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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

  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 PRESENTATION)

    EPA Science Inventory

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

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

  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 (DNAPL CONFERENCE)

    EPA Science Inventory

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

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

    NASA Technical Reports Server (NTRS)

    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.; Gómez-Yáñez, 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. Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons

    SciTech Connect

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

    2000-05-15

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

  11. TREATMENT OF GROUND WATER WITH ZERO VALENT IRON (ZVI)

    EPA Science Inventory

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

  12. 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...

  13. Feasibility of amending slurry walls with zero-valent iron

    SciTech Connect

    Rabideau, A.J.; Shen, P.; Khandelwal, A.

    1999-04-01

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

  14. Synthesis, Characterization, and Properties of Zero-Valent Iron Nanoparticles

    SciTech Connect

    Baer, Donald R.; Tratnyek, P. G.; Qiang, You; Amonette, James E.; Linehan, John C.; Sarathy, Vaishnavi; Nurmi, J. T.; Wang, Chong M.; Antony, Jiji

    2007-04-04

    This chapter provides an overview of synthesis, characterization and property measurements techniques important for making understanding the nature of zero valent iron nanoparticles. The chemical reactivity of nanometer-sized materials can be quite different from that of either bulk forms of a material or the individual atoms and molecules that comprise it. Advances in our ability to synthesize, visualize, characterize and model these materials have created new opportunities to control the rates and products of chemical reactions in ways not previously possible. Zero valent iron (ZVI), including non-nanoparticle forms for iron, is one of the most promising remediation technologies for the removal of mobile chlorinated hydrocarbons and reducible inorganic anions for ground water. ZVI nanoparticles may have great potential to assist environmental remediation, but there are significant scientific and technological questions that remain to be answered. Understanding of ZVI reactive metal core-shell nanoparticles requires use of particles that are as well characterized and understood as possible. In this chapter we describe the issues and provide examples that include synthesis of nanoparticles, analytical characterization of the particles and finally measurements of their chemical properties.

  15. Reductive dehalogenation of trichloroethylene using zero-valent iron

    SciTech Connect

    Gotpagar, J.; Grulke, E.; Bhattacharyya, D.

    1997-12-31

    Reductive dehalogenation of hazardous organics using zero-valent metals is a promising technology. The purpose of this study was to examine the effect of feed concentration, initial pH, metal loading and particle size of metal on the degradation of trichloroethylene (TCE), using zero-valent iron. The degradation rate was found to be first order with respect to the organic molecule, thus the conversion was independent of initial TCE concentration. The amount of TCE degraded at any given time was found to be directly proportional to the dissolved iron in solution. The metal surface area plays a crucial role in the process. Twofold increase in the pseudo first order rate constant was obtained when the metal particle size was decreased from 370 {mu}m by factor of 2.5. For iron surface area per unit volume (S/V) of solution < 1000 m{sup -1}, the TCE degradation rate constant increased linearly with S/V ratio. 20 refs., 8 figs., 1 tab.

  16. Tactic response of bacteria to zero-valent iron nanoparticles.

    PubMed

    Ortega-Calvo, José-Julio; Jimenez-Sanchez, Celia; Pratarolo, Paolo; Pullin, Huw; Scott, Thomas B; Thompson, Ian P

    2016-06-01

    The microbial assessment of pollutant toxicity rarely includes behavioral responses. In this study, we investigated the tactic response of Pseudomonas putida G7, a representative of soil bacterium, towards engineered zero-valent iron nanoparticles (nZVIs), as a new end-point assessment of toxicity. The study integrated the characterization of size distribution and charge of nZVIs and tactic reaction response by means of inverted capillary assay and computer-assisted motion analysis of motility behavior. Iron nanoparticles (diameter ≤ 100 nm) were prepared in the absence of oxygen to prevent aggregation, and then exposed in aerobic conditions. We first demonstrate that iron nanoparticles can elicit a negative tactic response in bacteria at low but environmentally-relevant, sub-lethal concentrations (1-10 μg/L). Cells were repelled by nZVIs in the concentration gradients created inside the capillaries, and a significant increase in turning events, characteristic of negative taxis, was detected under exposure to nZVIs. These tactic responses were not detectable after sustained exposure of the nanoparticles to oxygen. This new behavioral assessment may be prospected for the design of sensitive bioassays for nanomaterial toxicity. PMID:26967351

  17. Zero-valent iron colloid emplacement in sand columns

    SciTech Connect

    Cantrell, K.J.; Kaplan, D.I.

    1997-05-01

    Application of chemically reactive barriers to mitigate contaminant migration is an active area of research and development. Studies were conducted to evaluate a novel approach of emplacing chemically reactive barriers composed of zero-valent iron (Fe{sup 0}) by injecting suspensions of colloidal-size Fe{sup 0} particles into porous media. The specific objective of this study was to evaluate the effect of influent colloid concentration, rate, and volume of colloidal suspensions on Fe{sup 0} colloid emplacement in sand columns. Relatively even distributions of Fe{sup 0} throughout a sand column were obtained at low influent colloid concentrations and high injection rates. As the concentration of influent suspensions was increased, a point was reached beyond which a significant increase in the filtration of Fe{sup 0} particles near the front of the column was observed. This point was also found to occur at lower influent colloid concentrations as the injection rate was decreased, i.e., there was an interactive effect of influent colloid concentration and injection rate on the extent of filtration that occurred near the front of the column. As the volume of the colloidal suspension injected into the column was increased, the distribution of Fe{sup 0} colloids within the column became increasingly even.

  18. Electrochemical depassivation of zero-valent iron for trichloroethene reduction.

    PubMed

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

    2012-11-15

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

  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

  20. 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.

  1. 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

  2. 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

  3. Reductive dechlorination of chlorinated solvents by zero-valent iron, iron oxide and iron sulfide minerals

    SciTech Connect

    Sivavec, T.M.; Horney, D.P.

    1996-10-01

    The degradation of chlorinated solvents by reduction at the surface of zero-valent metals and bimetallic systems has emerged as an important approach to the in-situ remediation of ground water. Reduction by iron metal was studied in batch and column systems to develop a mechanistic understanding of the reaction chemistry and to determine the factors that affect dechlorination rate and long term performance in field applications.

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

    EPA Science Inventory

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

  5. 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 ...

  6. 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 ...

  7. Abiotic remediation of nitro-aromatic groundwater contaminants by zero-valent iron

    SciTech Connect

    Agrawal, A.; Tratnyek, P.G.

    1994-03-18

    Recent laboratory and field experiments have shown that some halogenated hydrocarbons undergo rapid reductive dehalogenation with zero-valent iron and the application of this process is being developed for in-situ remediation of contaminated groundwater. However, from can also reduce other organic substances and is commonly used to synthesize reduction products nitro compounds.

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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.

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

    SciTech Connect

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

    1998-09-01

    A series of laboratory experiments were performed to elucidate the chromium transformation and precipitation reactions caused by the corrosion of zero-valent iron in water-based systems. Reaction rates were determined for chromate reduction in the presence of different types of iron and in systems with iron mixed with aquifer materials. Various geochemical parameters were measured to confirm the proposed reactions. Laboratory experiments were scaled up to pilot and full-scale field demonstrations. Intensive geochemical sampling in the field tests corroborate laboratory results and successfully demonstrate the effectiveness of this innovative in situ approach to remediate chromate-contaminated ground water using a permeable reactive barrier composed of zero-valent iron.

  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. Sorption of PCE in a reactive zero-valent iron system

    SciTech Connect

    Campbell, T.J.; Burris, D.R.

    1995-12-01

    The degradation of the chlorinated solvents perchloroethylene (PCE) and trichloroethylene (TCE) by reduction on the surface of zero-valent iron has emerged in recent years as a potentially viable approach to the remediation of chlorinated solvent-contaminated groundwaters. The sorption of PCE in a batch reactive zero-valent iron system was examined in this study. Aqueous PCE concentrations and total system PCE masses were determined in batch time-series experiments used to ascertain degradation kinetics. Sorbed concentrations were calculated using the difference between the aqueous phase and total system masses. The results showed Langmuir isotherm behavior which is consistent with a model of a finite number of available sorption sites. The kinetics of sorption could not be determined since degradation was also occurring. Knowledge of sorption to reactive and non-reactive sites is of importance in gaining a thorough understanding of the performance-behavior of the flow-through reactive systems envisioned for remediation technologies.

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

    EPA Science Inventory

    The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. An exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes ...

  18. Zero-valent iron removal rates of aqueous Cr(VI) measured under flow conditions

    SciTech Connect

    Kaplan, Daniel I.; Gilmore, Tyler J.

    2004-06-30

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

  19. Environmental application and ecological significance of nano-zero valent iron.

    PubMed

    Yirsaw, Biruck D; Megharaj, Mallavarapu; Chen, Zuliang; Naidu, Ravi

    2016-06-01

    Toxicity studies considering both the bare and stabilized forms of zero valent iron nanoparticles (nZVI) could be timely, given that ecological risks identified are minimized through modification or with substitution of approaches in the synthesis, development and environmental application of the nanoparticles before succeeding to volume production. This review is focused on the fate, transport and toxicological implications of the bare nZVI and surface modified particles used for environmental applications. PMID:27266305

  20. 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...

  1. Quantitative evaluation of pathways involved in trichloroethylene reduction by zero-valent metals: Iron and zinc

    SciTech Connect

    Arnold, W.; Roberts, A.L.; Burris, D.R.; Campbell, T.J.

    1995-12-31

    In order to design in situ remediation systems using zero-valent metals, the mechanism and kinetics of chlorinated solvent degradation by zero-valent metals need clarification. These issues are addressed by conducting detailed investigations of the pathways involved in trichloroethylene (TCE) reduction by two zero-valent metals. Analyses are based on batch reaction data for chloroethylene reduction by iron and zinc. Experiments were conducted using TCE and each readily available reaction product of TCE degradation as a starting material and monitoring the disappearance of the parent chemical and the appearance of reaction products over time. Models were developed by working backwards through the hypothesized reaction sequence. Determining rate constants for the latter steps in the pathway, inserting them into the more complex models for more highly oxidized compounds, and obtaining rate constants for the remaining steps in the transformation of the oxidized species was repeated until a model for trichloroethylene was developed. Results indicate that reactions may not occur via a process of sequential hydrogenolysis or hydrogenation. Ethylene and/or ethane production are too rapid to be accounted for in this manner. The product distribution, especially the presence of acetylene, can only be explained by invoking reductive elimination reactions.

  2. In situ remediation of chromium contaminated groundwater using zero valent iron

    SciTech Connect

    Blowes, D.W.; Ptacek, C.J.; Hanton-Fong, C.J.; Jambor, J.L.

    1995-12-01

    In situ porous reactive walls, using zero-valent iron as a reductant, are an alternative technology for the treatment of groundwater contaminated with electroactive elements, such as Cr(VI). Laboratory column and batch experiments were conducted to assess the treatment of Cr(VI) using zero-valent iron in the form of iron filings. Batch tests were conducted with and without calcite addition. Batch test results indicate that removal using iron filings is rapid, with initial Cr(VI) concentrations reduced from approximately 20 mg/L to < 0.05 mg/L within 3 hours. Iron filings retained from the batch tests were examined mineralogically. The results indicate that the most abundant secondary minerals are goethite, lepidocrocite, maghemite and hematite. Of these minerals, the most abundant was goethite. No discrete chromium-bearing phases were detected, but chromium-rich zones, containing up to 27.3 wt.% Cr as Cr(OH){sub 3}, were detected within the iron oxyhydroxides, most notably within the goethite. A flow-through column experiment, conducted at a flow rate of 10 m/a indicated continuing treatment of Cr(VI) at concentrations of approximately 20 mg/L to <0.05 mg/L for more than 130 pore volumes.

