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Sample records for chromium ions

  1. Chromium Ions Improve Moisure Resistance of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

    1986-01-01

    Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

  2. Process for improving moisture resistance of epoxy resins by addition of chromium ions

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; Stoakley, D. M.; St.clair, T. L.; Singh, J. J. (Inventor)

    1985-01-01

    A process for improving the moisture resistance properties of epoxidized TGMDA and DGEBA resin system by chemically incorporating chromium ions is described. The addition of chromium ions is believed to prevent the absorption of water molecules.

  3. Chromium ion plating studies for enhancement of bearing lifetime

    NASA Technical Reports Server (NTRS)

    Davis, J. H.

    1982-01-01

    Six 440-C hardened stainless steel roller bearing test rods were ion plated with various chromium films of thicknesses from .2 microns to 7 microns. The thinner (approximately .2 microns) coating sample had 3 times the fatigue life of the unplated (standard) specimens. Contrastingly, the samples having thicker coatings (several microns) had short fatigue lives (about 3% of the unplated standard).

  4. Chromium silicide formation by ion mixing

    NASA Technical Reports Server (NTRS)

    Shreter, U.; So, F. C. T.; Nicolet, M.-A.

    1984-01-01

    The formation of CrSi2 by ion mixing was studied as a function of temperature, silicide thickness and irradiated interface. Samples were prepared by annealing evaporated couples of Cr on Si and Si on Cr at 450 C for short times to form Si/CrSi2/Cr sandwiches. Xenon beams with energies up to 300 keV and fluences up to 8 x 10 to the 15th per sq cm were used for mixing at temperatures between 20 and 300 C. Penetrating only the Cr/CrSi2 interface at temperatures above 150 C induces further growth of the silicide as a uniform stoichiometric layer. The growth rate does not depend on the thickness of the initially formed silicide at least up to a thickness of 150 nm. The amount of growth depends linearly on the density of energy deposited at the interface. The growth is temperature dependent with an apparent activation energy of 0.2 eV. Irradiating only through the Si/CrSi2 interface does not induce silicide growth. It is concluded that the formation of CrSi2 by ion beam mixing is an interface-limited process and that the limiting reaction occurs at the Cr/CrSi2 interface.

  5. Kinetics of chromium ion absorption by cross-linked polyacrylate films

    NASA Technical Reports Server (NTRS)

    May, C. E.

    1984-01-01

    Three cross-linked ion exchange membranes were studied as to their ability to absorb chromium ion from aqueous chromium III nitrate solutions. Attention was given to the mechanism of absorption, composition of the absorbed product, and the chemical bonding. The membranes were: calcium polyacrylate, polyacrylic acid, and a copolymer of acrylic acid and vinyl alcohol. For the calcium polyacrylate and the copolymer, parabolic kinetics were observed, indicating the formation of a chromium polyacrylate phase as a coating on the membrane. The rate of absorption is controlled by the diffusion of the chromium ion through this coating. The product formed in the copolymer involves the formation of a coordination complex of a chromium ion with 6 carboxylic acid groups from the same molecule. The absorption of the chromium ion by the polyacrylic acid membranes appears to be more complicated, involving cross-linking. This is due to the coordination of the chromium ion with carboxylic acid groups from more than one polymer molecule. The absorption rate of the chromium ion by the calcium salt membrane was found to be more rapid than that by the free polyacrylic acid membrane.

  6. Aqueous corrosion of ion beam mixed Ta films on 13% chromium steel

    NASA Astrophysics Data System (ADS)

    Huang, N. K.

    1993-06-01

    The effect of aqueous corrosion of ion beam mixed Ta on 13 wt% chromium steel in 1M H 2SO 4 or 0.1N NaCl solution has been investigated. The results show that Ta ion mixing can evidently improve the corrosion resistance of chromium steel. The corrosion resistances of the ion beam mixed Ta films are affected by the nature of the substrates. Some suggestions are proposed according to microanalysis results by using SEM, RBS and XPS techniques.

  7. Chromium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of chromium (Cr) on glucose and insulin metabolism are well documented. Normal dietary intake of Cr appears to be suboptimal because several studies have reported beneficial effects of Cr in people with elevated blood glucose or type 2 diabetes eating conventional diets. Stresses that ...

  8. Transport of trivalent and hexavalent chromium through different ion-selective membranes in acidic aqueous media

    SciTech Connect

    Costa, R.F.D.; Rodrigues, M.A.S.; Ferreira, J.Z.

    1998-06-01

    The aim of this work was to evaluate the transport of trivalent and hexavalent chromium through anion- and cation-selective membranes using two- and three-compartment electrodialysis cells. Tests were done with acidic solutions of trivalent chromium ions, Cr{sup 3+}, and hexavalent chromium ions, Cr{sub 2}O{sub 7}{sup 2{minus}}. In each situation the transport of metallic ions through the membrane was evaluated. In the tests with trivalent chromium, Nafion 417 and Selemion CMT cation-selective membranes were used, and in the tests with hexavalent chromium, Selemion AMT membrane was used. The influence of SO{sub 4}{sup 2{minus}} ions and of the concentration of H{sup +} ions in the solutions was also analyzed. Results showed the oxidation of the Cr{sup 3+} ion at the anode and the reduction of the Cr{sub 2}O{sub 7}{sup 2{minus}} ion at the cathode. The maximum yield in the process was reached when hexavalent chromium solutions were used in the absence of sulfate ions and a Selemion AMT membrane in a three-compartment cell.

  9. Determination of hexavalent chromium in cosmetic products by ion chromatography and postcolumn derivatization.

    PubMed

    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

  10. Aluminum and chromium ion particle studies for enhancement of surface properties

    NASA Technical Reports Server (NTRS)

    1982-01-01

    An experimental project was undertaken which produced ion plated coatings on steel substrates. About twenty tensile samples of 4340 steel were ion plated in the Denton system with aluminum using resistance heating evaporation boats. In the V.T.A. 7375 system, ten samples were chromium ion plated; four on 4340 steel disks and the other six onto 440-C stainless steel rods for roller bearing wear improvement testing. Each of the samples was plated on a separate run to correlate the film parameters with the run parameters. Some of the chromium literature was reviewed, and improvements to the vacuum system were made.

  11. Rolling contact fatigue life of chromium ion plated 440C bearing steel

    NASA Technical Reports Server (NTRS)

    Bhat, B. N.; Davis, J. H.

    1985-01-01

    Rolling contact fatigue (RCF) test specimens of heat treated 440C bearing steel were chromium ion plated in thicknesses from 0.1 to 8.0 micron and tested in RCF tester using 700 ksi maximum Hertzian stress. Heavy coatings, greater than about 5 micron in thickness, peeled off or spalled readily, whereas thin coatings, less than 3 micron thick, were tenacious and did not come off. Furthermore, significant improvement in RCF life was obtained with thin chromium ion plated test specimens. The average increase in B10 life was 75% compared with unplated 440C. These preliminary results indicate that ion plating is a promising way to improve bearing life.

  12. Unmodified starch as water-soluble binding polymer for chromium ions removal via polymer enhanced ultrafiltration system

    PubMed Central

    2014-01-01

    Background In this study the removal of Chromium (III) and Chromium (VI) ions are investigated via polymer enhanced ultrafiltration under important process parameters. This study proposes the use of unmodified starch as a novel polymer in the ultrafiltration process and its performance on the removal of chromium ions was compared with a commonly used polymer, polyethylene glycol. Methods The experiments were carried out at 1.5 bar and different pH values by using 10 kDa hollow fiber membrane operating in a cross-flow mode. Results The best chromium ions removal obtained approached 99% for Chromium (III) ion by unmodified starch at alkaline pH region and at pH 7 for Chromium (VI) ions retention by polyethylene glycol. Permeate flux behavior are fluctuated for both chromium ions tested at high metal ion concentrations. Low concentration of unmodified starch is applied to reduce gelatinization behavior. Conclusions The findings suggest that binding of chromium ions by unmodified starch is related to granule structure which is probably a principal indicator of the non-ionic behavior of unmodified starch. PMID:24618019

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

    SciTech Connect

    Troyanchuk, I. O. Bushinsky, M. V.; Tereshko, N. V.; Dobryanskii, V. M.; Sikolenko, V.; Többens, D. M.

    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.

  14. Sputtering of cobalt and chromium by argon and xenon ions near the threshold energy region

    NASA Technical Reports Server (NTRS)

    Handoo, A. K.; Ray, P. K.

    1993-01-01

    Sputtering yields of cobalt and chromium by argon and xenon ions with energies below 50 eV are reported. The targets were electroplated on copper substrates. Measurable sputtering yields were obtained from cobalt with ion energies as low as 10 eV. The ion beams were produced by an ion gun. A radioactive tracer technique was used for the quantitative measurement of the sputtering yield. Co-57 and Cr-51 were used as tracers. The yield-energy curves are observed to be concave, which brings into question the practice of finding threshold energies by linear extrapolation.

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

    PubMed

    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

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

    PubMed

    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. PMID:24878058

  17. Removal of chromium from electroplating industry effluents by ion exchange resins.

    PubMed

    Cavaco, Sofia A; Fernandes, Sandra; Quina, Margarida M; Ferreira, Licínio M

    2007-06-18

    Effluent discharged from the chromium electroplating industry contains a large number of metals, including chromium, copper, nickel, zinc, manganese and lead. The ion exchange process is an alternative technique for application in the treatment of industrial wastewater containing heavy metals and indeed it has proven to be very promising in the removal and recovery of valuable species. The main objective of the present work is to evaluate the performance of commercial ion exchange resins for removing chromium trivalent from industrial effluents, and for this purpose two resins were tested: a chelating exchange resin (Diaion CR11) and a weak cationic resin (Amberlite IRC86). In order to evaluate the sorption capacity of the resins some equilibrium experiments were carried out, being the temperature and pH the main variables considered. The chromium solutions employed in the experiments were synthetic solutions and industrial effluents. In addition, a transient test was also performed as an attempt to understand the kinetic behaviour of the process. PMID:17336455

  18. EPR and XRD Spectroscopies of the Chromium Ions in the ZSM-5 Zeolite

    NASA Astrophysics Data System (ADS)

    Trif, Eleonora; Strugaru, Dorina; Marcu, Cristina; Russu, R.; Gheorghe, Gabriela; Ivan, I.

    The introduction of chromium into silica-high zeolite of ZSM-5 type was carried out by heating homogeneous mechanical mixtures of H-form zeolite with the CrO3 compound. X-ray diffraction and paramagnetic resonance methods were used to follow the thermal stability of the zeolite, the framework alteration, as well as the nature of the chromium complexes formed during solid phase reactions. For low contents of oxide (x≤5% wt. CrO3) in mixtures, the thermal stability, T=1070°C, of the zeolite phase is not affected by the presence of the reaction products. The treatment of mixtures in air and in vacuum leads to the location of several isolated Cr(III) and Cr(V) complexes in cation positions. The low-field resonances at g=3.72 and/or g=5-6 indicate the presence of isolated Cr(III) species in orthorhombically distorted octahedral environments. Several Cr(V) species were also detected, two of them exhibiting a superhyperfine structure (aAl=0.63-0.73 mT) caused by the interaction of the Cr(V) ions with 27Al (I=5/2) of the zeolite framework. Generally, the signals arising from the isolated ions are overlapped by broad resonances typical for chromium-rich phases. Drastic changes of the spectra, upon ingress of gas-phase molecules (air, H2O, O2) over the calcined samples, certify the unsaturated character of the Cr complexes formed during the treatments. It is one characteristic feature of the H-ZSM-5 zeolites which results in the special catalytic activity of the chromium-containing zeolites.

  19. Removal of chromium ions from wastewater by duckweed, Lemna minor L. by using a pilot system with continuous flow.

    PubMed

    Uysal, Y

    2013-12-15

    The aim of this study was to determine the ability of Lemna minor to remove Cr (VI) ions from wastewater in a continuous flow pond system. This system was used to simulate a wastewater treatment pond and a natural wetland as habitat of plants. In order to find optimal conditions for chromium removal, ponds were operated with aqueous solutions having different pH (4.0-7.0) and chromium concentration of 0.25 mgCr(+6)/L, then plants were exposed to different chromium concentrations (0.25-5.0 mgCr(+6)/L) at pH 4.0. Chromium concentrations, both in biomass and wastewater, were measured and removal efficiency was determined throughout water flow. Growth factors such as growth rates, chlorophyll contents and dry/fresh weight ratios of plants were also determined to measure toxic effects of chromium. The percentages of chromium uptake (PMU) and bioconcentration factors (BCF) were calculated for each run. The highest accumulated chromium concentration (4.423 mgCr/g) was found in plants grown in the first chamber of pond operated at pH 4.0 and 5.0 mgCr/L, while the minimum accumulated chromium concentration (0.122 mgCr/g) was in plants grown in the last chamber of pond operated at pH 4.0 and 0.25 mgCr(+6)/L. PMID:24231333

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

    PubMed

    Pehlivan, Erol; Altun, Türkan

    2008-06-30

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

  1. Highly sensitive detection of chromium (III) ions by resonance Rayleigh scattering enhanced by gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Min; Cai, Huai-Hong; Yang, Fen; Lin, Dewen; Yang, Pei-Hui; Cai, Jiye

    2014-01-01

    Simple and sensitive determination of chromium (III) ions (Cr3+) has potential applications for detecting trace contamination in environment. Here, the assay is based on the enhancement of resonance Rayleigh scattering (RRS) by Cr3+-induced aggregation of citrate-capped gold nanoparticles (AuNPs). Transmission electron microscopy (TEM) and UV-vis absorption spectroscopy were employed to characterize the nanostructures and spectroscopic properties of the Cr3+-AuNP system. The experiment conditions, such as reaction time, pH value, salt concentration and interfering ions, were investigated. The combination of signal amplification of Cr3+-citrate chelation with high sensitivity of RRS technique allow a selective assay of Cr3+ ions with a detection limit of up to 1.0 pM. The overall assay can be carried out at room temperature within only twenty minutes, making it suitable for high-throughput routine applications in environment and food samples.

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

    SciTech Connect

    Bibler, J.P.; Meaker, T.F.; O`Steen, A.B.

    1992-09-30

    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{sup +} and OH{sup {minus}} 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Annealing of chromium oxycarbide coatings deposited by plasma immersion ion processing (PIIP) for aluminum die casting

    NASA Astrophysics Data System (ADS)

    Peters, A. M.; He, X. M.; Trkula, M.; Nastasi, M.

    2001-04-01

    Chromium oxycarbide coatings have been investigated for use as non-wetting coatings for aluminum die casting. This paper examines Cr-C-O coating stability and non-wetability at elevated temperatures for extended periods. Coatings were deposited onto 304 stainless steel from chromium carbonyl [Cr(CO) 6] by plasma immersion ion processing. The coatings were annealed in air at an aluminum die casting temperature of 700°C up to 8 h. Coatings were analyzed using resonant ion backscattering spectroscopy, nanoindentation and pin-on-disk tribometry. Molten aluminum was used to determine coating wetting and contact angle. Results indicate that the surface oxide layer reaches a maximum thickness of 900 nm. Oxygen concentrations in the coatings increased from 24% to 34%, while the surface concentration rose to almost 45%. Hardness values ranged from 22.1 to 6.7 GPa, wear coefficients ranged from 21 to 8×10 -6 mm3/ Nm and contact angles ranged from 156° to 127°.

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

    PubMed

    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

  6. Release of nickel and chromium ions in the saliva of patients with fixed orthodontic appliance: An in-vivo study

    PubMed Central

    Dwivedi, Anoop; Tikku, Tripti; Khanna, Rohit; Maurya, Rana Pratap; Verma, Geeta; Murthy, R. C.

    2015-01-01

    Introduction: Various components of fixed orthodontic appliances are continuously interacting with saliva and other fluids in the mouth releasing various metal ions including nickel and chromium that can cause damaging effects if their concentration exceeds above the toxic dose. Aim: To determine and compare the level of nickel and chromium in the saliva of patients undergoing fixed orthodontic treatment at different time periods. Materials and Methods: The sample of saliva of 13 patients was taken at different time periods that is: Group 1 (before appliance placement), Group II, III, and IV (after 1-week, 1-month, and 3 months of appliance placement respectively). The fixed appliance comprised of brackets, bands, buccal tubes, lingual sheath, transpalatal arch and wires composed of Ni-Ti and stainless steel. The level of ions was determined using graphite furnace atomic absorption spectro-photometry. The data thus obtained were statistically analyzed using SPSS Statistical Analysis Software (Version 15.0). Results: Level of nickel and chromium in saliva was highest in Group II and lowest in Groups I for both the ions. On comparison among different Groups, it was statistically significant for all the groups (<0.001) except between Group III and Group IV. Conclusion: The release of nickel and chromium was maximum at 1-week and then the level gradually declined. These values were well below the toxic dose of these ions. The results should be viewed with caution in subjects with Ni hypersensitivity. PMID:26668455

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

    SciTech Connect

    Bibler, J.P.; Meaker, T.F.; O'Steen, A.B.

    1992-09-30

    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[sup +] and OH[sup [minus

  8. Combined cytotoxicity and genotoxicity of a marine toxin and seafood contaminant metal ions (chromium and cadmium).

    PubMed

    Souid-Mensi, Ghada; Moukha, Serge; Maaroufi, Khira; Creppy, Edmond E

    2008-02-01

    Algal bloom with consequent production of marine toxins contaminating bivalves is increasing in costal regions worldwide because of sea water quality worsening. Contamination of seafood by diarrheic shellfish poisoning toxins (DSP) together with metals is frequently reported, a phenomenon not fully explained yet. In this context, metal ions were assayed in clams collected from the banned area of Boughrara, Tunisia, contaminated by Gymnodinium and other algae such as Dinophysis sp, accumulated by these bivalves. The presence of toxic metals ions such as Chromium (Cr) and Cadmium (Cd) in meat, shells, and water released by the clams prompted us to experiment in Caco-2 intestinal cell line toxic effects of these heavy metals ions in combination with okadaic acid, one DSP present in clams to assess the potential global toxicity. Cr and Cd produce additive effects in (i) reactive oxygen species production, (ii) cytotoxicity as assessed by the mitochondrial activity testing method (MTT test), and (iii) DNA lesions evaluated by agarose gel electrophoresis and acridine orange staining. Exaggerated DNA fragmentation is observed, suggesting an overloading of repair capacity of Caco-2 cells. The apoptosis suggested by a DNA fragment sizing (180-200 bp) in agarose gel and mechanisms underlying these additive effects in Caco-2 cells still need to be more comprehensively explained. PMID:18214935

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples

    SciTech Connect

    Liu, Xi; Xiang, Jun-Jian; Tang, Yong; Zhang, Xiao-Li; Fu, Qiang-Qiang; Zou, Jun-Hui; Lin, Yuehe

    2012-09-01

    An immunochromatographic assay (ICA) using gold nanoparticles coated with monoclonal antibody (McAb) for the detection of chromium ions (Cr) in water and serum samples was developed, optimized, and validated. Gold nanoparticles coated with affinity- purified monoclonal antibodies against isothiocyanobenzyl-EDTA (iEDTA)-chelated Cr3+ were used as the detecting reagent in this completive immunoassay-based one- step test strip. The ICA was investigated to measure chromium speciation in water samples. Chromium standard samples of 0-80 ng/mL in water were determined by the test strips. The results showed that the visual lowest detection limit (LDL) of the test strip was 50.0 ng/mL. A portable colorimetric lateral flow reader was used for the quantification of Cr. The results indicated that the linear range of the ICA with colorimetric detection was 5-80 ng/mL. The ICA was also validated for the detection of chromium ions in serum samples. The test trips showed high stability in that they could be stored at at 37 C for at least 12 weeks without significant loss of activity. The test strip also showed good selectivity for Cr detection with negligible interference from other heavy metals. Because of its low cost and short testing time (within 5 min), the test strip is especially suitable for on-site large- scale screening of Cr-polluted water samples, biomonitoring of Cr exposure, and many other field applications.

  11. Ion Molecule Reactions of Gas-Phase Chromium Oxyanions:CrxOyHz- + O2

    SciTech Connect

    Anita K. Gianotto; Brittany D. M. Hodges; Peter de B. Harrington; Anthony Appelhans; John E. Olson; Gary S. Groenewold

    2003-10-01

    Chromium oxyanions, CrxOyHz-, were generated in the gas-phase using a quadrupole ion trap secondary ion mass spectrometer (IT-SIMS), where they were reacted with O2. Only CrO2- of the Cr1OyHz- envelope was observed to react with oxygen, producing primarily CrO3-. The rate constant for the reaction of CrO2- with O2 was 38% of the Langevin collision constant at 310 K. CrO3-, CrO4-, and CrO4H- were unreactive with O2 in the ion trap. In contrast, Cr2O4- was observed to react with O2 producing CrO3- + CrO3 via oxidative degradation at a rate that was 15% efficient. The presence of background water facilitated the reaction of Cr2O4- + H2O to form Cr2O5H2-; the hydrated product ion Cr2O5H2- reacted with O2 to form Cr2O6- (with concurrent elimination of H2O) at a rate that was 6% efficient. Cr2O5- also reacted with O2 to form Cr2O7- (4% efficient) and Cr2O6- + O (2% efficient); these reactions proceeded in parallel. By comparison, Cr2O6- was unreactive with O2, and in fact, no further O2 addition could be observed for any of the Cr2O6Hz- anions. Generalizing, CrxOyHz- species that have low coordinate, low oxidation state metal centers are susceptible to O2 oxidation. However, when the metal coordination is >3, or when the formal oxidation state is =5, reactivity stops.

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

    PubMed

    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

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

    SciTech Connect

    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.

  14. Ratiometric near-infrared chemosensor for trivalent chromium ion based on tricarboyanine in living cells.

    PubMed

    Li, Chun-Yan; Kong, Xue-Fei; Li, Yong-Fei; Weng, Chao; Tang, Jia-Liang; Liu, Dan; Zhu, Wei-Guo

    2014-05-01

    A tricarboyanine derivative (IRPP) is applied as a ratiometric near-infrared chemosensor for detecting trivalent chromium ions (Cr(3+)) in living cells. Upon the addition of Cr(3+) to a solution of IRPP, large-scale shifts in the emission spectrum (from 755 nm to 561 nm) are observed. In the newly developed sensing system, these well-resolved emission peaks yield a sensing system that covers a linear range from 1.0×10(-7) to 1.0×10(-5) M with a detection limit of 2.5×10(-8) M. The experimental results show the response behavior of IRPP towards Cr(3+) is pH independent under neutral conditions (6.0-7.5). Most importantly, the fast response time (less than 3 min) and selectivity for Cr(3+) over other common metal ions provide a strong argument for the use of this sensor in real world applications. As a proof of concept, the proposed chemosensor has been used to detect and quantify Cr(3+) in river water samples and to image Cr(3+) in living cells with encouraging results. PMID:24759750

  15. Corrosion, ion release and Mott–Schottky probe of chromium oxide coatings in saline solution with potential for orthopaedic implant applications

    NASA Astrophysics Data System (ADS)

    Ogwu, A. A.; Oje, A. M.; Kavanagh, J.

    2016-04-01

    We report our investigation on chromium oxide thin film coatings that show a negligible ion release during electrochemical corrosion testing in saline solution. The chemical constituents of the films prepared by reactive magnetron sputtering were identified to be predominantly Cr2O3 based on Raman spectroscopy anti-symmetric stretching vibration modes for CrIII–O and other peaks and an FTIR spectroscopy E u vibrational mode at 409 cm‑1. X-ray photoelectron spectroscopy, multiplet fitting for 2P 3/2 and 2P 1/2 states also confirmed the predominantly Cr2O3 stoichiometry in the films. The prepared chromium oxide coatings showed superior pitting corrosion resistance compared to the native chromium oxide films on bare uncoated stainless steel when tested under open circuit potential, potentiodynamic polarisation and cyclic voltammetry in saline solution. The chromium ion released into solution during the corrosion testing of stainless steel substrates coated with chromium oxide coatings was found to be negligibly small based on atomic absorption spectroscopy measurements. Our Mott–Schottky analysis investigation showed that the negligibly small ion release from the chromium oxide coated steel substrates is most likely due to a much lower defect density on the surface of the deposited coatings compared to the native oxide layer on the uncoated steel substrates. This opens up the opportunity for using chromium oxide surface coatings in hip, knee and other orthopaedic implants where possible metal ion release in vivo still poses a great challenge.

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

    NASA Astrophysics Data System (ADS)

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

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

  17. Evaluation of Nickel and Chromium Ion Release During Fixed Orthodontic Treatment Using Inductively Coupled Plasma-Mass Spectrometer: An In Vivo Study

    PubMed Central

    Nayak, Rabindra S; Khanna, Bharti; Pasha, Azam; Vinay, K; Narayan, Anjali; Chaitra, K

    2015-01-01

    Background: Fixed orthodontic appliances with the use of stainless steel brackets and archwires made of nitinol have a corrosive potential in the oral environment. Nickel and chromium ions released from these appliances act as allergens apart from being cytotoxic, mutagenic and carcinogenic in smaller quantities in the range of nanograms. This study was done to evaluate the release of nickel and chromium ions from orthodontic appliances in the oral cavity using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Materials and Methods: Saliva samples from 30 orthodontic patients undergoing treatment with 0.022″ MBT mechanotherapy were collected prior to commencement of treatment, after initial aligning wires and after 10-12 months of treatment. Salivary nickel and chromium ion concentration was measured in parts per billion (ppb) using ICP-MS. Results: Mean, standard deviation and range were computed for the concentrations of ions obtained. Results analyzed using ANOVA indicated a statistically significant increase of 10.35 ppb in nickel ion concentration and 33.53 ppb in chromium ion concentration after initial alignment. The ionic concentration at the end of 10-12 months of treatment showed a statistically significant increase in of 17.92 ppb for chromium and a statistically insignificant decrease in nickel ion concentration by 1.58 ppb. Pearson’s correlation coefficient showed a positive correlation for an increase in nickel concentration after aligning, but not at the end of 10-12 months. A positive correlation was seen for an increase in chromium ion concentration at both time intervals. Conclusion: Nickel and chromium ion concentration in saliva even though below the recommended daily allowance should not be ignored in light of the new knowledge regarding effects of these ions at the molecular level and the allergic potential. Careful and detailed medical history of allergy is essential. Nickel free alternatives should form an essential part of an

  18. Chromium localization in plant tissues of Lycopersicum esculentum Mill using ICP-MS and ion microscopy (SIMS)

    NASA Astrophysics Data System (ADS)

    Mangabeira, Pedro Antonio; Gavrilov, Konstantin L.; Almeida, Alex-Alan Furtado de; Oliveira, Arno Heeren; Severo, Maria Isabel; Rosa, Tiago Santana; Silva, Delmira da Costa; Labejof, Lise; Escaig, Françoise; Levi-Setti, Riccardo; Mielke, Marcelo Schramm; Loustalot, Florence Grenier; Galle, Pierre

    2006-03-01

    High-resolution imaging secondary ion mass spectrometry (HRI-SIMS) in combination with inductively coupled plasma mass spectrometry (ICP-MS) were utilised to determine specific sites of chromium concentration in tomato plant tissues (roots, stems and leaves). The tissues were obtained from plants grown for 2 months in hydroponic conditions with Cr added in a form chromium salt (CrCl 3·6H 2O) to concentrations of 25 and 50 mg/L. The chemical fixation procedure used permit to localize only insoluble or strongly bound Cr components in tomato plant tissue. In this work no quantitative SIMS analysis was made. HRI-SIMS analysis revealed that the transport of chromium is restricted to the vascular system of roots, stems and leaves. No Cr was detected in epidermis, palisade parenchyma and spongy parenchyma cells of the leaves. The SIMS-300 spectra obtained from the tissues confirm the HRI-SIMS observations. The roots, and especially walls of xylem vessels, were determined as the principal site of chromium accumulation in tomato plants.

  19. Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples

    PubMed Central

    Liu, Xi; Xiang, Jun-Jian; Tang, Yong; Zhang, Xiao-Li; Fu, Qiang-Qiang; Zou, Jun-Hui; Lin, YueHe

    2012-01-01

    An immunochromatographic assay (ICA) using gold nanoparticles coated with monoclonal antibody (McAb) for the detection of chromium ions (Cr) in water and serum samples was developed, optimized and validated. Gold nanoparticles coated with affinity-purified monoclonal antibodies against isothiocyanobenzyl-EDTA (iEDTA)-chelated Cr3+ were used as the detecting reagent in this completive immunoassay-based one-step test strip. The ICA was investigated to measure chromium speciation (Cr3+ and Cr6+ ions) in water samples. Chromium standard samples of 0-80 ng/mL in water were determined by the test strips. The results showed that the visual lowest detection limit (LDL) of the test strip was 50.0 ng/mL. A portable colorimetric lateral flow reader was used for the quantification of Cr. The results indicated that the linear range of the ICA with colorimetric detection was 5-80 ng/mL. The ICA was also validated for the detection of chromium ions in serum samples. The test trips showed high stability in that they could be stored at 37°C for at least 12 weeks without significant loss of activity. The test strip also showed good selectivity for Cr detection with negligible interference from other heavy metals. Because of its low cost and short testing time (within 5 min), the test strip is especially suitable for on-site large-scale screening of Cr-polluted water samples, biomonitoring of Cr exposure, and many other field applications. PMID:22938612

  20. Removal of chromium ions from waste waters using reverse osmosis AG and SWHR membranes

    NASA Astrophysics Data System (ADS)

    Çimen, Aysel; Kılıçel, Fevzi; Arslan, Gülşin

    2014-05-01

    The aim of this work is to investigate removal of chromium from waste waters. The effect of pH and concentration of the feed water and operating pressure on the chromium rejection were also investigated. In the study; the reverse osmosis (RO) technique and the sea water high rejection (SWHR) and high rejection brackish water (AG) membrane were used for the separation process. Results of the study indicated that chromium rejection mostly depends on the membrane type, pH of the feed water and operating pressure. Also pH of the feed water was found to be 3 for the effective removal of chromium. Furthermore the rejection efficiency of the membranes was found to be in the order of AG > SWHR. For two membranes, chromium rejection increased with increasing operating pressure. Finally, waste water sample containing 7542 mg/L (with 100 mg/L) of chromium was treated by using RO technique with AG membrane. RO could be efficiently used (with >91% rejection) for the removal of chromium from waste water sample.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Chromium adsorption by lignin

    SciTech Connect

    Lalvani, S.B.; Huebner, A.; Wiltowski, T.S.

    2000-01-01

    Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the US Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.

  3. Chromium Grain-boundary Segregation and Effect of Ion Beam Cleaning on Fe-Ni-Cr Alloys

    SciTech Connect

    Saraf, Laxmikant V.

    2011-04-01

    The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Fe-Ni-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Fe-Ni-Cr is looked upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Fe-Ni-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Fe-Ni-Cr alloy.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Trivalent chromium electrolyte and process employing reducing agents

    SciTech Connect

    Tomaszewski, T.W.

    1984-10-16

    An aqueous acidic trivalent chromium electrolyte and process for electrodepositing chromium platings comprising an electrolyte containing trivalent chromium ions, a complexing agent, halide ions, ammonium ions and a reducing agent comprising an ion selected from the group consisting of scandium, yttrium, lanthanum, titanium, zirconium, hafnium, molybdenum, arsenic, selenium, tellurium, cerium, uranium, and tin present in an amount effective to maintain the concentration of hexavalent chromium ions formed in the bath at a level at which satisfactory chromium electrodeposits are obtained.

  6. Release of Chromium from Orthopaedic Arthroplasties

    PubMed Central

    Afolaranmi, G.A.; Tettey, J; Meek, R.M.D; Grant, M.H

    2008-01-01

    Many orthopaedic implants are composed of alloys containing chromium. Of particular relevance is the increasing number of Cobalt Chromium bearing arthroplasies being inserted into young patients with osteoarthritis. Such implants will release chromium ions. These patients will be exposed to the released chromium for over 50 years in some cases. The subsequent chromium ion metabolism and redistribution in fluid and tissue compartments is complex. In addition, the potential biological effects of chromium are also controversial, including DNA and chromosomal damage, reduction in CD8 lymphocyte levels and possible hypersensitivity reactions (ALVAL). The establishment of these issues and the measurement of chromium in biological fluids is the subject of this review. PMID:19461924

  7. Electrodialysis regeneration of chromium-containing solutions

    SciTech Connect

    Kizim, N.F.; Lar'kov, A.P.; Sharova, E.Yu.

    1987-10-10

    The authors describe a process based on a combination of electrodialysis and continuous ion exchange for the purification of chromium-containing waste water resulting from chromium plating processes and for the recovery and recycling of both the chromium and the water. Treatment and monitoring equipment is described and energy consumption scenarios are optimized for chromium removal efficiency.

  8. Binary iron-chromium oxide as negative electrode for lithium-ion micro-batteries - spectroscopic and microscopic characterization

    NASA Astrophysics Data System (ADS)

    Tian, Bingbing; Światowska, Jolanta; Maurice, Vincent; Zanna, Sandrine; Seyeux, Antoine; Marcus, Philippe

    2015-10-01

    (Fe,Cr)-binary oxide thin film electrodes were prepared as negative electrode material for lithium-ion micro-batteries by thermal growth on a stainless steel (AISI 410, FeCr12.5) current collector. The mechanisms of lithiation/delithiation were investigated by means of electrochemical (CV, galvanostatic cycling), spectroscopic (XPS, ToF-SIMS) and microscopic (SEM, AFM) analytical techniques. The as-prepared (Fe, Cr)-binary oxide electrodes exhibit a good cycling performance except the first discharge/charge cycle where a high irreversible capacity is observed due to formation of a solid electrolyte interphase (SEI) layer. The influence of substituting an oxidized iron by an oxidized chromium (CrxFe2-xO3 phase) was evaluated. The data show that the inferior electrochemical conversion activity of substituted oxidized chromium results in hindering lithium transport in the bulk thin film electrode. It was observed that the irreversible morphology modifications together with SEI evolution are critical to capacity degradation while retaining good coulombic efficiency.

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

    SciTech Connect

    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

    NASA Astrophysics Data System (ADS)

    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. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

  12. Ion-exchange resin for removing hexavalent chromium from ground water at treatment facility C: Data on removal capacity, regeneration efficiency, and operation

    SciTech Connect

    Bahowick, S.; Dobie, D.; Kumamoto, G.

    1996-12-31

    Lawrence Livermore National Laboratory (LLNL) is operated for the Department of Energy by the University of California. In July 1987, LLNL was placed on the National Priorities List based on the presence of volatile organic compounds (VOCs) in ground water. The July 1992 Record of Decision stipulates air stripping for treatment of VOCs and ion-exchange to treat chromium in the ground water for Treatment Facility C (TFC). TFC, which was activated in October 1993, was designed to treat influent ground water at 60 gpm with concentrations of hexavalent chromium averaging 30 ppb. The ion exchange system removes the hexavalent chromium to below its limit of detection (2 ppb). The resin used is a strongly basic Type I quaternary ammonium anion exchange resin with a styrene-divinylbenzene copolymer gel matrix. The total hexavalent chromium removed from the ground water as of October 8, 1995 was 660 grams. An initial operating capacity was achieved of 6.4 grams CrO{sub 4}{sup 2{minus}} removal per ft{sup 3} of resin, but this was observed to vary over the next two years. Variation was observed in the rate of breakthrough. The regeneration process was optimized to minimize waste produced and maximize regeneration of the resin. Elevated levels of chloride, sulfate, nitrate, potassium 40 and uranium have been observed in the regeneration waste. Because of the potassium and uranium content, the regenerated waste had to be disposed of as mixed waste.

  13. Lithium chromium pyrophosphate as an insertion material for Li-ion batteries.

    PubMed

    Reichardt, Martin; Sallard, Sébastien; Novák, Petr; Villevieille, Claire

    2015-12-01

    Lithium chromium pyrophosphate (LiCrP2O7) and carbon-coated LiCrP2O7 (LiCrP2O7/C) were synthesized by solid-state and sol-gel routes, respectively. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and conductivity measurements. LiCrP2O7 powder has a conductivity of ~ 10(-8) S cm(-1), ~ 10(4) times smaller than LiCrP2O7/C (~ 10(-4) S cm(-1)). LiCrP2O7/C is electrochemically active, mainly between 1.8 and 2.2 V versus Li(+)/Li (Cr(3+)/Cr(2+) redox couple), whereas LiCrP2O7 has limited electrochemical activity. LiCrP2O7/C delivers a reversible specific charge up to ~ 105 mAh g(-1) after 100 cycles, close to the theoretical limit of 115 mAh g(-1). Operando XRD experiments show slight peak shifts between 2.2 and 4.8 V versus Li(+)/Li, and a reversible amorphization between 1.8 and 2.2 V versus Li(+)/Li, suggesting an insertion reaction mechanism. PMID:26634722

  14. Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells.

    PubMed

    Amuda, O S; Adelowo, F E; Ologunde, M O

    2009-02-01

    A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63mgCr(VI)/g at initial pH of 3.0 at 30 degrees C for the particle size of 1.00-1.25mm with the use of 12.5, 16.5 and 2.1g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater. PMID:19022632

  15. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    Major accomplishments under NASA grant NAG-1-1346 are summarized. (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed and several design parameters to be used for the construction of a femtosecond forsterite laser were revealed by simulation. (2) femtosecond pulses from a continuous wave mode-locked chromium doped forsterite laser were generated. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured. (3) Self-mode-locked operation of the Cr:forsterite laser was achieved. Synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking. The pulses generated had an FWHM of 105 fs and were tunable between 1230-1270 nm. (4) Numerical calculations indicated that the pair of SF 14 prisms used in the cavity compensated for quadratic phase but introduced a large cubic phase term. Further calculations of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same amount of quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was observed in the stability of the self mode-locked forsterite laser and in the ease of achieving mode locking. Using the same experimental arrangement and a new forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

  16. Frictional and structural characterization of ion-nitrided low and high chromium steels

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1985-01-01

    Low Cr steels AISI 41410, AISI 4340, and high Cr austenitic stainless steels AISI 304, AISI 316 were ion nitrided in a dc glow discharge plasma consisting of a 75 percent H2 - 25 percent N2 mixture. Surface compound layer phases were identified, and compound layer microhardness and diffusion zone microhardness profiles were established. Distinct differences in surface compound layer hardness and diffusion zone profiles were determined between the low and high Cr alloy steels. The high Cr stainless steels after ion nitriding displayed a hard compound layer and an abrupt diffusion zone. The compound layers of the high Cr stainless steels had a columnar structure which accounts for brittleness when layers are exposed to contact stresses. The ion nitrided surfaces of high and low Cr steels displayed a low coefficient of friction with respect to the untreated surfaces when examined in a pin and disk tribotester.

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

    PubMed

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

    2016-07-15

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

  18. Removal of chromium hexavalent ion from aqueous solutions using biopolymer chitosan coated with poly 3-methyl thiophene polymer.

