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Sample records for beir vi study

  1. Status report on the National Research Council`s BEIR VI study

    Energy Technology Data Exchange (ETDEWEB)

    Douple, E.

    1995-10-01

    The objectives of the committee on Biological Radiation Effects of Ionizing Radiation VI (BEIR) are to : assist the EPA in phase I by collecting and evaluating information on ongoing studies and results of studies published since the BEIR VI report of 1988 on the health effects of exposure to radon progeny; to perform a full scale reassessment of the health effects if a phase II study is warranted on the basis of phase I results. The BEIR VI working groups consists of miner data sets and analysis; residential studies; smoking and nonsmoking interactions; exposure and dosimetry; cellular and molecular studies; risk models and uncertainties; and animal studies.

  2. Health Effects of Exposure to Radon. BEIR VI

    International Nuclear Information System (INIS)

    This National Research Council's report of the sixth Committee on Biological effects of Ionizing Radiations (BEIR VI) addresses the risk of lung cancer associated with exposure to radon and its radioactive progeny. Radon, a naturally occurring gas formed from the decay of uranium in the earth, has been conclusively shown in epidemiologic studies of underground miners to cause lung cancer. There is supporting evidence from experimental studies of animals that confirm radon as a cause of lung cancer and from molecular and cellular studies that provide an understanding of the mechanisms by which radon causes lung cancer. In addition to being present at high concentrations in many types of underground mines, radon is found in homes and is also present outdoors, raising concerns that radon in homes increases lung-cancer risk for the general population. For the purpose of developing public policy to manage the risk associated with indoor radon, there is a need to characterize the possible across the range of exposures received by the population. The BEIR VI committee faced the task of estimating the risks associated with indoor radon across the full range of exposures and providing an indication of the uncertainty to be attached to risk estimates across this range. In preparing this report, the BEIR VI committee, in response to its charge, reviewed the entire body of data on radon and lung cancer, integrating findings from epidemiologic studies with evidence from animal experiments and other lines of laboratory investigation. The committee also considered the substantial evidence on smoking and cancer and the more limited evidence on the combined effect of smoking and radon. The report's elements include comprehensive reviews of the cellular and molecular basis of radon carcinogenesis and of the dosimetry of radon in the respiratory tract, of the epidemiologic studies of miners and the general population, and of the combined effects of radon and other occupational

  3. BEIR VI report. Public summary: the health effects of exposure to indoor radon

    International Nuclear Information System (INIS)

    For centuries it has been known that some underground miners suffered from higher rates of lung cancer than the general population. In recent decades, a growing body of evidence has casually linked their lung cancers to exposure to high levels of radon and also to cigarette smoking. The connection between radon and lung cancer in miners has raised concern that radon in homes might be causing lung cancer in the general population, although the radon levels in most homes are much lower than in most mines. The National Research Council study, which has been carried out by the sixth Committee on Biological Effects of Ionizing Radiations (BEIR VI), has used the most recent information available to estimate the risks posed by exposure to radon in homes. The most direct way to assess the risks posed by radon in homes is to measure radon exposures among people who have lung cancer and compare them with exposures among people who have not developed lung cancer. Several such studies have been completed, and several are under way. The studies have not produced a definitive answer, primarily because the risk is likely to be very small at the low exposure encountered from most homes and because it is difficult to estimate radon exposures that people have received over their lifetimes. In addition, it is clear that far more lung cancers are caused by smoking that are caused by radon. The risk of lung cancer caused by smoking is much higher than the risk of lung cancer caused by indoor radon. Most of the radon-related deaths among smokers would not have occurred if the victims had not smoked. Furthermore, there is evidence for a synergistic interaction between smoking and radon. In other words, the number of cancers induced in ever-smokers by radon is greater than one would expect from the additive effects of smoking along and radon alone. Nevertheless, the estimated 15400 or 21800 deaths attributed to radon in combination with cigarette-smoking and radon alone in never

  4. BEIR modeling approach as compared to the UNSCEAR lifetime risk

    International Nuclear Information System (INIS)

    The methods of deriving risk numbers from the UNSCEAR report and the BEIR report are compared. The UNSCEAR lifetime risk is simple to use and probably appropriate for such uses as derivation of standards. The BEIR life table approach is more complex but does provide information useful for deriving individual risk to be used in studies of probability of causation. In addition, the BEIR risk estimates can be varied to accommodate the age distribution of the population actually exposed

  5. BEIR-III controverly

    Energy Technology Data Exchange (ETDEWEB)

    Fabrikant, J.I.

    1980-06-01

    How certain of the areas addressed by the Committee on the Biological Effects of Ionizing Radiation (BEIR) have attempted to deal with the scientific basis for establishing appropriate radiation protection guides is discussed, and what effect this may have on decision-making for the regulation of societal activities concerned with the health effects in human populations exposed to low-level radiation. (ACR)

  6. BEIR-III controverly

    International Nuclear Information System (INIS)

    How certain of the areas addressed by the Committee on the Biological Effects of Ionizing Radiation (BEIR) have attempted to deal with the scientific basis for establishing appropriate radiation protection guides is discussed, and what effect this may have on decision-making for the regulation of societal activities concerned with the health effects in human populations exposed to low-level radiation

  7. SUPPORT FOR BEIR VII

    Science.gov (United States)

    The office is supporting the continued funding of National Academy of Sciences Study to update our understanding of the effects of low-level radiation. In particular, this study, entitled the Biological Effects of Ionizing Radiation VII, will draw upon the most recent data avail...

  8. Comments on the DDREF estimate of the BEIR VII Committee.

    Science.gov (United States)

    Hoel, David G

    2015-03-01

    Radiation cancer risk estimates have been based primarily on the atomic bomb survivor cohorts, which involve an acute exposure. To adjust for lower dose and continuous exposures, a dose and dose rate effectiveness factor (DDREF) is applied to the acute risk estimates. The commonly accepted value for the DDREF at 1 Gy by the ICRP and the NCRP has been 2. BEIR VII changed this by estimating the value to be 1.5 including an uncertainty distribution. The BEIR VII committee used the atomic bomb solid cancer incidence data to make this estimation, and they chose to truncate the data at 1.5 Gy. The Committee also used the Oak Ridge mouse studies and estimated a DDREF based on these data. Finally they used the animal data-derived DDREF distribution as a Bayesian prior distribution for the atomic bomb survivor DDREF distribution and used the posterior distribution as their DDREF result. The resulting distribution had a maximum likelihood estimate of 1.4, and the Committee chose 1.5 as their best estimate. The purpose of this paper is to reexamine the BEIR VII analysis of both the atomic bomb survivor data and the mouse data. Based upon this analysis, the author concludes that changing the DDREF from 2 to 1.5 is not justified. PMID:25627947

  9. Ionizing radiation risk assessment, BEIR IV

    International Nuclear Information System (INIS)

    This report of the Subpanel discusses the potential impact on Federal agencies and indicates individual risk factors that could be used by them in risk assessment. The approach used in this CIRRPC report was to consider the risk factors presented in BEIR IV for each radionuclide (or group radioelements) and to make some judgments regarding their validity and/or the uncertainties involved. The coverage of Radon-222 and its progeny dominated the BEIR IV report and this Subpanel felt is was proper to devote more attention to this radionuclide family. This risk factor presented in BEIR IV for radon is 350 cancer deaths per million person-working level months (WLM) of exposure for a lifetime. There is a range of opinions on the conversion from WLM to absorbed dose. As discussed in the text, the use of the WLM concept makes it difficult or infeasible to compare the risk factor for radon with that of other radionuclides which are based on organ dose. This report also includes a discussion of certain fundamental scientific and operational issues that may have decisive effect upon risk factor selection. These adjunct items are dealt with under separate headings and include discussions of threshold dose considerations, extrapolation to low doses, and age at exposure

  10. Studies in Sulphonamides - Part VI

    Directory of Open Access Journals (Sweden)

    G. S. Saharia

    1972-04-01

    Full Text Available Five different 1:3-diaryl propane-1:3-diones, 1-(m-nitrophenyl-3-phenyl-, 1-(m-nitrophenyl-3-(p-methoxyphenyl-, 1-(p-methoxyphenyl-3-(p-bromophenyl-and 1-(pmethoxyphenyl-3-(p-chorophenyl propane-1:3-diones have been synthesised and coupled with eight different diazotised sulphonamide bases to give 1:3-diary 1-2(substituted sulphonamidobenzeneazo propane-1:3-dicnes. The pharmacological properties of all these azo-compounds have been studied in vitro by the cup-plate method.

  11. Model or metaphor. More comments on the BEIR III report

    International Nuclear Information System (INIS)

    Data have been obtained for Hiroshima and Nagasaki from which were prepared the estimates of somatic risk coefficients for ionizing radiation presented in the BEIR III Report. Several Poisson regression models of these data by both Bayesian and Sampling Theory methods. The results of the evaluations disclose some interesting idiosyncracies in the statistical methods by which the BEIR III estimates and inferences were obtained. The paper presents these results in the format of a textual criticism of the foundations of the received estimates of risk that are presented in the Somatic Effects Sections of the BEIR III Report. Whatever the resolution of the current difficulties with the validity of the T65 estimates of dose, the utility of any estimates of risk coefficients depends upon the suitability of the statistical methods by which any estimates of dose are mapped into estimates of risk. The statistical methods of the BEIR III Report seem idiosyncratic. Use of standard methods discloses that its rival models (LQ-L, L-L AND Q-L) may be more effective as metaphors of expression than as models of radiation response

  12. BEIR VII: What's old, What's new, and What challenges remain?

    International Nuclear Information System (INIS)

    The Biological Effects of Ionizing Radiation (BEIR VII) Committee reviewed evidence since the 1990 BEIR V report and developed BEIR VII risk estimates, including a linear, no-threshold dose-response relationship between exposure to ionizing radiation and the development of cancer in humans for exposures up to 0.1 Sv, quantifying the lifetime risks for both cancer mortality and incidence as a function of age at exposure and sex, primarily based on the Japanese atomic-bomb survivor data. If 100 people with an age distribution typical of the U.S. population receive an acute exposure of 0.1 Sv, one person would be expected to eventually develop cancer from this exposure, while 42 of the 100 people would be expected to develop cancer from other causes. The committee estimated the risk following radiation exposure for both incidence and mortality for 11 specific cancer sites. The total risk of heritable genetic diseases from parents exposed prior to conception was 3,000 to 4,700 cases per million progeny per Sv, 0.4-0.6% compared to an estimated baseline risk of 738,000 cases per million. Noncancer diseases such as cardiovascular disease can result from exposures to high doses of radiation, but the data available at this time are not sufficient to develop reliable estimates of risk for these noncancer outcomes at low doses of radiation. Twelve specific recommendations were presented as needs for future research. (author)

  13. A technical review and assessment of the BEIR V [Biological Effects of Ionizing Radiation V] report

    International Nuclear Information System (INIS)

    This report was prepared by the DOE BEIR V Technical Review Committee (TRC) to provide a technical review and assessment of the National Research Council's Bilogical Effects of Ionizing Radiation (BEIR) Committee's Report entitled ''Health Effects of Exposure to Low Levels of Ionizing Radiation'' (BEIR V). This report contains seven sections. The first section serves as an introduction and reviews the charge to the TRC. The second section is a chapter-by- chapter summary of the BEIR V Report. The third section is a summary of the risk estimates and conclusions of the BEIR V Committee for genetic effects, cancer induction, and in utero effects. The fourth section is a summary and analysis of the new scientific information used by the BEIR V Committee in developing its risk recommendations and conclusions. The fifth section is an assessment of the scientific information and methods used by the BEIR V Committee in developing their risk estimates and conclusions and an analysis of the key assumptions underlying the use of these risk estimates in risk assessment. The sixth section is the TRC'S assessment of the regulatory implications of the BEIR V risk estimates and conclusions for DOE nuclear operations. The seventh and final section is the TRC'S recommended actions for DOE's consideration concerning the BEIR V Report risk estimates and conclusions. 23 refs., 5 tabs

  14. IV-VI ferromagnetic semiconductors recent studies

    Directory of Open Access Journals (Sweden)

    Dobrowolski W.

    2006-01-01

    Full Text Available In some IV-VI semimagnetic semiconductors, the RKKY interaction can dominate over the standard d-d superexchange and become the driving mechanism for ion-ion coupling. In effect, for low hole concentrations the Mn ion system is in a paramagnetic phase, whereas for higher ones it reveals typical ferromagnetic behavior. In this paper, recent work on IV-VI ferromagnetic (SnMnTe, PbSnMnTe and GeMnTe systems will be presented. In particular, the influence of the presence of two types of magnetic ions (transition metal: Mn and rare earth metal: Eu or Er incorporated into a semiconductor matrix on magnetic properties of resultant semimagnetic semiconductor will be described.

  15. Human health effects of low doses of ionizing radiation: the BEIR III controversy

    International Nuclear Information System (INIS)

    Controversy in the BEIR III Subcommittee on Somatic Effects concerning human health effects of low doses of low-LET radiation has centered on (a) the appropriate dose-response relationship by which extrapolation to low doses of data obtained at relatively high doses should be governed, and (b) the appropriate human evidence which should be the basis of estimation of lifetime cancer risk from radiation exposure. It is shown that the use of the linear no-threshold dose-response relationship for extrapolation purposes is an excellent approximation that is in agreement with widely accepted fundamental radiobiological principles. The appropriate human data for derivation of cancer risks are the composite age-specific risks derived from all epidemiologic studies of human cancer resulting from partial-body and whole-body radiation exposure; this composite is in good agreement with the currently available cancer incidence dose-response data obtained from the Nagasaki Tumor Registry. The current version of BEIR III significantly underestimates the radiation-induced cancer risk because it ignores the effect of high-dose-rate, low-LET radiation on cell survival in relation to cancer induction probability, and because it emphasizes cancer mortality rather than cancer incidence. The controversy and the way in which it was resolved raises important questions about how the public and its representatives can in the future obtain objective scientific evaluations of issues that may have significant economic, social, and political implications

  16. Spectrophotometric study of neptunium (VI) complexation by nitrate ions

    International Nuclear Information System (INIS)

    Neptunium(VI) complexation by nitrate ions was investigated by visible and near-infrared spectrophotometry, a technique suitable for observing the appearance and evolution of the species in solution. In the absence of reference spectra for Np(VI) nitrate- complexes, mathematical (factor analysis) tools were used to interpret the spectra. These chemo-metric techniques were first tested and validated on a simpler chemical system: Np(VI)complexation by the SiW11O398- anion. The test media used to investigate Np(VI) nitrate- complexes generally contain nitrate and perchlorate salts at high concentrations (high ionic strength). Media effects arising from the presence of cations, acidity or the perchlorate ion concentration are therefore significant, and no doubt account for the scattered values of the complexation constants published in the literature. The evolution of the neptunium spectra according to the parameters of the reaction medium illustrated these effects and allowed them to be quantified by a global 'perturbation constant'. In order to minimize the spectrum modifications due to media effects, the neptunium nitrate-complexes were studied at constant ionic strength in weak acidic media (2 mol.kg-1H2O) in the presence of sodium salts. The bulk formation constants and the spectrum of the NpO2(NO3)+ complex were determined for ionic strength values of 2.2, 4, 6 and 8 mol.kg-1H2O. The constants remained on the same order of magnitude regardless of the ionic strength; the thermodynamic constant β10 determined from them according to specific interaction theory is thus probably of little significance. Conversely, the bulk constants can be corrected for the effects of the perchlorate ions by taking the global 'perturbation constant' into account. (author)

  17. A comparison of radiological risk assessment models: Risk assessment models used by the BEIR V Committee, UNSCEAR, ICRP, and EPA (for NESHAP)

    International Nuclear Information System (INIS)

    Radiological risk assessments and resulting risk estimates have been developed by numerous national and international organizations, including the National Research Council's fifth Committee on the Biological Effects of Ionizing Radiations (BEIR V), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Commission on Radiological Protection (ICRP). A fourth organization, the Environmental Protection Agency (EPA), has also performed a risk assessment as a basis for the National Emission Standards for Hazardous Air Pollutants (NESHAP). This paper compares the EPA's model of risk assessment with the models used by the BEIR V Committee, UNSCEAR, and ICRP. Comparison is made of the values chosen by each organization for several model parameters: populations used in studies and population transfer coefficients, dose-response curves and dose-rate effects, risk projection methods, and risk estimates. This comparison suggests that the EPA has based its risk assessment on outdated information and that the organization should consider adopting the method used by the BEIR V Committee, UNSCEAR, or ICRP

  18. A comparison of radiological risk assessment models: Risk assessment models used by the BEIR V Committee, UNSCEAR, ICRP, and EPA (for NESHAP)

    Energy Technology Data Exchange (ETDEWEB)

    Wahl, L.E.

    1994-03-01

    Radiological risk assessments and resulting risk estimates have been developed by numerous national and international organizations, including the National Research Council`s fifth Committee on the Biological Effects of Ionizing Radiations (BEIR V), the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Commission on Radiological Protection (ICRP). A fourth organization, the Environmental Protection Agency (EPA), has also performed a risk assessment as a basis for the National Emission Standards for Hazardous Air Pollutants (NESHAP). This paper compares the EPA`s model of risk assessment with the models used by the BEIR V Committee, UNSCEAR, and ICRP. Comparison is made of the values chosen by each organization for several model parameters: populations used in studies and population transfer coefficients, dose-response curves and dose-rate effects, risk projection methods, and risk estimates. This comparison suggests that the EPA has based its risk assessment on outdated information and that the organization should consider adopting the method used by the BEIR V Committee, UNSCEAR, or ICRP.

  19. Radon and lung cancer: The BEIR IV Report

    International Nuclear Information System (INIS)

    The National Academy of Sciences' BEIR IV Report (1988) deals primarily with lung cancer risks in human populations exposed to internally deposited alpha-emitting Rn and its decay products. Quantitative risk estimates for lung cancer are derived from analyses of epidemiologic data. A modified excess relative risk model of lung cancer mortality of worker exposure to Rn progeny in underground miners is developed. This models the excess risk per WLM (working level month) in terms of time intervals prior to an attained age, and is dependent on time since exposure and age at risk. Risk projections for the general public in indoor domestic environments are presented and cover exposure situations of current public health concern. For example, lifetime exposure to 1 WLM y-1 is estimated to increase the number of deaths due to lung cancer by a factor of about 1.5 over the current rate for both males and females in a population having the current prevalence of cigarette smoking. Occupational exposure to 4 WLM y-1 from ages 20 to 40 y is projected to increase lung cancer deaths in the general population by a factor of 1.6 over the current rate of this age cohort. In all of these cases, most of the increased risk occurs to smokers for whom the risk is up to 10 times greater than for nonsmokers. Discussion includes the extrapolation of estimates of lung cancer mortality risks from the underground miner data to the general population exposed to Rn and its decay products in the indoor domestic environment

  20. Risks of low-LET radiation as given in BEIR-III and previous reports

    International Nuclear Information System (INIS)

    This report presents the conclusions of a review of the report ΣThe Effects on Populations of Exposure to Low Levels of Ionizing RadiationΣ, BEIR-III, published by the U.S. National Academy of Sciences in 1980 and other related reports. The committee concludes that, in as far as the estimates of risk from low-LET radiation are concerned, the BEIR-III report does not provide any new data that might suggest that the present dose limits promulgated by the AECB should be changed

  1. Risk estimation and decision-making: implications of the 1980 BEIR-III report

    Energy Technology Data Exchange (ETDEWEB)

    Fabrikant, J.I.

    1981-04-01

    The report gives a general background of the implications the current Report of the Committee on the Biological Effects of Ionizing Radiation (The BEIR-III Report) may have on societal decision-making in the regulation of activities concerned with the health effects of low-level radiation. (ACR)

  2. BEIR-III report and its implications for radiation protection and public health policy

    Energy Technology Data Exchange (ETDEWEB)

    Fabrikant, J.I.

    1980-03-01

    A general background is given of the implications the BEIR-III Report may have on societal decision-making in the regulation of activities concerned with the health effects of low-level radiation. The scientific basis for establishing appropriate radiation protection guides are discussed. (ACR)

  3. BEIR-III report and its implications for radiation protection and public health policy

    International Nuclear Information System (INIS)

    A general background is given of the implications the BEIR-III Report may have on societal decision-making in the regulation of activities concerned with the health effects of low-level radiation. The scientific basis for establishing appropriate radiation protection guides are discussed

  4. Risk estimation and decision-making: implications of the 1980 BEIR-III report

    International Nuclear Information System (INIS)

    The report gives a general background of the implications the current Report of the Committee on the Biological Effects of Ionizing Radiation (The BEIR-III Report) may have on societal decision-making in the regulation of activities concerned with the health effects of low-level radiation

  5. Synthesis and Structural Studies of 1-Deoxybaccatin VI Derivatives

    Institute of Scientific and Technical Information of China (English)

    LIN,Hai-Xia; WANG,Dian-Long; CHEN,Jian-Min; CHEN,Min-Qin

    2008-01-01

    Synthesis and crystal structures of 1-deoxybaccatin VI derivatives, and the influence of C(9), C(10), and C(13) substituents of the tetracyclic moiety on molecular conformations were investigated. Comparison of conformations of 1-deoxybaccatin VI derivatives reveals subtle conformational variations in the tetracyclic ring system due to deacetylation at C(10) and C(13), and 9,10-acetonide. Additionally, C(2)-benzoyl group exhibits an unexpected conformational flexibility in 1-deoxybaccatin VI derivatives, which may be relevant to the bioactivity of taxanes.

  6. Contribution to the study of the redox couple Np(VI)/Np(V) in the presence of uranium(VI) in solutions of nitric acid and nitrous acid

    International Nuclear Information System (INIS)

    The redox behavior of the Np(VI)/Np(V) couple was the subject of a spectrometric study of the Np(VI) reduction reaction in nitric acid solutions (4 to 5 M) containing variable concentrations (1.5 to 3.5 x 10-3 M) of nitrous acid. A low nitrous acid concentration and a high nitric acid concentration were found to favor the stabilization of Np(VI). The stoichiometric coefficients of nitrous acid and nitric acid in the Np(VI) reduction reaction were determined thermodynamically, although only the reaction order with respect to HNO2 could be calculated from a kinetic analysis. Adding nitrate ions to a HNO3/HNO2 solution enhanced the stability of neptunium at oxidation state +VI, but also increased the reduction rate. When uranium(VI) was added to the HNO3/HNO2 solutions, the total quantity of neptunium at oxidation state +V (either free or as a Np(V)-U(VI) complex) remained practically unchanged, as did the Np(VI) reduction rate. The electrochemical behavior of the Np(VI)/Np(V) couple was investigated in a weak acidic medium by voltammetry with an ultra-micro-electrode (UME). The oxidation wave limiting current variation was a linear function of the Np(V) concentration when a gold UME was used, but not with a platinum UME; the reduction wave limiting current variation versus the Np(V) concentration was linear with either gold or platinum UMEs. The presence of the Np(V)-U(VI) complex in the neptunium solutions was characterized by a shift in the normal apparent potential of the Np(VI)/Np(V) couple toward anodic potentials consistent with the previously determined values of the complexation constants. (author)

  7. Density functional study of uranyl (VI) amidoxime complexes

    International Nuclear Information System (INIS)

    Uranyl (VI) amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated under a generalized gradient approximation (GGA). Comparison of (acet) uranyl amidoxime complexes ([UO2(AO)n]2−n, 1 ≤ n ≤ 4) with available experimental data shows an excellent agreement. In addition, the U−O(1), U−O(3), C(1)−N(2), and C(3)−N(4) bond lengths of [UO2(CH3AO)4]2− are longer than experimental data by about 0.088, 0.05, 0.1, and 0.056 Å. The angles of N(3)−O(3)−U, O(2)−N(1)−C(1), N(3)−C(3)−N(4), N(4)−C(3)−C(4), and C(4)−C(3)−N(3) are different from each other, which is due to existing interaction between oxygen in uranyl and hydrogen in amino group. This interaction is found to be intra-molecular hydrogen bond. Studies on the bond orders, Mulliken charges, and Mulliken populations demonstrate that uranyl oxo group functions as hydrogen-bond acceptors and H atoms in ligands act as hydrogen-bond donors forming hydrogen bonds within the complex

  8. Integrated Ecogenomics Study for Bioremediation of Cr(VI) at Hanford 100H Area

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Romy; Chakraborty, Romy

    2008-08-12

    Hexavalent chromium is a widespread contaminant found in groundwater. In order to stimulate microbially mediated Cr(VI)-reduction, a poly-lactate compound was injected into Cr(VI)-contaminated aquifers at site 100H at Hanford. Investigation of bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products revealed a stimulation of Pseudomonas, Desulfovibrio and Geobacter species amongst others. Enrichment of these organisms coincided with continued Cr(VI) depletion. Functional gene-array analysis of DNA from monitoring well indicated high abundance of genes involved in nitrate-reduction, sulfate-reduction, iron-reduction, methanogenesis, chromium tolerance/reduction. Clone-library data revealed Psedomonas was the dominant genus in these samples. Based on above results, we conducted lab investigations to study the dominant anaerobic culturable microbial populations present at this site and their role in Cr(VI)-reduction. Enrichments using defined anaerobic media resulted in isolation of an iron-reducing, a sulfate-reducing and a nitrate-reducing isolate among several others. Preliminary 16S rDNA sequence analysis identified the isolates as Geobacter metallireducens, Pseudomonas stutzeri and Desulfovibrio vulgaris species respectively. The Pseudomonas isolate utilized acetate, lactate, glycerol and pyruvate as alternative carbon sources, and reduced Cr(VI). Anaerobic washed cell suspension of strain HLN reduced almost 95?M Cr(VI) within 4 hr. Further, with 100?M Cr(VI) as sole electron-acceptor, cells grew to 4.05 x 107 /ml over 24 h after an initial lag, demonstrating direct enzymatic Cr(VI) reduction coupled to growth. These results demonstrate that Cr(VI)-immobilization at Hanford 100H site could be mediated by direct microbial metabolism in addition to indirect chemical reduction of Cr(VI) by end-products of microbial activity.

  9. AM(VI) PARTITIONING STUDIES: FY14 FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Bruce J Mincher

    2014-10-01

    The use of higher oxidation states of americium in partitioning from the lanthanides is under continued investigation by the sigma team. This is based on the hypothesis that Am(VI) can be produced and remain stable in irradiated first cycle raffinate solution long enough to perform solvent extraction for separations. The stability of Am(VI) to autoreduction was measured using millimolar americium concentrations in a 1-cm cell with a Cary 6000 UV/Vis spectrophotometer for data acquisition. At millimolar americium concentrations, Am(VI) is stable enough against its own autoreduction for separations purposes. A second major accomplishment during FY14 was the hot test. Americium oxidation and extraction was performed using a centrifugal contactor-based test bed consisting of an extraction stage and two stripping stages. Sixty-three percent americium extraction was obtained in one extraction stage, in agreement with batch contacts. Promising electrochemical oxidation results have also been obtained, using terpyridine ligand derivatized electrodes for binding of Am(III). Approximately 50 % of the Am(III) was oxidized to Am(V) over the course of 1 hour. It is believed that this is the first demonstration of the electrolytic oxidation of americium in a non-complexing solution. Finally, an initial investigation of Am(VI) extraction using diethylhexylbutyramide (DEHBA) was performed.

  10. A Salmonella Typhimurium-Typhi genomic chimera: a model to study Vi polysaccharide capsule function in vivo.

    Directory of Open Access Journals (Sweden)

    Angela M Jansen

    2011-07-01

    Full Text Available The Vi capsular polysaccharide is a virulence-associated factor expressed by Salmonella enterica serotype Typhi but absent from virtually all other Salmonella serotypes. In order to study this determinant in vivo, we characterised a Vi-positive S. Typhimurium (C5.507 Vi(+, harbouring the Salmonella pathogenicity island (SPI-7, which encodes the Vi locus. S. Typhimurium C5.507 Vi(+ colonised and persisted in mice at similar levels compared to the parent strain, S. Typhimurium C5. However, the innate immune response to infection with C5.507 Vi(+ and SGB1, an isogenic derivative not expressing Vi, differed markedly. Infection with C5.507 Vi(+ resulted in a significant reduction in cellular trafficking of innate immune cells, including PMN and NK cells, compared to SGB1 Vi(- infected animals. C5.507 Vi(+ infection stimulated reduced numbers of TNF-α, MIP-2 and perforin producing cells compared to SGB1 Vi(-. The modulating effect associated with Vi was not observed in MyD88(-/- and was reduced in TLR4(-/- mice. The presence of the Vi capsule also correlated with induction of the anti-inflammatory cytokine IL-10 in vivo, a factor that impacted on chemotaxis and the activation of immune cells in vitro.

  11. Biosorption of Cr(VI) from AqueousSolution Using New Adsorbent: Equilibrium and Thermodynamic Study

    OpenAIRE

    Zainal, Israa G.

    2010-01-01

    Biosorption is one such emerging technology which utilized naturally occurring waste materials to sequester heavy metals from polluted water. In the present study cinnamon was utilized for Cr(VI) removal from aqueous solutions.It was found that a time of two hours was sufficient for sorption to attain equilibrium. The optimum pH was 2 for Cr(VI) removal. Temprature has little influence on the biosorption process. The Cr(VI) removal decreased with increase in temperature. The biosorption data ...

  12. Extraction studies of uranium(VI) and thorium(IV) with tributylphosphine oxide

    International Nuclear Information System (INIS)

    Tributylphosphine oxide is proposed as an extractant for uranium(VI) and thorium(IV) from salicylate media. The optimum extraction conditions were evaluated by studying various parameters such as pH, sodium salicylate concentration, tributylphosphine oxide concentration, diluents and shaking time. The extracted species were ascertained by logD-logC plots. The method is simple, fast, precise and permits the separation of uranium(VI) and thorium(IV) in binary as well as multicomponent systems. The method is also applied for the determination of uranium(VI) and thorium(IV) in monazite sand samples. (author)

  13. Study of sorption-retarded U(VI) diffusion in Hanford silt/clay material

    International Nuclear Information System (INIS)

    A diffusion cell method was developed to measure the effective aqueous diffusion coefficient for U(VI) under strictly controlled chemical conditions within the inter-particle pores of silt/clay sediment from the DOE Hanford site, WA. 'Inward-flux' diffusion studies were conducted in which U(VI) concentrations in both aqueous and solid phases were measured as a function of distance into the cell under conditions of constant concentration at the cell boundaries. A sequential extraction method was developed to measure sorbed U(VI) content in the solid phase, while accounting for the non-negligible extractable background U(VI). U(VI) diffusion data were found to be consistent with a model that assumed that: (1) a single effective aqueous diffusion coefficient could be used to simulate the coupled diffusion of various aqueous U(VI) species, and (2) the local equilibrium assumption (LEA) is appropriate for modeling the effects of sorption under the given experimental conditions. An effective aqueous diffusion coefficient (De) of 1.6 x 10-6 cm2/s was obtained under conditions of pH 8.0 and calcite saturation that are relevant to the subsurface conditions at some regions of the Hanford site. The developed experimental techniques provide a practical approach for measuring effective aqueous U(VI) diffusivity in sorptive porous media

  14. Treatment of selected pharmaceuticals by ferrate(VI): performance, kinetic studies and identification of oxidation products.

    Science.gov (United States)

    Zhou, Zhengwei; Jiang, Jia-Qian

    2015-03-15

    The performance of ferrate(VI) in treating sulfamethoxazole (SMX), diclofenac (DCF), carbamazepine (CBZ) and bezafibrate (BZF) in test solutions containing the four compounds was investigated. A series of jar-test experiments was performed on a bench-scale at pH 6-9 and at a ferrate(VI) dose of 1-5 mg Fe/L. The results suggested that ferrate(VI) can effectively remove SMX, DCF and CBZ from the test solutions, with greater than 80% removal under optimum conditions. However, the removal efficiency of BZF was very low, less than 25% under the studied conditions. Increasing the dose of ferrate(VI) improved the treatment performance, while the influence of solution pH on ferrate(VI) performance varied among the different target compounds. Ferrate(VI) demonstrated the highest reactivity with SMX at pH 8 and pH 9 (20 °C), with apparent second-order rate constants of 360±17 M(-1) s(-1) and 1.26±0.02 M(-1) s(-1), respectively. However, BZF showed the lowest removal by ferrate(VI) with the smallest rate constants (less than 0.5 M(-1) s(-1)) at pH 8 and pH 9. Furthermore, a number of oxidation products (OPs) of SMX, DCF and CBZ during ferrate(VI) oxidation were detected by liquid chromatography and mass spectrometry (LC-MS), and their degradation pathways were tentatively proposed. No OPs of BZF were detected during ferrate(VI) oxidation. PMID:25063450

  15. Synthesis, characterization, thermal and electrical studies of poly schiff base chelates of VO(IV), MoO2(VI) and UO2(VI)

    International Nuclear Information System (INIS)

    Polychelates of VO (IV), MoO2 (VI) and UO2(VI) with Schiff base ligand 2,4 dihydoxy-5-acetyl acetophenone-1,4-diaminobutane (DHADAB) have been synthesized and characterized by elemental analysis, IR and electronic spectra, 1H-NMR spectra, magnetic susceptibility, electrical conductivity measurements and thermogravimetric analysis. An octahedral geometry has been assigned to MoO2(VI) and UO2(VI) complexes while square pyramidal geometry for VO(IV) complexes. The thermal behaviour of the chelates was studied and kinetic parameters were determined by Coats-Redfern method and suggest more ordered activated state in complex formation. The solid state electrical conductivity of the ligand and its polychelates have been studied and it increases with increasing the temperature indicates their semiconducting behaviour. (author)

  16. Hydration study of limestone blended cement in the presence of hazardous wastes containing Cr(VI)

    International Nuclear Information System (INIS)

    Considering the increasing use of limestone cement manufacture, the present paper tends to characterize limestone behavior in the presence of Cr(VI). The research reported herein provides information regarding the effect of Cr(VI) from industrial wastes in the limestone cement hydration. The cementitious materials were ordinary Portland cement, as reference, and limestone blended cement. The hydration and physicomechanical properties of cementitious materials and the influence of chromium at an early age were studied with X-ray diffraction (XRD), infrared spectroscopy (FTIR), conductimetric and mechanical tests. Portland cement pastes with the addition of Cr(VI) were examined and leaching behavior with respect to water and acid solution were investigated. This study indicates that Cr(VI) modifies the rate and the components obtained during the cement hydration

  17. Sorption mechanism of U(VI) on to natural soil system: a study using intra-particle diffusion model

    International Nuclear Information System (INIS)

    The rate of U(VI) adsorption onto natural soils from different parent materials has been studied experimentally using the batch adsorption method at five different initial U(VI) concentrations. The utility of Weber and Morris Interparticle diffusion model for describing the mechanism and kinetics of sorption is discussed. The study reveals that the mechanism of U(VI) sorption involves three steps such as: external surface adsorption, gradual adsorption stage which is the rate determining step and the last portion refers to the final equilibrium stage. The steps involved in sorption of U(VI) on to soil is same irrespective of soil types and initial U(VI) concentration. (author)

  18. Study of new U(VI) and Pu(VI) coprecipitation methods for the preparation of (U,Pu)O2

    International Nuclear Information System (INIS)

    Two U(VI) and Pu(VI) coprecipitation methods have been studied, for the definition of new processes to prepare (U,Pu)O2 mixed oxides suitable for making MoX fuels or fast breeder reactor fuels. The first system is based on the coprecipitation of a new U(VI), Pu(VI) compound; ammonium uranoplutonate, where as a second system is related to the precipitation of uranyl plutonyl monocarbonate. Experimental conditions to optimize the precipitation and the filtration steps of these two systems have been determined. After calcination under reducing conditions, the mixed oxides obtained are characterized according to different techniques: granulometry, thermogravimetry, solubility in boiling HNO3 solutions. The properties of such oxides are excellent. The possible processes for preparing (U, Pu)O2 using these new routes are compared with those actually exploited

  19. Adsorption studies on fruits of Gular (Ficus glomerata): Removal of Cr(VI) from synthetic wastewater

    International Nuclear Information System (INIS)

    The adsorption of Cr(VI) was studied in batch system using fruits of Ficus glomerata as adsorbent. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate surface morphology and active functional groups present on the adsorbent surface. Thermodynamic parameters like free energy change (ΔG0), enthalpy (ΔH0) and entropy (ΔS0) indicate the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were fitted well with Langmuir isotherm at 50 deg. C. The magnitude of mean free energy indicates chemical nature of adsorption. The breakthrough and exhaustive capacities were found to be 5 and 23.1 mg g-1 respectively. The applicability of the adsorbent has been demonstrated by removing Cr(VI) from electroplating wastewater.

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

    Directory of Open Access Journals (Sweden)

    Batukhan Tatykaev

    2013-05-01

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

  1. Kinetic and thermodynamic studies of U(VI) adsorption using Dowex-Marathon resin

    International Nuclear Information System (INIS)

    The kinetics and thermodynamics of U(VI) adsorption on Dowex-Marathon anionic resin have been studied. The process was well described by the pseudo-second order kinetic model for 0.02-0.1 M U(VI) concentration. The activation energy of U(VI) adsorption on Dowex-Marathon resin was determined: 6.62 ± 0.16 kJ/mol, indicating that the adsorption has a low potential barrier and corresponds to a physisorption. The thermodynamic parameter were evaluated: ΔGdeg = (-6.37)/(-9.23) kJ/mol, for temperature range: 20-60 deg C; ΔHdeg = 14.57 kJ/mol and ΔSdeg = 71.48 J/mol K, the U(VI) adsorption being spontaneous and endothermic. (author)

  2. Study of Cr(VI) Detoxification By basalt Inhabiting Bacteria Using NAA And ESR Methods

    International Nuclear Information System (INIS)

    Mixtures of heavy metals have polluted many industrial regions in the world. The environmental contamination with heavy metals has become a serious health concern. Since metal ions cannot be destroyed in environments, factors which influence the detoxification of metals can dictate the metal toxicity to ecological receptors. Indigenous bacteria have been considered as a potential candidate for detoxifying heavy metal ions. Molecular insight into the fate of heavy metal species in bacteria is important in the development of new bio technologies to clean-up contaminated sites. In our study chromium(VI), a widespread environmental pollution. was selected as a model heavy metal.Today there are only few studies that examine how microorganisms respond to chromium stress at higher doses. Instrumental neutron activation analysis (NAA) and electron spin resonance (ESR) methods were applied to evaluate the potential of indigenous bacteria to detoxify Cr(VI) from heavily contaminated environment. The microbial reduction of toxic Cr(VI) to less toxic Cr(III) was studied in batch systems in the presence of high concentrations of Cr(VI) (50-1000 mg/L). Gram-positive Arthrobacter oxydans isolated from Columbia basalts (USA) that have been polluted with mixtures of heavy metals, radionuclides and organic compounds and also two Gram-positive bacteria isolated from polluted basalts from the Republic of Georgia were tested under aerobic conditions. All the bacterial samples were exposed to Cr(VI) action at a given concentration for five days. NAA revealed that A. oxydans is able to accumulate Cr(VI) efficiently in the concentration range 50-500 mg/L. Dose-dependent ESR measurements of the formation of Cr(Ill) complexes (g=2.02, line width=650 gauss) in bacterial cells confirmed this character of Cr(VI) detoxification. The similar results are obtained for one of the bacterial isolate. For the other bacterium, the content of chromium inside the cells is increased continuously by

  3. Kinetic and thermodynamic studies of the biosorption of Cr(VI) by Pinus sylvestris Linn

    International Nuclear Information System (INIS)

    Biosorption equilibrium, kinetics and thermodynamics of chromium(VI) ions onto cone biomass were studied in a batch system with respect to temperature and initial metal ion concentration. The biosorption efficiency of chromium ions to the cone biomass decreased as the initial concentration of metal ions was increased. But cone biomass of Pinus sylvestris Linn. exhibited the highest Cr(VI) uptake capacity at 45 oC. The biosorption efficiency increased from 67% to 84% with an increase in temperature from 25 to 45 deg. C at an initial Cr(VI) concentration of 300 mg/L. The Langmuir isotherm model was applied to experimental equilibrium data of Cr(VI) biosorption depending on temperature. According to Langmuir isotherm, the monolayer saturation capacity (Qmax) is 238.10 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data for initial Cr(VI). The pseudo-second-order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first-order kinetic model. The activation energy of biosorption (Ea) was determined as 41.74 kJ/mol using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of biosorption (ΔGo, ΔHo and ΔSo) were also evaluated

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

    Science.gov (United States)

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

    2006-01-01

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

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

    International Nuclear Information System (INIS)

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

  6. Studies on Cr(VI) removal from aqueous solutions by nanotitania under visible light and dark conditions

    Indian Academy of Sciences (India)

    Madona Lien Paul; Jastin Samuel; Rajdeep Roy; Natarajan Chandrasekaran; Amitava Mukherjee

    2015-04-01

    The current study deals with Cr(VI) removal by nanotitania under fluorescent light and dark conditions. The equilibrium removal capacities, 85.85 and 59.4 mg of Cr(VI)g−1 of nanoparticle were noted for nanotitania interacted under light and dark conditions, respectively, at optimized conditions (pH: 7.0, contact time: 30 min, initial Cr(VI) concentration: 20 mg l−1, nanoparticle dosage: 0.1 g l−1). Under both the conditions, the equilibrium removal data fitted well with the Langmuir isotherm model. The nanotitania followed a second-order kinetics under light condition whereas a pseudo-second-order kinetics was observed under dark condition. The surface characterization of nanotitania was carried out by zeta potential measurement and transmission electron microscope (TEM). Fourier transform infrared (FT-IR) studies carried out under light and dark conditions indicate the interaction of surface functional groups to Cr(VI). Cr(VI) removal study carried out in the Cr(VI)–Cr(III) mixture showed a decrease in Cr(VI) removal capacity with increase in Cr(III) concentration. A 92% regeneration of nanoparticle was observed indicating efficient reusability of the system. The applicability of the nanotitania in Cr(VI) contaminated water was studied by spiking Cr(VI) in natural water matrices like ground water and lake water.

  7. BEIR-III report and the health effects of low-level radiation

    Energy Technology Data Exchange (ETDEWEB)

    Fabrikant, J.I.

    1980-01-01

    The present BEIR-III Committee has not highlighted any controversy over the health effects of low-level radiation. In its evaluation of the experimental data and epidemiological surveys, the Committee has carefully reviewed and assessed the value of all the available scientific evidence for estimating numerical risk coefficients for the health hazards to human populations exposed to low levels of ionizing radiation. Responsible public awareness of the possible health effects of ionizing radiations from medical and industrial radiation exposure, centers on three important matters of societal concern: (1) to place into perspective the extent of harm to the health of man and his descendants to be expected in the present and in the future from those societal activities involving ionizing radiation; (2) to develop quantitative indices of harm based on dose-effect relationships; such indices could then be used with prudent caution to introduce concepts of the regulation of population doses on the basis of somatic and genetic risks; and (3) to identify the magnitude and extent of radiation activities which could cause harm, to assess their relative significance, and to provide a framework for recommendations on how to reduce unnecessary radiation exposure to human populations. The main difference of the BEIR Committee Report is not so much from new data or new interpretations of existing data, but rather from a philosophical approach and appraisal of existing and future radiation protection resulting from an atmosphere of constantly changing societal conditions and public attitudes. (PCS)

  8. Leukaemia mortality in three UK nuclear industry workforces: comparison with the BEIR V model

    International Nuclear Information System (INIS)

    Our previous comparison of risk of death from leukaemia associated with external radiation dose in over 75000 UK nuclear industry workers with that for adult Japanese atomic bomb survivors reported by UNSCEAR in 1988, suggested that the estimated excess relative risk per Sv in the two populations was similar (ratio of risks = 1.1, 90% confidence interval +0.2 to +3.1). The further analysis described here, which compares leukaemia risk in the workers with that predicted by the linear term of the BEIR V model for leukaemia, resulted in a ratio of 1.3 (90% confidence interval -0.2 to +4.5). Leukaemia risk in this population of nuclear industry workers is therefore consistent with that predicted by the BEIR V model. That our data are also compatible with risks from zero to around five times those predicted by this model demonstrates that even a very substantial occupational cohort such as ours can provide only a limited amount of information about the magnitude of leukaemia risks in adults exposed to low doses of external radiation relative to those exposed to high doses and high dose rates. (author)

  9. BEIR-III report and the health effects of low-level radiation

    International Nuclear Information System (INIS)

    The present BEIR-III Committee has not highlighted any controversy over the health effects of low-level radiation. In its evaluation of the experimental data and epidemiological surveys, the Committee has carefully reviewed and assessed the value of all the available scientific evidence for estimating numerical risk coefficients for the health hazards to human populations exposed to low levels of ionizing radiation. Responsible public awareness of the possible health effects of ionizing radiations from medical and industrial radiation exposure, centers on three important matters of societal concern: (1) to place into perspective the extent of harm to the health of man and his descendants to be expected in the present and in the future from those societal activities involving ionizing radiation; (2) to develop quantitative indices of harm based on dose-effect relationships; such indices could then be used with prudent caution to introduce concepts of the regulation of population doses on the basis of somatic and genetic risks; and (3) to identify the magnitude and extent of radiation activities which could cause harm, to assess their relative significance, and to provide a framework for recommendations on how to reduce unnecessary radiation exposure to human populations. The main difference of the BEIR Committee Report is not so much from new data or new interpretations of existing data, but rather from a philosophical approach and appraisal of existing and future radiation protection resulting from an atmosphere of constantly changing societal conditions and public attitudes

  10. Photochemical study on uranyl(VI) tributylphosphate in supercritical CO2 and the first uranyl(VI) photoreduction carried out in supercritical fluid

    International Nuclear Information System (INIS)

    The photochemistry of uranyl(VI)-tributylphosphate (TBP) complex in supercritical carbon dioxide (scCO2) was studied in the pressure range of 8-40 MPa and from 289 to 336 K. Deactivation rate constants decreased with the increase of pressure. Temperature dependence analysis of the deactivation rate constants indicated that scCO2 contributes differently to deactivation processes from liquid phase CO2 based on activation barriers. An UV irradiation experiment proved photochemical reduction of uranyl(VI)-TBP complex by ethanol in scCO2. (author)

  11. Recommendations concerning the scientific foundation of radiohygienic policy based on the UNSCEAR-77, -82 and BEIR reports

    International Nuclear Information System (INIS)

    This report studies to what extent the UNSCEAR-77 report and other more recent scientific literature (in particular the BEIR-80 and UNSCEAR-82 reports) support the risk factors mentioned in ICRP-26, which formed the basis of the weighting factors per organ, recommended by the International Commission on Radiological Protection. It discusses the nature and size of the different contributions to the exposure to ionizing radiation both on a global level and with respect to the Dutch situation. An estimate is given of the average total annual dose equivalent for the world population, for the population of the Netherlands and for radiological workers in the Netherlands. An extensive discussion is presented of the dose-effect relationships of stochastic radiation effects in the female breast, the thyroid, red bone marrow, bone tissue, the lungs, other organs and the whole body. Furthermore consideration is given to nonstochastic effects in the lens of the eye and in the skin and to the late effects of radiotherapy. Finally the effects of prenatal irradiation and the genetic effects of ionizing radiation are discussed. Subsequently the risk factors used by ICRP in formulating its recommendations in publication ICRP-26, are compared with the risk factors mentioned in the scientific literature. (Auth.)

  12. A study of solid-liquid phase equilibria of Pu(VI) and U(VI) in aqueous carbonate systems

    International Nuclear Information System (INIS)

    Solubility products of PuO2CO3(s) and UO2CO3(s) are determined in 0.1 M NaClO4 at 22 ± 1 C under 100%, 1% and 0.03% CO2. The carbonate precipitates of Pu(VI) and U(VI), prepared under 100% CO2 at neutral pH, are characterized by powder diffraction measurement, IR spectroscopy and UV spectroscopy. The solubility experiment is carried out in different CO32-concentrations and pH. The speciation of PuO22+ and UO22+ in equilibrium solutions is made by UV spectroscopy and the total concentrations of Pu(VI) and U(VI) are determined by liquid scintillation spectrometry and ICP-AES, respectively. The concentration correlation of [MO22+] vs. [CO32-] gives a slope of negative unity, while [MO22+] vs. pH shows a slope of -2 irrespective of CO2 partial pressure. The fact concludes that the present experiment comprises solid-liquid phase equilibrium reactions with only MO2CO3(s). The solubility products converted to zero ionic strength are found to be logKspo = -14.84 ± 0.10 for PuO2CO3(s) and logKspo = -14.22 ± 0.14 for UO2CO3(s). (orig.)

  13. Highly efficient detoxification of Cr(VI) by chitosan–Fe(III) complex: Process and mechanism studies

    International Nuclear Information System (INIS)

    Highlights: ► Cr(VI) detoxification by chitosan–Fe(III) complex was in high efficiency. ► XAFS and XPS were used to decipher the mechanism of Cr(VI) detoxification. ► The -OH on C-6 of chitosan served as an electron donor during Cr(VI) reduction. ► The geometrical arrangement of adsorbed Cr(VI) was similar as Cr(III). ► Mechanism for detoxification of Cr(VI) by chitosan–Fe(III) complex was elucidated. -- Abstract: Metal–biopolymer complexes has recently gained significant attention as an effective adsorbent used for the removal of Cr(VI) from water. Unfortunately, despite increasing research efforts in the field of removal efficiency, whether this kind of complex can reduce Cr(VI) to less-toxic Cr(III) and what are the mechanisms of detoxification processes are still unknown. In this study, despite the highly adsorption efficiency (maximum adsorption capacity of 173.1 mg/g in 10 min), the significant improvement of Cr(VI) reduction by chitosan–Fe(III) complex compared with normal crosslinked chitoan has been demonstrated. In addition, the structure of chitosan–Fe(III) complex and its functional groups concerned with Cr(VI) detoxification have been characterized by the powerful spectroscopic techniques X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XPS spectra indicated that the primary alcoholic function on C-6 served as an electron donor during Cr(VI) reduction and was oxidized to a carbonyl group. The X-ray adsorption near edge spectra (XANES) of the Cr(VI)-treated chitosan–Fe(III) complex revealed the similar geometrical arrangement of Cr species as that in Cr(III)-bound chitosan–Fe(III). Overall, a possible process and mechanism for highly efficient detoxification of Cr(VI) by chitosan–Fe(III) complex has been elucidate

  14. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

    International Nuclear Information System (INIS)

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  15. Effects of ICRP Publication 30 and the 1980 Beir report on hazard assessments of high-level waste

    International Nuclear Information System (INIS)

    ICRP Publication 30 (ICRP30) gives the radiation dose to various body organs in Sv per Bq, which are readily translated into rad per curie ingested for various radioisotopes; the 1980 BEIR Report (BEIR III) gives the risk of fatal cancer per rad of dose to each body organ; the ORIGEN 2 Code gives the curies per tonne of initial uranium fuel in high level waste and in spent fuel. The product of these, Ci/tonne X rad/Ci X risk/rad gives the risk/tonne in terms of fatal cancer doses, if ingested, per tonne of uranium. When the resulting curves are compared with those calculated previously (based on ICRP Publication 2 and the 1972 BEIR Report), the hazard is less for the first century but much more thereafter. The principal sources of this greatly increased hazard is the 100-fold increase in absorption through the gut for 237Np in ICRP 30, plus the high cancer risk from radiation to liver in BEIR III. Some consequences of these changes and some scientific questions relevant to ascertaining their validity are discussed. (author)

  16. Bench-scale column experiments to study the containment of Cr(VI) in confined aquifers by bio-transformation.

    Science.gov (United States)

    Shashidhar, T; Philip, Ligy; Murty Bhallamudi, S

    2006-04-17

    Bench-scale soil column experiments were conducted to study the effectiveness of Cr(VI) containment in confined aquifers using in situ bio-transformation. Batch adsorption studies were carried out to estimate the adsorption capacities of two different soils for Cr(VI) and Cr(III). Bio-kinetic parameters were evaluated for the enriched microbial system. The inhibition constant, evaluated using Monod's inhibition model, was found to be 11.46 mg/L of Cr(VI). Transport studies indicated that it would not be possible to contain Cr(VI) by adsorption alone. Transport and bio-transformation studies indicated that the pore velocity and the initial bio-mass concentration significantly affect the containment process. In situ bio-remediation is effective in the case of silty aquifers. Cr(VI) concentration of 25 mg/L was effectively contained within 60 cm of a confined silty aquifer. Cr(VI) containment could be achieved in sandy aquifers when the pore velocity was very low and the initial augmented bio-mass was high. A bio-barrier of approximately one meter width would be able to contain Cr(VI) if the initial Cr(VI) concentration is as much as 25 mg/L. PMID:16263213

  17. Uranium(VI) interaction with pyrite (FeS{sub 2}). Chemical and spectroscopic studies

    Energy Technology Data Exchange (ETDEWEB)

    Eglizaud, N.; Descostes, M. [CEA Saclay, DEN/DANS/DPC/SECR/Lab. de Mesures et Modelisation de la Migration des Radionucleides, Gif-sur-Yvette (France); Miserque, F.; Schlegel, M. [CEA Saclay, DEN/DANS/DPC/SCP/Lab. de Reactivite aux Surfaces et Interfaces, Gif-sur-Yvette (France); Simoni, E. [Inst. de Physique Nucleaire d' Orsay, Univ. Paris Sud, Orsay (France)

    2006-07-01

    The mechanism of uranium(VI) interaction with pyrite was studied by solution chemistry and X-ray photoelectron spectroscopy (XPS). Natural pyrite was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). After equilibration in 10{sup -2}molL{sup -1} NaNO{sub 3}, pyrite was reacted with uranium(VI) by the batch method in an anoxic glove box (P{sub O{sub 2}} < 1 ppm) at ambient temperature. The reaction products of uranium, iron and sulphur were characterized (oxidation state, chemical environment) by XPS. Quantitative analysis revealed that only a few atomic percent of uranium is retained at the pyrite surface. The U4f core level binding energies are consistent with the coexistence of an uranium(VI) species and of uranium in a reduced form. No sulphur oxidation products were observed by XPS, but spectral decomposition of the Fe2p lines revealed the presence of iron(III) oxide or (oxy)hydroxide. These results seem to point to a redox reaction between uranium(VI) and pyrite. (orig.)

  18. Biosorption of uranium(VI) by free and entrapped Chlamydomonas reinhardtii. Kinetic, equilibrium and thermodynamic studies

    International Nuclear Information System (INIS)

    Biosorption of uranium from aqueous solution onto the free and entrapped algae, 'Chlamydomonas reinhardtii' in carboxymethyl cellulose (CMC) beads was investigated in a batch system using bare CMC beads as a control system. CMC can be a potential natural biosorbent for radionuclide removal as it contains carboxyl groups. However, limited information is available with the biosorption of uranium by CMC, when adsorption isotherm, kinetics and thermodynamics parameters are concerned. The biosorbent preparations were characterized by swelling tests, FTIR, and surface area studies. The effects of pH, temperature, ionic strength, biosorbent dosage, and initial uranium concentrations on uranium biosorption were investigated. Freely suspended algae exhibited the highest uranium uptake capacity with an initial uranium ion concentration of 1,000 mg/L at pH of 4.5 and at 25 deg C. The removal of U(VI) ion from the aqueous solution with all the tested biosorbents increased as the initial concentration of U(VI) ion increased in the medium. Maximum biosorption capacities for free algal cells, entrapped algal cells, and bare CMC beads were found to be 337.2, 196.8, and 153.4 mg U(VI)/g, respectively. The kinetic studies indicated that the biosorption of U(VI) ion was well described by the pseudo-second order kinetic model. The variations in enthalpy and entropy for the tested biosorbent were calculated from the experimental data. The algal cells entrapped beads were regenerated using 10 mM HNO3, with up to 94 % recovery. Algal cells entrapped CMC beads is a low cost and a potential composite biosorbent with high biosorption capacity for the removal of U(VI) from waters. (author)

  19. Efficient uranium(VI) biosorption on grapefruit peel. Kinetic study and thermodynamic parameters

    International Nuclear Information System (INIS)

    The uranium(VI) biosorption by grapefruit peel was studied from aqueous solutions. Batch experiments was conducted to evaluate the effect of contact time, initial uranium(VI) concentration, initial pH, adsorbent dose, salt concentration and temperature. The equilibrium process was well described by the Langmuir, Redlich-Peterson and Koble-Corrigan isotherm models, with maximum sorption capacity of 140.79 mg g-1 at 298 K. The pseudo second order model and Elovish model adequately describe the kinetic data in comparison to the pseudo first order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle diffusion processes. The effective diffusion parameter Di and Df values were estimated at different initial concentration and the average values were determined to be 1.167 x 10-7 and 4.078 x 10-8 cm2 s-1. Thermodynamic parameters showed that the biosorption of uranium(VI) onto grapefruit peel biomass was feasible, spontaneous and endothermic under studied conditions. The physical and chemical properties of the adsorbent were determined by SEM, TG-DSC, XRD and elemental analysis and the nature of biomass-uranium (VI) interactions was evaluated by FTIR analysis, which showed the participation of COOH, OH and NH2 groups in the biosorption process. Adsorbents could be regenerated using 0.05 mol L-1 HCl solution at least three cycles, with up to 80% recovery. Thus, the biomass used in this work proved to be effective materials for the treatment of uranium (VI) bearing aqueous solutions. (author)

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

    International Nuclear Information System (INIS)

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

  1. Wilderness Study Report : Volume VI : Kenai National Moose Range

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — In order to conform to the Wilderness Act of 1964, a study was conducted by the Bureau of Sport Fisheries and Wildlife personnel to ascertain which of the Kenai...

