Calculational assessment of critical experiments with mixed-oxide fuel pin arrays moderated by organic solution

International Nuclear Information System (INIS)

Smolen, G.R.; Funabashi, H.

1987-01-01

Critical experiments have been conducted with organically moderated mixed-oxide (MOX) fuel pin assemblies at the Pacific Northwest Lab. Critical Mass Lab. These experiments are part of a joint exchange program between the US Dept. of Energy and the Power Reactor and Nuclear Fuel Development Corp. of Japan in the area of criticality data development. The purpose of these experiments is to benchmark computer codes and cross-section libraries and to assess the reactivity difference between systems moderated by water and those moderated by an organic solution. Past studies have indicated that some organic mixtures may be better moderators than water. This topic is of particular importance to the criticality safety of fuel processing plants where fissile material is dissolved in organic solutions during the solvent extraction process. In the past, it has been assumed that the codes and libraries benchmarked with water-moderated experiments were adequate when performing design and licensing studies of organically moderated systems. Calculations presented in this paper indicated that the Scale code system and the 27-energy-group cross-section library accurately compute k/sub eff/ for organically moderated MOX fuel pin assemblies. Furthermore, the reactivity of an organic solution with a 32 vol % TBP/68 vol% NPH mixture in a heterogeneous configuration is the same, for practical purposes, as water

Calculational assessment of critical experiments with mixed oxide fuel pin arrays moderated by organic solution

International Nuclear Information System (INIS)

Smolen, G.R.

1987-01-01

Critical experiments have been conducted with organic-moderated mixed oxide (MOX) fuel pin assemblies at the Pacific Northwest Laboratory (PNL) Critical Mass Laboratory (CML). These experiments are part of a joint exchange program between the United States Department of Energy (USDOE) and the Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan in the area of criticality data development. The purpose of these experiments is to benchmark computer codes and cross-section libraries and to assess the reactivity difference between systems moderated by water and those moderated by an organic solution. Past studies have indicated that some organic mixtures may be better moderators than water. This topic is of particular importance to the criticality safety of fuel processing plants where fissile material is dissolved in organic solutions during the solvent extraction process. In the past, it has been assumed that the codes and libraries benchmarked with water-moderated experiments were adequate when performing design and licensing studies of organic-moderated systems. Calculations presented in this paper indicated that the SCALE code system and the 27-energy-group cross-section accurately compute k-effectives for organic moderated MOX fuel-pin assemblies. Furthermore, the reactivity of an organic solution with a 32-vol-% TBP/68-vol-% NPH mixture in a heterogeneous configuration is the same, for practical purposes, as water. 5 refs

Method of producing deuterium-oxide-enriched water

International Nuclear Information System (INIS)

Mandel, H.

1976-01-01

A method and apparatus for producing deuterium-oxide-enriched water (e.g., as a source of deuterium-rich gas mixtures) are disclosed wherein the multiplicity of individual cooling cycles of a power plant are connected in replenishment cascade so that fresh feed water with a naturally occurring level of deuterium oxide is supplied to replace the vaporization losses, sludge losses and withdrawn portion of water in a first cooling cycle, the withdrawn water being fed as the feed water to the subsequent cooling cycle or stage and serving as the sole feed-water input to the latter. At the end of the replenishment-cascade system, the withdrawn water has a high concentration of deuterium oxide and may serve as a source of water for the production of heavy water or deuterium-enriched gas by conventional methods of removing deuterium oxide or deuterium from the deuterium-oxide-enriched water. Each cooling cycle may form part of a thermal or nuclear power plant in which a turbine is driven by part of the energy and air-cooling of the water takes place in the atmosphere, e.g., in a cooling tower

Hot water extraction with in situ wet oxidation: Kinetics of PAHs removal from soil

International Nuclear Information System (INIS)

Dadkhah, Ali A.; Akgerman, Aydin

2006-01-01

Finding environmentally friendly and cost-effective methods to remediate soils contaminated with polycyclic aromatic hydrocarbons (PAHs) is currently a major concern of researchers. In this study, a series of small-scale semi-continuous extractions - with and without in situ wet oxidation - were performed on soils polluted with PAHs, using subcritical water (i.e. liquid water at high temperatures and pressures, but below the critical point) as the removal agent. Experiments were performed in a 300 mL reactor using an aged soil sample. To find the desorption isotherms and oxidation reaction rates, semi-continuous experiments with residence times of 1 and 2 h were performed using aged soil at 250 deg. C and hydrogen peroxide as oxidizing agent. In all combined extraction and oxidation flow experiments, PAHs in the remaining soil after the experiments were almost undetectable. In combined extraction and oxidation no PAHs could be detected in the liquid phase after the first 30 min of the experiments. Based on these results, extraction with hot water, if combined with oxidation, should reduce the cost of remediation and can be used as a feasible alternative technique for remediating contaminated soils and sediments

An engineered polypeptide around nano-sized manganese-calcium oxide: copying plants for water oxidation.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Ghobadi, Mohadeseh Zarei; Sarvi, Bahram; Haghighi, Behzad

2015-09-14

Synthesis of new efficient catalysts inspired by Nature is a key goal in the production of clean fuel. Different compounds based on manganese oxide have been investigated in order to find their water-oxidation activity. Herein, we introduce a novel engineered polypeptide containing tyrosine around nano-sized manganese-calcium oxide, which was shown to be a highly active catalyst toward water oxidation at low overpotential (240 mV), with high turnover frequency of 1.5 × 10(-2) s(-1) at pH = 6.3 in the Mn(III)/Mn(IV) oxidation range. The compound is a novel structural and efficient functional model for the water-oxidizing complex in Photosystem II. A new proposed clever strategy used by Nature in water oxidation is also discussed. The new model of the water-oxidizing complex opens a new perspective for synthesis of efficient water-oxidation catalysts.

On the Design of Oxide Films, Nanomaterials, and Heterostructures for Solar Water Oxidation Photoanodes

Science.gov (United States)

Kronawitter, Coleman Xaver

Photoelectrochemistry and its associated technologies show unique potential to facilitate the large-scale production of solar fuels—those energy-rich chemicals obtained through conversion processes driven by solar energy, mimicking the photosynthetic process of green plants. The critical component of photoelectrochemical devices designed for this purpose is the semiconductor photoelectrode, which must be optically absorptive, chemically stable, and possess the required electronic band alignment with respect to the redox couple of the electrolyte to drive the relevant electrochemical reactions. After many decades of investigation, the primary technological obstacle remains the development of photoelectrode structures capable of efficient and stable conversion of light with visible frequencies, which is abundant in the solar spectrum. Metal oxides represent one of the few material classes that can be made photoactive and remain stable to perform the required functions. The unique range of functional properties of oxides, and especially the oxides of transition metals, relates to their associated diversity of cation oxidation states, cation electronic configurations, and crystal structures. In this dissertation, the use of metal oxide films, nanomaterials, and heterostructures in photoelectrodes enabling the solar-driven oxidation of water and generation of hydrogen fuel is examined. A range of transition- and post-transition-metal oxide material systems and nanoscale architectures is presented. The first chapters present results related to electrodes based on alpha-phase iron(III) oxide, a promising visible-light-active material widely investigated for this application. Studies of porous films fabricated by physical vapor deposition reveal the importance of structural quality, as determined by the deposition substrate temperature, on photoelectrochemical performance. Heterostructures with nanoscale feature dimensionality are explored and reviewed in a later chapter

POST CRITICAL HEAT TRANSFER AND FUEL CLADDING OXIDATION

Directory of Open Access Journals (Sweden)

Vojtěch Caha

2016-12-01

Full Text Available The knowledge of heat transfer coefficient in the post critical heat flux region in nuclear reactor safety is very important. Although the nuclear reactors normally operate at conditions where critical heat flux (CHF is not reached, accidents where dryout occur are possible. Most serious postulated accidents are a loss of coolant accident or reactivity initiated accident which can lead to CHF or post CHF conditions and possible disruption of core integrity. Moreover, this is also influenced by an oxide layer on the cladding surface. The paper deals with the study of mathematical models and correlations used for heat transfer calculation, especially in post dryout region, and fuel cladding oxidation kinetics of currently operated nuclear reactors. The study is focused on increasing of accuracy and reliability of safety limit calculations (e.g. DNBR or fuel cladding temperature. The paper presents coupled code which was developed for the solution of forced convection flow in heated channel and oxidation of fuel cladding. The code is capable of calculating temperature distribution in the coolant, cladding and fuel and also the thickness of an oxide layer.

Super critical water reactors

International Nuclear Information System (INIS)

Dumaz, P.; Antoni, O; Arnoux, P.; Bergeron, A; Renault, C.; Rimpault, G.

2005-01-01

Water is used as a calori-porter and moderator in the most major nuclear centers which are actually in function. In the pressurized water reactor (PWR) and boiling water reactor (BWR), water is maintained under critical point of water (21 bar, 374 Centigrade) which limits the efficiency of thermodynamic cycle of energy conversion (yield gain of about 33%) Crossing the critical point, one can then use s upercritical water , the obtained pressure and temperature allow a significant yield gains. In addition, the supercritical water offers important properties. Particularly there is no more possible coexistence between vapor and liquid. Therefore, we don't have more boiling problem, one of the phenomena which limits the specific power of PWR and BWR. Since 1950s, the reactor of supercritical water was the subject of studies more or less detailed but neglected. From the early 1990s, this type of conception benefits of some additional interests. Therefore, in the international term G eneration IV , the supercritical water reactors had been considered as one of the big options for study as Generation IV reactors. In the CEA, an active city has engaged from 1930 with the participation to a European program: The HPWR (High Performance Light Water Reactor). In this contest, the R and D studies are focused on the fields of neutrons, thermodynamic and materials. The CEA intends to pursue a limited effort of R and D in this field, in the framework of international cooperation, preferring the study of versions of rapid spectrum. (author)

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.

2014-11-05

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system p-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts.

Formation of ZnO at zinc oxidation by near- and supercritical water under the constant electric field

Science.gov (United States)

Shishkin, A. V.; Sokol, M. Ya.; Shatrova, A. V.; Fedyaeva, O. N.; Vostrikov, A. A.

2014-12-01

The work has detected an influence of a constant electric field (up to E = 300 kV/m) on the structure of a nanocrystalline layer of zinc oxide, formed on the surface of a planar zinc anode in water under supercritical (673 K and 23 MPa) and near-critical (673 K and 17. 5 MPa) conditions. The effect of an increase of zinc oxidation rate with an increase in E is observed under supercritical conditions and is absent at near-critical ones. Increase in the field strength leads to the formation of a looser structure in the inner part of the zinc oxide layer.

Steam oxidation of 9-12%Cr steels. Critical evaluation and implications for practical application

Energy Technology Data Exchange (ETDEWEB)

Zurek, J.; Quadakkers, W.J. [Forschungszentrum Juelich GmbH (DE). Inst. fuer Energieforschung (IEF); Bruycker, E. de; Huysmans, S. [Laborelec, Linkebeek (Belgium)

2010-07-01

In new and future generation Power Plants, creep resistant steels selected for high-temperature components are subjected to a large variety of service environments. In many of these applications, water vapor has been found to substantially alter the technologically relevant properties mainly growth rate and adherence, of the surface oxides. Various data sets exist in the literature for steam oxidation for this type of steels, however these data show a substantial deviation. These differences can be related to e.g. ''batch to batch'' variation, oxidation conditions, surface treatment, difference between laboratory/power plants data, etc. Therefore these literature data need careful and critical verification when being used to estimate the long term materials behaviour in real power generation plants. The paper discusses the existing steam oxidation data for a number of selected steels, i.e. P91, P92 and VM12, thereby putting main emphasis on discussing the parameters which are responsible for observed variations in oxidation rates for the various types of materials. (orig.)

Atomic origins of water-vapour-promoted alloy oxidation.

Science.gov (United States)

Luo, Langli; Su, Mao; Yan, Pengfei; Zou, Lianfeng; Schreiber, Daniel K; Baer, Donald R; Zhu, Zihua; Zhou, Guangwen; Wang, Yanting; Bruemmer, Stephen M; Xu, Zhijie; Wang, Chongmin

2018-05-07

The presence of water vapour, intentional or unavoidable, is crucial to many materials applications, such as in steam generators, turbine engines, fuel cells, catalysts and corrosion 1-4 . Phenomenologically, water vapour has been noted to accelerate oxidation of metals and alloys 5,6 . However, the atomistic mechanisms behind such oxidation remain elusive. Through direct in situ atomic-scale transmission electron microscopy observations and density functional theory calculations, we reveal that water-vapour-enhanced oxidation of a nickel-chromium alloy is associated with proton-dissolution-promoted formation, migration, and clustering of both cation and anion vacancies. Protons derived from water dissociation can occupy interstitial positions in the oxide lattice, consequently lowering vacancy formation energy and decreasing the diffusion barrier of both cations and anions, which leads to enhanced oxidation in moist environments at elevated temperatures. This work provides insights into water-vapour-enhanced alloy oxidation and has significant implications in other material and chemical processes involving water vapour, such as corrosion, heterogeneous catalysis and ionic conduction.

Evaluation of tubular reactor designs for supercritical water oxidation of U.S. Department of Energy mixed waste

International Nuclear Information System (INIS)

Barnes, C.M.

1994-12-01

Supercritical water oxidation (SCWO) is an emerging technology for industrial waste treatment and is being developed for treatment of the US Department of Energy (DOE) mixed hazardous and radioactive wastes. In the SCWO process, wastes containing organic material are oxidized in the presence of water at conditions of temperature and pressure above the critical point of water, 374 C and 22.1 MPa. DOE mixed wastes consist of a broad spectrum of liquids, sludges, and solids containing a wide variety of organic components plus inorganic components including radionuclides. This report is a review and evaluation of tubular reactor designs for supercritical water oxidation of US Department of Energy mixed waste. Tubular reactors are evaluated against requirements for treatment of US Department of Energy mixed waste. Requirements that play major roles in the evaluation include achieving acceptable corrosion, deposition, and heat removal rates. A general evaluation is made of tubular reactors and specific reactors are discussed. Based on the evaluations, recommendations are made regarding continued development of supercritical water oxidation reactors for US Department of Energy mixed waste

Zinc oxide nanoparticles for water disinfection

Directory of Open Access Journals (Sweden)

Emelita Asuncion S. Dimapilis

2018-03-01

Full Text Available The world faces a growing challenge for adequate clean water due to threats coming from increasing demand and decreasing supply. Although there are existing technologies for water disinfection, their limitations, particularly the formation of disinfection-by-products, have led to researches on alternative methods. Zinc oxide, an essential chemical in the rubber and pharmaceutical industries, has attracted interest as antimicrobial agent. In nanoscale, zinc oxide has shown antimicrobial properties which make its potential great for various applications. This review discusses the synthesis of zinc oxide with focus on precipitation method, its antimicrobial property and the factors affecting it, disinfection mechanisms, and the potential application to water disinfection.

Uranium oxidation: Characterization of oxides formed by reaction with water by infrared and sorption analyses

Science.gov (United States)

Fuller, E. L.; Smyrl, N. R.; Condon, J. B.; Eager, M. H.

1984-04-01

Three different uranium oxide samples have been characterized with respect to the different preparation techniques. The results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. Inert gas sorption analyses and diffuse reflectance infrared studies combined with electron microscopy prove valuable in defining the chemistry and morphology of the oxidic products and hydrated intermediates.

Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Rahimi, Fahime; Fathollahzadeh, Maryam; Haghighi, Behzad; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-07-28

Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) ~ 2.6.

Criticality benchmark guide for light-water-reactor fuel in transportation and storage packages

International Nuclear Information System (INIS)

Lichtenwalter, J.J.; Bowman, S.M.; DeHart, M.D.; Hopper, C.M.

1997-03-01

This report is designed as a guide for performing criticality benchmark calculations for light-water-reactor (LWR) fuel applications. The guide provides documentation of 180 criticality experiments with geometries, materials, and neutron interaction characteristics representative of transportation packages containing LWR fuel or uranium oxide pellets or powder. These experiments should benefit the U.S. Nuclear Regulatory Commission (NRC) staff and licensees in validation of computational methods used in LWR fuel storage and transportation concerns. The experiments are classified by key parameters such as enrichment, water/fuel volume, hydrogen-to-fissile ratio (H/X), and lattice pitch. Groups of experiments with common features such as separator plates, shielding walls, and soluble boron are also identified. In addition, a sample validation using these experiments and a statistical analysis of the results are provided. Recommendations for selecting suitable experiments and determination of calculational bias and uncertainty are presented as part of this benchmark guide

Stable Water Oxidation in Acid Using Manganese-Modified TiO2 Protective Coatings.

Science.gov (United States)

Siddiqi, Georges; Luo, Zhenya; Xie, Yujun; Pan, Zhenhua; Zhu, Qianhong; Röhr, Jason A; Cha, Judy J; Hu, Shu

2018-06-06

Accomplishing acid-stable water oxidation is a critical matter for achieving both long-lasting water-splitting devices and other fuel-forming electro- and photocatalytic processes. Because water oxidation releases protons into the local electrolytic environment, it becomes increasingly acidic during device operation, which leads to corrosion of the photoactive component and hence loss in device performance and lifetime. In this work, we show that thin films of manganese-modified titania, (Ti,Mn)O x , topped with an iridium catalyst, can be used in a coating stabilization scheme for acid-stable water oxidation. We achieved a device lifetime of more than 100 h in pH = 0 acid. We successfully grew (Ti,Mn)O x coatings with uniform elemental distributions over a wide range of manganese compositions using atomic layer deposition (ALD), and using X-ray photoelectron spectroscopy, we show that (Ti,Mn)O x films grown in this manner give rise to closer-to-valence-band Fermi levels, which can be further tuned with annealing. In contrast to the normally n-type or intrinsic TiO 2 coatings, annealed (Ti,Mn)O x films can make direct charge transfer to a Fe(CN) 6 3-/4- redox couple dissolved in aqueous electrolytes. Using the Fe(CN) 6 3-/4- redox, we further demonstrated anodic charge transfer through the (Ti,Mn)O x films to high work function metals, such as iridium and gold, which is not previously possible with ALD-grown TiO 2 . We correlated changes in the crystallinity (amorphous to rutile TiO 2 ) and oxidation state (2+ to 3+) of the annealed (Ti,Mn)O x films to their hole conductivity and electrochemical stability in acid. Finally, by combining (Ti,Mn)O x coatings with iridium, an acid-stable water-oxidation anode, using acid-sensitive conductive fluorine-doped tin oxides, was achieved.

Semiconductor photocatalysts for water oxidation: current status and challenges.

Science.gov (United States)

Yang, Lingling; Zhou, Han; Fan, Tongxiang; Zhang, Di

2014-04-21

Artificial photosynthesis is a highly-promising strategy to convert solar energy into hydrogen energy for the relief of the global energy crisis. Water oxidation is the bottleneck for its kinetic and energetic complexity in the further enhancement of the overall efficiency of the artificial photosystem. Developing efficient and cost-effective photocatalysts for water oxidation is a growing desire, and semiconductor photocatalysts have recently attracted more attention due to their stability and simplicity. This article reviews the recent advancement of semiconductor photocatalysts with a focus on the relationship between material optimization and water oxidation efficiency. A brief introduction to artificial photosynthesis and water oxidation is given first, followed by an explanation of the basic rules and mechanisms of semiconductor particulate photocatalysts for water oxidation as theoretical references for discussions of componential, surface structure, and crystal structure modification. O2-evolving photocatalysts in Z-scheme systems are also introduced to demonstrate practical applications of water oxidation photocatalysts in artificial photosystems. The final part proposes some challenges based on the dynamics and energetics of photoholes which are fundamental to the enhancement of water oxidation efficiency, as well as on the simulation of natural water oxidation that will be a trend in future research.

Methane oxidation in anoxic lake waters

Science.gov (United States)

Su, Guangyi; Zopfi, Jakob; Niemann, Helge; Lehmann, Moritz

2017-04-01

Freshwater habitats such as lakes are important sources of methante (CH4), however, most studies in lacustrine environments so far provided evidence for aerobic methane oxidation only, and little is known about the importance of anaerobic oxidation of CH4 (AOM) in anoxic lake waters. In marine environments, sulfate reduction coupled to AOM by archaea has been recognized as important sinks of CH4. More recently, the discorvery of anaerobic methane oxidizing denitrifying bacteria represents a novel and possible alternative AOM pathway, involving reactive nitrogen species (e.g., nitrate and nitrite) as electron acceptors in the absence of oxygen. We investigate anaerobic methane oxidation in the water column of two hydrochemically contrasting sites in Lake Lugano, Switzerland. The South Basin displays seasonal stratification, the development of a benthic nepheloid layer and anoxia during summer and fall. The North Basin is permanently stratified with anoxic conditions below 115m water depth. Both Basins accumulate seasonally (South Basin) or permanently (North Basin) large amounts of CH4 in the water column below the chemocline, providing ideal conditions for methanotrophic microorganisms. Previous work revealed a high potential for aerobic methane oxidation within the anoxic water column, but no evidence for true AOM. Here, we show depth distribution data of dissolved CH4, methane oxidation rates and nutrients at both sites. In addition, we performed high resolution phylogenetic analyses of microbial community structures and conducted radio-label incubation experiments with concentrated biomass from anoxic waters and potential alternative electron acceptor additions (nitrate, nitrite and sulfate). First results from the unamended experiments revealed maximum activity of methane oxidation below the redoxcline in both basins. While the incubation experiments neither provided clear evidence for NOx- nor sulfate-dependent AOM, the phylogenetic analysis revealed the

Supramolecular water oxidation with Ru-bda-based catalysts.

Science.gov (United States)

Richmond, Craig J; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni

2014-12-22

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda=2,2'-bipyridine-6,6'-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s(-1) , respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Oxidation and fractal surface roughness on the wettability and critical heat flux of glass-peened zirconium alloy tubes

International Nuclear Information System (INIS)

Fong, R.W.L.; Nitheanandan, T.; Bullock, C.D.; Slater, L.F.; McRae, G.A.

2003-05-01

Glass-bead peening the outside surfaces of zirconium alloy tubes has been shown to increase the Critical Heat Flux (CHF) in pool boiling of water. The CHF is found to correlate with the fractal roughness of the metal tube surfaces. In this study on the effect of oxidation on glass-peened surfaces, test measurements for CHF, surface wettability and roughness have been evaluated using various glass-peened and oxidized zirconium alloy tubes. The results show that oxidation changes the solid-liquid contact angle (i.e., decreases wettability of the metal-oxide surface), but does not change the fractal surface roughness, appreciably. Thus, oxidation of the glass-peened surfaces of zirconium alloy tubes is not expected to degrade the CHF enhancement obtained by glass-bead peening. (author)

Water oxidation catalysts and methods of use thereof

Energy Technology Data Exchange (ETDEWEB)

Hill, Craig L.; Gueletii, Yurii V.; Musaev, Djamaladdin G.; Yin, Qiushi; Botar, Bogdan

2017-12-05

Homogeneous water oxidation catalysts (WOCs) for the oxidation of water to produce hydrogen ions and oxygen, and methods of making and using thereof are described herein. In a preferred embodiment, the WOC is a polyoxometalate WOC which is hydrolytically stable, oxidatively stable, and thermally stable. The WOC oxidized waters in the presence of an oxidant. The oxidant can be generated photochemically, using light, such as sunlight, or electrochemically using a positively biased electrode. The hydrogen ions are subsequently reduced to form hydrogen gas, for example, using a hydrogen evolution catalyst (HEC). The hydrogen gas can be used as a fuel in combustion reactions and/or in hydrogen fuel cells. The catalysts described herein exhibit higher turn over numbers, faster turn over frequencies, and/or higher oxygen yields than prior art catalysts.

Application of graphene oxide in water treatment

Science.gov (United States)

Liu, Yongchen

2017-11-01

Graphene oxide has good hydrophilicity and has been tried to use it into thin films for water treatment in recent years. In this paper, the preparation methods of graphene oxide membrane are reviewed, including vacuum suction filtration, spray coating, spin coating, dip coating and the layer by layer method. Secondly, the mechanism of mass transfer of graphene membrane is introduced in detail. The application of the graphene oxide membrane, modified graphene oxide membrane and graphene hybrid membranes were discussed in RO, vaporization, nanofiltration and other aspects. Finally, the development and application of graphene membrane in water treatment were discussed.

Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study.

Science.gov (United States)

Li, Qibin; Xiao, Yitian; Shi, Xiaoyang; Song, Shufeng

2017-09-07

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system.

Critical heat flux on micro-structured zircaloy surfaces for flow boiling of water at low pressures

International Nuclear Information System (INIS)

Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T.

2012-01-01

The influence of surface structure on critical heat flux for flow boiling of water was investigated for Zircaloy tubes in a vertical annular test section. The objectives were to find suitable surface modification processes for Zircaloy tubes and to test their critical heat flux performance in comparison to the smooth tube. Surface structures with micro-channels, porous layer, oxidized layer, and elevations in micro- and nano-scale were produced on a section of a Zircaloy cladding tube. These modified tubes were tested in an internally heated vertical annulus with a heated length of 326 mm and an inner and outer diameter of 9.5 and 18 mm. The experiments were performed with mass fluxes of 250 and 400 kg/(m 2 s), outlet pressures between 120 and 300 kPa, and constant inlet subcooling enthalpy of 167 kJ/kg. Only a small influence of modified surface structures on critical heat flux was observed for the pressure of 120 kPa in the present test section geometry. However, with increasing pressure the critical heat flux could increase up to 29% using the surface structured tubes with micro-channels, porous and oxidized layers. Capillary effects and increased nucleation site density are assumed to improve the critical heat flux performance. (authors)

Critical currents and superconductivity ferromagnetism coexistence in high-Tc oxides

CERN Document Server

Khene, Samir

2016-01-01

The book comprises six chapters which deal with the critical currents and the ferromagnetism-superconductivity coexistence in high-Tc oxides. It begins by gathering key data for superconducting state and the fundamental properties of the conventional superconductors, followed by a recap of the basic theories of superconductivity. It then discusses the differences introduced by the structural anisotropy on the Ginzburg-Landau approach and the Lawrence-Doniach model before addressing the dynamics of vortices and the ferromagnetism-superconductivity coexistence in high-Tc oxides, and provides an outline of the pinning phenomena of vortices in these materials, in particular the pinning of vortices by the spins. It elucidates the methods to improve the properties of superconducting materials for industrial applications. This optimization aims at obtaining critical temperatures and densities of critical currents at the maximum level possible. Whereas the primary objective is the basic mechanisms pushing the superco...

Supercritical Water Oxidation Total Organic Carbon (TOC) Analysis

Science.gov (United States)

The work presented here is the evaluation of the modified wet‐oxidation method described as Supercritical Water Oxidation (SCWO) for the analysis of total organic carbon (TOC) in very difficult oil/gas produced water sample matrices.

Spatial distribution of water supply reliability and critical links of water supply to crucial water consumers under an earthquake

International Nuclear Information System (INIS)

Wang Yu; Au, S.-K.

2009-01-01

This paper describes a process to characterize spatial distribution of water supply reliability among various consumers in a water system and proposes methods to identify critical links of water supply to crucial water consumers under an earthquake. Probabilistic performance of water supply is reflected by the probability of satisfying consumers' water demand, Damage Consequence Index (DCI) and Upgrade Benefit Index (UBI). The process is illustrated using a hypothetical water supply system, where direct Monte Carlo simulation is used for estimating the performance indices. The reliability of water supply to consumers varies spatially, depending on their respective locations in the system and system configuration. The UBI is adopted as a primary index in the identification of critical links for crucial water consumers. A pipe with a relatively large damage probability is likely to have a relatively large UBI, and hence, to be a critical link. The concept of efficient frontier is employed to identify critical links of water supply to crucial water consumers. It is found that a group of links that have the largest UBI individually do not necessarily have the largest group UBI, or be the group of critical links

Shippingport LWBR (Th/U Oxide) Fuel Characteristics for Disposal Criticality Analysis

International Nuclear Information System (INIS)

Taylor, L. L.; Loo, H. H.

1999-01-01

Department of Energy (DOE)-owned spent nuclear fuels encompass many fuel types. In an effort to facilitate criticality analysis for these various fuel types, they were categorized into eight characteristic fuel groups with emphasis on fuel matrix composition. Out of each fuel group, a representative fuel type was chosen for analysis as a bounding case within that fuel group. Generally, burnup data, fissile enrichments, and total fuel and fissile mass govern the selection of the representative or candidate fuel within that group. The Shippingport Light Water Breeder Reactor (LWBR) fuels incorporate more of the conventional materials (zirconium cladding/heavy metal oxides) and fabrication details (rods and spacers) that make them comparable to a typical commercial fuel assembly. The LWBR seed/blanket configuration tested a light-water breeder concept with Th-232/U-233 binary fuel matrix. Reactor design used several assembly configurations at different locations within the same core . The seed assemblies contain the greatest fissile mass per (displaced) unit volume, but the blanket assemblies actually contain more fissile mass in a larger volume; the atom-densities are comparable

Water oxidation catalyzed by mononuclear ruthenium complexes with a 2,2'-bipyridine-6,6'-dicarboxylate (bda) ligand: how ligand environment influences the catalytic behavior.

Science.gov (United States)

Staehle, Robert; Tong, Lianpeng; Wang, Lei; Duan, Lele; Fischer, Andreas; Ahlquist, Mårten S G; Sun, Licheng; Rau, Sven

2014-02-03

A new water oxidation catalyst [Ru(III)(bda)(mmi)(OH2)](CF3SO3) (2, H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; mmi = 1,3-dimethylimidazolium-2-ylidene) containing an axial N-heterocyclic carbene ligand and one aqua ligand was synthesized and fully characterized. The kinetics of catalytic water oxidation by 2 were measured using stopped-flow technique, and key intermediates in the catalytic cycle were probed by density functional theory calculations. While analogous Ru-bda water oxidation catalysts [Ru(bda)L2] (L = pyridyl ligands) are supposed to catalyze water oxidation through a bimolecular coupling pathway, our study points out that 2, surprisingly, undergoes a single-site water nucleophilic attack (acid-base) pathway. The diversion of catalytic mechanisms is mainly ascribed to the different ligand environments, from nonaqua ligands to an aqua ligand. Findings in this work provide some critical proof for our previous hypothesis about how alternation of ancillary ligands of water oxidation catalysts influences their catalytic efficiency.

Successful treatment with supercritical water oxidation

International Nuclear Information System (INIS)

Jensen, R.

1994-01-01

Supercritical Water Oxidation (SCWO) operates in a totally enclosed system. It uses water at high temperatures and high pressure to chemically change wastes. Oily substances become soluble and complex hydrocarbons are converted into water and carbon dioxide. Research and development on SCWO is described

Hydrogen-water deuterium exchange over metal oxide promoted nickel catalysts

Energy Technology Data Exchange (ETDEWEB)

Sagert, N H; Shaw-Wood, P E; Pouteau, R M.L. [Atomic Energy of Canada Ltd., Pinawa, Manitoba. Whiteshell Nuclear Research Establishment

1975-11-01

Specific rates have been measured for hydrogen-water deuterium isotope exchange over unsupported nickel promoted with about 20% of various metal oxides. The oxides used were Cr/sub 2/O/sub 3/, MoO/sub 2/, MnO, WO/sub 2/-WO/sub 3/, and UO/sub 2/. Nickel surface areas, which are required to measure the specific rates, were determined by hydrogen chemisorption. Specific rates were measured as a function of temperature in the range 353 to 573 K and as a function of the partial pressure of hydrogen and water over a 10-fold range of partial pressure. The molybdenum and tungsten oxides gave the highest specific rates, and manganese and uranium oxides the lowest. Chromium oxide was intermediate, although it gave the highest rate per gram of catalyst. The orders with respect to hydrogen and water over molybdenum oxide and tungsten oxide promoted nickel were consistent with a mechanism in which nickel oxide is formed from the reaction of water with the catalyst, and then is reduced by hydrogen. Over manganese and uranium oxide promoted catalysts, these orders are consistent with a mechanism in which adsorbed water exchanges with chemisorbed hydrogen atoms on the nickel surface. Chromium oxide is intermediate. It was noted that those oxides which favored the nickel oxide route had electronic work functions closest to those of metallic nickel and nickel oxide.

The location of the second critical point of water

Science.gov (United States)

Kanno, Hitoshi; Miyata, Kuniharu

2006-05-01

Based on the DTA data for homogeneous ice nucleation of emulsified liquid water at low temperatures and high pressures, the location of the second critical point (SCP) of water, which is expected to exist in addition to the normal liquid-vapor critical point, is estimated to be at 145 K pressure). It is shown that SCP is closely associated with the break point of the curve for the homogeneous ice nucleation temperature ( TH) of liquid water and with the transition between low density and high density amorphous solid water (LDA and HDA). Although the existence of SCP has become more realistic, the location seems to be less favorable to the water model of the second-critical-point interpretation.

Anodic oxidation of InP in pure water

International Nuclear Information System (INIS)

Robach, Y.; Joseph, J.; Bergignat, E.; Hollinger, G.

1989-01-01

It is shown that thin InP native oxide films can be grown by anodization of InP in pure water. An interfacial phosphorus-rich In(PO 3 ) 3 -like condensed phosphate is obtained this way. This condensed phosphate has good passivating properties and can be used in electronic device technology. The chemical composition of these native oxides was found similar to that of an anodic oxide grown in an anodization in glycol and water (AGW) electrolyte. From the similarity between the two depth profiles observed in pure water and AGW electrolyte, they can conclude that dissolution phenomena do not seem to play a major role. The oxide growth seems to be controlled by the drift of ionic species under the electric field

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Moghaddam, Atefeh Nemati; Yang, Young Nam; Aro, Eva-Mari; Carpentier, Robert; Eaton-Rye, Julian J; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

2012-10-01

The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 Å resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.

Self-Assembled Amphiphilic Water Oxidation Catalysts: Control of O-O Bond Formation Pathways by Different Aggregation Patterns.

Science.gov (United States)

Yang, Bing; Jiang, Xin; Guo, Qing; Lei, Tao; Zhang, Li-Ping; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

2016-05-17

The oxidation of water to molecular oxygen is the key step to realize water splitting from both biological and chemical perspective. In an effort to understand how water oxidation occurs on a molecular level, a large number of molecular catalysts have been synthesized to find an easy access to higher oxidation states as well as their capacity to make O-O bond. However, most of them function in a mixture of organic solvent and water and the O-O bond formation pathway is still a subject of intense debate. Herein, we design the first amphiphilic Ru-bda (H2 bda=2,2'-bipyridine-6,6'-dicarboxylic acid) water oxidation catalysts (WOCs) of formula [Ru(II) (bda)(4-OTEG-pyridine)2 ] (1, OTEG=OCH2 CH2 OCH2 CH2 OCH3 ) and [Ru(II) (bda)(PySO3 Na)2 ] (2, PySO3 (-) =pyridine-3-sulfonate), which possess good solubility in water. Dynamic light scattering (DLS), scanning electron microscope (SEM), critical aggregation concentration (CAC) experiments and product analysis demonstrate that they enable to self-assemble in water and form the O-O bond through different routes even though they have the same bda(2-) backbone. This work illustrates for the first time that the O-O bond formation pathway can be regulated by the interaction of ancillary ligands at supramolecular level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Critical mass variation of 239Pu with water dilution

International Nuclear Information System (INIS)

Pearlstein, S.

1996-01-01

The critical mass of an unreflected solid sphere of 239 Pu is ∼ 10 kg. The increase in critical mass observed for small water dilutions of unreflected 239 Pu spheres is paradoxical. Introducing small amounts of water uniformly throughout the sphere increases the spherical volume containing the same amount of 239 Pu as the critical solid sphere. The increase in radius decreases the surface-to-volume ratio of the sphere, which has the effect to first order of decreasing the neutron leakage, which is proportional to the surface, relative to the fissions, which are proportional to the volume. The reduction in neutron leakage is expected to reduce the critical mass, but instead, the critical mass is observed to increase. It is discussed how changes in the fast neutron spectrum with corresponding changes in the nuclear parameters result in an increase in critical mass for small water dilutions

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

Science.gov (United States)

Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

2014-08-01

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Edge reactivity and water-assisted dissociation on cobalt oxide nanoislands

International Nuclear Information System (INIS)

Fester, J.; García-Melchor, M.; Walton, A. S.; Bajdich, M.

2017-01-01

Here, transition metal oxides show great promise as Earth-abundant catalysts for the oxygen evolution reaction in electrochemical water splitting. However, progress in the development of highly active oxide nanostructures is hampered by a lack of knowledge of the location and nature of the active sites. Here we show, through atom-resolved scanning tunnelling microscopy, X-ray spectroscopy and computational modelling, how hydroxyls form from water dissociation at under coordinated cobalt edge sites of cobalt oxide nanoislands. Surprisingly, we find that an additional water molecule acts to promote all the elementary steps of the dissociation process and subsequent hydrogen migration, revealing the important assisting role of a water molecule in its own dissociation process on a metal oxide. Inspired by the experimental findings, we theoretically model the oxygen evolution reaction activity of cobalt oxide nanoislands and show that the nanoparticle metal edges also display favourable adsorption energetics for water oxidation under electrochemical conditions.

Water coning. An empirical formula for the critical oil-production rate

Energy Technology Data Exchange (ETDEWEB)

Schols, R S

1972-01-01

The production of oil through a well that partly penetrates an oil layer underlain by water causes the oil/water interface to deform into a bell shape, usually referred to as water coning. To prevent water- breakthrough as a result of water coning, a knowledge of critical rates is necessary. Experiments are described in which critical rates were measured as a function of the relevant parameters. The experiments were conducted in Hele Shaw models, suitable for radial flow. From the experimental data, an empirical formula for critical rates was derived in dimensionless form. Approximate theoretical solutions for the critical rate appear in literature. A comparison of critical rates calculated according to these solutions with those from the empirical formula shows that these literature data give either too high or too low values for the critical rates.

Peracids in water treatment:a critical review

OpenAIRE

Luukkonen, T. (Tero); Pehkonen, S. O. (Simo O.)

2017-01-01

Abstract Peracids have gained interest in the water treatment over the last few decades. Peracetic acid (CH₃CO₃H) has already become an accepted alternative disinfectant in wastewater disinfection whereas performic acid (CHO₃H) has been studied much less, although it is also already commercially available. Additionally, peracids have been studied for drinking water disinfection, oxidation of aqueous (micro)pollutants, sludge treatment, and ballast water treatment, to name just a few exampl...

Oxidation and photo-oxidation of water on TiO2 surface

DEFF Research Database (Denmark)

Valdes, A.; Qu, Z.W.; Kroes, G.J.

2008-01-01

The oxidation and photo-oxidation of water on the rutile TiO2(110) surface is investigated using density functional theory (DFT) calculations. We investigate the relative stability of different surface terminations of TiO2 interacting with H2O and analyze the overpotential needed for the electrol...

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation.

Science.gov (United States)

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H; Navrotsky, Alexandra

2013-05-28

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.

Analysis of mixed oxide fuel critical experiments with neutronics analysis codes for boiling water reactors

International Nuclear Information System (INIS)

Tamitani, Masashi; Maruyama, Hiromi; Ishii, Kazuya; Izutsu, Sadayuki; Yamaguchi, Masao

2000-01-01

Critical experiments of UO 2 and full mixed oxide (MOX) fuel cores conducted at the Tank-type Critical Assembly (TCA) were analyzed using BWR design-purpose codes HINES and CERES with ENDF/B files and Monte Carlo fine analysis codes VMONT and MVP with the JENDL-3.2 library. The averaged values of the multiplication factors calculated with HINES/CERES, VMONT and MVP agreed with those of experiments within 0.3%Δk. The values by the design-purpose codes showed a small difference of 0.1%Δk between UO 2 and MOX cores. Monte Carlo code results showed that the JENDL-3.2 library had a tendency to overestimate the multiplication factors of UO 2 cores by about 0.3%Δk compared with those values of MOX cores. The root mean square errors of calculated power distributions were less than 1% for HINES/CERES and VMONT. These results showed that (1) the accuracy of these codes when applied to full MOX cores was almost the same as their accuracy for UO 2 cores, which confirmed the accuracy of present core design codes for full MOX cores; and (2) the accuracy of the 190-energy-group Monte Carlo calculation code VMONT was almost the same as that of the continuous-energy Monte Carlo calculation code MVP. (author)

Benchmark critical experiments on low-enriched uranium oxide systems with H/U = 0.77

International Nuclear Information System (INIS)

Tuck, G.; Oh, I.

1979-08-01

Ten benchmark experiments were performed at the Critical Mass Laboratory at Rockwell International's Rocky Flats Plant, Golden, Colorado, for the US Nuclear Regulatory Commission. They provide accurate criticality data for low-enriched damp uranium oxide (U 3 O 8 ) systems. The core studied consisted of 152 mm cubical aluminum cans containing an average of 15,129 g of low-enriched (4.46% 235 U) uranium oxide compacted to a density of 4.68 g/cm 3 and with an H/U atomic ratio of 0.77. One hundred twenty five (125) of these cans were arranged in an approx. 770 mm cubical array. Since the oxide alone cannot be made critical in an array of this size, an enriched (approx. 93% 235 U) metal or solution driver was used to achieve criticality. Measurements are reported for systems having the least practical reflection and for systems reflected by approx. 254-mm-thick concrete or plastic. Under the three reflection conditions, the mass of the uranium metal driver ranged from 29.87 kg to 33.54 kg for an oxide core of 1864.6 kg. For an oxide core of 1824.9 kg, the weight of the high concentration (351.2 kg U/m 3 ) solution driver varied from 14.07 kg to 16.14 kg, and the weight of the low concentration (86.4 kg U/m 3 ) solution driver from 12.4 kg to 14.0 kg

Kinetics and mechanism of methane oxidation in supercritical water

International Nuclear Information System (INIS)

Rofer, C.K.; Streit, G.E.

1988-10-01

This project, is a Hazardous Waste Remedial Actions Program (HAZWRAP) Research and Development task being carried out by the Los Alamos National Laboratory. Its objective is to achieve an understanding of the technology for use in scaling up and applying oxidation in supercritical water as a viable process for treating a variety of Department of Energy Defense Programs (DOE-DP) waste streams. This report presents experimental results for the kinetics of the oxidation of methane and methanol in supercritical water and computer modeling results for the oxidation of carbonmonoxide and methane in supercritical water. The experimental and modeling results obtained to date on these one-carbon model compounds indicate that the mechanism of oxidation in supercritical water can be represented by free-radical reactions with appropriate modifications for high pressure and the high water concentration. If these current trends are sustained, a large body of existing literature data on the kinetics of elementary reactions can be utilized to predict the behavior of other compounds and their mixtures. 7 refs., 4 figs., 3 tabs

ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION

Science.gov (United States)

This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. This information is provided to assist remedial project managers, contractors...

Flow analysis in a supercritical water oxidation reactor

International Nuclear Information System (INIS)

Oh, C.H.; Kochan, R.J.; Beller, J.M.

1996-01-01

Supercritical water oxidation (SCWO), also known as hydrothermal oxidation (HTO), involves the oxidation of hazardous waste at conditions of elevated temperature and pressure (e.g., 500 C--600 C and 234.4 bar) in the presence of approximately 90% of water and a 10% to 20% excess amount of oxidant over the stoichiometric requirement. Under these conditions, organic compounds are completely miscible with supercritical water, oxygen and nitrogen, and are rapidly oxidized to carbon dioxide and water. The essential part of the process is the reactor. Many reactor designs such as tubular, vertical vessel, and transpiring wall type have been proposed, patented, and tested at both bench and pilot scales. These designs and performances need to be scaled up to a waste throughput 10--100 times that currently being tested. Scaling of this magnitude will be done by creating a numerical thermal-hydraulic model of the smaller reactor for which test data is available, validating the model against the available data, and then using the validated model to investigate the larger reactor performance. This paper presents a flow analysis of the MODAR bench scale reactor (vertical vessel type). These results will help in the design of the reactor in an efficient manner because the flow mixing coupled with chemical kinetics eventually affects the process destruction efficiency

Oxide/water interfaces: how the surface chemistry modifies interfacial water properties

International Nuclear Information System (INIS)

Gaigeot, Marie-Pierre; Sprik, Michiel; Sulpizi, Marialore

2012-01-01

The organization of water at the interface with silica and alumina oxides is analysed using density functional theory-based molecular dynamics simulation (DFT-MD). The interfacial hydrogen bonding is investigated in detail and related to the chemistry of the oxide surfaces by computing the surface charge density and acidity. We find that water molecules hydrogen-bonded to the surface have different orientations depending on the strength of the hydrogen bonds and use this observation to explain the features in the surface vibrational spectra measured by sum frequency generation spectroscopy. In particular, ‘ice-like’ and ‘liquid-like’ features in these spectra are interpreted as the result of hydrogen bonds of different strengths between surface silanols/aluminols and water. (paper)

Critical assessment of finite element analysis applied to metal–oxide interface roughness in oxidising zirconium alloys

Energy Technology Data Exchange (ETDEWEB)

Platt, P., E-mail: Philip.Platt@manchester.ac.uk [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Frankel, P. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Gass, M. [AMEC, Walton House, Faraday Street, Birchwood Park, Risley, Warrington WA3 6GA (United Kingdom); Preuss, M. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom)

2015-09-15

As a nuclear fuel cladding material, zirconium alloys act as a barrier between the fuel and pressurised steam or lithiated water environment. Controlling degradation mechanisms such as oxidation is essential to extending the in-service lifetime of the fuel. At temperatures of ∼360 °C zirconium alloys are known to exhibit cyclical, approximately cubic corrosion kinetics. With acceleration in the oxidation kinetics occurring every ∼2 μm of oxide growth, and being associated with the formation of a network of lateral cracks. Finite element analysis has been used previously to explain the lateral crack formation by the development of localised out-of-plane tensile stresses at the metal–oxide interface. This work uses the Abaqus finite element code to assess critically current approaches to representing the oxidation of zirconium alloys, with relation to undulations at the metal–oxide interface and localised stress generation. This includes comparison of axisymmetric and 3D quartered modelling approaches, and investigates the effect of interface geometry and plasticity in the metal substrate. Particular focus is placed on the application of the anisotropic strain tensor used to represent the oxidation mechanism, which is typically applied with a fixed coordinate system. Assessment of the impact of the tensor showed that 99% of the localised tensile stresses originated from the out-of-plane component of the strain tensor, rather than the in-plane expansion as was previously thought. Discussion is given to the difficulties associated with this modelling approach and the requirements for future simulations of the oxidation of zirconium alloys.