    PubMed

    Hena, Sufia

    2010-09-15

    Adsorption capacity of Cr(VI) onto chitosan coated with poly 3-methyl thiophene synthesized chemically was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees), standard enthalpy (DeltaH degrees) and standard entropy (DeltaS degrees) were evaluated. Adsorption kinetics of Cr(VI) ions onto chitosan coated with poly 3-methyl thiophene were analyzed by pseudo-first-order and pseudo-second-order models. The Langmuir, Freundlich and Temkin isotherms were used to describe the adsorption equilibrium studies of chitosan coated with poly 3-methyl thiophene at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherms in the temperature range studied. The results show that the chitosan coated with poly 3-methyl thiophene can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported. In order to find out the possibility of regeneration and reuse of exhausted adsorbent, desorption studies were also performed. PMID:20627405

  19. Reaction between Chromium(III) and EDTA Ions: an Overlooked Mechanism of Case Study Reaction of Chemical Kinetics.

    PubMed

    Cerar, Janez

    2015-01-01

    Widely cited and accepted explanation of reaction mechanism of the case study reaction of chemical kinetics between Cr(III) ions and ethylenediaminetetraacetic acid (EDTA) contradicts modern chromium(III) coordination chemistry data. Absorption UV and visible light spectra were recorded during the reaction between aqueous solution of Cr(NO(3))(3) and EDTA in order to obtain new information about this reaction. Analysis of the spectra showed that only very small fraction of intermediates may be present in solution during the course of the reaction. The reaction scheme was established and according to it calculations based on a simplified model were carried out. Literature data for constants were used if known, otherwise, adjusted values of their sound estimates were applied. Reasonable agreement of the model calculations with the experimental data was obtained for pH values 3.8 and 4.5 but the model failed to reproduce measured rate of reaction at pH 5.5, probably due to the use of the oversimplified model. PMID:26454587

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

    PubMed

    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. Evaluation of effect of galvanic corrosion between nickel-chromium metal and titanium on ion release and cell toxicity

    PubMed Central

    Choi, Jung-Yun

    2015-01-01

    PURPOSE The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens (10×10×1.5 mm) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing

  2. Application of dolochar in the removal of cadmium and hexavalent chromium ions from aqueous solutions.

    PubMed

    Panda, L; Das, B; Rao, D S; Mishra, B K

    2011-08-30

    Dolochar, a waste material generated in sponge iron industry, is processed and put to test as an adsorbent for removal of Cd(II) and Cr(VI) ions from aqueous solutions. The dolochar samples were characterised to determine the different phases and their distribution by reflection microscopy. The analysis indicated that the sample consists of metallic iron, fused carbon, and Ca-Mg bearing phases (Ca-Mg-silicate-oxide) along with lots of voids and pores. The fixed carbon (FC) content of the material is 13.8% with a Langmuir surface area of 81.6m(2)/g and micropore area of 34.1m(2)/g. Batch adsorption experiments have been conducted to study the sorption behaviour of Cd(II) and Cr(VI) ions on dolochar as a function of particle size, contact time, adsorbent dosages, pH and temperature. It is observed that higher pH and temperature enhances sorption of Cd(II) ions. In contrast, the adsorption for Cr(VI) is found to be better in acidic pH in comparison to alkaline media. The equilibrium adsorption isotherm data are tested by applying both Langmuir and Freundlich isotherm models. It is observed that Langmuir isotherm model fitted better compared to the Freundlich model indicating monolayer adsorption. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° indicate the effectiveness of dolochar to remove Cd(II) and Cr(VI) ions from aqueous solution. The kinetics of adsorption is found to better fit to pseudo second order reaction. PMID:21723036

  3. Ion-exchanger colorimetry-I Micro determination of chromium, iron, copper and cobalt in water.

    PubMed

    Yoshimura, K; Waki, H; Ohashi, S

    1976-06-01

    A new sensitive, colorimetric method based on the direct measurement of light-absorption by an ion-exchange resin phase, which has sorbed the sample complex species, has been developed. Determinations ofchromium(VI) with diphenylearbazide, iron(II) with 1,10-phenanthroline, copper with Zincon and cobalt with thiocyanate have more than ten times the sensitivity obtainable with conventional solution colorimetry. The present method can be applied to natural water samples containing very low levels of these metals. PMID:18961894

  4. Coated wire chromium(III) ion-selective electrode based on azamacrocycles.

    PubMed

    Sil, Aparna; Ijeri, Vijaykumar S; Srivastava, Ashwini K

    2004-03-01

    Tetraazacyclotetradecane, tetratosyltetraaza 12C4, and tritosyltriaza 9C3 have been explored as electroactive materials for preparing coated wire ion-selective electrodes (CWISEs) for Cr(III) ions. The best performance was observed for the membrane comprising electroactive material (tetratosyltetraaza 12C4), plasticizer (dibutyl phthalate), and poly(vinyl chloride) in the optimum ratio 5:60:35 (w/w). Linear Nernstian response for this electrode was obtained over the total Cr(III) concentration range of 1 x 10(-1) to 1 x 10(-7) M in 0.05 M NH4NO3 medium, with a slope of 20 +/- 1 mV per decade change. The working pH range of the electrode was 1.8-5.5. Selectivity coefficients of some mono, divalent, and trivalent metal ions were determined. Analyses of electroplating bath solutions, chromating, and effluent samples have been carried out using this CWISE and the results are found to be comparable with those obtained by using conventional methods or by AAS. PMID:15214433

  5. In situ ATR-FTIR spectroscopic study of adsorption of perchlorate, sulfate, and thiosulfate ions onto chromium(III) oxide hydroxide thin films

    SciTech Connect

    Degenhardt, J.; McQuillan, A.J.

    1999-06-22

    A thin chromium oxide hydroxide colloid film has been used as a model of the passive stainless steel surface for studies of anion adsorption from aqueous solutions. The adsorption of perchlorate, sulfate, and thiosulfate ions has been investigated by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Surface charge was monitored from the surface excess concentrations of tetramethylammonium ions and of perchlorate ions using the infrared spectroscopic STIRS technique. The colloid film showed a high positive charge at low pH and a low negative charge at high pH. The adsorption of sulfate was only observed for a positive surface charge. The infrared spectrum of adsorbed sulfate coordination to surface Cr(III) ions. Thiosulfate gave adsorption behavior analogous to sulfate. Adsorption isotherms for sulfate and for thiosulfate were determined from infrared spectral data, and Langmuir binding constants of (2.3 {plus{underscore}minus} 0.4) x 10{sup 5} and (1.4 {plus{underscore}minus} 0.4) x 10{sup 5} M{sup {minus}1} were obtained for the respective adsorbates. The lack of chemical binding of sulfate and of thiosulfate to the chromium oxide hydroxide surface may be part of the basis for the corrosion-promoting properties of these ions at stainless steel surfaces.

  6. Hollow tin/chromium whiskers

    NASA Astrophysics Data System (ADS)

    Cheng, Jing; Vianco, Paul T.; Li, James C. M.

    2010-05-01

    Tin whiskers have been an engineering challenge for over five decades. The mechanism has not been agreed upon thus far. This experiment aimed to identify a mechanism by applying compressive stresses to a tin film evaporated on silicon substrate with an adhesion layer of chromium in between. A phenomenon was observed in which hollow whiskers grew inside depleted areas. Using focused ion beam, the hollow whiskers were found to contain both tin and chromium. At the bottom of the depleted areas, thin tin/tin oxide film remained over the chromium layer. It indicates that tin transport occurred along the interface between tin and chromium layers.

  7. Laser action in chromium-activated forsterite for near-infrared excitation: Is Cr/sup 4 +/ the lasing ion

    SciTech Connect

    Petricevic, V.; Gayen, S.K.; Alfano, R.R.

    1988-12-26

    Room-temperature pulsed laser action has been obtained in chromium-activated forsterite (Cr:Mg/sub 2/SiO/sub 4/) for excitation of the near-infrared absorption band of the system by the 1064 nm radiation from a Nd:YAG laser. The characteristics of laser emission are similar to those observed for 532 nm pumping. It is suggested that the laser action is due to a ''center'' other than the trivalent chromium (Cr/sup 3 +/), presumably the tetravalent chromium (Cr/sup 4 +/).

  8. Atom probe field ion microscopy investigation of boron containing martensitic 9 Pct chromium steel

    NASA Astrophysics Data System (ADS)

    Hofer, P.; Miller, M. K.; Babu, S. S.; David, S. A.; Cerjak, H.

    2000-03-01

    The chemical compositions of the ferrite matrix and various other phases in an Fe-0.17 C-9 Cr-1.55 Mo-0.27 V-0.015 N-0.01B (mass pct) steel in as-received and crept conditions were measured with atom probe field ion microscopy (APFIM). The results showed the presence of some residual boron within the ferrite matrix. Analyses showed that boron was distributed within M23C6, M6C, MX, and Laves phases. Phosphor atoms were detected at the M23C6-ferrite interface in the crept condition. The results are compared to predictions from thermodynamic calculations.

  9. Mechanism of oxidation of alkyl and superoxo complexes of chromium (III) by aquamanganese(III) ions

    SciTech Connect

    Jee, Joo-Eun; Pestovsky, Oleg; Hidayat, Irene; Szajna-Fuller; Bakac, Andreja

    2010-07-01

    The reaction between aqueous manganese(III) ions, Mn(H{sub 2}O){sub 6}{sup 3+}, and (H{sub 2}O){sub 5}CrOO{sup 2+} has a 1:1 stoichiometry and generates Cr(H{sub 2}O){sub 6}{sup 3+} and O{sub 2} as products. The mixed second-order rate constant exhibits an [H{sup +}] dependence that identifies the hexaaquamanganese ion as the reactive form at 0.5 {le} [H{sup +}] {le} 3.0 mol L{sup -1}, k{sub H} = 350 {+-} 10 (mol L{sup -1}){sup -1} s{sup -1}. The reactivity of (H{sub 2}O)5MnOH{sup 2+} is negligible under these conditions, most likely because the much lower reduction potential of this hydrolytic form results in unfavorable thermodynamics for the overall reaction. Mn(H{sub 2}O){sub 6}{sup 3+} also oxidizes a benzylchromium ion, (H{sub 2}O)5CrCH{sub 2}Ph{sup 2+}, with a rate constant k = 273 {+-} 13 (mol L{sup -1}){sup -1} s{sup -1} in 3.0 mol L{sup -1} HClO{sub 4}. The reaction has a 2:1 [Mn(H{sub 2}O){sub 6}{sup 3+}]/[(H{sub 2}O){sub 5}CrCH{sub 2}Ph{sup 2+}] stoichiometry and generates benzyl alcohol as the sole organic product. The data are consistent with oxidative homolysis which generates benzyl radicals followed by rapid oxidation of the radicals with the second equivalent of Mn(H{sub 2}O){sub 6}{sup 3+}. The unexpected similarity between the rate constants for the Mn(H{sub 2}O){sub 6}{sup 3+} oxidation of (H{sub 2}O){sub 5}CrOO{sup 2+} and (H{sub 2}O){sub 5}CrCH{sub 2}Ph{sup 2+} is discussed.

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

    USGS Publications Warehouse

    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.

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

    PubMed

    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

  12. Inhibitory and stimulating effect of single and multi-metal ions on hexavalent chromium reduction by Acinetobacter sp. Cr-B2.

    PubMed

    Hora, Anuradha; Shetty K, Vidya

    2014-12-01

    Potential application of chromium reducing bacteria for industrial scale wastewater treatment demands that effect of presence of other metal ions on rate of Cr(VI) reduction be investigated, as industrial wastewaters contain many toxic metal ions. In the current study, the effect of different heavy metal ions (nickel, zinc, cadmium, copper, lead, iron) on chromium reduction by a novel strain of Acinetobacter sp. Cr-B2 that shows high tolerance up to 1,100 mg/L and high Cr(VI) reducing capacity was investigated. The alteration in Cr(VI) reduction capacity of Cr-B2 was studied both in presence of individual metal ions and in the presence of multi-metal ions at different concentrations. The study showed that the Cr(VI) reduction rates decreased in presence of Ni(2+), Zn(2+) and Cd(2+) when present individually. Pb(2+) at lower concentration did not show significant effect while Cu(2+) and Fe(3+) stimulated the rate of Cr(VI) reduction. In the studies on multi-metal ions, it was observed that in presence of Cu(2+) and Fe(3+), the inhibiting effect of Ni(2+), Zn(2+), Cd(2+) and Pb(2+) on Cr(VI) reduction was reduced. Each of these metals affect the overall rate of Cr(VI) reduction by Cr-B2. This work highlights the need to consider the presence of other heavy metal ions in wastewater when assessing the bioreduction of Cr(VI) and while designing the bioreactors for the purpose, as rate of reduction is altered by their presence. PMID:25292151

  13. Ion-Molecule Reaction of Gas-Phase Chromium Oxyanions: CrxOyHz- + H2O

    SciTech Connect

    Gianotto, Anita Kay; Hodges, Brittany DM; Benson, Michael Timothy; Harrington, Peter Boves; Appelhans, Anthony David; Olson, John Eric; Groenewold, Gary Steven

    2003-08-01

    Chromium oxyanions having the general formula CrxOyHz- play a key role in many industrial, environmental, and analytical processes, which motivated investigations of their intrinsic reactivity. Reactions with water are perhaps the most significant, and were studied by generating CrxOyHz- in the gas phase using a quadrupole ion trap secondary ion mass spectrometer. Of the ions in the Cr1OyHz envelope (y = 2, 3, 4; z = 0, 1), only CrO2- was observed to react with H2O, producing the hydrated CrO3H2- at a slow rate (~0.07% of the ion-molecule collision constant at 310 K). CrO3-, CrO4-, and CrO4H- were unreactive. In contrast, Cr2O4-, Cr2O5-, and Cr2O5H2- displayed a considerable tendency to react with H2O. Cr2O4- underwent sequential reactions with H2O, initially producing Cr2O5H2- at a rate that was ~7% efficient. Cr2O5H2- then reacted with a second H2O by addition to form Cr2O6H4- (1.8% efficient) and by OH abstraction to form Cr2O6H3- (0.6% efficient). The reactions of Cr2O5- were similar to those of Cr2O5H2-: Cr2O5- underwent addition to form Cr2O6H2- (3% efficient) and OH abstraction to form Cr2O6H- (<1% efficient). By comparison, Cr2O6- was unreactive with H2O, and in fact, no further H2O addition could be observed for any of the Cr2O6Hz- anions. Hartree-Fock ab initio calculations showed that reactive CrxOyHz- species underwent nucleophilic attack by the incoming H2O molecules, which produced an initially formed adduct in which the water O was bound to a Cr center. The experimental and computational studies suggested that Cr2OyHz- species that have bi- or tricoordinated Cr centers are susceptible to attack by H2O; however, when the metal becomes tetracoordinate, reactivity stops. For the Cr2OyHz- anions the lowest energy structures all contained rhombic Cr2O2 rings with pendant O atoms and/or OH groups. The initially formed [Cr2Oy- + H2O] adducts underwent H rearrangement to a gem O atom to produce stable dihydroxy structures. The calculations indicated that

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Luminescence from chromium-neodymium-doped lithium niobate

    NASA Astrophysics Data System (ADS)

    Mahpoud, S.; Chamiel, N.; Weiss, A. M.; Rosenbluh, M.; Herman, A.; Shoham, A.; Lipavsky, B.; Rotman, S. R.

    1999-10-01

    Luminescence from chromium-neodymium-doped lithium niobate (LiNbO 3) was experimentally measured to determine the degree of non-radiative energy transfer between chromium and neodymium ions. Evidence is presented for two different time constants for emission from chromium ions in the material, indicating that non-radiative transfer does occur. Differences between quasi-continuous pumping and pulsed excitation are discussed.

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

    PubMed

    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

  18. EPR study of chromium-doped forsterite crystals: Cr3+( M1) with associated trivalent ions Al3+ and Sc3+

    NASA Astrophysics Data System (ADS)

    Ryabov, I. D.

    2012-10-01

    Electron paramagnetic resonance (EPR) study of single crystals of forsterite co-doped with chromium and scandium has revealed, apart from the known paramagnetic centers Cr3+( M1) and Cr3+( M1)- V_{{{{Mg}}^{2 + } }} ( M2) (Ryabov in Phys Chem Miner 38:177-184, 2011), a new center Cr3+( M1)- V_{{{{Mg}}^{2 + } }} ( M2)-Sc3+ formed by a Cr3+ ion substituting for Mg2+ at the M1 structural position with a nearest-neighbor Mg2+ vacancy at the M2 position and a Sc3+ ion presumably at the nearest-neighbor M1 position. For this center, the conventional zero-field splitting parameters D and E and the principal g values have been determined as follows: D = 33,172(29) MHz, E = 8,482(13) MHz, g = [1.9808(2), 1.9778(2), 1.9739(2)]. The center has been compared with the known ion pair Cr3+( M1)-Al3+ (Bershov et al. in Phys Chem Miner 9:95-101, 1983), for which the refined EPR data have been obtained. Based on these data, the known sharp M1″ line at 13,967 cm-1 (with the splitting of 1.8 cm-1), observed in low-temperature luminescence spectra of chromium-doped forsterite crystals (Glynn et al. in J Lumin 48, 49:541-544, 1991), has been ascribed to the Cr3+( M1)-Al3+ center. It has been found that the concentration of the new center increases from 0 up to 4.4 × 1015 mg-1, whereas that of the Cr3+( M1) and Cr3+( M1)- V_{{{{Mg}}^{2 + } }} ( M2) centers quickly decreases from 7.4 × 1015 mg-1 down to 3 × 1015 mg-1 and from 2.7 × 1015 mg-1 down to 0.5 × 1015 mg-1, i.e., by a factor of 2.5 and 5.4, respectively, with an increase of the Sc content from 0 up to 0.22 wt % (at the same Cr content 0.25 wt %) in the melt. When the Sc content exceeds that of Cr, the concentration of the new center decreases most likely due to the formation of the Sc3+( M1)- V_{{{{Mg}}^{2 + } }} ( M2)-Sc3+ complex instead of the Cr3+( M1)- V_{{{{Mg}}^{2 + } }} ( M2)-Sc3+ center. The formation of such ordered neutral complex is in agreement with the experimental results, concerning the incorporation of Sc

  19. Sensitized spectrophotometric determination of Cr(III) ion for speciation of chromium ion in surfactant media using α-benzoin oxime

    NASA Astrophysics Data System (ADS)

    Ghaedi, Mehrorang; Asadpour, Enayat; Vafaie, Azam

    2006-01-01

    A simple and accurate micellanized spectrophotometric method for determination of trace amounts of Cr(III) ion in tab and top water and a synthetic mixture has been described. The micellar method is based on effect of organized molecular assemblies such as micelles in spectrophotometric measurement due to their effect on the systems of interest. The ability of micellar system in solubilizing of sparingly soluble ligand or complexes has been used for increasing figures of merit of an analytical method. Due to solubility increasing in aqueous media requirement for a primary extraction can be eliminated. Using the α-benzoin oxime (α-BO) spectrophotometric determination of Cr(III) ion has been performed and results are compared. The spectrophotometric determination of Cr(III) ion using α-BO in the presence of non-ionic surfactant Triton X-100 has been performed. The influence of type and amount of surfactant, pH, complexation time and amount of ligand were examined. Finally, the repeatability, accuracy and the effect of interfering ions on the determination of Cr(III) ion was evaluated. The proposed methods successfully with recovery yield of almost 100% have been applied to the rapid and simple determination of Cr(III) ion in the real samples. There is a good agreement between methods and atomic absorption spectrometry. The Beers law is obeyed over the concentration range of 0.1-13.7 μg mL-1 for micellar media. The detection limit is 0.8 ng mL-1. The molar absorptivity of complex is 5350 L mol-1 cm-1.

  20. Sensitized spectrophotometric determination of Cr(III) ion for speciation of chromium ion in surfactant media using alpha-benzoin oxime.

    PubMed

    Ghaedi, Mehrorang; Asadpour, Enayat; Vafaie, Azam

    2006-01-01

    A simple and accurate micellanized spectrophotometric method for determination of trace amounts of Cr(III) ion in tab and top water and a synthetic mixture has been described. The micellar method is based on effect of organized molecular assemblies such as micelles in spectrophotometric measurement due to their effect on the systems of interest. The ability of micellar system in solubilizing of sparingly soluble ligand or complexes has been used for increasing figures of merit of an analytical method. Due to solubility increasing in aqueous media requirement for a primary extraction can be eliminated. Using the alpha-benzoin oxime (alpha-BO) spectrophotometric determination of Cr(III) ion has been performed and results are compared. The spectrophotometric determination of Cr(III) ion using alpha-BO in the presence of non-ionic surfactant Triton X-100 has been performed. The influence of type and amount of surfactant, pH, complexation time and amount of ligand were examined. Finally, the repeatability, accuracy and the effect of interfering ions on the determination of Cr(III) ion was evaluated. The proposed methods successfully with recovery yield of almost 100% have been applied to the rapid and simple determination of Cr(III) ion in the real samples. There is a good agreement between methods and atomic absorption spectrometry. The Beers law is obeyed over the concentration range of 0.1-13.7 microg mL(-1) for micellar media. The detection limit is 0.8 ng mL(-1). The molar absorptivity of complex is 5350 L mol(-1) cm(-1). PMID:16344251

  1. Chromium toxicity tolerance of Solanum nigrum L. and Parthenium hysterophorus L. plants with reference to ion pattern, antioxidation activity and root exudation.

    PubMed

    UdDin, Islam; Bano, Asghari; Masood, Sajid

    2015-03-01

    Chromium (Cr), being a highly toxic metal, adversely affects the mineral uptake and metabolic processes in plants when present in excess. The current study was aimed at investigating the Cr accumulation in various plant tissues and its relation to the antioxidation activity and root exudation. Plants were grown in soil spiked with different concentrations of Cr for three weeks in pots and analysed for different growth, antioxidants and ion attributes. Furthermore, plants treated with different concentrations of Cr in pots were shifted to rhizobox-like system for 48h and organic acids were monitored in the mucilage dissolved from the plant root surface, mirroring rhizospheric solution. The results revealed that the Cr application at 1mM increased the shoot fresh and dry weight and root dry weight of Solanum nigrum, whereas the opposite was observed for Parthenium hysterophorus when compared with lower levels of Cr (0.5mM) or control treatment. In both plant species, Cr and Cl concentrations were increased while Ca, Mg and K concentrations in root, shoot and root exudates were decreased with increasing levels of Cr. Higher levels of Cr treatments enhanced the activities of SOD, POD and proline content in leaves of S. nigrum, whereas lower levels of Cr treatment were found to have stimulatory effects in P. hysterophorus. P. hysterophorus exhibited highest exudation of organic acid contents. With increasing levels of Cr treatments, citric acid concentration in root exudates increased by 35% and 44% in S. nigrum, whereas 20% and 76% in P. hysterophorus. Cr toxicity was responsible for the shoot growth reduction of S. nigrum and P. hysterophorus, however, shoot growth response was different at different levels of applied Cr. Consequently, Cr stress negatively altered the plant physiology and biochemistry. However, the enhanced antioxidant production, Cl uptake and root exudation are the physiological and biochemical indicators for the plant adaptations in biotic systems

  2. Hexavalent Chromium Workshop

    EPA Science Inventory

    EPA is developing an updated IRIS assessment of hexavalent chromium. This assessment will evaluate the potential health effects of hexavalent chromium from oral and inhalation exposures. An important component of determining the cancer causing potential of ingested hexavalent chr...

  3. Chromium and Genomic Stability

    PubMed Central

    Wise, Sandra S.; Wise, John Pierce

    2014-01-01

    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 highly toxic and carcinogenic with no nutritional value. Recent data indicate that it causes genomic instability and also has no role in promoting genomic stability. PMID:22192535

  4. Chromium in diet

    MedlinePlus

    ... and carbohydrates . It stimulates fatty acid and cholesterol synthesis, which are important for brain function and other body processes. Chromium also aids in insulin action and glucose metabolism.

  5. Sodium sulfur container with chromium/chromium oxide coating

    DOEpatents

    Ludwig, Frank A.; Higley, Lin R.

    1981-01-01

    A coating of chromium/chromium oxide is disclosed for coating the surfaces of electrically conducting components of a sodium sulfur battery. This chromium/chromium oxide coating is placed on the surfaces of the electrically conducting components of the battery which are in contact with molten polysulfide and sulfur reactants during battery operation.

  6. Physicochemical state of cobalt and chromium in natural waters of the arid zone of the USSR

    SciTech Connect

    Isamatov, E.E.; Kist, A.A.; Kulmatov, R.A.; Volkov, A.A.; Rakhmatov, U.

    1988-01-01

    The authors discuss results of a comprehensive study of the environmental and chemical behavior of trace amounts of cobalt and chromium ions and compounds in waters of the Aral Sea and Amu Darya and Syr Darya rivers in the Soviet Union. The methods used in the determinations include thermodynamic assessments of the ionic composition of the waters and a direct determination of the cobalt and chromium compounds using neutron activation analysis and isotopic and ion exchange analysis for chromium 51 and cobalt 60.

  7. Dermatological toxicity of hexavalent chromium.

    PubMed

    Shelnutt, Susan R; Goad, Phillip; Belsito, Donald V

    2007-06-01

    Hexavalent chromium causes two types of dermatological toxicities: allergic contact dermatitis (ACD) and skin ulcers. This report reviews the etiology, prevalence, pathology, dose-response, and prognosis of both of these reactions. Reports in the literature indicate that repeated exposure to hexavalent chromium in concentrations of 4-25 ppm can both induce sensitization and elicit chromium ACD. Exposure to 20 ppm hexavalent chromium can cause skin ulcers in nonsensitized people. The prevalence of chromium sensitivity in cement workers, exposed to 10-20 ppm hexavalent chromium for years, is approximately 4-5%. Chromium ACD can be a chronic debilitating disease, perhaps because chromium is ubiquitous in foods and in the environment and is difficult to avoid. Due to the high rates of sensitization in populations chronically exposed to chromium and the chronic nature of chromium ACD, some investigators recommend reducing the hexavalent chromiumconcentrations in consumer products, such as detergents, to less than 5 ppm. PMID:17612952

  8. Kinetic and mechanism of the oxidation of chromium(III) complex with anthranil- N, N-diacetic acid by periodate ion in acidic aqueous solutions

    NASA Astrophysics Data System (ADS)

    Ali, Ismat H.

    2015-06-01

    The kinetics of oxidation of [CrIII(atda)(H2O)2] (atda = anthranil- N, N-diacetato) complex by IO{4/-} was studied spectrophotometrically in aqueous solutions with pH range 2.20-3.34, 0.30 M ionic strength and in 20.0-40.0°C temperature range. The rate law of the reaction exhibited saturation kinetics. Values of the rate constant for the electron transfer process, the equilibrium constant for dissociation of [CrIII (atda)(H2O)2] to [CrIII (atda) (H2O)OH]+ + H+ and the pre-equilibrium formation constant were calculated. The thermodynamic activation parameters are reported. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of the IVII to chromium(III).

  9. Electrodeposition of amorphous ternary nickel-chromium-phosphorus alloy

    DOEpatents

    Guilinger, Terry R.

    1990-01-01

    Amorphous ternary nickel-chromium-phosphorus alloys are electrodeposited from a bath comprising a nickel salt, a chromium salt, a phosphorus source such as sodium hypophosphite, a complexing agent for the nickel ions, supporting salts to increase conductivity, and a buffering agent. The process is carried out at about room temperature and requires a current density between about 20 to 40 A/dm.sup.2.

  10. Quantum-mechanical study of state and structure of diphenylcarbazide and its reaction with chromium

    SciTech Connect

    Golobitskii, G.B.; Gen; L.I.; Ivanov, V.M.

    1985-04-01

    The detection and determination of chromium in chromium-containing wastewaters is very important in practice due to the application of chromium on an industrial scale. A quantitative determination of chromium is also important from the ecological point of view, since chromium (VI) compounds are carcinogenic. This paper studies the state of the reagent diphenylcarbazide (DPC) and its oxidation products in different media, the structure of DPC, and its reaction with chromium ions in an acidic medium by a combination of quantum-mechanical and spectrophotometric methods. It is shown that in weakly acidic or neutral media, DPC exists preferentially in a keto form. Free-valence indexes were calculated to explain the high reactivity of DPC and ease of conversion into diphenylcarbonzone (DPCone) in an alkaline medium. A structure of the complex of chromium (III) with DPCone was proposed and it was shown that the ligands in the complex are present in both keto and enol forms, the latter form predominating.

  11. Corrosion behavior of chromium in molten carbonate

    SciTech Connect

    Vossen, J.P.T.; Makkus, R.C.; Wit, J.H.W. de

    1996-01-01

    The corrosion behavior of Cr in molten carbonate was investigated with electrochemical techniques in combination with quenching after polarization at fixed potentials. Between {minus}1,700 and {minus}1,500 mV carbon deposition takes place on the surface. The stationary corrosion product formed on Cr after polarization at {minus}1,700 mV is probably chromium carbide. Between {minus}1,600 and {minus}300 mV a LiCrO{sub 2}-layer is present on the surface of the Cr. At potentials above approximately {minus}500 mV chromate formation and dissolution take place. When the potential increases, the oxidation rate of the Cr increases due to the larger driving force for oxidation. In the potential region where oxygen vacancies are filled and bivalent chromium ions are oxidized, the conductivity of the scale decreases and the oxidation rate is determined by the transport properties of the scale: the passive properties of the LiCrO{sub 2}-scale have improved. In the anodic scan of a cyclic voltammogram two peaks can be observed, corresponding with the oxidation of point defects, and the formation of instable intermediate chromium oxide. These reactions are accompanied by the formation of lithium chromite. While scanning cathodically, first chromate ions are reduced. At very cathodic potentials trivalent Cr ions are reduced to bivalent Cr ions and point defects, which are incorporated in the LiCrO{sub 2}-lattice, and water is reduced. These reactions may be accompanied by the reduction of the instable chromium oxide formed during the preceding anodic scan. Near {minus}1,700 mV carbonate decomposes, lithium chromite is reduced and possibly carbide formation also takes place.

  12. The analytical biochemistry of chromium.

    PubMed Central

    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 matrices while preserving its oxidation state. Typical recoveries are 90 to 105% in samples spiked with both trivalent and hexavalent chromium. Determination of hexavalent chromium after extraction with sodium carbonate-sodium hydroxide solution, coupled with the determination of total chromium after nitric acid-hydrogen peroxide digestion, has been applied to the evaluation of chromium speciation in airborne particulates, sludges, and biological tissues. PMID:1935842

  13. Mineral of the month: chromium

    USGS Publications Warehouse

    Papp, John F.

    2005-01-01

    Chromium is one of the most indispensable industrial metals and it plays an essential but hidden role in daily life. Chromium is used in many consumer and building products, and it contributes to a clean, efficient and healthy environment.

  14. Co(II)-mediated effects of plain and plasma immersion ion implanted cobalt-chromium alloys on the osteogenic differentiation of human mesenchymal stem cells.

    PubMed

    Schröck, Kathleen; Lutz, Johanna; Mändl, Stephan; Hacker, Michael C; Kamprad, Manja; Schulz-Siegmund, Michaela

    2015-03-01

    Medical CoCr is one of the main alloys used for metal-on-metal prosthesis in patients with total hip arthroplasty. CoCr surfaces modified by nitrogen plasma immersion ion implantation (PIII) are characterized by improved wear resistance but also showed increased Co(II) ion release under in vitro conditions. For the first time, CoCr modified by nitrogen PIII was evaluated with regard to its effect on the osteogenic differentiation of MSC. The activity of alkaline phosphatase, the expression of the osteogenic genes Runt-related transcription factor 2, osteopontin as well as integrin-binding bone sialoprotein and the production of osteocalcin and hydroxyapatite were determined. The results of our study demonstrate that Co(II) ions released from the alloy affected the osteogenic differentiation of MSC. Distinct differences in differentiation markers were found between pristine and modified alloys for osteocalcin but not for integrin-binding sialoprotein and hydroxyapatite. Interestingly, osteopontin was upregulated in naive and differentiated MSC by Co(II) ions and modified CoCr, likely through the induction of a cellular hypoxic response. The findings of this study contribute to a better understanding of possible risk factors with regard to a clinical applicability of surface modified CoCr implant materials. PMID:25469667

  15. The chemistry of chromium and some resulting analytical problems.

    PubMed Central

    Shupack, S I

    1991-01-01

    Chromium, named for its many-colored compounds, exists in the oxidation states of -2 to +6 inclusively. The compounds exhibit a wide range of geometries including square planar, tetrahedral, octahedral, and various distorted geometries. Chromium is found in nature principally as the chromite ore FeCr2O4 in which chromium is in the +3 state. The existence of a particular oxidation state is dependent on many factors including pH, redox potentials, and kinetics. Thermodynamically, +3 and +2 are the most stable states, while the +3 and +6 oxidation states are the most common ones found in aqueous solution. Kinetically, chromium +3 is substitutionally inert: for water exchange k(sec-1) = 2.5 x 10(-6), due to the presence of the half-filled d(t2g)3.4A2g state. On the other hand, protonation/deprotonation is quite rapid. Polymerization is very slow but is promoted at higher pHs; acid cleavage of the protonated oligomers is also quite slow. Chromium +6 as the chromate ion is strongly oxidizing at low pHs and less so in basic solution. The chromate ion does form some polyacids and polyanions. These factors must be considered in analyzing samples for total chromium and for the amounts of each oxidation state. Images FIGURE 1. PMID:1935853

  16. Chromium and aging

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aging is associated with increased blood glucose, insulin, blood lipids, and fat mass, and decreased lean body mass leading to increased incidences of diabetes and cardiovascular diseases. Improved chromium nutrition is associated with improvements in all of these variables. Insulin sensitivity de...

  17. Stabilized chromium oxide film

    DOEpatents

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  18. Stabilized chromium oxide film

    DOEpatents

    Garwin, Edward L.; Nyaiesh, Ali R.

    1988-01-01

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  19. Chromium(VI)

    Integrated Risk Information System (IRIS)

    Chromium ( VI ) ; CASRN 18540 - 29 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  20. Kinetics of reduction of a series of pentaaquo(pyridine)chromium(III) ions by 1-hydroxy-1-methylethyl radicals: evidence for electron transfer to pyridine

    SciTech Connect

    Bakac, A.; Butkovic, V.; Espenson, J.H.; Marcec, R.; Orhanovic, M.

    1986-07-16

    The title reaction was investigated for a series of (H/sub 2/O)/sub 5/Cr(NC/sub 5/H/sub 4/X)/sup 3 +/ ions. The rate constants are correlated by the Hammett equation. These data, in comparison to other cases in the literature, provide support for a mechanism in which a pyridyl radical, coordinated to Cr(III), is first formed. Subsequent intramolecular electron transfer to produce Cr/sup 2 +/ and pyH/sup +/ occurs more rapidly. Additional members of the series of free pyridinium ions, C/sub 5/H/sub 4/XNH/sup +/, were also investigated. 32 references, 2 figures, 4 tables.

  1. A simple method of chromium coating using a ferrotype plate for scanning electron microscopy.

    PubMed

    Mitsushima, A; Inoué, T

    1993-12-01

    A simple method of chromium coating was developed. A chromium ferrotype plate for drying photoprints was used as a target of a planar magnetron ion-sputter coater. As a result, a high quality chromium film was obtained on dried specimens at room temperature without cooling. The grain size, measuring 1-2 nm in diameter, was small enough for observations of ultrastructures such as F1 particles on the inner mitochondrial membrane. In routine studies under x 100,000, however, chromium coating was not recommended because of its low emission of secondary electrons. PMID:8176338

  2. Electrochemical behaviour of a cobalt-chromium-molybdenum dental alloy in artificial salivas: Influence of phosphate ions and mucin components.

    PubMed

    de Aguiar, S R M M; Nicolai, M; Almeida, M; Gomes, A

    2015-01-01

    The stability of the Co-Cr-Mo dental alloy immersed in artificial salivas (pH 6.7) was investigated over 24 h. Three artificial salivas have been studied: saline saliva (saliva I); saline saliva buffered with phosphate ions (saliva II) and saliva II plus mucin molecules (saliva III). For all the systems, open circuit potential shift positively over 24 hours of immersion. Data extracted from the steady-state polarization curves demonstrated that the Co-Cr-Mo alloy has higher corrosion potential in saliva III, lower corrosion potential in saliva I and lower initial corrosion resistance in saliva III. After 24 hours of immersion in the artificial salivas, the Co-Cr-Mo alloy presents high corrosion stability, due to the protective action created by the presence of corrosion products. From the analysis of the breakdown potential it was concluded that, the presence of the phosphate ions and mucin promote the oxidation process, inducing the formation of etch pits. Regarding the effect of the mucin concentration in the corrosion behaviour of the Co-Cr-Mo dental alloy, it was observed a negative shift in the corrosion potential, pointing to a cathodic inhibitor role for the mucin molecules. Nevertheless, no correlation between the mucin concentration and corrosion rate was possible to establish. PMID:25585980

  3. AES XPS study of chromium carbides and chromium iron carbides

    NASA Astrophysics Data System (ADS)

    Detroye, M.; Reniers, F.; Buess-Herman, C.; Vereecken, J.

    1999-04-01

    The nature of chromium rich carbides which precipitate at grain boundaries in steels is still not perfectly understood. We performed a multitechnique approach on model chromium carbide and chromium-iron carbide samples: Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and High Energy Electron Diffraction (HEED) were used to characterise the samples. Significant chemical shifts were observed for the Cr, Fe and C XPS peaks in the M 7C 3 compound (M stands for metal), indicating unambiguously that the compound formed is a mixed iron-chromium carbide.

  4. Bacterial reduction of chromium

    SciTech Connect

    Schmieman, E.A.; Yonge, D.R.; Johnstone, D.L.

    1997-12-31

    A mixed culture was enriched from surface soil obtained from an eastern United States site highly contaminated with chromate. Growth of the culture was inhibited by a chromium concentration of 12 mg/L. Another mixed culture was enriched from subsurface soil obtained from the Hanford reservation, at the fringe of a chromate plume. The enrichment medium was minimal salts solution augmented with acetate as the carbon source, nitrate as the terminal electron acceptor, and various levels of chromate. This mixed culture exhibited chromate tolerance, but not chromate reduction capability, when growing anaerobically on this medium. However, this culture did exhibit chromate reduction capability when growing anaerobically on TSB. Growth of this culture was not inhibited by a chromium concentration of 12 mg/L. Mixed cultures exhibited decreasing diversity with increasing levels of chromate in the enrichment medium. An in situ bioremediation strategy is suggested for chromate contaminated soil and groundwater. 16 refs., 5 figs., 1 tab.

  5. Studies of chromium gettering

    SciTech Connect

    Simpkins, J.E.; Mioduszewski, P.; Stratton, L.W.

    1982-01-01

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions.

  6. Isotope shift in chromium

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Jarosz, A.; Stefańska, D.; Dembczyński, J.; Stachowska, E.

    2005-01-01

    Thirty-three spectral lines of chromium atom in the blue-violet region (425-465 nm) have been investigated with the method of laser-induced resonance fluorescence on an atomic beam. For all the lines, the isotope shifts for every pair of chromium isotopes have been determined. The lines can be divided into six groups, according to the configuration of the upper and lower levels. Electronic factors of the field shift and the specific mass shift ( Fik and MikSMS, respectively) have been evaluated and the values for each pure configuration involved have been determined. Comparison of the values Fik and MikSMS to the ab initio calculations results has been performed. The presence of crossed second order (CSO) effects has been observed.

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

    PubMed

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

    2014-05-21

    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. PMID:24710730

  8. 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

    NASA Astrophysics Data System (ADS)

    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.

  9. Comparison of the Chromium Distribution in New Super Koropon Primer to 30 Year Old Super Koropon Using Focused Ion Beam/Scanning Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Lomness, Janice K.; Calle, Luz Marina

    2006-01-01

    Super Koropon primer (MB0125-055) plays a significant role in the corrosion protection of areas throughout the Orbiter. Because the Shuttle Program relies so heavily upon the performance of the Koropon primer, it is necessary to fully understand all aspects of the behavior of the coating. One area where little understanding of the Koropon primer still exists is the level of risk associated with age related degradation. Recently, efforts were undertaken to better understand the age life of the Koropon primer and to gain some insight into the aging process of this coating. In that study, an aluminum access panel from the Orbiter Enterprise was used to investigate the performance of the old Koropon film. A control panel was also used to study the performance of new Koropon coating. Preliminary investigations into the performance of aged Super Koropon primer indicated a significant decrease in corrosion protection. This investigation serves as an example of how Focused Ion Beam/Scanning Microscopy can be used to characterize the changes that occur as coatings age.

  10. The removal of hexavalent chromium from water by ferrous sulfate

    SciTech Connect

    Lin, C.J.J.; Vesilind, P.A.