  3. Synthesis, characterization, and reactivity of cellulose modified nano zero-valent iron for dye discoloration

    NASA Astrophysics Data System (ADS)

    Wang, Xiangyu; Wang, Pei; Ma, Jun; Liu, Huiling; Ning, Ping

    2015-08-01

    Nano zero-valent iron (NZVI) was innovatively and successfully modified by using hydroxyethyl cellulose (HEC) and hydroxypropylmethyl cellulose (HPMC) as dispersants. The systematic characterization observations (including XRD, SEM and TEM) illustrate that, compared with bare nano zero-valent iron particles (BNZVI), the particle sizes of hydroxyethyl cellulose modified (ENZVI) and hydroxypropylmethyl cellulose modified (PNZVI) were decreased, while the dispersity and antioxidizability of ENZVI and PNZVI particles were increased. The discoloration efficiencies of ENZVI, PNZVI, and BNZVI were compared by using dyes (including orange II, methyl orange, methyl blue, and methylene blue) as target pollutant. The results show that both the discoloration efficiency and reaction rate of ENZVI and PNZVI are higher than that of BNZVI. In addition, effects of dispersant content, dye type, pH value, initial dye concentration, iron dosage, and reaction temperature on discoloration efficiencies were studied. The results show that discoloration efficiency was decreased by increasing initial pH value and dye concentration, and it was increased with the increase the iron dosage and reaction temperature. Under optimized NZVI addition of 0.7 g L-1, the discoloration efficiencies of ENZVI and PNZVI were increased to 96.33% and 98.62%, respectively. And the possible discoloration pathway and dispersant modification mechanism of NZVI were discussed. This study suggests hydroxyethyl cellulose and hydroxypropylmethyl cellulose dispersed NZVI can be utilized as a promising modified nano-material for degradation of dye wastewater.

  4. 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).

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. Kinetic controls on the performance of remediation technologies based on zero-valent iron

    SciTech Connect

    Tratnyek, P.G.; Scherer, M.M.

    1998-07-01

    The kinetics of dechlorination by zero-valent iron are usually best described by surface-area normalized, pseudo first-order rate constants (k{sub SA}). For input parameters in preliminary design calculations and generalized modeling exercises, typical values of k{sub SA} for the major groundwater contaminants have been obtained by averaging previously published data. These average values of k{sub SA} (k{sub SA}{sup avg})are also appropriate for correlation analysis, which can be used to assess the role that chemical structure plays in determining rates of dechlorination by zero-valent iron. Toward this end, the authors have developed a quantitative structure-activity relationship (QSAR) that relates k{sup avg}{sub SA} to energies of the lowest unoccupied molecular orbital (E{sub LUMO}) for the various chlorinated solvents. The WSAR can be used to predict k{sub SA}'s for compounds for which experimental data are not yet available.

  11. Processes affecting reductive dechlorination of chlorinated solvents by zero-valent iron

    SciTech Connect

    Matheson, L.J.; Tratnyek, P.G.

    1993-12-31

    Zero-valent iron may participate in the reductive dechlorination process by three different mechanisms: direct, electrolytic reduction; reduction by hydrogen produced during the corrosion process; and reduction by dissolved (ferrous) iron that is also produced by corroding iron. The first step of electrolytic reduction is presumably, the transfer of one electron from the metal surface to the organic molecule. This results in an organic anion radical that may then lose a halide anion to give a carbon-centered radical, and oxidized iron, which is eventually released to the solution as Fe{sup 2+}. The goal of this research is to provide a comprehensive survey of the mechanisms that affect the performance of this reactive barrier technology.

  12. Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum.

    PubMed

    Tiraferri, Alberto; Chen, Kai Loon; Sethi, Rajandrea; Elimelech, Menachem

    2008-08-01

    Injection of nanoscale zero-valent iron (NZVI) is potentially a promising technology for remediation of contaminated groundwaters. However, the efficiency of this process is significantly hindered by the rapid aggregation of the iron nanoparticles. The aim of this study was to enhance the colloidal stability of the nanoparticles through the addition of the "green" polymer guar gum. We evaluated the properties of guar gum and its influence on the surface properties, particle size, aggregation, and sedimentation of iron nanoparticles. Commercial iron nanoparticles were dispersed in guar gum solutions, and their aggregation and sedimentation behaviors were compared to those of bare iron nanoparticles and commercial nanoparticles modified with a biodegradable polymer (polyaspartate). High performance size exclusion chromatography, charge titration, and viscosity assessment showed that guar gum is a high molecular weight polymer which is nearly neutrally charged, rendering it suitable for steric stabilization of the iron nanoparticles. Electrophoretic mobility measurements demonstrated the ability of guar gum to adsorb on the nanoparticles, forming a slightly negatively charged layer. Dynamic light scattering experiments were conducted to estimate the particle size of the different nanoparticle suspensions and to determine the aggregation behavior at different ionic strengths. Guar gum effectively reduced the hydrodynamic radius of the bare nanoparticles from 500 nm to less than 200 nm and prevented aggregation of the nanoparticles even at very high salt concentrations (0.5 M NaCl and 3 mM CaCl(2)). Sedimentation profiles of the different nanoparticle suspensions confirmed the improved stability of the iron nanoparticles in the presence of guar gum. The results strongly suggest that guar gum can be used to effectively deliver stabilized zero-valent iron nanoparticles for remediation of contaminated groundwater aquifers. PMID:18508073

  13. 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

  14. Enhanced reduction of nitrate by supported nanoscale zero-valent iron prepared in ethanol-water solution.

    PubMed

    Park, Heesu; Park, Yong-Min; Oh, Soo-Kyeong; You, Kyoung-Min; Lee, Sang-Hyup

    2009-03-01

    Nanoscale zero-valent iron is famous for its high reactivity originating from its high surface area, and has emerged as an extension of granular zero-valent iron technology. Due to its extremely small size, nanosized iron cannot be used as a medium in a permeable reactive barrier system, which is the most popular application of granular iron. To overcome this shortcoming, supported nanoscale zero-valent iron was created. In addition to this, the preparation solution was modified to enhance the reactivity. An ethanol/water solvent containing a dispersant of polyethylene glycol was used to synthesize nanoscale iron. This preparation was done in the presence of an ion-exchange resin as a supporting material. Nanoscale zero-valent iron was formed and bound to the granular resin at the same time through the borohydride reduction of an iron salt, and the resulting product was compared with that prepared in a conventional way of using water only. Switching the preparation solution increased the supported nanoscale iron's BET surface area and Fe content from 31.63 m2 g(-1) and 18.19 mg Fe g(-1) to 38.10 m2 g(-1) and 22.44 mg Fe g(-1), respectively. Kinetic analysis from batch tests revealed that a higher denitrification rate was achieved by the supported nanoscale zero-valent iron prepared in the modified way. The pseudo-first-order reaction constant of 0.462 h(-1) suggested that the reactivity of the supported iron, prepared in ethanol/water, increased by 61% compared with the one prepared in water. The higher rates of reaction, based on higher specific area and iron content, suggest that this new supported nanoscale iron can be used successfully for permeable reactive barriers. PMID:19438058

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  16. Dechlorination of 1,2,3-trichloropropane by zero-valent iron

    SciTech Connect

    Focht, R.M.; Gillham, R.W.

    1995-12-01

    This study investigated the dechlorination of aqueous 1,2,3-trichloropropane in the presence of zero-valent iron. Using flow-through column procedures, the rate of dechlorination was significantly enhanced by the presence of iron, with the half life decreasing in proportion to the iron surface area to solution volume ratio. Unlike previous results obtained for chlorinated C{sub 1} and C{sub 2} compounds, half-lives increased significantly over time, at rates ranging from 5.0 to 13.9 minutes per pore volume of water passed through the column. No accumulation of chlorinated products of degradation was detected, and the principal products of degradation were Cl{sup -} and propene. The products of degradation and the trends in pH suggest reductive dechlorination and dehydrochlorination to be the degradation mechanisms.

  17. 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

  18. Zero-valent iron-promoted dechlorination of polychlorinated biphenyls (PCBs)

    SciTech Connect

    Chuang, Fei-Wen; Larson, R.A.

    1995-12-01

    Zero-valent iron promoted the dechlorination of PCBs (Aroclors 1221 and 1254) at elevated temperatures in an oxygen-limited environment. At temperatures higher than 300{degrees}C, dechlorination of Aroclor 1221 began to occur; at 400{degrees}C, the major reaction product, biphenyl, was observed in highest yield. (At this temperature most of the PCBs were dechlorinated to biphenyl within 10 min.) At temperatures of 500{degrees}C or higher, dechlorination and other reactions of PCBs took place. At 600{degrees}C, almost all PCBs were destroyed by reactions other than hydrogenolytic dechlorination. Similar reactions were observed with the more highly chlorinated Aroclor 1254. Water or other impurities associated with the iron surface may donate protons or hydrogen atoms to the PCBs and take part in other reactions.

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

    SciTech Connect

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

    1998-09-01

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

  20. Enhanced Biogas Production from Nanoscale Zero Valent Iron-Amended Anaerobic Bioreactors

    PubMed Central

    Carpenter, Alexis Wells; Laughton, Stephanie N.; Wiesner, Mark R.

    2015-01-01

    Abstract Addition of nanoscale zero valent iron (NZVI) to anaerobic batch reactors to enhance methanogenic activity is described. Two NZVI systems were tested: a commercially available NZVI (cNZVI) slurry and a freshly synthesized NZVI (sNZVI) suspension that was prepared immediately before addition to the reactors. In both systems, the addition of NZVI increased pH and decreased oxidation/reduction potential compared with unamended control reactors. Biodegradation of a model brewery wastewater was enhanced as indicated by an increase in chemical oxygen demand removal with both sNZVI and cNZVI amendments at all concentrations tested (1.25–5.0 g Fe/L). Methane production increased for all NZVI-amended bioreactors, with a maximum increase of 28% achieved on the addition of 2.5 and 5.0 g/L cNZVI. Addition of bulk zero-valent iron resulted in only a 5% increase in methane, indicating the advantage of using the nanoscale particles. NZVI amendments further improved produced biogas by decreasing the amount of CO2 released from the bioreactor by approximately 58%. Overall, addition of cNZVI proved more beneficial than the sNZVI at equal iron concentrations, due to decreased colloidal stability and larger effective particle size of sNZVI. Although some have reported cytotoxicity of NZVI to anaerobic microorganisms, work presented here suggests that NZVI of a certain particle size and reactivity can serve as an amendment to anaerobic digesters to enhance degradation and increase the value of the produced biogas, yielding a more energy-efficient anaerobic method for wastewater treatment. PMID:26339183

  1. The use of zero-valent iron filtration to reduce Escherichia coli and Listeria innocua in irrigation water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction: Irrigation water can be a source of contamination in outbreaks associated with produce. Zero-valent iron (ZVI) filtration has been effective in E. coli O157:H12 in irrigation water, but has not been evaluated against Listeria spp. Purpose: To 1) determine effectiveness of ZVI filters...

  2. 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...

  3. 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...

  4. 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...

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

    PubMed

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

    2012-12-01

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

  6. Zero-valent iron for the removal of soluble uranium in simulated DOE site groundwater

    SciTech Connect

    Bostick, W.D.; Jarabek, R.J.; Fiedor, J.N.

    1997-12-31

    Groundwater at the Bear Creek Valley Characterization Area, located at the Oak Ridge Y-12 Plant, is contaminated with regulated metals and volatile organic compounds (VOCs) due to former site activities and disposal practices. The contaminant of principle concern, from the perspective of protecting human health, is soluble uranium, which is present in some waters at concentrations up to a few parts-per-million. We present product speciation and relative reaction kinetics; for removal of soluble uranium under oxic and anoxic conditions with use of zero-valent iron. Under oxic conditions, U(VI) is rapidly and strongly sorbed to hydrous ferric oxide particulate ({open_quotes}rust{close_quotes}), whereas uranium is slowly and incompletely reduced to U(IV) under anoxic conditions.