Oxidation behavior of austenitic iron-base ODS alloy in supercritical water

Energy Technology Data Exchange (ETDEWEB)

Behnamian, Y.; Dong, Z.; Zahiri, R.; Kohandehghan, A.; Mitlin, D., E-mail: behnamia@ualberta.ca, E-mail: zdong@ualberta.ca, E-mail: kohandeh@ualberta.ca, E-mail: rzahiris@ualberta.ca, E-mail: dave.mitlin@ualberta.ca [Univ. of Alberta, Edmondon, AB (Canada); Zhou, Z., E-mail: zhouzhj@mater.ustb.edu.cn [Univ. of Science and Tech. Beijing, Beijing (China); Chen, W.; Luo, J., E-mail: weixing.chen@ualberta.ca, E-mail: Jingli.luo@ualberta.ca [Univ. of Alberta, Edmonton, AB (Canada); Zheng, W., E-mail: wenyue@nrcan.gc.ca [Natural Resources Canada, Canmet MATERIALS, Hamilton, ON (Canada); Guzonas, D. [Atomic Energy of Canada Limited, Chalk River, ON (Canada)

2014-07-01

In this study, the effect of exposure time on the corrosion of the 304 stainless steel based oxide dispersion strengthened alloy, SS304ODS, in supercritical water was investigated at 650 {sup o}C with constant dissolved oxygen concentration. The results show that the oxidation of SS304ODS in supercritical water followed a parabolic law at 650 {sup o}C. Discontinuous oxide scale with two distinct layers has formed after 550 hours. The inner layer was chromium-rich while the outer layer was iron-rich (Magnetite). The oxide islands grow with increasing the exposure time. With increasing exposure time, the quantity of oxide islands increased in which major preferential growth along oxide-substrate interface was observed. The possible mechanism of SS304ODS oxidation in supercritical water was also discussed. (author)

Lipid oxidation in base algae oil and water-in-algae oil emulsion: Impact of natural antioxidants and emulsifiers.

Science.gov (United States)

Chen, Bingcan; Rao, Jiajia; Ding, Yangping; McClements, David Julian; Decker, Eric Andrew

2016-07-01

The impact of natural hydrophilic antioxidants, metal chelators, and hydrophilic antioxidant/metal chelator mixture on the oxidative stability of base algae oil and water-in-algae oil emulsion was investigated. The results showed that green tea extract and ascorbic acid had greatest protective effect against algae oil oxidation and generated four day lag phase, whereas rosmarinic acid, grape seed extract, grape seed extract polymer, deferoxamine (DFO), and ethylenediaminetetraacetic acid (EDTA) had no significant protective effect. Besides, there was no synergistic effect observed between natural antioxidants and ascorbic acid. The emulsifiers are critical to the physicochemical stability of water-in-algae oil emulsions. Polyglycerol polyricinoleate (PGPR) promoted the oxidation of emulsion. Conversely, the protective effect on algae oil oxidation was appreciated when defatted soybean lecithin (PC 75) or defatted lyso-lecithin (Lyso-PC) was added. The role of hydrophilic antioxidants in emulsion was similar to that in algae oil except EDTA which demonstrated strong antioxidative effect in emulsion. The results could provide information to build up stable food products containing polyunsaturated fatty acids (PUFA). Copyright © 2016 Elsevier Ltd. All rights reserved.

Supercritical water oxidation treatment of textile sludge.

Science.gov (United States)

Zhang, Jie; Wang, Shuzhong; Li, Yanhui; Lu, Jinling; Chen, Senlin; Luo, XingQi

2017-08-01

In this work, we studied the supercritical water oxidation (SCWO) of the textile sludge, the hydrothermal conversion of typical textile compounds and the corrosion properties of stainless steel 316. Moreover, the influence mechanisms of NaOH during these related processes were explored. The results show that decomposition efficiency for organic matter in liquid phase of the textile sludge was improved with the increment of reaction temperature or oxidation coefficient. However, the organic substance in solid phase can be oxidized completely in supercritical water. Serious coking occurred during the high pressure water at 250-450°C for the Reactive Orange 7, while at 300 and 350°C for the polyvinyl alcohol. The addition of NaOH not only accelerated the destruction of organic contaminants in the SCWO reactor, but effectively inhibited the dehydration conversion of textile compounds during the preheating process, which was favorable for the treatment system of textile sludge. The corrosion experiment results indicate that the stainless steel 316 could be competent for the body materials of the reactor and the heat exchangers. Furthermore, there was prominent enhancement of sodium hydroxide for the corrosion resistance of 316 in subcritical water. On the contrary the effect was almost none during SCWO.

An effective method of UV-oxidation of dissolved organic carbon in natural waters for radiocarbon analysis by accelerator mass spectrometry

Science.gov (United States)

Xue, Yuejun; Ge, Tiantian; Wang, Xuchen

2015-12-01

Radiocarbon (14C) measurement of dissolved organic carbon (DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry (AMS). The UV-oxidation system and method show 95%±4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low (about 3 µg C) that is critical for 14C analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for 14C studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.

Critical current characteristics in high T/sub c/ oxide superconductors

International Nuclear Information System (INIS)

Matsushita, T.; Ni, B.

1989-01-01

Critical current densities are theoretically estimated for single-crystalline thin films, polycrystalline bulk materials with oriented and random textures of superconducting oxides. The percolation theory is used and the effect of depression of the transport current through grain boundaries is taken into account. A comparison is made with existing experimental results

Superconductor made by electrolyzed and oxidized water

OpenAIRE

Liu, Chia-Jyi; Wu, Tsung-Hsien; Hsu, Lin-Li; Wang, Jung-Sheng; Chen, Shu-Yo; Chang, Wei Jen; Lin, Jiunn-Yuan

2006-01-01

By deintercalation of Na+ followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of gamma-Na0.7CoO2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na0.35(H2O)1.3CoO2-delta with the c-axis expanded from c = 10.9 anstrom to c = 19.6 anstrom. In this paper, we demonstrate that the superconducting phase of c = 19.6 anstrom can be directly obtained by simply immersing gamma-Na0.7CoO2 powders in electrolyzed/oxidized (EO) water, wh...

Water clustering on nanostructured iron oxide films

DEFF Research Database (Denmark)

Merte, Lindsay Richard; Bechstein, Ralf; Peng, G.

2014-01-01

, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moire-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer...... islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous...

Carrier dynamics of a visible-light-responsive Ta3N5 photoanode for water oxidation

KAUST Repository

Ziani, Ahmed; Nurlaela, Ela; Dhawale, Dattatray Sadashiv; Silva, Diego Alves; Alarousu, Erkki; Mohammed, Omar F.; Takanabe, Kazuhiro

2015-01-01

The physicochemical properties of a tantalum nitride (Ta3N5) photoanode were investigated in detail to understand the fundamental aspects associated with the photoelectrochemical (PEC) water oxidation. The Ta3N5 thin films were synthesized using DC magnetron sputtering followed by annealing in air and nitridation under ammonia (NH3). A polycrystalline structure with a dense morphology of the monoclinic Ta3N5 films was obtained. A relatively low absorption coefficient (104 to 105 cm-1) in the visible light range was measured for Ta3N5, consistent with the nature of the indirect band-gap. Ultra-fast spectroscopic measurements revealed that the Ta3N5 with different thicknesses films possess low transport properties and fast carrier recombination (<10 ps). These critical kinetic properties of Ta3N5 as a photoanode may necessitate high overpotentials to achieve appreciable photocurrents for water oxidation (onset ∼0.6 V vs. RHE). This journal is

Photocatalytic Water Oxidation on ZnO: A Review

Directory of Open Access Journals (Sweden)

Sharifah Bee Abdul Hamid

2017-03-01

Full Text Available The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO.

Destruction of energetic materials by supercritical water oxidation

International Nuclear Information System (INIS)

Beulow, S.J.; Dyer, R.B.; Harradine, D.M.; Robinson, J.M.; Oldenborg, R.C.; Funk, K.A.; McInroy, R.E.; Sanchez, J.A.; Spontarelli, T.

1993-01-01

Supercritical water oxidation is a relatively low-temperature process that can give high destruction efficiencies for a variety of hazardous chemical wastes. Results are presented examining the destruction of high explosives and propellants in supercritical water and the use of low temperature, low pressure hydrolysis as a pretreatment process. Reactions of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), nitroguanidine (NQ), pentaerythritol tetranitrate (PETN), and 2,4,6-trinitrotoluene (TNT) are examined in a flow reactor operated at temperatures between 400 degrees C and 650 degrees C. Explosives are introduced into the reactor at concentrations below the solubility limits. For each of the compounds, over 99.9% is destroyed in less than 30 seconds at temperatures above 600 degrees C. The reactions produce primarily N 2 , N 2 O,CO 2 , and some nitrate and nitrite ions. The distribution of reaction products depends on reactor pressure, temperature, and oxidizer concentration. Kinetics studies of the reactions of nitrate and nitrite ions with various reducing reagents in supercritical water show that they can be rapidly and completely destroyed at temperatures above 525 degrees C. The use of slurries and hydrolysis to introduce high concentrations of explosives into a supercritical water reactor is examined. For some compounds the rate of reaction depends on particle size. The hydrolysis of explosives at low temperatures (<100 degrees C) and low pressures (<1 atm) under basic conditions produces water soluble, non-explosive products which are easily destroyed by supercritical water oxidation. Large pieces of explosives (13 cm diameter) have been successfully hydrolyzed. The rate, extent, and products of the hydrolysis depend on the type and concentration of base. Results from the base hydrolysis of triple base propellant M31A1E1 and the subsequent supercritical water oxidation of the hydrolysis products are presented

Nonaqueous electrocatalytic water oxidation by a surface-bound Ru(bda)(L)₂ complex.

Science.gov (United States)

Sheridan, Matthew V; Sherman, Benjamin D; Wee, Kyung-Ryang; Marquard, Seth L; Gold, Alexander S; Meyer, Thomas J

2016-04-21

The rate of electrocatalytic water oxidation by the heterogeneous water oxidation catalyst [Ru(bda)(4-O(CH2)3P(O3H2)2-pyr)2], , (pyr = pyridine; bda = 2,2'-bipyridine-6,6'-dicarboxylate) on metal oxide surfaces is greatly enhanced relative to water as the solvent. In these experiments with propylene carbonate (PC) as the nonaqueous solvent, water is the limiting reagent. Mechanistic studies point to atom proton transfer (APT) as the rate limiting step in water oxidation catalysis.

Selective Electrochemical Generation of Hydrogen Peroxide from Water Oxidation

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Nørskov, Jens K.

2015-01-01

evolution and form hydrogen peroxide. Using density functional theory calculations, we show that the free energy of adsorbed OH* can be used to determine selectivity trends between the 2e(-) water oxidation to H2O2 and the 4e(-) oxidation to O2. We show that materials which bind oxygen intermediates...... sufficiently weakly, such as SnO2, can activate hydrogen peroxide evolution. We present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively....

Thermodynamic properties of water in the critical region

International Nuclear Information System (INIS)

Veloso, Marcelo A.

2009-01-01

The supercritical-water-cooled reactor (SCWR) is one of the nuclear reactor technologies selected for research and development under the Generation IV program. SCWRs offer the potential for high thermal efficiencies and considerable plant simplifications for improved economics. One of the main characteristics of critical water is the strong variations of its thermal-physical properties in the vicinity of the critical point. These large variations may result in an unusual heat transfer behavior. The 1967 IFC Formulation for Industrial Use, which until 1998 formed the basis of steam tables used in many areas of steam power industry throughout the world since the late 1960's, has been now replaced with the IAPWS IF-97 Formulation for the Thermodynamic Properties of Water and Steam for Industrial Use, adopted by the International Association for the Properties of Water and Steam (IAPWS) in 1997. An IAPWS release points out that this new formulation has some unsatisfactory features in the immediate vicinity of the critical point. In order to investigate this singular aspect, which is crucial to better understand the heat transfer mechanism in a SCWR system, predictions by the IAPWS-IF97 formulation will be compared with thermodynamic properties values predicted by an alternative crossover equation of state as well as with experimental data found in literature. (author)

Efficient electrochemical water oxidation in neutral and near-neutral systems by nanoscale silver-oxide catalyst

KAUST Repository

Joya, Khurram Saleem; Ahmad, Zahoor; Joya, Yasir Faheem; Garcia Esparza, Angel T.; de Groot, Huub

2016-01-01

In electrocatalytic water splitting systems pursuing for renewable energy using sun light, developing robust, stable and easy accessible materials operating under mild chemical conditions is pivotal. We present here unique nano-particulate type silver-oxide (AgOx-NP) based robust and highly stable electrocatalyst for efficient water oxidation. The AgOx-NP is generated in situ in a HCO3–/CO2 system under benign conditions. Mircographs show that they exhibit nanoscale box type squared nano-bipyramidal configuration. The oxygen generation is initiated at low overpotential, and a sustained O2 evolution current density of > 1.1 mA cm–2 is achieved during prolonged-period water electrolysis. The AgOx-NP electrocatalyst performs exceptionally well in metal-ions free neutral or near-neutral carbonate, phosphate and borate buffers relative to recently reported Co-oxide and Ni-oxide based heterogeneous electrocatalysts, which are unstable in metal-ions free electrolyte and tend to degrade with time and lose catalytic performance during long-term experimental tests.

Efficient electrochemical water oxidation in neutral and near-neutral systems by nanoscale silver-oxide catalyst

KAUST Repository

Joya, Khurram Saleem

2016-07-19

In electrocatalytic water splitting systems pursuing for renewable energy using sun light, developing robust, stable and easy accessible materials operating under mild chemical conditions is pivotal. We present here unique nano-particulate type silver-oxide (AgOx-NP) based robust and highly stable electrocatalyst for efficient water oxidation. The AgOx-NP is generated in situ in a HCO3–/CO2 system under benign conditions. Mircographs show that they exhibit nanoscale box type squared nano-bipyramidal configuration. The oxygen generation is initiated at low overpotential, and a sustained O2 evolution current density of > 1.1 mA cm–2 is achieved during prolonged-period water electrolysis. The AgOx-NP electrocatalyst performs exceptionally well in metal-ions free neutral or near-neutral carbonate, phosphate and borate buffers relative to recently reported Co-oxide and Ni-oxide based heterogeneous electrocatalysts, which are unstable in metal-ions free electrolyte and tend to degrade with time and lose catalytic performance during long-term experimental tests.

The Bare Critical Assembly of Natural Uranium and Heavy Water

Energy Technology Data Exchange (ETDEWEB)

Popovic, D [Boris Kidric Institute of Nuclear Sciences, Vinca, Belgrade (Yugoslavia)

1958-07-01

The first reactor built in Yugoslavia was the bare zero energy heavy water and natural uranium assembly at the Boris Kidric Institute of Nuclear Sciences, Belgrade. The reactor went critical on April 29, 1958. The possession of four tons of natural uranium metal and the temporary availability of seven tons of heavy water encouraged the staff of the Institute to build a critical assembly. A critical assembly was chosen, rather than high flux reactor, because the heavy water was available only temporarily. Besides, a 10 MW, enriched uranium, research reactor is being built at the same Institute and should be ready for operation late this year. It was supposed that the zero energy reactor would provide experience in carrying out critical experiments, operational experience with nuclear reactors, and the possibility for an extensive program in reactor physics. (author)

Strongly oxidizing perylene-3,4-dicarboximides for use in water oxidation photoelectrochemical cells

Energy Technology Data Exchange (ETDEWEB)

Lindquist, Rebecca J.; Phelan, Brian T.; Reynal, Anna; Margulies, Eric A.; Shoer, Leah E.; Durrant, James R.; Wasielewski, Michael R.

2016-01-01

Perylene-3,4-dicarboximide (PMI) based chromophores have demonstrated the ability to inject electrons into TiO2 for dye-sensitized solar cell applications and to accept electrons from metal complexes relevant to water oxidation, but they are nearly unexplored for use in photoelectrochemical cells (PECs) for solar fuels generation. A series of related PMIs with high oxidation potentials and carboxylate binding groups was synthesized and investigated for this purpose. Charge injection and recombination dynamics were measured using transient absorption (TA) spectroscopy on the picosecond to second timescales. The dynamics and electron injection yields were correlated with the PMI energetics and structures. Injection began in less than 1 ps for the dye with the best performance and a significant charge-separated state yield remained at long times. Finally, this chromophore was used to oxidize a covalently bound water oxidation precatalyst following electron injection into TiO2 to demonstrate the utility of the dyes for use in PECs.

Water formation via HCl oxidation on Cu(1 0 0)

Energy Technology Data Exchange (ETDEWEB)

Suleiman, Ibrahim A., E-mail: isuleman@taibahu.edu.sa [College of Engineering, Taibah University, Yanbu 41911 (Saudi Arabia); Radny, Marian W. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Institute of Physics, Poznan University of Technology, 62-956 Poznan (Poland); Gladys, Michael J.; Smith, Phillip V. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Mackie, John C. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); School of Chemistry, The University of Sydney (Australia); Stockenhuber, Michael; Kennedy, Eric M. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Dlugogorski, Bogdan Z. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); School of Engineering and Information Technology, Murdoch University, Perth (Australia)

2014-04-01

Graphical abstract: This work investigates water formation on the Cu(1 0 0) surface via HCl oxidation using density functional theory and periodic slabs. We show that there are two different pathways for water formation on the surface depending on the temperature and oxygen coverage. - Highlights: • Pre-adsorbed chlorine increases the stability of water on Cu(1 0 0). • Two different pathways describe water formation on Cu(1 0 0) via HCl oxidation. • The mechanism of H{sub 2}O formation depends on the temperature and oxygen coverage. - Abstract: Using density functional theory and periodic slabs, we have studied water formation via HCl oxidation on the Cu(1 0 0) surface. We show that while adsorbed chlorine increases the stability of water on the Cu(1 0 0) surface, water molecules dissociate immediately when located next to an oxygen atom. We also show that these competing interactions, when arising from HCl reacting with oxygen on Cu(1 0 0), lead to water formation according to two different pathways depending on the temperature and oxygen coverage.

Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour.

Science.gov (United States)

Martin, T L; Coe, C; Bagot, P A J; Morrall, P; Smith, G D W; Scott, T; Moody, M P

2016-07-12

Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium hydride was observed at the oxide-metal interface. Exposure to deuterated water vapour produced an equivalent deuteride signal at the metal-oxide interface, confirming the hydride as originating via the water vapour oxidation mechanism. Hydroxide ions were detected uniformly throughout the oxide, yet showed reduced prominence at the metal interface. These results support a proposed mechanism for the oxidation of uranium in water vapour environments where the transport of hydroxyl species and the formation of hydride are key to understanding the observed behaviour.

Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour

Science.gov (United States)

Martin, T. L.; Coe, C.; Bagot, P. A. J.; Morrall, P.; Smith, G. D. W.; Scott, T.; Moody, M. P.

2016-07-01

Understanding the corrosion of uranium is important for its safe, long-term storage. Uranium metal corrodes rapidly in air, but the exact mechanism remains subject to debate. Atom Probe Tomography was used to investigate the surface microstructure of metallic depleted uranium specimens following polishing and exposure to moist air. A complex, corrugated metal-oxide interface was observed, with approximately 60 at.% oxygen content within the oxide. Interestingly, a very thin (~5 nm) interfacial layer of uranium hydride was observed at the oxide-metal interface. Exposure to deuterated water vapour produced an equivalent deuteride signal at the metal-oxide interface, confirming the hydride as originating via the water vapour oxidation mechanism. Hydroxide ions were detected uniformly throughout the oxide, yet showed reduced prominence at the metal interface. These results support a proposed mechanism for the oxidation of uranium in water vapour environments where the transport of hydroxyl species and the formation of hydride are key to understanding the observed behaviour.

Critical heat flux experiments in a circular tube with heavy water and light water. (AWBA Development Program)

International Nuclear Information System (INIS)

Williams, C.L.; Beus, S.G.

1980-05-01

Experiments were performed to establish the critical heat flux (CHF) characteristics of heavy water and light water. Testing was performed with the up-flow of heavy and of light water within a 0.3744 inch inside diameter circular tube with 72.3 inches of heated length. Comparisons were made between heavy water and light water critical heat flux levels for the same local equilibrium quality at CHF, operating pressure, and nominal mass velocity. Results showed that heavy water CHF values were, on the average, 8 percent below the light water CHF values

Photosynthetic water oxidation: binding and activation of substrate waters for O-O bond formation.

Science.gov (United States)

Vinyard, David J; Khan, Sahr; Brudvig, Gary W

2015-01-01

Photosynthetic water oxidation occurs at the oxygen-evolving complex (OEC) of Photosystem II (PSII). The OEC, which contains a Mn4CaO5 inorganic cluster ligated by oxides, waters and amino-acid residues, cycles through five redox intermediates known as S(i) states (i = 0-4). The electronic and structural properties of the transient S4 intermediate that forms the O-O bond are not well understood. In order to gain insight into how water is activated for O-O bond formation in the S4 intermediate, we have performed a detailed analysis of S-state dependent substrate water binding kinetics taking into consideration data from Mn coordination complexes. This analysis supports a model in which the substrate waters are both bound as terminal ligands and react via a water-nucleophile attack mechanism.

Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

Science.gov (United States)

Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

2015-07-21

The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven

Solar photocatalytic water oxidation over Ag3PO4/g-C3N4 composite materials mediated by metallic Ag and graphene

Science.gov (United States)

Cui, Xingkai; Tian, Lin; Xian, Xiaozhai; Tang, Hua; Yang, Xiaofei

2018-02-01

Solar-driven water splitting over semiconductor-based photocatalysts provides direct conversion of solar energy to chemical energy, in which electron-hole separation and charge transport are critical for enhancing the photocatalytic activity of semiconducting materials. Moreover, the search for active photocatalysts that efficiently oxidize water remains a challenging task. Here, we demonstrate that a series of Ag3PO4/Ag/graphene/graphitic carbon nitride (g-C3N4) heterostructured materials can drive photocatalytic water oxidation efficiently under LED illumination. The water oxidation behavior of as-prepared composite photocatalysts in relation to the added amount of g-C3N4 and the roles of electron mediators was investigated in detail. Based on the illuminated Z-scheme photocatalytic mechanism, the photogenerated electrons and holes can be separated effectively and the electron-hole recombination of bulk material is suppressed. The reduced metallic Ag nanoparticles were found to function as the center for the accumulation of electrons from Ag3PO4 and holes from g-C3N4. By exploiting the proper addition of g-C3N4 into the composite, photocatalytic oxygen evolution performance over the heterostructured materials could be suitably tuned, which resulted in highly efficient water oxidation.

Water flooding criticality study for ZrH flight reactor

International Nuclear Information System (INIS)

Anderson, R.V.

1970-01-01

Five analytical criticality calculations were performed to study the effects of: (1) water reflecting only (no core flooding), (2) water reflection with 10 percent core flooding, (3) water reflection with 35 percent flooding, (4) water reflection plus complete core flooding, and (5) the negative reactivity feedback associated with rapid core expansion induced by a destructive transient. (U.S.)

Myofibrillar protein oxidation affects filament charges, aggregation and water-holding

NARCIS (Netherlands)

Bao, Yulong; Boeren, Sjef; Ertbjerg, Per

2018-01-01

Hypochlorous acid (HClO) is a strong oxidant that is able to mediate protein oxidation. In order to study the effect of oxidation on charges, aggregation and water-holding of myofibrillar proteins, extracted myofibrils were oxidized by incubation with different concentrations of HClO (0, 1, 5,

Probability of Criticality for MOX SNF

International Nuclear Information System (INIS)

P. Gottlieb

1999-01-01

The purpose of this calculation is to provide a conservative (upper bound) estimate of the probability of criticality for mixed oxide (MOX) spent nuclear fuel (SNF) of the Westinghouse pressurized water reactor (PWR) design that has been proposed for use. with the Plutonium Disposition Program (Ref. 1, p. 2). This calculation uses a Monte Carlo technique similar to that used for ordinary commercial SNF (Ref. 2, Sections 2 and 5.2). Several scenarios, covering a range of parameters, are evaluated for criticality. Parameters specifying the loss of fission products and iron oxide from the waste package are particularly important. This calculation is associated with disposal of MOX SNF

Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

Science.gov (United States)

Milucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel MM; Schubert, Carsten J

2015-01-01

Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes. PMID:25679533

Water reactivity with mixed oxide (U,Pu)O2 surfaces

International Nuclear Information System (INIS)

Gaillard, Jeremy

2013-01-01

The interaction of water with actinides oxide surfaces remains poorly understood. The adsorption of water on PuO 2 surface and (U,Pu)O 2 surface leads to hydrogen generation through radiolysis but also surface evolution. The study of water interaction with mixed oxide (U,Pu)O 2 and PuO 2 surfaces requires the implementation of non intrusive techniques. The study of the hydration of CeO 2 surface is used to study the effectiveness of different techniques. The results show that the water adsorption leads to the surface evolution through the formation of a hydroxide superficial layer. The reactivity of water on the surface depends on the calcination temperature of the oxide precursor. The thermal treatment of hydrated surfaces can regenerate the surface. The study on CeO 2 hydration emphasizes the relevancies of these techniques in studying the hydration of surfaces. The hydrogen generation through water radiolysis is studied with an experimental methodology based on constant relative humidity in the radiolysis cell. The hydrogen accumulation is linear for the first hours and then tends to a steady state content. A mechanism of hydrogen consumption is proposed to explain the existence of the steady state of hydrogen content. This mechanism enables to explain also the evolution of the oxide surface during hydrogen generation experiments as shown by the evolution of hydrogen accumulation kinetics. The accumulation kinetics depends on the dose rate, specific surface area and the relative humidity but also on the oxide aging. The plutonium percentage appears to be a crucial parameter in hydrogen accumulation kinetics. (author) [fr

The critical singularities of water and its significance in the hydrothermal mineralization of uranium

International Nuclear Information System (INIS)

Hu Baoqun; Lv Guxian; Wang Fangzheng; Sun Zhanxue; Zhu Peng

2008-01-01

Water is the main composition of the geo-fiuid. With the changes of temperature and pressure, its phases and physicochemical properties will vary and the critical singularity occur at the critical point of second-order phase transition. These changes of water will enormously affect the hydrothermal mineralizations. This paper has introduced the types and characteristics of water phase transitions, studied the phase transitions of water in the lithosphere and showed the critical singularity of water with the example of the isobaric heat capacity. The conclusions are as follow: (1) the critical singularities of water are the most obvious as the temperature and pressure near to the critical constants of water; (2) Because the temperature changes with the pressure according to the thermal curve in the lithosphere, it is difficult to find a place where the temperature and pressure can be at the critical constants at same time except the coupling effect of the hydrothermal processes, intermediate-acidic magmatism and faulting; (3) To the hydrothermal mineralization, the significances of water's critical singularities at least include the sharp variation of solubility and instantaneous high pressure to conduct the deposit of ore-forming materials and fault formation. (authors)

Criticality safety analysis of a calciner exit chute

International Nuclear Information System (INIS)

Haught, C.F.; Basoglu, B.; Brewer, R.W.; Hollenback, D.F.; Wilkinson, A.D.; Dodds, H.L.

1994-01-01

Calcination of uranyl nitrate into uranium oxide is part of normal operations of some enrichment plants. Typically, a calciner discharges uranium oxide powder (U 3 O 8 ) into an exit chute that directs the powder into a receiving can located in a glove box. One possible scenario for a criticality accident is the exit chute becoming blocked with powder near its discharge. The blockage restricts the flow of powder causing the exit chute to become filled with the powder. If blockage does occur, the height of the powder could reach a level that would not be safe from a criticality point of view. In this analysis, the subcritical height limit is examined for 98% enriched U 3 O 8 in the exit chute with full water reflection and optimal water moderation. The height limit for ensuring criticality safety during such an accumulation is 28.2 cm above the top of the discharge pipe at the bottom of the chute. Chute design variations are also evaluated with full water reflection and optimal water moderation. Subcritical configurations for the exit chute variation are developed, but the configurations are not safe when combined with the calciner. To ensure criticality safety, modifications must be made to the calciner tube or safety measures must be implemented if these designs are to be utilized with 98% enriched material. A geometrically safe configuration for the exit chute is developed for a blockage of 20% enriched powder with full water reflection and optimal water moderation, and this configuration is safe when combined with the existing calciner

Criticality safety analysis for plutonium dissolver using silver mediated electrolytic oxidation method

International Nuclear Information System (INIS)

Umeda, Miki; Sugikawa, Susumu; Nakamura, Kazuhito; Egashira, Tetsurou

1998-08-01

Design and construction of a plutonium dissolver using silver mediated electrolytic oxidation method are promoted in NUCEF. Criticality safety analysis for the plutonium dissolver is described in this report. The electrolytic plutonium dissolver consists of connection pipes and three pots for MOX powder supply, circulation and electrolysis. The criticality control for the dissolver is made by geometrically safe shape with mass limitation. Monte Carlo code KENO-IV using MGCL-137 library based on ENDF/B-IV was used for the criticality safety analysis for the plutonium dissolver. Considering the required size for construction and criticality safety, diameter of pot and distance between two pots were determined. On this condition, the criticality safety analysis for the plutonium dissolver with connection pipes was carried out. As the result of the criticality safety analysis, an effective neutron multiplication factor keff of 0.91 was obtained and the criticality safety of the plutonium dissolver was confirmed on the basis of criteria of ≤0.95. (author)

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

International Nuclear Information System (INIS)

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

2016-01-01

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study. Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2 /H 2 O binary mixtures are computationally studied here for the first time and their critical parameters are reported.

Study of Advanced Oxidation System for Water Treatment

International Nuclear Information System (INIS)

Widdi Usada; Bambang Siswanto; Suryadi; Agus Purwadi; Isyuniarto

2007-01-01

Hygiene water is still a big problem globally as well as energy and food, especially in Indonesia where more than 70 % lived in Java island. One of the efforts in treating hygiene water is to recycle the used water. In this case it is needed clean water technology. Many methods have been done, this paper describes the advanced oxidation technology system based on ozone, titania and plasma discharge. (author)

Iron oxidation kinetics and phosphorus immobilization at the groundwater-surface water interface

Science.gov (United States)

van der Grift, Bas; Rozemeijer, Joachim; Griffioen, Jasper; van der Velde, Ype

2014-05-01

Eutrophication of freshwater environments following diffuse nutrient loads is a widely recognized water quality problem in catchments. Fluxes of non-point P sources to surface waters originate from surface runoff and flow from soil water and groundwater into surface water. The availability of P in surface waters is controlled strongly by biogeochemical nutrient cycling processes at the soil-water interface. The mechanisms and rates of the iron oxidation process with associated binding of phosphate during exfiltration of anaerobic Fe(II) bearing groundwater are among the key unknowns in P retention processes in surface waters in delta areas where the shallow groundwater is typically pH-neutral to slightly acid, anoxic, iron-rich. We developed an experimental field set-up to study the dynamics in Fe(II) oxidation and mechanisms of P immobilization at the groundwater-surface water interface in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. The exfiltrating groundwater was captured in in-stream reservoirs constructed in the ditch. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we quantified Fe(II) oxidation kinetics and P immobilization processes across the seasons. This study showed that seasonal changes in climatic conditions affect the Fe(II) oxidation process. In winter time the dissolved iron concentrations in the in-stream reservoirs reached the levels of the anaerobic groundwater. In summer time, the dissolved iron concentrations of the water in the reservoirs are low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into the reservoirs. Higher discharges, lower temperatures and lower pH of the exfiltrated groundwater in winter compared to summer shifts the location of the redox transition zone

Cholesterol Protects the Oxidized Lipid Bilayer from Water Injury

DEFF Research Database (Denmark)

Owen, Michael C; Kulig, Waldemar; Rog, Tomasz

2018-01-01

In an effort to delineate how cholesterol protects membrane structure under oxidative stress conditions, we monitored the changes to the structure of lipid bilayers comprising 30 mol% cholesterol and an increasing concentration of Class B oxidized 1-palmitoyl-2-oleoylphosphatidylcholine (POPC...... in a characteristic reduction in bilayer thickness and increase in area per lipid, thereby increasing the exposure of the membrane hydrophobic region to water. However, cholesterol was observed to help reduce water injury by moving into the bilayer core and forming more hydrogen bonds with the oxPLs. Cholesterol also...... resists altering its tilt angle, helping to maintain membrane integrity. Water that enters the 1-nm-thick core region remains part of the bulk water on either side of the bilayer, with relatively few water molecules able to traverse through the bilayer. In cholesterol-rich membranes, the bilayer does...

Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR)

Energy Technology Data Exchange (ETDEWEB)

Roth, Justine P. [Johns Hopkins Univ., Baltimore, MD (United States)

2015-03-03

Isotopic Studies of O-O Bond Formation During Water Oxidation (SISGR) Research during the project period focused primarily on mechanisms of water oxidation by structurally defined transition metal complexes. Competitive oxygen isotope fractionation of water, mediated by oxidized precursors or reduced catalysts together with ceric, Ce(IV), ammonium nitrate in aqueous media, afforded oxygen-18 kinetic isotope effects (O-18 KIEs). Measurement, calculation, and interpretation of O-18 KIEs, described in the accompanying report has important ramifications for the production of electricity and solar hydrogen (as fuel). The catalysis division of BES has acknowledged that understanding mechanisms of transition metal catalyzed water oxidation has major ramifications, potentially leading to transformation of the global economy and natural environment in years to come. Yet, because of program restructuring and decreased availability of funds, it was recommended that the Solar Photochemistry sub-division of BES would be a more appropriate parent program for support of continued research.

Critical experiments simulating accidental water immersion of highly enriched uranium dioxide fuel elements

International Nuclear Information System (INIS)

Ponomarev-Stepnoi, N.N.; Glushkov, L.S.

2003-01-01

The paper focuses on experimental analysis of nuclear criticality safety at accidental water immersion of fuel elements of the Russian TOPAZ-2 space nuclear power system reactor. The structure of water-moderated heterogeneous critical assemblies at the NARCISS facility is described in detail, including sizes, compositions, densities of materials of the main assembly components for various core configurations. Critical parameters of the assemblies measured for varying number of fuel elements, height of fuel material in fuel elements and their arrangement in the water moderator with a uniform or variable spacing are presented. It has been found from the experiments that at accidental water immersion of fuel elements involved, the minimum critical mass equal to approximately 20 kg of uranium dioxide is achieved at 31-37 fuel elements. The paper gives an example of a physical model of the water-moderated heterogeneous critical assembly with a detailed characterization of its main components that can be used for calculations using different neutronic codes, including Monte Carlo ones. (author)

Electrochemical Water-Splitting Based on Hypochlorite Oxidation

Czech Academy of Sciences Publication Activity Database

Minhová Macounová, Kateřina; Simic, N.; Ahlberg, E.; Krtil, Petr

2015-01-01

Roč. 137, č. 23 (2015), s. 7262-7265 ISSN 0002-7863 Institutional support: RVO:61388955 Keywords : electrochemistry * hypochlorite oxidation * water-splitting Subject RIV: CG - Electrochemistry Impact factor: 13.038, year: 2015

Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

International Nuclear Information System (INIS)

Liu, C.-J.; Wu, T.-H.; Hsu, L.-L.; Wang, J.-S.; Chen, S.-Y.

2007-01-01

By deintercalation of Na + followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of γ-Na 0.7 CoO 2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na 0.35 (H 2 O) 1.3 CoO 2-δ with the c-axis expanded from c ∼ 10.9 A to c ∼ 19.6 A. In this paper, we demonstrate that the superconducting phase of c ∼ 19.6 A can be directly obtained by simply immersing γ-Na 0.7 CoO 2 powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c ∼ 19.6 A phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides

Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

Science.gov (United States)

Liu, Chia-Jyi; Wu, Tsung-Hsien; Hsu, Lin-Li; Wang, Jung-Sheng; Chen, Shu-Yo

2007-09-01

By deintercalation of Na+ followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of γ-Na0.7CoO2 undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na0.35(H2O)1.3CoO2-δ with the c-axis expanded from c ≈ 10.9 Å to c ≈ 19.6 Å. In this paper, we demonstrate that the superconducting phase of c ≈ 19.6 Å can be directly obtained by simply immersing γ-Na0.7CoO2 powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c ≈ 19.6 Å phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides.

Synthesis of superconducting cobalt oxyhydrates using a novel method: Electrolyzed and oxidized water

Energy Technology Data Exchange (ETDEWEB)

Liu, C.-J. [Department of Physics, National Changhua University of Education, Changhua 50007, Taiwan (China)], E-mail: liucj@cc.ncue.edu.tw; Wu, T.-H.; Hsu, L.-L.; Wang, J.-S.; Chen, S.-Y. [Department of Physics, National Changhua University of Education, Changhua 50007, Taiwan (China)

2007-09-01

By deintercalation of Na{sup +} followed by inserting bilayers of water molecules into the host lattice, the layered cobalt oxide of {gamma}-Na{sub 0.7}CoO{sub 2} undergoes a topotactic transformation to a layered cobalt oxyhydrate of Na{sub 0.35}(H{sub 2}O){sub 1.3}CoO{sub 2-{delta}} with the c-axis expanded from c {approx} 10.9 A to c {approx} 19.6 A. In this paper, we demonstrate that the superconducting phase of c {approx} 19.6 A can be directly obtained by simply immersing {gamma}-Na{sub 0.7}CoO{sub 2} powders in electrolyzed/oxidized (EO) water, which is readily available from a commercial electrolyzed water generator. We found that high oxidation-reduction potential of EO water drives the oxidation of the cobalt ions accompanying by the formation of the superconductive c {approx} 19.6 A phase. Our results demonstrate how EO water can be used to oxidize the cobalt ions and hence form superconducting cobalt oxyhydrates in a clean and simple way and may provide an economic and environment-friendly route to oxidize the transition metal of complex metal oxides.

Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters

Science.gov (United States)

Ward, B. B.; Kilpatrick, K. A.; Novelli, P. C.; Scranton, M. I.

1987-01-01

Measured biological oxidation rates of methane in near-surface waters of the Cariaco Basin are compared with the diffusional fluxes computed from concentration gradients of methane in the surface layer. Methane fluxes and oxidation rates were investigated in surface waters, at the oxic/anoxic interface, and in deep anoxic waters. It is shown that the surface-waters oxidation of methane is a mechanism which modulates the flux of methane from marine waters to the atmosphere.

Destruction of an industrial wastewater by supercritical water oxidation in a transpiring wall reactor

International Nuclear Information System (INIS)

Bermejo, M.D.; Cocero, M.J.

2006-01-01

The supercritical water oxidation (SCWO) is a technology that takes advantage of the special properties of water in the surroundings of critical point of water to completely oxidize wastes in residence times lower than 1 min. The problems caused by the harsh operational conditions of the SCWO process are being solved by new reactor designs, such as the transpiring wall reactor (TWR). In this work, the operational parameters of a TWR have been studied for the treatment of an industrial wastewater. As a result, the process has been optimized for a feed flow of 16 kg/h with feed inlet temperatures higher than 300 deg. C and transpiring flow relation (R) between 0.2 and 0.6 working with an 8% (w/w) isopropanol (IPA) as a fuel. The experimental data and a mathematical model have been applied for the destruction of an industrial waste containing acetic acid and crotonaldehyde as main compounds. As the model predicted, removal efficiencies higher than 99.9% were obtained, resulting in effluents with 2 ppm total organic carbon (TOC) at feed flow of 16 kg/h, 320 deg. C of feed temperature and R = 0.32. An effluent TOC of 35 ppm under conditions feed flow of 18 kg/h, feed inlet temperatures of 290 deg. C, reaction temperatures of 570 deg. C and R = 0.6

Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films.

Science.gov (United States)

Sun, Ke; Saadi, Fadl H; Lichterman, Michael F; Hale, William G; Wang, Hsin-Ping; Zhou, Xinghao; Plymale, Noah T; Omelchenko, Stefan T; He, Jr-Hau; Papadantonakis, Kimberly M; Brunschwig, Bruce S; Lewis, Nathan S

2015-03-24

Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiOx films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O2(g).

Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films

KAUST Repository

Sun, Ke; Saadi, Fadl H.; Lichterman, Michael F.; Hale, William G.; Wang, Hsinping; Zhou, Xinghao; Plymale, Noah T.; Omelchenko, Stefan T.; He, Jr-Hau; Papadantonakis, Kimberly M.; Brunschwig, Bruce S.; Lewis, Nathan S.

2015-01-01

Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide

Water: A Critical Material Enabling Space Exploration

Science.gov (United States)

Pickering, Karen D.

2014-01-01

Water is one of the most critical materials in human spaceflight. The availability of water defines the duration of a space mission; the volume of water required for a long-duration space mission becomes too large, heavy, and expensive for launch vehicles to carry. Since the mission duration is limited by the amount of water a space vehicle can carry, the capability to recycle water enables space exploration. In addition, water management in microgravity impacts spaceflight in other respects, such as the recent emergency termination of a spacewalk caused by free water in an astronaut's spacesuit helmet. A variety of separation technologies are used onboard spacecraft to ensure that water is always available for use, and meets the stringent water quality required for human space exploration. These separation technologies are often adapted for use in a microgravity environment, where water behaves in unique ways. The use of distillation, membrane processes, ion exchange and granular activated carbon will be reviewed. Examples of microgravity effects on operations will also be presented. A roadmap for future technologies, needed to supply water resources for the exploration of Mars, will also be reviewed.

Oxidation behavior of steels and Alloy 800 in supercritical water

International Nuclear Information System (INIS)

Olmedo, A.M.; Bordoni, R.; Dominguez, G.; Alvarez, M.G.

2011-01-01

The oxidation behavior of a ferritic-martensitic steel T91 and a martensitic steel AISI 403 up to 750 h, and of AISI 316L and Alloy 800 up to 336 h in deaerated supercritical water, 450ºC-25 MPa, was investigated in this paper. After exposure up to 750 h, the weight gain data, for steels T91 and AISI 403, was fitted by ∆W=k t n , were n are similar for both steels and k is a little higher for T91. The oxide films grown in the steels were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction. The films were adherent and exhibited a low porosity. For this low oxygen content supercritical water exposure, the oxide scale exhibited a typical duplex structure, in which the scale is composed of an outer iron oxide layer of magnetite (Fe 3 O 4 ) and an inner iron/chromium oxide layer of a non-stoichiometric iron chromite (Fe,Cr) 3 O 4 . Preliminary results, with AISI 316L and Alloy 800, for two exposure periods (168 and 336 h), are also reported. The morphology shown for the oxide films grown on both materials up to 336 h of oxidation in supercritical water, resembles that of a duplex layer film like that shown by stainless steels and Alloy 800 oxide films grown in a in a high temperature and pressure (220-350ºC) of a primary or secondary coolant of a plant. (author) [es

Electrochemical Water Oxidation by a Catalyst-Modified Metal-Organic Framework Thin Film

Energy Technology Data Exchange (ETDEWEB)

Lin, Shaoyang; Pineda-Galvan, Yuliana; Maza, William A.; Epley, Charity C.; Zhu, Jie; Kessinger, Matthew C.; Pushkar, Yulia; Morris, Amanda J. (VP); (Purdue)

2016-12-15

Water oxidation, a key component in artificial photosynthesis, requires high overpotentials and exhibits slow reaction kinetics that necessitates the use of stable and efficient heterogeneous water-oxidation catalysts (WOCs). Here, we report the synthesis of UiO-67 metal–organic framework (MOF) thin films doped with [Ru(tpy)(dcbpy)OH2]2+ (tpy=2,2':6',2''-terpyridine, dcbpy=5,5'-dicarboxy-2,2'-bipyridine) on conducting surfaces and their propensity for electrochemical water oxidation. The electrocatalyst oxidized water with a turnover frequency (TOF) of (0.2±0.1) s-1 at 1.71 V versus the normal hydrogen electrode (NHE) in buffered solution (pH~7) and exhibited structural and electrochemical stability. The electroactive sites were distributed throughout the MOF thin film on the basis of scan-ratedependent voltammetry studies. This work demonstrates a promising way to immobilize large concentrations of electroactive WOCs into a highly robust MOF scaffold and paves the way for future photoelectrochemical water-splitting systems.

Highly Enhanced Photoelectrochemical Water Oxidation Efficiency Based on Triadic Quantum Dot/Layered Double Hydroxide/BiVO ₄ Photoanodes

Energy Technology Data Exchange (ETDEWEB)

Tang, Yanqun; Wang, Ruirui; Yang, Ye; Yan, Dongpeng; Xiang, Xu

2016-08-03

The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is -1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.

Electrocatalytic Water Oxidation by a Homogeneous Copper Catalyst Disfavors Single-Site Mechanisms.

Science.gov (United States)

Koepke, Sara J; Light, Kenneth M; VanNatta, Peter E; Wiley, Keaton M; Kieber-Emmons, Matthew T

2017-06-28

Deployment of solar fuels derived from water requires robust oxygen-evolving catalysts made from earth abundant materials. Copper has recently received much attention in this regard. Mechanistic parallels between Cu and single-site Ru/Ir/Mn water oxidation catalysts, including intermediacy of terminal Cu oxo/oxyl species, are prevalent in the literature; however, intermediacy of late transition metal oxo species would be remarkable given the high d-electron count would fill antibonding orbitals, making these species high in energy. This may suggest alternate pathways are at work in copper-based water oxidation. This report characterizes a dinuclear copper water oxidation catalyst, {[(L)Cu(II)] 2 -(μ-OH) 2 }(OTf) 2 (L = Me 2 TMPA = bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine) in which water oxidation proceeds with high Faradaic efficiency (>90%) and moderate rates (33 s -1 at ∼1 V overpotential, pH 12.5). A large kinetic isotope effect (k H /k D = 20) suggests proton coupled electron transfer in the initial oxidation as the rate-determining step. This species partially dissociates in aqueous solution at pH 12.5 to generate a mononuclear {[(L)Cu(II)(OH)]} + adduct (K eq = 0.0041). Calculations that reproduce the experimental findings reveal that oxidation of either the mononuclear or dinuclear species results in a common dinuclear intermediate, {[LCu(III)] 2 -(μ-O) 2 } 2+ , which avoids formation of terminal Cu(IV)═O/Cu(III)-O • intermediates. Calculations further reveal that both intermolecular water nucleophilic attack and redox isomerization of {[LCu(III)] 2 -(μ-O) 2 } 2+ are energetically accessible pathways for O-O bond formation. The consequences of these findings are discussed in relation to differences in water oxidation pathways between Cu catalysts and catalysts based on Ru, Ir, and Mn.

Reprint of "How do components of real cloud water affect aqueous pyruvate oxidation?"

Science.gov (United States)

Boris, Alexandra J.; Desyaterik, Yury; Collett, Jeffrey L.

2015-01-01

Chemical oxidation of dissolved volatile or semi-volatile organic compounds within fog and cloud droplets in the atmosphere could be a major pathway for secondary organic aerosol (SOA) formation. This proposed pathway consists of: (1) dissolution of organic chemicals from the gas phase into a droplet; (2) reaction with an aqueous phase oxidant to yield low volatility products; and (3) formation of particle phase organic matter as the droplet evaporates. The common approach to simulating aqueous SOA (aqSOA) reactions is photo-oxidation of laboratory standards in pure water. Reactions leading to aqSOA formation should be studied within real cloud and fog water to determine whether additional competing processes might alter apparent rates of reaction as indicated by rates of reactant loss or product formation. To evaluate and identify the origin of any cloud water matrix effects on one example of observed aqSOA production, pyruvate oxidation experiments simulating aqSOA formation were monitored within pure water, real cloud water samples, and an aqueous solution of inorganic salts. Two analysis methods were used: online electrospray ionization high-resolution time-of-flight mass spectrometry (ESI-HR-ToF-MS), and offline anion exchange chromatography (IC) with quantitative conductivity and qualitative ESI-HR-ToF-MS detection. The apparent rate of oxidation of pyruvate was slowed in cloud water matrices: overall measured degradation rates of pyruvate were lower than in pure water. This can be at least partially accounted for by the observed formation of pyruvate from reactions of other cloud water components. Organic constituents of cloud water also compete for oxidants and/or UV light, contributing to the observed slowed degradation rates of pyruvate. The oxidation of pyruvate was not significantly affected by the presence of inorganic anions (nitrate and sulfate) at cloud-relevant concentrations. Future bulk studies of aqSOA formation reactions using simplified

Critical water stress levels in Pinus patula seedlings and their ...

