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Sample records for chromium vi reduction

  1. Reduction of Chromium-VI by Chromium Resistant Lactobacilli: A Prospective Bacterium for Bioremediation

    OpenAIRE

    Mishra, Ritesh; Sinha, Vartika; Kannan, Ambrose; Upreti, Raj K.

    2012-01-01

    Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr (VI) and Cr (III). Highly soluble hexavalent chromium is carcinogenic due to its oxidizing nature. It is well established that the intestinal bacteria including Lactobacilli have regulatory effect on intestinal homeostasis and a breakdown in the relationship between intestinal cells and bacteria results in the manifestation of gastrointestinal (GI) disorders. In this study Cr (VI) resistance was developed in La...

  2. Study of reduction of chromium (VI by calcium polysulfide using spectrophotometric method

    Directory of Open Access Journals (Sweden)

    Batukhan Tatykaev

    2013-05-01

    Full Text Available The paper presents  the results of the study on reduction  of  Cr2O72-   to   Cr3 +  by aqueous solution of calcium polysulfide  using spectrophotometric method. Concentrations  of Cr (VI were determined on the basis of the absorption spectrum at the wavelength range 350 - 372 nm. The change of the concentration of Cr (VI during on reduction by calcium polysulfide has been shown.  The influence of pH on the rate of reducing of Cr (VI to Cr (III was considered: the rate of reducing of hexavalent chromium decreases with increasing pH. The data obtained show that recycling Cr (VI in industrial scale potentially effective at  the pH = 5.

  3. Solid state reduction of chromium (VI) pollution for Al2O3-Cr metal ceramics application

    Science.gov (United States)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yangai; Tang, Hao; Min, Xin; Wu, Xiaowen

    2016-04-01

    Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3-Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3-Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3-Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

  4. Chromium isotopic fractionation during Cr(VI) reduction by Bacillus sp. under aerobic conditions.

    Science.gov (United States)

    Xu, Fen; Ma, Teng; Zhou, Lian; Hu, Zhifang; Shi, Liu

    2015-07-01

    This study investigated the fractionation of chromium isotopes during chromium reduction by Bacillus sp. under aerobic condition, variable carbon source (glucose) concentration (0, 0.1, 1, 2.5 and 10mM), and incubation temperatures (4, 15, 25 and 37°C). The results revealed that the δ(53)Cr values in the residual Cr(VI) increased with the degree of Cr reduction, and followed a Rayleigh fractionation model. The addition of glucose only slightly affected cell-specific Cr(VI) reduction rates (cSRR). However, the value of ε (2.00±0.21‰) in the experiments with different concentrations of glucose (0.1, 1, 2.5 and 10mM) was smaller than that from the experiment without glucose (3.74±0.16‰). The results indicated that the cell-specific reduction rate is not the sole control on the degree of isotopic fractionation, and different metabolic pathways would result in differing degrees of Cr isotopic fractionation. The cSRR decreased with decreasing temperature, showing that the values of ε were 7.62±0.36‰, 4.59±0.28‰, 3.09±0.16‰ and 1.99±0.23‰ at temperatures of 4, 15, 25 and 37°C, respectively. It shown that increasing cSRR linked to decreasing fractionations has been associated with increasing temperatures. Overall, our results revealed that temperature is a primary factor affecting Cr isotopic fractionation under microbial actions. PMID:25777078

  5. Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron

    International Nuclear Information System (INIS)

    Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power α which is the order of the chemical reaction occurring at surface. We assumed α = 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.

  6. Chromium(VI) reduction by ascorbate: role of reactive intermediates in DNA damage in vitro.

    OpenAIRE

    Stearns, D M; Courtney, K D; Giangrande, P H; Phieffer, L S; Wetterhahn, K E

    1994-01-01

    Reaction of chromium(VI) with one equivalent of ascorbate was studied by electron paramagnetic resonance spectroscopy in the presence of 0.10 M 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) at room temperature in 0.10 M (N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]) (HEPES) and 0.05 M tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffers (pH 7.0 room temperature). Chromium(V), ascorbyl radical, and carbon-based DMPO-radical adducts were observed. A higher level of Cr(V) was ob...

  7. Enhanced photocatalytic activity of chromium(VI) reduction and EDTA oxidization by photoelectrocatalysis combining cationic exchange membrane processes

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Hung-Te, E-mail: der11065@hotmail.com [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China); Chen, Shiao-Shing, E-mail: f10919@ntut.edu.tw [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China); Tang, Yi-Fang, E-mail: sweet39005@hotmail.com [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China); Hsi, Hsing-Cheng, E-mail: hchsi@ntut.edu.tw [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 106, Taiwan (China)

    2013-03-15

    Highlights: ► Chromium(VI) reduction and EDTA oxidization were conducted by photoelectrocatalysis. ► Apply the concept of cationic exchange membrane to enhance the conversion efficiency. ► The optimum TiO{sub 2} loading of 1 g/L was observed at acidic pH with current density 4 mA/cm{sup 2}. ► Transformation pathway of EDTA was determined from analyzed byproducts and molecular orbital package analysis. -- Abstract: A novel technology of photoelectrocatalysis (PEC) combining with cationic exchange membrane (CEM) was proposed for simultaneous reduction of chromium(VI) and oxidization of EDTA. The application of CEM was used to enhance the efficiency for prevention of the re-oxidation of reduced chromium with the electron–hole pairs. In this study, effects of current density, pH, TiO{sub 2} dosage, hydraulic retention time (HRT), light intensity and EDTA/Cr(VI) molar ratio were all investigated. The results showed that the optimum conversion efficiency occurred at 4 mA/cm{sup 2} with the presence of CEM. Higher conversion efficiencies were observed at lower pH due to the electrostatic attractions between positive charged Ti-OH{sub 2}{sup +}, and negatively charged Cr(VI) and EDTA. The optimum TiO{sub 2} loading of 1 g/L was depended mainly on the acidic pH range, especially at higher HRT and irradiation intensity. In addition, higher EDTA/Cr(VI) molar ratio enhanced the reduction efficiency of Cr(VI), indicating EDTA plays the role of hole scavenger in this system. Moreover, incomplete EDTA decomposition contributes to the occurrence of intermediates, including nitrilotriacetic acid, iminodiacetic acid, glycine, oxamic acid, lyoxylic acid, oxalic acid, acetic acid and formic acid, as identified by GC/MS. Consequently, transformation pathway was determined from these analyzed byproducts and molecular orbital package analysis.

  8. Enhanced photocatalytic activity of chromium(VI) reduction and EDTA oxidization by photoelectrocatalysis combining cationic exchange membrane processes

    International Nuclear Information System (INIS)

    Highlights: ► Chromium(VI) reduction and EDTA oxidization were conducted by photoelectrocatalysis. ► Apply the concept of cationic exchange membrane to enhance the conversion efficiency. ► The optimum TiO2 loading of 1 g/L was observed at acidic pH with current density 4 mA/cm2. ► Transformation pathway of EDTA was determined from analyzed byproducts and molecular orbital package analysis. -- Abstract: A novel technology of photoelectrocatalysis (PEC) combining with cationic exchange membrane (CEM) was proposed for simultaneous reduction of chromium(VI) and oxidization of EDTA. The application of CEM was used to enhance the efficiency for prevention of the re-oxidation of reduced chromium with the electron–hole pairs. In this study, effects of current density, pH, TiO2 dosage, hydraulic retention time (HRT), light intensity and EDTA/Cr(VI) molar ratio were all investigated. The results showed that the optimum conversion efficiency occurred at 4 mA/cm2 with the presence of CEM. Higher conversion efficiencies were observed at lower pH due to the electrostatic attractions between positive charged Ti-OH2+, and negatively charged Cr(VI) and EDTA. The optimum TiO2 loading of 1 g/L was depended mainly on the acidic pH range, especially at higher HRT and irradiation intensity. In addition, higher EDTA/Cr(VI) molar ratio enhanced the reduction efficiency of Cr(VI), indicating EDTA plays the role of hole scavenger in this system. Moreover, incomplete EDTA decomposition contributes to the occurrence of intermediates, including nitrilotriacetic acid, iminodiacetic acid, glycine, oxamic acid, lyoxylic acid, oxalic acid, acetic acid and formic acid, as identified by GC/MS. Consequently, transformation pathway was determined from these analyzed byproducts and molecular orbital package analysis

  9. Chromium isotope variation along a contaminated groundwater plume: a coupled Cr(VI)- reduction, advective mixing perspective

    Science.gov (United States)

    Bullen, T.; Izbicki, J.

    2007-12-01

    Chromium (Cr) is a common contaminant in groundwater, used in electroplating, leather tanning, wood preservation, and as an anti-corrosion agent. Cr occurs in two oxidation states in groundwater: Cr(VI) is highly soluble and mobile, and is a carcinogen; Cr(III) is generally insoluble, immobile and less toxic than Cr(VI). Reduction of Cr(VI) to Cr(III) is thus a central issue in approaches to Cr(VI) contaminant remediation in aquifers. Aqueous Cr(VI) occurs mainly as the chromate (CrO22-) and bichromate (HCrO2-) oxyanions, while Cr(III) is mainly "hexaquo" Cr(H2O)63+. Cr has four naturally-occurring stable isotopes: 50Cr, 52Cr, 53Cr and 54Cr. When Cr(VI) is reduced to Cr(III), the strong Cr-O bond must be broken, resulting in isotopic selection. Ellis et al. (2002) demonstrated that for reduction of Cr(VI) on magnetite and in natural sediment slurries, the change of isotopic composition of the remnant Cr(VI) pool was described by a Rayleigh fractionation model having fractionation factor ɛCr(VI)-Cr(III) = 3.4‰. We attempted to use Cr isotopes as a monitor of Cr(VI) reduction at a field site in Hinkley, California (USA) where groundwater contaminated with Cr(VI) has been under assessment for remediation. Groundwater containing up to 5 ppm Cr(VI) has migrated down-gradient from the contamination source through the fluvial to alluvial sediments to form a well-defined plume. Uncontaminated groundwater in the aquifer immediately adjacent to the plume has naturally-occurring Cr(VI) of 4 ppb or less (CH2M-Hill). In early 2006, colleagues from CH2M-Hill collected 17 samples of groundwater from within and adjacent to the plume. On a plot of δ53Cr vs. log Cr(VI), the data array is strikingly linear and differs markedly from the trend predicted for reduction of Cr(VI) in the contaminated water. There appear to be two groups of data: four samples with δ53Cr >+2‰ and Cr(VI) 15 ppb. Simple mixing lines between the groundwater samples having <4 ppb Cr(VI), taken to be

  10. Removal of chromium from Cr(VI) polluted wastewaters by reduction with scrap iron and subsequent precipitation of resulted cations.

    Science.gov (United States)

    Gheju, M; Balcu, I

    2011-11-30

    This work presents investigations on the total removal of chromium from Cr(VI) aqueous solutions by reduction with scrap iron and subsequent precipitation of the resulted cations with NaOH. The process was detrimentally affected by a compactly passivation film occurred at scrap iron surface, mainly composed of Cr(III) and Fe(III). Maximum removal efficiency of the Cr(total) and Fe(total) achieved in the clarifier under circumneutral and alkaline (pH 9.1) conditions was 98.5% and 100%, respectively. The optimum precipitation pH range which resulted from this study is 7.6-8.0. Fe(total) and Cr(total) were almost entirely removed in the clarifier as Fe(III) and Cr(III) species; however, after Cr(VI) breakthrough in column effluent, chromium was partially removed in the clarifier also as Cr(VI), by coprecipitation with cationic species. As long the column effluent was free of Cr(VI), the average Cr(total) removal efficiency of the packed column and clarifier was 10.8% and 78.8%, respectively. Our results clearly indicated that Cr(VI) contaminated wastewater can be successfully treated by combining reduction with scrap iron and chemical precipitation with NaOH. PMID:21955659

  11. Enhanced photocatalytic activity of chromium(VI) reduction and EDTA oxidization by photoelectrocatalysis combining cationic exchange membrane processes.

    Science.gov (United States)

    Hsu, Hung-Te; Chen, Shiao-Shing; Tang, Yi-Fang; Hsi, Hsing-Cheng

    2013-03-15

    A novel technology of photoelectrocatalysis (PEC) combining with cationic exchange membrane (CEM) was proposed for simultaneous reduction of chromium(VI) and oxidization of EDTA. The application of CEM was used to enhance the efficiency for prevention of the re-oxidation of reduced chromium with the electron-hole pairs. In this study, effects of current density, pH, TiO2 dosage, hydraulic retention time (HRT), light intensity and EDTA/Cr(VI) molar ratio were all investigated. The results showed that the optimum conversion efficiency occurred at 4mA/cm(2) with the presence of CEM. Higher conversion efficiencies were observed at lower pH due to the electrostatic attractions between positive charged TiOH2(+), and negatively charged Cr(VI) and EDTA. The optimum TiO2 loading of 1g/L was depended mainly on the acidic pH range, especially at higher HRT and irradiation intensity. In addition, higher EDTA/Cr(VI) molar ratio enhanced the reduction efficiency of Cr(VI), indicating EDTA plays the role of hole scavenger in this system. Moreover, incomplete EDTA decomposition contributes to the occurrence of intermediates, including nitrilotriacetic acid, iminodiacetic acid, glycine, oxamic acid, lyoxylic acid, oxalic acid, acetic acid and formic acid, as identified by GC/MS. Consequently, transformation pathway was determined from these analyzed byproducts and molecular orbital package analysis. PMID:23380448

  12. Reduction of Chromium(VI) by Locally Isolated Pseudomonas sp. C-171

    OpenAIRE

    Rahman, Mujeeb Ur; GUL, Shereen; HAQ, Mohammad Zahoor UL

    2007-01-01

    A strain of Pseudomonas sp. C-171 capable of tolerating hexavalent chromium (Cr+6) up to 2000 ppm as potassium dichromate was isolated from domestic sewage. The Cr+6 reduction was checked by growing the isolated strain in a medium containing potassium dichromate as Cr+6 source. The rate of growth of Pseudomonas sp. C-171 decreased with the increase in Cr+6 concentration of the medium. The maximum rate of chromium reduction was observed during the log phase of bacterium growth. The reduction o...

  13. [Reduction Kinetics of Cr (VI) in Chromium Contaminated Soil by Nanoscale Zerovalent Iron-copper Bimetallic].

    Science.gov (United States)

    Ma, Shao-yun; Zhu, Fang; Shang, Zhi-feng

    2016-05-15

    Nanoscale zerovalent iron-copper bimetallic (nZVI/Cu) was produced by liquid-phase reduction and characterized by SEM and XRD. The remediation of Cr (VI) contaminated soil was conducted with nZVI/Cu, and the affecting factors and reduction kinetics were investigated. The results indicated that nZVI/Cu was effective in the degradation of Cr(VI) in soil at an initial pH of 7 at 30'C.After 10 min of reaction, Cr(VI) in the soil was completely degraded when the. concentration of nZVI/Cu was 2 g · L⁻' and the concentration of Cr(VI) in contaminated soil was 88 mg · kg⁻¹. nZVI/Cu amount, pH value, reaction temperature, and the concentration of humic acid affected the degradation of Cr(VI). The removal efficiency of Cr(VI)--increased with increasing reaction temperature and decreased with increasing initial pH value. Humic acid had a certain impact on the degradation of Cr(W) in soil. The removal of Cr (VI) followed the pseudo first order reduction kinetics model, and the relationship between the reduction rate and the reaction temperature accorded with Arrhenius law, and the reaction activation energy (Ea) was 104.26 kJ · mol⁻¹. PMID:27506053

  14. Effects of Reductants on Phytoextraction of Chromium (VI) by Ipomoea aquatica.

    Science.gov (United States)

    Ton, Shan-Shin; Lee, Ming-Wei; Yang, Yin-Hsin; Hoi, Soi-Keong; Cheng, Wen-Che; Wang, Kai-Sung; Chang, Han-Hsin; Chang, Shih-Hsien

    2015-01-01

    Reductants are often used to reduce Cr(VI) in chemical treatments, yet the effects of the reductants on Cr(VI) phytoremediation are not fully understood. This study investigates the effects of different reductants on Cr(VI) phytoremediation by Ipomoea aquatica in simulated solution with 3 mg L(-1) of Cr(VI), pH0 of 6, and an incubation time of 5 days. Results indicate that the applications of S2O3(2-), Fe0, and Fe2+ at low doses notably increased root Cr concentrations, which were obviously higher than that those in the control (Cr6+ alone). However, high reductant concentrations decreased bioaccumulation of Cr in the roots and shoots of the plant. Statistical results indicate that Cr concentrations were significantly and negatively correlated with Fe concentrations in the roots and shoots of the plant (p<0.05). This suggest that Fe accumulation inhibited Cr accumulation in the plant. A Cr(VI) concentration of 3 mg L(-1) caused short, brown lateral roots with tip necrosis, leaf chlorosis, and noticeable shoot wilting. The leaf necrosis and shoot wilting is caused by oxidative damage of lateral roots by Cr(VI) rather than by the reactive oxygen species generated by the oxidative stress. Addition of the reductants effectively reduced these plant injuries. PMID:25495933

  15. Chromium(VI) reduction by catechol(amine)s results in DNA cleavage in vitro

    DEFF Research Database (Denmark)

    Pattison, D I; Davies, Michael Jonathan; Levina, A;

    2001-01-01

    (VI)/catechol(amine) mixtures with plasmid DNA have been investigated to model a potential route to Cr(VI)-induced genotoxicity. Reduction of Cr(VI) by 3,4-dihydroxyphenylalanine (DOPA) (1), dopamine (2), or adrenaline (3) produces species that cause extensive DNA damage, but the products of similar reactions with catechol (4......) or 4-tert-butylcatechol (5) do not damage DNA. The Cr(VI)/catechol(amine) reactions have been studied at low added H(2)O(2) concentrations, which lead to enhanced DNA cleavage with 1 and induce DNA cleavage with 4. The Cr(V) and organic intermediates generated by the reactions of Cr(VI) with 1 or 4......-acetyl-Tyr with tyrosinase, respectively) were correlated with the DNA cleaving abilities of the products of these reactions. The reaction of Cr(VI) with enzymatically generated 1 produced significant amounts of H(2)O(2) and caused significant DNA damage, but the N-acetyl-DOPA did not. The extent of in vitro DNA...

  16. Reaction of chromium(VI) with glutathione or with hydrogen peroxide: identification of reactive intermediates and their role in chromium(VI)-induced DNA damage.

    OpenAIRE

    Aiyar, J; Berkovits, H J; Floyd, R A; Wetterhahn, K E

    1991-01-01

    The types of reactive intermediates generated upon reduction of chromium(VI) by glutathione or hydrogen peroxide and the resulting DNA damage have been determined. In vitro, reaction of chromium(VI) with glutathione led to formation of two chromium(V) complexes and the glutathione thiyl radical. When chromium(VI) was reacted with DNA in the presence of glutathione, chromium-DNA adducts were obtained, with no DNA strand breakage. The level of chromium-DNA adduct formation correlated with chrom...

  17. Chromium (VI) adsorption on boehmite

    Energy Technology Data Exchange (ETDEWEB)

    Granados-Correa, F. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)], E-mail: fgc@nuclear.inin.mx; Jimenez-Becerril, J. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)

    2009-03-15

    Boehmite was synthesized and characterized in order to study the adsorption behavior and the removal of Cr(VI) ions from aqueous solutions as a function of contact time, initial pH solution, amount of adsorbent and initial metal ion concentration, using batch technique. Adsorption data of Cr(VI) on the boehmite were analyzed according to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293, 303, 313 and 323 K temperatures. The kinetic values and thermodynamic parameters from the adsorption process show that the Cr(VI) ions adsorption on boehmite is an endothermic and spontaneous process. These results show that the boehmite could be considered as a potential adsorbent for chromium ions in aqueous solutions.

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

    Science.gov (United States)

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

    2013-03-01

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

  19. EPR studies of chromium(V) intermediates generated via reduction of chromium(VI) by DOPA and related catecholamines

    DEFF Research Database (Denmark)

    Pattison, D I; Lay, P A; Davies, Michael Jonathan

    2000-01-01

    The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals. These...

  20. Biodegradation of phenol with chromium(VI) reduction in an anaerobic fixed-biofilm process-Kinetic model and reactor performance

    International Nuclear Information System (INIS)

    A mathematical model system was derived to describe the simultaneous removal of phenol biodegradation with chromium(VI) reduction in an anaerobic fixed-biofilm reactor. The model system incorporates diffusive mass transport and double Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to validate the kinetic model system. Batch kinetic tests were conducted independently to evaluate the biokinetic parameters used in the model simulation. The removal efficiencies of phenol and chromium(VI) in an anaerobic fixed-biofilm process were approximately 980 mg/g and 910 mg/g, respectively, under a steady-state condition. In the steady state, model-predicted biofilm thickness reached up to 350 μm and suspended cells in the effluent were 85 mg cell/l. The experimental results agree closely with the results of the model simulations.

  1. A reinvestigation of EXAFS and EPR spectroscopic measurements of chromium(VI) reduction by coir pith

    International Nuclear Information System (INIS)

    New measurements using extended X-ray absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR) techniques are consistent with Cr in the Cr(III) oxidation state as the main product from the adsorption of Cr(VI) on coir pith. These confirm the previous X-ray measurements, but differ from the results of previous EPR studies, which indicated that Cr(V) was the main form of Cr. The reason for this discrepancy is the presence of a broad signal from Cr(III) in an unsymmetrical environment that was missed previously; the Cr(V) component is in fact only a minor reaction product. As a result of this problem with spectral acquisition and interpretation, some simple recommendations are presented for conducting EPR investigations on natural systems.

  2. Chromium(III) and chromium(VI) surface treated galvanized steel for outdoor constructions: environmental aspects.

    Science.gov (United States)

    Lindström, David; Hedberg, Yolanda; Odnevall Wallinder, Inger

    2010-06-01

    The long-term degradation of chromium(III) (Zn-Cr(III)) and chromium(VI)-based (Zn-Cr(VI)) surface treatments on galvanized steel and their capacities to hinder the release of zinc induced by atmospheric corrosion at nonsheltered urban and marine exposure conditions for 2 years are investigated. Compared to bare zinc sheet, both surface treatments revealed high corrosion protection abilities and capacities to hinder the release of zinc, still evident after 2 years of exposure. The zinc barrier properties of the thinner Zn-Cr(VI) (10 nm) treatment were during the first 100 days of urban exposure slightly improved compared with Zn-Cr(III) (35 nm). However, their long-term protection capacities were inverse. Released concentrations of total chromium correspond to annual release rates less than 0.000032 (Zn-Cr(III)) and 0.00014 g Cr m(-2) yr(-1) (Zn-Cr(VI)) after 1 year of urban exposure. Aging by indoor storage of the surface treatments prior to outdoor exposure reduced the released Cr concentrations from the surface treatments. No Cr(VI) was released from the aged surfaces but from the freshly exposed Zn-Cr(VI). Marine exposure conditions resulted in a faster reduction of chromate to chromium(III)oxide compared with urban conditions, and a significantly lower amount of both chromium(III) and chromium(VI) released from Zn-Cr(VI) at the marine site compared with the urban site. PMID:20462267

  3. Occupational exposure to chromium(VI compounds

    Directory of Open Access Journals (Sweden)

    Jolanta Skowroń

    2015-07-01

    Full Text Available This article discusses the effect of chromium(VI (Cr(VI on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV for chromium(VI of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL document chromium(VI concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2–14 cases per 1000 exposed workers. Exposure to chromium(VI compounds expressed in Cr(VI of 0.01 mg Cr(VI/m3 is responsible for the increased number of lung cancer cases in 1–6 per 1000 people employed in this condition for the whole period of professional activity. Med Pr 2015;66(3:407–427

  4. [Occupational exposure to chromium(VI) compounds].

    Science.gov (United States)

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

    This article discusses the effect of chromium(VI) (Cr(VI)) on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI) compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV) for chromium(VI) of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL) document chromium(VI) concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2-14 cases per 1000 exposed workers. Exposure to chromium(VI) compounds expressed in Cr(VI) of 0.01 mg Cr(VI)/m3; is responsible for the increased number of lung cancer cases in 1-6 per 1000 people employed in this condition for the whole period of professional activity. PMID:26325053

  5. Biosorption potency of Aspergillus niger for removal of chromium (VI).

    Science.gov (United States)

    Srivastava, Shaili; Thakur, Indu Shekhar

    2006-09-01

    Aspergillus niger isolated from soil and effluent of leather tanning mills had higher activity to remove chromium. The potency of Aspergillus niger was evaluated in shake flask culture by absorption of chromium at pH 6 and temperature 30 degrees C. The results of the study indicated removal of more than 75% chromium by Aspergillus niger determined by diphenylcarbazide colorimetric assay and atomic absorption spectrophotometry after 7 days. Study of microbial Cr(VI) reduction and identification of reduction intermediates has been hindered by the lack of analytical techniques that can identify the oxidation state with subcellular spatial resolution. Therefore, removal of chromium was further substantiated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), which indicated an accumulation of chromium in the fungal mycelium. PMID:16874547

  6. Role of paramagnetic chromium in chromium(VI)-induced damage in cultured mammalian cells.

    OpenAIRE

    Sugiyama, M

    1994-01-01

    Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic chromium in chromium(VI)-induced damage in intac...

  7. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1926.51 Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1926.51. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  8. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1910.141. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  9. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas provided by the employer shall also... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i)...

  10. Reduction of Hexavalent Chromium by Viable Cells of Chromium Resistant Bacteria Isolated from Chromite Mining Environment

    OpenAIRE

    Satarupa Dey; Baishali Pandit; A. K. Paul

    2014-01-01

    Environmental contamination of hexavalent chromium [Cr(VI)] is of serious concern for its toxicity as well as mutagenic and carcinogenic effects. Bacterial chromate reduction is a cost-effective technology for detoxification as well as removal of Cr(VI) from polluted environment. Chromium resistant and reducing bacteria, belonging to Arthrobacter, Pseudomonas, and Corynebacterium isolated from chromite mine overburden and seepage samples of Orissa, India, were found to tolerate 12–18 mM Cr(VI...

  11. Thermal stabilization of chromium(VI) in kaolin.

    Science.gov (United States)

    Wei, Yu-Ling; Chiu, Shu-Yuan; Tsai, Hsien-Neng; Yang, Yaw-Wen; Lee, Jyh-Fu

    2002-11-01

    Reduction of Cr(VI) by heating may be a useful detoxification mechanism for thermal immobilization. Using X-ray absorption spectroscopy, the change of speciation of chromium in 105 degrees C dried 3.7% Cr(VI)-sorbed kaolin further heated at 500, 900, or 1100 degrees C was studied. The 105 degrees C dried 3.7% Cr(VI)-sorbed kaolin sample was prepared by mixing 1.5 L of 0.257 M CrO3 solution (pH 0.71) with 0.5 kg of kaolin powder for 48 h, and then the slurry was heated (dried) at 105 degrees C until a constant weight was reached. The toxicity characteristic leaching procedure method was used to determine the percentage of leached chromium from all heated samples. In all 500-900 degrees C heated Cr(VI)-sorbed kaolin samples, Cr2O3 transformed from the hydrated Cr(VI) by a 4-h heat application was identified by the X-ray absorption near edge structure and extended X-ray absorption fine structure (EXAFS) spectroscopy as the key species that is leaching-resistant due to its low solubility. For the 1100 degrees C heated Cr(VI)-sorbed kaolin sample, the Fourier transform of its EXAFS spectrum indicates that the intensity of the peaks at 2.45 (Cr-Cr shell of Cr2O3) and 5.00 A (Cr-Cr and Cr-O shells of Cr2O3) without phase shift correction is either relatively smaller or disappearing, compared with that of the 500-900 degrees C heated Cr(VI)-sorbed kaolin samples. It is suggested that chromium octahedra were bridged to silica tetrahedra and incorporated in minerals formed at 1100 degrees C, such as mullite or sillimanite, since these phases were detected by XRD. Cr of this form is not easily leached. PMID:12433175

  12. Removal of chromium(VI) from saline wastewaters by

    OpenAIRE

    AKSU, Zümriye

    2002-01-01

    Some industrial wastewaters contain higher quantities of salts besides chromium(VI) ions so the effect of these salts on the biosorption of chromium(VI) should be investigated. The biosorption of chromium (VI) from saline solutions on two strains of living Dunaliella algae were tested under laboratory conditions as a function of pH, initial metal ion and salt (NaCl) concentrations in a batch system. The biosorption capacity of both Dunaliella strains strongly de...

  13. Selective Reduction of Cr(VI in Chromium, Copper and Arsenic (CCA Mixed Waste Streams Using UV/TiO2 Photocatalysis

    Directory of Open Access Journals (Sweden)

    Shan Zheng

    2015-02-01

    Full Text Available The highly toxic Cr(VI is a critical component in the Chromated Copper Arsenate (CCA formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI to less toxic Cr(III in the presence of arsenate, As(V, and copper, Cu(II. The rapid conversion of Cr(VI to Cr(III during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI reduction demonstrating the reduction of Cr(VI is independent of dissolved oxygen. Reduction of Cu(II and As(V does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI reduction. The Cr(VI reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI in mixed waste streams under a variety of conditions.

  14. Selective reduction of Cr(VI) in chromium, copper and arsenic (CCA) mixed waste streams using UV/TiO2 photocatalysis.

    Science.gov (United States)

    Zheng, Shan; Jiang, Wenjun; Rashid, Mamun; Cai, Yong; Dionysiou, Dionysios D; O'Shea, Kevin E

    2015-01-01

    The highly toxic Cr(VI) is a critical component in the Chromated Copper Arsenate (CCA) formulations extensively employed as wood preservatives. Remediation of CCA mixed waste and discarded treated wood products is a significant challenge. We demonstrate that UV/TiO2 photocatalysis effectively reduces Cr(VI) to less toxic Cr(III) in the presence of arsenate, As(V), and copper, Cu(II). The rapid conversion of Cr(VI) to Cr(III) during UV/TiO2 photocatalysis occurs over a range of concentrations, solution pH and at different Cr:As:Cu ratios. The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI) reduction demonstrating the reduction of Cr(VI) is independent of dissolved oxygen. Reduction of Cu(II) and As(V) does not occur under the photocatalytic conditions employed herein and the presence of these two in the tertiary mixtures had a minimal effect on Cr(VI) reduction. The Cr(VI) reduction was however, significantly enhanced by the addition of formic acid, which can act as a hole scavenger and enhance the reduction processes initiated by the conduction band electron. Our results demonstrate UV/TiO2 photocatalysis effectively reduces Cr(VI) in mixed waste streams under a variety of conditions. PMID:25654531

  15. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag

    International Nuclear Information System (INIS)

    Hexavalent chromium (Cr) is a toxic element causing serious environmental threat. Recently, more and more attention is paid to the bio-remediation of Cr (VI) in the contaminated soils. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag at a steel-alloy factory in Hunan Province, China, was investigated in the present study. The results showed that when sufficient nutrients were amended into the contaminated soils, total Cr (VI) concentration declined from the initial value of 462.8 to 10 mg kg-1 at 10 days and the removal rate was 97.8%. Water soluble Cr (VI) decreased from the initial concentration of 383.8 to 1.7 mg kg-1. Exchangeable Cr (VI) and carbonates-bound Cr (VI) were removed by 92.6% and 82.4%, respectively. Meanwhile, four Cr (VI) resistant bacterial strains were isolated from the soil under the chromium-containing slag. Only one strain showed a high ability for Cr (VI) reduction in liquid culture. This strain was identified as Pannonibacter phragmitetus sp. by gene sequencing of 16S rRNA. X-ray photoelectron spectroscope (XPS) analysis indicated that Cr (VI) was reduced into trivalent chromium. The results suggest that indigenous bacterial strains have potential application for Cr (VI) remediation in the soils contaminated by chromium-containing slag.

  16. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag.

    Science.gov (United States)

    Chai, Liyuan; Huang, Shunhong; Yang, Zhihui; Peng, Bing; Huang, Yan; Chen, Yuehui

    2009-08-15

    Hexavalent chromium (Cr) is a toxic element causing serious environmental threat. Recently, more and more attention is paid to the bio-remediation of Cr (VI) in the contaminated soils. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag at a steel-alloy factory in Hunan Province, China, was investigated in the present study. The results showed that when sufficient nutrients were amended into the contaminated soils, total Cr (VI) concentration declined from the initial value of 462.8 to 10 mg kg(-1) at 10 days and the removal rate was 97.8%. Water soluble Cr (VI) decreased from the initial concentration of 383.8 to 1.7 mg kg(-1). Exchangeable Cr (VI) and carbonates-bound Cr (VI) were removed by 92.6% and 82.4%, respectively. Meanwhile, four Cr (VI) resistant bacterial strains were isolated from the soil under the chromium-containing slag. Only one strain showed a high ability for Cr (VI) reduction in liquid culture. This strain was identified as Pannonibacter phragmitetus sp. by gene sequencing of 16S rRNA. X-ray photoelectron spectroscope (XPS) analysis indicated that Cr (VI) was reduced into trivalent chromium. The results suggest that indigenous bacterial strains have potential application for Cr (VI) remediation in the soils contaminated by chromium-containing slag. PMID:19246154

  17. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag

    Energy Technology Data Exchange (ETDEWEB)

    Chai Liyuan; Huang Shunhong [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Yang Zhihui, E-mail: yangzh@mail.csu.edu.cn [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Peng Bing; Huang Yan; Chen Yuehui [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China)

    2009-08-15

    Hexavalent chromium (Cr) is a toxic element causing serious environmental threat. Recently, more and more attention is paid to the bio-remediation of Cr (VI) in the contaminated soils. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag at a steel-alloy factory in Hunan Province, China, was investigated in the present study. The results showed that when sufficient nutrients were amended into the contaminated soils, total Cr (VI) concentration declined from the initial value of 462.8 to 10 mg kg{sup -1} at 10 days and the removal rate was 97.8%. Water soluble Cr (VI) decreased from the initial concentration of 383.8 to 1.7 mg kg{sup -1}. Exchangeable Cr (VI) and carbonates-bound Cr (VI) were removed by 92.6% and 82.4%, respectively. Meanwhile, four Cr (VI) resistant bacterial strains were isolated from the soil under the chromium-containing slag. Only one strain showed a high ability for Cr (VI) reduction in liquid culture. This strain was identified as Pannonibacter phragmitetus sp. by gene sequencing of 16S rRNA. X-ray photoelectron spectroscope (XPS) analysis indicated that Cr (VI) was reduced into trivalent chromium. The results suggest that indigenous bacterial strains have potential application for Cr (VI) remediation in the soils contaminated by chromium-containing slag.

  18. Chemodynamics of chromium reduction in soils: Implications to bioavailability

    International Nuclear Information System (INIS)

    Highlights: • Examined the effects of sorption, pH and C sources on Cr(VI) reduction and toxicity. • The rate of Cr(VI) reduction decreased with an increase in Cr(VI) adsorption and pH. • The proton dynamics in Cr(VI) reduction was assessed in relation to remediation. • A novel black carbon showed the highest reduction rate of Cr(VI) in soils. • Black carbon decreased the bioavailability and phytotoxicity of Cr(VI) in soils. -- Abstract: Chromium toxicity in soils can be mitigated by reduction of Cr(VI) to Cr(III) which is influenced by the presence of free Cr(VI) species in soil solution, and the supply of protons and electrons. In this study, the effects of Cr(VI) adsorption (i.e. availability of free Cr(VI) species in soil solution), soil pH (i.e. supply of protons) and three electron donor carbon sources [black carbon (BC), chicken manure biochar (CMB) and cow manure (CM)] on the reduction of Cr(VI) to Cr(III) in soils were investigated. The results indicated that the rate of Cr(VI) reduction decreased with an increase in Cr(VI) adsorption and soil pH, which is attributed to decreased supply of free Cr(VI) ions and protons, respectively. Among the three different amendments tested, BC showed the highest rate of Cr(VI) reduction followed by CM and CMB. Furthermore, addition of BC, CM and CMB decreased the bioavailability of Cr(VI) in contaminated soils. The high efficiency of BC on Cr(VI) reduction was due to the electron donor's functional groups such as phenolic, hydroxyl, carbonyl and amides. The study demonstrated that free form of Cr(VI) ions in soil solution and carbon amendments enriched with acidic functional groups favored the reduction of Cr(VI), thereby mitigating its bioavailability and toxicity in contaminated soils

  19. Chromium reduction in Pseudomonas putida.

    OpenAIRE

    Ishibashi, Y.; Cervantes, C; Silver, S

    1990-01-01

    Reduction of hexavalent chromium (chromate) to less-toxic trivalent chromium was studied by using cell suspensions and cell-free supernatant fluids from Pseudomonas putida PRS2000. Chromate reductase activity was associated with soluble protein and not with the membrane fraction. The crude enzyme activity was heat labile and showed a Km of 40 microM CrO4(2-). Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells.

  20. Chromium reduction in Pseudomonas putida.

    Science.gov (United States)

    Ishibashi, Y; Cervantes, C; Silver, S

    1990-01-01

    Reduction of hexavalent chromium (chromate) to less-toxic trivalent chromium was studied by using cell suspensions and cell-free supernatant fluids from Pseudomonas putida PRS2000. Chromate reductase activity was associated with soluble protein and not with the membrane fraction. The crude enzyme activity was heat labile and showed a Km of 40 microM CrO4(2-). Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells. PMID:2389940

  1. Effects of vitamins on chromium(VI)-induced damage.

    OpenAIRE

    Sugiyama, M

    1991-01-01

    The effects of vitamin E and vitamin B2 on DNA damage and cellular reduction of chromium(VI) were investigated using Chinese hamster V-79 cells. Pretreatment with alpha-tocopherol succinate (vitamin E) resulted in a decrease of DNA single-strand breaks produced by Na2CrO4, while similar treatment with riboflavin (vitamin B2) enhanced levels of DNA breaks. In contrast, levels of DNA-protein crosslinks induced by Na2CrO4 were unaffected by these vitamins. Electron spin resonance (ESR) studies s...

  2. Application of immobilized nanotubular TiO2 electrode for photocatalytic hydrogen evolution: Reduction of hexavalent chromium (Cr(VI)) in water

    International Nuclear Information System (INIS)

    In this study, immobilized TiO2 electrode is applied to reduce toxic Cr(VI) to non-toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powder TiO2, a novel technique of immobilization based on anodization was applied and investigated under various experimental conditions. The anodization was performed at 20 V-5 deg. C for 45 min with 0.5% hydrofluoric acid, and then the anodized samples were annealed under oxygen stream in the range 450-850 deg. C. Based on the results of the experiments, the photocatalytic Cr(VI) reduction was favorable in acidic conditions, with ∼98% of the Cr(VI) being reduced within 2 h at pH 3. Among the samples tested under same anodizing condition, the nanotubular TiO2 annealed at 450 and 550 deg. C showed highest reduction efficiencies of Cr(VI). In addition, the surface characterizations (zeta potential, XRD, and SEM) of these samples proved that the Cr(VI) reduction efficiency was higher under acidic conditions and at a lower annealing temperature. From this research, it was concluded that the anodized TiO2 has the potential to be a useful technology for environmental remediation as well as photocatalytic hydrogen production from water

  3. Treatment of hexavalent chromium Cr (VI) in tanning effluent

    International Nuclear Information System (INIS)

    Most common chemical used in chrome tanning is basic chromium sulphate (BCS). Manufacturing of BCS involves many steps producing liquid waste. Waste generated at every stage contains Cr (VI), which must be reduced to Cr (III) before being disposed to the environment. Different methods were studied for the reduction of toxic Cr (III). Pickle liquor (waste of electroplating industry) can also be used for the reduction of hexavalent chromium Cr (vi) along with other reducing materials / chemicals. In an electroplating process metal is treated with HCl or H/sub 2/SO/sub 4/ to remove scales and rust, the pickled items are then washed with water, washing contains FeCl/sub 2/ or fees/sub 4/ respectively called pickle liquor. During waste treatment pH adjustment to 6.0 - 9.0 and settling the sludge, is discharged to the lagoon. The sludge obtained is dried and disposed off in landfills. Other reducing agents like sodium bisulphite and sulfur dioxide were also studied, but pickle liquor was found to be more effective and economical. (author)

  4. Adsorption Properties of Chromium (VI by Chitosan Coated Montmorillonite

    Directory of Open Access Journals (Sweden)

    Dahe Fan

    2006-01-01

    Full Text Available The adsorption of chromium (VI by Chitosan Coated Montmorillonite (CCM from aqueous solution was studied. To evaluate the adsorption capacity, the effects of pH, initial concentration and temperature on the adsorption were investigated. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation and the thermodynamic parameters (ΔH, ΔG, ΔS were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between CCM and chromium (VI was significantly physical, the negative ΔH constant at lower temperature confirmed that the more chromium (VI was adsorbed by chitosan coated montmorillonite at lower temperature. The kinetics of the sorption process of chromium (VI on chitosan coated montmorillonite were investigated using the pseudo-first order and pseudo-second order kinetics, results showed that the pseudo-second order equation model provided the best correlation with the experimental results.

  5. Biosorption of Chromium (VI) from Aqueous Solutions onto Fungal Biomass

    OpenAIRE

    Ismael Acosta R.; Xöchitl Rodríguez; Conrado Gutiérrez; Ma. de Guadalupe Moctezuma

    2004-01-01

    The biosorption of chromium (VI) on eighteen different natural biosorbents: Natural sediment, chitosan, chitin, Aspergillus flavus I-V, Aspergillus fumigatus I-ll, Helmintosporium sp, Cladosporium sp, Mucor rouxii mutant, M. rouxii IM-80, Mucor sp-I and 2, Candida albicans and Cryptococcus neoformans was studied in this work. It was found that the biomass of C. neoformans, natural sediment, Helmintosporium sp and chitosan was more efficient to remove chromium (VI) (determined spectrophotometr...

  6. Simultaneous determination of chromium(III) and chromium(VI) in aqueous solutions by ion chromatography and chemiluminescence detection

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Jøns, O; Nielsen, B

    1992-01-01

    A method for the simultaneous determination of chromium(iii) and chromium(vi) in a flow system based on chemiluminescence was developed. A Dionex cation-exchange guard column was used to separate chromium(iii) from chromium(vi), and chromium(vi) was reduced by potassium sulfite, whereupon both sp....... The detection limit was 0.5 micrograms l-1 for both species. Data were in agreement with Zeeman-effect background corrected atomic absorption spectrometry measurements....

  7. Reduction of hexavalent chromium by ferrous iron: A process of chromium isotope fractionation and its relevance to natural environments

    DEFF Research Database (Denmark)

    Døssing, Lasse Nørbye; Dideriksen, Knud; Stipp, Susan Louise Svane;

    2011-01-01

    Stable chromium (Cr) isotopes can be used as a tracer for changing redox conditions in modern marine systems and in the geological record. We have investigated isotope fractionation during reduction of Cr(VI)aq by Fe(II)aq. Reduction of Cr(VI)aq by Fe(II)aq in batch experiments leads to significant...

  8. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande 1749-016 Lisboa (Portugal); Santos, Erika [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

    2010-04-15

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L{sup -1} U(VI) and 99% of 13 mg L{sup -1} Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  9. Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

    International Nuclear Information System (INIS)

    Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L-1 U(VI) and 99% of 13 mg L-1 Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

  10. ANTIBIOTIC RESISTANCE AND CHROMIUM REDUCTION PATTERN AMONG ACTINOMYCETES

    Directory of Open Access Journals (Sweden)

    Preeti Jain

    2012-01-01

    Full Text Available Actinomycetes, one of the most important groups of microbes, exhibit many interesting activities such as degradation and transformation of organic and metal substrates together with production of antibiotics. With these bioactivities, actinomycetes would play an important role in the webs of the marine environment. The present study was designed to evaluate the antibiotic resistance pattern, antibiotic producing potential and chromium resistance as well as chromium reduction potential of a range of actinomycetes isolated from marine environments. Actinomycetes were isolated from marine sediment samples obtained from St. Martin’s Island in Bangladesh. Antibiotic resistance among the selected isolates was studied against 10 different antibiotics by disc diffusion method and antibiotic producing potential was assessed by the perpendicular streak method. The isolates were screened for resistance towards heavy metal Cr(VI on culture plates supplemented with Cr(VI at concentrations ranging from 1-5 mM of Cr(VI. Highly resistant isolates were subjected to screening for Cr(VI reduction activity, which was estimated using the Cr(VI specific colorimetric reagent 1, 5-diphenylcarbazide. Out of the total 30 different selected isolates, 25 (83.33% showed resistance against more than three antibiotics and 6 (20% showed resistance to more than six antibiotics. Ninety three percent of the isolates showed MAR index greater than 0.2 and tolerance to Cr(VI at 1mM of initial Cr(VI. None of the isolates displayed antimicrobial activity against the organisms tested. Among the isolates tested for chromate reduction, two were most efficient showing complete reduction of 1mM Cr(VI within 24 h. These two isolates (SM-11, SM-20 were capable of reducing chromate even at high initial Cr(VI concentrations. Remarkably, the isolate SM-11 was found to reduce 82.67%, 44.34% of Cr(VI at 2.5mM, 5mM of initial Cr(VI concentrations respectively, within 72h of incubation. The

  11. Chemodynamics of chromium reduction in soils: Implications to bioavailability

    Energy Technology Data Exchange (ETDEWEB)

    Choppala, Girish [Centre for Environmental Risk Assessment and Remediation, Building-X, University of South Australia, Mawson Lakes, South Australia 5095 (Australia); Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, PO Box 486, Salisbury, South Australia 5106 (Australia); Bolan, Nanthi, E-mail: Nanthi.Bolan@unisa.edu.au [Centre for Environmental Risk Assessment and Remediation, Building-X, University of South Australia, Mawson Lakes, South Australia 5095 (Australia); Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, PO Box 486, Salisbury, South Australia 5106 (Australia); Seshadri, Balaji [Centre for Environmental Risk Assessment and Remediation, Building-X, University of South Australia, Mawson Lakes, South Australia 5095 (Australia); Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, PO Box 486, Salisbury, South Australia 5106 (Australia)

    2013-10-15

    Highlights: • Examined the effects of sorption, pH and C sources on Cr(VI) reduction and toxicity. • The rate of Cr(VI) reduction decreased with an increase in Cr(VI) adsorption and pH. • The proton dynamics in Cr(VI) reduction was assessed in relation to remediation. • A novel black carbon showed the highest reduction rate of Cr(VI) in soils. • Black carbon decreased the bioavailability and phytotoxicity of Cr(VI) in soils. -- Abstract: Chromium toxicity in soils can be mitigated by reduction of Cr(VI) to Cr(III) which is influenced by the presence of free Cr(VI) species in soil solution, and the supply of protons and electrons. In this study, the effects of Cr(VI) adsorption (i.e. availability of free Cr(VI) species in soil solution), soil pH (i.e. supply of protons) and three electron donor carbon sources [black carbon (BC), chicken manure biochar (CMB) and cow manure (CM)] on the reduction of Cr(VI) to Cr(III) in soils were investigated. The results indicated that the rate of Cr(VI) reduction decreased with an increase in Cr(VI) adsorption and soil pH, which is attributed to decreased supply of free Cr(VI) ions and protons, respectively. Among the three different amendments tested, BC showed the highest rate of Cr(VI) reduction followed by CM and CMB. Furthermore, addition of BC, CM and CMB decreased the bioavailability of Cr(VI) in contaminated soils. The high efficiency of BC on Cr(VI) reduction was due to the electron donor's functional groups such as phenolic, hydroxyl, carbonyl and amides. The study demonstrated that free form of Cr(VI) ions in soil solution and carbon amendments enriched with acidic functional groups favored the reduction of Cr(VI), thereby mitigating its bioavailability and toxicity in contaminated soils.

  12. Cr(VI) reduction in aqueous solutions by siderite.

    Science.gov (United States)

    Erdem, Mehmet; Gür, Faruk; Tümen, Fikret

    2004-09-10

    Hexavalent chromium is a common and toxic pollutant in soils and wastewaters. Reduction of the mobile Cr(VI) to less mobile and less toxic Cr(III) is a solution for decontamination of industrial effluents. In this study, the reduction of hexavalent chromium in aqueous solutions by siderite was investigated. The influences of amount of acid, contact time, siderite dosage, initial Cr(VI) concentration, temperature and particle size of siderite have been tested in batch runs. The process was found to be acid, temperature and concentration dependent. The amount of acid is the most effective parameter affecting the Cr(VI) reduction since carbonaceous gangue minerals consume acid by side reactions. The highest Cr(VI) reduction efficiency (100%) occurred in the 50 mg/l Cr(VI) solution containing two times acid with respect to stoichiometric amount of Cr(VI) and at the conditions of siderite dosage 20 g/l, contact time 120 min and temperature 25 degrees C. Reduction efficiency increased with increase in temperature and decrease in particle size. The reduction capacity of siderite was found to be 17 mg-Cr(VI)/g. PMID:15363534

  13. Natural and induced reduction of hexavalent chromium in soil

    Science.gov (United States)

    Leita, Liviana; Margon, Alja; Sinicco, Tania; Mondini, Claudio; Valentini, Massimiliano; Cantone, Pierpaolo

    2013-04-01

    Even though naturally elevated levels of chromium can be found naturally in some soils, distressing amounts of the hexavalent form (CrVI) are largely restricted to sites contaminated by anthropogenic activities. In fact, the widespread use of chromium in various industries and the frequently associated inadequate disposal of its by-products and wastes have created serious environmental pollution problems in many parts of the world. CrVI is toxic to plants, animals and humans and exhibits also mutagenic effects. However, being a strong oxidant, CrVI can be readily reduced to the much less harmful trivalent form (CrIII) when suitable electron donors are present in the environment. CrIII is relatively insoluble, less available for biological uptake, and thus definitely less toxic for web-biota. Various electron donors in soil can be involved in CrVI reduction in soil. The efficiency of CrVI reducing abiotic agents such as ferrous iron and sulphur compounds is well documented. Furthermore, CrVI reduction is also known to be significantly enhanced by a wide variety of cell-produced monosaccharides, including glucose. In this study we evaluated the dynamics of hexavalent chromium (CrVI) reduction in contaminated soil amended or not with iron sulphate or/and glucose and assessed the effects of CrVI on native or glucose-induced soil microbial biomass size and activity. CrVI negatively affected both soil microbial activity and the size of the microbial biomass. During the incubation period, the concentration of CrVI in soil decreased over time whether iron sulphate or/and glucose was added or not, but with different reduction rates. Soil therefore displayed a natural attenuation capacity towards chromate reduction. Addition of iron sulphate or/and glucose, however, increased the reduction rate by both abiotic and biotic mechanisms. Our data suggest that glucose is likely to have exerted an indirect role in the increased rate of CrVI reduction by promoting growth of

  14. Photoreduction of chromium(VI) in the presence of algae, Chlorella vulgaris

    Energy Technology Data Exchange (ETDEWEB)

    Deng Lin [School of Resources and Environmental Science, Wuhan University, Wuhan 430072 (China); Wang Hongli [School of Resources and Environmental Science, Wuhan University, Wuhan 430072 (China); Deng Nansheng [School of Resources and Environmental Science, Wuhan University, Wuhan 430072 (China)]. E-mail: nsdengwhu@163.com

    2006-11-16

    In this thesis, the photochemical reduction of hexavalent chromium Cr(VI) in the presence of algae, Chlorella vulgaris, was investigated under the irradiation of metal halide lamps ({lambda}=365nm, 250W). The affecting factors of photochemical reduction were studied in detail, such as exposure time, initial Cr(VI) concentration, initial algae concentration and pH. The rate of Cr(VI) photochemical reduction increased with algae concentration increasing, exposure time increasing, initial Cr(VI) concentration decreasing and the decrease of pH. When pH increased to 6, the rate of Cr(VI) photochemical reduction nearly vanished. When initial Cr(VI) concentration ranged from 0.4 to 1.0mgL{sup -1} and initial algae concentration ranged from ABS{sub algae} (the absorbency of algae)=0.025 to ABS{sub algae}=0.180, According to the results of kinetic analyses, the kinetic equation of Cr(VI) photochemical reduction in aqueous solution with algae under 250W metal halide lamps was V{sub 0}=kC{sub 0}{sup 0.1718}A{sub algae}{sup 0.5235} (C{sub 0} was initial concentration of Cr(VI); A{sub algae} was initial concentration of algae) under the condition of pH 4.

  15. Microbial reduction of hexavalent Chromium under vadose zone conditions

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, D S.(unknown); Brockman, Fred J.(BATTELLE (PACIFIC NW LAB)); Bowman, Robert (VISITORS); Kieft, Thomas L.(BATTELLE (PACIFIC NW LAB))

    2003-01-01

    Hexavalent chromium[Cr(VI)] is a common constituent of wastes associated with nuclear reactor operation and fuel processing. Improper disposal at facilities in arid and semi-arid regions has led to contamination of underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) contamination using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those found in the vadose zone, and to evaluate the potential for enhancing biological reduction of Cr(VI) through the addition of nutrients. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic carbon (molasses). Nutrient amendments resulted in up to 87% Cr(VI) reduction in unsaturated batch experiments. Molasses and nitrate additions to 15-cm length unsaturated flow columns receiving 65 mg L-1 Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-day experiment. All of the immobilized Cr was in the form of Cr (III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy; and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  16. Selective Chromium(VI) Ligands Identified Using Combinatorial Peptoid Libraries

    Science.gov (United States)

    Knight, Abigail S.; Zhou, Effie Y.; Pelton, Jeffrey G.; Francis, Matthew B.

    2013-01-01

    Hexavalent chromium (Cr(VI)) is a world-wide water contaminant that is currently without cost-effective and efficient remediation strategies. This is in part due to a lack of ligands that can bind it amid an excess of innocuous ions in aqueous solution. We present herein the design and application of a peptoid-based library of ligand candidates for toxic metal ions. A selective screening process was used to identify members of the library that can bind to Cr(VI) species at neutral pH and in the presence of a large excess of spectator ions. Eleven sequences were identified, and their affinities were compared using titrations monitored with UV-Vis spectroscopy. To identify the interactions involved in coordination and specificity, we evaluated the effects of sequence substitutions and backbone variation in the highest affinity structure. Additional characterization of the complex formed between this sequence and Cr(VI) was performed using NMR spectroscopy. To evaluate the ability of the developed sequences to remediate contaminated solutions, the structures were synthesized on a solid-phase resin and incubated with environmental water samples that contained simulated levels of chromium contamination. The synthetic structures demonstrated the ability to reduce the amount of toxic chromium to levels within the range of the EPA contamination guidelines. In addition to providing some of the first selective ligands for Cr(VI), these studies highlight the promise of peptoid sequences as easily-prepared components of environmental remediation materials. PMID:24195610

  17. Facile Synthesis of g-C3N4 Nanosheets/ZnO Nanocomposites with Enhanced Photocatalytic Activity in Reduction of Aqueous Chromium(VI under Visible Light

    Directory of Open Access Journals (Sweden)

    Xiaoya Yuan

    2016-09-01

    Full Text Available Graphitic-C3N4 nanosheets (CN/ZnO photocatalysts (CN/ZnO with different CN loadings were successfully prepared via a simple precipitation-calcination in the presence of exfoliated C3N4 nanosheets. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD, scanning electron microscopy (SEM, high-resolution transmission electron microscopy (HRTEM, X-ray photoelectron spectroscopy (XPS, UV-Vis diffuse reflectance spectroscopy (DRS and photoluminescence spectra (PL. The results showed that hexagonal wurzite-phase ZnO nanoparticles were randomly distributed onto the CN nanosheets with a well-bonded interface between the two components in the CN/ZnO composites. The performance of the photocatalytic Cr(VI reduction indicated that CN/ZnO exhibited better photocatalytic activity than pure ZnO under visible-light irradiation and the photocatalyst composite with a lower loading of CN sheets eventually displayed higher activity. The enhanced performance of CN/ZnO photocatalysts could be ascribed to the increased absorption of the visible light and the effective transfer and separation of the photogenerated charge carriers.

  18. Hexavalent Chromium Reduction and Its Distribution in the Cell and Medium by Chromium Resistant Fusarium solani

    Directory of Open Access Journals (Sweden)

    Mousumi Sen

    2013-01-01

    Full Text Available In the present work, batch biosorption of Cr(VI was studied using the fungal strain isolated from soil. The fungal strain was characterized as Fusarium solani. The total Cr distribution in the biomass (fungus and in the media obtained from the experiment conducted at 500 mg l -1 initial Cr(VI concentration and pH 5.0. The results indicated both intracellular and extracellular accumulation and enzymatic reduction of Cr(VI and this was supported by the Transmission Electron Microscopic (TEM observation at the same Cr(VI concentration and pH value. Chromium elution from Fusarium solani containing Cr was then tried out using a number of chromium eluting reagents and a maximum Cr could be eluted using 0.5N sodium hydroxide solution without destructing the biomass structure. The total Cr was recovered by pH adjustment from both biomass and media was found to be 44% of the initial Cr(VI concentration (500 mg l-1.

  19. Chromium isotope inventory of Cr(VI)-polluted groundwaters at four industrial sites in Central Europe

    Science.gov (United States)

    Novak, Martin; Martinkova, Eva; Chrastny, Vladislav; Stepanova, Marketa; Curik, Jan; Szurmanova, Zdenka; Cron, Marcel; Tylcer, Jiri; Sebek, Ondrej

    2016-04-01

    Chromium is one of the most toxic elements, especially in its dissolved Cr(VI) form. In the Czech Republic (Central Europe), massive contamination of groundwater has been reported at more than 200 industrial operations. Under suitable conditions, i.e., low Eh, and high availability of reductive agents, Cr(VI) in groundwater may be spontaneously reduced to solid, largely non-toxic Cr(III). This process is associated with a Cr isotope fractionation, with the residual liquid Cr(VI) becoming enriched in the heavier isotope 53Cr. At industrial operations that have been closed and/or where no further leakage of Cr(VI) occurs, the contaminated groundwater plume may be viewed as a closed system. At such sites, an increasing degree of Cr(VI) reduction should result in an increasing del53/52Cr value of the residual liquid. Here we present del53/52Cr systematics at four contaminated Czech sites, focusing on groundwaters. At two of the four sites (Zlate Hory, Loucna) we were also able to analyze the source of contamination. Chromium in the electroplating solutes was isotopically relatively light, with del53/52Cr values close a Cr isotope mass balance.

  20. Photocatalytic Reduction of Hexavalent Chromium Induced by Photolysis of Ferric/tartrate Complex

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xianghua; Ding, Shimin; Zhang, Lixian [Yangtze Normal Univ., Fuling (China)

    2012-11-15

    Photocatalytic reduction of hexavalent chromium (Cr(VI)) in ferric-tartrate system under irradiation of visible light was investigated. Effects of light resources, initial pH value and initial concentration of various reactants on Cr(VI) photocatalytic reduction were studied. Photoreaction kinetics was discussed and a possible photochemical pathway was proposed. The results indicate that Fe(III)-tartrate system is able to rapidly and effectively photocatalytically reduce Cr(VI) utilizing visible light. Initial pH variations results in the concentration changes of Fe(III)-tartrate complex in this system, and pH at 3.0 is optimal for Cr(VI) photocatalytic reduction. Efficiency of Cr(VI) photocatalytic reduction increases with increasing initial concentrations of Cr(VI), Fe(III) and tartrate. Kinetics analysis indicates that initial Fe(III) concentration affects Cr(VI) photoreduction most significantly.

  1. Chromium(VI) release from leather and metals can be detected with a diphenylcarbazide spot test

    DEFF Research Database (Denmark)

    Bregnbak, David; Johansen, Jeanne D.; Jellesen, Morten Stendahl;

    2015-01-01

    exposures. To evaluate the use of diphenylcarbazide (DPC) as a spot test reagent for the identification of chromium(VI) release. A colorimetric chromium(VI) spot test based on DPC was prepared and used on different items from small market surveys. The DPC spot test was able to identify chromium(VI) release...... at 0.5 ppm without interference from other pure metals, alloys, or leather. A market survey using the test showed no chromium(VI) release from work tools (0/100). However, chromium(VI) release from metal screws (7/60), one earring (1/50), leather shoes (4/100) and leather gloves (6/11) was observed...

  2. Soil dehydrogenase activity in the presence of chromium (III) and (VI)

    OpenAIRE

    Wolińska A.; Stępniewska Z.

    2005-01-01

    The paper presents the influence of chromium forms (III) and (VI) on the soil dehydrogenase activity. Enzyme activities can be considered effective indicators of soil quality changes resulting from environmental stress or management practices. It was found that chromium compounds have detrimental effects on soil dehydrogenase activity. After the addition of chromium, a rapid and significant decrease in enzymatic activities was observed.

  3. Specific extraction of chromium(VI) using supercritical fluid extraction.

    Science.gov (United States)

    Foy, G P; Pacey, G E

    2000-02-01

    In some situations, it is no longer sufficient to give a total concentration of a metal. Instead, what is required to understand the potential toxicity of a sample is the concentration of metal species or oxidation state. When developing species specific methods, the major concern is that the integrity of the species ratio is not changed. In other words, the sample preparation or the analytical method will not convert metal ions from one oxidation state to another. Normal extraction techniques and chromatography methods have shown some tendencies to change species ratios. An ideal extraction method would extract the metal efficiently while retaining the metal's oxidation state. The properties of supercritical fluids should approach the ideal of retention of oxidation states. For example, the need for speciation of chromium is obvious since Cr(III) is considered an essential element while Cr(VI) is thought to be toxic and carcinogenic. This paper presents the results of a species specific extraction of Cr(VI) using two different carbamate derivatives as the chelator. Supercritical fluid extraction (SFE) coupled with a fluorinated dithiocarbamate and a methanol modifier allows extraction of 1 ppm Cr(VI) from a solid matrix with a recovery level of 88.4+/-2.57% using the NIST standard sample. The optimized conditions using the HP 7680 supercritical fluid extractor were: 0.1 ml of methanol, 0.05 ml of pure water, and 0.01 g of chelate via a saturation chamber. PMID:18967865

  4. Nopalea cochenillifera, a potential chromium (VI) hyperaccumulator plant.

    Science.gov (United States)

    Adki, Vinayak S; Jadhav, Jyoti P; Bapat, Vishwas A

    2013-02-01

    Hexavalant chromium [Cr(VI)] tolerance and accumulation in in vitro grown Nopalea cochenillifera Salm. Dyck. plants was investigated. A micropropagation protocol was establish for a rapid multiplication of N. cochenillifera and [Cr(VI)] tolerance and accumulation was studied in in vitro grown cultures. Cr concentration was estimated by atomic absorption spectroscopy in roots and shoots to confirm plant's hyperaccumulation capacity. Plants showed tolerance up to 100 μM K(2)Cr(2)O(7) without any significant changes in root growth after 16 days treatment; whereas, chlorophyll content in plants treated with 1 and 10 μM K(2)Cr(2)O(7) were not so different than the control plant. The levels of lipid peroxidation and protein oxidation increased significantly (p 100 μM) inhibited the activities of CAT and SOD. Roots accumulated a maximum of 25,263.396 ± 1,722.672 mg Cr Kg(-1) dry weight (DW); while the highest concentration of Cr in N. cochenillifera shoots was 705.714 ± 32.324 mg Cr Kg(-1) DW. N. cochenillifera could be a prospective hyperaccumulator plant of Cr(VI) and a promising candidate for phytoremediation purposes. PMID:22914913

  5. Simultaneously photocatalytic treatment of hexavalent chromium (Cr(VI)) and endocrine disrupting compounds (EDCs) using rotating reactor under solar irradiation

    International Nuclear Information System (INIS)

    Highlights: • Self-rotating reactor including TiO2 NTs is applied under solar irradiation. • Simultaneously photocatalysis of Cr(VI) and EDCs is observed to be up to 95%. • Photocatalytic reactions of Cr(VI) and EDCs are favorable under acidic pH. • Charge interaction and hole scavenge between TiO2 and pollutants are synergy factors. - Abstract: In this study, simultaneous treatments, reduction of hexavalent chromium (Cr(VI)) and oxidation of endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and 17β-estradiol (E2), were investigated with a rotating photocatalytic reactor including TiO2 nanotubes formed on titanium mesh substrates under solar UV irradiation. In the laboratory tests with a rotating type I reactor, synergy effects of the simultaneous photocatalytic reduction and oxidation of inorganic (Cr(VI)) and organic (BPA) pollutants were achieved. Particularly, the concurrent photocatalytic reduction of Cr(VI) and oxidation of BPA was higher under acidic conditions. The enhanced reaction efficiency of both pollutants was attributed to a stronger charge interaction between TiO2 nanotubes (positive charge) and the anionic form of Cr(VI) (negative charge), which are prevented recombination (electron–hole pair) by the hole scavenging effect of BPA. In the extended outdoor tests with a rotating type II reactor under solar irradiation, the experiment was extended to examine the simultaneous reduction of Cr(VI) in the presence of additional EDCs, such as EE2 and E2 as well as BPA. The findings showed that synergic effect of both photocatalytic reduction and oxidation was confirmed with single-component (Cr(VI) only), two-components (Cr(VI)/BPA, Cr(VI)/EE2, and Cr(VI)/E2), and four-components (Cr(VI)/BPA/EE2/E2) under various solar irradiation conditions

  6. Simultaneously photocatalytic treatment of hexavalent chromium (Cr(VI)) and endocrine disrupting compounds (EDCs) using rotating reactor under solar irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Youngji [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Yonsei University, Department of Chemical and Biomolecular Engineering, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Joo, Hyunku [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Her, Namguk [Korea Army Academy at Young-Cheon, Department of Chemistry and Environmental Science, 135-1 Changhari, Kokyungmeon, Young-cheon, Gyeongbuk 770-849 (Korea, Republic of); Yoon, Yeomin [University of South Carolina, Department of Civil and Environmental Engineering, Columbia, SC 29208 (United States); Sohn, Jinsik [Kookmin University, School of Civil and Environmental Engineering, 77 Jeongneung-ro, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Kim, Sungpyo [Korea University, Department of Environmental Engineering, Sejong 339-700 (Korea, Republic of); Yoon, Jaekyung, E-mail: jyoon@kier.re.kr [Korea Institute of Energy Research, New and Renewable Energy Research Division, Hydrogen Laboratory, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)

    2015-05-15

    Highlights: • Self-rotating reactor including TiO{sub 2} NTs is applied under solar irradiation. • Simultaneously photocatalysis of Cr(VI) and EDCs is observed to be up to 95%. • Photocatalytic reactions of Cr(VI) and EDCs are favorable under acidic pH. • Charge interaction and hole scavenge between TiO{sub 2} and pollutants are synergy factors. - Abstract: In this study, simultaneous treatments, reduction of hexavalent chromium (Cr(VI)) and oxidation of endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and 17β-estradiol (E2), were investigated with a rotating photocatalytic reactor including TiO{sub 2} nanotubes formed on titanium mesh substrates under solar UV irradiation. In the laboratory tests with a rotating type I reactor, synergy effects of the simultaneous photocatalytic reduction and oxidation of inorganic (Cr(VI)) and organic (BPA) pollutants were achieved. Particularly, the concurrent photocatalytic reduction of Cr(VI) and oxidation of BPA was higher under acidic conditions. The enhanced reaction efficiency of both pollutants was attributed to a stronger charge interaction between TiO{sub 2} nanotubes (positive charge) and the anionic form of Cr(VI) (negative charge), which are prevented recombination (electron–hole pair) by the hole scavenging effect of BPA. In the extended outdoor tests with a rotating type II reactor under solar irradiation, the experiment was extended to examine the simultaneous reduction of Cr(VI) in the presence of additional EDCs, such as EE2 and E2 as well as BPA. The findings showed that synergic effect of both photocatalytic reduction and oxidation was confirmed with single-component (Cr(VI) only), two-components (Cr(VI)/BPA, Cr(VI)/EE2, and Cr(VI)/E2), and four-components (Cr(VI)/BPA/EE2/E2) under various solar irradiation conditions.

  7. REDUKSI LOGAM BERAT CHROMIUM (VI DENGAN FOTOKATALIS KOMPOSIT TiO2-SiO2

    Directory of Open Access Journals (Sweden)

    Candra Purnawan

    2013-10-01

    Full Text Available AbstractsComposite TiO2-SiO2 has been synthesized using sol-gel process with starting materialsTiCl4 and Na2SiO3. The purposes of this research were to know the effect of compositecomposition, pH solution and UV radiation time for reduced Chromium (VI cations. Theidentification and characterization of composite were done by infrared spectroscopy (IRand X-Ray Diffraction. Condition of Chromium (VI reduction by composite TiO2-SiO2 werecarried out with variation of composite TiO2-SiO2 concentration or the ratio Ti:Si were1:0,1 ; 1:0,5 ; 1:1 ; 1:1,5 ; 1:2. Variation of pH solution in 3,0; 3,5; 4,0; 4,5; 5,0; 5,5; 6,0; 6,5;7,0 and variation of UV radiation times in 2, 4, 6, 12, 18, 24, 30, 36, 42, 48 hours.The result showed that XRD characteristic of TiO2-SiO2 composite showed 2q peaks at 22.94degrees and 36.24 degrees. IR characteristic of TiO2-SiO2 showed absorption of Ti-O-Si inthe wave number 962 cm-1. The optimum reduction of Chromium (VI cations using TiO2-SiO2 composite in Ti:Si = 1:1 composition, pH 3 and with 18 hours radiation times.

  8. Proposed adsorption-diffusion model for characterizing chromium(VI) removal using dried water hyacinth roots

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Debasish; Mukherjee, Paramartha; Bandyopadhyay, Amitava [Department of Chemical Engineering, University of Calcutta, Kolkata (India); Das, Sudip Kumar [Department of Chemical Technology, University of Calcutta, Kolkata (India)

    2010-08-15

    Experiments have been carried out to characterize the adsorption of chromium(VI) in the aqueous phase onto dried roots of water hyacinth. Results revealed a very high degree of removal efficiency ({proportional_to}100%). Theoretical analyzes are also made for describing the sorption and diffusion processes. The effective pore diffusivity of chromium(VI) in the water hyacinth roots is determined by a suitable global optimization technique. The depth of penetration, on the other hand, has been estimated for various initial concentrations of chromium(VI). Theoretically predicted concentration profiles are in excellent agreement with the experimental values. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  9. Hexavalent chromium reduction in a sulfur reducing packed-bed bioreactor

    International Nuclear Information System (INIS)

    Highlights: ► Elemental sulfur can be used as electron acceptor for sulfide production. ► Biogenically produced sulfide reduces Cr(VI) to the much less toxic and immobile form of Cr(III). ► Sulfur packed bioreactor is efficient for Cr(VI) containing wastewater treatment. ► Reduced form of chromium precipitates in the bioreactor. - Abstract: The most commonly used approach for the detoxification of hazardous industrial effluents and wastewaters containing Cr(VI) is its reduction to the much less toxic and immobile form of Cr(III). This study investigates the cleanup of Cr(VI) containing wastewaters using elemental sulfur as electron acceptor, for the production of hydrogen sulfide that induces Cr(VI) reduction. An elemental sulfur reducing packed-bed bioreactor was operated at 28–30 °C for more than 250 days under varying influent Cr(VI) concentrations (5.0–50.0 mg/L) and hydraulic retention times (HRTs, 0.36–1.0 day). Ethanol or acetate (1000 mg/L COD) was used as carbon source and electron donor. The degree of COD oxidation varied between 30% and 85%, depending on the operating conditions and the type of organic carbon source. The oxidation of organic matter was coupled with the production of hydrogen sulfide, which reached a maximum concentration of 750 mg/L. The biologically produced hydrogen sulfide reduced Cr(VI) chemically to Cr(III) that precipitated in the reactor. Reduction of Cr(VI) and removal efficiency of total chromium always exceeded 97% and 85%, respectively, implying that the reduced chromium was retained in the bioreactor. This study showed that sulfur can be used as an electron acceptor to produce hydrogen sulfide that induces efficient reduction and immobilization of Cr(VI), thus enabling decontamination of Cr(VI) polluted wastewaters.

