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Sample records for chromium ions

  1. Defect transformation in GSGG crystals during chromium ion activation

    International Nuclear Information System (INIS)

    Absorption and induced absorption spectra, dose dependence of induced absorption, thermoluminescence of GSGG crystals, nominally pure and activated with chromium and neodymium ions in different concentrations, are investigated. It is shown that it is chromium ion presence in large concentration that decreases the induced coloration in GSGG crystals after γ-irradiation at 300 K. Optimum concentration of chromium ions for the minimum of induced coloration are found. The mechanism of decrease of induced coloration consisting in Fermi level displacement by chromium ion activation is established. Defect concentration and localization and recombination possibilities of electrons and holes in GSGG crystals are estimated by computer simulation

  2. 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.

    1997-01-01

    A sensitive method for the simultaneous determination of chromium(III) and chromium(VI) was chromatography and chemiluminescence detection. Two Dionex ion-exchange guard columns in series, CG5 and AG7, were used to separate chromium(III) from chromium(VI). Chromium(VI) was reduced by potassium su...

  3. A REVIEW OF BIOSORPTION OF CHROMIUM IONS BY MICROORGANISMS

    OpenAIRE

    Inga Zinicovscaia

    2012-01-01

    Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The main source of chromium pollution including the Republic o Moldova is industry. It is a great need to develop new eco-friendly methods of chromium removal. Biosorption of heavy metals is a most promising technology involved in the removal of toxic metals from industrial waste streams and natural waters. This article is an extended abstract of a communication presented at the...

  4. Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

    OpenAIRE

    Uzaşçı Sesil; Tezcan Filiz; Bedia Erim F.

    2014-01-01

    Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, contrary to the traditional calcium alginate beads. The adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h and the removal efficiency of chromium (VI) was found as 95%. The adsorption data fit well with Langmuir and Freundlich isotherms. The maximum chromium (VI) adsorpt...

  5. A REVIEW OF BIOSORPTION OF CHROMIUM IONS BY MICROORGANISMS

    Directory of Open Access Journals (Sweden)

    Inga Zinicovscaia

    2012-12-01

    Full Text Available Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The main source of chromium pollution including the Republic o Moldova is industry. It is a great need to develop new eco-friendly methods of chromium removal. Biosorption of heavy metals is a most promising technology involved in the removal of toxic metals from industrial waste streams and natural waters. This article is an extended abstract of a communication presented at the Conference Ecological Chemistry 2012

  6. 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

  7. Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

    Directory of Open Access Journals (Sweden)

    Uzaşçı Sesil

    2014-07-01

    Full Text Available Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, contrary to the traditional calcium alginate beads. The adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h and the removal efficiency of chromium (VI was found as 95%. The adsorption data fit well with Langmuir and Freundlich isotherms. The maximum chromium (VI adsorption capacity determined from Langmuir isotherm was 36.5 mg/g dry alginate beads. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium (VI from contaminated waters.

  8. 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...

  9. Ability of Bacillus mucilaginosus GY03 Strain to Adsorb Chromium Ions

    Institute of Scientific and Technical Information of China (English)

    CHEN Ye; LIAN Bin

    2005-01-01

    A research with Bacillus mucilaginosus cultured in nitrogen-free medium for forming a flocculant material to adsorb Cr+6 was conducted to determine the effects of different pH, volume, treatment time, and chromium (Ⅵ) concentrations on chromium (Ⅵ) adsorption by microbial flocculant (MBF), which was produced from the B. mucilaginosus GY03 strain. The results showed that MBF had outstanding flocculation on chromium (Ⅵ). Based on the results of a oneway experiment and actual wastewater treatment conditions, the optimum conditions, obtained by using orthogonal experiments, for chromium (Ⅵ) adsorption by MBF were: Cr6+ solution pH of 9, flocculant material volume of 15 mL,treatment time of 12 h and chromium ion concentration of 30 mg L-1. The results demonstrated that the MBF produced from GY03 could be used in the chromium-containing wastewater treatment. Meanwhile, after extraction and analysis of the MBF polysaccharides, it was found that MBF was mainly composed of glycoprotein. Analysis on constituents of monosaccharide showed that polysaccharides of B. mucilaginosus were composed of rhamnose, glucose etc. Thus, because it was applied over a wide range of pH, in small amounts and had a rapid flocculation speed the flocculant used in this experiment had a vast field of application potential.

  10. Magnetic properties of manganites doped with gallium, iron, and chromium ions

    International Nuclear Information System (INIS)

    The magnetization and the crystal structure of the La0.7Sr0.3Mn1−xMxO3 (M = Ga, Fe, Cr; x ≤ 0.3) systems are studied. The substitution of gallium and chromium is shown to cause phase separation into antiferromagnetic and ferromagnetic phases, whereas the substitution of iron for manganese stabilizes a spinglass state. The ferromagnetic phase in the chromium-substituted compositions is much more stable than that in the case of substitution by iron ions or diamagnetic gallium ions. The magnetic properties are explained in terms of the model of superexchange interactions and the localization of most eg electrons of manganese. The stabilization of ferromagnetism in the chromium-substituted compositions can be caused by the fact that the positive and negative contributions to the superexchange interaction between Mn3+ and Cr3+ ions are close to each other but the antiferromagnetic part of the exchange is predominant. Moreover, some chromium ions are in the tetravalent state, which maintains the optimum doping conditions

  11. Magnetic properties of manganites doped with gallium, iron, and chromium ions

    Energy Technology Data Exchange (ETDEWEB)

    Troyanchuk, I. O., E-mail: troyan@physics.by; Bushinsky, M. V.; Tereshko, N. V. [National Academy of Sciences of Belarus, Scientific and Practical Materials Research Center (Belarus); Dobryanskii, V. M. [Belarussian State Agrarian Technical University (Belarus); Sikolenko, V. [Joint Institute for Nuclear Research (Russian Federation); Többens, D. M. [Helmholtz Center (Germany)

    2015-05-15

    The magnetization and the crystal structure of the La{sub 0.7}Sr{sub 0.3}Mn{sub 1−x}M{sub x}O{sub 3} (M = Ga, Fe, Cr; x ≤ 0.3) systems are studied. The substitution of gallium and chromium is shown to cause phase separation into antiferromagnetic and ferromagnetic phases, whereas the substitution of iron for manganese stabilizes a spinglass state. The ferromagnetic phase in the chromium-substituted compositions is much more stable than that in the case of substitution by iron ions or diamagnetic gallium ions. The magnetic properties are explained in terms of the model of superexchange interactions and the localization of most e{sub g} electrons of manganese. The stabilization of ferromagnetism in the chromium-substituted compositions can be caused by the fact that the positive and negative contributions to the superexchange interaction between Mn{sup 3+} and Cr{sup 3+} ions are close to each other but the antiferromagnetic part of the exchange is predominant. Moreover, some chromium ions are in the tetravalent state, which maintains the optimum doping conditions.

  12. 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

  13. Interactions of chromium ions with starch granules in an aqueous environment.

    Science.gov (United States)

    Szczygieł, Jadwiga; Dyrek, Krystyna; Kruczała, Krzysztof; Bidzińska, Ewa; Brożek-Mucha, Zuzanna; Wenda, Elżbieta; Wieczorek, Jerzy; Szymońska, Joanna

    2014-06-26

    In this study, interactions of dichromate ions with potato starch granules in highly acidic aqueous solutions and at different temperatures were investigated. It was found that the process underwent a reduction of Cr(2)O(7)(2-) to Cr(3+) accompanied by the formation of intermediate Cr(5+) ions detected by electron paramagnetic resonance (EPR) spectroscopy. The reactions took place after the attachment of dichromate anions to the granules and resulted in a lowering of the Cr(2)O(7)(2-) initial content in the solution. The newly formed Cr(3+) ions were both accumulated by the granules or remained in the solution. It was observed for the first time that the quantity of such ions taken by the granules from the solution was noticeably higher than that delivered by trivalent chromium salt solution. It was revealed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) that the chromium ions were not only adsorbed on the granule surface but also introduced into the granule interior and evenly distributed there. An activation energy of the reduction reaction equal to 65 kJ·mol(-1) and the optimal parameters of the process were established. The proposed mechanism could be useful for the bioremediation of industrial effluents polluted by hexavalent chromium compounds.

  14. Metal-on-metal bearings in total hip arthroplasties : Influence of cobalt chromium ions on bacterial growth and biofilm formation

    NARCIS (Netherlands)

    Hosman, Anton H.; van der Mei, Henny C.; Bulstra, Sjoerd K.; Busscher, Henk J.; Neut, Danielle

    2009-01-01

    Metal-on-metal (MOM) bearings involving cobalt-chromium (Co-Cr) alloys in total hip arthroplasties are becoming more and more popular due to their low wear. Consequences of corrosion products of Co-Cr alloys are for the most part unclear, and the influence of cobalt and chromium ions on biofilm form

  15. Chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties

    DEFF Research Database (Denmark)

    Jantzen, Christopher; Jørgensen, Henrik L; Duus, Benn R;

    2013-01-01

    Widely different metal ion concentrations in blood and serum have been reported with metal-on-metal (MoM) implants. We reviewed the literature on blood and serum ion concentrations of chromium (Cr) and cobalt (Co) following various MoM hip arthroplasties.......Widely different metal ion concentrations in blood and serum have been reported with metal-on-metal (MoM) implants. We reviewed the literature on blood and serum ion concentrations of chromium (Cr) and cobalt (Co) following various MoM hip arthroplasties....

  16. Electrokinetic migration studies on removal of chromium and uranyl ions from 904-A trench soil

    International Nuclear Information System (INIS)

    This report describes a laboratory-scale study, in which electrokinetic migration technology was used to remove chromium and uranium, as well as other ions, from soil taken from a bore hole adjacent to the 904-A trench at the Savannah River Technology Center. Imposition of an electric current on humid (not saturated) soil successfully caused cations to migrate through the pore water of the soil to the cathode, where they were captured in an ISOLOCKTm polymer matrix and in a cation exchange resin incorporated in the polymer. Chemicals circulated through the anode/polymer and cathode/polymer were able to control pH excursions in the electrokinetic-cells by reacting with the H+ and OH- generated at the anode and cathode, respectively. The study indicates that ions adsorbed on the surface of the soil as well as those in the pores of soil particles can be caused to migrate through the soil to an appropriate electrode. After 10 days of operation at 20--25 V and 2 mA, approximately 65% of the chromium was removed from two 3.5 kg soil samples. A 57% removal of uranium was achieved. The study shows that electrokinetic migration, using the ISOLOCK trademark polymer will be effective as an in situ treatment method for the removal of metal ion contaminants in soil adjacent to the 904-A trench

  17. Temperature dependence of the luminescence spectra of garnet crystals doped with chromium ions

    Science.gov (United States)

    Orucu, Humeyra; Ozen, Gonul; Collins, John; Di Bartolo, Baldassare

    2009-05-01

    We have investigated the spectral behavior of a number of garnet crystals doped with chromium ions in a range of temperatures from 25 to 800 K. The crystals we considered are, in order of decreasing crystalline field, Y3Al5O12 (YAG), Gd3Ga5O12 (GGG) and Gd3Sc2Ga3O12 (GSGG). By investigating their luminescence spectra, including their vibronic spectra, over a very broad range of temperatures, we attempt to obtain a fuller picture of the processes following excitation.

  18. Site-selective spectroscopy of garnet crystals doped with chromium ions.

    Science.gov (United States)

    Örücü, Hümeyra; Özen, Gönül; Di Bartolo, Baldassare; Collins, John

    2012-09-01

    Site-selective spectroscopy is a tool that can be used to uncover the presence of multiple sites available to optically active ions in host lattices. In this Article, we present techniques that can be applied to appraise the different sites that may occur in systems where charge compensation is required or in systems where such compensation is not present. We then consider some garnet crystals doped with chromium ions. For the Cr-doped garnets (YAG, GGG, GSGG, and CYMGG), we present luminescence and lifetime data over a wide temperature range, and infer not only the presence of different centers, but also the interaction among them as a function of temperature. PMID:22867053

  19. Recovery and reuse of hexavalent chromium from aqueous solutions by a hybrid technique of electrodialysis and ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Gayathri, R. [Sengunthar Engineering College, Tiruchengode (India). Dept. of Civil Engineering], e-mail: gay3civil@gmail.com; Senthil Kumar, P. [SSN College of Engineering, Chennai (India). Dept. of Chemical Engineering], E-mail: senthilkumarp@ssn.edu.in

    2010-01-15

    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. (author)

  20. Synergy between hexavalent chromium ions and TiO2 nanoparticles inside TUD-1 in the photocatalytic oxidation of propane, a spectroscopic study

    Science.gov (United States)

    Hamdy, Mohamed S.

    2016-02-01

    Siliceous TUD-1 mesoporous material was bi-functionalized by titanium dioxide nanoparticles and hexavalent chromium ions. The synthesis was carried out by one-pot procedure based on sol-gel technique. The photocatalytic performance of the prepared material was evaluated in the oxidation of propane under the illumination of ultraviolet light (wavelength = 360 nm) and monitored by in situ Fourier transform infrared spectroscopy. The photocatalytic activity of the prepared material exhibited an extra-ordinary activity than the reference samples that contain either hexavalent chromium ions or titanium dioxide nanoparticles only, confirming the true synergy between hexavalent chromium and tetravalent titanium ions of titanium dioxide nanoparticles.

  1. Reactions of the excited state of polypyridyl chromium(III) ion

    Energy Technology Data Exchange (ETDEWEB)

    Steffan, C.

    1990-09-21

    There has been much recent interest in the photochemistry and photophysics of transition metal polypyridine complexes due to the possibility of their use in solar energy conversion systems. The excited state of these compounds are known to undergo useful electron transfer and energy transfer reactions. This work attempts to elucidate the mechanism of the quenching of *CrL{sub 3}{sup 3+} (where L = 2,2{prime}-bipyridine, 4,4{prime}-dimethyl-2,2{prime}-bipyridine, 1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-methyl-1,10-phenanthroline) by oxalate ions in neutral pH. Evidence suggests an ion-pairing pre-equilibrium followed by rate limiting electron transfer to produce CrL{sub 3}{sup 2+} and CO{sub 2}{sup {minus}} can then react with ground state chromium(III) species to produce another mole of the reduced product or it can produce a secondary transient as in the case of phenanthroline and substituted phenanthroline complexes. The secondary transient reacts to produce CrL{sub 3}{sup 2+} in a subsequent reaction. 85 refs., 24 figs., 7 tabs.

  2. Effect of the Chromium Ion Adsorption on the Photoluminescent Properties of Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    V.V. Shimanovska

    2016-03-01

    Full Text Available We have studied the photoluminescence (PL of nanocrystalline titanium dioxide (TiO2, synthesized by the thermal hydrolysis in the form of anatase (A or rutile (R, the surface of which has been modified by adsorption of chromium ions (Cr3+. The samples were characterized by X-ray diffraction, X-ray fluorescence, Raman spectroscopy and optical absorption. PL spectra were excited by a nitrogen UV laser. It was found that the processes of the PL emission and optical absorption near the band gap edge of anatase and rutile TiO2 occur with the same electronic transitions. In the Cr3+-doped R/TiO2, the process of nonradiative Auger recombination leads to the quenching of the PL intensity. The Cr3+ ion doping in А/TiO2 leads to short-wave and long-wave shifts of the PL peaks due to the Burstein-Moss effect and due to the contribution of radiation "tails" of the electron density of states, respectively. PL intensity of the Cr3+-doped A/TiO2 at low concentration of Cr3+ (up to 0.5 at. % increases in comparison with the undoped A/TiO2 due to the formation of additional centers of radiative recombination of carriers. With increasing concentration of Cr3+ (~ 1.0 at. %, the TiO2 PL intensity decreases due to the concentration quenching.

  3. Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions.

    Science.gov (United States)

    Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

    2016-01-01

    In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater. PMID:27598142

  4. Coordination and ion-ion interactions of chromium centers in alkaline earth zinc borate glasses probed by electron paramagnetic resonance and optical spectroscopy

    Science.gov (United States)

    Sumalatha, B.; Omkaram, I.; Rajavardana Rao, T.; Linga Raju, Ch

    2013-05-01

    Electron paramagnetic resonance (EPR), optical absorption and FT-IR studies have been carried out on chromium ions incorporated in alkaline earth zinc borate glasses. The EPR spectra exhibit two resonance signals with effective g values at g ≈ 1.99 and ≈1.97. The resonance signal at g ≈ 1.99 is attributed to the contribution from both the exchange coupled Cr3+-Cr3+ ion pairs and the isolated Cr3+ ions and the resonance signal at g ≈ 1.97 is due to Cr5+ ions. The paramagnetic susceptibility (χ) was calculated from the EPR data at various (123-303 K) temperatures and the Curie temperature (θp) was calculated from the 1/χ-T graph. The optical absorption spectra exhibit three bands at ˜360 nm, ˜440 nm and a broad band at ˜615 nm characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal-field splitting parameter Dq and the Racah parameters (B and C) have been evaluated. From the ultraviolet edges, the optical band gap energies (Eopt) and Urbach energy (ΔE) are calculated. The theoretical optical basicity (Λth) of these glasses has also been evaluated. Chromium ions doped alkaline earth zinc borate glasses show BO3 and BO4 structural units in the FT-IR studies.

  5. Hydrophobic Poly(ionic liquid) for Highly Effective Separation of Methyl Blue and Chromium Ions from Water

    OpenAIRE

    Jie Kong; Hao Mi; Zhiguo Jiang

    2013-01-01

    The hydrophobic poly(ionic liquid) of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (PVI-TFSI) containing imidazolium cations and bis(trifluoromethanesulfonyl)imide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI)] from water. The adsorption of methyl blue and Cr(VI) in PVI-TSFI/water system reached equilibrium stage within 60 min and 12 h, and the maximum adsorbed percentage for methyl blue and Cr(VI) was 97.6% and 98.0%, respectively. ...

  6. Transformation of valence states and luminescence of chromium ions in the YAG:Cr, Mg and GGG:Cr, Mg single crystalline films

    Science.gov (United States)

    Zakharko, Ya. M.; Luchechko, A. P.; Syvorotka, I. M.; Syvorotka, I. I.; Ubizskii, S. B.; Melnyk, S. S.

    2005-01-01

    Peculiarities of absorption spectra and recombination luminescence of Y3Al5O12 (YAG) and Cd3Ga5O12 (GGG) single crystalline films co-doped with chromium and magnesium have been studied. The change of impurities concentration and annealing of samples in the reducing atmosphere have an influence on absorption in the visible and UV range. Using the results on absorption coefficient measurements in the band of 480 nm and in the absorption bands of Cr3+ ions, it was determined, that near 50% of the chromium ions located in octahedral sites are in the Cr4+ state in films with high chromium concentration. The investigation of thermostimulated luminescence confirms the existence of Cr2+ trap centres in the irradiated films caused by the magnesium dopant.

  7. Transformation of valence states and luminescence of chromium ions in the YAG:Cr, Mg and GGG:Cr, Mg single crystalline films

    International Nuclear Information System (INIS)

    Peculiarities of absorption spectra and recombination luminescence of Y3Al5O12 (YAG) and Cd3Ga5O12 (GGG) single crystalline films co-doped with chromium and magnesium have been studied. The change of impurities concentration and annealing of samples in the reducing atmosphere have an influence on absorption in the visible and UV range. Using the results on absorption coefficient measurements in the band of 480 nm and in the absorption bands of Cr3+ ions, it was determined, that near 50% of the chromium ions located in octahedral sites are in the Cr4+ state in films with high chromium concentration. The investigation of thermostimulated luminescence confirms the existence of Cr2+ trap centres in the irradiated films caused by the magnesium dopant. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Comparative Biosorption Studies of Hexavalent Chromium Ion onto Raw and Modified Palm Branches

    OpenAIRE

    Mona A. Shouman; Nady A. Fathy; Soheir A. Khedr; Amina A. Attia

    2013-01-01

    The waste of palm branches (PB) was tested for its ability to remove chromium (VI) from aqueous solution by batch and column experiments. Palm branches chemically modified with an oxidizing agent (sulphuric acid) then coated with chitosan and surfactant (hexadecyl trimethyl ammonium bromide surfactant, HDTMA), respectively, were carried out to improve the removal performance of PB. The results of their Cr (VI) removal performances are pH dependent. The adsorption data could be well interprete...

  9. Efficiencies and Optimization of Weak Base Anion Ion-Exchange Resin for Groundwater Hexavalent Chromium Removal at Hanford

    Energy Technology Data Exchange (ETDEWEB)

    Nesham, Dean O.; Ivarson, Kristine A.; Hanson, James P.; Miller, Charles W.; Meyers, P.; Jaschke, Naomi M.

    2014-02-03

    The U.S. Department of Energy’s (DOE’s) contractor, CH2M HILL Plateau Remediation Company, has successfully converted a series of groundwater treatment facilities to use a new treatment resin that is delivering more than $3 million in annual cost savings and efficiency in treating groundwater contamination at the DOE Hanford Site in southeastern Washington State. During the production era, the nuclear reactors at the Hanford Site required a continuous supply of high-quality cooling water during operations. Cooling water consumption ranged from about 151,417 to 378,541 L/min (40,000 to 100,000 gal/min) per reactor, depending on specific operating conditions. Water from the Columbia River was filtered and treated chemically prior to use as cooling water, including the addition of sodium dichromate as a corrosion inhibitor. Hexavalent chromium was the primary component of the sodium dichromate and was introduced into the groundwater at the Hanford Site as a result of planned and unplanned discharges from the reactors starting in 1944. Groundwater contamination by hexavalent chromium and other contaminants related to nuclear reactor operations resulted in the need for groundwater remedial actions within the Hanford Site reactor areas. Beginning in 1995, groundwater treatment methods were evaluated, leading to the use of pump-and-treat facilities with ion exchange using Dowex™ 21K, a regenerable, strong-base anion exchange resin. This required regeneration of the resin, which was performed offsite. In 2008, DOE recognized that regulatory agreements would require significant expansion for the groundwater chromium treatment capacity. As a result, CH2M HILL performed testing at the Hanford Site in 2009 and 2010 to demonstrate resin performance in the specific groundwater chemistry at different waste sites. The testing demonstrated that a weak-base anion, single-use resin, specifically ResinTech SIR-700 ®, was effective at removing chromium, had a significantly

  10. Glutamine-containing “turn-on” fluorescence sensor for the highly sensitive and selective detection of chromium (III) ion in water

    Science.gov (United States)

    Zhao, Meili; Ma, Liguo; Zhang, Min; Cao, Weiguang; Yang, Liting; Ma, Li-Jun

    2013-12-01

    In this study, we reported a new fluorescence sensor for chromium (III) ion, dansyl-L-glutamine (1). The sensor displayed a unique selective fluorescence “turn-on” response to Cr3+ over other common metal ions in water. Notably, 1 still showed a ratiometric response to Cr3+ in UV-vis absorption spectra. The binding mechanism of 1 to Cr3+ was further clarified by using NMR and ESI-MS spectra. The experiment results indicated that the dual-responses of 1 to Cr3+ should attribute to the coordination of deprotonated sulfonamide group with Cr3+ and the protonation of the dimethylamino group due to the coordination of Cr3+ for 1. In addition, two chloride ions also coordinated to the complex of sensor-chromium (III) ion, which further strengthened the conformation of 1-Cr3+.

  11. Dynamic adsorption of chromium ions onto natural and crosslinked chitosan membranes for wastewater treatment

    Directory of Open Access Journals (Sweden)

    Emerson Meneghetti

    2010-03-01

    Full Text Available Water pollution with heavy metals is a matter of major concern for public health and also for natural resource management. The present study investigated the effect of chemical modifications on biopolymeric adsorbents (based on chitosan membranes for chromium removal using fixed-bed dynamic adsorption technique. Parameters such as flow rate, initial concentration and crosslinking agents were evaluated, from a practical point-of-view, in order to optimize the adsorption capacity of natural, glutaraldehyde and epichlorohydrin crosslinked chitosan membranes. The adsorption capacity of natural and epiclorohydrin-crosslinked chitosan membranes were very close to each other; however, glutaraldehyde-crosslinked chitosan membranes presented nearly twice the adsorption capacity compared to the other membranes, being the most promising adsorbent in such mass-transfer systems.

  12. Comparative Biosorption Studies of Hexavalent Chromium Ion onto Raw and Modified Palm Branches

    Directory of Open Access Journals (Sweden)

    Mona A. Shouman

    2013-01-01

    Full Text Available The waste of palm branches (PB was tested for its ability to remove chromium (VI from aqueous solution by batch and column experiments. Palm branches chemically modified with an oxidizing agent (sulphuric acid then coated with chitosan and surfactant (hexadecyl trimethyl ammonium bromide surfactant, HDTMA, respectively, were carried out to improve the removal performance of PB. The results of their Cr (VI removal performances are pH dependent. The adsorption data could be well interpreted by the Langmuir, Freundlich, and Flory-Huggins isotherm models. The maximum adsorption capacity obtained from the Langmuir model for the chitosan coated oxidized palm branches is 55 mg/mg. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved. The biosorbents were successfully regenerated using 1 M HCL solution.

  13. Analysis of hexavalent chromium in Colla corii asini with on-line sample pretreatment valve-switching ion chromatography.

    Science.gov (United States)

    Yang, Yuling; He, Jie; Huang, Zhongping; Zhong, Naifei; Zhu, Zuoyi; Jiang, Renyu; You, Jinghua; Lu, Xiuyang; Zhu, Yan; He, Shiwei

    2013-08-30

    An ion chromatography (IC) system with on-line sample pretreatment using valve-switching technique was developed for the determination of hexavalent chromium (Cr(VI)) in Colla corii asini. Colla corii asini is a complicated sample with organics as main matrix. In this work, a polymer-based reversed-phase column was used as a pretreatment column. Via valve-switching technique, sample solution with target ions were eluted from a collection loop to analytical columns, with matrix eliminated on-line. Under the optimized separation conditions, the method showed good linearity (r=0.9998) in the range of 0.004-1.0mg/L and satisfactory repeatability (RSD<3%, n=6). The limit of detection (LOD) was 1.4μg/L (S/N=3). The average spiked recoveries of Cr(VI) were 93.4-102.0%. The result showed that the on-line sample pretreatment IC system was convenient and practical for the determination of trace Cr(VI) in Colla corii asini samples.

  14. Hydrophobic Poly(ionic liquid for Highly Effective Separation of Methyl Blue and Chromium Ions from Water

    Directory of Open Access Journals (Sweden)

    Jie Kong

    2013-10-01

    Full Text Available The hydrophobic poly(ionic liquid of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonylimide (PVI-TFSI containing imidazolium cations and bis(trifluoromethanesulfonylimide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI] from water. The adsorption of methyl blue and Cr(VI in PVI-TSFI/water system reached equilibrium stage within 60 min and 12 h, and the maximum adsorbed percentage for methyl blue and Cr(VI was 97.6% and 98.0%, respectively. The adsorption regi me of either methyl blue or Cr(VI for PVI-TFSI was in correspondence with the Langmuir adsorption model. The maximum adsorption capacity of PVI-TFSI for methyl blue and Cr(VI was determined as 476.2 and 17.9 mg/g, respectively. The hydrophobic poly(ionic liquid with a remarkable adsorbent capacity of methyl blue and Cr(VI can be conveniently synthesized and shows potential in water treatment for the effective separation of organic dyes or heavy metal ions.

  15. Solvent extraction of seven trivalent metal ions in aqueous perchlorate solutions with trioctylphosphine oxide in hexane and rapid extraction of chromium(III)

    International Nuclear Information System (INIS)

    Solvent extraction of scandium(III), yttrium(III), lanthanum(III), europium(III), gallium(III), indium(III), and chromium(III) in weakly acidified 1 mol dm-3 NaClO4 solutions with trioctylphosphine oxide (TOPO) in hexane was studied. The extraction equilibrium was established by the two phase agitation for within 3 min and the extracted species except chromium(III) were found to be M(TOPO)43+(ClO4-)3. The extraction of chromium(III) was also achieved by the two phase agitation for only a short time but, from the dependence of the extraction on the TOPO concentration, the extracted species was assumed to be Cr(TOPO)63+(ClO4-)3. Since the inert Cr(H2O)63+ was so rapidly extracted and the solvation number was higher than that of the other metal ions, the TOPO molecules were assumed to combine with the hydrating water molecules by hydrogen bonds which can be formed in a short time even when the metal ion was inert. The chromium(III) was also extracted rapidly from 1 mol dm-3 NaSCN, NaNO3, NaBr, and NaCl solutions with TOPO in hexane and the extraction was better from NaSCN solution than from NaClO4 solution but it was not effective from the solutions of other salts. (author)

  16. Bioremediation of Chromium ions with filamentous Yeast Trichosporon cutaneum R57

    Directory of Open Access Journals (Sweden)

    Ram Chandra Bajgai

    2012-01-01

    Full Text Available Heavy metal pollution is a serious environmental issue today. Recognizing the ability of microorganisms and biological materials to remove them from the polluted sites makes it cheaper method of heavy metal remediation. Microorganisms remove metals as a result of biosorption and bioaccumulation. In the present work, filamentous yeast Trichosporon cutaneum R57 was cultivated on batch in Andreev medium containing biotin, thiamine and glucose. Metal chromium was added in concentration ranging from 0-10mM (K2Cr2O7.7H2O to the culture during the stationary phase of the culture growth. Viability, glucose consumption and removal efficiency of the strain was studied. 1.5mM of K2Cr2O7.7H2O was found to be lethal to the strain, consumes maximum glucose at 5mM and removes maximum at 1mM concentration. Removal efficiency decreases with increase in metal concentration.

  17. Electronic structure and Fano antiresonance of chromium Cr(III) ions in alkali silicate glasses

    International Nuclear Information System (INIS)

    The optical properties of the Cr3+ doped in alkali silicate glasses X2O–SiO2 with different modifier cations X=Li, Na and K have been investigated by Villian et al. This work investigates a theoretical crystal-field analysis of the electronic energy levels of Cr3+ in these glasses. This analysis based on the Racah theory was carried out for the Chromium (III) center with an Oh site symmetry. The objective of this study is to determine the effect of glass matrix modifier on the Racah B, C and crystal-field Dq parameters. The effect of the glass matrix environment on these parameters is also reported by comparison with alkali cadmium borosulphate, phosphate and borate glasses. The interference dips observed in the broad band 4T2g(4F) result from interaction with the 2Eg(2G) and 2T1g(2G) sharp levels are known as the Fano antiresonance model. This feature is qualitatively studied using the adiabatic potential surfaces for the quartet 4T2g(4F) and doublet 2Eg(2G) levels. - Highlights: • The electronic structure of Cr3+ in alkali silicate glasses X2O–SiO2 (X=Li,Na,K) was performed. • The theoretical study, based on Racah theory, permits us to deduce the energy levels. • The observed interference dip in absorption spectra is related to Fano antiresonance

  18. Electronic structure and Fano antiresonance of chromium Cr(III) ions in alkali silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Taktak, Olfa, E-mail: taktak.olfa@gmail.com; Souissi, Hajer; Souha, Kammoun

    2015-05-15

    The optical properties of the Cr{sup 3+} doped in alkali silicate glasses X{sub 2}O–SiO{sub 2} with different modifier cations X=Li, Na and K have been investigated by Villian et al. This work investigates a theoretical crystal-field analysis of the electronic energy levels of Cr{sup 3+} in these glasses. This analysis based on the Racah theory was carried out for the Chromium (III) center with an O{sub h} site symmetry. The objective of this study is to determine the effect of glass matrix modifier on the Racah B, C and crystal-field Dq parameters. The effect of the glass matrix environment on these parameters is also reported by comparison with alkali cadmium borosulphate, phosphate and borate glasses. The interference dips observed in the broad band {sup 4}T{sub 2g}({sup 4}F) result from interaction with the {sup 2}E{sub g}({sup 2}G) and {sup 2}T{sub 1g}({sup 2}G) sharp levels are known as the Fano antiresonance model. This feature is qualitatively studied using the adiabatic potential surfaces for the quartet {sup 4}T{sub 2g}({sup 4}F) and doublet {sup 2}E{sub g}({sup 2}G) levels. - Highlights: • The electronic structure of Cr{sup 3+} in alkali silicate glasses X{sub 2}O–SiO{sub 2} (X=Li,Na,K) was performed. • The theoretical study, based on Racah theory, permits us to deduce the energy levels. • The observed interference dip in absorption spectra is related to Fano antiresonance.

  19. Coordination and ion–ion interactions of chromium centers in alkaline earth zinc borate glasses probed by electron paramagnetic resonance and optical spectroscopy

    International Nuclear Information System (INIS)

    Electron paramagnetic resonance (EPR), optical absorption and FT-IR studies have been carried out on chromium ions incorporated in alkaline earth zinc borate glasses. The EPR spectra exhibit two resonance signals with effective g values at g ≈ 1.99 and ≈1.97. The resonance signal at g ≈ 1.99 is attributed to the contribution from both the exchange coupled Cr3+–Cr3+ ion pairs and the isolated Cr3+ ions and the resonance signal at g ≈ 1.97 is due to Cr5+ ions. The paramagnetic susceptibility (χ) was calculated from the EPR data at various (123–303 K) temperatures and the Curie temperature (θp) was calculated from the 1/χ–T graph. The optical absorption spectra exhibit three bands at ∼360 nm, ∼440 nm and a broad band at ∼615 nm characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal-field splitting parameter Dq and the Racah parameters (B and C) have been evaluated. From the ultraviolet edges, the optical band gap energies (Eopt) and Urbach energy (ΔE) are calculated. The theoretical optical basicity (Λth) of these glasses has also been evaluated. Chromium ions doped alkaline earth zinc borate glasses show BO3 and BO4 structural units in the FT-IR studies. (paper)

  20. Removal of hexavalent chromium ions using CuO nanoparticles for water purification applications.

    Science.gov (United States)

    Gupta, Vinod Kumar; Chandra, Ramesh; Tyagi, Inderjeet; Verma, Monu

    2016-09-15

    Copper(II) oxide nanoparticles were synthesized at low temperature using cold finger assisted magnetron sputtering technique and were applied as adsorbent for the rapid removal of noxious Cr(VI) ions from the solvent phase. The average size of CuO nanoparticles from TEM analysis was found to be 8nm in addition to this the BET surface area (84.327m(2)/g) was found to be significantly high in comparison to the previously CuO nanoparticles synthesized via green route. The synthesized CuO nanoparticles is crystalline in nature and exhibits monoclinic phase, which was confirmed using various analytical techniques such as SAED, XRD and Raman analysis. The impact of influential parameters including pH, adsorbent dose, contact time, stirring speed, initial Cr(VI) ions concentration, and temperature were optimized using batch adsorption method in order to obtain maximum removal of Cr(VI) ions. From the thermodynamic parameters, the positive value of enthalpy (ΔH) and negative value of Gibbs free energy (ΔG) indicate the endothermic and spontaneous nature of Cr(VI) ions adsorption, respectively. The adsorption kinetics data was well fitted and found to be in good agreement with the pseudo second order kinetic behaviour. PMID:27285779

  1. 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.

  2. 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.

  3. 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...

  4. Transformation of valence states and luminescence of chromium ions in the YAG:Cr, Mg and GGG:Cr, Mg single crystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Zakharko, Ya.M.; Luchechko, A.P. [Faculty of Electronics, Ivan Franko National University of Lviv, 107 Tarnavskogo St., Lviv 79017 (Ukraine); Syvorotka, I.M.; Syvorotka, I.I.; Melnyk, S.S. [Institute for Materials SRC ' ' Carat' ' , 202 Stryjska St., Lviv 79031 (Ukraine); Ubizskii, S.B. [Institute for Materials SRC ' ' Carat' ' , 202 Stryjska St., Lviv 79031 (Ukraine); Institute for Telecommunication, Radioelectronics and Electronic Engineering, Lviv Polytechnic National University, 12 Bandera St., Lviv 79013 (Ukraine)

    2005-01-01

    Peculiarities of absorption spectra and recombination luminescence of Y{sub 3}Al{sub 5}O{sub 12} (YAG) and Cd{sub 3}Ga{sub 5}O{sub 12} (GGG) single crystalline films co-doped with chromium and magnesium have been studied. The change of impurities concentration and annealing of samples in the reducing atmosphere have an influence on absorption in the visible and UV range. Using the results on absorption coefficient measurements in the band of 480 nm and in the absorption bands of Cr{sup 3+} ions, it was determined, that near 50% of the chromium ions located in octahedral sites are in the Cr{sup 4+} state in films with high chromium concentration. The investigation of thermostimulated luminescence confirms the existence of Cr{sup 2+} trap centres in the irradiated films caused by the magnesium dopant. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Kappaphycus alvarezii waste biomass: A potential biosorbent for chromium ions removal

    Institute of Scientific and Technical Information of China (English)

    Oon Lee Kang; Nazaruddin Ramli; Mamot Said; Musa Ahmad; Suhaimi Md Yasir; Arbakariya Ariff

    2011-01-01

    The Cr(Ⅲ) sorption experiments onto Kappaphycus alvarezii waste biomass were conducted at different pH values (2-6) under the conditions of initial metal concentration of 10-50 mg/L and the chemical compositions of Cr-Cu and Ct-Cd.The Cr(Ⅲ) sorption capacities were slightly dependent on pH, and the maximum sorption capacity was 0.86 mg/g at pH 3.The sorption capacities increased with increase in the initial metal concentration, whereas it was suppressed by the presence of Cu(Ⅱ) and Cd(Ⅲ) in the solution.The Cr(Ⅲ) sorption equilibrium was evaluated using Langmuir, Freundlich and BET isotherms.The sorption mechanisms were characterised using scanning electron microscopy and Fourier transform infrared spectroscopy.The main mechanisms were ion exchange coupled with a complexation mechanism.Kappaphycus alvarezii waste biomass represents a potential for Ct(Ⅲ) ion removal from aqueous solution.

  6. Ion exchange separation of chromium from natural water matrix for stable isotope mass spectrometric analysis

    Science.gov (United States)

    Ball, J.W.; Bassett, R.L.

    2000-01-01

    A method has been developed for separating the Cr dissolved in natural water from matrix elements and determination of its stable isotope ratios using solid-source thermal-ionization mass spectrometry (TIMS). The separation method takes advantage of the existence of the oxidized form of Cr as an oxyanion to separate it from interfering cations using anion-exchange chromatography, and of the reduced form of Cr as a positively charged ion to separate it from interfering anions such as sulfate. Subsequent processing of the separated sample eliminates residual organic material for application to a solid source filament. Ratios for 53Cr/52Cr for National Institute of Standards and Technology Standard Reference Material 979 can be measured using the silica gel-boric acid technique with a filament-to-filament standard deviation in the mean 53Cr/52Cr ratio for 50 replicates of 0.00005 or less. (C) 2000 Elsevier Science B.V. All rights reserved.

  7. 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

  8. Impact of incorporation of chromium on electrochemical properties of LiFePO4/C for Li-ion batteries

    OpenAIRE

    Naik Amol; Zhou Jian; Gao Chao; Liu Guizhen; Wang Lin

    2015-01-01

    LiFe0.95Cr0.05PO4/C was successfully synthesized by one-step solid-state reaction using a single mode microwave reactor. The effect of incorporation of chromium on LiFePO4 lattice parameters was systematically investigated by X-ray diffraction. Surface analysis was done by scanning electron microscopy and transmission electron microscopy. The ratio of amorphous to graphitic carbon was determined from Raman spectroscopic data. The influence of chromium incorporation on electrochemical properti...

  9. Removal of hexavalent chromium ions by Yarrowia lipolytica cells modified with phyto-inspired Fe0/Fe3O4 nanoparticles

    Science.gov (United States)

    Rao, Ashit; Bankar, Ashok; Kumar, Ameeta Ravi; Gosavi, Suresh; Zinjarde, Smita

    2013-03-01

    The removal of hexavalent chromium [Cr (VI)], an important ground water pollutant by phyto-inspired Fe0/Fe3O4 nanocomposite-modified cells of Yarrowia lipolytica (NCIM 3589 and NCIM 3590), was investigated. Electron microscopy and magnetometer studies indicated an effective modification of yeast cell surfaces by the nanocomposites. The effect of pH, temperature, agitation speed, contact time and initial metal ion concentration on the removal of Cr (VI) was determined. The specific uptake values at pH 2.0 were 186.32 ± 3.17 and 137.31 ± 4.53 mg g- 1 for NCIM 3589 and NCIM 3590, respectively, when 1000 mg L- 1 of metal ion concentrations were used. The equilibrium data fitted to Scatchard, Langmuir and linearized Freundlich models suggesting that adsorption played a role in the removal of Cr (VI) ions. The surface modified yeast cells displayed higher values of Langmuir and Scatchard coefficients than the unmodified cells indicating that the former were more efficient in Cr (VI) removal. The enhanced detoxification of Cr (VI) ions by this composite material could be attributed to the reductive power of the Fe0/Fe3O4 nanocomposites as well the yeast cell surface functional groups.

  10. Impact of incorporation of chromium on electrochemical properties of LiFePO4/C for Li-ion batteries

    Directory of Open Access Journals (Sweden)

    Naik Amol

    2015-12-01

    Full Text Available LiFe0.95Cr0.05PO4/C was successfully synthesized by one-step solid-state reaction using a single mode microwave reactor. The effect of incorporation of chromium on LiFePO4 lattice parameters was systematically investigated by X-ray diffraction. Surface analysis was done by scanning electron microscopy and transmission electron microscopy. The ratio of amorphous to graphitic carbon was determined from Raman spectroscopic data. The influence of chromium incorporation on electrochemical properties was studied by recording charge/discharge cycles combined with electrochemical impedance spectroscopy (EIS and cyclic voltammetry. It was found that Cr incorporation significantly enhanced the electrochemical performance of LiFePO4 at all current densities up to 10 C. LiFe0.95Cr0.05PO4/C prepared exhibited the best performance with an initial specific discharge capacity of 157.7, 144.8, 138.3, 131.0, 124.1 and 111.1 mAh·g−1 at 0.1 C, 0.5 C, 1.0 C, 2.0 C, 5 C and 10 C, respectively. The doped sample displayed excellent capacity retention, which was substantially superior than that of pristine LiFePO4/C at a higher current rate.

  11. Simulated spatial and temporal dependence of chromium concentration in pure Fe and Fesbnd 14%Cr under high dpa ion irradiation

    Science.gov (United States)

    Vörtler, K.; Mamivand, M.; Barnard, L.; Szlufarska, I.; Garner, F. A.; Morgan, D.

    2016-10-01

    In this work we develop an ab initio informed rate theory model to track the spatial and temporal evolution of implanted ions (Cr+) in Fe and Fesbnd 14%Cr during high dose irradiation. We focus on the influence of the specimen surface, the depth dependence of ion-induced damage, the damage rate, and the consequences of ion implantation, all of which influence the depth dependence of alloy composition evolving with continued irradiation. We investigate chemical segregation effects in the material by considering the diffusion of the irradiation-induced defects. Moreover, we explore how temperature, grain size, grain boundary sink strength, and defect production bias modify the resulting distribution of alloy composition. Our results show that the implanted ion profile can be quite different than the predicted SRIM implantation profile due to radiation enhanced transport and segregation.

  12. The effects of alkaline earth metal ions and halogen ions on the chromium oxide activities in alkaline earth metal oxide-halide-Cr2O3 system fluxes

    Science.gov (United States)

    Li, Lian-Fu; Jiang, Mao-Fa; Wang, Wen-Zhong; Chen, Zhao-Ping

    2000-06-01

    The solid electrolyte cell — Mo|Cr + Cr2O3‖ZrO2(MgO)‖{Cu-Cr}alloy + (Cr2O3)fluxes|Mo+ is used at 1673 K to determine Cr2O3 activities in MO-MX 2-Cr2O3 (M = Ca2+, Ba2-, X = F- or Cl-) ternary fluxes, which are in equilibrium with the copper-chromium binary alloy. The ternary isothermal phase diagrams of CaO-CaF2-Cr2O3 and BaO-BaCl2-Cr2O3 system fluxes are inferred on the basis of the experimental results and binary phase diagrams. The results indicate that Cr2O3 activities in all fluxes always decrease with the increase of the X MO /X MX2 ratio. Partial replacement of BaO in BaO-BaF2-Cr2O3 fluxes by CaO is acceptable for economy and efficiency considerations. At the same time, partial substitution of BaO for CaO in CaO-CaF2-Cr2O3 fluxes is advantageous for phosphorus removal and chromium retention as a result of the increased Cr2O3 activities, increased basicities, and widening of the liquid zones. Compared to those in BaO-BaF2-Cr2O3 fluxes, Cr2O3 activities in CaO-CaF2-Cr2O3 fluxes approximately follow the same curve as the former, although the position and the width of the liquid zones are considerably different, and activities in BaO-BaCl2-Cr2O3 fluxes are higher at the lower Cr2O3 content, or vice versa. The activity coefficients of Cr2O3 in the fluxes decrease with the increase of the X MO /X MX 2 ratios.

  13. Synthesis of hydrophobic cross-linked polyzwitterionic acid for simultaneous sorption of Eriochrome black T and chromium ions from binary hazardous waters.

    Science.gov (United States)

    Saleh, Tawfik A; Muhammad, Auwal M; Ali, Shaikh A

    2016-04-15

    Hydrophobic cross-linked polyzwitterionic acid (HCPZA) containing long chain (C18) hydrophobes and residues of a glutamic acid having unquenched nitrogen valency was synthesized. Exploiting the chelating ability of the amino acid residues to scavenge toxic metals and the hydrophobic surface to scoop up the organic contaminants, the resin HCPZA was evaluated for simultaneous removal of chromium and Eriochrome black T (EBT) from wastewaters. The structure and morphology of the polymer before and after sorption were characterized by using FTIR, TGA, EDX and SEM. The effect of various parameters such as contact time, pH and initial concentrations were investigated to arrive at optimum conditions. The adsorption of Eriochrome black T and Cr (III) on HCPZA reached equilibrium in 30 min. The mechanism of adsorption was investigated using kinetic, diffusion and isotherm models. The adsorption kinetic data were described well by the pseudo-second order model and by the Freundlich isotherm model. EDX analysis confirmed the adsorption of Cr (III) and EBT on the polymer. The hydrophobic resin exhibited a remarkable simultaneous adsorption capacity for EBT and Cr (III) and thus demonstrated its potential to be a promising adsorbent for removal of dyes and heavy metal ions from wastewaters. PMID:26854746

  14. Synthesis of hydrophobic cross-linked polyzwitterionic acid for simultaneous sorption of Eriochrome black T and chromium ions from binary hazardous waters.

    Science.gov (United States)

    Saleh, Tawfik A; Muhammad, Auwal M; Ali, Shaikh A

    2016-04-15

    Hydrophobic cross-linked polyzwitterionic acid (HCPZA) containing long chain (C18) hydrophobes and residues of a glutamic acid having unquenched nitrogen valency was synthesized. Exploiting the chelating ability of the amino acid residues to scavenge toxic metals and the hydrophobic surface to scoop up the organic contaminants, the resin HCPZA was evaluated for simultaneous removal of chromium and Eriochrome black T (EBT) from wastewaters. The structure and morphology of the polymer before and after sorption were characterized by using FTIR, TGA, EDX and SEM. The effect of various parameters such as contact time, pH and initial concentrations were investigated to arrive at optimum conditions. The adsorption of Eriochrome black T and Cr (III) on HCPZA reached equilibrium in 30 min. The mechanism of adsorption was investigated using kinetic, diffusion and isotherm models. The adsorption kinetic data were described well by the pseudo-second order model and by the Freundlich isotherm model. EDX analysis confirmed the adsorption of Cr (III) and EBT on the polymer. The hydrophobic resin exhibited a remarkable simultaneous adsorption capacity for EBT and Cr (III) and thus demonstrated its potential to be a promising adsorbent for removal of dyes and heavy metal ions from wastewaters.

  15. THE IMPACT OF ACID ACTIVATION PARAMETERS OF DARK BROWN LOAM ON ITS SORPTION PROPERTIES TO CHROMIUM (III) IONS

    OpenAIRE

    Бовсуновський, Є.О.; Національний авіаційний університет; Рябчевський, О.В.; Національний авіаційний університет; Годовська, Ю.Я.; Національний авіаційний університет; Личманенко, О.Г.; Національний авіаційний університет

    2012-01-01

     Today the purification of waste water from heavy metals is an actual environmental problem, which is due to the existence of these different forms of pollution (in the form of salts, oxides etc.). The using of environmentally safe materials can be the direction of solution of this problem. One of them is a common natural sorbent - dark brown loam.  Large reserves of this material, cheapness, very high adsorption, ion exchange and filtration properties provide the practical and economic feasi...

  16. Speciation Analysis of Chromium in Cromium Slag and Adsorption of Chromium Ions on Activated Carbon%铬渣中铬的形态分析及活性炭对铬吸附影响因素的研究

    Institute of Scientific and Technical Information of China (English)

    廖伯凯; 张玉贵; 聂翠微; 毛磊; 童仕唐

    2013-01-01

    Speciation of Cr in Chromium slag was evaluated using a short three-step sequential extraction procedure with CaCl2, DTPA and TEA as leaching agent. In addition, the effects of the amount of activated carbon, the type of activated carbon, pH values of leaching agent, the temperature and time of adsorption on the adsorption of chromium were studied. The results showed that Chromium in the chromium slag mainly exists in the form of residual and mobilized fractions. The optimal adsorption conditions are as follows: the temperature is 20℃, pH value is 4, the amount of nitric acid modified activated carbon is 0.3 g / 3 g chromium slag, and adsorption time is 60 minutes.%以CaCl2,二乙基三胺五乙酸(DTPA)和三乙胺TEA(TEA)作为提取剂,用简化的3步连续提取法对铬渣中铬的形态进行分析,研究了活性炭的用量、活性炭的类型、浸提液pH值、吸附温度以及吸附时间对浸提液中的铬吸附的影响.结果表明,铬渣中的铬主要以可活动态和残渣态的形式存在.处理3 g铬渣,硝酸改性活性炭用量为0.3 g,在20℃,pH值为4,吸附时间为60 min时活性炭对铬的吸附效果最佳.

  17. 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 ...

  18. Chromium in diet

    Science.gov (United States)

    The best source of chromium is brewer's yeast. However, many people do not use brewer's yeast because it causes bloating ( abdominal distention ) and nausea . Other good sources of chromium include ...

  19. Analysis of molybdenum, chromium, vanadium and iron by polarographic techniques

    International Nuclear Information System (INIS)

    The application of direct current Tast polarograph, differential pulse polarography and phase-selective alternative current Tast polarography to the problem of determining molybdenum, chromium, vanadium and iron in various supporting electrolytes is reported. The effect of the supporting electrolyte on the wave/peak potential and sensitivity of the metal ion have been examined. The polarographic methods were applied for simultaneous determination of chromium (3)/chromium (6), vanadium (4), vanadium (5) and iron (2)/iron (3) in different supporting electrolytes

  20. Chromium and Genomic Stability

    OpenAIRE

    Wise, Sandra S.; Wise, John Pierce

    2011-01-01

    Many metals serve as micronutrients which protect against genomic instability. Chromium is most abundant in its trivalent and hexavalent forms. Trivalent chromium has historically been considered an essential element, though recent data indicate that while it can have pharmacological effects and value, it is not essential. There are no data indicating that trivalent chromium promotes genomic stability and, instead may promote genomic instability. Hexavalent chromium is widely accepted as high...

  1. Experimental skin deposition of chromium on the hands following handling of samples of leather and metal

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P.; Jellesen, Morten Stendahl;

    2016-01-01

    Background: Chromium is an important skin sensitizer. Exposure to it has been regulated in cement, and recently in leather. Studies on the deposition of chromium ions on the skin as a result of handling different chromium-containing materials are sparse, but could improve the risk assessment...... of contact sensitization and allergic contact dermatitis caused by chromium. Objectives: To determine whether the handling of chromium-containing samples of leather and metal results in the deposition of chromium onto the skin. Methods: Five healthy volunteers participated. For 30 min, they handled samples...... of leather and metal known to contain and release chromium. Skin deposition of chromium was assessed with the acid wipe sampling technique. Results: Acid wipe sampling of the participants' fingers showed chromium deposition on the skin in all participants who had been exposed to leather (range 0.01–0.20 µg...