African Journals Online (AJOL)

Critical water stress levels in Pinus patula seedlings and their relation to measures of seedling morphology. ... Southern Forests: a Journal of Forest Science ... A pot trial was implemented to determine the effect of soil water stress following transplanting on shoot water potential and stomatal conductance of Pinus patula ...

Critical behavior in the system cyclopentanone + water + secondary butyl alcohol

Science.gov (United States)

Krishna, U. Santhi; Unni, P. K. Madhavan

2018-05-01

We report detailed measurements of coexistence surface in the ternary system cylcopentanone + water + secondary butyl alcohol. The coexistence surface is seen to have an unusual tunnel like feature and is a potential system in which special critical points such as the Quadruple Critical Point (QCP) could be studied. Analysis of coexistence curves indicates that the system shows 3D-Ising like critical behavior.

Molecular water oxidation mechanisms followed by transition metals: state of the art.

Science.gov (United States)

Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

2014-02-18

One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for

Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films

KAUST Repository

Sun, Ke

2015-03-11

Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiOx films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O2(g). © 2015, National Academy of Sciences. All rights reserved.

Oxidation of oily sludge in supercritical water

International Nuclear Information System (INIS)

Cui Baochen; Cui Fuyi; Jing Guolin; Xu Shengli; Huo Weijing; Liu Shuzhi

2009-01-01

The oxidation of oily sludge in supercritical water is performed in a batch reactor at reaction temperatures between 663 and 723 K, the reaction times between 1 and 10 min and pressure between 23 and 27 MPa. Effect of reaction parameters such as reaction time, temperature, pressure, O 2 excess and initial COD on oxidation of oily sludge is investigated. The results indicate that chemical oxygen demand (COD) removal rate of 92% can be reached in 10 min. COD removal rate increases as the reaction time, temperature and initial COD increase. Pressure and O 2 excess have no remarkable affect on reaction. By taking into account the dependence of reaction rate on COD concentration, a global power-law rate expression was regressed from experimental data. The resulting pre-exponential factor was 8.99 x 10 14 (mol L -1 ) -0.405 s -1 ; the activation energy was 213.13 ± 1.33 kJ/mol; and the reaction order for oily sludge (based on COD) is 1.405. It was concluded that supercritical water oxidation (SCWO) is a rapidly emerging oily sludge processing technology.

Alpha Radiolysis of Sorbed Water on Uranium Oxides and Uranium Oxyfluorides

Energy Technology Data Exchange (ETDEWEB)

Icenhour, A.S.

2003-09-10

The radiolysis of sorbed water and other impurities contained in actinide oxides has been the focus of a number of studies related to the establishment of criteria for the safe storage and transport of these materials. Gamma radiolysis studies have previously been performed on uranium oxides and oxyfluorides (UO{sub 3}, U{sub 3}O{sub 8}, and UO{sub 2}F{sub 2}) to evaluate the long-term storage characteristics of {sup 233}U. This report describes a similar study for alpha radiolysis. Uranium oxides and oxyfluorides (with {sup 238}U as the surrogate for {sup 233}U) were subjected to relatively high alpha radiation doses (235 to 634 MGy) by doping with {sup 244}Cm. The typical irradiation time for these samples was about 1.5 years, which would be equivalent to more than 50 years irradiation by a {sup 233}U sample. Both dry and wet (up to 10 wt % water) samples were examined in an effort to identify the gas pressure and composition changes that occurred as a result of radiolysis. This study shows that several competing reactions occur during radiolysis, with the net effect that only very low pressures of hydrogen, nitrogen, and carbon dioxide are generated from the water, nitrate, and carbon impurities, respectively, associated with the oxides. In the absence of nitrate impurities, no pressures greater than 1000 torr are generated. Usually, however, the oxygen in the air atmosphere over the oxides is consumed with the corresponding oxidation of the uranium oxide. In the presence of up to 10 wt % water, the oxides first show a small pressure rise followed by a net decrease due to the oxygen consumption and the attainment of a steady-state pressure where the rate of generation of gaseous components is balanced by their recombination and/or consumption in the oxide phase. These results clearly demonstrate that alpha radiolysis of either wet or dry {sup 233}U oxides will not produce deleterious pressures or gaseous components that could compromise the long-term storage of

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni A.

2014-01-01

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses

Electrochemical Oxidation of PAHs in Water from Harbor Sediment Purification

DEFF Research Database (Denmark)

Muff, Jens; Søgaard, Erik Gydesen

2010-01-01

generated oxidant solution with a free chlorine concentration of 2 gL-1. Both strategies resulted in a successful degradation of 5 PAHs to fulfil the discharge limit on 0.010 µgL-1. The intermixing-with-oxidant approach can also be applied as a method to address the actual sediment matrix....... of the discharge water addressing primarily polycyclic aromatic hydrocarbons (PAHs). PAHs are by-products of incomplete combustion of organic materials with recalcitrant and strong mutagenic/carcinogenic properties, due to their benzene analogue structures. PAHs are hydrophobic compounds and their persistence...... evidence for the importance of the indirect oxidation mechanism in the degradation of the PAHs. The proof-of-concept study was conducted both by a direct treatment approach and an intermixing-with-oxidant approach, where the contaminated water was intermixed in different ratios with an electrochemically...

Heats of immersion in the thorium oxide-water system at elevated temperatures

International Nuclear Information System (INIS)

Holmes, H.F.

1976-01-01

The surface properties of ThO 2 were studied by heat of immersion calorimetry at 25 to 200 0 C. Results show that the integral heat of immersion of thorium oxide contains contributions which reflect considerable interaction with several layers of water adjacent to the oxide surface. It would be desirable to know the heat capacity changes which occur in the multilayer adsorption of water on an oxide surface. However, such data are not available and their acquisition would be an extremely difficult task. Structuring (a negative ΔCp) of several layers of water (by increased hydrogen bonding) adjacent to an oxide surface could explain an increase in the heat of immersion as the immersion temperature is increased. The more energetic, heterogeneous, high-surface-area samples are expected to induce more order in the adjacent water layers than the less energetic samples. This interpretation is similar to that offered for the temperature dependence of the heat of solution of the alkali halides

Effect of metal oxide nanoparticles on Godavari river water treatment

Science.gov (United States)

Goud, Ravi Kumar; Ajay Kumar, V.; Reddy, T. Rakesh; Vinod, B.; Shravani, S.

2018-05-01

Nowadays there is a continuously increasing worldwide concern for the development of water treatment technologies. In the area of water purification, nanotechnology offers the possibility of an efficient removal of pollutants and germs. Nanomaterials reveal good results than other techniques used in water treatment because of its high surface area to volume ratio. In the present work, iron oxide and copper oxide nanoparticles were synthesized by simple heating method. The synthesized nanoparticles were used to purify Godavari river water. The effect of nanoparticles at 70°C temperature, 12 centimeter of sand bed height and pH of 8 shows good results as compared to simple sand bed filter. The attained values of BOD5, COD and Turbidity were in permissible limit of world health organization.

Biological iron oxidation by Gallionella spp. in drinking water production under fully aerated conditions.

Science.gov (United States)

de Vet, W W J M; Dinkla, I J T; Rietveld, L C; van Loosdrecht, M C M

2011-11-01

Iron oxidation under neutral conditions (pH 6.5-8) may be a homo- or heterogeneous chemically- or a biologically-mediated process. The chemical oxidation is supposed to outpace the biological process under slightly alkaline conditions (pH 7-8). The iron oxidation kinetics and growth of Gallionella spp. - obligatory chemolithotrophic iron oxidizers - were assessed in natural, organic carbon-containing water, in continuous lab-scale reactors and full-scale groundwater trickling filters in the Netherlands. From Gallionella cell numbers determined by qPCR, balances were made for all systems. The homogeneous chemical iron oxidation occurred in accordance with the literature, but was retarded by a low water temperature (13 °C). The contribution of the heterogeneous chemical oxidation was, despite the presence of freshly formed iron oxyhydroxides, much lower than in previous studies in ultrapure water. This could be caused by the adsorption of natural organic matter (NOM) on the iron oxide surfaces. In the oxygen-saturated natural water with a pH ranging from 6.5 to 7.7, Gallionella spp. grew uninhibited and biological iron oxidation was an important, and probably the dominant, process. Gallionella growth was not even inhibited in a full-scale filter after plate aeration. From this we conclude that Gallionella spp. can grow under neutral pH and fully aerated conditions when the chemical iron oxidation is retarded by low water temperature and inhibition of the autocatalytic iron oxidation. Copyright © 2011 Elsevier Ltd. All rights reserved.

The Manipulation of Hydrophobicity in Catalyst Design for Applications of Aerobic Alcohols Oxidation and Electrocatalytic Water Oxidation

KAUST Repository

Chen, Batian

2016-05-17

Hydrophobicity is the generalized characteristic of non-polar substances that brings about their exclusion from aqueous phases. This property, entropic in its nature, drives key self-assembly and phase separation processes in water. Protein folding, the formation of DNA double helix, the existence of lipid bilayers and the wetting properties of leaf surfaces are all due to hydrophobic interactions. Inspired by Nature, we aimed to use hydrophobicity for creating novel and improved catalytic systems. (I) A number of fluorous amphiphilic star block-copolymers containing a tris(benzyltriazolylmethyl)amine motif have been prepared. These polymers assembled into well-defined nanostructures in water, and their mode of assembly could be controlled by changing the composition of the polymer. The polymers were used for enzyme-inspired catalysis of alcohol oxidation. (II) An enzyme-inspired catalytic system based on a rationally designed multifunctional surfactant was developed. The resulting micelles feature metal-binding sites and stable free radical moieties as well as fluorous pockets that attract and preconcentrate molecular oxygen. In the presence of copper ions, the micelles effect chemoselective aerobic alcohol oxidation under ambient conditions in water, a transformation that is challenging to achieve nonenzymatically. (III) Development of a facile means of photo/electrocatalytic water splitting is one of the main barriers to establishing of a solar hydrogen economy. Of the two half-reactions involved in splitting water into O2 and H2, water oxidation presents the most challenge due to its mechanistic complexity. A practical water oxidation catalyst must be highly active, yet inexpensive and indefinitely stable under harsh oxidative conditions. Here, I shall describe the synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine, (BimH)3. A wide range of catalysts differing in their electronic properties

Water-oxidation catalysis by synthetic manganese oxides--systematic variations of the calcium birnessite theme.

Science.gov (United States)

Frey, Carolin E; Wiechen, Mathias; Kurz, Philipp

2014-03-21

Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction for the conversion of renewable energy into storable fuels. High catalytic rates were especially observed for birnessites which contain calcium as part of their structures. With the aim to systematically improve the catalytic performance of such oxide materials, we used a flexible synthetic route to prepare three series of calcium birnessites, where we varied the calcium concentrations, the ripening times of the original precipitates and the temperature of the heat treatment following the initial synthetic steps (tempering) during the preparation process. The products were carefully analysed by a number of analytical techniques and then probed for WOC activity using the Ce(4+)-system. We find that our set of twenty closely related manganese oxides shows large, but somewhat systematic alterations in catalytic rates, indicating the importance of synthesis parameters for maximum catalytic performance. The catalyst of the series for which the highest water-oxidation rate was found is a birnessite of medium calcium content (Ca : Mn ratio 0.2 : 1) that had been subjected to a tempering temperature of 400 °C. On the basis of the detailed analysis of the results, a WOC reaction scheme for birnessites is proposed to explain the observed trends in reactivity.

BWR [boiling water reactor] core criticality versus water level during an ATWS [anticipated transient without scram] event

International Nuclear Information System (INIS)

Sehgal, B.R.; Peng, C.M.; Maly, J.

1988-01-01

The BWR [boiling water reactor] emergency procedures guidelines recommend management of core water level to reduce the power generated during an anticipated transient without scram (ATWS) event. BWR power level variation has traditionally been calculated in the system codes using a 1-D [one-dimensional] 2-group neutron kinetics model to determine criticality. This methodology used also for calculating criticality of the partially covered BWR cores has, however, never been validated against data. In this paper, the power level versus water level issues in an ATWS severe accident are introduced and the accuracy of the traditional methodology is investigated by comparing with measured data. It is found that the 1-D 2-group treatment is not adequate for accurate predictions of criticality and therefore the system power level for the water level variations that may be encountered in a prototypical ATWS severe accident. It is believed that the current predictions for power level may be too high

N-nitrosodimethylamine (NDMA) formation potential of amine-based water treatment polymers: Effects of in situ chloramination, breakpoint chlorination, and pre-oxidation.

Science.gov (United States)

Park, Sang Hyuck; Padhye, Lokesh P; Wang, Pei; Cho, Min; Kim, Jae-Hong; Huang, Ching-Hua

2015-01-23

Recent studies show that cationic amine-based water treatment polymers may be important precursors that contribute to formation of the probable human carcinogen N-nitrosodimethylamine (NDMA) during water treatment and disinfection. To better understand how water treatment parameters affect NDMA formation from the polymers, the effects of in situ chloramination, breakpoint chlorination, and pre-oxidation on the NDMA formation from the polymers were investigated. NDMA formation potential (NDMA-FP) as well as dimethylamine (DMA) residual concentration were measured from poly(epichlorohydrin dimethylamine) (polyamine) and poly(diallyldimethylammonium chloride) (polyDADMAC) solutions upon reactions with oxidants including free chlorine, chlorine dioxide, ozone, and monochloramine under different treatment conditions. The results supported that dichloramine (NHCl2) formation was the critical factor affecting NDMA formation from the polymers during in situ chloramination. The highest NDMA formation from the polymers occurred near the breakpoint of chlorination. Polymer chain breakdown and transformation of the released DMA and other intermediates were important factors affecting NDMA formation from the polymers in pre-oxidation followed by post-chloramination. Pre-oxidation generally reduced NDMA-FP of the polymers; however, the treatments involving pre-ozonation increased polyDADMAC's NDMA-FP and DMA release. The strategies for reducing NDMA formation from the polymers may include the avoidance of the conditions favorable to NHCl2 formation and the avoidance of polymer exposure to strong oxidants such as ozone. Copyright © 2014 Elsevier B.V. All rights reserved.

Heavy water critical experiments on plutonium lattice

International Nuclear Information System (INIS)

Miyawaki, Yoshio; Shiba, Kiminori

1975-06-01

This report is the summary of physics study on plutonium lattice made in Heavy Water Critical Experiment Section of PNC. By using Deuterium Critical Assembly, physics study on plutonium lattice has been carried out since 1972. Experiments on following items were performed in a core having 22.5 cm square lattice pitch. (1) Material buckling (2) Lattice parameters (3) Local power distribution factor (4) Gross flux distribution in two region core (5) Control rod worth. Experimental results were compared with theoretical ones calculated by METHUSELAH II code. It is concluded from this study that calculation by METHUSELAH II code has acceptable accuracy in the prediction on plutonium lattice. (author)

Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water

Science.gov (United States)

van der Grift, B.; Rozemeijer, J. C.; Griffioen, J.; van der Velde, Y.

2014-11-01

The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients

Chlorination of bromide-containing waters: Enhanced bromate formation in the presence ofsynthetic metal oxides and deposits formed indrinking water distribution systems

KAUST Repository

Liu, Chao; von Gunten, Urs; Croue, Jean-Philippe

2013-01-01

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate>>sulfate>bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. © 2013 Elsevier Ltd.

Chlorination of bromide-containing waters: Enhanced bromate formation in the presence ofsynthetic metal oxides and deposits formed indrinking water distribution systems

KAUST Repository

Liu, Chao

2013-09-01

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate>>sulfate>bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. © 2013 Elsevier Ltd.

The anti-aging and anti-oxidation effects of tea water extract in Caenorhabditis elegans.

Science.gov (United States)

Fei, Tianyi; Fei, Jian; Huang, Fang; Xie, Tianpei; Xu, Jifeng; Zhou, Yi; Yang, Ping

2017-10-15

Tea includes puer tea, black tea, green tea and many others. By using model organism Caenorhabditis elegans, the anti-aging and anti-oxidation effects of tea water extract were systemically examined in this study. We found that water extract of puer tea, black tea and green tea all increased the lifespan of worms, postponed Aβ-induced progressive paralysis in Alzheimer's disease transgenic worms, and improved the tolerance of worms to the oxidative stress induced by heavy metal Cr 6+ . Moreover, the anti-oxidation effects of tea water extract at low concentration were different among 4 kinds of brands of green tea. The underlying mechanisms were further explored using genetically manipulated-mutant worms. The anti-oxidative stress effects of green tea water extract depend on the dietary restriction and germline signaling pathways, but not the FOXO and mitochondrial respiratory chain signals. Therefore, tea water extract provides benefits of anti-aging, anti-AD and anti-oxidation. Copyright © 2017. Published by Elsevier Inc.

Examination of Critical Length Effect in Copper Interconnects With Oxide and Low-k Dielectrics

International Nuclear Information System (INIS)

Thrasher, Stacye; Gall, Martin; Justison, Patrick; Hernandez, Richard; Kawasaki, Hisao; Capasso, Cristiano; Nguyen, Timothy

2004-01-01

As technology moves toward faster microelectronic devices with smaller feature sizes, copper is replacing aluminum-copper alloy and low-k dielectric is replacing oxide as the materials of choice for advanced interconnect integrations. Copper not only brings to the table the advantage of lower resistivity, but also exhibits better electromigration performance when compared to Al(Cu). Low-k dielectric materials are advantageous because they reduce power consumption and improve signal delay. Due to these advantages, the industry trend is moving towards integrating copper and low-k dielectric for high performance interconnects. The purpose of this study is to evaluate the critical length effect in single-inlaid copper interconnects and determine the critical product (jl)c, for a variety of integrations, examining the effect of ILD (oxide vs. low-k), geometry, and stress temperature

Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

2012-04-28

CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered. This journal is © The Royal Society of Chemistry 2012

The potential of large critical currents in the high Tc oxides

International Nuclear Information System (INIS)

Deutcher, G.

1993-01-01

The potential for high critical current densities is examined. on a thermodynamical basis, the energy scale for vortex pinning can be derived for instance from a measurement of the width of the critical region. This energy scale is of the order of 0.2 eV in YBCO, which is sufficient for practical applications. Another important parameter is the short coherence length. The inner plane length, of the order of a few lattice spacing, is favorable for pinning by point defects. But the very short outer plane length gives rise to anomalous magnetic behavior, unfavorable for high-field applications at high temperature; this is true in particular in most anisotropic oxides, such as the Bi compounds (author)

COAL CONVERSION WASTEWATER TREATMENT BY CATALYTIC OXIDATION IN SUPERCRITICAL WATER; FINAL

International Nuclear Information System (INIS)

Phillip E. Savage

1999-01-01

Wastewaters from coal-conversion processes contain phenolic compounds in appreciable concentrations. These compounds need to be removed so that the water can be discharged or re-used. Catalytic oxidation in supercritical water is one potential means of treating coal-conversion wastewaters, and this project examined the reactions of phenol over different heterogeneous oxidation catalysts in supercritical water. More specifically, we examined the oxidation of phenol over a commercial catalyst and over bulk MnO(sub 2), bulk TiO(sub 2), and CuO supported on Al(sub 2) O(sub 3). We used phenol as the model pollutant because it is ubiquitous in coal-conversion wastewaters and there is a large database for non-catalytic supercritical water oxidation (SCWO) with which we can contrast results from catalytic SCWO. The overall objective of this research project is to obtain the reaction engineering information required to evaluate the utility of catalytic supercritical water oxidation for treating wastes arising from coal conversion processes. All four materials were active for catalytic supercritical water oxidation. Indeed, all four materials produced phenol conversions and CO(sub 2) yields in excess of those obtained from purely homogeneous, uncatalyzed oxidation reactions. The commercial catalyst was so active that we could not reliably measure reaction rates that were not limited by pore diffusion. Therefore, we performed experiments with bulk transition metal oxides. The bulk MnO(sub 2) and TiO(sub 2) catalysts enhance both the phenol disappearance and CO(sub 2) formation rates during SCWO. MnO(sub 2) does not affect the selectivity to CO(sub 2), or to the phenol dimers at a given phenol conversion. However, the selectivities to CO(sub 2) are increased and the selectivities to phenol dimers are decreased in the presence of TiO(sub 2) , which are desirable trends for a catalytic SCWO process. The role of the catalyst appears to be accelerating the rate of formation of

Critical Dimensions of Water-tamped Slabs and Spheres of Active Material

Science.gov (United States)

Greuling, E.; Argo, H.: Chew, G.; Frankel, M. E.; Konopinski, E.J.; Marvin, C.; Teller, E.

1946-08-06

The magnitude and distribution of the fission rate per unit area produced by three energy groups of moderated neutrons reflected from a water tamper into one side of an infinite slab of active material is calculated approximately in section II. This rate is directly proportional to the current density of fast neutrons from the active material incident on the water tamper. The critical slab thickness is obtained in section III by solving an inhomogeneous transport integral equation for the fast-neutron current density into the tamper. Extensive use is made of the formulae derived in "The Mathematical Development of the End-Point Method" by Frankel and Goldberg. In section IV slight alterations in the theory outlined in sections II and III were made so that one could approximately compute the critical radius of a water-tamper sphere of active material. The derived formulae were applied to calculate the critical dimensions of water-tamped slabs and spheres of solid UF{sub 6} leaving various (25) isotope enrichment fractions. Decl. Dec. 16, 1955.

Separation of tritiated water using graphene oxide membrane

Energy Technology Data Exchange (ETDEWEB)

Sevigny, Gary J. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Motkuri, Radha K. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Gotthold, David W. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Fifield, Leonard S. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Frost, Anthony P. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Bratton, Wesley [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

2015-06-28

In future nuclear fuel reprocessing plants and possibly for nuclear power plants, the cleanup of tritiated water will be needed for hundreds of thousands of gallons of water with low activities of tritium. This cleanup concept utilizes graphene oxide laminar membranes (GOx) for the separation of low-concentration (10-3-10 µCi/g) tritiated water to create water that can be released to the environment and a much smaller waste stream with higher tritium concentrations. Graphene oxide membranes consist of hierarchically stacked, overlapping molecular layers and represent a new class of materials. A permeation rate test was performed with a 2-µm-thick cast Asbury membrane using mixed gas permeability testing with zero air (highly purified atmosphere) and with air humidified with either H2O or D2O to a nominal 50% relative humidity. The membrane permeability for both H2O and D2O was high with N2 and O2 at the system measurement limit. The membrane water permeation rate was compared to a Nafion® membrane and the GOx permeation was approximately twice as high at room temperature. The H2O vapor permeation rate was 5.9 × 102 cc/m2/min (1.2 × 10-6 g/min-cm2), which is typical for graphene oxide membranes. To demonstrate the feasibility of such isotopic water separation through GOX laminar membranes, an experimental setup was constructed to use pressure-driven separation by heating the isotopic water mixture at one side of the membrane to create steam while cooling the other side. Several membranes were tested and were prepared using different starting materials and by different pretreatment methods. The average separation result was 0.8 for deuterium and 0.6 for tritium. Higher or lower temperatures may also improve separation efficiency but neither has been tested yet. A rough estimate of cost compared to current technology was also included as an indication of potential viability of the process. The relative process costs were based on the rough size of facility to

Biogeochemical control points in a water-limited critical zone

Science.gov (United States)

Chorover, J.; Brooks, P. D.; Gallery, R. E.; McIntosh, J. C.; Olshansky, Y.; Rasmussen, C.

2017-12-01

The routing of water and carbon through complex terrain is postulated to control structure evolution in the sub-humid critical zone of the southwestern US. By combining measurements of land-atmosphere exchange, ecohydrologic partitioning, and subsurface biogeochemistry, we seek to quantify how a heterogeneous (in time and space) distribution of "reactants" impacts both short-term (sub-)catchment response (e.g., pore and surface water chemical dynamics) and long-term landscape evolution (e.g., soil geochemistry/morphology and regolith weathering depth) in watersheds underlain by rhyolite and schist. Instrumented pedons in convergent, planar, and divergent landscape positions show distinct depth-dependent responses to precipitation events. Wetting front propagation, dissolved carbon flux and associated biogeochemical responses (e.g., pulses of CO2 production, O2 depletion, solute release) vary with topography, revealing the influence of lateral subsidies of water and carbon. The impacts of these episodes on the evolution of porous media heterogeneity is being investigated by statistical analysis of pore water chemistry, chemical/spectroscopic studies of solid phase organo-mineral products, sensor-derived water characteristic curves, and quantification of co-located microbial community activity/composition. Our results highlight the interacting effects of critical zone structure and convergent hydrologic flows in the evolution of biogeochemical control points.

Photoanodic Hybrid Semiconductor–Molecular Heterojunction for Solar Water Oxidation

KAUST Repository

Joya, Khurram Saleem

2015-06-29

Inorganic photo-responsive semiconducting materials have been employed in photoelectrochemical(PEC) water oxidation devicesin pursuit of solar to fuel conversion.[1]The reaction kinetics in semiconductors is limited by poor contact at the interfaces, and charge transfer is impeded by surface defects and the grain boundaries.[2]It has shown that successful surface functionalization of the photo-responsive semiconducting materials with co-catalysts can maximize the charge separation, hole delivery and its effective consumption, and enhances the efficiency and performane of the PEC based water oxidation assembly.[3]We present here unique modification of photoanodic hematite (α-Fe2O3) and bismuth vanadate (BiVO4) with molecular co-catalysts for enhanced photoelectrochemical water oxidation (Figure 1). These hybrid inorganic–organometallic heterojunctions manifest impressive cathodic shifts in the onset potentials, and the photocurrent densities have been enhanced by > 90% at all potentials relative to uncatalyzed α-Fe2O3 or BiVO4, and other catalyst-semiconductor based heterojunctions.This is a novel development in the solar to fuel conversion field, and is crucially important for designing a tandem device where light interfere very little with the catalyst layer on top of semiconducting light absorber.

New Ir Bis-Carbonyl Precursor for Water Oxidation Catalysis

Energy Technology Data Exchange (ETDEWEB)

Huang, Daria L. [Department of Chemistry, Yale University, 225; Beltrán-Suito, Rodrigo [Department of Chemistry, Yale University, 225; Thomsen, Julianne M. [Department of Chemistry, Yale University, 225; Hashmi, Sara M. [Department of Chemical and Environmental; Materna, Kelly L. [Department of Chemistry, Yale University, 225; Sheehan, Stafford W. [Catalytic Innovations LLC, 70 Crandall; Mercado, Brandon Q. [Department of Chemistry, Yale University, 225; Brudvig, Gary W. [Department of Chemistry, Yale University, 225; Crabtree, Robert H. [Department of Chemistry, Yale University, 225

2016-02-05

This paper introduces IrI(CO)2(pyalc) (pyalc = (2-pyridyl)-2-propanoate) as an atom-efficient precursor for Ir-based homogeneous oxidation catalysis. This compound was chosen to simplify analysis of the water oxidation catalyst species formed by the previously reported Cp*IrIII(pyalc)OH water oxidation precatalyst. Here, we present a comparative study on the chemical and catalytic properties of these two precursors. Previous studies show that oxidative activation of Cp*Ir-based precursors with NaIO4 results in formation of a blue IrIV species. This activation is concomitant with the loss of the placeholder Cp* ligand which oxidatively degrades to form acetic acid, iodate, and other obligatory byproducts. The activation process requires substantial amounts of primary oxidant, and the degradation products complicate analysis of the resulting IrIV species. The species formed from oxidation of the Ir(CO)2(pyalc) precursor, on the other hand, lacks these degradation products (the CO ligands are easily lost upon oxidation) which allows for more detailed examination of the resulting Ir(pyalc) active species both catalytically and spectroscopically, although complete structural analysis is still elusive. Once Ir(CO)2(pyalc) is activated, the system requires acetic acid or acetate to prevent the formation of nanoparticles. Investigation of the activated bis-carbonyl complex also suggests several Ir(pyalc) isomers may exist in solution. By 1H NMR, activated Ir(CO)2(pyalc) has fewer isomers than activated Cp*Ir complexes, allowing for advanced characterization. Future research in this direction is expected to contribute to a better structural understanding of the active species. A diol crystallization agent was needed for the structure determination of 3.

Mechanisms and energetics of surface reactions at the copper-water interface. A critical literature review with implications for the debate on corrosion of copper in anoxic water

Energy Technology Data Exchange (ETDEWEB)

Johansson, Adam Johannes; Brinck, Tore [Applied Physical Chemistry, KTH Royal Inst. of Technology, Stockholm (Sweden)

2012-06-15

In order to make a critical analysis of the discussion of corrosion of copper in pure anoxic water it is necessary to understand the chemical reactivity at the copper-water interface. Even though the most fundamental issue, i.e. the nature and existence of a hypothetical product that is thermodynamically stable, is still under debate, it is clear that if anoxic corrosion really exists, it must be initiated through oxidative surface reactions at the copper-water interface. This report presents a survey of the peer reviewed literature on the reactivity of copper surfaces in water. Reactions discussed involve molecular adsorption of water, dissociation of the OH-bonds in adsorbed water molecules and hydroxyl groups, the disproportionation/synproportionation equilibrium between hydroxyl groups/hydroxide ions, water molecules and atomic oxygen, the surface diffusion of adsorbed species, and the formation of hydrogen gas (molecular hydrogen). Experimental, as well as theoretical (quantum chemical) studies are reviewed. It is concluded that a limited amount of hydrogen gas (H{sub 2}) should be formed as the result of dissociative water adsorption at certain copper surfaces. Quantitative estimates of the amounts of H2 that could form at the copper-water interface are made. Assuming that the water-cleavage/hydrogen-formation reaction proceeds on an ideal [110] or [100] surface until a hydroxyl monolayer (ML) is reached, the amount of H{sub 2} formed is {approx} 2.4 ng cm{sup -2} copper surface. Based on the literature cited, this is most likely possible, thermodynamically as well as kinetically. Although not proven, it is not unlikely that the reaction can proceed until an oxide ML is formed, which would give 4.8 ng cm{sup -2}. If the formation of an oxide ML is thermodynamically feasible the surface will probably react further, since Cu{sub 2}O(s) is known to activate and cleave the water molecule when it adsorbs at the Cu{sub 2}O(s) surface. Assuming the formation of a

Self-assembling of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers in aqueous solution and at the silica-water interface

International Nuclear Information System (INIS)

Leyh, B.; Vangeyte, P.; Heinrich, M.; Auvray, L.; De Clercq, C.; Jerome, R.

2004-01-01

Small-angle neutron scattering is used to investigate the self-assembling behaviour of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers with various block lengths (i) in aqueous solution, (ii) in aqueous solution with the addition of sodium dodecyl sulphate (SDS) and (iii) at the silica-water interface. Micelles are observed under our experimental conditions due to the very small critical micellar concentration of these copolymers (0.01 g/l). The poly(ε-caprolactone) core is surrounded by a poly(ethylene oxide) corona. The micellar form factors have been measured at low copolymer concentrations (0.2 wt%) under selected contrast matching conditions. The data have been fitted to various analytical models to extract the micellar core and corona sizes. SDS is shown to induce partial micelle disruption together with an increase of the poly(ethylene oxide) corona extension from 25% (without SDS) to 70% (with SDS) of a completely extended PEO 114 chain. Our data at the silica-water interface are compatible with the adsorption of micelles

Engineering metal (hydr)oxide sorbents for removal of arsenate and similar weak-acid oxyanion contaminants: A critical review with emphasis on factors governing sorption processes.

Science.gov (United States)

Hristovski, Kiril D; Markovski, Jasmina

2017-11-15

To create an integrative foundation for engineering of the next generation inexpensive sorbent systems, this critical review addresses the existing knowledge gap in factor/performance relationships between weak-acid oxyanion contaminants and metal (hydr)oxide sorbents. In-depth understanding of fundamental thermodynamics and kinetics mechanisms, material fabrication, and analytical and characterization techniques, is necessary to engineer sorbent that exhibit high capacity, selectivity, stability, durability and mass transport of contaminants under a wide range of operating and water matrix conditions requirements. From the perspective of thermodynamics and kinetics, this critical review examines the factors affecting sorbent performances and analyzes the existing research to elucidate future directions aimed at developing novel sorbents for removal of weak-acid oxyanion contaminants from water. Only sorbents that allow construction of simple and inexpensive water treatment systems adapted to overcome fiscal and technological barriers burdening small communities could pave the road for providing inexpensive potable water to millions of people. Novel sorbents, which exhibit (1) poor performances in realistic operating and water matrix conditions and/or (2) do not comply with the purely driven economics factors of production scalability or cost expectations, are predestined to never be commercialized. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of Adsorbed Water on the Oxygen Evolution Reaction on Oxides

DEFF Research Database (Denmark)

Siahrostami, Samira; Vojvodic, Aleksandra

2015-01-01

We study the interface between adsorbed water and stoichiometric, defect-free (110) rutile oxide surfaces of TiO2, RuO2, and IrO2 in order to understand how water influences the stabilities of the intermediates of the oxygen evolution reaction (OER). In our model the water is treated as explicitly...... molecules binding to bridging oxygens. The third chain interacts weakly and predominantly with the H2O molecules of the second layer, resembling bulk water. We find that the stability of the water layer close to the oxide surface is almost the same as the one found on flat metal surfaces, such as the Pt(111...... of RuO2 and IrO2, while it is increased by similar to 0.4 eV for TiO2....

Water Sorption and Gamma Radiolysis Studies for Uranium Oxides

Energy Technology Data Exchange (ETDEWEB)

Icenhour, A.S.

2002-02-27

During the development of a standard for the safe, long-term storage of {sup 233}U-containing materials, several areas were identified that needed additional experimental studies. These studies were related to the perceived potential for the radiolytic generation of large pressures or explosive concentrations of gases in storage containers. This report documents the results of studies on the sorption of water by various uranium oxides and on the gamma radiolysis of uranium oxides containing various amounts of sorbed moisture. In all of the experiments, {sup 238}U was used as a surrogate for the {sup 233}U. For the water sorption experiments, uranium oxide samples were prepared and exposed to known levels of humidity to establish the water uptake rate. Subsequently, the amount of water removed was studied by heating samples in a oven at fixed temperatures and by thermogravimetric analysis (TGA)/differential thermal analysis (DTA). It was demonstrated that heating at 650 C adequately removes all moisture from the samples. Uranium-238 oxides were irradiated in a {sup 60}Co source and in the high-gamma-radiation fields provided by spent nuclear fuel elements of the High Flux Isotope Reactor. For hydrated samples of UO{sub 3}, H{sub 2} was the primary gas produced; but the total gas pressure increase reached steady value of about 10 psi. This production appears to be a function of the dose and the amount of water present. Oxygen in the hydrated UO{sub 3} sample atmosphere was typically depleted, and no significant pressure rise was observed. Heat treatment of the UO{sub 3} {center_dot} xH{sub 2}O at 650 C would result in conversion to U{sub 3}O{sub 8} and eliminate the H{sub 2} production. For all of the U{sub 3}O{sub 8} samples loaded in air and irradiated with gamma radiation, a pressure decrease was seen and little, if any, H{sub 2} was produced--even for samples with up to 9 wt % moisture content. Hence, these results demonstrated that the efforts to remove trace

[Ultrasound induced the formation of nitric oxide and nitrosonium ions in water and aqueous solutions].

Science.gov (United States)

Stepuro, I I; Adamchuk, R I; Stepuro, V I

2004-01-01

Nitric oxide, nitrosonium ions, nitrites, and nitrates are formed in water saturated with air under the action of ultrasound. Nitrosonium ions react with water and hydrogen peroxide to form nitrites and nitrates in sonicated solution, correspondingly. Nitric oxide is practically completely released from sonicated water into the atmosphere and reacts with air oxygen, forming NOx compounds. The oxidation of nitric oxide in aqueous medium by hydroxyl radicals and dissolved oxygen is a minor route of the formation of nitrites and nitrates in ultrasonic field.

Criticality evaluations with moderators other than water for uranium metal fuels

International Nuclear Information System (INIS)

Toffer, H.; Tollefson, D.A.; Finfrock, S.H.

1986-01-01

Occasionally, nuclear criticality safety analyses of fissile material handling operations or transport situations require consideration of moderation other than water. Such moderators could be oils, plastics, wood, concrete, carbon, or even wet sand. All of these materials contain either hydrogen, carbon, or mixtures of the two elements as the principal moderators. Other elements as part of the compounds or mixtures contribute less to the neutron slowing down process and can possibly be significant parasitic neutron absorbers. Results of a series of calculations are presented illustrating the impact of various moderators on critical masses or critical parameters as a function of lattice pitch for different uranium metal fuel elements at low 235 U enrichments. Several nuclear criticality safety analyses performed at the Hanford N Reactor, operated by UNC Nuclear Industries for the US Department of Energy, have considered alternative moderators to assure that water moderation represented the most limiting case

Estimation of Oxidation Kinetics and Oxide Scale Void Position of Ferritic-Martensitic Steels in Supercritical Water

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Li Sun

2017-01-01

Full Text Available Exfoliation of oxide scales from high-temperature heating surfaces of power boilers threatened the safety of supercritical power generating units. According to available space model, the oxidation kinetics of two ferritic-martensitic steels are developed to predict in supercritical water at 400°C, 500°C, and 600°C. The iron diffusion coefficients in magnetite and Fe-Cr spinel are extrapolated from studies of Backhaus and Töpfer. According to Fe-Cr-O ternary phase diagram, oxygen partial pressure at the steel/Fe-Cr spinel oxide interface is determined. The oxygen partial pressure at the magnetite/supercritical water interface meets the equivalent oxygen partial pressure when system equilibrium has been attained. The relative error between calculated values and experimental values is analyzed and the reasons of error are suggested. The research results show that the results of simulation at 600°C are approximately close to experimental results. The iron diffusion coefficient is discontinuous in the duplex scale of two ferritic-martensitic steels. The simulation results of thicknesses of the oxide scale on tubes (T91 of final superheater of a 600 MW supercritical boiler are compared with field measurement data and calculation results by Adrian’s method. The calculated void positions of oxide scales are in good agreement with a cross-sectional SEM image of the oxide layers.

Optical modeling of nickel-base alloys oxidized in pressurized water reactor

Energy Technology Data Exchange (ETDEWEB)

Clair, A. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, BP 47870, 21078 Dijon cedex (France); Foucault, M.; Calonne, O. [Areva ANP, Centre Technique Departement Corrosion-Chimie, 30 Bd de l' industrie, BP 181, 71205 Le Creusot (France); Finot, E., E-mail: Eric.Finot@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, BP 47870, 21078 Dijon cedex (France)

2012-10-01

The knowledge of the aging process involved in the primary water of pressurized water reactor entails investigating a mixed growth mechanism in the corrosion of nickel-base alloys. A mixed growth induces an anionic inner oxide and a cationic diffusion parallel to a dissolution-precipitation process forms the outer zone. The in situ monitoring of the oxidation kinetics requires the modeling of the oxide layer stratification with the full knowledge of the optical constants related to each component. Here, we report the dielectric constants of the alloys 600 and 690 measured by spectroscopic ellipsometry and fitted to a Drude-Lorentz model. A robust optical stratification model was determined using focused ion beam cross-section of thin foils examined by transmission electron microscopy. Dielectric constants of the inner oxide layer depleted in chromium were assimilated to those of the nickel thin film. The optical constants of both the spinels and extern layer were determined. - Highlights: Black-Right-Pointing-Pointer Spectroscopic ellipsometry of Ni-base alloy oxidation in pressurized water reactor Black-Right-Pointing-Pointer Measurements of the dielectric constants of the alloys Black-Right-Pointing-Pointer Optical simulation of the mixed oxidation process using a three stack model Black-Right-Pointing-Pointer Scattered crystallites cationic outer layer; linear Ni-gradient bottom layer Black-Right-Pointing-Pointer Determination of the refractive index of the spinel and the Cr{sub 2}O{sub 3} layers.

Emissions of nitrous oxide and methane from surface and ground waters in Germany

International Nuclear Information System (INIS)

Hiessl, H.

1993-01-01

The paper provides a first estimation of the contribution of inland freshwater systems (surface waters and ground waters) to the emission of the greenhouse gases nitrous oxide and methane in Germany. These amounts are compared to other main sources for the emission of nitrous oxide and methane. (orig.) [de

Using Iron-Manganese Co-Oxide Filter Film to Remove Ammonium from Surface Water.

Science.gov (United States)

Zhang, Ruifeng; Huang, Tinglin; Wen, Gang; Chen, Yongpan; Cao, Xin; Zhang, Beibei

2017-07-19

An iron-manganese co-oxide filter film (MeO x ) has been proven to be a good catalyst for the chemical catalytic oxidation of ammonium in groundwater. Compared with groundwater, surface water is generally used more widely and has characteristics that make ammonium removal more difficult. In this study, MeO x was used to remove ammonium from surface water. It indicated that the average ammonium removal efficiency of MeO x was greater than 90%, even though the water quality changed dramatically and the water temperature was reduced to about 6-8 °C. Then, through inactivating microorganisms, it showed that the removal capability of MeO x included both biological (accounted for about 41.05%) and chemical catalytic oxidation and chemical catalytic oxidation (accounted for about 58.95%). The investigation of the characterizations suggested that MeO x was formed by abiotic ways and the main elements on the surface of MeO x were distributed homogenously. The analysis of the catalytic oxidation process indicated that ammonia nitrogen may interact with MeO x as both ammonia molecules and ammonium ions and the active species of O₂ were possibly • O and O₂ - .

Electrosynthesis of Biomimetic Manganese-Calcium Oxides for Water Oxidation Catalysis--Atomic Structure and Functionality.

Science.gov (United States)

González-Flores, Diego; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Martínez-Moreno, Elías; Pasquini, Chiara; Mohammadi, Mohammad Reza; Klingan, Katharina; Gernet, Ulrich; Fischer, Anna; Dau, Holger

2016-02-19

Water-oxidizing calcium-manganese oxides, which mimic the inorganic core of the biological catalyst, were synthesized and structurally characterized by X-ray absorption spectroscopy at the manganese and calcium K edges. The amorphous, birnesite-type oxides are obtained through a simple protocol that involves electrodeposition followed by active-site creation through annealing at moderate temperatures. Calcium ions are inessential, but tune the electrocatalytic properties. For increasing calcium/manganese molar ratios, both Tafel slopes and exchange current densities decrease gradually, resulting in optimal catalytic performance at calcium/manganese molar ratios of close to 10 %. Tracking UV/Vis absorption changes during electrochemical operation suggests that inactive oxides reach their highest, all-Mn(IV) oxidation state at comparably low electrode potentials. The ability to undergo redox transitions and the presence of a minor fraction of Mn(III) ions at catalytic potentials is identified as a prerequisite for catalytic activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of Metal Oxide Heterostructures in Arsenic Removal from Contaminated Water

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Lei Chen

2014-01-01

Full Text Available It has become one of the major environmental problems for people worldwide to be exposed to high arsenic concentrations through contaminated drinking water, and even the long-term intake of small doses of arsenic has a carcinogenic effect. As an efficient and economic approach for the purification of arsenic-containing water, the adsorbents in adsorption processes have been widely studied. Among a variety of adsorbents reported, the metal oxide heterostructures with high surface area and specific affinity for arsenic adsorption from aqueous systems have demonstrated a promising performance in practical applications. This review paper aims to summarize briefly the metal oxide heterostructures in arsenic removal from contaminated water, so as to provide efficient, economic, and robust solutions for water purification.

Supercritical water oxidation data acquisition testing. Final report, Volume I

International Nuclear Information System (INIS)

1996-11-01

This report discusses the phase one testing of a data acquisition system for a supercritical water waste oxidation system. The system is designed to destroy a wide range of organic materials in mixed wastes. The design and testing of the MODAR Oxidizer is discussed. An analysis of the optimized runs is included

Characterization of interfacial reactions and oxide films on 316L stainless steel in various simulated PWR primary water environments

Energy Technology Data Exchange (ETDEWEB)

Chen, Junjie; Xiao, Qian [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steels, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Lu, Zhanpeng, E-mail: zplu@t.shu.edu.cn [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China); State Key Laboratory of Advanced Special Steels, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, 149 Yanchang Road, Shanghai, 200072 (China); Ru, Xiangkun; Peng, Hao; Xiong, Qi; Li, Hongjuan [Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Mailbox 269, 149 Yanchang Road, Shanghai, 200072 (China)

2017-06-15

The effect of water chemistry on the electrochemical and oxidizing behaviors of 316L SS was investigated in hydrogenated, deaerated and oxygenated PWR primary water at 310 °C. Water chemistry significantly influenced the electrochemical impedance spectroscopy parameters. The highest charge-transfer resistance and oxide-film resistance occurred in oxygenated water. The highest electric double-layer capacitance and constant phase element of the oxide film were in hydrogenated water. The oxide films formed in deaerated and hydrogenated environments were similar in composition but different in morphology. An oxide film with spinel outer particles and a compact and Cr-rich inner layer was formed in both hydrogenated and deaerated water. Larger and more loosely distributed outer oxide particles were formed in deaerated water. In oxygenated water, an oxide film with hematite outer particles and a porous and Ni-rich inner layer was formed. The reaction kinetics parameters obtained by electrochemical impedance spectroscopy measurements and oxidation film properties relating to the steady or quasi-steady state conditions in the time-period of measurements could provide fundamental information for understanding stress corrosion cracking processes and controlling parameters. - Highlights: •Long-term EIS measurements of 316L SS in simulated PWR primary water. •Highest charge-transfer resistance and oxide film resistance in oxygenated water. •Highest electric double-layer capacitance and oxide film CPE in hydrogenated water. •Similar compositions, different shapes of oxides in deaerated/hydrogenated water. •Inner layer Cr-rich in hydrogenated/deaerated water, Ni-rich in oxygenated water.

Effect of Magnesium Oxide Nanoparticles on Water Glass Structure

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Bobrowski A.

2012-09-01

Full Text Available An attempt has been made to determine the effect of an addition of colloidal suspensions of the nanoparticles of magnesium oxide on the structure of water glass, which is a binder for moulding and core sands. Nanoparticles of magnesium oxide MgO in propanol and ethanol were introduced in the same mass content (5wt.% and structural changes were determined by measurement of the FT-IR absorption spectra.

Mechanism of water oxidation by trivalent ruthenium trisdipyridyl complex

International Nuclear Information System (INIS)

Moravskij, A.P.; Khannanov, N.K.; Khramov, A.V.; Shafirovich, V.Ya.

1983-01-01

Results of kinetic investigation of water oxidation reaction with photogenerated single-electron oxidizer-trisdipyridyl complex of Ru(3) are presented. CoCl 2 x6H 2 O within the concentration range of [Co 2+ ] 0 =5x10 -7 - 5x10 -5 M was used as a reaction catalyst. The method of stopped flow with spectrophotometric recording was used in order to control the reaction kinetics

Effects of water turbidity and different temperatures on oxidative stress in caddisfly (Stenopsyche marmorata) larvae.