  2. Re-evaluation of benefit-risk analysis for mammographic screening in Japan using prevalence model and BEIR VII report

    International Nuclear Information System (INIS)

    The risk of radiation exposure associated with mammography in breast cancer screening must be considered. In this study, we re-evaluated the benefit vs. risk of the mammographic procedure used for breast cancer screening in Japan, assuming a screening interval of 2 years with 2 mammography views for women aged 40-49 years and 1 view for those aged 50 years or more. We also used a new breast tissue weighting factor defined by ICRP2007 and the life-time mortality coefficient defined by BEIR. The effective radiation dose used in mammography was assumed to be 0.72 mSv and 0.36 mSv for women aged 40-49 and 50 years or more respectively. The risk was expressed as loss of life expectancy (person-day) due to a single screening test. On the other hand, the benefit of screening was calculated on the basis of the number of lives saved by a stage shift of breast cancer detected by screening and then multiplying by the average life expectancy. Thus the benefit was expressed as the gain of life expectancy (person-day) due to a single screening. Finally, the benefit/risk ratio was obtained as: gain of life expectancy/loss of life expectancy as a function of age at which the benefit/risk ratio exceeded 1.0. In this study we showed that the benefit/risk ratio exceeds 1.0 from age of 25 years old or more in Japanese breast cancer screening, and so our screening is justified because the lowest age for the screenee is set at 40 years old. (author)

  3. Biosorption of Cr (VI) ion from aqueous solution by maize husk: isothermal, kinetics and thermodynamic study

    International Nuclear Information System (INIS)

    The kinetics, equilibrium and thermodynamic of the biosorption of Cr (VI) ion onto maize husk biomass from aqueous solution were investigated. The effects of contact time, initial metal concentration, pH, temperature as well as modification with oxalic acid on biosorption capacity were studied. The maximum biosorption capacity of the untreated corn shaft biomass (UTCS) was found to be 28.49 mg g-1 which slightly increased to 29.33 mg g/sup -1/ when treated with oxalic acid treated corn shaft biomass (ATCS). The kinetics studies showed that the biosorption process of the metal ion fitted well with second order model. The calculated thermodynamic parameters (delta Go, delta Ho and delta S') showed that the biosorption of Cr (VI) ion onto the biomass maize husk is feasible, spontaneous and exothermic in nature. (author)

  4. Studies of kinetic of Cr(VI adsorption in chitosan magnetic particles by radiochemistry method

    International Nuclear Information System (INIS)

    There are a number of processes which are used for remove or recovery metals from waters and waste waters. However, such processes are expensive and sometimes ineffective, especially when metals are present in solution at very low concentrations. Alternative and more efficient processes than ones usually employed are being intensively investigated as sorption. Biosorption of metals is already sufficiently known and its mechanisms have been intensely studied. Therefore, the efficiency and the mechanism of Cr(VI) ions uptake in chitosan magnetic particles obtained by suspension crosslinking technique were studied. These particles were spherical in shape and had a high porosity degree, a low saturation magnetization and a low percentage of swelling. The Cr(VI) ions uptake onto chitosan magnetic particles followed a mechanism of second order, suggesting chemical adsorption. (author)

  5. Spectrophotometric study of neptunium (VI) complexation by nitrate ions; Etude par spectrophotometrie de la complexation du neptunium au degre d'oxydation (VI) par les ions nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Pochon, P. [CEA/VALRHO - site de Marcoule, Dept. de Recherche en Retraitement et en Vitrification (DRRV), 30 - Marcoule (France)]|[Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France)]|[Centre Regional Associe de Lyon, 69 (France)

    2000-07-01

    Neptunium(VI) complexation by nitrate ions was investigated by visible and near-infrared spectrophotometry, a technique suitable for observing the appearance and evolution of the species in solution. In the absence of reference spectra for Np(VI) nitrate- complexes, mathematical (factor analysis) tools were used to interpret the spectra. These chemo-metric techniques were first tested and validated on a simpler chemical system: Np(VI)complexation by the SiW{sub 11}O{sub 39}{sup 8-} anion. The test media used to investigate Np(VI) nitrate- complexes generally contain nitrate and perchlorate salts at high concentrations (high ionic strength). Media effects arising from the presence of cations, acidity or the perchlorate ion concentration are therefore significant, and no doubt account for the scattered values of the complexation constants published in the literature. The evolution of the neptunium spectra according to the parameters of the reaction medium illustrated these effects and allowed them to be quantified by a global 'perturbation constant'. In order to minimize the spectrum modifications due to media effects, the neptunium nitrate-complexes were studied at constant ionic strength in weak acidic media (2 mol.kg{sup -1}{sub H2O}) in the presence of sodium salts. The bulk formation constants and the spectrum of the NpO{sub 2}(NO{sub 3}){sup +} complex were determined for ionic strength values of 2.2, 4, 6 and 8 mol.kg{sup -1}{sub H2O}. The constants remained on the same order of magnitude regardless of the ionic strength; the thermodynamic constant {beta}{sub 1}{sup 0} determined from them according to specific interaction theory is thus probably of little significance. Conversely, the bulk constants can be corrected for the effects of the perchlorate ions by taking the global 'perturbation constant' into account. (author)

  6. Spectroscopic studies on U(VI)-salicylate complex formation with multiple equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Cha, W.; Cho, H.R.; Jung, E.C.; Park, K.K.; Kim, W.H.; Song, K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Nuclear Chemistry Research Div.

    2012-07-01

    This study investigates multiple equilibria related to the formation of the U(VI)-salicylate complex in a pH range of 3.0-5.5 using UV-Vis absorption and fluorescence measurement techniques. The absorbance changes at the characteristic charge-transfer bands of the complex were monitored, and the results indicated the presence of multiple equilibria and the formation of both 1:1 and 1:2 (U(VI):salicylate) complexes possessing bi-dentate chelate structures. The determined step-wise formation constants (log K{sub 1:1} and log K{sub 1:2}) are as follows: 12.5 {+-} 0.1 and 11.4 {+-} 0.2 for salicylate, 11.2 {+-} 0.1 and 10.1 {+-} 0.2 for 5-sulfosalicylate, and 12.4 {+-} 0.1 and 11.4 {+-} 0.1 for 2,6-dihydroxybenzoate, respectively. The molar absorptivities of the complexes are also provided. Furthermore, time-resolved laser-induced luminescence spectra of U(VI) species demonstrate the presence of both a dynamic and static quenching process upon the addition of a salicylate ligand. Particularly for the luminescent hydroxouranyl species, a strong static quenching effect is observed. The results suggest that both the UO{sub 2}(HSal){sup +} and the U(VI)-Sal chelate complexes serve as ground-state complexes that induce static quenching. The Stern-Volmer parameters were derived based on the measured luminescent intensity and lifetime data. The static quenching constants (log K{sub S}) obtained are 3.3 {+-} 0.1, 4.9 {+-} 0.1, and 4.4 {+-} 0.1 for UO{sub 2}{sup 2+}, (UO{sub 2}){sub 2}(OH){sub 2}{sup 2+} and (UO{sub 2}){sub 3}(OH){sub 5}{sup +}, respectively. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-12-30

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Mise, Shashikant; Patil, Trupti Nagendra

    2015-09-01

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

  10. Spectroscopic studies of U(VI) sorption at the kaolinite-water interface. Final report

    International Nuclear Information System (INIS)

    Efficient use of U as a resource and safe handling, recycling and disposal of U-containing wastes require an understanding of the factors controlling the fate of U, where fate refers to the destination of U, typically expressed as an environmental medium or a process phase. The sorption process constitutes a change in elemental fate. Partitioning of an element from solution to a solid phase, or sorption, can be divided into three broad categories: adsorption, surface precipitation, and absorption. Extended X-ray absorption fine structure (EXAFS), a type of X-ray absorption spectroscopy (XAS), offers the possibility for distinguishing among different modes of sorption by characterizing the atomic environment of the sorbing element. In this study, the authors use EXAFS to determine the structure of U(VI) sorption complexes at the kaolinite-water interface. In Chapter One, they present an overview of selected aspects of U structural chemistry as a basis for considering the structural environment of U at the solid-water interface. To evaluate the utility of XAS for characterization of the structural environment of U(VI) at the solid-water interface, they have carried out an in-depth analysis of XAS data from U(VI)-containing solid and solution model compounds, which they describe in Chapter Two. In Chapter three, they consider sorption of U by kaolinite as a means of effecting the removal of U from surface collection pond waters on the Rocky Flats Plant site in northern Colorado

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

    Directory of Open Access Journals (Sweden)

    K. SHIVA PRASHANTH KUMAR

    2014-08-01

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

  12. Kinetics and equilibrium studies for sorption of Cu (II) and Cr (VI) ions onto polymeric composite resins

    International Nuclear Information System (INIS)

    The sorption behavior of Cu (II) and Cr (VI) ions from aqueous solutions was studied using polymeric composite resins. Batch sorption experiments were performed as a function of hydrogen ion concentration, complexing agent concentration, resin weight and ionic strength. Kinetic parameters as a function of initial ion concentration were determined to predict the sorption behavior of Cu (II) and Cr (VI) onto polymeric composite resins. The equilibrium data could be fitted by the frendlich adsorption isotherm equation

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

    OpenAIRE

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

    2015-01-01

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

  14. Uranium (VI) adsorption on synthesized 4A and P1 zeolites: Equilibrium, kinetic, and thermodynamic studies

    International Nuclear Information System (INIS)

    The present work deals with the investigation of the use of synthesized 4A and P1 zeolites in the adsorption of uranium (VI) ions from liquid effluents (with initial concentrations of 100, 85 and 80 mgL-1). Batch experiments were performed and the effects of temperature, solid-liquid ratio, pH and initial UO22+ ion concentration were studied, and the optimal parameters were determined. The kinetic and thermodynamic aspects of the process as well as the diffusion mechanism have been studied. The obtained results showed that 4A and P1 zeolites are very effective adsorbents. (authors)

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

    Science.gov (United States)

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

    2005-01-31

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

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-01-31

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

  18. Studies on 4-[N-(furfural) amino] antipyrine complexes of thorium (IV) and dioxouranium (VI)

    International Nuclear Information System (INIS)

    Thorium (IV) and dioxouranium (VI) complexes of Schiff base 4-[N-(furfural) amino] antipyrine (FFAP) derived from furfural and 4-aminoantipyrine having general composition ThX4.nL (X = Cl-, Br-, NCS-or NO3-, n = 2; x = I- or ClO4-n = 3, L = FFAP) and UO2X2.nL (X Br-, I-, NCS-,NO3- or CH3COO-, n = 2; X = ClO4-n = 3, L = FFAP) have been synthesized and characterized by molecular weight, conductivity, IR spectral and thermoanalytical studies. (author)

  19. Polarographic study of dioxo-uranium(VI)-8-hydroxyquinoline-succinate system and thermodynamic parameters

    International Nuclear Information System (INIS)

    The dioxo-uranium(VI)-8-hydroxyquinoline-succinate system has been studied polarographically at constant ionic strength (μ = 0.6 M KCl) in aqueous alcohol (7:3) at different temperatures. The reduction of the simple and mixed complexes is reversible and diffusion controlled. The DeFord-Hume and Schaap-McMaster methods have been applied in the determination of composition and stability constants of the simple and mixed complexes respectively. The thermodynamic parameters ΔG, ΔH and ΔS have also been calculated. (author)

  20. Studies of Cr (VI) uptake by a green resin: dry cow dung

    International Nuclear Information System (INIS)

    In the present investigation dry cow dung powder has been employed as an indigenous, inexpensive and eco-friendly material for the removal of Cr (VI) from aqueous medium. The effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration and concentration of metal ion etc. have been studied. Many naturally available materials are used for the adsorption of heavy metal pollutant, where most of them are modified physically or chemically. Dry cow dung powder has been utilized with simple chemical treatment thus manifesting the principle of Green Chemistry. (author)

  1. Natural History and Galsulfase Treatment in Mucopolysaccharidosis VI (MPS VI, Maroteaux-Lamy Syndrome) — 10 Year Follow-up of Patients Who Previously Participated in an MPS VI Survey Study

    Science.gov (United States)

    Giugliani, Roberto; Lampe, Christina; Guffon, Nathalie; Ketteridge, David; Teles, Elisa Leão; Wraith, James E.; Jones, Simon A; Piscia-Nichols, Cheri; Lin, Ping; Quartel, Adrian; Harmatz, Paul

    2014-01-01

    Mucopolysaccharidosis VI (MPS VI) is a clinically heterogeneous and progressive disorder with multiorgan manifestations caused by deficient N-acetlylgalactosamine-4-sulfatase activity. A cross-sectional Survey Study in individuals (n=121) affected with MPS VI was conducted between 2001–2002 to establish demographics, urinary glycosaminoglycan (GAG) levels, and clinical progression of disease. We conducted a Resurvey Study (ClinicalTrials.gov: NCT01387854) to obtain 10-year follow-up data, including medical histories and clinical assessments (n=59), and survival status over 12-years (n=117). Patients received a mean (SD) of 6.8 (2.2) years of galsulfase ERT between baseline (Survey Study) and follow-up. ERT patients increased in height by 20.4 cm in the 4–7 year-old baseline age group and by 16.8 cm in the 8–12 year-old baseline age group. ERT patients 200 µg/mg baseline uGAG levels increased FVC by 48% in the <13 year-old and by 15% in the ≥13 year-old baseline age group. ERT patients who completed the 6-minute walk test demonstrated a mean (SD) increase of 65.7 (100.6) m. Cardiac outcomes did not significantly improve or worsen. Observed mortality rate among naïve patients was 50% (7/14) and 16.5% (17/103) in the ERT group (unadjusted hazard ratio, 0.24; 95% CI, 0.10 to 0.59). Long-term galsulfase ERT was associated with improvements in pulmonary functions and endurance, stabilized cardiac function and increased survival. PMID:24764221

  2. A preliminary study on the adsorptive removal of Cr(VI) using seaweed, Hydrilla verticillata

    International Nuclear Information System (INIS)

    The Cr(VI) adsorption efficiency of the seaweed, Hydrilla verticillata, was studied in batches. The adsorbent was characterized using SEM, BET surface area analyzer, Malvern particle size analyzer, EDAX and FT-IR. Cr(VI) removal efficiency of the adsorbent was studied as a function of different adsorption parameters such as contact time, stirring speed, pH, adsorbent dose, particle size, adsorbate concentration, and temperature. Langmuir, Freundlich, and Temkin adsorption isotherm equations were used in the equilibrium modeling. The adsorption process followed pseudo second-order kinetics and intra-particle diffusion was found to be the rate-controlling step. Experimental data follow Langmuir adsorption isotherm. Thermodynamic parameters such as Gibbs free energy and enthalpy of the adsorption process were evaluated to find out the feasibility of the adsorption process. The negative values of Gibb's free energy and positive enthalpy values show the feasibility and endothermic nature of the process. The significance of different adsorption parameters along with their combined effect on the adsorption process has been established through a full 24 factorial design. Among the different adsorption parameters, pH has the most influential effect on the adsorption process followed by adsorbate concentration and combined effects of all the four parameters were tested. The correlation among different adsorption parameters were studied using multi-variate analysis.

  3. Uranium (VI) interaction with pyrite (FeS{sub 2}): chemical and spectroscopic studies

    Energy Technology Data Exchange (ETDEWEB)

    Eglizaud, N.; Descostes, M. [Commissariat a l' Energie Atomique de Saclay, DEN/DPC/SECR/Laboratoire de Mesures et Modelisation de la Migration des Radionucleides, bat. 450, BP11, 91191 Gif sur Yvette cedex (France); Miserque, F.; Schlegel, M. [Commissariat a l' Energie Atomique de Saclay, DEN/DPC/SCP/Laboratoire de Reactivite des Surfaces et Interfaces, bat 191, BP11, 91191 Gif sur Yvette cedex (France); Simoni, E. [Institut de Physique Nucleaire d' Orsay, Universite Paris XI, bat 100, 91406 Orsay cedex (France)

    2005-07-01

    Full text of publication follows: Actinides released from nuclear waste repositories may be retained by natural solids, either by coprecipitation or by sorption reactions. Sorption of actinides on natural minerals has already been extensively studied but the coupling of this retention with redox reactions has been scarcely investigated. Pyrite (FeS{sub 2}) is a ubiquitous, redox-sensitive mineral that may possibly adsorb and reduce redox-sensitive species such as uranium (VI). However, the molecular mechanism of uranium (VI) possible sorption and reduction on pyrite has not been clarified yet. Natural pyrite, well characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), zeta potential measurements and mass titration, was ground to 50 {mu}m to 100 {mu}m particles, and chemically treated to remove mineralogical impurities and oxidation products. As pyrite may dissolve and oxidize when immersed alone in aqueous solutions, both the solution composition and the properties of the solid surface in presence, or in absence of uranium, were analysed. Pyrite hydrous equilibration and sorption experiments were performed in an anoxic glove box (vpm O{sub 2} < 1 ppm), at ambient temperature. After equilibration in 10{sup -2} mol.L{sup -1} NaNO{sub 3}, pyrite was reacted with uranium (VI) by the batches method. Reaction kinetics, pH (imposed by either HNO{sub 3} or NaOH), Eh, and dissolved uranium concentration (using both natural uranium and radiotracers) were analysed. Dissolved and colloidal iron and sulphur were measured to quantify pyrite dissolution. Pyrite surface was studied by XPS to clarify the oxidation degree and chemical environment of uranium, iron, sulphur and oxygen species. At elevated uranium concentrations (2.10{sup -3} mol.L{sup -1}), pH decreases (from 6.1 to 3.7) whereas no uranium uptake could be quantified from solution concentrations. At lower uranium concentrations (10{sup -7} mol.L{sup -1}) no such p

  4. A relativistic study of the photochemistry of the uranyl(VI) ion in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Real, F.; Wahlgren, U. [Alballova University Center, Stockholm University, Fysikum, 104-91 Stockholm, (Sweden); Vallet, V. [Laboratoire PhLAM, Universite des Sciences et Technologies de Lille 1 CNRS UMR8523, 59655 Villeneuve d Ascq Cedex, (France); Marian, C. [Institut fur Theoretische Chemie und Computerchemie Heinrich-Heine-Universitat Universitatsstr. 40225 Dusseldorf (Georgia); Grenthe, I. [KTH Royal Institute of Technology, Inorganic Chemistry Se-10044 Stockholm, (Sweden)

    2007-07-01

    Complete text of publication follows: The U-O bond in the uranyl(VI) ion is in general considered to be kinetically inert in thermal reactions, such as isotope exchange reactions. However, a fast isotope exchange can take place in photochemical reactions under UV irradiation as exemplified by the reaction: U{sup 17}O{sub 2}(H{sub 2}O){sub 5}{sup 2+} + H{sub 2}*0 {yields} U{sup 17}O{sub 2}(H{sub 2}O){sub 5}{sup 2+} + H{sub 2}O (1) Under daylight, no exchange takes place, or the rate of exchange is very slow. This suggests that the reaction involves the excited-states of the uranyl(VI). 1) A comparison between wave-function theory and density-functional theory: The first part of this talk will discuss benchmark calculations of the excited states of the bare uranyl(VI) ion so that we can choose the computational cost effective ab initio method for the study of the photochemistry of actinide compounds. Before exploring the mechanism of exchange it is necessary to have information on the chemistry of the excited states and their electronic structure. It seems reasonable to assume that 'yl'-isotope exchange is related to the U-O{sub yl} stretching modes and following the work of Pierloot and van Besien [1] we have therefore studied the a{sub g}- and a{sub u}-modes of the U-O{sub yl} bond using different methods such as CASPT2, TD-DFT and DFT-MRCI and different basis set and description of the heavy-element. The scalar-relativistic effects were included using either the Douglas-Kroll Hamiltonian in the case of all-electron calculations or an RECP small core from the Stuttgart Library. The {sup 3}{gamma}{sub g} state seems to be a good candidate for the photochemically 'active' state where the increase of the U-O{sub yl} localizes the wave function and gives distant 'yl' oxygen attains radical character. 2) Photochemistry of the uranyl(VI) in aqueous solution: In the case of the photochemistry of the uranyl(VI), we suggest that the first step

  5. Contribution to the study of the redox couple Np(VI)/Np(V) in the presence of uranium(VI) in solutions of nitric acid and nitrous acid; Contribution a l'etude du comportement redox du couple Np(VI)/Np(V) en presence d'uranium VI dans les solutions constituees d'acide nitrique et d'acide nitreux

    Energy Technology Data Exchange (ETDEWEB)

    Arpigny, S. [CEA Marcoule, Dept. de Radiochimie et Procedes, DRP, 30 (France)

    2001-07-01

    The redox behavior of the Np(VI)/Np(V) couple was the subject of a spectrometric study of the Np(VI) reduction reaction in nitric acid solutions (4 to 5 M) containing variable concentrations (1.5 to 3.5 x 10{sup -3} M) of nitrous acid. A low nitrous acid concentration and a high nitric acid concentration were found to favor the stabilization of Np(VI). The stoichiometric coefficients of nitrous acid and nitric acid in the Np(VI) reduction reaction were determined thermodynamically, although only the reaction order with respect to HNO{sub 2} could be calculated from a kinetic analysis. Adding nitrate ions to a HNO{sub 3}/HNO{sub 2} solution enhanced the stability of neptunium at oxidation state +VI, but also increased the reduction rate. When uranium(VI) was added to the HNO{sub 3}/HNO{sub 2} solutions, the total quantity of neptunium at oxidation state +V (either free or as a Np(V)-U(VI) complex) remained practically unchanged, as did the Np(VI) reduction rate. The electrochemical behavior of the Np(VI)/Np(V) couple was investigated in a weak acidic medium by voltammetry with an ultra-micro-electrode (UME). The oxidation wave limiting current variation was a linear function of the Np(V) concentration when a gold UME was used, but not with a platinum UME; the reduction wave limiting current variation versus the Np(V) concentration was linear with either gold or platinum UMEs. The presence of the Np(V)-U(VI) complex in the neptunium solutions was characterized by a shift in the normal apparent potential of the Np(VI)/Np(V) couple toward anodic potentials consistent with the previously determined values of the complexation constants. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Bayat, Belgin

    2002-12-02

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

  7. Cr(VI) and conductivity as Indicators of surface water pollution from ferrochrome production in South Africa: four case studies

    OpenAIRE

    Loock-Hattingh, M.M.; J. P. Beukes; van Zyl, P. G.; L. R. Tiedt

    2015-01-01

    South Africa is one of the largest ferrochromium (FeCr) producers. Most FeCr is exported to developed countries. Therefore the impact of this industry is of national and international importance. Cr(VI) and conductivity of surface water in four case study areas, near five FeCr smelters were monitored for approximately 1 year. Results indicated that FeCr production in three case study areas had a negative influence on the Cr(VI) concentration and/or the conductivity of surface w...

  8. Structural study and properties of the alkali metal, nitrosyl, and ammonium hepta- and octafluorouranates(VI)

    International Nuclear Information System (INIS)

    The thermal decomposition of the heptafluorouranates(VI) of the alkali metals is shown to take place in two steps. The first step gives the octafluorouranates(VI) and UF6, and the decomposition rate is noticeable at temperatures above 100, 130, 150, and 2100C for the Na, K, Rb, and Cs salts, respectively. The second step for Na2UF8 yields pure NaF and UF6 above 3000C, whereas the decomposition temperatures for the K, Rb, and Cs salts are above 300, 350, and 4000C, respectively. Depending on the decomposition conditions, F2 and M2UF7(M = K, Rb, Cs) or F2, UF6, and M3UF8 are formed. The heptafluorouranates(VI) of all the cations studied, except for ammonium, were shown to exhibit dimorphism. The parameters of their cubic form were obtained and are as follows: KUF7; a = 5.22 A; RbUF7; a = 5.385 A; CsUF7; a = 5.517 A; NOUF7; a = 5.334 A; NH4UF7; a = 5.393 A; NaUF7(fccub), a = 8.511 A, Z = 4. The x-ray pattern of the low-symmetry form of CsUF7 just below the solid transition temperature (15 +- 10C) was indexed with a tetragonal cell where a = 5.50 A and c = 5.37 A. The x-ray diagrams of the low symmetry form of the other MUF7 salts were not indexed, whereas those of the octafluorouranates were indexed with orthorhombic cells. The vibrational spectra of the hepta- and octafluorouranates were found to be very dependent on the temperature, and for the same temperature on the cation size. Some trends observed in this study, like the thermal decomposition temperatures or the relative symmetries, are thought to arise from the differences in the cation--anion interaction. This interaction is stronger with smaller cations, which results in more distorted anions, less ionic U--F bonds, and paradoxically less stable complexes

  9. Long-term effect of nitrate on Cr(VI) removal by Fe(0): column studies.

    Science.gov (United States)

    Wei, Minghai; Yuan, Fang; Huang, Guoxin; Chen, Honghan; Liu, Fei

    2016-05-01

    Lab-scale parallel continuous-flow column experiments were performed to assess the long-term effect of nitrate (NO3 (-)) on hexavalent chromium (Cr(VI)) removal by scrap iron (Fe(0)). The first column (L1) was fed with the Cr(VI) solution and the second column (L2) was loaded with the Cr(VI) + NO3 (-) solution. Raman spectroscopy and scanning electron microscopy energy-dispersive X-ray analyses (SEM-EDS) were conducted to investigate the changes of the iron oxides on Fe(0). The results showed that the process of Cr(VI) removal by Fe(0) was divided into three different stages in the presence of NO3 (-): inhibition period (film on the Fe(0) surface as well as an electron mediator that facilitated electron transport from Fe(0) to adsorbed Cr(VI). PMID:26797949

  10. Study on the electrolytic reduction of Uranium-VI to Uranium-IV in a nitrate system

    International Nuclear Information System (INIS)

    The determination of the best conditions to prepare hydrazine stabilized uranium (IV) nitrate solutions for utilization in Purex flowsheets is dealt with. Electrolytic reduction of U(VI) has been selected as the basic method, using an open electrolytic cell with titanum and platinum electrodes. The hydrazine concentration, the current density, acidity, U(VI) concentration and reduction time were the parameters studied and U(IV)/U(VI) ratio was used to evaluate the degree of reduction. From the results it could be concluded that the technique is reliable. The U(IV) solutions remains constant for at least two weeks and can be used in the chemical processing of irradiated uranium fuels. (Author)

  11. Equilibrium and kinetics study of uranium(VI) from aqueous solution by Citrus limetta peels

    International Nuclear Information System (INIS)

    The potential of the biowaste Citrus limetta peels (CLP) was assessed for adsorption of uranium(VI) from uranyl nitrate solution. Maximum adsorption capacity of 75.33 mg g-1 was achieved at pH 4, showing drastic falls thereafter. This was attributed to the presence of UO22+, UO2OH+, (UO2)3(OH)5+ and (UO2)2(OH)22+ ions. The peels were characterized for elucidating the role of functional groups and morphology on the sorption capacity. The isotherm studies revealed that Langmuir, Freundlich as well as Sips models give the best fit for the experimental data observing pseudo second order kinetics. The equilibrium was achieved in 90 min. The adsorption shows complex mechanism, took place by both physical and ion-exchange mechanism. (author)

  12. Uranium (VI) sorption on Geothite and Magnetite: Experimental study and surface complexation modelling

    International Nuclear Information System (INIS)

    This report deal with the study of the U(VI) sorption on two important iron oxides: magnetite and goethite. Magnetite in the most important and member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Apart from magnetite, goethite, hematite and siderite have also been reported as possible corrosion products of steel canisters under repository conditions. In particular, goethite (α-FeOOH) is a ferric hydroxide very common in nature and, since it is one of the thermodynamically most stable at room temperature, it is expected to be the main end member of many iron oxide transformations in a wide range of environmental conditions. (Author)

  13. Reduction of Pu(VI) on Fe surfaces: soft x-ray absorption and resonant inelastic scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Butorin, S.M.; Kvashnina, K.O.; Modin, A.; Nordgren, J. (Dept. of Physics and Materials Science, Uppsala Univ., Uppsala (Sweden)); Guo, J.H. (Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States)); Shuh, D.K. (Chemical Science Div., Lawrence Berkeley National Laboratory, Berkeley, CA (United States)); Werme, L. (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2009-03-15

    Based on analysis of spectral shapes, their dependence on the energy of incident photons and comparison with model calculations and experimental data from the reference sample we can conclude that plutonium from the Pu(VI) solution sorbed on Fe surfaces is likely to be reduced and Pu species sorbed on the Fe foils are mainly in the form of Pu (IV). Current results correlate with what was observed for for Np (V) and U (VI) in our previous studies. Furthermore, combined analysis of present data with model atomic multiplet calculations of RIXS and XAS spectra suggests that significant presence of Pu(III) on the Fe foils is unlikely

  14. Mucopolysaccharidosis VI

    OpenAIRE

    Harmatz Paul; Nicely Helen; Valayannopoulos Vassili; Turbeville Sean

    2010-01-01

    Abstract Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease with progressive multisystem involvement, associated with a deficiency of arylsulfatase B leading to the accumulation of dermatan sulfate. Birth prevalence is between 1 in 43,261 and 1 in 1,505,160 live births. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The characteristic skeletal dysplasia includes short stature, dysostosis multiplex and degenerative joint disease. Rapidly ...

  15. Cr(VI) and Conductivity as Indicators of Surface Water Pollution from Ferrochrome Production in South Africa: Four Case Studies

    Science.gov (United States)

    Loock-Hattingh, M. M.; Beukes, J. P.; van Zyl, P. G.; Tiedt, L. R.

    2015-10-01

    South Africa is one of the largest ferrochromium (FeCr) producers. Most FeCr is exported to developed countries. Therefore the impact of this industry is of national and international importance. Cr(VI) and conductivity of surface water in four case study areas, near five FeCr smelters were monitored for approximately 1 year. Results indicated that FeCr production in three case study areas had a negative influence on the Cr(VI) concentration and/or the conductivity of surface waters. In the remaining case study areas, drinking water, originating from groundwater, was severely polluted with Cr(VI). The main factors causing pollution were surface run-off and/or seepage, while atmospheric deposition did not seem to contribute significantly. The extinction of diatoms during a severe Cr(VI) surface water pollution event (concentrations up to 216 µg/L) in one of the case study areas was also observed, which clearly indicates the ecological impact of such surface water pollution events.

  16. Oxidative degradation of triazine- and sulfonylurea-based herbicides using Fe(VI): The case study of atrazine and iodosulfuron with kinetics and degradation products

    Science.gov (United States)

    The occurrence of common herbicides (Atrazine, ATZ and Iodosufuron, IDS), in waters presents potential risk to human and ecological health. The oxidative degradation of ATZ and IDS by ferrate(VI) (FeVIO42-, Fe(VI)) is studied at different pH levels where kinetically observed se...

  17. TRLFS Studies on Indirect Determination of U(IV) in Biological Samples Containing Mixed U(IV/VI) Species

    International Nuclear Information System (INIS)

    The microbial-mediated metal reduction process has been viewed as a long-term remedial approach for in situ immobilization of radionuclide under anaerobic conditions in aquifers and saturated soils. Such approach depends on the fact that many radionuclides of concern including uranium are redox active and less soluble in their reduced form. Thus, the interaction of uranium with microorganisms has been the subject of considerable effort over the past decade. Uranium reduction occurs as a result of dynamic metabolic activity of microbials and biochemical reactions. The typical incubation system of uranium reducing bacteria such as sulfate-reducing Desulfovibrionales contains various geochemical components including electron donors (e.g., acetate, lactate, ethanol, thiol or glucose), anionic electron acceptors (sulfate and nitrate) and metal ions (Fe(II/III), Mn, Ni, etc.). The anoxic growth of bacteria results in uranium reduction by forming U(IV) aggregates or colloids. In most studies the isolation of U(IV) from U(VI) largely depends on filtration of precipitates and centrifugal separation of colloidal particles. Such U(IV) species were subsequently analyzed via ICP-MS for elemental uranium or kinetic phosphorescence analysis (KPA) in form of U(VI) although the relative proportion of U(IV) and U(VI) in the frozen samples can be estimated using X-ray absorption spectroscopy. However, recent studies report the formation of extracellular uranite nanoparticles, which may suspend in the resultant filtrate and supernatant solutions. Thus, the development of an analytical technique capable of estimating the dissolved or suspended U(IV) species is further required for better understanding of the bacterial-mediated uranium sequestration and dissolution process. In this study we explore the possibility of using TRLFS (time-resolved laser-induced fluorescence spectroscopy) to indirectly measure the concentration of U(IV) as well as that of U(VI) in bacterial culture media

  18. Study of molybdenum (VI) complexation and precipitation by zirconium (IV) in strongly acid medium. Application to nuclear spent fuel dissolution

    International Nuclear Information System (INIS)

    These last years the formation of solid deposits has been observed in the dissolution workshops of the La Hague plant. A sample of the solid was withdrawn for expertise: molybdenum and zirconium are the two major components of the solid, identified as zirconium molybdate. This thesis consisted in the approach of the mechanisms in solution liable to induce precipitate formation. After a bibliographical overview on the chemistry of Mo(VI) in highly acidic solution, this system was studied by absorption spectrophotometry in perchloric medium. The implication of two major forms of Mo(VI) in a dimerization equilibrium was confirmed by this way and by 95Mo NMR. The principal parameters governing this equilibrium were identified. It is thus shown that the molybdenum dimerization reaction is exothermic. Disturbance of the Mo(VI) system in highly acidic solution by Zr(IV) was also studied. In a restricted experimental field, for which 'conventional' exploitation methodologies had to be adapted to the system, a main complex of stoichiometry 1:1 between Mo(VI) and Zr(IV) was found. The precipitation study of Mo(VI) by Zr(IV) under conditions close to those of the dissolution medium of nuclear spent fuel was undertaken. The main parameters which control precipitation kinetics were identified. The results obtained reveal that precipitation is controlled by a single macroscopic process and therefore can be described by a single equation. The solid obtained is composed of only one phase presenting a Mo:Zr non-stoichiometry when compared to the theoretical formula ZrMo2O7(OH)2,2H2O. At last, on the basis of the research results, a descriptive mechanism of the system is proposed in which intervenes a 1:1 intermediate complex, much more soluble than a probable 2:1 precipitation precursor. (author)

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

    International Nuclear Information System (INIS)

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

  20. Error analysis of equilibrium studies for the almond shell activated carbon adsorption of Cr(VI) from aqueous solutions

    International Nuclear Information System (INIS)

    In this study, the preparation of activated carbon from almond shell with H2SO4 activation and its ability to remove toxic hexavalent chromium from aqueous solutions are reported. The influences of several operating parameters such as pH, particle size and temperature on the adsorption capacity were investigated. Adsorption of Cr(VI) is found to be highly pH, particle size and temperature dependent. Four adsorption isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich were used to analyze the equilibrium data. The Langmuir isotherm provided the best correlation for Cr(VI) onto the almond shell activated carbon (ASC). Adsorption capacity was calculated from the Langmuir isotherm as 190.3 mg/g at 323 K. Thermodynamic parameters were evaluated and the adsorption was endothermic showing monolayer adsorption of Cr(VI). Five error functions were used to treat the equilibrium data using non-linear optimization techniques for evaluating the fit of the isotherm equations. The highest correlation for the isotherm equations in this system was obtained for the Freundlich isotherm. ASC is found to be inexpensive and effective adsorbent for removal of Cr(VI) from aqueous solutions

  1. First principles study of thermoelectric properties of IV-VI semiconductor superlattices

    Science.gov (United States)

    Borges, P. D.; Petersen, J. E.; Scolfaro, L.; Leite Alves, H. W.; Myers, T. H.

    2015-03-01

    Thermoelectric materials (TE) have attracted great attention due to their ability to convert heat directly into electricity. However, to be commercially competitive with existing technology, TE devices must have a higher value of figure of merit ZT. It has been proposed to improve ZT by using multilayered systems or superlattices (SLs) resulting in 1D or 2D carrier confinement, reduction of the phonon thermal conductivity, and introduction of anisotropy effects. Here we study the TE properties of IV-VI derived semiconductor SLs. By using the Boltzmann transport theory, within the constant scattering time approximation, in conjunction with first principles calculations, we study the Seebeck coefficient (S) and ZT of PbTe/SnTe SLs. The calculated S shows good agreement with recent experimental data. An anisotropic behavior is observed for low carrier concentrations less than 10⌃18cm⌃-3. For T = 900 K, a large value of ZTparallel to the SL axis equal to 2.6 is predicted for n =1.2x10⌃18cm⌃-3, whereas ZT perpendicular to the SL axis peaks at the value 1.4 for n =5.5x10⌃17 cm⌃-3. Both electrical conductivity enhancement and reduction of thermal conductivity are analyzed, and a comparison with other multilayered systems such as planar-doped PbTe is done. Support from CNPq and Texas State University.

  2. Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

    Indian Academy of Sciences (India)

    Zahra Asadi; Mozaffar Asadi; Azade Zeinali; Mohammad Ranjkeshshorkaei; Karla Fejfarova; Vaclav Eigner; Michal Dusek; Aliakbar Dehnokhalaji

    2014-11-01

    Uranyl(VI) complexes with unsymmetrical N2O2 Schiff base ligands were synthesized and characterized. Their characterization was performed using UV-Vis, 1H NMR, cyclic voltammetry, single-crystal X-ray crystallography, IR, TG and C.H.N. techniques. X-ray crystallography of the complexes show that beside coordination of the tetradentate Schiff base, one DMF molecule is also coordinated. In order to investigate the effect of the substitutional groups of the Schiff base on the oxidation and reduction potentials, we used the cyclic voltammetry method. Electrochemistry of these complexes showed that the presence of electron releasing groups accelerates oxidation of the complexes. The kinetics of thermal decomposition was studied using thermal gravimetric method (TG) and Coats-Redfern equation. According to Coats-Redfern plots, the kinetics of thermal decomposition of the studied complexes is first-order in all stages. Also the kinetics and mechanism of the exchange reaction of the coordinated solvent with tributylphosphine was carried out in solution, using spectrophotometric method. As a result, the second order rate constants at four temperatures and the activation parameters were calculated showing an associative mechanism for all corresponding complexes. It was concluded that the steric and the electronic properties of the complexes influence the reaction rate significantly.

  3. Complexation of Gluconate with Uranium(VI) in Acidic Solutions: Thermodynamic Study with Structural Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhicheng; Helms, G.; Clark, S. B.; Tian, Guoxin; Zanonato, PierLuigi; Rao, Linfeng

    2009-01-05

    Within the pC{sub H} range of 2.5 to 4.2, gluconate forms three uranyl complexes UO{sub 2}(GH{sub 4}){sup +}, UO{sub 2}(GH{sub 3})(aq), and UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -}, through the following reactions: (1) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 4}){sup +}, (2) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(aq) + H{sup +}, and (3) UO{sub 2}{sup 2+} + 2GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} + H{sup +}. Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log {Beta}{sub 1} = 2.2 {+-} 0.3 and {Delta}H{sub 1} = 7.5 {+-} 1.3 kJ mol{sup -1} for reaction (1), log {Beta}{sub 2} = -(0.38 {+-} 0.05) and {Delta}H{sub 2} = 15.4 {+-} 0.3 kJ mol{sup -1} for reaction (2), and log {Beta}{sub 3} = 1.3 {+-} 0.2 and {Delta}H{sub 3} = 14.6 {+-} 0.3 kJ mol{sup -1} for reaction (3), at I = 1.0 M NaClO{sub 4} and t = 25 C. The UO{sub 2}(GH{sub 4}){sup +} complex forms through the bidentate carboxylate binding to U(VI). In the UO{sub 2}(GH{sub 3})(aq) complex, hydroxyl-deprotonated gluconate (GH{sub 3}{sup 2-}) coordinates to U(VI) through the five-membered ring chelation. For the UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} complex, multiple coordination modes are suggested. These results are discussed in the context of trivalent and pentavalent actinide complexation by gluconate.

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

    Science.gov (United States)

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

    2013-04-01

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

  5. Electrochemical studies on bis(β-diketonato)(dimethyl sulfoxide)dioxouranium(VI) in dimethyl sulfoxide

    International Nuclear Information System (INIS)

    Electrochemical studies on UVIO2(β-diketonato)2d mso [β-diketonate=dibenzoylmethanate (dbm), trifluoroacetylacetonate (tfacac), hexafluoroacetylacetonate (hfacac), dmso=dimethyl sulfoxide] complexes in DMSO containing tetrabutylammonium perchlorate (supporting electrolyte) have been carried out using cyclic voltammetry (CV) and normal pulse voltammetry (NPV). As a result, it was found that the UVIO2(tfacac or hfacac)2dmso complexes are reduced to U(V) species reversibly and that the UVIO2(dbm)2dmso complex is quasi-reversibly reduced to U(V) species. The formal redox potentials (E /V, vs. Ag/AgCl and vs. ferrocene/ferricinium in parentheses) for the U(VI)/U(V) couple are -0.44 (-0.97) for UVIO2(hfacac)2dmso, -0.52 (-1.05) for UVIO2(tfacac)2dmso, and -0.83 (-1.36) for UVIO2(dbm)2dmso. Furthermore, the E values were found to correlate with the pKa values of β-diketones, i.e. the E values decrease with an increase in the pKa value. (orig.)

  6. Preparation of N-1 -naphthyl benzo- and N-phenyl benzo hydroxamic acids and study of their extractability towards Fe (III), Cr (VI) and U (VI)

    International Nuclear Information System (INIS)

    Two aryl hydroxamic acids were prepared; The N-phenyl benzo hydroxamic acid and the N-1- naphthyl benzohydroxamic acid the first one was prepared by the partial reduction of nitrobenzene to the β-phenyl hydroxylamine and coupling the latter with benzyl chloride. The reduction was carried out using ammonium chloride and zinc dust; this pair failed after so many attempts to give the N-1- naphthyl hydroxylamine. So the latter was prepared by using a somewhat milder reducing agent; hydrogen sulphide and ammonia gas in absolute alcohol. The two acids were obtained using the modified procedure of Tandon coupling the hydroxylamine with benzoyl chloride. The two acids were characterized by their melting points, elemental analysis, their I.R functional group frequencies and by their characteristic colour tests with vanadium (VI) and Iron (III). The acids were used for the extraction and spectrophotometric determination for iron (III), Chromium (VI), and Uranium (VI) from different molar solution, PH and from synthetic sea water. The maximum recovery of iron (III) occurred at PH 4 and PH 5 giving 92.25 and 91.25% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 100% at PH 5 with other acid. The maximum recovery of Chromium (VI) occurred at 3MH2SO4 of 97.50% when using N-1-naphthyl benzohydroxamic acid and a maximum of 94.25% at the same molar concentration with N-phenyl benzo hydroxamic acid. The maximum recovery for Uranium (VI) was occurred at PH 7 giving 100% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 85% at PH 7 and PH* with the other acid. The two reagents give sharp colour with both iron (III) and chromium (VI), so trials were carried out to compare the curves obtained with that of the original reagent i.e. Thiocynate and diphenylcarbazide, which give a smaller slope.(Author)

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

    Science.gov (United States)

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

    2009-12-30

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

  8. TRLFS Studies on luminescence enhancement of U(VI) using oxidants for quencher species in samples

    International Nuclear Information System (INIS)

    The pulse laser-based method detects photo luminescent emission of U(VI) so that it is highly sensitive for non-isotopic al determination of total uranium concentration. Thus, this method has been used for detection of trace quantity of uranium in the environmental, geological, and bioassay samples. One of widely-used pulse laser-based methods is kinetic phosphorescence analysis (KPA), of which instrument is commercially available. The intensity and lifetime of characteristic phosphorescence at 515-520 nm of hexavalent uranium are measured with an excitation wavelength of 425 nm. Particularly in KPA the use of phosphate-based luminescence enhancing agent (LEA) leading to the formation of uranyl-phosphate complexes extends the luminescence (LM) lifetime of uranium (> ∼ 200 μs) and subsequently the overall luminescence intensity. In KPA, however, an extensive sample pretreatment procedure is required to reduce the luminescence quenching effects of ions and molecules present in samples. During such procedures the uranium species in low oxidation states are also oxidized to hexavalent uranium so that the measurement of the total uranium concentration can be achieved. In general, a series of high temperature dry and wet ashing procedures is implemented prior to the addition of LEA to decompose the interfering substances. The aim of this study is to examine the characteristics of the interfering species exhibiting significant quenching effects and to develop a way of minimizing the time required for the sample pretreatment step particularly for certain oxidizable quencher species. In fact, in a previous study we reported that significant LM quenching effects are observed from those possessing chemical reduction capability such as Fe(II) and cysteine. Under such sample conditions it is shown that the conventional KPA is not applicable due to the short lifetime (< ∼ 1 μs), therefore a time-resolved laser-induced fluorescence spectroscopy (TRLFS) capable of monitoring

  9. Studies on U(VI)-salicylate Charge Transfer Complex Formation by Using Time-resolved Laser Fluorescence Spectroscopy

    International Nuclear Information System (INIS)

    Organic ligands, such as humic and fulvic acids, play important roles in dissolution and migration of actinide radionuclide species. They can form stable actinide complexes in the presence of inorganic ions like hydroxides and carbonates. Therefore, the structural mimics of such ligands containing carboxylic and phenolic functional groups have been targets of studies to understand their chemical behaviors migrating actinides under geological groundwater conditions. Among many carboxylic ligands salycylate (SA) is useful to examine the role of phenolic groups on humic substances. Salicylate ion can form ligand-to-metal chargetransfer (LMCT) complexes with various metal ions. It has been shown that the fluorescence of SA is suppressed in the presence of Cu(II) or Eu(III) at pH 4 by forming ground state complexes. While uranyl ions also can form complex with SA, the dominant species at pH 4-7 region is known to be an 1:1 complex. However, the chemical structures reported on this 1:1 species are different among [UO2SA]0, [UO2(OH)SAH]0 and [UO2(OH)SA]-. For α- hydroxycarboxylates cyclic chelate structures were suggested where both carboxylate and phenolate groups simultaneously bind to uranyl ion. In the present study we investigate aqueous U(VI)- SA complex systems by using UV-Vis absorbance measurement and highly sensitive time-resolved laserinduced fluorescence spectroscopic (TRLFS) technique. The U(VI)-SA complex shows two characteristic charge-transfer (CT) bands at higher pH (> 4), which we found useful to examine the complexation equilibrium. Further, the TRLFS method is used to study the fluorescence (FL) quenching of U(VI) species, particularly for hydroxouranyl species at pH 4.5 of which FL is significantly suppressed as SA concentration elevates in aqueous solution. Fluorescence quenching mechanism in conjunction with the formation of U(VI)-SA CT complex is discussed

  10. Synthesis, structure and DFT study of cymantrenyl Fischer carbene complexes of group VI and VII transition metals

    Science.gov (United States)

    Fraser, Roan; van Rooyen, Petrus H.; Landman, Marilé

    2016-02-01

    Bi- and trimetallic carbene complexes of group VI and VII transition metals (Cr, Mo, W, Mn and Re), with CpMn(CO)3 as the initial synthon, have been synthesised according to the classical Fischer methodology. Crystal structures of the novel carbene complexes with general formula [Mx(CO)y-1{C(OEt)(MnCp(CO)3)}], where x = 1 then y = 3 or 6; x = 2 then y = 10, of the complexes are reported. A density functional theory (DFT) study was undertaken to determine natural bonding orbitals (NBOs) and conformational as well as isomeric aspects of the polymetallic complexes. Application of the second-order perturbation theory (SOPT) of the natural bond orbital (NBO) method revealed stabilizing interactions between the methylene C-H bonds and the carbonyl ligands of the carbene metal moiety. These stabilization interactions show a linear decrease for the group VI metal carbene complexes down the group.

  11. Developing Spectroscopic Ellipsometry to Study II-Vi and Diluted Magnetic Semiconductors

    Science.gov (United States)

    Kim, Young-Dong

    We have constructed a rotating analyzer spectroscopic ellipsometer (RAE) to study effects of magnetic and nonmagnetic doping on the E_1 and E _1 + Delta_1 band gap energies in ZnSe-based II-VI semiconductors. To remove the natural surface oxide overlayer which distorts the intrinsic dielectric response of the sample, a chemical etching technique using dilute NH_4OH solution was developed. The successful removal of the oxide overlayer on ZnSe was confirmed via the XPS technique. For diluted magnetic semiconductors (DMS), we found that the E_1 and E _1 + Delta_1 band gap energies increase with x for Zn_{1-x}Fe _{x}Se and Zn_ {1-x}Co_{x}Se, and decrease with x for Zn_{1-x} Mn_{x}Se. An sp -d direct exchange interaction model which explained the Gamma-point band gap energy of Zn _{1-x}Mn_ {x}Se was applied. The calculated band gap energies at the L-point are only consistent with Zn _{1-x}Mn_ {x}Se data. We showed that an sp-d hybridization model, which includes the location of the energy levels of the magnetic impurity d-levels can account for the concentration dependence of E_1 and E _1 + Delta_1 band gap energies of all three materials. For Zn_{x}Cd _{1-x}Se systems, all spectral features of CdSe were identified as E_0, E_0 + Delta_0, E_1, E_1 + Delta_1, E_2, and E _sp{0}{'} threshold energies from band structure calculations using a nonlocal empirical pseudopotential method. Many-body effect has to be included in the calculation of the dielectric function of CdSe to obtain good agreement with the measured spectrum. Concentration dependent spin-orbit splitting band gap Delta _1(x) is well explained by the statistical fluctuation of the alloy composition.

  12. Studies on biosorption of Cr(VI) on a green resin: dry cow dung powder and tracer technique

    International Nuclear Information System (INIS)

    The present investigation entails the application of dry cow dung powder (DCP) as an indigenous, inexpensive and eco-friendly material for the removal of Cr(VI) from aqueous medium. Batch biosorption experiments were conducted employing 51Cr(VI) as a tracer and the effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration, agitation speed, concentration of metal ions and interfering effect of different salts etc. were studied. The kinetic studies were carried out employing various models but the best fitting was given by Lagergren Pseudo-second order model with high correlation coefficient R2 value of 0.997 and adsorption capacity of 10.20 mg/g. The thermodynamic parameters for biosorption were evaluated as ΔG = -2.837 kJ/mol, ΔH = -4.757 kJ/mol and ΔS = 16.64 J/mol K, which indicated spontaneous and exothermic process with high affinity of DCP for Cr(VI). Many naturally available materials are used for the biosorption of heavy metal pollutants, where most of them are physically or chemically modified. In this research work, DCP has been utilized without any pre or post chemical treatment. Thus it manifests the principle of green chemistry and proves to be an eco-friendly resin. (orig.)

  13. Synthesis, structures, electrochemical studies and antioxidant activities of cis-dioxomolybdenum(VI) complexes of the new bisthiocarbohydrazones

    Science.gov (United States)

    Kaya, Yeliz; Erçağ, Ayşe; Koca, Atıf

    2015-12-01

    Potentially pentadentate ONSNO donor new Schiff bases were prepared by the condensation of thiocarbodihydrazide with 3,5-dibromosalicylaldehyde (H3L1), 3-bromo-5-chlorosalicy-laldehyde (H3L2) and 3,5-dichlorosalicylaldehyde (H3L3). The reactions between bis (acetylacetonato) dioxomolybdenum(VI) and Schiff bases in the presence of donor solvents yielded neutral cis-dioxomolybdenum(VI) complexes with the general formula [MoO2HL(D)] (HL = tridentate ONS donor Schiff base ligand; HL1, HL2, HL3) and D = methanol, ethanol, dimethyl sulfoxide, dimethylformamide, pyridine). All the compounds were characterized by elemental analysis, UV, IR, 1H NMR spectroscopies. The thermal properties of the complexes were also investigated by thermogravimetry technique and the thermal behavior depending on the second ligand molecule was discussed. The synthesized compounds were screened for their antioxidant capacity by using the cupric reducing antioxidant capacity (CUPRAC) method. In addition, electrochemical behaviors of the complexes were studied using cyclic voltammetry and square wave voltammetry. Half wave potentials (E1/2) are significantly influenced with the central metal ions, but slightly influenced with the nature of substituents on thiocarbohydrazone ligands. In situ spectroelectrochemical studies were employed to determine the spectra of electrogenerated species of the complexes and to assign the redox processes. The fluorescence properties of the bisthiocarbohydrazone ligands and their dioxomolybdenum(VI) complexes in DMSO solutions were investigated.

  14. Studies on biosorption of Cr(VI) on a green resin: dry cow dung powder and tracer technique

    Energy Technology Data Exchange (ETDEWEB)

    Barot, N.S.; Bagla, H.K. [Kishinchand Chellaram College, Mumbai (India). Nuclear and Radiochemistry Dept.

    2012-07-01

    The present investigation entails the application of dry cow dung powder (DCP) as an indigenous, inexpensive and eco-friendly material for the removal of Cr(VI) from aqueous medium. Batch biosorption experiments were conducted employing {sup 51}Cr(VI) as a tracer and the effect of various process parameters such as optimum pH, temperature, amount of resin, time of equilibration, agitation speed, concentration of metal ions and interfering effect of different salts etc. were studied. The kinetic studies were carried out employing various models but the best fitting was given by Lagergren Pseudo-second order model with high correlation coefficient R{sup 2} value of 0.997 and adsorption capacity of 10.20 mg/g. The thermodynamic parameters for biosorption were evaluated as {Delta}G = -2.837 kJ/mol, {Delta}H = -4.757 kJ/mol and {Delta}S = 16.64 J/mol K, which indicated spontaneous and exothermic process with high affinity of DCP for Cr(VI). Many naturally available materials are used for the biosorption of heavy metal pollutants, where most of them are physically or chemically modified. In this research work, DCP has been utilized without any pre or post chemical treatment. Thus it manifests the principle of green chemistry and proves to be an eco-friendly resin. (orig.)

  15. Study of uranium(VI) speciation in phosphoric acid solutions and of its recovery by solvent extraction

    International Nuclear Information System (INIS)

    Because small amounts of uranium are present in phosphate rocks, wet phosphoric acids may contain up to 300 ppm of uranium(VI). Therefore, such acids are a cost-effective unconventional source of this metal. Its recovery is a challenge for metallurgical firms which must develop reliable and selective solvent extraction processes. Such processes need to know the chemical equilibria involved in the extraction process, the speciation of uranium and its thermodynamics in solution. These two last points have been investigated in this work. Firstly, the most probable species of uranium(VI) in phosphoric acid solutions have been selected thanks to a detailed review of the literature. Then, a thermodynamic model founded on an equation of state for electrolytes has been built according these hypotheses. It has been validated with speciation data coming from original ATR-IR spectroscopy measurements. Finally, the composition of the aqueous phosphoric acid solutions and the activity coefficients obtained have been combined with a chemical model of uranium(VI) extraction into an organic phase containing a synergistic mixture of bis(2-ethylhexyl)phosphoric acid (D2EHPA) and tri-n-octylphosphine oxide (TOPO) in order to represent the variation of the distribution coefficient of uranium(VI) with H3PO4 concentration. This model had been previously developed at Chimie ParisTech at a given concentration of H3PO4 (i.e., 5,3 mol/L), but in the present study we have tested its validity in an extended range of phosphoric acid concentrations (i.e., 1-7 mol/L) and improved it. (author)

  16. Field and Numerical Modeling Study of Reductive Bioimmobilization of Cr (VI) in Groundwater at Hanford 100-H Site

    Science.gov (United States)

    Hazen, T. C.; Sonnenthal, E. L.; Mukhopadhyay, S.; Steefel, C. I.; Long, P. E.; Faybishenko, B.

    2009-12-01

    The 2004-2008 field experiment at the Hanford 100-H Site showed that a single injection of the hydrogen release compound (HRC)—a mixture of slow release glycerol polylactate, fast disassociating lactic acid, and glycerol into groundwater— stimulated an increase in biomass and a depletion of terminal electron acceptors, resulting in a significant decrease in soluble Cr (VI). The Cr (VI) concentration remained below the background concentration in the downgradient pumping/monitoring well, and below the detection limit in the injection well, for more than 3 years after the initial HRC injection in 2004. Reaction-transport modeling of the field experiment was performed to elucidate reaction pathways and rates of biogeochemical processes governing Cr (VI) bioimmobilization. Field observation data were used to develop a 3-D hydraulic and reaction-transport-isotopic model, simulated using the TOUGHREACT code. This model was used to assess the degradation kinetics of the HRC, the effects of lactate and acetate-induced bioreduction of Cr and Fe, and the effects on Cr and Sr isotopic compositions in the fluids and mineral phases (calcite dissolution in the acidic plume and precipitation at the fringes). The 2008 experiment involved reinjection of HRC into the same zones as the earlier injection and likely resulted in dissolution of previously precipitated Cr (Fe) hydroxides and additional calcite dissolution in sediments outside of the wellbore. Detailed results of the integrated field and modeling study will be presented.

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

    International Nuclear Information System (INIS)

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

  18. Spectroscopic Study on the Ternary Complex Formation of U(VI) with Salicylic Acid

    International Nuclear Information System (INIS)

    From the nuclear chemical point of view, ternary complex formation of actinide ions with ligands has attracted attention for understanding radionuclides' migration in the environment. There are various ligands in natural aquatic systems which can form stable ternary actinide complexes. Humic substance in a near-neutral groundwater is one of them and carboxylic groups in a humic substance are considered as the most likely functional group which interacts with actinides. In this work, the formation of the ternary complex of U(VI) with salicylic acid (SAH2) was investigated by two different laser-based spectroscopic methods, i.e., laser-induced breakdown detection (LIBD) and time-resolved laser fluorescence spectroscopy (TRLFS). The notable features are as follows: (i) the breakdown probability increases slightly, (ii) the absorbance of U(VI) increases, whereas the fluorescence intensity decreases with increasing salicylic acid concentration. The increase of the breakdown probability indicates that insoluble species are formed due to the complexation of U(VI) with SAH2. The decrease of the fluorescence intensity is due to the quenching effect of the SAH2 in the complexes. With regards to the instrumentation, the characteristics of a newly developed LIBD system adopting a probe beam deflection method are presented. We report also on the improved speciation sensitivity (∼10-9M for UO22+) of the TRLFS system

  19. Adsorption thermodynamic and desorption studies of U(VI) on modified silica gel (SiAPMS-HL)

    International Nuclear Information System (INIS)

    In this study, the adsorption process was examined by various isotherm models Langmuir, Freundlich and Dubinin-Radushkevich and equilibrium data were successfully described by Langmuir model. Adsorption thermodynamics of uranium (VI) on modified silica gel (SiAPMS-HL) has been studied within a temperature range from 293 to 333 K and the thermodynamic parameters, such as equilibrium constant (KD), standard free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°), have been obtained. The desorption studies were conducted in batch system to investigate the kind, concentration and volume of the eluent. (author)

  20. Combined effect of radon exposure and smoking on lung cancer risk - result of a case-control study among Czech miners

    International Nuclear Information System (INIS)

    Because of the predominant role of cigarette smoking as a cause of lung cancer, an understanding of the joint effect of smoking and radon exposure is needed for the assessment of the risk from radon. The aim of the present work is to verify differences in smoking specific risk coefficients observed earlier (BEIR VI). The present study includes two cohorts of uranium miners in west and central Bohemia and one cohort of burnt clay miners exposed to radon. In the nested study, for each case of lung cancer (observed in 1954-2007) with smoking data up to three controls were selected from all cohort members matched by year of birth, age, and the cohort. Data on smoking in the study were collected from subjects in person, from medical records, and from relatives. The statistical assessment of the study was based on conditional logistic regression with linear dependence of estimated relative risk on radon exposure

  1. Mucopolysaccharidosis VI

    Directory of Open Access Journals (Sweden)

    Harmatz Paul

    2010-04-01

    Full Text Available Abstract Mucopolysaccharidosis VI (MPS VI is a lysosomal storage disease with progressive multisystem involvement, associated with a deficiency of arylsulfatase B leading to the accumulation of dermatan sulfate. Birth prevalence is between 1 in 43,261 and 1 in 1,505,160 live births. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The characteristic skeletal dysplasia includes short stature, dysostosis multiplex and degenerative joint disease. Rapidly progressing forms may have onset from birth, elevated urinary glycosaminoglycans (generally >100 μg/mg creatinine, severe dysostosis multiplex, short stature, and death before the 2nd or 3rd decades. A more slowly progressing form has been described as having later onset, mildly elevated glycosaminoglycans (generally ARSB gene, located in chromosome 5 (5q13-5q14. Over 130 ARSB mutations have been reported, causing absent or reduced arylsulfatase B (N-acetylgalactosamine 4-sulfatase activity and interrupted dermatan sulfate and chondroitin sulfate degradation. Diagnosis generally requires evidence of clinical phenotype, arylsulfatase B enzyme activity ®, clinical management was limited to supportive care and hematopoietic stem cell transplantation. Galsulfase is now widely available and is a specific therapy providing improved endurance with an acceptable safety profile. Prognosis is variable depending on the age of onset, rate of disease progression, age at initiation of ERT and on the quality of the medical care provided.