  10. Probing chromium(III) from chromium(VI) in cells by a fluorescent sensor

    Science.gov (United States)

    Hu, Xiangquan; Chai, Jie; Liu, Yanfei; Liu, Bin; Yang, Binsheng

    2016-01-01

    Cellular uptake of Cr(VI), followed by its reduction to Cr(III) with the formation of kinetically inert Cr(III) complexes, is a complex process. To better understand its physiological and pathological functions, efficient methods for the monitoring of Cr(VI) are desired. In this paper a selective fluorescent probe L, rhodamine hydrazide bearing a benzo[b]furan-2-carboxaldehyde group, was demonstrated as a red chemosensor for Cr(III) at about 586 nm. This probe has been used to probe Cr(III) which is reduced from Cr(VI) by reductants such as glutathione (GSH), vitamin C, cysteine (Cys), H2O2 and Dithiothreitol (DTT) by fluorescence spectra. Cr(VI) metabolism in vivo is primarily driven by Vc and GSH. Vc could reduce CrO42 - to Cr(III) in a faster rate than GSH. The indirectly detection limit for Cr(VI) by L + GSH system was determined to be 0.06 μM at pH = 6.2. Moreover, the confocal microscopy image experiments indicated that Cr(VI) can be reduced to Cr(III) inside cells rapidly and the resulted Cr(III) can be captured and imaged timely by L.

  11. Phytoremediation potential and nutrient status of Barringtonia acutangula Gaerth. Tree seedlings grown under different chromium (CrVI) treatments.

    Science.gov (United States)

    Kumar, Dharmendra; Tripathi, Durgesh Kumar; Chauhan, Devendra Kumar

    2014-02-01

    To investigate the effect of different chromium (CrVI) treatments on seedlings of semi-aquatic plant Barringtonia acutangula, hydroponic experiments were conducted. Results revealed that B. acutangula could tolerate much higher CrVI concentration accumulated about 751-2,703 mg kg(-1) dry weight in roots and 50-1,101 mg kg(-1) dry weight in shoots, respectively, under 1.0, 2.0, 3.0, 4.0, and 5.0 mM chromium treatments. CrVI exposure at 1.0-4.0 mM does not exhibit toxicity signs; however, up to 4.0 mM CrVI exposure causes significant decline in growth parameters. Content of macronutrients such as Ca and K decreased under different Cr treatments in roots and shoots, while Mg content of roots and shoots did not influence at the range of 1.0-4.0 mM Cr; however, significant decrease at 5.0 mM Cr, besides P content, significantly shows increasing trends, respectively. Interestingly, sulfur content of roots and shoots show increasing trends at 1.0-2.0 mM Cr; however, severe decrease of up to 3.0-5.0 mM is shown in CrVI treatments. Furthermore, micronutrients content were enhanced under CrVI treatments excluding Cu and Fe since they show significant reduction in shoots as well as in roots. Bioaccumulation factor were also calculated on the basis of results obtained which shows the value of >1 without viewing chromium toxicity symptoms. This study demonstrated that B. acutangula could tolerate CrVI concentrations up to 1.0-4.0 mM Cr which may be useful in chromium phytoremediation programs. PMID:24399023

  12. Comparison of toxic effects of chromium III and VI on Tomato plants

    OpenAIRE

    Silva, Ricardo; Quaresma, Raquel; Coelho, Renato; Costa, Alexandra; Luisa, Martins; Mourato, Miguel; Henriques, Fernando

    2005-01-01

    Toxic effects of diverse concentrations of chromium III and VI on Tomato plants in hidoculture media. Diverse plant growth parameters, as well as diverse physiological parameters(leaf water potential and conductance, net photosynthesis and chlorophyll fluorescence) were measured.

  13. NEW BIO-SORBENTS IN THE CONTROL OF CHROMIUM (VI) POLLUTION IN WASTE WATERS

    OpenAIRE

    K. P.C. Sekha; R. V. Vishnu Babu; T. Rohini,; K. Ravindhranath

    2012-01-01

    The sorption abilities of leaves powders of Bhringraj, Aerva lanata,TrianthemaportulacastrumL for extracting Chromium (VI) from polluted waters have been studied with respect tovarious physicochemical parameters such as pH, sorption dosage and equilibrium time. The conditions formaximum removal of Chromium (VI) have been optimized. Ten fold excess of common cation ions present innatural waters, viz., Ca2+,Mg2+, Cu2+, Zn2+,Ni2+and Fe2+have synergistic effect in increasing the % removalof Chrom...

  14. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    Energy Technology Data Exchange (ETDEWEB)

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  15. Cr(VI) reduction in wastewater using a bimetallic galvanic reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lugo-Lugo, Violeta [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Barrera-Diaz, Carlos, E-mail: cbarrera@uaemex.mx [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Bilyeu, Bryan [Xavier University of Louisiana, Department of Chemistry, 1 Drexel Drive, New Orleans, LA 70125 (United States); Balderas-Hernandez, Patricia [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico); Urena-Nunez, Fernando [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Col. Escandon, Delegacion Miguel Hidalgo, C.P. 11801, Mexico, D.F. (Mexico); Sanchez-Mendieta, Victor [Centro Conjunto de Investigacion en Quimica Sustentable UAEM-UNAM, Universidad Autonoma del Estado de Mexico, Facultad de Quimica. Paseo Colon interseccion Paseo Tollocan S/N. C.P. 50120, Toluca (Mexico)

    2010-04-15

    The electrochemical reduction of Cr(VI)-Cr(III) in wastewater by iron and copper-iron bimetallic plates was evaluated and optimized. Iron has been used as a reducing agent, but in this work a copper-iron galvanic system in the form of bimetallic plates is applied to reducing hexavalent chromium. The optimal pH (2) and ratio of copper to iron surface areas (3.5:1) were determined in batch studies, achieving a 100% reduction in about 25 min. The Cr(VI) reduction kinetics for the bimetallic system fit a first order mechanism with a correlation of 0.9935. Thermodynamic analysis shows that the Cr(VI) reduction is possible at any pH value. However, at pH values above 3.0 for iron and 5.5 for chromium insoluble species appear, indicating that the reaction will be hindered. Continuous column studies indicate that the bimetallic copper-iron galvanic system has a reduction capacity of 9.5890 mg Cr(VI) cm{sup -2} iron, whereas iron alone only has a capacity of 0.1269 mg Cr(VI) cm{sup -2}. The bimetallic copper-iron galvanic system is much more effective in reducing hexavalent chromium than iron alone. The exhausted plates were analyzed by SEM, EDS, and XRD to determine the mechanism and the surface effects, especially surface fouling.

  16. Cr(VI) reduction in wastewater using a bimetallic galvanic reactor

    International Nuclear Information System (INIS)

    The electrochemical reduction of Cr(VI)-Cr(III) in wastewater by iron and copper-iron bimetallic plates was evaluated and optimized. Iron has been used as a reducing agent, but in this work a copper-iron galvanic system in the form of bimetallic plates is applied to reducing hexavalent chromium. The optimal pH (2) and ratio of copper to iron surface areas (3.5:1) were determined in batch studies, achieving a 100% reduction in about 25 min. The Cr(VI) reduction kinetics for the bimetallic system fit a first order mechanism with a correlation of 0.9935. Thermodynamic analysis shows that the Cr(VI) reduction is possible at any pH value. However, at pH values above 3.0 for iron and 5.5 for chromium insoluble species appear, indicating that the reaction will be hindered. Continuous column studies indicate that the bimetallic copper-iron galvanic system has a reduction capacity of 9.5890 mg Cr(VI) cm-2 iron, whereas iron alone only has a capacity of 0.1269 mg Cr(VI) cm-2. The bimetallic copper-iron galvanic system is much more effective in reducing hexavalent chromium than iron alone. The exhausted plates were analyzed by SEM, EDS, and XRD to determine the mechanism and the surface effects, especially surface fouling.

  17. Hexavalent chromium reduction by Acinetobacter haemolyticus isolated from heavy-metal contaminated wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Zakaria, Zainul Akmar [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Zakaria, Zainoha [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Surif, Salmijah [Department of Environmental Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Ahmad, Wan Azlina [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia)]. E-mail: azlina@kimia.fs.utm.my

    2007-07-19

    Possible application of a locally isolated environmental isolate, Acinetobacter haemolyticus to remediate Cr(VI) contamination in water system was demonstrated. Cr(VI) reduction by A. haemolyticus seems to favour the lower concentrations (10-30 mg/L). However, incomplete Cr(VI) reduction occurred at 70-100 mg/L Cr(VI). Initial specific reduction rate increased with Cr(VI) concentrations. Cr(VI) reduction was not affected by 1 or 10 mM sodium azide (metabolic inhibitor), 10 mM of PO{sub 4} {sup 3-}, SO{sub 4} {sup 2-}, SO{sub 3} {sup 2-}, NO{sub 3} {sup -} or 30 mg/L of Pb(II), Zn(II), Cd(II) ions. However, heat treatment caused significant dropped in Cr(VI) reduction to less than 20% only. A. haemolyticus cells loses its shape and size after exposure to 10 and 50 mg Cr(VI)/L as revealed from TEM examination. The presence of electron-dense particles in the cytoplasmic region of the bacteria suggested deposition of chromium in the cells.

  18. Fe(III), Cr(VI), and Fe(III) mediated Cr(VI) reduction in alkaline media using a Halomonas isolate from Soap Lake, Washington.

    Science.gov (United States)

    VanEngelen, Michael R; Peyton, Brent M; Mormile, Melanie R; Pinkart, Holly C

    2008-11-01

    Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention.Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates. PMID:18401687

  19. Ultrasensitive photoelectrochemical determination of chromium(VI) in water samples by ion-imprinted/formate anion-incorporated graphitic carbon nitride nanostructured hybrid.

    Science.gov (United States)

    Fang, Tian; Yang, Xiaomin; Zhang, Lizhi; Gong, Jingming

    2016-07-15

    A rapid and highly sensitive photoelectrochemical (PEC) method has been proposed for the determination of trace amounts of chromium in water samples under visible-light irradiation. Here, a unique nanostructured hybrid of formate anion incorporated graphitic carbon nitride (F-g-C3N4) is smartly integrated with a Cr(VI) ion-imprinted polymer (IIP) as a photoactive electrode (denoted as IIP@F-g-C3N4). The nanohybrid of F-g-C3N4 exhibits an enhanced charge separation with substantially improved PEC responses versus g-C3N4. The newly designed IIP@F-g-C3N4 PEC sensor exhibits high sensitivity and selectivity for the determination of Cr(VI) because it offers efficient photogenerated electron reduction toward Cr(VI). The PEC analysis is highly linear over Cr(VI) concentrations ranging from 0.01 to 100.00ppb with a detection limit of 0.006ppb (S/N=3). Our approach can be used to detect Cr(VI), Cr(III) and the total chromium level in aqueous solution through oxidation of Cr(III) to Cr(VI) and the determination of the total chromium as Cr(VI). In practical applications, this low-cost and sensitive assay has been successfully applied for speciation determination of chromium in environmental water samples. PMID:27017396

  20. Reduction of hexavalent chromium by fasted and fed human gastric fluid. II. Ex vivo gastric reduction modeling.

    Science.gov (United States)

    Kirman, Christopher R; Suh, Mina; Hays, Sean M; Gürleyük, Hakan; Gerads, Russ; De Flora, Silvio; Parker, William; Lin, Shu; Haws, Laurie C; Harris, Mark A; Proctor, Deborah M

    2016-09-01

    To extend previous models of hexavalent chromium [Cr(VI)] reduction by gastric fluid (GF), ex vivo experiments were conducted to address data gaps and limitations identified with respect to (1) GF dilution in the model; (2) reduction of Cr(VI) in fed human GF samples; (3) the number of Cr(VI) reduction pools present in human GF under fed, fasted, and proton pump inhibitor (PPI)-use conditions; and (4) an appropriate form for the pH-dependence of Cr(VI) reduction rate constants. Rates and capacities of Cr(VI) reduction were characterized in gastric contents from fed and fasted volunteers, and from fasted pre-operative patients treated with PPIs. Reduction capacities were first estimated over a 4-h reduction period. Once reduction capacity was established, a dual-spike approach was used in speciated isotope dilution mass spectrometry analyses to characterize the concentration-dependence of the 2nd order reduction rate constants. These data, when combined with previously collected data, were well described by a three-pool model (pool 1 = fast reaction with low capacity; pool 2 = slow reaction with higher capacity; pool 3 = very slow reaction with higher capacity) using pH-dependent rate constants characterized by a piecewise, log-linear relationship. These data indicate that human gastric samples, like those collected from rats and mice, contain multiple pools of reducing agents, and low concentrations of Cr(VI) (<0.7 mg/L) are reduced more rapidly than high concentrations. The data and revised modeling results herein provide improved characterization of Cr(VI) gastric reduction kinetics, critical for Cr(VI) pharmacokinetic modeling and human health risk assessment. PMID:27396814

  1. Packed-bed column biosorption of chromium(VI) and nickel(II) onto Fenton modified Hydrilla verticillata dried biomass.

    Science.gov (United States)

    Mishra, Ashutosh; Tripathi, Brahma Dutt; Rai, Ashwani Kumar

    2016-10-01

    The present study represents the first attempt to investigate the biosorption potential of Fenton modified Hydrilla verticillata dried biomass (FMB) in removing chromium(VI) and nickel(II) ions from wastewater using up-flow packed-bed column reactor. Effects of different packed-bed column parameters such as bed height, flow rate, influent metal ion concentration and particle size were examined. The outcome of the column experiments illustrated that highest bed height (25cm); lowest flow rate (10mLmin(-1)), lowest influent metal concentration (5mgL(-1)) and smallest particle size range (0.25-0.50mm) are favourable for biosorption. The maximum biosorption capacity of FMB for chromium(VI) and nickel(II) removal were estimated to be 89.32 and 87.18mgg(-1) respectively. The breakthrough curves were analyzed using Bed Depth Service Time (BDST) and Thomas models. The experimental results obtained agree to both the models. Column regeneration experiments were also carried out using 0.1M HNO3. Results revealed good reusability of FMB during ten cycles of sorption and desorption. Performance of FMB-packed column in treating secondary effluent was also tested under identical experimental conditions. Results demonstrated significant reduction in chromium(VI) and nickel(II) ions concentration after the biosorption process. PMID:27400422

  2. Adsorption of Chromium(VI from Aqueous Solutions by Coffee Polyphenol-Formaldehyde/Acetaldehyde Resins

    Directory of Open Access Journals (Sweden)

    Khudbudin Mulani

    2013-01-01

    Full Text Available Removal of chromium(VI from wastewater is essential as it is toxic. Thus, removal of chromium(VI was performed using coffee polyphenol-formaldehyde/acetaldehyde resins as adsorbents. Adsorbent resins were prepared by condensation of decaffeinated coffee powder with formaldehyde/acetaldehyde and used for the removal of Cr(VI ions from aqueous solutions. A simple and sensitive solid phase extraction procedure was applied for the determination of chromium at trace levels by spectroscopic method using 1,5-diphenylcarbazide reagent. The adsorption of Cr(VI on the coffee polyphenol-formaldehyde/acetaldehyde resins was monitored by FTIR and EDX analysis. The metal adsorption parameters such as contact time, pH, Cr(VI ion concentration, and adsorbent dose were investigated. For Cr(VI, the maximum adsorption capacity of coffee polyphenol-formaldehyde resins was 98% at pH 2. The experimental results showed that Cr(VI bound strongly with coffee polyphenol-formaldehyde/acetaldehyde resins and utilization of resins could be improved greatly by reuse.

  3. A Comprehensive Review on Nickel (II) And Chromium VI Toxicities - Possible Antioxidant (Allium Sativum Linn) Defenses

    OpenAIRE

    Kusal K. Das

    2009-01-01

    The toxicity associated with nickel (II) and chromium (VI) is mainly due to generation of reactive oxygen species (ROS) with subsequent oxidative deterioration of biological macromolecules. Both nickel and chromium can generate free radicals (FR) directly from molecular oxygen in a two step process to produce superoxide anion and in continued process, produce highly toxic hydroxyl radical. The pro-oxidative effects are compounded by fact that they also inhibit antioxidant enzymes and deplete ...

  4. Reduction of Hexavalent Chromium Using L-Cysteine Capped Nickel Nanocatalysts

    Directory of Open Access Journals (Sweden)

    Razium Ali Soomro

    2013-06-01

    Full Text Available The aim of this study was to reduce the highly toxic hexavalent chromium Cr(VI into less toxic chromium Cr(III species by using nickel nanoparticles (Ni NPs as catalysts in order to provide safety to the aqueous environment. In the first phase Ni NPs were synthesized in ethylene glycol and capped with l-cysteine by a modified microwave irradiation method using NaOH as the accelerator. The formed Ni NPs were characterized by various techniques such as UV-Visible spectroscopy, Fourier Transform Infra-red (FTIR spectroscopy and Scanning Electron Microscopy (SEM. In the second phase the formed Ni NPs were immobilized on glass surfaces and employed as catalyst for the reduction of Cr(VI ions. According to observations, 99% reduction of Cr(VI ions was achieved in the presence of 0.5 mg of Ni NPs catalyst in just five minutes as compared to nickel powder that showed only 16% reduction in 15 minutes. The study has a great impact on the aqueous pollution control of Cr(VI especially caused by the discharge of waste water from several industries utilizing Cr(VI containing salt as one of the essential gradients.

  5. Removal of chromium (VI) from aqueous solution using treated oil palm fibre.

    Science.gov (United States)

    Isa, Mohamed Hasnain; Ibrahim, Naimah; Aziz, Hamidi Abdul; Adlan, Mohd Nordin; Sabiani, Nor Habsah Md; Zinatizadeh, Ali Akbar Lorestani; Kutty, Shamsul Rahman Mohamed

    2008-04-01

    This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution. PMID:17714862

  6. Experimental Monitoring of Cr(VI) Bio-reduction Using Electrochemical Geophysics

    International Nuclear Information System (INIS)

    Many Department of Energy (DOE) sites are contaminated with highly carcinogenic hexavalent chromium (Cr(VI)). In this research, we explore the feasibility of applying complex resistivity to the detection and monitoring of microbially-induced reduction of hexavalent chromium (Cr(VI)) to a less toxic form (Cr(III)). We hope to measure the change in ionic concentration that occurs during this reduction reaction. This form of reduction promises to be an attractive alternative to more expensive remedial treatment methods. The specific goal of this research is to define the minimum and maximum concentration of the chemical and biological compounds in contaminated samples for which the Cr(VI) - Cr(III) reduction processes could be detected via complex resistivity. There are three sets of experiments, each comprised of three sample columns. The first experiment compares three concentrations of Cr(VI) at the same bacterial cell concentration. The second experiment establishes background samples with, and without, Cr(VI) and bacterial cells. The third experiment examines the influence of three different bacterial cell counts on the same concentration of Cr(VI). A polarization relaxation mechanism was observed between 10 and 50 Hz. The polarization mechanism, unfortunately, was not unique to bio-chemically active samples. Spectral analysis of complex resistivity data, however, showed that the frequency where the phase minimum occurred was not constant for bio-chemically active samples throughout the experiment. A significant shifts in phase minima occurred between 10 to 20 Hz from the initiation to completion of Cr(VI) reduction. This phenomena was quantified using the Cole-Cole model and the Marquardt-Levenberg nonlinear least square minimization method. The data suggests that the relaxation time and the time constant of this relaxation are the Cole-Cole parameters most sensitive to changes in biologically-induced reduction of Cr(VI)

  7. BIOSORPTION OF CHROMIUM (VI FROM INDUSTRIAL EFFLUENT BY WILD ANDMUTANT TYPE STRAIN OF SACCHAROMYCES CEREVISIAE AND ITS IMMOBILIZED FORM

    Directory of Open Access Journals (Sweden)

    K Selvam, K Arungandhi, B Vishnupriya, T Shanmuga priya and M Yamuna

    2013-01-01

    Full Text Available Biosorption of chromium was studied by wild type Saccharomyces cerevisiae strain, mutant strain, immobilized-wild type and mutant strain. Chromium absorption pattern was observed in all experimental conditions. Hexavalent chromium (VI was analyzed by diphenyl carbazide method, by oxidizing the trivalent chromium (III. The percentage efficiency of wild type S. cerevisiae and its mutant strain, immobilized-wild type and mutant strain were 94.8%, 98.7%, 97.4% and 100% respectively. S. cerevisiae mutant strain and their immobilized form was found to be effective in biosorption of chromium (VI than the wild type forms.

  8. Cr(VI) reduction at rutile-catalyzed cathode in microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Lu, Anhuai; Ding, Hongrui; Yan, Yunhua; Wang, Changqiu; Zen, Cuiping; Wang, Xin [The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Jin, Song [MWH Americas, 3665 JFK Parkway, Suite 206, Fort Collins, CO 80525 (United States); Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071 (United States)

    2009-07-15

    Cathodic reduction of hexavalent chromium (Cr(VI)) and simultaneous power generation were successfully achieved in a microbial fuel cell (MFC) containing a novel rutile-coated cathode. The selected rutile was previously characterized to be sensitive to visible light and capable of both non-photo- and photocatalysis. In the MFCs containing rutile-coated cathode, Cr(VI) was rapidly reduced in the cathode chamber in presence and absence of light irradiation; and the rate of Cr(VI) reduction under light irradiation was substantially higher than that in the dark. Under light irradiation, 97% of Cr(VI) (initial concentration 26 mg/L) was reduced within 26 h, which was 1.6 x faster than that in the dark controls in which only background non-photocatalysis occurred. The maximal potential generated under light irradiation was 0.80 vs. 0.55 V in the dark controls. These results indicate that photocatalysis at the rutile-coated cathode in the MFCs might have lowered the cathodic overpotential, and enhanced electron transfer from the cathode to Cr(VI) for its reduction. In addition, photoexcited electrons generated during the cathode photocatalysis might also have contributed to the higher Cr(VI) reduction rates when under light irradiation. This work assessed natural rutile as a novel cathodic catalyst for MFCs in power generation; particularly it extended the practical merits of conventional MFCs to cathodic reduction of environmental contaminants such as Cr(VI). (author)

  9. Prevention of chromium(VI) formation by improving the tannery processes

    OpenAIRE

    Font Vallès, Joaquim; Rius Carrasco, Antoni; Marsal Monge, Agustín; Hauber, Christiane; Tommaselli, Michelle

    2006-01-01

    This work has been funded by the European Commission through the Chrom6less Project (CRAFT -1999-71638). The objectives of the project were: - Establishment of the analytical methodology which provided reproducible results that may be free of interferences. - Identification of the factors that facilitated or impeded the transformation of Cr(III) to Cr(VI). - Establishment of the best conditions that allowed the production of chromium(VI) free leather, even during the l...

  10. Toxic hexavalent chromium reduction by Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium

    Science.gov (United States)

    Rehman, Fatima; Faisal, Muhammad

    2015-05-01

    Three bacterial strains Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium were investigated when grown in Luria-Bertani (LB) medium at 500 μg/mL Cr(VI). The hexavalent chromium reduction was measured by growing the strains in DeLeo and Ehrlich (1994) medium at 200 and 400 μg/mL K2CrO4. The optimal Cr (VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 51%, 39%, and 41%, respectively, at an initial K2CrO4 concentration of 200 μg/mL at pH 3 and temperature 37°C. At an initial chromate concentration of 400 μg/mL, the Cr(VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 24%, 19%, and 18%, respectively at pH 3 at 37°C after 24 h. These strains have ability to reduce toxic hexavalent chromium to the less mobile trivalent chromium at a wide range of different environmental conditions and can be useful for the treatment of contaminated wastewater and soils.

  11. Behaviour of chromium(VI) in stormwater soil infiltration systems

    DEFF Research Database (Denmark)

    Cederkvist, Karin; Ingvertsen, Simon T.; Jensen, Marina B.;

    2013-01-01

    mm in 2 h) and extreme (100 mm in 3 h) rain events. The objectives were to understand the behaviour of the anionic and toxic Cr(VI) in soil at neutral pH and to asses treatment efficiency towards Cr(VI). During normal rain events Cr(VI) was largely retained (more than 50, even though pH was neutral......, while under extreme rain events approximately 20% of Cr(VI) was retained. In both cases effluent concentrations of Cr(VI) would exceed the threshold value of 3.4 mu g/L if the infiltrated water were introduced to freshwater environments. More knowledge on the composition of the stormwater runoff, and...

  12. [Advances in molecular mechanism of bacterial reduction of hexavalent chromium].

    Science.gov (United States)

    Li, Dou; Zhao, You-Cai; Song, Li-Yan; Yin, Ya-Jie; Wang, Yang-Qing; Xu, Zhong-Hui

    2014-04-01

    Cr(VI) has been causing serious environmental pollution due to its carcinogenicity, teratogenicity and strong migration. Reduction of Cr( VI) to Cr(III), a precipitation that is much less toxic, is an efficient strategy to control Cr pollution. Within the strategy, bacterial reduction of Cr(VI) to Cr(III) has been considered as one of the best bioremediation methods because of its efficiency, environment friendly, and low cost; however, the molecular mechanism remains large unknown. This review summarizes Cr(VI) reduction bacterial species and its application in pollution control, elaborates the pathways of Cr( VI) reduction and functional proteins involved, concludes the molecular mechanism of baterial reduction Cr(VI), and discusses the orientation of the future research. PMID:24946623

  13. Hexavalent chromium reduction by chromate-resistant haloalkaliphilic Halomonas sp. M-Cr newly isolated from tannery effluent

    OpenAIRE

    Mabrouk, Mona E.M.; Arayes, Mervat A.; Sabry, Soraya A.

    2014-01-01

    The current study aimed to isolate and characterize a chromate-resistant bacterium from tannery effluent, able to reduce Cr(VI) aerobically at high pH and salinity. Environmental contamination by hexavalent chromium, Cr(VI), presents a serious public health problem. Enrichment led to the isolation of 12 bacteria displaying different degrees of chromate reduction. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparison indicated that the most potent strain b...

  14. BIOSORPTION OF CHROMIUM (VI) FROM INDUSTRIAL EFFLUENT BY WILD ANDMUTANT TYPE STRAIN OF SACCHAROMYCES CEREVISIAE AND ITS IMMOBILIZED FORM

    OpenAIRE

    K Selvam, K Arungandhi, B Vishnupriya, T Shanmuga priya and M Yamuna

    2013-01-01

    Biosorption of chromium was studied by wild type Saccharomyces cerevisiae strain, mutant strain, immobilized-wild type and mutant strain. Chromium absorption pattern was observed in all experimental conditions. Hexavalent chromium (VI) was analyzed by diphenyl carbazide method, by oxidizing the trivalent chromium (III). The percentage efficiency of wild type S. cerevisiae and its mutant strain, immobilized-wild type and mutant strain were 94.8%, 98.7%, 97.4% and 100% respectively. S. cerevisi...

  15. [Ecotoxicological effect and soil environmental criteria of the heavy metal chromium(VI)].

    Science.gov (United States)

    Wang, Xiao-Nan; Liu, Zheng-Tao; Wang, Wan-Hua; Zhang, Cong; Chen, Li-Hong

    2014-08-01

    Nowadays, systematic studies about water quality criteria are being carried out in China, but studies on soil environmental criteria are comparatively insufficient. In this study, germination and root growth of 8 terrestrial plants (Triticum aestivum, Lactuca sativa, Cucumis sativus, Zea mays, Brassica pekinensis, Glycine max, Allium tuberosum and Solanum lycopersicum) and growth inhibition of 1 terrestrial animal (Achatina fulica) were used to determine the chronic ecotoxicological effects of chromium (VI) using the agricultural moisture soil of Baoding. In addition, with the native toxicity data selected, the HC5 (hazardous concentration for 5% of species) and the ecological protected soil environmental criteria of chromium (VI) in Baoding moisture soil were calculated using the log-normal species sensitivity distribution (SSD) method. Results showed that the no observed effect concentration (NOEC) values for the growth of the terrestrial plants T. aestivum, L. sativa, C. sativus, Z. mays, B. pekinensis, G. max, A. tuberosum, S. lycopersicum, and the terrestrial invertebrate snail A. fulica were 19.0, 21.0, 28.0, 32.0, 28.0, 32.0, 32.0, 12.0 and 20.0 mg x kg(-1), respectively. The comparison of species toxicity data that were tested in the same conditions showed that the terrestrial plant S. lycopersicum was the most sensitive species to chromium (VI), T. aestivum and L. sativa had the same sensitivity to chromium (VI) exposure, whereas, plants C. sativus, Z. mays, B. pekinensis, G. max and A. tuberosum had the same sensitivity to chromium (VI) exposure. Finally, the HC5 value of chromium (VI) in the moisture soil of Baoding was calculated to be 7.7 (4.1 < CI < 11. 3) mg x kg(-1) using the log-normal SSD method, and the ecological protected soil environmental criteria of chromium (VI) was 1.5-7.7 mg x kg(-1). With the investigation of this work, we expect that it could provide useful information for the study of soil environmental criteria in China. PMID:25338393

  16. Fluorescent silver nanoclusters for ultrasensitive determination of chromium(VI) in aqueous solution.

    Science.gov (United States)

    Zhang, Jian Rong; Zeng, Ai Lian; Luo, Hong Qun; Li, Nian Bing

    2016-03-01

    In this work, a simple and sensitive Cr(VI) sensor is proposed based on fluorescent polyethyleneimine-stabilized Ag nanoclusters, which allows the determination over a wide concentration range of 0.1 nM-3.0 μM and with a detection limit as low as 0.04 nΜ and a good selectivity. The quenching mechanism was discussed in terms of the absorption and fluorescence spectra, suggesting that Cr(VI) is connected to Ag nanoclusters by hydrogen bond between the oxygen atom at the vertex of tetrahedron structure of Cr(VI) and the amino nitrogen of polyethyleneimine that surrounded Ag nanoclusters and electron transfer from Ag nanoclusters to highly electron-deficient Cr(VI) results in fluorescence quenching. Despite the failure to quench the fluorescence efficiently, Cr(III) can also be measured using the proposed Ag nanoclusters by being oxidized to Cr(VI) in alkaline solution (pH ∼ 9) containing H2O2. Therefore, our approach could be used to detect Cr(VI), Cr(III) and the total chromium level in aqueous solution. In addition, Cr(VI) analysis in real water samples were satisfactory, indicating this method could be practically promising for chromium measurements. PMID:26546705

  17. Reduction U(VI) using jones reductor

    International Nuclear Information System (INIS)

    Reduction of dissolved oxide uranium in sulfuric acid use of reductor Jones Zn (Hg) was carried out. The reduced uranium sulfate solution was analyzed its U(IV) by measuring its absorbance on 652 nm and compared to oxidation U(IV) solution with KMnO4 solution. It was found that the comparison was in a good agreement. However, measuring of absorbance of U(VI) solution on 429 nm result of oxidation U(IV) with KMnO4 solution was not change. (author)

  18. A revised model of ex-vivo reduction of hexavalent chromium in human and rodent gastric juices

    Energy Technology Data Exchange (ETDEWEB)

    Schlosser, Paul M., E-mail: schlosser.paul@epa.gov; Sasso, Alan F.

    2014-10-15

    Chronic oral exposure to hexavalent chromium (Cr-VI) in drinking water has been shown to induce tumors in the mouse gastrointestinal (GI) tract and rat oral cavity. The same is not true for trivalent chromium (Cr-III). Thus reduction of Cr-VI to Cr-III in gastric juices is considered a protective mechanism, and it has been suggested that the difference between the rate of reduction among mice, rats, and humans could explain or predict differences in sensitivity to Cr-VI. We evaluated previously published models of gastric reduction and believe that they do not fully describe the data on reduction as a function of Cr-VI concentration, time, and (in humans) pH. The previous models are parsimonious in assuming only a single reducing agent in rodents and describing pH-dependence using a simple function. We present a revised model that assumes three pools of reducing agents in rats and mice with pH-dependence based on known speciation chemistry. While the revised model uses more fitted parameters than the original model, they are adequately identifiable given the available data, and the fit of the revised model to the full range of data is shown to be significantly improved. Hence the revised model should provide better predictions of Cr-VI reduction when integrated into a corresponding PBPK model. - Highlights: • Hexavalent chromium (Cr-VI) reduction in gastric juices is a key detoxifying step. • pH-dependent Cr-VI reduction rates are explained using known chemical speciation. • Reduction in rodents appears to involve multiple pools of electron donors. • Reduction appears to continue after 60 min, although more slowly than initial rates.

  19. A revised model of ex-vivo reduction of hexavalent chromium in human and rodent gastric juices

    International Nuclear Information System (INIS)

    Chronic oral exposure to hexavalent chromium (Cr-VI) in drinking water has been shown to induce tumors in the mouse gastrointestinal (GI) tract and rat oral cavity. The same is not true for trivalent chromium (Cr-III). Thus reduction of Cr-VI to Cr-III in gastric juices is considered a protective mechanism, and it has been suggested that the difference between the rate of reduction among mice, rats, and humans could explain or predict differences in sensitivity to Cr-VI. We evaluated previously published models of gastric reduction and believe that they do not fully describe the data on reduction as a function of Cr-VI concentration, time, and (in humans) pH. The previous models are parsimonious in assuming only a single reducing agent in rodents and describing pH-dependence using a simple function. We present a revised model that assumes three pools of reducing agents in rats and mice with pH-dependence based on known speciation chemistry. While the revised model uses more fitted parameters than the original model, they are adequately identifiable given the available data, and the fit of the revised model to the full range of data is shown to be significantly improved. Hence the revised model should provide better predictions of Cr-VI reduction when integrated into a corresponding PBPK model. - Highlights: • Hexavalent chromium (Cr-VI) reduction in gastric juices is a key detoxifying step. • pH-dependent Cr-VI reduction rates are explained using known chemical speciation. • Reduction in rodents appears to involve multiple pools of electron donors. • Reduction appears to continue after 60 min, although more slowly than initial rates

  20. Evaluating the risk of chromium reoxidation in aquifer sediments following a reductive bioremediation treatment

    Science.gov (United States)

    Varadharajan, C.; Nico, P. S.; Yang, L.; Han, R.; Bill, M.; Larsen, J.; Van Hise, A.; Molins, S.; Steefel, C.; Conrad, M. E.; Lim, H.; Brodie, E. L.; Beller, H. R.

    2011-12-01

    Remediation of chromium contamination typically involves reducing the toxic and soluble hexavalent form, Cr(VI), to the relatively harmless and mostly immobile trivalent state, Cr(III). The objective of this study is to investigate the potential for reduced chromium precipitates to be remobilized under oxidizing conditions that are expected to be prevalent some time after the bioremediation treatment is completed. In an initial phase of the experiment, reduction under anaerobic conditions was observed for over 12 months by subjecting flow-through columns containing homogenized sediments from the Hanford 100H aquifer to different dominant electron acceptors, i.e. NO3-, Fe(III), or SO42-, in the presence of 5 μM Cr(VI) and 5 mM lactate. Cr(VI) was depleted in the effluent solutions of the nitrate-treated columns, all of which exhibited denitrification, as well as in sulfate-amended columns in which fermentative conditions became dominant (with a minor amount of sulfate reduction). In the second phase of the study, oxygenated water with 2 mM nitrate was flowed through the denitrifying and fermentative columns for several months, without addition of Cr(VI) or lactate. The results show that the chromium that precipitated in the denitrifying columns was steadily mobilized under the oxidizing conditions, although the concentration of Cr(VI) in the effluent remained low (effluent from the fermentative sulfate-amended column. Reducing conditions were sustained in the fermentative column despite the continuous influx of O2, as indicated by the decrease of nitrate and accumulation of nitrite, potentially due to the presence of sulfides precipitated during the initial reducing phase of the experiment. The results from this study suggest that the biogeochemical conditions present during the reductive treatment phase can substantially impact the long-term sustainability of the remediation effort.

  1. Improved biosorption for Cr(VI) reduction and removal by Arthrobacter viscosus using zeolite

    OpenAIRE

    Silva, Bruna Andreia Nogueira Airosa; Figueiredo, Hugo; Quintelas, C.; Neves, Isabel C.; Tavares, M.T.

    2012-01-01

    The aim of the present work was to optimize the reduction and removal of chromium from aqueous solutions by a biosorption system consisting of a bacteria supported on a zeolite. The system proposed combines the biosorption properties of Arthrobacter viscosus, with the ion exchange capacity of NaY zeolite. Experiments were also performed without the zeolite for comparison purposes. Experimental parameters such as solution pH, biomass concentration and initial Cr(VI) concentration were investig...

  2. Box-Behnken experimental design for chromium(VI) ions removal by bacterial cellulose-magnetite composites.

    Science.gov (United States)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jinga, Sorin Ion; Mihalache, Nicoleta; Botez, Adriana; Matei, Cristian; Berger, Daniela; Damian, Celina Maria; Ionita, Valentin

    2016-10-01

    In this study bacterial cellulose-magnetite composites were synthesised for the removal of chromium(VI) from aqueous solutions. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the bacterial cellulose-magnetite composites and to reveal the uniform dispersion of nanomagnetite in the BC matrix. Magnetic properties were also measured to confirm the magnetite immobilization on bacterial cellulose membrane. The effects of initial Cr(VI) concentration, solution pH and solid/liquid ratio upon chromium removal were examined using the statistical Box-Behnken Design. Because of the possibility of magnetite dissolution during chromium(VI) adsorption, the degree of iron leaching was also analysed in the same conditions as Cr(VI) adsorption. From the factors affecting chromium(VI) adsorption the most important was solution pH. The highest Cr(VI) removal efficiency was observed at pH 4, accompanied by the lowest iron leaching in the solution. The adsorption experiments also indicated that the adsorption process of chromium(VI) is well described by Freundlich adsorption model. Our results proved that the BC-magnetite composites could be used for an efficient removal of chromium(VI) from diluted solutions with a minimum magnetite dissolution during operation. PMID:27343705

  3. Reduction of hexavalent chromium by fasted and fed human gastric fluid. I. Chemical reduction and mitigation of mutagenicity.

    Science.gov (United States)

    De Flora, Silvio; Camoirano, Anna; Micale, Rosanna T; La Maestra, Sebastiano; Savarino, Vincenzo; Zentilin, Patrizia; Marabotto, Elisa; Suh, Mina; Proctor, Deborah M

    2016-09-01

    Evaluation of the reducing capacity of human gastric fluid from healthy individuals, under fasted and fed conditions, is critical for assessing the cancer hazard posed by ingested hexavalent chromium [Cr(VI)] and for developing quantitative physiologically-based pharmacokinetic models used in risk assessment. In the present study, the patterns of Cr(VI) reduction were evaluated in 16 paired pre- and post-meal gastric fluid samples collected from 8 healthy volunteers. Human gastric fluid was effective both in reducing Cr(VI), as measured by using the s-diphenylcarbazide colorimetric method, and in attenuating mutagenicity in the Ames test. The mean (±SE) Cr(VI)-reducing ability of post-meal samples (20.4±2.6μgCr(VI)/mL gastric fluid) was significantly higher than that of pre-meal samples (10.2±2.3μgCr(VI)/mL gastric fluid). When using the mutagenicity assay, the decrease of mutagenicity produced by pre-meal and post-meal samples corresponded to reduction of 13.3±1.9 and 25.6±2.8μgCr(VI)/mL gastric fluid, respectively. These data are comparable to parallel results conducted by using speciated isotope dilution mass spectrometry. Cr(VI) reduction was rapid, with >70% of total reduction occurring within 1min and 98% of reduction is achieved within 30min with post-meal gastric fluid at pH2.0. pH dependence was observed with decreasing Cr(VI) reducing capacity at higher pH. Attenuation of the mutagenic response is consistent with the lack of DNA damage observed in the gastrointestinal tract of rodents following administration of ≤180ppm Cr(VI) for up to 90days in drinking water. Quantifying Cr(VI) reduction kinetics in the human gastrointestinal tract is necessary for assessing the potential hazards posed by Cr(VI) in drinking water. PMID:27404458

  4. Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities

    Energy Technology Data Exchange (ETDEWEB)

    Somenahally, Anil C [ORNL; Mosher, Jennifer J [ORNL; Yuan, Tong [University of Oklahoma; Phelps, Tommy Joe [ORNL; Brown, Steven D [ORNL; Yang, Zamin Koo [ORNL; Hazen, Terry C [ORNL; Arkin, Adam [Lawrence Berkeley National Laboratory (LBNL); Palumbo, Anthony Vito [ORNL; Van Nostrand, Dr. Joy D. [Oklahoma University; Zhou, Jizhong [University of Oklahoma; Elias, Dwayne A [ORNL

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.

  5. Adsorption and desorption characteristics of imidazole-modified silica for chromium(VI)

    International Nuclear Information System (INIS)

    Imidazole-modified silica adsorbent with chloride as counter ion (SilprIm-Cl) was synthesized and characterized by scanning electron microscope, infrared spectra, thermogravimetric analysis, elemental analysis and BET analysis. The adsorption of chromium(VI) from aqueous solutions onto the SilprIm-Cl was investigated at varying pH, contact time, initial Cr(VI) concentration, adsorbent amount and temperature. The experimental results showed that the modification of silica with imidazole enhanced significantly the adsorption capacity for Cr(VI). The SilprIm-Cl was of primary anion-exchange adsorption nature, pH and excess Cl− ions in solutions affected significantly the adsorption of chromium(VI). The adsorption isotherms would be well defined with Langmuir model instead of Freundlich model. The adsorption process follows the pseudo-second-order kinetics. The maximum adsorption capacity of Cr(VI) of 47.79 mg g−1 with an initial Cr(VI) concentration of 150 mg L−1 was achieved at pH of 2.0. The adsorption–desorption experiments of the SilprIm-Cl exhibited that the adsorbent could be regenerated and reused eight times at least by simple washings with NaCl and water in turn.

  6. Adsorption and desorption characteristics of imidazole-modified silica for chromium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhike, E-mail: wzk@htu.cn; Ye, Cunling; Wang, Xueyuan; Li, Juan

    2013-12-15

    Imidazole-modified silica adsorbent with chloride as counter ion (SilprIm-Cl) was synthesized and characterized by scanning electron microscope, infrared spectra, thermogravimetric analysis, elemental analysis and BET analysis. The adsorption of chromium(VI) from aqueous solutions onto the SilprIm-Cl was investigated at varying pH, contact time, initial Cr(VI) concentration, adsorbent amount and temperature. The experimental results showed that the modification of silica with imidazole enhanced significantly the adsorption capacity for Cr(VI). The SilprIm-Cl was of primary anion-exchange adsorption nature, pH and excess Cl{sup −} ions in solutions affected significantly the adsorption of chromium(VI). The adsorption isotherms would be well defined with Langmuir model instead of Freundlich model. The adsorption process follows the pseudo-second-order kinetics. The maximum adsorption capacity of Cr(VI) of 47.79 mg g{sup −1} with an initial Cr(VI) concentration of 150 mg L{sup −1} was achieved at pH of 2.0. The adsorption–desorption experiments of the SilprIm-Cl exhibited that the adsorbent could be regenerated and reused eight times at least by simple washings with NaCl and water in turn.

  7. Cr(VI reduction by cell-free extract of thermophillic Bacillus fusiformis NTR9

    Directory of Open Access Journals (Sweden)

    Pranee Pattanapipitpaisal

    2013-08-01

    Full Text Available Residual chromium compounds in discharged effluents is a serious problem, due to hexavalent chromium or chromate[Cr(VI] being extremely toxic and showing mutagenic and carcinogenic effects on biological systems. The bacterial enzymaticCr(VI reduction can occur and this could be an effective method of detoxifying Cr(VI polluted effluent. The present studycharacterized Cr(VI reductase activity of cell-free extracts (CFE of thermophilic chromate-reducing bacteria, Bacillusfusiformis NTR9. Results showed that the optimum temperature and pH for Cr(VI reductase activity of CFE was 80°C andpH 7, respectively. The reductase activity remained at 60.34% and 26.44% after 30 minutes of exposure to 70 and 90°C,respectively, suggesting a heat stable enzyme. Moreover, the enzyme was resistant under acidic and neutral condition but itsstability was decreased under alkaline condition. The Cr(VI reductase activity of CFE was enhanced when exposed in Cu2+and Fe3+ by 188.19% and 180.38%, respectively. The Cr(VI reductase activity could be reduced to 72.19% and 8.95% in thepresence of Mn2+ and Ag+, respectively. Mg2+, Zn2+, As3+ and electron acceptors like sulfate and nitrate had no affect on Cr(VIreductase activity. The external electron donors (glucose, glycerol, citrate, malate, succinate, and acetate, but not NADHwere essential to improve the chromate reductase activity of NTR9 strain. The chromate reductase was mainly associatedwith the soluble fraction in the cytoplasm of the bacterial cell. The molecular weight of the enzyme was 20 KDa. The resultsshowed that Cr(VI reductase could be a good candidate for detoxification of Cr(VI in industrial effluents.

  8. Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process

    International Nuclear Information System (INIS)

    In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water. Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium-cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption-desorption process were observed by TEM. Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution.

  9. Response Surface Modeling and Optimization of Chromium (VI Removal from Waste Water using Custard Apple Peel Powder

    Directory of Open Access Journals (Sweden)

    Darapureddi KRISHNA

    2014-06-01

    Full Text Available The potential use of custard apple peel powder for the removal of chromium (VI from waste water has been investigated in batch mode experiments. Influences of parameters like initial chromium (VI concentration (5 - 30 mg/l, pH (2 - 4, and biomass dosage (8 - 12 g/l on chromium (VI adsorption were examined using response surface methodology. The Box-Behnken experimental design in response surface methodology was used for designing the experiments as well as for full response surface estimation and 15 trials per the model were run. The optimum conditions for maximum removal of chromium (VI from the waste water are as follows: adsorbent dosage (10.3613 g/l, pH (2.78459 and initial chromium (VI concentration (9.03197 mg/l. The maximum percentage removal of chromium at optimum conditions was 92.82 % (with metal uptake of 2.3045 mg/g. The high correlation coefficient (R2 = 0.997 between the model and the experimental data showed that the model was able to predict efficiently the percentage removal of chromium (VI from waste water using custard apple peel powder.

  10. Cr(Vi) reduction capacity of activated sludge as affected by nitrogen and carbon sources, microbial acclimation and cell multiplication

    Energy Technology Data Exchange (ETDEWEB)

    Ferro Orozco, A.M., E-mail: mferro@cidca.org.ar [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA) CCT La Plata CONICET - Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ) La Plata (Argentina); Contreras, E.M.; Zaritzky, N.E. [Centro de Investigacion y Desarrollo en Criotecnologia de Alimentos (CIDCA) CCT La Plata CONICET - Fac. de Cs. Exactas, UNLP. 47 y 116 (B1900AJJ) La Plata (Argentina); Fac. de Ingenieria, UNLP. 47 y 1 (B1900AJJ) - La Plata (Argentina)

    2010-04-15

    The objectives of the present work were: (i) to analyze the capacity of activated sludge to reduce hexavalent chromium using different carbon sources as electron donors in batch reactors, (ii) to determine the relationship between biomass growth and the amount of Cr(VI) reduced considering the effect of the nitrogen to carbon source ratio, and (iii) to determine the effect of the Cr(VI) acclimation stage on the performance of the biological chromium reduction assessing the stability of the Cr(VI) reduction capacity of the activated sludge. The highest specific Cr(VI) removal rate (q{sub Cr}) was attained with cheese whey or lactose as electron donors decreasing in the following order: cheese whey {approx} lactose > glucose > citrate > acetate. Batch assays with different nitrogen to carbon source ratio demonstrated that biological Cr(VI) reduction is associated to the cell multiplication phase; as a result, maximum Cr(VI) removal rates occur when there is no substrate limitation. The biomass can be acclimated to the presence of Cr(VI) and generate new cells that maintain the ability to reduce chromate. Therefore, the activated sludge process could be applied to a continuous Cr(VI) removal process.

  11. Cr(Vi) reduction capacity of activated sludge as affected by nitrogen and carbon sources, microbial acclimation and cell multiplication

    International Nuclear Information System (INIS)

    The objectives of the present work were: (i) to analyze the capacity of activated sludge to reduce hexavalent chromium using different carbon sources as electron donors in batch reactors, (ii) to determine the relationship between biomass growth and the amount of Cr(VI) reduced considering the effect of the nitrogen to carbon source ratio, and (iii) to determine the effect of the Cr(VI) acclimation stage on the performance of the biological chromium reduction assessing the stability of the Cr(VI) reduction capacity of the activated sludge. The highest specific Cr(VI) removal rate (qCr) was attained with cheese whey or lactose as electron donors decreasing in the following order: cheese whey ∼ lactose > glucose > citrate > acetate. Batch assays with different nitrogen to carbon source ratio demonstrated that biological Cr(VI) reduction is associated to the cell multiplication phase; as a result, maximum Cr(VI) removal rates occur when there is no substrate limitation. The biomass can be acclimated to the presence of Cr(VI) and generate new cells that maintain the ability to reduce chromate. Therefore, the activated sludge process could be applied to a continuous Cr(VI) removal process.

  12. Biochemical study on the protective role of folic acid in rabbits treated with chromium (VI).

    Science.gov (United States)

    El-Demerdash, Fatma M; Yousef, Mokhtar I; Elaswad, Fathia A M

    2006-01-01

    Deleterious effects of chromium (VI) compounds are diversified affecting almost all the organ systems in a wide variety of animals. Therefore, the present study was carried out to determine the effectiveness of folic acid (FA) in alleviating the toxicity of chromium (VI) on certain biochemical parameters, lipid peroxidation, and enzyme activities of male New Zealand white rabbits. Six rabbits per group were assigned to one of four treatment groups: 0 mg FA and 0 mg Cr(VI)/kg BW (control); 8.3 microg FA/kg BW; 5 mg Cr(VI)/kg BW; 5 mg Cr(VI) plus 8.3 microg FA/kg BW, respectively. Rabbits were orally administered their respective doses every day for 10 weeks. Results obtained showed that Cr(VI) significantly (P GST), and decreased the content of sulfhydryl groups (SH groups) in liver, testes, brain, kidney, and lung. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AlP), acid phosphatase (AcP), and lactate dehydrogenase (LDH) were significantly decreased in liver and testes due to Cr(VI) administration. Also, AlP and AcP activities were significantly decreased in kidney and lung. The activity of acetylcholinesterase (AChE) was significantly decreased in brain and plasma. Contrariwise, the activities of AST and ALT were significantly increased in plasma, while AlP and AcP decreased. Chromium (VI) treatment caused a significant decrease in plasma total protein (TP) and globulin, and increased total lipids (TL), cholesterol, glucose, urea, creatinine, and bilirubin concentrations. Folic acid alone significantly decreased the levels of free radicals in liver, brain, and kidney, and increased the content of SH-group. The activities of AST, ALT, and LDH in liver; AST, ALT, AlP, AcP, and LDH in testes; AcP in kidney; AlP and AcP in lung, and LDH in brain were significantly increased. Plasma TP and albumin were increased, while urea and creatinine were decreased. The presence of FA with Cr(VI) restored the changes in

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

    Science.gov (United States)

    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

  14. Chromium

    Science.gov (United States)

    ... health risks of too much chromium? Chromium and medication interactions Supplemental sources of chromium Chromium and Healthful Diets References Disclaimer What foods provide chromium? Chromium is widely distributed in the ...

  15. NANOSTRUCTURED POROUS SILICON AND LUMINESCENT POLYSILOLES AS CHEMICAL SENSORS FOR CARCINOGENIC CHROMIUM(VI) AND ARSENIC(V)

    Science.gov (United States)

    The chief goal is to develop new selective solid state sensors for carcinogenic and toxic chromium(VI) and arsenic(V) in water based on redox quenching of the luminescence from nanostructured porous silicon and polysiloles.

  16. Low temperature reduction of hexavalent chromium by a microbial enrichment consortium and a novel strain of Arthrobacter aurescens

    Directory of Open Access Journals (Sweden)

    Thompson Vicki S

    2006-01-01

    Full Text Available Abstract Background Chromium is a transition metal most commonly found in the environment in its trivalent [Cr(III] and hexavalent [Cr(VI] forms. The EPA maximum total chromium contaminant level for drinking water is 0.1 mg/l (0.1 ppm. Many water sources, especially underground sources, are at low temperatures (less than or equal to 15 Centigrade year round. It is important to evaluate the possibility of microbial remediation of Cr(VI contamination using microorganisms adapted to these low temperatures (psychrophiles. Results Core samples obtained from a Cr(VI contaminated aquifer at the Hanford facility in Washington were enriched in Vogel Bonner medium at 10 Centigrade with 0, 25, 50, 100, 200, 400 and 1000 mg/l Cr(VI. The extent of Cr(VI reduction was evaluated using the diphenyl carbazide assay. Resistance to Cr(VI up to and including 1000 mg/l Cr(VI was observed in the consortium experiments. Reduction was slow or not observed at and above 100 mg/l Cr(VI using the enrichment consortium. Average time to complete reduction of Cr(VI in the 30 and 60 mg/l Cr(VI cultures of the consortium was 8 and 17 days, respectively at 10 Centigrade. Lyophilized consortium cells did not demonstrate adsorption of Cr(VI over a 24 hour period. Successful isolation of a Cr(VI reducing organism (designated P4 from the consortium was confirmed by 16S rDNA amplification and sequencing. Average time to complete reduction of Cr(VI at 10 Centigrade in the 25 and 50 mg/l Cr(VI cultures of the isolate P4 was 3 and 5 days, respectively. The 16S rDNA sequence from isolate P4 identified this organism as a strain of Arthrobacter aurescens, a species that has not previously been shown to be capable of low temperature Cr(VI reduction. Conclusion A. aurescens, indigenous to the subsurface, has the potential to be a predominant metal reducer in enhanced, in situ subsurface bioremediation efforts involving Cr(VI and possibly other heavy metals and radionuclides.

  17. Thermal detoxification and bloating of chromium(VI) with bentonite

    International Nuclear Information System (INIS)

    This study stabilizes and bloats Cr(VI)-sorbed bentonite by heating at high temperature. Cr leaching decreases with increasing temperatures. Heating the sample at 1100 oC results in a non-detectable Cr concentration in the leachate, equivalent to a Cr leaching percent less than 0.001% (i.e., Cr TCLP concentration -1 of leachate). Morphology observed with a scanning electron microscopy indicates the occurrence of sintering of the sample heated at 1100 oC. The heated samples also show the occurrence of a vesicant process at 1100 oC. X-ray absorption spectroscopy results indicate that heating at 500 oC for 4 h can convert approximately 87% Cr(VI) into Cr(III) that is negligibly toxic; Cr2O3 was detected to be the most abundant Cr species. After heating at higher temperatures, namely 900-1100 oC, almost all doped Cr(VI) is reduced to Cr(III) as inferred from the height of the pre-edge peak of XANES spectra and/or from XANES simulation.

  18. Reduction of Cr(VI) to Cr(III) by green rust - sulphate

    Science.gov (United States)

    Skovbjerg, L.; Stipp, S.

    2003-04-01

    Chromium is widely used in industrial processes such as leather tanning, electro-plating and as colour pigments. Unfortunately, hexavalent chromium is both toxic and very soluble so it can be a problem for groundwater resources. Given the right redox conditions, however, Cr(VI) can be reduced to trivalent chromium, which is much less soluble and is an essential trace nutrient. Fe(II), an element common in soil and sediments under anaerobic conditions, can serve as a reducing agent for Cr(VI). Green Rust (GR) is a layered Fe(II),Fe(III)-hydroxide with various anions compensating charge in the interlayers. It is very effective in reducing Cr(VI) to Cr(III). GR exists in nature and is thought to be precursor for the formation of Fe(III)-oxides and oxyhydroxides at the redox boundary. It may be that the formation of GR is a key process in the effectiveness of reactive barriers for groundwater remediation that are based on Fe(0). The purpose of this work is to investigate the mechanisms controlling Cr(VI) reduction by Green Rust, to examine the effect of Cr adsorption and incorporation on GR morphology and composition, and to define the role of parameters such as interlayer anion, initial Cr(VI) concentration and time. We are using freshly synthesised material that has not been dried to avoid structural changes that may accompany dehydration and rehydration. X-Ray Diffraction (XRD) is used to characterise mineral structural changes and Atomic Force Microscopy (AFM), to examine changes in morphology as reactions take place. By adjusting the concentration of Cr(VI), we can control the rate of surface change and we can observe the nanoscale particles directly.

  19. Chromium reduction from slag on electromelting of stainless steel

    International Nuclear Information System (INIS)

    Specific features of chromium reduction from the slag on electromelting of stainless steel type Kh18N10T according to one- or two-slag procedure were studied. It was shown that one-slag melting technology allows double decrease of chromium losses in the form of incompletely reduced oxides. This occurs due to additional chemical reactions between metal and slag on their combined pouring into the ladle. 1 ref.; 3 figs

  20. Transcriptomic Analysis of Cultured Whale Skin Cells Exposed to Hexavalent Chromium [Cr(VI)

    OpenAIRE

    Pabuwal, Vagmita; Boswell, Mikki; Pasquali, Amanda; Wise, Sandra S.; Kumar, Suresh; Shen, Yingjia; Garcia, Tzintzuni; LaCerte, Carolyne; Wise, John Pierce; Warren, Wesley; Walter, Ronald B.

    2013-01-01

    Hexavalent chromium Cr(VI) is known to produce cytotoxic effects in humans and is a highly toxic environmental contaminant. Interestingly, it has been shown that free ranging sperm whales (Phyester macrocephalus) may have exceedingly high levels of Cr in their skin. Also, it has been demonstrated that skin cells from whales appear more resistant to both cytotoxicity and clastogenicity upon Cr exposure compared to human cells. However, the molecular genetic mechanisms employed in whale skin ce...

  1. A Comprehensive Review on Nickel (II And Chromium VI Toxicities - Possible Antioxidant (Allium Sativum Linn Defenses

    Directory of Open Access Journals (Sweden)

    Kusal K.Das

    2009-12-01

    Full Text Available The toxicity associated with nickel (II and chromium (VI is mainly due to generation of reactive oxygen species (ROS with subsequent oxidative deterioration of biological macromolecules. Both nickel and chromium can generate free radicals (FR directly from molecular oxygen in a two step process to produce superoxide anion and in continued process, produce highly toxic hydroxyl radical. The pro-oxidative effects are compounded by fact that they also inhibit antioxidant enzymes and deplete intracellular glutathione. Garlic (Allium sativum has played an important dietary and medicinal role throughout the history of mankind. Garlic has the potential to enhance the endogenous antioxidant status in nickel as well as hexavalent chromium induced lipid peroxidation in normal and diabetic rats.

  2. Coals as sorbents for the removal and reduction of hexavalent chromium from aqueous waste streams

    Energy Technology Data Exchange (ETDEWEB)

    Lakatos, J.; Brown, S.D.; Snape, C.E. [University of Miskolc, Miskolc (Hungary). Dept. of Analytical Chemistry

    2002-03-01

    The aim of this study is to demonstrate the potential of coals as a low-cost reactive barrier material for environmental protection applications, with the ability to prevent leaching of toxic Cr(VI) and other transition metals. Depending upon the type of ion and the surface functionalities, the uptake can involve ion sorption, ion exchange, chelation and redox mechanisms with the surface functionalities being considered as partners in electron transfer processes. The capacity for Cr(VI) uptake of low rank coals and oxidized bituminous coals has been found to lie within the range 02-0.6 mM g{sup -1}. Air oxidation of bituminous coals can increase their Cr(VI) removal capacities. The effect of air oxidation of coals on uptake capacity was more pronounced for Cr(VI) than Cr(III) but less than for Hg(II) and the other ions (Ca{sup 2+}, Ba{sup 2+}, Zn{sup 2+}, Cd{sup 2}) investigated. As previously found for Hg(II), redox mechanisms plays an important role in Cr(VI) uptake, with resultant Cr(III) is exchanged back into solution by hydrogen ions, but some of the sorbed chromium is irreversibly bound to the coal. The reduction of Cr(VI) alone is often considered a satisfactory solution in view of Cr(III) being essentially nontoxic. 56 refs., 11 figs., 1 tab.

  3. Adsorption Studies of Chromium(VI) on Activated Carbon Derived from Mangifera indica (Mango) Seed Shell

    Science.gov (United States)

    Mise, Shashikant; Patil, Trupti Nagendra

    2015-09-01

    The removal of chromium(VI) from synthetic sample by adsorption on activated carbon prepared from Mangifera indica (mango) seed shell have been carried out at room temperature 32 ± 1 °C. The removal of chromium(VI) from synthetic sample by adsorption on two types of activated carbon, physical activation and chemical activation (Calcium chloride and Sodium chloride), Impregnation Ratio's (IR) 0.25, 0.50, 0.75 for optimum time, optimum dosages and variation of pH were studied. It is observed that contact time differs for different carbons i.e. for physically and chemically activated carbons. The contact time decreases for chemically activated carbon compared to the physically activated carbon. It was observed that as dosage increases the adsorption increased along with the increase in impregnation ratio. It was also noted that as I.R. increases the surface area of Mangifera indica shell carbon increased. These dosage data were considered in the construction of isotherms and it was found that adsorption obeys Freundlich Isotherm and does not obey Langmuir Isotherm. The maximum removal of chromium (VI) was obtained in highly acidic medium at a pH of 1.50.

  4. Optimization of chromium(VI biosorption using gooseberry seeds by response surface methodology

    Directory of Open Access Journals (Sweden)

    J. Aravind

    2016-01-01

    Full Text Available The current investigation presents the role of gooseberry (Phyllanthus acidus seeds as an effective biosorbent for remediating chromium (VI, a toxic heavy metal pollutant commonly found in effluents from tanneries and relevant industries. Biosorption was affected by pH, temperature and initial metal concentration. Furthermore, there is a need to understand the holistic effect of all variables to ascertain the best possible conditions for adsorption, therefore, these factors were considered and a total of 17 trials were run according to the Box Behnken design. Quadratic model had maximum R2 value (0.9984 and larger F value (1109.92. From the Analysis Of Variance table and R2 value, quadratic model was predicted to be the significant model with the best fit to the generated experimental data. The optimal parameters obtained from the contour plot for the maximum removal of chromium(VI were initial metal concentration of 60 mg/L, pH value of 2, and temperature of 27°C. Under these conditions, maximum removal of 92% was obtained. Thus this biosorbent substantially eliminates chromium(VI under optimized conditions, enabling its use in larger scale.

  5. Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Kamakura, Nao, E-mail: minnie04_tb@yahoo.co.jp; Inui, Tetsuo; Kitano, Masaru; Nakamura, Toshihiro

    2014-03-01

    A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac){sub 3}) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac){sub 3} and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac){sub 3} was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L{sup −1} nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L{sup −1} nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac){sub 3} using infrared spectroscopy. The eluate of Cr(acac){sub 3} was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac){sub 3} aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac){sub 3} exhibited desirable results (96.0%–107%) when 5 μg of each species (50 μg L{sup −1}) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac){sub 3} was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively). - Highlights: • A determination method of Cr(III), Cr(VI), and Cr(III) acetylacetonate in water was developed. • The combination of ion-exchange resin disks with metal furnace AAS was used. • No effect of humic acid on the recovery of Cr(III) acetylacetonate was

  6. Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

    International Nuclear Information System (INIS)

    A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L−1 nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L−1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%–107%) when 5 μg of each species (50 μg L−1) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively). - Highlights: • A determination method of Cr(III), Cr(VI), and Cr(III) acetylacetonate in water was developed. • The combination of ion-exchange resin disks with metal furnace AAS was used. • No effect of humic acid on the recovery of Cr(III) acetylacetonate was observed. • The proposed method enabled the determination of three Cr

  7. Hexavalent chromium reduction and energy recovery by using dual-chambered microbial fuel cell.

    Science.gov (United States)

    Gangadharan, Praveena; Nambi, Indumathi M

    2015-01-01

    Microbial fuel cell (MFC) technology is utilized to treat hexavalent chromium (Cr(VI)) from wastewater and to generate electricity simultaneously. The Cr(VI) is bioelectrochemically reduced to non-toxic Cr(III) form in the presence of an organic electron donor in a dual-chambered MFC. The Cr(VI) as catholyte and artificial wastewater inoculated with anaerobic sludge as anolyte, Cr(VI) at 100 mg/L was completely removed within 48 h (initial pH value 2.0). The total amount of Cr recovered was 99.87% by the precipitation of Cr(III) on the surface of the cathode. In addition to that 78.4% of total organic carbon reduction was achieved at the anode chamber within 13 days of operation. Furthermore, the maximum power density of 767.01 mW/m² (2.08 mA/m²) was achieved by MFCs at ambient conditions. The present work has successfully demonstrated the feasibility of using MFCs for simultaneous energy production from wastewater and reduction of toxic Cr(VI) to non-toxic Cr(III). PMID:25714633

  8. Reduction of Cr(VI) and survival in Cr-contaminated sites by Caulobacter crescentus

    Science.gov (United States)

    Hu, P.; Chakraborty, R.; Brodie, E. L.; Andersen, G. L.; Hazen, T. C.

    2008-12-01

    The Caulobacter spp. is known to be able to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Recent studies have shown that Caulobacter crescentus can grow in chemically defined medium containing up to 1 mM uranium. Whole-genome transcriptional analysis and electron microscopic imaging of heavy metal stresses in Caulobacter crescentus also provided insight and evidence that the bacterium used an array of defensive mechanisms to deal with heavy metal stresses. In addition to up-regulated enzymes protecting against oxidative stress, DNA repair and down-regulated potential chromium transport, one of the major gene groups respond to chromium stress is "electron transport process and cytochrome oxidases", including cytochrome c oxidases, raising the possibility that the cells can employ the cytochromes to reduce chromium. Analysis of the microbial community at the chromium contaminated DOE site at Hanford, WA revealed the presence of Caulobacter spp. As an oligotroph, Caulobacter can play a significant role in chromium reduction in the environment where the nutrients are limited. This result was confirmed by both 16S rDNA based microarray (Phylochip) as well as by MDA-based clone library data. Based on these results we further investigated the capability of this organism to reduce Cr(VI) using the well known model strain Caulobacter crescentus CB15N. Preliminary cell suspension experiments were set up with glucose as the electron donor and Cr(VI) as the electron acceptor in phosphate based M2 salts buffer. After 22 hours almost 27% of Cr(VI) was reduced in the incubations containing active cells relative to the controls containing heat killed cells. Also, in another set of controls with no electron acceptor added, cells showed no increase in cell density during that time demonstrating that the reduction of Cr(VI) by cells of Caulobacter was due to biological activity. Future experiments will investigate the components

  9. Biosorption of chromium(VI) ion from aqueous solutions using walnut, hazelnut and almond shell.

    Science.gov (United States)

    Pehlivan, Erol; Altun, Türkan

    2008-06-30

    The potential to remove Cr(VI) ion from aqueous solutions through biosorption using, the shells of Walnut (WNS) (Juglans regia), Hazelnut (HNS) (Corylus avellana) and Almond (AS) (Prunus dulcis) was investigated in batch experiments. The equilibrium adsorption level was determined to be a function of the solution contact time and concentration. Kinetic experiments revealed that the dilute chromium solutions reached equilibrium within 100 min. The biosorptive capacity of the shells was dependent on the pH of the chromium solution, with pH 3.5 being optimal. Adsorption of Cr(VI) ion uptake is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.5, depending on the biomaterial, that correspond to equilibrium pH values of 3.5 for (WNS), 3.5 for (HNS) and 3.2 for (AS). The adsorption data fit well with the Langmuir isotherm model. The sorption process conformed to the Langmuir isotherm with maximum Cr(VI) ion sorption capacities of 8.01, 8.28, and 3.40 mg/g for WNS, HNS and AS, respectively. Percentage removal by WNS, HNS and AS was 85.32, 88.46 and 55.00%, respectively at a concentration of 0.5 mM. HNS presented the highest adsorption capacities for the Cr(VI) ion. PMID:18179865

  10. Chromium(VI) stimulates Fyn to initiate innate immune gene induction in human airway epithelial cells

    Science.gov (United States)

    Nemec, Antonia A.; Zubritsky, Lindsey M.; Barchowsky, Aaron

    2009-01-01

    Mechanisms for pathogenic metal signaling in airway injury or disease promotion are poorly understood. It is widely believed that one mechanism for pathogenic and possible carcinogenic effects of inhaled chromium (Cr(VI)) is inhibition of inducible gene transactivation. However, we recently reported that Cr(VI) inhibition of Sp1-dependent transactivation required signal transducer and activator of transcription 1 (STAT1)-dependent expression of an inhibitory protein in airway epithelium. Thus, Cr(VI) exposures can induce genes and we hypothesized this induction resulted from Cr(VI) signaling through an innate immune-like STAT1-dependent pathway initiated by Fyn. Exposure of human airway epithelial (BEAS-2B) cells to Cr(VI) selectively transactivated STAT-responsive interferon-stimulated response element (ISRE) and induced ISRE-driven transactivation of interferon regulatory factor 7 (IRF7), without affecting the gamma interferon-activated site (GAS)-driven IRF1 expression. Cr(VI)-induced IRF7 was absent or greatly reduced in cells that lacked STAT1, were treated with the Src family kinase inhibitor, PP2, or lacked Fyn. Expressing Fyn, but not Src, in mouse embryonic fibroblasts cells null for Src, Yes, and Fyn restored Cr(VI)-stimulated STAT1 tyrosine phosphorylation and IRF7 expression. Finally, shRNA knockdown of Fyn in BEAS-2B cells prevented Cr(VI)-activated STAT1 transactivation of IRF7. These data support a novel mechanism through which Cr(VI) stimulates Fyn to initiate interferon-like signaling for STAT1-dependent gene transactivation. PMID:19994902

  11. Determination of chromium(III), chromium(VI), manganese(II) and manganese(VII) by EDXRF method

    International Nuclear Information System (INIS)

    This paper describes EDXRF, a quick, sensitive and selective method for determining Cr(III), Cr(VI), Mn(II) and Mn(VII) in environmental and industrial liquid samples via preconcentration with ammonium pyrrolidine dithiocarbamate (APDC) and diethylenetriaminepentaacetic acid (DTPA). The effect of pH in the range of 3-11 on the recovery of Cr(III), Cr(VI), Mn(II) and Mn(VII) was investigated separately and in combination. The influence of organic matter, carbonate species and elements V and Fe was also tested on the recovery of each chromium and manganese species (separately/in combination) over the whole pH range in order to simulate conditions in natural waters that usually contain a certain amount of dissolved organic matter and carbonate ions. Characteristic of different species to create complexes with APDC and DTPA in the different pH ranges makes possible to separate those two species. All created complexes of Cr(III), Cr(VI), Mn(II) and Mn(VIII) with APDC and DTPA were characterised by IR spectroscopy.(author)

  12. Antioxidant Activity of Lawsonia inermis Extracts Inhibits Chromium(VI-Induced Cellular and DNA Toxicity

    Directory of Open Access Journals (Sweden)

    Gunjan Guha

    2011-01-01

    Full Text Available Hexavalent chromium Cr(VI is a very strong oxidant which consequently causes high cytotoxicity through oxidative stress. Prevention of Cr(VI-induced cellular damage has been sought in this study in aqueous and methanolic extracts of Lawsonia inermis Linn. (Lythraceae, commonly known as Henna. The extracts showed significant (P < .05 potential in scavenging free radicals (DPPH• and ABTS•+ and Fe3+, and in inhibiting lipid peroxidation. DNA damage caused by exposure of pBR322 to Cr(VI-UV is markedly inhibited by both extracts in varying degrees. A distinct decline in Cr(VI-induced cytotoxicity was noticed in MDA-MB-435S (human breast carcinoma cells with an increase in dosage of both extracts individually. Furthermore, both extracts proved to contain a high content of phenolic compounds which were found to have a strong and significant (P < .05 positive correlation to the radical scavenging potential, lipid peroxidation inhibition capacity and cyto-protective efficiency against Cr(VI-induced oxidative cellular damage. HPLC analysis identified some of the major phenolic compounds in both extracts, which might be responsible for the antioxidant potential and the properties of DNA and cyto-protection. This study contributes to the search for natural resources that might yield potent therapeutic drugs against Cr(VI-induced oxidative cell damage.