    1995-12-31

    The redox reaction of hexavalent chromium and ferrous sulfate is investigated in his study. Hexavalent chromium, a highly toxic and mobile anion, could exist in raw water used as a public water supply due to the industrial chromium contamination of natural water or due to natural oxidation of trivalent chromium. Ferrous sulfate is one of the widely used coagulants in water treatment plants and has good reducing ability. Because of its reducing capacity, ferrous sulfate can be applied to remove hexavalent chromium from water. The required contact time to reach equilibrium, the effectiveness of Cr(VI) reduction at different initial pH, and the required ferrous sulfate dosage for complete reduction are investigated. The redox reaction can be completed within 10 minutes, allowing 30 mg/L of hexavalent chromium to react with stoichiometric dosage of ferrous sulfate in deionized water, regardless of the initial pH. The pH of the solution is depressed during the progress of the reaction due to the hydrolysis of the produced Fe(III) and Cr(III) ions from the reaction. Dissolved oxygen in water is found to interfere with the redox reaction by consuming ferrous ions when the initial pH of solutions is high. In deionized water, complete Cr(VI) reduction can be achieved by applying excess ferrous sulfate under the condition of this study. It is also achievable when the raw water from Durham Water Treatment Plant is used as the reaction medium, without additional dosage of ferrous sulfate. Based on the results, simultaneous removal of hexavalent chromium in water treatment by applying ferrous sulfate as the coagulant is theoretically feasible.

  11. Synthesis and characterization of titanium carbide, titanium boron carbonitride, titanium boride/titanium carbide and titanium carbide/chromium carbide multilayer coatings by reactive and ion beam assisted, electron beam-physical vapor deposition (EB-PVD)

    NASA Astrophysics Data System (ADS)

    Wolfe, Douglas Edward

    The purpose of the present work was to investigate the synthesis of titanium carbide, TiBCN, TiB2/TiC and TiC/Cr23C6 multilayer coatings by several methods of electron beam-physical vapor deposition (EB-PVD) and examine the affects of various processing parameters on the properties and microstructures of the coatings. TiC was successfully deposited by reactive ion beam assisted (RIBA), EB-PVD and the results were compared to various titanium carbide coatings deposited by a variety of techniques. The affects of substrate temperature and ion beam current density were correlated with composition, hardness, changes in the lattice parameter, degree of crystallographic texture, residual stress, surface morphology, and microstructure. The average Vicker's hardness number was found to increase with increasing ion beam current density and increase over the substrate temperature range of 250°C to 650°C. The average Vicker's hardness number decreased at a substrate temperature of 750°C as a result of texturing and microstructure. The present investigation shows that the average Vicker's hardness number is not only a function of the composition, but also the microstructure including the degree of crystallographic texture. TiB2/TiC multilayer coatings were deposited by argon ion beam assisted, EB-PVD with varying number of total layers to two different film thicknesses under slightly different deposition conditions. In both cases, the hardness of the coatings increased with increasing number of total layers. The adhesion of the coatings ranged from 30 N to 50 N, with the better adhesion values obtained with the thinner coatings. The crystallographic texture coefficients of both the TiC and TiB2 layers were found to change with increasing number of total layers. The multilayer design was found to significantly affect the microstructure and grain size of the deposited coatings. The fracture toughness was found to decrease with increasing number of total layers and was

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

    PubMed

    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

  13. CHROMIUM, METABOLIC SYNDROME AND DIABESITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Suboptimal intakes of the essential nutrient, chromium, are characterized by elevated blood glucose, insulin resistance, obesity, hypertriglyceridemia, and low HDL. These are also signs and symptoms of the metabolic syndrome. Improvements due to increased intake of chromium are related to the degr...

  14. Electrodeposited tungsten-nickel-boron: A replacement for hexavalent chromium

    SciTech Connect

    Steffani, C.; Meltzer, M.

    1995-04-01

    Chromium, deposited from acidic solutions of its hexavalent ion, has been the rule for wear resistant, corrosion resistant coatings for many years. Although chromium coatings are durable, the plating process generates air emissions, effluent rinse waters, and process solutions that are toxic, suspected carcinogens, and a risk to human health and the environment. Tungsten-nickel-boron (W-Ni-B) alloy deposition is a potential substitute for hexavalent chrome. It has excellent wear, corrosion, and mechanical properties and also may be less of an environmental risk. This study examines the electroplating process and deposit properties of W-Ni-B and compares them with those of hexavalent chrome.

  15. Groundwater contaminant by hexavalent chromium

    SciTech Connect

    Parsons, C.

    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.

  16. Binding of trivalent chromium to serum transferrin is sufficiently rapid to be physiologically relevant.

    PubMed

    Deng, Ge; Wu, Kristi; Cruce, Alex A; Bowman, Michael K; Vincent, John B

    2015-02-01

    Transferrin, the major iron transport protein in the blood, also transports trivalent chromium in vivo. Recent in vitro studies have, however, suggested that the binding of chromic ions to apotransferrin is too slow to be biologically relevant. Nevertheless, the in vitro studies have generally failed to adequately take physiological bicarbonate concentrations into account. In aqueous buffer (with ambient (bi)carbonate concentrations), the binding of chromium to transferrin is too slow to be physiologically relevant, taking days to reach equilibrium with the protein's associated conformational changes. However, in the presence of 25mM (bi)carbonate, the concentration in human blood, chromic ions bind rapidly and tightly to transferrin. Details of the kinetics of chromium binding to human serum transferrin and conalbumin (egg white transferrin) in the presence of bicarbonate and other major potential chromium ligands are described and are consistent with transferrin being the major chromic ion transporter from the blood to tissues. PMID:25528477

  17. Hexavalent chromium monitor

    DOEpatents

    Tao, Shiquan; Winstead, Christopher B.

    2005-04-12

    A monitor is provided for use in measuring the concentration of hexavalent chromium in a liquid, such as water. The monitor includes a sample cell, a light source, and a photodetector. The sample cell is in the form of a liquid-core waveguide, the sample cell defining an interior core and acting as a receiver for the liquid to be analyzed, the interior surface of the sample cell having a refractive index of less than 1.33. The light source is in communication with a first end of the sample cell for emitting radiation having a wavelength of about and between 350 to 390 nm into the interior core of the waveguide. The photodetector is in communication with a second end of the waveguide for measuring the absorption of the radiation emitted by the light source by the liquid in the sample cell. The monitor may also include a processor electronically coupled to the photodetector for receipt of an absorption signal to determine the concentration of hexavalent chromium in the liquid.

  18. Spectroscopic characteristics of chromium-doped mullite glass-ceramics

    SciTech Connect

    Wojtowicz, A.J.; Meng, W.; Lempicki, A.; Beall, G.H.; Hall, D.W.

    1988-06-01

    The chromium (3+) ion has been widely used as an optical activator in solid-state, tunable laser materials. High octahedral field-stabilization energy and resistance against both oxidation and reduction minimize the dependence of chromium (3+) on the solid-state host matrix. However, the high sensitivity of electronic structure on crystal field strength makes the appropriate choice of host the condition for success. Characteristics of chromium-doped mullite ceramics are discussed with reference to possible laser applications. Dominant features are attributed to large and inherent spectroscopic inhomogeneity of mullite. The spectroscopic data are analyzed using a generalized McCumber theory. The peak-stimulated emission cross section is 0.54 x 10 to the -20 sq cm. This together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  19. A possible role for chromium(III) in genotoxicity.

    PubMed Central

    Snow, E T

    1991-01-01

    Chromium is found in the environment in two major forms: reduced CrIII and CrVI, or chromate. Chromate, the most biologically active species, is readily taken up by living cells and reduced intracellularly, via reactive intermediates, to stable CrIII species. CrIII, the most abundant form of chromium in the environment, does not readily cross cell membranes and is relatively inactive in vivo. However, intracellular CrIII can react slowly with both nucleic acids and proteins and can be genotoxic. We have investigated the genotoxicity of CrIII in vitro using a DNA replication assay and in vivo by CaCl2-mediated transfection of chromium-treated DNA into Escherichia coli. When DNA replication was measured on a CrIII-treated template using purified DNA polymerases (either bacterial or mammalian), both the rate of DNA replication and the amount of incorporation per polymerase binding event (processivity) were greatly increased relative to controls. When transfected into E. coli, CrIII-treated M13mp2 bacteriophage DNA showed a dose-dependent increase in mutation frequency. These results suggest that CrIII alters the interaction between the DNA template and the polymerase such that the binding strength of the DNA polymerase is increased and the fidelity of DNA replication is decreased. These interactions may contribute to the mutagenicity of chromium ions in vivo and suggest that CrIII can contribute to chromium-mediated carcinogenesis. Images FIGURE 3. PMID:1935855

  20. Microbial exudate promoted dissolution and transformation of chromium containing minerals

    NASA Astrophysics Data System (ADS)

    Saad, E. M.; Sun, J.; Tang, Y.

    2015-12-01

    Because of its utility in many industrial processes, chromium has become the second most common metal contaminant in the United States. The two most common oxidation states of chromium in nature are Cr(III), which is highly immobile, and Cr(VI), which is highly mobile and toxic. In both natural and engineered environments, the most common remediation of Cr(VI) is through reduction, which results in chromium sequestration in the low solubility mixed Cr(III)-Fe(III) (oxy)hydroxide phases. Consequently, the stability of these minerals must be examined to assess the fate of chromium in the subsurface. We examined the dissolution of mixed Cr(III)-Fe(III) (oxy)hydroxides in the presence of common microbial exudates, including the siderophore desferrioxamine B (DFOB; a common organic ligand secreted by most microbes with high affinity for ferric iron and other trivalent metal ions) and oxalate (a common organic acid produced by microbes). The solids exhibited incongruent dissolution with preferential leaching of Fe from the solid phase. Over time, this leads to a more Cr rich mineral, which is known to be more soluble than the corresponding mixed mineral phase. We are currently investigating the structure of the reacted mineral phases and soluble Cr(III) species, as well as the potential oxidation and remobilization of the soluble Cr species. Results from this study will provide insights regarding the long term transport and fate of chromium in the natural environment in the presence of microbial activities.

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

    NASA Astrophysics Data System (ADS)

    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

  2. Chromium isotopes as indicators of hexavalent chromium reduction

    SciTech Connect

    Johnson, Thomas M.

    2012-03-20

    This is the final report for a university research project which advanced development of a new technology for identifying chemical reduction of hexavalent chromium contamination in groundwater systems. Reduction renders mobile and toxic hexavalent chromium immobile and less toxic. The new method uses stable isotope ratio measurements, which are made using multicollector ICP-mass spectrometry. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.

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

    PubMed

    Sugiyama, M

    1994-09-01

    Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic chromium in chromium(VI)-induced damage in intact cultured cells is discussed, based upon our studies with antioxidants including vitamin E (alpha-tocopherol), B2 (riboflavin), C (ascorbic acid), and so on. These studies appear to confirm the participation of paramagnetic Cr such as chromium(V) and Chromium(III) in chromium(VI)-induced cellular damage. PMID:7843124

  4. Bioaccumulation of chromium from tannery wastewater: an approach for chrome recovery and reuse.

    PubMed

    Aravindhan, Rathinam; Madhan, Balaraman; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni; Ramasami, Thirumalachari

    2004-01-01

    The presence of chromium in the effluent is a major concern for the tanning industry. Currently, chemical precipitation methods are practiced for the removal of chromium from the effluent, but that leads to the formation of chrome-bearing solid wastes. The other membrane separation and ion exchange methods available are unfeasible due to their cost. In this study, the removal of chromium from tannery effluent has been carried out using abundantly available brown seaweed Sargassum wightii. Simulated chrome tanning solution was used for the standardization of experimental trials. Various factors influencing the uptake of chromium, viz., quantity of seaweed, concentrations of chromium, pH of the chrome-bearing wastewater, and duration of treatment, have been studied. Chemical modification of the seaweed through pretreatment with sulfuric acid, magnesium chloride, and calcium chloride showed improved uptake of chromium. Langmuir and Freundlich isotherms have been fitted for various quantities of seaweed. The dynamic method of treatment of protonated seaweed with simulated chrome tanning solution at a pH of 3.5-3.8 for a duration of 6 h gave the maximum uptake of about 83%. A similar uptake has been established for commercial chrome tanning wastewater containing the same concentration of chromium. The Sargassum species exhibited a maximum uptake of 35 mg of chromium per gram of seaweed. Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, and flame photometry studies have been carried out to understand the mechanistic pathway for the removal of chromium. The potential reuse of chromium-containing seaweed for the preparation of basic chromium sulfate (tanning agent) has been demonstrated. PMID:14740751

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

    SciTech Connect

    Gomez-Gonzalez, Sergio Efrain; Carbajal-Arizaga, Gregorio Guadalupe; Manriquez-Gonzalez, Ricardo; De la Cruz-Hernandez, Wencel; Gomez-Salazar, Sergio

    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.

  6. Influence of chromium interaction with native and impurity defects on optical and luminescence properties of ZnSe:Cr crystals

    NASA Astrophysics Data System (ADS)

    Radevici, I.; Sushkevich, K.; Colibaba, G.; Sirkeli, V.; Huhtinen, H.; Nedeoglo, N.; Nedeoglo, D.; Paturi, P.

    2013-11-01

    Luminescent properties of the chromium doped zinc selenide crystals with various concentrations of the doping impurity in 0.03-0.30 at. % range within the temperature interval from 6 K to 300 K were studied. Chromium doping was performed in various technological processes: during the growth by chemical vapor transport method; during the growth from melt; by thermal diffusion from the Bi + Cr melt or by thermal diffusion from gas. Possibility of chromium-bound excitons formation was shown, as well as chromium impurity participation in formation of emission bands in IR spectral region. A mechanism of chromium doping impurity interaction with uncontrolled background impurities and zinc selenide structural defects was proposed based on experimental data. An assumption about resonant energy transfer between double charged chromium ions and complexes based on crystals vacancy defects was made.

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

    PubMed

    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. PMID:17030417

  8. Chromium reduction in Pseudomonas putida

    SciTech Connect

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

    1990-07-01

    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 K{sub m} of 40 {mu}M CrO{sub 4}{sup 2{minus}}. Neither sulfate nor nitrate affected chromate reduction either in vitro or with intact cells.

  9. Biotreatment of chromium (VI) effluents

    SciTech Connect

    Tavares, T.; Neto, P.; Martins, C.

    1995-12-31

    The presence of heavy metals in industrial wastewaters is still a serious problem for some local small and medium size industries. Particularly electroplating and tanneries produce highly concentrated chromium effluents, which are treated by traditional physico-chemical processes. Those are able to reduce the total chromium concentration from some hundreds of mg.l{sup {minus}1} to very low concentrations, but the allowable final value of 0.1 mg.l{sup {minus}1} is hardly obtained as the referred processes become too costly for those small and medium size industries. The aim of these studies is the definition of an efficient system, economically attractive and friendly to the environment, based on the ability of some microorganisms to concentrate heavy metals. This system would be used as a final treatment step to remove low concentrations of hexavalent chromium. Three different bacteria were used in batch systems to evaluate their resistance to Cr(VI) and their ability to reduce it to the trivalent form. The results were compared with those obtained with microorganisms isolated from sludge of treatment plants receiving wastewater loaded with chromium. One of those bacteria was supported on granular activated carbon and the biofilm was optimized in terms of adhesion and removal efficiency. The chromium adsorption capacity of the support was also studied as albeit it is known that adsorption is not used for heavy metals removal, granular activated carbon is an excellent immobilization support for the biofilm and certainly has some responsibility on the chromium fixation process.

  10. Development of a new electrokinetic technique for decontamination of hexavalent chromium from low surface charged soils

    SciTech Connect

    Haran, B.S.; Popov, B.N.; Zheng, Guanghong; White, R.E.

    1996-12-31

    A new in-situ technique was developed for hexavalent chromium removal from sand. Imposition of constant potential gradient across the soil matrix through a graphite cathode and iron anode resulted in successful migration of chromate towards the anode. The hexavalent chromium ions are reduced to harmless trivalent form by chemical reaction with the anodic dissolution product, Fe{sup 2+}. 23 refs., 14 figs.

  11. Synthesis and characterization of chromium(III) Schiff base complexes: antimicrobial activity and its electrocatalytic sensing ability of catechol.

    PubMed

    Kumar, S Praveen; Suresh, R; Giribabu, K; Manigandan, R; Munusamy, S; Muthamizh, S; Narayanan, V

    2015-03-15

    A series of acyclic Schiff base chromium(III) complexes were synthesized with the aid of microwave irradiation method. The complexes were characterized on the basis of elemental analysis, spectral analysis such as UV-Visible, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) spectroscopies and electrospray ionization (ESI) mass spectrometry. Electrochemical analysis of the complexes indicates the presence of chromium ion in +3 oxidation state. Cr (III) ion is stabilized by the tetradentate Schiff base ligand through its nitrogen and phenolic oxygen. From the spectral studies it is understood that the synthesized chromium(III) complexes exhibits octahedral geometry. Antimicrobial activity of chromium complexes was investigated towards the Gram positive and Gram negative bacteria. In the present work, an attempt was made to fabricate a new kind of modified electrode based on chromium Schiff base complexes for the detection of catechol at nanomolar level. PMID:25576940

  12. Evaluation of aquatic toxicities of chromium and chromium-containing effluents in reference to chromium electroplating industries.

    PubMed

    Baral, A; Engelken, R; Stephens, W; Farris, J; Hannigan, R

    2006-05-01

    This study evaluated aquatic toxicities of chromium and chromium-containing laboratory samples representative of effluents from chromium electroplating industries, and compared the aquatic environmental risks of hexavalent and trivalent chromium electroplating operations. Trivalent chromium electroplating has emerged as an acceptable alternative to hazardous hexavalent chromium electroplating. This process substitution has reduced the human health impact in the workplace and minimized the production of hazardous sludge regulated under the Resource Conservation and Recovery Act (RCRA). The thrust behind this research was to investigate whether trivalent chromium electroplating operations have lower adverse impacts on standardized toxicity test organisms. Ceriodaphnia dubia and Pimephales promelas were used to investigate toxicities of trivalent chromium (Cr (III)), hexavalent chromium (Cr (VI)), and industrial effluents. In agreement with previous studies, Cr (III) was found to be less toxic than Cr (VI). Despite having several organic and inorganic constituents in the effluents obtained from trivalent chromium plating baths, they exhibited less adverse effects to C. dubia than effluents obtained from hexavalent chromium electroplating baths. Thus, transition from hexavalent to trivalent chromium electroplating processes may be justified. However, because of the presence of organic constituents such as formate, oxalate, and triethylene glycol in effluents, trivalent chromium electroplating operations may face additional regulatory requirements for removal of total organic carbon. PMID:16418891

  13. Mare Chromium Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This crater, located in Mare Chromium, shows evidence of exterior modification, with little interior modification. While the rim is still visible, the ejecta blanket has been removed or covered. There is some material at the bottom of the crater, but the interior retains the bowl shape from the initial formation of the crater.

    Image information: VIS instrument. Latitude -34.4, Longitude 174.4 East (185.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. ADVANCES IN HEXAVALENT CHROMIUM REMOVAL AT HANFORD

    SciTech Connect

    NESHEM DO; RIDDELLE J

    2012-01-30

    At the Hanford Site, chromium was used as a corrosion inhibitor in the reactor cooling water and was introduced into the groundwater as a result of planned and unplanned discharges from reactors during plutonium production since 1944. Beginning in 1995, groundwater treatment methods were evaluated leading to the use of pump and treat facilities with ion exchange using Dowex 21 K, a regenerable strong base anion exchange resin. This required regeneration of the resin, which is currently performed offsite. Resin was installed in a 4 vessel train, with resin removal required from the lead vessel approximately once a month. In 2007, there were 8 trains (32 vessels) in operation. In 2008, DOE recognized that regulatory agreements would require significant expansion in the groundwater chromium treatment capacity. Previous experience from one of the DOE project managers led to identification of a possible alternative resin, and the contractor was requested to evaluate alternative resins for both cost and programmatic risk reductions. Testing was performed onsite in 2009 and 2010, using a variety of potential resins in two separate facilities with groundwater from specific remediation sites to demonstrate resin performance in the specific groundwater chemistry at each site. The testing demonstrated that a weak base anion single-use resin, ResinTech SIR-700, was effective at removing chromium, had a significantly higher capacity, could be disposed of efficiently on site, and would eliminate the complexities and programmatic risks from sampling, packaging, transportation and return of resin for regeneration. This resin was installed in Hanford's newest groundwater treatment facility, called 100-DX, which began operations in November, 2010, and used in a sister facility, 100-HX, which started up in September of 2011. This increased chromium treatment capacity to 25 trains (100 vessels). The resin is also being tested in existing facilities that utilize Dowex 21 K for

  15. Chromium-induced kidney disease

    SciTech Connect

    Wedeen, R.P. ); Qian, Lifen )

    1991-05-01

    Kidney disease is often cited as one of the adverse effects of chromium, yet chronic renal disease due to occupational or environmental exposure to chromium has not been reported. Occasional cases of acute tubular necrosis (ATN) following massive absorption of chromate have been described. Chromate-induced ATN has been extensively studied in experimental animals following parenteral administration of large doses of potassium chromate (hexavalent). The chromate is selectively accumulated in the convoluted proximal tubule where necrosis occurs. An adverse long-term effect of low-dose chromium exposure on the kidneys is suggested by reports of low molecular weight (LMW) proteinuria in chromium workers. Excessive urinary excretion of {beta}{sub 2}-microglobulin, a specific proximal tubule brush border protein, and retinol-binding protein has been reported among chrome palters and welders. However, LMW proteinuria occurs after a variety of physiologic stresses, is usually reversible, and cannot by itself be considered evidence of chromic renal disease. Chromate-induced ATN and LMW proteinuria in chromium workers, nevertheless, raise the possibility that low-level, long-term exposure may produce persistent renal injury. The absence of evidence of chromate-induced chromic renal disease cannot be interpreted as evidence of the absence of such injury.

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

    PubMed Central

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

    2013-01-01

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

  17. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  18. Carcinogen risk assessment of chromium compounds

    SciTech Connect

    Gibb, H.J.; Chen, C.W.; Hiremath, C.B.

    1988-06-01

    Hexavalent chromium has been identified as a human carcinogen. Evidence to support this contention derives from epidemiologic, animal, and genotoxicity studies. Although workers exposed to both trivalent and hexavalent chromium have been shown to be at an excess risk of respiratory cancer, only hexavalent chromium has been shown to be carcinogenic in animals. Both hexavalent and trivalent chromium have been shown to be mutagenic, but the evidence for hexavalent chromium is somewhat stronger than that for trivalent chromium. The quantitative estimation of the cancer risk due to hexavalent chromium in the ambient air is calculated on the basis of lung-cancer mortality data for chromate production workers. The lifetime respiratory cancer risk due to 1 microgram/cu m) of hexavalent chromium in the ambient air is estimated to be 1.2 x .002 on the basis of Mancuso's data and 9.4 x .003 on the basis of the Braver et al. data.

  19. Chromium at High Pressure

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    2012-02-01

    Chromium has long served as the archetype of spin density wave magnetism. Recently, Jaramillo and collaborators have shown that Cr also serves as an archetype of magnetic quantum criticality. Using a combination of x-ray diffraction and electrical transport measurements at high pressures and cryogenic temperatures in a diamond anvil cell, they have demonstrated that the N'eel transition (TN) can be continuously suppressed to zero, with no sign of a concurrent structural transition. The order parameter undergoes a broad regime of exponential suppression, consistent with the weak coupling paradigm, before deviating from a BCS-like ground state within a narrow but accessible quantum critical regime. The quantum criticality is characterized by mean field scaling of TN and non mean field scaling of the transport coefficients, which points to a fluctuation-induced reconstruction of the critical Fermi surface. A comparison between pressure and chemical doping as means to suppress TN sheds light on different routes to the quantum critical point and the relevance of Fermi surface nesting and disorder at this quantum phase transition. The work by Jaramillo et al. is broadly relevant to the study of magnetic quantum criticality in a physically pure and theoretically tractable system that balances elements of weak and strong coupling. [4pt] [1] R. Jaramillo, Y. Feng, J. Wang & T. F. Rosenbaum. Signatures of quantum criticality in pure Cr at high pressure. Proc. Natl. Acad. Sci. USA 107, 13631 (2010). [0pt] [2] R. Jaramillo, Y. Feng, J. C. Lang, Z. Islam, G. Srajer, P. B. Littlewood, D. B. McWhan & T. F. Rosenbaum. Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition. Nature 459, 405 (2009).

  20. Aqueous trivalent chromium photoproduction in natural waters

    SciTech Connect

    Kaczynski, S.E.; Kieber, R.J. )

    1993-08-01

    Field studies indicate Cr(III) is photochemically produced at two freshwater lakes in southeastern North Carolina. Results of controlled photolysis experiments with marine and estuarine samples suggest this process may be common to many natural water systems. This photogeneration mechanism sheds new insight into the existence of the thermodynamically unstable Cr(III) ion in oxygenated surface waters. Sixty-eight water samples from seven water bodies in the southeastern United States (fresh, estuarine, and marine) displayed a range of total aqueous inorganic chromium from <0.01 nM to 1.05 nM, with variable amounts of the trivalent and hexavalent species. These are the first Cr(III) and Cr(VI) values reported for all these aqueous systems and some of the first ever for nonmarine environments. 24 refs., 5 figs., 1 tab.

  1. The gelation mechanism of chromium(III)

    SciTech Connect

    Shu, P.

    1988-05-01

    Chromium(III) is commonly used crosslinker for preparing profile control gels with polymers having carboxylate and amide functionalities. Cr(III) is applied in many forms. For example, it can be used in the form of simple chromic salts of chloride and sulfate, or as complexed Cr(III) used in leather tanning, or as in-situ generated Cr(III) from the redox reaction of dichromate and bisulfite or thiourea. The gelation rate, and gel quality, doped on which form of Cr(III) is used. The author has found that the Cr olates, produced by hydrolysis of Cr(III) ions, are the reactive crosslinking species. The different gelation rates are due to the different degrees of olation. Furthermore, by controlling the degree of hydrolysis Cr(III) derived from various sources mentioned above can exhibit the same gelation rate.

  2. Precipitating Chromium Impurities in Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Salama, A. M.

    1982-01-01

    Two new treatments for silicon wafers improve solar-cell conversion efficiency by precipitating electrically-active chromium impurities. One method is simple heat treatment. Other involves laser-induced damage followed by similar heat treatment. Chromium is one impurity of concern in metallurgical-grade silicon for solar cells. In new treatment, chromium active centers are made electrically inactive by precipitating chromium from solid solution, enabling use of lower grade, lower cost silicon in cell manufacture.

  3. Turkey liver - a chromium enriched food source

    SciTech Connect

    Polansky, M.M.; Bryden, N.A.; Richards, M.; Anderson, R.A.

    1986-03-01

    There are presently no known foods for humans that are particularly good sources of chromium. As a means of obtaining Cr enriched foods, turkeys were fed diets containing various levels of supplemental chromium. Four groups of 6-month old turkey hens were fed either the basal diet for laying hens or this diet supplemented with 25, 100 or 200 ..mu..g of chromium as chromium chloride per g of diet. Liver Cr concentration of the turkeys sacrificed after 1 week increased from 7 ng/g (wet wt) while consuming the basal diet to 15, 48 and 68 ng/g, respectively, while consuming the diets with supplemental chromium. Comparable values for the turkeys sacrificed after 5 weeks were 2, 43, 170 and 325 ng/g. Similar trends but higher chromium values were observed for kidney samples. The chromium contents of the dark and white meat and eggs were not altered significantly. Chromium concentrations of the pancreas, gizzard and heart increased marginally; final chromium concentrations were less than 23 ng/g even after 5 weeks on the highest level of supplemental chromium. Chromium content of spleen and lungs was approximately 2-fold higher than that of the pancreas, gizzard or heart. Therefore, turkey liver is a food source suitable for Cr enrichment while the eggs, dark and white meat and other edible parts do not appear to be enriched following chromium supplementation.

  4. Cytogenetic effects of hexavalent chromium in Bulgarian chromium platers.

    PubMed

    Benova, Donka; Hadjidekova, Valeria; Hristova, Rossitza; Nikolova, Teodora; Boulanova, Minka; Georgieva, Ivanka; Grigorova, Mira; Popov, Todor; Panev, Teodor; Georgieva, Rossitza; Natarajan, Adayapalam T; Darroudi, Firouz; Nilsson, Robert

    2002-02-15

    The aim of the present study was to evaluate the genotoxic effects of hexavalent chromium (Cr(VI)) in vivo in exposed Bulgarian chromium platers by using classical cytogenetic and molecular cytogenetic analyses of peripheral lymphocytes and exfoliated buccal cells. No significant difference was observed between the exposed workers and the controls with regard to the frequency of cells with chromosome aberrations (CAs) using conventional Giemsa staining and in the frequency of sister chromatid exchanges (SCEs). However, there was a significant increase in the number of cells with micronuclei (MN) in peripheral lymphocytes from chromium exposed workers as compared to the controls. In the buccal cells from these workers, this increase was even more pronounced. Cytosine arabinoside (AraC), an inhibitor of DNA synthesis and repair, was found to significantly increase the levels of MN in vitro in the lymphocytes of both groups. The increase was more expressed in the lymphocytes of chromium exposed workers. Both centromere positive (C(+)) as well as centromere negative (C(-)) MN were observed by the fluorescence in situ hybridization (FISH) technique in both of the cell types studied. No difference between C(+) and C(-) MN frequencies was found in the lymphocytes as well as in the buccal cells. Thus, Cr(VI) appears to have both clastogenic as well as aneugenic effects in humans. PMID:11815242

  5. Removal of Cr(VI) from chromium contaminated sites by washing with hot water

    SciTech Connect

    Ososkov, V.; Bozzelli, J.W.; Kebbekus, B.B.

    1994-12-31

    Extraction of chromium from a mixture of ore processing residue and soil (slag) by hot water and dilute alkali (0.01M NaOH) washing is studied. It was found that hexavalent chromium, which is the most dangerous and mobile form of chromium, can be effectively removed (95--99%) from slag by washing with these extraction solutions. The extracting liquid can be reused after removing the Cr(VI) ions by ion-exchange technologies. Trivalent chromium is strongly adsorbed by clay minerals and remains in the residue after this mild extraction. The hot water or mild hot alkali washing is recommended as a rapid and inexpensive treatment for chromium-contaminated sites to prevent chromium(VI) migration through soils into groundwater or dispersion as a dust into the atmosphere. Cr(III) remaining in the residue may then be left on-site, preferably with the addition of a reducing agent to prevent conversion to CR(VI) until further clean up is mandated.

  6. Chromium content of selected Greek foods.

    PubMed

    Bratakos, Michael S; Lazos, Evangelos S; Bratakos, Sotirios M

    2002-05-01

    The total chromium content of a wide variety of Greek foods was determined by graphite furnace atomic absorption spectroscopy (GFAAS). Meat, fish and seafood, cereals and pulses were rich sources of chromium (>0.100 microg/g). Fruits, milk, oils and fats and sugar were poor sources. Differences in chromium content were found between different food classes from Greece and those from some other countries. Based on available food consumption data and chromium levels in this study, it was estimated that the chromium intake of Greeks is 143 microg/day, with vegetables, cereals and meat being the main contributors. PMID:12083715

  7. Chromium Chemistry in the Subsurface

    EPA Science Inventory

    Chromium (VI) (Cr) is carcinogenic and a threat to human and ecological health. There are adequate and acceptable methods to characterize and assess Cr contaminated sites. Cr chemistry in the environment is well understood. There are documented methods to address Cr contaminat...

  8. Chromium(III), insoluble salts

    Integrated Risk Information System (IRIS)

    Chromium ( III ) , insoluble salts ; CASRN 16065 - 83 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments

  9. The use of trivalent chromium bath to obtain a solar selective black chromium coating

    NASA Astrophysics Data System (ADS)

    Survilienė, S.; Češūnienė, A.; Juškėnas, R.; Selskienė, A.; Bučinskienė, D.; Kalinauskas, P.; Juškevičius, K.; Jurevičiūtė, I.

    2014-06-01

    Black chromium coatings were electrodeposited from a trivalent chromium bath using a ZnO additive as a second main component. Black chromium was electrodeposited on steel and copper plates and substrates plated with bright nickel prior to black chromium electrodeposition. The black chromium coatings were characterized by XRD and SEM. The XRD data suggest that the phase structure of black chromium may be defined as a zinc solid solution in chromium or a chromium solid solution in zinc depending on the chromium/zinc ratio in the deposit. The role of substrate finish was evaluated through the corrosion resistance and reflectance of black chromium. According to corrosion tests the samples plated with bright nickel prior to black chromium deposition have shown the highest corrosion resistance. The electrodeposited black chromium possesses good optical properties for the absorption of solar energy. The absorption coefficient of black chromium was found to be over 0.99 for the samples obtained without the Ni undercoat and below 0.99 for those obtained with the use of Ni undercoat. However, the use of nickel undercoat before black chromium plating is recommended because it remarkably improves the corrosion resistance of samples.

  10. Simultaneous Electrodialytic Preconcentration and Speciation of Chromium(III) and Chromium(VI).

    PubMed

    Ohira, Shin-Ichi; Nakamura, Koretaka; Shelor, C Phillip; Dasgupta, Purnendu K; Toda, Kei

    2015-11-17

    Large amounts of chromium (Cr) compounds are used for manufacturing of various products and various chemical processes. Some inevitably find their way into the environment. Environmental Cr is dominantly inorganic and is either in the cationic +3 oxidation state or in the anionic oxochromium +6 oxidation state. The two differ dramatically in their implications; Cr(III) is essential to human nutrition and even sold as a supplement, while Cr(VI) is a potent carcinogen. Drinking water standards for chromium may be based on total Cr or Cr(VI) only. Thus, Cr speciation analysis is very important. Despite their high sensitivity, atomic spectrometric techniques or induction coupled plasma-mass spectrometry (ICP-MS) cannot directly differentiate the oxidation states. We present here a new electrodialytic separation concept. Sample analyte ions are quantitatively transferred via appropriately ionically functionalized dialysis membranes into individual receptors that are introduced into the ICP-MS. There was no significant conversion of Cr(VI) to Cr(III) or vice versa during the very short (6 s) separation process. Effects of salinity (up to ∼20 mM NaCl) can be eliminated with proper membrane functionalization and receptor optimization. With the ICP-MS detector we used, the limits of detection for either form of Cr was 0.1 μg/L without preconcentration. Up to 10-fold preconcentration was readily possible by increasing the donor solution flow rate relative to the acceptor solution flow rates. The proposed approach permits simultaneous matrix isolation, preconcentration, and chromium speciation. PMID:26507203

  11. Characterization of titanium chromium nitride nanocomposite protective coatings

    NASA Astrophysics Data System (ADS)

    Aouadi, S. M.; Wong, K. C.; Mitchell, K. A. R.; Namavar, F.; Tobin, E.; Mihut, D. M.; Rohde, S. L.

    2004-05-01

    The structural, chemical, optical and mechanical properties of titanium chromium nitride nanocrystalline films deposited by ion beam-assisted deposition were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, nanoindentation and wear testing. Coatings were deposited on silicon and stainless steel substrates with growth temperatures of 150 and 400 °C. The concentration of titanium and chromium in the film was regulated by controlling their evaporation rates. The nitrogen concentration was controlled by varying the nitrogen ion current. X-ray diffraction and X-ray photoelectron spectroscopy measurements indicated that the films deposited at 150 °C formed solid solutions whereas those produced at 400 °C formed nanocomposites. The optical constants were measured using spectroscopic ellipsometry. A correlation between the elemental/phase composition and optical constants was established. The mechanical properties of the coatings were evaluated using nanohardness testing and were found to depend on composition. The nanocomposite films were the hardest (hardness of 30 GPa and elastic modulus of 300 GPa). Tribological properties of titanium chromium nitride coated 440 C stainless steel coupons were evaluated using a ball-on-disk tribometer. These tests were conducted under a load of 50 N for 1.5 million cycles at 180 rpm. Coatings deposited at high temperature did not show any signs of wear.

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

    PubMed

    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). PMID:23937937

  13. Electrodeposition of cobalt-chromium alloy from trivalent chromium solutions

    SciTech Connect

    Dasarathy, H.; Riley, C.; Coble, H.D. . Dept. of Chemistry and Materials Science)

    1994-07-01

    Cobalt-chromium alloy was deposited from plating solutions containing cobalt(II) chloride and chromium(III) chloride at 3.5 pH. The deposits were obtained using both single and mixed complex solutions. Deposit morphology showed significant dependence on the complexing agent(s) used. Partitioning of the two components in the deposit as determined by energy dispersive spectroscopy depended on plating parameters such as concentration ratio of the two salts in the solution, complexing agent, type of current (both dc and pulsed current were studied), and current density. X-ray photoelectron spectroscopy spectra collected from as-deposited alloy revealed the presence of both oxides and metals. X-ray diffraction spectra for the alloy deposit indicated solid solution formation.

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

    PubMed

    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

  15. The effects of aluminum, iron, chromium, and yttrium on rat intestinal smooth muscle in vitro.

    PubMed

    Cunat, L; Membre, H; Marchal, L; Chaussidon, M; Burnel, D

    1998-01-01

    The modification of peristaltic activity in the presence of several metal ions has been investigated in the rat intestine by the isolated organ technique. The metals tested modify the intestinal movements: aluminum, chromium, and yttrium cause a decrease of amplitude, while iron showed no effect. By use of microscopic techniques, the presence of yttrium hydroxide was observed in the intestinal tissues. Iron also appears as a precipitate outside of the intestinal serosal, which may explain why iron did not modify the peristaltism. Chromium and aluminum were not apparent to microscope, despite being detected and quantified in the tissues by means of atomic emission spectrometer. We conclude that the trivalent ions of these elements may operate differently on the mechanisms of intestinal contractions: yttrium precipitates in intercellular spaces, iron precipitates outside the intestines, and chromium and aluminum remain in solution and are distributed homogeneously in the smooth intestinal muscle. PMID:9845462

  16. Characterization of the organic component of low-molecular-weight chromium-binding substance and its binding of chromium.

    PubMed

    Chen, Yuan; Watson, Heather M; Gao, Junjie; Sinha, Sarmistha Halder; Cassady, Carolyn J; Vincent, John B

    2011-07-01

    Chromium was proposed to be an essential element over 50 y ago and was shown to have therapeutic potential in treating the symptoms of type 2 diabetes; however, its mechanism of action at a molecular level is unknown. One chromium-binding biomolecule, low-molecular weight chromium-binding substance (LMWCr or chromodulin), has been found to be biologically active in in vitro assays and proposed as a potential candidate for the in vivo biologically active form of chromium. Characterization of the organic component of LMWCr has proven difficult. Treating bovine LMWCr with trifluoroacetic acid followed by purification on a graphite powder micro-column generates a heptapeptide fragment of LMWCr. The peptide sequence of the fragment was analyzed by MS and tandem MS (MS/MS and MS/MS/MS) using collision-induced dissociation and post-source decay. Two candidate sequences, pEEEEGDD and pEEEGEDD (where pE is pyroglutamate), were identified from the MS/MS experiments; additional tandem MS suggests the sequence is pEEEEGDD. The N-terminal glutamate residues explain the inability to sequence LMWCr by the Edman method. Langmuir isotherms and Hill plots were used to analyze the binding constants of chromic ions to synthetic peptides similar in composition to apoLMWCr. The sequence pEEEEGDD was found to bind 4 chromic ions per peptide with nearly identical cooperativity and binding constants to those of apoLMWCr. This work should lead to further studies elucidating or eliminating a potential role for LMWCr in treating the symptoms of type 2 diabetes and other conditions resulting from improper carbohydrate and lipid metabolism. PMID:21593351

  17. Welding of high chromium steels

    NASA Technical Reports Server (NTRS)

    Miller, W B

    1928-01-01

    A brief description is given of different groups of high chromium steels (rustless iron and stainless steels) according to their composition and more generally accepted names. The welding procedure for a given group will be much the same regardless of the slight variations in chemical composition which may exist within a certain group. Information is given for the tensile properties (yield point and ultimate strength) of metal sheets and welds before and after annealing on coupons one and one-half inches wide. Since welds in rustless iron containing 16 to 18 percent chromium and 7 to 12 percent nickel show the best combination of strength and ductility in the 'as welded' or annealed condition, it is considered the best alloy to use for welded construction.