  2. Adsorption of toxic metal ion Cr(VI) from aqueous state by TiO2-MCM-41: Equilibrium and kinetic studies

    International Nuclear Information System (INIS)

    Highlights: ► Adsorption of toxic Cr(VI). ► Immobilization of various weight percentage of titania on MCM-41. ► Equilibrium, kinetic and thermodynamic study of adsorption of Cr(VI) onto TiO2-MCM-41. - Abstract: This paper deals with the immobilization of various weight percentage of TiO2 on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier Transform Infrared (FTIR) analysis, UV–vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO2 but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO2-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO2 loading was more than 20 wt.%, the adsorption activity (25)TiO2-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO2 and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO2-MCM-41. The adsorption of Cr(VI) onto (20)TiO2-MCM-41 at pH ∼ 5.5 and temperature 323 K was 91% at 100 mg/L Cr(VI) metal ion concentration in 80 min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO2-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode.

  3. Adsorption of toxic metal ion Cr(VI) from aqueous state by TiO{sub 2}-MCM-41: Equilibrium and kinetic studies

    Energy Technology Data Exchange (ETDEWEB)

    Parida, Kulamani, E-mail: paridakulamani@yahoo.com [Colloids and Material Chemistry Department, Institute of Minerals and Materials Technology (CSIR), Bhubaneswar 751013, Odisha (India); Mishra, Krushna Gopal [Chemistry Wing, School of Applied Sciences, KIIT University, Bhubaneswar 751024, Odisha (India); Dash, Suresh Kumar [Department of Chemistry, Institute of Technical Education and Research, Siksha ' O' Anusandhan University, Bhubaneswar 751030, Odisha (India)

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer Adsorption of toxic Cr(VI). Black-Right-Pointing-Pointer Immobilization of various weight percentage of titania on MCM-41. Black-Right-Pointing-Pointer Equilibrium, kinetic and thermodynamic study of adsorption of Cr(VI) onto TiO{sub 2}-MCM-41. - Abstract: This paper deals with the immobilization of various weight percentage of TiO{sub 2} on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier Transform Infrared (FTIR) analysis, UV-vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO{sub 2} but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO{sub 2}-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO{sub 2} loading was more than 20 wt.%, the adsorption activity (25)TiO{sub 2}-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO{sub 2} and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO{sub 2}-MCM-41. The adsorption of Cr(VI) onto (20)TiO{sub 2}-MCM-41 at pH {approx} 5.5 and temperature 323 K was 91% at 100 mg/L Cr(VI) metal ion concentration in 80 min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO{sub 2}-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode.

  4. NUEVO ESTUDIO DEL TEMPLO VI (TEMPLO DE LAS INSCRIPCIONES DE TIKAL, GUATEMALA (New Study of the Tikal Temple VI (Temple of the Inscriptions, Guatemala

    Directory of Open Access Journals (Sweden)

    Dmitri Beliaev

    2016-03-01

    Full Text Available El presente trabajo analiza los datos sobre la cronología del Templo VI (Templo de las Inscripciones de Tikal. Durante el trabajo de la segunda fase del proyecto «Atlas Epigráfico de Petén» (abril-mayo de 2014, fue documentada la inscripción en la crestería del templo, el texto jeroglífico del Clásico Tardío más grande del Petén y uno de los más extensos de todas las Tierras Bajas mayas. La secuencia de la construcción del relieve y estuco modelado observada en la crestería, junto con los datos epigráficos, muestra que el Templo VI fue construido en dos fases. La primera incluyó la edificación de la pirámide basal, el santuario y el relieve en la fachada este de la crestería, dedicados por el rey Yihk’in Chan K’awil en 735. En la segunda fase, fechada hacia 766, el templo fue ampliado y adornado con los relieves de las fachadas norte y sur. ENGLISH: In this paper, data related to the chronology of Temple VI (The Temple of the Inscriptions at Tikal is analyzed. During the second season of fieldwork on the “Atlas Epigráfico de Petén” project (April-May 2014, we documented the inscription on the roof comb of the temple, which is the largest hieroglyphic text from the Late Classic at Petén and one of the largest in the Maya Lowlands. The construction sequence of the relief and sculpted stucco observed on the roof comb, combined with epigraphic data, demonstrates that Temple VI was constructed in two phases. The first included the raising of the basal pyramid, the upper sanctuary, and the relief on the eastern façade of the roof comb, dedicated by the king Yihk’in Chan K’awil in 735 A.D. During the second phase, dated to around 766 A.D., the temple was enlarged and adorned with the reliefs on the north and south facades.

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

    Science.gov (United States)

    Izbicki, John A.; Groover, Krishangi

    2016-01-01

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

  6. Effect of temperature on the solvent extraction studies of U(VI) by aliquat 336/RTIL

    International Nuclear Information System (INIS)

    The solvent extraction of U(VI) from aqueous hydrochloric acid into 1-hexyl-1-methyl pyrrolidinium bis (trifluromethyl sulphonyl) imide Room Temperature Ionic Liquid (RTIL) by aliquat 336 (tricaprylyl methyl ammonium chloride) was carried out at four different temperatures (298K, 303K, 308K, 313K). The least square's analysis of the extraction data indicated that one extractant molecule takes part in the extraction reaction at all the four temperatures. The thermodynamic values indicated that negative ΔG, ΔH favour the extraction reaction while negative ΔS counteracts the reaction. (author)

  7. The mechanism study of trace Cr(VI) removal from water using Fe{sup 0} nanorods modified with chitosan in porous anodic alumina

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Li, E-mail: sunli@wtu.edu.cn [School of Mechanical Engineering and Automation, Wuhan Textile University, Wuhan 430073 (China); Yuan, Zhigang, E-mail: zgyuan@mail.ustc.edu.cn [School of Mechanical Engineering and Automation, Wuhan Textile University, Wuhan 430073 (China); Gong, Wenbang [School of Mechanical Engineering and Automation, Wuhan Textile University, Wuhan 430073 (China); Zhang, Lide [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zili; Su, Gongbing; Han, Donggui [School of Mechanical Engineering and Automation, Wuhan Textile University, Wuhan 430073 (China)

    2015-02-15

    Highlights: • PAA can limit the size, disperse Fe{sup 0} nanorods and protect them from oxidation. • PAA and chitosan act as bridges between Fe{sup 0} and Cr(VI) by the surface charges. • The adsorption capacity calculated (118.76 mg g{sup −1}) agreed with the measured one. • Trace Cr(VI) removal was a spontaneous adsorption reduction process. - Abstract: Fe{sup 0} nanorods modified with chitosan in porous anodic alumina (PAA) were prepared as adsorbent. Adsorption of trace Cr(VI) onto adsorbent was tested as a function of solution pH value, initial Cr(VI) concentration and adsorption time. The results showed that PAA can limit the size, disperse Fe{sup 0} nanorods and protect them from oxidation. In the adsorption process, it was found that both PAA and chitosan can supply bridges between Fe{sup 0} nanorods and Cr(VI) through the surface electrostatic attraction, and a small amount of PAA was etched. The optimum adsorption capacity obtained from the Langmuir model is 118.76 mg g{sup −1} which agrees with the experimental value at pH 5.0. X-ray photoelectron spectroscopy revealed that Cr(VI) was reduced to Cr(III) on the adsorbent surface. The adsorption behavior of Cr(VI) onto adsorbent was fitted well with the Langmuir model. The adsorption process followed the pseudo-second-order kinetic model, which implied that the adsorption process was chemisorptions. Intraparticle diffusion study shows that the internal diffusion of adsorbent is not the sole rate-controlling step. The Gibbs free energy change (ΔG° < 0) indicated that the process of Cr(VI) onto adsorbent was spontaneous. Besides, the aluminum sheets could be regenerated and be anodized to produce PAA.

  8. Oxocomplexes of Mo(VI) and W(VI) with 8-hydroxyquinoline-5-sulfonate in solution: structural studies and the effect of the metal ion on the photophysical behaviour.

    Science.gov (United States)

    Ramos, M Luísa; Justino, Licínia L G; Abreu, Paulo E; Fonseca, Sofia M; Burrows, Hugh D

    2015-11-28

    Multinuclear ((1)H, (13)C, (95)Mo and (183)W) NMR spectroscopy, combined with DFT calculations, provides detailed information on the complexation between the Mo(VI) and W(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, Mo(VI) and W(VI) oxoions form three homologous complexes with 8-HQS in water in the pH range 2-8. Two of these, detected at pH complex, dominant at slightly higher pH values (5-8) for solutions with a 1 : 1 metal : ligand molar ratio, has a binuclear M2O5(2+) centre coordinated to two 8-HQS ligands. The two metal atoms are bridged by three oxygen atoms, two coming from 8-HQS, together with the M-O-M bridge of the bimetallic centre. We show that the long-range exchange corrected BOP functional with local response dispersion (LCBOPLRD), together with explicit solvent molecules, leads to geometries that readily converge to equilibrium structures having realistic bridging O8-HQS-M bonds. Previous attempts to calculate the structures of such binuclear complexes using DFT with the B3LYP functional have failed due to difficulties in treating the weak interaction in these bridged structures. We believe that the LCBOPLRD method may be of more general application in theoretical studies in related binuclear metal complexes. UV/visible absorption and luminescence spectra of all the complexes have also been recorded. The complex between Mo(vi) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest that this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states close to the emitting ligand-based level which quench the emission. However, with W(VI), DFT calculations show that the LMCT states are now much higher in energy than the ligand based levels, leading to a marked increase in fluorescence. PMID:26498366

  9. Kinetics and equilibrium studies for sorption of Cu(II) and Cr(Vi) Ions onto polymeric composite resins

    International Nuclear Information System (INIS)

    The sorption behavior of Cu(II) and Cr(Vi) ions from aqueous solutions was studied using polymeric composite resins. Batch sorption experiments were performed as a function of hydrogen ion concentration, presence of complexing agent, effect of sorbent dosage and ionic strength. Kinetic parameters as a function of initial ion concentration were determined to predict the sorption behavior of Cu(Il) and Cr(Vi) onto polymeric composite resins. The equilibrium data could be fitted by the Freundlich adsorption isotherm equation. Industrial and mining waste water are important sources of heavy metals pollution (Quek et al, 1998). Chromium compounds are widely used by modern industries, resulting in large quantities of this element being discharged into the environment. Some of the main uses of chromium compounds are: plastic coating of surfaces, electroplating of metal, leather tanning and finishing, and in pigments and wood preservative (Korngold et al., 2003 and (Demirbas et al., 2004). Chromium occurs in waste water resulting from these operations is in both trivalent Cr(III) and hexavalent Cr(Vi) forms. The presence of Cu(II) in wastewater is also a problem. Copper is used extensively by electrical industries, in fungicides and in anti-fouling paints. When Cu is ingested at high concentrations, it become toxic to humans, causing cancer and promoting oxidation. The present method for removal of Cu(II) is to be precipitated as copper hydroxide by liming. However, with this process, residual Cu remains a problem (Findon et al, 1993). Owing to their wide uses, the efficient removal of toxic metal ions from waste water is an important and widely studied research area where a number of technologies have been developed over the years (Deans et al., 1992). The most important of these methods are filtration, chemical precipitation, ion exchange, sorption, electrodeposition and membrane systems. All these approaches have their inherent advantages and limitations

  10. Experimental study of the U(VI)-Humate-H{sub 2}O system with respect to the pH (4-12) at T = 25 deg C, 0.1MPa; Etude expeimentale du systeme U (VI) - Humate - H{sub 2}O en fonction du pH (4-12) a T = 25 deg C, 0.1MPa

    Energy Technology Data Exchange (ETDEWEB)

    Pourtier, E.; Deng, C. [UHP Nancy1, UMR7566G2R, 54 - Vandoeuvre-les-Nancy (France); Nguyen-Trung, C. [CREGU, 54 - Vandoeuvre les Nancy (France); Perdicakis, M.; Bordg, D. [LCPME, 54 - Villers-les-Nancy (France)

    2009-07-01

    Within the frame of the investigation of interactions between uranium (VI) and hydrosoluble organic compounds for the prediction of the evolution of this ion in natural aquatic systems, and in order to obtain some missing data, the authors report a systematic experimental investigation of the interactions between U(VI) and humate in aqueous media. This study comprises a synthesis of humic acid, detection, identification and characterization of U(VI)-humate compounds with respect to different parameters (pH, U(VI) content and humate chemical composition), and the determination of conditional formation constants with respect to the pH. Significant results are commented

  11. Studies on the Extraction Region of the Type VI RF Driven H- Ion Source

    Science.gov (United States)

    McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.

    2002-11-01

    IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the

  12. NUEVO ESTUDIO DEL TEMPLO VI (TEMPLO DE LAS INSCRIPCIONES) DE TIKAL, GUATEMALA (New Study of the Tikal Temple VI (Temple of the Inscriptions), Guatemala)

    OpenAIRE

    Dmitri Beliaev; Mónica de León Antillón; Philipp Galeev; Sergei Vepretskii

    2016-01-01

    El presente trabajo analiza los datos sobre la cronología del Templo VI (Templo de las Inscripciones) de Tikal. Durante el trabajo de la segunda fase del proyecto «Atlas Epigráfico de Petén» (abril-mayo de 2014), fue documentada la inscripción en la crestería del templo, el texto jeroglífico del Clásico Tardío más grande del Petén y uno de los más extensos de todas las Tierras Bajas mayas. La secuencia de la construcción del relieve y estuco modelado observada en la crestería, junto con los d...

  13. Solvent extraction studies on uranium (VI) with high molecular weight carboxylic acids from acetate medium

    International Nuclear Information System (INIS)

    Carboxylic acids are cation exchanger type of extractant which extract metal ions from weak acidic solutions by ion exchange mechanism. They are present as dimer (H2A2) in the non polar organic diluents. High molecular weight carboxylic acids such as versatic 10 acid and naphthenic acid are used for the separation of high purity of yttrium from heavy fraction of rare earths. Extraction behavior of rare earths with different types of carboxylic acids is also reported. Literature survey revealed that the extraction behavior of uranium from aqueous solutions with carboxylic acids is scanty. An attempt has been made in the present work to examine the extraction behavior of U(VI) with three different types of high molecular weight carboxylic acids namely cekanoic acid, neoheptanoic acid and versatic 10 acid dissolved in xylene. Extraction of metal ions is very much dependent on pH of the solution

  14. Study on uranium(VI) biosorption of marine-derived fungus treated by cetyltrimethyl ammonium bromide

    International Nuclear Information System (INIS)

    Fusarium sp. ZZF51 was chemically treated by cetyltrimethyl ammonium bromide to explore its potential for the removal of uranium(VI). The experimental results showed that the biosorption capacity and the removal efficiency for the modified mycelium under optimal conditions were 400.10 mg g-1 and 96.02 %, respectively, which were more than those of the native biomass (21.42 mg g-1 and 61.89 %). Lagergren's pseudo-second-order kinetic model and Langumir isotherm model showed the better agreement with the experimental data. SEM experiment indicated the mycelium could provide ready access and rich surface area for uranium binding, and FTIR analysis revealed that hydroxyl, carbonyl, especially for nitrogen groups played important roles in biosorption. (author)

  15. Studies on the kinetics and mechanism of complex formation in the reactions of ferron with iron (III) and uranium (VI)

    International Nuclear Information System (INIS)

    The equilibria and kinetics of the reactions of ferron (7-iodo-8-hydroxyquindine-5-sulphonic acid) with iron(III) and uranium(VI) have been followed by stopped flow spectrophotometry under the conditions of mono-complex formation. The equilibrium constants obtained spectrophotmetrically have been compared with those obtained from kinetic studies. In the case of iron(III), in the acidity range, [H+]=(2.8-10.0)x10-2 mol dm-3, among the different possible reaction path-ways, the reaction has been found to proceed mainly through the interaction of Fe(OH)(aq)2+ and partially deprotonated form (LH-) of the ligand. In the case of uranium(VI), in the acidity range, [H+]=(2.5-25.0)x10-5 mol dm-3, a dual path mechanism involving UO2(aq)2+ and UO2(OH)(aq)- and the partially deprotonated (LH-) form of the ligand is consistent with the observations. The results in each case are in agreement with the Eigen mechanism and the characteristic water exchange rates have been obtained in each case, as a rough estimate, from the experimental data. Activation parameters (ΔHsup(≠) and ΔSsup(≠) for each path have been determined and compared. (author). 23 refs., 5 figs., 2 tabs

  16. Aqueous U(VI) interaction with magnetite nanoparticles in a mixed flow reactor system: HR-XANES study

    Science.gov (United States)

    Pidchenko, I.; Heberling, F.; Kvashnina, KO; Finck, N.; Schild, D.; Bohnert, E.; Schäfer, T.; Rothe, J.; Geckeis, H.; Vitova, T.

    2016-05-01

    The redox variations and changes in local atomic environment of uranium (U) interacted with the magnetite nanoparticles were studied in a proof of principle experiment by the U L3 and M4 edges high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We designed and applied a mixed flow reactor (MFR) set-up to maintain dynamic flow conditions during U-magnetite interactions. Formation of hydrolyzed, bi- and poly-nuclear U species were excluded by slow continuous injection of U(VI) (10-6 M) and pH control integrated in the MFR set-up. The applied U HR-XANES technique is more sensitive to minor changes in the U redox states and bonding compared to the conventional XANES method. Major U(VI) contribution in uranyl type of bonding is found in the magnetite nanoparticles after three days operation time of the MFR. Indications for shortening of the U-Oaxial bond length for the magnetite compared to the maghemite system are present too.

  17. Second cancer incidence risk estimates using BEIR VII models for standard and complex external beam radiotherapy for early breast cancer

    Energy Technology Data Exchange (ETDEWEB)

    Donovan, E. M.; James, H.; Bonora, M.; Yarnold, J. R.; Evans, P. M. [Joint Department of Physics, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Sutton SM2 5PT (United Kingdom); Physics Department, Ipswich Hospital NHS Foundation Trust, Ipswich IP4 5PD (United Kingdom); Department of Academic Radiotherapy, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton SM2 5PT, United Kingdom and School of Radiotherapy, University of Milan, Milan 20122 (Italy); Department of Academic Radiotherapy, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton SM2 5PT (United Kingdom); Centre for Vision Speech and Signal Processing, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2012-10-15

    Purpose: To compare organ specific cancer incidence risks for standard and complex external beam radiotherapy (including cone beam CT verification) following breast conservation surgery for early breast cancer.Method: Doses from breast radiotherapy and kilovoltage cone beam CT (CBCT) exposures were obtained from thermoluminescent dosimeter measurements in an anthropomorphic phantom in which the positions of radiosensitive organs were delineated. Five treatment deliveries were investigated: (i) conventional tangential field whole breast radiotherapy (WBRT), (ii) noncoplanar conformal delivery applicable to accelerated partial beast irradiation (APBI), (iii) two-volume simultaneous integrated boost (SIB) treatment, (iv) forward planned three-volume SIB, and (v) inverse-planned three volume SIB. Conformal and intensity modulated radiotherapy methods were used to plan the complex treatments. Techniques spanned the range from simple methods appropriate for patient cohorts with a low cancer recurrence risk to complex plans relevant to cohorts with high recurrence risk. Delineated organs at risk included brain, salivary glands, thyroid, contralateral breast, left and right lung, esophagus, stomach, liver, colon, and bladder. Biological Effects of Ionizing Radiation (BEIR) VII cancer incidence models were applied to the measured mean organ doses to determine lifetime attributable risk (LAR) for ages at exposure from 35 to 80 yr according to radiotherapy techniques, and included dose from the CBCT imaging. Results: All LAR decreased with age at exposure and were lowest for brain, thyroid, liver, and bladder (<0.1%). There was little dependence of LAR on radiotherapy technique for these organs and for colon and stomach. LAR values for the lungs for the three SIB techniques were two to three times those from WBRT and APBI. Uncertainties in the LAR models outweigh any differences in lung LAR between the SIB methods. Constraints in the planning of the SIB methods ensured that

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

    Science.gov (United States)

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

    2010-02-01

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

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

    International Nuclear Information System (INIS)

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

  20. IR Fingerprints of U(VI) Nitrate Monoamides Complexes: A Joint Experimental and Theoretical Study

    International Nuclear Information System (INIS)

    Infrared spectra or 0. 5 mol. L-1 uranium(VI) nitrate monoamide complexes in toluene have been recorded and compared with infrared spectra calculated by DFT. The investigated monoamides were N, N-dimethylformamide (DMF), N, N-dibutyl-formamide (DBF), and N, N-dicyclohexyl-formamide (DeHF). The validity of DFT calculations for describing uranium nitrate monoamide complexes has been confirmed as a fair agreement between experimental and calculated spectra was obtained. Furthermore, a topological analysis of the electron density has been carried out to characterize monoamide-uranium interactions. From this work, it appears that the increase of stability of uranyl-monoamide complexes may be directly linked to the degree of polarization of the ligands in interaction with uranyl-nitrate. Among the investigated monoamides, the most stable complex is UO2(NO3)2.2DcHF. This complex is characterized by a high positive charge delocalization in the outer part or the ligand molecule, which leads to a more concentrated positive charge close to the uranyl cation (UO22+), thus strengthening the electrostatic interaction between the metal and the ligand. (authors)

  1. Dynamic NMR study of ligand exchange reactions in U(VI)-phosphonic acid systems

    International Nuclear Information System (INIS)

    The rates of hydrogen ion exchange on phosphonic acid ligands and that of phosphonate ligand exchange on selected uranyl-phosphonate complexes have been investigated by dynamic NMR spectroscopy. The spin-spin relaxation time (ln(1/T2)) for H+ exchange on the fee ligands exhibits a parabolic dependence on reciprocal temperature (1/T (K-1)). The empirical fit parameters are correlated with the activation parameters (ΔH*, ΔS*, ΔCp*) by adapting the statistical mechanical framework developed by Braibanti et al. to the Eyring activated complex theory. The correlation of the apparent activation enthalpy with temperature indicates that 6--11 water molecules participate in the transition from reactants to activated complex for ligand proton exchange reactions, depending on the ligand. Mechanistic details of ligand exchange reactions of phosphonic acid complexants onto the corresponding uranium(VI) complexes are not fully developed, but the negative values for ΔS* imply increased order in the transition to the activated complex. Though ΔH* for ligand exchange covers a range of 15 kJ/mol, the free energy of activation (ΔG*) is nearly constant for the series of ligands, implying substantial entropy compensation in the activation process. Application of the Marcus relationship defines a correlation between ΔG* and the thermodynamic stability (ΔG degree) for the 1:2 uranyl complexes with methanediphosphonic acid and 1-hydroxyethane-1,1-diphosphonic acid

  2. Study on adsorption of uranium(VI) on clay and its significance for control of ground water pollution

    International Nuclear Information System (INIS)

    The batch experiments for adsorption of uranium (VI) on clay collected from the bottom of a huge mill-tailing in southern China were conducted. The results show that the adsorption of uranium (VI) on clay is a obviously nonlinear function of pH in solution, leaching a maximum around neutral pH and decreasing rapidly towards more acidic or alkaline conditions. The diffuse layer model (DLM) which describes the adsorption of uranium (VI) on clay was established according to the surface complexation approach, and it simulates the experimental data successfully. The calibration displays that the model has strong capacity to predict uranium (VI) sorption behavior under different thermodynamic condition. The simulating results indicate that U(VI) adsorption on clay is affected by solid-liquid ratio (M/V) obviously at low pH and controlled by HCO3- and Co32- in solution at high pH

  3. Analytical use of zide ion. Chemical equilibrium studies and correlates in U(VI)/N3 and Co(III)/N3 systems

    International Nuclear Information System (INIS)

    A monographic study about the azide ion and its structure, as well as, references about the uranyl ion in aqueous medium, and its possible hydrolysis products are shown. Spectral studies of the U(VI), Fe (III) and Cu(II) systems, in azide medium are analyzed. (M.J.C.)

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

    Directory of Open Access Journals (Sweden)

    J. Aravind

    2015-07-01

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

  5. Isotherm Modelling, Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology for Effective Removal of Cr(VI) Using Fungal Biomass

    OpenAIRE

    Melvin Samuel S; Evy Alice Abigail M; Ramalingam Chidambaram

    2015-01-01

    Biosorption is a promising alternative method to replace the existing conventional technique for Cr(VI) removal from the industrial effluent. In the present experimental design, the removal of Cr(VI) from the aqueous solution was studied by Aspergillus niger MSR4 under different environmental conditions in the batch systems. The optimum conditions of biosorption were determined by investigating pH (2.0) and temperature (27°C). The effects of parameters such as biomass dosage (g/L), initial Cr...

  6. Kinetic-spectrophotometric determination of molybdenum(VI) and tungsten(VI) in mixtures

    International Nuclear Information System (INIS)

    A simple kinetic-spectrophotometric method is described for the determination of molybdenum(VI) and tungsten(VI) in mixtures, without prior separation. The method is based on the catalytic effect of molybdenum(VI) and tungsten(VI) on the 2,4-diaminophenol dihydrochloride (DAP) by hydrogen peroxide in acidic medium. The reaction was followed spectrophotometrically by measuring the rate of change in absorbance with time at 500 nm. A partial inhibition in the catalytic activity of each catalyst, when the other one is present, at all ratios of Mo(VI):W(VI) mixtures studied was observed. On the other hand, the catalytic activity of tungsten(VI) dropped to zero whilst that of molybdenum(VI) decreased slightly, in the presence of citrate ions. Two sets of experiments were carried out, the first in the absence and the other in the presence of citrate, and the resolution of Mo(VI)/W(VI) mixtures was achieved by solving two simultaneous equations. Various molar ratios of Mo(VI):W(VI), at the 10-6 M level, from 0.2:1 to 5:1 can be determined with satisfactory precision and accuracy. The selectivity of the method was investigated and the method was applied successfully to the determination of molybdenum and tungsten in each other's presence in steel. (authors)

  7. Study on the internal relationship of U(VI) and U in uranium ore and ore with uranium

    International Nuclear Information System (INIS)

    The influence of melt time and melt temperature on U(VI) and U(IV) in uranium ore and uranium measurement were discussed. And the internal relationship between U(VI) and U(IV) in uranium ore with high content (≥100μg/g) and with low content (≥100 μg/g) were investigated respective, by analyzing theory of uranium ore and rule of U(VI) and U(IV). The results indicated that efficiency analysis of U(VI) and U(IV) could be achieved when melted for 3 hour and temperature reached 65 degree C. The content of total uranium equals to the content of U(VI) added U(IV) when the content of U up to high in uranium ore and ore with uranium. But for low U samples, the relationship between U(VI) and U(IV) follows math connection: U(VI)=A560/A583 x Utotal. This math connection used to analyze the low content samples can decrease analysis steps infinitely and also can improve working efficiency. (authors)

  8. Controversial issues confronting the BEIR III committee: implications for radiation protection

    International Nuclear Information System (INIS)

    This paper reviews the state-of-the-art for conducting risk assessment studies, especially known and unknown factors relative to radioinduced cancer or other diseases, sources of scientific and epidemiological data, dose-response models used, and uncertainties which limit precision of estimation of excess radiation risks. These are related to decision making for radiation protection policy

  9. Controversial issues confronting the BEIR III committee: implications for radiation protection

    Energy Technology Data Exchange (ETDEWEB)

    Fabrikant, J.I.

    1981-05-01

    This paper reviews the state-of-the-art for conducting risk assessment studies, especially known and unknown factors relative to radioinduced cancer or other diseases, sources of scientific and epidemiological data, dose-response models used, and uncertainties which limit precision of estimation of excess radiation risks. These are related to decision making for radiation protection policy. (PSB)

  10. Cu vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Andrzej; Pettyn

    1999-01-01

    LA DEKDUA LECIONOu vi longe atendis min?—Danuta:Saluton,Banjo!—Barbara:Saluton!—D:Cu vi longe atendis min?—B:Tute ne.Mi jus venis i tien.—D:Mi esperas,ke nun vi estas libera.—B:Mi estas tute libera,do ni povas iriien,kien vi deziras.—D:Bone.Mi proponas do,ke unue niiru al magazenoj fari aetojn kaj

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

    International Nuclear Information System (INIS)

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

  12. Study on the Advertising Management of Fashion Magazines Under the Media Environment. A Case Study of"ViVi"

    Institute of Scientific and Technical Information of China (English)

    Linghu Kerui

    2015-01-01

    Magazine advertising as a major source of income, the quality of its operations is critical to the development and survival of the magazine. However, under the new media environment, traditional advertising management is no longer adapted to the times, media operators must find their own inadequacies of advertising business, through business innovation to gain a firm foothold in the competition torrent. This paper as the research object of "ViVi'" , analyzes the advertising management and the problem under the new media environment. Finally, offer the suggestion for fashion magazines to better development advertising under the new media environment.

  13. The sorption of uranium(VI) and neptunium(V) onto surfaces of selected metal oxides and alumosilicates studied by in situ vibrational spectroscopy

    International Nuclear Information System (INIS)

    The migration behavior of actinides and other radioactive contaminants in the environment is controlled by prominent molecular phenomena such as hydrolysis and complexation reactions in aqueous solutions as well as the diffusion and sorption onto minerals present along groundwater flow paths. These reactions significantly influence the mobility and bioavailability of the metal ions in the environment, in particular at liquid-solid interfaces. Hence, for the assessment of migration processes the knowledge of the mechanisms occurring at interfaces is crucial. The required structural information can be obtained using various spectroscopic techniques. In the present study, the speciation of uranium(VI) and neptunium(V) at environmentally relevant mineral-water interfaces of oxides of titania, alumina, silica, zinc, and alumosilicates has been investigated by the application of attenuated total reflection Fouriertransform infrared (ATR FT-IR) spectroscopy. Moreover, the distribution of the hydrolysis products in micromolar aqueous solutions of U(VI) and Np(V/VI) at ambient atmosphere has been characterized for the first time, by a combination of ATR FT-IR spectroscopy, near infrared (NIR) absorption spectroscopy, and speciation modeling applying updated thermodynamic databases. From the infrared spectra, a significant change of the U(VI) speciation is derived upon lowering the U(VI) concentration from the milli- to the micromolar range, strongly suggesting the dominance of monomeric U(VI) hydrolysis products in the micromolar solutions. In contradiction to the predicted speciation, monomeric hydroxo species are already present at pH ≥ 2.5 and become dominant at pH 3. At higher pH levels (> 6), a complex speciation is evidenced including carbonate containing complexes. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3, and they are comparatively discussed with U(VI

  14. Equilibrium, kinetic and thermodynamic studies on the removal of U(VI) by low cost agricultural waste

    OpenAIRE

    Kausar, A.; Bhatti, H.N.; MacKinnon, G.

    2013-01-01

    In this research, biosorption efficiency of different agro-wastes were evaluated with rice husk showing maximum biosorption capacity among the selected biosorbents. Optimization of native, SDS-treated and immobilized rice husk adsorption parameters including pH, biosorbent amount, contact time, initial U(VI) concentration and temperature for maximum U(VI) removal was investigated. Maximum biosorption capacity for native (29.56 mg g-1) and immobilized biomass (17.59 mg g-1) was ...

  15. Study of Mo (VI) removal from aqueous solution: application of different mathematical models to continuous biosorption data

    OpenAIRE

    Fatemeh Kafshgari; Ali Reza Keshtkar; Mohammad Ali Mousavian

    2013-01-01

    Abstract Molybdenum (VI) biosorption process was investigated by marine algae Cystoseria indica pretreated with 0.1 M CaCl2 solution in a packed bed column. The biosorbent was characterized by FTIR, BET and SEM analyses. The results showed that Mo (VI) ions should be chelated with the hydroxyl, carboxyl and amine groups of the biomass. The effects of inlet metal concentration and flow rate on biosorption process were investigated and the experimental breakthrough curves were obtained. Results...

  16. A spectroscopic study of the effect of ligand complexation on the reduction of uranium(VI) by anthraquinone-2,6-disulfonate (AH2DS)

    International Nuclear Information System (INIS)

    In this paper, the reduction rate of uranyl complexes with hydroxide, carbonate, EDTA, and desferriferrioxamine B (DFB) by anthraquinone-2,6-disulfonate (AH2DS) is studied by stopped-flow kinetic technique under anoxic atmosphere. The apparent reaction rates varied with ligand type, solution pH, and U(VI) concentration. For each ligand, a single largest pseudo-1st order reaction rate constant, kobs, within the studied pH range was observed, suggesting the influence of pH-dependent speciation on the U(VI) reduction rate. The maximum reaction rate found in each case followed the order of OH- > CO32- > EDTA > DFB, in reverse order of the trend of the thermodynamic stability of the uranyl complexes and ionic sizes of the ligands. The pH-dependent rates were modeled using a second-order rate expression that was assumed to be dependent on a single U(VI) complex and an AH2DS species. By quantitatively comparing the calculated and measured apparent rate constants as a function of pH, species AHDS3- was suggested as the primary reductant in all cases examined. Species UO2CO3(aq), UO2HEDTA-, and (UO2)2(OH)22+ were suggested as the principal electron acceptors among the U(VI) species mixture in each of the carbonate, EDTA, and hydroxyl systems, respectively. (orig.)

  17. Isolation, characterization and a study of the solvolytic reactions in non-aqueous media of some dioxomolybdenum (VI) chelates and the solvolytic studies in methanol of a few other dioxomdybdenum (VI) complexes with monoligands

    International Nuclear Information System (INIS)

    Two dioxomolybdenum(VI) chelates having the compositions MoO2(en)Cl2 and MoO2(Sal2en.H2)Cl2 [Sal2enH2 = N, N'-disalicyl ethylenediimine] are isolated by reacting MoO2Cl2H2O with the appropriate ligands in suitable solvents and they have been characterised by IR, TGA and magnetic susceptibility studies. The former undergoes 'base solvolysis' and the latter 'acid solvolysis' in methanol as followed by their conductance measurement in the said solvent. Such conductance study reveals that the complexes MoO2Cl2L2 (L = pyridine, 4-nitropyridine and quinoline N-oxides; triphenyl phosphine oxide; hexamethyl phosphoramide and dimethyl sulphoxide) also undergo 'base solvolysis' in methanol but at a very high dilution (approximately 10-4M) the triphenyl phosphine oxide, quinoline N-oxide and dimethyl sulphoxide complexes probably undergo further decomposition ( a maxima in √ Csub(M)vs.Λsub(M) plots) when the organic ligand molecules leave the inner sphere of coordination and the solvated organic ligands associate with the protons to a marked extent. This observation suggests that the standard free energy change accompanying the transfer of H+[ΔGsub(t)sup(o)(H+)] from methanol to the methanolated ligand species in these three cases are negative. A probable qualitative theoretical model in the case of the DMSO complexes has also been incorporated. (author)

  18. U(VI) and Eu(III) ion sorption in the interface solution-phosphate solids: Structural study and mechanisms

    International Nuclear Information System (INIS)

    As part of the storage of nuclear wastes in a deep underground disposal, radionuclides sorption on geological or engineered barriers is one of the most important factor which could enhance retardation. Thus, the knowledge of such mechanisms is needed. For this purpose, we chose to experimentally define sorption equilibria before performing simulation of retention data. Several phosphate compounds are potential candidates as engineered barrier additives. We considered Th4(PO4)4P2O7, Zr2O(PO4)2 which allow to study the effect of PO4 and P2O7 groups separately. Eu(III) and U(IV) ions were used as structural probes in order to simulate actinides (III) and (VI) behavior. X-ray powder diffraction, IR spectroscopy and electron probe microanalysis were used to characterized the synthesized solids. Electrophoretic measurements showed an amphoteric behavior of surface sites. Moreover, laser spectro-fluorimetry experiments indicated that no diffusion phenomena of the sorbed ion inside the solid occurs. Thus, we considered that a surface complexation model should be applied. Laser spectro-fluorimetry and XPS allowed to determine the nature of surface sites. ZrP2O7 presents only one single site (P2O7 groups) whereas Th4(PO4)4P2O7 and Zr2O(PO4)2 admit two types of sites (PO4/P2O7 and PO4/oxo groups, respectively). Sorbed species were identified using laser spectro-fluorimetry which indicate that, in KNO3 0.5 M medium and for a known surface site, there are two surface complexes for U(VI) (sorption of UO2+2 et de UO2NO+3 species) and only one for Eu(III) (sorption of EuNO2+3). They are linked to the substrate as bidentate inner sphere complexes (EXAFS study). Surface acidity constants were determined by simulation of potentiometric titration curves obtained for each solid suspension using FITEQL code (CCM). As sorption equilibria were defined, experimental retention data simulation was performed with respect to structural study results. (authors)

  19. Diverse anisotropy of phonon transport in two-dimensional group IV-VI compounds: A comparative study

    Science.gov (United States)

    Qin, Guangzhao; Qin, Zhenzhen; Fang, Wu-Zhang; Zhang, Li-Chuan; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming; Su, Gang

    2016-05-01

    New classes of two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport is a fundamental physical parameter. In this paper, we systematically investigated the phonon transport properties of the 2D orthorhombic group IV-VI compounds of GeS, GeSe, SnS and SnSe by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite their similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, Young's modulus and lattice thermal conductivity (κ), etc. Especially, the κ along the zigzag and armchair directions of monolayer GeS shows the strongest anisotropy while monolayer SnS and SnSe show almost isotropy in phonon transport. The origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in details. With limited size, the κ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications to nanoscale thermoelectrics and thermal management. Our study offers fundamental understanding of the anisotropic phonon transport properties of 2D materials, and would be of significance for further study, modulation and applications in emerging technologies.

  20. Diverse anisotropy of phonon transport in two-dimensional group IV-VI compounds: A comparative study.

    Science.gov (United States)

    Qin, Guangzhao; Qin, Zhenzhen; Fang, Wu-Zhang; Zhang, Li-Chuan; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming; Su, Gang

    2016-06-01

    New classes of two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport is a fundamental physical parameter. In this paper, we systematically investigated the phonon transport properties of the 2D orthorhombic group IV-VI compounds of GeS, GeSe, SnS and SnSe by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite their similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, Young's modulus and lattice thermal conductivity (κ), etc. Especially, the κ along the zigzag and armchair directions of monolayer GeS shows the strongest anisotropy while monolayer SnS and SnSe show almost isotropy in phonon transport. The origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in details. With limited size, the κ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications to nanoscale thermoelectrics and thermal management. Our study offers fundamental understanding of the anisotropic phonon transport properties of 2D materials, and would be of significance for further study, modulation and applications in emerging technologies. PMID:27189263

  1. Modeling and Speciation Study of Uranium(VI) and Technetium(VII) Coextraction with DEHiBA.

    Science.gov (United States)

    Moeyaert, Pauline; Dumas, Thomas; Guillaumont, Dominique; Kvashnina, Kristina; Sorel, Christian; Miguirditchian, Manuel; Moisy, Philippe; Dufrêche, Jean-François

    2016-07-01

    The N,N-dialkylamide DEHiBA (N,N-di-2-ethylhexyl-isobutyramide) is a promising alternative extractant to TBP (tri-n-butylphosphate) to selectively extract uranium(VI) from plutonium(IV) and spent nuclear fuel fission products. Extraction of technetium, present as pertechnetic acid (HTcO4) in the spent fuel solution, by DEHiBA was studied for different nitric acid and uranium concentrations. The uranium(VI) and technetium(VII) coextraction mechanism with DEHiBA was investigated to better understand the behavior of technetium in the solvent extraction process. Uranium and technetium distribution ratios were first determined from batch experiments. On the basis of these data, a thermodynamic model was developed. This model takes into account deviations from ideality in the aqueous phase using the simple solution concept. A good representation of uranium and technetium distribution data was obtained when considering the formation of (DEHiBA)i(HNO3)j(HTcO4)k complexes, as well as mixed (DEHiBA)2(UO2)(NO3)(TcO4) and (DEHiBA)3(UO2)(NO3)(TcO4)(HNO3) complexes, where one pertechnetate anion replaces one nitrate in the uranium coordination sphere in the two complexes (DEHiBA)2(UO2)(NO3)2 and (DEHiBA)3(UO2)(NO3)2(HNO3). Combination of complementary spectroscopic techniques (FT-IR and X-ray absorption) supported by theoretical calculations (density functional theory) enabled full characterization of the formation of mixed uranium-technetium species (DEHiBA)2(UO2)(NO3)(TcO4) in the organic phase for the first time. The structural parameters of this complex are reported in the paper and lead to the conclusion that the pertechnetate group coordinates the uranyl cation in a monodentate fashion in the inner coordination sphere. This study shows how combining a macroscopic approach (distribution data acquisition and modeling) with molecular-scale investigations (FT-IR and X-ray absorption analysis supported by theoretical calculations) can provide a new insight into the description

  2. Biosorption of uranium(VI) from aqueous solutions by Ca-pretreated Cystoseira indica alga: Breakthrough curves studies and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi, Morteza [Faculty of Nuclear Engineering, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Keshtkar, Ali Reza, E-mail: akeshtkar@aeoi.org.ir [Nuclear Fuel Cycle School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Dabbagh, Reza [Nuclear Science Research School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Jaber Safdari, S. [Nuclear Fuel Cycle School, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of)

    2011-05-15

    Uranium(VI) biosorption from aqueous solutions containing 60 mg l{sup -1} metal concentration by Ca-pretreated Cystoseira indica alga was studied in a packed bed column with 1.5 cm internal diameter. The effect of bed height and flow rate on biosorption process was investigated and the experimental breakthrough curves were obtained. Results showed that by increasing the bed height, the breakthrough and exhaustion times increased and the slope of breakthrough curves decreased. Also, it was observed that the controlled-rate step shifted from external to internal mass transfer limitations, as the flow rate increased. The maximum uptake capacity, 318.15 mg g{sup -1}, and total metal removal, 59.32%, were obtained at flow rate of 2.3 ml min{sup -1} and bed height of 6 cm. The column was regenerated using 0.1 M HCl solution and sorption-desorption studies were carried out for three cycles. The obtained results confirmed that reusability of this biosorbent is possible. The results obtained agreed well with the bed depth service time model. In addition, for estimations of the parameters necessary for the design of a large-scale packed bed column, the experimental data were also fitted to the Thomas, Yan and Belter models and were found to agree with the experimental data fairly well.

  3. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    International Nuclear Information System (INIS)

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  4. Biosorption of uranium(VI) from aqueous solutions by Ca-pretreated Cystoseira indica alga: Breakthrough curves studies and modeling

    International Nuclear Information System (INIS)

    Uranium(VI) biosorption from aqueous solutions containing 60 mg l-1 metal concentration by Ca-pretreated Cystoseira indica alga was studied in a packed bed column with 1.5 cm internal diameter. The effect of bed height and flow rate on biosorption process was investigated and the experimental breakthrough curves were obtained. Results showed that by increasing the bed height, the breakthrough and exhaustion times increased and the slope of breakthrough curves decreased. Also, it was observed that the controlled-rate step shifted from external to internal mass transfer limitations, as the flow rate increased. The maximum uptake capacity, 318.15 mg g-1, and total metal removal, 59.32%, were obtained at flow rate of 2.3 ml min-1 and bed height of 6 cm. The column was regenerated using 0.1 M HCl solution and sorption-desorption studies were carried out for three cycles. The obtained results confirmed that reusability of this biosorbent is possible. The results obtained agreed well with the bed depth service time model. In addition, for estimations of the parameters necessary for the design of a large-scale packed bed column, the experimental data were also fitted to the Thomas, Yan and Belter models and were found to agree with the experimental data fairly well.

  5. A study of the cavity polariton under strong excitation:dynamics and nonlinearities in II-VI micro-cavities

    International Nuclear Information System (INIS)

    This work contains an experimental study of the photoluminescence dynamics of cavity polaritons in strong coupling micro-cavities based on II-VI semiconductor compounds. The small exciton size and the strong exciton binding energy in these materials allowed us to study the strong coupling regime between photon and exciton up to high excitation densities, exploring the linear and non-linear emission regimes. Our main experimental techniques are picosecond time-resolved and angular photoluminescence spectroscopy. In the linear regime and for a negative photon-exciton detuning, we observe a suppression of the polariton relaxation by the emission of acoustic phonons leading to a non-equilibrium polariton distribution on the lower branch. This 'bottleneck' effect, which has already been described for polaritons in bulk semiconductors, results from the pronounced photon like character of the polaritons near k(parallel) = 0 in this configuration. At high excitation densities, non-linear relaxation processes, namely final state stimulation of the relaxation and polariton-polariton scattering, bypass this bottleneck giving rise to a very rapid relaxation down to the bottom of the band. We show that this dramatic change in the relaxation dynamics is finally responsible of the super-linear increase of the polariton emission from these states. (author)

  6. Spectroscopic study on the role of TiO2 in the adsorption of Eu(III) and U(VI) on silica surfaces in aqueous solutions

    International Nuclear Information System (INIS)

    Highlights: • Enhanced adsorption of Eu(III) and U(VI) onto TiO2-coated silica. • Enhanced Eu(III) luminescence and lifetime on TiO2-coated silica. • Energy transfer from TiO2 of TiO2-coated silica to Eu(III) in solutions. - Abstract: To determine the effects of TiO2 on the adsorption of actinides onto mineral surfaces in groundwater, silica was partially coated with TiO2, and Eu(III) and U(VI) were individually adsorbed from separate 0.1 mM concentration solutions. The TiO2-coated silica showed higher Eu(III) and U(VI) adsorption capacities for increasing amounts of TiO2 coated on the silica surfaces, and thus the existence of TiO2 can decrease the mobility of Eu(III) and U(VI) contaminants. In luminescence studies, it was found that TiO2 considerably enhanced the luminescence of the adsorbed Eu(III) indicating that TiO2–Eu(III) forms surface complexes which may decrease the number of water molecules at the inner sphere of Eu(III), but this was not observed for U(VI). An energy transfer from the TiO2 to the Eu(III) was confirmed in this case of amorphous TiO2-coated silica in Eu(III) solutions, and an increase of the luminescence lifetime of Eu(III) for increasing concentrations of coated TiO2 was also observed

  7. A New Method to Define the VI-Ts Diagram Using Subpixel Vegetation and Soil Information: A Case Study over a Semiarid Agricultural Region in the North China Plain

    Directory of Open Access Journals (Sweden)

    Masataka Watanabe

    2008-10-01

    Full Text Available The VI-Ts diagram determined by the scatter points of the vegetation index (VI and surface temperature (Ts has been widely applied in land surface studies. In the VI-Ts diagram, dry point is defined as a pixel with maximum Ts and minimum VI, while wet point is defined as a pixel with minimum Ts and maximum VI. If both dry and wet points can be obtained simultaneously, a triangular VI-Ts diagram can be readily defined. However, traditional methods cannot define an ideal VI-Ts diagram if there are no full ranges of land surface moisture and VI, such as during rainy season or in a period with a narrow VI range. In this study, a new method was proposed to define the VI-Ts diagram based on the subpixel vegetation and soil information, which was independent of the full ranges of land surface moisture and VI. In this method, a simple approach was firstly proposed to decompose Ts of a given pixel into two components, the surface temperatures of soil (Tsoil and vegetation (Tveg, by means of Ts and VI information of neighboring pixels. The minimum Tveg and maximum Tsoil were then used to determine the wet and dry points respectively within a given sampling window. This method was tested over a 30 km × 30 km semiarid agricultural area in the North China Plain through 2003 using Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER and MODerate-resolution Imaging Spectroradiometer (MODIS data. The wet and dry points obtained from our proposed method and from a traditional method were compared with those obtained from ground data within the sampling window with the 30 km × 30 km size. Results show that Tsoil and Tveg can be obtained with acceptable accuracies, and that our proposed method can define reasonable VI-Ts diagrams over a semiarid agricultural region throughout the whole year, even for both cases of rainy season and narrow range of VI.

  8. Interaction of uranium(VI) with bioligands present in human biological fluids. The case study of urea and uric acid

    International Nuclear Information System (INIS)

    The complexation of uranium(VI) with bioligands found in human biological fluids, viz, urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log β110 = 4.67 ± 0.29 for uric acid and log β110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

  9. Chromium (VI) adsorption on boehmite

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-03-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-15

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

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

    International Nuclear Information System (INIS)

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

  12. Cu vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Andrzej; Pettyn

    1999-01-01

    LA DEKA LECIONOKiom da mono vi bezonas?—Barbara:Mi foriras aeti ion pormani.u vi deziras ion de mi?—Sinjoro Petro(la edzo de Barbara):Aetu por mi skatolon da cigaredoj aǔeble...aetu por mi du skatolojn dacigaredoj kaj unu skatolon da alume-toj.—B:Bone.u vi ankoraǔ deziras ion?—P:Ne,dankon.Estasio.u vihavas monon?

  13. Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

    Czech Academy of Sciences Publication Activity Database

    Asadi, Z.; Asadi, M.; Zeinali, A.; Ranjkeshshorkaei, M.; Fejfarová, Karla; Eigner, Václav; Dušek, Michal; Dehnokhalaji, A.

    2014-01-01

    Roč. 126, č. 6 (2014), s. 1673-1683. ISSN 0974-3626 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : uranyl schiff base complexes * kinetic study * kinetics of thermal decomposition * X-ray crystallography * cyclic voltammetry Subject RIV: CA - Inorganic Chemistry Impact factor: 1.191, year: 2014

  14. Human genetic studies in areas of high natural radiation VI. Genetical load and ethnic group

    International Nuclear Information System (INIS)

    The load of mutations disclosed by inbreeding, according to the ethnic group of the parents, has been analyzed in our data. Besides the total of the population, a sample with no alien ancestrals has also been analyzed. Genetic load has been studied for absortions, still births, pos-natal mortality, total mortality, anomalies, total mortality + anomalies, and abnormalities in general

  15. A study of the core of the Shapley Concentration VI. Spectral properties of galaxies

    CERN Document Server

    Baldi, A; Zucca, E; Baldi, Alessandro; Bardelli, Sandro; Zucca, Elena

    2001-01-01

    We present the results of a study of the spectral properties of galaxies in the central part of the Shapley Concentration, covering an extremely wide range of densities, from the rich cluster cores to the underlying supercluster environment. Our sample is homogeneous, in a well defined magnitude range (17=study the properties of galaxies at different densities: cluster, intercluster (i.e. galaxies in the supercluster but outside clusters) and field environment. No significant differences are present between samples at low density regimes (i.e. intercluster and field galaxies). Cluster galaxies, instead, not only have values significantly different from...

  16. Spin-flip-Raman studies of semimagnetic II-VI heterostructures; Spin-flip-Raman-Untersuchungen an semimagnetischen II-VI-Halbleiter-Quantentroegen und Volumenproben

    Energy Technology Data Exchange (ETDEWEB)

    Lentze, Michael

    2009-03-18

    In the present doctoral thesis, spin flip Raman studies of semimagnetic (Zn,Mn)Se samples were in the focus of interest. Quantum wells as well as bulk-like materials were investigated. The main goal was a better understanding of the exchange interaction behaviour of heavily n-doped semimagnetic samples. The influence of doping on the exchange interaction is of special relevance with regard to spintronics applications. Several series of high quality MBE-grown (Zn,Mn)Se-samples samples were available. (orig.)

  17. A study of low-cost adsorbent materials for removing Cr(VI from aqueous waste effluent

    Directory of Open Access Journals (Sweden)

    Claudia Vargas-Niño

    2011-01-01

    Full Text Available  The present paper shows very high potential for two types of solid (a commercial alumina and material obtained by composting, i.e. matured compost on Cr(VI adsorption/elimination in aqueous solution using a concentration range close to those previously detected in waste-water from Colombian industries. Both had important properties for eliminating Cr(VI, the compost being more important as it represents low-cost material. Optimal conditions for chromium adsorption on alumina and compost were established. Initial Cr(VI alumina concentration was 10 mgL-1, with 100 mL/g volume of solution per adsorbent mass, pH=2.0, 1 hour equilibrium time and 150 rpm stirring. For compost, initial Cr(VI concentration was = 3 mg L-1, 50 mL/g volume of solution per adsorbent mass, pH=2.5, 3 hour equilibrium time and 150 rpm stirring. The experiments showed that compost adsorption properties could be enhanced by adding small quantities of alumina. Compost could thus be chosen as a promising material for use in bioremediation chromium-containing waste water in a management programme for using solid waste in for minimising environmental impact.  

  18. A study of nanostructured gold modified glassy carbon electrode for the determination of trace Cr(VI)

    Indian Academy of Sciences (India)

    Benzhi Liu; Liyuan Lu; Min Wang; Yanqin Zi

    2008-09-01

    A nanostructured gold modified glassy carbon electrode (Aunano/GCE) was employed for the determination of trace chromium(VI). To prepare Aunano/GCE, the GCE was immersed into KAuCl4 solution and electrodeposition was conducted at the potential of -0.4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles were deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analysed to ensure that common interference in the determination of chromium(VI) by square wave voltammetry, do not influence the electrochemical response of the latter element. The results show that this method allows for Cr(VI) determinations with a much lower detection limit (0.01 g L-1) in the presence of excess of Cr(III) than the commonly used diethylenetriammine pentaacetic acid (DTPA) method. The method was applied to determine levels of chromium(VI) in tap water and sewage water.

  19. Time-resolved optical studies of wide-gap II-VI semiconductor heterostructures

    Science.gov (United States)

    Wang, Hong

    ZnSe and ZnSe-based quantum well and superlattice structures are potential candidates for light emitting devices and other optical devices such as switches and modulators working in the blue-green wavelength range. Carrier dynamics studies of these structures are important in evaluating device performance as well as understanding the underlying physical processes. In this thesis, a carrier dynamics investigation is conducted for temperature from 77K to 295K on CdZnSSe/ZnSSe single quantum well structure (SQW) and ZnSe/ZnSTe superlattice fabricated by molecular beam epitaxy (MBE). Two experimental techniques with femtosecond time resolution are used in this work: up-conversion technique for time- resolved photoluminescence (PL) and pump-probe technique for time-resolved differential absorption studies. For both heterostructures, the radiative recombination is dominated by exciton transition due to the large exciton binding energy as a result of quantum confinement effect. The measured decay time of free exciton PL in CdZnSSe/ZnSSe SQW increases linearly with increasing temperature which agrees with the theoretical prediction by considering the conservation of momentum requirement for radiative recombination. However, the recombination of free carriers is also observed in CdZnSSe/ZnSSe SQW for the whole temperature range studied. On the other hand, in ZnSe/ZnSTe superlattice structures, the non- radiative recombination processes are non-negligible even at 77K and become more important in higher temperature range. The relaxation processes such as spectral hole burning, carrier thermalization and hot-carrier cooling are observed in ZnSe/ZnSTe superlattices at room temperature (295K) by the femtosecond pump-probe measurements. A rapid cooling of the thermalized hot- carrier from 763K to 450K within 4ps is deduced. A large optical nonlinearity (i.e., the induced absorption change) around the heavy-hole exciton energy is also obtained.

  20. Effect of structure of N,N dialkyl amides on the extraction of U(VI) and Th(IV): a thermodynamic study

    International Nuclear Information System (INIS)

    The temperature effect on the extraction behaviour of U(VI) and Th(IV) from 3 M HNO3 employing 1 M solutions of N,N dialkyl amides with varying alkyl substituents on the Cα atom viz. di(2-ethylhexyl)acetamide (D2EHAA), di(2-ethylhexyl)propionamide (D2EHPRA), di(2-ethylhexyl)isobutyramide (D2EHIBA) and di(2-ethylhexyl)pivalamide (D2EHPVA) in n-dodecane has been investigated. These studies indicate that the extraction reactions of U(VI) and Th(IV) are enthalpy stabilised while the entropy factor counteracts the extraction. An attempt has been made to correlate the thermodynamic parameters with the structure of the extractant molecules. (orig.)

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

    OpenAIRE

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

    2013-01-01

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

  2. Study of Mo (VI Removal from Aqueous Solution: Application of Different Mathematical Models to Continuous Biosorption Data

    Directory of Open Access Journals (Sweden)

    Fatemeh Kafshgari

    2013-01-01

    Full Text Available Molybdenum (VI biosorption process was investigated by marine algae Cystoseria indica pretreated with 0.1 M CaCl2 solution in a packed bed column. The biosorbent was characterized by FTIR, BET and SEM analyses. The results showed that Mo (VI ions should be chelated with the hydroxyl, carboxyl and amine groups of the biomass. The effects of inlet metal concentration and flow rate on biosorption process were investigated and the experimental breakthrough curves were obtained. Results showed that the maximum biosorption capacity of Ca-pretreated C. indica for Mo (VI was found to be 18.32 mg/g at optimum flow rate of (1.4 mL/min. The controlled-rate step shifted from external to internal mass transfer limitations, as the flow rate increased. Also, it was observed that the breakthrough and exhaustion time decreased from 17.14 hr to 9.05 hr and from 0.006 h to 0.002 hr respectively, with the increase of flow rate from 0.7 to 2.1 ML/min. The increase in the initial concentration of Mo (VI solution from 30 to 95 ml min-1 increases the adsorption capacity from 18.32 to 30.19 mg/g and decreases the percentage of Mo (VI removal from 61 to 38%. Also, the treated volume was the greatest (1.42 L at the lowest inlet concentration. Column data obtained under different conditions were described using the Thomas, Yoon and Nelson, Yan and Belter models. The breakthrough curve predictions by Belter model were found to be very satisfactory.

  3. Study of Mo (VI removal from aqueous solution: application of different mathematical models to continuous biosorption data

    Directory of Open Access Journals (Sweden)

    Kafshgari Fatemeh

    2013-01-01

    Full Text Available Abstract Molybdenum (VI biosorption process was investigated by marine algae Cystoseria indica pretreated with 0.1 M CaCl2 solution in a packed bed column. The biosorbent was characterized by FTIR, BET and SEM analyses. The results showed that Mo (VI ions should be chelated with the hydroxyl, carboxyl and amine groups of the biomass. The effects of inlet metal concentration and flow rate on biosorption process were investigated and the experimental breakthrough curves were obtained. Results showed that the maximum biosorption capacity of Ca-pretreated C. indica for Mo (VI was found to be 18.32 mg/g at optimum flow rate of (1.4 mL/min. The controlled-rate step shifted from external to internal mass transfer limitations, as the flow rate increased. Also, it was observed that the breakthrough and exhaustion time decreased from 17.14 hr to 9.05 hr and from 0.006 h to 0.002 hr respectively, with the increase of flow rate from 0.7 to 2.1 ML/min. The increase in the initial concentration of Mo (VI solution from 30 to 95 ml min-1 increases the adsorption capacity from 18.32 to 30.19 mg/g and decreases the percentage of Mo (VI removal from 61 to 38%. Also, the treated volume was the greatest (1.42 L at the lowest inlet concentration. Column data obtained under different conditions were described using the Thomas, Yoon and Nelson, Yan and Belter models. The breakthrough curve predictions by Belter model were found to be very satisfactory.