Science.gov (United States)

Suzuki, Jumpei; Imamura, Masahiro; Nakano, Daisuke; Yamamoto, Ryosuke; Fujita, Masafumi

2018-07-15

Anthropogenic water turbidity derived from suspended solids (SS) is caused by reservoir sediment management practices such as drawdown flushing. Turbid water induces stress in many aquatic organisms, but the effects of turbidity on oxidative stress responses in aquatic insects have not yet been demonstrated. Here, we examined antioxidant responses, oxidative damage, and energy reserves in caddisfly (Stenopsyche marmorata) larvae exposed to turbid water (0 mg SS L -1 , 500 mg SS L -1 , and 2000 mg SS L -1 ) at different temperatures. We evaluated the combined effects of turbid water and temperature by measuring oxidative stress and using metabolic biomarkers. No turbidity level was significantly lethal to S. marmorata larvae. Moreover, there were no significant differences in antioxidant response or oxidative damage between the control and turbid water treatments at a low temperature (10 °C). However, at a high temperature (25 °C), turbid water modulated the activity of the antioxidant enzymes superoxide dismutase and catalase and the oxygen radical absorbance capacity as an indicator of the redox state of the insect larvae. Antioxidant defenses require energy, and high temperature was associated with low energy reserves, which might limit the capability of organisms to counteract reactive oxygen species. Moreover, co-exposure to turbid water and high temperature caused fluctuation of antioxidant defenses and increased the oxidative damage caused by the production of reactive oxygen species. Furthermore, the combined effect of high temperature and turbid water on antioxidant defenses and oxidative damage was larger than the individual effects. Therefore, our results demonstrate that exposure to both turbid water and high temperature generates additive and synergistic interactions causing oxidative stress in this aquatic insect species. Copyright © 2018. Published by Elsevier B.V.

Transformation of a Cp*-iridium(III) precatalyst for water oxidation when exposed to oxidative stress.

Science.gov (United States)

Zuccaccia, Cristiano; Bellachioma, Gianfranco; Bortolini, Olga; Bucci, Alberto; Savini, Arianna; Macchioni, Alceo

2014-03-17

The reaction of [Cp*Ir(bzpy)NO3 ] (1; bzpy=2-benzoylpyridine, Cp*=pentamethylcyclopentadienyl anion), a competent water-oxidation catalyst, with several oxidants (H2 O2 , NaIO4 , cerium ammonium nitrate (CAN)) was studied to intercept and characterize possible intermediates of the oxidative transformation. NMR spectroscopy and ESI-MS techniques provided evidence for the formation of many species that all had the intact Ir-bzpy moiety and a gradually more oxidized Cp* ligand. Initially, an oxygen atom is trapped in between two carbon atoms of Cp* and iridium, which gives an oxygen-Ir coordinated epoxide, whereas the remaining three carbon atoms of Cp* are involved in a η(3) interaction with iridium (2 a). Formal addition of H2 O to 2 a or H2 O2 to 1 leads to 2 b, in which a double MeCOH functionalization of Cp* is present with one MeCOH engaged in an interaction with iridium. The structure of 2 b was unambiguously determined in the solid state and in solution by X-ray single-crystal diffractometry and advanced NMR spectroscopic techniques, respectively. Further oxidation led to the opening of Cp* and transformation of the diol into a diketone with one carbonyl coordinated at the metal (2 c). A η(3) interaction between the three non-oxygenated carbons of "ex-Cp*" and iridium is also present in both 2 b and 2 c. Isolated 2 b and mixtures of 2 a-c species were tested in water-oxidation catalysis by using CAN as sacrificial oxidant. They showed substantially the same activity than 1 (turnover frequency values ranged from 9 to 14 min(-1) ). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chlorination of bromide-containing waters: enhanced bromate formation in the presence of synthetic metal oxides and deposits formed in drinking water distribution systems.

Science.gov (United States)

Liu, Chao; von Gunten, Urs; Croué, Jean-Philippe

2013-09-15

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate > sulfate > bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. Copyright © 2013 Elsevier Ltd. All rights reserved.

The study on a new superconductor (oxide Ba-Y-Cu) with high critical temperature Tc by positron annihilation

International Nuclear Information System (INIS)

Zhang Caigu; Yu Zhuxing; Wang Zhu; Huang Zhe; Zhou Jun

1987-01-01

The study on a new superconductor oxide Ba-Y-Cu with high critical temperature Tc is described. The experimental results show that positron lifetime reducing reflects variable curve of resistance with temperature. A peak of positron lifetime is appeared at critical temperature

Application of cylinder symmetry to iron and titanium oxidation by oxygen or hydrogen-water vapour mixes

International Nuclear Information System (INIS)

Raynaud, Pierre

1980-01-01

This research thesis addresses the study of the oxidation reaction in the case of corrosion of iron by oxygen, hydrogen sulphide or hydrogen-water vapour mixes, and in the case of oxidation of titanium and of titanium nitride by hydrogen-water vapour mixes. It first addresses the corrosion of iron by oxygen with an experiment performed in cylinder symmetry: description of operational conditions, discussion of kinetic curves, development of a law of generation of multiple layers in cylinder symmetry, analytical exploitation of experimental results. The second part addresses the oxidation of iron by hydrogen-water vapour mixes: experimental conditions, influence of temperature on kinetics, micrographic study (oxide morphology, coating morphology, interpretation of differences with the case of plane symmetry), discussion of the influence of cylinder symmetry on oxidation kinetics. The third part addresses the oxidation of titanium by hydrogen-water vapour mixes: global kinetic evolution, reaction products and micrographic examination, morphology and texture studies, discussion of the oxidation mechanism and of cylinder symmetry [fr

Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media

Science.gov (United States)

Blasco-Ahicart, Marta; Soriano-López, Joaquín; Carbó, Jorge J.; Poblet, Josep M.; Galan-Mascaros, J. R.

2018-01-01

Water splitting is a promising approach to the efficient and cost-effective production of renewable fuels, but water oxidation remains a bottleneck in its technological development because it largely relies on noble-metal catalysts. Although inexpensive transition-metal oxides are competitive water oxidation catalysts in alkaline media, they cannot compete with noble metals in acidic media, in which hydrogen production is easier and faster. Here, we report a water oxidation catalyst based on earth-abundant metals that performs well in acidic conditions. Specifically, we report the enhanced catalytic activity of insoluble salts of polyoxometalates with caesium or barium counter-cations for oxygen evolution. In particular, the barium salt of a cobalt-phosphotungstate polyanion outperforms the state-of-the-art IrO2 catalyst even at pH < 1, with an overpotential of 189 mV at 1 mA cm-2. In addition, we find that a carbon-paste conducting support with a hydrocarbon binder can improve the stability of metal-oxide catalysts in acidic media by providing a hydrophobic environment.

Criticality calculations for homogeneous mixtures of uranium and plutonium

International Nuclear Information System (INIS)

Spiegelberg, R. de S.H.

1981-05-01

Critical parameters were calculated using the one-dimensional multigroup transport theory. Calculations have been performed for water mixture of uranium metal and uranium oxides and plutonium nitrates to determine the dimensions of simple critical geometries (sphere and cylinder). The results of the calculations were plotted showing critical parameters (volume, radius or critical mass). The critical values obtained in Handbuch zur Kritikalitat were used to compare with critical parameters. A sensitivity study for the influences of mesh space size, multigroup structure and order of the S sub(n) approximation on the critical radius was carried out. The GAMTEC-II code was used to generate multigroup cross sections data. Critical radius were calculated using the one-dimensional multigroup transport code DTF-IV. (Author) [pt

Criticality safety of spent fuel casks considering water inleakage

International Nuclear Information System (INIS)

Osgood, N.L.; Withee, C.J.; Easton, E.P.

2004-01-01

A fundamental safety design parameter for all fissile material packages is that a single package must be critically safe even if water leaks into the containment system. In addition, criticality safety must be assured for arrays of packages under normal conditions of transport (undamaged packages) and under hypothetical accident conditions (damaged packages). The U.S. Nuclear Regulatory Commission staff has revised the review protocol for demonstrating criticality safety for spent fuel casks. Previous review guidance specified that water inleakage be considered under accident conditions. This practice was based on the fact that the leak tightness of spent fuel casks is typically demonstrated by use of structural analysis and not by physical testing. In addition, since a single package was shown to be safe with water inleakage, it was concluded that this analysis was also applicable to an array of damaged packages, since the heavy shield walls in spent fuel casks neutronically isolate each cask in the array. Inherent in this conclusion is that the fuel assembly geometry does not change significantly, even under drop test conditions. Requests for shipping fuel with burnup exceeding 40 GWd/MTU, including very high burnups exceeding 60 GWD/MTU, caused a reassessment of this assumption. Fuel cladding structural strength and ductility were not clearly predictable for these higher burnups. Therefore the single package analysis for an undamaged package may not be applicable for the damaged package. NRC staff developed a new practice for review of spent fuel casks under accident conditions. The practice presents two methods for approval that would allow an assessment of potential reconfiguration of the fuel assembly under accident conditions, or, alternatively, a demonstration of the water-exclusion boundary through physical testing

Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water

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Chen Shuei-Yuan

2010-01-01

Full Text Available Abstract Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.

A simple method for determining the critical point of the soil water retention curve

DEFF Research Database (Denmark)

Chen, Chong; Hu, Kelin; Ren, Tusheng

2017-01-01

he transition point between capillary water and adsorbed water, which is the critical point Pc [defined by the critical matric potential (ψc) and the critical water content (θc)] of the soil water retention curve (SWRC), demarcates the energy and water content region where flow is dominated......, a fixed tangent line method was developed to estimate Pc as an alternative to the commonly used flexible tangent line method. The relationships between Pc, and particle-size distribution and specific surface area (SSA) were analyzed. For 27 soils with various textures, the mean RMSE of water content from...... the fixed tangent line method was 0.007 g g–1, which was slightly better than that of the flexible tangent line method. With increasing clay content or SSA, ψc was more negative initially but became less negative at clay contents above ∼30%. Increasing the silt contents resulted in more negative ψc values...

Exposure of critical group of population to water radionuclides in area affected by uranium ore mining

Energy Technology Data Exchange (ETDEWEB)

Hladka, E; Zavadsky, M; Solnicka, H; Heroldova, J

1985-08-01

Waste waters from the uranium industry are decontaminated and then discharged into water courses. Inhabitants of the nearest village on the river form the critical group with regard to radiation burden. The critical radionuclides are Usub(nat), Ra 226, Pb 210 and Po 210 whose concentrations were determined in drinking water, in the water course and in plants watered with water from the river. From obtained data on the consumption of foods of own production and of water for drinking and cooking, a weighted sum was made of the intake of critical radionuclides per year on the conservative assumption that ingestion is the sole form of intake (permissible ingestion under Notice 59/72, Coll. of Laws). Under the said criteria the intake of radionuclides from water and foods of own production is for the critical population group 27 times less than the permissible intake for the population. Decontaminated waste waters from the operation of uranium industries contribute to the radiation burden of the population only negligibly. Radionuclides from the investigated sources represent a minute fraction of permissible intake.

Separation of radionuclides from water by magnesium oxide adsorption

International Nuclear Information System (INIS)

Tseng, Chia-Lian; Lo, Jem-Mau; Yeh, Si-Jung

1987-01-01

Adsorption by magnesium oxide of more than forty radionuclides in respective ionic species in water was observed. Generally, the radionuclides in di-valent and/or multi-valent cations are favorably adsorbed by magnesium oxide; but not for the those in mono-valent cations. In addition, the adsorption by magnesium oxide was not effective to most of the radionuclides in negative ionic species. From the observations, the adsorption mechanism is more prominently by the ion exchange of the di- or multi-valent cation species with the hydrous magnesium oxide. Separation of the radionuclides related to the corrosion products possibly produced in a nuclear power plant from natural seawater was attempted by the magnesium oxide adsorption method. It should be emphasized that the adsorption method was found to be practical for separating radionuclides from a large quantity of natural seawater with high recovery and high reproducibility. (author)

Thermo-chemical production of hydrogen from water by metal oxides fixed on ceramic substrates

International Nuclear Information System (INIS)

Roeb, M.; Monnerie, N.; Schmitz, M.; Sattler, C.; Konstandopoulos, A.G.; Agrafiotis, C.; Zaspalis, V.T.; Nalbandian, L.; Steele, A.; Stobbe, P.

2006-01-01

In the European project HYDROSOL a simple two-step thermo-chemical cycle process has been developed and investigated. It is based on metal oxide redox pair systems, which can split water molecules by abstracting oxygen atoms and reversibly incorporating them into their lattice. If concentrated solar radiation is used as the heat source one has a promising method in hand to produce hydrogen without any environmentally critical emissions. The basic idea is to combine a support capable of achieving high temperatures when heated by concentrated solar radiation, with a redox pair system suitable for water dissociation and at the same time for regeneration at these temperatures, so that complete operation of the whole process could be achieved by a single solar energy converter. The feasibility of the process has proven possible in a mini-plant scale using concentrated sunlight provided by the solar furnace in Cologne. Suitable redox materials as coatings and a dedicated receiver-reactor have been developed to produce hydrogen with significant conversions by repeating several subsequent water splitting and regeneration steps. In a design study a possible way of operating the process in commercial scale is demonstrated. (authors)

Surface water acidification and critical loads: exploring the F-factor

Directory of Open Access Journals (Sweden)

K. Bishop

2009-11-01

Full Text Available As acid deposition decreases, uncertainties in methods for calculating critical loads become more important when judgements have to be made about whether or not further emission reductions are needed. An important aspect of one type of model that has been used to calculate surface water critical loads is the empirical F-factor which estimates the degree to which acid deposition is neutralised before it reaches a lake at any particular point in time relative to the pre-industrial, steady-state water chemistry conditions.

In this paper we will examine how well the empirical F-functions are able to estimate pre-industrial lake chemistry as lake chemistry changes during different phases of acidification and recovery. To accomplish this, we use the dynamic, process-oriented biogeochemical model SAFE to generate a plausible time series of annual runoff chemistry for ca. 140 Swedish catchments between 1800 and 2100. These annual hydrochemistry data are then used to generate empirical F-factors that are compared to the "actual" F-factor seen in the SAFE data for each lake and year in the time series. The dynamics of the F-factor as catchments acidify, and then recover are not widely recognised.

Our results suggest that the F-factor approach worked best during the acidification phase when soil processes buffer incoming acidity. However, the empirical functions for estimating F from contemporary lake chemistry are not well suited to the recovery phase when the F-factor turns negative due to recovery processes in the soil. This happens when acid deposition has depleted the soil store of BC, and then acid deposition declines, reducing the leaching of base cations to levels below those in the pre-industrial era. An estimate of critical load from water chemistry during recovery and empirical F functions would therefore result in critical loads that are too low. Therefore, the empirical estimates of the F-factor are a significant source of

In situ Raman Spectroscopy of Oxide Films on Zirconium Alloy in Simulated PWR Primary Water Condition

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Ho; Choi, Kyoung Joon; Yoo, Seung Chang; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

2016-05-15

The two layered oxide structure is formed in pre-transition oxide for the zirconium alloy in high temperature water environment. It is known that the corrosion rate is related to the volume fraction of zirconium oxide and the pores in the oxides; therefore, the aim of this paper is to investigate the oxidation behavior in the pretransition zirconium oxide in high-temperature water chemistry. In this work, Raman spectroscopy was used for in situ investigations for characterizing the phase of zirconium oxide. In situ Raman spectroscopy is a well-suited technique for investigating in detail the characteristics of oxide films in a high-temperature corrosion environment. In previous studies, an in situ Raman system was developed for investigating the oxides on nickel-based alloys and low alloy steels in high-temperature water environment. Also, the early stage oxidation behavior of zirconium alloy with different dissolved hydrogen concentration environments in high temperature water was treated in the authors' previous study. In this study, a specific zirconium alloy was oxidized and investigated with in situ Raman spectroscopy for 100 d oxidation, which is close to the first transition time of the zirconium alloy oxidation. The ex situ investigation methods such as transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were used to further characterize the zirconium oxide structure. As oxidation time increased, the Raman peaks of tetragonal zirconium oxide were merged or became weaker. However, the monoclinic zirconium oxide peaks became distinct. The tetragonal zirconium oxide was just found near the O/M interface and this could explain the Raman spectra difference between the 30 d result and others.

Iron Is the Active Site in Nickel/Iron Water Oxidation Electrocatalysts

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Bryan M. Hunter

2018-04-01

Full Text Available Efficient catalysis of the oxygen-evolution half-reaction (OER is a pivotal requirement for the development of practical solar-driven water splitting devices. Heterogeneous OER electrocatalysts containing first-row transition metal oxides and hydroxides have attracted considerable recent interest, owing in part to the high abundance and low cost of starting materials. Among the best performing OER electrocatalysts are mixed Fe/Ni layered double hydroxides (LDH. A review of the available experimental data leads to the conclusion that iron is the active site for [NiFe]-LDH-catalyzed alkaline water oxidation.

Subcritical and supercritical water oxidation of organic, wet wastes for carbon cycling in regenerative life support systems

Science.gov (United States)

Ronsse, Frederik; Lasseur, Christophe; Rebeyre, Pierre; Clauwaert, Peter; Luther, Amanda; Rabaey, Korneel; Zhang, Dong Dong; López Barreiro, Diego; Prins, Wolter; Brilman, Wim

2016-07-01

For long-term human spaceflight missions, one of the major requirements is the regenerative life support system which has to be capable of recycling carbon, nutrients and water from both solid and liquid wastes generated by the crew and by the local production of food through living organisms (higher plants, fungi, algae, bacteria, …). The European Space Agency's Life Support System, envisioned by the MELiSSA project, consists of a 5 compartment artificial ecosystem, in which the waste receiving compartment (so-called compartment I or briefly 'CI') is based on thermophilic fermentation. However, as the waste generated by the crew compartment and food production compartment contain typical plant fibres (lignin, cellulose and hemicellulose), these recalcitrant fibres end up largely unaffected in the digestate (sludge) generated in the C-I compartment. Therefore, the C-I compartment has to be supplemented with a so-called fibre degradation unit (in short, FDU) for further oxidation or degradation of said plant fibres. A potential solution to degrading these plant fibres and other recalcitrant organics is their oxidation, by means of subcritical or supercritical water, into reusable CO2 while retaining the nutrients in an organic-free liquid effluent. By taking advantage of the altered physicochemical properties of water above or near its critical point (647 K, 22.1 MPa) - including increased solubility of non-polar compounds and oxygen, ion product and diffusivity - process conditions can be created for rapid oxidation of C into CO2. In this research, the oxidizer is provided as a hydrogen peroxide solution which, at elevated temperature, will dissociated into O2. The purpose of this study is to identify ideal process conditions which (a) ensure complete oxidation of carbon, (b) retaining the nutrients other than C in the liquid effluent and (c) require as little oxidizer as possible. Experiments were conducted on a continuous, tubular heated reactor and on batch

Electrolysis of water on (oxidized) metal surfaces

DEFF Research Database (Denmark)

Rossmeisl, Jan; Logadottir, Ashildur; Nørskov, Jens Kehlet

2005-01-01

Density functional theory calculations are used as the basis for an analysis of the electrochemical process, where by water is split to form molecular oxygen and hydrogen. We develop a method for obtaining the thermochemistry of the electrochemical water splitting process as a function of the bias...... directly from the electronic structure calculations. We consider electrodes of Pt(111) and Au(111) in detail and then discuss trends for a series of different metals. We show that the difficult step in the water splitting process is the formation of superoxy-type (OOH) species on the surface...... by the splitting of a water molecule on top an adsorbed oxygen atom. One conclusion is that this is only possible on metal surfaces that are (partly) oxidized. We show that the binding energies of the different intermediates are linearly correlated for a number of metals. In a simple analysis, where the linear...

Biological efficacy and toxic effect of emergency water disinfection process based on advanced oxidation technology.

Science.gov (United States)

Tian, Yiping; Yuan, Xiaoli; Xu, Shujing; Li, Rihong; Zhou, Xinying; Zhang, Zhitao

2015-12-01

An innovative and removable water treatment system consisted of strong electric field discharge and hydrodynamic cavitation based on advanced oxidation technologies was developed for reactive free radicals producing and waterborne pathogens eliminating in the present study. The biological efficacy and toxic effects of this advanced oxidation system were evaluated during water disinfection treatments. Bench tests were carried out with synthetic microbial-contaminated water, as well as source water in rainy season from a reservoir of Dalian city (Liaoning Province, China). Results showed that high inactivation efficiency of Escherichia coli (>5 log) could be obtained for synthetic contaminated water at a low concentration (0.5-0.7 mg L(-1)) of total oxidants in 3-10 s. The numbers of wild total bacteria (108 × 10(3) CFU mL(-1)) and total coliforms (260 × 10(2) MPN 100 mL(-1)) in source water greatly reduced to 50 and 0 CFU mL(-1) respectively after treated by the advanced oxidation system, which meet the microbiological standards of drinking water, and especially that the inactivation efficiency of total coliforms could reach 100%. Meanwhile, source water qualities were greatly improved during the disinfection processes. The values of UV254 in particular were significantly reduced (60-80%) by reactive free radicals. Moreover, the concentrations of possible disinfection by-products (formaldehyde and bromide) in treated water were lower than detection limits, indicating that there was no harmful effect on water after the treatments. These investigations are helpful for the ecotoxicological studies of advanced oxidation system in the treatments of chemical polluted water or waste water. The findings of this work suggest that the developed water treatment system is ideal in the acute phases of emergencies, which also could offer additional advantages over a wide range of applications in water pollution control.

Photoanodic Hybrid Semiconductor–Molecular Heterojunction for Solar Water Oxidation

KAUST Repository

Joya, Khurram Saleem; Takanabe, Kazuhiro

2015-01-01

Inorganic photo-responsive semiconducting materials have been employed in photoelectrochemical(PEC) water oxidation devicesin pursuit of solar to fuel conversion.[1]The reaction kinetics in semiconductors is limited by poor contact at the interfaces

A critical discussion of the physics of wood–water interactions

DEFF Research Database (Denmark)

Thybring, Emil Engelund; Thygesen, L. G.; Svensson, Staffan

2013-01-01

This paper reviews recent findings on wood–water interaction and puts them into context of established knowledge in the field. Several new findings challenge prevalent theories and are critically discussed in an attempt to advance current knowledge and highlight gaps. The focus of this review...... is put on water in the broadest concept of wood products, that is, the living tree is not considered. Moreover, the review covers the basic wood–water relation, states and transitions. Secondary effects such as the ability of water to alter physical properties of wood are only discussed in cases where...

Water surface coverage effects on reactivity of plasma oxidized Ti films

International Nuclear Information System (INIS)

Pranevicius, L.; Pranevicius, L.L.; Vilkinis, P.; Baltaragis, S.; Gedvilas, K.

2014-01-01

Highlights: • The reactivity of Ti films immersed in water vapor plasma depends on the surface water coverage. • The adsorbed water monolayers are disintegrated into atomic constituents on the hydrophilic TiO 2 under plasma radiation. • The TiO 2 surface covered by water multilayer loses its ability to split adsorbed water molecules under plasma radiation. - Abstract: The behavior of the adsorbed water on the surface of thin sputter deposited Ti films maintained at room temperature was investigated in dependence on the thickness of the resulting adsorbed water layer, controllably injecting water vapor into plasma. The surface morphology and microstructure were used to characterize the surfaces of plasma treated titanium films. Presented experimental results showed that titanium films immersed in water vapor plasma at pressure of 10–100 Pa promoted the photocatalytic activity of overall water splitting. The surfaces of plasma oxidized titanium covered by an adsorbed hydroxyl-rich island structure water layer and activated by plasma radiation became highly chemically reactive. As water vapor pressure increased up to 300–500 Pa, the formed water multilayer diminished the water oxidation and, consequently, water splitting efficiency decreased. Analysis of the experimental results gave important insights into the role an adsorbed water layer on surface of titanium exposed to water vapor plasma on its chemical activity and plasma activated electrochemical processes, and elucidated the surface reactions that could lead to the split of water molecules

Photocatalytic Oxidation in Drinking Water Treatment Using Hypochlorite and Titanium Dioxide

NARCIS (Netherlands)

El-Kalliny, A.S.M.

2013-01-01

The main focus of this thesis is to study the advanced oxidation processes (AOPs) of water pollutants via UV/hypochlorite (homogeneous AOPs), and UV solar light/TiO2 (heterogeneous AOPs) in which the highly oxidative hydroxyl radicals (•OH) are produced. These radicals are capable of destructing the

UO{sub 2} surface oxidation by mixtures of water vapor and hydrogen as a function of temperature

Energy Technology Data Exchange (ETDEWEB)

Espriu-Gascon, A., E-mail: alexandra.espriu@upc.edu [Department of Chemical Engineering, Universitat Politècnica Catalunya-Barcelona Tech, Diagonal 647, E-08028 Barcelona (Spain); Llorca, J.; Domínguez, M. [Institut de Tècniques Energètiques (INTE), Universitat Politècnica Catalunya-Barcelona Tech, Diagonal 647, E-08028 Barcelona (Spain); Centre for Research in NanoEngineering (CRNE), Universitat Politècnica Catalunya-Barcelona Tech, Diagonal 647, E-08028 Barcelona (Spain); Giménez, J.; Casas, I. [Department of Chemical Engineering, Universitat Politècnica Catalunya-Barcelona Tech, Diagonal 647, E-08028 Barcelona (Spain); Pablo, J. de [Department of Chemical Engineering, Universitat Politècnica Catalunya-Barcelona Tech, Diagonal 647, E-08028 Barcelona (Spain); Fundació CTM Centre Tecnològic, Plaça de la Ciència 2, E-08243 Manresa (Spain)

2015-12-15

In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water vapor on the UO{sub 2} surface as a function of temperature. The experiments were performed in situ inside a high pressure chamber attached to the XPS instrument. UO{sub 2} samples were put in contact with either hydrogen or argon streams, saturated with water at room temperature, and the sample surface evolution was analyzed by XPS. In the case of the water vapor/argon experiments, one experiment at 350 °C was performed and, in the case of the water vapor/hydrogen experiments, the temperatures used inside the reactor were 60, 120, 200 and 350 °C. On one hand, in presence of argon, the results obtained showed that the water vapor in the argon stream oxidized 93% of the U(IV) in the sample surface. On the other hand, the degree of UO{sub 2} surface oxidation showed a different dependence on the temperature in the experiments performed in the presence of hydrogen: the maximum surface oxidation occurred at 120 °C, where 65.4% of U(IV) in the sample surface was oxidized, while at higher temperatures, the surface oxidation decreased. This observation is attributed to the increase of hydrogen reducing effect when temperature increases which prevents part of the oxidation of the UO{sub 2} surface by the water vapor. - Highlights: • UO{sub 2} surface has been oxidized by water vapor in an argon stream at 350 °C. • H{sub 2} reduced more uranium oxidation produced by water at 350 °C when compared to Ar. • In H{sub 2} presence, the uranium oxidation produced by water depends on the temperature.

Criticality evaluation of BWR MOX fuel transport packages using average Pu content

International Nuclear Information System (INIS)

Mattera, C.; Martinotti, B.

2004-01-01

Currently in France, criticality studies in transport configurations for Boiling Water Reactor Mixed Oxide fuel assemblies are based on conservative hypothesis assuming that all rods (Mixed Oxide (Uranium and Plutonium), Uranium Oxide, Uranium and Gadolinium Oxide rods) are Mixed Oxide rods with the same Plutonium-content, corresponding to the maximum value. In that way, the real heterogeneous mapping of the assembly is masked and covered by a homogeneous Plutonium-content assembly, enriched at the maximum value. As this calculation hypothesis is extremely conservative, COGEMA LOGISTICS has studied a new calculation method based on the average Plutonium-content in the criticality studies. The use of the average Plutonium-content instead of the real Plutonium-content profiles provides a highest reactivity value that makes it globally conservative. This method can be applied for all Boiling Water Reactor Mixed Oxide complete fuel assemblies of type 8 x 8, 9 x 9 and 10 x 10 which Plutonium-content in mass weight does not exceed 15%; it provides advantages which are discussed in our approach. With this new method, for the same package reactivity, the Pu-content allowed in the package design approval can be higher. The COGEMA LOGISTICS' new method allows, at the design stage, to optimise the basket, materials or geometry for higher payload, keeping the same reactivity

Use of gas-phase ethanol to mitigate extreme UV/water oxidation of extreme UV optics

Science.gov (United States)

Klebanoff, L. E.; Malinowski, M. E.; Clift, W. M.; Steinhaus, C.; Grunow, P.

2004-03-01

A technique is described that uses a gas-phase species to mitigate the oxidation of a Mo/Si multilayer optic caused by either extreme UV (EUV) or electron-induced dissociation of adsorbed water vapor. It is found that introduction of ethanol (EtOH) into a water-rich gas-phase environment inhibits oxidation of the outermost Si layer of the Mo/Si EUV reflective coating. Auger electron spectroscopy, sputter Auger depth profiling, EUV reflectivity, and photocurrent measurements are presented that reveal the EUV/water- and electron/water-derived optic oxidation can be suppressed at the water partial pressures used in the tests (~2×10-7-2×10-5 Torr). The ethanol appears to function differently in two time regimes. At early times, ethanol decomposes on the optic surface, providing reactive carbon atoms that scavenge reactive oxygen atoms before they can oxidize the outermost Si layer. At later times, the reactive carbon atoms form a thin (~5 Å), possibly self-limited, graphitic layer that inhibits water adsorption on the optic surface. .

Critical sizes of light-water moderated UO2 and PuO2-UO2 lattices

International Nuclear Information System (INIS)

Tsuruta, Harumichi; Kobayashi, Iwao; Suzuki, Takenori; Ohno, Akio; Murakami, Kiyonobu

1978-02-01

Experimental critical sizes are presented for a total of about 250 lattices with 2.6 w/o UO 2 and 3.0 w/o PuO 2 -natural UO 2 fuel rods. The moderator was H 2 O and water-to-fuel volume ratios in the lattice cells ranged from 1.50 to 3.00 in the UO 2 lattices and from 2.42 to 5.55 in the PuO 2 -UO 2 lattices. The critical sizes were determined with the number of the fuel rods and a water level which were required to make the lattice critical in the shape of a rectangular parallelepiped over the temperature range from room temperature to 80 0 C. Reactivity variations of the PuO 2 -UO 2 lattices due to decaying of 241 Pu to 241 Am were traced during 3 years. Some critical sizes of the UO 2 and PuO 2 -UO 2 lattices with a water gap and of the UO 2 lattices with liquid poison in the moderator are also reported. Some physics parameters, such as the temperature coefficient of reactivity, the water-level worth, the reflector saving, the ratio between a migration area and an infinite multiplication factor and the critical buckling, are shown in relation to the critical sizes of the unperturbed lattices without the water gap and liquid poison. (auth.)

Criticality parameters for uranyl nitrate or plutonium nitrate systems in tributyl phosphate/kerosine and water

International Nuclear Information System (INIS)

Weber, W.

1985-01-01

This report presents the calculated values of smallest critical masses and volumina and neutron physical parameters for uranyl nitrate (3, 4, 5% U-235) or plutonium nitrate (5% Pu-240), each in a 30 per cent solution of tributyl phosphate (TBP)/kerosine. For the corresponding nitrate-water solutions, newly calculated results are presented together with a revised solution density model. A comparison of the data shows to what extent the criticality of nitrate-TBP/kerosine systems can be assessed on the basis of nitrate-water parameters, revealing that such data can be applied to uranyl nitrate/water systems, taking into account that the smallest critical mass of uranyl nitrate-TBP/kerosine systems, up to a 5 p.c. U-235 enrichment, is by 4.5 p.c. at the most smaller than that of UNH-water solutions. Plutonium nitrate (5% Pu-240) in the TBP/kerosine solution will have a smallest critical mass of up to 7 p.c. smaller, as compared with the water data. The suitability of the computing methods and cross-sections used is verified by recalculating experiments carried out to determine the lowest critical enrichment of uranyl nitrate. The calculated results are well in agreement with experimental data. The lowest critical enrichment is calculated to be 2.10 p.c. in the isotope U-235. (orig.) [de

Computational Modeling of Cobalt-based Water Oxidation: Current Status and Future Challenges

Science.gov (United States)

Schilling, Mauro; Luber, Sandra

2018-04-01

A lot of effort is nowadays put into the development of novel water oxidation catalysts. In this context mechanistic studies are crucial in order to elucidate the reaction mechanisms governing this complex process, new design paradigms and strategies how to improve the stability and efficiency of those catalysis. This review is focused on recent theoretical mechanistic studies in the field of homogeneous cobalt-based water oxidation catalysts. In the first part, computational methodologies and protocols are summarized and evaluated on the basis of their applicability towards real catalytic or smaller model systems, whereby special emphasis is laid on the choice of an appropriate model system. In the second part, an overview of mechanistic studies is presented, from which conceptual guidelines are drawn on how to approach novel studies of catalysts and how to further develop the field of computational modeling of water oxidation reactions.

Computational Modeling of Cobalt-Based Water Oxidation: Current Status and Future Challenges

Directory of Open Access Journals (Sweden)

Mauro Schilling

2018-04-01

Full Text Available A lot of effort is nowadays put into the development of novel water oxidation catalysts. In this context, mechanistic studies are crucial in order to elucidate the reaction mechanisms governing this complex process, new design paradigms and strategies how to improve the stability and efficiency of those catalysts. This review is focused on recent theoretical mechanistic studies in the field of homogeneous cobalt-based water oxidation catalysts. In the first part, computational methodologies and protocols are summarized and evaluated on the basis of their applicability toward real catalytic or smaller model systems, whereby special emphasis is laid on the choice of an appropriate model system. In the second part, an overview of mechanistic studies is presented, from which conceptual guidelines are drawn on how to approach novel studies of catalysts and how to further develop the field of computational modeling of water oxidation reactions.

On the effect of interaction of molybdenum trioxide and magnesium oxide in water

International Nuclear Information System (INIS)

Bunin, V.M.; Karelin, A.I.; Solov'eva, L.N.

1992-01-01

Interaction of molybdenum trioxide and magnesium oxide in water was studied. It is shown that molybdenum trioxide forms consecutively magnesium molybdate, dimolybdate and magnesium polymolybdates with magnesium oxide

Zirconium metal-water oxidation kinetics. I. Thermometry

International Nuclear Information System (INIS)

Cathcart, J.V.; McElroy, D.L.; Pawel, R.E.; Perkins, R.A.; Williams, R.K.; Yurek, G.J.

1976-02-01

A description is given of the thermometry techniques used in the Zirconium Metal--Water Oxidation Kinetics Program. Temperature measurements in the range 900 to 1500 0 C are made in three experimental systems: two oxidation apparatuses and the annealing furnace used in a corollary study of the diffusion of oxygen in β-Zircaloy. Carefully calibrated Pt vs Pt--10 percent Rh thermocouples are employed in all three apparatuses, while a Pt--6 percent Rh vs Pt-- 30 percent Rh thermocouple and an optical pyrometer are used in addition in the annealing furnace. Features of the experimental systems pertaining to thermocouple installation, temperature control, emf measurements, etc. are described, and potential temperature-measurement error sources are discussed in detail. The accuracy of the temperature measurements is analyzed

Long-term criticality control in radioactive waste disposal facilities using depleted uranium

International Nuclear Information System (INIS)

Forsberg, C.W.

1997-01-01

Plant photosynthesis has created a unique planetary-wide geochemistry - an oxidizing atmosphere with oxidizing surface waters on a planetary body with chemically reducing conditions near or at some distance below the surface. Uranium is four orders of magnitude more soluble under chemically oxidizing conditions than it is under chemically reducing conditions. Thus, uranium tends to leach from surface rock and disposal sites, move with groundwater, and concentrate where chemically reducing conditions appear. Earth's geochemistry concentrates uranium and can separate uranium from all other elements except oxygen, hydrogen (in water), and silicon (silicates, etc). Fissile isotopes include 235 U, 233 U, and many higher actinides that eventually decay to one of these two uranium isotopes. The potential for nuclear criticality exists if the precipitated uranium from disposal sites has a significant fissile enrichment, mass, and volume. The earth's geochemistry suggests that isotopic dilution of fissile materials in waste with 238 U is a preferred strategy to prevent long-term nuclear criticality in and beyond the boundaries of waste disposal facilities because the 238 U does not separate from the fissile uranium isotopes. Geological, laboratory, and theoretical data indicate that the potential for nuclear criticality can be minimized by diluting fissile materials with- 238 U to 1 wt % 235 U equivalent

Deteriorations of pulmonary function, elevated carbon monoxide levels and increased oxidative stress amongst water-pipe smokers

Directory of Open Access Journals (Sweden)

Funda Karaduman Yalcin

2017-10-01

Full Text Available Objectives: A water pipe (hookah is a tobacco smoking tool which is thought to be more harmless than a cigarette, and there are no adequate studies about its hazards to health. Water-pipe smoking is threatening health of the youth in the world today. The objective of this study has been to investigate the carbon monoxide (CO levels in breath, examine the changes in pulmonary function tests (PFT and to assess the change of the oxidative stress parameters in blood after smoking a water pipe. Material and Methods: This study is a cross-sectional analytical study that has included 50 volunteers who smoke a water pipe and the control group of 50 volunteers who smoke neither a cigarette nor a water pipe. Carbon monoxide levels were measured in the breath and pulmonary function tests (PFTs were performed before and after smoking a water pipe. Blood samples were taken from either the volunteer control group or water-pipe smokers group after smoking a water pipe for the purpose of evaluation of the parameters of oxidative stress. Results: Carbon monoxide values were measured to be 8.08±7.4 ppm and 28.08±16.5 ppm before and after smoking a water pipe, respectively. This increment was found statistically significant. There were also significant reductions in PFTs after smoking a water pipe. Total oxidative status (TOS, total antioxidant status (TAS and oxidative stress index (OSI were found prominently higher after smoking a water pipe for the group of water-pipe smokers than for the control group. Conclusions: This study has shown that water-pipe smoking leads to deterioration in pulmonary function and increases oxidative stress. To the best of our knowledge this study is the only one that has shown the effect of water-pipe smoking on oxidative stress. More studies must be planned to show the side effects of water-pipe habit and protective policies should be planned especially for young people in Europe. Int J Occup Med Environ Health 2017;30(5:731�

Session 6: Water depollution from aniline and phenol by air oxidation and adsorptive-catalytic oxidation in liquid phase

Energy Technology Data Exchange (ETDEWEB)

Dobrynkin, N.M.; Batygina, M.V.; Noskov, A.S. [Boreskov Institute of Catalysis of Siberian Branch of Russian Academy of Sciences, Pr. Ak. Lavrentieva (Russian Federation)

2004-07-01

This paper is devoted to development of carbon catalysts and application of catalytic wet air oxidation for deep cleaning of polluted waters. The described catalysts and method are solving the problem of development environmentally reliable method for fluids treatment and allow carrying out the adsorption of pollutants on carbon CAPM (catalytically active porous material) with following regeneration of the CAPM without the loss of adsorptive qualities. The experiments have shown a principal capability simultaneously to use carbon CAPM as adsorbent and either as catalyst, or as a catalyst support for oxidation of aniline and phenol in water solutions. (authors)

Chemical oxidation of unsymmetrical dimethylhydrazine transformation products in water

NARCIS (Netherlands)

Abilev, M.; Kenessov, B.N.; Batyrbekova, S.; Grotenhuis, J.T.C.

2015-01-01

Oxidation of unsymmetrical dimethylhydrazine (UDMH) during a water treatment has several disadvantages including formation of stable toxic byproducts. Effectiveness of treatment methods in relation to UDMH transformation products is currently poorly studied. This work considers the effectiveness of

Kinetics of Chronic Oxidation of NBG-17 Nuclear Graphite by Water Vapor

Energy Technology Data Exchange (ETDEWEB)

Contescu, Cristian I [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Burchell, Timothy D [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mee, Robert [Univ. of Tennessee, Knoxville, TN (United States)

2015-05-01

This report presents the results of kinetic measurements during accelerated oxidation tests of NBG-17 nuclear graphite by low concentration of water vapor and hydrogen in ultra-high purity helium. The objective is to determine the parameters in the Langmuir-Hinshelwood (L-H) equation describing the oxidation kinetics of nuclear graphite in the helium coolant of high temperature gas-cooled reactors (HTGR). Although the helium coolant chemistry is strictly controlled during normal operating conditions, trace amounts of moisture (predictably < 0.2 ppm) cannot be avoided. Prolonged exposure of graphite components to water vapor at high temperature will cause very slow (chronic) oxidation over the lifetime of graphite components. This behavior must be understood and predicted for the design and safe operation of gas-cooled nuclear reactors. The results reported here show that, in general, oxidation by water of graphite NBG-17 obeys the L-H mechanism, previously documented for other graphite grades. However, the characteristic kinetic parameters that best describe oxidation rates measured for graphite NBG-17 are different than those reported previously for grades H-451 (General Atomics, 1978) and PCEA (ORNL, 2013). In some specific conditions, certain deviations from the generally accepted L-H model were observed for graphite NBG-17. This graphite is manufactured in Germany by SGL Carbon Group and is a possible candidate for the fuel elements and reflector blocks of HTGR.

Possibilities of practical usage of dispersed aluminim oxidation by liquid water

Science.gov (United States)

Larichev, M. N.; Laricheva, O. O.; Shaitura, N. S.; Shkolnikov, E. I.

2012-12-01

The goal of this work is to show the possibility of practical usage of the environmentally pure oxidation process of preliminarily dispersed aluminum (aluminum powders of the ASD or PAD grade according to TU (Technical Specifications) 48-5-226-87, which are serially produced in industry) with liquid water in order to obtain gaseous hydrogen in volumes sufficient to provide the operation of energizers based on airhydrogen fuel cells (AHFC) for portable and stationary devices (up to 3 kW). It is shown that the synthesis of aluminum oxides-hydroxides with the specified phase and chemical compositions as well as the particle shape and size can be provided simultaneously with producing commercial hydrogen. The practical usage of hydrogen, which is formed in the oxidation reaction of metallic aluminum with liquid water at pressures close to atmospheric (particularly, to service AHFCs), requires reaction intensification to increase the oxidation rate of aluminum. In this work, we considered the aspects of practical implementation of thermal, ultrasonic, and chemical activation as well as their combinations for this purpose. As the chemical activator of oxidation, we used the additives of calcium oxide (<5% of the mass of oxidized aluminum). Application of each activation method affects the phase and chemical compositions as well as the structure of formed aluminum hydroxides, which provides the possibility of their reproducible production. Thus, simultaneously with the production of commercial hydrogen, solid oxidation products satisfying the needs of industry in aluminum oxides and having the specified composition, purity, and particle shape and size can be synthesized. The acquired experimental results and elements of the design of specially developed industrial apparatuses, which were used when performing this work, can be applied when designing the model of the hydrogen generator—the prototype of the hydrogen generator for portable and stationary devices or devices

Nitrification and the ammonia-oxidizing communities in the central Baltic Sea water column

Science.gov (United States)

Jäntti, Helena; Ward, Bess B.; Dippner, Joachim W.; Hietanen, Susanna

2018-03-01

The redoxclines that form between the oxic and anoxic water layers in the central Baltic Sea are sites of intensive nitrogen cycling. To gain better understanding of nitrification, we measured the biogeochemical properties along with potential nitrification rates and analyzed the assemblages of ammonia-oxidizing bacteria and archaea using functional gene microarrays. To estimate nitrification in the entire water column, we constructed a regression model for the nitrification rates and applied it to the conditions prevailing in the area in 2008-2012. The highest ammonia oxidation rates were found in a thin layer at the top of the redoxcline and the rates quickly decreased below detection limit when oxygen was exhausted. This is probably because extensive suboxic layers, which are known to harbor pelagic nitrification, are formed only for short periods after inflows in the Baltic Sea. The nitrification rates were some of the highest measured in the water columns, but the thickness of the layer where conditions were favorable for nitrification, was very small and it remained fairly stable between years. However, the depth of the nitrification layer varied substantially between years, particularly in the eastern Gotland Basin (EGB) due to turbulence in the water column. The ammonia oxidizer communities clustered differently between the eastern and western Gotland Basin (WGB) and the composition of ammonia-oxidizing assemblages correlated with the environmental variables. The ammonia oxidizer community composition was more even in the EGB, which may be related to physical instability of the redoxcline that does not allow predominance of a single archetype, whereas in the WGB, where the position of the redoxcline is more constant, the ammonia-oxidizing community was less even. Overall the ammonia-oxidizing communities in the Baltic Sea redoxclines were very evenly distributed compared to other marine environments where microarrays have been applied previously.

Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

Science.gov (United States)

Kafentzi, Maria-Chrysanthi; Papadakis, Raffaello; Gennarini, Federica; Kochem, Amélie; Iranzo, Olga; Le Mest, Yves; Le Poul, Nicolas; Tron, Thierry; Faure, Bruno; Simaan, A Jalila; Réglier, Marius

2018-04-06

Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H 2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf) 2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used. This complex, which contains an oxidizable substrate moiety (indane), is used as a tool to monitor an intramolecular oxygen atom transfer reaction. Electrochemical properties were investigated and, upon electrolysis at 1.30 V versus a normal hydrogen electrode (NHE), both dioxygen production and oxygenation of the indane moiety were observed. The ligand was oxidized in a highly diastereoselective manner, which indicated that the observed reactivity was mediated by metal-centered reactive species. The pH dependence of the reactivity was monitored and correlated with speciation deduced from different techniques, ranging from potentiometric titrations to spectroscopic studies and DFT calculations. Water oxidation for dioxygen production occurs at neutral pH and is probably mediated by the oxidation of a mononuclear copper(II) precursor. It is achieved with a rather low overpotential (280 mV at pH 7), although with limited efficiency. On the other hand, oxygenation is maximum at pH 8-8.5 and is probably mediated by the electrochemical oxidation of an antiferromagnetically coupled dinuclear bis(μ-hydroxo) copper(II) precursor. This constitutes the first example of copper-centered oxidative water activation for a selective oxygenation reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold-Catalyzed Aerobic Oxidation of 5-Hydroxymethylfurfural in Water at Ambient Temperature

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Woodley, John

2009-01-01

The aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, is examined in water with a titania-supported gold-nanoparticle catalyst at ambient temperature (30 degrees C). The selectivity of the reaction towords 2,5-furandicarboxylic acid and the intermediate oxidation...

Sensitization of Nanocrystalline Metal Oxides with a Phosphonate-Functionalized Perylene Diimide for Photoelectrochemical Water Oxidation with a CoOx Catalyst.

