonstrated that degradation mechanism of 2,4-DCP using coarse sand-supported ZVI included adsorption, desorption, and dechlorination. 2,4-DCP adsorption was described as pseudo-second-order kinetic model. It was concluded that dechlorination was the key reaction pathway, ZVI and hydrogen are prime reductants in dechlorination of 2,4-DCP using ZVI. PMID:26104904

  11. Removal of selenite by zero-valent iron combined with ultrasound: Se(IV) concentration changes, Se(VI) generation, and reaction mechanism.

    PubMed

    Fu, Fenglian; Lu, Jianwei; Cheng, Zihang; Tang, Bing

    2016-03-01

    In this paper, the performance and application of zero-valent iron (ZVI) assisted by ultrasonic irradiation for the removal of selenite (Se(IV)) in wastewater was evaluated and reaction mechanism of Se(IV) with ZVI in such systems was investigated. A series of batch experiments were conducted to determine the effects of ultrasound power, pH, ZVI concentration, N2 and air on Se(IV) removal. ZVI before and after reaction with Se(IV) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results indicated that ultrasound can lead to a significant synergy in the removal of Se(IV) by ZVI because ultrasound can promote the generation of OH and accelerate the advanced Fenton process. The primary reaction products of ZVI and Se(IV) were Se(0), ferrihydrite, and Fe2O3. PMID:26585013

  12. The fate of iron nanoparticles in environmental waters treated with nanoscale zero-valent iron, FeONPs and Fe3O4NPs.

    PubMed

    Peeters, Kelly; Lespes, Gaëtane; Zuliani, Tea; Ščančar, Janez; Milačič, Radmila

    2016-05-01

    Among the different nanoparticles (NPs) that are used in the remediation of contaminated environmental waters, iron nanoparticles (FeNPs) are the most frequently applied. However, if these FeNPs remain in the waters after the treatment, they can cause a hazard to the environment. In this work the time dependent size distribution of iron particles was investigated in Milli-Q water, forest spring water and landfill leachate after a variety of FeNP treatments. The efficiency of the metal removal by the FeNPs was also examined. The concentrations of the metals in the aqueous samples were determined before and after the nano-remediation by inductively coupled plasma mass spectrometry (ICP-MS). The data revealed that the settling and removal of the FeNPs after the treatment of the waters was related to the sample characteristics and the ways of dispersing the NPs. When mixing was used for the dispersion, the nano zero-valent iron (nZVI), FeONPs and Fe3O4NPs settled quickly in the Milli-Q water, the forest spring water and the landfill leachate. Dispersion with tertramethylammonium hydroxide (TMAH) resulted in a slower settling of the iron aggregates. In the Milli-Q and forest spring waters treated with FeONPs and dispersed by TMAH, the nanosized iron remained in solution as long as 24 h after the treatment and could represent a potential threat in environmental waters with a low ionic strength. The removal of the metals strongly depended on the type of FeNPs, the chemical speciation of the elements and the sample matrix. If the FeNPs are contaminated by a particular metal, this contaminant could be, during the NPs treatment, released into the water that is being remediated. PMID:26971807

  13. The removal of chromium (VI) and lead (II) from groundwater using sepiolite-supported nanoscale zero-valent iron (S-NZVI).

    PubMed

    Fu, Rongbing; Yang, Yingpin; Xu, Zhen; Zhang, Xian; Guo, Xiaopin; Bi, Dongsu

    2015-11-01

    In this study, the synthesis and characterization of sepiolite-supported nanoscale zero-valent iron particles (S-NZVI) was investigated for the adsorption/reduction of Cr(VI) and Pb(II) ions. Nanoscale zero-valent iron (NZVI) supported on sepiolite was successfully used to remove Cr(VI) and Pb(II) from groundwater with high efficiency. The removal mechanism was proposed as a two-step interaction including both the physical adsorption of Cr(VI) and Pb(II) on the surface or inner layers of the sepiolite-supported NZVI particles and the subsequent reduction of Cr(VI) to Cr(III) and Pb(II) to Pb(0) by NZVI. The immobilization of the NZVI particles on the surface of sepiolite could help to overcome the disadvantage of NZVI particles, which have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both the effective surface area and reaction performance. The techniques of XRD, XPS, BET, Zeta potential, and TEM were used to characterize the S-NZVI and interaction between S-NZVI and heavy metals. The appropriate S-NZVI dosage was 1.6 g L(-1). The removal efficiency of Cr(VI) and Pb(II) by S-NZVI was not affected to any considerable extent by the presence of co-existing ions, such as H2PO4(-), SiO3(2-), Ca(2+) and HCO3(-). The Cr(VI) and Pb(II) removal kinetics followed a pseudo-first-order rate expression, and both Langmuir isotherm model and Freundlich isotherm model were proposed. The results suggested that supporting NZVI on sepiolite had the potential to become a promising technique for in situ heavy metal-contaminated groundwater remediation. PMID:26267258

  14. Nanoscale zero-valent iron for the removal of Zn2+, Zn(II)-EDTA and Zn(II)-citrate from aqueous solutions.

    PubMed

    Kržišnik, Nina; Mladenovič, Ana; Škapin, Andrijana Sever; Škrlep, Luka; Ščančar, Janez; Milačič, Radmila

    2014-04-01

    The parameters which influence the removal of different zinc (Zn) species: Zn(2+), Zn(II)-EDTA and Zn(II)-citrate from aqueous solutions by nanoparticles of zero-valent iron (nZVI) were investigated at environmental relevant pH values. Untreated, surface modified and silica-fume supported nZVI were applied at different iron loads and contact times to Zn solutions, which were buffered to pH 5.3, 6.0 and 7.0. The results revealed that pH, the type of nZVI, the iron load, the contact time, and the Zn species all had a significant influence on the efficiency of removal. Zn(2+), Zn(II)-EDTA and Zn(II)-citrate were the most effectively removed from aqueous solutions by untreated nZVI. Zn(2+) removal was governed mainly by adsorption onto precipitated iron oxides. Complete removal of Zn(2+) and Zn(II)-citrate was obtained at all pH values investigated. The removal of strong Zn(II)-EDTA complex was successful only at acidic pH, which favored degradation of Zn(II)-EDTA. Consequently, the released Zn(2+) was completely removed from the solution by adsorption onto iron oxides. PMID:24463023

  15. 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

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

    2009-09-01

    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

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

    PubMed

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

    2015-01-01

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

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

    EPA Science Inventory

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

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

    SciTech Connect

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

    2006-03-20

    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.

  19. 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)

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

    2008-01-01

    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.

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

    PubMed

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

    2008-01-28

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

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

    PubMed

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

    2009-04-01

    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

  2. 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) ...

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  4. Effect of nanoscale zero-valent iron and magnetite (Fe3O4) on the fate of metals during anaerobic digestion of sludge.

    PubMed

    Suanon, Fidèle; Sun, Qian; Mama, Daouda; Li, Jiangwei; Dimon, Biaou; Yu, Chang-Ping

    2016-01-01

    Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas renewable energy. In this study, two different iron nanoparticles [nanoscale zero-valent iron (nZVI) and magnetite (Fe3O4)] were used in the mesophilic AD processes (37 ± 1 °C) to improve biogas production. In addition, changes of heavy metal (Cd, Co, Cu, Zn, Ni and Cr) speciation during AD of sludge with and without iron nanoparticles have been investigated. Concentrations of metals in the initial sludge were as follows: 63.1, 73.4, 1102.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis) for Cd, Co, Cu, Zn, Ni and Cr, respectively. Sequential fractionation showed that metals were predominantly bonded to organic matter and carbonates in the initial sludge. Compared with AD without iron nanoparticles, the application of iron nanoparticles (at dose of 0.5% in this study) showed positive impact not only on biogas production, but also on improvement of metals stabilization in the digestate. Metals were found concentrated in Fe-Mn bound and residual fractions and little was accumulated in the liquid digestate and most mobile fractions of solid digestate (water soluble, exchangeable and carbonates bound). Therefore, iron nanoparticles when properly used, could improve not only biogas yield, but also regulate and control the mobilization of metals during AD process. However, our study also observed that iron nanoparticles could promote the immobilization of phosphorus within the sludge during AD, and more research is needed to fully address the mechanism behind this phenomenon and the impact on future phosphorus reuse. PMID:26613183

  5. DDT degradation efficiency and ecotoxicological effects of two types of nano-sized zero-valent iron (nZVI) in water and soil.

    PubMed

    El-Temsah, Yehia S; Sevcu, Alena; Bobcikova, Katerina; Cernik, Miroslav; Joner, Erik J

    2016-02-01

    Nano-scale zero-valent iron (nZVI) has been conceived for cost-efficient degradation of chlorinated pollutants in soil as an alternative to e.g permeable reactive barriers or excavation. Little is however known about its efficiency in degradation of the ubiquitous environmental pollutant DDT and its secondary effects on organisms. Here, two types of nZVI (type B made using precipitation with borohydride, and type T produced by gas phase reduction of iron oxides under H2) were compared for efficiency in degradation of DDT in water and in a historically (>45 years) contaminated soil (24 mg kg(-1) DDT). Further, the ecotoxicity of soil and water was tested on plants (barley and flax), earthworms (Eisenia fetida), ostracods (Heterocypris incongruens), and bacteria (Escherichia coli). Both types of nZVI effectively degraded DDT in water, but showed lower degradation of aged DDT in soil. Both types of nZVI had negative impact on the tested organisms, with nZVI-T giving least adverse effects. Negative effects were mostly due to oxidation of nZVI, resulting in O2 consumption and excess Fe(II) in water and soil. PMID:26598990

  6. Decomplexation and subsequent reductive removal of EDTA-chelated Cu II by zero-valent iron coupled with a weak magnetic field: Performances and mechanisms.

    PubMed

    Guan, Xiaohong; Jiang, Xiao; Qiao, Junlian; Zhou, Gongming

    2015-12-30

    The feasibility of EDTA-chelated Cu(II) (Cu(II)-EDTA) removal by zero-valent iron (Fe(0)) in the presence of a weak magnetic field (WMF) and the involved mechanisms were systematically investigated. Fe(0) combined with WMF (Fe(0)/WMF) was very effective for removing Cu(II)-EDTA at pH 4.0-6.0 with the rate constants ranging from 0.1190 min(-1) to 0.0704 min(-1). Little passivation of Fe(0) was observed during Cu(II)-EDTA removal by Fe(0)/WMF in 8 consecutive runs when 10.0 mg L(-1) Cu(II)-EDTA was dosed before the initiation of each run. The evidences presented in this study verified that Cu(II)-EDTA was removed by decomplexation followed by reduction/adsorption. In brief, Fe(II) released from Fe(0) corrosion was rapidly oxidized by oxygen to Fe(III) to chelate with EDTA and release free Cu(II), and the detached Cu(II) ions were subsequently reduced/removed by Fe(0)/Fe(II) and co-precipitated by the generated iron (hydr)-oxides. To advance the application of Fe(0)/WMF technology in real practice, a magnetic propeller agitator was designed to offer WMF inside the reactor, which could greatly improve Cu(II)-EDTA removal by Fe(0) and be easily amplified. PMID:26296073

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

    NASA Astrophysics Data System (ADS)

    Kesavan, Sathees Kumar

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

  8. Are reproduction impairments of free spawning marine invertebrates exposed to zero-valent nano-iron associated with dissolution of nanoparticles?

    PubMed

    Kadar, Eniko; Dyson, Oliver; Handy, Richard D; Al-Subiai, Sherain N

    2013-03-01

    Studies were carried out to assess the effects of coating applied to zero-valent nano-iron (nZVI) on early life stage development of three key marine invertebrate species Mytilus galloprovincialis, Ciona intestinalis and Psammechinus milliaris. Embryo development was assessed following a 2-h exposure of the sperm to concentrations of two nZVIs of up to 10 mg l(-1) followed by in vitro fertilisation. Disruption of embryo development was most severe in sea squirts followed by mussel, while the urchin embryos were not significantly affected as compared with controls. An over twofold decrease in fertilisation success alongside significant delay in the embryo development was observed, and the effect was more severe with the coated form, possibly owing to its better colloidal stability. We provide in vitro evidence for the rapid dissolution (within 2 h) of nZVI in seawater to a degree that concentration of total solute Fe released from the coated ZVI particles exceeds safe limits of NOECs established for dissolved Fe. PMID:22263896

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

    PubMed

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

    2013-01-01

    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 μg/L and mercury from over 100 μg/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

  10. Enhanced sequestration of Cr(VI) by nanoscale zero-valent iron supported on layered double hydroxide by batch and XAFS study.

    PubMed

    Sheng, Guodong; Hu, Jun; Li, Hui; Li, Jiaxing; Huang, Yuying

    2016-04-01

    Herein, the reduction of nanoscale zero-valent iron (NZVI) and adsorption of layered double hydroxides (LDH) to sequester Cr(VI) were well combined by the immobilization of NZVI onto LDH surface (NZVI/LDH). The characterization results revealed that LDH decreased NZVI aggregation and thus increased Cr(VI) sequestration. The batch results indicated that Cr(VI) sequestration by NZVI/LDH was higher than that of NZVI, and superior to the sum of reduction and adsorption. The LDH with good anion exchange property allowed the adsorption of Cr(VI), facilitating interfacial reaction by increasing the local concentration of Cr(VI) in the NZVI vicinity. X-ray absorption near edge structure (XANES) results indicated that Cr(VI) was almost completely reduced to Cr(III) by NZVI/LDH, but Cr(VI) was partly reduced to Cr(III) by NZVI with a trace of Cr(VI) adsorbed on corrosion products. The coordination environment of Cr from extended X-ray absorption fine structure (EXAFS) analysis revealed that LDH could be a good scavenger for the insoluble products produced during reaction. So, the insoluble products on NZVI could be reduced, and its reactivity could be maintained. These results demonstrated that NZVI/LDH exhibits multiple functionalities relevant to the remediation of Cr(VI)-contaminated sites. PMID:26807943

  11. Determination of rate constants and branching ratios for TCE degradation by zero-valent iron using a chain decay multispecies model.

    PubMed

    Hwang, Hyoun-Tae; Jeen, Sung-Wook; Sudicky, Edward A; Illman, Walter A

    2015-01-01

    The applicability of a newly-developed chain-decay multispecies model (CMM) was validated by obtaining kinetic rate constants and branching ratios along the reaction pathways of trichloroethene (TCE) reduction by zero-valent iron (ZVI) from column experiments. Changes in rate constants and branching ratios for individual reactions for degradation products over time for two columns under different geochemical conditions were examined to provide ranges of those parameters expected over the long-term. As compared to the column receiving deionized water, the column receiving dissolved CaCO3 showed higher mean degradation rates for TCE and all of its degradation products. However, the column experienced faster reactivity loss toward TCE degradation due to precipitation of secondary carbonate minerals, as indicated by a higher value for the ratio of maximum to minimum TCE degradation rate observed over time. From the calculated branching ratios, it was found that TCE and cis-dichloroethene (cis-DCE) were dominantly dechlorinated to chloroacetylene and acetylene, respectively, through reductive elimination for both columns. The CMM model, validated by the column test data in this study, provides a convenient tool to determine simultaneously the critical design parameters for permeable reactive barriers and natural attenuation such as rate constants and branching ratios. PMID:25827100

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

    PubMed

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

    2015-03-01

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

  13. Transport of sucrose-modified nanoscale zero-valent iron in saturated porous media: role of media size, injection rate and input concentration.

    PubMed

    Li, Hui; Zhao, Yong-sheng; Han, Zhan-tao; Hong, Mei

    2015-01-01

    The growing use of nanoscale zero-valent iron (NZVI) in the remediation of contaminated groundwater raises concerns regarding its transport in aquifers. Laboratory-scale sand-packed column experiments were conducted with bare and sucrose-modified NZVI (SM-NZVI) to improve our understanding of the transport of the nanoparticles in saturated porous media, as well as the role of media size, suspension injection rate and concentration on the nanoparticle behavior. As the main indicative parameters, the normalized effluent concentration was measured and the deposition rate coefficient (k) was calculated for different simulated conditions. Overall, compared to the high retention of bare NZVI in the saturated silica column, SM-NZVI suspension could travel through the coarse sand column easily. However, the transport of SM-NZVI particles was not very satisfactory in a smaller size granular matrix especially in fine silica sand. Furthermore, the value of k regularly decreased with the increasing injection rate of suspension but increased with suspension concentration, which could reflect the role of these factors in the SM-NZVI travel process. The calculation of k-value at the tests condition adequately described the experimental results from the point of deposition dynamics, which meant the assumption of first-order deposition kinetics for the transport of NZVI particles was reasonable and feasible. PMID:26524436

  14. Investigation of heavy metal (Cu, Pb, Cd, and Cr) stabilization in river sediment by nano-zero-valent iron/activated carbon composite.

    PubMed

    Chen, Wei-Fang; Zhang, Jinghui; Zhang, Xiaomao; Wang, Weiya; Li, Yuxiang

    2016-01-01

    Nano-zero-valent iron/activated carbon (nZVI/AC) composite was evaluated for its effectiveness in the stabilization of Cu, Pb, Cd, and Cr in dredged river sediment. Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) were adopted to compare the effects of nZVI/AC dosage, particle size, time duration, and temperature on heavy metal leachability. The results show that leachability dropped considerably with the addition of nZVI/AC and powdered particles in the size of 0.075-0.18 mm was more effective in stabilization than granular ones. Stabilization effect was stable in long-term and robust against changes in temperature. Tessier sequential extraction revealed that heavy metals were associated with solid particle, inorganic or organic matters in sediment. The addition of nZVI/AC was able to convert relatively weakly bound heavy metals into more strongly bound species and thus reduce the bioavailability and toxicity. Also, the standard potential of heavy metals may decide the mechanism of stabilization process. PMID:26370818

  15. Interaction between Cu2+ and different types of surface-modified nanoscale zero-valent iron during their transport in porous media.

    PubMed

    Dong, Haoran; Zeng, Guangming; Zhang, Chang; Liang, Jie; Ahmad, Kito; Xu, Piao; He, Xiaoxiao; Lai, Mingyong

    2015-06-01

    This study investigated the interaction between Cu2+ and nano zero-valent iron (NZVI) coated with three types of stabilizers (i.e., polyacrylic acid [PAA], Tween-20 and starch) by examining the Cu2+ uptake, colloidal stability and mobility of surface-modified NZVI (SM-NZVI) in the presence of Cu2+. The uptake of Cu2+ by SM-NZVI and the colloidal stability of the Cu-bearing SM-NZVI were examined in batch tests. The results showed that NZVI coated with different modifiers exhibited different affinities for Cu2+, which resulted in varying colloidal stability of different SM-NZVI in the presence of Cu2+. The presence of Cu2+ exerted a slight influence on the aggregation and settling of NZVI modified with PAA or Tween-20. However, the presence of Cu2+ caused significant aggregation and sedimentation of starch-modified NZVI, which is due to Cu2+ complexation with the starch molecules coated on the surface of the particles. Column experiments were conducted to investigate the co-transport of Cu2+ in association with SM-NZVI in water-saturated quartz sand. It was presumed that a physical straining mechanism accounted for the retention of Cu-bearing SM-NZVI in the porous media. Moreover, the enhanced aggregation of SM-NZVI in the presence of Cu2+ may be contributing to this straining effect. PMID:26040744

  16. Synthesis, physical properties and application of the zero-valent iron/titanium dioxide heterocomposite having high activity for the sustainable photocatalytic removal of hexavalent chromium in water.

    PubMed

    Petala, Eleni; Baikousi, Maria; Karakassides, Michael A; Zoppellaro, Giorgio; Filip, Jan; Tuček, Jiří; Vasilopoulos, Konstantinos C; Pechoušek, Jiří; Zbořil, Radek

    2016-04-21

    A magnetic photocatalytic material composed of nanoscale zero-valent iron (nZVI) homogeneously distributed over a mesoporous nanocrystalline TiO2 matrix has been prepared by a multistage chemical process, including sol-gel technique, wet impregnation, and chemical reduction. X-ray powder diffraction and Raman spectroscopy were used for the structural and chemical characterization of the magnetic photocatalyst, while bulk magnetization measurements and scanning/transmission electron microscopy were employed to determine the physical and textural properties of the photocatalyst. The synthesized nZVI@TiO2 photocatalyst shows very high efficiency in the removal of hexavalent chromium, Cr(vi), from water. The degradation rate follows a pseudo-first-order kinetic model. Most importantly, the remarkable efficiency of the photocatalyst is found to be due to the synergistic contributions of both counterparts, nZVI and TiO2, as validated by comparative experiments with neat TiO2 and nZVI@TiO2 under UV-C irradiation and without irradiation. New insights into the mechanism of synergistic degradation of chromium(vi) and suppressed oxidation of nZVI particles in the composite material are proposed and therein discussed. PMID:27035846

  17. Treatment of aqueous bisphenol A using nano-sized zero-valent iron in the presence of hydrogen peroxide and persulfate oxidants.

