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Sample records for chromium 47

  1. Chromium

    MedlinePlus

    ... Mertz W. Chromium in human nutrition: a review. J Nutr 1993;123:626-33. Mertz W. Interaction ... metabolism by chromium(III) in malnourished infants. Am J Clin Nutr 1968;21:203-11. Jeejeebhoy KN, ...

  2. 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 ...

  3. Chromium - blood test

    MedlinePlus

    Serum chromium ... This test may be done to diagnose chromium poisoning or deficiency. ... Serum chromium level normally is less than or equal to 1.4 micrograms/milliliter (mcg/mL). Normal value ranges ...

  4. Chromium in diet

    MedlinePlus

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

  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. Chromium carcinogenicity: California strategies.

    PubMed

    Alexeeff, G V; Satin, K; Painter, P; Zeise, L; Popejoy, C; Murchison, G

    1989-10-01

    Hexavalent chromium was identified by California as a toxic air contaminant (TAC) in January 1986. The California Department of Health Services (CDHS) concurred with the findings of the International Agency for Research on Cancer that there is sufficient evidence to demonstrate the carcinogenicity of chromium in both animals and humans. CDHS did not find any compelling evidence demonstrating the existence of a threshold with respect to chromium carcinogenesis. Experimental data was judged inadequate to assess potential human reproductive risks from ambient exposures. Other health effects were not expected to occur at ambient levels. The theoretically increased lifetime carcinogenic risk from a continuous lifetime exposure to hexavalent chromium fell within the range 12-146 cancer cases per nanogram hexavalent chromium per cubic meter of air per million people exposed, depending on the potency estimate used. The primary sources found to contribute significantly to the risk of exposure were chrome platers, chromic acid anodizing facilities and cooling towers utilizing hexavalent chromium as a corrosion inhibitor. Evaluation of genotoxicity data, animal studies and epidemiological studies indicates that further consideration should be given to the potential carcinogenicity of hexavalent chromium via the oral route.

  7. The carcinogenicity of chromium

    PubMed Central

    Norseth, Tor

    1981-01-01

    The carcinogenicity of chromium compounds is reviewed with specific attention to the gaps in knowledge for risk estimation and research needs. The most important problems at present are whether trivalent chromium compounds cause cancer, and whether there is a difference in cancer causing effects between the soluble and the slightly soluble hexavalent compounds in the practical exposure situation. Dose estimates for risk estimation based on epidemiological investigations are also lacking. Present evidence indicates that the trivalent chromium compounds do not cause cancer although high concentrations in some in vitro systems have shown genetic toxicity. Hexavalent chromium compounds cause cancer in humans, in experimental animals and exert genetic toxicity in bacteria and in mammalian cells in vitro. Epidemiological evidence and animal experiments indicate that the slightly soluble hexavalent salts are the most potent carcinogens, but proper identification and characterization of exposure patterns in epidemiological work are lacking. Workers also tend to have mixed exposures. Soluble and slightly soluble salts are equally potent genotoxic agents in vitro. Further work for establishing dose estimates for risk evaluation in epidemiological work is important. In vitro systems should be applied for further identification of the mechanism of the carcinogenic effects, and animal experiments are urgent for comparison of the carcinogenic potency of the different hexavalent salts. Hexavalent chromium salts must be regarded as established carcinogens, and proper action should be taken in all industries with regard to such exposure. At present the carcinogenic risk to the general population caused by chromium compounds seems to be negligible, chromium in cigarettes, however, is an uncertainty in this respect. The amount of chromium and the type of chromium compounds inhaled from cigarettes is not known. PMID:7023928

  8. 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.

  9. 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.

  10. 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

  11. Sex hormones and semen quality in welders exposed to hexavalent chromium.

    PubMed

    Bonde, J P; Ernst, E

    1992-07-01

    Recent experimental studies in rodents document the spermatotoxic effects of water-soluble hexavalent chromium. Welders comprise, worldwide, a major occupational group with acknowledged exposure to chromium. This study examines the relationship between semen quality and chromium in the urine and blood of a population of 30 tungsten inert gas (TIG) stainless steel welders, 30 mild steel welders and 47 non-welding workers. Each subject provided two to three semen samples. The chromium concentration ranged from 0.17 to 4.74 nmol mmol1 creatinine (median 1.08) in post-shift spot urine and from 6.0 to 46.4 nmol l-1 in blood. None of several semen parameters deteriorated with increasing level of internal exposure to chromium. Low-level exposure to hexavalent chromium associated with TIG stainless steel and mild steel welding do not appear to be a major hazard for human spermatogenesis. PMID:1354973

  12. 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

  13. 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.

  14. 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...

  15. 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.

  16. Intracellular chromium reduction.

    PubMed

    Arslan, P; Beltrame, M; Tomasi, A

    1987-10-22

    Two steps are involved in the uptake of Cr(VI): (1) the diffusion of the anion CrO4(2-) through a facilitated transport system, presumably the non-specific anion carrier and (2) the intracellular reduction of Cr(VI) to Cr(III). The intracellular reduction of Cr(VI), keeping the cytoplasmic concentration of Cr(VI) low, facilitates accumulation of chromate from extracellular medium into the cell. In the present paper, a direct demonstration of intracellular chromium reduction is provided by means of electron paramagnetic (spin) resonance (EPR) spectroscopy. Incubation of metabolically active rat thymocytes with chromate originates a signal which can be attributed to a paramagnetic species of chromium, Cr(V) or Cr(III). The EPR signal is originated by intracellular reduction of chromium since: (1) it is observed only when cells are incubated with chromate, (2) it is present even after extensive washings of the cells in a chromium-free medium; (3) it is abolished when cells are incubated with drugs able to reduce the glutathione pool, i.e., diethylmaleate or phorone; and (4) it is abolished when cells are incubated in the presence of a specific inhibitor of the anion carrier, 4-acetamido-4'-isothiocyanatostilbene-2-2'-disulfonic acid. PMID:2820507

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. Chromium toxicity in plants.

    PubMed

    Shanker, Arun K; Cervantes, Carlos; Loza-Tavera, Herminia; Avudainayagam, S

    2005-07-01

    Due to its wide industrial use, chromium is considered a serious environmental pollutant. Contamination of soil and water by chromium (Cr) is of recent concern. Toxicity of Cr to plants depends on its valence state: Cr(VI) is highly toxic and mobile whereas Cr(III) is less toxic. Since plants lack a specific transport system for Cr, it is taken up by carriers of essential ions such as sulfate or iron. Toxic effects of Cr on plant growth and development include alterations in the germination process as well as in the growth of roots, stems and leaves, which may affect total dry matter production and yield. Cr also causes deleterious effects on plant physiological processes such as photosynthesis, water relations and mineral nutrition. Metabolic alterations by Cr exposure have also been described in plants either by a direct effect on enzymes or other metabolites or by its ability to generate reactive oxygen species which may cause oxidative stress. The potential of plants with the capacity to accumulate or to stabilize Cr compounds for bioremediation of Cr contamination has gained interest in recent years. PMID:15878200

  4. 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.

  5. 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

  6. 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.

  7. Chromium reduction in Pseudomonas putida.

    PubMed Central

    Ishibashi, Y; Cervantes, C; Silver, S

    1990-01-01

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

  8. Chromium Stable Isotope Fractionation During Abiotic Reduction of Hexavalent Chromium

    NASA Astrophysics Data System (ADS)

    Kitchen, J. W.; Johnson, T. M.; Bullen, T. D.

    2004-12-01

    Chromium, a common surface water and ground water contaminant, occurs as Cr(VI), which is soluble and toxic, and Cr(III), which is insoluble and less toxic. Reduction of Cr(VI) to Cr(III) is often the most important reaction controlling attenuation of Cr plumes, and Cr stable isotope (53Cr/52Cr) measurements show great promise as indicators of this reaction. Cr(VI) reduction involves a kinetic isotope effect; lighter isotopes react at greater rates and heavier isotopes become increasingly enriched in the remaining Cr(VI) with increasing extent of reduction. If the size of this effect can be constrained well, then precise estimates of reduction are possible. Cr(VI) reduction can be mediated by microbes, or may occur abiotically in the presence of Fe(II) and a variety of organic compounds. A recent study of bacterial reduction of Cr(VI) under low electron donor conditions yielded a Cr isotope fractionation factor of 1000lnα = 4.1 ± 0.2. A previous study of abiotic reduction indicated a fractionation factor of 1000lnα = 3.4 ± 0.2, but this work was limited to 3 experiments. The present study provides a more detailed look at Cr isotope fractionation induced by abiotic Cr(VI) reduction by: Fe(II); mandelic acid with alumina and goethite catalysts; and humic substances. Reduction occurred slowly, over days or weeks. The fractionation factor for the organic reductants (all at pH=4), including two surface-catalyzed mandelic acid reactions, two fulvic reactions, and one humic reaction,- was 1000lnα = 3.0 ± 0.4, with no statistically significant differences between experiments. The fractionation factors for the Fe(II) experiments were 4.7 ± 0.3, 3.7 ± 0.2, and 2.9 ± 0.2 for pH = 4, 5, and 6, respectively. Further work is necessary to better constrain this pH dependence and to determine if it occurs with the organic reductants. The overall variability in the size of the Cr isotope fractionation during Cr(VI) reduction translates into a moderate level of uncertainty

  9. 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.

  10. Galvanic cells including cobalt-chromium alloys.

    PubMed

    Gjerdet, N R

    1980-01-01

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

  11. Study on anaerobic treatment of wastewater containing hexavalent chromium.

    PubMed

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-06-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and COD(Cr) of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms.

  12. Study on anaerobic treatment of wastewater containing hexavalent chromium*

    PubMed Central

    Xu, Yan-bin; Xiao, Hua-hua; Sun, Shui-yu

    2005-01-01

    A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentrations ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear superiority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microorganisms. PMID:15909347

  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. Antiferromagnetism in chromium

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    I present two experimental studies of the spin density wave antiferromagnetic order in elemental Chromium. The first addresses the response of the magnetic ground state to applied pressure. The spin and charge order parameters are probed at high pressure and low temperature in a diamond anvil cell using monochromatic X-ray diffraction. We find that the magnetism is suppressed exponentially with pressure, providing a canonical example of a weak-coupling, mean-field ground state, before terminating at a quantum phase transition. We confirm the harmonic relationship between the spin and charge degrees of freedom in the low temperature regime, and we identify the microscopic coupling between pressure and magnetism. The discovery of the long-sought-after quantum critical regime sets the stage for a complete study of antiferromagnetic quantum criticality in this clean model system. The second study addresses the thermodynamics and transport properties of antiferromagnetic domain structure. We find a robust thermal hysteresis in the longitudinal and Hall resistivities of sub-mm bulk Cr samples. The temperature limits of the hysteresis are correlated with domain wall fluctuations and freezing. The persistent sign of the hysteresis and the macroscopic return point memory warrant a new understanding of domain wall energetics. By combining electrical transport and X-ray microdiffraction measurements we are able to pinpoint the effects of antiferromagnetic domain walls on electron transport.

  15. 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.

  16. Toxic effects of chromium and its compounds.

    PubMed

    Baruthio, F

    1992-01-01

    Chromium was discovered in 1797 by Vauquelin. Numerous industrial applications raised chromium to a very important economic element. At the same time, with the development of its uses, the adverse effects of chromium compounds in human health were being defined. Trivalent chromium is an essential trace element in humans and in animals. Chromium as pure metal has no adverse effect. Little toxic effect is attributed to trivalent chromium when present in very large quantities. Both acute and chronic toxicity of chromium are mainly caused by hexavalent compounds. The most important toxic effects, after contact, inhalation, or ingestion of hexavalent chromium compounds are the following: dermatitis, allergic and eczematous skin reactions, skin and mucous membrane ulcerations, perforation of the nasal septum, allergic asthmatic reactions, bronchial carcinomas, gastro-enteritis, hepatocellular deficiency, and renal oligo anuric deficiency. Prevention of occupational risks, biological monitoring of workers, and treatment of poisoning are also reported.

  17. 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.

  18. 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.

  19. Environmental biochemistry of chromium.

    PubMed

    Losi, M E; Amrhein, C; Frankenberger, W T

    1994-01-01

    Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming

  20. 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

  1. 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...

  2. 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

  3. 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.

  4. 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...

  5. Evaluation of a chemical etching solution for nickel-chromium-beryllium and chromium-cobalt alloys.

    PubMed

    Ferrari, M; Cagidiaco, M C; Borracchini, A; Bertelli, E

    1989-11-01

    Two chemical etching solutions were capable of providing micromechanical retention in two nickel-chromium-beryllium alloys and in a chromium-cobalt alloy. A resin matrix was used to verify the quality of etching on the metal surfaces. The chemical etching solutions created high microretentive surfaces in nickel-chromium-beryllium alloy but the chromium-cobalt alloy surfaces after etching were less retentive. Improved chemical etching technique should encourage expanded use of the resin-bonded retainers.

  6. 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.

  7. 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 ...

  8. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... efficient in removing mono-dispersed particles of 0.3 micrometers in diameter or larger. Historical... means that disperses chromium (VI) into the air or onto an employee's body. (iii) The employer shall... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs,...

  9. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... efficient in removing mono-dispersed particles of 0.3 micrometers in diameter or larger. Historical... means that disperses chromium (VI) into the air or onto an employee's body. (iii) The employer shall... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs,...

  10. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... efficient in removing mono-dispersed particles of 0.3 micrometers in diameter or larger. Historical... means that disperses chromium (VI) into the air or onto an employee's body. (iii) The employer shall... change rooms in conformance with 29 CFR 1910.141. Where skin contact with chromium (VI) occurs,...

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

    PubMed

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

    2014-10-01

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

  12. Urinary chromium as an indicator of the exposure of welders to chromium.

    PubMed

    Tola, S; Kilpiö, J; Virtamo, M; Haapa, K

    1977-12-01

    Five welders working with high alloy Cr-Ni steel and one working with mild steel were followed during one work week. The chromium concentration in air was measured concomitantly with urinary chromium determinations. The water-soluble chromium concentrations in air exceeded 0.05 mg/m3 during welding with coated electrodes, but metal inert-gas (MIG) welding produced much lower concentrations. The proportion of water-soluble hexavalent chromium in the air was usually more than 50% of the total chromium concentration during welding with coated electrodes, whereas less than 10% of the chromium produced during MIG welding was in a water-soluble. Since water-soluble chromium (hexavalent) is the more important biologically, the determination of both water-soluble and water-insoluble chromium concentrations is emphasized instead of the measurement of the total concentration. The urinary chromium concentration proved to be a good indicator of short-term exposure to water-soluble chromium when exposure was above the current threshold limit value of 0.05 mg/m3, concentrations of more than 30 microgram/g of creatinine representing an exposure level higher than the threshold limit value.

  13. 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.

  14. 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

  15. [Examination of nickel and chromium contents in selected herbs, herbal fruit teas and their infusions].

    PubMed

    Błoniarz, Jadwiga; Zareba, Stanisław; Rahnama, Mansur

    2004-01-01

    The aim of this study was to determine the contents of nickel and chromium (the trace elements that are necessary for the human organism only in specified amounts) in selected dry herbs, herbal-fruit teas and their water extracts. This examination was expected to answer the question whether infusions or decoctions may constitute the additional source of these elements, or whether the amounts of nickel and chromium included in them may be dangerous for the human organism. The samples were dry mineralized at the temperature of 450 degrees C. Atomic absorption spectrometry (AAS) was performed using SOLAAR M5 appliance produced by a US-based Thermo Elemental company; nickel contents were determined from the organic phase, and chromium directly from the mineralisate. Nickel contents ranged on average from 0.56 microg/g to 2.68 microg/g in herbs and from 0.99 microg/g to 1.70 microg/g in herbal fruit teas. On average 40.0% to 82.5% of the amount present in dry, raw material passed into the infusions. The determined amounts of chromium ranged from 0.57 microg/g to 1.36 microg/g in herbs, and from 0.47 microg/g to 1.17 microg/g in herbal fruit teas (average values). The maximum extraction of this element into the infusion or decoction equaled 85.0%. The contents of nickel and chromium in the examined dry herb samples were comparable to results obtained by authors of the other papers. Infusions or decoctions of the examined herbs and herbal fruit teas contain the amounts of these elements that do not harm health and may constitute an additional source of nickel and chromium for the human organism. PMID:15682946

  16. 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

  17. 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)

  18. 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.

  19. 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.

  20. 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.

  1. Outline of occupational chromium poisoning in China.

    PubMed

    Yang, Yuan; Liu, Hong; Xiang, Xian-hong; Liu, Fu-you

    2013-06-01

    The present study analyzed the feature of occupational chromium poisoning in China since the 1980s. The collected data were acquired from 18 previous surveys of chromium poisoning in 14 cities of China. The method of risk assessment was applied to calculate the relative risk and 95% CI, p < 0.05 was considered as a significant risk. The results showed that nasal disease was the most common sign of occupational chromium poisoning, and the prevalence rate of nasal disease was 17.83% in total population of 6,998. Further, the risk analysis showed that occupational chromium poisoning led to an increased risk of lung or liver cancer in male workers due to the definite carcinogenicity of hexavalent chromium. Significantly, an increased risk of spontaneous or threatened abortion was also found in female workers. In conclusion, these studies suggest that early detection of impaired reproductive function or impaired lung or liver function in female or male workers is essential for controlling occupational chromium poisoning in China. PMID:23604023

  2. 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.

  3. The measurement of volatile chromium in biological materials.

    PubMed

    Shapcott, D; Khoury, K; Demers, P P; Vobecky, J; Vobecky, J

    1977-10-01

    Chromium is an essential trace element in mammals since dietary chromium deficiency results in glucose intolerance due to decreased sensitivity to insulin. In humans, both adults and children with glucose intolerance have been improved by treatment with chromium. Furthermore, chromium deficiency has been implicated as a causative factor in hypercholesterolemia and atherosclerosis. However, little is known of the metabolism of chromium in humans, primarily because of analytical difficulties. The biologically active form of chromium is the "glucose tolerance factor" (GTF) which is a co-ordination complex of trivalent chromium with nicotinic acid and certain amino acids. At physiological pH, ionic chromium as a simple inorganic salt is insoluble in water, but trivalent chromium forms stable complexes with ascorbic acid, amino acids and other substances present in blood and tissue. Chromium is present in serum, bound to protein and also as dialysable or ultrafiltrable chromium (free chromium). The free chromium includes G.T.F. and other coordination complexes and represents the metabolically active form of the element; the ratio free/protein bound chromium in serum varies within the individual according to the diet and the metabolic state. PMID:912855

  4. 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

  5. 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.

  6. 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.

  7. Oral Chromium Exposure and Toxicity

    PubMed Central

    Sun, Hong; Brocato, Jason

    2015-01-01

    Hexavalent chromium [Cr(VI)] is a known carcinogen when inhaled. However, inhalational exposure to Cr(VI) affects only a small portion of the population, mainly by occupational exposures. In contrast, oral exposure to Cr(VI) is widespread and affects many people throughout the globe. In 2008, the National Toxicology Program (NTP) released a 2-year study demonstrating that ingested Cr(VI) was carcinogenic in rats and mice. The effects of Cr(VI) oral exposure is mitigated by reduction in the gut, however a portion evades the reductive detoxification and reaches target tissues. Once Cr(VI) enters the cell, it ultimately gets reduced to Cr(III), which mediates its toxicity via induction of oxidative stress during the reduction while Cr intermediates react with protein and DNA. Cr(III) can form adducts with DNA that may lead to mutations. This review will discuss the potential adverse effects of oral exposure to Cr(VI) by presenting up-to-date human and animal studies, examining the underlying mechanisms that mediate Cr(VI) toxicity, as well as highlighting opportunities for future research. PMID:26231506

  8. 7 CFR 47.47 - Additional definitions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Additional definitions. 47.47 Section 47.47 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE MARKETING OF PERISHABLE AGRICULTURAL...

  9. 7 CFR 47.47 - Additional definitions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Additional definitions. 47.47 Section 47.47 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE MARKETING OF PERISHABLE AGRICULTURAL...

  10. Oral bioavailability of chromium from a specific site

    SciTech Connect

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

    1991-05-01

    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 {mu}g/kg for 14 days as chromium-contaminated soil, as CaCrO{sub 4}, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hours 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. 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 and the chromium in feces and urine was determined on days 1, 2, 7, and 8. 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 CaCrO{sub 4}. The total recovery of chromium in any of the 2-day periods was less than 50% of the chromium administered during that period.

  11. 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.

  12. [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.

  13. 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.

  14. Chromium Stable Isotope Fractionation During Bacterial Reduction of Hexavalent Chromium

    NASA Astrophysics Data System (ADS)

    Sikora, E. R.; Johnson, T. M.; Bullen, T. D.

    2004-05-01

    Chromium is a common contaminant in surface water and ground water. It is redox-active, occurring as Cr(VI), which is soluble and toxic, and Cr(III), which is insoluble and less toxic. Reduction of Cr(VI) to Cr(III) is often the most important reaction controlling attenuation of Cr plumes, and Cr stable isotope (53Cr/52Cr) measurements show great promise as indicators of this reaction. Previous results indicate Cr(VI) reduction involves a kinetic isotope effect; lighter isotopes reduce at greater rates and heavier isotopes become increasingly enriched in the remaining Cr(VI) with increasing extent of reduction. If the size of this effect can be constrained well, then precise estimates of reduction are possible. The few experiments completed to date involved abiotic Cr(VI) reduction and indicated a fractionation factor of 1000lnα = 3.4 ± 0.2. Abiotic reduction by Fe(II), organic compounds, and other agents is possible in natural settings, but some bacteria are known to reduce Cr(VI) as well. This study determined Cr fractionation factors for anaerobic reduction by Shewanella Oneidensis MR-1. Previous studies of kinetic isotope effects during reduction of sulfate, selenate, and nitrate reveal that fractionation factors depend on the metabolic states of the bacteria. Those in rich media usually induce less fractionation than those in leaner conditions. Concentrations of electron donors and other nutrients are usually small in natural settings, so we suspended MR-1 cells in buffer solutions with small concentrations of lactate or formate, and Cr(VI). Reduction occurred slowly, over days or weeks. The calculated value of 1000lnα was 4.1 ± 0.2 for several experiments with a range of donor concentrations between 3.6 and 100 micromolar. This suggests that under the lean conditions found in most aquifers, the kinetic isotope effect induced by bacterial reduction is roughly equal to that induced by abiotic reduction, and that the Cr isotope method will be useful for

  15. 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.

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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.

  2. 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....

  3. 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... 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....

  4. 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... 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. 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

  6. 21 CFR 73.2327 - 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. 73.2327 Section 73.2327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens shall conform in identify and specifications to...

  7. 21 CFR 73.2327 - 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. 73.2327 Section 73.2327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens shall conform in identify and specifications to...

  8. 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...

  9. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium hydroxide green. 73.2326 Section 73.2326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and specifications.The color additive chromium hydroxide green shall conform in identity and specifications to...

  10. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  11. 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....

  12. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium hydroxide green. 73.2326 Section 73.2326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and specifications.The color additive chromium hydroxide green shall conform in identity and specifications to...

  13. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  14. 21 CFR 73.1327 - 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. 73.1327 Section 73.1327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color...

  15. 21 CFR 73.1327 - 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. 73.1327 Section 73.1327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color...

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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).

  1. 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

  2. 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.

  3. Purification and chromium-excretory function of low-molecular-weight, chromium-binding substances from dog liver.

    PubMed

    Wada, O; Wu, G Y; Yamamoto, A; Manabe, S; Ono, T

    1983-10-01

    From liver of dogs injected iv with potassium dichromate (38 mg/kg body wt), a low-molecular-weight chromium-binding substance (LMCr) was purified into two subfractions, LMCr I and LMCr II, which differ in physical and chemical properties. LMCr I was identified to be an anionic, organic chromium compound with a molecular weight of 1500. It contained glutamic acid, glycine, and cysteine as the predominant amino acids and firmly bound chromium in a ratio of one chromium(III) to one molecule of LMCr I. LMCr II was isolated in crystalline form and demonstrated to be a water-soluble, inorganic chromium(III) complex consisting of Na2HPO4 . 7H2O and Na2HPO4 . 2H2O. Although its crystallization reduced the chromium content, it had a maximum chromium-binding capacity as much as one chromium per one phosphorus in water. The mixture of LMCr I and LMCr II as approximated to be the natural composition showed a lower acute toxicity as measured by lethality in mice and had higher rates of urinary excretion and renal clearance in rabbits, accompanied by lower rates of renal tubular reabsorption and retention in kidney and liver than potassium dichromate(VI) and chromium(III) chloride. Pretreatment with chromium-free LMCr II remarkably reduced the mortality rates of mice acutely poisoned with chromium chloride. These results indicate that LMCr plays an important role in the detoxification and excretion of chromium in mammals. PMID:6617615

  4. 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.

  5. 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%.

  6. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... and compounds in construction, except: (2) Exposures that occur in the application of pesticides... 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...

  7. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and compounds in construction, except: (2) Exposures that occur in the application of pesticides... 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...

  8. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... that occur in the application of pesticides regulated by the Environmental Protection Agency or another... 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...

  9. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... that occur in the application of pesticides regulated by the Environmental Protection Agency or another... 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...

  10. 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...

  11. 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)).

  12. 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.

  13. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... them by the use of respiratory protection that complies with the requirements of paragraph (f) of this... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  14. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... use of respiratory protection that complies with the requirements of paragraph (f) of this section... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  15. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... use of respiratory protection that complies with the requirements of paragraph (f) of this section... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  16. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... them by the use of respiratory protection that complies with the requirements of paragraph (f) of this... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  17. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... use of respiratory protection that complies with the requirements of paragraph (f) of this section... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  18. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... chromium (VI); any history of respiratory system dysfunction; any history of asthma, dermatitis, skin... them by the use of respiratory protection that complies with the requirements of paragraph (f) of this... achieve compliance with the PEL. (f) Respiratory protection—(1) General. Where respiratory protection...

  19. 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

  20. 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.

  1. Electronic structure and chemical bonding of amorphous chromium carbide thin films

    NASA Astrophysics Data System (ADS)

    Magnuson, Martin; Andersson, Matilda; Lu, Jun; Hultman, Lars; Jansson, Ulf

    2012-06-01

    The microstructure, electronic structure and chemical bonding of chromium carbide thin films with different carbon contents have been investigated with high-resolution transmission electron microscopy, electron energy loss spectroscopy and soft x-ray absorption-emission spectroscopies. Most of the films can be described as amorphous nanocomposites with non-crystalline CrCx in an amorphous carbon matrix. At high carbon contents, graphene-like structures are formed in the amorphous carbon matrix. At 47 at.% carbon content, randomly oriented nanocrystallites are formed creating a complex microstructure of three components. The soft x-ray absorption-emission study shows additional peak structures exhibiting non-octahedral coordination and bonding.

  2. Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves.

    PubMed

    Nakkeeran, E; Saranya, N; Giri Nandagopal, M S; Santhiagu, A; Selvaraju, N

    2016-08-01

    In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions.

  3. Lead, cadmium and chromium in raw and boiled portions of Norway lobster.

    PubMed

    Perugini, Monia; Visciano, Pierina; Manera, Maurizio; Abete, Maria Cesarina; Tarasco, Renata; Amorena, Michele

    2014-01-01

    Lead, cadmium and chromium levels were determined in different raw and boiled portions of Norway lobster caught in the central Adriatic Sea (Italy). In raw specimens, the lowest concentrations were always detected in the white meat. Lead and cadmium content in the edible portion never exceeded the maximum levels set by European legislation. The highest cadmium and chromium values (0.47 ± 0.04 and 0.62 ± 0.13 mg/kg wet weight, respectively) were detected in the brown meat, while the highest lead concentrations were found in the exoskeleton (0.21 ± 0.01 mg/kg wet weight). Also, the boiled samples showed the lowest metal levels in the white meat, even if a significant increase (p < 0.01) was found for lead and cadmium compared to the corresponding raw portions. Among metals, chromium showed the highest concentrations in both raw and boiled portions, but up to now, the European legislation did not envisage any limits in seafood. PMID:24784349

  4. Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves.

    PubMed

    Nakkeeran, E; Saranya, N; Giri Nandagopal, M S; Santhiagu, A; Selvaraju, N

    2016-08-01

    In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions. PMID:26853060

  5. Estimation of Release of Nickel and Chromium by Indian Made Orthodontic Appliance in Saliva

    PubMed Central

    Parashar, Sandeep; Gupta, Ankur; Hegde, Chatura; Anand, Neelima

    2015-01-01

    Introduction With increasing use of Indian made orthodontic materials, need was felt to know nickel and chromium release from these material. Materials and Methods This study was conducted on simulated appliances consisting of brackets (022″Roth, Modern orthodontics, Ludhiana, India), from second premolar to central incisor, buccal tube and 0.019×0.025- inch SS arch wires secured with SS ligatures. Immersion was done in artificial saliva. Samples were analysed to using Atomic Absorption Photospectrometer (GVC ScientificEquipment Pvt. Ltd Australia) at AES Laboratories (P) Ltd., Noida India on 1st, 7th, 14th and 28th day. Results SPSS (ver 17, Inc., Chicago, Illinois, USA) was used toperform the statistical analysis. Descriptive statistics i.e. median and 25 and75 percentiles were used. Peak nickel release was on 7th day and subsequently declined over 14th and 28th day. The peak level of chromium concentration was on 14th day, which declined thereafter. Conclusion Average daily release of nickel and chromium over a period of one month was 97.368 μg/day and 47.664 μg/day respectively. The estimated release rates were approximately 32% and 16% of the reported average daily dietary. PMID:26501018

  6. 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.

  7. 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

  8. International strategic minerals inventory summary report; chromium

    USGS Publications Warehouse

    DeYoung, J.H.; 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.

  9. Bose-Einstein condensation of chromium.

    PubMed

    Griesmaier, Axel; Werner, Jörg; Hensler, Sven; Stuhler, Jürgen; Pfau, Tilman

    2005-04-29

    We report on the generation of a Bose-Einstein condensate in a gas of chromium atoms, which have an exceptionally large magnetic dipole moment and therefore underlie anisotropic long-range interactions. The preparation of the chromium condensate requires novel cooling strategies that are adapted to its special electronic and magnetic properties. The final step to reach quantum degeneracy is forced evaporative cooling of 52Cr atoms within a crossed optical dipole trap. At a critical temperature of T(c) approximately 700 nK, we observe Bose-Einstein condensation by the appearance of a two-component velocity distribution. We are able to produce almost pure condensates with more than 50,000 condensed 52Cr atoms.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Chromium films obtained by pyrolysis of bis(arene)chromium complexes in presence of sulfur-containing additives

    SciTech Connect

    Lugin, A.S.; Polikarpov, V.B.; Dodonov, V.A.; Klement'ev, E.K.

    1988-11-20

    Sulfur and its compounds catalyze deposition of chromium during thermal decomposition of its bis(arene) complexes. In this investigation we studied the influence of diphenyl and dibenzyl sulfides on this process. The character of the dependence of the rate of chromium deposition on the dibenzyl sulfide concentration in the original mixture shows that sulfur compounds, like chlorinated additives, have a promoting effect on the autocatalytic process of pyrolysis of bis(arene) chromium complexes. Aromatic sulfides raise the rate of chromium deposition, suppress secondary processes of ligands dehydrogenation, and accordingly lower the carbon contents in the deposits during thermal decomposition of bis(arene)chromium complexes. Sulfur compounds direct the deposition process toward formation of ordered crystalline phases of chromium and its carbides.

  18. 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...

  19. Electronic and magnetic structure of chromium surfaces and chromium monolayers on iron

    SciTech Connect

    Victora, R.H.; Falicov, L.M.

    1985-05-01

    Chromium surfaces and Cr monolayers atop Fe have greatly enhanced magnetizations relative to bulk. The Cr (100) surface is ferromagnetic with a spin polarization of 3.00; the (110) surface is antiferromagnetic. A Cr monolayer is ferromagnetic atop either the (100) or (110) Fe surfaces; the former has a large polarization of 3.63.

  20. Examination of chromium-chromium silicide composites and methods of improving toughness

    NASA Astrophysics Data System (ADS)

    Cruse, Terry Alan

    1998-09-01

    Crsb3Si has many desirable properties for use as a high temperature structural material: a high melting point, high stiffness and good chemical resistance. However, like many intermetallics, it suffers from a low toughness at room temperature. To overcome this limitation, ductile second phase toughening has been examined using chromium as the second phase. Specimens of Cr-Crsb3Si composites were produced by powder metallurgy techniques. The mechanical properties of these composites were evaluated using microhardness indentation to calculate a toughness value and in some cases notched three-point bend bars were also used. Examination of the Cr phase of these composites indicated that it lacked sufficient toughness itself to produce the desired toughness in the composite. Mechanical alloying was then used to create chromium alloys that were hot pressed and tested using the three-point bend method. The addition of 0.5 at. % V to Cr with 7.0 at. % Si (representative of the chromium phase of the composite) showed the largest increase in toughness, a 60% increase. Chromium with 0.5 at. % V was then used to make a composite with Crsb3Si. Mechanical alloying was also used to produce a (Cr,Mo)sb3Si material, which should have superior high temperature properties compared to Crsb3Si. This material was then used to produce composites with Cr and Cr-0.5 V. The composites had twice the toughness compared with similar composites produced with Crsb3Si.