  7. Installation of a subsurface groundwater treatment wall composed of granular zero-valent iron

    SciTech Connect

    Yamane, C.L.; Warner, S.D.; Gallinatti, J.D.

    1995-12-01

    A subsurface treatment wan (consisting of granular, zero-valent iron and gravel) and low-permeability slurry wall system was installed as the final remedy at a former semiconductor manufacturing facility in the south San Francisco Bay area. The property has been vacant since 1983, and the former facility`s lease recently expired. This treatment wall replaced a groundwater pump and treat system that was installed as an interim remedy in 1987. While the pump and treat system may have been acceptable to regulatory agencies as a final site remedy, the treatment wall was proposed and eventually selected as the final remedy because it would eliminate above-ground treatment systems on the property and thereby have little to no effect on the property`s future use; it would eliminate the necessity for weekly operation and maintenance and therefore avoid access issues that might arise after the tenant`s lease expired; and it would greatly reduce total remediation costs.

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

    SciTech Connect

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

    2011-02-18

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

  9. Remediation of hexavalent chromium contaminated soil by biochar-supported zero-valent iron nanoparticles.

    PubMed

    Su, Huijie; Fang, Zhanqiang; Tsang, Pokeung Eric; Zheng, Liuchun; Cheng, Wen; Fang, Jianzhang; Zhao, Dongye

    2016-11-15

    In this study, a kind of high-efficiency and low-cost biochar-supported zero-valent iron nanoparticles (nZVI@BC) was synthesised and used in the remediation of Cr(VI)-contaminated soil. The remediation tests indicated that the immobilisation efficiency of Cr(VI) and Crtotal was 100% and 91.94%, respectively, by 8g nZVI@BC per kg soil for 15 d of remediation. Further investigations showed that exchangeable Cr was almost completely converted to Fe-Mn oxides and organic matter. Moreover, nZVI@BC could effectively improve soil fertility and reduce the leachability of Fe caused by nZVI. At the same time, the cabbage mustard growth experiments indicated that the phytotoxicity of Cr(VI) and Fe in the seedlings was effectively decreased by nZVI@BC treatment, and that the cabbage mustard growth was enhanced. PMID:27469041

  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. Trichloroethene Reduction within a Nonaqueous Phase Liquid using Zero Valent Iron

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    The application of reactive slurries or suspensions (usually of reactive zero valent iron particles) is being considered for treatment of dense non-aqueous phase liquid (DNAPL) source zones. Effective treatment of NAPL source zones with reactive particles requires delivery of particles within the vicinity of the NAPL. To date, iron-mediated remediation technologies rely on the use of aqueous-based particle suspensions. When utilizing these aqueous-based suspensions of reactive iron particles, contaminant transformation is dependent on dissolution of contaminants from the DNAPL prior to reaction. The reliance upon dissolution kinetics may introduce a rate limitation during treatment of DNAPL source zones with aqueous-based reactive slurries. Incorporation of the reactive particles into the NAPL (i.e., reduction occurring within the NAPL) may alleviate any dissolution limitation associated with aqueous-based reactive slurries. This exploratory research evaluated the feasibility of creating iron-mediated TCE reduction within a NAPL. Emphasis was placed on elucidating the role of water in the reductive dechlorination process when it occurs within a NAPL. Batch experiments were conducted in 125 mL reactors containing iron particles and NAPLs of various composition under an argon atmosphere. For these proof-of-concept experiments, NAPL mixtures were designed to ensure initial TCE concentration was constant. Results suggest that iron-mediated reactions within chlorinated ethene DNAPLs are feasible, though the viability of controlling both the iron content and chemistry of DNAPL located within the subsurface remains unknown.

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

    SciTech Connect

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

    1999-08-01

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

  15. 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.

  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

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

    SciTech Connect

    Ming-Chin Chang; Hung-Yee Shu; Wen-Pin Hsieh; Min-Chao Wang

    2007-02-15

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

  18. 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.

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

    PubMed

    Chang, Ming-Chin; Shu, Hung-Yee; Hsieh, Wen-Pin; Wang, Min-Chao

    2007-02-01

    The sites contaminated with recalcitrant polycyclic aromatic hydrocarbons (PAHs) are serious environmental problems ubiquitously. Some PAHs have proven to be carcinogenic and hazardous. Therefore, the innovative PAH in situ remediation technologies have to be developed instantaneously. Recently, the nanoscale zero-valent iron (ZVI) particles have been successfully applied for dechlorination of organic pollutants in water, yet little research has investigated for the soil remediation so far. The objective in this work was to take advantage of nanoscale ZVI particles to remove PAHs in soil. The experimental factors such as reaction time, particle diameter and iron dosage and surface area were considered and optimized. From the results, both microscale and nanoscale ZVI were capable to remove the target compound. The higher removal efficiencies of nanoscale ZVI particles were obtained because the specific surface areas were about several dozens larger than that of commercially microscale ZVI particles. The optimal parameters were observed as 0.2 g iron/2 mL water in 60 min and 150 rpm by nanoscale ZVI. Additionally, the results proved that nanoscale ZVI particles are a promising technology for soil remediation and are encouraged in the near future environmental applications. Additionally, the empirical equation developed for pyrene removal efficiency provided the good explanation of reaction behavior. Ultimately, the calculated values by this equation were in a good agreement with the experimental data. PMID:17355083

  20. 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

  1. 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

  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. 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.

  4. Mobility and Deposition 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. E.

    2013-12-01

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

  5. Design and evaluation of an in-situ ground water treatment wall composed of zero-valent iron

    SciTech Connect

    Gallinatti, J.D.; Warner, S.D.; Yamane, C.L.; Szerdy, F.S.; Hankins, D.A.; Major, D.W.

    1995-09-01

    An in-situ permeable treatment wall using zero-valent iron for the remediation of ground water affected by chlorinated volatile organic compounds (VOCs) was recently constructed in Sunnyvale, California. Because this site was the first full-scale application of this technology as a final remedy of VOC-affected ground water, it provides a framework for assessing the factors that must be considered when moving from laboratory studies of this treatment technology to design and construction of a full-scale treatment system. Experience from this case study is valuable for both practical design considerations and as incentives for future research. The patented treatment process, licensed by Environmental Technologies Inc., utilizes granular zero-valent iron as a porous medium to enhance the degradation of VOCs dissolved in ground water. The dissolved VOCs, such as 1,1,1-trichloroethylene (TCE), that pass through the granular iron matrix are transformed through the oxidation of the iron and reductive dechlorination of the organic compound to a final end product consisting chiefly of chloride and ethylene. The degradation process appears to be abiotic and half-lifes of the transformations are several orders of magnitude faster in the presence of zero-valent granular iron than observed in the ambient environment.

  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. 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

  8. 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

  9. Perchlorate reduction by autotrophic bacteria in the presence of zero-valent iron.

    PubMed

    Yu, Xueyuan; Amrhein, Christopher; Deshusses, Marc A; Matsumoto, Mark R

    2006-02-15

    A series of batch experiments were performed to study the combination of zero-valent iron (ZVI) with perchlorate-reducing microorganisms (PRMs) to remove perchlorate from groundwater. In this method, H2 produced during the process of iron corrosion by water is used by PRMs as an electron donor to reduce perchlorate to chloride. Perchlorate degradation rates followed Monod kinetics, with a normalized maximum utilization rate (rmax) of 9200 microg g(-1) (dry wt) h(-1) and a half-velocity constant (Ks) of 8900 microg L(-1). The overall rate of perchlorate reduction was affected by the biomass density within the system. An increase in the OD600 from 0.025 to 0.08 led to a corresponding 4-fold increase of perchlorate reduction rate. PRM adaptation to the local environment and initiation of perchlorate reduction was rapid under neutral pH conditions. At the initial OD600 of 0.015, perchlorate reduction followed pseudo-first-order reaction rates with constants of 0.059 and 0.033 h(-1) at initial pH 7 and 8, respectively. Once perchlorate reduction was established, the bioreductive process was insensitive to the increases of pH from near neutral to 9.0. In the presence of nitrate, perchlorate reduction rate was reduced, but not inhibited completely. PMID:16572793

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

    PubMed Central

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

    2012-01-01

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

  11. Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media.

    PubMed

    Yang, Zhangmei; Qiu, Xinhong; Fang, Zhanqiang; Pokeung, Tsang

    2015-01-01

    Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media. Degradation of decabromodiphenyl ether (BDE209) was more efficient by SiO2@FeOOH@Fe than by 'bare' NZVI. Breakthrough curves and mass recovery showed the mobility of SiO2@FeOOH@Fe in granular media was better than that of bare NZVI. It increased greatly in the presence of natural organic matter (NOM) and decreased when high Ca2+ and Mg2+ concentrations were encountered. Analysis of the transport data on the basis of filtration theory showed diffusion to be the main mechanism for particle removal in silicon sand. Increasing the NOM may decrease agglomeration of the grains of sand, which has a positive effect on the mobility of SiO2@FeOOH@Fe. Presumably, increasing the concentrations of Ca2+ and Mg2+ compresses the diffuse double layer of SiO2@FeOOH@Fe, resulting in a reduction of mobility. PMID:26067499

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

    PubMed

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

    2009-03-01

    The effects of sediment-isolated bacteria and phosphate on the efficacy of zero valent iron (ZVI) for the dechlorination of trichloroethylene (TCE) were examined in batch experiments. TCE (0.3 mM) and a constant concentration of sediment bacteria were simultaneously exposed to ZVI in the presence of 0 mmol, 15 mmol, and 30 mmol of phosphate. TCE profiles, starting from 0.3 mM to about 0.1 mM, exhibited two-phase of sorption kinetics at all three phosphate concentrations without the sediment bacteria. TCE removal was less and slower with phosphate in the system. With the sediment bacteria, however, more TCE was removed with the sediment bacteria than without it, unlike our initial hypothesis. With the sediment bacteria and phosphate, the concentration of ferrous (0.505 mM) ions was doubled that with phosphate only (0.271 mM). The sediment bacteria in this research, mainly Bacillus sp., could contribute to the long-term stability of ZVI reactivity for dechlorination of TCE in sediment. The sediment bacteria in this research could reduce the iron or chelate the evolved ferrous ions to retain the reducing reactivity of ZVI. PMID:19184703

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

    PubMed

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

    2011-04-15

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

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

    PubMed

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

    2005-12-01

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

  15. [Performance Recoverability of Denitrifying Granular Sludge Under the Stressing Effect of Nanoscale Zero-valent Iron].

    PubMed

    Wang, Fan-fan; Qian, Fei-yue; Shen, Yao-liang; Wang, Jian-fang; Zhang, Yue-ru; Liu, Guo-xun

    2016-04-15

    To explore the potential stressing effect of nanoscale zero-valent iron (nZVI) on denitrifying granular sludge (DGS), the evolution of DGS denitrifying performance under different C/N ratios was investigated in this study, by carrying out batch tests of eight successive periods with the nZVI shock-loading. The results showed that the specific denitrification rate of µ value decreased when the nZVI dosage was higher than 5 mg · L⁻¹. Meanwhile, a positive correlation between the inhibition ratio (IR) of µ value and substrate C/N ratios or nZVI dosage was observed. When the nZVI dosage reached 100 mg · L⁻¹, both extracellular protein and polysaccharides concentrations decreased obviously. It would be beneficial to promote the recovery of DGS denitrifying activity and reduce the COD demanding to remove unit mass of nitrate, by increasing external carbon source with C/N ratios of higher than 4. On the basis of Freundlich and Langmuir adsorption isotherms, when higher C/N ratio was provided, stronger bioadsorption of nZVI would be achieved. During the recovery period, a significant improvement of DCS denitrifying performance under the high C/N ratio was expected, due to the continuous washout of total iron in sludge phase (Qe), while the µ value would reach or approach the one of the control group when Qe was lower than 0.4 mg · g⁻¹. PMID:27548972

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

    PubMed

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

    2007-08-17

    Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5-31.8% could be achieved under the optimal condition of coagulation, i.e. 400mg/L of Fe(2)(SO(4))3 as coagulant at pH 3.0-5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10 g/L active carbon and 30 g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation-reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000 Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process. PMID:17267104

  17. 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 ...