    PubMed

    Girit, B; Dursun, D; Olmez-Hanci, T; Arslan-Alaton, I

    2015-01-01

    Bisphenol A (BPA) is an industrial pollutant considered as one of the major endocrine-disrupting chemicals found in natural waters. In the present study, the use of a commercial, air-stable, zero-valent iron (ZVI) powder, consisting of Fe0 surface stabilized nanoparticles was examined for the treatment of 20 mg/L, aqueous BPA solutions. The influence of pH (3, 5, 7), addition of hydrogen peroxide (HP) and persulfate (PS) oxidants (0.0, 1.25 and 2.5 mM) as well as temperature (25 and 50 °C) was studied for BPA treatment with 1 g/L ZVI. ZVI coupled with HP or PS provided an effective treatment system, which was based on rapid ZVI-mediated decomposition of the above-mentioned oxidants, resulting in complete BPA as well as significant total organic carbon (TOC) (88%) removals, in particular when PS was employed as the oxidant. Increasing the PS concentration and reaction temperature dramatically enhanced PS decomposition and BPA removal rates, whereas HP was not very effective in TOC removals and at elevated temperatures. According to the bioassays conducted with Vibrio fischeri and Pseudokirchneriella subcapitata, the acute toxicity of aqueous BPA fluctuated at first but decreased appreciably at the end of ZVI/PS treatment. PMID:26067507

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

    PubMed Central

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

    2014-01-01

    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

  19. Stability and pH-independence of nano-zero-valent iron intercalated montmorillonite and its application on Cr(VI) removal.

    PubMed

    Wu, Limei; Liao, Libing; Lv, Guocheng; Qin, Faxiang

    2015-08-01

    Composite of nano-zero-valent iron and montmorillonite (NZVI/MMT) was prepared by inserting NZVI into the interlayer of montmorillonite. The unique structure montmorillonite with isolated exchangeable Fe(III) cations residing near the sites of structural negative charges inhibited the agglomeration of ZVI and result in the formation of ZVI particles in the montmorillonite interlayer regions. NZVI/MMT was demonstrated to possess large specific surface area and outstanding reducibility that encourage rapid and stable reaction with Cr (VI). Besides, the intercalation also makes NZVI well dispersed and more stable in the interlayer, thereby improving the reaction capacity by 16 times. The effects of pH value, initial concentration of Cr (VI) and reaction time on Cr (VI) removal have also been investigated in detail. According to PXRD and XPS characterization, NZVI/Cr (VI) redox reaction occurred in the interlayer of MMT. The study of NZVI/MMT is instrumental to the development of remediation technologies for persistent environmental contaminants. PMID:26011800

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

    PubMed Central

    Xu, Lejin; Wang, Jianlong

    2013-01-01

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

  1. Boron nitride nanoplates supported zero-valent iron nanocomposites for enhanced decolorization of methyl orange with the assistance of ultrasonic irradiation.

    PubMed

    Zha, Yiming; Wang, Tianlin

    2016-01-01

    In this work, boron nitride nanoplates (BNNPs) supported nanoscale zero-valent iron (nZVI) was prepared through facile liquid-phase chemical reduction of ferric ion by borohydride under ambient conditions in the presence of BNNPs. The nZVI@BNNPs hybrids were characterized by scanning electron microscopy, X-ray diffraction and magnetic properties measurement. The hybrid material was evaluated for decolorization of a common azo dye, methyl orange (MO), with the assistance of ultrasonic irradiation. Results exhibited that a complete decolorization of 100 mg/L MO was achieved within 6 min using nZVI@BNNPs as the active material. Compared with bare nZVI and BNNPs, nZVI@BNNPs provided a faster reaction process for MO decolorization. The kinetic rate constants of MO decolorization reached 0.8175 min(-1) under ultrasound-assisted condition due to the synergistic effect of ultrasonic irradiation. Fluorescence spectrum experiment confirmed that hydroxyl radicals could be generated in the system combined nZVI with ultrasonic irradiation, and as a result, hydroxyl radicals would contribute to the decolorization process of MO. PMID:26819388

  2. [Solidification/Stabilization of Chromite Ore Processing Residue (COPR) Using Zero-Valent Iron and Lime-Activated Ground Granulated Blast Furnace Slag].

    PubMed

    Chen, Zhong-lin; Li, Jin-chunzi; Wang, Bin-yuan; Fan, Lei-tao; Shen, Ji-min

    2015-08-01

    The solidification/stabilization (S/S) of chromite ore processing residue (COPR) was performed using zero-valent iron (ZVI) and lime-activated ground granulated blast furnace slag (GGBFS). The degree of Cr immobilization was evaluated using the leaching procedure, mineral composition analysis and morphology analysis. Semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The results showed that after reduction, all of the S/S treated COPR samples met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg x L(-1)), the compressive strength of all the S/S samples could meet the compressive strength standard (15 MPa) for producing clay bricks, and Cr existed as the specie that bound to Fe/Mn oxides in the S/S samples. At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels. PMID:26592036

  3. The enhancement effect of pre-reduction using zero-valent iron on the solidification of chromite ore processing residue by blast furnace slag and calcium hydroxide.

    PubMed

    Li, Jinchunzi; Chen, Zhonglin; Shen, Jimin; Wang, Binyuan; Fan, Leitao

    2015-09-01

    A bench scale study was performed to assess the effectiveness of the solidification of chromite ore processing residue (COPR) by blast furnace slag and calcium hydroxide, and investigate the enhancement effect of pre-reduction using zero-valent iron (ZVI) on the solidification treatment. The degree of Cr immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as the solid waste-extraction procedure for leaching toxicity-sulfuric acid & nitric acid method (Chinese standard HJ/T299-2007). Strength tests and semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The experimental results showed that the performance of pre-reduction/solidification (S/S) was superior to that of solidification alone. After pre-reduction, all of the S/S treated COPR samples met the TCLP limit for total Cr (5 mg L(-1)), whereas the samples with a COPR content below 40% met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg L(-1)). At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels. PMID:25929874

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

    PubMed

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

    2013-09-15

    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, H₂O₂ to Fe(II) molar ratio, H₂O₂ 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

  5. The use of the core-shell structure of zero-valent iron nanoparticles (NZVI) for long-term removal of sulphide in sludge during anaerobic digestion.

    PubMed

    Su, Lianghu; Zhen, Guangyin; Zhang, Longjiang; Zhao, Youcai; Niu, Dongjie; Chai, Xiaoli

    2015-12-01

    A core-shell structure results in zero-valent iron nanoparticles (NZVI) with manifold functional properties. In this study, the long-term effects of NZVI on hydrogen sulphide removal in an anaerobic sludge digester were investigated. Within 20 days, the average hydrogen sulphide content in the biogas was successfully reduced from 300 (or 3620 of sulphate-rich sludge) mg Nm(-3) to 6.1 (121), 0.9 (3.3) and 0.5 (1.3) mg Nm(-3) in the presence of 0.05, 0.10 and 0.20% (wt) NZVI, respectively. Methane yield was enhanced at the low NZVI dose (0.05-0.10%) but decreased at the elevated dose (0.20%). Methane production and volatile solid degradation analyses implied that doses of 0.5-0.10% NZVI could accelerate sludge stabilization during anaerobic digestion. The phosphorus fractionation profile suggested that methane production could be inhibited at the elevated NZVI dose, partly due to the limited availability of soluble phosphorus due to the immobilization of bioavailable-P through the formation of vivianite. An analysis of the reducible inorganic sulphur species revealed that the elimination of hydrogen sulphide occurred via the reaction between hydrogen sulphide and the oxide shell of NZVI, which mainly formed FeS and some FeS2 and S(0). PMID:26565792

  6. Synthesis of kaolin supported nanoscale zero-valent iron and its degradation mechanism of Direct Fast Black G in aqueous solution

    SciTech Connect

    Jin, Xiaoying; Chen, Zhengxian; Zhou, Rongbing; Chen, Zuliang

    2015-01-15

    Graphical abstract: UV–visible spectra of DFBG solution using K-nZVI (1:1) nanoparticles. (a) Before reaction; (b) during reaction; (c) after reaction. - Highlights: • Kaolin-supported Fe{sup 0} nanoparticle (K-nZVI) was synthesized. • Degradation of Direct Fast Black by K-nZVI was studied. • K-nZVI was characterized by SEM, XRD, UV and FIIR. • Degradation mechanism of Direct Fast Black was proposed. - Abstract: Calcinated kaolin supported nanoscale zero-valent iron (K-nZVI) was synthesized and used for the removal of tetrad azo-group dye-Direct Fast Black G (DFBG) from aqueous solution. The results demonstrated that after reacting for 10 min with an initial concentration of DFBG 100 mg L{sup −1} (pH 9.49), 78.60% of DFBG was removed using K-nZVI, while only 41.39% and 12.56% of DFBG were removed using nZVI and kaolin, respectively. K-nZVI with a mass ratio of nZVI nanoparticles versus kaolin at 1:1 was found to have a high degree of reactivity. Furthermore, scanning electron microscopy (SEM) confirmed that nZVI was better dispersed when kaolin was present. XRD patterns indicated that iron oxides were formed after reaction. Fourier transforms infrared spectra (FTIR) and UV–visible demonstrated that the peak in the visible light region of DFBG was degraded and new bands were observed. Kinetics studies showed that the degradation of DFBG fitted well to the pseudo first-order model. The degradation of DFBG by K-nZVI was based on its adsorption onto kaolin and iron oxides, and subsequently reduction using nZVI was proposed. A significant outcome emerged in that 99.84% of DFBG in wastewater was removed using K-nZVI after reacting for 60 min.

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

    NASA Astrophysics Data System (ADS)

    Ruiz, Nancy Elaine

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

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

    EPA Science Inventory

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

  9. Influence of solution composition and column aging on the reduction of nitroaromatic compounds by zero-valent iron.

    PubMed

    Klausen, J; Ranke, J; Schwarzenbach, R P

    2001-08-01

    Granular iron is used in reactive permeable barriers for the reductive treatment of organic and inorganic groundwater contaminants. The technology is well established, however, its long-term performance and the importance of the groundwater composition are not yet well understood. Here, the influence of chloride, nitrate, silicate, and Aldrich humic acid on the reactivity of Master Builder iron was studied under anoxic conditions using small packed columns and 2-nitrotoluene (2-NT) as a model contaminant. After initially complete reduction of 2-NT to 2-aminotoluene (2-AT) in the column, possibly under mass-transfer controlled conditions, the reactivity of the iron was found to decrease substantially. In the presence of chloride, this decrease was slowed while exposure to silicate resulted in a very quick loss of iron reactivity. Nitrate was found to interfere strongly with the effect of chloride. These observations are interpreted in terms of corrosion inhibition/promotion and competition. Our results suggest that reactive barrier performance may be strongly affected by the composition of the treated groundwater. PMID:11482637

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

    PubMed

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

    2015-04-22

    In this article, a novel composite (Mg(OH)2 supported nanoscale zerovalent iron (denoted as nZVI@Mg(OH)2) was prepared and characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy method. The morphology analysis revealed that Mg(OH)2 appeared as self-supported flower-like spheres, and nano Fe0 particles were uniformly immobilized on the surface of their "flower petals", thus aggregation of Fe0 particles was minimized. Then the Pb(II) removal performance was tested by batch experiments. The composite presented exceptional removal capacity (1986.6 mg/g) compared with Mg(OH)2 and nanoscale zerovalent iron due to the synergistic effect. Mechanisms were also explored by a comparative study of the phase, morphology, and surface valence state of composite before and after reaction, indicating that at least three paths are involved in the synergistic removal process: (1) Pb(II) adsorption by Mg(OH)2 (companied with ion exchange reaction); (2) Pb(II) reduction to Pb0 by nanoscale zerovalent iron; and (3) Pb(II) precipitation as Pb(OH)2. The hydroxies provided by Mg(OH)2 can dramatically promote the role of nanoscale zerovalent iron as reducer, thus greatly enhancing the whole Pb(II) sequestration process. The excellent performance shown in our research potentially provides an alternative technique for Pb(II) pollution treatment. PMID:25826707

  11. Carbothermal synthesis of ordered mesoporous carbon-supported nano zero-valent iron with enhanced stability and activity for hexavalent chromium reduction.

    PubMed

    Dai, Ying; Hu, Yuchen; Jiang, Baojiang; Zou, Jinlong; Tian, Guohui; Fu, Honggang

    2016-05-15

    Composites of nano zero-valent iron (nZVI) and ordered mesoporous carbon (OMC) are prepared by using simultaneous carbothermal reduction methods. The reactivity and stability of nZVI are expected to be enhanced by embedding it in the ordered pore channels. The structure characteristics of nZVI/OMC and the removal pathway for hexavalent chromium (Cr(VI)) by nZVI/OMC are investigated. Results show that nZVI/OMC with a surface area of 715.16m(2)g(-1) is obtained at 900°C. nZVI with particle sizes of 20-30nm is uniformly embedded in the OMC skeleton. The stability of nZVI is enhanced by surrounding it with a broad carbon layer and a little γ-Fe is derived from the passivation of α-Fe. Detection of ferric state (Fe 2p3/2, around 711.2eV) species confirms that part of the nZVI on the outer surface is inevitably oxidized by O2, even when unused. The removal efficiency of Cr(VI) (50mgL(-1)) by nZVI/OMC is near 99% within 10min through reduction (dominant mechanism) and adsorption. nZVI/OMC has the advantage in removal efficiency and reusability in comparison to nZVI/C, OMC and nZVI. This study suggests that nZVI/OMC has the potential for remediation of heavy metal pollution in water. PMID:25898797

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

    PubMed

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

    2014-06-15

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

  13. 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

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

    2001-01-01

    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.

  14. A fabrication strategy for nanosized zero valent iron (nZVI)-polymeric anion exchanger composites with tunable structure for nitrate reduction.

    PubMed

    Jiang, Zhenmao; Zhang, Shujuan; Pan, Bingcai; Wang, Wenfeng; Wang, Xiaoshu; Lv, Lu; Zhang, Weiming; Zhang, Quanxing

    2012-09-30

    To reveal how the distribution of nanoscale zero-valent iron (nZVI) affect their reduction efficiency of its polymer-based composites and to further develop a simple strategy to tune the structure of the composites, we prepared four nZVI-polymerstyrene anion exchanger composites with similar nZVI loadings (13.5-14.4 Fe % in mass) but different distributions just through varying the concentration of NaBH(4) (0.9, 1.8, 3.6, and 7.2% in mass) solution during reduction of nZVI precursor (FeCl(4)(-) anions). As observed by SEM-EDX images, increasing the NaBH(4) concentration resulted in a more uniform nZVI distribution within the polymer, and thereto higher NH(4)(+)N production, faster reaction rate and more gaseous products during its reduction of nitrate and nitrite. nZVI distribution of the composites was suggested to greatly depend upon two processes, the hydrolyzation of anionic FeCl(4)(-) into cationic Fe(3+) and the reduction of both Fe(III) species by NaBH(4). Higher NaBH(4) concentration favored its faster diffusion into the inside polymer and in situ reduction of Fe(III) species into nZVI, causing a more uniform nZVI distribution. The results reported herein suggest that adjusting the NaBH(4) concentration was a simple and effective method to control the nZVI distribution in the supporting polymers, and indirectly tune the reactivity of the resultant nZVI hybrids. PMID:22795842

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

    SciTech Connect

    Weathers, L.

    1998-06-01

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

  16. Influence of calcium ions on the colloidal stability of surface-modified nano zero-valent iron in the absence or presence of humic acid.

    PubMed

    Dong, Haoran; Lo, Irene M C

    2013-05-01

    To decrease aggregation and enhance the mobility of nano zero-valent iron (NZVI) used for in-situ groundwater remediation, the surface of such NZVI must be modified using organic stabilizers, which can provide electrostatic repulsion, and steric or electrosteric stabilization. However, the stability of the nanoparticles can also be affected by groundwater components such as cations and humic acid (HA). In this study, the effect of Ca(2+) on the colloidal stability of NZVI coated with three types of stabilizers (i.e., polyacrylic acid (PAA), Tween-20 and starch) was evaluated in the absence or presence of HA. Differing stability behavior was observed for different surface-modified NZVIs. The presence of Ca(2+) exerted a slight influence on the settling of NZVI modified with PAA or Tween-20, in the absence or presence of HA. However, the presence of Ca(2+) caused significant aggregation and sedimentation for starch-modified NZVI in the absence of HA, and induced an even higher degree of aggregation and sedimentation in the presence of HA. It is presumed that, in the absence of HA, starch-modified NZVI particles undergo attachment with each other via Ca(2+) complexation with the coated starch molecules on the surface of the particles, thus enhancing the aggregation and the following sedimentation of starch-modified NZVI. However, in the presence of HA, spectroscopic analysis of the starch-modified NZVI aggregates indicated that the bridging interaction of HA with Ca(2+) was the predominant mechanism for the enhanced aggregation. PMID:23466217

  17. Enhanced As(III) oxidation and removal by combined use of zero valent iron and hydrogen peroxide in aerated waters at neutral pH values.

    PubMed

    Katsoyiannis, Ioannis A; Voegelin, Andreas; Zouboulis, Anastasios I; Hug, Stephan J

    2015-10-30

    The oxidation and removal of As(III) by commercially available micro-scale zero-valent iron (mZVI) was studied in aerated synthetic groundwater with initially 6.7 μM As(III) at neutral pH values. Batch experiments were performed to investigate the influence of ZVI and H2O2 concentrations on As(III) oxidation and removal. Oxidation and removal kinetics was significantly increased by increasing ZVI concentration or by adding H2O2 in micromolar concentrations slightly higher than that of initial As(III). Observed half-lifes for arsenic removal without added H2O2 were 81-17 min at ZVI concentrations of 0.15-2.5 g/L, respectively. X-ray absorption spectroscopy (XAS) confirmed that almost all As(III) was converted to As(V) after 2 h of reaction in the pH range 5-9. Addition of 9.6 μM H2O2 to 0.15 g/L ZVI suspensions diminished half-lifes for arsenic removal from 81 to 32 min and for As(III) oxidation from 77 to 8 min, i.e., by approximately a factor of 10. The increased rate of As(III) oxidation is attributable to enhanced formation of oxidants by the Fenton reaction with higher initial concentrations of H2O2. In practice, results of this study suggest that addition of small amounts (<1 mg/L) of H2O2 in various forms (e.g. stable and widely available Na-percarbonate) to water prior to treatment could significantly enhance As(III) oxidation and removal with ZVI. PMID:25935405

  18. Fate of As(V)-treated nano zero-valent iron: determination of arsenic desorption potential under varying environmental conditions by phosphate extraction.

    PubMed

    Dong, Haoran; Guan, Xiaohong; Lo, Irene M C

    2012-09-01

    Nano zero-valent iron (NZVI) offers a promising approach for arsenic remediation, but the spent NZVI with elevated arsenic content could arouse safety concerns. This study investigated the fate of As(V)-treated NZVI (As-NZVI), by examining the desorption potential of As under varying conditions. The desorption kinetics of As from As-NZVI as induced by phosphate was well described by a biphasic rate model. The effects of As(V)/NZVI mass ratio, pH, and aging time on arsenic desorption from As-NZVI by phosphate were investigated. Less arsenic desorption was observed at lower pH or higher As(V)/NZVI mass ratio, where stronger complexes (bidentate) formed between As(V) and NZVI corrosion products as indicated by FTIR analysis. Compared with the fresh As-NZVI, the amount of phosphate-extractable As significantly decreased in As-NZVI aged for 30 or 60 days. The results of the sequential extraction experiments demonstrated that a larger fraction of As was sorbed in the crystalline phases after aging, making it less susceptible to phosphate displacement. However, at pH 9, a slightly higher proportion of phosphate-extractable As was observed in the 60-day sample than in the 30-day sample. XPS results revealed the transformation of As(V) to more easily desorbed As(III) during aging and a higher As(III)/As(V) ratio in the 60-day sample at pH 9, which might have resulted in the higher desorption. PMID:22673340

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Nanoscale zero-valent iron (nZVI) assembled on magnetic Fe3O4/graphene for chromium (VI) removal from aqueous solution.

    PubMed

    Lv, Xiaoshu; Xue, Xiaoqin; Jiang, Guangming; Wu, Donglei; Sheng, Tiantian; Zhou, Hongyi; Xu, Xinhua

    2014-03-01

    Nanoscale Zero-Valent Iron (nZVI) assembled on magnetic Fe3O4/graphene (nZVI@MG) nanocomposites was synthesized for Cr(VI) removal from aqueous solution. nZVI particles were perfectly dispersed either among Fe3O4 nanoparticles (Fe3O4 NPs) or above the basal plane of graphene. This material shows Cr(VI) removal efficiency of 83.8%, much higher than those of individuals (18.0% for nZVI, 21.6% for Fe3O4 NPs and 23.7% for graphene) and even their sum of 63.3%. The removal process obeys pseudo-second-order adsorption model, suggesting that adsorption is rate-controlling step. Maximum Cr(VI) adsorption capacity varies from 66.2 to 101.0 mg g(-1) with decreasing pH from 8.0 to 3.0 at 30°C. Negative ΔG and ΔH indicate spontaneous tendency and exothermic nature. Robust performance of nZVI@MG arises from the formation of micro-nZVI-graphene/nZVI-Fe3O4 batteries and strong adsorption capability of broad graphene sheet/Fe3O4 surfaces. Electrons released by nZVI spread all over the surfaces of graphene and Fe3O4, and the adsorbed Cr(VI) ions on them capture these floating electrons and reduce to Cr(III). Fe3O4 NPs also served as protection shell to prevent nZVI from agglomeration and passivation. PMID:24407658

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

    PubMed

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

    2013-06-01

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

  2. 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...

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

    EPA Science Inventory

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

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

    PubMed

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

    2009-05-01

    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

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

    PubMed Central

    2014-01-01

    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 μg/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/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 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

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

    PubMed

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

    2012-07-25

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

  7. Simple combination of oxidants with zero-valent-iron (ZVI) achieved very rapid and highly efficient removal of heavy metals from water.