  2. 不同形态铬离子与牛血清白蛋白结合的反应机制%Binding interaction mechanism between different forms of chromium ion and bovine serum albumin

    Institute of Scientific and Technical Information of China (English)

    郭明; 刘咪咪; 李铭慧; 许梦莹

    2013-01-01

    The binding reaction mechanism between different forms of chromium ion and bovine serum albumin (BSA) was investigated using affinity capillary electrophoresis ( ACE) method, and a comparative analysis was carried out. An interaction model of the ligand (Cr(Ⅲ) and Cr(Ⅵ)) binding with the receptor (BSA) was established under simulated physiological conditions. Based on the changes of effective mobility of BSA, the apparent binding constants of Cr( Ⅲ ) -BSA and chromium (Ⅵ) -BSA were calculated by a nonlinear fitting equation and the differences of binding reaction between chromium ( Ⅲ ) and chromium (Ⅵ) with BSA was quantificational characterized. The results showed that the obvious valence correlation existed between the binding reactions of Cr (Ⅲ ) , Cr (Ⅵ) and bovine serum albumin ( BSA ) , and with the changes of concentrations of Cr(Ⅲ ) and Cr(Ⅵ) , the obvious dose-effect relationship existed between metal Cr irons with BSA. A conclusion about a quick balance system of the binding reaction between Cr( Ⅲ ) and Cr(Ⅵ) with BSA was also acquired by analyzing electropherogram. This work has a referential meaning for the further analysis of the binding reaction mechanism of different metal iron forms and protein molecule.%利用亲和毛细管电泳法研究了不同形态铬离子与牛血清白蛋白(BSA)结合的反应机制并进行了比较分析.模拟生理条件下,构建配体Cr(Ⅲ)、Cr(Ⅵ)与受体(BSA)相互作用模型,依据BSA有效淌度的变化,通过非线性模拟方程计算Cr(Ⅲ)-BSA和Cr(Ⅵ)-BSA结合反应的表观结合常数KCr(M)-BSA、KCr(Ⅵ)-BSA,定量表征Cr(Ⅲ)、Cr(Ⅵ)与BSA结合反应的差异性.结果表明,CrⅢ)、Cr(Ⅵ)与BSA的结合反应与金属离子形态之间存在明显的价态相关性,而同一形态金属离子随着Cr(Ⅲ)、CrⅥ)浓度的变化与BSA均存在量效关系,同时通过解析电泳谱图获得了CrⅢ)、Cr(Ⅵ)与BSA结合反应均为快平衡体系的结论.

  3. Removal of Chromium and Lead from Industrial Wastewater Using

    Directory of Open Access Journals (Sweden)

    Mohamed Hilal

    2013-04-01

    Full Text Available In this research an attempt is made on the ability of aerobic treatment of synthetic solutions containing lead and chromium using effective microorganisms within the reactor. To achieve the desired objectives of the research, synthetic aqueous solutions of lead and chromium was used in the concentration of chromium and lead ions of 5, 10,50 and 100 mg / l .The work was done at constant pH equal to 4.5 and temperature of 30 ± 1 º C. Effective microorganisms solutions was added to the reactor at Vol.% of 1/50 ,1/100 ,1/500 and 1/1000, with retention time was 24 hours to measure the heavy metals concentration the atomic absorption device was used. The experimental results showed that each 1mg / l of lead and chromium ions need 24 mg of effective microorganisms to achieve removal of 92.0% and 82.60% for lead and chromium respectively. Increasing the concentration of effective microorganisms increases the surface of adsorption and thus increasing the removal efficiency. It is found that the microorganisms activity occur in the first five hours of processing and about 94% of adsorption capacity of biomass will take place. It is also found the selectivity of microorganisms to lead ions is higher than for chromium ions.

  4. 重金属铬离子对胎鼠及仔鼠发育的影响%Analysis on reproductive and developmental effects on pregnant mice and fetals after maternal exposure to chromium ions

    Institute of Scientific and Technical Information of China (English)

    张文彬; 刘璠

    2011-01-01

    Objective To investigate the effects of chromium ions on embryos of pregnant ICR mouse and the development of offspring,and to provide experimental basis Mr the possible impact on pregnancy of chromium ions after hip surface replacement. Methods 56 pregnant female ICR mice were divided into high,medium and low-dose groups as well as control group,14 mice in each group.The experimental groups were fed with different doses of potassium dichromate and treated.While the control group were fed with distilled water. 36 mice were sacrificed on the 19th day of pregnant. Implantation, luteal number, total litter birth weight, placental weight, number of living births, and stillbirths number were measured. As for the other 20 female Wistar mice, living birth number of offspring, sex ratio, body weight, body length, and tail length were observed and recorded. On the 42nd day, pups were sacrificed; the content of chromium in liver and serum was determined, and the liver tissue was taken for pathological examination. Results With the dose increased, the total number of implantation in the high dose group tended to decrease, compared with the control group. The high dose group had a lower embryo survival rate and higher embryo mortality than control group. Chromium content of serum and liver was higher in the high dose group than in the low dose group, and the difference was significant (P <0. 01) . Large particles appeared in the lipid droplets of liver cells in high dose group offspring, as well as chromosome concentration, and mitochondrial number reducing. Conclusion This study suggested low-dose chromium has no effect on offspring growth, high-dose chromium ions have more significant impact on pregnant mice and the development of offspring, and as for the offspring, the toxic effects still exist in vivo.%目的 探讨重金属铬离子对孕ICR小鼠胚胎以及仔鼠的发育影响,为行人工全髋关节表面置换术后重金属铬离子对妊娠机体可能产生的

  5. Substoichiometric extraction of chromium

    International Nuclear Information System (INIS)

    Substoichiometric extraction of chromium with tetraphenylarsonium chloride (TPACl), tri-n-octylamine (TNOA), diethylammonium diethyldithiocarbamate (DDDC) and ammonium pyrrolidinedithiocarbamate (APDC) was examined in detail. Chromium can be extracted substoichiometrically in a pH range, which is 1.1-2.6 for the TPACl compound, 0.6-2.3 for the TNOA compound, 5.1-6.4 for the DDDC chelate and 3.9-4.9 for the APDC chelate. Chromium in high-purity calcium carbonate, Orchard Leaves (NBS SRM-1571) and Brewers Yeast (NBS SRM-1569) was determined by neutron activation analysis combined with substoichiometric extraction by DDDC and APDC. The values of 2.0+-0.02 ppm and 2.6+-0.2 ppm were obtained for Brewers Yeast and Orchard Leaves, respectively. These values were in good agreement with those reported by NBS. The reaction mechanism and the reaction ratio between hexavalent chromium and dithiocarbamate are also discussed. (author)

  6. The carcinogenicity of chromium

    OpenAIRE

    Norseth, Tor

    1981-01-01

    The carcinogenicity of chromium compounds is reviewed with specific attention to the gaps in knowledge for risk estimation and research needs. The most important problems at present are whether trivalent chromium compounds cause cancer, and whether there is a difference in cancer causing effects between the soluble and the slightly soluble hexavalent compounds in the practical exposure situation. Dose estimates for risk estimation based on epidemiological investigations are also lacking. Pres...

  7. Fabrication, Validation, and Performance Evaluation of a New Sampling System for the In-Situ Chemical Speciation of Chromium Ions in Groundwater Using Supported Liquid Membranes (SLMs)

    OpenAIRE

    Owens, Lesley Shantell

    2013-01-01

    A sampler has been fabricated to facilitate the in-situ speciation of Cr. Teflon® was selected as the material for the samplers because of its inert chemical nature. The design of the sampler is based on the Supported Liquid Membrane (SLM) extraction technique, which utilizes charged organic carrier molecules loaded onto a polymeric (Teflon®) support membrane and the principles of electrostatics to selectively transport Cr ions through an ion-pairing mechanism. Cr ions in the feed solution th...

  8. Obtaining decorative chromium plating from trivalent chromium solutions

    OpenAIRE

    Óscar Javier Suárez García

    2010-01-01

    The present work was aimed at a qualitative evaluation, in the laboratory, of different alternatives for assembling and operating a trivalent chromium bath for decorative chromium plating. Different chromium concentration solutions and different complexing agents were used. The initial result of this analysis was that chloride, formate and acetate solutions produced the best results. Solution preparation conditions were evaluated: temperature, chromium III complex formation time and also ...

  9. The analytical biochemistry of chromium.

    OpenAIRE

    Katz, S A

    1991-01-01

    The essentiality and carcinogenicity of chromium depend on its chemical form. Oxidation state and solubility are particularly important in determining the biological effects of chromium compounds. For this reason, total chromium measurements are of little value in assessing its nutritional benefits or its toxicological hazards. Aqueous sodium carbonate-sodium hydroxide solutions have been successfully used for extracting hexavalent chromium from a variety of environmental and biological matri...

  10. Chromium in potatoes

    International Nuclear Information System (INIS)

    Chromium concentration in potatoes was determined, and tubes were labeled either intrinsically or extrinsically with radioactive chromate (51Cr). A labeled chromium complex was isolated from preparations of raw, baked, or fried potatoes and chromatographed on gel permeation media. Potato pulp and peel contained 1.63 and 2.70 μg of Cr/g tissue, respectively. There was no correlation between the two, nor did they respond similarly to changes of variety or locations. No significant differences were apparent in relative migration of the isolated complexes except between raw and cooked extrinsically labeled preparations

  11. Radiochemical Study on the Separation of Chromium-51 from the Irradiated Target by Using Commercial and/or Synthesized Ion Exchanger

    International Nuclear Information System (INIS)

    This work involves the following steps:1- Preparation of Triton X-100 Cerium(IV) Phosphate (TX-100CeP) as a surface active ion exchanger or organometallic molecules. 2- Characterization of the TX-100CeP by different methods (i.e. IR, TGA/DTA X-ray diffraction, X-ray fluorescence and elemental analysis). 3- Development a method for separation and quantification of Cr(III) and Cr(VI) by using high pressure liquid chromatography (HPLC). 4- Separation of 51Cr(III) from Cr(VI) in the target of K2CrO4 on TX-100CeP and Permutit as a commercial ion exchanger. 5- Quality control on the separated 51Cr(III).

  12. Suppression of interference in the AAS determination of chromium by use of ammonium bifluoride.

    Science.gov (United States)

    Purushottam, A; Naidu, P P; Lal, S S

    1973-07-01

    Addition of 1% of ammonium bifluoride successfully suppresses interference by diverse ions in the atomic-absorption determination of chromium(VI). If the sample solutions also contain chromium(III) addition of 1% of ammonium bifluoride and 0.2% of sodium sulphate is recommended for the suppression.

  13. 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...

  14. Simultaneous determination of migratory chromium species in toy materials by ion chromatography and ICP-MS%IC-ICP-MS联用法测定玩具材料中可迁移的六价铬与三价铬

    Institute of Scientific and Technical Information of China (English)

    林莉; 郑翊; 卫碧文; 于文佳; 陆文伟; 胡忠阳

    2013-01-01

    A method was developed for the determination of migratory Cr species by ion chromatography (IC)coupled with ICP-MS.Migratable chromium species were extracted by a stomach acid stimulant and then adjusted to neutral by ammonia.Using 0.07 mol/L NH4Cl as the mobile phase,Cr(Ⅲ) and Cr(Ⅵ) were seperated on an ion exchange column IonPac AG17C,and quantitative analysis was done by ICP-MS.The whole test lasted 5 minutes or so.Results of recovery test of real samples recovery test ranged between 90.0% and 105.4% with the RSD between 2.0% and 7.2%.The detection limits (S/N =3) were 0.25 μg/L for Cr(Ⅲ)and 0.039 μg/L for Cr(Ⅵ).%建立了一种IC与ICP-MS联用分析玩具材料中可迁移的Cr(Ⅲ)与Cr(Ⅵ)的分析方法.采用胃酸模拟溶液萃取玩具材料中的Cr (Ⅲ)与Cr(Ⅵ),萃取液用氨水调至中性,以NH4Cl为流动相,季铵盐离子交换柱为分离柱的离子色谱分离,最后用ICP-MS外标法定量.Cr(Ⅲ)和Cr(Ⅵ)的线性范围分别为0.05~5 mg/kg和0.005 ~0.5mg/kg;加标回收率90.0%~105.4%;RSD为2.0%~7.2%;Cr(Ⅲ)和Cr(Ⅵ)的检出限(S/N =3)分别为0.25 μg/L和0.029 μg/L.

  15. Ion nitriding post-oxidation as an alternative technique to electrolytic chromium; Nitruracion post-oxidacion ionica como tecnica alternativa al cromado electrolitico

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Guillen, J. C.; Granda-Gutierrez, E.E.; Campa-Castilla, A.; Perez-Aguilar, S.I.; Garza-Gomez, A.; Candelas-Ramirez, J.; Mendez-Mendez, R. [COMIMSA. Corporacion Mexicana de Investigacion en Materiales S.A. de C.V., Saltillo, Coahuila (Mexico)]. E-mail: jcarlos@comimsa.com

    2010-11-15

    The effect of temperature and processing time during post-oxidation on hardness and corrosion resistance of AISI 1045 samples treated through nitriding and post-oxidation in a pulsed plasma discharge is evaluated in this paper. Also, a comparative analysis of the mechanical properties obtained with the dual nitriding - post oxidation process versus those properties of typical hard chrome coatings was performed with an aim to propose an alternative technique to the processes of galvanic coatings. The latter revealed that the process of ion nitriding and post-oxidation provides similar properties in hardness and improves the corrosion resistance compared to the hard chrome case. It is conclude that the technique of ion nitriding and post-oxidation is a non environmental harmful technology with strong potential to replace highly polluting electroplating techniques for application of hard chrome coatings. [Spanish] En el presente trabajo se evalua el efecto del tiempo y la temperatura de post-oxidacion sobre las propiedades de dureza y resistencia a la corrosion de muestras de acero AISI 1045 sometido al proceso de nitruracion post-oxidacion ionica en plasmas pulsados. Asi mismo, con el objetivo de fundamentar la propuesta de utilizacion de la nitruracion post-oxidacion ionica como una tecnica alternativa a los procesos galvanicos para aplicacion de recubrimientos de cromo duro, se realizo un analisis comparativo de propiedades, evidenciando que, mediante el proceso nitruracion postoxidacion ionica, es posible obtener caracteristicas similares en dureza y mejores en resistencia a la corrosion que las tipicas obtenidas para el cromo duro. Los resultados obtenidos permiten postular una tecnica que no dana al medio ambiente, como lo es la nitruracion post-oxidacion ionica, como candidata potencial para sustituir las tecnicas galvanicas altamente contaminantes para aplicacion de cromo duro.

  16. The study and application of a new chromium(Ⅲ) ion selective electrode%一种新型的铬(Ⅲ)离子选择性电极的研制与应用

    Institute of Scientific and Technical Information of China (English)

    汪沂; 崔普选; 庞月建

    2012-01-01

      以水杨醛和硫代氨基脲合成的席夫碱水杨醛缩-硫代氨基脲为中性载体,将其与碳粉混合,以液体石蜡为粘合剂,制备了新型的铬(Ⅲ)离子选择性电极.在室温下,电极对Cr3+的能斯特响应浓度范围为4.00×10-7~1.00×10-2 mol/L,斜率为20.31 mV/dec,检测下限为1.58×10-7 mol/L.电极的响应时间小于20s,pH使用范围广(3.20~5.80),稳定性好,使用寿命长.在选定的条件下,用固定干扰离子法(FIM)考察了10余种离子的干扰情况,结果显示,电极对Cr3+具有较好的选择性.以该离子选择性电极为指示电极,饱和甘汞电极为参比电极,用直接电位法对废水中的Cr3+进行测定,结果令人满意.%  A sensitive film of carbon paste doped with a new schiff base Salicylaldehyde-Hydrazine-carboth-ioamide (SDHC, synthesized in the lab) as a carrier was prepared for development of a fresh chromium(Ⅲ) ion-se-lective electrode. The electrode exhibts Nernstian response to Cr(Ⅲ) over a range of 4.00×10-7~1.00×10-2 mol/L, with a slope of 20.31 mV per decade and a detection limit of 1.58 ×10-7 mol/L. It has a fast response time (less than 20 s) over the whole concentration range, and could be used for at least 2 weeks without any considerable diver-gences in its potentials. In the research, the potential of the electrode is independent of pH in the range of 3.20~5.80. The selectivity coefficient values of the proposed electrode as determined by mixed interference method(FIM) exhibits very good selectivity for Cr (Ⅲ) over a wide variety of common metal ions. Above all, the electrode has been successfully used as an indicator electrode in determining the chromium contents in the wastewater with the methord of potentiometry, and the result is excellent.

  17. A simple route to synthesize conductive stimuli-responsive polypyrrole nanocomposite hydrogel particles with strong magnetic properties and their performance for removal of hexavalent chromium ions from aqueous solution

    Science.gov (United States)

    Ahmad, Hasan; Rahman, Mohammad Mostafizar; Ali, Mohammad Azgar; Minami, Hideto; Tauer, Klaus; Gafur, Mohammad Abdul; Rahman, Mohammad Mahbubor

    2016-08-01

    A combination of maghemite polypyrrole (PPy/γ-Fe2O3) and stimuli-responsive properties in the same hydrogel microspheres is expected to enhance their application potential in various fields such as tissue engineering, regenerative medicine, biosensors, biomedical applications and removal of heavy metals from waste water, catalysis etc. In this investigation a simple two step process is used to prepare conductive stimuli-responsive polypyrrole (PPy) composite hydrogel particles with strong magnetic properties. Poly(styrene-methacrylic acid-N-isopropylacrylamide-polyethelene glycol methacrylate) or P(S-NIPAM-MAA-PEGMA) hydrogel seed particles are first prepared by soap-free precipitation copolymerization. The copolymer hydrogel particles exhibited both temperature- and pH-responsive volume phase transition. Conductive P(S-NIPAM-MAA-PEGMA)/PPy/γ-Fe2O3 nanocomposite hydrogel particles are then prepared by seeded chemical oxidative polymerization of pyrrole in the presence of P(S-NIPAM-MAA-PEGMA) hydrogel seed particles using FeCl3 as a oxidant and p-toluene sulfonic acid (p-TSA) as a dopant. In the reaction system FeCl3 functioned as a source of Fe(III) for the formation of γ-Fe2O3. This reaction also requires the initial presence of Fe(II) provided by the addition of FeCl2. The size and size distribution, surface structure, and morphology of the prepared conductive composite hydrogel particles are confirmed by FTIR, electron micrographs, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV-visible spectroscopy. The performance of nanocomposite hydrogel particles has been evaluated for the removal of hexavalent chromium (Cr) ions from water.

  18. Effect of low X-ray dose irradiation on properties triglycine sulfate doped by chromium

    CERN Document Server

    Kamysheva, L N; Golitsyna, O M

    2002-01-01

    One studied effect of X-ray low dose on pulse re-polarization in triglycine sulfate crystals (TGS) with various concentration of chromium ions. It is shown that within 20.0 deg C-T sub c temperature range alpha activation field values depend unambiguously on radiation dose for various polarity switching current pulses. One detected decrease of unipolarity of TGS crystal caused by chromium ions due to interaction of radiation defects with impurity ones

  19. Performance of Laterite Soil Grains as Adsorbent in the Removal of Chromium

    OpenAIRE

    Syama I J; Arun Kumar Thalla; Manu D S

    2015-01-01

    The present study aims to examine the efficiency of laterite grains (LG) and acid activated laterite grains (AALG) as an adsorbent for removal hexavalent chromium and ferric ion from synthetic wastewater, under laboratory conditions. Adsorption of hexavalent chromium and ferric ion from synthetic wastewater is examined by batch and column studies wherein it is found to be dependent on pH, Contact time, adsorbent dosage and initial adsorbate concentration. Percentage removal enhances with the ...

  20. Dimensionally Controlled Lithiation of Chromium Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Fister, Tim T. [Argonne National Lab. (ANL), Argonne, IL (United States); Hu, Xianyi [Northwestern Univ., Evanston, IL (United States); Esbenshade, Jennifer [Univ. of Illinois, Urbana-Champaign, IL (United States); Chen, Xiao [Northwestern Univ., Evanston, IL (United States); Wu, Jinsong [Northwestern Univ., Evanston, IL (United States); Dravid, Vinayak [Northwestern Univ., Evanston, IL (United States); Bedzyk, Michael [Northwestern Univ., Evanston, IL (United States); Long, Brandon [Argonne National Lab. (ANL), Argonne, IL (United States); Gewirth, Andrew A. [Univ. of Illinois, Urbana-Champaign, IL (United States); Shi, Bing [Argonne National Lab. (ANL), Argonne, IL (United States); Schlepütz, Christian M. [Argonne National Lab. (ANL), Argonne, IL (United States); Fenter, Paul [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-12

    Oxide conversion reactions are an alternative approach for high capacity lithium ion batteries but are known to suffer from structural irreversibility associated with the phase separation and reconstitution of reduced metal species and Li2O. In particular, the morphology of the reduced metal species is thought to play a critical role in the electrochemical properties of a conversion material. Here we use a model electrode with alternating layers of chromium and chromium oxide to better understand and control these phase changes in real-time and at molecular length scales. Despite lacking crystallinity at the atomic scale, this superstructure is observed (with X-ray reflectivity, XR) to lithiate and delithiate in a purely one-dimensional manner, preserving the layered structure. The XR data show that the metal layers act as nucleation sites for the reduction of chromium in the conversion reaction. Irreversibility during delithiation is due to the formation of a ternary phase, LiCrO2, which can be further delithiated at higher potentials. The results reveal that the combination of confining lithiation to nanoscale sheets of Li2O and the availability of reaction sites in the metal layers in the layered structure is a strategy for improving the reversibility and mass transport properties that can be used in a wide range of conversion materials.

  1. Biosorption and biotransformation of chromium by Serratia sp. isolated from tannery effluent.

    Science.gov (United States)

    Srivastava, Shaili; Thakur, Indu Shekhar

    2012-01-01

    A bacterium isolated from soil and sediment ofa leather tanning mill's effluent was identified as Serratia sp. by the analysis of 16S rDNA. Scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) and transmission electron microscopy (TEM) were used to assess morphological changes and confirm chromium biosorption in Serratia sp. both in a shake-flask culture containing chromium and in a tannery wastewater. The SEMEDX and the elemental analysis of the chromate-containing samples confirmed the binding of chromium with the bacterial biomass. The TEM exhibited chromium accumulation throughout the bacterial cell, with some granular deposits in the cell periphery and in the cytoplasm. X-ray diffraction analysis (XRD) was used to quantify the chromium and to determine the chemical nature of the metal-microbe interaction. The XRD data showed the crystalline character of the precipitates, which consisted of mainly calcium chromium oxide, chromium fluoride phosphate and related organo-Cr(III) complex crystals. The XRD data also revealed a strong involvement of cellular carboxyl and phosphate groups in chromium binding by the bacterial biomass. The results of the study indicated that a combined mechanism of ion-exchange, complexation, croprecipitation and immobilization was involved in the biosorption of chromium by bacterial cells in contaminated environments. PMID:22519094

  2. Groundwater contaminant by hexavalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, C. [Univ. of Texas, Austin, TX (United States)

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  3. A study of the process of desorption of hexavalent chromium

    Directory of Open Access Journals (Sweden)

    W.B. Amorim

    2003-09-01

    Full Text Available In this work the process of desorption of hexavalent chromium, a toxic metal ion, from the marine algae Sargassum sp, following biosorption experiments 2³ factorial design was studied. A technique was applied to three eluents: HCl, H2SO4 and EDTA. Three factors of importance were evaluated: concentration of eluent, the ratio between mass of biosorbent and volume of eluent (S/L and process time. A statistical analysis of the experimental results showed that the three variables evaluated are significant for all three eluents. The models for chromium desorption were validated, as the results agreed well with the observed values. Through use of the response surface methodology, a factorial design based optimization technique; it was possible to identify the most suitable eluent and the interval of values for the process variables that resulted in the most significant desorption of chromium, which is relevant information for work aiming at process optimization.

  4. Highly efficient and recyclable triple-shelled Ag@Fe3O4@SiO2@TiO2 photocatalysts for degradation of organic pollutants and reduction of hexavalent chromium ions

    Science.gov (United States)

    Su, Jianwei; Zhang, Yunxia; Xu, Sichao; Wang, Shuan; Ding, Hualin; Pan, Shusheng; Wang, Guozhong; Li, Guanghai; Zhao, Huijun

    2014-04-01

    Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2 (P25), pure TiO2 microspheres, Fe3O4@SiO2@TiO2 and annealed Ag@Fe3O4@SiO2@TiO2 nanocomposites, the as-obtained amorphous triple-shelled Ag@Fe3O4@SiO2@TiO2 hierarchical nanospheres exhibit a markedly enhanced visible light or sunlight photocatalytic activity towards the photodegradation of methylene blue and photoreduction of hexavalent chromium ions in wastewater. The outstanding photocatalytic activities of the plasmonic photocatalyst are mainly due to the enhanced light harvesting, reduced transport paths for both mass and charge transport, reduced recombination probability of photogenerated electrons/holes, near field electromagnetic enhancement and efficient scattering from the plasmonic nanostructure, increased surface-to-volume ratio and active sites in three dimensional (3D) hierarchical porous nanostructures, and improved photo/chemical stability. More importantly, the hierarchical nanostructured Ag@Fe3O4@SiO2@TiO2 photocatalysts could be easily collected and separated by applying an external magnetic field and reused at least five times without any appreciable reduction in photocatalytic efficiency. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, make these multifunctional nanostructures promising candidates to remediate aquatic contaminants and meet the demands of future environmental issues.Herein, we demonstrate the design and fabrication of the well-defined triple-shelled Ag@Fe3O4@SiO2@TiO2 nanospheres with burr-shaped hierarchical structures, in which the multiple distinct functional components are integrated wonderfully into a single nanostructure. In comparison with commercial TiO2

  5. 自动电位滴定法测定工业铬酸酐中氯离子含量方法研究%The Research Method to Determine Chloride Ion Content in Chromium Trioxide for Industrial Use with Automatic Potentiometric Titration

    Institute of Scientific and Technical Information of China (English)

    胡清启; 孙宁

    2015-01-01

    用乙醇作还原剂,将铬酸酐中CrO42-还原为Cr3+,再用硝酸银标准溶液滴定,以电位变化率最大点确定反应终点,求出氯离子含量。就精密度和加标回收进行实验,并对方法展开分析与讨论,该方法的建立对工业生产铬酸酐中氯离子指标的控制具有指导意义。%Reduce the CrO42+to Cr3+in chromium trioxide with ethanol as the reductant ,then determine the content of chloride ion using AgNO3 standard solution to titrate to the end point that has a biggest change of potential. Conduct an experiment for calculating the precision and standard addition recovery of the method,and then analysis and discuss about the method.This method has a guiding significance for controlling the content of chloride ion in the industrial production of chromium trioxide.

  6. On texture formation of chromium electrodeposits

    DEFF Research Database (Denmark)

    Nielsen, Christian Bergenstof; Leisner, Peter; Horsewell, Andy

    1998-01-01

    The microstructure, texture and hardness of electrodeposited hard, direct current (DC) chromium and pulsed reversed chromium has been investigated. These investigations suggest that the growth and texture of hard chromium is controlled by inhibition processes and reactions. Further, it has been e...... established that codeposition of Cr2O3 nanoparticles is a general feature of DC chromium electrodeposition....

  7. 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

  8. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Gonzalez, Sergio Efrain [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Carbajal-Arizaga, Gregorio Guadalupe [Departamento de Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Manriquez-Gonzalez, Ricardo [Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Km 15.5, carretera Guadalajara-Nogales, Las Agujas, C.P. 45020 Zapopan, Jalisco (Mexico); De la Cruz-Hernandez, Wencel [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 carretera Tijuana-Ensenada, C.P. 22830 Ensenada, Baja California (Mexico); Gomez-Salazar, Sergio, E-mail: sergio.gomez@cucei.udg.mx [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico)

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  9. Chromium trace determination in inorganic, organic and aqueous samples with isotope dilution mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Goetz, A.; Heumann, K.G.

    1988-06-01

    It is shown that chromium traces in different inorganic, organic and aqueous samples can be determined over a wide concentration range with isotope dilution mass spectrometry. Electrolytic or chromatographic isolation steps are added to a system of sample preparation units for oligo-element determinations to analyse chromium besides other heavy metals. The isotope ratio /sup 52/Cr//sup 53/Cr is measured in a thermal quadrupole mass spectrometer using a single-filament ion source with additions of silica gel and boric acid. In water samples, which contain humic substances, chromium concentrations of a few ng/g and less can be determined with relative standard deviations of about 1% and better. A differentiation is possible into the total chromium content and into chromium species which carry out isotope exchange reactions and those which are inert for an isotope exchange reaction. The chromium concentrations of four standard reference materials (two plants BCR 60 and 61, one tissue BCR 278, one sewage sludge BCR 144), which are not certified for chromium, are determined to be 29.4 ..mu..g/g, 534 ..mu..g/g, 0.78 ..mu..g/g, and 466.1 ..mu..g/g, respectively. In three different sediments total chromium concentrations between 100 ..mu..g/g and 180 ..mu..g/g are analysed with relative standard deviations of 0.6%-1.2%.

  10. Hexavalent chromium removal from wastewater using aniline formaldehyde condensate coated silica gel.

    Science.gov (United States)

    Kumar, P Albino; Ray, Manabendra; Chakraborty, Saswati

    2007-05-01

    A resinous polymer, aniline formaldehyde condensate (AFC) coated on silica gel was used as an adsorbent in batch system for removal of hexavalent chromium from aqueous solution by considering the effects of various parameters like reaction pH, dose of AFC coated silica gel, initial Cr(VI) concentration and aniline to formaldehyde ratio in AFC synthesis. The optimum pH for total chromium [Cr(VI) and Cr(III)] adsorption was observed as 3. Total chromium adsorption was second order and equilibrium was achieved within 90-120 min. Aniline to formaldehyde ratio of 1.6:1 during AFC synthesis was ideal for chromium removal. Total chromium adsorption followed Freundlich's isotherm with adsorption capacity of 65 mg/g at initial Cr(VI) 200mg/L. Total chromium removal was explained as combinations of electrostatic attraction of acid chromate ion by protonated AFC, reduction of Cr(VI) to Cr(III) and bond formation of Cr(III) with nitrogen atom of AFC. Almost 40-84% of adsorbed chromium was recovered during desorption by NaOH, EDTA and mineral acids. AFC coated silica gel can be effectively used for treatment of chromium containing wastewaters as an alternative.

  11. 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.

  12. Study of the mechanism of chromium cluster formation by laser microprobe mass spectrometry. Correlation with theoretical computations

    Science.gov (United States)

    Hachimi, A.; Poitevin, E.; Krier, G.; Muller, J. F.; Ruiz-Lopez, M. F.

    1995-05-01

    Different stoichiometries of micrometric particles of powdered chromium oxides and salts are examined by time-of-flight laser microprobe mass spectrometry (TOF-LMMS). The negative cluster ion distributions show a good correlation with the stoichiometry of the chromium in the oxide. We have noticed a great spectral similarity between chromium(VI) oxide and hydrated chromium(III), salts leading to difficulties in differentiating these two kinds of compounds and determining the valency of chromium. The formation of CrO4- ions could be associated with product hydration, and could modify the fingerprint spectra of the chromium oxides and salts. We demonstrate that the CrO4- ion arises from collision between molecules present in the plasma generated by laser ablation. The mechanism of cluster formation is closely associated with the presence of neutral or ionized species (water, sulfate, nitrate, etc.). In particular, the hydration effect is very marked in the initial chromium salt. To confirm these results, an FT ion cyclotron MS investigation has been carried out, which allowed determination of the laser power dependence and relative stability of CrO-, CrO-2 and CrO3-. Results from a theoretical study of these types of cluster ions are presented and compared with the experimental data.

  13. Removal of chromium complex dye from aqueous solutions using strongly basic and weakly basic anion exchangers

    OpenAIRE

    Kauspediene, D.; Kazlauskiene E.; Selskiene, A.

    2010-01-01

    Removal of chromium complex dye from aqueous solutions by sorption onto a weakly basic, acrylic matrix anion exchanger Purolite A845 and a strongly basic, polystyrene matrix anion exchanger Purolite A 500P has been investigated under various experimental conditions: the initial dye concentration, pH and temperature. The sorption of chromium complex dye proceeds as a result of miscellaneous interactions between the dye and anion exchanger: ion exchange and physical sorption. The removal effici...

  14. Self-focusing in chromium-doped potassium niobate single ceramic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Castillo T, J.; Gonzalez M, S.; Aguirre L, A.; Hernandez, M.B.; Aguilar M, J.A. [Instituto de Fisica y Matematicas, Universidad Tecnologica de la Mixteca, 69000, Huajuapan de Leon, Oaxaca (Mexico); Hernandez A, J. [lFUNAM, PO Box 20-364, 01000 Mexico, DF (Mexico)]. e-mail: jaimec@mixteco.utm.mx

    2006-07-01

    The self-focusing and nonlinear optical absorption in a chromium-doped potassium niobate single ceramic crystal have been investigated. The third-order electric susceptibility X{sup (3)} at continuous 532 nm radiation is estimated based on a band transport model describing photo refractive properties for this electro-optic material. An anisotropic behavior on its nonlinear optical absorption properties has also been observed due to the presence of chromium ions. (Author)

  15. Efficacy of Agricultural Wastes in the Removal of Hexavalent Chromium- A Review.

    OpenAIRE

    N Muthulakshmi Andal; S. Charulatha

    2013-01-01

    Hexavalent Chromium is a major pollutant released during several industrial operations. It is also reported as one of the metals known to be carcinogenic and has an adverse potential to modify the DNA transcription process. The removal of hexavalent chromium has been studied by various authors employing adsorbents developed from waste agro by-products to assess their adsorption characteristics. This paper focuses on the comparison of some agro based products in the removal of Cr(VI) ions. An ...

  16. Galvanic cells including cobalt-chromium alloys.

    Science.gov (United States)

    Gjerdet, N R

    1980-01-01

    Galvanic cells may be created when dentures made of cobalt-chromium alloys are placed on teeth with metallic restorations. The power of such cells was evaluated in an in vitro galvanic using amalgams, gold alloy, and nickel-chromium alloys. The amalgams and one of the nickel-chromium alloys revealed high corrosion currents when placed in contact with cobalt-chromium alloy, the conventional amalgam showing the highest values. The gold alloy and another nickel-chromium alloy exhibited low corrosion currents and they were noble with respect to cobalt-chromium.

  17. Serum chromium levels sampled with steel needle versus plastic IV cannula. Does method matter?

    DEFF Research Database (Denmark)

    Penny, Jeannette Ø; Overgaard, Søren

    2010-01-01

    PURPOSE: Modern metal-on-metal (MoM) joint articulations releases metal ions to the body. Research tries to establish how much this elevates metal ion levels and whether it causes adverse effects. The steel needle that samples the blood may introduce additional chromium to the sample thereby caus...

  18. Hydrogen permeation through chromium

    International Nuclear Information System (INIS)

    Steady state and non-steady state measurements of hydrogen permeation through metallic chromium are reported. The experiments have been conducted by use of hydrogen and deuterium within a pressure range of 10-8 - 1 bar and temperatures between 600 - 8000C. Numerical values for the physical quantities permeability, diffusion constant and solubility could be derived. At an upstream pressure above around 10-3 bar classical Sieverts-low was found (permeation rate proportional √p) with activation energies Qsub(perm) = 65 kJoule/mole, Qsub(Diff) = 4-8 kJoule/mole, Qsub(Sol) = 57-61 kJoule/mole for the respective processes involved. The isotopic effect between H and D of the permeabilities could be represented by a factor of 1,5 independence on temperature. All non steady-state measurements could be approximated reasonably well by classical diffusion kinetics. Below up-stream pressures of approx.= 10-7 bar the kinetics was no longer diffusion controlled, the dependence on up-stream pressure changed from √p -> p, the activation energy for permetation increased to 127 kJoule/mole and the isotopic factor resulted in about 2-3. (orig.)

  19. 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

  20. Iron monosulfide as a scavenger for dissolved hexavalent chromium and cadmium.

    Science.gov (United States)

    Jo, S; Lee, J Y; Kong, S H; Choi, J; Park, J W

    2008-09-01

    Iron sulfide minerals are common components of soil/sedimentary environments. Reactions near the surfaces of iron sulfides play important roles in metal retention, mobility, and bioavailability. A series of batch experiments was conducted to study the removal of aqueous chromium and cadmium by iron monosulfide. Hexavalent chromium was reduced to Cr(III) by iron monosulfide with simultaneous precipitation of chromium and iron oxyhydroxide. In contrast to chromium, the primary retention mechanism of cadmium by iron monosulfide was lattice exchange. Surface adsorption to iron monosulfide and precipitation with sulfide on the iron monosulfide surface also contributed to the removal of aqueous cadmium. New phases of both chromium and cadmium were confirmed with transmission electron microscopy. The solution pH was an important factor in this research; it can change particle surface charge and metal species, hence affecting the removal of chromium, but not cadmium. Ferrous ions without FeS exhibited less Cr(VI) removal than with FeS, which might be owing to sulfides from FeS and the existence of the solid phase. Iron monosulfide exhibited higher removal efficiency for chromium and cadmium than zero valent iron and other iron oxide minerals, and the synergistic effect of ferrous iron and sulfide appeared to cause this result.

  1. Chromium(III) -- chromium(VI) interconversions in seawater

    NARCIS (Netherlands)

    Weijden, C.H. van der; Reith, M.

    1982-01-01

    The stable form of dissolved chromium in oxygenated seawater is Cr(VI). But Cr(III)-species are also present at an analytically significant level. It is shown that Cr(III) is oxidized only slowly by dissolved oxygen, and that manganese oxide is a strong catalyst for such oxidation. However, the low

  2. The effect of hydrogen peroxide on the electrochemical corrosion properties and metal ions release of nickel-chromium dental alloys%H2O2对镍铬合金电化学腐蚀性能及离子析出的影响

    Institute of Scientific and Technical Information of China (English)

    王珏; 乔广艳

    2013-01-01

    PURPOSE: To investigate the effect of hydrogen peroxide on the electrochemical corrosion and metal ions release of nickel-chromium dental alloys. METHODS: The corrosion resistance of nickel-chromium dental alloys was compared by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PD) methods in artificial saliva after immersed in different concentrations of hydrogen peroxide for 112 h. The metal ions released from nickel-chromium dental alloys to the artificial saliva were detected after electrochemical measurements using inductively coupled plasma mass spectrometry (ICP-MS). The data was statistically analyzed by analysis of variance (ANOVA) using SPSS 13.0 software package. RESULTS: The electrochemical experiment showed that the sequence of polarization resistance in equivalent circuit (Rct), corrosion potential (Ecorr), pitting breakdown potential (Eb), and the difference between Ecorr and Eb representing the "pseudo-passivation" (△E) of nickel-chromium alloys in artificial saliva was 30% < 10% < 0%(P<0.05). Furthermore, the metal ions including Ni, Cr, and Mo were released from the Ni-Cr alloys to the artificial saliva, and the order of the concentrations of metal ions was 0% < 10% < 30% (P<0.05). CONCLUSIONS: The corrosion resistance of nickel-chromium dental alloys decrease after immersed in different concentrations of hydrogen peroxide for 112 h. Nickel-chromium dental alloys are more prone to corrosion in the artificial saliva with the concentration of hydrogen peroxide increased, and more metal ions are released in the artificial saliva. Supported by Natural Science Foundation of Shanghai Municipality (12ZR1427200), Shanghai Municipal Health Bureau Fund (20124172) and Shanghai Municipal Health Bureau Youth Fund (20114Y053).%目的:比较不同浓度H2O2对镍铬合金电化学腐蚀性能及离子析出的影响.方法:应用电化学工作站的电化学阻抗谱法和动电位极化曲线法,对不同浓度H2O2浸泡112

  3. Determination of chromium combined with DNA, RNA and protein in chromium-rich brewer's yeast

    International Nuclear Information System (INIS)

    The contents of chromium in the DNA, RNA and protein fractions separated from chromium-rich and normal brewer's yeast were determined with the neutron activation analysis in order to study the combination of Cr with DNA, RNA and protein in chromium-rich brewer's yeast. The results showed that the extracting rats and concentrations of DNA, RNA and protein had no significant difference in two types of yeast, but the chromium contents of DNA, RNA and protein in the chromium-rich yeast were significantly higher than those in the normal. In addition, the content of chromium in DNA was much higher than that in RNA and protein, which indicated that the inorganic chromium compounds entered into the yeast cell, during the yeast cultivation in the culture medium containing chromium were converted into organic chromium compounds combined with DNA, RNA and protein

  4. BWR chromium chemistry

    International Nuclear Information System (INIS)

    This report addresses the concern about higher total specific conductivity in the reactor recirculation loop water due to the chromate ion. This concern is particularly high at plants where all other ionic species have been reduced through careful attention to makeup and condensate polisher operations. An EPRI Chromate Workshop was held in November 1990 to consider the issues raised by observed levels of chromate ion (generally 5 to 50 ppB). While BWRs on normal water chemistry were the only ones observing chromate, even plants on hydrogen water chemistry (HWC) observe sharp spikes of conductivity due to chromate whenever the hydrogen supply was interrupted after a reasonably long HWC operational period. The consensus of the workshop attendees was that chromate was not a concern as an agent causing pipe cracking compared to the more common species such as chloride and sulfate. However, the data are somewhat ambiguous for levels of chromate above 50 ppB. Adjustments to the weighing factors for the various ionic species in the industry chemistry performance index are suggested to allow for the known relative higher aggressiveness of other species relative to that of chromate

  5. Influence of the chromium and ytterbium co-doping on the photoluminescence of zinc selenide crystals

    Institute of Scientific and Technical Information of China (English)

    I Radevici

    2014-01-01

    The luminescent properties of ZnSe, ZnSe:Cr (0.05 at.%Cr), ZnSe:Yb (0.03 at.%Yb) and ZnSe:Cr:Yb (0.05 at.%Cr, 0.05 at.%Yb) crystals, doped during the growth process by the chemical vapor transport method, were studied within the temperature in-terval of 6-300 K. At the 6 K temperature in the visible spectral range 2 bands were observed:a band in the excitonic spectral region and a band of self-activated luminescence. It was shown that co-doping of zinc selenide crystals with the chromium and ytterbium led to the combination of the impurities influence on the photoluminescent properties. At the liquid helium temperature in the middle in-frared range of the spectra of the ytterbium and chromium co-doped crystal a band with the maximum localized at 1.7 µm was ob-served, which was overlapped with a complex band in the middle-IR spectral range, characteristic for the chromium doped ZnSe crys-tals. On the basis of obtained data an interaction mechanism of the chromium and ytterbium co-doping impurities was proposed. Guided by the existent model of the ytterbium ion incorporation in the selenide sublattice of the ZnSe crystals, an assumption about stabilization of single charged chromium ions in the zinc sublattice crystal nodes, by means of formation of the local charge compen-sating clusters, was made. It was assumed that the resonant energy transfer from one chromium ion to another, which led to the con-centration quenching of the IR emission in the ZnSe:Cr PL spectra, would lead to the broadening of the IR emission in the spectra of ytterbium and chromium co-doped zinc selenide crystals.

  6. Selective and sensitive detection of chromium(VI) in waters using electrospray ionization mass spectrometry.

    Science.gov (United States)

    Weldy, Effie; Wolff, Chloe; Miao, Zhixin; Chen, Hao

    2013-09-01

    From 2000 through 2011, there were 14 criminal cases of violations of the Clean Water Act involving the discharge of chromium, a toxic heavy metal, into drinking and surface water sources. As chromium(VI), a potential carcinogen present in the environment, represents a significant safety concern, it is currently the subject of an EPA health risk assessment. Therefore, sensitive and selective detection of this species is highly desired. This study reports the analysis of chromium(VI) in water samples by electrospray ionization mass spectrometry (ESI-MS) following its reduction and complexation with ammonium pyrrolidinedithiocarbamate (APDC). The reduction and subsequent complexation produce a characteristic [Cr(III)O]-PDC complex which can be detected as a protonated ion of m/z 507 in the positive ion mode. The detection is selective to chromium(VI) under acidic pH, even in the presence of chromium(III) and other metal ions, providing high specificity. Different water samples were examined, including deionized, tap, and river waters, and sensitive detection was achieved. In the case of deionized water, quantification over the concentration range of 3.7 to 148ppb gave an excellent correlation coefficient of 0.9904 using the enhanced MS mode scan. Using the single-reaction monitoring (SRM) mode (monitoring the characteristic fragmentation of m/z 507 to m/z 360), the limit of detection (LOD) was found to be 0.25ppb. The LOD of chromium(VI) for both tap and river water samples was determined to be 2.0ppb. A preconcentration strategy using simple vacuum evaporation of the aqueous sample was shown to further improve the ESI signal by 15 fold. This method, with high sensitivity and selectivity, should provide a timely solution for the real-world analysis of toxic chromium(VI).

  7. Synthesis of chromium containing pigments from chromium galvanic sludges.

    Science.gov (United States)

    Andreola, F; Barbieri, L; Bondioli, F; Cannio, M; Ferrari, A M; Lancellotti, I

    2008-08-15

    In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium(III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to color ceramic material. Two different pigments pink CaCr(0.04)Sn(0.97)SiO(5) and green Ca(3)Cr(2)(SiO(4))(3) were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furthermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr(2)O(3). The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr-Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr(2)O(3). PMID:18289775

  8. Synthesis of chromium containing pigments from chromium galvanic sludges

    Energy Technology Data Exchange (ETDEWEB)

    Andreola, F.; Barbieri, L. [Dipartimento di Ingegneria dei Materiali e dell' Ambiente, Universita di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy); Bondioli, F. [Dipartimento di Ingegneria dei Materiali e dell' Ambiente, Universita di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy)], E-mail: bondioli.federica@unimore.it; Cannio, M. [Dipartimento di Ingegneria dei Materiali e dell' Ambiente, Universita di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy); Ferrari, A.M. [Dipartimento di Scienza e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, Viale Amendola 2, 42100 Reggio Emilia (Italy); Lancellotti, I. [Dipartimento di Ingegneria dei Materiali e dell' Ambiente, Universita di Modena e Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy)

    2008-08-15

    In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium(III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to color ceramic material. Two different pigments pink CaCr{sub 0.04}Sn{sub 0.97}SiO{sub 5} and green Ca{sub 3}Cr{sub 2}(SiO{sub 4}){sub 3} were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furthermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr{sub 2}O{sub 3}. The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr-Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr{sub 2}O{sub 3}.

  9. Tissues and urinary chromium concentrations in rats fed high-chromium diets

    International Nuclear Information System (INIS)

    Complete text of publication follows. Chromium is an essential trace elements and enhances the function of insulin as a form of chromodulin. In the subjects with a certain type of diabetics, 200 to 1,000 μg/d of chromium is administered to reduced the symptoms of diabetics. However, although there are not any health-promotive effects of chromium-administration in healthy subjects, various types of chromium supplements are commercially available in many countries; the adverse effects caused by an excessive chromium intake are feared. In the present study, to clarify the tolerable upper limit of chromium, tissue and urinary chromium concentrations, liver function and iron status were examined in rats fed high-chromium diets. Thirty-six male 4-weeks Wistar rats were divided into six groups and fed casein-based diets containing 1, 10 or 100 μg/g of chromium as chromium chloride (CrCl3) or chromium picolinate (CrPic) for 4 weeks. After the feeding, chromium concentrations in liver, kidney, small intestine and tibia were determined by inductively coupled plasma-mass spectrometry. In addition, urine samples were collected on 3rd to 4th week and their chromium concentrations were also determined. Chromium concentrations in liver, kidney, small intestine and tibia were elevated with increase of dietary chromium concentration. Urinary chromium excretion was also elevated with the increase of dietary chromium and the rate of urinary chromium excretion was less than 2% to dietary chromium intake in all the experimental groups. In the administration of 100 μg/g of chromium, rats given CrCl3 showed significantly higher tibia chromium concentration and lower urinary chromium excretion than those given CrPic. There were not any differences in iron status among the experimental groups. Activities of serum aspartate aminotransferase and alanine aminotransferase in rats fed diet containing 100 μg/g of chromium as CrPic were significantly higher than those in rats fed other diets.

  10. Influence of chromium concentration on the electron magnetic resonance linewidth of Cr3+ in SrTiO3

    Directory of Open Access Journals (Sweden)

    Ronaldo Sergio de Biasi

    2012-06-01

    Full Text Available Electron magnetic resonance (EMR spectra of Cr3+ ions in samples of chromium-doped strontium titanate (SrTiO3 have been studied at room temperature for chromium concentrations between 0.20 and 1.00 mol%. According to previous studies, chromium substitutes Ti4+ sites in the lattice and its preferred valence state is Cr4+, which is EMR silent in the X-band, but the trivalent state can be produced by illumination or codoping with Nb. In the present work, the codoping method was used; the results show the electron magnetic resonance linewidth of the Cr3+ spectrum increases with increasing chromium concentration and that the range of the exchange interaction between Cr3+ ions is about 0.96 nm.

  11. Soils contaminated with hexavalent chromium

    OpenAIRE

    Fonseca, Bruna Catarina da Silva

    2011-01-01

    Tese de doutoramento em Engenharia Química e Biológica The interest in environmental soil science has been growing in the last years due to the continuous degradation of this major natural resource. With this in mind, and because chromium and lead are two of the most toxic heavy metals frequently detected as soil contaminants in the Portuguese territory, the study and development of few remediation techniques and the indissociable description of the sorption and migration of...

  12. The Cytotoxicity and Genotoxicity of Hexavalent Chromium in Steller Sea Lion Lung Fibroblasts Compared to Human Lung Fibroblasts

    OpenAIRE

    Wise, John Pierce; Wise, Sandra S.; Holmes, Amie L.; LaCerte, Carolyne; Shaffiey, Fariba; Aboueissa, AbouEl-Makarim

    2010-01-01

    In this study we directly compared soluble and particulate chromate cytotoxicity and genotoxicity in human (Homo sapiens) and sea lion (Eumetopias jubatus) lung fibroblasts. Our results show that hexavalent chromium induces increased cell death and chromosome damage in both human and sea lion cells with increasing intracellular chromium ion levels. The data further indicate that both sodium chromate and lead chromate are less cytotoxic and genotoxic to sea lion cells than human cells, based o...

  13. Chromium Waste Treatment from Leather Manufacture Using Electron Beam Radiation Technic

    International Nuclear Information System (INIS)

    Leather manufacture chromium waste treatment using chemical methods have an essential disadvantage, because of the production of the secondary contamination of wastes and separated sediments used by reagents. Therefore, a new technique is needed to solve this problem. The aim of the research to learn the advantages of electron beam radiation for chromium waste treatment. Water radiolysis can be produced by the interaction between electron beam and water or liquid substances. This phenomenon produces many reducing agents and ions that could reduce chromium concentrations in the liquid waste. Ethyl alcohol as a scavenger was added in the waste samples, then the pH of varied from 1, 4, 8 to 12, then were irradiated. Irradiation were done by Electron Beam Machine with dose 15, 25, and 35 kGy. After irradiation, chromium concentration in the samples were analyzed by AAS and UV-vis spectrophotometer. The results had shown that chromium could be reduced by high dose electron beam. The optimum reduction of chromium was achieved at liquid waste pH 8 and irradiation dose 35 kGy. (author)

  14. Inoculation of chromium white cast iron

    Directory of Open Access Journals (Sweden)

    D. Kopyciński

    2009-01-01

    Full Text Available It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structureof castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

  15. REMOVAL OF HEXAVALENT CHROMIUM FROM DRINKING WATER

    OpenAIRE

    A. R. Asgari ، F. Vaezi ، S. Nasseri ، O. Dördelmann ، A. H. Mahvi ، E. Dehghani Fard

    2008-01-01

    Removal of chromium can be accomplished by various methods but none of them is cost-effective in meeting drinking water standards. For this study, granular ferric hydroxide was used as adsorbent for removal of hexavalent chromium. Besides, the effects of changing contact time, pH and concentrations of competitive anions were determined for different amounts of granular ferric hydroxide. It was found that granular ferric hydroxide has a high capacity for adsorption of hexavalent chromium from ...

  16. BIOSORPTION OF CHROMIUM(Ⅵ) IONS FROM AQUEOUS SOLUTION BY A NOVEL BACTERIAL EXOPOLYMERS%细菌胞外高聚物对水中六价铬的生物吸附特性

    Institute of Scientific and Technical Information of China (English)

    王竞; 陶颖; 周集体; 宫小燕

    2001-01-01

    Biosorption of Chromium(Ⅵ) was investigated by a Novel Bacterial exopolymers from Pseudomonas sp GX4-1. It was found that the optimum initial pH for Cr(Ⅵ) biosorption is 0.5-2.0; the biosorption process may be divided into the following phases:1)a fast biosorption phase with 75% Cr(Ⅵ) uptaken within 5 min: 2)first-order kinetics phase from 10 to 40min; 3)equilibrium phase; and biosorption process is fit for Languir model.%本文研究了一新型细胞外聚合物WJ-I对水中重金属Cr(Ⅵ)的吸附特性。结果表明,WJ-I对Cr(Ⅵ)吸附的最佳pH为0.5~2.0。Cr(Ⅵ)的吸附可分为三个阶段;快速吸附阶段(5min);一级动力学吸附阶段(10~40min);吸附平衡阶段(50min以后)。整个吸附过程符合langmuir吸附模型。

  17. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    Science.gov (United States)

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants.

  18. 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.