  1. 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)

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

    PubMed Central

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

    2012-01-01

    Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr (VI) and Cr (III). Highly soluble hexavalent chromium is carcinogenic due to its oxidizing nature. It is well established that the intestinal bacteria including Lactobacilli have regulatory effect on intestinal homeostasis and a breakdown in the relationship between intestinal cells and bacteria results in the manifestation of gastrointestinal (GI) disorders. In this study Cr (VI) resistance was developed in Lactobacillus strains and the reduction of Cr (VI) was evaluated. All resistant strains showed similarities with their respective normal strains and did not acquire resistance to various antibiotics. A complete bacterial reduction of 32ppm Cr (VI) was observed within 6 to 8 hours. The presence of chromate reducing enzyme have also been established following the partial purification (2 to 5 fold) and characterization of chromate reductase in Lactobacillus strains. The chromate reductase of our strains showed optimum activity at pH 6.0 and 30°C. To our knowledge; these strains are fast in Cr (VI) reduction than any other known bacteria. The results suggest that chromate- resistant Lactobacillus strains would be useful for chromium detoxification from GI-tract as well as for bioremediation of hexavalent chromium from contaminated environment. PMID:22736899

  3. Soil washing of chromium- and cadmium-contaminated sludge using acids and ethylenediaminetetra acetic acid chelating agent.

    PubMed

    Gitipour, Saeid; Ahmadi, Soheil; Madadian, Edris; Ardestani, Mojtaba

    2016-01-01

    In this research, the effect of soil washing in the removal of chromium- and cadmium-contaminated sludge samples collected from Pond 2 of the Tehran Oil Refinery was investigated. These metals are considered as hazardous substances for human health and the environment. The carcinogenicity of chromate dust has been established for a long time. Cadmium is also a potential environmental toxicant. This study was carried out by collecting sludge samples from different locations in Pond 2. Soil washing was conducted to treat the samples. Chemical agents, such as acetic acid, ethylenediaminetetra acetic acid (EDTA) and hydrochloric acid, were used as washing solutions to remove chromium and cadmium from sludge samples. The results of this study indicated that the highest removal efficiencies from the sludge samples were achieved using a 0.3 M HCl solution with 82.69% and 74.47% for chromium and cadmium, respectively. EDTA (0.1 M) in the best condition extracted 66.81% of cadmium and 72.52% of chromium from the sludges. The lowest efficiency values for the samples, however, were achieved using 3 M acetic acid with 41.7% and 46.96% removals for cadmium and chromium, respectively. The analysis of washed sludge indicated that the heavy metals removal decreased in the order of 3 M acetic acid < 0.1 M EDTA<0.3 M HCl, thus hydrochloric acid appears to offer a greater potential as a washing agent in remediating the sludge samples.

  4. Soil washing of chromium- and cadmium-contaminated sludge using acids and ethylenediaminetetra acetic acid chelating agent.

    PubMed

    Gitipour, Saeid; Ahmadi, Soheil; Madadian, Edris; Ardestani, Mojtaba

    2016-01-01

    In this research, the effect of soil washing in the removal of chromium- and cadmium-contaminated sludge samples collected from Pond 2 of the Tehran Oil Refinery was investigated. These metals are considered as hazardous substances for human health and the environment. The carcinogenicity of chromate dust has been established for a long time. Cadmium is also a potential environmental toxicant. This study was carried out by collecting sludge samples from different locations in Pond 2. Soil washing was conducted to treat the samples. Chemical agents, such as acetic acid, ethylenediaminetetra acetic acid (EDTA) and hydrochloric acid, were used as washing solutions to remove chromium and cadmium from sludge samples. The results of this study indicated that the highest removal efficiencies from the sludge samples were achieved using a 0.3 M HCl solution with 82.69% and 74.47% for chromium and cadmium, respectively. EDTA (0.1 M) in the best condition extracted 66.81% of cadmium and 72.52% of chromium from the sludges. The lowest efficiency values for the samples, however, were achieved using 3 M acetic acid with 41.7% and 46.96% removals for cadmium and chromium, respectively. The analysis of washed sludge indicated that the heavy metals removal decreased in the order of 3 M acetic acid < 0.1 M EDTA<0.3 M HCl, thus hydrochloric acid appears to offer a greater potential as a washing agent in remediating the sludge samples. PMID:26599728

  5. Nickel and chromium isotopes in Allende inclusions

    NASA Technical Reports Server (NTRS)

    Birck, J. L.; Lugmair, G. W.

    1988-01-01

    High-precision nickel and chromium isotopic measurements were carried out on nine Allende inclusions. It is found that Ni-62, Ni-64, excesses are present in at least three of the samples. The results suggest that the most likely mechanism for the anomalies is a neutron-rich statistical equilibrium process. An indication of elevated Ni-60 is found in almost every inclusion measured. This effect is thought to be related to the decay of now extinct Fe-60. An upper limit of 1.6 X 10 to the -6th is calculated for the Fe-60/Fe-56 ratio at the time these Allende inclusions crystallized.

  6. Environmental durability of electroplated black chromium

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1981-01-01

    A study was undertaken to determine the durability of nickel-black chromium plated aluminum in an outdoor rural industrial, and seacoast environment. Test panels were exposed to these environments for 60, 36, and 13 months, respectively. The results of this study showed that no significant optical degradation occurred from exposure to either of these environments, although a considerable amount of corrosion occurred on the panels exposed to the seacoast environment. The rural and industrial atmosphere produced only a slight amount of corrosion on test panels.

  7. Chromium-Makes stainless steel stainless

    USGS Publications Warehouse

    Kropschot, S.J.; Doebrich, Jeff

    2010-01-01

    Chromium, a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point, is a silvery white, hard, and bright metal plating on steel and other material. Commonly known as chrome, it is one of the most important and indispensable industrial metals because of its hardness and resistance to corrosion. But it is used for more than the production of stainless steel and nonferrous alloys; it is also used to create pigments and chemicals used to process leather.

  8. 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

  9. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b)...

  10. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b)...

  11. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b)...

  12. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... area of the eye. (d) Labeling requirements. The label of the color additive and of any mixtures... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  13. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... area of the eye. (d) Labeling requirements. The label of the color additive and of any mixtures... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  14. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... area of the eye. (d) Labeling requirements. The label of the color additive and of any mixtures... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  15. The commensurate spin excitation in chromium: A polarised neutron investigation

    SciTech Connect

    Pynn, R. ); Stirling, W.G. . Dept. of Physics); Severing, A. )

    1991-01-01

    A polarised neutron experiment with neutron energy analysis has been performed with a single-Q sample of chromium in a large magnetic field. The 4-meV commensurate'' mode is found to involve spin fluctuations parallel to the ordered chromium moments. 8 refs., 3 figs.

  16. 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

  17. Embryo- and fetotoxicity of chromium in pregestationally exposed mice

    SciTech Connect

    Junaid, M.; Murthy, R.C.; Saxena, D.K.

    1996-10-01

    Chromium, an essential element in the human body required for proper carbohydrate, protein, and fat metabolism, is reported to impair gestational development of offspring of workers chronically exposed to this metal in the work place. Workers in chromium based industries can be exposed to concentrations two orders of magnitude higher than the general population. Among the general population, residents living near chromate production sites may be exposed to high levels of chromium (VI) in air or to elevated levels (40 - 50,000 ppm) of chromium in effluents. Shmitova reported afterbirth and puerperal hemorrhages in women industrially exposed to this metal and observed high chromium levels in blood and urine of pregnant women and in fetal and cord blood. Chromium readily passes the placental barrier and reaches the growing fetus. Exposure of mice to chromium during various gestational periods resulted in embryo and fetotoxic effects. This study looks at the role of body chromium accumulated pregestationally on embryo and fetal development and its subsequent transfer to feto-placental sites. 25 refs., 3 tabs.

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

    EPA Science Inventory

  1. Chromium crystal chemistry mullite-spinel refractory ceramics

    SciTech Connect

    Levy, D.; Gualtieri, A.; Quartieri, S.; Artioli, G.; Valle, M.

    1999-03-15

    A small amount of chromium oxide was added to a mullite-spinel refractory mixture to improve its thermal and mechanical properties. Two different compositions of mullite-spinel refractory were studied to define the crystal structures hosting the chromium cations, and the chromium solubility in spinel (MgAl{sub 2{minus}x}Cr{sub x}O{sub 4}) was determined. Powder X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and scanning electron microscopy (SEM) elemental distribution maps were used to determine the chromium crystal chemistry in the system. The observed maximum solubility of chromium in spinel was found at x = 1.2, but the presence of mullite in the mixture caused a strong decrease of this value. The chromium distribution among the crystal phases reflects the different reaction paths of the two samples: a stage involving spinel and melt drives all present chromium in the spinel, while a simultaneous crystallization of spinel-mullite distributes chromium cations between mullite, spinel, and secondary corundum.

  2. 76 FR 8773 - Superalloy Degassed Chromium From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-15

    ... applicable deadline.'' (75 FR 80457). Accordingly, pursuant to section 751(c) of the Tariff Act of 1930 (19 U... COMMISSION Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission... 2010 to determine whether revocation of the antidumping duty order on superalloy degassed chromium...

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

    PubMed

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

    2007-08-17

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

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Chromium absorption in the vascularly perfused rat intestine

    SciTech Connect

    Dowling, H.J.; Offenbacher, E.G.; Pi-Sunyer, F.X.

    1986-03-01

    The mechanism of chromium (Cr) absorption by the rat small intestine was investigated using a double perfusion technique wherein the luman of the small intestine and the vasculature supplying it were separately perfused. The intestinal perfusate (IP) was a nutrient-rich tissue culture medium (TCM) with added inorganic Cr and /sup 51/Cr. The vascular perfusate (VP) was a Krebs-Ringer bicarbonate solution (KRB) containing 4.7% dextran, 0.1% glucose and 5% human serum. Cr absorption was calculated by the amount of /sup 51/Cr detected in the VP. To determine the transport mechanism for Cr, its absorption into the VP was measured at various Cr concentrations of the IP ranging from 10-400 ppb CrCl/sub 3/. The amount of Cr absorbed into the blood rose linearly with the intestinal Cr concentration suggesting a process of simple diffusion. Manipulations of the VP and IP constituents were made to investigate their effects on Cr absorption. When serum was omitted from the VP, Cr adsorption was suppressed, suggesting that serum component(s) are necessary for optimal Cr absorption. When either of 2 plasma transport proteins (apo-transferrin, albumin) were added to the serum-free VP at physiological levels, Cr absorption returned to, but did not exceed, control levels. When the TCM was replaced with a KRB solution; Cr absorption was suppressed indicating that there are nutrient(s) of the TCM which facilitate Cr absorption. Further suppression occurred when a Cr concentration gradient opposing Cr absorption was created (IP at 100 ppb Cr, VP at 400 ppb Cr).

  10. 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.

  11. 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.

  12. 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

  13. Half life of chromium in serum and urine in a former plasma cutter of stainless steel

    PubMed Central

    Petersen, R.; Thomsen, J. F.; Jorgensen, N. K.; Mikkelsen, S.

    2000-01-01

    For 8 years chromium in serum and urine has been followed up in a former plasma cutter of stainless steel who was exposed to airborne dust and fumes containing chromium during this work. After the first examination for serum chromium the exposure ended. Serum chromium concentration has been measured seven times during the period and was initially very high and has subsequently dropped slowly. The half life was 40 months in serum. Urinary chromium has been measured five times. The half life was 129 months in urine. The study shows that exposure to airborne dust and fumes containing chromium may cause accumulation of chromium in the body, and that when exposure ends, elimination of chromium is very slow. Previous studies suggest that chromium mainly accumulates in the lungs.


Keywords: chromium half life; plasma cutting; stainless steel PMID:10711283

  14. 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.

  15. Laser processing of high-chromium nickel-chromium coatings deposited by various thermal spraying methods

    SciTech Connect

    Longa, Y.; Takemoto, M. . Coll. of Science and Engineering)

    1994-11-01

    High-chromium Ni-Cr coatings were deposited by thermal spraying in air and in an argon gas atmosphere. Coatings sprayed in Ar gas were free of pores and defects and of the same chemical composition as the spraying material. Following thermal spraying for each coating, laser glazing or laser gas alloying was applied to provide a protective chromium oxide film, produced by the intermediate oxidation process on top of the coatings. Five types of coatings were treated: (1) arc and (2) flame spraying in Ar, (3) arc and (4) flame spraying in air, and (5) low-pressure plasma spraying (LPPS). Oxide formation mechanisms during laser processing were studied, and the oxidation and hot-corrosion resistance of the coatings in the presence of a sulfate-vanadate fused salt at 900 C in air were examined. High-chromium Ni-Cr coatings deposited by thermal spraying, and they are used mostly to prevent ash attack of boilers and furnace tubes in power plants and oil refineries.

  16. Mutagenic and carcinogenic actions of chromium and its compounds.

    PubMed

    Mamyrbaev, Arstan Abdramanovich; Dzharkenov, Timur Agataevich; Imangazina, Zina Amangalievna; Satybaldieva, Umit Abulkhairovna

    2015-05-01

    Numerous experimental observations have been made on microorganisms and culture of the cells of mammals as well as the accounting of the chromosomal aberrations in the bone marrow cells of the mammals and of human cells displayed that the chromium and its compounds possess a pronounced mutagenic effect. Translocation test, induction record of DNA damage and repair systems in the mammalian and human cells with greater precision proves the presence of the mutagenic effect of the chromium and its compounds, which in turn is dependent on dose and time of this metal intoxication. Chromium and its compounds have pronounced mutagenic effect, on increased admission to organism of mammals and protozoa.

  17. Evolution of dispersion of high temperature chromium compounds

    NASA Astrophysics Data System (ADS)

    Shiryaeva, L. S.; Nozdrin, I. V.; Rudneva, V. V.; Galevsky, G. V.

    2016-09-01

    Chromium compound - boride Cr3B2 and carbide Cr3C2 are hard, wear-resistant, chemically inert materials, demanded for production of protective coatings of metals and cermets as components and alloying additives of tungsten free solid alloys. Future prospects for expansion of boride and chromium carbide usage are related to their production in the form of nanopowders. The researches into change of the particles shape and size of high-temperature chromium compounds in the conditions of plasma flow were carried out. There is coarsening of boride and carbonitride particles of nanoscale level at the reduction in the linear velocity of their growth.

  18. Pyrolysis of chromium rich tanning industrial wastes and utilization of carbonized wastes in metallurgical process.

    PubMed

    Tôrres Filho, Artur; Lange, Liséte Celina; de Melo, Gilberto Caldeira Bandeira; Praes, Gustavo Eduardo

    2016-02-01

    Pyrolysis is the thermal degradation of organic material in oxygen-free or very lean oxygen atmosphere. This study evaluates the use of pyrolysis for conversion of leather wastes from chromium tanning processes into Carbonized Leather Residues (CLR), and the utilization of CLR in metallurgical processes through the production of iron ore pellets. CLR was used to replace mineral coal in proportions of 10% and 25% on fixed carbon basis content in the mixtures for pellets preparation. Experimental conversions were performed on a pilot scale pyrolysis plant and a pelletizing reactor of the "pot grate" type. The results demonstrated the technical feasibility of using the charcoal product from animal origin as an energy source, with recovery of up to 76.47% of chromium contained in CLR in the final produced of iron ore pellets. Pellets with 25% replacement of fixed carbon in the coal showed an enhanced compressive strength, with an average value of 344kgfpellet(-1), compared to 300kgfpellet(-1) for standard produced pellets. PMID:26691602

  19. Pyrolysis of chromium rich tanning industrial wastes and utilization of carbonized wastes in metallurgical process.

    PubMed

    Tôrres Filho, Artur; Lange, Liséte Celina; de Melo, Gilberto Caldeira Bandeira; Praes, Gustavo Eduardo

    2016-02-01

    Pyrolysis is the thermal degradation of organic material in oxygen-free or very lean oxygen atmosphere. This study evaluates the use of pyrolysis for conversion of leather wastes from chromium tanning processes into Carbonized Leather Residues (CLR), and the utilization of CLR in metallurgical processes through the production of iron ore pellets. CLR was used to replace mineral coal in proportions of 10% and 25% on fixed carbon basis content in the mixtures for pellets preparation. Experimental conversions were performed on a pilot scale pyrolysis plant and a pelletizing reactor of the "pot grate" type. The results demonstrated the technical feasibility of using the charcoal product from animal origin as an energy source, with recovery of up to 76.47% of chromium contained in CLR in the final produced of iron ore pellets. Pellets with 25% replacement of fixed carbon in the coal showed an enhanced compressive strength, with an average value of 344kgfpellet(-1), compared to 300kgfpellet(-1) for standard produced pellets.

  20. Chromium detoxification by fixed-film bioreactors

    SciTech Connect

    Chirwa, E.M.N.; Wang, Y.T.

    1996-11-01

    In this study, completely mixed, continuous flow bioreactors were utilized to detoxify chromium. Glass beads were incorporated as a support medium for two strains of bacteria, Bacillus sp. and Pseudomonas fluorescens LB300 (LB300), growing aerobically in two separate reactors. Aerobic conditions were maintained in the reactors by continuously supplying fresh air to the liquid through gas exchange chambers installed on the recycle line of the bioreactors. Results obtained showed that near complete removal of chromate was possible for influent concentrations up to 200 mg/L for Bacillus sp., and up to 100 mg/L for LB300 at 24 hours liquid detention time. Similar results were obtained for corresponding loading rates at 12 hours and 6 hours liquid detention time.

  1. 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.

  2. 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

  3. Application of biomarkers in Epaulet grouper (Epinephelus stoliczkae) to assess chromium pollution in the Chabahar Bay and Gulf of Oman.

    PubMed

    Sadeghi, Parvin; Kazerouni, Faranak; Savari, Ahmad; Movahedinia, Abdolali; Safahieh, Alireza; Ajdari, Daniel

    2015-06-15

    In the present study plasma levels of erythropoietin (EPO) hormone and kidney histological changes were assessed as biomarkers to evaluate the chromium pollution in Epaulet grouper (Epinephelus stoliczkae) obtained from different areas in Chabahar Bay and Gulf of Oman. Chemical analyses included the evaluation of chromium in the fish kidney tissue and sediment. The highest and lowest concentrations of chromium were measured in the kidney of fish and sediment collected from Konarak (47.53±1.23 and 110±1.4 μg g(-1)) and the mouth of Chabahar Bay (3.43±1.31 and 13.5±3.23 μg g(-1)), respectively. There was significant difference (P<0.05) of EPO plasma levels between Konarak, Beris and Ramin stations with the mouth of Chabahar Bay as the cleanest station. Reduction of Bowman's space, occlusion of the tubule lumen, leukocytes infiltration, melanomacrophage centers aggregation, nuclear vacuolation, nuclei hypertrophy of tubule cells, necrosis of the tubules, lifting of the tubular basement membrane and dilatation of glomerular capillaries were the most alterations observed in the kidney. The HAI values of Epaulet grouper from Konarak, Beris and Ramin stations were significantly higher than other stations (P<0.05). It was concluded that selected biomarkers as a first investigation could be useful tools to environmental biomonitoring programs.

  4. 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

  5. Possible adverse effect of chromium in occupational exposure of tannery workers.

    PubMed

    Kornhauser, Carlos; Wróbel, Katarzyna; Wróbel, Kazimierz; Malacara, Juan Manuel; Nava, Laura Eugenia; Gómez, Leobardo; González, Rita

    2002-04-01

    Our aim was to investigate the adverse effects of occupational exposure to trivalent chromium. We measured chromium and iron levels in serum and urine and hemoglobin levels in tannery workers and unexposed persons. We studied three groups of subjects. Group 1 included 15 non-smoking male tannery workers highly exposed to chromium from tanning and retanning departments. Group 2 included 14 non-smoking male tannery workers with moderate chromium exposure from dying, drying and finishing departments. Group 3 included 11 healthy, non-smoking male subjects without direct chromium exposure. Higher serum chromium levels were observed in groups 1 and 2 with respect to group 3 (mean values respectively: 0.43; 0.25 and 0.13 microg x l(-1)). Urine chromium levels in group 1 were higher than those in controls (mean values: 1.78 and 1.35 microg x l(-1)). In group 1 an inverse association was found between serum chromium and urine iron (-0.524), urine chromium and hemoglobin (-0.594) and between the urine chromium to iron ratio and hemoglobin (-0.693, p<0.05). The results suggest a chromium adverse effect on iron metabolism, possibly associated with excessive body chromium accumulation. In conclusion, chromium urine test could be recommended for diagnosis of chromium adverse effect on iron metabolism. Further studies are needed to quantify the relationship between urine chromium and hemoglobin metabolism.

  6. Electronic structure and chemical bonding of amorphous chromium carbide thin films.

    PubMed

    Magnuson, Martin; Andersson, Matilda; Lu, Jun; Hultman, Lars; Jansson, Ulf

    2012-06-01

    The microstructure, electronic structure and chemical bonding of chromium carbide thin films with different carbon contents have been investigated with high-resolution transmission electron microscopy, electron energy loss spectroscopy and soft x-ray absorption-emission spectroscopies. Most of the films can be described as amorphous nanocomposites with non-crystalline CrC(x) in an amorphous carbon matrix. At high carbon contents, graphene-like structures are formed in the amorphous carbon matrix. At 47 at.% carbon content, randomly oriented nanocrystallites are formed creating a complex microstructure of three components. The soft x-ray absorption-emission study shows additional peak structures exhibiting non-octahedral coordination and bonding. PMID:22553115

  7. 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.

  8. 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,...

  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 73.2326 - 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,...

  11. 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...

  12. 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...

  13. 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...

  14. 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.

  15. 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.

  16. 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 ...

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

    SciTech Connect

    Chen, A.; Sridharan, K.; Dodd, R.A.; Conrad, J.R.; Qiu, X.; Hamdi, A.H.; Elmoursi, A.A.; Malaczynski, G.W.; Horne, W.G.

    1995-12-31

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

  18. Cancer hazards caused by nickel and chromium exposure.

    PubMed

    Norseth, T

    1980-01-01

    An increased risk of cancer associated with nickel refining and with chromate production has been known for some decades. The occupational exposure pattern of both nickel and chromium is very complex. Even though nickel carbonyl is an experimental carcinogen, there are no data supporting its carcinogenicity in humans. Nickel subsulfide may be the most potent carcinogen among the different nickel compounds. A correlation between lung cancer and exposure to chromates has been shown in several studies. As yet, there are no epidemiologic data indicating carcinogenicity of chromium(III) salts. Hexavalent chromium, however, has been suggested as the causative carcinogen among platers and ferrochromium workers. There is an urgent need for careful dose registration before a quantitative cancer risk analysis can be performed for the nickel and chromium industry. PMID:7463513

  19. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... the Contracting Officer, the Contractor shall not provide any deliverable or construction material... chromium materials during subsequent sustainment phases of the deliverable or construction material. (2... subcontracts for supplies, maintenance and repair services, or construction materials. (End of clause)...

  20. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... the Contracting Officer, the Contractor shall not provide any deliverable or construction material... chromium materials during subsequent sustainment phases of the deliverable or construction material. (2... services, or construction materials. (End of clause)...

  1. [Occupational diseases caused by chromium and its compounds].

    PubMed

    Hassmanová, V; Vanĕcková, J; Bousová, K

    2000-01-01

    The present paper demonstrates by documentary evidence occupational diseases caused by chromium and its compounds. Perforations of the nasal septum were diagnosed in 20 males and 9 females, the last one in 1980. Most of them worked in chromium-plating shops. Other diseases, including bronchial asthma, allergic rhinitis, and contact allergic eczemas, were examined in 1985-1999. Bronchial asthma was reported in a textile dyer who was in contact with chromium dyes for 32 years and two allergic rhinitides (a welder and an electroplater) were reported in 1987 as "other damage to health resulting from work." Out of 103 contact allergic eczemas, only 24 diseases, i.e. less than one quarter, were healed in 1999. Improvements were observed in 59 of them and 20 diseases persist. There was an exceptional finding of a chromium ulcer (pigeonneaux) on the lower extremity of a builder.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  8. 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... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  9. 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... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  10. 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... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  11. 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... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may...

  12. 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

  13. 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

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

    PubMed

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

    2006-03-01

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

  15. 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.

  16. Laser damage to optical components induced by surface chromium particles

    NASA Astrophysics Data System (ADS)

    Palmier, Stephanie S. P.; Tovena, Isabelle; Courchinoux, Roger; Josse, Michel A.; Rullier, Jean Luc; Bertussi, Bertrand; Natoli, Jean Yves; Servant, Laurent; Talaga, David

    2005-02-01

    To obtain better understanding of particulate contamination, chromium dots (50 x 50 &mum2) were deposited on a silica substrate by photolithography. The aim in using this sample is to observe the mechanism of damage initiation that can be attributed to surface contamination of micro-metric size. A Nd:YAG laser irradiated the sample at 1064 nm for different fluences and also different numbers of shots. Several methods were used to characterise the laser effects on the chromium dots and the silica substrate: "Nomarski", "atomic force" and photothermal microscope observations. The laser fluence is found to be the most important parameter for the behaviour of the chromium dots. At low fluence (<1 J/cm2), they become cracked (fractured). At medium fluence (around 1 J/cm2) chromium fusion is reached and chromium oxide appears. Finally at higher fluence (3 J/cm2), although chromium dots are blown off the substrate and small damage to silica occurs on the first shot, the subsequent shots do not lead to a dramatic increase in the damage.

  17. 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.

  18. Optically Induced Oscillations of Chromium Coated Silicon Microstructures

    NASA Astrophysics Data System (ADS)

    Pitcher, Robert John

    Available from UMI in association with The British Library. This thesis reports the effects of chromium layers on the vibrational properties of silicon microengineered structures designed as pressure sensors. Both excitation and interrogation have been achieved by optical means. Particular attention has been paid to the optically induced vibrational amplitude, Q factor and phase angle between the motion of the resonator and the incident pulsed laser light used to excite the resonator. Two silicon structures have been investigated: bridges fabricated at Birmingham University and extensively characterised by researchers at Strathclyde University, and devices fabricated at STC Technology Ltd. in Harlow. For both structures the addition of chromium layers onto the surface has had the effect of increasing the value of the amplitude divided by the Q factor. This increase occurs after a layer of chromium of about 15 nm thickness has already been deposited onto the silicon. It has also been found that the value of the Q factor of the resonators has decreased with the addition of chromium layers. The phase angle of the motion has also been found to be sensitive to the thickness of the chromium layer. This angle has been observed to increase from approximately zero for bare silicon to about 40^circ for a few hundred Angstroms, returning towards zero phase for chromium layers of comparable thickness to the silicon thickness.

  19. Chemisorption of chromium acetylacetonate on porous high surface area silica

    NASA Astrophysics Data System (ADS)

    Haukka, Suvi; Lakomaa, Eeva-Liisa; Suntola, Tuomo

    1994-01-01

    Atomic layer epitaxy (ALE) reactions (i.e. saturating gas-solid reactions) of chromium acetylacetonate (Cr(acac) 3) at 200-280°C with silica preheated at 200-820°C were studied by determining chromium and carbon concentrations, recording FTIR spectra, and reacting Cr(acac) 3 with the silylated silica surface. Cr(acac) 3 was found to be selectively chemisorbed to silica through reaction with the isolated OH groups, leading to release of one acac ligand. The relatively large size of the supported chromium complex that formed had a highly controlling effect on the amount of chromium atoms bound. In addition to this steric hindrance, the saturation density of chromium could be further regulated by the preheat temperature of the silica, which determines the number of OH groups, and by the reaction temperature. The reaction with the silylated silica surface provided a means for achieving an even lower saturation density of chromium and confirmed that the strongly H-bonded OH groups present on silica preheated at 200°C were only partly reactive. The ligands of the surface complex could be removed by water vapor and air treatment.

  20. 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

  1. Cytokine detection for the diagnosis of chromium allergy*

    PubMed Central

    Martins, Luis Eduardo Agner Machado; dos Reis, Vitor Manoel Silva

    2013-01-01

    BACKGROUND Patch testing remains the gold standard method for the identification of the etiologic agent of allergic contact dermatitis. However, it is a subjective, time-consuming exam whose technique demands special care and which presents some contraindications, which hamper its use. In a recent study, we showed that the proliferation assay can suitably replace patch testing for the diagnosis of chromium allergy, which had been previously demonstrated only for nickel allergy. In this study, we try to refine the method by reducing the incubation period of cultures for lymphocyte proliferation assays in response to chromium. OBJECTIVE Develop an alternative or complementary diagnostic test for chromium allergic contact dermatitis. METHODS We compared the production of 9 cytokines (IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17 and RANTES) between 18 chromium-allergic patients and 19 controls. RESULTS Chromium increased the production of IFN-y, IL-5, IL-2 and IL-13 in allergic patients, but only IL-2 and especially IL-13 helped discriminate allergic patients from controls. The sensitivity, specificity and accuracy found with IL-13 were about 80%. CONCLUSIONS IL-13 and IL-2 detection may be used to diagnose chromium allergy in 2-day cultures. However, in general, the 6-day cultures seem to be superior for this purpose. PMID:24173176

  2. 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

  3. 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

  4. Establishment of a reference value for chromium in the blood for biological monitoring among occupational chromium workers.

    PubMed

    Li, Ping; Li, Yang; Zhang, Ji; Yu, Shan-Fa; Wang, Zhi-Liang; Jia, Guang

    2016-10-01

    The concentration of chromium in the blood (CrB) has been confirmed as a biomarker for occupational chromium exposure, but its biological exposure indices (BEIs) are still unclear, so we collected data from the years 2006 and 2008 (Shandong Province, China) to analyze the relationship between the concentration of chromium in the air (CrA) of the workplaces and CrB to establish a reference value of CrB for biological monitoring of occupational workers. The levels of the indicators for nasal injury, kidney (β2 microglobulin (β2-MG)), and genetic damages (8-hydroxy-deoxyguanosine (8-OHdG) and micronucleus (MN)) were measured in all subjects of the year 2011 (Henan Province, China) to verify the protective effect in this reference value of CrB. Compared with the control groups, the concentrations of CrA and CrB in chromium exposed groups were significantly higher (P < 0.05). Positive correlations were found between CrA and CrB in chromium exposed groups (r 2006 = 0.60, r 2008 = 0.35) in the years 2006 and 2008. According to the occupational exposure limitation of CrA (50 μg/m(3), China), the reference value of CrB was recommended to 20 μg/L. The levels of nasal injury, β2-MG, 8-OhdG, and MN were not significantly different between the low chromium exposed group (CrB ≤ 20 μg/L) and the control group, while the levels of β2-MG, 8-OHdG, and MN were statistically different in the high chromium exposed group than that in the control group. This research proved that only in occupational workers, CrB could be used as a biomarker to show chromium exposure in the environment. The recommended reference value of CrB was 20 μg/L.

  5. 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.

  6. 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.

  7. Chromium supplements: differences in utilization by humans

    SciTech Connect

    Bizem, H.R.; Kies, C.; Fox, H.M.

    1986-03-01

    Chromium (Cr) in the +3 oxidation state has been widely administered to subjects to examine the effects of Cr supplementation. The objective of the current project was to compare the differences in utilization of 2 Cr supplements in adult Midwestern women. Each woman serving as her own control randomly received the basal diet alone, basal diet + brewer's yeast and basal diet + chelated Cr containing 42 ..mu..g, 242 ..mu..g and 242 ..mu..g Cr daily, respectively. Treated urine and blood serum samples were analyzed in duplicate for Cr content using a Varian Techtron Atomic Absorption Spectrophotometer model 1275 equipped with a graphite furnace attachment. Mean urinary Cr excretion was similar for subjects consuming the basal diet alone or with the brewer's yeast supplement (0.16 ..mu..g/day). Use of chelated Cr supplementation led to significantly higher urinary Cr excretion (0.317 ..mu..g/day, P<0.03). This suggests that Cr supplied by chelated Cr was better than that supplied by yeast, although both supplements were apparently poorly absorbed in comparison to the Cr supplied by the diet. Blood serum Cr concentrations were not significantly altered by the experimental treatments.

  8. 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.

  9. 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.