    PubMed

    Guo, Xuejun; Yang, Zhe; Dong, Haiyang; Guan, Xiaohong; Ren, Qidong; Lv, Xiaofang; Jin, Xin

    2016-01-01

    This study, for the first time, demonstrated a continuously accelerated Fe(0) corrosion driven by common oxidants (i.e., NaClO, KMnO4 or H2O2) and thereby the rapid and efficient removal of heavy metals (HMs) by zero-valent iron (ZVI) under the experimental conditions of jar tests and column running. ZVI simply coupled with NaClO, KMnO4 or H2O2 (0.5 mM) resulted in almost complete As(V) removal within only 10 min with 1000 μg/L of initial As(V) at initial pH of 7.5(±0.1) and liquid solid ratio of 200:1. Simultaneous removal of 200 μg/L of initial Cd(II) and Hg(II) to 2.4-4.4 μg/L for Cd(II) and to 4.0-5.0 μg/L for Hg(II) were achieved within 30 min. No deterioration of HM removal was observed during the ten recycles of jar tests. The ZVI columns activated by 0.1 mM of oxidants had stably treated 40,200 (NaClO), 20,295 (KMnO4) and 40,200 (H2O2) bed volumes (BV) of HM-contaminated drinking water, but with no any indication of As breakthrough (<10 μg/L) even at short empty bed contact time (EBCT) of 8.0 min. The high efficiency of HMs removal from both the jar tests and column running implied a continuous and stable activation (overcoming of iron passivation) of Fe(0) surface by the oxidants. Via the proper increase in oxidant dosing, the ZVI/oxidant combination was applicable to treat highly As(V)-contaminated wastewater. During Fe(0) surface corrosion accelerated by oxidants, a large amount of fresh and reactive iron oxides and oxyhydroxides were continuously generated, which were responsible for the rapid and efficient removal of HMs through multiple mechanisms including adsorption and co-precipitation. A steady state of Fe(0) surface activation and HM removal enabled this simply coupled system to remove HMs with high speed, efficiency and perdurability. PMID:26575476

  8. 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)

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

    2013-12-01

    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.

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

    PubMed

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

    2014-03-01

    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

  10. Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

    PubMed

    Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori

    2016-02-01

    The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0. PMID:26519806

  11. Biogenic nano-magnetite and nano-zero valent iron treatment of alkaline Cr(VI) leachate and chromite ore processing residue

    PubMed Central

    Watts, Mathew P.; Coker, Victoria S.; Parry, Stephen A.; Pattrick, Richard A.D.; Thomas, Russell A.P.; Kalin, Robert; Lloyd, Jonathan R.

    2015-01-01

    Highly reactive nano-scale biogenic magnetite (BnM), synthesized by the Fe(III)-reducing bacterium Geobacter sulfurreducens, was tested for the potential to remediate alkaline Cr(VI) contaminated waters associated with chromite ore processing residue (COPR). The performance of this biomaterial, targeting aqueous Cr(VI) removal, was compared to a synthetic alternative, nano-scale zero valent iron (nZVI). Samples of highly contaminated alkaline groundwater and COPR solid waste were obtained from a contaminated site in Glasgow, UK. During batch reactivity tests, Cr(VI) removal from groundwater was inhibited by ∼25% (BnM) and ∼50% (nZVI) when compared to the treatment of less chemically complex model pH 12 Cr(VI) solutions. In both the model Cr(VI) solutions and contaminated groundwater experiments the surface of the nanoparticles became passivated, preventing complete coupling of their available electrons to Cr(VI) reduction. To investigate this process, the surfaces of the reacted samples were analyzed by TEM-EDX, XAS and XPS, confirming Cr(VI) reduction to the less soluble Cr(III) on the nanoparticle surface. In groundwater reacted samples the presence of Ca, Si and S was also noted on the surface of the nanoparticles, and is likely responsible for earlier onset of passivation. Treatment of the solid COPR material in contact with water, by addition of increasing weight % of the nanoparticles, resulted in a decrease in aqueous Cr(VI) concentrations to below detection limits, via the addition of ⩾5% w/w BnM or ⩾1% w/w nZVI. XANES analysis of the Cr K edge, showed that the % Cr(VI) in the COPR dropped from 26% to a minimum of 4–7% by the addition of 5% w/w BnM or 2% w/w nZVI, with higher additions unable to reduce the remaining Cr(VI). The treated materials exhibited minimal re-mobilization of soluble Cr(VI) by re-equilibration with atmospheric oxygen, with the bulk of the Cr remaining in the solid fraction. Both nanoparticles exhibited a considerable capacity for the remediation of COPR related Cr(VI) contamination, with the synthetic nZVI demonstrating greater reactivity than the BnM. However, the biosynthesized BnM was also capable of significant Cr(VI) reduction and demonstrated a greater efficiency for the coupling of its electrons towards Cr(VI) reduction than the nZVI. PMID:26109747

  12. Aquifer modification: an approach to improve the mobility of nanoscale zero-valent iron particles used for in situ groundwater remediation

    NASA Astrophysics Data System (ADS)

    MicicBatka, Vesna; Schmid, Doris; Marko, Florian; Velimirovic, Milica; Wagner, Stephan; von der Kammer, Frank; Hofmann, Thilo

    2015-04-01

    Successful emplacement of nanoscale zero-valent iron (nZVI) within the contaminated source zone is a prerequisite for the use of nZVI technology in groundwater remediation. Emplacement of nZVI is influenced i.e., by the injection technique and the injection velocity applied, as well as by the mobility of nZVI in the subsurface. Whereas processes linked to the injection can be controlled by the remediation practitioners, the mobility of nZVI in the subsurface remains limited. Even though mobility of nZVI is somewhat improved by surface coating with polyelectrolytes, it is still greatly affected by the groundwater composition and physical and chemical heterogeneities of aquifer grains. In order to promote mobility of nZVI it is needed to alter the surface charge heterogeneities of aquifer grains. Modifying the aquifer grain's surfaces by means of polyelectrolyte coating is an approach proposed to increase the overall negative surface charge of the aquifer grain surfaces, hinder deposition of nZVI onto aquifer grains, and finally promote nZVI mobility. In this study the effect of different polyelectrolytes on the nZVI mobility is tested in natural sands deriving from real brownfield sites that are proposed to be remediated using the nZVI technology. Sands collected from brownfield sites were characterized in terms of grain size distribution, mineralogical and chemical composition, and organic carbon content. Furthermore, surface charge of these sands was determined in both, low- and high ionic strength background solutions. Finally, changes of the sand's surface charges were examined after addition of the proposed aquifer modifiers, lignin sulfonate and humic acid. Surface charge of brownfield sands in low ionic strength background solution is more negative compared to that in high ionic strength background solution. An increase in negative surface potential of brownfield sand was recorded when aquifer modifiers were applied in a background solution with low ionic strength, indicating their potential to improve nZVI mobility under comparable environmental conditions. In contrast, no significant change of the surface potential of brownfield sand was observed when aquifer modifiers were applied in a background solution with high ionic strength. The potential of the aquifer modifiers to promote the mobility of nZVI was furthermore tested in flow-through columns, starting with the one filled with natural quartz sand with rough surface, low ionic strength background solutions and pre-injecting lignin sulfonate in concentration of 50 mg/L. The preliminary results showed that the pre-injection of lignin sulfonate does increase mobility of nZVI under this experimental condition. Further mobility tests will be carried out in order to elucidate the potential of the aquifer modifiers to promote the mobility of nZVI in sands with a complex mineralogy and in the background solutions with varying ionic strength, in order to account for the condition that resemble those at polluted sites. This research receives funding from the European Union's Seventh Framework Programme FP7/2007-2013 under grant agreement n°309517.

  13. An insight in magnetic field enhanced zero-valent iron/H2O2 Fenton-like systems: Critical role and evolution of the pristine iron oxides layer

    PubMed Central

    Xiang, Wei; Zhang, Beiping; Zhou, Tao; Wu, Xiaohui; Mao, Juan

    2016-01-01

    This study demonstrated the synergistic degradation of 4-chlorophenol (4-CP) achieved in a magnetic field (MF) enhanced zero-valent iron (ZVI)/H2O2 Fenton-like (FL) system and revealed an interesting correlative dependence relationship between MF and the pristine iron oxides layer (FexOy) on ZVI particles. First, a comparative investigation between the FL and MF-FL systems was conducted under different experimental conditions. The MF-FL system could suppress the duration of initial lag degradation phase one order of magnitude in addition of the significant enhancement in overall 4-CP degradation. Monitoring of intermediates/products indicated that MF would just accelerate the Fenton reactions to produce hydroxyl radical more rapidly. Evolutions of simultaneously released dissolved iron species suggested that MF would not only improve mass-transfer of the initial heterogeneous reactions, but also modify the pristine ZVI surface. Characterizations of the specific prepared ZVI samples evidenced that MF would induce a special evolution mechanism of the ZVI particles surface depending on the existence of FexOy layer. It comprised of an initial rapid point dissolution of FexOy and a following pitting corrosion of the exposed Fe0 reactive sites, finally leading to appearance of a particular rugged surface topography with numerous adjacent Fe0 pits and FexOy tubercles. PMID:27053228

  14. An insight in magnetic field enhanced zero-valent iron/H2O2 Fenton-like systems: Critical role and evolution of the pristine iron oxides layer.

    PubMed

    Xiang, Wei; Zhang, Beiping; Zhou, Tao; Wu, Xiaohui; Mao, Juan

    2016-01-01

    This study demonstrated the synergistic degradation of 4-chlorophenol (4-CP) achieved in a magnetic field (MF) enhanced zero-valent iron (ZVI)/H2O2 Fenton-like (FL) system and revealed an interesting correlative dependence relationship between MF and the pristine iron oxides layer (FexOy) on ZVI particles. First, a comparative investigation between the FL and MF-FL systems was conducted under different experimental conditions. The MF-FL system could suppress the duration of initial lag degradation phase one order of magnitude in addition of the significant enhancement in overall 4-CP degradation. Monitoring of intermediates/products indicated that MF would just accelerate the Fenton reactions to produce hydroxyl radical more rapidly. Evolutions of simultaneously released dissolved iron species suggested that MF would not only improve mass-transfer of the initial heterogeneous reactions, but also modify the pristine ZVI surface. Characterizations of the specific prepared ZVI samples evidenced that MF would induce a special evolution mechanism of the ZVI particles surface depending on the existence of FexOy layer. It comprised of an initial rapid point dissolution of FexOy and a following pitting corrosion of the exposed Fe(0) reactive sites, finally leading to appearance of a particular rugged surface topography with numerous adjacent Fe(0) pits and FexOy tubercles. PMID:27053228

  15. An insight in magnetic field enhanced zero-valent iron/H2O2 Fenton-like systems: Critical role and evolution of the pristine iron oxides layer

    NASA Astrophysics Data System (ADS)

    Xiang, Wei; Zhang, Beiping; Zhou, Tao; Wu, Xiaohui; Mao, Juan

    2016-04-01

    This study demonstrated the synergistic degradation of 4-chlorophenol (4-CP) achieved in a magnetic field (MF) enhanced zero-valent iron (ZVI)/H2O2 Fenton-like (FL) system and revealed an interesting correlative dependence relationship between MF and the pristine iron oxides layer (FexOy) on ZVI particles. First, a comparative investigation between the FL and MF-FL systems was conducted under different experimental conditions. The MF-FL system could suppress the duration of initial lag degradation phase one order of magnitude in addition of the significant enhancement in overall 4-CP degradation. Monitoring of intermediates/products indicated that MF would just accelerate the Fenton reactions to produce hydroxyl radical more rapidly. Evolutions of simultaneously released dissolved iron species suggested that MF would not only improve mass-transfer of the initial heterogeneous reactions, but also modify the pristine ZVI surface. Characterizations of the specific prepared ZVI samples evidenced that MF would induce a special evolution mechanism of the ZVI particles surface depending on the existence of FexOy layer. It comprised of an initial rapid point dissolution of FexOy and a following pitting corrosion of the exposed Fe0 reactive sites, finally leading to appearance of a particular rugged surface topography with numerous adjacent Fe0 pits and FexOy tubercles.

  16. Influences of redox transformation, metal complexation and aggregation of fulvic acid and humic acid on Cr(VI) and As(V) removal by zero-valent iron.

    PubMed

    Mak, Mark S H; Lo, Irene M C

    2011-06-01

    This study investigated the removal kinetics and mechanisms of Cr(VI) and As(V) by Fe(0) in the presence of fulvic acid (FA) and humic acid (HA) by means of batch experiments. The focus was on the involvements of FA and HA in redox reactions, metal complexation, and iron corrosion product aggregation in the removal of Cr(VI) and As(V) removal by Fe(0). Synthetic groundwater was used as the background electrolyte to simulate typical groundwater. The results showed faster Cr(VI) removal in the presence of HA compared to FA. Fluorescence spectroscopy revealed that no redox reaction occurred in the FA and HA. The results of the speciation modeling indicate that the free Fe(II) concentration was higher in the presence of HA, resulting in a higher removal rate of Cr(VI). However, the removal of As(V) was inhibited in the HA solution. Speciation modeling showed that the concentration of dissolved metal-natural organic matter (metal-NOM) complexes significantly affected the aggregation of the iron corrosion products which in turn affected the removal of As(V). The aggregation was found to be induced by gel-bridging of metal-NOM with the iron corrosion products. The effects of metal-NOM on the aggregation of the iron corrosion products were further confirmed by TEM studies. Larger sizes of iron corrosion products were formed in the FA solution compared to HA solution. This study can shed light on understanding the relationships between the properties of NOM (especially the content of metal-binding sites) and the removal of Cr(VI) and As(V) by Fe(0). PMID:21530997

  17. Uranium(VI) reduction by nanoscale zero-valent iron in anoxic batch systems: The role of Fe(II) and Fe(III)

    SciTech Connect

    Yan, Sen; Chen, Yongheng; Xiang, Wu; Bao, Zhengyu; Liu, Chongxuan; Deng, Baolin

    2014-12-01

    The role of Fe(II) and Fe(III) on U(VI) reduction by nanoscale zerovalent iron (nanoFe0) was investigated using two iron chelators 1,10-phenanthroline and triethanolamine (TEA) under a CO2-free anoxic condition. The results showed U(VI) reduction was strongly inhibited by 1,10-phenanthroline and TEA in a pH range from 6.92 to 9.03. For instance, at pH 6.92 the observed U(VI) reduction rates decreased by 80.7% and 82.3% in the presence of 1,10-phenanthroline and TEA, respectively. The inhibition was attributed to the formation of stable complexes between 1,10-phenanthroline and Fe(II) or TEA and Fe(III). In the absence of iron chelators, U(VI) reduction can be enhanced by surface-bound Fe(II) on nanoFe0. Our results suggested that Fe(III) and Fe(II) probably acted as an electron shuttle to mediate the transfer of electrons from nanoFe0 to U(VI), therefore a combined system with Fe(II), Fe(III) and nanoFe0 can facilitate the U(VI) reductive immobilization in the contaminated groundwater.

  18. pH dependence of Fenton reagent generation and As(III) oxidation and removal by corrosion of zero valent iron in aerated water.

    PubMed

    Katsoyiannis, Ioannis A; Ruettimann, Thomas; Hug, Stephan J

    2008-10-01

    Corrosion of zerovalent iron (ZVI) in oxygen-containing water produces reactive intermediates that can oxidize various organic and inorganic compounds. We investigated the kinetics and mechanism of Fenton reagent generation and As(III) oxidation and removal by ZVI (0.1m2/g) from pH 3-11 in aerated water. Observed half-lives for the oxidation of initially 500 microg/L As(III) by 150 mg Fe(0)/L were 26-80 min at pH 3-9. At pH 11, no As(III) oxidation was observed during the first two hours. Dissolved Fe(III) reached 325, 140, and 6 microM at pH 3, 5, and 7. H2O2 concentrations peaked within 10 min at 1.2, 0.4, and < 0.1 microM at pH 3, 5, and 7, and then decreased to undetectable levels. Addition of 2,2'-bipyridine (1-3 mM), prevented Fe(II) oxidation by O2 and H2O2 and inhibited As(III)oxidation. 2-propanol (14 mM), scavenging OH-radicals, quenched the As(III) oxidation at pH 3, but had almost no effect at pH 5 and 7. Experimental data and kinetic modeling suggest that As(III) was oxidized mainly in solution by the Fenton reaction and removed by sorption on newly formed hydrous ferric oxides. OH-radials are the main oxidant for As(III) at low pH, whereas a more selective oxidant oxidizes As(III) at circumneutral pH. PMID:18939581

  19. 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...

  20. 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...

  1. The remediation performance of a specific electrokinetics integrated with zero-valent metals for perchloroethylene contaminated soils.

    PubMed

    Chang, Jih-Hsing; Cheng, Shu-Fen

    2006-04-17

    This research was conducted to evaluate an integrated technique, combination of the electrokinetics (EK) and zero-valent metal (ZVM), for remediation of the perchloroethylene (PCE) contaminated soils. Various experimental conditions were controlled such as different voltage gradients, the position of ZVM, and ZVM species. The appropriate operational parameters are concluded as follows: (1) 0.01 M sodium carbonate serves as the working solution; (2) the voltage gradient is controlled at 1.0 V/cm; (3) ZVM wall is settled close to the anode. Based on the above operation conditions, the pH value of working solution can maintain at neutral range for avoiding the soil acidification. Neutral pH also causes the system to stay at a stable status of electricity consumption. The removal efficiency reaches 99% and 90% for decontaminating the PCE in the pore-water and the soil, respectively, after a 10-day treatment. The zero-valent zinc performs better PCE degradation than zero-valent iron. Moreover, the soils treated by EK+ZVM still possess their original properties. PMID:16214288

  2. Emplacement of zero-valent metal for remediation of deep contaminant plumes

    SciTech Connect

    Hubble, D.W.; Gillham, R.W.; Cherry, J.A.

    1997-12-31

    Some groundwater plumes containing chlorinated solvent contaminants are found to be so deep that current in situ remediation technologies cannot be economically applied. Also, source zones are often found to be too deep for removal or inaccessible due to surface features. Plumes emanating from these sources require containment or treatment. Containment technologies are available for shallow sites (< 15 m) and are being developed for greater depths. However, it is important to advance the science of reactive treatment - both for cut off of plumes and to contain and treat source zones. Zero-valent metal technology has been used for remediation of solvent plumes at sites in Canada, the UK and at several industrial and military sites in the USA. To date, all of the plumes treated with zero-valent metal (granular iron) have been at depths less than 15 m. This paper gives preliminary results of research into methods to emplace granular iron at depths in the range of 15 to 60 m. The study included review of available and emerging methods of installing barrier or reactive material and the selection, preliminary design and costing of several methods. The design of a treatment system for a 122 m wide PCE plume that, immediately down gradient from its source, extends from a depth of 24 to 37 m below the ground surface is used as a demonstration site. Both Permeable Reactive Wall and Funnel-and-Gate{trademark} systems were considered. The emplacement methods selected for preliminary design and costing were slurry wall, driven/vibrated beam, deep soil mixing and hydrofracturing injection. For each of these methods, the iron must be slurried for ease of pumping and placement using biodegradable polymer viscosifiers that leave the iron reactive.

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

    PubMed

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

    2011-01-01

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

  4. Applications of zero-valent silicon nanostructures in biomedicine.

    PubMed

    Kafshgari, Morteza Hasanzadeh; Voelcker, Nicolas H; Harding, Frances J

    2015-08-01

    Zero-valent, or elemental, silicon nanostructures exhibit a number of properties that render them attractive for applications in nanomedicine. These materials hold significant promise for improving existing diagnostic and therapeutic techniques. This review summarizes some of the essential aspects of the fabrication techniques used to generate these fascinating nanostructures, comparing their material properties and suitability for biomedical applications. We examine the literature in regards to toxicity, biocompatibility and biodistribution of silicon nanoparticles, nanowires and nanotubes, with an emphasis on surface modification and its influence on cell adhesion and endocytosis. In the final part of this review, our attention is focused on current applications of the fabricated silicon nanostructures in nanomedicine, specifically examining drug and gene delivery, bioimaging and biosensing. PMID:26295171

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

    SciTech Connect

    Jory A. Yarmoff; Christopher Amrhein

    2002-04-23

    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.

  6. Mitigation of Irrigation Water Using Zero-Valent Iron Treatment

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. ZERO-VALENT IRON PRB APPLICATION EXPANDS TO ARSENIC REMOVAL

    EPA Science Inventory

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  9. The experimental study of Cr6+ contaminated water remediation by zero-valent nano-Fe

    NASA Astrophysics Data System (ADS)

    Sun, X. N.; Liu, A. P.; Chen, Q. F.; Wang, X.

    2015-09-01

    In recent years, researchers have developed a number of new types of zero-valent nano-Fe remediation materials applied in the remediation of contaminated soil and water, which has attracted wide attentions. This paper selected soil leaching wastewater severely contaminated by chromium as target of the study and chose zero-valent nano-Fe, Na2SO3 and NaHSO3 for comparison experiments to study the effects on removing Cr6+ under experimental conditions of different pH values, dosages and reaction times. As is shown in the experiments, zero-valent nano-Fe has the highest removal rates for Cr6+, while the reaction of Na2SO3 is the slowest under the same conditions. However, both removal rates are prone to be stable after 10 min. Dosages do not make a distinct difference and the pH value has the least effect on the repair of zero-valent nano-Fe.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

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

    PubMed

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

    2015-01-01

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

  12. Synthesis of zero-valent copper-chitosan nanocomposites and their application for treatment of hexavalent chromium.

    PubMed

    Wu, Shao-Jung; Liou, Tzong-Horng; Mi, Fwu-Long

    2009-10-01

    This study used ionotropic crosslinking to synthesize chitosan-tripolyphosphate chelating resin beads, which are used to fabricate zero-valent copper-chitosan nanocomposites. The copper nanoparticles were dispersed on chitosan-tripolyphosphate beads, and were thus able to maintain appropriate dispersion and stability, which greatly improves their applicability. The fabrication process contains two steps: using chitosan-tripolyphosphate beads to adsorb Cu(II) ions, followed by chemical reduction to reduce Cu(II) ions to zero-valent copper. This study explored the adsorption of synthesized chitosan-tripolyphosphate beads to Cu(II) ions, and used SEM/EDS, XPS, and TEM to examine the properties of zero-valent copper-chitosan nanocomposites. The results showed that, the adsorption behavior of hexavalent chromium from aqueous solution onto fabricated nanocomposites has better adsorption capacity than that of the chitosan-tripolyphosphate beads. PMID:19414251

  13. Nanoscale zero valent supported by Zeolite and Montmorillonite: Template effect of the removal of lead ion from an aqueous solution.