Science.gov (United States)

Kirner, Joel T; Finke, Richard G

2017-08-23

A planar organic thin film composed of a perylene diimide dye (N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide, PMPDI) with photoelectrochemically deposited cobalt oxide (CoO x ) catalyst was previously shown to photoelectrochemically oxidize water (DOI: 10.1021/am405598w). Herein, the same PMPDI dye is studied for the sensitization of different nanostructured metal oxide (nano-MO x ) films in a dye-sensitized photoelectrochemical cell architecture. Dye adsorption kinetics and saturation decreases in the order TiO 2 > SnO 2 ≫ WO 3 . Despite highest initial dye loading on TiO 2 films, photocurrent with hydroquinone (H 2 Q) sacrificial reductant in pH 7 aqueous solution is much higher on SnO 2 films, likely due to a higher driving force for charge injection into the more positive conduction band energy of SnO 2 . Dyeing conditions and SnO 2 film thickness were subsequently optimized to achieve light-harvesting efficiency >99% at the λ max of the dye, and absorbed photon-to-current efficiency of 13% with H 2 Q, a 2-fold improvement over the previous thin-film architecture. A CoO x water-oxidation catalyst was photoelectrochemically deposited, allowing for photoelectrochemical water oxidation with a faradaic efficiency of 31 ± 7%, thus demonstrating the second example of a water-oxidizing, dye-sensitized photoelectrolysis cell composed entirely of earth-abundant materials. However, deposition of CoO x always results in lower photocurrent due to enhanced recombination between catalyst and photoinjected electrons in SnO 2 , as confirmed by open-circuit photovoltage measurements. Possible future studies to enhance photoanode performance are discussed, including alternative catalyst deposition strategies or structural derivatization of the perylene dye.

DETERMINATION OF THE RATES AND PRODUCTS OF FERROUS IRON OXIDATION IN ARSENIC-CONTAMINATED POND WATER.

Science.gov (United States)

Dissolved ferrous iron and arsenic in the presence of insufficient oxygenated ground water is released into a pond. When the mixing of ferrous iron and oxygenated water within the pond occurs, the ferrous iron is oxidized and precipitated as an iron oxide. Groups of experiments...

performance calculations of gadolinium oxide and boron nitride coated fuel

International Nuclear Information System (INIS)

Tanker, E.; Uslu, I.; Disbudak, H.; Guenduez, G.

1997-01-01

A comparative study was performed on the behaviour of natural uranium dioxide-gadolinium oxide mixture fuel and boron nitride coated low enriched fuel in a pressurized water reactor. A fuel element containing one burnable poison fuel pins was modeled with the computer code WIMS, and burn-up dependent critically, fissile isotope inventory and two dimensional power distribution were obtained. Calculations were performed for burnable poison fuels containing 5% and 10% gadolinium oxide and for those coated with 1μ,5μ and 10μ of boron nitride. Boron nitride coating was found superior to gadolinium oxide on account of its smoother criticality curve, lower power peaks and insignificant change in fissile isotope content

Self-propagating solar light reduction of graphite oxide in water

Energy Technology Data Exchange (ETDEWEB)

Todorova, N.; Giannakopoulou, T.; Boukos, N.; Vermisoglou, E. [Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 41 Attikis (Greece); Lekakou, C. [Division of Mechanical, Medical, and Aerospace Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford (United Kingdom); Trapalis, C., E-mail: c.trapalis@inn.demokritos.gr [Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 41 Attikis (Greece)

2017-01-01

Highlights: • Graphite oxide was partially reduced by solar light irradiation in water media. • No addition of catalysts nor reductive agent were used for the reduction. • Specific capacitance increased stepwise with increase of irradiation time. • Self-propagating reduction of graphene oxide by solar light is suggested. - Abstract: Graphite Oxide (GtO) is commonly used as an intermediate material for preparation of graphene in the form of reduced graphene oxide (rGO). Being a semiconductor with tunable band gap rGO is often coupled with various photocatalysts to enhance their visible light activity. The behavior of such rGO-based composites could be affected after prolonged exposure to solar light. In the present work, the alteration of the GtO properties under solar light irradiation is investigated. Water dispersions of GtO manufactured by oxidation of natural graphite via Hummers method were irradiated into solar light simulator for different periods of time without addition of catalysts or reductive agent. The FT-IR analysis of the treated dispersions revealed gradual reduction of the GtO with the increase of the irradiation time. The XRD, FT-IR and XPS analyses of the obtained solid materials confirmed the transition of GtO to rGO under solar light irradiation. The reduction of the GtO was also manifested by the CV measurements that revealed stepwise increase of the specific capacitance connected with the restoration of the sp{sup 2} domains. Photothermal self-propagating reduction of graphene oxide in aqueous media under solar light irradiation is suggested as a possible mechanism. The self-photoreduction of GtO utilizing solar light provides a green, sustainable route towards preparation of reduced graphene oxide. However, the instability of the GtO and partially reduced GO under irradiation should be considered when choosing the field of its application.

Environmentally Assisted Cracking of Alloys at Temperatures near and above the Critical Temperature of Water

International Nuclear Information System (INIS)

Watanabe, Yutaka

2008-01-01

Physical properties of water, such as dielectric constant and ionic product, significantly vary with the density of water. In the supercritical conditions, since density of water widely varies with pressure, pressure has a strong influence on physical properties of water. Dielectric constant represents a character of water as a solvent, which determines solubility of an inorganic compound including metal oxides. Dissociation equilibrium of an acid is also strongly dependent on water density. Dissociation constant of acid rises with increased density of water, resulting in drop of pH. Density of water and the density-related physical properties of water, therefore, are the major governing factors of corrosion and environmentally assisted cracking of metals in supercritical aqueous solutions. This paper discusses importance of 'physical properties of water' in understanding corrosion and cracking behavior of alloys in supercritical water environments, based on experimental data and estimated solubility of metal oxides. It has been pointed out that the water density can have significant effects on stress corrosion cracking (SCC) susceptibility of metals in supercritical water, when dissolution of metal plays the key role in the cracking phenomena

The Oxidative Stress Response in Elite Water Polo Players: Effects of Genetic Background.

Science.gov (United States)

Vecchio, Mercurio; Currò, Monica; Trimarchi, Fabio; Naccari, Sergio; Caccamo, Daniela; Ientile, Riccardo; Barreca, Davide; Di Mauro, Debora

2017-01-01

Acute exercise is known to induce oxidative stress. Here we assessed the effects of gene polymorphisms SOD2 A16V, CAT -844 G>A, and GPx-1 rs1800668 C>T on oxidative stress markers in 28 elite water polo male players prior to and after a routinely programmed friendly match. The mean plasma concentrations of derivatives of reactive oxygen metabolites (dROMs), as well as lactic dehydrogenase (LDH) activity, creatine kinase (CK) activity, CK-MB, and myoglobin, were significantly increased after exercise, while blood antioxidant potential (BAP) and total free thiols were significantly decreased, compared with those measured before exercise. Advanced oxidation protein products (AOPP) were also increased after exercise but not significantly. We observed that water polo players having either AV16 or VV16 SOD genotype exhibited a significant increase of postexercise AOPP, LDH, CK, and myoglobin plasma levels in comparison with wild-type athletes. Water polo players having either CAT -844 GA or GPx1 CT genotype showed a significant increase of postexercise dROMs plasma levels and, respectively, GPx and CAT enzyme activities in comparison with wild-type subjects. These preliminary results suggest that the screening for gene variants of antioxidant enzymes could be useful to assess individual susceptibility to oxidative stress and muscle damage in water polo players.

QSAR analysis for nano-sized layered manganese-calcium oxide in water oxidation: An application of chemometric methods in artificial photosynthesis.

Science.gov (United States)

Shahbazy, Mohammad; Kompany-Zareh, Mohsen; Najafpour, Mohammad Mahdi

2015-11-01

Water oxidation is among the most important reactions in artificial photosynthesis, and nano-sized layered manganese-calcium oxides are efficient catalysts toward this reaction. Herein, a quantitative structure-activity relationship (QSAR) model was constructed to predict the catalytic activities of twenty manganese-calcium oxides toward water oxidation using multiple linear regression (MLR) and genetic algorithm (GA) for multivariate calibration and feature selection, respectively. Although there are eight controlled parameters during synthesizing of the desired catalysts including ripening time, temperature, manganese content, calcium content, potassium content, the ratio of calcium:manganese, the average manganese oxidation state and the surface of catalyst, by using GA only three of them (potassium content, the ratio of calcium:manganese and the average manganese oxidation state) were selected as the most effective parameters on catalytic activities of these compounds. The model's accuracy criteria such as R(2)test and Q(2)test in order to predict catalytic rate for external test set experiments; were equal to 0.941 and 0.906, respectively. Therefore, model reveals acceptable capability to anticipate the catalytic activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Determinants of Nitrous Oxide Emission from Agricultural Drainage Waters

International Nuclear Information System (INIS)

Reay, D. S.; Edwards, A. C.; Smith, K. A.

2004-01-01

Emissions of the powerful greenhouse gas nitrous oxide (N 2 O) from agricultural drainage waters are poorly quantified and its determinants are not fully understood. Nitrous oxide formation in agricultural soils is known to increase in response to N fertiliser application, but the response of N 2 O in field drainage waters is unknown. This investigation combined an intensive study of the direct flux of N 2 O from the surface of a fertilised barley field with measurement of dissolved N 2 O and nitrate (NO 3 ) concentrations in the same field's drainage waters. Dissolved N 2 O in drainage waters showed a clear response to field N fertilisation, following an identical pattern to direct N 2 O flux from the field surface. The range in N 2 O concentrations between individual field drains sampled on the same day was large, indicating considerable spatial variability exists at the farm scale. A consistent pattern of very rapid outgassing of the dissolved N 2 O in open drainage ditches was accentuated at a weir, where increased turbulence led to a clear drop in dissolved N 2 O concentration. This study underlines the need for carefully planned sampling campaigns wherever whole farm or catchment N 2 O emission budgets are attempted. It adds weight to the argument for the downward revision of the IPCC emission factor (EF 5 -g) for NO 3 in drainage waters

Determinants of nitrous oxide emission from agricultural drainage waters

International Nuclear Information System (INIS)

Reay, D. S.; Edwards, A. C.; Smith, K. A.

2005-01-01

Emissions of the powerful greenhouse gas nitrous oxide (N 2 O) from agricultural drainage waters are poorly quantified and its determinants are not fully understood. Nitrous oxide formation in agricultural soils is known to increase in response to N fertiliser application, but the response of N 2 O in field drainage waters is unknown. This investigation combined an intensive study of the direct flux of N 2 O from the surface of a fertilised barley field with measurement of dissolved N 2 O and nitrate (NO 3 ) concentrations in the same field's drainage waters. Dissolved N 2 O in drainage waters showed a clear response to field N fertilisation, following an identical pattern to direct N 2 O flux from the field surface. The range in N 2 O concentrations between individual field drains sampled on the same day was large, indicating considerable spatial variability exists at the farm scale. A consistent pattern of very rapid outgassing of the dissolved N 2 O in open drainage ditches was accentuated at a weir, where increased turbulence led to a clear drop in dissolved N 2 O concentration. This study underlines the need for carefully planned sampling campaigns wherever whole farm or catchment N 2 O emission budgets are attempted. It adds weight to the argument for the downward revision of the IPCC emission factor (EF 5 -g) for NO 3 in drainage waters

Graphene oxide papers with high water adsorption capacity for air dehumidification.

Science.gov (United States)

Liu, Renlong; Gong, Tao; Zhang, Kan; Lee, Changgu

2017-08-29

Graphene oxide (GO) has shown a high potential to adsorb and store water molecules due to the oxygen-containing functional groups on its hydrophilic surface. In this study, we characterized the water absorbing properties of graphene oxide in the form of papers. We fabricated three kinds of graphene oxide papers, two with rich oxygen functional groups and one with partial chemical reduction, to vary the oxygen/carbon ratio and found that the paper with high oxygen content has higher moisture adsorption capability. For the GO paper with reduction, the overall moisture absorbance was reduced. However, the absorbance at high humidity was significantly improved due to direct formation of multilayer water vapor in the system, which derived from the weak interaction between the adsorbent and the adsorbate. To demonstrate one application of GO papers as a desiccant, we tested grape fruits with and without GO paper. The fruits with a GO paper exhibited longer-term preservation with delayed mold gathering because of desiccation effect from the paper. Our results suggest that GO will find numerous practical applications as a desiccant and is a promising material for moisture desiccation and food preservation.

Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?

Science.gov (United States)

Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

2013-08-19

Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions.

Investigation of the precipitation of Na2SO4 in supercritical water

DEFF Research Database (Denmark)

Voisin, T.; Erriguible, A.; Philippot, G.

2017-01-01

solubility in sub-and supercritical water is determined on a wide temperature range using a continuous set-up. Crystallite sizes formed after precipitation are measured with in situ synchrotron wide angle X-ray scattering (WAXS). Combining these experimental results, a numerical modeling of the precipitation......SuperCritical Water Oxidation process (SCWO) is a promising technology for treating toxic and/or complex chemical wastes with very good efficiency. Above its critical point (374 degrees C, 22.1 MPa), water exhibits particular properties and organic compounds can be easily dissolved and degraded...... with the addition of oxidizing agents. But these interesting properties imply a main drawback regarding inorganic compounds. Highly soluble at ambient temperature in water, these inorganics (such as salts) are no longer soluble in supercritical water and precipitate into solids, creating plugs in SCWO processes...

For the criticality of water reflected homogeneous arrays and heterogeneous reactor fuel elements

Energy Technology Data Exchange (ETDEWEB)

Mueller, Hj; Rabitsch, H; Schuerrer, F [Technische Univ., Graz (Austria). Inst. fuer Theoretische Physik und Reaktorphysik

1980-01-01

The smallest critical masses for fuel elements of research reactors having a medium and high enrichment are calculated. The results fit close on the known critical masses of power reactors with low enrichment. The comparison of the critical masses of reactor fuel elements and homogenized uranium dioxide water systems yields the influence of the homogeneity and of the cladding on the criticality. A coefficient for heterogeneity is suggested which takes into consideration these influences.

Ion exchange resins destruction in a stirred supercritical water oxidation reactor

International Nuclear Information System (INIS)

Leybros, A.; Roubaud, A.; Guichardon, P.; Boutin, O.

2010-01-01

Spent ion exchange resins (IERs) are radioactive process wastes for which there is no satisfactory industrial treatment. Supercritical water oxidation offers a viable treatment alternative to destroy the organic structure of resins, used to remove radioactivity. Up to now, studies carried out in supercritical water for IER destruction showed that degradation rates higher than 99% are difficult to obtain even using a catalyst or a large oxidant excess. In this study, a co-fuel, isopropanol, has been used in order to improve degradation rates by initiating the oxidation reaction and increasing temperature of the reaction medium. Concentrations up to 20 wt% were tested for anionic and cationic resins. Total organic carbon reduction rates higher than 99% were obtained from this process, without the use of a catalyst. The influence of operating parameters such as IERs feed concentration, nature and counterions of exchanged IERs were also studied. (authors)

Criticality experiments with low enriched UO2 fuel rods in water containing dissolved gadolinium

International Nuclear Information System (INIS)

Bierman, S.R.; Murphy, E.S.; Clayton, E.D.; Keay, R.T.

1984-02-01

The results obtained in a criticality experiments program performed for British Nuclear Fuels, Ltd. (BNFL) under contract with the United States Department of Energy (USDOE) are presented in this report along with a complete description of the experiments. The experiments involved low enriched UO 2 and PuO 2 -UO 2 fuel rods in water containing dissolved gadolinium, and are in direct support of BNFL plans to use soluble compounds of the neutron poison gadolinium as a primary criticality safeguard in the reprocessing of low enriched nuclear fuels. The experiments were designed primarily to provide data for validating a calculation method being developed for BNFL design and safety assessments, and to obtain data for the use of gadolinium as a neutron poison in nuclear chemical plant operations - particularly fuel dissolution. The experiments program covers a wide range of neutron moderation (near optimum to very under-moderated) and a wide range of gadolinium concentration (zero to about 2.5 g Gd/l). The measurements provide critical and subcritical k/sub eff/ data (1 greater than or equal to k/sub eff/ greater than or equal to 0.87) on fuel-water assemblies of UO 2 rods at two enrichments (2.35 wt % and 4.31 wt % 235 U) and on mixed fuel-water assemblies of UO 2 and PuO 2 -UO 2 rods containing 4.31 wt % 235 U and 2 wt % PuO 2 in natural UO 2 respectively. Critical size of the lattices was determined with water containing no gadolinium and with water containing dissolved gadolinium nitrate. Pulsed neutron source measurements were performed to determine subcritical k/sub eff/ values as additional amounts of gadolinium were successively dissolved in the water of each critical assembly. Fission rate measurements in 235 U using solid state track recorders were made in each of the three unpoisoned critical assemblies, and in the near-optimum moderated and the close-packed poisoned assemblies of this fuel

Bromorhodamines - new singlet oxygen photosensitizers for oxidative water and wastewater treatment

Energy Technology Data Exchange (ETDEWEB)

Slivka, L.; Alekseeva, V.; Kuznetsova, N.; Marinina, L.; Savvina, L.; Kaliya, O.; Lukyanets, E.; Vorozhtsov, G. [Organic Intermediates and Dyes Inst., Moscow (Russian Federation); Krasnovsky, A.; Butorina, D. [Inst. of Biochemistry RAS, Moscow (Russian Federation)

2003-07-01

The cationic mono-, di- and tetrabromoderivatives of rhodamine 123 have been synthesized and studied as sensitizers for singlet oxygen formation in application for oxidative water treatment. Singlet oxygen quantum yields for compounds under investigation have been determined by using its near IR luminescence at 1270 nm. Bromorhodamines123 have been shown to sensitize the formation of singlet oxygen in aqueous solution with high quantum yields. Efficient oxidation of tryptophan in aqueous solutions sensitized by dibromorhodamine 123 has been demonstrated. This dye was tested as sensitizer for photodynamic treatment of water contaminated with coliform bacteria. It was shown to participate in the photosensitization of coliform bacteria, resulting in their efficient killing. (orig.)

Water-mediated interactions between trimethylamine-N-oxide and urea.

Science.gov (United States)

Hunger, Johannes; Ottosson, Niklas; Mazur, Kamila; Bonn, Mischa; Bakker, Huib J

2015-01-07

The amphiphilic osmolyte trimethylamine-N-oxide (TMAO) is commonly found in natural organisms, where it counteracts biochemical stress associated with urea in aqueous environments. Despite the important role of TMAO as osmoprotectant, the mechanism behind TMAO's action has remained elusive. Here, we study the interaction between urea, TMAO, and water in solution using broadband (100 MHz-1.6 THz) dielectric spectroscopy. We find that the previously reported tight hydrogen bonds between 3 water molecules and the hydrophilic amine oxide group of TMAO, remain intact at all investigated concentrations of urea, showing that no significant hydrogen bonding occurs between the two co-solutes. Despite the absence of direct TMAO-urea interactions, the solute reorientation times of urea and TMAO show an anomalous nonlinear increase with concentration, for ternary mixtures containing equal amounts of TMAO and urea. The nonlinear increase of the reorientation correlates with changes in the viscosity, showing that the combination of TMAO and urea cooperatively enhances the hydrogen-bond structure of the ternary solutions. This nonlinear increase is indicative of water mediated interaction between the two solutes and is not observed if urea is combined with other amphiphilic solutes.

Determination of Ammonia Oxidizing Bacteria and Nitrate Oxidizing Bacteria in Wastewater and Bioreactors

Science.gov (United States)

Francis, Somilez Asya

2014-01-01

The process of water purification has many different physical, chemical, and biological processes. One part of the biological process is the task of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Both play critical roles in the treatment of wastewater by oxidizing toxic compounds. The broad term is nitrification, a naturally occurring process that is carried out by AOB and NOB by using oxidation to convert ammonia to nitrite and nitrite to nitrate. To monitor this biological activity, bacterial staining was performed on wastewater contained in inoculum tanks and biofilm samples from bioreactors. Using microscopy and qPCR, the purpose of this experiment was to determine if the population of AOB and NOB in wastewater and membrane bioreactors changed depending on temperature and hibernation conditions to determine the optimal parameters for AOB/NOB culture to effectively clean wastewater.

Rational Design of a Water-Storable Hierarchical Architecture Decorated with Amorphous Barium Oxide and Nickel Nanoparticles as a Solid Oxide Fuel Cell Anode with Excellent Sulfur Tolerance.

Science.gov (United States)

Song, Yufei; Wang, Wei; Ge, Lei; Xu, Xiaomin; Zhang, Zhenbao; Julião, Paulo Sérgio Barros; Zhou, Wei; Shao, Zongping

2017-11-01

Solid oxide fuel cells (SOFCs), which can directly convert chemical energy stored in fuels into electric power, represent a useful technology for a more sustainable future. They are particularly attractive given that they can be easily integrated into the currently available fossil fuel infrastructure to realize an ideal clean energy system. However, the widespread use of the SOFC technology is hindered by sulfur poisoning at the anode caused by the sulfur impurities in fossil fuels. Therefore, improving the sulfur tolerance of the anode is critical for developing SOFCs for use with fossil fuels. Herein, a novel, highly active, sulfur-tolerant anode for intermediate-temperature SOFCs is prepared via a facile impregnation and limited reaction protocol. During synthesis, Ni nanoparticles, water-storable BaZr 0.4 Ce 0.4 Y 0.2 O 3- δ (BZCY) perovskite, and amorphous BaO are formed in situ and deposited on the surface of a Sm 0.2 Ce 0.8 O 1.9 (SDC) scaffold. More specifically, a porous SDC scaffold is impregnated with a well-designed proton-conducting perovskite oxide liquid precursor with the nominal composition of Ba(Zr 0.4 Ce 0.4 Y 0.2 ) 0.8 Ni 0.2 O 3- δ (BZCYN), calcined and reduced in hydrogen. The as-synthesized hierarchical architecture exhibits high H 2 electro-oxidation activity, excellent operational stability, superior sulfur tolerance, and good thermal cyclability. This work demonstrates the potential of combining nanocatalysts and water-storable materials in advanced electrocatalysts for SOFCs.

Fate and transformation of graphene oxide in marine waters

Science.gov (United States)

One common use of graphene family nanomaterials (GFNs) is as functional and/or antifouling coatings, which may ultimately lead to their release into the natural environment. The fate of graphene oxide (GO), a common type of GFN, in natural waters is currently not well understood....

Water vapour and carbon dioxide decrease nitric oxide readings

NARCIS (Netherlands)

vanderMark, TW; Kort, E; Meijer, RJ; Postma, DS; Koeter, GH

Measurement of nitric oxide levels in exhaled ah-is commonly performed using a chemiluminescence detector. However, water vapour and carbon dioxide affect the chemiluminescence process, The influence of these gases at the concentrations present in exhaled air has not vet been studied. For this in

HACCP (Hazard Analysis and Critical Control Points) to guarantee safe water reuse and drinking water production--a case study.

Science.gov (United States)

Dewettinck, T; Van Houtte, E; Geenens, D; Van Hege, K; Verstraete, W

2001-01-01

To obtain a sustainable water catchment in the dune area of the Flemish west coast, the integration of treated domestic wastewater in the existing potable water production process is planned. The hygienic hazards associated with the introduction of treated domestic wastewater into the water cycle are well recognised. Therefore, the concept of HACCP (Hazard Analysis and Critical Control Points) was used to guarantee hygienically safe drinking water production. Taking into account the literature data on the removal efficiencies of the proposed advanced treatment steps with regard to enteric viruses and protozoa and after setting high quality limits based on the recent progress in quantitative risk assessment, the critical control points (CCPs) and points of attention (POAs) were identified. Based on the HACCP analysis a specific monitoring strategy was developed which focused on the control of these CCPs and POAs.

The Effect of the Concentration of Oxidant, Cr(VI), on the Iron Oxidation in Saline Water

Science.gov (United States)

Ahn, H.; Jo, H. Y.; Ryu, J. H.; Koh, Y. K.

2014-12-01

Deep geological disposal is currently considered as the most appropriate method to isolate high level radioactive wastes (HLRWs) from the ecosystem. If groundwater seeps into underground disposal facilities, water molecules can be dissociated to radicals or peroxides, which can oxidize metal canisters and HLRWs. The oxidized radionuclides with a high solubility can be dissolved in the groundwater. Some dissolved radionuclides can act as oxidants. The continuous radiolysis of water molecules, which results from continuous seepage of groundwater, can enable the continuous production of the radioactive oxidants, resulting in an increase in concentration of oxidants. In this study, the effect of oxidant concentration on iron oxidation in the presence of salt was evaluated. Zero valent iron (ZVI) particles were reacted with Cr(VI) solutions with initial Cr(VI) concentrations ranged from 50 to 300 mg/L in reactors. The initial pH and NaCl concentration were fixed at 3 and 0.5 M, respectively. An increase in the initial Cr(VI) concentration caused an increase in the rate and extend of H2 gas production. The decrement of Cr(VI) was increased as the initial Cr(VI) concentration was increased. The penetration of H+ ions in the presence Cl- ions through the passive film on the ZVI particles caused the reaction between H+ ions and ZVI particles, producing H2 gas and Fe2+ ions. The passive film was damaged during the reaction due to the eruption of H2 gas or peptization by Cl- ions. The Fe2+ ions were reacted with Cr(VI) ions in the solution, producing Fe(III)-Cr(III) (oxy)hydroxides on the passive film of ZVI particles or in the solution as colloidal particles. The Fe(III)-Cr(III) (oxy)hydroxides tends to be precipitated as colloidal particles at a high Cr(VI) concentration and precipitated on the passive film at a low Cr(VI) concentration. The passive film was repaired or thickened by additional formation of Fe(III)-Cr(III) (oxy)hydroxides at a lower Cr(VI) concentration.

Transboundary water justice: a combined reading of literature on critical transboundary water interaction and "justice", for analysis and diplomacy

NARCIS (Netherlands)

Zeitoun, M.; Warner, J.F.; Mirumachi, N.; Matthews, N.; McLaughlin, K.

2014-01-01

By reviewing and blending two main bodies of research (critical transboundary water interaction analysis and centuries of thought on social justice) this paper seeks to improve international transboundary water interaction analysis and diplomacy. Various implications for transboundary analysis and

Studies of the role of water in the electrocatalysis of methanol oxidation

Science.gov (United States)

Lin, Andrew S.; Kowalak, Albert D.; O'Grady, William E.

The oxidation of methanol has been carried out on electrodes prepared by evaporating Pt directly onto a Nafion membrane and then introducing the methanol either in the gas-fed mode or directly from the electrolyte in the electrolyte-fed mode. It was found that the oxidation carried out using a gas-fed electrode was shifted 100-150 mV more cathodic than the electrolyte-fed electrode. A similar set of experiments was carried out using hydrophobic gas-diffusion electrodes and similar results were obtained. These results suggest that the mechanism of the methanol oxidation reaction depends on the nature of the surroundings and the orientation of the methanol with respect to the electrode surface. In the electrolyte-fed configuration the methanol will be in a hydrogen-bonded water cluster allowing the carbon end of the molecule to more readily approach the catalyst surface. While in the gas-fed configuration the methanol will interact with the water or oxidic surface through the hydroxyl end of the molecule. Clearly, these two possible mechanisms will lead to different products and one may enhance the rate of the direct oxidation of methanol as observed in this work.

RATES OF IRON OXIDATION AND ARSENIC SORPTION DURING GROUND WATER-SURFACE WATER MIXING AT A HAZARDOUS WASTE SITE

Science.gov (United States)

The fate of arsenic discharged from contaminated ground water to a pond at a hazardous waste site is controlled, in part, by the rate of ferrous iron oxidation-precipitation and arsenic sorption. Laboratory experiments were conducted using site-derived water to assess the impact...

Adsorption of dodecylamine hydrochloride on graphene oxide in water

Directory of Open Access Journals (Sweden)

Peng Chen

Full Text Available Cationic surfactants in water are difficult to be degraded, leading to serious water pollution. In this work, graphene oxide (GO was used as an adsorbent for removing Dodecylamine Hydrochloride (DACl, a representative cationic surfactant. X-ray diffraction (XRD, FT-IR spectroscopy and atomic force microscope (AFM were used to characterize the prepared GO. The adsorption of DACl on GO have been investigated through measurements of adsorption capacity, zeta potential, FTIR, and X-ray photoelectron spectroscopy (XPS. The experimental results have shown that the adsorption kinetics could be described as a rate-limiting pseudo second-order process, and the adsorption isotherm agreed well with the Freundlich model. GO was a good adsorbent for DACl removal, compared with coal fly ash and powdered activated carbon. The adsorption process was endothermic, and could be attributed to electrostatic interaction and hydrogen bonding between DACl and GO. Keywords: Graphene oxide, Dodecylamine hydrochloride, Adsorption isotherm, Adsorption mechanisms

The Oxidative Stress Response in Elite Water Polo Players: Effects of Genetic Background

Directory of Open Access Journals (Sweden)

Mercurio Vecchio

2017-01-01

Full Text Available Acute exercise is known to induce oxidative stress. Here we assessed the effects of gene polymorphisms SOD2 A16V, CAT −844 G>A, and GPx-1 rs1800668 C>T on oxidative stress markers in 28 elite water polo male players prior to and after a routinely programmed friendly match. The mean plasma concentrations of derivatives of reactive oxygen metabolites (dROMs, as well as lactic dehydrogenase (LDH activity, creatine kinase (CK activity, CK-MB, and myoglobin, were significantly increased after exercise, while blood antioxidant potential (BAP and total free thiols were significantly decreased, compared with those measured before exercise. Advanced oxidation protein products (AOPP were also increased after exercise but not significantly. We observed that water polo players having either AV16 or VV16 SOD genotype exhibited a significant increase of postexercise AOPP, LDH, CK, and myoglobin plasma levels in comparison with wild-type athletes. Water polo players having either CAT −844 GA or GPx1 CT genotype showed a significant increase of postexercise dROMs plasma levels and, respectively, GPx and CAT enzyme activities in comparison with wild-type subjects. These preliminary results suggest that the screening for gene variants of antioxidant enzymes could be useful to assess individual susceptibility to oxidative stress and muscle damage in water polo players.

Criticality safety evaluation report for the cold vacuum drying facility's process water handling system

International Nuclear Information System (INIS)

NELSON, J.V.

1999-01-01

This report addresses the criticality concerns associated with process water handling in the Cold Vacuum Drying Facility. The controls and limitations on equipment design and operations to control potential criticality occurrences are identified

Oxidation of PCEA nuclear graphite by low water concentrations in helium

Energy Technology Data Exchange (ETDEWEB)

Contescu, Cristian I., E-mail: ContescuCI@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6087 (United States); Mee, Robert W. [Department of Business Analytics and Statistics, University of Tennessee, Knoxville, TN 37996-0525 (United States); Wang, Peng [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6087 (United States); Romanova, Anna V.; Burchell, Timothy D. [Department of Business Analytics and Statistics, University of Tennessee, Knoxville, TN 37996-0525 (United States)

2014-10-15

Accelerated oxidation tests were performed to determine kinetic parameters of the chronic oxidation reaction (i.e. slow, continuous, and persistent) of PCEA graphite in contact with helium coolant containing low moisture concentrations in high temperature gas-cooled reactors. To the authors’ knowledge such a study has not been done since the detailed analysis of reaction of H-451 graphite with steam (Velasquez, Hightower, Burnette, 1978). Since that H-451 graphite is now unavailable, it is urgently needed to characterize chronic oxidation behavior of new graphite grades that are being considered for use in gas-cooled reactors. The Langmuir–Hinshelwood mechanism of carbon oxidation by water results in a non-linear reaction rate expression, with at least six different parameters. They were determined in accelerated oxidation experiments that covered a large range of temperatures (800–1100 °C), and partial pressures of water (15–850 Pa) and hydrogen (30–150 Pa) and used graphite specimens thin enough (4 mm) in order to avoid diffusion effects. Data analysis employed a statistical method based on multiple likelihood estimation of parameters and simultaneous fitting of non-linear equations. The results show significant material-specific differences between graphite grades PCEA and H-451 which were attributed to microstructural dissimilarity between the two materials. It is concluded that kinetic data cannot be transferred from one graphite grade to another.

Methane oxidation with low O2/CH4 ratios in the present of water: Combustion or reforming

International Nuclear Information System (INIS)

Geng, Haojie; Yang, Zhongqing; Zhang, Li; Ran, Jingyu; Yan, Yunfei

2017-01-01

Highlights: • Copper catalyst displays an inhibitory effect of water while cobalt catalyst does not. • Both catalysts show their catalytic ability for oxidation and reforming reaction. • Oxidation precedes reforming in methane reaction over both catalysts. • Water participates in reforming reaction and shows increasing effect in high temperature. - Abstract: This paper investigates the reaction of methane over copper and cobalt catalysts under oxygen-deficient conditions with added water. A fixed-bed reactor, TPD analysis, in situ DRIFTS study, and temperature detection were used to test the activity of the methane reaction, water adsorption on the metal surface, OH group behavior, and the endothermic and exothermic processes of the reaction. The results show that the inhibitory effect of water mainly occurs at a low temperature and methane conversion decreases when water is introduced into the feed. Water easily adsorbs on metal clusters and forms OH groups at low temperatures. Copper tends to adsorb more water than cobalt and shows a stronger inhibitory effect. The DRIFTS spectra of the Cu catalyst show strong OH peaks during the reaction, of which the magnitudes increase with the water pressure. When the reaction temperature rises (750 °C), water begins to serve as an oxidant and participates in the reforming reaction. Both catalysts show a transition process between the oxidation and reforming reactions as the temperature increases. Co displays a better catalytic performance in the reforming reaction. Oxidation precedes reforming; water does not participate in the reaction if the oxygen is not fully consumed.

Anodic oxidation as a new practical procedure for water disinfection

Energy Technology Data Exchange (ETDEWEB)

Kirmaier, N; Schoeberl, M

1980-05-01

The anodic oxidation could be developed for practical purposes by extensive scientific investigations and engineering optimization. Its safe bactericide, virucide, fungicide and bacteriostatic effect combined with engineering advantages makes it an essential component for water processing.

Critical role of surfactants in the formation of digestively-ripened, ultra-small (r<2 nm) copper oxide quantum dots

Science.gov (United States)

Talluri, Bhusankar; Prasad, Edamana; Thomas, Tiju

2018-04-01

Synthesis of ultra-small (r photovoltaics to sensing. Digestive ripening (DR), a method for preparing uniformly-sized particles is critically influenced by nature and concentrations of the starting materials, solvent, and surfactant. To better understand the DR process there is a need to study the effect of each synthetic parameter. In this work, we investigate the effect of surfactant on a ceramic-DR process, with copper oxide as the chosen material. To study the influence of surfactant; aminoalcohols (triethanolamine, diethanolamine, monoethanolamine), alkylamines (ethyl amine) and aqua ligands are chosen. Digestively ripened quantum dots (QDs) are formed in case of all surfactants except ethyl amine and water. Aminoalchols based surfactants which contain both hydroxyl and amine moieties are efficient ligands (due to their chelation ability) for achieving DR. With the increase of denticity of the ligand, average size of QDs do not vary; however the variance in size does. QDs formed using aminoalchols are more monodispersed when compared to alkyl amine and aqua ligand systems. Furthermore, absorption and photoluminescence spectra suggest that choice of surfactant is important for achieving DR in ceramic nanostructures (when compared to other parameters). Hard-soft-acid-base-interactions between surfactant and copper oxide seem primarily responsible for the observed DR in copper oxide QDs. The absorption and photoluminescence spectra indicate that the energy migration and relaxation pathways taking place in DR QDs depend on the type of capping agent used.

Atomically Monodisperse Nickel Nanoclusters as Highly Active Electrocatalysts for Water Oxidation

KAUST Repository

Joya, Khurram

2016-04-08

Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 and initiate the oxygen evolution at an amazingly low overpotential of ~1.51 V (vs RHE; η ≈ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm–2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec–1 is observed using Ni4(PET)8. These results are comparable to the state-of-the art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm–2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

Decoupling photochemical Fe(II) oxidation from shallow-water BIF deposition

DEFF Research Database (Denmark)

Konhauser, Kurt; Amskold, Larry; Lalonde, Stefan

2007-01-01

to the rise of atmospheric oxygen and the development of a protective ozone layer, the Earth's surface was subjected to high levels of ultraviolet radiation. Bulk ocean waters that were anoxic at this time could have supported high concentrations of dissolved Fe(II). Under such conditions, dissolved ferrous...... for biology [Fran??ois, L.M., 1986, Extensive deposition of banded iron formations was possible without photosynthesis. Nature 320, 352-354]. Here, we evaluate the potential importance of photochemical oxidation using a combination of experiments and thermodynamic models. The experiments simulate......-type systems, then we are driven to conclude that oxide-facies BIF are the product of a rapid, non-photochemical oxidative process, the most likely candidates being direct or indirect biological oxidation, and that a significant fraction of BIF could have initially been deposited as ferrous minerals. ?? 2007...

Thermal aspects of mixed oxide fuel in application to supercritical water-cooled nuclear reactors

Energy Technology Data Exchange (ETDEWEB)

Grande, L.; Peiman, W.; Rodriguez-Prado, A.; Villamere, B.; Mikhael, S.; Allison, L.; Pioro, I., E-mail: lisa.grande@mycampus.uoit.ca, E-mail: igor.pioro@uoit.ca [Univ. of Ontario Inst. of Tech., Faculty of Energy Systems and Nuclear Science, Oshawa, Ontario (Canada)

2010-07-01

SuperCritical Water-cooled nuclear Reactors (SCWRs) are a renewed technology being developed as one of the Generation IV reactor concepts. This reactor type uses a light water coolant at temperatures and pressures above its critical point. These elevated operating conditions will improve Nuclear Power Plant (NPP) thermal efficiencies by 10 - 15% compared to those of current NPPs. Also, SCWRs will have the ability to utilize a direct cycle, thus decreasing NPP capital and operational costs. The SCWR core has 2 configurations: 1) Pressure Vessel (PV) -type enclosing a fuel assembly and 2) Pressure Tube (PT) -type consisting of individual pressurized channels containing fuel bundles. Canada and Russia are developing PT-type SCWRs. In particular, the Canadian SCWR reactor has an output of 1200 MW{sub el} and will operate at a pressure of 25 MPa with inlet and outlet fuel-channel temperatures of 350 and 625°C, respectively. These extreme operating conditions require alternative fuels and materials to be investigated. Current CANadian Deuterium Uranium (CANDU) nuclear reactor fuel-channel design is based on the use of uranium dioxide (UO{sub 2}) fuel; zirconium alloy sheath (clad) bundle, pressure and calandria tubes. Alternative fuels should be considered to supplement depleting world uranium reserves. This paper studies general thermal aspects of using Mixed OXide (MOX) fuel in an Inconel-600 sheath in a generic PT-type SCWR. The bulk fluid, sheath and fuel centerline temperatures along with the Heat Transfer Coefficient (HTC) profiles were calculated at uniform and non-uniform Axial Heat Flux Profiles (AHFPs). (author)

Phase equilibria and critical phenomena in the cesium nitrate-water-diethylamine ternary system

International Nuclear Information System (INIS)

Il'in, K.K.; Kurskij, V.F.; Cherkasov, D.G.

2008-01-01

Phase equilibria and critical events in ternary cesium nitrate-water-diethylamine system, where border binary liquid system is characterized by aliquation with lower critical temperature of solution (LCTS), have been investigated by visual-polythermal method in the 60-150 Deg C range. Interaction of cesium nitrate in the water-diethylamine system leads to lowering of its LCTS from 146.1 to 69.3 Deg C and decrease of mutual solubility. Distribution ratios of diethylamine between water and organic phases of monotectic equilibrium are calculated at different temperatures. Diethylamine salting out from aqueous solutions by cesium nitrates becomes stronger with rising temperature. Plotted isotherms of phase confirms generalized scheme of topological transformations of ternary systems phase diagrams: salt-binary solvent with salting out

Supercritical water oxidation data acquisition testing. Final report, Volume II

International Nuclear Information System (INIS)

1996-11-01

Supercritical Water Oxidation (SCWO) technology holds great promise for treating mixed wastes, in an environmentally safe and efficient manner. In the spring of 1994 the US Department of Energy (DOE), Idaho Operations Office awarded Stone ampersand Webster Engineering Corporation, of Boston Massachusetts and its sub-contractor MODAR, Inc. of Natick Massachusetts a Supercritical Water Oxidation Data Acquisition Testing (SCWODAT) program. The SCWODAT program was contracted through a Cooperative Agreement that was co-funded by the US Department of Energy and the Strategic Environmental Research and Development Program. The SCWODAT testing scope outlined by the DOE in the original Cooperative Agreement and amendments thereto was initiated in June 1994 and successfully completed in December 1995. The SCWODAT program provided further information and operational data on the effectiveness of treating both simulated mixed waste and typical Navy hazardous waste using the MODAR SCWO technology

Post-treatment of reclaimed waste water based on an electrochemical advanced oxidation process

Science.gov (United States)

Verostko, Charles E.; Murphy, Oliver J.; Hitchens, G. D.; Salinas, Carlos E.; Rogers, Tom D.

1992-01-01

The purification of reclaimed water is essential to water reclamation technology life-support systems in lunar/Mars habitats. An electrochemical UV reactor is being developed which generates oxidants, operates at low temperatures, and requires no chemical expendables. The reactor is the basis for an advanced oxidation process in which electrochemically generated ozone and hydrogen peroxide are used in combination with ultraviolet light irradiation to produce hydroxyl radicals. Results from this process are presented which demonstrate concept feasibility for removal of organic impurities and disinfection of water for potable and hygiene reuse. Power, size requirements, Faradaic efficiency, and process reaction kinetics are discussed. At the completion of this development effort the reactor system will be installed in JSC's regenerative water recovery test facility for evaluation to compare this technique with other candidate processes.

Critical Power Response to Power Oscillations in Boiling Water Reactors

International Nuclear Information System (INIS)

Farawila, Yousef M.; Pruitt, Douglas W.

2003-01-01

The response of the critical power ratio to boiling water reactor (BWR) power oscillations is essential to the methods and practice of mitigating the effects of unstable density waves. Previous methods for calculating generic critical power response utilized direct time-domain simulations of unstable reactors. In this paper, advances in understanding the nature of the BWR oscillations and critical power phenomena are combined to develop a new method for calculating the critical power response. As the constraint of the reactor state - being at or slightly beyond the instability threshold - is removed, the new method allows the calculation of sensitivities to different operation and design parameters separately, and thus allows tighter safety margins to be used. The sensitivity to flow rate and the resulting oscillation frequency change are given special attention to evaluate the extension of the oscillation 'detect-and-suppress' methods to internal pump plants where the flow rate at natural circulation and oscillation frequency are much lower than jet pump plants

Metal release behavior of surface oxidized stainless steels into flowing high temperature pure water

International Nuclear Information System (INIS)

Fujiwara, Kazuo; Tomari, Haruo; Nakayama, Takenori; Shimogori, Kazutoshi; Ishigure, Kenkichi; Matsuura, Chihiro; Fujita, Norihiko; Ono, Shoichi.

1987-01-01

In order to clarify the effect of oxidation treatment of Type 304 SS on the inhibition of metal release into high temperature pure water, metal release rate of individual alloying element into flowing deionized water containing 50 ppb dissolved oxygen was measured as the function of exposure time on representative specimens oxidized in air and steam. The behavior of metal release was also discussed in relation to the structure of surface films. Among the alloying elements the amount of Fe ion, Cr ion and Fe crud in high temperature pure water tended to saturate with the exposure time and that of Ni ion and Co ion tended to increase monotonously with the exposure time for all specimens tested. And the treatment of steam-oxidation was the most effective to decrease the metal release of alloying elements and the treatment by air-oxidation also decreased the metal release. These tendencies were confirmed to correlate well with the structure of the surface films as it was in the results in the static autoclave test. (author)

In-reactor oxidation of zircaloy-4 under low water vapor pressures

Science.gov (United States)

Luscher, Walter G.; Senor, David J.; Clayton, Kevin K.; Longhurst, Glen R.

2015-01-01

Complementary in- and ex-reactor oxidation tests have been performed to evaluate the oxidation and hydrogen absorption performance of Zircaloy-4 (Zr-4) under relatively low partial pressures (300 and 1000 Pa) of water vapor at specified test temperatures (330 and 370 °C). Data from these tests will be used to support the fabrication of components intended for isotope-producing targets and provide information regarding the temperature and pressure dependence of oxidation and hydrogen absorption of Zr-4 over the specified range of test conditions. Comparisons between in- and ex-reactor test results were performed to evaluate the influence of irradiation.

In-reactor oxidation of zircaloy-4 under low water vapor pressures

International Nuclear Information System (INIS)

Luscher, Walter G.; Senor, David J.; Clayton, Kevin K.; Longhurst, Glen R.

2015-01-01

Complementary in- and ex-reactor oxidation tests have been performed to evaluate the oxidation and hydrogen absorption performance of Zircaloy-4 (Zr-4) under relatively low partial pressures (300 and 1000 Pa) of water vapor at specified test temperatures (330 and 370 ℃). Data from these tests will be used to support the fabrication of components intended for isotope-producing targets and provide information regarding the temperature and pressure dependence of oxidation and hydrogen absorption of Zr- 4 over the specified range of test conditions. Comparisons between in- and ex-reactor test results were performed to evaluate the influence of irradiation.

Organosilane oxidation by water catalysed by large gold nanoparticles in a membrane reactor

NARCIS (Netherlands)

Gitis, V.; Beerthuis, R.; Shiju, N.R.; Rothenberg, G.

2014-01-01

We show that gold nanoparticles catalyse the oxidation of organosilanes using water as oxidant at ambient conditions. Remarkably, monodispersions of small gold particles (3.5 nm diameter) and large ones (6-18 nm diameter) give equally good conversion rates. This is important because separating large

Application of secondary ion mass spectrometry to the study of a corrosion process: oxidation of uranium by water

International Nuclear Information System (INIS)

Cristy, S.S.; Condon, J.B.

1985-01-01

Corrosion of metals is an extremely important field with great economic and engineering implications at the Oak Ridge Y-12 Plant. To effectively combat corrosion, one must understand the processes occurring. This paper shows the utility of Secondary Ion Mass Spectrometry (SIMS) data for elucidating the processes occurring in one particular corrosion process - the oxidation of uranium by water - and for validating a theoretical model. It had long been known that the oxidation of uranium by water is retarded by the presence of oxygen gas and the retardation has been assumed to occur by site blocking at the surface. However, when alternate isotopic exposures were made, followed by exposure to a mixture of 16 O 2 and 18 OH 2 , the rapid exchange of 16 O and 18 O occurred in the oxide layer, but the further oxidation by water in this and subsequent exposures was retarded for up to 21 hours. This shows graphically that OH 2 is not held up at the surface and that the retarding mechanism is effective at the oxide/metal interface rather than at the surface. The effectiveness of the O 2 to retard the further water oxidation was much reduced if no water-formed oxide layer were present. The effectiveness was also crystallite related. 12 refs., 5 figs

3. International conference on oxidation technologies for water and wastewater treatment. Special topic: AOP's for recycling and reuse

Energy Technology Data Exchange (ETDEWEB)

Vogelpohl, A. (ed.)