  10. Hexavalent chromium-resistant bacteria isolated from river sediments.

    PubMed Central

    Luli, G W; Talnagi, J W; Strohl, W R; Pfister, R M

    1983-01-01

    Hexavalent chromium [Cr(VI)] is a known carcinogen and mutagen; however, the actual mechanisms of Cr toxicity are unknown. Two approaches were used to isolate Cr(VI)-resistant bacteria from metal-contaminated river sediments. Diluted sediments were plated directly onto a peptone-yeast extract (PYE) medium containing 0 to 100 micrograms of Cr(VI) ml-1. Approximately 8.4 x 10(5) CFU g-1 were recovered on 0 microgram of Cr(VI) ml-1, whereas 4.0 x 10(2) CFU g-1 were recovered on PYE plus 100 micrograms of Cr(VI) ml-1. Alternatively, continuous culture enrichment techniques were employed using PYE and 100 micrograms Cr(VI) ml-1 input at dilution rates of 0.02 and 0.10 h-1. After six residence periods, 10(9) CFU were recovered on PYE agar containing 0 microgram of Cr(VI) ml-1 and 10(7) CFU on PYE agar plus 100 micrograms of Cr(VI) ml-1. Of 89 isolates obtained by direct plating onto PYE, 47% were resistant to 100 micrograms of Cr(VI) ml-1, and 29% were resistant to 250 micrograms of Cr(VI) ml-1. When the same isolates were plated onto PYE containing Cr(III), 88% were resistant to 100 micrograms ml-1 but only 2% were resistant to 250 micrograms ml-1. Cr, Co, Sb, and Zn were found in significantly higher concentrations at an industry-related contaminated site than at a site 11 km downstream. Total Cr in the sediments at the contaminated site averaged 586 micrograms (dry weight) g-1, and the downstream site averaged 71 micrograms (dry weight) g-1. The Cr recovered from acid-digested Ottawa River sediment samples was predominantly hexavalent. Five acid digestion procedures followed by atomic absorption spectroscopy were compared and found to be 30 to 70% efficient for recovery of Cr relative to neutron activation analysis. A population of aerobic, heterotrophic bacteria was recovered from sediments containing elevated levels of Cr.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6639032

  11. 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.

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

    SciTech Connect

    Fanchiang, Y.T; Bose, R.N.; Gelerinter, E.; Gould, E.S.

    1985-12-18

    The chelated (carboxylato)chromium(V) anion bis(2-hydroxy-2-ethylbutyrato)oxochromate(V) (I), ((Lig)/sub 2/Cr(O))/sup -/, reacts with oxovanadium(IV) to form a strongly absorbing species (lambda/sub max/ = 515 nm; epsilon = 1.7 x 10/sup 3/ M/sup -1/) in the presence of 2-hydroxy-2-ethylbutyric acid buffers (pH 2-4). EPR data support 1:1 stoichiometry with VO/sup 2 +/ in deficiency, indicating the formation of a chromium(IV) species by reduction. With excess VO/sup 2 +/ a chromium(III) product was obtained. Spectral and ion-exchange properties of this product correspond to those observed for the titanium(III) and iron(II) reductions of chromium(V) and are consistent with the formulation of the product as a bis(hydroxycarboxylate) chelate of (H/sub 2/O)/sub 2/Cr/sup III/. With excess vanadium(IV), the reaction exhibits triphasic kinetics. The remaining step of the reaction is the reduction of the chromium(IV) intermediate with VO/sup 2 +/. Rates for all steps increase with decreasing (H/sup +/) and level off at low (H/sup +/). The limiting rate constants for the formation of the chromium(IV) intermediate by the (Lig)/sub 3/Cr(O)/sup 2 -/ and (Lig)/sub 2/Cr(O)/sup -/ pathways are 2.8 x 10/sup 3/ and 2.2 x 10/sup 2/ M/sup -1/s/sup -1/. The bimolecular limiting rate constant for the reduction of chromium(IV) is computed to be 7.7 x 10/sup 2/ M/sup -1/ s/sup -1/. 33 references, 7 tables.

  13. [Occupational exposure to hexavalent chromium during aircraft painting].

    PubMed

    Gherardi, M; Gatto, M P; Gordiani, A; Paci, E; Proietto, A

    2007-01-01

    Hygienists are interested in hexavalent chromium due to its genotoxic and carcinogenic effect on humans. The use of products containing hexavalent chromium is decreasing in many industrial fields because of the substitution with less-toxic compounds. In the aeronautical industry, however, the chromate are added to primer paint as a corrosion inhibitor of aircrafts surfaces: so hexavalent chromium compounds are available in many primers with a composition ranging from 10% to 13%. The application of these primers by using electrostatic guns potentially exposes painting and coating workers at high concentrations of aerosols containing Cr(VI). The aim of the present study is the evaluation of professional exposure to hexavalent chromium during aircraft painting, by adopting both environmental personal sampling and biological monitoring. To valuate workers exposure levels the personal measurements results have been compared with the exposure limit values (TLV-TWA) and the urinary chromium contents with the biological exposure indices (IBE). Moreover the strategy of coupling environmental sampling with biological monitoring seems to be a useful instrument to measure the validity of the individual protection devices.

  14. 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.

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

    PubMed

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

    2006-06-01

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

  16. 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.

  17. 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.

  18. Impact of pyrolysis process on the chromium behavior of COPR.

    PubMed

    Zhang, Dalei; He, Shengbing; Dai, Luwei; Xie, Yaning; Wu, Deyi; Bu, Guanhua; Peng, Kangjin; Kong, Hainan

    2009-12-30

    The effect of pyrolysis process with sewage sludge on the chromium behavior of chromite ore processing residue (COPR) was examined in this study. The behavior of chromium was characterized in term of chromium oxidation test, pH-static leaching tests, column leaching test and sequential extraction test. As a sequence of pyrolysis process, the Cr(VI) in COPR was effectively reduced from 5057 mg kg(-1) for untreated COPR to 8.6 mg kg(-1) for treated COPR at temperature over 600 degrees C, which is far below the New Jersey Department of Environmental Protection regulatory limit of 240 mg kg(-1). As a result, the amount of exchangeable and carbonate-bound Cr fractions, the most mobile for the environment, were largely reduced. At the same time, the amount of the other three Cr fractions which are much less mobile become augmented. pH static test showed that the chromium in the treated COPR at pyrolysis temperature above 400 degrees C was quite stable at pH>7. Column study also indicated that only negligible amount of chromium of the treated COPR at above 600 degrees C can be released by the acid rain.

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

    PubMed

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

    2016-10-01

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

  20. 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...

  1. 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.

  2. 75 FR 18041 - Defense Federal Acquisition Regulation Supplement; Minimizing Use of Hexavalent Chromium (DFARS...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-08

    ... requirements for minimizing the use of hexavalent chromium in defense weapon systems, subsystems, components... INFORMATION: A. Background Hexavalent chromium is a significant chemical in numerous DoD weapon systems...

  3. 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)

  4. 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...

  5. 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.

  6. 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.

  7. Circadian reduction of chromium in the gastric environment.

    PubMed

    De Flora, S; Badolati, G S; Serra, D; Picciotto, A; Magnolia, M R; Savarino, V

    1987-11-01

    Samples of gastric juice from variously treated subjects efficiently reduced hexavalent chromium and decreased its mutagenicity. Chromium reduction was due to thermostable components of gastric secretions and was favoured by the acidity of the intragastric environment. The circadian monitoring of pH and of chromium reduction, as assessed by colorimetric analysis at hourly intervals, showed a basal activity (less than 10 micrograms/ml gastric juice) during the night and interdigestive periods, and peaks (tens of micrograms/ml) during the 3-4-h periods after each meal. Assays in the Ames reversion test confirmed that the decrease in mutagenicity of sodium dichromate produced by gastric juice was significantly enhanced after meals. This physiological mechanism is expected to provide an important protective barrier against the oral toxicity of this metal, and may explain its lack of oral carcinogenicity.

  8. Inhalation toxicity of chromium from Whetlerite dust in rats.

    PubMed

    Hilaski, R; Katz, S; Salem, H

    1992-08-01

    The acute inhalation toxicity and metabolic fate of chromium and copper from Whetlerite dust in rats were investigated. Groups of male and female, Sprague-Dawley rats were exposed to Whetlerite dust and base carbon dust as outlined in the OECD Limit Test guidelines. At 14, 28 and 180 days post-exposure, rats were evaluated for gross pathological changes and tissues were collected for chromium and copper determination. Four deaths occurred during or post-exposure, but did not appear to be compound related. No gross pathological changes were observed at necropsy in either group. Organ chromium concentrations were below detection limits of 0.5 micrograms Cr/g dry tissue in both exposure groups. According to OECD guidelines, neither Whetlerite dust nor base carbon dust demonstrated an acute inhalation toxicity.

  9. 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.

  10. 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,

  11. The nature of temper brittleness of high-chromium ferrite

    SciTech Connect

    Sarrak, V.I.; Suvorova, S.O.; Golovin, I.S.; Mishin, V.M.; Kislyuk, I.V.

    1995-03-01

    The reasons for development of {open_quotes}475{degrees}C brittleness{close_quotes} of high-chromium ferritic steels are considered from the standpoint of fracture mechanics. It is shown that the general rise in the curve of temperature-dependent local flow stress has the decisive influence on the position of the ductile-to-brittle transformation temperature and the increase in it as the result of a hold at temperatures of development of brittleness. The established effect is related to the change in the parameters determining dislocation mobility, that is, the activation energy of dislocation movement in high-chromium ferrite and the resistance to microplastic deformation, both caused by processes of separation into layers of high-chromium ferrite and decomposition of the interstitial solid solution.

  12. 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.

  13. 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

  14. 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....

  15. 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....

  16. 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....

  17. 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....

  18. 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....

  19. The toxicology of chromium with respect to its chemical speciation: a review.

    PubMed

    Katz, S A; Salem, H

    1993-01-01

    The properties of trivalent and hexavalent chromium are reviewed with respect to acute and chronic oral toxicity, dermal toxicity, systemic toxicity, toxicokinetics, cytotoxicity, genotoxicity and carcinogenicity. The hexavalent chromium compounds appear to be 10-100 times more toxic than the trivalent chromium compounds when both are administered by the oral route. Dermal irritancy and allergy are more frequently caused by contact with soluble hexavalent chromium compounds. The cytotoxicity of soluble and insoluble hexavalent chromium compounds to fibroblasts is 100-1000 times greater than that demonstrated by trivalent chromium compounds. In short-term tests, the hexavalent chromium compounds demonstrated genotoxic effects four times more frequently than did the trivalent chromium compounds. Carcinogenicity appears to be associated with the inhalation of the less soluble/insoluble hexavalent chromium compounds. The toxicology of chromium does not reside with the elemental form. It varies greatly among a wide variety of very different chromium compounds. Oxidation state and solubility are particularly important factors in considering the toxicity of chromium with respect to its chemical speciation.

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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.

  15. 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...

  16. 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...

  17. 76 FR 20349 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-12

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

  18. 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...

  19. 75 FR 60454 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-30

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

  20. 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...

  1. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... chromium air emissions increases the risk of lung cancer. Federal Law prohibits use of this substance in...) Definitions. Definitions in section 3 of the Toxic Substances Control Act, 15 U.S.C. 2602, apply to this... chromium means the oxidation state of chromium with an oxidation number of +6; a coordination......

  2. Reaction diffusion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems

    NASA Technical Reports Server (NTRS)

    Levine, S. R.

    1977-01-01

    The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general mutliphase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1,000, 1,095, 1,150, or 1,205 C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The beta source strength concept provided a method (1) for correlating beta recession rate constants with composition; (2) for determining reliable average total, diffusion, and constitutional activation energies; and (3) for calculating interdiffusion coefficients.

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

    PubMed

    Dheeba, B; Sampathkumar, P; Kannan, K

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  5. Increasing total and biologically active chromium in wheat grain and spinach by spraying with chromium salts

    SciTech Connect

    Vicini, F.A.; Ellis, B.G.

    1981-06-01

    Recently, chromium has been shown to be necessary for glucose metabolism in man. But most plant species greatly restrict the uptake of Cr. This study was conducted to determine if both total and biologically active Cr could be increased in wheat grain or spinach by spraying the plants with either Cr/sub 2/(SO/sub 4/)/sub 3/ or Cr-EDTA. Concentrations of Cr in wheat grain were about doubled in a greenhouse experiment by spraying with either Cr source. Biologically active Cr (estimated by extraction with ethanol or NH/sub 4/OH) was increased from about 40 to greater than 50% of total Cr when wheat was sprayed with Cr salts. Total Cr in spinach leaves was increased by as much as 10-fold by spraying, with the sulfate source being more effective than the EDTA.

  6. 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.

  7. Hot corrosion resistance of nickel-chromium-aluminum alloys

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Barret, C. A.

    1977-01-01

    The hot corrosion resistance of nickel-chromium-aluminum alloys 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. From these equations corrosion isopleths were prepared. Compositional regions with the best hot corrosion resistance were identified.

  8. Hydrolytic polymerization of chromium (III). 2. A trimeric species

    SciTech Connect

    Finholt, J.E.; Thompson, M.E.; Connick, R.E.

    1981-12-01

    With use of an ion-exchange displacement elution, a green species was separated from mixtures of Cr(III) polymers and its absorption spectrum determined. The hydroxides per chromium atom were found to be 4/3, and the charge per chromium atom was shown to be consistent with this value. The degree of polymerization of freezing point depression was close to 3. Measurements are reported for the equilibrium quotient for the formation of the trimer from the monomer. The ESR spectrum and magnetic susceptibility were determined, and the results are discussed in terms of possible structures.

  9. Chromium boron surfaced nickel-iron base alloys

    NASA Technical Reports Server (NTRS)

    Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

    1984-01-01

    Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

  10. 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.

  11. 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.

  12. A review of chromium, molybdenum, and tungsten alloys

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.

    1975-01-01

    The mechanical properties of chromium, molybdenum, and tungsten alloys are reviewed with particular emphasis on high-temperature strength and low-temperature ductility. Precipitate strengthening is highly effective at 0.4 to 0.8 times the melting temperature in these metals, with HfC being most effective in tungsten and molybdenum, and Ta(B,C) most effective in chromium. Low-temperature ductility can be improved by alloying to promote rhenium ductilizing or solution softening. The low-temperature mechanical properties of these alloys appear related to electronic interactions rather than to the usual metallurgical considerations.

  13. Nickel and chromium cycles: Stocks and flows project part IV

    NASA Astrophysics Data System (ADS)

    Reck, Barbara K.; Gordon, Robert B.

    2008-07-01

    Nickel and chromium are essential ingredients in alloys increasingly important for energy-efficient, environmentally friendly modern technology. Quantitative assessment of the flows of these metals through the world economy from resource extraction to final disposal informs resource policy, energy planning, environmental science, and waste management. This article summarizes the worldwide technological cycles of nickel and chromium in 2000. Stainless steel is the major use of these metals, but they serve numerous other special needs, as in superalloys for high-temperature service, as plating materials, and in coinage. Because they are used primarily in alloys, novel recycling issues arise as their use becomes more widespread.

  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. Dielectric properties of polyamide 12-chromium(III) oxide nanocomposites

    NASA Astrophysics Data System (ADS)

    Zuev, Vjacheslav V.; Shapoval, Ekaterina S.; Sakhatskii, Aleksandr S.

    2016-08-01

    Broadband dielectric spectroscopy was employed to study polymer nanocomposites based on PA12 filled with of nanosized chromium(III) oxide. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. Three relaxation processes and Maxwell-Wagner-Sillars (MWS) interfacial polarizations were observed. It was found that presence of nanosized amphoteric chromium(III) oxide leads to softening of polyamide matrix that manifested in decrease of the activation energy of the α- and β-relaxation processes and glass transition temperatures. The softening of polymer matrix is the reason of the decrease of mechanical strength of polymer nanocomposites as compared with neat PA12.

  16. Reducing chromium losses from a chromium plating bath. 1987 summer intern report. Project conducted at New Dimension Plating, Hutchinson, Minnesota

    SciTech Connect

    Achman, D.

    1987-12-31

    The company employs about forty people and operates for one or two eight hour shifts with an average of 315 racks of chrome plating per eight hour day. They plate a variety of metals including copper, nickel, gold, brass and chromium. Chromium is the major metal plated and is usually the last step in plating cycle. Most parts are copper plated and then nickel plated in preparation for chrome plating. The main difference between New Dimension Plating and other plating shops is the variety of parts plated. As New Dimension Plating is a job shop, a wide range of parts such as motorcycle accessories, stove parts, and custom items are metal finished. The plating lines are manual, meaning employees dip the racks into the tanks by hand. This fact along with the fact that parts vary greatly in size and shape accounts for the significant drag-out on the chromium plating line.

  17. Reactor target from metal chromium for "pure" high-intensive artificial neutrino source

    NASA Astrophysics Data System (ADS)

    Gavrin, V. N.; Kozlova, Yu. P.; Veretenkin, E. P.; Logachev, A. V.; Logacheva, A. I.; Lednev, I. S.; Okunkova, A. A.

    2016-03-01

    The paper presents the first results of development of manufacturing technology of metallic chromium targets from highly enriched isotope 50Cr for irradiation in a high flux nuclear reactor to obtain a compact high intensity neutrino source with low content of radionuclide impurities and minimum losses of enriched isotope. The main technological stages are the hydrolysis of chromyl fluoride, the electrochemical reduction of metallic chromium, the hot isostatic pressing of chromium powder and the electrical discharge machining of chromium bars. The technological stages of hot isostatic pressing of chromium powder and of electrical discharge machining of Cr rods have been tested.

  18. 21 CFR 176.160 - Chromium (Cr III) complex of N-ethyl-N-heptadecylfluoro-octane sulfonyl glycine.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Chromium (Cr III) complex of N-ethyl-N... § 176.160 Chromium (Cr III) complex of N-ethyl-N-heptadecylfluoro-octane sulfonyl glycine. The chromium... by weight of the chromium (Cr III) complex of heptadecylfluoro-octane sulfonic acid may be...

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

    EPA Science Inventory

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

  20. Hydrolytic polymerization of chromium(III). I. Two dimeric species

    SciTech Connect

    Thompson, M.; Connick, R.E.

    1981-07-01

    In addition to the well-known doubly bridged chromium(III) dimer ((H/sub 2/O)/sub 4/Cr(OH)/sub 2/Cr(H/sub 2/O)/sub 4/)/sup 4 +/, a second dimer of formula ((H/sub 2/O)/sub 5/CrOHCr(H/sub 2/O)/sub 5/)/sup 5 +/ has been found. The formula of the latter was established through equilibrium measurements and freezing point depression. The equilibrium between Cr/sup 3 +/ and the doubly bridged dimer was measured at various ionic strengths and temperatures. The equilibrium between the doubly bridged and singly bridged dimers is shifted strongly toward the latter only at high acidities, with roughly equal concentrations at 2 M acid. Electron spin resonance spectra were taken for both dimers in order to obtain g values. The latter were used with magnetic susceptibility measurements to calculate the spin-spin coupling constants between the two chromiums of these species. Comparison is made with the coupling constants of other bridged chromium(III) compounds, and the results are shown to be in reasonable agreement. The striking difference in magnetic susceptibility between the doubly bridged chromium dimer and the iron(III) dimer of empirical formula Fe/sub 2/(OH)/sub 2//sup 4 +/ is discussed in terms of possible structures and electronic interactions.

  1. 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).

  2. Extended followup of a cohort of chromium production workers

    PubMed Central

    Lees, Peter St. John; Wang, Jing; Grace O'Leary, Keri

    2015-01-01

    Background The current study evaluates the mortality of 2,354 workers first employed at a Baltimore chromate production plant between 1950 and 1974. Methods The National Death Index (NDI Plus) was used to determine vital status and cause of death. Cumulative chromium (VI) exposure and nasal and skin irritation were evaluated as risk factors for lung cancer mortality. Results There are 91,186 person‐years of observation and 217 lung cancer deaths. Cumulative chromium (VI) exposure, nasal irritation, nasal perforation, nasal ulceration, and other forms of irritation (e.g., skin irritation) were associated with lung cancer mortality. Conclusion Cumulative chromium (VI) exposure was a risk factor for lung cancer death. Cancer deaths, other than lung cancer, were not significantly elevated. Irritation may be a possible mechanism for chromium (VI)‐induced lung cancer. Am. J. Ind. Med. 58:905–913, 2015. © 2015 The Authors. American Journal of Industrial Medicine Published by Wiley Periodicals, Inc. PMID:26041683

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

    EPA Science Inventory

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

  4. Adsorption and oxidation of aniline and anisidine by chromium ferrocyanide.

    PubMed

    Alam, Tanveer; Tarannum, Hina; Ali, Shah Raj; Kamaluddin

    2002-01-15

    The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.

  5. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Food, Drug, and Cosmetic Act with respect to the contact lenses in which the additive is used. (c... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium oxide greens. 73.3111 Section 73.3111 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING...

  6. Moss biomonitoring of air pollution with chromium in Croatia.

    PubMed

    Vučković, Ivana; Spirić, Zdravko; Stafilov, Trajče; Kušan, Vladimir

    2013-01-01

    The purpose of this study was to determine the atmospheric deposition of chromium in Croatia by using moss biomonitoring technique and atomic emission spectrometry with inductively coupled plasma (ICP-AES). Moss samples (Hylocomium splendens, Hypnum cupressiforme, Brachythecium rutabulum and Homalothecium Sericeum) were collected from 121 sampling sites evenly distributed over the country, during the summer and autumn of 2010. Collected samples were air dried, then cleaned and digested by using microwave digestion system. The median value obtained in this study (1.94 mg kg⁻¹) compared with the median value of previous investigation performed in 2006 (2.75 mg kg⁻¹) shows that the content of chromium decreased. Higher contents of chromium were found in moss samples collected in the regions of Central Croatia, in/near the cities of Zagreb, Sisak and Kutina, which, in the most of the cases, are result of anthropogenic activities. In Costal Croatia, higher values have a natural origin due to the significantly higher content of Cr in soil from this region. The results were compared with those from similar studies in neighboring and other Balkan countries. It was established that the content of chromium in Croatia is lower than in the most of these countries.

  7. Chromium-Catalyzed Asymmetric Dearomatization Addition Reactions of Halomethyl Heteroarenes.

    PubMed

    Tian, Qingshan; Bai, Jing; Chen, Bin; Zhang, Guozhu

    2016-04-15

    The first asymmetric dearomatization addition reaction of halomethyl arenes including benzofuran and benzothiophene was enabled by chromium catalysis. A variety of aldehydes served as suitable electrophiles under mild reaction conditions. Molecular complexities are quickly increased in a highly diastereo- and enantioselective manner.

  8. New alloys to conserve critical elements. [replacing chromium in steels

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1978-01-01

    Previous studies and surveys on availability of domestic reserves have shown that chromium is a most critical element within the U.S. metal industry. More precisely, the bulk of chromium is consumed in the production of stainless steels, specifically Type 304 stainless steel (304SS) which contains 18% Cr. The present paper deals with means of reducing chromium in commercial stainless steels by substituting more abundant or less expensive elements with the intent of maintaining the properties of 304SS. The discussion focuses on some of the oxidation and corrosion properties of new substitute stainless steels with only 12% Cr, which represents a potential saving of 33% of the chromium consumed in the production of 304SS. The alloying elements substituted for Cr in 304SS are selected according to their potential for protective oxide formation during high-temperature oxidation; these are Al, Si, Ti, Y, and misch metal which is 99.7% rare-earth metals containing 50 to 55% cerium. Other alloying elements to impart corrosion resistance are Mn, Mo, and V.

  9. Toxicity and Mutagenicity of Hexavalent Chromium on Salmonella typhimurium

    PubMed Central

    Petrilli, Fernando L.; De Flora, Silvio

    1977-01-01

    Four hexavalent and two trivalent chromium compounds were tested for toxicity and mutagenicity by means of the Salmonella typhimurium/mammalian-microsome test. All hexavalent compounds yielded a complete inhibition of bacterial growth at doses of 400 to 800 μg/plate, a significant increase of his+ revertant colonies at doses ranging from 10 to 200 μg, and no effect at doses of less than 10 μg. The distinctive sensitivity of the four Salmonella strains tested (TA1535, TA1537, TA98, and TA100) suggested that hexavalent chromium directly interacts with bacterial deoxyribonucleic acid by causing both frameshift mutations and basepair substitutions. The latter mutations, which are prevalent, are amplified by an error-prone recombinational repair of the damaged deoxyribonucleic acid. On the average, 1 μmol of hexavalent chromium yielded approximately 500 revertants of the TA100 strain, irrespective of the compound tested (sodium dichromate, calcium chromate, potassium chromate, or chromic acid). The mutagenic potency of the hexavalent metal was not enhanced by adding the microsomal fraction of rat hepatocytes, induced either with sodium barbital or with Aroclor 1254. The two trivalent compounds (chromium potassium sulfate and chromic chloride), with or without the microsomal fraction, were neither toxic nor mutagenic for the bacterial tester strains. Images PMID:326184

  10. 75 FR 67100 - Superalloy Degassed Chromium From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-01

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

  11. Measurement of chromium VI and chromium III in stainless steel welding fumes with electrom spectroscopy for chemical analysis and neutron activation analysis.

    PubMed

    Lautner, G M; Carver, J C; Konzen, R B

    1978-08-01

    Electron Spectroscopy for Chemical Analysis (ESCA) was explored as a means of studying the oxidation state of chromium in SMAC (coated electrode) stainless steel welding fume collected on Nucleopore filters in the laboratory. Chromuim VI and III (as a percent of the total chromium) obtained from ESCA analysis was applied to results from Neutron Activation Analysis (NAA) to yield an average of 69 microgram chromium VI per sample. Diphenylcarbazide/atomic absorption (DPC/AA) results are reported for samples submitted to an industrial laboratory. Possible chemical species and solubility of chromium VI in stainless steel fumes is discussed in light of analogy between the SMAC process and the manufacturing process for chromates.

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

    PubMed

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

    2016-04-01

    The simulation of Cr(VI) behavior in an unsaturated zone and aquifer, using a 3D experimental set-up were performed to illustrate the distribution, transport and transformation of Cr(VI), and further to reveal the potential harm of Cr(VI) after entering the groundwater. The result indicated that chromium(VI) was transported in the vertical direction, meanwhile, was transported in the horizontal direction under the influence of groundwater flow. The direction and distance away from the pollution source zone had great effect on the chromium(VI) concentration. At the sampling sites near the pollution source zone, there was a sudden increase of chromium(VI) concentration. The concentration of chromium(III) concentration in some random effluent samples was not detected. Chromium had not only transported but also had fraction and specie transformation in the unsaturated zone and aquifer. The relative concentration of residue fraction chromium was decreased with time. The content of Fe-Mn oxide fraction chromium was increased with time. The relative content of exchangeable and carbonate-bound fraction chromium was lower and the content variations were not obvious. Chromium(VI) (91-98%) was first reduced to chromium(III) rapidly. The oxidation reaction occurred later and the relative content of chromium(VI) was increased again. The presence of manganese oxides under favorable soil conditions can promote the reoxidation of Cr(III) to Cr(VI). PMID:26736171

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

    PubMed

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

    2016-04-01

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

  14. Controlling chromium slag pollution utilising scavengers: a case of Shandong Province, China.

    PubMed

    Liu, Changhao; Côté, Raymond P

    2015-04-01

    The problem of chromium slag pollution is a great challenge for China. It is now an urgent task for China to take effective measures to eliminate chromium slag pollution. This article examines the case of the treatment of chromium slag in Shandong Province and explores how chromium slag pollution can be eliminated in Shandong Province. It shows that the chromium slag stockpiled by the chemical plants was successfully utilised by local steel companies, who act as 'scavenger companies'. The driving mechanism, seeking a potential 'scavenger company' within the local region and the role of the local government on the case of Shandong Province are discussed. This article concludes that local steel companies can be utilised to effectively and efficiently treat the chromium slag while benefiting the steel companies. The local governments need to play multiple roles in solving the problem of chromium slag pollution. Seeking and identifying 'scavenger companies' within a region could be an important approach to reducing pollution within the region.

  15. Ailanthus Altissima and Phragmites Australis for chromium removal from a contaminated soil.

    PubMed

    Ranieri, Ezio; Fratino, Umberto; Petrella, Andrea; Torretta, Vincenzo; Rada, Elena Cristina

    2016-08-01

    The comparative effectiveness for hexavalent chromium removal from irrigation water, using two selected plant species (Phragmites australis and Ailanthus altissima) planted in soil contaminated with hexavalent chromium, has been studied in the present work. Total chromium removal from water was ranging from 55 % (Phragmites) to 61 % (Ailanthus). After 360 days, the contaminated soil dropped from 70 (initial) to 36 and 41 mg Cr/kg (dry soil), for Phragmites and Ailanthus, respectively. Phragmites accumulated the highest amount of chromium in the roots (1910 mg Cr/kg(dry tissue)), compared with 358 mg Cr/kg(dry tissue) for Ailanthus roots. Most of chromium was found in trivalent form in all plant tissues. Ailanthus had the lowest affinity for Cr(VI) reduction in the root tissues. Phragmites indicated the highest chromium translocation potential, from roots to stems. Both plant species showed good potentialities to be used in phytoremediation installations for chromium removal.

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

    PubMed

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

    2016-09-01

    Spatio-temporal cancer mortality studies in Spain have revealed patterns for some tumours which display a distribution that is similar across the sexes and persists over time. Such characteristics would be common to tumours that shared risk factors, including the chemical soil composition. The objective of the present study is to assess the association between levels of chromium and arsenic in soil and the cancer mortality. This is an ecological cancer mortality study at municipal level, covering 861,440 cancer deaths in 7917 Spanish mainland towns from 1999 to 2008. Chromium and arsenic topsoil levels (partial extraction) were determined by ICP-MS at 13,317 sampling points. To estimate the effect of these concentrations on mortality, we fitted Besag, York and Mollié models, which included, as explanatory variables, each town's chromium and arsenic soil levels, estimated by kriging. In addition, we also fitted geostatistical-spatial models including sample locations and town centroids (non-aligned data), using the integrated nested Laplace approximation (INLA) and stochastic partial differential equations (SPDE). All results were adjusted for socio-demographic variables and proximity to industrial emissions. The results showed a statistical association in men and women alike, between arsenic soil levels and mortality due to cancers of the stomach, pancreas, lung and brain and non-Hodgkin's lymphomas (NHL). Among men, an association was observed with cancers of the prostate, buccal cavity and pharynx, oesophagus, colorectal and kidney. Chromium topsoil levels were associated with mortality among women alone, in cancers of the upper gastrointestinal tract, breast and NHL. Our results suggest that chronic exposure arising from low levels of arsenic and chromium in topsoil could be a potential risk factor for developing cancer. PMID:27239676

  17. Development of ductile high-strength chromium alloys, phase 2

    NASA Technical Reports Server (NTRS)

    Filippi, A. M.

    1973-01-01

    Strength and ductility were evaluated for chromium alloys dispersion hardened with the putative TaC, TaB, CbC, and CbB compounds. TaC and TaB proved to be the most potent strengtheners, but when combined, their effect far outweighed that produced individually. Tests at 1422 K (2100 F) on an alloy containing these two compounds at the combined level of 0.5 m/o revealed a 495 MN/sq m (70 ksi) tensile strength for wrought material, and a 100 hour rupture strength of 208 MN/sq m (30 ksi) when solution annealed and aged to maximize creep resistance. These levels of high temperature strength greatly exceed that reported for any other chromium-base alloy. The ductile-to-brittle transition temperature (DBTT) of the two phase strengthened alloy occurred at approximately 588 K (600 F) when heat treated to optimize creep strength and was not improved by fabrication to produce a wrought and recovered microstructure. The lowest DBTT measured on any of the alloys investigated was 422 K (300 F). Strengthening phases actually formed in Cr-Ta-B and Cr-Cb-B compositions are probable M2CrB2 (M=Ta or Cb) compounds of tetragonal crystal structure. The likely habit relationship between these compounds and chromium is postulated. Cube habit coherency was identified for TaC precipitation in chromium by electron microscopy. In another study, the maximum solubility of carbon in chromium was indicated to lie between 3/4 and 1 a/o and that of boron to be 1/2 a/o.

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

    PubMed

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

    2016-09-01

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

  19. Manganese chromium isotope systematics of carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Shukolyukov, A.; Lugmair, G. W.

    2006-10-01

    In this article we present the results of Cr isotope investigations of different types of carbonaceous chondrites and of the pallasite Eagle Station. The 53Cr/ 52Cr ratios in the bulk samples of carbonaceous chondrites are correlated with 55Mn/ 52Cr ratios. The slope of the correlation line yields a 53Mn/ 55Mn ratio of (8.5 ± 1.5) × 10 - 6 at the time of Mn/Cr fractionation. Mapping this ratio onto an absolute time scale yields a time for this event of 4568.1 + 0.8/- 1.1 Ma ago. This time is very similar to the formation age of Efremovka CAIs of 4567.2 ± 0.6 Ma [Y. Amelin, A. N. Krot, I. D. Hutcheon, A. A. Ulyanov, Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions, Science 297 (2002) 1678-1683], to a time of the chondrule formation of 4568 ± 1 Ma ago [L.E. Nyquist, D. Lindstrom, D. Mittlefehldt, C.-Y. Shih, H. Wiesmann, S. Wentworth, R. Martinez, Manganese-chromium formation intervals for chondrules from the Bishunpur and Chainpur meteorites, Meteorit. Planet. Sci. 36 (2001) 911-938], which, most likely, constrains early global high-temperature Mn/Cr fractionation in a nebular setting. The bulk samples of carbonaceous chondrites exhibit clear 54Cr excesses ( 54Cr *) that are correlated with the 53Cr excesses ( 53Cr *) and also with Mn/Cr ratios. One possible explanation of this correlation is that 54Cr * is also radiogenic, like 53Cr *, and was formed by the decay of the short-lived parent radionuclide 54Mn. The very short half-life of 54Mn of 312 days would require that both short-lived radionuclides 53Mn and 54Mn were generated locally in spallation reactions during the early period of an active sun. The alternative and possibly more plausible explanation is the heterogeneous addition of presolar material. The presolar component, enriched in 54Cr, is mostly contained in the matrix of carbonaceous chondrites. The relative amount of matrix decreases in the sequence CI > CM > CO,CV. A large proportion of Mn is associated with the matrix while

  20. 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.