  13. Biodegradation of the metallic carcinogen hexavalent chromium Cr(VI by an indigenously isolated bacterial strain

    Directory of Open Access Journals (Sweden)

    Das Alok

    2010-01-01

    Full Text Available Background : Hexavalent chromium [Cr(VI], a potential mutagen and carcinogen, is regularly introduced into the environment through diverse anthropogenic activities, including electroplating, leather tanning, and pigment manufacturing. Human exposure to this toxic metal ion not only causes potential human health hazards but also affects other life forms. The World Health Organization, the International Agency for Research on Cancer, and the Environmental Protection Agency have determined that Cr(VI compounds are known human carcinogens. The Sukinda valley in Jajpur District, Orissa, is known for its deposit of chromite ore, producing nearly 98% of the chromite ore in India and one of the prime open cast chromite ore mines in the world (CES, Orissa Newsletter. Materials and Methods: Our investigation involved microbial remediation of Cr(VI without producing any byproduct. Bacterial cultures tolerating high concentrations of Cr were isolated from the soil sample collected from the chromite-contaminated sites of Sukinda, and their bioaccumulation properties were investigated. Strains capable of growing at 250 mg/L Cr(VI were considered as Cr resistant. Results: The experimental investigation showed the maximum specific Cr uptake at pH 7 and temperature 30oC. At about 50 mg/L initial Cr(VI concentrations, uptake of the selected potential strain exceeded 98% within 12 h of incubation. The bacterial isolate was identified by 16S rRNA sequencing as Brevebacterium casei. Conclusion: Results indicated promising approach for microbial remediation of effluents containing elevated levels of Cr(VI.

  14. Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

    Science.gov (United States)

    Kamakura, Nao; Inui, Tetsuo; Kitano, Masaru; Nakamura, Toshihiro

    A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L- 1 nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L- 1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%-107%) when 5 μg of each species (50 μg L- 1) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively).

  15. Remoción de Cromo (VI por una Cepa de Paecilomyces sp Resistente a Cromato Removal of Chromium (VI in a Chromate-Resistant Strain of Paecilomyces sp

    Directory of Open Access Journals (Sweden)

    Juan F Cárdenas-González

    2011-01-01

    Full Text Available Se analizó la capacidad de remoción de Cr(VI de una cepa de Paecilomyces sp. Cuando el hongo se incubó en medio mínimo con glucosa y otras fuentes de carbono comerciales y de bajo costo, como azúcar moscabada y piloncillo ó glicerol, en presencia de 50 mg/L de Cr(VI, removió totalmente el Cr(VI. La reducción a Cr(III ocurre en el medio de cultivo después de 7 días de incubación a 28°C, pH 4.0, y un inoculo de 38 mg. El hongo también redujo eficientemente la concentración de Cr(VI a partir de tierra contaminada. Los resultados indican que la cepa de Paecilomyces sp tiene la capacidad de reducir Cr(VI a Cr(III, y por lo tanto puede utilizarse para eliminar la contaminación por Cr(VI.The ability to reduce chromium (VI by a fungal strain of Paecilomyces sp was studied. When it was incubated in minimal medium with glucose and other inexpensive commercial carbon sources such as unrefined and brown sugar or glycerol, in the presence of 50 mg/L of Cr(VI, the strain caused complete removal of Cr(VI. The reduction to Cr (III occurs in the growth medium after 7 days of incubation, at 28°C, pH 4.0, and inoculum of 38 mg. Also, the fungi efficiently reduced the concentration of Cr(VI from contaminated soil wastes. The results indicate that the fungal strain of Paecilomyces sp has the capacity of reducing Cr(VI to Cr(III, and therefore it could be useful for the removal of Cr(VI pollution.

  16. Spectrophotometric Quantification of Toxicologically Relevant Concentrations of Chromium(VI in Cosmetic Pigments and Eyeshadow Using Synthetic Lachrymal Fluid Extraction

    Directory of Open Access Journals (Sweden)

    Sarah Wurster

    2012-01-01

    Full Text Available Chromium(VI salts are possible contaminants of the chromium(III pigments used as colorants in eyeshadow preparations. The use of products containing these contaminants poses acute risks for sensitization and contact allergies. Chromium(VI compounds are also classified as carcinogenic to humans (IARC group 1. An analytical method to analyse trace levels of chromium(VI in eyeshadow was developed in this study. The method is based on an extraction of the chromium(VI from the sample using a maximum extraction with alkali and additionally with synthetic lachrymal fluid to simulate physiological conditions. Following derivatization with 1,5-diphenylcarbazide, the extracted chromium(VI is then quantified by spectrophotometry (540 nm. Validation tests indicated a method standard deviation (inter- and intraday of 8.7% and a linear range up to 25 mg/kg. The average recovery was 107.9%, and the detection limit was 2.7 mg/kg. The applicability of the procedure was confirmed by the analysis of pigments and authentic eyeshadow matrices.

  17. Synthesis and characterization of polyaniline/zeolite nanocomposite for the removal of chromium(VI from aqueous solution

    Directory of Open Access Journals (Sweden)

    Abdulsalam A. Shyaa

    2015-01-01

    Batch adsorption experiments were used to investigate the effect of various experimental parameters on the equilibrium adsorption of chromium(VI on PANI/zeolite nanocomposite. The adsorption characteristics of the composite toward Cr(VI in dilute aqueous solution were followed spectrophotometrically. The effect of contact time, size of the sorbent and the concentration of Cr(VI in solution on the metal uptake behavior of the composite were studied. It has been observed that the capacity of chromium adsorption on PANI/zeolite increases with initial metal concentration, the metal ion adsorption on surfactant is well represented by the Freundlich isotherm.

  18. Removal of Cr(VI) from aqueous solution by flocculant with the capacity of reduction and chelation

    International Nuclear Information System (INIS)

    Highlights: ► We report a novel flocculant with the properties of reduction and chelation for Cr. ► The removal of Cr(VI) by the flocculant depends highly on pH value. ► Some coexisting ions inhibit Cr (VI) removal, but promote total Cr removal. ► Cr and turbidity can be removed simultaneously in the treated wastewater. ► The interaction mechanism is investigated by FTIR and SEM. -- Abstract: A novel agent polyethyleneimine-sodium xanthogenate (PEX) with the multifunction of reduction, chelation, flocculation and precipitation was synthesized by using polyethyleneimine (PEI), carbon disulfide (CS2), and sodium hydroxide (NaOH). The effects of different important parameters, such as pH value, initial Cr(VI) concentration, coexisting ions and turbidity etc., on the removal of chromium from aqueous solution by PEX were investigated in flocculation experiments. The experiments results demonstrated that PEX could efficiently remove Cr(VI) and total Cr (Cr(VI) + Cr(III)) in strongly acidic media. It was proved that the presence of coexisting ions (Na+, Ca2+, F−, Cl−, and SO42−) in the solution had a little influence on the removal of chromium. Furthermore, it was conformed that Cr(VI) ions and turbidity could be simultaneously removed when water samples contained both Cr(VI) ions and turbidity. Finally, the mechanism of interaction between chromium and PEX was further confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results reveal that dithiocarboxylic acid groups on PEX macromolecule play a major role in Cr(VI) reduction and Cr(III) chelation, and the flocs formation is attributed to the interparticle bridging mechanism of PEX

  19. Removal of Cr(VI) from aqueous solution by flocculant with the capacity of reduction and chelation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gang, E-mail: gangw99@163.com [School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070 (China); Chang, Qing; Han, Xiaoting; Zhang, Mingyue [School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu 730070 (China)

    2013-03-15

    Highlights: ► We report a novel flocculant with the properties of reduction and chelation for Cr. ► The removal of Cr(VI) by the flocculant depends highly on pH value. ► Some coexisting ions inhibit Cr (VI) removal, but promote total Cr removal. ► Cr and turbidity can be removed simultaneously in the treated wastewater. ► The interaction mechanism is investigated by FTIR and SEM. -- Abstract: A novel agent polyethyleneimine-sodium xanthogenate (PEX) with the multifunction of reduction, chelation, flocculation and precipitation was synthesized by using polyethyleneimine (PEI), carbon disulfide (CS{sub 2}), and sodium hydroxide (NaOH). The effects of different important parameters, such as pH value, initial Cr(VI) concentration, coexisting ions and turbidity etc., on the removal of chromium from aqueous solution by PEX were investigated in flocculation experiments. The experiments results demonstrated that PEX could efficiently remove Cr(VI) and total Cr (Cr(VI) + Cr(III)) in strongly acidic media. It was proved that the presence of coexisting ions (Na{sup +}, Ca{sup 2+}, F{sup −}, Cl{sup −}, and SO{sub 4}{sup 2−}) in the solution had a little influence on the removal of chromium. Furthermore, it was conformed that Cr(VI) ions and turbidity could be simultaneously removed when water samples contained both Cr(VI) ions and turbidity. Finally, the mechanism of interaction between chromium and PEX was further confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results reveal that dithiocarboxylic acid groups on PEX macromolecule play a major role in Cr(VI) reduction and Cr(III) chelation, and the flocs formation is attributed to the interparticle bridging mechanism of PEX.

  20. Determination of Cr(III, Cr(VI and total chromium in atmospheric aerosol samples

    Directory of Open Access Journals (Sweden)

    Catrambone M.

    2013-04-01

    Full Text Available This study addresses the optimization and validation of an analytical method based on the ultrasound-assisted extraction of soluble Cr from atmospheric particulate matter (PM and subsequent determination of Cr(III and Cr(VI by catalytic adsorptive stripping voltammetry (CAdSV by using diethylenetriammino pentaacetic acid (DTPA as complexing agent in the presence of nitrate. We evaluated the influence of various filter materials and of extracting conditions and validated the method on both reference material and real PM10 samples. The accuracy of total extractable Cr determination was checked by parallel ICP-OES measurements. The determination of total chromium was performed by ED-XRF. Results of field campaigns carried out in two industrial areas (North Italy and Tunis and at a peri-urban site near Rome are reported. At the peri-urban site, the total Cr concentration in PM10 ranged from 2 to 5 ng/m3, with a soluble fraction of 5-13%, and Cr(VI concentration was always below the detection limits (50 pg/m3. In the industrial area of Northern Italy, total Cr concentration ranged between 6 and 11 ng/m3, the soluble fraction was about 11-28% and detectable amounts of Cr(VI were found, with a Cr(VI/Cr(III ratio ranging from 0.5 to 2.5. A further increase of Cr(VI concentration was evidenced at the industrial site of Tunis, where the total Cr concentration ranged from 6 to 26 ng/m3, with a soluble fraction accounting for about 8-44% and a Cr(VI/Cr(III ranging from 1.6 to 3.6. The results of size-segregated samples, collected in Northen Italy by a 10-stage cascade impactor, indicate a relevant fine fraction of Cr(VI, with Cr(VI/Cr(III ratios increasing with the decrease of particle size.

  1. Bioelectrochemical Chromium(VI) Removal in Plant-Microbial Fuel Cells.

    Science.gov (United States)

    Habibul, Nuzahat; Hu, Yi; Wang, Yun-Kun; Chen, Wei; Yu, Han-Qing; Sheng, Guo-Ping

    2016-04-01

    Plant-microbial fuel cell (PMFC) is a renewable and sustainable energy technology that generates electricity with living plants. However, little information is available regarding the application of PMFC for the remediation of heavy metal contaminated water or soil. In this study, the potential for the removal of heavy metal Cr(VI) using PMFC was evaluated, and the performance of the PMFC at various initial Cr(VI) contents was investigated. The Cr(VI) removal efficiency could reached 99% under various conditions. Both the Cr(VI) removal rates and the removal efficiencies increased with the increasing initial Cr(VI) concentration. Furthermore, the long-term operation of the PMFC indicated that the system was stable and sustainable for Cr(VI) removal. The mass balance results and XPS analysis results demonstrate that only a small amount of soluble Cr(III) remained in the PMFC and that most Cr(III) precipitated in the form of the Cr(OH)3(s) or was adsorbed onto the electrodes. The PMFC experiments of without acetate addition also show that plants can provide carbon source for MFC through secrete root exudates and bioelectrochemical reduction of Cr(VI) was the main mechanism for the Cr(VI) removal. These results extend the application fields of PMFC and might provide a new insight for Cr(VI) removal from wastewater or soil. PMID:26962848

  2. Chromium(VI) adsorption from aqueous solution onto Moroccan Al-pillared and cationic surfactant stevensite.

    Science.gov (United States)

    Benhammou, Abdelaziz; Yaacoubi, Abdelrani; Nibou, Lahbib; Tanouti, Boumediane

    2007-02-01

    Batch adsorption of the chromium(VI) onto Moroccan stevensite pillared by Keggin aluminium hydroxypolycation (Al-stevensite) and cationic surfactant cetyltrimethylammoniumbromide (CTA-stevensite) was investigated. The results showed that the CTA-stevensite has a higher affinity than that of Al-stevensite for chromium(VI) adsorption. The adsorption capacities for natural stevensite, Al-stevensite and CTA-stevensite calculated according to the Dubinin-Kaganer-Radushkevich isotherm (DKR) are 13.7, 75.4 and 195.6mmolkg(-1), respectively. The study of the pH effect showed that the optimal range corresponding to the Cr(VI) maximum adsorption on Al-stevensite is pH 3.5-6 and that on CTA-stevensite is pH 2-6. The adsorption rates evaluated according to the pseudo-second-order model are 7.2, 207.2 and 178.5mmolkg(-1)min(-1) for the natural stevensite, Al-stevensite and CTA-stevensite, respectively. The low values of the adsorption energy calculated by (DKR) suggest that anion exchange is the main mechanism that governs the chromate adsorption. PMID:16876943

  3. The oxidation and reduction of chromium of stainless steels in an eletric arc furnace

    OpenAIRE

    Arh, B.; F. Tehovnik

    2011-01-01

    The oxidation of chromium during the elaboration of stainless steels occurs with oxygen in solution blown inthe melt and with oxides in the slag. A higher content of silicon in the furnace charge decreases the extent of oxidation of chromium, however, the efficient reduction of chromium from the slag is of essential importance for a minimal loss of chromium. In this survey, the theory of the oxidation of chromium, its reduction from the slag and the conditions for the formation of foaming sla...

  4. Liquid-liquid extraction of chromium (VI) from sulfuric acid solutions using tri-n-dodecylamine/kerosene

    International Nuclear Information System (INIS)

    Extraction of chromium (VI) from sulfuric acid solutions with tri-n-dodecylamine containing octanol-1 as a modifier in kerosene was investigated. All parameters influencing the extraction of chromium (VI) (time of agitation, concentrations of chromium (VI), sulfuric acid, tri-n-dodecylamine and temperature) were studied. Forst of all, tri-n-dodecylamine reacts with sulfuric acid to form tri-n-dodecylamine sulfate and bisulfate salts, then, dichromate ions is extracted by amine bisulfate. The mathematical treatment of the obtained date enabled us to calculate the formation of equilibrium constant of (TDAH)2SO4 TDAHHSO4 and (TDAH)2 Cγ2O7 at 25 Centigrade and have been found to be K1=109.642(14/mol4), K2= 10-0.899(L/mol) and Kex 1010.55 respectively. Stripping of more than 99% of chromium (VI) from the organic phase of tri-n-dodecylamine/kerosene can be easily achieved in two stages using 0.05 M sodium carbonate solution. The synergistic effect of tri-n-butylphosphate and tri-n-octylphosphine oxide on the extraction of chromium (VI) were also studied. (author)

  5. Photocatalytic reduction of hexavalent chromium at gold nanoparticles modified titania nanotubes

    International Nuclear Information System (INIS)

    N-[3-(Trimethoxysilyl)propyl]ethylenediamine (EDAS) silicate supported titanium dioxide nanotubes-gold ((TiO2 NTs-Au)NCM) nanocomposite material (EDAS/(TiO2 NTs-Au)NCM) was prepared by deposition–precipitation method and characterized by diffuse reflectance spectra, X-ray diffraction pattern, Brunauer–Emmett–Teller surface area analysis, transmission electron micrographs, scanning electron micrographs and energy-dispersive X-ray spectra analysis. The photocatalytic activity of the EDAS/(TiO2 NTs-Au)NCM in the film form was investigated towards the reduction of toxic hexavalent chromium (Cr(VI)) into trivalent chromium (Cr(III)) in the presence of oxalic acid as an electron donor. The EDAS/(TiO2 NTs-Au)NCM film exhibited higher photocatalytic activity when compared to the photocatalytic activities of pristine TiO2 nanoparticles and TiO2 nanotubes (TiO2 NTs) which can be attributed to the effective photoinduced interfacial charge transfer from the (TiO2 NTs-Au)NCM to Cr(VI) through Au nanoparticles (Aunps). The Aunps present in the TiO2 NTs act as an electron sink for the photogenerated electrons that minimizes the charge recombination process at the TiO2 NTs. The Aunps on the TiO2 NTs surface facilitates the transfer of photogenerated electrons to the Cr(VI) leading to the formation of Cr(III) ions. - Highlights: • Gold modified titania nanotubes are used to design solid-phase photocatalyst. • Gold nanoparticles deposition increases the surface area of titania nanotubes. • Gold on titania nanotubes improves the photocatalytic reduction of Cr(VI). • The holes produced at the titania nanotubes are scavenged by oxalic acid. • Gold modified titania nanotubes is a potential candidate for treatment of heavy metals

  6. Selective extraction of chromium (VI) from multicomponent acidic solutions by emulsion liquid membranes using tributhylphosphate as carrier

    International Nuclear Information System (INIS)

    The facilitated extraction of Cr(VI) through an emulsion liquid membrane (ELM) was investigated, using tributyl phosphate (TBP) as mobile carrier. The emulsion liquid membrane phase consists of kerosene as diluent, TBP as carrier, SPAN 80 as surfactant and (NH4)2CO3 solution as stripping phase. The extraction of chromium (VI) has been studied under various experimental conditions and have been determined the influences of surfactant concentration, extractant concentration, stripping solution base concentration, mixing speed, phase ratio, treatment ratio, chromium (VI) and HCl concentrations of the feed solution. It was observed that the extraction rate of Cr(VI) was affected by changes of surfactant concentration, extractant concentration, stripping solution base concentration, and mixing speed. The results obtained showed that by appropriate selection of the extraction and stability conditions, nearly all of chromium (VI) ions present in the feed solution were extracted within 2-4 min. The separation factors of chromium (VI) with respect to cobalt, nickel, copper, cadmium and zinc ions, based on initial feed concentration, have experimentally determined.

  7. "Involvement of metabolic reactive intermediate Cr (IV in Chromium (VI cytotoxic effects "

    Directory of Open Access Journals (Sweden)

    Pourahmad J

    2001-08-01

    Full Text Available Addition of Cr VI (dichromate to isolated rat hepatocytes results in rapid glutathione oxidation, reactive oxygen species (ROS formation, lipid peroxidation, decreased mitochondrial membrane potential and lysosomal membrane rupture before hepatocyte lysis occurred. Cytotoxicity was prevented by ROS scavengers, antioxidants, and glutamine (ATP generator. Hepatocyte dichlorofluorescin oxidation to dichlorofluorescein (DCF to determine ROS formation was inhibited by mannitol (a hydroxyl radical scavenger or butylated hydroxyanisole and butylated hydroxytoluene (antioxidants. The Cr VI reductive mechanism required for toxicity is not known. Cytochrome P450 inhibitors, Particularly CYP 2E1 inhibitors, but not inhibitors of DT diaphorase or glutathione reductase also prevented cytotoxicity. This suggests that P450 reductase and/or reduced cytochrome P450 contributes to Cr VI reduction to Cr IV. Glutathione depleted hepatocytes were resistant to Cr (VI toxicity and much less dichlorofluorescin oxidation occurred. Reduction of dichromate by glutathione or cysteine in vitro was also accompanied by oxygen uptake and was inhibited by Mn II (a Cr IV reductant. Cr VI induced cytotoxicity and ROS formation was also inhibited by Mn II, which suggests that, Cr IV and Cr IV GSH mediate "ROS" formation in isolated hepatocytes. In conclusion Cr VI cytotoxicity is associated with mitochondrial/lysosomal toxicity by the metabolic reactive intermediate Cr IV and “ROS”.

  8. Characterization of Physical, Thermal and Structural Properties of Chromium (VI) Oxide Powder: Impact of Biofield Treatment

    OpenAIRE

    Trivedi, Mahendra; Branton, Alice; Trivedi, Dahryn; Nayak, Gopal

    2015-01-01

    Chromium (VI) oxide (CrO3) has gained extensive attention due to its versatile physical and chemical properties. The objective of the present study was to evaluate the impact of biofield treatment on physical, thermal and structural properties of CrO3 powder. In this study, CrO3 powder was divided into two parts i.e. control and treatment. Control part was remained as untreated and treated part received Mr. Trivedi’s biofield treatment. Subsequently, control and treated CrO3 samples were char...

  9. Hexavalent Chromium (Cr(VI)) Down-Regulates Acetylation of Histone H4 at Lysine 16 through Induction of Stressor Protein Nupr1

    Science.gov (United States)

    Chen, Danqi; Kluz, Thomas; Fang, Lei; Zhang, Xiaoru; Sun, Hong; Jin, Chunyuan; Costa, Max

    2016-01-01

    The environmental and occupational carcinogen Hexavalent Chromium (Cr(VI)) has been shown to cause lung cancer in humans when inhaled. In spite of a considerable research effort, the mechanisms of Cr(VI)-induced carcinogenesis remain largely unknown. Nupr1 (nuclear protein 1) is a small, highly basic, and unfolded protein with molecular weight of 8,800 daltons and is induced by a variety of stressors. Studies in animal models have suggested that Nupr1 is a key factor in the development of lung and pancreatic cancers, with little known about the underlying molecular mechanisms. Here we report that the level of Nupr1 is significantly increased in human bronchial epithelial BEAS2B cells following exposure to Cr(VI) through epigenetic mechanisms. Interestingly, Cr(VI) exposure also results in the loss of acetylation at histone H4K16, which is considered a ‘hallmark’ of human cancer. Cr(VI)-induced reduction of H4K16 acetylation appears to be caused by the induction of Nupr1, since (a) overexpression of Nupr1 decreased the levels of both H4K16 acetylation and the histone acetyltransferase MOF (male absent on the first; also known as Kat8, Myst 1), which specifically acetylates H4K16; (b) the loss of acetylation of H4K16 upon Cr(VI) exposure is greatly compromised by knockdown of Nupr1. Moreover, Nupr1-induced reduction of H4K16 acetylation correlates with the transcriptional down-regulation at several genomic loci. Notably, overexpression of Nupr1 induces anchorage-independent cell growth and knockdown of Nupr1 expression prevents Cr(VI)-induced cell transformation. We propose that Cr(VI) induces Nupr1 and rapidly perturbs gene expression by downregulating H4K16 acetylation, thereby contributing to Cr(VI)-induced carcinogenesis. PMID:27285315

  10. Hexavalent Chromium (Cr(VI)) Down-Regulates Acetylation of Histone H4 at Lysine 16 through Induction of Stressor Protein Nupr1.

    Science.gov (United States)

    Chen, Danqi; Kluz, Thomas; Fang, Lei; Zhang, Xiaoru; Sun, Hong; Jin, Chunyuan; Costa, Max

    2016-01-01

    The environmental and occupational carcinogen Hexavalent Chromium (Cr(VI)) has been shown to cause lung cancer in humans when inhaled. In spite of a considerable research effort, the mechanisms of Cr(VI)-induced carcinogenesis remain largely unknown. Nupr1 (nuclear protein 1) is a small, highly basic, and unfolded protein with molecular weight of 8,800 daltons and is induced by a variety of stressors. Studies in animal models have suggested that Nupr1 is a key factor in the development of lung and pancreatic cancers, with little known about the underlying molecular mechanisms. Here we report that the level of Nupr1 is significantly increased in human bronchial epithelial BEAS2B cells following exposure to Cr(VI) through epigenetic mechanisms. Interestingly, Cr(VI) exposure also results in the loss of acetylation at histone H4K16, which is considered a 'hallmark' of human cancer. Cr(VI)-induced reduction of H4K16 acetylation appears to be caused by the induction of Nupr1, since (a) overexpression of Nupr1 decreased the levels of both H4K16 acetylation and the histone acetyltransferase MOF (male absent on the first; also known as Kat8, Myst 1), which specifically acetylates H4K16; (b) the loss of acetylation of H4K16 upon Cr(VI) exposure is greatly compromised by knockdown of Nupr1. Moreover, Nupr1-induced reduction of H4K16 acetylation correlates with the transcriptional down-regulation at several genomic loci. Notably, overexpression of Nupr1 induces anchorage-independent cell growth and knockdown of Nupr1 expression prevents Cr(VI)-induced cell transformation. We propose that Cr(VI) induces Nupr1 and rapidly perturbs gene expression by downregulating H4K16 acetylation, thereby contributing to Cr(VI)-induced carcinogenesis. PMID:27285315

  11. Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

    OpenAIRE

    Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J. G.

    2013-01-01

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. Th...

  12. Oxidative stress-related lung dysfunction by chromium(VI): alleviation by Citrus aurantium L.

    Science.gov (United States)

    Soudani, Nejla; Rafrafi, Moez; Ben Amara, Ibtissem; Hakim, Ahmed; Troudi, Afef; Zeghal, Khaled Mounir; Ben Salah, Hichem; Boudawara, Tahia; Zeghal, Najiba

    2013-06-01

    Chromium(VI), a very strong oxidant, causes high cytotoxicity through oxidative stress in tissue systems. Our study investigated the potential ability of ethanolic Citrus aurantium L., family Rutaceae extract, used as a nutritional supplement, to alleviate lung oxidative damage induced by Cr(VI). A high-performance liquid chromatography coupled with a mass spectrometer method was developed to separate and identify flavonoids in C. aurantium L. Six flavonoids were identified, as (1) poncirin, (2) naringin, (3) naringenin, (4) quercetin, (5) isosinensetin, and (6) tetramethyl-o-isoscutellarein. Adult Wistar rats, used in this study, were divided into six groups of six animals each: group I served as controls which received standard diet, group II received via drinking water K2Cr2O7 alone (700 ppm), groups III and IV were pretreated for 10 days with ethanol extract of C. aurantium L. at doses of 100 and 300 mg/kg body weight/day, respectively, and then K2Cr2O7 was administrated during 3 weeks, and groups V and VI received during 10 days only C. aurantium L. ethanol extract at doses of 100 and 300 mg/kg/day, respectively. Ethanol extract of C. aurantium L. was administered orally. Rats exposed to Cr(VI) showed in lung an increase in malondialdehyde and protein carbonyl levels and a decrease in sulflydryl content, glutathione, nonprotein thiol, and vitamins C and E levels. Decreases in enzyme activities such as in Na(+)K(+) ATPase, catalase, glutathione peroxidase, and superoxide dismutase were noted. Pretreatment with C. aurantium L. of chromium-treated rats ameliorated all biochemical parameters. Lung histological studies confirmed the biochemical parameters and the beneficial role of C. aurantium L. PMID:22972417

  13. Hexavalent chromium [Cr(VI)] removal by the electrochemical ion-exchange process.

    Science.gov (United States)

    Dharnaik, Amit Shivputra; Ghosh, Pranab Kumar

    2014-01-01

    In the present investigation, the performance of a laboratory-scale plate and frame-type electrochemical ion-exchange (EIX) cell on removal ofhexavalent chromium from synthetic wastewater containing 5 mg/l of Cr(VI) was evaluated under varying applied voltages. Ruthenium dioxide-coated titanium plate (RuO2/Ti) was used as anode and stainless steel plates as cathode. The EIX cell was run at different hydraulic retention time (HRT). Before using in the electrochemical cell, the capacity of ion-exchange resin was evaluated through kinetic and isotherm equilibrium tests in batch mode. The batch kinetic study result showed that the equilibrium time for effective ion exchange with resin is 2 h. The isotherm equilibrium data fit well to both Freundlich and Langmuir isotherms. Maximum capacity (qm) of resin calculated from Langmuir isotherm was 71.42 mg/g. Up to 99% of chromium removal was noticed in the EIX cell containing fresh resin at applied voltages of 10 V and higher. Migration of chromium ion to anode chamber was not noticed while performing the experiment with fresh resin. As high as 50% removal of chromium was observed from the middle chamber containing exhausted resin at an applied voltage of 25 V when the influent flow rate was maintained at 45 min of HRT. The performance of the reactor was increased to 72% when the influent flow rate was decreased to maintain at 90 min of HRT. Build-up of chromium in the anode chamber took place when exhausted resin was used in the process. PMID:25145180

  14. Phosphinic acid functionalized carbon nanotubes for sensitive and selective sensing of chromium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Deep, Akash, E-mail: dr.akashdeep@csio.res.in; Sharma, Amit L.; Tuteja, Satish K.; Paul, A.K.

    2014-08-15

    Highlights: • SWCNTs have been conjugated with bis(2,4,4-trimethylpentyl) phosphinic acid (PA/d). • SWCNT-PA/d adduct is demonstrated for electrochemical sensing of Cr(VI). • Linear response is obtained for 0.01–10 ppb Cr(VI). • Sensitivity and the limit of detection are 35 ± 4 nA/ppb and 0.01 ppb, respectively. • Proposed sensing of Cr(VI) is selective with respect to many other metals. - Abstract: Single-walled carbon nanotubes (SWCNTs) have been functionalized with a phosphinic acid derivative ‘bis(2,4,4-trimethylpentyl) phosphinic acid’ (PA/d). It has been achieved by treating the chlorinated SWCNTs with PA/d at 80 °C. Successful functionalization and different nanomaterial properties have been investigated by UV–vis–NIR, FTIR, Raman spectroscopy, AFM and FE-SEM. PA/d conjugated SWCNTs (CNT–PA) are dispersible in some common organic solvents, e.g. CH{sub 2}Cl{sub 2}, DMF, CHCl{sub 3}, and THF. The ‘CNT–PA’ complex was spin-casted on boron doped silicon wafer. Thus fabricated sensing electrode is demonstrated for sensitive and selective electrochemical sensing of chromium(VI) ions. A linear response is obtained over a wide range of Cr(VI) concentration (0.01–10 ppb). The sensor's sensitivity and the limit of detection are observed to be 35 ± 4 nA/ppb and 0.01 ppb, respectively. The practical utility of the proposed sensor is demonstrated by determining the Cr(VI) concentration in an industrial effluent sample and an underground water sample.

  15. Chromium(Ⅵ) Reduction in Wheat Rhizosphere

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Reduction of Cr(Ⅵ) to Cr(Ⅲ) were studied in a fresh wheat rhizosphere soil (Kuroboku, high humic andosol) pretreated with a basal fertilizer consisting of (NH4)2SO4, P2O5 and KH2PO4 and with K2Cr2O7 by using a rhizobox system. It was found that rhizosphere exerted a positive effect on Cr(Ⅵ) reduction.Part of the reason was the decrease of pH in the rhizosphere due to application of (NH4)2SO4, implying that application of physiologically acid fertilizers would reduce Cr(Ⅵ) toxicity to plants.

  16. Experimental and mathematical modeling studies on Cr(VI) reduction by CRB, SRB and IRB, individually and in combination.

    Science.gov (United States)

    Somasundaram, V; Philip, Ligy; Bhallamudi, S Murty

    2009-12-30

    Cr(VI) reduction studies were carried out with chromium reducing bacteria (CRB), sulphate reducing bacteria (SRB) and iron reducing bacteria (IRB), individually and in combination. Biokinetic parameters such as maximum specific growth rate (micro(max)), half saturation constant (K(s)), yield coefficient (Y(T)) and inhibition coefficient (K(i)) for individual cultures were evaluated. A mathematical model was proposed for simulating the chromium reduction, COD utilization and biomass growth, by individual cultures as well as by a combination of two or three different cultures, for different initial Cr(VI), SO(4)(2-) and Fe(III) concentrations. The biokinetic parameters evaluated from one set of experiments for individual cultures were utilized in all the validation studies. The performance of the mathematical model in terms of the dimensionless modified coefficient of efficiency (E) indicated that the proposed model simulates the system behavior very well. PMID:19692172

  17. Plutonium(VI) accumulation and reduction by lichen biomass: correlation with U(VI).

    Science.gov (United States)

    Ohnuki, Toshihiko; Aoyagi, Hisao; Kitatsuji, Yoshihiro; Samadfam, Mohammad; Kimura, Yasuhiko; William Purvis, O

    2004-01-01

    The uptake of plutonium(VI) and uranium(VI) by lichen biomass was studied in the foliose lichen Parmotrema tinctorum to elucidate the migration behavior of Pu and U in the terrestrial environment. Pu and U uptake by P. tinctorum averaged 0.040+/-0.010 and 0.055+/-0.015 g gdry (-1), respectively, after 96 h incubation with 4.0 x 10(14) mol 1(-1) Pu solutions of pH 3, 4 and 5. SEM observations showed that the accumulated Pu is evenly distributed on the upper and lower surfaces of P. tinctorum, in contrast to U(VI), which accumulated in both cortical and medullary layers. UV/VIS absorption spectroscopy demonstrates that a fraction of Pu(VI) in the solution is reduced to Pu(V) by the organic substances released from P. tinctorum, and the accumulated Pu on the surface is reduced to Pu(IV), while U(VI) keeps the oxidation state of VI. Since the solubility of Pu(IV) hydroxides is very low, reduced Pu(VI) does not penetrate to the medullary layers, but is probably precipitated as Pu(IV) hydroxides on the cortical lichen surface. It is concluded that the uptake and reduction of Pu(VI) by lichens is important to determine the mobilization and oxidation states of Pu in the terrestrial environment. PMID:15381325

  18. Chromium speciation in particulate matter samples (Cr(VI)/Cr(III) stability in solutions of leaching agents)

    International Nuclear Information System (INIS)

    Complete text of publication follows. In recent years extensive research was conducted to estimate the bioavailability and toxicity of metals in environmental samples. Substantial health risk could be associated with high particulate matter concentrations in ambient air and with a consumption of contaminated food-stuffs, both accompanied by an occurrence of toxic elements. One of the main causes of exceedance of ambient air quality limit values is traffic, despite emissions reductions. Among other factors, the mobility of an element is usually related to its chemical properties and the toxicity mainly to its oxidation state. Thus, chromium in the hexavalent form, Cr(VI), has long been recognized as a carcinogen and mutagen at low sub-ppm levels. Therefore, in this work, the presence and stability of Cr(VI)/Cr(III) species have been determined in particular matter of urban dust samples (the modified BCR three step sequential extraction procedure). For testing of stability and presence of Cr species a coupled technique connecting on-line HPLC with element-sensitive detector ICP-OES has been used (chromium was detected on line 205,560 nm). The anion exchange column Hamilton PRP-X100 (250 x 4,6 mm, 5 μm, PEEK, (Hamilton, USA)) was used for separation of Cr species. Optimal conditions for the separation were following: mobile phase 50 mmol x l-1 CH3COOH and 10 mmol xl-1 NaClO4 (pH 7.0; flow rate 1.5 ml x min-1), injected 200 μl of the sample, addition of 30 μg x ml-1 CDTA to the sample for a transfer of Cr(III) to anion complex. This combined technique allowed to determine 10 μg of Cr(III) and 13 μg of Cr(VI) in the sample (absolute LOD). It was found out that all three extraction agents used for a fractionation of elements negatively influenced the stability of Cr(VI) species in the solution immediately after their contact with the sample. The quantitatively smallest influence was found for the acetic acid. Probably this is a reason why only species of Cr

  19. Study on application of biological iron sulfide composites in treating vanadium-extraction wastewater containing chromium (VI) and chromium reclamation.

    Science.gov (United States)

    Xie, Yi-Fei; Li, Xu-Dong; Li, Fu-De

    2013-04-01

    In this study, the Cr(VI)-resistant properties and regeneration characteristics of biological iron sulfide composites were investigated, which consist of sulfate reducing bacteria (SRB) and its in situ synthesized nanosized iron sulfides. Then the application of the composites in treating vanadium-extraction wastewater containing high concentration Cr(VI) and reclaiming Cr were performed. It was found that SRB in composites still survived after being used to treat vanadium-extraction wastewater, which could reduce reaction products Fe3+ and sulphur into Fe2+ and S2 by using them as the electron accepters and thus regenerating biological iron sulfide composites. The SRB also could be resistant to 600 mgl(-1) Cr(VI) and reduce it gradually. Based on the Cr(VI)-resistant properties and regeneration characteristics of the composites, a reduction-regeneration recirculation process for treating vanadium-extraction wastewater and reclamation of Cr was developed. The results indicated that the contaminants in effluent reached the Chinese discharge standard of pollutants for vanadium industry (GB 26452-2011), i.e. the concentration of total Cr(TCr) was less than 0.912 mgl(-1), Cr(VI) was less than 0.017 mgl(-1) and V was less than 0.260 mgl(-1). After 10 cycles of treatment, the Cr2O3 content in sludge reached 41.03%, and the ratio of Cr2O3/FeO was 7.35. The sludge reached the chemical and metallurgical (hydrometallurgy) grade of chromite ore and could be reclaimed. PMID:24620597

  20. Chromium Biosorption from Cr(VI) Aqueous Solutions by Cupressus lusitanica Bark: Kinetics, Equilibrium and Thermodynamic Studies

    OpenAIRE

    Alma Rosa Netzahuatl-Muñoz; María del Carmen Cristiani-Urbina; Eliseo Cristiani-Urbina

    2015-01-01

    The present study investigated the kinetics, equilibrium and thermodynamics of chromium (Cr) ion biosorption from Cr(VI) aqueous solutions by Cupressus lusitanica bark (CLB). CLB total Cr biosorption capacity strongly depended on operating variables such as initial Cr(VI) concentration and contact time: as these variables rose, total Cr biosorption capacity increased significantly. Total Cr biosorption rate also increased with rising solution temperature. The pseudo-second-order model describ...

  1. Occurrence and speciation of polymeric chromium(III), monomeric chromium(III) and chromium(VI) in environmental samples.

    Science.gov (United States)

    Hu, Ligang; Cai, Yong; Jiang, Guibin

    2016-08-01

    Laboratory experiments suggest that polymeric Cr(III) could exist in aqueous solution for a relative long period of time. However, the occurrence of polymeric Cr(III) has not been reported in environmental media due partially to the lack of method for speciating polymeric Cr. We observed an unknown Cr species during the course of study on speciation of Cr in the leachates of chromated-copper-arsenate (CCA)-treated wood. Efforts were made to identify structure of the unknown Cr species. Considering the forms of Cr existed in the CCA-treated woods, we mainly focused our efforts to determine if the unknown species were polymeric Cr(III), complex of Cr/As or complex of Cr with dissolved organic matter (DOM). In order to evaluate whether polymeric Cr(III) largely exist in wood leachates, high performance liquid chromatography coupled with inductively coupled mass spectrometry (HPLC-ICPMS was used) for simultaneous speciation of monomeric Cr(III), polymeric Cr(III), and Cr(VI). In addition to wood leachates where polymeric Cr (III) ranged from 39.1 to 67.4%, occurrence of the unknown Cr species in other environmental matrices, including surface waters, tap and waste waters, was also investigated. It was found that polymeric Cr(III) could exist in environmental samples containing μg/L level of Cr, at a level up to 60% of total Cr, suggesting that polymeric Cr(III) could significantly exist in natural environments. Failure in quantifying polymeric Cr(III) would lead to the underestimation of total Cr and bias in Cr speciation. The environmental implication of the presence of polymeric Cr(III) species in the environment deserves further study. PMID:27156211

  2. [Remediation of chromium (VI) contaminated soils using permeable reactive composite electrodes technology].

    Science.gov (United States)

    Fu, Rong-Bing; Liu, Fang; Ma, Jin; Zhang, Chang-Bo; He, Guo-Fu

    2012-01-01

    Electrokinetic transport processes have been shown to have potential for the effective removal of heavy metals from soils. However, pH changes near the anode and cathode limit their widespread application in the remediation of contaminated soils. Permeable reactive composite electrodes (PRCE) were made by attaching reactive materials such as Fe(0) and zeolite to the electrodes, and the effects of the composite electrodes on pH control, chromium removal efficiency and Cr speciation changes were studied in the electrokinetic remediation process of Cr( VI) contaminated soil. Composite electrodes consisting of permeable reactive materials gave better pH control and Cr removal efficiency compared to traditional electrodes, and a Fe(0) + zeolite reactive layer in the anode exhibited the best performance compared to zeolite or Fe(0) alone. After 5 days of electrokinetic remediation with a DC voltage of 2 V x cm(-1), the Fe(0) + zeolite reactive layer lowered the pH fluctuation, maintained the soil pH in the range of 5.5 to 8.5, raised the Cr(VI) removal efficiency up to 97% in any soil section, produced lower Cr(III) residues, enhanced the amount of Cr retention up to 8 and 1.8 times respectively, and transformed 98% of the Cr(VI) into lower toxicity Cr(III). This study provides a theoretical basis for the exploitation of permeable reactive composite electrodes which are a practical option for future applications. PMID:22452223

  3. Interaction of Cr(VI) reduction and denitrification by strain Pseudomonas aeruginosa PCN-2 under aerobic conditions.

    Science.gov (United States)

    He, Da; Zheng, Maosheng; Ma, Tao; Li, Can; Ni, Jinren

    2015-06-01

    Inhibition of efficient denitrification in presence of toxic heavy metals is one of the current problems encountered in municipal wastewater treatment plants. This paper presents how to remove hexavalent chromium (Cr(VI)) and nitrate simultaneously by the novel strain Pseudomonas aeruginosa PCN-2 under aerobic conditions. The capability of strain PCN-2 for Cr(VI) and nitrate reduction was confirmed by PCR analysis of gene ChrR, napA, nirS, cnorB, nosZ, while Cr(VI) reduction was proved via an initial single-electron transfer through Cr(V) detection using electron paramagnetic resonance. Experimental results demonstrated that Cr(VI) and nitrate reduction by strain PCN-2 was much faster at pH 8-9 and higher initial cell concentration. However, increasing Cr(VI) concentration would inhibit aerobic denitrification process and result in an significant delay of nitrate reduction or N2O accumulation, which was attributed to competition between three electron acceptors, i.e., Cr(VI), O2 and nitrate in the electron transport chain. PMID:25795449

  4. Near-anode focusing phenomenon caused by the high anolyte concentration in the electrokinetic remediation of chromium(VI)-contaminated soil

    International Nuclear Information System (INIS)

    Graphical abstract: Mechanism illustration of the focusing band by ion-induced potential gradient well trapping effect (IIPGWTE), Cr(VI) denotes the CrO42−/HCrO4− ions; ION denotes all other ions except Cr(VI) ions. The potential gradient (Ea) and ions’ velocity (va) in the soil near the anode was lower than that in other parts (Ec, vc) forming a potential gradient well, because of invasion of anolytes (from the left end). Highlights: ► High anolyte concentration causes focusing phenomena in soil near anode. ► Low pH value aggravates the focusing phenomenon. ► Focusing phenomenon significantly increase the remediation duration and energy consumption. - Abstract: The effects of the concentration and the low pH value of anolyte on the electrokinetic remediation (EKR) of chromium-contaminated soil were investigated using chromium-spiked kaolin-gypsum soil. Results of visual observation and X-ray fluorescence analysis show that high anolyte concentrations could cause an ion-induced potential gradient well trapping effect on the soil near the anode, and consequently cause a focusing phenomenon (FP) without chemical precipitation. This FP significantly prolonged the remediation duration and reduced chromium removal. The low pH value of soil aggravated the FP, resulting in a quasi-dead zone near the anode caused by the reduction in soil resistance, rather than the adsorption of chromium (VI) ions. The high anolyte concentration also resulted in high energy consumption. The FP and low pH value collectively decreased the energy efficiency by more than 96%. This kind of FP can be predicted via the online monitoring of the potential gradient profiles of the soil between the electrodes in the EKR.

  5. Near-anode focusing phenomenon caused by the high anolyte concentration in the electrokinetic remediation of chromium(VI)-contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dong, E-mail: lidongbayan@cqu.edu.cn [School of Resources and Environmental Science, Chongqing University, Chongqing, 400030 (China); Xiong, Zhen; Nie, Yang; Niu, Yuan-Yuan; Wang, Li [School of Resources and Environmental Science, Chongqing University, Chongqing, 400030 (China); Liu, Yuan-Yuan [School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing, 400030 (China)

    2012-08-30

    Graphical abstract: Mechanism illustration of the focusing band by ion-induced potential gradient well trapping effect (IIPGWTE), Cr(VI) denotes the CrO{sub 4}{sup 2-}/HCrO{sub 4}{sup -} ions; ION denotes all other ions except Cr(VI) ions. The potential gradient (Ea) and ions' velocity (v{sub a}) in the soil near the anode was lower than that in other parts (Ec, v{sub c}) forming a potential gradient well, because of invasion of anolytes (from the left end). Highlights: Black-Right-Pointing-Pointer High anolyte concentration causes focusing phenomena in soil near anode. Black-Right-Pointing-Pointer Low pH value aggravates the focusing phenomenon. Black-Right-Pointing-Pointer Focusing phenomenon significantly increase the remediation duration and energy consumption. - Abstract: The effects of the concentration and the low pH value of anolyte on the electrokinetic remediation (EKR) of chromium-contaminated soil were investigated using chromium-spiked kaolin-gypsum soil. Results of visual observation and X-ray fluorescence analysis show that high anolyte concentrations could cause an ion-induced potential gradient well trapping effect on the soil near the anode, and consequently cause a focusing phenomenon (FP) without chemical precipitation. This FP significantly prolonged the remediation duration and reduced chromium removal. The low pH value of soil aggravated the FP, resulting in a quasi-dead zone near the anode caused by the reduction in soil resistance, rather than the adsorption of chromium (VI) ions. The high anolyte concentration also resulted in high energy consumption. The FP and low pH value collectively decreased the energy efficiency by more than 96%. This kind of FP can be predicted via the online monitoring of the potential gradient profiles of the soil between the electrodes in the EKR.

  6. Assessment of chromium(VI) release from 848 jewellery items by use of a diphenylcarbazide spot test

    DEFF Research Database (Denmark)

    Bregnbak, David; Johansen, Jeanne D.; Hamann, Dathan;

    2016-01-01

    We recently evaluated and validated a diphenylcarbazide(DPC)-based screening spot test that can detect the release of chromium(VI) ions (≥0.5 ppm) from various metallic items and leather goods (1). We then screened a selection of metal screws, leather shoes, and gloves, as well as 50 earrings, and...

  7. Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica

    International Nuclear Information System (INIS)

    The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 deg. C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2 h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73 ± 1.3 mg g-1 at a concentration of 950 ppm and 46.09 ± 0.23 mg g-1 at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.

  8. Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica

    Energy Technology Data Exchange (ETDEWEB)

    Bankar, Ashok V.; Kumar, Ameeta R. [Institute of Bioinformatics and Biotechnology, University of Pune, Pune 411 007 (India); Zinjarde, Smita S., E-mail: smita@unipune.ernet.in [Institute of Bioinformatics and Biotechnology, University of Pune, Pune 411 007 (India)

    2009-10-15

    The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 deg. C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2 h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73 {+-} 1.3 mg g{sup -1} at a concentration of 950 ppm and 46.09 {+-} 0.23 mg g{sup -1} at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.

  9. Synthesis and characterization of polyurethane-cellulose acetate blend membrane for chromium (VI) removal.

    Science.gov (United States)

    Riaz, Tabinda; Ahmad, Adnan; Saleemi, Sidra; Adrees, Muhammad; Jamshed, Fahad; Hai, Abdul Moqeet; Jamil, Tahir

    2016-11-20

    Blended membranes of polyurethane and cellulose acetate were prepared, characterized and investigated for their performance. Various ratios of cellulose acetate were employed to prepare four different blend membranes. The characteristics of both pure and blend membranes were investigated and results were compared to distinguish their properties. Functional group analysis was carried out by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) of pure and blend samples. Contact angle measurement and water content were evaluated to determine the membrane hydrophilicity. Moreover, the membrane morphology was studied by scanning electron microscopy (SEM). The membrane permeation properties and ability to reject chromium (VI) ions were tested at various pH and pressure by utilizing different salt concentrations. PMID:27561531

  10. Application of artificial neural network (ANN in Biosorption modeling of Chromium (VI from aqueous solutions

    Directory of Open Access Journals (Sweden)

    F Mohammadi

    2016-03-01

    Full Text Available Background and Objectives: In this work, biosorption of hexavalent chromium from aqueous solution with excess municipal sludge was studied. Moreover, the performance of neural networks to predict the biosorption rate was investigated. Materials and Methods: The effect of operational parameters including initial metal concentration, initial pH, agitation speed, adsorbent dosage, and agitation time on the biosorption of chromium was assessed in a batch system. A part of the experimental results was modeled using Feed-Forward Back propagation Neural Network (FFBP-ANN. Another part of the test results was simulated to assess the model accuracy. Transfer function in the hidden layers and output layers and the number of neurons in the hidden layers were optimized. Results: The maximum removal of chromium obtained from batch studies was more than 96% in 90 mg/L initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/L. Maximum biosorption capacity was 41.69 mg/g. Biosorption data of Cr(VI are described well by Freundlich isotherm model and adsorption kinetic followed pseudo-second order model.  Tangent sigmoid function determined was the most appropriate transfer function in the hidden and output layer. The optimal number of neurons in hidden layers was 13. Predictions of model showed excellent correlation (R=0.984 with the target vector. Simulations performed by the developed neural network model showed good agreement with experimental results. Conclusion: Overall, it can be concluded that excess municipal sludge performs well for the removal of Cr ions from aqueous solution as a biological and low cost biosorbent. FFBP-ANN is an appropriate technique for modeling, estimating, and prediction of biosorption process If the Levenberg-Marquardt training function, tangent sigmoid transfer function in the hidden and output layers and the number of neurons is between 1.6 to 1.8 times the input data, proper predication results could be

  11. Cr (VI electromechimal reduction using RVG 4OOO graphite felt as the electrode

    Directory of Open Access Journals (Sweden)

    E.O. Vilar

    2003-09-01

    Full Text Available Even in at very low concentrations, heavy metals in industrial waste constitute environmental and health risks. The U.S. Department of Health and Human Services has recognized as chromium compounds and defined carcinogens the level acceptable in drinking water as being only 0.05 ppm. The objective of this work was the electrochemical reduction of hexavalent chromium Cr (VI to Cr (III ions in a dilute synthetic solution of K2Cr2O7 and Na2SO4 (0.05N. A plug-flow reactor with an RVG 4000 graphite felt (Le Carbone Lorraine, France electrode was used for this work. Its morphological characteristics such as specific variables surface, porosity, average fibre diameter and permeability were determined. The influencing process selectivity such as initial concentration of Cr (VI, solution pH, current intensity and conversion yield are considered. The fractional conversion achieved in the plug-flow reactor in the present work, was about 90%.

  12. Enhancing microbial iron reduction in hyperalkaline, chromium contaminated sediments by pH amendment

    International Nuclear Information System (INIS)

    Soil collected from beneath a chromite ore processing residue (COPR) disposal site contained a diverse population of anaerobic alkaliphiles, despite receiving a continuous influx of a Cr(VI) contaminated, hyperalkaline leachate (pH 12.2). Chromium was found to have accumulated in this soil as a result of an abiotic reaction of Cr(VI) with Fe(II) present in the soil. This sediment associated Fe(II) was, therefore, acting as a natural reactive zone beneath the COPR and thereby preventing the spread of Cr(VI). In anaerobic microcosm experiments soil microorganisms were able to reduce NO3- at pH 11.2 coupled to the oxidation of electron donors derived from the original soil organic matter, but progressive anoxia did not develop to the point of Fe reduction over a period of 9 months. It is not clear, therefore, if Fe(II) can be actively replenished by microbial processes occurring within the soil at in situ conditions. Sodium bicarbonate was added to this soil to investigate whether bioreduction of Fe in hyperalkaline Cr contaminated soils could be enhanced by reducing the pH to a value optimal for many alkaliphilic bacteria. The addition of NaHCO3 produced a well buffered system with a pH of ∼9.3 and Fe reducing conditions developed within 1 month once complete denitrification had occurred. Fe(III) reduction was associated with an increase in the proportion of genetic clone libraries that were from the phylum Firmicutes, suggesting that these species are responsible for the Fe(III) reduction observed. Amendment of the pH using bicarbonate may provide a suitable strategy for stimulating the bioreduction of Fe(III) in COPR leachate contaminated soils or other environments where microbial reduction is inhibited by elevated pH.

  13. Near-anode focusing phenomenon caused by the high anolyte concentration in the electrokinetic remediation of chromium(VI)-contaminated soil.

    Science.gov (United States)

    Li, Dong; Xiong, Zhen; Nie, Yang; Niu, Yuan-Yuan; Wang, Li; Liu, Yuan-Yuan

    2012-08-30

    The effects of the concentration and the low pH value of anolyte on the electrokinetic remediation (EKR) of chromium-contaminated soil were investigated using chromium-spiked kaolin-gypsum soil. Results of visual observation and X-ray fluorescence analysis show that high anolyte concentrations could cause an ion-induced potential gradient well trapping effect on the soil near the anode, and consequently cause a focusing phenomenon (FP) without chemical precipitation. This FP significantly prolonged the remediation duration and reduced chromium removal. The low pH value of soil aggravated the FP, resulting in a quasi-dead zone near the anode caused by the reduction in soil resistance, rather than the adsorption of chromium (VI) ions. The high anolyte concentration also resulted in high energy consumption. The FP and low pH value collectively decreased the energy efficiency by more than 96%. This kind of FP can be predicted via the online monitoring of the potential gradient profiles of the soil between the electrodes in the EKR. PMID:22738769

  14. Application of chromium stable isotopes to the evaluation of Cr(VI) contamination in groundwater and rock leachates from central Euboea and the Assopos basin (Greece)

    DEFF Research Database (Denmark)

    Economou-Eliopoulos, Maria; Frei, Robert; Atsarou, Cathy

    2014-01-01

    Major and trace elements (a) in groundwater, ultramafic rocks from natural outcrops and soil samples from cultivated sites of Central Euboea and Assopos basin, and (b) in experimentally produced laboratory water leachates of rocks and soils were investigated by SEM/EDS, XRD and ICP/MS. In addition......, stable chromium isotopes (expressed as δ53Cr values) were measured in groundwater and leachates in order to identify potential sources for Cr-contamination. The higher Cr(VI) concentrations in soil leachates compared to those in the rock pulp leachates potentially can be explained by the presence...... signatures. The variation in δ53Cr values (0.84 to 1.98‰ in groundwater from Euboea, and from 0.98 to 1.03‰ in samples from the Assopos basin) imply initial oxidative mobilization of Cr(VI) from the ultramafic host rocks, followed by reductive processes that lead to immobilization of portions of Cr...

  15. Chromium(III, VI) speciation analysis with preconcentration on a maleic acid-functionalized XAD sorbent

    International Nuclear Information System (INIS)

    Chromium may exist in environmental waters as Cr(III) and Cr(IV), the latter being the toxic and carcinogenic form. Since atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry can only yield information on total Cr concentration, a polymer resin bearing O,O-donor chelating groups such as the maleic acid-functionalized XAD-(CO)CH-CH-COOH resin was synthesized to selectively retain Cr(III) at pH 4.0-5.5. The dynamic breakthrough capacity of the resin for Cr(III) at pH 5.0 was 7.52 mg g-1, and the preconcentration factor extended to 250-300. Chromium(III) in the presence of 250-fold Cr(VI)--which was not retained--could be effectively preconcentrated on the NH4+-form of the resin and determined by AAS or diphenylcarbazide (DPC) spectrophotometry. When Cr(VI) was reduced to Cr(III) with Na2SO3 solution brought to pH 1 by the addition of 1 M H2SO4, and preconcentrated on the resin, total Cr could be determined. The developed method was validated with a blended coal sample CRM-1632. Since the adsorption behavior as a function of pH of possible interferent metal ions, e.g. Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Fe(III), was similar to that of Cr(III), selective elution of Cr(III) from the resin was realized using a mixture of 1 wt.% H2O2+1 M NH3. The eluate containing Cr as chromate could be directly analyzed by diphenyl carbazide spectrophotometry without any adverse effect from the common interferents of this method, i.e. Fe(III), Cu(II) Hg(II), VO3-, MoO42- and WO42-. Various synthetic waste solutions typical of electroplating bath effluents containing Cr, Cu, Ni, Zn, Na, Ca, cyanide (and chemical oxidation demand (COD), achieved by glucose addition) were subjected to pretreatment procedures such as hypochlorite oxidation (of cyanide) and catalytic oxidation (of COD) with peroxodisulfate. Chromium determination gave satisfactory results. The combined column preconcentration--selective elution

  16. Efficacy of mangrove leaf powder for bioremediation of chromium (VI) from aqueous solutions: kinetic and thermodynamic evaluation

    Science.gov (United States)

    Sathish, Thadikamala; Vinithkumar, N. V.; Dharani, G.; Kirubagaran, R.

    2014-03-01

    Biosorption of heavy metals by bio-materials has been posited as a potential alternative to the existing physicochemical technologies for detoxification and recovery of toxic and valuable metals from wastewaters. In this context, the role of mangrove leaf powder (MLP) as biosorbent for chromium removal was investigated. In the present study, the effect of process parameters such as particle size, solution pH, initial concentration of Cr(VI) ion and adsorbent dose on chromium removal by MLP was investigated. The maximum sorption was observed at particle size 0.5 mm and pH 2.0. The adsorption data follow the pseudo second-order kinetics model. The isotherms denote that Langmuir model is the best fitted than Freundlich model. The maximum adsorption capacity (Q 0) of 60.24 mg/g of Cr(VI) at 30 min on MLP was determined using the Langmuir model. The adsorption isotherm model indicates that the chromium is adsorbing as monolayer on the surface of MLP with heterogeneous energetic distribution of active sites. Various thermodynamic parameters, such as Gibb's free energy (∆G °), enthalpy (∆H °) and entropy (∆S °) have been calculated. The thermodynamic data revealed that the adsorption of chromium ions onto MLP is endothermic in nature and a spontaneous process. The results of the present study suggest that MLP is an effective bioremediation measure for removal of high concentration of Cr(VI) in waste waters.

  17. Protective effect of vitamin E on chromium (VI)-induced cytotoxicity and lipid peroxidation in primary cultures of rat Hepatocytes

    Energy Technology Data Exchange (ETDEWEB)

    Susa, Nobuyuki [Department of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori (Japan); Ueno, Shunji [Department of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori (Japan); Furukawa, Yoshinori [Department of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori (Japan); Sugiyama, Masayasu [Asunaro Pharmacy, Tobataku, Kitakyushu (Japan)

    1996-11-01

    Pretreatment of primary cultures of rat hepatocytes with {alpha}-tocopherol succinate (vitamin E) for 20 h prior to exposure to K{sub 2}Cr{sub 2}O{sub 7}resulted in a marked decrease of chromium (VI)-induced cytotoxicity, as evaluated by the leakage of lactate dehydrogenase, without affecting cellular uptake and subcellular distribution of chromium. The levels of chromium (VI)-induced lipid peroxidation, as monitored by malondialdehyde formation, were also inhibited by pretreatment with the vitamin. Pretreatment with vitamin E normalized the levels of nonenzymatic antioxidants such as glutathione and vitamin C suppressed by dichromate, and caused a distinct accumulation of vitamin E in hepatocytes. However, vitamin E pretreatment did not affect the activities of enzymatic antioxidants including glutathione reductase, superoxide dismutase, and catalase suppressed by dichromate. These results indicate that the protective effect of vitamin E against chromium (VI)-induced cytotoxicity as well as lipid peroxidation, may be associated more with the level of nonenzymatic antioxidants than the activity of enzymatic antioxidants. (orig.). With 2 figs., 3 tabs.

  18. The oxidation and reduction of chromium of stainless steels in an eletric arc furnace

    Directory of Open Access Journals (Sweden)

    B. Arh

    2011-07-01

    Full Text Available The oxidation of chromium during the elaboration of stainless steels occurs with oxygen in solution blown inthe melt and with oxides in the slag. A higher content of silicon in the furnace charge decreases the extent of oxidation of chromium, however, the efficient reduction of chromium from the slag is of essential importance for a minimal loss of chromium. In this survey, the theory of the oxidation of chromium, its reduction from the slag and the conditions for the formation of foaming slag are discussed.

  19. Microbial community changes during sustained Cr(VI) reduction at the 100H site in Hanford, WA

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Romy; Brodie, Eoin L; Faybishenko, Boris; Piceno, Yvette M; Tom, Lauren; Choudhuri, Swati; Beller, Harry R; Liu, Jenny; Torok, Tamas; Joyner, Dominique C; Joachimiak, Marcin P; Zhou, Aifen; Van Nostrand, Joy D; Zhou, Joe; Long, Phil E; Newcomer, Darrell R; Andersen, Gary L; Hazen, Terry C.

    2010-05-17

    Hexavalent Chromium is a widespread contaminant found in soil, sediment, and groundwater. In order to stimulate microbially-mediated reduction of Cr(VI), a poly-lactate compound (HRC) was injected into the Chromium-contaminated aquifer at the Hanford (WA) 100H site in 2004. Cr(VI) concentrations rapidly declined to below the detection limit and remained so for more than three years after injection. Based on the results of the bacterial community composition using high-density DNA 16S rRNA gene microarrays, we observed the community to transition through denitrifying, ironreducing and sulfate-reducing populations. As a result, we specifically focused isolation efforts on three bacterial species that were significant components of the community. Positive enrichments in defined anaerobic media resulted in the isolation of an iron-reducing Geobacter metallireducens-like isolate, a sulfate-reducing Desulfovibrio vukgaris-like strain and a nitrate-reducing Pseudomonas stutzeri-like isolate among several others. All of these isolates were capable of reducing Cr(VI) anoxically and have been submitted for genome sequencing to JGI. To further characterize the microbial, and geochemical mechanisms associated with in situ Cr(VI) reduction at the site, additional HRC was injected in 2008. The goal was to restimulate the indigenous microbial community and to regenerate the reducing conditions necessary for continued Cr(VI) bio-immobilization in the groundwater. Analysis of the microbial populations post-injection revealed that they recovered to a similar density as after the first injection in 2004. In this study, we present the results from our investigation into microbially-mediated Cr(VI) reduction at Hanford, and a comparison of the microbial community development following two HRC injections four years apart.

  20. Chi-square analysis of the reduction of ATP levels in L-02 hepatocytes by hexavalent chromium

    Directory of Open Access Journals (Sweden)

    Yang Yuan

    2012-06-01

    Full Text Available This study explored the reduction of adenosine triphosphate (ATP levels in L-02 hepatocytes by hexavalent chromium (Cr(VI using chi-square analysis. Cells were treated with 2, 4, 8, 16, or 32 μM Cr(VI for 12, 24, or 36 h. Methyl thiazolyl tetrazolium (MTT experiments and measurements of intracellular ATP levels were performed by spectrophotometry or bioluminescence assays following Cr(VI treatment. The chi-square test was used to determine the difference between cell survival rate and ATP levels. For the chi-square analysis, the results of the MTT or ATP experiments were transformed into a relative ratio with respect to the control (%. The relative ATP levels increased at 12 h, decreased at 24 h, and increased slightly again at 36 h following 4, 8, 16, 32 μM Cr(VI treatment, corresponding to a "V-shaped" curve. Furthermore, the results of the chi-square analysis demonstrated a significant difference of the ATP level in the 32-μM Cr(VI group (P < 0.05. The results suggest that the chi-square test can be applied to analyze the interference effects of Cr(VI on ATP levels in L-02 hepatocytes. The decreased ATP levels at 24 h indicated disruption of mitochondrial energy metabolism and the slight increase of ATP levels at 36 h indicated partial recovery of mitochondrial function or activated glycolysis in L-02 hepatocytes.

  1. Effect of chromium (VI) exposure on antioxidant defense status and trace element homeostasis in acute experiment in rat.

    Science.gov (United States)

    Kotyzová, Dana; Hodková, Anna; Bludovská, Monika; Eybl, Vladislav

    2015-11-01

    Occupational exposure to hexavalent chromium (Cr(VI)) compounds is of concern in many Cr-related industries and their surrounding environment. Cr(VI) is a proven toxin and carcinogen. The Cr(VI) compounds are easily absorbed, can diffuse across cell membranes, and have strong oxidative potential. Despite intensive studies of Cr(VI) pro-oxidative effects, limited data exist on the influence of Cr(VI) on selenoenzymes thioredoxin reductase (TrxR) and glutathione peroxidase (GPx)-important components of antioxidant defense system. This study investigates the effect of Cr(VI) exposure on antioxidant defense status, with focus on these selenoenzymes, and on trace element homeostasis in an acute experiment in rat. Male Wistar rats (130-140g) were assigned to two groups of 8 animals: I. control; and II. Cr(VI) treated. The animals in Cr(VI) group were administered a single dose of K2Cr2O7 (20 mg /kg, intraperitoneally (ip)). The control group received saline solution. After 24 h, the animals were sacrificed and the liver and kidneys were examined for lipid peroxidation (LP; thiobarbituric acid reactive substances (TBARS) concentration), the level of reduced glutathione (GSH) and the activities of GPx-1, TrxR-1, and glutathione reductase (GR). Samples of tissues were also used to estimate Cr accumulation and alterations in zinc, copper, and iron levels. The acute Cr(VI) exposure caused an increase in both hepatic and renal LP (by 70%, p effect of Cr(VI) was found on TrxR-1 activity in both the liver and the kidneys. The ability of Cr(VI) to cause TrxR inhibition could contribute to its cytotoxic effects. Further investigation of oxidative responses in different in vivo models may enable the development of strategies to protect against Cr(VI) oxidative damage. PMID:23625905

  2. Root uptake and reduction of hexavalent chromium by aquatic macrophytes as assessed by high-resolution X-ray emission.

    Science.gov (United States)

    Espinoza-Quiñones, Fernando R; Martin, Neiva; Stutz, Guillermo; Tirao, German; Palácio, Soraya M; Rizzutto, Márcia A; Módenes, Aparecido N; Silva, Fernando G; Szymanski, Nayara; Kroumov, Alexander D

    2009-09-01

    Aquatic macrophytes Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes were chosen to investigate the Cr(VI) reduced by root-based biosorption in a chromium uptake experiment, using a high-resolution XRF technique. These plants were grown in hydroponics medium supplied with non-toxic Cr concentrations during a 27-day metal uptake experiment. The high-resolution Cr-Kbeta fluorescence spectra for dried root tissues and Cr reference material (100% Cr, Cr(2)O(3), and CrO(3)) were measured using an XRF spectrometer. For all species of aquatic plant treated with Cr(VI), the energy of the Cr-Kbeta(2,5) line was shifted around 8 eV below the same spectral line identified for the Cr(VI) reference, but it was also near to the line identified for the Cr(III) reference. Moreover, there was a lack of the strong Cr-Kbeta'' line assigned to the Cr(VI) reference material within the Cr(VI)-treated plant spectra, suggesting the reduction of Cr(VI) for other less toxic oxidation states of Cr. As all Cr-Kbeta spectra of root tissue species were compared, the peak energies and lineshape patterns of the Cr-Kbeta(2,5) line are coincident for the same aquatic plant species, when they were treated with Cr(III) and Cr(VI). Based on the experimental evidence, the Cr(VI) reduction process has happened during metal biosorption by these plants. PMID:19595427

  3. The reduction of Np(VI) and Pu(VI) by organic chelating agents

    International Nuclear Information System (INIS)

    The reduction of NpO2+ and PuO22+ by oxalate. citrate, and ethylenediaminetetraacetic acid (EDTA) was investigated in low ionic strength media and brines. This was done to help establish the stability of the An(VI) oxidation state in the presence of organic complexants. The stability of the An(VI) oxidation state depended on the pH and relative strength of the various oxidation state-specific complexes. At low ionic strength and pH 6, NpO2O2+ was rapidly reduced to form NpO2+ organic complexes. At longer times, Np(IV) organic complexes were observed in the presence of citrate. PuO22+ was predominantly reduced to Pu4+, resulting in the formation of organic complexes or polymeric/hydrolytic precipitates. The relative rates of reduction to the An(V) complex were EDTA > citrate > oxalate. Subsequent reduction to An(IV) complexes, however, occurred in the following order: citrate > EDTA > oxalate because of the stability of the An(V)-EDTA complex. The presence of organic complexants led to the rapid reduction of NpO22+ and PuO2P2+ in G-seep brine at pHs 5 and 7. At pHs 8 and 10 in ERDA-6 brine, carbonate and hydrolytic complexes predominated and slowed down or prevented the reduction of An(VI) by the organics present

  4. Photocatalytic reduction of hexavalent chromium at gold nanoparticles modified titania nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Pandikumar, Alagarsamy; Ramaraj, Ramasamy, E-mail: ramarajr@yahoo.com

    2013-09-16

    N-[3-(Trimethoxysilyl)propyl]ethylenediamine (EDAS) silicate supported titanium dioxide nanotubes-gold ((TiO{sub 2} NTs-Au){sub NCM}) nanocomposite material (EDAS/(TiO{sub 2} NTs-Au){sub NCM}) was prepared by deposition–precipitation method and characterized by diffuse reflectance spectra, X-ray diffraction pattern, Brunauer–Emmett–Teller surface area analysis, transmission electron micrographs, scanning electron micrographs and energy-dispersive X-ray spectra analysis. The photocatalytic activity of the EDAS/(TiO{sub 2} NTs-Au){sub NCM} in the film form was investigated towards the reduction of toxic hexavalent chromium (Cr(VI)) into trivalent chromium (Cr(III)) in the presence of oxalic acid as an electron donor. The EDAS/(TiO{sub 2} NTs-Au){sub NCM} film exhibited higher photocatalytic activity when compared to the photocatalytic activities of pristine TiO{sub 2} nanoparticles and TiO{sub 2} nanotubes (TiO{sub 2} NTs) which can be attributed to the effective photoinduced interfacial charge transfer from the (TiO{sub 2} NTs-Au){sub NCM} to Cr(VI) through Au nanoparticles (Au{sub nps}). The Au{sub nps} present in the TiO{sub 2} NTs act as an electron sink for the photogenerated electrons that minimizes the charge recombination process at the TiO{sub 2} NTs. The Au{sub nps} on the TiO{sub 2} NTs surface facilitates the transfer of photogenerated electrons to the Cr(VI) leading to the formation of Cr(III) ions. - Highlights: • Gold modified titania nanotubes are used to design solid-phase photocatalyst. • Gold nanoparticles deposition increases the surface area of titania nanotubes. • Gold on titania nanotubes improves the photocatalytic reduction of Cr(VI). • The holes produced at the titania nanotubes are scavenged by oxalic acid. • Gold modified titania nanotubes is a potential candidate for treatment of heavy metals.