  4. VI. A study of leaching of 14C-labelled coumaphos in soil columns

    International Nuclear Information System (INIS)

    Leaching of 14C-labelled coumaphos from aged dipping vat suspension was studied in 50 cm long x 20 cm diameter cores of undisturbed soil in mini-lysimeters. The vat suspension, previously aged for 6 months, was deposited to the top of the columns in lysimeters which were kept outdoors. The leachate was periodically collected over 6 months and analysed for radioactivity. At the end of this period soil columns were cut in 10 cm sections and the radioactivity present in each section was determined by combustion of homogenized soil samples. Radioactivity was also extracted from the soil samples with methanol by using Soxhlet apparatus and the extract analysed for total radioactivity. The extract was analysed by TLC for coumaphos and degradation products. No radioactivity was detected in the leachate. Most of the radioactivity (91-100%) was found in the top 10 cm section of the soil, indicating that coumaphos in the discarded waste does not leach below the top section of the soil and does not have high potential to contaminate ground water. Of the total radioactivity in the top section 62-75% was extractable and rest remained soil bound. The extractable radioactivity was coumaphos and no degradation products were detected. (author)

  5. A kinetic study of the complexation reaction between the dioxoururanium(VI) ion and arsenazo III

    International Nuclear Information System (INIS)

    The rates of formation of the 1:1 complexes between the aquo UO22+ ion and Arsenazo III were determined in 2.0 M perchloric acid solutions. The kinetic data are consistent with a first-order approach to equilibrium due to the concentration conditions under which the reaction was studied. Rate and activation parameters for the forward reaction at 25.0deg C are kf=2.14 ± (0.08)x105 M-1 sec-1, ΔH*f=30.1 ± (6.0) kJ/mol and ΔS*f=-42.2 ± (20.2) J/molxK, respectively. For the corresponding reverse reaction at 25.0deg C, kr=8.86 ± (0.44) sec-1, ΔH*r=48.2 ± (0.1) kJ/mol and ΔS*r=-65.3 ± (4.1) J/molxK. Equilibrium parameters are used to calculate at 25deg C, ΔG0=-25.0 ± (5.3) J/mol, ΔH0=-18.1 ± (0.3) kJ/mol, and ΔS0=23.1 ± (10.6) J/molxK. (orig.)

  6. [Neurotoxicity of chemical substances in the workplace. VI. Longitudinal study of persons occupationally exposed to mercury].

    Science.gov (United States)

    Triebig, G; Grobe, T; Saure, E; Schaller, K H; Weltle, D; Valentin, H

    1984-01-01

    A longitudinal study was performed on eleven persons, who had been chronically exposed to mercury (Hg) (3 to 31 years, median 5 years) in 1977, 1980 resp., and 1982. During their work in a chemical plant they had had contact to elemental Hg and various inorganic as well as organic mercury compounds. The main purpose of the investigation was the evaluation of possible adverse effects to the nervous system caused by mercury. The internal Hg-exposure was measured by mercury analysis in blood (Hg-B) and in urine (Hg-U). Furthermore "time-weighted average" levels were calculated on the basis of former Hg-determinations from 1974 to 1982. For Hg-B these values ranged between 26 and 104 microgram/dl (median 42 microgram/l) and for Hg-U between 73 and 434 microgram/g creatinine (median 233 microgram/g creatinine) (upper normal levels: Hg-B: 5 microgram/l; Hg-U: 5 microgram/g creatinine). The determination of the peripheral nerve conduction velocities (NLG) of motor and sensory fibers as well as the registration of somatosensory-evoked potentials (SEP) revealed no pathological results, except one borderline case. The NLG- and SEP-values did not significantly differ from those of non exposed persons or from those of former NLG-determinations. No correlations were found between indicators of Hg-exposure and neurophysiological parameters regarding dose-effect-relationship. Statistical differences resulted in the time-dependent test of the psychological test battery performed in comparison to age-matched control persons of equal socio-economous status. In additional, significant relationships were calculated between Hg-exposure and these tests. Considering the inter- and intraindividual variations of the psychological test results, there were no substantial alterations in the total findings over the observed period except for one case. Workers with Hg-exposure below the current BAT-values (Hg-B 50 microgram/l, Hg-U 200 microgram/l) showed no pathological findings in the

  7. Cu vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Andrzej; Pettyn

    2000-01-01

    LA DEKKVARA LEOIONOMi havas por vi surprizon—Barbara:Bonan matenon!—Petro:Bonan matenon,mia kara!—B Mi havas pot vi surprizon.—P:Viiam havas pot mi surprizojn.—B:Sed hodiaǔ mi parolas treserioze."Okaze de via naskitago ak-

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

    Science.gov (United States)

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

    2011-05-01

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

  9. Room temperature synthesis of hydrated nickel(III) oxide and study of its effect on Cr(VI) ions removal and bacterial culture

    Science.gov (United States)

    Dey, Sayan; Bhattacharjee, Swarupananda; Bose, Raj Shekhar; Ghosh, Chandan Kr.

    2015-06-01

    Cr(VI) ion is a toxic inorganic affluent that causes carcinogenic effects on the human body. Another problem that requires immediate attention is the fouling of water borne metal surface by micro-organisms. The present study aims to suggest the synthesis of Ni2O3·H2O nanoparticles and to investigate its heavy metal adsorption capacity and bacteriotoxicity in order to address the current global problems. Stable Ni2O3·H2O nanoparticles having various particle sizes were synthesized using active halogenation of nickel(II) precursor at different temperatures. Phase purity was investigated by X-ray diffraction technique. Due to high surface area, surface heterogeneity and surface polarity, they show excellent adsorption affinity (up to 73.9 % removal capacity) of heavy metal ions like Cr(VI). Adsorption isotherms (Freundlich and Langmuir) are plotted for them. Kinetics of the adsorption process reveals it to be pseudo-first-order kinetic in nature. They are also found to be fairly toxic to bacterial subcultures. Maximum value of the minimum inhibitory concentration and minimum bactericidal concentration were found to be ~0.54 and 0.58 mg/l for particles synthesized at 70 °C. It was observed that Cr(VI) adsorption highly depends on the surface heterogeneity, while the bactericidal effect depends on the size of the nanoparticles so-prepared. Hence, the prepared particles could be used as a potential material for Cr(VI) ion removal and as an antifouling agent.

  10. Interaction of U(VI) with Äspö diorite: A batch and in situ ATR FT-IR sorption study

    International Nuclear Information System (INIS)

    Highlights: • The composition of Äspö groundwater is the key parameter controlling speciation and mobility of U(VI) in the environment. • Formation of Ca2UO2(CO3)3(aq) in Äspö groundwater is spectroscopically confirmed. • This complex causes a low sorption affinity of U(VI) to diorite and stabilizes U(VI) against reduction. - Abstract: Pristine diorite drill cores, obtained from the Äspö Hard Rock Laboratory (HRL, Sweden), were used to study the retention properties of fresh, anoxic crystalline rock material towards the redox-sensitive uranium. Batch sorption experiments and spectroscopic methods were applied for this study. The impact of various parameters, such as solid-to-liquid ratio (2–200 g/L), grain size (0.063–0.2 mm, 0.5–1 mm, 1–2 mm), temperature (room temperature and 10 °C), contact time (5–108 days), initial U(VI) concentration (3 × 10−9 to 6 × 10−5 M), and background electrolyte (synthetic Äspö groundwater and 0.1 M NaClO4) on the U(VI) sorption onto anoxic diorite was studied under anoxic conditions (N2). Comparatively, U(VI) sorption onto oxidized diorite material was studied under ambient atmosphere (pCO2 = 10−3.5 atm). Conventional distribution coefficients, Kd, and surface area normalized distribution coefficients, Ka, were determined. The Kd value for the U(VI) sorption onto anoxic diorite in synthetic Äspö groundwater under anoxic conditions by investigating the sorption isotherm amounts to 3.8 ± 0.6 L/kg which corresponds to Ka = 0.0030 ± 0.0005 cm (grain size 1–2 mm). This indicates a weak U sorption onto diorite which can be attributed to the occurrence of the neutral complex Ca2UO2(CO3)3(aq) in solution. This complex was verified as predominating U species in synthetic Äspö groundwater by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Compared to U sorption at room temperature under anoxic conditions, U sorption is further reduced at decreased temperature (10 °C) and under ambient

  11. LABORATORY STUDY FOR THE REDUCTION OF CHROME (VI) TO CHROME (III) USING SODIUM METABISULFITE UNDER ACIDIC CONDITIONS

    International Nuclear Information System (INIS)

    This report describes the results from RPP-PLAN-32738, 'Test Plan for the Effluent Treatment Facility to Reduce Chrome(VI) to Chrome(I1I) in the Secondary Waste Stream', using sodium metabisulfite. Appendix A presents the report as submitted by the Center for Laboratory Sciences (CLS) to CH2M HILL Hanford Group, Inc. The CLS carried out the laboratory effort under Contract Number 21065, release Number 30. This report extracts the more pertinent aspects of the laboratory effort

  12. Cranial mononeuropathy VI

    Science.gov (United States)

    ... may reduce the risk by controlling their blood sugar. Alternative Names Abducens paralysis; Abducens palsy; Lateral rectus palsy; Vith nerve palsy; Cranial nerve VI palsy Images Central nervous system and peripheral nervous system References Rucker JC. Cranial ...

  13. Analytical studies of plutonium containing solutions by Laser-Raman-Spectroscopy (LRS) with special regard to the Pu(IV)-Ru(III)-HNO3 and Pu(VI)-H2O2-reactions

    International Nuclear Information System (INIS)

    In spent nuclear fuel reprocessing by the Purex process it is attempted to apply as far as possible automated analytical equipment, which is directly coupled to the process stream. This paper describes the optical coupling of Laser-Raman-Spectroscopy (LRS) with commercial fiber optics in a 900 geometry to a test apparatus within a glovebox. It was possible to show that in nitric acid solutions Pu(VI), Pu(V), U(VI), and nitrate can be detected simultaneously without interference. The suitability of LRS for the Pu(VI) and Pu(V) detection was demonstrated by the example of two reactions, namely the oxidation of Pu(IV) to Pu(VI) in nitric acid solution in the presence of Ru(NO)-complexes and the reduction of Pu(VI) to Pu(V) by H2O2. In the study of the Pu(IV)-Ru(NO)-reaction the temperature and the concentrations of the individual reactants were varied and in addition the concentration of F-, which as a strong complexing agent for Pu(IV) exerts a considerable influence on the reaction rate. The results of these experiments were used to estimate the reaction orders for the individual reactants by the method of initial rates. The course of the reduction of Pu(VI) to Pu(V) with H2O2 was studied for different temperatures, pH-values and F--concentrations. (orig./RB)

  14. Comparative Study on Biosorption of Zn(II), Cu(II) and Cr(VI) from Textile Dye Effluent Using Sawdust and Neem Leaves Powder

    OpenAIRE

    Gopalakrishnan, K; Manivannan, V.; T. Jeyadoss

    2010-01-01

    The performance of the low cost adsorbents such as sawdust and neem leaves powder in removing the heavy metals like Zn(II), Cu(II) and Cr(VI) from textile dye effluent are reported. Adsorbent dosage, pH and contact time were taken as parameters for biosorption study. Removal of heavy metal ions from the textile dye effluent increases with increase in adsorbent dosage. The influence of pH and contact time was maximum for removal of heavy metal ions. The presence of the decreased heavy metal to...

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

    Science.gov (United States)

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

    2004-01-01

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

  16. Genetic risks from radiation: recent assessments by the BEIR and UNSCEAR Committees and suggestions as to how future research can improve such estimates

    International Nuclear Information System (INIS)

    Recently two widely-recognized committees, namely the UNSCEAR and BEIR Committees, have reevaluated their estimates of genetic risks from radiation. Their estimates for gene mutations are based on two different approaches, one being the doubling-dose approach and the other being a new direct approach based on an empirical determination of the amount of dominant induced damage in the skeletons of mice in the first generation following irradiation. The estimates made by these committees are in reasonably good agreement and suggest that the genetic risks from present exposures resulting from nuclear power production are small. There is room for much improvement in the reliability of the risk estimates. The relatively new approach of measuring the amount of induced damage to the mouse skeleton shows great promise of improving knowledge about how changes in the mutation frequency affect the incidence of genetic disorders. Such findings may have considerable influence on genetic risk estimates for radiation and on the development of risk estimates for other less-well-understood environmental mutagens

  17. Study of solvent effects on complex formation of tungsten (VI) with ethylenediaminediacetic acid in aqueous solutions of propanol

    International Nuclear Information System (INIS)

    Spectrophotometric and potentiometric techniques were used to determine the formation constants of the species formed in the systems H+ + W(VI) + ethylenediaminediacetic acid and H+ + ethylenediaminediacetic acid in aqueous solutions of propanol at 25 deg C and constant ionic strength 0.1 mol dm-3 of sodium perchlorate. The composition of the complex was determined by the continuous variations method. It was shown that tungsten (VI) forms a mononuclear 1 : 1 complex with ethylenediaminediacetic acid of the type WO3L3- at -log[H+] = 5.8. The formation constants in various media were analyzed in terms of Kamlet and Taft's parameters. Solvents have been parameterized by scales of dipolarity/polarizability π*, hydrogen-bond donor strength α, and hydrogen-bond acceptor strength β. Linear dependence on these solvent parameters are used to correlate and predict a wide variety of solvent effects, as well as to provide an analysis of them. Linear relationships are observed when logKS is plotted versus π*. Finally, the results are discussed in terms of the effect of solvent on complexation

  18. Study of uranium(VI) and radium(II) sorption at trace level on kaolinite using a multisite ion exchange model.

    Science.gov (United States)

    Reinoso-Maset, Estela; Ly, Jacques

    2016-06-01

    Uranium and the long-lived decay product radium-226 are abundantly present in mine wastes produced during uranium extraction activities. In the case of release to the surrounding environment, these radionuclides are at trace level compared to groundwater solutes, and the presence, content and properties of clay minerals in the host environment influence the extent of radionuclide sorption and, in turn, migration. Since clays are known to have the distinctive property of retaining ions, the aim of this work was to study the sorption of trace U(VI) and Ra(II) on a common phyllosilicate mineral, kaolinite, in the presence of excess K, a common groundwater cation, in order to obtain a thermodynamic database that describes the ion exchange equilibria occurring at the mineral-solution interface. Following a detailed experimental protocol using chemical and radiochemical analytical techniques, batch experiments over a wide pH range (from 2 to 11) and fixed concentration (ca. 10(-9) M), and additional adsorption isotherms at two different solution pH (6.2 and 10.4) over a concentration range (10(-10) to 10(-4) M) were carried out to measure the distribution coefficient (Kd) of U(VI) and Ra(II) sorption on kaolinite. The experimental sorption data was processed according to a general multisite sorbent/multispecies sorbate ion exchange model, which allowed deducing the charge of adsorbed species and the stoichiometry of the associated adsorption equilibria on kaolinite's surface sites. Aqueous speciation calculations predicted Ra(II) as Ra(2+) over the working pH range, and its adsorption curves and isotherms were explained using three sorption sites. Adsorption of U(VI) occurred on four sorption sites and was governed by its solution speciation, with positively charged hydroxylated (UO2(2+) and UO2(OH)(+)) and silicate (UO2(H3SiO4)(+)) species being adsorbed between pH 2 and 6, whereas its negatively charged forms (UO2(OH)3(-) and UO2(OH)4(2-)) dominated U(VI) sorption at

  19. Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A first-principles study

    CERN Document Server

    Qin, Guangzhao; Fang, Wu-Zhang; Zhang, Li-Chuan; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming; Su, Gang

    2016-01-01

    New class two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport property is one of the fundamental physical parameters. In this paper, we systematically investigated the phonon transport properties of 2D orthorhombic IV-VI compounds of $GeS$, $GeSe$, $SnS$ and $SnSe$ by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite the similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as group velocity, Young's modulus and lattice thermal conductivity ($\\kappa$), etc. Especially, the $\\kappa$ along the zigzag and armchair directions of monolayer $GeS$ shows the strongest anisotropy while monolayer $SnS$ and $SnSe$ shows an almost isotropy in p...

  20. Study of epidemiological risk of lung cancer in Mexico due indoor radon exposure

    Science.gov (United States)

    Ángeles, A.; Espinosa, G.

    2014-07-01

    In this work the lifetime relative risks (LRR) of lung cancer due to exposure to indoor 222Rn on the Mexican population is calculated. Cigarette smoking is the number one risk factor for lung cancer (LC), because that, to calculate the number of cases of LC due to exposure to 222Rn is necessary considers the number of cases of LC for smoking cigarette. The lung cancer mortality rates published by the "Secretaría de Salud" (SSA), the mexican population data published by the "Consejo Nacional de Población" (CONAPO), smoking data in the mexican population, published by the "Comisión Nacional Contra las Adicciones" (CONADIC), the "Organización Panamericana de la Salud" (OPS) and indoor 222Rn concentrations in Mexico published in several recent studies are used. To calculate the lifetime relative risks (LRR) for different segments of the Mexican population, firstly the Excess Relative Risk (ERR) is calculated using the method developed by the BEIR VI committee and subsequently modified by the USEPA and published in the report "EPA Assessment of Risks from Radon in Homes". The excess relative risks were then used to calculate the corresponding lifetime relative risks, again using the method developed by the BEIR VI committee. The lifetime relative risks for Mexican male and female eversmokers and Mexican male and female never-smokers were calculated for radon concentrations spanning the range found in recent studies of indoor radon concentrations in Mexico. The lifetime relative risks of lung cancer induced by lifetime exposure to the mexican average indoor radon concentration were estimated to be 1.44 and 1.40 for never-smokers mexican females and males respectively, and 1.19 and 1.17 for ever-smokers Mexican females and males respectively. The Mexican population LRR values obtained in relation to the USA and Canada LRR published values in ever-smokers for both gender are similar with differences less than 4%, in case of never-smokers in relation with Canada

  1. Study of molybdenum (VI) complexation and precipitation by zirconium (IV) in strongly acid medium. Application to nuclear spent fuel dissolution; Etude de la complexation et de la precipitation du molybdene (VI) par le zirconium (IV) en milieu tres acide. Application a la dissolution du combustible nucleaire irradie

    Energy Technology Data Exchange (ETDEWEB)

    Esbelin, E

    1999-07-01

    These last years the formation of solid deposits has been observed in the dissolution workshops of the La Hague plant. A sample of the solid was withdrawn for expertise: molybdenum and zirconium are the two major components of the solid, identified as zirconium molybdate. This thesis consisted in the approach of the mechanisms in solution liable to induce precipitate formation. After a bibliographical overview on the chemistry of Mo(VI) in highly acidic solution, this system was studied by absorption spectrophotometry in perchloric medium. The implication of two major forms of Mo(VI) in a dimerization equilibrium was confirmed by this way and by {sup 95}Mo NMR. The principal parameters governing this equilibrium were identified. It is thus shown that the molybdenum dimerization reaction is exothermic. Disturbance of the Mo(VI) system in highly acidic solution by Zr(IV) was also studied. In a restricted experimental field, for which 'conventional' exploitation methodologies had to be adapted to the system, a main complex of stoichiometry 1:1 between Mo(VI) and Zr(IV) was found. The precipitation study of Mo(VI) by Zr(IV) under conditions close to those of the dissolution medium of nuclear spent fuel was undertaken. The main parameters which control precipitation kinetics were identified. The results obtained reveal that precipitation is controlled by a single macroscopic process and therefore can be described by a single equation. The solid obtained is composed of only one phase presenting a Mo:Zr non-stoichiometry when compared to the theoretical formula ZrMo{sub 2}O{sub 7}(OH){sub 2},2H{sub 2}O. At last, on the basis of the research results, a descriptive mechanism of the system is proposed in which intervenes a 1:1 intermediate complex, much more soluble than a probable 2:1 precipitation precursor. (author)

  2. Enhanced sequestration of Cr(VI) by nanoscale zero-valent iron supported on layered double hydroxide by batch and XAFS study.

    Science.gov (United States)

    Sheng, Guodong; Hu, Jun; Li, Hui; Li, Jiaxing; Huang, Yuying

    2016-04-01

    Herein, the reduction of nanoscale zero-valent iron (NZVI) and adsorption of layered double hydroxides (LDH) to sequester Cr(VI) were well combined by the immobilization of NZVI onto LDH surface (NZVI/LDH). The characterization results revealed that LDH decreased NZVI aggregation and thus increased Cr(VI) sequestration. The batch results indicated that Cr(VI) sequestration by NZVI/LDH was higher than that of NZVI, and superior to the sum of reduction and adsorption. The LDH with good anion exchange property allowed the adsorption of Cr(VI), facilitating interfacial reaction by increasing the local concentration of Cr(VI) in the NZVI vicinity. X-ray absorption near edge structure (XANES) results indicated that Cr(VI) was almost completely reduced to Cr(III) by NZVI/LDH, but Cr(VI) was partly reduced to Cr(III) by NZVI with a trace of Cr(VI) adsorbed on corrosion products. The coordination environment of Cr from extended X-ray absorption fine structure (EXAFS) analysis revealed that LDH could be a good scavenger for the insoluble products produced during reaction. So, the insoluble products on NZVI could be reduced, and its reactivity could be maintained. These results demonstrated that NZVI/LDH exhibits multiple functionalities relevant to the remediation of Cr(VI)-contaminated sites. PMID:26807943

  3. Skal vi danse apokalypso?

    DEFF Research Database (Denmark)

    Hansen, Kim Toft

    2009-01-01

    Den danske forfatter Lene Andersen satte sig for år tilbage for at sætte verden stævne. Det er siden blevet til storværket Baade Og, der nu tager de sidste skridt hen mod sin afslutning. Værket er skrevet under pseudonymet Jesper Knallhatt, og det næstsidste bind Torsdag er netop udkommet. De før...... formaningerne, ender nytestamentelige dommedagsprofetier med at gå i opfyldelse. Skal vi danse apokalypso, eller skal vi rent faktisk tage de verdslige problemer seriøst op til overvejelse?...

  4. Genetics Home Reference: mucopolysaccharidosis type VI

    Science.gov (United States)

    ... Understand Genetics Home Health Conditions mucopolysaccharidosis type VI mucopolysaccharidosis type VI Enable Javascript to view the expand/ ... boxes. Print All Open All Close All Description Mucopolysaccharidosis type VI (MPS VI), also known as Maroteaux- ...

  5. Electrochemical studies of U(VI)/U(IV) redox reaction in 1M H{sub 2}SO{sub 4} at single-walled carbon nanotubes (SWCNTs) modified gold (Au) electrode

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ruma; Aggarwal,S.K. [Bhabha Atomic Reseach Centre, Trombay, Mumbai (India). Fuel Chemistry Div.

    2013-08-01

    Electrochemistry of U(VI)/U(IV) couple in 1 M H{sub 2}SO{sub 4} was studied on bare and SWCNT modified gold (Au) electrodes by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The gold electrode modified with single-walled carbon nanotubes (SWCNTs-Au) was characterized by scanning electron microscopy (SEM). Electrocatalysis of U(VI)/U(IV) redox reaction was observed on SWCNT-Au. The lower charge transfer resistance at SWCNT-Au promoted the rate of electron transfer reaction of U(VI)/U(IV) couple. These results are interesting to develop electroanalytical methodologies for uranium determination using SWCNT modified electrodes. To the best of our knowledge, this is the first study on the electrocatalysis of uranium on SWCNT modified electrode. (orig.)

  6. Studies on the sorption behaviour of arsenazo-I, U(Vi) and Th(IV) species from aqueous solutions of arsenazo-I on different types of ion exchangers

    International Nuclear Information System (INIS)

    Three different types of ion exchangers namely dowex-50 w x 8, Ag-2 x 8 and chelex-100 are used to study the sorption behaviour of Th(IV) and U(Vi) from solutions of arsenazo-I. The sorption behaviour of arsenazo-I itself is also studied. possible species sorbed on these resins or present in solutions of U(Vi)-and Th(IV)-arsenazo-I at different concentration and at different hydrogen ion concentrations are identified. From the obtained data, optimal conditions for separating the two elements are recommended. The possibility of individual concentration of Th(IV) and U(Vi) as coloured arsenazo-I complexes on Ag-2 x 8 is evaluated. 5 figs., 1 tab

  7. u vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Andrzej; Pettyn

    1999-01-01

    LA DEKTRIA LECIONOMi preferas bonan glaciaonBarbara kaj Danuta faris aetojnkaj nun ili estas en kafejo kaj interparo-las.—Danuta:Kion vi trinkos, Banjo?—Barbara:Mi ankoraǚ ne scias. Sedmi tre soifas kaj ankaǚ malsatas.—D:Mi ankaǚ devas ion mani. Sed itie en la menuo ne estas manajoj...

  8. Comparative studies on co-extraction of macro amounts of uranium(VI) and plutonium(IV) with N,N-di-n-hexyloctanamide and tri-n-butyl phosphate

    International Nuclear Information System (INIS)

    Co-extraction behaviour of U(VI) and Pu(IV), with emphasis on plutonium extraction, has been studied in the presence of macro amounts of U(VI) and Pu(IV) from aqueous nitric acid media employing 1 M solutions of N,N-di-n-hexyloctanamide (DHOA) and tri-n-butyl phosphate (TBP) in n-dodecane. Results indicate that plutonium concentrations in the aqueous raffinates with DHOA are distinctly lower as compared to TBP over the entire range of acidity studied. (author)

  9. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  10. A study on selective precipitation of U(VI) by hydrophilic cyclic urea derivatives for development of a reprocessing system based on precipitation method

    International Nuclear Information System (INIS)

    Selective precipitation ability of 2-imidazolidone (EU) and tetrahydro-2-pyrimidinone (PU) for U(VI) species in HNO3 solutions containing U(VI), U(IV) (simulant of Pu(IV)), and simulated fission products (FPs) was investigated. As a result, it was found that these compounds precipitate almost quantitatively U(VI) as UO2(NO3)2L2 (L = EU, PU) from 3.0 M HNO3 solution. In contrast, these urea derivatives form neither solid precipitates nor oily products with U(IV) in HNO3 solutions containing only U(IV) species and even in U(VI)-U(IV) admixture system. Therefore, the separation of U(VI) from U(IV) was demonstrated to be achieved in use of EU and PU. Furthermore, EU and PU are capable to remove most of simulated FPs[Sr(II), Ru(III), Rh(III), Re(VII) La(III), Ce(III), Pr(III), Nd(III), and Sm(III)] from U(VI) to give their decontamination factors (DFs) higher than 100, while those values of Zr(IV), Mo(VI), Pd(II), and Ba(II) are necessary to be improved in both systems. From these results, it is expected that EU and PU are the promising precipitants for selective separation of U(VI) from HNO3 solutions dissolving spent FBR fuels. (author)

  11. Interactions between U(VI) and bovine serum albumin

    International Nuclear Information System (INIS)

    Interest in bio-toxicology of uranium resulting from its radioactive heavy metal property has been growing enormously in recent years. The interactions between uranium(VI) [U(VI)] and bovine serum albumin (BSA) at physiological pH were studied by spectroscopic methods. Fluorescence results revealed the formation of BSA-U(VI) complex, the binding constants as well as the number of binding sites were determined. In particular, the effects of U(VI) binding on the secondary structures of BSA were examined by means of Fourier transformation infrared spectroscopy equipped with attenuated total reflection (FT-IR/ATR). It was found that the α-helix component of BSA decreased gradually with increasing concentration of U(VI). In contrast, the β-sheets, turns, and random coil structures all increased correspondingly. Our work would shed light on the possible interaction mechanism between U(VI) and proteins in aqueous solutions. (author)

  12. New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Uygun, Murat, E-mail: muygun@adu.edu.tr [Adnan Menderes University, Kocarl Latin-Small-Letter-Dotless-I Vocational and Training School (Turkey); Feyzioglu, Esra; Oezcal Latin-Small-Letter-Dotless-I skan, Emir; Caka, Mueserref; Ergen, Aygen; Akgoel, Sinan [Ege University, Department of Biochemistry, Faculty of Science (Turkey); Denizli, Adil [Hacettepe University, Department of Chemistry, Faculty of Science (Turkey)

    2013-08-15

    The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO{sub 3} solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m{sup 2}/g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities.

  13. A FEASIBILITY STUDY ON USING ViSP’S 3D MODEL-BASED TRACKER FOR UAV POSE ESTIMATION IN OUTDOOR ENVIRONMENTS

    Directory of Open Access Journals (Sweden)

    J. Li-Chee-Ming

    2015-08-01

    Full Text Available This paper presents a novel application of the Visual Servoing Platform’s (ViSP for small UAV pose estimation in outdoor environments. Given an initial approximation for the camera position and orientation, or camera pose, ViSP automatically establishes and continuously tracks corresponding features between an image sequence and a 3D wireframe model of the environment. As ViSP has been demonstrated to perform well in small and cluttered indoor environments, this paper explores the application of ViSP for UAV mapping of outdoor landscapes and tracking of large objects (i.e. building models. Our presented experiments demonstrate the data obtainable by the UAV, assess ViSP’s data processing strategies, and evaluate the performance of the tracker.

  14. Plasmon resonance enhanced photocatalysis under visible light with Au/Cu-TiO2 nanoparticles: Removal Cr (VI) from water as a case of study

    KAUST Repository

    Gondal, M. A.

    2013-12-01

    Gold modified copper doped titania (Au/Cu:TiO2) nanoparticles were synthesized by a modified sol gel method and characterized using XRD, optical and TEM based techniques. The as-prepared material contained anatase phase particles with quasi-spherical morphology, showing enhanced absorption in the visible region and low photoluminescence emission intensity. Photocatalytic reduction of Cr (VI) in aqueous suspension with the Au/Cu:TiO2catalyst under 532 nm laser radiation and a visible broad band lamp source yielded 96% and 45% removal, respectively, without any additives. The enhanced photocatalytic activity can be attributed to the improved plasmonic effect due to gold modification and the expanded visible absorption due to copper doping. Moreover a comparative study of the material properties and catalytic activity of TiO2, Cu-TiO2and Au/Cu-TiO2 was carried out. © 2013 by American Scientific Publishers.

  15. Solvent extraction studies on Th(IV) and U(VI) using polyethylene glycol (PEG) based aqueous biphasic system (ABS) with 18-crown-6

    International Nuclear Information System (INIS)

    Extraction of Th(IV) and U(VI) using PEG-2000/(NH4)2SO4 (40% w/w of each) aqueous biphasic system (ABS) with 18-crown-6 (18-C-6) as the extractant was studied at four fixed temperatures in the range 288 to 318 K. The species extracted were identified to be [Th . (18-C-6)](SO4)2 and [UO2 . (18-C-6)]SO4 by the slope ratio method. The equilibrium constant (K) was evaluated for the extraction reactions. The thermodynamic parameters evaluated by the temperature coefficient method at 298 K showed that the reaction is favoured by decrease in enthalpy and counteracted by decrease in entropy. The large decrease in the enthalpy values was attributed to direct bonding of crown ether to the central metal atom (i.e. the formation of inner sphere complex). (orig.)

  16. Optical phonon modes of III-V nanoparticles and indium phosphide/II-VI core-shell nanoparticles: A Raman and infrared study

    Science.gov (United States)

    Manciu, Felicia Speranta

    The prospects for realizing efficient nanoparticle light emitters in the visible/near IR for communications and bio-medical applications have benefited from progress in chemical fabrication of nanoparticles. III-V semiconductor nanopaticles such as GaP and InP are promising materials for the development of "blue" and "green" emitters, respectively, due to their large effective bandgaps. Enhanced emission efficiency has been achieved for core-shell nanoparticles, since inorganic shell materials increase electronic tunability and may decrease surface defects that often occur for nanoparticles capped with organic molecules. Also, the emission wavelength of InP nanoparticle cores can be tuned from green to red by changing the shell material in InP/II-VI core-shell nanoparticles. Investigations of phonon modes in nanocrystals are of both fundamental and applied interest. In the former case the optical phonon modes, such as surface/interface modes, are dependent on the nanoparticle dimensions, and also can provide information about dynamical properties of the nanoparticles and test the validity of various theoretical approaches. In the latter case the vibronic properties of nanoparticle emitters are controlled by confined phonons and modifications of the electron-phonon interaction by the confinement. Thus, the objective of the present thesis is the detailed study of the phonon modes of III-V nanoparticles (GaP and InP) and InP/II-VI core-shell nanoparticles by IR absorption and Raman scattering spectroscopies, and an elucidation of their complex vibrational properties. With the exception of three samples (two GaP and one InP), all samples were synthesized by a novel colloidal chemistry method, which does not requires added surfactant, but rather treatment of the corresponding precursors in octadecene noncoordinative solvent. Sample quality was characterized by ED, TEM and X-ray diffraction. Based on a comparison with a dielectric continuum model, the observed features

  17. Organophosphinic, phosphonic acids and their binary mixtures as extractants for molybdenum(VI) and uranium(VI) from aqueous HCl media

    International Nuclear Information System (INIS)

    Extraction studies of uranium(VI) and molybdenum(VI) with organophosphoric, phosphinic acid and its thiosubstituted derivatives have been carried out from 0.1-1.0M HCl solutions. The extracted species are proposed to be UO2R2 and MoO2CIR on the basis of slope analysis for uranium(VI) and molybdenum(VI), respectively. The extraction efficiencies of PC-88A, Cyanex 272, Cyanex 301 and Cyanex 302 in the extraction of molybdenum(VI) and uranium(VI) are compared. Synergistic effects have been studied with binary mixtures of extractants. Separation of molybdenum(VI) from uranium(VI) is feasible by Cyanex 301 from 1M HCl, the separation factor logβ being 2.3. (author) 20 refs.; 5 figs.; 14 tabs

  18. A study of low-cost adsorbent materials for removing Cr(VI from aqueous waste effluent Estudio de materiales adsorbentes de bajo costo para remover Cr(VI de efluentes acuosos

    Directory of Open Access Journals (Sweden)

    Castillo Serna Elianna

    2011-05-01

    Full Text Available  

    The present paper shows very high potential for two types of solid (a commercial alumina and material obtained by composting, i.e. matured compost on Cr(VI adsorption/elimination in aqueous solution using a concentration range close to those previously detected in waste-water from Colombian industries. Both had important properties for eliminating Cr(VI, the compost being more important as it represents low-cost material. Optimal conditions for chromium adsorption on alumina and compost were established. Initial Cr(VI alumina concentration was 10 mgL-1, with 100 mL/g volume of solution per adsorbent mass, pH=2.0, 1 hour equilibrium time and 150 rpm stirring. For compost, initial Cr(VI concentration was = 3 mg L-1, 50 mL/g volume of solution per adsorbent mass, pH=2.5, 3 hour equilibrium time and 150 rpm stirring. The experiments showed that compost adsorption properties could be enhanced by adding small quantities of alumina. Compost could thus be chosen as a promising material for use in bioremediation chromium-containing waste water in a management programme for using solid waste in for minimising environmental impact.

     

     

    Uranium(VI) diffusion in low-permeability subsurface materials

    International Nuclear Information System (INIS)

    Uranium(VI) diffusion was investigated in a fine-grained saprolite sediment that was collected from U.S. Department of Energy (DOE) Oak Ridge site, TN, where uranium contamination in groundwater is a major environmental concern. U(VI) diffusion was studied in a diffusion cell with one cell end in contact with a large, air-equilibrated electrolyte reservoir. The pH, carbonate and U(VI) concentrations in the reservoir solution were varied to investigate the effect of solution chemical composition and uranyl speciation on U(VI) diffusion. The rates of U(VI) diffusion were evaluated by monitoring the U(VI) concentration in the reservoir solution as a function of time; and by measuring the total concentration of U(VI) extracted from the sediment as a function of time and distance in the diffusion cells. The estimated apparent rate of U(VI) diffusion varied significantly with pH, with the slowest rate observed at pH 7 as a result of strong adsorptive retardation. The estimated retardation factor was generally consistent with a surface complexation model. Numerical simulations indicated that a species-based diffusion model that incorporated both aqueous and surface complexation reactions was required to describe U(VI) diffusion in the low permeability material under variable geochemical conditions. Our results implied that low permeability materials will play an important role in storing U(VI) and attenuating U(VI) plume migration at circumneutral pH conditions, and will serve as a long-term source for releasing U(VI) back to the nearby aquifer during and after aquifer decontamination. (orig.)

  19. An interdisciplinary knowledge translation intervention in long-term care: Study protocol for the vitamin D and osteoporosis study (ViDOS pilot cluster randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Kennedy Courtney C

    2012-05-01

    Full Text Available Abstract Background Knowledge translation (KT research in long-term care (LTC is still in its early stages. This protocol describes the evaluation of a multifaceted, interdisciplinary KT intervention aimed at integrating evidence-based osteoporosis and fracture prevention strategies into LTC care processes. Methods and design The Vitamin D and Osteoporosis Study (ViDOS is underway in 40 LTC homes (n = 19 intervention, n = 21 control across Ontario, Canada. The primary objectives of this study are to assess the feasibility of delivering the KT intervention, and clinically, to increase the percent of LTC residents prescribed ≥800 IU of vitamin D daily. Eligibility criteria are LTC homes that are serviced by our partner pharmacy provider and have more than one prescribing physician. The target audience within each LTC home is the Professional Advisory Committee (PAC, an interdisciplinary team who meets quarterly. The key elements of the intervention are three interactive educational sessions led by an expert opinion leader, action planning using a quality improvement cycle, audit and feedback reports, nominated internal champions, and reminders/point-of-care tools. Control homes do not receive any intervention, however both intervention and control homes received educational materials as part of the Ontario Osteoporosis Strategy. Primary outcomes are feasibility measures (recruitment, retention, attendance at educational sessions, action plan items identified and initiated, internal champions identified, performance reports provided and reviewed, and vitamin D (≥800 IU/daily prescribing at 6 and 12 months. Secondary outcomes include the proportion of residents prescribed calcium supplements and osteoporosis medications, and falls and fractures. Qualitative methods will examine the experience of the LTC team with the KT intervention. Homes are centrally randomized to intervention and control groups in blocks of variable size using

  1. Thermodynamical analysis of the fission product release in the ORNL VI-3 and VI-5 tests

    International Nuclear Information System (INIS)

    The thermodynamical equilibrium hypothesis has been applied to the tests ORNL (Oak Ridge National Laboratory) VI-3 and VI-5 (Vertical Induction heated), to study fission release products. Irradiated fuel samples were heated under oxidizing (VI-3) and reducing (VI-5) controlled atmosphere. They can be compared to the Vercors 4 and 5 tests. The thermodynamical calculus results of barium and ruthenium fission products release, agree in the lump with measures, whatever the gas phase nature. The strontium release calculus under reducing atmosphere, is largely upper than those measured and correctly evaluated under oxidizing atmosphere. These results confirm those obtained for Vercors 4 and 5 and show the interest of the select model. (A.L.B.)

  2. Structural and electrochemical studies on uranyl(VI) complex with pentadentate Schiff base ligand: A guide to stable uranyl(V)

    International Nuclear Information System (INIS)

    A U(VI) complex with N,N'-disalicylidenediethylenetriaminate (saldien2-) was characterized by single crystal X-ray analysis and X-ray absorption fine structure (XAFS) spectroscopy, and its electrochemical behavior in a DMSO solution was studied. The obtained U(VI)-saldien2- complex recrystallized from DMSO was identified as orthorhombic UVIO2(saldien)·DMSO. All coordination sites in the equatorial plane of UO22+ are occupied by coordinating O and N atoms of saldien2-. Comparing a k3-weighted U LIII-edge EXAFS spectra of UVIO2(saldien) in DMSO and DMF solutions with that in solid state, the molecular structure of UVIO2(saldien) remains even in the solutions. Quasi-reversible redox waves of UVIO2(saldien) were observed at E0' = -1.582 ± 0.005 V vs. Fc/Fc+ (ΔEp = 0.080-0.170 V at v = 0.010-0.500 V·s-1) in DMSO. UV-Vis-NIR absorption spectral change with the electrochemical reduction of UVIO2(saldien) using the spectroelectrochemical technique shows isosbestic points clearly, indicating that the electrochemical reaction of UVIO2(saldien) is only present. Using the absorbance change and the Nernstian equation, the electron stoichiometry in the reduction of UVIO2(saldien) in DMSO was determined as 0.929. This quantity close to unity reveals a redox reaction, UVIO2(saldien) + e- = [UVO2(saldien)]-, i.e., UVIO2(saldien) without unidentate ligands results in the stable U(V) complex, [UVO2(saldien)]-, in DMSO. This U(V) species also shows the characteristic absorption bands of U(V) at 630, 700, 830, 1390, and 1890 nm as well as other U(V) complexes.

  3. u vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Abdrzej; Pettyn

    2000-01-01

    LA DEKSESA LECIONO Oni povas ci tie bone babili Ni trovigas en la restoracio "Fabelo", kie okazas nun la naskigtaga festeno de Petro. —Danuta: "Fabelo" estas tre agrabla. —K: Jes, oni povas ci tie bone mangi kaj ankau bone babili, car la orkestro ne estas tro brua. —D: Ec la plej bona orkestro Renas, kiam gi estas tro brua. —K: Vi pravas. Rigardu, tie en la an

  4. Intelsat VI antenna system

    Science.gov (United States)

    Caulfield, M. F.; Lane, S. O.; Taormina, F. A.

    The antenna system design of a series of five new communications satellites known as Intelsat VI is described in detail. Each satellite will utilize 50 transponders operating in the C and K band portions of the frequency spectrum. The transponders are interconnectible using either static switch matrices or a network which provides satellite switched time division multiple access capability. The antenna coverages, characteristics, and special design features are shown and discussed.

  5. Preparation and characterization of surface imprinted polymer for selective sorption of uranium(VI)

    International Nuclear Information System (INIS)

    A new surface ion-imprinted polymer for the selective sorption of U(VI) from aqueous solution was prepared by copolymerization of a binary complex of U(VI) with methacrylic acid. The adsorption behavior of U(VI) onto the imprinted polymer was investigated by batch experiments and the results demonstrated that the maximum adsorption capacity of U(VI)-imprinted and non-imprinted polymers was found to be 35.92 and 22.58 mg g-1, respectively. The selectivity study revealed that the U(VI)-imprinted polymer exhibited excellent selectivity and affinity toward U(VI) in the presence of competitive metal ions. (author)

  6. An experimental study on the inhibitory effect of high concentration bicarbonate on the reduction of U(VI) in groundwater by functionalized indigenous microbial communities

    International Nuclear Information System (INIS)

    The anaerobic microcosms amended with 30 mM bicarbonate and without bicarbonate were established, respectively, and the reduction of U(VI) in the microcosms by functionalized indigenous microbial communities was investigated. Results of the chemical extraction and XANES analysis showed that the proportions of U(IV) in the microcosms amended with bicarbonate were 10 % lower than without bicarbonate at day 46. The amount of Cellulomonadaceae, Desulfovibrionaceae, Peptococcaceae and Veillonellaceae amended with bicarbonate was lower than without bicarbonate, so the reduction of U(VI) was less. The experimental results show that the high concentration bicarbonate has a significantly inhibitory effect on the reduction of U(VI). (author)

  7. ViA: a perceptual visualization assistant

    Science.gov (United States)

    Healey, Chris G.; St. Amant, Robert; Elhaddad, Mahmoud S.

    2000-05-01

    This paper describes an automated visualized assistant called ViA. ViA is designed to help users construct perceptually optical visualizations to represent, explore, and analyze large, complex, multidimensional datasets. We have approached this problem by studying what is known about the control of human visual attention. By harnessing the low-level human visual system, we can support our dual goals of rapid and accurate visualization. Perceptual guidelines that we have built using psychophysical experiments form the basis for ViA. ViA uses modified mixed-initiative planning algorithms from artificial intelligence to search of perceptually optical data attribute to visual feature mappings. Our perceptual guidelines are integrated into evaluation engines that provide evaluation weights for a given data-feature mapping, and hints on how that mapping might be improved. ViA begins by asking users a set of simple questions about their dataset and the analysis tasks they want to perform. Answers to these questions are used in combination with the evaluation engines to identify and intelligently pursue promising data-feature mappings. The result is an automatically-generated set of mappings that are perceptually salient, but that also respect the context of the dataset and users' preferences about how they want to visualize their data.

  8. Study of the role of magnetite in the immobilisation of U(VI) by reduction to U(IV) under the presence of H{sub 2}(g) in hydrogen carbonate medium

    Energy Technology Data Exchange (ETDEWEB)

    Rovira, Miquel; Pablo, Joan de [Centre Tecnologic de Manresa (Spain); El Aamrani, Souad [Univ. Politecnica de Catalunya, Barcelona (Spain); Duro, Lara; Grive, Mireia; Bruno, Jordi [Enviros Spain SL (Spain)

    2003-01-01

    This report corresponds to the work carried out during the period March 2001-July 2002. The interaction of Uranium(VI) in hydrogen carbonate medium with commercial magnetite as well as with magnetite formed as a corrosion product on the surface of a steel coupon has been studied. The influence of the hydrogen pressure and the mass of magnetite have been two of the factors studied in detail. Results obtained with commercial magnetite indicates that uranium concentration in solution can be explained taking into account the solubility of UO{sub 2}(am) at the experimental conditions employed (pe+pH{approx}6) and at different hydrogen pressures. The uranium(VI) reduction has been clearly demonstrated by using X-Ray Absorption Near Edge Structure (XANES). Experiments performed during 30 days in hydrogen atmosphere showed a reduction of the 80% of U(VI). Results obtained by using X-Ray Photoelectron Spectroscopy also corroborate the U(VI) reduction on the surface of the magnetite. In the case of magnetite obtained on a steel coupon, it seems that the presence of zero-valent iron below the magnetite surface might account for an increase of the electronic density at the surface and, therefore causing a preferential oxidation of the structural iron in front of the experiment conducted with commercial magnetite. Uranium concentration seems also to be controlled by UO{sub 2}(am) solubility.

  9. Study of the role of magnetite in the immobilisation of U(VI) by reduction to U(IV) under the presence of H2(g) in hydrogen carbonate medium

    International Nuclear Information System (INIS)

    This report corresponds to the work carried out during the period March 2001-July 2002. The interaction of Uranium(VI) in hydrogen carbonate medium with commercial magnetite as well as with magnetite formed as a corrosion product on the surface of a steel coupon has been studied. The influence of the hydrogen pressure and the mass of magnetite have been two of the factors studied in detail. Results obtained with commercial magnetite indicates that uranium concentration in solution can be explained taking into account the solubility of UO2(am) at the experimental conditions employed (pe+pH∼6) and at different hydrogen pressures. The uranium(VI) reduction has been clearly demonstrated by using X-Ray Absorption Near Edge Structure (XANES). Experiments performed during 30 days in hydrogen atmosphere showed a reduction of the 80% of U(VI). Results obtained by using X-Ray Photoelectron Spectroscopy also corroborate the U(VI) reduction on the surface of the magnetite. In the case of magnetite obtained on a steel coupon, it seems that the presence of zero-valent iron below the magnetite surface might account for an increase of the electronic density at the surface and, therefore causing a preferential oxidation of the structural iron in front of the experiment conducted with commercial magnetite. Uranium concentration seems also to be controlled by UO2(am) solubility

  10. On the connection between the metal-enriched intergalactic medium and galaxies: an O VI-galaxy cross-correlation study at z < 1

    Science.gov (United States)

    Finn, Charles W.; Morris, Simon L.; Tejos, Nicolas; Crighton, Neil H. M.; Perry, Robert; Fumagalli, Michele; Bielby, Rich; Theuns, Tom; Schaye, Joop; Shanks, Tom; Liske, Jochen; Gunawardhana, Madusha L. P.; Bartle, Stephanie

    2016-07-01

    We present new results on the auto- and cross-correlation functions of galaxies and O VI absorbers in a ˜18 Gpc3 comoving volume at z r⊥, r∥). We furthermore infer the corresponding `real-space' correlation functions, ξ(r), by projecting ξ(r⊥, r∥) along r∥, and assuming a power-law form, ξ(r) = (r/r0)-γ. Comparing the results from the absorber-galaxy cross-correlation function, ξag, the galaxy autocorrelation function, ξgg, and the absorber autocorrelation function, ξaa, we constrain the statistical connection between galaxies and the metal-enriched intergalactic medium as a function of star formation activity. We also compare these results to predictions from the EAGLE cosmological hydrodynamical simulation and find a reasonable agreement. We find that: (i) O VI absorbers show very little velocity dispersion with respect to galaxies on ˜ Mpc scales, likely ≲100 km s-1; (ii) O VI absorbers are less clustered, and potentially more extended around galaxies than galaxies are around themselves; (iii) on ≳100 kpc scales, the likelihood of finding O VI absorbers around star-forming galaxies is similar to the likelihood of finding O VI absorbers around non-star-forming galaxies; and (iv) O VI absorbers are either not ubiquitous to galaxies in our sample, or their distribution around them is patchy on scales ≳100 kpc (or both), at least for the column densities at which most are currently detected.

  11. Study of the adsorption of Cr(VI) by tannic acid immobilised powdered activated carbon from micro-polluted water in the presence of dissolved humic acid.

    Science.gov (United States)

    Gong, Xujin; Li, Weiguang; Wang, Ke; Hu, Jinhua

    2013-08-01

    The adsorption of Cr(VI) (0.500 mg/L) onto food-grade tannic-acid immobilised powdered activated carbon (TA-PAC) in the presence of dissolved humic acid (DHA) was investigated at 280 K as a function of pH, along with the adsorption capacities and the adsorption isotherms for chromium ions. The results showed that the presence of DHA improved the adsorption capacities of Cr(VI) and its reduction product (Cr(III)) over a wide pH range (4.0-8.0). The main mechanism for metal-DHA complexation in the Cr(VI) system was the reduction of Cr(VI) followed by complexation between Cr(III) and DHA. The Freundlich isotherms yielded the best fits to all data (R(2)=0.9951, qm=5.639 mg/g) in the presence of DHA. The adsorption mechanisms of Cr(VI) onto TA-PAC in the presence of DHA were summarized into three categories: (i) binding by anion adsorption, (ii) Cr(VI) reduction followed by Cr(III) adsorption, and (iii) adsorption of Cr(III)-DHA complexes. PMID:23453800

  12. CTR diffraction and grazing-incidence EXAFS study of U(VI) adsorption onto α-Al 2O 3 and α-Fe 2O 3 (11¯02) surfaces

    Science.gov (United States)

    Catalano, Jeffrey G.; Trainor, Thomas P.; Eng, Peter J.; Waychunas, Glenn A.; Brown, Gordon E.

    2005-07-01

    Evaluation of the long-term health risks of uranium contamination in soils, sediments, and groundwater requires a fundamental understanding of the various processes affecting subsurface transport of uranium, including adsorption processes at mineral/water interfaces. In this study, the sites of binding and surface complexation of U(VI) adsorbed on the (11¯02) surfaces of α-Al 2O 3 and α-Fe 2O 3 have been determined using crystal truncation rod (CTR) diffraction and grazing incidence extended X-ray absorption fine structure (GI-EXAFS) spectroscopy. The available binding sites on the (11¯02) surfaces were constrained through bond valence and steric analyses. On both surfaces, U(VI) forms uranyl-carbonato ternary complexes to surface oxygens that are singly coordinated to aluminum or iron. On the α-Al 2O 3 (11¯02) surface, a monodentate complex results, whereas on the α-Fe 2O 3 (11¯02) surface, the binding is bidentate to adjacent singly coordinated oxygen sites (i.e., binuclear). Differences in protonation of the singly coordinated oxygen atoms, surface charging, U(VI) aqueous speciation, substrate structure, or the electronic structure of surface functional groups may be the cause of these differences in adsorption geometry. Both XPS and CTR diffraction reveal higher U(VI) surface coverages on the α-Fe 2O 3 (11¯02) surface than on the α-Al 2O 3 (11¯02) surface. This difference cannot be the result of differences in defect concentration alone as CTR diffraction is not sensitive to U(VI) sorbed to defect sites, implying that the α-Fe 2O 3 (11¯02) surface has an intrinsically higher affinity for U(VI). The surface complexes observed in this study are different from the bidentate, mononuclear complexes typically derived for U(VI) on powdered aluminum- and iron-(oxyhydr)oxides and clay minerals using U L III-edge EXAFS spectroscopy. However, the presence of monodentate, mononuclear and bidentate, binuclear complexes may have been overlooked in past EXAFS

  13. Uranium(VI) uptake by synthetic calcium silicate hydrates

    International Nuclear Information System (INIS)

    The immobilization of U(VI) by C-S-H phases under conditions relevant for the cementitious near field of a repository for radioactive waste has been investigated. C-S-H phases have been synthesized using two different procedures: the 'direct reaction' method and the 'solution reaction' method. The stabilities of alkaline solutions of U(VI) (presence of precipitates or colloidal material) were studied prior to sorption and co-precipitation tests in order to determine the experimental U(VI) solubility limits. These U(VI) solubility limits were compared with the U(VI) solubilities obtained from thermodynamic speciation calculations assuming the presence of combinations of different solid U(VI) phases. The solid phase controlling U(VI) solubility in the present experiments was found to be CaUO4s). The U(VI) uptake kinetics and sorption isotherms on C-S-H phases with different C:S ratios were determined under various chemical conditions; e.g., sorption and co-precipitation experiments and different pH's. U(VI) was found to sorb fast and very strongly on C-S-H phases with distribution ratios (Rd values) ranging in value between 103 L kg-1 and 106 L kg-1. Both sorption and co-precipitation experiments resulted in Rd values which were very similar, thus indicating that no additional sorption sites for U(VI) were generated in the co-precipitation process. Furthermore, C-S-H synthesis procedures did not have a significant influence on U(VI) uptake. The U(VI) sorption isotherms were found to be non-linear, and further, increasing Ca concentrations resulted in increasing U(VI) uptake. The latter observation suggests that U(VI) uptake is controlled by a solubility-limiting process, while the former observation further indicates that pure Ca-uranate is not the solubility-limiting phase. It is proposed that a solid solution containing Ca and UO22+ could control U(VI) uptake by C-S-H phases. (authors)

  14. Vi lever i en verden af ting

    DEFF Research Database (Denmark)

    Helms, Niels Henrik

    2009-01-01

    Vi lever i en verden af ting Vi lever i en verden af ting. Menneskeligt frembragte påvirkninger, konstruktioner og manipulationer af vores natur, hvis det da er vores natur. Vi lever også i et særligt innovations-regime, hvor vi bliver vurderet på og defineret af, hvad og hvordan vi kan bidrage med...

  15. Use of polyethylene glycol (PEG) based aqueous biphasic system (ABS) for the extraction of Pu(IV), Pu(VI) and Am(III) with 18-crown-6. A thermodynamic study

    International Nuclear Information System (INIS)

    Extraction of Pu(IV), Pu(VI) and Am(III) using PEG-2000/ (NH4)2SO4 (40% w/w of each) ABS with 18-crown-6 (18-C-6) as the extractant was studied at four fixed temperatures in the range 288 to 318 K. The distribution ratios follow the order: Pu(VI) > Pu(IV) > Am(III). The species extracted were identified to be [Pu x 2(18-C-6)](SO4)2, [PuO2 x (18-C-6)]SO4 and [Am x 2(18-C-6)](SO4)1.5 for Pu(IV), Pu(VI) and Am(III), respectively. The equilibrium constants (K) evaluated for the extraction reactions follow the order, KPu(IV) > KPu(VI) > KAm(III) as expected in accordance with the axial charge experienced by the incoming ligand (18-C-6). The thermodynamic parameters evaluated at 298 K showed the reaction to be stabilized by the decrease in enthalpy and counteracted by the decrease in entropy in all the three cases. The large decrease in the enthalpy observed in all the cases showed that there is direct bonding of crown ether to the central metal atom (i.e., the formation of inner sphere complex). (author)

  16. Type VI Collagen Regulates Dermal Matrix Assembly and Fibroblast Motility.

    Science.gov (United States)

    Theocharidis, Georgios; Drymoussi, Zoe; Kao, Alexander P; Barber, Asa H; Lee, David A; Braun, Kristin M; Connelly, John T

    2016-01-01

    Type VI collagen is a nonfibrillar collagen expressed in many connective tissues and implicated in extracellular matrix (ECM) organization. We hypothesized that type VI collagen regulates matrix assembly and cell function within the dermis of the skin. In the present study we examined the expression pattern of type VI collagen in normal and wounded skin and investigated its specific function in new matrix deposition by human dermal fibroblasts. Type VI collagen was expressed throughout the dermis of intact human skin, at the expanding margins of human keloid samples, and in the granulation tissue of newly deposited ECM in a mouse model of wound healing. Generation of cell-derived matrices (CDMs) by human dermal fibroblasts with stable knockdown of COL6A1 revealed that type VI collagen-deficient matrices were significantly thinner and contained more aligned, thicker, and widely spaced fibers than CDMs produced by normal fibroblasts. In addition, there was significantly less total collagen and sulfated proteoglycans present in the type VI collagen-depleted matrices. Normal fibroblasts cultured on de-cellularized CDMs lacking type VI collagen displayed increased cell spreading, migration speed, and persistence. Taken together, these findings indicate that type VI collagen is a key regulator of dermal matrix assembly, composition, and fibroblast behavior and may play an important role in wound healing and tissue regeneration. PMID:26763426

  17. Syntheses, Spectral, Surface Morphological and Gamma Ray Irradiation Studies of Some Oxomolybdenum(V) and Dioxomolybdenum(VI) Complexes of an Azo Dye Derived from 4-aminoantipyrine

    International Nuclear Information System (INIS)

    Syntheses of some novel oxomolybdenum(V) and dioxomolybdenum(VI) complexes with an azo dye meth-oxyphenolazoantipyrine (HL) derived from 4-aminoantipyrine and 2-methoxyphenol are reported. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility data, IR, UV-Vis, 1H NMR, EPR and FAB mass spectral studies. The physicochemical studies and spectral data indicate that HL acts as a bidentate chelating ligand. The complexes have the general formulae [MoO(HL)XCl2] and [MoO2(HL)XCl],where X=Cl, NCS or NO3. All the complexes are found to have distorted octahedral geometry. Structural and morphological characterization of the complexes [MoO(HL)Cl3](1) and [MoO2(HL)Cl2](4) before and after gamma ray irradiation,was performed by X-ray diffraction and scanning electron microscopy(SEM). The ligand and the complexes were screened for their possible antimicrobial activities

  18. Selectivity enhancement of phosphate based functional polymeric gels towards Uranium(VI) using ion imprinting

    International Nuclear Information System (INIS)

    The imprinting of gel containing polymer chains of ethylene glycol methacrylate phosphate (EGMP) for U(VI) ions were carried out. The U(VI) imprinting has been carried out in pure EGMP and in EGMP: poly(ethylene glycol) methacrylate (PEGMA) = 1:9 composition. Complexation of the monomer with template (U(VI)) followed by polymerization have been used to imprint the U(VI) onto the polymer chains. The comparison of uptake studies of U(VI) and Pu(IV) at 3 M HNO3 shows increased selectivity of U(VI) relative to Pu(IV) for both the gel compositions. The less uptake of U(VI) for imprinted EGMP:PEGMA gel relative to pure imprinted EGMP gel at tracer level can be possibly due to the requirement of two EGMP units in the vicinity for U(VI) complexation. (author)

  19. Biosorption of uranium (VI) by immobilized Aspergillus fumigatus beads

    International Nuclear Information System (INIS)

    Biosorption of uranium (VI) ions by immobilized Aspergillus fumigatus beads was investigated in a batch system. The influences of solution pH, biosorbent dose, U (VI) concentration, and contact time on U (VI) biosorption were studied. The results indicated that the adsorption capacity was strongly affected by the solution pH, the biosorbent dose and initial U (VI) concentration. Optimum biosorption was observed at pH 5.0, biosrobent dose (w/v) 2.5%, initial U (VI) concentration 60 mg L-1. Biosorption equilibrium was established in 120 min. The adsorption process conformed to the Freunlich and Temkin isothermal adsorption models. The dynamic adsorption model conformed to pseudo-second order model.