    PubMed

    Arancibia-Miranda, Nicolás; Baltazar, Samuel E; García, Alejandra; Muñoz-Lira, Daniela; Sepúlveda, Pamela; Rubio, María A; Altbir, Dora

    2016-01-15

    In this work, we have studied the Pb(2+) sorption capacity of Zeolite (Z) and Montmorillonite (Mt) functionalized with nanoscale zero-valent iron (nZVI), at 50% w/w, obtained by means of an impregnating process with a solvent excess. The composites were characterized by several techniques including X-ray diffraction; scanning electron microscopy (SEM); BET area; isoelectric point (IEP); and, finally a magnetic response. Comparatively significant differences in terms of electrophoretic and magnetic characteristics were found between the pristine materials and the composites. Both structures show a high efficiency and velocity in the removal of Pb(2+) up to 99.0% (200.0 ppm) after 40 min of reaction time. The removal kinetics of Pb(2+) is adequately described by the pseudo second-order kinetic model, and the maximum adsorbed amounts (q(e)) of this analyte are in close accordance with the experimental results. The intraparticle diffusion model shows that this is not the only rate-limiting step, this being the Langmuir model which was well adjusted to our experimental data. Therefore, maximum sorption capacities were found to be 115.1±11.0, 105.5±9.0, 68.3±1.3, 54.2±1.3, and 50.3±4.2 mg g(-1), for Mt-nZVI, Z-nZVI, Zeolite, Mt, and nZVI, respectively. The higher sorption capacities can be attributed to the synergetic behavior between the clay and iron nanoparticles, as a consequence of the clay coating process with nZVI. These results suggest that both composites could be used as an efficient adsorbent for the removal of lead from contaminated water sources. PMID:26384998

  14. Kinetics of reductive dechlorination of 1,2,3,4-TCDD in the presence of zero-valent zinc.

    PubMed

    Wang, Zhiyuan; Huang, Weilin; Fennell, Donna E; Peng, Ping'an

    2008-03-01

    Polychlorinated dibenzo-p-dioxins (PCDDs) are toxic and widespread persistent organic pollutants (POPs). Cost-effective technologies for destroying or detoxifying PCDDs are in high demand. The overall purpose of this study was to develop a zero-valent zinc based technology for transforming toxic PCDDs to less- or non-toxic forms. We measured the dechlorination rates of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) in the presence of zero-valent zinc under aqueous conditions, identified the daughter compounds of the reaction, and constructed possible pathways for the reactions. The reaction rates of daughter compounds with zero-valent zinc were also measured independently. Our results showed that the zero-valent zinc is a suitable candidate for reducing PCDDs. Reductive dechlorination of 1,2,3,4-TCDD was stepwise and complete to dibenzo-p-dioxin (DD) mainly via 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD), 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD), 1-chlorodibenzo-p-dioxin (1-MCDD) to DD and via 1,2,4-TrCDD, 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD), 2-chlorodibenzo-p-dioxin (2-MCDD) to DD. In each separate system, the observed half-lives of 1,2,3,4-TCDD, 1,2,3-TrCDD, 1,2,4-TrCDD, 1,2-DCDD, 1,3-DCDD, 1,4-DCDD and 2,3-DCDD are 0.56, 2.62, 5.71, 24.93, 41.53, 93.67 and 169.06 h respectively. The tendency of rate constant follows TCDD>TrCDD>DCDD. Our results suggest that zero-valent zinc is a suitable candidate for rapidly reducing highly chlorinated PCDDs to less or non-chlorinated daughter products. PMID:17977573

  15. Cryptic Role of Zero-Valent Sulfur in Metal and Metalloid Geochemistry in Euxinic Waters

    NASA Astrophysics Data System (ADS)

    Helz, G. R.

    2014-12-01

    Natural waters that are isolated from the atmosphere in confined aquifers, euxinic basins and sediment pore waters often become sulfidic. These waters are conventionally described simply as reducing environments. But because nature does not constrain their exposure to reducing equivalents (e.g. from organic matter) and oxidizing equivalents (e.g. from Fe,Mn oxides), these reducing environments in fact vary cryptically in their redox characteristics. The implications for trace metal and metalloid cycles are only beginning to be explored. The activity of zero-valent sulfur (aS0), a virtual thermodynamic property, is a potentially useful index for describing this variation. At a particular temperature and ionic strength, aS0 can be quantified from knowledge of pH and the total S(0) to total S(-II) ratio. Although data are incomplete, the deep waters of the Black Sea (aS0 ca. 0.3) appear to be more reducing than the deep waters of the Cariaco Basin (aS0 ca. 0.5) even though both are perennially sulfidic. An apparent manifestation is a greater preponderance of greigite relative to mackinawite in the Cariaco Basin. Interestingly, greigite is stable relative to mackinawite in both basins but predominates only at the higher aS0. Values of aS0 in sulfidic natural waters span the range over which Hg-polysulfide complexes gain predominance over Hg sulfide complexes. Competition between these ligands is thought to influence biological methylation, mercury's route into aquatic and human food chains. In sulfidic deep ground waters, the redox state and consequent mobility of As, a global human hazard, will depend on aS0. At intermediate sulfide concentrations, higher aS0 favors more highly charged and thus less mobile As(V) species relative to As(III) species despite the overall reducing characteristics of such waters. Helz, G.R. (2014) Activity of zero-valent sulfur in sulfidic natural waters. Geochem. Trans. In press.

  16. Photocatalysis using zero-valent nano-copper for degrading methyl orange under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Liú, Dan; Wang, Guoqiang; Liŭ, Dan; Lin, Junhong; He, Yingqiao; Li, Xiangru; Li, Ziheng

    2016-03-01

    As one of zero-valent transition metals, nano-copper was synthesized by a simple chemical reduction route and its photocatalytic activity was appraised by the degradation rate of methyl orange (MO) in aqueous solution under irradiation of a three-band fluorescent lamp. The results showed that nano-copper possessed visible-light photocatalytic activity. The finite-difference time-domain (FDTD) method was used to simulate the electric field distribution of nano-copper. From the results of simulation, it found that there was an enhancement electric field in course of light absorption on the surface of nano-copper, different morphology resulted in a diverse electric field distribution. Enhancement electric field intensity decided the visible-light photocatalytic activity of nano-copper. So the activity was affected by the morphology of nano-copper, as the size reduced and surface roughness increased, could be enhanced. It did be worth noting that the nanoscale of copper played the fatal decisive role for whether copper has the ability to degrade MO. So As-prepared nano-copper may be a novel visible-light photocatalytic material to treat organic pollution.

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

    SciTech Connect

    Phillips, Jonathan; Luhrs, Claudia; Lesman, Zayd; Soliman, Haytham; Zea, Hugo

    2010-01-01

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

  18. Chromate reduction by zero-valent Al metal as catalyzed by polyoxometalate.

    PubMed

    Lin, C J; Wang, S L; Huang, P M; Tzou, Y M; Liu, J C; Chen, C C; Chen, J H; Lin, C

    2009-12-01

    In spite of a high reduction potential of zero-valent Al (ZVAl), its ability to reduce Cr(VI), a widespread pollutant, to less toxic Cr(III) remains to be uncovered. In the present study, Cr(VI) reduction by ZVAl was conducted to evaluate the potential application of Al as a reductant for Cr(VI). Polyoxometalate (POM, HNa(2)PW(12)O(40)), a catalyst, was used to accelerate Cr(VI) reduction by Al. The reaction of 0.192mM Cr(VI) on ZVAl was investigated in the presence of N(2) or O(2) at pH 1. A slight decrease in Cr(VI) concentration was observed on as-received (uncleaned) ZVAl due to the presence of oxide layer with a low surface area (ca. 3.4x10(-3)m(2)/g) of ZVAl. On addition of 0.1mM POM, Cr(VI) reduction on uncleaned ZVAl increased significantly. This is attributed to the unique properties of POM, which has a Brphinsted acidity higher than usual inorganic acids such as H(2)SO(4) and HCl. Thus, POM could remove rapidly the oxidize layer on ZVAl, followed by acting as a shuttle for electron transfer from ZVAl to Cr(VI). Under a N(2) atmosphere, one- or two-electron reduction of POM by ZVAl was responsible for Cr(VI) reduction in the early stage of the reaction. However, during reaction with ZVAl over 120min, three-electron reduction of POM predominated over Cr(VI) reduction. On interaction of O(2) with reduced POM, the formation of H(2)O(2) was responsible for subsequent Cr(VI) reduction. The results suggest that POM is an efficient catalyst for Cr(VI) reduction by Al due to the extremely rapid consumption of reduced POM or H(2)O(2) by Cr(VI). PMID:19729183

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

    NASA Astrophysics Data System (ADS)

    Lee, Giehyeon; Park, Jaeseon

    2013-02-01

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

  20. Polychlorinated ethane reaction with zero-valent zinc: pathways and rate control

    NASA Astrophysics Data System (ADS)

    Arnold, William A.; Ball, William P.; Roberts, A. Lynn

    1999-12-01

    Efficient design of zero-valent metal permeable `barriers' for the reduction of organohalides requires information regarding the pertinent reaction rates as well as an understanding of the resultant distribution of products. In this study, the pathways and kinetics for reaction of polychlorinated ethanes with Zn(0) have been examined in batch reactors. Reductive β-elimination was the only route through which hexachloroethane (HCA), 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), 1,1,2-trichloroethane (1,1,2-TCA) and 1,2-dichloroethane (1,2-DCA) reacted. Pentachloroethane (PCA) reacted via concurrent reductive β-elimination (93%) and hydrolysis (7%). As previously demonstrated, 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethane (1,1-DCA) reacted predominantly via reductive α-elimination. Attempts to correlate BET surface area-normalized rate constants ( kSA-BET) with one-electron reduction potential ( E1) met with limited success, as HCA, PCA, 1,1,1,2-TeCA, and 1,1,1-TCA reacted at nearly identical rates despite substantial differences in E1 values. Comparison of the pseudo-first-order rate constants ( kobs) for these species with rate constants ( kLa) obtained from a correlation for mass transfer to suspended particles revealed that the reaction of these species was mass transfer limited even though reaction rates were unaffected by mixing speed. Calculations suggest that mass transfer limitations may also play a role in the design of treatment systems for highly reactive species, with overall rate constants predicted to increase with flow velocity.

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

    PubMed

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

    2015-03-01

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

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

    PubMed

    Ileri, Burcu; Ayyildiz, Onder; Apaydin, Omer

    2015-07-15

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

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

    EPA Science Inventory

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

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

    SciTech Connect

    Yarmoff, J.A.; Amrhein, C.

    1998-06-01

    'Contaminated groundwater and surface waters are a problem throughout the US and the world. In many instances, the types of contamination can be directly attributed to man''s actions. For instance, the burial of wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater and surface water contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements that are soluble and mobile in soils and aquifers. Oxyanions of selenium, chromium, uranium, arsenic, and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. In addition, the careless disposal of cleaning solvents, such as carbon tetrachloride and trichloroethylene, has further contaminated many groundwaters at these sites. Oxyanions of selenium, nitrogen, arsenic, vanadium, uranium, chromium, and molybdenum are contaminants in agricultural areas of the Western US. The management of these waters requires treatment to remove the contaminants before reuse or surface water disposal. In one instance in the Central Valley of California, the discharge of selenate-contaminated shallow groundwater to a wildlife refuge caused catastrophic bird deaths and deformities of embryos. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used on an experimental basis. Both in-situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. Only limited success has been achieved in the field, partly because the basic surface chemical reactions are not well understood. The authors are performing fundamental investigations of the interactions of the relevant chlorinated solvents, and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop the fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures. As of May 1998, they have performed both bulk chemical measurements of the reduction reactions and surface science studies of model chemical systems. During these first two years of funding, the authors have made significant progress in both areas. Initially, they focused primarily on the reduction of selenate by elemental iron. They also performed some work with chromate, perchlorate, uranyl, and carbon tetrachloride. In the following sections some of the progress is described.'

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed

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

    2002-12-15

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

  8. 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...

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory investigation was conducted to evaluate four iron-based filter materials for trace element contaminant water treatment. The iron-based filter materials evaluated were zero valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and iron oxide/hydroxide (IOH). Only fi...

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

    SciTech Connect

    Yarmoff, J.A.; Amrhein, C.

    1997-01-01

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

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

    PubMed

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

    2012-07-01

    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 μM total Ag) containing an excess of cysteine (400 μM). Within 48 h, up to 47% of the silver had dissolved, as indicated by filtration of the samples with a 0.025-μm 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

  13. Travel distance and transformation of injected emulsified zerovalent iron nanoparticles in the subsurface during two and half years.

    PubMed

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

    2013-08-01

    Nanoscale zerovalent iron (NZVI) such as Toda Kogyo RNIP-10DS has been used for site remediation, yet information is lacking regarding how far injected NZVI can travel, how long it lasts, and how it transforms to other minerals in a groundwater system. Previously we reported effective mass destruction of chlorinated ethenes dominated by tetrachloroethene (PCE) using emulsified zerovalent iron (EZVI) nanoparticles of RNIP-10DS in a shallow aquifer (1-6 m below ground surface, BGS) at Site 45, Marine Corps Recruit Depot, Parris Island, South Carolina, USA. Here we report test results on transport and transformation of injected EZVI in the subsurface. We employed two EZVI delivery methods: pneumatic injection and direct injection. Effective delivery of EZVI to the targeted zone was achieved with pneumatic injection showing a travel distance from injection points of up to 2.1 m and direct injection showing a travel distance up to 0.89 m. X-ray diffraction and scanning electron microscopy studies on particles harvested from well purge waters indicated that injected black colored NZVI (α-Fe(0)) was transformed largely to black colored cube-like and plate-like magnetites (Fe3O4, 0.1-1 μm, 0-9 months), then to orange colored irregularly shaped lepidocrocite (γ-FeOOH, 0.1-1 μm, 9 months to 2.5 years), then to yellowish lath-like goethite (α-FeOOH, 2-5 μm, 2.5 years) and ferrihydrite-like spherical particles (0.05-0.1 μm) in the top portion of the aquifer (1-2 m BGS). No α-Fe(0) was found in most monitoring wells three months after injection. The formed iron oxides appeared to have a wider range of particle size (submicron to 5 μm) than the pristine NZVI (35-140 nm). Injected NZVI was largely transformed to magnetite (0.1-1 μm) during two and half years in the lower portion of the aquifer (3-6 m). PMID:23562563

  14. THE DIVERSITY OF CONTAMINANT REDUCTION REACTIONS BY ZERO-VALENT IRON: ROLE OF THE REDUCTATE. (R827117)

    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...

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

    SciTech Connect

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

    2007-08-17

    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.

  16. Experimental design and response surface modelling for optimization of vat dye from water by nano zero valent iron (NZVI).

    PubMed

    Arabi, Simin; Sohrabi, Mahmoud Reza

    2013-01-01

    In this study, NZVI particles was prepared and studied for the removal of vat green 1 dye from aqueous solution. A four-factor central composite design (CCD) combined with response surface modeling (RSM) to evaluate the combined effects of variables as well as optimization was employed for maximizing the dye removal by prepared NZVI based on 30 different experimental data obtained in a batch study. Four independent variables, viz. NZVI dose (0.1-0.9 g/L), pH (1.5-9.5), contact time (20-100 s), and initial dye concentration (10-50 mg/L) were transform to coded values and quadratic model was built to predict the responses. The significant of independent variables and their interactions were tested by the analysis of variance (ANOVA). Adequacy of the model was tested by the correlation between experimental and predicted values of the response and enumeration of prediction errors. The ANOVA results indicated that the proposed model can be used to navigate the design space. Optimization of the variables for maximum adsorption of dye by NZVI particles was performed using quadratic model. The predicted maximum adsorption efficiency (96.97%) under the optimum conditions of the process variables (NZVI dose 0.5 g/L, pH 4, contact time 60 s, and initial dye concentration 30 mg/L) was very close to the experimental value (96.16%) determined in batch experiment. In the optimization, R2 and R2adj correlation coefficients for the model were evaluated as 0.95 and 0.90, respectively. PMID:24362989

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

    PubMed

    Dong, Guohui; Ai, Zhihui; Zhang, Lizhi

    2014-12-01

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

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

    EPA Science Inventory

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

  19. Iron Nanoparticles in Reactive Environmental Barriers

    SciTech Connect

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

    2003-09-23

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

  20. REMOVAL OF TNT AND RDX FROM WATER AND SOIL USING IRON METAL. (R825549C043)

    EPA Science Inventory

    Contaminated water and soil at active or abandoned munitions plants is a serious problem since these compounds pose risks to human health and can be toxic to aquatic and terrestrial life. Our objective was to determine if zero-valent iron (Fe0) could be used to p...

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

    EPA Science Inventory

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

  2. Use of Electrophoresis for Transporting Nano-Iron in Porous Media

    EPA Science Inventory

    Research was conducted to evaluate if electrophoresis could transport surface stabilized nanoscale zero-valent iron (nZVI) through fine grained sand with the intent of remediating a contaminant in situ. The experimental procedure involved determining the transport rates of poly...

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

    EPA Science Inventory

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

  4. 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

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

    2012-08-30

    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

  5. EFFECTS OF CARBONATE SPECIES ON THE KINETICS OF DECHLORINATION OF 1,1,1-TRICHLOROETHANE BY ZERO-VALENT IRON. (R827117)

    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...

  6. IN SITU REMEDIATION OF CONTAMINANTS IN GROUND WATER & SOILS USING PERMEABLE REACTIVE BARRIERS (PHASE I, CHROMIUM, CHLORINATED ORGANICS & ZERO-VALENT IRON) RSRP3

    EPA Science Inventory

    The primary objective of this research is to select an effective reductant for detoxification and immobilization of hexavalent chromium present in the soils/sediments collected from the old plating shop of the U.S. Coast Guard Air Support Center, Elizabeth City, North Carolina. ...

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

    EPA Science Inventory

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

  8. Comparative study on the reactivity of Fe/Cu bimetallic particles and zero valent iron (ZVI) under different conditions of N2, air or without aeration.

    PubMed

    Xiong, Zhaokun; Lai, Bo; Yang, Ping; Zhou, Yuexi; Wang, Juling; Fang, Shuping

    2015-10-30

    In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater. PMID:25978189

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

    SciTech Connect

    Kaplan, D.

    2002-12-18

    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 Outfall Delta (TNX OD), by subsurface and overland flow. A multi-faceted strategy has been proposed recently for mitigating contaminant migration at the site. The intent of this remediation strategy is not only to minimize contaminant leaching in a cost-effective manner, but also to minimize harm to the sensitive TNX wetland ecosystem.

  10. 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 Stations Launch Complex 34, FL, in 2002 to 2005 to evaluate the technologys efficacy in enhancing in situ dehalogenation of dense nonaqueous-phase liquid (DNAPL) ...

  11. 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) ...

  12. THE EFFECT OF SMECTITE ON THE CORROSION OF IRON METAL

    SciTech Connect

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

    2012-04-24

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

  13. RCRA corrective measures using a permeable reactive iron wall US Coast Guard Support Center, Elizabeth City, North Carolina

    SciTech Connect

    Schmithors, W.L.; Vardy, J.A.

    1997-12-31

    A chromic acid release was discovered at a former electroplating shop at the U.S. Coast Guard Support Center in Elizabeth City, North Carolina. Initial investigative activities indicated that chromic acid had migrated into the subsurface soils and groundwater. In addition, trichloroethylene (TCE) was also discovered in groundwater during subsequent investigations of the hexavalent chromium (Cr VI) plume. Corrective measures were required under the Resource Conservation and Recovery Act (RCRA). The in-situ remediation method, proposed under RCRA Interim Measures to passively treat the groundwater contaminants, uses reactive zero-valent iron to reductively dechlorinate the chlorinated compounds and to mineralize the hexavalent chromium. A 47 meter by 0.6 meter subsurface permeable iron wall was installed downgradient of the source area to a depth of 7 meters using a direct trenching machine. The iron filings were placed in the ground as the soils were excavated from the subsurface. This is the first time that direct trenching was used to install reactive zero-valent iron filings. Over 250 metric tons of iron filings were used as the reactive material in the barrier wall. Installation of the iron filings took one full day. Extensive negotiations with regulatory agencies were required to use this technology under the current facility Hazardous Waste Management Permit. All waste soils generated during the excavation activities were contained and treated on site. Once contaminant concentrations were reduced the waste soils were used as fill material.