  5. In vivo and in vitro effects of chromium VI on anterior pituitary hormone release and cell viability

    International Nuclear Information System (INIS)

    Hexavalent chromium (Cr VI) is a highly toxic metal and an environmental pollutant. Different studies indicate that Cr VI exposure adversely affects reproductive functions. This metal has been shown to affect several tissues and organs but Cr VI effects on pituitary gland have not been reported. Anterior pituitary hormones are central for the body homeostasis and have a fundamental role in reproductive physiology. The aim of this study was to evaluate the effect of Cr VI at the pituitary level both in vivo and in vitro. We showed that Cr VI accumulates in the pituitary and hypothalamus, and decreases serum prolactin levels in vivo but observed no effects on LH levels. In anterior pituitary cells in culture, the effect of Cr VI on hormone secretion followed the same differential pattern. Besides, lactotrophs were more sensitive to the toxicity of the metal. As a result of oxidative stress generation, Cr VI induced apoptosis evidenced by nuclear fragmentation and caspase 3 activation. Our results indicate that the anterior pituitary gland can be a target of Cr VI toxicity in vivo and in vitro, thus producing a negative impact on the hypothalamic-pituitary-gonadal axis and affecting the normal endocrine function

  6. The development of a method for the simultaneous measurement of cerium (IV) and chromium (VI) species in nitric acid media - 16124

    International Nuclear Information System (INIS)

    The corrosion of stainless steel in nitric acid media is a major concern for the nuclear industry. Several reprocessing schemes such as PUREX (Plutonium Uranium Reduction Extraction) and UREX (Uranium Reduction Extraction) utilise nitric acid media, and an understanding of the behaviour of key chemical species in these process streams is vital if their effect on associated corrosion reactions and their rates is to be accurately assessed and quantified. This will allow for more accurate prediction of the working lifetime of any stainless steel surface in contact with the process stream in question. Two such key species that are found in nuclear process streams are cerium as Ce (IV) and chromium as Cr(VI), both of which may act as corrosion accelerants. The redox chemistry of cerium and chromium in highly active liquor (HAL) will depend on nitrous acid concentration, temperature, acidity, total nitrate and possibly the influence of other dissolved species and hence an analytical technique for the on-line measurement of these quantities would be useful for lifetime prediction and corrosion prevention. As a result of this, a strategy for the simultaneous measurement of both Ce(IV) and Cr(VI) species in the presence of other ions typically found in process streams (such as Iron, Magnesium Neodymium and Aluminium) has been developed. The work presented will discuss the design and implementation of the electrochemical techniques that we have used in the development of this strategy and in the measurement of the species in question. (authors)

  7. Permeation of chromium salts through human skin in vitro

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Fullerton, A; Avnstorp, C;

    1992-01-01

    of the dichromate solution. Chromium skin levels increased with increasing concentrations of applied chromium salts up to 0.034 M Cr. The amount of chromium in recipient phase and skin layers increased with increasing pH when the applied solution contained potassium dichromate. This was ascribed to a decreased skin...... barrier function of the skin. The amount of chromium found in all skin layers after application of chromium chloride decreased with increasing pH due to lower solubility of the salt. The % of chromium found in the recipient phase as chromium(VI) increased with increasing total chromium concentration...... indicating a limited reduction ability of the skin in vitro....

  8. Reduction of hexavalent chromium by the thermophilic methanogen Methanothermobacter thermautotrophicus

    Science.gov (United States)

    Singh, Rajesh; Dong, Hailiang; Liu, Deng; Zhao, Linduo; Marts, Amy R.; Farquhar, Erik; Tierney, David L.; Almquist, Catherine B.; Briggs, Brandon R.

    2015-01-01

    Despite significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70 °C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations using 1,5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to 1.9 μM h-1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature subsurface radioactive waste disposal

  9. Conversion of Chromium(III) Propionate to Chromate/dichromate(VI) by the Advanced Oxidation Process. Pretreatment of a Biomimetic Complex for Metal Analysis

    OpenAIRE

    Lynn Rodman, D.; Carrington, Nathan A.; Xue, Zi-Ling

    2006-01-01

    The use of H2O2 and UV irradiation to remove organic ligands in a chromium(III) complex for the subsequent chromium analysis is reported. The Advanced Oxidation Process (AOP) using a 5.5-W UV lamp, H2O2 and Fe2+/Fe3+ as catalyst (photo Fenton process) was found to give complete and quantitative Cr(III) → Cr(VI) conversion and removal of ligands in chromium(III) propionate [Cr3O(O2CCH2CH3)6(H2O)3]NO3, a biomimetic chromium species, as subsequent chromium analyses by the 1,5-diphenylcarbazide m...

  10. Electrochemical reduction of hexavalent chromium in ground water

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, S. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

    Electrochemical reduction of hexavalent chromium (Cr{sup +6}) to its trivalent state (Cr{sup +3}) is showing promising results in treating ground water at Lawrence Livermore National Laboratory`s (LLNL`s) Main Site. An electrolytic cell using stainless-steel and brass electrodes has been found to offer the most efficient reduction while yielding the least amount of precipitate. Trials have successfully lowered concentrations of Cr{sup +6} to below 11 parts per billion (micrograms/liter), the California state standard. We ran several trials to determine optimal voltage for running the cell; each trial consisted of applying a voltage between 6V and 48V for ten minutes through samples obtained at Treatment Facility C(TFC). No conclusive data has been obtained yet.

  11. Montmorillonite-supported magnetite nanoparticles for the removal of hexavalent chromium [Cr(VI)] from aqueous solutions

    International Nuclear Information System (INIS)

    Montmorillonite-supported magnetite nanoparticles were prepared by co-precipitation and hydrosol method. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the magnetite nanoparticles without and with montmorillonite support are around 25 and 15 nm, respectively. The montmorillonite-supported magnetite nanoparticles exist on the surface or inside the interparticle pores of clays, with better dispersing and less coaggregation than the ones without montmorillonite support. Batch tests were carried out to investigate the removal mechanism of hexavalent chromium [Cr(VI)] by these synthesized magnetite nanoparticles. The Cr(VI) uptake was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed the Pseudo-second-order model. The adsorption data of unsupported and clay-supported magnetite nanoparticles fit well with the Langmuir and Freundlich isotherm equations. The montmorillonite-supported magnetite nanoparticles showed a much better adsorption capacity per unit mass of magnetite (15.3 mg/g) than unsupported magnetite (10.6 mg/g), and were more thermally stable than their unsupported counterparts. These fundamental results demonstrate that the montmorillonite-supported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

  12. The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi in leather

    Directory of Open Access Journals (Sweden)

    W. F. Fuck

    2011-06-01

    Full Text Available Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI, the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI formation led to recommendations for regulation in the leather industry.

  13. The influence of Chromium supplied by tanning and wet finishing processes on the formation of cr(vi) in leather

    OpenAIRE

    W. F. Fuck; M Gutterres; N. R. Marcílio; S. Bordingnon

    2011-01-01

    Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III) from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI) in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI) was always below the ...

  14. Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater

    Science.gov (United States)

    Mills, Christopher T.; Morrison, Jean M.; Goldhaber, Martin B.; Ellefsen, Karl J.

    2011-01-01

    Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacramento Valley of California where Cr(VI) concentrations in groundwater can approach or exceed 50 μg L−1. To characterize Cr geochemistry in the area, samples from several soil auger cores (approximately 4 m deep) and drill cores (approximately 25 m deep) were analyzed for total concentrations of 44 major, minor and trace elements, Cr associated with labile Mn and Fe oxides, and Cr(VI). Total concentrations of Cr in these samples ranged from 140 to 2220 mg per kg soil. Between 9 and 70 mg per kg soil was released by selective extractions that target Fe oxides, but essentially no Cr was associated with the abundant reactive Mn oxides (up to ~1000 mg hydroxylamine-reducible Mn per kg soil was present). Both borehole magnetic susceptibility surveys performed at some of the drill core sites and relative differences between Cr released in a 4-acid digestion versus total Cr (lithium metaborate fusion digestion) suggest that the majority of total Cr in the samples is present in refractory chromite minerals transported from ultramafic exposures in the Coast Range Mountains. Chromium(VI) in the samples studied ranged from 0 to 42 μg kg−1, representing a minute fraction of total Cr. Chromium(VI) content was typically below detection in surface soils (top 10 cm) where soil organic matter was high, and increased with increasing depth in the soil auger cores as organic matter decreased. Maximum concentrations of Cr(VI) were up to 3 times greater in the deeper drill core samples than the shallow auger cores. Although Cr(VI) in these vadose zone soils and sediments was only a

  15. Simultaneous Adsorption of Chromium (VI) and Phosphate by Calcined Mg-Al-CO{sub 3} Layered Double Hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Song, Xiulan; Wu, Yuhong [Taiyuan Univ. of Technology, Shanxi (China)

    2014-06-15

    The adsorption characteristics of chromium (VI) and phosphate on calcined Mg-Al-CO{sub 3} layered double hydroxides (CLDH) were investigated in single and binary systems. A series of batch experiments were performed to study the influence of various experimental parameters. In this study, CLDH exhibited a high adsorption capacity for Cr (VI) and P in a single system. The experimental data were close to the theoretical adsorption capacity given by the Langmuir isotherm, the calculating adsorption capacities of Cr (VI) and P were up to 70.42 mg/g and 97.09 mg/g, respectively. It was found that the initial pH was approximately 6 and it took 24 h to reach equilibrium when P and Cr (VI) were added simultaneously. The experimental data were best fitted by a pseudo-second-order kinetics model. Competitive adsorption between Cr (VI) and P existed in the binary system. The presence of Cr (VI) had no significant influence on P adsorption. However, the suppression of Cr (VI) adsorption was obvious when the initial concentration of P was up to 10 mg/L with a concentration of 0.5 g/L of CLDH.

  16. Simultaneous Adsorption of Chromium (VI) and Phosphate by Calcined Mg-Al-CO3 Layered Double Hydroxides

    International Nuclear Information System (INIS)

    The adsorption characteristics of chromium (VI) and phosphate on calcined Mg-Al-CO3 layered double hydroxides (CLDH) were investigated in single and binary systems. A series of batch experiments were performed to study the influence of various experimental parameters. In this study, CLDH exhibited a high adsorption capacity for Cr (VI) and P in a single system. The experimental data were close to the theoretical adsorption capacity given by the Langmuir isotherm, the calculating adsorption capacities of Cr (VI) and P were up to 70.42 mg/g and 97.09 mg/g, respectively. It was found that the initial pH was approximately 6 and it took 24 h to reach equilibrium when P and Cr (VI) were added simultaneously. The experimental data were best fitted by a pseudo-second-order kinetics model. Competitive adsorption between Cr (VI) and P existed in the binary system. The presence of Cr (VI) had no significant influence on P adsorption. However, the suppression of Cr (VI) adsorption was obvious when the initial concentration of P was up to 10 mg/L with a concentration of 0.5 g/L of CLDH

  17. Lead, mercury, cadmium, chromium, nickel, copper, zinc, calcium, iron, manganese and chromium (VI) levels in Nigeria and United States of America cement dust.

    Science.gov (United States)

    Ogunbileje, J O; Sadagoparamanujam, V-M; Anetor, J I; Farombi, E O; Akinosun, O M; Okorodudu, A O

    2013-03-01

    This study was aimed at investigating the relative abundance of heavy metals in cement dust from different cement dust factories in order to predict their possible roles in the severity of cement dust toxicity. The concentrations of total mercury (Hg), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), manganese (Mn), lead (Pb), iron (Fe) and chromium (VI) (Cr (VI)) levels in cement dust and clinker samples from Nigeria and cement dust sample from the United States of America (USA) were determined using graphite furnace atomic absorption (GFAAS), while Zn and Ca were measured by flame atomic absorption spectrophotometry (FAAS), and Cr (VI) by colorimetric method. Total Cu, Ni and Mn were significantly higher in cement dust sample from USA (pcement dust compared with Nigeria cement dust or clinker (pcement dust and clinker (pMercury was more in both Nigeria cement dust and clinker (pcement dust contain mixture of metals that are known human carcinogens and also have been implicated in other debilitating health conditions. Additionally, it revealed that metal content concentrations are factory dependent. This study appears to indicate the need for additional human studies relating the toxicity of these metals and their health impacts on cement factory workers. PMID:23261125

  18. Preconcentrative separation of chromium(III) species from chromium(VI) by cloud point extraction and determination by flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    We describe a high-throughput technique for the determination of chromium species in water samples by flame atomic absorption spectrometry (FAAS) after preconcentrative separation of Cr(III) species from Cr(VI) by cloud point extraction (CPE) using diethyldithiocarbamate (DDTC) as the chelating agent and the nonionic surfactant Triton X-100 as the extractant. The Cr(III)-DDTC complex is extracted if the temperature is higher than the CPE temperature of Triton X-100, while Cr(VI) remains in the aqueous phase. The Cr(III) in the surfactant phase was analyzed by FAAS, and the concentration of Cr(VI) was calculated by subtraction of Cr(III) from total chromium which was directly determined by FAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. The detection limit for Cr(III) was 0. 08 μg L-1with an enrichment factor of 98, and the relative standard deviation was 1. 2% (n = 3, c = 100 μg L-1). A certified reference material and several water samples were analyzed with satisfactory results. (author)

  19. Reduction of chromium oxides with calcium carbide during thestainless steelmaking process

    Directory of Open Access Journals (Sweden)

    B. Arh

    2015-04-01

    Full Text Available An efficient reduction of chromium from slag requires an appropriate reduction agent for the given steelmaking technology. The usual slag reduction praxis consists of carbon injections and additions of ferrosilicon and aluminum.Reduction of chromium containing slags with calcium carbide is an appealing alternative. Calcium carbide is a strong reduction agent that unlike ferrosilicon and aluminum also provides the possibility of foaming slag formation.Experimental work regarding chromium slag reduction with calcium carbide towards usual slag reduction praxis is described in this work. The results show that higher reduction rates in the stage of refining period of the melt and higher level of overall chromium reduction from slag can be reached with the blowing of CaC2.

  20. Electron transfer. 75. Reduction of carboxylato-bound chromium(V) with vanadium(IV). Intervention of chromium(IV)

    International Nuclear Information System (INIS)

    The chelated (carboxylato)chromium(V) anion bis(2-hydroxy-2-ethylbutyrato)oxochromate(V) (I), [(Lig)2Cr(O)]-, reacts with oxovanadium(IV) to form a strongly absorbing species (lambda/sub max/ = 515 nm; epsilon = 1.7 x 103 M-1) in the presence of 2-hydroxy-2-ethylbutyric acid buffers (pH 2-4). EPR data support 1:1 stoichiometry with VO2+ in deficiency, indicating the formation of a chromium(IV) species by reduction. With excess VO2+ a chromium(III) product was obtained. Spectral and ion-exchange properties of this product correspond to those observed for the titanium(III) and iron(II) reductions of chromium(V) and are consistent with the formulation of the product as a bis(hydroxycarboxylate) chelate of (H2O)2Cr/sup III/. With excess vanadium(IV), the reaction exhibits triphasic kinetics. The remaining step of the reaction is the reduction of the chromium(IV) intermediate with VO2+. Rates for all steps increase with decreasing [H+] and level off at low [H+]. The limiting rate constants for the formation of the chromium(IV) intermediate by the (Lig)3Cr(O)2- and (Lig)2Cr(O)- pathways are 2.8 x 103 and 2.2 x 102 M-1s-1. The bimolecular limiting rate constant for the reduction of chromium(IV) is computed to be 7.7 x 102 M-1 s-1. 33 references, 7 tables

  1. Transcriptomic analysis of cultured whale skin cells exposed to hexavalent chromium [Cr(VI)].

    Science.gov (United States)

    Pabuwal, Vagmita; Boswell, Mikki; Pasquali, Amanda; Wise, Sandra S; Kumar, Suresh; Shen, Yingjia; Garcia, Tzintzuni; Lacerte, Carolyne; Wise, John Pierce; Wise, John Pierce; Warren, Wesley; Walter, Ronald B

    2013-06-15

    Hexavalent chromium Cr(VI) is known to produce cytotoxic effects in humans and is a highly toxic environmental contaminant. Interestingly, it has been shown that free ranging sperm whales (Phyester macrocephalus) may have exceedingly high levels of Cr in their skin. Also, it has been demonstrated that skin cells from whales appear more resistant to both cytotoxicity and clastogenicity upon Cr exposure compared to human cells. However, the molecular genetic mechanisms employed in whale skin cells that might lead to Cr tolerance are unknown. In an effort to understand the underlying mechanisms of Cr(VI) tolerance and to illuminate global gene expression patterns modulated by Cr, we exposed whale skin cells in culture to varying levels of Cr(VI) (i.e., 0.0, 0.5, 1.0 and 5.0 μg/cm²) followed by short read (100 bp) next generation RNA sequencing (RNA-seq). RNA-seq reads from all exposures (≈280 million reads) were pooled to generate a de novo reference transcriptome assembly. The resulting whale reference assembly had 11K contigs and an N50 of 2954 bp. Using the reads from each dose (0.0, 0.5, 1.0 and 5.0 μg/cm²) we performed RNA-seq based gene expression analysis that identified 35 up-regulated genes and 19 down-regulated genes. The experimental results suggest that low dose exposure to Cr (1.0 μg/cm²) serves to induce up-regulation of oxidative stress response genes, DNA repair genes and cell cycle regulator genes. However, at higher doses (5.0 μg/cm²) the DNA repair genes appeared down-regulated while other genes that were induced suggest the initiation of cytotoxicity. The set of genes identified that show regulatory modulation at different Cr doses provide specific candidates for further studies aimed at determination of how whales exhibit resistance to Cr toxicity and what role(s) reactive oxygen species (ROS) may play in this process. PMID:23584427

  2. Analysis of incorporation cadmium and chromium VI by yeast strains using neutron activation

    International Nuclear Information System (INIS)

    Industrial and agricultural activities discharge in environment metals as Cd, Cu, Ni, Co, Zn, Pb and Cr. These metals pollute the environment, and contaminate foods which, when consumed, can cause damage to animals and human health. Common physic-chemical processes are not suitable for remediation of diluted effluents (concentration of metals until 100 ppm) because of their high cost. However bioremediation could be can an alternative for treatment these effluents. The success of bioremediation process involves the technology improve, based on a raw abundant, low cost and, effective material. Biological organisms remove metals through of two processes: Bioaccumulation (depend of metabolism to incorporate metal, therefore, use living cells) and Biosorption (adhesion of metals in compounds present in surface, therefore, cells can be dead). The objective of this research is to evaluate if an isolated yeast of cachaca fermentation can be used for metal capture. Thus, we compared the capacity of this yeast dead or live, to incorporate cadmium and chromium VI. We used the neutron activation technique to determine the concentration of the metal incorporated by the cells. The neutron activation was an easy, rapid and suitable technique to do these metal determinations in yeast cells. Living organisms need trace quantities of metals essential (Mg, Fe, Cu, Mn, Zn), but some heavy metals, as cadmium and mercury, don't have any biological function. Heavy metals incorporation can cause cell damage such as oxidative stress. We evaluated one stress oxidative markers in live yeast which incorporated metal: peroxidation of lipid. (author)

  3. Removal of hexavalent chromium [Cr(VI)] from aqueous solutions by the diatomite-supported/unsupported magnetite nanoparticles.

    Science.gov (United States)

    Yuan, Peng; Liu, Dong; Fan, Mingde; Yang, Dan; Zhu, Runliang; Ge, Fei; Zhu, JianXi; He, Hongping

    2010-01-15

    Diatomite-supported/unsupported magnetite nanoparticles were prepared by co-precipitation and hydrosol methods, and characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the unsupported and supported magnetite nanoparticles are around 25 and 15 nm, respectively. The supported magnetite nanoparticles exist on the surface or inside the pores of diatom shells, with better dispersing and less coaggregation than the unsupported ones. The uptake of hexavalent chromium [Cr(VI)] on the synthesized magnetite nanoparticles was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium [Cr(III)]. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed a pseudo-second-order model. The adsorption data of diatomite-supported/unsupported magnetite fit well with the Langmuir isotherm equation. The supported magnetite showed a better adsorption capacity per unit mass of magnetite than unsupported magnetite, and was more thermally stable than their unsupported counterparts. These results indicate that the diatomite-supported/unsupported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution. PMID:19748178

  4. Linear sweep anodic stripping voltammetry: Determination of Chromium (VI) using synthesized gold nanoparticles modified screen-printed electrode

    Indian Academy of Sciences (India)

    Salamatu Aliyu Tukur; Nor Azah Yusof; Reza Hajian

    2015-06-01

    A highly sensitive electrochemical sensor has been constructed for determination of Cr(VI) with the lowest limit of detection (LOD) reported to date using gold nanoparticles (AuNPs) modified screen-printed electrode (SPE). The modification of SPE by casting pure AuNPs increases the sensitivity for detection of Cr(VI) ion using anodic stripping voltammetry. Cr(VI) ions are reduced to chromium metal on SPE-AuNPs by applying deposition potential of –1.1 V for 180 s. Afterwards, the oxidation peak current of chromium is obtained by linear sweep voltammetry in the range of −1.0 V to 0.2 V. Under the optimized conditions (HClO4, 0.06 mol L−1; deposition potential, –1.1 V; deposition time, 180s; scan rate, 0.1 V s−1), the limit of detection (LOD) was 1.6 pg mL−1. The fabricated electrode was successfully used for detection of Cr(VI) in tap and seawater.

  5. ADSORPTION OF CHROMIUM (VI FROM AQUEOUS SOLUTIONS BY DIFFERENT ADMIXTURES – A BATCH EQUILIBRIUM TEST STUDY

    Directory of Open Access Journals (Sweden)

    K. SHIVA PRASHANTH KUMAR

    2014-08-01

    Full Text Available Wide variety of inorganic compounds such as nutrients and trace metals, organic chemicals, radioactive contaminants and pathogens are commonly present as contaminants in the groundwater. Migration of contaminants in soil involves important mechanisms such as molecular diffusion, dispersion under physical processes, adsorption, precipitation and oxidation - reduction under chemical processes and biodegradation under biological process. Cr (VI is a major and dangerous contaminant as per the ground water is concerned. There are numerous research work carried out with concentrated efforts by the researchers towards removal of Cr (VI contaminant from aqueous solutions. There are few studies relevant to Cr (VI removal with respect to utilization of low cost admixtures and also soil type. In the present study, different low cost admixtures like rice husk (RH, shredded tyre (ST and fly ash (FA are used to understand the performance in removal of Cr (VI from aqueous solution and also two different soil types are used along with the admixture. The results are discussed in terms of sorption capacity and performance of individual admixture and combination of admixture with soil in removal of contaminant. The fly ash, rice husk and shredded tyre admixtures are used and the results revealed that the shredded tyre showed higher performance in removal of contaminant concentration. Also, the soil which has more fine particle content (size<0.075 mm IS sieve showed reasonable reduction in concentration of contaminant at the lower levels of contaminant initial concentration. The sorption capacity results of Cr (VI contaminant, treated with various admixtures are further validated with the published work of other investigators. The shredded tyre (ST showed more adsorption capacity, i.e., 3.283 mg/g at pH of 4.8. For other admixtures, adsorption capacity value is varying in the range of 0.07 mg/g to 1.7 mg/g. Only in case of activated alumina and modified saw dust

  6. Graphene quantum dots as on-off-on fluorescent probes for chromium(VI) and ascorbic acid

    International Nuclear Information System (INIS)

    We report that graphene quantum dots (GQDs) are viable fluorescent probes for the determination of chromium(VI) and ascorbic acid in an on-off-on mode. The fluorescence of GQDs is strongly quenched by Cr(VI) mainly due to an inner filter effect and static quenching. This shifts the system to the “off” status. The quenching mechanism of this fluorescent system was investigated in some detail. Fluorescence intensity is inversely proportional to the concentration of Cr(VI) in the 0.05 to 500 μM concentration range with a 3.7 nM detection limit. The fluorescence of GQDs-Cr(VI) system is converted back to “on” by adding ascorbic acid which will reduce yellow Cr(VI) ion, thereby eliminating the inner filter effect and static quenching. The relative intensity of restored fluorescence is directly proportional to the concentration of ascorbic acid in the 1.0 to 500 μM range, and the limit of detection is 0.51 μM. There are almost no interferences to commonly encountered other substances. The methods were applied to the determination of Cr(VI) in spiked tape, lake and river waters, and of ascorbic acid in a tablet and human urine. Both gave satisfactory results. (author)

  7. An organic-reagent-free method for determination of chromium(VI) in steel alloys, sewage sludge and wastewater.

    Science.gov (United States)

    Fan, Jing; Sun, Yuping; Wang, Jianji; Fan, Maohong

    2009-04-27

    One of the active areas of green chemistry research and development is in the development of new analytical methods and techniques that reduce and eliminate the use and generation of hazardous substances. In this work, a rapid and organic-reagent-free method was developed for the determination of chromium(VI) by sequential injection analysis (SIA). The method was based on the detection of a blue unstable intermediate compound resulting from the reaction of Cr(VI) with hydrogen peroxide (H(2)O(2)) in acidic medium. H(2)O(2) and its reaction products were environmentally friendly, and chromogenic reagents and organic solvents were not used in the proposed method. Different SIA parameters have been optimized and used to obtain the analytical figures of merit. Under the optimum experimental conditions, the linear range for Cr(VI) was 0.5-100.0 microg mL(-1), and the detection limit was 0.16 microg mL(-1). The sample throughput was 80 h(-1), and the total volume of only 145 microL was consumed in each determination of Cr(VI). The method was applied for the determination of Cr(VI) in seven real samples, including alloy steel, sewage sludge and wastewater samples, and the results were compared with those obtained by atomic absorption spectrometry as well as with the certified value of Cr(VI) in standard reference material. Statistical analysis revealed that there was no significant difference at 95% confidence level. PMID:19362620

  8. MODELING HEXAVALENT CHROMIUM REDUCTION IN GROUND- WATER IN FIELD-SCALE TRANSPORT AND LABORATORY BATCH EXPERIMENTS

    Science.gov (United States)

    A plausible and consistent model is developed to obtain a quantitative description of the gradual disappearance of hexavalent chromium (Cr(VI)) from groundwater in a small-scale field tracer test and in batch kinetic experiments using aquifer sediments under similar chemical cond...

  9. In vitro development and improvement of chromium (vi)-affected adventitious roots of solanum tuberosum l. with ga/sub 3/ and iaa application

    International Nuclear Information System (INIS)

    This study was undertaken In vitro to investigate the inhibitory effects of Chromium (Cr) VI by using K/sub 2/Cr/sub 2/O/sub 7/ on the growth of adventitious roots of potato (Solanum tuberosum L. cv Desiree). Another objective was to determine possible reversal of the detrimental growth effects with suitable combinations of GA/sub 3/ and IAA. It was observed that the applied Cr VI (100 ppm) alone in MS media inhibited root growth. However, addition of selected combinations of GA/sub 3/ and IAA in the MS media along with Cr VI improved the root growth. The plants grown on MS medium + 100 ppm K/sub 2/Cr/sub 2/O/sub 7/ resulted in reduction in number of adventitious roots up to 36.26%, number of rootlets (80.64%), diameter (37.27%), fresh and dry weights (72.96 and 84.74%, respectively) in comparison with control (MS medium). MS media containing 100 ppm K/sub 2/Cr/sub 2/O/sub 7/ + 20 ppm GA/sub 3/ + 16 ppm IAA enhanced the average number of roots from 4.78 to 62.6, number of rootlets from 2.6 to 28.2, diameter from 0.13 mm to 0.68 mm, fresh weight from 34.4 mg to 1234.75 mg and dry weight from 1.8 mg to 80.40 mg compared with cultures grown on MS + 100 ppm Cr (VI). The results thus highlight the fact that the deleterious effects of Cr VI on potato growth In vitro can be reversed with suitable hormonal treatments. Furthermore, this research has possible implications on large scale potato cultivation under heavy metal stress in a broader sense. (author)

  10. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite.

    Science.gov (United States)

    Benhammou, A; Yaacoubi, A; Nibou, L; Tanouti, B

    2005-01-31

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na(2)S(2)O(4). Then, the adsorption experiments were studied in batch reactors at 25+/-3 degrees C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg(-1)min(-1) and that of Cr(VI) is 7.21 mmol kg(-1)min(-1). The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg(-1) (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg(-1). The mechanism of Hg(II) and Cr(VI) adsorption was discussed. PMID:15629583

  11. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

    International Nuclear Information System (INIS)

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na2S2O4. Then, the adsorption experiments were studied in batch reactors at 25 ± 3 deg. C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg-1 min-1 and that of Cr(VI) is 7.21 mmol kg-1 min-1. The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg-1 (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg-1. The mechanism of Hg(II) and Cr(VI) adsorption was discussed

  12. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

    Energy Technology Data Exchange (ETDEWEB)

    Benhammou, A. [Ecole Superieure de Technologie, Route Dar Si Aissa, BP: 89 Safi (Morocco)]. E-mail: benhammou_ab@yahoo.fr; Yaacoubi, A. [Faculte des Sciences Semlalia, Avenue My Abdellah, BP: 2390 Marrakech (Morocco); Nibou, L. [Ecole Superieure de Technologie, Route Dar Si Aissa, BP: 89 Safi (Morocco); Tanouti, B. [Faculte des Sciences Semlalia, Avenue My Abdellah, BP: 2390 Marrakech (Morocco)

    2005-01-31

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na{sub 2}S{sub 2}O{sub 4}. Then, the adsorption experiments were studied in batch reactors at 25 {+-} 3 deg. C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg{sup -1} min{sup -1} and that of Cr(VI) is 7.21 mmol kg{sup -1} min{sup -1}. The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg{sup -1} (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg{sup -1}. The mechanism of Hg(II) and Cr(VI) adsorption was discussed.

  13. Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

    Directory of Open Access Journals (Sweden)

    Arundhati Pal

    2013-06-01

    Full Text Available Bacillus sphaericus AND 303, a Cr(VI-resistant and reducing bacterium reported from serpentine outcrops of Andaman was evaluated for Cr(VI reduction using immobilized cells under batch culture. Screening of inert matrices for entrapment of whole cells indicated that polyvinyl alchohol-alginate was the most effective one reducing 87.5% of 20 µM Cr(VI in 24 h. The rate of chromate reduction was dependent on initial Cr(VI and biomass concentrations. The PVA cell beads were recycled three times without cell leakage and disintegration. The reduction efficiency was improved in the presence of glucose and glycerol as electron donors leading to complete reduction. However, the presence of additional metal ions was inhibitory to Cr(VI reduction. It could be emphasized that PVA-alginate immobilized cells of B. sphaericus AND 303 could be used as a continuous bioprocess in treating Cr(VI contaminated effluents.

  14. Effect of trace metals and electron shuttle on simultaneous reduction of reactive black-5 azo dye and hexavalent chromium in liquid medium by Pseudomonas sp.

    Science.gov (United States)

    Mahmood, Shahid; Khalid, Azeem; Arshad, Muhammad; Ahmad, Riaz

    2015-11-01

    This study demonstrates the role of electron shuttles and trace metals in the biotransformation of azo dye reactive black-5 and hexavalent chromium (CrVI) that are released simultaneously in tannery effluent. Previously isolated bacterial strain Pseudomonas putida KI was used for the simultaneous reduction of the dye (100 mg L(-1)) and CrVI (2 mg L(-1)) in a mineral salts medium (MSM). Among various trace metals, only Cu(II) had a stimulating effect on the bacterial-mediated reduction process. Application of electron shuttles such as hydroquinone and uric acid at a low concentration (1mM) had a positive effect on the reduction process and caused simultaneous reduction of 100% dye and 97% CrVI in 12-18 h. Mannitol, EDTA and sodium benzoate at all concentrations (ranging from 1 to 9 mM) showed an inhibitory effect on the reduction of reactive black-5 and CrVI. An inverse linear relationship between the velocity of reaction (V) and the concentration [S] of electron shuttles was observed. The results imply that both types and concentration of an electron shuttle and trace metals can affect the simultaneous reduction of reactive black-5 and CrVI. PMID:25556007

  15. Groundwater contaminated with hexavalent chromium [Cr (VI]: a health survey and clinical examination of community inhabitants (Kanpur, India.

    Directory of Open Access Journals (Sweden)

    Priti Sharma

    Full Text Available BACKGROUND: We assessed the health effects of hexavalent chromium groundwater contamination (from tanneries and chrome sulfate manufacturing in Kanpur, India. METHODS: The health status of residents living in areas with high Cr (VI groundwater contamination (N = 186 were compared to residents with similar social and demographic features living in communities having no elevated Cr (VI levels (N = 230. Subjects were recruited at health camps in both the areas. Health status was evaluated with health questionnaires, spirometry and blood hematology measures. Cr (VI was measured in groundwater samples by diphenylcarbazide reagent method. RESULTS: Residents from communities with known Cr (VI contamination had more self-reports of digestive and dermatological disorders and hematological abnormalities. GI distress was reported in 39.2% vs. 17.2% males (AOR = 3.1 and 39.3% vs. 21% females (AOR = 2.44; skin abnormalities in 24.5% vs. 9.2% males (AOR = 3.48 and 25% vs. 4.9% females (AOR = 6.57. Residents from affected communities had greater RBCs (among 30.7% males and 46.1% females, lower MCVs (among 62.8% males and less platelets (among 68% males and 72% females than matched controls. There were no differences in leucocytes count and spirometry parameters. CONCLUSIONS: Living in communities with Cr (VI groundwater is associated with gastrointestinal and dermatological complaints and abnormal hematological function. Limitations of this study include small sample size and the lack of long term follow-up.

  16. Investigations on photoelectrocatalytic reduction of Cr(VI) over titanium dioxide anode and metal cathode

    International Nuclear Information System (INIS)

    Photocatalytic and photoelectrocatalytic (PEC) reductions of Cr(VI) based on TiO2 thin films were investigated under various conditions. Photogenerated electrons transferred from TiO2 thin film to cathode can contribute to PEC reduction of Cr(VI) only when the Fermi level of cathode lies above the chemical potential of Cr(VI), almost independent on the applied voltage of the direct current. In addition, the TiO2-coated anode is the major site that accommodates the PEC reduction of Cr(VI) with hole scavenger citric acid, regardless of the Fermi level of the cathode. Although electron transfer from TiO2 to Cr(VI) is an exothermic process, the photogenerated holes in TiO2 can markedly hamper Cr(VI) reduction over the TiO2 thin film by oxidizing the lower-valence Cr back to Cr(VI), which may be counteracted by the citric acid. This research provides some in-depth insights on developing photocatalysts which enable highly efficient PEC reduction of Cr(VI) in the future. - Highlights: • Cr(VI) reduction on TiO2 photoanode is dominant with the addition of citric acid. • Cr(VI) is reduced on photocathode with Fermi level above Cr(VI) chemical potential. • Photogenerated holes can hamper Cr(VI) photoreduction over TiO2

  17. Study of the biosorption of chromium (VI) on crosslinked-quaternary chitosan for their application on the bioremediation of waster waters

    International Nuclear Information System (INIS)

    In this work, the stoichiometric amounts of the amino-quaternaries and cross-linker were studied to produce the most stable cross-linked quaternary Chitosan (QC2). Preliminary assays were carried out to test the improvement in their mechanical and chemical properties (extreme conditions, surface area and thermogravimetry). Then, the adsorption of chromium (VI) on the QC2 was studied at changing experimental conditions like: pH, adsorbent dose, initial chromium concentration and ionic strength. Moreover, the kinetics of the process was also evaluated as well as the optimization, the desorption of chromium (VI) from the adsorbent for metal recovery and adsorbent recycling. Finally, was characterized by using instrumental techniques such as FTIR, SEM. These tools allowed us to investigate the adsorption mechanism. The calculated parameters indicate a high adsorbent/adsorbato affinity for QC2 with a maximum adsorption capacity of 208 mg g-1 for Cr (VI), elucidating its potential use for the removal of chromium from aqueous solutions. Also showed a pseudo-second order adsorption kinetics with a velocity constant of 0.289 g.mg-1.min-1. Desorption of chromium was efficiently accomplish with a mixture of 1M of NaCl and NaOH, reaching a recovery up to 99.78% of the initial metal concentration at pH 4.5. Finally, high ionic strength shows an effect on the adsorption of chromium (VI) onto the studied adsorbents. (author)

  18. Memory Effect of Mg―Al Hydrotalcites and Its Chromium(VI) Adsorption Property

    OpenAIRE

    ZHAO Ce, ZENG Hong-Yan, WANG Ya-Ju, LIU Ping-Le, LI Yu-Qin, YANG Yong-Jie

    2011-01-01

    Mg―Al hydrotalcite (MAH) with high crystallinity was prepared using urea method. The memory effect and the chromium(VI) adsorption property of Mg―Al Hydrotalcites were studied. The MAH, reconstructed MAH (RMAH), calcined MAH (MAO) and calcined RMAH (RMAO) were characterized by XRD, FT―IR, SEM and DSC as well as self―deconvolution analyses. The results showed that the MAH and RMAH possessed a layered structure of hyd...

  19. Cr stable isotopes as indicators of Cr(VI) reduction in groundwater: a detailed time-series study of a point-source plume.

    Science.gov (United States)

    Berna, Emily C; Johnson, Thomas M; Makdisi, Richard S; Basu, Anirban

    2010-02-01

    Chromium stable isotope ratios show promise as indicators of Cr(VI) reduction in groundwater, but no published study has yet demonstrated that expected relationships between (53)Cr/(52)Cr and Cr(VI) concentration, position, and time occur in an actual groundwater plume. We present an extensive data set from a point-source plume in Berkeley, CA; data extend over 5 years and 14 locations covering the entire plume. We interpret the data using a Rayleigh distillation model with an effective fractionation factor that incorporates an intrinsic fractionation factor determined from incubations of site sediments and accounts for reservoir effects in the restricted subsurface zones where Cr(VI) reduction is thought to occur. The groundwater (53)Cr/(52)Cr and Cr(VI) concentration data are consistent with a scenario where the system has reached a steady state: Cr(VI) reduction continues, the extent of reduction at any point is constant over time, reduction proceeds to completion at the downgradient edge of the plume, and the plume is no longer advancing. The overall consistency of the results with a reasonable model for the site supports the use of Cr isotope-based estimates of reduction, but we discuss current uncertainties and limitations of the approach as well. PMID:20039722

  20. Chromium plating pollution source reduction by plasma source ion implantation

    International Nuclear Information System (INIS)

    There is growing concern over the environmental toxicity and workers' health issues due to the chemical baths and rinse water used in the hard chromium plating process. In this regard the significant hardening response of chromium to nitrogen ion implantation can be environmentally beneficial from the standpoint of decreasing the thickness and the frequency of application of chromium plating. In this paper the results of a study of nitrogen ion implantation of chrome plated test flats using the non-line-of-sight Plasma Source Ion Implantation (PSII) process, are discussed. Surface characterization was performed using Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), and Electron Spectroscopy for Chemical Analysis (ESCA). The surface properties were evaluated using a microhardness tester, a pin-on-disk wear tester, and a corrosion measurement system. Industrial field testing of nitrogen PSII treated chromium plated parts showed an improvement by a factor of two compared to the unimplanted case

  1. Adsorption of chromium(VI) from aqueous solutions by glycidylmethacrylate-grafted-densified cellulose with quaternary ammonium groups

    Science.gov (United States)

    Anirudhan, T. S.; Nima, J.; Divya, P. L.

    2013-08-01

    This study successfully synthesized a new adsorbent by ethylation of glycidylmethacrylate grafted aminated titanium dioxide densified cellulose (Et-AMPGDC), to remove chromium(VI) from aqueous solutions. The adsorbent was characterized by the FTIR, XRD, SEM and TG-DTG measurements. Batch adsorption technique using Et-AMPGDC was applied for the removal of Cr(VI) from aqueous solution and waste water. The contact time necessary to attain equilibrium and the optimum pH were found to be 1 h and 4.5, respectively. The kinetics of sorption of Cr(VI) ions was described by a pseudo-second-order kinetic model. The equilibrium isotherm data were analyzed using the Langmuir and Freundlich isotherm equations and the adsorption process was reflected by Langmuir isotherm. The maximum adsorption capacity was evaluated to be 123.60 mg/g. The electroplating industrial wastewater samples were treated with Et-AMPGDC to demonstrate its efficiency in removing Cr(VI) from wastewater. Almost complete removal was possible with 100 mg of the adsorbent from 50 mL of wastewater sample. Desorption efficiency was achieved by treatment with 0.1 M NaOH and five adsorption-desorption cycles were performed without significant decrease in adsorption capacity.

  2. A review of chemical, electrochemical and biological methods for aqueous Cr(VI) reduction.

    Science.gov (United States)

    Barrera-Díaz, Carlos E; Lugo-Lugo, Violeta; Bilyeu, Bryan

    2012-07-15

    Hexavalent chromium is of particular environmental concern due to its toxicity and mobility and is challenging to remove from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. It does not form insoluble compounds in aqueous solutions, so separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, Cr(III) cations are not. Like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI) to Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. In this review, we describe the environmental implications of Cr(VI) presence in aqueous solutions, the chemical species that could be present and then we describe the technologies available to efficiently reduce hexavalent chromium. PMID:22608208

  3. Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

    OpenAIRE

    Arundhati Pal; Sudeshna Datta; Amal K. Paul

    2013-01-01

    Bacillus sphaericus AND 303, a Cr(VI)-resistant and reducing bacterium reported from serpentine outcrops of Andaman was evaluated for Cr(VI) reduction using immobilized cells under batch culture. Screening of inert matrices for entrapment of whole cells indicated that polyvinyl alchohol-alginate was the most effective one reducing 87.5% of 20 µM Cr(VI) in 24 h. The rate of chromate reduction was dependent on initial Cr(VI) and biomass concentrations. The PVA cell beads were recycled three tim...

  4. STEMS AND THEIR ASHES OF SOME HERBAL PLANTS AS ADSORBENTS IN THE REMOVAL OF CHROMIUM (VI FROM WASTE WATERS

    Directory of Open Access Journals (Sweden)

    V. Krishna Veni

    2013-03-01

    Full Text Available A thorough investigation is made to explore the surface sorption abilities of powders of stems and their ashes of some herbal plants in controlling the Chromium (VI pollution in waste waters. It is found that the powders of stems and their ashes of Achyranthes aspera, Mentha, Emblica officinalis, Hybiscus roja sinensis, Ocimum sanctum and Psidium guajava have strong affinity towards Chromate at low pH values. % of removal of Chromate is found to be pH sensitive and also depends on sorption concentration and time of equilibration. The conditions for the maximum extraction of Chromate at minimum dosage of sorbent and equilibration time have been optimized. More than 90.0% of removal of Chromate is found. Sorbent concentrations and time needed for the maximum removal of Chromate is less for the ashes of stems than with the raw stem powders. The presence of ten fold excesses of Cations : Ca2+, Mg2+ , Cu2, Zn2+ and Ni2 + and anions like NO3 - ,Chloride, Fluoride and Carbonate have marginally effected the % removal of Chromium (VI while Sulphate and Phosphate showed some interference with some sorbents but even with them, the % of extractability never comes down to 71.0%. The adoptability of the methodologies developed in this work are tested with respect to diverse waste water samples collected from industrial effluents and in natural lakes and found to be remarkably successful.

  5. Brief report on thermodynamics of chromium slags and kinetic modelling of chromite reduction (1995-96)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Yamping; Holappa, L. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Metallurgy

    1996-12-31

    This article summaries the research work on thermodynamics of chromium slags and kinetic modelling of chromite reduction. The thermodynamic properties of FeCr slag systems were calculated with the regular solution model. The effects of CaO/MgO ratio, Al{sub 2}0{sub 3} amount as well as the slag basicity on the activities of chromium oxides and the oxidation state of chromium were examined. The calculated results were compared to the experimental data in the literature. In the kinetic modelling of the chromite reduction, the reduction possibilities and tendencies of the chromite constitutes with CO were analysed based on the thermodynamic calculation. Two reaction models, a structural grain model and a multi-layers reaction model, were constructed and applied to simulate the chromite pellet reduction and chromite lumpy ore reduction, respectively. The calculated reduction rates were compared with the experimental measurements and the reaction mechanisms were discussed. (orig.) SULA 2 Research Programme; 4 refs.

  6. A plan for study of hexavalent chromium, CR(VI) in groundwater near a mapped plume, Hinkley, California, 2016

    Science.gov (United States)

    Izbicki, John A.; Groover, Krishangi

    2016-01-01

    The Pacific Gas and Electric Company (PG&E) Hinkley compressor station, in the Mojave Desert 80 miles northeast of Los Angeles, is used to compress natural gas as it is transported through a pipeline from Texas to California. Between 1952 and 1964, cooling water used at the compressor station was treated with a compound containing chromium to prevent corrosion. After cooling, the wastewater was discharged to unlined ponds, resulting in contamination of soil and groundwater in the underlying alluvial aquifer (Lahontan Regional Water Quality Control Board, 2013). Since 1964, cooling-water management practices have been used that do not contribute chromium to groundwater.In 2007, a PG&E study of the natural background concentrations of hexavalent chromium, Cr(VI), in groundwater estimated average concentrations in the Hinkley area to be 1.2 micrograms per liter (μg/L), with a 95-percent upper-confidence limit of 3.1 μg/L (CH2M-Hill, 2007). The 3.1 μg/L upper-confidence limit was adopted by the Lahontan Regional Water Quality Control Board (RWQCB) as the maximum background concentration used to map the plume extent. In response to criticism of the study’s methodology, and an increase in the mapped extent of the plume between 2008 and 2011, the Lahontan RWQCB (Lahontan Regional Water Quality Control Board, 2012) agreed that the 2007 PG&E background-concentration study be updated.The purpose of the updated background study is to evaluate the presence of natural and man-made Cr(VI) near Hinkley, Calif. The study also is to estimate natural background Cr(VI) concentrations in the aquifer upgradient and downgradient from the mapped Cr(VI) contamination plume, as well as in the plume and near its margins. The study was developed by the U.S. Geological Survey (USGS) in collaboration with a technical working group (TWG) composed of community members, the Independent Review Panel (IRP) Manager (Project Navigator, Ltd.), the Lahontan RWQCB, PG&E, and consultants for PG&E.&E.

  7. Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis

    OpenAIRE

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

    2012-01-01

    The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric curre...

  8. Forensic investigation of a chromium(VI) groundwater plume in Thiva, Greece

    Energy Technology Data Exchange (ETDEWEB)

    Panagiotakis, I. [National Technical Univ. of Athens, Zografou (Greece); Dermatas, D. [National Technical Univ. of Athens, Zografou (Greece); Vatseris, C. [Intergeo-Environmental Technology Ltd., Thessaloniki (Greece); Chrysochoou, M. [Univ. of Connecticut, Storrs, CT (United States); Papassiopi, N. [National Technical Univ. of Athens, Zografou (Greece); Xenidis, A. [National Technical Univ. of Athens, Zografou (Greece); Vaxevanidou, K. [National Technical Univ. of Athens, Zografou (Greece)

    2015-01-01

    We conducted a forensic investigation with the aim of decoupling the contribution of geogenic and anthropogenic Cr(VI) sources in the wider area of Thiva. Groundwater and topsoil samples were collected from two Cr(VI) groundwater plumes of 160 μg/L and 75 μg/L. A series of evidence support the view that the origin of Cr(VI) detected in groundwater is mainly geogenic. These are: (a) the presence of Cr in topsoil of the wider area, (b) the moderate Cr(VI) groundwater concentrations, (c) the high Ni levels within the Cr(VI) plumes, (d) the predominance of Mn(IV), which is a prerequisite for Cr(III) oxidation to Cr(VI), and (e) the absence of co-contaminants. This study also revealed that, although both Cr(VI) plumes are clearly of geogenic origin, the plume with the elevated Cr(VI) values, in the north of Thiva town, exhibits also an anthropogenic component, which can potentially be attributed to the alkaline environment associated with the old uncontrolled landfill of Thiva and the industrial cluster located in this area.

  9. Thermodynamic analysis of sorption isotherms of chromium(VI) anionic species on reed biomass

    International Nuclear Information System (INIS)

    A new sorbent material for removing Cr(VI) anionic species from aqueous solutions has been investigated. Adsorption equilibrium and thermodynamics of Cr(VI) anionic species onto reed biomass were studied at different initial concentrations, sorbent concentrations, pH levels, temperatures, and ionic strength. Equilibrium isotherm was analyzed by Langmuir model. The experimental sorption data fit the model very well. The maximum sorption capacity of Cr(VI) onto reed biomass was found to be 33 mg . g-1. It was noted that the Cr(VI) adsorption by reed biomass decreased with increase in pH. An increase in temperature resulted in a higher Cr(VI) loading per unit weight of the adsorbent. Removal of Cr(VI) by reed biomass seems to be mainly by chemisorption. The change in entropy (ΔS0) and heat of adsorption (ΔH0) for Cr(VI) adsorption on reed biomass were estimated as 2205 kJ . kg-1 . K-1 and 822 kJ . kg-1, respectively. The values of isosteric heat of adsorption varied with the surface loading of Cr(VI)

  10. X-ray absorption spectroscopy study of chromium recovered from Cr(VI)-containing water with rice husk

    International Nuclear Information System (INIS)

    The characteristics of the richness in silica and the high porosity of rice husk enable its application as a good, yet cheap, heavy metal adsorbent from wastewater. This study used rice husk to sorb Cr(VI) from wastewater that contained 2000 mg Cr(VI) l-1. Results of a scanning electron microscopy (SEM) experiment indicate a considerable morphology alteration of the rice husk after the sorption experiments. 13C-nuclear magnetic resonance (NMR) measurements show significant decrease in intensity of all the following peaks: carbonylic, carboxylic, aromatic, polysaccharides, carbohydrates and aliphatics. The X-ray absorption near edge structure (XANES) result indicates that about 70% and 90% of the Cr(VI) sorbed on the rice husk after the 12 and 48 h sorption experiments, respectively, were in Cr(III) forms. In the 12 h sorbed rice husk sample, the chromium species distribution is 41% organic Cr(III) +27%Cr(OH)3+32%CrO3, while in the 48 h sorbed one, it is 57% organic Cr(III) +31%Cr(OH)3+12%CrO3

  11. A MIXED CHEMICAL REDUCTANT FOR TREATING HEXAVALENT CHROMIUM IN A CHROMITE ORE PROCESSING SOLID WASTE

    Science.gov (United States)

    We evaluated a method for delivering ferrous iron into the subsurface to enhance chemical reduction of Cr(VI) in a chromite ore processing solid waste (COPSW). The COPSW is characterized by high pH (8.5 -11.5), high Cr(VI) concentrations in the solid phase (up to 550 mg kg-1) and...

  12. Phycoremediation of Chromium (VI) by Nitella and impact of calcium encrustation

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Pattiyage I.A. [Department of Environmental Science and Technology, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8770 (Japan); Asaeda, Takashi, E-mail: asaeda@mail.saitama-u.ac.jp [Department of Environmental Science and Technology, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8770 (Japan)

    2009-07-30

    This article discusses the applicability of the Charophyte, Nitella pseudoflabellata in the remediation of Cr (VI) contaminated waters at different calcifying potentials. Its growth was found to be positively correlated with Ca in water (CaW), but marginally significant in the presence of Cr (VI) in water (CrW). High CaW resulted in calcite encrustation on the plant cell wall. CaW was found to be aiding Cr (VI) fixation in the long run, as this correlated positively with both CaW and CrW. However, Ca interfered with passive Cr (VI) accumulation in live plant matter at low CrW concentrations ({<=}0.2 mg/L). Biosorption by dead plant matter seemed to be the major mechanism as the dead plant organs contained >1 mg/g Cr dry weight of plant. Cr (VI) concentrations greater than 0.4 mg/L were too toxic, showing maximum quantum efficiency of PSII photochemistry (F{sub v}/F{sub m}) values < 0.63. The opposite was noticed (F{sub v}/F{sub m} > 0.76) when Cr (VI) was less than 0.2 mg/L. Elongation curve patterns based on shoot lengths showed similar scenarios. In all cases high CaW units with calcite encrustation found to be least affected by Cr (VI) toxicity. Optimum remediation was obtained using a combination of high Ca and Cr (VI) in the case of passive (short-term) operation and low Ca and Cr (VI) for active (long-term) operation. Under the passive scenario, plants accumulated above 1.2 mg/g Cr dry weight whereas in the active case, accumulation was 0.8 mg/g Cr dry weight. We conclude that Nitella-mediated Cr (VI) remediation is a promising technique within the range and conditions investigated.

  13. Characterization of the biochemical-pathway of uranium (VI) reduction in facultative anaerobic bacteria.

    Science.gov (United States)

    Mtimunye, Phalazane J; Chirwa, Evans M N

    2014-10-01

    Cultures of U(VI) reducing bacteria sourced from abandoned uranium mine tailing dam were evaluated for their ability to reduce U(VI) to U(IV). The species in the cultures reduced U(VI) in solutions with initial U(VI) concentration up to 400mgL(-)(1) under a near neutral pH of 6.5. The electron flow pathway and fate of reduced species was also analysed in the individual species in order to evaluate the potential for control and optimisation of the reduction potential at the biochemical level. The results showed that U(VI) reduction in live cells was completely blocked by the NADH-dehydrogenase inhibitor, rotenone (C23H22O6), and thioredoxin inhibitor, cadmium chloride (CdCl2), showing that U(VI) reduction involves the electron flow through NADH-dehydrogenase, a primary electron donor to the electron transport respiratory (ETR) system. Mass balance analysis of uranium species aided by visual and electron microscopy suggest that most U(VI) reduction occurred on the cell surface of the isolated species. This finding indicates the possibility of easy uranium recovery for beneficial use through biological remediation. Should the U(VI) be reduced inside the cell, recovery would require complete disruption of the cells and therefore would be difficult. The study contributes new knowledge on the underlying mechanisms in the U(VI) reduction in facultative anaerobes. PMID:25065785

  14. Determination of Hexavalent Chromium (Cr(VI)) Concentrations via Ion Chromatography and UV-Vis Spectrophotometry in Samples Collected from Nacogdoches Wastewater Treatment Plant, East Texas (USA)

    OpenAIRE

    Onchoke, Kefa K.; Sasu, Salomey A.

    2016-01-01

    The concentration of hexavalent chromium (Cr(VI)), a toxic environmental pollutant and carcinogen, was determined in samples collected from Nacogdoches Wastewater Treatment Plant (NWWTP) using ion chromatography and UV-visible spectrophotometry (IC, UV-Vis). On reaction with 1,5-diphenylcarbazide (DPC) Cr+6 forms a 1,5-diphenylcarbazide-Cr(VI) complex, which is then analyzed at 530 nm and 540 nm, respectively. Via ion chromatography Cr(VI) concentrations were in the range of 0.00190±0.0020 an...

  15. Chromium (VI removal from aqueous solutions by purolite base anion-exchange resins with gel structure

    Directory of Open Access Journals (Sweden)

    Balan Catalin

    2013-01-01

    Full Text Available The removal of Cr (VI from aqueous solution using two strong base anionic resins with gel structure, Purolite A-400 (styrene-divinylbenzene matrix and Purolite A-850 (acrylic matrix was investigated in batch technique. The sorption efficiency was determined as a function of phases contact time, solution pH, resin dose, temperature and initial Cr (VI concentration. The percentage of Cr (VI removed reaches maximum values (up to 99 % in the pH range 4 - 5.3 under a resin dose of 6 g/L and of Cr (VI concentration up to 100 mg/L. An increase in temperature has a positive effect on the Cr (VI sorption process. The equilibrium sorption data were fitted with the Freundlich, Langmuir and Dubinin-Radushkevich isotherm models, using both linear and nonlinear regression method. The Langmuir model very well verifies the experimental data and gives the maximum sorption capacity of 120.55 mg Cr (VI/g and 95.82 mg Cr (VI/g for A-400 and A-850 resins, respectively. The thermodynamic study and mean free energy of sorption values calculated using Dubinin-Radushkevich equation indicated the sorption is a chemical endothermic process. The kinetic data were well described by pseudo-second order kinetic equation and the sorption process is controlled by external (film diffusion and intraparticle diffusion.

  16. Sorption of chromium (VI) by Mg/Fe hydrotalcite type compunds

    International Nuclear Information System (INIS)

    The synthesis by co-precipitation and characterization by X-ray diffraction, Raman and Mössbauer spectroscopies of Mg-Fe-hydrotalcite compounds, and their sorption capacities for Cr(VI) in aqueous media were carried out. The average sorption capacity of Cr(VI) for the non-thermal treated samples was of 6.2 mg/g. The ferrihydrite was omnipresent in all prepared hydrotalcite samples. A brief discussion is made on the role of both the hydrotalcite and ferrihydrite for removing such amount of Cr(VI)

  17. Equilibrium and kinetic study on chromium (VI removal from simulated waste water using gooseberry seeds as a novel biosorbent

    Directory of Open Access Journals (Sweden)

    J. Aravind

    2015-07-01

    Full Text Available Gooseberry seed (Phyllanthus acidus was used as an adsorbent to determine its feasibility for the removal of Cr(VI. Various parameters such as pH, temperature, contact time, initial metal concentration and adsorbent dosage were investigated to determine the biosorption performance. Equilibrium was attained within 60 minutes and maximum removal of 96% was achieved under the optimum conditions at pH 2. The adsorption phenomenon demonstrated here was monolayer represented by Langmuir isotherm with R2 value of 0.992 and the Langmuir constants k and q0 was found to be 0.0061 (L/mg and 19.23 (mg/g. The adsorption system obeyed Pseudo second order kinetics with R2 value of 0.999. The results of the present study indicated that gooseberry seed powder can be employed as adsorbent for the effective removal of hexavalent chromium economically.

  18. Study of the effects of chromium exposure on sulfur metabolic pathways in the model plant Medicago truncatula

    Science.gov (United States)

    Chromium is a common contaminant that is more toxic as hexavalent species [Cr(VI)] than trivalent species [Cr(III)]. Some plants absorb chromium and reduce Cr(VI) to Cr(III), yet the uptake and reduction mechanisms are still unknown. Sulfur is a constituent of two essential amino acids and plays an ...

  19. Accurate quantification of total chromium and its speciation form Cr(VI) in water by ICP-DRC-IDMS and HPLC/ICP-DRC-IDMS.

    Science.gov (United States)

    Markiewicz, Barbara; Komorowicz, Izabela; Barałkiewicz, Danuta

    2016-05-15

    Two analytical procedures have been developed for the determination of total chromium (TCr) and its highly toxic species, i.e. Cr(VI) in water samples using the following methods: inductively coupled plasma dynamic reaction cell isotope dilution mass spectrometry (ICP-DRC-IDMS) and high performance liquid chromatography inductively coupled plasma dynamic reaction cell isotope dilution mass spectrometry (HPLC/ICP-DRC-IDMS). Spectral interferences, predominantly occurring in chromium determination, were removed using a dynamic reaction cell (DRC). The presented procedures facilitate the quantification of trace amounts - below 1 µg L(-1) of TCr and individual Cr species - in various water matrices including drinking water and still bottled water with different mineral composition. Special attention has been paid to the adequate preparation of isotopically enriched (53)Cr(VI) standard solution in order to avoid artifacts in chromium speciation. Both procedures were fully validated as well as establishing the traceability and estimation of the uncertainty of measurement were carried out. Application of all of the above mentioned elements and of the isotope dilution technique, which provides the highest quality of metrological traceability, allowed to obtain reliable and high quality results of chromium determination in water samples. Additionally, the comparison of two methods: HPLC/ICP-DRC-MS and HPLC/ICP-DRC-IDMS for Cr(VI) determination, was submitted basing on the validation parameters. As a result, the lower values for these parameters were obtained using the second method. PMID:26992546

  20. "Involvement of metabolic reactive intermediate Cr (IV) in Chromium (VI) cytotoxic effects "

    OpenAIRE

    Pourahmad J; O’Brien PJ

    2001-01-01

    Addition of Cr VI (dichromate) to isolated rat hepatocytes results in rapid glutathione oxidation, reactive oxygen species (ROS) formation, lipid peroxidation, decreased mitochondrial membrane potential and lysosomal membrane rupture before hepatocyte lysis occurred. Cytotoxicity was prevented by ROS scavengers, antioxidants, and glutamine (ATP generator). Hepatocyte dichlorofluorescin oxidation to dichlorofluorescein (DCF) to determine ROS formation was inhibited by mannitol (a hydroxyl radi...

  1. Prosopis laevigata a potential chromium (VI) and cadmium (II) hyperaccumulator desert plant.

    Science.gov (United States)

    Buendía-González, L; Orozco-Villafuerte, J; Cruz-Sosa, F; Barrera-Díaz, C E; Vernon-Carter, E J

    2010-08-01

    The bioaccumulation of Cr(VI) and Cd(II) in Prosopis laevigata and the effect of these heavy metals on plant growth were assessed. P. laevigata seeds were cultured during 50 days on modified Murashige-Skoog medium supplemented with four different concentrations of Cr(VI) (0-3.4mM) and Cd(II) (0-2.2mM), respectively. Heavy metals did not stop germination, but smaller plants with fewer leaves and secondary roots were produced. Seedlings showed an accumulation of 8176 and 21,437 mg Cd kg(-1) and of 5461 and 8090 mg Cr kg(-1) dry weight, in shoot and root, when cultured with 0.65 mM Cd(II) and 3.4mM Cr(VI), respectively. These results indicated that significant translocation from the roots unto aerial parts took place. A bioaccumulation factor greater than 100 for Cd and 24 for Cr was exhibited by the seedlings. P. laevigata can be considered as a potential hyperaccumulator of Cd(II) and Cr(VI) species and considered as a promising candidate for phytoremediation purposes. PMID:20347590

  2. Aminopyridine modified Spirulina platensis biomass for chromium(VI) adsorption in aqueous solution.

    Science.gov (United States)

    Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

    2016-01-01

    Chemical modification of Spirulina platensis biomass was realized by sequential treatment of algal surface with epichlorohydrin and aminopyridine. Adsorptive properties of Cr(VI) ions on native and aminopyridine modified algal biomass were investigated by varying pH, contact time, ionic strength, initial Cr(VI) concentration, and temperature. FTIR and analytical analysis indicated that carboxyl and amino groups were the major functional groups for Cr(VI) ions adsorption. The optimum adsorption was observed at pH 3.0 for native and modified algal biomasses. The adsorption capacity was found to be 79.6 and 158.7 mg g(-1), for native and modified algal biomasses, respectively. For continuous system studies, the experiments were conducted to study the effect of important design parameters such as flow rate and initial concentration of metal ions, and the maximum sorption capacity was observed at a flow rate of 50 mL h(-1), and Cr(VI) ions concentration 200 mg L(-1) with modified biomass. Experimental data fitted a pseudo-second-order equation. The regeneration performance was observed to be 89.6% and 94.3% for native and modified algal biomass, respectively. PMID:27533866

  3. Estimation of chromium (VI) in various body parts of local chicken

    International Nuclear Information System (INIS)

    Chicken is a common type of meat source in our food. It is fed with the feed containing small pieces of leather having Cr (VI) which persisted in it during chrome tanning process. The core purpose of present study was to determine the concentration of Cr (VI) in different body parts of chicken like leg, arm, head, heart, liver and bone. Estimation of Cr (VI) was done by preparing the sample solutions after ashing and digestion with nitric acid, by atomic absorption spectrophotometer. The results depicted that the meat part of leg had higher mean concentration (1.266 mg/kg) with 0.037 mg/kg standard error while the lowest average concentration was found in arm (0.233 mg/kg) with standard error as 0.019 mg/kg. In case of bones, the maximum mean concentration was found in head (1.433 mg/kg) with standard error as 0.670 mg/kg. The concentration of Cr (VI) was not found similar in meat and bones of chicken by employing Kruskal Wallis Test. (author)

  4. Mechanism of the reduction of hexavalent chromium by organo-montmorillonite supported iron nanoparticles

    International Nuclear Information System (INIS)

    Highlights: ► Organo-montmorillonite supported iron nanoparticles were found to be more efficient in the removal of Cr(VI) than unsupported iron nanoparticles. ► The iron nanoparticles were accommodated by the sectional structure of the clay minerals which were helpful to protect the nanoparticles from aggregating. ► XPS and XANES provided some direct information about the reduction mechanisms. ► The structure of the supported iron nanoparticles was stable in the reaction with Cr(VI). - Abstract: Iron nanoparticles exhibit greater reactivity than micro-sized Fe0, and they impart advantages for groundwater remediation. In this paper, supported iron nanoparticles were synthesized to further enhance the speed and efficiency of remediation. Natural montmorillonite and organo-montmorillonite were chosen as supporting materials. The capacity of supported iron nanoparticles was evaluated, compared to unsupported iron nanoparticles, for the reduction of aqueous Cr(VI). The reduction of Cr(VI) was much greater with organo-montmorillonite supported iron nanoparticles and fitted the pseudo-second order equation better. With a dose at 0.47 g/L, a total removal capacity of 106 mg Cr/g Fe0 was obtained. Other factors that affect the efficiency of Cr(VI) removal, such as pH values, the initial Cr(VI) concentration and storage time of nanoparticles were investigated. X-ray photoelectron spectrometry (XPS) and X-ray absorption near edge structure (XANES) were used to figure out the mechanism of the removal of Cr(VI). XPS indicated that the Cr(VI) bound to the particle surface was completely reduced to Cr(III) under a range of conditions. XANES confirmed that the Cr(VI) reacted with iron nanoparticles was completely reduced to Cr(III).

  5. Cr isotope fractionation factors for Cr(VI) reduction by a metabolically diverse group of bacteria

    Science.gov (United States)

    Basu, Anirban; Johnson, Thomas M.; Sanford, Robert A.

    2014-10-01

    Reduction of Cr(VI) is an important process that determines the geochemical behavior, mobility and bioavailability of Cr in both terrestrial and marine environments. Many metabolically diverse microorganisms possess Cr(VI) reduction capacity. Cr(VI) reduction fractionates Cr isotopes and thus 53Cr/52Cr ratios can be used to monitor Cr(VI) reduction and redox conditions. The magnitude of isotopic fractionation (ε) for a variety of microbial reduction mechanisms must be known for accurate interpretation of observed shifts in 53Cr/52Cr ratios. We determined isotopic fractionation factors for Cr(VI) reduction by metal reducers Geobacter sulfurreducens and Shewanella sp. strain NR, a denitrifying soil bacterium Pseudomonas stutzeri DCP-Ps1, and a sulfate reducer Desulfovibrio vulgaris. All bacteria investigated in this study produced significant Cr isotope fractionation. The fractionation (ε) for G. sulfurreducens, Shewanella sp. (NR), P. stutzeri DCP-Ps1, and D. vulgaris were -3.03‰ ± 0.12‰, -2.17‰ ± 0.22‰, -3.14‰ ± 0.13‰, and -3.01‰ ± 0.11‰, respectively. Despite differences in microbial strains in this study, the ε did not vary significantly except for Shewanella sp. (NR). Our results suggest that strong isotopic fractionation is induced during Cr(VI) reduction under electron donor poor (∼300 μM) conditions.

  6. Bioadsorción de Cromo (VI en Solución Acuosa por la Biomasa Celular de Cryptococcus neoformans y Helminthosporium sp Biosorption of Chromium (VI from Aqueous Solutions by Fungal Biomass of Cryptococcus neoformans and Helminthosporium sp

    Directory of Open Access Journals (Sweden)

    I. Acosta

    2005-01-01

    Full Text Available Se determinó la bioadsorción de Cromo (VI en solución por la biomasa celular de la levadura capsulada Cryptococcus neoformans y del hongo micelial Helminthosporium sp, por el método colorimétrico de la difenilcarbazida. La biomasa de C. neoformans fue más eficiente en la remoción de Cromo (VI en solución (98% que la de Helminthosporium sp (65%. La mayor bioadsorción para C. neoformans fue a pH=2.0 +/- 0.2, mientras que para Helminthosporium sp fue a pH=4.0 +/- 0.2, ambas a 28oC durante 24 horas con 0.2 mg/L de biomasa celular. Se concluye que las biomasas fúngicas remueven eficientemente Cromo (VI en solución y pueden utilizarse para descontaminar nichos acuáticos contaminados con este metal.A determination was made on the biosorption of dissolved Chromium (VI using cellular biomass of the encapsulated yeast Cryptococcus neoformans and the mycelial fungus Helminthosporium sp. using a diphenylcarbazide colorimetric method. The C. neoformans biomass was more efficient in removing Chromium (VI from solution (98% than the Helminthosporium sp. (65%. The highest biosorption for C. neoformans was at pH 2.0 + 0.02, while for Helminthosporium sp this occurred at pH 4.0 + 0.2 , both at 28°C for 24 h employing 0.2 mg/L of cellular biomass. It is concluded that the fungal biomasses efficiently removed Chromium (VI from solution and could be used for decontamination of aquatic habitats polluted with this metal.