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

    PubMed

    Kim, Heonki; Yang, Haewon; Kim, Juyoung

    2014-01-01

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

  19. 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.

  20. [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

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

    PubMed

    Ma, Xingmao; Gurung, Arun; Deng, Yang

    2013-01-15

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

  2. 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

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

    PubMed

    Lacinova, Lenka; Kvapil, Petr; Cernik, Miroslav

    2012-01-01

    Two parallel pilot experiments were performed at Kurivody (Czech Republic) in order to compare two reductive remedial technologies for chlorinated ethenes - microbial dehalogenation assisted by lactate and chemical dehalogenation with zero-valent iron (nZVI) nanoparticles. The methods were applied at a site contaminated by tetrachlorethylene (PCE) and trichlorethylene (TCE), with total concentrations from 10 to 50 mg/l. Concentrations of chlorinated ethenes, inorganic components of interest, pH and oxidation reduction potential (ORP) were monitored at the site for a period up to 650 days. The method of biological reductive dechlorination supported by lactate showed a considerable removal of PCE and TCE, but temporary accumulation of transient reaction product 1,2-cis-dihloroethene. Reductive dechlorination with nZVI showed a significant reduction in the concentration of chlorinated ethenes without a formation of intermediate products. The development of pH showed only small changes due to the high buffering capacity of the aquifer. Both methods differ in the initial development of ORP, but over the long term showed similar values around 100 mV. Significant differences were observed for chemical oxygen demand, where groundwater after the application of nZVI showed no change in comparison to the application of lactate. The reductive effects of both agents were verified by changes in inorganic compound concentrations. PMID:22720397

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  5. 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)

  6. The use of zero-valent iron and ultrasonic energy for in-situ groundwater remediation

    SciTech Connect

    Afiouni, G.F.; Clausen, C.A.; Geiger, C.L.; Reinhart, D.; Ruiz, N.E.

    1996-12-31

    Contamination in groundwater in general and drinking water in particular has become a major concern in the twentieth century. EPA strictly regulates the amount of acceptable contamination to extremely low levels for chemical industries. Old techniques, such as pump-and-treat, has proven to have some limitation in dropping the concentrations to acceptable levels thus forcing research groups to look into other alternatives for groundwater remediation. A new technique is to implement an in situ treatment of groundwater depending mainly on the natural water flow through a treatment wall. This active wall would consist of zero-valent-iron, with high surface area to mass ratio, in order to accelerate the kinetics of the dehalogenation of chlorinated organic molecules, mainly trichloroethylene TCE, into environmentally acceptable hydrocarbons that can be consumed by microorganisms underground. In addition, ultrasonic chemistry is co-applied in order to replenish the oxidized metal surface area i.e. to help in maintaining wall activity which theoretically should increase the wall lifetime. Data from both batch and column reactions show the feasibility of such a procedure. Kinetic data will be presented.

  7. Ageing decreases the phytotoxicity of zero-valent iron nanoparticles in soil cultivated with Oryza sativa.

    PubMed

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

    2016-08-01

    This paper was aimed to study the impact of "ageing" (aged in non-saturated soil for 2 and 4 weeks prior to exposure) nanoscale zero-valent iron (nZVI) on the terrestrial plant. The effects of nZVI on Oryza Sativa germination, seedlings growth, chlorophyll biosynthesis, oxidative stress and the activities of antioxidant enzymes at low (250 mg/kg) and high (1000 mg/kg) concentrations were investigated in this study. The results showed that neither the freshly added nor the "ageing" nZVI to the soil had a significant effect on germination, regardless of concentration. At the low concentration, the freshly added nZVI had no visible toxic effects on the rice seedlings growth, but the rice seedlings exhibited obvious toxic symptoms at the high concentration. At the high concentration, toxicity effects of nZVI were reduced after aging with 2 and 4 weeks in soils compared to fresh nZVI, but the "ageing" nZVI continued to significantly inhibit the rice seedlings growth compared with the control, and the inhibition rates of 2 and 4-week-old nZVI were not significantly different. The mechanism of ageing decreased the phytotoxicity of nZVI was due to nZVI particles incomplete oxidation, and some of which had remained in the soil after 4 weeks aged. PMID:27207497

  8. 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.

  9. 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

  10. Reductive Removal of Selenate in Water Using Stabilized Zero-Valent Iron Nanoparticles.

    PubMed

    Liu, Hongfang; Cai, Zhengqing; Zhao, Xiao; Zhao, Dongye; Qian, Tianwei; Bozack, Michael; Zhang, Mingang

    2016-08-01

    Polysaccharide-stabilized zero-valent iron (ZVI) nanoparticles were synthesized using sodium carboxymethyl cellulose (CMC) or starch as stabilizer, and tested for reductive removal of selenate in water. Batch kinetic tests showed that the stabilized ZVI nanoparticles offer much faster selenate removal than bare ZVI particles at both pH 6.0 and pH 8.4. X-ray photoelectron spectroscopy (XPS) analyses confirmed Se(VI) was transformed to Se(IV) and Se(0), which are removed along with the nanoparticles. Neutral pH (~7) was found to be most favorable for the reductive removal. Decreasing pH to 5.0 or increasing it to 8.0 reduced the removal rate of CMC-stabilized ZVI by a factor of 4.6 or 1.3, respectively, based on the observed first-order-rate constant. Dissolved organic matter (DOM) at 5 mg/L as total organic carbon (TOC) had modest inhibitive effect, but DOM at 25 mg/L TOC decreased selenate removal by 25%. The stabilized nanoparticles hold the potential to facilitate in situ remediation of selenate-contaminated soil and groundwater. PMID:27456140

  11. 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.

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

    SciTech Connect

    Kaplan, D.I.

    2002-05-10

    Studies were undertaken to measure the rate of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as Fe(0). The pseudo-first-order rate coefficients measured under flow conditions were comparable to those previously measured under batch conditions that had significantly greater ratios of solution volume to Fe(0) surface area. Between the range of 20 and 100 weight percent Fe(0), there was little measurable change in the reaction kinetics. Thus, it may be possible to include sand into the reactive filter packs in the event it is necessary to increase filter pack porosity or to decrease the accumulation of secondary reaction products that may lead to filter pack plugging. Background water chemistry had only marginal effects on reaction rate coefficients. The reaction rates measured in this study indicated that an Fe(0) filter pack could be used to lower Cr(VI) concentrations by several orders of magnitude in a once-through mode of operation of the Reactive Well Technology.

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

    PubMed

    Bayer, Peter; Finkel, Michael

    2005-06-01

    Multiple contaminant mixtures in groundwater may not efficiently be treated by a single technology if contaminants possess rather different properties with respect to sorptivity, solubility, and degradation potential. An obvious choice is to use sequenced units of the generally accepted treatment materials zero valent iron (ZVI) and granular activated carbon (GAC). However, as the results of this modelling study suggest, the required dimensions of both reactor units may strongly differ from those expected on the grounds of a contaminant-specific design. This is revealed by performing an analysis for a broad spectrum of design alternatives through numerical experiments for selected patterns of contaminant mixtures consisting of monochlorobenzene, tetrachloroethylene, trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), and vinyl chloride (VC). It is shown that efficient treatment can be achieved only if competitive sorption effects in the GAC unit as well as the formation of intermediate products in the ZVI unit are carefully taken into account. Cost-optimal designs turned out to vary extremely depending on the prevailing conditions concerning contaminant concentrations, branching ratios, and unit costs of both reactor materials. Where VC is the critical contaminant, due to high initial concentration or extensive production as an intermediate, two options are cost-effective: an oversized ZVI unit with an oversized GAC unit or a pure GAC reactor. PMID:15949610

  14. 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

  15. Degradation of bromamine acid by nanoscale zero-valent iron (nZVI) supported on sepiolite.

    PubMed

    Fei, Xuening; Cao, Lingyun; Zhou, Lifeng; Gu, Yingchun; Wang, Xiaoyang

    2012-01-01

    Sepiolite, a natural nano-material, was chosen as a carrier to prepare supported nanoscale zero-valent iron (nZVI). The effects of preparation conditions, including mass ratio of nZVI and activated sepiolite and preparation pH value, on properties of the supported nZVI were investigated. The results showed that the optimal mass ratio of nZVI and sepiolite was 1.12:1 and the optimal pH value was 7. The supported nZVI was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive spectrometer (EDS), and furthermore an analogy model of the supported nZVI was set up. Compared with the nZVI itself, the supported nZVI was more stable in air and possessed better water dispersibility, which were beneficial for the degradation of bromamine acid aqueous solution. The degradation characteristics, such as effects of supported nZVI dosage, initial concentration and initial pH value of the solution on the decolorization efficiency were also investigated. The results showed that in an acidic environment the supported nZVI with a dosage of 2 g/L showed high activity in the degradation of bromamine acid with an initial concentration of 1,000 mg/L, and the degree of decolorization could reach up to 98%. PMID:23109568

  16. 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.

  17. 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

  18. Reaction pathway and oxidation mechanisms of dibutyl phthalate by persulfate activated with zero-valent iron.

    PubMed

    Li, Huanxuan; Wan, Jinquan; Ma, Yongwen; Wang, Yan

    2016-08-15

    This study investigated reaction pathway and oxidation mechanisms of dibutyl phthalate (DBP) by persulfate (PS) activated with zero-valent iron (ZVI). The DBP degradation was studied at three pH values (acidic, neutral and basic) in the presence of different organic scavengers. Using a chemical probe method, both sulfate radical (SO4(-)) and hydroxyl radical (·OH) were found to be primary oxidants at pH3.0 and pH7.0, respectively while ·OH was the major specie to oxidize DBP at pH11.0. A similar result was found in an experiment of Electron Spin Resonance spin-trapping where in addition to OH, superoxide radical (O2(-)) was detected at pH11.0. The transformation of degradation products including dimethyl phthalate (DMP), diethyl phthalate (DEP), phthalic anhydride, and acetophenone exhibited diverse variation during the reaction processes. The phthalic anhydride concentration appeared to be maximum at all pHs. Another eleven intermediate products were also found at pH3.0 by GC-MS and HPLC analysis, and their degradation mechanisms and pathways were proposed. It was suggested that dealkylation, hydroxylation, decarboxylation and hydrogen extraction were the dominant degradation mechanisms of DBP at pH3.0. PMID:27125682

  19. 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

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

    PubMed

    Singh, Ritu; Misra, Virendra; Singh, Rana Pratap

    2012-06-01

    Batch experiments were conducted on ground water samples collected from a site contaminated with Cr(VI) to evaluate the redox potential of zero-valent iron (Fe(0)) nanoparticles for remediation of Cr(VI)-contaminated ground water. For this, various samples of contaminated ground water were allowed to react with various loadings of Fe(0) nanoparticles for a reaction period of 60 min. Data showed 100% reduction of Cr(VI) in all the contaminated ground water samples after treatment with 0.20 gL(-1) of Fe(0) nanoparticles. An increase in the reduction of Cr(VI) from 45% to 100% was noticed with the increase in the loading of Fe(0) nanoparticles from 0.05 to 0.20 gL(-1). Reaction kinetics of Cr(VI) reduction showed pseudo first-order kinetics with rate constant in the range of 1.1 × 10(-3) to 3.9 × 10(-3) min(-1). This work demonstrates the potential utility of Fe(0) nanoparticles in treatment and remediation of Cr(VI)-contaminated water source. PMID:21769560

  1. 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

  2. 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

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

    PubMed

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

    2014-12-01

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

  4. 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)

