XPS study of graphene oxide reduction induced by (100) and (111)-oriented Si substrates

Science.gov (United States)

Priante, F.; Salim, M.; Ottaviano, L.; Perrozzi, F.

2018-02-01

The reduction of graphene oxide (GO) has been extensively studied in literature in order to let GO partially recover the properties of graphene. Most of the techniques proposed to reduce GO are based on high temperature annealing or chemical reduction. A new procedure, based on the direct reduction of GO by etched Si substrate, was recently proposed in literature. In the present work, we accurately investigated the Si-GO interaction with x-ray photoelectron spectroscopy. In order to avoid external substrate oxidation factors we used EtOH as the GO solvent instead of water, and thermal annealing was carried out in UHV. We investigated the effect of Si(100), Si(111) and Au substrates on GO, to probe the role played by both the substrate composition and substrate orientation during the reduction process. A similar degree of GO reduction was observed for all samples but only after thermal annealing, ruling out the direct reduction effect of the substrate.

A study of integrated cathode assembly for electrolytic reduction of uranium oxide in LiCl-Li2O molten salt

International Nuclear Information System (INIS)

Park, Sung Bin; Seo, Jung Seok; Kang, Dae Seung; Kwon, Sun Kil; Park, Seong Won

2004-01-01

Interest of electrolytic reduction of uranium oxide is increasing in treatment of spent metal fuels. Argonne National Laboratory (ANL) has reported the experimental results of electrochemical reduction of uranium oxide fuel in bench-scale apparatus with cyclic voltammetry, and has designed high-capacity reduction (HCR) cells and conducted three kg-scale UO 2 reduction runs. From the cyclic voltammograms, the mechanism of electrolytic reduction of metal oxides is analyzed. The uranium oxide in LiCl-Li 2 O is converted to uranium metal according to the two mechanism; direct and indirect electrolytic reduction. In this study, cyclic voltammograms for LiCl-3wt% Li 2 O system and U 3 O 8 -LiCl-3wt% Li 2 O system using the 325-mesh stainless steel screen in cathode assembly have been obtained. Direct electrolytic reduction of uranium oxide in LiCl-3wt% Li 2 O molten salt has been conducted

Low Temperature Selective Catalytic Reduction of Nitrogen Oxides in Production of Nitric Acid by the Use of Liquid

Directory of Open Access Journals (Sweden)

Kabljanac, Ž.

2011-11-01

Full Text Available This paper presents the application of low-temperature selective catalytic reduction of nitrous oxides in the tail gas of the dual-pressure process of nitric acid production. The process of selective catalytic reduction is carried out using the TiO2/WO3 heterogeneous catalyst applied on a ceramic honeycomb structure with a high geometric surface area per volume. The process design parameters for nitric acid production by the dual-pressure procedure in a capacity range from 75 to 100 % in comparison with designed capacity for one production line is shown in the Table 1. Shown is the effectiveness of selective catalytic reduction in the temperature range of the tail gas from 180 to 230 °C with direct application of liquid ammonia, without prior evaporation to gaseous state. The results of inlet and outlet concentrations of nitrous oxides in the tail gas of the nitric acid production process are shown in Figures 1 and 2. Figure 3 shows the temperature dependence of the selective catalytic reduction of nitrous oxides expressed as NO2in the tail gas of nitric acid production with the application of a constant mass flow of liquid ammonia of 13,0 kg h-1 and average inlet mass concentration of the nitrous oxides expressed as NO2of 800,0 mgm-3 during 100 % production capacity. The specially designed liquid-ammonia direct-dosing system along with the effective homogenization of the tail gas resulted in emission levels of nitrous oxides expressed as NO2 in tail gas ranging from 100,0 to 185,0 mg m-3. The applied low-temperature selective catalytic reduction of the nitrous oxides in the tail gases by direct use of liquid ammonia is shown in Figure 4. It is shown that low-temperature selective catalytic reduction with direct application of liquid ammonia opens a new opportunity in the reduction of nitrous oxide emissions during nitric acid production without the risk of dangerous ammonium nitrate occurring in the process of subsequent energy utilization of

Study of the Electrolytic Reduction of Uranium Oxide in LiCl-Li2O Molten Salts with an Integrated Cathode Assembly

International Nuclear Information System (INIS)

Park, Sung Bin; Seo, Chung Seok; Kang, Dae Seung; Kwon, Seon Gil; Park, Seong Won

2005-01-01

The electrolytic reduction of uranium oxide in a LiCl-Li 2 O molten salt system has been studied in a 10 g U 3 O 3 /batch-scale experimental apparatus with an integrated cathode assembly at 650 .deg. C. The integrated cathode assembly consists of an electric conductor, the uranium oxide to be reduced and the membrane for loading the uranium oxide. From the cyclic voltammograms for the LiCl-3 wt% Li 3 O system and the U 3 O 3 -LiCl-3 wt% Li 2 O system according to the materials of the membrane in the cathode assembly, the mechanisms of the predominant reduction reactions in the electrolytic reactor cell were to be understood; direct and indirect electrolytic reduction of uranium oxide. Direct and indirect electrolytic reductions have been performed with the integrated cathode assembly. Using the 325-mesh stainless steel screen the uranium oxide failed to be reduced to uranium metal by a direct and indirect electrolytic reduction because of a low current efficiency and with the porous magnesia membrane the uranium oxide was reduced successfully to uranium metal by an indirect electrolytic reduction because of a high current efficiency.

Green reduction of graphene oxide using alanine

International Nuclear Information System (INIS)

Wang, Jiabin; Salihi, Elif Caliskan; Šiller, Lidija

2017-01-01

There remains a real need for the easy, eco-friendly and scalable preparation method of graphene due to various potential applications. Chemical reduction is the most versatile method for the large scale production of graphene. Here we report the operating conditions for a one-step, economical and green synthesis method for the reduction of graphene oxide using a biomolecule (alanine). Graphene oxide was produced by the oxidation and exfoliation of natural graphite flake with strong oxidants using Hummers method (Hummers and Offeman, 1958), but the method was revised in our laboratory to set up a safe and environmentally friendly route. The reduction of graphene oxide was investigated using alanine at various operating conditions in order to set up optimum conditions (treatment time, temperature and concentration of the reagent). Samples have been characterized by using UV–Visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction analysis. - Highlights: • An environmentally friendly route was reported for the chemical reduction of graphene oxide (GO). • Alanine could reduce GO to rGO (reduced graphene oxide) without using any stabilizer or alcaline medium. • Characterization studies confirmed the successful deoxygenation of GO.

Green reduction of graphene oxide using alanine

Energy Technology Data Exchange (ETDEWEB)

Wang, Jiabin [Newcastle University, School of Chemical Engineering and Advanced Materials, Newcastle upon Tyne NE1 7RU (United Kingdom); Salihi, Elif Caliskan, E-mail: caliskanelif@gmail.com [Newcastle University, School of Chemical Engineering and Advanced Materials, Newcastle upon Tyne NE1 7RU (United Kingdom); Marmara University, Faculty of Pharmacy, Department of Basic Pharmaceutical Sciences, 34668 Istanbul (Turkey); Šiller, Lidija [Newcastle University, School of Chemical Engineering and Advanced Materials, Newcastle upon Tyne NE1 7RU (United Kingdom)

2017-03-01

There remains a real need for the easy, eco-friendly and scalable preparation method of graphene due to various potential applications. Chemical reduction is the most versatile method for the large scale production of graphene. Here we report the operating conditions for a one-step, economical and green synthesis method for the reduction of graphene oxide using a biomolecule (alanine). Graphene oxide was produced by the oxidation and exfoliation of natural graphite flake with strong oxidants using Hummers method (Hummers and Offeman, 1958), but the method was revised in our laboratory to set up a safe and environmentally friendly route. The reduction of graphene oxide was investigated using alanine at various operating conditions in order to set up optimum conditions (treatment time, temperature and concentration of the reagent). Samples have been characterized by using UV–Visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction analysis. - Highlights: • An environmentally friendly route was reported for the chemical reduction of graphene oxide (GO). • Alanine could reduce GO to rGO (reduced graphene oxide) without using any stabilizer or alcaline medium. • Characterization studies confirmed the successful deoxygenation of GO.

A study on direct alloying with molybdenum oxides by feed wire method

Directory of Open Access Journals (Sweden)

Jingjing Zou

2018-04-01

Full Text Available Direct alloying with molybdenum oxides has been regarded in years; the main addition methods are adding to the bottom of electric arc furnace (EAF with scrap, adding to the ladle during the converter tapping and mixing molybdenum oxide, lime and reductant to prepare pellet added to basic oxygen furnace (BOF. In this paper, a new method for direct alloying with molybdenum trioxide is proposed, adding molybdenum trioxide molten steel by feeding wire method in ladle furnace (LF refining process. The feasibility of molybdenum oxide reduction, the influence rules of bottom-blown on liquid steel fluidity and the yield of molybdenum by feeding wire method were analyzed. Results show that molybdenum oxide can be reduced by [Al], [Si], [C], and even [Fe] in molten steel. Bottom blowing position has a significant influence on the flow of molten steel when the permeable brick is located in 1/2 radius. The yields of Mo are higher than 97% for the experiments with feed wire method, the implementation of direct alloying with molybdenum trioxide by feed wire method works even better than that uses of ferromolybdenum in the traditional process.

Localized conductive patterning via focused electron beam reduction of graphene oxide

Energy Technology Data Exchange (ETDEWEB)

Kim, Songkil; Henry, Mathias [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Kulkarni, Dhaval D.; Zackowski, Paul; Jang, Seung Soon; Tsukruk, Vladimir V. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Fedorov, Andrei G., E-mail: agf@gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2015-03-30

We report on a method for “direct-write” conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

Reduction Rates for Higher Americium Oxidation States in Nitric Acid

Energy Technology Data Exchange (ETDEWEB)

Grimes, Travis Shane [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mincher, Bruce Jay [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schmitt, Nicholas C [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-09-30

The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

Recovery Of Nickel From Spent Nickel-Cadmium Batteries Using A Direct Reduction Process

Directory of Open Access Journals (Sweden)

Shin D.J.

2015-06-01

Full Text Available Most nickel is produced as Ferro-Nickel through a smelting process from Ni-bearing ore. However, these days, there have been some problems in nickel production due to exhaustion and the low-grade of Ni-bearing ore. Moreover, the smelting process results in a large amount of wastewater, slag and environmental risk. Therefore, in this research, spent Ni-Cd batteries were used as a base material instead of Ni-bearing ore for the recovery of Fe-Ni alloy through a direct reduction process. Spent Ni-Cd batteries contain 24wt% Ni, 18.5wt% Cd, 12.1% C and 27.5wt% polymers such as KOH. For pre-treatment, Cd was vaporized at 1024K. In order to evaluate the reduction conditions of nickel oxide and iron oxide, pre-treated spent Ni-Cd batteries were experimented on under various temperatures, gas-atmospheres and crucible materials. By a series of process, alloys containing 75 wt% Ni and 20 wt% Fe were produced. From the results, the reduction mechanism of nickel oxide and iron oxide were investigated.

Kinetics of the reduction of uranium oxide catalysts

International Nuclear Information System (INIS)

Heynen, H.W.G.; Camp-van Berkel, M.M.; Bann, H.S. van der

1977-01-01

The reduction of uranium oxide and uranium oxide on alumina catalysts by ethylbenzene and by hydrogen has been studied in a thermobalance. Ethylbenzene mole fractions between 0.0026 and 0.052 and hydrogen mole fractions between 0.1 and 0.6 were applied at temperatures of 425--530 0 C. During the reduction the uranium oxides are converted into UO 2 . The rate of reduction of pure uranium oxide appears to be constant in the composition region UO/sub 2.6/-UO/sub 2.25/. The extent of this region is independent of the concentration of the reducing agents and of the reaction temperature. The constant rate is explained in terms of a constant oxygen pressure which is in equilibrium with the two solid phases, U 3 O/sub 8-x/ and U 4 O 9 . The reduction rate is first order in hydrogen and zero order in ethylbenzene with activation energies of 120 and 190 kJ mol -1 , respectively. Oxygen diffusion through the lattice is probably not rate limiting. The reduction behavior of uranium oxide on alumina is different from that of pure uranium oxide; the rate of reduction continuously decreases with increasing degree of reduction. An explanation for this behavior has been given by visualizing this catalyst as a set of isolated uranium oxide crystallites with a relative wide variation of diameters, in an alumina matrix. At the beginning of the reduction, carbon dioxide and water are the only reaction products. Thereafter, benzene is found as well and, finally, at U/O ratios below 2.25, styrene also appears in the reactor outlet

Electrochemical reduction of actinides oxides in molten salts

International Nuclear Information System (INIS)

Claux, B.

2011-01-01

Reactive metals are currently produced from their oxide by multiple steps reduction techniques. A one step route from the oxide to the metal has been suggested for metallic titanium production by electrolysis in high temperature molten chloride salts. In the so-called FFC process, titanium oxide is electrochemically reduced at the cathode, generating O 2- ions, which are converted on a graphite anode into carbon oxide or dioxide. After this process, the spent salt can in principle be reused for several batches which is particularly attractive for a nuclear application in terms of waste minimization. In this work, the electrochemical reduction process of cerium oxide (IV) is studied in CaCl 2 and CaCl 2 -KCl melts to understand the oxide reduction mechanism. Cerium is used as a chemical analogue of actinides. Electrolysis on 10 grams of cerium oxide are made to find optimal conditions for the conversion of actinides oxides into metals. The scale-up to hundred grams of oxide is also discussed. (author) [fr

Advanced Experimental Analysis of Controls on Microbial Fe(III) Oxide Reduction - Final Report - 09/16/1996 - 03/16/2001; FINAL

International Nuclear Information System (INIS)

Roden, Eric E.

2001-01-01

Considering the broad influence that microbial Fe(III) oxide reduction can have on subsurface metal/organic contaminant biogeochemistry, understanding the mechanisms that control this process is critical for predicting the behavior and fate of these contaminants in anaerobic subsurface environments. Knowledge of the factors that influence the rates of growth and activity of Fe(III) oxide-reducing bacteria is critical for predicting (i.e., modeling) the long-term influence of these organisms on the fate of contaminants in the subsurface, and for effectively utilizing Fe(III) oxide reduction and associated geochemical affects for the purpose of subsurface metal/organic contamination bioremediation. This research project will refine existing models for microbiological and geochemical controls on Fe(III) oxide reduction, using laboratory reactor systems that mimic, to varying degrees, the physical and chemical conditions of the subsurface. Novel experimental methods for studying the kinetics of microbial Fe(III) oxide reduction and measuring growth rates of Fe(III) oxide-reducing bacteria will be developed. These new methodologies will be directly applicable to studies on subsurface contaminant transformations directly coupled to or influenced by microbial Fe(III) oxide reduction

Technologies for the Reduction of Nitrogen Oxides Emissions

Directory of Open Access Journals (Sweden)

Paulica Arsenie

2015-06-01

Full Text Available When it comes to gas turbines, their main problem concerning pollutant emissions is represented by nitric oxides. Among other emissions, sulphur oxides being much reduced due to the use of liquid distilled and gas fuels with a low content of sulphur. Using water or steam injection became the favourite method during the '80s and especially the '90s since "dry" methods and catalytic reduction were both at the beginning of the development phase. Catalytic convertors have been used since the '80s and they are still used although the costs of renewing the catalyst are very high. In the last twenty years a gradual decrease has been registered on the limits of nitric oxides from 75 ppm to 25 ppm, and now the target is oriented towards the 9 ppm level. The evolution of burning technologies of combustion makes it possible to control the level of production of nitric oxides even from the source without being necessary to use "humid" methods. This, of course, opened the market for gas turbines because they can function even in areas with limited quality water reserves, such as maritime platforms and in the desert. In this paper, we are going to show that, although water injection is still used, "dry" control technologies of burning became favourite methods for the majority of users on the industrial power generators market. The great dependency between the creation of nitric oxides and the temperature reveals the effect of direct water or steam injection on reducing nitric oxides. Recent research showed that a reduction up to 85% of nitric oxides may be obtained by using the water or steam injection all together with the improvement of aerodynamic character of the burning room.