  19. Performance of Laterite Soil Grains as Adsorbent in the Removal of Chromium

    Directory of Open Access Journals (Sweden)

    Syama I J

    2015-04-01

    Full Text Available The present study aims to examine the efficiency of laterite grains (LG and acid activated laterite grains (AALG as an adsorbent for removal hexavalent chromium and ferric ion from synthetic wastewater, under laboratory conditions. Adsorption of hexavalent chromium and ferric ion from synthetic wastewater is examined by batch and column studies wherein it is found to be dependent on pH, Contact time, adsorbent dosage and initial adsorbate concentration. Percentage removal enhances with the increase in adsorbent dosage and with low pH, the optimal removal is achieved at pH=2. AALG is found to investigate possibility of improvement in removal efficiency of hexavalent chromium. The removal efficiency of AALG is found to be significantly higher than the efficiency obtained from LG, at pH=7. An adsorbent dosage 2g of LG is found to be optimum for removal of ferric ion with low initial concentration of 2.5 mg/L. The equilibrium adsorption data obtained from batch studies were fitted with Langmuir and freundlich isotherm for both hexavalent chromium and ferric ions. The percentage removal obtained from batch adsorption studies were found to be higher than that obtained by column studies for both the adsorbates.

  20. Fabrication of chitosan-magnetite nanocomposite strip for chromium removal

    Science.gov (United States)

    Sureshkumar, Vaishnavi; Kiruba Daniel, S. C. G.; Ruckmani, K.; Sivakumar, M.

    2016-02-01

    Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe3O4) were synthesized using chemical co-precipitation method at 80 °C. The nanoparticles were characterized using UV-visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K2Cr2O7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

  1. Genesis and transport of hexavalent chromium in the system ophiolitic rocks - groundwater

    Science.gov (United States)

    Shchegolikhina, Anastasia; Guadagnini, Laura; Guadagnini, Alberto

    2015-04-01

    Our study aims at contributing to the quantification and characterization of chromium transport processes from host rocks and soil matrices to groundwater. We focus on dissolved hexavalent chromium detected in groundwaters of geological regions with ophiolitic rocks (ophiolites and serpentinites) inclusions due to its critical ecological impact. (Oze et al., 2004). Despite the large number of analyses on the occurrence of high concentrations of hazardous hexavalent chromium ions in natural waters, only few studies were performed with the objective of identifying and investigating the geochemical reactions which could occur in the natural system rock - groundwater - dissolved chromium (Fantoni et al., 2002, Stephen and James, 2004, Lelli et al., 2013). In this context, there is a need for integration of results obtained from diverse studies in various regions and settings to improve our knowledge repository. Our theoretical analyses are grounded and driven by practical scenarios detected in subsurface reservoirs exploited for civil and industrial use located in the Emilia-Romagna region (Italy). Available experimental datasets are complemented with data from other international regional-scale settings (Altay mountains region, Russia). Modeling of chromium transformation and migration particularly includes characterization of the multispecies geochemical system. A key aspect of our study is the analysis of the complex competitive sorption processes governing heavy metal evolution in groundwater. The results of the research allow assessing the critical qualitative features of the mechanisms of hexavalent chromium ion mobilization from host rocks and soils and the ensuing transformation and migration to groundwater under the influence of diverse environmental factors. The study is then complemented by the quantification of the main sources of uncertainty associated with prediction of heavy metal contamination levels in the groundwater system explored. Fantoni, D

  2. 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....

  3. 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

  4. Electrodeposition of chromium from trivalent chromium urea bath containing sulfate and chloride

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The reduction of Cr( Ⅲ) to Cr( Ⅱ ) on copper electrode in trivalent chromium urea bath containing chromium sulfate and chromium chloride as chromium source has been investigated by potentiodynamic sweep. The transfer coefficient α for reduction of Cr( Ⅲ ) to Cr( Ⅱ ) on copper electrode was calculated as 0.46. The reduction is a quasi-reversible process. J-t responses at different potential steps showed that the generation and adsorption characteristics of carboxylate bridged oligomer are relevant to cathode potential. The interface behavior between electrode and solution for Cr( Ⅲ ) complex is a critical factor influencing sustained electrode position of chromium. The hypotheses of the electro-inducing polymerization of Cr( Ⅲ ) was proposed. The potential scope in which sustained chromium deposits can be prepared is from- 1.3 V to- 1.7 V (vs SCE) in the urea bath. Bright chromium deposits with thickness of 30 μm can be prepared in the bath.

  5. Alkane dehydrogenation over supported chromium oxide catalysts

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Schoonheydt, R.A.

    1999-01-01

    The dehydrogenation of alkanes over supported chromium oxide catalysts in the absence of oxygen is of high interest for the industrial production of propene and isobutene. In this review, a critical overview is given of the current knowledge nowadays available about chromium-based dehydrogenation ca

  6. Assay of In Vivo Chromium with a Hollow-fiber Dialysis Sensor

    Science.gov (United States)

    Ly, Suw Young; Yoo, Hai-Soo; Jung, Minki; Ko, Kwang Hee; Kim, Byung Jin; Lee, Ki Chul; Choi, Byung Min

    2010-01-01

    The analytical in vivo chromium ion was searched for using a voltammetric hollow-fiber dialysis sensor via square wave stripping voltammetry (SW) , cyclic voltammetry (CV) , and chronoamperometry. Under optimum parameters, the analytical results indicated linear working ranges of 50~400 mg/l CV and 10~80 μg/l SW within a 30-sec accumulation time. The analytical detection limit (S/N) was 6.0 μg/l. The developed method can be applied to in vivo tissues and in ex vivo toxicity assay, as well as to other materials that require chromium analysis. PMID:24278529

  7. Evaluation of NaX and NaY packed beds for chromium uptake from multicomponent solution

    Directory of Open Access Journals (Sweden)

    Maria Angélica Simões Dornellas de Barros

    2014-04-01

    Full Text Available In this paper the removal of chromium from Cr/Ca/Mg/K and Cr/Ca/Mg/K/Na solutions was investigated in NaX and NaY packed beds. The breakthrough curves presented some overshooting phenomena where chromium ions displaced the previous exchanged cations. Length of unused bed, overall mass transfer coefficient, operational ratio and dimensionless variance were obtained. According to such mass transfer parameters it was concluded that the chromium uptake is influenced by the competition and interaction of the entering ions. Such influences were verified through some differences in the dynamic selectivity obtained for each system. NaY seemed to have a higher affinity towards Cr3+ and its sites were more efficiently used in the ion exchange process.

  8. Studies on chromium(III removal from aqueous solutions by sorption on Sphagnum moss peat

    Directory of Open Access Journals (Sweden)

    MATEI MACOVEANU

    2009-08-01

    Full Text Available Batch sorption experiments were performed for the removal of chromium(III ions from aqueous solutions using Romanian Sphagnum moss peat (untreated and treated with NaCl solution as sorbent. In order to establish the best conditions for the sorption of chromium(III, the influence of initial pH, contact time, peat dose and metal ion concentration was investigated. The Freundlich, Langmuir and Dubinin–Radushkevich models were applied to describe the sorption isotherms and to calculate its constants. The experimental data fitted well to the Langmuir model with a maximum sorption capacity of 18.6 mg Cr(III/g of peat. The mean free energy of sorption suggests that the binding of Cr(III on peat occurred through an ion exchange mechanism. The kinetic data evaluated by pseudo-first order and pseudo-second order kinetic models showed that the sorption of chromium onto the peat followed a pseudo-second order rate equation. The chromium(III could be easily eluted from the loaded peat using 0.10 M HCl and the peat may be reused in several sorption/desorption cycles. The experimental results indicated the potential of Sphagnum moss peat for removal of Cr(III from wastewaters.

  9. [Bioremediation of chromium (VI) contaminated site by reduction and microbial stabilization of chromium].

    Science.gov (United States)

    Zheng, Jia-Chuan; Zhang, Jian-Rong; Liu, Xi-Wen; Xu, Qian; Shi, Wei-Lin

    2014-10-01

    Chromium (VI) contaminated soil samples were collected from a chemical plant in Suzhou. Firstly, the reduced soil was prepared by adding reagent (Stone-sulfure reagent) into polluted soil to transfer most chromium (VI) into chromium (III), then a nutrient solution was introduced into the reduced soil, and the stabilized soil was obtained after 60 days culturing. The chromium (VI) content of the three kinds of soil was analyzed. The results showed that the chromium (VI) content in toxicity characteristic leaching liquid (TCLL) dropped by 96. 8% (from 8.26 mg · L(-1) to 0.26 mg · L(-1)), and the total chromium content dropped by 95.7% (from 14.66 mg · L(-1) to 0.63 mg · L(-1)) after bioremediation in 5% nutrient solution. Additionally, the durability of chromium stabilization was tested by potassium permanganate oxidation and sterilization of microbe-treated soil. After oxidation, the chromium (VI) content in TCLL of the reduced soil was increased from 8.26 mg · L(-1) to 14.68 mg · L(-1). However, the content after bioremediation was decreased to 2.68 mg · L(-1). The results of sterilization demonstrated that the death of microbe had no significant effect on the stabilization of chromium. Consequently, the research in this paper demonstrated the feasibility of bioremediation of chromium (VI) polluted soil through reduction followed by stabilization/soilidification, and provided a technique with low cost but high efficiency.

  10. Chromium containing silica: effect of ultrasonic and purification methods on color products

    International Nuclear Information System (INIS)

    Chromium containing silica has numerous applications, such as: fiber-optics, luminescent materials, catalysts and pigments. In paint and ceramic pigments, chromate and dichromate ions, and silica are largely used. In this paper, it has been investigated the effect of pH, heating methods, and ultrasonic stirring on chromium oxidation states coprecipitated with silica. The material has been obtained from the coprecipitation of an aqueous diluted sodium silicate solution and acid chromium nitrate solution, purified by extractions and dialysis, and dried with microwave oven. Products have been characterized by X-ray powder diffraction, infrared vibrational spectroscopy and nitrogem adsorption isotherm (BET). Coprecipitates are non cristalline and the specific surface area value for sample obtained by conventional heating is smaller than the one for sample obtained by ultrasonic method. It is possible to obtain silica with different colors from blue due to the Cr(III), to yellow due to the Cr (VI), depending on the precipitation, purification and drying methods. (author)

  11. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  12. Bainitic chromium-tungsten steels with 3 pct chromium

    International Nuclear Information System (INIS)

    Previous work on 3Cr-1.5MoV (nominally Fe-3Cr-2.5Mo-0.25V-0.1C), 2.25Cr-2W (Fe-2.25Cr-2W-0.1C), and 2.25Cr-2WV (Fe-2.25Cr-2W-0.25V-0.1C) steels indicated that the impact toughness of these steels depended on the microstructure of the bainite formed during continuous cooling from the austenization temperature. Microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of nonclassical microstructures were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2.25Cr-2W and 2.25Cr-2WV steel compositions to increase their hardenability. Charpy testing indicated that the new 3Cr-W and 3Cr-WV steels had improved impact toughness, as demonstrated by lower ductile-brittle transition temperatures and higher upper-shelf energies. This improvement occurred with less tempering than was necessary to achieve similar toughness for the 2.25Cr steels and for high-chromium (9 to 12 pct Cr) Cr-W and Cr-Mo steels

  13. Chromium

    Science.gov (United States)

    ... 6+), a toxic form that results from industrial pollution. This fact sheet focuses exclusively on trivalent (3+) ... 1 medium 1 Banana, 1 medium 1 Green beans, ½ cup 1 What are recommended intakes of ...

  14. Structural effects of metallic chromium on its electrochemical behavior

    Directory of Open Access Journals (Sweden)

    VELIMIR RADMILOVIC

    2007-06-01

    Full Text Available Chromium dissolution in aqueous sulfuric acid solution of pH 1 was studied electrochemically on chromium electrodes with different crystallographic structures. A slow potentiodynamic method was used for the electrochemical measurements in deaerated solutions (purgedwith nitrogen,while the Cr(III ions in the solution after the corrosion were determined by atomic absorption spectrometry. Three electrode materials with a very dominant crystallite orientation resembling single crystal structures (i.e., 111 and 110 confirmed by the electron backscattering diffraction (EBSD, were used in the experiments. The (111 structures were somewhat more active electrochemically (both anodic and cathodic than the (110 structure. However, Cr electrochemically deposited in standard plating bath, assumed from literature data to has also the (111 structure, was more than 4 times active for anodic dissolution and, by the same number, less active for cathodic hydrogen evolution. The concentrations of Cr(III ions determined in the solution after definite times of corrosion of all the materials showed almost two times larger dissolution rates than observed electrochemically by three different electrochemical methods (Wagner–Traud, Stern–Geary, electrochemical impedance spectroscopy. This is explained by the simultaneous occurrence of potential independent chemical dissolution of Cr, by a direct reaction of metallic Cr with H2O molecules, proposed a long time ago by Kolotyrkin and coworkers.

  15. Optical and structural properties of chromium impurities in niobium–gallium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Costa, G.K.B. [Instituto de Física, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ 20559-900 (Brazil); Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, RJ 22453-900 (Brazil); López, A. [Instituto de Física, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ 20559-900 (Brazil); Carvalho, I.C.S. [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, RJ 22453-900 (Brazil); Nakamura, O. [Instituto de Física, Universidade Federal da Bahia, Salvador, BA 40210-340 (Brazil); Cella, N. [Instituto Politécnico, Universidade do Estado do Rio de Janeiro, P.O. Box 97282, Nova Friburgo, RJ 28601-970 (Brazil); Sosman, L.P., E-mail: sosman@uerj.br [Instituto de Física, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ 20559-900 (Brazil)

    2014-12-15

    In this work, the optical properties of the gallium–niobium oxide doped with chromium ions were investigated. The samples were obtained by wet chemical and solid-state methods, investigated by X-ray powder diffraction and the data were refined by Rietveld methods. The morphology was determined by scanning electron microscope (SEM) images. The photoluminescence, excitation and photoacoustic measurements showed broad and intense bands in the red region of the spectrum, associated with energy transitions of chromium ions in octahedral sites. From the optical spectra and using the crystal field theory, the energy parameters were obtained. - Highlights: • Cr{sup 3+} doped niobium–gallium oxides were prepared by solid state reaction and wet chemical method. • We show bands in red region. • Spectra are associated to Cr{sup 3+} ions in octahedral sites.

  16. Reproductive toxicological aspects of chromium in males

    International Nuclear Information System (INIS)

    To expand our present understanding of the effects of chromium on male fertility a number of studies were designed to achieve this through the use of chromium intoxicated experimental animals and through investigation of sexual hormones and sperm quality in welders. Also in view of the lack of an experimental model for effects of noxious substance on the epididymal spermatozoa the main objectives of the series of studies reviewed here were: A. To establish a model for evaluation of epididymal sperm count and motility in the rat. B. To investigate and compare the effects of tri- and hexavalent chromium on epididymal spermatozoa. Further to describe the effects of low-dose long-time exposure of rats to the most toxicological interesting chromium oxidative state - hexavalent chromium. C. By the use of autoradiography and γ-countinuing to expand the present knowledge on the distribution of chromium in the body with special reference to the male reproductive organs. D. To describe the effects of exposure to hexavalent chromium in welding fume on levels of sexual hormones and semen parameters in welders. (EG)

  17. A Study of Chromium Adsorption on Natural Goethite Biomineralized with Iron Bacteria

    Institute of Scientific and Technical Information of China (English)

    SUN Zhenya; ZHU Chunshui; HUANG Jiangbo; GONG Wenqi; CHEN Hesheng; MU Shanbin

    2006-01-01

    Goethite, especially biogenic goethite, has high specific surface area and great capacity for the adsorption of many contaminants including metal ions and organic chelates. Chromium is a redox actively toxic metal ion that exists as either CrⅢ or CrⅥ in nature, and as such it is essential to understand its behavior of adsorption on natural goethite mineralized by iron bacteria, as Gallionella and Leptothrix in water body. The adsorption of Cr3+ and CrⅥ on naturally biomineralized goethite is studied in this paper. The results show that both Langmuir and Freundlich adsorption isothermal models are able to accurately describe the adsorption of these two ions. Investigation of SEM/EDS,TEM/EDS indicates that the two ions do not adsorb homogeneously on goethite owing to the different microstructures of goethite, and that the microspherical goethite has a greater adsorption capacity for chromium ions than the helical one. XPS data show that redox reaction of chromium on the surface of biomineralized goethite takes place in the adsorption of both Cr3+ and CrⅥ. The CrⅥ adsorbed on biogoethite is much easier to transform into CrⅢ than the oxidization of CrⅢ on the bio-goethite.

  18. REMOVAL OF CHROMIUM FROM AQUEOUS SOLUTION USING LOCALLY AVAILABLE INEXPENSIVE TARO AND WATER HYACINTH AS BIOSORBENT

    Directory of Open Access Journals (Sweden)

    Shahjalal Khandaker

    2016-04-01

    Full Text Available In this investigation, locally available and inexpensive Taro and Water Hyacinth were used as biosorbents to remove chromium from synthetic wastewater. The removal of this metal ion from water in the batch and column method have been studied and discussed. Adsorption kinetics and equilibrium isotherm studies were also carried out. The material exhibits good adsorption capacity and the data follow both Freundlich and Langmuir models. Scanning Electronic Microscopic image was also used to understand the surface characteristics of biosorbent before and after biosorption studies. Effects of various factors such as pH, adsorbent dose, adsorbate initial concentration, particle size etc. were analyzed. The initial concentrations of chromium were considered 5-30mgL-1 in batch method and only 4mgL-1 in column method. The maximum chromium adsorbed was 1.64 mgg-1 and 4.44 mgg-1 in Batch method and 1.15 mgg-1 and 0.75 mgg-1 in Column method. Batch and Column desorption and regeneration studies were conducted. Column desorption studies indicated that both of these biosorbents could be reused for removing heavy metals. Results of the laboratory experiments show that the performance of Taro and Water Hyacinth prove that they can effectively be used as low cost biosorbents for the removal of chromium from wastewater.KEYWORDS:   adsorption; chromium removal; Taro; water hyacinth; batch method; column studies

  19. Simultaneously Recovering High-Purity Chromium and Removing Organic Pollutants from Tannery Effluent

    Directory of Open Access Journals (Sweden)

    Jie Zong

    2016-01-01

    Full Text Available Chromium pollution is a serious issue because of carcinogenic toxicities of the pollutants and low recovery rate of chromium because of the presence of organic, such as protein and fat. In this work, high recovery rate and high purity of the chromium ion were successfully prepared by the way of acid enzyme, flocculant, and Fenton oxidation. The experiments were characterized by TG, TOC, UV-VIS, and SEM. In the work, the tannery waste chrome liquor was used as experimental material. The results showed that the percentage of reduction of TOC in the tannery waste chrome liquor by method of Fenton oxidation, acid enzyme, and the flocculant was 71.15%, 65.26%, and 22.05%, respectively. Therefore, the organism content of chrome tanning waste liquid was greatly reduced through the pretreatment. And the application experiment showed that the properties and grain surface and fibers of the tanned leather with commercial chromium powder and chrome tanning agent prepared from the chromium waste liquid treated with Fenton are nearly the same.

  20. Removal and Recovery of Chromium from Solutions Simulating Tannery Wastewater by Strong Acid Cation Exchanger

    Directory of Open Access Journals (Sweden)

    Gulten Cetin

    2013-01-01

    Full Text Available The process in this study was conducted on removal of chromium(III in a solution simulating a typical spent chrome tanning bath by the resin having matrix of styrene-divinylbenzene-based macroporous sulphonate, Amberjet 1200Na. The column experiments were carried out with the bed volumes of the resin as 751 mL and 1016 mL for different installation systems of the laboratory-scale pilot plant. The feeding solutions in the bed volumes of 200 and 190 were used for each installation system. The regeneration behaviour of the resin was determined by using reverse regeneration procedure with the solution of hydrogen peroxide in alkaline. The regeneration kinetics of the exhausted resin was examined with a range of the solutions having different concentration series of the alkaline hydrogen peroxide. The solutions of the basic chromium sulphate were recycled for each installation system following the regeneration cycles. The chromium ions in effluent were quantitatively eluted, and satisfactory removal of chromium(III and recovery of chromium(VI were achieved.

  1. In vitro percutaneous absorption of chromium powder and the effect of skin cleanser.

    Science.gov (United States)

    Larese Filon, Francesca; D'Agostin, Flavia; Crosera, Matteo; Adami, Gianpiero; Bovenzi, Massimo; Maina, Giovanni

    2008-09-01

    The present study tried to investigate, using a synthetic sweat at pH 4.5, whether metallic chromium can pass through the skin (in vitro) and the effect of rapid skin decontamination with a common detergent. A suspension of chromium powder in synthetic sweat at pH 4.5 was prepared and shaken with a stirring plate at room temperature for 30 min. Human skin membranes were set up in Franz-diffusion cells and 1 ml of the freshly made suspension was applied to the outer surface of the skin for 24h. The tests were performed without and with decontamination using the cleanser 30 min after the start of exposure. The appearance of metal ions in the aqueous receptor phase was quantified by Electro Thermal Atomic Absorption Spectroscopy (ETAAS) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Speciation analysis and measurements of chromium skin content were also performed. Chromium skin permeation was demonstrated in in vitro experiments using the Franz cell system, giving a permeation flux of 0.84+/-0.25 ng cm(-2)h(-1) and a lag time of 1.1+/-0.7h. The cleaning procedure stop Cr permeation but its concentration into the skin significantly increased (Mann-Whitney U test P<0.03). The results revealed that chromium applied as powder can pass through the skin and that decontamination, done after 30 min of exposure, prevent Cr skin permeation but increase Cr content into the skin.

  2. Screen-printed sensor for batch and flow injection potentiometric chromium(VI) monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Moreno, Raul A.; Gismera, M.J.; Sevilla, M.T.; Procopio, Jesus R. [Facultad de Ciencias, Universidad Autonoma de Madrid, Departamento de Quimica Analitica y Analisis Instrumental, Madrid (Spain)

    2010-05-15

    A disposable screen-printed electrode was designed and evaluated for direct detection of chromium(VI) in batch and flow analysis. The carbon screen-printed electrode was modified with a graphite-epoxy composite. The optimal graphite-epoxy matrix contains 37.5% graphite powder, 12.5% diphenylcarbohydrazide, a selective compound for chromium(VI), and 50% epoxy resin. The principal analytical parameters of the potentiometric response in batch and flow analysis were optimized and calculated. The screen-printed sensor exhibits a response time of 20 {+-} 1 s. In flow analysis, the analytical frequency of sampling is 70 injections per hour using 0.1 M NaNO{sub 3} solution at pH 3 as the carrier, a flow rate of 2.5 mL.min{sup -1}, and an injection sample volume of 0.50 mL. The sensor shows potentiometric responses that are very selective for chromium(VI) ions and optimal detection limits in both static mode (2.1 x 10{sup -7} M) and online analysis (9.4 x 10{sup -7} M). The disposable potentiometric sensor was employed to determine toxicity levels of chromium(VI) in mineral, tap, and river waters by flow-injection potentiometry and batch potentiometry. Chromium(VI) determination was also carried out with successful results in leachates from municipal solid waste landfills. (orig.)

  3. Synthesis of Chromium (Ⅲ) 5-aminosalicylate

    Institute of Scientific and Technical Information of China (English)

    LI Wei; HAO Er-jun; JIANG Yu-qin

    2004-01-01

    As we all known that diabetes is a chronic disease with major health consequences.Research has revealed that the occurrence of diabetes have great thing to do with the chromium deficient. Almost 40 years after the first report of glucose tolerance factor(GTF) [1], no conclusive evidence for an isolable ,biologically active form of chromium exited. Three materials have been proposed to be the biologically active form of chromium: "glucose tolerance factor", chromium Picolinate and low-molecular-weight chromium-binding substance (LWMCr) [2] . So there is potential for the design of new chromium drugs .5-Aminosalicylic acid (5-ASA) is identified as an active component in the therapy of inflammatory bowel disease (IBD) such as Crohn's disease and ulcerative colitis . The therapeutic action of 5-ASA is believed to be coupled to its ability to act as a free radical scavenger [3-4],acting locally on the inflamed colonic mucosa [5-7]. However, the clinical use of 5-ASA is limited, since orally administered 5-ASA is rapidly and completely absorbed from the upper gastrointestinal tract and therefore the local therapeutic effects of 5-ASA in the colon is hardly expected.In this paper, we report the synthesis of chromium(Ⅲ)5-aminosalicylate from 5-ASA and CrCl3. 6H2O.The synthesis route is as follow:The complex has been characterized by elemental analysis, IR spectra, X-ray powder diffractionand TG-DTA . They indicate that the structure is tris(5-ASA) Chromium . Experiments show that thecomplex has a good activity for supplement tiny dietary chromium, lowering blood glucose levels,lowering serum lipid levels and in creasing lean body mass .

  4. Characteristics of chromium-allergic dermatitis patients prior to regulatory intervention for chromium in leather

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P; Zachariae, Claus;

    2014-01-01

    BACKGROUND: Chromium-tanned leather articles currently constitute the most important cause of contact allergy to chromium in Denmark. A regulation on the content of hexavalent chromium in leather was adopted in November 2013 by the EU member states. OBJECTIVES: To characterize patients...... with chromium allergy and their disease, to serve as a baseline for future studies on the potential effect of the new regulation on chromium in leather. METHODS: A questionnaire case-control study was performed on 155 dermatitis patients with positive patch test reactions to potassium dichromate and a matched...... control group of 621 dermatitis patients. Comparisons were made by use of a χ(2) -test and the Mann-Whitney U-test. Logistic regression analyses were used to test for associations. RESULTS: Sixty-six per cent of chromium-allergic patients had a positive history of contact dermatitis caused by leather...

  5. 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...

  6. Potentiometry: A Chromium (III) -- EDTA Complex

    Science.gov (United States)

    Hoppe, J. I.; Howell, P. J.

    1975-01-01

    Describes an experiment that involves the preparation of a chromium (III)-EDTA compound, a study of its infrared spectrum, and the potentiometric determination of two successive acid dissociation constants. (Author/GS)

  7. AEROSOL BEHAVIOR IN CHROMIUM WASTE INCINERATION

    Institute of Scientific and Technical Information of China (English)

    Suyuan Yu

    2003-01-01

    Cr2O3 is considered as the dominant incineration product during the combustion disposal of chromium waste. A hydrogen/air diffusion flame was employed to simulate the industrial process of incineration. Cr2O3 aerosols were generated inside the flame by the gas phase reaction of chromium and oxygen. Chromium came from the rapid decomposition of chromium hexacarbonyl (Cr(CO)6) at room temperature and was carried into the combustion chamber by hydrogen. Aerosol and clusters can then be easily formed in the flame by nucleation and coagulation. A two dimensional Discrete-Sectional Model (DSM) was adopted to calculate the Cr2O3 aerosol behavior. The experimental measurement method was Dynamic Light Scattering. The numerically predicted results agreed well with those of the experimental measurement. Both results show that the Cr2O3 aerosol size reached about 70 nanometers at the flame top.

  8. Localized Corrosion of Chromium Coated Steel

    NARCIS (Netherlands)

    Zhang, X.; Beentjes, P.; Mol, A.; Terryn, H.

    2006-01-01

    In this paper, we report on the studies of the local corrosion behaviour of chromium-coated ultra low carbon steel in NaCl solution using polarization, electrochemical impedance spectroscopy (EIS) and SVET.

  9. Synthesis and Characterization of Chromium Oxide Nanoparticles

    OpenAIRE

    Vivek Sheel Jaswal; Avnish Kumar Arora; Joginder Singh; Mayank Kinger; Vishnu Dev Gupta

    2014-01-01

    Chromium oxide nanoparticles (NPs)have been rapidly synthesized by precipitation method using ammomia as precipitating agent and are characterized by using X-ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), UV-Visible absorption (UV), Infrared Spectoscopy (IR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). XRD studies show that chromium oxide NP is formed as Cr2O3 and it has hexagonal structure. The shape and particle size of the synthesized Cr2O3 NP...

  10. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

  11. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

  12. Coordination Modes of a Schiff Base Derived from Substituted 2-Aminothiazole with Chromium(III, Manganese(II, Iron(II, Cobalt(II, Nickel(II and Copper(II Metal Ions: Synthesis, Spectroscopic and Antimicrobial Studies

    Directory of Open Access Journals (Sweden)

    Ambit Thakar

    2011-01-01

    Full Text Available Transition metal complexes of Cr(III, Mn(II, Fe(II, Co(II, Ni(II and Cu(II metal ions with general stoichiometry [ML2.2H2O] and [ML3], where M= Mn(II, Cr(III, Fe(II, Co(II, Ni(II and Cu(II, L= Schiff base derived from the condensation of 2-amino-4(4’-phenyl/methylphenyl-5-methyl-thiazole with 4-acetyl-1(3-chloro phenyl-3-methyl-2-pyrazoline-5-ones, have been synthesized and structurally characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements and spectral techniques like IR, UV, 1H NMR, 13C NMR and Mass Spectra. All the complexes were found to be octahedral geometry. The ligand and its complexes have been screened for their antifungal and antibacterial activities against three fungi, i.e. Alternaria brassicae, Aspergillus niger and Fesarium oxysporum and two bacteria, i.e. Xanthomonas compestris and Pseudomonas aeruginosa.

  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. Chemotherapeutic efficacy of an ethanolic Moringa oleifera leaf extract against chromium-induced testicular toxicity in rats.

    Science.gov (United States)

    Sadek, K M

    2014-01-01

    This study was conducted to determine the mechanism underlying the chemotherapeutic efficacy of an ethanolic Moringa oleifera leaf extract (MOLEE) against chromium-induced impairments of rat testes using biochemical methods. Twenty male Wistar rats were divided into four groups of five animals each. Group I (control), group II injected potassium dichromate (8 mg kg(-1) ) i.p., group III gastrogavaged MOLEE (500 mg kg(-1) ) p.o. and group IV received (potassium dichromate plus MOLEE) by the same doses for 60 days. After the blood samples were collected, the animals were sacrificed to determine the testicular antioxidant status and sperm parameters. The chromium-treated group exhibited a significant decrease in testicular antioxidant enzymatic activities, local immunity and sperm parameters as well as an increase in inflammatory markers when compared with the control and MOLEE-treated group. However, concurrent administration of chromium and MOLEE significantly ameliorated the chromium effects on the sperm parameters, local immunity, inflammatory markers and antioxidant enzymatic activities compared with rats exposed to chromium alone. This study concludes that chronic exposure to chromium produces clear testicular toxicity, which can either be prevented or at least decreased by concomitant administration of MOLEE. Interestingly, the metal ion chelation could attribute partly the antioxidant activities of MOLEE.

  15. Removal of High Concentration Chromium by a Foam-separating Technique Using Casein Proteins as a Foaming Reagent

    Science.gov (United States)

    Sugimoto, Futoshi

    Foam separation of high concentration chromium in leather tanning wastewater was investigated using casein protein as a foaming reagent5mL of5w/v% ammonium acetate buffer was added to the sample chromium water. After adjusting the pH to 9.0,4g/L concentrations of casein and gelatin solution were added to recovery the coagulating flocs of chromium resulting foam separation. The sample water containing chromium flocs was incased in reactor, then mixed with distilled water and 1mL of ethanol to sum 200mL total. The foam separation was performed at time intervals of 3min with an air flow rate of 300mL/min. With casein reagent, the removal rate of chromium was not influenced by the presence of NaCl, however, the rate decreased tendency using with the use of gelatin. The proposed method, utilizing 4g/L of casein solution with water, was not influenced by the presence of calcium (<34mM), magnesium (<1mM), carbonate (<0.5mM), bicarbonate (<1.2mM) nor sulfate (<350mM) ions, and is ideal for foam separation in chromium concentrations of about 100mgCr/L.

  16. Direct access to macroporous chromium nitride and chromium titanium nitride with inverse opal structure.

    Science.gov (United States)

    Zhao, Weitian; DiSalvo, Francis J

    2015-03-21

    We report a facile synthesis of single-phase, nanocrystalline macroporous chromium nitride and chromium titanium nitride with an inverse opal morphology. The material is characterized using XRD, SEM, HR-TEM/STEM, TGA and XPS. Interconversion of macroporous CrN to Cr2O3 and back to CrN while retaining the inverse opal morphology is also demonstrated.

  17. Diminishing Chromium Use on Combined Chromium-Gambier Tanning Process Upon the Characteristics of Tanned Leather

    Directory of Open Access Journals (Sweden)

    A. Kasim

    2014-04-01

    Full Text Available The research was aimed to investigate the influence of minimizing chromium use on combined chromium-gambier process upon the characteristics of tanned leather. At the first stage of tanning process, chromium was used and in the second stage it was replaced by gambier. The raw material used was dried saline-preserved goat skin. The treatments applied on the tanning process were the different concentrations of chromium ranging from the highest level of 6% to the lowest level of 1% which was then re-tanned by using 8% concentration of gambier. The examination parameters included chemical and physical properties as well as visual investigation on the tanned leather in accordance with SNI-06-0463-1989-A. The result showed that the tanning process by using 2% chromium in the first step and 8% gambier in the second step was a treatment combination producing tanned leather that met the standard. The examination on tanned leather resulted from such treatment showed 56.33% rawhide, 17.45% of bound tannin, 31.22% of tanning level, tensile strength 386.30 kg/cm2, flexibility 31.91%, leather width 1.3 mm, density 0.75 g/cm3, the leather was quite elastic with light brownish color. In conclusion, minimizing the use of chromium in the combined tanning process of chromium and gambier can be implemented to the lowest of 2% chromium concentration and 8% gambier in the first and second step, respectively.

  18. Chromium(VI) but not chromium(III) species decrease mitoxantrone affinity to DNA.

    Science.gov (United States)

    Nowicka, Anna M; Stojek, Zbigniew; Hepel, Maria

    2013-01-31

    Binding of mitoxantrone (MXT) to double-stranded DNA has been investigated as a model drug-DNA binding system to evaluate the effects of various forms of chromium on the binding properties. We have found that Cr(III), which binds strongly to DNA, does not affect the MXT affinity to DNA. In contrast, Cr(VI), in the form of chromate ions CrO(4)(2-), decreases the MXT affinity to DNA despite electrostatic repulsions with phosphate-deoxyribose chains of DNA. The MXT-DNA binding constant was found to decrease from (1.96 ± 0.005) × 10(5) to (0.77 ± 0.018) × 10(5) M(-1) for Cr(VI) concentration changing from 0 to 30 μM. The influence of Cr(VI) on MXT-DNA binding has been attributed to the oxidation of guanine residue, thus interrupting the intercalation of MXT into the DNA double helix at the preferential CpG intercalation site. This supposition is corroborated by the observed increase in the MXT binding site size from 2 bp (base pairs) to 4-6 bp in the presence of Cr(VI). The measurements of the MXT-DNA binding constant and the MXT binding site size on a DNA molecule have been carried out using spectroscopic, voltammetric, and nanogravimetric techniques, providing useful information on the mechanism of the interactions.

  19. Chromium removal through biosorption and bioaccumulation by bacteria from tannery effluents contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Mohammad Zubair [Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh (India); Ahmad, Shamim [Microbiology Division, Institute of Ophthalmology, Faculty of Medicine, J.N. Medical College, Aligarh Muslim University, Aligarh (India)

    2011-03-15

    Four bacterial isolates (two resistant and two sensitive to chromium) were isolated from soil contaminated with tannery effluents at Jajmau (Kanpur), India, and were identified by 16S rDNA gene sequencing as Stenotrophomonas maltophilia, Exiguobacterium sp., Pantoea sp., and Aeromonas sp. Biosorption of chromium by dried and living biomasses was determined in the resistant and sensitive isolates. The effect of pH, initial metal concentration, and contact time on biosorption was studied. At pH 2.5 the living biomass of chromium resistant isolate Exiguobacterium sp. ZM-2 biosorbed maximum amount of Cr{sup 6+} (29.8 mg/g) whereas the dried biomass of this isolate biosorbed 20.1 mg/g at an initial concentration of 100 mg/L. In case of chromate sensitive isolates, much difference was not observed in biosorption capacities between their dried and living biomasses. The maximum biosorption of Cr{sup 3+} was observed at pH 4.5. However, biosorption was identical in resistant and sensitive isolates. The data on chromium biosorption were analyzed using Langmuir and Freundlich isotherm model. The biosorption data of Cr{sup 6+} and Cr{sup 3+} from aqueous solution were better fitted in Langmuir isotherm model compared to Freundlich isotherm model. Metal recovery through desorption was observed better with dried biomasses compared to the living biomasses for both types of chromium ions. Bioaccumulation of chromate was found higher in chromate resistant isolates compared to the chromate sensitive isolates. Transmission electron microscopy confirmed the accumulation of chromium in cytoplasm in the resistant isolates. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Lateral stress evolution in chromium sulfide cermets with varying excess chromium

    Science.gov (United States)

    Petel, O. E.; Appleby-Thomas, G. J.; Wood, D. C.; Capozzi, A.; Nabavi, A.; Goroshin, S.; Frost, D. L.; Hazell, P. J.

    2016-04-01

    The shock response of chromium sulfide-chromium, a cermet of potential interest as a matrix material for ballistic applications, has been investigated at two molar ratios. Using a combustion synthesis technique allowed for control of the molar ratio of the material, which was investigated under near-stoichiometric (cermet) and excess chromium (interpenetrating composite) conditions, representing chromium:sulfur molar ratios of 1.15:1 and 4:1, respectively. The compacts were investigated via the plate-impact technique, which allowed the material to be loaded under a one-dimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress in both materials. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time for the two molar ratio conditions. The two materials exhibited identical material strength despite variations in their excess chromium contents.

  1. The oxygen isotope composition of dissolved chromate: a new tool for determining sources of chromium contamination in groundwater

    Science.gov (United States)

    Bullen, T.; Widory, D.

    2009-05-01

    Hexavalent chromium (Cr(VI)) is a widespread carcinogen in groundwater, derived from both anthropogenic and natural sources. A large range of chromium isotope composition has been demonstrated for dissolved Cr(VI) in groundwater, resulting from the large isotope fractionation accompanying reduction of Cr(VI) to trivalent chromium (Cr(III)). As a result, the isotopic composition of chromium in dissolved chromate is beginning to prove useful for determining the sources of chromium in contaminated groundwater, but considered alone can likewise be non-diagnostic due to overlapping compositional ranges of potential anthropogenic and natural sources. Based on the strong Cr-O bond in the chromate molecule implied by the large chromium isotope fractionation accompanying Cr(VI) reduction, we have proposed that oxygen will remain closely linked to chromium in the chromate molecule and thus can be used to better constrain chromate sources through a Cr-O "multi-tracer" approach. In a series of laboratory experiments using isotopically "enriched" water and "normal" chromate, we have demonstrated that there is insignificant isotopic exchange between oxygen in chromate and water for residence times as long as one year, and thus chromate will retain the oxygen isotope composition of its source during extended transport in groundwater. We have likewise demonstrated that sufficient chromate for oxygen isotope analysis can be successfully isolated from a chemically complex groundwater sample through a series of precipitation, ion exchange and heating procedures. Although our current approach of measuring 100 micromolar samples of chromate using TCEA- gas mass spectrometry is straightforward and robust, we are also developing a negative-ion thermal ionization mass spectrometry technique in order to greatly reduce the sample size requirement. We are currently applying this novel technique at an electric power facility in California and a metal plating facility in France in order to

  2. 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.

  3. 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...

  4. Chromium poisoning in (La,Sr)MnO3 cathode: Three-dimensional simulation of a solid oxide fuel cell

    Science.gov (United States)

    Miyoshi, Kota; Iwai, Hiroshi; Kishimoto, Masashi; Saito, Motohiro; Yoshida, Hideo

    2016-09-01

    A three-dimensional numerical model of a single solid oxide fuel cell (SOFC) considering chromium poisoning on the cathode side has been developed to investigate the evolution of the SOFC performance over long-term operation. The degradation model applied in the simulation describes the loss of the cathode electrochemical activity as a decrease in the active triple-phase boundary (TPB) length. The calculations are conducted for two types of cell: lanthanum strontium manganite (LSM)/yttria-stabilized zirconia (YSZ)/Ni-YSZ and LSM-YSZ/YSZ/Ni-YSZ. Their electrode microstructures are acquired by imaging with a focused ion beam scanning-electron microscope (FIB-SEM). The simulation results qualitatively reproduce the trends of chromium poisoning reported in the literature. It has been revealed that the performance degradation by chromium is primarily due to an increase in the cathode activation overpotential. In addition, in the LSM-YSZ composite cathode, TPBs in the vicinity of the cathode-electrolyte interface preferentially deteriorate, shifting the active reaction site towards the cathode surface. This also results in an increase in the cathode ohmic loss associated with oxide ion conduction through the YSZ phase. The effects of the cell temperature, the partial pressure of steam at the chromium source, the cathode microstructure, and the cathode thickness on chromium poisoning are also discussed.

  5. Chromium, chromium isotopes and selected trace elements, western Mojave Desert, USA

    Energy Technology Data Exchange (ETDEWEB)

    Izbicki, John A. [U.S. Geological Survey, 4165 Spruance Road, Suite O, San Diego, CA 92123 (United States)], E-mail: jaizbick@usgs.gov; Ball, James W. [U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado, CO 80303 (United States); Bullen, Thomas D. [U.S. Geological Survey, 345 Middlefield Road, Building 15, McKelvey Building, MS-420, Menlo Park, CA 94025 (United States); Sutley, Stephen J. [Denver Federal Center, P.O. Box 25046, MS-964, Denver, CO 80225-0046 (United States)

    2008-05-15

    Chromium(VI) concentrations in excess of the California Maximum Contaminant Level (MCL) of 50 {mu}g/L occur naturally in alkaline, oxic ground-water in alluvial aquifers in the western Mojave Desert, southern California. The highest concentrations were measured in aquifers eroded from mafic rock, but Cr(VI) as high as 27 {mu}g/L was measured in aquifers eroded from granitic rock. Chromium(VI) concentrations did not exceed 5 {mu}g/L at pH < 7.5 regardless of geology. {delta}{sup 53}Cr values in native ground-water ranged from 0.7 to 5.1 per mille and values were fractionated relative to the average {delta}{sup 53}Cr composition of 0 per mille in the earth's crust. Positive {delta}{sup 53}Cr values of 1.2 and 2.3 per mille were measured in ground-water recharge areas having low Cr concentrations, consistent with the addition of Cr(VI) that was fractionated on mineral surfaces prior to entering solution. {delta}{sup 53}Cr values, although variable, did not consistently increase or decrease with increasing Cr concentrations as ground-water flowed down gradient through more oxic portions of the aquifer. However, increasing {delta}{sup 53}Cr values were observed as dissolved O{sub 2} concentrations decreased, and Cr(VI) was reduced to Cr(III), and subsequently removed from solution. As a result, the highest {delta}{sup 53}Cr values were measured in water from deep wells, and wells in discharge areas near dry lakes at the downgradient end of long flow paths through alluvial aquifers. {delta}{sup 53}Cr values at an industrial site overlying mafic alluvium having high natural background Cr(VI) concentrations ranged from -0.1 to 3.2 per mille . Near zero {delta}{sup 53}Cr values at the site were the result of anthropogenic Cr. However, mixing with native ground-water and fractionation of Cr within the plume increased {delta}{sup 53}Cr values at the site. Although {delta}{sup 53}Cr was not necessarily diagnostic of anthropogenic Cr, it was possible to identify the extent

  6. cis-Difluoridobis(1,10-phenanthroline)chromium(III) perchlorate monohydrate

    DEFF Research Database (Denmark)

    Birk, Torben; Bendix, Jesper; Weihe, Högni

    2008-01-01

    The title complex, [CrF(2)(C(12)H(8)N(2))(2)]ClO(4)·H(2)O, displays a slightly distorted octa-hedral coordination geometry around the central chromium(III) ion. The Cr environment is composed of a cis arrangement of two 1,10-phenanthroline [average Cr(III)-N = 2.0726 (10) Å] and two fluoride...

  7. Serum chromium levels in gestational diabetes mellitus

    Directory of Open Access Journals (Sweden)

    P G Sundararaman

    2012-01-01

    Full Text Available Objective: To measure serum chromium level in women with gestational diabetes mellitus (GDM from Chennai, South India. Materials and Methods: Thirty women with gestational diabetes, 60 age matched controls. Inclusion criteria: Gestational age 22-28 weeks, age group 20-35 years. Exclusion Criteria: Gestational age beyond 28 weeks, malnutrition or presence of infection. Serum chromium was measured using inductive couple plasma emission spectrometer. Results: Serum chromium levels of women with GDM, 1.59+/-0.02 ng/ml (range: 0.16-4.0 ng/ml were lower than in controls (4.58+/-0.62 ng/ml; range 0.82-5.33 ng/ml (P < 0.001. However, there were no significant differences among cases and controls when subdivided by parity. Conclusions: Women with GDM from a South Indian city had lower levels of serum chromium compared to pregnant women without GDM. Studies may be done whether chromium supplementation is useful in this group of women.

  8. Cycling performance of the iron-chromium redox energy storage system

    Science.gov (United States)

    Gahn, R. F.; Hagedorn, N. H.; Johnson, J. A.

    1985-01-01

    Extended charge-discharge cycling of this electrochemical storage system at 65 C was performed on 14.5 sq cm single cells and a four cell, 867 sq cm bipolar stack. Both the anolyte and catholyte reactant fluids contained 1 molar concentrations of iron and chromium chlorides in hydrochloric acid and were separated by a low-selectivity, cation-exchange membrane. The effect of cycling on the chromium electrode and the cation-exchange membrane was determined. Bismuth and bismuth-lead catalyzed chromium electrodes and a radiation-grafted polyethylene membrane were evaluated by cycling between 5 and 85 percent state-of-charge at 80 mA/sq cm and by periodic charge-discharge polarization measurements to 140 mA/sq cm. Gradual performance losses were observed during cycling but were recoverable by completely discharging the system. Good scale-up to the 867 sq cm stack was achieved. The only difference appeared to be an unexplained resistive-type loss which resulted in a 75 percent W-hr efficiency (at 80 mA/sq cm versus 81 percent for the 14.5 sq cm cell). A new rebalance cell was developed to maintain reactant ionic balance. The cell successfully reduced ferric ions in the iron reactant stream to ferrous ions while chloride ions were oxidized to chlorine gas.

  9. Application of zeolite-Arthrobacter viscosus system for the removal of heavy metal and dye : chromium and azure B

    OpenAIRE

    Rosales, E.; Pazos, M.; Sanromán, M. A.; Tavares, M. T.

    2012-01-01

    A hybrid system combining the ion-exchange properties of a NaY zeolite and the characteristics of the bacterium Arthrobacter viscosus was investigated to treat polluted effluents with dye and toxic metals. In this study, the dye and the metal ion employed were a thiazine dye, Azure B, and chromium (VI), respectively. Initially, the removal of dye by the zeolite was tested. The analysis of dye equilibrium isotherms data was done using Langmuir, Freundlich, Sips and Redlich–Peterson models. Red...

  10. Identification of autoionizing states of atomic chromium for resonance photo-ionization at the ISOLDE-RILIS

    OpenAIRE

    Goodacre, T Day; Chrysalidis, K; Fedorovc, D; Fedosseev, V. N.; Marsh, B A; Molkanov, P; Rossel, R.E.; Rothe, S.; Seiffert, C.

    2015-01-01

    The resonance ionization laser ion source (RILIS) is the principal ion source of the ISOLDE radioactive beam facility based at CERN. Using the method of in-source resonance ionization spectroscopy, an optimal three-step, three-resonance photo-ionization scheme has been developed for chromium. The scheme uses an ionizing transition to one of the 14 newly observed autoionizing states. This work increases the range of ISOLDE-RILIS ionized beams to 32 chemical elements. Details of the spectroscop...

  11. Flashlamp-pumped lasing of chromium-doped GSG garnet

    International Nuclear Information System (INIS)

    The implications for the practical use of chromium:GSGG in lamp-pumped tunable lasers are discussed in this paper. The authors report here some major improvements in the performance of the flashlamp-pumped chromium:GSGG laser

  12. Concentration profiles and electrochemical properties of chromium and nickel implanted iron

    International Nuclear Information System (INIS)

    The concentration profiles of chromium and nickel implanted in pure iron were measured with a secondary ion mass analyzer. The electrochemical properties of implanted iron were investigated by means of a cyclic voltammetry in 0.5 M acetate buffer solution (pH = 5.0 +- 0.1). Chromium, nickel and argon ion implantations have been carried out with doses of 1 x 1016 -- 1 x 1017 ions/cm2 at an energy of 150 keV. The target temperature during ion implantation rised to --1800C from room temperature by the heating effect of ion beam itself. The profile of Cr implanted in pure iron has two peaks; the first peak near the surface and the second peak near the depth predicted by the range theory. However, the first peak was not found in the specimen 1 st-implanted with Ni. The electrochemical properties of Cr implanted iron approach to that of Fe-18% Cr bulk alloy (SUS 430), as the dose increases. The polarization curve of Cr implanted iron with 1 x 1017 ions/cm2 is almost the same as that of SUS 430. The polarization curve of Ni and Cr implanted iron is similar to that of Fe-18%Cr-8%Ni bulk alloy (SUS 304) after annealing at --3000C for 20 min. These results show that Cr and Ni implanted surface layer is useful for the improvement of corrosion resistance of iron. (author)

  13. Removal of hexavalent chromium from aqueous solution by agricultural waste biomass

    International Nuclear Information System (INIS)

    In the present study adsorption of Cr(VI) from aqueous solutions onto different agricultural wastes, viz., sugarcane bagasse, maize corn cob and Jatropha oil cake under various experimental conditions has been studied. Effects of adsorbent dosage, Cr(VI) concentration, pH and contact time on the adsorption of hexavalent chromium were investigated. The concentration of chromium in the test solution was determined spectrophotometrically. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of chromium ions on to studied adsorbents. SEMs of the adsorbents were recorded to explore the morphology of the studied adsorbents. Maximum adsorption was observed in the acidic medium at pH 2 with a contact time of 60 min at 250 rpm stirring speed. Jatropha oil cake had better adsorption capacity than sugarcane bagasse and maize corn cob under identical experimental conditions. The applicability of the Langmuir and Freundlich adsorption isotherms was tested. The results showed that studied adsorbents can be an attractive low cost alternative for the treatment of wastewaters in batched or stirred mode reactors containing lower concentrations of chromium

  14. 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.

  15. Determination of chromium combined with DNA, RNA and proteins in chromium-rich brewer's yeast by NAA

    International Nuclear Information System (INIS)

    The content of chromium in the DNA, RNA and protein fractions separated from chromium-rich and normal brewer's yeast was determined by neutron activation analysis (NAA). Our results show that the extracted relative amounts and concentrations of DNA, RNA and proteins have no significant difference for two types of yeast, but the chromium content in DNA, RNA and proteins fractions extracted from the chromium-rich yeast are substantially higher than those from the normal. In addition, the concentration of chromium in DNA is much higher than that in RNA and proteins. It is evident that the inorganic chromium compounds can enter the yeast cell during the yeast cultivation in the chromium-containing culture medium and are converted into organic chromium species, which are combined with DNA, RNA and proteins. (author)

  16. Hexavalent and trivalent chromium in leather: What should be done?

    Science.gov (United States)

    Moretto, Angelo

    2015-11-01

    Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions.

  17. Chromium allergy and dermatitis: prevalence and main findings

    DEFF Research Database (Denmark)

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

    2015-01-01

    The history of chromium as an allergen goes back more than a century, and includesan interventional success with national legislation that led to significant changes inthe epidemiology of chromium allergy in construction workers. The 2015 EU Leather Regulation once again put a focus on chromium...

  18. Thermodynamic properties of chromium bearing slags and minerals. A review

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Yanping; Holappa, L.

    1996-12-31

    In this report, the thermodynamic properties of chromium bearing slags and minerals were reviewed based on the available information in the literature. It includes the analysing methods for oxidation state of chromium in slags, oxidation state of chromium and activities of chromium oxides in slags and minerals. The phase diagrams of chromium oxide systems and chromium distributions between slag and metal phases are also covered ill this review. Concerning the analysing methods, it was found that most of the available approaches are limited to iron free slag systems and the sample preparation is very sensitive to the analysing results. In silicate slags under reducing atmosphere, divalent and trivalent chromium co-exist in the slags. It is agreed that the fraction of divalent chromium to total chromium increases with higher temperature, lower slag basicity and oxygen potential. For the slags under oxidising atmosphere, trivalent, pentavalent and hexavalent states were reported to be stable. The activities of CrO and CrO{sub 1.5} were concluded to have positive deviation from ideal solution. Slag basicity has a positive effect and temperature has a negative effect on the activities of chromium oxides. The phase diagrams of the Cr-O, binary, and ternary chromium containing oxide systems have been examined systematically. The analysis shows that the data on the quaternary and quinary systems are insufficient, and require further investigation. The most important features of the chromium containing silicate slags are the large miscibility gaps and the stability of the chromite spinel. (orig.) (76 refs.)