  5. Remediation of trichloroethylene-contaminated groundwater by three modifier-coated microscale zero-valent iron.

    PubMed

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

    2016-07-01

    Building a microscale zero-valent iron (mZVI) reaction zone is a promising in situ remediation technology for restoring groundwater contaminated by trichloroethylene (TCE). In order to determine a suitable modifier that could not only overcome gravity sedimentation of mZVI but also improve its remediation efficiency for TCE, the three biopolymers xanthan gum (XG), guargum (GG), and carboxymethyl cellulose (CMC) were employed to coat mZVI for surface modification. The suspension stability of the modified mZVI and its TCE removal efficiency were systematically investigated. The result indicated that XG as a shear-thinning fluid showed the most remarkable efficiency of preventing mZVI from gravity sedimentation and enhancing the TCE removal efficiency by mZVI. In a 480-h experiment, the presence of XG (3 g L(-1)) increased the TCE removal efficiency by 31.85 %, whereas GG (3 g L(-1)) and CMC (3 g L(-1)) merely increased by 15.61 and 9.69 % respectively. The pH value, Eh value, and concentration of ferrous ion as functions of the reaction time were recorded in all the reaction systems, which indicated that XG worked best in buffering the pH value of the solution and inhibiting surface passivation of mZVI. PMID:27068901

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

    PubMed

    HonetschlÄgerová, Lenka; Janouškovcová, Petra; Kubal, Martin

    2016-01-01

    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

  7. 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

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

    PubMed

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

    2001-02-01

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

  9. Study on treatment of coking wastewater by biofilm reactors combined with zero-valent iron process.

    PubMed

    Lai, Peng; Zhao, Hua-Zhang; Zeng, Ming; Ni, Jin-Ren

    2009-03-15

    Experiments were conducted to investigate the behavior of the integrated system with biofilm reactors and zero-valent iron (ZVI) process for coking wastewater treatment. Particular attention was paid to the performance of the integrated system for removal of organic and inorganic nitrogen compounds. Maximal removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH(3)-N) and total inorganic nitrogen (TIN) were up to 96.1, 99.2 and 92.3%, respectively. Moreover, it was found that some phenolic compounds were effectively removed. The refractory organic compounds were primarily removed in ZVI process of the integrated system. These compounds, with molecular weights either ranged 10,000-30,000 Da or 0-2000 Da, were mainly the humic acid (HA) and hydrophilic (HyI) compounds. Oxidation-reduction and coagulation were the main removal mechanisms in ZVI process, which could enhance the biodegradability of the system effluent. Furthermore, the integrated system showed a rapid recovery performance against the sudden loading shock and remained high efficiencies for pollutants removal. Overall, the integrated system was proved feasible for coking wastewater treatment in practical applications. PMID:18639983

  10. 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

  11. 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

  12. 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.

  13. 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

  14. Effects of pH on dechlorination of trichloroethylene by zero-valent iron.

    PubMed

    Chen, J L; Al-Abed, S R; Ryan, J A; Li, Z

    2001-05-30

    The surface normalized reaction rate constants (k(sa)) of trichloroethylene (TCE) and zero-valent iron (ZVI) were quantified in batch reactors at pH values between 1.7 and 10. The k(sa) of TCE linearly decreased from 0.044 to 0.009l/hm(2) between pH 3.8 and 8.0, whereas the k(sa) at pH 1.7 was more than an order higher than that at pH 3.8. The degradation of TCE was not observed at pH values of 9 and 10. The k(sa) of iron corrosion linearly decreased from 0.092 to 0.018l/hm(2) between pH 4.9 and 9.8, whereas it is significantly higher at pH 1.7 and 3.8. The k(sa) of TCE was 30-300 times higher than those reported in literature. The difference can be attributed to the pH effects and precipitation of iron hydroxide. The k(sa) of TCE degradation and iron corrosion at a head space of 6 and 10ml were about twice of those at zero head space. The effect was attributed to the formation of hydrogen bubbles on ZVI, which hindered the transport the TCE between the solution and reaction sites on ZVI. The optimal TCE degradation rate was achieved at a pH of 4.9. This suggests that lowering solution pH might not expedite the degradation rate of TCE by ZVI as it also caused faster disappearance of ZVI, and hence decreased the ZVI surface concentration. PMID:11348735

  15. 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.

  16. Oxygen controlled product formation in CCl{sub 4} dechlorination using zero-valent iron

    SciTech Connect

    Helland, B.R.; Alvarez, P.J.J.; Schnoor, J.L.

    1995-12-01

    Carbon tetrachloride (CCl{sub 4}) was abiotically dechlorinated using zero-valent iron powder (Fe{sup o}) to yield chloroform (CHCl{sub 3}) and methylene chloride (CH{sub 2}Cl{sub 2}), which did not undergo further dechlorination. Dechlorination was rapid and approximated first-order kinetics in the range of concentrations tested (CCl{sub 4}: 1.5 to 5.5 {mu}M; Fe{sup o}: 1 to 10 g per 265 mL distilled deionized water). Initial dechlorination rate coefficients for anoxic batch reactors (0.290 {plus_minus} 0.009 hr{sup -1} for 1 g Fe{sup o}; 1.723 {plus_minus} 0.078 hr{sup -1} for 10 g Fe{sup o}) increased with iron surface area (initially 2.4 {plus_minus} 0.2 m{sup 2}/g). Dechlorination also occurred under oxic conditions, although rates were significantly slower (e.g., 0.085 {plus_minus} 0.041 hr{sup -1} for 1 g Fe{sup o} and 7.4 mg/L initial dissolved oxygen). Rate coefficients increased with time, probably due to an increase in reactive surface area from pitting and dissolution of the iron surface. A rapid pH increase was synchronous to dissolved oxygen consumption, and the pH remained constant after oxygen depletion. This was attributed to the proton and oxygen consuming aerobic corrosion of the Fe{sup o} surface. Recalcitrant CH{sub 2}Cl{sub 2} was decreased in the presence of dissolved oxygen, which reacted with dechlorinated intermediates to yield less environmentally onerous products such as formic acid and carbon monoxide.

  17. 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

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

    PubMed

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

    2014-08-01

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

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

    SciTech Connect

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

    1998-11-01

    This study was undertaken to determine the effectiveness of zero-valent iron (Fe{sup 0}) and several adsorbent materials in removing uranium (U) from contaminated groundwater and to investigate the rates and mechanisms that are involved in the reactions. Fe{sup 0} filings were used as reductants, and the adsorbents included peat materials, iron oxides, and a carbon-based sorbent (Cercona Bone-Char). Results indicate that Fe{sup 0} filings are much more effective than the adsorbents in removing uranyl (UO{sub 2}{sup 2+}) from the aqueous solution. Nearly 100% of U was removed through reactions with Fe{sup 0} at an initial concentration up to 76 mM. Results from the batch adsorption and desorption and from spectroscopic studies indicate that reductive precipitation of U on Fe{sup 0} is the major reaction pathway. Only a small percentage of UO{sub 2}{sup 2+} appeared to be adsorbed on the corrosion products of Fe{sup 0} and could be desorbed by leaching with a carbonate solution. The study also showed that the reduced U(IV) species on Fe{sup 0} surfaces could be reoxidized and potentially remobilized when the reduced system becomes more oxidized. Results of this research support the application of the permeable reactive barrier technology using Fe{sup 0} as a reactive media to intercept U and other groundwater contaminants migrating to the tributaries of Bear Creek at the US Department of Energy`s Y-12 Plant located in Oak Ridge, TN.

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

    SciTech Connect

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

    2003-03-01

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

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

    SciTech Connect

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

    1999-07-01

    The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe{sup 0}). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe{sup 0} filings and resulted in the formation of a suite of mineral precipitates. HCO{sub 3}{sup {minus}} ions in SO{sub 4}{sup 2{minus}}-containing water were particularly corrosive to Fe{sup 0}, resulting in the formation of ferrous carbonate and enhanced H{sub 2} gas generation that stimulated the growth of microbial populations and increased SO{sub 4}{sup 2{minus}} reduction. Major mineral precipitates identified included lepidocrocite, akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO{sub 4}{sup 2{minus}} that became significant after about 2 months of column operations. This study demonstrates that biogeochemical influences on the performance and reaction of Fe{sup 0} may be minimal in the short term, necessitating longer-term operations to observe the effects of biogeochemical reactions on the performance of Fe{sup 0} barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from biogeochemical processes could reduce the reactivity and permeability of Fe{sup 0} beds, thereby decreasing treatment efficiency.

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

    SciTech Connect

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

    2007-02-15

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

  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. Performance enhancement of zero valent iron based systems using depassivators: Optimization and kinetic mechanisms.

    PubMed

    Ansaf, Karim Vayalunkal Karottu; Ambika, Selvaraj; Nambi, Indumathi Manivannan

    2016-10-01

    The long-term ability of Zero-Valent Iron (ZVI) in contaminant removal relies on the effectiveness of iron to serve as electron donor, which makes it a versatile remediation material. However, the formation of oxide and hydroxide layers results in passive layer on ZVI surface during contaminant removal hinders its reactivity. The focus of this research was to evaluate the performance of corrosive agents such as acetic acid (HAc), aluminium sulphate (Alum) and potassium chloride (KCl) as depassivators to overcome passivation for sustainability and longevity. Batch experiments using seven combinations of the above chemicals were conducted to optimize the dosage of depassivators based on passive layer removal. The influence of depassivators in catalytic activity of ZVI in removing Cr(6+) was evaluated. The passive layer on ZVI particles was characterized using Scanning Electron Microscopy (SEM) and confirmed by Energy-Dispersive X-ray spectroscopy (EDAX) analysis. The major mechanisms in passive layer removal was found to be H(+) ion embrittlement followed by uniform depassivation when [HAc] was used and pitting corrosion when [Alum] and [KCl]were used. All the seven sets of chemicals enabled depassivation, but considering the criteria of maximum depassivation, catalytic activity and long term reactivity the depassivation treatments were effective in order as [HAc-Alum] > [HAc-Alum-KCl] >[HAc] > [Alum] > [HAc-KCl] > [KCl] > [Alum-KCl]. The kinetic rate of ZVI using [HAc-Alum] and [Alum] was relatively unchanged over the pH range of 4-10, made it suitable for ex-situ remediation. This insignificant influence of initial pH in catalytic activity of ZVI along with the improvement in longevity and sustainability makes it suitable for effective water treatment applications. The present work has successfully demonstrated that chemical depassivation can restore considerable reactivity of ZVI in the existing permeable reactive barriers. PMID:27395028

  5. 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

  6. 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

  7. ZERO-VALENT IRON REMOVAL RATES OF AQUEOUS Cr(VI) MEASURED UNDER FLOW CONDITIONS

    SciTech Connect

    Kaplan, Daniel I.; Gilmore, Tyler J.

    2004-06-01

    The rates of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), was measured under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as Fe(0). Dissolved Cr(VI) concentration, dissolved O2 concentration, and Eh data indicated that Cr(VI) removal from the aqueous phase was mass-transfer limited. All pseudo-first-order regression fits to the data were significant (P≤0.05), however, they did not capture many of the salient aspects of the data, including that the removal rate often decreased as contact time increased. As such, application of these rate coefficients to predict long-term Cr(VI) removal were compromised. The rate coefficients measured under flow conditions were comparable to those measured previously under batch conditions with significantly greater solution:solid ratios. Between the range of 20 and 100 wt-% Fe(0) in the column, there was little measurable change in the reaction kinetics. Thus, it may be possible to include sand into the reactive filter packs in the event it is necessary to increase filter pack porosity or to decrease the accumulation of secondary reaction products that may lead to filter pack plugging. Background water chemistry (0.2 M NaHCO3, distilled water, and a carbonate-dominated groundwater) had only marginal, if any, effects on reaction rate coefficients. The reaction rates measured in this study indicated that an Fe(0) filter pack could be used to lower Cr(VI) concentrations by several orders of magnitude in a once-through mode of operation of the Reactive Well Technology.