  1. Republic P-47B Thunderbolt

    NASA Technical Reports Server (NTRS)

    1942-01-01

    Republic P-47B Thunderbolt: The Republic P-47B Thunderbolt was one of the great fighters used by the U. S. Army Air Force in World War II, and crews praised its ability to absorb punishment. This P-47B was used by NACA engineers to study the horizontal tail loads experienced by a fighter during abrupt maneuvers.

  2. Republic P-47C Thunderbolt

    NASA Technical Reports Server (NTRS)

    1943-01-01

    Republic P-47C Thunderbolt: Republic's P-47 was one example of a perfect marriage of airframe and power plant. The engine of this P-47C was still under study, as can be ascertained by the survey rake for measuring propeller thrust. This rake protrudes from the fuselage just behind the cowling ahead and in front of the wing.

  3. Republic P-47C Thunderbolt

    NASA Technical Reports Server (NTRS)

    1943-01-01

    Republic P-47C Thunderbolt: Republic's P-47 was one example of a perfect marriage of airframe and power plant. The engine of this P-47C was still under study, as can ascertained by the survey rake for measuring propeller thrust. This rake protrudes from the fuselage just behind the cowling ahead and in front of the wing.

  4. Urinary levels of nickel and chromium associated with dental restoration by nickel–chromium based alloys

    PubMed Central

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

    2013-01-01

    This paper aims to investigate if the dental restoration of nickel–chromium based alloy (Ni–Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni–Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of <1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of <1, 1 to <3 and 3 to <6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni–Cr alloy restoration need to be investigated. PMID:23579466

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

    PubMed

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

    2013-03-01

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

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

    PubMed

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

    2013-01-31

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

  7. Finished leather waste chromium acid extraction and anaerobic biodegradation of the products.

    PubMed

    Ferreira, Maria J; Almeida, Manuel F; Pinho, Sílvia C; Santos, Isabel C

    2010-06-01

    Due to the amounts of chromium in the leachate resulting from leather leaching tests, chromium sulfate tanned leather wastes are very often considered hazardous wastes. To overcome this problem, one option could be recovering the chromium and, consequently, lowering its content in the leather scrap. With this objective, chromium leather scrap was leached with sulfuric acid solutions at low temperature also aiming at maximizing chromium removal with minimum attack of the leather matrix. The effects of leather scrap dimension, sulfuric acid and sodium sulfate concentration in the solutions, as well as extraction time and temperature on chromium recovery were studied, and, additionally, organic matrix degradation was evaluated. The best conditions found for chromium recovery were leather scrap conditioning using 25mL of concentrated H(2)SO(4)/L solution at 293 or 313K during 3 or 6days. Under such conditions, 30-60+/-5% of chromium was recovered and as low as 3-6+/-1% of the leather total organic carbon (TOC) was dissolved. Using such treatment, the leather scrap area and volume are reduced and the residue is a more brittle material showing enhanced anaerobic biodegradability. Although good recovery results were achieved, due to the fact that the amount of chromium in eluate exceeded the threshold value this waste was still hazardous. Thus, it needs to be methodically washed in order to remove all the chromium de-linked from collagen.

  8. Crossover and valence band Kβ X-rays of chromium oxides

    NASA Astrophysics Data System (ADS)

    Fazinić, Stjepko; Mandić, Luka; Kavčič, Matjaž; Božičević, Iva

    2011-06-01

    Kβ X-ray spectra of chromium metal and selected chromium oxides were measured twice using medium resolution flat crystal spectrometer and high resolution spectrometer employing Johansson geometry after excitation with 2 MeV proton beams. The positions and intensities of crossover ( Kβ″) and valence ( Kβ2,5) band X-rays relative to the primary Kβ X-ray components were extracted in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms and theoretical predictions. The obtained results in peak relative positions and intensities were analyzed in order to study dependence on the chromium oxidation states and chromium-oxygen bond lengths in selected chromium oxides. Our results obtained by both spectrometers confirm that the linear trend observed for the valence peak relative energy shift as a function of chromium oxidation number does not depend on the experimental resolution. Experimental results for normalized intensities (i.e. relative intensities divided with the number of chromium-oxygen pairs) of crossover and valence band X-rays obtained by both spectrometers are in very good agreement, and follow exponential relationship with the average Cr―O bond lengths in corresponding chromium oxides. The observed trends in crossover and valence X-rays normalized intensities could be used to measure the average chromium-oxygen bond length in various chromium oxides, with the sum of both crossover and valence X-ray normalized intensities being the most sensitive measure.

  9. Method for heat treating iron-nickel-chromium alloy

    DOEpatents

    Not Available

    1980-04-03

    A method is described for heat treating an age-hardenable iron-nickel-chromium alloy to obtain a morphology of the gamma-double prime phase enveloping the gamma-prime, the alloy consisting essentially of about 25 to 45% nickel, 10 to 16% chromium, 1.5 to 3% of an element selected from the group consisting of molybdenum and niobium, about 2% titanium, about 3% aluminum, and the remainder substantially all iron. To obtain optimum results, the alloy is heated to a temperature of 1025 to 1075/sup 0/C for 2 to 5 minutes, cold-worked about 20 to 60%, aged at a temperature of about 775/sup 0/C for 8 hours followed by an air-cool, and then heated to a temperature in the range of 650 to 700/sup 0/C for 2 hours followed by an air-cool.

  10. Method for heat treating iron-nickel-chromium alloy

    DOEpatents

    Korenko, Michael K.

    1980-01-01

    A method for heat treating an age-hardenable iron-nickel-chromium alloy to obtain a morphology of the gamma-double prime phase enveloping the gamma-prime phase, the alloy consisting essentially of about 40 to 50% nickel, 7.5 to 14% chromium, 1.5 to 4% niobium, 0.3 to 0.75% silicon, 1 to 3% titanium, 0.1 to 0.5% aluminum, 0.02 to 1% carbon, 0.002 to 0.0015% boron and the remain substantially all iron. To obtain optimal results, the alloy is cold-worked 20 to 60% followed by heating at 1050.degree. C. for 1/2 hour with an air-cool plus heating at 800.degree. C. for 2 hours with a furnace cool to 625.degree. C. The alloy is then held at 625.degree. C. for 12 hours, followed by an air-cool.

  11. Method for heat treating iron-nickel-chromium alloy

    DOEpatents

    Merrick, Howard F.; Korenko, Michael K.

    1982-01-01

    A method for heat treating an age-hardenable iron-nickel-chromium alloy to obtain a bimodal distribution of gamma prime phase within a network of dislocations, the alloy consisting essentially of about 25% to 45% nickel, 10% to 16% chromium, 1.5% to 3% of an element selected from the group consisting of molybdenum and niobium, about 2% titanium, about 3% aluminum, and the remainder substantially all iron. To obtain optimum results, the alloy is heated to a temperature of 1025.degree. C. to 1075.degree. C. for 2-5 minutes, cold-worked about 20% to 60%, aged at a temperature of about 775.degree. C. for 8 hours followed by an air-cool, and then heated to a temperature in the range of 650.degree. C. to 700.degree. C. for 2 hours followed by an air-cool.

  12. Cobalt-chromium-titanium alloy for removable partial dentures.

    PubMed

    Iwama, C Y; Preston, J D

    1997-01-01

    Pure elemental titanium was alloyed with cobalt and chromium in dilutions of 4%, 5%, and 6% to evaluate the suitability of the resulting alloy for removable partial denture frameworks. The physical properties of the Co-Cr-Ti alloy were compared to the properties of a commercial pure titanium and Vitallium. Clasp replicas were cast in Co-Cr-Ti and Vitallium and subjected to cyclic deflection. Representative specimens from the fatigue failure tests were then evaluated using scanning electron microscopy and analyzed for elemental content. The 5% titanium dilution of cobalt-chromium proved to have the best physical properties and was used for comparison with the pure titanium and Vitallium. The Co-Cr-5% Ti had significantly better physical properties than pure titanium and a greater flexure fatigue limit than the Vitallium alloy.

  13. Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

    PubMed

    Marzouk, Ikhlass; Dammak, Lassaad; Hamrouni, Béchir

    2013-02-01

    In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

  14. A platinum-chromium steel for cardiovascular stents.

    PubMed

    O'Brien, Barry J; Stinson, Jon S; Larsen, Steve R; Eppihimer, Michael J; Carroll, William M

    2010-05-01

    The desire to reduce the strut thickness of cardiovascular stents has driven the development of a new high strength radiopaque alloy, based on additions of platinum to a chromium-rich iron based matrix. This paper reports on initial development of the alloy and the rationale for selection of the composition. Data is presented for tensile and microstructural characterization, surface oxide analysis, corrosion resistance and endothelial cell response of the alloy. The results demonstrate the solid solution strengthening effect of the platinum, with an average yield strength of 480 MPa achieved. The material surface consists of primarily chromium oxide which contributes to the high corrosion resistance observed. The cell assay result suggests that surfaces of this Pt-enhanced alloy endothelialize in a manner comparable to stainless steel.

  15. Study of an analytical method for hexavalent chromium.

    PubMed

    Bhargava, O P; Bumsted, H E; Grunder, F I; Hunt, B L; Manning, G E; Riemann, R A; Samuels, J K; Tatone, V; Waldschmidt, S J; Hernandez, P

    1983-06-01

    The diphenylcarbazide colorimetric method was evaluated by analyzing spiked PVC filters prepared by an AIHA-accredited consultant laboratory for chromium (VI). All seven participating laboratories received the samples and performed the analyses at the same time. Three laboratories simultaneously tested three alternative analytical procedures. Reduced amounts of chromium (VI) were found by both the consultant and participating laboratories when using the test procedure and one of the alternative methods. Two of the alternative analytical methods, both of which involve an alkaline extraction procedure, provided higher recoveries and more precise values for the test filters. It appears that the alkaline extraction procedure may be more appropriate for occupational health samples taken in steel industry environments which may include several interferents. Suggestions are made for further studies to determine the most appropriate analytical method.

  16. A mathematical model for the iron/chromium redox battery

    NASA Technical Reports Server (NTRS)

    Fedkiw, P. S.; Watts, R. W.

    1984-01-01

    A mathematical model has been developed to describe the isothermal operation of a single anode-separator-cathode unit cell in a redox-flow battery and has been applied to the NASA iron/chromium system. The model, based on porous electrode theory, incorporates redox kinetics, mass transfer, and ohmic effects as well as the parasitic hydrogen reaction which occurs in the chromium electrode. A numerical parameter study was carried out to predict cell performance to aid in the rational design, scale-up, and operation of the flow battery. The calculations demonstrate: (1) an optimum electrode thickness and electrolyte flow rate exist; (2) the amount of hydrogen evolved and, hence, cycle faradaic efficiency, can be affected by cell geometry, flow rate, and charging procedure; (3) countercurrent flow results in enhanced cell performance over cocurrent flow; and (4) elevated temperature operation enhances cell performance.

  17. NaCl-induced accelerated oxidation of chromium

    SciTech Connect

    Shinata, Y.; Nishi, Y.

    1986-10-01

    This paper describes new phenomena about chloride-induced ;accelerated oxidation of chromium. Thermal analysis was adopted to examine the oxidation, which was studied particularly in the case of NaCl. The presence of NaCl remarkably accelerates the oxidation of chromium. The process occurs below the melting point of NaCl, and the main reaction product is Cr/sub 2/O/sub 3/. In the accelerated oxidation NaCl plays a catalytic role because it is not consumed significantly in the process. DTA analysis reveals that the heat of reaction also accelerates the rate of oxidation, especially at an early stage of the reaction. The accelerated oxidation takes place similarly under the presence of chlorides other than NaCl, but the oxidation rate depends on the kind of salt. Therefore the Cl/sup -/ anion plays an important role in the process, while the nature of the cation affects the rate of acceleration.

  18. [Contribution of the incidence of urban sewage spreading to dietary chromium].

    PubMed

    Adrian, J

    1991-01-01

    The sewage sludges contain fertilizing matters that justify their use in agriculture. Simultaneously, they hold minerals that are directly proportional to the nature and intensity of industrial activity. The more abundant are chromium, lead, zinc; cadmium and mercury are also found. The concentration in chromium varies from 0.2 to 20.0 g/kg of dry matter. Its assimilation by the rootlet and, later, its intestinal absorption, are essentially dependent on its chemical state; the hexavalent forms have a high biodisponibility and are more toxic than the trivalent compounds. In vegetals, the assimilated chromium is stopped in the root, associated to iron hydrates; a small fraction reaches the leaves and a weaker part comes up to the grain. (Table I). If the concentration of chromium--mainly hexavalent salts--is very important in soil, the mechanism of regulation in the rootlet becomes inefficacious and chromium diffuses in the whole plant (Table II). The development of spraying of sludges and composts will increase the quantity and efficiency of chromium in vegetals, because of various factors: the wastes of many industries: chromium plating plants, tanneries, painting and dyeing industries throw out hexavalent chromium; if the sewage sludges are purified by an irradiation treatment, it will tend to oxidize the whole chromium in hexavalent forms; at last, the presence of sewage sludges in the arable soil favours the assimilation of chromium by inhibiting that of iron (Figure 1). Then, in absence of iron hydrates that regularize the diffusion of chromium in the plant, this latter tends to overrun more easily the aerial tissues and organs of vegetals. On the whole, the spraying of sewage sludges supplies the soil with chromium that will easily be assimilated by the plant, considering that it will be mainly at an hexavalent state. Compared with other trace elements held in the sludges, chromium is assimilated by the plant in a clearly more important proportion (Table III

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

    PubMed Central

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

    2013-01-01

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081

  20. Diffusion and leachability index studies on stabilization of chromium contaminated soil using fly ash.

    PubMed

    Kanchinadham, Sri Bala Kameswari; Narasimman, L M; Pedaballe, Vihita; Kalyanaraman, Chitra

    2015-10-30

    Experiments were performed to establish a feasible treatment process for the solidification and stabilization (S/S) of soil contaminated by leaching of Cr(VI) from Chromite ore processing residue (COPR). Reduction of the highly mobile Cr(VI) was performed using calcium polysulfide (CaS5) with a dosage of 3 times the molar stoichiometric ratio for the initial concentration of Cr(VI) present in the chromium contaminated soil (CCS). The CCS was solidified and stabilized (S/S) using fly ash (FA) in various proportions i.e., 1:1, 1:2, 1:3 (FA: CCS) with and without using reducing agent i.e., CaS5. Leachability tests such as Toxicity Characteristic Leaching Procedure (TCLP) and semi-dynamic long term leachability tests indicated that the CaS5 was effective in reduction of Cr(VI) followed by the S/S process. Leachability Index was derived from the results of the semi-dynamic long term leachability tests and was between 8 and 9, indicating that FA is an effective treatment for disposal into secured landfills for CCS. The characteristic compressive strength of the CaS5 treated CCS with FA mortar blocks were between 24.47 and 40.49 kg/cm(2). Considering the cost of CaS5 and FA, a total expenditure of Rs. 7826 i.e., US $ 130.4 would be required for remediation of one tonne of CCS.

  1. Diffusion and leachability index studies on stabilization of chromium contaminated soil using fly ash.

    PubMed

    Kanchinadham, Sri Bala Kameswari; Narasimman, L M; Pedaballe, Vihita; Kalyanaraman, Chitra

    2015-10-30

    Experiments were performed to establish a feasible treatment process for the solidification and stabilization (S/S) of soil contaminated by leaching of Cr(VI) from Chromite ore processing residue (COPR). Reduction of the highly mobile Cr(VI) was performed using calcium polysulfide (CaS5) with a dosage of 3 times the molar stoichiometric ratio for the initial concentration of Cr(VI) present in the chromium contaminated soil (CCS). The CCS was solidified and stabilized (S/S) using fly ash (FA) in various proportions i.e., 1:1, 1:2, 1:3 (FA: CCS) with and without using reducing agent i.e., CaS5. Leachability tests such as Toxicity Characteristic Leaching Procedure (TCLP) and semi-dynamic long term leachability tests indicated that the CaS5 was effective in reduction of Cr(VI) followed by the S/S process. Leachability Index was derived from the results of the semi-dynamic long term leachability tests and was between 8 and 9, indicating that FA is an effective treatment for disposal into secured landfills for CCS. The characteristic compressive strength of the CaS5 treated CCS with FA mortar blocks were between 24.47 and 40.49 kg/cm(2). Considering the cost of CaS5 and FA, a total expenditure of Rs. 7826 i.e., US $ 130.4 would be required for remediation of one tonne of CCS. PMID:25942695

  2. Spectroscopic characteristics of chromium doped mullite glass-ceramics

    SciTech Connect

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

    1988-06-01

    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/sup -20/ cm/sup 2/. This, together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  3. XANES of Chromium in Sludges Used as Soil Ameliorants

    SciTech Connect

    Naftel, S.J.; Martin, R.R.; Sham, T.K.; Hart, B.; Powell, M.A.

    2010-12-01

    Samples of sewage sludges proposed for use as soil ameliorants in an Indo-Canadian project were tested for chromium content. Standard aqua regia extractions found one sludge to have excessive amounts of Cr. X-ray absorption near-edge structure (XANES) spectroscopy, however, indicated that the Cr was present in the relatively benign Cr(III) oxidation state in all the sludge samples.

  4. Study of Chromium Oxide Activities in EAF Slags

    NASA Astrophysics Data System (ADS)

    Yan, Baijun; Li, Fan; Wang, Hui; Sichen, Du

    2016-02-01

    The activity coefficients of chromium in Cu-Cr melts were determined by equilibrating liquid copper with solid Cr2O3 in CO-CO2 atmosphere. The temperature dependence of the activity coefficients of chromium in Cu-Cr melts could be expressed as lg γ_{Cr}(s)^{0} = { 3 2 5 9( ± 1 8 6} )/T - 0. 5 9( { ± 0. 1} ). Based on the above results, the activities of bivalent and trivalent chromium oxide in some slags at 1873 K (1600 °C) were measured. The slags were equilibrated with Cu-Cr melts under two oxygen partial pressures ( {p_{O}_{ 2} }} } = 6.9 × 10-4 and 1.8 × 10-6 Pa, respectively). The morphology of the quenched slags and the solubility of chromium oxide in the melts were investigated by EPMA, SEM, and XRD. Under both oxygen partial pressures, the slags were saturated by the solid solution MgAl2- x Cr x O4- δ . At the low oxygen partial pressure (1.8 × 10-6 Pa), the content of Cr in the liquid phase varied from 0.4 to 1.6 mass pct with the total Cr content in the slags increasing from 1.3 to 10.8 mass pct. At the high oxygen partial pressure (6.9 × 10-4 Pa), the content of Cr in the liquid phase decreased to the level of 0.2 to 0.6 mass pct. Both the activities of CrO and Cr2O3 in slag were found to increase approximately linearly with the increase of the total Cr content in slag. While the oxygen partial pressure had minor effect on the activity of Cr2O3 in the slag, it had significant effect on the activity of CrO.

  5. Occupational Exposure to Chromium of Assembly Workers in Aviation Industries.

    PubMed

    Genovese, G; Castiglia, L; Pieri, M; Novi, C; d'Angelo, R; Sannolo, N; Lamberti, M; Miraglia, N

    2015-01-01

    Aircraft are constructed by modules that are covered by a "primer" layer, which can often contain hexavalent chromium [Cr(VI)], known carcinogen to humans. While the occupational exposure to Cr(VI) during aircraft painting is ascertained, the exposure assessment of assembly workers (assemblers) requires investigations. Three biological monitoring campaigns (BM-I,II,III) were performed in an aviation industry, on homogeneous groups of assemblers (N = 43) and controls (N = 23), by measuring chromium concentrations in end-shift urine collected at the end of the working week and the chromium concentration difference between end- and before-shift urines. BM-I was conducted on full-time workers, BM-II was performed on workers after a 3-4 day absence from work, BM-III on workers using ecoprimers with lower Cr(VI) content. Samples were analyzed by atomic absorption spectroscopy and mean values were compared by T-test. Even if Cr concentrations measured during BM-I were lower than Biological Exposure Indices by ACGIH, statistically significant differences were found between urinary Cr concentrations of workers and controls. Despite 3-4 days of absence from work, urinary chromium concentrations measured during BM-II were still higher than references from nonoccupationally exposed populations. In the BM-III campaign, the obtained preliminary results suggested the efficacy of using ecoprimers. The healthcare of workers exposed to carcinogenic agents follows the principle of limiting the exposure to "the minimum technically possible". The obtained results evidence that assemblers of aviation industries, whose task does not involve the direct use of primers containing Cr(VI), show an albeit slight occupational exposure to Cr(VI), that must be carefully taken into consideration in planning suitable prevention measures during risk assessment and management processes.

  6. Magnesium, zinc, and chromium nutriture and physical activity.

    PubMed

    Lukaski, H C

    2000-08-01

    Magnesium, zinc, and chromium are mineral elements required in modest amounts to maintain health and optimal physiologic function. For physically active persons, adequate amounts of these micronutrients are needed in the diet to ensure the capacity for increased energy expenditure and work performance. Most physically active individuals consume diets that provide amounts of magnesium and zinc sufficient to meet population standards. Women tend to consume less of these minerals than is recommended, in part because they eat less food than men. Inadequate intakes of magnesium and zinc have been reported for participants in activities requiring restriction of body weight. Dietary chromium is difficult to estimate because of a lack of appropriate reference databases. Acute, intense activity results in short-term increases in both urine and sweat losses of minerals that apparently diminish during recovery in the days after exercise. Supplemental magnesium and zinc apparently improve strength and muscle metabolism. However, evidence is lacking as to whether these observations relate to impaired nutritional status or a pharmacologic effect. Chromium supplementation of young men and women does not promote muscle accretion, fat loss, or gains in strength. Physically active individuals with concerns about meeting guidelines for nutrient intake should be counseled to select and consume foods with high nutrient densities rather than to rely on nutritional supplements. The indiscriminate use of mineral supplements can adversely affect physiologic function and impair health.

  7. Changes in oxidation state of chromium during LDEF exposure

    NASA Technical Reports Server (NTRS)

    Golden, Johnny L.

    1992-01-01

    The solar collector used for the McDonnell-Douglas Cascade Variable Heat Pipe, Experiment A0076 (Michael Grote - Principal Investigator) was finished with black chromium plating as a thermal control coating. The coating is metallic for low emittance, and is finely microcrystalline to a dimension which yields its high absorptivity. An underplate of nickel was applied to the aluminum absorber plate in order to achieve optimal absorptance characteristics from the black chromium plate surface. Experiment A0076 was located at tray position F9, receiving a projected 8.7 x 10 exp 21 atomic oxygen atoms/sq cm and 11,200 ESH solar radiation. During retrieval, it was observed that the aluminized kapton thermal blankets covering most of the tray were severely eroded by atomic oxygen, and that a 'flap' of aluminum foil was overlaying a roughly triangular shaped portion of the absorber panel. The aluminum foil 'flap' was lost sometime between the Long Duration Exposure Facility (LDEF) retrieval and deintegration. At deintegration, the black chromium was observed to have discolored where it had been covered by the foil 'flap'. A summary of the investigation into the cause of the discoloration is presented.

  8. Bioremediation of hexavalent chromium by a cyanobacterial mat

    NASA Astrophysics Data System (ADS)

    Shukla, Dhara; Vankar, Padma S.; Srivastava, Sarvesh Kumar

    2012-12-01

    The study comprises the use of cyanobacterial mat (collected from tannery effluent site) to remove hexavalent chromium. This mat was consortium of cyanobacteria/blue-green algae such as Chlorella sp., Phormidium sp. and Oscillatoria sp. The adsorption experiments were carried out in batches using chromium concentrations 2-10, 15-30 and 300 ppm at pH 5.5-6.2. The adsorption started within 15 min; however, 96 % reduction in metal concentration was observed within 210 min. The adsorption phenomenon was confirmed by Fourier transform-infrared spectroscopy and energy dispersive X-ray analysis. This biosorption fitted Freundlich adsorption isotherm very well. It was observed that the best adsorption was at 4 ppm, and at 25 ppm in the chosen concentration ranges. Scanning electron micrograph showed the physiology of mat, indicating sites for metal uptake. The main focus was collection of the cyanobacterial mat from local environments and its chromium removal potential at pH 5.5-6.2.

  9. Chromium and arsenic in contaminated soils (Review of publications)

    NASA Astrophysics Data System (ADS)

    Vodyanitskii, Yu. N.

    2009-05-01

    In the last decades, the chromium clarke in the world’s soils has been revised and reduced; at present, it is equal to 70 mg/kg. No maximal permissible concentration is accepted for the total chromium content in the soils of Russia; it appears reasonable to use the Western European and North American standards in Russia and to take the average value of the maximal permissible concentration equal to 200 mg Cr/kg. Chromium toxicity depends on its oxidizing status. The hazardous effect decreases with the reduction of Cr(VI) to Cr(III). There are various chemical reducers of Cr(VI), including sulfides, dissolved organic substance, aqueous Fe(II) and minerals enriched in Fe(II), and Fe(0). As-containing ore tailings represent a powerful source of technogenic arsenic. Significant environment contamination with natural As is registered in a number of Asian countries. The maximal permissible concentration of total arsenic is equal to 2 mg/kg in Russian soils; it is probably underestimated, because it is lower than the As clarke in soil (5 mg/kg). The approximately permissible concentration (APC) values for As look more reasonable. Arsenic toxicity depends on its oxidation degree: As(III) is 2-3 times more toxic than As(V).

  10. Growth of chromium carbide in a hot wall DLICVD reactor.

    PubMed

    Boisselier, G; Maury, F; Schuster, F

    2011-09-01

    Chromium carbide coatings were grown at 748 K in a hot wall CVD reactor fed by sublimation of bis(benzene)chromium, BBC (MOCVD) and by direct liquid injection using a BBC/toluene solution (DLICVD). The two types of coatings exhibit an amorphous structure and the same C content (22 at.%). DLICVD permits delivering higher mass flow rate of precursors and consequently the growth rate is 3 times higher and the thickness uniformity is better than using MOCVD. Chromium metal deposition has also been investigated by DLICVD in this hot wall reactor using BBC/toluene/additive as precursor. The purpose of the additive is to block carbide formation. Two additives have been studied: (i) hexachlorobenzene (C6Cl6) and (ii) thiophenol (C6H5SH). The ratio additive/BBC required for Cr metal deposition is a few percent. In this process, C6Cl6 is not decomposed and only traces of Cl (0.4 at.%) are found in the coatings. For a ratio C6Cl6/BBC > 27% the growth of any coating is blocked. The gas phase containing C6H5SH is more reactive since the onset of deposition occurs approximately 50 K before the temperature of the chlorinated compound. Furthermore, a sulfur contamination of 3 at.% has been analyzed in the coatings revealing a partial decomposition of the additive. The results are detailed and discussed in relation with previous works. PMID:22097571

  11. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    NASA Astrophysics Data System (ADS)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  12. 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 %.

  13. Hexavalent chromium emissions from aerospace operations: A case study

    SciTech Connect

    Chaurushia, A.; Bajza, C.

    1994-12-31

    Northrop Aircraft Division (NAD) is subject to several air toxic regulations such as EPA SARA Title 3, California Assembly Bill 2588 (AB2588), and Proposition 65 and is a voluntary participant in air toxic emissions reduction programs such as the EPA 33/50 and MERIT Program. To quantify emissions, NAD initially followed regulatory guidelines which recommend that emission inventories of air toxics be based on engineering assumptions and conservative emission factors in absence of specific source test data. NAD was concerned that Chromium VI emissions from NAD`s spray coating and chemical tank line operations were not representative due to these techniques. More recently, NAD has relied upon information from its ongoing source testing program to determine emission rates of Chromium VI. Based on these source test results, NAD revised emission calculations for use in Chromium VI inventories, impact assessments and control strategies. NAD has been successful in demonstrating a significant difference between emissions calculated utilizing the source test results and emissions based on the traditional mass balance using agency suggested methods.

  14. Eolian transport of geogenic hexavalent chromium to ground water

    USGS Publications Warehouse

    Wood, W.W.; Clark, D.; Imes, J.L.; Councell, T.B.

    2010-01-01

    A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr+6) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 μg/L Cr+6) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr+3 in the minerals is oxidized to Cr+6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr+6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr+6 concentration in the aquifer.

  15. Origin and concentration profile of chromium in a Greek aquifer.

    PubMed

    Dermatas, Dimitris; Mpouras, Thanasis; Chrysochoou, Maria; Panagiotakis, Iraklis; Vatseris, Christos; Linardos, Nikos; Theologou, Eleni; Boboti, Nefeli; Xenidis, Anthimos; Papassiopi, Nymphodora; Sakellariou, Lefki

    2015-01-01

    In this paper the origin and concentration of chromium (Cr) in an ophiolitic aquifer in Vergina, northern Greece were investigated. The study area has only agricultural activity so that industrial Cr contamination was precluded. Soil sampling included topsoil and drillcore samples collected down to 98 m depth. Groundwater samples were collected from three existing wells and a spring at the area and from different depths of the soil boring using the discrete sampling method. Mineralogical analysis of soils confirmed the presence of ultramafic minerals, including chrysotile and chromite. Soil elemental analysis showed significant concentration of total chromium (Crtot; max 12,000 mg/kg) and hexavalent chromium (Cr(VI); max 7.5mg/kg). Significant Crtot (91 μg/L) and Cr(VI) (64 μg/L) concentrations exceeding the drinking water limit of 50 μg/L were also detected in groundwater. In both the discrete soil and groundwater samples a decreasing trend of Cr(VI) concentration was observed with increasing depth, while Crtot increased. The increasing trend in Crtot is attributed to the increasing contribution of unweathered ultramafic minerals with depth, while the decreasing Cr(VI) may be related to the increasing soil pH that does not favor Cr(III) oxidation by Mn-oxides.

  16. Stainless Steel Leaches Nickel and Chromium into Foods During Cooking

    PubMed Central

    Kamerud, Kristin L.; Hobbie, Kevin A.; Anderson, Kim A.

    2014-01-01

    Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel saucepan; cooking times of 2 to 20 hours, ten consecutive cooking cycles, and four commercial tomato sauces. After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After six hours of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34 fold and Cr increased approximately 35 fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, though significant metal contributions to foods were still observed. The tenth cooking cycle, resulted in an average of 88 μg of Ni and 86 μg of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage. PMID:23984718

  17. Chromium(VI) bioremediation by aquatic macrophyte Callitriche cophocarpa Sendtn.

    PubMed

    Augustynowicz, Joanna; Grosicki, Marek; Hanus-Fajerska, Ewa; Lekka, Małgorzata; Waloszek, Andrzej; Kołoczek, Henryk

    2010-05-01

    Callitriche cophocarpa (water-starwort)--aquatic widespread macrophyte--was found to be an excellent chromium accumulator. The plants were exposed to various chromium(VI) concentration ranging from 50 to 700 microM in a hydroponic culture up to ca. 3 weeks. Physiological conditions of shoots were monitored via measuring potential photosynthesis quantum efficiency (F(v)/F(m)) and photosynthetic pigment contents. Additionally, the structure of leaves was analyzed using optical and atomic force microscopy (AFM). It has been shown that plants grown in 50 microM Cr(VI) solution exhibited photosynthetic activity and shoot and leaf morphology similar to control plants. Moreover, at the same time the average Cr concentration in their shoots reached about 470 mg kg(-1)d.w. after 10d and up to 1000 mg kg(-1)d.w. after 3 weeks of culture while in control plants did not exceed a few mgkg(-1)d.w. Our results point to Callitriche cophocarpa as a very promising species to be used in the investigation of chromium(VI) phytoremediation mechanisms as well as a good candidate for wastewaters remediation purpose. PMID:20385400

  18. Stainless steel leaches nickel and chromium into foods during cooking.

    PubMed

    Kamerud, Kristin L; Hobbie, Kevin A; Anderson, Kim A

    2013-10-01

    Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized. This study examined stainless steel grades, cooking time, repetitive cooking cycles, and multiple types of tomato sauces for their effects on nickel and chromium leaching. Trials included three types of stainless steels and a stainless steel saucepan, cooking times of 2-20 h, 10 consecutive cooking cycles, and four commercial tomato sauces. After a simulated cooking process, samples were analyzed by ICP-MS for Ni and Cr. After 6 h of cooking, Ni and Cr concentrations in tomato sauce increased up to 26- and 7-fold, respectively, depending on the grade of stainless steel. Longer cooking durations resulted in additional increases in metal leaching, where Ni concentrations increased 34-fold and Cr increased approximately 35-fold from sauces cooked without stainless steel. Cooking with new stainless steel resulted in the largest increases. Metal leaching decreases with sequential cooking cycles and stabilized after the sixth cooking cycle, although significant metal contributions to foods were still observed. The tenth cooking cycle resulted in an average of 88 μg of Ni and 86 μg of Cr leached per 126 g serving of tomato sauce. Stainless steel cookware can be an overlooked source of nickel and chromium, where the contribution is dependent on stainless steel grade, cooking time, and cookware usage.

  19. Achieving Zero Stress in Iridium, Chromium, and Nickle Thin Films

    NASA Technical Reports Server (NTRS)

    Broadway, David M.; Weimer, Jeffrey; Gurgew, Danielle; Lis, Tomasz; Ramsey, Brian D.; O'Dell, Stephen L.; Ames, A.; Bruni, R.