  7. Removal of chromium (VI) ions from aqueous solutions by using Kiwi shell

    OpenAIRE

    KHAJESADEGH, Maryam; SABERMAHANİ, Fatemeh; MADADİ MAHANİ, Nosrat

    2015-01-01

    Abstract. Kiwi shell, an waste material, was investigated as an adsorbent for the removal of Cr(IV) toxic metal from aqueous solutions. Batch experiments have been performed as a function of pH, contact time, dose of sorbent, initial Cr(IV) concentration, strength ionic and temperature. The experiments showed that the adsorption process was quick and the equilibrium attained within 20 min. Evaluation using Langmuir gave sorption capacity 6.23 mg g-1. Chromium uptake by Kiwi shell was best des...

  8. Biosorption of copper(II and chromium(VI by modified tea fungus

    Directory of Open Access Journals (Sweden)

    Šćiban Marina B.

    2012-01-01

    Full Text Available The tea fungus was found to have good adsorption capacities for heavy metal ions. In this work it was treated with HCl or NaOH at 20°C or 100°C, with the aim to improve its adsorption ability. The sorption of Cu(II and Cr(VI ions from aqueous solutions by raw and treated tea fungus was investigated in the batch mode. The largest quantity of adsorbed Cu(II, of about 55 mg/g, was achieved by tea fungus modified with NaOH at 100°C. For Cr(VI, the largest quantity of adsorbed anions, of about 58 mg/g, was achieved by the adsorbent modified with NaOH at 20°C. It was shown that acid modification of tea fungus biomass was not effective. [Projekat Ministarstva nauke Republike Srbije, br. III 43005 i br. TR 31002

  9. Evaluation of batch biosorption of chromium (vi) from aqueous solution by chemically modified polyalthia longifolia leaves

    International Nuclear Information System (INIS)

    Removal of toxic metals from surface water is a significant matter of concern. Biosorption is emerging as an economical and eco friendly methodology for the removal of toxic chemicals from waste water. Optimization of operating conditions has a large impact on the efficiency of this process. Simple untreated and chemically modified Polyalthia longifolia leaves were used to study biosorption of Cr (VI) from aqueous media within various experimental conditions and their efficiency of biosorption were compared. The effects of different conditions, such as contact time of solution with bio sorbent, temperature, pH, biosorbent dose and agitation speed for the removal of Cr (VI) were studied. It is found that acid treated Polyalthia longifolia leaves have greater biosorption capacity as compared to untreated and base treated leaves. Langmuir and Freundlich isotherms were also applied to evaluate maximum biosorption capacity of simple untreated and chemically modified Polyalthia longifolia leaves for Cr (VI). This research work is of great importance in regard of practical waste water treatment by biosorption. (author)

  10. Removal of chromium(VI) from wastewater using phosphoric acid treated activated carbon

    Science.gov (United States)

    Suganthi, N.

    2013-06-01

    Activated carbon prepared by phosphoric acid treatment of tamarind nuts (seeds) was investigated for the removal of Cr(VI) from aqueous solutions. The characteristics of phosphorylated tamarind nut carbon (PTNC) were evaluated for porosity and surface area. The effect of contact time, pH, adsorbent dose and particle size variation were studied to evaluate the potential applicability of carbon for treating Cr(VI) containing wastewater. The adsorbent data were modeled by Langmiur and Freundlich classical adsorption isotherms. The kinetic studies showed that Cr(VI) adsorption on PTNC was in compliance with the pseudo-second-order kinetic model. Desorption studies indicated that ion-exchange mechanism was operating. The continuous adsorption was studied in glass columns of 2.5 cm diameter using electroplating wastewater to ascertain the practical applicability of PTNC in large scale. The mechanism of adsorption was found to be ion-exchange process and was supported by FTIR spectroscopy. The surface modification after adsorption was confirmed by SEM studies.

  11. Phase and substance transformations during carbothermic reduction of main elements in chromium ore

    International Nuclear Information System (INIS)

    On the basis of thermodynamic analysis and the elaboration of chromium oxide metallizing and carbonization parameters the phase and substance transformations during carbothermic reduction of main elements are studied as applied to manufacturing chromium-bearing briquettes from the ore. The mechanism of transformations on the way to a final form of element presence is revealed. The initial briquette consists mainly of Cr2O3 and Fe2O3 oxides. Active interaction between chromium oxides and carbon is observed after drying and results in an essential amount of Cr7C3 and Cr23C6 carbides. Further thermal treatment is accompanied by intense carbide formation with the appearance of new carbides Cr3C2 and Fe3C

  12. Synthesis of chromium and ferrochromium alloy in molten salts by the electro-reduction method

    Directory of Open Access Journals (Sweden)

    Ge X.

    2015-01-01

    Full Text Available In this work, we successfully applied the Fray-Farthing-Chen Cambridge electro-reduction process on the preparation of chromium from chromium oxide, and for the first time, the synthesis of ferrochromium alloy from chromium oxide and iron oxide mixture and the chromite ore in molten calcium chloride. The present work systematically investigated the influences of sintered temperature of the solid precursor, electrochemical potential, electrolysis temperature and time on the products by using a set of advanced characterization techniques, including XRD and SEM/EDS analyses. In particular, our results show that this process is energy-friendly and technically-feasible for the direct extraction of ferrochromium alloy from chromite ore. Our findings thus provide useful insights for designing a novel green process to produce ferrochromium alloy from low-grade chromite ore or stainless steel slag.

  13. Improvement on simultaneous determination of chromium species in aqueous solution by ion chromatography and chemiluminescence detection

    DEFF Research Database (Denmark)

    Gammelgaard, Bente; Liao, Y.P.; Jons, O.

    sulphite, whereupon both species were detected by use of the luminol-hydrogen peroxide chemiluminescence system. Parameters affecting retention times and resolution of the separator columns, such as eluent pH, eluent composition, reductant pH and concentration, and flow rates were optimized. Furthermore......, the stabilities of reductant and luminol solutions were studied. The linear range of the calibration curve for chromium(III) and chromium(VI) was 1-400 mu g l(-1). The detection limit was 0.12 mu g l(-1) for chromium(III) and 0.09 mu g l(-1) for chromium(VI), respectively. The precision at the 20 mu g...

  14. Effects of combining biological treatment and activated carbon on hexavalent chromium reduction.

    Science.gov (United States)

    Orozco, A M Ferro; Contreras, E M; Zaritzky, N E

    2011-02-01

    The objectives of the present work were: (a) to analyze the Cr(VI) removal by combining activated sludge (AS) with powdered activated carbon (PAC), (b) to analyze the effect of PAC and Cr(VI) on the growth kinetics of activated sludge, and (c) to determine if the combined method (AS-PAC) for Cr(VI) removal can be considered additive or synergistic with respect to the individual processes. Chromate removal was improved by increasing PAC concentrations in both PAC and AS-PAC systems. Cr(VI) removal using the AS-PAC system was higher than using AS or PAC. The increase of Cr(VI) caused longer lag phase and lower observed specific growth rate (μ(obs)), biomass yield (Y(X/S)), and specific growth substrate consumption rate (q(S)) of activated sludge; additionally, PAC did not enhance the growth kinetic parameters (μ(obs), Y(X/S), q(S)). Cr(VI) reduction in AS-PAC system was the result of the additive effect of each individual Cr(VI) removal process. PMID:21123053

  15. Effect of Garlic (Allium sativum) on Heavy Metal (Nickel II and ChromiumVI) Induced Alteration of Serum Lipid Profile in Male Albino Rats

    OpenAIRE

    Kusal K. Das; Dhundasi, Salim A; Swastika N. Das; Amrita Das Gupta

    2008-01-01

    We have studied the effect of simultaneous oral treatment of aqueous garlic extract (Allium sativum) on heavy metal (nickel II and chromium VI) induced changes in serum lipid profile. Nickel sulfate and potassium dichromate treated rats showed a significant increase in serum low density lipoprotein-cholesterol (LDL-C), very low density lipoprotein-cholesterol (VLDL-C) and triglyceride (TG) level as well as decrease in serum high density lipoprotein-cholesterol (HDL-C) level. Simultaneous garl...

  16. Selective extraction of chromium(VI) using a leaching procedure with sodium carbonate from some plant leaves, soil and sediment samples

    International Nuclear Information System (INIS)

    Speciation of chromium in some plant leaves, soil and sediment samples was carried out by selective leaching of Cr(VI) using a sodium carbonate leaching procedure. Total chromium from the samples was extracted using aqua regia and oxidative acid digestion, respectively. The concentrations of chromium species in the extracts were determined using by graphite furnace atomic absorption spectrometry (GFAAS). Uncoated graphite furnace tubes were used as an atomizer. Due to the presence of relatively high amounts of Na2CO3 in the resulting samples, the possible influences of Na2CO3 on the absorbance signals were checked. There is no interference of Na2CO3 on the chromium absorbance up to 0.1 mol L-1 Na2CO3. A limit of detection (LOD) for determination of Cr(VI) in 0.1 Na2CO3 solution by GFAAS was found to be 0.93 μg L-1. The procedure was applied to environmental samples. The relative standard deviation, R.S.D. as precision for 10 replicate measurements of 20 μ L-1 Cr in processed soil sample was 4.2%.

  17. Exposure to chromium (VI) in the drinking water increases susceptibility to UV-induced skin tumors in hairless mice

    International Nuclear Information System (INIS)

    Hexavalent chromium (Cr (VI)) is a well known-human carcinogen with exposures occurring in both occupational and environmental settings. Although lung carcinogenicity has been well documented for occupational exposure via inhalation, the carcinogenic hazard of drinking water exposure to Cr (VI) has yet to be established. We used a hairless mouse model to study the effects of K2CrO4 in the drinking water on ultraviolet radiation (UVR)-induced skin tumors. Hairless mice were unexposed or exposed to UVR alone (1.2 kJ/m2), K2CrO4 alone at 2.5 and 5.0 ppm, or the combination of UVR and K2CrO4 at 0.5, 2.5, and 5.0 ppm. Mice were observed on a weekly basis for the appearance of skin tumors larger than 2 mm. All the mice were euthanized on day 182. The skin tumors were excised and subsequently analyzed microscopically for malignancy by histopathology. There was a total absence of observable skin tumors in untreated mice and in mice exposed to chromate alone. However, there was a dose-dependent increase in the number of skin tumors greater than 2 mm in mice exposed to K2CrO4 and UV compared with mice exposed to UV alone. The increase in tumors larger than 2 mm was statistically significant (P 2CrO4 at the two highest K2CrO4 doses (2.5 and 5.0 ppm), and there was a statistically significant increase in the numbers of malignant tumors per mouse in the UVR plus K2CrO4 (5 ppm) group compared with UV alone. The data presented here indicate that K2CrO4 increases the number of UV-induced skin tumors in a dose-dependent manner, and these results support the concern that regulatory agencies have relative to the carcinogenic health hazards of widespread human exposure to Cr (VI) in drinking water

  18. Hexavalent chromium [Cr(VI)] removal by acid modified waste activated carbons.

    Science.gov (United States)

    Ghosh, Pranab Kumar

    2009-11-15

    Fresh activated carbon (AC) and waste activated carbon (WAC) were pretreated by heating with mineral acids (sulfuric acid and nitric acid) at high temperature to prepare several grades of adsorbents to evaluate their performance on Cr(VI) removal from aqueous phase. Effects of temperature, agitation speed and pH were tested, and optimum conditions were evaluated. Kinetic study was performed under optimum conditions with several grades of modified adsorbents to know the rates of adsorption. Batch adsorption equilibrium data followed both, Freuindlich and Langmuir isotherms. Maximum adsorption capacity (q(max)) of the selected adsorbents treated with sulfuric acid (MWAC 1) and nitric acid (MWAC 2), calculated from Langmuir isotherm are 7.485 and 10.929 mg/g, respectively. Nitric acid treated adsorbent (MWAC 2) was used for column study to determine the constants of bed depth service time (BDST) model for adsorption column design. PMID:19553008

  19. Toxicity of combined chromium(VI) and phenanthrene pollution on the seed germination, stem lengths, and fresh weights of higher plants.

    Science.gov (United States)

    Hu, Shuangqing; Gu, Hairong; Cui, Chunyan; Ji, Rong

    2016-08-01

    Studies of the interaction and toxicity of pollutant combinations such as heavy metals and PAHs are of practical importance in the remediation and monitoring of the industrial soil environment. This study investigated the single and combined toxicity of chromium(VI) and phenanthrene on three important higher plants: mung beans (Phaseolus aureus), pakchoi cabbage (Brassica chinensis), and rice (Oryza sativa). In experiments using artificial soil matrix, the EC10 and EC20 of the two pollutants, alone and in combination, were analyzed with respect to seed germination, stem length, and above-ground fresh weight of these higher plants. The additive index method was used to evaluate the combined biological toxicity of chromium(VI) and phenanthrene. The results showed that the EC20 of chromium(VI) on the stem lengths of mung beans, pakchoi cabbage, and rice was 289, 248, and 550 mg kg(-1), respectively. The corresponding EC20 values for the fresh weights of the three plants were 334, 307, and 551 mg kg(-1). The EC20 of phenanthrene on the stem lengths of mung beans, pakchoi cabbage, and rice was 528, 426, and 628 mg kg(-1), respectively. The corresponding EC20 values for the fresh weights of the three plants were 696, 585, and 768 mg kg(-1). The EC20 of a combination of chromium(VI) and phenanthrene on the stem lengths of mung beans, pakchoi cabbage, and rice was 192, 173, and 279 mg kg(-1), respectively, and 200, 205, and 271 mg kg(-1) for the fresh weights of the three plants. The single and combined exposure of soil to chromium(VI) and phenanthrene had deleterious effects on plants in the early stage of growth. Overall, pakchoi cabbage was more sensitive than mung beans and rice. The two pollutants exerted synergistic effects on the stem lengths and above-ground fresh weights of both mung beans and rice but antagonistic effects on pakchoi cabbage. The results of this study also suggested pakchoi cabbage as a sensitive indicator of soil pollution. PMID

  20. Ferrous sulphate mono and heptahydrate reduction of hexavalent chromium in cement: effectiveness and storability

    Directory of Open Access Journals (Sweden)

    Valverde, J. L.

    2005-09-01

    Full Text Available In Community legislation, substances containing hexavalent chromium are classified as carcinogenic, mutagenic and sensitizing. In cement, hexavalent chromium intensifies sensitization and may set off severe allergic reactions in workers in routine contact with the product, whether in the factory or on construction sites. The allergic or contact dermatitis causes is a very painful disease that may lead to permanent worker disability. According to Directive 2003/53/EC of the European Parliament and the Council, Governments of all member countries will be required to prohibit the marketing and use, as of 17 January 2005, of any cement or cement preparation containing more than 2 ppm of chromium (VI. Hexavalent chromium can be reduced with ferrous sulphate to trivalent chromium, which is water-insoluble and therefore innocuous to the skin. The present paper reports the effects of adding ferrous sulphate mono- or heptahydrate to a commercial cement and the storage time of the mix on the concentration of hexavalent chromium. The salts studied were found to effectively reduce hexavalent chromium in cement for at least three months.

    Las sustancias que contienen cromo hexavalente están clasificadas en la legislación comunitaria como sustancias carcinogénicas, mutagénicas y sensibilizantes. El cromo hexavalente del cemento potencia la sensibilización y provoca graves reacciones alérgicas que sufren bastante a menudo los trabajadores que lo manipulan habitualmente, ya sea en fábrica o en el sector de la construcción. La dermatitis alérgica o de contacto que produce es muy dolorosa y puede dejar a los trabajadores en estado de discapacidad. La Directiva 2003/53/CE del Parlamento Europeo y del Consejo, exige a los Gobiernos de los países miembros, que a partir del 17 de enero de 2005, prohiban el uso y la comercialización de todos aquellos cementos y preparados que contengan cemento, cuyo contenido en cromo (VI soluble, una vez hidratados

  1. Kinetics of Voluminal Reduction of Chromium Ore Fines Containing Coal by Microwave Heating

    Institute of Scientific and Technical Information of China (English)

    CHEN Jin; WANG She-bin; ZHANG Meng; LIU Jin-ying; ZHOU Jian-xiong

    2008-01-01

    The kinetics of voluminal reduction of chromium ore fines containing coal(COFCC)by microwave heating was studied.When the molar ratio of carbon to oxygen was 0.84 and that of CaO to SiO2 was 0.39 in COFCC,the temperature-rising rate of COFCC by microwave heating was 62.5℃/min,68.75℃/min,70.59℃/rain,and 72.22℃/min at 1 000℃,1100℃,1200℃,and 1300℃,respectively.The results show that the voluminal reduction of COFCC by microwave heating at solid-solid phase is first order reaction,with the apparent activation energy of 51.480 kJ/mol.The limiting step of reaction rate for the overall reaction is the mass transfer of CO in the reduced product layer between dielectric particles of chromium ore and coal.

  2. Sediment studies of the biological factors controlling the reduction of U(VI)

    International Nuclear Information System (INIS)

    Studies were conducted primarily with sediments, both in laboratory incubations and in a field experiment, with supporting studies with pure cultures. To our knowledge the sediment studies were the first on microbial U(VI) reduction in actual uranium-contaminated subsurface sediments, under conditions that mimic those found in situ. Important findings included: (1) U(VI) reduction is a biotic process in subsurface sediments. (2) U(VI) reduction can be stimulated most effectively with the addition of acetate. Although it had been speculated that microbial U(VI) reduction might be capable of this type of environmental remediation ever since the discovery of microbial U(VI) reduction, this had not been previously demonstrated under environmentally relevant conditions. (3) U(VI) is reduced concurrently with Fe(III) and prior to sulfate reduction. U(VI) and Fe(III) reduction proceeded concurrently, accompanied by a dramatic enrichment in organisms in the Geobacteraceae. Sulfate-reducing microorganisms do not appear to be important components of the microbial community reducing U(VI) in these subsurface sediments. (4) Nitrate has important influences on U(VI) reduction. Nitrate inhibits the reduction of metals until nitrate is depleted. Fe(III)-reducing microorganisms such as Geobacter metallireducens and Desulfitobacterium species can oxidize Fe(II) with the reduction of nitrate which is an important consideration because our previous studies have demonstrated that freshly precipitated Fe(III) oxides can reoxidize U(IV) to U(VI). The discovery that G. metallireducens can ''run backwards'' and oxidize U(IV) when nitrate is present reveals another mechanism preventing precipitation of U(IV) in the presence of nitrate as well as potential novel strategy for removing uranium from the subsurface after a site has been remediated. (5) Importance of understanding Fe(III) forms available for microbial reduction. Fe(III) is orders of magnitude more abundant than U(VI) as an

  3. Hexavalent chromium reduction by aerobic heterotrophic bacteria indigenous to chromite mine overburden

    Directory of Open Access Journals (Sweden)

    Dey Satarupa

    2013-01-01

    Full Text Available Microbiological analysis of overburden samples collected from chromite mining areas of Orissa, India revealed that they are rich in microbial density as well as diversity and dominated by Gramnegative (58% bacteria. The phenotypically distinguishable bacterial isolates (130 showed wide degree of tolerance to chromium (2-8 mM when tested in peptone yeast extract glucose agar medium. Isolates (92 tolerating 2 mM chromium exhibited different degrees of Cr+6 reducing activity in chemically defined Vogel Bonner (VB broth and complex KSC medium. Three potent isolates, two belonging to Arthrobacter spp. and one to Pseudomonas sp. were able to reduce more than 50 and 80% of 2 mM chromium in defined and complex media respectively. Along with Cr+6 (MIC 8.6-17.8 mM, the isolates showed tolerance to Ni+2, Fe+3, Cu+2 and Co+2 but were extremely sensitive to Hg+2 followed by Cd+2, Mn+2 and Zn+2. In addition, they were resistant to antibiotics like penicillin, methicillin, ampicillin, neomycin and polymyxin B. During growth under shake-flask conditions, Arthrobacter SUK 1201 and SUK 1205 showed 100% reduction of 2 mM Cr+6 in KSC medium with simultaneous formation of insoluble precipitates of chromium salts. Both the isolates were also equally capable of completely reducing the Cr+6 present in mine seepage when grown in mine seepage supplemented with VB concentrate.

  4. Rice husk: an alternate and low cost material for treating chromium (VI) containing water

    International Nuclear Information System (INIS)

    This paper shows the ability of the native rice husk to remove ions of Cr (VI) in simulated water from tanneries in laboratory conditions. The influences of the variables pH, metal concentration, dosage and contact time on adsorption process was evaluated. It was found a removal more than 94% at pH value of 1, dosage of 3 g/L, concentration of 3 mg/L, at a speed of 127 rpm and at a time of 720 min. The results were evaluated with a 95% level of significance using the statistical tool ANOVA. The information regarding the balance process was fitted to the models of Freundlich, Langmuir, Dubinin-Raduskevich and Thempkin obtaining a better correlation with the Langmuir isotherm with an adsorption capacity of 1.25 mg/g at a pH value of 1. In order to prove the occurrence of structural changes on the adsorbent material, analysis was performed through the DRIFT technique (diffuse reflectance infrared spectroscopy) before and after the removal process and as well abromatological analyses to determine any variation in its composition.

  5. O impacto do crômio nos sistemas biológicos The impact of chromium on biological systems

    OpenAIRE

    Alba Denise de Queiroz Ferreira

    2002-01-01

    The impact of biological chromium's activity may be beneficial or not. This review presents the most relevant chemical aspects of these "two faces" of chromium by covering first, the efforts toward a clearer understanding of the carcinogenic properties of chromium compounds. The biomimetic chemistry of Cr(V) complexes illustrates the interactions of the intermediates formed by Cr(VI) reduction with DNA or oligonucleotides. The importance of trivalent chromium as an essential element is also e...

  6. Biological groundwater treatment for chromium removal at low hexavalent chromium concentrations.

    Science.gov (United States)

    Mamais, Daniel; Noutsopoulos, Constantinos; Kavallari, Ioanna; Nyktari, Eleni; Kaldis, Apostolos; Panousi, Eleni; Nikitopoulos, George; Antoniou, Kornilia; Nasioka, Maria

    2016-06-01

    The objective of this work is to develop and evaluate biological groundwater treatment systems that will achieve hexavalent chromium reduction and total chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range. Three lab-scale units operated, as sequencing batch reactors (SBR) under aerobic, anaerobic and anaerobic-aerobic conditions. All systems received groundwater with a Cr(VI) content of 200 μg/L. In order to support biological growth, groundwater was supplemented with milk, liquid cheese whey or a mixture of sugar and milk to achieve a COD concentration of 200 mg/L. The results demonstrate that a fully anaerobic system or an anaerobic-aerobic system dosed with simple or complex external organic carbon sources can lead to practically complete Cr(VI) reduction to Cr(III). The temperature dependency of maximum Cr(VI) removal rates can be described by the Arrhenius relationship. Total chromium removal in the biological treatment systems was not complete because a significant portion of Cr(III) remained in solution. An integrated system comprising of an anaerobic SBR followed by a sand filter achieved more than 95% total chromium removal thus resulting in average effluent total and dissolved chromium concentrations of 7 μg/L and 3 μg/L, respectively. PMID:26971177

  7. Absorption Reduction Capacity with Chromium (Cr) and Cadmium (Cd) Contaminants of Vetiver Phytoremediation Process on Compost Soil

    OpenAIRE

    Ahamad Zubair; Mary Selintung

    2016-01-01

    This study aims to analyze the large of reduction capacity of chromium metals and cadmium in the soil compost media and absorption capacity of chrome and cadmium in phytoremediation process of vetiver; to compare the reduction-absorption capacities of chromium and cadmium metals in phytoremediation process of vetiver (Vetivera zizanioides). The study was carried out for 2 months with a range of sampling every 7 days, and then analyzed by using Atomic Absorption Spectrophotometer (...

  8. THE CONSEQUENCES ON BLOOD GSH DYNAMICS ON WISTAR FEMALE RATS AT AD LIBITUM CHROMIUM (VI ADMINISTRATION DURING THE GESTATION AFTER THE WEAN

    Directory of Open Access Journals (Sweden)

    CORINA GRĂVILĂ

    2013-07-01

    Full Text Available Chromium (VI is a widely used industrial chemical, extensively used in paints, metal finishes, steel including stainless steel manufacturing, alloy cast irons, chrome, and wood treatment. In nature chromium occurs in divalent, trivalent and hexavalent forms. Hexavalent chromium predominates over the trivalent form in natural waters. We have studied the influence of potassium dichromate (K2Cr2O7 on blood GSH values in rats. This study was carried out on 28 Wistar adult female rats, divided in 3 experimental groups (E and one control group (C. The rats were feed with 25ppm (LOAEL, 50ppm and 75ppm potassium dichromate, ad libitum, in drinking water, during the gestation. The control batch received tap water. Reduced glutathione (GSH was measured quantitatively after the wean using a Perkin-Elmer spectrophotometer, through Beutler et al. method, at 412nm. This study reports that potassium dichromate exposure induced the depletion of blood GSH because Cr(VI can generate reactive oxygen species (ROS. It can induce oxidative stress and toxicity.

  9. Dispersion of Iron Nanoparticles by Polymer-Based Hybrid Material for Reduction of Hexavalent Chromium

    Directory of Open Access Journals (Sweden)

    Syed Wasim Ali

    2015-01-01

    Full Text Available A gel type acrylic acid resin, based on ethyl acrylate-co-1,7-octadiene, has been synthesized by suspension polymerization at 20% cross-linking and subsequent hydrolysis by H2SO4. Capacity of the resin was observed to be 8.90 meq/g or 3.28 meq/mL. The iron nanoparticles used in this study were synthesized by ferrous sulphate method by using LiBH4 as a reductant and characterized by SEM, TEM, XRD, surface area, and electrical properties. Later, the resin was applied for the dispersion of iron nanoparticles over its surface for the reduction of Cr(VI and subsequent adsorption of Fe(III and Cr(III as byproducts. In the column studies the reduction of Cr(VI and the adsorption of Cr(III and Fe(III have been observed up to 240 μmole/L.

  10. The removal of toxic metals from liquid effluents by ion exchange resins. Part I: Chromium(VI/Sulphate/Dowex 1x8

    Directory of Open Access Journals (Sweden)

    Alguacil, F. J.

    2002-08-01

    Full Text Available The removal of chromium (VI from sulphuric acid solutions using the Dowex 1x8 resin has been investigated. The influence of several variables such as the stirring speed, temperature, the sulphuric acid and metal concentrations in the aqueous phase and the variation of the amount of resin added has been studied. Various aqueous solutions were used for the elution of the metal. Although concentrated nitric acid elutes chromium, this can be best accomplished using hydrazine sulphate solutions which at the same time reduce the toxic Cr (VI to the less toxic trivalent chromium state. Results obtained from batch experiments were applied to a continuous system using vertical columns. Moreover, an analytical application of the system in the determination of Cr (VI presents in the leachate of an EAF dust was investigated by transfering the methodology to an on-line flow injection system.

    Se estudia la eliminación de cromo(VI presente en disoluciones de ácido sulfúrico mediante la resina Dowex 1x8. Las variables experimentales estudiadas fueron: velocidad de agitación, temperatura, las concentraciones de metal y ácido sulfúrico en el medio acuoso y la cantidad de resina añadida. Se utilizaron diversas disoluciones acuosas para eluir al metal. Aunque el ácido nítrico se puede utilizar como eluyente, la operación de elución parece ser más eficiente cuando se emplean disoluciones de sulfato de hidracina que, al mismo tiempo, reduce el cromo(VI a cromo(III. Los resultados obtenidos en los ensayos en discontinuo se han experimentado en sistemas en continuo, utilizando mini-columnas. Por último, se ha aplicado el sistema a la determinación analítica del cromo(VI presente en los lixiviados de un polvo de horno de arco eléctrico, transfiriendo la tecnología a un sistema on-line con inyección de flujo.

  11. Plutonium(IV) peroxide formation in nitric medium and kinetics Pu(VI) reduction by hydrogen peroxide

    International Nuclear Information System (INIS)

    Reduction of plutonium (VI) to Pu(IV) with hydrogen peroxide is a step in industrial processes used to purify plutonium nitrate solutions. This operation must be carefully controlled, in order to avoid any formation of the Pu(IV) peroxide green precipitate and to obtain exclusively Pu(IV). This led us to study the acidity and Pu and H2O2 concentrations influences on the precipitate appearance and to perform a Pu(VI) reduction kinetic study on a wide range of acidities ([HNO3]: 0.5 to 8 M), plutonium concentrations ([Pu(VI)]: 0.1 to 0.8 M) and [H2O2]/[Pu(VI)] ratio (from 1 to 8). Thus, the domain of Pu(IV) peroxide formation and the reactional paths were established. With the exception of 0.5 M nitric acid medium, the kinetic curves show two distinct regims: the first one corresponds to an induction period where the Pu(VI) concentration doesn't change, the second corresponds to a linear decrease of Pu(VI). An increase of the temperature greatly accelerates the Pu(VI) reduction rate while [H2O2]/[Pu(VI)] has almost no influence. The Pu(VI) total reduction time decreases when initial concentration of plutonium increases. By increasing nitric acid concentration from 0.5 M to 6 M, the total Pu(VI) reduction time decreases. This time increases when [HNO3] varies from 6 M to 8 M. (orig.)

  12. Chromium resistance of dandelion (Taraxacum platypecidum Diels.) and bermudagrass (Cynodon dactylon [Linn.] Pers.) is enhanced by arbuscular mycorrhiza in Cr(VI)-contaminated soils.

    Science.gov (United States)

    Wu, Song-Lin; Chen, Bao-Dong; Sun, Yu-Qing; Ren, Bai-Hui; Zhang, Xin; Wang, You-Shan

    2014-09-01

    In a greenhouse pot experiment, dandelion (Taraxacum platypecidum Diels.) and bermudagrass (Cynodon dactylon[Linn.] Pers.), inoculated with and without arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis, were grown in chromium (Cr)-amended soils (0 mg/kg, 5 mg/kg, 10 mg/kg, and 20 mg/kg Cr[VI]) to test whether arbuscular mycorrhizal (AM) symbiosis can improve Cr tolerance in different plant species. The experimental results indicated that the dry weights of both plant species were dramatically increased by AM symbiosis. Mycorrhizal colonization increased plant P concentrations and decreased Cr concentrations and Cr translocation from roots to shoots for dandelion; in contrast, mycorrhizal colonization decreased plant Cr concentrations without improvement of P nutrition in bermudagrass. Chromium speciation analysis revealed that AM symbiosis potentially altered Cr species and bioavailability in the rhizosphere. The study confirmed the protective effects of AMF on host plants under Cr contaminations. PMID:24920536

  13. Bioremediation of chromium solutions and chromium containing wastewaters.

    Science.gov (United States)

    Malaviya, Piyush; Singh, Asha

    2016-08-01

    Cr(VI) represents a serious threat to human health, living resources and ecological system as it is persistent, carcinogenic and toxic, whereas, Cr(III), another stable oxidation state of Cr, is less toxic and can be readily precipitated out of solution. The conventional methods of Cr(VI) removal from wastewaters comprise of chemical reduction followed by chemical precipitation. However, these methods utilize large amounts of chemicals and generate toxic sludge. This necessitates the need for devising an eco-technological strategy that would use the untapped potential of the biological world for remediation of Cr(VI) containing wastewaters. Among several viable approaches, biotransformation of Cr(VI) to relatively non-toxic Cr(III) by chromium resistant bacteria offers an economical- and environment-friendly option for its detoxification. Various studies on use of Cr(VI) tolerant viable bacterial isolates for treatment of Cr(VI) containing solutions and wastewater have been reported. Therefore, a detailed account of mechanisms and processes involved in bioreduction of Cr(VI) from solutions and wastewaters by bacterial isolates are the focus of this review article in addition to a discussion on toxicity of Cr(VI) on bacterial strains and various factors affecting Cr(VI) bioreduction. PMID:25358056

  14. Microbial reduction of uranium(VI) in sediments of different lithologies collected from Sellafield

    International Nuclear Information System (INIS)

    Highlights: • U(VI)(aq) mobility can be controlled by stimulating biogeochemical interactions. • Indigenous microbes in varied sediments reduced U(VI) to insoluble U(IV). • Sediment cell numbers and amount of bioavailable Fe(III) could limit this process. - Abstract: The presence of uranium in groundwater at nuclear sites can be controlled by microbial processes. Here we describe the results from stimulating microbial reduction of U(VI) in sediment samples obtained from a nuclear-licensed site in the UK. A variety of different lithology sediments were selected to represent the heterogeneity of the subsurface at a site underlain by glacial outwash deposits and sandstone. The natural sediment microbial communities were stimulated via the addition of an acetate/lactate electron donor mix and were monitored for changes in geochemistry and molecular ecology. Most sediments facilitated the removal of 12 ppm U(VI) during the onset of Fe(III)-reducing conditions; this was reflected by an increase in the proportion of known Fe(III)- and U(VI)-reducing species. However U(VI) remained in solution in two sediments and Fe(III)-reducing conditions did not develop. Sequential extractions, addition of an Fe(III)-enrichment culture and most probable number enumerations revealed that a lack of bioavailable iron or low cell numbers of Fe(III)-reducing bacteria may be responsible. These results highlight the potential for stimulation of microbial U(VI)-reduction to be used as a bioremediation strategy at UK nuclear sites, and they emphasise the importance of both site-specific and borehole-specific investigations to be completed prior to implementation

  15. Analytical applications of N-phenyl-n-butyro hydroxamic and N-p-tolyl-n-butyro hydroxamic acids towards chromium (VI), copper (II), iron (III) and uranium (VI)

    International Nuclear Information System (INIS)

    Two aliphatic hydroxamic acids were prepared; N-phenyl-n-butyro hydroxamic acid and N-p-tolyl-n-butyro hydroxamic acid, by the reaction of β-phenylhydroxylamine and p-tolyl hydroxylamine with n-butyryl chloride. The acids were identified by: their melting points, characteristic reactions with acidic solutions of vanadium (V) and iron (III), infrared spectroscopy, nitrogen content and molecular weight determination. The extractability of these acids towards Cr (VI), Cu (II), Fe (III) and U (VI) were investigated at different pH values and molar acid concentrations. N-phenyl-n- butyro hydroxamic acid has a maximum extraction (98.80%) for Cr (VI) at 4 M H2SO4, (83.25%) for Cu (II) at pH 6, (99.17%) for Fe (III) at pH 5 and (99.76%) at 4 M HNO3 for U (VI) respectively. N-p-tolyl-n-butyro hydroxamic acid has a maximum extraction (98.40%) for Cr (VI)at 4 M H2 SO4, (81.30%) for Cu (II) at pH 6, (92.80%) for Fe (III) at pH 5 and (99.64%) for U (VI) at 4 M HNO3, respectively. The ratios of the metal to ligands were determined by job method (continuous variation method) and were found to be 1:2 for Cr (VI) and U (VI). (Author)

  16. Soil humic acids may favour the persistence of hexavalent chromium in soil

    International Nuclear Information System (INIS)

    The interaction between hexavalent chromium Cr(VI), as K2CrO4, and standard humic acids (HAs) in bulk solution was studied using three complementary analytical methods: UV-Visible spectroscopy, X-ray absorption spectroscopy and differential pulse stripping voltammetry. The observed UV-Vis and X-ray absorption spectra showed that, under our experimental conditions, HAs did not induce reduction of Cr(VI) to its trivalent chemical form. The interaction between Cr(VI) and HAs has rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes. The reported results could contribute towards explaining the relative persistence of ecotoxic hexavalent chromium in soils. - Humic acids (HAs) did not induce reduction of Cr(VI) to its trivalent chemical form, as the interaction between Cr(VI) and HAs rather led to the formation of Cr(VI)-HAs micelles via supramolecular chemical processes.

  17. Electrochemically enhanced reduction of hexavalent chromium in contaminated clay: Kinetics, energy consumption, and application of pulse current

    DEFF Research Database (Denmark)

    Sun, Tian Ran; Pamukcu, Sibel; Ottosen, Lisbeth M.;

    2015-01-01

    Electrochemically enhanced reduction of Cr(VI) in clay medium is a technique based on inputting extra energy into the clay to drive the favorable redox reaction. In this study, the reducing reagent Fe(II) was transported into Cr(VI) spiked kaolinite clay by direct current to investigate the depen...

  18. Surface catalysis of uranium(VI) reduction by iron(II)

    Science.gov (United States)

    Liger, Emmanuelle; Charlet, Laurent; Van Cappellen, Philippe

    1999-10-01

    Colloidal hematite (α-Fe2O3) is used as model solid to investigate the kinetic effect of specific adsorption interactions on the chemical reduction of uranyl (UVIO22+) by ferrous iron. Acid-base titrations and Fe(II) and uranyl adsorption experiments are performed on hematite suspensions, under O2- and CO2-free conditions. The results are explained in terms of a constant capacitance surface complexation model of the hematite-aqueous solution interface. Two distinct Fe(II) surface complexes are required to reproduce the data: (≡FeIIIOFeII)+ (or ≡FeIIIOFeII(OH2)n+) and ≡FeIIIOFeIIOH0 (or ≡FeIIIOFeII(OH2)n-1OH0). The latter complex represents a significant fraction of total adsorbed Fe(II) at pH > 6.5. Uranyl binding to the hematite particles is characterized by a sharp adsorption edge between pH 4 and pH 5.5. Because of the absence of competing aqueous carbonate complexes, uranyl remains completely adsorbed at pH > 7. A single mononuclear surface complex accounts for the adsorption of uranyl over the entire range of experimental conditions. Although thermodynamically feasible, no reaction between uranyl and Fe(II) is observed in homogeneous solution at pH 7.5, for periods of up to three days. In hematite suspensions, however, surface-bound uranyl reacts on a time scale of hours. Based on Fourier Transformed Infrared spectra, chemical reduction of U(VI) is inferred to be the mechanism responsible for the disappearance of uranyl. The kinetics of uranyl reduction are quantified by measuring the decrease with time of the concentration of U(VI) extractable from the hematite particles by NaHCO3. In the presence of excess Fe(II), the initial rate of U(VI) reduction exhibits a first-order dependence on the concentration of adsorbed uranyl. The pseudo-first-order rate constant varies with pH (range, 6-7.5) and the total (dissolved + adsorbed) concentration of Fe(II) (range, 2-160 μM). When analyzing the rate data in terms of the calculated surface speciation, the

  19. Effect of Set Potential on Hexavalent Chromium Reduction and Electricity Generation from Biocathode Microbial Fuel Cells

    KAUST Repository

    Huang, Liping

    2011-06-01

    Setting a biocathode potential at ?300 mV improved the subsequent performance of an MFC for Cr(VI) reduction compared to a control (no set potential). With this set potential, the startup time was reduced to 19 days, the reduction of Cr(VI) was improved to 19.7 mg/L d, and the maximum power density was increased to 6.4 W/m3 compared to the control (26 days, 14.0 mg/L d and 4.1 W/m3). Set potentials of ?150 mV and ?300 mV also improved system performance and led to similarly higher utilization of metabolic energy gained (PMEG) than set potentials of +200 mV and ?450 mV. We observed putative pili at ?150 and ?300 mV potentials, and aggregated precipitates on bacterial surfaces in both poised and nonpoised controls. These tests show that there are optimal potentials that can be set for developing a Cr(VI) biocathode. © 2011 American Chemical Society.

  20. Kinetics and Mechanism of Paracetamol Oxidation by Chromium(VI in Absence and Presence of Manganese(II and Sodiumdodecyl Sulphate

    Directory of Open Access Journals (Sweden)

    Maqsood Ahmad Malik

    2007-11-01

    Full Text Available The kinetics of paracetamol oxidation are first order each in [paracetamol] and [HClO4]. The kinetic study shows that the oxidation proceeds in two steps. The effects of anionic micelles of sodiumdodecyl sulphate (SDS and complexing agents (ethylenediammine tetraacetic acid (EDTA and 2,2′-bipyridyl (bpy were also studied. Fast kinetic spectrophotometric method has been described for the determination of paracetamol. The method is based on the catalytic effect of manganese(II on the oxidation of paracetamol by chromium(VI in the presence of HClO4 (= 0.23 mol dm−3. Optimum reaction time is 4 to 6 minutes at a temperature of 30∘C. The addition of manganese(II ions largely decreased the absorbance of chromium(VI at 350 nm. This reaction can be utilized for the determination of paracetamol in drugs.

  1. Graphene/biofilm composites for enhancement of hexavalent chromium reduction and electricity production in a biocathode microbial fuel cell.

    Science.gov (United States)

    Song, Tian-Shun; Jin, Yuejuan; Bao, Jingjing; Kang, Dongzhou; Xie, Jingjing

    2016-11-01

    In this study, a simple method of biocathode fabrication in a Cr(VI)-reducing microbial fuel cell (MFC) is demonstrated. A self-assembling graphene was decorated onto the biocathode microbially, constructing a graphene/biofilm, in situ. The maximum power density of the MFC with a graphene biocathode is 5.7 times that of the MFC with a graphite felt biocathode. Cr(VI) reduction was also enhanced, resulting in 100% removal of Cr(VI) within 48h, at 40mg/L Cr(VI), compared with only 58.3% removal of Cr(VI) in the MFC with a graphite felt biocathode. Cyclic voltammogram analyses showed that the graphene biocathode had faster electron transfer kinetics than the graphite felt version. Energy dispersive spectrometer (EDS) and X-ray photoelectron spectra (XPS) analysis revealed a possible adsorption-reduction mechanism for Cr(VI) reduction via the graphene biocathode. This study attempts to improve the efficiency of the biocathode in the Cr(VI)-reducing MFC, and provides a useful candidate method for the treatment of Cr(VI) contaminated wastewater, under neutral conditions. PMID:27262274

  2. Thermal incorporation behavior during the reduction and stabilization of chromium wastes

    OpenAIRE

    Yang, Jun; 楊駿

    2015-01-01

    The possibility of employing periclase to stabilize chromium in chromium wastes into spinel-based ceramics through thermal method was investigated by heating mixture of simulated chromium waste and magnesium oxide. Different types of magnesium oxide precursors were introduced to incorporate chromium oxide into magnesiochromite (MgCr2O4) ranging from 550 ºC to 1350 ºC. Magnesium oxide precursors of both types can effectively incorporate chromium oxide but via different mechanisms. Three main f...

  3. Reduction and immobilization of hexavalent chromium by microbially reduced Fe-bearing clay minerals

    Science.gov (United States)

    Bishop, Michael E.; Glasser, Paul; Dong, Hailiang; Arey, Bruce; Kovarik, Libor

    2014-05-01

    Hexavalent chromium (Cr6+) is a major contaminant in the environment. As a redox-sensitive element, the fate and toxicity of chromium is controlled by reduction-oxidation (redox) reactions. Previous research has shown the ability of structural Fe(II) in naturally present and chemically reduced clay minerals to reduce Cr6+ to Cr(III) as a way of immobilization and detoxification. However, it is still poorly known whether or not structural Fe(II) in biologically reduced clay minerals exhibits a similar reactivity and if so, what the kinetics and mechanisms of Cr6+ reduction are. The objective of this study was to determine the kinetics and possible mechanisms of Cr6+ reduction by structural Fe(II) in microbially reduced clay minerals and the nature of reduced Cr(III). Structural Fe(III) in nontronite (NAu-2), montmorillonite (SWy-2), chlorite (CCa-2), and clay-rich sediments from the Ringold Formation of the Hanford site of Washington State, USA was first bioreduced to Fe(II) by an iron-reducing bacterium Geobacter sulfurreducens with acetate as the sole electron donor and anthraquinone-2,6-disulfonate (AQDS) as electron shuttle in synthetic groundwater (pH 7). Biogenic Fe(II) was then used to reduce aqueous Cr6+ at three different temperatures, 10, 20, and 30 °C, in order to determine the temperature dependence of the redox reaction between Cr6+ and clay-Fe(II). The results showed that nontronite and montmorillonite were most effective in reducing aqueous Cr6+ at all three temperatures. In contrast, most Fe(II) in chlorite was not reactive towards Cr6+ reduction at 10 °C, though at 30 °C there was some reduction. For all the clay minerals, the ratio of total Fe(II) oxidized to Cr6+ reduced was close to the expected stoichiometric value of 3. Characterization of the Cr-clay reaction product with scanning electron microscopy with focused ion beam and transmission electron microscopy with electron energy loss spectroscopy revealed that reduced chromium was possibly

  4. Reduction And Immobilization Of Hexavalent Chromium By Microbially Reduced Fe-bearing Clay Minerals

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, Michael E.; Glasser, Paul; Dong, Hailiang; Arey, Bruce W.; Kovarik, Libor

    2014-05-15

    Hexavalent chromium (Cr6+) is a major contaminant in the environment. As a redox-sensitive element, the fate and toxicity of chromium is controlled by reduction-oxidation (redox) reactions. Previous research has shown the ability of structural Fe(II) in naturally present and chemically reduced clay minerals to reduce Cr6+ to Cr(III) as a way of immobilization and detoxification. However, it is still poorly known whether or not structural Fe(II) in biologically reduced clay minerals exhibits a similar reactivity and if so, what the kinetics and mechanisms of Cr6+ reduction are. The objective of this study was to determine the kinetics and possible mechanisms of Cr6+ reduction by structural Fe(II) in microbially reduced clay minerals and the nature of reduced Cr(III). Structural Fe(III) in nontronite (NAu-2), montmorillonite (SWy-2), chlorite (CCa-2), and clay-rich sediments from the Ringold Formation of the Hanford site of Washington State, USA was first bioreduced to Fe(II) by an iron-reducing bacterium Geobacter sulfurreducens with acetate as the sole electron donor and anthraquinone-2,6-disulfate (AQDS) as electron shuttle in synthetic groundwater (pH 7). Biogenic Fe(II) was then used to reduce aqueous Cr6+ at three different temperatures, 10°, 20°, and 30°C, in order to determine the temperature dependence of the redox reaction between Cr6+ and clay-Fe(II). The results showed that nontronite and montmorillonite were most effective in reducing aqueous Cr6+ at all three temperatures. In contrast, most Fe(II) in chlorite was not reactive towards Cr6+ reduction at 10°C, though at 30°C there was some reduction. For all the clay minerals, the ratio of total Fe(II) oxidized to Cr6+ reduced was close to the expected stoichiometric value of 3. Characterization of the Cr-clay reaction product with scanning electron microscopy with focused ion beam and transmission electron microscopy with electron energy loss spectroscopy revealed that reduced chromium was possibly

  5. A kinetic study of biological Cr(VI) reduction in trickling filters with different filter media types

    International Nuclear Information System (INIS)

    Two pilot-scale trickling filters were used in order to estimate Cr(VI) reduction through biological mechanisms in biofilm reactors operated in SBR mode with recirculation using different filter media types, i.e. plastic media and calcitic gravel. The feed concentrations of Cr(VI) examined were about 5, 10, 20, 30, 50 and 100 mg/l, while the concentration of the organic carbon was constant at 400 mg/l, in order to avoid carbon limitations in the bulk liquid. Maximum reduction rates of 4.8 and 4.7 g Cr(VI)/d were observed for feed Cr(VI) concentration of about 5 mg Cr(VI)/l, for the filters with the plastic support material and the gravel media, respectively. The reduction rates were significantly affected by the feed Cr(VI) concentration in both bioreactors. A dual-enzyme kinetic model was used in order to describe Cr(VI) reduction by aerobically grown mixed cultures. Model predictions were found to correspond very closely to experimental quantitative observations of Cr(VI) reduction at both pilot-scale trickling filters used

  6. Reduction of Fe(III), Cr(VI), U(VI), and Tc(VII) by Deinococcus radiodurans R1.

    Science.gov (United States)

    Fredrickson, J K; Kostandarithes, H M; Li, S W; Plymale, A E; Daly, M J

    2000-05-01

    Deinococcus radiodurans is an exceptionally radiation-resistant microorganism capable of surviving acute exposures to ionizing radiation doses of 15,000 Gy and previously described as having a strictly aerobic respiratory metabolism. Under strict anaerobic conditions, D. radiodurans R1 reduced Fe(III)-nitrilotriacetic acid coupled to the oxidation of lactate to CO(2) and acetate but was unable to link this process to growth. D. radiodurans reduced the humic acid analog anthraquinone-2,6-disulfonate (AQDS) to its dihydroquinone form, AH(2)DS, which subsequently transferred electrons to the Fe(III) oxides hydrous ferric oxide and goethite via a previously described electron shuttle mechanism. D. radiodurans reduced the solid-phase Fe(III) oxides in the presence of either 0.1 mM AQDS or leonardite humic acids (2 mg ml(-1)) but not in their absence. D. radiodurans also reduced U(VI) and Tc(VII) in the presence of AQDS. In contrast, Cr(VI) was directly reduced in anaerobic cultures with lactate although the rate of reduction was higher in the presence of AQDS. The results are the first evidence that D. radiodurans can reduce Fe(III) coupled to the oxidation of lactate or other organic compounds. Also, D. radiodurans, in combination with humic acids or synthetic electron shuttle agents, can reduce U and Tc and thus has potential applications for remediation of metal- and radionuclide-contaminated sites where ionizing radiation or other DNA-damaging agents may restrict the activity of more sensitive organisms. PMID:10788374

  7. Reduction of Fe(III), Cr(VI), U(VI), and Tc(VII) by Deinococcus radiodurans R1

    Energy Technology Data Exchange (ETDEWEB)

    Fredrickson, J.K.; Kostandarithes, H.M.; Li, S.W.; Plymake, A.E.; Daly, M.J.

    2000-05-01

    Deinococcus radiodurans is an exceptionally radiation-resistant microorganism capable of surviving acute exposures to ionizing radiation doses of 15,000 Gy and previously described as having a strictly aerobic respiratory metabolism. Under strict anaerobic conditions, D. radiodurans R1 reduced Fe(III)-nitrilotriacetic acid coupled to the oxidation of lactate to CO{sub 2} and acetate but was unable to link this process to growth. D. radiodurans reduced the humic acid analog anthraquinone-2,6-disulfonate (AQDS) to its dihydroquinone form, AH{sub 2}DS, which subsequently transferred electrons to the Fe(III) oxides hydrous ferric oxide and goethite via a previously described electron shuttle mechanism. D. radiodurans reduced the solid-phase Fe(III) oxides in the presence of either 0.1 mM AQDS or leonardite humic acids (2 mg ml{sup {minus}1}) but not in their absence. D. radiodurans also reduced U(VI) and Tc(VII) in the presence of AQDS. In contrast, Cr(VI) was directly reduced in anaerobic cultures with lactate although the rate of reduction was higher in the presence of AQDS. The results are the first evidence that D. radiodurans can reduce Fe(III) coupled to the oxidation of lactate or other organic compounds. Also, D. radiodurans, in combination with humic acids or synthetic electron shuttle agents, can reduce U and Tc and thus has potential applications for remediation of metal- and radionuclide-contaminated sites where ionizing radiation or other DNA-damaging agents may restrict the activity of more sensitive organisms.

  8. Reduction of Fe(III), Cr(VI), U(VI), and Tc(VII) by Deinococcus radiodurans R1

    International Nuclear Information System (INIS)

    Deinococcus radiodurans is an exceptionally radiation-resistant microorganism capable of surviving acute exposures to ionizing radiation doses of 15,000 Gy and previously described as having a strictly aerobic respiratory metabolism. Under strict anaerobic conditions, D. radiodurans R1 reduced Fe(III)-nitrilotriacetic acid coupled to the oxidation of lactate to CO2 and acetate but was unable to link this process to growth. D. radiodurans reduced the humic acid analog anthraquinone-2,6-disulfonate (AQDS) to its dihydroquinone form, AH2DS, which subsequently transferred electrons to the Fe(III) oxides hydrous ferric oxide and goethite via a previously described electron shuttle mechanism. D. radiodurans reduced the solid-phase Fe(III) oxides in the presence of either 0.1 mM AQDS or leonardite humic acids (2 mg ml-1) but not in their absence. D. radiodurans also reduced U(VI) and Tc(VII) in the presence of AQDS. In contrast, Cr(VI) was directly reduced in anaerobic cultures with lactate although the rate of reduction was higher in the presence of AQDS. The results are the first evidence that D. radiodurans can reduce Fe(III) coupled to the oxidation of lactate or other organic compounds. Also, D. radiodurans, in combination with humic acids or synthetic electron shuttle agents, can reduce U and Tc and thus has potential applications for remediation of metal- and radionuclide-contaminated sites where ionizing radiation or other DNA-damaging agents may restrict the activity of more sensitive organisms

  9. Chromate reduction is expedited by bacteria engineered to produce the compatible solute trehalose.

    Science.gov (United States)

    Frederick, Tamlyn M; Taylor, Erin A; Willis, Jennifer L; Shultz, Matthew S; Woodruff, Peter J

    2013-08-01

    The toxicity and solubility of chromium(VI) can be decreased by certain microbes that reduce chromium(VI) to chromium(III). However, these bacteria do not escape unscathed from this process. Chromium(VI) reduction damages the essential macromolecules of living systems. Trehalose protects organisms from chemical stress but has not been tested in the context of bioremediation. We engineered bacteria to produce trehalose and found that they then reduced 1 mM chromium(VI) to chromium(III), whereas wild-type cells were only able to reduce half that amount. Thus, by providing bacteria with a biochemical defense against the side-effects of chromate reduction may be a new approach to cleaning up sites that are contaminated with high levels of chromate. PMID:23563698

  10. Reduction of Cr(VI) facilitated by biogenetic jarosite and analysis of its influencing factors with response surface methodology

    International Nuclear Information System (INIS)

    In this paper, the facilitating role of biogenetic jarosite in the reduction of Cr(VI) by sulfide and its mechanism were investigated through batch experiments and analysis of X-ray photoelectron spectrum (XPS). To study the effects of operational parameters on the reduction of Cr(VI) by sulfide, four operational parameters (pH of solution, operation temperature, loading of jarosite and reaction time) were considered as input variables for response surface methodology (RSM). Graphical response surfaces and contour plots were used to evaluate the effect of interaction between operational parameters on the reduction of Cr(VI). The results suggest that a cycle process of converting Fe(III) to Fe(II) occurred on the surface of jarosite and markedly accelerated the reduction of Cr(VI) by sulfide. For example, the efficiency of Cr(VI) reduced by sulfide increased from 20.5% to 100% when jarosite (1 g/L) was added to the homogenous reaction system at pH = 8 within 40 min. The analysis of variance (ANOVA) revealed a high coefficient of determination (p-value 2 = 97.99%, Adj-R2 = 95.98%) between experimental Cr(VI) removal efficiency and predicted one by RSM developed model. The Pareto analysis results demonstrated that the pH of solution was the most significant term of the developed model. Operation temperature, loading of jarosite and reaction time exhibited synergistic effects on the reduction of Cr(VI), and the effect of interaction between independent factors on the response factor can't be ignored. - Highlights: • Jarosite can markedly accelerate the reduction of Cr(VI) by sulfide. • Jarosite served as a bridge in electron transportation between sulfide and Cr(VI). • The effects of operational parameters on Cr(VI) reduction were evaluated by RSM

  11. Kinetic study of the reduction of Np(VI) with humic acid

    International Nuclear Information System (INIS)

    237Np is one of the most long-life and toxic nuclides in the high level nuclear waste, and will become the primary hazard in the final nuclear waste disposal after a long time of storage, so it is important to study the chemical behaviour of Np. Humic acid is a kind of organic compound reduction in nature. The study of the kinetics of the reduction of Np(VI) with humic acid will afford a basis for further study of the chemical behaviour of Np in the environmental water. Considering the rapid exchange of Np valences during this experiment, extractants TTA and TOPO are used to analyze simultaneously three Np valences (VI), (V) and (IV)

  12. Reduction kinetics of the dioxouranium(VI) ion bound to synthetic polyelectrolytes in aqueous solutions

    International Nuclear Information System (INIS)

    The characterization of actinide ion interactions with naturally occurring polyelectrolytes (e.g., humic substances) is necessary for developing a satisfactory model of actinide behavior in ecosystems. Synthetic polyelectrolytes having only carboxylic acid functional groups can be used to assess the importance of these groups in humic substances. This study examines the reduction of the dioxouranium (VI) ion in the presence of poly (acrylic acid) and poly (maleic acid) using a viologen radical generated by pulse-radiolysis techniques. The observed rate parameters for dioxo-uranium (VI) reduction show unexpected results as a function of polyelectrolyte concentration, degree of neutralization, and contact time. These results along with a possible mechanistic interpretation are discussed

  13. Flow-through Column Experiments and Modeling of Microbially Mediated Cr(VI) Reduction at Hanford 100H

    Science.gov (United States)

    Yang, L.; Molins, S.; Beller, H. R.; Brodie, E. L.; Steefel, C.; Nico, P. S.; Han, R.

    2010-12-01

    Microbially mediated Cr(VI) reduction at the Hanford 100H area was investigated by flow-through column experiments. Three separate experiments were conducted to promote microbial activities associated with denitrification, iron and sulfate reduction, respectively. Replicate columns packed with natural sediments from the site under anaerobic environment were injected with 5mM Lactate as the electron donor and 5 μM Cr(VI) in all experiments. Sulfate and nitrate solutions were added to act as the main electron acceptors in the respective experiments, while iron columns relied on the indigenous sediment iron (and manganese) oxides as electron acceptors. Column effluent solutions were analyzed by IC and ICP-MS to monitor the microbial consumption/conversion of lactate and the associated Cr(VI) reduction. Biogeochemical reactive transport modeling was performed to gain further insights into the reaction mechanisms and Cr(VI) bioreduction rates. All experimental columns showed a reduction of the injected Cr(VI). Columns under denitrifying conditions showed the least Cr(VI) reduction at early stages (ammonium, and called for an additional source of N to account for the measured reduction rates. Iron columns were the least active with undetectable consumption of the injected lactate, slowest cell growth, and the smallest change in Cr(VI) concentrations during the course of the experiment. In contrast, columns under sulfate-reducing/fermentative conditions exhibited the greatest Cr(VI) reduction capacity. Two sulfate columns evolved to complete lactate fermentation with acetate and propionate produced in the column effluent after 40 days of experiments. These fermenting columns showed a complete removal of injected Cr(VI), visible precipitation of sulfide minerals, and a significant increase in effluent Fe and Mn concentrations. Reactive transport simulations suggested that direct reduction of Cr(VI) by Fe(II) and Mn(II) released from the sediment could account for the

  14. Environmental Factors Affecting Chromium-Manganese Oxidation-Reduction Reactions in Soil

    Institute of Scientific and Technical Information of China (English)

    D.O.P.TREBIEN; L.BORTOLON; M.J.TEDESCO; C.A.BISSANI; F.A.O.CAMARGO

    2011-01-01

    Disposal of chromium (Cr) hexavalent form, Cr(Ⅵ), in soils as additions in organic fertilizers, liming materials or plant nutrient sources can be dangerous since Cr(Ⅵ) can be highly toxic to plants, animals, and humans. In order to explore soil conditions that lead to Cr(Ⅵ) generation, this study were performed using a Paleudult (Dystic Nitosol) from a region that has a high concentration of tannery operations in the Rio Grande do Sul State, southern Brazil. Three laboratory incubation experiments were carried out to examine the influences of soil moisture content and concentration of cobalt and organic matter additions on soil Cr(Ⅵ) formation and release and manganese (Mn) oxide reduction with a salt of chromium chloride (CrCl3) and tannery sludge as inorganic and organic sources of Cr(Ⅲ), respectively. The amount of Cr(Ⅲ) oxidation depended on the concentration of easily reducible Mn oxides and the oxidation was more intense at the soil water contents in which Mn(Ⅲ/Ⅳ) oxides were more stable. Soluble organic compounds in soil decreased Cr(Ⅵ) formation due to Cr(Ⅲ) complexation. This mechanism also resulted in the decrease in the oxidation of Cr(Ⅲ) due to the tannery sludge additions. Chromium(Ⅲ) oxidation to Cr(Ⅵ) at the solid/solution interface involved the following mechanisms:the formation of a precursor complex on manganese (Mn) oxide surfaces, followed by electron transfer from Cr(Ⅲ) to Mn(Ⅲ or Ⅳ),the formation of a successor complex with Mn(Ⅱ) and Cr(Ⅵ), and the breakdown of the successor complex and release of Mn(Ⅱ) and Cr(Ⅵ) into the soil solution.

  15. Differential Isotopic Fractionation during Cr(VI) Reduction by an Aquifer-Derived Bacterium under Aerobic versus Denitrifying Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Han, R.; Qin, L.; Brown, S. T.; Christensen, J. N.; Beller, H. R.

    2012-01-27

    We studied Cr isotopic fractionation during Cr(VI) reduction by Pseudomonas stutzeri strain RCH2. Finally, despite the fact that strain RCH2 reduces Cr(VI) cometabolically under both aerobic and denitrifying conditions and at similar specific rates, fractionation was markedly different under these two conditions (ε was ~2‰ aerobically and ~0.4‰ under denitrifying conditions).

  16. Biotite dissolution and Cr(VI) reduction at elevated pH and ionic strength

    Science.gov (United States)

    He, Y. Thomas; Bigham, Jerry M.; Traina, Samuel J.

    2005-08-01

    The effects of elevated pH, ionic strength, and temperature on sediments in the vadose zone are of primary importance in modeling contaminant transport and understanding the environmental impact of tank leakage at nuclear waste storage facilities like those of the Hanford site. This study was designed to investigate biotite dissolution under simulated high level waste (HLW) conditions and its impact on Cr(VI) reduction and immobilization. Biotite dissolution increased with NaOH concentrations in the range of 0.1 to 2 mol L -1. There was a corresponding release of K, Fe, Si, and Al to solution, with Si and Al showing a complex pattern due to the formation of secondary zeolite minerals. Dissolved Fe concentrations were an order of magnitude lower than the other elements, possibly due to the formation of green rust and Fe(OH) 2. The reduction of Cr(VI) to Cr(III) also increased with increased NaOH concentration. A homogeneous reduction of chromate by Fe(II) aq released through biotite dissolution was probably the primary pathway responsible for this reaction. Greater ionic strengths increased biotite dissolution and consequently increased Fe(II) aq release and Cr(VI) removal. The results indicated that HLW would cause phyllosilicate dissolution and the formation of secondary precipitates that would have a major impact on radionuclide and contaminant transport in the vadose zone at the Hanford site.

  17. El té verde en la quimioprevención in vivo del daño genotóxico inducido por metales cancerígenos (cromo [VI] Green tea and its role on chemoprevention in vivo of genotoxic damage induced by carcinogenic metals (Chromium [VI

    Directory of Open Access Journals (Sweden)

    M. C. García-Rodríguez

    2012-08-01

    treatment with chromium trioxide, (iv treatment with green tea and chromium trioxide. The green tea was administrated via intragastric tube every 12 hours over two days (4 doses of 0.25 ml infusions 1.6 g/7.5 ml and ad libitum (5.6 ml/day for 10 days infusions of 3.2 g/100 ml, while chromium trioxide was administrated via intraperitoneal (20 mg/kg. Blood samples were obtained from the caudal vein, the number of MN in EPC was assessed at 0, 24, 48 and 72 hours after the treatments. Results: The group treated with green tea showed no significant statistical changes in the average of MN. On the other hand, the group that was dosed with the chromium trioxide showed an increase between 4 and 8 MN, which was statistically significant when compared with control group, which confirmed the genotoxic damage. When the green tea treatment was administered before the application of chromium trioxide, there was a decrease in MN frequencies of 31 and 62% at 72 hours, 20 and 35% at 48 hours and 18 and 31% at 24 hours with intragastric and ad libitum respectively, compared with the group treated only with chromium trioxide. Hence, green tea reduced the genotoxic damage induced by chromium trioxide, and the highest protection was presented at 72 hours. Conclusions: Our findings support the protective effects of green tea against the damage of genetic material, induced by metal compounds such as chromium [VI], suggesting that its antioxidant compounds are those that have a chemopreventive effect on the EOX generated by the Cr [VI] during its reduction to Cr (III. The fact that the largest decrease in the frequency of MN was observed at 72 hours and ad libitum treatment, suggests that, the protective effect depends on the bioavailability, pharmacodynamics and pharmacokinetics of the active ingredient in green tea, so the administration of green tea for a long period of time before the exposure to Cr [VI] could have a more consistent preventive effect.

  18. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Ramirez, Esthela, E-mail: ramosre@quijote.ugto.mx [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A. [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico); Olguin Gutierrez, Maria T. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico)

    2009-12-30

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N{sub 2} adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

  19. Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

    International Nuclear Information System (INIS)

    In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N2 adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

  20. Inhibition of CO poisoning on Pt catalyst coupled with the reduction of toxic hexavalent chromium in a dual-functional fuel cell

    OpenAIRE

    Dong Young Chung; Hyoung-il Kim; Young-Hoon Chung; Myeong Jae Lee; Sung Jong Yoo; Alok D. Bokare; Wonyong Choi; Yung-Eun Sung

    2014-01-01

    We propose a method to enhance the fuel cell efficiency with the simultaneous removal of toxic heavy metal ions. Carbon monoxide (CO), an intermediate of methanol oxidation that is primarily responsible for Pt catalyst deactivation, can be used as an in-situ reducing agent for hexavalent chromium (Cr (VI)) with reactivating the CO-poisoned Pt catalyst. Using electro-oxidation measurements, the oxidation of adsorbed CO molecules coupled with the concurrent conversion of Cr (VI) to Cr (III) was...

  1. Separation and determination of chromium (iii) chromium (vi), gold (iii) and arsenic (v) by capillary zone electrophoresis using 2-acetylpyridine-4-phenylthiosemicarbazone as complexing reagent

    International Nuclear Information System (INIS)

    Capillary zone electrophoretic procedure has been developed for the speciation of Cr (III) and Cr (VI) along with separation from Au (III) and As (V) as chelate compounds of 2-acetylpyridine-4-phenylthiosemicarbazone (APPT). APPT reacts with Cr (III), Cr (VI), Au (III) and As (V) to form water-methanol soluble chelates which absorb maximally within 360 - 418 nm with molar absorptivity of 3.2 * 103 to 1.2*104 L mol-1cm-1. Off line pre-capillary complexes of the cations prepared were introduced onto uncoated fused silica capillary of 54 cm effective length with 75 micro m id by auto-sampler and separated with background electrolyte (BGE) system of oxalate buffer at pH-4 at an applied voltage of +15 kV. Photodiode array detection was carried out at 241 nm. Linear calibrations were obtained within 1-80 micro gmL-1 for all the cations. The separation and quantitation was repeatable in terms of migration time and peak height with relative standard deviation (RSD) within 2% (n=4). The limit of detection (LOD) measured were 0.125 micro gmL-1, 1.0 micro gmL-1, 0.2 micro gmL-1 and 0.1 respectively for Au(III), As(V), Cr (III) and Cr(VI). The limits of quantitation (LOQ) were in the range of 0.375- 3.0 micro gmL-1. The method was applied for the determination of Cr (III) from tap water, Cr (VI) from industrial effluents and Au (III) and As (V) from pore water of coal mines with RSD within 4%. The results of analysis were supported by standard addition method and rechecked by atomic absorption spectrometry (AAS). (author)

  2. RICE BRAN CARBON: AN ALTERNATIVE TO COMMERCIAL ACTIVATED CARBON FOR THE REMOVAL OF HEXAVALENT CHROMIUM FROM AQUEOUS SOLUTION

    Directory of Open Access Journals (Sweden)

    Syed Hadi Hasan

    2010-06-01

    Full Text Available Rice bran carbon (RBC prepared from rice bran (an agricultural waste was successfully utilized for the removal of hexavalent chromium from aqueous solution. The potentiality of RBC was tested and compared with commercial activated carbon (CAC, and it was found that RBC removed 95% of hexavalent chromium at pH 2, 1000 µM Cr(VI concentration, temperature 30 oC, and adsorbent dose of 2 g/L. The maximum uptake of total chromium obtained by applying the Langmuir isotherm model was 138.88 mg/g for RBC, which was found comparable to that obtained by utilizing CAC (116.28 mg/g at 40 oC. The removal of Cr(VI was found maximum at a proton to chromium ratio of 10 and chromium to carbon ratio of 0.052, and these ratios were found to be applicable over a range of Cr(VI concentrations. The removal of Cr(VI, at low pH (< 2.0, was not only due to sorption of Cr(VI but also because of reduction of Cr(VI into less toxic Cr(III, which was also adsorbed on the surface of the sorbent. The rate of reduction removal of Cr(VI followed pseudo-first order kinetics, whereas the sorption of total chromium followed pseudo-second order kinetics for both the types of activated carbons.

  3. Evaluating the toxicity of environmental concentrations of waterborne chromium (VI) to a model teleost, Oncorhynchus mykiss: a comparative study of in vivo and in vitro.

    Science.gov (United States)

    Li, Zhi-Hua; Li, Ping; Randak, Tomas

    2011-05-01

    Toxic effects of environmental concentrations (50, 100, and 200μg/L) of waterborne chromium (VI) were evaluated in rainbow trout by comparison of in vitro and in vivo assays. Multiple biomarkers were measured including oxidative stress indices and antioxidant response parameters in liver and brain, as well as Na(+)-K(+)-ATPase in gill. Superoxide dismutase (SOD) and glutathione reductase (GR) activities were significantly induced (1.54-fold and 1.37-fold, respectively) in fish brain in vivo, but no significant differences were observed in any other biomarker or in vivo test group. Oxidative stress was apparent in vitro as significantly higher levels of oxidative indices, with the highest induction of TBARS and CP found in brain at 200μg/L Cr(VI) (2.41-fold and 1.95-fold, respectively), and SOD and GR activities and reduced glutathione in brain were significantly inhibited (65%, 44%, and 36%, respectively). In vitro Na(+)-K(+)-ATPase activity in gill was also significantly inhibited at concentrations of 100 and 200μg/L (69% and 45%, respectively). Short-term exposure to environmental concentrations of Cr(VI) does not therefore evoke marked effects in fish in vivo. Based on the present results, a set of in vitro tests with tissue homogenate can be evoked more remarkable effects by the lower concentrations of Cr(VI) than in vivo, which could provide some useful information and might be a potential alternative approach for monitoring heavy metal pollution in aquatic environments. However, it needs more detailed studies in other area, such as hormonal response or genotoxicity, before these findings could be applied in the field investigation. PMID:21324377

  4. Batch, Kinetic and Equilibrium Studies of Chromium (Vi From Aqueous Phase Using Activated Carbon Derived From Lantana Camara Fruit

    Directory of Open Access Journals (Sweden)

    K. Nithya

    2015-12-01

    Full Text Available Batch experiments have been conducted to determine the maximum adsorption capacity of activated carbon derived from Lantana camara fruit to remove hexavalent chromium from aqueous solution. The removal efficiency and uptake capacity of the biosorbent were determined by varying several batch level parameters. Highest removal efficiency of the biosorbent was found to be almost 99% under optimal conditions. Maximum monolayer adsorption capacity was determined to be 86 mg/g. The experimental data best fitted with Langmuir adsorption isotherm and pseudo second order model. These findings conclude that the selected biosorbent has more promising features in binding hexavalent chromium in aqueous media.