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

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

  15. Effect of Cement on Emulsified Asphalt Mixtures

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

  16. Iron

    MedlinePlus

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

  17. Proteins and emulsifiers at liquid interfaces.

    PubMed

    Wilde, Peter; Mackie, Alan; Husband, Fiona; Gunning, Patrick; Morris, Victor

    2004-05-20

    The interfacial properties of proteins and emulsifiers have been studied extensively in the field of food colloid research. Emulsions form the basis of a huge range of food products and are generally stabilised by either protein and/or emulsifiers. Proteins have been shown to stabilise emulsions by forming a viscoelastic, adsorbed layer on the oil droplets, which form a physical barrier to coalescence. Emulsifiers can be oil or water soluble, forming a fluid, close-packed layer at the interface with a low interfacial tension. This results in an emulsion with a small droplet size distribution, stabilised by the fluid Gibbs-Marangoni mechanism or weak electrostatic repulsion. In real food emulsions, there is usually a mixture of proteins and emulsifiers competing for the interfacial area. This can produce a finer emulsion, however, the emulsifiers break down the viscoelastic protein-adsorbed layer, resulting in an emulsion with reduced stability. We present a review recent work that aims to characterise the composition, structure and physical properties of mixed protein-emulsifier interfaces, in an effort to understand the mechanisms behind the stability behaviour of food emulsion systems. PMID:15072929

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

    PubMed

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

    2014-07-01

    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

  19. Iron

    MedlinePlus

    ... plant foods as well as heme iron in animal foods. Life Stage Recommended Amount Birth to 6 ... with how your body absorbs, uses, or breaks down nutrients. Iron and healthful eating People should get ...

  20. IRON

    EPA Science Inventory

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

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

    NASA Astrophysics Data System (ADS)

    Allred, B. J.

    2009-12-01

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

  2. Treatment of emulsified oils by electrocoagulation: pulsed voltage applications.

    PubMed

    Genc, Ayten; Bakirci, Busra

    2015-01-01

    The effect of pulsed voltage application on energy consumption during electrocoagulation was investigated. Three voltage profiles having the same arithmetic average with respect to time were applied to the electrodes. The specific energy consumption for these profiles were evaluated and analyzed together with oil removal efficiencies. The effects of applied voltages, electrode materials, electrode configurations, and pH on oil removal efficiency were determined. Electrocoagulation experiments were performed by using synthetic and real wastewater samples. The pulsed voltages saved energy during the electrocoagulation process. In continuous operation, energy saving was as high as 48%. Aluminum electrodes used for the treatment of emulsified oils resulted in higher oil removal efficiencies in comparison with stainless steel and iron electrodes. When the electrodes gap was less than 1 cm, higher oil removal efficiencies were obtained. The highest oil removal efficiencies were 95% and 35% for the batch and continuous operating modes, respectively. PMID:25909730

  3. 7 CFR 58.722 - Emulsifying agents.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Emulsifying agents. 58.722 Section 58.722 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE (CONTINUED) REGULATIONS AND STANDARDS UNDER THE AGRICULTURAL MARKETING ACT OF 1946...

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

    PubMed Central

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

    2011-01-01

    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

  5. Electroremediation of PCB contaminated soil combined with iron nanoparticles: Effect of the soil type.

    PubMed

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

    2015-07-01

    Polychlorinated biphenyls (PCB) are carcinogenic and persistent organic pollutants that accumulate in soils and sediments. Currently, there is no cost-effective and sustainable remediation technology for these contaminants. In this work, a new combination of electrodialytic remediation and zero valent iron particles in a two-compartment cell is tested and compared to a more conventional combination of electrokinetic remediation and nZVI in a three-compartment cell. In the new two-compartment cell, the soil is suspended and stirred simultaneously with the addition of zero valent iron nanoparticles. Remediation experiments are made with two different historically PCB contaminated soils, which differ in both soil composition and contamination source. Soil 1 is a mix of soils with spills of transformer oils, while Soil 2 is a superficial soil from a decommissioned school where PCB were used as windows sealants. Saponin, a natural surfactant, was also tested to increase the PCB desorption from soils and enhance dechlorination. Remediation of Soil 1 (with highest pH, carbonate content, organic matter and PCB concentrations) obtained the maximum 83% and 60% PCB removal with the two-compartment and the three-compartment cell, respectively. The highest removal with Soil 2 were 58% and 45%, in the two-compartment and the three-compartment cell, respectively, in the experiments without direct current. The pH of the soil suspension in the two-compartment treatment appears to be a determining factor for the PCB dechlorination, and this cell allowed a uniform distribution of the nanoparticles in the soil, while there was iron accumulation in the injection reservoir in the three-compartment cell. PMID:25841071

  6. Valiant 'Zero-Valent' Effort Restores Contaminated Grounds

    NASA Technical Reports Server (NTRS)

    2005-01-01

    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.

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

    PubMed

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

    2011-02-01

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

  8. Enhancing the lipid productivity of yeasts with trace concentrations of iron nanoparticles.

    PubMed

    Pádrová, Karolína; Čejková, Alena; Cajthaml, Tomáš; Kolouchová, Irena; Vítová, Milada; Sigler, Karel; Řezanka, Tomáš

    2016-07-01

    Oxidative stress induced by zero-valent iron nanoparticles (nZVIs) was used to improve lipid accumulation in various oleaginous and non-oleginous yeasts-Candida sp., Kluyveromyces polysporus, Rhodotorula glutinis, Saccharomyces cerevisiae, Torulospora delbrueckii, Trichosporon cutaneum, and Yarrowia lipolytica. The highest lipid yields occurred at 9-13 mg/L nZVIs. Gas chromatography-mass spectrometry was used for the quantitative and qualitative analysis of the fatty acids. It showed an increasing abundance of polyunsaturated fatty acids, especially essential linoleic acid, in the presence of nZVIs. Our results suggest that nZVIs can be used to improve not only lipid production by oleaginous microorganisms but also the nutritional value of biosynthesized unsaturated fatty acids. PMID:26683688

  9. Efficient degradation of trichloroethylene in water using persulfate activated by reduced graphene oxide-iron nanocomposite.

    PubMed

    Ahmad, Ayyaz; Gu, Xiaogang; Li, Li; Lv, Shuguang; Xu, Yisheng; Guo, Xuhong

    2015-11-01

    Graphene oxide (GO) and nano-sized zero-valent iron-reduced graphene oxide (nZVI-rGO) composite were prepared. The GO and nZVI-rGO composite were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), energy-dispersive spectroscopy (EDS), and Raman spectroscopy. The size of nZVI was about 6 nm as observed by TEM. The system of nZVI-rGO and persulfate (PS) was used for the degradation of trichloroethylene (TCE) in water, and showed 26.5% more efficiency as compared to nZVI/PS system. The different parameters were studied to determine the efficiency of nZVI-rGO to activate the PS system for the TCE degradation. By increasing the PS amount, TCE removal was also improved while no obvious effect was observed by varying the catalyst loading. Degradation was decreased as the TCE initial concentration was increased from 20 to 100 mg/L. Moreover, when initial solution pH was increased, efficiency deteriorated to 80%. Bicarbonate showed more negative effect on TCE removal among the solution matrix. To better understand the effects of radical species in the system, the scavenger tests were performed. The •SO4(-) and •O2(-) were predominant species responsible for TCE removal. The nZVI-rGO-activated PS process shows potential applications in remediation of highly toxic organic contaminants such as TCE present in the groundwater. Graphical abstract Persulfate activated by reduced graphene oxide and nano-sized zero-valent iron composite can be used for efficient degradation of trichloroethylene (TCE) in water. PMID:26162447

  10. In vitro studies on silver implanted pure iron by metal vapor vacuum arc technique.

    PubMed

    Huang, Tao; Cheng, Yan; Zheng, Yufeng

    2016-06-01

    Pure iron has been verified as a promising biodegradable metal for absorbable cardiovascular stent usage. However, the degradation rate of pure iron is too slow. To accelerate the degradation of the surface of pure iron, silver ions were implanted into pure iron by metal vapor vacuum arc (MEVVA) source at an extracted voltage of 40keV. The implanted influence was up to 2×10(17)ions/cm(2). The composition and depth profiles, corrosion behavior and biocompatibility of Ag ion implanted pure iron were investigated. The implantation depths of Ag was around 60nm. The element Ag existed as Ag2O in the outermost layer, then gradually transited to metal atoms in zero valent state with depth increase. The implantation of Ag ions accelerated the corrosion rate of pure iron matrix, and exhibited much more uniform corrosion behavior. For cytotoxicity assessment, the implantation of Ag ions slightly decreased the viability of all kinds of cell lines used in these tests. The hemolysis rate of Ag ion implanted pure iron was lower than 2%, which was acceptable, whereas the platelet adhesion tests indicated the implantation of Ag ions might increase the risk of thrombosis. PMID:26925722

  11. Emulsifier of Arthrobacter RAG-1: specificity of hydrocarbon substrate.

    PubMed Central

    Rosenberg, E; Perry, A; Gibson, D T; Gutnick, D L

    1979-01-01

    The purified extracellular emulsifying factor produced by Arthrobacter RAG-1 (EF-RAG) emulsified light petroleum oil, diesel oil, and a variety of crude oils and gas oils. Although kerosine and gasoline were emulsified poorly by EF-RAG, they were converted into good substrates for emulsification by addition of aromatic compounds, such as 2-methylnaphthalene. Neither aromatic nor aliphatic fractions of crude oil were emulsified by EF-RAG; however, mixtures containing both fractions were emulsified. Pure aliphatic or aromatic hydrocarbons were emulsified poorly by EF-RAG. Binary mixtures containing an aliphatic and an aromatic hydrocarbon, however, were excellent substrates for EF-RAG-induced emulsification. Of a variety of alkylcyclohexane and alkylbenzene derivatives tested, only hexyl- or heptylbenzene and octyl- or decylcyclohexane were effectively emulsified by EF-RAG. These data indicate that for EF-RAG to induce emulsification of hydrocarbons in water, the hydrocarbon substrate must contain both aliphatic and cyclic components. With binary mixtures of methylnaphthalene and hexadecane, maximum emulsion was obtained with 25% hexadecane. PMID:453821

  12. Mineral precipitation and porosity losses in granular iron columns.

    PubMed

    Mackenzie, P D; Horney, D P; Sivavec, T M

    1999-08-12

    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 principally to mineral precipitation promoted by dissolved oxygen in the influent groundwater and is an issue in aerobic aquifers or in above-ground canister tests. Designs to minimize plugging in field applications where the groundwater is oxygenated include the use of larger iron particles and admixing sand of comparable size with the iron particles. Beyond the entrance zone, the groundwater in anaerobic and mineral precipitation leads to porosity losses in the bulk iron media, potentially reducing flow through the treatment zone. The nature of the mineral precipitation and the factors that affect extent of mineral precipitation have been examined by a variety of tools, including tracer tests, aqueous inorganic profiles, and surface analytical techniques. At short treatment times, porosity losses as measured by tracer tests are due mainly to Fe(OH)(2) precipitates and possible entrapment of a film of hydrogen gas on the iron surfaces. Over longer treatment times, precipitation of Fe(OH)(2) and FeCO(3) in low carbonate waters and of Fe(OH)(2), FeCO(3) and CaCO(3) in higher carbonate waters begin to dominate porosity losses. The control of pH within the iron media by addition of ferrous sulfide was shown not to reduce significantly calcium and carbonate precipitates, indicating that mineral precipitation is controlled by more than simple carbonate equilibrium considerations. PMID:10518662

  13. Iron and organo-bentonite for the reduction and sorption of trichloroethylene.

    PubMed

    Cho, Hyun-Hee; Lee, Taeyoon; Hwang, Sun-Jin; Park, Jae-Woo

    2005-01-01

    Hybrid barriers using dechlorination and immobilization were studied to remove trichloroethylene (TCE) in this study. Hybrid barriers of iron filings and organo (hexadecyltrimethylammonium, HDTMA)-bentonite were simulated in columns to assess the performance of the hybrid barriers. TCE reduction rate for the mixture of zero valent iron (ZVI) and HDTMA-bentonite was approximately seven times higher than that for ZVI, suggesting the reduction of TCE was accelerated when HDTMA-bentonite was mixed with ZVI. For the column of two separate layers of iron and HDTMA-bentonite, TCE reduction rate was nearly similar to that for ZVI alone, but the partition coefficient (Kd) was 4.5 times higher than that for ZVI only. TCE was immobilized in the first layer with HDTMA-bentonite due to sorption, and then dechlorinated in the second layer with iron filings due to reduction. The HDTMA-bentonite and minimally-desorbed HDTMA from the organo-bentonite are believed to contribute the increase in TCE concentration on iron surface so that more TCE could be available for reduction. Therefore, the incorporation of HDTMA-bentonite into ZVI not only can effectively retard the transport of chlorinated organic contaminants from landfill leachate or oil shock in subsurface environment, also can expedite the reduction rate of TCE. PMID:15522338

  14. Mechanistic Insights into Homogeneous and Heterogeneous Asymmetric Iron Catalysis

    NASA Astrophysics Data System (ADS)

    Sonnenberg, Jessica

    Our group has been focused on replacing toxic and expensive precious metal catalysts with iron for the synthesis of enantiopure compounds for industrial applications. During an investigation into the mechanism of asymmetric transfer hydrogenation with our first generation iron-(P-N-N-P) catalysts we found substantial evidence for zero-valent iron nanoparticles coated in chiral ligand acting as the active site. Extensive experimental and computational experiments were undertaken which included NMR, DFT, reaction profile analysis, substoichiometric poisoning, electron microscope imaging, XPS and multiphasic analysis, all of which supported the fact that NPs were the active species in catalysis. Reversibility of this asymmetric reaction on the nanoparticle surface was then probed using oxidative kinetic resolution of racemic alcohols, yielding modest enantiopurity and high turnover frequencies (TOF) for a range of aromatic alcohols. Efficient dehydrogenation of ammonia-borane for hydrogen evolution and the formation of B-N oligomers was also shown using the NP system, yielding highly active systems, with a maximum TOF of 3.66 H2/s-1 . We have also begun to focus on the development of iron catalysts for asymmetric direct hydrogenation of ketones using hydrogen gas. New chiral iron-(P-N-P) catalysts were developed and shown to be quite active and selective for a wide range of substrates. Mechanistic investigations primarily using NMR and DFT indicated that a highly active trans-dihydride species was being formed during catalyst activation. Lastly, a new library of chiral P-N-P and P-NH-P ligands were developed, as well as their corresponding iron complexes, some of which show promise for the development of future generations of active asymmetric direct hydrogenation catalysts.

  15. Self emulsifying drug delivery system (SEDDS) for phytoconstituents: a review.

    PubMed

    Chouhan, Neeraj; Mittal, Vineet; Kaushik, Deepak; Khatkar, Anurag; Raina, Mitali

    2015-01-01

    The self emulsifying drug delivery system (SEDDS) is considered to be the novel technique for the delivery of lipophillic plant actives. The self emulsifying (SE) formulation significantly enhance the solubility and bioavailability of poorly aqueous soluble phytoconstituents. The self emulsifying drug delivery system (SEDDS) can be developed for such plant actives to enhance the oral bioavailability using different excipients (lipid, surfactant, co solvent etc.) and their concentration is selected on the basis of pre formulation studies like phase equilibrium studies, solvent capacity of oil for drug and mutual miscibility of excipients. The present review focuses mainly on the development of SEDDS and effect of excipients on oral bioavailability and aqueous solubility of poorly water soluble phytoconstituents/ derived products. A recent list of patents issued for self emulsifying herbal formulation has also been included. The research data for various self emulsifying herbal formulation and patents issued were reviewed using different databases such as PubMed, Google Scholar, Google patents, Scopus and Web of Science. In a nutshell, we can say that SEDDS was established as a novel drug delivery system for herbals and with the advances in this technique, lots of patents on herbal SEDDS can be translated into the commercial products. PMID:25335929

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

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    Technical developments have now made it possible to emplace granular zero-valent iron (Fe 0) in fractured media to create a Fe 0 fracture reactive barrier (Fe 0 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 was partly filled with what was intended to be a uniform thickness of iron. Partial treatment of TCE by iron demonstrated that the concept of a Fe 0 FRB is practical, but was less than anticipated for an iron layer of uniform thickness. When the experiment was disassembled, evidence of discrete channelised flow was noted and attributed to imperfect placement of the iron. To evaluate the effect of the channel flow, an explicit Channel Model was developed that simplifies this complex flow regime into a conceptualised set of uniform and parallel channels. The mathematical representation of this conceptualisation directly accounts for (i) flow channels and immobile fluid arising from the non-uniform iron placement, (ii) mass transfer from the open fracture to iron and immobile fluid regions, and (iii) degradation in the iron regions. A favourable comparison between laboratory data and the results from the developed mathematical model suggests that the model is capable of representing TCE degradation in fractures with non-uniform iron placement. In order to apply this Channel Model concept to a Fe 0 FRB system, a simplified, or implicit, Lumped Channel Model was developed where the physical and chemical processes in the iron layer and immobile fluid regions are captured by a first-order lumped rate parameter. The performance of this Lumped Channel Model was compared to laboratory data, and benchmarked against the Channel Model. The advantages of the Lumped Channel Model are that the degradation of TCE in the system is represented by a first-order parameter that can be used directly in readily available numerical simulators.

  17. Solutions Remediate Contaminated Groundwater

    NASA Technical Reports Server (NTRS)

    2010-01-01

    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.

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

    PubMed

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

    2012-12-30

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

  19. Antibacterial activity and cytocompatibility of titanium oxide coating modified by iron ion implantation.

    PubMed

    Tian, Yaxin; Cao, Huiliang; Qiao, Yuqin; Meng, Fanhao; Liu, Xuanyong

    2014-10-01

    In this work, zero valent iron nanoparticles (Fezero-NPs) and iron oxide nanoparticles (Feox-NPs) were synthesized at the subsurface and surface regions of titanium oxide coatings (TOCs) by plasma immersion ion implantation. This novel Fe-NPs/TOC system showed negligible iron releasing, great electron storage capability and excellent cytocompatibility in vitro. Importantly, the system showed selective antibacterial ability which can kill Staphylococcus aureus under dark conditions but has no obvious antibacterial effect against Escherichia coli. Owing to a bipolar Schottky barrier between Fezero-NPs/TOC and Fezero-NPs/Feox-NPs, electrons could be captured by the Fezero-NPs bounded at the subsurface region of the coating. This electron storage capability of the Fe-NPs/TOC system induced extracellular electron transportation and accumulation of adequate valence-band holes (h(+)) at the external side, which caused oxidation damage to S. aureus cells in the dark. No obvious biocide effect against E. coli resulted from lack of electron transfer ability between E. coli and substrate materials. This work may open up a novel and controlled strategy to design coatings of implants with antibacterial ability and cytocompatibility for medical applications. PMID:24914826

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

    PubMed Central

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

    2012-01-01

    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

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

    PubMed

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

    2009-01-01

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

  2. Nitrate removal using electrokinetic/iron wall processes

    SciTech Connect

    Chew, C.F.; Zhang, T.C.

    1997-12-31

    The feasibility of using electrokinetics coupled with a zero-valent iron (Fe{sup 0}) treatment wall to abiotically remediate nitrate-contaminated soils was investigated. Upon completion of each test run, the contaminated soil specimen was sliced into five parts and analyzed for nitrate-nitrogen, ammonia-nitrogen, and nitrite-nitrogen. Nitrogen mass balance was used to determine the major transformation products. In control experiments where only electrokinetics was used at various constant voltages, 25 to 37% of the nitrate-nitrogen was transformed. The amount of nitrate-nitrogen transformed improved when a Fe{sup 0} wall (20 g or about 8--10% by weight) was placed near the anode. For test runs at various constant voltages, the amount of nitrate-nitrogen transformed ranged from 54 to 87%. By switching to constant currents, the amount of nitrate-nitrogen transformed was about 84--88%. The major transformation products were ammonia-nitrogen and nitrogen gases. Nitrite-nitrogen was around 1% or less in all experimental runs.

  3. In-situ Pb(2+) remediation using nano iron particles.

    PubMed

    Tehrani, Mohammad Reza Fadaei; Shamsai, Abolfazl; Vossughi, Manoochehr

    2015-01-01

    Originally, application of nano zero valent iron (nZVI) particles for the removal of lead (Pb(2+)) in porous media was studied. At first, stabilized nZVI (S-nZVI) was prepared and characterized, then used in batch and continuous systems. Based on the batch experiments, corresponding reaction kinetics well fitted with the pseudo-first-order adsorption model, and reaction rate ranged from 0.01 to 0.04 g/mg/min depend on solution pH and the molar ratio between Fe and Pb. In batch tests, optimal condition with more than 90% removal efficiency at 60 min was observed at a pH range of 4 to 6 and Fe/Pb ratio more than 2.5. Continuous experiments exposed that Pb(2+) remediation was as well influenced by seepage velocity, grain size, and type of porous media. The maximum Pb(2+) removal efficiency in batch and bench-scale systems were 97% and 81%, correspondingly. The results have shown the ability of S-nZVI to use in permeable reactive barriers, as an efficient adsorbent for Pb(2+), because of its excellent stability, high reducing power, and a large surface area. PMID:25763187

  4. Optimization of soil mixing technology through metallic iron addition.

    SciTech Connect

    Moos, L. P.

    1999-01-15

    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.