  18. Food Chromium Contents, Chromium Dietary Intakes And Related Biological Variables In French Free-Living Elderly

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chromium (Cr III), an essential trace element, functions in potentiating insulin sensitivity, regulating glucose homeostasis, improving lipid profile, and maintaining lean body mass. Glucose intolerance and chromium deficiency increase with age, and could be aggravating factors of the metabolic synd...

  19. Effect Of Chromium Underlayer On The Properties Of Nano-Crystalline Diamond Films

    SciTech Connect

    Garratt, Elias; AlFaify, Salem; Yoshitake, T.; Katamune, Yuki; Bowden, Mark; Nandasiri, Manjula I.; Ghantasala, S.; Mancini, D. C.; Thevuthasan, Suntharampillai; Kayani, A.

    2013-01-11

    This paper investigated the effect of chromium underlayer on the structure, microstructure and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on silicon substrate with a thin film of chromium as an underlayer. The composition, structure and microstructure of the deposited layers were analyzed using non-Rutherford Backscattering Spectrometry, Raman Spectroscopy, Near-Edge X-Ray Absorption Fine Structure, X-ray Diffraction and Atomic Force Microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analysis determined consistency between sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

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

    PubMed

    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. PMID:26315594

  1. TRANSPORT OF CHROMIUM AND SELENIUM IN A PRISTINE SAND AND GRAVEL AQUIFER: ROLE OF ADSORPTION PROCESSES

    EPA Science Inventory

    Field transport experiments were conducted in an oxic sand and gravel aquifer using Br (bromide ion), Cr (chromium, injected as Cr(VI)), Se (selenium, injected as Se(VI)), and other tracers. The aquifer has mildly acidic pH values and low concentrations of dissolved salts. Within...

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

    NASA Astrophysics Data System (ADS)

    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

  3. Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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 %.

  5. Structural, morphological and optical properties of chromium oxide nanoparticles

    SciTech Connect

    Babukutty, Blessy; Parakkal, Fasalurahman; Nair, Swapna S.; Bhalero, G. M.; Aravind, P. B.

    2015-06-24

    Chromium oxide nanoparticles are synthesized by reduction route from chloride precursors with surfactant, trioctylphosphine oxide (TOPO). Structural and morphological characterization are analyzed using X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Transmission Electron micrographs show that the average grain size lies in the range 5nm to 10nm. Optical characterization has been done by UV-VIS spectrophotometer. Distinct optical absorptions of Cr{sup 3+} ions show hinting towards the presence of Cr{sub 2}O{sub 3}. Presence of oxygen is also confirmed from Electron Energy Loss Spectroscopy (EELS) studies.

  6. Structural, morphological and optical properties of chromium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Babukutty, Blessy; Parakkal, Fasalurahman; Bhalero, G. M.; Aravind, P. B.; Nair, Swapna S.

    2015-06-01

    Chromium oxide nanoparticles are synthesized by reduction route from chloride precursors with surfactant, trioctylphosphine oxide (TOPO). Structural and morphological characterization are analyzed using X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Transmission Electron micrographs show that the average grain size lies in the range 5nm to 10nm. Optical characterization has been done by UV-VIS spectrophotometer. Distinct optical absorptions of Cr3+ ions show hinting towards the presence of Cr2O3. Presence of oxygen is also confirmed from Electron Energy Loss Spectroscopy (EELS) studies.

  7. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 7 2014-07-01 2014-07-01 false Chromium (VI). 1915.1026 Section 1915.1026 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) OCCUPATIONAL SAFETY AND HEALTH STANDARDS FOR SHIPYARD EMPLOYMENT Toxic and Hazardous Substances § 1915.1026 Chromium (VI). (a) Scope....

  8. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 6 2012-07-01 2012-07-01 false Chromium (VI). 1910.1026 Section 1910.1026 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) OCCUPATIONAL SAFETY AND HEALTH STANDARDS (CONTINUED) Toxic and Hazardous Substances § 1910.1026 Chromium (VI). (a) Scope. (1) This...

  9. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 8 2013-07-01 2013-07-01 false Chromium (VI). 1926.1126 Section 1926.1126 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Toxic and Hazardous Substances § 1926.1126 Chromium (VI). (a) Scope. (1) This...

  10. Environmental Durability of Electroplated Black Chromium

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1983-01-01

    Report describes tests of durability of electroplated black chromium coatings on solar-collector panels in rural, industrial, and seacoast environments for 60, 36, and 13 months, respectively. Black-chromium coating showed exceptionally-good optical durability in all three environments.

  11. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  12. CARCINOGEN RISK ASSESSMENT OF CHROMIUM COMPOUNDS

    EPA Science Inventory

    Hexavalent chromium has been identified as a human carcinogen. Evidence to support this contention derives from epidemiologic, animal, and genotoxicity studies. Although workers exposed to both trivalent and hexavalent chromium have been shown to be at an excess risk of respirato...

  13. Effect of chromium doping on the correlated electronic structure of V2O3

    NASA Astrophysics Data System (ADS)

    Grieger, Daniel; Lechermann, Frank

    2014-09-01

    The archetypical strongly correlated Mott-phenomena compound V2O3 is known to show a paramagnetic metal-insulator transition driven by doping with chromium atoms and/or (negative) pressure. Via charge self-consistent density-functional theory+dynamical mean-field theory calculations we demonstrate that these two routes cannot be understood as equivalent. An explicit description of Cr-doped V2O3 by means of supercell calculations and the virtual crystal approximation is performed. Introducing chromium's additional electron to the system is shown to modify the overall many-body electronic structure substantially. Chromium doping increases electronic correlations which in addition induce charge transfers between Cr and the remaining V ions. Thereby the transition-metal orbital polarization is increased by the electron doping, in close agreement with experimental findings.

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

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J.

    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.

  15. Chromium

    MedlinePlus

    ... the research to date is inconclusive. No large, randomized, controlled clinical trials testing this hypothesis have been ... risk of developing the disease. A review of randomized controlled clinical trials evaluated this hypothesis [ 35 ]. This ...

  16. Analytical speciation of chromium in in-vitro cultures of chromate-resistant filamentous fungi.

    PubMed

    Acevedo Aguilar, Francisco Javier; Wrobel, Kazimierz; Lokits, Kirk; Caruso, Joseph A; Coreño Alonso, Alejandro; Gutiérrez Corona, J Felix; Wrobel, Katarzyna

    2008-09-01

    In this work, different analytical speciation schemes have been used to study the reduction of Cr(VI) by a chromate-resistant strain of filamentous fungi Ed8 (Aspergillus sp), indigenous to contaminated industrial wastes. As demonstrated previously, this strain has the capability to reduce chromate present in the growth medium without its accumulation in the biomass, yet the reduced chromium end-products have not been characterized. Liquid growth medium, initially containing 50 mg L(-1) Cr(VI), was analyzed for Cr(III)/Cr(VI) and for total Cr at different time intervals (0-24 h) after inoculation with fungi. Three hyphenated procedures, based on the Cr(III)-EDTA formation and species separation by anion-exchange or ion-pairing reversed-phase chromatography with ICP-MS or DAD detection were used. The results obtained for Cr(VI) in each case were consistent, demonstrating efficient reduction of chromate during 24 h of Ed8 growth. However, pre-column complexation with EDTA did not ensure complete recovery of the reduced forms of chromium in the above procedures. An alternative speciation scheme, based on extraction of Cr(VI)-benzyltributylammonium bromide (BTAB) ion pairs into chloroform and subsequent determination of residual chromium by ICP-MS has provided evidence on the effective conversion of chromate into reduced chromium species in the growth medium. The results indicate the feasibility of using Ed8 strain for chromate bioremediation purposes. Analytically it can be concluded that speciation of chromium in biological systems should not be limited to its two most common oxidation states, because the actual reduced chromium species are not converted quantitatively to Cr(III)-EDTA. PMID:18665354

  17. Immobilization of chromium-contaminated soil by means of microwave energy.

    PubMed

    Tai, H S; Jou, C J

    1999-03-19

    To reduce the amount of hazardous wastes contaminated by heavy metals, a new technology to immobilize heavy metal ions is desired. Microwave (MW) technology which can be used to vitrify the contaminated soil wastes and immobilize the heavy metal ions for this purpose to satisfy the leachate test standard. We found that 90%+ of the chromium-contaminated soil went through the glass/ceramic transformation and was thus vitrified after being radiated with MW for 60 min. The chromium ion (Cr6+) concentration in the leaching test of all the vitrified soil samples is less than 1 mg/l, below the USEPA regulatory limit of 5.0 mg/l. This technology may become a major treatment method for hazardous wastes if the large-scale field test proves to be successful. In this paper, we will present the experimental conditions, the results and the future projects. PMID:10337402

  18. Mechanisms of hexavalent chromium resistance and removal by microorganisms.

    PubMed

    Joutey, Nezha Tahri; Sayel, Hanane; Bahafid, Wifak; El Ghachtouli, Naïma

    2015-01-01

    Chromium has been and is extensively used worldwide in multiple industrial processes and is routinely discharged to the environment from such processes. Therefore, this heavy metal is a potential threat to the environment and to public health, primarily because it is non-biodegradable and environmentally persistent. Chromium exists in several oxidation states, the most stable of which are trivalent Cr(Ill) and hexavalent Cr(VI) species. Each species possesses its own individual chemical characteristics and produces its own biological effects. For example, Cr (Ill) is an essential oligoelement for humans, whereas Cr(VI) is carcinogenic and mutagenic. Several chemical methods are used to remove Cr(VI) from contaminated sites. Each of these methods has advantages and disadvantages. Currently, bioremediation is often the preferred method to deal with Cr contaminated sites, because it is eco-friendly, cost-effective and is a "natural" technology. Many yeast, bacterial and fungal species have been assessed for their suitability to reduce or remove Cr(VI) contamination. The mechanisms by which these microorganisms resist and reduce Cr(VI) are variable and are species dependent. There are several Cr-resistance mechanisms that are displayed by microorganisms. These include active efflux of Cr compounds, metabolic reduction of Cr(VI) to Cr (ill), and either intercellular or extracellular prec1p1tation. Microbial Cr (VI) removal typically involves three stages: binding of chromium to the cell surface, translocation of chromium into the cell, and reduction of Cr(VI) to Cr (ill). Cr(VI) reduction by microorganisms may proceed on the cell surface, outside the cell, or intracellularly, either directly via chromate reductase enzymes, or indirectly via metabolite reduction of Cr(VI). The uptake of chromium ions is a biphasic process. The primary step is known as biosorption, a metabolic energyindependent process. Thereafter, bioaccumulation occurs, but is much slower, and is

  19. Spectroscopic and biological activity studies of the chromium-binding peptide EEEEGDD.

    PubMed

    Arakawa, Hirohumi; Kandadi, Machender R; Panzhinskiy, Evgeniy; Belmore, Kenneth; Deng, Ge; Love, Ebony; Robertson, Preshus M; Commodore, Juliette J; Cassady, Carolyn J; Nair, Sreejayan; Vincent, John B

    2016-06-01

    While trivalent chromium has been shown at high doses to have pharmacological effects improving insulin resistance in rodent models of insulin resistance, the mechanism of action of chromium at a molecular level is not known. The chromium-binding and transport agent low-molecular-weight chromium-binding substance (LMWCr) has been proposed to be the biologically active form of chromium. LMWCr has recently been shown to be comprised of a heptapeptide of the sequence EEEEDGG. The binding of Cr(3+) to this heptapeptide has been examined. Mass spectrometric and a variety of spectroscopic studies have shown that multiple chromic ions bind to the peptide in an octahedral fashion through carboxylate groups and potentially small anionic ligands such as oxide and hydroxide. A complex of Cr and the peptide when administered intravenously to mice is able to decrease area under the curve in intravenous glucose tolerance tests. It can also restore insulin-stimulated glucose uptake in myotubes rendered insulin resistant by treating them with a high-glucose media. PMID:26898644

  20. Biosorption of cadmium, chromium, lead, and zinc by biomass of Medicago sativa (alfalfa)

    SciTech Connect

    Gardea-Torresdey, J.L.; Gonzalez, J.H.; Tiemann, K.J.; Rodriguez, O.

    1996-12-31

    Previous laboratory batch experiments of Medicago sativa (alfalfa) indicated that the African shoots population had an excellent ability to bind copper(II) and nickel(II) ions from aqueous solution. Batch laboratory pH profile, time dependency, and capacity experiments were performed to determine the binding ability of the African shoots to cadmium(II), chromium(III), chromium(VI), lead(II), and zinc(II). Batch pH profile experiments for the mentioned ions indicated that the optimum pH for metal binding is approximately 5.0. Time dependency experiments for the metal ions showed that for all the metals studied, binding to the African alfalfa shoots occurred within five minutes. Binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 7.1 mg Cd, 7.7 mg Cr(III), 43 mg Pb(II), and 4.9 mg Zn(II). However, no binding occurred for chromium(VI). Nearly all of the metals studied were recovered by treatment with 0.1M HCl, with the exception of chromium(III). Column experiments were performed to study the binding of Cd(II), Cr(III), Cr(VI), Pb(II), and Zn(II) to silica-immobilized African alfalfa shoots under flow conditions. These experiments showed that the silica-immobilized African alfalfa shoots were effective for removing metal ions from solution, and over 90% of the bound Pb(II), Cu(II), Ni(II), and Zn(II), and over 70% Cd(II), were recovered after treatment with four bed volumes of 0.1M HCl. The results from these studies will be useful for a novel phytofiltration technology to remove and recover heavy metal ions from aqueous solution.

  1. Occupational asthma due to chromium.

    PubMed

    Leroyer, C; Dewitte, J D; Bassanets, A; Boutoux, M; Daniel, C; Clavier, J

    1998-01-01

    We describe a 28-year-old subject employed as a roofer in a construction company since the age of 19, who developed work-related symptoms of a cough, shortness of breath, wheezing, rhinitis and headaches. A description of a usual day at work suggested that the symptoms worsened while he was sawing corrugated fiber cement. Baseline spirometry was normal, and there was a mild bronchial hyperresponsiveness to carbachol. A skin patch test to chromium was negative. A specific inhalation challenge showed a boderline fall in forced expiratory volume in 1 s (FEV1) after exposure to fiber cement dust. Exposure to nebulization of potassium dichromate (K2Cr2O7), at 0.1 mg.ml-1 for 30 min, was followed by an immediate fall by 20% FEV1. Simultaneously, a significant increase in bronchial hyperresponsiveness was demonstrated. PMID:9782225

  2. Potential of Live Spirulina platensis on Biosorption of Hexavalent Chromium and Its Conversion to Trivalent Chromium.

    PubMed

    Colla, Luciane Maria; Dal'Magro, Clinei; De Rossi, Andreia; Thomé, Antônio; Reinehr, Christian Oliveira; Bertolin, Telma Elita; Costa, Jorge Alberto Vieira

    2015-01-01

    Microalga biomass has been described worldwide according their capacity to realize biosorption of toxic metals. Chromium is one of the most toxic metals that could contaminate superficial and underground water. Considering the importance of Spirulina biomass in production of supplements for humans and for animal feed we assessed the biosorption of hexavalent chromium by living Spirulina platensis and its capacity to convert hexavalent chromium to trivalent chromium, less toxic, through its metabolism during growth. The active biomass was grown in Zarrouk medium diluted to 50% with distilled water, keeping the experiments under controlled conditions of aeration, temperature of 30°C and lighting of 1,800 lux. Hexavalent chromium was added using a potassium dichromate solution in fed-batch mode with the aim of evaluate the effect of several additions contaminant in the kinetic parameters of the culture. Cell growth was affected by the presence of chromium added at the beginning of cultures, and the best growth rates were obtained at lower metal concentrations in the medium. The biomass removed until 65.2% of hexavalent chromium added to the media, being 90.4% converted into trivalent chromium in the media and 9.6% retained in the biomass as trivalent chromium (0.931 mg.g(-1)). PMID:25436450

  3. Determination of chromium(III) and total chromium in marine waters.

    PubMed

    Gardner, M J; Ravenscroft, J E

    1996-03-01

    The development of an analytical technique is described which may be used to determine chromium, chromium(III) and chromium(VI) in estuarine and coastal waters. The method is based on selective micro-solvent extraction with subsequent GFAAS. The technique has been applied in a major North Sea estuary. The results obtained confirm that thermodynamic factors alone cannot be relied upon to describe the form of chromium in estuaries. Kinetic factors appear to have a strong influence over speciation and lead to the persistence of Cr(III) species in environments where Cr(VI) would be expected to be present. PMID:15067453

  4. Efficiency of silicon solar cells containing chromium

    NASA Technical Reports Server (NTRS)

    Salama, A. M. (Inventor)

    1982-01-01

    Efficiency of silicon solar cells containing about one quadrillon atoms cu cm of chromium is improved about 26% by thermal annealing of the silicon wafer at a temperature of 200 C to form chromium precipitates having a diameter of less than 1 Angstrom. Further improvement in efficiency is achieved by scribing laser lines onto the back surface of the wafer at a spacing of at least 0.5 mm and at a depth of less than 13 micrometers to preferentially precipitate chromium near the back surface and away from the junction region of the device. This provides an economical way to improve the deleterious effects of chromium, one of the impurities present in metallurgical grade silicon mateial.

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

    ERIC Educational Resources Information Center

    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)

  6. Efficiency of silicon solar cells containing chromium

    DOEpatents

    Frosch, Robert A. Administrator of the National Aeronautics and Space; Salama, Amal M.

    1982-01-01

    Efficiency of silicon solar cells containing about 10.sup.15 atoms/cm.sup.3 of chromium is improved about 26% by thermal annealing of the silicon wafer at a temperature of 200.degree. C. to form chromium precipitates having a diameter of less than 1 Angstrom. Further improvement in efficiency is achieved by scribing laser lines onto the back surface of the wafer at a spacing of at least 0.5 mm and at a depth of less than 13 micrometers to preferentially precipitate chromium near the back surface and away from the junction region of the device. This provides an economical way to improve the deleterious effects of chromium, one of the impurities present in metallurgical grade silicon material.

  7. Chemical Speciation of Chromium in Drilling Muds

    SciTech Connect

    Taguchi, Takeyoshi; Yoshii, Mitsuru; Shinoda, Kohzo

    2007-02-02

    Drilling muds are made of bentonite and other clays, and/or polymers, mixed with water to the desired viscosity. Without the drilling muds, corporations could not drill for oil and gas and we would have hardly any of the fuels and lubricants considered essential for modern industrial civilization. There are hundreds of drilling muds used and some kinds of drilling muds contain chromium. The chemical states of chromium in muds have been studied carefully due to concerns about the environmental influence. However it is difficult to determine the chemical state of chromium in drilling muds directly by conventional analytical methods. We have studied the chemical form of chromium in drilling muds by using a laboratory XAFS system and a synchrotron facility.

  8. Effect of pH, ionic strength, and background electrolytes on Cr(VI) and total chromium removal by acorn shell of Quercus crassipes Humb. & Bonpl.

    PubMed

    Aranda-García, Erick; Morales-Barrera, Liliana; Pineda-Camacho, Gabriela; Cristiani-Urbina, Eliseo

    2014-10-01

    The ability of Quercus crassipes acorn shells (QCS) to remove Cr(VI) and total chromium from aqueous solutions was investigated as a function of the solution pH, ionic strength, and background electrolytes. It was found that Cr(VI) and total chromium removal by QCS depended strongly on the pH of the solution. Cr(VI) removal rate increased as the solution pH decreased. The optimum pH for total chromium removal varied depending on contact time. NaCl ionic strengths lower than 200 mM did not affect chromium removal. The presence of 20 mM monovalent cations and anions, and of divalent cations, slightly decreased the removal of Cr(VI) and total chromium by QCS; in contrast, divalent anions (SO₄(2-), PO₄(2-), CO₃(2-)) significantly affected the removal of Cr(VI) and total chromium. The biosorption kinetics of chromium ions followed the pseudo-second-order model at all solution pH levels, NaCl ionic strengths and background electrolytes tested. Results suggest that QCS may be a potential low-cost biosorbent for the removal of Cr(VI) and total chromium from aqueous solutions containing various impurities. PMID:24880725

  9. Attenuation of chromium toxicity by bioremediation technology.

    PubMed

    Mohanty, Monalisa; Patra, Hemanta Kumar

    2011-01-01

    Chromium is an important toxic environmental pollutant. Chromium pollution results largely from industrial activities, but other natural and anthropogenic sources also contribute to the problem. Plants that are exposed to environmental contamination by chromium are affected in diverse ways, including a tendency to suffer metabolic stress. The stress imposed by Cr exposure also extends to oxidative metabolic stress in plants that leads to the generation of active toxic oxygen free radicals. Such active free radicals degrade essential biomolecules and distort plant biological membranes. In this chapter, we describe sources of environmental chromium contamination, and provide information about the toxic impact of chromium on plant growth and metabolism. In addition, we address different phytoremediation processes that are being studied for use worldwide, in contaminated regions, to address and mitigate Cr pollution. There has been a long history of attempts to successfully mitigate the toxic effects of chromium-contaminated soil on plants and other organisms. One common approach, the shifting of polluted soil to landfills, is expensive and imposes environmental risks and health hazards of its own. Therefore, alternative eco-friendly bioremediation approaches are much in demand for cleaning chromium-polluted areas. To achieve its cleaning effects, bioremediation utilizes living organisms (bacteria, algae, fungi, and plants) that are capable of absorbing and processing chromium residues in ways which amend or eliminate it. Phytoremediation (bioremediation with plants) techniques are increasingly being used to reduce heavy metal contamination and to minimize the hazards of heavy metal toxicity. To achieve this, several processes, viz., rhizofiltration, phytoextraction, phytodetoxification, phytostabilization, and phytovolatilization, have been developed and are showing utility in practice, or promise. Sources of new native hyperaccumulator plants for use at contaminated

  10. Electrodeposition of microcrystalline chromium from fused salts

    SciTech Connect

    Vargas, T.; Varma, R.; Brown, A.

    1987-01-01

    Chromium can be conveniently electroplated from fused chloride electrolytes. The deposition from LiCl-KCl (eutectic)-CrCl/sub 2/ melts is known to produce large crystal grains. Large grain size and other problems encountered in the electrodeposition of microcrystalline chromium from fused salt are discussed. The results indicate that combined use of forced electrolyte convection and a nucleating pulse in conjunction with a periodic reverse pulse produces fine-grained deposits.

  11. EPR study of the effect of partial pressure of oxygen in the growth atmosphere on concentration of chromium centers in synthetic forsterite

    NASA Astrophysics Data System (ADS)

    Akhmetzyanov, D. A.; Dudnikova, V. B.; Zharikov, E. V.; Zhiteitsev, E. R.; Zaitseva, O. N.; Konovalov, A. A.; Tarasov, V. F.

    2013-03-01

    Samples of synthetic forsterite doped with chromium and grown in an argon atmosphere with different oxygen concentrations (at a partial pressure of oxygen in the range from 0.03 to 0.78 kPa) have been studied using multifrequency electron paramagnetic resonance (EPR) spectroscopy. It has been demonstrated how the oxidizing properties of the atmosphere during the growth of crystals affect the relative concentration of di-, tri-, and tetravalent chromium ions in the samples. The structure of trivalent chromium impurity centers has been discussed.

  12. Effect of metal ions on positron annihilation characteristics in metal ion containing epoxies

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; St. Clair, A. K.; Stoakley, D. M.; Holt, W. H.; Mock, W., Jr.

    1984-01-01

    In the course of developing improved moisture-resistant epoxy resins, two different types of epoxy resins containing variable mole ratios of chromium ions per polymer repeat unit were developed. Positron annihilation characteristics have been investigated in these resins as a function of their metal ion content. In both cases, the presence of metal ions reduces the lifetime as well as the intensity of the long life component. The long life component intensity reduction is considerably more pronounced than the lifetime reduction. These results have been discussed in terms of increased unpaired electron density at Ps formation sites due to the presence of chromium ions in the matrix.

  13. Bioremediation of chromium solutions and chromium containing wastewaters.

    PubMed

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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. PMID:24215114

  16. Tunneling corrosion mechanism of 25% chromium-20% nickel-niobium stainless steel in highly oxidizing nitric acid

    SciTech Connect

    Kajimura, H.; Harada, M.; Okada, T.; Nagano, H.; Okubo, M.

    1995-07-01

    Austenitic stainless steel (SS) is used commonly in chemical plants dealing with nitric acid (HNO{sub 3}) because of its high corrosion resistance. However, even SS tends to corrode intergranularly in highly oxidizing HNO{sub 3} containing oxidizing chromium or cerium ions, such as Cr{sup 6+} or Ce{sup 4+}. Furthermore, pitting corrosion, so-called tunneling corrosion or end-grain attack, occurs on the forgings in highly oxidizing HNO{sub 3}. The mechanism of tunneling corrosion and its countermeasures for a 25% Cr-20% Ni-Nb steel (UNS S31040) in a mock reprocessing plant were studied. Results indicated tunneling corrosion was a type of pitting corrosion with general and intergranular attack on pit surfaces. It propagated along metal flows with penetrations up to 2 mm in diameter and 6 mm in depth. Rates of tunneling corrosion were 3 to 13 times faster than general corrosion. Tunneling corrosion initiated and propagated parallel to metal flows on the local parts where chromium content was depleted. This method of corrosion was caused both by preferential corrosion of a low-chromium part and corrosion accelerated by the galvanic action between a low-chromium part as an anode and a high-chromium part as a cathode. The electroslag remelting process completely resolved this problem by making ingots free from continuous chromium segregation.

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

    PubMed

    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. PMID:25705745

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

    PubMed Central

    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 < 0.5). Conclusion: There was no substantial release of nickel and chromium from 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

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

    NASA Astrophysics Data System (ADS)

    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.

  20. The First Chromium-53 Solid-State Nuclear Magnetic Resonance Spectra of Diamagnetic Chromium(0) and Chromium(VI) Compounds

    SciTech Connect

    Bryce, David L.; Wasylishen, Roderick E.

    2001-01-01

    Chromium-53 is a spin-3/2 nucleus with a relatively small magnetic moment, low natural abundance, and large quadrupole moment. These properties have severely hampered the development of 53Cr NMR, especially in the solid state. In this Communication, the first 53Cr solid-state NMR spectra of prototypal diamagnetic chromium(0) and chromium(VI) compounds are presented. Specifically, analyses of 53Cr NMR spectra of solid hexacarbonylchromium(0), caesium chromate(VI), and potassium chromate(VI) have allowed for the determination of 53Cr quadrupolar coupling parameters and the first chromium chemical shift (CS) tensors. This work demonstrates the potential of 53Cr solid-state NMR, in particular the extreme sensitivity of the 53Cr quadrupolar coupling constant to the local chromium environment. Comparisons are made to known 53Cr NMR parameters available from solution studies, and to the 95Mo solid-state NMR parameters of analogous molybdenum compounds. The influence of crystal symmetry present in isomorphic Cr(CO)6 and Mo(CO)6 is strongly reflected in the magnitudes of the metal nuclei CS tensors and in their orientation with respect to their corresponding electric field gradient tensors.

  1. Hydrolysis of iron and chromium fluorides: mechanism and kinetics.

    PubMed

    Gálvez, José L; Dufour, Javier; Negro, Carlos; López-Mateos, Federico

    2008-06-15

    Fluoride complexes of metallic ions are one of the main problems when processing industrial effluents with high content of fluoride anion. The most important case is derived from pickling treatment of stainless steel, which is performed with HNO3/HF mixtures to remove oxides scale formed over the metal surface. Waste from this process, spent pickling liquor, must be treated for recovering metallic and acid content. Conventional treatments produce a final effluent with high quantity of fluoride complexes of iron and chromium. This work proposes a hydrolysis treatment of these solid metal fluorides by reacting them with a basic agent. Metal oxides are obtained, while fluoride is released to solution as a solved salt, which can be easily recovered as hydrofluoric acid. Solid iron and chromium fluorides, mainly K2FeF5(s) and CrF3(s), obtained in the UCM treatment process, were employed in this work. Optimal hydrolysis operating conditions were obtained by means of a factorial design: media must be basic but pH cannot be higher than 9.5, temperature from 40 to 70 degrees C and alkali concentration (potassium hydroxide) below 1.1 mol L(-1). Secondary reactions have been detected, which are probably due to fluoride adsorption onto obtained oxides surface. Mechanism of reaction consists of several stages, involving solid fluoride dissolution and complexes decomposition. Hydrolysis kinetics has been modeled with classical crystal dissolution kinetics, based on mass transfer phenomena. PMID:17988794

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

    NASA Astrophysics Data System (ADS)

    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.

  3. The effect of chromium substitution on improving electrochemical performance of low-cost Fe-Mn based Li-rich layered oxide as cathode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Taolin; Li, Li; Chen, Shi; Chen, Renjie; Zhang, Xiaoxiao; Lu, Jun; Wu, Feng; Amine, Khalil

    2014-01-01

    Novel lithium-rich cathode materials, LiFe1-xCrxO2·Li2MnO3 (x = 0, 0.1, 0.25, 0.5), have been successfully synthesized using a co-precipitation method followed by hydrothermal and calcination treatment. The effects of Cr substitution on the structure and electrochemical properties of these materials are investigated. These composite materials with layered structure are mainly composed of agglomerated spherical particles with uniform particle size distribution. The sample with x = 0.1 delivers higher initial discharge capacity and higher initial Coulombic efficiency, which is believed to be associated with the oxidation of Cr3+ suggested by the CV curve. This sample also exhibits better rate capability than samples with other “x” values due to its low charge transfer resistance. The best cycling stability and highest reversible discharge capacity (226 mAh g-1 after 50 cycles) are obtained for the sample with x = 0.25. Excessive Cr substitution of Fe in the composite may suppress the oxygen release from Li2MnO3 on the first charging, which is helpful to stabilize the composite structure. This study not only provides a rational design approach for high-capacity cathode materials, but also demonstrates that the LiFe1-xCrxO2·Li2MnO3, is very attractive as cathode materials for lithium-ion batteries, providing that the amount of Cr substitution can be controlled appropriately.

  4. Chromium Recycling in the United States in 1998

    USGS Publications Warehouse

    Papp, John F.

    2001-01-01

    The purpose of this report is to illustrate the extent to which chromium was recycled in the United States in 1998 and to identify chromium-recycling trends. The major use of chromium was in the metallurgical industry to make stainless steel; substantially less chromium was used in the refractory and chemical industries. In this study, the only chromium recycling reported was that which was a part of stainless steel scrap reuse. In 1998, 20 percent of the U.S. apparent consumption of chromium was secondary (from recycling); the remaining 80 percent was based on net chromium commodity imports and stock adjustments. Chromite ore was not mined in the United States in 1998. In 1998, 75,300 metric tons (t) of chromium contained in old scrap was consumed in the United States; it was valued at $66.4 million. Old scrap generated contained 132,000 t of chromium. The old scrap recycling efficiency was 87 percent, and the recycling rate was 20 percent. About 18,000 t of chromium in old scrap was unrecovered. New scrap consumed contained 28,600 t of chromium, which yielded a new-to-old-scrap ratio of 28:72. U.S. chromium-bearing stainless steel scrap net exports were valued at $154 million and were estimated to have contained 41,000 t of chromium.

  5. Production of Chromium Oxide from Turkish Chromite Concentrate Using Ethanol

    NASA Astrophysics Data System (ADS)

    Aktas, S.; Eyuboglu, C.; Morcali, M. H.; Özbey, S.; Sucuoglu, Y.

    2015-05-01

    In this study, the possibility of chromium extraction from Turkish chromite concentrate and the production of chromium oxide were investigated. For the conversion of chromium(III) into chromium(VI), NaOH was employed, as well as air with a rate of 20 L/min. The effects of the base amount, fusing temperature, and fusing time on the chromium conversion percentage were investigated in detail. The conversion kinetics of chromium(III) to chromium(VI) was also undertaken. Following the steps of dissolving the sodium chromate in water and filtering, aluminum hydroxide was precipitated by adjusting the pH level of the solution. The chromium(VI) solution was subsequently converted to Cr(III) by the combination of sulfuric acid and ethanol. Interestingly, it was observed that ethanol precipitated chromium as chromium(VI) at mildly acidic pH levels, although this effect is more pronounced for K2Cr2O7 than Na2Cr2O7. On the other hand, in the strongly acidic regime, ethanol acted as a reducing agent role in that chromium(VI) was converted into Cr(III) whereas ethanol itself was oxidized to carbon dioxide and water. Subsequently, chromium hydroxide was obtained by the help of sodium hydroxide and converted to chromium oxide by heating at 800 °C, as indicated in thermo gravimetric analysis (TGA).

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

    USGS Publications Warehouse

    Izbicki, J.A.; Ball, J.W.; Bullen, T.D.; Sutley, S.J.

    2008-01-01

    Chromium(VI) concentrations in excess of the California Maximum Contaminant Level (MCL) of 50 ??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 ??g/L was measured in aquifers eroded from granitic rock. Chromium(VI) concentrations did not exceed 5 ??g/L at pH < 7.5 regardless of geology. ??53Cr values in native ground-water ranged from 0.7 to 5.1??? and values were fractionated relative to the average ??53Cr composition of 0??? in the earth's crust. Positive ??53Cr values of 1.2 and 2.3??? 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. ??53Cr 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 ??53Cr values were observed as dissolved O2 concentrations decreased, and Cr(VI) was reduced to Cr(III), and subsequently removed from solution. As a result, the highest ??53Cr 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. ??53Cr values at an industrial site overlying mafic alluvium having high natural background Cr(VI) concentrations ranged from -0.1 to 3.2???. Near zero ??53Cr values at the site were the result of anthropogenic Cr. However, mixing with native ground-water and fractionation of Cr within the plume increased ??53Cr values at the site. Although ??53Cr was not necessarily diagnostic of anthropogenic Cr, it was possible to identify the extent of anthropogenic Cr at the site on the basis of the ??53Cr values in conjunction with major-ion data, and the ??18O and ??D composition of water from wells.

  7. The detection of hexavalent chromium by organically doped sol-gels

    SciTech Connect

    Wong, P.W.; Mackenzie, J.D.

    1994-12-31

    The sol-gel process can be used to produce porous inorganic matrices that are doped with organic molecules. These doped gels can be used as a quantitative method for the spectrophotometric determination of trace concentrations of metallic ions. For the detection of hexavalent chromium, malachite green was used as the dopant. Preliminary results indicate concentrations on the order of 5 ppb are detectable using this method.

  8. The enriched chromium neutrino source for GALLEX

    SciTech Connect

    Hartmann, F.X.; Hahn, R.L.

    1991-01-18

    The preparation and study of an intense source of neutrinos in the form of neutron irradiated materials which are enriched in Cr-50 for use in the GALLEX solar neutrino experiment are discussed. Chromyl fluoride gas is enriched in the Cr-50 isotope by gas centrifugation and subsequently converted to a very stable form of chromium oxide. The results of neutron activation analyses of such chromium samples indicate low levels of any long-lived activities, but show that short-lived activities, in particular Na-24, may be of concern. These results show that irradiating chromium oxide enriched in Cr-50 is preferable to irradiating either natural chromium or argon gas as a means of producing a neutrino source to calibrate the GALLEX detector. These results of the impurity level analysis of the enriched chromyl fluoride gas and its conversion to the oxide are also of interest to work in progress by other members of the Collaboration investigating an alternative conversion of the enriched gas to chromium metal. 35 refs., 12 figs., 5 tabs.

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

    PubMed

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1985-12-01

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  12. Cycling Performance of the Iron-Chromium Redox Energy Storage System

    NASA Technical Reports Server (NTRS)

    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.

  13. NONCARCINOGENIC EFFECTS OF CHROMIUM: UPDATE TO HEALTH ASSESSMENT DOCUMENT

    EPA Science Inventory

    This 1990 document updates the 1984 Health Assessment Document for Chromium by addressing issues regarding noncarcinogenic health effects of chromium: oxidation states and persistence of these states in the environment, sampling and analytical methodology to differentiate these o...

  14. Chromium sensitized garnets for mid-IR lasers

    NASA Astrophysics Data System (ADS)

    Moulton, Peter F.

    1990-01-01

    The characteristics of chromium-sensitized solid state lasers operating in the mid-infrared wavelength region were studied. There was continued work on crystals doped with holmium and erbium, operating in the 2100 and 2800 nm regions. In addition, preliminary measurements were made on the laser performance of thulium around 2010 nm. For all these materials the effect of pump pulse length on output energy and overall efficiency was measured. A flashlamp-pumped Cr,Nd:GSGG slab laser was operated and characterized at 1061 and 1310 nm. Measurements included comparison of normal mode slope efficiencies, input-output vs. pump pulse length, characterization of thermal lensing and measurement of Q-switched performance at 1061 nm. Spectroscopic properties of GGG crystals doped with Ce4+ ions were measured, including absorption and emission spectra and fluorescence lifetime.

  15. Chromium isotopic anomalies in the Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Esat, T. M.; Ireland, T. R.

    1989-02-01

    The abundances of chromium isotopes, in refractory inclusions from the Allende meteorite, show wide-spread anomalies. The chromium isotope anomalies are similar in pattern to the anomalies discovered in Ca and Ti. The largest effects occur at the neutron-rich isotopes Ca-48, Ti-50 and Cr-54. Individual Cr-rich pink spinels, from the Murchison meteorite, exhibit large and variable excesses in Cr-53 and Cr-54 including the largest Cr-53 anomaly so far reported. Magnesium isotopes, in Murchison Cr-poor blue spinels, also show variable anomalies in Mg-26 including mass-dependent fractionation favoring the lighter isotopes. The Cr-53, Cr-54 and Mg-26 anomalies in Murchison spinels are indicative of a heterogeneous distribution of magnesium and chromium isotopes in the early solar nebula and require a contribution from several nucleosynthetic components in addition to physicochemical processing.

  16. High-temperature creep of polycrystalline chromium

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Klopp, W. D.

    1972-01-01

    The creep properties of high-purity, polycrystalline chromium were determined over the temperature range 0.51 to 0.78 T sub m, where T sub m is the melting temperature. Creep rates determined from step-load creep tests can be represented by the general creep equation; epsilon/D = k((sigma/E) to the nth power) where epsilon is the minimum creep rate, D is the diffusivity, k is the creep rate constant, sigma is the applied stress, E is the modulus, and n is the stress exponent, equal to 4.3 for chromium. This correlation and metallographic observations suggest a dislocation climb mechanism is operative in the creep of chromium over the temperature range investigated.

  17. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 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...

  18. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    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...

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

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 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. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 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...

  1. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 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...

  2. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (JUN 2013) (a) Definitions. As used...

  3. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (MAY 2011) (a) Definitions. As used...

  4. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  5. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  6. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  7. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (MAY 2011) (a) Definitions. As used...