  19. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  20. Hexavalent and trivalent chromium in leather: What should be done?

    Science.gov (United States)

    Moretto, Angelo

    2015-11-01

    Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions. PMID:26361854

  1. Collisional properties of trapped cold chromium atoms

    CERN Document Server

    Pavlovich, Z; Côté, R; Sadeghpour, H R; Pavlovic, Zoran; Roos, Bjoern O.; Côté, Robin

    2004-01-01

    We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to buffer-gas and magneto-optical cooling of chromium atoms. We calculate ab initio potential energy curves for Cr2 and the van der Waals coefficient C6, and construct interaction potentials between two colliding Cr atoms. We explore the effect of shape resonances on elastic cross section, and find that they dramatically affect the thermalization rate. Our calculated value for the s-wave scattering length is compared in magnitude with a recent measurement at ultracold temperatures.

  2. Studying chromium biosorption using arabica coffee leaves

    Directory of Open Access Journals (Sweden)

    Luis Carlos Florez García

    2010-05-01

    Full Text Available This work was aimed at providing an alternative for removing heavy metals such as chromium from waste water (effluent from the leather industry and galvanoplasty (coating with a thin layer of metal by electrochemical means, using coffee leaves as bio- mass. Using arabica coffee (Castle variety leaves led to 82% chromium removal efficiency for 1,000 mg/L synthetic dissolutions in 4 pH dissolution operating conditions, 0 rpm agitation, 0.149 mm diameter biomass particle size and 0.85 g/ml biomass / dissolution volume ratio.

  3. Strategies for chromium bioremediation of tannery effluent.

    Science.gov (United States)

    Garg, Satyendra Kumar; Tripathi, Manikant; Srinath, Thiruneelakantan

    2012-01-01

    Bioremediation offers the possibility of using living organisms (bacteria, fungi, algae,or plants), but primarily microorganisms, to degrade or remove environmental contaminants, and transform them into nontoxic or less-toxic forms. The major advantages of bioremediation over conventional physicochemical and biological treatment methods include low cost, good efficiency, minimization of chemicals, reduced quantity of secondary sludge, regeneration of cell biomass, and the possibility of recover-ing pollutant metals. Leather industries, which extensively employ chromium compounds in the tanning process, discharge spent-chromium-laden effluent into nearby water bodies. Worldwide, chromium is known to be one of the most common inorganic contaminants of groundwater at pollutant hazardous sites. Hexavalent chromium poses a health risk to all forms of life. Bioremediation of chromium extant in tannery waste involves different strategies that include biosorption, bioaccumulation,bioreduction, and immobilization of biomaterial(s). Biosorption is a nondirected physiochemical interaction that occurs between metal species and the cellular components of biological species. It is metabolism-dependent when living biomass is employed, and metabolism-independent in dead cell biomass. Dead cell biomass is much more effective than living cell biomass at biosorping heavy metals, including chromium. Bioaccumulation is a metabolically active process in living organisms that works through adsorption, intracellular accumulation, and bioprecipitation mechanisms. In bioreduction processes, microorganisms alter the oxidation/reduction state of toxic metals through direct or indirect biological and chemical process(es).Bioreduction of Cr6+ to Cr3+ not only decreases the chromium toxicity to living organisms, but also helps precipitate chromium at a neutral pH for further physical removal,thus offering promise as a bioremediation strategy. However, biosorption, bioaccumulation, and

  4. Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2014-01-01

    Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

  5. Use of Ethylenediaminetetraacetic Acid as a Scavenger for Chromium from “Wet Blue” Leather Waste: Thermodynamic and Kinetics Parameters

    Directory of Open Access Journals (Sweden)

    José E. Resende

    2014-01-01

    Full Text Available One serious consequence of the current consumer society is the transformation of the environment into a waste receptacle arising from human activities. Because of the potential toxic effects of chromium solid waste containing this metal there are grounds for serious concern for the tanning and leather processing industry. The application of tannery waste as organic fertilizer has led to extensive contamination by chromium in agricultural areas and may cause the accumulation of this metal in soils and plants. This work evaluated the extraction of Cr+3 and Cr+6 contained in solid waste from the leather industry through density functional theory (DFT calculations. The Gibbs free energy calculations reveal that the chelator ethylenediaminetetraacetic acid (EDTA forms more stable complexes with metal ions of chromium compared with the structures of the complexes [Cr(NTA(H2O2] and [Cr-collagen], the latter used to simulate the protein bound chrome leather.

  6. Electrodeposition of black chromium thin films from trivalent chromium-ionic liquid solution

    OpenAIRE

    Eugénio, S.; Vilar, Rui; C. M. Rangel; Baskaran, I.

    2009-01-01

    In the present study, black chromium thin films were electrodeposited from a solution of 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIm][BF4] ionic liquid containing trivalent chromium (Cr(III)). Homogeneous and well adherent coatings have been obtained on nickel, copper and stainless steel substrates. The nucleation and growth of the films were investigated by cyclic voltammetry and current-density/time transient techniques. SEM/EDS, XPS and XRD were used to study the morphology, chem...

  7. 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...

  8. 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...

  9. The electronic structure of antiferromagnetic chromium

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    1981-01-01

    The author has used the local spin density formalism to perform self-consistent calculations of the electronic structure of chromium in the non-magnetic and commensurate antiferromagnetic phases, as a function of the lattice parameter. A change of a few per cent in the atomic radius brings...

  10. Flashlamp-pumped lasing of chromium: GSGG

    International Nuclear Information System (INIS)

    Lasing action in chromium-doped gadolinium scandium gallium garnet (Cr:GSGG) is well established for both CW/sup (1)/ and flashlamp/sup (2)/ pumping. This paper describes an investigation of flashlamp-pumped Cr:GSGG lasers and indicates some of the factors which limit performance

  11. Defect structure of electrodeposited chromium layers

    CERN Document Server

    Marek, T; Vertes, A; El-Sharif, M; McDougall, J; Chisolm, C U

    2000-01-01

    Positron annihilation spectroscopy was applied to study the effects of pre-treatment and composition of substrates on the quality and defect structure of electrodeposited thick chromium coatings. The results show that both parameters are important, and a scenario is proposed why the mechanically polished substrate gives more defective film than the electro polished one.

  12. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... Enhancements In Lieu of LEV Retrofitting • Eductors. Many chemical baths are currently mixed via air agitation... requirements of the Hazard Communication Standard, 29 CFR 1910.1200. (3) Cleaning and replacement. (i) The... CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide...

  13. 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

  14. 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

  15. A Kinetic Model of Chromium in a Flame

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Chromium has been identified as a carcinogenic metal.Incineration is the useful method for disposal of toxic chromium hazard waste and a chromium kinetic model in a flame is very important to study chromium oxidation.Chromium chemical kinetics over a range of temperatures of a hydrogen/air flame is proposed.Nine chromium compounds and fifty-eight reversible chemical reactions were considered The forward reaction rates are calculated based on the molecular collision approach for unknown ones and Arrhenius's Law for known ones.The backward reaction rates were calculated according to forward reaction rates, the equilibrium constants and chemical thermodynamics.It is verified by several equilibrium cases and is tested by a hydrogen/air diffusion flame.The results show that the kinetic model could be used in cases in which the chromium kinetics play an important role in a flame

  16. A Comparative Study of Biodegradation of Nickel and Chromium from Space Maintainers: An in vitro Study

    Science.gov (United States)

    Anand, Ashish; Sharma, Arun; Kumar, Piush; Sachdeva, Shobhit; Sachdev, Vinod

    2015-01-01

    ABSTRACT Objective: The aim of the study was to compare and evaluate the in vitro biodegradation of nickel and chromium from space maintainers, made of three different companies, i.e (Dantaurum, Rocky mountain and Dtech) in artificial saliva. Materials and methods: The study comprised of 30 space maintainers out of which 10 were fabricated using Dantaurum, 10 using Rocky mountain and 10 using Dtech band materials. Stainless steel wire (Dantaurum, Rocky mountain and Konark) was used for making loops and Leone solder and flux was used for soldering. Each group was further divided into four subgroups containing 1, 2, 3 and 4 space maintainers respectively. The space maintainers in each subgroup were placed in separate glass beakers containing 100 ml of artificial saliva at 37°C for 4 weeks. Salivary samples from each beaker was analyzed for nickel and chromium ions separately on days 1, 7, 14, 21 and 28 days using inductively coupled plasma-optical emission spectrophotometer. Results: Total release of nickel and chromium from all band and loop space maintainers ranged from 0.020 to 1.524 ppm and 0.002 to 0.289 ppm respectively. The release of nickel and chromium between the groups and within the groups was not significant (p space maintainers made of Dantaurum, Rocky mountain and Dtech which could cause any toxicity. How to cite this article: Anand A, Sharma A, Kumar P, Sandhu M, Sachdeva S, Sachdev V. A Comparative Study of Biodegradation of Nickel and Chromium from Space Maintainers: An in vitro Study. Int J Clin Pediatr Dent 2015; 8(1):37-41. PMID:26124579

  17. Cr3+ NMR for Multiferroic Chromium spinel ZnCr2Se4

    Science.gov (United States)

    Park, Sejun; Kwon, Sangil; Lee, Soonchil; Khim, Seunghyun; Bhoi, Dilip Kumar; Kim, Kee Hoon

    Multiferroic systems including ZnCr2Se4, the chromium spinel with helical spin structure, have been in huge interest for decades due to its physical variety and applicability. In the temperature range between 21K and 80K, this material shows negative thermal expansion. Due to the bond frustration, the spins of the chromium ions order helically below the transition temperature, 21K, though the exchange constant tends to make a ferro-order. The anomalous 1storder-like magnetic transition is yet clarified and still an interesting topic. To probe microscopic origin of these features, we measured zero-field NMR of Cr3+ ions having nuclear spin 3/2. Six peaks were observed revealing Nuclear Quadrupole Resonance(NQR) and anisotropic hyperfine field at chromium sites. The NQR spectrum reveals that the structure is highly distorted below the magnetic transition temperature where the normal Jahn-Teller distortion is absent. Temperature dependence of the spectrum is also measured to obtain the magnetization as a function of temperature.

  18. 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.

  19. Using microalgae scenedesmus obliquus in the removal of chromium present in plating wastewaters

    International Nuclear Information System (INIS)

    Dumping wastewaters from plating industry with a high content in chromium is a potential hazard for people and environment. It is known that some metals, including the heavy metals, at low concentrations participate in different metabolic routes, but at high concentration are toxic for many living organisms. Some microorganism taking the heavy metals from the environment are capable of concentrating and accumulating large quantities of them in different citiplasmatic structures with no-toxic effects. Microalgaehave affinity by the polyvalent metals making possible their use as depollutant agent in waters that contains dissolved metallic ions as alternative methods when others methods of recycle are unusable. In this report a chromium removal study from a plating wastewater, using scenedesmus obliquus culture was made. The removal efficiency of Cr (VI) was 12% and Cr (III) was 27% and for condition of algae's immobilization removal of Cr (III) was 95%. (Author) 19 refs

  20. Mössbauer study of the iron atom state in modified chromium dioxide

    Science.gov (United States)

    Bondarevskii, S. I.; Eremin, V. V.; Panchuk, V. V.; Semenov, V. G.; Osmolovsky, M. G.

    2016-01-01

    Powders of modified chromium dioxide produced by the hydrothermal method were studied using 57Fe Mössbauer spectroscopy at a temperature of 298 K. The content of the modifier, i.e., 57Fe compound, was varied from 2 to 10 mmol/mol Cr at a Sb content of 2.2 and 10 mmol/mol Cr. It was shown that, independently of concentrations, Fe3+ ions are distributed between three magnetic solid solutions (sextets): based on CrO2 (bulk material and iron-enriched surface layer), based on Cr2O3, and surface β-CrOOH (doublet). In this case, chromium atoms were not substituted in the CrSbO4 nucleation (12 nm in size) phase with an accuracy up to the Mössbauer factor. It was assumed that the powder coercivity, in addition to the size factor, is controlled by the iron concentration in the CrO2 surface layer.

  1. Acute toxicity and toxic interaction of chromium and nickel to common guppy Poecilia reticulata (Peters)

    Energy Technology Data Exchange (ETDEWEB)

    Khangarot, B.S.; Ray, P.K. (Industrial Toxicology Research Centre, Lucknow (India))

    1990-06-01

    The acute toxicity of heavy metals in combination to the common guppy has been reported. Information on the combined effects of chromium and nickel to fish is rather scarce. Toxicity of nickel and chromium to fish is generally low. These two elements are usually less toxic than silver, cadmium, copper and thallium; depending on test conditions, these may also be less hazardous than zinc, lead and arsenic. The present study was undertaken to investigate the acute toxicity of Ni and Cr singly and the toxic interaction of these two metal ions on survival of the common guppy, Poecilia reticulata (Peters). This species was selected for static bioassays because it can be easily cultured and raised under laboratory conditions through a complete life cycle, and it is one of the most common fish used for laboratory toxicity studies.

  2. 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.

  3. Elementary surface processes during reactive magnetron sputtering of chromium

    Energy Technology Data Exchange (ETDEWEB)

    Monje, Sascha; Corbella, Carles, E-mail: carles.corbella@rub.de; Keudell, Achim von [Research Group Reactive Plasmas, Ruhr-University Bochum, Universitystr. 150, 44801 Bochum (Germany)

    2015-10-07

    The elementary surface processes occurring on chromium targets exposed to reactive plasmas have been mimicked in beam experiments by using quantified fluxes of Ar ions (400–800 eV) and oxygen atoms and molecules. For this, quartz crystal microbalances were previously coated with Cr thin films by means of high-power pulsed magnetron sputtering. The measured growth and etching rates were fitted by flux balance equations, which provided sputter yields of around 0.05 for the compound phase and a sticking coefficient of O{sub 2} of 0.38 on the bare Cr surface. Further fitted parameters were the oxygen implantation efficiency and the density of oxidation sites at the surface. The increase in site density with a factor 4 at early phases of reactive sputtering is identified as a relevant mechanism of Cr oxidation. This ion-enhanced oxygen uptake can be attributed to Cr surface roughening and knock-on implantation of oxygen atoms deeper into the target. This work, besides providing fundamental data to control oxidation state of Cr targets, shows that the extended Berg's model constitutes a robust set of rate equations suitable to describe reactive magnetron sputtering of metals.

  4. Incorporation of chromium into TiO2 nanopowders

    International Nuclear Information System (INIS)

    Highlights: • Nanopowders of TiO2:Cr with different amount of Cr dopant were obtained by flame spray synthesis, FSS. • Increase in the optical absorption and a shift of the absorption edge were observed upon Cr doping. • HERFD-XANES measurements indicated that the average valence state of titanium ions was preserved. • Increasing magnetic susceptibility of a paramagnetic character was observed upon Cr doping. - Abstract: The paper reports on the results of a study of optical, electronic and magnetic properties of TiO2 nanopowders doped with Cr ions. Diffused reflectance spectra reveal an increase in the optical absorption and a shift of the absorption edge towards lower energies upon Cr doping. Direct information on the Ti electronic state and the symmetry of its nearest environment is obtained from XANES Ti K-edge spectra. Magnetic behaviour is probed by means of the temperature dependence of DC magnetic susceptibility. Increasing magnetic susceptibility of a paramagnetic character is observed upon increasing chromium doping. The Curie constant of TiO2:10 at.% Cr sample (0.12 emu K/mol Oe) is lower than that expected for Cr3+ (0.1875 emu K/mol Oe) possibly due to the appearance of Cr4+ or the presence of the orbital contribution to the magnetic moment

  5. CHROMIUM INDUCED CYTOTOXICITY IN BLACKGRAM (VIGNA MUNGO L.

    Directory of Open Access Journals (Sweden)

    A. Chidambaram ، P. Sundaramoorthy ، A. Murugan ، K. Sankar Ganesh ، L. Baskaran

    2009-01-01

    Full Text Available Chromium is known to be highly toxic to biological systems. This study was designed to determine the mutagenic effects of different concentrations (0, 10, 25, 50, 100 and 200 mg/L of hexavalent chromium on root tip cells of blackgram (Vigna mungo L. Hepper. The blackgram seeds were equi-spacially arranged in sterilized petriplates lined with filter paper and they were treated with different concentrations of chromium solution. In germination studies, the morphological growth parameters such as germination percentage, root length, shoot length fresh weight and dry weight of blackgram seedlings were decreased with increasing dose of chromium concentrations. No germination of blackgram seeds was recorded at 300mg/l chromium concentration. Chromosome aberration assay was used to determine the mitotic indices and rate of chromosome aberration in blackgram root tip cells due to chromium treatment. The results showed that the mitotic indices were complicated due to different concentrations of chromium. However, the increase in chromium concentration has led to a gradual increase in the percentage of chromosomal aberration and mitotic index. The chromosome length, absolute chromosome length and average chromosome lengths were gradually found to decrease. There was no considerable change in 2n number of chromosome with the increase in chromium concentrations. It is concluded that the hexavalent chromium has significant mutagenic effect on the root tip cells of blackgram.

  6. Chromium supplementation improved post-stroke brain infarction and hyperglycemia.

    Science.gov (United States)

    Chen, Wen-Ying; Mao, Frank Chiahung; Liu, Chia-Hsin; Kuan, Yu-Hsiang; Lai, Nai-Wei; Wu, Chih-Cheng; Chen, Chun-Jung

    2016-04-01

    Hyperglycemia is common after acute stroke and is associated with a worse outcome of stroke. Thus, a better understanding of stress hyperglycemia is helpful to the prevention and therapeutic treatment of stroke. Chromium is an essential nutrient required for optimal insulin activity and normal carbohydrate and lipid metabolism. Beyond its nutritional effects, dietary supplement of chromium causes beneficial outcomes against several diseases, in particular diabetes-associated complications. In this study, we investigated whether post-stroke hyperglycemia involved chromium dynamic mobilization in a rat model of permanent focal cerebral ischemia and whether dietary supplement of chromium improved post-stroke injury and alterations. Stroke rats developed brain infarction, hyperglycemia, hyperinsulinemia, glucose intolerance, and insulin resistance. Post-stroke hyperglycemia was accompanied by elevated secretion of counter-regulatory hormones including glucagon, corticosterone, and norepinephrine, decreased insulin signaling in skeletal muscles, and increased hepatic gluconeogenesis. Correlation studies revealed that counter-regulatory hormone secretion showed a positive correlation with chromium loss and blood glucose increased together with chromium loss. Daily chromium supplementation increased tissue chromium levels, attenuated brain infarction, improved hyperglycemia, and decreased plasma levels of glucagon and corticosterone in stroke rats. Our findings suggest that stroke rats show disturbance of tissue chromium homeostasis with a net loss through urinary excretion and chromium mobilization and loss might be an alternative mechanism responsible for post-stroke hyperglycemia. PMID:26477944

  7. A novel hydrolysis method to synthesize chromium hydroxide nanoparticles and its catalytic effect in the thermal decomposition of ammonium perchlorate

    International Nuclear Information System (INIS)

    Highlights: ► Synthesis of Cr(OH)3 nanoparticles in Cr3+–F− aqueous solution. ► The F− ion tailors coagulated materials, Cr(OH)3 nanoparticles are obtained. ► Adding nanosized Cr(OH)3, AP thermal decomposition temperature decreases to 200 °C. ► The nanosized Cr(OH)3 catalyzes NH3 oxidation, accelerating AP thermal decomposition. - Abstract: A procedure for the preparation of spherical Cr(OH)3 nanoparticles was developed based on the aging of chromium nitrate aqueous solutions in the presence of sodium fluoride, urea, and polyvinylpyrrolidone. Using scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy, the morphological characteristics of Cr(OH)3 were controlled by altering the molar ratio of fluoride ion to chromium ion, as well as the initial pH and chromium ion concentration. The prepared nanosized Cr(OH)3 decreased the temperature required to decompose ammonium perchlorate from 450 °C to about 250 °C as the catalyst. The possible catalytic mechanism of the thermal decomposition of ammonium perchlorate was also discussed.

  8. Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

    Science.gov (United States)

    Dettmer, Aline; Nunes, Keila Guerra Pacheco; Gutterres, Mariliz; Marcílio, Nilson Romeu

    2010-04-15

    Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept.

  9. Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

    Science.gov (United States)

    Dettmer, Aline; Nunes, Keila Guerra Pacheco; Gutterres, Mariliz; Marcílio, Nilson Romeu

    2010-04-15

    Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept. PMID:20031309

  10. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    International Nuclear Information System (INIS)

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr2O3 layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr2O3 layer. The α-Cr2O3 layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%

  11. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)

    2014-12-01

    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  12. Synthesis and Characterization of Chromium Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Vivek Sheel Jaswal

    2014-06-01

    Full Text Available Chromium oxide nanoparticles (NPshave been rapidly synthesized by precipitation method using ammomia as precipitating agent and are characterized by using X-ray Diffraction (XRD, Thermo Gravimetric Analysis (TGA, UV-Visible absorption (UV, Infrared Spectoscopy (IR, Scanning Electron Microscopy (SEM and Transmission Electron Microscopy (TEM. XRD studies show that chromium oxide NP is formed as Cr2O3 and it has hexagonal structure. The shape and particle size of the synthesized Cr2O3 NPs is determined by SEM and TEM. The images showed that the size of NPs of Cr2O3 varied from 20 nm to 70 nm with average crystalline size 45 nm. UV-Visible absorption and IR spectoscopy confirm the formation of nanosized Cr2O3. TGA verifies that the Cr2O3 NPs are thermally stable upto 1000 °C.

  13. CHROMIUM(II) AMIDES - SYNTHESIS AND STRUCTURES

    NARCIS (Netherlands)

    EDEMA, JJH; GAMBAROTTA, S; MEETSMA, A; SPEK, AL; SMEETS, WJJ; CHIANG, MY

    1993-01-01

    A novel class of mono- and di-meric chromium(II) amides has been prepared and characterized. Reaction of [CrCl2(thf)2] (thf = tetrahydrofuran) with 2 equivalents of M(NR2) (R = C6H11, Pr(i), Ph, or phenothiazinyl; M = Li or Na) allowed the formation of the homoleptic amides [{Cr(mu-NR2)(NR2)}2] (R =

  14. Stainless chromium-nickel steels. Chapter I

    International Nuclear Information System (INIS)

    The chemical composition is tabulated of 90 chromium-nickel stainless steels and alloys given in volume %. The values are also given of the corrosion resistance of the steels and alloys. The tables show data on the surface condition or the methods of material working, types and chemical composition of the medium where corrosion resistance tests were carried out, temperature, pressure, time of tests, corrosion rates, corrosion types, and literature references. A total of 35 references is given. (J.B.)

  15. Chromium--a material for fusion technology

    International Nuclear Information System (INIS)

    Due to their low neutron-induced radioactivity chromium based materials are considered to be candidates for structure materials in fusion technology. In this paper investigations are presented of unirradiated chromium with a purity of 99.96% (DUCROPUR) and a dispersion strengthened chromium alloy Cr5Fe1Y2O3 (DUCROLLOY). Both materials have been produced in a powder metallurgical route. Mechanical tests of smooth and pre-cracked specimens have been performed in a wide temperature range. Below 280 deg. C the fracture toughness values of DUCROPUR are very low (1/2), above the transition temperature they exceed 500 MPa m1/2. Large plastic deformations have been observed. DUCROLLOY does not indicate such a significant increase of fracture toughness in the tested temperature range. But above 400 deg. C large plastic deformations can be obtained in bending samples, too. The fatigue crack propagation behaviour of DUCROPUR at 300 deg. C is similar to that of a ductile metal

  16. Chromium Enrichment on P11 Ferritic Steel by Pack Cementation

    Directory of Open Access Journals (Sweden)

    Fauzi F. A.

    2016-01-01

    Full Text Available The future thermal power plant is expected to operate at higher temperature to improve its efficiency and to reduce greenhouse gas emission. This target requires better corrosion properties of ferritic steels, which commonly used as materials for superheater and reheater of boiler tubes. In this work, chromium enrichment on the surface of ferritic steel is studied. The deposited chromium is expected to become a reservoir for the formation of chromia protective layer. Chromium was deposited on the substrate of steel by pack cementation process for two hours at the temperature of 850ºC, 950ºC and 1050ºC, respectively. XRD analysis indicated that chromium was successfully deposited at all temperatures. Somehow, SEM cross sectional image showed that continuous layer of chromium was not continuously formed at 850oC. Therefore, this research clarify that chromium enrichment by pack cementation may be conducted at the temperature above 950°C.

  17. Effect of polyethylene glycol on electrochemically deposited trivalent chromium layers

    Institute of Scientific and Technical Information of China (English)

    Joo-Yul LEE; Man KIM; Sik-Chol KWON

    2009-01-01

    The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry, open circuit potential transition, electrochemical impedance spectroscopy, scanning electron microscopy and X-ray photoelectron spectrometry. It is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode surface. And the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance, lower polarization resistance, and higher capacitance in a corrosive atmosphere. It is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol, which means easier electrochemical codeposition of chromium and carbon, not single chromium deposition.

  18. Non-chromatographic speciation of chromium at sub-ppb levels using cloud point extraction in the presence of unmodified silver nanoparticles.

    Science.gov (United States)

    López-García, Ignacio; Vicente-Martínez, Yesica; Hernández-Córdoba, Manuel

    2015-01-01

    The cloud point extraction (CPE) of silver nanoparticles (AgNPs) by Triton X-114 allows chromium (III) ions to be transferred to the surfactant-rich phase, where they can be measured by electrothermal atomic absorption spectrometry. Using 20 mL sample and 50 μL Triton X-114 (30% w/v), the enrichment factor was 1150, and calibration graphs were obtained in the 5-100 ng L(-1) chromium range in the presence of 5 µg L(-1) AgNPs. Speciation of trivalent and hexavalent chromium was achieved by carrying out two CPE experiments, one of them in the presence of ethylenediaminetetraacetate. While in the first experiment, in absence of the complexing agent, the concentration of total chromium was obtained, the analytical signal measured in the presence of this chemical allowed the chromium (VI) concentration to be measured, being that of chromium (III) calculated by difference. The reliability of the procedure was verified by using three standard reference materials before applying to water, beer and wine samples.

  19. Photocatalytic Removal of Hexavalet Chromium and Divalent Nickel fromAqueous Solution by UV Irradiation in the Presence of Titanium Dioxide Vanoparticles

    Directory of Open Access Journals (Sweden)

    M.R Samarghandi

    2010-10-01

    Full Text Available "n "n "nBackgrounds and Objectives: Industrial wastewater included the heavy metal is one of the important sources of environmental pollution. Hexavalent chromiumand divalent nickel are founded in plating wastewater which is harmful for human health and environment. Therefore, the purpose of this research is investigation of photocatalytic removal of hexavalent chromium and divalent nickel from aqueous solution using UV/TiO2 process in a batch system."nMaterials andMethods: At first, reactor was designed. Then, optimumdosage of TiO2 was obtained equal to 1 g/L, with variation TiO2 dosage at constant pH and initial concentrations of hexavalent chromium and divalent nickel. The effect of pH, contact time and initial concentration of hexavalent chromium was studied at the constant amount of TiO2 (1gr/L."nResults: The result showed that photocatalytic removal efficiency increased with increasing reaction time and TiO2 dosage. In addition, it was found that removal efficiency of hexavalent chromium was decreased by increasing initial chromium concentration and pH. But, photocatalytic removal efficiency of nickel ion was increased and decreased by increasing of pH and initial nickel concentration, respectively."nConclusion: The results showed that UV/TiO2 was an effective method in removal of hexavalent chromium and divalent nickel from aqueous solutions

  20. New technology for comprehensive utilization of aluminum-chromium residue from chromium salts production

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; QI Tian-gui; JIANG Xin-min; ZHOU Qiu-sheng; LIU Gui-hua; PENG Zhi-hong; HAN Deng-lun; ZHANG Zhong-yuan; YANG Kun-shan

    2008-01-01

    Colloidal aluminum-chromium residue(ACR) was mass-produced in chromate production process, and the large energy consumption and high recovery cost existed in traditional methods of utilizing such ACR. To overcome those problems, a new comprehensive method was proposed to deal with the ACR, and was proven valid in industry. In the new process, the chromate was separated firstly from the colloidal ACR by ripening and washing with additives, by which more than 95% hexavalent chromium was recovered. The chromium-free aluminum residue(CFAR), after properly dispersed, was digested at 120-130 ℃ and more than 90% alumina can be recovered. And then the pregnant aluminate solution obtained from digestion was seeded to precipitate aluminum hydroxide. This new method can successfully recover both alumina and sodium chromate, and thus realize the comprehensive utilization of ACR from chromate industry.

  1. CHROMIUM INDUCED CYTOTOXICITY IN BLACKGRAM (VIGNA MUNGO L.)

    OpenAIRE

    A. Chidambaram ، P. Sundaramoorthy ، A. Murugan ، K. Sankar Ganesh ، L. Baskaran

    2009-01-01

    Chromium is known to be highly toxic to biological systems. This study was designed to determine the mutagenic effects of different concentrations (0, 10, 25, 50, 100 and 200 mg/L) of hexavalent chromium on root tip cells of blackgram (Vigna mungo L. Hepper). The blackgram seeds were equi-spacially arranged in sterilized petriplates lined with filter paper and they were treated with different concentrations of chromium solution. In germination studies, the morphological growth parameters such...

  2. Processes affecting the remediation of chromium-contaminated sites.

    OpenAIRE

    Palmer, C.D.; Wittbrodt, P R

    1991-01-01

    The remediation of chromium-contaminated sites requires knowledge of the processes that control the migration and transformation of chromium. Advection, dispersion, and diffusion are physical processes affecting the rate at which contaminants can migrate in the subsurface. Heterogeneity is an important factor that affects the contribution of each of these mechanisms to the migration of chromium-laden waters. Redox reactions, chemical speciation, adsorption/desorption phenomena, and precipitat...

  3. Production of a chromium Bose-Einstein condensate

    OpenAIRE

    Griesmaier, Axel; Stuhler, Jürgen; Pfau, Tilman

    2005-01-01

    The recent achievement of Bose-Einstein condensation of chromium atoms [1] has opened longed-for experimental access to a degenerate quantum gas with long-range and anisotropic interaction. Due to the large magnetic moment of chromium atoms of 6 {$\\mu$}B, in contrast to other Bose- Einstein condensates (BECs), magnetic dipole-dipole interaction plays an important role in a chromium BEC. Many new physical properties of degenerate gases arising from these magnetic forces have been predicted in ...

  4. Increase of chromium utilization in stainless steel melting

    International Nuclear Information System (INIS)

    The processes of deoxidizing when melting stainless 18-10 steels in electric are furnaces by the method of remelting with wastes are investigated. The dependences of amount of reduced chromium on silicon consumption are made more precise. It is shown that it is useful to apply aluminium for deoxidation of acid high-chromium slags. Based on the data on pilot melts the extent to which aluminium can be used as a reducing agent for chromium is estimated. 3 refs., 2 figs

  5. Chromium depletion from stainless steels during vacuum annealing

    International Nuclear Information System (INIS)

    The behaviour of chromium during selective evaporation by high temperature vacuum annealing has been investigated by means of energy dispersive X-ray analysis and by neutron activation analysis. It was established that the rate of chromium loss from austenitic stainless steels 316 and 321 is controlled by chromium inter-diffusion rather than tracer diffusion in the alloy. Two important parameters in selective removal of chromium from alloy steels are the variation in the chromium surface concentration with time and the depletion profile in the alloy. The present work gives support for the model in which loss of chromium is dependent on its diffusivity in the alloy and on an interface transfer coefficient. The results showed that the surface concentration of chromium decreased with increasing vacuum annealing time. The chromium depletion profile in the metal was in accord with the previous derived model, apart from an anomalous near surface region. Here the higher resolution of a neutron activation technique indicated a region within approximately 2 microns of the surface where the chromium concentration decreased more steeply than expected. (author)

  6. 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.

  7. Tribological Characteristics of Chromium-active Carbon Electroplated Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    GUKa-fi; HUAMeng; Yi-min

    2004-01-01

    A process of chromium electroplating using a standard bath with additives and active carbon particles was reported, and the tribological behaviors of the composite coatings using the pin-on-disk tester and the table wear tester were i nvestig(aed. Experimental results indicate that the electroplated chromium-active carbon composite coatings exhibited the low friction coefficient anti excellent anti-wear properties whets coffered with the normal chromium electroplated ones. The formation of active carbon particles within the chromium matrices can be explained by SEM analysis and the mechanis of wear resistance of the composite coatings were studied.

  8. 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.

  9. 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.

  10. Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

    DEFF Research Database (Denmark)

    2000-01-01

    Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...... by replacement of the nitride ions with oxide ions in the molten carbonate electrolyte....

  11. Investigation of alternative phosphating treatments for nickel and hexavalent chromium elimination

    International Nuclear Information System (INIS)

    obtained with passivation treatment in niobium containing solution could be considered as a promising alternative to replace passivation with hexavalent chromium ions. Despite of the promising results, adjustments in the baths to obtain stability are still needed and should guide the next steps of the subject of this research. (author)

  12. Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide.

    Science.gov (United States)

    Bedemo, Agaje; Chandravanshi, Bhagwan Singh; Zewge, Feleke

    2016-01-01

    Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3-10). The optimum conditions for the removal of Cr(III) were found to be at pH 4-6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent. PMID:27547663

  13. Determination of chromium, cobalt and nickel in tissue samples by radiochemical activation analysis

    International Nuclear Information System (INIS)

    A radiochemical neutron activation analysis method for the determination of chromium, cobalt and nickel in tissue samples. A radiochemical neutron activation analysis method for the determination of chromium, cobalt and nickel has been developed. The destruction device used consisted of a combined wet-ashing-distillation and ion-exchange system. Six samples could be treated at the same time. The samples were wet-ashed with H*L2SO*L4-H*L2O*L2 mixture. Volatile elements were distilled as bromide compounds with HBr*H-. The distillation residue in 8M HCl was passed through hydrated antimony pentoxide (HAP) in order to remove disturbing *H2*H4Na-activity and through a Dowex 2 x 8 column so as to retain *H6*H0Co (formed from *H5*H8Ni). Chromium was elutriated from the column and precipitated as Cr(OH)*L3 for the removal of disturbing *H3*H2P-activity. The standards and samples were treated in a similar manner each so that the yield determination is not necessarily needed. The yields by tracer experiments were (43 +- 5) % for Cr, (93 +- 4) % for Co and (88 +- 14) % for Ni. The precision and accuracy of the method were studied by using reference materials of the National Bureau of Standards (NBS) and the International Atomic Energy Agency (IAEA)

  14. HEXAVALENT CHROMIUM REMOVAL FROM AQUEOUS SOLUTIONS BY PLEUROTUS OSTREATUS SPENT BIOMASS.

    Directory of Open Access Journals (Sweden)

    D.CAROL

    2012-01-01

    Full Text Available The Pleurotus ostreatus spent biomass after the harvest, is a waste which was used as a potential sorbent after coating it with chitosan an deacetylated derivative from chitin the most abundant carbohydratesecond to cellulose .The study is an attempt to elaborate and justify the optional utility of Spent Pleurotus ostreatus biomass for hexavalent chromium removal from aqueous industrial effluents. The effect of experimental parameters such as pH, biosorbent dosage, biosorbent dosage, initial metal concentration, temperature and sorption time is very striking from the obtained results .The Freundlich isotherm and Langmuir isotherm fitted well to the data of Cr (VI sorption capacity of Spent Pleurotus biomass. The intraparticle diffusion plot suggest that the sorption process proceeds by surface adsorption alone in case of activated spentbiomass but when coated with chitosan the process is sorption along with intra particle diffusion or pore diffusion. The overall adsorption process was endothermic and spontaneous innature.EDX analysis indicated the presence of hexavalent chromium ions on the surface of chitosan coated spent Pleurotus biomass. The resultssuggest that the enhanced spent biomass could be employed as an efficient adsorbent for the removal of hexavalent chromium from industrial effluents as well as from contaminated water sources.

  15. 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...

  16. Oxidation state of chromium associated with cell surfaces of Shewanella oneidensis during chromate reduction

    Energy Technology Data Exchange (ETDEWEB)

    Neal, Andrew L.; Lowe, Kristine; Daulton, Tyrone L.; Jones-Meehan, Joanne; Little, Brenda J

    2002-12-30

    Employing electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS), we demonstrate that in both aerobic and anaerobic culture Shewanella oneidensis cells are capable of chromate reduction. No Cr(VI) or Cr(V) species were identified at the cell surfaces in Cr 2p{sub 3/}ore photoelectron spectra. More chromium was associated with cell surfaces recovered from anaerobic medium than aerobic. Multiplet-splitting models derived for Cr(III) and Cr(IV) were employed to determine contributions from each ion to Cr 2p{sub 3/2} photopeaks collected from the various cell treatments. Whilst in all cases Cr(III) was the major ion associated with cell surfaces, a significant contribution was identified due to Cr(IV) in anaerobically grown cells. The Cr(IV) contribution was far less when cells were grown aerobically. Moreover, when anaerobically grown cells were exposed to oxygen very little re-oxidation of Cr-precipitates occurred, the precipitates were again identified as a mixture of Cr(III) and Cr(IV). A positive relationship was observed between amounts of chromium and phosphorous associated with cell surfaces resulting from the various treatments, suggesting the precipitates included Cr(III)-phosphate. The fact that Cr(IV) remained associated with precipitates following re-oxidation suggests that under anaerobic conditions the intermediate ion is afforded sufficient stability to be incorporated within the precipitate matrix and thus conferred a degree of protection from oxidation.

  17. Optical spectroscopy of trivalent chromium in sol-gel lithium niobate

    OpenAIRE

    Krebs, J. K.; Happek, U.

    2005-01-01

    We report on the characterization of sol-gel derived lithium niobate via trivalent chromium probe ions, a study that is motivated by recent reports on the synthesis of high quality sol-gel lithium niobate (LiNbO$_3$). In order to assess the quality of sol-gel derived LiNbO$_3$, we incorporate Cr$^{3+}$ during the hydrolysis stage of the sol-gel process. A comparison of the Cr$^{3+}$ emission and photo-excitation data on both sol-gel and melt-grown LiNbO$_3$ shows that the sol-gel derived mate...

  18. Mechanisms of color centor formation in chromium-containing scandium garnet crystals

    International Nuclear Information System (INIS)

    Mekhanisms of absorption induced by UV pumping radiation in chromium-containing crystals of scandium garnets (GSGG:Cr3+; GSGG:Cr3+, Nd3+; ISGG:Cr3+) are revealed. It is experimentally ascertained that color center formation processes in two-activated crystals are sufficiently suppressed. This is conditioned by a reduction of contribution to the process of coloring of charges released by shortwave pumping radiation from Cr3+ ion metastable level, the population of which in a two-activated crystal is low due to efficient Cr3+→Nd3+ energy transfer

  19. Oxygen and chromium self-diffusion in Cr sub(2)O sub(3)

    International Nuclear Information System (INIS)

    The oxygen and chromium diffusivities in Cr sub(2)O sub(3) single crystals and polycrystals were determined by ion implantation, thick film methods, and isotopic exchange, using the sup(54)Cr, sup(5)Cr and sup(18)O isotopes. Depth profiling was made by SIMS, and the diffusion coefficients were computed using a general solution of the Fick's law taking into account evaporation and exchange at the surface. Lattice and grain boundary self-diffusion coefficients were determined as a function of temperature and oxygen pressure. (author)

  20. 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

  1. Chromium (VI) biosorption by immobilized Aspergillus niger in continuous flow system with special reference to FTIR analysis.

    Science.gov (United States)

    Chhikara, S; Hooda, A; Rana, L; Dhankhar, R

    2010-09-01

    Aspergillus niger was treated with acid and immobilized in calcium alginate matrix. The dynamic removal of Cr (VI) ion was studied using continuously fed column packed with immobilized biosorbent beads. Column experiments were carried out to study the effect of various bed heights (20, 30, 40 cm) under different flow rates (5, 7.5, 10 ml min(-1)) on efficiency of biosorption. The maximum time (1020 minutes; 17 hr) before breakthrough point was observed in case of 40 cm bed height with flow rate of 5ml min(-1). FTIR analysis of acid treated immobilized A. niger was used fora qualitative and preliminary analysis of chemical functional groups present on its cell wall which provided the information on nature of cell wall and Cr (VI) interaction during the process of biosorption. The IR spectra of biosorbent recorded before and after chromium biosorption had shown some changes in the band patterns, which were finally analyzed and was found that chemical interaction such as ion-exchange between carboxyl (-COOH), hydroxyl (-OH) and amine (-NH2) group of biosorbent and Chromium ion were mainlyinvolved in biosorption of Cr (VI) onto A. niger cell wall surface. The biosorbed metal was eluted from biosorbent by using 0.1 M H2SO4 as eluant. Immobilized biosorbent could be reused for five consecutive biosorption and desorption cycles without apparent loss of efficiency after its reconditioning. Considering all above factors together this paper discusses the efficient chromium biosorption process carried out by immobilized A. niger biosorbent. PMID:21387903

  2. Molecular aspects of glucose dehydration by chromium chlorides in ionic liquids.

    Science.gov (United States)

    Zhang, Yanmei; Pidko, Evgeny A; Hensen, Emiel J M

    2011-05-01

    A combined experimental and computational study of the ionic-liquid-mediated dehydration of glucose and fructose by Cr(II) and Cr(III) chlorides has been performed. The ability of chromium to selectively dehydrate glucose to 5-hydroxymethylfurfural (HMF) in the ionic liquid 1-ethyl-3-methyl imidazolium chloride does not depend on the oxidation state of chromium. Nevertheless, Cr(III) exhibits higher activity and selectivity to HMF than Cr(II) . Anhydrous CrCl(2) and CrCl(3)⋅6 H(2)O readily catalyze glucose dehydration with HMF yields of 60 and 72%, respectively, after 3 h. Anhydrous CrCl(3) has a lower activity, because it only slowly dissolves in the reaction mixture. The transformation of glucose to HMF involves the formation of fructose as an intermediate. The exceptional catalytic performance of the chromium catalysts is explained by their unique ability to catalyze glucose to fructose isomerization and fructose to HMF dehydration with high selectivity. Side reactions leading to humins by means of condensation reactions take predominantly place during fructose dehydration. The higher HMF selectivity for Cr(III) is tentatively explained by the higher activity in fructose dehydration compared to Cr(II) . This limits the concentration of intermediates that are involved in bimolecular condensation reactions. Model DFT calculations indicate a substantially lower activation barrier for glucose isomerization by Cr(III) compared to Cr(II) . Qualitatively, glucose isomerization follows a similar mechanism for Cr(II) and Cr(III) . The mechanism involves ring opening of D-glucopyranose coordinated to a single Cr ion, followed by a transient self-organization of catalytic chromium complexes that promotes the rate-determining hydrogen-shift step.

  3. 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.

  4. IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft)

    Science.gov (United States)

    [UPDATE] New Schedule for IRIS Hexavalent Chromium Assessment In Feb 2012, EPA developed a new schedule for completing the IRIS hexavalent chromium assessment. Based on the recommendations of the external peer review panel, which met in May 2011 to review the dra...

  5. Chromium and Polyphenols From Cinnamon Improve Insulin Sensitivity

    Science.gov (United States)

    Naturally occurring compounds that have been shown to improve insulin sensitivity include chromium and polyphenols found in cinnamon. These compounds also have similar effects on insulin signaling and glucose control. The signs of chromium deficiency are similar to those for the metabolic syndrome ...

  6. Safety, absorption, and antioxidant effects of chromium histidine

    Science.gov (United States)

    Supplemental chromium has been shown to be involved in the alleviation of the metabolic syndrome, glucose intolerance, polycystic ovary syndrome, depression, excess body fat, and gestational, steroid-induced, and type 2 diabetes. Chromium amino acid complexes that contained histidine displayed cons...

  7. Toxicity and adaptation of Dictyosphaerium chlorelloides to extreme chromium contamination.

    Science.gov (United States)

    Sánchez-Fortún, Sebastián; López-Rodas, Victoria; Navarro, Macarena; Marvá, Fernando; D'ors, Ana; Rouco, Mónica; Haigh-Florez, David; Costas, Eduardo

    2009-09-01

    Metals are often spilled by industries into inland water environments, with adverse consequences. Numerous papers have reported that heavy metals produce massive destruction of algae. Nevertheless, algal populations seem to become tolerant when they have had previous exposures to heavy metals. Because the mechanisms allowing heavy metal tolerance of algae are not yet known, the present study analyzed the effect of hexavalent chromium on growth and photosynthetic performance of Dictyosphaerium chlorelloides, stressing on the adaptation mechanisms to chromium contamination. Growth and photosynthetic performance of algal cells were inhibited by Cr(VI) at 10 mg/L, and the 72-h median inhibition concentration was established as 1.64 and 1.54 mg/L, respectively. However, after further incubation for a three month period in an environment with 25 mg/L of chromium, some rare, chromium-resistant cells occasionally were found. A Luria-Delbrück fluctuation analysis was performed to distinguish between resistant algae arising from rare, spontaneous mutations and resistant algae arising from physiological adaptation and other adaptive mechanisms. Resistant cells arose only by spontaneous mutations before the addition of chromium, with a rate of 1.77 x 10(-6) mutants per cell division. From a practical point of view, the use of both chromium-sensitive and chromium-resistant genotypes could make possible a specific algal biosensor for chromium. PMID:19323601

  8. Residual Chromium in Leather by Instrumental Neutron Activation Analysis

    Directory of Open Access Journals (Sweden)

    S. Okoh

    2012-01-01

    Full Text Available Problem statement: Most tanning processes employ the use of chromium sulphate. For chromium tanned leather, finished products may contain high amount of residual chromium. This may pose some health hazards, since chromium is known to be toxic at elevated concentration. This justifies the need for the study. Approach: Various samples of leather were collected from a tannery, a leather crafts market, a leather dump site and from local tanners all in Kano, Nigeria in 2009. The samples were irradiated for 6 h in the inner site of the Nigerian Research Reactor (NIRR-1 at a flux of 5×1011 ncm-2 sec-1. Results: After evaluating the spectrum, the mean results for chromium in the samples were determined as 2.33±0.3, 2.23±0.3 and 2.93±0.4% for samples from the tannery, leather crafts market and leather dump sites respectively. Chromium concentration in samples collected from local tanners who use tannins from Acacia nilotica as tanning agent was below the detection limit of Instrumental Neutron Activation Analysis (INAA technique used in the study. Conclusion: Although, the concentrations of chromium in the analysed samples were not much higher than what were obtained in literature, they may be enough to sensitize the population that is allergic to chromium.

  9. Studies on the process aspects related to chemical decontamination of chromium-containing alloys with redox processes

    International Nuclear Information System (INIS)

    Presence of chromium in the oxide layer makes oxidative pre-treatment with oxidizing agents such as potassium permanganate (KMnO4) a must for the decontamination of stainless steels and other chromium containing alloys. The effectiveness of pre-treatment with oxidizing reagent varies with the conditions of treatment such as temperature, concentration and whether the medium is acidic or alkaline. A comparative study of the two acidic oxidizing agents, i.e., nitric acid-permanganate and permanganic acid was made. The dissolution behavior of copper and its oxide in permanganic acid was found to be comparable to that of chromium oxide. Citric acid and ascorbic acid were investigated as alternatives to oxalic acid for the reduction/decomposition of permanganate left over after the oxidizing pre-treatment step. It has been established that the reduction of chromate by citric acid is instantaneous only in presence of Mn2+ ions. It has also been established that reduction of residual permanganate can be achieved with ascorbic acid and with minimum chemical requirement. The capabilities of nitrilotriacetic acid (NTA)-ascorbic acid mixture for the dissolution of hematite have been explored. This study would help to choose the suitable oxidizing agent, the reducing agent used for decomposition of permanganate and to optimize the concentration of reducing formulation so that the process of decontamination is achieved with a minimum requirement of chemicals. The generation of radioactive ion exchange resin as waste is therefore held at a minimum. Ion exchange studies with metal ion complexes of relevance to decontamination were carried out with a view to choose a suitable type of ion exchanger. It has been established that treatment of the ion exchange resin with brine solution can solve the problem of leaching out of non-ionic organics from the resin. (orig.)

  10. CHROMIUM BIOACCUMULATION FROM COMPOSTS AND VERMICOMPOSTS BASED ON TANNERY SLUDGES

    Directory of Open Access Journals (Sweden)

    Krzysztof GONDEK

    2008-07-01

    Full Text Available Storage of waste substances is not indifferent to ecological equilibrium in the environment therefore should not be the ultimate way to limit waste arduousness. Therefore, the conducted investigations aimed to determine the effect of tannery composts and vermicomposts loaded with chromium on this element bioaccumulation in earthworm bodies and biomass of selected plants. Chromium in composts and vermicomposts based on tannery sludges occurred in small quantities and easily soluble compounds. Chromium concentrations in redworm biomass points to this metal accumulation in Eisenia fetida body tissues. This element content in redworm biomass was signifi cantly positively correlated with its content in composts. Chromium content in plants was diversifi ed and on treatments was generally smaller than on mineral treatment or farmyard manure. Chromium absorbed by plants was stored mainly in the root systems, and over the norm content of this element found in vermicomposts did not cause its excessive accumulation in plant biomass.

  11. Bioleaching of chromium from tannery sludge by indigenous Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Wang, Yuan-Shan; Pan, Zhi-Yan; Lang, Jian-Min; Xu, Jian-Miao; Zheng, Yu-Guo

    2007-08-17

    Chromium in tannery sludge will cause serious environmental problems and is toxic to organisms. The acidophilic sulfur-oxidizing Acidithiobacillus thiooxidans can leach heavy metals form urban and industrial wastes. This study examined the ability of an indigenous sulfur-oxidizing A. thiooxidans to leach chromium from tannery sludge. The results showed that the pH of sludge mixture inoculated with the indigenous A. thiooxidans decreased to around 2.0 after 4 days. After 6 days incubation in shaking flasks at 30 degrees C and 160 rpm, up to 99% of chromium was solubilized from tannery sludge. When treated in a 2-l bubble column bioreactor for 5 days at 30 degrees C and aeration of 0.5 vvm, 99.7% of chromium was leached from tannery sludge. The results demonstrated that chromium in tannery sludge can be efficiently leached by the indigenous A. thiooxidans.

  12. 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

  13. Identification of autoionizing states of atomic chromium for resonance photo-ionization at the ISOLDE-RILIS

    CERN Document Server

    Goodacre, T Day; Fedorovc, D; Fedosseev, V N; Marsh, B A; Molkanov, P; Rossel, R E; Rothe, S; Seiffert, C

    2015-01-01

    The resonance ionization laser ion source (RILIS) is the principal ion source of the ISOLDE radioactive beam facility based at CERN. Using the method of in-source resonance ionization spectroscopy, an optimal three-step, three-resonance photo-ionization scheme has been developed for chromium. The scheme uses an ionizing transition to one of the 14 newly observed autoionizing states. This work increases the range of ISOLDE-RILIS ionized beams to 32 chemical elements. Details of the spectroscopic studies are described and the new ionization scheme is summarized. A link to the complete version of this document will be added here following publication:

  14. Selenium protection from cadmium and chromium poisoning

    International Nuclear Information System (INIS)

    The interaction of selenium with cadmium and chromium was studied in 168 chicken-broilers (DWCxWR) divided into four equal groups. Eight-week old control animals received an intravenous dose of /sup 115m/Cd Chloride 370 KBq/Kg (Group I), or 51Cr Chloride 370 KBq/Kg (Group II). The kinetics of these isotopes were studied by scintillation spectrometry (NaI/TI) carried out for whole blood, plasma, plasma proteins, urine, feces and homogenates of all organs at various time intervals. Animals in Groups III and IV received eight subcutaneous doses of sodium selenate (5ug) at 8-week intervals prior to /sup 115m/Cd or 51Cr. The kinetics of these elements were studied as in the previous two groups. It was found that selenium affected those kinetics in two ways: (a) by increasing the excretion of Cd by 11 +/- 3% (P < 0.001) and that of Cr by 7 +/- 1% (P < 0.001); and (b) by favoring redistribution of those elements, with significant (P < 0.001) reductions in liver, endocrine glands and kidney and increases (P < 0.01) in bone. The study suggests that selenium protects the animals' vital organs from environmental pollutants, such as cadmium and chromium

  15. In situ synchrotron X-ray diffraction study of the effect of chromium additions to the steel and solution on CO2 corrosion of pipeline steels

    International Nuclear Information System (INIS)

    Highlights: •We studied the effect of chromium on CO2 corrosion processes. •Chromium addition accelerates the onset of siderite and chukanovite precipitation. •One of the key effects is to decrease the critical supersaturation for siderite nucleation. -- Abstract: We demonstrate the important effects of chromium in the steel composition and of Cr3+ ions in solution on the nucleation and growth of corrosion layers in a CO2 environment. We propose that high-valent metal cations in solution (within the boundary layer) catalyse the nucleation of siderite, which otherwise has a high critical supersaturation for precipitation. One of the key effects of small alloy additions to the steel is to put into the local solution species that decrease the critical supersaturation for siderite and modify the growth rate of the scale, thereby promoting the formation of an adherent and protective scale

  16. Transmission electron microscope study of fusion-environment radiation damage in iron and iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Horton, L.L.S.