  5. Environmental application of millimetre-scale sponge iron (s-Fe(0)) particles (III): The effect of surface silver.

    PubMed

    Ju, Yongming; Yu, Yunjiang; Wang, Xiaoyan; Zhang, Sukun; Liu, Runlong; Fu, Jianping; Han, Jinglei; Fang, Jiande; Dionysiou, Dionysios D

    2015-12-15

    To enhance the dechlorination reactivity of millimetric sponge iron (s-Fe(0)), a facile one-pot method was used to decorate s-Fe(0) with Ag(+) ions under ambient conditions. The results recorded by X-ray diffraction patterns, X-ray photoelectron spectra and high-resolution transmission electron microscopy demonstrated that the growth of Ag(0) was dominated primarily by (111) plane with a mean length of ∼20 nm. The roles of Ag(0) loading, catalyst dosage, particle size, initial pH and contaminant concentration were assessed during the removal of pentachlorophenol (PCP). Catalyst recyclability was also studied. The results revealed that 3-5mm s-Fe(0) particles with 5 wt% Ag(0) loading exhibited the best performance with a dose of 3.0 g per 60 mL PCP solution. In addition, the dechlorination of PCP followed two-step, pseudo-first-order reaction kinetics, and Ag(0)-s-Fe(0) was advantageous compared with bimetals of nanoscale zero-valent iron, iron power and iron flakes. The dechlorination mechanism of PCP over Ag(0)-s-Fe(0) was attributed to the surface Ag(0) decoration, which catalyzed the formation of reactive hydrogen atoms for indirect reaction, and the direct electron transfer via Fe-Ag(0) galvanic cells for direct reaction. This suggests that Ag-based bimetals of s-Fe(0) have great potential in the pretreatment of organic halogen compounds in aqueous solution. PMID:26276702

  6. Inhibition of bacterial growth by iron oxide nanoparticles with and without attached drug: Have we conquered the antibiotic resistance problem?

    NASA Astrophysics Data System (ADS)

    Armijo, Leisha M.; Jain, Priyanka; Malagodi, Angelina; Fornelli, F. Zuly; Hayat, Allison; Rivera, Antonio C.; French, Michael; Smyth, Hugh D. C.; Osiński, Marek

    2015-03-01

    Pseudomonas aeruginosa is among the top three leading causative opportunistic human pathogens, possessing one of the largest bacterial genomes and an exceptionally large proportion of regulatory genes therein. It has been known for more than a decade that the size and complexity of the P. aeruginosa genome is responsible for the adaptability and resilience of the bacteria to include its ability to resist many disinfectants and antibiotics. We have investigated the susceptibility of P. aeruginosa bacterial biofilms to iron oxide (magnetite) nanoparticles (NPs) with and without attached drug (tobramycin). We also characterized the susceptibility of zero-valent iron NPs, which are known to inactivate microbes. The particles, having an average diameter of 16 nm were capped with natural alginate, thus doubling the hydrodynamic size. Nanoparticle-drug conjugates were produced via cross-linking drug and alginate functional groups. Drug conjugates were investigated in the interest of determining dosage, during these dosage-curve experiments, NPs unbound to drug were tested in cultures as a negative control. Surprisingly, we found that the iron oxide NPs inhibited bacterial growth, and thus, biofilm formation without the addition of antibiotic drug. The inhibitory dosages of iron oxide NPs were investigated and the minimum inhibitory concentrations are presented. These findings suggest that NP-drug conjugates may overcome the antibiotic drug resistance common in P. aeruginosa infections.

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

    PubMed

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

    2013-02-01

    Global water shortages caused by rapidly expanding population, escalating water consumption, and dwindling water reserves have rendered water reuse a strategically significant approach to meet current and future water demand. This study is the first to our knowledge to evaluate the technical feasibility of iron-mediated aeration (IMA), an innovative, potentially economical, holistic, oxidizing co-precipitation process operating at room temperature, atmospheric pressure, and neutral pH, for water reuse. In the IMA process, dissolved oxygen (O₂) was continuously activated by zero-valent iron (Fe⁰) to produce reactive oxygen species (ROS) at ambient pH, temperature, and pressure. Concurrently, iron sludge was generated as a result of iron corrosion. Bench-scale tests were conducted to study the performance of IMA for treatment of secondary effluent, natural surface water, and simulated contaminated water. The following removal efficiencies were achieved: 82.2% glyoxylic acid, ~100% formaldehyde as an oxidation product of glyoxylic acid, 94% of Ca²⁺ and associated alkalinity, 44% of chemical oxygen demand (COD), 26% of electrical conductivity (EC), 98% of di-n-butyl phthalate (DBP), 80% of 17β-estradiol (E2), 45% of total nitrogen (TN), 96% of total phosphorus (TP), 99.8% of total Cr, >90% of total Ni, 99% of color, 3.2 log removal of total coliform, and 2.4 log removal of E. Coli. Removal was attributed principally to chemical oxidation, precipitation, co-precipitation, coagulation, adsorption, and air stripping concurrently occurring during the IMA treatment. Results suggest that IMA is a promising treatment technology for water reuse. PMID:23232032

  8. Grape seed and apple tannins: emulsifying and antioxidant properties.

    PubMed

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

    2015-07-01

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

  9. Studies on gum of Moringa oleifera for its emulsifying properties

    PubMed Central

    Panda, Dibya Sundar

    2014-01-01

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

  10. Preparation and characterization of antibacterial Senegalia (Acacia) senegal/iron-silica bio-nanocomposites

    NASA Astrophysics Data System (ADS)

    Şişmanoğlu, Tuba; Karakuş, Selcan; Birer, Özgür; Soylu, Gülin Selda Pozan; Kolan, Ayşen; Tan, Ezgi; Ürk, Öykü; Akdut, Gizem; Kilislioglu, Ayben

    2015-11-01

    Many studies that research bio-nanocomposites utilize techniques that involve the dispersion of strengthening components like silica, metal and metal oxides through a host biopolymer matrix. The biggest success factor for the bio-nanocomposite is having a smooth integration of organic and inorganic phases. This interattraction between the surfaces of inorganic particles and organic molecules are vital for good dispersion. In this study, a novel biodegradable antibacterial material was developed using gum arabic from Senegalia senegal (stabilizer), silica (structure reinforcer) and zero valent iron particles. Silica particles work to not only strengthen the mechanical properties of the Senegalia senegal but also prevent the accumulation of ZVI nanoparticles due to attraction between hydroxyl groups and FeO. The gum arabic/Fe-SiO2 bio-nanocomposite showed effective antibacterial property against the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Using Scanning electron microscopy, homogeneous dispersion and uniform particle size was viewed in the biopolymer. X-ray diffraction studies of iron particles organization in Senegalia senegal also showed that the main portion of iron was crystalline and in the form of FeO and Fe0. X-ray photoelectron spectroscopy was used to evaluate the chemical composition of the surface but no appreciable peak was measured for the iron before Ar etching. These results suggest that the surface of iron nanoparticles consist mainly of a layer of iron oxides in the form of FeO. Thermal gravimetric analysis was used to determine the thermal stability and absorbed moisture content.

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

    PubMed

    Zhang, Qi

    2015-01-01

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

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

    PubMed

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

    2014-01-01

    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

  13. Nanosynthesis of Iron Based Material for Green Energy

    NASA Astrophysics Data System (ADS)

    Kirkeminde, Alec W.

    In this work, nanosynthesis of multiple iron-based materials are explored to further their use in green renewable-energy applications. First, the nanosynthesis of the abundant, non-toxic semi-conductor Iron Disulfide (Iron Pyrite, Fool's Gold, FeS2) is investigated. Within these studies, it became possible to tune the shape of the FeS2 nanoparticles easily by modifying injection temperatures and iron precursors. From here, the growth mechanisms of the different shapes were elucidated by examining different time points within the synthesis. It was discovered that the FeS2 did not grow by Ostwald Ripening, but instead by Oriented Attachment. Knowing this, it was possible to not only further the shapes of FeS2 nanoparticles, but also manipulate the size and crystallinity. Focus was then shifted to creating larger micron sized FeS2 crystals. Larger crystals where achieved by a unique FeS nanowire precursor followed by sulfurization. The dominant crystal surface of these crystals could be regulated simply by the time and temperature of the sulfurization. Second, synthetic control of magnetic nanoparticles was examined. A novel synthesis of Iron Palladium (FePd) made possible by interdiffusion of iron into palladium nanocores was identified. Furthermore, a shell of Iron oxide (Fe2O3) could facilely be grown on the FePd nanoparticles, generating a FePd/Fe2O3 core/shell nanoparticle. These FePd/Fe2O3 core/shell particles provided an excellent foundation to create an L10- FePd/α-Fe exchange-coupled nanocomposite that exhibited improved magnetic properties compared to its single phase FePd counterpart. However, the stabilizing ligand used within this FePd synthesis doped into the final nanoparticles, degraded the magnetic properties. iii To overcome the dopant ligand problem, a novel nanoalloy synthetic strategy of Metal Redox was developed. The Metal Redox strategy utilized the inherent reducing power of zero-valent metal sources to create a vast sampling of metal nanoalloys without the need of ligands or excess reducing agents. Stoichiometry of these nanoalloys could be readily adjusted by temperature and explained by simple chemical equilibrium concepts. The Metal Redox methodology was then expanded to shape control and tri-metallic alloys. Finally, the unique MnBi nanoalloy system was created using Metal Redox, making it the first ever reported solution processed formation of this material.

  14. Biochar Supported Nanoscale Iron Particles for the Efficient Removal of Methyl Orange Dye in Aqueous Solutions

    PubMed Central

    Zhao, Shichen; Yan, Jingchun; Qian, Linbo; Chen, Mengfang

    2015-01-01

    The presence of organic contaminants in industrial effluents is an environmental concern of increasing global importance. One innovative technology for treating contaminated industrial effluents is nanoscale zero-valent iron supported on biochar (nZVI/BC). Based on Transmission Electron Microscopy, X-Ray Diffraction, and Brunauer-Emmett-Teller characterizations, the nZVI was well dispersed on the biochar and aggregation was dramatically reduced. Methyl orange (MO) served as the representative organic contaminant for verifying the effectiveness of the composite. Using decolorization efficiency as an indicator of treatment effectiveness, increasing doses of nZVI/BC yielded progressively better results with 98.51% of MO decolorized by 0.6 g/L of composite at an nZVI/BC mass ratio of 1:5. The superior decolorization efficiency of the nZVI/BC was attributed to the increase in the dispersion and reactivity of nZVI while biochar increasing the contact area with contaminant and the adsorption of composites. Additionally, the buffering function of acid-washed biochar could be in favor of maintaining the reactivity of nZVI. Furthermore, the aging nZVI/BC for 30 day was able to maintain the removal efficiency indicating that the oxidation of nZVI may be delayed in the presence of biochar. Therefore, the composite of nZVI/BC could represent an effective functional material for treating wastewater containing organic dyes in the future. PMID:26204523

  15. Biochar Supported Nanoscale Iron Particles for the Efficient Removal of Methyl Orange Dye in Aqueous Solutions.

    PubMed

    Han, Lu; Xue, Song; Zhao, Shichen; Yan, Jingchun; Qian, Linbo; Chen, Mengfang

    2015-01-01

    The presence of organic contaminants in industrial effluents is an environmental concern of increasing global importance. One innovative technology for treating contaminated industrial effluents is nanoscale zero-valent iron supported on biochar (nZVI/BC). Based on Transmission Electron Microscopy, X-Ray Diffraction, and Brunauer-Emmett-Teller characterizations, the nZVI was well dispersed on the biochar and aggregation was dramatically reduced. Methyl orange (MO) served as the representative organic contaminant for verifying the effectiveness of the composite. Using decolorization efficiency as an indicator of treatment effectiveness, increasing doses of nZVI/BC yielded progressively better results with 98.51% of MO decolorized by 0.6 g/L of composite at an nZVI/BC mass ratio of 1:5. The superior decolorization efficiency of the nZVI/BC was attributed to the increase in the dispersion and reactivity of nZVI while biochar increasing the contact area with contaminant and the adsorption of composites. Additionally, the buffering function of acid-washed biochar could be in favor of maintaining the reactivity of nZVI. Furthermore, the aging nZVI/BC for 30 day was able to maintain the removal efficiency indicating that the oxidation of nZVI may be delayed in the presence of biochar. Therefore, the composite of nZVI/BC could represent an effective functional material for treating wastewater containing organic dyes in the future. PMID:26204523

  16. Floatable, macroporous structured alginate sphere supporting iron nanoparticles used for emergent Cr(VI) spill treatment.

    PubMed

    Huang, Jian-Fei; Li, Yong-Tao; Wu, Jin-Hua; Cao, Piao-Yang; Liu, Yong-Lin; Jiang, Gang-Biao

    2016-08-01

    Treatment of hexavalent chromium (Cr(VI)) spill accident is a great challenge due to its high toxicity, sudden and extensiveness. In this study, we designed and fabricated a hierarchical, ordered and macroporous structured alginate sphere to support in-situ synthesized zero-valent iron nanoparticle (the alginate-nZVI sphere). Field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS) images showed well dispersion of nZVI on the composite. This alginate-nZVI sphere exhibited good separability in effective removal of Cr(VI). The result from Cr(VI) removal experiment demonstrated a Cr(VI) removal efficiency of 98.2% at equilibrium time, which can be ascribed to the well dispersion of the nZVI. In addition, the alginate-nZVI sphere was effective in Cr(VI) removal in a wide range of pH from 3.0 to 11.0, by the merit of alginate substrate. Hence, the alginate-nZVI sphere might be a promising agent for an emergent Cr(VI) spill treatment by enhancing the dispersion, stabilization and separation properties of nZVI. PMID:27112857

  17. Iron nanoparticles decoration onto three-dimensional graphene for rapid and efficient degradation of azo dye.

    PubMed

    Wang, Wei; Cheng, Yilin; Kong, Tao; Cheng, Guosheng

    2015-12-15

    Porous three-dimensional graphene (3DG) prepared by chemical vapor deposition, was utilized as a matrix to support nanoscale zero-valent iron (nZVI) particles. The strategies to manipulate the morphology, distribution and size of nZVI particles on the 3DG support were demonstrated. The immobilized nZVI particles with a size of 100nm and dense deposition were achieved. A 94.5% of orange IV azo dye was removed in 60min using nZVI particles immobilized 3DG (3DG-Fe), whereas only 70.9% was removed by free Fe nanoparticles in aqueous solution. Meanwhile, a reaction rate with orange IV of 3DG-Fe was approximately 5-fold faster than that of free Fe nanoparticles. The effects of 3DG-Fe dosage, dye concentration, reaction pH and temperature on dye degradation were also addressed. Those results imply that both lowering pH and increasing temperature led to higher reaction efficiency and rate. The kinetic data reveal that the degradation process of orange IV dye, modeled by the pseudo-first-order kinetics, might involve adsorption and redox reaction with an activation energy of 39.2kJ/mol. PMID:26091894

  18. Freeze-drying of emulsified systems: A review.

    PubMed

    Morais, Andreza Rochelle do Vale; Alencar, Éverton do Nascimento; Xavier Júnior, Francisco Humberto; Oliveira, Christian Melo de; Marcelino, Henrique Rodrigues; Barratt, Gillian; Fessi, Hatem; Egito, Eryvaldo Sócrates Tabosa do; Elaissari, Abdelhamid

    2016-04-30

    Colloidal systems such as emulsions, microemulsions and nanoemulsions are able to transport active molecules, enhance their solubility and stability and minimize their side effects. However, since they are dispersions with an aqueous continuous phase they have some disadvantages such as the risk of microbiological contamination, degradation by hydrolysis, physico-chemical instability and loss of pharmacological activity of the drug. Freeze drying, in which the water is removed from the preparation by sublimation under vacuum, has been suggested as a means to resolve these problems. Lyophilized products are very stable and are easy to transport and store. However, there is very little information in the literature about the application of this technique to emulsified systems. The aim of this review is to evaluate the lyophilization process as a tool for increasing the shelf life of emulsified systems such as emulsions, microemulsions and nanoemulsions. In addition, the mechanism of cryoprotection and the techniques that can be used to characterize the freeze-dried systems are discussed. PMID:26943974

  19. Emulsifiers and thickeners on extrusion-cooked instant rice product.

    PubMed

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

    2013-08-01

    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), α-amylase sensitivity, water soluble index (WAI) and adhesive for extrudates, while the thickeners addition increased extrudates DG, bulk density (BD), WSC, α-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

  20. [Bread staling. Simultaneous effect of bacterial alpha-amylase and emulsifier on firmness and pasting properties of bread crumbs++].

    PubMed

    Grossmann, M V; de Barber, C B

    1997-09-01

    The effect of bacterial alpha-amylase and an emulsifier on firmness and amylograph characteristics of bread crumb during storage was studied. The bread which contained these additives was less firm and stalled more slowly than the control. The enzyme and the emulsifier retarded firmness but the emulsifier inhibited the action of the alpha-amylase. The regulatory action of the emulsifier also was observed on amylograph characteristics of bread crumb (peak viscosity, cool viscosity and setback). PMID:9673677

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

    SciTech Connect

    Watson, D.B.

    2003-12-30

    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.

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

    NASA Astrophysics Data System (ADS)

    Xie, Yang

    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.

  3. Biogeochemistry of Two Types of Permeable Reafctive Barriers, Organic Carbon and Iron-bearing Organic Carbon for Mine Drainage treatment: Column experiments

    SciTech Connect

    Guo, Q.; Blowes, D

    2009-01-01

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

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

    PubMed

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

    2015-04-28

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

  5. Heterobimetallic Complexes That Bond Vanadium to Iron, Cobalt, and Nickel.

    PubMed

    Clouston, Laura J; Bernales, Varinia; Cammarota, Ryan C; Carlson, Rebecca K; Bill, Eckhard; Gagliardi, Laura; Lu, Connie C

    2015-12-21

    Zero-valent iron, cobalt, and nickel were installed into the metalloligand V[N(o-(NCH2P((i)Pr)2)C6H4)3] (1, VL), generating the heterobimetallic trio FeVL (2), CoVL (3), and NiVL (4), respectively. In addition, the one-electron-oxidized analogues [FeVL]X ([2(ox)]X, where X(-) = BPh4 or PF6) and [CoVL]BPh4 ([3(ox)]BPh4) were prepared. The complexes were characterized by a host of physical methods, including cyclic voltammetry, X-ray crystallography, magnetic susceptibility, electronic absorption, NMR, electron paramagnetic resonance (EPR), and Mssbauer spectroscopies. The CoV and FeV heterobimetallic compounds have short M-V bond lengths that are consistent with M-M multiple bonding. As revealed by theoretical calculations, the M-V bond is triple in 2, 2(ox), and 3(ox), double in 3, and dative (Ni ? V) in 4. The (d-d)(10) species, 2 and 3(ox), are diamagnetic and exhibit large diamagnetic anisotropies of -4700 10(-36) m(3)/molecule. Complexes 2 and 3(ox) are also characterized by intense visible bands at 760 and 610 nm (? > 1000 M(-1) cm(-1)), respectively, which correspond to an intermetal (M ? V) charge-transfer transition. Magnetic susceptibility measurements and EPR characterization establish S = (1)/2 ground states for (d-d)(9) 2(ox) and (d-d)(11) 3, while (d-d)(12) 4 is S = 1 based on Evans' method. PMID:26636345

  6. Advances in the generation of a new emulsified fuel

    NASA Astrophysics Data System (ADS)

    Chávez, A.; Ramírez, M.; Medina, E.; Bolado, R.; Mora, J.

    2011-08-01

    The development of a new emulsified fuel is described, from the conceptual idea to the semi-industrial tests of the final product. The starting point was the necessity to lower the particulate matter (PM) emissions produced by the combustion of more than 200 MBD of heavy fuel oil (HFO) used for electric power conversion. The major component of HFO is a vacuum residue of the oil refining process mixed with light cycle oils to make it pumpable. An alternative to handle and burn the high viscosity residue (solid at room temperature) is by converting it in an oil-in-water emulsion. The best emulsions resulted of 70% residue in 30% water, Sauter Mean Diameter of 10-20 μm and a stability of more than 90 days. Spray burning tests of the emulsion against HFO in a semi-industrial 500 kW furnace showed a reduction in PM emissions of 24-36%.

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

    PubMed

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

    2008-11-01

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

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

    PubMed Central

    Lee, Changha; Sedlak, David L.

    2009-01-01

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

  9. Arsenic removal with composite iron matrix filters in Bangladesh: a field and laboratory study.

    PubMed

    Neumann, Anke; Kaegi, Ralf; Voegelin, Andreas; Hussam, Abul; Munir, Abul K M; Hug, Stephan J

    2013-05-01

    The main arsenic mitigation measures in Bangladesh, well-switching and deep tube wells, have reduced As exposure, but water treatment is important where As-free water is not available. Zero-valent iron (ZVI) based SONO household filters, developed in Bangladesh, remove As by corrosion of locally available inexpensive surplus iron and sand filtration in two buckets. We investigated As removal in SONO filters in the field and laboratory, covering a range of typical groundwater concentrations (in mg/L) of As (0.14-0.96), Fe (0-17), P (0-4.4), Ca (45-162), and Mn (0-2.8). Depending on influent Fe(II) concentrations, 20-80% As was removed in the top sand layer, but As removal to safe levels occurred in the ZVI-layer of the first bucket. Residual As, Fe, and Mn were removed after re-aeration in the sand of the second bucket. New and over 8-year-old filters removed As to <50 μg/L and mostly to <10 μg/L and Mn to <0.2 mg/L. Vertical concentration profiles revealed formation of Fe(II) by corrosion of Fe(0) with O2 and incorporation of As into forming amorphous Fe phases in the composite iron matrix (CIM) of newer filters and predominantly magnetite in older filters. As mass balances indicated that users filtered less than reported volumes of water, pointing to the need for more educational efforts. All tested SONO filters provided safe drinking water without replacement for up to over 8 years of use. PMID:23647491

  10. A shift in pathway of iron-mediated perchloroethylene reduction in the presence of sorbed surfactant--a column study.