    2015-01-01

    We examine a method for achieving zero intrinsic stress in thin films of iridium, chromium, and nickel deposited by magnetron sputter deposition. The examination of the stress in these materials is motivated by efforts to advance the optical performance of light-weight x-ray space telescopes into the regime of sub-arc second resolution that rely on control of the film stress to values within 10-100 MPa. A characteristic feature of the intrinsic stress behavior in chromium and nickel is their sensitivity to the magnitude and sign of the intrinsic stress with argon gas pressure, including the existence of a critical pressure that results in zero film stress. This critical pressure scales linearly with the film's density. While the effect of stress reversal with argon pressure has been previously reported by Hoffman and others for nickel and chromium, we have discovered a similar behavior for iridium. Additionally, we have identified zero stress in iridium shortly after island coalescence. This feature of film growth is used for achieving a total internal stress of -2.89 MPa for a 15.8 nm thick iridium film. The surface roughness of this low-stress film was examined using scanning probe microscopy (SPM) and x-ray reflectivity (XRR) at CuKa and these results presented and discussed.

  20. Structural and magnetic properties of chromium doped zinc ferrite

    SciTech Connect

    Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena; Mohammed, E. M.; Joseph, Shaji

    2014-01-28

    Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)

  1. Dietary chromium supplementation for targeted treatment of diabetes patients with comorbid depression and binge eating.

    PubMed

    Brownley, Kimberly A; Boettiger, Charlotte A; Young, Laura; Cefalu, William T

    2015-07-01

    Dietary chromium supplementation for the treatment of diabetes remains controversial. The prevailing view that chromium supplementation for glucose regulation is unjustified has been based upon prior studies showing mixed, modest-sized effects in patients with type 2 diabetes (T2DM). Based on chromium's potential to improve insulin, dopamine, and serotonin function, we hypothesize that chromium has a greater glucoregulatory effect in individuals who have concurrent disturbances in dopamine and serotonin function--that is, complex patients with comorbid diabetes, depression, and binge eating. We propose, as suggested by the collective data to date, the need to go beyond the "one size fits all" approach to chromium supplementation and put forth a series of experiments designed to link physiological and neurobehavioral processes in the chromium response phenotype.

  2. X-616 Chromium Sludge Lagoons pictorial overview, Piketon, Ohio. Environmental Restoration Program

    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.

  3. Effect of tritium on corrosion behavior of chromium in 0.01 N sulfuric acid solution

    SciTech Connect

    Oyaidzu, M.; Isobe, K.; Hayashi, T.

    2015-03-15

    The effects of tritium on the corrosion behavior of chromium in 0.01 N sulfuric solution have been investigated in the present study. Electrochemical experiments have been carried our for pure chromium. At first, the concentration dependence of sulfuric acid solution on anodic polarization behavior of chromium was experimented, resulting in that 0.01 N one was found appropriate. The dependence of both dissolved oxygen and tritium concentration on anodic behavior of chromium were performed. It was found from that the self-passivation of chromium induced by dissolved oxygen was inhibited in tritiated solution resulting in the enhancement of the corrosion. As a consequence it is highly likely that the elution of chromium by highly oxidative radiolysis products would explain the passivation inhibitory effect of SUS304 stainless steel observed in tritiated solutions.

  4. The effect of formic acid concentration on the conductivity and corrosion resistance of chromium carbide coatings electroplated with trivalent chromium

    NASA Astrophysics Data System (ADS)

    Lu, Chen-En; Pu, Nen-Wen; Hou, Kung-Hsu; Tseng, Chun-Chieh; Ger, Ming-Der

    2013-10-01

    Different concentrations of formic acid were added into a trivalent chromium electroplating solution to produce chromium carbide (Crsbnd C) coatings. The influence of the formic acid concentration on chemical composition, microstructure, surface morphology, corrosion resistance, conductivity and carbon content of the resulting Crsbnd C coatings was studied. Formic acid was found to increase the carbon content in the coatings so as to form Crsbnd C films. These coatings had a nearly amorphous structure containing Cr, Cr2O3, and various Crsbnd C compounds with carbon content uniformly distributed throughout the coatings. The carbon content and the conductivity of the Crsbnd C layer were correlated with formic acid concentration. For a formic acid concentration of 2 M, the Crsbnd C layer had the highest carbon content (∼28%), the lowest contact resistance, and the best corrosion resistance along with a corrosion current density of ∼6.4 × 10-7 A/cm2.

  5. 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.

  6. Chromium(III) Binding Phage Screening for the Selective Adsorption of Cr(III) and Chromium Speciation.

    PubMed

    Yang, Ting; Zhang, Xiao-Yu; Zhang, Xiao-Xiao; Chen, Ming-Li; Wang, Jian-Hua

    2015-09-30

    The screening of suitable sorption medium is the key for highly selective solid phase extraction (SPE) of heavy metals. Herein, we demonstrate a universal protocol for producing selective SPE adsorbent through an evolutional approach based on phage display peptide library. By choosing chromium(III) as the model target, immobilized Cr(III) resins are first prepared using Ni-NTA affinity resins for the interaction with NEB heptapeptide phage library. After three rounds of positive biopanning against target Cr(III) and negative biopanning against foreign metal species, Cr(III) binding phages with high selectivity are obtained. The binding affinity and selectivity are further assessed with ELISA. The phages bearing peptide (YKASLIT) is finally chosen and immobilized on cytopore beads for Cr(III) preconcentration. The retained Cr(III) is efficiently recovered by 0.10 mol L(-1) HNO3 and quantified with ICP-MS. By loading 4000 μL of sample solution at pH 7.0 for 2 h and stripping with 400 μL of 0.10 mol L(-1) HNO3, a linear range of 0.05-0.50 μg L(-1) is achieved along with an enrichment factor of 7.1. The limit of detection is derived to be 15 ng L(-1) (3σ, n = 7) with a RSD of 3.6% (0.25 μg L(-1), n = 7). The procedure is validated by analyzing chromium content in a certified reference material GBW08608 (simulate water). In addition, chromium speciation in real water samples is demonstrated. Cr(VI) is first converted into Cr(III), and the latter subjected to the sorption onto the Cr(III) binding phage, followed by elution and quantification of the total chromium amount, and finally speciation is achieved by difference.

  7. Chromium(III) Binding Phage Screening for the Selective Adsorption of Cr(III) and Chromium Speciation.

    PubMed

    Yang, Ting; Zhang, Xiao-Yu; Zhang, Xiao-Xiao; Chen, Ming-Li; Wang, Jian-Hua

    2015-09-30

    The screening of suitable sorption medium is the key for highly selective solid phase extraction (SPE) of heavy metals. Herein, we demonstrate a universal protocol for producing selective SPE adsorbent through an evolutional approach based on phage display peptide library. By choosing chromium(III) as the model target, immobilized Cr(III) resins are first prepared using Ni-NTA affinity resins for the interaction with NEB heptapeptide phage library. After three rounds of positive biopanning against target Cr(III) and negative biopanning against foreign metal species, Cr(III) binding phages with high selectivity are obtained. The binding affinity and selectivity are further assessed with ELISA. The phages bearing peptide (YKASLIT) is finally chosen and immobilized on cytopore beads for Cr(III) preconcentration. The retained Cr(III) is efficiently recovered by 0.10 mol L(-1) HNO3 and quantified with ICP-MS. By loading 4000 μL of sample solution at pH 7.0 for 2 h and stripping with 400 μL of 0.10 mol L(-1) HNO3, a linear range of 0.05-0.50 μg L(-1) is achieved along with an enrichment factor of 7.1. The limit of detection is derived to be 15 ng L(-1) (3σ, n = 7) with a RSD of 3.6% (0.25 μg L(-1), n = 7). The procedure is validated by analyzing chromium content in a certified reference material GBW08608 (simulate water). In addition, chromium speciation in real water samples is demonstrated. Cr(VI) is first converted into Cr(III), and the latter subjected to the sorption onto the Cr(III) binding phage, followed by elution and quantification of the total chromium amount, and finally speciation is achieved by difference. PMID:26346061

  8. Chromium Isotopes in Marine Carbonates - an Indicator for Climatic Change?

    NASA Astrophysics Data System (ADS)

    Frei, R.; Gaucher, C.

    2010-12-01

    Chromium (Cr) stable isotopes experience an increased interest as a tracer of Cr (VI) reduction in groundwater and thus showed their potential as a monitor of remediation of anthropogenic and natural contamination in water (Berna et al., 2009; Izbicki et al., 2008). Chromium stable isotopes in Fe-rich chemical sediments (BIFs and Fe-cherts) have recently also been used as a tracer for Earth's atmospheric oxygenation through time (Frei et al., 2009). We have applied the Cr isotope system to organic-rich carbonates from a late Ediacaran succession in Uruguay (Polanco Formation), from which we have previously analyzed BIFs with extremely fractionated (δ53Cr up to 5.0 ‰) Cr isotope signatures that are part of an underlying deep water clastic sediment (shale-dominated) sequence (Yerbal Formation) deposited in a glacio-marine environment (Gaucher et al.,2004). δ53Cr values of organic rich carbonates correlate with positive and negative carbon isotope excursions (δ13C PDB between -3 and +3 ‰) and with systematic changes in strontium isotope compositions, commonly interpreted as to reflect fluctuations in organic (photosynthetic algae) production related to fluctuations in atmospheric oxygen and weathering intensities, respectively. Slightly positively fractioned δ53Cr values (up to +0.25‰), paralleling positive (δ13C PDB and 87Sr/86Sr ratio excursions would thereby trace elevated atmospheric oxygen levels/pulses possibly related to glacier retreat/melting stages that caused bioproductivity to increase. While the causal link between these multiple isotopic tracers and the mechanisms of Cr stripping into carbonates has to be further investigated in detail, the first indications from this study point to a potentially promising use of stable Cr isotopes in organic-rich carbonates to monitor fluctuations of atmospheric oxygen, particularly over the Neoproterozoic and Phanerozoic ice age periods. E.C. Berna et al. (2010) Cr stable isotopes as indicators of Cr

  9. Determination of total chromium in tanned leather samples used in car industry.

    PubMed

    Zeiner, Michaela; Rezić, Iva; Ujević, Darko; Steffan, Ilse

    2011-03-01

    Despite the high competition of synthetic fibers leather is nowadays still widely used for many applications. In order to ensure a sufficient stability of the skin matrix against many factors, such as microbial degradation, heat and sweat, a tanning process is indispensable. Using chromium (III) for this purpose offers a multitude of advantages, thus this way of tanning is widely applied. During the use of chromium tanned leather as clothing material as well as for decoration/covering purposes, chromium is extracted from the leather and may then cause nocuous effects to human skin, e.g. allergic reactions. Thus the knowledge of the total chromium content of leather samples expected to come into prolonged touch with human skin is very important. In car industry leather is used as cover for seats, steering wheel and gearshift lever The chromium contents often chromium tanned leather samples used in car industry were determined. First all samples were dried at 65 degrees C overnight and then cut in small pieces using a ceramic knife, weighed and analyzed by inductively coupled plasma--optical emission spectrometry (ICP-OES) after acidic microwave assisted digestion. The total chromium amounts found were in the range from 19 mg/g up to 32 mg/g. The extraction yield of chromium from leather samples in sweat is approximately 2-7%. Thus especially during long journeys in summer chromium can be extracted in amounts which may cause nocuous effects for example on the palm of the hands or on the back.

  10. Hexavalent chromium in the ground and surface waters near Telluride, Colorado; preliminary data report

    USGS Publications Warehouse

    Grove, David B.; Miller, R.L.; Konikow, L.F.; O'Boyle, P. S.

    1979-01-01

    Data showing results of 38 groundwater and 25 surface-water samples analyzed for hexavalent chromium are presented. Most samples were taken within the Telluride, Colo., city limits during October 1978. Twenty-four of the 38 groundwater samples (63%) contained more than 50 micrograms per liter of hexavalent chromium. Excluding the mill tailings pond 6 of the 23 surface-water samples (26%) contained more than 50 micrograms per liter of hexavalent chromium. Hexavalent chromium concentrations in groundwaters ranged from 0 to 2700 micrograms per liter and in surface waters from 0 to 160 micrograms per liter. (USGS)

  11. Studies on copper alloys containing chromium on the copper side phase diagram

    NASA Technical Reports Server (NTRS)

    Doi, T.

    1984-01-01

    Specimens were prepared from vacuum melted alloys of high purity vacuum melted copper and electrolytic chromium. The liquidus and eutectic point were determined by thermal analysis. The eutectic temperature is 1974.8 F and its composition is 1.28 wt% of chromium. The determination of solid solubility of chromium in copper was made by microscopic observation and electrical resistivity measurement. The solubility of chromium in solid copper is 0.6 wt% at 1050 F, 0.4 wt% at 1000 F, 0.25 wt% at 950 F, 0.17 wt% at 900 F, and 0.30 wt% at 840 F.

  12. Bioremediation of hexavalent chromium (VI) by a soil-borne bacterium, Enterobacter cloacae B2-DHA.

    PubMed

    Rahman, Aminur; Nahar, Noor; Nawani, Neelu N; Jass, Jana; Hossain, Khaled; Saud, Zahangir Alam; Saha, Ananda K; Ghosh, Sibdas; Olsson, Björn; Mandal, Abul

    2015-01-01

    Chromium and chromium containing compounds are discharged into the nature as waste from anthropogenic activities, such as industries, agriculture, forest farming, mining and metallurgy. Continued disposal of these compounds to the environment leads to development of various lethal diseases in both humans and animals. In this paper, we report a soil borne bacterium, B2-DHA that can be used as a vehicle to effectively remove chromium from the contaminated sources. B2-DHA is resistant to chromium with a MIC value of 1000 µg mL(-1) potassium chromate. The bacterium has been identified as a Gram negative, Enterobacter cloacae based on biochemical characteristics and 16S rRNA gene analysis. TOF-SIMS and ICP-MS analyses confirmed intracellular accumulation of chromium and thus its removal from the contaminated liquid medium. Chromium accumulation in cells was 320 µg/g of cells dry biomass after 120-h exposure, and thus it reduced the chromium concentration in the liquid medium by as much as 81%. Environmental scanning electron micrograph revealed the effect of metals on cellular morphology of the isolates. Altogether, our results indicate that B2-DHA has the potential to reduce chromium significantly to safe levels from the contaminated environments and suggest the potential use of this bacterium in reducing human exposure to chromium, hence avoiding poisoning.

  13. Excess chromium alters uptake and translocation of certain nutrients in citrullus.

    PubMed

    Dube, B K; Tewari, Kamlesh; Chatterjee, J; Chatterjee, C

    2003-12-01

    Citrullus plants were grown in refined sand with varying levels of chromium to determine their tolerance limit to excess chromium. The plants were maintained in control nutrient solution for 24 days and on the 25th day chromium as dichromate was added at 0.05, 0.1, 0.2, 0.3 and 0.4 mM. A control set of plants was grown in the same nutrient solution without chromium. At chromium levels >0.2 mM plants showed growth depression, with chlorosis and loss of turgor of middle leaves. Affected leaves had narrow lamina; tendrils were thin, short and did not have coiling property. Later chlorosis became severe and changed to necrosis in patches. Petiole along with lamina became wilted, rugged and hung down due to complete loss of water. At lower chromium concentration, (0.05, 0.1 and 0.2 mM) only depression in growth was observed. With increase in chromium concentration of nutrient solution accumulation of chromium in different parts of Citrullus was increased. Increase in concentrations of phosphorus, manganese and decrease in iron, copper, zinc and sulphur were observed in leaves. Toxicity of chromium was greater at 0.2-0.4 mM, compared to lower concentrations. Threshold of toxicity and toxicity of Cr in old leaves were, respectively, 0.9 and 3.9 microg g(-1) dry matter of citrullus.

  14. Speciation of Chromium in Soil and Sludge in the Surrounding Tannery Region, Ranipet, Tamil Nadu

    PubMed Central

    Mandal, Badal Kumar; Vankayala, Raviraj; Uday Kumar, L.

    2011-01-01

    The distribution and mobility of chromium in the soils and sludge surrounding a tannery waste dumping area was investigated to evaluate its vertical and lateral movement of operational speciation which was determined in six steps to fractionate the material in the soil and sludge into (i) water soluble, (ii) exchangeable, (iii) carbonate bound, (iv) reducible, (v) oxidizable, and (vi) residual phases. The present study shows that about 63.7% of total chromium is mobilisable, and 36.3% of total chromium is nonbioavailable in soil, whereas about 30.2% of total chromium is mobilisable, and 69.8% of total chromium is non-bioavailable in sludge. In contaminated sites the concentration of chromium was found to be higher in the reducible phase in soils (31.3%) and oxidisable phases in sludge (56.3%) which act as the scavenger of chromium in polluted soils. These results also indicate that iron and manganese rich soil can hold chromium that will be bioavailable to plants and biota. Thus, results of this study can indicate the status of bioavailable of chromium in this area, using sequential extraction technique. So a suitable and proper management of handling tannery sludge in the said area will be urgently needed to the surrounding environment as well as ecosystems. PMID:23724287

  15. Bacillus species enhance growth parameters of chickpea (Cicer arietinum L.) in chromium stressed soils.

    PubMed

    Wani, Parvaze Ahmad; Khan, Mohammad Saghir

    2010-11-01

    Pollution of the agricultural land by the toxic chromium is a global threat that has accelerated dramatically since the beginning of industrial revolution. Toxic chromium affects both the microbial diversity as well as reduces the growth of the plants. Understanding the effect of the chromium reducing and plant growth promoting rhizobacteria on chickpea crop will be useful. Chromium reducing and plant growth promoting Bacillus species PSB10 significantly improved growth, nodulation, chlorophyll, leghaemoglobin, seed yield and grain protein of chickpea crop grown in the presence of different concentrations of chromium compared to the plants grown in the absence of bio-inoculant. The strain also reduced the uptake of chromium in roots, shoots and grains of chickpea crop compared to plants grown in the absence of bio-inoculant. This study thus suggested that the Bacillus species PSB10 due to its intrinsic abilities of growth promotion and attenuation of the toxic effects of chromium could be exploited for remediation of chromium from chromium contaminated sites.

  16. Progress in the chemistry of chromium(V) doping agents used in polarized target materials

    SciTech Connect

    Krumpolc, M. ); Hill, D. ); Struhrmann, H.B. , Hamburg . Hamburger Synchrotronstrahlungslabor)

    1990-01-01

    We wish to report progress in two areas of the chromium (V)-based doping agents: Two commonly used chromium (V) complexes, I and II, have been synthesized in perdeuterated form (i.e., all hydrogens replaced by deuterium). They are sodium bis(2-ethyl-2-deuteroxy-butyrato)oxochromate(V)monodeuterate, IV, (acronym EDBA-Cr(V)), and sodium bis(2-deuteroxy-2-methylpropionato)oxochromate(V), III, (acronym DMPA-Cr(V)). A synthetic route leading to the preparation of stable, chromium(III)-free solutions of chromium(V) in diols (1,2-ethanediol/ethylene glycol/and 1,2-propanediol/propylene glycol/) has been outlined.

  17. The determination of nanogram amounts of Chromium in urine by x-ray fluorescence spectroscopy

    USGS Publications Warehouse

    Beyermann, K.; Rose, H.J.; Christian, R.P.

    1969-01-01

    Nanogram amounts of chromium can be extracted as oxinate into chloform. By treatment of the chloroform layer 3 M hydrochloric acid, oxinates of other elements and excess of reagent are removed, leaving a chloroform solution of the chromium chelate only. This solution is concentrated and transferred to the top of a small brass rod acting as sample holder. The intensity of the X-ray fluorescence of the Cr K?? line is measured with curved crystal optics. Chromium amounts greater than 5 ng can be detected. The application of the procedure to the analysis of the chromium content of urine is demonstrated. ?? 1969.

  18. Surface Reactions Limiting Chromium(VI) Generation from Naturally Derived Chromium(III) Minerals

    NASA Astrophysics Data System (ADS)

    Hausladen, D.; Fendorf, S. E.

    2015-12-01

    Chromium(III)-bearing minerals, commonly found in serpentinite and ultramaphic rocks, are ubiquitous in California soils and along convergent plate boundaries worldwide. Elevated concentrations of carcinogenic Cr(VI) have been measured in groundwater throughout the state, even in aquifers untouched by anthropogenic contamination. In most natural systems, manganese oxides are the only known, kinetically viable, oxidant of Cr(III). Numerous laboratory studies have demonstrated a finite capacity of Mn-oxides to generate Cr(VI) before surface alterations inhibit further Cr-oxidation. The extent to which these processes dictate the inhibition, and subsequent regeneration, of Mn-oxidation capacity within structured soils and sediments is not well understood. Here we use artificial soil aggregates made of Fe(III),Cr(III)-hydroxide-coated quartz sand and surrounded by aerated solute flow (pH 8, 30mM HEPES, 10mM HCO3-) to investigate C(VI) generation within ultramafic rock derived sediment and processes inhibiting manganese reactivity. We found that while Cr(VI)-production scaled with Cr-mineral solubility; Cr(VI) effluent concentrations from aggregates of both lower and higher solubility Cr(III)-minerals peaked very soon after reaction with birnessite (within 2 days and 4 days, respectively). Once Cr(VI) production plateaued (t=22 days) aggregate influent was acidified (pH 5, 30mM C2H3O2-). Despite increasing Cr(III) solubility at lower pH, aqueous Cr(VI) production further decreased. A secondary pulse of Cr(VI) generation was seen only after the surrounding solute returned to initial conditions (pH 8). As with the initial pulse, Cr(VI) concentration scaled with mineral solubility. Collectively, our results demonstrate the extent that natural fluctuations in groundwater composition, both as a result of irrigation or precipitation events, have the potential to both regenerate and inhibit Mn-oxide surfaces. These synthetic soil aggregates provide insight into how fluctuating

  19. Thermodynamics, Kinetics, and Activation energy Studies of the sorption of chromium(III) and chromium(VI) to a Mn3O4 nanomaterial

    PubMed Central

    Cantu, Yvette; Remes, Abril; Reyna, Alejandra; Martinez, Denise; Villarreal, Jahaziel; Ramos, Hilda; Trevino, Samantha; Tamez, C.; Martinez, A.; Eubanks, T.; Parsons, J. G.

    2014-01-01

    In this study, a manganese oxide, Mn3O4 was used to remove chromium(III) and chromium(VI) from aqueous solutions. The Mn3O4 nanomaterial was synthesized through a precipitation method, and was characterized using XRD, which confirmed the material had a crystal structure similar to hausmannite. In addition, using Scherrer’s equation it was determined that the nanomaterial had an average grain size of 19.5 ± 1.10 nm. A study of the effects of pH on the binding of chromium(III) and chromium(VI) showed that the optimum binding pH was 4 and 3 respectively. Batch isotherm studies were performed to determine the binding capacity of chromium(III), which was determined to be 18.7 mg/g, 41.7 mg/g, and 54.4 mg/g respectively for 4°C, 21°C, and 45°C. Chromium(VI) on the other hand had lower binding capacities of 2.5 mg/g, 4.3 mg/g, and 5.8 mg/g for 4°C, 21°C, 45°C, respectively. Thermodynamic studies performed indicated the sorption process was for the most part controlled by physisorption. The ΔG for the sorption of chromium(III) and Chromium(VI) ranged from −0.9 to −13 kJ/mol, indicating a spontaneous reaction was occurring. The enthalpy indicated a endothermic reaction was occurring during the binding and show ΔH values of 70.6 and 19.1 kJ.mol for chromium(III) and Chromium(VI), respectively. In addition, ΔS for the reaction had positive values of 267 and 73 J/mol for chromium(III) and chromium(VI) which indicate a spontaneous reaction. In addition, the sorption process was found to follow pseudo second order kinetic and the activation energy studies indicated the binding process occurred through chemisorption. PMID:25097453

  20. Serum Chromium Levels in Type 2 Diabetic Patients and Its Association with Glycaemic Control

    PubMed Central

    Manikandan, Senthil; Nair, Lal Devayanivasudevan; Karuthodiyil, Rajendran; Vijayarajan, Nikhilan; Gnanasekar, Rajiv; Kapil, Vivian V.; Mohamed, Azeem S.

    2015-01-01

    Introduction Chromium is an essential micronutrient which is required for the normal functioning of insulin and regulation of blood sugar levels. It acts as a vital antioxidant for maintaining insulin homeostasis. In diabetes mellitus, the free radical production is increased and levels of antioxidants like chromium, vanadium, selenium and manganese are reduced. There have been previous studies to suggest that low serum levels of chromium are associated with poorer glycaemic control. Aim To study the level of serum chromium in newly diagnosed patients with type 2 diabetes mellitus and its association with glycaemic control. Materials and Methods Serum chromium concentration was determined by using inductively coupled Plasma – Optical Emission Spectophotometry in 42 newly diagnosed type 2 diabetes mellitus patients without any pre-existing complications. They were divided into 2 groups – well controlled (HbA1c ≤7.0%) and uncontrolled groups (HbA1c >7.0%). Results Mean serum chromium concentration measured in uncontrolled type 2 diabetic patients was significantly lower (0.065 ± 0.03 mcg/L vs 0.103 ± 0.04 mcg/L, p< 0.05). There was a statistically significant inverse linear correlation of the HbA1c values and the serum chromium concentration (r= -0.6514, p < 0.0001). There was also a decrease in chromium levels across both the groups with advancing age and the decrease being significant beyond 40 years of age (p<0.05). Conclusion The results of our study describes the relationship between serum chromium levels and control of type 2 diabetes mellitus. Significant reduction in chromium levels are probable indicators of metabolic response to oxidative stress in patients with type 2 diabetes mellitus. Further large scale studies relating serum chromium and type 2 diabetes mellitus may help to understand more about the exact relationship. PMID:26676175

  1. Iron-rich Oklahoma clays as a natural source of chromium in monitoring wells.

    PubMed

    Scott, Dane; Apblett, Allen; Materer, Nicholas F

    2011-12-01

    Water samples, drawn from groundwater monitoring wells located southeast of Oklahoma City, OK, were found to contain elevated concentrations of total chromium with an apparent source localized to the area surrounding each well. Since these monitoring wells are located in areas with no historic chromium usage, industrial sources of chromium were ruled out. Water testing was performed on twelve monitoring wells in the area that historically had elevated total chromium concentrations ranging from 10-4900 micrograms per litre. Filtered water samples were found to be free of chromium contamination, indicating that the source of the chromium is the suspended solids. Analysis of these solids by acid digestion and a sequential extraction technique revealed that the chromium was primarily associated with iron-containing solids. X-ray diffraction identified goethite, an iron oxide hydroxide, as the dominant iron-containing phase in the suspended solids. The mineralogy in this region is dominated by interbedded red-bed sandstone and mudstone whose mineral content includes mixed-layer illite-smectite, hematite, goethite, gypsum and dolomite. Elemental analysis of soil samples collected as a function of depth in the locale of the monitoring wells indicated that the iron rich clays contain a natural source of chromium. The elevated levels of total chromium are most likely due to the dissolution of silica and alumina from the chromium containing iron clays in the basic well water, resulting in the release of fine suspended solids that naturally have high chromium concentrations. These results should be applicable to other areas containing iron-rich clays.

  2. Effect of Chromium Supplementation on Glucose Metabolism and Lipids: A Systematic Review with Meta-Analysis of Randomized Controlled Trials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objective. A systematic review of the effect of chromium supplementation on glucose metabolism and lipid levels. Research Design and Methods. Literature search conducted in MEDLINE and Commonwealth Agricultural Bureau. Eligible studies were English language randomized controlled trials of chromium ...

  3. Application of the relativistic theory of magnetic scattering of X-rays to ferromagnetic Fe and Cr 47Fe 53 alloy

    NASA Astrophysics Data System (ADS)

    Arola, E.; Strange, P.; Kulikov, N. I.; Woods, M. J.; Gyorffy, B. L.

    1998-01-01

    We apply our recent formalism of magnetic scattering of X-rays to ferromagnetic iron and Cr 47Fe 53 alloy. The theory has been constructed in the framework of the fully relativistic spin-polarized KKR-type multiple-scattering theory. We discuss how to adapt our theory for substitutionally random alloys in context of the coherent potential approximation (CPA) and apply it to anomalous magnetic scattering of X-rays at the LII,III absorption edges of iron and chromium in Cr 47Fe 53.

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

    PubMed

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

    2002-11-01

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

  5. Chromium Isotopes Record Fluctuations in Precambrian Biospheric Oxygenation

    NASA Astrophysics Data System (ADS)

    Frei, R.; Gaucher, C.; Poulton, S. W.; Canfield, D. E.

    2009-12-01

    There is a direct relationship between life, oxygen, and the surface chemistry of the Earth. Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps, near the beginning and the end of the Proterozoic Eon (2500 to 542 million years ago), but the details of this history are unclear. The geochemical behaviour of chromium (Cr) is highly sensitive to the redox state of the surface environment as oxidative weathering processes produce the oxidised hexavalent [Cr(VI)] form. Oxidation of reduced trivaltent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. The fractionated Cr isotope signature is then tranfered by riverine transport to the sea. Here, we use Cr stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of Earth’s atmosphere-hydrosphere system. Fractionated Cr isotopes indicate the accumulation of Cr(VI) in ocean surface waters ~2.8 to 2.6 billion years (Gyr) ago and a likely transient elevation in atmospheric and surface ocean oxygen prior to the first great rise of oxygen 2.45-2.2 Gyr ago (the Great Oxidation Event; GOE). In contrast, Cr isotopes in ~1.88 Gyr old BIFs are not fractionated, indicating a major decline in atmospheric oxygen and demonstrating that the GOE did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, ~800 to 542 million years (Myr) ago, we observe strong positive fractionations in Cr isotopes (δ53Cr up to +4.9 ‰) providing independent support for increased surface oxygenation at this time. This may have stimulated rapid evolution of macroscopic multicellular life. Our chromium isotope data thus provide new insights into the oxygenation history of the Earth, and highlight its use as a powerful redox tracer in aquatic systems.

  6. 30 CFR 47.52 - MSDS contents.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false MSDS contents. 47.52 Section 47.52 Mineral... COMMUNICATION (HazCom) Material Safety Data Sheets (MSDS) § 47.52 MSDS contents. When an operator must prepare... available, for the categories listed in Table 47.52 as follows: Table 47.52—Contents of MSDS...

  7. 30 CFR 47.52 - MSDS contents.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false MSDS contents. 47.52 Section 47.52 Mineral... COMMUNICATION (HazCom) Material Safety Data Sheets (MSDS) § 47.52 MSDS contents. When an operator must prepare... available, for the categories listed in Table 47.52 as follows: Table 47.52—Contents of MSDS...

  8. Reflections on hexavalent chromium: health hazards of an industrial heavyweight.

    PubMed Central

    Pellerin, C; Booker, S M

    2000-01-01

    Chromium has been used commercially in the United States for more than 100 years in metal alloys and other compounds, as a pigment, and in the tanning and metal plating industries, and many studies have looked at its effects in terms of occupational health. But, although scientists know that Cr(VI) is a human carcinogen and that it can cause other deleterious health effects including kidney and liver damage, certain questions remain about the metal's effects, such as which routes of exposures are dangerous for humans. PMID:11017901

  9. 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.

  10. Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes.

    PubMed

    Stevens, Charlotte J; Nichol, Gary S; Arnold, Polly L; Love, Jason B

    2013-12-01

    The new binuclear chromium Pacman complex [Cr2(L)] of the Schiff base pyrrole macrocycle H4L has been synthesized and structurally characterized. Addition of isocyanide, C≡NR (R = xylyl, (t)Bu), or triphenylphosphine oxide donors to [Cr2(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr2(μ-CNR)(L)], in which the isocyanides bridge the two Cr(II) centers, and [Cr2(OPPh3)2(L)], a Cr(II) phosphine oxide adduct with the ligands exogenous to the cleft.

  11. Procedure for granulokinetic studies in the horse with chromium-51

    SciTech Connect

    Carakostas, M.C.; Moore, W.E.; Smith, J.E.

    1981-04-01

    A procedure with chromium-51 (51Cr) as the cell label that maintains high-cell viability for studying granulocyte kinetics in horses is described. The procedure combines and modifies several methods for isolating leukocytes and granulocytes for use in the horse when a large volume of labeled cells is required. Also described is an improved technique for measuring granulocyte specific activity in large serial blood samples, using a Ficoll-sedimentation method. The procedure should be useful for determining granulocyte kinetics in the horse, the only major domestic species for which such data are not available.

  12. Physiological changes induced by chromium stress in plants: an overview.

    PubMed

    Hayat, Shamsul; Khalique, Gulshan; Irfan, Mohammad; Wani, Arif Shafi; Tripathi, Bhumi Nath; Ahmad, Aqil

    2012-07-01

    This article presents an overview of the mechanism of chromium (Cr) stress in plants. Toxic effects of Cr on plant growth and development depend primarily on its valence state. Cr(VI) is highly toxic and mobile whereas Cr(III) is less toxic. Cr-induced oxidative stress involves induction of lipid peroxidation in plants that cause severe damage to cell membranes which includes degradation of photosynthetic pigments causing deterioration in growth. The potential of plants with the adequacy to accumulate or to stabilize Cr compounds for bioremediation of Cr contamination has gained engrossment in recent years.