  8. Assessing the capacity of zero valent iron nanofluids to remediate NAPL-polluted porous media.

    PubMed

    Tsakiroglou, Christos; Terzi, Katerina; Sikinioti-Lock, Alexandra; Hajdu, Kata; Aggelopoulos, Christos

    2016-09-01

    A variety of aqueous suspensions (nanofluids) of zero-valent nano-particles (nZVI) are prepared by wet chemistry techniques, their stability and longevity is evaluated by physic-chemical methods of characterization, and their reactivity toward the dechlorination of per-chloro-ethylene (PCE) is examined with tests in batch reactors. For assessing the mobility, longevity and reactivity of nZVI suspensions (nanofluids), under flow-through conditions, visualization multiphase flow and transport tests are performed on a glass-etched pore network. The nZVI breakthrough curves are constructed by measuring the transient variation of the iron concentration in the effluent with atomic absorption spectroscopy. The capacity of nZVI to remediate the bulk phase of PCE is quantified by detecting the mass loss rate of PCE ganglia trapped in glass-etched pore networks during the continuous injection of nZVI suspension or pure water. The nZVI injection in porous media is simulated as an advection- dispersion process by accounting for the attachment/detachment of nanoparticles on the pore-walls, and describing the kinetics of PCE dissolution and reaction by 1st order equations. Visualization experiments reveal that the gradual elimination of PCE ganglia by the injected nZVI is associated with the preferential "erosion" of the upstream interfacial regions. The step controlling the overall process kinetics might be either (i) the enhanced PCE dissolution or (ii) the direct reaction of bulk PCE with the nZVI deposited upon the ganglia interfaces. Inverse modeling of the experiments under the simplifying assumption of one active mechanism indicates that the estimated kinetic coefficients are increasing functions of the flow rate. PMID:26875604

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

    PubMed

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

    2013-11-01

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

  10. 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.

  11. Mechanisms of NOx removal from flue gas by zero valent iron

    SciTech Connect

    Shiao-Shing Chen; Chih-Yu Cheng; Jung-Chun Chang; Chih-Hui Tang

    2006-06-15

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

  12. Effect of coating on the environmental applications of zero valent iron nanoparticles: the lindane case.

    PubMed

    San Román, I; Galdames, A; Alonso, M L; Bartolomé, L; Vilas, J L; Alonso, R M

    2016-09-15

    Commercial stabilized slurry of zero-valent iron nanoparticles (nZVI) as well as laboratory-synthesized polymer-stabilized NZVI nanoparticles were used for lindane (γ-hexachlorocyclohexane) degradation studies in aqueous solution. In the present study, polymer-stabilized iron nanoparticles were stabilized using polyethylene glycol (PEG, Mn ~400 and ~950-1050) and polytetrahydrofuran (PTHF, Mn ~650). To study the effectiveness of the different nanoparticles, a quantitative monitorization of lindane degradation by using solid-phase extraction (SPE) and a qualitative measurement of generated volatile by-products by headspace-solid phase microextraction (HS-SPME) followed by GC/MS were carried out. The obtained data were compared and contrasted with the results obtained in previous work. Results showed that the nanoparticles studied in this work possess superior dechlorination performance compared with previous observations. The freshly prepared Fe(0)-PEG400, Fe(0)-PEG1050 and Fe(0)-PTHF exhibited high reactivity during the dechlorination process of lindane in a very short time. The results obtained with the synthesized nanoparticles were similar to those obtained with commercial nanoparticles. However, in all cases reactivity decreased at reaction's late stage. Degradation of lindane by the studied nanoparticles removed 99.9% of the lindane initial concentration after 72h, except for Fe(0)-PTHF nanoparticles, for which the reaction stopped after 5min. In all cases, the reaction followed a second order kinetics. Finally, comparing the results from this study with our previous work, where different nature polymers were considered (Fe(0)-CMC, Fe(0)-PAA and Fe(0)-PAP), more gradual degradation profile of lindane was observed for Fe(0)-PAA and Fe(0)-CMC. It should be noted that in the present case, the reaction of lindane was speeded up with commercial and Fe(0)-PEG nanoparticles. Nevertheless, in the later case, the composition of by-products was affected by the presence

  13. 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

  14. 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

  15. 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

  16. Synergistic degradation of chlorinated hydrocarbons with microorganisms and zero valent iron

    NASA Astrophysics Data System (ADS)

    Schöftner, Philipp; Summer, Dorothea; Leitner, Simon; Watzinger, Andrea; Wimmer, Bernhard; Reichenauer, Thomas

    2016-04-01

    Sites contaminated with chlorinated hydrocarbons (CHC) are located mainly within build-up regions. Therefore in most cases only in-situ technologies without excavation of soil material can be used for remediation. This project examines a novel in-situ remediation method, in which the biotic degradation via bacteria is combined with abiotic degradation via zero-valent iron particles (ZVI). ZVI particles are injected into the aquifer where CHC-molecules are reductively dechlorinated. However Fe0 is also oxidized by reaction with water leading to generation of H2 without any CHC degradation. To achieve biotic degradation often strictly anaerobic strains of the bacteria Dehalococcoides are used. These bacteria can dechlorinate CHC by utilizing H2. By combining these processes the H2, produced during the anaerobic corrosion of Fe0, could be used by bacteria for further CHC degradation. Therefore the amount of used Fe0 and as a consequence also remediation costs could be reduced. Additionally the continuous supply of H2 could make the bacterial degradation more controllable. Different Fe0 particles (nano- and micro-scale) were tested for their perchloroethene (PCE) degradation rate and H2 production rate in microcosms. PCE-degradation rate by different bacterial cultures was investigated in the same microcosm system. In course of these experiments the 13C enrichment factors of the PCE degradation of the different particles and cultures were determined to enable the differentiation of biotic and abiotic degradation. Preliminary results showed, that the nano-scale particles reacted faster with PCE and water than their micro-scaled counterparts. The PCE degradation via micro-scaled particles lead to 13C enrichment factors in the range of -3,6 ‰ ± 0,6 to -9,5 ‰ ± 0,2. With one of the examined bacterial cultures a fast reduction of PCE to ethene was observed. Although PCE and TCE were completely degraded by this culture the metabolites DCE and VC could still be detected

  17. 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

  18. 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

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

    PubMed

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

    2013-10-15

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

  20. 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

  1. 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

  2. The influences of iron characteristics, operating conditions and solution chemistry on contaminants removal by zero-valent iron: A review.

    PubMed

    Sun, Yuankui; Li, Jinxiang; Huang, Tinglin; Guan, Xiaohong

    2016-09-01

    For successful application of a zero-valent iron (ZVI) system, of particular interest is the performance of ZVI under various conditions. The current review comprehensively summarizes the potential effects of the major influencing factors, such as iron intrinsic characteristics (e.g., surface area, iron impurities and oxide films), operating conditions (e.g., pH, dissolved oxygen, iron dosage, iron pretreatment, mixing conditions and temperature) and solution chemistry (e.g., anions, cations and natural organic matter) on the performance of ZVI reported in literature. It was demonstrated that all of the factors could exert significant effects on the ZVI performance toward contaminants removal, negatively or positively. Depending on the removal mechanisms of the respective contaminants and other environmental conditions, an individual variable may exhibit different effects. On the other hand, many of these influences have not been well understood or cannot be individually isolated in experimental or natural systems. Thus, more research is required in order to elucidate the exact roles and mechanisms of each factor in affecting the performance of ZVI. Furthermore, based on these understandings, future research may attempt to establish some feasible strategies to minimize the deteriorating effects and utilize the positive effects so as to improve the performance of ZVI. PMID:27206056

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

  8. In situ remediation of ground water contaminated with chromate and chlorinated solvents using zero-valent iron: A field study

    SciTech Connect

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

    1995-12-01

    A small-scale field test was recently initiated to evaluate the in situ remediation of ground water contaminated with chromate and chlorinated organics using a permeable reactive barrier. The barrier was composed of an iron metal-coarse sand-native aquifer solid mixture, and was installed using a staggered {open_quotes}fence{close_quotes} design through large hollow-stem augers. The objectives of the project were to evaluate the ability of the cylinders or {open_quotes}fence posts{close_quotes} to remove contaminants from solution immediately downgradient and adjacent to the iron cylinders, evaluate the resultant changes in aqueous geochemistry induced by the presence of the zero-valent iron, and identify chemical, physical and biological processes which may affect long-term performance of such remedial technologies.

  9. 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...

  10. 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

  11. 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

  12. 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.

  13. 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...

  14. 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...

  15. 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...

  16. 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 ...

  17. 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.

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

    PubMed

    Dang, Hongyu; Zhang, Yongxiang; Du, Peiwen

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Dai, C.; Zhang, Y.

    2015-12-01

    The nanoscale particle and low oxidation reduction potential make nano zero-valent iron (nZVI) an efficient sorbent and reductant for treating many kinds of organic contaminants and heavy metals.The structures of nanoscale zero-valent iron (nZVI) particles are evolving in reactions, and the reactions are influenced by the evolved structures. In order to understand the detail removal process, it is important to investigate the interactions between reactions and structural evolution. In this work, reactions between nZVI and Co2+ at different initial concentrations in anoxic aqueous solutions (to eliminate the effects of O2) were tracked for 10 days using a variety of methods including inductively coupled plasma optical emission spectrometry (ICP-OES), high resolution-transmission electron microscopy (HR-TEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). Continuous removal and reduction of Co2+ by nZVI caused by structural evolution were revealed in reaction processes. The system pH (pH measured in mixture), which controls the stability of coprecipitation and the corrosion rate of nZVI, was deemed as the determining factors of structural evolutions. X-ray photoelectron spectroscopy (XPS) results showed that the formation and dissolution of sheet structure impacts on the ratio of Fe (0) on nZVI's surface and the surface reduction of Co2+. The cavity structure provides the possibility of Co migrating from surface to inside of nZVI leading a continuous removal. A subacidity condition could accelerate the evolution to improve the removal of Co2+ and the results of structural controlled reactions further indicated that the removal was suspended by sheet structure and enhanced by cavity structure. The results in this study revealed "structural influence" for fully and dynamically understanding nZVI's reactions.

  20. 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

  1. 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

  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. 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.