    1982-07-01

    A transmission electron microscopy study of radiation damage microstructures in iron and iron-chromium alloys has been performed. This study consisted of both qualitative and quantitative characterization of the dislocation and cavity microstructures, including determination of vacancy/interstitial character and Burgers vectors for dislocation loops and analysis of the cavity morphology. The effects of irradiation temperature, fluence, helium implantation, and chromium content were investigated. Neutron irradiation (iron specimens, 1 dpa, 455 to 1000 K) and triple-beam ion irradiation (Fe-10% Cr specimens, 10 dpa, 725 to 950 K; Fe-10% Cr specimens, 850 K, 0.3 to 100 dpa; and Fe, Fe-5% Cr, Fe-10% Cr specimens, 850 K, 10 dpa) were employed. In the triple-beam ion irradiation procedure, simultaneous bombardment with 4 MeV Fe/sup + +/ ions and energetic He/sup +/ and D/sub 2//sup +/ ions was used to simulate the fusion environment (10 at. ppM He/dpa and 41 at. ppM D/dpa). In addition, single-beam 4 MeV Fe/sup + +/ ion irradiations of Fe-10% Cr both with and without pre-injection of helium and deuterium were performed.

  17. Transmission electron microscope study of fusion-environment radiation damage in iron and iron-chromium alloys

    International Nuclear Information System (INIS)

    A transmission electron microscopy study of radiation damage microstructures in iron and iron-chromium alloys has been performed. This study consisted of both qualitative and quantitative characterization of the dislocation and cavity microstructures, including determination of vacancy/interstitial character and Burgers vectors for dislocation loops and analysis of the cavity morphology. The effects of irradiation temperature, fluence, helium implantation, and chromium content were investigated. Neutron irradiation (iron specimens, 1 dpa, 455 to 1000 K) and triple-beam ion irradiation (Fe-10% Cr specimens, 10 dpa, 725 to 950 K; Fe-10% Cr specimens, 850 K, 0.3 to 100 dpa; and Fe, Fe-5% Cr, Fe-10% Cr specimens, 850 K, 10 dpa) were employed. In the triple-beam ion irradiation procedure, simultaneous bombardment with 4 MeV Fe++ ions and energetic He+ and D2+ ions was used to simulate the fusion environment (10 at. ppM He/dpa and 41 at. ppM D/dpa). In addition, single-beam 4 MeV Fe++ ion irradiations of Fe-10% Cr both with and without pre-injection of helium and deuterium were performed

  18. Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

  19. 75 FR 65067 - National Emission Standards for Hazardous Air Pollutant Emissions: Hard and Decorative Chromium...

    Science.gov (United States)

    2010-10-21

    ... Decorative Chromium Electroplating and Chromium Anodizing Tanks; Group I Polymers and Resins; Marine Tank...: Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks; Group I Polymers and Resins... Tanks. Group I Polymers and Resins Production.. Scott Throwe, (202) 564-7013,...

  20. 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.

  1. Identifying genes and gene networks involved in chromium metabolism and detoxification in Crambe abyssinica

    Energy Technology Data Exchange (ETDEWEB)

    Zulfiqar, Asma, E-mail: asmazulfiqar08@yahoo.com [Department of Plant, Soil, and Insect Sciences, 270 Stockbridge Road, University of Massachusetts Amherst, MA 01003 (United States); Paulose, Bibin, E-mail: bpaulose@psis.umass.edu [Department of Plant, Soil, and Insect Sciences, 270 Stockbridge Road, University of Massachusetts Amherst, MA 01003 (United States); Chhikara, Sudesh, E-mail: sudesh@psis.umass.edu [Department of Plant, Soil, and Insect Sciences, 270 Stockbridge Road, University of Massachusetts Amherst, MA 01003 (United States); Dhankher, Om Parkash, E-mail: parkash@psis.umass.edu [Department of Plant, Soil, and Insect Sciences, 270 Stockbridge Road, University of Massachusetts Amherst, MA 01003 (United States)

    2011-10-15

    Chromium pollution is a serious environmental problem with few cost-effective remediation strategies available. Crambe abyssinica (a member of Brassicaseae), a non-food, fast growing high biomass crop, is an ideal candidate for phytoremediation of heavy metals contaminated soils. The present study used a PCR-Select Suppression Subtraction Hybridization approach in C. abyssinica to isolate differentially expressed genes in response to Cr exposure. A total of 72 differentially expressed subtracted cDNAs were sequenced and found to represent 43 genes. The subtracted cDNAs suggest that Cr stress significantly affects pathways related to stress/defense, ion transporters, sulfur assimilation, cell signaling, protein degradation, photosynthesis and cell metabolism. The regulation of these genes in response to Cr exposure was further confirmed by semi-quantitative RT-PCR. Characterization of these differentially expressed genes may enable the engineering of non-food, high-biomass plants, including C. abyssinica, for phytoremediation of Cr-contaminated soils and sediments. - Highlights: > Molecular mechanism of Cr uptake and detoxification in plants is not well known. > We identified differentially regulated genes upon Cr exposure in Crambe abyssinica. > 72 Cr-induced subtracted cDNAs were sequenced and found to represent 43 genes. > Pathways linked to stress, ion transport, and sulfur assimilation were affected. > This is the first Cr transcriptome study in a crop with phytoremediation potential. - This study describes the identification and isolation of differentially expressed genes involved in chromium metabolism and detoxification in a non-food industrial oil crop Crambe abyssinica.

  2. 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.

  3. WATER HYACINTH BIOMASS (WHB FOR THE BIOSORPTION OF HEXAVALENT CHROMIUM: OPTIMIZATION OF PROCESS PARAMETERS

    Directory of Open Access Journals (Sweden)

    Syed Hadi Hasan

    2010-05-01

    Full Text Available Water hyacinth (Eichhornia crassipes biomass has been used for many years for the remediation of heavy metals. The present study successfully utilizes the dried powdered biomass of the aerial part (stem and leaves of water hyacinth for biosorption of hexavalent chromium. The effect of various parameters (viz. pH, initial metal ion concentration and temperature on the removal of Cr(VI was studied by conducting only 15 sets of sorption runs using Box-Behnken Design (BBD. The pH had a negative and temperature and concentration had positive effects on uptake of chromium. The predicted results (obtained using an empirical linear polynomial model were found to be in good agreement (R2 = 99.8% with the experimental results. The predicted maximum removal of Cr(VI (91.5181 mg/g can be achieved at pH 2.0, initial metal ion concentration 300 mg/L, and temperature 40 °C. The sorption capacity of sorbent was also calculated using a Langmuir sorption isotherm model and was found to be 101 mg/g at 40 C and pH 2.0.

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

    Science.gov (United States)

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

    2012-01-01

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

  5. 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.

  6. Acetabular bone density and metal ions after metal-on-metal versus metal-on-polyethylene total hip arthroplasty; short-term results

    NARCIS (Netherlands)

    Zijlstra, Wierd P.; van der Veen, Hugo C.; van den Akker-Scheek, Inge; Zee, Mark J. M.; Bulstra, Sjoerd K.; van Raay, Jos J. A. M.

    2014-01-01

    Information on periprosthetic acetabular bone density is lacking for metal-on-metal total hip arthroplasties. These bearings use cobalt-chromium instead of titanium acetabular components, which could lead to stress shielding and hence periprosthetic bone loss. Cobalt and chromium ions have detriment

  7. Chromium-induced membrane damage: protective role of ascorbic acid

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Importance of chromium as environmental toxicant is largely due to impact on the body to produce cellular toxicity. The impact of chromium and their supplementation with ascorbic acid was studied on plasma membrane of liver and kidney in male Wistar rats (80 - 100gbody weight). It has been observed that the intoxication with chromium ( i. p. ) at the dose of 0.8 mg/100g body weight per day for a period of 28 days causes significant increase in the level of cholesterol and decrease in the level of phospbolipid of both liver and kidney. The alkaline pbosphatase, total ATPase and Na + -K + -ATPase activities were significantly decreased in both liver and kidney after chromium treatment,except total ATPase activity of kidney. It is suggested that chromium exposure at the present dose and duration induce for the alterations of structure and function of both liver and kidney plasma membrane. Ascorbic acid ( i.p. at the dose of 0.5 mg,/100g body weight per day for period of 28 days) supplementation can reduce these structural changes in the plasma membrane of liver and kidney. But the functional changes can not be completely replenished by the ascorbic acid supplementation in response to chromium exposure. So it is also suggested that ascorbic acid (nutritional antioxidant) is useful free radical scavenger to restrain the chromium-induced membrane damage.

  8. Bioavailability of a potato chromium complex to the laboratory rat

    International Nuclear Information System (INIS)

    Research objectives were to study the effect of food source, preparation method and chemical form on bioavailability of chromium. Chromium concentration in potatoes was determined and tubers labeled either intrinsically or extrinsically with radioactive chromate. A labeled chromium complexes was isolated from preparations of raw, baked or fried potatoes and chromatographed on gel permeation media. Availability of the potato chromium complex to the rat was examined in three feeding studies. Animals were dosed with radioactive extrinsically or intrinsically labeled potato extract or with chromate. A labeled chromium complex was isolated from gastrointestinal contents of rats and chromatographed. Potato pulp and peel contained 1.63 and 2.70 μg Cr/g tissue respectively. True and apparent absorption from extrinsically labeled feedings were 33.4 +/- 4.7 and 29.8 +/- 11.2% respectively, and no differences existed between absorption from raw and cooked potatoes. Absorption from the extrinsic labeled potatoes differed significantly from absorption of inorganic chromatium. Apparent absorption of raw (11.1 +/- 7.9%) and cooked (-0.7 +/- 2.8%) intrinsically labeled feedings differed significantly. Absorption of inorganic chromium was 17.8% (true) and 11.5% (apparent). Examination of the chromium complex isolated from gastrointestinal tract contents showed enlargement of the complex in the stomach after consumption

  9. Stabilization of chromium salt in ordinary portland cement

    Indian Academy of Sciences (India)

    Damir Barbir; Pero Dabić; Petar Krolo

    2012-12-01

    Ordinary Portland cement (OPC) samples containing the chromium salt have been investigated using differential microcalorimetry, conductometry and Fourier transform infrared spectroscopic analysis. The effect of chromium on OPC hydration was evaluated by continuous observing of early hydration. The microcalorimetrical results show that with increasing the share of chromium salt, heat maximums assume lower values and the occurrence of the maximum registered in the earlier hydration times. Conductometrical measurements show that with increasing addition of chromium salt, curve did not show any specific shape, immediate drop in specific conductivity is noticed and the maximum is reached earlier. This coincides with microcalorimetrical results. It can be concluded that the addition of chromium does not affect the mechanism of the hydration process, but it does affect the kinetic parameters and dynamics of the cement hydration process. It was found that chromium salt addition to the cement–water system is acceptable up to 2 wt.%. According to standard EN 196-3 for OPC, the beginning of binding time should occur after 60 minutes. Increased amount of chromium over 2 wt.% significantly accelerate the beginning of binding time and for the system it is not acceptable.

  10. Chromium speciation in rainwater: temporal variability and atmospheric deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kieber, R.J.; Willey, J.D.; Zvalaren, S.D. [University of North Carolina at Wilmington, Wilmington, NC (United States). Dept. of Chemistry

    2002-12-15

    Chromium is released into the atmosphere by a variety of anthropogenic activities which include steel manufacturing, leather tanning, wood presentation and fossil fuel combustion. The concentrations of the various chromium species were determined in 89 rainwater samples collected in Wilmington, NC from October 1, 1999 to December 31, 2001. Volume weighted annual average concentrations of Cr{sub total}, particulate Cr, Cr(III)(aq), and Cr(VI)(aq) were 4.6, 2.2, 0.8 and 1.2 nM, respectively. There was distinct seasonal and diurnal variability in the concentrations of the various chromium species. Chromium emissions to the global atmosphere by both natural and anthropogenic sources are estimated to be 2.2 x 10{sup 9} mol/yr. Using rainwater concentration data along with other published rainwater Cr concentrations and an estimate for total global annual rain, the total global flux of chromium removed from the atmosphere via wet deposition is 2.1 x 10{sup 9} mol/yr. This represents complete removal of Cr and indicates that essentially all chromium released into the global atmosphere is removed via rain. About half this chromium is dissolved with roughly equal concentrations of toxic Cr(VI) and relatively harmless Cr(III) species. 48 refs., 4 figs., 3 tabs.

  11. Chromium liquid waste inertization in an inorganic alkali activated matrix: Leaching and NMR multinuclear approach

    Energy Technology Data Exchange (ETDEWEB)

    Ponzoni, Chiara, E-mail: chiara.ponzoni@unimore.it [University of Modena and Reggio Emilia, Department of Engineering “Enzo Ferrari”, Modena (Italy); Lancellotti, Isabella; Barbieri, Luisa [University of Modena and Reggio Emilia, Department of Engineering “Enzo Ferrari”, Modena (Italy); Spinella, Alberto; Saladino, Maria Luisa [University of Palermo CGA-UniNetLab, Palermo (Italy); Martino, Delia Chillura [University of Palermo, Department STEBICEF, Palermo (Italy); Caponetti, Eugenio [University of Palermo CGA-UniNetLab, Palermo (Italy); University of Palermo, Department STEBICEF, Palermo (Italy); Armetta, Francesco [University of Palermo, Department STEBICEF, Palermo (Italy); Leonelli, Cristina [University of Modena and Reggio Emilia, Department of Engineering “Enzo Ferrari”, Modena (Italy)

    2015-04-09

    Highlights: • Inertization of chromium liquid waste in aluminosilicate matrix. • Water less inertization technique exploiting the waste water content. • Liquid waste inertization without drying step. • Long term stabilization study through leaching test. • SEM analysis and {sup 29}Si and {sup 27}Al MAS NMR in relation with long curing time. - Abstract: A class of inorganic binders, also known as geopolymers, can be obtained by alkali activation of aluminosilicate powders at room temperature. The process is affected by many parameters (curing time, curing temperature, relative humidity etc.) and leads to a resistant matrix usable for inertization of hazardous waste. In this study an industrial liquid waste containing a high amount of chromium (≈2.3 wt%) in the form of metalorganic salts is inertized into a metakaolin based geopolymer matrix. One of the innovative aspects is the exploitation of the water contained in the waste for the geopolymerization process. This avoided any drying treatment, a common step in the management of liquid hazardous waste. The evolution of the process - from the precursor dissolution to the final geopolymer matrix hardening - of different geopolymers containing a waste amount ranging from 3 to 20% wt and their capability to inertize chromium cations were studied by: i) the leaching tests, according to the EN 12,457 regulation, at different curing times (15, 28, 90 and 540 days) monitoring releases of chromium ions (Cr(III) and Cr(VI)) and the cations constituting the aluminosilicate matrix (Na, Si, Al); ii) the humidity variation for different curing times (15 and 540 days); iii) SEM characterization at different curing times (28 and 540 days); iv) the trend of the solution conductivity and pH during the leaching test; v) the characterization of the short-range ordering in terms of T−O−T bonds (where T is Al or Si) by {sup 29}Si and {sup 27}Al solid state magic-angle spinning nuclear magnetic resonance (ss MAS NMR) for

  12. Workshop on effects of chromium coating on Nb3Sn superconductor strand: Proceedings

    International Nuclear Information System (INIS)

    This report discusses the following topics: Chromium coating on superconductor strand -- an overview; technology of chromium plating; comparison of wires plated by different platers; search for chromium in copper; strand manufactures' presentations; chromium plating at the Lawrence Livermore National Laboratory; a first look at a chromium plating process development project tailored for T.P.X. and I.T.E.R. strand; and influence of chromium diffusion and related phenomena on the reference ratios of bare and chromium plated Nb3Sn strand

  13. Workshop on effects of chromium coating on Nb{sub 3}Sn superconductor strand: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    1994-04-12

    This report discusses the following topics: Chromium coating on superconductor strand -- an overview; technology of chromium plating; comparison of wires plated by different platers; search for chromium in copper; strand manufactures` presentations; chromium plating at the Lawrence Livermore National Laboratory; a first look at a chromium plating process development project tailored for T.P.X. and I.T.E.R. strand; and influence of chromium diffusion and related phenomena on the reference ratios of bare and chromium plated Nb{sub 3}Sn strand.

  14. Fertilizers and Mixed Crop Cultivation of Chromium Tolerant and Sensitive Plants under Chromium Toxicity

    OpenAIRE

    B. Dheeba; Sampathkumar, P; Kannan, K.

    2015-01-01

    Zea mays (maize) and Vigna radiata (green gram) are found to be the chromium (Cr) tolerant and sensitive plants, respectively. In the present paper, we investigate the reduction of the toxicity of Cr in the sensitive plants by the mixed crop cultivation in the field using various amendments. Further, the potassium dichromate was used as the source of hexavalent Cr. The results indicated that Cr adversely affects both the growth and yield of plants. The soil properties vary with Cr and differe...

  15. Thick-target PIXE analysis of chromium, copper and arsenic impregnated lumber

    Science.gov (United States)

    Saarela, K.-E.; Harju, L.; Lill, J.-O.; Rajander, J.; Lindroos, A.; Heselius, S.-J.

    1999-04-01

    Chromium, copper and arsenic (CCA) have for decades been used for wood preservation. Of these elements especially arsenic is very toxic. As CCA impregnated wood is still today used for many construction purposes, a monitoring of these metal ions is of great environmental importance. Thick-target PIXE is a powerful method for the determination of trace metals in wood. The TTPIXE method enabled study of variations of the elemental concentrations in lumber treated with CCA impregnation solution. Distribution patterns were obtained for both naturally occurring elements and elements introduced in the treatment process. During the impregnation process a desorption of e.g. alkali metal ions takes place from the wood. The sensitivity of the method is improved by dry ashing of the samples prior to PIXE analysis. The TTPIXE method was calibrated and validated using international certified reference materials (CRM) based on wood material.

  16. Microbial Diversity of Chromium-Contaminated Soils and Characterization of Six Chromium-Removing Bacteria

    Science.gov (United States)

    He, Zhiguo; Hu, Yuting; Yin, Zhen; Hu, Yuehua; Zhong, Hui

    2016-06-01

    Three soil samples obtained from different sites adjacent to a chromium slag heap in a steel alloy factory were taken to examine the effect of chromium contamination on soil bacterial diversity as determined by construction of 16S rDNA clone libraries and sequencing of selected clones based on restriction fragment length polymorphism (RFLP) analysis. Results revealed that Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Alphaproteobacteria occurred in all three soil samples, although the three samples differed in their total diversity. Sample 1 had the highest microbial diversity covering 12 different classes, while Sample 3 had the lowest microbial diversity. Strains of six different species were successfully isolated, one of which was identified as Zobellella denitrificans. To our knowledge, this is the first report of a strain belonging to the genus Zobellella able to resist and reduce chromium. Among all isolates studied, Bacillus odysseyi YH2 exhibited the highest Cr(VI)-reducing capability, with a total removal of 23.5 % of an initial Cr(VI) concentration of 350 mg L-1.

  17. 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...

  18. Effects of Supplemental Dietary Chromium on Yield and Nutrient Digestibility of Laying Hens Under Low Temperature

    OpenAIRE

    ŞAHİN, Kazım; ERTAŞ, O. Nihat; GÜLER, Talat; ÇİFTÇİ, Mehmet

    2001-01-01

    This study was conducted to determine the effects of chromium picolinate (CrPi) added into diet containing 710.3 ppb chromium on yield and nutrient digestibility of laying hens at low temperature. Forty-six-week-old laying hens were randomly assigned to four groups of 30 hens per group. Treatment groups were fed different supplemental dietary chromium levels. Thus, hens were fed diets with no supplemental chromium (Control Group), 100 ppb of supplemental chromium (100 Group), 200 ppb of s...

  19. The fate of chromium during tropical weathering

    DEFF Research Database (Denmark)

    Berger, Alfons; Frei, Robert

    2014-01-01

    We performed a mineral, geochemical and Cr–Sr–Pb isotope study on a laterite profile developed on ca. 540 Ma old tonalitic bedrock in Madagascar with special emphasis on the behavior of chromium during tropical weathering. The observed strong depletions of Ca, Si, and P, and enrichment of Fe and Al...... of the soil profile relative to stage one altered saprolite. This gain in Cr is accompanied by decreasing δ53Cr values and can be explained by partial immobilization (possibly by adsorption/coprecipitation on/with Fe-oxy-hydroxides) of mobile Cr(III) during upward transport in the weathering profile....... The negatively fractionated δ53Cr values measured in the weathering profile relative to the unaltered tonalitic bedrock characterized by a high temperature magmatic inventory Cr isotope signature are consistent with loss of a positively fractionated Cr(VI) pool formed during weathering. The predicted existence...

  20. 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

  1. Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

    Institute of Scientific and Technical Information of China (English)

    HUANG Shun-hong; PENG Bing; YANG Zhi-hui; CHAI Li-yuan; ZHOU Li-cheng

    2009-01-01

    The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.

  2. Optical emission from laser-produced chromium and magnesium plasma under the effect of two sequential laser pulses

    Indian Academy of Sciences (India)

    V N Rai; F Y Yueh; J P Singh

    2005-12-01

    Parametric study of optical emission from two successive laser pulses produced chromium and magnesium plasma is presented. The line emission from chromium and magnesium plasma showed an increase by more than six times for double laser pulse excitation than for single-pulse excitation. An optimum increase in emission intensity was noted for inter-pulse delay of ∼ 2–3 s for all the elements. The experimental observations were qualitatively explained on the basis of absorption of second laser pulse in the pre-formed (by first laser) coronal plasma by inverse Bremsstrahlung process, which were found responsible for the excitation of more ions and atoms in the plasma. This process starts as the plasma scale length becomes greater than the laser wavelength. This study further indicated the suitability of this technique in the field of elemental analysis.

  3. Observed transitions in n = 2 ground configurations of copper, nickel, iron, chromium and germanium in tokamak discharges

    International Nuclear Information System (INIS)

    A number of spectrum lines of highly ionized copper, nickel, iron, chromium, and germanium have been observed and the corresponding transitions identified. The element under study is introduced into the discharge of the PLT Tokamak by means of rapid ablation by a laser pulse. The ionization state is generally distinguishable from the time behavior of the emitted light. New identifications of transitions are based on predicted wavelengths (from isoelectronic extrapolation and other data) and on approximate expected intensities. All the transitions pertain to the ground configurations of the respective ions, which are the only states strongly populated at tokamak plasma conditions. These lines are expected to be useful for spectroscopic plasma diagnostics in the 1-3 keV temperature range, and they provide direct measurement of intersystem energy separations from chromium through copper in the oxygen, nitrogen, and carbon isoelectronic sequences

  4. Effects of Chromium(VI) and Chromium(III) on Desulfovibrio vulgaris Cells

    Energy Technology Data Exchange (ETDEWEB)

    M.E. Clark; A. Klonowska; S.B. Thieman; B. Giles; J.D. Wall; and M.W. Fields

    2007-04-19

    Desulfovibrio vulgaris ATCC 29579 is a well studied sulfate reducer that has known capabilities of reducing heavy metals and radionuclides, like chromium and uranium. Cultures grown in a defined medium (i.e. LS4D) had a lag period of approximately 40 h when exposed to 50 μMof Cr(VI). Substrate analysis revealed that although chromium is reduced within the first 5 h, growth does not resume for another 35 h. During this time, small amounts of lactate are still utilized but the reduction of sulfate does not occur. Sulfate reduction occurs concurrently with the accumulation of acetate approximately 40 h after inoculation, when growth resumes. Similar amounts of hydrogen are produced during this time compared to hydrogen production by cells not exposed to Cr(VI); therefore an accumulation of hydrogen cannot account for the utilization of lactate. There is a significant decrease in the carbohydrate to protein ratio at approximately 25 h, and this result indicated that lactate is not converted to glycogen. Most probable number analysis indicated that cell viability decreased steadily after inoculation and reached approximately 6 x 104 cells/ml 20 h post-chromium exposure. Regeneration of reducing conditions during chromium exposure does not induce growth and in fact may make the growth conditions even more unfavorable. This result suggested that an increase in Eh was not solely responsible for the decline in viability. Cell pellets collected 10 h after chromium-exposure were unable to resume growth when suspended into fresh medium. Supernatants from these pellets were able to support cell growth upon re- inoculation. D. vulgaris cells treated with a non-dose dependent addition of ascorbate at the same time of Cr(VI) addition did not enter a lag period. Ascorbate added 3 h post-Cr(VI) exposure did not prevent the growth lag. These results indicated that Desulfovibrio utilized lactate to reduce Cr(VI) without the reduction of sulfate, that the decline in cell viability and

  5. Scientific Opinion on ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS

    2012-11-01

    Full Text Available The Panel on Food Additives and Nutrient Sources added to Food (ANS provides a scientific opinion re-evaluating the safety of ChromoPrecise® cellular bound chromium yeast added for nutritional purposes as a source of chromium in food supplements and the bioavailability of chromium from this source. ChromoPrecise® is a yeast preparation with an enriched trivalent chromium content, obtained by culture of Saccharomyces cerevisiae in the presence of chromium chloride. A daily intake of 100 µg chromium(III. There are limited data on the nature and identity of the organic chromium(III compounds contained in chromium-enriched yeast and on their toxicokinetic and toxicodynamic behaviour in the body. Overall, the Panel concluded that the bioavailability in man of chromium from chromium-enriched yeast is potentially up to approximately ten times higher than that of chromium from chromium chloride. A NOAEL of 2500 mg/kg bw/day ChromoPrecise® was identified in a 90-day feeding study in rats; no evidence of adverse effects of chromium yeasts were reported in other animal studies investigating the effects of dietary supplementation with chromium yeast. ChromoPrecise® chromium yeast was non-genotoxic in a range of in vitro genotoxicity studies. Although no information was available on the chronic toxicity, carcinogenicity or reproductive toxicity of ChromoPrecise® chromium yeast, the ANS Panel has previously concluded that trivalent chromium is not carcinogenic, and limited data on other chromium yeasts provide no evidence of an effect on reproductive endpoints. No adverse effects have been reported in clinical efficacy trials with chromium yeasts. The Panel concluded that the use of ChromoPrecise® chromium yeast in food supplements is not of concern, despite the lack of data on the nature and identity of the organic chromium(III compounds contained in the product, provided that the intake does not exceed 250 μg/day, as recommended by the WHO.

  6. A comparative study of the removal of trivalent chromium from aqueous solutions by bentonite and expanded perlite.

    Science.gov (United States)

    Chakir, Achraf; Bessiere, Jacques; Kacemi, Kacem E L; Marouf, Bouchaïb

    2002-11-11

    Local bentonite and expanded perlite (Morocco) have been characterised and used for the removal of trivalent chromium from aqueous solutions. The kinetic study had showed that the uptake of Cr(III) by bentonite is very rapid compared to expanded perlite. To calculate the sorption capacities of the two sorbents, at different pH, the experimental data points have been fitted to the Freundlich and Langmuir models, respectively, for bentonite and expanded perlite. For both sorbents the sorption capacity increases with increasing the pH of the suspensions. The removal efficiency has been calculated for both sorbents resulting that bentonite (96% of Cr(III) was removed) is more effective in removing trivalent chromium from aqueous solution than expanded perlite (40% of Cr(III) was removed). In the absence of Cr(III) ions, both bentonite and expanded perlite samples yield negative zeta potential in the pH range of 2-11. The changes of expanded perlite charge, from negative to positive, observed after contact with trivalent chromium(III) solutions was related to Cr(III) sorption on the surface of the solid. Thus, it was concluded that surface complexation plays an important role in the sorption of Cr(III) species on expanded perlite. In the case of bentonite, cation-exchange is the predominate mechanism for sorption of trivalent chromium ions, wherefore no net changes of zeta potential was observed after Cr(III) sorption. X-ray photoelectron spectroscopy measurements, at different pH values, were also made to corroborate the zeta potential results.

  7. 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

  8. Contingency plans for chromium utilization. Publication NMAB-335

    International Nuclear Information System (INIS)

    The United States depends entirely on foreign sources for the critical material, chromium, making it very vulnerable to supply disruptions. This vulnerability results because chromium is essential for the fabrication of corrosion-resisting steels and high-temperature, oxidation-resisting alloys in applications that are vital to the nation's technological well-being; because no substitutes are known for these materials in those applications; and because the known, substantial deposits of chromite ore are only in a few geographical locations that could become inaccessible to the United States as a result of political actions. The effectiveness of programs such as stockpiling, conservation, and research and development for substitutes to reduce the impact of disruption of imports of chromite and ferrochromium are discussed. Alternatives for decreasing chromium consumption also are identified for chromium-containing materials in the areas of design, processing, and substitution

  9. Fabrication of high rate chromium getter sources for fusion applications

    International Nuclear Information System (INIS)

    Design and fabrication techniques are described for the manufacture of large-capacity chromium getter sources, analogous to the commercially available titanium getter source known as Ti-Ball, manufactured by Varian Associates

  10. IRIS Toxicological Review of Hexavalent Chromium (Peer Review Plan)

    Science.gov (United States)

    EPA is conducting a peer review of the scientific basis supporting the human health hazard and dose-response assessment of hexavalent chromium that will appear on the Integrated Risk Information System (IRIS) database.

  11. Chromium and Polyphenols from Cinnamon and Insulin Sensitivity

    Science.gov (United States)

    Factors that improve insulin sensitivity usually lead to improvements in risk factors associated with the metabolic syndrome, diabetes, and cardiovascular diseases. Naturally occurring bioactive compounds that have been shown to improve insulin sensitivity include chromium and polyphenols found in ...

  12. The diffusion of chromium in a duplex alloy steel

    International Nuclear Information System (INIS)

    Diffusion of chromium in a duplex stainless steel containing approximately 8% ferrite has been investigated in the temperature range 600 to 10000C using the standard serial sectioning technique. The resulting concentration profiles exhibited up to four distinct regions. The two main regions are attributed to volume diffusion in the austenite and ferrite phases, the other zones being due to short circuiting paths. Volume diffusion in the austenite phase is in good agreement with chromium diffusion in Type 316 steel. The chromium diffusion coefficient in the ferrite phase of approximate composition 25 wt % Cr, 5 wt % Ni is given by: Dsub(α) = (6.0(+11,-3)) x 10-6 exp - ((212+-5)/RT) m2s-1 the activation energy being expressed in kJ.mol-1. Little evidence was found for enhanced chromium diffusion along austenite/ferrite interface boundaries. (author)

  13. 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...

  14. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  15. Thermodynamic Equilibrium Diagrams of Sulphur-Chromium System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The chemical and electrochemical equilibria in the presence of gaseous phase were investigated. Many substances, which consisted of sulphur and chromium, were considered. Various thermodynamic equilibria were calculated in different pressures. Calculation results were shown as log p―1/T and E―T diagrams. These diagrams may be used to study the corrosion of chromium in sulphur-containing circumstances. The diagrams are also used to thermodynami-cally determine the existence area of various substances and so on.

  16. Stereology of carbide phase in modified hypereutectic chromium cast iron

    OpenAIRE

    J. Suchoń; A. Studnicki; M. Przybył

    2010-01-01

    In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C), ferroniobium (FeNb) and mixture of ferroniobium and rare-earth (RE). The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  17. SCIENCE AND TECHNOLOGY ACTIVITIES FOR CHROMIUM IN THE 100 AREAS

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN SW

    2009-07-02

    {sm_bullet} Primary Objective: Protect the Columbia River - Focus is control and treatment of contamination at or near the shoreline, which is influenced by bank storage {sm_bullet} Secondary Objective: Reduce hexavalent chromium to <48 parts per billion (ppb) in aquifer (drinking water standard) - Large plumes with isolated areas of high chromium concentrations (> 40,000 ppb), - Unknown source location(s); probably originating in reactor operation areas

  18. Genetic Predisposition for Dermal Problems in Hexavalent Chromium Exposed Population

    OpenAIRE

    Priti Sharma; Vipin Bihari; Agarwal, Sudhir K.; Goel, Sudhir K.

    2012-01-01

    We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108)...

  19. Performance of chromium nitride based coatings under plastic processing conditions

    OpenAIRE

    Cunha, l.; Andritschky, M.; Pischow, K.; Wang, Z.(Institute of High Energy Physics, Beijing, China); Zarychta, A.; Miranda, A. S.; A.M. Cunha

    2000-01-01

    Chromium nitride based coatings were produced in the form of monolithic and multilayer coatings, by DC and RF reactive magnetron sputtering. These coatings were deposited onto stainless steel and tool steel substrates. Chromium nitride coatings have;proved to be wear and corrosion resistant. The combination of these characteristics was necessary to protect surfaces during plastic processing. In order to select the best coatings, some mechanical and tribological tests were performed. Har...

  20. DANGER OF HEXAVALENT CHROMIUM AND STRATEGY FOR THE REMEDITATION

    OpenAIRE

    Aniruddha Roy; Ayan Das; Nirmal Paul

    2013-01-01

    Some metals as micronutrients have a major role in the life and growth process of plants and animals. However, certain forms of some metals may also act as toxic material even in relatively small quantities. Chromium is such a metal, whose concentration above a certain limit may cause a serious problem to the health of living organisms. Chromium (Cr) may occur in several chemical forms in organic and inorganic systems. In biological systems only Cr (III) and Cr (VI) are signifi...

  1. 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

  2. Enhancing collagen stability through nanostructures containing chromium(III) oxide.

    Science.gov (United States)

    Sangeetha, Selvam; Ramamoorthy, Usha; Sreeram, Kalarical Janardhanan; Nair, Balachandran Unni

    2012-12-01

    Stabilization of collagen for various applications employs chemicals such as aldehydes, metal ions, polyphenols, etc. Stability against enzymatic, thermal and mechanical degradation is required for a range of biomedical applications. The premise of this research is to explore the use of nanoparticles with suitable functionalization/encapsulation to crosslink with collagen, such that the three dimensional architecture had the desired stability. Collagen solution prepared as per standard protocols is treated with chromium(III) oxide nanoparticules encapsulated within a polymeric matrix (polystyrene-block-polyacrylic acid copolymer). Selectivity towards encapsulation was ensured by the reaction in dimethyl sulfoxide, where the PS groups popped out and encapsulated the Cr(2)O(3). Subsequently when immersed in aqueous solution, PAA units popped up to react with functional groups of collagen. The interaction with collagen was monitored through techniques such as CD, FTIR, viscosity measurements, stress analysis. CD studies and FTIR showed no degradation of collagen. Thermal stability was enhanced upon interaction of nanostructures with collagen. Self-assembly of collagen was delayed but not inhibited, indicating a compete binding of the metal oxide encapsulated polymer to collagen. Metal oxide nanoparticles encapsulated within a polymeric matrix could provide thermal and mechanical stability to collagen. The formed fibrils of collagen could serve as ideal material for various smart applications such as slow/sustained drug release. The study is also relevant to the leather industry in that the nanostructures can diffuse through the highly networked collagen fibre bundles in skin matrix easily, thus overcoming the rate limiting step of diffusion. PMID:22766281

  3. Evaluating trivalent chromium toxicity on wild terrestrial and wetland plants.

    Science.gov (United States)

    Lukina, A O; Boutin, C; Rowland, O; Carpenter, D J

    2016-11-01

    Elevated chromium levels in soil from mining can impact the environment, including plants. Mining of chromium is concentrated in South Africa, several Asian countries, and potentially in Northern Ontario, Canada, raising concerns since chromium toxicity to wild plants is poorly understood. In the first experiment, concentration-response tests were conducted to evaluate effects of chromium on terrestrial and wetland plants. Following established guidelines using artificial soil, seeds of 32 species were exposed to chromium (Cr(3+)) at concentrations simulating contamination (0-1000 mg kg(-1)). This study found that low levels of chromium (250 mg kg(-1)) adversely affected the germination of 22% of species (33% of all families), while higher levels (500 and 1000 mg kg(-1)) affected 69% and 94% of species, respectively, from 89% of the families. Secondly, effects on seedbanks were studied using soil collected in Northern Ontario and exposed to Cr(3+) at equivalent concentrations (0-1000 mg kg(-1)). Effects were less severe in the seedbank study with significant differences only observed at 1000 mg kg(-1). Seeds exposed to Cr(3+) during stratification were greatly affected. Seed size was a contributing factor as was possibly the seed coat barrier. This study represents an initial step in understanding Cr(3+) toxicity on wild plants and could form the basis for future risk assessments. PMID:27543852

  4. Lime enhanced chromium removal in advanced integrated wastewater pond system.

    Science.gov (United States)

    Tadesse, I; Isoaho, S A; Green, F B; Puhakka, J A

    2006-03-01

    The removal of trivalent chromium from a combined tannery effluent in horizontal settling tanks and subsequent Advanced Integrated Wastewater Pond System (AIWPS) reactors was investigated. The raw combined effluent from Modjo tannery had pH in the range of 11.2-12. At this pH, a trivalent chromium removal of 46-72% was obtained in the horizontal settling tanks after a one-day detention time. Trivalent chromium precipitated as chromium hydroxide, Cr(OH)3. 58-95% Cr(III) was removed in the advanced facultative pond (AFP) where the water column pH of 7.2-8.4 was close to pH 8, which is the optimum precipitation pH for trivalent chromium. Chromium removals in the secondary facultative pond (SFP) and maturation pond (MP) were 30-50% and 6-16%, respectively. With Cr(III) concentration of 0.2-0.8 mg/l in the final treated effluent, the AIWPS preceded by horizontal settling tanks produced effluent that could easily meet most of the current Cr(III) discharge limits to receive water bodies.

  5. Radiometric and spectrophotometric studies of the behavior of chromium(VI) oxide in concentrated perchloric acid

    Energy Technology Data Exchange (ETDEWEB)

    Pezzin, S.H.; Collins, C.H.; Collins, K.E. [Universidade Estadual de Campinas (Brazil). Inst. de Quimica; Archundia, C. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Ciencias Nucleares

    1997-11-01

    A study of the behavior of {sup 51}CrO{sub 3} in 70% HClO{sub 4} over the temperature range from 20 to 194 C by means of Cr-51 labelling, UV-VIS spectrophotometry and ion exchange chromatography, shows that the solubility of {sup 51}CrO{sub 3} depends on a competition between the dissolution process and the acid reduction of solution phase Cr(VI). These processes occur simultaneously and are dependent on both the temperature and the concentration of Cr(VI), as shown by comparison between radiometric measurements (where total chromium can be accurately determined) and spectrophotometric measurements (where only the Cr(VI) is detectable at the wavelengths studied). These conclusions are confirmed by PbCrO{sub 4} precipitation of {sup 51}Cr(VI), where at 194 C, 97% of the total chromium appears as Pb{sup 51}CrO{sub 4} while at 86 C only 5% does. Cation exchange chromatography of the solution after brief contact of {sup 51}CrO{sub 3} with concentrated HClO{sub 4} at 20 C shows only traces of {sup 51}Cr(VI), most of the radioactivity eluting as {sup 51}Cr(H{sub 2}O){sup 3+}{sub 6}, with smaller amounts of species with +2 and +1 charges. These results imply serious limitations to the spectrophotometric determination of low concentrations of total chromium in alloys or in biological material which use dissolution in 70% HClO{sub 4} as a primary analytical step. (orig.)

  6. 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

  7. Survey of Nano filtration Performance for Hexavalent Chromium Removal fromWater Containing Sulfate

    Directory of Open Access Journals (Sweden)

    Gh.R Moussavi

    2010-10-01

    Full Text Available "n "n "nBackgrounds and Objectives: Geological situation and/or anthropogenic contamination contain an increased concentration of ions such as hexavalent chromium as well as some other dissolved components such as sulfate in the upper of the establishedMCLs (50µg/L. In this paper, simultaneous removal of Cr (VI and sulfate from water was investigated using nanofiltration as a promising method for reaching drinking water standards."nMaterials and Methods: For varying pressure, pH , anion and cation solution effect, Sulfate and Cr (VI concentration which have chosen were levels found in drinking water sources (Cr=0.1- 0.5mg/L and (SO4-2= 100-800mg/L.Experiments were performed using NaCl, Na2SO4,K2 Cr2O7and anhydrous CrCl3. 6H2O which prepared with de mineralized water on procedure detailed in standard methods. All salts were purchased from Merck Corporation with purity over 99'."nResults: The results for hexavalent chromium experiments showed that when the concentration decreases, the chromate anions were given a better retention to 4 bars (96'. But when the concentration increases, concentration polarization led to increased removal of Cr (VI (98'. For Cr (III the influences of the ionic strength as well as the concentrations were strongly dependant on rejection but operating pressure were found weak. In addition, with increasing total dissolved solids, perfect rejection of chromium was seen. The effect of pH showed that better retention was obtained at natural and basic pH."nConclusion: This study indicates that the nature of anions and cations, driven pressure and pH have significant effect on nano filtration operation. Research findings show that it seems nano filtration is a very good promising method of simultaneous removal of Cr (VI and sulfate from water.

  8. USE OF TWO DIGESTION METHODS IN THE EVALUATION OF CHROMIUM CONTENT IN CATTLE'S MEAT SUPPLEMENTED WITH CHROMIUM CHELATES

    OpenAIRE

    R. L. T. Andrade; P.S.A. Moreira; R. Arruda; F. J. Lourenço; C. Palhari, F. F. Faria, V. B. Arevalo; Faria, F. F.; V. B. Arevalo

    2015-01-01

    The present study aimed to analyze the chromium content in beef using two digestion methods. There were used samples from 24 18-month-old male cattle, and twelve of them were supplemented and twelve were not supplemented with chromium chelate. These samples were evaluated by atomic absorption spectroscopy, previously submitted to digestion method using nitric acid (65%) with hydrogen peroxide (35%) and to digestion method, using solution of nitric perchloric acid in the proportion 3:1. Immedi...

  9. Activation of bentonite to remove the chromium from waste water produced by panning industry, and studying the chromium recovery efficiency

    International Nuclear Information System (INIS)

    The fast development of tanning industry led to an increase in environmental problems resulting from discharging its wastes to the surrounding environment. Thus solving this problem became one of the most important aims that the researchers work on. The chromium content of the industrial water wastes of the tanning industry considered as the main pollutant for the environment. The Aleppo Bentonite is used in early research to remove the chromium from the industrial waste water.The current research aims to find a method to activate the Aleppo Bentonite in order to increase the effective removal of chromium from the industrial waste water which is produced by tanning industry, as well as to specify the optimal conditions for chromium recovery.This study used the Aleppo Bentonite, whose origin is Tal Ajar-Aleppo to study the activation aspects using Sulfuric Acid, Hydrochloric Acid and Nitric Acid, in addition to study the recovery aspects using the same acids and hydrogen peroxide and to specify the optimal conditions for chromium recovery through applying some experiments based on three main factors: concentration, settling time and temperature.It was observed from the applied experiments that it is possible to recover chromium from Bentonite efficiently up to (80% - 90%) by treating the Bentonite with hydrogen peroxide(33% concentration) at room temperature, or by treating it with hydrogen peroxide(8.25% concentration) at 75oC, while the settling time factor proved that full recovery of chromium is obtained during the first hour, and increasing the time factor does not affect the efficiency of chromium recovery. (author)

  10. 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.

  11. Low energy spin excitations in chromium metal

    Energy Technology Data Exchange (ETDEWEB)

    Pynn, R. [Los Alamos National Lab., NM (United States); Azuah, R.T. [Hahn-Meitner-Inst., Berlin (Germany); Stirling, W.G. [Univ. of Liverpool (United Kingdom). Dept. of Physics; Kulda, J. [Inst. Laue Langevin, Grenoble (France)

    1997-12-31

    Neutron scattering experiments with full polarization analysis have been performed with a single crystal of chromium to study the low-energy spin fluctuations in the transverse spin density wave (TSDW) state. A number of remarkable results have been found. Inelastic scattering observed close to the TSDW satellite positions at (1 {+-} {delta},0,0) does not behave as expected for magnon scattering. In particular, the scattering corresponds to almost equally strong magnetization fluctuations both parallel and perpendicular to the ordered moments of the TSDW phase. As the Neel temperature is approached from below, scattering at the commensurate wavevector (1,0,0) increases in intensity as a result of critical scattering at silent satellites (1,0, {+-} {delta}) being included within the spectrometer resolution function. This effect, first observed by Sternlieb et al, does not account for all of the inelastic scattering around the (1,0,0) position, however, Rather, there are further collective excitations, apparently emanating from the TSDW satellites, which correspond to magnetic fluctuations parallel to the ordered TSDW moments. These branches have a group velocity that is close to that of (1,0,0) longitudinal acoustic (LA) phonons, but assigning their origin to magneto-elastic scattering raises other unanswered questions.

  12. Enhancement of surface properties of SAE 1020 by chromium plasma immersion recoil implantation

    Science.gov (United States)

    Ueda, M.; Mello, C. B.; Beloto, A. F.; Rossi, J. O.; Reuther, H.

    2007-04-01

    SAE 1020 steel is commonly used as concrete reinforcement and small machine parts, but despite its good mechanical properties, as ductility, hardness and wear resistance, it is susceptible to severe corrosion. It is well known that chromium content above 12% in Fe alloys increases their corrosion resistance. In order to obtain this improvement, we studied the introduction of chromium atoms into the matrix of SAE 1020 steel by recoil implantation process using a plasma immersion ion implantation (PIII) system. Potentiodynamic scans showed that the presence of Cr film leads to a gain in the corrosion potential, from -650 mV to -400 mV. After PIII treatment, the corrosion potential increased further to -340 mV, but the corrosion current density presented no significant change. Vickers microhardness tests showed surface hardness increase of up to about 27% for the treated samples. Auger electron spectroscopy showed that, for a 30 nm film, Cr was introduced for about 20 nm into the steel matrix. Tribology tests, of pin-on-disk type, showed that friction coefficient of treated samples was reduced by about 50% and a change in wear mechanism, from adhesive to abrasive mode, occurred.

  13. Efficacy of Agricultural Wastes in the Removal of Hexavalent Chromium- A Review.

    Directory of Open Access Journals (Sweden)

    N Muthulakshmi Andal

    2013-08-01

    Full Text Available Hexavalent Chromium is a major pollutant released during several industrial operations. It is also reported as one of the metals known to be carcinogenic and has an adverse potential to modify the DNA transcription process. The removal of hexavalent chromium has been studied by various authors employing adsorbents developed from waste agro by-products to assess their adsorption characteristics. This paper focuses on the comparison of some agro based products in the removal of Cr(VI ions. An extensive list of agricultural based products such as Coconut Coir, Prunus amygdalus, Cissus quadrangularis, Soapnut Acacia, Justicia adhatoda, Bhringraj, Aerva lanata, Trianthema portulacastrum, Tephrosia purpurea, Solanum nigrum, Datura metel, Cleome viscose, Asparagus racemosus for the removal of Cr(VI from aqueous solutions and the discharged effluents from industries are reviewed in this work. As chemically modified adsorbents exhibit higher adsorption capacity, a number of chemicals have been utilized for the required modifications of the adsorbent materials in the research articles. The results declared by the authors have been compared and summarized for further probe into the extensive utilization of the employed materials.

  14. Two fold modified chitosan for enhanced adsorption of hexavalent chromium from simulated wastewater and industrial effluents.

    Science.gov (United States)

    Kahu, S S; Shekhawat, A; Saravanan, D; Jugade, R M

    2016-08-01

    Ionic solid (Ethylhexadecyldimethylammoniumbromide) impregnated phosphated chitosan (ISPC) was synthesized and applied for enhanced adsorption of hexavalent chromium from industrial effluent. The compound obtained was extensively characterized using instrumental techniques like FT-IR, TGA-DTA, XRD, SEM, BET and EDX. ISPC showed high adsorption capacity of 266.67mg/g in accordance with Langmuir isotherm model at pH 3.0 due to the presence of multiple sites which contribute for ion pair and electrostatic interactions with Cr(VI) species. The sorption kinetics and thermodynamic studies revealed that adsorption of Cr(VI) followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. Applicability of ISPC for higher sample volumes was discerned through column studies. The real chrome plating industry effluent was effectively treated with total chromium recovery of 94%. The used ISPC was regenerated simply by dilute ammonium hydroxide treatment and tested for ten adsorption-desorption cycles with marginal decrease in adsorption efficiency. PMID:27112874

  15. Performance enhancement of iron-chromium redox flow batteries by employing interdigitated flow fields

    Science.gov (United States)

    Zeng, Y. K.; Zhou, X. L.; Zeng, L.; Yan, X. H.; Zhao, T. S.

    2016-09-01

    The catalyst for the negative electrode of iron-chromium redox flow batteries (ICRFBs) is commonly prepared by adding a small amount of Bi3+ ions in the electrolyte and synchronously electrodepositing metallic particles onto the electrode surface at the beginning of charge process. Achieving a uniform catalyst distribution in the porous electrode, which is closely related to the flow field design, is critically important to improve the ICRFB performance. In this work, the effects of flow field designs on catalyst electrodeposition and battery performance are investigated. It is found that compared to the serpentine flow field (SFF) design, the interdigitated flow field (IFF) forces the electrolyte through the porous electrode between the neighboring channels and enhances species transport during the processes of both the catalyst electrodeposition and iron/chromium redox reactions, thus enabling a more uniform catalyst distribution and higher mass transport limitation. It is further demonstrated that the energy efficiency of the ICRFB with the IFF reaches 80.7% at a high current density (320 mA cm-2), which is 8.2% higher than that of the ICRFB with the SFF. With such a high performance and intrinsically low-cost active materials, the ICRFB with the IFF offers a great promise for large-scale energy storage.

  16. 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.

  17. Spectroscopic and dielectric response of zinc bismuth phosphate glasses as a function of chromium content

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Srinivasa [Department of Physics, S.V.R.M. College, Nagaram 522268, A.P. (India); Babu, P. Ramesh; Vijay, R.; Narendrudu, T.; Veeraiah, N. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P. (India); Rao, D. Krishna, E-mail: krdhanekula@yahoo.co.in [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P. (India)

    2014-09-15

    Graphical abstract: 20ZnF{sub 2}–(20 − x)Bi{sub 2}O{sub 3}–60P{sub 2}O{sub 5}:xCr{sub 2}O{sub 3} (0 ≤ x ≤2 mol%) glasses are prepared by melt quenching technique. The optical absorption spectra of present glasses are analyzed as a function of chromium content. The absorption bands are assigned to {sup 4}A{sub 2g}(F) ⟶ {sup 4}T{sub 1g}(F), {sup 4}A{sub 2g}(F) ⟶ {sup 4}T{sub 2g}(F), {sup 4}A{sub 2g}(F) ⟶ {sup 2}T{sub 1g}(G) and {sup 4}A{sub 2g}(F) ⟶ {sup 2}E{sub g}(G) transitions of Cr{sup 3+} ions. - Highlights: • ZnF{sub 2}–Bi{sub 2}O{sub 3}–P{sub 2}O{sub 5}:Cr{sub 2}O{sub 3} glasses were prepared by melt quenching and annealing. • Spectroscopic and dielectric properties of chromium ions were investigated. • ESR and optical absorption spectra indicate the co-existence of Cr{sup 6+} ions with Cr{sup 5+} ions and Cr{sup 3+} ions. • Cr{sup 3+} ions act as modifiers and influence the semiconducting nature of the glass system. - Abstract: 20ZnF{sub 2}–(20 − x)Bi{sub 2}O{sub 3}–60P{sub 2}O{sub 5}:xCr{sub 2}O{sub 3} (0 ≤ x ≤2 mol%) glasses are prepared by melt quenching technique. Amorphous nature of these samples is confirmed by X-ray diffraction (XRD) analysis. FTIR study reveals bands due to CrO{sub 6}(o{sub d}) and CrO{sub 4}{sup 2−}(T{sub d}) units along with conventional phosphate groups. The optical absorption and ESR studies of present glasses are analyzed as a function of chromium content. The absorption bands are assigned to {sup 4}A{sub 2g}(F) ⟶ {sup 4}T{sub 1g}(F), {sup 4}A{sub 2g}(F) ⟶ {sup 4}T{sub 2g}(F), {sup 4}A{sub 2g}(F) ⟶ {sup 2}T{sub 1g}(G) and {sup 4}A{sub 2g}(F) ⟶ {sup 2}E{sub g}(G) transitions of Cr{sup 3+} ions. The highest concentration of Cr{sup 3+} ions (in octahedral sites, with network modifying positions) is found in the sample with 2.0 mol% of Cr{sub 2}O{sub 3}. The analysis of dielectric properties indicates a gradual increase in semiconducting character with increase in the concentration of

  18. Chromium liquid waste inertization in an inorganic alkali activated matrix: leaching and NMR multinuclear approach.

    Science.gov (United States)

    Ponzoni, Chiara; Lancellotti, Isabella; Barbieri, Luisa; Spinella, Alberto; Saladino, Maria Luisa; Martino, Delia Chillura; Caponetti, Eugenio; Armetta, Francesco; Leonelli, Cristina

    2015-04-01

    A class of inorganic binders, also known as geopolymers, can be obtained by alkali activation of aluminosilicate powders at room temperature. The process is affected by many parameters (curing time, curing temperature, relative humidity etc.) and leads to a resistant matrix usable for inertization of hazardous waste. In this study an industrial liquid waste containing a high amount of chromium (≈ 2.3 wt%) in the form of metalorganic salts is inertized into a metakaolin based geopolymer matrix. One of the innovative aspects is the exploitation of the water contained in the waste for the geopolymerization process. This avoided any drying treatment, a common step in the management of liquid hazardous waste. The evolution of the process--from the precursor dissolution to the final geopolymer matrix hardening--of different geopolymers containing a waste amount ranging from 3 to 20%wt and their capability to inertize chromium cations were studied by: i) the leaching tests, according to the EN 12,457 regulation, at different curing times (15, 28, 90 and 540 days) monitoring releases of chromium ions (Cr(III) and Cr(VI)) and the cations constituting the aluminosilicate matrix (Na, Si, Al); ii) the humidity variation for different curing times (15 and 540 days); iii) SEM characterization at different curing times (28 and 540 days); iv) the trend of the solution conductivity and pH during the leaching test; v) the characterization of the short-range ordering in terms of TOT bonds (where T is Al or Si) by (29)Si and (27)Al solid state magic-angle spinning nuclear magnetic resonance (ss MAS NMR) for geopolymers containing high amounts of waste (10-20%wt). The results show the formation of a stable matrix after only 15 days independently on the waste amount introduced; the longer curing times increase the matrices stabilities and their ability to immobilize chromium cations. The maximum amount of waste that can be inertized is around 10 wt% after a curing time of 28 days

  19. Cobalt-chromium-molybdenum alloy causes metal accumulation and metallothionein up-regulation in rat liver and kidney

    DEFF Research Database (Denmark)

    Jakobsen, Stig Storgaard; Danscher, Gorm; Stoltenberg, Meredin;

    2007-01-01

    Cobalt-chromium-molybdenum (CoCrMo) metal-on-metal hip prosthesis has had a revival due to their excellent wear properties. However, particulate wear debris and metal ions liberated from the CoCrMo alloys might cause carcinogenicity, hypersensitivity, local and general tissue toxicity, genotoxicity...... and inflammation-generating qualities. Nine months after implanting small pieces of CoCrMo alloy intramuscularly and intraperitoneally in rats, we analysed the accumulation of metals with a multi-element analysis, and the levels of metallothionein I/II with real-time reverse transcriptase-polymerase chain reaction...... in liver and kidney. We found that metal ions are liberated from CoCrMo alloys and suggest that they are released by dissolucytosis, a process where macrophages causes the metallic surface to release metal ions. Animals with intramuscular implants accumulated metal in liver and kidney and metallohionein I...