  8. Effects of exercise on chromium levels. Is supplementation required?

    PubMed

    Clarkson, P M

    1997-06-01

    It is estimated that most individuals are not ingesting sufficient amounts of chromium in their diets. Although there is little information on chromium intake in athletes, many athletes ingest more calories than do non-athletes so their chromium intake should be adequate. However, athletes who restrict calories to maintain low bodyweights could compromise their chromium status. Some evidence also shows that exercise may increase chromium loss into the urine. At present, it is not known whether this loss necessitates additional chromium in the diet or whether the body will increase retention in response to the loss. Chromium deficiency is thought to contribute to glucose intolerance and unhealthy blood lipid profiles. The primary function of chromium is to potentiate the effects of insulin, and thereby alter glucose, amino acid and fat metabolism. Chromium supplements have been purported to increase muscle mass and decrease body fat. However, the preponderance of evidence has not supported this claim. There is little information available on the long term use of chromium supplements, but at present, supplements within the Estimated Safe and Adequate Daily Dietary Allowance (ESADDI) level do not appear harmful. The prudent course of action for athletes would be to ingest foods rich in chromium and perhaps take a multivitamin/mineral supplement containing no more than the ESADDI of chromium. PMID:9219318

  9. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide...

  10. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium oxide greens. 73.1327 Section 73.1327 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens...

  11. REVIEWS OF THE ENVIRONMENTAL EFFECTS OF POLLUTANTS: III. CHROMIUM

    EPA Science Inventory

    The report is a review of the scientific literature on the biological and environmental effects of chromium. Included in the review are a general summary and a comprehensive discussion of the following topics as related to chromium and specific chromium compounds: physical and ch...

  12. Avoidance behavior of young black ducks treated with chromium

    USGS Publications Warehouse

    Heinz, G.H.; Haseltine, S.D.

    1981-01-01

    Pairs of adult black ducks (Anas rubripes) were fed a diet containing 0, 20, or 200 ppm chromium in the form of chromium potassium sulfate. Ducklings from these pairs were fed the same diets as adults and were tested for their avoidance responses to a fright stimulus. Neither level of chromium had a significant effect on avoidance behavior.

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

    PubMed

    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

  14. SAFETY OF TRIVALENT CHROMIUM COMPLEXES USED IN NUTRIENT SUPPLEMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Toxicity studies regarding trivalent chromium have often been completed under conditions that are not designed to reflect conditions that would be encountered under normal physiological conditions. We have shown that the incorporation of chromium into tissues of rats from chromium chloride and chro...

  15. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

  16. Synthesis and characterisation of chromium carbides

    NASA Astrophysics Data System (ADS)

    Detroye, M.; Reniers, F.; Buess-Herman, C.; Vereecken, J.

    1997-11-01

    This paper presents the synthesis and the characterisation of various chromium carbide compounds. Thin Cr 23C 6 films were deposited by reactive sputtering while Cr 7C 3 films were formed by the carburisation of chromium films in a CH 4/H 2 atmosphere. Cr xC y powders were synthesised from various precursors (Cr, CrN, Cr 2O 3) by reaction with CH 4/H 2 at high temperature. The samples were characterised by AES, XRD and electron diffraction. The effects of the experimental parameters (gas composition, temperature, reaction time) on the purity, the phase formed and the composition of the product of reaction are examined and discussed.

  17. Strategies for chromium bioremediation of tannery effluent.

    PubMed

    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

  18. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  19. In Vitro Selection of Chromium-Dependent DNAzymes for Sensing Chromium(III) and Chromium(VI).

    PubMed

    Zhou, Wenhu; Vazin, Mahsa; Yu, Tianmeng; Ding, Jinsong; Liu, Juewen

    2016-07-01

    Chromium is a very important analyte for environmental monitoring, and developing biosensors for chromium is a long-standing analytical challenge. In this work, in vitro selection of RNA-cleaving DNAzymes was carried out in the presence of Cr(3+) . The most active DNAzyme turned out to be the previously reported lanthanide-dependent Ce13d DNAzyme. Although the Ce13d activity was about 150-fold lower with Cr(3+) than that with lanthanides, the activity of lanthanides and other competing metals was masked by using a phosphate buffer; this left Cr(3+) as the only metal that could activate Ce13d. With 100 μm Cr(3+) , the cleavage rate is 1.6 h(-1) at pH 6. By using a molecular beacon design, Cr(3+) was measured with a detection limit of 70 nm, which was significantly lower than the United States Environmental Protection Agency (EPA) limit (11 μm). Cr(4+) was measured after reduction by NaBH4 to Cr(3+) , and it could be sensed with a similar detection limit of 140 nm Cr(4+) ; this value was lower than the EPA limit of 300 nm. This sensor was tested for chromium speciation analysis in a real sample, and the results supported its application for environmental monitoring. At the same time, it has enhanced our understanding of the interactions between chromium and DNA. PMID:27249536

  20. Bis(toluene)chromium(I) [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl and [1,2,5]thiadiazolo[3,4-b]pyrazinidyl: new heterospin (S1 = S2 = ½) radical-ion salts.

    PubMed

    Semenov, Nikolay A; Pushkarevsky, Nikolay A; Suturina, Elizaveta A; Chulanova, Elena A; Kuratieva, Natalia V; Bogomyakov, Artem S; Irtegova, Irina G; Vasilieva, Nadezhda V; Konstantinova, Lidia S; Gritsan, Nina P; Rakitin, Oleg A; Ovcharenko, Victor I; Konchenko, Sergey N; Zibarev, Andrey V

    2013-06-01

    Bis(toluene)chromium(0), Cr(0)(η(6)-C7H8)2 (3), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) and [1,2,5]thiadiazolo[3,4-b]pyrazine (2) in a tetrahydrofuran solvent with the formation of heterospin, S1 = S2 = ½, radical-ion salts [3](+)[1](-) (4) and [3](+)[2](-) (5) isolated in high yields. The salts 4 and 5 were characterized by single-crystal X-ray diffraction (XRD), solution and solid-state electron paramagnetic resonance, and magnetic susceptibility measurements in the temperature range 2-300 K. Despite the formal similarity of the salts, their crystal structures were very different and, in contrast to 4, in 5 anions were disordered. For the XRD structures of the salts, parameters of the Heisenberg spin Hamiltonian were calculated using the CASSCF/NEVPT2 and broken-symmetry density functional theory approaches, and the complex magnetic motifs featuring the dominance of antiferromagnetic (AF) interactions were revealed. The experimental χT temperature dependences of the salts were simulated using the Van Vleck formula and a diagonalization of the matrix of the Heisenberg spin Hamiltonian for the clusters of 12 paramagnetic species with periodic boundary conditions. According to the calculations and χT temperature dependence simulation, a simplified magnetic model can be suggested for the salt 4 with AF interactions between the anions ([1](-)···[1](-), J1 = -5.77 cm(-1)) and anions and cations ([1](-)···[3](+), J2 = -0.84 cm(-1)). The magnetic structure of the salt 5 is much more complex and can be characterized by AF interactions between the anions, [2](-)···[2](-), and by both AF and ferromagnetic (FM) interactions between the anions and cations, [2](-)···[3](+). The contribution from FM interactions to the magnetic properties of the salt 5 is in qualitative agreement with the positive value of the Weiss constant Θ (0.4 K), whereas for salt 4, the constant is negative (-7.1 K). PMID:23687983

  1. Synthesis and characterization of new copper-chromium layered double hydroxides pillared with polyoxovanadates

    SciTech Connect

    Depege, C.; Bigey, L.; Forano, C.

    1996-11-01

    In this study, the authors have focused on the intercalation by ion-exchange of some polyoxovanadate anions from aqueous solution (decavanadate V{sub 10}O{sub 28{sup 6-}}, tetravanadate V{sub 4}O{sub 12}{sup 4-}, and pyrovanadate V{sub 2}O{sub 7}{sup 4-}) into the layers of a copper chromium hydrotalcite-like compound, PXRD, FTIR, TGA, and EXAFS studies have provided information about the specific oxovanadate ions in the interlayers and their orientation. Thermal treatment of these LDHs was also examined. A grafting process of pyrovanadate anions onto the hydroxylated sheets has been demonstrated at room temperature.

  2. Removal of chromium from wastewater by reverse osmosis

    NASA Astrophysics Data System (ADS)

    Çimen, Aysel

    2015-07-01

    Removal of chromium from wastewaters has been studied and the optimal process conditions were determined. The reverse osmosis (RO) technique, the sea water high rejection (SWHR) and high rejection brackish water (AG, SE, and SG) membranes were used. The chromium rejection depended on membrane type, pH of the feed water and operating pressure. The removal of chromium was most effective when the feed water pH 3. The rejection efficiency of the membranes increased in the order AG > SWHR > SG > SE. RO method can be efficiently used (with >91% rejection) for the removal of chromium from wastewater of chromium coating processes.

  3. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... provide change rooms in conformance with 29 CFR 1926.51 Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1926.51. Eating and drinking areas... records are maintained and made available in accordance with 29 CFR 1910.1020. (2) Historical...

  4. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas... records are maintained and made available in accordance with 29 CFR 1910.1020. (2) Historical...

  5. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... provide change rooms in conformance with 29 CFR 1926.51 Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1926.51. Eating and drinking areas... records are maintained and made available in accordance with 29 CFR 1910.1020. (2) Historical...

  6. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas... records are maintained and made available in accordance with 29 CFR 1910.1020. (2) Historical...

  7. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1910.141. Eating and drinking areas... Communication Standard, 29 CFR 1910.1200. (k) Medical surveillance—(1) General. (i) The employer shall...

  8. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs, the employer shall provide washing facilities in conformance with 29 CFR 1910.141. Eating and drinking areas... Communication Standard, 29 CFR 1910.1200. (k) Medical surveillance—(1) General. (i) The employer shall...

  9. Method for welding chromium molybdenum steels

    DOEpatents

    Sikka, Vinod K.

    1986-01-01

    Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

  10. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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 washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas provided by the employer shall...

  11. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  12. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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 washing facilities in conformance with 29 CFR 1915.97. Eating and drinking areas provided by the employer shall...

  13. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  14. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... efficient in removing mono-dispersed particles of 0.3 micrometers in diameter or larger. Historical... 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...

  15. HEALTH ASSESSMENT DOCUMENT FOR CHROMIUM. FINAL REPORT

    EPA Science Inventory

    The full document represents a comprehensive data base that considers all sources of chromium in the environment, the likelihood for its exposure to humans, and the possible consequences to man and lower organisms from its absorption. This information is integrated into a format ...

  16. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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 washing facilities in conformance with 29 CFR 1910.141. Eating and drinking areas provided by the employer shall...

  17. Chemical behavior of acidified chromium (3) solutions

    SciTech Connect

    Terman, D.K.

    1981-05-01

    A unique energy-storage system has been developed at NASA's Lewis Research Center called REDOX. This NASA-REDOX system is an electrochemical storage device that utilized the oxidation and reduction of two fully soluble redox couples for charging and discharging. The redox couples now being investigated are acidified chloride solutions of chromium (Cr(+2)/Cr(+3)) and iron (Fe(+2)/Fe(+3)).

  18. Trace Elements Excluding Iron - Chromium and Zinc

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The percentage of middle-aged US adults who are participating in leisure-time physical activities is growing. These adults also seek credible information about specific supplements that the public press routinely describes as necessary to enable increases in physical performance. Chromium and zinc a...

  19. FATE OF CHROMIUM (III) IN CHLORINATED WATER

    EPA Science Inventory

    The oxidation of trivalent chromium, Cr(III), to the more toxic Cr(VI) in chlorinated water is thermodynamically feasible and was the subject of the study. The study found that free available chlorine (FAC) readily converts Cr(III) to Cr(VI) at a rate that is highly dependent upo...

  20. Nickel-chromium-silicon brazing filler metal

    DOEpatents

    Martini, Angelo J.; Gourley, Bruce R.

    1976-01-01

    A brazing filler metal containing, by weight percent, 23-35% chromium, 9-12% silicon, a maximum of 0.15% carbon, and the remainder nickel. The maximum amount of elements other than those noted above is 1.00%.

  1. The role of mitochondria in chromium carcinogenesis

    SciTech Connect

    Rossi, S.C. )

    1987-01-01

    The uptake and reduction of chromium(VI) compounds are crucial to their carcinogenicity. Many cellular systems have been shown to reduce chromium(VI). The ability of mitochondria to reduce chromate in vitro was investigated using rat liver submitochondrial particles (SMPs), which contain the electron transport chain, and isolated rat liver mitochondria. SMPs with NADH as substrate reduced chromate as shown by EPR and UV-VIS spectroscopic studies. Chromate was reduced to a chromium(V) species, which was detectable by EPR. SMPs with succinate as substrate were less effective in reducing chromate relative to NADH-driven chromate-reductase activity. SMPs show a higher rate of oxygen depletion with NADH as substrate as compared to succinate as substrate. In SMPs with NADH as substrate, rotenone, antimycin and cyanide all produced a {approx}40% inhibition of chromate-reductase activity. In SMPs with succinate as substrate, cyanide and antimycin produced {approx}50% inhibition of chromate-reductase activity and rotenone caused no detectable inhibition. In vivo studies of rats injected with sodium dichromate spiked with {sup 51}Cr showed that after 24 hr, chromium was bound preferentially to mitochondrial DNA relative to nuclear DNA by a factor of {approximately}1500.

  2. Development of low-chromium, chromium-tungsten steels for fusion

    NASA Astrophysics Data System (ADS)

    Klueh, R. L.; Alexander, D. J.; Kenik, E. A.

    1995-12-01

    High-chromium (9-12% Cr) CrMo and CrW ferritic steels are favored as candidates for fusion applications. In early work to develop reduced-activation steels, an Fe2.25Cr2W-0.25V-O.1C steel (designated 2.25Cr-2WV) had better strength than an Fe9Cr2W-0.25V-0.07Tra-0.1C (9Cr-2WVTa) steel (compositions are in weight percent). However, the 2.25Cr-2WV had poor impact properties, as determined by the ductile-brittle transition temperature and upper-shelf energy of subsize Charpy impact specimens. Because low-chromium steels have some advantages over high-chromium steels, a program to develop low-chromium steels is in progress. Microstructural analysis indicated that the reason for the inferior impact toughness of the 2.25Cr-2WV was the granular bainite obtained when the steel was normalized. Properties can be improved by developing an acicular bainite microstructure by increasing the cooling rate after austenitization. Alternatively, acicular bainite can be promoted by increasing the hardenability. Hardenability was changed by adding small amounts of boron and additional chromium to the 2.250-2WV composition. A combination of B, Cr, and Ta additions resulted in low-chromium reduced-activation steels with mechanical properties comparable to those of 9Cr-2WVTa.

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

    PubMed

    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

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

    PubMed

    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

  5. Nephrotoxic and hepatotoxic effects of chromium compounds in rats

    SciTech Connect

    Laborda, R.; Diaz-Mayans, J.; Nunez, A.

    1986-03-01

    The nephrotoxic, hepatotoxic and cardiotoxic actions of hexavalent chromium compounds, as well as their effects on lung, blood and circulation may contribute to the fatal outcome of chromium intoxication. Although trivalent chromium have been regarded as relatively biologically inert, there are a few salts of chromium III that have been found to be carcinogenic when inhaled, ingested or brought in contact with the tissues. Sensitive persons and industry workers have been subjects of dermatitis, respiratory tract injuries and digestive ulcers due to chromium compounds. In this work, the authors have studied the effect of trivalent and hexavalent chromium compounds on rats measuring the transaminases (GOT and GPT), urea and creatinine levels in serum of chromium poisoned animals at different times.

  6. The soda-ash roasting of chromite ore processing residue for the reclamation of chromium

    NASA Astrophysics Data System (ADS)

    Antony, M. P.; Tathavadkar, V. D.; Calvert, C. C.; Jha, A.

    2001-12-01

    Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste stream, for landfills. In recent years, the concern over environmental pollution from hexavalent chromium (Cr6+) from the waste residue has become a major problem for the chromium chemical industry. The main purpose of this investigation is to recover chromium oxide present in the waste residue as sodium chromate. Cr2O3 in the residue is distributed between the two spinel solid solutions, Mg(Al,Cr)2O4 and γ-Fe2O3. The residue from the sodium chromate production process was analyzed both physically and chemically. The compositions of the mineral phases were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The influence of alkali addition on the overall reaction rate is examined. The kinetics of the chromium extraction reaction resulting from the residue of the soda-ash roasting process under an oxidizing atmosphere is also investigated. It is shown that the experimental results for the roasting reaction can be best described by the Ginstling and Brounshtein (GB) equation for diffusion-controlled kinetics. The apparent activation energy for the roasting reaction was calculated to be between 85 and 90 kJ·mol-1 in the temperature range 1223 to 1473 K. The kinetics of leaching of Cr3+ ions using the aqueous phase from the process residue is also studied by treating the waste into acid solutions with different concentrations.

  7. Removal of copper, chromium, and arsenic from CCA-treated wood onto chitin and chitosan.

    PubMed

    Kartal, S Nami; Imamura, Yuji

    2005-02-01

    Chitin and chitosan are naturally abundant biopolymers which are of interest to research concerning the sorption of metal ions since the amine and hydroxyl groups on their chemical structures act as chelation sites for metal ions. This study evaluates the removal of copper, chromium, and arsenic elements from chromated copper arsenate (CCA)-treated wood via biosorption by chitin and chitosan. Exposing CCA-treated sawdust to various amounts of chitin and chitosan for 1, 5, and 10 days enhanced removal of CCA components compared to remediation by deionized water only. Remediation with a solution containing 2.5 g chitin for 10 days removed 74% copper, 62% chromium, and 63% arsenic from treated sawdust. Remediation of treated sawdust samples using the same amount of chitosan as chitin resulted in 57% copper, 43% chromium, and 30% arsenic removal. The results suggest that chitin and chitosan have a potential to remove copper element from CCA-treated wood. Thus, these more abundant natural amino polysaccharides could be important in the remediation of waste wood treated with the newest formulations of organometallic copper compounds and other water-borne wood preservatives containing copper. PMID:15474943

  8. Cr3+ NMR for Multiferroic Chromium spinel ZnCr2Se4

    NASA Astrophysics Data System (ADS)

    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.

  9. Oral bioavailability of chromium from a specific site.

    PubMed Central

    Witmer, C M; Harris, R; Shupack, S I

    1991-01-01

    Analysis of soil from a specific site in New Jersey indicated a low level of sodium and chromium present as a calcium compound. Chromium was then administered orally to young, mature male rats at a level of 240 micrograms/kg for 14 days as chromium-contaminated soil, as CaCrO4, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hr after the last dosing, and tissues were taken immediately for chromium analysis. Blood, muscle, and liver contained the highest levels of chromium in these animals, although kidney contained the highest concentration per gram of tissue. The total amount of chromium in the tissues was less than 2% of the administered chromium. In a study of the excretion of chromium, the animals were dosed orally for 8 days (with CaCrO4 or contaminated soil, each at the level of 240 mumole Cr/kg), and the chromium in feces and urine was determined on days 1, 2, 7, and 8. After cessation of dosing for 27 days, the same rats were dosed for 2 days at the same level, and chromium in urine and feces was determined for the 2 days. The animals administered the chromium in soil had higher levels of chromium in both urine and feces on all days compared to the group fed the CaCrO4. The total recovery of chromium in any of the 2-day periods was less than 50% of the chromium administered during that period. PMID:1935839

  10. REMOVAL OF CHROMIUM FROM ION EXCHANGE REGENERANT SOLUTION

    EPA Science Inventory

    The purpose of the present study was to establish means of removing the chromate (Cr(VI)) from spent regenerant solution, thus rendering it a non-toxic brine. In the bench-scale study, the Cr(VI) was reduced to Cr(III) and then precipitated as Cr(OH)3(s). Sulfite, hydrazine, and ...

  11. Investigation of simultaneous biosorption of copper(II) and chromium(VI) on dried Chlorella vulgaris from binary metal mixtures: Application of multicomponent adsorption isotherms

    SciTech Connect

    Aksu, Z.; Acikel, U.; Kutsal, T.

    1999-02-01

    Although the biosorption of single metal ions to various kinds of microorganisms has been extensively studied and the adsorption isotherms have been developed for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of multimetal ions systems. In this study the simultaneous biosorption of copper(II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for chromium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or chromium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ions systems at these two pH values, and expressed by the mono- and multicomponent Langmuir and Freundlich adsorption models. Model parameters were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in the concentration ranges studied.

  12. The need for combined inorganic, biochemical, and nutritional studies of chromium(III).

    PubMed

    Vincent, John B; Love, Sharifa T

    2012-09-01

    The history of biochemical and nutritional studies of the element is unfortunately full of twists and turns, most leading to dead ends. Chromium (Cr), as the trivalent ion, has been proposed to be an essential element, a body mass and muscle development agent, and, in the form of the most popular Cr-containing nutritional supplement, to be toxic when given orally to mammals. None of these proposals, despite significant attention in the popular media, has proven to be correct. Trivalent chromium has also been proposed as a therapeutic agent to increase insulin sensitivity and affect lipid metabolism, although a molecular mechanism for such actions has not been elucidated. Greater cooperative research interactions between nutritionists, biochemists, and chemists might have avoided the earlier issues in nutritional and biochemical Cr research and is necessary to establish the potential role of Cr as a therapeutic agent at a molecular level. PMID:22976981

  13. Kinetics of Chromium(III) Transport Through a Liquid Membrane Containing DNNSA as a Carrier

    PubMed Central

    Religa, Paweł; Gawroński, Roman; Gierycz, Paweł

    2009-01-01

    Kinetics of Cr(III) ions transport through a bulk liquid membrane containing dinonylnaphthalenesulfonic acid (DNNSA) as a carrier, flowing over aqueous phases, has been examined. Special attention has been paid to the effect of the membrane’s velocity flow on the chromium concentration decrease in a feed phase. For the description of relationships of chromium(III) concentration in particular phases with the time, a model based on the assumption of consecutive first-order reactions was proposed. Satisfactory compatibility of experiments and model results have been obtained both for the membrane flow velocities below 0.0034 m·s−1 when the interfaces begin to fluctuate slightly and for low initial Cr(III) concentration in the feed phase. PMID:19399232

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Electronic States of Half-Metallic Chromium Oxides Probed by 53Cr NMR

    NASA Astrophysics Data System (ADS)

    Takeda, Hikaru; Shimizu, Yasuhiro; Itoh, Masayuki; Isobe, Masahiko; Ueda, Yutaka

    2012-12-01

    We have performed 53Cr NMR measurements to investigate local electronic states of K2Cr8O16 and CrO2 which are ferromagnetic half-metals with high valent chromium ions. In the ferromagnetic metallic phases of both oxides, we observed at least two 53Cr NMR spectra which are inconsistent with crystallographically inequivalent one chromium site on a tetragonal lattice, the hollandite structure (symmetry I4/m) of K2Cr8O16 and the rutile structure (P42mnm) of CrO2. The origin of this anomalous electronic state may be associated with an electronic phase separation in double exchange systems with the mixed valence.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  19. Chromium Diffusion Doping on ZnSe Crystals

    NASA Technical Reports Server (NTRS)

    Journigan, Troy D.; Chen, K.-T.; Chen, H.; Burger, A.; Schaffers, K.; Page, R. H.; Payne, S. A.

    1997-01-01

    Chromium doped zinc selenide crystal have recently been demonstrated to be a promising material for near-IR room temperature tunable lasers which have an emission range of 2-3 micrometers. In this study a new diffusion doping process has been developed for incorporation of Cr(+2) ion into ZnSe wafers. This process has been successfully performed under isothermal conditions, at temperatures above 800 C. Concentrations in excess of 10(exp 19) Cr(+2) ions/cu cm, an order of magnitude larger than previously reported in melt grown ZnSe material, have been obtained by diffusion doping, as estimated from optical absorption measurements. The diffusivity was estimated to be about 10(exp -8) sq cm/sec using a thin film diffusion model. Resistivity was derived from current-voltage measurements and in the range of 10(exp 13) and 10(exp 16) omega-cm. The emission spectra and temperature dependent lifetime data will also be presented and discussed.

  20. Elementary surface processes during reactive magnetron sputtering of chromium

    SciTech Connect

    Monje, Sascha; Corbella, Carles Keudell, Achim von

    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.

  1. Incorporation of chromium into TiO{sub 2} nanopowders

    SciTech Connect

    Kollbek, Kamila; Sikora, Marcin; Kapusta, Czesław; Szlachetko, Jakub; Radecka, Marta; Lyson-Sypien, Barbara; Zakrzewska, Katarzyna

    2015-04-15

    Highlights: • Nanopowders of TiO{sub 2}: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 TiO{sub 2} 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 TiO{sub 2}:10 at.% Cr sample (0.12 emu K/mol Oe) is lower than that expected for Cr{sup 3+} (0.1875 emu K/mol Oe) possibly due to the appearance of Cr{sup 4+} or the presence of the orbital contribution to the magnetic moment.

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

    PubMed

    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

  3. International strategic minerals inventory summary report; chromium

    USGS Publications Warehouse

    DeYoung, J.H., Jr.; Lee, M.P.; Lipin, B.R.

    1984-01-01

    Major world resources of chromium, a strategic mineral commodity, are described in this summary report of information in the International Strategic Minerals Inventory {ISMI}. ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, and the United States of America. This report, designed to be of benefit to policy analysts, contains two parts. Part I presents an overview of the resources and potential supply of chromium on the basis of inventory information. Part II contains tables of some of the geologic information and mineral-resource and production data that were collected by ISMI participants.

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

    SciTech Connect

    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

  5. Observational Approach to Chromium Site Remediation - 13266

    SciTech Connect

    Scott Myers, R.

    2013-07-01

    Production reactors at the U.S. Department of Energy's (DOE) Hanford Site in Richland, Washington, required massive quantities of water for reactor cooling and material processing. To reduce corrosion and the build-up of scale in pipelines and cooling systems, sodium dichromate was added to the water feedstock. Spills and other releases at the makeup facilities, as well as leaks from miles of pipelines, have led to numerous areas with chromium-contaminated soil and groundwater, threatening fish populations in the nearby Columbia River. Pump-and-treat systems have been installed to remove chromium from the groundwater, but significant contamination remain in the soil column and poses a continuing threat to groundwater and the Columbia River. Washington Closure Hanford, DOE, and regulators are working on a team approach that implements the observational approach, a strategy for effectively dealing with the uncertainties inherent in subsurface conditions. Remediation of large, complex waste sites at a federal facility is a daunting effort. It is particularly difficult to perform the work in an environment of rapid response to changing field and contamination conditions. The observational approach, developed by geotechnical engineers to accommodate the inherent uncertainties in subsurface conditions, is a powerful and appropriate method for site remediation. It offers a structured means of quickly moving into full remediation and responding to the variations and changing conditions inherent in waste site cleanups. A number of significant factors, however, complicate the application of the observational approach for chromium site remediation. Conceptual models of contamination and site conditions are difficult to establish and get consensus on. Mid-stream revisions to the design of large excavations are time-consuming and costly. And regulatory constraints and contract performance incentives can be impediments to the flexible responses required under the observational

  6. Laser action in chromium-doped forsterite

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.; Yamagishi, Kiyoshi; Anzai, H.

    1988-01-01

    This paper reports on pulsed laser operation obtained in chromium-activated forsterite Cr(3+):Mg2SiO4 at room temperature. The spectrum of the free-running laser peaks at 1235 nm and a bandwidth of about 22 nm. The spectral range of the laser emission is expected to extend from 850 to 1300, provided the parasitic impurity absorption may be minimized by improved crystal growth techique.

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

    PubMed

    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. PMID:25476274

  8. X-616 Chromium Sludge Lagoons pictorial overview, Piketon, Ohio

    SciTech Connect

    Not Available

    1992-10-01

    The Portsmouth Gaseous Diffusion Plant uses large quantities of water for process cooling. The X-616 Liquid Effluent Control Facility was placed in operation in December 1976 to treat recirculation cooling water blowdown from the process cooling system. A chromium-based corrosion inhibitor was used in the cooling water system. A chromium sludge was produced in a clarifier to control chromium levels in the water. Chromium sludge produced by this process was stored in two surface impoundments called the X-616 Chromium Sludge Lagoons. The sludge was toxic due to its chromium concentration and therefore required treatment. The sludge was treated, turning it into a sanitary waste, and buried in an Ohio EPA approved landfill. The plant's process cooling water system has changed to a more environmentally acceptable phosphate-based inhibitor. Closure activities at X-616 began in August 1990, with all construction activities completed in June 1991, at a total cost of $8.0 million.

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

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The United States depends entirely on foreign sources for the critical material, chromium, making it very vulnerable to supply disruptions. 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.

  10. Method of trivalent chromium concentration determination by atomic spectrometry

    DOEpatents

    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.

  11. Stabilization and solidification of chromium-contaminated soil

    SciTech Connect

    Cherne, C.A.; Thomson, B.M.; Conway, R.

    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.

  12. Effect of processing cement to concrete on hexavalent chromium levels.

    PubMed

    Turk, K; Rietschel, R L

    1993-04-01

    Hexavalent chromium sensitization is known to occur from exposure to cement. Concrete is a mixture of cement, sand, rock, and water. Admixtures are compounds used to retard or accelerate concrete setting time. Some countries use ferrous sulfate to reduce hexavalent chromium in cement. We evaluated and compared hexavalent chromium levels in cement, rock (aggregate), and wet and dry concrete in samples from Singapore, Ireland, Denmark, Australia, and the United States. Cement from Denmark contains ferrous sulfate. The effect of representative admixtures on hexavalent chromium concentration in concrete was also evaluated, but technical limitations made evaluation difficult. Soluble chromium levels in cement ranged from 0.225 mg/kg in the US sample to 0.036 mg/kg in the Singapore sample. Aggregate chromium levels ranged from 0.083 mg/kg in the Denmark sample to < 0.002 mg/kg in the Ireland sample. Fresh US concrete, with 1.27 mg/kg hexavalent chromium, contained the highest level. The Denmark sample, with ferrous sulfate added, was lowest (< 0.01 mg/kg). Hardened concrete levels ranged from 0.104 mg/kg from the Ireland sample to 0.002 mg/kg from the Singapore sample. Therefore, hexavalent chromium levels do appear to be influenced by admixtures and by processing from powdered cement to dry concrete. Ferrous sulfate significantly reduced hexavalent chromium levels in fresh cement. PMID:8508629

  13. Studies on the essentiality of chromium in ruminants

    SciTech Connect

    Samsell, L.J.; Spears, J.W.

    1986-03-01

    Although chromium has been established as an essential trace element for certain animal species, no requirement has been shown for ruminants. Sixteen female lambs (35 kg) were used in an attempt to determine if chromium is essential in the ruminant. Animals were individually housed in all plastic pens and fed twice daily either a low chromium (100 ppb) torula yeast based diet or the basal diet supplemented with 10 ppm chromium as CrCl/sub 3/. Blood samples obtained prior to the morning feeding and 2 and 6 hr post-feeding on days 28 and 56 indicated no significant treatment differences in plasma glucose or serum free fatty acids. By day 56, serum cholesterol tended to be lower in chromium supplemented lambs (60.9 vs 71.7 mg/dl). Lambs in the chromium supplemented treatment also tended to gain more efficiently through 56 days (.130 vs .118 gain/fed). On day 84, lambs were bled after a 48 hr fast, refed, then bled again at 2 and 6 hr post-feeding. Plasma glucose and serum free fatty acids were not affected by chromium at the end of the 48 hr fast or when lambs were refed following fasting. At 84 days both total serum cholesterol and HDL-cholesterol were lower in lambs receiving supplemental chromium. These results suggest that chromium may have a biological role in the ruminant.

  14. Quantitative chemical analysis of nickel-chromium dental casting alloys.

    PubMed

    Nagayama, K; Kuroiwa, A; Ando, Y; Hashimoto, H

    1990-01-01

    Twenty-nine brands of dental casting nickel-chromium alloys made in Japan for small castings were analyzed by electron probe X-ray microanalyzer. Nickel-chromium alloys for metal-ceramic application were composed primarily of nickel, chromium, and molybdenum with the exception of one brand. Of the nickel-chromium alloys for inlay, crown, and bridgework applications, 11 of the 22 alloys were up to the standard of the Ministry of Welfare specifications. And additive metal elements of these alloys were molybdenum, iron, copper, manganese, aluminum, silicon, tin, indium, silver, titanium, and gallium. PMID:2134288

  15. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  16. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  17. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 28 2013-07-01 2013-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  18. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  19. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 28 2012-07-01 2012-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  20. Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column.

    PubMed

    Rajesh, N; Mishra, Braja Gopal; Pareek, Pawan Kumar

    2008-02-01

    A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1microgmL(-1) chromium(VI) with a detection limit of 6microgL(-1). A highest preconcentration factor of 25 could be obtained for 250mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples. PMID:17604681

  1. Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column

    NASA Astrophysics Data System (ADS)

    Rajesh, N.; Mishra, Braja Gopal; Pareek, Pawan Kumar

    2008-02-01

    A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1 μg mL -1 chromium(VI) with a detection limit of 6 μg L -1. A highest preconcentration factor of 25 could be obtained for 250 mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples.

  2. Synthesis of magnetic alginate hybrid beads for efficient chromium (VI) removal.

    PubMed

    Gopalakannan, Venkatrajan; Viswanathan, Natrayasamy

    2015-01-01

    Recently magnetic bio-composites have attracted the attention of scientists because of their unique characteristics like selectivity and high sorption capacity. In the present study, Fe3O4@Alg-Ce magnetic composite beads were developed by incorporating Fe3O4 particles onto alginate (Alg) biopolymer followed by cross-linking with Ce(3+) ions. The synthesized magnetic beads were characterized using FTIR and SEM with EDAX analysis and utilized for chromium (VI) removal in batch mode. A comparative adsorption performance of Fe3O4 particles, calcium alginate (CaAlg) composite and Fe3O4@Alg-Ce magnetic hybrid beads was made. The magnetic alginate beads possess an enhanced SC of 14.29 mg/g than CaAlg composite and Fe3O4 particles which possess SC of 9.45 and 9.72 mg/g respectively. The various sorption influencing parameters like contact time, pH, challenger anions, initial chromium concentration and temperature were optimized. The adsorption process was explained using Freundlich and Langmuir isotherms. The sorption kinetics was fitted well with the pseudo second order and intra particle diffusion model. The calculated thermodynamic parameters indicate the nature of chromium sorption is spontaneous and endothermic. PMID:25256552

  3. Low temperature dry etching of chromium towards control at sub-5 nm dimensions.

    PubMed

    Staaks, Daniel; Yang, XiaoMin; Lee, Kim Y; Dhuey, Scott D; Sassolini, Simone; Rangelow, Ivo W; Olynick, Deirdre L

    2016-10-14

    Patterned chromium and its compounds are crucial materials for nanoscale patterning and chromium based devices. Here we investigate how temperature can be used to control chromium etching using chlorine/oxygen gas mixtures. Oxygen/chlorine ratios between 0% and 100% and temperatures between -100 °C and +40 °C are studied. Spectroscopic ellipsometry is used to precisely measure rates, chlorination, and the thickness dependence of n and k. Working in the extremes of oxygen content (very high or very low) and lower temperatures, we find rates can be controlled to nanometers per minute. Activation energies are measured and show that etch mechanisms are both temperature and oxygen level dependent. Furthermore, we find that etching temperature can manipulate the surface chemistry. One surprising consequence is that at low oxygen levels, Etching rates increase with decreasing temperature. Preliminary feature-profile studies show the extremes of temperature and oxygen provide advantages over commonly used room temperature processing conditions. One example is with higher ion energies at -100 °C, where etching products deposit. PMID:27606715

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

    PubMed

    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

  5. Synthesis, reaction and structure of a series of chromium(III) complexes containing oxalate ligand

    NASA Astrophysics Data System (ADS)

    Chen, Xu-Fang; Liu, Li; Ma, Jian-Gong; Yi, Long; Cheng, Peng; Liao, Dai-Zheng; Yan, Shi-Ping; Jiang, Zong-Hui

    2005-08-01

    A series of chromium(III) complexes [Cr(bipy)(HC2O4)2]Cl·3H2O (1), [Cr(phen)(HC2O4)2]Cl·3H2O (2), [Cr(phen)2(C2O4)]ClO4 (3), [Cr2(bipy)4(C2O4)](SO4)·(bipy)0.5·H2O (4) and [Mn(phen)2(H2O)2]2[Cr(phen)(C2O4)2]3ClO4·14H2O (5) were synthesized (bipy=4,4‧-bipyridine, phen=1,10-phenanthroline), while the crystal structures of 1 and 3-5 have been determined by X-ray analysis. 1 and 3 are mononuclear complexes, 4 contains binuclear chromium(III) ions and 5 is a 3D supromolecule formed by complicated hydrogen bonding. 1-3 are potential molecular bricks of chromium(III) building blocks for synthesis heterometallic complexes. When we use these molecular bricks as ligands to react with other metal salts, unexpected complexes 4 and 5 are isolated in water solution. The synthesis conditions and reaction results are also discussed.

  6. [The complexes of copper, manganese and chromium with enzymatic hydrolysate of pig spleen: research in vitro].

    PubMed

    Zorin, S N; Sidorova, Yu S; Pleten, A P; Mazo, V K

    2016-01-01

    This report describes the preparation and the results of physical and chemical analysis of complexes of enzymatic hydrolysate of pig spleen (EHPS) with manganese, copper and chromium. The complexes were prepared using schemes including the reaction of complexation of inorganic cations with EHPS-peptides structures and application of membrane technology. The process of microfiltration of the resulting mixtures was carried out in tangential flow and low molecular weight fractions were collected. Solutions of copper and manganese complexes with EHPS were subjected to nanofiltration to remove inorganic ions from the reaction mixture. The obtained preparations were lyophilic dried and the molecular weight distribution of the protein fractions in Cu-EHPS, Mn-EHPS and Cr-EHPS complexes was analyzed by exclusion medium pressure liquid chromatography. The percentage relation of fractions with specific molecular weight range was calculated by applying the weighted integration of chromatograms. The determination of copper, manganese and chromium levels in the complexes was performed by atomic absorption method. The content of microelements in the preparations is for copper 16.5 ± 0.3 mg/g, for manganese--24.9 ± 0.5 mg/g and for chromium--2.5 ± 0.2 mg/g. PMID:27228705

  7. Inducible chromate reductase exhibiting extracellular activity in Bacillus methylotrophicus for chromium bioremediation.

    PubMed

    Sandana Mala, John Geraldine; Sujatha, Dhanasingh; Rose, Chellan

    2015-01-01

    Chromium toxicity is one of the major causes of environmental pollution due to its heavy discharge in industrial wastewaters. Chromate reduction is a viable method to detoxify hexavalent chromium to nontoxic trivalent species mediated by enzymes and metabolites. A new Bacillus methylotrophicus strain was isolated from tannery sludge and was an efficient candidate for chromate reduction. An initial chromate reductase activity of 212.84 U/mg protein was obtained at 48 h in a low-cost defined medium formulation with 0.25 mM chromate. The extracellular enzyme was inducible at 12h substrate addition with 312.99 U/mg at 48 h. Reduced glutathione was required for enhanced specific activity of 356.48 U/mg. Enzyme activity was optimum at pH 7.0 and at 30 °C, and was stable in the presence of EDTA, DTT and metal ions. The enzyme exhibited a Vmax of 59.89 μM/min/mg protein and a Km of 86.5 μM, suggesting feasibility of the reaction with K₂Cr₂O₇ as substrate. Application of the crude reductase in tannery effluent resulted in 91.3% chromate reduction at 48 h. An enzyme-mediated chromate reduction process has therefore been developed for bioremediation of toxic chromium sp. in industrial effluents. PMID:24985094

  8. Chromium reduces the in vitro activity and fidelity of DNA replication mediated by the human cell DNA synthesome

    SciTech Connect

    Dai Heqiao; Liu Jianying; Malkas, Linda H.; Catalano, Jennifer; Alagharu, Srilakshmi

    2009-04-15

    Hexavalent chromium Cr(VI) is known to be a carcinogenic metal ion, with a complicated mechanism of action. It can be found within our environment in soil and water contaminated by manufacturing processes. Cr(VI) ion is readily taken up by cells, and is recognized to be both genotoxic and cytotoxic; following its reduction to the stable trivalent form of the ion, chromium(Cr(III)), within cells. This form of the ion is known to impede the activity of cellular DNA polymerase and polymerase-mediated DNA replication. Here, we report the effects of chromium on the activity and fidelity of the DNA replication process mediated by the human cell DNA synthesome. The DNA synthesome is a functional multiprotein complex that is fully competent to carry-out each phase of the DNA replication process. The IC{sub 50} of Cr(III) toward the activity of DNA synthesome-associated DNA polymerases {alpha}, {delta} and {epsilon} is 15, 45 and 125 {mu}M, respectively. Cr(III) inhibits synthesome-mediated DNA synthesis (IC{sub 50} = 88 {mu}M), and significantly reduces the fidelity of synthesome-mediated DNA replication. The mutation frequency induced by the different concentrations of Cr(III) ion used in our assays ranges from 2-13 fold higher than that which occurs spontaneously, and the types of mutations include single nucleotide substitutions, insertions, and deletions. Single nucleotide substitutions are the predominant type of mutation, and they occur primarily at GC base-pairs. Cr(III) ion produces a lower number of transition and a higher number of transversion mutations than occur spontaneously. Unlike Cr(III), Cr(VI) ion has little effect on the in vitro DNA synthetic activity and fidelity of the DNA synthesome, but does significantly inhibit DNA synthesis in intact cells. Cell growth and proliferation is also arrested by increasing concentrations of Cr(VI) ion. Our studies provide evidence indicating that the chromium ion induced decrease in the fidelity and activity of

  9. Origin of ferromagnetism enhancement in bi-layer chromium-doped indium zinc oxides

    SciTech Connect

    Hsu, C. Y.