Green reduction of graphene oxide using alanine.

Science.gov (United States)

Wang, Jiabin; Salihi, Elif Caliskan; Šiller, Lidija

2017-03-01

There remains a real need for the easy, eco-friendly and scalable preparation method of graphene due to various potential applications. Chemical reduction is the most versatile method for the large scale production of graphene. Here we report the operating conditions for a one-step, economical and green synthesis method for the reduction of graphene oxide using a biomolecule (alanine). Graphene oxide was produced by the oxidation and exfoliation of natural graphite flake with strong oxidants using Hummers method (Hummers and Offeman, 1958), but the method was revised in our laboratory to set up a safe and environmentally friendly route. The reduction of graphene oxide was investigated using alanine at various operating conditions in order to set up optimum conditions (treatment time, temperature and concentration of the reagent). Samples have been characterized by using UV-Visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction analysis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

In situ sonochemical reduction and direct functionalization of graphene oxide: A robust approach with thermal and biomedical applications.

Science.gov (United States)

Maktedar, Shrikant S; Mehetre, Shantilal S; Avashthi, Gopal; Singh, Man

2017-01-01

The rapid, robust, scalable and non-hazardous sonochemical approach for in situ reduction and direct functionalization of graphene oxide has been developed for non-toxic biomedical applications. The graphene oxide (GrO) was directly functionalized with tryptamine (TA) without using any hazardous acylating and coupling reagents. The reaction was completed within 20min. An impact of ultrasound was inferred for a direct functionalization with other conventional methods. The evolved electronic states were confirmed with near edge X-ray absorption fine structure (NEXAFS). The direct covalent functionalization and formation of f-(TA) GrO was proven with FTIR, 13 C solid state NMR, XPS, XRD, Raman' HRTEM, AFM and TGA. The total percentage weight loss in TGA confirms an enhanced thermal stability of f-(TA) GrO. The f-(TA) GrO was further explored for an investigation of in vitro antimicrobial activity to ensure the health and environmental safety. An outstanding antibacterial activity of f-(TA) GrO was found against gram positive Staphylococcus aureus at MIC 128mgmL -1 . It confirms a suitability of f-(TA) GrO for thermally stable antibacterial coating. The f-(TA) GrO showed 39.14-48.9% antioxidant activities, evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The inherent cytotoxicity of f-(TA) GrO was evaluated with SRB assay to living cells, MCF-7 and Vero. The estimated cell viabilities were >80% upon addition of f-(TA) GrO over a wide concentration range of 10-80μgmL -1 . The high cytocompatibility of f-(TA) GrO confirms the low toxicity and an excellent biocompatibility. The morphological effect on Vero cell line, evidently confirmed the biocompatibility of f-(TA) GrO. Therefore, f-(TA) GrO was emerged as an advanced functional biomaterial for thermal and biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanisms of electrochemical reduction and oxidation of nitric oxide

NARCIS (Netherlands)

Vooys, de A.C.A.; Beltramo, G.L.; Riet, van B.; Veen, van J.A.R.; Koper, M.T.M.

2004-01-01

A summary is given of recent work on the reactivity of nitric oxide on various metal electrodes. The significant differences between the reactivity of adsorbed NO and NO in solution are pointed out, both for the reduction and the oxidation reaction(s). Whereas adsorbed NO can be reduced only to

Development of reduction technology for oxide fuel. Behaviour of rare-earth in lithium reduction process

International Nuclear Information System (INIS)

Kato, Tetsuya; Usami, Tsuyoshi; Yuda, Ryoichi; Kurata, Masateru; Moriyama, Hirotake

2000-01-01

Solubility measurements of rare-earth oxides in molten LiCl-Li 2 O salt and reduction tests of UO 2 doped with rare-earth oxides were carried out to determine the behavior of rare-earths in lithium reduction process. The solubility of rare-earth oxides increases in the order of Gd 2 O concentration. In multi-element systems including 6 rare-earth oxides, the solubility of each element is smaller than that in the individual systems. In the reduction tests, more than 90% of UO 2 was reduced within 1 hour after starting reduction and about 7% of rare-earths eluded into the LiCl molten salt bath containing Li 2 O which is formed by the reduction of UO 2 . The rare-earth concentrations in the bath were evaluated using the solubility data, assuming that rare-earth oxides in multi-element systems form solid solution as the equilibrium solid phase and that the activity coefficients in the solid phase are independent of the compositions. The calculated concentrations are consistent with the experimental ones obtained in the reduction tests. (author)

Study on the influences of reduction temperature on nickel-yttria-stabilized zirconia solid oxide fuel cell anode using nickel oxide-film electrode

Science.gov (United States)

Jiao, Zhenjun; Ueno, Ai; Suzuki, Yuji; Shikazono, Naoki

2016-10-01

In this study, the reduction processes of nickel oxide at different temperatures were investigated using nickel-film anode to study the influences of reduction temperature on the initial performances and stability of nickel-yttria-stabilized zirconia anode. Compared to conventional nickel-yttria-stabilized zirconia composite cermet anode, nickel-film anode has the advantage of direct observation at nickel-yttria-stabilized zirconia interface. The microstructural changes were characterized by scanning electron microscopy. The reduction process of nickel oxide is considered to be determined by the competition between the mechanisms of volume reduction in nickel oxide-nickel reaction and nickel sintering. Electrochemical impedance spectroscopy was applied to analyze the time variation of the nickel-film anode electrochemical characteristics. The anode performances and microstructural changes before and after 100 hours discharging and open circuit operations were analyzed. The degradation of nickel-film anode is considered to be determined by the co-effect between the nickel sintering and the change of nickel-yttria-stabilized zirconia interface bonding condition.

Direct synthesis of graphene nanosheets support Pd nanodendrites for electrocatalytic formic acid oxidation

Institute of Scientific and Technical Information of China (English)

杨苏东; 陈琳

2015-01-01

We report a solvothermal method preparation of dendritic Pd nanoparticles (DPNs) and spherical Pd nanoparticles (SPNs) supported on reduced graphene oxide (RGO). Drastically different morphologies of Pd NPs with nanodendritic structures or spherical structures were observed on graphene by controlling the reduction degree of graphene oxide (GO) un-der mild conditions. In addition to being a commonplace substrate, GO plays a more important role that relies on its surface groups, which serves as a shape-directing agent to direct the dendritic growth. As a result, the obtained DPNs/RGO catalyst exhibits a significantly enhanced electro-catalytic behavior for the oxidation of formic acid compared to the SPNs/RGO catalyst.

Direct reform of graphite oxide electrodes by using ambient plasma for supercapacitor applications

Science.gov (United States)

Kim, Ho Jun; Jeong, Hae Kyung

2017-10-01

Ambient plasma is applied to graphite oxide electrodes directly to improve electrochemical properties for supercapacitor applications. Surface morphology of the electrodes after the plasma treatment changes dramatically and amount of oxygen reduced significantly, demonstrating a reduction effect on the graphite oxide electrode by the ambient plasma. Equivalent series resistance of the electrode also reduced from 108 Ω to 84 Ω after the plasma treatment. Corresponding specific capacitance, therefore, increases from 0.45 F cm-2 to 0.85 F cm-2, proving that the ambient plasma treatment is very efficient, clean, economic, and environment-friendly method to reform the graphite oxide electrodes directly for the supercapacitor applications.

Reduction of graphene oxide and its effect on square resistance of reduced graphene oxide films

Energy Technology Data Exchange (ETDEWEB)

Hou, Zhaoxia; Zhou, Yin; Li, Guang Bin; Wang, Shaohong; Wang, Mei Han; Hu, Xiaodan; Li, Siming [Liaoning Province Key Laboratory of New Functional Materials and Chemical Technology, School ofMechanical Engineering, Shenyang University, Shenyang (China)

2015-06-15

Graphite oxide was prepared via the modified Hummers’ method and graphene via chemical reduction. Deoxygenation efficiency of graphene oxide was compared among single reductants including sodium borohydride, hydrohalic acids, hydrazine hydrate, and vitamin C. Two-step reduction of graphene oxide was primarily studied. The reduced graphene oxide was characterized by XRD, TG, SEM, XPS, and Raman spectroscopy. Square resistance was measured as well. Results showed that films with single-step N2H4 reduction have the best transmittance and electrical conductivity with square resistance of ~5746 Ω/sq at 70% transmittance. This provided an experimental basis of using graphene for electronic device applications.

PREPARATION OF WC-Co POWDER BY DIRECT REDUCTION AND CARBONIZATION

Institute of Scientific and Technical Information of China (English)

Zhonglai Yi; Gangqin Shao; Xinglong Duan; Peng Sun; Xiaoliang Shi; Zhen Xiong; Jingkun Guo

2005-01-01

A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed.Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder (CoWO4/WO3)was first formed by a spray-pyrolysis technique, which was then mixed with carbon black and converted to WC-Co composite powder at 950℃ for 4 h in N2 atmosphere. The resulting powder has a particle size of 100-300 nm.

2-22 Study of Oxidation/reduction Volatilization Technology

Institute of Scientific and Technical Information of China (English)

Tan; Cunmin[1; Cao; Shiwei[1; Tian; Yuan[1; Qin; Zhi[1

2015-01-01

As an advanced dry head-end processing of spent fuel reprocessing, the oxidation-reduction volatilization technology will use for pulverizing uranium oxide ceramic pellets, decladding, and removal of most of volatile and semi-volatile fission elements, 3H, 14C, Kr, Xe, I, Cs, Ru and Tc, from fuel prior to main treatment process. The AIROX and ORIOX process, including circulation of oxidation in oxygen atmosphere and reduction in hydrogen atmosphere, researched on international at present, is considered to be the first choice for head-end processing.

Effects of Borax on the Reduction of Pre-oxidized Panzhihua Ilmenite

Science.gov (United States)

Guo, Yufeng; Zheng, Fuqiang; Jiang, Tao; Chen, Feng; Wang, Shuai; Qiu, Guanzhou

2018-01-01

The effects of borax (sodium borate) on the enhancement reduction of pre-oxidized Panzhihua ilmenite were investigated. The effects of borax on the mineral phase transformation, microstructures, crystal cell parameter, melting point and Mg distribution were studied to reveal the mechanism of enhancement reduction. Under the constant reduction conditions, the borax could reduce the reduction activation energy of pre-oxidized ilmenite. The reduction kinetics analysis indicated that the reduction rate was controlled by interfacial chemical reaction. The reduction activation energy of the pre-oxidized ilmenite with 4% borax was 80.263 kJ/mol, which was 28.585 kJ/mol less than that of the pre-oxidized ilmenite without borax. Borax could eliminate the migration of Mg into the reduced particle center. The crystal cell parameter of the reduced product was increased by adding borax. Borax could improve the growth of dendritic crystals in the pre-oxidized ilmenite.

Electrodeposition of uranium metal by reduction of uranium oxides in molten Lif-KF=NaF-CaF 2-UF4

International Nuclear Information System (INIS)

Pao, D.S.; Burris, L.; Steunenberg, R.K.; Tomczuk, Z.

1990-01-01

Although electrolytic reduction of uranium oxides was shown to be feasible in the early 1960's it is recognized that considerable improvement in the electrolytic reduction technology must be achieved for practical applications. This exploratory work on electrolytic reduction of uranium oxide was undertaken to investigate potential improvements in the technology. The approach taken was to deposit solid uranium metal directly on a solid cathode at temperatures below the melting point of uranium (1132 degrees C). The lower temperature electrolytic reduction process has several advantages over the existing chemical reduction processes. It lessens materials problems and special heating and insulating requirements associated with high-temperature operations. It removes most impurities. It does not produce the large quantities of byproduct oxides wastes typical of chemical reduction processes

Large Scale Reduction of Graphite Oxide Project

Science.gov (United States)

Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

2015-01-01

This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.

Influence of additives on selective noncatalytic reduction of nitric oxide with ammonia in circulating fluidized bed boilers

DEFF Research Database (Denmark)

Leckner, Bo; Karlsson, Maria; Dam-Johansen, Kim

1991-01-01

The application of selective noncatalytic reduction of nitric oxide with ammonia in circulating fluidized bed boilers is investigated. Special attention is directed to the use of additives to the ammonia so that the efficiency of the NO reduction at lower temperatures can be increased. Tests under...

Reduction of Graphene Oxide to Graphene by Using Gamma Irradiation

International Nuclear Information System (INIS)

Shamellia Sharin; Irman Abdul Rahman; Ainee Fatimah Ahmad

2015-01-01

This research aims to gauge the ability of gamma radiation to induce the reduction of graphene oxide to graphene. Graphene oxide powders were dispersed into a mixture of alcohol and deionized water, and the mixture was then irradiated with a "6"0Co source using a GammaCell 220 Excel irradiator at absorbed doses of 0, 5, 15, 20 and 35 kGy. According to characterization using Fourier Transformed Infrared Spectroscopy (FTIR), it can be seen that almost every oxygen-containing functional group has been removed after irradiation of the graphene oxide mixture. Reduction of graphene oxide was also proven from the characterization using UV-Vis Spectroscopy, in which the wavelength of graphene oxide at 237 nm was red-shifted to 277 nm after being irradiated and the peak at 292 nm, (indicating the carboxyl group) disappears in the UV-Vis spectrum of reduced graphene oxide. Morphology of graphene oxide also changed from a smooth and flat surface to crumpled. The ratio of carbon/ oxygen in the graphene oxide was lower than the carbon/ oxygen of reduced graphene oxide. At the end of the experiment, it can be deduced that graphene oxide underwent reduction, characterized before and after irradiation using Emission Scanned Electron Microscopy and Energy Dispersive X-ray, Fourier Transformed Infrared Spectroscopy and UV-Vis Spectroscopy. Therefore, we postulate that the irradiation technique that induces reduction, can be used to obtain reduced graphene oxide from graphene oxide. (author)

Graphene oxide reduction by microwave heating

International Nuclear Information System (INIS)

Longo, Angela; Carotenuto, Gianfranco

2016-01-01

The possibility to prepare thermal reduced graphene oxide (Tr-GO) colloidal suspensions by microwave heating of graphene oxide (GO) suspensions in N-methyl-2-pyrrolidone (NMP) has been investigated. According to transmission electron microscopy (TEM) and absorption and emission spectroscopy characterization, such a type of thermal reduction does not lead to graphene quantum dots formation because only mono-functional oxygen-containing groups are removed.

Graphene oxide reduction by microwave heating

Energy Technology Data Exchange (ETDEWEB)

Longo, Angela; Carotenuto, Gianfranco [Institute for Polymers, Composites, and Biomaterials, National Research Council, Piazzale Enrico Fermi 1, 80055 Portici (Italy)

2016-05-18

The possibility to prepare thermal reduced graphene oxide (Tr-GO) colloidal suspensions by microwave heating of graphene oxide (GO) suspensions in N-methyl-2-pyrrolidone (NMP) has been investigated. According to transmission electron microscopy (TEM) and absorption and emission spectroscopy characterization, such a type of thermal reduction does not lead to graphene quantum dots formation because only mono-functional oxygen-containing groups are removed.