  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. 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...

  2. Effect of partial pressure of reactive gas on chromium nitride and chromium oxide deposited by arc ion plating

    Institute of Scientific and Technical Information of China (English)

    LI Ming-sheng; FENG Chang-jie; WANG Fu-hui

    2006-01-01

    The effects of reactive gas partial pressure on droplet formation,deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings,as nitrogen partial pressure increases,the number and size of droplets increases,the deposition rate initially increases obviously and then slowly,and the preferred orientation of CrN changes from high-index plane to low-index one. For Cr2O3 coatings,with the increase of oxygen partial pressure,the number and size of droplets decreases,the deposition rate decreases and the (300) becomes the preferred orientation. These differences are ascribed to the formation of CrN (with a lower melting point) and Cr2O3 (with a higher melting point) on the surface of Cr target during the deposition of CrN and Cr2O3. Complete coatings CrN or Cr2O3 film can be formed when reactive gas partial pressure gets up to 0.1 Pa. The optimized N2 partial pressure for CrN deposition is about 0.1-0.2 Pa in order to suppress the formation of droplets and the suitable O2 partial pressure for Cr2O3 deposition is approximately 0.1 Pa for the attempt to prevent the peel of the coating.

  3. Effect Of Oxidation On Chromium Leaching And Redox Capacity Of Slag-Containing Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Almond, P. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Stefanko, D. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Langton, C. A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2013-03-01

    The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO4- in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases [Shuh, et al., 1994, Shuh, et al., 2000, Shuh, et al., 2003]. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O4-, which is very soluble. Consequently the rate of technetium oxidation front advancement into a monolith and the technetium leaching profile as a function of depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate was used as a non-radioactive surrogate for pertechnetate in simulated waste form samples. Depth discrete subsamples were cut from material exposed to Savannah River Site (SRS) field cured conditions. The subsamples were prepared and analyzed for both reduction capacity and chromium leachability. Results from field-cured samples indicate that the depth at which leachable chromium was detected advanced further into the sample exposed for 302 days compared to the sample exposed to air for 118 days (at least 50 mm compared to at least 20 mm). Data for only two exposure time intervals is currently available. Data for additional exposure times are required to develop an equation for the oxidation front progression. Reduction capacity measurements (per the Angus-Glasser method, which is a measurement of the ability of a material to chemically reduce Ce(IV) to Ce

  4. Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed

    OpenAIRE

    Fei Xu; Xu Liu; Yijiao Chen; Ke Zhang; Heng Xu

    2016-01-01

    A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 5...

  5. Low-chromium reduced-activation ferritic steels for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  6. Bioaccumulation and biosorption of chromium by Aspergillus niger MTCC 2594.

    Science.gov (United States)

    Sandana Mala, John Geraldine; Unni Nair, Balachandran; Puvanakrishnan, Rengarajulu

    2006-06-01

    Chromium toxicity is of prime concern due to chrome tanning processes in the leather sector. Chrome tanning results in the discharge of toxic levels of chromium causing pollution hazards. Chromium levels of Cr(III) and Cr(VI) were high above permissible limits in chrome samples after chrome tanning. The potential of Aspergillus niger MTCC 2594 to accumulate chromium as well as its biosorption capacity is investigated in this study. Bioaccumulation of Cr(III) and Cr(VI) in the spent chrome liquor has resulted in a 75-78% reduction of the initial Cr content in 24-36 h. A. niger biomass is found to be very effective in the biosorption of Cr(III) and Cr(VI) in spent chrome liquor. Maximum adsorption of 83% for biosorption of Cr(III) at 48 h and 79% of Cr(VI) at 36 h in spent chrome liquor is observed. The biosorption characteristics fit well with Langmuir and Freundlich isotherms and the adsorption parameters are evaluated. The biosorption of Cr also follows Lagergren kinetics. A. niger biomass is effectively used for the biosorption of chromium with 79-83% Cr removal in 36-48 h.

  7. Chromium propionate enhances adipogenic differentiation of bovine intramuscular adipocytes

    Directory of Open Access Journals (Sweden)

    Rebecca eTokach

    2015-09-01

    Full Text Available In vitro experiments were performed to determine the effects of increasing concentrations of chromium propionate on mRNA and protein abundance of different enzymes and receptors. Intramuscular and subcutaneous preadipocytes and bovine satellite cells were isolated from the longissimus muscle to determine the effect of treatment on glucose transporter type 4 (GLUT4 and peroxisome proliferator-activated receptor γ mRNA and GLUT4 protein abundance. Preadipocyte cultures were treated with differentiation media plus either sodium propionate or different concentrations of chromium propionate (CrPro for 96, 120, and 144 h before harvest. This study indicated adipogenesis of the bovine intramuscular adipocytes were more sensitive to the treatment of chromium propionate as compared to subcutaneous adipocytes. Enhancement of adenosine monophosphate-activated protein kinase and GLUT4 mRNA by CrPro treatment may enhance glucose uptake in intramuscular adipocytes. Chromium propionate decreased GLUT4 protein levels in muscle cell cultures suggesting those cells have increased efficiency of glucose uptake due to exposure to increased levels of CrPro. In contrast, each of the two adipogenic lines had opposing responses to the CrPro. It appeared that CrPro had the most stimulative effect of GLUT4 response in the intramuscular adipocytes as compared to subcutaneous adipocytes. These findings indicated opportunities to potentially augment marbling in beef cattle fed chromium propionate during the finishing phase.

  8. Anthropogenic chromium emissions in china from 1990 to 2009.

    Science.gov (United States)

    Cheng, Hongguang; Zhou, Tan; Li, Qian; Lu, Lu; Lin, Chunye

    2014-01-01

    An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×10⁵ t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×10⁴ t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of 15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water. PMID:24505309

  9. Anthropogenic chromium emissions in china from 1990 to 2009.

    Directory of Open Access Journals (Sweden)

    Hongguang Cheng

    Full Text Available An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×10⁵ t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×10⁴ t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of 15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water.

  10. Enhancement of chromium uptake in tanning using oxazolidine.

    Science.gov (United States)

    Sundarapandiyan, S; Brutto, Patrick E; Siddhartha, G; Ramesh, R; Ramanaiah, B; Saravanan, P; Mandal, A B

    2011-06-15

    Monocyclic and bicyclic oxazolidines were offered at three different junctures of chrome tanning process viz. prior to BCS offer, along with BCS and after basification. It was found that oxazolidine when offered after basification brought about better chromium uptake and reduction of chromium load in the wastewater. Offer of oxazolidine was also varied. Increase in offer of oxazolidine from 0.25% to 1% was found to enhance the chromium uptake and decrease the chromium load in wastewater. But the increase in uptake was not proportionate to the increase in oxazolidine offer more than 0.75%. Offer of 1% Zoldine ZA 78 (monocyclic oxazolidine) and Zoldine ZE (bicyclic oxazolidine) after basification brought about 63.4% and 73.1% enhancement in chrome content in leather compared to control where oxazolidine was not offered. The tone of the wetblue was found to be altered moderately. However this did not call for any process adjustments in wet-finishing. The oxazolidine treated leathers were found to be immensely fuller and tighter. It was found experimentally that offer of 1% of oxazolidine facilitated reduction in the offer of syntans administered for filling and grain tightening by around 46%. Oxazolidine could bring about significant reduction in cost of chemicals apart from resulting environmental benefits due to enhancement of chromium uptake during tanning. PMID:21536383

  11. Reduction of chromium oxide from slags

    Directory of Open Access Journals (Sweden)

    Gutiérrez-Paredes, J.

    2005-12-01

    Full Text Available Experimental and theoretical work were performed to estimate the effect of slag basicity and amount of reducing agents on the reduction of chromium oxide from the slag which interacted with molten steel at 1,600 °C. The slag system contained CaO, MgO, SiO2, CaF2 and Cr2O3 together with Fe-alloys (Fe-Si and Fe-Si-Mg. The CaF2 and MgO contents in the slags were 10 mass % each; Cr2O3 was 25%. The amount of the ferroalloys ranged from 12.5 to 50 g per 100 g of slag. The (CaO+MgO/SiO2 ratio was held at 1 and 2. The Cr yield was determined using both Fe-alloys as reducing agents. Some estimations were made to determine the theoretical effect of temperature, slag basicity, (CaO+MgO/SiO2, and amount of reducing agents in the slag on the chromium recovery. The FACT (Facility for the Analysis of Chemical Thermodynamics computational package is used to determine the equilibrium between the slag and molten steel.

    En el presente trabajo se realiza un estudio teórico y experimental para determinar el efecto de la basicidad de la escoria y la cantidad de agentes reductores sobre la reducción de óxidos de cromo contenidos en la escoria, la cual está en contacto con acero líquido a 1.600 °C. La escoria se prepara con los reactivos CaO, MgO, SiO2, CaF2 y ferroaleaciones (Fe-Si y Fe-Si-Mg. Los contenidos de CaF2 y MgO en la escoria son de 10 %, cada uno, y el de Cr2O3 es 25 %. La cantidad de la ferroaleación varía de 12,5 a 50 g por cada 100 g de escoria. La relación (CaO+MgO/SiO2 tiene los valores de 1 y 2. Se determina la eficiencia de recuperación de cromo empleando los dos tipos de ferroaleaciones. Se realizaron cálculos para determinar el efecto teórico de la temperatura, la basicidad de la escoria, (CaO+MgO/SiO2, y la cantidad de agentes reductores sobre la reducci

  12. TREATABILITY TEST REPORT FOR THE REMOVAL OF CHROMIUM FROM GROUNDWATER AT 100-D AREA USING ELECTROCOAGULATION

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN SW

    2009-09-24

    The U.S. Department of Energy (DOE) has committed to accelerate cleanup of contaminated groundwater along the Columbia River. The current treatment approach was driven by a series of Interim Action Records of Decision (IAROD) issued in the mid-1990s. Part of the approach for acceleration involves increasing the rate of groundwater extraction for the chromium plume north of the 100-D Reactor and injecting the treated water in strategic locations to hydraulically direct contaminated groundwater toward the extraction wells. The current treatment system uses ion exchange for Cr(VI) removal, with off-site regeneration of the ion exchange resins. Higher flow rates will increase the cost and frequency of ion exchange resin regeneration; therefore, alternative technologies are being considered for treatment at high flow rates. One of these technologies, electrocoagulation (EC), was evaluated through a pilot-scale treatability test. The primary purpose of the treatability study was to determine the effectiveness of Cr(VI) removal and the robustness/implementability of an EC system. Secondary purposes of the study were to gather information about derivative wastes and to obtain data applicable to scaling the process from the treatability scale to full-scale. The treatability study work plan identified a performance objective and four operational objectives. The performance objective for the treatability study was to determine the efficiency (effectiveness) of hexavalent chromium removal from the groundwater, with a desired concentration of {le} 20 micrograms per liter ({micro}g/L) Cr(VI) in the effluent prior to re-injection. Influent and effluent total chromium and hexavalent chromium data were collected using a field test kit for multiple samples per week, and from off-site laboratory analysis of samples collected approximately monthly. These data met all data quality requirements. Two of three effluent chromium samples analyzed in the off-site (that is, fixed) laboratory

  13. Electrochemical modification of chromium surfaces using 4-nitro- and4-fluorobenzenediazonium salts

    DEFF Research Database (Denmark)

    Hinge, Mogens; Cecatto, Marcel; Kingshott, Peter;

    2009-01-01

    Chromium surfaces can be electrografted with organic surface films using 4-nitro- or 4-fluorobenzenediazonium salts, despite the fact that the surfaces are covered with a protective chromium oxide layer...

  14. 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...

  15. Effective bioleaching of chromium in tannery sludge with an enriched sulfur-oxidizing bacterial community.

    Science.gov (United States)

    Zeng, Jing; Gou, Min; Tang, Yue-Qin; Li, Guo-Ying; Sun, Zhao-Yong; Kida, Kenji

    2016-10-01

    In this study, a sulfur-oxidizing community was enriched from activated sludge generated in tannery wastewater treatment plants. Bioleaching of tannery sludge containing 0.9-1.2% chromium was investigated to evaluate the effectiveness of the enriched community, the effect of chromium binding forms on bioleaching efficiency, and the dominant microbes contributing to chromium bioleaching. Sludge samples inoculated with the enriched community presented 79.9-96.8% of chromium leaching efficiencies, much higher than those without the enriched community. High bioleaching efficiencies of over 95% were achieved for chromium in reducible fraction, while 60.9-97.9% were observed for chromium in oxidizable and residual fractions. Acidithiobacillus thiooxidans, the predominant bacteria in the enriched community, played an important role in bioleaching, whereas some indigenous heterotrophic species in sludge might have had a supporting role. The results indicated that A. thiooxidans-dominant enriched microbial community had high chromium bioleaching efficiency, and chromium binding forms affected the bioleaching performance.

  16. CHROMIUM ELECTROANALYSIS AT SCREEN PRINTED ELECTRODE MODIFIED BY THIN FILMS OF NICKEL

    Science.gov (United States)

    A rapid and potentially cost-effective electrochemical method is reported for analysis of chromium (VI) and Chromium(III) using a nickel modified screen printed carbon ink electrode. Electrochemical characteristics of nickel modified electrode as well voltammetric behavior f...

  17. Characterization of TBP containing polysiloxane membrane/insulator/semiconductor structures for hexavalent chromium detection

    Energy Technology Data Exchange (ETDEWEB)

    Zazoua, A. [Universite de Jijel, BP 98, Ouled Aissa, 18000 Jijel (Algeria); Universite de Annaba, BP 12, El-Hadjar, Annaba (Algeria); Kherrat, R.; Samar, M.H. [Universite de Annaba, BP 12, El-Hadjar, Annaba (Algeria); Errachid, A. [Laboratori de Nanobioenginyeria-IBEC, CIBER, Parc Cientific de Barcelona (PCB)-Departament d' Electronica. Universitat de Barcelona, C/Marti i Franques 1, 08028 Barcelona (Spain); Jaffrezic-Renault, N. [LSA - UMR 5180 CNRS - Universite Claude Bernard Lyon 1, 69622 Villeurbanne cedex (France)], E-mail: nicole.jaffrezic@univ-lyon1.fr; Bessueille, F.; Leonard, D. [LSA - UMR 5180 CNRS - Universite Claude Bernard Lyon 1, 69622 Villeurbanne cedex (France)

    2008-07-01

    A hexavalent chromium-sensitive EMIS sensor (electrolyte membrane insulator semiconductor sensor) is prepared by deposition of a tributylphosphate (TBP) ionophore-containing siloprene membrane on a Si/SiO{sub 2}/Si{sub 3}N{sub 4} structure. The developed EMIS sensor was studied by means of impedance spectroscopy, capacitance-voltage, X-ray photoelectron spectrometry and FT-IR spectroscopy. From the flat-band shift of the EMIS structure, the nersntian response to the anionic species Cr{sub 2}O{sub 7}{sup -} was demonstrated. The linear range of detection is 10{sup -4} M to 10{sup -1} M and the detection limit is 10{sup -5} M. Sulfate and chloride anions are shown not to be interfering whereas carbonate ions present a pK{sup pot} equal to 0.19.

  18. Enhanced chromium (VI) adsorption using nanosized chitosan fibers tailored by electrospinning.

    Science.gov (United States)

    Li, Lei; Li, Yanxiang; Cao, Lixia; Yang, Chuanfang

    2015-07-10

    Stacked chitosan nanofibers with an average diameter of 75 nm were successfully produced by electrospinning using 5 wt% chitosan in acetic acid as the spinning solution. The fibers were then cross-linked with glutaraldehyde to remove chromium [Cr(VI)] from water via static adsorption. It was found that the adsorption correlated well with pseudo-second order kinetic model, and followed a mixed isotherm of Freundlich and Langmuir. The maximum nanofibers adsorption capacity was 131.58 mg/g, more than doubled that of chitosan powders. Common co-ions such as Cl(-), NO3(-), Na(+), Ca(2+) and Mg(2+) had little or no effect on the adsorption but SO4(2-) was an exception. Fourier transform infrared spectroscopy and X-ray photoelectron spectrophotometer analyses indicated that both amino and hydroxyl groups of chitosan were engaged in the adsorption. PMID:25857976

  19. Preparation of Chromium Oxide Coatings on Aluminum Borate Whiskers by a Hydrothermal Deposition Process

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Aluminum borate whiskers (9Al2O32B2O3) can be used to reinforce aluminum alloys to produce light and strong composites. However, the adverse interfacial reactions between the whiskers and the aluminum alloys inhibit their practical uses; therefore, a protective coating is needed on whiskers. In this work, aluminum borate whiskers were coated with chromium-coating deposits in a hydrothermal solution containing CrCl3, Na2C4H4O6, NaPH2O2, and H3BO3. The presence of the impurity P in the hydrothermal deposits can be avoided by reducing the amount of NaPH2O2 in the coating solution. Thermodynamic analysis was used to discuss the behavior of ions in the coating process. The subsequent heating of the hydrothermal products in air at 800 ℃ yielded smooth Cr2O3 films with a thickness of 0.060.07 μm.

  20. Cadmium and chromium removal kinetics from solution by two aquatic macrophytes.

    Science.gov (United States)

    Suñe, N; Sánchez, G; Caffaratti, S; Maine, M A

    2007-01-01

    The aim of this work was to determine chromium and cadmium bioaccumulation processes of two free-floating macrophytes commonly used in wetlands for water treatment: Salvinia herzogii and Pistia stratiotes. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The most important processes of Cd uptake are biological ones in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes. The main processes of Cr uptake in both macrophytes are adsorption, chelation and ion exchange. The slow stage is different for each species and metal. Cr precipitation induced by roots occurs in P. stratiotes. Cr uptake through leaves is probably the main cause of the increase of Cr in the aerial parts of S. herzogii. PMID:16815611

  1. 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

  2. Scientific Opinion on chromium(III lactate tri-hydrate as a source of chromium added for nutritional purposes to foodstuff

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS

    2012-10-01

    Full Text Available

    The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion on the safety and bioavailability of chromium(III lactate tri-hydrate as a source of chromium(III added for nutritional purposes to foodstuffs. The safety of chromium itself, in terms of the amounts that may be consumed, is outside the remit of this Panel. No new data have been provided as regards the safety and bioavailability of chromium from chromium(III lactate tri-hydrate. The Panel concurs with its earlier views stating that no evidence was provided supporting the bioavailability of chromium from chromium(III lactate tri-hydrate. Chromium(III lactate tri-hydrate is claimed to be freely soluble in water, however, chromium(III lactate tri-hydrate exists as a weak complex that may influence the bioavailability of chromium(III in the gastrointestinal tract. The Panel re-iterates that because of the complex chemistry of chromium(III lactate tri-hydrate in aqueous solutions and its limited solubility at pH >5, the bioavailability of chromium(III from chromium(III lactate tri-hydrate is low. Based on a conservative exposure estimate, the Panel calculated the combined intake of chromium(III from supplements and from foods fortified with chromium(III lactate tri-hydrate, for both adults and children, to be approximately 240 μg chromium(III/day, which is below the value of 250 µg/day established by the WHO for supplemental intake of chromium that should not be exceeded. The Panel noted that the use of chromium(III lactate tri-hydrate in the form of a premix with lactose, added to foods, would result in an exposure at the mean for adults of approximately 7-37 mg lactose/day (0.12-0.62 μg lactose/kg bw/day and to 36-192 μg lactate/day (0.60-3.20 μg/kg bw/day. Given that subjects with lactose maldigestion will tolerate up to 12 g of lactose with no or minor symptoms, these levels are not of safety concern.

  3. 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 ...

  4. Investigation of hexavalent chromium removal from Synthetic wastewater by using Peaganum

    OpenAIRE

    Ali Akbar Taghizadeh; Maryam khodadadi; Taher Shahriary; Hadighe Dorri; mahla zaferanieh; rasoul khosravi

    2012-01-01

    Background and Aim: Discharge of industrial wastewater containing hexavalent chromium into the environment can have harmful effects to the types of organisms. So, chromium should remove before discharging to the environment with an effective method. The purpose of this study of is hexavalent chromium removed with Peganum harmala granular seeds(PGS).   Materials and Methods: In this experimental study, The removal of hexavalent chromium with using PGS, with changes in time, pH, adsorbent dose,...

  5. Solid phase extraction, separation and preconcentration of rare elements thorium(IV), uranium(VI), zirconium(IV), cerium(IV) and chromium(III) amid several other foreign ions with eriochrome black T anchored to 3-D networking silica gel.

    Science.gov (United States)

    Srivastava, Bhavya; Barman, Milan K; Chatterjee, Mousumi; Roy, Dipika; Mandal, Bhabatosh

    2016-06-17

    The present work reports the systematic studies on extraction, separation and preconcentration of Th(IV), U(VI), Zr(IV), Ce(IV) and Cr(III) amid several other foreign ions using EBT anchored {SiO2}n3-D microarray. The effect of various sorption parameters, such as pH, concentration, temperature, sample volume, flow-rate and co-existing foreign ions were investigated. Quantitative sorption was ensured at solution pH: 6.0-6.5 for Th(IV), Ce(IV), Cr(III) and pH: 2.75-3.0 for Zr(IV), U(VI) couple. Analysis on extracted species and extraction sites reveals that [Th4(μ(2)-OH)8(H2O)4](8+), [Ce6(μ(2)-OH)12(H2O)5](12+), [Cr3(μ(2)-OH)4(H2O)](5+), [(UO2)3(μ(2)-OH)5(H2O)3](+) and [Zr4(μ(2)-OH)8(H2O)0.5](8+) for the respective metal ions gets extracted at HOMO of the extractor. HOMO-{metal ion species} was found to be 1:1 complexation. Sorption was endothermic, entropy-gaining, instantaneous and spontaneous in nature. A density functional theory (DFT) calculation has been performed to analyze the 3-D structure and electronic distribution of the synthesized extractor. PMID:27185054

  6. Solid phase extraction, separation and preconcentration of rare elements thorium(IV), uranium(VI), zirconium(IV), cerium(IV) and chromium(III) amid several other foreign ions with eriochrome black T anchored to 3-D networking silica gel.

    Science.gov (United States)

    Srivastava, Bhavya; Barman, Milan K; Chatterjee, Mousumi; Roy, Dipika; Mandal, Bhabatosh

    2016-06-17

    The present work reports the systematic studies on extraction, separation and preconcentration of Th(IV), U(VI), Zr(IV), Ce(IV) and Cr(III) amid several other foreign ions using EBT anchored {SiO2}n3-D microarray. The effect of various sorption parameters, such as pH, concentration, temperature, sample volume, flow-rate and co-existing foreign ions were investigated. Quantitative sorption was ensured at solution pH: 6.0-6.5 for Th(IV), Ce(IV), Cr(III) and pH: 2.75-3.0 for Zr(IV), U(VI) couple. Analysis on extracted species and extraction sites reveals that [Th4(μ(2)-OH)8(H2O)4](8+), [Ce6(μ(2)-OH)12(H2O)5](12+), [Cr3(μ(2)-OH)4(H2O)](5+), [(UO2)3(μ(2)-OH)5(H2O)3](+) and [Zr4(μ(2)-OH)8(H2O)0.5](8+) for the respective metal ions gets extracted at HOMO of the extractor. HOMO-{metal ion species} was found to be 1:1 complexation. Sorption was endothermic, entropy-gaining, instantaneous and spontaneous in nature. A density functional theory (DFT) calculation has been performed to analyze the 3-D structure and electronic distribution of the synthesized extractor.

  7. Influence of chromium, oxygen, carbon and nitrogen on iron viscosity

    International Nuclear Information System (INIS)

    Kinetic viscosity of 70 beforehand melted iron samples with additions of chromium (up to 2%) and carbon (up to 1%) has been investigated. Different conditions of melting brought about differences in oxygen and nitrogen contents. Viscosity of most samples has been determined in the 1550-1650 deg C temperature range. It is stated that small additions to pure iron of each of the investigated elements (O, Cr, C, N) decrease its viscosity. Combined effect of these additions on viscosity is inadditive. Simultaneous introduction of oxygen and carbon may result in increase of melt viscosity. The same fact is observed at combined introduction of chromium and nitrogen. Simultaneous introduction of other impurities-chromium with oxygen or carbon, nitrogen with oxygen causes amplification of their individual effect. Reasons for the observed regularities result from changes in energies of interparticle interactions in the melt and therefore rebuilding of structure of its short-range order

  8. Structural and magnetic properties of chromium doped zinc ferrite

    International Nuclear Information System (INIS)

    Zinc chromium ferrites with chemical formula ZnCrxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

  9. 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.

  10. Electron magnetic resonance investigation of chromium diffusion in yttria powders

    Energy Technology Data Exchange (ETDEWEB)

    Biasi, R.S. de, E-mail: rsbiasi@ime.eb.b [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, Pr. General Tiburcio, 80, 22290-270 Rio de Janeiro, RJ (Brazil); Grillo, M.L.N., E-mail: mluciag@uerj.b [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

    2010-03-01

    The electron magnetic resonance (EMR) technique was used to investigate the diffusion of chromium in yttria (Y{sub 2}O{sub 3}) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E{sub A}=342+-5 kJ mol{sup -1}. This value is larger than the activation energy for the diffusion of chromium in rutile (TiO{sub 2}), periclase (MgO) and cobalt monoxide (CoO) and smaller than the activation energy for the diffusion of chromium in chrysoberyl (BeAl{sub 2}O{sub 4}).

  11. Identifying genes and gene networks involved in chromium metabolism and detoxification in Crambe abyssinica

    International Nuclear Information System (INIS)

    Chromium pollution is a serious environmental problem with few cost-effective remediation strategies available. Crambe abyssinica (a member of Brassicaseae), a non-food, fast growing high biomass crop, is an ideal candidate for phytoremediation of heavy metals contaminated soils. The present study used a PCR-Select Suppression Subtraction Hybridization approach in C. abyssinica to isolate differentially expressed genes in response to Cr exposure. A total of 72 differentially expressed subtracted cDNAs were sequenced and found to represent 43 genes. The subtracted cDNAs suggest that Cr stress significantly affects pathways related to stress/defense, ion transporters, sulfur assimilation, cell signaling, protein degradation, photosynthesis and cell metabolism. The regulation of these genes in response to Cr exposure was further confirmed by semi-quantitative RT-PCR. Characterization of these differentially expressed genes may enable the engineering of non-food, high-biomass plants, including C. abyssinica, for phytoremediation of Cr-contaminated soils and sediments. - Highlights: → Molecular mechanism of Cr uptake and detoxification in plants is not well known. → We identified differentially regulated genes upon Cr exposure in Crambe abyssinica. → 72 Cr-induced subtracted cDNAs were sequenced and found to represent 43 genes. → Pathways linked to stress, ion transport, and sulfur assimilation were affected. → This is the first Cr transcriptome study in a crop with phytoremediation potential. - This study describes the identification and isolation of differentially expressed genes involved in chromium metabolism and detoxification in a non-food industrial oil crop Crambe abyssinica.

  12. Chromium accumulation by the hyperaccumulator plant Leersia hexandra Swartz.

    Science.gov (United States)

    Zhang, Xue-Hong; Liu, Jie; Huang, Hai-Tao; Chen, Jun; Zhu, Yi-Nian; Wang, Dun-Qiu

    2007-04-01

    Leersia hexandra Swartz (Gramineae), which occurs in Southern China, has been found to be a new chromium hyperaccumulator by means of field survey and pot-culture experiment. The field survey showed that this species had an extraordinary accumulation capacity for chromium. The maximum Cr concentration in the dry leaf matter was 2978 mg kg(-1) on the side of a pond near an electroplating factory. The average concentration of chromium in the leaves was 18.86 times as that in the pond sediment, and 297.41 times as that in the pond water. Under conditions of the nutrient solution culture, it was found that L. hexandra had a high tolerance and accumulation capacity to Cr(III) and Cr(VI). Under 60 mg l(-1) Cr(III) and 10 mg l(-1) Cr(VI) treatment, there was no significant decrease of biomass in the leaves of L. hexandra (p>0.05). The highest bioaccumulation coefficients of the leaves for Cr(III) and Cr(VI) were 486.8 and 72.1, respectively. However, L. hexandra had a higher accumulation capacity for Cr(III) than for Cr(VI). At the Cr(III) concentration of 10 mg l(-1) in the culture solution, the concentration of chromium in leaves was 4868 mg kg(-1), while at the same Cr(VI) concentration, the concentration of chromium in leaves was only 597 mg kg(-1). These results confirmed that L. hexandra is a chromium hyperaccumulator which grows rapidly with a great tolerance to Cr and broad ecological amplitude. This species could provide a new plant resource that explores the mechanism of Cr hyperaccumulation, and has potential for usage in the phytoremediation of Cr-contaminated soil and water. PMID:17207838

  13. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  14. 75 FR 60454 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Science.gov (United States)

    2010-09-30

    ... AGENCY Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the..., ``Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the Integrated Risk..., 2010. The listening session on the draft assessment for hexavalent chromium will be held on November...

  15. 76 FR 20349 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Science.gov (United States)

    2011-04-12

    ... AGENCY Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the..., ``Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the Integrated Risk... workshop on the draft assessment for Hexavalent Chromium will be held on May 12, 2011, beginning at 8:30...

  16. 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...

  17. Speciation dependent radiotracer studies on chromium preconcentration using iron doped calcium alginate biopolymer

    International Nuclear Information System (INIS)

    The work aims to study the differential attitude of Ca-alginate (CA) and Fe-doped calcium alginate (Fe-CA) and towards Cr(III) and Cr (IV) so that, depending on the oxidation state of chromium effluent, environmentally sustainable methodologies can be prescribed for removal of chromium. Throughout the experiment 51Cr has been used as the precursor of stable chromium

  18. Evaluation of flexural bond strength of porcelain to used nickel-chromium alloy in various percentages

    Directory of Open Access Journals (Sweden)

    VNV Madhav

    2012-01-01

    Fresh nickel-chromium alloy shows the greatest porcelain adherence.There is no significant change in bond strength of ceramic to alloy with up to 75% of used nickel-chromium alloy.At least 25%- of new alloy should be added when recycled nickel-chromium alloy is being used for metal ceramic restorations.

  19. Fertilizers and Mixed Crop Cultivation of Chromium Tolerant and Sensitive Plants under Chromium Toxicity.

    Science.gov (United States)

    Dheeba, B; Sampathkumar, P; Kannan, K

    2015-01-01

    Zea mays (maize) and Vigna radiata (green gram) are found to be the chromium (Cr) tolerant and sensitive plants, respectively. In the present paper, we investigate the reduction of the toxicity of Cr in the sensitive plants by the mixed crop cultivation in the field using various amendments. Further, the potassium dichromate was used as the source of hexavalent Cr. The results indicated that Cr adversely affects both the growth and yield of plants. The soil properties vary with Cr and different fertilizer amendments and the yield of both plants were affected by Cr. We conclude that metal accumulation of seeds of green gram was higher than corn and the application of single fertilizer either farm yard manure (FYM) or nitrogen, phosphorous, and potassium (NPK) enhances the growth and yield of both the tolerant and sensitive plants in the mixed crop cultivations. PMID:25709647

  20. Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys.

    Science.gov (United States)

    Chen, Bo; Xia, Gang; Cao, Xin-Ming; Wang, Jue; Xu, Bi-Yao; Huang, Pu; Chen, Yue; Jiang, Qing-Wu

    2013-03-01

    This paper aims to investigate if the dental restoration of nickel-chromium based alloy (Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

  1. Primary and secondary crystallization of modified hypoeutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2010-04-01

    Full Text Available The paper presents investigations of crystallization of modified hypoeutectic wear resistant chromium cast iron which contains carbon about 2% and chromium on three levels (12%, 18% and 25%. Three substances were applied to the modification ( boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and mischmetal (RE. The investigations of crystallization were conducted the DTA method in DTA-C and DTA-Is testers. The influence on the course of the process of primary and secondary crystallization was observed.

  2. Use of chitosan for chromium removal from exhausted tanning baths.

    Science.gov (United States)

    Cesaro, Raffaele; Fabbricino, Massimiliano; Lanzetta, Rosa; Mancino, Anna; Naviglio, Biagio; Parrilli, Michelangelo; Sartorio, Roberto; Tomaselli, Michele; Tortora, Gelsomina

    2008-01-01

    A novel approach, based on chitosan heavy-metal sequestrating ability, is proposed for chromium(III) removal from spent tanning liquor. Experimental results, obtained at lab-scale using real wastewater, are presented and discussed. Resulting efficiencies are extremely high, and strongly dependent on chitosan dose and pH value. Comparative analyses with other polysaccharides is also carried out showing that amine groups are more efficient than carboxyl and sulphate ones. Chromium recovery from sorption complexes and chitosan regeneration is finally proposed to optimize the whole process.

  3. Effect of inhaled chromium on pulmonary AlAT

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, M.D.; Siso, M.; Baker, K.; Chen, L.C.; Schlesinger, R.B. [New York University, Tuxedo Park, NY (United States). School of Medicine, Dept. of Environmental Medicine

    2002-07-01

    A major health hazard to coal miners is development of emphysema following long-term exposure to coal dust. One mechanism underlying development of emphysema is the oxidation of critical methionine (Met) residues in antiproteolytic factor, alpha1-antitrypsin (AlAT) resulting in a protease-antiprotease imbalance in the lung. Several studies have documented an association between the incidence and severity of emphysema among miners and their exposure to crystalline silica (SiO{sub 2}). However, what remains unclear is the role of other co-inhaled nonemphysematogenic nonoxidant inorganic constituent in disease pathogenesis. We hypothesize that in miners, inhaled trivalent chromium (Cr{sup 3+}, the only form of Cr in coal) may potentially affect lung AlAT activity in situ via Cr complexing with Met residues, and thereby exacerbate any SiO{sub 2}-induced imbalance. To ascertain if Cr{sup 3+} could, in fact, affect AlAT activity, in vitro studies were done to assess elastase inhibitory activity following AlAT incubation with soluble Cr{sup 3+}. In addition, to determine if Cr{sup 3+} found in the lungs as detoxification products of inhaled hexavalent Cr could affect AlAT in situ, lavages from the lungs of chromate-exposed rats were also analyzed for elastase inhibitory activity The in vitro results indicate that Cr{sup 3+} ions clearly inhibited AlAT function, with an IC50 of 1.1 mM being estimated under the experimental conditions used. The in vivo results indicate that long-term inhalation (12 wk or longer) of chromate-bearing atmospheres also gave rise to significant (i.e., 50-70%) inhibition of the antielastase activity of AlAT. Together, these results clearly suggest that the Cr{sup 3+} present in coal dusts could potentially act to inhibit AlAT activity in the lungs of miners and thereby promote the emphysema togenicity of SiO{sub 2} or of other emphysematogens present as coconstituents in these dusts.

  4. LIGAND AND ALKALI-METAL CATION CONTROL ON THE MOLECULAR COMPLEXITY OF ANIONIC CHROMIUM(II) ARYLOXIDES - PREPARATION AND CRYSTAL-STRUCTURE OF DIMERIC (PHO)10CR2LI6(THF)6 AND (2,6-ME2C6H3O)6CR2LI2(THF)4 AND TRIMERIC (GUO)14CR3NA9CL [GUO = (ORTHO-CH3O)C6H4O] WITH AN ENCAPSULATED CHLORIDE-ION

    NARCIS (Netherlands)

    EDEMA, JJH; MEETSMA, A; GAMBAROTTA, S; KHAN, SI; SMEETS, WJJ; SPEK, AL

    1991-01-01

    Two new anionic, dimeric chromium(II) alkoxides, (PhO)10Cr2Li6(THF)6 (3) and (2,6-Me2C6H3O)6Cr2Li2(THF)4 (4), have been prepared and characterized by X-ray structure determination. The two complexes possess similar Cr2(OR)2 cores with a fairly long Cr-Cr distance [Cr...Cr' = 3.149 (2) and 3.091 (1)

  5. A spectrophotometric study of cerium IV and chromium VI species in nuclear fuel reprocessing process streams

    Science.gov (United States)

    Nickson, I. D.; Boxall, C.; Jackson, A.; Whillock, G. O. H.

    2010-03-01

    Nuclear fuel reprocessing schemes such as PUREX and UREX utilise HNO3 media. An understanding of the corrosion of process engineering materials such as stainless steel in such media is a major concern for the nuclear industry. Two key species are cerium and chromium which, as Ce(IV), Cr(VI), may act as corrosion accelerants. An on-line analytical technique for these quantities would be useful for determining the relationship between corrosion rate and [Ce(IV)] and [Cr(VI)]. Consequently, a strategy for simultaneous quantification of Ce(IV), Cr(VI) and Cr(III) in the presence of other ions found in average burn-up Magnox / PWR fuel reprocessing stream (Fe, Mg, Nd, Al) is being developed. This involves simultaneous UV-vis absorbance measurement at 620, 540, 450 nm, wavelengths where Ce and Cr absorb but other ions do not. Mixed solutions of Cr(VI) and Ce(IV) are found to present higher absorbance values at 540 nm than those predicted from absorbances recorded from single component solutions of those ions. This is attributed to the formation of a 3:1 Cr(VI)-Ce(IV) complex and we report on the complexation and UV-visible spectrophotometric characteristics of this species. To the best of our knowledge this is the first experimental study of this complex in aqueous nitric acid solution systems.

  6. Anisotropic dewetting of ion irradiated solid films

    Energy Technology Data Exchange (ETDEWEB)

    Repetto, L., E-mail: luca.repetto@unige.it [Dipartimento di fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, B. [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, G.; Piano, E.; Valbusa, U. [Dipartimento di fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

    2013-11-15

    Experiments of irradiation with 30 keV Ga ions were conducted on ultrathin chromium films on rippled silicon substrates. The evolution of their surface morphology, as detected by real time scanning electron microscopy, shows an apparent differential sputtering yield for regions of positive and negative curvature which is in contrast with the standard theory for curvature depending sputtering yield. In particular, at the end of the irradiation process, chromium wires are left in the valleys of the substrate. This result was explained in terms of local melting caused by the ion impact and of a process of dewetting under the concurring actions of surface tension and Van der Waals forces while ion sputtering is active. The interpretation of the reported experimental results are fully supported by numeric simulations implementing the same continuum model used to explain ion induced spinodal dewetting. This hierarchical self-organization process breaks the symmetry of previously demonstrated ion induced dewetting, making possible to create new structures by using the same fundamental effects.

  7. Effect of halides addition on the ligand field of chromium in alkali borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, M.A., E-mail: moukhtar_hassan@yahoo.com

    2013-10-15

    Highlights: •The 10 KM–64.7 B{sub 2}O{sub 3}–25 Na{sub 2}O–0.3 Cr{sub 2}O{sub 3} (M = Cl, Br and I) glassy system was prepared by a quenching method. •Optical basicity, ligand field theory optical band gap energy, refractive index, ESR and IR were studied. •The electronegativity plays an important role in deforming the crystal field around the transition metal ions. •The crystal-field sites of KCl or KBr sample are very strong compared to the very weak one in the KI sample. -- Abstract: Borate oxide glass system of composition 10 KM–64.7 B{sub 2}O{sub 3}–25 Na{sub 2}O–0.3 Cr{sub 2}O{sub 3} (M = Cl, Br and I) was prepared by conventional melt quenching technique. The amorphous nature of the investigated glasses was checked by the X-ray diffraction (XRD) technique. The optical basicity of the system has been calculated, and was found to increase by going from KCl to KBr and to KI. Optical absorption spectra were recorded in the UV–visible range. Through a careful analysis of the data, the ligand field parameters (crystal field strength Dq, Racah parameters B and nephelauxetic functions h) and the optical parameters (optical band gap, Urbach tail band width, and refractive index) have been estimated. The obtained results reveal a strong correlation between that ligand field parameters and the type of halogen atom; the crystal-field strength of KCl or KBr samples are very pronounced but it is rather weak in the KI sample. Electron spin resonance (ESR) has been used to probe the valency of the Chromium ions. The resulting ESR parameters revealed that chromium ions are predominantly in the trivalent state with traces of hexavalent state. Using Infrared spectroscopy (IR) information on the boron structural units has been obtained. The N{sub 4} ratio increases by replacing the KCl by KBr or KI, and it was found that the tetrahedral coordination of Cr{sup +} ions becomes preferential in the host glasses with increasing the optical basicity.

  8. 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.

  9. Friction and wear behavior of chromium carbide coatings

    International Nuclear Information System (INIS)

    Chromium carbides, tungsten carbide, and chromium oxide have been tested and evaluated as coatings to protect high-temperature gas-cooled reactor (HTGR) steam generator and other HTGR components from adhesion, galling associated with sliding wear or from fretting. Tests were performed in commercially-pure helium and in helium doped with various gaseous impurities (H2, H2O, CH4, CO) to simulate the primary coolant of an HTGR. Several types of chromium carbide coatings including Cr3C2, Cr7C3, and Cr23C6, were tested for wear resistance and resistance to long-term spalling. Tungsten carbide and chromium oxide coatings were tested in sliding wear tests. Cr23C6-NiCr coatings showed the best performance (from 400 to 8160C) whether they were applied by detonation gun or plasma gun spraying methods. The presence of the Cr23C6-NiCr coatings did not affect the creep rupture properties of Alloy 800H substrates at temperatures up to 7600C. Low-cycle fatigue life of similar specimens at 5930C was reduced to 10 to 20% when tested in the 1 to 0.6% strain range

  10. Porosity of detonation coatings on the base of chromium carbide

    International Nuclear Information System (INIS)

    Porosity of detonation coatings on the base of chromium carbide is estimated by the hydrostatic weighing. The open porosity value dependence on the distance of spraying, depth of the charge, ratio and volume of the detonator barrie filing with gas components is established. Pore distribution in the cross section of a specimen tested for porosity is studied by the methods of metallographic analysis

  11. Intestinal absorption of chromium as affected by wheat bran

    Energy Technology Data Exchange (ETDEWEB)

    Keim, K.S.; Holloway, C.L.; Hegsted, M.

    1986-03-01

    This study was designed to investigate the influence of dietary fiber, as found in wheat bran, on the absorption of chromium. Twenty male Sprague-Dawley rats were divided into two groups of 10. The control was fed a semi-purified diet containing casein, methionine, cornstarch, sucrose, corn oil, mineral and vitamin mix, and choline bitartrate. The experimental group was fed the same diet but with soft red winter wheat bran added to a level of 35% of the diet at the expense of sucrose. To determine chromium absorption and uptake by selected tissues, rats were fasted for 24 hr, fed 5 g of the respective diet, 2 hr later intubated with 100..mu..Ci of Cr-51of sacrificed 24 hr later. The rats wee housed in metabolic cages after the Cr-51 intubation. The addition of wheat brand to the diet did not significantly affect chromium absorption as measured by percent dose of Cr-51 in the 24 hr urine. The percent dose in the control group was 0.68 +/- 0.20% (mean +/- SEM) and in the experimental group 0.63 +/- 0.24% (mean +/-SEM) (N.S.). The cr-51 uptake of liver, spleen, jejunum, and blood was not statistically different between groups. These results indicate that dietary fiber as found in wheat bran does not impair intestinal absorption of chromium.

  12. 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.

  13. 75 FR 67100 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2010-11-01

    ... superalloy degassed chromium from Japan (70 FR 76030). The Commission is conducting a review to determine..., subparts A, D, E, and F (19 CFR part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1... rule 201.15(b)(19 CFR 201.15(b)), 73 FR 24609 (May 5, 2008). This advice was developed in...

  14. 76 FR 8773 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2011-02-15

    ... applicable deadline.'' (75 FR 80457). Accordingly, pursuant to section 751(c) of the Tariff Act of 1930 (19 U... COMMISSION Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission... Japan would be likely to lead to continuation or recurrence of material injury. On December 22,...

  15. Intestinal absorption of chromium as affected by wheat bran

    International Nuclear Information System (INIS)

    This study was designed to investigate the influence of dietary fiber, as found in wheat bran, on the absorption of chromium. Twenty male Sprague-Dawley rats were divided into two groups of 10. The control was fed a semi-purified diet containing casein, methionine, cornstarch, sucrose, corn oil, mineral and vitamin mix, and choline bitartrate. The experimental group was fed the same diet but with soft red winter wheat bran added to a level of 35% of the diet at the expense of sucrose. To determine chromium absorption and uptake by selected tissues, rats were fasted for 24 hr, fed 5 g of the respective diet, 2 hr later intubated with 100μCi of Cr-51of sacrificed 24 hr later. The rats wee housed in metabolic cages after the Cr-51 intubation. The addition of wheat brand to the diet did not significantly affect chromium absorption as measured by percent dose of Cr-51 in the 24 hr urine. The percent dose in the control group was 0.68 +/- 0.20% (mean +/- SEM) and in the experimental group 0.63 +/- 0.24% (mean +/-SEM) (N.S.). The cr-51 uptake of liver, spleen, jejunum, and blood was not statistically different between groups. These results indicate that dietary fiber as found in wheat bran does not impair intestinal absorption of chromium

  16. Invariant coefficients of diffusion in iron-chromium-nickel system

    Energy Technology Data Exchange (ETDEWEB)

    Mokrov, A.P.; Akimov, V.K.; Golubev, V.G.

    1984-02-01

    The temperature and concentration dependences of the Dsub(c) coefficients in the ..gamma..-phase of iron-chromium-nickel system are determined. It is proposed to described mutual diffusion in multicomponent systems using invariant, i.e. independent of the choice of solvent, coefficients of diffusion. The assumption that their temperature dependence follows the Arrhenius law is confirmed by the experiment.

  17. Invariant coefficients of diffusion in iron-chromium-nickel system

    International Nuclear Information System (INIS)

    The temperature and concentration dependences of the Dsub(c) coefficients in the γ-phase of iron-chromium-nickel system are determined. It is proposed to described mutual diffusion in mul-- ticomponent systems using invariant, i. e. independent of the choice of solvent, coefficients of diffusion. The assumption that their temperature dependence follows the Arrhenius law is confirmed by the experiment

  18. Differents remediation methodos for lead, chromium and cadmium contaminated soils

    International Nuclear Information System (INIS)

    The usage of phosphates in the remediation of plots contaminated with heavy metals appears to be a good strategy to lessen the danger of these metals. This study analyses the effect of the mobilization of: Lead, chromium and cadmium by utilizing diverse forms of phosphates in contaminated soils of three different origins with ph modification and without it

  19. IRIS TOXICOLOGICAL REVIEW OF HEXAVALENT CHROMIUM (INTERAGENCY SCIENCE CONSULTATION DRAFT)

    Science.gov (United States)

    On Septemeber 30, 2010, the draft Toxicological Review of Hexavalent Chromium and the charge to external peer reviewers were released for external peer review and public comment. The Toxicological Review and charge were reviewed internally by EPA and by other federal agenc...

  20. Chromium isotope fractionation during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    The chromium (Cr) isotopic composition of carbonates can potentially be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track paleoenvironmental changes, for example related to the rise of oxygen during...

  1. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes;

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track...

  2. Discovery of Chromium, Manganese, Nickel, and Copper Isotopes

    OpenAIRE

    Garofali, K.; Robinson, R; Thoennessen, M

    2010-01-01

    Twenty-seven chromium, twenty-five manganese, thirty-one nickel and twenty-six copper isotopes have so far been observed and the discovery of these isotopes is discussed. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  3. Chromium stable isotope fractionation in modern biogeochemical cycling

    DEFF Research Database (Denmark)

    Paulukat, Cora Stefanie

    Chromium (Cr) is, due to its redox-sensitive properties, a powerful tracer for redox processes in environmental studies. Changes in its preferred oxidation state (III and VI) are accompanied by Crisotope fractionation. The Cr-isotope system is a promising tool to reconstruct the evolution of free...

  4. FEATURES OF CHROMIUM DOPING OF WEAR-RESISTANT CAST IRON

    Directory of Open Access Journals (Sweden)

    V. V. Netrebko

    2013-01-01

    Full Text Available The aim of this work analysis of the influence of chromium on the process of carbide formation, changes in chemical composition of the metal substrate in the areas adjacent to the carbides and at the hardness of iron while economy nickel and manganesealloying.

  5. Production performance of quails given chromium organic in ration

    Directory of Open Access Journals (Sweden)

    Deden Sudrajat

    2014-12-01

    Full Text Available Egg production of quails depends on quality of ration. Nutrient manipulation by chromiun inclusion in ration is a possible way to improve production. It is known that chromium mineral in form of GTF in blood has a role not only in enhancement of glucose entering cells through improvement of insulin activity but also in metabolism of lipid and synthesis of protein and elimination of heat stress to improve egg production. This study aimed at assessing egg production of quails fed ration containing chromium-yeast. Sixty-four quails aged 40 days were used. A completely randomized design with 4 treatments and 4 replication was applied in this study. Treatment consisted of commercial ration + Cr 0 ppm (R1, commercial ration + Cr 0.5 ppm (R2, commercial ration + Cr 1 ppm (R3, and commercial ration+ Cr 1.5 ppm (R4. Measurements were taken on feed intake, egg weight, egg mass production, hen day, feed conversion rate, egg index, and egg shell thickness. Results showed that A ration containing organic chromium as much as 1,5 ppm did not affect feed intake, egg production, egg weight, and eggshell thickness, however lowered feed conversion rate by up to 32.25% from that of control. Supplementation of 0,5 ppm chromium in the ration lowered the value of eggs index in the fourth week.

  6. Chromium toxicity to nitrifying bacteria: implications to wastewater treatment

    Science.gov (United States)

    Chromium, a heavy metal that enters wastewater treatment plants (WWTPs) through industrial discharges, can be toxic to microorganisms carrying out important processes within biological wastewater treatment systems. The effect of Cr(III) and Cr(VI) on ammonia dependent specific ox...