  13. Resource geopolitics: US dependence on South African chromium

    SciTech Connect

    Butts, K.H.

    1985-01-01

    The growth of technology, especially military technology, has heightened demand for certain critical mineral resources. Strategically important to the industrialized nations, these resources are increasingly available only through overseas trade. The concentration of many of these resources in politically unstable areas of the world has rendered the industrialized nations vulnerable to supply dislocation. Nowhere is this more evident than in the dependence of the United States (US) upon African minerals. This study examines these dependencies, especially with respect to South Africa's chromium and ferrochromium, in order to address the geopolitically important variables concerning resource access and the determination of US policy toward the mineral-rich region of Southern Africa.

  14. MODELING THE RATE-CONTROLLED SORPTION OF HEXAVALENT CHROMIUM.

    USGS Publications Warehouse

    Grove, D.B.; Stollenwerk, K.G.

    1985-01-01

    Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

  15. Chromium Renderserver: Scalable and Open Source Remote RenderingInfrastructure

    SciTech Connect

    Paul, Brian; Ahern, Sean; Bethel, E. Wes; Brugger, Eric; Cook,Rich; Daniel, Jamison; Lewis, Ken; Owen, Jens; Southard, Dale

    2007-12-01

    Chromium Renderserver (CRRS) is software infrastructure thatprovides the ability for one or more users to run and view image outputfrom unmodified, interactive OpenGL and X11 applications on a remote,parallel computational platform equipped with graphics hardwareaccelerators via industry-standard Layer 7 network protocolsand clientviewers. The new contributions of this work include a solution to theproblem of synchronizing X11 and OpenGL command streams, remote deliveryof parallel hardware-accelerated rendering, and a performance analysis ofseveral different optimizations that are generally applicable to avariety of rendering architectures. CRRSis fully operational, Open Sourcesoftware.

  16. Development of the revised drinking water standard for chromium.

    PubMed

    Goldhaber, S; Vogt, C

    1989-10-01

    Comprehensive regulations are being developed to limit human exposure to contamination in drinking water by the United States Environmental Protection Agency (EPA) under the authority of the Safe Drinking Water Act (SDWA). These regulations are being developed in several phases and include synthetic organic chemicals, inorganic chemicals, microbiological contaminants and radionuclides. This paper addresses the fundamental concepts and approaches used by EPA in setting drinking water regulations and how EPA is using these concepts to revise the drinking water standard for chromium. PMID:2602936

  17. Luminescent properties of alumina ceramics doped with chromium oxide

    NASA Astrophysics Data System (ADS)

    Kortov, V.; Kiryakov, A.; Pustovarov, V.

    2016-08-01

    Ceramics doped with chromium oxide were synthesized from alumina nanopowder at high heating and cooling rates. XRD analysis of the obtained samples shows that they consist mainly of Al2O3 α-phase. Photoluminescence (PL) spectra in the visible spectral region and thermoluminescence (TL) curves were measured. An effect of the dopant concentration on the intensity and shape of the PL bands as well as on the TL yield was found. Annealing of the quenching defects which emerged during the synthesis changed the PL spectra. The centers responsible for PL and TL in the synthesized ceramics were identified.

  18. Industry participation workshop: Chromium electroplating of superconductor strand. Proceedings

    SciTech Connect

    1994-12-13

    The primary objective of the workshop was to inform US plating vendors about the opportunity to participate in the effort on Cr plating of large quantities of superconducting wires required for the ITER and the TPX projects and DOE`s interest in developing several reliable and high quality suppliers of Chromium plating services for the superconducting strand industry. The objective was also to inform plating vendors about the Cr plating technology developed in LLNL and invite interested plating vendors to get the technology. Finally the workshop was intended to inform the plating vendors about the plan to get verification of capability of two to four vendors for Cr plating of superconducting strands.

  19. Evaluating Foraminifera as an Archive for Seawater Chromium Isotopic Composition

    NASA Astrophysics Data System (ADS)

    Wang, X.; Planavsky, N.; Hull, P. M.; Tripati, A.; Reinhard, C.; Zou, H.; Elder, L. E.; Henehan, M. J.

    2015-12-01

    In recent years there has been growing interest in using chromium isotopes (δ53Cr) as a proxy to investigate the redox evolution of Earth's ocean-atmosphere system throughout geological history. Potential archives for seawater δ53Cr that have been identified to date include iron formations and organic-rich siliciclastic sediments. However, these types of sediments are not common and they are discontinuous over geologic time. As a result, alternative types of archives are needed. Here we evaluate the utility of foraminifera tests as a recorder of seawater δ53Cr. Core-tops used were from different ocean basins. Mono-specific samples of Globigerinoides sacculifer, Orbulina universa, Pulleniatina obliquiloculata, Globoratalia crassula-crassaformis, Globoratalia truncatulinoides, and Globigerinella siphonifera were isolated to investigate inter-species isotope fractionation. Chromium concentrations were measured by isotope dilution method to be 0.1-0.3 μg/g. The δ53Cr values of these species range from 0.2‰ to 2.4‰, with an analytical uncertainty of 0.3‰ (95% confidence). Despite the high analytical uncertainty due to the extremely low levels of Cr present, there is still large detectable variation in foraminiferal δ53Cr values, which overlap presently available seawater values (Bonnand et al., 2013; Scheiderich et al., 2015). Possible explanations for such variations in foraminiferal δ53Cr values include heterogeneity of seawater δ53Cr in the modern oceans, and/or photobiochemical redox cycling of Cr in the surface oceans. Therefore, care should be taken when using foraminifera to reconstruct past seawater δ53Cr values. ReferencesBonnand, P., James, R., Parkinson, I., Connelly, D., Fairchild, I., 2013. The chromium isotopic composition of seawater and marine carbonates. Earth and Planetary Science Letters, 382: 10-20. Scheiderich, K., Amini, M., Holmden, C., Francois, R., 2015. Global variability of chromium isotopes in seawater demonstrated by Pacific

  20. Chromium Contamination in Leon Valley Mexico: Insights from Chromium Stable Isotopes

    NASA Astrophysics Data System (ADS)

    Villalobos-Aragon, A.; Ellis, A. S.; Armienta, M. A.; Morton, O.; Johnson, T. M.; Glessner, J. J.

    2008-12-01

    Chromium (Cr) is a contaminant commonly found in surface and groundwater. In nature Cr commonly occurs in two valences: Cr(VI) is highly mobile, toxic and carcinogenic, while Cr(III) is less mobile. Cr was first detected in groundwater in the Leon Valley region (located in central Mexico) in 1975 (Rodriguez and Armienta, 1995). Previous work proposed an anthropogenic origin for a high concentration plume near the industrial Buenavista (BV), while the larger sub ppb plume located near San Juan de Otates (SJO) is assumed to be caused by weathering of the SJO pyroxenite. Cr stable isotopes have been shown to be useful in monitoring reduction and can also be used to infer redox and transport conditions in natural settings and the goals of our research are: 1) use stable isotope values (δ53Cr) to monitor Cr behavior in the Leon Valley, 2) identify sources (industrial vs. weathering of ultramafic rocks). Since 1975, the highly contaminated BV area is showing a decrease in groundwater Cr(VI) concentrations. Our sampling in 2007 show Cr(VI) concentrations decreasing from 0.005mg/l to 121mg/l to 0.002mg/l to 95.1mg/l. However, the Cr waste piles still exit and Cr(VI) concentrations from leachate collection ponds range from 1.2g/l to 6.8g/l. Isotopic values obtained from leaching experiments performed on the waste pile samples show enriched δ53Cr values (0.76‰ to 3.25‰) either indicating varying reduction or that the waste is fractionated during the ore processing. δ53Cr values for groundwater range from 0.33‰ to 0.46‰, indicating minimal reduction and lack of available reducing agents. The lack of variation of isotopic values seen in the groundwater plume is also consistent with the results of previous studies showing insignificant fractionation due to sorption within the plume (Villalobos-Aragon et al., 2008). The unfractionated Cr(VI) in groundwater vs. those of the waste piles, considered the contamination source, suggests that either 1) the Cr in the waste

  1. Leaching behavior of chromium in chrome shaving generated in tanning process and its stabilization.

    PubMed

    Erdem, Mehmet; Ozverdi, Arzu

    2008-08-15

    In this study, leaching properties and pollution potential of chromium in chrome shaving (CS), which is a solid residue of leather industry, containing 2.27% Cr were investigated and thermal stabilization procedure was applied to the CS for chromium immobilization. For this purpose, firstly, effects of the liquid/solid ratio, contact time, pH and sequential extraction on the leaching behavior of chromium in the CS were studied. It was determined that the CS-caused chromium pollution is a hazardous material for environment. Thermal stabilization procedure was applied to the CS in the temperature range of 250-500 degrees C for the chromium immobilization. Effective stabilization of chromium in the CS was achieved by heating of CS at 350 degrees C under CO(2) atmosphere. Leaching experiments were also carried out with the samples obtained from the stabilization process and the results compared with that of the CS. Also, TCLP test method was applied to the samples to determine pollution potentials and discharge situations of the CS and its stabilization products. While the chromium concentrations in the test solutions of all samples stabilized thermally at above 350 degrees C were below the USEPA regulatory limit of 5 mg/l, the concentration of chromium leached out from the CS was 30-fold bigger than the USEPA regulatory limit.

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

    PubMed

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

    1973-07-01

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

  3. Characterization and mobility of geogenic chromium in soils and river bed sediments of Asopos basin.

    PubMed

    Lilli, Maria A; Moraetis, Daniel; Nikolaidis, Nikolaos P; Karatzas, George P; Kalogerakis, Nicolas

    2015-01-01

    A field and laboratory study was conducted to assess the origin and mobility of CrVI in Asopos basin in Greece. Sampling was designed in such way as to capture the spatial variability of chromium occurring in sediments and soils in different lithological units in the area. Physicochemical and geochemical characterization of surface agricultural soils obtained from river terraces and river bed sediments was conducted in order to determine the natural background of chromium. Lithologies with strong calcareous, siliceous and ultramafic components were identified using principal component analysis. Laboratory mobility studies quantified the rates of chromium sorption and release from soils and their capacity to adsorb chromium. Heavy metal analysis and local geology study support the hypothesis that the main source of chromium is of geogenic origin. Chromium distribution in Asopos river bed was influenced from the eroded products derived from extensive areas with ultramafic rocks the last 5Ma. The mobility studies showed that leaching process was very fast and sorption capacity was significant and capable to retain chromium in case of waste release in the river. Finally the mobility of chromium release is limited due to existing attenuation capacity controlled by ferric oxides coatings on the soil and sediments.

  4. 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.

  5. The impact of humic acid on chromium phytoextraction by aquatic macrophyte Lemna minor.

    PubMed

    Kalčíková, Gabriela; Zupančič, Marija; Jemec, Anita; Gotvajn, Andreja Žgajnar

    2016-03-01

    Studies assessing chromium phytoextration from natural waters rarely consider potential implications of chromium speciation in the presence of ubiquitous humic substances. Therefore, the present study investigated the influence of environmentally relevant concentration of humic acid (TOC = 10 mg L(-1)) on chromium speciation (Cr = 0.15 mg L(-1)) and consequently on phytoextraction by aquatic macrophyte duckweed Lemna minor. In absence of humic acid, only hexavalent chromium was present in water samples and easily taken up by L. minor. Chromium uptake resulted in a significant reduction of growth rate by 22% and decrease of chlorophyll a and chlorophyll b contents by 48% and 43%, respectively. On the other hand, presence of humic acid significantly reduced chromium bioavailability (57% Cr uptake decrease) and consequently it did not cause any measurable effect to duckweed. Such effect was related to abiotic reduction of hexavalent chromium species to trivalent. Hence, findings of our study suggest that presence of humic acid and chromium speciation cannot be neglected during phytoextraction studies.

  6. Chromium Carbide Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiaki; Kawasaki, Hiroharu; Terajima, Ryou; Emura, Masanari

    1999-06-01

    Chromium carbide thin films are synthesized on Si(100)substrates by a pulsed Nd:YAG laser deposition method at differentsubstrate temperatures. Glancing-angle X-ray diffraction shows that acrystalline chromium carbide film can be prepared at the substratetemperature of 700°C. Grain size of the films, examined witha field-emission secondary electron microscope, increases withincreasing substrate temperature.

  7. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... section. Other examples of hexavalent chromium compounds that can be used to treat water are: Chromic acid... containing hexavalent chromium which can be used to treat water, either alone or in combination with other chemicals, where the mixture can be used to treat water. (12) Industrial cooling tower means any...

  8. Insulin Resistance and Body Weight: Recent Human Studies Documenting the Benefits of Supplemental Chromium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The essentiality of chromium for humans was confirmed more than three decades ago with the studies showing that patients on total parenteral nutritrion (TPN) developed severe diabetic-like symptoms that could be reversed by the addition of chromium to their parenteral nutrition solutions. Since the...

  9. Chromium supplementation alters the performance, metabolism, and immune response of feedlot cattle during the receiving period

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crossbreed steers (n = 180; 507 +/- 13 lb) were fed during a 56-d receiving period to determine if supplementing chromium (Cr; KemTRACEbrandChromiumPropionate 0.04%, Kemin Industries) would improve feedlot performance and health of newly received cattle. A completely randomized block design (36 pens...

  10. Chromium supplementation enhances the metabolic response of steers to lipopolysaccharide (LPS) challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effect of chromium (Cr; KemTRACE®brandChromiumProprionate 0.04%, Kemin Industries) supplementation on the metabolic response to LPS challenge was examined. Steers (n=20; 235±4 kg body weight (BW)) received a premix that added 0 (Con) or 0.2 mg/kg Cr to the total diet (DM (dry matter) basis) for ...

  11. Toxicity assessment and geochemical model of chromium leaching from AOD slag.

    PubMed

    Liu, Bao; Li, Junguo; Zeng, Yanan; Wang, Ziming

    2016-02-01

    AOD (Argon Oxygen Decarburization) slag is a by-product of the stainless steel refining process. The leaching toxicity of chromium from AOD slag cannot be ignored in the recycling process of the AOD slag. To assess the leaching toxicity of the AOD slag, batch leaching tests have been performed. PHREEQC simulations combined with FactSage were carried out based on the detailed mineralogical analysis and petrophysical data. Moreover, Pourbaix diagram of the Cr-H2O system was protracted by HSC 5.0 software to explore the chromium speciation in leachates. It was found that AOD slag leachate is an alkaline and reductive solution. The Pourbaix diagram of the Cr-H2O system indicated that trivalent chromium, such as Cr(OH)4(-), is the major chromium species in the experimental Eh-pH region considered. However, toxic hexavalent chromium was released with maximum concentrations of 30 µg L(-1) and 18 µg L(-1) at L/S 10 and 100, respectively, during the earlier leaching stage. It concluded that the AOD slag possessed a certain leaching toxicity. After 10 d of leaching, trivalent chromium was the dominant species in the leachates, which corresponded to the results of PHREEQC simulation. Leaching toxicity of AOD slag is based on the chromium speciation and its transformation. Great attention should be focused on such factors as aging, crystal form of chromium-enriched minerals, and electrochemical characteristics of the leachates.

  12. Teaching the Properties of Chromium's Oxidation States with a Case Study Method

    ERIC Educational Resources Information Center

    Ozdilek, Zehra

    2015-01-01

    The purpose of this study was to investigate how a mixed-method case study affects pre-service science teachers' awareness of hexavalent chromium pollution and content knowledge about the properties of chromium's different oxidation states. The study was conducted in Turkey with 55 sophomores during the fall semester of 2013-2014. The…

  13. The impact of humic acid on chromium phytoextraction by aquatic macrophyte Lemna minor.

    PubMed

    Kalčíková, Gabriela; Zupančič, Marija; Jemec, Anita; Gotvajn, Andreja Žgajnar

    2016-03-01

    Studies assessing chromium phytoextration from natural waters rarely consider potential implications of chromium speciation in the presence of ubiquitous humic substances. Therefore, the present study investigated the influence of environmentally relevant concentration of humic acid (TOC = 10 mg L(-1)) on chromium speciation (Cr = 0.15 mg L(-1)) and consequently on phytoextraction by aquatic macrophyte duckweed Lemna minor. In absence of humic acid, only hexavalent chromium was present in water samples and easily taken up by L. minor. Chromium uptake resulted in a significant reduction of growth rate by 22% and decrease of chlorophyll a and chlorophyll b contents by 48% and 43%, respectively. On the other hand, presence of humic acid significantly reduced chromium bioavailability (57% Cr uptake decrease) and consequently it did not cause any measurable effect to duckweed. Such effect was related to abiotic reduction of hexavalent chromium species to trivalent. Hence, findings of our study suggest that presence of humic acid and chromium speciation cannot be neglected during phytoextraction studies. PMID:26766370

  14. Environmental optimization of chromium recovery from tannery sludge using a life cycle assessment approach.

    PubMed

    Kiliç, Eylem; Puig, Rita; Baquero, Grau; Font, Joaquim; Colak, Selime; Gürler, Deniz

    2011-08-15

    Life cycle assessment (LCA) was used to evaluate the environmental impact of an oxidative chromium recovery method from tannery sludge, in comparison with the usual landfilling process. Three improvement options (water reduction, byproduct use and anaerobic sludge digestion) were considered. The results showed that the proposed chromium recovery process would be better environmentally than conventional landfilling in all the evaluated impact categories if the amount of chromium recovered was 43 kg per ton of sludge. This amount could be recovered if the chromium concentration was about 20 times higher than that considered in this study. Alternatively, a lower chromium concentration would produce a better result if the recovery method was optimized and implemented at industrial rather than laboratory scale, and if more accurate data were provided on environmental credits for avoiding the chromium production process. Thus, the recovery method is environmentally beneficial when tannery sludge contains a chromium concentration of about 100,000 ppm. According to the literature, such concentrations are not unusual. The results could serve as the basis for further environmental improvements in chromium recovery and tannery sludge management and should be used in decision-making processes, especially for end-of-pipe treatments.

  15. IN SITU TREATMENT OF SOIL AND GROUNDWATER CONTAMINATED WITH CHROMIUM - TECHNICAL RESOURCE GUIDE

    EPA Science Inventory

    New information and treatment approaches have been developed for chromium-contaminated soil and groundwater treatment. The prupose of this report is to bring together the most current information pertaining to the science of chromium contamination and the insitu treatment and co...

  16. Chromium supplementation enhances the acute phase response of steers to a lipopolysaccharide (LPS) challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study examined the effect of chromium supplementation on the response of steers to an LPS challenge. Twenty crossbred steers (235±4 kg BW) received 0 ppb (Control; C) or 200 ppb chromium propionate (CHR) for 55 days. Steers were fitted with jugular catheters and rectal temperature (RT) recording...

  17. 76 FR 71926 - Defense Federal Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-21

    .... SUPPLEMENTARY INFORMATION: I. Background DoD published a final rule at in the Federal Register at 76 FR 25569 on... Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to Commercial Items (DFARS Case... hexavalent chromium. DATES: Comment Date: Comments on the proposed rule should be submitted in writing to...

  18. 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

    ... Act of 1995 (44 U.S.C. 3506 et seq.) and Secretary of Labor's Order No. 1-2012 (77 FR 3912). Signed at... 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...

  19. Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

    PubMed

    Gonzalez, Maximiliano R; Pereyra, Andrea M; Torres Sánchez, Rosa M; Basaldella, Elena I

    2013-10-15

    A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.

  20. 40 CFR 721.10239 - Trivalent chromium complexes of a substituted beta-naphthol amine azo dye (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Trivalent chromium complexes of a... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10239 Trivalent chromium complexes of... subject to reporting. (1) The chemical substance identified generically as trivalent chromium complexes...

  1. 40 CFR 721.10239 - Trivalent chromium complexes of a substituted beta-naphthol amine azo dye (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Trivalent chromium complexes of a... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10239 Trivalent chromium complexes of... subject to reporting. (1) The chemical substance identified generically as trivalent chromium complexes...

  2. 40 CFR 721.10239 - Trivalent chromium complexes of a substituted beta-naphthol amine azo dye (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Trivalent chromium complexes of a... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10239 Trivalent chromium complexes of... subject to reporting. (1) The chemical substance identified generically as trivalent chromium complexes...

  3. 21 CFR 176.160 - Chromium (Cr III) complex of N-ethyl-N-heptadecylfluoro-octane sulfonyl glycine.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Chromium (Cr III) complex of N-ethyl-N... § 176.160 Chromium (Cr III) complex of N-ethyl-N-heptadecylfluoro-octane sulfonyl glycine. The chromium (Cr III) complex of N-ethyl - N -heptadecylfluoro-octane sulfonyl glycine containing up to 20...

  4. Information profiles on potential occupational hazards: Inorganic chromium compounds. Draft report (Second)

    SciTech Connect

    Not Available

    1982-02-01

    Information profiles are presented for the following inorganic chromium compounds: chromic(VI) acid, chromic(III) hydroxide, chromic(III) oxide, chromic(III) sulfate, chromic(III) sulfate (basic), chromium dioxide, potassium dichromate(VI), lead chromate, sodium-chromate(VI), sodium-dichromate(VI), and zinc-yellow-chromate(VI). Biological effects of hexavalent chromium in humans included skin ulceration, dermatitis, nasal membrane irritation and ulceration, nasal septal perforation, rhinitis, nosebleed, nephritis, liver damage, epigastric pain, pulmonary congestion and edema, and erosion and discoloration of teeth. Chromium(VI) compounds caused mutations in a variety of systems. Exposure to trivalent chromium in the work place has caused contact dermatitis and chrome ulcers. Epidemiological studies indicated respiratory carcinogenicity among workers occupationally exposed during chromate production.

  5. Chelation of chromium(VI) by combining deferasirox and deferiprone in rats.

    PubMed

    Iranmanesh, Marzieh; Fatemi, S Jamil A; Ebrahimpour, Roza; Dahooee Balooch, Faezeh

    2013-06-01

    The present research is aimed to characterize the potential efficiency of two chelators after chromium(VI) administration for 60 days following two doses of 15 and 30 mg/kg chromium(VI) per body weight daily to male rats. However, the hypothesis that the two chelators might be more efficient as combined therapy than as single therapy in removing chromium(VI) from rat organs was considered. In this way, two known chelators deferasirox and deferiprone were chosen and given orally as a single or combined therapy for a period of 1 week. Chromium(VI) and iron concentrations in tissues were determined by flame atomic absorption spectroscopy. The combined chelation therapy results show that deferasirox and deferiprone are able to remove chromium(VI) ions from various tissues while iron concentration returned to normal levels and symptoms also decreased.

  6. Reaction layer formation at the graphite/copper-chromium alloy interface

    NASA Technical Reports Server (NTRS)

    Devincent, Sandra M.; Michal, Gary M.

    1993-01-01

    Sessile drop tests were used to obtain information about copper chromium alloys that suitably wet graphite. Characterization of graphite/copper-chromium alloy interfaces subjected to elevated temperatures were conducted using scanning electron micrography, energy dispersive spectroscopy, Auger electron spectroscopy, and X-ray diffraction analyses. These analyses indicate that during sessile drop tests conducted at 1130 C for one hour, copper alloys containing greater than 0.98 percent chromium form continuous reaction layers of approximately 10 micron thickness. The reaction layers adhere to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 degrees or less. X-ray diffraction results indicate that the reaction layer is chromium carbide. The kinetics of reaction layer formation were modelled in terms of bulk diffusion mechanisms. Reaction layer thickness is controlled initially by the diffusion of Cr out of Cu alloy and later by the diffusion of C through chromium carbide.

  7. Stability of chromium (III) sulfate in atmospheres containing oxygen and sulfur

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, B. D.; Nelson, H. G.

    1978-01-01

    The stability of chromium sulfate in the temperature range from 880 K to 1040 K was determined by employing a dynamic gas-solid equilibration technique. The solid chromium sulfate was equilibrated in a gas stream of controlled SO3 potential. Thermogravimetric and differential thermal analyses were used to follow the decomposition of chromium sulfate. X-ray diffraction analysis indicated that the decomposition product was crystalline Cr2O3 and that the mutual solubility between Cr2(SO4)3 and Cr2O3 was negligible. Over the temperature range investigated, the decomposition pressure were significantly high so that chromium sulfate is not expected to form on commercial alloys containing chromium when exposed to gaseous environments containing oxygen and sulfur (such as those encountered in coal gasification).

  8. Reaction layer formation at the graphite/copper-chromium alloy interface

    NASA Technical Reports Server (NTRS)

    Devincent, Sandra M.; Michal, Gary M.

    1992-01-01

    Sessile drop tests were used to obtain information about copper chromium alloys that suitably wet graphite. Characterization of graphite/copper-chromium alloy interfaces subjected to elevated temperatures were conducted using scanning electron micrography, energy dispersive spectroscopy, auger electron spectroscopy, and x ray diffraction analyses. These analyses indicate that during sessile drop tests conducted at 1130 C for one hour, copper alloys containing greater than 0.98 percent chromium form continuous reaction layers of approximately 10 micron thickness. The reaction layers adhere to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 degrees or less. X ray diffraction results indicate that the reaction layer is chromium carbide. The kinetics of reaction layer formation were modelled in terms of bulk diffusion mechanisms. Reaction layer thickness is controlled initially by the diffusion of Cr out of Cu alloy and later by the diffusion of C through chromium carbide.

  9. Development of Alkaline Oxidative Dissolution Methods for Chromium (III) Compounds Present in Hanford Site Tank Sludges

    SciTech Connect

    NN Krot; VP Shilov; AM Fedoseev; NA Budantseva; MV Nikonov; AB Yusov; AYu Garnov; IA Charushnikova; VP Perminov; LN Astafurova; TS Lapitskaya; VI Makarenkov

    1999-07-02

    The high-level radioactive waste sludge in the underground storage tanks at the Hanford Site contains various chromium(III)solid phases. Dissolution and removal of chromium from tank waste sludges is desirable prior to high-level waste vitrification because increased volume is required to incorporate the residual chromium. Unfortunately, dissolution of chromium from the sludge to form Cr(OH){sub 4}{sup {minus}} through treatment with heated NaOH solution (also used to dissolve aluminum phases and metathesize phosphates to sodium salts) generally has been unsuccessful in tests with both simulated and genuine Hanford waste sludges. Oxidative dissolution of the Cr(III) compounds to form soluble chromate has been proposed as an alternative chromium solid phase dissolution method and results of limited prior testing have been reported.

  10. Unconventional drop in the electrical resistance of chromium metal thin films at low temperature

    NASA Astrophysics Data System (ADS)

    Ohashi, M.; Ohashi, K.; Sawabu, M.; Miyagawa, M.; Kubota, T.; Takanashi, K.

    2016-09-01

    We studied the electrical resistance of single-crystal and polycrystalline chromium films. The ρ (T) curve of single-crystal films decrease with decreasing temperature and show humps at around 300 K consistent with the bulk chromium being an itinerant antiferromagnet. In the polycrystalline films, on the other hand, the ρ (T) curves deviate from those of the bulk chromium. Moreover, we observed sudden decrease in the resistance around 1.5 K. Although previous studies suggested that chromium films become superconductive (Schmidt et al. (1972) [12]), it is difficult to conclude whether a superconducting transition occurs because the electrical resistivity is not zero in all films. No anomaly was detected by resistance measurements around room temperature, and the sudden decrease in the resistance at low temperature may be attributed to the suppression of antiferromagnetic interaction by thinning down the chromium element.

  11. The correlation between swelling and radiation-induced segregation in iron-chromium-nickel alloys.

    SciTech Connect

    Allen, T. R.; Busby, J. T.; Kenik, E. A.; Was, G. S.

    1998-03-05

    The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is estimated using diffusivities derived from grain boundary segregation measurements in irradiated iron-chromium-nickel alloys. The resistance to void swelling in iron- and nickel-base alloys correlates with the segregation and both are functions of bulk alloy composition. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted. Additionally, swelling is shown to be greater in alloys in which the RIS profiles are slow to develop.

  12. Synthesis of axially chiral benzamides utilizing tricarbonyl(arene)chromium complexes.

    PubMed

    Koide, H; Uemura, M

    2000-06-01

    Axially chiral N,N-diethyl 2,6-disubstituted benzamides were stereo-selectively prepared utilizing planar chiral (arene)chromium complexes as an enantiomerically active form by following two methods. Ortho-lithiation of the enantiomerically pure planar chiral tricarbonyl(N,N-diethyl 2-methylbenzamide)chromium complex followed by electrophilic quenching gave axially chiral 2-methyl-6-substituted N,N-diethyl benzamide chromium complexes. Photo-oxidative demetalation produced the chromium-free axially chiral benzamides as optically active compounds. An alternative method for the preparation of axial chiral benzamides is an enantioselective lithiation at the benzylic methyl of meso tricarbonyl(N,N-diethyl 2,6-dimethylbenzamide)chromium with appropriate chiral lithium amide base followed by quenching with alkyl halides. PMID:10824151

  13. [Measured and Predicted Aquatic Life Criteria and Risk Assessment of Chromium (VI) in Liaohe River].

    PubMed

    Wang, Xiao-nan; Yan, Zhen-guang; Liu, Zheng-tao; Zhang, Cong; Wang, Wei-li

    2015-07-01

    In this study, toxicity data of aquatic species in Liaohe River for heavy metal chromium (VI) was collected and selected. The aquatic life criteria for chromium (VI) in Liaohe River was derived based on these toxicity data. Moreover, water samples of 25 sites in Liaohe River were collected, and the concentrations of chromium (VI) in these samples were analyzed. Finally, ecological risk assessment of chromium (VI) in Liaohe River was performed. Moreover, interspecies correlation estimation method (ICE) established by US EPA was used to predict the acute toxicity of species in Liaohe River, and aquatic life criteria based on predicted toxicity data was derived. The results showed that: the measured CMC (criteria maximum concentration), measured CCC (criteria continuous concentration) and the predicted CMC were 17. 73, 12. 15 and 13. 97 µg . L -1, respectively. Therefore, the ICE method could be used to predict the aquatic life criteria, because the predicted criteria value was very similar to the measured criteria value. Analysis of chromium (V) showed that the chromium (VI) concentrations of the 25 sites in Liaohe River were all below Class I or Class II water quality standards (GB 3838-2002), and the water quality was in good condition. However, for the potential risk of chromium (VI) exposure to the aquatic life of Liaohe River, the result of ecological risk assessment showed that chromium (V) concentrations in 7 sites exceeded the CCC in July, and chromium (VI) concentrations in 6 sites exceeded the CCC in December. Therefore, unacceptable effect on aquatic species caused by chromium (VI) exposure might have occurred in some sites of Liaohe River.

  14. Bioavailability of chromium in soils and sediments at a former leather tannery site

    SciTech Connect

    Pacquin, P.R.; Di Toro, D.M.; De Rosa, L.; Maiello, J.; Kerrigan, J.

    1995-12-31

    Bioavailability is a fundamental consideration in the equilibrium partitioning method used by EPA to develop sediment quality criteria (SOC). Even so, the bioavailability of metals in soils and sediments is often overlooked in ecological risk assessments for Superfund sites. This paper summarizes field and laboratory data for chromium levels in biota, soil and sediment samples from an abandoned tannery site and presents a method for characterizing the bioavailable fraction of chromium in these media. Chromium levels in soils and sediments at the former tannery site are about 1,000 times higher than levels at control sites (30,000 ppm versus 30 ppm). The elevated chromium levels are due to previously released tannery wastes, which contain high levels of chromium as a result of the tanning process. In contrast to chromium levels in soils and sediments, levels in terrestrial biota (earthworms, vegetation, and meadow voles) and aquatic biota (minnows, crayfish and mayfly nymphs) at the site are only about 2 to 20 times higher than control area samples. Biota:Soil and Biota:Sediment Accumulation Factors (BSAFs, total chromium basis) for the site are about one to five percent of control area BSAFs. This difference indicates that chromium at the site is relatively non-bioavailable. Sequential extraction techniques were used to characterize the manner in which the chromium is bound to soil and sediment at the site. The extraction results are compared with the biota field data and it appears that the exchangeable chromium fraction is indicative of the bioavailable fraction. The implications of these results to a screening level ecological risk assessment are presented.

  15. Investigate of atmospheric arsenic, cadmium, chromium, lead, and mercury levels in moss species found around Zilkale, by EDXRF Spectrometry

    NASA Astrophysics Data System (ADS)

    Akçay, Nilay; Batan, Nevzat; Ćinar, Yunus

    2016-04-01

    Zilkale is a castle located in Fırtına Valley and it is one of the most important historical structures in Çamlihemşin district of Rize Province in the Black Sea Region of Turkey. The castle surrounded by very high mountains that poke up into the clouds, and it rains here all year round. Tourism businesses or industrial plants are not so much there yet. In recent years, Zilkale region has begun the attract tourist, people on treaking holidays in the Kaçkar. But many domestic and foreign tourists come to this region by own car or tour buses. The aim of this study is to investigate the atmospheric concentrations of arsenic, cadmium, chromium, lead, and mercury levels in five different moss species collected around Zilkale by using Energy Dispersive X-ray Fluorescence (EDXRF) Spectrometry. The average concentrations of heavy metals in moss samples ranged from 0.79-4.63 ppm for arsenic, 54.47-143.39 ppm for chromium, 39.97-81.03 ppm for lead. The values of cadmium and mercury were found below the detection limit. This study has shown that Hypnum cupressiforme, Abietinella abietina, Rhytidium rugosum, Plagiomnium undulate, and Thuidium tamariscinum samples collected around Zilkale were used to assess the potential contamination of atmospheric As, Cd, Cr, Pb, Hg contamination in the region and made important contributions toward the understanding of atmospheric As, Cd, Cr, Pb, Hg baseline data can be used for identification of changes in the levels of these heavy metals in the studied area.