  20. Kinetic studies on the extraction of uranium(VI) from phosphoric acid medium by bulk liquid membrane containing di-2-ethylhexyl phosphoric acid

    International Nuclear Information System (INIS)

    To go through the first stage of industrial solvent extraction process in order to recover uranium from phosphate rocks by liquid membrane techniques, as a simple model, the kinetics of facilitated transport of uranium(VI) from a dilute phosphoric acid medium into more concentrated phosphoric acid media as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier was studied. The influence of phosphoric acid concentration in the source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (ke, ks, tmax, Jmax) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJ mol-1 for extraction and stripping, respectively. The values of calculated activation energy indicated that both the extraction and stripping processes were controlled by mixed regime (both kinetic and diffusion). In addition, the influence of adding trioctyl-phosphine oxide into the membrane phase as a synergic agent on the transport kinetics was determined. (author)

  1. Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI).

    Science.gov (United States)

    Gerber, U; Zirnstein, I; Krawczyk-Bärsch, E; Lünsdorf, H; Arnold, T; Merroun, M L

    2016-11-01

    The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation by means of controlled underground flooding. Nevertheless, the flooding water has to be cleaned up by a conventional wastewater treatment plant. In this study, the uranium(VI) removal and tolerance mechanisms of the gram-negative betaproteobacterium Acidovorax facilis were investigated by a multidisciplinary approach combining wet chemistry, flow cytometry, and microscopy. The kinetics of uranium removal and the corresponding mechanisms were investigated. The results showed a biphasic process of uranium removal characterized by a first phase where 95% of uranium was removed within the first 8h followed by a second phase that reached equilibrium after 24h. The bacterial cells displayed a total uranium removal capacity of 130mgU/g dry biomass. The removal of uranium was also temperature-dependent, indicating that metabolic activity heavily influenced bacterial interactions with uranium. TEM analyses showed biosorption on the cell surface and intracellular accumulation of uranium. Uranium tolerance tests showed that A. facilis was able to withstand concentrations up to 0.1mM. This work demonstrates that A. facilis is a suitable candidate for in situ bioremediation of flooding water in Königstein as well as for other contaminated waste waters. PMID:27262280

  2. Test results of Salmonella typing by the NRLs-Salmonella in the Member States of the EU and the EnterNet Laboratories - Collaborative study VI (2001) on typing of Salmonella

    OpenAIRE

    Korver H; Raes M; Maas HME; Ward LR; Wannet WJB; Henken AM; PHLS-Colindale/London; MGB; LIS

    2002-01-01

    Test results of Salmonella sero- and phage typing and antimicrobial susceptibility testing by the National Reference Laboratories for Salmonella in the Member States of the European Union and the EnterNet Laboratories: Collaborative study VI (2001) for Salmonella. The sixth collaborative typing study for Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, The Netherlands) in collaboration with the Public Health Laboratory Services (PHLS), ...

  3. Sustainable development around the Lake Victoria basin, part 1, : a case study of farmers'perception of the VI Agroforestry Project Masaka/Rakai, Uganda, from a gender perspective

    OpenAIRE

    Nilsson, Sara

    2004-01-01

    During the years the awareness of gender issues has increased in the international arena and the importance of including gender aspects in development projects has been emphasised. This Master’s thesis is based on a case study of the VI Agroforestry Project (VIAFP) in Uganda and is one of the two subprojects of the study Sustainable development around the Lake Victoria basin, with the purpose to investigate the importance of local anchoring and active participation in the work towards sustain...

  4. Econophys-Kolkata VI Conference

    CERN Document Server

    Chakrabarti, Bikas; Chakraborti, Anirban; Ghosh, Asim

    2013-01-01

    The primary goal of the book is to present the ideas and research findings of active researchers such as physicists, economists, mathematicians and financial engineers working in the field of “Econophysics,” who have undertaken the task of modeling and analyzing systemic risk, network dynamics and other topics. Of primary interest in these studies is the aspect of systemic risk, which has long been identified as a potential scenario in which financial institutions trigger a dangerous contagion mechanism, spreading from the financial economy to the real economy. This type of risk, long confined to the monetary market, has spread considerably in the recent past, culminating in the subprime crisis of 2008. As such, understanding and controlling systemic risk has become an extremely important societal and economic challenge. The Econophys-Kolkata VI conference proceedings are dedicated to addressing a number of key issues involved. Several leading researchers in these fields report on their recent work and al...

  5. On the connection between the metal-enriched intergalactic medium and galaxies: an O VI-galaxy cross-correlation study at z < 1

    Science.gov (United States)

    Finn, Charles W.; Morris, Simon L.; Tejos, Nicolas; Crighton, Neil H. M.; Perry, Robert; Fumagalli, Michele; Bielby, Rich; Theuns, Tom; Schaye, Joop; Shanks, Tom; Liske, Jochen; Gunawardhana, Madusha L. P.; Bartle, Stephanie

    2016-04-01

    We present new results on the auto- and cross-correlation functions of galaxies and O VI absorbers in a ˜18~Gpc3 comoving volume at z . We use a sample of 51 296 galaxies and 140 O VIabsorbers in the column density range 13 ≲ log N ≲ 15 to measure two-point correlation functions in the two dimensions transverse and orthogonal to the line-of-sight ξ(r⊥, r∥). We furthermore infer the corresponding `real-space' correlation functions, ξ(r), by projecting ξ(r⊥, r∥) along r∥, and assuming a power-law form, ξ(r) = (r/r0)-γ. Comparing the results from the absorber-galaxy cross-correlation function, ξag, the galaxy auto-correlation function, ξgg, and the absorber auto-correlation function, ξaa, we constrain the statistical connection between galaxies and the metal-enriched intergalactic medium as a function of star-formation activity. We also compare these results to predictions from the EAGLE cosmological hydrodynamical simulation and find a reasonable agreement. We find that: (i) O VI absorbers show very little velocity dispersion with respect to galaxies on ˜ Mpc scales, likely ≲ 100 km s-1; (ii) O VI absorbers are less clustered, and potentially more extended around galaxies than galaxies are around themselves; (iii) On ≳ 100 kpc scales, the likelihood of finding O VI absorbers around star-forming galaxies is similar to the likelihood of finding O VI absorbers around non star-forming galaxies; and (iv) O VI absorbers are either not ubiquitous to galaxies in our sample, or their distribution around them is patchy on scales ≳ 100 kpc (or both), at least for the column densities at which most are currently detected.

  6. ViPAR

    DEFF Research Database (Denmark)

    Carter, Kim W; Francis, Richard W; Bresnahan, M; Gissler, M; Grønborg, T K; Gross, R; Gunnes, N; Hammond, G; Hornig, M; Hultman, C M; Huttunen, J; Langridge, A; Leonard, H; Newman, S; Parner, E T; Petersson, G; Reichenberg, A; Sandin, S; Schendel, Diana; Schalkwyk, L; Sourander, A; Steadman, C; Stoltenberg, C; Suominen, A; Surén, P; Susser, E; Sylvester Vethanayagam, A; Yusof, Z

    2015-01-01

    free and open source methods to provide researchers with a web-based platform to analyse datasets housed in disparate locations. METHODS: Database federation permits controlled access to remotely located datasets from a central location. The Secure Shell protocol allows data to be securely exchanged......PAR infrastructure, remote sites manage their own harmonized research dataset in a database hosted at their site, while a central server hosts the data federation component and a secure analysis portal. When an analysis is initiated, requested data are retrieved from each remote site and virtually pooled at the...... central site. The data are then analysed by statistical software and, on completion, results of the analysis are returned to the user and the virtually pooled data are removed from memory. CONCLUSIONS: ViPAR is a secure, flexible and powerful analysis platform built on open source technology that is...

  7. Synergetic Transformations of Multiple Pollutants Driven by Cr(VI)-Sulfite Reactions.

    Science.gov (United States)

    Jiang, Bo; Liu, Yukun; Zheng, Jingtang; Tan, Minghui; Wang, Zhaohui; Wu, Mingbo

    2015-10-20

    Reduction of Cr(VI) is often deemed necessary to detoxify chromium contaminants; however, few investigations utilized this reaction for the purpose of treating other industrial wastewaters. Here a widely used Cr(VI)-sulfite reaction system was upgraded to simultaneously transform multiple pollutants, namely, the reduction of Cr(VI) and oxidation of sulfite and other organic/inorganic pollutants in an acidic solution. As(III) was selected as a probe pollutant to examine the oxidation capacity of a Cr(VI)-sulfite system. Both (•)OH and SO4(•-) were considered as the primary oxidants for As(III) oxidation, based on the results of electron spin resonance, fluorescence spectroscopy, and specific radicals quenching. As(III)-scavenging, oxidative radicals greatly accelerated Cr(VI) reduction and simultaneously consumed less sulfite. In comparison with a Cr(VI)-H2O2 system with 50 μM Cr(VI), Cr(VI), the sulfite system had excellent performance for both As(III) oxidation and Cr(VI) reduction at pH 3.5. Moreover, in this escalated process, less sulfite was required to reduce Cr(VI) than the traditional Cr(VI) reduction by sulfite process. This effectively improves the environmental compatibility of this Cr(VI) detoxification process, alleviating the potential for SO2 release and sulfate ion production in water. Generally, this study provides an excellent example of a "waste control by waste" strategy for the detoxification of multiple industrial pollutants. PMID:26384045

  8. Dissolution studies of natural analogues spent fuel and U(VI)-Silicon phases of and oxidative alteration process

    International Nuclear Information System (INIS)

    In order to understand the long-term behavior of the nuclear spent fuel in geological repository conditions, we have performed dissolution studies with natural analogues to UO2 as well as with solid phases representatives of the oxidative alteration pathway of uranium dioxide, as observed in both natural environment and laboratory studies. In all cases, we have studied the influence of the bicarbonate concentration in the dissolution process, as a first approximation to the groundwater composition of a granitic environment, where carbonate is one of the most important complexing agents. As a natural analogue to the nuclear spent fuel some uraninite samples from the Oklo are deposit in Gabon, where chain fission reactions took place 2000 millions years ago, as well as a pitchblende sample from the mine Fe ore deposit, in Salamanca (spain) have been studied. The studies have been performed at 25 and 60 deg C and 60 deg C, and they have focussed on the determination of both the thermodynamic and the kinetic properties of the different samples studied, using batch and continuous experimental methodologies, respectively. (Author)

  9. Protostars and Planets VI

    Science.gov (United States)

    Beuther, Henrik; Klessen, Ralf S.; Dullemond, Cornelis P.; Henning, Thomas

    The Protostars and Planets book and conference series has been a long-standing tradition that commenced with the first meeting led by Tom Gehrels and held in Tucson, Arizona, in 1978. The goal then, as it still is today, was to bridge the gap between the fields of star and planet formation as well as the investigation of planetary systems and planets. As Tom Gehrels stated in the preface to the first Protostars and Planets book, "Cross-fertilization of information and understanding is bound to occur when investigators who are familiar with the stellar and interstellar phases meet with those who study the early phases of solar system formation." The central goal remained the same for the subsequent editions of the books and conferences Protostars and Planets II in 1984, Protostars and Planets III in 1990, Protostars and Planets IV in 1998, and Protostars and Planets V in 2005, but has now been greatly expanded by the flood of new discoveries in the field of exoplanet science. The original concept of the Protostars and Planets series also formed the basis for the sixth conference in the series, which took place on July 15-20, 2013. It was held for the first time outside of the United States in the bustling university town of Heidelberg, Germany. The meeting attracted 852 participants from 32 countries, and was centered around 38 review talks and more than 600 posters. The review talks were expanded to form the 38 chapters of this book, written by a total of 250 contributing authors. This Protostars and Planets volume reflects the current state-of-the-art in star and planet formation, and tightly connects the fields with each other. It is structured into four sections covering key aspects of molecular cloud and star formation, disk formation and evolution, planetary systems, and astrophysical conditions for life. All poster presentations from the conference can be found at www.ppvi.org. In the eight years that have passed since the fifth conference and book in the

  10. A luminescence line-narrowing spectroscopic study of the uranium(VI) interaction with cementitious materials and titanium dioxide

    OpenAIRE

    Tits, Jan; Walther, Clemens; Stumpf, Thorsten; Mace, Nathalie; Wieland, Erich

    2015-01-01

    Non-selective luminescence spectroscopy and luminescence line-narrowing spectroscopy were used to study the retention of UO22+ on titanium dioxide (TiO2), synthetic calcium silicate hydrate (C-S-H) phases and hardened cement paste (HCP). Non-selective luminescence spectra showed strong inhomogeneous line broadening resulting from a strongly disordered UO22+ bonding environment. This problem was largely overcome by using luminescence line-narrowing spectroscopy. This technique allowed unambigu...

  11. Small angle neutron scattering study of U(VI) third phase formation in HNO3/DHDECMP–-dodecane system

    Indian Academy of Sciences (India)

    K V Lohithakshan; V K Aswal; S K Aggarwal

    2008-11-01

    Small angle neutron scattering studies (SANS) were carried out to understand the formation of third phase in DHDECMP–dodecane–UO2(NO3)2/HNO3 system. It was observed that third phase formation takes place due to the formation of UO2(NO3)2. DHDECMP reverse micelles in the dodecane phase. SANS data obtained were interpreted with particle interaction model using Baxter sticky spheres model.

  12. Studies on phycobiliproteins in Algae. VI. Light-harvesting phycobiliprotein pigments in some Rhodophyta from the Adriatic Sea

    OpenAIRE

    Bazyli Czeczuga

    2014-01-01

    The phycobiliprotein content in 5 species of red algae from the coast of the Adriatic Sea' was studied by chromatography on Sephadex G-100. The phycobiliproteins, R-phycoerythrin, C-phycocyanin and allophycocyanin were identified. The total content of phycobiliproteins ranged from 0.152 (Phyllophora nervosa) to 1.874 mg•g-1 dry wt. (Plocamium cartilagineum). The dominant phycobiliproteins were found to belong to the phycocyanin group, this resulting from complementary chromatic adaptation.

  13. Studies on phycobiliproteins in Algae. VI. Light-harvesting phycobiliprotein pigments in some Rhodophyta from the Adriatic Sea

    Directory of Open Access Journals (Sweden)

    Bazyli Czeczuga

    2014-02-01

    Full Text Available The phycobiliprotein content in 5 species of red algae from the coast of the Adriatic Sea' was studied by chromatography on Sephadex G-100. The phycobiliproteins, R-phycoerythrin, C-phycocyanin and allophycocyanin were identified. The total content of phycobiliproteins ranged from 0.152 (Phyllophora nervosa to 1.874 mg•g-1 dry wt. (Plocamium cartilagineum. The dominant phycobiliproteins were found to belong to the phycocyanin group, this resulting from complementary chromatic adaptation.

  14. Social vulnerability assessment using spatial multi-criteria analysis (SEVI model) and the Social Vulnerability Index (SoVI model) - a case study for Bucharest, Romania

    Science.gov (United States)

    Armaş, I.; Gavriş, A.

    2013-06-01

    In recent decades, the development of vulnerability frameworks has enlarged the research in the natural hazards field. Despite progress in developing the vulnerability studies, there is more to investigate regarding the quantitative approach and clarification of the conceptual explanation of the social component. At the same time, some disaster-prone areas register limited attention. Among these, Romania's capital city, Bucharest, is the most earthquake-prone capital in Europe and the tenth in the world. The location is used to assess two multi-criteria methods for aggregating complex indicators: the social vulnerability index (SoVI model) and the spatial multi-criteria social vulnerability index (SEVI model). Using the data of the 2002 census we reduce the indicators through a factor analytical approach to create the indices and examine if they bear any resemblance to the known vulnerability of Bucharest city through an exploratory spatial data analysis (ESDA). This is a critical issue that may provide better understanding of the social vulnerability in the city and appropriate information for authorities and stakeholders to consider in their decision making. The study emphasizes that social vulnerability is an urban process that increased in a post-communist Bucharest, raising the concern that the population at risk lacks the capacity to cope with disasters. The assessment of the indices indicates a significant and similar clustering pattern of the census administrative units, with an overlap between the clustering areas affected by high social vulnerability. Our proposed SEVI model suggests adjustment sensitivity, useful in the expert-opinion accuracy.

  15. Oxidising alternative species to chromium VI in zinc-galvanised steel surface treatment. Part 2. An electrochemical study

    International Nuclear Information System (INIS)

    In the first part of this work, the authors present the main results and conclusions of a morphological and chemical study carried out on zinc conversion layers (ZCLs) obtained with oxidising alternative passivation baths, that includes molybdates, permanganates, van[ates and tungstates. A good chromate-based bath was used as reference. In this second part of the work, the authors present the main results obtained on selected zinc conversion layers (ZCLs), using a.c. electrochemical impedance spectroscopy (EIS). The results obtained were correlated with the morphological and chemical data obtained with the same ZCLs in the first part of this work. Finally, it is concluded that the alternative ZCLs studied, does not seem to be as efficient as that obtained with a chromate-based passivation bath used as reference. It is believed that a better understanding of the mechanisms involved in the ZCL's formation, can be useful for studying, in the very near future, possible synergetic effects between molybdates and other chemical species. (orig.)

  16. Effect of Phosphate on U(VI) Sorption to Montmorillonite: Ternary Complexation and Precipitation Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Troyer, Lyndsay D.; Maillot, Fabien; Wang, Zheming; Wang, Zimeng; Mehta, Vrajesh; Giammar, Daniel; Catalano, Jeffrey G.

    2016-02-15

    reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface

  17. Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

    Science.gov (United States)

    Troyer, Lyndsay D.; Maillot, Fabien; Wang, Zheming; Wang, Zimeng; Mehta, Vrajesh S.; Giammar, Daniel E.; Catalano, Jeffrey G.

    2016-02-01

    reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface.

  18. Voltammetric behaviour of uranium(VI) in sulfuric acid solutions containing pyridine

    International Nuclear Information System (INIS)

    It was shown that 8.8 x 10-5 to 4.4 x 10-3 M uranium(VI) solutions in sulfuric acid containing pyridine give a clearly defined cathodic peak with a height proportional to uranium(VI) concentration. Under the specified conditions, the electroreduction of uranium(VI) is irreversible and involves one electron, the limiting current of uranium(VI) is diffusion- and kinetically controlled. The kinetic parameters of the process under study were determined, and the effect of associated elements on the voltammetric behavior of uranium(VI) in pyridine-containing sulfuric acid supporting electrolytes was estimated

  19. Mechanism of uranium(VI) uptake by Saccharomyces cerevisiae under environmentally relevant conditions: Batch, HRTEM, and FTIR studies

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xia, E-mail: lux2009@lzu.edu.cn; Zhou, Xiao-jiao; Wang, Tie-shan, E-mail: tswang@lzu.edu.cn

    2013-11-15

    Highlights: • Equilibrium reaches very rapid within 15 min. • pH shift towards neutral indicates release of hydroxyl ions. • High ionic strength inhabits biosorption capacity. • Uptake capacity of heat-killed cells is an order of magnitude higher than live one. • Electrostatic interaction, precipitation, and complexation are the main mechanisms. -- Abstract: Biosorption is of significance for the safety evaluation of high-level nuclear wastes repositories and remediation of radioactive contamination places. Quantitive study and structural characterization of uranium uptake by both live and heat-killed Saccharomyces cerevisiae at environmentally relevant uranium concentration and with different ionic strengths were carried out. Kinetic investigation showed the equilibrium reached within 15 min. In equilibrium studies, pH shift towards neutral indicated release of hydroxyl ions. pH was the most important factor, which partly affected electrostatic interaction between uranyl ions and S. cerevisiae surface. The high ionic strength inhibited biosorption capacity, which can be explained by a competitive reaction between sodium ions and uranyl ions. Heat killing process significantly enhanced biosorption capacity, showing an order of magnitude higher than that of live cells. High resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray (EDX) showed needle-like uranium-phosphate precipitation formed on the cell walls for both live and heat-killed cells. Besides, dark-field micrographs displayed considerable similar uranium-phosphate precipitation presented outside the heat-killed cells. The phosphate released during heat-killing process. FTIR illustrated function groups hydroxyl, carboxyl, phosphate, and amino groups played important role in complexation with uranium.

  20. Polarography of uranium(VI)-salicylic acid system

    International Nuclear Information System (INIS)

    Uranium(VI)-salicylic acid system has been studied polarographically in perchloric acid medium. Varying concentrations of HClO4 and salicylic acid have been used. The nature of the polarographic waves is irreversible. (author)

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

    Science.gov (United States)

    Erdem, Mehmet; Gür, Faruk; Tümen, Fikret

    2004-09-10

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

  2. Counter-current extraction and separation of U(VI) from a mixture of U(VI)-Th(IV)-Y(III) using tris-2-ethyl hexyl phosphate (TEHP)

    International Nuclear Information System (INIS)

    Evaluation of tris-2-ethyl hexyl phosphate (TEHP) for counter-current extraction and separation of U(VI) from a mixture of U(VI)-Th(IV)-Y(III) from nitric acid medium was carried out under wide experimental conditions. Batch extraction studies were carried out to investigate the effect of nitric acid concentration in feed solution, U(VI)/Th(IV) ratio and extractant concentration and the results were compared with established solvent such as tri-n-butyl phosphate (TBP) for separation of U(VI) from nitric acid medium. McCabe-Thiele diagrams for extraction as well as stripping of U(VI) were constructed under simulated conditions. Based on batch experiments, six stage counter-current extraction studies were conducted under various TEHP concentration and it was observed that 0.1 M TEHP/n-paraffin was most suitable for selective recovery of U(VI) from a mixture of U(VI)-Th(IV). An optimized condition, 0.1 M TEHP/n-paraffin, 2 M HNO3 in feed and six number of stages was evaluated for selective extraction and stripping of U(VI) from a solution containing mixture of U(VI)-Th(IV)-Y(III) in nitric acid medium. The U(VI) in strip solution was precipitated using 30 % H2O2 at pH ∼3. Average particle size of the final precipitate was found to be ∼33 μm. (author)

  3. A luminescence line-narrowing spectroscopic study of the uranium(VI) interaction with cementitious materials and titanium dioxide.

    Science.gov (United States)

    Tits, Jan; Walther, Clemens; Stumpf, Thorsten; Macé, Nathalie; Wieland, Erich

    2015-01-21

    Non-selective luminescence spectroscopy and luminescence line-narrowing spectroscopy were used to study the retention of UO2(2+) on titanium dioxide (TiO2), synthetic calcium silicate hydrate (C-S-H) phases and hardened cement paste (HCP). Non-selective luminescence spectra showed strong inhomogeneous line broadening resulting from a strongly disordered UO2(2+) bonding environment. This problem was largely overcome by using luminescence line-narrowing spectroscopy. This technique allowed unambiguous identification of three different types of UO2(2+) sorbed species on C-S-H phases and HCP. Comparison with spectra of UO2(2+) sorbed onto TiO2 further allowed these species to be assigned to a surface complex, an incorporated species and an uranate-like surface precipitate. This information provides the basis for mechanistic models describing the UO2(2+) sorption onto C-S-H phases and HCP and the assessment of the mobility of this radionuclide in a deep geological repository for low and intermediate level radioactive waste (L/ILW) as this kind of waste is often solidified with cement prior to storage. PMID:25407092

  4. Influence of uranium (VI) on the metabolic activity of stable multispecies biofilms studied by oxygen microsensors and fluorescence microscopy

    Science.gov (United States)

    Krawczyk-Bärsch, Evelyn; Grossmann, Kay; Arnold, Thuro; Hofmann, Susann; Wobus, Axel

    2008-11-01

    The effect of uranium added in ecologically relevant concentrations (1 × 10 -5 and 1 × 10 -6 M) to stable multispecies biofilms was studied by electrochemical oxygen microsensors with tip diameters of 10 μm and by confocal laser fluorescence microscopy (CLSM). The microsensor profile measurements in the stable multispecies biofilms exposed to uranium showed that the oxygen concentration decreased faster with increasing biofilm depth compared to the uranium free biofilms. In the uranium containing biofilms, the oxygen consumption, calculated from the steady-state microprofiles, showed high consumption rates of up to 61.7 nmol cm -3 s -1 in the top layer (0-70 μm) and much lower consumption rates in the lower zone of the biofilms. Staining experiments with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and 4,6-diamidino-2-phenylindole (DAPI) confirmed the high respiratory activities of the bacteria in the upper layer. Analysis of the amplified 16S rRNA gene fragments showed that the addition of uranium in ecologically relevant concentrations did not change the bacterial diversity in the stable multispecies biofilms and is therefore not responsible for the different oxygen profiles in the biofilms. The fast decrease in the oxygen concentrations in the biofilm profiles showed that the bacteria in the top region of the biofilms, i.e., the metabolically most active biofilm zone, battle the toxic effects of aqueous uranium with an increased respiratory activity. This increased respiratory activity results in O 2 depleted zones closer to the biofilm/air interface which may trigger uranium redox processes, since suitable redox partners, e.g., extracellular polymeric substance (EPS) and other organics (e.g., metabolites), are sufficiently available in the biofilm porewaters. Such redox reactions may lead to precipitation of uranium (IV) solids and consequently to a removal of uranium from the aqueous phase.

  5. ViFiLite Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ViFiLite is a wireless infrastructure that utilizes the advantages of a V-band technology in supporting data gathering for structural health monitoring as well as...

  6. Cinética e equilíbrio de adsorção dos oxiânions Cr (VI, Mo (VI e Se (VI pelo sal de amônio quaternário de quitosana Kinetics and equilibrium of adsorption of oxyanions Cr (VI, Mo (VI and Se (VI by quaternary ammonium chitosan salt

    Directory of Open Access Journals (Sweden)

    Viviane A. Spinelli

    2005-07-01

    one gram of cross-linked quaternary chitosan salt adsorbed 68.3 mg of chromium, 63.4 mg of molybdenum and 90.0 mg of selenium. The adsorption process followed a pseudo second-order kinetic rate equation and the equilibrium regarding the three ions was reached after 200 minutes. The studies from X-ray dispersive energy showed that the main adsorption mechanism is ionic exchange among Cl- groups on the polymer surface by oxyanions from solution and the anionic exchanger showed the following selectivity order: Cr (VI > Mo (VI > Se (VI.

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

    Science.gov (United States)

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

    2008-11-01

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

  8. The effectiveness of four organic matter amendments for decreasing resin-extractable Cr(VI) in Cr(VI)-contaminated soils.

    Science.gov (United States)

    Chiu, Chien-Chih; Cheng, Chia-Jung; Lin, Tzu-Huei; Juang, Kai-Wei; Lee, Dar-Yuan

    2009-01-30

    This paper compared the effectiveness of four organic materials for decreasing the amounts of soil extractable Cr(VI) in Cr(VI)-contaminated soils using the DOWEX M4195 resin-extraction method. Organic matters were added into Cr(VI)-spiked soils [500 mg Cr(VI)(kgsoil)(-1)] in the form of sugarcane dregs compost (SCDC), cattle-dung compost (CDC), soybean meal (SBM) and rice bran (RB), in the amounts of 0, 1%, and 2% by dry weight, respectively. The results indicated that adding only 1% organic matter to the studied soils could effectively decrease the amount of soil resin-extractable Cr(VI) after 12 days of incubation. The decrease of resin-extractable Cr(VI) by organic materials was mainly the result from the reduction of Cr(VI) to Cr(III) supported by the XANES spectroscopy. Among the four tested organic materials, SBM and RB had higher effectiveness in decreasing soil resin-extractable Cr(VI) than CDC and SCDC. This result may be due to the fact that SBM and RB have more dissolved organic carbon (DOC) and protein than CDC and SCDC. Therefore, it was concluded that the contents of DOC and protein are the main factors that determine the effectiveness of organic materials for decreasing the amounts of soil available Cr(VI) in Cr(VI)-contaminated soils. PMID:18524481

  9. Alpha-benzoinoxime. Extracting agent for uranium(VI), tungsten(VI), molybdenum(VI) and some transition metals of the iron family

    International Nuclear Information System (INIS)

    The effect of pH on the percent extraction of vanadium(V), iron(II), cobalt(II), nickel(II), copper(II), molybdenum(VI), tungsten(VI) and uranium(VI) by α-benzoinoxime in different solvents has been studies. The maximum recovery is not appreciably affected by the nature of the solvent, but occurs at different pH values for different metals. The pH corresponding to maximum extraction increases with increasing hydrolysis pK of the species in aqueous solution, and decreases with increasing stability constant of the complexes formed. Alpha-benzoinoxime allows the separation of these metal ions into three groups: V(V), Mo(VI) and W(VI) are extracted at pH=2, U(VI) at pH=5, Fe(II), Cu(II), Co(II) and Ni(II) at around pH=10. (author) 13 refs.; 2 figs.; 1 tab

  10. Studies on foliicolous fungi VI

    NARCIS (Netherlands)

    Hosagoudar, V.B.

    2002-01-01

    An account is given of three foliicolous fungi from India. Two new species, viz. Clasterosporium cyperacearum and Questieriella grewiae are described. Dysrhynchis uncinata forms a new generic and specific record to India and is reported on an endemic host.

  11. Study of the temperature influence during the uranium (Vi) sorption on surface of ZrP2O7 in presence of oxalic and salicylic acid

    International Nuclear Information System (INIS)

    This work studies the effect of temperature on the uranium (Vi) sorption onto zirconium diphosphate in the presence of organic acids (oxalic and salicylic acids). Zirconium diphosphate was synthesized by a chemical condensation reaction and characterized using several analytical techniques, in order to check its purity. This point is very important because the presence of any impurities or secondary phases may interfere with the hydration and sorption process. Prior to the sorption experiments, three batches of zirconium diphosphate were pre-equilibrated with NaClO4, oxalic acid or salicylic acid solutions. The hydrated solids were washed and dried and then again characterized in order to study the interactions between organic acids and zirconium diphosphate surface. Uranium sorption onto zirconium diphosphate (pre-equilibrated with NaClO4, oxalic acid and salicylic acid solutions) was investigated as a function of ph, organic acid and temperature (20, 40 y 60 grades C). Thermodynamic parameters for the sorption reactions (enthalpy change, entropy change and Gibbs free energy change) were determined from temperature dependence of distribution coefficient by using the Vant Hoff equation. Solids characterization after hydration shows that exist an interaction between organic acids and ZrP2O7. This fact was confirmed with the microcalorimetry study, the reaction heat for hydration of zirconium diphosphate in NaClO4 solution was exothermic (-269.59 mJ) and for hydration of zirconium diphosphate in oxalic acid solution was endothermic (53.64 mJ). The experimental results showed important differences in the sorption mechanisms for the reaction of Uranium with ZrP2O7 in the presence and absence of organic acids. For the zirconium diphosphate hydrated with oxalic acid, the sorption percentage was 50% from lowest ph values. For the zirconium diphosphate hydrated with salicylic acid, the initial concentration of uranium was 6 x 10-4 M and a percentage of 10% was observed in

  12. BIOSORPTION OF CR (VI BY RESTING CELLS OF ASPERGILLUS SP.

    Directory of Open Access Journals (Sweden)

    M. Sen , M. Ghosh Dastidar

    2007-01-01

    Full Text Available Biosorption of Cr(VI from aqueous solution was studied in a batch bioreactor using the resting cells of filamentous fungal biomass (Aspergillus sp. isolated from industrial wastewaters. The specific Cr(VI removal (mg/g of dried biomass decreased with increase in pH and increased with increase in initial Cr(VI concentration, upto 500 mg/L. By increasing biomass concentration from 2.4 to 5.2 g/L, the specific metal removal remained almost constant. The studies carried out by using the resting cells from various stages of growth indicated maximum Cr(VI removal of 34.8 mg/g using the biomass from the beginning of the stationary phase. The adsorption equilibrium constants Qº (42.9 mg/g and b (0.0091/mg were obtained from the Langmuir adsorption isotherm model.

  13. ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    A.P. Deditius; S. Utsunomiya; R.C. Ewing

    2006-02-21

    Uranium-(VI) phases are the primary alteration products of the UO{sub 2} in spent nuclear fuel and the UO{sub 2+x}, in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO{sub 2}{sup 2+} polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO{sub 2+x}, to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements.

  14. Cr(VI) removal from aqueous solution by dried activated sludge biomass

    International Nuclear Information System (INIS)

    Batch experiments were conducted to remove Cr(VI) from aqueous solution using activated sludge biomass. The effects of acid pretreatment of the biomass, initial pH, biomass and Cr(VI) concentrations on Cr(VI) removal efficiency were investigated. Proton consumption during the removal process and the reducing capacity of sludge biomass were studied. The results show that acid pretreatment could significantly improve Cr(VI) removal efficiency and increase Cr(VI) reducing capacity by 20.4%. Cr(VI) removal was remarkably pH-dependent; lower pH (pH = 1, 2) facilitated Cr(VI) reduction while higher pH (pH = 3, 4) favored sorption of the converted Cr(III). Lower Cr(VI) concentration as well as higher biomass concentration could accelerate Cr(VI) removal. Cr(VI) reduction was not the only reason for proton consumption in the removal process. Pseudo-second-order adsorption kinetic model could successfully simulate Cr(VI) removal except under higher pH conditions (pH = 3, 4).

  15. Complex molybdates of U(VI) and Np(VI)

    International Nuclear Information System (INIS)

    Double molybdates of uranyl with monovalent cations are known - Na2UO2(MoO4)2.6H2O and K2UO2(MoO4)2 .4H2O, and also with divalent cations - M(UO2)3(MoO4)4 8H2O (M = Mg, Zn). It is established by spectrophotometrical method, that the degree of uranyl complexation in acidified water molybdate solutions is great. The solutions have strong luminescence and are metastable. After several days from them the bright yellow crystal product of composition: Na2UO2(MoO4)2.4H2O is isolated. With change of conditions, for example, temperature and ratio [Mo]:[H+] from acidified solutions of sodium molybdate only the complex of the specified composition is obtained. Neptunyl forms in water solutions of sodium molybdate 1-2M, probably, several complexes because the isobestic points in spectra of Np(VI) at various concentrations of molybdate are absent. From such solutions in time the dark - marsh crystals of composition: Na2NpO2(MoO4)2.4H2O are isolated. From acidified solutions of sodium molybdate the complexes of other structure are formed. With replacement of sodium by cesium the crystals Cs2NpO2(MoO4). 2H2O are formed. The behavior of uranyl and neptunyl differs also in solutions of ammonium paramolybdate: (NH4)2UO2(MoO4).2H2O and (NH4)2NpO2.(MoO4)2.2H2O are formed correspondingly. From sodium molybdate solutions at the presence of some organic solvents was isolated mixed-valent complex of composition: Na6[Np(V)O2]2[Np(VI)O2](MoO4)5.13H2O. The study of thermal and spectral behavior of the synthesized solid complexes also specifies the difference in properties of uranyl and neptunyl in investigated compounds and even in isostructural compounds

  16. Equilibrium biosorption studies of wastewater U(VI), Cu(II) and Ni(II) by the brown alga Cystoseira indica in single, binary and ternary metal systems

    International Nuclear Information System (INIS)

    Biosorption of U(VI), Cu(II) and Ni(II) onto Cystoseira indica was investigated in single, binary and ternary metal systems. The single-ion biosorption results showed that the affinity order of metal ions on C. indica was Cu(II) > Ni(II) > U(VI) and the mechanism of metal ions biosorption on this biomass was physisorption. The binary and ternary biosorption data were interpreted using the multicomponent isotherms. Competitive biosorption results showed that the metal biosorption decreased with increasing the concentrations of other metal ions and an antagonistic effect was observed in binary and ternary systems. Also, the inhibitory effect increased with increasing the initial metal ions concentrations. (author)

  17. Extraction chromatographic studies on Am(III) and U(VI) using Cyanex-923 impregnated Chromosorb W in nitric acid medium

    International Nuclear Information System (INIS)

    The uptake of Am(III) and U(VI) has been investigated under varying nitric acid concentrations (0.01-3 M HNO3) by an extraction chromatographic resin material viz. Cyanex-923 coated on Chromosorb W. Whereas quantitative sorption of U(VI) was observed throughout the [HNO3] range, DAm values showed a maximum at 0.1 M HNO3. Presence of 5 M NaNO3 enhanced the DAm values significantly up to 0.1 M HNO3. In column experiments, breakthrough capacity was evaluated as 42 ± 2 mg of Nd(Am) per gram of the resin material. 1.5 ml of 8 M HNO3 was sufficient to elute ∼ 98.5% of the sorbed Nd(Am). (author)

  18. Kinetic desorption and sorption of U(VI) during reactive transport in a contaminated Hanford sediment.

    Science.gov (United States)

    Qafoku, Nikolla P; Zachara, John M; Liu, Chongxuan; Gassman, Paul L; Qafoku, Odeta S; Smith, Steven C

    2005-05-01

    Column experiments were conducted to investigate U(VI) desorption and sorption kinetics in a sand-textured, U(VI)-contaminated (22.7 micromol kg(-1)) capillary fringe sediment from the U.S. Department of Energy (DOE) Hanford site. Saturated column experiments were performed under mildly alkaline conditions representative of the Hanford site where uranyl-carbonate and calcium-uranyl-carbonate complexes dominate aqueous speciation. A U(VI)-free solution was used to study contaminant U(VI) desorption in columns where different flow rates were applied. Sorbed, contaminant U(VI) was partially labile (11.8%), and extended leaching times and water volumes were required for complete desorption of the labile fraction. Uranium-(VI) sorption was studied after the desorption of labile, contaminant U(VI) using different U(VI) concentrations in the leaching solution. Strong kinetic effects were observed for both U(VI) sorption and desorption, with half-life ranging from 8.5 to 48.5 h for sorption and from 39.3 to 150 h for desorption. Although U(VI) is semi-mobile in mildly alkaline, subsurface environments, we observed substantial U(VI) adsorption, significant retardation during transport, and atypical breakthrough curves with extended tailing. A distributed rate model was applied to describe the effluent data and to allow comparisons between the desorption rate of contaminant U(VI) with the rate of shortterm U(VI) sorption. Desorption was the slower process. We speculate that the kinetic behavior results from transport or chemical phenomena within the phyllosilicate-dominated fine fraction present in the sediment. Our results suggest that U(VI) release and transport in the vadose zone and aquifer system from which the sediment was obtained are kinetically controlled. PMID:15926566

  19. Synthesis, characterization, and exciton dynamics of II-VI semiconducting nanomaterials and ab-initio studies for applications in explosives sensing

    OpenAIRE

    Cooper, Jason Kyle

    2013-01-01

    II-VI semiconducting nanostructures have been intensively researched as promising materials in applications including sensing, light emitting diodes (LEDs), lasers, photoelectrochemical (PEC) materials for water splitting and photo-catalysis, and dye or quantum dot sensitized solar cells. On the nanoscale, structural morphology plays a significant role in determining optical, electronic, and physical properties, and thus consequently affects the ultimate device properties. In zero-d...

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

    OpenAIRE

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

    2004-01-01

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

  1. Cr(VI) speciation in foods by HPLC-ICP-MS: investigation of Cr(VI)/food interactions by size exclusion and Cr(VI) determination and stability by ion-exchange on-line separations.

    Science.gov (United States)

    Vacchina, Véronique; de la Calle, Inmaculada; Séby, Fabienne

    2015-05-01

    A method has been developed for the specific and sensitive determination of Cr(VI) in foods. First, the interactions between Cr(VI) and the matrices were investigated by size-exclusion HPLC-ICP-MS (SEC-ICP-MS). Evidence was found for the complexation of Cr(VI) potentially present with the ligands. For quantification of Cr(VI), the method was based on an alkaline extraction (NH4OH solution at pH 11.5) followed by Cr(VI) determination by anion-exchange HPLC-ICP-MS. Analytical performances of the method were satisfactory in terms of linearity, specificity, accuracy, repeatability, and intermediate precision. Detection limits ranged from 1 to 10 μg/kg, depending on the matrices investigated. The method was then applied for the determination of Cr(VI) in several products (dairy products, flour, chocolate, vegetables, fruits, meat, fish, eggs, and beverages) from different brands and origins. Cr(VI) was found in none of the samples investigated. To further investigate the reason for this absence, a stability study of spiked Cr(VI) was therefore conducted. A semi-skimmed cow milk was selected for this study. Cr(VI) was shown to be unstable in this matrix with a degradation rate increasing with the temperature. PMID:25772568

  2. Voltammetric determination of Se(IV) and Se(VI) in saline samples-Studies with seawater, hydrothermal and hemodialysis fluids

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Paulo C. do, E-mail: npaulo@quimica.ufsm.br [Departamento de Quimica, Universidade Federal de Santa Maria, C.P. 5051, 97105-970 Santa Maria, RS (Brazil); Jost, Cristiane L.; Carvalho, Leandro M. de; Bohrer, Denise [Departamento de Quimica, Universidade Federal de Santa Maria, C.P. 5051, 97105-970 Santa Maria, RS (Brazil); Koschinsky, Andrea [School of Engineering and Science, Geosciences and Astrophysics, Jacobs University Bremen GmbH, P.O. Box 750561, D-28725 Bremen (Germany)

    2009-08-26

    Determination of Se(IV) and Se(VI) in high saline media was investigated by cathodic stripping voltammetry (CSV). The voltammetric method was applied to assay selenium in seawater, hydrothermal and hemodialysis fluids. The influence of ionic strength on selenium determination is discussed. The CSV method was based on the co-electrodeposition of Se(IV) with Cu(II) ions and Se(VI) determined by difference after sample UV-irradiation for photolytic selenium reduction. UV-irradiation was also used as sample pre-treatment for organic matter decomposition. Detection limit of 0.030 {mu}g L{sup -1} (240 s deposition time) and relative standard deviation (RSD) of 6.19% (n = 5) for 5.0 {mu}g L{sup -1} of Se(IV) were calculated. Linear calibration range for selenium was observed from 1.0 to 100.0 {mu}g L{sup -1}. Concerning the pre-treatment step, best results were obtained by using 60 min UV-irradiation interval in H{sub 2}O{sub 2}/HCl medium. Se(VI) was reduced to the Se(IV) electroactive species with recoveries between 91.7% and 112.9%. Interferents were also investigated.

  3. 贝尔凹陷油成藏要素空间匹配关系及对油成藏的控制作用%Spatial Matching Relation of Oil Reservoir Forming Factors and Its Control Effect on Reservoir Formation in Beir Depression

    Institute of Scientific and Technical Information of China (English)

    付广; 牟敦山

    2012-01-01

    通过贝尔凹陷油成藏要素——南屯组源岩、裂缝及断层圈闭和源断裂的空间匹配关系研究得到,贝尔凹陷裂缝和断层圈闭与南屯组源岩在空间上有4种接触关系,第一种是布达特群裂缝圈闭位于南屯组源岩侧上方,由T5—T1源断裂连接;第二种是南屯组断层圈闭位于南屯组源岩内,由T23-T1源断裂连接;第三种是南屯组断层圈闭位于南屯组源岩外侧,由T23—T1断裂沟通的砂体连接;第四种是大磨拐河组二段断层圈闭位于南屯组源岩之上,由T23-T1断裂连接。贝尔凹陷3个成藏要素空间匹配关系对油成藏与分布的控制作用表现在以下3个方面:①南屯组源岩分布控制着油藏分布;②油藏均沿源断裂分布;③圈闭距南屯组源岩距离越近越有利于油藏形成。%Beier Depression is one of second tectonic units in Lake Beier depression, development from the bottom of the bed rock of the Upper Triassic Budate Group ( T3 b), the Tongbomiao group (J2t) of Upper Jurassic, Nantun group ( Kin) , Damoguaihe group(Kid) and Yimin group( K1y) of Lower Cretaceous, Qingyuangang group( K1q) Forma- tion of the Yimin group and the upper Cretaceous. Combined with results of previous studies, this paper considers source rock, trap, and the source fault are main control factors of hydrocarbon accumulation in Beir depression. Oil and gas mainly from dark mudstone of Klrt and source rock with better conditions, to provide sufficient oil source for hydrocarbon migration and accumulation in Beir depression. Traps are mainly two kinds of type, crack traps and fault traps include fault block, fault seal and fault lithologic traps in Beir depression. The reservoirs of T3 b and K1 d and source rocks of K1 n located in different layers, faults should be oil migration transporting main pathway. By studies on spatial matching relation of oil reservoir forming factors in Beier depression--K1 n source rock

  4. Thermodynamical analysis of the fission product release in the ORNL VI-3 and VI-5 tests; Analyse thermodynamique du relachement des produits de fission dans les essais ORNL VI-3 et VI-5

    Energy Technology Data Exchange (ETDEWEB)

    Defoort, J.; Froment, K

    1998-06-01

    The thermodynamical equilibrium hypothesis has been applied to the tests ORNL (Oak Ridge National Laboratory) VI-3 and VI-5 (Vertical Induction heated), to study fission release products. Irradiated fuel samples were heated under oxidizing (VI-3) and reducing (VI-5) controlled atmosphere. They can be compared to the Vercors 4 and 5 tests. The thermodynamical calculus results of barium and ruthenium fission products release, agree in the lump with measures, whatever the gas phase nature. The strontium release calculus under reducing atmosphere, is largely upper than those measured and correctly evaluated under oxidizing atmosphere. These results confirm those obtained for Vercors 4 and 5 and show the interest of the select model. (A.L.B.)

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

    Directory of Open Access Journals (Sweden)

    Dahe Fan

    2006-01-01

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

  6. Extraction behavior of uranium(VI) with polyurethane foam

    International Nuclear Information System (INIS)

    The extraction of uranium(VI) from aqueous solution with polyether-based polyurethane (PU) foam was studied. The effects of the kinds and concentrations of nitrate salts, uranium(VI) concentration, temperature, nitric acid concentration, pH, the content of poly(ethylene oxide) in the polyurethane foam, and the ratio of PU foam weight and solution volume on the extraction of uranium(VI) were investigated. The interferences of fluoride and carbonate ions on the extraction of uranium(VI) were also examined, and methods to overcome both interferences were suggested. It was found that no uranium was extracted in the absence of a nitrate salting-out agent, and the extraction behaviors of uranium(IV) with polyurethane foam could be explained in terms of an etherlike solvent extraction mechanism. In addition, the percentage extraction of a multiple stage was also estimated theoretically

  7. VI-14, a novel flavonoid derivative, inhibits migration and invasion of human breast cancer cells

    International Nuclear Information System (INIS)

    It has been well characterized that flavonoids possess pronounced anticancer potentials including anti-angiogenesis, anti-metastasis, and pro-apoptosis. Herein, we report, for the first time, that VI-14, a novel flavonoid derivative, possesses anti-cancer properties. The purpose of this study is to investigate the anti-migration and anti-invasion activities of VI-14 in breast cancer cells. Our data indicate that VI-14 inhibits adhesion, migration and invasion of MDA-MB-231 and MDA-MB-435 human breast cancer cells. MDA-MB-231 cells treated with VI-14 display reduced activities and expressions of ECM degradation-associated proteins including matrix metalloproteinase 2 (MMP-2) and 9 (MMP-9) at both the protein and mRNA levels. Meanwhile, VI-14 treatment induces an up-regulated expression of tissue inhibitor of metalloproteinase 1 (TIMP-1) and 2 (TIMP-2) in MDA-MB-231 cells. Western blotting results show that phosphorylation levels of critical components of the MAPK signaling pathway, including ERK, JNK and P38, are dramatically decreased in VI-14-treated MDA-MB-231 cells. Furthermore, treatment of VI-14 significantly decreases the nuclear levels and the binding ability of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1). Taken together, our data suggest that VI-14 treatment suppresses migration and motility of breast cancer cells, and VI-14 may be a potential compound for cancer therapy. Highlights: ► We report for the first time that VI-14 possesses anti-cancer properties. ► VI-14 weakens the adhesion, migration and invasion of human breast cancer cells. ► VI-14 decreases the activities and expressions of MMP-2/9. ► VI-14 suppresses the phosphorylation levels of the MAPK signaling pathway. ► VI-14 decreases the nuclear levels and the binding ability of NF-κB and AP-1.

  8. VI-14, a novel flavonoid derivative, inhibits migration and invasion of human breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fanni; Li, Chenglin; Zhang, Haiwei; Lu, Zhijian [State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009 (China); Li, Zhiyu; You, Qidong [Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009 (China); Lu, Na [State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009 (China); Guo, Qinglong, E-mail: anticancer_drug@yahoo.com.cn [State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210009 (China)

    2012-06-01

    It has been well characterized that flavonoids possess pronounced anticancer potentials including anti-angiogenesis, anti-metastasis, and pro-apoptosis. Herein, we report, for the first time, that VI-14, a novel flavonoid derivative, possesses anti-cancer properties. The purpose of this study is to investigate the anti-migration and anti-invasion activities of VI-14 in breast cancer cells. Our data indicate that VI-14 inhibits adhesion, migration and invasion of MDA-MB-231 and MDA-MB-435 human breast cancer cells. MDA-MB-231 cells treated with VI-14 display reduced activities and expressions of ECM degradation-associated proteins including matrix metalloproteinase 2 (MMP-2) and 9 (MMP-9) at both the protein and mRNA levels. Meanwhile, VI-14 treatment induces an up-regulated expression of tissue inhibitor of metalloproteinase 1 (TIMP-1) and 2 (TIMP-2) in MDA-MB-231 cells. Western blotting results show that phosphorylation levels of critical components of the MAPK signaling pathway, including ERK, JNK and P38, are dramatically decreased in VI-14-treated MDA-MB-231 cells. Furthermore, treatment of VI-14 significantly decreases the nuclear levels and the binding ability of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1). Taken together, our data suggest that VI-14 treatment suppresses migration and motility of breast cancer cells, and VI-14 may be a potential compound for cancer therapy. Highlights: ► We report for the first time that VI-14 possesses anti-cancer properties. ► VI-14 weakens the adhesion, migration and invasion of human breast cancer cells. ► VI-14 decreases the activities and expressions of MMP-2/9. ► VI-14 suppresses the phosphorylation levels of the MAPK signaling pathway. ► VI-14 decreases the nuclear levels and the binding ability of NF-κB and AP-1.

  9. Síntese eletroquímica do ion ferrato(VI) Eletrochemical synthesis of iron(VI) ferrate

    OpenAIRE

    Maria Augusta de Luca; Sérgio João de Luca; Maria Alice Santana

    2003-01-01

    The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathod...

  10. Studies on the extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions of Arsenazo-I with HDEHP, HTTA, TDA and TCMA

    International Nuclear Information System (INIS)

    The extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions containing Arsenazo-I with the organic solvents tridodecylamine (TDA), 1-[thenoyl-(2)[-3-3-3-trifluoroacetone (HTTA), di(2-ethylhexyl) phosphoric acid (HDEHP) and tricaprymethylammonium chloride (TCMA) in xylene has been investigated. Effect of hydrogen ion concentration in the aqueous phase, Arsenazo-I concentration, as well as the effect of solvent concentration on the extraction was studied. Some alternatives for separation of the elements studied were recommended enabling the spectrophotometric determination of these elements using Arsenazo-I without interference. (author). 21 refs., 10 figs

  11. Salivary carbonic anhydrase isoenzyme VI

    Science.gov (United States)

    Kivelä, Jyrki; Parkkila, Seppo; Parkkila, Anna-Kaisa; Leinonen, Jukka; Rajaniemi, Hannu

    1999-01-01

    The carbonic anhydrases (CAs) participate in the maintenance of pH homeostasis in various tissues and biological fluids of the human body by catalysing the reversible reaction CO2+ H2O ⇌ HCO3−+ H+ (Davenport & Fisher, 1938; Davenport, 1939; Maren, 1967). Carbonic anhydrase isoenzyme VI (CA VI) is the only secretory isoenzyme of the mammalian CA gene family. It is exclusively expressed in the serous acinar cells of the parotid and submandibular glands, from where it is secreted into the saliva. In this review, we will discuss recent advances in research focused on the physiological role of salivary CA VI in the oral cavity and upper alimentary canal. PMID:10523402

  12. Efficacy and safety of vi-tetanus toxoid conjugated typhoid vaccine (PedaTyph™) in Indian children: School based cluster randomized study.

    Science.gov (United States)

    Mitra, Monjori; Shah, Nitin; Ghosh, Apurba; Chatterjee, Suparna; Kaur, Iqbal; Bhattacharya, Nisha; Basu, Suparna

    2016-04-01

    Vi polysaccharide typhoid vaccines cannot be used in children tetanus toxoids (Vi-TT) induces protective levels even in children <2 years. We evaluated efficacy and safety following vaccination with a Vi-TT vaccine in children 6 months to 12 years of age. Overall, 1765 subjects were recruited from two registered municipal urban slums of southern Kolkata. Most of the children of the slum dwellers attended the schools in the locality which was selected with permission from the school authority. Schools were randomly divided into vaccinated (Test group) and unvaccinated group (Control group). Children and their siblings of test group received 2-doses of PedaTyph™ vaccine at 6 weeks interval. Control group received vaccines as per national guidelines. Adverse events (AEs) were examined after 30 minutes, 1 month and clinical events were observed till 12 months post-vaccination. Incidence of culture positive typhoid fever in the control group was 1.27% vis-a-vis none in vaccine group during 12 months. In subgroup evaluated for immunogenicity, an antibody titer value of 1.8 EU/ml (95% CI: 1.5 EU/ml, 2.2 EU/ml), 32 EU/ml (95% CI: 27.0 EU/ml, 39.0 EU/ml) and 14 EU/ml (95% CI: 12.0 EU/ml, 17.0 EU/ml) at baseline, 6 weeks and 12 months, respectively was observed. Sero-conversion among the sub-group was 100% after 6 weeks of post-vaccination and 83% after 12 months considering 4-fold rise from baseline. The efficacy of vaccine was 100 % (95% CI: 97.6%, 100%) in the first year of follow-up with minimal AEs post vaccination. Vi conjugate typhoid vaccine conferred 100% protection against typhoid fever in 1765 children 6 months to 12 years of age with high immunogenicity in a subgroup from the vaccine arm. PMID:26901576

  13. Fortellinger om Vi-et-hjem. : Et retrospektivt studie av seks vietnamesiske menns erfaringer fra sin oppvekst på institusjon.

    OpenAIRE

    2009-01-01

    Denne oppgaven tar for seg fortellingene til noen av de første vietnamesiske innvandrerne som kom til Norge. De intervjuede kom som barn i 1968-69. De var blitt skadet i Vietnamkrigen og kom til Norge for å få behandling de ikke kunne få i Vietnam. Etter endt sykehusopphold ble det bygget et hjem til barna. Vi-et-hjem prosjektet var et frivillig initiativ, hvor barna kom til Norge via den norske arbeidsgruppen for den humanitære hjelpeorganisasjonen Terre des Hommes. De intervjuede er i dag b...

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2009-08-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-08-15

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

  17. The use of endomarketing in credit unions: a case study of the UFVCredi and the Unicred-Viçosa O emprego do endomarketing em cooperativas de crédito: estudo de caso da UFV-Credi e da Unicred-Viçosa

    Directory of Open Access Journals (Sweden)

    Henrique Lopes Dornelas

    2002-11-01

    Full Text Available Endomarketing can be considered as a group of activities concerned with the internal aspects of the organization, whose purpose is to value the human being. In order to become competitive, the Credit Unions should adopt Endomarketing strategies that combine motivation, training and communication elements. The purpose of the present work was to verify how the Credit Union of the Workers of the Federal University of Viçosa Ltd. / UFV-CREDI and the Credit Union of the Doctors and Health-related Professionals of Viçosa Ltd. – UNICRED/VIÇOSA – MG are using the tools offered by Endomarketing. In the methodology, a study concerning the Endomarketing and the Credit Unions war carried out. After that, the employees and the members of the Credit Unions were asked to answer a questionnaire. After the analysis of the obtained data, it was concluded that UFV-CREDI and UNICRED/VIÇOSA-MG have effectively reached their objectives because their Endomarketing strategies have presented positive results, making it possible for them to get new members as well as to keep their members and employees motivated and satisfied with the products and services offered by the Credit Unions.O Endomarketing pode ser conceituado como um conjunto de atividades voltadas para o interior da organização, cuja finalidade é valorizar o ser humano. Para que as cooperativas de crédito sejam competitivas, elas devem adotar estratégias de Endomarketing, que combinem elementos de motivação, treinamento e comunicação. Procurou-se com o presente estudo, verificar como a Cooperativa de Economia e Crédito Mútuo dos Servidores da Universidade Federal de Viçosa – LTDA / UFV-CREDI e a Cooperativa de Economia e Crédito Mútuo dos Médicos e demais Profissionais da Saúde de Viçosa Ltda – UNICRED/VIÇOSA-MG estão utilizando as ferramentas oferecidas pelo Endomarketing. Na metodologia foi realizado um estudo acerca do Endomarketing e das cooperativas de crédito, para

  18. VI Tallinna arhitektuuritriennaal / Leonhard Lapin

    Index Scriptorium Estoniae

    Lapin, Leonhard, 1947-

    2005-01-01

    15.-17. IX Tallinnas Niguliste kirikus toimuval VI Tallinna arhitektuuritriennaalil esinevad inglise arhitektuurikriitik Peter Davey, šveitsi arhitekt Peter Zumthor, soome arhitekt Juha Leviskä, eesti arhitekt Vilen Künnapu, eesti kunstiajaloolane Juhan Maiste jt. Külastatakse KUMU, tutvutab autor Pekka Vapaavuori

  19. Molecular evolution of type VI intermediate filament proteins

    Directory of Open Access Journals (Sweden)

    Vincent Michel

    2007-09-01

    Full Text Available Abstract Background Tanabin, transitin and nestin are type VI intermediate filament (IF proteins that are developmentally regulated in frogs, birds and mammals, respectively. Tanabin is expressed in the growth cones of embryonic vertebrate neurons, whereas transitin and nestin are found in myogenic and neurogenic cells. Another type VI IF protein, synemin, is expressed in undifferentiated and mature muscle cells of birds and mammals. In addition to an IF-typical α-helical core domain, type VI IF proteins are characterized by a long C-terminal tail often containing distinct repeated motifs. The molecular evolution of type VI IF proteins remains poorly studied. Results To examine the evolutionary history of type VI IF proteins, sequence comparisons, BLAST searches, synteny studies and phylogenic analyses were performed. This study provides new evidence that tanabin, transitin and nestin are indeed orthologous type VI IF proteins. It demonstrates that tanabin, transitin and nestin genes share intron positions and sequence identities, have a similar chromosomal context and display closely related positions in phylogenic analyses. Despite this homology, fast evolution rates of their C-terminal extremity have caused the appearance of repeated motifs with distinct biological activities. In particular, our in silico and in vitro analyses of their tail domain have shown that (avian transitin, but not (mammalian nestin, contains a repeat domain displaying nucleotide hydrolysis activity. Conclusion These analyses of the evolutionary history of the IF proteins fit with a model in which type VI IFs form a branch distinct from NF proteins and are composed of two major proteins: synemin and nestin orthologs. Rapid evolution of the C-terminal extremity of nestin orthologs could be responsible for their divergent functions.