  7. DANGER OF HEXAVALENT CHROMIUM AND STRATEGY FOR THE REMEDITATION

    Directory of Open Access Journals (Sweden)

    Aniruddha Roy

    2013-02-01

    Full Text Available Some metals as micronutrients have a major role in the life and growth process of plants and animals. However, certain forms of some metals may also act as toxic material even in relatively small quantities. Chromium is such a metal, whose concentration above a certain limit may cause a serious problem to the health of living organisms. Chromium (Cr may occur in several chemical forms in organic and inorganic systems. In biological systems only Cr (III and Cr (VI are significant. Among these two states, trivalent chromium (Cr-III is considered as an essential component, while hexavalent Chromium (Cr-VI in biological system has been detected as responsible for so many diseases, even some specific forms of cancer. This paper intends to present the adverse effect of Cr(VI on environment as well as on human beings and also try to find a way out to dissolve the problem by a newly developed efficient and cost effective technique.

  8. Effects of chromium picolinate supplementation in type 2 diabetic patients

    Directory of Open Access Journals (Sweden)

    Niladê Rosinski Rocha

    2014-10-01

    Full Text Available The effects of chromium picolinate in Type 2 diabetic patients are investigated.  Seventeen Type 2 diabetic patients were randomly divided into two groups. The experimental group received fiber-rich hypocaloric diet and chromium picolinate whereas the control group received fiber-rich hypocaloric diet and placebo. The chromium picolinate was offered twice a day at the dose of 100 μg. Anthropometric data such as blood pressure, fasting glycemia and glycated hemoglobin (HbA1c were measured and these parameters were evaluated again after 90 days. No difference was reported in rates of body weight, waist, hip, body mass index, blood pressure and fasting glycemia (Control vs. Experimental groups after treatment. However, a decrease (p = 0.0405 of HbA1c occurred in the experimental group when the pre- and post-treatment rates were compared. HbA1c data showed that chromium picolinate improved the glycemic control in Type 2 diabetes.

  9. Absorption of Nickel, Chromium, and Iron by the Root Surface of Primary Molars Covered with Stainless Steel Crowns

    Directory of Open Access Journals (Sweden)

    David Keinan

    2010-01-01

    Full Text Available Objective. The purpose of this study was to analyze the absorption of metal ions released from stainless steel crowns by root surface of primary molars. Study Design. Laboratory research: The study included 34 primary molars, exfoliated or extracted during routine dental treatment. 17 molars were covered with stainless-steel crowns for more than two years and compared to 17 intact primary molars. Chemical content of the mesial or distal root surface, 1 mm apically to the crown or the cemento-enamel junction (CEJ, was analyzed. An energy dispersive X-ray spectrometer (EDS was used for chemical analysis. Results. Higher amounts of nickel, chromium, and iron (5-6 times were found in the cementum of molars covered with stainless-steel crowns compared to intact molars. The differences between groups were highly significant (<.001. Significance. Stainless-steel crowns release nickel, chromium, and iron in oral environment, and the ions are absorbed by the primary molars roots. The additional burden of allergenic metals should be reduced if possible.

  10. Use of natural mordenite to remove chromium (III) and to neutralize pH of alkaline waste waters.

    Science.gov (United States)

    Córdova-Rodríguez, Valduvina; Rodríguez-Iznaga, Inocente; Acosta-Chávez, Raquel María; Chávez-Rivas, Fernando; Petranovskii, Vitalii; Pestryakov, Alexey

    2016-01-01

    The natural mordenite from Palmarito de Cauto deposit (PZ), Cuba, was studied in this work as an ion exchanger to remove Cr(3+) cations from alkaline aqueous solutions at different pH and chromium concentrations. The mordenite stability under cyclic treatment processes with alkaline solutions and its capacity to decrease the pH of the solutions was also analyzed. It was shown that PZ removes Cr(3+) ions from alkaline solutions, and it happens independently of the starting chromium concentration and the pH of the exchange solution used. This material has an important neutralizing effect on alkaline solutions, expressed in a significant pH decrease from the early stages of the treatments. For solutions with initial pH equal to 11, it decreases to a value of around seven. The stability of this material is not affected significantly after continuous cyclic treatment with NaOH solution, which shows that mordenite, in particular from Palmarito de Cauto deposit, has high stability in alkaline solutions. The results are important as they suggest that natural zeolites may be of interest in treatments of alkaline industrial waste effluents. PMID:26818904

  11. 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.

  12. A comparative study of all-vanadium and iron-chromium redox flow batteries for large-scale energy storage

    Science.gov (United States)

    Zeng, Y. K.; Zhao, T. S.; An, L.; Zhou, X. L.; Wei, L.

    2015-12-01

    The promise of redox flow batteries (RFBs) utilizing soluble redox couples, such as all vanadium ions as well as iron and chromium ions, is becoming increasingly recognized for large-scale energy storage of renewables such as wind and solar, owing to their unique advantages including scalability, intrinsic safety, and long cycle life. An ongoing question associated with these two RFBs is determining whether the vanadium redox flow battery (VRFB) or iron-chromium redox flow battery (ICRFB) is more suitable and competitive for large-scale energy storage. To address this concern, a comparative study has been conducted for the two types of battery based on their charge-discharge performance, cycle performance, and capital cost. It is found that: i) the two batteries have similar energy efficiencies at high current densities; ii) the ICRFB exhibits a higher capacity decay rate than does the VRFB; and iii) the ICRFB is much less expensive in capital costs when operated at high power densities or at large capacities.

  13. PLEPS study of ions implanted RAFM steels

    Science.gov (United States)

    Sojak, S.; Slugeň, V.; Egger, W.; Ravelli, L.; Petriska, M.; Veterníková, J.; Stacho, M.; Sabelová, V.

    2014-04-01

    Current nuclear power plants (NPP) require radiation, heat and mechanical resistance of their structural materials with the ability to stay operational during NPP planned lifetime. Radiation damage much higher, than in the current NPP, is expected in new generations of nuclear power plants, such as Generation IV and fusion reactors. Investigation of perspective structural materials for new generations of nuclear power plants is among others focused on study of reduced activation ferritic/martensitic (RAFM) steels. These steels have good characteristics as reduced activation, good resistance to volume swelling, good radiation, and heat resistance. Our experiments were focused on the study of microstructural changes of binary Fe-Cr alloys with different chromium content after irradiation, experimentally simulated by ion implantations. Fe-Cr alloys were examined, by Pulsed Low Energy Positron System (PLEPS) at FRM II reactor in Garching (Munich), after helium ion implantations at the dose of 0.1 C/cm2. The investigation was focused on the chromium effect and the radiation defects resistivity. In particular, the vacancy type defects (monovacancies, vacancy clusters) have been studied. Based on our previous results achieved by conventional lifetime technique, the decrease of the defects size with increasing content of chromium is expected also for PLEPS measurements.

  14. Chromium(VI) transport and fate in unsaturated zone and aquifer: 3D Sandbox results.

    Science.gov (United States)

    Zhao, Xingmin; Sobecky, Patricia A; Zhao, Lanpo; Crawford, Patrice; Li, Mingtang

    2016-04-01

    The simulation of Cr(VI) behavior in an unsaturated zone and aquifer, using a 3D experimental set-up were performed to illustrate the distribution, transport and transformation of Cr(VI), and further to reveal the potential harm of Cr(VI) after entering the groundwater. The result indicated that chromium(VI) was transported in the vertical direction, meanwhile, was transported in the horizontal direction under the influence of groundwater flow. The direction and distance away from the pollution source zone had great effect on the chromium(VI) concentration. At the sampling sites near the pollution source zone, there was a sudden increase of chromium(VI) concentration. The concentration of chromium(III) concentration in some random effluent samples was not detected. Chromium had not only transported but also had fraction and specie transformation in the unsaturated zone and aquifer. The relative concentration of residue fraction chromium was decreased with time. The content of Fe-Mn oxide fraction chromium was increased with time. The relative content of exchangeable and carbonate-bound fraction chromium was lower and the content variations were not obvious. Chromium(VI) (91-98%) was first reduced to chromium(III) rapidly. The oxidation reaction occurred later and the relative content of chromium(VI) was increased again. The presence of manganese oxides under favorable soil conditions can promote the reoxidation of Cr(III) to Cr(VI).

  15. Structure and morphology studies of chromium film at elevated temperature in hypersonic environment

    Indian Academy of Sciences (India)

    G M Hegde; V Kulkarni; M Nagaboopathy; K P J Reddy

    2012-06-01

    This paper presents the after shock heated structural and morphological studies of chromium film coated on hypersonic test model as a passive drag reduction element. The structural changes and the composition of phases of chromium due to shock heating (2850 K) are characterized using X-ray diffraction studies. Surface morphology changes of chromium coating have been studied using scanning electron microscopy (SEM) before and after shock heating. Significant amount of chromium ablation and sublimation from the model surface is noticed from SEM micrographs. Traces of randomly oriented chromium oxides formed along the coated surface confirm surface reaction of chromium with oxygen present behind the shock. Large traces of amorphous chromium oxide phases are also observed.

  16. Determination of Chromium in Beef Heifers Nellore Supplemented with Chelate Chrome

    Directory of Open Access Journals (Sweden)

    P.S.A Moreira

    2013-11-01

    Full Text Available The objective of this work was to determine the amount of total chromium in beef heifers supplemented with chelated chromium in the rearing and finishing. We used 80 Nelore heifers at 12 months of age with mineral supplementation associated or not to chelate chromium, with average live weight of 220 kg. Were selected 36 heifer seach experimental group for analysis of meat samples. For the determination of chromium residue in the muscle tissue of the sample was1.5 g digested in a mixture of 5 ml 65% nitric acid and 1 ml of 30% hydrogen peroxide at 120° C for 12 hours block microdigestor. The total content of chromium was determined by spectrophotometry of atomic absorption flame. The experimental design was completely randomized and the results were analyzed by analysis of variance (ANOVA at 5% significance. It is concluded that the inclusion of chromium in the chelate heifers mineral supplementation increased the chromium content in the meat

  17. Contribution of photoelectron spectrometry and infrared spectrometry to the study of various oxidised forms of chromium

    International Nuclear Information System (INIS)

    Securate knowledge of internal surface of primary coolant circuits of PWR is required for an estimation of dissolution of used materials and for estimation of decontamination efficiency. The binding energies of various electron levels of chromium were determined by photoelectron spectrometry (ESCA), both for the metal and for certain compounds. Because of the intensities of the signals obtained the 2 p 3/2 level alone can be used for analytical purposes. Owing to a possible interference between this level due to hexavalent chromium and a satellite peak caused by trivalent chromium the method is not able to show up small amounts of chromium VI in chromium III. Simultaneous detection of the hexavalent and trivalent forms was achieved by infrared spectrometry. The problem of revealing traces of chromium VI in surface layers of trivalent chromium oxide has thus been solved

  18. Laboratory scale studies on removal of chromium from industrial wastes

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Chromium being one of the major toxic pollutants is discharged from electroplating and chrome tanning processes and is also found in the effluents of dyes, paint pigments, manufacturing units etc. Chromium exists in aqueous systems in both trivalent (Cr 3+) and hexavalent (Cr 6+) forms. The hexavalent form is carcinogenic and toxic to aquatic life, whereas Cr3+ is however comparatively less toxic. This study was undertaken to investigate the total chromium removal from industrial effluents by chemical means in order to achieve the Pakistan NEQS level of 1 mg/L by the methods of reduction and precipitation. The study was conducted in four phases.In phase I, the optimum pH and cost effective reducing agent among the four popular commercial chemicals was selected. As a result, pH of 2 was found to be most suitable and sodium meta bisulfate was found to be the most cost effective reducing agent respectively. Phase II showed that lower dose of sodium meta bisulfate was sufficient to obtain 100 % efficiency in reducing Cr6+ to Cr3+, and it was noted that reaction time had no significance in the whole process. A design curve for reduction process was established which can act as a tool for treatment of industrial effluents.Phase III studies indicated the best pH was 8.5 for precipitation of Cr 3+ to chromium hydroxide by using lime. An efficiency of 100 % was achievable and a settling time of 30 minutes produced clear effluent. Finally in Phase IV actual waste samples from chrome tanning and electroplating industries, when precipitated at pH of 12 gave 100 % efficiency at a settling time of 30 minutes and confirmed that chemical means of reduction and precipitation is a feasible and viable solution for treating chromium wastes from industries.

  19. Arsenic and chromium topsoil levels and cancer mortality in Spain.

    Science.gov (United States)

    Núñez, Olivier; Fernández-Navarro, Pablo; Martín-Méndez, Iván; Bel-Lan, Alejandro; Locutura, Juan F; López-Abente, Gonzalo

    2016-09-01

    Spatio-temporal cancer mortality studies in Spain have revealed patterns for some tumours which display a distribution that is similar across the sexes and persists over time. Such characteristics would be common to tumours that shared risk factors, including the chemical soil composition. The objective of the present study is to assess the association between levels of chromium and arsenic in soil and the cancer mortality. This is an ecological cancer mortality study at municipal level, covering 861,440 cancer deaths in 7917 Spanish mainland towns from 1999 to 2008. Chromium and arsenic topsoil levels (partial extraction) were determined by ICP-MS at 13,317 sampling points. To estimate the effect of these concentrations on mortality, we fitted Besag, York and Mollié models, which included, as explanatory variables, each town's chromium and arsenic soil levels, estimated by kriging. In addition, we also fitted geostatistical-spatial models including sample locations and town centroids (non-aligned data), using the integrated nested Laplace approximation (INLA) and stochastic partial differential equations (SPDE). All results were adjusted for socio-demographic variables and proximity to industrial emissions. The results showed a statistical association in men and women alike, between arsenic soil levels and mortality due to cancers of the stomach, pancreas, lung and brain and non-Hodgkin's lymphomas (NHL). Among men, an association was observed with cancers of the prostate, buccal cavity and pharynx, oesophagus, colorectal and kidney. Chromium topsoil levels were associated with mortality among women alone, in cancers of the upper gastrointestinal tract, breast and NHL. Our results suggest that chronic exposure arising from low levels of arsenic and chromium in topsoil could be a potential risk factor for developing cancer.

  20. Sorption of chromium in soils of the Cerrado Goias, Brazil

    Directory of Open Access Journals (Sweden)

    Welershon José de Castro

    2010-08-01

    Full Text Available Land application of tannery sludge, which usually contain high levels of chromium, and considerable amounts of organic matter, macronutrients and micronutrients may contribute to the improvement of soil fertility and plant nutrition, and constitutes a form of disposal residue in the environment. The objective of this work was to determine the sorption isotherms of metal chromium (Cr+3 in a Ultisol, Oxisol Typic Acrustox, Quartzipsamment and Kandic Oxisol, identify soil classes that are prone to chromium mobility, and characterize the potential of agricultural soils of Goiás that are subject to groundwater contamination by the potentially toxic metal. For the establishment of sorption isotherms, solutions were prepared at 1:10 in volume. Air dried samples of 5.0 cm3 of each class of soil were placed in triplicates in beakers of 250.0 cm3. A solution containing 50.0 cm3 of the potentially toxic metal was added to solution. The solutions were prepared in CaCl2.(2H2O (0.01 mol.L-1 as electrolyte support and employing the basic chromium sulphate as a source of metal. Adjustments were made to the polynomial regression between the concentrations of potentially toxic levels of metal contaminants in the solution depending on the concentration of metal in the filtered solution after equilibrium. The Quartzipsamment showed lower retention compared to other classes of soils. Therefore it is more vulnerable to groundwater contamination if industrial wastes containing trivalent chromium are used as fertilizer.

  1. Raman spectroscopy of supported chromium oxide catalysts : determination of chromium-oxygen bond distances and bond orders

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Wachs, I.E.

    1996-01-01

    An empirical correlation is described for relating Raman stretching frequencies of chromium—oxygen (Cr—O) bonds to their bond lengths in chromium oxide reference compounds. An exponential fit of crystallographically determined Cr—O bond lengths to Cr—O Raman symmetric stretching frequencies (800–130

  2. 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...

  3. Activated carbon adsorption for chromium treatment and recovery; Adsorbimento di cromo su carboni attivi a scopo di recupero e decontaminazione

    Energy Technology Data Exchange (ETDEWEB)

    Baroncelli, F.; Castelli, S.; De Francesco, M. [ENEA, Casaccia (Italy). Area Energia e Innovazione

    1994-05-01

    The capability of actived carbon systems to adsorb chromium from wastewater of galvanic industry is valued. Batch tests and column tests are carried out with good results. An activated carbon with acidic surface oxides can adsorb both chromate and chromium (III); chromate is reduced in situ and then adsorbed as chromium (III). Chromium can be desorbed from carbon by an acid or basic treatment obtaining respectively chromium (III) or chromate solutions. Carbon can be regenerated many times without evident signs of deterioration.

  4. The effect of dietary supplementation with different forms and levels of organic chromium on broilers meat quality

    OpenAIRE

    Keleman Svetlana P.; Kevrešan Slavko E.; Supić Boriša; Perić Lidija; Strugar Vladimir

    2006-01-01

    This paper deals with the effect of supplementation with the three different preparations of organic chromium complexes: the ethylenediaminetetraacetic acid complex with chromium; chromium (III)­lysine and chromium picolinate, on broilers meat quality. In every preparation supplementing broilers diet chromium was present at the three different levels: 0.2; 0.4 and 0.6 mg/kg. The meat quality was monitored with respect to the following parameters: the contents of fat, protein, minerals and wat...

  5. Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2008-01-01

    Full Text Available Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface thickness. Methods. The research was performed as an experimental study. Per six metal-ceramic samples of nickel-chromium alloy (Wiron99 and cobalt-chromium alloy (Wirobond C were made each. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Analysis Energy Dispersive X-ray (EDX (Oxford Instruments and Scanning Electon Microscop (SEM analysis (JEOL were used to determine thickness of metal-ceramic interface together with PC Software for quantification of visual information's (KVI POPOVAC. Results. Results of this research introduced significant differences between thickness of metal-ceramic interface in every examined recycle generation. Recasting had negative effect on thickness of metal-ceramic interface of the examined alloys. This research showed almost linear reduction of elastic modulus up to the 12th generation of recycling. Conclusion. Recasting of nickel-chromium and cobaltchromium alloys is not recommended because of reduced thickness of metal-ceramic interface of these alloys. Instead of recycling, the alloy residues should be returned to the manufacturers.

  6. Bioadsorption and bioaccumulation of chromium trivalent in Cr(III)-tolerant microalgae: a mechanisms for chromium resistance.

    Science.gov (United States)

    Pereira, M; Bartolomé, M C; Sánchez-Fortún, S

    2013-10-01

    Anthropogenic activity constantly releases heavy metals into the environment. The heavy metal chromium has a wide industrial use and exists in two stable oxidation states: trivalent and hexavalent. While hexavalent chromium uptake in plant cells has been reported that an active process by carrying essential anions, the cation Cr(III) appears to be taken up inactively. Dictyosphaerium chlorelloides (Dc1M), an unicellular green alga is a well-studied cell biological model organism. The present study was carried out to investigate the toxic effect of chromium exposures on wild-type Cr(III)-sensitive (Dc1M(wt)) and Cr(III)-tolerant (Dc1M(Cr(III)R30)) strains of these green algae, and to determine the potential mechanism of chromium resistance. Using cell growth as endpoint to determine Cr(III)-sensitivity, the IC₅₀(₇₂) values obtained show significant differences of sensitivity between wild type and Cr(III)-tolerant cells. Scanning electron microscopy (SEM) showed significant morphological differences between both strains, such as decrease in cell size or reducing the coefficient of form; and transmission electron microscopy (TEM) revealed ultrastructural changes such as increased vacuolization and cell wall thickening in the Cr(III)-tolerant strain with respect to the wild-type strain. Energy dispersive X-ray analysis (SEM/XEDS) revealed that Cr(III)-tolerant D. chlorelloides cells are able to accumulate considerable amounts of chromium distributed in cell wall (bioadsorption) as well as in cytoplasm, vacuoles, and chloroplast (bio-accumulation). Morphological changes of Cr(III)-tolerant D. chlorelloides cells and the presence of these electron-dense bodies in their cell structures can be understood as a Cr(III) detoxification mechanism. PMID:23810518

  7. 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

  8. 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

  9. 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

  10. Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys

    Institute of Scientific and Technical Information of China (English)

    Bo Chen; Gang Xia; Xin-Ming Cao; Jue Wang; Bi-Yao Xu; Pu Huang; Yue Chen; Qing-Wu Jiang

    2013-01-01

    This paper aims to investigate if the dental restoration of nickel-chromium based alloy (Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of 〈 1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of 〈1, 1 to 〈3 and 3 to 〈6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

  11. A computational investigation of boron-doped chromium and chromium clusters by density functional theory

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The geometries,stabilities and electronic properties of Crn and CrnB(n=2-9) clusters have been systematically investigated by density functional theory.The results suggest that the lowest energy structures for CrnB clusters can be obtained by substituting one Cr atom in Crn+1 clusters with B atom.The geometries of CrnB clusters are similar to that of Crn+1 clusters except for local structural distortion.The second-order difference and fragmentation energy show Cr4,Cr6,Cr8,Cr3B,Cr5B and Cr8B cluster are the most stable among these studied clusters.The impurity B increases the stabilities of chromium cluster.When B is doped on the Crn clusters,cluster geometry does dominate positive role in enhancing their stability.The doped B atom does not change the coupling way of the Cr site in Crn clusters,but breaks the symmetry and the Cr atoms are no longer equivalent.The doped B atom increases the total magnetic moments of Crn in most cases.

  12. A metastable chromium carbide powder obtained by carburization of a metastable chromium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Loubiere, S. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Laurent, C. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Bonino, J.P. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Rousset, A. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique

    1996-10-15

    A metastable Cr{sub 3}C{sub 2-x} carbide powder is prepared by carburization of a metastable chromium oxide in H{sub 2}-CH{sub 4} atmosphere under the appropriate conditions (temperature, dwell time and CH{sub 4} content). A very high specific surface area (greater than 210 m{sup 2} g{sup -1}) of the starting oxide is necessary to avoid the formation of the sole stable Cr{sub 3}C{sub 2} phase. The transformation from the stable Cr{sub 3}C{sub 2} to the metastable Cr{sub 3}C{sub 2-x} is observed for the first time. The driving force could be an epitaxial effect between Cr{sub 3}C{sub 2-x} and the surrounding graphite layer. This is consistent with the observation that the formation of graphite layers by CH{sub 4} cracking is easier in the Cr{sub 3}C{sub 2-x}-containing powders. (orig.)

  13. 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

  14. Hexavalent chromium removal and bioelectricity generation by Ochrobactrum sp. YC211 under different oxygen conditions.

    Science.gov (United States)

    Chen, Chih-Yu; Cheng, Chiu-Yu; Chen, Ching-Kuo; Hsieh, Min-Chi; Lin, Ssu-Ting; Ho, Kuo-Ying; Li, Jo-Wei; Lin, Chia-Pei; Chung, Ying-Chien

    2016-01-01

    Bioremediation is an environmentally friendly method of reducing heavy metal concentration and toxicity. A chromium-reducing bacterial strain, isolated from the vicinity of an electroplate factory, was identified as Ochrobactrum sp. YC211. The efficiency and capacity per time of Ochrobactrum sp. YC211 for hexavalent chromium (Cr(VI)) removal under anaerobic conditions were superior to those under aerobic conditions. An acceptable removal efficiency (96.5 ± 0.6%) corresponding to 30.2 ± 0.8 mg-Cr (g-dry cell weight-h)(-1) was achieved by Ochrobactrum sp. YC211 at 300 mg L(-1) Cr(VI). A temperature of 30°C and pH 7 were the optimal parameters for Cr(VI) removal. By examining reactivated cells, permeabilized cells, and cell-free extract, we determined that Cr(VI) removal by Ochrobactrum sp. YC211 under anaerobic conditions mainly occurred in the soluble fraction of the cell and can be regarded as an enzymatic reaction. The results also indicated that an Ochrobactrum sp. YC211 microbial fuel cell (MFC) with an anaerobic anode was considerably superior to that with an aerobic anode in bioelectricity generation and Cr(VI) removal. The maximum power density and Cr(VI) removal efficiency of the MFC were 445 ± 3.2 mW m(-2) and 97.2 ± 0.3%, respectively. Additionally, the effects of coexisting ions (Cu(2+), Zn(2+), Ni(2+), SO4(2-), and Cl(-)) in the anolyte on the MFC performance and Cr(VI) removal were nonsignificant (P > 0.05). To our knowledge, this is the first report to compare Cr(VI) removal by different cells and MFC types under aerobic and anaerobic conditions. PMID:26889692

  15. Chromium uptake by Saccharomyces cerevisiae and isolation of glucose tolerance factor from yeast biomass

    Indian Academy of Sciences (India)

    Vlatka Gulan Zetic; Vesna Stehlik-Tomas; Slobodan Grba; Lavoslav Lutilsky; Damir Kozlek

    2001-06-01

    Fermentations with yeast Saccharomyces cerevisiae in semiaerobic and in static conditions with the addition of chromic chloride into the used molasses medium were analysed. It was proved that the addition of optimal amounts of CrCl3 into the basal medium enhanced the kinetics of alcohol fermentations. The addition of 200 mg/l CrCl3 into the medium stimulated both the yeast growth and the ethanol production in all experimental conditions. On the other hand, the results showed that Cr3+ ions were incorporated into yeast cells during fermentation. Under these conditions the accumulation of Cr3+ ions was performed by yeast cells during the exponential growth phase, and with enriched amounts of 30–45 g/gd.m. of cells. Yeast biomass enriched with chromium ions was extracted with 0.1 mol/l NH4OH assuming that the extracts had the glucose tolerance factor (GTF). Then the extracts were passed through a gel-filtration column in order to isolate and purify the GTF. The presence of GTF in the purified fractions was determined by measuring the absorbance at 260 nm. It is evident from the obtained results that the added purified fractions enhanced the rates of CO2 production as well as the glucose utilization during alcoholic fermentation. As expected, the enhancement of both rates depended on the amounts of extracts added to the fermentation substrate. Thus, it is evident that purified extracts contained the GTF compound, and that Cr3+ ions were bonded to the protein molecule.

  16. Thermal and Photochemical Reactions of NO2 on a Chromium (III) Oxide Surface

    Science.gov (United States)

    Nishino, N.; Finlayson-Pitts, B. J.

    2011-12-01

    Chromium oxide (Cr2O3) is a major component of the oxide layer on stainless steel surfaces. It is also widely used as pigment in paints and roofs and as a protective coating on various surfaces. While many studies have focused on the catalytic activity of Cr2O3 surfaces for selective catalytic reduction (SCR), less attention has been paid to its surface chemistry involving atmospherically important species such as NO2 under atmospheric conditions. In this study, we have investigated thermal and photochemical reactions of NO2 in the presence and the absence of water vapor, using a thin layer of Cr2O3 as a model for the surface of stainless steel as well as other similarly coated surfaces in the boundary layer. A 30 nm thick Cr2O3 film was deposited on a germanium attenuated total reflectance (ATR) crystal, and the changes in the surface species were monitored by Fourier Transform Infrared (FTIR) spectroscopy. Upon NO2 adsorption, nitrate (NO3-) ions appeared likely coordinated to Cr3+ ion(s). The NO3- peaks reversibly shifted when water vapor was added, suggesting that NO3- become solvated. Irradiation at 311 nm led to a decrease in NO3- ions under both dry and humid conditions. The major gas-phase species formed by the irradiation was NO under dry conditions, while NO2 was mainly formed in the presence of H2O. Possible mechanisms and the implications for heterogeneous NO2 chemistry in the boundary layer will be discussed. The results will also be compared to similar chemistry on other surfaces.

  17. A Study of the High Temperature on Chromium Carbide

    International Nuclear Information System (INIS)

    The oxidation rates of chromium carbide have been measured at 900 to 1300 .deg. C and oxygen pressures between 2x10-2 8 x 10-2 Pa using thermogravimetric analysis method. Oxidation behavior of chromium carbide appeared to change very sensitively with both temperature and oxygen pressure. In case with the oxygen pressure lower than 8 x 10-2 Pa, the weight gain in the specimen due to the formation of chromium oxide occurred linearly with time at the every temperature studied, but when the oxygen pressure was increased up to 8 x 10-2Pa, the weight gain behavior versus time showed entirely different tendency. That is, in the temperature range of 900 .deg. C to 1000 .deg. C weight gain occurred, however in the range of 1000 .deg. C to 1300 .deg. C weight lost was observed. The reason for the observed linear kinetics could be inferred as follows. As the oxidation of carbide proceeded carbon monoxide would build up at the interface of the chromium oxide and carbide. If the equilibrium pressure of carbon monoxide at the interface exceeds the gas pressure at the outer specimen surface, the oxide scale formed on it might be cracked exposing new carbide sites on which oxidation could occur successively. Through a thermodynamic consideration it was judged that the above deduction was reasonable. On the other hand, the weight lost mentioned above was explained that it could occur mainly due to the further oxidation of Cr2O3 to the volatile CrO3 at the corresponding experimental conditions. Weight loss phenomenon mentioned before which was observed in the oxidation of chromium carbide was also clearified by X-ray diffraction method and SEM. That is, at 900 .deg. C stable oxide of chromium, (Cr2O3) was identified easily on the specimen surface. However, at 1300 .deg. C, only a few amount of this stable oxide could be found on to specimen surface, indicating Cr2O3 had been evaporated to CrO3 gas

  18. Metal ion levels and lymphocyte counts

    DEFF Research Database (Denmark)

    Penny, Jeannette Ø; Varmarken, Jens-Erik; Ovesen, Ole;

    2013-01-01

    ) and investigated whether cobalt and chromium ions affected the lymphocyte counts. METHOD: In a randomized controlled trial, we followed 19 RHA patients and 19 THA patients. Lymphocyte subsets and chromium and cobalt ion concentrations were measured at baseline, at 8 weeks, at 6 months, and at 1 and 2 years...... of cobalt ions in particular on T-cells with 2-year whole-blood cobalt regression coefficients for CD3+ of -0.10 (95% CI: -0.16 to -0.04) × 10(9) cells/parts per billion (ppb), for CD3+CD4+ of -0.06 (-0.09 to -0.03) × 10(9) cells/ppb, and for CD3(+)CD8(+) of -0.02 (-0.03 to -0.00) × 10(9) cells....../ppb. INTERPRETATION: Circulating T-lymphocyte levels may decline after surgery, regardless of implant type. Metal ions-particularly cobalt-may have a general depressive effect on T- and B-lymphocyte levels. Registered with ClinicalTrials.gov under # NCT01113762....

  19. Toxic Effects of Lanthanum, Cerium, Chromium and Zinc on Potamogeton Malaianus

    Institute of Scientific and Technical Information of China (English)

    Wang Xue; Shi Guoxin; Xu Qinsong; Wang Chuntao

    2005-01-01

    The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and soluble protein increase to a certain degree and then decrease under La3+, Ce3+, Zn2+ stress, while there is a constantly dropping tendency under Cr6+ stress. The four ions have different effects on protective enzyme systems of Potamogeton malaianus. They can induce rises of the activities of catalase (CAT) and peroxides (POD) at lower concentration, however, with the increase of ions concentration, the activities decline. The change of SOD activity is exactly opposite to that of CAT and POD activity. It falls at first and rises later. An increasing tendency of MDA content appears with the increasing concentration. The toxicities of La3+, Zn2+, Ce3+ and Cr6+ become more serious in the order. The lethal concentration of Cr6+ to Potamogeton malaianus ranges from 0.5 to 1 mg·L-1, that of Ce3+ and Zn2+ ranges from 3 to 5 mg·L-1, and that of La3+ ranges from 7 to 10 mg·L-1. The toxic mechanism of La3+ and Ce3+ is similar to that of Cr6+ and Zn2+.

  20. Cadmium and chromium removal kinetics from solution by two aquatic macrophytes

    International Nuclear Information System (INIS)

    The aim of this work was to determine chromium and cadmium bioaccumulation processes of two free-floating macrophytes commonly used in wetlands for water treatment: Salvinia herzogii and Pistia stratiotes. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The most important processes of Cd uptake are biological ones in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes. The main processes of Cr uptake in both macrophytes are adsorption, chelation and ion exchange. The slow stage is different for each species and metal. Cr precipitation induced by roots occurs in P. stratiotes. Cr uptake through leaves is probably the main cause of the increase of Cr in the aerial parts of S. herzogii. - Cd uptake processes are biological processes in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes, whereas Cr uptake processes in both macrophytes are adsorption, chelation and ion exchange

  1. Finished leather waste chromium acid extraction and anaerobic biodegradation of the products.

    Science.gov (United States)

    Ferreira, Maria J; Almeida, Manuel F; Pinho, Sílvia C; Santos, Isabel C

    2010-06-01

    Due to the amounts of chromium in the leachate resulting from leather leaching tests, chromium sulfate tanned leather wastes are very often considered hazardous wastes. To overcome this problem, one option could be recovering the chromium and, consequently, lowering its content in the leather scrap. With this objective, chromium leather scrap was leached with sulfuric acid solutions at low temperature also aiming at maximizing chromium removal with minimum attack of the leather matrix. The effects of leather scrap dimension, sulfuric acid and sodium sulfate concentration in the solutions, as well as extraction time and temperature on chromium recovery were studied, and, additionally, organic matrix degradation was evaluated. The best conditions found for chromium recovery were leather scrap conditioning using 25mL of concentrated H(2)SO(4)/L solution at 293 or 313K during 3 or 6days. Under such conditions, 30-60+/-5% of chromium was recovered and as low as 3-6+/-1% of the leather total organic carbon (TOC) was dissolved. Using such treatment, the leather scrap area and volume are reduced and the residue is a more brittle material showing enhanced anaerobic biodegradability. Although good recovery results were achieved, due to the fact that the amount of chromium in eluate exceeded the threshold value this waste was still hazardous. Thus, it needs to be methodically washed in order to remove all the chromium de-linked from collagen.

  2. Investigation of the surface composition of electrodeposited black chromium by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Survilienė, S., E-mail: sveta@ktl.mii.lt; Češūnienė, A.; Jasulaitienė, V.; Jurevičiūtė, I.

    2015-01-01

    Highlights: • Black chromium electrodeposited from a Cr(III) bath is composed of oxide, hydroxide and metallic chromium. • Metallic phase is absent in black chromium electrodeposited from a Cr(III) + ZnO bath. • The near-surface layer is rich in hydroxides, whereas oxides of both metals predominate in the depth of the coatings. - Abstract: The paper reviews black chromium electrodeposited from a trivalent chromium bath containing ZnO as a second main component. The chemical compositions of the top layers of the black chromium coatings were studied by the X-ray photoelectron spectroscopy method. The surface of black chromium was found to be almost entirely covered with organic substances. To gain information on the state of each element in the deposit bulk, the layer-by-layer etching of the black chromium surface with argon gas was used. Analysis of XPS spectra has shown that the top layers of black chromium without zinc are composed of various Cr(III) components, organic substances and metallic Cr, whereas metallic Cr is almost absent in black chromium containing some amount of Zn(II) compounds. The ratios of metal/oxide phases were found to be 10/27 and 2/28 for black chromium without and with zinc, respectively. It has been determined that owing to the presence of ZnO in the Cr(III) bath, the percentage of metallic chromium is substantially reduced in black chromium which is quite important for good solar selective characteristics of the coating. The results confirm some of earlier observations and provide new information on the composition of the near-surface layers.

  3. Investigation of the surface composition of electrodeposited black chromium by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • Black chromium electrodeposited from a Cr(III) bath is composed of oxide, hydroxide and metallic chromium. • Metallic phase is absent in black chromium electrodeposited from a Cr(III) + ZnO bath. • The near-surface layer is rich in hydroxides, whereas oxides of both metals predominate in the depth of the coatings. - Abstract: The paper reviews black chromium electrodeposited from a trivalent chromium bath containing ZnO as a second main component. The chemical compositions of the top layers of the black chromium coatings were studied by the X-ray photoelectron spectroscopy method. The surface of black chromium was found to be almost entirely covered with organic substances. To gain information on the state of each element in the deposit bulk, the layer-by-layer etching of the black chromium surface with argon gas was used. Analysis of XPS spectra has shown that the top layers of black chromium without zinc are composed of various Cr(III) components, organic substances and metallic Cr, whereas metallic Cr is almost absent in black chromium containing some amount of Zn(II) compounds. The ratios of metal/oxide phases were found to be 10/27 and 2/28 for black chromium without and with zinc, respectively. It has been determined that owing to the presence of ZnO in the Cr(III) bath, the percentage of metallic chromium is substantially reduced in black chromium which is quite important for good solar selective characteristics of the coating. The results confirm some of earlier observations and provide new information on the composition of the near-surface layers

  4. Internal Friction In The PFN Ceramics With Chromium Dopand

    OpenAIRE

    Zachariasz R.; Bochenek D.; Bruś B.

    2015-01-01

    An aim of this work was to determine an influence of an admixture, the chromium (for x from 0.01 to 0.06), on the mechanical properties of the PFN ceramics. The ceramics with chemical composition Pb(Fe0.5−xCrxNb0.5)O3 was synthesized in two steps from simple oxides PbO, Fe2O3, Nb2O5, Cr2O3. The first stage was based on obtaining the FeNbO4 from the Fe2O3 and Nb2O5 simple oxides. At this stage an admixture in a form the Cr2O3 chromium oxide was added to the solution. In the second stage the Pb...

  5. Hexavalent chromium effects on carbon assimilation in Selenastrum capricornutum

    International Nuclear Information System (INIS)

    One of the difficulties in assessing toxic substances such as metals and complex organic compounds is the duration of the necessary tests. It would be beneficial to have available standardized tests of short duration that would allow a reduction in necessary manpower and overall cost as well as provide a method to evaluate chemicals that are readily degraded (i.e., within a few hours). One method available is the short-term photosynthesis response of algae to a given toxicant. Photosynthesis is not only a critical physiological response but is also one for which standard, accurate methods are available. The 14C method has been used to study the effects of chromium on algae. More recently, it was proposed that the 14C method be used to measure short-term photosynthetic response as a standard algal bioassay. The present study was designed to further evaluate, via photosynthetic response, the potential effects of hexavalent chromium on Selenastrum capricornutum

  6. A mathematical model for the iron/chromium redox battery

    Science.gov (United States)

    Fedkiw, P. S.; Watts, R. W.

    1984-01-01

    A mathematical model has been developed to describe the isothermal operation of a single anode-separator-cathode unit cell in a redox-flow battery and has been applied to the NASA iron/chromium system. The model, based on porous electrode theory, incorporates redox kinetics, mass transfer, and ohmic effects as well as the parasitic hydrogen reaction which occurs in the chromium electrode. A numerical parameter study was carried out to predict cell performance to aid in the rational design, scale-up, and operation of the flow battery. The calculations demonstrate: (1) an optimum electrode thickness and electrolyte flow rate exist; (2) the amount of hydrogen evolved and, hence, cycle faradaic efficiency, can be affected by cell geometry, flow rate, and charging procedure; (3) countercurrent flow results in enhanced cell performance over cocurrent flow; and (4) elevated temperature operation enhances cell performance.

  7. Low energy magnetic fluctuations in the TSDW phase of chromium

    Energy Technology Data Exchange (ETDEWEB)

    Azuah, R.T. [Hahn-Meitner Inst., Berlin (Germany); Kulda, J. [Inst. Laue Langevin, Grenoble (France); Pynn, R. [Los Alamos National Lab., NM (United States); Stirling, W.G. [Univ. of Liverpool (United Kingdom). Dept. of Physics

    1997-12-01

    A polarized neutron study of chromium carried out in a field of 6T applied to a single-domain single-Q crystal indicates that the inelastic intensity observed close to the transverse spin density wave (TSDW) satellite positions (1 {+-} {delta}, 0,0) does not behave as expected for spin-wave scattering. In particular, the signal corresponds to magnetization fluctuations of almost equal magnitude both parallel and perpendicular to the ordered moments in the TSDW phase.

  8. Study of Chromium Oxide Activities in EAF Slags

    Science.gov (United States)

    Yan, Baijun; Li, Fan; Wang, Hui; Sichen, Du

    2016-02-01

    The activity coefficients of chromium in Cu-Cr melts were determined by equilibrating liquid copper with solid Cr2O3 in CO-CO2 atmosphere. The temperature dependence of the activity coefficients of chromium in Cu-Cr melts could be expressed as lg γ_{Cr}(s)^{0} = { 3 2 5 9( ± 1 8 6} )/T - 0. 5 9( { ± 0. 1} ). Based on the above results, the activities of bivalent and trivalent chromium oxide in some slags at 1873 K (1600 °C) were measured. The slags were equilibrated with Cu-Cr melts under two oxygen partial pressures ( {p_{O}_{ 2} }} } = 6.9 × 10-4 and 1.8 × 10-6 Pa, respectively). The morphology of the quenched slags and the solubility of chromium oxide in the melts were investigated by EPMA, SEM, and XRD. Under both oxygen partial pressures, the slags were saturated by the solid solution MgAl2- x Cr x O4- δ . At the low oxygen partial pressure (1.8 × 10-6 Pa), the content of Cr in the liquid phase varied from 0.4 to 1.6 mass pct with the total Cr content in the slags increasing from 1.3 to 10.8 mass pct. At the high oxygen partial pressure (6.9 × 10-4 Pa), the content of Cr in the liquid phase decreased to the level of 0.2 to 0.6 mass pct. Both the activities of CrO and Cr2O3 in slag were found to increase approximately linearly with the increase of the total Cr content in slag. While the oxygen partial pressure had minor effect on the activity of Cr2O3 in the slag, it had significant effect on the activity of CrO.

  9. Fretting damage of high carbon chromium bearing steel

    OpenAIRE

    Kuno, Masato

    1988-01-01

    This thesis consists of four sections, the fretting wear properties of high carbon chromium bearing steel; the effect of debris during fretting wear; an introduction of a new fretting wear test apparatus used in this study; and the effects of fretting damage parameters on rolling bearings. The tests were operated under unlubricated conditions. Using a crossed cylinder contact arrangement, the tests were carried out with the normal load of 3N, slip amplitude of 50µm, and frequency of 30Hz ...

  10. Chromium propionate enhances adipogenic differentiation of bovine intramuscular adipocytes

    OpenAIRE

    Rebecca eTokach; Flavio eRibeiro; Ki Yong eChung; Whitney eRounds; Johnson, Bradley J.

    2015-01-01

    In vitro experiments were performed to determine the effects of increasing concentrations of chromium propionate on mRNA and protein abundance of different enzymes and receptors. Intramuscular and subcutaneous preadipocytes and bovine satellite cells were isolated from the longissimus muscle to determine the effect of treatment on glucose transporter type 4 (GLUT4) and peroxisome proliferator-activated receptor γ mRNA and GLUT4 protein abundance. Preadipocyte cultures were treated with diffe...

  11. Chromium Propionate Enhances Adipogenic Differentiation of Bovine Intramuscular Adipocytes

    OpenAIRE

    Tokach, Rebecca J.; Ribeiro, Flavio R. B.; Chung, Ki Yong; Rounds, Whitney; Johnson, Bradley J.

    2015-01-01

    In vitro experiments were performed to determine the effects of increasing concentrations of chromium propionate (CrPro) on mRNA and protein abundance of different enzymes and receptors. Intramuscular (IM) and subcutaneous (SC) preadipocytes and bovine satellite cells were isolated from the longissimus muscle to determine the effect of treatment on glucose transporter type 4 (GLUT4) and peroxisome proliferator-activated receptor γ mRNA and GLUT4 protein abundance. Preadipocyte cultures were t...

  12. Recovery of Chromium from Waste Taning Liquors by Magnesium Oxide

    Directory of Open Access Journals (Sweden)

    Mahmood M. Barbooti

    2010-10-01

    Full Text Available This is a case study of AL-Za’afaraniya tanning factory, 15 km to the south of Baghdad, to spot light on simple chemical treatment of the discharged water to solve the environmental problems associated with its chromium content management. The treatment was extended to the recovery and reuse of chromium. Chromium was precipitated by the addition of magnesium oxide which also aid as a neutralizer for the acidic effluent. The laboratory treatment was carried out to find the optimum conditions. The wastewater samples were taken from the outline area of the tannery. Box-Wilson method was adopted to find useful relationships between the operating variables (temperature, mixing period and magnesium oxide dose and the pH and chromium content of effluent. The experimental data were successfully fitted to second order polynomial mathematical models for the treatment. The most favorable operating conditions for the treatment were: temperature, 30 ºC; mixing period, 50 min and magnesium oxide concentration, 3000 mg/L. On using the optimum conditions a mathematical model simulating the operation for the treatment was obtained as follows:Cr = 6.0848 – 0.001839 X11 – 0.105334 X12 – 0.041038 X13pH = 10.29086 – 0.001223 X11 – 0.140043 X12 – 0.00953 X13Experimentally Cr concentration was decreased to about (0.5 mg/L in wastewater after raising the pH value to (7.35 by adding magnesium oxide.

  13. Soils contaminated with hexavalent chromium : sorption, migration and remediation

    OpenAIRE

    Fonseca, Bruna

    2011-01-01

    The interest in environmental soil science has been growing in the last years due to the continuous degradation of this major natural resource. In this work, a representative sample of a typical loamy sand soil was collected in Porto, Portugal, in a zone of intensive agriculture activity. This soil was used for a series of tests concerning the adsorption, transport and fate of hexavalent chromium. The adsorption equilibrium and sorption kinetics were evaluated through the fitting of several m...

  14. Bioleaching of hexavalent chromium from soils using acidithiobacillus thiooxidans

    OpenAIRE

    Fonseca, Bruna; Rodrigues, Joana; Queiroz, A.M.; Tavares, Teresa

    2010-01-01

    The continuous and growing degradation of the environment, due to several anthropogenic activities, is a main concern of the scientific community. Consequently, the development of low cost techniques to clean air, water and soils are under intense investigation. In this study, the focused problem is the soil contamination by hexavalent chromium, which is known for its several industrial applications - production of stainless steel, textile dyes, wood preservation and leather tanning - its hig...

  15. 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 ...

  16. Innovative soil treatment process design for removal of trivalent chromium

    Energy Technology Data Exchange (ETDEWEB)

    Stallings, J.H. [Air Force, Wright-Patterson AFB, OH (United States). Aeronautical Systems Center; Durkin, M.E. [Hughes Missile Systems Co., Tucson, AZ (United States)

    1997-12-31

    A soil treatment process has been developed as part of a US Air Force environmental compliance project at Air Force Plant 44, Tucson, AZ for treating soil contaminated with heavy metals including trivalent chromium, cadmium, copper, and nickel. The process was designed to treat a total of 133,000 tons of soil in a 400 ton per day facility. Features of the soil treatment process include physical treatment and separation, and a chemical treatment process of the remaining fines using a hypochlorite leach allowing chromium to be solubilized at a high pH. After treating, fines are washed in three stage countercurrent thickeners and chromium hydroxide cake is recovered as a final produce from the leach solution. Treatability studies were conducted, laboratory and a pilot plant was built. Process design criteria and flow sheet, material balances, as well as preliminary equipment selection and sizing for the facility have been completed. Facility was designed for the removal of Cr at a concentration of an average of 1230 mg/kg from the soil and meeting a risk based clean-closure limit of 400 mg/kg of Cr. Capital costs for the 400 tpd plant were estimated at 9.6 million with an operating and maintenance cost of $54 per ton As process is most economic for large quantities of soil with relatively low concentrations of contaminants, it was not used in final closure when the estimated volume of contaminated soil removed dropped to 65,000 tons and concentration of chromium increased up to 4000 mg/kg. However, the process could have application in situations where economics and location warrant.

  17. Fabrication and characterisation of uranium, molybdenum, chromium, niobium and aluminium

    International Nuclear Information System (INIS)

    This paper describes fabrication of binary uranium alloys by melting and casting. The following alloys with nominal composition were obtained by melting in the vacuum furnace: uranium with niobium contents from 0.5%- 4.0% and uranium with molybdenum contents from 0.4% - 1.2%. Uranium alloys with chromium content from 0.4% - 1.2% and uranium alloy with 0.12% of aluminium were obtained by vacuum induction furnace (electric arc melting)

  18. Intragranular Chromium Nitride Precipitates in Duplex and Superduplex Stainless Steel

    OpenAIRE

    Iversen, Torunn Hjulstad

    2012-01-01

    Intragranular chromium nitrides is a phenomenon with detrimental effects on material properties in superduplex stainless steels which have not received much attention. Precipitation of nitrides occurs when the ferritic phase becomes supersaturated with nitrogen and there is insufficient time during cooling for diffusion of nitrogen into austenite. Heat treatment was carried out at between 1060◦C and 1160◦C to study the materials susceptibility to nitride precipitation with...

  19. Evidence of weak ferromagnetism in chromium(III) oxide particles

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez-Vazquez, Carlos E-mail: qfmatcvv@usc.es; Banobre-Lopez, Manuel; Lopez-Quintela, M.A.; Hueso, L.E.; Rivas, J

    2004-05-01

    The low temperature (4chromium(III) oxide particles have been studied. A clear evidence of the presence of weak ferromagnetism is observed below 250 K. The magnetisation curves as a function of the applied field show coercive fields due to the canted antiferromagnetism of the particles. Around 55 K a maximum is observed in the zero-field-cooled curves; this maximum can be assumed as a blocking temperature, similarly to ultrafine ferromagnetic particles.

  20. Chronic Maternal Dietary Chromium Restriction Modulates Visceral Adiposity

    OpenAIRE

    Padmavathi, Inagadapa J.N.; Rao, K Rajender; Venu, Lagishetty; Ganeshan, Manisha; Kumar, K. Anand; Rao, Ch. Narasima; Harishankar, Nemani; Ismail, Ayesha; Raghunath, Manchala

    2009-01-01

    OBJECTIVE We demonstrated previously that chronic maternal micronutrient restriction altered the body composition in rat offspring and may predispose offspring to adult-onset diseases. Chromium (Cr) regulates glucose and fat metabolism. The objective of this study is to determine the long-term effects of maternal Cr restriction on adipose tissue development and function in a rat model. RESEARCH DESIGN AND METHODS Female weanling WNIN rats received, ad libitum, a control diet or the same with ...

  1. Chromium and manganese interactions in streptozocin-diabetic rats

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.L.; Jarrett, C.R.; Adeleye, B.O.; Stoecker, B.J. (Oklahoma State Univ., Stillwater (United States))

    1991-03-15

    Weanling male rats were fed casein-based diets low in chromium and manganese ({minus}Cr-MN) or supplemented with 1 ppm chromium as chromium chloride (+Cr) and/or 55 ppm manganese as manganous carbonate in a factorial design. After 7 weeks on the experimental diets, half of the rats in each group were injected on 2 consecutive days with 55 mg/kg streptozocin (STZ) in citrate buffer pH 4. Four weeks after injection, serum glucose in the diabetic group supplement with both Cr and Mn was not different from non-diabetic animals; however, diabetic animals in {minus}Cr groups or in the +Cr-Mn group had significantly elevated serum glucose. Serum insulin was reduced by STZ. A significant interaction between Mn and diabetes affected serum cortisol concentrations. More new tissue was formed on a polyvinyl sponge inserted under the skin in +Mn animals. In this study, the STZ animals were more sensitive than the control animals to dietary Cr and Mn concentrations.

  2. Magnesium, zinc, and chromium nutriture and physical activity.

    Science.gov (United States)

    Lukaski, H C

    2000-08-01

    Magnesium, zinc, and chromium are mineral elements required in modest amounts to maintain health and optimal physiologic function. For physically active persons, adequate amounts of these micronutrients are needed in the diet to ensure the capacity for increased energy expenditure and work performance. Most physically active individuals consume diets that provide amounts of magnesium and zinc sufficient to meet population standards. Women tend to consume less of these minerals than is recommended, in part because they eat less food than men. Inadequate intakes of magnesium and zinc have been reported for participants in activities requiring restriction of body weight. Dietary chromium is difficult to estimate because of a lack of appropriate reference databases. Acute, intense activity results in short-term increases in both urine and sweat losses of minerals that apparently diminish during recovery in the days after exercise. Supplemental magnesium and zinc apparently improve strength and muscle metabolism. However, evidence is lacking as to whether these observations relate to impaired nutritional status or a pharmacologic effect. Chromium supplementation of young men and women does not promote muscle accretion, fat loss, or gains in strength. Physically active individuals with concerns about meeting guidelines for nutrient intake should be counseled to select and consume foods with high nutrient densities rather than to rely on nutritional supplements. The indiscriminate use of mineral supplements can adversely affect physiologic function and impair health.

  3. Structure and growth of oxide on iron-chromium alloys

    International Nuclear Information System (INIS)

    Several oxides form during the initial stages of oxidation of iron-chromium alloys at 400 to 6000C in CO2-1%CO gas. The nature of the oxidation product depends upon crystallographic orientation and composition of the substrate, and can be explained by considering the maximum solubility of chromium in different oxide phases together with interfacial and strain energy factors. Kinetics of oxidation together with micrographic observations indicate that, as oxidation proceeds spinel oxide M3O4 nucleates at sites on the substrate surface associated with asperities. The spinel nuclei grow laterally and vertically until they coalesce and the scale subsequently thickens according to a parabolic rate law. The duplex structure of scales is interpreted in terms of an outward diffusion of cations together with simultaneous growth of an inner layer in the space created by this outward movement. Scale porosity provides a route for gas-phase transport of oxidant to support the growth of the inner layer. Regularly spaced lamellar voids which may form in the inner layer are believed to be associated with a cyclic vacancy condensation process. Enrichment of the inner layer in chromium is explained by analysis of the possible diffusion path networks in close-packed oxides. Some comments are made concerning possible practical applications of these data. (author)

  4. Study on anaerobic treatment of wastewater containing hexavalent chromium.

    Science.gov (United States)

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-06-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and COD(Cr) of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms.