  5. Nitrification inhibition by hexavalent chromium Cr(VI)--Microbial ecology, gene expression and off-gas emissions.

    Science.gov (United States)

    Kim, Young Mo; Park, Hongkeun; Chandran, Kartik

    2016-04-01

    The goal of this study was to investigate the responses in the physiology, microbial ecology and gene expression of nitrifying bacteria to imposition of and recovery from Cr(VI) loading in a lab-scale nitrification bioreactor. Exposure to Cr(VI) in the reactor strongly inhibited nitrification performance resulting in a parallel decrease in nitrate production and ammonia consumption. Cr(VI) exposure also led to an overall decrease in total bacterial concentrations in the reactor. However, the fraction of ammonia oxidizing bacteria (AOB) decreased to a greater extent than the fraction of nitrite oxidizing bacteria (NOB). In terms of functional gene expression, a rapid decrease in the transcript concentrations of amoA gene coding for ammonia oxidation in AOB was observed in response to the Cr(VI) shock. In contrast, transcript concentrations of the nxrA gene coding for nitrite oxidation in NOB were relatively unchanged compared to Cr(VI) pre-exposure levels. Therefore, Cr(VI) exposure selectively and directly inhibited activity of AOB, which indirectly resulted in substrate (nitrite) limitation to NOB. Significantly, trends in amoA expression preceded performance trends both during imposition of and recovery from inhibition. During recovery from the Cr(VI) shock, the high ammonia concentrations in the bioreactor resulted in an irreversible shift towards AOB populations, which are expected to be more competitive in high ammonia environments. An inadvertent impact during recovery was increased emission of nitrous oxide (N2O) and nitric oxide (NO), consistent with recent findings linking AOB activity and the production of these gases. Therefore, Cr(VI) exposure elicited multiple responses on the microbial ecology, gene expression and both aqueous and gaseous nitrogenous conversion in a nitrification process. A complementary interrogation of these multiple responses facilitated an understanding of both direct and indirect inhibitory impacts on nitrification. PMID:26874778

  6. Natural biosorbents (garlic stem and horse chesnut shell) for removal of chromium(VI) from aqueous solutions.

    Science.gov (United States)

    Parlayıcı, Şerife; Pehlivan, Erol

    2015-12-01

    The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions. PMID:26581609

  7. A chromium nitride/carbon nitride containing graphitic carbon nanocapsule hybrid as a Pt-free electrocatalyst for oxygen reduction.

    Science.gov (United States)

    Zhao, Lu; Wang, Lei; Yu, Peng; Zhao, Dongdong; Tian, Chungui; Feng, He; Ma, Jing; Fu, Honggang

    2015-08-11

    Chromium nitride nanoparticles supported on graphitic carbon nanocapsules containing carbon nitride (CrN/GC) have been synthesized by a solvothermal-assisted ion-exchange route. As a Pt-free catalyst, the CrN/GC hybrid exhibits superior activity, stability, methanol immunity and a dominant 4-electron pathway towards oxygen reduction reaction. PMID:26145711

  8. INJECTION OF A FERROUS SULFATE/SODIUM DITHIONITE REDUCTANT FOR IN-SITU TREATMENT OF HEXAVALENT CHROMIUM

    Science.gov (United States)

    An in situ pilot study was conducted to evaluate the performance of a ferrous iron-based reductant solution in treating hexavalent chromium within a saturated zone source area at a former industrial site in Charleston, South Carolina (USA). The hexavalent source area, consisting...

  9. Inhibition of CO poisoning on Pt catalyst coupled with the reduction of toxic hexavalent chromium in a dual-functional fuel cell

    Science.gov (United States)

    Chung, Dong Young; Kim, Hyoung-Il; Chung, Young-Hoon; Lee, Myeong Jae; Yoo, Sung Jong; Bokare, Alok D.; Choi, Wonyong; Sung, Yung-Eun

    2014-12-01

    We propose a method to enhance the fuel cell efficiency with the simultaneous removal of toxic heavy metal ions. Carbon monoxide (CO), an intermediate of methanol oxidation that is primarily responsible for Pt catalyst deactivation, can be used as an in-situ reducing agent for hexavalent chromium (Cr (VI)) with reactivating the CO-poisoned Pt catalyst. Using electro-oxidation measurements, the oxidation of adsorbed CO molecules coupled with the concurrent conversion of Cr (VI) to Cr (III) was confirmed. This concept was also successfully applied to a methanol fuel cell to enhance its performance efficiency and to remove toxic Cr (VI) at the same time.

  10. Comparative study of adsorption properties of Turkish fly ashes II. The case of chromium (VI) and cadmium (II)

    Energy Technology Data Exchange (ETDEWEB)

    Bayat, Belgin

    2002-12-02

    The purpose of the study described in this paper was to compare the removal of Cr(VI) and Cd(II) from an aqueous solution using two different Turkish fly ashes; Afsin-Elbistan and Seyitomer as adsorbents. The influence of four parameters (contact time, solution pH, initial metal concentration in solution and ash quality) on the removal at 20{+-}2 deg. C was studied. Fly ashes were found to have a higher adsorption capacity for the adsorption of Cd(II) as compared to Cr(VI) and both Cr(VI) and Cd(II) required an equilibrium time of 2 h. The adsorption of Cr(VI) was higher at pH 4.0 for Afsin-Elbistan fly ash (25.46%) and pH 3.0 for Seyitomer fly ash (30.91%) while Cd(II) was adsorbed to a greater extent (98.43% for Afsin-Elbistan fly ash and 65.24% for Seyitomer fly ash) at pH 7.0. The adsorption of Cd(II) increased with an increase in the concentrations of these metals in solution while Cr(VI) adsorption decreased by both fly ashes. The lime (crystalline CaO) content in fly ash seemed to be a significant factor in influencing Cr(VI) and Cd(II) ions removal. The linear forms of the Langmuir and Freundlich equations were utilised for experiments with metal concentrations of 55{+-}2 mg/l for Cr(VI) and 6{+-}0.2 mg/l for Cd(II) as functions of solution pH (3.0-8.0). The adsorption of Cr(VI) on both fly ashes was not described by both the Langmuir and Freundlich isotherms while Cd(II) adsorption on both fly ashes satisfied only the Langmuir isotherm model. The adsorption capacities of both fly ashes were nearly three times less than that of activated carbon for the removal of Cr(VI) while Afsin-Elbistan fly ash with high-calcium content was as effective as activated carbon for the removal of Cd(II). Therefore, there are possibilities for use the adsorption of Cd(II) ions onto fly ash with high-calcium content in practical applications in Turkey.

  11. Aqueous Cr(VI) reduction by electrodeposited zero-valent iron at neutral pH: Acceleration by organic matters

    Energy Technology Data Exchange (ETDEWEB)

    Liu Junxi; Wang Chuan; Shi Jianying [Institute of Optoelectronic and Functional Composite Materials, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Liu Hong [Institute of Optoelectronic and Functional Composite Materials, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)], E-mail: ceshliu@mail.sysu.edu.cn; Tong Yexiang [Institute of Optoelectronic and Functional Composite Materials, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)], E-mail: chedhx@mail.sysu.edu.cn

    2009-04-15

    This work investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe{sup 0}) at neutral pH. The ED Fe{sup 0} prepared in a solution containing mixture of saccharin, L-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe{sup 0} was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe{sup 0} activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe{sup 0} corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xia, E-mail: lygsunxia@163.com [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); School of Chemistry and Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Yan, Yubo [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Li, Jiansheng, E-mail: lijsh@mail.njust.edu.cn [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Han, Weiqing [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang, Lianjun, E-mail: wanglj@mail.njust.edu.cn [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2014-02-15

    Highlights: • Zero-valent iron nanoparticles were incorporated in the pores of SBA-15 rods. • Mechanism of the Cr(VI) removal by NZVIs/SBA-15 was proposed. • A low pH value was in favor of the Cr(VI) removal. • Humic acid (HA) had a negligible effect on the reactivity of NZVIs/SBA-15. • The stable reduction of NZVIs/SBA-15 was observed within six cycles. -- Abstract: Nanoscale zero-valent iron particles (NZVIs) were incorporated inside the channels of SBA-15 rods by a “two solvents” reduction technique and used to remove Cr(VI) from groundwater. The resulting NZVIs/SBA-15 composites before and after reaction were characterized by N{sub 2} adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results helped to propose the mechanism of Cr(VI) removal by NZVIs/SBA-15, where Cr(VI) in aqueous was firstly impregnated into the channels of the silica, then adsorbed on the surfaces of the incorporated NZVIs and reduced to Cr(III) directly in the inner pores of the silica. Corrosion products included Fe{sub 2}O{sub 3}, FeO(OH), Fe{sub 3}O{sub 4} and Cr{sub 2}FeO{sub 4}. Batch experiments revealed that Cr(VI) removal decreased from 99.7% to 92.8% when the initial solution pH increased from 5.5 to 9.0, accompanied by the decrease of the k{sub obs} from 0.600 to 0.024 min{sup −1}. Humic acid (HA) had a little effect on the removal efficiency of Cr(VI) by NZVIs/SBA-15 but could decrease the reduction rate. The stable reduction of NZVIs/SBA-15 was observed within six cycles. NZVIs/SBA-15 composites offer a promising alternative material to remove heavy metals from groundwater.

  13. Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1.

    Science.gov (United States)

    Icopini, Gary A; Lack, Joe G; Hersman, Larry E; Neu, Mary P; Boukhalfa, Hakim

    2009-06-01

    We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu [a mixture of Pu(VI) and Pu(V)] to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures. PMID:19363069

  14. Layer-by-Layer films based on biopolymers extracted from red seaweeds and polyaniline for applications in electrochemical sensors of chromium VI

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • LbL films based on PANI and polysaccharides of seaweeds were produced and applied sensors of Cr (VI). - Abstract: This paper proposes a new application for natural polysaccharides (agar and carrageenan), both extracted from the cell wall of red seaweeds. Thin films were prepared by the Layer-by-Layer (LbL) self-assembly technique onto ITO (tin-doped indium oxide), where the polysaccharides of interest were deposited in layers alternating with polyaniline (PANI). The films developed were characterized by cyclic voltammetry (CV), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopy (AFM). Results showed the presence of agar as well as carrageenan, which improves the electrochemical stability of the conducting polymer in an acid medium. The interactions at the molecular level between PANI and the biopolymers affected the most appropriate sequence of deposition as employed in the process of material immobilization and also influenced the resulting morphology. Among the films studied, the most promising system as regards electrochemical measurements was the ITO/agar/PANI system, which was subsequently employed in the electrochemical detection of chromium (VI)

  15. Activated carbons from waste of oil-palm kernel shells, sawdust and tannery leather scraps and application to chromium(VI), phenol, and methylene blue dye adsorption.

    Science.gov (United States)

    Montoya-Suarez, Sergio; Colpas-Castillo, Fredy; Meza-Fuentes, Edgardo; Rodríguez-Ruiz, Johana; Fernandez-Maestre, Roberto

    2016-01-01

    Phenol, chromium, and dyes are continuously dumped into water bodies; the adsorption of these contaminants on activated carbon is a low-cost alternative for water remediation. We synthesized activated carbons from industrial waste of palm oil seed husks (kernel shells), sawdust, and tannery leather scraps. These materials were heated for 24 h at 600, 700 or 800°C, activated at 900°C with CO2 and characterized by proximate analysis and measurement of specific surface area (Brunauer-Emmett-Teller (BET) and Langmuir), and microporosity (t-plot). Isotherms showed micropores and mesopores in activated carbons. Palm seed activated carbon showed the highest fixed carbon content (96%), and Langmuir specific surface areas up to 1,268 m2/g, higher than those from sawdust (581 m2/g) and leather scraps (400 m2/g). The carbons were applied to adsorption of Cr(VI), phenol, and methylene blue dye from aqueous solutions. Phenol adsorption on activated carbons was 78-82 mg/g; on palm seed activated carbons, Cr(VI) adsorption at pH 7 was 0.35-0.37 mg/g, and methylene blue adsorption was 40-110 mg/g, higher than those from sawdust and leather scraps. Activated carbons from palm seed are promising materials to remove contaminants from the environment and represent an alternative application for vegetal wastes instead of dumping into landfills. PMID:26744931

  16. Layer-by-Layer films based on biopolymers extracted from red seaweeds and polyaniline for applications in electrochemical sensors of chromium VI

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira Farias, Emanuel Airton de; Corrêa dos Santos, Marianne; Araujo Dionísio, Natália de; Quelemes, Patrick V.; Souza Almeida Leite, José Roberto de [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Eaton, Peter [UCIBIO, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal); Alves da Silva, Durcilene [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Eiras, Carla, E-mail: eiras@cnpq.br [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Laboratório Interdisciplinar de Materiais Avançados, LIMAV, CCN, UFPI, Teresina, PI 64049-550 (Brazil)

    2015-10-15

    Graphical abstract: - Highlights: • LbL films based on PANI and polysaccharides of seaweeds were produced and applied sensors of Cr (VI). - Abstract: This paper proposes a new application for natural polysaccharides (agar and carrageenan), both extracted from the cell wall of red seaweeds. Thin films were prepared by the Layer-by-Layer (LbL) self-assembly technique onto ITO (tin-doped indium oxide), where the polysaccharides of interest were deposited in layers alternating with polyaniline (PANI). The films developed were characterized by cyclic voltammetry (CV), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopy (AFM). Results showed the presence of agar as well as carrageenan, which improves the electrochemical stability of the conducting polymer in an acid medium. The interactions at the molecular level between PANI and the biopolymers affected the most appropriate sequence of deposition as employed in the process of material immobilization and also influenced the resulting morphology. Among the films studied, the most promising system as regards electrochemical measurements was the ITO/agar/PANI system, which was subsequently employed in the electrochemical detection of chromium (VI)

  17. The Photocatalytic Reduction of Hexavalent Chromium by Controllable Mesoporous Anatase TiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Vorrada Loryuenyong

    2014-01-01

    Full Text Available Titania (TiO2 nanoparticles with periodical mesopore size (up to 150 Å have successfully been synthesized by sol-gel template method, using titanium(IV tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different quantities of activated carbon (0%, 5%, and 10% by weight were used as templates to control the porosity and particle size of titania nanoparticles. The templates were completely removed during the calcination in air at 500°C for 3 hr. The results showed that the specific surface area of titania is increased with increasing activated carbon content. The optical bandgap of synthesized titania exhibits a blue shift by 0.3–0.6 eV when compared to the reported value for the bulk anatase and rutile phases. The photocatalytic activity of porous titania is determined with its reduction efficiency of hexavalent chromium (Cr6+. The reduction efficiency is optimized under ultraviolet illumination.

  18. Characterizations of nano-TiO{sub 2}/diatomite composites and their photocatalytic reduction of aqueous Cr (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Qing; Li, Hui; Zheng, Shuilin, E-mail: shuilinzh@sina.com; Sun, Zhiming, E-mail: szmcumtb@hotmail.com

    2014-08-30

    Graphical abstract: Nano-TiO{sub 2}/diatomite (DIA) composites were successfully synthesized by a typical hydrolysis precipitation method. The composites show good photocatalytic activity and stability for aqueous Cr (VI) removal. - Highlights: • TiO{sub 2} nanoparticles/diatomite composite was synthesized and characterized. • The composite exhibited a good photocatalytic performance in Cr (VI) reduction. • The photocatalyst showed good photocatalytic stability. • The composite is a promising material for Cr (VI) photocatalytic reduction. - Abstract: In this paper, the TiO{sub 2} nanoparticles were immobilized on diatomite (DIA) via a typical hydrolysis precipitation process using TiCl{sub 4} as precursor. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TiO{sub 2} nanoparticles with the average grain size of around 7–14 nm were well deposited on the surface of diatomite. The photocatalytic activity toward the reduction of aqueous Cr (VI) was demonstrated under UV light. The influence of initial pH values, catalyst amount, illumination intensity and initial concentration of Cr (VI) on photocatalytic reduction of Cr (VI) were investigated. Compared with the commercial TiO{sub 2} (P25, Degussa), the TiO{sub 2}/DIA composites had better reactive activity because of their relatively higher adsorption capacity. Furthermore, the prepared photocatalyst exhibited relatively good photocatalytic stability depending on the reusability tests.

  19. An efficient ultrasound assisted approach for the impregnation of room temperature ionic liquid onto Dowex 1 × 8 resin matrix and its application toward the enhanced adsorption of chromium (VI)

    International Nuclear Information System (INIS)

    Highlights: ► Ultrasound assisted impregnation of an ionic liquid in a Dowex resin matrix is studied through various physicochemical and spectroscopic techniques. ► Chromium is adsorbed with a high adsorption capacity of 230.9 mg g−1. ► The adsorbent is regenerated using HCl–ascorbic acid mixture. ► Chromium could be effectively detoxified from an industrial effluent and the developed method was validated with the analysis of a certified reference material. - Abstract: The work discussed in this paper is based on the utilization of ultrasound in conjunction with an ionic liquid (Aliquat 336) impregnated Dowex 1 × 8 resin for the effective adsorption of chromium. Ionic liquids are known for their selectivity toward metal extraction and ultrasonic medium offers efficient energy transfer for impregnating the ionic liquid in the resin matrix. The molecular interaction between the ionic liquid impregnated resin and chromium was studied through various physicochemical and spectroscopic techniques. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, adsorbent dosage, temperature and interference of foreign ions was studied in detail. Chromium (VI) was quantitatively adsorbed in the pH range of 3.5–4, with a high adsorption capacity of 230.9 mg g−1 in conformity with the Langmuir isotherm model. The study of thermodynamic parameters showed that the adsorption process is exothermic and spontaneous. The adsorbent could be regenerated using 1 mol L−1 HCl–0.28 mol L−1 ascorbic acid mixture. Chromium could be effectively detoxified from an industrial effluent and finally the developed method was validated with the analysis of a certified reference material (BCR-715). The obtained results indicated that the ultrasonic assisted impregnation of the room temperature ionic liquid significantly enhances and improves the removal efficiency of Cr(VI).

  20. An efficient ultrasound assisted approach for the impregnation of room temperature ionic liquid onto Dowex 1 Multiplication-Sign 8 resin matrix and its application toward the enhanced adsorption of chromium (VI)

    Energy Technology Data Exchange (ETDEWEB)

    Kalidhasan, S.; Santhana Krishna Kumar, A. [Department of Chemistry, Birla Institute of Technology and Science (BITS), Pilani-Hyderabad Campus, Jawahar Nagar, Shameerpet Mandal, R. R. Dist 500 078, AP (India); Vidya Rajesh [Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani-Hyderabad Campus, Jawahar Nagar, Shameerpet Mandal, R. R. Dist 500 078, AP (India); Rajesh, N., E-mail: nrajesh05@gmail.com [Department of Chemistry, Birla Institute of Technology and Science (BITS), Pilani-Hyderabad Campus, Jawahar Nagar, Shameerpet Mandal, R. R. Dist 500 078, AP (India)

    2012-04-30

    Highlights: Black-Right-Pointing-Pointer Ultrasound assisted impregnation of an ionic liquid in a Dowex resin matrix is studied through various physicochemical and spectroscopic techniques. Black-Right-Pointing-Pointer Chromium is adsorbed with a high adsorption capacity of 230.9 mg g{sup -1}. Black-Right-Pointing-Pointer The adsorbent is regenerated using HCl-ascorbic acid mixture. Black-Right-Pointing-Pointer Chromium could be effectively detoxified from an industrial effluent and the developed method was validated with the analysis of a certified reference material. - Abstract: The work discussed in this paper is based on the utilization of ultrasound in conjunction with an ionic liquid (Aliquat 336) impregnated Dowex 1 Multiplication-Sign 8 resin for the effective adsorption of chromium. Ionic liquids are known for their selectivity toward metal extraction and ultrasonic medium offers efficient energy transfer for impregnating the ionic liquid in the resin matrix. The molecular interaction between the ionic liquid impregnated resin and chromium was studied through various physicochemical and spectroscopic techniques. The influence of various analytical parameters on the adsorption of Cr(VI) such as pH, adsorbent dosage, temperature and interference of foreign ions was studied in detail. Chromium (VI) was quantitatively adsorbed in the pH range of 3.5-4, with a high adsorption capacity of 230.9 mg g{sup -1} in conformity with the Langmuir isotherm model. The study of thermodynamic parameters showed that the adsorption process is exothermic and spontaneous. The adsorbent could be regenerated using 1 mol L{sup -1} HCl-0.28 mol L{sup -1} ascorbic acid mixture. Chromium could be effectively detoxified from an industrial effluent and finally the developed method was validated with the analysis of a certified reference material (BCR-715). The obtained results indicated that the ultrasonic assisted impregnation of the room temperature ionic liquid significantly

  1. Adsorption of chromium(VI) and Rhodamine B by surface modified tannery waste: Kinetic, mechanistic and thermodynamic studies

    International Nuclear Information System (INIS)

    In this study, various activation methods have been employed to examine the potential reuse of tannery residual biomass (TRB) obtained from vegetable tanning process for the removal of Cr(VI) and Rhodamine B (RB) from aqueous solution. The maximum BET surface area (10.42 m2/g), honey comb pore distribution and uptake of both Cr(VI) and RB were achieved when only 3-fold volume of HCl was used to activate the biomass. The pH and temperature experiment showed that they have considerable impact on the adsorption capacity of the used adsorbent. The presence of other ions (Na+, Ca2+ and NH4+) significantly reduces the metal uptake but marginal enhancement in the dye removal was observed when Na+ and NH4+ ions were present in the solution. The equilibrium data fitted satisfactorily with the Langmuir model and monolayer sorption capacity obtained as 177-217 and 213-250 mg/g for Cr(VI) and RB at 30-50 deg. C, respectively. The sorption kinetics was found to follow the pseudo-second-order kinetic model. The increase in adsorption capacity for both metal and dye with increase in temperature indicates that the uptake was endothermic in nature. The results indicate that the HCl modified TRB (A-TRB) could be employed as a low cost adsorbent for the removal of both Cr(VI) and RB from the aqueous solution including industrial wastewater.

  2. Highly efficient chromium(VI) adsorption with nanofibrous filter paper prepared through electrospinning chitosan/polymethylmethacrylate composite.

    Science.gov (United States)

    Li, Zhengyang; Li, Tingting; An, Libao; Fu, Pengfei; Gao, Cangjian; Zhang, Zhiming

    2016-02-10

    Chitosan/polymethylmethacrylate (PMMA) composite nanofibrous membrane was prepared by electrospinning technique with a single solvent system. Characterization with Fourier transformation infrared spectroscopy (FT-IR) indicated that there was weak interaction (such as hydrogen bonds) between PMMA and chitosan. Scanning electron microscopy (SEM) measurements illustrated that the average diameter of the composite nanofibers decreased as the chitosan content was increased, while the number of nano/micrometer sized beads increased in the membrane. The composite nanofibrous membrane with chitosan:PMMA ratio of 0.3:1.0 exhibited a maximum adsorption capacity (67.0 mg g(-1)) of Cr(VI) in static adsorption, which was nearly three times higher than that of chitosan powder (22.9 mg g(-1)). The adsorption capacity of Cr(VI) via filtration became even higher, where the maximum value was 92.5 mg g(-1) at pH 3.0. Notably, most of Cr(VI) has been removed after the first filtration at all pH values (2.0-6.0) investigated in this report. The adsorption capacity of the composite nanofibrous membrane decreased slightly (17.1%) after three filtration cycles even with the solution of pH 2.0, which shall be attributed to the enhanced mechanical strength and acid fastness of the composite membrane. X-ray photoelectron spectroscopy (XPS) analysis indicated that amino groups played an important role in the adsorption of Cr(VI). PMID:26686112

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

    Science.gov (United States)

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

    2016-05-15

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

  4. Resistance of Solid-Phase U(VI) to Microbial Reduction during In Situ Bioremediation of Uranium-Contaminated Groundwater

    OpenAIRE

    Ortiz-Bernad, Irene; Anderson, Robert T.; Vrionis, Helen A.; Lovley, Derek R.

    2004-01-01

    Speciation of solid-phase uranium in uranium-contaminated subsurface sediments undergoing uranium bioremediation demonstrated that although microbial reduction of soluble U(VI) readily immobilized uranium as U(IV), a substantial portion of the U(VI) in the aquifer was strongly associated with the sediments and was not microbially reducible. These results have important implications for in situ uranium bioremediation strategies.

  5. Vanadium(III) as an analytical reagent: The titrimetric determination of iron, copper, thallium, molybdenum, uranium, vanadium, chromium and manganese.

    Science.gov (United States)

    Mandal, S K

    1979-02-01

    Vanadium(III) solutions can be used in direct titrations of iron(III), copper(II), thallium(III), molybdenum(VI), uranium(VI), vanadium(V), chromium(VI) and manganese(VII) in milligram amounts. The titrations are done at 70-80 degrees for iron(III), copper(II), thallium(III), molybdenum(VI) and at room temperature for vanadium(V), chromium(VI) and manganese(VII). Uranium(VI) is titrated at 70-80 degrees in presence of iron(II). The vanadium(III) solution is prepared by reduction of vanadium(V) to vanadium(IV) with sulphur dioxide, followed by addition of phosphoric acid and reduction with iodide, and is reasonably stable. PMID:18962393

  6. Reduction of Cr(VI) to Cr(III) by wetland plants: Potential for in situ heavy metal detoxification

    Energy Technology Data Exchange (ETDEWEB)

    Lytle, C.M.; Qian, J.H.; Hansen, D.; Zayed, A.; Terry, N. [Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology; Lytle, F.W. [The EXAFS Co., Pioche, NV (United States); Yang, N. [Sandia National Labs., Livermore, CA (United States)

    1998-10-15

    Reduction of heavy metals in situ by plants may be a useful detoxification mechanism for phytoremediation. Using X-ray spectroscopy, the authors show that Eichhornia crassipes (water hyacinth), supplied with Cr(VI) in nutrient culture, accumulated nontoxic Cr(III) in root and shoot tissues. The reduction of Cr(VI) to Cr(III) appeared to occur in the fine lateral roots. The Cr(III) was subsequently translocated to leaf tissues. Extended X-ray absorption fine structure of Cr in leaf and petiole differed when compared to Cr in roots. In roots, Cr(III) was hydrated by water, but in petiole and more so in leaf, a portion of the Cr(III) may be bound to oxalate ligands. This suggests that E. crassipes detoxified Cr(VI) upon root uptake and transported a portion of the detoxified Cr to leaf tissues. Cr-rich crystalline structures were observed on the leaf surface. The chemical species of Cr in other plants, collected from wetlands that contained Cr(VI)-contaminated wastewater, was also found to be Cr(III). The authors propose that this plant-based reduction of Cr(VI) by E. crassipes has the potential to be used for the in situ detoxification of Cr(VI)-contaminated wastestreams.

  7. Preparation and properties of N-Phenylbutyrohydroxamic acid and N-p-Chlorophenylbutyrohydroxamic acid and their uses as extracting agents for Chromium (VI), Molybdenum (VI), Titanium (IV) and Uranium (VI)

    International Nuclear Information System (INIS)

    Two lignads, N-phenylbutyrohydroxamic acid (1), N-p-chlorophenylbutyryl chloride with β phenyl-hydroylamine and N-p-chlorophenylhydroxylamine, respectively. The acids prepared were identified and characterised through their reactions with Vanadiun (V) and iron (III), their melting points, infra-red spectra and nitrogen content. The extractive properties of these acids towards the metals Cr (VI), Mo (VI), Ti (IV) and U (VI) were examined at different PH values. The percentage of maximum extraction with the two acids was found to be as follows : for Cr (VI) at PH 1, (100%) for both acids, Mo (VI) at PH 2 (33.34%) with acid (I) and (16.67%) with acid (II) and U (VI) at PH 6 (72%) with acid (I) and (76%) with acid (II). The metal: Ligand complexes ratios were determined by using the continuous variation method, the ratio of the two ligands with four metals was found to be 1:2. Finally the suitability of the two acids for spectrophotometric determination of four metals was examined.(Author)

  8. Potential of surface complexation and redox modeling for chromium(VI) adsorption on local materials as liners for waste containment facilities

    OpenAIRE

    MOHAMMED, Syed Abu Sayeed

    2013-01-01

    The main aim of this paper was to model the behavior of red soil and black cotton soil along with fly ash mixture to sorption of chromium at different ranges of pH. Visual MINTEQ version 3.0 was used; it was found that the model predicted the behavior accurately and this was compared with an experimental work done earlier. By conducting this simulation study, it was found that surface complexation and reduction played an important role in the sorption process, which gave a new impetus...

  9. Investigation of the adsorption-reduction mechanisms of hexavalent chromium by ramie biochars of different pyrolytic temperatures.

    Science.gov (United States)

    Zhou, Lu; Liu, Yunguo; Liu, Shaobo; Yin, Yicheng; Zeng, Guangming; Tan, Xiaofei; Hu, Xi; Hu, Xinjiang; Jiang, Luhua; Ding, Yang; Liu, Shaoheng; Huang, Xixian

    2016-10-01

    To investigate the relationship between Cr(VI) adsorption mechanisms and physio-chemical properties of biochar, ramie residues were oxygen-limited pyrolyzed under temperature varying from 300 to 600°C. Batch adsorption experiments indicated that higher pyrolysis temperature limits Cr(VI) sorption in terms of capacity and affinity due to a higher aromatic structure and fewer polar functional groups in biochar. Both electrostatic (physical) and ionic (chemical) interactions were involved in the Cr(VI) removal. For low-temperature biochar, the simple physical adsorption was limited and the significant improvement in Cr(VI) sorption was attributed to abundant carboxyl and hydroxyl groups. The adsorption-reduction mechanisms could be concluded that Cr(VI) ions were electrostatically attracted by the positively charged biochar surface and reduced to Cr(III), and then the converted Cr(III) was retained or discharged into the solution. The study demonstrates ramie residues can be converted into biochar as a low-cost and effective sorbent for Cr(VI) removal. PMID:27376834

  10. Optimization of operational conditions for batchwise biosorption of chromium (VI) using chemically treated alstonia scholaris leaves as biosorbent

    International Nuclear Information System (INIS)

    Biosorption has attracted attention as a cost-effective tool for the treatment of metal-bearing wastewater. While using novel bio sorbents, optimization of operating conditions becomes more important for the efficiency of the process. In this study, a novel biosorbent i.e. Alstonia scholaris leaves were used for biosorption of Cr (VI) from aqueous media. The effect of various parameters, such as contact time of solution with biosorbent, temperature, pH, biosorbent dose and agitation speed were studied. A comparative study of modification of biosorbent using acid and base was also performed. It has been found that acid treated Alstonia scholaris leaves have greater biosorption capacity as compared to untreated and base treated leaves. Optimum conditions for removing Cr (VI) using acid treated biosorbent were: 0.2 g/50 mL of biosorbent, 50 deg. C temperature, 15 minutes contact time, 300 rpm stirring speed and 2.0 pH. Langmuir and Freundlich isotherms were also employed to evaluate maximum biosorption capacity of untreated and chemically treated Alstonia scholaris leaves for Cr (VI). (author)

  11. Solid phase extraction of chromium(VI) using Aliquat336 immobilized on a thin film of multiwall carbon nanotubes

    International Nuclear Information System (INIS)

    We report on a novel and selective method for the preconcentration and determination of Cr(VI) in aqueous samples. Cr(VI) is adsorbed - in a 'batch mode' - on multiwalled carbon nanotubes covered with Aliquat 336 and then determined directly, i.e., on the solid, by X-ray fluorescence spectrometry. This reduces the number of reagents and minimizes sample handling. The method combines the advantages of solid-phase extraction with the benefits of the XRF method in that the large areas required by the carbon nanotubes make them a promising solid sorbent for preconcentration. The enrichment factor was calculated after considering that the thin film obtained from the 10 mL solution of 1 mg L-1 of Cr(VI) has a real thickness of 0.04 mm and a final diameter of 16.7 mm, so that the volume deposited on the pellet is 0.0088 cm3 and the preconcentration factor is 1000. (author)

  12. Optimization of Extracellular Polymeric Substances production using Azotobacter beijreinckii and Bacillus subtilis and its application in chromium (VI) removal.

    Science.gov (United States)

    Chug, Ravneet; Gour, Vinod Singh; Mathur, Shruti; Kothari, S L

    2016-08-01

    Extracellular Polymeric Substances (EPS) of microbial origin are complex biopolymers and vary greatly in their chemical composition. They have a great potential in chelation of metal ions. In this work, the effect of growth phase, temperature and pH on production of EPS by two bacteria Azotobacter beijreinckii and Bacillus subtilis have been studied. Extracted EPS was used to remove Cr(VI) from aqueous system. A. beijreinckii produced maximum EPS after 24h at pH 7 and temperature 30°C while B. subtilis produced maximum EPS after 96h at pH 7 and temperature 37°C. For an initial concentration of 10ppm, 26% and 48% Cr(VI) removal was recorded for EPS derived from A. beijreinckii and B. subtilis respectively. The presence of functional groups on EPS and their interaction with Cr(VI) was confirmed using Fourier-transform infrared (FTIR) spectra analysis. In both the bacteria, carboxyl and phosphate groups show involvement in metal binding. PMID:27183236

  13. Cr(VI) photocatalytic reduction: Effects of simultaneous organics oxidation and of gold nanoparticles photodeposition on TiO2

    International Nuclear Information System (INIS)

    Highlights: ► The Cr(VI) photocatalytic reduction rate is limited by the charge separation efficiency. ► In the presence of hole scavengers, the reaction rate increases with adsorption. ► Direct or indirect hole scavengers differently affect Cr(VI) photoreduction on TiO2. ► Au nanoparticles deposition on TiO2 has scarce effect on photocatalytic reactions. ► The Au photodeposition treatment affects TiO2 surface properties and photoactivity. - Abstract: Commercial TiO2 samples with different phase composition and surface area were tested as photocatalysts in the photoinduced reduction of Cr(VI) in aqueous suspensions at pH 3.7 under UV–visible light irradiation. This reaction was also coupled with the simultaneous photocatalytic oxidation of the pollutant azo dye Acid Orange 8 (AO8) and of formic acid, acting as hole scavengers. The co-presence of oxidizable and reducible species ensured better separation of photogenerated charge carriers, resulting in a higher rate of both organics’ oxidation and Cr(VI) reduction, especially in the case of high surface area anatase TiO2, having the strongest affinity for Cr(VI) and AO8, as demonstrated by competitive adsorption tests. The effects on Cr(VI) photocatalytic reduction of gold nanoparticles photodeposited on TiO2 and of the Au loading were also investigated, aiming at ascertaining if this noble metal plays a role in the electron transfer processes involved in Cr(VI) reduction.

  14. Biliary excretion of chromium in the rat

    International Nuclear Information System (INIS)

    The relative amount of chromium excreted in rat bile after injection of Cr-III is much less than after injection of Cr-VI, about 0.1% and from 6-8% during 5 hours respectively, for corresponding dose levels. The liver to bile ratio was 50-100 for Cr-III injection for Cr-VI the ratio was 2-3. With doses up to 18 μmol Cr/kg, only Cr-III was found in bile even after injection of CR-VI.Glutathione depletion of the liver with cyclohexene oxide decreased chromium excretion in bile. Such treatment also decresed the reduction of Cr-VI to Cr-III in the liver cell as only Cr-VI was found in bile. A different distribution of Cr-III in the liver dependent on whether derived from Cr-VI or taken up by the liver as such must be assumed. Taking into account the usual low penetration of biological membranes by Cr-III, a possible active transport mechanism or a specific diffusable Cr-III compound must be postulated. (author)

  15. Kinetic analysis and modeling of oleate and ethanol stimulated uranium (VI) bio-reduction in contaminated sediments under sulfate reduction conditions

    International Nuclear Information System (INIS)

    Microcosm tests with uranium contaminated sediments were performed to explore the feasibility of using oleate as a slow-release electron donor for U(VI) reduction in comparison to ethanol. Oleate degradation proceeded more slowly than ethanol with acetate produced as an intermediate for both electron donors under a range of initial sulfate concentrations. A kinetic microbial reduction model was developed and implemented to describe and compare the reduction of sulfate and U(VI) with oleate or ethanol. The reaction path model considers detailed oleate/ethanol degradation and the production and consumption of intermediates, acetate and hydrogen. Although significant assumptions are made, the model tracked the major trend of sulfate and U(VI) reduction and describes the successive production and consumption of acetate, concurrent with microbial reduction of aqueous sulfate and U(VI) species. The model results imply that the overall rate of U(VI) bioreduction is influenced by both the degradation rate of organic substrates and consumption rate of intermediate products.

  16. Study on the electrolytic reduction of Uranium-VI to Uranium-IV in a nitrate system

    International Nuclear Information System (INIS)

    The determination of the best conditions to prepare hydrazine stabilized uranium (IV) nitrate solutions for utilization in Purex flowsheets is dealt with. Electrolytic reduction of U(VI) has been selected as the basic method, using an open electrolytic cell with titanum and platinum electrodes. The hydrazine concentration, the current density, acidity, U(VI) concentration and reduction time were the parameters studied and U(IV)/U(VI) ratio was used to evaluate the degree of reduction. From the results it could be concluded that the technique is reliable. The U(IV) solutions remains constant for at least two weeks and can be used in the chemical processing of irradiated uranium fuels. (Author)

  17. Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

    Science.gov (United States)

    Yokoyama, Seiji; Okazaki, Kohei; Sasano, Junji; Izaki, Masanobu

    2014-02-01

    Hexavalent chromium (Cr(VI)) is well-known to be a strong oxidizer, and is recognized as a carcinogen. Therefore, it is regulated for drinking water, soil, groundwater and sea by the environmental quality standards all over the world. In this study, it was attempted to remove Cr(VI) ion in a carbonic acid solution by the oxidizing slag that was discharged from the normal steelmaking process in an electric arc furnace. After the addition of the slag into the aqueous solution contained Cr(VI) ion, concentrations of Cr(VI) ion and total chromium (Cr(VI) + trivalent chromium (Cr(III)) ions decreased to lower detection limit of them. Therefore, the used slag could reduce Cr(VI) and fix Cr(III) ion on the slag. While Cr(VI) ion existed in the solution, iron did not dissolve from the slag. From the relation between predicted dissolution amount of iron(II) ion and amount of decrease in Cr(VI) ion, the Cr(VI) ion did not react with iron(II) ion dissolved from the slag. Therefore, Cr(VI) ion was removed by the reductive reaction between Cr(VI) ion and the iron(II) oxide (FeO) in the slag. This reaction progressed on the newly appeared surface of iron(II) oxide due to the dissolution of phase composed of calcium etc., which existed around iron(II) oxide grain in the slag.

  18. Chromium (VI) ion adsorption features of chitosan film and its chitosan/zeolite conjugate 13X film

    OpenAIRE

    Maria Teresa Tavares; Galba M. de Campos-Takaki; Villanueva, Emílio R.; Rosa Valéria S. Amorim; Anabelle C. L. Batista

    2011-01-01

    This research evaluated the importance of the adsorption properties of chitosan a chitosan/zeolite conjugate film for the removal of Cr(VI) ions from solutions in the 5–260 mg/L concentration range, when the pH was adjusted to 4.0 and 6.0. The uptake capacities of the films formed by chitosan and by the chitosan/zeolite conjugate were calculated by mass balance. The equilibrium isotherms were fitted to the Langmuir, Freundlich and Redlich-Peterson models. The chitosan film seems to be a good ...

  19. Ferrous sulphate mono and heptahydrate reduction of hexavalent chromium in cement: effectiveness and storability

    OpenAIRE

    Valverde, J. L.; Lobato, J.; I. Fernández; Marijuán, L.; Pérez-Mohedano, S.; Talero, R.

    2005-01-01

    In Community legislation, substances containing hexavalent chromium are classified as carcinogenic, mutagenic and sensitizing. In cement, hexavalent chromium intensifies sensitization and may set off severe allergic reactions in workers in routine contact with the product, whether in the factory or on construction sites. The allergic or contact dermatitis causes is a very painful disease that may lead to permanent worker disability. According to Directive 2003/53/EC of the European Parliament...

  20. Hexavalent chromium reduction by aerobic heterotrophic bacteria indigenous to chromite mine overburden

    OpenAIRE

    Dey Satarupa; A. K. Paul

    2013-01-01

    Microbiological analysis of overburden samples collected from chromite mining areas of Orissa, India revealed that they are rich in microbial density as well as diversity and dominated by Gram-negative (58%) bacteria. The phenotypically distinguishable bacterial isolates (130) showed wide degree of tolerance to chromium (2–8 mM) when tested in peptone yeast extract glucose agar medium. Isolates (92) tolerating 2 mM chromium exhibited different degrees of Cr+6 reducing activity in chemically d...

  1. Synergetic Transformations of Multiple Pollutants Driven by Cr(VI)-Sulfite Reactions.

    Science.gov (United States)

    Jiang, Bo; Liu, Yukun; Zheng, Jingtang; Tan, Minghui; Wang, Zhaohui; Wu, Mingbo

    2015-10-20

    Reduction of Cr(VI) is often deemed necessary to detoxify chromium contaminants; however, few investigations utilized this reaction for the purpose of treating other industrial wastewaters. Here a widely used Cr(VI)-sulfite reaction system was upgraded to simultaneously transform multiple pollutants, namely, the reduction of Cr(VI) and oxidation of sulfite and other organic/inorganic pollutants in an acidic solution. As(III) was selected as a probe pollutant to examine the oxidation capacity of a Cr(VI)-sulfite system. Both (•)OH and SO4(•-) were considered as the primary oxidants for As(III) oxidation, based on the results of electron spin resonance, fluorescence spectroscopy, and specific radicals quenching. As(III)-scavenging, oxidative radicals greatly accelerated Cr(VI) reduction and simultaneously consumed less sulfite. In comparison with a Cr(VI)-H2O2 system with 50 μM Cr(VI), Cr(VI), the sulfite system had excellent performance for both As(III) oxidation and Cr(VI) reduction at pH 3.5. Moreover, in this escalated process, less sulfite was required to reduce Cr(VI) than the traditional Cr(VI) reduction by sulfite process. This effectively improves the environmental compatibility of this Cr(VI) detoxification process, alleviating the potential for SO2 release and sulfate ion production in water. Generally, this study provides an excellent example of a "waste control by waste" strategy for the detoxification of multiple industrial pollutants. PMID:26384045

  2. Absorption Reduction Capacity with Chromium (Cr and Cadmium (Cd Contaminants of Vetiver Phytoremediation Process on Compost Soil

    Directory of Open Access Journals (Sweden)

    Ahamad Zubair

    2016-01-01

    Full Text Available This study aims to analyze the large of reduction capacity of chromium metals and cadmium in the soil compost media and absorption capacity of chrome and cadmium in phytoremediation process of vetiver; to compare the reduction-absorption capacities of chromium and cadmium metals in phytoremediation process of vetiver (Vetivera zizanioides. The study was carried out for 2 months with a range of sampling every 7 days, and then analyzed by using Atomic Absorption Spectrophotometer (AAS. Contaminants used as artificial contaminants containing heavy metals chromium (Cr and cadmium (Cd. This study is an experimental research includes two variables. First, the variations of Cr concentrations used were 400 ppm, 600 ppm and 800 ppm and Cd concentrations used were 40 ppm, 60 ppm, 800 ppm. Secondly, the variations of total plant are 3, 6, and 9 plant. The period of observation is made every week. Planting media used is compost soil with compost and clay composition of 20%, 30% and 40%. The results of study showed that there are a significant relationship between the reduction capacity of Cr and Cd of compost soil and the absorption capacity of Cr and Cd for vetiver (Vetiveria zizanioides. The higher of Cr and Cd decreases in soil followed by increased levels of Cr and Cd in vetiver (Vetiveria zizanioides. The capacity of Cr reduction varies between 57% - 86% and Cd 36% - 64% where as the absorption capacity of vetiver on Cr between 38% - 75% and Cd between 34%-74%. The capacity of reduction-absorption of Cr is relatively higher than Cd in phytoremediation process of vetiver.

  3. Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xiaoling [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Ma, Lena Q., E-mail: lqma@ufl.edu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046 (China); Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Gress, Julia; Harris, Willie [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314 (United States)

    2014-02-01

    Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L{sup −1} enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO{sub 2}. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.

  4. Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L−1 enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO2. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions

  5. Permeable Reactive Biobarriers for In Situ Cr(VI) Reduction: Bench Scale Tests Using Cellulomonas sp. Strain ES6

    Energy Technology Data Exchange (ETDEWEB)

    Sridhar Viamajala; Brent M. Peyton; Robin Gerlach; Vaideeswaran; William A. Apel; James N. Petersen

    2008-12-01

    Chromate (Cr(VI)) reduction studies were performed in bench scale flow columns using the fermentative subsurface isolate Cellulomonas sp. strain ES6. In these tests, columns packed with either quartz sand or hydrous ferric oxide (HFO)-coated quartz sand, were inoculated with strain ES6 and fed nutrients to stimulate growth before nutrient-free Cr(VI) solutions were injected. Results show that in columns containing quartz sand, a continuous inflow of 2 mg/L Cr(VI) was reduced to below detection limits in the effluent for durations of up to 5.7 residence times after nutrient injection was discontinued proving the ability of strain ES6 to reduce chromate in the absence of an external electron donor. In the HFO-containing columns, Cr(VI) reduction was significantly prolonged and effluent Cr(VI) concentrations remained below detectable levels for periods of up to 66 residence times after nutrient injection was discontinued. Fe was detected in the effluent of the HFO-containing columns throughout the period of Cr(VI) removal indicating that the insoluble Fe(III) bearing solids were being continuously reduced to form soluble Fe(II) resulting in prolonged abiotic Cr(VI) reduction. Thus, growth of Cellulomonas within the soil columns resulted in formation of permeable reactive barriers that could reduce Cr(VI) and Fe(III) for extended periods even in the absence of external electron donors. Other bioremediation systems employing Fe(II)-mediated reactions require a continuous presence of external nutrients to regenerate Fe(II). After depletion of nutrients, contaminant removal within these systems occurs by reaction with surface-associated Fe(II) that can rapidly become inaccessible due to formation of crystalline Fe-minerals or other precipitates. The ability of fermentative organisms like Cellulomonas to reduce metals without continuous nutrient supply in the subsurface offers a viable and economical alternative technology for in situ remediation of Cr(VI

  6. Reduction of Uranium(VI) under Sulfate-reducing Conditions in the Presence of Fe(III)-(hydr)oxides

    Energy Technology Data Exchange (ETDEWEB)

    Sani, Rajesh K.; Peyton, Brent M.; Amonette, James E.; Geesey, Gill G.

    2004-06-01

    U(VI) dissolved in a modified lactate-C medium (either sulfate- or lactate-limited) was reacted with a mixture of an Fe(III)-(hydr)oxide mineral (hematite, goethite, or ferrihydrite) and quartz under anoxic conditions and equivalent mineral surface areas. After sorption equilibration, the suspensions were inoculated with a sulfate-reducing bacterium (SRB, Desulfovibrio desulfuricans G20). Inoculation of the suspensions containing sulfate-limited medium yielded significant SRB growth, along with concomitant reduction of sulfate and removal of U(VI) from solution. Inoculation of the suspensions containing lactate-limited medium yielded similar results while lactate was still present. Once the lactate was depleted, however, some of the U that had been removed from solution was re-solubilized in the hematite treatment and, to a lesser extent, in the goethite treatment. No re-solubilization was observed in the lactate-limited ferrihydrite treatment even after a prolonged incubation of four months. Analysis by U L3-edge XANES spectroscopy of mineral specimens sampled without inoculation yielded a typical U(VI) spectrum. Mineral specimens sampled at the end of the experiment yielded spectra similar to that of uraninite, thus providing strong evidence for SRB-promoted removal of U(VI) from solution by reductive precipitation of uraninite. Consequently, U re-solubilization was attributed to re-oxidation of the uraninite by Fe(III) present in the (hydr)oxide phases. Our results thus suggest that inoculation with SRB mediates reduction of soluble U(VI) to an insoluble U(IV) oxide so long as a suitable electron donor is available. Depletion of the electron donor may result in partial re-oxidation of the U(IV) to soluble U(VI) species when the surfaces of crystalline Fe(III) (hydr)oxides are incompletely reduced by reaction with SRB-generated sulfide.

  7. Catalytic Spectrophotometric Determination of Chromium

    OpenAIRE

    STOYANOVA, Angelina Miltcheva

    2005-01-01

    The catalytic effect of chromium(III) and chromium(VI) on the oxidation of sulfanilic acid by hydrogen peroxide was studied. The reaction was followed spectrophotometrically by measuring the absorbance of the reaction product at 360 nm. Under the optimum conditions 2 calibration graphs (for chromium(III) up to 100 ng mL-1, and for chromium(VI) up to 200 ng mL-1) were obtained, using the ``fixed time'' method with detection limits of 4.9 ng mL-1 and 3.8 ng mL-1, respectively...

  8. Facile Synthesis of n-type (AgIn)(x)Zn(2(1-x))S2/p-type Ag2S Nanocomposite for Visible Light Photocatalytic Reduction To Detoxify Hexavalent Chromium.

    Science.gov (United States)

    Abdullah, Hairus; Kuo, Dong-Hau

    2015-12-01

    n-type (AgIn)(x)Zn(2(1-x))S2/p-type Ag2S nanocomposites with 10%, 20%, and 30% Ag2S loading were successfully synthesized via the simple solvothermal and sol gel methods. The as-prepared nanocomposites were characterized, and their visible light photocatalytic reductions were tested for detoxification of hexavalent chromium (Cr(VI)). The results showed only 20 mg of the as-prepared nanocomposites could reduce 100 mL of 20 ppm potassium dichromate by almost 100% in less than 90 min without adding any hole scavenger agents and pH adjustment (pH = 7). The good photocatalytic reduction was related to the narrower bandgap of (AgIn)(x)Zn(2(1-x))S2 solid solution because of the hybridized orbitals of Ag, In, Zn, and S and low recombination rate of photogenerated electron and hole pairs due to the effectiveness of p-type Ag2S and n-type (AgIn)(x)Zn(2(1-x))S2 nanoheterojunctions. This work not only gives a contribution to the creation of visible light photocatalysis for wide-bandgap semiconductors, but also extends our technological viewpoints in designing highly efficient metal sulfide photocatalyst. To the best of our knowledge, this work is the first finding of a high photocatalytic reduction of hexavalent chromium under visible light illumination by simultaneously using both concepts of p-n nanoheterojunction and solid solution in our photocatalyst design. In this present work, these concepts were used to replace the use of hole scavenger agents, which were commonly used by many other works to retard the recombination rate of photoinduced electron and hole pairs for photodegradation of hexavalent chromium. PMID:26575792

  9. Microstructural characterisation of chromium slags

    OpenAIRE

    Burja, J.; F. Tehovnik; Vode, F.; Arh, B.

    2015-01-01

    In this chromium slags that form during melting of chromium alloyed steels are examined. During melting and oxidation of these steel grades a considerable amount of chromium is lost, and gained back with slag reduction. Laboratory experiments were performed to study the mechanism of chromium oxide reduction by silicon. Slags chemistry and phase composition have a strong effect on the steelmaking process. Phase analysis revealed two types of chromium oxides, calcium chromites and chromite spin...

  10. Single-Cell Imaging and Spectroscopic Analyses of Cr(VI) Reduction on the Surface of Bacterial Cells

    OpenAIRE

    Wang, Yuanmin; Sevinc, Papatya C.; Balchik, Sara M.; Fridrickson, Jim; Shi, Liang; Lu, H. Peter

    2013-01-01

    We investigate single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process, using Raman spectroscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Our experiments indicate that the toxic and highly soluble Cr(VI) can be efficiently reduced to the less toxic and non-soluble Cr2O3 nanoparticles by MR-1. Cr2O3 is observed to emerge as nanoparticles ads...

  11. Radiation-induced reduction of chromium(Ⅵ) in aqueous solution by γ-irradiation in a laboratory-scale

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Radiation-induced reduction of chromium(Ⅵ)(Cr(Ⅵ) by γ-irradiation was studied with an initial concentration of 42 mg/L in aqueous solutions. Several factors which might affect the reduction of Cr(Ⅵ) to Cr(Ⅲ) were examined. pH of aqueous solution affects the reduction efficiency significantly. Acidic condition of aqueous solution accelerates the process. At pH 2, a reduction of 86.2%was achieved with the absorbed dose of 15 kGy, while, with the same dose, at pH 5 and 7, the reduction of Cr (Ⅵ) were only 36.3%and 22.2%, respectively. Ethanol (0.1% in V:V) and sodium carbonate (1 mmol/L) were added into the solution respectively as relatively non-toxic hydroxyl radical scavengers. Reduction rate increased greatly in the presence of ethanol at each pH. Reduction efficiency of Cr(Ⅵ) was enhanced in neutral condition with the addition of sodium carbonate, however, no enhancement was found in acidic condition. The reduction of Cr(Ⅵ) was restrained when the solution was saturated with oxygen; however, the restraint was not significant.

  12. Comparative evaluation of five plant extracts and juices for nanoiron synthesis and application for hexavalent chromium reduction.

    Science.gov (United States)

    Mystrioti, C; Xanthopoulou, T D; Papassiopi, N; Xenidis, A

    2016-01-01

    The effectiveness of five plant extracts and juices, i.e. extracts of Camellia sinensis (green tea, GT), Syzygium aromaticum (clove, CL), Mentha spicata (spearmint, SM), Punica granatum juice (pomegranate, PG) and Red Wine (RW), for the production of nanoiron suspensions and their application for Cr(VI) reduction was investigated. Polyphenols contained in extracts act as reducing agents for iron ions in aqueous solutions, forming thus iron nanoparticles, and stabilize the nanoparticles produced from further oxidation and agglomeration. The maximum amount of polyphenols extracted per g of herbs was obtained at herb mass to water volume ratio varying from 10 to 20g/L. Suspensions of nanoparticles with sizes below 60nm were produced by mixing iron chloride solution with the plant extracts and juices investigated. The maximum concentration of nanoiron in suspensions was estimated to 22mM, obtained using RW and PG at a mixing ratio of iron solution to extract equal to 2. Lower concentrations, up to 18mM, were achieved using GT and CL extracts. Therefore, PG juice and RW were considered as more effective for nanoiron production, and, together with GT extracts, they were selected for the production of nanoiron suspensions, which have been proven effective for Cr(VI) reduction, reaching removal capacity as high as 500mg Cr(VI) per g of iron in nanoparticles. PMID:26356183

  13. Modeling of kinetics of Cr(VI) sorption onto grape stalk waste in a stirred batch reactor

    International Nuclear Information System (INIS)

    Recently, Cr(VI) removal by grape stalks has been postulated to follow two mechanisms, adsorption and reduction to trivalent chromium. Nevertheless, the rate at which both processes take place and the possible simultaneity of both processes has not been investigated. In this work, kinetics of Cr(VI) sorption onto grape stalk waste has been studied. Experiments were carried out at different temperatures but at a constant pH (3 ± 0.1) in a stirred batch reactor. Results showed that three steps take place in the process of Cr(VI) sorption onto grape stalk waste: Cr(VI) sorption, Cr(VI) reduction to Cr(III) and the adsorption of the formed Cr(III). Taking into account the evidences above mentioned, a model has been developed to predict Cr(VI) sorption on grape stalks on the basis of (i) irreversible reduction of Cr(VI) to Cr(III) reaction, whose reaction rate is assumed to be proportional to the Cr(VI) concentration in solution and (ii) adsorption and desorption of Cr(VI) and formed Cr(III) assuming that all the processes follow Langmuir type kinetics. The proposed model fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The proposed model would be helpful for researchers in the field of Cr(VI) biosorption to design and predict the performance of sorption processes.

  14. Combined remediation technology for the reduction and bioleaching of hexavalent chromium from soils using acidithiobacillus thiooxidans

    OpenAIRE

    Fonseca, B.; Rodrigues, Joana Lúcia; Mendes, T.S.; Queiroz, A.M.; Tavares, T

    2014-01-01

    Contamination of soils due to the release of effluents or deposition of wastes containing hexavalent chromium has been arising serious environmental problems. Therefore, the development of cost effectiveness but also ecological cleaning techniques is a matter of great concern among the scientific community. Bioremediation is attracting more and more attention due to its efficiency, low impact in the ecosystems and low cost. In particular, this study approaches a bioleaching tec...

  15. Isolation and characterization of a chromium-resistant bacterium Serratia sp. Cr-10 from a chromate-contaminated site

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kundi; Li, Fuli [Chinese Academy of Sciences, Qingdao (China). Qingdao Inst. of Bioenergy and Bioprocess Technology

    2011-05-15

    A novel bacterium, Cr-10, was isolated from a chromium-contaminated site and capable of removing toxic chromium species from solution by reducing hexavalent chromium to an insoluble precipitate. Sequence analysis of 16S rRNA gene of strain Cr-10 showed that it was most closely related to Serratia rubidaea JCM 1240{sup T} (97.68%). Physiological and chemotaxonomic data also supported that strain Cr-10 was identified as Serratia sp., a genus which was never specially reported chromate-resistant before. Serratia sp., Cr-10 was tolerant to a concentration of 1,500 mg Cr(VI) L{sup -1}, which was the highest level reported until now. The optimum pH and temperature for reduction of Cr(VI) by Serratia sp. Cr-10 were found to be 7.0 and 37 C, respectively. The Cr(VI) reduction was significantly influenced by additional carbon sources, and among them fructose and lactose offered maximum reduction, with a rate of 0.28 and 0.25 mg Cr(VI) L{sup -1} h{sup -1}, respectively. The cell-free extracts and filtrate of the culture were able to reduce Cr(VI) while concentration of total chromium remained stable in the process, indicating that the enzyme-catalyzed mechanism was applied in Cr(VI) reduction by the isolate. Additionally, it was found that there was hardly any chromium on the cell surface of the strain, further supporting that reduction, rather than bioadsorption, plays a major role in the Cr(VI) removal. (orig.)

  16. Integrated Ecogenomics Study for Bioremediation of Cr(VI) at Hanford 100H Area

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Romy; Chakraborty, Romy

    2008-08-12

    Hexavalent chromium is a widespread contaminant found in groundwater. In order to stimulate microbially mediated Cr(VI)-reduction, a poly-lactate compound was injected into Cr(VI)-contaminated aquifers at site 100H at Hanford. Investigation of bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products revealed a stimulation of Pseudomonas, Desulfovibrio and Geobacter species amongst others. Enrichment of these organisms coincided with continued Cr(VI) depletion. Functional gene-array analysis of DNA from monitoring well indicated high abundance of genes involved in nitrate-reduction, sulfate-reduction, iron-reduction, methanogenesis, chromium tolerance/reduction. Clone-library data revealed Psedomonas was the dominant genus in these samples. Based on above results, we conducted lab investigations to study the dominant anaerobic culturable microbial populations present at this site and their role in Cr(VI)-reduction. Enrichments using defined anaerobic media resulted in isolation of an iron-reducing, a sulfate-reducing and a nitrate-reducing isolate among several others. Preliminary 16S rDNA sequence analysis identified the isolates as Geobacter metallireducens, Pseudomonas stutzeri and Desulfovibrio vulgaris species respectively. The Pseudomonas isolate utilized acetate, lactate, glycerol and pyruvate as alternative carbon sources, and reduced Cr(VI). Anaerobic washed cell suspension of strain HLN reduced almost 95?M Cr(VI) within 4 hr. Further, with 100?M Cr(VI) as sole electron-acceptor, cells grew to 4.05 x 107 /ml over 24 h after an initial lag, demonstrating direct enzymatic Cr(VI) reduction coupled to growth. These results demonstrate that Cr(VI)-immobilization at Hanford 100H site could be mediated by direct microbial metabolism in addition to indirect chemical reduction of Cr(VI) by end-products of microbial activity.

  17. An experimental study on the inhibitory effect of high concentration bicarbonate on the reduction of U(VI) in groundwater by functionalized indigenous microbial communities

    International Nuclear Information System (INIS)

    The anaerobic microcosms amended with 30 mM bicarbonate and without bicarbonate were established, respectively, and the reduction of U(VI) in the microcosms by functionalized indigenous microbial communities was investigated. Results of the chemical extraction and XANES analysis showed that the proportions of U(IV) in the microcosms amended with bicarbonate were 10 % lower than without bicarbonate at day 46. The amount of Cellulomonadaceae, Desulfovibrionaceae, Peptococcaceae and Veillonellaceae amended with bicarbonate was lower than without bicarbonate, so the reduction of U(VI) was less. The experimental results show that the high concentration bicarbonate has a significantly inhibitory effect on the reduction of U(VI). (author)

  18. Metaproteomics Identifies the Protein Machinery Involved in Metal and Radionuclide Reduction in Subsurface Microbiomes and Elucidates Mechanisms and U(VI) Reduction Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Pfiffner, Susan M. [Univ. of Tennessee, Knoxville, TN (United States); Löffler, Frank [Univ. of Tennessee, Knoxville, TN (United States); Ritalahti, Kirsti [Univ. of Tennessee, Knoxville, TN (United States); Sayler, Gary [Univ. of Tennessee, Knoxville, TN (United States); Layton, Alice [Univ. of Tennessee, Knoxville, TN (United States); Hettich, Robert [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-08-31

    The overall goal for this funded project was to develop and exploit environmental metaproteomics tools to identify biomarkers for monitoring microbial activity affecting U speciation at U-contaminated sites, correlate metaproteomics profiles with geochemical parameters and U(VI) reduction activity (or lack thereof), elucidate mechanisms contributing to U(VI) reduction, and provide remediation project managers with additional information to make science-based site management decisions for achieving cleanup goals more efficiently. Although significant progress has been made in elucidating the microbiology contribution to metal and radionuclide reduction, the cellular components, pathway(s), and mechanisms involved in U trans-formation remain poorly understood. Recent advances in (meta)proteomics technology enable detailed studies of complex samples, including environmental samples, which differ between sites and even show considerable variability within the same site (e.g., the Oak Ridge IFRC site). Additionally, site-specific geochemical conditions affect microbial activity and function, suggesting generalized assessment and interpretations may not suffice. This research effort integrated current understanding of the microbiology and biochemistry of U(VI) reduction and capitalize on advances in proteomics technology made over the past few years. Field-related analyses used Oak Ridge IFRC field ground water samples from locations where slow-release substrate biostimulation has been implemented to accelerate in situ U(VI) reduction rates. Our overarching hypothesis was that the metabolic signature in environmental samples, as deciphered by the metaproteome measurements, would show a relationship with U(VI) reduction activity. Since metaproteomic and metagenomic characterizations were computationally challenging and time-consuming, we used a tiered approach that combines database mining, controlled laboratory studies, U(VI) reduction activity measurements, phylogenetic

  19. On-line pre-reduction of Se(VI) by thiourea for selenium speciation by hydride generation

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Jianhua [Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Wang Qiuquan [Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China)]. E-mail: qqwang@xmu.edu.cn; Ma Yuning [Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Yang Limin [Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Huang Benli [Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China)

    2006-07-15

    In this study, thiourea (TU) was novelly developed as a reduction reagent for on-line pre-reduction of selenium(VI) before conventional hydride generation (HG) by KBH{sub 4}/NaOH-HCl. After TU on-line pre-reduction, the HG efficiency of Se(VI) has been greatly improved and because even higher than that of the same amount of Se(IV) obtained in the conventional HG system. The possible pre-reduction mechanism is discussed. The detection limit (DL) of selenate reaches 10 pg mL{sup -1} when using on-line TU pre-reduction followed by HG atomic fluorescence detection. When TU pre-reduction followed by HG is used as an interface between ion-pair high performance liquid chromatography and atomic fluorescence spectrometry, selenocystine, selenomethionine, selenite and selenate can be measured simultaneously and quantitatively. The DLs of these are 0.06, 0.08, 0.05 and 0.04 ng mL{sup -1}, respectively, and the relative standard deviations of 9 duplicate runs for all the 4 species are less than 5%. Furthermore, it was successfully applied to Se speciation analysis of cultured garlic samples, and validated by determination of total selenium and selenium species in certified reference material NIST 1946.

  20. Assessment of the removal mechanism of hexavalent chromium from aqueous solutions by olive stone.

    Science.gov (United States)

    Martín-Lara, María Ángeles; Calero de Hoces, Mónica; Ronda Gálvez, Alicia; Pérez Muñoz, Antonio; Trujillo Miranda, Ma Carmen

    2016-01-01

    The objectives of this study were to study the removal mechanism of Cr(VI) by natural olive stone (OS) and to present a sequential-batch process for the removal of total chromium (original Cr(VI) and Cr(III) derived from reduction of Cr(VI) during biosorption at acidic conditions). First, experiments were conducted varying pH from 1 to 4, and showed that a combined effect of biosorption and reduction is involved in the Cr(VI) removal. Then, X-ray photoelectron spectroscopy and desorption tests were employed to verify the oxidation state of the chromium bound to OS and to elucidate the removal mechanism of Cr(VI) by this material. The goal of these tests was to confirm that Cr(III) is the species mainly absorbed by OS. Finally, the possibility of total chromium removal by biosorption in a sequential-batch process was analyzed. In the first stage, 96.38% of Cr(VI) is removed by OS and reduced to Cr(III). In the second stage, approximately 31% of the total Cr concentration was removed. However, the Cr(III) released in the first stage is not completely removed, and it could suggest that the Cr(III) could be in a hydrated compound or a complex, which could be more difficult to remove under these conditions. PMID:27232404

  1. Effects of Incubation Conditions on Cr(VI) Reduction by c-type Cytochromes in Intact Shewanella oneidensis MR-1 Cells

    Science.gov (United States)

    Han, Rui; Li, Fangbai; Liu, Tongxu; Li, Xiaomin; Wu, Yundang; Wang, Ying; Chen, Dandan

    2016-01-01

    It is widely recognized that the outer membrane c-type cytochromes (OM c-Cyts) of metal-reducing bacteria play a key role in microbial metal reduction processes. However, the in situ redox status of OM c-Cyts during microbial metal reduction processes remain poorly understood. In this study, diffuse-transmission UV/Vis spectroscopy is used to investigate the in situ spectral reaction of Cr(VI) reduction by c-Cyts in intact Shewanella oneidensis MR-1 cells under different incubation conditions. The reduced c-Cyts decreased transiently at the beginning and then recovered gradually over time. The Cr(VI) reduction rates decreased with increasing initial Cr(VI) concentrations, and Cr(III) was identified as a reduced product. The presence of Cr(III) substantially inhibited Cr(VI) reduction and the recovery of reduced c-Cyts, indicating that Cr(III) might inhibit cell growth. Cr(VI) reduction rates increased with increasing cell density. The highest Cr(VI) reduction rate and fastest recovery of c-Cyts were obtained at pH 7.0 and 30°C, with sodium lactate serving as an electron donor. The presence of O2 strongly inhibited Cr(VI) reduction, suggesting that O2 might compete with Cr(VI) as an electron acceptor in cells. This study provides a case of directly examining in vivo reaction properties of an outer-membrane enzyme during microbial metal reduction processes under non-invasive physiological conditions. PMID:27242759

  2. Influence of Reactive Transport on the Reduction of U(VI) in the Presence of Fe(III) and Nitrate: Implications for U(VI) Immobilization by Bioremediation/Bioba

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Brian D.

    2004-06-01

    The research in FY04 was focused in five specific topics: (1) U(VI) sorption on microbially and abiotically reduced sediments, (2) oxidation of biogenic U(IV) in presence of Fe(II), (3) U(VI) reduction by reduced sediments, (4) kinetics of U(VI) sorption on natural sediments under conditions of flow, and (5) NMR imaging of S. onidensis biofilms in porous media. Two manuscripts are currently in review, and another five (or four?) manuscripts are currently in preparation for submission.

  3. Application of NAA method to study chromium uptake by Arthrobacter oxydans

    International Nuclear Information System (INIS)

    To study chromium uptake by Arthrobacter oxydans (Cr(VI)-reducer bacteria isolated from Columbia basalt rocks, USA) instrumental neutron activation analysis method was applied. It was established that chromate accumulation is dose-dependent and it is more intensive in the interval of concentrations of Cr(VI) (10-50 mg/l). At low concentrations of Cr(VI) (up to 50 mg/l) the most intensive formation of Cr(V) was also found (using ESR method). Besides, it was estimated that reduction from Cr(VI) to Cr(V) is faster process than the uptake of Cr(VI). According to ENAA measurements Cr(III), in constant to Cr(VI), is not accumulated in Arthrobacter oxydans cells up to concentration of 200 mg/l. Using epithermal neutron activation analysis the background levels of 17 major, minor and trace elements were determined in Arthrobacter oxydans

  4. Combined abiotic and biotic in-situ reduction of hexavalent chromium in groundwater using nZVI and whey: A remedial pilot test.