Large Scale Reduction of Graphite Oxide

Data.gov (United States)

National Aeronautics and Space Administration — This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction...

Electrochemical reduction of cerium oxides in molten salts

International Nuclear Information System (INIS)

Claux, B.; Serp, J.; Fouletier, J.

2011-01-01

This brief article describes a pyrochemical process that is used by CEA to turn actinide oxides into metal actinides. This process is applied to Cerium oxides (CeO 2 ) that simulate actinide oxides well chemically as cerium belongs to the lanthanide family. The process is in fact an electrolysis of cerium oxide in a bath of molten calcium chloride salt whose temperature is between 800 and 900 Celsius degrees. At those temperatures calcium chloride becomes a ionic liquid (Ca 2+ and Cl - ) that is a good electrical conductor and is particularly well-adapted as solvent to an electrolytic process. The electrolysis current allows the transformation of solvent Ca 2+ ions into metal calcium which, in turn, can reduce cerium oxide into metal cerium through chromatically. Experimental data shows the reduction of up to 90% of 10 g samples of CeO 2 in a 6 hour long electrolysis while the best reduction rate ever known was 80% so far. This result is all the more promising that cerium oxides are more difficult to reduce than actinide oxides from the thermodynamical perspective

Simultaneous nitrate reduction and acetaminophen oxidation using the continuous-flow chemical-less VUV process as an integrated advanced oxidation and reduction process

Energy Technology Data Exchange (ETDEWEB)

Moussavi, Gholamreza, E-mail: moussavi@modares.ac.ir; Shekoohiyan, Sakine

2016-11-15

Highlights: • Simultaneous advanced oxidation and reduction processes were explored in VUV system. • Complete reduction of nitrate to N{sub 2} was achieved at the presence of acetaminophen. • Complete degradation of acetaminophen was achieved at the presence of nitrate. • Over 95% of acetaminophen was mineralized in the VUV photoreactor. • VUV is a chemical-less advanced process for treating water emerging contaminants. - Abstract: This work was aimed at investigating the performance of the continuous-flow VUV photoreactor as a novel chemical-less advanced process for simultaneously oxidizing acetaminophen (ACT) as a model of pharmaceuticals and reducing nitrate in a single reactor. Solution pH was an important parameter affecting the performance of VUV; the highest ACT oxidation and nitrate reduction attained at solution pH between 6 and 8. The ACT was oxidized mainly by HO· while the aqueous electrons were the main working agents in the reduction of nitrate. The performance of VUV photoreactor improved with the increase of hydraulic retention time (HRT); the complete degradation of ACT and ∼99% reduction of nitrate with 100% N{sub 2} selectivity achieved at HRT of 80 min. The VUV effluent concentrations of nitrite and ammonium at HRT of 80 min were below the drinking water standards. The real water sample contaminated with the ACT and nitrate was efficiently treated in the VUV photoreactor. Therefore, the VUV photoreactor is a chemical-less advanced process in which both advanced oxidation and advanced reduction reactions are accomplished. This unique feature possesses VUV photoreactor as a promising method of treating water contaminated with both pharmaceutical and nitrate.

Simultaneous nitrate reduction and acetaminophen oxidation using the continuous-flow chemical-less VUV process as an integrated advanced oxidation and reduction process

International Nuclear Information System (INIS)

Moussavi, Gholamreza; Shekoohiyan, Sakine

2016-01-01

Highlights: • Simultaneous advanced oxidation and reduction processes were explored in VUV system. • Complete reduction of nitrate to N_2 was achieved at the presence of acetaminophen. • Complete degradation of acetaminophen was achieved at the presence of nitrate. • Over 95% of acetaminophen was mineralized in the VUV photoreactor. • VUV is a chemical-less advanced process for treating water emerging contaminants. - Abstract: This work was aimed at investigating the performance of the continuous-flow VUV photoreactor as a novel chemical-less advanced process for simultaneously oxidizing acetaminophen (ACT) as a model of pharmaceuticals and reducing nitrate in a single reactor. Solution pH was an important parameter affecting the performance of VUV; the highest ACT oxidation and nitrate reduction attained at solution pH between 6 and 8. The ACT was oxidized mainly by HO· while the aqueous electrons were the main working agents in the reduction of nitrate. The performance of VUV photoreactor improved with the increase of hydraulic retention time (HRT); the complete degradation of ACT and ∼99% reduction of nitrate with 100% N_2 selectivity achieved at HRT of 80 min. The VUV effluent concentrations of nitrite and ammonium at HRT of 80 min were below the drinking water standards. The real water sample contaminated with the ACT and nitrate was efficiently treated in the VUV photoreactor. Therefore, the VUV photoreactor is a chemical-less advanced process in which both advanced oxidation and advanced reduction reactions are accomplished. This unique feature possesses VUV photoreactor as a promising method of treating water contaminated with both pharmaceutical and nitrate.

In Vitro Enzymatic Reduction Kinetics of Mineral Oxides by Membrane Fractions from Shewanella oneidensis MR-1

International Nuclear Information System (INIS)

Ruebush, S.; Icopini, G.; Brantley, S.; Tien, M.

2006-01-01

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite

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.

Iron oxide reduction in methane-rich deep Baltic Sea sediments

DEFF Research Database (Denmark)

Egger, Matthias; Hagens, Mathilde; Sapart, Celia J.

2017-01-01

/L transition. Our results reveal a complex interplay between production, oxidation and transport of methane showing that besides organoclastic Fe reduction, oxidation of downward migrating methane with Fe oxides may also explain the elevated concentrations of dissolved ferrous Fe in deep Baltic Sea sediments...... profiles and numerical modeling, we propose that a potential coupling between Fe oxide reduction and methane oxidation likely affects deep Fe cycling and related biogeochemical processes, such as burial of phosphorus, in systems subject to changes in organic matter loading or bottom water salinity....

Mechanisms for Fe(III) oxide reduction in sedimentary environments

Science.gov (United States)

Nevin, Kelly P.; Lovely, Derek R.

2002-01-01

Although it was previously considered that Fe(III)-reducing microorganisms must come into direct contact with Fe(III) oxides in order to reduce them, recent studies have suggested that electron-shuttling compounds and/or Fe(III) chelators, either naturally present or produced by the Fe(III)-reducing microorganisms themselves, may alleviate the need for the Fe(III) reducers to establish direct contact with Fe(III) oxides. Studies with Shewanella alga strain BrY and Fe(III) oxides sequestered within microporous beads demonstrated for the first time that this organism releases a compound(s) that permits electron transfer to Fe(III) oxides which the organism cannot directly contact. Furthermore, as much as 450 w M dissolved Fe(III) was detected in cultures of S. alga growing in Fe(III) oxide medium, suggesting that this organism releases compounds that can solublize Fe(III) from Fe(III) oxide. These results contrast with previous studies, which demonstrated that Geobacter metallireducens does not produce electron-shuttles or Fe(III) chelators. Some freshwater aquatic sediments and groundwaters contained compounds, which could act as electron shuttles by accepting electrons from G. metallireducens and then transferring the electrons to Fe(III). However, other samples lacked significant electron-shuttling capacity. Spectroscopic studies indicated that the electron-shuttling capacity of the waters was not only associated with the presence of humic substances, but water extracts of walnut, oak, and maple leaves contained electron-shuttling compounds did not appear to be humic substances. Porewater from a freshwater aquatic sediment and groundwater from a petroleum-contaminated aquifer contained dissolved Fe(III) (4-16 w M), suggesting that soluble Fe(III) may be available as an electron acceptor in some sedimentary environments. These results demonstrate that in order to accurately model the mechanisms for Fe(III) reduction in sedimentary environments it will be necessary

State of the direct reduction and reduction smelting processes

Directory of Open Access Journals (Sweden)

Markotić A.

2002-01-01

Full Text Available For quite a long time efforts have been made to develop processes for producing iron i.e. steel without employing conventional procedures - from ore, coke, blast furnace, iron, electric arc furnace, converter to steel. The insufficient availability and the high price of the coking coals have forced many countries to research and adopt the non-coke-consuming reduction and metal manufacturing processes (non-coke metallurgy, direct reduction, direct processes. This paper represents a survey of the most relevant processes from this domain by the end of 2000, which display a constant increase in the modern process metallurgy.

Ultrasound assisted simultaneous reduction and direct functionalization of graphene oxide with thermal and cytotoxicity profile.

Science.gov (United States)

Maktedar, Shrikant S; Avashthi, Gopal; Singh, Man

2017-01-01

The new sonochemical approach for simultaneous reduction and direct functionalization of graphene oxide (GrO) has been developed. The GrO was functionalized with 2-Aminobenzoxazole (2-ABOZ) in twenty min with complete deletion of hazardous steps. The significance of ultrasound was exemplified with the comparative conventional methods. The newly prepared f-(2-ABOZ)GrO was extensively characterized with near edge X-ray absorption fine structure (NEXAFS) spectroscopy, 13 C solid state NMR, XPS, XRD, HRTEM, SAED, AFM, Raman, UV-vis, FTIR and TGA. The thermal stability of f-(2-ABOZ)GrO was confirmed with total percentage weight loss in TGA. The biological activity of f-(2-ABOZ)GrO was explored with MCF-7 and Vero cell lines. The inherent cytotoxicity was evaluated with SRB assay at 10, 20, 40 and 80μgmL -1 . The estimated cell viabilities were >78% with f-(2-ABOZ) GrO. A high cytocompatibility of f-(2-ABOZ)GrO was ensured with in vitro evaluation on living cell lines, and low toxicity of f-(2-ABOZ)GrO was confirmed its excellent biocompatibility. The morphological effect on Vero cell line evidently supports the formation of biocompatible f-(2-ABOZ)GrO. Therefore, f-(2-ABOZ)GrO was emerged as an advanced functional material for thermally stable biocompatible coatings. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparative study of synthesis and reduction methods for graphene oxide

KAUST Repository

Alazmi, Amira; Rasul, Shahid; Patole, Shashikant P.; Da Costa, Pedro M. F. J.

2016-01-01

Graphene oxide (GO) and reduced graphene oxide (rGO) have congregated much interest as promising active materials for a variety of applications such as electrodes for supercapacitors. Yet, partially given the absence of comparative studies in synthesis methodologies, a lack of understanding persists on how to best tailor these materials. In this work, the effect of using different graphene oxidation-reduction strategies in the structure and chemistry of rGOs is systematically discussed. Two of the most popular oxidation routes in the literature were used to obtain GO. Subsequently, two sets of rGO powders were synthesised employing three different reduction routes, totalling six separate products. It is shown that the extension of the structural rearrangement in rGOs is not just dependent on the reduction step but also on the approach followed for the initial graphite oxidation.

Comparative study of synthesis and reduction methods for graphene oxide

KAUST Repository

Alazmi, Amira

2016-05-14

Graphene oxide (GO) and reduced graphene oxide (rGO) have congregated much interest as promising active materials for a variety of applications such as electrodes for supercapacitors. Yet, partially given the absence of comparative studies in synthesis methodologies, a lack of understanding persists on how to best tailor these materials. In this work, the effect of using different graphene oxidation-reduction strategies in the structure and chemistry of rGOs is systematically discussed. Two of the most popular oxidation routes in the literature were used to obtain GO. Subsequently, two sets of rGO powders were synthesised employing three different reduction routes, totalling six separate products. It is shown that the extension of the structural rearrangement in rGOs is not just dependent on the reduction step but also on the approach followed for the initial graphite oxidation.

Mercury mobilization and speciation linked to bacterial iron oxide and sulfate reduction: A column study to mimic reactive transfer in an anoxic aquifer.

Science.gov (United States)

Hellal, Jennifer; Guédron, Stéphane; Huguet, Lucie; Schäfer, Jörg; Laperche, Valérie; Joulian, Catherine; Lanceleur, Laurent; Burnol, André; Ghestem, Jean-Philippe; Garrido, Francis; Battaglia-Brunet, Fabienne

2015-09-01

Mercury (Hg) mobility and speciation in subsurface aquifers is directly linked to its surrounding geochemical and microbial environment. The role of bacteria on Hg speciation (i.e., methylation, demethylation and reduction) is well documented, however little data is available on their impact on Hg mobility. The aim of this study was to test if (i) Hg mobility is due to either direct iron oxide reduction by iron reducing bacteria (IRB) or indirect iron reduction by sulfide produced by sulfate reducing bacteria (SRB), and (ii) to investigate its subsequent fate and speciation. Experiments were carried out in an original column setup combining geochemical and microbiological approaches that mimic an aquifer including an interface of iron-rich and iron depleted zones. Two identical glass columns containing iron oxides spiked with Hg(II) were submitted to (i) direct iron reduction by IRB and (ii) to indirect iron reduction by sulfides produced by SRB. Results show that in both columns Hg was leached and methylated during the height of bacterial activity. In the column where IRB are dominant, Hg methylation and leaching from the column was directly correlated to bacterial iron reduction (i.e., Fe(II) release). In opposition, when SRB are dominant, produced sulfide induced indirect iron oxide reduction and rapid adsorption of leached Hg (or produced methylmercury) on neoformed iron sulfides (e.g., Mackinawite) or its precipitation as HgS. At the end of the SRB column experiment, when iron-oxide reduction was complete, filtered Hg and Fe concentrations increased at the outlet suggesting a leaching of Hg bound to FeS colloids that may be a dominant mechanism of Hg transport in aquifer environments. These experimental results highlight different biogeochemical mechanisms that can occur in stratified sub-surface aquifers where bacterial activities play a major role on Hg mobility and changes in speciation. Copyright © 2015 Elsevier B.V. All rights reserved.

The Nernst equation applied to oxidation-reduction reactions in myoglobin and hemoglobin. Evaluation of the parameters.

Science.gov (United States)

Saroff, Harry A

Analyses of the binding of oxygen to monomers such as myoglobin employ the Mass Action equation. The Mass Action equation, as such, is not directly applicable for the analysis of the binding of oxygen to oligomers such as hemoglobin. When the binding of oxygen to hemoglobin is analyzed, models incorporating extensions of mass action are employed. Oxidation-reduction reactions of the heme group in myoglobin and hemoglobin involve the binding and dissociation of electrons. This reaction is described with the Nernst equation. The Nernst equation is applicable only to a monomeric species even if the number of electrons involved is greater than unity. To analyze the oxidation-reduction reaction in a molecule such as hemoglobin a model is required which incorporates extensions of the Nernst equation. This communication develops models employing the Nernst equation for oxidation-reduction reactions analogous to those employed for hemoglobin in the analysis of the oxygenation (binding of oxygen) reaction.