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

    PubMed

    Schäfer, Dirk; Köber, Ralf; Dahmke, Andreas

    2003-09-01

    The successful dechlorination of mixtures of chlorinated hydrocarbons with zero-valent metals requires information concerning the kinetics of simultaneous degradation of different contaminants. This includes intraspecies competitive effects (loading of the reactive iron surface by a single contaminant) as well as interspecies competition of several contaminants for the reactive sites available. In columns packed with zero-valent iron, the degradation behaviour of trichloroethylene (TCE), cis-dichloroethylene (DCE) and mixtures of both was measured in order to investigate interspecies competition. Although a decreasing rate of dechlorination is to be expected, when several degradable substances compete for the reactive sites on the iron surface, TCE degradation is nearly unaffected by the presence of cis-DCE. In contrast, cis-DCE degradation rates decrease significantly when TCE is added. A new modelling approach is developed in order to identify and quantify the observed competitive effects. The numerical model TBC (Transport, Biochemistry and Chemistry, Schäfer et al., 1998a) is used to describe adsorption, desorption and dechlorination in a mechanistic way. Adsorption and degradation of a contaminant based on a limited number of reactive sites leads to a combined zero- and first-order degradation kinetics for high and low concentrations, respectively. The adsorption of several contaminants with different sorption parameters to a limited reactive surface causes interspecies competition. The reaction scheme and the parameters required are successfully transferred from Arnold and Roberts (2000b) to the model TBC. The degradation behaviour of the mixed contamination observed in the column experiments can be related to the adsorption properties of TCE and cis-DCE. By predicting the degradation of the single substances TCE and cis-DCE as well as mixtures of both, the calibrated model is used to investigate the effects of interspecies competition on the design of

  5. 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

  6. 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

  7. 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

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

    PubMed

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

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

  9. A combined process of adsorption and Fenton-like oxidation for furfural removal using zero-valent iron residue.

    PubMed

    Li, Furong; Bao, Jianguo; Zhang, Tian C; Lei, Yutian

    2015-01-01

    In this study, the feasibility of using a combined adsorption and Fenton-like oxidation process (with zero-valent iron (ZVI) residue from heat wraps as an absorbent and catalyst) to remove furfural in the solution was evaluated. The influencing parameters (e.g. pH, H2O2 concentration, initial furfural concentration) and the reusability of ZVI residue (to replace the iron powder) were estimated. The ZVI residue was found to have much better adsorption effect on furfural at pH 2.0 compared with pH 6.7. For Fenton-like reaction alone with ZVI residue, the highest furfural removal of 97.5% was observed at the concentration of 0.176 mol/L H2O2, and all of the samples had >80% removal efficiency at different initial furfural concentrations of 2, 10, 20, 30 and 40 mmol/L. However, with a combined adsorption and Fenton-like oxidation, the removal efficiency of furfural was nearly 100% for all treatments. The ZVI residue used for furfural removal was much better than that of iron powder in the Fenton-like reaction at a seven-cycle experiment. This study suggests the combined process of adsorption and Fenton-like oxidation using ZVI residue is effective for the treatment of furfural in the liquid. PMID:26006292

  10. Characterization of preferential flow paths between boreholes in fractured rock using a nanoscale zero-valent iron tracer test

    NASA Astrophysics Data System (ADS)

    Chuang, Po-Yu; Chia, Yeeping; Liou, Ya-Hsuan; Teng, Mao-Hua; Liu, Ching-Yi; Lee, Tsai-Ping

    2016-05-01

    Recent advances in borehole geophysical techniques have improved characterization of cross-hole fracture flow. The direct detection of preferential flow paths in fractured rock, however, remains to be resolved. In this study, a novel approach using nanoscale zero-valent iron (nZVI or `nano-iron') as a tracer was developed for detecting fracture flow paths directly. Generally, only a few rock fractures are permeable while most are much less permeable. A heat-pulse flowmeter can be used to detect changes in flow velocity for delineating permeable fracture zones in the borehole and providing the design basis for the tracer test. When nano-iron particles are released in an injection well, they can migrate through the connecting permeable fracture and be attracted to a magnet array when arriving in an observation well. Such an attraction of incoming iron nanoparticles by the magnet can provide quantitative information for locating the position of the tracer inlet. A series of field experiments were conducted in two wells in fractured rock at a hydrogeological research station in Taiwan, to test the cross-hole migration of the nano-iron tracer through permeable connected fractures. The fluid conductivity recorded in the observation well confirmed the arrival of the injected nano-iron slurry. All of the iron nanoparticles attracted to the magnet array in the observation well were found at the depth of a permeable fracture zone delineated by the flowmeter. This study has demonstrated that integrating the nano-iron tracer test with flowmeter measurement has the potential to characterize preferential flow paths in fractured rock.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Zero-valent iron (ZVI) installed in permeable reactive barriers (PRBs) has been shown to be an effective remediation agent for several contaminants, including arsenic (As), a redox-active oxyanion present in reduced form as arsenite, AsO3(3-), and in oxidized form as arsenate, AsO4(3-). Work performed has shown greater removal of arsenic by iron sulfide (FeS), as mackinawite, than by ZVI under anaerobic conditions, recommending the use of FeS in PRB systems. For both ZVI and FeS PRB systems, the interaction of the reactive porous media with groundwater species, and calcium and carbonate in particular, is key to maintaining the permeability and reactivity of the PRB, both of which are necessary for continued treatment. If geochemical conditions are favorable, CaCO3(s) may precipitate, thus reducing permeability and passivating the reactive surface, preventing further remediation. In a statistical review of field PRB performance (Henderson and Demond, Env. Eng. Sci., 2007), it was found that alkalinity, as an indicator of the potential for precipitation of carbonate solids, was correlated to increased risk of PRB failure. A combination of experimental and geochemical modeling approaches is being used to investigate the quantity of calcium carbonate formation in anaerobic FeS and ZVI systems. Column tests with FeS to date have resulted in behavior unlike that observed with ZVI. In the ZVI columns, a pH increase has allowed the precipitation of CaCO3(s), which led to a reduction in permeability. In the FeS columns, the effluent pH and aqueous calcium concentrations were essentially the same as the influent, suggesting that the buffer capacity of carbonate prevented a pH increase, thus precluding the precipitation of CaCO3(s). Geochemical modeling suggests that the interaction of carbonate and FeS may self-regulate in PRB systems: at high carbonate concentrations, when the precipitation of CaCO3(s) could reduce permeability, the buffer capacity provided by the carbonate

  12. 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

  13. 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

  14. 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

  15. Enhanced ultrasound-assisted degradation of methyl orange and metronidazole by rectorite-supported nanoscale zero-valent iron.

    PubMed

    Yuan, Na; Zhang, Gaoke; Guo, Sheng; Wan, Zhen

    2016-01-01

    In this study, the rectorite-supported nanoscale zero-valent iron (nZVI/R) was synthesized through a reduction method. X-ray diffraction analysis showed the existence of the nZVI in the nZVI/R composite and X-ray photoelectron spectroscopy analysis indicated that the nZVI particles were partly oxidized into iron oxide. Scanning electron microscopy analysis revealed that the nZVI particles were highly dispersed on the surface of the rectorite. The specific surface area of the nZVI/R composite is 21.43 m(2)/g, which was higher than that of rectorite (4.30 m(2)/g) and nZVI (17.97 m(2)/g). In the presence of ultrasound (US), the degradation of methyl orange and metronidazole by the nZVI/R composite was over 93% and 97% within 20 min, respectively, which is much higher than that by the rectorite and the nZVI. The degradation ratio of methyl orange and metronidazole by the nZVI/R composite under US was 1.7 and 1.8 times as high as that by the nZVI/R composite without US, respectively. The mechanism of the enhanced degradation of methyl orange and metronidazole under US irradiation was studied. These results indicate that the US/nZVI/R process has great potential application value for treatment of dye wastewater and medicine wastewater. PMID:26384884

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

    PubMed

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

    2015-01-01

    The estimation of nanoscale zero-valent iron (nZVI) reactivity after its injection into the subsurface is essential for its application in groundwater remediation. In the present study H₂ generation of commercially available nZVI and novel milled nZVI flakes were investigated in column experiments with varying nZVI loads (ranging from 8 to 43 g nZVI per kg sand). H₂ evolution rates were determined for column experiments without and with hydrogen carbonate and/or calcium. On average 0.29 mmol H₂/L per g Fe⁰ evolved within the first 30 days in column experiments with spherical, commercial nZVI particles. The H₂ evolution developed almost independently of the water matrices applied. The application of nZVI flakes resulted in lower H₂ generation rates. In general corrosion rates accelerated linearly with increasing initial amounts of iron. This was evident in experiments with both particle types. Concentration profiles of carbonate and calcium in influent and effluent were used to estimate corrosion products and precipitates. Despite the presence of high concentrations of inorganic carbon, Fe²⁺ reacted preferably with hydroxide ions to form ferrous hydroxide which is the precursor of magnetite. As a result only minor passivation of the reactive nZVI was observed. PMID:25462777

  17. 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

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

    PubMed

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

    2015-03-01

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

  19. 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

  20. 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

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

    PubMed

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

    2011-01-01

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

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

    PubMed

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

    2007-04-01

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

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

    PubMed

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

    2014-04-01

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

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

    SciTech Connect

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

    1996-12-31

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

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

    PubMed

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

    2013-02-01

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

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

    PubMed

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

    2013-04-01

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

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Reductive removal of 2,4-dinitrotoluene and 2,4-dichlorophenol with zero-valent iron-included biochar.

    PubMed

    Oh, Seok-Young; Seo, Yong-Deuk; Ryu, Kwang-Sun

    2016-09-01

    In order to remediate organic contaminants in natural waters and soils, a novel zero-valent iron [Fe(0)]-included biochar was synthesized via slow pyrolysis. 2,4-Dinitrotoluene (DNT) and 2,4-dichlorophenol (DCP) were removed in water via sorption to the Fe(0)-included biochar. Compared to sorption control without Fe(0), the sorbed DNT and DCP were further transformed to reduction products by Fe(0)-included biochar. Compared to the reduction control with Fe(0), the presence of biochar promoted the reductive transformation of DNT and DCP. Increasing the pyrolysis temperature resulted in enhancing the removal of DNT and DCP, suggesting that the aromaticity of biochar may be responsible for the removal. The yields of the reduction products also indicated that unlike the direct reduction by Fe(0), different reduction pathways existed in the reduction of DNT and DCP with Fe(0)-included biochar. The results suggest that Fe(0)-included biochar is a viable option to immobilize and transform redox-sensitive organic contaminants in natural environments. PMID:27343454

  12. 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

  13. Simulation of antimony adsorption on nano-zero valent iron and kaolinite and analyzing the influencing parameters.

    PubMed

    Saeidnia, Setareh; Asadollahfardi, Gholamreza; Darban, Ahmad Khodadadi; Mohseni, Mehdi

    2016-01-01

    Antimony is one of the most toxic pollutants in industrial and mineral wastewaters threatening the life of humans and other creatures. We simulated the adsorption of antimony in the presence of nano-zero valent iron (nZVI) adsorbent, on kaolinite and in the presence of nZVI coated on kaolinite from mineral wastewater using VISUAL MINTEQ 3.1 software. Our aim was to determine the factors affecting the adsorption of antimony by applying simulation. The simulation was performed using an adsorption model of a diffuse layer model. The results of the simulation indicated that the nZVI concentration, initial concentrations of antimony and pH factor are effective on the adsorption of antimony. In the conducted stimulation, the optimum pH was 2-5 and the highest adsorption occurred in an acidic state. With increasing initial concentrations of antimony in the simulation, we concluded that nZVI had absorbed various concentrations above 90% and, by increasing the concentration of nZVI, antimony adsorption rate increased. The increased surface area of nZVI and the expansion of more interchangeable surfaces available for reaction with antimony ions causes more antimony ions to be adsorbed. In all cases, the coefficient of determination between the laboratory results and the model predictions that was obtained was more than 0.9. PMID:27191572

  14. 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

  15. Sulfur and oxygen isotope tracing in zero valent iron based In situ remediation system for metal contaminants.

    PubMed

    Kumar, Naresh; Millot, Romain; Battaglia-Brunet, Fabienne; Négrel, Philippe; Diels, Ludo; Rose, Jérôme; Bastiaens, Leen

    2013-01-01

    In the present study, controlled laboratory column experiments were conducted to understand the biogeochemical changes during the microbial sulfate reduction. Sulfur and oxygen isotopes of sulfate were followed during sulfate reduction in zero valent iron incubated flow through columns at a constant temperature of 20±1°C for 90 d. Sulfur isotope signatures show considerable variation during biological sulfate reduction in our columns in comparison to abiotic columns where no changes were observed. The magnitude of the enrichment in δ(34)S values ranged from 9.4‰ to 10.3‰ compared to initial value of 2.3‰, having total fractionation δS between biotic and abiotic columns as much as 6.1‰. Sulfur isotope fractionation was directly proportional to the sulfate reduction rates in the columns. Oxygen isotopes in this experiment seem less sensitive to microbial activities and more likely to be influenced by isotopic exchange with ambient water. A linear relationship is observed between δ(34)S and δ(18)O in biotic conditions and we also highlight a good relationship between δ(34)S and sulfate reduction rate in biotic columns. PMID:23000047

  16. 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

  17. 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

  18. 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

  19. An overview of preparation and applications of stabilized zero-valent iron nanoparticles for soil and groundwater remediation.