  5. Study on anaerobic treatment of wastewater containing hexavalent chromium*

    Science.gov (United States)

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms. PMID:15909347

  6. Study on anaerobic treatment of wastewater containing hexavalent chromium

    Institute of Scientific and Technical Information of China (English)

    XU Yan-bin; XIAO Hua-hua; SUN Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr ofwastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L,the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms.

  7. Response of soil catalase activity to chromium contamination

    Institute of Scientific and Technical Information of China (English)

    Zofia St(e)pniewska; Agnieszka Woli(n)ska; Joanna Ziomek

    2009-01-01

    The impact of chromium (III) and (VI) forms on soil catalase activity is presented.The Orthic Podzol, Haplic Phaeozem and Mollic Gleysol from different depths were used in the experiment.The soil samples were amended with solution of Cr(III) using CrCl3, and with Cr(VI) using K2Cr2O7 in the concentration range from 0 to 20 mg/kg, whereas the samples without the addition of chromium served as control.Catalase activity was assayed by one of the commonly used spectrophotometric methods.As it is demonstrated in the experiment, both Cr(III) and Cr(VI) forms have ability to reduce soil catalase activity.A chromium dose of 20 mg/kg caused the inhibition of catalase activity and the corresponding contamination levels ranged from 75% to 92% for Cr(III) and 68% to 76% for Cr(VI), with relation to the control.Catalase activity reached maximum in the soil material from surface layers (0-25 cm), typically characterized by the highest content of organic matter creating favorable conditions for microorganisms.

  8. Eolian transport of geogenic hexavalent chromium to ground water

    Science.gov (United States)

    Wood, W.W.; Clark, D.; Imes, J.L.; Councell, T.B.

    2010-01-01

    A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr+6) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 μg/L Cr+6) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr+3 in the minerals is oxidized to Cr+6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr+6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr+6 concentration in the aquifer.

  9. Bioremediation of hexavalent chromium by a cyanobacterial mat

    Science.gov (United States)

    Shukla, Dhara; Vankar, Padma S.; Srivastava, Sarvesh Kumar

    2012-12-01

    The study comprises the use of cyanobacterial mat (collected from tannery effluent site) to remove hexavalent chromium. This mat was consortium of cyanobacteria/blue-green algae such as Chlorella sp., Phormidium sp. and Oscillatoria sp. The adsorption experiments were carried out in batches using chromium concentrations 2-10, 15-30 and 300 ppm at pH 5.5-6.2. The adsorption started within 15 min; however, 96 % reduction in metal concentration was observed within 210 min. The adsorption phenomenon was confirmed by Fourier transform-infrared spectroscopy and energy dispersive X-ray analysis. This biosorption fitted Freundlich adsorption isotherm very well. It was observed that the best adsorption was at 4 ppm, and at 25 ppm in the chosen concentration ranges. Scanning electron micrograph showed the physiology of mat, indicating sites for metal uptake. The main focus was collection of the cyanobacterial mat from local environments and its chromium removal potential at pH 5.5-6.2.

  10. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    Science.gov (United States)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  11. The chromium site in doped glassy lithium tetraborate

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, T.D. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Echeverria, E.; Beniwal, Sumit [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States); Adamiv, V.T.; Burak, Ya. V.; Enders, Axel [Institute of Physical Optics, 23 Dragomanov Street, Lviv 79005 (Ukraine); Petrosky, J.C.; McClory, J.W. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Dowben, P.A., E-mail: pdowben1@unl.edu [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States)

    2014-10-15

    Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we find that Cr substitutes primarily in the Li{sup +} site as a dopant in lithium tetraborate Li{sub 2}B{sub 4}O{sub 7} glasses, in this case 98.4Li{sub 2}B{sub 4}O{sub 7}–1.6Cr{sub 2}O{sub 3} or nominally Li{sub 1.98}Cr{sub 0.025}B{sub 4}O{sub 7}. This strong preference for a single site is nonetheless accompanied by site distortions and some site disorder, helping explain the optical properties of chromium doped Li{sub 2}B{sub 4}O{sub 7} glasses. The resulting O coordination shell has a contraction of the Cr–O bond lengths as compared to the Li–O bond lengths. There is also an increase in the O coordination number. - Graphical abstract: Lithium tetraborate: labeled are the B1 and B2 sites, where the latter correspond to BO{sub 3} and BO{sub 4} structures respectively. - Highlights: • Adoption of the Li + site for chromium dopants in lithium tetraborate identified. • Increased oxygen coordination for glass over the crystalline lithium tetraborate. • Distortions about the doping chromium characterized. • Local bond order is preserved in spite of the glassy nature.

  12. Preparation of Silica Modified with 2-Mercaptoimidazole and its SorptionProperties of Chromium(III

    Directory of Open Access Journals (Sweden)

    Harry Budiman

    2009-01-01

    Full Text Available Modified silica gel was prepared to remove the heavy metal of chromium(III from water sample. Silica gel was used as supporting material and the 2-mercaptoimidazole was immobilized onto surface silica so that the silica would have selective properties to adsorb the heavy metal chromium(III through the formation of coordination compound between the 2-mercaptoimidazole and chromium(III. The characterization of modified silica gel was carried out by analyzing the Fourier Transform Infrared Spectrum of this material in order to ensure the immobilization of 2-mercaptoimidazole onto the surface. The effect of pH solution, initial concentration of chromium(III, and interaction time were investigated in batch mode to find the adsorption properties of chromium(III onto modified silica. The condition optimum of these parameters was applied to determine the removal percentage of chromium(III in water sample using the modified silica gel

  13. Biological monitoring of occupational exposure to different chromium compounds at various valency states

    Energy Technology Data Exchange (ETDEWEB)

    Mutti, A.; Pedroni, C.; Arfini, G.; Franchini, I.; Minoia, C.; Micoli, G.; Baldi, C.

    1984-01-01

    Chromium concentrations in the air were measured in seven different workroom environments, where exposure to water soluble hexavalent or trivalent compounds was expected. Urinary excretion of chromium was measured before and after the same arbitrarily chosen working day. End-of-shift urinary chromium and its increase above pre-exposure levels were closely related to the concentration of water soluble chromium (VI) in the air. The values corresponding to 50 micrograms m-3 in the air, which is the current threshold limit value in most countries, were 29.8 and 12.2 micrograms g-1 of creatinine, respectively. Urinary chromium in workers exposed to water insoluble chromates or to water soluble chromic (III) sulphate was definitely higher than that observed in subjects not occupationally exposed to chromium compounds, but it cannot be recommended as short-term exposure test for evaluation of the job-related hazard.

  14. Determination of Chromium(III) Picolinate Using High Performance Liquid Chromatography-Ultraviolet Spectrophotometry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Il; Woo, Dong Jin; Kang, Dae Kyung [EASY BIO System, Inc, Chonan (Korea, Republic of); Lee, Myung Hee [Pollin, Inc, Seoul (Korea, Republic of); Woo, Gun Jo [Korea Food and Drug Administration, Seoul (Korea, Republic of); Cha, Ki Won [Inha University, Incheon (Korea, Republic of)

    2003-10-15

    Cr-(pic){sub 3} has been widely used as food additives, drugs, and feed additives. Accordingly, its determination method should be established. In the present paper, we have studied the determination method of chromium(III) picolinate accurately using ESI-MS on-lined with HPLC. Chromium(III) picolinate in feed products was determined successfully. Chromium(III) is very well known as an essential mineral. It is suggested as a cofactor in the maintenance of both normal lipid and carbohydrate metabolism by assisting the action of insulin on a cell membrane. According to the National Research Council, the daily recommended intake of chromium(III) is 50-200 μg. Several organic chromium(III) complexes have been reported to have significantly higher absorption and tissue incorporation activity than inorganic salts such as chromium(III) chloride.

  15. Chemical composition and structural transformations of amorphous chromium coatings electrodeposited from Cr(III) electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Safonova, Olga V. [Swiss-Norwegian Beamlines at European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France); Vykhodtseva, Ludmila N. [Department of Electrochemistry, Faculty of Chemistry, Moscow State University, 119991 Moscow (Russian Federation); Polyakov, Nikolai A. [A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119991 Moscow (Russian Federation); Swarbrick, Janine C. [European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France); Sikora, Marcin [European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France); Department of Solid State Physics, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Av. Mickiewicza 30, 30-059 Krakow (Poland); Glatzel, Pieter [European Synchrotron Radiation Facility, 38043 Grenoble Cedex (France); Safonov, Viktor A., E-mail: safon@elch.chem.msu.r [Department of Electrochemistry, Faculty of Chemistry, Moscow State University, 119991 Moscow (Russian Federation)

    2010-12-15

    Amorphous chromium coatings were electrodeposited from Cr(III)-based solutions containing organic (HCOONa) or phosphorus-containing (NaH{sub 2}PO{sub 2}) additives. Their structure was studied by a combination of X-ray diffraction (XRD), valence-to-core X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) at the Cr K-edge. Metalloid atoms (C or P) incorporated in electroplates structure are chemically bonded to chromium (i.e. are located in the first coordination shell). Upon annealing at elevated temperatures in vacuum, these amorphous coatings crystallize into a mixture of phases containing metallic chromium and chromium carbides or chromium phosphides. Quantitative analysis of valence-to-core XES data demonstrates that the average local structure of chromium in the amorphous coatings does not change significantly during crystallization.

  16. Chromium related degradation of solid oxide fuel cells; Chrom-bezogene Degradation von Festoxid-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Anita

    2011-05-04

    Solid Oxide Fuel Cells (SOFCs) offer a high potential for application as an auxiliary power unit (APU) for heavy goods vehicles as well as combined heat and power (CHP) systems. SOFCs are especially attractive due to their high efficiencies and the use of different fuel types. However, optimization in terms of long term stability and costs are still necessary. This work characterized the degradation of SOFCs with lanthanum strontium manganite (LSM) cathodes under chromium influence. Galvanostatic cell tests were carried out at 800 C with operation times from 250 - 3000 h and variation of the chromium source and current density. The current densities of j = 0 (A)/(cm{sup 2}), j = 0,3 (A)/(cm{sup 2}) and j = 0,5 (A)/(cm{sup 2}) were applied. The high temperature ferritic alloy Crofer22APU was used as a chromium source. Variation of the chromium source was realized by coating the Crofer22APU insert with the chromium retention layer Mn{sub 3}O{sub 4} and the cathode contact layer LCC10. Cell degradation was analyzed with regard to cell voltage, current density and area specific resistance (ASR). Microstructural alterations of the cathode as well as chromium content and distribution across the cell were investigated after completion of the cell tests. For cells with a chromium source present and operation with a nonzero current density, the course of cell degradation was divided into three phases: a run-in, weak linear degradation and strong linear degradation. A decrease of the chromium release rate by means of different coatings stretched the course of degradation along the timescale. Strong degradation, which is characterized by a significant increase in ASR as well as a decrease of current density at the operating point, was only observed when a chromium source in the setup was comb ined with operation of the cell with a non-zero current density. Operation of the cell with a chromium source but no current density caused a degradation of current density at the

  17. USE OF TWO DIGESTION METHODS IN THE EVALUATION OF CHROMIUM CONTENT IN CATTLE'S MEAT SUPPLEMENTED WITH CHROMIUM CHELATES

    Directory of Open Access Journals (Sweden)

    R. L. T. de Andrade

    2015-06-01

    Full Text Available The present study aimed to analyze the chromium content in beef using two digestion methods. There were used samples from 24 18-month-old male cattle, and twelve of them were supplemented and twelve were not supplemented with chromium chelate. These samples were evaluated by atomic absorption spectroscopy, previously submitted to digestion method using nitric acid (65% with hydrogen peroxide (35% and to digestion method, using solution of nitric perchloric acid in the proportion 3:1. Immediately after the slaughter, the carcasses were sent to sanitary maturation. After 24 hours, samples between 12th and 13th rib in the muscle Longissimus Thoracis were taken. For evaluation, it was used completely randomized design (Die and analysis of variance (ANOVA at 5% of significance level. The results didn't evidenced any significant difference (p>0,05 between the (cromo content, regardless the supplementation. The same happened with the digestion methods used.

  18. Characteristics of Aerosols Containing Chromium and Nickel From Some Thermal Spraying Operations

    OpenAIRE

    Bohgard, Mats; Welinder, Hans; Akselsson, Roland

    1983-01-01

    Characterization of aerosols, emitted from five methods of thermal spraying with materials containing chromium and nickel were carried out. The characterization procedure includes the determinations of the metal content, the particle size distribution, the oxidation state of chromium and a measure of the solubility of chromium. Three different kinds of samplers and the analytical methods PIXE (Particle Induced X-ray Emission analysis), ESCA (Electron Spectroscopy for Chemical Analysis), AAS (...

  19. Optimization and Modeling of Hexavalent Chromium Removal from Aqueous Solution Via Adsorption on Multiwalled Carbon Nanotubes

    OpenAIRE

    Mina Gholipour; Hassan Hashemipour Rafsanjani; Ataollah Soltani Goharrizi

    2011-01-01

    Hexavalent chromium and its derivatives are potential pollutant due to their mortal affects. Therefore, It is essential to remove these components from wastewaters before disposal. Adsorption can be effective and versatile method for removing of hexavalent chromium. In this article, removal of hexavalent chromium via adsorption on multiwalled carbon nanotubes was investigated as a function of adsorbent dosage, initial solution pH, initial Cr(VI) concentrations, contact time and temperature. T...

  20. Enhancing phytoremediation of chromium-stressed soils through plant-growth-promoting bacteria

    OpenAIRE

    Munees Ahemad

    2015-01-01

    Chromium, specifically hexavalent chromium is one of the most toxic pollutants that are released into soils by various anthropogenic activities. It has numerous adverse effects not only on plant system but also on beneficial soil microorganisms which are the indicators of soil fertility and health. Recent emergence of phytoremediation as an environmental friendly and economical approach to decontaminate the chromium stressed soils has received wider attention. But major drawback of this proce...

  1. Removal of hexavalent chromium of contaminated soil by coupling electrokinetic remediation and permeable reactive biobarriers

    OpenAIRE

    Fonseca, Bruna; Pazos, M.; Tavares, M. T.; Sanromán, M. A.

    2012-01-01

    PURPOSE: In this study, a novel and ecological alternative have been developed to treat soils contaminated with hexavalent chromium coupling two well-known systems: electrokinetic remediation and permeable reactive biobarriers. The electric field promotes the electromigration of the hexavalent chromium oxyanions towards the anode. The biobarriers were placed before the anode electrode, in order to promote the reduction and retention of the chromium migrating in its direction. Thus, this t...

  2. Determination of Chromium Content in Human Skin by Means of Neutron Activation Analysis

    International Nuclear Information System (INIS)

    Chromium eczema is a well-known phenomenon in dermatological practice. Different explanations may be given for it. According to one of these the specific texture of the skin of patients is assumed to allow more chromium to pass through the upper layers. As a result, the chromium accumulates faster in the dermis of patients so that a critical value is reached sooner. Another explanation might be that die sensitivity threshold for chromium in patients is lower than in normal persons and can more easily be exceeded. To distinguish between these possibilities and to obtain more information, an investigation was started in which the chromium content in the skin was compared for eczema patients and normal people. The sample weight (10 mg) and the chromium content (0.2 - 0.4 ppm) involved require a sensitive technique. Neutron activation analysis is well suited to this purpose. Under our operation conditions (irradiation time 10 days, neutron flux 1014n/cm2s) it is possible to determine quantities as low as 5 x 10-11 g of chromium. Preliminary experiments show relatively large variations in chromium content of comparable samples, even in skin samples taken from the back of a single person. It is further suggested by the results of these experiments that the chromium content in the skin of eczema patients is lower than in that of normal patients. The results of the analysis may be seriously affected by chromium contamination during sample preparation. Therefore chromium-free instruments must be used. To avoid chromium migration in the skin due to degeneration processes, samples must be taken from persons alive or shortly after their death. (author)

  3. Potentiometric anion selectivity of polymer-membrane electrodes based on cobalt, chromium, and aluminum salens

    Energy Technology Data Exchange (ETDEWEB)

    Badr, Ibrahim H.A. [Department of Chemistry, Faculty of Science, Ain Shams University, P.O. Box 11566, Cairo (Egypt)]. E-mail: ibadr1@yahoo.com

    2006-06-16

    Metallo-salens of cobalt(II) (Co-Sal), chromium(III) (Cr-Sal), and aluminum(III) (Al-Sal) are used as the active ionophores within plasticized poly(vinyl chloride) membranes. It is shown that central metal-ion plays a critical role in directing the ionophore selectivity. Polymer-membrane electrodes based on Co-Sal, Cr-Sal, and Al-Sal are demonstrated to exhibit enhanced responses and selectivity toward nitrite/thiocyanate, thiocyanate, and fluoride anions, respectively. The improved anion selectivity of the three ionophore systems is shown to deviate significantly from the classical Hofmeister pattern that is based only on ion lipophilicity. For example, optimized membrane electrodes for nitrite ion based on Co-Sal exhibit logK{sub Nitrite,Anion}{sup pot} values of -5.22, -4.66, -4.48, -2.5 towards bromide, perchlorate, nitrate, and iodide anions, respectively. Optimized membrane electrodes based on Co-Sal and Cr-Sal show near-Nernstian responses towards nitrite (-57.9+/-0.9mV/decade) and thiocyanate (-56.9+/-0.8mV/decade), respectively, with fast response and recovery times. In contrast, Al-Sal based membrane electrodes respond to fluoride ion in a super-Nernstian (-70+/-3mV/decade) and nearly an irreversible mode. The operative response mechanism of Co-Sal, Cr-Sal, and Al-Sal membrane electrodes is examined using the effect of added ionic sites on the potentiometric response characteristics. It is demonstrated that addition of lipophilic anionic sites to membrane electrodes based on the utilized metallo-salens enhances the selectivity towards the primary ion, while addition of cationic sites resulted in Hofmeister selectivity patterns suggesting that the operative response mechanism is of the charged carrier type. Electron spin resonance (ESR) data indicates that Co(II) metal-ion center of Co-Sal ionophore undergoes oxidation to Co(III). This process leads to formation of a charged anion-carrier that is consistent with the response behavior obtained for Co

  4. 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).

  5. 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

  6. Chromium Isotopes in Marine Carbonates - an Indicator for Climatic Change?

    Science.gov (United States)

    Frei, R.; Gaucher, C.

    2010-12-01

    Chromium (Cr) stable isotopes experience an increased interest as a tracer of Cr (VI) reduction in groundwater and thus showed their potential as a monitor of remediation of anthropogenic and natural contamination in water (Berna et al., 2009; Izbicki et al., 2008). Chromium stable isotopes in Fe-rich chemical sediments (BIFs and Fe-cherts) have recently also been used as a tracer for Earth's atmospheric oxygenation through time (Frei et al., 2009). We have applied the Cr isotope system to organic-rich carbonates from a late Ediacaran succession in Uruguay (Polanco Formation), from which we have previously analyzed BIFs with extremely fractionated (δ53Cr up to 5.0 ‰) Cr isotope signatures that are part of an underlying deep water clastic sediment (shale-dominated) sequence (Yerbal Formation) deposited in a glacio-marine environment (Gaucher et al.,2004). δ53Cr values of organic rich carbonates correlate with positive and negative carbon isotope excursions (δ13C PDB between -3 and +3 ‰) and with systematic changes in strontium isotope compositions, commonly interpreted as to reflect fluctuations in organic (photosynthetic algae) production related to fluctuations in atmospheric oxygen and weathering intensities, respectively. Slightly positively fractioned δ53Cr values (up to +0.25‰), paralleling positive (δ13C PDB and 87Sr/86Sr ratio excursions would thereby trace elevated atmospheric oxygen levels/pulses possibly related to glacier retreat/melting stages that caused bioproductivity to increase. While the causal link between these multiple isotopic tracers and the mechanisms of Cr stripping into carbonates has to be further investigated in detail, the first indications from this study point to a potentially promising use of stable Cr isotopes in organic-rich carbonates to monitor fluctuations of atmospheric oxygen, particularly over the Neoproterozoic and Phanerozoic ice age periods. E.C. Berna et al. (2010) Cr stable isotopes as indicators of Cr

  7. Progress in the chemistry of chromium(V) doping agents used in polarized target materials

    Energy Technology Data Exchange (ETDEWEB)

    Krumpolc, M. (Illinois Univ., Chicago, IL (USA)); Hill, D. (Argonne National Lab., IL (USA)); Struhrmann, H.B. (Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany, F.R.). Hamburger Synchrotronstrahlungslabor)

    1990-01-01

    We wish to report progress in two areas of the chromium (V)-based doping agents: Two commonly used chromium (V) complexes, I and II, have been synthesized in perdeuterated form (i.e., all hydrogens replaced by deuterium). They are sodium bis(2-ethyl-2-deuteroxy-butyrato)oxochromate(V)monodeuterate, IV, (acronym EDBA-Cr(V)), and sodium bis(2-deuteroxy-2-methylpropionato)oxochromate(V), III, (acronym DMPA-Cr(V)). A synthetic route leading to the preparation of stable, chromium(III)-free solutions of chromium(V) in diols (1,2-ethanediol/ethylene glycol/and 1,2-propanediol/propylene glycol/) has been outlined.

  8. Determination of total chromium in tanned leather samples used in car industry.

    Science.gov (United States)

    Zeiner, Michaela; Rezić, Iva; Ujević, Darko; Steffan, Ilse

    2011-03-01

    Despite the high competition of synthetic fibers leather is nowadays still widely used for many applications. In order to ensure a sufficient stability of the skin matrix against many factors, such as microbial degradation, heat and sweat, a tanning process is indispensable. Using chromium (III) for this purpose offers a multitude of advantages, thus this way of tanning is widely applied. During the use of chromium tanned leather as clothing material as well as for decoration/covering purposes, chromium is extracted from the leather and may then cause nocuous effects to human skin, e.g. allergic reactions. Thus the knowledge of the total chromium content of leather samples expected to come into prolonged touch with human skin is very important. In car industry leather is used as cover for seats, steering wheel and gearshift lever The chromium contents often chromium tanned leather samples used in car industry were determined. First all samples were dried at 65 degrees C overnight and then cut in small pieces using a ceramic knife, weighed and analyzed by inductively coupled plasma--optical emission spectrometry (ICP-OES) after acidic microwave assisted digestion. The total chromium amounts found were in the range from 19 mg/g up to 32 mg/g. The extraction yield of chromium from leather samples in sweat is approximately 2-7%. Thus especially during long journeys in summer chromium can be extracted in amounts which may cause nocuous effects for example on the palm of the hands or on the back.

  9. 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 directly on the skin surface or it can be absorbed through the skin, especially if the skin surface is damaged. The prooxidative effects of chromium (VI) inhibit antioxidant enzymes and deplete intracellular glutathione in living systems and act as hematotoxic, immunotoxic, hepatotoxic, pulmonary toxic, and nephrotoxic agents. In this review, we particularly address the hexavalent chromium-induced generation of reactive oxygen species and increased lipid peroxidation in humans and animals, and the possible role of garlic (Allium sativum Linn) as a protective antioxidant. PMID:22865357

  10. Chromium recovery from exhausted baths generated in plating processes and its reuse in the tanning industry.

    Science.gov (United States)

    Torras, Josep; Buj, Irene; Rovira, Miquel; de Pablo, Joan

    2012-03-30

    Chromium plating used for functional purposes provides an extremely hard, wear and corrosion resistant layer by means of electrolytic deposition. Typical layer thicknesses range between 2.5 and 500 μm. Chromium electroplating baths contain high concentrations of Cr(VI) with chromium trioxide (CrO(3)) as the chromium source. When because of technical or economic reasons a bath gets exhausted, a waste containing mainly chromium as dichromate as well as other heavy metals is generated. Chromium may then be purified for use in other industrial processes with different requirements. In this work, a sustainable system for using galvanic wastes as reagents in the leather tanning industry, thus reducing quantity of wastes to be treated, is presented. Metal cations present in the chromium exhausted bath were precipitated with NaOH. Then, the solution containing mainly soluble Cr(VI) was separated. By means of sodium sulphite in acidic conditions, Cr(VI) was reduced to Cr(III) as chromium (III) sulphate. From chromium (III) sulphate a basic Cr(III) sulphate may be obtained, which is one of most used compounds in the tanning industry. Cr(III) concentration in the final solution allows its reuse without concentration, but with a slight dilution. PMID:22326242

  11. A search for luminescence of the trivalent manganese ion in solid aluminates

    NARCIS (Netherlands)

    Die, A. van; Leenaers, A.C.H.I.; Weg, W.F. van der; Blasse, G.

    1987-01-01

    As an alternative way of examining the prospects of the trivalent manganese ion as a luminescent centre in glasses, Al2O3:Mn, ZnAl2O4:Mn and LaAlO3:Mn were investigated by means of spectrofluorometry. The luminescent species identified were divalent and tetravalent manganese and impurities (chromium

  12. The development and characterization of ion exchange membranes for selected electrochemical power sources

    Science.gov (United States)

    Arnold, C., Jr.; Assink, R. A.

    The work is reviewed on the development and characterization of ion exchange membranes in an effort to improve the efficiency of three flowing electrolyte batteries. The batteries are: (1) NASA's iron chromium redox battery; (2) Lockheed's zinc ferricyanide battery; and (3) Johnson Control's zinc bromine battery. These batteries were developed for solar photovoltaic, utility load leveling, and electric vehicle applications, respectively.

  13. Biosorption of hexavalent chromium by raw and acid-treated green alga Oedogonium hatei from aqueous solutions

    International Nuclear Information System (INIS)

    The hexavalent chromium, Cr(VI), biosorption by raw and acid-treated Oedogonium hatei were studied from aqueous solutions. Batch experiments were conducted to determine the biosorption properties of the biomass. The optimum conditions of biosorption were found to be: a biomass dose of 0.8 g/L, contact time of 110 min, pH and temperature 2.0 and 318 K respectively. Both Langmuir and Freundlich isotherm equations could fit the equilibrium data. Under the optimal conditions, the biosorption capacities of the raw and acid-treated algae were 31 and 35.2 mg Cr(VI) per g of dry adsorbent, respectively. Thermodynamic parameters showed that the adsorption of Cr(VI) onto algal biomass was feasible, spontaneous and endothermic under studied conditions. The pseudo-first-order kinetic model adequately describe the kinetic data in comparison to second-order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle diffusion processes. The physical and chemical properties of the biosorbent were determined and the nature of biomass-metal ions interactions were evaluated by FTIR analysis, which showed the participation of -COOH, -OH and -NH2 groups in the biosorption process. Biosorbents could be regenerated using 0.1 M NaOH solution, with up to 75% recovery. Thus, the biomass used in this work proved to be effective materials for the treatment of chromium bearing aqueous solutions

  14. Sensitization of neodymium by chromium and cerium in La1-xNdxMgAl11O19 laser material

    International Nuclear Information System (INIS)

    Lanthanum-magnesium hexaaluminate LaMg Al11O19 (LNA) with magnetoplumbitelike structure is of considerable interest as a solid-state laser material. Compared to YAG:Nd it presents some advantages, among which are the particular emission wavelengths at 1.054 and 1.082μm tunable over 3.5 and 8.0μm respectively. The hexaaluminate matrix makes possible the substitution of large amounts of Al or Mg by transition metal ions without modifying the crystal growth abilities. This has prompted to investigate the possibilities of sensitizing the neodymium fluorescence in LNA. Such sensitization has led to a dramatic increase of the laser efficiency in the well-known garnet compound GSGG:Nd:Cr. In the lanthanum aluminate, chromium substitutes aluminum preferentially in a distorted octahedral site close to the lanthanide one. Detailed investigations of the Nd3+ fluorescence intensities in LNA and LNA:Cr as well as studies of the fluorescence decay profile of Cr3+ and Nd3+ in the double-doped hexaaluminates indicate that the chromium-neodymium energy transfer is highly efficient in this material

  15. Influence of Nano-Ceria Sol-Gel Coating on Oxidation Behavior of Chromium at 1 000℃

    Institute of Scientific and Technical Information of China (English)

    JIN Hui-ming; ZHOU Xiao-wei; ZHANG Lin-nan

    2009-01-01

    Isothermal oxidation behavior of chromium with and without nanon sol-gel CeO_2 coating is studied at 1 000 ℃ in air. Scanning electron microscopy (SEM)and transmission electron microscopy (TEM)are used to examine the sur-face morphology and mierostructure of the oxide films. It is found that ceria coating greatly improves the anti-oxida-tion property of chromium. Laser Raman spectrometer and X-ray diffraction spectrometer (XRD)are also used to study the stress level in oxide films formed on ceria-coated and ceria-free Cr. Secondary ion mass spectrometer (SIMS)is used to examine Cr, O and Ce element distribution in depth in oxide films. Results show that nano-ceria application greatly reduces the growth speed and grain size of Cr_2O_3 film, and this fine grained Cr_2O_3 film probably has better high temperature plasticity, i.e. , oxide film relieves part of the compressive stress by means of creeping. Meanwhile, CeO_2 changes the oxide film growth mechanism from predominant cation outward diffusion to anion in-ward diffusion. XRD and Raman testing results both show the stress declination effect due to nano-CeO_2 application, and their discrepancy in the rare earth effect is analyzed.

  16. Investigation of alternative phosphating treatments for nickel and hexavalent chromium elimination; Investigacao de tratamentos alternativos de fosfatizacao para eliminacao do niquel e cromo hexavalente

    Energy Technology Data Exchange (ETDEWEB)

    Jazbinsek, Luiz Antonio Rossi

    2014-07-01

    obtained with passivation treatment in niobium containing solution could be considered as a promising alternative to replace passivation with hexavalent chromium ions. Despite of the promising results, adjustments in the baths to obtain stability are still needed and should guide the next steps of the subject of this research. (author)

  17. Surface Reactions Limiting Chromium(VI) Generation from Naturally Derived Chromium(III) Minerals

    Science.gov (United States)

    Hausladen, D.; Fendorf, S. E.

    2015-12-01

    Chromium(III)-bearing minerals, commonly found in serpentinite and ultramaphic rocks, are ubiquitous in California soils and along convergent plate boundaries worldwide. Elevated concentrations of carcinogenic Cr(VI) have been measured in groundwater throughout the state, even in aquifers untouched by anthropogenic contamination. In most natural systems, manganese oxides are the only known, kinetically viable, oxidant of Cr(III). Numerous laboratory studies have demonstrated a finite capacity of Mn-oxides to generate Cr(VI) before surface alterations inhibit further Cr-oxidation. The extent to which these processes dictate the inhibition, and subsequent regeneration, of Mn-oxidation capacity within structured soils and sediments is not well understood. Here we use artificial soil aggregates made of Fe(III),Cr(III)-hydroxide-coated quartz sand and surrounded by aerated solute flow (pH 8, 30mM HEPES, 10mM HCO3-) to investigate C(VI) generation within ultramafic rock derived sediment and processes inhibiting manganese reactivity. We found that while Cr(VI)-production scaled with Cr-mineral solubility; Cr(VI) effluent concentrations from aggregates of both lower and higher solubility Cr(III)-minerals peaked very soon after reaction with birnessite (within 2 days and 4 days, respectively). Once Cr(VI) production plateaued (t=22 days) aggregate influent was acidified (pH 5, 30mM C2H3O2-). Despite increasing Cr(III) solubility at lower pH, aqueous Cr(VI) production further decreased. A secondary pulse of Cr(VI) generation was seen only after the surrounding solute returned to initial conditions (pH 8). As with the initial pulse, Cr(VI) concentration scaled with mineral solubility. Collectively, our results demonstrate the extent that natural fluctuations in groundwater composition, both as a result of irrigation or precipitation events, have the potential to both regenerate and inhibit Mn-oxide surfaces. These synthetic soil aggregates provide insight into how fluctuating

  18. A Comparative Study of Chromium and Cadmium Removal from Their Common Aqueous Solution by Batch Operation Using Tea Factory Waste as Adsorbent

    Directory of Open Access Journals (Sweden)

    Jibesh Datta

    2014-06-01

    Full Text Available The process of adsorption is a powerful tool for the treatment of industrial wastewater. In the recent years many studies have been conducted to evaluate the effectiveness of various locally available economical adsorbents for the removal of various heavy metals from the waste water. In the present study tea factory waste is used as adsorbent and its capacity to remove toxic heavy metals chromium and cadmium from their combined solution is investigated. Batch adsorption study is conducted to find the adsorption capacity of the adsorbent and the effect of the three important process parameters, i.e. agitation rate, adsorbent dose and initial metal ion concentration is evaluated. The maximum adsorption capacity of 24.88 mg/g and 23.92 mg/g is observed in case of cadmium and chromium respectively. It is also found that the removal efficiency of cadmium is higher than that of chromium in all cases. The experimental results are also found to be well fitted in the Langmuir and Freundlich Isotherm model.

  19. Ultrasound-assisted cloud point extraction for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in water samples

    Science.gov (United States)

    Hashemi, Mahdi; Daryanavard, Seyed Mosayeb

    Ultrasound-assisted cloud point extraction (UACPE) procedure was developed for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in environmental water samples. The method is based on the reduction of Cr(VI) by iodide in acidic media and subsequently formation of I3- anion. The I3- formed can further react with cetyltrimethylammonium bromide (CTAB) and induce its clouding due to formation of an ion-association complex. The formed complex was separated from solution and dissolved in ethanol for spectrophotometric measurement. Cerium(IV) ammonium sulphate was chosen as an oxidizing reagent for pre-oxidation step of Cr(III) to Cr(VI) species before the addition of iodide to the system, up to chromium in trivalent can be determined by the procedure. Experimental parameters for both spectrophotometric reaction and extraction procedure have been optimized. Under optimized conditions Cr(VI) can be determined in the range 20-400 ng mL-1 (R2 = 0.999). Detection limit, preconcentration factor and relative standard deviation were 12 ng mL-1, 20.0 and 2.2% (n = 5), respectively with 10 mL sample volumes. The proposed method has been successfully applied for determination of chromium(V) in spiked water, synthetic seawater and electroplating wastewater samples with average recoveries of 100.1, 99.4 and 99.1%, respectively.

  20. Microstructure and surface properties of chromium-doped diamond-like carbon thin films fabricated by high power pulsed magnetron sputtering

    International Nuclear Information System (INIS)

    High power pulsed magnetron sputtering (HPPMS) has attracted much interest due to the large plasma density and high ionization rate of sputtered materials. It is expected to produce a highly ionized C flux from a graphite target but unfortunately, the ionization rate of carbon is still very small and the discharge on a solid carbon target is unstable as well. In this work, a stable discharged chromium target is used in the preparation of chromium-doped diamond-like carbon (Cr-DLC) films in HPPMS in reactive C2H2 gas, but the unstable graphite. The chromium concentration in the Cr-DLC films is limited by surface poisoning due to reactive gas. Less than 2% of Cr is incorporated into the DLC films at C2H2 flow rate of 5 sccm or higher. However, as a result of the high ionization rate of the reactive gas in HPPMS, intense ion bombardment of the substrate is realized. The films show a smooth surface and a dense structure with a large sp3 concentration. As the C2H2 flow increase, the sp3 fraction increase and the sp3 to sp2 ratio increase to 0.75 at a C2H2 flow rate of 10 sccm. Compared to the substrate, the Cr-DLC films have lower friction and exhibit excellent corrosion resistance.

  1. Effect of Heavy Metal Chromium (Ⅵ) on Growth of Spirulina%重金属离子铬(Ⅵ)对螺旋藻生长的影响

    Institute of Scientific and Technical Information of China (English)

    张少斌; 穆杨; 刘慧; 史广胜

    2012-01-01

    研究了不同质量浓度的重金属离子铬(Ⅵ)对螺旋藻生长及其藻胆蛋白含量的影响.结果表明:铬(Ⅵ)在一定浓度范围内(<10 mg/L)能够提高螺旋藻藻胆蛋白的含量,对螺旋藻的生长具有促进作用.当铬(Ⅵ)浓度过高(>10 mg/L)时,螺旋藻藻胆蛋白含量下降,螺旋藻的生长受到较强抑制.%In this paper, the effect of heavy metal ion chromium (VI) with different mass concentrations on the growth and phy-cobiliprotein content of spirulina was studied. The results showed that chromium (VI) with proper concentration ( < 10 mg/L) could increase the content of phycobiliprotein in spirulina, and accelerate the growth of spirulina. The content of phycobiliprotein in spirulina decreased and the growth of spirulina was inhibited when the concentration of chromium (VI) was above 10 mg/L.

  2. Practical applications of ion beam and plasma processing for improving corrosion and wear protection

    CERN Document Server

    Klingenberg, M L; Wei, R; Demaret, J; Hirvonen, J

    2002-01-01

    A multi-year project for the US Army has been investigating the use of various ion beam and plasma-based surface treatments to improve the corrosion and wear properties of military hardware. These processes are intended to be complementary to, rather than competing with, other promising macro scale coating processes such high velocity oxy-fuel (HVOF) deposition, particularly in non-line-of- sight and flash chrome replacement applications. It is believed that these processes can improve the tribological and corrosion behavior of parts without significantly altering the dimensions of the part, thereby eliminating the need for further machining operations and reducing overall production costs. The ion beam processes chosen are relatively mature, low-cost processes that can be scaled-up. The key methods that have been considered under this program include nitrogen ion implantation into electroplated hard chrome, ion beam assisted chromium and chromium nitride coatings, and plasma-deposited diamond- like carbon an...

  3. One pot synthesis of metal ion anchored alginate-gelatin binary biocomposite for efficient Cr(VI) removal.

    Science.gov (United States)

    Gopalakannan, Venkatrajan; Viswanathan, Natrayasamy

    2016-02-01

    Biopolymers are widely used for the removal of chromium from aqueous medium but it possesses limitations like poor sorption capacity and low stability. To overcome the limitations of biopolymers and to improve their properties, the present study was designed in such a way to develop a novel sorbent with enhanced chromium sorption capacity and better stability by synthesizing metal ion cross-linked binary biocomposites using biopolymers like alginate and gelatin cross-linked with Ca2+, Ce3+ and Zr4+ ions namely Ca@AlgGel, Ce@AlgGel and Zr@AlgGel composites. The functional groups, agglomeration, surface area, surface morphology, elemental analysis and thermal stability of the composites were investigated by FTIR, TEM, BET, SEM with EDAX and TGA analysis. The chromium removal studies of the biocomposites were carried out in batch mode. The sorption process was optimized by varying the influencing aspects like contact time, dosage, presence of common ions, pH, initial chromium concentration and temperature. The maximum sorption capacity of Ca@AlgGel, Ce@AlgGel and Zr@AlgGel composites were found to be 19.40, 24.50 and 25.40 mg/g, respectively. The sorption data was fitted by using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic parameters indicate the nature of chromium sorption. The suitability of the composite materials was also tested under the field conditions.

  4. 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.

  5. Electrogenerated Chemiluminescence Behavior of Au nanoparticles-hybridized Pb (II) metal-organic framework and its application in selective sensing hexavalent chromium

    OpenAIRE

    Hongmin Ma; Xiaojian Li; Tao Yan; Yan Li; Haiyang Liu; Yong Zhang; Dan Wu; Bin Du; Qin Wei

    2016-01-01

    In this work, a novel electrochemiluminescence (ECL) sensor based on Au nanoparticles-hybridized Pb (II)-β-cyclodextrin (Pb-β-CD) metal-organic framework for detecting hexavalent chromium (Cr(VI)) was developed. Pb-β-CD shows excellent ECL behavior and unexpected reducing ability towards Au ions. Au nanoparticles could massively form on the surface of Pb-β-CD (Au@Pb-β-CD) without use of any additional reducing agent. In the presence of coreactant K2S2O8, the ECL emission of Pb-β-CD was enhanc...

  6. High temperature oxidation of iron-chromium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, Lars

    2003-06-15

    The high temperature oxidation of the ferritic alloy Fe78Cr22 has been investigated in the present work. The effect of small alloying additions of cerium and/or silicon was also investigated. The alloys were oxidized at 973, 1173 and 1373 K in either air or a hydrogen/argon mixture. The various reaction atmospheres contained between 0.02 and 50% water vapour. The oxide scales formed on the various alloys at 973 K consisted of thin chromia layers. The oxide scales grown on the alloys at 1173 K also consisted of a chromia layer. The microstructure of the chromia scales was found to depend on the reaction atmosphere. The chromia scales grown in hydrogen/argon atmospheres formed oxide whiskers and oxide ridges at the surface of the scales, while the chromia scales grown in air formed larger oxide grains near the surface. This difference in oxide microstructure was due to the vaporization of chromium species from the chromia scales grown in air. Two different growth mechanisms are proposed for the growth of oxide whiskers. The growth rate of the chromia scales was independent of the oxygen activity. This is explained by a growth mechanism of the chromia scales, where the growth is governed by the diffusion of interstitial chromium. The addition of silicon to the iron-chromium alloy resulted in the formation of silica particles beneath the chromia scale. The presence of silicon in the alloy was found to decrease the growth rate of the chromia scale. This is explained by a blocking mechanism, where the silica particles beneath the chromia scale partly block the outwards diffusion of chromium from the alloy to the chromia scale. The addition of cerium to the iron-chromium alloy improved the adhesion of the chromia scale to the alloy and decreased the growth rate of chromia. It was observed that the minimum concentration of cerium in the alloy should be 0.3 at.% in order to observe an effect of the cerium addition. The effect of cerium is explained by the &apos

  7. 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

  8. Chromium Isotopes Record Fluctuations in Precambrian Biospheric Oxygenation

    Science.gov (United States)

    Frei, R.; Gaucher, C.; Poulton, S. W.; Canfield, D. E.

    2009-12-01

    There is a direct relationship between life, oxygen, and the surface chemistry of the Earth. Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps, near the beginning and the end of the Proterozoic Eon (2500 to 542 million years ago), but the details of this history are unclear. The geochemical behaviour of chromium (Cr) is highly sensitive to the redox state of the surface environment as oxidative weathering processes produce the oxidised hexavalent [Cr(VI)] form. Oxidation of reduced trivaltent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. The fractionated Cr isotope signature is then tranfered by riverine transport to the sea. Here, we use Cr stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of Earth’s atmosphere-hydrosphere system. Fractionated Cr isotopes indicate the accumulation of Cr(VI) in ocean surface waters ~2.8 to 2.6 billion years (Gyr) ago and a likely transient elevation in atmospheric and surface ocean oxygen prior to the first great rise of oxygen 2.45-2.2 Gyr ago (the Great Oxidation Event; GOE). In contrast, Cr isotopes in ~1.88 Gyr old BIFs are not fractionated, indicating a major decline in atmospheric oxygen and demonstrating that the GOE did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, ~800 to 542 million years (Myr) ago, we observe strong positive fractionations in Cr isotopes (δ53Cr up to +4.9 ‰) providing independent support for increased surface oxygenation at this time. This may have stimulated rapid evolution of macroscopic multicellular life. Our chromium isotope data thus provide new insights into the oxygenation history of the Earth, and highlight its use as a powerful redox tracer in aquatic systems.

  9. Skin permeation and cutaneous hypersensitivity as a basis for making risk assessments of chromium as a soil contaminant.

    OpenAIRE

    Bagdon, R E; Hazen, R E

    1991-01-01

    A literature review of experimental and human exposure studies of skin permeation and cutaneous hypersensitivity reactions evoked by chromium was carried out to provide a basis for making a risk assessment of chromium as a soil contaminant. In vitro and in vivo studies demonstrated that 1 to 4% of the applied dose of hexavalent and trivalent chromium to guinea pig skin penetrated skin within 5 to 24 hr after application. Ultrastructural investigations showed that hexavalent chromium localized...

  10. 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...

  11. Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes.

    Science.gov (United States)

    Stevens, Charlotte J; Nichol, Gary S; Arnold, Polly L; Love, Jason B

    2013-12-01

    The new binuclear chromium Pacman complex [Cr2(L)] of the Schiff base pyrrole macrocycle H4L has been synthesized and structurally characterized. Addition of isocyanide, C≡NR (R = xylyl, (t)Bu), or triphenylphosphine oxide donors to [Cr2(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr2(μ-CNR)(L)], in which the isocyanides bridge the two Cr(II) centers, and [Cr2(OPPh3)2(L)], a Cr(II) phosphine oxide adduct with the ligands exogenous to the cleft.

  12. Chromium Renderserver: Scalable and Open Source Remote RenderingInfrastructure

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Brian; Ahern, Sean; Bethel, E. Wes; Brugger, Eric; Cook,Rich; Daniel, Jamison; Lewis, Ken; Owen, Jens; Southard, Dale

    2007-12-01

    Chromium Renderserver (CRRS) is software infrastructure thatprovides the ability for one or more users to run and view image outputfrom unmodified, interactive OpenGL and X11 applications on a remote,parallel computational platform equipped with graphics hardwareaccelerators via industry-standard Layer 7 network protocolsand clientviewers. The new contributions of this work include a solution to theproblem of synchronizing X11 and OpenGL command streams, remote deliveryof parallel hardware-accelerated rendering, and a performance analysis ofseveral different optimizations that are generally applicable to avariety of rendering architectures. CRRSis fully operational, Open Sourcesoftware.

  13. Study on anaerobic treatment of wastewater containing hexavalent chromium*

    OpenAIRE

    Xu, Yan-Bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment ...

  14. Alkaline stress corrosion of iron-nickel-chromium austenitic alloys

    International Nuclear Information System (INIS)

    This research thesis reports the study of the behaviour in stress corrosion of austenitic iron-nickel-chromium alloys by means of tensile tests at imposed strain rate, in a soda solution at 50 pc in water and 350 degrees C. The author shows that the mechanical-chemical model allows the experimental curves to be found again, provided the adjustment of characteristic parameters, on the one hand, of corrosion kinetics, and on the other hand, of deformation kinetics. A classification of the studied alloys is proposed

  15. MODELING THE RATE-CONTROLLED SORPTION OF HEXAVALENT CHROMIUM.

    Science.gov (United States)

    Grove, D.B.; Stollenwerk, K.G.

    1985-01-01

    Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

  16. Chromium Doped ZnS Nanostructures: Structural and Optical Characteristics

    Science.gov (United States)

    Gogoi, D. P.; Das, U.; Ahmed, G. A.; Mohanta, D.; Choudhury, A.; Stanciu, G. A.

    2009-06-01

    Chromium doped ZnS nanoparticles arranged in the form of fractals were fabricated by using inexpensive physico-chemical route. The Cr:ZnS samples were characterized by diffraction and spectroscopic techniques. Unexpected growth of fractals with several micrometer dimensions and of core size 1 μm (tip to tip) was confirmed through TEM micrographs. At higher magnification, we found that individual fractals consist of spherical nanoparticles of average size leading to such organized structures describing fractal pattern is encountered in this work.

  17. Evaluating Foraminifera as an Archive for Seawater Chromium Isotopic Composition

    Science.gov (United States)

    Wang, X.; Planavsky, N.; Hull, P. M.; Tripati, A.; Reinhard, C.; Zou, H.; Elder, L. E.; Henehan, M. J.

    2015-12-01

    In recent years there has been growing interest in using chromium isotopes (δ53Cr) as a proxy to investigate the redox evolution of Earth's ocean-atmosphere system throughout geological history. Potential archives for seawater δ53Cr that have been identified to date include iron formations and organic-rich siliciclastic sediments. However, these types of sediments are not common and they are discontinuous over geologic time. As a result, alternative types of archives are needed. Here we evaluate the utility of foraminifera tests as a recorder of seawater δ53Cr. Core-tops used were from different ocean basins. Mono-specific samples of Globigerinoides sacculifer, Orbulina universa, Pulleniatina obliquiloculata, Globoratalia crassula-crassaformis, Globoratalia truncatulinoides, and Globigerinella siphonifera were isolated to investigate inter-species isotope fractionation. Chromium concentrations were measured by isotope dilution method to be 0.1-0.3 μg/g. The δ53Cr values of these species range from 0.2‰ to 2.4‰, with an analytical uncertainty of 0.3‰ (95% confidence). Despite the high analytical uncertainty due to the extremely low levels of Cr present, there is still large detectable variation in foraminiferal δ53Cr values, which overlap presently available seawater values (Bonnand et al., 2013; Scheiderich et al., 2015). Possible explanations for such variations in foraminiferal δ53Cr values include heterogeneity of seawater δ53Cr in the modern oceans, and/or photobiochemical redox cycling of Cr in the surface oceans. Therefore, care should be taken when using foraminifera to reconstruct past seawater δ53Cr values. ReferencesBonnand, P., James, R., Parkinson, I., Connelly, D., Fairchild, I., 2013. The chromium isotopic composition of seawater and marine carbonates. Earth and Planetary Science Letters, 382: 10-20. Scheiderich, K., Amini, M., Holmden, C., Francois, R., 2015. Global variability of chromium isotopes in seawater demonstrated by Pacific

  18. Environmental optimization of chromium recovery from tannery sludge using a life cycle assessment approach.

    Science.gov (United States)

    Kiliç, Eylem; Puig, Rita; Baquero, Grau; Font, Joaquim; Colak, Selime; Gürler, Deniz

    2011-08-15

    Life cycle assessment (LCA) was used to evaluate the environmental impact of an oxidative chromium recovery method from tannery sludge, in comparison with the usual landfilling process. Three improvement options (water reduction, byproduct use and anaerobic sludge digestion) were considered. The results showed that the proposed chromium recovery process would be better environmentally than conventional landfilling in all the evaluated impact categories if the amount of chromium recovered was 43 kg per ton of sludge. This amount could be recovered if the chromium concentration was about 20 times higher than that considered in this study. Alternatively, a lower chromium concentration would produce a better result if the recovery method was optimized and implemented at industrial rather than laboratory scale, and if more accurate data were provided on environmental credits for avoiding the chromium production process. Thus, the recovery method is environmentally beneficial when tannery sludge contains a chromium concentration of about 100,000 ppm. According to the literature, such concentrations are not unusual. The results could serve as the basis for further environmental improvements in chromium recovery and tannery sludge management and should be used in decision-making processes, especially for end-of-pipe treatments.

  19. Evaluation of chromium concentration in cattle feces using different acid digestion and spectrophotometric quantification techniques

    Directory of Open Access Journals (Sweden)

    N.K.P. Souza

    2013-10-01

    Full Text Available The objective of this work was to evaluate combinations between acid digestion techniques and spectrophotometric quantification to measure chromium concentration in cattle feces. Digestion techniques were evaluated based on the use of nitric and perchloric acids, sulfuric and perchloric acids, and phosphoric acid. The chromium quantification in the solutions was performed by colorimetry and by atomic absorption spectrophotometry (AAS. When AAS was used, the addition of calcium chloride to the solutions as a releasing agent was also evaluated. Several standard samples containing known chromium contents were produced (0, 2, 4, 6, 8 and 10g of chromium per kg of feces using cattle feces obtained from three different animals to evaluate the accuracy of the different combinations of techniques. The accuracy was evaluated by adjusting a simple linear regression model of the estimated values on the actual values of chromium content in the standard samples. Regardless of the digestion technique, the chromium content estimates in the standard samples obtained by colorimetry were not accurate (P0.05. The use of the digestion technique in phosphoric acid provided incomplete recovery of the fecal chromium (P0.05 fecal chromium contents.

  20. Leaching behavior of chromium in chrome shaving generated in tanning process and its stabilization.

    Science.gov (United States)

    Erdem, Mehmet; Ozverdi, Arzu

    2008-08-15

    In this study, leaching properties and pollution potential of chromium in chrome shaving (CS), which is a solid residue of leather industry, containing 2.27% Cr were investigated and thermal stabilization procedure was applied to the CS for chromium immobilization. For this purpose, firstly, effects of the liquid/solid ratio, contact time, pH and sequential extraction on the leaching behavior of chromium in the CS were studied. It was determined that the CS-caused chromium pollution is a hazardous material for environment. Thermal stabilization procedure was applied to the CS in the temperature range of 250-500 degrees C for the chromium immobilization. Effective stabilization of chromium in the CS was achieved by heating of CS at 350 degrees C under CO(2) atmosphere. Leaching experiments were also carried out with the samples obtained from the stabilization process and the results compared with that of the CS. Also, TCLP test method was applied to the samples to determine pollution potentials and discharge situations of the CS and its stabilization products. While the chromium concentrations in the test solutions of all samples stabilized thermally at above 350 degrees C were below the USEPA regulatory limit of 5 mg/l, the concentration of chromium leached out from the CS was 30-fold bigger than the USEPA regulatory limit.