  20. Bliver vi aldrig mætte?

    DEFF Research Database (Denmark)

    Christensen, Toke Haunstrup

    Vi har de sidste 100 år oplevet en utrolig vækst i den materielle levestandard. Mobiltelefoner og IT er eksempler på dette. Men det høje forbrug sætter kloden under pres. Bliver vi aldrig ”mætte” af forbruget? Og har vi et ansvar som enkeltpersoner?...

  1. Modification of zirconium diphosphate with salicylic acid and its effect on the uranium (Vi) sorption

    International Nuclear Information System (INIS)

    The surface of zirconium diphosphate (ZrP2O7) was modified with salicylic acid and its effect was evaluated on the uranium (Vi) sorption. The modified surface of the material was analyzed with different analytical techniques among which are included the atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. This analysis allowed showing that the salicylic acid is being held on the surface of the zirconium diphosphate. The reactivity of modified zirconium diphosphate compared with uranium (Vi) was investigated using the classical method of batch sorption. The analysis of sorption isotherms shows that the salicylic acid has an important effect in the uranium (Vi) sorption. According to the study conducted, the interaction among the uranium (Vi) and the surface of zirconium diphosphate modified with the salicylic acid most likely leads to the complexes formation of binary (U(Vi)/ZrP2O7) and ternary (U(Vi)/salicylate/ZrP2O7) surface. (Author)

  2. Synergistic effect of HBMPPT with PSO, DOSO and TBP on the extraction of U(VI) and on the separation of U(VI) and Th(IV)

    International Nuclear Information System (INIS)

    Some popular neutral extractants (PSO-petroleum sulfoxide, DOSO-di-n-octyl sulfoxide, TBP-tributylphosphate etc.) were chosen as synergist to study the synergistic effect on the extraction reaction with HBMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione) for U(VI), and the synergistic separation ability of HBMPPT for U(VI) and Th(IV). The synergistic extraction ability shown by the studied systems for U(VI) is as follows: PSO > DOSO > TBP, and the same sequence was also verified for the separation coefficient of U(VI) and Th(IV). The synergistic complexes may be presented as: UO2NO3 x BMPPT x S and UO2(BMPPT)2 x S for U(VI) (S is PSO, DOSO or TBP). (author)

  3. viDA Thereapeutics, Inc. Business Plan

    OpenAIRE

    Lee, Nancy; Lestou, Valia S

    2008-01-01

    viDA Therapeutics Inc. (herein called viDA), with headquarters in Vancouver, British Columbia, was incorporated in April of 2008. viDA is a new specialty biotechnology company focused on the discovery, development and commercialization of first-in-class drugs for the treatment of age-related degenerative processes, such as age related wrinkling and hair loss. viDA has chosen a distinct company strategy, focusing strongly on the development and marketing of specialty products. viDA bases its b...

  4. Biosorption of Cr(VI)_ and Cr(III)_Arthrobacter species

    OpenAIRE

    Gelagutashvili, E.; Pataraia, E. Ginturi D.; Gurielidze, M.

    2011-01-01

    The biosorption of Cr(VI)_ and Cr(III)_ Arthrobacter species (Arthrobacter globiformis and Arthrobacter oxidas) was studied simultaneous application dialysis and atomic absorption analysis. Also biosorption of Cr(VI) in the presence of Zn(II) during growth of Arthrobacter species and Cr(III) in the presence of Mn(II) were discussed. Comparative Cr(VI)_ and Cr(III)_ Arthrobacter species shown, that Cr(III) was more effectively adsorbed by both bacterium than Cr(VI). The adsorption capacity is ...

  5. Treatment of combined sewer overflows using ferrate (VI).

    Science.gov (United States)

    Gandhi, Rohan; Ray, Ajay K; Sharma, Virender K; Nakhla, George

    2014-11-01

    This paper presents the results of a study conducted on the treatment of combined sewer overflows using ferrate (VI) [Fe (VI)]. At a Fe (VI) dose of 0.24 mg/L, total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), total biochemical oxygen demand (TBOD5), soluble biochemical oxygen demand (SBOD5), total suspended solids (TSS), volatile suspended solids (VSS), total phosphorus (TP), total nitrogen (TN), and soluble TN removal efficiencies of 71, 75, 69, 68, 72, 83, 64, 38, and 36%, respectively, were achieved. Kinetic studies revealed that a contact time of only 15 minutes is sufficient to achieve secondary effluent criteria. An innovative technique of using primary sludge (PS) and thickened waste activated sludge as a source for the in situ synthesis of ferrate was developed. A comparative study of treatment efficiencies achieved by Fe (VI) generated from different sources was done. At 0.1 mg/L dose of Fe (VI) synthesized from PS, TCOD, SCOD, TSS, VSS, TP, and TN removal efficiencies of 60, 62, 63, 67, 30, and 25%, respectively, were achieved. PMID:25509525

  6. Interaction of neptunyl(V) and uranyl(VI) with EDTA in NaCl media: experimental study and Pitzer modeling

    International Nuclear Information System (INIS)

    The complexation of Np(V) and U(VI) by EDTA has been investigated in solutions of 0.3 to 5 m NaCl with pH 2 to 9 at 25 C. A solvent extraction method with HDEHP in heptane was used to measure the stability constants of the species NpO2H2Y-, NpO2HY2-, NpO2Y3-, UO2HY-, and UO2Y2-. The constants showed a small dependence on ionic strength between 1 and 5 m NaCl. The data were modeled using the ion-interaction model of Pitzer. Binary interaction parameters are reported for each ion pair necessary to fully represent EDTA deprotonation, and complexation of neptunyl and uranyl with EDTA in 0 to 5 m NaCl solutions. (orig.)

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

    Science.gov (United States)

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

    2002-11-01

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

  8. Thermal, spectral, magnetic and biological studies of thiosemicarbazones complexes with metal ions: Cu(II), Co(II), Ni(II), Fe(III), Zn(II), Mn(II) and UO2(VI)

    International Nuclear Information System (INIS)

    Thiosemicarbazones ligands, isatin-3-thiosemicarbazone(HIT) and N-acetylisatin-3-thiosemicarbazone (HAIT), which have tridentate ONN coordinating sites were prepared. The complexes of both ligands with Cu(II), Co(II), Ni(II), Fe(III), Zn(II), Mn(II) and UO2(VI) ions were isolated. The ligands and their metal complexes were characterized by elemental analysis, IR, UV-Vis and mass spectra, also by conductance, magnetic moment and TG-DSC measurements. All the transition metal complexes have octahedral configurations, except Cu-complexes which have planar geometry and the UO2(VI) complexes which have coordination number 8 and may acquire the distorted dodecahedral geometry. Thermal studies explored the possibility of obtaining new complexes. Inversion from octahedral to square-planar configuration occurred upon heating the parent Ni-HIAT complex to form the corresponding pyrolytic product. The antifungal activity against the tested organisms showed that some metal complexes enhanced the activity with respect to the parent ligands. (author)

  9. A laboratory study of the oxidation of non toxic Cr(III) to toxic Cr(VI) by OH• free radicals in simulated atmospheric water droplets conditions: Potential environmental impact

    International Nuclear Information System (INIS)

    Highlights: • Oxidation of non toxic Cr(III) to toxic Cr(VI) is a major environmental hazard. • oxidation by OH. free radicals generated by water radiolysis. • Oxidation is maximum at pH 4. • A mechanism is proposed. - Abstract: In atmospheric waters, oxidation of Cr(III) to Cr(VI) by OH• free radicals is a major environmental hazard since non-toxic species is transformed into toxic one. It is important to obtain some details concerning this oxidation reaction. In this study we simulated this oxidation by steady state radiolysis using 60Co radioactive source and pulse radiolysis technique using a 2.5 MeV van de Graaff electron accelerator and investigated its kinetics in the pH range 1 to 9. Our findings showed that the reaction was highly pH dependant with a maximum yield at pH 4. The electron transfer proceeds via an inner sphere mechanism with (i) formation of the [OH• –Cr(III)] adduct with an equilibrium constant of 2.34 × 104 mol−1 dm−3 then (ii) followed by an electron transfer from Cr(III) to OH• within the adduct with a rate constant of 2.51 × 104 s−1. The implication of this oxidation to atmospheric chromium contamination is discussed

  10. Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium.

    Science.gov (United States)

    Watts, Mathew P; Khijniak, Tatiana V; Boothman, Christopher; Lloyd, Jonathan R

    2015-08-15

    Chromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to the Halomonas genus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as an in situ treatment of COPR and other alkaline Cr(VI)-contaminated environments. PMID:26048926

  11. Ferrate(VI) oxidation of tetrabromobisphenol A in comparison with bisphenol A.

    Science.gov (United States)

    Yang, Bin; Ying, Guang-Guo; Chen, Zhi-Feng; Zhao, Jian-Liang; Peng, Fu-Qiang; Chen, Xiao-Wen

    2014-10-01

    Ferrate(VI) (Fe(VI)) oxidative removal of various organic micropollutants mainly depends on the reactivity of Fe(VI) to target micropollutants and coexisting constituents present in source water. This study evaluated the potential of Fe(VI) oxidation of the brominated flame retardant tetrabromobisphenol A (TBBPA) by using reaction kinetics, products identification and toxicity evaluation, and investigated the influencing effects of humic acid and clay particles on Fe(VI) removal of TBBPA in comparison with bisphenol A (BPA). The obtained apparent second-order rate constants (k(app)) for Fe(VI) reaction with TBBPA ranged from 7.9(±0.3) × 10(3) M(-1) s(-1) to 3.3(±0.1) × 10(1) M(-1) s(-1) with the half-life (t1/2) ranging from 1.7 s to 419.3 s at pH 7.0-10 for an Fe(VI) concentration of 10 mg L(-1). Easier oxidation by Fe(VI) was observed for TBBPA than for BPA. Fe(VI) can destroy and transform the TBBPA molecule through β-scission reaction, yielding the chemical species of low bromine-substituted products. More importantly, the oxidation of TBBPA by Fe(VI) led to the loss of its multiple hormonal activities (androgenic, antiestrogenic and antiandrogenic activities). The organic component humic acid decreased the TBBPA and BPA reactions with Fe(VI), while the inorganic component montmorillonite had no effect on their removal within the tested concentrations. Increasing the Fe(VI) dosage can reduce the effects of soluble organic matter and clay particles present in source waters on the degradation process, leading to the complete removal of target micropollutants. PMID:24956603

  12. U(VI) and Eu(III) ion sorption in the interface solution-phosphate solids: Structural study and mechanisms; Sorption des ions U(VI) et Eu(III) a l`interface solution - solides phosphates: Etude structurale et mechanismes

    Energy Technology Data Exchange (ETDEWEB)

    Drot, Romuald [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1998-09-18

    As part of the storage of nuclear wastes in a deep underground disposal, radionuclides sorption on geological or engineered barriers is one of the most important factor which could enhance retardation. Thus, the knowledge of such mechanisms is needed. For this purpose, we chose to experimentally define sorption equilibria before performing simulation of retention data. Several phosphate compounds are potential candidates as engineered barrier additives. We considered Th{sub 4}(PO{sub 4}){sub 4}P{sub 2}O{sub 7}, Zr{sub 2}O(PO{sub 4}){sub 2} which allow to study the effect of PO{sub 4} and P{sub 2}O{sub 7} groups separately. Eu(III) and U(IV) ions were used as structural probes in order to simulate actinides (III) and (VI) behavior. X-ray powder diffraction, IR spectroscopy and electron probe microanalysis were used to characterized the synthesized solids. Electrophoretic measurements showed an amphoteric behavior of surface sites. Moreover, laser spectro-fluorimetry experiments indicated that no diffusion phenomena of the sorbed ion inside the solid occurs. Thus, we considered that a surface complexation model should be applied. Laser spectro-fluorimetry and XPS allowed to determine the nature of surface sites. ZrP{sub 2}O{sub 7} presents only one single site (P{sub 2}O{sub 7} groups) whereas Th{sub 4}(PO{sub 4}){sub 4}P{sub 2}O{sub 7} and Zr{sub 2}O(PO{sub 4}){sub 2} admit two types of sites (PO{sub 4}/P{sub 2}O{sub 7} and PO{sub 4}/oxo groups, respectively). Sorbed species were identified using laser spectro-fluorimetry which indicate that, in KNO{sub 3} 0.5 M medium and for a known surface site, there are two surface complexes for U(VI) (sorption of UO{sup 2+}{sub 2} et de UO{sub 2}NO{sup +}{sub 3} species) and only one for Eu(III) (sorption of EuNO{sup 2+}{sub 3}). They are linked to the substrate as bidentate inner sphere complexes (EXAFS study). Surface acidity constants were determined by simulation of potentiometric titration curves obtained for each solid

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

    Mtimunye, Phalazane J; Chirwa, Evans M N

    2014-10-01

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

  15. Transient groundwater chemistry near a river: Effects on U(VI) transport in laboratory column experiments

    Science.gov (United States)

    Yin, Jun; Haggerty, Roy; Stoliker, Deborah L.; Kent, Douglas B.; Istok, Jonathan D.; Greskowiak, Janek; Zachara, John M.

    2011-01-01

    In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity and low Ca concentrations (Columbia River water) enhanced adsorption and reduced aqueous concentrations. Conversely, high alkalinity and high Ca concentrations (Hanford groundwater) reduced adsorption and increased aqueous concentrations of U(VI). An equilibrium surface complexation model calibrated using laboratory batch experiments accounted for the decrease in U(VI) adsorption observed with increasing (bi)carbonate concentrations and other aqueous chemical conditions. In the column experiment, alternating pulses of river and groundwater caused swings in aqueous U(VI) concentration. A multispecies multirate surface complexation reactive transport model simulated most of the major U(VI) changes in two column experiments. The modeling results also indicated that U(VI) transport in the studied sediment could be simulated by using a single kinetic rate without loss of accuracy in the simulations. Moreover, the capability of the model to predict U(VI) transport in Hanford groundwater under transient chemical conditions depends significantly on the knowledge of real-time change of local groundwater chemistry.

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

    Science.gov (United States)

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

    2008-04-01

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

  17. Benchmark analysis of MCNP trademark ENDF/B-VI iron

    International Nuclear Information System (INIS)

    The MCNP ENDF/B-VI iron cross-section data was subjected to four benchmark studies as part of the Hiroshima/Nagasaki dose re-evaluation for the National Academy of Science and the Defense Nuclear Agency. The four benchmark studies were: (1) the iron sphere benchmarks from the Lawrence Livermore Pulsed Spheres; (2) the Oak Ridge National Laboratory Fusion Reactor Shielding Benchmark; (3) a 76-cm diameter iron sphere benchmark done at the University of Illinois; (4) the Oak Ridge National Laboratory Benchmark for Neutron Transport through Iron. MCNP4A was used to model each benchmark and computational results from the ENDF/B-VI iron evaluations were compared to ENDF/B-IV, ENDF/B-V, the MCNP Recommended Data Set (which includes Los Alamos National Laboratory Group T-2 evaluations), and experimental data. The results show that the ENDF/B-VI iron evaluations are as good as, or better than, previous data sets

  18. Extraction of Mo(VI) and U(VI) by alamine 310 and its mixtures from HCl solution

    International Nuclear Information System (INIS)

    Studies on the extraction of molybdenum(VI) and uranium(VI) from HCl solution by triisodecyl amine (Alamine 310), tri-n-butyl phosphate (TBP), di-n-pentylsulphoxide (DPSO) and their mixtures in benzene, in the range of 1-10 M aq. HCl, show that extractions are quantitative in most cases in the higher acidity range 6-8 M. Extraction by bis(2,4,4-trimethyl pentyl) dithiophosphinic acid (Cyanex 301) and its mixtures studied in the range of 0.2-1 M aq. HCl shows quantitative extraction for both the metals by Cyanex 301 and Alamine 310 mixtures only at lower acidity (∼0.2 M). The SCN- ion has a profound influence on the extraction of uranium(VI) by mixtures of 5% (v/v) Alamine 310 and 5% (v/v) TBP from 1 M HCl and the extraction is ∼95% at ∼0.2 M SCN- concentration. Synergism is marked in the extraction of molybdenum(VI) for the mixtures of Alamine 310 and TBP, Alamine 310 and Cyanex 301, and for uranium(VI), by mixtures of Alamine 310 and DPSO as well as Alamine 310 and Cyanex 301. (orig.)

  19. Retention of U(VI) onto silica in presence of model organic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Pham, T.T.H.; Mercier-Bion, F.; Drot, R.; Lagarde, G.; Simoni, E. [Groupe de Radiochimie, IPNO, Universite Paris 11, Orsay, 91406 (France); Lambert, J. [LCPME, 405 rue de Vandoeuvre, Villers-les-Nancy, 54600 (France)

    2008-07-01

    It is well-known that the organic matter influences the retention of ions onto mineral surfaces. However, the major part of concerned studies implies humic substances and complex solids. Another approach for identifying the sorption mechanisms is possible by studying simpler solids than those present in natural medium. So, silica is chosen as mineral surface because of its abundance in soils and of the presence of Si-O groups in clayey minerals. Uranium (VI) is selected as cation. Simple organic molecules like acetic (one carboxylic group) and oxalic (two carboxylic functions) acids are considered as models of the natural organic matter for understanding their role in the retention of U(VI) onto powders and slides of silica. Binary (organics/silica, U(VI)/silica) and ternary systems (organics/silica/U(VI)) are studied by complementary approaches. Sorption edges as function of pH are obtained by liquid scintillation methods and capillary electrophoresis. Different spectroscopic techniques are used to deduce the interactions between the organic matter and U(VI) sorbed onto the silica whose: Time-Resolved Laser induced Fluorescence Spectroscopy (TRLFS), X-ray Photoelectron Spectroscopy (XPS), Nuclear Microprobe Analysis (NMA). The results of the effect of these model organic molecules onto the U(VI) retention showed a good agreement between the different techniques. Concerning the acetic acid, there are not differences in the sorption percentages of uranyl (see the figure). All these results indicate that the uranyl-acetate complexes stay in the aqueous solution rather than sorbing onto the silica. On the contrary, oxalic acid influences the sorption of U(VI) onto the silica surface. The sorption percentage of U(VI) in the ternary system (oxalic acid/silica/U(VI)) is lower than the binary system (U(VI)/silica) (see the figure). So, the presence of oxalic acid decreases the sorption of U(VI) onto the silica surface. (authors)

  20. Physico-chemical studies on the composition of complex thiosulphates of metals Part VI: Potentiometric studies on the reaction between cadmium nitrate and sodium thiosulphate

    Directory of Open Access Journals (Sweden)

    M. S. Bhadraver

    1962-07-01

    Full Text Available The  formation and composition of cadmium thiosulphate complex has been studied  by potentiometric titrations between cadmium nitrate and sodium thiosulphate both by direct and the inverse methods.the equivalence point obtained from the maximum value of De/Dc corresponds to t e formation of a compound having the composition CdS2O3 when Cd (NO32 was added from a micro-burette to sodium thiosulphate in the electtode vessel.

  1. Inhibition of corrosion of zinc by Cr(VI)and Cr(III) treatments

    NARCIS (Netherlands)

    Zhang, X.; Bos, C. van den; Hovestad, A.; Terryn, H.; Wit, J.H.W. de

    2007-01-01

    The corrosion behavior of Cr(VI) and Cr(III) treated zinc has been studied using scanning Kelvin probe (SKP), potentiodynamic polarization and elctrochemical impedance spectroscopy (EIS). The Volta potentials measured on the Cr(VI) or the CR(III)-A treated zinc area by SKP in a humid chamber are mor

  2. A contribution to the study of the extraction of mineral acids and of actinide (IV) and (VI) cations by N,N-dialkylamides

    International Nuclear Information System (INIS)

    N,N-dialkylamides are alternate extractants to tributylphosphate, TBP, for the actinides separation in nuclear fuel reprocessing. N,N-di (2-ethyl hexyl) butyramide and N,N-di (2 ethyl hexyl) isobutyramide are selected for their sufficient extraction and partition ability towards actinides (IV) and (VI) without coextracting fission products. Mechanisms of HNO3, UO22+, Pu4+, Th4+ are investigated. Nitric acid extraction is due to the competitive formation of the species (HNO3)L2, (HNO3)L, (HNO3)2L (L: DOBA or DOiBA). An hydrogen bond is the driving force of the transfer. For low acidity media, amides are neutral extractants. Physical interactions, between free ligand and metallic complex, arise for high amide concentrations. Taking into account the non-ideality of the organic medium by a hard spheres mixture model, we estimate that such interactions are far from negligible and very specific to the amide group. Unlike TBP, when increasing acidity, amides behave as anionic extractants. DOBA and DOiBA appear to be satisfactory extractants for fuel reprocessing

  3. Extraction and Separation of Uranium (VI) and Thorium (IV) Using Tri-n-dodecylamine Impregnated Resins

    International Nuclear Information System (INIS)

    Extraction of U(VI) and Th(IV) from chloride and nitrate solutions with tri-n- dodecylamine impregnated on Amberlite XAD4, was investigated. The distribution of U(VI) and Th(IV) was studied at different concentrations of acid, salting-out agent, extractant, aqueous metal ion and other parameters. Absorption spectral studies have been investigated for uranium species in both aqueous HCl solution and the resin phase. From these studies, it is suggested that the tetrachloro complex of U(VI) is formed in the extraction of uranium (VI) from hydrochloric acid solutions by TDA impregnated resin. Stripping of the extracted U(VI) and Th(IV) was assayed with HCl and HNO3. Finally, the separation of uranium from thorium and fission products in HCl media was achieved

  4. Insights into the extraction of U(VI) in Aliquat-336 ionic liquids

    International Nuclear Information System (INIS)

    In view of the unique advantages, we exploited miscibility of Aliquat-336 based ionic liquid namely, tri-n-octylmethylammonium bis-(2-ethylhexyl)phosphate ((A336)+(DEHP)-) to modify the extraction behavior of U(VI) and Pu(IV) in a PUREX solvent, namely 1.1 M tri-n-butyl phosphate (TBP) in n-dodecane (n-DD). The extraction behavior of U(VI) in 1.1 M TBP/n-DD was studied in the presence and absence of (A336)+(DEHP)-. The discrepancy in the extraction behavior observed in these systems was probed by measuring the distribution ratio of U(VI) as a function of various parameters. The extraction of U(VI) in (A336)+(DEHP)-/n-DD alone was studied to understand the role of ionic liquid in the PUREX solvent during extraction. The distribution ratio of U(VI) in (A336)+(DEHP)-/n-DD decreased with increase in the concentration of nitric acid. Moreover, the extraction of U(VI) in (A336)+(DEHP)- medium was accompanied by the extraction of nitric acid leading to the formation of ionic liquid components namely (A336)+(NO3)- and HDEHP in organic phase. In view of this, the extraction of U(VI) in TBP/n-DD was also studied in the presence of these constituents. Extraction studies revealed that these constituents facilitated the extraction of U(VI) in organic phase. Synergic extraction of U(VI) was observed when HDEHP was employed in conjunction with (A336)+(NO3)- and TBP. The study also revealed that the distribution ratio of U(VI) and Pu(IV) obtained in ionic liquid medium was due to the synergic contributions of ionic liquid constituents as well as TBP. The details of our studies are reported in this paper

  5. Neptunium (VI) and neptunium (VI/V) mixed valence cluster compounds

    Energy Technology Data Exchange (ETDEWEB)

    May, Iain [Los Alamos National Laboratory

    2008-01-01

    Neptunium has three readily accessible oxidation states, IV, V and VI, which can coexist under certain conditions, with the aqueous soluble neptunyl(V) moiety, {l_brace}NpO{sub 2}{r_brace}{sup +}, of most environmental relevance. Careful control of Np chemistry is required during actinide separation processes. In addition, the long half life of the major alpha emitting isotope ({sup 237}Np, t{sub 1/2} = 2.144 x 10{sup 6} years) renders Np a major contributor to the radiotoxicity of nuclear waste as a function of time. Significant quantities of neptunium are generated in nuclear reactors and the current surge in interest in nuclear power will lead to an increase in our need to further understand the chemistry of this element. It is clearly of importance that Np chemistry is well understood and there have been several recent investigations into the structural, spectroscopic and magnetic properties of Np compounds. However, the vast majority of this chemistry has been performed in aqueous solution, prohibiting the use of air and moisture sensitive ligands. This is in stark contrast to uranium and thorium where inert atmosphere chemistry with moisture sensitive donor ligands has flourished, yielding greater insight into the structural and electronic properties of these early actinides. For the uranyl(VI) moiety, {l_brace}UO{sub 2}{r_brace}{sup 2+}, UO{sub 2}Cl{sub 2}(thf){sub 3} (and the desolvated dimer [UO{sub 2}Cl{sub 2}(thf)]{sub 2}) have proven to be excellent moisture-free reagents for inert atmosphere uranyl chemistry. These starting reagents have been used extensively within our group to study soft donor ligand coordination in the uranyl equatorial plane and oxo-activation to Lewis acid coordination. However, until now the absence of such a starting reagent for Np has limited our ability to extend this chemistry any further across the actinide series, which is required if we are to gain a more complete understanding of 5f element chemistry. The synthesis of [Np

  6. Removal of Cr(VI from aqueous solution using Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae

    Directory of Open Access Journals (Sweden)

    P. Sethuraman,

    2010-06-01

    Full Text Available The objective of this study is to investigate the removal efficiency of Cr(VI by Bacillus subtilis, Pseudomonas aeruginosa and Enterobacter cloacae from aqueous solution under different process conditions. Batch mode experiments were carried out as a function of solution pH, biosorbent dosage, Cr(VI concentration and contact time.The FT-IR spectra and SEM analysis of the biosorbent were recorded to analyse the number and position of the functional groups available for the binding of Cr(VI ions and to study the morphology of biosorbent. The batch isothermal equilibrium data were analyzed with Freundlich and Langmuir isotherm models. The kinetic models were examined with pseudo first order and pseudo second order kinetics. The results revealed that the Cr(VI is considerably adsorbed on bacterial biomass and it could be an economical method for the removal of Cr(VI from aqueous solution.

  7. Kinetics of Cr(III) and Cr(VI) removal from water by two floating macrophytes.

    Science.gov (United States)

    Maine, M A; Hadad, H R; Sánchez, G; Caffaratti, S; Pedro, M C

    2016-01-01

    The aim of this work was to compare Cr(III) and Cr(VI) removal kinetics from water by Pistia stratiotes and Salvinia herzogii. The accumulation in plant tissues and the effects of both Cr forms on plant growth were also evaluated. Plants were exposed to 2 and 6 mg L(-1) of Cr(III) or Cr(VI) during 30 days. At the end of the experiment, Cr(VI) removal percentages were significantly lower than those obtained for Cr(III) for both macrophytes. Cr(III) removal kinetics involved a fast and a slow component. The fast component was primarily responsible for Cr(III) removal while Cr(VI) removal kinetics involved only a slow process. Cr accumulated principally in the roots. In the Cr(VI) treatments a higher translocation from roots to aerial parts than in Cr(III) treatments was observed. Both macrophytes demonstrated a high ability to remove Cr(III) but not Cr(VI). Cr(III) inhibited the growth at the highest studied concentration of both macrophytes while Cr(VI) caused senescence. These results have important implications in the use of constructed wetlands for secondary industrial wastewater treatment. Common primary treatments of effluents containing Cr(VI) consists in its reduction to Cr(III). Cr(III) concentrations in these effluents are normally below the highest studied concentrations in this work. PMID:26366503

  8. Phytoremediation of Cr(VI) by Spirodela polyrrhiza (L.) Schleiden employing reducing and chelating agents.

    Science.gov (United States)

    Bala, Rajni; Thukral, Ashwani K

    2011-01-01

    Phytoremediation of Cr(VI) by Spirodela polyrrhiza in binary combinations with low molecular weight organic compounds (LMWOCs) with a reducing or chelating potential, viz., ascorbic acid, citric acid, tartaric acid, oxalic acid, lactic acid, and glycerol was studied in Cr(VI) containing hydroponic media. Significant increase in the relative dry weight of plants with respect to Cr(VI) treated controls was observed with ascorbic acid and glycerol. The uptake of chromium by S. polyrrhiza followed Michaelis-Menten kinetics of active ion uptake. Interaction between Cr and ascorbic acid, oxalic acid, and lactic acid decreased Cr uptake, whereas citric acid, glycerol, and tartaric acid increased it. Supplementation of LMWOCs to Cr(VI) containing media decreased the MDA content of the plants. Multiple regression models revealed that LMWOCs decrease lipid peroxidation independently, as well as that induced by Cr(VI). It was found that superoxide dismutase (SOD), guaiacol peroxidase (GPX), and catalase (CAT) activities were increased significantly in plants growing in media containing Cr(VI). The study established that lactic acid, citric acid, ascorbic acid, and glycerol were most effective in increasing the Cr(VI) phytoremediating potential of S. polyrrhiza and LMWOCs with reducing or chelating properties decrease Cr(VI) stress in S. polyrrhiza. PMID:21598777

  9. Bioprospecting of gum kondagogu (Cochlospermum gossypium) for bioremediation of uranium (VI) from aqueous solution and synthetic nuclear power reactor effluents

    International Nuclear Information System (INIS)

    An ecofriendly green chemistry method using a natural biopolymer, Gum Kondagogu (GK) for the removal of U (VI) from aqueous, simulated nuclear effluents was studied. The adsorption characteristic of GK towards U (VI) from aqueous solution was studied at varied pH, contact time, adsorbent dose, initial U (VI) concentration and temperature using UV–Visible spectroscopy and ICP-MS. Maximum adsorption was seen at pH 4, 0.1% GK with 60 min contact time at room temperature. The GK- U (VI) composite was characterized by FT-IR, zeta potential, TEM and SEM-EDAX. The Langmuir isotherm was found to be 487 mg of U (VI) g−1 of GK. The adsorption capacity and (%) of U (VI) was found to be 490 ± 5.4 mg g−1 and 98.5%. Moreover adsorption of U (VI) by GK was not influenced by other cations present in the simulated effluents. The adsorbed U (VI) was efficiently stripped from composite using 1 M HCl. - Highlights: • An eco-friendly method for removal of U (VI) from simulated nuclear effluents by Gum Kondagogu. • The Langmuir and Freundlich isotherm indicated favourable adsorption. • The adsorption (%) of U (VI) by GK was found to be 98.5%. • Desorption studies on biosorbed metal ions showed that HCl was a good eluent

  10. Mechanisms of U(VI) retention on montmorillonite and hectorite

    International Nuclear Information System (INIS)

    Complete text of publication follows: Introduction: Al- and Mg-smectites can retain significant amounts of U(VI) in soils, sediments, or glass weathered layers, and this sorption property can control the fate of this element in nuclear waste repositories. Possible retention mechanisms vary as a function of solution physico-chemical conditions, but also of the sorbate crystallo-chemistry. This study shows how distinct mechanisms can be observed for U(VI) sorption on montmorillonite and hectorite under similar conditions. Materials and methods: Suspensions of purified clay minerals (2 g/L hectorite or montmorillonite) were reacted in 0.5 M NaCl at pH 7.17 (hectorite) and 6.61 (montmorillonite) with 10 and 15 μM U(VI), respectively. Self-supporting films of reacted clay minerals were obtained by draining suspension aliquots on cellulose nitrate filters. Uranium L3-edge Polarized EXAFS (P-EXAFS) spectra of the self-supporting films were collected in fluorescence mode on the FAME beamline (ESRF, France). P-EXAFS data were reduced, and analyzed using standard procedures. Results and interpretation: Angular dependence of EXAFS spectra was observed for U(VI)-sorbed hectorite, but not montmorillonite. Sorbed U(VI) retained the uranyl conformation for both sorbates, with Oyl at 1.79 and 1.82 Angstroms on montmorillonite and hectorite, respectively. The equatorial Oeq shell was split in two subshells at 2.29 and 2.47 Angstroms for montmorillonite, and 2.35 and 2.53 Angstroms for hectorite, ruling out fully hydrated UO22+(aq). On montmorillonite, U(VI) was surrounded by ∼0.5 Al/Si at 3.30 Angstroms. This shell and the negligible angular dependence point to the formation of edge surface complexes, in line with previous studies [1, 2]. In contrast, for U(VI) on hectorite, only ∼0.2 Mg/Si near 3.2 Angstroms could be modelled, and no EXAFS contribution was observed beyond 3.6 Angstroms. This, and the significant spectral anisotropy suggest that U(VI) either sorbs to hectorite

  11. Rare mycetes of Romania, VI

    Directory of Open Access Journals (Sweden)

    Denes PAZMANY

    1987-08-01

    Full Text Available The paper it's a new contribution to the knowledge of the Macromycetes growing in Romania. There are presented 52 species collected from Central Transylvania, mostly of them new for mycoflora of the whole country. The chorological code used for the localization (MTB is that presented by D. PAZMANY (1986. In the enumeration of the species the paper follows KREISEL's system from "Handbuch fur Pilzfreunde VI" (1975: the species are grouped in 2 classes and 6 orders, mostly of them belongs to the order Agaricales. Ecological, chorological and taxonomical problems are discussed.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-11-16

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

  14. Amidoxime-grafted multiwalled carbon nanotubes by plasma techniques for efficient removal of uranium(VI)

    International Nuclear Information System (INIS)

    Highlights: • Amidoximated MWCNTs were synthesized by plasma techniques. • The surface modification remarkably enhanced U(VI) sorption capacity. • Process was endothermic, spontaneous, and pseudo-second-order chemisorption. • AO-g-MWCNTs showed more favorable selectivity to U(VI). • Mechanism of interaction between AO-g-MWCNTs and U(VI) was discussed and suggested. - Abstract: A novel solid-phase extractant, amidoxime-grafted multiwalled carbon nanotubes (AO-g-MWCNTs), has been synthesized using plasma techniques to selectively separate uranium from nuclear industrial effluents. The adsorbent was characterized by Fourier transform infrared spectra (FT-IR), elemental analysis, Raman, scanning electron microscopy (SEM), and thermal gravity analysis (TGA). Sorption behaviors of uranium(VI) on AO-g-MWCNTs were investigated by varying pH, contact time, initial uranium concentration, and temperature. An optimum sorption capacity of 145 mg g−1 (0.61 mmol g−1) for U(VI) was obtained at pH 4.5. X-ray photoelectron spectroscopy (XPS) has been used to explore the sorption mechanism of U(VI) on AO-g-MWCNTs. Furthermore, AO-g-MWCNTs could selectively adsorb U(VI) in aqueous solution containing co-existing ions (Mn2+, Co2+, Ni2+, Zn2+, Sr2+, Ba2+ and Cs+). This study shows that AO-g-MWCNTs are potential adsorbent for effective removal of U(VI) from aqueous solution

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

  16. Modelling Cr(VI) removal by a combined carbon-activated sludge system

    International Nuclear Information System (INIS)

    The combined carbon-activated sludge process has been proposed as an alternative to protect the biomass against toxic substances in wastewaters; however, the information about the effect of powdered-activated carbon (PAC) addition in activated sludge reactors for the treatment of wastewaters containing Cr(VI) is limited. The objectives of the present study were: (a) to evaluate the removal of hexavalent chromium by (i) activated sludge microorganisms in aerobic batch reactors, (ii) powdered-activated carbon, and (iii) the combined action of powdered-activated carbon and biomass; (b) to propose mathematical models that interpret the experimental results. Different Cr(VI) removal systems were tested: (S1) biomass (activated sludge), (S2) PAC, and (S3) the combined activated carbon-biomass system. A Monod-based mathematical model was used to describe the kinetics of Cr(VI) removal in the system S1. A first-order kinetics with respect to Cr(VI) and PAC respectively, was proposed to model the removal of Cr(VI) in the system S2. Cr(VI) removal in the combined carbon-biomass system (S3) was faster than both Cr(VI) removal using PAC or activated sludge individually. Results showed that the removal of Cr(VI) using the activated carbon-biomass system (S3) was adequately described by combining the kinetic equations proposed for the systems S1 and S2

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

    International Nuclear Information System (INIS)

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

  18. Removal of Cr (VI) with wheat-residue derived black carbon: Reaction mechanism and adsorption performance

    International Nuclear Information System (INIS)

    The removal of Cr (VI) from aqueous solutions using black carbon (BC) isolated from the burning residues of wheat straw was investigated as a function of pH, contact time, reaction temperature, supporting electrolyte concentration and analytical initial Cr (VI) concentration in batch studies. The effect of surface properties on the adsorption behavior of Cr (VI) was investigated with scanning electron microscope (SEM) equipped with the energy dispersive X-ray spectroscope (EDS) and Fourier transform-infrared (FTIR) spectroscopy. The removal mechanism of Cr (VI) onto the BC was investigated and the result showed that the adsorption reaction consumed a large amount of protons along the reduction of Cr (VI) to Cr (III). The oxidation of the BC took place concurrently to the chromium reduction and led to the formation of hydroxyl and carboxyl functions. An initial solution pH of 1.0 was most favorable for Cr (VI) removal. The adsorption process followed the pseudo-second order equation and Freundlich isotherm very well. The Cr (VI) adsorption was temperature-dependent and almost independent on the sodium chloride concentrations. The maximum adsorption capacity for Cr (VI) was found at 21.34 mg/g in an acidic medium, which is comparable to other low-cost adsorbents.

  19. Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal

    Institute of Scientific and Technical Information of China (English)

    杨卫春; 唐琼芝; 董舒宇; 柴立元; 王海鹰

    2016-01-01

    Magnetic chitosan composites (Fe3O4@chitosan) were synthesized in one single-step, characterized and applied in Cr(VI) removal from water. With the increase of loading proportion of chitosan, Cr(VI) adsorption capacity of Fe3O4@chitosan composites increased from 10.771 to 21.040 mg/g. The optimum adsorption capacities of Cr(VI) on Fe3O4@chitosan-3 were found in a pH range of 3.0−5.0. Kinetic study results show that the adsorption process follows pseudo-second-order model, indicating that the rate-limiting step in the adsorption of Cr(VI) involves chemisorptions. Moreover, FT-IR spectra analysis confirms that the amine and hydroxyl groups of chitosan are predominantly responsible for binding. Results from this work demonstrate that the prepared Fe3O4@chitosan composites possess great potential in Cr(VI) removal from contaminated water.

  20. X-ray diffraction study of epitaxial heterostructures of II-VI CdTe and ZnTe semiconductors; Etude par diffraction de rayons X d`heterostructures epitaxiees a base des semi-conducteurs II-VI CdTe et ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Bouchet-Boudet, N.

    1996-10-07

    This work deals with the structural study of II-VI semiconductor (CdTe and ZnTe) heterostructures by X-ray diffraction and reflectivity. These heterostructures have a high lattice parameter misfit and are grown by Molecular Beam Epitaxy. Two main subjects are developed: the characterization of ZnTe wires, grown by step propagation on a CdTe (001) vicinal surface, and the study of the vertical correlations in Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattices and superlattices made of ZnTe fractional layers spaced by CdTe. The growth of organised system is up to date; its aim is to realize quantum boxes (or wires) superlattices which are laterally and vertically ordered. The deformation along the growth axis induced by a ZnTe fractional layer inserted in a CdTe matrix is modelled, in the kinematical approximation, to reproduce the reflectivity measured around the substrate (004) Bragg peak. The lateral periodicity of the wires, deposited on a vicinal surface is a new and difficult subject. Some results are obtained on a vertical superlattice grown on a 1 deg. mis-cut surface. The in-plane and out-of-plane correlation lengths of a Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattice are deduced from the diffused scattered intensity measured at grazing incidence. The calculations are made within the `distorted Wave Born Approximation`. The vertical correlation in ZnTe boxes (or wines) superlattices can be measured around Bragg peaks. It is twice bigger in a superlattice grown on a 2 deg. mis-cut substrate than a nominal one. (author). 74 refs.

  1. Genetics Home Reference: collagen VI-related myopathy

    Science.gov (United States)

    ... Genetics Home Health Conditions collagen VI-related myopathy collagen VI-related myopathy Enable Javascript to view the ... boxes. Print All Open All Close All Description Collagen VI-related myopathy is a group of disorders ...

  2. Interaction of aerobic soil bacteria with plutonium(VI)

    International Nuclear Information System (INIS)

    We studied the interaction of Pu(VI) with Pseudomonas stutzeri ATCC 17588 and Bacillus sphaericus ATCC 14577, representatives of the main aerobic groups of soil bacteria present in the upper soil layers. The biosorption studies have shown that these soil bacteria accumulate high amounts of Pu(VI). The relative sorption efficiency toward Pu(VI) related to the amount of biomass used decreased with increasing biomass concentration due to increased agglomeration of the bacteria resulting in a decrease of the number of available complexing groups. Spores of Bacillus sphaericus showed a higher biosorption than the vegetative cells at low biomass concentration which decreased significantly with increasing biomass concentration. At higher biomass concentrations (> 0.7 g/L), the vegetative cells of both strains and the spores of B. sphaericus showed comparable sorption efficiencies. Investigations on the pH dependency of the biosorption and extraction studies with 0.01 M EDTA solution have shown that the biosorption of plutonium is a reversible process and the plutonium is bound by surface complexation. Optical absorption spectroscopy showed that one third of the initially present Pu(VI) was reduced to Pu(V) after 24 hours. Kinetic studies and solvent extraction to separate different oxidation states of Pu after contact with the biomass provided further information on the yield and the kinetics of the bacteria-mediated reduction. Long-term studies showed that also 16% of Pu(IV) was formed after one month. The slow kinetics of this process indicate that under our experimental conditions the Pu(IV) was not a produced by microbial reduction but seemed to be rather the result of the disproportionation of the formed Pu(V) or autoreduction of Pu(VI). (orig.)

  3. Modeling of kinetics of Cr(VI) sorption onto grape stalk waste in a stirred batch reactor

    International Nuclear Information System (INIS)

    Recently, Cr(VI) removal by grape stalks has been postulated to follow two mechanisms, adsorption and reduction to trivalent chromium. Nevertheless, the rate at which both processes take place and the possible simultaneity of both processes has not been investigated. In this work, kinetics of Cr(VI) sorption onto grape stalk waste has been studied. Experiments were carried out at different temperatures but at a constant pH (3 ± 0.1) in a stirred batch reactor. Results showed that three steps take place in the process of Cr(VI) sorption onto grape stalk waste: Cr(VI) sorption, Cr(VI) reduction to Cr(III) and the adsorption of the formed Cr(III). Taking into account the evidences above mentioned, a model has been developed to predict Cr(VI) sorption on grape stalks on the basis of (i) irreversible reduction of Cr(VI) to Cr(III) reaction, whose reaction rate is assumed to be proportional to the Cr(VI) concentration in solution and (ii) adsorption and desorption of Cr(VI) and formed Cr(III) assuming that all the processes follow Langmuir type kinetics. The proposed model fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The proposed model would be helpful for researchers in the field of Cr(VI) biosorption to design and predict the performance of sorption processes.

  4. Settleability and characteristics of ferrate(VI)-induced particles in advanced wastewater treatment.

    Science.gov (United States)

    Zheng, Lei; Deng, Yang

    2016-04-15

    Ferrate(VI) as an emerging water treatment agent has recently recaptured interests for advanced wastewater treatment. A large number of studies were published to report ferrate(VI)-driven oxidation for various water contaminants. In contrast, very few efforts were made to characterize ferrate(VI) resultant particles in water and wastewater. In this study, jar tests were performed to examine the settleability and characteristics of ferrate(VI)-induced iron oxide particles, particularly the non-settable fraction of these particles, after ferrate(VI) reduction in a biologically treated municipal wastewater. The particle settleability was evaluated through the measurement of turbidity and particulate iron concentration in the supernatant with the settling time. Results showed that a majority of ferrate(VI)-induced iron oxide aggregates remained suspended and caused an increased turbidity. For example, at a Fe(VI) dose of 5.0 mg/L and pH 7.50, 82% of the added iron remained in the supernatant and the turbidity was 8.97 NTU against the untreated sample turbidity (2.33 NTU) after 72-h settling. The poor settling property of these particles suggested that coagulation and flocculation did not perform well in the ferrate(VI) treatment. Particle size analysis and transmission electron microscopy (TEM) revealed that nano-scale particles were produced after ferrate(VI) decomposition, and gradually aggregated to form micro-scale larger particles in the secondary effluent. Zeta potentials of the non-settable ferrate(VI) resultant aggregates varied between -7.36 and -8.01 mV at pH 7.50 during the 72-h settling. The negative surface charges made the aggregates to be relatively stable in the wastewater matrix. PMID:26900976

  5. ■u vi parolas Esperante?

    Institute of Scientific and Technical Information of China (English)

    Andrzej; Pettyn

    2000-01-01

    LA DEKSEPA LECIONO Cu tio ci estas gripo? Barbara estas malsana kaj nun estas ce si kuracisto —Kuracisto: Bonan tagon! —Barbara: Bonan tagon! —Petro: Bonan tagon, sinjoro! —K: Vi efektive malbone aspektas, Kio estas al vi, sinjorino? —B: Mitre malbone fartas. Miaj kapo kaj gorgo doloras.

  6. Occupational exposure to chromium(VI compounds

    Directory of Open Access Journals (Sweden)

    Jolanta Skowroń

    2015-07-01

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

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

    Science.gov (United States)

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

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

  8. Når vi taler om 68

    DEFF Research Database (Denmark)

    Jensen, Henrik; Metz, Georg

    Når vi taler om 68 er en intellektuel samtale mellem to ligeværdige gentlemen og skallesmækkere. En essayistisk dyst om porno, RAF, Pittelkow og livsfilosofi......Når vi taler om 68 er en intellektuel samtale mellem to ligeværdige gentlemen og skallesmækkere. En essayistisk dyst om porno, RAF, Pittelkow og livsfilosofi...

  9. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haitao

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This method is first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  10. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haitao

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This methodis first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  11. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    International Nuclear Information System (INIS)

    In the last two decades, the field of nanoscience and nanotechnology has witnessed tremendous advancement in the synthesis and application of group II-VI colloidal nanocrystals. The synthesis based on high temperature decomposition of organometallic precursors has become one of the most successful methods of making group II-VI colloidal nanocrystals. This method is first demonstrated by Bawendi and coworkers in 1993 to prepare cadmium chalcogenide colloidal quantum dots and later extended by others to prepare other group II-VI quantum dots as well as anisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod. This dissertation focuses on the chemistry of this type of nanocrystal synthesis. The synthesis of group II-VI nanocrystals was studied by characterizing the molecular structures of the precursors and products and following their time evolution in the synthesis. Based on these results, a mechanism was proposed to account for the 2 reaction between the precursors that presumably produces monomer for the growth of nanocrystals. Theoretical study based on density functional theory calculations revealed the detailed free energy landscape of the precursor decomposition and monomer formation pathway. Based on the proposed reaction mechanism, a new synthetic method was designed that uses water as a novel reagent to control the diameter and the aspect ratio of CdSe and CdS nanorods

  12. The chemistry of uranium (VI), neptunium (VI), and plutonium (VI) in aqueous carbonate solutions

    International Nuclear Information System (INIS)

    The dynamic behavior of carbonate ion as a ligand that interacts with the hexavalent actinyl ions of U, Np, and Pu was examined by 13C NMR spectroscopy. The first-order rate parameter, k, that describes the exchange between bulk solution and bound carbonate decreases with increasing pH. At a pH of 10.0, and 25 degrees C, the respective values of k for the U(VI), Np(VI) complexes are 27.1 ± 0.3, 64.7 ± 3.3, and 706 ± 29. The variation of k with temperature was used to calculate the values of activation enthalpy ΔH double-dagger = 53 and 42 kJ mol-1; and activation entropy ΔS double-dagger = - 40 and - 71 J mol-1 K-1 for the uranyl and neptunyl systems, respectively. In this paper a plausible reaction scheme for the exchange reaction is considered. The influence of these slow carbonate-exchange reactions on selected electron-transfer reactions is noted

  13. Cranial nerves III, IV and VI

    International Nuclear Information System (INIS)

    Because of advances in CT and MR imaging, accurate identification and evaluation of cranial nerve lesions is now possible. Cranial nerves III, IV, and VI, providing motor and sensory control of the eye, can be evaluated as a unit. In this paper, the authors present an overview of the anatomy and pathology of these cranial nerves. We first illustrate their normal anatomic pathways from the brain stem to the orbit. This is followed by clinical examples of patients with a variety of isolated and complex palsies of these three cranial nerves. This is accomplished by inclusion of ocular photographs, correlative imaging studies, and the use of diagrams. Knowledge of the gross and imaging anatomy and the ophthalmologic manifestations of pathology affecting these three cranial nerves permits a tailored approach to their evaluation

  14. Effect of Salicylic and Picolinic Acids on the Adsorption of U(VI) onto Oxides

    International Nuclear Information System (INIS)

    The effect of organic acids on the adsorption of U(VI) onto oxide surfaces (TiO2(anatase), SiO2 (amorphous) and Al2O-3(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto TiO2 surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto SiO2 surface, however, picolinic acid enhances the adsorption of U(VI) onto SiO2 surface. The latter effect can be understood by considering the formation of a ternary surface complex on SiO2 surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface, In the case of Al2O-3, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the Al2O-3 surface, and an additional spectroscopic study is required.

  15. BIOSORPTION OF Cr(VI) FROM SYNTHETIC WASTEWATER USING THE FRUIT SHELL OF GULMOHAR (Delonix regia): APPLICATION TO ELECTROPLATING WASTEWATER

    OpenAIRE

    Attimodde Girirajanna Devi Prasad; Mohammed Abdulsalam Abdullah

    2010-01-01

    The biosorption of Cr(VI) from synthetic solutions and electroplating wastewater using the fruit shell of gulmohar has been investigated in a batch system. The effects of various parameters such as pH, contact time, adsorbent dosage, and initial concentration of Cr(VI) on the biosorption process were studied. The complete removal of Cr(VI) was observed at pH < 3.0. Studies indicated that both biosorption and bioreduction were involved in the removal of Cr(VI). The sorption equilibrium exhibit...

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

    Science.gov (United States)

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

    2013-01-01

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

  17. Role of RpoS in Fine-Tuning the Synthesis of Vi Capsular Polysaccharide in Salmonella enterica Serotype Typhi▿

    OpenAIRE

    Santander, Javier; Wanda, Soo-Young; Nickerson, Cheryl A.; Curtiss, Roy

    2006-01-01

    Regulation of the synthesis of Vi polysaccharide, a major virulence determinant in Salmonella enterica serotype Typhi, is under the control of two regulatory systems, ompR-envZ and rscB-rscC, which respond to changes in osmolarity. Some serotype Typhi strains exhibit overexpression of Vi polysaccharide, which masks clinical detection of lipopolysaccharide O antigen. This variation in Vi polysaccharide and O antigen display (VW variation) has been observed since the initial studies of serotype...

  18. Preparation and characterization of Pyridoxine complexes of Fe(III), Mo(VI), Cd(II), Hg(II), and U(VI)

    International Nuclear Information System (INIS)

    Pyridoxine (vit B6) reacts with Fe(III), Mo(VI), Cd(II), Hg(II), and U(VI) in aqueous medium to produce solid stable compounds. The compound were characterized by using elemetal analysis data (C'H'N) and different spectroscopic techniques (IR and UV-visible). Condutance behaviour of aqueous solution and the thermal decomposition nature of the complexes were also studied

  19. Solvent extraction of uranium(VI) by 3-hydroxy-2-methyl-1-phenyl-4-pyridone

    International Nuclear Information System (INIS)

    The extraction of uranium (VI) from aqueous hydrochloric or nitric acid solution by 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) dissolved in chloroform has been studied. Uranium(VI) is quantitatively extracted from the solutions in the range 5 3 at concentrations higher than 1 M. The composition of the extracted uranium(VI) species was studied in solution and in the solid state. The complex UO2X2HX was isolated from the chloroform solution. Solutions in chloroform, exhibit maximum absorbance at 319 nm; the molar absorptivity is 32,000 1 mole -1cm-1. Uranium can be determined spectrophotometrically in the organic phase. (author)

  20. Extraction and determination of microgram amounts of molybdenum (VI) and tungsten (VI) in carbon steel, mild steel, plain steel and Mn-Mo steel

    International Nuclear Information System (INIS)

    A method is proposed for the extraction of microgram amounts of molybdenum(VI) and tungsten(VI) from halide medium using tris(2-ethylhexyl) phosphate dissolved in toluene as an extractant. Various experimental parameters involved in the use of the method such as acid concentration, period of equilibration, nature of stripping agents and interference by diverse ions have been studied. The logD-logC plot is used to ascertain probable extractable species. The method has been applied for separation of molybdenum(VI) and tungsten(VI) in alloys like carbon steel, mild steel, plain steel and Mn-Mo steel. The analysis requires 15-20 min. (author). 9 refs., 1 tab

  1. Synthesis, characterization and thermal behaviour of VO(IV), MoO2(VI) and UO2(VI) complexes of hexadentate tetraanionic ligand

    International Nuclear Information System (INIS)

    A new Schiff base ligand 2,4-dihydroxy-5-acetylacetophenone-2-aminothiophenol (H2L) was prepared by condensation of 2,4-dihydroxy-5-acetylacetophenone and 2-aminothiophenol in ethanol-DMF. The complexes of VO(IV), MoO2(VI) and UO2(VI) have been prepared and characterized by elemental analyses, magnetic moment, IR and electronic spectral data and thermogravimetric analysis (TGA). The IR spectral data reveal that the ligand behaves a tetraanionic hexadentate in nature. TGA and IR studies confirm the presence of coordinated water molecule in the complexes. The kinetic analysis of the TG data was performed by using the Coats-Redfern method and activation energy has been calculated. The complexes of MoO2(VI) and UO2(VI) are found to be octahedral while VO(IV) complex is square pyramidal geometry. (author)

  2. Bioaccumulation of U(VI) by Sulfolobus acidocaldarius under moderate acidic conditions

    International Nuclear Information System (INIS)

    U(VI) accumulation by the acidothermophilic archaeon Sulfolobus acidocaldarius at a moderate acidic pH of 4.5 was investigated. This pH value is relevant for some heavy metal and uranium polluted environments where populations of S. acidocaldarius were found to persist. We demonstrate that U(VI) is rapidly complexed by the archaeal cells. A combination of X-ray absorption spectroscopy and time-resolved laser-induced fluorescence spectroscopy revealed that at pH 4.5 organic phosphate and carboxylic groups are involved in the U(VI) complexation. These results are in contrast to those published for most bacteria which at this pH precipitate U(VI) mainly in inorganic uranyl phosphate phases. As demonstrated by TEM only a limited part of the added U(VI) was biomineralized extracellularly in the case of the studied archaeon. Most of the U(VI) accumulates were localized in a form of intracellular deposits which were associated with the inner side of the cytoplasma membrane. Observed differences in U(VI) bioaccumulation between the studied archaeon and bacteria can be explained by the significant differences in their cell wall structures as well as by their different physiological characteristics. (orig.)

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

    Science.gov (United States)

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

    2015-11-01

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

  4. Pu(VI) hydrolysis: further evidence for a dimeric plutonyl hydroxide and contrasts with U(VI) chemistry.

    Science.gov (United States)

    Reilly, Sean D; Neu, Mary P

    2006-02-20

    A significant fraction of plutonium that is soluble in environmental waters and other aqueous solutions can be present as complexes of plutonyl, PuO2(2+). Few thermodynamic data are available for this ion, representing a problematic gap in plutonium chemistry and in the forecasting of radionuclide behavior under contamination and nuclear repository conditions. To address this need and more accurately determine the stoichiometry and stability of the basic hydrolytic products, we completed complimentary potentiometric and spectrophotometric studies of plutonium(VI) hydrolysis over the concentration range of 10(-2) to 10(-5) M Pu(VI). Dinuclear hydroxide species (PuO2)2(OH)2(2+) and (PuO2)2(OH)4(0)(aq) with hydrolysis constants log beta(2,2) = -7.79 +/- 0.20 and log beta(4,2) = -19.3 +/- 0.5 are indicated in all experiments of millimolar Pu(VI), 0.10 M NaNO3 solutions at 25 degrees C. At lower Pu(VI) concentrations, at and below 10(-4) M, the monomeric species PuO2OH+ and PuO2(OH)2(0)(aq) form with hydrolysis constants of log beta(1,1) = -5.76 +/- 0.07 and log beta(2,1) = -11.69 +/- 0.05, respectively. Distinct optical absorbance bands at 842 and 845 nm are reported for the mononuclear and dinuclear first hydrolysis species. Standard hydrolysis constants at zero ionic strength were calculated from the experimentally determined constants using the specific ion interaction theory. The Pu(VI) hydrolysis species and constants are compared with results from previous studies for plutonium and uranium. Major differences between uranyl and plutonyl hydrolysis are described. PMID:16472001

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

    Directory of Open Access Journals (Sweden)

    Juan F Cárdenas-González

    2011-01-01

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

  6. Learning the vi and Vim Editor

    CERN Document Server

    Robbins, Arnold; Hannah, Elbert

    2008-01-01

    There's nothing that hard-core Unix and Linux users are more fanatical about than their text editor. Editors are the subject of adoration and worship, or of scorn and ridicule, depending upon whether the topic of discussion is your editor or someone else's. vi has been the standard editor for close to 30 years. Popular on Unix and Linux, it has a growing following on Windows systems, too. Most experienced system administrators cite vi as their tool of choice. And since 1986, this book has been the guide for vi. However, Unix systems are not what they were 30 years ago, and neither is this

  7. Synergistic extraction of uranium (VI), thorium (IV) and cerium (III) by thenoyltri-fluoroacetone and phenanthroline

    International Nuclear Information System (INIS)

    The synergistic extraction of uranium(VI), thorium(IV) and cerium(III) with thenoyltrifluoroacetone (HTTA) and phenanthroline (phen) is studied. The extraction equilibrium constants are calculated and the mechanism of the synergistic extraction has been discussed

  8. The status of the seventh report in the series Biological Effects of Ionizing Radiations and a revised dosimetry for the Radiation Effects Research Foundation's A-bomb studies

    International Nuclear Information System (INIS)

    Results of a National Academies workshop and feasibility study led US Governmental agencies to request the Board on Radiation Effects Research of the National Research Council to commence a risk assessment study in 1998 as the seventh report in the series Biological Effects of Ionizing Radiations (BEIR VII). Originally targeted for completion in the autumn of 2001, the study Potential Health Effects of Exposure to Low Dose, Low-LET Ionizing Radiation was extended until the autumn of 2003 at the request of the sponsors. Two factors contributing to this decision are discussed: a revised dosimetry to update DS86 for the Radiation Effects Research Foundation's A-bomb-survivor studies and the potential for new information to become available from low-dose studies that are under way. Epidemiological and biological data since BEIR V are being considered by a BEIR VII committee composed of 17 members. The committee's statement of task is reviewed along with the major recommendations of the recent National Research Council report on the status of DS86 - recommendations that are being implemented by US and Japan dosimetry working groups. (author)

  9. Liquid-liquid extraction of uranium (VI) using Cyanex 272 in kerosene from sodium salicylate medium

    International Nuclear Information System (INIS)

    Liquid-liquid extraction of uranium (VI) from sodium salicylate media using Cyanex 272 in kerosene has been carried out. Uranium (VI) was quantitatively extracted from 1x10-4 M sodium salicylate with 5x10-4 M Cyanex 272 in kerosene. It was stripped quantitatively from the organic phase with 4M HCl and determined spectrophotometrically with arsenazo(III) at 600 nm. The effects of concentrations of sodium salicylate, metal ions and strippants have been studied. Separation of uranium (VI) from other elements was achieved from binary as well as from multicomponent mixtures. The method is simple, rapid and selective with good reproducibility (approximately ±2%). (author)

  10. Biosorption Potential of Trichoderma gamsii Biomass for Removal of Cr(VI) from Electroplating Industrial Effluent

    OpenAIRE

    Haresh Keharia; Kavita, B.