    PubMed

    Li, Zhaohui; Willms, Cari; Alley, Jeff; Zhang, Pengfei; Bowman, Robert S

    2006-12-01

    Surface modification of zero-valent iron (ZVI) to enhance its reduction rates for chlorinated ethanes and ethenes has recently attracted great attention. In this research, the enhancement of perchloroethylene (PCE) reduction by ZVI in the presence of sorbed micelles of the cationic surfactant hexadecyltrimethylammonium (HDTMA) was examined in a series of laboratory column tests with varying flow rates and input PCE concentrations. Model simulations using HYDRUS-1D showed that the overall pseudo first-order rate constants for PCE reduction by ZVI increased by a factor of four in the presence of sorbed HDTMA admicelles. The increase in reduction rate was attributed to a higher distribution coefficient (K(d)) for contaminant sorption on surfactant-modified ZVI (SM-ZVI) compared to untreated ZVI. Modeling results also showed that in the presence of HDTMA admicelles 58-100% of PCE reduction occurred via hydrogenolysis. In contrast, only 12-25% PCE underwent hydrogenolysis when HDTMA was absent. The significant increase in TCE production during PCE reduction by SM-ZVI verified a shift in reaction pathway previously observed in batch studies, most likely from beta-elimination to hydrogenolysis. Although this shift in reaction pathway resulted in a higher accumulation of TCE, the combined concentrations of chlorinated hydrocarbons in the effluent were 1.5-5 times lower when SM-ZVI rather than unmodified ZVI was used. PMID:17055029

  11. Understanding the toxicity of aggregated zero valent copper nanoparticles against Escherichia coli.

    PubMed

    Rispoli, Fred; Angelov, Angel; Badia, Daniel; Kumar, Amit; Seal, Sudipta; Shah, Vishal

    2010-08-15

    Copper nanoparticles are used in wide variety of applications and in the current study we report the antimicrobial activity of these particles. Influence of pH, temperature, aeration rate, concentration of nanoparticles and concentration of bacteria on the toxicity of copper nanoparticles against Escherichia coli have been studied using a centroid mixture design of experiment. The linear and quadratic regression model shows that the toxicity of copper nanoparticles not only depends on the primary effect of the parameters tested (pH, temperature, aeration, concentration of E. coli and concentration of nanoparticles), but also on the interactive effect of these parameters. PMID:20434839

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed

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

    2015-07-01

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

  14. 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

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

    2004-01-01

    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

  15. The Role of Endogenous Lipids in the Emulsifying Properties of Cocoa

    PubMed Central

    Gould, Joanne M.; Furse, Samuel; Wolf, Bettina

    2016-01-01

    This paper describes a study in which the emulsifying properties of cocoa material with and without its lipid fraction were explored. This study was motivated by the commercial interest in naturally-occurring particulate emulsifiers as opposed to the chemically modified emulsifying particles presently available for commercial use. The hypothesis was that endogenous lipids from cocoa were responsible for driving the formation of stable oil-in-water (o/w) emulsions. The data presented includes relative quantification of phospholipids from different commercially available cocoa material using 31P NMR spectroscopy and analyses of the emulsifying power of delipidified cocoa material. The commercially available cocoa material comprised several phospholipids, with phosphatidylcholine being the most abundant in all samples. Dispersions of delipidified cocoa material were found to drive the formation of o/w emulsions despite the absence of lipids. We therefore concluded that the emulsifying behavior of cocoa material is not entirely reliant upon the endogenous lipids. This suggests that cocoa material may have a new and potentially widespread use in industrial food preparation and may inform manufacturing strategies for novel food grade emulsifiers. PMID:27014680

  16. Changes in secondary structure of gluten proteins due to emulsifiers

    NASA Astrophysics Data System (ADS)

    Gómez, Analía V.; Ferrer, Evelina G.; Añón, María C.; Puppo, María C.

    2013-02-01

    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 α-helix conformation and a decrease in β-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 α-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.

  17. Partial oxidation ("aging") and surface modification decrease the toxicity of nanosized zerovalent iron.

    PubMed

    Phenrat, Tanapon; Long, Thomas C; Lowry, Gregory V; Veronesi, Bellina

    2009-01-01

    Nanoscale zero-valent iron (nZVI) is a "redox"-active nanomaterial used in the remediation of contaminated groundwater. To assess the effect of "aging" and surface modification on its potential neurotoxicity, cultured rodent microglia (BV2) and neurons (N27) were exposed to fresh nZVI, "aged" (>11 months) nZVI, magnetite, and polyaspartate surface-modified (SM) nZVI. Increases in various measures of oxidative stress indicated that BV2 microglia responded to these materials in the following rank order: nZVI > "aged" nZVI > magnetite = SM nZVI. Fresh nZVI produced morphological evidence of mitochondrial swelling and apoptosis. In N27 neurons, ATP levels were reduced in the following rank order: nZVI > SM-nZVI > "aged" nZVI = magnetite. Ultrastructurally, nZVI produced a perinuclear floccular material and cytoplasmic granularity. Both SM-nZVI produced intracellular deposits of nanosize particles in the N27. The physicochemical properties of each material, measured under exposure conditions, indicated that all had electronegative zeta potentials. The iron content of nZVI (approximately 35%) and SM-nZVI (approximately 25%) indicated high "redox" activity while that of "aged" and magnetite was neglibile. Sedimentation and agglomeration occurred in the following rank order: nZV > "aged" nZVI > magnetite > SM-nZVI. Correlating these properties with toxicity indicated that partial or complete oxidation of nZVI reduced its "redox" activity, agglomeration, sedimentation rate, and toxicity to mammalian cells. Surface modification decreased nZVI toxicity by reducing sedimentation which limited particle exposure to the cells. PMID:19209606

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  19. Iron Test

    MedlinePlus

    ... detect and help diagnose iron deficiency or iron overload. In people with anemia , these tests can help ... also be ordered when iron deficiency or iron overload is suspected. Early iron deficiency often goes unnoticed. ...

  20. Nanoscale and Microscale Iron Emulsions for Treating DNAPL

    NASA Technical Reports Server (NTRS)

    Geiger, Cherie L.

    2002-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  2. Iron Sulfide as a Sustainable Reactive Material for Permeable Reactive Barriers

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  3. In vitro study of effects of emulsified oil on broiler feed quality.

    PubMed

    Liu, Xiao-Chuan; Yang, Zai-Bin; Yang, Wei-Ren; Jiang, Shu-Zhen; Zhang, Gui-Guo

    2013-03-01

    An experiment was conducted to compare effects of emulsified soybean oil and non-emulsified soybean oil on the quality of broiler feed differing in the feed type and the broiler feeding stage in vitro. A 2 × 2 × 3 factorial arrangement was designed with two fat sources (soybean oil and emulsified oil), two feed types (mash and pellet) and three broiler feeding stages (starter, grower and finisher). Four samples of feeds were collected from each combination of factors at the beginning of the experiment and stored at 20°C. Subsamples were taken at 15-day intervals to determine the moisture content, peroxide value (PV), acid value (AV) and the total fungal count over a 45-day period; weight loss percentage was determined by weighting the samples at days 0, 15, 30 and 45; fines percentage in pellets was only determined at day 0. The emulsified oil reduced (P < 0.05) the fines percentage, increased (P < 0.05) the moisture content, decreased (P < 0.05) the weight loss percentage and PV, did not affect (P > 0.05) the AV and the total fungal count. Results showed that the emulsified oil decreased weight loss, increased pelletability, moisture content and oxidation stability without affecting fungal growth. PMID:23480703

  4. Effect of Hydrocolloids and Emulsifiers on Baking Quality of Composite Cassava-Maize-Wheat Breads

    PubMed Central

    Eduardo, Maria; Ahrné, Lilia

    2014-01-01

    Cassava is widely available worldwide but bread quality is impaired when cassava is used in the bread formulation. To overcome this problem, different improvers were tested in the preparation of composite cassava-maize-wheat (CMW) breads. Emulsifiers, diacetyl tartic acid ester of monoglycerides (DATEM), sodium stearoyl-2-lactylate (SSL), and lecithin (LC); and hydrocolloids, carboxymethylcellulose (CMC) and high-methylated pectin (HM pectin) were added during dough preparation of the composite flours (cassava-maize-wheat, 40 : 10 : 50). Each emulsifier was tested in combination with the hydrocolloids at levels of 0.1, 0.3, and 0.5% while hydrocolloids were used at a level of 3%. Bread quality attributes such as specific loaf volume, crust colour, crumb moisture, and firmness were measured. The specific volume of the fresh breads significantly improved with the addition of hydrocolloids (7.5 and 13%) and in combination with emulsifiers (from 7.9 to 27%) compared with bread produced without improvers. A significant improvement of brownness index and firmness of the composite flours breads was achieved with the addition of hydrocolloids and emulsifiers. The results show that emulsifiers and hydrocolloids can significantly improve the baking quality of CMW breads and thereby enhance the potential for using locally produced flours in bread baking. PMID:26904634

  5. Self-emulsifying excipient platform for improving technological properties of alginate-hydroxypropylcellulose pellets.

    PubMed

    Mannina, Paolo; Segale, Lorena; Giovannelli, Lorella; Bonda, Andrea Foglio; Pattarino, Franco

    2016-02-29

    In this work, alginate, alginate-pectin and alginate-hydroxypropylcellulose pellets were produced by ionotropic gelation and characterized. Ibuprofen was selected as model drug; it was suspended in the polymeric solution in crystalline form or dissolved in a self-emulsifying phase and then dispersed into the polymeric solution. The self-emulsifying excipient platform composed of Labrasol (PEG-8 caprylic/capric glycerides) and d-α-tocopherol polyethylene glycol 1000 succinate (TPGS), able to solubilize the drug was used to improve the technological and biopharmaceutical properties of the alginate pellets. The pellets had diameters between 1317 and 2026μm and a high drug content (>51%). DSC analysis showed the amorphous state of drug in the pellets containing the self-emulsifying phase. All the systems restricted drug release in conditions simulating the gastric environment and made the drug completely available at a pH value typical for the intestine. Only alginate-HPC systems containing the drug solubilized into the self-emulsifying phase showed the ability to partially control the release of ibuprofen at neutral pH. The self-emulsifying excipient platform is a useful tool to improve technological and biopharmaceutical properties of alginate-HPC pellets. PMID:26721727

  6. Effect of a single dose of emulsified versus capsular fish oils on plasma phospholipid fatty acids over 48 hours

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Emulsified fish oil supplements provide an alternative to encapsulated fish oils. Oil-in-water emulsions may offer an advantage in digestion and absorption thereby increasing the bioavailability of fatty acids. We evaluated the effect of three oil-in-water emulsified fish oils (Emulsion B, Emulsion ...

  7. Improving halva quality with dietary fibres of sesame seed coats and date pulp, enriched with emulsifier.

    PubMed

    Elleuch, Mohamed; Bedigian, Dorothea; Maazoun, Bouthaina; Besbes, Souhail; Blecker, Christophe; Attia, Hamadi

    2014-02-15

    Supplementation of halva with waste products of manufacturing, for example defatted sesame seed coats (testae) and date fibre concentrate, can improve its nutritional and organoleptic qualities. These constituents provide high fibre content and technological potential for retaining water and fat. Standard halva supplemented with date fibre concentrate, defatted sesame testae and emulsifier was evaluated for oil separation, texture and colour changes, sensory qualities and acceptability to a taste panel. Addition of both fibres with an emulsifier, improved emulsion stability and increased the hardness of halva significantly. The functional properties of sesame testae and date fibres promote nutrition and health, supplying polyphenol antioxidants and laxative benefits. PMID:24128542

  8. Comparison of different ibuprofen-amino acid compounds with respect to emulsifying and cytotoxic properties.

    PubMed

    Baydoun, Luma; Düvel, Andreas; Daniels, Rolf; Drust, Andreas; Goldhagen, Thorsten; Schwan, Irina; Zeidler, Christian; Müller-Goymann, Christel C

    2004-04-15

    Sodium ibuprofen (Ibu-Na) and different ibuprofen-amino acid compounds, lysinate (Ibu-Lys), arginate (Ibu-Arg) and histidinate (Ibu-His), were evaluated for emulsifying, haemolytic and cytotoxic properties. The highest reduction of surface tension was obtained with Ibu-Lys which shows good emulsifying qualities. At the same time, Ibu-Lys reveals the highest haemolytic activity and affects porcine cornea integrity. However, incorporation of Ibu-Lys into an emulsion system significantly decreases haemolysis. On the contrary Ibu-Arg, which shows a lower surface tension reduction, allows, unlike Ibu-Na and Ibu-His, for comparably stable emulsions with comparable erythrocyte damage. PMID:15072792

  9. Iron Chelation

    MedlinePlus

    ... iron overload and need treatment. What is iron overload? Iron chelation therapy is used when you have ... may want to perform: How quickly does iron overload happen? This is different for each person. It ...

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

    PubMed

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

    2014-09-15

    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 ∼2.9Å) and UFe (at ∼3.2Å) 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

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

    PubMed

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

    2014-10-15

    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

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

    PubMed

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

    2011-02-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    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 μg/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.

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

    PubMed

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

    2010-07-30

    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

  15. Kinetic study for phenol degradation by ZVI-assisted Fenton reaction and related iron corrosion investigated by X-ray absorption spectroscopy.

    PubMed

    Yoon, In-Ho; Yoo, Gursong; Hong, Hye-Jin; Kim, Jungmin; Kim, Min Gyu; Choi, Wang-Kyu; Yang, Ji-Won

    2016-02-01

    In this study, we investigated phenol degradation via zero-valent iron (ZVI)-assisted Fenton reaction through kinetic and spectroscopic analysis. In batch experiments, 100 mg/L of phenol was completely degraded, and 75% of TOC was removed within 3 min under an optimal hydrogen peroxide (H2O2) concentration (50 mM) via the Fenton reaction. In the absence of H2O2, oxygen (O2) was dissolved into the solution and produced H2O2, which resulted in phenol degradation. However, phenol removal efficiency was not very high compared to external H2O2 input. The Fenton reaction rapidly occurred at the surface of ZVI, and then phenol mobility from the solution to the ZVI surface was the rate determining step of the whole reaction. The pseudo-second order adsorption kinetic model well describes phenol removal, and its rate increased according to the H2O2 concentration. X-ray absorption spectroscopic analysis revealed that iron oxide (Fe-O bonding) was formed on ZVI with [H2O2] > 50 mM. A high concentration of H2O2 led to rapid degradation of phenol and caused corrosion on the ZVI surface, indicating that Fe(2+) ions were rapidly oxidized to Fe(3+) ions due to the Fenton reaction and that Fe(3+) was precipitated as iron oxide on the ZVI surface. However, ZVI did not show corroded characteristics in the absence of H2O2 due to the insufficient ZVI-assisted Fenton reaction and oxidation of Fe(2+) to Fe(3+). PMID:26692518

  16. 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...

  17. Combined chromatography and mass spectrometry for the molecular characterization of food emulsifiers.

    PubMed

    du Chatinier, Wilma; Janssen, Hans-Gerd

    2016-03-25

    Food emulsifiers are widely used to stabilise water-fat emulsions such as mayonnaise and dressings. They are prepared by oligomerisation of a poly-alcohol (as e.g. glycerol or citric acid) followed by a reaction with fatty acids. In order to gain insight in the chemical composition of different emulsifiers, a range of chromatographic methods including gas chromatography, size exclusion chromatography, normal phase- and reversed phase liquid chromatography either or not in combination with mass spectrometry was deployed. The different methods turned out to be highly complementary. By combining the information from different methods the polar head group and the fatty acid part of the emulsifier can be characterised in detail. Mass spectrometry is indispensable for establishing the number of polar molecules in the head group as well as for establishing the correct combinations of fatty acids in one molecule. Ten commercial emulsifiers were described at the level of number and type of polar groups and fatty acids present. PMID:26818238

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Molecular characteristics of corn fiber gum and their influence on its emulsifying properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The molecular characteristics of two purified arabinoxylan fractions derived from corn kernels, corn fiber gum-1 and 2 (CFG-1 and 2), have been studied and correlated with their emulsifying properties. CFG-1 and 2 fractions were isolated from different corn fiber sources by (a) a sequential alkali...

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

    SciTech Connect

    Lee, P.K.; Szuhaj, B.F.; Diego, A.

    1996-12-31

    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.

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

    PubMed

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

    2014-10-21

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

  2. Effects of inulin on the structure and emulsifying properties of protein components in dough.

    PubMed

    Liu, Juan; Luo, Denglin; Li, Xuan; Xu, Baocheng; Zhang, Xiaoyu; Liu, Jianxue

    2016-11-01

    High-purity gliadin, glutenin and gluten fractions were extracted from wheat gluten flour. To investigate the effects of three types of inulin with different degrees of polymerization (DP) on the emulsifying properties, disulfide contents, secondary structures and microstructures of these fractions, Turbidimetry, spectrophotometer, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used in this study. The results showed that the emulsifying activity of gliadin was higher than that of glutenin and gluten, but its emulsion stability was lower than that of glutenin. Adding inulin increased the emulsifying activity of the three protein fractions and emulsion stability of gliadin and gluten, but decreased the emulsion stability of glutenin and disulfide bond contents of glutenin and gluten. In the presence of inulin, the α-helical structure of the three proteins had no significant change, whereas the β-turn structure decreased and β-sheet structure increased. The SEM images showed that inulin had the most significant effect on the glutenin microstructure. In general, inulin with a higher DP had greater effects on the structure and emulsifying properties of protein components in dough. PMID:27211643

  3. Enhanced bioavailability of EPA from emulsified fish oil preparations versus capsular triacylglycerol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pre-emulsified fish oil supplements, an alternative to capsular triacylglycerol, may enhance the uptake of LCn3 fatty acids it contains. A randomized, Latin-square crossover design was used to compare the effects of four fish oil supplement preparations on phospholipid (PLFA) and chylomicron fatty ...

  4. 21 CFR 178.3400 - Emulsifiers and/or surface-active agents.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... citations affecting § 178.3400, see the List of CFR Sections Affected, which appears in the Finding Aids... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Emulsifiers and/or surface-active agents. 178.3400 Section 178.3400 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN...

  5. 21 CFR 178.3400 - Emulsifiers and/or surface-active agents.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Emulsifiers and/or surface-active agents. 178.3400 Section 178.3400 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND SANITIZERS Certain Adjuvants...

  6. 21 CFR 178.3400 - Emulsifiers and/or surface-active agents.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... Editorial Note: For Federal Register citations affecting § 178.3400, see the List of CFR Sections Affected... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Emulsifiers and/or surface-active agents. 178.3400 Section 178.3400 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN...

  7. 21 CFR 178.3400 - Emulsifiers and/or surface-active agents.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... citations affecting § 178.3400, see the List of CFR Sections Affected, which appears in the Finding Aids... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Emulsifiers and/or surface-active agents. 178.3400 Section 178.3400 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN...

  8. 21 CFR 178.3400 - Emulsifiers and/or surface-active agents.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... citations affecting § 178.3400, see the List of CFR Sections Affected, which appears in the Finding Aids... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Emulsifiers and/or surface-active agents. 178.3400 Section 178.3400 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN...

  9. 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...