2003-07-01

With the increasing pressure on a more effective and sustainable use of water resources, those water treatment technologies become more and more important which will allow for a recycling of wastewater for agricultural and/or industrial purposes. The so-called advanced oxidation processes (AOP's) belong to these technologies as they offer the potential of a complete conversion of the water pollutants to carbon dioxide, water and mineral salts. Despite the progress that has been achieved in understanding and applying AOP's, the most significant disadvantages of the oxidation technologies are the high investment and operating costs. As these technologies are the high investment and operating costs. As these technologies are based on radical reactions, more effective means of producing radicals and a deeper insight in the reaction pathways will be the key for generating radicals at lower costs as well as choosing the optimum process conditions and defining the applications where AOP's are most competitive. Two national, three international conferences with the publication of their papers in water science and technology (1997 and 2001) as well as the foundation of the IWA Specialist Group on AOP's in 2001 demonstrate the success and the necessity of this conference series. It is designed to bring forward the most recent advances in the fundamentals as well as the development and the application of AOP's especially in the field of water recycling reuse. It will help to disseminate new achievements in these areas and to identify future research and development needs. The increased number of interesting papers submitted will be the basis for a successful, fruitful and hopefully critical conference in Goslar. (orig.)

Aluminium oxide barrier films on polymeric web and their conversion for packaging applications

OpenAIRE

Struller, CF; Kelly, PJ; Copeland, NJ; Tobin, V; Assender, HE; Holliday, CW; Read, SJ

2013-01-01

In recent years, inorganic transparent barrier layers such as aluminium oxide or silicon oxide deposited onto polymer films have emerged as an attractive alternative to polymer based transparent barrier layers for flexible food packaging materials. For this application, barrier properties against water vapour and oxygen are critical. Aluminium oxide coatings can provide good barrier levels at thicknesses in the nanometre range, compared to several micrometres for polymer-based barrier layers....

Most oxidative stress response in water samples comes from unknown chemicals: the need for effect-based water quality trigger values.

Science.gov (United States)

Escher, Beate I; van Daele, Charlotte; Dutt, Mriga; Tang, Janet Y M; Altenburger, Rolf

2013-07-02

The induction of adaptive stress response pathways is an early and sensitive indicator of the presence of chemical and non-chemical stressors in cells. An important stress response is the Nrf-2 mediated oxidative stress response pathway where electrophilic chemicals or chemicals that cause the formation of reactive oxygen species initiate the production of antioxidants and metabolic detoxification enzymes. The AREc32 cell line is sensitive to chemicals inducing oxidative stress and has been previously applied for water quality monitoring of organic micropollutants and disinfection byproducts. Here we propose an algorithm for the derivation of effect-based water quality trigger values for this end point that is based on the combined effects of mixtures of regulated chemicals. Mixture experiments agreed with predictions by the mixture toxicity concept of concentration addition. The responses in the AREc32 and the concentrations of 269 individual chemicals were quantified in nine environmental samples, ranging from treated effluent, recycled water, stormwater to drinking water. The effects of the detected chemicals could explain less than 0.1% of the observed induction of the oxidative stress response in the sample, affirming the need to use effect-based trigger values that account for all chemicals present.

System Dynamics Approach for Critical Infrastructure and Decision Support. A Model for a Potable Water System.

Science.gov (United States)

Pasqualini, D.; Witkowski, M.

2005-12-01

The Critical Infrastructure Protection / Decision Support System (CIP/DSS) project, supported by the Science and Technology Office, has been developing a risk-informed Decision Support System that provides insights for making critical infrastructure protection decisions. The system considers seventeen different Department of Homeland Security defined Critical Infrastructures (potable water system, telecommunications, public health, economics, etc.) and their primary interdependencies. These infrastructures have been modeling in one model called CIP/DSS Metropolitan Model. The modeling approach used is a system dynamics modeling approach. System dynamics modeling combines control theory and the nonlinear dynamics theory, which is defined by a set of coupled differential equations, which seeks to explain how the structure of a given system determines its behavior. In this poster we present a system dynamics model for one of the seventeen critical infrastructures, a generic metropolitan potable water system (MPWS). Three are the goals: 1) to gain a better understanding of the MPWS infrastructure; 2) to identify improvements that would help protect MPWS; and 3) to understand the consequences, interdependencies, and impacts, when perturbations occur to the system. The model represents raw water sources, the metropolitan water treatment process, storage of treated water, damage and repair to the MPWS, distribution of water, and end user demand, but does not explicitly represent the detailed network topology of an actual MPWS. The MPWS model is dependent upon inputs from the metropolitan population, energy, telecommunication, public health, and transportation models as well as the national water and transportation models. We present modeling results and sensitivity analysis indicating critical choke points, negative and positive feedback loops in the system. A general scenario is also analyzed where the potable water system responds to a generic disruption.

DNA damage and oxidative stress in human liver cell L-02 caused by surface water extracts during drinking water treatment in a waterworks in China.

Science.gov (United States)

Xie, Shao-Hua; Liu, Ai-Lin; Chen, Yan-Yan; Zhang, Li; Zhang, Hui-Juan; Jin, Bang-Xiong; Lu, Wen-Hong; Li, Xiao-Yan; Lu, Wen-Qing

2010-04-01

Because of the daily and life-long exposure to disinfection by-products formed during drinking water treatment, potential adverse human health risk of drinking water disinfection is of great concern. Toxicological studies have shown that drinking water treatment increases the genotoxicity of surface water. Drinking water treatment is comprised of different potabilization steps, which greatly influence the levels of genotoxic products in the surface water and thus may alter the toxicity and genotoxicity of surface water. The aim of the present study was to understand the influence of specific steps on toxicity and genotoxicity during the treatment of surface water in a water treatment plant using liquid chlorine as the disinfectant in China. An integrated approach of the comet and oxidative stress assays was used in the study, and the results showed that both the prechlorination and postchlorination steps increased DNA damage and oxidative stress caused by water extracts in human derived L-02 cells while the tube settling and filtration steps had the opposite effect. This research also highlighted the usefulness of an integrated approach of the comet and oxidative stress assays in evaluating the genotoxicity of surface water during drinking water treatment. Copyright 2009 Wiley-Liss, Inc.

Criticality Data and its Application to Plant Clearance

International Nuclear Information System (INIS)

Chalmers, J.H.

1966-01-01

The results of a theoretical parametric survey of critical data for single homogeneous units of a number of compounds of uranium and plutonium are presented. Included are parameters for uranium metal-water systems between 93% and 5% enrichment; uranium oxide-water systems at 93% and from 10% to 2% enrichment; plutonium metal, nitrate, oxalate and oxide-water systems. The last mentioned inlcude the effect on mass and volume of 5 and 15% 240 Pu. The effects of the addition of nitric acid to both uranium and plutonium metal-water mixtures is considered within N/fissile ratios of 2-70 and 4-70 respectively. Also included are parameters for lattice arrangements of unclad uranium oxide rods of various diameters for enrichments between 1.3% and 5%. The method of calculation used for the majority of this work was Diffusion Theory using four energy groups. In some instances Monte Carlo calculations were made as a check on diffusion theory, in others Monte Carlo was used throughout. Some comparison is made with the results of other workers and with experiments in those instances where meaningful data checks-are available. The application of single unit data to-multi-body systems for plant clearance purposes is briefly discussed, and reference is made to other methods of calculation capable of dealing with arrays of non-standard geometries and units of complex shapes. (author)

Titanium-iridium oxide layer coating to suppress photocorrosion during photocatalytic water splitting

Energy Technology Data Exchange (ETDEWEB)

Kwon, Yongwoo; Lee, Hyunjoo [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kwon, Yongwoo; Lee, Hyunjoo [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2015-12-15

Photocatalysts with a small band gap energy have received a great deal of interest due their high solar conversion efficiencies. Cuprous oxide (Cu{sub 2}O) has attracted attention because of its small bandgap energy, a direct bandgap structure, its suitable band structure for water splitting, high absorption coefficient, non-toxicity, and its large abundance. However, it has poor stability due to the fickle oxidation states of copper. To enhance the stability and the production rate of hydrogen and oxygen, a TiIrOX overlayer was successfully formed on the Cu{sub 2}O under various synthesis conditions. The composition and oxidation state of the Ir species in the overlayer were optimized through the control of the Ir precursor and the amount of water. The Ir/Ti precursor molar ratio was linearly related to the surface Ir/Ti molar ratio. The addition of water converted the Ir precursor to IrO{sub 2}. The thickness of the overlayer was controlled by differing the synthesis times of the coating. Then, the largest amounts of hydrogen and oxygen were produced through the optimization of the TiIrOX overlayer with a higher IrO{sub 2} fraction and a thicker overlayer.

Adsorption of Cadmium Ions from Water on Double-walled Carbon Nanotubes/Iron Oxide Composite

Directory of Open Access Journals (Sweden)

Karima Seffah

2017-12-01

Full Text Available A new material (DWCNT/iron oxide for heavy metals removal was developed by combining the adsorption features of double-walled carbon nanotubes with the magnetic properties of iron oxides. Batch experiments were applied in order to evaluate adsorption capacity of the DWCNT/iron oxide composite for cadmium ions. The influence of operating parameters such as pH value, amount of adsorbent, initial adsorbate concentration and agitation speed was studied. The adsorption capacity of the DWCNT/iron oxide adsorbent for Cd2+ ions was 20.8 mg g-1, which is at the state of the art. The obtained results revealed that DWCNT/iron oxide composite is a very promising adsorbent for removal of Cd2+ ions from water under natural conditions. The advantage of the magnetic composite is that it can be used as adsorbent for contaminants in water and can be subsequently controlled and removed from the medium by a simple magnetic process.

X-ray photoelectron spectroscopy study of the initial oxidation of uranium metal in oxygen+water-vapour mixtures

International Nuclear Information System (INIS)

Allen, G.C.; Tucker, P.M.; Lewis, R.A.

1984-01-01

X-ray photoelectron spectroscopy (X.p.s.) has been used to study the chemical nature of the oxide film initially produced on clean uranium metal in oxygen + water-vapour atmospheres. The rate of reaction has been monitored and the nature of the surface film determined. From a consideration of the O 1s and U 4f X.p. spectra it has been possible to advance a mechanism which explains the complex nature of the surface oxide and the lack of satellite structure in the spectra. This is postulated to be a consequence of the way in which OH - is involved in the growth of the oxide and the presence of hydrogen in the surface film. The presence of oxygen retards the water oxidation reaction by inhibiting the decomposition of water vapour at the gas/oxide interface. (author)

X-ray photoelectron spectroscopy study of the initial oxidation of uranium metal in oxygen+water-vapour mixtures

Energy Technology Data Exchange (ETDEWEB)

Allen, G.C.; Tucker, P.M.; Lewis, R.A. (Central Electricity Generating Board, Berkeley (UK). Berkeley Nuclear Labs.)

1984-08-01

X-ray photoelectron spectroscopy (X.p.s.) has been used to study the chemical nature of the oxide film initially produced on clean uranium metal in oxygen + water-vapour atmospheres. The rate of reaction has been monitored and the nature of the surface film determined. From a consideration of the O 1s and U 4f X.p. spectra it has been possible to advance a mechanism which explains the complex nature of the surface oxide and the lack of satellite structure in the spectra. This is postulated to be a consequence of the way in which OH/sup -/ is involved in the growth of the oxide and the presence of hydrogen in the surface film. The presence of oxygen retards the water oxidation reaction by inhibiting the decomposition of water vapour at the gas/oxide interface.

Electrochemical and Spectroscopic Study of Mononuclear Ruthenium Water Oxidation Catalysts: A Combined Experimental and Theoretical Investigation

KAUST Repository

de Ruiter, J. M.

2016-09-20

One of the key challenges in designing light-driven artificial photosynthesis devices is the optimization of the catalytic water oxidation process. For this optimization it is crucial to establish the catalytic mechanism and the intermediates of the catalytic cycle, yet a full description is often difficult to obtain using only experimental data. Here we consider a series of mononuclear ruthenium water oxidation catalysts of the form [Ru(cy)(L)(H2O)](2+) (cy = p-cymene, L = 2,2\\'-bipyridine and its derivatives). The proposed catalytic cycle and intermediates are examined using density functional theory (DFT), radiation chemistry, spectroscopic techniques, and electrochemistry to establish the water oxidation mechanism. The stability of the catalyst is investigated using online electrochemical mass spectrometry (OLEMS). The comparison between the calculated absorption spectra of the proposed intermediates with experimental spectra, as well as free energy calculations with electrochemical data, provides strong evidence for the proposed pathway: a water oxidation catalytic cycle involving four proton-coupled electron transfer (PCET) steps. The thermodynamic bottleneck is identified as the third PCET step, which involves O-O bond formation. The good agreement between the optical and thermodynamic data and DFT predictions further confirms the general applicability of this methodology as a powerful tool in the characterization of water oxidation catalysts and for the interpretation of experimental observables.

Disinfection of titanium dioxide nanotubes using super-oxidized water decrease bacterial viability without disrupting osteoblast behavior

Energy Technology Data Exchange (ETDEWEB)

Beltrán-Partida, Ernesto [Department of Biomaterials, Dental Materials and Tissue Engineering, Faculty of Dentistry Mexicali, Autonomous University of Baja California, Av. Zotoluca and Chinampas St., 21040 Mexicali, Baja California (Mexico); Department of Corrosion and Materials, Engineering Institute, Autonomous University of Baja California, Blvd. Benito Juarez and Normal St., 21280 Mexicali, Baja California (Mexico); Valdez-Salas, Benjamín, E-mail: benval@uabc.edu.mx [Department of Corrosion and Materials, Engineering Institute, Autonomous University of Baja California, Blvd. Benito Juarez and Normal St., 21280 Mexicali, Baja California (Mexico); Escamilla, Alan; Curiel, Mario [Department of Corrosion and Materials, Engineering Institute, Autonomous University of Baja California, Blvd. Benito Juarez and Normal St., 21280 Mexicali, Baja California (Mexico); Valdez-Salas, Ernesto [Ixchel Medical Centre, Av. Bravo y Obregón, 21000 Mexicali, Baja California (Mexico); Nedev, Nicola [Department of Corrosion and Materials, Engineering Institute, Autonomous University of Baja California, Blvd. Benito Juarez and Normal St., 21280 Mexicali, Baja California (Mexico); Bastidas, Jose M. [National Centre for Metallurgical Research, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain)

2016-03-01

Amorphous titanium dioxide (TiO{sub 2}) nanotubes (NTs) on Ti6Al4V alloy were synthesized by anodization using a commercially available super-oxidized water (SOW). The NT surfaces were sterilized by ultraviolet (UV) irradiation and disinfected using SOW. The adhesion and cellular morphology of pig periosteal osteoblast (PPO) cells and the behavior of Staphylococcus aureus (S. aureus) cultured on the sterilized and disinfected surfaces were investigated. A non-anodized Ti6Al4V disc sterilized by UV irradiation (without SOW) was used as control. The results of this study reveal that the adhesion, morphology and filopodia development of PPO cells in NTs are dramatically improved, suggesting that SOW cleaning may not disrupt the benefits obtained by NTs. Significantly decreased bacterial viability in NTs after cleaning with SOW and comparing with non-cleaned NTs was seen. The results suggest that UV and SOW could be a recommendable method for implant sterilization and disinfection without altering osteoblast behavior while decreasing bacterial viability. - Highlights: • The effect of super-oxidized water cleaning was studied on Ti6Al4V nanotubes. • Super oxidized-water cleaning caused a decline in S. aureus viability. • Osteoblast behavior was not disrupted after super-oxidized water disinfection. • Super-oxidized water is suggested as a cleaning protocol for TiO{sub 2} nanotubes.

Disinfection of titanium dioxide nanotubes using super-oxidized water decrease bacterial viability without disrupting osteoblast behavior

International Nuclear Information System (INIS)

Beltrán-Partida, Ernesto; Valdez-Salas, Benjamín; Escamilla, Alan; Curiel, Mario; Valdez-Salas, Ernesto; Nedev, Nicola; Bastidas, Jose M.

2016-01-01

Amorphous titanium dioxide (TiO_2) nanotubes (NTs) on Ti6Al4V alloy were synthesized by anodization using a commercially available super-oxidized water (SOW). The NT surfaces were sterilized by ultraviolet (UV) irradiation and disinfected using SOW. The adhesion and cellular morphology of pig periosteal osteoblast (PPO) cells and the behavior of Staphylococcus aureus (S. aureus) cultured on the sterilized and disinfected surfaces were investigated. A non-anodized Ti6Al4V disc sterilized by UV irradiation (without SOW) was used as control. The results of this study reveal that the adhesion, morphology and filopodia development of PPO cells in NTs are dramatically improved, suggesting that SOW cleaning may not disrupt the benefits obtained by NTs. Significantly decreased bacterial viability in NTs after cleaning with SOW and comparing with non-cleaned NTs was seen. The results suggest that UV and SOW could be a recommendable method for implant sterilization and disinfection without altering osteoblast behavior while decreasing bacterial viability. - Highlights: • The effect of super-oxidized water cleaning was studied on Ti6Al4V nanotubes. • Super oxidized-water cleaning caused a decline in S. aureus viability. • Osteoblast behavior was not disrupted after super-oxidized water disinfection. • Super-oxidized water is suggested as a cleaning protocol for TiO_2 nanotubes.

Corrosion behavior of oxide dispersion strengthened ferritic steels in supercritical water

Energy Technology Data Exchange (ETDEWEB)

Gao, Wenhua [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240 (China); Guo, Xianglong, E-mail: guoxianglong@sjtu.edu.cn [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240 (China); Shen, Zhao [Department of Materials Science, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Zhang, Lefu, E-mail: lfzhang@sjtu.edu.cn [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Shanghai 200240 (China)

2017-04-01

The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer. - Highlights: • We evaluated the corrosion resistance of three different Cr content ODS steels at 650 °C in supercritical water. • Corrosion behavior of ODS steels is rarely reported and ODS steel may be promising material for generation IV reactors. • We found total opposite phenomenon compared to Lee's work before. Our result may be more reasonable.

Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

International Nuclear Information System (INIS)

Okoli, Chuka; Boutonnet, Magali; Järås, Sven; Rajarao-Kuttuva, Gunaratna

2012-01-01

Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

Energy Technology Data Exchange (ETDEWEB)

Okoli, Chuka [Royal Institute of Technology (KTH), Environmental Microbiology (Sweden); Boutonnet, Magali; Jaeras, Sven [Royal Institute of Technology (KTH), Chemical Technology (Sweden); Rajarao-Kuttuva, Gunaratna, E-mail: gkr@kth.se [Royal Institute of Technology (KTH), Environmental Microbiology (Sweden)

2012-10-15

Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

Protein-functionalized magnetic iron oxide nanoparticles: time efficient potential-water treatment

Science.gov (United States)

Okoli, Chuka; Boutonnet, Magali; Järås, Sven; Rajarao-Kuttuva, Gunaratna

2012-10-01

Recent advances in nanoscience suggest that the existing issues involving water quality could be resolved or greatly improved using nanomaterials, especially magnetic iron oxide nanoparticles. Magnetic nanoparticles have been synthesized for the development and use, in association with natural coagulant protein for water treatment. The nanoparticles size, morphology, structure, and magnetic properties were characterized by transmission electron microscope, X-ray diffraction, and superconducting quantum interference device magnetometry. Purified Moringa oleifera protein was attached onto microemulsions-prepared magnetic iron oxide nanoparticles (ME-MION) to form stable protein-functionalized magnetic nanoparticles (PMO+ME-MION). The turbidity removal efficiency in both synthetic and surface water samples were investigated and compared with the commonly used synthetic coagulant (alum) as well as PMO. More than 90 % turbidity could be removed from the surface waters within 12 min by magnetic separation of PMO+ME-MION; whereas gravimetrically, 70 % removal in high and low turbid waters can be achieved within 60 min. In contrast, alum requires 180 min to reduce the turbidity of low turbid water sample. These data support the advantage of separation with external magnetic field (magnetophoresis) over gravitational force. Time kinetics studies show a significant enhancement in ME-MION efficiency after binding with PMO implying the availability of large surface of the ME-MION. The coagulated particles (impurities) can be removed from PMO+ME-MION by washing with mild detergent or cleaning solution. To our knowledge, this is the first report on surface water turbidity removal using protein-functionalized magnetic nanoparticle.

Oxidative polymerization of lignins by laccase in water-acetone mixture.

Science.gov (United States)

Fiţigău, Ionița Firuța; Peter, Francisc; Boeriu, Carmen Gabriela

2013-01-01

The enzymatic oxidative polymerization of five technical lignins with different molecular properties, i.e. Soda Grass/Wheat straw Lignin, Organosolv Hardwood Lignin, Soda Wheat straw Lignin, Alkali pretreated Wheat straw Lignin, and Kraft Softwood was studied. All lignins were previously fractionated by acetone/water 50:50 (v/v) and the laccase-catalyzed polymerization of the low molecular weight fractions (Mw Reactivity of lignin substrates in laccase-catalyzed reactions was determined by monitoring the oxygen consumption. The oxidation reactions in 50% acetone in water mixture proceed with high rate for all tested lignins. Polymerization products were analyzed by size exclusion chromatography, FT-IR, and (31)P-NMR and evidence of important lignin modifications after incubation with laccase. Lignin polymers with higher molecular weight (Mw up to 17500 g/mol) were obtained. The obtained polymers have potential for applications in bioplastics, adhesives and as polymeric dispersants.

Criticality safety evaluation report for the Cold Vacuum Drying Facility's process water handling system

International Nuclear Information System (INIS)

Roblyer, S.D.

1998-01-01

This report addresses the criticality concerns associated with process water handling in the Cold Vacuum Drying Facility (CVDF). The controls and limitations on equipment design and operations to control potential criticality occurrences are identified. The effectiveness of equipment design and operation controls in preventing criticality occurrences during normal and abnormal conditions is evaluated and documented in this report. Spent nuclear fuel (SNF) is removed from existing canisters in both the K East and K West Basins and loaded into a multicanister overpack (MCO) in the K Basin pool. The MCO is housed in a shipping cask surrounded by clean water in the annulus between the exterior of the MCO and the interior of the shipping cask. The fuel consists of spent N Reactor and some single pass reactor fuel. The MCO is transported to the CVDF near the K Basins to remove process water from the MCO interior and from the shipping cask annulus. After the bulk water is removed from the MCO, any remaining free liquid is removed by drawing a vacuum on the MCO's interior. After cold vacuum drying is completed, the MCO is filled with an inert cover gas, the lid is replaced on the shipping cask, and the MCO is transported to the Canister Storage Building. The process water removed from the MCO contains fissionable materials from metallic uranium corrosion. The process water from the MCO is first collected in a geometrically safe process water conditioning receiver tank. The process water in the process water conditioning receiver tank is tested, then filtered, demineralized, and collected in the storage tank. The process water is finally removed from the storage tank and transported from the CVDF by truck

Ecosystem based river basin management planning in critical water catchment in Mongolia

Science.gov (United States)

Tugjamba, Navchaa; Sereeter, Erdenetuul; Gonchigjav, Sarantuya

2014-05-01

Developing the ecosystem based adaptation strategies to maintain water security in critical water catchments in Mongolia would be very significant. It will be base by reducing the vulnerability. "Ecosystem Based adaptation" is quite a new term in Mongolia and the ecosystem approach is a strategy for the integrated management of land, water and living resources that promotes conservation and sustainable use in an equitable way. To strengthen equitable economic development, food security, climate resilience and protection of the environment, the implementation of sustainable river basin management in critical water catchments is challenging in Mongolia. The Ulz river basin is considered one of the critical water catchments due to the temperature has increased by in average 1.30Ñ over the period 1976 to 2011. It is more intense than the global warming rate (0.740C/100 years) and a bit higher than the warming rate over whole Mongolia as well. From long-term observations and measurements it is clear that Ulz River has low water in a period of 1970-1980 and since the end of 1980s and middle of 1990s there were dominated years of the flood. However, under the influence of the global warming, climate changes of Mongolia and continuation of drought years with low water since the end of 1990s until today river water was sharply fallen and dried up. For the last ten years rivers are dried up and annual mean run-off is less by 3-5 times from long term mean value. The Ulz is the transboundary river basin and taking its origin from Ikh and Baga Burd springs on territory of Norovlin soum of Khentii province that flows through Khentii and Dornod provinces to the northeast, crossing the state border it flows in Baruun Tari located in Tari Lake concavity in Russia. Based on the integrative baseline study on the 'The Ulz River Basin Environmental and Socioeconomic condition', ecosystem based river basin management was planned. 'Water demand Calculator 3' (WDC) software was used to

Comparative studies of MOS-gate/oxide-passivated AlGaAs/InGaAs pHEMTs by using ozone water oxidation technique

International Nuclear Information System (INIS)

Lee, Ching-Sung; Hung, Chun-Tse; Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Ho, Chiu-Sheng; Lai, Ying-Nan

2012-01-01

Al 0.22 Ga 0.78 As/In 0.24 Ga 0.76 As pseudomorphic high-electron-mobility transistors (pHEMTs) with metal-oxide-semiconductor (MOS)-gate structure or oxide passivation by using ozone water oxidation treatment have been comprehensively investigated. Annihilated surface states, enhanced gate insulating property and improved device gain have been achieved by the devised MOS-gate structure and oxide passivation. The present MOS-gated or oxide-passivated pHEMTs have demonstrated superior device performances, including superior breakdown, device gain, noise figure, high-frequency characteristics and power performance. Temperature-dependent device characteristics of the present designs at 300–450 K are also studied. (paper)

Investigation of Iron Oxide Morphology in a Cyclic Redox Water Splitting Process for Hydrogen Generation

Directory of Open Access Journals (Sweden)

Michael M. Bobek

2012-10-01

Full Text Available A solar fuels generation research program is focused on hydrogen production by means of reactive metal water splitting in a cyclic iron-based redox process. Iron-based oxides are explored as an intermediary reactive material to dissociate water molecules at significantly reduced thermal energies. With a goal of studying the resulting oxide chemistry and morphology, chemical assistance via CO is used to complete the redox cycle. In order to exploit the unique characteristics of highly reactive materials at the solar reactor scale, a monolithic laboratory scale reactor has been designed to explore the redox cycle at temperatures ranging from 675 to 875 K. Using high resolution scanning electron microscope (SEM and electron dispersive X-ray spectroscopy (EDS, the oxide morphology and the oxide state are quantified, including spatial distributions. These images show the change of the oxide layers directly after oxidation and after reduction. The findings show a significant non-stoichiometric O/Fe gradient in the atomic ratio following oxidation, which is consistent with a previous kinetics model, and a relatively constant, non-stoichiometric O/Fe atomic ratio following reduction.

Oxidative dissolution of unirradiated Mimas MOX fuel (U/Pu oxides) in carbonated water under oxic and anoxic conditions

Energy Technology Data Exchange (ETDEWEB)

Odorowski, Mélina [CEA/DEN/DTCD/SECM/LMPA, BP 17171, 30207 Bagnols-sur-Cèze Cedex (France); MINES ParisTech, PSL Research University, Centre de Géosciences, 35 rue St Honoré, 77305 Fontainebleau (France); Jégou, Christophe, E-mail: christophe.jegou@cea.fr [CEA/DEN/DTCD/SECM/LMPA, BP 17171, 30207 Bagnols-sur-Cèze Cedex (France); De Windt, Laurent [MINES ParisTech, PSL Research University, Centre de Géosciences, 35 rue St Honoré, 77305 Fontainebleau (France); Broudic, Véronique; Peuget, Sylvain; Magnin, Magali; Tribet, Magaly [CEA/DEN/DTCD/SECM/LMPA, BP 17171, 30207 Bagnols-sur-Cèze Cedex (France); Martin, Christelle [Agence nationale pour la gestion des déchets radioactifs (Andra), DRD/CM, 1-7 rue Jean-Monnet, 92298 Châtenay-Malabry Cedex (France)

2016-01-15

Few studies exist concerning the alteration of Mimas Mixed-OXide (MOX) fuel, a mixed plutonium and uranium oxide, and data is needed to better understand its behavior under leaching, especially for radioactive waste disposal. In this study, two leaching experiments were conducted on unirradiated MOX fuel with a strong alpha activity (1.3 × 10{sup 9} Bq.g{sub MOX}{sup −1} reproducing the alpha activity of spent MOX fuel with a burnup of 47 GWd·t{sub HM}{sup −1} after 60 years of decay), one under air (oxic conditions) for 5 months and the other under argon (anoxic conditions with [O{sub 2}] < 1 ppm) for one year in carbonated water (10{sup −2} mol L{sup −1}). For each experiment, solution samples were taken over time and Eh and pH were monitored. The uranium in solution was assayed using a kinetic phosphorescence analyzer (KPA), plutonium and americium were analyzed by a radiochemical route, and H{sub 2}O{sub 2} generated by the water radiolysis was quantified by chemiluminescence. Surface characterizations were performed before and after leaching using Scanning Electron Microscopy (SEM), Electron Probe Microanalyzer (EPMA) and Raman spectroscopy. Solubility diagrams were calculated to support data discussion. The uranium releases from MOX pellets under both oxic and anoxic conditions were similar, demonstrating the predominant effect of alpha radiolysis on the oxidative dissolution of the pellets. The uranium released was found to be mostly in solution as carbonate species according to modeling, whereas the Am and Pu released were significantly sorbed or precipitated onto the TiO{sub 2} reactor. An intermediate fraction of Am (12%) was also present as colloids. SEM and EPMA results indicated a preferential dissolution of the UO{sub 2} matrix compared to the Pu-enriched agglomerates, and Raman spectroscopy showed the Pu-enriched agglomerates were slightly oxidized during leaching. Unlike Pu-enriched zones, the UO{sub 2} grains were much more

Synthesis of tungsten oxide, silver, and gold nanoparticles by radio frequency plasma in water

International Nuclear Information System (INIS)

Hattori, Yoshiaki; Nomura, Shinfuku; Mukasa, Shinobu; Toyota, Hiromichi; Inoue, Toru; Usui, Tomoya

2013-01-01

Highlights: •RF plasma in water was used for nanoparticle synthesis. •Nanoparticles were produced from erosion of metallic electrode. •Rectangular and spherical tungsten oxide nanoparticles were produced. •No oxidations of the silver and gold spherical nanoparticles were produced. -- Abstract: A process for synthesis of nanoparticles using plasma in water generated by a radio frequency of 27.12 MHz is proposed. Tungsten oxide, silver, and gold nanoparticles were produced at 20 kPa through erosion of a metallic electrode exposed to plasma. Characterization of the produced nanoparticles was carried out by XRD, absorption spectrum, and TEM. The nanoparticle sizes were compared with those produced by a similar technique using plasma in liquid

Water pollution abatement programme. The Czech Republic. Project 4.2. Assessing critical loads of acidity to surface waters in the Czech Republic. Critical loads of acidity to surface waters, north-eastern Bohemia and northern Moravia, The Czech Republic

Energy Technology Data Exchange (ETDEWEB)

Lien, L.; Raclavsky, K.; Raclavska, H.; Matysek, D.; Hovind, H.

1996-01-01

This report discusses estimates of critical loads of acidity to surface waters and their exceedances, for north-eastern Bohemia and Moravia in The Czech Republic. The survey covers 13 400 km{sup 2}, or 17% of the area of the country. Varying critical loads were observed within the examined region. 19% of the examined area showed exceedance of critical load and another 11% was close to exceedance. The survey should continue in Bohemia. 24 refs., 20 figs., 4 tabs.

Enhancing the Photovoltage of Ni/ n-Si Photoanode for Water Oxidation through a Rapid Thermal Process.

Science.gov (United States)

Li, Shengyang; She, Guangwei; Chen, Cheng; Zhang, Shaoyang; Mu, Lixuan; Guo, Xiangxin; Shi, Wensheng

2018-03-14

The Ni in the Ni/ n-Si photoanode can not only protect Si from corrosion, but also catalyze the water oxidation reaction. However, the high density of interface states at the Ni/ n-Si interface could pin the Fermi level of silicon, which will lower the Schottky barrier height of the Ni/ n-Si. As a result, a low photovoltage and consequent high onset potential of Ni/ n-Si photoanode for water oxidation were generated. In this study, the interfacial states of the Ni/ n-Si photoanodes were efficiently diminished through a rapid thermal process (RTP). Calculated from the Mott-Schottky plots, the Schottky barrier height of Ni/ n-Si was increased from 0.58 to 0.78 eV after RTP. Under the illumination of 100 mW cm -2 of the Xe lamp, the onset potential of the Ni/ n-Si photoanode for water oxidation was negatively shifted for 150 mV after RTP. Besides, the RTP-treated Ni/ n-Si photoanode exhibited a high stability during the PEC water oxidation of 8 h in 1 M KOH solution.

Criticality Safety Evaluation Report for the Cold Vacuum Drying (CVD) Facility's Process Water Handling System

International Nuclear Information System (INIS)

KESSLER, S.F.

2000-01-01

This report addresses the criticality concerns associated with process water handling in the Cold Vacuum Drying Facility. The controls and limitations on equipment design and operations to control potential criticality occurrences are identified

Measurement of water kinetics with deuterium oxide in lactating dairy cows

International Nuclear Information System (INIS)

Odwongo, W.O.; Conrad, H.R.; Staubus, A.E.; Harrison, J.H.

1985-01-01

Following intravenous infusion with approximately 300 mg deuterium oxide per kg body weight, blood was drawn from lactating Holsteins (Trial 1, n = 4, and Trial 2, n = 5) at suitable intervals for up to 12 days while the cows were maintained on dietary regimens to which they were well adapted. Time results for deuterium oxide concentration in blood were described best by the three-compartment open model system, which showed that the central, shallow peripheral, and deep peripheral body water compartments contained 27.1, 25.0, and 23.2% body weight in trial 1 and 33.7, 27.1, and 19.9% body weight in trial 2. Total body water estimates averaged 75.3 and 80.7% body weight during trials 1 and 2. Estimates for biological half-life of water were 4.6 and 3.2 days and those for water turnover were 68.9 and 109.7 liters/day, respectively. The data fitted the two-compartment open model system when observations made prior to 25 min post-administration were excluded from the analyses, because the central and shallow peripheral compartments were apparently lumped into one. Blood sampling at 0.5, 1, and 1.5 days following infusion and thereafter at 1-day intervals was adequate for the estimates of the one compartment open model system. Estimates of total body water, water biological half-life, and water turnover were similar for the different models. It is concluded that the three-compartment open model provides greater detail and insight into the water dynamics of lactating dairy cows having regular access to food and water, whereas the two- and one-compartment open model systems provide good approximations only

Water Resistant Container Technical Basis Document for the TA-55 Criticality Safety Program

Energy Technology Data Exchange (ETDEWEB)

Smith, Paul Herrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Teague, Jonathan Gayle [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-04-30

Criticality safety at TA-55 relies on nuclear material containers that are water resistant to prevent significant amounts of water from coming into contact with fissile material in the event of a fire that causes a breach of glovevbox confinement and subsequent fire water ingress. A “water tight container” is a container that will not allow more than 50ml of water ingress when fully submerged, except when under sufficient pressure to produce structural discontinuity. There are many types of containers, welded containers, hermetically sealed containers, filtered containers, etc.

Arsenic and antimony removal from drinking water by adsorption on granular ferric oxide.

Science.gov (United States)

Sazakli, Eleni; Zouvelou, Stavroula V; Kalavrouziotis, Ioannis; Leotsinidis, Michalis

2015-01-01

Arsenic and antimony occur in drinking water due to natural weathering or anthropogenic activities. There has been growing concern about their impact on health. The aim of this study was to assess the efficiency of a granular ferric oxide adsorbent medium to remove arsenic and antimony from drinking water via rapid small-scale column tests (RSSCTs). Three different water matrices - deionized, raw water treated with a reverse osmosis domestic device and raw water - were spiked with arsenic and/or antimony to a concentration of 100 μg L⁻¹. Both elements were successfully adsorbed onto the medium. The loadings until the guideline value was exceeded in the effluent were found to be 0.35-1.63 mg g⁻¹ for arsenic and 0.12-2.11 mg g⁻¹ for antimony, depending on the water matrix. Adsorption of one element was not substantially affected by the presence of the other. Aeration did not affect significantly the adsorption capacity. Granular ferric oxide could be employed for the simultaneous removal of arsenic and antimony from drinking water, whereas full-scale systems should be assessed via laboratory tests before their implementation.

Criticality Benchmark Analysis of Water-Reflected Uranium Oxyfluoride Slabs

International Nuclear Information System (INIS)

Marshall, Margaret A.; Bess, John D.

2009-01-01

A series of twelve experiments were conducted in the mid 1950's at the Oak Ridge National Laboratory Critical Experiments Facility to determine the critical conditions of a semi-infinite water-reflected slab of aqueous uranium oxyfluoride (UO2F2). A different slab thickness was used for each experiment. Results from the twelve experiment recorded in the laboratory notebook were published in Reference 1. Seven of the twelve experiments were determined to be acceptable benchmark experiments for the inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments. This evaluation will not only be available to handbook users for the validation of computer codes and integral cross-section data, but also for the reevaluation of experimental data used in the ANSI/ANS-8.1 standard. This evaluation is important as part of the technical basis of the subcritical slab limits in ANSI/ANS-8.1. The original publication of the experimental results was used for the determination of bias and bias uncertainties for subcritical slab limits, as documented by Hugh Clark's paper 'Subcritical Limits for Uranium-235 Systems'.

Applying the Msharpp Method in Risk Assessment for the Water Supply Critical Infrastructure Sector

Directory of Open Access Journals (Sweden)

Badea Dorel

2015-06-01

Full Text Available The paper highlights a manner to assess risks for an important sector of critical infrastructure, that of water supply, frequently regulated in international legal systems. We took into consideration the fact that risk is a problem related to the processes of decision making under conditions of uncertainty in most cases, so that by this approach we bring to the attention of critical infrastructure managers, drawing on their experience, a simple method that can be considered in a preliminary stage of risk assessment specific to water supply.

Simultaneous Oxidation and Sequestration of As(III) from Water by Using Redox Polymer-Based Fe(III) Oxide Nanocomposite.

Science.gov (United States)

Zhang, Xiaolin; Wu, Mengfei; Dong, Hao; Li, Hongchao; Pan, Bingcai

2017-06-06

Water decontamination from As(III) is an urgent but still challenging task. Herein, we fabricated a bifunctional nanocomposite HFO@PS-Cl for highly efficient removal of As(III), with active chlorine covalently binding spherical polystyrene host for in situ oxidation of As(III) to As(V), and Fe(III) hydroxide (HFO) nanoparticles (NPs) embedded inside for specific As(V) removal. HFO@PS-Cl could work effectively in a wide pH range (5-9), and other substances like sulfate, chloride, bicarbonate, silicate, and humic acid exert insignificant effect on As(III) removal. As(III) sequestration is realized via two pathways, that is, oxidation to As(V) by the active chlorine followed by specific As(V) adsorption onto HFO NPs, and As(III) adsorption onto HFO NPs followed by oxidation to As(V). The exhausted HFO@PS-Cl could be refreshed for cyclic runs with insignificant capacity loss by the combined regeneration strategy, that is, alkaline solution to rinse the adsorbed As(V) and NaClO solution to renew the host oxidation capability. In addition, fixed-bed experiments demonstrated that the HFO@PS-Cl column could generate >1760 bed volume (BV) effluent from a synthetic As(III)-containing groundwater to meet the drinking water standard (nanocomposites, HFO@PS-N and HFO@D201 could only generate 450 and 600 BV effluents under otherwise identical conditions.

Ammonia- and Nitrite-Oxidizing Bacterial Communities in a Pilot-Scale Chloraminated Drinking Water Distribution System

OpenAIRE

Regan, John M.; Harrington, Gregory W.; Noguera, Daniel R.

2002-01-01

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammon...

In situ Investigation of Oxide Films on Zirconium Alloy in PWR Primary Water Chemistry

Energy Technology Data Exchange (ETDEWEB)

Kim, Taeho; Choi, Kyoung Joon; Yoo, Seung Chang; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2015-05-15

Zirconium alloys are used as fuel cladding materials in nuclear power reactors, because these materials have a very low thermal neutron capture cross section as well as desirable mechanical properties. However, the Fukushima accident shows that the oxidation behavior of zirconium alloy is an important issue because the zirconium alloy functions as a shield of nuclear material (i.e., uranium, fission gas), and the degradation on zirconium cladding directly causes severe accident on nuclear power plant. Therefore, to ensure the safety of nuclear power reactors, the performance and sustainability of nuclear fuel should be understood. Currently, the water-metal interface is regarded as the rate-controlling site governing the rapid oxidation transition in high-burn-up fuels. Zirconium oxide is formed at the water-metal interface, and its structure and phase play an important role in determining its mechanical properties. In the early stage of the oxidation process, zirconium oxide with both tetragonal and monoclinic phases is formed. With an increase in the oxidation time to 150 h, the unstable tetragonal phase disappears and the monoclinic phase is dominant and possibly because of the stress relaxation according to previous and present results.

Water-Mediated Photochemical Treatments for Low-Temperature Passivation of Metal-Oxide Thin-Film Transistors.

Science.gov (United States)

Heo, Jae Sang; Jo, Jeong-Wan; Kang, Jingu; Jeong, Chan-Yong; Jeong, Hu Young; Kim, Sung Kyu; Kim, Kwanpyo; Kwon, Hyuck-In; Kim, Jaekyun; Kim, Yong-Hoon; Kim, Myung-Gil; Park, Sung Kyu

2016-04-27

The low-temperature electrical passivation of an amorphous oxide semiconductor (AOS) thin-film transistor (TFT) is achieved by a deep ultraviolet (DUV) light irradiation-water treatment-DUV irradiation (DWD) method. The water treatment of the first DUV-annealed amorphous indium-gallium-zinc-oxide (a-IGZO) thin film is likely to induce the preferred adsorption of water molecules at the oxygen vacancies and leads to subsequent hydroxide formation in the bulk a-IGZO films. Although the water treatment initially degraded the electrical performance of the a-IGZO TFTs, the second DUV irradiation on the water-treated devices may enable a more complete metal-oxygen-metal lattice formation while maintaining low oxygen vacancies in the oxide films. Overall, the stable and dense metal-oxygen-metal (M-O-M) network formation could be easily achieved at low temperatures (below 150 °C). The successful passivation of structural imperfections in the a-IGZO TFTs, such as hydroxyl group (OH-) and oxygen vacancies, mainly results in the enhanced electrical performances of the DWD-processed a-IGZO TFTs (on/off current ratio of 8.65 × 10(9), subthreshold slope of 0.16 V/decade, an average mobility of >6.94 cm(2) V(-1) s(-1), and a bias stability of ΔVTH IGZO TFTs.

Pebax®1657/Graphene oxide composite membranes for improved water vapor separation

KAUST Repository

Akhtar, Faheem Hassan; Kumar, Mahendra; Peinemann, Klaus-Viktor

2016-01-01

In this study composite mixed matrix membranes containing hydrophilic microphase-separated block copolymer (Pebax® 1657) and graphene oxide nanosheets were prepared using a dip coating method. Water vapor and N2 gas permeation were measured as a function of different parameters: (i) layer thickness, (ii) content of graphene oxide (GO), and (iii) content of reduced GO. Surprisingly, a concentration of only 2 wt% of GO nanosheets well dispersed in the Pebax layer boosted the selectivity 8 times by decreasing the water vapor permeance by only 12% whereas N2 gas permeance decreased by 70%. Using reduced GO instead, the water vapor permeance declined by up to 16% with no influence on the N2 gas permeance. We correlated the permeation properties of the mixed matrix membranes with different models and found, that both the modified Nielsen model and the Cussler model give good correlation with experimental findings.

Pebax®1657/Graphene oxide composite membranes for improved water vapor separation

KAUST Repository

Akhtar, Faheem Hassan

2016-11-02

In this study composite mixed matrix membranes containing hydrophilic microphase-separated block copolymer (Pebax® 1657) and graphene oxide nanosheets were prepared using a dip coating method. Water vapor and N2 gas permeation were measured as a function of different parameters: (i) layer thickness, (ii) content of graphene oxide (GO), and (iii) content of reduced GO. Surprisingly, a concentration of only 2 wt% of GO nanosheets well dispersed in the Pebax layer boosted the selectivity 8 times by decreasing the water vapor permeance by only 12% whereas N2 gas permeance decreased by 70%. Using reduced GO instead, the water vapor permeance declined by up to 16% with no influence on the N2 gas permeance. We correlated the permeation properties of the mixed matrix membranes with different models and found, that both the modified Nielsen model and the Cussler model give good correlation with experimental findings.

Critical discharge of initially subcooled water through slits

International Nuclear Information System (INIS)

Amos, C.N.; Schrock, V.E.

1983-09-01

This report describes an experimental investigation into the critical flow of initially subcooled water through rectangular slits. The study of such flows is relevant to the prediction of leak flow rates from cracks in piping, or pressure vessels, which contain sufficient enthalpy that vaporization will occur if they are allowed to expand to the ambient pressure. Two new analytical models, which allow for the generation of a metastable liquid phase, are developed. Experimental results are compared with the predictions of both these new models and with a Fanno Homogeneous Equilibrium Model

A model for oxidizing species concentrations in boiling water reactors

International Nuclear Information System (INIS)

Sun, B.; Chexal, B.; Pathania, R.; Chun, J.; Ballinger, R.; Abdollahian, D.

1993-01-01

To evaluate and control the intergranular stress corrosion cracking of boiling water reactor (BWR) vessel internal components requires knowledge of the concentration of oxidizing species that affects the electrochemical potentials in various regions of a BWR. In a BWR flow circuit, as water flows through the radiation field, the radiolysis process and chemical reactions lead to the production of species such as oxygen, hydrogen, and hydrogen peroxide. Since chemistry measurements are difficult inside BWRs, analytical tools have been developed by Ruiz and Lin, Ibe and Uchida and Chun and Ballinger for estimating the concentration of species that provide the necessary input for water chemistry control and material protection

Exogenous nitric oxide improves sugarcane growth and photosynthesis under water deficit.

Science.gov (United States)

Silveira, Neidiquele M; Frungillo, Lucas; Marcos, Fernanda C C; Pelegrino, Milena T; Miranda, Marcela T; Seabra, Amedea B; Salgado, Ione; Machado, Eduardo C; Ribeiro, Rafael V

2016-07-01

Nitric oxide (NO)-mediated redox signaling plays a role in alleviating the negative impact of water stress in sugarcane plants by improving root growth and photosynthesis. Drought is an environmental limitation affecting sugarcane growth and yield. The redox-active molecule nitric oxide (NO) is known to modulate plant responses to stressful conditions. NO may react with glutathione (GSH) to form S-nitrosoglutathione (GSNO), which is considered the main reservoir of NO in cells. Here, we investigate the role of NO in alleviating the effects of water deficit on growth and photosynthesis of sugarcane plants. Well-hydrated plants were compared to plants under drought and sprayed with mock (water) or GSNO at concentrations ranging from 10 to 1000 μM. Leaf GSNO sprayed plants showed significant improvement of relative water content and leaf and root dry matter under drought compared to mock-sprayed plants. Additionally, plants sprayed with GSNO (≥ 100 μM) showed higher leaf gas exchange and photochemical activity as compared to mock-sprayed plants under water deficit and after rehydration. Surprisingly, a raise in the total S-nitrosothiols content was observed in leaves sprayed with GSH or GSNO, suggesting a long-term role of NO-mediated responses to water deficit. Experiments with leaf discs fumigated with NO gas also suggested a role of NO in drought tolerance of sugarcane plants. Overall, our data indicate that the NO-mediated redox signaling plays a role in alleviating the negative effects of water stress in sugarcane plants by protecting the photosynthetic apparatus and improving shoot and root growth.