Reduction of nitric oxide by arc vaporized carbons (AVC)

Energy Technology Data Exchange (ETDEWEB)

Tsang, S C; Chen, Y K; Green, M L.H. [The Catalysis Centre, Inorganic Chemistry Laboratory, University of Oxford, Oxford (United Kingdom)

1996-07-04

The reduction of nitric oxide by arc vaporized carbons (AVC) including the compound C{sub 6}0, fullerene soot and carbon nanotubes, giving dinitrogen and carbon oxides has been studied. It is found that the AVC carbons are more active towards oxidation by NO than by oxygen gas at low temperatures (300-400C). In contrast, conventional carbons such as graphite and microporous carbons are more readily oxidised by oxygen than by NO. The addition of copper salts and to a lesser extent, cobalt salts, to fullerene soot substantially promote NO reduction. The high intrinsic activity for NO reduction by AVC carbons compared to graphitic carbons is attributed to the presence of five membered carbon rings in the AVC carbons

Application of a chronoamperometric measurement to the on-line monitoring of a lithium metal reduction for uranium oxide

International Nuclear Information System (INIS)

Kim, Tack-Jin; Cho, Young-Hwan; Choi, In-Kyu; Kang, Jun-Gill; Song, Kyuseok; Jee, Kwang-Yong

2008-01-01

Both a potentiometric and a chronoamperometric electrochemical technique have been applied in an attempt to develop an efficient method for an on-line monitoring of a lithium metal reduction process of uranium oxides at a high-temperature in a molten salt medium. As a result of this study, it was concluded that the chronoamperometric method provided a simple and effective way for a direct on-line monitoring measurement of a lithium metal reduction process of uranium oxides at 650 o C by the measuring electrical currents dependency on a variation of the reduction time for the reaction. A potentiometric method, by adopting a homemade oxide ion selective electrode made of ZrO 2 stabilized by a Y 2 O 3 doping, however, was found to be inappropriate for an on-line monitoring of the reduction reaction of uranium oxide in the presence of lithium metal due to an abnormal behavior of the adopted electrodes. The observed experimental results were discussed in detail by comparing them with previously published experimental data

In situ Reduction and Oxidation of Nickel from Solid Oxide Fuel Cells in a Transmission Electron Microscope

DEFF Research Database (Denmark)

Faes, Antonin; Jeangros, Quentin; Wagner, Jakob Birkedal

2009-01-01

Environmental transmission electron microscopy was used to characterize in situ the reduction and oxidation of nickel from a Ni/YSZ solid oxide fuel cell anode support between 300-500{degree sign}C. The reduction is done under low hydrogen pressure. The reduction initiates at the NiO/YSZ interface...

Simultaneous nitrate reduction and acetaminophen oxidation using the continuous-flow chemical-less VUV process as an integrated advanced oxidation and reduction process.

Science.gov (United States)

Moussavi, Gholamreza; Shekoohiyan, Sakine

2016-11-15

This work was aimed at investigating the performance of the continuous-flow VUV photoreactor as a novel chemical-less advanced process for simultaneously oxidizing acetaminophen (ACT) as a model of pharmaceuticals and reducing nitrate in a single reactor. Solution pH was an important parameter affecting the performance of VUV; the highest ACT oxidation and nitrate reduction attained at solution pH between 6 and 8. The ACT was oxidized mainly by HO while the aqueous electrons were the main working agents in the reduction of nitrate. The performance of VUV photoreactor improved with the increase of hydraulic retention time (HRT); the complete degradation of ACT and ∼99% reduction of nitrate with 100% N2 selectivity achieved at HRT of 80min. The VUV effluent concentrations of nitrite and ammonium at HRT of 80min were below the drinking water standards. The real water sample contaminated with the ACT and nitrate was efficiently treated in the VUV photoreactor. Therefore, the VUV photoreactor is a chemical-less advanced process in which both advanced oxidation and advanced reduction reactions are accomplished. This unique feature possesses VUV photoreactor as a promising method of treating water contaminated with both pharmaceutical and nitrate. Copyright © 2016 Elsevier B.V. All rights reserved.

Production of SmCo5 alloy by calciothermic reduction of samarium oxide

International Nuclear Information System (INIS)

Krishnan, T.S.; Gupta, C.K.

1988-01-01

Among the established permanent magnets, SmCo 5 magnet occupies the foremost position as it offers a unique combination of high energy product, coercivity and curie temperature. The SmCo 5 magnets are thus extensively used for high field applications. These are also best suited for use in environments where high demagnetizing field and high temperature are operative. Also, for applications where high performance and miniaturization are the over-riding considerations, the choice again falls on SmCo 5 magnets. The main deterrent to the widespread use of SmCo 5 magnet is its high cost. Both samarium and cobalt metals are high priced, and the magnets prepared from their directly melted alloy are thus naturally very expensive. An alternate process involving calcium reduction of their oxide intermediates has, therefore, been studied and the alloy prepared by this process has been evaluated and found satisfactory for magnet production. The process essentially involves compaction of the charge mix containing samarium oxide, cobalt oxide (or metal) and calcium metal and reduction of the charge compact at 1000-1300 degrees C in hydrogen atmosphere, followed by water and acid leaching, drying and classification

Green reduction of graphene oxide by ascorbic acid

Science.gov (United States)

Khosroshahi, Zahra; Kharaziha, Mahshid; Karimzadeh, Fathallah; Allafchian, Alireza

2018-01-01

Graphene, a single layer of sp2-hybridized carbon atoms in a hexagonal (two-dimensional honey-comb) lattice, has attracted strong scientific and technological interest due to its novel and excellent optical, chemical, electrical, mechanical and thermal properties. The solution-processable chemical reduction of Graphene oxide (GO is considered as the most favorable method regarding mass production of graphene. Generally, the reduction of GO is carried out by chemical approaches using different reductants such as hydrazine and sodium borohydride. These components are corrosive, combustible and highly toxic which may be dangerous for personnel health and the environment. Hence, these reducing agents are not promising choice for reducing of graphene oxide (GO). As a consequence, it is necessary for further development and optimization of eco-friendly, natural reducing agent for clean and effective reduction of GO. Ascorbic acid, an eco-friendly and natural reducing agents, having a mild reductive ability and nontoxic property. So, the aim of this research was to green synthesis of GO with ascorbic acid. For this purpose, the required amount of NaOH and ascorbic acid were added to GO solution (0.5 mg/ml) and were heated at 95 °C for 1 hour. According to the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and electrochemical results, GO were reduced with ascorbic acid like hydrazine with better electrochemical properties and ascorbic acid is an ideal substitute for hydrazine in the reduction of graphene oxide process.

Direct Coal Oxidation in Modified Solid Oxide Fuel Cells

DEFF Research Database (Denmark)

Deleebeeck, Lisa; Gil, Vanesa; Ippolito, Davide

2017-01-01

Hybrid direct carbon fuel cells employ a classical solid oxide fuel cell together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon-carbonate s......Hybrid direct carbon fuel cells employ a classical solid oxide fuel cell together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon......-carbonate slurry or anode layer. The nature of the coal affects both open circuit voltage and power output. Highest OCV and power densities were observed for bituminous coal and by adding manganese oxide or praseodymium-doped ceria to the carbon/carbonate mixture. Comparing the carbon black fueled performance...... bituminous coal (73 mW/cm2)....

Oxidative reduction of glove box wipers with a downdraft thermal oxidation system

International Nuclear Information System (INIS)

Phelps, M.R.; Wilcox, W.A.

1996-04-01

Wipers (rags) used for decontamination and glove box cleanup in the Plutonium Finishing Plant often become soaked with acid and plutonium-rich solutions. After use, these wipers are rinsed in a dilute NaOH solution and dried, but the formation of unstable nitrates and the hydrogen gas caused by hydrolysis are concerns that still must be addressed. This report gives the results of testing with a small downdraft thermal oxidation system that was constructed by Pacific Northwest National Laboratory to stabilize glove wiper waste, reduce the waste volume, and reclaim plutonium. Proof-of-principle testing was conducted with eight runs using various combinations of rag moisture and chemical pretreatment. All runs went to planned completion. Results of these tests indicate that the thermal oxidation system has the potential for providing significant reductions in waste volume. Weight reductions of 150:1 were easily obtainable during this project. Modifications could result in weight reductions of over 200:1, with possible volume reductions of 500:1

Electrochemical reduction of nitroaromatic compounds by single sheet iron oxide coated electrodes

Energy Technology Data Exchange (ETDEWEB)

Huang, Li-Zhi, E-mail: lizhi@plen.ku.dk [Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK–1871 Frederiksberg C (Denmark); Hansen, Hans Christian B. [Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK–1871 Frederiksberg C (Denmark); Bjerrum, Morten Jannik [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK–2100 København Ø (Denmark)

2016-04-05

Highlights: • Composite layers of single sheet iron oxides were coated on indium tin oxide electrodes. • Single sheet iron oxide is an electro-catalyst for reduction of nitroaromatic compounds in aqueous solution. • The reduction is well explained by a diffusion layer model. • The charge properties of the nitrophenols have an important influence on reduction. • Low-cost iron oxide based materials are promising electro-catalyst for water treatment. - Abstract: Nitroaromatic compounds are substantial hazard to the environment and to the supply of clean drinking water. We report here the successful reduction of nitroaromatic compounds by use of iron oxide coated electrodes, and demonstrate that single sheet iron oxides formed from layered iron(II)-iron(III) hydroxides have unusual electrocatalytic reactivity. Electrodes were produced by coating of single sheet iron oxides on indium tin oxide electrodes. A reduction current density of 10 to 30 μA cm{sup −2} was observed in stirred aqueous solution at pH 7 with concentrations of 25 to 400 μM of the nitroaromatic compound at a potential of −0.7 V vs. SHE. Fast mass transfer favors the initial reduction of the nitroaromatic compound which is well explained by a diffusion layer model. Reduction was found to comprise two consecutive reactions: a fast four-electron first-order reduction of the nitro-group to the hydroxylamine-intermediate (rate constant = 0.28 h{sup −1}) followed by a slower two-electron zero-order reduction resulting in the final amino product (rate constant = 6.9 μM h{sup −1}). The zero-order of the latter reduction was attributed to saturation of the electrode surface with hydroxylamine-intermediates which have a more negative half-wave potential than the parent compound. For reduction of nitroaromatic compounds, the SSI electrode is found superior to metal electrodes due to low cost and high stability, and superior to carbon-based electrodes in terms of high coulombic efficiency and

Direct Coal Oxidation in Modified Solid Oxide Fuel Cells

DEFF Research Database (Denmark)

Deleebeeck, Lisa; Gil, Vanesa; Ippolito, Davide

2015-01-01

Hybrid direct carbon fuel cells employ a classical solid oxide fuel cell together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon-carbonate s......Hybrid direct carbon fuel cells employ a classical solid oxide fuel cell together with carbon dispersed in a carbonate melt on the anode side. In a European project, the utilization of various coals has been investigated with and without addition of an oxidation catalyst to the carbon......-carbonate slurry or anode layer. The nature of the coal affects both open circuit voltage and power output. Highest OCV and power densities were observed for bituminous coal and by adding manganese oxide or praseodymium-doped ceria to the carbon/carbonate mixture. Comparing the carbon black fueled performance...... bituminous coal (73 mW/cm2). © 2015 ECS - The Electrochemical Society...

Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions

Energy Technology Data Exchange (ETDEWEB)

Yongxin Zhao; Michael D. Mann; Edwin S. Olson; John H. Pavlish; Grant E. Dunham [University of North Dakota, Grand Forks, ND (United States). Department of Chemical Engineering

2006-05-15

This paper is particularly related to elemental mercury (Hg{sup 0}) oxidation and divalent mercury (Hg{sup 2+} reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO{sub 2}). As a powerful oxidant and chlorinating reagent, Cl{sub 2} has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO{sub 2}, NO, as well as H{sub 2}O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO{sub 2} and NO on Hg{sup 0} oxidation and Hg{sup 2+} reduction with the intent of unraveling unrecognized interactions among Cl species, SO{sub 2}, and NO most importantly in the presence of H{sub 2}O. The experimental results demonstrated that SO{sub 2} and NO had pronounced inhibitory effects on Hg{sup 0} oxidation at high temperatures when H{sub 2}O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg{sup 2+} back into its elemental form. Data revealed that SO{sub 2} and NO were capable of promoting homogeneous reduction of Hg{sup 2+} to Hg{sup 0} with H{sub 2}O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H{sub 2}O was removed from the gas blend. 23 refs., 8 figs.

Study of film graphene/graphene oxide obtained by partial reduction chemical of oxide graphite

International Nuclear Information System (INIS)

Gascho, J.L.S.; Costa, S.F.; Hoepfner, J.C.; Pezzin, S.H.

2014-01-01

This study investigated the morphology of graphene/graphene oxide film obtained by partial chemical reduction of graphite oxide (OG) as well as its resistance to solvents. Films of graphene/graphene oxide are great candidates for replacement of indium oxide doped with tin (ITO) in photoelectric devices. The OG was obtained from natural graphite, by Hummer's method modified, and its reduction is made by using sodium borohydride. Infrared spectroscopy analysis of Fourier transform (FTIR), Xray diffraction (XRD) and scanning electron microscopy, high-resolution (SEM/FEG) for the characterization of graphene/graphene oxide film obtained were performed. This film proved to be resilient, not dispersing in any of the various tested solvents (such as ethanol, acetone and THF), even under tip sonication, this resistance being an important property for the applications. Furthermore, the film had a morphology similar to that obtained by other preparation methods.(author)

In-Situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes

Science.gov (United States)

2010-12-28

DATES COVERED (From - To) 1/29/10-9/30/10 4. TITLE AND SUBTITLE In situ optical studies of oxidation/reduction kinetics on SOFC cermet anodes 5a...0572 In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Department of Chemistry and Biochemistry Montana State University...of Research In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Principal Investigator Robert Walker Organization

Direct reduction of uranium oxide(U3O8) by Li metal and U-metal(Fe, Ni) alloy formation in molten LiCl medium

International Nuclear Information System (INIS)

Cho, Young Hwan; Kim, Tack Jin; Choi, In Kyu; Kim, Won Ho; Jee, Kwang Yong

2004-01-01

Molten salt based electrochemical processes are proposed as a promising method for the future nuclear programs and more specifically for spent fuel processing. The lithium reduction has been introduced to convert actinide oxides into corresponding actinide metal by using lithium metal as a reductant in molten LiCl medium. We have applied similar lab-scale experiments to reduce uranium oxide in an effort to gain additional information on rates and mechanisms

Investigation of the Reduction of Graphene Oxide by Lithium Triethylborohydride

Directory of Open Access Journals (Sweden)

Guangyuan Xu

2016-01-01

Full Text Available The chemical reduction of a wet colloidal suspension of graphene oxide is a cost-effective and adaptable method for large scale production of “quasi” graphene for a wide variety of optoelectronic applications. In this study, modified Hummers’ procedure was used to synthesize high quality graphene oxide at 50°C. This modified protocol thus eliminates the potentially hazardous second high-temperature step in Hummers’ method for the production of GO. Furthermore, the reduction of graphene oxide by lithium triethylborohydride is demonstrated for the first time. According to FT-IR, UV-Vis, TGA, Raman, SEM/EDS, and AFM results, the reduced graphene oxide (LiEt3BH-RGO has properties comparable to other reduced graphene oxide products reported in the literature.

Thermodynamic analysis of reduction reactions of niobium oxides

International Nuclear Information System (INIS)

Takano, C.

1981-01-01

Reduction processes of niobium oxides by hydrogen, carbon and aluminium are analysed thermodinamically. It is shown that reduction by hydrogen is not technically feasible. High purity of raw materials is required. In the carbothermic process impurities which react to form high stability carbides should be avoided. (Author) [pt

A device for reduction of metal oxides generated in electrokinetic separation equipment

International Nuclear Information System (INIS)

Kim, Gye-Nam; Kim, Seung-Soo; Kim, Il-Gook; Jeong, Jung-Whan; Choi, Jong-Won

2015-01-01

For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of the waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured 1.2 ton electrokinetic decontamination equipment. The optimum pH of electrolyte in cathode chamber for a reduction of volume of metal oxides was below 2.35. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil per batch was manufactured to remove uranium from soil with high removal efficiency during a short time. For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured electrokinetic equipment. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil was manufactured to remove uranium from soil during a short time

A device for reduction of metal oxides generated in electrokinetic separation equipment

Energy Technology Data Exchange (ETDEWEB)

Kim, Gye-Nam; Kim, Seung-Soo; Kim, Il-Gook; Jeong, Jung-Whan; Choi, Jong-Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of the waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured 1.2 ton electrokinetic decontamination equipment. The optimum pH of electrolyte in cathode chamber for a reduction of volume of metal oxides was below 2.35. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil per batch was manufactured to remove uranium from soil with high removal efficiency during a short time. For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured electrokinetic equipment. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil was manufactured to remove uranium from soil during a short time.