  16. Biosorption of aqueous chromium(VI) by Tamarindus indica seeds.

    PubMed

    Agarwal, G S; Bhuptawat, Hitendra Kumar; Chaudhari, Sanjeev

    2006-05-01

    The effectiveness of low cost agro-based materials namely, Tamarindus indica seed (TS), crushed coconut shell (CS), almond shell (AS), ground nut shell (GS) and walnut shell (WS) were evaluated for Cr(VI) removal. Batch test indicated that hexavalent chromium sorption capacity (q(e)) followed the sequence q(e)(TS) > q(e)(WS) > q(e)(AS) > q(e)(GS) > q(e)(CS). Due to high sorptive capacity, tamarind seed was selected for detailed sorption studies. Sorption kinetic data followed first order reversible kinetic fit model for all the sorbents. The equilibrium conditions were achieved within 150 min under the mixing conditions employed. Sorption equilibria exhibited better fit to Freundlich isotherms (R>0.92) than Langmuir isotherm (R approximately = 0.87). Hexavalent chromium sorption by TS decreased with increase in pH, and slightly reduced with increase in ionic strength. Cr(VI) removal by TS seems to be mainly by chemisorption. Desorption of Cr(VI) from Cr(VI) laden TS was quite less by distilled water and HCl. Whereas with NaOH, maximum desorption achieved was about 15.3%. When TS was used in downflow column mode, Cr(VI) removal was quite good but head loss increased as the run progressed and was stopped after 200 h.

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

    PubMed Central

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

    2012-01-01

    We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108) along with asymptomatic controls (n = 148) from a non contaminated reference community. Exposed symptomatic group consisted of 36.8% subjects who were GSTM1 null genotyped as compared to asymptomatic where only 19.4% subjects were null. The exposed subjects with GSTM1 null genotype were more susceptible to dermal adversities in comparison with wild genotyped subjects (OR = 2.42; 95% CI = 1.071–5.451). Age, smoking, gender or duration of residence were not found to have any confounding effect towards this association. Association with other genes was not statistically significant, nonetheless, possible contribution by these genes cannot be ruled out. In conclusion, variation in the polymorphic status of GSTM1 gene may influence dermal outcomes among residents from Cr(VI) contaminated areas. Further studies are therefore, needed to examine these observations among different population groups. PMID:22919465

  18. Hexavalent chromium induces chromosome instability in human urothelial cells.

    PubMed

    Wise, Sandra S; Holmes, Amie L; Liou, Louis; Adam, Rosalyn M; Wise, John Pierce

    2016-04-01

    Numerous metals are well-known human bladder carcinogens. Despite the significant occupational and public health concern of metals and bladder cancer, the carcinogenic mechanisms remain largely unknown. Chromium, in particular, is a metal of concern as incidences of bladder cancer have been found elevated in chromate workers, and there is an increasing concern for patients with metal hip implants. However, the impact of hexavalent chromium (Cr(VI)) on bladder cells has not been studied. We compared chromate toxicity in two bladder cell lines; primary human urothelial cells and hTERT-immortalized human urothelial cells. Cr(VI) induced a concentration- and time-dependent increase in chromosome damage in both cell lines, with the hTERT-immortalized cells exhibiting more chromosome damage than the primary cells. Chronic exposure to Cr(VI) also induced a concentration-dependent increase in aneuploid metaphases in both cell lines which was not observed after a 24h exposure. Aneuploidy induction was higher in the hTERT-immortalized cells. When we correct for uptake, Cr(VI) induces a similar amount of chromosome damage and aneuploidy suggesting that the differences in Cr(VI) sensitivity between the two cells lines were due to differences in uptake. The increase in chromosome instability after chronic chromate treatment suggests this may be a mechanism for chromate-induced bladder cancer, specifically, and may be a mechanism for metal-induced bladder cancer, in general. PMID:26908176

  19. Erosion of iron-chromium alloys by glass particles

    NASA Technical Reports Server (NTRS)

    Salik, J.; Buckley, D. H.

    1984-01-01

    The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

  20. Extraction and recovery of chromium from electroplating sludge.

    PubMed

    de Souza E Silva, Paula Tereza; de Mello, Nielson Torres; Menezes Duarte, Marta Maria; Montenegro, M Conceição B S M; Araújo, Alberto N; de Barros Neto, Benício; da Silva, Valdinete Lins

    2006-01-16

    This work reports a study of the extraction and recovery of chromium from the wastes (class I dangerous) generated by a galvanic manufacturer. Commercial HCl at room temperature was employed, and the conditions of the extraction process were optimized according to a sequential experimental design, which also included the acid concentration and contact time as variables. The best extraction conditions (80% v/v; 30 min; 97.6% Cr) for the chromic sludge were chosen in order to make the recovery process economically feasible. After each extraction, the residue was submitted to leaching essays, to assess environmental risks. It was found that sludge could be characterized as no longer dangerous. In the recovery study, a simple and low-cost technique was evaluated for selectivity based on an oxidation step with hydrogen peroxide. A 2(3) factorial design to assess the influence of oxidation time (min), temperature ( degrees C) and peroxide amount (mol/L) was employed. The best conditions, yielding a chromium recovery of about 92%, were a time of 60 min, a temperature of 60 degrees C and 2.1 mol/L peroxide. Additional essays revealed that the same result could be obtained with more economic conditions (40 min, 1.4 mol/L peroxide and 60 degrees C). This technique proved not only effective in comparison with existing alternatives, but also low costing. PMID:16144742

  1. Preconcentration Method on Modified Silica Fiber for Chromium Speciation

    PubMed Central

    Chahal, Varinder Kaur; Singh, Raghubir; Malik, Ashok Kumar; Matysik, Frank-Michael; Puri, Jugal Kishore

    2012-01-01

    A new method involving pre-concentration on modified silica fiber is described for the speciation of chromium(III) [Cr(III)] and chromium(VI) [Cr(VI)] in aqueous media. This method is based on the different chelating behavior of Cr(III) and Cr(VI) with morpholine-4-carbodithioate (MDTC). Both complexes are extracted on silica fiber modified by sol-gel technology by using 3-aminopropyltriethoxysilane (APS) as a precursor. All extracted samples are directly injected into an high-performance liquid chromatography injector for the simultaneous determination of Cr(III) and Cr(VI). Cr(VI) forms two different complexes, and Cr(III) forms a single complex with MDTC. Therefore, the concentration of Cr(VI) is determined directly from the peak area obtained at 5.4 min; whereas, the assay of Cr(III) is based on subtracting the peak area of Cr(VI) from the total peak area obtained at 4.3 min. Under the optimized conditions, the limits of detection for Cr(III) and Cr(VI) are found to be 0.7 ng/mL and 0.2 ng/mL, respectively. PMID:22291053

  2. Speciation of chromium in bread and breakfast cereals.

    PubMed

    Mathebula, Mpho Wendy; Mandiwana, Khakhathi; Panichev, Nikolas

    2017-02-15

    Bread and breakfast cereals are a major constituents of the human diet, yet their Cr(VI) content is not known. Chromium(VI) was determined in these products by high resolution continuum source atomic absorption spectrometer (HR-CS AAS) after leaching Cr(VI) with 0.10molL(-1) Na2CO3. The results showed that 33-73% of total Cr (58.17±5.12μgkg(-1)-156.1±6.66μgkg(-1)) in bread exist as Cr(VI) and the highest total Cr content was found in brown bread. It was shown that Cr(III) is oxidized to Cr(VI) during toasting of bread. Chromium(VI) content in breakfast cereals ranged between 20.4±4μgkg(-1) and 470.4±68μgkg(-1). Therefore, it can be concluded that bread and breakfast cereals contains Cr(VI) which does not exceed maximum acceptable concentration (MAC) of 0.003mgkg(-1)bw(-1)day(-1) through daily consumption of half a bowl (65g) of breakfast cereal and four slices of toasted (122g) or untoasted bread (160g). PMID:27664683

  3. Hexavalent chromium induces chromosome instability in human urothelial cells.

    PubMed

    Wise, Sandra S; Holmes, Amie L; Liou, Louis; Adam, Rosalyn M; Wise, John Pierce

    2016-04-01

    Numerous metals are well-known human bladder carcinogens. Despite the significant occupational and public health concern of metals and bladder cancer, the carcinogenic mechanisms remain largely unknown. Chromium, in particular, is a metal of concern as incidences of bladder cancer have been found elevated in chromate workers, and there is an increasing concern for patients with metal hip implants. However, the impact of hexavalent chromium (Cr(VI)) on bladder cells has not been studied. We compared chromate toxicity in two bladder cell lines; primary human urothelial cells and hTERT-immortalized human urothelial cells. Cr(VI) induced a concentration- and time-dependent increase in chromosome damage in both cell lines, with the hTERT-immortalized cells exhibiting more chromosome damage than the primary cells. Chronic exposure to Cr(VI) also induced a concentration-dependent increase in aneuploid metaphases in both cell lines which was not observed after a 24h exposure. Aneuploidy induction was higher in the hTERT-immortalized cells. When we correct for uptake, Cr(VI) induces a similar amount of chromosome damage and aneuploidy suggesting that the differences in Cr(VI) sensitivity between the two cells lines were due to differences in uptake. The increase in chromosome instability after chronic chromate treatment suggests this may be a mechanism for chromate-induced bladder cancer, specifically, and may be a mechanism for metal-induced bladder cancer, in general.

  4. Density functional theory and chromium: Insights from the dimers

    SciTech Connect

    Würdemann, Rolf; Kristoffersen, Henrik H.; Moseler, Michael; Walter, Michael

    2015-03-28

    The binding in small Cr clusters is re-investigated, where the correct description of the dimer in three charge states is used as criterion to assign the most suitable density functional theory approximation. The difficulty in chromium arises from the subtle interplay between energy gain from hybridization and energetic cost due to exchange between s and d based molecular orbitals. Variations in published bond lengths and binding energies are shown to arise from insufficient numerical representation of electron density and Kohn-Sham wave-functions. The best functional performance is found for gradient corrected (GGA) functionals and meta-GGAs, where we find severe differences between functionals from the same family due to the importance of exchange. Only the “best fit” from Bayesian error estimation is able to predict the correct energetics for all three charge states unambiguously. With this knowledge, we predict small bond-lengths to be exclusively present in Cr{sub 2} and Cr{sub 2}{sup −}. Already for the dimer cation, solely long bond-lengths appear, similar to what is found in the trimer and in chromium bulk.

  5. Boriding of high carbon high chromium cold work tool steel

    NASA Astrophysics Data System (ADS)

    Muhammad, W.

    2014-06-01

    High-carbon high-chromium cold work tool steels are widely used for blanking and cold forming of punches and dies. It is always advantageous to obtain an increased wear resistant surface to improve life and performance of these steels. In this connection boriding of a high-carbon high-chromium cold work die steel, D3, was conducted in a mixture of 30% B4C, 70% borax at 950 °C for two, four and six hours. Case depth of the borided layer obtained was between 40 to 80 μm. After boriding, the surface hardness achieved was between 1430 to 1544 HV depending upon the process time. X-ray diffraction studies confirmed the formation of a duplex compound layer consisting of FeB and Fe2B. It is generally considered that FeB is undesirable because of its inherent brittleness. Post boriding treatment (homogenization) transformed the compound layer into single-phase layer of Fe2B, while surface hardness decreased to 1345-1430 HV. Pin-on-disc wer test showed that wear resistance of the borided samples was superior as compared to non-borided material and increased with boriding time.

  6. Effects of chromium picolinate on beginning weight training students.

    PubMed

    Hasten, D L; Rome, E P; Franks, B D; Hegsted, M

    1992-12-01

    Changes in body weight (BW), a sum of three body circumferences (sigma C), a sum of three skinfolds (sigma SF), and the one-repetition maximum (1RM) for the squat (SQ) and bench press (BP) were examined in 59 college-age students (37 males [M], 22 females [F]) over a 12-week weight lifting program. Using a double-blind protocol, half of the students were given 200 micrograms/day chromium (Cr) in the form of chromium picolinate (CrPic) while the other half received a placebo (P). Therefore four groups were randomly formed: F-CrPic (n = 12), F-P (n = 10), M-CrPic (n = 18), and M-P (n = 19). All groups had significant increases in sigma C and significant decreases in sigma SF. No treatment effects were seen for the strength measurements, although the males experienced greater absolute increases. The only significant treatment effect found was due to the F-CrPic group gaining more BW (p = 0.0048) than the other three groups. It was concluded that CrPic supplementation had a greater effect on the females than on the males.

  7. Chromium-Assisted Synthesis of Platinum Nanocube Electrocatalysts

    SciTech Connect

    Loukrakpam, Rameshwori; Chang, Paul; Luo, Jin; Fang, Bin; Mott, Derrick; Bae, In-Tae; Naslund, H. R.; Engelhard, Mark H.; Zhong, Chuan-Jian

    2010-10-04

    This report describes a novel strategy of chromium-assisted shape control in the synthesis of platinum nanocubes with high monodispersity. The use of a certain concentration ratio of platinum vs. chromium precursors (typically 1:1) has been demonstrated to enable an effective adsorption of Cr species on the nanocrystal in selective blocking of the adsorption of capping molecules on the different surfaces for the nanocube formation. The cubic shape was evidenced by both high-resolution TEM and x-ray diffraction characterizations, whereas the composition was analyzed by both bulk and surfacesensitive techniques (DCP-AES, EDS and XPS). The results indicated that practically there was no Cr in the nanocubes or only a trace of Cr on the nanocrystal surfaces, demonstrating a high effectiveness in producing Pt nanocubes. A combination of effective oxidative leaving of the adsorbed Cr species and the weaker adsorption of capping molecules on Pt(111) constitutes the kinetic driving force for a faster growth rate of Pt(111) than Pt(100) faces. The understanding of the synergistic correlation between surface metal adsorption and ligand encapsulation in creating a difference in the kinetic growth on different nanocrystal facets has important implication to the design of advanced catalysts.

  8. 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

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

    PubMed

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

    2013-02-01

    Hexavalant chromium [Cr(VI)] tolerance and accumulation in in vitro grown Nopalea cochenillifera Salm. Dyck. plants was investigated. A micropropagation protocol was establish for a rapid multiplication of N. cochenillifera and [Cr(VI)] tolerance and accumulation was studied in in vitro grown cultures. Cr concentration was estimated by atomic absorption spectroscopy in roots and shoots to confirm plant's hyperaccumulation capacity. Plants showed tolerance up to 100 μM K(2)Cr(2)O(7) without any significant changes in root growth after 16 days treatment; whereas, chlorophyll content in plants treated with 1 and 10 μM K(2)Cr(2)O(7) were not so different than the control plant. The levels of lipid peroxidation and protein oxidation increased significantly (p < 0.01) with increasing concentration of chromium. Exposures of N. cochenillifera to lower concentrations of K(2)Cr(2)O(7) (≤ 10 μM) induced catalase (CAT) and superoxide dismutase (SOD) significantly (p < 0.001) but higher concentrations of K(2)Cr(2)O(7) (>100 μM) inhibited the activities of CAT and SOD. Roots accumulated a maximum of 25,263.396 ± 1,722.672 mg Cr Kg(-1) dry weight (DW); while the highest concentration of Cr in N. cochenillifera shoots was 705.714 ± 32.324 mg Cr Kg(-1) DW. N. cochenillifera could be a prospective hyperaccumulator plant of Cr(VI) and a promising candidate for phytoremediation purposes. PMID:22914913

  10. Adverse effects and bioconcentration of chromium in two freshwater rotifer species.

    PubMed

    Hernández-Ruiz, Esmeralda; Alvarado-Flores, Jesús; Rubio-Franchini, Isidoro; Ventura-Juárez, Javier; Rico-Martínez, Roberto

    2016-09-01

    Bioaccumulation of trivalent (CrIII) and hexavalent chromium (CrVI), and its adverse effects were studied in two rotifer species: Brachionus calyciflorus (two different strains), and Lecane quadridentata. Median Lethal Concentration (LC50) at 24 h of both species showed that CrVI is highly toxic: LC50 ranges from 4.7 × 10(-5) to 4 × 10(-6) mg L(-1)), compared with CrIII: LC50 ranges from 0.64 to 1.279 mg L(-1). Using the LC50 as an exposure concentration, and using atomic absorption, the bioconcentration factor (BCF) was obtained and BCFs of rotifers exposed to CrIII are four orders of magnitude lower than BCFs of rotifers exposed to CrVI. The effect of Cr on the elemental composition of the two species of rotifers in their structures by X-ray microanalysis by energy dispersion showed that Cr is found in intoxicated rotifers, but not in control rotifers. The basal immunoreactivity to metallothioneins is greater in B. calyciflorus than L. quadridentata. The immunoreactivity to metallothioneins decreases in B. calyciflorus when is exposed to CrIII, in contrast in L. quadridentata the immunoreactivity to metallothioneins increase when is exposed to CrIII, and the immunoreactivity to CrVI in L. quadridentata decrease. A mechanism is proposed in which the harder lorica of L. quadridentata acts as a barrier and accumulator of CrVI, and allows for attenuating responses like metallothionein production in L. quadridentata. Instead, in B. calyciflorus the lack of a harder lorica allows for deeper penetration of CrVI, and no time to produce attenuating measures. PMID:27258901

  11. Adverse effects and bioconcentration of chromium in two freshwater rotifer species.

    PubMed

    Hernández-Ruiz, Esmeralda; Alvarado-Flores, Jesús; Rubio-Franchini, Isidoro; Ventura-Juárez, Javier; Rico-Martínez, Roberto

    2016-09-01

    Bioaccumulation of trivalent (CrIII) and hexavalent chromium (CrVI), and its adverse effects were studied in two rotifer species: Brachionus calyciflorus (two different strains), and Lecane quadridentata. Median Lethal Concentration (LC50) at 24 h of both species showed that CrVI is highly toxic: LC50 ranges from 4.7 × 10(-5) to 4 × 10(-6) mg L(-1)), compared with CrIII: LC50 ranges from 0.64 to 1.279 mg L(-1). Using the LC50 as an exposure concentration, and using atomic absorption, the bioconcentration factor (BCF) was obtained and BCFs of rotifers exposed to CrIII are four orders of magnitude lower than BCFs of rotifers exposed to CrVI. The effect of Cr on the elemental composition of the two species of rotifers in their structures by X-ray microanalysis by energy dispersion showed that Cr is found in intoxicated rotifers, but not in control rotifers. The basal immunoreactivity to metallothioneins is greater in B. calyciflorus than L. quadridentata. The immunoreactivity to metallothioneins decreases in B. calyciflorus when is exposed to CrIII, in contrast in L. quadridentata the immunoreactivity to metallothioneins increase when is exposed to CrIII, and the immunoreactivity to CrVI in L. quadridentata decrease. A mechanism is proposed in which the harder lorica of L. quadridentata acts as a barrier and accumulator of CrVI, and allows for attenuating responses like metallothionein production in L. quadridentata. Instead, in B. calyciflorus the lack of a harder lorica allows for deeper penetration of CrVI, and no time to produce attenuating measures.

  12. A post-remediation assessment in Jersey City of the association of hexavalent chromium in house dust and urinary chromium in children.

    PubMed

    Black, Kathleen; Gochfeld, Michael; Lioy, Paul J; Fan, Zhi-Hua Tina; Yu, Chang Ho; Jeitner, Chris; Hernandez, Marta; Einstein, Stephanie A; Stern, Alan H

    2015-01-01

    Although all chromite ore processing residue (COPR) sites near residential neighborhoods in Jersey City, New Jersey have undergone remediation, recent studies found widespread, but low levels of hexavalent chromium (Cr(+6)) in house dust both in Jersey City and in communities with no known sources of Cr(+6). This study was designed as a follow-up to determine whether there is an association between current Cr(+6) levels in house dust and urinary chromium concentrations in young children. Dust samples (N=369) were collected from 123 homes. The median Cr(+6) concentration was 3.3 μg/g (mean±SD 5.2±7.5) and the median Cr(+6) loading was 1.1 μg/m(2) (1.9±3.1). These levels were not elevated compared with previously reported levels in background communities (median concentration=3.5 μg/g; median loading=2.8 μg/m(2)). Urinary chromium concentrations were measured in spot urine samples collected from 150 children, ages 3 months to 6 years. The median uncorrected urinary chromium concentration was 0.19 μg/l (0.22±0.16). Current urinary chromium concentrations were significantly lower than those previously reported before and during remediation (t-test; P<0.001). Urinary chromium concentrations were not significantly higher in homes with high (75th or 90th percentile) Cr(+6) dust levels (concentration or loading) compared with other homes. Multiple linear regression was used to examine the relationship between Cr(+6) levels (concentration and loading) in house dust and urinary chromium concentrations (uncorrected and specific gravity corrected). Contrary to pre-remediation studies, we did not find a positive association between Cr(+6) levels in house dust and urinary chromium concentrations. The findings indicate that current Cr(+6) levels in house dust are not positively associated with children's chromium exposure as measured by urinary chromium, and the children's exposure to Cr(+6) in house dust is below the level that could be identified by urine

  13. A post-remediation assessment in Jersey City of the association of hexavalent chromium in house dust and urinary chromium in children.

    PubMed

    Black, Kathleen; Gochfeld, Michael; Lioy, Paul J; Fan, Zhi-Hua Tina; Yu, Chang Ho; Jeitner, Chris; Hernandez, Marta; Einstein, Stephanie A; Stern, Alan H

    2015-01-01

    Although all chromite ore processing residue (COPR) sites near residential neighborhoods in Jersey City, New Jersey have undergone remediation, recent studies found widespread, but low levels of hexavalent chromium (Cr(+6)) in house dust both in Jersey City and in communities with no known sources of Cr(+6). This study was designed as a follow-up to determine whether there is an association between current Cr(+6) levels in house dust and urinary chromium concentrations in young children. Dust samples (N=369) were collected from 123 homes. The median Cr(+6) concentration was 3.3 μg/g (mean±SD 5.2±7.5) and the median Cr(+6) loading was 1.1 μg/m(2) (1.9±3.1). These levels were not elevated compared with previously reported levels in background communities (median concentration=3.5 μg/g; median loading=2.8 μg/m(2)). Urinary chromium concentrations were measured in spot urine samples collected from 150 children, ages 3 months to 6 years. The median uncorrected urinary chromium concentration was 0.19 μg/l (0.22±0.16). Current urinary chromium concentrations were significantly lower than those previously reported before and during remediation (t-test; P<0.001). Urinary chromium concentrations were not significantly higher in homes with high (75th or 90th percentile) Cr(+6) dust levels (concentration or loading) compared with other homes. Multiple linear regression was used to examine the relationship between Cr(+6) levels (concentration and loading) in house dust and urinary chromium concentrations (uncorrected and specific gravity corrected). Contrary to pre-remediation studies, we did not find a positive association between Cr(+6) levels in house dust and urinary chromium concentrations. The findings indicate that current Cr(+6) levels in house dust are not positively associated with children's chromium exposure as measured by urinary chromium, and the children's exposure to Cr(+6) in house dust is below the level that could be identified by urine

  14. Urinary chromium excretion, diurnal changes, and relationship to creatinine excretion in healthy and sick individuals of different ages.

    PubMed

    Gürson, C T; Saner, G

    1978-07-01

    Since urine is the main excretory pathway for chromium, this study was conducted to compare in normal individuals the daily urinary chromium excretion with a 4 hr sample, to investigate diurnal fluctuations of urinary chromium and age-dependent relationship between urinary chromium and creatinine excretion. The results can be summarized as 1) there was no significant difference between the observed 24 hr chromium excretion and 24 hr excretion calculated from the one 4 hr samples, 2) a diurnal variation was observed when urinary excretion was expressed as chromium per minute, but no time-related variation could be established when chromium/creatinine (Cr/Cre) ratios in samples from three different periods of the same day were compared, although a significant positive correlation existed between urinary chromium and creatinine concentration, 3) the Cr/Cre ratio was found to be age-dependent, 4) in malnourished children the Cr/Cre ratio was very high and significantly different from that of normal infants, 5) This ratio for the eight diabetics was found to be significantly higher when compared with normal adults. On the basis of these results, it is suggested that morning 4 hr urinary chromium reflects the daily chromium excretion and that the Cr/Cre ratio of single urine samples obtained during this period is a reliable criterion in the evaluation of chromium nutrition of individuals in different conditions, provided that the influence of age is taken into consideration.

  15. [In vitro percutaneous absorption of chromium powder and the effect of skin cleanser].

    PubMed

    D'Agostin, F; Crosera, M; Adami, G; Malvestio, A; Rosani, R; Bovenzi, M; Maina, G; Filon, F Larese

    2007-01-01

    Occupational chromium dermatitis occurs frequently among cement and metal workers, workers dealing with leather tanning and employees in the ceramic industry. The present study, using an in-vitro system, evaluated percutaneous absorption of chromium powder and the effect of rapid skin decontamination with a common detergent. Experiments were performed using the Franz diffusion cell method with human skin. Physiological solution was used as receiving phase and a suspension of chromium powder in synthetic sweat was used as donor phase. The tests were performed without or with decontamination using the cleanser 30 minutes after the start of exposure. The amount of chromium permeated through the skin was analysed by Inductively Coupled Plasma Atomic Emission Spectroscopy and Electro Thermal Atomic Absorption Spectroscopy. Speciation analysis and measurements of chromium skin content were also performed. We calculated a permeation flux of 0.843 +/- 0.25 ng cm(-2) h(-1) and a lag time of 1.1 +/- 0.7 h. The cleaning procedure significantly increased chromium skin content, whereas skin passage was not increased. These results showed that chromium powder can pass through the skin and that skin decontamination did not decrease skin absorption. Therefore, it is necessary to prevent skin contamination when using toxic agents.

  16. 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.

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

    PubMed

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

    2008-09-01

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

  18. Studies of chromium removal from tannery wastewaters by algae biosorbents, Spirogyra condensata and Rhizoclonium hieroglyphicum.

    PubMed

    Onyancha, Douglas; Mavura, Ward; Ngila, J Catherine; Ongoma, Peter; Chacha, Joseph

    2008-10-30

    Chromium in the effluent is a major concern for tanning industry. Chemical precipitation methods are commonly employed for the removal of chromium but this leads to formation of chrome-bearing solid waste, plus it is uneconomical when the concentration of chromium in the effluent is low. Ion exchange and membrane separation methods are relatively expensive. In this study, two algae namely, Spirogyra condensata and Rhizoclonium hieroglyphicum have been employed to remove chromium from tannery effluent. The effect of pH and chromium concentration showed S. condensata to exhibit maximum uptake of about 14 mg Cr(III)/g of algae at optimum pH of 5.0 whereas R. hieroglyphicum had 11.81 mg of Cr(III)/g of algae at pH of 4.0. Langmuir and Freundlich models were applied. Increase of initial concentration of Cr resulted to a decrease in adsorption efficiency. Dilute sulphuric acid (0.1M) showed good desorption efficiency (>75%). Interference from cations negatively impacted on biosorption of chromium. Immobilized algae on Amberlite XAD-8 in a glass column, gave better recovery of chromium in tannery effluent compared to a batch method with unimmobilized algae. Fourier transform infra red (FT-IR) analysis of the two algae revealed the presence of carboxyl groups as possible binding sites. PMID:18394792

  19. Studies of chromium removal from tannery wastewaters by algae biosorbents, Spirogyra condensata and Rhizoclonium hieroglyphicum.

    PubMed

    Onyancha, Douglas; Mavura, Ward; Ngila, J Catherine; Ongoma, Peter; Chacha, Joseph

    2008-10-30

    Chromium in the effluent is a major concern for tanning industry. Chemical precipitation methods are commonly employed for the removal of chromium but this leads to formation of chrome-bearing solid waste, plus it is uneconomical when the concentration of chromium in the effluent is low. Ion exchange and membrane separation methods are relatively expensive. In this study, two algae namely, Spirogyra condensata and Rhizoclonium hieroglyphicum have been employed to remove chromium from tannery effluent. The effect of pH and chromium concentration showed S. condensata to exhibit maximum uptake of about 14 mg Cr(III)/g of algae at optimum pH of 5.0 whereas R. hieroglyphicum had 11.81 mg of Cr(III)/g of algae at pH of 4.0. Langmuir and Freundlich models were applied. Increase of initial concentration of Cr resulted to a decrease in adsorption efficiency. Dilute sulphuric acid (0.1M) showed good desorption efficiency (>75%). Interference from cations negatively impacted on biosorption of chromium. Immobilized algae on Amberlite XAD-8 in a glass column, gave better recovery of chromium in tannery effluent compared to a batch method with unimmobilized algae. Fourier transform infra red (FT-IR) analysis of the two algae revealed the presence of carboxyl groups as possible binding sites.

  20. Effect of chromium on insulin secretion and glucose removal rate in the newborn.

    PubMed

    Saner, G; yüksel, T; Gürson, C T

    1980-02-01

    The effect of chromium on glucose removal rate (GRR) was investigated in the first 48 hr of life in 22 full-term newborns. Intravenous glucose tolerance test was performed in all babies in the first 24 hr. GRR was found 1.22 +/- 0.17% min. Sixteen of 22 babies received orally 250 micrograms CrCl3 6 H2O and the other six served as controls (no chromium). Intravenous glucose tolerance test was repeated on the 2nd day in all subjects. In the chromium administered group GRR increased from 1.34 +/- 0.19 to 2.58 +/- 0.45% min (P less than 0.01). In the controls, GRR on 2 consecutive days were found 0.90 +/- 0.36 and 2.04 +/- 0.32% min, respectively (P less than 0.05). The ratio of the difference between two GRR values to initial GRR showed no significant difference between the chromium-administered group and the controls. Chromium did not cause a significant change in plasma insulin. The low GRR observed in the newborn irrespective of administered chromium may be taken as evidence that similar to the relative delay in insulin release, the active role of chromium in plasma as glucose tolerance factor may also be inadequate in the early newborn period.

  1. Investigation of total and hexavalent chromium in filtered and unfiltered groundwater samples at the Tucson International Airport Superfund Site

    USGS Publications Warehouse

    Tillman, Fred; McCleskey, R. Blaine; Hermosillo, Edyth

    2016-01-01

    Potential health effects from hexavalent chromium in groundwater have recently become a concern to regulators at the Tucson International Airport Area Superfund site. In 2016, the U.S. Geological Survey sampled 46 wells in the area to characterize the nature and extent of chromium in groundwater, to understand what proportion of total chromium is in the hexavalent state, and to determine if substantial differences are present between filtered and unfiltered chromium concentrations. Results indicate detectable chromium concentrations in all wells, over 75 % of total chromium is in the hexavalent state in a majority of wells, and filtered and unfiltered results differ substantially in only a few high-turbidity total chromium samples.

  2. Identification of Chromium Resistant Bacteria from Dry Fly Ash Sample of Mejia MTPS Thermal Power Plant, West Bengal, India.

    PubMed

    Roychowdhury, Roopali; Mukherjee, Pritam; Roy, Madhumita

    2016-02-01

    Eight chromium resistant bacteria were isolated from a dry fly ash sample of DVC-MTPS thermal power plant located in Bankura, West Bengal, India. These isolates displayed different degrees of chromate reduction under aerobic conditions. According to 16S rDNA gene analysis, five of them were Staphylococcus, two were Bacillus and one was Micrococcus. The minimum inhibitory concentration towards chromium and the ability to reduce hexavalent chromium to trivalent chromium was highest in Staphylococcus haemolyticus strain HMR17. All the strains were resistant to multiple heavy metals (As, Cu, Cd, Co, Zn, Mn, Pb and Fe) and reduced toxic hexavalent chromium to relatively non toxic trivalent chromium even in the presence of these multiple heavy metals. All of them showed resistance to different antibiotics. In a soil microcosm study, S. haemolyticus strain HMR17 completely reduced 4 mM hexavalent chromium within 7 days of incubation.

  3. Investigation of Total and Hexavalent Chromium in Filtered and Unfiltered Groundwater Samples at the Tucson International Airport Superfund Site.

    PubMed

    Tillman, Fred D; McCleskey, R Blaine; Hermosillo, Edyth

    2016-10-01

    Potential health effects from hexavalent chromium in groundwater have recently become a concern to regulators at the Tucson International Airport Area Superfund site. In 2016, the U.S. Geological Survey sampled 46 wells in the area to characterize the nature and extent of chromium in groundwater, to understand what proportion of total chromium is in the hexavalent state, and to determine if substantial differences are present between filtered and unfiltered chromium concentrations. Results indicate detectable chromium concentrations in all wells, over 75 % of total chromium is in the hexavalent state in a majority of wells, and filtered and unfiltered results differ substantially in only a few high-turbidity total chromium samples.