    2012-01-01

    The potential use of acid-treated biomass of Trichoderma gamsii to remove hexavalent chromium ions from electroplating industrial effluent was evaluated. Electroplating industrial effluent contaminated with 5000 mg/L of Cr(VI) ions, collected from industrial estate of Gujarat, India, was mixed with acid-treated biomass of T. gamsii at biomass dose of 10 mg/mL. Effect of contact time and initial Cr(VI) ions was studied. The biosorption of Cr(VI) ions attained equilibrium at time interval of 24...

  11. Determination of U(VI) and Pu(IV) in nitric acid solutions with derivative spectroscopy

    International Nuclear Information System (INIS)

    The authors study the absorption spectra and fourth derivative spectra (FDS) of U(VI) and Pu(IV) in nitric acid solutions and the effect of impurities on FDS. The concentrations of U(VI) and Pu(IV) with peak-zero method at 415 nm and peak-area method between 472.5-479.5 nm are determined, respectively. When CHNO3 or CNO3- is in 1.5-3.0 mol/l, U(VI) can be directly determined by FDS, with the analysis deviation -4 mol/l

  12. Role of collagen VI in peripheral nerves and wound-induced hair regrowth

    OpenAIRE

    Chen, Peiwen

    2015-01-01

    Collagen VI is an extracellular matrix (ECM) molecule dynamically expressed in a variety of tissues, including peripheral nerves and skin. However, the role of collagen VI in the peripheral nervous system (PNS) and hair follicle growth is yet unknown. The main focus of my PhD study was to investigate the role and the underlying mechanisms of collagen VI in peripheral nerve myelination and function, in PNS regeneration, as well as in wound-induced hair growth. During the first year of my P...

  13. Gum Kondagogu nanocomposite: an effective biosorbent for removal of Uranium (VI) from aqueous solution

    International Nuclear Information System (INIS)

    Gum Kondagogu- nano-composite (KG-NC) has been efficiently used for removal of Uranium (VI) ions from aqueous solution. Different optimized conditions such as pH, U (VI) concentration, contact time and GK-NC concentration were determined. The amount of U (VI) adsorbed onto the KG-NC was found to be 193.3 ± 8.87 mg of uranium g-1 of nano-composite at pH 5.0 and 25°C. The results of the present study suggested that KG-NC could be suitable as green bio-adsorbent for removal of uranium ions from dilute aqueous solutions. (author)

  14. Ex-situ bioremediation of U(VI from contaminated mine water using Acidithiobacillus ferrooxidans strains

    Directory of Open Access Journals (Sweden)

    Maria eRomero-Gonzalez

    2016-05-01

    Full Text Available The ex-situ bioremoval of U(VI from contaminated water using Acidithiobacillus ferrooxidans strain 8455 and 13538 was studied under a range of pH and uranium concentrations. The effect of pH on the growth of bacteria was evaluated across the range 1.5 – 4.5 pH units. The respiration rate of At. ferrooxidans at different U(VI concentrations was quantified as a measure of the rate of metabolic activity over time using an oxygen electrode. The biosorption process was quantified using a uranyl nitrate solution, U-spiked growth media and U-contaminated mine water. The results showed that both strains of At. ferrooxidans are able to remove U(VI from solution at pH 2.5 – 4.5, exhibiting a buffering capacity at pH 3.5. The respiration rate of the micro-organism was affected at U(VI concentration of 30 mg L-1. The kinetics of the sorption fitted a pseudo-first order equation, and depended on the concentration of U(VI. The KD obtained from the biosorption experiments indicated that strain 8455 is more efficient for the removal of U(VI. A bioreactor designed to treat a solution of 100 mg U(VI L-1 removed at least 50% of the U(VI in water. The study demonstrated that At. ferrooxidans can be used for the ex-situ bioremediation of U(VI contaminated mine water.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-05-15

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

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

    Directory of Open Access Journals (Sweden)

    Balan Catalin

    2013-01-01

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

  18. Oxidation of Oil Sands Process-Affected Water by Potassium Ferrate(VI).

    Science.gov (United States)

    Wang, Chengjin; Klamerth, Nikolaus; Huang, Rongfu; Elnakar, Haitham; Gamal El-Din, Mohamed

    2016-04-19

    This paper investigates the oxidation of oil sands process-affected water (OSPW) by potassium ferrate(VI). Due to the selectivity of ferrate(VI) oxidation, two-ring and three-ring fluorescing aromatics were preferentially removed at doses removed only at doses ≥100 mg/L Fe(VI). Ferrate(VI) oxidation achieved 64.0% and 78.4% removal of naphthenic acids (NAs) at the dose of 200 mg/L and 400 mg/L Fe(VI) respectively, and NAs with high carbon number and ring number were removed preferentially. (1)H nuclear magnetic resonance ((1)H NMR) spectra indicated that the oxidation of fluorescing aromatics resulted in the opening of some aromatic rings. Electron paramagnetic resonance (EPR) analysis detected signals of organic radical intermediates, indicating that one-electron transfer is one of the probable mechanisms in the oxidation of NAs. The inhibition effect of OSPW on Vibrio fischeri and the toxicity effect on goldfish primary kidney macrophages (PKMs) were both reduced after ferrate(VI) oxidation. The fluorescing aromatics in OSPW were proposed to be an important contributor to this acute toxicity. Degradation of model compounds with ferrate(VI) was also investigated and the results confirmed our findings in OSPW study. PMID:27008571

  19. Moisture content-affected electrokinetic remediation of Cr(VI)-contaminated clay by a hydrocalumite barrier.

    Science.gov (United States)

    Xu, Yunfeng; Xu, Xiangjian; Hou, Hetian; Zhang, Jia; Zhang, Dayi; Qian, Guangren

    2016-04-01

    An electrokinetic-permeable reaction barrier (EK-PRB) system was introduced in this study with hydrocalumite as the barrier material. The combined system effectively remediated the Cr(VI)-contaminated clay after a 72-h treatment, and the Cr(VI) removal efficiency increased with the initial soil moisture content. Further evidence was found that the changing soil pH value and current density were highly associated with the initial moisture content, showing its important roles in the Cr(VI) removal process. Additionally, the total Cr removal efficiency was much lower than that of Cr(VI) owing to the partial conversion of Cr(VI) to Cr(III) in the electrokinetic remediation process. Under high soil moisture conditions (40%), the removal efficiency of Cr(VI) and total Cr was 96.6 and 67.3%, respectively. Further analysis also revealed the new mineral phase, chromate hydrocalumite, for Cr fixation in the hydrocalumite barrier, which was significantly affected by the initial soil moisture content. Our results showed that the EK-PRB system with a hydrocalumite barrier is highly promising with great potential for the effective remediation of Cr(VI)-contaminated clay and engineering implementation. PMID:26635219

  20. Comparison of uranium(VI) removal by Shewanella oneidensis MR-1 in flow and batch reactors

    International Nuclear Information System (INIS)

    To better understand the interactions among metal contaminants, nutrients, and microorganisms in subsurface under fracture-flow conditions, iron-reducing biofilms (pure cultures of Shewanella oneidensis MR-1) were grown in six fracture flow reactors (FFRs) of different geometries. The spatial and temporal distribution of nutrients, contaminant, and bacteria were examined using a tracer dye (brilliant blue FCF) and microscopy. The results showed that plugging by bacterial cells depended on the geometry of the reactor; and iron-reducing biofilms grown in FFRs had a definite U(VI)-reduction capacity. To find out the U(VI)-reduction capacity of iron-reducing biofilms, batch experiments of U(VI) reduction were performed in repetitive addition mode. U(VI)-reduction rates of stationary phase grown iron-reducing cultures with and without spent medium decreased after each U(VI) addition. At the end of the fourth U(VI)-addition, stationary phase iron-reducing cultures treated with U(VI) with and without spent medium yielded grey and black precipitates, respectively. These grey and black U precipitates were analyzed using High Resolution-Transmission Electron Microscopy, Energy-dispersive X-ray spectroscopy, and X-ray diffraction. Data for randomly selected area of black and grey U precipitates showed that reduced U particles (3-6 nm) were crystalline and amorphous in nature, respectively. This information obtained in this study could be used to develop substrate addition strategies for metal immobilization in subsurface fracture flow systems

  1. Actinide(IV) and actinide(VI) carbonate speciation studies by PAS and NMR spectroscopies. Yucca Mountain Project: Milestone report 3031-WBS 1.2.3.4.1.3.1

    International Nuclear Information System (INIS)

    Pulsed-laser photoacoustic spectroscopy (PAS) and Fourier-transform nuclear magnetic resonance (NMR) spectroscopy were used to study speciation of actinide(IV) and actinide(VI) ions (Np, Pu, Am) in aqueous carbonate solutions vs of pH, carbonate concentration, actinide content, and temperature. PAS focused on Pu(IV) speciation. Stability fields on a pH (8.4 to 12.0) versus total carbonate content (0.003 to 1.0 M) plot for dilute Pu(IV) carbonate species ([Pu]tot = 1 mM) were mapped. Four plutonium species, with absorption peaks at 486, 492, 500, and 512 nm were found. Loss of a single carbonate ligand does not account for the difference in speciation for the 486 and 492 nm absorption peaks, nor can any of the observed species be identified as colloidal Pu(IV). NMR data have been obtained for UO22+, PuO22+ and AmO22+. This report focuses on results for PuO22+. The ligand exchange reaction between free and coordinated carbonate on the PuO2(CO3)34- systems has been examined by variable temperature 13C NMR spectroscopy. In each of the six different PuO2(CO3)34- samples, two NMR signals are present, one for the free carbonate ligand and one for the carbonate ligand coordinated to a paramagnetic plutonium metal center. The single13C resonance line for coordinated carbonate is consistent with expectations of a monomeric PuO2(CO3)34- species in solution. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was used for determining of ligand exchange parameters for paramagnetic actinide complexes. Eyring analysis at standard conditions provided activation parameters of ΔH = 38 KJ/M and ΔS = -60 J/K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl(VI) carbonate complex self-exc

  2. Actinide(IV) and actinide(VI) carbonate speciation studies by PAS and NMR spectroscopies; Yucca Mountain Project: Milestone report 3031-WBS 1.2.3.4.1.3.1

    Energy Technology Data Exchange (ETDEWEB)

    Clark, D.L.; Ekberg, S.A.; Morris, D.E.; Palmer, P.D.; Tait, C.D.

    1994-09-01

    Pulsed-laser photoacoustic spectroscopy (PAS) and Fourier-transform nuclear magnetic resonance (NMR) spectroscopy were used to study speciation of actinide(IV) and actinide(VI) ions (Np, Pu, Am) in aqueous carbonate solutions vs pH, carbonate content, actinide content, temperature. PAS focused on Pu(IV) speciation. Stability fields on a pH (8.4 to 12.0) versus total carbonate content (0.003 to 1.0 M) plot for dilute Pu(IV) carbonate species ([Pu]{sub tot} = 1 mM) were mapped. Four plutonium species, with absorption peaks at 486, 492, 500, and 512 nm were found. Loss of a single carbonate ligand does not account for the difference in speciation for the 486 and 492 nm absorption peaks, nor can any of the observed species be identified as colloidal Pu(IV). NMR data have been obtained for UO{sub 2}{sup 2+}, PuO{sub 2}{sup 2+} and AmO{sub 2}{sup 2+}. This report focuses on results for PuO{sub 2}{sup 2+}. The ligand exchange reaction between free and coordinated carbonate on the PuO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} systems has been examined by variable temperature {sup 13}C NMR spectroscopy. In each of the six different PuO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} samples, two NMR signals are present, one for the free carbonate ligand and one for the carbonate ligand coordinated to a paramagnetic plutonium metal center. The single{sup 13}C resonance line for coordinated carbonate is consistent with expectations of a monomeric PuO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} species in solution. A modified Carr-Purcell-Meiboom-Gill NMR pulse sequence was used for determining ligand exchange parameters for paramagnetic actinide complexes. Eyring analysis at standard conditions provided activation parameters of {Delta}H = 38 KJ/M and {Delta}S = {minus}60 J/K for the plutonyl triscarbonate system, suggesting an associative transition state for the plutonyl(VI) carbonate complex self-exchange reaction.

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

    Science.gov (United States)

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

    2011-01-01

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

  4. Radiological findings in patients with mucopolysaccharidosis type VI; Manifestacoes radiologicas da mucopolissacaridose tipo VI

    Energy Technology Data Exchange (ETDEWEB)

    Turtelli, Celso Montenegro [Hospital Sao Domingos, Uberaba, MG (Brazil). Servico de Diagnostico por Imagem]. E-mail: celso@mednet.com.br

    2002-10-01

    The radiological findings in two siblings with mucopolysaccharidosis type VI (muco polysaccharide VI) are reported. Conventional radiographs of the skeleton and magnetic resonance imaging examination of the central nervous system were performed. Skeletal abnormalities in patients with mucopolysaccharidosis type VI have already well described by other authors and are generally similar to other mucopolysaccharides. Magnetic resonance imaging of the central nervous system may be helpful in the differential diagnosis, assessment of extension, and follow-up of these diseases. (author)

  5. 19 CFR Annex Vi to Part 351 - Countervailing Investigations Timeline

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Countervailing Investigations Timeline VI Annex VI to Part 351 Customs Duties INTERNATIONAL TRADE ADMINISTRATION, DEPARTMENT OF COMMERCE ANTIDUMPING AND COUNTERVAILING DUTIES Pt. 351, Annex VI Annex VI to Part 351—Countervailing Investigations Timeline ER19MY97.000...

  6. ViSIT: Visitor Survey Information Tool

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — ViSIT is an interactive web tool created by USGS to visualize the data collected as part of the National Wildlife Refuge Visitor Survey. The national survey was...

  7. Adsorption Properties of Bentonite with In Situ Immobilized Polyaniline Towards Anionic Forms of Cr(VI, Mo(VI, W(VI, V(V

    Directory of Open Access Journals (Sweden)

    Kateryna RYABCHENKO

    2016-05-01

    Full Text Available A new composite material bentonite-PANI was synthesized by in situ immobilization of polyaniline (PANI on the surface of natural mineral bentonite. It was established as a result of the modification of bentonite a surface area and an interlayer distance of mineral decrease and particles of bentonite transformed of irregular shape with different porosity on irregularly shaped particles of smaller size. It has been found that the total Cr(VI ions extraction took place under the acid conditions (pH=1 – 2 and W(VI ions have been well adsorbed in the pH range from 1 to 8 by the composite bentonite-PANI unlike the initial mineral. Whereas adsorption of oxo anions of V(V and Mo(VI made up some 50%. It is proved that the in situ immobilization of bentonite by polyaniline leads to increasing the value of adsorption capacity towards the investigated ions compared with the initial mineral. It was established that the adsorption properties of the synthesized composite with respect to the studied oxo ions were worse than the adsorption properties of composite vermiculite-PANI, similar to the composite Sokyryntsyy clinoptilolite-PANI and better than composites of polyaniline with Podilskyy saponite and Karelian shungite.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.6976

  8. SaVi: satellite constellation visualization

    CERN Document Server

    Wood, Lloyd

    2012-01-01

    SaVi, a program for visualizing satellite orbits, movement, and coverage, is maintained at the University of Surrey. This tool has been used for research in academic papers, and by industry companies designing and intending to deploy satellite constellations. It has also proven useful for demonstrating aspects of satellite constellations and their geometry, coverage and movement for educational and teaching purposes. SaVi is introduced and described briefly here.

  9. O VI IN THE LOCAL INTERSTELLAR MEDIUM

    International Nuclear Information System (INIS)

    We report the results of a search for O VI absorption in the spectra of 80 hot DA white dwarfs observed by the FUSE satellite. We have carried out a detailed analysis of the radial velocities of interstellar and (where present) stellar absorption lines for the entire sample of stars. In approximately 35% of cases (where photospheric material is detected), the velocity differences between the interstellar and photospheric components were beneath the resolution of the FUSE spectrographs. Therefore, in 65% of these stars the interstellar and photospheric contributions could be separated and the nature of the O VI component unambiguously determined. Furthermore, in other examples, where the spectra were of a high signal-to-noise, no photospheric material was found and any O VI detected was assumed to be interstellar. Building on the earlier work of Oegerle et al. and Savage and Lehner, we have increased the number of detections of interstellar O VI and, for the first time, compared their locations with both the soft X-ray background emission and new detailed maps of the distribution of neutral gas within the local interstellar medium. We find no strong evidence to support a spatial correlation between O VI and SXRB emission. In all but a few cases, the interstellar O VI was located at or beyond the boundaries of the local cavity. Hence, any T ∼ 300,000 K gas responsible for the O VI absorption may reside at the interface between the cavity and surrounding medium or in that medium itself. Consequently, it appears that there is much less O VI-bearing gas than previously stated within the inner rarefied regions of the local interstellar cavity.

  10. Molasses as an efficient low-cost carbon source for biological Cr(VI) removal

    Energy Technology Data Exchange (ETDEWEB)

    Michailides, Michail K. [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Tekerlekopoulou, Athanasia G., E-mail: atekerle@upatras.gr [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Akratos, Christos S.; Coles, Sandra [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Pavlou, Stavros [Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Stadiou Str., Platani, P.O. Box 1414, GR-26504 Patras (Greece); Department of Chemical Engineering, University of Patras, GR-26504 Patras (Greece); Vayenas, Dimitrios V. [Department of Environmental and Natural Resources Management, University of Patras, 2 G. Seferi Str., GR-30100 Agrinio (Greece); Institute of Chemical Engineering Sciences (FORTH/ICE-HT), Stadiou Str., Platani, P.O. Box 1414, GR-26504 Patras (Greece)

    2015-01-08

    Highlights: • Suspended and attached growth reactors were examined for Cr(VI) bio-reduction. • Molasses was proved an efficient and very low cost carbon source. • Molasses was more efficient than sugar in enhancing Cr(VI) reduction. • SBR with recirculation was the most proper operating mode. - Abstract: In the present study, indigenous microorganisms from industrial sludge were used to reduce the activity of Cr(VI). Molasses, a by-product of sugar processing, was selected as the carbon source (instead of sugar used in a previous work) as it is a low-cost energy source for bioprocesses. Initially, experiments were carried out in suspended growth batch reactors for Cr(VI) concentrations of 1.5–110 mg/L. The time required for complete Cr(VI) reduction increased with initial Cr(VI) concentration. Initial molasses concentration was also found to influence the Cr(VI) reduction rate. The optimal concentration for all initial Cr(VI) concentrations tested was 0.8 gC/L. Experiments were also carried out in packed-bed reactors. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter mode with a recirculation rate of 0.5 L/min lead to significantly high Cr(VI) reduction rates (up to 135 g/m{sup 2} d). The results of this work were compared with those of a similar work using sugar as the carbon source and indicate that molasses could prove a feasible technological solution to a serious environmental problem.

  11. Molasses as an efficient low-cost carbon source for biological Cr(VI) removal

    International Nuclear Information System (INIS)

    Highlights: • Suspended and attached growth reactors were examined for Cr(VI) bio-reduction. • Molasses was proved an efficient and very low cost carbon source. • Molasses was more efficient than sugar in enhancing Cr(VI) reduction. • SBR with recirculation was the most proper operating mode. - Abstract: In the present study, indigenous microorganisms from industrial sludge were used to reduce the activity of Cr(VI). Molasses, a by-product of sugar processing, was selected as the carbon source (instead of sugar used in a previous work) as it is a low-cost energy source for bioprocesses. Initially, experiments were carried out in suspended growth batch reactors for Cr(VI) concentrations of 1.5–110 mg/L. The time required for complete Cr(VI) reduction increased with initial Cr(VI) concentration. Initial molasses concentration was also found to influence the Cr(VI) reduction rate. The optimal concentration for all initial Cr(VI) concentrations tested was 0.8 gC/L. Experiments were also carried out in packed-bed reactors. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter mode with a recirculation rate of 0.5 L/min lead to significantly high Cr(VI) reduction rates (up to 135 g/m2 d). The results of this work were compared with those of a similar work using sugar as the carbon source and indicate that molasses could prove a feasible technological solution to a serious environmental problem

  12. A nuclear magnetic resonance study on ligand exchange reaction in U(VI) nitrate complex with n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in acetone containing oxalic acid

    International Nuclear Information System (INIS)

    In order to examine the effect of oxalic acid(H2ox) on the exchange reaction of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (oφcmpo) in U(VI) nitrate complex with oφcmpo, structural and kinetic studies have been carried out for the solutions prepared by dissolving UO2(NO3)2(oφcmpo), oφcmpo, and H2ox in CD3COCD3 using 31P and 13C NMR method. The number of coordinated oφcmpo was determined to be 2 by the area integration of 31P NMR signals of free and coordinated oφcmpo. From the area integration of 13C signals of free H2ox and coordinated oxalate(Cox), the number of Cox was estimated to be 1. Hence, the complex with composition ratio of UO22+:oφcmpo:Cox=1:2:1 was supposed to be formed in the present solution system. The exchange rate of oφcmpo in this complex was found to show a first-order dependence on the free oφcmpo concentrations and to decrease with increasing free H2ox concentrations. From these results, it is proposed that the exchange reaction of oφcmpo proceeds through the interchange(I) mechanism and that the retardation effect of free H2ox is due to the formation of outer-sphere complex. (author)

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

    Science.gov (United States)

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

    2013-03-01

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

  14. Interaction of aerobic soil bacteria with plutonium(VI)

    International Nuclear Information System (INIS)

    We studied the interaction of Pu(VI) with Pseudomonas stutzeri ATCC 17588 and Bacillus sphaericus ATCC 14577, representatives of the main aerobic groups of soil bacteria present in the upper soil layers. The accumulation studies have shown that these soil bacteria accumulate high amounts of Pu(VI). The sorption efficiency toward Pu(VI) decreased with increasing biomass concentration due to increased agglomeration of the bacteria resulting in a decreased total surface area and number of available complexing groups. Spores of Bacillus sphaericus showed a higher biosorption than the vegetative cells at low biomass concentration which decreased significantly with increasing biomass concentration. At higher biomass concentrations (> 0.7 g/L), the vegetative cells of both strains and the spores of B. sphaericus showed comparable sorption efficiencies. Investigations on the pH dependency of the biosorption and extraction studies with 0.01 M EDTA solution have shown that the biosorption of plutonium is a reversible process and the plutonium is bound by surface complexation. Optical absorption spectroscopy showed that one third of the initially present Pu(VI) was reduced to Pu(V) after 24 hours. Kinetic studies and solvent extraction to separate different oxidation states of Pu after contact with the biomass provided further information on the yield and the kinetics of the bacteria-mediated reduction. Long-term studies showed that also 16% of Pu(IV) was formed after one month. The comparison of the amount of Pu(IV) formed during that time period with literature data of the Pu(V) disproportionation, indicated that the Pu(IV) seemed to be rather the result of the disproportionation of the formed Pu(V) than of a further microbial reduction

  15. Study of the temperature influence during the uranium (Vi) sorption on surface of ZrP{sub 2}O{sub 7} in presence of oxalic and salicylic acid; Estudio de la influencia de la temperatura durante la sorcion de uranio (VI) en la superficie del ZrP{sub 2}O{sub 7} en presencia de acidos oxalico y salicilico

    Energy Technology Data Exchange (ETDEWEB)

    Garcia G, N.

    2013-07-01

    This work studies the effect of temperature on the uranium (Vi) sorption onto zirconium diphosphate in the presence of organic acids (oxalic and salicylic acids). Zirconium diphosphate was synthesized by a chemical condensation reaction and characterized using several analytical techniques, in order to check its purity. This point is very important because the presence of any impurities or secondary phases may interfere with the hydration and sorption process. Prior to the sorption experiments, three batches of zirconium diphosphate were pre-equilibrated with NaClO{sub 4}, oxalic acid or salicylic acid solutions. The hydrated solids were washed and dried and then again characterized in order to study the interactions between organic acids and zirconium diphosphate surface. Uranium sorption onto zirconium diphosphate (pre-equilibrated with NaClO{sub 4}, oxalic acid and salicylic acid solutions) was investigated as a function of ph, organic acid and temperature (20, 40 y 60 grades C). Thermodynamic parameters for the sorption reactions (enthalpy change, entropy change and Gibbs free energy change) were determined from temperature dependence of distribution coefficient by using the Vant Hoff equation. Solids characterization after hydration shows that exist an interaction between organic acids and ZrP{sub 2}O{sub 7}. This fact was confirmed with the microcalorimetry study, the reaction heat for hydration of zirconium diphosphate in NaClO{sub 4} solution was exothermic (-269.59 mJ) and for hydration of zirconium diphosphate in oxalic acid solution was endothermic (53.64 mJ). The experimental results showed important differences in the sorption mechanisms for the reaction of Uranium with ZrP{sub 2}O{sub 7} in the presence and absence of organic acids. For the zirconium diphosphate hydrated with oxalic acid, the sorption percentage was 50% from lowest ph values. For the zirconium diphosphate hydrated with salicylic acid, the initial concentration of uranium was 6 x 10

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-27

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

  17. Cr(VI) retention and transport through Fe(III)-coated natural zeolite.

    Science.gov (United States)

    Du, Gaoxiang; Li, Zhaohui; Liao, Libing; Hanson, Renee; Leick, Samantha; Hoeppner, Nicole; Jiang, Wei-Teh

    2012-06-30

    Cr(VI) is a group A chemical based on the weight of evidence of carcinogenicity. Its transport and retention in soils and groundwater have been studied extensively. Zeolite is a major component in deposits originated from volcanic ash and tuff after alteration. In this study, zeolite aggregates with the particle size of 1.4-2.4mm were preloaded with Fe(III). The influence of present Fe(III) on Cr(VI) retention by and transport through zeolite was studied under batch and column experiments. The added Fe(III) resulted in an enhanced Cr(VI) retention by the zeolite with a capacity of 82mg/kg. The Cr(VI) adsorption on Fe(III)-zeolite followed a pseudo-second order kinetically and the Freundlich adsorption isotherm thermodynamically. Fitting the column experimental data to HYDRUS-1D resulted in a retardation factor of 3 in comparison to 5 calculated from batch tests at an initial Cr(VI) concentration of 3mg/L. The results from this study showed that enhanced adsorption and retention of Cr(VI) may happen in soils derived from volcanic ash and tuff that contains significant amounts of zeolite with extensive Fe(III) coating. PMID:22542779

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

    OpenAIRE

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

    2012-01-01

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

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

    OpenAIRE

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

    2012-01-01

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

  20. Upscaling of U(VI) Desorption and Transport Using Decimeter-Scale Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Derrick

    2015-01-28

    Experimental work was used to validate modeling studies and develop multicontinuum models of U(VI) transport in a contaminated aquifer. At the bench scale, it has been shown that U(VI) desorption is rate-limited and that rates are dependent on the bicarbonate concentration. Two decimeter-scale experiments were conducted in order to help establish rigorous upscaling approaches that could be tested at the tracer test and plume scales.

  1. Upscaling of U(VI) Desorption and Transport Using Decimeter-Scale Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Derrick [Colorado School of Mines

    2014-12-22

    Experimental work was used to validate modeling studies and develop multicontinuum models of U(VI) transport in a contaminated aquifer. At the bench scale, it has been shown that U(VI) desorption is rate-limited and that rates are dependent on the bicarbonate concentration. Two decimeter-scale experiments were conducted in order to help establish rigorous upscaling approaches that could be tested at the tracer test and plume scales.

  2. Síntese eletroquímica do ion ferrato(VI)

    OpenAIRE

    Luca Maria Augusta de; Luca Sérgio João de; Santana Maria Alice

    2003-01-01

    The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathod...

  3. Reversion Of Disused Fishpond Lease Agreement Areas To Mangrove Forests In Region VI, Philippines

    OpenAIRE

    Alice Joan G. Ferrer; Jinky C. Hopanda; Michael Q. Orquejo; Alan Dino E. Moscoso; Resurreccion B. Sadaba

    2011-01-01

    This paper focuses on evaluating the reversion of disused Fishpond Lease Agreement areas in Region VI (Western Visayas), Philippines to mangrove forests. The rehabilitation and restoration of mangrove areas are important given the substantial decline of mangrove forests in the country, particularly in Region VI. The study used a two-stage and five-step evaluation process. The first stage assessed the processes of Fishpond Lease Agreement (FLA) cancellation and reversion of jurisdiction over d...

  4. FTIR Spectroscopic Characterization Of II-VI Semiconductors

    Science.gov (United States)

    Perry, G. L. E.; Szofran, F. R.

    1991-01-01

    Combination of commercial Fourier-transform infrared (FTIR) spectrometer with computer and special-purpose software constitutes highly automated facility for acquisition and processing of infrared transmission or reflection spectral image data. Intended principally to acquire transmission spectra of some compounds of elements in groups II and VI of periodic table. System used to characterize specimens of II/VI alloy semiconductors grown by directional solidification and quenching. Transmission-edge maps helpful in studies of flows, gradients of temperature, and coefficients of diffusion in solidifying melts. Data acquired by system include optical characteristics, and they both verify and complement data obtained by such other techniques as measurements of density and x-ray-dispersion analysis.

  5. O VI and H_2 Lines in Sunspots

    CERN Document Server

    Labrosse, N; Habbal, S R; Brown, D; Labrosse, Nicolas; Morgan, Huw; Habbal, Shadia Rifai; Brown, Daniel

    2006-01-01

    Sunspots are locations on the Sun where unique atmospheric conditions prevail. In particular, the very low temperatures found above sunspots allow the emission of H_2 lines. In this study we are interested in the radiation emitted by sunspots in the O VI lines at 1031.96 A and 1037.60 A. We use SOHO/SUMER observations of a sunspot performed in March 1999 and investigate the interaction between the O VI lines and a H_2 line at 1031.87 A found in the Werner band. The unique features of sunspots atmospheres may very well have important implications regarding the illumination of coronal O+5 ions in the low corona, affecting our interpretation of Doppler dimming diagnostics.

  6. Humic substances extraction, characterization and interaction with U(VI) at Ruprechtov site (CZ)

    International Nuclear Information System (INIS)

    The extent of complexation between natural humic acid (HA) and uranium(VI) has been investigated at the Ruprechtov natural analogue site, Czech Republic. Natural HA was extracted from the clay sediments enriched by organic matter and then characterized for their elemental composition, UV/Vis and infrared spectroscopic properties, exchange capacity and protonation constants. Moreover, the reference sample HA-leonardite was selected and studied for comparison. Complexation between natural HA and U(VI) was studied using the cation exchange technique at pH 5-6. The experimental work was focused on study dependence of U(VI) complexation with HA: (i) on the concentration of HA 1-40 mg/l, and (ii) on the concentration of U(VI) 1 x 10-5-1 x 10-7 M. The charge neutralization model (CNM) was used for evaluation of the experimental data, modified in a way, that the total charge was divided among the individual U(VI) species in solution under given conditions. The stability constant value was determined to be log β = 4.32 ± 0.50, LC=50-60%, being independent on the HA concentration at U(VI) concentrations of 1 x 10-4 M. On the other hand, a dependence on the stability constant for the different U(VI) concentrations was observed. At close to real conditions of the site (U(VI) = 1 x 10-7 M and mHA = 5 mg/l) the stability constant log β=6.16, LC=50.3-52.7%. (orig.)

  7. Humic substances extraction, characterization and interaction with U(VI) at Ruprechtov site (CZ)

    Energy Technology Data Exchange (ETDEWEB)

    Cervinka, R.; Havlova, V. [Nuclear Research Institute Rez (NRI) plc, Husinec-Rez (Czech Republic). Waste Disposal Dept.; Stamberg, K. [Czech Technical Univ., Prague (Czech Republic). Faculty of Nuclear Sciences and Physical Engineering; Noseck, U. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig (Germany)

    2011-07-01

    The extent of complexation between natural humic acid (HA) and uranium(VI) has been investigated at the Ruprechtov natural analogue site, Czech Republic. Natural HA was extracted from the clay sediments enriched by organic matter and then characterized for their elemental composition, UV/Vis and infrared spectroscopic properties, exchange capacity and protonation constants. Moreover, the reference sample HA-leonardite was selected and studied for comparison. Complexation between natural HA and U(VI) was studied using the cation exchange technique at pH 5-6. The experimental work was focused on study dependence of U(VI) complexation with HA: (i) on the concentration of HA 1-40 mg/l, and (ii) on the concentration of U(VI) 1 x 10{sup -5}-1 x 10{sup -7} M. The charge neutralization model (CNM) was used for evaluation of the experimental data, modified in a way, that the total charge was divided among the individual U(VI) species in solution under given conditions. The stability constant value was determined to be log {beta} = 4.32 {+-} 0.50, LC=50-60%, being independent on the HA concentration at U(VI) concentrations of 1 x 10{sup -4} M. On the other hand, a dependence on the stability constant for the different U(VI) concentrations was observed. At close to real conditions of the site (U(VI) = 1 x 10{sup -7} M and mHA = 5 mg/l) the stability constant log {beta}=6.16, LC=50.3-52.7%. (orig.)

  8. Removal of Cr(VI from Aqueous Environments Using Micelle-Clay Adsorption

    Directory of Open Access Journals (Sweden)

    Mohannad Qurie

    2013-01-01

    Full Text Available Removal of Cr(VI from aqueous solutions under different conditions was investigated using either clay (montmorillonite or micelle-clay complex, the last obtained by adsorbing critical micelle concentration of octadecyltrimethylammonium ions onto montmorillonite. Batch experiments showed the effects of contact time, adsorbent dosage, and pH on the removal efficiency of Cr(VI from aqueous solutions. Langmuir adsorption isotherm fitted the experimental data giving significant results. Filtration experiments using columns filled with micelle-clay complex mixed with sand were performed to assess Cr(VI removal efficiency under continuous flow at different pH values. The micelle-clay complex used in this study was capable of removing Cr(VI from aqueous solutions without any prior acidification of the sample. Results demonstrated that the removal effectiveness reached nearly 100% when using optimal conditions for both batch and continuous flow techniques.

  9. Derivative spectrophotometric determination of uranium (VI using diacetyl monoxime isonicotinoyl hydrazone (DMIH

    Directory of Open Access Journals (Sweden)

    ChandraSekhar Reddy Gadikota

    2011-08-01

    Full Text Available Uranium (VI forms a yellow coloured water soluble complex with diacetyl monoxime isonicotinoyl hydrazone (DMIH reagent in acidic buffer of pH 3.25 with ?max at 364 nm. The molar absorptivity and sandell’s sensitivity are 1.63 X 10 4 L.mol -1.cm-1 and 0.00307692 µg/cm 2, respectively. The Beer’s law validity range is 1.19–14.28 µg/mL. Uranium (VI forms (M:L 1:1 complex with DMIH and stability constant of the complex is 4.928 X 106 .The derivative spectrophotometric determination of U (VI was carried out by measuring peak height method. The developed derivative spectrophotometric method was employed for the determination of uranium (VI in rock and synthetic samples. The effect of various diverse ions was also studied.

  10. Adsorption of uranium(VI) and zirconium(IV) from acid solutions on silica gel

    International Nuclear Information System (INIS)

    Adsorption of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel was investigated by the batch equilibration method. The influence of shaking time and concentrations of nitric acid (i.e., pH of solution) and metal ions in solution were studied. Adsorption of uranium(VI) and zirconium(IV) increases with an increase of pH (decrease of nitric acid concentration) and ion concentrations. The adsorption mechanism of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel is proposed. It is shown that zirconium(IV) and uranium(VI) can be separated if the concentration of nitric acid in solution is higher than 0.01 mol/dm3

  11. Alkali-treated cellulose fibers for U(VI) separation and enrichment

    International Nuclear Information System (INIS)

    The present research work presents the study of cost effective cellulose fibers as sorbent for the U(VI) removal from nuclear wastewaters. Alkali-treated cellulose fibers (ATCFs) were extracted from alkaline peroxide mechanical pulp board by using CH3COOH and NaOH treatment. Sorption capability was ascertained by conducting batch experiments. The kinetic sorption of U(VI) on ATCFs could be described by the pseudo-second-order rate equation well. The results demonstrated that the sorption of U(VI) to ATCFs was strongly dependent of pH and weakly dependent of ionic strength. U(VI) sorption on ATCFs was mainly dominated by the outer-sphere complexation. (author)

  12. MCNP analysis of the Livermore pulsed spheres with ENDF/B-VI

    International Nuclear Information System (INIS)

    Twenty-five Livermore pulsed sphere experiments have been modeled with the MCNP4A code using ENDF/B-VI cross sections processed by the NJOY nuclear data processing system. These calculations have been compared to an earlier study using ENDF/B-V data using the MCNP4 code. These are the first MCNP4A benchmarks, the first ENDF/B-VI benchmarks with MCNP, and the first analysis of these NJOY-processed data. In general, these results validate the MCNP code, demonstrate that ENDF/B-VI and ENDF/B-V generally agree, and in some cases show that ENDF/B-VI gives better results than ENDF/B-V

  13. Savannah River Laboratory hydrogeochemical and stream sediment reconnaissance. Orientation study data release VI: Leesville, South Carolina, area. National Uranium Resource Evaluation Program

    International Nuclear Information System (INIS)

    Raw data from an orientation study in the Leesville, South Carolina, area are presented. The area comprises parts of Lexington, Aiken, and Saluda Counties, South Carolina. This report includes sample locality maps, uranium distribution maps, tables of water quality and field measurement data, and tables of uranium and other elemental concentrations

  14. Vi är till för kommuninvånarna” : En kvalitativ studie av musikavdelningen på Enköpings kommunbibliotek

    OpenAIRE

    Klang, Kent

    2011-01-01

    The aim of this study is to examine the significance of having a music department at the public library in Enköping, and how the organization of the phonograms is handled. The different areas examined are the reason of the reintroduction of a music department, its budget, its users, the work with selection, the marketing, statistical data concerning loans, the work with classification, indexing, and organization of the phonograms and the future of the music department. The empirical material ...

  15. Motif Penggunaan dan Kepuasan Menggunakan Path (Studi Korelasional Tentang Pengaruh Motif Penggunaan dan Kepuasan Menggunakan Jejaring sosial Path di Kalangan Masyarakat Pasar VI Kelurahan Padang Bulan Medan)

    OpenAIRE

    Dipta, Anna Mira

    2015-01-01

    This study entitled Effect of using and gratification of using social networking Path among the people in Padang Bulan Medan (CorrelationalEffect of using and gratification of using social networking Path among the people in Padang Bulan Medan). Path is a social network similar to its predecessor facebook. Path exclusive can only be used with smartphones based on IOS and android operating system. Path is a private social networking service application designed to bring users closer to family....

  16. Why College Students Want to Learn Asian Languages: A Comparative Study of Motivational Factors for the Selection of Chinese, Japanese, Korean and Vi-etnamese

    Directory of Open Access Journals (Sweden)

    Jack Jinghui Liu

    2008-01-01

    Full Text Available In recent years, more higher educational institutions started to offer less commonly taught languages, and the enrollments in Asian languages have been increasing. However, little was known about why students are interested in the study of a certain Asian lan-guage. This study investigates students’ motivation in the selection of one of four Asian languages: Chinese, Japanese, Korean and Viet-namese, and compares the motivational factors across these lan-guages. Ninety-nine college students who enrolled in the first semes-ter of one of these Asian language classes responded to a Likert-scale questionnaire and open-ended questions. The findings showed that a wide variety of reasons initially motivated college students to learn an Asian language. These fell into six major motivational fac-tors: cultural understanding, heritage-related factor, instrumental ori-entation, integrative orientation, achievement orientation, and admin-istrative. The study found that there were both similarities and differences in the motivational factors across the four Asian lan-guages. The cultural understanding and integrative orientation were the top two shared motivational factors, and administrative orienta-tion was a weak factor across all language groups. In addition, differ-ences in rank order among the six motivational factors were found between East Asian and Southeast Asian languages.

  17. Test results of Salmonella typing by the NRLs-Salmonella in the Member States of the EU and the EnterNet Laboratories - Collaborative study VI (2001) on typing of Salmonella

    OpenAIRE

    Korver H; Raes M; Maas HME; Ward LR; Wannet WJB; Henken AM; MGB; LIS

    2002-01-01

    Test resultaten van Salmonella sero- en faagtypering en antimicrobiele gevoeligheidsbepalingen door de Nationale Referentie Laboratoria voor Salmonella in de Lidstaten van de Europese Unie en EnterNet Laboratoria: Ringonderzoek VI (2001) voor Salmonella. Een zesde ringonderzoek betreffende de typering van Salmonella werd georganiseerd door het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) in samenwerking met Public Health Laboratory Services (PHLS...

  18. Studies on organometallic oxidants: Structure, redox properties, and magnetism of (C sub 5 H sub 5 )VBr sub 3 and (C sub 5 H sub 5 )VI sub 3

    Energy Technology Data Exchange (ETDEWEB)

    Morse, D.B.; Rauchfuss, T.B.; Wilson, S.R. (Univ. of Illinois, Urbana (United States))

    1991-02-20

    The preparation and properties of CpVBr{sub 3} and CpVI{sub 3} (Cp = {eta}{sup 5}-C{sub 5}H{sub 5}) are described. The compound CpVBr{sub 3} exhibits an E{sub 1/2} of 510 mV (vs Ag/AgCl) and is able to oxidize ferrocene. The salt (Cp{sub 2}Fe)(CpVBr{sub 3}) was characterized by infrared spectroscopy ({nu}{sub CH}(Cp{sub 2}Fe) = 857 cm{sup {minus}1}), {sup 57}Fe Moessbauer spectroscopy at 295 K ({delta}{sub 1} = 0.35, {delta}{sub 2} = 0.421 mm/s) and 150 K, variable-temperature magnetic susceptibility ({mu}{sub eff}(300 K) = 3.75 {mu}{sub B}), and H NMR spectroscopy. While CpVBr{sub 3} is more oxidizing than CpVCl{sub 3}, the authors find that CpVI{sub 3} is less oxidizing (E{sub 1/2} = 425 mV). In solution CpVI{sub 3} exists as two distinct species as shown by H NMR spectroscopy. The structure of CpVI{sub 3} was solved in the orthorhombic space group Pn2{sub 1}a (no. 33, alternate setting) with the lattice constants a = 11.847 (4) {Angstrom}, b = 11.304 (3) {Angstrom}, c = 7.532 (1) {Angstrom}, and Z = 4.

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

    International Nuclear Information System (INIS)

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

  20. Highly-Ionized Gas in the Galactic Halo A FUSE Survey of O VI Absorption toward 22 Halo Stars

    CERN Document Server

    Zsargo, J; Howk, J C; Savage, B D

    2003-01-01

    Far Ultraviolet Spectroscopic Explorer spectra of 22 Galactic halo stars are studied to determine the amount of O VI in the Galactic halo between ~0.3 and \\~10 kpc from the Galactic mid-plane. Strong O VI 1031.93 A absorption was detected toward 21 stars, and a reliable 3 sigma upper limit was obtained toward HD 97991. The weaker member of the O VI doublet at 1037.62 A could be studied toward only six stars. The observed columns are reasonably consistent with a patchy exponential O VI distribution with a mid-plane density of 1.7x10^(-8) cm^(-3) and scale height between 2.3 and 4 kpc. We do not see clear signs of strong high-velocity components in O VI absorption along the Galactic sight lines, which indicates the general absence of high velocity O VI within 2-5 kpc of the Galactic mid-plane. The correlation between the H I and O VI intermediate velocity absorption is also poor. The O VI velocity dispersions are much larger than the value of ~18 km/s expected from thermal broadening for gas at T~300,000 K, the...

  1. First-principles study on electronic and optical properties of Cu2ZnSiV I4 (VI=S, Se, and Te) quaternary semiconductors

    International Nuclear Information System (INIS)

    The electronic and optical properties of Cu2ZnSiS4, Cu2ZnSiSe4 and Cu2ZnSiTe4 in kesterite and stannite structures are systematically studied using first-principles calculations. Crystal field splitting, optical transitions, p-d bonding, and anti-bonding overlapping are analyzed. The physical and chemical trends in these properties are investigated with respect to the crystal structure and anion atomic number. The optical spectra, such as dielectric function, refractive index, reflectivity and absorption coefficient are explored in a broad range of energy. A good agreement between the calculated results and experimental data is obtained

  2. “Nu kör vi!” :  En kvalitativ studie kring fördelar och nackdelar med en traditionell dansundervisning

    OpenAIRE

    Svensson, Sara

    2011-01-01

    There is respect for the history of dance and my aim is to find out how the history affects the dancing youth today. The design of the dance lesson is often of a traditional stereotypical manner, both didactic and methodic, and it rarely appears to be questioned. I have danced for almost 20 years and I am a part of this tradition of movements, music, language and way of “being”. My ambition with this study is to go outside my own experience and offer insight and an overall picture of a, for t...

  3. First-principles study on electronic and optical properties of Cu2ZnSiV I4 (VI=S, Se, and Te quaternary semiconductors

    Directory of Open Access Journals (Sweden)

    Xuebiao Zhang

    2015-05-01

    Full Text Available The electronic and optical properties of Cu2ZnSiS4, Cu2ZnSiSe4 and Cu2ZnSiTe4 in kesterite and stannite structures are systematically studied using first-principles calculations. Crystal field splitting, optical transitions, p-d bonding, and anti-bonding overlapping are analyzed. The physical and chemical trends in these properties are investigated with respect to the crystal structure and anion atomic number. The optical spectra, such as dielectric function, refractive index, reflectivity and absorption coefficient are explored in a broad range of energy. A good agreement between the calculated results and experimental data is obtained.

  4. A novel radiotracer method to study the formation of surface adlayers in the course of Cr(VI) reduction on a gold electrode

    International Nuclear Information System (INIS)

    The aim of the work is to report some new findings obtained by in situ radiotracer and voltammetric studies of the simultaneous adsorption of HSO4-/SO42- (labeled with 35S) and Cr-containing species (labeled with 51Cr) on a gold electrode in the course of dichromate reduction in 1 mol/dm3 HClO4 supporting electrolyte. Special attention is paid to the detection and calculation method elaborated for the quantitative evaluation of the surface excess of radiolabeled Cr species via measurement of the intensity of low-energy X-rays (E = 4.90 keV) emitted by 51Cr

  5. Delineation and Diagnostic Criteria of Oral-Facial-Digital Syndrome Type VI

    Directory of Open Access Journals (Sweden)

    Poretti Andrea

    2012-01-01

    Full Text Available Abstract Oral-Facial-Digital Syndrome type VI (OFD VI represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD. In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1 MTS and one oral finding and polydactyly, or 2 MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD

  6. Insights into the extraction behavior of U(VI) in Aliquat-336 based ionic liquids

    International Nuclear Information System (INIS)

    The extraction behavior of U(VI) in the PUREX solvent namely 1.1 M tri-n-butyl phosphate (TBP) in n-dodecane (n-DD) was studied in the presence and absence of the ionic liquid, tri-n-octylmethylammonium bis-(2-ethylhexyl)phosphate ([A336]+[DEHP]-). The discrepancy in the extraction behavior observed in these systems was probed by measuring the distribution ratio of U(VI) as a function of various parameters. The distribution ratio of U(VI) in 0.03 M [A336]+[DEHP]-/n-DD decreased with increase in the concentration of nitric acid. The extraction of U(VI) was accompanied by the extraction of nitric acid leading to the formation of ionic liquid constituents namely tri-n-octylmethylammonium nitrate ([A336]+[NO3]-) and bis(2-ethylhexyl)phosphoric acid (HDEHP). Therefore, the distribution ratio of U(VI) in the PUREX solvent was measured in the presence of these constituents also. The study revealed that extraction of U(VI) was controlled essentially by the synergistic contribution of TBP and the constituents of ionic liquid.

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

    Science.gov (United States)

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

    2014-10-01

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

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

    Directory of Open Access Journals (Sweden)

    Gunjan Guha

    2011-01-01

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

  9. Synthesis and crystal structure of new Np(VI) and Pu(VI) phthalates, Na4{AnO2[(OOC)2C6H4]3} · nH2O

    International Nuclear Information System (INIS)

    Double phthalates of Np(VI) and Pu(VI) of the composition Na4[AnO2L3] · nH2O [An=Np, Pu; L = (OOC)2C6H4] were synthesized in the crystalline form and studied by monocrystal X-ray diffraction. The compounds are isostructural, their crystals consist of complex anions [AnO2L3]4- and Na+ cations, forming neutral layers; water molecules are located between the layers. The coordination polyhedra of An(VI) are hexagonal bipyramids, whose average planes are formed by oxygen atoms of three phthalate anions. In passing from Np(VI) to Pu(VI), the actinide contraction is reflected to a greater extent in the variation of the bond lengths with apical oxygen atoms of the bipyramids, whereas the An-O bond lengths in the equatorial plane of the bipyramids vary insignificantly

  10. Merilni modul za višino kvadrokopterja nad tlemi

    OpenAIRE

    Klajderič, Aljoša

    2016-01-01

    Tematika diplomske naloge je opis in izdelava višinomera za kvadrokopterje. Višinomer je instrument, ki meri višino objekta nad ravnjo nadmorske višine. Za merjenje višine se uporabljajo metode, ki temeljijo na preletu ultrazvočnega valovanja ter na razliki zračnega tlaka. Merilniški modul meri višino na obeh fizikalnih načelih, torej na preletu ultrazvočnega valovanja, tlačni razliki in na fuzijski ravni oziroma na združitvi obeh fizikalnih načel. Namen diplomske naloge je bilo razumeti omej...

  11. Characterization of uranium(VI) sorption by organobentonite

    International Nuclear Information System (INIS)

    The U(VI) sorption on the bentonite modified by hexadecyltrimethylammonium bromide (HDTMA) was studied in the concentration range: 0.0001-0.001 mol/dm3 in the aqueous phase and in the pH range: 3-10. The experiments concerning the pH influence on the molar absorption coefficient cb of U(VI) in the bentonite phase showed that the species: UO22+, UO2(OH)+, UO2(OH)2 UO2(OH)3-, UO2(OH)42-, (UO2)3(OH)5+, (UO2)3(OH)7-, present in the aqueous phase, are responsible for uranium sorption. Their sorption parameters K were determined and it is evident that for higher concentrations of HDTMA+ cations in the bentonite phase, i.e. for b96-b157 bentonite, the presence of anionic species: UO2(OH)3-, UO2(OH)42-, and (UO2)3(OH)7- in the aqueous phase results in the increase of U(VI) molar absorption coefficient cb in the sorbent phase.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2013-02-01

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

  14. Annual report of Nuclear Reactor Laboratory, Kinki University. Vol 1. (1961). Studies on the radioactive contamination due to nuclear detonations I-VI

    International Nuclear Information System (INIS)

    An unusually large amount of strong radioactive ash was produced by the thermonuclear test conducted on March 1954 at the Bikini Atoll in the South Pacific by the United States Atomic Energy Commission. Under such circumstances, to meet the urgent needs of public health, the studies on the radioactivity of Bikini ash and the radioactive contamination of environment have been started, from the health physics standpoint, with the initiative of the author under close cooperation with the public health officers of local governments in Osaka district since the middle of March 4 1954, when the author was the head of the Department of Biophysics, Osaka City University, School of Medicine. The estimation of the probable dose of radiation the might have been received during their dosage and the accurate estimation of beta-ray energies and the detection of alpha-ray activity as well as the identification of various radioactive nuclides included in the Bikini ash were considered to be urgently needed items of information in estimating the possible hazard due to the internal as well as the external irradiation from the health physics point of view

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

    Directory of Open Access Journals (Sweden)

    Catrambone M.

    2013-04-01

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

  16. Amidoxime-grafted multiwalled carbon nanotubes by plasma techniques for efficient removal of uranium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yun [Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Fundamental Science on Radioactive Geology and Exploration Technology Laboratory, East China Institute of Technology, Nanchang, Jiangxi 330013 (China); Gu, Zexing; Yang, Jijun; Liao, Jiali; Yang, Yuanyou [Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Liu, Ning, E-mail: nliu720@scu.edu.cn [Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Tang, Jun, E-mail: tangjun@scu.edu.cn [Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China)

    2014-11-30

    Highlights: • Amidoximated MWCNTs were synthesized by plasma techniques. • The surface modification remarkably enhanced U(VI) sorption capacity. • Process was endothermic, spontaneous, and pseudo-second-order chemisorption. • AO-g-MWCNTs showed more favorable selectivity to U(VI). • Mechanism of interaction between AO-g-MWCNTs and U(VI) was discussed and suggested. - Abstract: A novel solid-phase extractant, amidoxime-grafted multiwalled carbon nanotubes (AO-g-MWCNTs), has been synthesized using plasma techniques to selectively separate uranium from nuclear industrial effluents. The adsorbent was characterized by Fourier transform infrared spectra (FT-IR), elemental analysis, Raman, scanning electron microscopy (SEM), and thermal gravity analysis (TGA). Sorption behaviors of uranium(VI) on AO-g-MWCNTs were investigated by varying pH, contact time, initial uranium concentration, and temperature. An optimum sorption capacity of 145 mg g{sup −1} (0.61 mmol g{sup −1}) for U(VI) was obtained at pH 4.5. X-ray photoelectron spectroscopy (XPS) has been used to explore the sorption mechanism of U(VI) on AO-g-MWCNTs. Furthermore, AO-g-MWCNTs could selectively adsorb U(VI) in aqueous solution containing co-existing ions (Mn{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Zn{sup 2+}, Sr{sup 2+}, Ba{sup 2+} and Cs{sup +}). This study shows that AO-g-MWCNTs are potential adsorbent for effective removal of U(VI) from aqueous solution.

  17. Synthesis and application of magnetic hydrogel for Cr(VI) removal from contaminated water

    KAUST Repository

    Tang, Samuel C N

    2010-11-01

    Many magnetic adsorbents reported in the literature, such as iron oxides, for Cr(VI) removal have been found effective only in low pH environments. Moreover, the application of polymeric hydrogels on heavy metal removal has been hindered by difficulties in separation by filtration. In this study, a magnetic cationic hydrogel was synthesized for Cr(VI) removal from contaminated water, making use of the advantages of magnetic adsorbents and polymeric hydrogels. The magnetic hydrogel was produced by imbedding 10-nm γ-Fe2O 3 nanoparticles into the polymeric matrix via radical polymerization. Characterization of the hydrogel was undertaken with Fourier transform infrared and vibrating sample magnetometer; swelling properties were tested and anionic adsorption capacity was evaluated. The magnetic hydrogel showed a superior Cr(VI) removal capacity compared to commercial products such as MIEX®. Cr(VI) removal was independent of solution pH. Results show that Cr(VI) removal kinetics was improved drastically by grinding the bulk hydrogel into powder form. At relevant concentrations, common water anions (e.g., Cl-, SO4 2-, PO4 3-) and natural organic matter did not exhibit significant inhibition of Cr(VI) adsorption onto the hydrogel. Results of vibrating sample magnetometer indicate that the magnetic hydrogel can be easily separated from treatment systems. Regeneration of the magnetic hydrogel can be easily achieved by washing the Cr(VI)-loaded hydrogel with 0.5 M NaCl solution, with a recovery rate of about 90% of Cr(VI). © Copyright 2010, Mary Ann Liebert, Inc. 2010.

  18. Bicarbonate impact on U(VI) bioreduction in a shallow alluvial aquifer

    Science.gov (United States)

    Long, Philip E.; Williams, Kenneth H.; Davis, James A.; Fox, Patricia M.; Wilkins, Michael J.; Yabusaki, Steven B.; Fang, Yilin; Waichler, Scott R.; Berman, Elena S. F.; Gupta, Manish; Chandler, Darrell P.; Murray, Chris; Peacock, Aaron D.; Giloteaux, Ludovic; Handley, Kim M.; Lovley, Derek R.; Banfield, Jillian F.

    2015-02-01

    Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al., 2003; Williams et al., 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al., 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ∼3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction in the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in

  19. New low cost sorbents for Cr(VI – batch and column experiments

    Directory of Open Access Journals (Sweden)

    Šillerová H.

    2013-04-01

    Full Text Available The use of agricultural byproducts and industrial biowaste materials has been shown to be an attractive technique for removing Cr(VI from contaminated waste waters. In this study, used brewers draff, peat moss, sawdust, grape stalks and husks were investigated as novel biosorbents for Cr(VI. The material was tested in two different modifications. The material was dried, cut and sieved and part of it was subjected to acid (2 M H2SO4 and alkali (0.5 M NaOH pre-treatments to remove starch, proteins and sugars. Fourier transform infrared rays analysis on solid phase (FTIR-ATR was used to determine the main functional groups that might control the metal uptake. Batch experiments were performed at different pH values (3, 4.5, 6 and at various initial concentration of Cr(VI (25–2012;250 mg L−1. Two equilibrium empirical models, Langmuir and Freundlich, were used to describe Cr(VI adsorption. In order to identify possible reduction processes, ion exchange separation on the AG1-X8 resin was used to separate the anionic Cr(VI and the reduced cationic Cr(III from the aqueous phase after biosorption. As expected, Cr(VI removal was pH-dependent and fitted well both the Langmuir and Freundlich isotherm models. The ion exchange separation showed that Cr(VI reduction had occurred in the solution during biosorption. The efficiency of draff as a biosorbent was comparable (or even higher to highly organic materials (e.g., composted peat showing its potential application for Cr(VI decontamination.

  20. Bicarbonate Impact on U(VI) Bioreduction in a Shallow Alluvial Aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Long, Philip E.; Williams, Kenneth H.; Davis, James A.; Fox, Patricia M.; Wilkins, Michael J.; Yabusaki, Steven B.; Fang, Yilin; Waichler, Scott R.; Berman, Elena S.; Gupta, Manish; Chandler, Darrell P.; Murray, Christopher J.; Peacock, Aaron D.; Giloteaux, L.; Handley, Kim M.; Lovley, Derek R.; Banfield, Jillian F.