Catalytic/non-catalytic combination process for nitrogen oxides reduction

International Nuclear Information System (INIS)

Luftglass, B.K.; Sun, W.H.; Hofmann, J.E.

1992-01-01

This patent describes a process for the reduction of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel. It comprises introducing a nitrogenous treatment agent comprising urea, one or more of the hydrolysis products of urea, ammonia, compounds which produce ammonia as a by-product, ammonium salts of organic acids, 5- or 6-membered heterocyclic hydrocarbons having at least one cyclic nitrogen, hydroxy amino hydrocarbons, or mixtures thereof into the effluent at an effluent temperature between about 1200 degrees F and about 2100 degrees F; and contacting the treated effluent under conditions effective to reduce the nitrogen oxides in the effluent with a catalyst effective for the reduction of nitrogen oxides in the presence of ammonia

REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

Science.gov (United States)

Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...

Solid-state Water-mediated Transport Reduction of Nanostructured Iron Oxides

International Nuclear Information System (INIS)

Smirnov, Vladimir M.; Povarov, Vladimir G.; Voronkov, Gennadii P.; Semenov, Valentin G.; Murin, Igor' V.; Gittsovich, Viktor N.; Sinel'nikov, Boris M.

2001-01-01

The Fe 2+ /Fe 3+ ratio in two-dimensional iron oxide nanosructures (nanolayers with a thickness of 0.3-1.5 nm on silica surface) may be precisely controlled using the transport reduction (TR) technique. The species ≡-O-Fe(OH) 2 and (≡Si-O-) 2 -FeOH forming the surface monolayer are not reduced at 400-600 deg. C because of their covalent bonding to the silica surface, as demonstrated by Moessbauer spectroscopy. Iron oxide microparticles (microstructures) obtained by the impregnation technique, being chemically unbound to silica, are subjected to reduction at T ≥ 500 deg. C with formation of metallic iron in the form of α-Fe. Transport reduction of supported nanostructures (consisting of 1 or 4 monolayers) at T ≥ 600 deg. C produces bulk iron(II) silicate and metallic iron phases. The structural-chemical transformations occurring in transport reduction of supported iron oxide nanolayers are proved to be governed by specific phase processes in the nanostructures themselves

Sustainability in Ironmaking: The Rise of Direct Reduction

Science.gov (United States)

Battle, Thomas P.

Modern-day direct reduction of iron first developed as a small-scale, low capital and operating cost alternative to the blast furnace. Since commercialization of continuous DR technology in the late 1960s, the market for the products of direct reduction has grown to more than 74 million tonnes in 2012. The initial advantages of DR plants over BF facilities have grown over the years, for several reasons, including the increased size of DR modules, lower energy and emissions (particularly CO2), along with the flexibility to use a number of different reductants. The development of DR technology over the past forty years will be emphasized in this presentation, including recent developments that allow for even more direct sustainability comparisons with the iron blast furnace — and even combine the two technologies for improved synergies. Also briefly discussed will be the possibilities of using direct reduction for non-ferrous ores.

Reduction-oxidation Enabled Glass-ceramics to Stainless Steel Bonding Part I: screening of doping oxidants

Energy Technology Data Exchange (ETDEWEB)

Dai, Steve Xunhu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

Lithium silicate-based glass-ceramics with high coefficients of thermal expansion, designed to form matched hermetic seals in 304L stainless steel housing, show little evidence of interfacial chemical bonding, despite extensive inter-diffusion at the glass-ceramic-stainless steel (GC-SS) interface. A series of glass-ceramic compositions modified with a variety of oxidants, AgO, FeO, NiO, PbO, SnO, CuO, CoO, MoO₃ and WO₃, are examined for the feasibility of forming bonding oxides through reduction-oxidation (redox) at the GC-SS interface. The oxidants were selected according to their Gibbs free energy to allow for oxidation of Cr/Mn/Si from stainless steel, and yet to prevent a reduction of P2O5 in the glass-ceramic where the P₂O₅ is to form Li₃PO₄ nuclei for growth of high expansion crystalline SiO₂ phases. Other than the CuO and CoO modified glass-ceramics, bonding from interfacial redox reactions were not achieved in the modified glass-ceramics, either because of poor wetting on the stainless steel or a reduction of the oxidants at the surface of glass-ceramic specimens rather than the GC-SS interface.

Evolution of thermal stress and failure probability during reduction and re-oxidation of solid oxide fuel cell

Science.gov (United States)

Wang, Yu; Jiang, Wenchun; Luo, Yun; Zhang, Yucai; Tu, Shan-Tung

2017-12-01

The reduction and re-oxidation of anode have significant effects on the integrity of the solid oxide fuel cell (SOFC) sealed by the glass-ceramic (GC). The mechanical failure is mainly controlled by the stress distribution. Therefore, a three dimensional model of SOFC is established to investigate the stress evolution during the reduction and re-oxidation by finite element method (FEM) in this paper, and the failure probability is calculated using the Weibull method. The results demonstrate that the reduction of anode can decrease the thermal stresses and reduce the failure probability due to the volumetric contraction and porosity increasing. The re-oxidation can result in a remarkable increase of the thermal stresses, and the failure probabilities of anode, cathode, electrolyte and GC all increase to 1, which is mainly due to the large linear strain rather than the porosity decreasing. The cathode and electrolyte fail as soon as the linear strains are about 0.03% and 0.07%. Therefore, the re-oxidation should be controlled to ensure the integrity, and a lower re-oxidation temperature can decrease the stress and failure probability.

Catalytic activity of lanthanum oxide for the reduction of cyclohexanone

International Nuclear Information System (INIS)

Sugunan, S.; Sherly, K.B.

1994-01-01

Lanthanum oxides, La 2 O 3 has been found to be an effective catalyst for the liquid phase reduction of cyclohexanone. The catalytic activities of La 2 O 3 activated at 300, 500 and 800 degC and its mixed oxides with alumina for the reduction of cylcohexanone with 2-propanol have been determined and the data parallel that of the electron donating properties of the catalysts. The electron donating properties of the catalysts have been determined from the adsorption of electron acceptors of different electron affinities on the surface of these oxides. (author). 15 refs., 2 figs., 1 tab

Suspension Hydrogen Reduction of Iron Oxide Concentrates

Energy Technology Data Exchange (ETDEWEB)

H.Y. Sohn

2008-03-31

The objective of the project is to develop a new ironmaking technology based on hydrogen and fine iron oxide concentrates in a suspension reduction process. The ultimate objective of the new technology is to replace the blast furnace and to drastically reduce CO2 emissions in the steel industry. The goals of this phase of development are; the performance of detailed material and energy balances, thermochemical and equilibrium calculations for sulfur and phosphorus impurities, the determination of the complete kinetics of hydrogen reduction and bench-scale testing of the suspension reduction process using a large laboratory flash reactor.

Green reduction of graphene oxide via Lycium barbarum extract

Energy Technology Data Exchange (ETDEWEB)

Hou, Dandan, E-mail: houdandan114@163.com; Liu, Qinfu, E-mail: lqf@cumtb.edu.cn; Cheng, Hongfei, E-mail: h.cheng@cumtb.edu.cn; Zhang, Hao, E-mail: 1073261516@qq.com; Wang, Sen, E-mail: wscumtb@163.com

2017-02-15

The synthesis of graphene from graphene oxide (GO) usually involves toxic reducing agents that are harmful to human health and the environment. Here, we report a facile approach for effective reduction of GO, for the first time, using Lycium barbarum extract as a green and natural reducing agent. The morphology and de-oxidation efficiency of the reduced graphene were characterized and results showed that Lycium barbarum extract can effectively reduce GO into few layered graphene with a high carbon to oxygen ratio (6.5), comparable to that of GO reduced by hydrazine hydrate (6.6). The possible reduction mechanism of GO may be due to the active components existing in Lycium barbarum fruits, which have high binding affinity to the oxygen containing groups to form their corresponding oxides and other by-products. This method avoided the use of any nocuous chemicals, thus facilitating the mass production of graphene and graphene-based bio-materials. - Graphical abstract: Schematic illustration of the preparation of reduced graphene by Lycium barbarum extract. - Highlights: • The Lycium barbarum extract was used for the reduction of graphene oxide. • The obtained few layered graphene exhibited high carbon to oxygen ratio. • This approach can be applied in the preparation of graphene-based bio-materials.

Preparation of graphite derivatives by selective reduction of graphite oxide and isocyanate functionalization

Energy Technology Data Exchange (ETDEWEB)

Santha Kumar, Arunjunai Raja Shankar [Materials Science Centre, Indian Institute of Technology, Kharagpur, 721302, West Bengal (India); Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Piana, Francesco [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Organic Chemistry of Polymers, Technische Universität Dresden, 01062, Dresden (Germany); Mičušík, Matej [Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 845 41, Bratislava (Slovakia); Pionteck, Jürgen, E-mail: pionteck@ipfdd.de [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Banerjee, Susanta [Materials Science Centre, Indian Institute of Technology, Kharagpur, 721302, West Bengal (India); Voit, Brigitte [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069, Dresden (Germany); Organic Chemistry of Polymers, Technische Universität Dresden, 01062, Dresden (Germany)

2016-10-01

Heavily oxidized and ordered graphene nanoplatelets were produced from natural graphite by oxidation using a mixture of phosphoric acid, sulphuric acid, and potassium permanganate (Marcano's method). The atomic percentage of oxygen in the graphite oxide produced was more than 30% confirmed by XPS studies. The graphite oxide produced had intact basal planes and remains in a layered structure with interlayer distance of 0.8 nm, analyzed by WAXS. The graphite oxide was treated with 4,4′-methylenebis(phenyl isocyanate) (MDI) to produce grafted isocyanate functionalization. Introduction of these bulky functional groups widens the interlayer distance to 1.3 nm. In addition, two reduction methods, namely benzyl alcohol mediated reduction and thermal reduction were carried out on isocyanate modified and unmodified graphite oxides and compared to each other. The decrease in the oxygen content and the sp{sup 3} defect-repair were studied with XPS and RAMAN spectroscopy. Compared to the thermal reduction process, which is connected with large material loss, the benzyl alcohol mediated reduction process is highly effective in defect repair. This resulted in an increase of conductivity of at least 9 orders of magnitude compared to the graphite oxide. - Highlights: • Preparation of GO by Marcano's method results in defined interlayer spacing. • Treatment of GO with diisocyanate widens the interlayer spacing to 1.3 nm. • Chemical reduction of GO with benzyl alcohol is effective in defect repair. • Electrical conductivity increases by 9 orders of magnitude during chemical reduction. • The isocyanate functionalization is stable under chemical reducing conditions.

Electrochemical reduction of cerium oxide into metal

Energy Technology Data Exchange (ETDEWEB)

Claux, Benoit [CEA, Valduc, F-21120 Is-sur-Tille (France); Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France); Serp, Jerome, E-mail: jerome.serp@cea.f [CEA, Valduc, F-21120 Is-sur-Tille (France); Fouletier, Jacques [Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France)

2011-02-28

The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO{sub 2} reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO{sub 2} into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO{sub 2} were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl{sub 2}-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

Studies toward the oxidative and reductive activation of C-S bonds in 2'-S-aryl-2'-thiouridine derivatives.

Science.gov (United States)

Rayala, Ramanjaneyulu; Giuglio-Tonolo, Alain; Broggi, Julie; Terme, Thierry; Vanelle, Patrice; Theard, Patricia; Médebielle, Maurice; Wnuk, Stanislaw F

2016-04-21

Studies directed toward the oxidative and reductive desulfurization of readily available 2'- S -aryl-2'-thiouridine derivatives were investigated with the prospect to functionalize the C2'-position of nucleosides. The oxidative desulfurization-difluorination strategy was successful on 2-(arylthio)alkanoate surrogates, while extension of the combination of oxidants and fluoride sources was not an efficient fluorination protocol when applied to 2'- S -aryl-2'-thiouridine derivatives, resulting mainly in C5-halogenation of the pyrimidine ring and C2'-monofluorination without desulfurization. Cyclic voltammetry of 2'-arylsulfonyl-2'-deoxyuridines and their 2'-fluorinated analogues showed that cleavage of the arylsulfone moiety could occur, although at relatively high cathodic potentials. While reductive-desulfonylation of 2'-arylsulfonyl-2'-deoxyuridines with organic electron donors (OEDs) gave predominantly base-induced furan type products, chemical (OED) and electrochemical reductive-desulfonylation of the α-fluorosulfone derivatives yielded the 2'-deoxy-2'-fluorouridine and 2',3'-didehydro-2',3'-dideoxy-2'-fluorouridine derivatives. These results provided good evidence of the generation of a C2'-anion through carbon-sulfur bond cleavage, opening new horizons for the reductive-functionalization approaches in nucleosides.

Studies toward the oxidative and reductive activation of C-S bonds in 2'-S-aryl-2'-thiouridine derivatives

Science.gov (United States)

Rayala, Ramanjaneyulu; Giuglio-Tonolo, Alain; Broggi, Julie; Terme, Thierry; Vanelle, Patrice; Theard, Patricia; Médebielle, Maurice; Wnuk, Stanislaw F.

2016-01-01

Studies directed toward the oxidative and reductive desulfurization of readily available 2'-S-aryl-2'-thiouridine derivatives were investigated with the prospect to functionalize the C2'-position of nucleosides. The oxidative desulfurization-difluorination strategy was successful on 2-(arylthio)alkanoate surrogates, while extension of the combination of oxidants and fluoride sources was not an efficient fluorination protocol when applied to 2'-S-aryl-2'-thiouridine derivatives, resulting mainly in C5-halogenation of the pyrimidine ring and C2'-monofluorination without desulfurization. Cyclic voltammetry of 2'-arylsulfonyl-2'-deoxyuridines and their 2'-fluorinated analogues showed that cleavage of the arylsulfone moiety could occur, although at relatively high cathodic potentials. While reductive-desulfonylation of 2'-arylsulfonyl-2'-deoxyuridines with organic electron donors (OEDs) gave predominantly base-induced furan type products, chemical (OED) and electrochemical reductive-desulfonylation of the α-fluorosulfone derivatives yielded the 2'-deoxy-2'-fluorouridine and 2',3'-didehydro-2',3'-dideoxy-2'-fluorouridine derivatives. These results provided good evidence of the generation of a C2'-anion through carbon-sulfur bond cleavage, opening new horizons for the reductive-functionalization approaches in nucleosides. PMID:27019535

CuO reduction induced formation of CuO/Cu2O hybrid oxides

Science.gov (United States)

Yuan, Lu; Yin, Qiyue; Wang, Yiqian; Zhou, Guangwen

2013-12-01

Reduction of CuO nanowires results in the formation of a unique hierarchical hybrid nanostructure, in which the parent oxide phase (CuO) works as the skeleton while the lower oxide (Cu2O) resulting from the reduction reaction forms as partially embedded nanoparticles that decorate the skeleton of the parent oxide. Using in situ transmission electron microscopy observations of the reduction process of CuO nanowires, we demonstrate that the formation of such a hierarchical hybrid oxide structure is induced by topotactic nucleation and growth of Cu2O islands on the parent CuO nanowires.

Nitrous oxide reduction in nodules: denitrification or N2 fixation?

International Nuclear Information System (INIS)

Coyne, M.S.; Focht, D.D.