    Science.gov (United States)

    Němeček, Jan; Pokorný, Petr; Lacinová, Lenka; Černík, Miroslav; Masopustová, Zuzana; Lhotský, Ondřej; Filipová, Alena; Cajthaml, Tomáš

    2015-12-30

    The paper describes a pilot remediation test combining two Cr(VI) geofixation methods - chemical reduction by nanoscale zero-valent iron (nZVI) and subsequent biotic reduction supported by whey. Combination of the methods exploited the advantages of both - a rapid decrease in Cr(VI) concentrations by nZVI, which prevented further spreading of the contamination and facilitated subsequent use of the cheaper biological method. Successive application of whey as an organic substrate to promote biotic reduction of Cr(VI) after application of nZVI resulted in a further and long-term decrease in the Cr(VI) contents in the groundwater. The effect of biotic reduction was observed even in a monitoring well located at a distance of 22 m from the substrate injection wells after 10 months. The results indicated a reciprocal effect of both the phases - nZVI oxidized to Fe(III) during the abiotic phase was microbially reduced back to Fe(II) and acted as a reducing agent for Cr(VI) even when the microbial density was already low due to the consumed substrate. Community analysis with pyrosequencing of the 16S rRNA genes further confirmed partial recycling of nZVI in the form of Fe(II), where the results showed that the Cr(VI) reducing process was mediated mainly by iron-reducing and sulfate-reducing bacteria. PMID:26292054

  5. About the performance of Sphaerotilus natans to reduce hexavalent chromium in batch and continuous reactors

    International Nuclear Information System (INIS)

    The hexavalent chromium biological reduction constitutes a safe and economical detoxification procedure of wastewaters containing Cr(VI). However, little research has been done to evaluate Cr(VI) tolerance and reduction capacity of microbial cultures under different growth conditions. The aims of this work were (a) to evaluate the capacity of Sphaerotilus natans to reduce Cr(VI) to Cr(III) in a continuous system limited in carbon and energy source or in nitrogen source, (b) to evaluate the toxic effect of Cr(VI) on this microorganism, (c) to carry out a complete analysis of Cr(VI) reduction by S. natans not only in continuous regime but also in batch system, and (d) to model the obtained results mathematically. S. natans exhibited great resistance to Cr(VI) (19-78 mg l-1) and optimal growth in continuous and batch systems using a mineral medium supplemented only with citric acid as organic substrate. In carbon- and energy-limited continuous systems, a maximum percentual decrease in Cr(VI) by 13% was reached for low influent Cr(VI) concentration (4.3-5.32 mgCr(VI) l-1); the efficiency of the process did not notoriously increase as the length of cellular residence time was increased from 4.16 to 50 h. A nitrogen-limited continuous operation with a cellular residence time of 28.5 h resulted in a Cr(VI) decrease of approximately 26-32%. In batch system, a mathematical model allowed to predict the Cr(VI) concentration as a function of time and the ratio between the initial Cr(VI) concentration and that of the biomass. High concentrations of initial Cr(VI) and biomass produced the highest performance of the process of Cr(VI) reduction reached in batch system, aspects which should be considered in detoxification strategies of wastewaters.

  6. Microbial biotechnology for remediation of aquatic habitats polluted with chromium

    Directory of Open Access Journals (Sweden)

    Viorica Coşier

    2008-12-01

    Full Text Available Chromium may occur in nine different forms of oxidation ranging from ?II to +VI, with forms II, III and VI as the most commonly encountered. In Cluj county, chromium pollution dates well back in time and has caused important dysfunction to the mechanical-biological wastewater purification station of the city of Cluj (Coşier & Diţă 1996. The purpose of this study was to develop one microbial method able to reduce hexavalent chromium (mobile, permeable to cell membrane, carcinogenic and mutagenic (Ishikawa et al 1994 to the trivalent form (insoluble and an essential element for humans (Song et al 2006. Different sources of chromium-reducing bacteria and many sources of carbon and energy added to the Kvasnikov mineral basal medium (Komori et al 1990 with increasing amount of chromate (200- 1000 mg/l were tested. Two bacterial strains, able to reduce even 1000 mg chromate/l, were isolated in pure culture. For one of these bacterial strains, we determined the optimum conditions for the reduction of Cr (VI.

  7. Chemical and microbial remediation of hexavalent chromium from contaminated soil and mining/metallurgical solid waste: a review.

    Science.gov (United States)

    Dhal, B; Thatoi, H N; Das, N N; Pandey, B D

    2013-04-15

    Chromium is a highly toxic non-essential metal for microorganisms and plants, and its occurrence is rare in nature. Lower to higher chromium containing effluents and solid wastes released by activities such as mining, metal plating, wood preservation, ink manufacture, dyes, pigments, glass and ceramics, tanning and textile industries, and corrosion inhibitors in cooling water, induce pollution and may cause major health hazards. Besides, natural processes (weathering and biochemical) also contribute to the mobility of chromium which enters in to the soil affecting the plant growth and metabolic functions of the living species. Generally, chemical processes are used for Cr- remediation. However, with the inference derived from the diverse Cr-resistance mechanism displayed by microorganisms and the plants including biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux, bioremediation is emerging as a potential tool to address the problem of Cr(VI) pollution. This review focuses on the chemistry of chromium, its use, and toxicity and mobility in soil, while assessing its concentration in effluents/wastes which becomes the source of pollution. In order to conserve the environment and resources, the chemical/biological remediation processes for Cr(VI) and their efficiency have been summarised in some detail. The interaction of chromium with various microbial/bacterial strains isolated and their reduction capacity towards Cr(VI) are also discussed. PMID:23467183

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-01

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

  9. Cr(VI) sorption/desorption on untreated and mussel-shell-treated soil materials: fractionation and effects of pH and chromium concentration

    Science.gov (United States)

    Otero, M.; Cutillas-Barreiro, L.; Nóvoa-Muñoz, J. C.; Arias-Estévez, M.; Fernández-Sanjurjo, M. J.; Álvarez-Rodríguez, E.; Núñez-Delgado, A.

    2015-04-01

    We used batch-type experiments to study Cr(VI) sorption/desorption on granitic material, forest soil, pyritic material, mussel shell, and on forest soil and granitic material amended with 12 t ha-1 (1.2 kg m -2) shell, considering the effects of varying Cr(VI) concentration and pH. Sequential extractions were carried out to fractionate adsorbed Cr(VI) and to determine the stability of Cr(VI) retention. The pyritic material had the highest Cr(VI) retention capacity, whereas the granitic material showed the lowest retention potential. When high Cr concentrations were added, some saturation of the adsorbent surfaces became apparent, but Cr release remained low. The highest Cr retention was achieved at a very acid pH value, with release progressively increasing as a function of increasing pH. The amendment with 12 t ha-1 mussel shell did not cause marked changes in Cr(VI) retention. Sorption data were satisfactory adjusted to the Freundlich model. Regarding Cr(VI) fractionation, the soluble fraction (weakly bound) was dominant in mussel shell and in the unamended and amended granitic material, whereas more stable fractions dominated in the pyritic material (residual fraction) and in the forest soil (oxidizable fraction). In conclusion, the pyritic material presented the highest Cr(VI) retention capacity, while the retention was low and weak on the granitic material; mussel shell was not characterized by a marked Cr(VI) retention potential, and it did not cause remarkable increase in Cr(VI) retention when used to amend the granitic material or the forest soil.

  10. Catalytic reduction of U(VI) to U(IV) using hydrogen with platinum loaded on alumina and silica

    International Nuclear Information System (INIS)

    During the reprocessing of spent nuclear fuel, uranium (U) and plutonium (Pu) are together extracted by employing tri-n-butyl phosphate (TBP)/dodecane mixture and their partitioning is achieved by adding uranous nitrate. The partitioning agent, uranous is conventionally produced by the electrolytic reduction of uranyl nitrate. An alternate route for the reduction of U from (VI) to (IV) using hydrogen (H2) as reductant was developed using platinum (Pt) based catalyst. Improvements in the development of the catalyst have been carried out in order to reduce the requirement of Pt without affecting the reduction performance. Experiments using 2 wt% Pt loaded on alumina beads and alumina powder have been performed and results are discussed. As the catalyst supported on alumina was found to be unstable in acidic environment, Pt loaded on silica powder has also been developed. Pt loaded on alumina and silica substrates have been tried to envisage the reduction behaviour using H2 as reductant in presence of hydrazine nitrate which acts as U(IV) stabiliser as well as reductant. Parametric studies have been carried out to optimise the process parameters namely pressure, temperature, U concentration, free acidity, hydrazine concentration and catalyst to U (C/U) ratio. 2 wt% Pt loaded on silica has been selected for further scale up studies for making uranous. (author)

  11. Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li [Pennsylvania State Univ., State College, PA (United States); Li, Li [Pennsylvania State Univ., State College, PA (United States)

    2015-10-22

    The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in natural systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport

  12. Competitive Biosorption of Chromium(VI), Iron(III) and Copper(II) Ions From Binary Metal Mixtures By R.arrhizus and C. vulgaris

    OpenAIRE

    SAĞ, Yeşim; AÇIKEL, Ünsal; AKSU, Zümriye; KUTSAL, Tülin

    1998-01-01

    In this study, the simultaneous adsorption process of Cr(VI), Fe(III) by R. arrhizus and C. vulgaris and Cu(II) in pairs of metal mixtures were investigated and compared to single component systems. The capabilities of the fungal and the algal biomass to bind two metals simultaneously in solution are shown as a function of pH, metal combinations and levels of metal concentration. The effects of the co-presence of Cr(VI)-Fe(III) and Cr(VI)-Cu(II) ions together in aquatic solutions on the bi...

  13. Chromium Resistant Bacteria: Impact on Plant Growth in Soil Microcosm

    Directory of Open Access Journals (Sweden)

    Sayel Hanane

    2014-07-01

    Full Text Available Three chromium resistant bacterial strains, Pseudomonas fluorescens PF28, Enterobacter amnigenus EA31 and Enterococcus gallinarum S34 isolated from tannery waste contaminated soil were used in this study. All strains could resist a high concentration of K2Cr2O7 that is up to 300 mg/L. The effect of these strains on clover plants (Trifolium campestre in the presence of two chromium salts CrCl3 and K2Cr2O7 was studied in soil microcosm. Application of chromium salts adversely affected seed germination, root and shoot length. Bacterial inoculation improved the growth parameters under chromate stress when compared with non inoculated respective controls. There was observed more than 50% reduction of Cr(VI in inoculated soil microcosms, as compared to the uninoculated soil under the same conditions. The results obtained in this study are significant for the bioremediation of chromate pollution.

  14. MIL-53(Fe) as a highly efficient bifunctional photocatalyst for the simultaneous reduction of Cr(VI) and oxidation of dyes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Ruowen; Jing, Fenfen; Shen, Lijuan; Qin, Na; Wu, Ling, E-mail: wuling@fzu.edu.cn

    2015-04-28

    Highlights: • Fe(III)-based MOF was firstly applied to the photocatalytic reduction reaction. • MIL-53(Fe) exhibited an outstanding photocatalytic activity for reduction of Cr(VI). • A first systematic study of the Fe(III)-based MOF as bifunctional photocatalyst. • Dyes and Cr(VI) could be also converted simultaneously over MIL-53(Fe). • MIL-53(Fe) was performed a stable and reusable visible-light-driven photocatalyst. - Abstract: A bifunctional photocatalyst-Fe-benzenedicarboxylate (MIL-53(Fe)) has been synthesized successfully via a facile solvothermal method. The resulting MIL-53(Fe) photocatalyst exhibited an excellent visible light (λ ≥ 420 nm) photocatalytic activity for the reduction of Cr(VI), the reduction rate have reached about 100% after 40 min of visible light irradiation, which has been more efficient than that of N-doped TiO{sub 2} (85%) under identical experimental conditions. Further experimental results have revealed that the photocatalytic activity of MIL-53(Fe) for the reduction of Cr(VI) can be drastically affected by the pH value of the reaction solution, the hole scavenger and atmosphere. Moreover, MIL-53(Fe) has exhibited considerable photocatalytic activity in the mixed systems (Cr(VI)/dyes). After 6 h of visible light illumination, the reduction ratio of Cr(VI) and the degradation ratio of dyes have been exceed 60% and 80%, respectively. More significantly, the synergistic effect can also be found during the process of photocatalytic treatment of Cr(VI) contained wastewater under the same photocatalytic reaction conditions, which makes it a potential candidate for environmental restoration. Finally, a possible reaction mechanism has also been investigated in detail.

  15. MIL-53(Fe) as a highly efficient bifunctional photocatalyst for the simultaneous reduction of Cr(VI) and oxidation of dyes

    International Nuclear Information System (INIS)

    Highlights: • Fe(III)-based MOF was firstly applied to the photocatalytic reduction reaction. • MIL-53(Fe) exhibited an outstanding photocatalytic activity for reduction of Cr(VI). • A first systematic study of the Fe(III)-based MOF as bifunctional photocatalyst. • Dyes and Cr(VI) could be also converted simultaneously over MIL-53(Fe). • MIL-53(Fe) was performed a stable and reusable visible-light-driven photocatalyst. - Abstract: A bifunctional photocatalyst-Fe-benzenedicarboxylate (MIL-53(Fe)) has been synthesized successfully via a facile solvothermal method. The resulting MIL-53(Fe) photocatalyst exhibited an excellent visible light (λ ≥ 420 nm) photocatalytic activity for the reduction of Cr(VI), the reduction rate have reached about 100% after 40 min of visible light irradiation, which has been more efficient than that of N-doped TiO2 (85%) under identical experimental conditions. Further experimental results have revealed that the photocatalytic activity of MIL-53(Fe) for the reduction of Cr(VI) can be drastically affected by the pH value of the reaction solution, the hole scavenger and atmosphere. Moreover, MIL-53(Fe) has exhibited considerable photocatalytic activity in the mixed systems (Cr(VI)/dyes). After 6 h of visible light illumination, the reduction ratio of Cr(VI) and the degradation ratio of dyes have been exceed 60% and 80%, respectively. More significantly, the synergistic effect can also be found during the process of photocatalytic treatment of Cr(VI) contained wastewater under the same photocatalytic reaction conditions, which makes it a potential candidate for environmental restoration. Finally, a possible reaction mechanism has also been investigated in detail

  16. Remoción de Cromo (VI) por una Cepa de Paecilomyces sp Resistente a Cromato Removal of Chromium (VI) in a Chromate-Resistant Strain of Paecilomyces sp

    OpenAIRE

    Cárdenas-González, Juan F.; Martínez-Juárez, Víctor M.; Ismael Acosta-Rodríguez

    2011-01-01

    Se analizó la capacidad de remoción de Cr(VI) de una cepa de Paecilomyces sp. Cuando el hongo se incubó en medio mínimo con glucosa y otras fuentes de carbono comerciales y de bajo costo, como azúcar moscabada y piloncillo ó glicerol, en presencia de 50 mg/L de Cr(VI), removió totalmente el Cr(VI). La reducción a Cr(III) ocurre en el medio de cultivo después de 7 días de incubación a 28°C, pH 4.0, y un inoculo de 38 mg. El hongo también redujo eficientemente la concentración de Cr(VI) a parti...

  17. IN SITU CHEMICAL REDUCTION OF CR(VI) IN GROUNDWATER USING A COMBINATION OF FERROUS SULFATE AND SODIUM DITHIONITE: A FIELD INVESTIGATION

    Science.gov (United States)

    A field pilot test was conducted to evaluate the effectiveness of a FeSO4 + Na2S2O4 reductant solution blend for in situ saturated zone treatment of dissolved-phase Cr(VI) at the former Macalloy Corporation site in Charleston, SC. The reductant blend was injected into the path o...

  18. Pyridine appended L-methionine: A novel chelating resin for pH dependent Cr speciation with scanning electron microscopic evidence and monitoring of yeast mediated green bio-reduction of Cr(VI) to Cr(III) in environmental samples

    International Nuclear Information System (INIS)

    Chemical speciation and pH dependent separation of Cr(III) and Cr(VI) species in environmental samples have been achieved by solid phase extraction using a new chelating resin containing pyridine appended L-methionine. Cr(III) is completely sorbed on the resin at pH 8.0 and Cr(VI) at pH 2.0. Hence a pH dependent separation of Cr(III) and Cr(VI) is possible with a limit of detection of 1.6 μg mL-1 and 0.6 μg mL-1 respectively. The sorption capacity of the resin for Cr(III) and Cr(VI) is 2.8 mmol g-1 and 1.3 mmol g-1 respectively. The sorption of chromium on the resin is supported by scanning electron microscopy (SEM). Complete desorption of Cr(III) and Cr(VI) from 1 g of Cr loaded resin was achieved using 10 mL of 2 mol L-1 HNO3 and 6 mL of 3 mol L-1 HNO3 respectively. Quantitative recoveries of Cr(III) (pH 8.0) and Cr(VI) (pH 2.0) were found to be 96.0% and 98.0% respectively. Reduction efficiency of Rhodotornula mucilaginosa yeast from Cr(VI) to Cr(III) was monitored with this new resin. Concentrations of metal ions were measured by flame atomic absorption spectroscopy (FAAS).

  19. Effect of FeSO4.7H2O and SnCl2.2H2O added as Chromium (VI) Reducers in Ordinary Portland Cement

    OpenAIRE

    Devesh K. Sharma; Rekha Sharma

    2015-01-01

    The paper compared the effect of additives such as FeSO4.2H2O and SnCl2.2H2O on reduction of water soluble Cr(VI), in ordinary Portland cement (43 grades). The determination of water soluble Cr(VI) from cement samples was precisely conducted by DPC-Spectrophotometer technique. The compressive strength testing of the cement mortar samples was carried out. In addition, hydration properties of cement paste (with and without additives) are reported in this paper. Hydration products were also stud...

  20. Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction

    International Nuclear Information System (INIS)

    Highlights: • NH2 functionalized MIL-125(Ti) was fabricated by a facile solvothermal method. • The photocatalyst could reduce Cr(VI)–Cr(III) under visible light irradiation. • The Ti3+–Ti4+ intervalence electron transfer is important for Cr(VI) reduction. • Used NH2-MIL-125(Ti) can be recycled for the photocatalytic reduction. - Abstract: Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH2-MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH2-MIL-125(Ti) were well characterized by XRD, SEM, XPS, N2 adsorption–desorption measurements, thermogravimetric analysis and UV–vis diffuse reflectance spectra (DRS). It is revealed that the NH2-MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH2-MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti3+–Ti4+ intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater

  1. Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium.

    Science.gov (United States)

    Watts, Mathew P; Khijniak, Tatiana V; Boothman, Christopher; Lloyd, Jonathan R

    2015-08-15

    Chromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to the Halomonas genus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as an in situ treatment of COPR and other alkaline Cr(VI)-contaminated environments. PMID:26048926

  2. Biosorption of hexavalent chromium in a tannery industry wastewater using fungi species

    OpenAIRE

    Sivakumar, D.

    2016-01-01

    The isolated fungi species of different kinds from chromium contaminated soil sites located in Nagalkeni, Chennai were used for reducing chromium(VI) in a tannery industry wastewater of Nagalkeni, Chennai.  The experiments were conducted to know biosorption potential of isolated fungi species for removing chromium(VI) in a tannery industry wastewater against the different pH, fungi biomass and chromium(VI) concentration (dilution ratio).  The results of this study indicated that the order of ...

  3. Adsorción de Cromo (VI en Solución Acuosa sobre Fibra de Carbón Activado Adsorption of Chromium (VI from Aqueous Solution onto Activated Carbon Fiber

    Directory of Open Access Journals (Sweden)

    Roberto Leyva

    2008-01-01

    Full Text Available En este trabajo se estudia la adsorción de Cr(VI en solución acuosa sobre una fibra de carbón activado tipo fieltro. Los datos de equilibrio de adsorción de Cr(VI sobre la fibra se obtuvieron en un adsorbedor de lote y la concentración de Cr(VI se determinó por un método colorimétrico. La isoterma de Freundlich ajustó bastante bien los datos experimentales. La capacidad de adsorción disminuyó considerablemente incrementando el pH de 4 a 10, pero aumentó ligeramente incrementando la temperatura de 15 a 35°C. El efecto del pH se debió a las interacciones electrostáticas entre la superficie y los aniones de Cr(VI en solución. La capacidad de adsorción se comparó con las capacidades de carbones activados granulares de avellana y coco. La capacidad de la fibra fue el doble de la de carbones de cáscara de avellana y la mitad de la de carbones de cáscara de coco.The adsorption of Cr(VI from aqueous solution on an activated carbon fiber of felt type, was studied. The adsorption equilibrium data of Cr(VI on the fiber were obtained in a batch adsorber and the concentration of Cr(VI was determined by a colorimetric method. The Freundlich isotherm fitted reasonably well the experimental data. The Cr(VI adsorption capacity of the fiber decreased considerably while increasing the solution pH from 4 to 10 but slightly increased as the temperature increased from 15 to 35°C. The effect of the pH was due to the electrostatic interactions between the surface of the fiber and the Cr(VI anions in solution. The adsorption capacity of the fiber was compared to those of granular activated carbons made from hazelnut shell and from coconut shell. The adsorption capacity of the fiber was twice that of the hazelnut carbon and half of that of the coconut carbon.

  4. Chromium(VI)-induced Production of Reactive Oxygen Species, Change of Plasma Membrane Potential and Dissipation of Mitochondria Membrane Potential in Chinese Hamster Lung Cell Cultures

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective To examine whether Reactive Oxygen Species (ROS) is generated, and whether plasma membrane potential and mitochondrial membrane potential are depolarized in Chinese Hamster Lung (CHL) cell lines exposed to Cr (VI). Methods CHL cells were incubated with Cr(VI) at 10 μmol/L, 2.5 μmol/L, 0.65 μmol/L for 3 and 6 hours, respectively. The production of ROS was performed by using 2,7_dichlorofluorescin diacetate; The changes in plasma membrane potential were estimated using fluorescent cationic dye DiBAC4; And the changes in mitochondria membrane potential were estimated using fluorescent dye Rhodamine 123. Results The ROS levels in CHL cells increased in all treated groups compared with the control group (P<0.01); The plasma membrane potential and mitochondrial membrane potential in CHL cells dissipated after incubated with Cr(VI) at 10 μmol/L for 3 hours and 6 hours (P<0.01), at 2.5 μmol/L for 6 hours (P<0.01 or 0.05). Conclusion Cr(VI) causes the dissipation of plasma membrane potential and mitochondrial membrane potential in CHL cell cultures, and Cr(VI)_induced ROS may play a role in the injuries.

  5. Diverse anaerobic Cr(VI) tolerant bacteria from Cr(VI)-contaminated 100H site at Hanford

    Science.gov (United States)

    Chakraborty, R.; Phan, R.; Lam, S.; Leung, C.; Brodie, E. L.; Hazen, T. C.

    2007-12-01

    Hexavalent Chromium [Cr(VI)] is a widespread contaminant found in soil, sediment, and ground water. Cr(VI) is more soluble, toxic, carcinogenic, and mutagenic compared to its reduced form Cr(III). In order to stimulate microbially mediated reduction of Cr(VI), a poly-lactate compound HRC was injected into the chromium contaminated aquifers at site 100H at Hanford. Based on the results of the bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products, we recently investigated the diversity of the dominant anaerobic culturable microbial population present at this site and their role in Cr(VI) reduction. Positive enrichments set up at 30°C using specific defined anaerobic media resulted in the isolation of an iron reducing isolate strain HAF, a sulfate reducing isolate strain HBLS and a nitrate reducing isolate, strain HLN among several others. Preliminary 16S rDNA sequence analysis identifies strain HAF as Geobacter metallireducens, strain HLN as Pseudomonas stutzeri and strain HBLS as a member of Desulfovibrio species. Strain HAF isolated with acetate as the electron donor utilized propionate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Growth was optimal at 37°C, pH of 6.5 and 0% salinity. Strain HLN isolated with lactate as electron donor utilized acetate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Optimal growth was observed at 37°C, at a pH of 7.5 and 0.3% salinity. Anaerobic active washed cell suspension of strain HLN reduced almost 95 micromolar Cr(VI) within 4 hours relative to controls. Further, with 100 micromolar Cr(VI) as the sole electron acceptor, cells of strain HLN grew to cell numbers of 4.05X 107/ml over a period of 24hrs after an initial lag, demonstrating direct enzymatic Cr(VI) reduction by this species. 10mM lactate served as the sole electron donor. These results demonstrate that Cr(VI

  6. The interplay between thiol-compounds against chromium (VI) in the freshwater green alga Monoraphidium convolutum: Toxicology, photosynthesis, and oxidative stress at a glance

    International Nuclear Information System (INIS)

    In this paper, the multifaceted Cr(VI) toxicity over the freshwater green alga Monoraphidium convolutum was assessed by concomitantly monitoring thiol-dependent redox balances, photosynthesis activity and growth-survival scores. Control group showed exponential growth rate at (5.78 ± 0.29) division/day until 8th day with linear increasing chlorophyll a/protein ratios (CHLa/PROT) throughout the period. Cultures of M. convolutum were exposed for 5 days to Cr(VI) concentrations from 0 up to 100 mg/L showing that CHLa/PROT ratios were sensibly affected, in agreement to the calculated LC50,48h (5.38 ± 0.72) mg/L from the concentration-response curve of cell mortality after 48 h. Regarding photosynthesis effects, Cr(VI) concentrations >1.0 mg/L showed significant increases in short-term (after 2 h) electron transfer rates (ETR) and quantum yields of photosystem II (ΦPSII), followed by subsequent decline of both parameters after 48 and 72 h. Biochemical analyses showed that maximal GSH concentrations in algal cultures were observed upon 1 mg Cr(VI)/L and higher dichromate concentrations dramatically increased the activity of antioxidant GSH-dependent enzymes ascorbate peroxidase and glutathione reductase. However, no variation was observed in the cellular GSH levels, whereas GSSG and lipid peroxidation indexes abruptly increased upon 10 mg Cr(VI)/L exposure. Altogether, plant physiology, photosynthesis and biochemical data suggest that the GSH-dependent antioxidant system is capable to sustain M. convolutum viability through efficient photosynthesis activity and adequate antioxidant responses up to Cr(VI) concentrations of 1.0 mg/L, when redox unbalances were first evidenced.

  7. The potential impact of microbial Fe(III) reduction on subsurface U(VI) mobility at a low level radioactive waste storage site

    Energy Technology Data Exchange (ETDEWEB)

    Wilkins, M.J.; Livens, F.R.; Vaughan, D.J.; Lloyd, J.R. [Williamson Research Centre for Molecular Environmental Science and School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Beadle, I.; Small, J.S. [British Nuclear Fuels plc, Risley, Warrington WA3 6AS (United Kingdom)

    2005-07-01

    Full text of publication follows: Fe(III) oxy-hydroxides have the potential to be utilised as terminal electron acceptors by indigenous microbial communities in the British Nuclear Fuels (BNFL) low level radioactive waste storage site at Drigg (Cumbria, UK) and these organisms may have a critical control on the biogeochemical cycling of several environmentally important radionuclides. In terms of radiological impact at Drigg, uranium is the most significant contributor to radiological impact and it is strongly influenced by biogeochemical processes. In terms of mass (moles) it is also the most abundant radionuclide in the Drigg inventory. Thus, the potential biotic and abiotic effects of Fe(III) reduction on U(VI) mobility in the Drigg subsurface are of interest. Culture-dependent and molecular techniques showed that the sediments in and around the Drigg site contained a diversity of Fe(III)-reducing bacteria. A series of microcosm experiments were utilised to create environmentally relevant experimental conditions. Microcosms set up using Drigg sediment and synthetic ground water were spiked with 100 {mu}M U(VI) and acetate as an electron donor. U(VI) concentrations in groundwater were measured using a chemical assay while total U levels were determined using ICP-MS. Fe(II) levels were determined using the ferrozine method. Sediment surface areas were measured using BET analysis. The low surface area of the sediments resulted in only a small proportion of the 100 {mu}M U(VI) spike sorbing onto mineral surfaces. The addition of ferri-hydrite to some microcosms resulted in an immediate lowering of soluble U(VI) concentrations, suggesting that the formation of soluble U(VI) complexes were not responsible for the minimal adsorption. The presence of biogenic Fe(II) in the microcosms did not affect the soluble U(VI) concentration. Similarly, soluble U(VI) levels remained unchanged when sediments were spiked with U(VI) post-microbial Fe(III) reduction. However, a

  8. The potential impact of microbial Fe(III) reduction on subsurface U(VI) mobility at a low level radioactive waste storage site

    International Nuclear Information System (INIS)

    Full text of publication follows: Fe(III) oxy-hydroxides have the potential to be utilised as terminal electron acceptors by indigenous microbial communities in the British Nuclear Fuels (BNFL) low level radioactive waste storage site at Drigg (Cumbria, UK) and these organisms may have a critical control on the biogeochemical cycling of several environmentally important radionuclides. In terms of radiological impact at Drigg, uranium is the most significant contributor to radiological impact and it is strongly influenced by biogeochemical processes. In terms of mass (moles) it is also the most abundant radionuclide in the Drigg inventory. Thus, the potential biotic and abiotic effects of Fe(III) reduction on U(VI) mobility in the Drigg subsurface are of interest. Culture-dependent and molecular techniques showed that the sediments in and around the Drigg site contained a diversity of Fe(III)-reducing bacteria. A series of microcosm experiments were utilised to create environmentally relevant experimental conditions. Microcosms set up using Drigg sediment and synthetic ground water were spiked with 100 μM U(VI) and acetate as an electron donor. U(VI) concentrations in groundwater were measured using a chemical assay while total U levels were determined using ICP-MS. Fe(II) levels were determined using the ferrozine method. Sediment surface areas were measured using BET analysis. The low surface area of the sediments resulted in only a small proportion of the 100 μM U(VI) spike sorbing onto mineral surfaces. The addition of ferri-hydrite to some microcosms resulted in an immediate lowering of soluble U(VI) concentrations, suggesting that the formation of soluble U(VI) complexes were not responsible for the minimal adsorption. The presence of biogenic Fe(II) in the microcosms did not affect the soluble U(VI) concentration. Similarly, soluble U(VI) levels remained unchanged when sediments were spiked with U(VI) post-microbial Fe(III) reduction. However, a lowering in

  9. Biosorption system produced from biofilms supported on Faujasite (FAU) zeolite, process for obtaining it and its usage for removal of hexavalent chromium (Cr(VI))

    OpenAIRE

    Tavares, M. T.; Neves, Isabel C.

    2008-01-01

    The present invention refers to a biosorption system composed of a bacterial biofilm supported in synthetic zeolites, for usage in various types of industry for the removal of hexavalent chromium, through the retention of metal ions in the biofilm, in solutions with concentrations between 50 and 250 mgCr/L, process for obtaining it and respective usages. This process consists in obtaining a bacterial biofilm of Arthrobacter viscosus, supported on a faujasite (FAU) zeolite. The biofilm promote...

  10. Reduction of U(VI) and Toxic Metals by Desulfovibrio Cytochrome C3

    Energy Technology Data Exchange (ETDEWEB)

    Wall, Judy D

    2013-04-11

    The central objective of our proposed research was twofold: 1) to investigate the structure-function relationship of Desulfovibrio desulfuricans (now Desulfovibrio alaskensis G20) cytochrome c3 with uranium and 2) to elucidate the mechanism for uranium reduction in vitro and in vivo. Physiological analysis of a mutant of D. desulfuricans with a mutation of the gene encoding the type 1 tetraheme cytochrome c3 had demonstrated that uranium reduction was negatively impacted while sulfate reduction was not if lactate were the electron donor. This was thought to be due to the presence of a branched pathway of electron flow from lactate leading to sulfate reduction. Our experimental plan was to elucidate the structural and mechanistic details of uranium reduction involving cytochrome c3.

  11. Determination of hexavalent chromium in exhaled breath condensate and environmental air among chrome plating workers

    International Nuclear Information System (INIS)

    Chromium speciation has attracted attention because of the different toxicity of Cr(III), which is considered relatively non-toxic, and Cr(VI), which can cross cell membranes mainly as a chromate anion and has been classified as a class I human carcinogen. The aims of the present study were to measure soluble Cr(VI) levels in environmental samples, to develop a simple method of quantifying Cr(VI) in exhaled breath condensate (EBC), and to follow the kinetics of EBC Cr(VI) in chrome plating workers. Personal air samples were collected from 10 chrome platers; EBC was collected from the same workers immediately after the work shift on Tuesday and before the work shift on the following Wednesday. Environmental and EBC Cr(VI) levels were determined by means of colorimetry and electrothermal absorption atomic spectrometry, respectively. The method of detecting Cr(VI) in environmental air was based on the extraction of the Cr(VI)-diphenylcarbazide (Cr(VI)-DPC) complex in 1-butanol, whereas EBC Cr(VI) was determined using a solvent extraction of Cr(VI) as an ion pair with tetrabutylammonium ion, and subsequent direct determination of the complex (Cr(VI)-DPC) in EBC. Kinetic data showed that airborne Cr(VI) was reduced by 50% in airway lining fluid sampled at the end of exposure and that there was a further 50% reduction after about 15 h. The persistence of Cr(VI) in EBC supports the use of EBC in assessing target tissue levels of Cr(VI)

  12. In Situ Spectral Kinetics of Cr(VI) Reduction by c-Type Cytochromes in A Suspension of Living Shewanella putrefaciens 200

    Science.gov (United States)

    Liu, Tongxu; Li, Xiaomin; Li, Fangbai; Han, Rui; Wu, Yundang; Yuan, Xiu; Wang, Ying

    2016-07-01

    Although c-type cytochromes (c-Cyts) mediating metal reduction have been mainly investigated with in vitro purified proteins of dissimilatory metal reducing bacteria, the in vivo behavior of c-Cyts is still unclear given the difficulty in measuring the proteins of intact cells. Here, c-Cyts in living Shewanella putrefaciens 200 (SP200) was successfully quantified using diffuse-transmission UV/Vis spectroscopy due to the strong absorbance of hemes, and the in situ spectral kinetics of Cr(VI) reduction by c-Cyts were examined over time. The reduced product Cr(III) observed on the cell surface may play a role in inhibiting the Cr(VI) reduction and reducing the cell numbers with high concentrations (>200 μM) of Cr(VI) evidenced by the 16S rRNA analysis. A brief kinetic model was established with two predominant reactions, redox transformation of c-Cyts and Cr(VI) reduction by reduced c-Cyts, but the fitting curves were not well-matched with c-Cyts data. The Cr(III)-induced inhibitory effect to the cellular function of redox transformation of c-Cyts was then added to the model, resulting in substantially improved the model fitting. This study provides a case of directly examining the reaction properties of outer-membrane enzyme during microbial metal reduction processes under physiological conditions.

  13. Development of U isotope fractionation as an indictor or U(VI) reduction in uranium plumes

    Energy Technology Data Exchange (ETDEWEB)

    Lundstrom, Craig [Univ. of Illinois, Urbana-Champaign, IL (United States); Johnson, Thomas [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2016-02-16

    This is the final report for a university research project that advanced development of a new technology for identifying chemical reduction of uranium contamination in groundwater at the Rifle Field Challenge site. Reduction changes mobile hexavalent uranium into immobile U(IV). The stable isotope ratio (238U/235U) measurements of U using multicollector ICP-mass spectrometry were performed to understand the chemical reduction and sorption processes during various field experiments. In addition laboratory experiments were performed to better understand the isotopic fractionations. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.

  14. Recovery of Chromium Ions From Electroplating Wastewater by Flotation, Gamma Irradiation and Adsorption onto Hydrogels

    International Nuclear Information System (INIS)

    At present, the wastewater treatment facilities in many plating plants are approaching their time for replacement. On this occasion there is a strong requirement to re-evaluate the wastewater treatment measures from the point of view of treatment technology. Laboratory investigation was undertaken on the flotation of Cr (VI) from aqueous suspension over whole ph range, aiming at the separation of chromium by flotation. The cationic surfactant (hexadecyl triethyl ammonium bromide) was applied as a collector. Surface properties, in particular the critical micelle concentration, the effectiveness of surface tension reduction, efficiency, surface excess and the minimum surface area were measured at 30 μ C. The electro-flotation was applied with and without the collector at different times for the removal of chromium (VI). The results were discussed in term of surface properties of the collectors at the solution/air interface. Further work took place by irradiating the water samples by gamma- irradiation to reduce the highly toxic Cr(VI) to the much less toxic and less soluble Cr1 in water; therefore, there is a potential for the complete removal of chromium from aqueous solutions. The possibility of using hydrogels for the uptake of irradiated chromium solutions by different hydrogels was investigated. The structure of the hydrogels was estimated by using FT1R and the pore structure of the hydrogels before and after dictating with chromium ions was monitored by SEM. The adsorption studies show that, it is ph dependent. Lowering of the chromium concentration below the maximum permissible value have been achieved after the treatment of chromium solution by flotation, gamma irradiation and adsorption onto hydrogels

  15. Synergistic photoelectrochemical reduction of Cr(VI) and oxidation of organic pollutants by g-C3N4/TiO2-NTs electrodes.

    Science.gov (United States)

    Zhang, Yi; Wang, Qiang; Lu, Jiani; Wang, Qi; Cong, Yanqing

    2016-11-01

    The g-C3N4/TiO2-NTs electrodes were synthesized by a dip-coating procedure followed by high-temperature annealing used in photoelectrochemical process. From the results, a simultaneous and rapid reduction of Cr(VI) and degradation of phenol in Cr(VI)/phenol system was observed with photoelectrocatalytic activity under UV-visible light irradiation than photocatalytic and electrocatalytic activities. The different kinds of Cr(VI)/organic pollutants systems were also investigated systematically. In addition, different scavengers were also added in Cr(VI)/phenol and Cr(VI)/benzyl alcohol systems to indicate that the hydroxyl radicals and superoxide radicals were the most major active species for the denomination of Cr(VI) and organic pollutants. The intermediates of phenol and benzyl alcohol were also detected during the reaction in order to deduce the photoelectrocatalysis mechanism underg-C3N4/TiO2-NTs electrodes that the charge separation was improved and subsequently electron-transfer efficiency was higher. PMID:27479456

  16. The reduction of Np(VI) and Np(V) by tit dihydroxyurea and its application to the U/Np separation in the PUREX process

    International Nuclear Information System (INIS)

    The reduction of Np(VI) and Np(V) by Dihydroxyurea (DHU) was studied by spectrophotometry. The results show that the reduction of Np(VI) to Np(V) by DHU is particularly fast. The apparent rate constant is 1.86s-1 at 4 C as [HNO3] = 0.44 M and [DHU] = 7.5 x 10-2 M. While further reduction of Np(V) to Np(IV) is so slow that no Np(IV) is observed in 2 h. The reduction back-extraction behavior of Np(VI) in 30% tri-butyl phosphate/kerosene was firstly investigated under conditions of different temperature, different concentrations of DHU and HNO3 and various phase contact time, respectively. The results show that 98% of Np(VI) in the organic phase can be stripped rapidly to the aqueous phase by DHU under the given experimental conditions. As the concentration of HNO3 in the aqueous phase increases, the stripping efficiency decreases. While the stripping efficiency increases with the increase of the concentration of DHU. Simulating the 1B contactor of the PUREX process using DHU as the stripping agent, the SFU/Np equals to 183 under the given experimental conditions. It indicates that Np will follow with Pu in the U/Pu separation stage in the reprocessing of spent fuels. (orig.)

  17. Batch wise removal of chromium (vi) by adsorption on novel synthesized poly aniline composites with various brans and iso thermal modeling of equilibrium data

    International Nuclear Information System (INIS)

    Summary: Several novel adsorbents have been investigated now-a-days for removal of poisonous substances from waste water. In this research work, poly aniline composites with rice bran, maize bran and wheat bran had been synthesized and applied for the adsorption of Cr(Vi) from waste water. Morphological changes occurring in the surface of composites were characterized by recording their FT-IR spectra. Rice bran, maize bran and wheat bran modified the surface morphology of polyaniline by preventing the aggregation of monomers resulting in improved adsorption capacity. Operational conditions were optimized and applied to Langmuir and Freundlich isotherms for investigating the adsorption mechanism and maximum sorption capacity. Thermodynamic studies positively showed the feasibleness of these adsorbents for the removal of Cr(Vi). (author)

  18. Determination of chromium(VI) in water by PIXE analysis using ion exchange paper. Limit of detection and interference by coexisting anions

    International Nuclear Information System (INIS)

    Concerning the PIXE analysis of Cr(VI) in water using ion-exchange filters, the limit of detection (LOD) and the influence of matrix anions were investigated. In order to look for the experimental condition for obtaining the minimum LOD, we measured the Cr-Kα X-ray counts and background counts under the Kα X-ray peak as a function of the incident proton energy and the thickness of the Mylar absorber foil in front of the detector. To investigate the interference by coexisting anions, each of PO43-, SO42-, NO3-, Cl-, and F- ions and Cr(VI) ions were mixed in aqueous solutions and adsorbed on DE81-DEAE cellulose paper, a weakly basic anion exchanger with diethylaminoethyl functional groups. Then the filter samples were measured by PIXE using 2.5 MeV proton beams. We obtained a LOD of 0.16 μg or 8 ppb for 20 mL samples at a proton energy of 2.5 MeV and a Mylar film thickness of 50 or 100 μm. The experimental results on the mixed solutions indicated that NO3-, Cl-, and F- as coexisting ions didn't interfere significantly with determination of a 50 μg/L Cr(VI) concentration for 40 mL total solution volume, despite the total amount of anions was about 90% of ion exchange capacity of a filter. On the other hand, slight interferences by PO43- ions were observed. However, under the same condition, we found that if the total amount of SO42- ions was higher than 20% of ion exchange capacity, they induced significant interferences in determining Cr(VI). (author)

  19. Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid–glycine co-doped polyaniline

    Energy Technology Data Exchange (ETDEWEB)

    Mo, Xi [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Yang, Zhao-hui, E-mail: yzh@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Xu, Hai-yin; Zeng, Guang-ming; Huang, Jing; Yang, Xia; Song, Pei-pei; Wang, Li-ke [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

    2015-04-09

    Highlights: • RVC/PANI-SA-GLY electrode was applied as a novel electrode material for accelerated removal of Cr(VI). • Faster reduction kinetics of Cr(VI) was observed by RVC/PANI-SA-GLY electrode when compared with RVC/PANI-SA and RVC electrode. • Cr(VI) removal experienced an adsorption-reduction system built by RVC/PANI-SA-GLY electrode. • The stability of RVC/PANI-SA-GLY electrode was relatively satisfactory. - Abstract: Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption–electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid–glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption–reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO{sub 4}{sup −}. Eventually, the

  20. Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid–glycine co-doped polyaniline

    International Nuclear Information System (INIS)

    Highlights: • RVC/PANI-SA-GLY electrode was applied as a novel electrode material for accelerated removal of Cr(VI). • Faster reduction kinetics of Cr(VI) was observed by RVC/PANI-SA-GLY electrode when compared with RVC/PANI-SA and RVC electrode. • Cr(VI) removal experienced an adsorption-reduction system built by RVC/PANI-SA-GLY electrode. • The stability of RVC/PANI-SA-GLY electrode was relatively satisfactory. - Abstract: Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption–electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid–glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption–reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO4−. Eventually, the stability of

  1. Temperature and ph kinetics for enhanced biosorption of cr (vi) by highly chromium resistant fungi gliocladium spp.zic/sub 2063/

    International Nuclear Information System (INIS)

    This study investigates the kinetics of Cr (VI) biosorption by locally isolated high Cr tolerant fungus Gliocladium sp. ZIC/sub 2063/. The effect of two most important variables pH and temperature was investigated for enhanced Cr (VI) biosorption. The applicability of the Langmuir and Freundlich models for the different parameters was tested. The result showed that the most suitable sorption temperature was 30 degree C with maximum biosorption rate of 185.69 mg/l. The data showed that the sorption process is spontaneous and exothermic in nature and that lower solution temperatures favors metal ion removal by the biomass. Similarly Cr (VI) uptake by Gliocladium sp. ZIC/sub 2063/ was maximum at optimum pH of 3.5. The findings of this investigation suggest that pH and temperature plays a significant role in enhancing the biosorption rate. The coefficient of determination (R2) of both models were mostly greater than 0.9. This indicates that biosorption data is best fitted in both models. (author)

  2. Aqueous complexation reactions governing the rate and extent of biogeochemical U(VI) reduction

    International Nuclear Information System (INIS)

    The proposed research will elucidate the principal biogeochemical reactions that govern the concentration, chemical speciation, and reactivity of the redox-sensitive contaminant uranium. The results will provide an improved understanding and predictive capability of the mechanisms that govern the biogeochemical reduction of uranium in subsurface environments

  3. Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro–nano networks

    Energy Technology Data Exchange (ETDEWEB)

    He, Lulu [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China); Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Wang, Min; Zhang, Guilong [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Qiu, Guannan [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences and Anhui Province, Hefei, Anhui 230031 (China); Bioenergy Forest Research Center of State Forestry Administration, Hefei 230031 (China); Zhang, Xin, E-mail: xinzhang@ahau.edu.cn [School of Life Sciences, Anhui Agricultural University, Hefei 230036 (China)

    2015-08-30

    Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na{sub 2}S{sub 2}O{sub 3} supported by attapulgite (ATP) micro–nano networks. • ATP micro–nano networks was induced by high-energy electron beam irradiation. • LRA can effectively control the migration of Cr(VI) and reducing Cr(VI) to Cr(III). • LRA displayed high performance on the remediation of heavy metal contaminated soil. - Abstract: In this work, a long-duration remediation agent (LRA) on hexavalent chromium (Cr(VI)) was developed using sodium thiosulfate (ST) supported by attapulgite (ATP) micro–nano networks induced through high-energy electron beam (HEEB) irradiation. The ATP networks could effectively reduce the leaching amount of Cr(VI) in soil. More importantly, the ATP networks could significantly control the leaching behavior of ST, and then prolong the duration and increase the reduction efficiency of ST on Cr(VI). As a result, LRA displayed high performance on controlling the migration of Cr(VI) and reducing Cr(VI) to Cr(III). Additionally, pot experiment indicated that LRA could effectively decrease the absorbed amount of Cr(VI) in corn, and reduce the inhibition effect of Cr(VI) on the growth of corn. Therefore, this work could provide a facile approach to remediate the Cr(VI)-contaminated soil and lower the harmful effect of Cr(VI) on crop.

  4. Remediation of Cr(VI) contaminated soil using long-duration sodium thiosulfate supported by micro–nano networks

    International Nuclear Information System (INIS)

    Highlights: • This work aims to develop a long-duration remediation agent (LRA). • LRA was obtained using Na2S2O3 supported by attapulgite (ATP) micro–nano networks. • ATP micro–nano networks was induced by high-energy electron beam irradiation. • LRA can effectively control the migration of Cr(VI) and reducing Cr(VI) to Cr(III). • LRA displayed high performance on the remediation of heavy metal contaminated soil. - Abstract: In this work, a long-duration remediation agent (LRA) on hexavalent chromium (Cr(VI)) was developed using sodium thiosulfate (ST) supported by attapulgite (ATP) micro–nano networks induced through high-energy electron beam (HEEB) irradiation. The ATP networks could effectively reduce the leaching amount of Cr(VI) in soil. More importantly, the ATP networks could significantly control the leaching behavior of ST, and then prolong the duration and increase the reduction efficiency of ST on Cr(VI). As a result, LRA displayed high performance on controlling the migration of Cr(VI) and reducing Cr(VI) to Cr(III). Additionally, pot experiment indicated that LRA could effectively decrease the absorbed amount of Cr(VI) in corn, and reduce the inhibition effect of Cr(VI) on the growth of corn. Therefore, this work could provide a facile approach to remediate the Cr(VI)-contaminated soil and lower the harmful effect of Cr(VI) on crop

  5. Influence of Reactive Transport on the Reduction of U(VI) in the Presence of Fe(III) and Nitrate: Implications for U(VI) Immobilization by Bioremediation / Biobarriers- Final Report

    Energy Technology Data Exchange (ETDEWEB)

    B.D. Wood

    2007-01-01

    Subsurface contamination by metals and radionuclides represent some of the most challenging remediation problems confronting the Department of Energy (DOE) complex. In situ remediation of these contaminants by dissimilatory metal reducing bacteria (DMRB) has been proposed as a potential cost effective remediation strategy. The primary focus of this research is to determine the mechanisms by which the fluxes of electron acceptors, electron donors, and other species can be controlled to maximize the transfer of reductive equivalents to the aqueous and solid phases. The proposed research is unique in the NABIR portfolio in that it focuses on (i) the role of flow and transport in the initiation of biostimulation and the successful sequestration of metals and radionuclides [specifically U(VI)], (ii) the subsequent reductive capacity and stability of the reduced sediments produced by the biostimulation process, and (iii) the potential for altering the growth of biomass in the subsurface by the addition of specific metabolic uncoupling compounds. A scientifically-based understanding of these phenomena are critical to the ability to design successful bioremediation schemes. The laboratory research will employ Shewanella putrefaciens (CN32), a facultative DMRB that can use Fe(III) oxides as a terminal electron acceptor. Sediment-packed columns will be inoculated with this organism, and the reduction of U(VI) by the DMRB will be stimulated by the addition of a carbon and energy source in the presence of Fe(III). Separate column experiments will be conducted to independently examine: (1) the importance of the abiotic reduction of U(VI) by biogenic Fe(II); (2) the influence of the transport process on Fe(III) reduction and U(VI) immobilization, with emphasis on methods for controlling the fluxes of aqueous species to maximize uranium reduction; (3) the reductive capacity of biologically-reduced sediments (with respect to re-oxidation by convective fluxes of O2 and NO3-) and

  6. Influence of Reactive Transport on the Reduction of U(VI) in the Presence of Fe(III) and Nitrate: Implications for U(VI) Immobilization by Bioremediation/Biobarriers - Final Report

    International Nuclear Information System (INIS)

    Subsurface contamination by metals and radionuclides represent some of the most challenging remediation problems confronting the Department of Energy (DOE) complex. In situ remediation of these contaminants by dissimilatory metal reducing bacteria (DMRB) has been proposed as a potential cost effective remediation strategy. The primary focus of this research is to determine the mechanisms by which the fluxes of electron acceptors, electron donors, and other species can be controlled to maximize the transfer of reductive equivalents to the aqueous and solid phases. The proposed research is unique in the NABIR portfolio in that it focuses on (i) the role of flow and transport in the initiation of biostimulation and the successful sequestration of metals and radionuclides [specifically U(VI)], (ii) the subsequent reductive capacity and stability of the reduced sediments produced by the biostimulation process, and (iii) the potential for altering the growth of biomass in the subsurface by the addition of specific metabolic uncoupling compounds. A scientifically-based understanding of these phenomena are critical to the ability to design successful bioremediation schemes. The laboratory research will employ Shewanella putrefaciens (CN32), a facultative DMRB that can use Fe(III) oxides as a terminal electron acceptor. Sediment-packed columns will be inoculated with this organism, and the reduction of U(VI) by the DMRB will be stimulated by the addition of a carbon and energy source in the presence of Fe(III). Separate column experiments will be conducted to independently examine: (1) the importance of the abiotic reduction of U(VI) by biogenic Fe(II); (2) the influence of the transport process on Fe(III) reduction and U(VI) immobilization, with emphasis on methods for controlling the fluxes of aqueous species to maximize uranium reduction; (3) the reductive capacity of biologically-reduced sediments (with respect to re-oxidation by convective fluxes of O2 and NO3-) and

  7. A spectroscopic study of the effect of ligand complexation on the reduction of uranium(VI) by anthraquinone-2,6-disulfonate (AH2DS)

    International Nuclear Information System (INIS)

    In this paper, the reduction rate of uranyl complexes with hydroxide, carbonate, EDTA, and desferriferrioxamine B (DFB) by anthraquinone-2,6-disulfonate (AH2DS) is studied by stopped-flow kinetic technique under anoxic atmosphere. The apparent reaction rates varied with ligand type, solution pH, and U(VI) concentration. For each ligand, a single largest pseudo-1st order reaction rate constant, kobs, within the studied pH range was observed, suggesting the influence of pH-dependent speciation on the U(VI) reduction rate. The maximum reaction rate found in each case followed the order of OH- > CO32- > EDTA > DFB, in reverse order of the trend of the thermodynamic stability of the uranyl complexes and ionic sizes of the ligands. The pH-dependent rates were modeled using a second-order rate expression that was assumed to be dependent on a single U(VI) complex and an AH2DS species. By quantitatively comparing the calculated and measured apparent rate constants as a function of pH, species AHDS3- was suggested as the primary reductant in all cases examined. Species UO2CO3(aq), UO2HEDTA-, and (UO2)2(OH)22+ were suggested as the principal electron acceptors among the U(VI) species mixture in each of the carbonate, EDTA, and hydroxyl systems, respectively. (orig.)

  8. U(VI) speciation and reduction in acid chloride fluids in hydrothermal conditions: from transport to deposition of uranium in unconformity-related deposits

    International Nuclear Information System (INIS)

    Circulations of acidic chloride brines in the earth's crust are associated with several types of uranium deposits, particularly unconformity-related uranium (URU) deposits. The spectacular high grade combined with the large tonnage of these deposits is at the origin of the key questions concerning the geological processes responsible for U transport and precipitation. The aim of this work is to performed experimental studies of U(VI) speciation and its reduction to U(IV) subsequently precipitation to uraninite under hydrothermal condition. About uranium transport, the study of U(VI) speciation in acidic brines at high temperature is performed by Raman and XAS spectroscopy, showing the coexistence of several uranyl chloride complexes UO2Cln2-n (n = 0 - 5). From this study, complexation constants are proposed. The strong capability of chloride to complex uranyl is at the origin of the transport of U(VI) at high concentration in acidic chloride brines. Concerning uranium precipitation, the reactivity of four potential reductants under conditions relevant for URU deposits genesis is investigated: H2, CH4, Fe(II) and the C-graphite. The kinetics of reduction reaction is measured as a function of temperature, salinity, pH and concentration of reductant. H2, CH4, and the C-graphite are very efficient while Fe(II) is not able to reduce U(VI) in same conditions. The duration of the mineralizing event is controlled by (i) the U concentration in the ore-forming fluids and (ii) by the generation of gaseous reductants, and not by the reduction kinetics. These mobile and efficient gaseous reductant could be at the origin of the extremely focus and massive character of ore in URU deposits. Finally, first partition coefficients uraninite/fluid of trace elements are obtained. This last part opens-up new perspectives on (i) REE signatures interpretation for a given type of uranium deposit (ii) and reconstruction of mineralizing fluids composition. (author)

  9. Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures

    International Nuclear Information System (INIS)

    Highlights: • No published or well recognized MOA for Cr(VI)-induced lung tumors exists. • MOA analysis for Cr(VI)-induced lung cancer was conducted to inform risk assessment. • Cr(VI) epidemiologic, toxicokinetic, toxicological, mechanistic data were evaluated. • Weight of evidence does not support a mutagenic MOA for Cr(VI)-induced lung cancer. • Non-linear approaches should be considered for evaluating Cr(VI) lung cancer risk. - Abstract: Inhalation of hexavalent chromium [Cr(VI)] is associated with increased lung cancer risk among workers in several industries, most notably chromate production workers exposed to high concentrations of Cr(VI) (≥100 μg/m3), for which clear exposure–response relationships and respiratory irritation and tissue damage have been reported. Data from this industry are used to assess lung cancer risk associated with environmental and current occupational exposures, occurring at concentrations that are significantly lower. There is considerable uncertainty in the low dose extrapolation of historical occupational epidemiology data to assess risk at current exposures because no published or well recognized mode of action (MOA) for Cr(VI)-induced lung tumors exists. We conducted a MOA analysis for Cr(VI)-induced lung cancer evaluating toxicokinetic and toxicological data in humans and rodents and mechanistic data to assess plausibility, dose–response, and temporal concordance for potential MOAs. Toxicokinetic data support that extracellular reduction of Cr(VI), which limits intracellular absorption of Cr(VI) and Cr(VI)-induced toxicity, can be overwhelmed at high exposure levels. In vivo genotoxicity and mutagenicity data are mostly negative and do not support a mutagenic MOA. Further, both chronic bioassays and the epidemiologic literature support that lung cancer occurs at exposures that cause tissue damage. Based on this MOA analysis, the overall weight of evidence supports a MOA involving deposition and accumulation of

  10. Removal of Cr (VI) with wheat-residue derived black carbon: Reaction mechanism and adsorption performance

    International Nuclear Information System (INIS)

    The removal of Cr (VI) from aqueous solutions using black carbon (BC) isolated from the burning residues of wheat straw was investigated as a function of pH, contact time, reaction temperature, supporting electrolyte concentration and analytical initial Cr (VI) concentration in batch studies. The effect of surface properties on the adsorption behavior of Cr (VI) was investigated with scanning electron microscope (SEM) equipped with the energy dispersive X-ray spectroscope (EDS) and Fourier transform-infrared (FTIR) spectroscopy. The removal mechanism of Cr (VI) onto the BC was investigated and the result showed that the adsorption reaction consumed a large amount of protons along the reduction of Cr (VI) to Cr (III). The oxidation of the BC took place concurrently to the chromium reduction and led to the formation of hydroxyl and carboxyl functions. An initial solution pH of 1.0 was most favorable for Cr (VI) removal. The adsorption process followed the pseudo-second order equation and Freundlich isotherm very well. The Cr (VI) adsorption was temperature-dependent and almost independent on the sodium chloride concentrations. The maximum adsorption capacity for Cr (VI) was found at 21.34 mg/g in an acidic medium, which is comparable to other low-cost adsorbents.

  11. Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(VI) reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hou [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yuan, Xingzhong, E-mail: yxz@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wu, Yan [College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Chen, Xiaohong [School of Business, Central South University, Changsha 410083 (China); Leng, Lijian; Wu, Zhibin; Jiang, Longbo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Li, Hui [Institute of Bio-energy, Hunan Academy of Forestry, Changsha 410004 (China)

    2015-04-09

    Highlights: • NH{sub 2} functionalized MIL-125(Ti) was fabricated by a facile solvothermal method. • The photocatalyst could reduce Cr(VI)–Cr(III) under visible light irradiation. • The Ti{sup 3+}–Ti{sup 4+} intervalence electron transfer is important for Cr(VI) reduction. • Used NH{sub 2}-MIL-125(Ti) can be recycled for the photocatalytic reduction. - Abstract: Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH{sub 2}-MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH{sub 2}-MIL-125(Ti) were well characterized by XRD, SEM, XPS, N{sub 2} adsorption–desorption measurements, thermogravimetric analysis and UV–vis diffuse reflectance spectra (DRS). It is revealed that the NH{sub 2}-MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH{sub 2}-MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti{sup 3+}–Ti{sup 4+} intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater.

  12. On the removal of hexavalent chromium from a Class F fly ash.

    Science.gov (United States)

    Huggins, F E; Rezaee, M; Honaker, R Q; Hower, J C

    2016-05-01

    Coarse and fine samples of a Class F fly ash obtained from commercial combustion of Illinois bituminous coal have been exposed to two long-term leaching tests designed to simulate conditions in waste impoundments. ICP-AES analysis indicated that the coarse and fine fly ash samples contained 135 and 171mg/kg Cr, respectively. Measurements by XAFS spectroscopy showed that the ash samples originally contained 5 and 8% of the chromium, respectively, in the hexavalent oxidation state, Cr(VI). After exposure to water for more than four months, the percentage of chromium as Cr(VI) in the fly-ash decreased significantly for the coarse and fine fly-ash in both tests. Combining the XAFS data with ICP-AES data on the concentration of chromium in the leachates indicated that, after the nineteen-week-long, more aggressive, kinetic test on the coarse fly ash, approximately 60% of the Cr(VI) had been leached, 20% had been reduced to Cr(III) and retained in the ash, and 20% remained as Cr(VI) in the ash. In contrast, during the six-month-long baseline test, very little Cr was actually leached from either the coarse or the fine fly-ash (<0.1mg/kg); rather, about 66% and 20%, respectively, of the original Cr(VI) in the coarse and fine fly-ash was retained in the ash in that form, while the remainder, 34% and 80%, respectively, was reduced and retained in the ash as Cr(III). The results are interpreted as indicating that Cr(VI) present in Class F fly-ash can be reduced to Cr(III) when in contact with water and that such chemical reduction can compete with physical removal of Cr(VI) from the ash by aqueous leaching. PMID:26951722

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

    Czech Academy of Sciences Publication Activity Database

    Němeček, J.; Lhotský, O.; Cajthaml, Tomáš

    485-486, č. 2 (2014), s. 739-747. ISSN 0048-9697 R&D Projects: GA TA ČR TE01020218; GA MŠk ED0005/01/01; GA TA ČR TA01021792 Institutional support: RVO:61388971 Keywords : nanoparticles * hexavalent chromium * bioremediation Subject RIV: EE - Microbiology, Virology Impact factor: 4.099, year: 2014

  14. Preparation of N-1 -naphthyl benzo- and N-phenyl benzo hydroxamic acids and study of their extractability towards Fe (III), Cr (VI) and U (VI)

    International Nuclear Information System (INIS)

    Two aryl hydroxamic acids were prepared; The N-phenyl benzo hydroxamic acid and the N-1- naphthyl benzohydroxamic acid the first one was prepared by the partial reduction of nitrobenzene to the β-phenyl hydroxylamine and coupling the latter with benzyl chloride. The reduction was carried out using ammonium chloride and zinc dust; this pair failed after so many attempts to give the N-1- naphthyl hydroxylamine. So the latter was prepared by using a somewhat milder reducing agent; hydrogen sulphide and ammonia gas in absolute alcohol. The two acids were obtained using the modified procedure of Tandon coupling the hydroxylamine with benzoyl chloride. The two acids were characterized by their melting points, elemental analysis, their I.R functional group frequencies and by their characteristic colour tests with vanadium (VI) and Iron (III). The acids were used for the extraction and spectrophotometric determination for iron (III), Chromium (VI), and Uranium (VI) from different molar solution, PH and from synthetic sea water. The maximum recovery of iron (III) occurred at PH 4 and PH 5 giving 92.25 and 91.25% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 100% at PH 5 with other acid. The maximum recovery of Chromium (VI) occurred at 3MH2SO4 of 97.50% when using N-1-naphthyl benzohydroxamic acid and a maximum of 94.25% at the same molar concentration with N-phenyl benzo hydroxamic acid. The maximum recovery for Uranium (VI) was occurred at PH 7 giving 100% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 85% at PH 7 and PH* with the other acid. The two reagents give sharp colour with both iron (III) and chromium (VI), so trials were carried out to compare the curves obtained with that of the original reagent i.e. Thiocynate and diphenylcarbazide, which give a smaller slope.(Author)

  15. Chromium in leather footwear-risk assessment of chromium allergy and dermatitis

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Strandesen, Maria; Poulsen, Pia B;

    2012-01-01

    Background. Chromium-tanned leather footwear, which releases >3 ppm hexavalent Cr(VI), may pose a risk of sensitizing and eliciting allergic dermatitis. Objectives. To determine the content and potential release of chromium in leather footwear and to discuss the prevention of chromium contact...... allergy and dermatitis. Methods. Sixty pairs of leather shoes, sandals and boots (20 children's, 20 men's, and 20 women's) were purchased in Copenhagen and examined with X-ray fluorescence spectroscopy. Chromium was extracted according to the International Standard, ISO 17075. The detection level for Cr......(VI) was 3 ppm. Results. Chromium was identified in 95% of leather footwear products, the median content being 1.7% (range 0-3.3%). No association with store category or footwear category was found. A tendency for there to be a higher chromium content in footwear with high prices was shown (p(trend) = 0...

  16. FORMATION AND DESTRUCTION OF HEXAVALENT CHROMIUM IN A LABORATORY SWIRL FLAME INCINERATOR

    Science.gov (United States)

    The partitioning of chromium (Cr) in combustion systems was investigated theoretically and experimentally. Theoretical predictions were based on chemical equilibrium and suggested that hexavalent chromium [Cr(VI)] was favored by the presence of chlorine (Cl) and diminished by the...

  17. Global transcriptome analysis of hexavalent chromium stress responses in Staphylococcus aureus LZ-01.

    Science.gov (United States)

    Zhang, Xiaowei; Wu, Wenyang; Virgo, Nolan; Zou, Luming; Liu, Pu; Li, Xiangkai

    2014-10-01

    Staphylococcus aureus strain LZ-01, isolated from the Lanzhou reaches of the Yellow River, is capable of reducing Cr(VI) to Cr(III) aerobically. We employed transcriptome sequencing analysis to identify genes involved in Cr(VI) stress responses in S. aureus LZ-01. Our results showed that 512 of the 2,370 predicted genes displayed up-regulation (>2-fold), and 49 genes were down-regulated (128 genes were annotated to encode proteins involved in cellular processes; 68 were categorized to transport and binding proteins; 26 were involved in DNA repair and 32 were associated with regulatory functions. To further elucidate the Cr(VI) resistance and reduction mechanism, we carried out physiological tests and quantitative PCR analysis. Both RNA-seq and qRT-PCR data showed genes encoding a thioredoxin reductase and main subunits of cytochrome c oxidase complex were up-regulated upon Cr(VI) treatment. Either cadmium or NaN3 treatment could inhibit Cr(VI) reduction which indicates that thioredoxin and cytochrome are involved in Cr(VI) reduction strain LZ-01. 29 ABC-type metal/multidrug transporters and efflux pumps were up-regulated, suggesting that they are involved in Cr(VI) resistance by pumping chromium ions out of cells. The up-regulation of 26 DNA repair genes demonstrate that Cr(VI) is toxic to DNA and those DNA protection proteins need to be responded for Cr(VI) stress. Based on these results, the mechanism of strain LZ-01 resists and reduces Cr(VI) is revealed. PMID:25086489

  18. Observations of surface-mediated reduction of Pu(VI) to Pu(IV) on hematite nanoparticles by ATR FT-IR

    International Nuclear Information System (INIS)

    Previous studies have shown that mineral surfaces may facilitate the reduction of plutonium though the mechanisms of the reduction are still unknown. The objective of this study is to use batch sorption and attenuated total reflectance Fourier transform infrared spectroscopy experiments to observe the surface-mediated reduction of plutonium on hematite nanoparticles. These techniques allow for in situ measurement of reduction of plutonium with time and may lead to a better understanding of the mechanisms of surface mediated reduction of plutonium. For the first time, ATR FT-IR peaks for Pu(VI) sorbed to hematite are measured at ∝ 916 cm-1, respectively. The decrease in peak intensity with time provides a real-time, direct measurement of Pu(VI) reduction on the hematite surface. In this work pseudo first order rate constants estimated at the high loadings (22 mgPu/ghematite, 1.34 x 10-6 MPu/m2) for ATR FT-IR are approximately 10 x slower than at trace concentrations based on previous work. It is proposed that the reduced rate constant at higher Pu loadings occurs after the reduction capacity due to trace Fe(II) has been exhausted and is dependent on the oxidation of water and possibly electron shuttling based on the semiconducting nature of hematite. Therefore, the reduction rate at higher loadings is possibly due to the thermodynamic favorability of Pu(IV)-hydroxide complexes.

  19. Observations of surface-mediated reduction of Pu(VI) to Pu(IV) on hematite nanoparticles by ATR FT-IR

    Energy Technology Data Exchange (ETDEWEB)

    Emerson, Hilary P. [Florida International Univ., Applied Research Center, Miami, FL (United States); Powell, Brian A. [Clemson Univ., Dept. of Enviromental Engineering and Earth Sciences, Anderson, SC (United States)

    2015-07-01

    Previous studies have shown that mineral surfaces may facilitate the reduction of plutonium though the mechanisms of the reduction are still unknown. The objective of this study is to use batch sorption and attenuated total reflectance Fourier transform infrared spectroscopy experiments to observe the surface-mediated reduction of plutonium on hematite nanoparticles. These techniques allow for in situ measurement of reduction of plutonium with time and may lead to a better understanding of the mechanisms of surface mediated reduction of plutonium. For the first time, ATR FT-IR peaks for Pu(VI) sorbed to hematite are measured at ∝ 916 cm{sup -1}, respectively. The decrease in peak intensity with time provides a real-time, direct measurement of Pu(VI) reduction on the hematite surface. In this work pseudo first order rate constants estimated at the high loadings (22 mg{sub Pu}/g{sub hematite}, 1.34 x 10{sup -6} M{sub Pu}/m{sup 2}) for ATR FT-IR are approximately 10 x slower than at trace concentrations based on previous work. It is proposed that the reduced rate constant at higher Pu loadings occurs after the reduction capacity due to trace Fe(II) has been exhausted and is dependent on the oxidation of water and possibly electron shuttling based on the semiconducting nature of hematite. Therefore, the reduction rate at higher loadings is possibly due to the thermodynamic favorability of Pu(IV)-hydroxide complexes.

  20. Delta Chromium-53/52 isotopic composition of native and contaminated groundwater, Mojave Desert, USA

    International Nuclear Information System (INIS)

    Chromium(VI) concentrations in groundwater sampled from three contaminant plumes in aquifers in the Mojave Desert near Hinkley, Topock and El Mirage, California, USA, were as high as 2600, 5800 and 330 μg/L, respectively. δ53/52Cr compositions from more than 50 samples collected within these plumes ranged from near 0‰ to almost 4‰ near the plume margins. Assuming only reductive fractionation of Cr(VI) to Cr(III) within the plume, apparent fractionation factors for δ53/52Cr isotopes ranged from εapp = 0.3 to 0.4 within the Hinkley and Topock plumes, respectively, and only the El Mirage plume had a fractionation factor similar to the laboratory derived value of ε = 3.5. One possible explanation for the difference between field and laboratory fractionation factors at the Hinkley and Topock sites is localized reductive fractionation of Cr(VI) to Cr(III), with subsequent advective mixing of native and contaminated water near the plume margin. Chromium(VI) concentrations and δ53/52Cr isotopic compositions did not uniquely define the source of Cr near the plume margin, or the extent of reductive fractionation within the plume. However, Cr(VI) and δ53/52Cr data contribute to understanding of the interaction between reductive and mixing processes that occur within and near the margins of Cr contamination plumes. Reductive fractionation of Cr(VI) predominates in plumes having higher εapp, these plumes may be suitable for monitored natural attenuation. In contrast, advective mixing predominates in plumes having lower εapp, the highly dispersed margins of these plumes may be difficult to define and manage.

  1. Delta Chromium-53/52 isotopic composition of native and contaminated groundwater, Mojave Desert, USA

    Science.gov (United States)

    Izbicki, John A.; Bullen, Thomas D.; Martin, Peter; Schroth, Brian

    2012-01-01

    Chromium(VI) concentrations in groundwater sampled from three contaminant plumes in aquifers in the Mojave Desert near Hinkley, Topock and El Mirage, California, USA, were as high as 2600, 5800 and 330 μg/L, respectively. δ53/52Cr compositions from more than 50 samples collected within these plumes ranged from near 0‰ to almost 4‰ near the plume margins. Assuming only reductive fractionation of Cr(VI) to Cr(III) within the plume, apparent fractionation factors for δ53/52Cr isotopes ranged from εapp = 0.3 to 0.4 within the Hinkley and Topock plumes, respectively, and only the El Mirage plume had a fractionation factor similar to the laboratory derived value of ε = 3.5. One possible explanation for the difference between field and laboratory fractionation factors at the Hinkley and Topock sites is localized reductive fractionation of Cr(VI) to Cr(III), with subsequent advective mixing of native and contaminated water near the plume margin. Chromium(VI) concentrations and δ53/52Cr isotopic compositions did not uniquely define the source of Cr near the plume margin, or the extent of reductive fractionation within the plume. However, Cr(VI) and δ53/52Cr data contribute to understanding of the interaction between reductive and mixing processes that occur within and near the margins of Cr contamination plumes. Reductive fractionation of Cr(VI) predominates in plumes having higher εapp, these plumes may be suitable for monitored natural attenuation. In contrast, advective mixing predominates in plumes having lower εapp, the highly dispersed margins of these plumes may be difficult to define and manage.