    2012-08-06

    This work demonstrates that by controlling the rapid thermal annealing temperature, amorphous chromium-doped indium zinc oxide films develop an amorphous-crystalline bi-layer structure and show magnetization up to {approx}30 emu/cm{sup 3}. The crystalline layer arises from significant out-diffusion of Zn from surfaces, leading to a large difference in the Zn:In ratio in amorphous and crystalline layers. Doped Cr ions in amorphous and crystalline layers form different valence configurations, creating a charge reservoir which transfers electrons through amorphous-crystalline interfaces and in turn enhances ferromagnetism.

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

    SciTech Connect

    Krebs, J.K.; Happek, U.

    2005-12-19

    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{sub 3}). In order to assess the quality of sol-gel derived LiNbO{sub 3}, we incorporate Cr{sup 3+} during the hydrolysis stage of the sol-gel process. A comparison of the Cr{sup 3+} emission and photoexcitation data on both sol-gel and melt-grown LiNbO{sub 3} shows that the sol-gel derived material is highly stoichiometric.

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

    PubMed

    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

  12. COST EFFECTIVE CONTROL OF HEXAVALENT CHROMIUM AIR EMISSIONS FROM FUNCTIONAL CHROMIUM ELECTROPLATING

    EPA Science Inventory

    This paper will summrize thie pollution prevention (p2) method to control stack emissions from hard chromium plating operations performed by the USEPA's National Risk Management Research Laboratory (NRMRL) over the last four years. During literature research and user surveys, it...

  13. A Laboratory Procedure for the Reduction of Chromium(VI) to Chromium(III).

    ERIC Educational Resources Information Center

    Lunn, George; Sansone, Eric B.

    1989-01-01

    Chromium(VI) compounds are classified as oxidizers and must be specially packaged and transported for disposal while Cr(III) compounds are considered nonoxidizers. A process which reduces Cr(VI) to Cr(III) by adding sodium metabisulfite followed by neutralization with magnesium hydroxide is explored. (MVL)

  14. ALUMINUM AND CHROMIUM LEACHING WORKSHOP WHITEPAPER

    SciTech Connect

    McCabe, D; Jeff Pike, J; Bill Wilmarth, B

    2007-04-25

    A workshop was held on January 23-24, 2007 to discuss the status of processes to leach constituents from High Level Waste (HLW) sludges at the Hanford and Savannah River Sites. The objective of the workshop was to examine the needs and requirements for the HLW flowsheet for each site, discuss the status of knowledge of the leaching processes, communicate the research plans, and identify opportunities for synergy to address knowledge gaps. The purpose of leaching of non-radioactive constituents from the sludge waste is to reduce the burden of material that must be vitrified in the HLW melter systems, resulting in reduced HLW glass waste volume, reduced disposal costs, shorter process schedules, and higher facility throughput rates. The leaching process is estimated to reduce the operating life cycle of SRS by seven years and decrease the number of HLW canisters to be disposed in the Repository by 1000 [Gillam et al., 2006]. Comparably at Hanford, the aluminum and chromium leaching processes are estimated to reduce the operating life cycle of the Waste Treatment Plant by 20 years and decrease the number of canisters to the Repository by 15,000-30,000 [Gilbert, 2007]. These leaching processes will save the Department of Energy (DOE) billions of dollars in clean up and disposal costs. The primary constituents targeted for removal by leaching are aluminum and chromium. It is desirable to have some aluminum in glass to improve its durability; however, too much aluminum can increase the sludge viscosity, glass viscosity, and reduce overall process throughput. Chromium leaching is necessary to prevent formation of crystalline compounds in the glass, but is only needed at Hanford because of differences in the sludge waste chemistry at the two sites. Improving glass formulations to increase tolerance of aluminum and chromium is another approach to decrease HLW glass volume. It is likely that an optimum condition can be found by both performing leaching and improving

  15. Urinary chromium concentrations in humans following ingestion of safe doses of hexavalent and trivalent chromium: Implications for biomonitoring

    SciTech Connect

    Finley, B.L.; Scott, P.K.; Norton, R.L.

    1996-08-09

    This study evaluates the significance of increased urinary chromium concentrations as a marker of chromium exposure and potential health risk. Six human volunteers ingested trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)] at doses that are known to be safe but higher than typical levels. The following dosing regimen was used: d 1-7, 200 {mu}g/d chromium picolinate; d 8-10, Cr(VI) ingestion at the U.S. Environmental Protection Agency (EPA) reference dose (RfD) of 0.005 mg/kg/d; d 11-13, no dose; d 14-16, Cr(III) ingestion at the U.S. EPA RfD of 1.0 mg/kg/d; and 17-18, postdose. Findings are as follows: (1) ingestion of 200 {mu}g/d of chromium picolinate yielded significantly elevated urine concentrations such that each participant routinely exceeded background, (2) ingestion of the Cr(VI) RfD (0.005 mg/kg/d) yielded individual mean urinary chromium levels (1.2-2.3 {mu}g/L) and a pooled mean urinary chromium level (2.4 {mu}g/L) that significantly exceeded background, and (3) ingestion of the Cr(III) RfD yielded no significantly exceeded background, and (3) ingestion of the Cr(III) RfD yielded no significant increase in urinary chromium concentrations, indicating that little, if any, absorption occurred. Our work identified three critical issues that need to be accounted for in any future studies that will use urinary chromium as a marker of exposure. First, a minimum urinary chromium concentration of approximately 2 {mu}g/L should be used as a screening level to critically identify individuals who may have experienced elevated exposures to chromium. Second, if Cr(III) levels in soils are known to be less than 80,000 ppm and the Cr(III) is insoluble, urinary chromium concentrations are not an appropriate marker of exposure. Third, newer forms of chromium supplements that contain organic forms of Cr(III) must be considered potential confounders and their contribution to residential chromium uptake must be carefully evaluated. 19 refs., 7 figs., 3 tabs.

  16. Improved Atmospheric Sampling of Hexavalent Chromium

    PubMed Central

    Torkmahalleh, Mehdi Amouei; Yu, Chang-Ho; Lin, Lin; Fan, Zhihua (Tina); Swift, Julie L.; Bonanno, Linda; Rasmussen, Don H.; Holsen, Thomas M.; Hopke, Philip K.

    2015-01-01

    Hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) are the primary chromium oxidation states found in ambient atmospheric particulate matter. While Cr(III) is relatively nontoxic, Cr(VI) is toxic and exposure to Cr(VI) may lead to cancer, nasal damage, asthma, bronchitis, and pneumonitis. Accurate measurement of the ambient Cr(VI) concentrations is an environmental challenge since Cr(VI) can be reduced to Cr(III) and vice versa during sampling. In the present study, a new Cr(VI) sampler (Clarkson sampler) was designed, constructed, and field tested to improve the sampling of Cr(VI) in ambient air. The new Clarkson Cr(VI) sampler was based on the concept that deliquescence during sampling leads to aqueous phase reactions. Thus, the relative humidity of the sampled air was reduced below the deliquescence relative humidity (DRH) of the ambient particles. The new sampler was operated to collect Total Suspended Particles (TSP), and compared side-by-side with the current National Air Toxics Trends Stations (NATTS) Cr(VI) sampler that is utilized in the United States Environmental Protection Agency (USEPA) air toxics monitoring program. Side-by-side field testing of the samplers occurred in Elizabeth, NJ during the winter and summer of 2012. The average recovery values of Cr(VI) spikes after 24 hour sampling intervals during summer and winter sampling were 57 and 72%, respectively, for the Clarkson sampler, while the corresponding average values for NATTS samplers were 46% for both summer and winter sampling, respectively. Preventing the ambient aerosol collected on the filters from deliquescing is a key to improving the sampling of Cr(VI). PMID:24344574

  17. Improved atmospheric sampling of hexavalent chromium.

    PubMed

    Torkmahalleh, Mehdi Amouei; Yu, Chang-Ho; Lin, Lin; Fan, Zhihua; Swift, Julie L; Bonanno, Linda; Rasmussen, Don H; Holsen, Thomas M; Hopke, Philip K

    2013-11-01

    Hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) are the primary chromium oxidation states found in ambient atmospheric particulate matter. While Cr(III) is relatively nontoxic, Cr(VI) is toxic and exposure to Cr(VI) may lead to cancer, nasal damage, asthma, bronchitis, and pneumonitis. Accurate measurement of the ambient Cr(VI) concentrations is an environmental challenge since Cr(VI) can be reduced to Cr(III) and vice versa during sampling. In the present study, a new Cr(VI) sampler (Clarkson sampler) was designed, constructed, and field tested to improve the sampling of Cr(VI) in ambient air. The new Clarkson Cr(VI) sampler was based on the concept that deliquescence during sampling leads to aqueous phase reactions. Thus, the relative humidity of the sampled air was reduced below the deliquescence relative humidity (DRH) of the ambient particles. The new sampler was operated to collect total suspended particles (TSP), and compared side-by-side with the current National Air Toxics Trends Stations (NATTS) Cr(VI) sampler that is utilized in the US. Environmental Protection Agency (EPA) air toxics monitoring program. Side-by-side field testing of the samplers occurred in Elizabeth, NJ during the winter and summer of 2012. The average recovery values of Cr(VI) spikes after 24-hr sampling intervals during summer and winter sampling were 57 and 72%, respectively, for the Clarkson sampler while the corresponding average values for NATTS samplers were 46% for both summer and winter sampling, respectively. Preventing the ambient aerosol collected on the filters from deliquescing is a key to improving the sampling of Cr(VI). PMID:24344574

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

    PubMed

    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

  19. Chromium and Polyphenols From Cinnamon Improve Insulin Sensitivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  20. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O). (2) Color additive mixtures for drug use made with chromium hydroxide green may contain only those diluents listed in this subpart as safe and suitable for use in color additive mixtures for coloring...

  1. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O). (2) Color additive mixtures for drug use made with chromium hydroxide green may contain only those diluents listed in this subpart as safe and suitable for use in color additive mixtures for coloring...

  2. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O). (2) Color additive mixtures for drug use made with chromium hydroxide green may contain only those diluents listed in this subpart as safe and suitable for use in color additive mixtures for coloring...

  3. AMORPHOUS ALLOY SURFACE COATINGS FOR HARD CHROMIUM REPLACEMENT - PHASE I

    EPA Science Inventory

    Hard chromium coatings (0.25 to10 mil thick) are used extensively for imparting wear and erosion resistance to components in both industrial and military applications. The most common means of depositing hard chromium has been through the use of chromic acid baths containing ...

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

    PubMed Central

    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 precipitation/dissolution reactions control the transformation and mobility of chromium. The reduction of CrVI to CrIII can occur in the presence of ferrous iron in solution or in mineral phases, reduced sulfur compounds, or soil organic matter. At neutral to alkaline pH, the CrIII precipitates as amorphous hydroxides or forms complexes with organic matter. CrIII is oxidized by manganese dioxide, a common mineral found in many soils. Solid-phase precipitates of hexavalent chromium such as barium chromate can serve either as sources or sinks for CrVI. Adsorption of CrVI in soils increases with decreasing chromium concentration, making it more difficult to remove the chromium as the concentration decreases during pump-and-treat remediation. Knowledge of these chemical and physical processes is important in developing and selecting effective, cost-efficient remediation designs for chromium-contaminated sites. PMID:1935849

  5. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O). (2) Color additive mixtures for drug use made with chromium hydroxide green may contain only those diluents listed in this subpart as safe and suitable for use in color additive mixtures for coloring...

  6. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium oxide greens. 73.3111 Section 73.3111 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a)...

  7. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium oxide greens. 73.3111 Section 73.3111 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a)...

  8. ACTIVATED CARBON PROCESS FOR TREATMENT OF WASTEWATERS CONTAINING HEXAVALENT CHROMIUM

    EPA Science Inventory

    The removal of hexavalent chromium, Cr(VI), from dilute aqueous solution by an activated carbon process has been investigated. Two removal mechanisms were observed; hexavalent chromium species were removed by adsorption onto the interior carbon surface and/or through reduction to...

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

    EPA Science Inventory

  1. Zinc recovery and waste sludge minimization from chromium passivation baths.

    PubMed

    Diban, Nazely; Mediavilla, Rosa; Urtiaga, Ane; Ortiz, Inmaculada

    2011-08-30

    This work reports the feasibility of applying emulsion pertraction technology (EPT) aiming at zinc recovery and waste minimization in the zinc electroplating processes that include Cr (III) passivation. The assessment consists of firstly the lifetime extension of the passivation baths by selective removal of the tramp ions zinc and iron, and secondly, the recovery of zinc for further reuse. Spent passivation baths from a local industry were tested, being the major metallic content: Cr(3+) 9000mg L(-1), Zn(2+) 12,000mg L(-1), Fe(3+) 100mg L(-1). Working in a Liqui-Cel hollow fiber membrane contactor and using the extractant bis(2,4,4-trimethylpentyl) phosphinic acid, reduction of zinc and iron concentrations below 60mg L(-1) and 2mg L(-1), respectively were obtained, while trivalent chromium, the active metal that generates the passivation layer, was retained in the baths. Zinc was selectively transferred to an acidic stripping phase that in the experimental time reached a concentration of 157,000mg L(-1). Zinc recovery by electrowinning from the acidic stripping phase without any pretreatment of the electrolyte solution provided a purity of 98.5%, matching the lower commercial zinc grade. As a result of the extension of the life time of the passivation bath, significant environmental advantages are derived such as minimization of the volume of hazardous wastes and savings in the consumption of raw materials. PMID:21704452

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

    PubMed

    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

  3. Chromium allergy and dermatitis: prevalence and main findings.

    PubMed

    Bregnbak, David; Johansen, Jeanne D; Jellesen, Morten S; Zachariae, Claus; Menné, Torkil; Thyssen, Jacob P

    2015-11-01

    The history of chromium as an allergen goes back more than a century, and includes an interventional success with national legislation that led to significant changes in the epidemiology of chromium allergy in construction workers. The 2015 EU Leather Regulation once again put a focus on chromium allergy, emphasizing that the investigation of chromium allergy is still far from complete. Our review article on chromium focuses on the allergen's chemical properties, its potential exposure sources, and the allergen's interaction with the skin, and also provides an overview of the regulations, and analyses the epidemiological pattern between nations and across continents. We provide an update on the allergen from a dermatological point of view, and conclude that much still remains to be discovered about the allergen, and that continued surveillance of exposure sources and prevalence rates is necessary. PMID:26104877

  4. External biomarkers to assess chromium toxicity in adult Lepomis macrochirus

    SciTech Connect

    Gendusa, T.C.; Beitinger, T.L. )

    1992-02-01

    Chromium is widely used in the production of stainless steel, bricks, pigments, dyes, and in the tanning, textile, and chemical industries, commonly found in the aquatic environment and known to elicit acute and chronic toxicity to aquatic life. In water, chromium tends to speciate into Cr{sup 3+} (trivalent) and Cr{sup +6} (hexavalent). Speciation of chromium is primarily dependent upon water chemistry, e.g., oxygenation, pH, organic content and amount of particulate matter and the bioavailability of each chromium form is different mainly because of the low solubility of Cr{sup +3}. The objective of this research was to evaluate the efficacy of eight potential biomarkers to indicate stress of chromium exposure in adult bluegill (Lepomis macrochirus).

  5. Abnormal deposits of chromium in the pathological human brain.

    PubMed Central

    Duckett, S

    1986-01-01

    Three patients presented with encephalopathies: an undiagnosed degenerative disease of the brain, a degenerative cerebral disease in a patient with a myeloma but without a myelomatous deposit in the CNS and a malignant astrocytoma. Perivascular pallidal deposits (vascular siderosis) containing chromium, phosphorus and calcium plus sometimes traces of other elements were present in the three cases. Such deposits were present in the pallidal parenchyma and around vessels in the cerebellum in one case. Calcium and phosphorus are always present in any CNS calcification but the presence of chromium has not been reported. Chromium and its compounds (ingested, injected or inhaled) are toxic to humans and animals in trace doses. Approximately 900 cases of chromium intoxication have been reported and usually have had dermatological or pulmonary lesions (including cancer) but there is no report of involvement of the CNS. Sublethal doses of chromium nitrate injected intraperitoneally in rats and rabbits results in the presence of chromium in the brain. A thorough investigation was made to find the source of the chromium in these patients. Chromium was found to be present in trace amounts in the radiological contrast agents administered to these patients and in the KCl replacement solution and in mylanta, an antacid, given to one case. The evidence that chromium induced pathological changes in these three brains is circumstantial but shows that chromium can penetrate the human brain. This study indicates that vascular siderosis found in the brains of the majority of middle-aged and elderly humans is not simply an anecdotal pathological curiosity, but that it can serve as a route of entry for toxic products into the brain. Images PMID:3958742

  6. Release of chromium from soils with persulfate chemical oxidation.

    PubMed

    Kaur, Kawalpreet; Crimi, Michelle

    2014-01-01

    An important part of the evaluation of the effectiveness of persulfate in situ chemical oxidation (ISCO) for treating organic contaminants is to identify and understand its potential impact on metal co-contaminants in the subsurface. Chromium is a redox-sensitive and toxic metal the release of which poses considerable risk to human health. The objective of this study was to investigate the impact of persulfate chemical oxidation on the release of chromium from three soils varying in physical-chemical properties. Soils were treated with unactivated and activated persulfate [activated with Fe(II), Fe(II)-EDTA, and alkaline pH] at two different concentrations (i.e., 41 mM and 2.1 mM persulfate) for 48 h and 6 months and were analyzed for release of chromium. Results show that release of chromium with persulfate chemical oxidation depends on the soil type and the activation method. Sandy soil with low oxidant demand released more chromium compared to soils with high oxidant demand. More chromium was released with alkaline pH activation. Alkaline pH and high Eh conditions favor oxidation of Cr(III) to Cr(VI), which is the main mechanism of release of chromium with persulfate chemical oxidation. Unactivated and Fe(II)-activated persulfate decreased pH and at low pH in absence of EDTA chromium release is not a concern. These results indicate that chromium release can be anticipated based on the given site and treatment conditions, and ISCO system can be designed to minimize potential chromium release when treating soils and groundwater contaminated with both organic and metal contaminants. PMID:24028318

  7. Determination of chromium in treated crayfish, Procambarus clarkii, by electrothermal ASS: study of chromium accumulation in different tissues

    SciTech Connect

    Hernandez, F.; Diaz, J.; Medina, J.; Del Ramo, J.; Pastor, A.

    1986-06-01

    In the present study, the authors investigated the accumulation of chromium in muscle, hepatopancreas, antennal glands, and gills of Procambarus clarkii (Girard) from Lake Albufera following Cr(VI)-exposure. Determinations of chromium were made by using Electrothermal Atomic Absorption Spectroscopy and the standard additions method.

  8. CRITICAL EVALUATION OF DIFFERENTIAL PULSE POLAROGRAPHY FOR DETERMINING CHROMIUM(III) AND CHROMIUM(VI) IN WATER SAMPLES

    EPA Science Inventory

    The Tennessee Valley Authority critically evaluated differential pulse polarography for determining chromium(VI) and chromium(III) in water samples from coal-fired steam-electric generating stations. After addition of reagents to overcome interference, the peak currents for chrom...

  9. Recoating mirrors having a chromium underlayer

    NASA Astrophysics Data System (ADS)

    Khounsary, Ali M.; Eng, Peter J.; Assoufid, Lahsen; Macrander, Albert T.; Qian, Jun

    2004-01-01

    X-ray mirrors and multilayers are used to reflect, focus, or monochromatize x-ray beams. Substrate materials are typically silicon, fused silica, Zerodur, ULE, or metals such as molybdenum, copper, or stainless steel. Substrates are polished to a few angstroms rms roughness and often coated with one or more layers to provide the desired spectral reflectivity. Coatings can be damaged as a result of mishandling, contamination and/or chemical reaction, prolonged exposure to x-rays, exposure to poor vacuum, aging, or peeling due to poor coating adhesion and/or high stress. Incomplete or out-of-spec coatings may render an optic unacceptable. In all these cases, it is highly desirable to be able to completely strip off a coating and recoat the substrate without the need for repolishing it. This is particularly important for optical substrates that are expensive or have a long fabrication lead-time. This paper describes one such scheme. It involves pre-coating of mirror reflecting surfaces with a thin layer of chromium. Subsequent coatings can be stripped by etching away the chromium underlayer without damaging the substrate. Experimental results show that surface roughness is unaffected by the etching process in silicon and zerodur, the two substrate material tested so far. The process is expected to be equally applicable to other glasses and can be extended to other substrate materials using appropriate underlayer / etchant combinations.

  10. Chromium(VI) bioremediation by probiotics.

    PubMed

    Younan, Soraia; Sakita, Gabriel Z; Albuquerque, Talita R; Keller, Rogéria; Bremer-Neto, Hermann

    2016-09-01

    Chromium is a common mineral in the earth's crust and can be released into the environment from anthropogenic sources. Intake of hexavalent chromium (Cr(VI)) through drinking water and food causes toxic effects, leading to serious diseases, and is a commonly reported environmental problem. Microorganisms can mitigate or prevent the toxic effects caused by heavy metals in addition to having effective resistance mechanisms to prevent cell damage and bind to these metals, sequestering them from the cell surface and removing them from the body. Species of Lactobacillus, Streptococcus, Bacillus and Bifidobacterium present in the human mouth and gut and in fermented foods have the ability to bind and detoxify some of these substances. This review address the primary topics related to Cr(VI) poisoning in animals and humans and the use of probiotics as a way to mitigate or prevent the toxic effects caused by Cr(VI). Further advances in the genetic knowledge of such microorganisms may lead to discoveries which will clarify the most active microorganisms that act as bioprotectants in bodies exposed to Cr(VI) and are an affordable option for people and animals intoxicated by the oral route. © 2016 Society of Chemical Industry. PMID:26997541

  11. Oxidative damage of DNA by chromium(V) complexes: relative importance of base versus sugar oxidation.

    PubMed Central

    Bose, R N; Moghaddas, S; Mazzer, P A; Dudones, L P; Joudah, L; Stroup, D

    1999-01-01

    Chromium(V)-mediated oxidative damage of deoxy-ribonucleic acids was investigated at neutral pH in aqueous solution by utilizing bis(2-ethyl-2-hydroxy-butanato)oxochromate(V) (I) and bis(hydroxyethyl)-amino-tris(hydroxymethyl)methane)oxochromate(V) (II). Single-stranded and double-stranded (ds) calf thymus and human placenta DNA, as well as two oligomers, 5'-GATCTAGTAGGAGGACAAATAGTGTTTG-3' and 5'-GATCCAAGCAAACACTATTTGTCCTCCTACTA-3', were reacted with the chromium(V) complexes. Most products were separated and characterized by chroma-tographic and spectroscopic methods. Polyacrylamide gel electrophoresis experiments reveal more damage at G sites in comparison to other bases. Three primary oxidation products, 5-methylene-2-furanone (5-MF), furfural and 8-oxo-2'-deoxyguanosine, were characterized. A minor product, which appears to be thymine propenal, was also observed. The dsDNA produces more furfural than furanone. The formation of these two products resulted from hydrogen ion or hydride transfer from C1' and C5' positions of the ribose to the oxo-chromium(V) center. Since no enhancements of these products (except propenal) were observed in the presence of oxygen, mechanisms pertaining to the participation of activated oxygen species may be ruled out. The oxidation of the G base is most likely associated with an oxygen atom transfer from the oxo-metallates to the double bond between C8 and N7 of the purine ring. The formation of the propenal may be associated with an oxygen-activated species, since a marginal enhancement of this product was observed in the presence of oxygen. The formation of furfural in higher abundance over 5-MF for dsDNA was attributed to the ease of hydrogen ion (or hydride transfer) from the C5' compared to C1' position of the ribose within a Cr(V)-DNA intermediate in which the metal center is bound to the phosphate diester moiety. PMID:10219096

  12. Oxidative damage of DNA by chromium(V) complexes: relative importance of base versus sugar oxidation.

    PubMed

    Bose, R N; Moghaddas, S; Mazzer, P A; Dudones, L P; Joudah, L; Stroup, D

    1999-05-15

    Chromium(V)-mediated oxidative damage of deoxy-ribonucleic acids was investigated at neutral pH in aqueous solution by utilizing bis(2-ethyl-2-hydroxy-butanato)oxochromate(V) (I) and bis(hydroxyethyl)-amino-tris(hydroxymethyl)methane)oxochromate(V) (II). Single-stranded and double-stranded (ds) calf thymus and human placenta DNA, as well as two oligomers, 5'-GATCTAGTAGGAGGACAAATAGTGTTTG-3' and 5'-GATCCAAGCAAACACTATTTGTCCTCCTACTA-3', were reacted with the chromium(V) complexes. Most products were separated and characterized by chroma-tographic and spectroscopic methods. Polyacrylamide gel electrophoresis experiments reveal more damage at G sites in comparison to other bases. Three primary oxidation products, 5-methylene-2-furanone (5-MF), furfural and 8-oxo-2'-deoxyguanosine, were characterized. A minor product, which appears to be thymine propenal, was also observed. The dsDNA produces more furfural than furanone. The formation of these two products resulted from hydrogen ion or hydride transfer from C1' and C5' positions of the ribose to the oxo-chromium(V) center. Since no enhancements of these products (except propenal) were observed in the presence of oxygen, mechanisms pertaining to the participation of activated oxygen species may be ruled out. The oxidation of the G base is most likely associated with an oxygen atom transfer from the oxo-metallates to the double bond between C8 and N7 of the purine ring. The formation of the propenal may be associated with an oxygen-activated species, since a marginal enhancement of this product was observed in the presence of oxygen. The formation of furfural in higher abundance over 5-MF for dsDNA was attributed to the ease of hydrogen ion (or hydride transfer) from the C5' compared to C1' position of the ribose within a Cr(V)-DNA intermediate in which the metal center is bound to the phosphate diester moiety. PMID:10219096

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

    SciTech Connect

    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.

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

    SciTech Connect

    Not Available

    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.

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

    PubMed

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

    2012-12-30

    The potential for chemical reduction of hexavalent chromium Cr(VI) in contaminated water and formation of a stable precipitate by Zero Valent Iron (ZVI) anode electrolysis is evaluated in separated electrodes system. Oxidation of iron electrodes produces ferrous ions causing the development of a reducing environment in the anolyte, chemical reduction of Cr(VI) to Cr(III) and formation of stable iron-chromium precipitates. Cr(VI) transformation rates are dependent on the applied electric current density. Increasing the electric current increases the transformation rates; however, the process is more efficient under lower volumetric current density (for example 1.5 mA L(-1) in this study). The transformation follows a zero order rate that is dependent on the electric current density. Cr(VI) transformation occurs in the anolyte when the electrodes are separated as well as when the electrolytes (anolyte/catholyte) are mixed, as used in electrocoagulation. The study shows that the transformation occurs in the anolyte as a result of ferrous ion formation and the product is a stable Fe(15)Cr(5)(OH)(60) precipitate. PMID:23284182

  16. Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

    SciTech Connect

    Petkova, P.; Andreici, E.-L.; Avram, N. M.

    2014-11-24

    The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.

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

    PubMed Central

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

    2012-01-01

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

  18. Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

    NASA Astrophysics Data System (ADS)

    Petkova, P.; Andreici, E.-L.; Avram, N. M.

    2014-11-01

    The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.

  19. NOM and alkalinity interference in trace-level hexavalent chromium analysis.

    PubMed

    Parks, Jeffrey L; McNeill, Laurie; Edwards, Marc

    2014-12-01

    Three analytical methods were evaluated for hexavalent and trivalent chromium analyses in the presence of natural organic matter (NOM) and alkalinity. Each method was tested using a simulated tap water with 1 μg L(-1) Cr(VI) and 0.8 μg L(-1) Cr(III) and several concentrations of NOM and/or alkalinity. An ion chromatograph with post column reaction cell conforming to USEPA Method 218.7 could accurately quantify Cr(VI) in the presence of up to 8 mg CL(-1) NOM and up to 170 mg L(-1) as CaCO3 alkalinity, and no oxidation of chromium was observed when 0.8 μg L(-1) Cr(III) was also present. A high-performance liquid chromatography coupled with inductively coupled plasma (HPLC-ICPMS) method and a field speciation method were also evaluated. Each of these methods was unaffected by the presence of alkalinity; however, the presence of NOM created issues. For the HPLC-ICPMS method, as the concentration of NOM increased the recovery of Cr(VI) decreased, resulting in a 'false negative' for Cr(VI). However, for the field speciation method, Cr(III) was complexed by NOM and carried through the ion exchange column, resulting in a 'false positive' for Cr(VI). PMID:25159403

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

    SciTech Connect

    Gilbert, H.K.

    1985-01-01

    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 ..mu..g 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.

  1. Kinetics of chromium(VI) reduction by ferrous iron

    SciTech Connect

    Batchelor, B.; Schlautman, M.; Hwang, I.; Wang, R.

    1998-09-01

    Chromium is a primary inorganic contaminant of concern at the Pantex Plant. Chromium concentrations have been found to be two orders of magnitude higher than the drinking water standards, particularly in certain wells in the perched aquifer below Zone 12. In situ reduction of a mobile form of chromium, Cr(VI) to an immobile form, Cr(III), was examined as a viable option to active soil restoration. Successfully immobilizing chromium in the vadose zone as Cr(III) will reduce the amount of chromium that reaches the groundwater table. The results from the solution experiments indicated that chromium was rapidly and stoichiometrically reduced by Fe(II) in solution. Also, the slurry experiments showed that the aquifer solids removed Fe(II) from solution, but a portion of the iron removed remained available for reaction with Cr(VI), but at a slower rate. A model to predict different amounts of iron pseudo-components was developed, which allowed prediction of iron amounts required to reduce chromium under in situ conditions.

  2. Mode of occurrence of chromium in four US coals

    USGS Publications Warehouse

    Huggins, Frank E.; Shah, N.; Huffman, G.P.; Kolker, A.; Crowley, S.; Palmer, C.A.; Finkelman, R.B.

    2000-01-01

    The mode of occurrence of chromium in three US bituminous coals and one US subbituminous has been examined using both X-ray absorption fine structure (XAFS) spectroscopy and a selective leaching protocol supplemented by scanning electron microscopy (SEM) and electron microprobe measurements. A synthesis of results from both methods indicates that chromium occurs principally in two forms in the bituminous coals: the major occurrence of chromium is associated with the macerals and is not readily leached by any reagent, whereas a second, lesser occurrence, which is leachable in hydrofluoric acid (HF), is associated with the clay mineral, illite. The former occurrence is believed to be a small particle oxyhydroxide phase (CrO(OH)). One coal also contained a small fraction (<5%) of the chromium in the form of a chromian magnetite, and the leaching protocol indicated the possibility of a similar small fraction of chromium in sulfide form in all three coals. There was little agreement between the two techniques on the mode of occurrence of chromium in the subbituminous coal; however, only a limited number of subbituminous coals have been analyzed by either technique. The chromium in all four coals was trivalent as no evidence was found for the Cr6+ oxidation state in any coal.

  3. Investigation of the threshold for allergic reactivity to chromium.

    PubMed

    Basketter, D; Horev, L; Slodovnik, D; Merimes, S; Trattner, A; Ingber, A

    2001-02-01

    Allergy to chromium is relatively common, often in association with exposure to cement or in leather manufacture. However, in certain locations, there appears to be a relatively large cohort of chromium-sensitive individuals whose allergy cannot be explained by these common sources. In particular, this group include Israeli housewives with persistent hand eczema and concomitant patch test positivity to chromium. The causation of their allergy has been linked with relatively high levels of chromium contamination in household products. To provide further information in respect of the definition of safe levels for such products, we examined 17 chromium-allergic individuals to determine their threshold for reaction under closed patch test and repeated open application test (ROAT) conditions. The data derived indicated that, on normal skin, the patch test threshold was 10 ppm chromium; in the presence of an irritant (sodium lauryl sulfate) the threshold was closer to 1 ppm, 2/17 subjects giving 1+ reactions at this concentration. In the more realistic exposure conditions of the ROAT, 8/14 individuals failed to react to 50 ppm, whilst 3/15 reacted to 5 ppm. Interestingly, there was very poor correlation between patch test sensitivity and ROAT sensitivity. To ensure the large majority of chromium-allergic individuals do not suffer elicitation of their allergy, as well as to limit the development of new chromium-sensitive subjects, it is recommended that household products adhere to a previously published standard of a maximum limit of 5 ppm, with an ultimate target of 1 ppm contamination by chromium. PMID:11205406

  4. Spectroscopic analysis of chromium bioremediation products

    NASA Astrophysics Data System (ADS)

    Varadharajan, C.; Nico, P. S.; Yang, L.; Marcus, M. A.; Steefel, C.; Larsen, J. T.; Beller, H. R.; Brodie, E. L.

    2010-12-01

    Remediation of chromium contamination frequently involves reducing the toxic and soluble hexavalent form, Cr(VI), to the relatively harmless and mostly immobile trivalent state, Cr(III). The objective of this study is to identify the biogeochemical reactions that control in situ chromium reduction in the presence of different dominant electron acceptors, i.e., NO3-, Fe(III), and SO42-. It was hypothesized that indirect, abiotic reduction of Cr(VI) by reduced metabolic products [Fe(II) and sulfides] would dominate over direct enzymatic reduction by denitrifying, iron-reducing, or sulfate-reducing bacteria. It is further hypothesized that the enzymatic reduction of Cr(VI) would produce relatively pure chromium hydroxide precipitates, whereas indirect reduction would result in mixed Cr-Fe hydroxide solid phases. Flow-through columns containing homogenized sediments from the 100H site at Hanford, WA were subjected to nitrate-, sulfate- or iron-reducing conditions in the presence of 5 µM Cr(VI) and 5 mM lactate. Cr(VI) was depleted in the effluent solutions from the nitrate- and sulfate-reducing columns; however only a small amount of Cr(VI) was removed under iron-reducing conditions. Preliminary analysis of micro X-ray absorption spectra indicate that the untreated and iron-reducing column sediments contained pre-existing Cr in the form of primary minerals, e.g. chromite and/or Cr-bearing micas. However, there was an increase in the relative abundance of mixed-phase Cr-Fe hydroxides, i.e., Cr1-xFex(OH)3 in the nitrate- and sulfate-treated columns. A possible explanation for the observations is that the production of Fe(II) was enhanced under the nitrate- and sulfate- reducing conditions, and was most likely sulfide-driven in the latter case. The Fe(II) was subsequently available for reduction of Cr(VI) resulting in the mixed-phase precipitates. The results from the spectroscopic analysis support the hypothesis that Fe(II)-mediated Cr reduction prevails over direct

  5. Removal of hexavalent chromium by biosorption process in rotating packed bed.

    PubMed

    Panda, M; Bhowal, A; Datta, S

    2011-10-01

    Removal of hexavalent chromium ions from an aqueous solution by crude tamarind (Tamarindus indica) fruit shell was examined in a rotating packed bed contactor by continuously recirculating a given volume of solution through the bed. Reduction of Cr(VI) to Cr(III) within the biosorbent appeared to be the removal mechanism. Depletion rate of Cr(VI) from, and release of reduced Cr(III) ions into the aqueous phase, was influenced by mass transfer resistance besides pH and packing depth. A mathematical model considering the reduction reaction to be irreversible and incorporating intraparticle and external phase mass transfer resistances represented the experimental data adequately. The study indicated that the limitations of fixed bed contactor operating under terrestrial gravity in intensifying mass transfer rates for this system can be overcome with rotating packed bed due to liquid flow under centrifugal acceleration. PMID:21819035

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

    PubMed

    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). PMID:26894618

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

    NASA Astrophysics Data System (ADS)

    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.

  8. [Blood and urine chromium: compared values between chromium exposed workers and common people].

    PubMed

    Provenzani, A; Verso, M G; Picciotto, D

    2008-01-01

    Aim of present study is the valutation and quantification of chromium in blood and urine. We compared 3 groups of persons formed by building workers, in particular masons, because cement contains potassium chromate that is dangerous for health, and by common people: urban population and outside the town population. In fact, exposure to CrVI risk is high for people who live near chromate industries. We maked a medical examination, blood and instrumental tests, chromium measuring in blood (recent exposure indicator) and urine (recent and previous indicator). Then we used statistical methods to estimate obtained values of blood and urine chromium among professional exposed people and common people. At the end we think that preventive measures in working environment reduced exposure to CrVI but environmental exposure (for example road dust from catalytic converter erosion, from brake lining erosion, cement dust and tobacco smoke), in the last years, has increased. So there are no difference between urban population and outside the town population and there are also no difference with professional exposed people for work prevention according to law in force, that let down professional risk using safe limits. PMID:18700674

  9. Fluid-rock interactions between xanthan-chromium(III) gel systems and dolomite core material

    SciTech Connect

    McCool, C.S.; Green, D.W.; Willhite, G.P.

    1995-11-01

    Gelation of chromium(III)-xanthan systems in dolomite core material was investigated. Compositional changes in the gelant caused by interactions with the dolomite core material resulted in low permeability reductions for gelants prepared with chromium chloride, chromium acetate and a chromium diamine salt. The primary cause of incomplete gelation in the dolomite material was the increase in gelant pH that resulted in precipitation of chromium.

  10. Evaluation of chromium in red blood cells as an indicator of exposure to hexavalent chromium: An in vitro study.

    PubMed

    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

  11. Self-Lubricating Composite Containing Chromium Oxide

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher (Inventor); Edmonds, Brian J. (Inventor)

    1999-01-01

    A self lubricating. friction and wear reducing composite material useful over a wide temperature range of from cryogenic temperature up to about 900 C. contains 60 80 wt. % of particulate Cr2O3, dispersed in a metal binder of a metal alloy containing Cr and at least 50 wt. % of Ni, Cr or a mature of Ni and Cr. It also contains 5-20 wt. % of a fluoride of at least one Group I, Group II or rare earth metal and. optionally, 5-20 wt. % of a low temperature lubricant metal, such as Ag. Au, Pt, Pd, Rh and Cu. This composite exhibits less oxidation instability and less abrasiveness than composites containing chromium carbide, is readily applied using plasma spray and can be ground and polished with a silicon carbide abrasive.

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

    SciTech Connect

    Hinnov, E.; Suckewer, S.; Cohen, S.; Sato, K.

    1981-11-01

    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.

  13. Sorptive removal of trivalent and hexavalent chromium from binary aqueous solutions by composite alginate-goethite beads.