1987-01-01

Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor + ) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor - ) rhizobium strain (32H1) were incubated with 1% 15 N 2 O (95 atom% 15 N) in the following three atmospheres: aerobic with C 2 H 2 (10%), aerobic without C 2 H 2 , and anaerobic (argon atmosphere) without C 2 H 2 . The greatest production of 15 N 2 occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more 15 N 2 was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N 2 O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase

Monte Carlo radiative transfer simulation of a cavity solar reactor for the reduction of cerium oxide

Energy Technology Data Exchange (ETDEWEB)

Villafan-Vidales, H.I.; Arancibia-Bulnes, C.A.; Dehesa-Carrasco, U. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Col. Centro, A.P. 34, Temixco, Morelos 62580 (Mexico); Romero-Paredes, H. [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No.186, Col. Vicentina, A.P. 55-534, Mexico D.F 09340 (Mexico)

2009-01-15

Radiative heat transfer in a solar thermochemical reactor for the thermal reduction of cerium oxide is simulated with the Monte Carlo method. The directional characteristics and the power distribution of the concentrated solar radiation that enters the cavity is obtained by carrying out a Monte Carlo ray tracing of a paraboloidal concentrator. It is considered that the reactor contains a gas/particle suspension directly exposed to concentrated solar radiation. The suspension is treated as a non-isothermal, non-gray, absorbing, emitting, and anisotropically scattering medium. The transport coefficients of the particles are obtained from Mie-scattering theory by using the optical properties of cerium oxide. From the simulations, the aperture radius and the particle concentration were optimized to match the characteristics of the considered concentrator. (author)

Cathodic reduction of the duplex oxide films formed on copper in air with high relative humidity at 60 deg C

International Nuclear Information System (INIS)

Seo, M.; Ishikawa, Y.; Kodaira, M.; Sugimoto, A.; Nakayama, S.; Watanabe, M.; Furuya, S.; Minamitani, R.; Miyata, Y.; Nishikata, A.; Notoya, T.

2005-01-01

The cathodic reduction of duplex air-formed oxide film on copper was performed at a constant current density of i c = -50 μA cm -2 in deaerated 0.1 M KCl solution to investigate the sequence of cathodic reduction of each oxide layer and its mechanism. The single-phase thick CuO film on copper was also cathodically reduced at i c = -50 μA cm -2 or -2.5 mA cm -2 . The surface characterizations of the air-formed oxide film and single-phase CuO film before cathodic reduction and after partial or complete cathodic reduction were performed by XPS and X-ray diffraction, respectively. The two plateau regions appeared in the potential vs. time curve during cathodic reduction of the duplex air-formed oxide film on copper, while one plateau region was observed in the potential-time curve during cathodic reduction of the single-phase CuO film on copper. The potential in the first plateau region for the air-formed film coincided with that in the plateau region for the CuO film. The results of XPS and X-ray diffraction suggested that in the first plateau region, the outer CuO layer is directly reduced to metallic Cu, while in the second plateau region, the inner Cu 2 O layer is reduced to metallic Cu

Laser-Induced Reductive Sintering of Nickel Oxide Nanoparticles under Ambient Conditions

KAUST Repository

Paeng, Dongwoo; Lee, Daeho; Yeo, Junyeob; Yoo, Jae-Hyuck; Allen, Frances I.; Kim, Eunpa; So, Hongyun; Park, Hee K.; Minor, Andrew M.; Grigoropoulos, Costas P.

2015-01-01

© 2015 American Chemical Society. This work is concerned with the kinetics of laser-induced reductive sintering of nonstoichiometric crystalline nickel oxide (NiO) nanoparticles (NPs) under ambient conditions. The mechanism of photophysical reductive sintering upon irradiation using a 514.5 nm continuous-wave (CW) laser on NiO NP thin films has been studied through modulating the laser power density and illumination time. Protons produced due to high-temperature decomposition of the solvent present in the NiO NP ink, oxygen vacancies in the NiO NPs, and electronic excitation in the NiO NPs by laser irradiation all affect the early stage of the reductive sintering process. Once NiO NPs are reduced by laser irradiation to Ni, they begin to coalesce, forming a conducting material. In situ optical and electrical measurements during the reductive sintering process take advantage of the distinct differences between the oxide and the metallic phases to monitor the transient evolution of the process. We observe four regimes: oxidation, reduction, sintering, and reoxidation. A characteristic time scale is assigned to each regime.

Laser-Induced Reductive Sintering of Nickel Oxide Nanoparticles under Ambient Conditions

KAUST Repository

Paeng, Dongwoo

2015-03-19

© 2015 American Chemical Society. This work is concerned with the kinetics of laser-induced reductive sintering of nonstoichiometric crystalline nickel oxide (NiO) nanoparticles (NPs) under ambient conditions. The mechanism of photophysical reductive sintering upon irradiation using a 514.5 nm continuous-wave (CW) laser on NiO NP thin films has been studied through modulating the laser power density and illumination time. Protons produced due to high-temperature decomposition of the solvent present in the NiO NP ink, oxygen vacancies in the NiO NPs, and electronic excitation in the NiO NPs by laser irradiation all affect the early stage of the reductive sintering process. Once NiO NPs are reduced by laser irradiation to Ni, they begin to coalesce, forming a conducting material. In situ optical and electrical measurements during the reductive sintering process take advantage of the distinct differences between the oxide and the metallic phases to monitor the transient evolution of the process. We observe four regimes: oxidation, reduction, sintering, and reoxidation. A characteristic time scale is assigned to each regime.

Transformation of Leaf-like Zinc Dendrite in Oxidation and Reduction Cycle

International Nuclear Information System (INIS)

Nakata, Akiyoshi; Murayama, Haruno; Fukuda, Katsutoshi; Yamane, Tomokazu; Arai, Hajime; Hirai, Toshiro; Uchimoto, Yoshiharu; Yamaki, Jun-ichi; Ogumi, Zempachi

2015-01-01

Highlights: • Leaf-like zinc dendrites change to leaf-like residual oxides at high oxidation current density (10 mA cm −2 ) whereas it completely dissolves at low oxidation current density (1 mA cm −2 ). • Leaf-like residual oxide products is transformed to zinc deposits with particulate morphology, resulting in good rechargeability. • The residual zinc oxide provides sufficient zincate on its reduction, preventing the diffusion-limited condition that causes leaf-like dendrite formation. - Abstract: Zinc is a promising negative electrode material for aqueous battery systems whereas it shows insufficient rechargeability for use in secondary batteries. It has been reported that leaf-like dendrite deposits are often the origin of cell-failure, however, their nature and behavior on discharge (oxidation) - charge (reduction) cycling have been only poorly understood. Here we investigate the transformation of the leaf-like zinc dendrites using ex-situ scanning electron microscopy, X-ray computational tomography and in-situ X-ray diffraction. It is shown that the leaf-like zinc dendrites obtained under diffusion-limited conditions are nearly completely dissolved at a low oxidation current density of 1 mA cm −2 and cause re-evolution of the zinc dendrites. Oxidation at a high current density of 10 mA cm −2 leads to the formation of leaf-like zinc oxide residual products that result in particulate zinc deposits in the following reduction process, enabling good rechargeability. The reaction behavior of this oxide residue is detailed and discussed for the development of long-life zinc electrodes

Simulation of uranium oxides reduction kinetics by hydrogen. Reactivities of germination and growth

International Nuclear Information System (INIS)

Brun, C.

1997-01-01

The aim of this work is to simulate the reduction by hydrogen of the tri-uranium octo-oxide U 3 O 8 (obtained by uranium trioxide calcination) into uranium dioxide. The kinetics curves have been obtained by thermal gravimetric analysis, the hydrogen and steam pressures being defined. The geometrical modeling which has allowed to explain the trend of the kinetics curves and of the velocity curves is an anisotropic germination-growth modeling. The powder is supposed to be formed of spherical grains with the same radius. The germs of the new UO 2 phase appear at the surface of the U 3 O 8 grains with a specific germination frequency. The growth reactivity is anisotropic and is very large in the tangential direction to the grains surface. Then, the uranium dioxide growths inside the grain and the limiting step is the grain surface. The variations of the growth reactivity and of the germination specific frequency in terms of the gases partial pressures and of the temperature have been explained by two different mechanisms. The limiting step of the growth mechanism is the desorption of water in the uranium dioxide surface. Concerning the germination mechanism the limiting step is a water desorption too but in the tri-uranium octo-oxide surface. The same geometrical modeling and the same germination and growth mechanisms have been applied to the reduction of a tri-uranium octo-oxide obtained by calcination of hydrated uranium trioxide. The values of the germination specific frequency of this solid are nevertheless weaker than those of the solid obtained by direct calcination of the uranium trioxide. (O.M.)

Directing the Branching Growth of Cuprous Oxide by OH- Ions

Science.gov (United States)

Chen, Kunfeng; Si, Yunfei; Xue, Dongfeng

The effect of OH- ions on the branching growth of cuprous oxide microcrystals was systematically studied by a reduction route, where copper-citrate complexes were reduced by glucose under alkaline conditions. Different copper salts including Cu(NO3)2, CuCl2, CuSO4, and Cu(Ac)2 were used in this work. The results indicate that the Cu2O branching growth habit is closely correlated to the concentration of OH- ions, which plays an important role in directing the diffusion-limited branching growth of Cu2O and influencing the reduction power of glucose. A variety of Cu2O branching patterns including 6-pod, 8-pod and 24-pod branches, have been achieved without using template and surfactant. The current method can provide a good platform for studying the growth mechanism of microcrystal branching patterns.

Extracting metals directly from metal oxides

International Nuclear Information System (INIS)

Wai, C.M.; Smart, N.G.; Phelps, C.

1997-01-01

A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of β-diketones, halogenated β-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process. 4 figs

Biotechnological aspects of anaerobic oxidation of methane coupled to sulfate reduction

NARCIS (Netherlands)

Meulepas, R.J.W.

2009-01-01

Sulfate reduction (SR) can be used for the removal and recovery of metals and oxidized sulfur compounds from waste streams. Sulfate-reducing bacteria reduce oxidized sulfur compounds to sulfide. Subsequently, sulfide can precipitate dissolved metals or can be oxidized to elemental sulfur. Both metal

Iron alloy Fischer-tropsch catalysts--1. Oxidation-reduction studies of the Fe-Ni system

Energy Technology Data Exchange (ETDEWEB)

Unmuth, E.E.; Schwartz, L.H.; Butt, J.B.

1980-01-01

Catalysts containing 5% iron, nickel, or 4:1 iron-nickel on silica were hydrogen-reduced at 425/sup 0/C for 12 or 24 hr, reoxidized in air for 2 or 4 hr, reduced again in hydrogen for 12 hr, and studied at each treatment step by Moessbauer spectroscopy, X-ray diffraction, and temperature-programed desorption. The nickel was reduced directly to the metal, redispersed during the oxidation, and gave 20% smaller particles in the second reduction than in the first reduction. The ..cap alpha..-Fe/sub 2/O/sub 3/ reduced via an Fe/sub 3/O/sub 4/ intermediate and yielded approx. 70% metallic iron and the second reduction produced about the same particle size as the first reduction. The alloy catalyst reduced into a mixture of two phases, a face-centered cubic phase containing approx. 37.5% Ni, i.e., the bulk equilibrium value, and a body-centered cubic phase, and the particle sizes obtained in the first and second reductions were similar. The activation energies for the reduction were determined.

Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2010-01-01

The electrochemical reduction of nitrous oxide and oxygen has been studied on cone-shaped electrodes of La1-xSrxFeO3-delta perovskites in an all solid state cell, using cyclic voltammetry. It was shown that the activity of the La1-xSrxFeO3-delta perovskites for the electrochemical reduction...... of nitrous oxide mainly depends on the amount of Fe(III) and oxide ion vacancies. The activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of nitrous oxide is much lower than the activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of oxygen...

The Semireduced Mechanism for Nitric Oxide Reduction by Non-Heme Diiron Complexes: Modeling Flavodiiron Nitric Oxide Reductases.

Science.gov (United States)

White, Corey J; Speelman, Amy L; Kupper, Claudia; Demeshko, Serhiy; Meyer, Franc; Shanahan, James P; Alp, E Ercan; Hu, Michael; Zhao, Jiyong; Lehnert, Nicolai

2018-02-21

Flavodiiron nitric oxide reductases (FNORs) are a subclass of flavodiiron proteins (FDPs) capable of preferential binding and subsequent reduction of NO to N 2 O. FNORs are found in certain pathogenic bacteria, equipping them with resistance to nitrosative stress, generated as a part of the immune defense in humans, and allowing them to proliferate. Here, we report the spectroscopic characterization and detailed reactivity studies of the diiron dinitrosyl model complex [Fe 2 (BPMP)(OPr)(NO) 2 ](OTf) 2 for the FNOR active site that is capable of reducing NO to N 2 O [Zheng et al., J. Am. Chem. Soc. 2013, 135, 4902-4905]. Using UV-vis spectroscopy, cyclic voltammetry, and spectro-electrochemistry, we show that one reductive equivalent is in fact sufficient for the quantitative generation of N 2 O, following a semireduced reaction mechanism. This reaction is very efficient and produces N 2 O with a first-order rate constant k > 10 2 s -1 . Further isotope labeling studies confirm an intramolecular N-N coupling mechanism, consistent with the rapid time scale of the reduction and a very low barrier for N-N bond formation. Accordingly, the reaction proceeds at -80 °C, allowing for the direct observation of the mixed-valent product of the reaction. At higher temperatures, the initial reaction product is unstable and decays, ultimately generating the diferrous complex [Fe 2 (BPMP)(OPr) 2 ](OTf) and an unidentified ferric product. These results combined offer deep insight into the mechanism of NO reduction by the relevant model complex [Fe 2 (BPMP)(OPr)(NO) 2 ] 2+ and provide direct evidence that the semireduced mechanism would constitute a highly efficient pathway to accomplish NO reduction to N 2 O in FNORs and in synthetic catalysts.

Au/iron oxide catalysts: temperature programmed reduction and X-ray diffraction characterization

International Nuclear Information System (INIS)

Neri, G.; Visco, A.M.; Galvagno, S.; Donato, A.; Panzalorto, M.

1999-01-01

Gold on iron oxides catalysts have been characterized by temperature programmed reduction (TPR) and X-ray diffraction spectroscopy (XRD). The influence of preparation method, gold loading and pretreatment conditions on the reducibility of iron oxides have been investigated. On the impregnated Au/iron oxide catalysts as well as on the support alone the partial reduction of Fe(III) oxy(hydroxides) to Fe 3 O 4 starts in the 550 and 700 K temperature range. On the coprecipitated samples, the temperature of formation of Fe 3 O 4 is strongly dependent on the presence of gold. The reduction temperature is lowered as the gold loading is increased. The reduction of Fe 3 O 4 to FeO occurs at about 900 K and is not dependent on the presence of gold and the preparation method. It is suggested that the effect of gold on the reducibility of the iron oxides is related to an increase of the structural defects and/or of the surface hydroxyl groups. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Volatile organic compounds and oxides of nitrogen. Further emission reductions

Energy Technology Data Exchange (ETDEWEB)

Froste, H [comp.

1997-12-31

This report presents the current status in relation to achievement of the Swedish Environmental target set by Parliament to reduce emission of volatile organic compounds by 50 per cent between 1988 and 2000. It also instructed the Agency to formulate proposed measures to achieve a 50 per cent reduction of emission of nitrogen oxides between 1985 and 2005. The report presents an overall account of emission trends for volatile organic compounds (from all sectors) and nitrogen oxides (from the industry sector) and steps proposed to achieve further emission reductions. 43 refs

Volatile organic compounds and oxides of nitrogen. Further emission reductions

Energy Technology Data Exchange (ETDEWEB)

Froste, H. [comp.