COMPARISON OF METHODS FOR ETHYLHEXYL 4-METHOXYCINNAMATE ACID ESTER OXIDATION IN WATER MEDIUM

Directory of Open Access Journals (Sweden)

Waldemar Studziński

2017-07-01

Full Text Available The aim of studies was to compare an impact of oxidizing agents on degradation of ethylhexyl 4-methoxycinnamate acid (EHMC. The oxidation reaction was carried out in the presence of sodium hypochlorite, hydrogen peroxide and ozone with/without UV radiation. EHMC degradation and analysis of products were performed using gas chromatograph coupled with mass spectrometry detector. The most effective method of EHMC degradation turned out to be ozonation with participation of UV radiation. In this system, degradation proceeded the most quickly and generated formation of small amount of by-products (2-propyl-1-pentanol; 4-metoxybenzaldehyde and Z-EHMC. Under the influence of sodium hypochlorite, the numerous chloroorganic products were formed, which can cause secondary contamination of water. Application of appropriate oxidation processes can contribute to degradation of micropollutants and thus to improvement of water quality.

Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

International Nuclear Information System (INIS)

Bory, Benjamin F.; Meskers, Stefan C. J.; Rocha, Paulo R. F.; Gomes, Henrique L.; Leeuw, Dago M. de

2015-01-01

Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10 17  m −2 . We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching

(Liquid + liquid) phase equilibrium and critical behavior of binary solution {heavy water + 2,6-dimethylpyridine}

International Nuclear Information System (INIS)

Xu, Chen; Chai, Shouning; Yin, Tianxiang; Chen, Zhiyun; Shen, Weiguo

2015-01-01

Highlights: • Coexistence curves, heat capacities and turbidities were measured. • Deuterium effect on coexistence curves was discussed. • Universal critical amplitude ratios were tested. • Asymmetry of coexistence curves was analyzed by the complete scaling theory. - Abstract: The (liquid + liquid) coexistence curves, the isobaric heat capacities per unit volume and the turbidities for the binary solution of {heavy water + 2,6-dimethylpyridine} have been precisely measured. The values of the critical exponents were obtained, which confirmed the 3D-Ising universality. It was found that the critical temperature dropped by 5.9 K and the critical amplitude of the coexistence curve significantly increased as compared to the binary solution of {water + 2,6-dimethylpyridine}. The complete scaling theory was applied to well describe the asymmetric behavior of the diameter of the coexistence curve as the heat capacity contribution was considered. Moreover, the values of the critical amplitudes of the correlation length and the osmotic compressibility were deduced, which together with the critical amplitudes of the coexistence curve and the heat capacity to test universal amplitude ratios

Numerical analysis of the reactivity for the dry lattices above the water level of the critical fuel cores

International Nuclear Information System (INIS)

Nauchi, Yasushi; Kameyama, Takanori

2003-01-01

Criticality analysis has been performed for dozens of tank type cores in which fuel lattices are loaded vertically and partially immersed in light water. The reactivity effect of dry part of lattices stuck above the critical water level has been calculated using the continuous energy Monte Carlo method. The reactivity effect exceeds 0.8% both for MOX and UOX fuel lattices of large buckling (B z 2 > 0.0025 cm -2 ). It is evaluated that at least 20 cm length of fuel rods above the critical water level has significant reactivity effect. (author)

Solid oxide electrolysis cell for decomposition of tritiated water

International Nuclear Information System (INIS)

Konishi, S.; Katsuta, H.; Naruse, Y.; Ohno, H.; Yoshida, H.

1984-01-01

The decomposition of tritiated water vapor with solid oxide electrolysis cell was proposed for the application to the D-T fusion reactor system. This method is essentially free from problems such as large tritium inventory, radiation damage, and generation of solid waste, so it is expected to be a promising one. Electrolysis of water vapor in argon carrier was performed using tube-type stabilized zirconia cell with porous platinum electrodes in the temperature range of 500 0 C to 950 0 C. High conversion ratio from water to hydrogen up to 99.9% was achieved. The characteristics of the cell is deduced from the Nernst's equation and conversion ratio is described as the function of the open circuit voltage. Experimental results agreed with the equation. Isotope effect in electrolysis is also discussed and experiments with heavy water were carried out. Obtained separation factor was slightly higher than the theoretical value

The impact of water concentration on the catalytic oxidation of ethanol on platinum electrode in concentrated phosphoric acid

Energy Technology Data Exchange (ETDEWEB)

Camargo, A.P.M.; Previdello, B.A.F.; Varela, H.; Gonzalez, E.R. [Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, C.P. 780, CEP 13560-970 Sao Carlos, SP (Brazil)

2010-01-15

The electro-oxidation of ethanol on platinum in phosphoric acid opens the door to promote the oxidation reaction at higher temperatures. However, the effect of the presence of water is not well understood. In this work, the electro-oxidation of ethanol on platinum was studied in concentrated phosphoric acid containing different concentrations of water at room temperature. The results show that effect of bulk water on the rate electro-oxidation is highest at 0.60 V and decreases for increasing potentials. This was suggested as due to the increasing formation of oxygenated species on the electrode surface with potential, which in turn is more efficient than the increase of water content in the electrolyte. Altogether, these results were interpreted as an evidence of a Langmuir-Hinshelwood step involving oxygenated species as one of the adsorbed partners. (author)

OPTIMUM, CRITICAL AND THRESHOLD VALUES FOR WATER OXYGENATION FOR MULLETS (MUGILIDAE AND FLATFISHES (PLEURONECTIDAE IN ONTOGENESIS

Directory of Open Access Journals (Sweden)

P. Shekk

2014-12-01

Full Text Available Purpose. To determine the optimum, critical, and threshold values of water oxygenation for embryos, larvae and fingerlings of mullets and flatfishes under different temperature conditions. Methodology. Oxygen consumption was studied in chronic experiments with «interrupted flow» method with automatic fixation of dissolved oxygen in water with the aid of an oxygen sensor and automatic, continuous recording of the obtained results. «Critical» (Pcrit., and the «threshold» (Pthr. oxygen tension in the water have been determined. Findings. Under optimum conditions, the normal embryogenesis of mullets and flatfish to the gastrulation stage, provided 90–130% oxygen saturation. The critical content was 80–85%, the threshold – 65–70% of the saturation. At the stage of «movable embryo» depending on water temperature and fish species, the optimum range of water oxygenation was within 70‒127.1%. The most tolerant to oxygen deficiency was flounder Platichthys luscus (Pcrit – 25.4–27,5; Pthr. – 20.5–22.5%, the least resistant to hypoxia was striped mullet Mugil серhalus (Pcrit. – 50–60; Pthr. – 35–40%. The limits of the critical and threshold concentration of dissolved oxygen directly depended on the temperature and salinity, at which embryogenesis occurred. An increase in water temperature and salinity resulted in an increase in critical and threshold values for oxygen tension embryos. Mullet and flatfish fingerlings in all stages of development had a high tolerance to hypoxia, which increased as they grew. They were resistant to the oversaturation of water with oxygen. The most demanding for the oxygen regime are larvae and fingerlings of striped mullet and Liza aurata. Hypoxia tolerance of Psetta maeoticus (Psetta maeoticus and flounder at all stages of development is very high. The fingerlings of these species can endure reduction of the dissolved oxygen in water to 2.10 and 1.65 mgO2/dm3 respectively for a long time

Surface chemistry of metals and their oxides in high temperature water

International Nuclear Information System (INIS)

Tomlinson, M.

1975-01-01

Examination of oxide and metal surfaces in water at high temperature by a broad spectrum of techniques is bringing understanding of corrosion product movement and alleviation of activity transport in CANDU-type reactor primary coolant circuits. (Author)

Nitric oxide reduces oxidative damage induced by water stress in sunflower plants

Directory of Open Access Journals (Sweden)

Inês Cechin

2015-06-01

Full Text Available Drought is one of the main environmental constraints that can reduce plant yield. Nitric oxide (NO is a signal molecule involved in plant responses to several environmental stresses. The objective of this study was to investigate the cytoprotective effect of a single foliar application of 0, 1, 10 or 100 µM of the NO donor sodium nitroprusside (SNP in sunflower plants under water stress. Water stressed plants treated with 1μM SNP showed an increase in the relative water content compared with 0 μM SNP. Drought reduced the shoot dry weight but SNP applications did not result in alleviation of drought effects. Neither drought nor water stress plus SNP applications altered the content of photosynthetic pigments. Stomatal conductance was reduced by drought and this reduction was accompanied by a significant reduction in intercellular CO2 concentration and photosynthesis. Treatment with SNP did not reverse the effect of drought on the gas exchange characteristics. Drought increased the level of malondialdehyde (MDA and proline and reduced pirogalol peroxidase (PG-POD activity, but did not affect the activity of superoxide dismutase (SOD. When the water stressed plants were treated with 10 μM SNP, the activity of PG-POD and the content of proline were increased and the level of MDA was decreased. The results show that the adverse effects of water stress on sunflower plants are dependent on the external NO concentration. The action of NO may be explained by its ability to increase the levels of antioxidant compounds and the activity of ROS-scavenging enzymes.

Oxidation kinetics of model compounds of metabolic waste in supercritical water

Science.gov (United States)

Webley, Paul A.; Holgate, Henry R.; Stevenson, David M.; Tester, Jefferson W.

1990-01-01

In this NASA-funded study, the oxidation kinetics of methanol and ammonia in supercritical water have been experimentally determined in an isothermal plug flow reactor. Theoretical studies have also been carried out to characterize key reaction pathways. Methanol oxidation rates were found to be proportional to the first power of methanol concentration and independent of oxygen concentration and were highly activated with an activation energy of approximately 98 kcal/mole over the temperature range 480 to 540 C at 246 bar. The oxidation of ammonia was found to be catalytic with an activation energy of 38 kcal/mole over temperatures ranging from 640 to 700 C. An elementary reaction model for methanol oxidation was applied after correction for the effect of high pressure on the rate constants. The conversion of methanol predicted by the model was in good agreement with experimental data.

Thermolysis of scrap tire and rubber in sub/super-critical water.

Science.gov (United States)

Li, Qinghai; Li, Fuxin; Meng, Aihong; Tan, Zhongchao; Zhang, Yanguo

2018-01-01

The rapid growth of waste tires has become a serious environmental issue. Energy and material recovery is regarded as a promising use for waste tires. Thermolysis of scrap tire (ST), natural rubber (NR), and styrene-butadiene rubber (SBR) was carried out in subcritical and supercritical water using a temperature-pressure independent adjustable batch tubular reactor. As a result, oil yields increased as temperature and pressure increased, and they reached maximum values as the state of water was near the critical point. However, further increases in water temperature and pressure reduced the oil yields. The maximum oil yield of 21.21% was obtained at 420 °C and 18 MPa with a reaction time of 40 min. The relative molecular weights of the chemicals in the oil products were in the range of 70-140 g/mole. The oil produced from ST, NR, and SBR contained similar chemical compounds, but the oil yield of SR was between those of NR and SBR. The oil yield from thermolysis of subcritical or supercritical water should be further improved. The main gaseous products, including CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , and C 3 H 8 , increased with reaction time, temperature, and pressure, whereas the solid residues, including carbon black and impurities, decreased. These results provide useful information to develop a sub/super-critical water thermolysis process for energy and material regeneration from waste tires. Copyright © 2017 Elsevier Ltd. All rights reserved.

The emulsifying and tribological properties of modified graphene oxide in oil-in-water emulsion

NARCIS (Netherlands)

Wu, Yinglei; Zeng, Xiangqiong; Ren, Tianhui; de Vries, Erik G.; van der Heide, Emile

2017-01-01

Graphene oxide (GO) was asymmetric chemically modified with myristyltrimethylammonium bromide (TTAB) to get modified graphene oxide (MGO). This MGO was used as an emulsifier and additive in oil-in-water emulsion. The emulsifying tests showed MGO greatly improved the stability of base emulsion and

Ceramic media amended with metal oxide for the capture of viruses in drinking water.

Science.gov (United States)

Brown, J; Sobsey, M D

2009-04-01

Ceramic materials that can adsorb and/or inactivate viruses in water may find widespread application in low-tech drinking-water treatment technologies in developing countries, where porous ceramic filters and ceramic granular media filters are increasingly promoted for that purpose. We examined the adsorption and subsequent inactivation of bacteriophages MS2 and (phiX-174 on five ceramic media in batch adsorption studies to determine media suitability for use in a ceramic water filter application. The media examined were a kaolinitic ceramic medium and four kaolinitic ceramic media amended with iron or aluminium oxides that had been incorporated into the kaolinitic clays before firing. Batch adsorption tests indicate increased sorption and inactivation of surrogate viruses by media amended with Fe and Al oxide, with FeOOH-amended ceramic inactivating all bacteriophages up to 8 log10. Unmodified ceramic was a poor adsorbent of bacteriophages at less than 1 log10 adsorption-inactivation and high recovery of sorbed phages. These studies suggest that contact with ceramic media, modified with electropositive Fe or Al oxides, can reduce bacteriophages in waters to a greater extent than unmodified ceramic.

Chemical oxidation methods in the closure of paper mill water circulations; Hapetustekniikoiden kaeyttoe metsaeteollisuuden vesikiertojen sulkemisessa - EKT 04

Energy Technology Data Exchange (ETDEWEB)

Laari, A.; Kallas, J. [Lappeenranta Univ. of Technology (Finland); Korhonen, S. [Kuopio Univ. (Finland); Tuhkanen, T. [Mikkelin Ammattikorkeakoulu, Mikkeli (Finland)

1998-12-31

When water circulations are closed some harmful compounds tend to accumulate in the circulation waters. These compounds include lipophilic extractives, like resin and fatty acids, triglycerides and sterols, but also other compounds, like lignins, lignans and sugars. Microbial growth will increase due to elevated organic concentrations. The purpose of this project is to find out the possibilities of the use of ozonation and wet oxidation in the treatment of paper mill water circulations. In chemical oxidation organic matter is destroyed in oxidation reactions. Especially lipophilic extractives are selectively oxidated by ozone. Chemical oxidation reactions are carried out in gas-liquid reactors, where ozone or oxygen are transferred from gas to liquid phase where the oxidation reactions happen. One target of the project is to estimate kinetic parameters for different groups of compounds on the basis of experimental data. Kinetic parameters are then used in modelling of reactors and in estimation of process costs. (orig.)

Chemical oxidation methods in the closure of paper mill water circulations; Hapetustekniikoiden kaeyttoe metsaeteollisuuden vesikiertojen sulkemisessa - EKT 04

Energy Technology Data Exchange (ETDEWEB)

Laari, A; Kallas, J [Lappeenranta Univ. of Technology (Finland); Korhonen, S [Kuopio Univ. (Finland); Tuhkanen, T [Mikkelin Ammattikorkeakoulu, Mikkeli (Finland)

1999-12-31

When water circulations are closed some harmful compounds tend to accumulate in the circulation waters. These compounds include lipophilic extractives, like resin and fatty acids, triglycerides and sterols, but also other compounds, like lignins, lignans and sugars. Microbial growth will increase due to elevated organic concentrations. The purpose of this project is to find out the possibilities of the use of ozonation and wet oxidation in the treatment of paper mill water circulations. In chemical oxidation organic matter is destroyed in oxidation reactions. Especially lipophilic extractives are selectively oxidated by ozone. Chemical oxidation reactions are carried out in gas-liquid reactors, where ozone or oxygen are transferred from gas to liquid phase where the oxidation reactions happen. One target of the project is to estimate kinetic parameters for different groups of compounds on the basis of experimental data. Kinetic parameters are then used in modelling of reactors and in estimation of process costs. (orig.)

Two factors important to the criticality potential of spent fuel in geologic repositories

International Nuclear Information System (INIS)

Gore, B.F.; Jenquin, U.P.

1981-02-01

Two factors important to the criticality potential of spent fuel in geologic repositories are: the residual fissile content of the fuel, and the extent to which geochemical processes might somehow separate and accumulate plutonium from other spent fuel materials. This paper presents the results of two calculational surveys defining conditions required for criticality. In the first, homogeneous spherical mixtures of spent fuel actinide oxides and water with water reflection are analyzed. Graphs of minimum critical mass vs duration of in-reactor exposure are presented. Parametric variations from a base case are explored, including the effects of initial enrichment, post exposure radioactive decay and addition of rock materials to the mixture. In the second study, homogeneous spherical mixtures devoid of water, containing plutonium and a neutronically optimized rock material, with a thick rock neutron reflector are analyzed. Graphs of Pu critical mass are presented as a function of concentration over the range from 2 to 100 g Pu/l. Parametric variations from a base case are explored, including effects of rock composition, 240 Pu content and uranium contamination of the plutonium

Water quality assessment using the AREc32 reporter gene assay indicative of the oxidative stress response pathway.

Science.gov (United States)

Escher, Beate I; Dutt, Mriga; Maylin, Erin; Tang, Janet Y M; Toze, Simon; Wolf, C Roland; Lang, Matti

2012-11-01

The reporter gene assay AREc32 is based on the induction of the Nrf2 mediated oxidative stress response pathway in the human breast cancer cell line MCF7, where eight copies of the antioxidant response element (ARE) are linked to a reporter gene encoding for luciferase. The Nrf2-ARE pathway is responsive to many chemicals that cause oxidative stress, among them a large number of pesticides and skin irritants. We adopted and validated the AREc32 bioassay for water quality testing. tert-Butylhydroquinone served as the positive control, phenol as the negative control and other reactive chemicals were assessed for their specificity. An environmentally relevant reference chemical, benzo(a)pyrene was the most potent inducer of all tested chemicals. The concentration causing an induction ratio (IR) of 1.5 (EC(IR1.5)) was chosen as the effect benchmark value. The assay was applied to 21 water samples ranging from sewage to drinking water, including secondary treatment and various tertiary treatment options (ozonation, biologically activated carbon filtration, membrane filtration, reverse osmosis, advanced oxidation, chlorination, chloramination). The samples were enriched by solid phase extraction. In most samples the oxidative stress response was far more sensitive than cytotoxicity. The primary and secondary treated effluent exceeded the effect threshold IR 1.5 at a relative enrichment factor (REF) of 1, i.e., the native samples were active. All tertiary treated samples were less potent and their EC(IR1.5) lay between REF 1 and 10. The Nrf2 pathway was induced at a REF of approximately 10 for surface waters and drinking water, and above this enrichment cytotoxicity took over in most samples and quenched the induction. The blank (ultrapure water run through the sample enrichment process) was cytotoxic at an REF of 100, which is the limit of concentrations range that can be evaluated. Treatment typically decreased both the cytotoxicity and oxidative stress response apart

An Alternative Reaction Pathway for Iridium Catalyzed Water Oxidation Driven by CAN

KAUST Repository

Bucci, Alberto; Menendez Rodriguez, Gabriel; Bellachioma, Gianfranco; Zuccaccia, Cristiano; Poater, Albert; Cavallo, Luigi; Macchioni, Alceo

2016-01-01

The generation of solar fuels by means of a photosynthetic apparatus strongly relies on the development of an efficient water oxidation catalyst (WOC). Cerium ammonium nitrate (CAN) is the most commonly used sacrificial oxidant to explore the potentiality of WOCs. It is usually assumed that CAN has the unique role to oxidatively energize WOCs, making them capable to offer a low energy reaction pathway to transform H2O to O2. Herein we show that CAN might have a much more relevant and direct role in WO, mainly related to the capture and liberation of O–O containing molecular moieties.

An Alternative Reaction Pathway for Iridium Catalyzed Water Oxidation Driven by CAN

KAUST Repository

Bucci, Alberto

2016-06-10

The generation of solar fuels by means of a photosynthetic apparatus strongly relies on the development of an efficient water oxidation catalyst (WOC). Cerium ammonium nitrate (CAN) is the most commonly used sacrificial oxidant to explore the potentiality of WOCs. It is usually assumed that CAN has the unique role to oxidatively energize WOCs, making them capable to offer a low energy reaction pathway to transform H2O to O2. Herein we show that CAN might have a much more relevant and direct role in WO, mainly related to the capture and liberation of O–O containing molecular moieties.

Electrochemical advanced oxidation processes as decentralized water treatment technologies to remediate domestic washing machine effluents.

Science.gov (United States)

Dos Santos, Alexsandro Jhones; Costa, Emily Cintia Tossi de Araújo; da Silva, Djalma Ribeiro; Garcia-Segura, Sergi; Martínez-Huitle, Carlos Alberto

2018-03-01

Water scarcity is one of the major concerns worldwide. In order to secure this appreciated natural resource, management and development of water treatment technologies are mandatory. One feasible alternative is the consideration of water recycling/reuse at the household scale. Here, the treatment of actual washing machine effluent by electrochemical advanced oxidation processes was considered. Electrochemical oxidation and electro-Fenton technologies can be applied as decentralized small-scale water treatment devices. Therefore, efficient decolorization and total organic abatement have been followed. The results demonstrate the promising performance of solar photoelectro-Fenton process, where complete color and organic removal was attained after 240 min of treatment under optimum conditions by applying a current density of 66.6 mA cm -2 . Thus, electrochemical technologies emerge as promising water-sustainable approaches.

Bench-scale study of the effect of phosphate on an aerobic iron oxidation plant for mine water treatment.

Science.gov (United States)

Tischler, Judith S; Wiacek, Claudia; Janneck, Eberhard; Schlömann, Michael

2014-01-01

At the opencast pit Nochten acidic iron- and sulfate-rich mine waters are treated biotechnologically in a mine-water treatment plant by microbial iron oxidation. Due to the low phosphate concentration in such waters the treatment plant was simulated in bench-scale to investigate the influence of addition of potassium dihydrogen phosphate on chemical and biological parameters of the mine-water treatment. As a result of the phosphate addition the number of cells increased, which resulted in an increase of the iron oxidation rate in the reactor with phosphate addition by a factor of 1.7 compared to a reference approach without phosphate addition. Terminal restriction fragment length polymorphism (T-RFLP) analysis during the cultivation revealed a shift of the microbial community depending on the phosphate addition. While almost exclusively iron-oxidizing bacteria related to "Ferrovum" sp. were detected with phosphate addition, the microbial community was more diverse without phosphate addition. In the latter case, iron-oxidizing bacteria ("Ferrovum" sp., Acidithiobacillus spp.) as well as non-iron-oxidizing bacteria (Acidiphilium sp.) were identified. Copyright © 2013 Elsevier Ltd. All rights reserved.

Chemical oxidation of unsymmetrical dimethylhydrazine transformation products in water

Directory of Open Access Journals (Sweden)

Madi Abilev

2015-03-01

Full Text Available Oxidation of unsymmetrical dimethylhydrazine (UDMH during a water treatment has several disadvantages including formation of stable toxic byproducts. Effectiveness of treatment methods in relation to UDMH transformation products is currently poorly studied. This work considers the effectiveness of chemical oxidants in respect to main metabolites of UDMH – 1-formyl-2,2-dimethylhydrazine, dimethylaminoacetontrile, N-nitrosodimethylamine and 1-methyl-1H-1,2,4-triazole. Experiments on chemical oxidation by Fenton's reagent, potassium permanganate and sodium nitrite were conducted. Quantitative determination was performed by HPLC. Oxidation products were identified by gas chromatography-mass spectrometry in combination with solid-phase microextraction. 1-Formyl-2,2-dimethylhydrazine was completely oxidized by Fenton's reagent with formation of formaldehyde N-formyl-N-methyl-hydrazone, 1,4-dihydro-1,4-dimethyl-5H-tetrazol-5-one by the action of potassium permanganate and N-methyl-N-nitro-methanamine in the presence of sodium nitrite. Oxidation of 1-formyl-2,2-dimethylhydrazine also resulted in formation of N-nitrosodimethylamine. Oxidation of dimethylaminoacetontrile proceeded with formation of hydroxyacetonitrile, dimethylformamide and 1,2,5-trimethylpyrrole. After 30 days, dimethylaminoacetontrile was not detected in the presence of Fenton’s reagent and potassium permanganate, but it’s concentration in samples with sodium nitrite was 77.3 mg/L. In the presence of Fenton’s reagent, potassium permanganate and sodium nitrite after 30 days, N-nitrosodimethylamine concentration decreased by 85, 80 and 50%, respectively. In control sample, N-nitrosodimethylamine concentration decreased by 50%, indicating that sodium nitrite has no effect of on N-nitrosodimethylamine concentration. Only Fenton's reagent allowed to reduce the concentration of 1-methyl-1H-1,2,4-triazole to 50% in 30 days. In the presence of other oxidants, 1-methyl-1H-1,2,4-triazole

Effect of Leaves of Caesalpinia decapetala on Oxidative Stability of Oil-in-Water Emulsions

Directory of Open Access Journals (Sweden)

María Gabriela Gallego

2017-03-01

Full Text Available Caesalpinia decapetala (Roth Alston (Fabaceae (CD is used in folk medicine to prevent colds and treat bronchitis. This plant has antitumor and antioxidant activity. The antioxidant effects of an extract from Caesalpinia decapetala (Fabaceae were assessed by storage of model food oil-in-water emulsions with analysis of primary and secondary oxidation products. The antioxidant capacity of the plant extract was evaluated by the diphenylpicrylhydrazyl (DPPH, Trolox equivalent antioxidant capacity (TEAC, oxygen radical absorbance capacity (ORAC and ferric reducing antioxidant power (FRAP assays and by electron paramagnetic resonance (EPR spectroscopy. Lyophilized extracts of CD were added at concentrations of 0.002%, 0.02% and 0.2% into oil-in-water emulsions, which were stored for 30 days at 33 ± 1 °C, and then, oxidative stability was evaluated. The CD extract had high antioxidant activity (700 ± 70 µmol Trolox/g dry plant for the ORAC assay, mainly due to its phenolic components: gallic acid, quercetin, catechin, 4-hydroxybenzoic acid and p-coumaric acid. At a concentration of 0.2%, the extract significantly reduced the oxidative deterioration of oil-in-water emulsions. The results of the present study show the possibility of utilizing CD as a promising source of natural antioxidants for retarding lipid oxidation in the food and cosmetic industries.

Hierarchically porous, ultra-strong reduced graphene oxide-cellulose nanocrystal sponges for exceptional adsorption of water contaminants

DEFF Research Database (Denmark)

Yousefi, Nariman; Wong, Kerwin K.W.; Hosseinidoust, Zeinab

2018-01-01

Self-assembly of graphene oxide (GO) nanosheets into porous 3D sponges is a promising approach to exploit their capacity to adsorb contaminants while facilitating the recovery of the nanosheets from treated water. Yet, forming mechanically robust sponges with suitable adsorption properties presents...... a significant challenge. Ultra-strong and highly porous 3D sponges are formed using GO, vitamin C (VC), and cellulose nanocrystals (CNCs) - natural nanorods isolated from wood pulp. CNCs provide a robust scaffold for the partially reduced GO (rGO) nanosheets resulting in an exceptionally stiff nanohybrid....... The concentration of VC as a reducing agent plays a critical role in tailoring the pore architecture of the sponges. By using excess amounts of VC, a unique hierarchical pore structure is achieved, where VC grains act as soft templates for forming millimeter-sized pores, the walls of which are also porous...

Boosting water oxidation layer-by-layer.

Science.gov (United States)

Hidalgo-Acosta, Jonnathan C; Scanlon, Micheál D; Méndez, Manuel A; Amstutz, Véronique; Vrubel, Heron; Opallo, Marcin; Girault, Hubert H

2016-04-07

Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2 NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and sizes. UV/vis spectroscopic and spectro-electrochemical studies confirmed that the total surface coverage and electrochemically addressable surface coverage of IrO2 NPs increased linearly with the number of bilayers up to 10 bilayers. The voltammetry of the modified electrode was that of hydrous iridium oxide films (HIROFs) with an observed super-Nernstian pH response of the Ir(III)/Ir(IV) and Ir(IV)-Ir(IV)/Ir(IV)-Ir(V) redox transitions and Nernstian shift of the oxygen evolution onset potential. The overpotential of the oxygen evolution reaction (OER) was essentially pH independent, varying only from 0.22 V to 0.28 V (at a current density of 0.1 mA cm(-2)), moving from acidic to alkaline conditions. Bulk electrolysis experiments revealed that the IrO2/PDDA films were stable and adherent under acidic and neutral conditions but degraded in alkaline solutions. Oxygen was evolved with Faradaic efficiencies approaching 100% under acidic (pH 1) and neutral (pH 7) conditions, and 88% in alkaline solutions (pH 13). This layer-by-layer approach forms the basis of future large-scale OER electrode development using ink-jet printing technology.

Formation of assimilable organic carbon during oxidation of natural waters with ozone, chlorine dioxide, chlorine, permanganate, and ferrate.

Science.gov (United States)

Ramseier, Maaike K; Peter, Andreas; Traber, Jacqueline; von Gunten, Urs

2011-02-01

Five oxidants, ozone, chlorine dioxide, chlorine, permanganate, and ferrate were studied with regard to the formation of assimilable organic carbon (AOC) and oxalate in absence and presence of cyanobacteria in lake water matrices. Ozone and ferrate formed significant amounts of AOC, i.e. more than 100 μg/L AOC were formed with 4.6 mg/L ozone and ferrate in water with 3.8 mg/L dissolved organic carbon. In the same water samples chlorine dioxide, chlorine, and permanganate produced no or only limited AOC. When cyanobacterial cells (Aphanizomenon gracile) were added to the water, an AOC increase was detected with ozone, permanganate, and ferrate, probably due to cell lysis. This was confirmed by the increase of extracellular geosmin, a substance found in the selected cyanobacterial cells. AOC formation by chlorine and chlorine dioxide was not affected by the presence of the cells. The formation of oxalate upon oxidation was found to be a linear function of the oxidant consumption for all five oxidants. The following molar yields were measured in three different water matrices based on oxidant consumed: 2.4-4.4% for ozone, 1.0-2.8% for chlorine dioxide and chlorine, 1.1-1.2% for ferrate, and 11-16% for permanganate. Furthermore, oxalate was formed in similar concentrations as trihalomethanes during chlorination (yield ∼ 1% based on chlorine consumed). Oxalate formation kinetics and stoichiometry did not correspond to the AOC formation. Therefore, oxalate cannot be used as a surrogate for AOC formation during oxidative water treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Solid oxide electrolysis cell for decomposition of tritiated water

International Nuclear Information System (INIS)

Konishi, S.; Ohno, H.; Yoshida, H.; Katsuta, H.; Naruse, Y.

1986-01-01

The decomposition of tritiated water vapor by means of solid oxide electrolysis cells has been proposed for the application to the D-T fusion reactor system. This method is essentially free from problems such as large tritium inventory, radiation damage, and generation of solid waste, so it is expected to be a promising one. Electrolysis of water vapor in an argon carrier was performed using a tube-type stabilized zirconia cell with porous platinum electrodes over the temperature range 500-950 0 C. High conversion ratios from water to hydrogen, of up to 99.9%, were achieved. The characteristics of the cell were deduced from the Nernst equation and the conversion ratios expressed as a function of the IR-free voltage. Experimental results agreed with the equation. The isotope effect in electrolysis is also discussed and experiments with heavy water were carried out. The obtained separation factor was slightly higher than the theoretical value. (author)

IN-SITU FENTON OXIDATION: A CRITICAL ANALYSIS

Science.gov (United States)

In-situ Fenton oxidation (ISFO) is a rapidly emerging technology which involves the injection of hydrogen peroxide (H2O2) and other chemical reagents into the subsurface for the purpose of oxidizing and transforming contaminants. ISFO is being applied at an increasing number of ...

Selenide-Based Electrocatalysts and Scaffolds for Water Oxidation Applications

KAUST Repository

Xia, Chuan; Jiang, Qiu; Zhao, Chao; Hedhili, Mohamed N.; Alshareef, Husam N.

2015-01-01

Selenide-based electrocatalysts and scaffolds on carbon cloth are successfully fabricated and demonstrated for enhanced water oxidation applications. A max­imum current density of 97.5 mA cm−2 at an overpotential of a mere 300 mV and a small Tafel slope of 77 mV dec−1 are achieved, suggesting the potential of these materials to serve as advanced oxygen evolution reaction catalysts.

Selenide-Based Electrocatalysts and Scaffolds for Water Oxidation Applications

KAUST Repository

Xia, Chuan

2015-11-05

Selenide-based electrocatalysts and scaffolds on carbon cloth are successfully fabricated and demonstrated for enhanced water oxidation applications. A max­imum current density of 97.5 mA cm−2 at an overpotential of a mere 300 mV and a small Tafel slope of 77 mV dec−1 are achieved, suggesting the potential of these materials to serve as advanced oxygen evolution reaction catalysts.

Solvation of graphite oxide in water-methanol binary polar solvents

Energy Technology Data Exchange (ETDEWEB)

You, Shujie; Yu, Junchun; Sundqvist, Bertil; Talyzin, Alexandr V. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2012-12-15

The phase transition between two solvated phases was studied by DSC for graphite oxide (GO) powders immersed in water-methanol mixtures of various compositions. GO forms solid solvates with two different compositions when immersed in methanol. Reversible phase transition between two solvate states due to insertion/desertion of methanol monolayer occurs upon temperature variations. The temperature point and the enthalpy ({Delta}H) of the phase transition are maximal for pure methanol and decrease linearly with increase of water fraction up to 30%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Promotion of Water-mediated Carbon Removal by Nanostructured Barium Oxide/nickel Interfaces

Energy Technology Data Exchange (ETDEWEB)

L Yang; Y Choi; W Qin; H Chen; K Blinn; M Liu; P Liu; J Bai; T Tyson; M Liu

2011-12-31

The existing Ni-yttria-stabilized zirconia anodes in solid oxide fuel cells (SOFCs) perform poorly in carbon-containing fuels because of coking and deactivation at desired operating temperatures. Here we report a new anode with nanostructured barium oxide/nickel (BaO/Ni) interfaces for low-cost SOFCs, demonstrating high power density and stability in C{sub 3}H{sub 8}, CO and gasified carbon fuels at 750 C. Synchrotron-based X-ray analyses and microscopy reveal that nanosized BaO islands grow on the Ni surface, creating numerous nanostructured BaO/Ni interfaces that readily adsorb water and facilitate water-mediated carbon removal reactions. Density functional theory calculations predict that the dissociated OH from H2O on BaO reacts with C on Ni near the BaO/Ni interface to produce CO and H species, which are then electrochemically oxidized at the triple-phase boundaries of the anode. This anode offers potential for ushering in a new generation of SOFCs for efficient, low-emission conversion of readily available fuels to electricity.

Ruthenium water oxidation catalysts containing the non-planar tetradentate ligand, biisoquinoline dicarboxylic acid (biqaH2).

Science.gov (United States)

Scherrer, Dominik; Schilling, Mauro; Luber, Sandra; Fox, Thomas; Spingler, Bernhard; Alberto, Roger; Richmond, Craig J

2016-12-06

Two ruthenium complexes containing the tetradentate ligand [1,1'-biisoquinoline]-3,3'-dicarboxylic acid, and 4-picoline or 6-bromoisoquinoline as axial ligands have been prepared. The complexes have been fully characterised and initial studies on their potential to function as molecular water oxidation catalysts have been performed. Both complexes catalyse the oxidation of water in acidic media with Ce IV as a stoichiometric chemical oxidant, although turnover numbers and turnover frequencies are modest when compared with the closely related Ru-bda and Ru-pda analogues. Barriers for the water nucleophilic attack and intermolecular coupling pathways were obtained from density functional theory calculations and the crucial influence of the ligand framework in determining the most favourable reaction pathway was elucidated from a combined analysis of the theoretical and experimental results.

Supercritical Water Oxidation: A Solution for the Elimination of Back-End Organic Reprocessing Wastes

Energy Technology Data Exchange (ETDEWEB)

Leybros, A.; Roubaud, A.; Turc, H.A.; Fournel, B. [Supercritical fluids and membranes Laboratory, CEA Valrho, BP 17171, 30207 Bagnols/Ceze Cedex (France)

2008-07-01

Supercritical water oxidation (SCWO) is a very efficient technique for total elimination of organic wastes from reprocessing activities on the way of 'zero wastes' facilities. This technology uses the properties of supercritical water (P > 221 bars and T > 647 K) to obtain a good mixing between oxygen (the oxidant) and the organic waste. Thereby, the oxidation reaction is fast and complete. Using the SCWO process, contamination contained in organic materials like spent solvents can be confined in a closed space, like a reactor in a glovebox. A new application is tested for the treatment of solid organic wastes like ion exchange resins (IER). Experiments are made with suspensions of IER in water and isopropyl-alcohol. A nuclear version of the process with the double shell reactor has been constructed and is being tested. The aim of this work is to obtain a treatment capacity of 1 kg/h for the nuclear version with the same global set-up, concept of process and security as well as contamination management as for a 200 g/h pilot. (authors)

Supercritical Water Oxidation: A Solution for the Elimination of Back-End Organic Reprocessing Wastes

International Nuclear Information System (INIS)

Leybros, A.; Roubaud, A.; Turc, H.A.; Fournel, B.

2008-01-01

Supercritical water oxidation (SCWO) is a very efficient technique for total elimination of organic wastes from reprocessing activities on the way of 'zero wastes' facilities. This technology uses the properties of supercritical water (P > 221 bars and T > 647 K) to obtain a good mixing between oxygen (the oxidant) and the organic waste. Thereby, the oxidation reaction is fast and complete. Using the SCWO process, contamination contained in organic materials like spent solvents can be confined in a closed space, like a reactor in a glovebox. A new application is tested for the treatment of solid organic wastes like ion exchange resins (IER). Experiments are made with suspensions of IER in water and isopropyl-alcohol. A nuclear version of the process with the double shell reactor has been constructed and is being tested. The aim of this work is to obtain a treatment capacity of 1 kg/h for the nuclear version with the same global set-up, concept of process and security as well as contamination management as for a 200 g/h pilot. (authors)

Exploring the Relationship between Critical Thinking Style and Water Conservation Behavior: Implications for Extension

Science.gov (United States)

Owens, Courtney T.; Lamm, Alexa J.

2016-01-01

In the past several years Cooperative Extension has focused on developing educational programs that address water conservation, specifically for individuals using exorbitant amounts of water, with limited success. However, few research studies have examined how the way people think, including their critical thinking styles, can be used to inform…

Oxidative Stress and Antioxidant Therapy in Critically Ill Polytrauma Patients with Severe Head Injury

Directory of Open Access Journals (Sweden)

Luca Loredana

2015-05-01

Full Text Available Traumatic Brain Injury (TBI is one of the leading causes of death among critically ill patients from the Intensive Care Units (ICU. After primary traumatic injuries, secondary complications occur, which are responsible for the progressive degradation of the clinical status in this type of patients. These include severe inflammation, biochemical and physiological imbalances and disruption of the cellular functionality. The redox cellular potential is determined by the oxidant/antioxidant ratio. Redox potential is disturbed in case of TBI leading to oxidative stress (OS. A series of agression factors that accumulate after primary traumatic injuries lead to secondary lesions represented by brain ischemia and hypoxia, inflammatory and metabolic factors, coagulopathy, microvascular damage, neurotransmitter accumulation, blood-brain barrier disruption, excitotoxic damage, blood-spinal cord barrier damage, and mitochondrial dysfunctions. A cascade of pathophysiological events lead to accelerated production of free radicals (FR that further sustain the OS. To minimize the OS and restore normal oxidant/antioxidant ratio, a series of antioxidant substances is recommended to be administrated (vitamin C, vitamin E, resveratrol, N-acetylcysteine. In this paper we present the biochemical and pathophysiological mechanism of action of FR in patients with TBI and the antioxidant therapy available.

Effect of Support in Heterogeneous Ruthenium Catalysts Used for the Selective Aerobic Oxidation of HMF in Water

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Riisager, Anders

2011-01-01

Heterogeneous ruthenium-based catalysts were applied in the selective, aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, to form 2,5-furandicarboxylic acid. The oxidation reactions were performed in water with dioxygen as the oxidant at different pressures without...

Inter-annual variations in water yield to lakes in northeastern Alberta: implications for estimating critical loads of acidity

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Roderick HAZEWINKEL

2010-08-01

Full Text Available Stable isotopes of water were applied to estimate water yield to fifty lakes in northeastern Alberta as part of an acid sensitivity study underway since 2002 in the Athabasca Oil Sands Region (AOSR. Herein, we apply site-specific water yields for each lake to calculate critical loads of acidity using water chemistry data and a steady-state water chemistry model. The main goal of this research was to improve site-specific critical load estimates and to understand the sensitivity to hydrologic variability across a Boreal Plains region under significant oil sands development pressure. Overall, catchment water yields were found to vary significantly over the seven year monitoring period, with distinct variations among lakes and between different regions, overprinted by inter-annual climate-driven shifts. Analysis of critical load estimates based on site-specific water yields suggests that caution must be applied to establish hydrologic conditions and define extremes at specific sites in order to protect more sensitive ecosystems. In general, lakes with low (high water yield tended to be more (less acid sensitive but were typically less (more affected by interannual hydrological variations. While it has been customary to use long-term water yields to define a static critical load for lakes, we find that spatial and temporal variability in water yield may limit effectiveness of this type of assessment in areas of the Boreal Plain characterized by heterogeneous runoff and without a long-term lake-gauging network. Implications for predicting acidification risk are discussed for the AOSR.

Nano-sized Mn3O4 and β-MnOOH from the decomposition of β-cyclodextrin-Mn: 2. The water-oxidizing activities.

Science.gov (United States)

Najafpour, Mohammad Mahdi; Mostafalu, Ramin; Hołyńska, Małgorzata; Ebrahimi, Foad; Kaboudin, Babak

2015-11-01

Nano-sized Mn oxides contain Mn3O4, β-MnOOH and Mn2O3 have been prepared by a previously reported method using thermal decomposition of β-cyclodextrin-Mn complexes. In the next step, the water-oxidizing activities of these Mn oxides using cerium(IV) ammonium nitrate as a chemical oxidant are studied. The turnover frequencies for β-MnO(OH) and Mn3O4 are 0.24 and 0.01-0.17 (mmol O2/mol Mns), respectively. Subsequently, water-oxidizing activities of these compounds are compared to the other previously reported Mn oxides. Important factors affecting water oxidation by these Mn oxides are also discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Study mechanism of growth and spallation of oxide scales formed after T91 steel oxidation in water vapor at 550 C

International Nuclear Information System (INIS)

Demizieux, Marie-Christine

2015-01-01

In the framework of the development of Generation IV reactors and specifically in the new Sodium Fast Reactor (SFR) project, Fe-9Cr ferritic-martensitic steels are candidates as structural materials for steam generators. Indeed, Fe-9Cr steels are already widely used in high temperature steam environments - like boilers and steam turbines- for their combination of creep strength and high thermal properties. Many studies have been focused on Fe-9Cr steels oxidation behavior between 550 C-700 C.Depending on the oxidizing environment, formation of a triplex (Fe-Cr spinel/magnetite/hematite) or duplex (Fe-Cr spinel/magnetite) oxide scales are reported.. Besides, for long time exposure in steam, the exfoliation of oxide scales can cause serious problems such as tube obstruction and steam turbine erosion. Consequently, this work has been dedicated to study, on the one hand the oxidation kinetics of T91 steel in water vapor environments, and on the other hand, the mechanisms leading to the spallation of the oxide scale. Oxidation tests have been carried out at 550 C in pure water vapor and in Ar/D_2O/H_2 environments with different hydrogen contents. Based on an analytical resolution, a quantitative modeling has shown that the 'available space model' proposed in the literature for duplex oxide scale formation well reproduces both scales growth kinetics and spinel oxide stoichiometry. Then, oxidized samples have been precisely characterized and it turns out that buckling then spalling of the oxide scale is always located in the magnetite layer. Voids observed in the magnetite layer are major initiation sites of de-cohesion of the outer oxide scale. A mechanism of formation of these voids has been proposed, in accordance with the mechanism of duplex scale formation. The derived model based on the assumption that vacancies accumulate where the iron vacancies flux divergence is maximal gives a good estimation of the location of pores inside the magnetite layer. Then, in order

On the crystalline structures of iron oxides formed during the removal process of iron in water

International Nuclear Information System (INIS)

Cho, Bongyeon; Fujita, Kenji; Oda, Katsuro; Ino, Hiromitsu

1993-01-01

The iron oxide samples collected from both filtration and batch reactors were analysed by X-ray diffraction and Moessbauer spectroscopy. In the filtration of water containing iron, the oxidized form of iron was determined to be ferrihydrite. In contrast, in the batch experiment without filtration, iron was oxidized to microcrystalline goethite. (orig.)

Effect of surface modification on the corrosion resistivity in supercritical water

International Nuclear Information System (INIS)

Penttila, S.; Horvath, A.; Toivonen, A.; Zolnai, Z.

2011-01-01

This paper summarizes the results of high temperature corrosion studies of the candidate austenitic alloys at relevant operating conditions for SCWR. The high temperature and pressure above the thermodynamic critical point of water result in higher oxidation rate which might be critical for thin-wall components like fuel cladding. The goal of this work was to study the effect of surface preparation on the oxidation rate on Ti-stabilized austenitic alloy 1.4970. Surfaces were prepared with ion implantation using He"+- and N"+-ions. Samples were immersed in supercritical water at 650"oC/25 MPa, for up to 2000 hours. Added to this, conventional surface treatments were conducted for austenitic alloy 316L tube samples in order to study the effect of cold work in sample surface on corrosion resistance. The corrosion rate was evaluated by measuring the weight change of the samples. The compositions of the oxide layers were analyzed using scanning electron microscope (SEM) in conjunction with Energy Dispersive Spectroscopy (EDS). (author)

Catalytic Water Oxidation by a Bio-inspired Nickel Complex with Redox Active Ligand

Science.gov (United States)

Wang, Dong; Bruner, Charlie O.

2017-01-01

The oxidation of water to dioxygen is important in natural photosynthesis. One of nature’s strategies for managing such multi-electron transfer reactions is to employ redox active metal-organic cofactor arrays. One prototype example is the copper-tyrosinate active site found in galactose oxidase. In this work, we have implemented such a strategy to develop a bio-inspired nickel-phenolate complex capable of catalyzing the oxidation of water to O2 electrochemically at neutral pH with a modest overpotential. The employment of the redox-active ligand turned out to be a useful strategy to avoid the formation of high-valent nickel intermediates while a reasonable turnover rate (0.15 s−1) is retained. PMID:29099176

Preparation and Application of Water-in-Oil Emulsions Stabilized by Modified Graphene Oxide

Directory of Open Access Journals (Sweden)

Xiaoma Fei

2016-08-01

Full Text Available A series of alkyl chain modified graphene oxides (AmGO with different alkyl chain length and content was fabricated using a reducing reaction between graphene oxide (GO and alkyl amine. Then AmGO was used as a graphene-based particle emulsifier to stabilize Pickering emulsion. Compared with the emulsion stabilized by GO, which was oil-in-water type, all the emulsions stabilized by AmGO were water-in-oil type. The effects of alkyl chain length and alkyl chain content on the emulsion properties of AmGO were investigated. The emulsions stabilized by AmGO showed good stability within a wide range of pH (from pH = 1 to pH = 13 and salt concentrations (from 0.1 to 1000 mM. In addition, the application of water-in-oil emulsions stabilized by AmGO was investigated. AmGO/polyaniline nanocomposite (AmGO/PANi was prepared through an emulsion approach, and its supercapacitor performance was investigated. This research broadens the application of AmGO as a water-in-oil type emulsion stabilizer and in preparing graphene-based functional materials.