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

    PubMed

    Chen, L; Liu, H

    2012-09-01

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

  11. Emission of burning emulsified diesel oil with sodium sulfate in salty atmospheric air.

    PubMed

    Lin, Cherng-Yuan; Pan, Jenq-Yih

    2003-01-01

    The effects of sodium sulfate in fuel oil and salty atmospheric air on the emission characteristics of furnaces or boilers burned with emulsified diesel oils are considered in this study. An industrial cylindrical furnace made of stainless steel associated with an automatic oil-fired burner was used for the emission measurements. Both neat diesel oil and emulsified diesel oil with distilled water were used as the tested oils. A homogenizing and emulsifying machine was employed to stir the diesel oil and sodium sulfate powder into a homogeneous oil mixture, and to prepare emulsions of micro-droplets of water dispersed in diesel oil. The experimental results showed that the existence of sodium chloride in atmospheric air enhanced SO2 formation. The use of emulsified diesel oil with 300-ppm sodium sulfate as fuel reduced the burning gas temperature and NOx emission while increased O2 emission. Moreover, the presence of sodium chloride in atmospheric air hindered the completeness of the combustion process and thus resulted in lower burning efficiency and larger excess oxygen emission. PMID:14672327

  12. Emulsified halothane produces long-term epidural anesthetic effect: a study in rabbits.

    PubMed

    Li, Fengshan; Liao, Daqing; Liu, Jin; Xiao, Lin; Guo, Jiao; Yi, Mingliang; Zhou, Cheng

    2015-01-01

    Previous studies have demonstrated that volatile anesthetics could produce local anesthesia. Emulsified isoflurane at 8% has been reported to produce epidural anesthetic effect in rabbits. This study was designed to investigate the long-term epidural anesthetic effect of emulsified halothane in rabbits. In this study, 40 healthy adult rabbits (weighting 2.0-2.5 kg) with an epidural catheter were randomly divided into 4 groups (n=10/group), receiving epidural administration of 1% lidocaine (lido group), 8% emulsified isoflurane 1ml (8% E-iso group), 8% emulsified halothane (8% E-Halo group) and 12% emulsified halothane (12% E-Halo group). After administration, sensory and motor functions as well as consciousness state were assessed until 60 minutes after sensory and motor function returned to its baseline or at least for 180 min. After epidural anesthesia, all the rabbits were continuously observed for 7 days and sacrificed for pathological evaluations. As a result, all the four study solutions produced typical epidural anesthesia. Onset times of sensory and motor function blockade were similar among the four groups (P>0.05). Duration of sensory blockade in 12% E-Halo group (83±13 min) was significantly longer than other groups: 51±12 min in 8% E-Halo group (P<0.01), 57±8 min in 8% E-iso group (P<0.01) and 47±9 min in lido group (P<0.01). Duration of sensory blockade in 8% E-iso group is longer than lido group (P<0.05). Duration of motor blockade in 12% E-Halo group (81±12 min) was also significantly longer than other groups: 40±8 min in 8% E-Halo group (P<0.01), 37±3 min in 8% E-iso group (P<0.01), 37±6 min in lido group (P<0.01). Normal consciousness was found in the rabbits from 8% E-Halo, 8% E-iso and lido groups while there were four rabbits in 12% E-Halo group (4/10) showed a light sedation. For all the rabbits, no pathological injury was found. The present study demonstrates that emulsified halothane produces reversible concentration-dependent epidural anesthesia and at 12% (v/v), emulsified halothane could produce long-term anesthesia without pathological injury. PMID:26191147

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

    PubMed

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

    2014-08-01

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

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

    PubMed Central

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

    2014-01-01

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

  15. The Acinetobacter outer membrane protein A (OmpA) is a secreted emulsifier.

    PubMed

    Walzer, Gil; Rosenberg, Eugene; Ron, Eliora Z

    2006-06-01

    Acinetobacter strains use hydrophobic carbon sources and most of them are efficient oil degraders. They secrete a variety of emulsifiers which are efficient in producing and stabilizing oil-in-water emulsions. The bioemulsifier of Acinetobacter radioresistens KA53 (Alasan) is a high-mass complex of proteins and polysaccharides. The major emulsification activity of this complex is associated with a 45 kDa protein (AlnA), which is homologous to the outer membrane protein OmpA. The emulsification ability of AlnA depends on the presence of hydrophobic residues in the four loops spanning the transmembrane domains. The finding of a secreted OmpA was unexpected, in view of the fact that this protein is essential in all Gram-negative bacteria, has four trans-membrane domains and is considered to be an integral structural component of the outer membrane. However, secretion of an OmpA with emulsifying ability could be of physiological importance in the utilization of hydrophobic substrates as carbon sources. Here we examined the possibility that secretion of OmpA with emulsifying activity is a general property of the oil-degrading Acinetobacter strains. The results indicate that OmpA is secreted in five strains of Acinetobacter, including strain Acinetobacter sp. ADP1 whose genome has been sequenced. The ompA genes of ADP1 and an additional strain, Acinetobacter sp. V-26 were cloned and sequenced. Structure analysis of the sequence of the two proteins indicated the existence of the hydrophobic regions, previously shown to be responsible for the emulsification activity of AlnA. Further examination of the recombinant OmpA proteins indicated that they are, indeed, strong emulsifiers, even when produced in Escherichia coli. The finding that Acinetobacter OmpA has emulsifying activity and that it is secreted in five strains of Acinetobacter may be physiologically significant and suggests the involvement of this protein in biodegradation of hydrophobic substrates, including hydrocarbons. PMID:16689723

  16. Emulsifying Activities of Purified Alasan Proteins from Acinetobacter radioresistens KA53

    PubMed Central

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

    2001-01-01

    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

  17. Emulsifying activities of purified Alasan proteins from Acinetobacter radioresistens KA53.

    PubMed

    Toren, A; Navon-Venezia, S; Ron, E Z; Rosenberg, E

    2001-03-01

    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

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

    PubMed

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

    2014-05-01

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

  19. 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) Other products may also contain iron.

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

    SciTech Connect

    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

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

  1. Physico-chemical studies and emulsifying properties of N-propyl-N-methylene phosphonic chitosan.

    PubMed

    Albertengo, Liliana; Farenzena, Sonia; Debbaudt, Adriana; Zuñiga, Adriana; Schulz, Pablo; Rodriguez, Maria Susana

    2013-02-15

    Chitosan is a modified, natural carbohydrate polymer derived by deacetylation of chitin. Due to the presence of two functional groups can undergo many chemical modifications. In a previous work we described the synthetic strategy and characterization of a novel soluble derivative: N-propyl-N-methylene phosphonic chitosan (PNMPC). In the study of some physicochemical properties, results showed that this modified chitosan aggregates in several steps when the concentration is increased. By addition of NaOH the initially coiled molecules stretch exposing more phosphonic acid groups to neutralization and finally give a cooperative reaction with OH((). PNMPC has emulsifying properties and gives O/W emulsions with quasi-monodisperse small droplets. Emulsions with 0.18% PNMPC and 30:70 o:w ratio exhibited the best emulsifying properties within the test range. This emulsion ratio showed high stability to long time storage and several successive freeze/thaw and heating/cooling cycles. PMID:23399201

  2. Ice nucleation in emulsified aqueous solutions of antifreeze protein type III and poly(vinyl alcohol).

    PubMed

    Inada, Takaaki; Koyama, Toshie; Goto, Fumitoshi; Seto, Takafumi

    2011-06-23

    Antifreeze protein (AFP) III and poly(vinyl alcohol) (PVA) are known as anti-ice nucleating agents (anti-INAs), which inhibit heterogeneous ice nucleation. However, the effectiveness of these anti-INAs in inhibiting ice nucleation in water-in-oil (W/O) emulsions, in which homogeneous ice nucleation can be experimentally simulated, is unclear. In this study, the ice nucleation temperature in emulsified solutions of AFP III, PVA, and other nonanti-INA polymers was measured, and then the nucleation rate was analyzed based on classical nucleation theory. Results showed that ice nucleation was surface-initiated and, except for PVA solutions, probably caused heterogeneously by the emulsifier, SPAN 65, at the droplet surfaces. In this nucleation mode, AFP III had no significant effect on the ice nucleation rate. In contrast, PVA exhibited ice-nucleating activity only at the droplet surfaces, suggesting that the nucleation is due to the interaction between PVA and SPAN 65. PMID:21619040

  3. Peroxidase-mediated conjugation of corn fiber gum and bovine serum albumin to improve emulsifying properties.

    PubMed

    Liu, Yan; Qiu, Shuang; Li, Jinlong; Chen, Hao; Tatsumi, Eizo; Yadav, Madhav; Yin, Lijun

    2015-03-15

    The emulsifying properties of corn fiber gum (CFG), a naturally occurring polysaccharide-protein complex, was improved by kinetically controlled formation of hetero-covalent linkages with bovine serum albumin (BSA), using horseradish peroxidase (HRP). The formation of hetero-crosslinked CFG-BSA conjugates was confirmed using ultraviolet-visible and Fourier-transform infrared analyses. The optimum CFG-BSA conjugates were prepared at a CFG:BSA weight ratio of 10:1, and peroxidase:BSA weight ratio of 1:4000. Selected CFG-BSA conjugates were used to prepare oil-in-water emulsions; the emulsifying properties were better than those of emulsions stabilized with only CFG or BSA. Measurements of mean droplet sizes and zeta potentials showed that CFG-BSA-conjugate-stabilized emulsions were less susceptible to environmental stresses, such as pH changes, high K ionic strengths, and freeze-thaw treatments than CFG- or BSA-stabilized emulsions. These conjugates have potential applications as novel emulsifiers in food industry. PMID:25542109

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

    SciTech Connect

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

    1983-02-01

    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 the hydrocarbon emulsifying activity. Both activities of the isolate were strongly inhibited by chymotrypsin treatment indicating the importance of the protein moiety for its activity. Hydrocarbon solubilization by the isolate showed a certain degree of specificity to pristane in modest agitation generally used in microbial cultivation, but this specificity was lost by vigorous agitation in a Waring blender. It was proposed that in the first case, solubilization was effected by a solubilizing factor specific to pristane, whereas in the latter ease, nonspecific solubilization occurred due to the action of the emulsifying factor. The rate of pristane solubilization by heat-treated culture broth under the conditions of agitation used in cultivation (rotary shaker, 120 rpm) was found to be ca. 750 mg L/sup -1/h/sup -1/ which was much larger than the maximal pristane uptake rate of 170 mg L/sup -1/h/sup -1/ observed during microbial growth on the substrate. It was concluded that hydrocarbon solubilization could satisfactorily account for the substrate uptake and growth.

  5. Emulsification by high frequency ultrasound using piezoelectric transducer: formation and stability of emulsifier free emulsion.

    PubMed

    Kaci, Messaouda; Meziani, Smail; Arab-Tehrany, Elmira; Gillet, Guillaume; Desjardins-Lavisse, Isabelle; Desobry, Stephane

    2014-05-01

    Emulsifier free emulsion was developed with a new patented technique for food and cosmetic applications. This emulsification process dispersed oil droplets in water without any emulsifier. Emulsions were prepared with different vegetable oil ratios 5%, 10% and 15% (v/v) using high frequency ultrasounds generated by piezoelectric ceramic transducer vibrating at 1.7 MHz. The emulsion was prepared with various emulsification times between 0 and 10h. Oil droplets size was measured by laser granulometry. The pH variation was monitored; electrophoretic mobility and conductivity variation were measured using Zêtasizer equipment during emulsification process. The results revealed that oil droplets average size decreased significantly (p<0.05) during the first 6h of emulsification process and that from 160 to 1 μm for emulsions with 5%, 10% and from 400 to 29 μm for emulsion with 15% of initial oil ratio. For all tested oil ratios, pH measurement showed significant decrease and negative electrophoretic mobility showed the accumulation of OH(-) at oil/water interface leading to droplets stability in the emulsion. The conductivity of emulsions showed a decrease of the ions quantity in solution, which indicated formation of positive charge layer around OH(-) structure. They constitute a double ionic layer around oil particles providing emulsion stability. This study showed a strong correlation between turbidity measurement and proportion of emulsified oil. PMID:24315670

  6. Influence of emulsifiers on the characteristics of polyurethane structures used as drug carrier

    PubMed Central

    2013-01-01

    Background Emulsifiers have a significant role in the emulsion polymerization by reducing the interfacial tension thus increasing the stability of colloidal dispersions of polymer nanostructures. This study evaluates the impact of four emulsifiers on the characteristics of polyurethane hollow structures used as drug delivery system. Results Polyurethane (PU) structures with high stability and sizes ranging from nano- to micro-scale were obtained by interfacial polyaddition combined with spontaneous emulsification. The pH of PU aqueous solutions (0.1% w/w) was slightly acidic, which is acceptable for products intended to be used on human skin. Agglomerated structures with irregular shapes were observed by scanning electron microscopy. The synthesized structures have melting points between 245-265°C and reveal promising results in different evaluations (TEWL, mexametry) on murine skin. Conclusions In this study hollow PU structures of reduced noxiousness were synthesized, their size and stability being influenced by emulsifiers. Such structures could be used in the pharmaceutical field as future drug delivery systems. PMID:23575277

  7. Interfacial and emulsifying properties of soybean peptides with different degrees of hydrolysis.

    PubMed

    Imura, Tomohiro; Nakayama, Mio; Taira, Toshiaki; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

    2015-01-01

    In this study, the effects of the degree of hydrolysis on the interfacial and emulsifying properties of soybean peptides were evaluated based on surface and interfacial tension, dynamic light scattering (DLS), and freeze-fracture transmission electron microscopy (FF-TEM) analyses. Of the five evaluated soybean peptides (SP95, SP87, SP75, SP49, and SP23), those with higher degrees of hydrolysis (SP95 and SP87) did not exhibit noticeable surface-active properties in water, whereas those with relatively low degrees of hydrolysis (SP75, SP49, and SP23) exhibited remarkable surface tension-lowering activity. The latter set (SP75, SP49, and SP23) also formed giant associates with average sizes ranging from 64.5 nm to 82.6 nm above their critical association concentration (CAC). Moreover, SP23 with the lowest degree of hydrolysis exhibited excellent emulsifying activity for soybean oil, and FF-TEM analysis demonstrated that the emulsions were stabilized by a lamella-like multilayer peptide structure on the oil droplets that prevented coagulation. The peptide with the lowest degree of hydrolysis (SP23) was effective not only for soybean oil emulsification, but also for the emulsification of liquid paraffin and silicon oil that are generally difficult to emulsify. PMID:25476545

  8. Oral bioavailability of silymarin phytocomplex formulated as self-emulsifying pellets.

    PubMed

    Iosio, T; Voinovich, D; Perissutti, B; Serdoz, F; Hasa, D; Grabnar, I; Acqua, S Dall'; Zara, G P; Muntoni, E; Pinto, J F

    2011-04-15

    The objective of this study was to develop new solid self-emulsifying pellets to deliver milk thistle extract (silymarin). These pellets were prepared via extrusion/spheronisation procedure, using a self-emulsifying system or SES (Akoline MCM, Miglyol, Tween 80, soy lecithin and propylene glycol), microcrystalline cellulose and lactose monohydrate. To select the most suitable formulations for extrusion and spheronisation, an experimental design of experiences was adopted. The screening amongst formulations (13 different blends) was performed preparing pellets and evaluating extrusion profiles and quality of the spheronised extrudates. The pellets were characterised for size and shape, density, force required to crush them. Although more than one type of pellets demonstrated adequate morphological and technological characteristics, pellets prepared from formulation 7 revealed the best properties and were selected for further biopharmaceutical investigations, including in vitro dissolution and in vivo trials on rats to study serum and lymph levels after oral administration of the pellets. These preliminary technological and pharmacokinetic data demonstrated that extrusion/spheronisation is a viable technology to produce self-emulsifying pellets of good quality and able to improve in vivo oral bioavailability of main components of a phytotherapeutic extract of more than 100 times by enhancing the lymphatic route of absorption. PMID:21111585

  9. New emulsifying and cryoprotective exopolysaccharide from Antarctic Pseudomonas sp. ID1.

    PubMed

    Carrión, Ornella; Delgado, Lidia; Mercade, Elena

    2015-03-01

    Pseudomonas sp. ID1 is a cold-adapted bacterium isolated from a marine sediment sample collected from South Shetland Islands (Antarctica) that is noted for the highly mucous appearance of its colonies. In this work, we have characterized an exopolysaccharide (EPS) produced by this strain, which is mainly composed of glucose, galactose and fucose, and has a molecular mass higher than 2×10(6) Da. We have also studied its potential biotechnological applications as an emulsifier and cryoprotectant agent. The EPS emulsifying activity against different food and cosmetic oils was much higher than commercial gums such as xanthan gum and arabic gum, and surfarctants such as Span 20. It formed highly stable emulsions against the cosmetic oil cetiol V, exhibiting pseudoplastic flow behavior, low thixotrophy and yield stress. The EPS of Pseudomonas sp. ID1 conferred significant cryoprotection for the strain itself as well as for other bacteria, including Escherichia coli, suggesting a universal cryoprotectant role. The cryoprotective activity of the EPS showed a clear dose-response relation at -20 °C and -80 °C and was significantly higher than that observed for the membrane stabilizer fetal bovine serum (FBS). These properties make the EPS of Pseudomonas sp. ID1 a promising alternative to commercial polysaccharides as an emulsifier and cryoprotectant agent for food, pharmaceutical and cosmetic industries. PMID:25498731

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

    PubMed Central

    2013-01-01

    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 (0.02–0.38 wt %, x1), emulsifier concentration (0.2–3.8 wt %, x2) and organic phase (dichloromethane) concentration (2–38 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 < 0.05) fitted for all studied response variables. The fitted polynomial regression models for the prediction of variations in the response variables showed high coefficients of determination (R2 > 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

  11. Removal of Emulsified Oil from Water by Fruiting Bodies of Macro-Fungus (Auricularia polytricha)

    PubMed Central

    Yang, Xunan; Guo, Mengting; Wu, Yinghai; Wu, Qunhe; Zhang, Renduo

    2014-01-01

    The aim of this study was to investigate the feasibility of utilizing the fruiting bodies of a jelly macro-fungus Auricularia polytricha as adsorbents to remove emulsified oil from water. The effects of several factors, including temperature, initial pH, agitation speed, and adsorbent dosage, were taken into account. Results showed that the optimized conditions for adsorption of A. polytricha were a temperature of 35°C, pH of 7.5, and agitation speed of 100 rpm. The adsorption kinetics were characterized by the pseudo-first order model, which showed the adsorption to be a fast physical process. The Langmuir-Freundlich isotherm described the adsorption very well and predicted the maximum adsorption capacity of 398 mg g−1, under optimized conditions. As illustrated by scanning electron micrographs, the oil particles were adsorbed onto the hairs covering the bottom surface and could be desorbed by normal temperature volatilization. The material could be used as an emulsified oil adsorbent at least three times, retaining more than 95% of the maximum adsorption capacity. The results demonstrated that the fruiting bodies of A. polytricha can be a useful adsorbent to remove emulsified oil from water. PMID:24743498

  12. Helix aspersa gelatin as an emulsifier and emulsion stabilizer: functional properties and effects on pancreatic lipolysis.

    PubMed

    Zarai, Zied; Balti, Rafik; Sila, Assaâd; Ben Ali, Yassine; Gargouri, Youssef

    2016-01-20

    Emulsions are widely used in food and pharmaceutical applications for the encapsulation, solubilization, entrapment, and controlled delivery of active ingredients. In order to fulfill the increasing demand for clean label excipients, natural polymers could be used to replace the potentially irritative synthetic surfactants used in emulsion formulation. In the present study, we have studied the properties of oil-in-water emulsions prepared with land snail gelatin (LSG) as the sole emulsifying agent, extracted and described for the first time. LSG was evaluated in terms of proximate composition, oil and water holding capacity, emulsifying and foaming properties, color and amino acid composition. Emulsions of trioctanoylglycerol (TC8) and olive oil were made at different gelatin/oil ratios and changes in droplet-size distribution were determined. The superior emulsifying properties of LSG, the susceptibility of gelatin protein emulsions increasing flocculation on storage, and the coalescence of gelatin emulsions following centrifugation were demonstrated. Furthermore, the effect of LSG on the activity of turkey pancreatic lipase (TPL) was evaluated through the pH-stat methodology with TC8 and olive oil emulsions. The LSG affected the TPL activity in a concentration-dependent way. Our results showed that LSG, comparably to gum arabic, increases the pancreatic lipase activity and improves its stability at the oil-water interface. PMID:26487504

  13. Self-emulsifying drug delivery systems: formulation and biopharmaceutic evaluation of an investigational lipophilic compound.

    PubMed

    Charman, S A; Charman, W N; Rogge, M C; Wilson, T D; Dutko, F J; Pouton, C W

    1992-01-01

    Self-emulsifying drug delivery systems (SEDDSs) represent a possible alternative to traditional oral formulations of lipophilic compounds. In the present study, a lipophilic compound, WIN 54954, was formulated in a medium chain triglyceride oil/nonionic surfactant mixture which exhibited self-emulsification under conditions of gentle agitation in an aqueous medium. The efficiency of emulsification was studied using a laser diffraction sizer to determine particle size distributions of the resultant emulsions. An optimized formulation which consisted of 25% (w/w) surfactant, 40% (w/w) oil, and 35% (w/w) WIN 54954 emulsified rapidly with gentle agitation in 0.1 N HCl (37 degrees C), producing dispersions with mean droplet diameters of less than 3 microns. The self-emulsifying preparation was compared to a polyethylene glycol 600 (PEG 600) solution formulation by administering each as prefilled soft gelatin capsules to fasted beagle dogs in a parallel crossover study. Pharmacokinetic parameters were determined and the absolute bioavailability of the drug was calculated by comparison to an i.v. injection. The SEDDS improved the reproducibility of the plasma profile in terms of the maximum plasma concentration (Cmax) and the time to reach the maximum concentration (tmax). There was no significant difference in the absolute bioavailability of WIN 54954 from either the SEDDS or the PEG formulations. PMID:1589415

  14. Partial purification and chemical characterization of a glycoprotein (putative hydrocolloid) emulsifier produced by a marine bacterium Antarctobacter.

    PubMed

    Gutiérrez, Tony; Mulloy, Barbara; Bavington, Charlie; Black, Kenny; Green, David H

    2007-10-01

    During screening for novel emulsifiers and surfactants, a marine alphaproteobacterium, Antarctobacter sp. TG22, was isolated and selected for its production of an extracellular emulsifying agent, AE22. This emulsifier was produced optimally in a low-nutrient seawater medium supplemented with glucose and was extractable by cold ethanol precipitation of the high-molecular-weight fraction (>100 kDa). Production of AE22 commenced towards the late exponential phase of growth, with maximum emulsifying activity detected after approximately 4 days of the cells entering the death phase. Chemical, chromatographic and nuclear magnetic resonance spectroscopic analysis confirmed AE22 to be a high-molecular-weight (>2,000 kDa) glycoprotein with high uronic acids content, thus denoting an apparent polyanionic structure. Functional characterization showed this polymer to compare well to xanthan gum and gum arabic as an emulsion-stabilizing agent for a range of different food oils. However, AE22 exhibited better stabilizing than emulsifying properties, which could be conferred by its viscosifying effect in solution or from certain chemical groups found on the polysaccharide or protein moieties of the polymer. This new high-molecular-weight glycoprotein exhibits interesting functional qualities that are comparable to other biopolymers of this type and shows particular promise as an emulsion-stabilizing agent in biotechnological applications. PMID:17641887

  15. Formulation Strategies to Improve the Bioavailability of Poorly Absorbed Drugs with Special Emphasis on Self-Emulsifying Systems

    PubMed Central

    Gupta, Shweta; Kesarla, Rajesh

    2013-01-01

    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

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

    SciTech Connect

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

    2005-12-14

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

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

    PubMed

    Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

    2014-10-01

    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 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

  18. 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)

    Gastone, Francesca; Tosco, Tiziana; Sethi, Rajandrea

    2014-10-01

    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.