1996-12-31

This report presents the current status in relation to achievement of the Swedish Environmental target set by Parliament to reduce emission of volatile organic compounds by 50 per cent between 1988 and 2000. It also instructed the Agency to formulate proposed measures to achieve a 50 per cent reduction of emission of nitrogen oxides between 1985 and 2005. The report presents an overall account of emission trends for volatile organic compounds (from all sectors) and nitrogen oxides (from the industry sector) and steps proposed to achieve further emission reductions. 43 refs

Solid oxide fuel cells fueled with reducible oxides

Science.gov (United States)

Chuang, Steven S.; Fan, Liang Shih

2018-01-09

A direct-electrochemical-oxidation fuel cell for generating electrical energy includes a cathode provided with an electrochemical-reduction catalyst that promotes formation of oxygen ions from an oxygen-containing source at the cathode, a solid-state reduced metal, a solid-state anode provided with an electrochemical-oxidation catalyst that promotes direct electrochemical oxidation of the solid-state reduced metal in the presence of the oxygen ions to produce electrical energy, and an electrolyte disposed to transmit the oxygen ions from the cathode to the solid-state anode. A method of operating a solid oxide fuel cell includes providing a direct-electrochemical-oxidation fuel cell comprising a solid-state reduced metal, oxidizing the solid-state reduced metal in the presence of oxygen ions through direct-electrochemical-oxidation to obtain a solid-state reducible metal oxide, and reducing the solid-state reducible metal oxide to obtain the solid-state reduced metal.

Enhanced electro-oxidation of ethanol using PtSn/CeO{sub 2}-C electrocatalyst prepared by an alcohol-reduction process

Energy Technology Data Exchange (ETDEWEB)

Neto, Almir Oliveira; Farias, Luciana A.; Dias, Ricardo R.; Brandalise, Michelle; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 - Cidade Universitaria, CEP 05508-900 Sao Paulo-SP (Brazil)

2008-09-15

PtSn/CeO{sub 2}-C electrocatalysts were prepared by an alcohol-reduction process using ethylene glycol as solvent and reduction agent and CeO{sub 2} and Vulcan Carbon XC72 as supports. The electrocatalysts were characterized by EDX and XRD. The electro-oxidation of ethanol was studied at room temperature by chronoamperometry. PtSn/CeO{sub 2}-C electrocatalyst with 15 wt% of CeO{sub 2} showed a significant increase of performance for ethanol oxidation compared to PtSn/C catalyst. Preliminary tests at 100C on a single cell of a direct ethanol fuel cell (DEFC) also confirm the results obtained by chronoamperometry. (author)

Cuprous oxide nanoparticles dispersed on reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction.

Science.gov (United States)

Yan, Xiao-Yan; Tong, Xi-Li; Zhang, Yue-Fei; Han, Xiao-Dong; Wang, Ying-Yong; Jin, Guo-Qiang; Qin, Yong; Guo, Xiang-Yun

2012-02-11

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction. This journal is © The Royal Society of Chemistry 2012

Direct 'delay' reductions of the Toda equation

International Nuclear Information System (INIS)

Joshi, Nalini

2009-01-01

A new direct method of obtaining reductions of the Toda equation is described. We find a canonical and complete class of all possible reductions under certain assumptions. The resulting equations are ordinary differential-difference equations, sometimes referred to as delay-differential equations. The representative equation of this class is hypothesized to be a new version of one of the classical Painleve equations. The Lax pair associated with this equation is obtained, also by reduction. (fast track communication)

Tuning the nonlinear optical absorption of reduced graphene oxide by chemical reduction.

Science.gov (United States)

Shi, Hongfei; Wang, Can; Sun, Zhipei; Zhou, Yueliang; Jin, Kuijuan; Redfern, Simon A T; Yang, Guozhen

2014-08-11

Reduced graphene oxides with varying degrees of reduction have been produced by hydrazine reduction of graphene oxide. The linear and nonlinear optical properties of both graphene oxide as well as the reduced graphene oxides have been measured by single beam Z-scan measurement in the picosecond region. The results reveal both saturable absorption and two-photon absorption, strongly dependent on the intensity of the pump pulse: saturable absorption occurs at lower pump pulse intensity (~1.5 GW/cm2 saturation intensity) whereas two-photon absorption dominates at higher intensities (≥5.7 GW/cm2). Intriguingly, we find that the two-photon absorption coefficient (from 1.5 cm/GW to 4.5cm/GW) and the saturation intensity (from 1 GW/cm2 to 2 GW/cm2) vary with chemical reduction, which is ascribed to the varying concentrations of sp2 domains and sp2 clusters in the reduced graphene oxides. Our results not only provide an insight into the evolution of the nonlinear optical coefficient in reduced graphene oxide, but also suggest that chemical engineering techniques may usefully be applied to tune the nonlinear optical properties of various nano-materials, including atomically thick graphene sheets.

Effects of Basicity and MgO in Slag on the Behaviors of Smelting Vanadium Titanomagnetite in the Direct Reduction-Electric Furnace Process

Directory of Open Access Journals (Sweden)

Tao Jiang

2016-05-01

Full Text Available The effects of basicity and MgO content on reduction behavior and separation of iron and slag during smelting vanadium titanomagnetite by electric furnace were investigated. The reduction behaviors affect the separation of iron and slag in the direct reduction-electric furnace process. The recovery rates of Fe, V, and Ti grades in iron were analyzed to determine the effects of basicity and MgO content on the reduction of iron oxides, vanadium oxides, and titanium oxides. The chemical compositions of vanadium-bearing iron and main phases of titanium slag were detected by XRF and XRD, respectively. The results show that the higher level of basicity is beneficial to the reduction ofiron oxides and vanadium oxides, and titanium content dropped in molten iron with the increasing basicity. As the content of MgO increased, the recovery rate of Fe increased slightly but the recovery rate of V increased considerably. The grades of Ti in molten iron were at a low level without significant change when MgO content was below 11%, but increased as MgO content increased to 12.75%. The optimum conditions for smelting vanadium titanomagnetite were about 11.38% content of MgO and quaternary basicity was about 1.10. The product, vanadium-bearing iron, can be applied in the converter steelmaking process, and titanium slag containing 50.34% TiO2 can be used by the acid leaching method.

C3 Epimerization of Glucose, via Regioselective Oxidation and Reduction

NARCIS (Netherlands)

Jumde, Varsha R.; Eisink, Niek N. H. M.; Witte, Martin D.; Minnaard, Adriaan J.

2016-01-01

Palladium-catalyzed oxidation can single out the secondary hydroxyl group at C3 in glucose, circumventing the more readily accessible hydroxyl at C6 and the more reactive anomeric hydroxyl. Oxidation followed by reduction results in either allose or allitol, each a rare sugar that is important in

Nitrous oxide production kinetics during nitrate reduction in river sediments.

Science.gov (United States)

Laverman, Anniet M; Garnier, Josette A; Mounier, Emmanuelle M; Roose-Amsaleg, Céline L

2010-03-01

A significant amount of nitrogen entering river basins is denitrified in riparian zones. The aim of this study was to evaluate the influence of nitrate and carbon concentrations on the kinetic parameters of nitrate reduction as well as nitrous oxide emissions in river sediments in a tributary of the Marne (the Seine basin, France). In order to determine these rates, we used flow-through reactors (FTRs) and slurry incubations; flow-through reactors allow determination of rates on intact sediment slices under controlled conditions compared to sediment homogenization in the often used slurry technique. Maximum nitrate reduction rates (R(m)) ranged between 3.0 and 7.1microg Ng(-1)h(-1), and affinity constant (K(m)) ranged from 7.4 to 30.7mg N-NO(3)(-)L(-1). These values were higher in slurry incubations with an R(m) of 37.9microg Ng(-1)h(-1) and a K(m) of 104mg N-NO(3)(-)L(-1). Nitrous oxide production rates did not follow Michaelis-Menten kinetics, and we deduced a rate constant with an average of 0.7 and 5.4ng Ng(-1)h(-1) for FTR and slurry experiments respectively. The addition of carbon (as acetate) showed that carbon was not limiting nitrate reduction rates in these sediments. Similar rates were obtained for FTR and slurries with carbon addition, confirming the hypothesis that homogenization increases rates due to release of and increasing access to carbon in slurries. Nitrous oxide production rates in FTR with carbon additions were low and represented less than 0.01% of the nitrate reduction rates and were even negligible in slurries. Maximum nitrate reduction rates revealed seasonality with high potential rates in fall and winter and low rates in late spring and summer. Under optimal conditions (anoxia, non-limiting nitrate and carbon), nitrous oxide emission rates were low, but significant (0.01% of the nitrate reduction rates). Copyright 2009 Elsevier Ltd. All rights reserved.

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li2O Salt

International Nuclear Information System (INIS)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon; Sohn, Jung Min

2016-01-01

In this study, the electrochemical reduction of RE 2 O 3 (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li 2 O. The electrochemical reduction behavior of the mixed RE 2 O 3 -NiO oxide has been investigated and the reduction path of RE 2 O 3 has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl 3 in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li 2 O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE 2 O 3 on the produced Ni to form intermetallic RENi 5 . The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd 2 O 3 was successfully converted to the metal in the presence of NiO.

Molecular Underpinnings of Fe(III Oxide Reduction by Shewanella oneidensis MR-1

Directory of Open Access Journals (Sweden)

Liang eShi

2012-02-01

Full Text Available In the absence of O2 and other electron acceptors, the Gram-negative bacterium Shewanella oneidensis MR-1 can use ferric [Fe(III] (oxy(hydroxide minerals as the terminal electron acceptors for anaerobic respiration. At circumneutral pH and in the absence of strong complexing ligands, Fe(III oxides are relatively insoluble and thus are external to the bacterial cells. S. oneidensis MR-1 has evolved the machinery (i.e., metal-reducing or Mtr pathway for transferring electrons across the entire cell envelope to the surface of extracellular Fe(III oxides. The protein components identified to date for the Mtr pathway include CymA, MtrA, MtrB, MtrC and OmcA. CymA is an inner-membrane tetraheme c-type cytochrome (c-Cyt that is proposed to oxidize the quinol in the inner-membrane and transfers the released electrons to redox proteins in the periplasm. Although the periplasmic proteins receiving electrons from CymA during Fe(III oxidation have not been identified, they are believed to relay the electrons to MtrA. A decaheme c-Cyt, MtrA is thought to be embedded in the trans outer-membrane and porin-like protein MtrB. Together, MtrAB deliver the electrons across the outer-membrane to the MtrC and OmcA on the outmost bacterial surface. Functioning as terminal reductases, the outer membrane and decaheme c-Cyts MtrC and OmcA can bind the surface of Fe(III oxides and transfer electrons directly to these minerals. To increase their reaction rates, MtrC and OmcA can use the flavins secreted by S. oneidensis MR-1 cells as diffusible co-factors for reduction of Fe(III oxides. MtrC and OmcA can also serve as the terminal reductases for soluble forms of Fe(III. Although our understanding of the Mtr pathway is still far from complete, it is the best characterized microbial pathway used for extracellular electron exchange. Characterizations of the Mtr pathway have made significant contributions to the molecular understanding of microbial reduction of Fe(III oxides.

Trace methane oxidation and the methane dependency of sulfate reduction in anaerobic granular sludge

KAUST Repository

Meulepas, Roel J.W.

2010-05-01

This study investigates the oxidation of labeled methane (CH4) and the CH4 dependence of sulfate reduction in three types of anaerobic granular sludge. In all samples, 13C-labeled CH4 was anaerobically oxidized to 13C-labeled CO2, while net endogenous CH4 production was observed. Labeled-CH4 oxidation rates followed CH4 production rates, and the presence of sulfate hampered both labeled-CH4 oxidation and methanogenesis. Labeled-CH4 oxidation was therefore linked to methanogenesis. This process is referred to as trace CH4 oxidation and has been demonstrated in methanogenic pure cultures. This study shows that the ratio between labeled-CH4 oxidation and methanogenesis is positively affected by the CH4 partial pressure and that this ratio is in methanogenic granular sludge more than 40 times higher than that in pure cultures of methanogens. The CH4 partial pressure also positively affected sulfate reduction and negatively affected methanogenesis: a repression of methanogenesis at elevated CH4 partial pressures confers an advantage to sulfate reducers that compete with methanogens for common substrates, formed from endogenous material. The oxidation of labeled CH 4 and the CH4 dependence of sulfate reduction are thus not necessarily evidence of anaerobic oxidation of CH4 coupled to sulfate reduction. © 2010 Federation of European Microbiological Societies.

Application of three-dimensional reduced graphene oxide-gold composite modified electrode for direct electrochemistry and electrocatalysis of myoglobin

International Nuclear Information System (INIS)

Shi, Fan; Xi, Jingwen; Hou, Fei; Han, Lin; Li, Guangjiu; Gong, Shixing; Chen, Chanxing; Sun, Wei

2016-01-01

In this paper a three-dimensional (3D) reduced graphene oxide (RGO) and gold (Au) composite was synthesized by electrodeposition and used for the electrode modification with carbon ionic liquid electrode (CILE) as the substrate electrode. Myoglobin (Mb) was further immobilized on the surface of 3D RGO–Au/CILE to obtain an electrochemical sensing platform. Direct electrochemistry of Mb on the modified electrode was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Mb with the modified electrode. The results can be ascribed to the presence of highly conductive 3D RGO–Au composite on the electrode surface that accelerate the electron transfer rate between the electroactive center of Mb and the electrode. The Mb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.2 to 36.0 mmol/L with the detection limit of 0.06 mmol/L (3σ). - Graphical abstract: Direct electrochemistry of myoglobin was realized on a three-dimensional reduced graphene oxide and gold nanocomposite modified carbon ionic liquid electrode. - Highlights: • A three-dimensional reduced graphene oxide and gold composite was synthesized by electrodeposition. • Myoglobin was immobilized on the modified electrode to obtain an electrochemical sensor. • Direct electrochemistry of myoglobin was realized on the modified electrode. • The myoglobin modified electrode showed excellent electrocatalytic reduction to trichloroacetic acid.

Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments.

Science.gov (United States)

Hansel, Colleen M; Lentini, Chris J; Tang, Yuanzhi; Johnston, David T; Wankel, Scott D; Jardine, Philip M

2015-11-01

A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration--a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder.

Reduction of a thin chromium oxide film on Inconel surface upon treatment with hydrogen plasma

Energy Technology Data Exchange (ETDEWEB)

Vesel, Alenka, E-mail: alenka.vesel@guest.arnes.si [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Mozetic, Miran [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Balat-Pichelin, Marianne [PROMES-CNRS Laboratory, 7 Rue du four solaire, 66120 Font Romeu Odeillo (France)

2016-11-30

Highlights: • Oxidized Inconel alloy was exposed to hydrogen at temperatures up to 1500 K. • Oxide reduction in hydrogen plasma started at approximately 1300 K. • AES depth profiling revealed complete reduction of oxides in plasma. • Oxides were not reduced, if the sample was heated just in hydrogen atmosphere. • Surface of reduced Inconel preserved the same composition as the bulk material. - Abstract: Inconel samples with a surface oxide film composed of solely chromium oxide with a thickness of approximately 700 nm were exposed to low-pressure hydrogen plasma at elevated temperatures to determine the suitable parameters for reduction of the oxide film. The hydrogen pressure during treatment was set to 60 Pa. Plasma was created by a surfaguide microwave discharge in a quartz glass tube to allow for a high dissociation fraction of hydrogen molecules. Auger electron depth profiling (AES) was used to determine the decay of the oxygen in the surface film and X-ray diffraction (XRD) to measure structural modifications. During hydrogen plasma treatment, the oxidized Inconel samples were heated to elevated temperatures. The reduction of the oxide film started at temperatures of approximately 1300 K (considering the emissivity of 0.85) and the oxide was reduced in about 10 s of treatment as revealed by AES. The XRD showed sharper substrate peaks after the reduction. Samples treated in hydrogen atmosphere under the same conditions have not been reduced up to approximately 1500 K indicating usefulness of plasma treatment.