    PubMed

    Lazaridis, N K; Charalambous, Ch

    2005-11-01

    In this study, the removal of hexavalent and trivalent chromium ions from binary aqueous solutions by composite alginate-goethite beads was investigated in a batch mode. Equilibrium sorption experiments were carried out at different temperatures and pH values. The data were correlated with Langmuir and Freundlich equations. The thermodynamic parameters calculated were: change in free energy, in enthalpy, in entropy and the heat of adsorption. The influence of mixing rate, sorbent concentration and sorbent particle size was studied at kinetic runs. The effective diffusion coefficients were evaluated by employing the homogeneous diffusion model and the shrinking core model for hexavalent and trivalent chromium, respectively. Desorption experiments were conducted by employing various eluants showed that the loaded material could be regenerated satisfactorily. PMID:16233908

  14. An EXAFS Study Of The Binding Of Chromium, Mercury And Copper On Natural, Crosslinked And Multilayer Chitosan Films

    SciTech Connect

    Goncalves de Paiva, Rafael; Silveira Vieira, Rodrigo; Gomes Aimoli, Cassiano; Masumi Beppu, Marisa

    2009-01-29

    The coordination environment of metal atoms involved in their adsorption on chitosan was studied by using EXAFS technique. Chromium, mercury and copper complexes were gotten on natural, crosslinked and multilayer chitosan films and the spectra of the distribution of neighbor atoms around the adsorbed central atom were obtained. All spectra were obtained in transmission mode and were collected around Hg (12284 eV) L edge, Cr (5989 eV) and Cu (8987 eV) K edges. For chromium ions, it was possible to observe that metal interaction is mainly performed on amino groups, on the other hand, it was not possible to distinguish if the metal interaction takes place preferentially on amino or hydroxyl group, for mercury and copper.

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

    SciTech Connect

    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

  16. Thermal and photochemical reactions of NO2 on chromium(III) oxide surfaces at atmospheric pressure.

    PubMed

    Nishino, Noriko; Finlayson-Pitts, Barbara J

    2012-12-01

    While many studies of heterogeneous chemistry on Cr(2)O(3) surfaces have focused on its catalytic activity, less is known about chemistry on this surface under atmospheric conditions. We report here studies of the thermal and photochemical reactions of NO(2) on Cr(2)O(3) at one atm in air. In order to follow surface species, the interaction of 16-120 ppm NO(2) with a 15 nm Cr(2)O(3) thin film deposited on a germanium crystal was monitored in a flow system using attenuated total reflectance (ATR) coupled to a Fourier transform infrared (FTIR) spectrometer. Gas phase products were monitored in the effluent of an ~285 ppm NO(2)-air mixture that had passed over Cr(2)O(3) powder in a flow system. A chemiluminescence NO(y) analyzer, a photometric O(3) analyzer and a long-path FTIR spectrometer were used to probe the gaseous products. In the absence of added water vapor, NO(2) formed nitrate (NO(3)(-)) ions coordinated to Cr(3+). These surface coordinated NO(3)(-) were reversibly solvated by water under humid conditions. In both dry and humid cases, nitrate ions decreased during irradiation of the surface at 302 nm, and NO and NO(2) were generated in the gas phase. Under dry conditions, NO was the major gaseous product while NO(2) was the dominant species in the presence of water vapor. Heating of the surface after exposure to NO(2) led to the generation of both NO(2) and NO under dry conditions, but only NO(2) in the presence of water vapor. Elemental chromium incorporated into metal alloys such as stainless steel is readily oxidized in contact with ambient air, forming a chromium-rich metal oxide surface layer. The results of these studies suggest that active photo- and thermal chemistry will occur when boundary layer materials containing chromium(III) or chromium oxide such as stainless steel, roofs, automobile bumpers etc. are exposed to NO(2) under tropospheric conditions. PMID:23090708

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

    EPA Science Inventory

    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.

  18. USE OF FUME SUPPRESSANTS IN HARD CHROMIUM BATHS - QUALITY TESTING

    EPA Science Inventory

    The EPA Common Sense Initiative (CSI) is a cooperative effort of government, industry, environmental and other stakeholder groups to find "cleaner, cheaper, smarter" approaches to environmental management in industrial sectors. The purpose of the project is to help hard chromium ...

  19. Chromate allergy: total chromium and hexavalent chromate in the air.

    PubMed

    Goh, C L; Wong, P H; Kwok, S F; Gan, S L

    1986-01-01

    This is a study on atmospheric concentration of total chromium and hexavalent chromate and its role in chromate sensitivity. Air concentration of total chromium and hexavalent chromate in a construction factory, a busy city area, a suburban area, a residential area, and a heavy industrial area were measured by air sampling pumps. Hexavalent chromate was not detected in any sampled areas. Two (concreting areas) of 8 locations in the construction factory had total chromium of 0.2 and 2.3 micrograms/m3 in the atmosphere. It appeared that the atmospheric concentration of total chromium and hexavalent chromate was negligible. These findings indicate that unexplained chromate sensitivity, as so often seen in patients attending a contact dermatitis clinic, is not attributable to exposure to hexavalent chromate in the air. PMID:2947791

  20. Corrosion behavior of porous chromium carbide in supercritical water

    NASA Astrophysics Data System (ADS)

    Dong, Ziqiang; Chen, Weixing; Zheng, Wenyue; Guzonas, Dave

    2012-01-01

    The corrosion behavior of highly porous chromium carbide (Cr 3C 2) prepared by a reactive sintering process was characterized at temperatures ranging from 375 °C to 625 °C in a supercritical water environment with a pressure of 25-30 MPa. The test results show that porous chromium carbide is stable in SCW environments at temperatures under 425 °C, above which disintegration occurred. The porous carbide was also tested under hydrothermal conditions of pressures between 12 MPa and 50 MPa at constant temperatures of 400 °C and 415 °C, respectively. The pressure showed little effect on the stability of chromium carbide in the tests at those temperatures. The mechanism of disintegration of chromium carbide in SCW environments is discussed.

  1. PBI REVERSE OSMOSIS MEMBRANE FOR CHROMIUM PLATING RINSE WATER

    EPA Science Inventory

    A laboratory research study was carried out to select and optimize polybenzimidazole (PBI) reverse osmosis (RO) membranes for the treatment of chromium plating rinse water. The effects of important film casting and annealing variables on RO properties were investigated. Membranes...

  2. Structure and magnetic properties of chromium doped cobalt molybdenum nitrides

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Żołnierkiewicz, Grzegorz; Typek, Janusz; Guskos, Aleksander; Adamski, Paweł; Moszyński, Dariusz

    2016-09-01

    Four nanocomposites containing mixed phases of Co3Mo3N and Co2Mo3N doped with chromium have been prepared. A linear fit is found for relation between Co2Mo3N and chromium concentrations. The magnetization in ZFC and FC modes at different temperatures (2-300 K) and in applied magnetic fields (up to 70 kOe) have been investigated. It has been detected that many magnetic characteristics of the studied four nanocomposites correlate not with the chromium concentration but with nanocrystallite sizes. The obtained results were interpreted in terms of magnetic core-shell model of a nanoparticle involving paramagnetic core with two magnetic sublattices and a ferromagnetic shell related to chromium doping.

  3. High performance supercapacitor from chromium oxide-nanotubes based electrodes

    NASA Astrophysics Data System (ADS)

    Lota, Grzegorz; Frackowiak, Elzbieta; Mittal, Jagjiwan; Monthioux, Marc

    2007-01-01

    Single wall carbon nanotubes (SWNTs) filled and doped with chromium oxide have been used as attractive electrodes for supercapacitors. Pseudocapacitance effects related to the presence of nanosized chromium oxide finely dispersed at the nanoscale together with high conducting properties of SWNTs allow building efficient electrodes from this hybrid material. Even if capacitance values are not very high (ca. 60 F g -1), however, extremely quick charge propagation was observed, doubtless due to the overall physical and textural properties of SWNT material. The positive effect - with respect to empty-SWNTs - brought by the presence of chromium oxide in and probably in-between the SWNTs indicates that chromium oxide is accessible to the electrolyte in spite of its encapsulated location, because of the numerous side entries created all along the SWNT walls during the filling step.

  4. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  5. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  6. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  7. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  8. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  9. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  10. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  11. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  12. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  13. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

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

    SciTech Connect

    Gabbard, W.A.; Simpkins, J.E.; Mioduszewski, P.; Edmonds, P.H.

    1983-01-01

    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.

  15. Molecular Mechanisms of Chromium in Alleviating Insulin Resistance

    PubMed Central

    Hua, Yinan; Clark, Suzanne; Ren, Jun; Sreejayan, Nair

    2011-01-01

    Type 2 diabetes is often associated with obesity, dyslipidemia, and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance. PMID:22423897

  16. The effect of chromium oxyhydroxide on solid oxide fuel cells.

    SciTech Connect

    Krumpelt, M.; Cruse, T. A.; Ingram, B. J.; Routbort, J. L.; Wang, S.; Salvador, P. A.; Chen, G.; Carnegie Mellon Univ.; NETL; Ohio Univ.

    2010-01-01

    Hexavalent chromium species like the oxyhydroxide, CrO{sub 2}(OH){sub 2}, or hexoxide, CrO{sub 3}, are electrochemically reduced to Cr{sub 2}O{sub 3} in solid oxide fuel cells and adversely affect the cell operating potentials. Using a narrowly focused beam from the Advanced Photon Source, such chromium oxide deposits were unequivocally identified in the active region of the cathode by X-ray diffraction, suggesting that the triple phase boundaries were partially blocked. Under fuel cell operating conditions, the reaction has an equilibrium potential of about 0.9 V and the rate of chromium oxide deposition is therefore dependent on the operating potential of the cell. It becomes diffusion limited after several hours of steady operation. At low operating potentials, lanthanum manganite cathodes begin to be reduced to MnO, which reacts with the chromium oxide to form the MnCr{sub 2}O{sub 4} spinel.

  17. Chromium and Polyphenols from Cinnamon and Insulin Sensitivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

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

    PubMed

    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

  19. Chromium induced contact dermatitis and indices for diagnosis.

    PubMed

    Khalil, S; Shouman, A E; El, S H; Moussa, E M

    1999-01-01

    Chromium exposure plays an important role in development of contact dermatitis. The prevalence of contact dermatitis among tannery workers and cement-exposed workers is high. This study was designed to determine the prevalence of contact dermatitis among some Egyptian workers exposed to chromium and to investigate the role of patch test and IgE immunoassay in diagnosis of contact dermatitis. Eighty-three male workers who were exposed to chromium were selected after application of certain exclusion criteria to be the target population of this study. Forty male workers away from exposure to chromium were taken to be the controls. All the exposed and non exposed workers were investigated through an interview questionnaire, clinical examination, patch test and determination of blood and urine chromium levels, absolute eosinophilic count and total IgE level. The results showed that there was no significant difference between exposed workers with clinically diagnosed contact dermatitis and the clinically free exposed workers regarding age and work duration. 7.7% of exposed workers with positive patch test suffered from contact dermatitis while 31.6% of exposed workers with negative patch test suffered from contact dermatitis. There was no statistically significant difference between clinically diagnosed contact dermatitis workers and clinically free workers regarding blood and urine chromium levels. IgE level and absolute eosinophilic count were statistically higher among exposed workers with contact dermatitis than among clinically free exposed workers. According to the results of this study, it is concluded that the diagnosis of skin hypersensitivity to chromium should depend upon the history of chromium exposure, clinical examination and a battery of investigations including IgE level, eosinophilic count and patch test. PMID:17219860

  20. Chromium (V) compounds as cathode material in electrochemical power sources

    DOEpatents

    Delnick, Frank M.; Guidotti, Ronald A.; McCarthy, David K.

    1985-01-01

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca.sub.5 (CrO.sub.4).sub.3 Cl, Ca.sub.5 (CrO.sub.4).sub.3 OH, and Cr.sub.2 O.sub.5. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

  1. Chromium (V) compounds as cathode material in electrochemical power sources

    DOEpatents

    Delnick, F.M.; Guidotti, R.A.; McCarthy, D.K.

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca/sub 5/(CrO/sub 4/)/sub 3/Cl, Ca/sub 5/(CrO/sub 4/)OH, and Cr/sub 2/O/sub 5/. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

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

    SciTech Connect

    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

  3. EMISSIONS OF METALS, CHROMIUM AND NICKEL SPECIES, AND ORGANICS FROM MUNICIPAL WASTEWATER SLUDGE INCINERATORS - VOLUME II: SITE 5 EMISSION TEST REPORT - HEXAVALENT CHROMIUM METHOD EVALUATION

    EPA Science Inventory

    At Site 5, three candidate samplIng methods and two candIdate analytical methods for hexavalent chromium were assessed. he conversion of hexavalent chromium (Cr+8) to ther valence states of chromium during sampling and sample storage was of primary concern. ethod 5-type samples a...

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

    PubMed

    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

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

    PubMed

    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

  6. Environmental monitoring of chromium in air, soil, and water.

    PubMed

    Vitale, R J; Mussoline, G R; Rinehimer, K A

    1997-08-01

    Historical uses of chromium have resulted in its widespread release into the environment. In recent years, a significant amount of research has evaluated the impact of chromium on human health and the environment. Additionally, numerous analytical methods have been developed to identify and quantitate chromium in environmental media in response to various state and federal mandates such as CERCLA, RCRA, CWA, CAA, and SWDA. Due to the significant toxicity differences between trivalent [Cr(III)] and hexavalent [Cr(VI)] chromium, it is essential that chromium be quantified in these two distinct valence states to assess the potential risks to exposure to each in environmental media. Speciation is equally important because of their marked differences in environmental behavior. As the knowledge of risks associated with each valence state has grown and regulatory requirements have evolved, methods to accurately quantitate these species at ever-decreasing concentrations within environmental media have also evolved. This paper addresses the challenges of chromium species quantitation and some of the most relevant current methods used for environmental monitoring, including ASTM Method D5281 for air, SW-846 Methods 3060A, 7196A and 7199 for soils, sediments, and waste, and U.S. EPA Method 218.6 for water. PMID:9380841

  7. Method for fabricating cermets of alumina-chromium systems

    DOEpatents

    Morgan, Chester S.

    1983-01-01

    Cermet insulators resistant to thermal and mechanical shock are prepared from alumina-chromium systems by providing an Al.sub.2 O.sub.3 material of about 0.5 to 7.0 micron size with a solid-hydrocarbon overcoating by slurring an effective amount of said solid hydrocarbon in a solvent mixture containing said Al.sub.2 O.sub.3 and thereafter evaporating said solvent, contacting said coated Al.sub.2 O.sub.3 with a solution of chromium precursor compound, heating the resulting mixture in a reducing environment to a temperature above the decomposition temperature of said chromium precursor compound but less than the melting temperature of the Al.sub.2 O.sub.3 or chromium for sufficient duration to yield a particulate compound having chromium essentially dispersed throughout the Al.sub.2 O.sub.3, and then densifying said particulate to provide said cermet characterized by a theoretical density in excess of 96% and having 0.1 to 10.0 vol.% elemental chromium metal present therein as a dispersed phase at the boundaries of the Al.sub.2 O.sub.3 material. Cermet components prepared thereby are useful in high temperature equipment, advanced heat engines, and nuclear-related equipment applications where electrical or thermal insulators are required.

  8. Chromium Exposure and Hygienic Behaviors in Printing Workers in Southern Thailand

    PubMed Central

    Decharat, Somsiri

    2015-01-01

    Objectives. The main objective of this study was to assess the chromium exposure levels in printing workers. The study evaluated the airborne, serum, and urinary chromium levels and determines any correlation between level of chromium in specimen and airborne chromium levels. Material and Methods. A cross-sectional study was conducted with 75 exposed and 75 matched nonexposed subjects. Air breathing zone was measured by furnace atomic absorption spectrophotometer. Serum and urine samples were collected to determine chromium levels by graphite furnaces atomic absorption spectrometer chromium analyzer. Results and Discussion. The printing workers' urinary chromium levels (6.86 ± 1.93 μg/g creatinine) and serum chromium levels (1.24 ± 1.13 μg/L) were significantly higher than the control group (p < 0.001 and p < 0.001). Work position, duration of work, personal protective equipment (PPE), and personal hygiene were significantly associated with urinary chromium level and serum chromium levels (p < 0.001 and p < 0.001). This study found a correlation between airborne chromium levels and urinary chromium levels (r = 0.247, p = 0.032). A multiple regression model was constructed. Significant predictors of urinary and serum chromium levels were shown in this study. Conclusion. Improvements in working conditions, occupational health training, and PPE use are recommended to reduce chromium exposure. PMID:26448746

  9. [Chromium content in foods and dietary intake estimation in the Northwest of Mexico].

    PubMed

    Grijalva Haro, M I; Ballesteros Vázquez, M N; Cabrera Pacheco, R M

    2001-03-01

    Chromium is an indispensable nutrient for the carbohydrates and lipids metabolism. In this study the chromium content in the twenty main foods of the diet from Northwestern Mexico was determined, as well as the daily mean intake which was estimated based on the food intake basket of this region. Chromium content was analyzed by atomic absorption spectrophotometry using the graphite furnace technique and previous digestion of foods in microwave oven. The chromium mean intake was estimated considering the chromium daily mean intake for person per day and the chromium content of the foods analyzed in this study. The range chromium content in the foods analyzed was between 0.0004 and 0.1641 microgram/g dry weight. White cheese showed the highest chromium content followed by pasta soup, wheat tortilla, bread and meat. The main foods chromium contributors in the diet were: wheat tortilla (20%), white cheese (11%), corn tortilla (11%), pasta soup (10%), milk (10%), meat (9%) and white bread (8%). The daily chromium intake was 30.43 +/- 1.6 micrograms/d. Chromium values obtained in the food analyzed are considered low. Moreover, chromium intake obtained from the diet is not enough to meet the safety and adequate daily chromium intake. Therefore, the population from the Northwestern Mexico has a suboptimal dietary chromium intake. PMID:11515227

  10. Reduction and immobilization of hexavalent chromium with coal- and humate-based sorbents.

    PubMed

    Janos, Pavel; Hůla, Václav; Bradnová, Petra; Pilarová, Vera; Sedlbauer, Josef

    2009-05-01

    Two kinds of the commercially available sorbents containing humic acids as active constituents were used for Cr(VI) reduction and removal, namely oxihumolite (naturally occurring weathered young brown coal) and iron humate (IH) (waste material produced during industrial manufacturing of humic substances). The mechanisms of the chromium removal involve the reduction of Cr(VI) (by humic substances or by Fe(II) ions) and subsequent binding of Cr(III) to a humic acid matrix. Other metal-binding mechanisms possibly effective in the process of Cr(VI) removal, e.g., coprecipitation or surface precipitation of Fe(III)/Cr(III) hydroxides, are also discussed. Oxihumolite was able to remove Cr(VI) from strongly acidic solutions with pH below ca. 2. IH, on the other hand, exhibited a maximum sorption capability in slightly acidic solutions with pH above ca. 3. Over the whole examined range (pH 1-5), however, IH was able to reduce Cr(VI) almost completely to its less toxic trivalent state. A sufficiently high sorption capacity (20 mg g(-1)) was found for chromium removal with IH in an unbuffered system, where the "natural" pH values governed by the buffering capacity of the sorbent itself ranged from 3.9 to 4.6. It follows from extraction studies with the loaded (spent) sorbents that chromium is bound strongly to the sorbent, and thus risks of its subsequent liberation into the environment are minimized. Similarity in the extraction behavior of the Cr(III)-loaded and Cr(VI)-loaded sorbents supported the above-mentioned mechanisms of the Cr(VI) removal. PMID:19215962

  11. Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies

    NASA Astrophysics Data System (ADS)

    Jauhar, Sheenu; Singhal, Sonal

    2014-10-01

    Nano-crystalline lanthanum ferrites substituted by chromium and copper having formula LaMxFe1-xO3 (M = Cr, Cu; 0.0 ⩽ x ⩽ 0.5) were synthesized using sol-gel auto-combustion method. The formation of ferrite particles was confirmed using Fourier Transform Infra-Red (FT-IR) spectra and powder X-ray Diffraction (XRD) techniques. The entire ferrite compositions were found to be pure phased with same symmetry as LaFeO3. The average crystallite size was calculated to be ∼60 nm. The ferrite compositions were observed to behave as semi-conductors, as their resistivity decreased with increasing temperature. These ferrite compositions were employed as catalysts in the decomposition of hydrogen peroxide solution (0.17 M). Pure LaFeO3 was found to have a very low catalytic activity towards the decomposition of hydrogen peroxide solution, while presence of copper in the lanthanum ferrite lattice was found to significantly enhance its catalytic activity. The rate constant in case of reactions catalysed by LaCu0.5Fe0.5O3 was nearly 25 times larger than that obtained from reactions catalysed by pure LaFeO3. However, chromium substitution was not found to influence the catalytic activity of lanthanum ferrites as chromium substituted lanthanum ferrites exhibited very low catalytic activity. This was explained on the basis of relative stability of oxidation states of the substituent ions and the presence of defects in the crystal lattice.

  12. Ion Implantatiion Improves Bearing-Surface Properties

    NASA Technical Reports Server (NTRS)

    Misra, M. S.; Kustas, F. M.

    1985-01-01

    Selected ions fired into rolling elements to increase resistance to rolling-contact fatique. Mask strips confine implantation to 105 degree arcs on cylindrical surfaces. Specimens kept cool by copper block through which refrigerant is circulated. Implanting nitrogen or titanium ions in metals improves resistance to fatigue, corrosion, and wear without altering bulk properties. Unlike such surface treatments as conventional nitriding, conventional carburizing, and coating, ion implantation is low-temperature process, requires no finishing operations, and produces highly-alloyed surface layer. Implantation process also helps conserve such strategic materials as chromium and cobalt by using them only where needed.

  13. Welding procedure specification: gas tungsten arc welding of nickel-chromium-iron and nickel-chromium-molybdenum

    SciTech Connect

    Wodtke, C.H.; Frizzell, D.R.; Plunkett, W.A.

    1985-08-01

    Procedure WPS-1303-ASME-8 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc welding of nickel-chromium-iron, N06600 (P-43), with filler metal ERNiCrFe-5 (F-43); and nickel-chromium-molybdenum, N06625 (P-43), with filler metal ERNiCrMo-3 (F-43); thickness range is 0.020 to 0.432 in.; shielding gas is argon.

  14. Chromium released from leather – I: exposure conditions that govern the release of chromium(III) and chromium(VI)

    PubMed Central

    Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

    2015-01-01

    Background Approximately 1–3% of the adult population in Europe is allergic to chromium (Cr). A new restriction in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) based on the ISO 17075 standard has recently been adopted in the EU to limit Cr(VI) in consumer and occupational leather products. Objectives The aim of this study was to critically assess key experimental parameters in this standard on the release of Cr(III) and Cr(VI) and their relevance for skin exposure. Material and methods Four differently tanned, unfinished, leather samples were systematically investigated for their release of Cr(III) and Cr(VI) in relation to surface area, key exposure parameters, temperature, ultraviolet irradiation, and time. Results Although the total release of Cr was largely unaffected by all investigated parameters, except exposure duration and temperature, the Cr oxidation state was highly dynamic, with reduced amounts of released Cr(VI) with time, owing to the simultaneous release of reducing agents from the leather. Significantly more Cr(III) than Cr(VI) was released from the Cr-tanned leather for all conditions tested, and it continued to be released in artificial sweat up to at least 1 week of exposure. Conclusions Several parameters were identified that influenced the outcome of the ISO 17075 test. PMID:25653094

  15. Chromium stable isotope fractionation during adsorption

    NASA Astrophysics Data System (ADS)

    Ellis, A.; Johnson, T.; Bullen, T.

    2003-04-01

    Chromium is a common anthropogenic contaminant in ground water. It is redox-active; the two common valences in natural waters are Cr(VI), which is highly soluble and toxic, and Cr(III), which is relatively insoluble. Redox reactions control Cr mobility in aqueous solutions with Cr(VI) reduction to Cr(III) controlling the attenuation of Cr in groundwater. Our previous study demonstrated that abiotic Cr(VI) reduction causes an isotope fractionation of -3.5 permil (53Cr/52Cr) and isotopes can therefore be used to calculate the extent of reduction. In the present study, experiments were conducted to measure Cr isotope fractionation during Cr(VI) sorption on Al203. Sorption of Cr(VI) could be important as a small isotope fractionation may get amplified along the edges of a Cr(VI) contaminated plume. A previous study demonstrated a similar process with Fe isotopes on anion exchange resin. Initial solutions of 200 mg/l Cr(VI) (as K2Cr2O7) and 0.1 mM KCl were made up. Sufficient solid Al203 was added to achieve 50% sorption. After equilibration, the solution was extracted by centrifuging and filtering with a 0.2 micron filter. Al203 was then added again to result in a further 50% sorption of the remaining Cr(VI). This process was repeated 10 times to amplify any isotopic fractionation between dissolved and adsorbed Cr(VI). The instantaneous stable isotope fractionation was calculated based on the δ 53Cr values of the initial and final Cr(VI) solutions. The results show that the stable isotope values measured in the solutions after the ten steps were within the uncertainty of the isotope value of the initial solution. Therefore, no significant stable isotope fractionation occurred. We are presently conducting experiments with goethite and expect similar results. Therefore, any fractionation of chromium stable isotopes observed in contaminant plumes are a result of processes other than adsorption (i.e., reduction).

  16. Enhancement of oxidative vaporization of chromium (III) oxide and chromium by oxygen atoms

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 were found to be markedly enhanced in the presence of O atoms. Investigations were conducted over the temperature range 470 to 1520 K. For Cr2O3 the enhancement was about 10 to the 9th power at 820 K in oxygen containing 2.5 percent atoms. Rapid oxidative vaporization of bare chromium was observed below 1070 K, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.

  17. Chromium-chromium interaction in a binuclear mixed-valent Cr(I)-Cr(II) complex.

    PubMed

    Alzamly, Ahmed; Gorelsky, Serge I; Gambarotta, Sandro; Korobkov, Ilia; Le Roy, Jennifer; Murugesu, Muralee

    2014-11-01

    A mixed-valent Cr(I)-Cr(II) binuclear complex, {κ(1),κ(2),κ(3)-N,P,P-cyclo[(Ph)PCH2N(CH2Ph)CH2]}2(CrCl2)[Cr(μ-Cl)(AlClMe2)]·4toluene (1), of a P2N2 cyclic ligand was obtained upon treatment of the chromium precursor with alkylaluminum. Complex 1 was accessible from either its trivalent or divalent precursors, and density functional theory calculations revealed the presence of only σ- and π-orbital interactions in the Cr-Cr bond. PMID:25310604

  18. Selective detection of heavy metal ions by self assembled chemical field effect transistors

    NASA Astrophysics Data System (ADS)

    Ruan, Hang; Kang, Yuhong; Gladwin, Elizabeth; Claus, Richard O.

    2015-04-01

    Multiple layer-by-layer sensor material modifications were designed and implemented to achieve selectivity of semiconductor based chemical field effect transistors (ChemFETs) to particular heavy metal ions. The ChemFET sensors were fabricated and modified in three ways, with the intent to initially target first mercury and lead ions and then chromium ions, respectively. Sensor characterization was performed with the gate regions of the sensor elements exposed to different concentrations of target heavy metal ion solutions. A minimum detection level in the range of 0.1 ppm and a 10%-90% response time of less than 10 s were demonstrated. By combining layer-by-layer gold nanoparticles and lead ionophores, a sensor is produced that is sensitive and selective not only to chromium but also to Cr3+ and Cr6+. This result supports the claim that high selectivity can be achieved by designing self-assembled bonding for lead, arsenic, chromium, cesium, mercury, and cadmium.

  19. A Rare Terminal Dinitrogen Complex of Chromium

    SciTech Connect

    Mock, Michael T.; Chen, Shentan; Rousseau, Roger J.; O'Hagan, Molly J.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.; Bullock, R. Morris

    2011-10-12

    The reduction of dinitrogen to ammonia from N2 and H2 is currently carried out by the Haber-Bosch process, an energy intensive process that requires high pressures and high temperatures and accounts for the production of millions of tons of ammonia per year. The development of a catalytic, energy-efficient process for N2 reduction is of great interest and remains a formidable challenge. In this communication, we are reporting the preparation, characterization and computational electronic structure analysis of a rare 'Chatt-type' ((P-P)2M(N2)2, P-P = diphosphine ligand) complex of chromium, cis-[Cr(N2)2(PPh2NBn2)2] and its reactivity with CO. This complex is supported by the diphosphine ligand PPh2NBn2, containing non-coordinating pendant amine bases, to serve as proton relays. Future studies for this complex are aimed at answering fundamental questions regarding the role of proton relays in the second coordination sphere in their ability to facilitate proton movement from an external acid to metal-bound dinitrogen ligands in the challenging multi-proton/electron reduction of N2 to ammonia.

  20. Uptake, Distribution and Speciation of Chromium

    SciTech Connect

    Bluskov,S.; Arocena, J.; Omotoso, O.; Young, J.

    2005-01-01

    Brassica juncea (Indian mustard) has been widely used in phytoremediation because of its capacity to accumulate high levels of chromium (Cr) and other metals. The present study was conducted to investigate mechanism(s) involved in Cr binding and sequestration by B. juncea. The plants were grown under greenhouse conditions in field-moist or air-dried soils, amended with 100 mg kg -1 of Cr (III or VI). The plant concentrated Cr mainly in the roots. B. juncea removed an average of 48 and 58 {mu}g Cr per plant from Cr (III) and Cr (VI)-treated soils, respectively. The uptake of Cr was not affected by the moisture status of the soils. X-ray absorption near-edge spectroscopy measurements showed only Cr (III) bound predominantly to formate and acetate ligands, in the bulk and rhizosphere soils, respectively. In the plant tissues, Cr (III) was detected, primarily as acetate in the roots and oxalate in the leaves. X-ray microprobe showed the sites of Cr localization, and probably sequestration, in epidermal and cortical cells in the roots and epidermal and spongy mesophyll cells in the leaves. These findings demonstrate the ability of B. juncea to detoxify more toxic Cr (VI), thereby making this plant a potential candidate for phytostabilization.

  1. Low energy spin excitations in chromium metal

    SciTech Connect

    Pynn, R.; Azuah, R.T.; Stirling, W.G.; Kulda, J.

    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.

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

    SciTech Connect

    Sugiyama, Masayasu )

    1991-05-01

    The effects of vitamin E and vitamin B{sub 2} on DNA damage and cellular reduction of chromium (VI) were investigated using Chinese hamster V-79 cells. pretreatment with {alpha}-tocopherol succinate (vitamin E) resulted in a decrease of DNA single-strand breaks produced by Na{sub 2}CrO{sub 4}, while similar treatment with riboflavin (vitamin B{sub 2}) enhanced levels of DNA breaks. Electron spin resonance (ESR) studies showed that incubation of cells with Na{sub 2}CrO{sub 4} resulted in the formation of both chromium (V) and chromium (III) complexes, and cellular pretreatment with vitamin E reduced the level of the chromium (V) complex, whereas pretreatment with vitamin B{sub 2} enhanced the level of this intermediate. ESR studies demonstrated that a chromium (V) species was formed by the reaction of Na{sub 2}CrO{sub 4} with vitamin B{sub 2} and that vitamin B{sub 2} enhanced the formation of hydroxyl radicals during the reaction of Na{sub 2}CrO{sub 4} and hydrogen peroxide. These results indicate that vitamin E and vitamin B{sub 2} are capable of altering the biological effects of carcinogenic chromium (VI) compounds, possibly through their abilities to modify levels of chromium (V) in cells. The results also suggest that chromate-induced cytotoxicity may not be directly correlated with the genotoxic effects of this metal. The importance of the role of vitamins in chromate-induced toxicity is discussed.

  3. Microstructure of a Creep-Resistant 10 Pct Chromium Steel Containing 250 ppm Boron

    NASA Astrophysics Data System (ADS)

    Golpayegani, Ardeshir; Liu, Fang; Svensson, Henrik; Andersson, Marcus; Andrén, Hans-Olof

    2011-04-01

    The microstructure of a trial martensitic chromium steel containing a high content of boron (250 ppm) was characterized in detail in the as-tempered and aged conditions. This steel has a similar composition and heat treatment as the TAF steel that still is unsurpassed in creep strength among all 9 to 12 pct chromium steels. Characterization was performed by using scanning electron microscopy, energy-filtered transmission electron microscopy, secondary ion mass spectroscopy, and atom probe tomography. Focus was placed on investigating different types of precipitates that play a key role in improving the creep resistance of these steels. The low tempering temperature of 963 K (690 °C) is enough for the precipitation of the full volume fraction of both MX and M23C6. A high boron content, more than 1 at. pct, was found in M23C6 precipitates and they grow slowly during aging. The high boron level in the steel results in metal borides rather than BN with the approximate formula (Mo0.66Cr0.34)2(Fe0.75V0.25)B2. Two families of MX precipitates were found, one at lath boundaries about 35 nm in size and one dense inside the laths, only 5 to 15 nm in size.

  4. Removal of hexavalent chromium from wastewater using a new composite chitosan biosorbent.

    PubMed

    Boddu, Veera M; Abburi, Krishnaiah; Talbott, Jonathan L; Smith, Edgar D

    2003-10-01

    A new composite chitosan biosorbent was prepared by coating chitosan, a glucosamine biopolymer, onto ceramic alumina. The composite bioadsorbent was characterized by high-temperature pyrolysis, porosimetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Batch isothermal equilibrium and continuous column adsorption experiments were conducted at 25 degrees C to evaluate the biosorbent for the removal of hexavalent chromium from synthetic as well as field samples obtained from chrome plating facilities. The effect of pH, sulfate, and chloride ion on adsorption was also investigated. The biosorbent loaded with Cr(VI) was regenerated using 0.1 M sodium hydroxide solution. A comparison of the results of the present investigation with those reported in the literature showed that chitosan coated on alumina exhibits greater adsorption capacity for chromium(VI). Further, experimental equilibrium data were fitted to Langmuir and Freundlich adsorption isotherms, and values of the parameters of the isotherms are reported. The ultimate capacity obtained from the Langmuir model is 153.85 mg/g chitosan. PMID:14572099

  5. Impact of environmental stress on biochemical parameters of bacteria reducing chromium

    PubMed Central

    Batool, Rida; Yrjälä, Kim; Hasnain, Shahida

    2014-01-01

    Chromium pollution is produced in connection with industrial processes like in tanneries. It has been suggested that bioremediation could be a good option for clean up. The stress effect of variable chromate levels, pHs and growth temperatures on biochemical parameters of two Cr(VI) reducing bacterial strains Pseudomonas aeruginosa Rb-1 and Ochrobactrum intermedium Rb-2 was investigated. Transmission electrone microscopy (TEM) was performed to study the intracellular distribution of Cr(VI). It was observed that initial stress of 1000 μgmL−1 caused significant enhancement of all studied biochemical parameters at pH 7.0 and growth temperature of 37 °C showing great bioremediation potential of the strains. Transmission electron microscopy revealed that the distribution of chromium precipitates was not uniform as they were distributed in the cytoplasm as well as found associated with the periplasm and outer membrane. Fourier transform infrared spectroscopy showed the possible involvement of carboxyl, amino, sulpohonate and hydroxyl groups present on the bacterial cell surface for the binding of Cr(VI) ions. Cr(VI) stress brought about changes in the distridution of these functional groups. It can be concluded that the investigated bacterial strains adjust well to Cr(VI) stress in terms of biochemical parameters and along that exhibited alteration in morphology. PMID:25242944

  6. Accumulation of chromium in root tissues of Eichhornia crassipes (Mart.) Solms. in Cachoeira river—Brazil

    NASA Astrophysics Data System (ADS)

    Mangabeira, P. A. O.; Labejof, L.; Lamperti, A.; de Almeida, A.-A. F.; Oliveira, A. H.; Escaig, F.; Severo, M. I. G.; Silva, D. da C.; Saloes, M.; Mielke, M. S.; Lucena, E. R.; Martins, M. C.; Santana, K. B.; Gavrilov, K. L.; Galle, P.; Levi-Setti, R.

    2004-06-01

    Heavy metals are not biodegradable and enter the food chain through a number of pathways causing progressive toxic actions due to the accumulation in different organs during a life span and long-term exposure to contaminated environments. Secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) were used to localize chromium in Eichhornia crassipes (Mart.) Solms. ICP-MS was used for the determination of Cr concentrations in water, sediments and plant samples in the Cachoeira basin, Bahia, Brazil. The results obtained by ICP-MS shows abnormally high values of Cr concentrations in water samples (0.38 μg/l), in soil samples (63 μg/g) and 70 μg/g in plant tissue. SIMS results show increased levels of Cr in the root cell wall and xylem vessel, these sites show high Cr accumulation. The ICP-MS data confirm E. crassipes like bioindicator plant. Chemical analysis using ICP-MS, confirms SIMS analysis on the presence of Cr in roots xylem cell walls. The use of ICP-MS, to investigate the same organs as the ones investigated by SIMS, provided complementary results on chromium study.

  7. Characterization and Oxidation of Chromium(III) by Sodium Hypochlorite in Alkaline Solutions

    SciTech Connect

    Jiang, Huijian; Rao, Linfeng; Zhang, Zhicheng; Rai, Dhanpat

    2006-07-01

    Chromium exists in nuclear waste sludges and is a problematic element in the vitrification process of high-level nuclear wastes. It is therefore necessary to treat the waste sludges to remove chromium prior to vitrification, by caustic leaching or oxidation of Cr(III) to Cr(VI). The objective of this study is to investigate the effect of oligomerization of Cr(III) on its oxidation by hypochlorite in alkaline solutions. Monomeric, dimeric and trimeric Cr(III) species in solution were separated by ion exchange. The kinetics of the oxidation of the separated species by hypochlorite in alkaline solutions was studied by UV/Vis absorption spectroscopy, and compared with the oxidation by hydrogen peroxide previously studied. Results indicate that hypochlorite can oxidize Cr(III) to Cr(VI) in alkaline solutions, but the rate of oxidation by hypochlorite is slower than that by hydrogen peroxide at the same alkalinity and concentrations of oxidants. The rate of oxidation of Cr(III) by both oxidants decreases as the concentration of sodium hydroxide is increased, but the oxidation by hypochlorite seems less affected by the degree of oligomerization of Cr(III) than that by peroxide. Compared with the oxidation by hydrogen peroxide where the major reaction pathway has an inverse order with respect to CNaOH, the oxidation by hypochlorite has a significant reaction pathway independent of [OH?].

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  10. The role of intergranular chromium carbides on intergranular oxidation of nickel based alloys in pressurized water reactors primary water

    NASA Astrophysics Data System (ADS)

    Gaslain, F. O. M.; Le, H. T.; Duhamel, C.; Guerre, C.; Laghoutaris, P.

    2016-02-01

    Alloy 600 is used in pressurized water reactors (PWRs) but is susceptible to primary water stress corrosion cracking (PWSCC). Intergranular chromium carbides have been found beneficial to reduce PWSCC. Focussed ion beam coupled with scanning electron microscopy (FIB/SEM) 3D tomography has been used to reconstruct the morphology of grain boundary oxide penetrations and their interaction with intergranular Cr carbides in Alloy 600 subjected to a PWR environment. In presence of intergranular Cr carbides, the intergranular oxide penetrations are less deep but larger than without carbide. However, the intergranular oxide volumes normalized by the grain boundary length for both samples are similar, which suggest that intergranular oxidation growth rate is not affected by carbides. Analytical transmission electron microscopy (TEM) shows that the intergranular oxide consists mainly in a spinel-type oxide containing nickel and chromium, except in the vicinity of Cr carbides where Cr2O3 was evidenced. The formation of chromium oxide may explain the lower intergranular oxide depth observed in grain boundaries containing Cr carbides.

  11. An investigation of the use of chromium, platinum and gold coating for scanning electron microscopy of casts of lymphoid tissues.