Nitrogen and Oxygen Isotope Effects of Ammonia Oxidation by Thermophilic Thaumarchaeota from a Geothermal Water Stream.

Science.gov (United States)

Nishizawa, Manabu; Sakai, Sanae; Konno, Uta; Nakahara, Nozomi; Takaki, Yoshihiro; Saito, Yumi; Imachi, Hiroyuki; Tasumi, Eiji; Makabe, Akiko; Koba, Keisuke; Takai, Ken

2016-08-01

Ammonia oxidation regulates the balance of reduced and oxidized nitrogen pools in nature. Although ammonia-oxidizing archaea have been recently recognized to often outnumber ammonia-oxidizing bacteria in various environments, the contribution of ammonia-oxidizing archaea is still uncertain due to difficulties in the in situ quantification of ammonia oxidation activity. Nitrogen and oxygen isotope ratios of nitrite (δ(15)NNO2- and δ(18)ONO2-, respectively) are geochemical tracers for evaluating the sources and the in situ rate of nitrite turnover determined from the activities of nitrification and denitrification; however, the isotope ratios of nitrite from archaeal ammonia oxidation have been characterized only for a few marine species. We first report the isotope effects of ammonia oxidation at 70°C by thermophilic Thaumarchaeota populations composed almost entirely of "Candidatus Nitrosocaldus." The nitrogen isotope effect of ammonia oxidation varied with ambient pH (25‰ to 32‰) and strongly suggests the oxidation of ammonia, not ammonium. The δ(18)O value of nitrite produced from ammonia oxidation varied with the δ(18)O value of water in the medium but was lower than the isotopic equilibrium value in water. Because experiments have shown that the half-life of abiotic oxygen isotope exchange between nitrite and water is longer than 33 h at 70°C and pH ≥6.6, the rate of ammonia oxidation by thermophilic Thaumarchaeota could be estimated using δ(18)ONO2- in geothermal environments, where the biological nitrite turnover is likely faster than 33 h. This study extended the range of application of nitrite isotopes as a geochemical clock of the ammonia oxidation activity to high-temperature environments. Because ammonia oxidation is generally the rate-limiting step in nitrification that regulates the balance of reduced and oxidized nitrogen pools in nature, it is important to understand the biological and environmental factors underlying the regulation of

Catalytic water oxidation by ruthenium(II) quaterpyridine (qpy) complexes: evidence for ruthenium(III) qpy-N,N'''-dioxide as the real catalysts.

Science.gov (United States)

Liu, Yingying; Ng, Siu-Mui; Yiu, Shek-Man; Lam, William W Y; Wei, Xi-Guang; Lau, Kai-Chung; Lau, Tai-Chu

2014-12-22

Polypyridyl and related ligands have been widely used for the development of water oxidation catalysts. Supposedly these ligands are oxidation-resistant and can stabilize high-oxidation-state intermediates. In this work a series of ruthenium(II) complexes [Ru(qpy)(L)2 ](2+) (qpy=2,2':6',2'':6'',2'''-quaterpyridine; L=substituted pyridine) have been synthesized and found to catalyze Ce(IV) -driven water oxidation, with turnover numbers of up to 2100. However, these ruthenium complexes are found to function only as precatalysts; first, they have to be oxidized to the qpy-N,N'''-dioxide (ONNO) complexes [Ru(ONNO)(L)2 ](3+) which are the real catalysts for water oxidation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fullerene-reduced graphene oxide composites obtained by ultrashort laser ablation of fullerite in water

Energy Technology Data Exchange (ETDEWEB)

De Bonis, A., E-mail: angela.debonis@unibas.it [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy); Curcio, M. [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy); Santagata, A. [CNR-ISM, U.O.S. Tito Scalo, Zona Industriale, 85050, Tito Scalo (PZ) (Italy); Rau, J.V. [CNR-ISM, Via del Fosso del Cavaliere, 100-00133, Rome (Italy); Galasso, A.; Teghil, R. [Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100, Potenza (Italy)

2015-05-01

Highlights: • Laser ablation of a fullerite target in water performed by an ultra-short laser source has been reported. • The formation of reduced graphene oxide has been described considering the laser ablation in liquid mechanism. • Fullerene-reduced graphene oxide composite, in the form of self assembled microtubes, has been described. - Abstract: The laser ablation in liquid of carbon-based solid targets is of particular interest thanks to the possibility of obtaining different carbon allotropes by varying the experimental parameters employed. The ablation of a fullerite target in water using a frequency-doubled Nd:glass laser source with a pulse duration of 250 fs and a frequency repetition rate of 10 Hz is presented. The obtained products have been characterized by transmission electron and atomic force microscopies and by X-ray photoelectron and micro-Raman spectroscopies. During the femtosecond laser ablation, the collapse of fullerene cages has been considered with the consequent formation of graphene oxide (GO) and its successive hydrogenation. The process of self-assembling in microtube structures of the formed reduced graphene oxide-fullerene composites has then been reported.

Design and analysis on super-critical water cooled power reactors

International Nuclear Information System (INIS)

Ishiwatari, Yuki

2005-01-01

The Super-Critical Water Cooled Power Reactors (SCPR) is cooled by 25 MPa supercritical water of 280degC at reactor inlet and greater than 500degC at reactor outlet and directly connected with turbine/generators with high energy conversion efficiency. This corresponds to the deletion of recirculation system and steam-water separation system of BWR type reactors or of pressurizer and steam generator of PWR type reactors. In addition to the design study of the university of Tokyo, technology development of the SCPR for practical use has started under the collaboration of industry and academia since 2000. Mockup single tube and bundle tests for heat transfer/fluid flow characteristics of the design have been conducted with 3D heat transfer analysis. Materials compatible with coolant conditions for fuel cans and reactor internals are also assessed. Overall evaluation of the reactor concept is under way. (T. Tanaka)

Photodegradation of neonicotinoid insecticides in water by semiconductor oxides.

Science.gov (United States)

Fenoll, José; Garrido, Isabel; Hellín, Pilar; Flores, Pilar; Navarro, Simón

2015-10-01

The photocatalytic degradation of three neonicotinoid insecticides (NIs), thiamethoxam (TH), imidacloprid (IM) and acetamiprid (AC), in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalysts under natural sunlight and artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the electron acceptor (Na2S2O8) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO2 alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such insecticides in optimal conditions and at constant volumetric rate of photon absorption. Thus, the complete disappearance of all the studied compounds was achieved after 10 and 30 min of artificial light irradiation, in the ZnO/Na2S2O8 and TiO2/Na2S2O8 systems, respectively. The highest degradation rate was noticed for IM, while the lowest rate constant was obtained for AC under artificial light irradiation. In addition, solar irradiation was more efficient compared to artificial light for the removal of these insecticides from water. The main photocatalytic intermediates detected during the degradation of NIs were identified.

Developments regarding the Bragg rule for stopping power and critical examination of its application to water

International Nuclear Information System (INIS)

Kamaratos, E.

1983-01-01

A critical comparison is made of various experimental findings regarding the Bragg additivity rule for stopping power. It appears that deviations from the Bragg additivity rule reported a long time ago and ascribed to chemical binding effects and phase effects are real, despite even recent statements of the contrary. Nevertheless, when the Bragg rule is applied to water, critical examination of very recent experimental results for the stopping power in the gaseous state of water, hydrogen and oxygen in this work suggest that the reported deviations from the Bragg additivity rule for the stopping power of gaseous water may be the result of experimental error. (orig.)

Doubling of critical heat flux using a grapheme oxide nanofluid and its repeatabiltiy

International Nuclear Information System (INIS)

Moon, Sung Bo; Bang, In Cheol

2013-01-01

CHF(Critical Heat Flux : heat flux which makes dramatic increase of temperature on heater surface) is one of the most important phenomena in the thermal hydraulic system. High CHF makes more thermal margin of heat transfer. This makes high efficiency and safety of power plant especially in nuclear power plant. Much smaller danger can be concerned to public society like radioactive material leakage in the accidents. Graphene Oxide which can be deposited on the heater surface makes nano-scale structures with enhancing thermal limit of heater. Three major models of enhancing limit of heater have been concerned in many heat transfer studies. In this study, wettability that is about ability to wet on surface and thermal activity which is about thermal property of coated layer are concerned to analyze the mechanism of CHF enhancing. Also, chemical reduction of Graphene Oxide(GO) to Reduced Graphene Oxide(RGO) on the surface will be concerned with one reason of changing wettability of nano-scale structure on the heater surface. We used GO nanofluid 0.001 volume percent. Two models are compared to explain how CHF is enhanced. Results show wettability increased with slightly reduced GO and structure. And in thermal activity model, the most powerful term, thickness of layer, is too small to affect thermal activity. It has low ability to explain how GO nanofluid can enhance CHF

Effect of water content on thermal oxidation of oleic acid investigated by combination of EPR spectroscopy and SPME-GC-MS/MS.

Science.gov (United States)

Chen, Hongjian; Cao, Peirang; Li, Bo; Sun, Dewei; Wang, Yong; Li, Jinwei; Liu, Yuanfa

2017-04-15

Promotion of water to the thermal oxidation of oleic acid was detected by the combination of EPR, SPME-GC-MS/MS and GC. Spin-trapping technique was used to identify and quantify the radical species formed during thermal oxidation of oleic acid by using DMPO as electron spin trap. The most abundant radical species were identified as DMPO-alkyl radical adducts. EPR intensity plateau of the samples with 5% water content was 140% higher than the samples without water. It implies oleic acid samples with high water content had high level of oxidation rates. The proportion of aldehydes of the samples with 2% water content was the maximum about 59.97%. Among the formed products, (E,E)-2,4-decadienal has genotoxic and cytotoxic effects, whose percentage was nearly twice comparing with that of 5-0% water content. This study demonstrated that higher water content in frying systems would contribute to seriously oxidation and degradation of oleic acids. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of supplementation of water-soluble vitamins on oxidative stress and blood pressure in prehypertensives.

Science.gov (United States)

Talikoti, Prashanth; Bobby, Zachariah; Hamide, Abdoul

2015-01-01

The objective of the study was to evaluate the effect of water-soluble vitamins on oxidative stress and blood pressure in prehypertensives. Sixty prehypertensives were recruited and randomized into 2 groups of 30 each. One group received water-soluble vitamins and the other placebo for 4 months. Further increase in blood pressure was not observed in the vitamin group which increased significantly in the placebo group at the end of 4 months. Malonedialdehyde and protein carbonylation were reduced during the course of treatment with vitamins whereas in the placebo group there was an increase in the level of malondialdehyde. In conclusion, supplementation of water-soluble vitamins in prehypertension reduces oxidative stress and its progression to hypertension.

Graphene oxide/ferric hydroxide composites for efficient arsenate removal from drinking water

International Nuclear Information System (INIS)

Zhang Kai; Dwivedi, Vineet; Chi Chunyan; Wu Jishan

2010-01-01

A series of novel composites based on graphene oxide (GO) cross-linked with ferric hydroxide was developed for effective removal of arsenate from contaminated drinking water. GO, which was used as a supporting matrix here, was firstly treated with ferrous sulfate. Then, the ferrous compound cross-linked with GO was in situ oxidized to ferric compound by hydrogen peroxide, followed by treating with ammonium hydroxide. The morphology and composition of the composites were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The ferric hydroxide was found to be homogenously impregnated onto GO sheets in amorphous form. These composites were evaluated as absorbents for arsenate removal from contaminated drinking water. For the water with arsenate concentration at 51.14 ppm, more than 95% of arsenate was absorbed by composite GO-Fe-5 with an absorption capacity of 23.78 mg arsenate/g of composite. Effective arsenate removal occurred in a wide range of pH from 4 to 9. However, the efficiency of arsenate removal was decreased when pH was increased to higher than 8.

Solubilization of docetaxel in poly(ethylene oxide)-block-poly(butylene/styrene oxide) micelles.

Science.gov (United States)

Elsabahy, Mahmoud; Perron, Marie-Eve; Bertrand, Nicolas; Yu, Ga-Er; Leroux, Jean-Christophe

2007-07-01

Poly(ethylene oxide)-block-poly(styrene oxide) (PEO-b-PSO) and PEO-b-poly(butylene oxide) (PEO-b-PBO) of different chain lengths were synthesized and characterized for their self-assembling properties in water by dynamic/static light scattering, spectrofluorimetry, and transmission electron microscopy. The resulting polymeric micelles were evaluated for their ability to solubilize and protect the anticancer drug docetaxel (DCTX) from degradation. The drug release kinetics as well as the cytotoxicity of the loaded micelles were assessed in vitro. All polymers formed micelles with a highly viscous core at low critical association concentrations (hydrolysis under accelerated stability testing conditions. Only PEO-b-PBO bearing 24 BO units afforded significant protection against degradation. In vitro, DCTX was released slower from the latter micelles, but all formulations possessed a similar cytotoxic effect against PC-3 prostate cancer cells. These data suggest that PEO-b-P(SO/BO) micelles could be used as alternatives to conventional surfactants for the solubilization of taxanes.

Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups

Energy Technology Data Exchange (ETDEWEB)

Salmeron, M.; Bluhm, H.; Tatarkhanov, M.; Ketteler, G.; Shimizu, T.K.; Mugarza, A.; Deng, Xingyi; Herranz, T.; Yamamoto, S.; Nilsson, A.

2008-09-01

The authors discuss the role of the presence of dangling H bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using Scanning Tunneling and Atomic Force Microscopies, and Photoelectron Spectroscopy, they have examined a variety of surfaces, including mica, oxides, and pure metals. They find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO{sub 2}, Cu{sub 2}O, SiO{sub 2} and Al{sub 2}O{sub 3}, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd, and Ru, the structure of the first water layer and whether or not it exhibits dangling H bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two II atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

Oxidation by UV and ozone of organic contaminants dissolved in deionized and raw mains water

International Nuclear Information System (INIS)

Francis, P.D.

1987-01-01

Organic contaminants dissolved in deionized pretreated and raw mains water were reacted with ultraviolet light and ozone. Ozone first was used for partial oxidation followed by ozone combined with ultraviolet radiation to produce total oxidation. The reduction of total organic carbon (TOC) level and direct oxidation of halogenated compounds were measured throughout the treatment process. The rate of TOC reduction was compared for ozone injected upstream and inside the reactor

Proton transport facilitating water-oxidation: the role of second sphere ligands surrounding the catalytic metal cluster.

Science.gov (United States)

Bao, Han; Dilbeck, Preston L; Burnap, Robert L

2013-10-01

The ability of PSII to extract electrons from water, with molecular oxygen as a by-product, is a remarkable biochemical and evolutionary innovation. From an evolutionary perspective, the invention of PSII approximately 2.7 Ga led to the accelerated accumulation of biomass in the biosphere and the accumulation of oxygen in the atmosphere, a combination that allowed for the evolution of a much more complex and extensive biosphere than would otherwise have been possible. From the biochemical and enzymatic perspective, PSII is remarkable because of the thermodynamic and kinetic obstacles that needed to have been overcome to oxidize water as the ultimate photosynthetic electron donor. This article focuses on how proton release is an integral part of how these kinetic and thermodynamic obstacles have been overcome: the sequential removal of protons from the active site of H2O-oxidation facilitates the multistep oxidation of the substrate water at the Mn4CaOx, the catalytic heart of the H2O-oxidation reaction. As noted previously, the facilitated deprotonation of the Mn4CaOx cluster exerts a redox-leveling function preventing the accumulation of excess positive charge on the cluster, which might otherwise hinder the already energetically difficult oxidation of water. Using recent results, including the characteristics of site-directed mutants, the role of the second sphere of amino acid ligands and the associated network of water molecules surrounding the Mn4CaOx is discussed in relation to proton transport in other systems. In addition to the redox-leveling function, a trapping function is assigned to the proton release step occurring immediately prior to the dioxygen chemistry. This trapping appears to involve a yet-to-be clarified gating mechanism that facilitates to coordinated release of a proton from the neighborhood of the active site thereby insuring that the backward charge-recombination reaction does not out-compete the forward reaction of dioxygen chemistry

Enhancing hydrophilicity and water permeability of PET track-etched membranes by advanced oxidation process

International Nuclear Information System (INIS)

Korolkov, Ilya V.; Mashentseva, Anastassiya A.; Güven, Olgun; Zdorovets, Maxim V.; Taltenov, Abzal A.

2015-01-01

In this study we present results on the application of advanced oxidation systems for effective and non-toxic oxidation of poly(ethylene terephthalate) track-etched membranes (PET TeMs) to improve their wettability and water transport properties. Two oxidizing systems: H 2 O 2 under UV irradiation (H 2 O 2 /UV) and Fenton system under visible light (Fenton/H 2 O 2 /Vis) were compared. The surface of functionalized PET TeMs was characterized by using colorimetric assay, contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results clearly showed that water permeability of PET TeMs treated with H 2 O 2 /UV was improved by 28 ± 5% compared with etched-only membrane, the same parameter was found to increase by 13 ± 4% in the case of Fenton/H 2 O 2 /Vis treatment. The proposed oxidation technique is very simple, environment friendly and not requiring special equipment or expensive chemicals. The surface hydrophilicity of the membranes stored for 360 days in air between paper sheets was analyzed by contact angle test, colorimetric assay to measure concentration of carboxylic groups on the surface with toluidine blue and XPS analysis. The hydrophilic properties of oxidized PET TeMs were found to be stable for a long period of time.

Enhancing hydrophilicity and water permeability of PET track-etched membranes by advanced oxidation process

Science.gov (United States)

Korolkov, Ilya V.; Mashentseva, Anastassiya A.; Güven, Olgun; Zdorovets, Maxim V.; Taltenov, Abzal A.

2015-12-01

In this study we present results on the application of advanced oxidation systems for effective and non-toxic oxidation of poly(ethylene terephthalate) track-etched membranes (PET TeMs) to improve their wettability and water transport properties. Two oxidizing systems: H2O2 under UV irradiation (H2O2/UV) and Fenton system under visible light (Fenton/H2O2/Vis) were compared. The surface of functionalized PET TeMs was characterized by using colorimetric assay, contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results clearly showed that water permeability of PET TeMs treated with H2O2/UV was improved by 28 ± 5% compared with etched-only membrane, the same parameter was found to increase by 13 ± 4% in the case of Fenton/H2O2/Vis treatment. The proposed oxidation technique is very simple, environment friendly and not requiring special equipment or expensive chemicals. The surface hydrophilicity of the membranes stored for 360 days in air between paper sheets was analyzed by contact angle test, colorimetric assay to measure concentration of carboxylic groups on the surface with toluidine blue and XPS analysis. The hydrophilic properties of oxidized PET TeMs were found to be stable for a long period of time.

Corrosion Behavior and Oxide Properties of Zr-Nb-Cu and Zr-Nb-Sn Alloy in High Dissolved Hydrogen Primary Water Chemistry

Energy Technology Data Exchange (ETDEWEB)

Lee, Yun Ju; Kim, Tae Ho; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

2016-05-15

The water-metal interface is regarded as rate-controlling site governing the rapid oxidation transition in high burn-up fuel. And the zirconium oxide is made in water-metal interface and its structure and phase do an important role in terms of oxide properties. During oxidation process, the protective tetragonal oxide layer develops at the interface due to accumulated high stress during oxide growth, and it turns into non-protective monoclinic oxide with increasing oxide thickness, thus decreasing the stress. It has been reported that Nb addition was proven to be very beneficial for increasing the corrosion resistance of the zirconium alloys. From a more recent study, Cu addition in Nb containing Zirconium alloy was reported to be effective for increasing corrosion resistance in water containing B and Li. According to the previous research conducted, Zr-Nb-Cu shows better corrosion resistance than Zircaloy-4. The dissolved hydrogen (DH) concentration is the key issue of primary water chemistry, and the effect of DH concentration on the corrosion rate of nickel based alloy has been researched. However, the effect of DH on the zirconium alloy corrosion mechanism was not fully investigated. In this study, the weight gain measurement, FIB-SEM analysis, and Raman spectroscopic measurement were conducted to investigate the effects of dissolved hydrogen concentration and the chemical composition on the corrosion resistance and oxide phase of Zr-Nb-Cu alloy and Zr-Nb-Sn alloy after oxidizing in a primary water environment for 20 d. The corrosion rate of Zr-Nb-Cu alloy is slow, when it is compared to Zr-Nb-Sn alloy. In SEM images, the oxide thickness of Zr-Nb-Cu alloy is measured to be around 1.06 μm it of Zr-Nb-Sn alloy is measured to be 1.15 μm. It is because of the Segregation made by Sn solute element when Sn solute element oxidized. And according to ex situ Raman spectra, Zr-Nb-Cu alloy oxide has more tetragonal zirconium oxide fraction than Zr-Nb-Sn alloy oxide.

Pore water geochemistry and the oxidation of sedimentary organic matter: Hatteras Abyssal Plain 1981

International Nuclear Information System (INIS)

Heggie, D.; Lewis, T.; Graham, D.

1985-01-01

This report presents the pore water geochemistry from R/V an Endeavor cruise to an area of the Hatteras Abyssal Plain between 31 0 45' - 34 0 00'N and 69 0 37.5 - 72 0 07.5'W. The authors report on the down core variations of the products of organic matter oxidation, the stoichiometry of reactions and make a preliminary assessment of the rates of organic matter oxidation at several core locations. The authors found concentrations of total inorganic nitrogen species; nitrate, nitrite and ammonia in pore waters to be less than those predicted from a model of organic matter oxidation (Froelich et al. 1979) in sediments. The observations indicate that nitrogen is depleted over carbon as compared to typical marine organic matter. The down-core nitrate profiles over the study area were used to infer depths at which oxygen is near totally consumed in the sediments and hence to compute rates of oxygen consumption. The authors found oxygen consumption rates to vary by nearly an order of magnitude between core locations (1.7 - >15μmO 2 cm -2 yr -1 ). A simple model which combines the computed rates of oxidant consumption and the stoichiometry of organic matter oxidation was used to make estimates of organic carbon oxidation rates. These latter were found to vary between 1.3 and > 11.5 μm C cm -2 yr -1 . Highest carbon oxidation rates were found at the western boundary of the study area, and in all cases oxygen consumption was responsible for >85% of carbon oxidized. 11 references, 5 figures, 4 tables

Effect of oxidation on the fatigue crack propagation behavior of Z3CN20.09M dyplex stainless steel in high temperature water

Energy Technology Data Exchange (ETDEWEB)

Wu, Huan Chun; Yang, Bin [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Chen, Yue Feng; Chen, Xu Dong [Collaborative Innovation Center of Steel Technology, Beijing (China)

2017-06-15

The fatigue crack propagation behaviors of Z3CN20.09M duplex stainless steel (DSS) were investigated by studying oxide films of specimens tested in 290°C water and air. The results indicate that a full oxide film that consisted of oxides and hydroxides was formed in 290°C water. By contrast, only a half-baked oxide film consisting of oxides was formed in 290°C air. Both environments are able to deteriorate the elastic modulus and hardness of the oxide films, especially the 290°C water. The fatigue lives of the specimens tested in 290°C air were about twice of those tested in 290°C water at all strain amplitudes. Moreover, the crack propagation rates of the specimen tested in 290°C water were confirmed to be faster than those tested in 290°C air, which was thought to be due to the deteriorative strength of the oxide films induced by the mutual promotion of oxidation and crack propagation at the crack tip. It is noteworthy that the crack propagation can be postponed by the ferrite phase in the DSS, especially when the specimens were tested in 290°C water.

The Behavior of the Ru-bda Water Oxidation Catalysts at Low Oxidation States.

Science.gov (United States)

Matheu, Roc; Ghaderian, Abolfazl; Francas, Laia; Chernev, Petko; Ertem, Mehmed; Benet-Buchholz, Jordi; Batista, Victor; Haumann, Michael; Gimbert-Suriñach, Carolina; Sala, Xavier; Llobet, Antoni

2018-06-13

The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature leading to complex [RuII(bda-κ-N2O)(MeCN)(N-NH2)2], 3. Finally in acidic aqueous solutions solvent water coordinates the Ru center forming {[RuII(bda-κ-(NO)3)(H2O)(N-NH3)2](H2O)n}2+, 42+, that is strongly hydrogen bonded with additional water molecules at the second coordination sphere. We have additionally characterized the one electron oxidized complex {[RuIII(bda-κ-(NO)3.5)(H2O)(N-NH3)2](H2O)n}3+, 53+. The coordination mode of the complexes has been studied both in the solid state and in solution through single-crystal XRD, X-ray absorption spectroscopy, variable-temperature NMR and DFT calculations. While the κ-N2O is the main coordination mode for 23+ and 3, an equilibrium that involves isomers with κ-N2O and κ-NO2 coordination modes and neighboring hydrogen bonded water molecules is observed for 42+ and 53+. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computationally Probing the Performance of Hybrid, Heterogeneous, and Homogeneous Iridium-Based Catalysts for Water Oxidation

Energy Technology Data Exchange (ETDEWEB)

García-Melchor, Max [SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford CA (United States); Vilella, Laia [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST),Tarragona (Spain); Departament de Quimica, Universitat Autonoma de Barcelona, Barcelona (Spain); López, Núria [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain); Vojvodic, Aleksandra [SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park CA (United States)

2016-04-29

An attractive strategy to improve the performance of water oxidation catalysts would be to anchor a homogeneous molecular catalyst on a heterogeneous solid surface to create a hybrid catalyst. The idea of this combined system is to take advantage of the individual properties of each of the two catalyst components. We use Density Functional Theory to determine the stability and activity of a model hybrid water oxidation catalyst consisting of a dimeric Ir complex attached on the IrO₂(110) surface through two oxygen atoms. We find that homogeneous catalysts can be bound to its matrix oxide without losing significant activity. Hence, designing hybrid systems that benefit from both the high tunability of activity of homogeneous catalysts and the stability of heterogeneous systems seems feasible.

The influence of water on the oxygen-silver interaction and on the oxidative dehydrogenation of methanol

NARCIS (Netherlands)

Lefferts, Leon; Van Ommen, Jan G.; Ross, Julian R H

1988-01-01

Experiments carried out using temperature-programmed desorption and reduction could detect no interaction between water and silver at 200 °C. However, separate experiments on the effect of water on the oxidative dehydrogenation of methanol over a silver catalyst showed that water affected the

TiO2-Based Advanced Oxidation Nanotechnologies For Water Purification And Reuse

Science.gov (United States)

TiO2 photocatalysis, one of the UV-based advanced oxidation technologies (AOTs) and nanotechnologies (AONs), has attracted great attention for the development of efficient water treatment and purification systems due to the effectiveness of TiO2 to generate ...

Influence of Zn injection on corrosion behavior and oxide film characteristics of 304 stainless steel in borated and lithiated high temperature water

International Nuclear Information System (INIS)

Wu, Xinqiang; Liu, Xiahe; Han, En-Hou; Ke, Wei

2012-09-01

Water chemistry of the reactor coolant system plays a major role in maintaining safety and reliability of light water reactor nuclear power plants (NPPs). Zn water chemistry into pressurized water reactors (PWRs) in order to reduce the radiation buildup in primary coolant system has been widely applied, and the reduction effect has been experimentally confirmed. Zn injection can also lessen the corrosion phenomena in high temperature pressurized water by changing oxide films formed on components materials. Both the radiation buildup and material corrosion resistance in PWR coolant system are closely dependent on the oxide films formed. However, the influence of Zn injection on the chemical composition and structure of the oxide films on their protective properties is still a matter of considerable debate. The influence of Zn injection on corrosion inhibition and environmental degradation has not been fully clarified yet. Therefore, the understanding of corrosion behaviour, oxide film characteristics and their protective property is of significance to clarify the environmentally assisted material failure problems in NPPs. In the present work, oxide films formed on nuclear-grade 304 SS exposed to borated and lithiated high temperature water environments at 300 deg. C up to 4000 h with or without 10 ppb Zn injection were investigated ex-situ. Without Zn injection, the oxide films mainly consisted of Fe 3 O 4 and FeCr 2 O 4 . With Zn injection, ZnFe 2 O 4 and ZnCr 2 O 4 were detected in the oxide films at the initial stage of immersion and ZnCr 2 O 4 became dominant after long-term immersion. It was believed that the above Zn-Fe and Zn-Cr spinel oxides were formed by substitution reactions between Zn 2+ and Fe 2+ . At the initial stage of immersion, water chemistry significantly affected the formation of the oxide films. Once a stable oxide film formed, it is rather difficult to change its structure through changing water chemistry. The potential-pH diagrams for Zn

A critical review of integrated urban water modelling – Urban drainage and beyond

DEFF Research Database (Denmark)

Bach, Peter M.; Rauch, Wolfgang; Mikkelsen, Peter Steen

2014-01-01

considerations (e.g. data issues, model structure, computational and integration-related aspects), common methodology for model development (through a systems approach), calibration/optimisation and uncertainty are discussed, placing importance on pragmatism and parsimony. Integrated urban water models should......Modelling interactions in urban drainage, water supply and broader integrated urban water systems has been conceptually and logistically challenging as evidenced in a diverse body of literature, found to be confusing and intimidating to new researchers. This review consolidates thirty years...... of research (initially driven by interest in urban drainage modelling) and critically reflects upon integrated modelling in the scope of urban water systems. We propose a typology to classify integrated urban water system models at one of four ‘degrees of integration’ (followed by its exemplification). Key...

Effect of water injection on nitric oxide emissions of a gas turbine combustor burning natural gas fuel

Science.gov (United States)

Marchionna, N. R.; Diehl, L. A.; Trout, A. M.

1973-01-01

The effect of direct water injection on the exhaust gas emissions of a turbojet combustor burning natural gas fuel was investigated. The results are compared with the results from similar tests using ASTM Jet-A fuel. Increasing water injection decreased the emissions of oxides of nitrogen (NOX) and increased the emissions of carbon monoxide and unburned hydrocarbons. The greatest percentage decrease in NOX with increasing water injection was at the lowest inlet-air temperature tested. The effect of increasing inlet-air temperature was to decrease the effect of the water injection. The reduction in NOX due to water injection was almost identical to the results obtained with Jet-A fuel. However, the emission indices of unburned hydrocarbons, carbon monoxide, and percentage nitric oxide in NOX were not.

Electrochemical approach to evaluate the mechanism of photocatalytic water splitting on oxide photocatalysts

International Nuclear Information System (INIS)

Matsumoto, Yasumichi; Unal, Ugur; Tanaka, Noriyuki; Kudo, Akihiko; Kato, Hideki

2004-01-01

Photoelectrochemical measurements of TiO 2 , NaTaO 3 , and Cr or Sb doped TiO 2 and SrTiO 3 photocatalysts were carried out in H 2 and O 2 saturated electrolytes in order to evaluate the reverse reactions during water photolysis. The poor activity of TiO 2 as a result of reverse photoreactions of O 2 reduction and H 2 oxidation was revealed with the respective high cathodic and anodic photocurrents. The rise in the photocurrents at NaTaO 3 after La doping was in harmony with the doping-induced increase in the photocatalytic activity. NiO loading suppresses the O 2 photoreverse reactions, which declines photocatalytic activity, and/or promotes the photo-oxidation of water, because the O 2 photo-reduction current was scarcely observed near the flatband potential. Photocurrents of O 2 reduction and H 2 oxidation were observed under visible light for the Cr and Sb doped SrTiO 3 and TiO 2 , respectively. These phenomena are in harmony with the previous reports on the photocatalysts examined with sacrificial reagents

Transformation of pharmaceuticals during oxidation/disinfection processes in drinking water treatment.

Science.gov (United States)

Postigo, Cristina; Richardson, Susan D

2014-08-30

Pharmaceuticals are emerging contaminants of concern and are widespread in the environment. While the levels of these substances in finished drinking waters are generally considered too low for human health concern, there are now concerns about their disinfection by-products (DBPs) that can form during drinking water treatment, which in some cases have been proven to be more toxic than the parent compounds. The present manuscript reviews the transformation products of pharmaceuticals generated in water during different disinfection processes, i.e. chlorination, ozonation, chloramination, chlorine dioxide, UV, and UV/hydrogen peroxide, and the main reaction pathways taking place. Most of the findings considered for this review come from controlled laboratory studies involving reactions of pharmaceuticals with these oxidants used in drinking water treatment. Copyright © 2014 Elsevier B.V. All rights reserved.

Warm Water Oxidation Verification - Scoping and Stirred Reactor Tests

Energy Technology Data Exchange (ETDEWEB)

Braley, Jenifer C.; Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2011-06-15

Scoping tests to evaluate the effects of agitation and pH adjustment on simulant sludge agglomeration and uranium metal oxidation at {approx}95 C were performed under Test Instructions(a,b) and as per sections 5.1 and 5.2 of this Test Plan prepared by AREVA. (c) The thermal testing occurred during the week of October 4-9, 2010. The results are reported here. For this testing, two uranium-containing simulant sludge types were evaluated: (1) a full uranium-containing K West (KW) container sludge simulant consisting of nine predominant sludge components; (2) a 50:50 uranium-mole basis mixture of uraninite [U(IV)] and metaschoepite [U(VI)]. This scoping study was conducted in support of the Sludge Treatment Project (STP) Phase 2 technology evaluation for the treatment and packaging of K-Basin sludge. The STP is managed by CH2M Hill Plateau Remediation Company (CHPRC) for the U.S. Department of Energy. Warm water ({approx}95 C) oxidation of sludge, followed by immobilization, has been proposed by AREVA and is one of the alternative flowsheets being considered to convert uranium metal to UO{sub 2} and eliminate H{sub 2} generation during final sludge disposition. Preliminary assessments of warm water oxidation have been conducted, and several issues have been identified that can best be evaluated through laboratory testing. The scoping evaluation documented here was specifically focused on the issue of the potential formation of high strength sludge agglomerates at the proposed 95 C process operating temperature. Prior hydrothermal tests conducted at 185 C produced significant physiochemical changes to genuine sludge, including the formation of monolithic concretions/agglomerates that exhibited shear strengths in excess of 100 kPa (Delegard et al. 2007).

Warm Water Oxidation Verification - Scoping and Stirred Reactor Tests

International Nuclear Information System (INIS)

Braley, Jenifer C.; Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2011-01-01

Scoping tests to evaluate the effects of agitation and pH adjustment on simulant sludge agglomeration and uranium metal oxidation at ∼95 C were performed under Test Instructions(a,b) and as per sections 5.1 and 5.2 of this Test Plan prepared by AREVA. (c) The thermal testing occurred during the week of October 4-9, 2010. The results are reported here. For this testing, two uranium-containing simulant sludge types were evaluated: (1) a full uranium-containing K West (KW) container sludge simulant consisting of nine predominant sludge components; (2) a 50:50 uranium-mole basis mixture of uraninite (U(IV)) and metaschoepite (U(VI)). This scoping study was conducted in support of the Sludge Treatment Project (STP) Phase 2 technology evaluation for the treatment and packaging of K-Basin sludge. The STP is managed by CH2M Hill Plateau Remediation Company (CHPRC) for the U.S. Department of Energy. Warm water (∼95 C) oxidation of sludge, followed by immobilization, has been proposed by AREVA and is one of the alternative flowsheets being considered to convert uranium metal to UO 2 and eliminate H 2 generation during final sludge disposition. Preliminary assessments of warm water oxidation have been conducted, and several issues have been identified that can best be evaluated through laboratory testing. The scoping evaluation documented here was specifically focused on the issue of the potential formation of high strength sludge agglomerates at the proposed 95 C process operating temperature. Prior hydrothermal tests conducted at 185 C produced significant physiochemical changes to genuine sludge, including the formation of monolithic concretions/agglomerates that exhibited shear strengths in excess of 100 kPa (Delegard et al. 2007).

Characterization of the oxide grown on Zr-20 Nb with different heat treatments in water at high temperature

International Nuclear Information System (INIS)

Olmedo, Ana M.; Bordoni, Roberto; Koenig, Patricia

2003-01-01

This work presents the corrosion behaviour of Zr-20 Nb alloy with different heat treatments. All the samples were annealed at 850 C degrees for one hour and cooled in air. After this heat treatment the sample coupons were aged at different temperatures and times. The corrosion kinetic of the different coupon samples were determined in water at 315 C degrees. The microstructure of the oxides were analysed using X-ray diffraction. The oxides grown in water steam at 400 C degrees, in coupons with a β Zr microstructure and in coupons aged in order to obtain a α Zr· + β Nb microstructure were also analysed. The oxides grown at the different temperatures and for all the microstructures were very adherent and black for all the times studied. The corrosion kinetics showed that the aging treatments decrease the corrosion rate of this material in degassed water at 315 C degrees and also in water steam at 400 C degrees. The greatest corrosion resistance is achieved for the equilibrium or near equilibrium microstructure of the samples and the presence of the · phase does not decrease the corrosion resistance of the material. The microstructure analysis of the oxides indicated that oxides grown on samples with β Zr microstructure are composed mainly by a Zr-Nb oxide of the type Nb 2 O 5· 6ZrO 2 , together with a small fraction of monoclinic ZrO 2 . Aging treatments produce an increase of the monoclinic phase and diminish the proportion of the mixed oxide. When the aging treatment gives the equilibrium or near equilibrium microstructure of α Zr· + β Nb , the oxide is composed mainly of monoclinic ZrO 2 , a small proportion of tetragonal component and also Nb 2 O 5 . (author)

Quantum mechanics/molecular mechanics simulation of the ligand vibrations of the water-oxidizing Mn4CaO5 cluster in photosystem II.

Science.gov (United States)

Nakamura, Shin; Noguchi, Takumi

2016-10-11

During photosynthesis, the light-driven oxidation of water performed by photosystem II (PSII) provides electrons necessary to fix CO 2 , in turn supporting life on Earth by liberating molecular oxygen. Recent high-resolution X-ray images of PSII show that the water-oxidizing center (WOC) is composed of an Mn 4 CaO 5 cluster with six carboxylate, one imidazole, and four water ligands. FTIR difference spectroscopy has shown significant structural changes of the WOC during the S-state cycle of water oxidation, especially within carboxylate groups. However, the roles that these carboxylate groups play in water oxidation as well as how they should be properly assigned in spectra are unresolved. In this study, we performed a normal mode analysis of the WOC using the quantum mechanics/molecular mechanics (QM/MM) method to simulate FTIR difference spectra on the S 1 to S 2 transition in the carboxylate stretching region. By evaluating WOC models with different oxidation and protonation states, we determined that models of high-oxidation states, Mn(III) 2 Mn(IV) 2 , satisfactorily reproduced experimental spectra from intact and Ca-depleted PSII compared with low-oxidation models. It is further suggested that the carboxylate groups bridging Ca and Mn ions within this center tune the reactivity of water ligands bound to Ca by shifting charge via their π conjugation.

Emulsification technique affects oxidative stability of fish oil-in-water emulsion

DEFF Research Database (Denmark)

Horn, Anna Frisenfeldt; Nielsen, Nina Skall; Jensen, Louise Helene Søgaard

of this study was therefore to compare lipid oxidation in 10% fish oil-in-water emulsions prepared by two different kinds of high pressure homogenizers i.e. a microfluidizer and a two valve high pressure homogenizer. Emulsions were made with equal droplet sizes, and with either 1% sodium caseinate or 1% whey...

Emulsification technique affects oxidative stability of fish oil-in-water emulsions

DEFF Research Database (Denmark)

Horn, Anna Frisenfeldt; Nielsen, Nina Skall; Jensen, Louise Helene Søgaard

of this study was to compare lipid oxidation in 10% fish oil-in-water emulsions prepared by two different kinds of high pressure homogenizers i.e. a microfluidizer and a two valve high pressure homogenizer. Emulsions were made with equal droplet sizes, and with either 1% sodium caseinate or 1% whey protein...

Water dispersal and functionalization of hydrophobic Iron oxide nanoparticles with lipid-modified poly(amidoamine) dendrimers

NARCIS (Netherlands)

Boni, A; Albertazzi, L.; Innocenti, C; Gemmi, M; Bifone, A

2013-01-01

A novel and facile method for water dispersal of hydrophobic iron oxide nanoparticles based on the amphiphilic PAMAM-C-12 dendrimer is described. Stable and highly concentrated water dispersions of multifunctional, magnetic nanoparticles were obtained with this single-step approach, and showed

Preparation, characterisation and critical flux determination of graphene oxide blended polysulfone (PSf) membranes in an MBR system.

Science.gov (United States)

Ravishankar, Harish; Roddick, Felicity; Navaratna, Dimuth; Jegatheesan, Veeriah

2018-05-01

Microfiltration membranes having different blends of graphene-oxide (GO) (0-1 wt%) and Polysulfone (PSf) (15-20 wt%) were prepared using the classical non-solvent induced phase inversion process. The prepared membranes were characterised for their structural morphology, surface properties, mechanical strength, porosity and pure water flux. Based on the initial characterisation results, four membranes (15 wt% PSf, 15 wt% PSf + 0.25 wt% GO, 15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) were chosen for critical flux study, that was conducted using flux-step method in a lab scale MBR system. In order to study the application potential of GO blended membranes, the critical flux of each membrane was evaluated in two operational modes i.e., continuous and intermittent modes with backwash. The membranes with maximal GO concentration (15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) showed higher critical flux (16.5, 12.8 L/m 2 h and 19, 15 L/m 2 h for continuous and intermittent mode, respectively). It was observed that the operational modes did not have a significant effect on the critical flux of the membranes with low GO concentration (15 wt% PSf and 15 wt% PSf + 0.25 wt% GO), indicating a minimal of 1 wt% GO was required for an observable effect that favoured intermittent mode of operation. Through these results, ideal operating condition was arrived (i.e., flux maintained at 6.4 L/m 2 h operated under intermittent mode) and the membranes 15 wt% PSf and 15 wt% PSf + 1 wt% GO were studied for their long-term operation. The positive effect of GO on filtration time, cleaning frequency and against fouling was demonstrated through long term TMP profile of the membranes, indicating the suitability of GO blended membrane for real time wastewater treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pu(V) as the stable form of oxidized plutonium in natural waters

International Nuclear Information System (INIS)

Orlandini, K.A.; Penrose, W.R.; Nelson, D.M.

1986-01-01

This work presents analytical evidence supporting the proposition that Pu(V) is the sole or predominant form of oxidized plutonium in natural waters. Two independent methods, the selective adsorption of Pu(VI) by silica gel, and the somewhat less selective coprecipitation of Pu(V) with calcium carbonate, were developed to separate Pu(V) from Pu(VI). Measurements of ambient plutonium in several natural waters by these methods found only Pu(V). In laboratory tracer studies, Pu(VI) was shown to be highly unstable in dilute bicarbonate solution and in Lake Michigan water, reducing in first-order fashion to Pu(V). (orig.)

Iron oxide hydroxide nanoflower assisted removal of arsenic from water

Energy Technology Data Exchange (ETDEWEB)

Raul, Prasanta Kumar, E-mail: prasanta.drdo@gmail.com [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India); Devi, Rashmi Rekha; Umlong, Iohborlang M. [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India); Thakur, Ashim Jyoti [Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam (India); Banerjee, Saumen; Veer, Vijay [Defence Research Laboratory, Post Bag No. 2, Tezpur 784001, Assam (India)

2014-01-01

Graphical abstract: Non-magnetic polycrystalline iron oxide hydroxide nanoparticle with flower like morphology is found to play as an effective adsorbent media to remove As(III) from 300 μg L{sup −1} to less than 10 μg L{sup −1} from drinking water over wide range of pH. TEM image clearly reveals that the nanoparticle looks flower like morphology with average particle size less than 20 nm. The maximum sorption capacity of the sorbent is found to be 475 μg g{sup −1} for arsenic at room temperature and the data fitted to different isotherm models indicate the heterogeneity of the adsorbent surface. The material can be regenerated up to 70% using dilute hydrochloric acid and it would be utilized for de-arsenification purposes. - Highlights: • The work includes synthesis of iron oxide hydroxide nanoflower and its applicability for the removal of arsenic from water. • The nanoparticle was characterized using modern instrumental methods like FESEM, TEM, BET, XRD, etc. • The maximum sorption capacity of the sorbent is found to be 475 μg g{sup −1} for arsenic at room temperature. • The sorption is multilayered on the heterogeneous surface of the nano adsorbent. • The mechanism of arsenic removal of IOH nanoflower follows both adsorption and ion-exchange. - Abstract: Non-magnetic polycrystalline iron oxide hydroxide nanoparticle with flower like morphology is found to play as an effective adsorbent media to remove As(III) from 300 μg L{sup −1} to less than 10 μg L{sup −1} from drinking water over wide range of pH. The nanoparticle was characterized by X-ray powder diffraction analysis (XRD), BET surface area, FTIR, FESEM and TEM images. TEM image clearly reveals flower like morphology with average particle size less than 20 nm. The nanoflower morphology is also supported by FESEM images. The maximum sorption capacity of the sorbent is found to be 475 μg g{sup −1} for arsenic and the data fitted to different isotherm models indicate the

International studies on burnup credit criticality safety by an OECD/NEA working group

International Nuclear Information System (INIS)

Brady, M.C.; Okuno, H.; DeHart, M.D.; Nouri, A.; Sartori, E.

1998-01-01

The results and conclusions from a six-year study by an international benchmarking group in the comparison of computational methods for evaluating burnup credit in criticality safety analyses is presented. Approximately 20 participants from 12 countries have provided results for most problems. Four detailed benchmark problems for pressurized-water-reactor fuel have been completed. Results from work being finalized, addressing burnup credit for boiling-water-reactor fuel, are discussed, as well as planned activities for additional benchmarks, including mixed-oxide fuels, and other activities

Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures

Science.gov (United States)

D'Urso, Luisa; Spadaro, Salvatore; Bonsignore, Martina; Santangelo, Saveria; Compagnini, Giuseppe; Neri, Fortunato; Fazio, Enza

2018-01-01

Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10-50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.

Bicarbonate-induced activation of H₂O₂ for metal-free oxidative desulfurization.

Science.gov (United States)

Bokare, Alok D; Choi, Wonyong

2016-03-05

Efficient oxidative desulfurization (ODS) of model oil containing dibenzothiophene (DBT) and aromatic thiophenic derivatives has been achieved at room temperature using hydrogen peroxide activation by inorganic bicarbonate (HCO3(-)). Using in-situ formation of peroxymonocarbonate as oxidant, the transformation of main model substrate DBT to corresponding DBT-sulfone was easily accomplished in biphasic reaction conditions. In the presence of water-acetonitrile polar phase, increasing the water content upto 50% decreased the extraction capacity more than 3 times, but ∼ 90% DBT oxidation was still achieved. The oxidizing capacity of bicarbonate catalyst was maintained during repeated ODS cycles, but DBT removal efficiency was critically dependent on the extraction capacity of the polar phase. Under heterogeneous reaction conditions, bicarbonate-modified ion-exchange resin achieved similar ODS activity compared to the homogeneous catalytic system. Additionally, the efficient formation of peroxymonocarbonate using gaseous CO2 precursor in alkaline conditions was also utilized for DBT oxidation. The present study proposes the NaHCO3/H2O2 catalytic system as an efficient and cheap metal-free alternative for the oxidative removal of aromatic sulfur compounds from fuel oil. Copyright © 2015 Elsevier B.V. All rights reserved.