  2. Effect of FeSO4.7H2O and SnCl2.2H2O added as Chromium (VI Reducers in Ordinary Portland Cement

    Directory of Open Access Journals (Sweden)

    Devesh K. Sharma

    2015-03-01

    Full Text Available The paper compared the effect of additives such as FeSO4.2H2O and SnCl2.2H2O on reduction of water soluble Cr(VI, in ordinary Portland cement (43 grades. The determination of water soluble Cr(VI from cement samples was precisely conducted by DPC-Spectrophotometer technique. The compressive strength testing of the cement mortar samples was carried out. In addition, hydration properties of cement paste (with and without additives are reported in this paper. Hydration products were also studied in detail by TGA, SEM and XRD. Tin chloride was found to be the most efficient additive for reducing Cr(VI in cement. XRD confirmed two phases such as monocarbonate and Friedel’s salt (at 2θ = 11.5 were formed during cement hydration in the presence of tin chloride but not confirmed the presence of calcium hydroxo-stannate. These studies showed significant retardation in early days hydration.

  3. Iron species in layered clay: efficient electron shuttles for simultaneous conversion of dyes and Cr(VI).

    Science.gov (United States)

    Liu, Renlan; Guo, Yaoguang; Wang, Zhaohui; Liu, Jianshe

    2014-01-01

    The simultaneous reduction of Chromium(VI) (Cr(VI)) and oxidation of cationic dyes in dispersions of Montmorillonite K10 (MK10) were examined under visible irradiation (λ>420 nm). The iron species (i.e. iron oxides, structural iron and exchangeable interlayer iron) in layered clays are active for catalytically reducing Cr(VI) by using Malachite green (MG) and Rhodamine B (RhB) as the electron donors. Molecular oxygen does not have a significant effect on clay-catalyzed Cr(VI) reduction, but is important for oxidative degradation of dye pollutants. MK10 catalysts are stable and reusable, and are therefore considered as a promising naturally-abundant material for decontamination of dye and heavy metals. PMID:24120014

  4. MOF catalysis of Fe(II)-to-Fe(III) reaction for an ultrafast and one-step generation of the Fe2O3@MOF composite and uranium(vi) reduction by iron(ii) under ambient conditions.

    Science.gov (United States)

    Xiong, Yang Yang; Li, Jian Qiang; Yan, Chang Sheng; Gao, Heng Ya; Zhou, Jian Ping; Gong, Le Le; Luo, Ming Biao; Zhang, Le; Meng, Pan Pan; Luo, Feng

    2016-08-01

    Herein, we demonstrate that Zn-MOF-74 enables the ultrafast and one-step generation of the Fe2O3@MOF composite once Zn-MOF-74 contacts with FeSO4 solution. This unique reaction can be further applied in catalysis of U(vi) reduction by Fe(ii) under ambient conditions. The results provide a highly renovated strategy for U(vi) reduction by Fe(ii) just under ambient conditions, which completely subvert all established methods about U(vi) reduction by Fe(ii) in which O2- and CO2-free conditions are absolutely required. PMID:27380820

  5. Use of iron oxide magnetic nanosorbents for Cr (VI removal from aqueous solutions: A review

    Directory of Open Access Journals (Sweden)

    Nirmala Ilankoon

    2014-10-01

    Full Text Available This review paper focuses on the use of iron oxide nanosorbents for the removal of hexavalent Chromium [Cr(VI], from aqueous media. Cr(VI is a well-known toxic heavy metal, which can cause severe damages to the human health even with the presence of trace levels. Chromium continuously enters into water streams from different sources. Several methods are available for Cr(VI removal and some of them are well established in industrial scale whilst some are still in laboratory scale. Reduction followed by chemical precipitation, adsorption, electro-kinetic remediation, membrane separation processes and bioremediation are some of the removal techniques. Each method is associated with both advantages and disadvantages. Currently, the use of nanosorbents for the aqueous chromium removal is popular among researchers and iron oxide nanoparticles are the most frequently used nanosorbents. This review paper summarizes the performance of different iron oxide nanosorbents studied on the last decade. The direct comparison of these results is difficult due to different experimental conditions used in each study. Adsorption isotherms and adsorption kinetics models are also discussed in this review paper. The effect of solution pH, temperature, initial Cr(VI concentration, adsorbent dosage and other coexisting ions are also briefly discussed. From the results it is evident that, more attention needs to be paid on the industrial application of the technologies which were successful in the laboratory scale.

  6. [Mechanisms of Cr (VI) toxicity to fish in aquatic environment: A review].

    Science.gov (United States)

    Chen, Hong-xing; Wu, Xing; Bi, Ran; Li, Li-xia; Gao, Mi; Li, Dan; Xie, Ling-tian

    2015-10-01

    With increasing consumption and applications of chromium in metallurgy, electroplating, tanning process and stainless steel industry, chromium contamination has become a global environmental problem. In general, Cr(VI) has higher permeability across the cell membrane than Cr(III) and hence is considered more toxic than Cr(III). Oxidative stress could be induced following reactive oxygen species (ROS) normally produced in fish under Cr(VI) exposure due to its variable valences. Furthermore, the intermediates of Cr, e.g. Cr(V) and Cr(IV) , produced by cellular reduction processes can bind with DNA and result in mutagenic effects. These combined effects will threaten the growth, development and population structure of different fish species. In this paper, we reviewed published results on the toxic effects of Cr(VI) in fish at levels of molecules, tissues, organs and individuals. The mechanisms of toxicity and detoxification of Cr(VI) in various aspects were discussed. In addition, we also put forward perspectives on the toxicity of chromium in aquatic organisms. PMID:26995935

  7. Cr(VI) Generation and Stability in Drinking Water

    OpenAIRE

    Chittaladakorn, Kathita

    2014-01-01

    The current US Environmental Protection Agency (USEPA) maximum contaminant level (MCL) for total chromium of 100 ppb is under revision to consider a specific level for Cr(VI), which has a proposed MCL of 10 ppb in California. Cr(VI) is a suspected carcinogen, and interconverts with the other most commonly found chromium species, Cr(III). To regulate and further understand the behavior of Cr(VI) in water systems, appropriate sample preservation methods are essential for accurate measurements. ...

  8. Kinetics of reductive stripping of Np(VI) by acetohydroxamic acid from 30%TBP/kerosene to nitrate medium using a high-speed stirred cell

    International Nuclear Information System (INIS)

    The kinetics of reductive stripping of Np(VI) by Acetohydroxamic Acid from 30%TBP/kerosene was investigated using a high-speed stirred cell designed by ourselves. The phase separator for sampling was simple and powerful. The interfacial areas of different stirring speeds were determined by microphotograph method at 21 C before the experiments. The effects of the different parameters as well as temperature were investigated systemically. The results showed that, at 21 C the rate equation is -d[Np(VI)]/dt = k(S/V)[Np(VI)]0.78[AHA]0.46[HNO3]-0.20 - k'(S/V)[Np(V)]2.87, where k = (8.7 ± 0.7) x 10-7(mol/L)-0.04 ms-1, k' = 1.1 ± 0.2(mol/L)-2.87 ms-1, as c[HNO3] <=1.0 mol/L, -d[Np(VI)]/dt = k(S/V)[Np(VI)]0.78[AHA]0.46[HNO3]-1.42 - k'(S/V)[Np(V)]2.87, where k = (3.2 ± 0.3) x 10-7 (mol/L)1.18 ms-1, k' = 1.1 ± 0.2(mol/L)-2.87 ms-1 as c[HNO3] > = 1.0 mol/L, and S is the interfacial area, V the organic phase volume. The reductive stripping process is controlled by chemical reactions (kinetics regime) taking place at the interface. The apparent activation energy is 13.5 ± 0.2 kJ/mol.

  9. Adsorção de cromo (VI por carvão ativado granular de soluções diluídas utilizando um sistema batelada sob pH controlado Chromium (VI adsorption by GAC from diluted solutions in batch system and controlled ph

    Directory of Open Access Journals (Sweden)

    Renata Santos Souza

    2009-09-01

    Full Text Available Na Amazônia o cromo é empregado principalmente na indústria de couro e de madeira, sendo responsável por vários problemas de saúde porque é tóxico para os seres vivos. A remoção de cromo de efluentes industriais é feita por meio de diversos processos como a adsorção. Este trabalho mostra os resultados da adsorção de Cr(VI por carvão ativado granular comercial (CAG como adsorvente de soluções diluídas empregando um sistema de adsorção batelada com controle de pH. Os grupos funcionais da superfície do CAG foram determinados pelo método de Boehm. Além disso, o efeito do pH na adsorção de Cr(VI, o equilíbrio e a cinética de adsorção foram estudados nas condições experimentais (pH = 6, MA = 6g, tempo de adsorção 90min.. Na superfície do CAG, os grupos carboxílicos foram determinados em maior concentração (MAS=0,43 mmol/gCAG, estes, presentes em concentrações elevadas aumentam a adsorção do metal, principalmente em valores de pH ácidos. A capacidade de adsorção é dependente do pH da solução, devido a sua influência nas propriedades de superfície do CAG e nas diferentes formas iônicas das soluções de Cr(VI. Os dados de equilíbrio da adsorção foram ajustados satisfatoriamente pela isoterma de Langmuir (R²=0,988, tipo favorável. A partir da cinética de adsorção a 5mg/L e 20mg/L, os resultados obtidos foram compatíveis com o valor limite preconizado na legislação nacional (Res. nº 357/05. Portanto, para o sistema experimental utilizando CAG foi eficiente na remoção de Cr(VI a partir de correntes líquidas contendo baixas concentrações do metal.In Amazonia, chromium is mainly used in the leather and wood industries. It is responsible for many health problems, because of its toxicity. These industries remove chromium waste by various processes, such as adsorption. This work shows the results of Cr(VI adsorption by commercial granular activated carbon (GAC as adsorbent from diluted

  10. Preparation of perovskite type titanium-bearing blast furnace slag photocatalyst doped with sulphate and investigation on reduction Cr(VI) using UV-vis light

    International Nuclear Information System (INIS)

    Perovskite type titanium-bearing blast furnace slag (TBBFS) and sulphate-modified titanium-bearing blast furnace slag (SO42-/TBBFS) photocatalysts were prepared by the high-energy ball milling method at different calcination temperature. The photocatalysts were characterized by XRD, FTIR, UV-vis diffuse reflectance spectra and SEM measurements. The photocatalytic activities of the different catalysts were evaluated by the photocatalytic reduction of Cr(VI) under UV-vis light irradiation. For the photocatalytic reduction of Cr(VI), the photocatalytic activities of TBBFS catalysts were found to be strongly dependent of the calcination temperature and TBBFS calcined at 700 deg. C showed a higher photocatalytic activity compared to other TBBFS catalysts. In contrast, sulphation of TBBFS improved the photocatalytic activities of SO42-/TBBFS catalysts. At low calcination temperature, the photocatalytic activities of SO42-/TBBFS catalysts were markedly higher than TBBFS prepared under high calcination temperature, suggesting that the presence of surface SO42- favored the photocatalytic reduction of Cr(VI)

  11. Total Reducing Capacity in Aquifer Minerals and Sediments: Quantifying the Potential to Attenuate Cr(VI) in Groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Sisman, S. Lara [Univ. of Virginia, Charlottesville, VA (United States); Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-20

    Hexavalent chromium, Cr(VI), is present in the environment as a byproduct of industrial processes. Due to its mobility and toxicity, it is crucial to attenuate or remove Cr(VI) from the environment. The objective of this investigation was to quantify potential natural attenuation, or reduction capacity, of reactive minerals and aquifer sediments. Samples of reduced-iron containing minerals such as ilmenite, as well as Puye Formation sediments representing a contaminated aquifer in New Mexico, were reacted with chromate. The change in Cr(VI) during the reaction was used to calculate reduction capacity. This study found that minerals that contain reduced iron, such as ilmenite, have high reducing capacities. The data indicated that sample history may impact reduction capacity tests due to surface passivation. Further, this investigation identified areas for future research including: a) refining the relationships between iron content, magnetic susceptibility and reduction capacity, and b) long term kinetic testing using fresh aquifer sediments.

  12. Total Reducing Capacity in Aquifer Minerals and Sediments: Quantifying the Potential to Attenuate Cr(VI) in Groundwater

    International Nuclear Information System (INIS)

    Hexavalent chromium, Cr(VI), is present in the environment as a byproduct of industrial processes. Due to its mobility and toxicity, it is crucial to attenuate or remove Cr(VI) from the environment. The objective of this investigation was to quantify potential natural attenuation, or reduction capacity, of reactive minerals and aquifer sediments. Samples of reduced-iron containing minerals such as ilmenite, as well as Puye Formation sediments representing a contaminated aquifer in New Mexico, were reacted with chromate. The change in Cr(VI) during the reaction was used to calculate reduction capacity. This study found that minerals that contain reduced iron, such as ilmenite, have high reducing capacities. The data indicated that sample history may impact reduction capacity tests due to surface passivation. Further, this investigation identified areas for future research including: a) refining the relationships between iron content, magnetic susceptibility and reduction capacity, and b) long term kinetic testing using fresh aquifer sediments.

  13. Cr (VI) induced oxidative stress and toxicity in cultured cerebellar granule neurons at different stages of development and protective effect of Rosmarinic acid.

    Science.gov (United States)

    Dashti, Abolfazl; Soodi, Maliheh; Amani, Nahid

    2016-03-01

    Chromium (Cr) is a widespread metal ion in the workplace, industrial effluent, and water. The toxicity of chromium (VI) on various organs including the liver, kidneys, and lung were studied, but little is known about neurotoxicity. In this study, neurotoxic effects of Cr (VI) have been investigated by cultured cerebellar granule neurons (CGNs). Immature and mature neurons were exposed to different concentrations of potassium dichromate for 24 h and cytotoxicity was measured by MTT assay. In addition, immature neurons were exposed for 5 days as regards cytotoxic effect in development stages. The reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and the protective effect of Rosmarinic acid on mature and immature neurons exposed to potassium dichromate, were measured. Furthermore, lipid peroxidation, glutathione peroxidase (GPx), and acetylcholinesterase activity in mature neurons were assessed following exposure to potassium dichromate. The results indicate that toxicity of Cr (VI) dependent on maturation steps. Cr (VI) was less toxic for immature neurons. Also, Cr (VI) induced MMP reduction and ROS production in both immature and mature neurons. In Cr (VI) treated neurons, increased lipid peroxidation and GPx activity but not acetylcholinesterase activity was observed. Interestingly, Rosmarinic acid, as a natural antioxidant, could protect mature but not immature neurons against Cr (VI) induced toxicity. Our findings revealed vulnerability of mature neurons to Cr (VI) induced toxicity and oxidative stress. PMID:25213303

  14. Ultra-trace level speciated isotope dilution measurement of Cr(VI) using ion chromatography tandem mass spectrometry in environmental waters.

    Science.gov (United States)

    Mädler, Stefanie; Todd, Aaron; Skip Kingston, H M; Pamuku, Matt; Sun, Fengrong; Tat, Cindy; Tooley, Robert J; Switzer, Teresa A; Furdui, Vasile I

    2016-08-15

    The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ngL(-1) concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4(-) → CrO3(-). Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7ngL(-1) Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2ngL(-1) and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences. PMID:27260441

  15. Facile synthesis of porous single crystalline ZnO nanoplates and their application in photocatalytic reduction of Cr(VI) in the presence of phenol

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Zhen [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Zhang, Yong-Xing [School of Physics and Electronic Information, Huaibei Normal University, Huaibei, Anhui 235000 (China); Meng, Fan-Li; Jia, Yong; Luo, Tao; Yu, Xin-Yao; Wang, Jin; Liu, Jin-Huai [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Xing-Jiu, E-mail: xingjiuhuang@iim.ac.cn [Research Center for Biomimetic Functional Materials and Sensing Devices, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2014-07-15

    Graphical abstract: - Highlights: • Porous single crystalline ZnO nanoplates were successfully synthesized. • The nanoplates were with 12 nm in thickness and tens nanometers in pore size. • A synergistic effect of enhanced Cr(VI) photoreduction and phenol degradation was observed. • A possible reaction mechanism was discussed. - Abstract: Porous single crystalline ZnO nanoplates were successfully synthesized through a facile and cost-effective hydrothermal process at low temperature condition, followed by annealing of the zinc carbonate hydroxide hydrate precursors. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) measurements. The porous single crystalline ZnO nanoplates are with 12 nm thickness and pore ranging from 10 nm to several tens of nanometers. The porous structure of the ZnO nanoplates caused large amount of surface defects which worked as photogenerated holes’ shallow trappers and largely restrained the recombination of photogenerated electrons and holes, resulting in a significantly high photocatalytic activity and durability toward the photoreduction of Cr(VI) under UV irradiation. Moreover, a synergistic effect, that is, increased photocatalytic reduction of Cr(VI) and degradation of phenol, can be observed. Furthermore, the synergistic photocatalytic mechanism has also been discussed. Those results present an enlightenment to employ porous single crystalline nanomaterials to remove Cr(VI) and organic pollutants simultaneously.

  16. Adsorption and reduction: combined effect of polyaniline emeraldine salt for removal of Cr(VI) from aqueous medium

    Indian Academy of Sciences (India)

    PURNIMA BARUAH; DEBAJYOTI MAHANTA

    2016-06-01

    In this study, we have reported the removal of Cr(VI) ions by polyaniline (PANI) particles from aqueous medium. PANI in its emeraldine salt (ES) form can interact with Cr(VI), which is present as HCrO$^{−}_4$ in two ways. The adsorption of HCrO$^{−}_4$ ions due to the electrostatic interaction between partially positively charged PANI backbone and Cr(VI) anions causes the major portion of Cr(VI) removal and a small portion of Cr(VI) is reduced to Cr(III) by PANI (ES). The adsorption follows Langmuir adsorption isotherm and second-order kinetic model. It is observed that the removal of Cr(VI) is negligibly effected by the presence of other anions in the aqueous medium. The adsorption capacity of PANI (ES) is found to be 123 mg g$^{−1}$, which is very high compared to activated carbonbased materials. The adsorbed anions can be desorbed by converting PANI emeraldine salt (ES) to PANI emeraldinebase (EB). The EB form of PANI can be converted into ES form by treating with acid, which can be reused as adsorbent. It is important to note that the PANI (ES) is oxidized by HCrO$^{−}_4$ ions which decrease the hydrophilicity of thesurface of PANI particles. This causes the decrease in adsorption capacity of recycled PANI.

  17. Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes.

    Science.gov (United States)

    Dima, Jimena Bernadette; Sequeiros, Cynthia; Zaritzky, Noemi E

    2015-12-01

    Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pH<2 due to the instability of CH particles in acid media. Langmuir isotherm described better than Freundlich and Temkin equations the equilibrium adsorption data. Pseudo-second order rate provided the best fitting to the kinetic data in comparison to pseudo-first order and Elovich equations. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water. PMID:26151484

  18. Oral exposure of mice to cadmium (II), chromium (VI) and their mixture induce oxidative- and endoplasmic reticulum-stress mediated apoptosis in the livers.

    Science.gov (United States)

    Jin, Yuanxiang; Zhang, Songbin; Tao, Runhua; Huang, Jie; He, Xingzhi; Qu, Lanya; Fu, Zhengwei

    2016-06-01

    Health concerns regarding the environmental heavy metals in wildlife and humans have increased in recent years. We evaluated the effects of exposure of mice to low doses of cadmium (Cd), chromium (Cr) and their mixtures on oxidative- and ER-stress. Male adult mice were orally exposed to Cd (0.5 and 2 mg kg(-1) ), Cr (1 and 4 mg kg(-1) ) and binary Cd+Cr mixtures (0.25 + 05 and 1 + 2 mg kg(-1) ) daily for 36 days. We observed that the bioaccumulation of Cd and Cr in the liver in a dose-dependent manner, and the Cd and Cr contents in the 2 mg kg(-1) Cd and 4 mg kg(-1) Cr treated groups reached 2.43 and 3.46 µg g(-1) liver weight. In addition, treatments with 2 mg kg(-1) Cd, 4 mg kg(-1) Cr or their mixture (1 + 2 mg kg(-1) ) significantly decreased body and liver weights, increased the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and activities of catalase (CAT) and glutathione peroxidase (GPX) in the liver. Moreover, Cd and Cr exposures also elevated the transcription of the oxidative- and endoplasmic reticulum (ER)-stress related genes including Cat, Gpx, heme oxygenase 1 (Ho-1), regulated protein 78 (Grp78), activating transcription factor 6 (Atf6) and proaoptotic CCAAT/-enhancer-binding protein homologous protein (Chop) in a dose dependent manner in the liver. And hepatic cytochrome c levels increased in all Cd, Cr or their mixture treated groups. Furthermore, the transcriptional status and the activities of Caspase 9 and Caspase 3 were increased significantly in the liver when exposed to high doses of Cd, Cr or their mixture. These results suggested that a long period exposure of mice to Cd or Cr has the potential to elicit oxidative- and ER-stress mediated apoptosis in their livers. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 693-705, 2016. PMID:25409916

  19. Role of Iron Anode Oxidation on Transformation of Chromium by Electrolysis.

    Science.gov (United States)

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

    2012-12-30

    The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L(-1) in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe(15)Cr(5)(OH)(60) precipitate. PMID:23284182

  20. Enhanced sludge processing of HLW: Hydrothermal oxidation of chromium, technetium, and complexants by nitrate. 1997 mid-year progress report

    International Nuclear Information System (INIS)

    'Treatment of High Level Waste (HLW) is the second most costly problem identified by OEM. In order to minimize costs of disposal, the volume of HLW requiring vitrification and long term storage must be reduced. Methods for efficient separation of chromium from waste sludges, such as the Hanford Tank Wastes (HTW), are key to achieving this goal since the allowed level of chromium in high level glass controls waste loading. At concentrations above 0.5 to 1.0 wt.% chromium prevents proper vitrification of the waste. Chromium in sludges most likely exists as extremely insoluble oxides and minerals, with chromium in the plus III oxidation state [1]. In order to solubilize and separate it from other sludge components, Cr(III) must be oxidized to the more soluble Cr(VI) state. Efficient separation of chromium from HLW could produce an estimated savings of $3.4B[2]. Additionally, the efficient separation of technetium [3], TRU, and other metals may require the reformulation of solids to free trapped species as well as the destruction of organic complexants. New chemical processes are needed to separate chromium and other metals from tank wastes. Ideally they should not utilize additional reagents which would increase waste volume or require subsequent removal. The goal of this project is to apply hydrothermal processing for enhanced chromium separation from HLW sludges. Initially, the authors seek to develop a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions. The authors also wish to evaluate the potential of hydrothermal processing for enhanced separations of technetium and TRU by examining technetium and TRU speciation at hydrothermal conditions optimal for chromium dissolution.'

  1. Study of Cr(VI) Detoxification By basalt Inhabiting Bacteria Using NAA And ESR Methods

    International Nuclear Information System (INIS)

    Mixtures of heavy metals have polluted many industrial regions in the world. The environmental contamination with heavy metals has become a serious health concern. Since metal ions cannot be destroyed in environments, factors which influence the detoxification of metals can dictate the metal toxicity to ecological receptors. Indigenous bacteria have been considered as a potential candidate for detoxifying heavy metal ions. Molecular insight into the fate of heavy metal species in bacteria is important in the development of new bio technologies to clean-up contaminated sites. In our study chromium(VI), a widespread environmental pollution. was selected as a model heavy metal.Today there are only few studies that examine how microorganisms respond to chromium stress at higher doses. Instrumental neutron activation analysis (NAA) and electron spin resonance (ESR) methods were applied to evaluate the potential of indigenous bacteria to detoxify Cr(VI) from heavily contaminated environment. The microbial reduction of toxic Cr(VI) to less toxic Cr(III) was studied in batch systems in the presence of high concentrations of Cr(VI) (50-1000 mg/L). Gram-positive Arthrobacter oxydans isolated from Columbia basalts (USA) that have been polluted with mixtures of heavy metals, radionuclides and organic compounds and also two Gram-positive bacteria isolated from polluted basalts from the Republic of Georgia were tested under aerobic conditions. All the bacterial samples were exposed to Cr(VI) action at a given concentration for five days. NAA revealed that A. oxydans is able to accumulate Cr(VI) efficiently in the concentration range 50-500 mg/L. Dose-dependent ESR measurements of the formation of Cr(Ill) complexes (g=2.02, line width=650 gauss) in bacterial cells confirmed this character of Cr(VI) detoxification. The similar results are obtained for one of the bacterial isolate. For the other bacterium, the content of chromium inside the cells is increased continuously by

  2. Recovery and reuse of hexavalent chromium from aqueous solutions by a hybrid technique of electrodialysis and ion exchange

    Directory of Open Access Journals (Sweden)

    R. Gayathri

    2010-03-01

    Full Text Available The chrome plating industry is one of the highly polluting industries whose effluent mainly consists of chromium(VI. This compound is highly toxic to aquatic life and human health. The rinse water constituents reflect the chrome plating bath characteristics; generally dead tank wash water contains about 1% of the plating bath concentration. Other metals and metal compounds usually considered as toxic can be precipitated out by suitably adjusting the pH of the wastewaters. However, Cr(VI is soluble in almost all pH ranges and therefore an efficient treatment is required for the removal and recovery of chromium, and also for the reuse of wastewaters. The present study aims to recover the chromium by a hybrid technique of electrodialysis and ion exchange for the removal and concentration of chromate ions from the effluent. The different modes of operation like batch recirculation process, batch recirculation process with continuous dipping and continuous process were carried out to remove and recover the chromium from the effluent and the percentage reductions of chromium were found to be 98.69%, 99.18% and 100%, respectively.

  3. Evaluation of chromium in red blood cells as an indicator of exposure to hexavalent chromium: An in vitro study.

    Science.gov (United States)

    Devoy, Jérôme; Géhin, Antoine; Müller, Samuel; Melczer, Mathieu; Remy, Aurélie; Antoine, Guillaume; Sponne, Isabelle

    2016-07-25

    Chromium(VI) compounds are classified as carcinogenic to humans. Whereas chromium measurements in urine and whole blood (i.e., including plasma) are indicative of recent exposure, chromium in red blood cells (RBC) is attributable specifically to Cr(VI) exposure. Before recommending Cr in RBC as a biological indicator of Cr(VI) exposure, in-vitro studies must be undertaken to assess its reliability. The present study examines the relationship between the chromium added to a blood sample and that subsequently found in the RBC. After incubation of total blood with chromium, RBC were isolated, counted and their viability assessed. Direct analysis of chromium in RBC was conducted using Atomic Absorption Spectrometry. Hexavalent, but not trivalent Cr, was seen to accumulate in the RBC and we found a strong correlation between the Cr(VI) concentration added to a blood sample and the amount of Cr in RBC. This relationship appears to be independent of the chemical properties of the human blood samples (e.g., different blood donors or different reducing capacities). Even though in-vivo studies are still needed to integrate our understanding of Cr(VI) toxicokinetics, our findings reinforce the idea that a single determination of the chromium concentration in RBC would enable biomonitoring of critical cases of Cr(VI) exposure. PMID:27178267

  4. Reduction of Pu(VI) on Fe surfaces: soft x-ray absorption and resonant inelastic scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Butorin, S.M.; Kvashnina, K.O.; Modin, A.; Nordgren, J. (Dept. of Physics and Materials Science, Uppsala Univ., Uppsala (Sweden)); Guo, J.H. (Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)); Shuh, D.K. (Chemical Science Div., Lawrence Berkeley National Laboratory, Berkeley, CA (United States)); Werme, L. (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2009-03-15

    Based on analysis of spectral shapes, their dependence on the energy of incident photons and comparison with model calculations and experimental data from the reference sample we can conclude that plutonium from the Pu(VI) solution sorbed on Fe surfaces is likely to be reduced and Pu species sorbed on the Fe foils are mainly in the form of Pu (IV). Current results correlate with what was observed for for Np (V) and U (VI) in our previous studies. Furthermore, combined analysis of present data with model atomic multiplet calculations of RIXS and XAS spectra suggests that significant presence of Pu(III) on the Fe foils is unlikely

  5. In Situ Long-Term Reductive Bioimmobilization of Cr(VI) in Groundwater Using Hydrogen Release Compound

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris; Hazen, Terry C.; Long, Philip E.; Brodie, Eoin L.; Conrad, Mark S.; Hubbard, Susan; Christensen, John N.; Joyner, Dominique; Borglin, Sharon; Chakraborty, Romy; Williams, Kenneth H.; Peterson, John E.; Chen, Jinsong; Brown, Shaun T.; Tokunaga, Tetsu K.; Wan, Jiamin; Firestone, Mary; Newcomer, Darrell R.; Resch, Charles T.; Cantrell, Kirk J.; Willett, Anna; Koenigsberg, Stephen

    2008-11-15

    Here we describe a novel approach for, and present evidence of the effectiveness of, long-term, in situ bioimmobilization of toxic and soluble Cr(VI) in groundwater using a 13C-labeled slow-release polylactate. A field experiment was conducted at Hanford (Washington), the U.S. Department of Energy nuclear site. A combination of in situ hydrogeological, geophysical, geochemical, and microbiological measurements and analyses of water samples and sediments provided detailed and reliable description of in situ biogeochemical processes. The results of this experiment show that a single lactate injection into Cr(VI)-contaminated groundwater stimulates an average increase in biomass by up to 50 times, from—5∙105 to 2.5∙107 cells/mL. The results also show a depletion of terminal electron acceptors O2, NO3-, and SO42- , and an increase in Fe2+. The biogeochemical processes, including the reaction of ferrous ion with hexavalent Cr, cause the formation of nontoxic and insoluble trivalent Cr precipitates. Cr(VI) concentration in the lactate injection well has remained below the background concentration in downgradient monitoring wells and below the drinking water standards for 3 years. The current studies suggest that Cr(VI) biogeochemical immobilization under these conditions may be fairly resilient, the applicability and degree of resilience under different redox conditions at this and other contaminated sites is currently under study.

  6. Facile synthesis of AgI/BiOI-Bi2O3 multi-heterojunctions with high visible light activity for Cr(VI) reduction.

    Science.gov (United States)

    Wang, Qi; Shi, Xiaodong; Liu, Enqin; Crittenden, John C; Ma, Xiangjuan; Zhang, Yi; Cong, Yanqing

    2016-11-01

    AgI sensitized BiOI-Bi2O3 composite (AgI/BiOI-Bi2O3) with multi-heterojunctions was prepared using simple etching-deposition process. Different characterization techniques were performed to investigate the structural, optical and electrical properties of the as-prepared photocatalysts. It was found that the ternary AgI/BiOI-Bi2O3 composite exhibited: (1) improved photocurrent response, (2) smaller band gap, (3) greatly reduced charge transfer resistance and (4) negative shift of flat band potential, which finally led to easier generation and more efficient separation of photo-generated electron-hole pairs at the hetero-interfaces. Thus, for the reduction of Cr(VI), AgI/BiOI-Bi2O3 exhibited excellent photocatalytic activity under visible light irradiation at near neutral pH. AgI/BiOI-Bi2O3 was optimized when the initial molar ratio of KI to Bi2O3 and AgNO3 to Bi2O3 was 1:1 and 10%, respectively. The estimated kCr(VI) on optimized AgI/BiOI-Bi2O3 was about 16 times that on pure Bi2O3. Good stability was also observed in cyclic runs, indicating that the current multi-heterostructured photocatalyst is highly desirable for the remediation of Cr(VI)-containing wastewater. PMID:27239723

  7. Morphology controlled synthesis of SnS₂ nanomaterial for promoting photocatalytic reduction of aqueous Cr(VI) under visible light.

    Science.gov (United States)

    Mondal, Chanchal; Ganguly, Mainak; Pal, Jaya; Roy, Anindita; Jana, Jayasmita; Pal, Tarasankar

    2014-04-15

    A mild, template free protocol has been demonstrated for SnS2 nanoflake formation at the gram level from SnCl2 and thioacetamide (TAA). The SnS2 nanoflakes congregate to nanoflowers and nanoyarns with variable TAA concentrations. BET measurements reveal that the synthesized nanomaterials are highly porous having very high surface area, and the nanoflower has higher surface area than the nanoyarn. The synthesized nanomaterial finds application for promoting photoreduction of extremely toxic and lethal Cr(VI) under visible light irradiation due to their porous nature. The nanoflowers photocatalyst is proved to be superior to nanoyarn due to the increased surface area and higher pore volume. It was also inferred that increased pH decreased the reaction rate. The present result suggests that the morphology-dependent photoreduction of Cr(VI) by SnS2 nanomaterial under visible light exposure will endorse a new technique for harvesting energy and purification of wastewater. PMID:24649847

  8. LABORATORY STUDY FOR THE REDUCTION OF CHROME (VI) TO CHROME (III) USING SODIUM METABISULFITE UNDER ACIDIC CONDITIONS

    International Nuclear Information System (INIS)

    This report describes the results from RPP-PLAN-32738, 'Test Plan for the Effluent Treatment Facility to Reduce Chrome(VI) to Chrome(I1I) in the Secondary Waste Stream', using sodium metabisulfite. Appendix A presents the report as submitted by the Center for Laboratory Sciences (CLS) to CH2M HILL Hanford Group, Inc. The CLS carried out the laboratory effort under Contract Number 21065, release Number 30. This report extracts the more pertinent aspects of the laboratory effort

  9. Field and Numerical Modeling Study of Reductive Bioimmobilization of Cr (VI) in Groundwater at Hanford 100-H Site

    Science.gov (United States)

    Hazen, T. C.; Sonnenthal, E. L.; Mukhopadhyay, S.; Steefel, C. I.; Long, P. E.; Faybishenko, B.

    2009-12-01

    The 2004-2008 field experiment at the Hanford 100-H Site showed that a single injection of the hydrogen release compound (HRC)—a mixture of slow release glycerol polylactate, fast disassociating lactic acid, and glycerol into groundwater— stimulated an increase in biomass and a depletion of terminal electron acceptors, resulting in a significant decrease in soluble Cr (VI). The Cr (VI) concentration remained below the background concentration in the downgradient pumping/monitoring well, and below the detection limit in the injection well, for more than 3 years after the initial HRC injection in 2004. Reaction-transport modeling of the field experiment was performed to elucidate reaction pathways and rates of biogeochemical processes governing Cr (VI) bioimmobilization. Field observation data were used to develop a 3-D hydraulic and reaction-transport-isotopic model, simulated using the TOUGHREACT code. This model was used to assess the degradation kinetics of the HRC, the effects of lactate and acetate-induced bioreduction of Cr and Fe, and the effects on Cr and Sr isotopic compositions in the fluids and mineral phases (calcite dissolution in the acidic plume and precipitation at the fringes). The 2008 experiment involved reinjection of HRC into the same zones as the earlier injection and likely resulted in dissolution of previously precipitated Cr (Fe) hydroxides and additional calcite dissolution in sediments outside of the wellbore. Detailed results of the integrated field and modeling study will be presented.

  10. 77 FR 61431 - Hexavalent Chromium Standards; Extension of the Office of Management and Budget's (OMB) Approval...

    Science.gov (United States)

    2012-10-09

    ... Occupational Safety and Health Administration Hexavalent Chromium Standards; Extension of the Office of...) approval of the information collection requirements specified in the Hexavalent Chromium Standards for... requirements specified in the Hexavalent Chromium (Cr(VI)) Standards for General Industry (29 CFR...

  11. Production of Nanocrystalline Magnetite for Adsorption of Cr(VI) Ions

    Science.gov (United States)

    Javadi, N.; Raygan, Sh.; Seyyed Ebrahimi, S. A.

    Higher environmental standards have made the removal of toxic metals such as hexavalent chromium from wastewater; an important problem for environmental protection. Iron oxide is a particularly interesting adsorbent to be considered for this application. In this study, a new method combining adsorption and magnetic separation was developed to remove Cr(VI) from wastewater. The nanocrystalline magnetite as adsorbent was produced via thermo- mechanical reduction of hematite. Various parameters which affect the adsorption of Cr(VI) such as time, pH, temperature and initial concentration were investigated using thermo-gravimeters (TG), X-Ray diffraction (XRD), scanning electron microscopy (SEM) and atomic adsorption spectroscopy (AAS) techniques. The maximum adsorption was occurred at pH 2. The adsorption data were fitted well to Langmuir isotherm model. The adsorption of Cr(VI) increased significantly with increasing of temperature and time.

  12. Sorption and desorption of Cr(VI) ions from water by biochars in different environmental conditions.

    Science.gov (United States)

    Tytłak, Aleksandra; Oleszczuk, Patryk; Dobrowolski, Ryszard

    2015-04-01

    In the present research, the potential of two biochars produced by the thermal decomposition of wheat straw (BCS) and wicker (BCW) for Cr(VI) ions removing from wastewater was investigated. The pH and the presence of chlorides and nitrates were also investigated. The Freundlich and Langmuir models were applied for the characterization of adsorption isotherms. The Langmuir model has better fitting of adsorption isotherms than the Freundlich model. The sorption process can be described by the pseudo second-order equation. The optimal adsorption capacities were obtained at pH 2 and were 24.6 and 23.6 mg/g for BCS and BCW, respectively. X-ray photoelectron spectroscopy (XPS) studies confirmed that Cr(III) ions were the most abundant chromium species on the biochars' surface. The results indicated that the sorption mechanism of Cr(VI) on biochar involves anionic and cationic adsorption combined with Cr(VI) species reduction. PMID:25378029

  13. Evaluation of the effects of various culture condition on Cr (VI)reduction by Shewanella oneidensis MR-1 in a novel high-throughputmini-bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yinjie J.; Laidlaw, David; Gani, Kishen; Keasling, Jay D.

    2006-03-16

    The growth and Cr(VI) reduction by Shewanella oneidensisMR-1 was examined using a mini-bioreactor system that independentlymonitors and controls pH, dissolved oxygen, and temperature for each ofits 24, 10-mL reactors. Independent monitoring and control of eachreactor in the cassette allows the exploration of a matrix ofenvironmental conditions known to influence S. oneidensis chromiumreduction. S. oneidensis MR-1 grew in minimal medium without amino acidor vitamin supplementation under aerobic conditions but required serineand glycine supplementation under anaerobic conditions. Growth wasinhibited by dissolved oxygen concentrations>80 percent. Lactatetransformation to acetate was enhanced by low concentration of dissolvedoxygen during the logarithmic growth phase. Between 11 and 35oC, thegrowth rate obeyed the Arrhenius reaction rate-temperature relationship,with a maximum growth rate occurring at 35oC. S. oneidensis MR-1 was ableto grow over a wide range of pH (6-9). At neutral pH and temperaturesranging from 30-35oC, S. oneidensis MR-1 reduced 100 mu M Cr(VI) toCr(III) within 20 minutes in the exponential growth phase, and the growthrate was not affected by the addition of chromate; it reduced chromateeven faster at temperatures between 35 and 39oC. At low temperatures(<25oC), acidic (pH<6.5), or alkaline (pH>8.5) conditions, 100mu M Cr(VI) strongly inhibited growth and chromate reduction. Themini-bioreactor system enabled the rapid determination of theseparameters reproducibly and easily by performing very few experiments.Besides its use for examining parameters of interest to environmentalremediation, the device will also allow one to quickly assess parametersfor optimal production of recombinant proteins or secondarymetabolites

  14. Stabilization and solidification of chromium-contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Cherne, C.A.; Thomson, B.M. [Univ. of New Mexico, Albuquerque, NM (United States). Civil Engineering Dept.; Conway, R. [Sandia National Labs., Albuquerque, NM (United States)

    1997-11-01

    Chromium-contaminated soil is a common environmental problem in the United States as a result of numerous industrial processes involving chromium. Hexavalent chromium [Cr(VI)] is the species of most concern because of its toxicity and mobility in groundwater. One method of diminishing the environmental impact of chromium is to reduce it to a trivalent oxidation state [Cr(III)], in which it is relatively insoluble and nontoxic. This study investigated a stabilization and solidification process to minimize the chromium concentration in the Toxicity Characteristic Leaching Procedure (TCLP) extract and to produce a solidified waste form with a compressive strength in the range of 150 to 300 pounds per square inch (psi). To minimize the chromium in the TCLP extract, the chromium had to be reduced to the trivalent oxidation state. The average used in this study was an alluvium contaminated with chromic and sulfuric acid solutions. The chromium concentration in the in the in situ soil was 1212 milligrams per kilogram (mg/kg) total chromium and 275 mg/kg Cr(VI). The effectiveness of iron, ferrous sulfate to reduce Cr(VI) was tested in batch experiments.

  15. Investigating the thermodynamics of the reduction of U(VI) to U(V) by Fe(II) using ab initio methods

    Energy Technology Data Exchange (ETDEWEB)

    Wahlgren, Ulf [Stockholm Univ. (Sweden). Physics Dept.

    2003-07-01

    In the present work, we have addressed an important redox reaction, the reduction of U(VI) to U(V) in the presence of Fe(II). Redox reactions are not only of fundamental interest, to understand them is essential when describing how chemical reactions of actinides in surface and groundwater systems affect their mobility in the biosphere, and the function of engineered systems for the containment of radioactive waste in underground repositories. In this context it is important to notice that spent nuclear fuel is predominantly a matrix of UO{sub 2} in which fission products and higher actinides are dispersed. In contact with water the fuel matrix will dissolve with a resulting release of the different radionuclides; the dissolution is a result of oxidation by radiolysis products or by intruding oxygen. In most technical system the nuclear waste is contained in canisters of iron/steel, which provide a large reduction capacity to the system and thus may prevent the transformation of sparingly soluble UO{sub 2} to more soluble U(VI) species. Corrosion and other redox reactions involving iron species are therefore of key importance for the safe performance of many nuclear waste installations; as these have to function over very long time periods it is highly desirable to base predictions of their future environmental effects on molecular understanding of the chemical reactions taking place.

  16. Investigating the thermodynamics of the reduction of U(VI) to U(V) by Fe(II) using ab initio methods

    International Nuclear Information System (INIS)

    In the present work, we have addressed an important redox reaction, the reduction of U(VI) to U(V) in the presence of Fe(II). Redox reactions are not only of fundamental interest, to understand them is essential when describing how chemical reactions of actinides in surface and groundwater systems affect their mobility in the biosphere, and the function of engineered systems for the containment of radioactive waste in underground repositories. In this context it is important to notice that spent nuclear fuel is predominantly a matrix of UO2 in which fission products and higher actinides are dispersed. In contact with water the fuel matrix will dissolve with a resulting release of the different radionuclides; the dissolution is a result of oxidation by radiolysis products or by intruding oxygen. In most technical system the nuclear waste is contained in canisters of iron/steel, which provide a large reduction capacity to the system and thus may prevent the transformation of sparingly soluble UO2 to more soluble U(VI) species. Corrosion and other redox reactions involving iron species are therefore of key importance for the safe performance of many nuclear waste installations; as these have to function over very long time periods it is highly desirable to base predictions of their future environmental effects on molecular understanding of the chemical reactions taking place

  17. Fabrication of bimodal-pore SrTiO3 microspheres with excellent photocatalytic performance for Cr(VI) reduction under simulated sunlight.

    Science.gov (United States)

    Yang, Dong; Sun, Yuanyuan; Tong, Zhenwei; Nan, Yanhu; Jiang, Zhongyi

    2016-07-15

    Solving the increasing contamination from toxic heavy metal ions in wastewater is an imperative issue in photocatalysis research area. In this study, three-dimensional (3D) porous SrTiO3 microspheres have been fabricated by a sol-gel-templating method using the agarose gel bead containing SrCO3 granules as the template. The resultant SrTiO3 microspheres, several tens of micrometers in diameter, exhibit a bimodal pore structure, in which the macropore about 70-150nm in size stems from SrCO3 granules and the mesopore about 3nm is formed via removing the agarose fiber embedded in the composite microspheres. The porous framework of SrTiO3 microspheres is assembled by regular single-crystalline SrTiO3 nanocubes with an edge length of 100±10nm. The highly interconnected porous network renders numerous pathways for the rapid mass transport, strong adsorption of reactants and multi-reflection of incident light. Moreover, the as-prepared SrTiO3 microspheres exhibit excellent photocatalytic performance for the Cr(VI) reduction under simulated sunlight, which can reduce nearly 100% Cr(VI) at pH 2 within 2h and retain a relatively high reduction ability after six recycles. PMID:27015378

  18. Synthesis, characterization and role of zero-valent iron nanoparticle in removal of hexavalent chromium from chromium-spiked soil

    International Nuclear Information System (INIS)

    Chromium is an important industrial metal used in various products/processes. Remediation of Cr contaminated sites present both technological and economic challenges, as conventional methods are often too expensive and difficult to operate. In the present investigation, Zero-valent iron (Fe0) nanoparticles were synthesized, characterized, and were tested for removal of Cr(VI) from the soil spiked with Cr(VI). Fe0 nanoparticles were synthesized by the reduction of ferric chloride with sodium borohydride and were characterized by UV–Vis (Ultra violet–Visible) and FTIR (Fourier transform infrared) spectroscopy. The UV–Vis spectrum of Fe0 nanoparticles suspended in 0.8% Carboxymethyl cellulose showed its absorption maxima at 235 nm. The presence of one band at 3,421 cm−1 ascribed to OH stretching vibration and the second at 1,641 cm−1 to OH bending vibration of surface-adsorbed water indicates the formation of ferrioxyhydroxide (FeOOH) layer on Fe0 nanoparticles. The mean crystalline dimension of Fe0 nanoparticles calculated by XRD (X-ray diffraction) using Scherer equation was 15.9 nm. Average size of Fe0 nanoparticles calculated from TEM (Transmission electron microscopy) images was found around 26 nm. Dynamic Light Scattering (DLS) also showed approximately the same size. Batch experiments were performed using various concentration of Fe0 nanoparticles for reduction of soil spiked with 100 mg kg−1 Cr(VI). The reduction potential of Fe0 nanoparticles at a concentration of 0.27 g L−1 was found to be 100% in 3 h. Reaction kinetics revealed a pseudo-first order kinetics. Factors like pH, contact time, stabilizer, and humic acid facilitates the reduction of Cr(VI).

  19. Determination of hexavalent chromium in cosmetic products by ion chromatography and postcolumn derivatization.

    Science.gov (United States)

    Kang, Eun Kyung; Lee, Somi; Park, Jin-Hee; Joo, Kyung-Mi; Jeong, Hye-Jin; Chang, Ih Seop

    2006-05-01

    Chromium hydroxide green [Cr(2)O(OH)(4)] and chromium oxide green (Cr(2)O(3)) are colouring agents for use in cosmetic products. These colourants may contain chromium (VI), which cause skin allergies through percutaneous adsorption on the skin. Eye shadow is a representative cosmetic product in which significant colourants are used. We analysed the chromium (VI) in the eye shadows by ion chromatography and post column derivatization. We optimize conditions of chromium (VI) analysis in eye shadows. During the pretreatment procedure, there are no exchange of chromium (III) to chromium (VI). This method has a limit of quantification for chromium (VI) of 1.0 microg l(-1), recovery rate of 100 +/- 3% and analysis time less than 10 min. This result is 300 times more sensitive than the high-performance liquid chromatography method. We applied the optimized method to analyse 22 eye shadows and 6 colouring agents. 2 out of 22 of the products contained more than 5 mg l(-1). In our previous work, 5 mg l(-1) of Cr represented a threshold level. There was much more Cr(VI) in the colouring agents. The Cr(VI) in one of the colouring agents was 97.6 mg l(-1). PMID:16689807

  20. Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2

    International Nuclear Information System (INIS)

    Visible light driven HCrO4- reduction was successfully achieved over the new hetero-system CuAl2O4/TiO2. The spinel, elaborated by nitrate route, was characterized photo electrochemically. The optical gap was found to be 1.70 eV and the transition is directly allowed. The conduction band (-1.05 VSCE) is located below that of TiO2, more negative than the HCrO4-/Cr3+ level (+0.58 VSCE) yielding a thermodynamically feasible chromate reduction upon visible illumination. CuAl2O4 is stable against photo corrosion by holes consumption reaction involving salicylic acid which favors the charges separation. There is a direct correlation between the dark adsorption and the photo activity. A reduction of more than 95% of chromate was achieved after 3 h irradiation at pH 2 with an optimal mass ratio (CuAl2O4/TiO2) equal to 1/3. The reduction follows a first order kinetic with a half life of ∼1 h and a quantum yield of 0.11% under polychromatic light. Prolonged illumination was accompanied by a deceleration of the Cr(VI) reduction thanks to the competitive water discharge. The hydrogen evolution, an issue of energetic concern, took place with a rate of 3.75 cm3 (g catalyst)-1 h-1.

  1. Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2.

    Science.gov (United States)

    Gherbi, R; Nasrallah, N; Amrane, A; Maachi, R; Trari, M

    2011-02-28

    Visible light driven HCrO(4)(-) reduction was successfully achieved over the new hetero-system CuAl(2)O(4)/TiO(2). The spinel, elaborated by nitrate route, was characterized photo electrochemically. The optical gap was found to be 1.70 eV and the transition is directly allowed. The conduction band (-1.05 V(SCE)) is located below that of TiO(2), more negative than the HCrO(4)(-)/Cr(3+) level (+0.58 V(SCE)) yielding a thermodynamically feasible chromate reduction upon visible illumination. CuAl(2)O(4) is stable against photo corrosion by holes consumption reaction involving salicylic acid which favors the charges separation. There is a direct correlation between the dark adsorption and the photo activity. A reduction of more than 95% of chromate was achieved after 3 h irradiation at pH 2 with an optimal mass ratio (CuAl(2)O(4)/TiO(2)) equal to 1/3. The reduction follows a first order kinetic with a half life of ∼1 h and a quantum yield of 0.11% under polychromatic light. Prolonged illumination was accompanied by a deceleration of the Cr(VI) reduction thanks to the competitive water discharge. The hydrogen evolution, an issue of energetic concern, took place with a rate of 3.75 cm(3) (g catalyst)(-1) h(-1). PMID:21177028

  2. Determination of hexavalent chromium in sludge incinerator emissions using ion chromatography and inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Arar, E.J.; Long, S.E. (Technology Applications, Inc., Cincinnati, OH (United States)); Martin, T.D.; Gold, S. (Environmental Monitoring Systems Lab., Cincinnati, OH (United States))

    1992-10-01

    A unique approach is described using ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) for the determination of hexavalent chromium [Cr(VI)] in wastewater sludge incinerator emissions. Quartz fiber filters, spiked with an isotopically enriched ([sup 50]Cr or [sup 53]Cr) chromate salt, were used to collect emission particulates. The enriched Cr(VI) isotope was used to monitor the reduction of Cr(IV) during sample collection using a pseudo-first-order reaction model and to calculate the rate of deposition of native Cr(VI) on the filters. At the end of the sampling period, the Cr(VI) was extracted from the filters with 0.1 N sodium hydroxide and determined by IC using postcolumn derivatization with 1,5-diphenylcarbohydrazide. To determine the ratio of enriched Cr(VI) to the native Cr(VI) emitted from the incinerator, an additional aliquot of the sample extract was preconcentrated by IC and the isotopic composition of the Cr(VI) fraction determined by ICP-MS. 21 refs., 4 figs., 3 figs.

  3. Common occurrence of a positive δ53Cr shift in Central European waters contaminated by geogenic/industrial chromium relative to source values.

    Science.gov (United States)

    Novak, Martin; Chrastny, Vladislav; Cadkova, Eva; Farkas, Juraj; Bullen, Thomas D; Tylcer, Jiri; Szurmanova, Zdenka; Cron, Marcel; Prechova, Eva; Curik, Jan; Stepanova, Marketa; Pasava, Jan; Erbanova, Lucie; Houskova, Marie; Puncochar, Karel; Hellerich, Lucas A

    2014-06-01

    Carcinogenic effects of hexavalent chromium in waters are of concern in many countries worldwide. We explored Cr isotope systematics at 11 sites in the Czech Republic and Poland. Geogenic Cr pollution was associated with serpentinite bodies at former convergent plate margins, while anthropogenic Cr pollution resulted from electroplating, tanning, and the chemical industry. Cr(VI) concentration in geogenic waters was less than 40 ppb. Anthropogenic waters contained up to 127,000 ppb Cr(VI). At both geogenic and anthropogenic sites, where known, the source of pollution had a low δ53Cr (contaminated waters was significantly higher (p<0.001) compared to δ53Cr of waters carrying geogenic Cr(VI), implying that either the effective fractionation factor or process extent was greater for Cr(VI) reduction than for Cr(III) oxidation. PMID:24779992

  4. 铬污染土壤的微生物修复%REDUCTION OF CHROMIUM CONTAMINATED SOILS BY MICROORGANSIM

    Institute of Scientific and Technical Information of China (English)

    许友泽; 杨志辉; 向仁军

    2011-01-01

    The removal of Cr ( Ⅵ ) in chromium-contaminated soil by indigeous microorganism with leaching experiment was investigated. The effect of culture medium composition, amount of culture medium and pH of leachate on Cr( Ⅵ ) removal was investigated. The results showed that the water soluble Cr( Ⅵ ) in soils was completely when culture medium was added. Cr( Ⅵ ) concentration in leachate decreased from 700.3mg·L-1 to the concentration lower than detectable level after leaching. Cr(Ⅵ) removal was not complete with carbonbased culture medium. However Cr ( Ⅵ ) was completely remediated by combination of the carbon and the nitrogen source. The optimal carbon source was glucose, and the optimal quantity was 4g· L- 1 of carbon source and 5g·L-1 of nitrogen source. The optimal pH was 7.5-8.5.%采用淋溶实验研究微生物对铬污染土壤中Cr(Ⅵ)的修复,研究培养基成分、培养基添加量及淋溶液pH值对修复效果的影响.结果表明,培养基淋溶能完全修复铬污染土壤中水溶性Cr(Ⅵ),浸出液中Cr(Ⅵ)浓度由初始的700.3mg·L-1降低至检出限以下.单独加入碳源作为培养基时,土壤中Cr(Ⅵ)不能得到完全修复,碳源与氮源结合作为培养基时能完全修复土壤中Cr(Ⅵ).最佳碳源为葡萄糖,最佳碳源和氮源量分别为4 g·L-1和5 g·L-1.最佳pH值范围为7.5-8.5.

  5. Mechanism of electron transfer in the bioadsorption of hexavalent chromium within Leersia hexandra Swartz granules by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Leersia hexandra Swartz biogranules were used to adsorb Cr(VI) from aqueous solutions. Batch biosorption experiments showed that the Cr(VI) concentration sharply decreases in the first 15 min. The main functional groups that may be involved in chromium sorption were determined using Fourier transform infrared spectroscopy. The use of X-ray photoelectron spectroscopy confirmed the reduction of Cr(VI) to Cr(III) through L. hexandra Sw. Results indicate that Cr(III) is the dominant species on the surface of the biogranules and that the redox reaction can be accomplished within 40 min. The mechanism of electron transfer during Cr(VI) reduction to Cr(III) was investigated. Protonation of the oxygen-containing groups produces electrostatic-sorption power over Cr(VI). The nitrogen-containing groups serve as the electron-donor groups in the process of reduction-sorption. Moreover, after the complete reduction of Cr(VI), the pH of the suspension significantly increases.

  6. Chemical states in XPS and Raman analysis during removal of Cr(VI) from contaminated water by mixed maghemite–magnetite nanoparticles

    International Nuclear Information System (INIS)

    Highlights: ► Cr(VI) adsorption on mixed maghemite–magnetite is spontaneous and endothermic. ► Theoretical multiplet analysis shows that during Cr adsorption, the amount of maghemite increases (from 70 to 89%). ► Fe(II) was transformed into Fe(III) by the redox reaction. ► Cr(VI) species were reduced to Cr(III) species on the mixed maghemite–magnetite. - Abstract: Mixed maghemite–magnetite has been used as adsorbent for Cr(VI) removal in this study. Results show that the adsorption capacity is enhanced with an increase in reaction temperature and decrease in free energy change. Thermodynamic study shows that Cr(VI) adsorption on the mixed maghemite and magnetite is endothermic in nature and is dependent on solution pH between 3 and 6. X-ray photoelectron spectroscopy (XPS) results demonstrate the theoretical multiplet peaks for iron and chromium adsorbed iron at the surface of the γ-Fe2O3 and Fe3O4 mixture. Theoretical multiplet analysis shows that during Cr adsorption, the amount of maghemite increases (from 70 to 89%). In magnetite spectra, the relative content of Fe(II) decreases from 8.2 to 3.6% indicating the reduction of magnetite in the mixture particles. In Raman spectroscopy studies, clear peaks of chromium on iron oxide were generated at 826 cm−1, which could be attributed to chemical interactions between chromium compound and iron oxide. From the results of Raman and XPS studies, electrostatic attraction and oxidation–reduction between chromium and mixed maghemite–magnetite are postulated as mechanisms for the removal of Cr(VI) from aqueous solutions.

  7. IN-VITRO BIOREDUCTION OF HEXAVALENT CHROMIUM BY VIABLE WHOLE CELLS OF Arthrobacter sp. SUK 1201

    Directory of Open Access Journals (Sweden)

    Satarupa Dey

    2014-08-01

    Full Text Available A chromium resistant and reducing bacterium Arthrobacter sp. SUK 1201 was isolated from chromite mine overburden dumps of Orissa, India. Viable whole cells of this isolate was capable of completely reducing 100 µM Cr(VI in chemically defined MS medium within 28 h of incubation under batch cultivation. Reduction of chromate increased with increased cell density and was maximum at a density of 1010 cells/ml, but the reduction potential of the suspended cells decreased with increase in Cr(VI concentration in the medium. Chromate reducing efficiency was promoted when glycerol and glucose was used as electron donors, while the optimum pH and temperature of Cr(VI reduction was found to be 7.0 and 35°C respectively. The reduction process was inhibited by divalent cations Ni, Co and Cd, but not by Cu and Fe. Similarly, carbonyl cyanide m-chlorophenylhydrazone (CCCP, N,N,-Di cyclohexyl carboiimide (DCC, sodium azide and sodium fluoride were inhibitory to chromate reduction, while in presence of 2,4 dinitrophenol (2,4 DNP chromate reduction by SUK 1201 cells remained unaffected.

  8. Visible light-responded C, N and S co-doped anatase TiO{sub 2} for photocatalytic reduction of Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Lei, X.F., E-mail: leixuefei69@163.com [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Xue, X.X.; Yang, H. [Institute of Metallurgical Resource and Environmental Engineering, Northeastern University, Shenyang 110819 (China); Liaoning Key Laboratory of Metallurgical Resource Recycling Science, Shenyang 110819 (China); Liaoning Engineering and Technology Research Center of Boron Resource, Comprehensive, Utilization, Shenyang 110819 (China); Liaoning Provincial Universities Key Laboratory of Boron Resource Ecological, Utilization, Technology and Boron Materials, Shenyang 110819 (China); Chen, C.; Li, X.; Pei, J.X.; Niu, M.C.; Yang, Y.T.; Gao, X.Y. [School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2015-10-15

    The (C, N and S) co-doped TiO{sub 2} (TH-TiO{sub 2}) samples were synthesized by a sol-gel method calcined at 500 °C, employing butyl titanate as the titanium source and thiourea as the dopant. The structures of TH-TiO{sub 2} samples were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectroscopy, Thermo gravimetry and differential thermal analysis (TG-DTA), Scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherms. The photocatalytic activities were checked through the photocatalytic reduction of Cr(VI) as a model compound under visible light irradiation. The results showed that the thiourea content played an important role on the microstructure and photocatalytic activity of the samples. According to XPS results, (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. TH-TiO{sub 2} samples with thiourea: Ti molar ratio of 1.5 exhibits higher photocatalytic activity than that of the other samples under visible light irradiation, which can be attributed to the synergic effect of the pure anatase structure, the higher light absorption characteristics in visible regions, separation efficiency of electron–hole pairs, the specific surface area and the optimum (C, N and S) content. - Graphical abstract: (C, N and S) co-doped TiO{sub 2} samples show good photocatalytic activity for Cr (VI) reduction under visible light irradiation. - Highlights: • (C, N and S) co-doping in TH-TiO{sub 2} samples can promote the formation of the pure anatase structure. • (C, N and S) atoms were successfully co-doped into the nanostructures of TH-TiO{sub 2} samples. • The band gap energy of TH-TiO{sub 2} samples reduced after (C, N and S) co-doping. • (C, N and S) co-doped TiO{sub 2} samples were effective for the photocatalytic reduction of Cr(VI) under visible light

  9. Analysis of a two-phase system of mass transfer and electro-reduction of uranium(VI) in nitric acid-hydrazine media

    International Nuclear Information System (INIS)

    Simulation for a dynamic analysis of the electrolytic preparation of U(IV) in two-phases system, which consisted of mass transfer of U(VI) from TBP phase into HNO3 solution and electrolytic reduction of U(VI) to U(IV) at a cathode in aqueous phase, was carried out in order to establish the most suitable operating condition and best electrode area as basic design data for the system. It was found that maintaining an appropriate mass transfer rate was more significant rather than enlarging the surface area of the cathode for more effective production yield of U(IV). The electrode area and the operation time affected deeply the production composition of U(IV) in the resulting aqueous phase. And optimal electrode areas were evaluated to meet production criteria of U(IV) of resulting solution in several system conditions. Though about 0.37M HNO3 was preferable to prepare the solution of U(IV), nitric acid concentration should be higher than 0.5M to prevent a hydrolysis of U(IV) in the aqueous phase. 6 figs., 24 refs. (Author)

  10. Biosorption of Hexavalent Chromium from Aqueous Medium with Opuntia Biomass

    OpenAIRE

    José A. Fernández-López; Angosto, José M.; María D. Avilés

    2014-01-01

    The biosorption of hexavalent chromium from aqueous solutions by Opuntia cladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) by Opuntia biomass was highly pH dependent, favoring higher ...

  11. Chromium oxidation state mapping in human cells

    Science.gov (United States)

    Ortega, R.; Fayard, B.; Salomé, M.; Devès, G.; Susini, J.

    2003-03-01

    The widespread use of chromium in industrial applications such as chemical production of pigments, refractory brick production, tanning, metallurgy, electroplating, and combustion of fuels has lead to human occupational exposure and to its increased introduction into the environment. Hexavalent chromium compounds are established carcinogens but their mechanism of cell transformation is not known. Up to now, no microanalytical technique was sensitive enough to allow the observation of chromium distribution, and oxidation state identification, within isolated cells at carcinogenic concentrations. In this experiment, we used successfully the ID-21 X-ray microscope to map Cr(VI) and total Cr distributions in cells exposed in vitro to soluble, and insoluble, Cr(VI) compounds. Exposure to soluble compounds, weak carcinogens, resulted in a homogeneous intracellular distribution of Cr, confirming by in situ measurement that Cr is present in the cell nucleus. Cr(VI) was never detected in cells which suggests a mechanism of rapid intracellular reducticn. On the other hand, exposure to insoluble compounds, strong carcinogens, also resulted in a homogeneous distribution of reduced forms of Cr in cells, and their nucleus. However, in this case, Cr(VI)-rich structures were observed into the cells suggesting that carcinogenicity is enhanced when oxidation reactions due to Cr(VI) chronic exposure are associated to Cr-DNA alterations.

  12. Reduction of Late In-Stent Stenosis in a Porcine Coronary Artery Model by Cobalt Chromium Stents with a Nanocoat of Polyphosphazene (Polyzene-F)

    International Nuclear Information System (INIS)

    The purpose of this study was to investigate the potential of nanoscale coating with the highly biocompatible polymer Polyzene-F (PZF), in combination with cobalt chromium and stainless steel stents, to reduce in-stent stenosis, thrombogenicity, and vessel wall injury and inflammation. One bare cobalt chromium, PZF-nanocoated stainless steel or PZF-nanocoated cobalt chromium stent was implanted in right coronary artery of 30 mini-pigs (4- or 12-week follow-up). Primary study end points were in-stent stenosis and thrombogenicity. Secondary study end points were vessel wall injury and inflammation as evaluated by microscopy and a new immunoreactivity score applying C-reactive protein (CRP), tumor-necrosis factor alpha (TNFα), and TGFβ. At 12 weeks, angiography showed a significantly lower average loss in lumen diameter (2.1% ± 3.05%) in PZF-nanocoated cobalt chromium stents compared with stents in the other groups (9.73% ± 4.93% for bare cobalt chromium stents and 9.71% ± 7% for PZF-nanocoated stainless steel stents; p = 0.04), which was confirmed at microscopy (neointima 40.7 ± 16 μm in PZF-nanocoated cobalt chromium stents, 74.7 ± 57.6 μm in bare cobalt chromium stents, and 141.5 ± 109 μm in PZF-nanocoated stainless steel stents; p = 0.04). Injury and inflammation scores were low in all stents and were without significant differences. PZF-nanocoated cobalt chromium stents provided the highest efficacy in reducing in-stent stenosis at long-term follow-up. The PZF nanocoat proved to be biocompatible with respect to thromboresistance and inflammation. Our data suggest that its combination with cobalt chromium stents might provide an interesting passive stent platform.

  13. USE OF MICRO X-RAY ABSORPTION SPECTROSCOPY AND DIFFRACTION TO DELINEATE Cr(VI) SPECIATION IN COPR

    Energy Technology Data Exchange (ETDEWEB)

    CHRYSOCHOOU, M.; MOON, D. H.; FAKRA, S.; MARCUS, M.; DERMATAS, D.; CHRISTODOULATOS, C.

    2010-06-22

    The speciation of Cr(VI) in Cromite Ore Processing Residue was investigated by means of bulk XRD, and a combination of micro-XRF, -XAS and -XRD at the Advanced Light Source (ALS), Berkeley, CA, U.S.A.. Bulk XRD yielded one group of phases that contained explicitly Cr(VI) in their structure, Calcium Aluminum Chromium Oxide Hydrates, accounting for 60% of the total Cr(VI). Micro-analyses at ALS yielded complimentary information, confirming that hydrogarnets and hydrotalcites, two mineral groups that can host Cr(VI) in their structure by substitution, were indeed Cr(VI) sinks. Chromatite (CaCrO4) was also identified by micro-XRD, which was not possible with bulk methods due to its low content. The acquisition of micro-XRF elemental maps enabled not only the identification of Cr(VI)-binding phases, but also the understanding of their location within the matrix. This information is invaluable when designing Cr(VI) treatment, to optimize release and availability for reduction.

  14. Method of trivalent chromium concentration determination by atomic spectrometry

    Science.gov (United States)

    Reheulishvili, Aleksandre N.; Tsibakhashvili, Neli Ya.

    2006-12-12

    A method is disclosed for determining the concentration of trivalent chromium Cr(III) in a sample. The addition of perchloric acid has been found to increase the atomic chromium spectrometric signal due to Cr(III), while leaving the signal due to hexavalent chromium Cr(VI) unchanged. This enables determination of the Cr(III) concentration without pre-concentration or pre-separation from chromium of other valences. The Cr(III) concentration may be measured using atomic absorption spectrometry, atomic emission spectrometry or atomic fluorescence spectrometry.

  15. Influence of Chelating Agents on Chromium Fate in Sediment

    Institute of Scientific and Technical Information of China (English)

    WANGXIAOCHANG; SUNJINHE; 等

    1996-01-01

    A laboratory investigation on reaction between chelating agents and chromium was conducted to evaluate the effect of chelating agents on the adsorption and desorption of chromium in sediment.The amount of adsorbed chromium(VI) in sediment decreased slightly by 5%-10% because of addition of chelating agents.Chelating agents inhibited the removal of Cr(Ⅲ)by sediment from solutions and the inhibiting effect was in the order:citric acid>tartaric acid>EDTA,Salicylic acid.No effect of chelating agents on desorption of chromium in sediment was observed.

  16. Biogeochemical Modeling of In Situ U(VI) Reduction and Immobilization with Emulsified Vegetable Oil as the Electron Donor at a Field Site in Oak Ridge, Tennessee

    Science.gov (United States)

    Tang, G.; Parker, J.; Wu, W.; Schadt, C. W.; Watson, D. B.; Brooks, S. C.; Orifrc Team

    2011-12-01

    A comprehensive biogeochemical model was developed to quantitatively describe the coupled hydrologic, geochemical and microbiological processes that occurred following injection of emulsified vegetable oil (EVO) as the electron donor to immobilize U(VI) at the Oak Ridge Integrated Field Research Challenge site (ORIFRC) in Tennessee. The model couples the degradation of EVO, production and oxidation of long-chain fatty acids (LCFA), glycerol, hydrogen and acetate, reduction of nitrate, manganese, ferrous iron, sulfate and uranium, and methanoganesis with growth of multiple microbial groups. The model describes the evolution of geochemistry and microbial populations not only in the aqueous phase as typically observed, but also in the mineral phase and therefore enables us to evaluate the applicability of rates from the literature for field scale assessment, estimate the retention and degradation rates of EVO and LCFA, and assess the influence of the coupled processes on fate and transport of U(VI). Our results suggested that syntrophic bacteria or metal reducers might catalyze LCFA oxidation in the downstream locations when sulfate was consumed, and competition between methanogens and others for electron donors and slow growth of methanogen might contribute to the sustained reducing condition. Among the large amount of hydrologic, geochemical and microbiological parameter values, the initial biomass, and the interactions (e.g., inhibition) of the microbial functional groups, and the rate and extent of Mn and Fe oxide reduction appear as the major sources of uncertainty. Our model provides a platform to conduct numerical experiments to study these interactions, and could be useful for further iterative experimental and modeling investigations into the bioreductive immobiliztion of radionuclide and metal contaminants in the subsurface.

  17. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    International Nuclear Information System (INIS)

    This study was undertaken to determine if chromium(+6) could exist in plutonium process solutions under normal operating conditions. Four individual reactions were studied: the rate of dissolution of stainless steel, which is the principal source of chromium in process solutions; the rate of oxidation of chromium(+3) to chromium(+6) by nitric acid; and the reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel and with oxalic acid. The stainless steel corrosion rate was found to increase with increasing nitric acid concentration, increasing hydrofluoric acid concentration, and increasing temperature. Oxidation of chromium(+3) to chromium(+6) was negligible at room temperature and only became significant in hot concentrated nitric acid. The rate of reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel or oxalic acid was found to be much greater than the rate of the reverse oxidation reaction. Based on these findings and taking into account normal operating conditions, it was determined that although there would be considerable chromium in plutonium process streams it would rarely be found in the (+6) oxidation state and would not exist in the (+6) state in the final process waste solutions

  18. Hexavalent chromium and its effect on health: possible protective role of garlic (Allium sativum Linn).

    Science.gov (United States)

    Das, Kusal K; Dhundasi, Salim A; Das, Swastika N

    2011-01-01

    Hexavalent chromium or chromium (VI) is a powerful epithelial irritant and a confirmed human carcinogen. This heavy metal is toxic to many plants, aquatic animals, and bacteria. Chromium (VI) which consists of 10%-15% total chromium usage, is principally used for metal plating (H2Cr2O7), as dyes, paint pigments, and leather tanning, etc. Industrial production of chromium (II) and (III) compounds are also available but in small amounts as compared to chromium (VI). Chromium (VI) can act as an oxidant direc