    PubMed

    Belz, G T; Auchterlonie, G J

    1995-01-01

    Resin casts replicate the internal structure of organs and provide a three-dimensional representation of the arrangement of vessels and intercellular spaces. Casting media are insulators and must be coated with a conductor to prevent sample charging and to allow the adequate production of secondary electrons from the specimen to generate sufficient signal to form a clear image. Visualization of surface structures depends largely on the metal coating. The use of gold or platinum, deposited on Mercox casts of lymphoid tissues using plasma-magnetron sputtering, and of chromium coating of casts by Penning ion-beam coating, was investigated. Casts were examined using a field emission scanning electron microscope at 3-3.5 kV. Thick coatings of gold were necessary to reduce cast charging but they obscured fine structural information. Charging effects were less pronounced when casts were coated with platinum, but charge lines were present at slow scan rates. The dimensions of cast impressions for both platinum and chromium coatings were similar to those described in fixed tissues. Negligible charging and maximal cast thermal stability and structural information was obtained from casts which were tumbled during chromium coating. PMID:7767633

  12. New mixed-valence chromium structure type: NH{sub 4}Cr(CrO{sub 4}){sub 2}

    SciTech Connect

    Casari, Barbara M. . E-mail: casari@chem.gu.se; Wingstrand, Erica; Langer, Vratislav

    2006-01-15

    Synthesis and crystal structure of a new structure type of mixed Cr(III)/Cr(VI) chromates is reported. NH{sub 4}Cr(CrO{sub 4}){sub 2} was prepared from CrO{sub 3} in the presence of (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 6}. Since this is the first preparation of mixed valence ternary chromium oxides from aqueous solution, a reaction pathway for this synthesis is suggested. The crystal structure of NH{sub 4}Cr(CrO{sub 4}){sub 2} has been determined from three-dimensional X-ray data collected at low temperature, 173K. The structure belongs to the orthorhombic space group Pnma, with a=14.5206(10), b=5.4826(4), c=8.7041(7)A and Z=4. The title compound consists of corner-sharing chromium(III) octahedra and chromium(VI) tetrahedra forming a three-dimensional network with the composition [Cr(CrO{sub 4}){sub 2}]{sub n}{sup n-}, containing channels in which zigzag rows of ammonium ions balance the net charge.

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

    PubMed

    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

  14. Electron-irradiation damage in chromium nitrides and chromium oxynitride thin films.

    PubMed

    Mitterbauer, Christoph; Grogger, Werner; Wilhartitz, Peter; Hofer, Ferdinand

    2006-01-01

    The aim of this work is to monitor changes of the N-K electron energy-loss near-edge structure (ELNES) of chromium nitride layers (CrN) introduced by electron irradiation in a transmission electron microscope (TEM). These changes are different for each sample material and seem to give an indication for a particular composition. The CrN samples (CrN and Cr(0.47)N(0.53)) were prepared on silicon wafers by reactive magnetron sputtering of a metallic chromium target in nitrogen plasma. In addition, a CrON sample (Cr(0.5)O(0.2)N(0.3)) was also investigated. This sample was prepared by the addition of oxygen to the plasma during film deposition. The ELNES of the N-K ionization edge of stoichiometric CrN shows a typical fine structure (peaks at 399.0 and 401.1 eV) and remains nearly unaffected even after high-current-density irradiation. On the other hand the N-K fine structures of Cr(0.47)N(0.53) and Cr(0.5)O(0.2)N(0.3) show a change of the ELNES with irradiation dose. This presumably arises from a 1s-pi*-transition of molecular nitrogen located at interstitial positions in these samples. PMID:16554164

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

    SciTech Connect

    Rao, P. Srinivasa; Babu, P. Ramesh; Vijay, R.; Narendrudu, T.; Veeraiah, N.; Rao, D. Krishna

    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

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

    SciTech Connect

    Almond, P. M.; Stefanko, D. B.; Langton, C. A.

    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

  17. Cytotoxicity and Genotoxicity of Hexavalent Chromium in Human and North Atlantic Right Whale (Eubalaena glacialis) Lung Cells

    PubMed Central

    Chen, Tânia Li; Wise, Sandra S.; Holmes, Amie; Shaffiey, Fariba; Wise, John Pierce; Thompson, W. Douglas; Kraus, Scott; Wise, John Pierce

    2009-01-01

    Humans and cetaceans are exposed to a wide range of contaminants. In this study, we compared the cytotoxic and genotoxic effects of a metal pollutant, hexavalent chromium [Cr(VI)], which has been shown to cause damage in lung cells from both humans and North Atlantic right whales. Our results show that Cr induces increased cell death and chromosome damage in lung cells from both species with increasing intracellular Cr ion levels. Soluble Cr(VI) induced less of a cytotoxic and genotoxic effect on administered dose in right whale (Eubalaena glacialis) cells than in human (Homo sapiens) cells. Whereas, particulate Cr(VI) induced a similar cytotoxic effect but less of a genotoxic effect based on administered dose in right whale cells than in human cells. Differences in chromium ion uptake explained some but not all of the soluble chromate-induced cell death and chromosome damage. Uptake differences of lead ions could explain the differences in particulate chromate-induced toxicity. The data show that both forms of Cr(VI) are less genotoxic to right whale than human lung cells, and that soluble Cr(VI) induces a similar cytotoxic effect in both right whale and human cells, while particulate Cr(VI) is more cytotoxic to right whale lung cells. PMID:19632355

  18. Hexavalent chromium reduction by bacteria from tannery effluent.

    PubMed

    Batool, Rida; Yrjala, Kim; Hasnain, Shahida

    2012-04-01

    Chromium is generated from several industrial processes. It occurs in different oxidation states, but Cr(III) and Cr(VI) are the most common ones. Cr(VI) is a toxic, soluble environmental contaminant. Some bacteria are able to reduce hexavalent chromium to the insoluble and less toxic Cr(III), and thus chromate bioremediation is of considerable interest. An indigenous chromium-reducing bacterial strain, Rb-2, isolated from a tannery water sample, was identified as Ochrobactrum intermedium, on the basis of 16S rRNA gene sequencing. The influence of factors like temperature of incubation, initial concentration of Cr, mobility of bacteria, and different carbon sources were studied to test the ability of the bacterium to reduce Cr(VI) under variable environmental conditions. The ability of the bacterial strain to reduce hexavalent chromium in artificial and industrial sewage water was evaluated. It was observed that the mechanism of resistance to metal was not due to the change in the permeability barrier of the cell membrane, and the enzyme activity was found to be inductive. Intracellular reduction of Cr(VI) was proven by reductase assay using cell-free extract. Scanning electron microscopy revealed chromium precipitates on bacterial cell surfaces, and transmission electron microscopy showed the outer as well as inner distribution of Cr(VI). This bacterial strain can be useful for Cr(VI) detoxification under a wide range of environmental conditions. PMID:22534304

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

    PubMed

    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

  20. Thermodynamics of chromium in UO2 fuel: A solubility model

    NASA Astrophysics Data System (ADS)

    Riglet-Martial, Ch.; Martin, Ph.; Testemale, D.; Sabathier-Devals, C.; Carlot, G.; Matheron, P.; Iltis, X.; Pasquet, U.; Valot, C.; Delafoy, C.; Largenton, R.

    2014-04-01

    The solubility and speciation of chromium in doped uranium oxide are measured in carefully controlled temperature and oxygen potential conditions using electron probe microanalysis (EPMA) and scanning electron spectroscopy (SEM). The examination of the samples by X-ray Absorption Spectroscopy (XAS) provides evidence that (i) chromium is soluble in the UO2 matrix under the +3 oxidation state only regardless of the sintering conditions which is in accordance with a soluble species of type CrO3/2 and (ii) soluble chromium exhibits octahedral symmetry with 6 atoms of oxygen forming CrO6 patterns in the UO2 structure. In consistency with all available experimental information including previously published data, the solubility of chromium in UO2 corresponding to each two-phase field with either Cr, CrO and Cr2O3 may be described in the ranges 1500 °C < T < 2000 °C and -460 < μO2 < -360 kJ/mol using the standard thermodynamic equations governing solubility equilibria. The characteristic parameters of the solubility laws in UO2 for the three chromium phases are derived.

  1. Predicting the impact of chromium on flow-accelerated corrosion

    SciTech Connect

    Chexal, B.; Goyette, L.F.; Horowitz, J.S.; Ruscak, M.

    1996-12-01

    Flow-Accelerated Corrosion (FAC) continues to cause problems in nuclear and fossil power plants. Many experiments have been performed to understand the mechanism of FAC. For approximately twenty years, it has ben widely recognized that the presence of small amounts of chromium will reduce the rate of FAC. This effect was quantified in the eighties by research performed in France, Germany and the Netherlands. The results of this research has been incorporated into the computer-based tools used by utility engineers to deal with this issue. For some time, plant data from Diablo Canyon has suggested that the existing correlations relating the concentration of chromium to the rate of FAC are conservative. Laboratory examinations have supported this observation. It appears that the existing correlations fail to capture a change in mechanism from a FAC process with linear kinetics to a general corrosion process with parabolic kinetics. This change in mechanism occurs at a chromium level of approximately 0.1%, within the allowable alloy range of typical carbon steel (ASTM/ASME A106 Grade B) used in power piping in most domestic plants. It has been difficult to obtain plant data that has sufficient chromium to develop a new correlation. Data from Diablo Canyon and the Dukovany Power Plant in the Czech Republic will be used to develop a new chromium correlation for predicting FAC rate.

  2. Treatability study for the stabilization of chromium contaminated waste

    SciTech Connect

    McGahan, J.F.; Martin, D.

    1994-12-31

    A process has been developed which immobilizes chromium in calcined uranyl nitrate mixed waste, resulting in a waste form disposable as radioactive, non hazardous waste. A prime contractor at the Idaho National Engineering Laboratory generates a radioactive waste contaminated with chromium. During handling, the waste becomes contaminated at a concentration sufficiently high to cause the waste to exceed the EPA`s Toxicity Characteristic Leaching Procedure (TCLP) leachable limit for chromium. A treatability test program was instigated to define the optimum conditions for the chemical reduction pretreatment step necessary for the stabilization of the contaminated waste. Sodium dithionite was determined to be the reducing agent of choice. A dithionite demand experiment was run to determine optimum dithionite dose. This dose, plus 67 percent excess, was added to each sample. Four different stabilization systems, at three different dosage levels, were investigated. The best performing reagent system was chosen for scale-up and more stringent performance testing. In one of the tested reagent systems, Portland cement sodium silicate and dithionite, all of the samples exhibited TCLP extract concentrations for chromium well below the regulatory limit. Portland cement/blast furnace slag blend had one passing sample, and for cement/fly ash and cement alone none of the samples had passing values for leachable chromium. The samples scaled-up passed the performance criteria and the process which is currently undergoing implementation at INEL has successfully converted mixed waste into radioactive waste for disposal.

  3. Enhancement of chromium uptake in tanning using oxazolidine.

    PubMed

    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

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

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A.

    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.

  5. Induction of SOS genes of Escherichia coli by chromium compounds

    SciTech Connect

    Llagostera, M.; Garrido, S.; Guerrero, R.; Barbe, J.

    1986-01-01

    The induction of several SOS genes of Escherichia coli such as recA, umuC, and sfiA by hexavalent (K/sub 2/Cr/sub 2/O/sub 7/, K/sub 2/CrO/sub 4/, and CrO/sub 3/) and trivalent (CrCl/sub 3/, Cr(NO/sub 3/)/sub 3/, and (CH/sub 3/COO)/sub 3/Cr) compounds of chromium was studied. Induction was measured as ..beta..-galactosidase activity, using lacZ gene fusions under the control region of different SOS genes. The hexavalent chromium forms induced the genes responsible for massive synthesis of RecA protein, error-prone repair, and inhibition of cell division. On the other hand, the trivalent chromium compounds were unable to induce any of the SOS genes tested. Individual assay of hexavalent chromium compounds showed that K/sub 2/Cr/sub 2/O/sub 7/ was a stronger inducing agent of those three SOS genes tested than K/sub 2/CrO/sub 4/, which, in turn, was stronger than CrO/sub 3/. All this data led to the conclusion that hexavalent chromium compounds, but not trivalent, are proficient agents of induction of the SOS system and can produce indirect mutagenesis in Escherichia coli.

  6. Anthropogenic Chromium Emissions in China from 1990 to 2009

    PubMed Central

    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 1.92×105t. 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 1.34×104t 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 of15.6% 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

  7. Chromium accumulation in three species of central Florida centrarchids

    SciTech Connect

    Campbell, K.R. |

    1995-02-01

    Stormwater ponds are required in Central Florida when land is developed to treat the resulting stormwater. The St. Johns River Water Management District, the agency that regulates stormwater discharges in Central Florida, frequently approves plans that create habitat for fish and wildlife by planting desirable wetland and aquatic vegetation in the littoral zones of stormwater ponds to compensate for the loss of wetlands. The various species of fish that inhabit stormwater ponds serve as a food source to wildlife, especially wading birds. The objective of this study was to determine if fish that live in stormwater treatment ponds in Orlando, Florida contained significant concentrations of chromium. In order to determine if there were differences in chromium concentrations in fish with different foraging strategies, three species of sunfish (Centrarchidae) with substantially different foraging strategies were selected for this study: largemouth bass (Micropterus salmoides), a predator; redear sunfish (Lepomis microlophus), a bottom feeder; and bluegill sunfish (Lepomis macrochirus), an omnivore. Many researchers have shown that large quantities of chromium are found in urban runoff. Chromium sources are largely associates with the operation of motor vehicles. Several investigators have determined that chromium from urban runoff concentrates in the sediment of stormwater ponds. Sediments represent the most concentrated physical pool of metals in aquatic environments, and they are ingested by many types of aquatic organisms. Most fish are capable of accumulating heavy metals from their diet and from water through their gills. 17 refs., 1 fig., 3 tabs.

  8. Thiocyanato Chromium (III) Complexes: Separation by Paper Electrophoresis and Estimate of Stability Constants

    ERIC Educational Resources Information Center

    Larsen, Erik; Eriksen, J.

    1975-01-01

    Describes an experiment wherein the student can demonstrate the existence of all the thiocyanato chromium complexes, estimate the stepwise formation constants, demonstrate the robustness of chromium III complexes, and show the principles of paper electrophoresis. (GS)

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

    EPA Science Inventory

    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...

  10. FORMATION AND DESTRUCTION OF HEXAVALENT CHROMIUM IN A LABORATORY SWIRL FLAME INCINERATOR

    EPA Science Inventory

    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...

  11. Final response to BDAT related comments document. D007. Characteristic wastes for chromium. Volume 1-G

    SciTech Connect

    Rosengrant, L.; Craig, R.

    1990-05-01

    The contents of this article include the following: treatment standards; treatment data; treatability of waste/group; total chromium vs hexavalent or trivalent chromium; miscellaneous; and comments on data.

  12. Chromium solubility in anhydrous Phase B

    NASA Astrophysics Data System (ADS)

    Bindi, Luca; Sirotkina, Ekaterina A.; Bobrov, Andrey V.; Nestola, Fabrizio; Irifune, Tetsuo

    2016-02-01

    The crystal structure and chemical composition of a crystal of (Mg14- x Cr x )(Si5- x Cr x )O24 ( x ≈ 0.30) anhydrous Phase B (Anh-B) synthesized in the model system MgCr2O4-Mg2SiO4 at 12 GPa and 1600 °C have been investigated. The compound was found to be orthorhombic, space group Pmcb, with lattice parameters a = 5.900(1), b = 14.218(2), c = 10.029(2) Å, V = 841.3(2) Å3 and Z = 2. The structure was refined to R 1 = 0.065 using 1492 independent reflections. Chromium was found to substitute for both Mg at the M3 site (with a mean bond distance of 2.145 Å) and Si at the octahedral Si1 site (mean bond distance: 1.856 Å), according to the reaction Mg2+ + Si4+ = 2Cr3+. Such substitutions cause a reduction in the volume of the M3 site and an increase in the volume of the Si-dominant octahedron with respect to the values typically observed for pure Anh-B and Fe2+-bearing Anh-B. Taking into account that Cr3+ is not expected to be Jahn-Teller active, it appears that both the Cr3+-for-Mg and Cr3+-for-Si substitutions in the Anh-B structure decrease the distortion of the octahedra. Electron microprobe analysis gave the Mg13.66(8)Si4.70(6)Cr0.62(4)O24 stoichiometry for the studied phase. The successful synthesis of this phase provides new information for the possible mineral assemblages occurring in the Earth's deep upper mantle and shed new light on the so-called X discontinuity that has been observed at 275-345 km depth in several subcontinental and subduction zone environments.

  13. Chromium enhances insulin responsiveness via AMPK.

    PubMed

    Hoffman, Nolan J; Penque, Brent A; Habegger, Kirk M; Sealls, Whitney; Tackett, Lixuan; Elmendorf, Jeffrey S

    2014-05-01

    Trivalent chromium (Cr(3+)) is known to improve glucose homeostasis. Cr(3+) has been shown to improve plasma membrane-based aspects of glucose transporter GLUT4 regulation and increase activity of the cellular energy sensor 5' AMP-activated protein kinase (AMPK). However, the mechanism(s) by which Cr(3+) improves insulin responsiveness and whether AMPK mediates this action is not known. In this study we tested if Cr(3+) protected against physiological hyperinsulinemia-induced plasma membrane cholesterol accumulation, cortical filamentous actin (F-actin) loss and insulin resistance in L6 skeletal muscle myotubes. In addition, we performed mechanistic studies to test our hypothesis that AMPK mediates the effects of Cr(3+) on GLUT4 and glucose transport regulation. Hyperinsulinemia-induced insulin-resistant L6 myotubes displayed excess membrane cholesterol and diminished cortical F-actin essential for effective glucose transport regulation. These membrane and cytoskeletal abnormalities were associated with defects in insulin-stimulated GLUT4 translocation and glucose transport. Supplementing the culture medium with pharmacologically relevant doses of Cr(3+) in the picolinate form (CrPic) protected against membrane cholesterol accumulation, F-actin loss, GLUT4 dysregulation and glucose transport dysfunction. Insulin signaling was neither impaired by hyperinsulinemic conditions nor enhanced by CrPic, whereas CrPic increased AMPK signaling. Mechanistically, siRNA-mediated depletion of AMPK abolished the protective effects of CrPic against GLUT4 and glucose transport dysregulation. Together these findings suggest that the micronutrient Cr(3+), via increasing AMPK activity, positively impacts skeletal muscle cell insulin sensitivity and glucose transport regulation. PMID:24725432

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

    PubMed

    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

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

    PubMed

    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

  16. Is the Pharmacological Mode of Action of Chromium(III) as a Second Messenger?

    PubMed

    Vincent, John B

    2015-07-01

    Although recent studies have shown that chromium (as the trivalent ion) is not an essential trace element, it has been demonstrated to generate beneficial effects at pharmacologically relevant doses on insulin sensitivity and cholesterol levels of rodent models of insulin insensitivity, including models of type 2 diabetes. The mode of action of Cr(III) at a molecular level is still an area of active debate; however, the movement of Cr(III) in the body, particularly in response to changes in insulin concentration, suggests that Cr(III) could act as a second messenger, amplifying insulin signaling. The evidence for the pharmacological mechanism of Cr(III)'s ability to increase insulin sensitivity by acting as a second messenger is reviewed, and proposals for testing this hypothesis are described. PMID:25595680

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

    PubMed

    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

  18. Factors affecting the adsorption of chromium (VI) on activated carbon

    SciTech Connect

    Yavuz, R.; Orbak, I.; Karatepe, N.

    2006-09-15

    The aim of this investigation was to determine the adsorption behavior of chromium (VI) on two different activated carbon samples produced from Tuncbilek lignite. The effects of the initial chromium (VI) concentration (250-1000 mg/L), temperature (297-323 K) and pH (2.0-9.5) on adsorption were investigated systematically. The effectiveness of the parameters on chromium adsorption was found to be in the order of pH, the initial Cr(VI) concentration and the temperature. Increasing the pH from 2.0 to 9.5 caused a decrease in adsorption. However, the adsorption was increased by increasing the initial Cr(VI) concentration and temperature. The multilinear mathematical model was also developed to predict the Cr(VI) adsorption on activated carbon samples within the experimental conditions.

  19. Extraction of Chromium from Carbon Ferrochromium Residual Wastes

    NASA Astrophysics Data System (ADS)

    Lazarevskiy, P. P.; Gizatulin, R. A.; Romanenko, Yu E.; Valuev, D. V.; Valueva, A. V.; Serikbol, A.

    2015-09-01

    This work reports the problem of processing residual wastes after producing carbon ferrochrome by recycling dust using a hydrometallurgical method with the purpose of extracting the basic component - chromium, The X-ray diffraction analysis results, chemical and granulometric compositions of dust from the carbon ferrochrome production are given, The method for the production of chemical-enrichment concentrate (CEC) by processing ferrous dust is described, with obtaining a middling product - sodium mono-chromate with its further reduction to chromium hydroxide, followed by autoclave leaching, and resulting in the production of chemically enriched chrome concentrate, The plant used for autoclave leaching and filtering is schematically depicted, The smelting process of metallic chromium using the ladle aluminothermic method is described,

  20. Toxic effects of chromium on Schistosoma haematobium miracidia

    SciTech Connect

    Wolmarans, C.T.; Yssel, E.; Hamilton-Attwell, V.L.

    1988-12-01

    Various heavy metals have recently been evaluated as molluscicides for freshwater snails, which act as intermediate hosts of trematode parasites of medical or veterinary importance. Very little information, however, is available on heavy metals that may be suitable to eliminate the parasites as such. Suitable compounds should also inhibit the penetration ability of parasites as well as stunt the development of those who do not penetrate their hosts. In the light of these requirements, the present study evaluated the effect of chromium on the miracidia of Schistosoma haematobium, which causes urinary bilharzia. Attention was mainly focused on (1) the chromium concentration which resulted in 100% mortality (2) the effect of chromium on the external and internal morphology of the miracidia, and (3) the ability of the miracidia to form sporocytes in vitro and in vivo and to penetrate their intermediate host snail, Bulinus africanus.

  1. Cold collisions of alkali-metal atoms and chromium atoms

    NASA Astrophysics Data System (ADS)

    Jeung, G.-H.; Hagebaum-Reignier, D.; Jamieson, M. J.

    2010-12-01

    We present ab initio potentials for ground state lithium, sodium, potassium and rubidium atoms interacting with ground state chromium atoms via the 6Σ+ and 8Σ+ states of the corresponding dimers. Each potential is matched to the leading van der Waals dispersion energy -C6/R6 - C8/R8 and an exchange energy; we list the values of C6, C8 and the exchange fitting parameters. We present calculated values from quantal and semi-classical approximations for the s-wave scattering length and effective range and the p-wave scattering volume for collisions of each of the alkali-metal atoms lithium, sodium, potassium and rubidium with 52chromium atoms and comment on s-wave scattering by 53chromium atoms.

  2. Fluidized bed electrowinning of chromium from very dilute solutions

    SciTech Connect

    Hu, X.; Bautista, R.G.

    1988-10-01

    The Fluidized Bed Electrochemical Reactor (FBER) was used to electrowin chromium from very dilute solutions, ranging in concentration from 0.52 to 3.12 g Cr/1 at pH = 2. The cathode consisted of particulate chromium (450-600 ..mu..m diam.) with a current feeder made of carbon bars and a tubular lead anode in a cylindrical cell. The current efficiency was in the range of 0.08-0.22. The bed expansion, deposition rate, conversion ratio of Cr(VI) to Cr(III) and voltage - current characteristic of the cell were studied. The results indicate that the use of the FBER will make possible the removal of chromium from very dilute solutions without the introduction of other chemicals which would need to be removed or treated further downstream to satisfy environmental abatement codes.

  3. The structural, electrical, and optical properties of hydrogenated chromium-doped CdO films

    SciTech Connect

    Dakhel, A.A.; Hamad, H.

    2013-12-15

    Cadmium oxide thin films doped with different amounts of chromium and annealed in hydrogen atmosphere have been grown on glass substrates by means of physical vapour deposition (PVD) method. The structural, electrical, and optical properties of the prepared Cr-doped CdO (CdO:Cr–H) films were systematically studied. The structural investigations show that the incorporated Cr ions mainly occupied locations in interstitial positions of CdO lattice. The bandgap engineer by Cr incorporation and hydrogenation were studied. The variations of the electrical parameters of CdO:Cr–H films with Cr incorporation and hydrogenation were investigated. It was established that among the investigated samples, the largest mobility and conductivity were measured with 1.5%:Cr–H film. Therefore, hydrogenated CdO:Cr films can be effectively used in different applications of near infrared-transparent-conducting-oxide (NIR-TCO). - Graphical abstract: Optoelectronic properties of synthesised chromium-doped CdO thin films. It was established that the largest mobility (53.4 cm{sup 2}/V.s) and conductivity (2136.8 S/cm) were measured in 1.5%:Cr–H doped CdO film. Therefore, such films can be effectively used in near infrared-transparent-conducting-oxide (NIR-TCO). - Highlights: • The properties of CdO films annealed in H{sub 2} gas were systematically studied. • Cr{sup 3+} ions most likely occupied interstitial locations in CdO lattice and as donors. • Improvement of conductivity parameters with Cr doping and H annealing. • Bandgap narrowing observed with Cd-doping.

  4. Chromium Therapy for Insulin Resistance Associated with HIV-Disease

    PubMed Central

    Stein, Seth A; Mc Nurlan, Margaret; Phillips, Brett T; Messina, Catherine; Mynarcik, Dennis; Gelato, Marie

    2014-01-01

    Objective With the advent of highly active anti-retroviral therapy, HIV disease has become a chronic condition, but with a number of metabolic complications including insulin resistance and diabetes mellitus, dyslipidemia and hypertension and an increased incidence of atherosclerosis. The aim of the current study was to test the safety and efficacy of chromium picolinate for HIV- associated insulin resistance. Materials/Methods The study was a randomized, double-blind, placebo-controlled trial with subjects receiving 500μg of chromium picolinate or placebo twice daily for two months. HIV- infected subjects were selected based on a fasting concentration of plasma glucose greater than 5.5mmol/L or a plasma glucose concentration of greater than 7.7mmol/L (but less than 11mmol/L) 2h after oral ingestion of 75g of glucose. Insulin sensitivity was assessed with a hyper-insulinemic-euglycemic clamp and glucose tolerance was assessed with the oral glucose tolerance test. Subjects were monitored closely for alterations in viral load, CD4+ cells, hemoglobin and hematocrit, kidney and liver function, and fasting lipid profiles. Results Forty-three subjects were enrolled and 39 completed the protocol (20 in the chromium-supplemented and 19 in the placebo arm). Following chromium-supplementation, there were no significant changes in either insulin sensitivity or glucose tolerance. There was a significant improvement in serum HDL cholesterol concentration in the group supplemented with chromium. Conclusions Chromium picolinate supplementation at this level was well-tolerated, but overall was not an effective therapy for insulin resistance in these HIV-infected subjects. PMID:25346863

  5. Toxic effects of chromium on tannery workers at Sialkot (Pakistan).

    PubMed

    Khan, Dilshad Ahmed; Mushtaq, Shahida; Khan, Farooq Ahmad; Khan, Muhammad Qaiser Alam

    2013-03-01

    Chromium is widely used in the leather industry, and tannery workers are under constant threat of adverse health effects due to its excessive exposure. Our objective was to find out the toxic effects of chromium on tannery workers at Sialkot, Pakistan. A total of 240 males consisting of 120 workers from tanneries at Sialkot and equal number of controls were included. Blood complete counts, high-sensitive C-reactive protein, malondialdehyde and routine biochemical tests were carried out by routine procedures. Chromium levels in blood (BCr) and urine were analyzed using graphite furnace atomic absorption spectrophotometer Perkin Elmer analyst-200. Results revealed that all the workers were male with average age of 33 years and 15 (13%) had skin rashes, 14 (12%) had chronic bronchitis, 10 (8%) had gastritis and 4 (3%) conjunctivitis. The tannery workers had significantly raised median (interquartile range) of BCr 569 (377-726) nmol/L as compared to 318 (245-397) nmol/L in the control (p < 0.001). Sixty-five (54%) workers had BCr levels above the upper limit set by Agency for Toxic Substance and Drug Registry. The urinary chromium excretion was significantly high in workers 131 (46-312) nmol/L as compared to 13 (3-26) nmol/L in controls (p < 0.01). The workers had hematological, hepatic and renal function impairment because of oxidative stress on body systems. It is concluded that about half of the workers had excessive exposure to chromium in the tanneries at Sialkot. They had significantly raised chromium levels in their biological fluids and adverse health effects due to enhanced oxidative stress and inflammatory changes. PMID:22258629

  6. The enzymatic hydrolysis of leather waste with chromium recycling

    SciTech Connect

    Kim, M.S.; Clesceri, L.S.

    1996-11-01

    The work of Taylor et al. (1990) has shown the potential for alkaline hydrolase enzymes for the solubilization of waste from the tanning industry. The authors have carried this work further to examine the mechanism whereby enzymes release chromium from leather waste. An alkaline digest of waste leather was used in this work. Treatment with strong alkali produced a thick slurry that contained 7,000 ppm chromium. The objective of this work is to optimize a closed cycle system for the recycling of chromium salts for tanning as well as a chrome-free product for use as a fertilizer. The authors are able to track the progress of the leather protein hydrolysis with polyacrylamide gel electrophoresis (PAGE). By means of PAGE, it is possible to determine the relationship between chromium release and the extent of protein hydrolysis. Rate constant for hydrolysis and chromium release have been developed for various hydrolysis conditions. Chemical precipitation of chromium from the hydrolysate results in a purified product for reuse in tanning. The chrome-free hydrolysate can be applied as a fertilizer either directly or as a dried product. There are more than 56,000 metric tons of tannery waste produced annually in the US. The majority of the organic solids can be converted into high quality fertilizers. Since the nitrogen is organic rather than inorganic, release is at a controlled rate since the microbody in the soil must make the nitrogen available for plant growth. Leather manufacturing is a world-wide industry. Conversion of leather waste to fertilizers can improve global productivity as well as solve a waste problem.

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

    PubMed

    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

  8. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 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....

  9. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 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....

  10. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 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....

  11. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    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....

  12. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 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....

  13. 77 FR 61431 - Hexavalent Chromium Standards; Extension of the Office of Management and Budget's (OMB) Approval...

    Federal Register 2010, 2011, 2012, 2013, 2014

    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...

  14. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  15. 40 CFR 424.70 - Applicability; description of the electrolytic chromium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... electrolytic chromium subcategory. 424.70 Section 424.70 Protection of Environment ENVIRONMENTAL PROTECTION... Electrolytic Chromium Subcategory § 424.70 Applicability; description of the electrolytic chromium subcategory. The provisions of this subpart are applicable to discharges resulting from the manufacture of...

  16. 40 CFR 424.70 - Applicability; description of the electrolytic chromium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... electrolytic chromium subcategory. 424.70 Section 424.70 Protection of Environment ENVIRONMENTAL PROTECTION... Electrolytic Chromium Subcategory § 424.70 Applicability; description of the electrolytic chromium subcategory. The provisions of this subpart are applicable to discharges resulting from the manufacture of...

  17. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  18. Chromium supplementation alters the glucose and lipid metabolism of feedlot cattle during the receiving period

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crossbreed steers (n = 20; 235 ± 4 kg) were fed 53 d during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brand Chromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0 (C...

  19. 40 CFR 424.70 - Applicability; description of the electrolytic chromium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... electrolytic chromium subcategory. 424.70 Section 424.70 Protection of Environment ENVIRONMENTAL PROTECTION... Electrolytic Chromium Subcategory § 424.70 Applicability; description of the electrolytic chromium subcategory. The provisions of this subpart are applicable to discharges resulting from the manufacture of...

  20. Enhancement of the acute phase response to lipopolysaccharide (LPS) challenge in steers supplemented with chromium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study examined the effect of chromium supplementation on the response of steers to an LPS challenge. Twenty steers received a premix that added 0 (control) or 0.2 mg/kg of chromium (KemTRACE®brandChromiumProprionate 0.04%, Kemin Industries) to the total diet on a dry matter basis for 55 d. Steer...

  1. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  2. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  3. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  4. Chromium supplementation alters both glucose and lipid metabolism in feedlot cattle during the receiving period

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crossbred steers (n = 20; 235 +/- 4 kg) were fed 53 days during a receiving period to determine if supplementing chromium (Cr; KemTRACE®brandChromium Propionate 0.04%, Kemin Industries) would alter the glucose or lipid metabolism of newly received cattle. Chromium premixes were supplemented to add 0...

  5. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  6. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject...

  7. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  8. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  9. 40 CFR 424.70 - Applicability; description of the electrolytic chromium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... electrolytic chromium subcategory. 424.70 Section 424.70 Protection of Environment ENVIRONMENTAL PROTECTION... Electrolytic Chromium Subcategory § 424.70 Applicability; description of the electrolytic chromium subcategory. The provisions of this subpart are applicable to discharges resulting from the manufacture of...

  10. 40 CFR 424.70 - Applicability; description of the electrolytic chromium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... electrolytic chromium subcategory. 424.70 Section 424.70 Protection of Environment ENVIRONMENTAL PROTECTION... Electrolytic Chromium Subcategory § 424.70 Applicability; description of the electrolytic chromium subcategory. The provisions of this subpart are applicable to discharges resulting from the manufacture of...

  11. 40 CFR 721.2097 - Azo chromium complex dyestuff preparation (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Azo chromium complex dyestuff... New Uses for Specific Chemical Substances § 721.2097 Azo chromium complex dyestuff preparation... substance identified generically as an azo chromium complex dyestuff preparation (PMN P-95-240) is...

  12. 48 CFR 252.223-7008 - Prohibition of Hexava-lent Chromium.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexava-lent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (JUN 2013) (a) Definitions. As used...

  13. The Effect of Manganese Additions on the Reactive Evaporation of Chromium in Ni-Cr Alloys

    SciTech Connect

    Holcomb, Gordon R.; Alman, David E.

    2004-10-20

    Chromium is used as an alloy addition in stainless steels and nickel-chromium alloys to form protective chromium oxide scales. Chromium oxide undergoes reactive evaporation in high temperature exposures in the presence of oxygen and/or water vapor. The deposition of gaseous chromium species onto solid oxide fuel cell electrodes can reduce the efficiency of the fuel cell. Manganese additions to the alloy can reduce the activity of chromium in the oxide, either from solid solution replacement of chromium with manganese (at low levels of manganese) or from the formation of manganese-chromium spinels (at high levels of manganese). This reduction in chromium activity leads to a predicted reduction in chromium evaporation by as much as a factor of 35 at 800 C and 55 at 700 C. The results of evaporation loss measurements on nickel-chromium-manganese alloys are compared with the predicted reduction. Quantifying the effects of manganese additions on chromium evaporation should aid alloy development of metallic interconnects and balance-of-plant alloys.

  14. Chromium does not belong in the diabetes treatment arsenal: Current evidence and future perspectives.

    PubMed

    Landman, Gijs Wd; Bilo, Henk Jg; Houweling, Sebastiaan T; Kleefstra, Nanne

    2014-04-15

    Chromium is considered to have positive effects on insulin sensitivity and is marketed as an adjunctive therapy for inducing glucose tolerance in cases of insulin resistance ("the glucose tolerance factor"). Case reports on patients who received prolonged parenteral nutrition indeed showed that the absence of trivalent chromium caused insulin resistance and diabetes. However, whether patients with type 2 diabetes can develop a clinically relevant chromium deficiency is unclear. This review summarizes the available evidence regarding the potential effectiveness of chromium supplementation on glycemic control (Hemoglobin A1c levels) in patients with type 2 diabetes. No studies investigating the long-term safety of chromium in humans were found. All clinical trials that have been performed had a relative short follow-up period. None of the trials investigated whether the patients had risk factors for chromium deficiency. The evidence from randomized trials in patients with type 2 diabetes demonstrated that chromium supplementation does not effectively improve glycemic control. The meta-analyses showed that chromium supplementation did not improve fasting plasma glucose levels. Moreover, there were no clinically relevant chromium effects on body weight in individuals with or without diabetes. Future studies should focus on reliable methods to estimate chromium status to identify patients at risk for pathological alterations in their metabolism associated with chromium deficiency. Given the present data, there is no evidence that supports advising patients with type 2 diabetes to take chromium supplements. PMID:24748929

  15. The effects of chromium and its compounds released to the Canadian environment: An ecological assessment

    SciTech Connect

    Breton, R.L.; Doyle, P.; Nriagu, J.

    1994-12-31

    Chromium is a naturally occurring element that is present principally in the trivalent or hexavalent forms in small amounts throughout the Canadian environment. Chromium ore is not currently mined in Canada; however, approximately 74,000 tonnes of various chromium-containing materials were imported into Canada in 1991. Both trivalent and hexavalent forms of chromium are released into the Canadian environment. Typical concentrations of dissolved hexavalent chromium in Lake Ontario and Lake Erie, and in rivers and streams in parts of British Columbia, Alberta, Ontario, and Quebec are 5 to 15 times greater than the effects threshold estimated for the most sensitive aquatic species. Average concentrations of chromium in soils contaminated with dissolved hexavalent chromium at several Canadian wood preservation facilities are 19 to 1,700 times greater than levels of hexavalent chromium reported to harm some plants and microbial communities. Based on these considerations, it is concluded that dissolved and soluble forms of hexavalent chromium are likely entering the environment in concentrations that are having harmful effects on sensitive species in the Canadian environment. Although trivalent chromium is likely the dominant chromium species in most sediments, soils, and biological tissues, there is insufficient information to determine whether organisms are adversely affected by exposure to trivalent chromium in Canada.

  16. Recovery of potential energy and chromium values from leather tannery wastes

    SciTech Connect

    Muralidhara, H.

    1982-06-01

    A method of recovering chromium values and potential energy from liquid and solid leather tannery wastes comprising pyrolyzing the tannery wastes to produce a burnable fuel product comprising gases and liquids and a substantially solid chromium-containing residue, recovering chromium compounds from the solid residue and using the fuel to supply energy for the system.

  17. VENTURI/VORTEX SCRUBBER AND PUSHED LIQUID RECIRCULATION SYSTEM FOR CONTROLLING/RECYCLING CHROMIUM ELECTROPLATING EMISSIONS

    EPA Science Inventory

    This Environmental Security Technology Certification Program (ESTCP) project demonstrated control technology for chromium air emissions. Chromium electroplating is an essential process for the U.S. Department of Defense (DoD) because chromium provides a surface coating with a com...

  18. Effective gain measurements in chromium-doped forsterite

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Seas, A.; Alfano, R. R.

    1991-01-01

    Effective gain cross section in tetravalent chromium-doped forsterite laser crystal was measured over the 1180-1330 nm spectral range. The experiment was performed using two collinear laser beams in a pump-and-probe arrangement. The peak-gain cross section from this measurement is estimated to be 1.9 x 10 to the -19th sq cm at 1215 nm, which is comparable to the value of about 2 x 10 to the -19th sq cm predicted by fluorescence linewidth and lifetime measurements. These results indicate that excited-state absorption is not a major loss mechanism in tetravalent chromium-doped forsterite.

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

    PubMed

    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. PMID:18725745

  20. Hot corrosion resistance of nickel-chromium-aluminum alloys

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Barrett, C. A.

    1977-01-01

    The hot corrosion resistance of nickel-chromium-aluminum alloy was examined by cyclically oxidizing sodium sulfate coated specimens in still air at 900, 1000 and 1100 C. The compositions tested were within the ternary region: Ni; Ni-50 at.% Cr; and Ni-50 at.% Al. At each temperature the corrosion data were statistically fitted to a third order regression equation as a function of chromium and aluminum contents. Corrosion isopleths were prepared from these equations. Compositional regions with the best hot corrosion resistance were identified.