    2015-02-01

    Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al. 2003, Williams et al. 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al. 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, that the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ~3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.

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

    Science.gov (United States)

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

    2016-10-01

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

  2. Comparison of Cr(VI) removal by activated sludge and dissolved organic matter (DOM): importance of UV light.

    Science.gov (United States)

    Gong, Yu-Feng; Song, Jia; Ren, Hai-Tao; Han, Xu

    2015-12-01

    Removal of toxic Cr(VI) by activated sludge and DOM derived from activated sludge was investigated in this study. A rapid increase in TOC concentration from 50.93 to 127.40 mg L(-1) is observed during the Cr(VI) removal process by activated sludge in the pH range of 2-9. Removal efficiencies of Cr(VI) by either activated sludge or DOM greatly decreased with the increasing initial pH. Kinetics of Cr(VI) removal by activated sludge indicate that both biosorption and bioreduction are involved in the Cr(VI) removal. Cr(VI) removal by DOM is slow in dark, but it is greatly enhanced when UV light is applied. The first-order constant increases from 0.0033 (in dark) to 0.079 min(-1) (UV illumination) at pH 2.0 and 1068 mg L(-1) DOM. The enhancement of Cr(VI) reduction is due to the generation of the reactive intermediates such as O2(●-) and DOM* as DOM absorbed light energy, which plays important roles in the reduction of Cr(VI). PMID:26300355

  3. Spectroscopic Studies of Solar Corona VI: Trend in Line-width Variation of Coronal Emission Lines with Height Independent of the Structure of Coronal Loops

    Indian Academy of Sciences (India)

    Jagdev Singh; Takashi Sakurai; Kiyoshi Ichimoto; S. Muneer

    2006-06-01

    We have obtained spectroscopic observations in coronal emission lines by choosing two lines simultaneously, one [Fe X] 6374 Å and the other [Fe XI] 7892 Å or [Fe XIII] 10747 Å or [Fe XIV] 5303 Å. We found that in 95 per cent of the coronal loops observed in 6374 Å, the FWHM of the emission line increases with height above the limb irrespective of the size, shape and orientation of the loop and that in case of 5303 Å line decreases with height in about 89 per cent of the coronal loops. The FWHM of 7892 Å and 10747 Å emission lines show intermediate behavior. The increase in the FWHM of 6374 Å line with height is the steepest among these four lines.We have also studied the intensity ratio and ratio of FWHM of these lines with respect to those of 6374 Å as a function height above the limb. We found that the intensity ratio of 7892 Å and 10747 Å lines with respect to 6374 Å line increases with height and that of 5303 Å to 6374 Å decreases with height above the limb. This implies that temperature in coronal loops will appear to increase with height in the intensity ratio plots of 7892 Å and 6374 Å; and 10747 Å and 6374 Å whereas it will appear to decrease with height in intensity ratio of 5303 Å to 6374 Å line versus height plot. These findings are up to a height of about 200 arcsec above the limb. The varying ratios with height indicate that relatively hotter and colder plasma in coronal loops interact with each other. Therefore, the observed increase in FWHM with height above the limb of coronal emission lines associated with plasma at about 1 MK may not be due to increase in non-thermal motions caused by coronal waves but due to interaction with the relatively hotter plasma. These findings also do not support the existing coronal loop models, which predict an increase in temperature of the loop with height above the limb.

  4. Studies of two-terminal and four-terminal polycrystalline thin film tandem solar cells based on II-VI materials

    Science.gov (United States)

    Parikh, Viral Y.

    Multijunction solar cells offer the most promising approach to achieve high conversion efficiency by efficient utilization of the solar spectrum. The work presented in this dissertation focuses on the challenges involved in the fabrication of a two-terminal and a four-terminal tandem device. In case of monolithically series-connected tandem devices, the individual optimization of the top and bottom cells is of crucial importance, as either of them may limit the current of the complete device. A major challenge in the development of these cascade solar cells is also the requirement of a low resistance, optically transparent interconnect junction. To meet these challenges, we have tried to optimize the performance of a single junction CdS/CdTe device by reducing the thickness of CdTe without compromising its efficiency. We have achieved a maximum efficiency of 12.1% for CdTe thickness of 0.9 mum which is similar to a standard 2.3 mum CdTe device in our laboratory. The performance of CdS/CdTe device has also been tested by depositing different transparent back contacts. A device efficiency of 9.1% has been obtained with ZnTe:N/ITO as the best transparent back contact. Bifacial illumination studies (J-V and QE) of these devices have been carried out to understand the current transport mechanism occurring at the hack contact. The requirements of the individual layers of an interconnect junction are reviewed and their optical and electrical properties investigated before fabricating a tandem device. The potential of HgCdTe as an absorber layer for a bottom cell is explored. We are able to achieve the best HgCdTe films with a desired bandgap of 1.1 eV at a substrate deposition temperature of 97°C. These films also have the morphological and electrical properties needed for cell fabrication. Cu-Au proves to be the best ohmic metal back contact to the CdS/HgCdTe device. An all-sputtered two-terminal tandem with CdS/CdTe as top cell and CdS/HgCdTe as bottom cell has been

  5. Spectroscopic studies, thermal analyses and biological evaluation of new V(IV), Zr(IV) and U(VI) moxifloxacin complexes

    Science.gov (United States)

    Sadeek, Sadeek A.; El-Shwiniy, Walaa H.; Zordok, Wael A.; Kotb, Essam

    2011-12-01

    The synthesis and characterization of the new solid complexes [VO(MOX) 2H 2O]SO 4·11H 2O, [ZrO(MOX) 2Cl]Cl·15H 2O and [UO 2(MOX) 3](NO 3) 2·3H 2O formed in the interaction of moxifloxacin (MOX) with VOSO 4·H 2O, ZrOCl 2·8H 2O and UO 2(NO 3) 2·6H 2O in methanol and acetone as a solvents at room temperature were reported. The isolated solid complexes have been characterized with melting points, elemental analysis, molar conductance, magnetic moments studies, spectral (UV-Visible, IR and 1HNMR) as well as thermal analyses (TGA and DTG). The results support the formation of the complexes and indicate that moxifloxacin reacts as a bidentate ligand chelate to the metal ion through the pyridone oxygen and one carboxylato oxygen. The kinetic parameters of thermogravimetric (TGA) and its differential (DTG), such as activation energies, E*, enthalpies, Δ H*, entropies, Δ S* and Gibbs free energies, Δ G*, have been evaluated by using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The proposed structure of the ligand and their complexes were detected by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The bond stretching force constant and length of the U dbnd O for the [UO 2(MOX) 3](NO 3) 2·3H 2O complex were calculated. The antibacterial activity of the free moxifloxacin ligand and their metal complexes have been tested against some selected bacterial strains such as: Streptococcus aureus K1, Bacillus subtilis K22, Brevibacterium otitidis K76, Escherichia coli K32, Pseudomonas aeruginosa SW1 and Klebsiella oxytoca K42. The complexes showed good antibacterial effect to the selected bacterial strains as compared to the free ligand and Zr(IV) complex is very highly significant compared with the other two complexes.

  6. Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

    International Nuclear Information System (INIS)

    Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L-1 of sunflower straw in an initial U (VI) concentration of 20 mg L-1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g-1) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir-Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g-1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent. (author)

  7. Elemental sulfur amendment decreases bio-available Cr-VI in soils impacted by leather tanneries.

    Science.gov (United States)

    Shi, Jingjing; Chen, Hualin; Arocena, Joselito M; Whitcombe, Todd; Thring, Ronald W; Memiaghe, Jeff Nze

    2016-05-01

    This study investigated the potential use of elemental S (S(0)) to convert Cr-VI to Cr-III which should decrease the bio-availability hence, toxicity of Cr-VI in soils. The bio-available fraction of Cr in soil was measured by phosphate buffer extraction (PBE) and the results showed that the fraction is about 10% of the total Cr-VI and varied from 12.8 to 42.5 mg kg(-1). The addition of 4.0 mg g(-1) S(0) decreased PBE Cr-VI to <0.4 mg kg(-1) limit established for Cr-VI toxicity in soils. Synchrotron-based X-ray absorption near-edge structure (XANES), X-ray fluorescence (XRF) and micro-XRD revealed that Cr-III was the dominant species (99% of total Cr) and Cr was retained by hematite and goethite in soil. Fe-containing minerals may have provided sufficient protection to render the dominant Cr-III species biochemically inert to redox processes in soils. It is concluded that S(0)amendment is a promising approach to remediate Cr-VI contaminated soils. PMID:26840517

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

    DEFF Research Database (Denmark)

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

    2001-01-01

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

  9. Floatable, macroporous structured alginate sphere supporting iron nanoparticles used for emergent Cr(VI) spill treatment.

    Science.gov (United States)

    Huang, Jian-Fei; Li, Yong-Tao; Wu, Jin-Hua; Cao, Piao-Yang; Liu, Yong-Lin; Jiang, Gang-Biao

    2016-08-01

    Treatment of hexavalent chromium (Cr(VI)) spill accident is a great challenge due to its high toxicity, sudden and extensiveness. In this study, we designed and fabricated a hierarchical, ordered and macroporous structured alginate sphere to support in-situ synthesized zero-valent iron nanoparticle (the alginate-nZVI sphere). Field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS) images showed well dispersion of nZVI on the composite. This alginate-nZVI sphere exhibited good separability in effective removal of Cr(VI). The result from Cr(VI) removal experiment demonstrated a Cr(VI) removal efficiency of 98.2% at equilibrium time, which can be ascribed to the well dispersion of the nZVI. In addition, the alginate-nZVI sphere was effective in Cr(VI) removal in a wide range of pH from 3.0 to 11.0, by the merit of alginate substrate. Hence, the alginate-nZVI sphere might be a promising agent for an emergent Cr(VI) spill treatment by enhancing the dispersion, stabilization and separation properties of nZVI. PMID:27112857

  10. Evaluation of ENDF/B-VI library with WIMS-AECL/RFSP Code system

    International Nuclear Information System (INIS)

    The object of this research is the evaluation of the cross-section charicteristics of ENDF/B-VI WIMS-AECL library against ENDF/B-V library previously used in the validation of WIMS-AECL code. validation of WIMS-AECL code had been carried out through the Phase-B post simulation of Wolsong Units 2, 3 and 4 before. Discrepancies between the calculated and measured values were thought to be mainly from observation errors and partly from the ENDF/B-V library. Till now, there had been various validation calculations for ENDF/B-VI library in the field of PWR but not in CANDU-PHWR. We herein, evaluated the ENDF/B-VI WIMS-AECL library for Wolsong Unit 4 by comparing the results with previous ones of ENDF/B-V for the same reactor unit with same WIMS/RFSP code system. It can be summarized that the Phase-B post simulation results of WIMS/RFSP with ENDF/B-VI are better than those of ENDF/B-V, because of less difference between calculated and measured values. There must be further study with different core conditions, however, for the exact evaluation of ENDF/B-VI WIMS-AECL library including calculations of many other physical parameters and the treatment of isotopes which is not in ENDF/B-VI but in ENDF/B-V

  11. Biosorption of Cr(VI)_ and Cr(III)_Arthrobacter species

    CERN Document Server

    Gelagutashvili, E; Gurielidze, M

    2011-01-01

    The biosorption of Cr(VI)_ and Cr(III)_ Arthrobacter species (Arthrobacter globiformis and Arthrobacter oxidas) was studied simultaneous application dialysis and atomic absorption analysis. Also biosorption of Cr(VI) in the presence of Zn(II) during growth of Arthrobacter species and Cr(III) in the presence of Mn(II) were discussed. Comparative Cr(VI)_ and Cr(III)_ Arthrobacter species shown, that Cr(III) was more effectively adsorbed by both bacterium than Cr(VI). The adsorption capacity is the same for both the Chromium-Arthrobacter systems. The biosorption constants for Cr(III) is higher than for Cr(VI) 5.7-5.9- fold for both species. Comparative Freundlich biosorption characteristics Cr(VI) Arthrobacter species of living and dry cells shown, that capacity(n) is in both cases the same(1.25,1.35). Dry cells have larger biosorption constant for both species, than living cells. Biosorption characteristics (K) and (n) for A. oxidas are without Mn(II) and in the presence of Mn(II) 2.6 x 10-4 (K), 1.37 (n) and 2...

  12. Inhibition of bone resorption by Tanshinone VI isolated from Salvia miltiorrhiza Bunge

    Directory of Open Access Journals (Sweden)

    V. Nicolin

    2010-05-01

    Full Text Available During the last decade, a more detailed knowledge of molecular mechanisms involved in osteoclastogenesis has driven research efforts in the development and screening of compound libraries of several small molecules that specifically inhibit the pathway involved in the commitment of the osteoclast precursor cells. Natural compounds that suppress osteoclast differentiation may have therapeutic value in treating osteoporosis and other bone erosive diseases such as rheumatoid arthritis or metastasis associated with bone loss. In ongoing investigation into anti-osteoporotic compounds from natural products we have analyzed the effect of Tanshinone VI on osteoclasts differentiation, using a physiologic three-dimensional osteoblast/bone marrow model of cell co-culture. Tanshinone VI is an abietane diterpene extracted from the root of Salvia miltiorrhiza Bunge (Labiatae, a Chinese traditional crude drug, ‘’Tan-Shen’’. Tashinone has been widely used in clinical practice for the prevention of cardiac diseases, arthritis and other inflammation-related disorders based on its pharmacological actions in multiple tissues. Although Tanshinone VI A has been used as a medicinal agent in the treatment of many diseases, its role in osteoclast-related bone diseases remains unknown. We showed previously that Tanshinone VI greatly inhibits osteoclast differentiation and suppresses bone resorption through disruption of the actin ring; subsequently, we intended to examine the precise inhibitory mechanism of Tanshinone VI on osteoclast differentiating factor. This study shows, for the first time, that Tanshinone VI prevents osteoclast differentiation by inhibiting RANKL expression and NFkB induction.

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

    Science.gov (United States)

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

    2015-01-01

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

  14. Cr(VI) retention and transport through Fe(III)-coated natural zeolite

    International Nuclear Information System (INIS)

    Graphical abstract: Breakthrough curves of Cr(VI) from columns packed with raw zeolite (a) and Fe(III)-zeolite (b). The solid line in (b) is the HYDRUS-1D fit to the observed data with adsorption term only, while the dashed line in (b) includes a reduction term in the HYDRUS-1D fit. Highlights: ► Zeolite modified with Fe(III) could be used for adsorption and retention of Cr(VI). ► The Fe present on zeolite was in an amorphous Fe(OH)3 form. ► A Cr(VI) adsorption capacity of 82 mg/kg was found on Fe(III)-zeolite. ► A Cr(VI) retardation factor of 3 or 5 was determined from column and batch studies. - Abstract: Cr(VI) is a group A chemical based on the weight of evidence of carcinogenicity. Its transport and retention in soils and groundwater have been studied extensively. Zeolite is a major component in deposits originated from volcanic ash and tuff after alteration. In this study, zeolite aggregates with the particle size of 1.4–2.4 mm were preloaded with Fe(III). The influence of present Fe(III) on Cr(VI) retention by and transport through zeolite was studied under batch and column experiments. The added Fe(III) resulted in an enhanced Cr(VI) retention by the zeolite with a capacity of 82 mg/kg. The Cr(VI) adsorption on Fe(III)-zeolite followed a pseudo-second order kinetically and the Freundlich adsorption isotherm thermodynamically. Fitting the column experimental data to HYDRUS-1D resulted in a retardation factor of 3 in comparison to 5 calculated from batch tests at an initial Cr(VI) concentration of 3 mg/L. The results from this study showed that enhanced adsorption and retention of Cr(VI) may happen in soils derived from volcanic ash and tuff that contains significant amounts of zeolite with extensive Fe(III) coating.

  15. Cr(VI) retention and transport through Fe(III)-coated natural zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Du, Gaoxiang [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Li, Zhaohui, E-mail: li@uwp.edu [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Geosciences Department, University of Wisconsin-Parkside, Kenosha, WI 53144 (United States); Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liao, Libing [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Hanson, Renee; Leick, Samantha; Hoeppner, Nicole [Geosciences Department, University of Wisconsin-Parkside, Kenosha, WI 53144 (United States); Jiang, Wei-Teh [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2012-06-30

    Graphical abstract: Breakthrough curves of Cr(VI) from columns packed with raw zeolite (a) and Fe(III)-zeolite (b). The solid line in (b) is the HYDRUS-1D fit to the observed data with adsorption term only, while the dashed line in (b) includes a reduction term in the HYDRUS-1D fit. Highlights: Black-Right-Pointing-Pointer Zeolite modified with Fe(III) could be used for adsorption and retention of Cr(VI). Black-Right-Pointing-Pointer The Fe present on zeolite was in an amorphous Fe(OH){sub 3} form. Black-Right-Pointing-Pointer A Cr(VI) adsorption capacity of 82 mg/kg was found on Fe(III)-zeolite. Black-Right-Pointing-Pointer A Cr(VI) retardation factor of 3 or 5 was determined from column and batch studies. - Abstract: Cr(VI) is a group A chemical based on the weight of evidence of carcinogenicity. Its transport and retention in soils and groundwater have been studied extensively. Zeolite is a major component in deposits originated from volcanic ash and tuff after alteration. In this study, zeolite aggregates with the particle size of 1.4-2.4 mm were preloaded with Fe(III). The influence of present Fe(III) on Cr(VI) retention by and transport through zeolite was studied under batch and column experiments. The added Fe(III) resulted in an enhanced Cr(VI) retention by the zeolite with a capacity of 82 mg/kg. The Cr(VI) adsorption on Fe(III)-zeolite followed a pseudo-second order kinetically and the Freundlich adsorption isotherm thermodynamically. Fitting the column experimental data to HYDRUS-1D resulted in a retardation factor of 3 in comparison to 5 calculated from batch tests at an initial Cr(VI) concentration of 3 mg/L. The results from this study showed that enhanced adsorption and retention of Cr(VI) may happen in soils derived from volcanic ash and tuff that contains significant amounts of zeolite with extensive Fe(III) coating.

  16. Negative impact of oxygen molecular activation on Cr(VI) removal with core–shell Fe@Fe2O3 nanowires

    International Nuclear Information System (INIS)

    Highlights: • The presence of oxygen inhibited Cr(VI) removal efficiency with nZVI by near 3 times. • Cr(VI) removal with nZVI was related to adsorption, reduction, co-precipitation, and adsorption reactions. • Molecular oxygen activation competed donor electrons from Fe0 core and surface bound Fe(II) of nZVI. • Thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell of nZVI leaded to the electron transfer inhibition. - Abstract: In this study, we demonstrate that the presence of oxygen molecule can inhibit Cr(VI) removal with core–shell Fe@Fe2O3 nanowires at neutral pH of 6.1. 100% of Cr(VI) removal was achieved by the Fe@Fe2O3 nanowires within 60 min in the anoxic condition, in contrast, only 81.2% of Cr(VI) was sequestrated in the oxic condition. Removal kinetics analysis indicated that the presence of oxygen could inhibit the Cr(VI) removal efficiency by near 3 times. XRD, SEM, and XPS analysis revealed that either the anoxic or oxic Cr(VI) removal was involved with adsorption, reduction, co-precipitation, and re-adsorption processes. More Cr(VI) was bound in a reduced state of Cr(III) in the anoxic process, while a thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell, leading to inhibiting the electron transfer, was found under the oxic process. The negative impact of oxygen molecule was attributed to the oxygen molecular activation which competed with Cr(VI) adsorbed for the consumption of donor electrons from Fe0 core and ferrous ions bound on the iron oxides surface under the oxic condition. This study sheds light on the understanding of the fate and transport of Cr(VI) in oxic and anoxic environment, as well provides helpful guide for optimizing Cr(VI) removal conditions in real applications

  17. ViHAP3D - Final report

    OpenAIRE

    Scopigno, Roberto

    2005-01-01

    Nearly all of our cultural heritage is inherently three-dimensional. Recent hard- and software developments enabled 3D computer graphics to be one of the most powerful means to represent complex data sets. The ViHAP3D project (ViHAP3D is an acronym for Virtual Heritage - High Quality 3D Acquisition and Presentation) aimed therefore at preserving, presenting, accessing, and promoting cultural heritage using interactive, high-quality 3D graphics. The vision of the project was to create an exact...

  18. EXAFS investigation on U(VI) immobilization in hardened cement paste. Influence of experimental conditions on speciation

    Energy Technology Data Exchange (ETDEWEB)

    Mace, N.; Wieland, E.; Daehn, R.; Tits, J. [Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Waste Management; Scheinost, A.C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology; Rossendorf Beamline (ROBL), Grenoble (France). ESRF

    2013-08-01

    Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the coordination environment of U(VI) in cementitious materials. The EXAFS measurements were carried out on U(VI)-doped samples prepared under varying conditions, such as samples from sorption, hydration and diffusion experiments, and using different cementitious materials, such as crushed hydrated hardened cement paste (HCP) and calcium silicate hydrates (C-S-H). The samples had U(VI) loadings ranging from 1700 {mu}g/g to 45000 {mu}g/g. Applying principal component analysis (PCA) on 13 EXAFS spectra (each spectra corresponding to a minimum of five different scans) of the low loading samples, one single species is obtained indicating a similar U(VI) coordination environment for both HCP and C-S-H samples. This result confirms that C-S-H phases control the uptake of U(VI) in the complex cement matrix. The coordination environment structure of this species is similar to a U(VI) surface complex or to U(VI) in uranyl silicate minerals (two axial O atoms at 1.82 {+-} 0.02 A; four equatorial O atoms at 2.25 {+-} 0.01 A; one Si atom at 3.10 {+-} 0.03 A). At high U(VI) loading, PCA revealed a second U(VI) species, with a coordination environment similar to that of U(VI) in calcium uranate (two axial O atoms at 1.94 {+-} 0.04 A; five equatorial O atoms at 2.26 {+-} 0.01 A; four Ca atoms at 3.69 {+-} 0.05 A and five U atoms at 3.85 {+-} 0.04 A). This study suggest that, at low U(VI) loading, U(VI) is bound to C-S-H phases in HCP while at high U(VI) loading, the immobilization of U(VI) in cementitious materials is mainly controlled by the precipitation of a calcium uranate-type phase. (orig.)

  19. Magnetic chitosan for removal of uranium (VI)

    International Nuclear Information System (INIS)

    The chitosan, an aminopolysaccharide formed for repeated units of D-glucosamine, is a deacetylation product of chitin. It presents favorable ionic properties acting as chelant, being considered a removing ionic of contaminants from water effluents. It has ample bioactivity, that is, is biocompatible, biodegradable, bioadhesive and biosorbent. The chitosan interacts for crosslinked by means of its active groups with other substances, can still coat superparamagnetic materials as magnetite nanoparticles producing one conjugated polymer-magnetite. Superparamagnetic materials are susceptible for the magnetic field, thus these particles can be attracted and grouped by a magnetic field and as they do not hold back the magnetization, they can be disagrouped and reused in processes for removal of contaminants from industrial effluents and waste water. The present work consisted of preparing coated magnetic magnetite particles with chitosan (PMQ). The PMQ powder has showed a magnetic response of intense attraction in the presence of a magnetic field without however becoming magnetic, a typical behavior of superparamagnetic material. It was characterized by Fourier transform infrared spectrometry and measurements of magnetization. Its performance of Uranium (VI) adsorption as uranyl species, U022+, was evaluated with regard to the influence of adsorbent dose, speed of agitation, pH, the contact time and had studied the isotherms of adsorption as well as the behavior of desorption using ions of carbonate and oxalate. The optimal pH to the best removal occurred in pH 5 and that the increase of the dose increases the removal, becoming constant above of 20 g.L-1. In the kinetic study the equilibrium was achieved after 20 minutes. The results of equilibrium isotherm agreed well with the Langmuir model, being the maximum adsorption capacity equal 41.7 mg.g-1. In the desorption studies were verified 94% of U022+ recovered with carbonate ion and 49.9% with oxalate ion. (author)

  20. An investigation of Cr(VI) removal with metallic iron in the co-presence of sand and/or MnO2.

    Science.gov (United States)

    Gheju, M; Balcu, I; Vancea, C

    2016-04-01

    This study focused on the influence of sand and/or MnO2 co-presence on the mechanism and kinetics of Cr(VI) removal with Fe(0). The process was investigated under acidic and well-mixed conditions, over the temperature range of 6-32 °C. It was shown that both mechanism and kinetics of the removal process were highly dependent on composition and dose of reactive mixture added to Cr(VI) solution. At 22 °C, indirect chemical reduction with Fe(II) was the main removal path in H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system removal of Cr(VI) occurred mainly via adsorption on MnO2. The pseudo zero-order kinetic model provided the best match for H2O-Fe(0)-Cr(VI) and H2O-Fe(0)-Sand-Cr(VI) system, while in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system the process fitted well to the pseudo second-order model. Temperature influenced the efficiency and kinetics of the process in all investigated systems, and the removal mechanism only in H2O-Fe(0)-MnO2-Cr(VI) and H2O-Fe(0)-MnO2-Sand-Cr(VI) system. PMID:26826456

  1. Structural, spectral analysis and DNA studies of heterocyclic thiosemicarbazone ligand and its Cr(III), Fe(III), Co(II) Hg(II), and U(VI) complexes

    Science.gov (United States)

    Yousef, T. A.; Abu El-Reash, G. M.; El Morshedy, R. M.

    2013-08-01

    The paper presents a combined experimental and computational study of novel Cr(III), Fe(III), Co(II), Hg(II) and U(VI) complexes of (E)-2-((3-hydroxynaphthalen-2-yl)methylene)-N-(pyridin-2-yl)hydrazinecarbothioamide (H2L). The ligand and its complexes have been characterized by elemental analyses, spectral (IR, UV-vis, 1H NMR and 13C NMR), magnetic and thermal studies. IR spectra show that H2L is coordinated to the metal ions in a mononegative bi or tri manner. The structures are suggested to be octahedral for all complexes except Hg(II) complex is tetrahedral. Theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, MM, Zindo/1, MM+ and PM3, methods. Satisfactory theoretical-experimental agreements were achieved by MM method for the ligand and PM3 for its complexes. DOS calculations carried out by MM (ADF) method for ligand Hg complex from which we concluded that the thiol form of the ligand is more active than thione form and this explains that the most complexation take place in that form. The calculated IR vibrations of the metal complexes, using the PM3 method was the nearest method for the experimental data, and it could be used for all complexes. Also, valuable information are obtained from calculation of molecular parameters for all compounds carried out by the previous methods of calculation (electronegativity of the coordination sites, net dipole moment of the metal complexes, values of heat of formation and binding energy) which approved that the complexes are more stable than ligand. The low value of ΔE could be expected to indicate H2L molecule has high inclination to bind with the metal ions. Furthermore, the kinetic and thermodynamic parameters for the different decomposition steps were calculated using the Coats-Redfern and Horowitz-Metzger methods. Finally, the biochemical studies showed that, complex 2, 4 have powerful and complete degradation effect on DNA. For the foremost majority of cases the

  2. Sorption mechanism of U(VI) on a reference montmorillonite. Binding to the internal and external surfaces

    International Nuclear Information System (INIS)

    Batch type experiments of U(VI) sorption on a reference montmorillonite (SWy-2) were carried out over wide ranges of pH, ionic strength, and total U(VI) concentration. The influences of these factors on the sorption behavior of U(VI) were analyzed to again a macroscopic understanding of the sorption mechanism. The sorption of U(VI) on montmorillonite showed a distinct dependency on ionic strength. When it was low (0.01 or 0.001M), almost all of the total U(VI) was sorbed over the whole pH range studied, therefore, the dependency on pH was not clear. But the sorption of U(VI) on montmorillonite showed a sorption pH edge in the high ionic strength condition (0.1M), like those on other clay minerals, kaolinite and chlorite. A mechanistic model was established by considering the mineral structure of montmorillonite together with our previous EPR result, which successfully explained the U(VI) sorption on montmorillonite over the whole range of experimental conditions. The model describes the U(VI) sorption on montmorillonite as simultaneous and competitive reactions of ion exchange and surface complexation, whose relative contribution to the total sorption depends on pH and ionic strength. At low ionic strength and low pH conditions, ion exchange was the dominant mechanism for U(VI) sorption on montmorillonite. At high ionic strength and high pH conditions, surface complexation was the dominant mechanism. At intermediate pH and ionic strength conditions, the two mechanisms contributed to the total U(VI) sorption to varying degrees. (author)

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

    International Nuclear Information System (INIS)

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

  4. Studies on new complexes of dioxo uranium(VI) and thorium(IV) with some schiff bases derived from trimethoprime salicyldehyde and o-vanillin (Paper No. AL-50)

    International Nuclear Information System (INIS)

    Dioxouranium(VI) and thorium(IV) form 1:1(Metal:Ligands) complexes with some schiff bases. The complexes have been characterized through elemental analyses, electronic and IR spectral, conductance and magnetic susceptibility measurements. They are considered dimeric or polymeric hexa or octa-coordinated arrangement around metal ion moiety. Force constants and U-O bond lengths have been calculated. (author). 1 tab

  5. Comparative studies on the extraction behaviour of U(VI), Am(III) and Nd(III) by OΦCMPO loaded Amberlite XAD-4 and XAD-7 resins

    International Nuclear Information System (INIS)

    This paper provides a comparison of the kinetics for the extraction of U(VI) and Am(III) from 3M HNO3 by Amberlite XAD-4 and XAD-7 resins loaded with octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide (OΦCMPO). The breakthrough capacities for the recovery of Nd(III) from 3M HNO3 by extraction chromatography using these CMPO loaded resins are also compared. (author)

  6. Det øvrige vi nyde

    DEFF Research Database (Denmark)

    Dam, Peder

    persiller, og at vi i dag kan kortlægge disse som egnsspecifikke persiller. Men den samlede størrelse af landgilden, angivet i fællesenheden tønder hartkorn, og de forskellige produkter, som landgilden blev ydet i, persillerne, var ikke en afspejling af produktionen, sådan som flere historikere har tolket...

  7. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

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

  8. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

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

  9. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

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

  10. 40 CFR Appendixes Vi-Vii to Part 600 - [Reserved

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false VI Appendixes VI-VII to Part 600 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Appendixes VI-VII to Part 600...

  11. Galsulfase (Naglazyme®) therapy in infants with mucopolysaccharidosis VI

    OpenAIRE

    Harmatz, Paul R.; Garcia, Paula; Guffon, Nathalie; Randolph, Linda M; Shediac, Renée; Braunlin, Elizabeth; Lachman, Ralph S.; Decker, Celeste

    2013-01-01

    Objective To evaluate the efficacy and safety of two dose levels of galsulfase (Naglazyme®) in infants with MPS VI. Study design This was a phase 4, multicenter, multinational, open-label, two-dose level study. Subjects were randomized 1:1 to receive weekly infusions of 1.0 or 2.0 mg/kg of galsulfase for a minimum of 52 weeks. Progression of skeletal dysplasia was determined by monitoring physical appearance, radiographic changes, and growth. Urinary glycosaminoglycan (GAG) levels, gross and ...

  12. ENDF-201, ENDF/B-VI summary documentation supplement 1, ENDF/HE-VI summary documentation

    International Nuclear Information System (INIS)

    The National Nuclear Data Center (NNDC) provides coordination for and serves as the secretariat to the Cross Section Evaluation Working Group (CSWEG). CSEWG is responsible for the oversight of the ENDF/B Evaluated Nuclear Data File. All data are checked and reviewed by CSEWG, and the file is maintained at the NNDC. For a description of the ENDF/B-VI file, see the ENDF-102 Data Formats and Procedures for the Evaluated Nuclear Data File ENDF-6. The purpose of this addendum to the ENDF/B-VI Summary Documentation is to provide documentation of Releases 1, 2, 3, and 4 for the ENDF/B-VI and ENDF/HE-VI evaluated nuclear data libraries. These releases contain many new and revised evaluations for the neutron, photo-atomic interaction, radioactive decay data, spontaneous fission product yield, neutron-induced fission product yield, thermal neutron scattering, proton, deuteron, and triton sublibraries. The summaries have been extracted mainly from the ENDF/B-VI File 1 comments (MT = 451), which have been checked, edited, and may also include supplementary information. Some summaries have been provided by the evaluators in electronic format, while others are extracted from reports on the evaluations. All references have been checked and corrected, or updated where appropriate. A list of the laboratories which have contributed evaluations used in ENDF/B-VI is given

  13. Valoração de contingente pelas modelagens logit e análise multivariada: um estudo de caso da disposição a aceitar compensação dos cafeicultores vinculados ao PRO-CAFÉ de Viçosa - MG Contingent valuation with modeling logit and multivariate analyses: a case study of the willingness of coffee planters linked to the PRO-COFFEE of Viçosa - MG to accept compensation

    Directory of Open Access Journals (Sweden)

    Pedro Silveira Máximo

    2009-12-01

    Full Text Available O objetivo deste estudo foi, justamente, identificar, entre os métodos LOGIT e a análise multivariada, qual a mais eficaz para estimar a Disposição a Aceitar Compensação (DAC dos cafeicultores quando o viés da utilidade marginal é passível de ocorrência. Para tal, foi elaborado um formulário com 33 perguntas envolvendo informações sobre características socioeconômicas dos cafeicultores, o uso da metodologia de valoração de contingente (MVC e do veículo de pagamento dos "Jogos de Lances", que revelou a Disposição a Aceitar uma Compensação (DAC na troca de um hectare de café por um hectare de mata. Como esperado, por causa do viés da utilidade marginal o método LOGIT foi incapaz de produzir resultados consistentes. Já a estimação da DAC pela análise multivariada mostrou que, caso o governo estivesse disposto a aumentar a provisão de mata em 70 ha, ele deveria despender 254.200 reais por ano, tratando apenas dos cafeicultores vinculados ao programa do PRO-CAFÉ.The object of this study was to identify which method, either LOGIT or multivariate analyses, was the most efficient to estimate the coffee planters' Willingness to Accept a Compensation, when there was a possibility of occurrence of marginal utility. For such, a questionnaire was formulated, with 33 questions involving information on coffee planters' socio - economic characteristics, the use of the methodology of contingent valuation (MCV, and the payment of the "offer game" that reveled the willingness to accept a compensation (WAC, by exchanging a hectare of coffee by a hectare of forest. As expected, because of the marginal utility's bias, the LOGIT method was unable to produce consistent results. However, when the WAC was estimated by multivariate analyses, the results showed that if the government is willing to increase the provision of forest to 70 hectares, it should pay out 254,200 reais (around 116,000 dollars, dealing only with the coffee planters

  14. Reactive oxygen species mediate Cr(VI)-induced carcinogenesis through PI3K/AKT-dependent activation of GSK-3β/β-catenin signaling

    Energy Technology Data Exchange (ETDEWEB)

    Son, Young-Ok; Pratheeshkumar, Poyil; Wang, Lei; Wang, Xin; Fan, Jia; Kim, Dong-Hern; Lee, Ju-Yeon; Zhang, Zhuo [Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305 (United States); Lee, Jeong-Chae [Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305 (United States); School of Dentistry and Institute of Oral Biosciences, Research Center of Bioactive Materials, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shi, Xianglin, E-mail: xshi5@email.uky.edu [Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305 (United States)

    2013-09-01

    Cr(VI) compounds are known human carcinogens that primarily target the lungs. Cr(VI) produces reactive oxygen species (ROS), but the exact effects of ROS on the signaling molecules involved in Cr(VI)-induced carcinogenesis have not been extensively studied. Chronic exposure of human bronchial epithelial cells to Cr(VI) at nanomolar concentrations (10–100 nM) for 3 months not only induced cell transformation, but also increased the potential of these cells to invade and migrate. Injection of Cr(VI)-stimulated cells into nude mice resulted in the formation of tumors. Chronic exposure to Cr(VI) increased levels of intracellular ROS and antiapoptotic proteins. Transfection with catalase or superoxide dismutase (SOD) prevented Cr(VI)-mediated increases in colony formation, cell invasion, migration, and xenograft tumors. While chronic Cr(VI) exposure led to activation of signaling cascades involving PI3K/AKT/GSK-3β/β-catenin and PI3K/AKT/mTOR, transfection with catalase or SOD markedly inhibited Cr(VI)-mediated activation of these signaling proteins. Inhibitors specific for AKT or β-catenin almost completely suppressed the Cr(VI)-mediated increase in total and active β-catenin proteins and colony formation. In particular, Cr(VI) suppressed autophagy of epithelial cells under nutrition deprivation. Furthermore, there was a marked induction of AKT, GSK-3β, β-catenin, mTOR, and carcinogenic markers in tumor tissues formed in mice after injection with Cr(VI)-stimulated cells. Collectively, our findings suggest that ROS is a key mediator of Cr(VI)-induced carcinogenesis through the activation of PI3K/AKT-dependent GSK-3β/β-catenin signaling and the promotion of cell survival mechanisms via the inhibition of apoptosis and autophagy. - Highlights: • Chronic exposure to Cr(VI) induces carcinogenic properties in BEAS-2B cells. • ROS play an important role in Cr(VI)-induced tumorigenicity of BEAS-2B cells. • PI3K/AKT/GSK-3β/β-catenin signaling involved in Cr(VI

  15. Reactive oxygen species mediate Cr(VI)-induced carcinogenesis through PI3K/AKT-dependent activation of GSK-3β/β-catenin signaling

    International Nuclear Information System (INIS)

    Cr(VI) compounds are known human carcinogens that primarily target the lungs. Cr(VI) produces reactive oxygen species (ROS), but the exact effects of ROS on the signaling molecules involved in Cr(VI)-induced carcinogenesis have not been extensively studied. Chronic exposure of human bronchial epithelial cells to Cr(VI) at nanomolar concentrations (10–100 nM) for 3 months not only induced cell transformation, but also increased the potential of these cells to invade and migrate. Injection of Cr(VI)-stimulated cells into nude mice resulted in the formation of tumors. Chronic exposure to Cr(VI) increased levels of intracellular ROS and antiapoptotic proteins. Transfection with catalase or superoxide dismutase (SOD) prevented Cr(VI)-mediated increases in colony formation, cell invasion, migration, and xenograft tumors. While chronic Cr(VI) exposure led to activation of signaling cascades involving PI3K/AKT/GSK-3β/β-catenin and PI3K/AKT/mTOR, transfection with catalase or SOD markedly inhibited Cr(VI)-mediated activation of these signaling proteins. Inhibitors specific for AKT or β-catenin almost completely suppressed the Cr(VI)-mediated increase in total and active β-catenin proteins and colony formation. In particular, Cr(VI) suppressed autophagy of epithelial cells under nutrition deprivation. Furthermore, there was a marked induction of AKT, GSK-3β, β-catenin, mTOR, and carcinogenic markers in tumor tissues formed in mice after injection with Cr(VI)-stimulated cells. Collectively, our findings suggest that ROS is a key mediator of Cr(VI)-induced carcinogenesis through the activation of PI3K/AKT-dependent GSK-3β/β-catenin signaling and the promotion of cell survival mechanisms via the inhibition of apoptosis and autophagy. - Highlights: • Chronic exposure to Cr(VI) induces carcinogenic properties in BEAS-2B cells. • ROS play an important role in Cr(VI)-induced tumorigenicity of BEAS-2B cells. • PI3K/AKT/GSK-3β/β-catenin signaling involved in Cr(VI

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-15

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

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

    International Nuclear Information System (INIS)

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

  18. A contribution to the study of the extraction of mineral acids and of actinide (IV) and (VI) cations by N,N-dialkylamides; Contribution a l'etude de l'extraction d'acides mineraux et de cations actinides aux degres d'oxydation (IV) et (VI) par des N,N-dialkylamides

    Energy Technology Data Exchange (ETDEWEB)

    Condamines, N.

    1990-03-15

    N,N-dialkylamides are alternate extractants to tributylphosphate, TBP, for the actinides separation in nuclear fuel reprocessing. N,N-di (2-ethyl hexyl) butyramide and N,N-di (2 ethyl hexyl) isobutyramide are selected for their sufficient extraction and partition ability towards actinides (IV) and (VI) without coextracting fission products. Mechanisms of HNO{sub 3}, UO{sub 2}{sup 2+}, Pu{sup 4+}, Th{sup 4+} are investigated. Nitric acid extraction is due to the competitive formation of the species (HNO{sub 3})L{sub 2}, (HNO{sub 3})L, (HNO{sub 3}){sub 2}L (L: DOBA or DOiBA). An hydrogen bond is the driving force of the transfer. For low acidity media, amides are neutral extractants. Physical interactions, between free ligand and metallic complex, arise for high amide concentrations. Taking into account the non-ideality of the organic medium by a hard spheres mixture model, we estimate that such interactions are far from negligible and very specific to the amide group. Unlike TBP, when increasing acidity, amides behave as anionic extractants. DOBA and DOiBA appear to be satisfactory extractants for fuel reprocessing.

  19. Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xiaoling [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Ma, Lena Q., E-mail: lqma@ufl.edu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046 (China); Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Gress, Julia; Harris, Willie [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314 (United States)

    2014-02-01

    Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L{sup −1} enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO{sub 2}. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.

  20. Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L−1 enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO2. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions

  1. Reactive oxygen species mediate Cr(VI)-induced carcinogenesis through PI3K/AKT-dependent activation of GSK-3 β/β-catenin signaling

    OpenAIRE

    Son, Young-Ok; Pratheeshkumar, Poyil; Lei, Wang; Wang, Xin; Kim, Dong-Hern; Lee, Ju-Yeon; Zhang, Zhuo; Lee, Jeong-Chae; Shi, Xianglin

    2013-01-01

    Cr(VI) compounds are known human carcinogens that primarily target the lungs. Cr(VI) produces reactive oxygen species (ROS), but the exact effects of ROS on the signaling molecules involved in Cr(VI)-induced carcinogenesis have not been extensively studied. Chronic exposure of human bronchial epithelial cells to Cr(VI) at nanomolar concentrations (10 - 100 nM) for 3 months not only induced cell transformation, but also increased the potential of these cells to invade and migrate. Injection of...

  2. Pericellular colocalisation and interactive properties of type VI collagen and perlecan in the intervertebral disc.

    Science.gov (United States)

    Hayes, A J; Shu, C C; Lord, M S; Little, C B; Whitelock, J M; Melrose, J

    2016-01-01

    The aim of this study was to immunolocalise type VI collagen and perlecan and determine their interactive properties in the intervertebral disc (IVD). Confocal laser scanning microscopy co-localised perlecan with type VI collagen as pericellular components of IVD cells and translamellar cross-bridges in ovine and murine IVDs. These cross-bridges were significantly less abundant in the heparin sulphate deficient Hspg2 exon 3 null mouse IVD than in wild type. This association of type VI collagen with elastic components provides clues as to its roles in conveying elastic recoil properties to annular tissues. Perlecan and type VI collagen were highly interactive in plasmon resonance studies. Pericellular colocalisation of perlecan and type VI collagen provides matrix stabilisation and cell-matrix communication which allows IVD cells to perceive and respond to perturbations in their biomechanical microenvironment. Perlecan, at the cell surface, provides an adhesive interface between the cell and its surrounding extracellular matrix. Elastic microfibrillar structures regulate tensional connective tissue development and function. The 2010 Global Burden of Disease study examined 291 disorders and identified disc degeneration and associated low back pain as the leading global musculoskeletal disorder emphasising its massive socioeconomic impact and the need for more effective treatment strategies. A greater understanding of how the IVD achieves its unique biomechanical functional properties is of great importance in the development of such therapeutic measures. PMID:27377666

  3. Lack of collagen VI promotes neurodegeneration by impairing autophagy and inducing apoptosis during aging.

    Science.gov (United States)

    Cescon, Matilde; Chen, Peiwen; Castagnaro, Silvia; Gregorio, Ilaria; Bonaldo, Paolo

    2016-05-01

    Collagen VI is an extracellular matrix (ECM) protein with a broad distribution in different tissues and mostly deposited at the close periphery of the cell surface. Previous studies revealed that collagen VI protects neurons from the toxicity of amyloid-βpeptides and from UV-induced damage. However, the physiological role of this protein in the central nervous system (CNS) remains unknown. Here, we established primary neural cultures from murine cortex and hippocampus, and carried out in vitro and in vivo studies in wild-type and collagen VI null (Col6a1-/-) mice. Col6a1-/- neural cultures displayed an increased incidence of spontaneous apoptosis and higher vulnerability to oxidative stress, accompanied by altered regulation of autophagy with increased p62 protein levels and decreased LC3 lipidation. Analysis of brain sections confirmed increased apoptosis and abnormal regulation of autophagy in the CNS of collagen VI-deficient animals. To investigate the in vivo physiological consequences of these CNS defects, we carried out functional studies and found that motor and memory task performances were impaired in aged Col6a1-/-mice. These findings indicate that lack of collagen VI leads to spontaneous apoptosis and defective autophagy in neural cells, and point at a protective role for this ECM protein in the CNS during physiological aging. PMID:27060109

  4. Extractive behavior of U(VI) in the paraffin soluble ionic liquid

    International Nuclear Information System (INIS)

    An Aliquat-336 based ionic liquid namely, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ((A3636)+(DEHP)-) was prepared and studied for the extraction of U(VI) from nitric acid medium. Since the ionic liquid, (A336)+(DEHP)-, was miscible in n-dodecane (n-DD), the extraction of U(VI) in the solution of tri-n-butylphosphate (TBP) in n-DD, was investigated in the presence of small concentrations of ionic liquid. The distribution ratio of U(VI) in 0.3 M (A336)+(DEHP)-/n-DD decreased with increase in the concentration of nitric acid. The effect of concentration of TBP, ionic liquid nitric acid and nitrate ion on the extraction of U(VI) in ionic liquid medium was studied. The mechanistic aspect of extraction was investigated by the slope analysis of the extraction data. The studies indicated the feasibility of modifying the extractive properties of U(VI) in TBP/n-DD using ionic liquid. (author)

  5. Collagens VI and XII form complexes mediating osteoblast interactions during osteogenesis.

    Science.gov (United States)

    Izu, Yayoi; Ezura, Yoichi; Koch, Manuel; Birk, David E; Noda, Masaki

    2016-06-01

    Bone formation is precisely regulated by cell-cell communication in osteoblasts. We have previously demonstrated that genetic deletion of Col6a1 or Col12a1 impairs osteoblast connections and/or communication in mice, resulting in bone mass reduction and bone fragility. Mutations of the genes encoding collagen VI cause Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM), which have overlapping phenotypes involving connective tissue and muscle. Recent studies have identified COL12A1 gene mutations in patients with UCMD- and BM-like disorders harboring no COL6 mutations, indicating the shared functions of these collagens in connective tissue homeostasis. The purpose of this investigation has been to test the hypothesis that collagens VI and XII have coordinate regulatory role(s) during bone formation. We analyzed the localization of collagens VI and XII relative to primary osteoblasts during osteogenesis. Immunofluorescence analysis demonstrated that collagens VI and XII colocalized in matrix bridges between adjacent cells during periods when osteoblasts were establishing cell-cell connections. Quantification of cells harboring collagen bridges demonstrated that matrix bridges were composed of collagens VI and XII but not collagen I. Interestingly, matrix bridge formation was impaired in osteoblasts deficient in either Col6a1 or Col12a1, suggesting that both collagens were indispensable for matrix bridge formation. These data demonstrate, for the first time, a functional relationship between collagens VI and XII during osteogenesis and indicate that a complex containing collagens VI and XII is essential for the formation of a communicating cellular network during bone formation. PMID:26753503

  6. Extraction and transport of uranium (VI) by polymer inclusion membranes incorporating Di-(2-ethylhexyl) phosphoric acid

    International Nuclear Information System (INIS)

    Di-(2-ethylhexyl) phosphoric acid (D2EHPA) is a commonly used extraction reagent for the separation of uranium from aqueous solutions. Previous work showed the suitability of a polymer inclusion membrane (PIM) based on D2EHPA and poly(vinyl chloride) (PVC) for the extraction and transport of uranium (VI) from sulfate solutions. This study investigates the influence of the main system parameters (i.e. stirring rate, percentage of D2EHPA in the membrane, initial U(VI) concentration, membrane thickness, and concentration of sulfuric acid) on the extraction process. A comprehensive mathematical model, describing the extraction of U(VI), was developed, numerically solved and fitted to the experimental extraction data to determine the values of the extraction constant and the diffusion coefficient of the U(VI)-D2EHPA complex in the membrane. The transport properties of the PVC/D2EHPA PIM have been further improved by adding o-nitrophenyloctyl ether as plasticizer. Fluxes of U(VI) as high as 1.5 x 10-6 mol m-2 S-1 were recorded using a membrane composed of 35% D2EHPA, 10% o-nitrophenyloctyl ether and 55% PVC (m/m) from a solution containing 100 mg L-1 U(VI) in 0.1 mol L-1 H2SO4 into a solution containing 6 mol L-1H2SO4. The effect of the counter-ion on the extraction and back extraction of uranium was also investigated and the membranes were tested for durability over repeated cycles of extraction and back-extraction. It was demonstrated that a 45% D2EHPA and 55% PVC PIM (m/m) allowed U(VI) to be completely separated thermodynamically from a range of common metal cations and kinetically from iron (III). (author)

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

    OpenAIRE

    Sugiyama, M

    1991-01-01

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

  8. Synthesis and characterization of dioxouranium (VI) complexes of Schiff bases derived from isatin, isovanillin and o-vanillin

    International Nuclear Information System (INIS)

    Three Schiff bases viz. isatin semicarbazone, isovanillin thiosemicarbazone, o-vanillin para-anisidine and their dioxouranium (VI) complexes have been synthesised and characterized by elemental analysis, IR and NMR spectral studies. (author). 19 refs., 1 tab

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

    Directory of Open Access Journals (Sweden)

    Abdulsalam A. Shyaa

    2015-01-01

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

  10. Extraction of U(VI) and Th(IV) in nitric acid medium with N,N,N',N'-tetrahexylsuccinylamide

    International Nuclear Information System (INIS)

    The extraction mechanisms of U(VI) and Th(IV) in nitric acid solutions with N,N,N',N'-tetrahexylsuccinylamide (THSA) were described. The effects of nitric acid concentration, THSA concentration and temperature on the distribution coefficients of U(VI) and Th(IV), and the back extraction behaviours of U(VI) and Th(IV) from organic phase were studied. The compositions of the complex are found to be UO2(NO3)2·THSA and Th(NO3)4·2THSA. The equilibrium constants and thermodynamical functions of the extraction reactions have been calculated

  11. Biosorption characteristics of uranium(VI) from aqueous solution by pummelo peel

    International Nuclear Information System (INIS)

    The biomass pummelo peel was chosen as a biosorbent for removal of uranium(VI) from aqueous solution. The feasibility of adsorption of U(VI) by Pummelo peel was studied with batch adsorption experiments. The effects of contact time, biosorbent dosage and pH on adsorption capacity were investigated in detail. The pummelo peel exhibited the highest U(VI) sorption capacity 270.71 mg/g at an initial pH of 5.5, concentration of 50 μg/mL, temperature 303 K and contacting time 7 h. The adsorption process of U(VI) was found to follow the pseudo-second-order kinetic equation. The adsorption isotherm study indicated that it followed both the Langmuir adsorption isotherm and the Freundlich adsorption isotherm. The thermodynamic parameters values calculated clearly indicated that the adsorption process was feasible, spontaneous and endothermic in nature. These properties show that the pummelo peel has potential application in the removal of the uranium(VI) from the radioactive waste water. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-04-15

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

  13. Surface complexation modeling of Cr(VI) adsorption at the goethite-water interface.

    Science.gov (United States)

    Xie, Jinyu; Gu, Xueyuan; Tong, Fei; Zhao, Yanping; Tan, Yinyue

    2015-10-01

    In this study, a charge distribution multisite surface complexation model (CD-MUSIC) for adsorption of chromate onto goethite was carefully developed. The adsorption of Cr(VI) on goethite was firstly investigated as a function of pH, ionic strength and Cr(VI) concentration. Results showed that an inner-sphere complexation mechanism was involved because the retention of Cr(VI) was little influenced by ionic strength. Then two surface species: a bidentate complex (≡Fe2O2CrOOH) and a monodentate complex (≡FeOCrO3(-3/2)), which is constrained by prior spectroscopic evidence were proposed to fit the macroscopic adsorption data. Modeling results showed that the bidentate complex was found to be the dominant species at low pH, whereas, with increasing pH, monodentate species became more pronounced. The model was then verified by prediction of competitive adsorption of chromate and phosphate at various ratios and ionic strengths. The model successfully predicted the inhibition of chromate with the presence of phosphate, suggesting phosphate has higher affinity to goethite surface than Cr(VI). Results showed that the model developed in this study for Cr(VI) onto goethite was applicable for various conditions. It is a useful supplement for the surface complexation model database for oxyanions onto goethite surfaces. PMID:26057103

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

    International Nuclear Information System (INIS)

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

  15. Extraction of Mo(VI) and U(VI) by alamine 310 and its mixtures from aq. HCl media

    International Nuclear Information System (INIS)

    Extractions of Mo(VI) and U(VI) by Alamine 310, TBP, DPSO and their mixtures are quantitative in the range 6-8 M, and by Cyanex 301 and its mixtures at lower acidity (∼0.2 M). Quantitative extraction of U(VI) is achieved by mixtures of Alamine 310 and TBP from 1 M HCl in presence of SCN- ion (∼0.2 M). Synergism is marked in the extraction of Mo(VI) by the mixtures of Alamine 310 and TBP/Cyanex 301, and for U(VI) by mixtures of Alamine 310 and DPSO/Cyanex 301. (author). 9 refs

  16. TREATMENT TESTS FOR EX SITU REMOVAL OF CHROMATE & NITRATE & URANIUM (VI) FROM HANFORD (100-HR-3) GROUNDWATER FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    BECK MA; DUNCAN JB

    1994-01-03

    This report describes batch and ion exchange column laboratory scale studies investigating ex situ methods to remove chromate (chromium [VI]), nitrate (NO{sub 3}{sup -}) and uranium (present as uranium [VI]) from contaminated Hanford site groundwaters. The technologies investigated include: chemical precipitation or coprecipitation to remove chromate and uranium; and anion exchange to remove chromate, uranium and nitrate. The technologies investigated were specified in the 100-HR-3 Groundwater Treatability Test Plan. The method suggested for future study is anion exchange.

  17. A novel method for amino starch preparation and its adsorption for Cu(II) and Cr(VI)

    International Nuclear Information System (INIS)

    A novel method was proposed to prepare amino starch by reacting ethylenediamine with previously synthesized dialdehyde starch. Different factors affecting the preparation, i.e., ethylenediamine concentration, ethylenediamine:dialdehyde starch molar ratio, pH, duration and temperature have been studied. The modified starch was characterized by IR spectroscopy, elemental analysis, X-ray diffraction and differential scanning calorimetry. The amino starch derivatives were evaluated as adsorbents. The adsorption activity for heavy metals such as Cu(II) and Cr(VI) by crosslinked amino starch was studied in terms of adsorption amount, kinetics and isotherm; and adsorbent reuse were also studied. Adsorption processes for Cu(II) and Cr(VI) on crosslinked amino starch fit a Langmuir isotherm, and adsorption for Cu(II) and Cr(VI) from aqueous solution was endothermic reactions. Crosslinked amino starch was very effective for the adsorption of Cu(II) and Cr(VI), and efficient in capacity, recycled.

  18. Diagnostic and treatment strategies in mucopolysaccharidosis VI

    Science.gov (United States)

    Vairo, Filippo; Federhen, Andressa; Baldo, Guilherme; Riegel, Mariluce; Burin, Maira; Leistner-Segal, Sandra; Giugliani, Roberto

    2015-01-01

    Mucopolysaccharidosis VI (MPS VI) is a very rare autosomal recessive disorder caused by mutations in the ARSB gene, which lead to deficient activity of the lysosomal enzyme ASB. This enzyme is important for the breakdown of the glycosaminoglycans (GAGs) dermatan sulfate and chondroitin sulfate, which accumulate in body tissues and organs of MPS VI patients. The storage of GAGs (especially dermatan sulfate) causes bone dysplasia, joint restriction, organomegaly, heart disease, and corneal clouding, among several other problems, and reduced life span. Despite the fact that most cases are severe, there is a spectrum of severity and some cases are so attenuated that diagnosis is made late in life. Although the analysis of urinary GAGs and/or the measurement of enzyme activity in dried blood spots are useful screening methods, the diagnosis is based in the demonstration of the enzyme deficiency in leucocytes or fibroblasts, and/or in the identification of pathogenic mutations in the ARSB gene. Specific treatment with enzyme replacement has been available since 2005. It is safe and effective, bringing measurable benefits and increased survival to patients. As several evidences indicate that early initiation of therapy may lead to a better outcome, newborn screening is being considered for this condition, and it is already in place in selected areas where the incidence of MPS VI is increased. However, as enzyme replacement therapy is not curative, associated therapies should be considered, and research on innovative therapies continues. The management of affected patients by a multidisciplinary team with experience in MPS diseases is highly recommended. PMID:26586959

  19. Diagnostic and treatment strategies in mucopolysaccharidosis VI.

    Science.gov (United States)

    Vairo, Filippo; Federhen, Andressa; Baldo, Guilherme; Riegel, Mariluce; Burin, Maira; Leistner-Segal, Sandra; Giugliani, Roberto

    2015-01-01

    Mucopolysaccharidosis VI (MPS VI) is a very rare autosomal recessive disorder caused by mutations in the ARSB gene, which lead to deficient activity of the lysosomal enzyme ASB. This enzyme is important for the breakdown of the glycosaminoglycans (GAGs) dermatan sulfate and chondroitin sulfate, which accumulate in body tissues and organs of MPS VI patients. The storage of GAGs (especially dermatan sulfate) causes bone dysplasia, joint restriction, organomegaly, heart disease, and corneal clouding, among several other problems, and reduced life span. Despite the fact that most cases are severe, there is a spectrum of severity and some cases are so attenuated that diagnosis is made late in life. Although the analysis of urinary GAGs and/or the measurement of enzyme activity in dried blood spots are useful screening methods, the diagnosis is based in the demonstration of the enzyme deficiency in leucocytes or fibroblasts, and/or in the identification of pathogenic mutations in the ARSB gene. Specific treatment with enzyme replacement has been available since 2005. It is safe and effective, bringing measurable benefits and increased survival to patients. As several evidences indicate that early initiation of therapy may lead to a better outcome, newborn screening is being considered for this condition, and it is already in place in selected areas where the incidence of MPS VI is increased. However, as enzyme replacement therapy is not curative, associated therapies should be considered, and research on innovative therapies continues. The management of affected patients by a multidisciplinary team with experience in MPS diseases is highly recommended. PMID:26586959

  20. Nanomaterials based on II-VI Semiconductors

    OpenAIRE

    Cozzarini, Luca

    2012-01-01

    This thesis describes: (i) synthesis and characterization of colloidal nanocrystals of II-VI semiconductor compounds; (II) development of two novel materials using such nanocrystals as “building blocks”: (IIa) a nanocrystals/polymer composite, to be used as phosphor in LED-based lighting devices; (IIb) an inorganic, nano-structured multiphase material, showing a promising geometry as an electronic intermediate band material. Different typologies of nanocrystals (single-phase, alloyed or ...