  4. Identification of Chromium Resistant Bacteria from Dry Fly Ash Sample of Mejia MTPS Thermal Power Plant, West Bengal, India.

    PubMed

    Roychowdhury, Roopali; Mukherjee, Pritam; Roy, Madhumita

    2016-02-01

    Eight chromium resistant bacteria were isolated from a dry fly ash sample of DVC-MTPS thermal power plant located in Bankura, West Bengal, India. These isolates displayed different degrees of chromate reduction under aerobic conditions. According to 16S rDNA gene analysis, five of them were Staphylococcus, two were Bacillus and one was Micrococcus. The minimum inhibitory concentration towards chromium and the ability to reduce hexavalent chromium to trivalent chromium was highest in Staphylococcus haemolyticus strain HMR17. All the strains were resistant to multiple heavy metals (As, Cu, Cd, Co, Zn, Mn, Pb and Fe) and reduced toxic hexavalent chromium to relatively non toxic trivalent chromium even in the presence of these multiple heavy metals. All of them showed resistance to different antibiotics. In a soil microcosm study, S. haemolyticus strain HMR17 completely reduced 4 mM hexavalent chromium within 7 days of incubation. PMID:26602566

  5. Natural and induced reduction of hexavalent chromium in soil

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    SciTech Connect

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

    2014-10-22

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 μM h₋1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of

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

    DOE PAGES

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

    2014-10-22

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions bymore » this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 μM h₋1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature

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

    PubMed Central

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

    2015-01-01

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 µM h−1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  10. Immunomodulatory effects of seabuckthorn (Hippophae rhamnoides L.) against chromium (VI) induced immunosuppression.

    PubMed

    Geetha, S; Singh, Vandana; Ram, M Sai; Ilavazhagan, G; Banerjee, P K; Sawhney, R C

    2005-10-01

    The present study reports the immunomodulatory effects of seabuckthorn (Hippophae rhamnoides L.) leaf extract on cellular and humoral immune response by studying delayed-type hypersensitivity response, IL-2, IL-4 and gamma-IFN levels and antibody titres in chromium-induced immunosuppressed animals. Oral feeding of chromium (30 mg/kg bw) significantly inhibited antibody production and S-RBC induced delayed-type hypersensitivity response. Administration of leaf extract (100 mg/kg bw) along with chromium significantly inhibited chromium-induced immunosuppression. To understand the immunomodulatory mechanism of leaf extract, in vitro studies were carried out using rat lymphocytes. Addition of chromium resulted in a significant decrease in lymphocyte size and increased ROS generation. The leaf extract of seabuckthorn significantly inhibited chromium-induced reactive oxygen species (ROS) generation and maintained the cell size identical to that of control cells. Chromium treatment markedly inhibited the mitochondrial transmembrane potential by larger lymphocytes in particular, while the leaf extract restored the same significantly. Chromium also inhibited significantly concanavalin A (ConA) induced IL-2, IL-4 and gamma-IFN production in rat lymphocytes. The leaf extract (100 microg/ml) alone stimulated IL-2 and gamma-IFN production even in the absence of ConA and also inhibited chromium-induced decline in IL-2 and gamma-IFN production but it did not change IL-4 production. These observations suggest that the leaf extract of seabuckthorn has significant immunomodulatory activity and specifically activates the cell-mediated immune response. PMID:16180095

  11. Effects of chromium nicotinate on performance, carcase characteristics and blood chemistry of growing turkeys.

    PubMed

    Chen, K L; Lu, J J; Lien, T F; Chiou, P W

    2001-07-01

    1. The objective of this trial was to study the effects of chromium nicotinate (Cr) supplementation on the performance, carcase characteristics and blood constituents of 9 to 22 week-old male turkeys. 2. Fifty-four 8-week-old male turkeys weighing 2.9 +/- 0.28 kg were allocated at random into 9 groups with 3 dietary treatments and 3 replicates. The dietary treatment was different dietary concentrations of chromium in the basal diet, to provide 0 (control), 1 or 3 mg/kg. The feeding trial lasted for 14 weeks. 3. Results showed that 1 mg/kg chromium supplementation significantly improved weight gain and food intake at 9 to 18 weeks of age but did not significantly influence performance at 19 to 22 week of age. The breast and thigh muscle were significantly increased in birds receiving 1 mg/kg chromium supplementation but were decreased by 3 mg/kg of supplementation. 4. Dietary chromium supplementation did not significantly influence other serum constituents, including insulin, HDL, VLDL+LDL, HDL-C, VLDL-C+LDL-C, total protein, albumin, and gamma-globulin at 18 and 22 weeks of age. 5. The serum triacylglycerol (TG) and uric acid contents were significantly increased, while glycerol and alpha-globulin were significantly reduced by 3 mg/kg chromium supplementation. However, 1 mg/kg chromium supplementation significantly reduced serum cholesterol and glycerol at 18-weeks old. At 22 weeks of age, 1 mg/kg chromium supplementation significantly increased serum glucose and decreased the uric acid concentration whereas 3 mg/kg chromium supplementation significantly increased the creatinine concentration and decreased beta-globulin concentration. PMID:11469563

  12. Chromium behavior during cement-production processes: a clinkerization, hydration, and leaching study.

    PubMed

    Sinyoung, Suthatip; Songsiriritthigul, Prayoon; Asavapisit, Suwimol; Kajitvichyanukul, Puangrat

    2011-07-15

    The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca(6)Al(4)Cr(2)O(15), Ca(5)Cr(3)O(12), Ca(5)Cr(2)SiO(12), and CaCr(2)O(7), with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca(5)(CrO(4))(3)OH, CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr(3+) from Ca(6)Al(4)Cr(2)O(15) and Cr(6+) from CaCr(2)O(7), CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.

  13. Natural occurrence of hexavalent chromium in the Aromas Red Sands Aquifer, California.

    PubMed

    Gonzalez, A R; Ndung'u, K; Flegal, A R

    2005-08-01

    To address increasing concerns of chromium contamination in the drinking water of Santa Cruz County, we designed a study to investigate the source(s) and spatial gradients of the chromium concentration and speciation in local aquifers. This study was catalyzed by a report (January 2001) bythe Soquel Creek Water District of elevated hexavalent chromium concentrations ranging from 6 to 36 microg L(-1), approaching the state's maximum concentration limit of 50 microg L(-1), in the Aromas Red Sands aquifer. To test the accuracy of those preliminary measurements, we collected groundwater using trace metal clean techniques from 11 sites in Santa Cruz County, including 10 from the aquifer with reportedly elevated chromium concentrations and 1 from an adjacent aquifer, the Purisima, and analyzed them fortotal chromium using inductively couple plasma mass spectrometry. Nine of the reportedly 10 contaminated sites had total chromium concentrations ranging from 5 to 39 microg L(-1), while one from the control site was below the limit of detection (0.01 microg L(-1)). We also measured the speciation of chromium at all sites using a solid supported membrane extraction coupled with graphite furnace atomic absorption spectrometry and determined that on average 84% of total chromium was Cr(VI). In addition to the groundwater analyses, a series of extractions were performed on sediment samples from both the Aromas Red Sands and Purisima aquifers. These tests were used to empirically characterize sediment trace metal (Cr, Fe, Mn) distributions in five phases providing information about the origin, availability, reactivity, and mobilization of these trace metals. Results from groundwater and sediment samples indicate that the chromium is naturally occurring in the Aromas Red Sands aquifer, possibly by Cr(III) mineral deposits being oxidized to Cr(VI) by manganese oxides in the aquifer.

  14. Characterization of Chromium Waste Form Based on Biocementation by Microbacterium sp. GM-1.

    PubMed

    Lun, Limei; Li, Dongwei; Yin, Yajie; Li, Dou; Xu, Guojing; Zhao, Ziqiang; Li, Shan

    2016-09-01

    This paper demonstrated a biocementation technology for chromium slag by strain GM-1, a calcifying ureolytic bacterium identified as Microbacterium, based on microbially induced calcium carbonate. The characterization of Microbacterium sp. GM-1 was assessed to know the growth curve in different concentrations of Cr(VI). Microbacterium sp. GM-1 was tolerant to a concentration of 120 mg/L Cr(VI). Chromium waste forms were prepared using chromium, sand, soil and bacterial culture. There we had three quality ratios (8:2:1; 8:1:1; 8:2:0.5) of material (chromium, sand and soil, respectively). Bacterial and control chromium waste forms were analyzed by thermal gravimetric analyzer. All bacterial forms (8:2:1; 8:1:1; 8:2:0.5 J) showed sharp weight loss near the decomposition temperature of calcium carbonate between 600 and 700 °C. It indicated that the efficient bacterial strain GM-1 had induced calcium carbonate precipitate during bioremediation process. A five step Cr(VI) sequential extraction was performed to evaluate its distribution pattern in chromium waste forms. The percentage of Cr(VI) was found to significantly be decreased in the exchangeable fraction of chromium waste forms and subsequently, that was markedly increased in carbonated fraction after biocementation by GM-1. Further, compressive strength test and leaching test were carried out. The results showed that chromium waste forms after biocementation had higher compressive strength and lower leaching toxicity. Additionally, the samples made of 8:1:1 (m/m/m) chromium + sand + soil were found to develop the highest compressive strength and stand the lowest concentration of Cr(VI) released into the environment. PMID:27407300

  15. Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with chromium

    NASA Astrophysics Data System (ADS)

    Orlova, E. I.; Kharitonova, E. P.; Novikova, N. E.; Sorokina, N. I.; Voronkova, V. I.

    2015-11-01

    Chromium-doped potassium titanyl phosphate single crystals have been synthesized and their physical properties have been studied. Doping with chromium barely affects the temperature of the ferroelectric phase transition but significantly reduces conductivity (by almost two orders of magnitude). A precise Xray diffraction study of K1.00Cr0.02Ti0.98OPO4 and K0.996Cr0.005Ti0.995OPO4 crystals has shown that chromium atoms are located near sites of titanium atoms.

  16. Reactions of chromium with gaseous NaCl in an oxygen environment

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    Target collection techniques and high pressure mass spectrometric sampling have been used to study the formation of volatile chromium-containing species in the reaction of Cr2O3 with O2 and NaCl gases. Experiments were performed at atmospheric pressure as a function of chromium temperature, oxygen pressure, and NaCl gas concentration. The major chromium-containing vapor species were found to be (NaCl)x CrO3 gas, with x = 1,2, and 3, which are products of heterogeneous reactions on the surface. The kinetics indicate first order dependence on oxygen and sodium chloride pressures.

  17. Impurities in chromium deposits produced by electroplating and physical vapor deposition

    SciTech Connect

    Dini, J.W.

    1994-05-01

    Impurity contents in electrodeposited (hexavalent and trivalent) chromium deposits and physically vapor deposited (thermal evaporation, electron beam evaporation and rf-sputtering) were compared. Oxygen is the key impurity obtained in electrodeposited films but it can be minimized in hexavalent plating solutions by operating at high temperature, e. g., 85 C. Electrodeposits produced in trivalent chromium plating solutions and physically vapor deposited films have much higher oxygen contents than electrodeposits produced in hexavalent chromium solutions operated at temperatures around 85 C. Depending on the target material used for physically vapor deposited films, these films can also have high amounts of other impurities.

  18. Peculiarities of Production of Chromium Carbonitride Nanopowder and Its Physical-Chemical Certification

    NASA Astrophysics Data System (ADS)

    Shiryaeva, L. S.; Nozdrin, I. V.; Galevsky, G. V.

    2015-09-01

    Scientific and technological basics of plasma synthesis of chromium carbonitride have been developed, including analysis of the current production state and application of chromium carbon compounds, defining characteristics of three-jet plasma reactor, modeling- mathematical study of interaction of raw materials and plasma streams, prediction of technological parameters of plasma stream based on the modeling results, selection of optimal technological option, implementation of plasma-metallurgical technology of chromium nitride production, its physical-chemical certification and defining technical-economical production factors.

  19. Oxidation of cyclohexanone and 2-hydroxycyclohexanone in presence of chromium naphthenate

    SciTech Connect

    Frerdin, B.G.; Borodina, O.V.; PerkelH, A.L.

    1986-06-01

    The authors determine the influence of the catalytic chromium salt on the course of conversion of cyclohexanone and 2-hydroxycyclohexanone. It is seen from data obtained by interpolation that the concentration of peroxides is considerably lower in the presence of the catalyst, evidently because of their higher decomposition rate. Decomposition of monofunctional secondary hydroperoxides in the presence of chromium salts gives higher ketone yields. In distinction from polymethylene hydrocarbons, which form carbonyl compounds, cyclohexanone is conerted in the presence of chromium salts predominantly through 2-hydroxycyclohexanone.

  20. Reliability and validity of expert assessment based on airborne and urinary measures of nickel and chromium exposure in the electroplating industry

    PubMed Central

    Chen, Yu-Cheng; Coble, Joseph B; Deziel, Nicole C.; Ji, Bu-Tian; Xue, Shouzheng; Lu, Wei; Stewart, Patricia A; Friesen, Melissa C

    2014-01-01

    The reliability and validity of six experts’ exposure ratings were evaluated for 64 nickel-exposed and 72 chromium-exposed workers from six Shanghai electroplating plants based on airborne and urinary nickel and chromium measurements. Three industrial hygienists and three occupational physicians independently ranked the exposure intensity of each metal on an ordinal scale (1–4) for each worker's job in two rounds: the first round was based on responses to an occupational history questionnaire and the second round also included responses to an electroplating industry-specific questionnaire. Spearman correlation (rs) was used to compare each rating's validity to its corresponding subject-specific arithmetic mean of four airborne or four urinary measurements. Reliability was moderately-high (weighted kappa range=0.60–0.64). Validity was poor to moderate (rs= -0.37–0.46) for both airborne and urinary concentrations of both metals. For airborne nickel concentrations, validity differed by plant. For dichotomized metrics, sensitivity and specificity were higher based on urinary measurements (47–78%) than airborne measurements (16–50%). Few patterns were observed by metal, assessment round, or expert type. These results suggest that, for electroplating exposures, experts can achieve moderately-high agreement and (reasonably) distinguish between low and high exposures when reviewing responses to in-depth questionnaires used in population-based case-control studies. PMID:24736099

  1. Reliability and validity of expert assessment based on airborne and urinary measures of nickel and chromium exposure in the electroplating industry.

    PubMed

    Chen, Yu-Cheng; Coble, Joseph B; Deziel, Nicole C; Ji, Bu-Tian; Xue, Shouzheng; Lu, Wei; Stewart, Patricia A; Friesen, Melissa C

    2014-11-01

    The reliability and validity of six experts' exposure ratings were evaluated for 64 nickel-exposed and 72 chromium-exposed workers from six Shanghai electroplating plants based on airborne and urinary nickel and chromium measurements. Three industrial hygienists and three occupational physicians independently ranked the exposure intensity of each metal on an ordinal scale (1-4) for each worker's job in two rounds: the first round was based on responses to an occupational history questionnaire and the second round also included responses to an electroplating industry-specific questionnaire. The Spearman correlation (r(s)) was used to compare each rating's validity to its corresponding subject-specific arithmetic mean of four airborne or four urinary measurements. Reliability was moderately high (weighted kappa range=0.60-0.64). Validity was poor to moderate (r(s)=-0.37-0.46) for both airborne and urinary concentrations of both metals. For airborne nickel concentrations, validity differed by plant. For dichotomized metrics, sensitivity and specificity were higher based on urinary measurements (47-78%) than airborne measurements (16-50%). Few patterns were observed by metal, assessment round, or expert type. These results suggest that, for electroplating exposures, experts can achieve moderately high agreement and (reasonably) distinguish between low and high exposures when reviewing responses to in-depth questionnaires used in population-based case-control studies.

  2. Epigenetics in metal carcinogenesis: nickel, arsenic, chromium and cadmium.

    PubMed

    Arita, Adriana; Costa, Max

    2009-01-01

    Although carcinogenic metals have been known to disrupt a wide range of cellular processes the precise mechanism by which these exert their carcinogenic effects is not known. Over the last decade or two, studies in the field of metal carcinogenesis suggest that epigenetic mechanisms may play a role in metal-induced carcinogenesis. In this review we summarize the evidence demonstrating that exposure to carcinogenic metals such as nickel, arsenic, chromium, and cadmium can perturb DNA methylation levels as well as global and gene specific histone tail posttranslational modification marks. We also wish to emphasize the importance in understanding that gene expression can be regulated by both genetic and epigenetic mechanisms and both these must be considered when studying the mechanism underlying the toxicity and cell-transforming ability of carcinogenic metals and other toxicants, and aberrant changes in gene expression that occur during disease states such as cancer.

  3. Chromium interactions in plants: current status and future strategies.

    PubMed

    Shanker, Arun Kumar; Djanaguiraman, Maduraimuthu; Venkateswarlu, Bandi

    2009-09-01

    Chromium has received relatively little attention from plant scientists compared to other heavy metals in recent times in spite of it being a very a hazardous environmental pollutant. One of the reasons for this is the complexity of the metal's interactions with biological systems and the difficulty in studying them. Although the possible mode of entry into the plants, resultant toxicity mechanisms and tolerance potential has been worked out in plants there is still a need to get a complete picture of the Cr-plant interactome. With the advent of hyphenated technologies and global gene/protein and metabolite expression/quantification techniques, studies to elucidate the complete metallome are possible albeit resource intensive. This minireview focuses on the recent developments in the field of Cr-plant interactions and proposes a model using a systems biology and integrated -omics approach to decipher the intricacies of Cr-plant interaction. PMID:21305140

  4. High strength nickel-chromium-iron austenitic alloy

    DOEpatents

    Gibson, Robert C.; Korenko, Michael K.

    1980-01-01

    A solid solution strengthened Ni-Cr-Fe alloy capable of retaining its strength at high temperatures and consisting essentially of 42 to 48% nickel, 11 to 13% chromium, 2.6 to 3.4% niobium, 0.2 to 1.2% silicon, 0.5 to 1.5% vanadium, 2.6 to 3.4% molybdenum, 0.1 to 0.3% aluminum, 0.1 to 0.3% titanium, 0.02 to 0.05% carbon, 0.002 to 0.015% boron, up to 0.06 zirconium, and the balance iron. After solution annealing at 1038.degree. C. for one hour, the alloy, when heated to a temperature of 650.degree. C., has a 2% yield strength of 307 MPa, an ultimate tensile strength of 513 MPa and a rupture strength of as high as 400 MPa after 100 hours.

  5. First principles investigation of chromium carbide, CrC

    NASA Astrophysics Data System (ADS)

    Kalemos, Apostolos; Dunning, Thom H.; Mavridis, Aristides

    2005-07-01

    We have investigated the electronic structure of 14 states of the experimentally unknown diatomic molecule chromium carbide, CrC, using standard multireference configuration interaction methods and high quality basis sets. We report potential curves, binding energies, and a number of spectroscopic parameters. The ground state of CrC, XΣ-3, displays triple-bond character with a binding energy of De=89kcal /mol and an internuclear separation of re=1.63Å. The first excited state (1Σ-5) lies 9.2kcal/mol higher. All the states studied are fairly ionic, featuring an electron transfer of 0.3-0.5e- from the metal atom to the carbon atom.

  6. First principles investigation of chromium carbide, CrC.

    PubMed

    Kalemos, Apostolos; Dunning, Thom H; Mavridis, Aristides

    2005-07-01

    We have investigated the electronic structure of 14 states of the experimentally unknown diatomic molecule chromium carbide, CrC, using standard multireference configuration interaction methods and high quality basis sets. We report potential curves, binding energies, and a number of spectroscopic parameters. The ground state of CrC, X 3Sigma-, displays triple-bond character with a binding energy of D(e)=89 kcal/mol and an internuclear separation of r(e)=1.63 A. The first excited state (1 5Sigma-) lies 9.2 kcal/mol higher. All the states studied are fairly ionic, featuring an electron transfer of 0.3-0.5e- from the metal atom to the carbon atom. PMID:16035830

  7. Hexavalent chromium is cytotoxic and genotoxic to American alligator cells.

    PubMed

    Wise, Sandra S; Wise, Catherine; Xie, Hong; Guillette, Louis J; Zhu, Cairong; Wise, John Pierce; Wise, John Pierce

    2016-02-01

    Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is a known human carcinogen and reproductive toxicant. We measured the cytotoxicity and genotoxicity of Cr(VI) in American alligator cells derived from scute tissue. We found that particulate and soluble Cr(VI) are both cytotoxic and genotoxic to alligator cells in a concentration-dependent manner. These data suggest that alligators may be used as a model for assessing the effects of environmental Cr(VI) contamination as well as for other metals of concern. PMID:26730726

  8. Interpreting atom probe data from chromium oxide scales.

    PubMed

    La Fontaine, Alexandre; Gault, Baptiste; Breen, Andrew; Stephenson, Leigh; Ceguerra, Anna V; Yang, Limei; Nguyen, Thuan Dinh; Zhang, Jianqiang; Young, David J; Cairney, Julie M

    2015-12-01

    Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed "laser sensitivity factor" is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite samples. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia.

  9. Theoretical study of the photoabsorption spectrum of small chromium clusters

    NASA Astrophysics Data System (ADS)

    Martínez, J. I.; Alonso, J. A.

    2007-11-01

    The photoabsorption spectra of CrN (N=2-11) clusters have been calculated using the time-dependent density functional theory. Different approximations for exchange and correlation lead to a similar picture for the spectra. Small chromium clusters show a dimerization effect that controls the initial growth of the clusters up to N=11 . This effect consists in the formation of robust Cr2 dimers with a strong bond and an unusually short bond length. The dimerization effect becomes reflected in the high-energy part of the absorption spectra: An excitation peak appears at energies near 20eV , and its intensity increases each time a new Cr dimer forms in the structure as the cluster grows. However, experimental detection of this effect will be hard because of the competition from ionization.

  10. Hexavalent chromium is cytotoxic and genotoxic to American alligator cells.

    PubMed

    Wise, Sandra S; Wise, Catherine; Xie, Hong; Guillette, Louis J; Zhu, Cairong; Wise, John Pierce; Wise, John Pierce

    2016-02-01

    Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is a known human carcinogen and reproductive toxicant. We measured the cytotoxicity and genotoxicity of Cr(VI) in American alligator cells derived from scute tissue. We found that particulate and soluble Cr(VI) are both cytotoxic and genotoxic to alligator cells in a concentration-dependent manner. These data suggest that alligators may be used as a model for assessing the effects of environmental Cr(VI) contamination as well as for other metals of concern.

  11. Hardness, elastic, and electronic properties of chromium monoboride

    SciTech Connect

    Han, Lei; Wang, Shanmin; Zhu, Jinlong; Han, Songbai; Li, Wenmin; Chen, Bijuan; Wang, Xiancheng; Yu, Xiaohui E-mail: liubc@jlu.edu.cn Long, Youwen; Cheng, Jinguang; Jin, Changqing; Liu, Baochang E-mail: liubc@jlu.edu.cn; Zhang, Ruifeng E-mail: liubc@jlu.edu.cn; Zhang, Jianzhong; Zhao, Yusheng

    2015-06-01

    We report high-pressure synthesis of chromium monoboride (CrB) at 6 GPa and 1400 K. The elastic and plastic behaviors have been investigated by hydrostatic compression experiment and micro-indentation measurement. CrB is elastically incompressible with a high bulk modulus of 269.0 (5.9) GPa and exhibits a high Vickers hardness of 19.6 (0.7) GPa under the load of 1 kg force. Based on first principles calculations, the observed mechanical properties are attributed to the polar covalent Cr-B bonds interconnected with strong zigzag B-B covalent bonding network. The presence of metallic Cr bilayers is presumably responsible for the weakest paths in shear deformation.

  12. Polyaniline coating with various substrates for hexavalent chromium removal

    NASA Astrophysics Data System (ADS)

    Qiu, Bin; Xu, Cuixia; Sun, Dezhi; Wang, Qiang; Gu, Hongbo; Zhang, Xin; Weeks, Brandon L.; Hopper, Jack; Ho, Thomas C.; Guo, Zhanhu; Wei, Suying

    2015-04-01

    Hexavalent chromium (Cr(VI)) contamination is increasingly serious in surface water and groundwater, therefore, its removal attracts increasing attention due to its highly toxic to human health. The cost effective and sustainable adsorbents are urgently needed for the remediation of Cr(VI) pollution. Polyanline (PANI), a conductive polymer, has demonstrated a great performance on Cr(VI) removal. But the recycling is the challenge for its application due to its small size. The PANI coating with various substrates is an effective approach to solve this problem. The synthesis methods and applications of the PANI coated magnetic Fe3O4, carbon fabric and cellulose composites for the Cr(VI) removal were reviewed. Finally, this review analyzed the Cr(VI) removal mechanisms by the PANI composites considering the substrate and the PANI coating.

  13. Development of RF sputtered chromium oxide coating for wear application

    NASA Technical Reports Server (NTRS)

    Bhushan, B.

    1979-01-01

    The radio frequency sputtering technique was used to deposite a hard refractory, chromium oxide coating on an Inconel X-750 foil 0.1 mm thick. Optimized sputtering parameters for a smooth and adherent coating were found to be as follows: target-to-substrate spacing, 41.3 mm; argon pressure, 5-10 mTorr; total power to the sputtering module, 400 W (voltage at the target, 1600 V), and a water-cooled substrate. The coating on the annealed foil was more adherent than that on the heat-treated foil. Substrate biasing during the sputter deposition of Cr2O3 adversely affected adherence by removing naturally occurring interfacial oxide layers. The deposited coatings were amorphous and oxygen deficient. Since amorphous materials are extremely hard, the structure was considered to be desirable.

  14. Hexavalent chromium stimulation of riboflavin synthesis in flavinogenic yeast.

    PubMed

    Fedorovych, D; Kszeminska, H; Babjak, L; Kaszycki, P; Koloczek, H

    2001-03-01

    Flavinogenic yeast overproduce riboflavin (RF) in iron-deprived media. In optimal growth media supplemented with Fe, hexavalent chromium 'Cr (VI)' treatment led to elevated RF synthesis in all cases of 37 flavinogenic strains studied. The level of RF production exceeded the rate observed at iron-deficient conditions. At sublethal Cr concentrations the RF oversynthesis over time correlated well with the growth-inhibitory adaptational period as manifested by the prolonged lag phase. The consecutive logarithmic biomass growth was accompanied by a drop in RF biosynthesis. Cr (VI)-induced RF overproduction was not a result of cellular iron level decrease. The treatment of yeast with Cr (VI) led to the stimulation of GTP-cyclohydrolase and RF-synthase activities, the key enzymes of the RF biosynthesis pathway. PMID:11368272

  15. Fracture and Delamination of Chromium Thin Films on Polymer Substrates

    NASA Astrophysics Data System (ADS)

    Cordill, M. J.; Taylor, A.; Schalko, J.; Dehm, G.

    2010-04-01

    New emerging technologies in the field of flexible electronic devices require that metal films adhere well and flex with polymer substrates. Common thin film materials used for these applications include copper (Cu) with an adhesion interlayer of chromium (Cr). Copper can be quite ductile and easily move with the polymer substrate. However, Cr is more brittle and fractures at lower strains than Cu. This study aims to examine the fracture and subsequent buckling and delamination of strained Cr films on polyimide (PI). In-situ scanning electron microscope (SEM) straining is used to systematically study the influence of film thickness on fracture and buckling strains. Film fracture and delamination depend on film thickness, and increases in crack and buckle density with decreasing thickness are explored by a shear lag model.

  16. AlGaAs diode pumped tunable chromium lasers

    DOEpatents

    Krupke, William F.; Payne, Stephen A.

    1992-01-01

    An all-solid-state laser system is disclosed wherein the laser is pumped in the longwave wing of the pump absorption band. By utilizing a laser material that will accept unusually high dopant concentrations without deleterious effects on the crystal lattice one is able to compensate for the decreased cross section in the wing of the absorption band, and the number of pump sources which can be used with such a material increases correspondingly. In a particular embodiment a chromium doped colquiriite-structure crystal such as Cr:LiSrAlF.sub.6 is the laser material. The invention avoids the problems associated with using AlGaInP diodes by doping the Cr:LiSrAlF.sub.6 heavily to enable efficient pumping in the longwave wing of the absorption band with more practical AlGaAs diodes.

  17. Electrochemical reduction of hexavalent chromium in ground water

    SciTech Connect

    Bansal, S.

    1994-12-01

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

  18. Carbides in a High-Chromium Ferritic/Martensitic Steel

    NASA Astrophysics Data System (ADS)

    Shen, Yin Zhong; Ji, Bo; Zhou, Xiao Ling; Zhu, Jun

    2014-06-01

    The precipitate phases in an 11 pct Cr ferritic/martensitic steel normalized at 1323 K (1050 °C) for 0.5 hour and tempered at 1053 K (780 °C) for 1.5 hours have been investigated. Except for dominant phases, Cr-rich M23C6 carbide and Nb-rich, Ta-Nb-rich, and V-rich MC carbides, needle-like precipitates with a typical size of 70 to 310 and 10 to 30 nm for the length of the long and short axis of the needles, respectively, were also observed on the extraction carbon replica of the steel. The typical metallic element composition of the needle-like precipitates is about 53-82Fe, 14-26Cr, 0.5-18Ta, 1-6W, and 2-5Co in atomic pct. Through energy dispersive X-ray analysis and electron diffraction along with calculations regarding lattice parameter and interplanar spacing, the needle-like precipitates were identified as a Fe-rich M5C2 carbide, which is not known to have been reported previously in high-chromium steels. The M5C2 carbide has a base-centered monoclinic crystal structure with the approximate lattice parameters a/ b/ c = 1.142/0.5186/0.5383 nm and β = 104.68 deg. The formation of the Fe-rich M5C2 carbides in the steel has been discussed. The effect of chromium content in matrix and boron addition on the precipitate phases in ferritic/martensitic steels has also been discussed.

  19. Probing neutrino nature at Borexino detector with chromium neutrino source

    NASA Astrophysics Data System (ADS)

    Sobków, W.; Błaut, A.

    2016-10-01

    In this paper, we indicate a possibility of utilizing the intense chromium source (˜ 370 PBq) in probing the neutrino nature in low energy neutrino experiments with the ultra-low threshold and background real-time Borexino detector located near the source (˜ 8 m). We analyse the elastic scattering of electron neutrinos (Dirac or Majorana, respectively) on the unpolarised electrons in the relativistic neutrino limit. We assume that the incoming neutrino beam is the superposition of left-right chiral states produced by the chromium source. Left chiral neutrinos may be detected by the standard V - A and non-standard scalar S_L, pseudoscalar P_L, tensor T_L interactions, while right chiral ones partake only in the exotic V + A and S_R, P_R, T_R interactions. Our model-independent study is carried out for the flavour (current) neutrino eigenstates. We compute the expected event number for the standard V-A interaction of the left chiral neutrinos using the current experimental values of standard couplings and in the case of left-right chiral superposition. We show that the significant decrement in the event number due to the interference terms between the standard and exotic interactions for the Majorana neutrinos may appear. We also demonstrate how the presence of the exotic couplings affects the energy spectrum of outgoing electrons, both for the Dirac and Majorana cases. The 90~% C.L. sensitivity contours in the planes of corresponding exotic couplings are found. The presence of interferences in the Majorana case gives the stronger constraints than for the Dirac neutrinos, even if the neutrino source is placed outside the detector.

  20. Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes

    NASA Astrophysics Data System (ADS)

    Frei, Robert; Gaucher, Claudio; Poulton, Simon W.; Canfield, Don E.

    2009-09-01

    Geochemical data suggest that oxygenation of the Earth's atmosphere occurred in two broad steps. The first rise in atmospheric oxygen is thought to have occurred between ~2.45 and 2.2Gyr ago, leading to a significant increase in atmospheric oxygen concentrations and concomitant oxygenation of the shallow surface ocean. The second increase in atmospheric oxygen appears to have taken place in distinct stages during the late Neoproterozoic era (~800-542Myr ago), ultimately leading to oxygenation of the deep ocean ~580Myr ago, but details of the evolution of atmospheric oxygenation remain uncertain. Here we use chromium (Cr) stable isotopes from banded iron formations (BIFs) to track the presence of Cr(VI) in Precambrian oceans, providing a time-resolved picture of the oxygenation history of the Earth's atmosphere-hydrosphere system. The geochemical behaviour of Cr is highly sensitive to the redox state of the surface environment because oxidative weathering processes produce the oxidized hexavalent [Cr(VI)] form. Oxidation of reduced trivalent [Cr(III)] chromium on land is accompanied by an isotopic fractionation, leading to enrichment of the mobile hexavalent form in the heavier isotope. Our fractionated Cr isotope data indicate the accumulation of Cr(VI) in ocean surface waters ~2.8 to 2.6Gyr ago and a likely transient elevation in atmospheric and surface ocean oxygenation before the first great rise of oxygen 2.45-2.2Gyr ago (the Great Oxidation Event). In ~1.88-Gyr-old BIFs we find that Cr isotopes are not fractionated, indicating a decline in atmospheric oxygen. Our findings suggest that the Great Oxidation Event did not lead to a unidirectional stepwise increase in atmospheric oxygen. In the late Neoproterozoic, we observe strong positive fractionations in Cr isotopes (δ53Cr up to +4.9‰), providing independent support for increased surface oxygenation at that time, which may have stimulated rapid evolution of macroscopic multicellular life.