    PubMed

    Zhao, Xiao; Liu, Wen; Cai, Zhengqing; Han, Bing; Qian, Tianwei; Zhao, Dongye

    2016-09-01

    Nano-scale zero-valent iron (nZVI) is one of the most intensively studied materials for environmental cleanup uses over the past 20 years or so. Freshly prepared nZVI is highly reactive due to its high specific surface area and strong reducing power. Over years, the classic borohydride reduction method for preparing nZVI has been modified by use of various stabilizers or surface modifiers to acquire more stable and soil deliverable nZVI for treatment of different organic and inorganic contaminants in water and soil. While most studies have been focused on testing nZVI for water treatment, the greater potential or advantage of nZVI appears to be for in situ remediation of contaminated soil and groundwater by directly delivering stabilized nZVI into the contaminated subsurface as it was proposed from the beginning. Compared to conventional remediation practices, the in situ remediation technique using stabilized nZVI offers some unique advantages. This work provides an update on the latest development of stabilized nZVI for various environmental cleanup uses, and overviews the evolution and environmental applications of stabilized nZVI. Commonly used stabilizers are compared and the stabilizing mechanisms are discussed. The effectiveness and constraints of the nZVI-based in situ remediation technology are summarized. This review also reveals some critical knowledge gaps and research needs, such as interactions between delivered nZVI and the local biogeochemical conditions. PMID:27206054

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

    PubMed

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

    2013-05-01

    Decolourization of direct azo dye, direct blue 15 (DB15), by an advanced Fenton process coupled with ultrasonic irradiation (Fenton/US) was investigated. Zero-valent iron (ZVI) aggregates were used as the catalyst. A positive synergistic effect occurred when Fenton's reagent was combined with ultrasonic irradiation. Experimental results showed that the optimum conditions for decolourization were pH 3.0, Fe(0) 1g/L, H(2)O(2) 5.15×10(-3)mol/L with ultrasound density of 120W/L at 60kHz. These conditions yielded 99% decolouration of 4.7×10(-5) M DB15 (4130 ADMI) solution within 10min. DB15 decolouration follows the first-order decolouration kinetics. Although the solutions containing H(2)CO(3), Cl(-), ClO(4)(-), NO(3)(-) and SO(4)(2-) ions did not have a significant effect on the decolouration, the H(2)PO(4)(-) ion did decrease the decolouration rate. High ultrasonic input power accelerated the reaction and increased decolourization efficiency. The cost effectiveness of this process at high ultrasound density could be controlled despite the high electricity costs incurred by the process. ZVI aggregates were reusable; however, an increase in the number of times ZVI was recycled decreased the decolourization rate. This study demonstrates that a Fenton/US process can effectively decolour the direct azo dye DB15 in wastewater. PMID:23187066

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Oxalate-assisted oxidative degradation of 4-chlorophenol in a bimetallic, zero-valent iron-aluminum/air/water system.

    PubMed

    Fan, Jinhong; Wang, Hongwu; Ma, Luming

    2016-08-01

    The reaction of zero-valent iron and aluminum with oxygen produced reactive oxidants that can oxidize 4-chlorophenol (4-CP). However, oxidant yield without metal surface cleaning to dissolve the native oxide layer or in the absence of ligands was too low for practical applications. The addition of oxalate (ox) to dissolved oxygen-saturated solution of Fe(0)-Al(0) significantly increased oxidant yield because of the dissolution, pH buffer, and complexing characteristics of ox. Ox-enhanced reactive oxidant generation was affected by ox concentration and solution pH. The critical effect of ox dosing was confirmed with the reactive species of [Fe(II)(ox)0] and [Fe(II)(ox)2 (2-)]. Systematic studies on the effect of the initial and in situ solution pH revealed that 4-CP oxidation was controlled by the continuous release of dissolved Fe(2+) and Al(3+), their fate, and the activation mechanisms of O2 reduction. The degradation pathway of 4-CP in ox-enhanced Fe(0)-Al(0)/O2 may follow the 4-chlorocatechol pathway. The robustness of the ox-enhanced Al(0)-Fe(0)-O2 process was determined with one-time dosing of ox. Therefore, ox is an ideal additive to enhancing the Fe(0)-Al(0)/O2 system for the oxidative degradation of aqueous organic pollutants. PMID:27180839

  10. Role of oxidative stress in inactivation of Escherichia coli BW25113 by nanoscale zero-valent iron.

    PubMed

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

    2016-09-15

    An Escherichia coli BW25113 wildtype strain and mutant strains lacking genes that protect against oxidative stress were examined at different growth phases for susceptibility to zero-valent iron (nZVI). Viability of cells was determined by the plate count method. All mutant strains were more susceptible than the wild type strain to nZVI; however, susceptibility differed among the mutant strains. Consistent with the role of rpoS as a global stress regulator, an rpoS gene knockout mutant exhibited the greatest susceptibility to nZVI under the majority of conditions tested (except exponential and declining phases at longer exposure time). Mutants lacking genes encoding the inducible and constitutively expressed cytosolic superoxide dismutases, sodA and sodB, respectively, were more susceptible to nZVI than a mutant lacking the gene encoding sodC, a periplasmic superoxide dismutase. This suggests that nZVI induces oxidative stress inside the cells via superoxide generation. Quantitative polymerase chain reaction was used to examine the expression of katG, a gene encoding the catalase-peroxidase enzyme, in nZVI-treated E. coli at different growth phases. Results showed that nZVI repressed the expression of katG in all but lag phases. PMID:26953142

  11. 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

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

    SciTech Connect

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

    2000-02-01

    This research investigated the long-term performance of zero-valent iron for mediating the reductive dechlorination of trichloroethylene (TCE). Over a 2-year period, rates of TCE dechlorination in columns packed with iron filings were measured in simulated groundwaters containing either 3 mM CaSO{sub 4}, 5 mM CaCl{sub 2}, or 5 mM Ca(NO{sub 3}){sub 2}. At early elapsed times, TCE reaction rates were pseudo-first-order in TCE concentration and were independent of the solution pH. With increasing elapsed time, reaction rates deviated from pseudo-first-order behavior due to reactive site saturation and increased iron surface passivation toward the influent end of each column. The extent of passivation was dependent on both the TCE concentration and the background electrolyte solution. For most of the investigation, TCE reaction rates in 3 mM CaSO{sub 4} and 5 mM CaCl{sub 2} solutions were statistically identical at the 0.05 confidence level. However, TCE reaction rates in 5 mM Ca(NO{sub 3}){sub 2} were slower. In columns operated using chloride- and sulfate-containing waters, the effective half-life for TCE dechlorination increased from approximately 400 min after 10 days elapsed to approximately 2,500 min after 667 days. The effective TCE half-life in the nitrate-containing water increased from approximately 1,500 min after 10 days to approximately 3,500 min after 667 days. Measurements of iron corrosion rates in nitrate and chloride solutions showed that nitrate contributed to increased iron surface passivation and decreased rates of iron corrosion. Corrosion current measurements indicated that halocarbon reduction on fresh iron surfaces was cathodically controlled, whereas on aged iron surfaces, iron corrosion was anodically controlled. Anodic control of iron corrosion contributed to the development of reactive site saturation with time and to similar reaction rates for TCE and perchloroethylene. Passivation of the iron surfaces was found to be dependent on the

  13. 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

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

    PubMed

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

    2010-11-01

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

  15. Removal of dissolved metals by zero-valent iron (ZVI): kinetics, equilibria, processes and implications for stormwater runoff treatment.

    PubMed

    Rangsivek, R; Jekel, M R

    2005-10-01

    Infiltration of stormwater runoff contaminated with metals is often questionable in several cases due to its long-term potential to cause deterioration of groundwater quality. To ensure the quality of filtrate, a pre-treatment of contaminated runoff is required. This study investigates the processes of copper and zinc ion removal from stormwater runoff using zero-valent iron (ZVI, Fe0). Kinetic and equilibrium tests were performed with laboratory-prepared and in situ stormwater runoff samples collected from roof, street and highway catchments. Based on the results, a substantial portion of Cu2+ is reduced and transformed to insoluble forms of Cu0 and Cu2O. Unlike copper, the adsorption and co-precipitation associated with freshly precipitated iron oxides play important roles for the removal of Zn2+. Investigations under various water quality conditions demonstrated a relatively minor impact on Cu2+ uptake rates. However, the different conditions apparently altered the removal stoichiometry and phases of the copper deposits. The removal rates of Zn2+ increase with higher dissolved oxygen (DO), ionic strength (IS), temperature (T) and pH. Dissolved organic carbon (DOC) in runoff samples forms complexes with metals and Fe2+, thereby kinetically decreasing the metal uptake rates. Furthermore, depending on its composition, a larger molecular weight organic fraction was found to preferentially compete for the adsorption sites. The study demonstrates that ZVI is a promising medium for achieving comparable capacity to a commercial adsorbent like granular ferric hydroxide (GFH). Long-term performance of ZVI, however, may be limited and governed by the formation of non-conductive layers of iron and cuprous oxides. PMID:16181656

  16. 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.

  17. 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

  18. 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

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

    PubMed

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Reardon, Eric J.

    2014-02-01

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

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

    PubMed

    Reardon, Eric J

    2014-02-01

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

  2. Interfacial phenomena affecting contaminant remediation with zero-valent iron metal

    SciTech Connect

    Tratnyek, P.G.; Johnson, T.; Schattauer, A.

    1995-12-31

    The purposes of this paper are to discuss the importance of oxygen (or anoxia) in organic contaminant degradation by granular iron metal, and to explore the various ways in which corrosion, precipitation, and mass transport effects on iron reactivity reflect interfacial phenomena. Studies illustrating the importance of zone-scale and grain-scale interfaces are summarized. The effect of O{sub 2} on dechlorination rates is also briefly discussed, along with possible reaction mechanisms.

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  6. 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.

  7. Simultaneous removal of NO and SO{sub 2} by high-temperature fluidized zero-valent iron processes

    SciTech Connect

    Shiao-Shing Chen; Chih-Yu Cheng; Chung-Cheng Wei; Chao-Heng Tseng

    2007-03-15

    A new approach to simultaneously remove nitrogen monoxide (NO) and sulfur dioxide (SO{sub 2}) by zero valent iron (ZVI) was investigated. Three different parameters, temperature, flux, and ZVI dosage, were tested in fluidized ZVI column studies containing 500 ppmv of NO and SO{sub 2}, respectively. Under the ZVI dosage of 0.5 g at flux of 0.6 L/cm{sub 2} min for temperature 573 K, there is neither NO nor SO{sub 2} reduction. For 623 K and 673 K, complete removal for NO and 90% removal for SO{sub 2} were achieved. For temperatures of 723 K and 773 K, 100% removal was achieved for both NO and SO{sub 2}. The amounts of NO or SO{sub 2} reduction increased as temperature increased, and linearities were observed with both correlation coefficients 0.97. Compared with NO, SO{sub 2} had earlier breakthrough because of a slower diffusion rate and less reactivity but higher mass reduction because of a higher molecular weight for SO{sub 2}. At the same temperature, both NO and SO{sub 2} reductions were constant regardless of either flux or ZVI dosage variation, but breakthrough time was affected by both flux and ZVI dosage. A parameter weight of ZVI/flux (W/F) was developed to represent these two parameters and assess the breakthrough time of NO and SO{sub 2}. Higher breakthrough time was achieved for higher W/F value. Longer breakthrough time and more NO and SO{sub 2} mass reduction were achieved for combined NO and SO{sub 2} than individual NO or SO{sub 2} treated by ZVI, and both oxidation and reduction reactions occurred. 15 refs., 8 figs., 1 tab.

  8. 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 0.5 g/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 0.05 g/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

  9. 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

  10. 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