Kinetics of oxidation of H2 and reduction of H2O in Ni-YSZ based solid oxide cells

DEFF Research Database (Denmark)

Ebbesen, Sune Dalgaard; Mogensen, Mogens Bjerg

2012-01-01

Reduction of H2O and oxidation of H2 was studied in a Ni-YSZ electrode supported Solid Oxide Cells produced at DTU Energy conversion (former Risø DTU). Polarisation (i-V) and electrochemical impedance spectroscopic characterisation show that the kinetics for reduction of H 2O is slower compared...... to oxidation of H2. The kinetic differences cannot be explained by the reaction mechanisms which are similar in the two cases but are rather an effect of the thermodynamics. The preliminary analysis performed in this study show that the slow kinetic for reduction is partly related to the endothermic nature...... of the reaction, cooling the active electrode, thereby leading to slower kinetics at low current densities. Likewise, the increased kinetic for oxidation was found to be related to the exothermic nature of the reaction, heating the active electrode, and thereby leading to faster kinetics. At higher current...

Effects of Adiponectin Including Reduction of Androstenedione Secretion and Ovarian Oxidative Stress Parameters In Vivo.

Directory of Open Access Journals (Sweden)

Fabio V Comim

Full Text Available Adiponectin is the most abundantly produced human adipokine with anti-inflammatory, anti-oxidative, and insulin-sensitizing properties. Evidence from in vitro studies has indicated that adiponectin has a potential role in reproduction because it reduces the production of androstenedione in bovine theca cells in vitro. However, this effect on androgen production has not yet been observed in vivo. The current study evaluated the effect of adiponectin on androstenedione secretion and oxidative stress parameters in a rodent model. Seven-week-old female Balb/c mice (n = 33, previously treated with equine gonadotropin chorionic, were assigned to one of four different treatments: Group 1, control (phosphate-buffered saline; Group 2, adiponectin 0.1 μg/mL; Group 3, adiponectin 1.0 μg/mL; Group 4, adiponectin 5.0 μg/mL. After 24 h, all animals were euthanized and androstenedione levels were measured in the serum while oxidative stress markers were quantified in whole ovary tissue. Female mice treated with adiponectin exhibited a significant reduction (about 60% in serum androstenedione levels in comparison to controls. Androstenedione levels decreased from 0.78 ± 0.4 ng/mL (mean ± SD in controls to 0.28 ± 0.06 ng/mL after adiponectin (5 μg/mL treatment (P = 0.01. This change in androgen secretion after 24 hours of treatment was associated with a significant reduction in the expression of CYP11A1 and STAR (but not CYP17A1. In addition, ovarian AOPP product levels, a direct product of protein oxidation, decreased significantly in adiponectin-treated mice (5 μg/mL; AOPP (mean ± SD decreased to 4.3 ± 2.1 μmol/L in comparison with that of the controls (11.5 ± 1.7 μmol/L; P = 0.0003. Our results demonstrated for the first time that acute treatment with adiponectin reduced the levels of a direct oxidative stress marker in the ovary as well as decreased androstenedione serum levels in vivo after 24 h.

Dual passivation of intrinsic defects at the compound semiconductor/oxide interface using an oxidant and a reductant.

Science.gov (United States)

Kent, Tyler; Chagarov, Evgeniy; Edmonds, Mary; Droopad, Ravi; Kummel, Andrew C

2015-05-26

Studies have shown that metal oxide semiconductor field-effect transistors fabricated utilizing compound semiconductors as the channel are limited in their electrical performance. This is attributed to imperfections at the semiconductor/oxide interface which cause electronic trap states, resulting in inefficient modulation of the Fermi level. The physical origin of these states is still debated mainly because of the difficulty in assigning a particular electronic state to a specific physical defect. To gain insight into the exact source of the electronic trap states, density functional theory was employed to model the intrinsic physical defects on the InGaAs (2 × 4) surface and to model the effective passivation of these defects by utilizing both an oxidant and a reductant to eliminate metallic bonds and dangling-bond-induced strain at the interface. Scanning tunneling microscopy and spectroscopy were employed to experimentally determine the physical and electronic defects and to verify the effectiveness of dual passivation with an oxidant and a reductant. While subsurface chemisorption of oxidants on compound semiconductor substrates can be detrimental, it has been shown theoretically and experimentally that oxidants are critical to removing metallic defects at oxide/compound semiconductor interfaces present in nanoscale channels, oxides, and other nanostructures.

Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals

Science.gov (United States)

Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R.K.; Kim, J.; Eberl, D.; Xu, Z.

2009-01-01

Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.

Mechanistic investigation of Fe(III) oxide reduction by low molecular weight organic sulfur species

Science.gov (United States)

Eitel, Eryn M.; Taillefert, Martial

2017-10-01

Low molecular weight organic sulfur species, often referred to as thiols, are known to be ubiquitous in aquatic environments and represent important chemical reductants of Fe(III) oxides. Thiols are excellent electron shuttles used during dissimilatory iron reduction, and in this capacity could indirectly affect the redox state of sediments, release adsorbed contaminants via reductive dissolution, and influence the carbon cycle through alteration of bacterial respiration processes. Interestingly, the reduction of Fe(III) oxides by thiols has not been previously investigated in environmentally relevant conditions, likely due to analytical limitations associated with the detection of thiols and their oxidized products. In this study, a novel electrochemical method was developed to simultaneously determine thiol/disulfide pair concentrations in situ during the reduction of ferrihydrite in batch reactors. First order rate laws with respect to initial thiol concentration were confirmed for Fe(III) oxyhydroxide reduction by four common thiols: cysteine, homocysteine, cysteamine, and glutathione. Zero order was determined for both Fe(III) oxyhydroxide and proton concentration at circumneutral pH. A kinetic model detailing the molecular mechanism of the reaction was optimized with proposed intermediate surface structures. Although metal oxide overall reduction rate constants were inversely proportional to the complexity of the thiol structure, the extent of metal reduction increased with structure complexity, indicating that surface complexes play a significant role in the ability of these thiols to reduce iron. Taken together, these results demonstrate the importance of considering the molecular reaction mechanism at the iron oxide surface when investigating the potential for thiols to act as electron shuttles during dissimilatory iron reduction in natural environments.

Mechanism of porcine liver xanthine oxidoreductase mediated N-oxide reduction of cyadox as revealed by docking and mutagenesis studies.

Directory of Open Access Journals (Sweden)

Chigang Chen

Full Text Available Xanthine oxidoreductase (XOR is a cytoplasmic molybdenum-containing oxidoreductase, catalyzing both endogenous purines and exogenous compounds. It is suggested that XOR in porcine hepatocytes catalyzes the N-oxide reduction of quinoxaline 1,4-di-N-oxides (QdNOs. To elucidate the molecular mechanism underlying this metabolism, the cDNA of porcine XOR was cloned and heterologously expressed in Spodoptera frugiperda insect cells. The bovine XOR, showing sequence identity of 91% to porcine XOR, was employed as template for homology modeling. By docking cyadox, a representative compound of QdNOs, into porcine XOR model, eight amino acid residues, Gly47, Asn352, Ser360, Arg427, Asp430, Asp431, Ser1227 and Lys1230, were located at distances of less than 4Å to cyadox. Site-directed mutagenesis was performed to analyze their catalytic functions. Compared with wild type porcine XOR, G47A, S360P, D431A, S1227A, and K1230A displayed altered kinetic parameters in cyadox reduction, similarly to that in xanthine oxidation, indicating these mutations influenced electron-donating process of xanthine before subsequent electron transfer to cyadox to fulfill the N-oxide reduction. Differently, R427E and D430H, both located in the 424-434 loop, exhibited a much lower K(m and a decreased V(max respectively in cyadox reduction. Arg427 may be related to the substrate binding of porcine XOR to cyadox, and Asp430 is suggested to be involved in the transfer of electron to cyadox. This study initially reveals the possible catalytic mechanism of porcine XOR in cyadox metabolism, providing with novel insights into the structure-function relationship of XOR in the reduction of exogenous di-N-oxides.

Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

Science.gov (United States)

Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

2015-11-01

Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential

Nitric oxide reduction and oxidation on stepped Pt[n(111)x(111)] electrodes

NARCIS (Netherlands)

Beltramo, G.L.; Koper, M.T.M.

2003-01-01

The structure sensitivity of the reduction and oxidation of saturated and subsaturated NO adlayers has been studied on a series of stepped Pt[n(111)×(111)] electrodes by cyclic and stripping voltammetry experiments in sulfuric and perchloric acid solution. In agreement with earlier experimental

Development of metallic uranium recovery technology from uranium oxide by Li reduction and electrorefining

International Nuclear Information System (INIS)

Tokiwai, Moriyasu; Kawabe, Akihiro; Yuda, Ryouichi; Usami, Tsuyoshi; Fujita, Reiko; Nakamura, Hitoshi; Yahata, Hidetsugu

2002-01-01

The purpose of the study is to develop technology for pre-treatment of oxide fuel reprocessing through pyroprocess. In the pre-treatment process, it is necessary to reduce actinide oxide to metallic form. This paper outlines some experimental results of uranium oxide reduction and recovery of refined metallic uranium in electrorefining. Both uranium oxide granules and pellets were used for the experiments. Uranium oxide granules was completely reduced by lithium in several hours at 650degC. Reduced uranium pellets by about 70% provided a simulation of partial reduction for the process flow design. Almost all adherent residues of Li and Li 2 O were successfully washed out with fresh LiCl salt. During electrorefining, metallic uranium deposited on the iron cathode as expected. The recovery efficiencies of metallic uranium from reduced uranium oxide granules and from pellets were about 90% and 50%, respectively. The mass balance data provided the technical bases of Li reduction and refining process flow for design. (author)

Simultaneous reduction and nitrogen functionalization of graphene oxide using lemon for metal-free oxygen reduction reaction

Science.gov (United States)

Begum, Halima; Ahmed, Mohammad Shamsuddin; Cho, Sung; Jeon, Seungwon

2017-12-01

Inspire by the vision of finding a simple and green method for simultaneous reduction and nitrogen (N)-functionalization of graphene oxide (GO), a N-rich reduced graphene oxide (rGO) has been synthesized through a facile and ecofriendly hydrothermal strategy while most of the existing methods are involving with multiple steps and highly toxic reducing agents that are harmful to human health and environment. In this paper, the simultaneous reduction and N-functionalization of GO using as available lemon juice (denoted as Lem-rGO) for metal-free electrocatalysis towards oxygen reduction reaction (ORR) is described. The proposed method is based on the reduction of GO using of the reducing and the N-precursor capability of ascorbic acid and citric acid as well as the nitrogenous compounds, respectively, that containing in lemon juice. The resultant Lem-rGO has higher reduction degree, higher specific surface area and better crystalline nature with N-incorporation than that of well investigated ascorbic acid and citric acid treated rGO. As a result, it shows better ORR electrocatalytic activity in respect to the improved onset potential, electron transfer rate and kinetics than those typical rGO catalysts. Moreover, it shows a significant tolerance to the anodic fuels and durability than the Pt/C during ORR.

In-situ sequential laser transfer and laser reduction of graphene oxide films

Science.gov (United States)

Papazoglou, S.; Petridis, C.; Kymakis, E.; Kennou, S.; Raptis, Y. S.; Chatzandroulis, S.; Zergioti, I.

2018-04-01

Achieving high quality transfer of graphene on selected substrates is a priority in device fabrication, especially where drop-on-demand applications are involved. In this work, we report an in-situ, fast, simple, and one step process that resulted in the reduction, transfer, and fabrication of reduced graphene oxide-based humidity sensors, using picosecond laser pulses. By tuning the laser illumination parameters, we managed to implement the sequential printing and reduction of graphene oxide flakes. The overall process lasted only a few seconds compared to a few hours that our group has previously published. DC current measurements, X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, and Raman Spectroscopy were employed in order to assess the efficiency of our approach. To demonstrate the applicability and the potential of the technique, laser printed reduced graphene oxide humidity sensors with a limit of detection of 1700 ppm are presented. The results demonstrated in this work provide a selective, rapid, and low-cost approach for sequential transfer and photochemical reduction of graphene oxide micro-patterns onto various substrates for flexible electronics and sensor applications.

Restraining Sodium Volatilization in the Ferric Bauxite Direct Reduction System

Directory of Open Access Journals (Sweden)

Wentao Hu

2016-03-01

Full Text Available Direct reduction is an emerging utilization technology of ferric bauxite. However, it requires much more sodium carbonate than ordinary bauxite does. The volatilization is one of the most significant parts of sodium carbonate consumption, as reported in previous studies. Based on the new direct reduction method for utilization of ferric bauxite, this paper has systematically investigated factors including heating temperature, heating time, and sodium carbonate dosage influencing sodium volatilization. For the purpose of reducing sodium volatilization, the Box–Benhken design was employed, and the possibility of separating iron and sodium after direct reduction was also investigated.

Pyro-Electrochemical Reduction of a Mixture of Rare Earth Oxides and NiO in LiCl molten Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun [Department of Chemical Engineering, Chungbuk National University, Cheongju (Korea, Republic of)

2017-06-15

An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

Study on electrolytic reduction with controlled oxygen flow for iron from molten oxide slag containing FeO

Directory of Open Access Journals (Sweden)

Gao Y.M.

2013-01-01

Full Text Available A ZrO2-based solid membrane electrolytic cell with controlled oxygen flow was constructed: graphite rod /[O]Fe+C saturated / ZrO2(MgO/(FeO slag/iron crucible. The feasibility of extraction of iron from molten oxide slag containing FeO at an applied voltage was investigated by means of the electrolytic cell. The effects of some important process factors on the FeO electrolytic reduction with the controlled oxygen flow were discussed. The results show that: solid iron can be extracted from molten oxide slag containing FeO at 1450ºC and an applied potential of 4V. These factors, such as precipitation and growth of solid iron dendrites, change of the cathode active area on the inner wall of the iron crucible and ion diffusion flux in the molten slag may affect the electrochemical reaction rate. The reduction for Fe2+ ions mainly appears on new iron dendrites of the iron crucible cathode, and a very small amount of iron are also formed on the MSZ (2.18% MgO partially stabilized zirconia tube/slag interface due to electronic conductance of MSZ tube. Internal electronic current through MSZ tube may change direction at earlier and later electrolytic reduction stage. It has a role of promoting electrolytic reduction for FeO in the molten slag at the earlier stage, but will lower the current efficiency at the later stage. The final reduction ratio of FeO in the molten slag can achieve 99%. A novel electrolytic method with controlled oxygen flow for iron from the molten oxide slag containing FeO was proposed. The theory of electrolytic reduction with the controlled oxygen flow was developed.

High potential oxidation-reduction titration of absorbance changes induced by pulsed laser and continuous light in chromatophores of photosynthesizing bacteria Rhodospirillum rubrum and Ectothiorhodospira shaposhnikovii

International Nuclear Information System (INIS)

Remennikov, S.M.; Chamorovsky, S.K.; Kononenko, A.A.; Venediktov, P.S.; Rubin, A.B.

1975-01-01

The photoreactions, activated both by pulsed laser and continuous light were studied in the membranes of isolated bacterial chromatophores poised at different oxidation-reduction potentials over a range of +200 mV to +500 mV. In Rhodospirillum rubrum a midpoint potential of oxidation-reduction curves for the laser-induced positive absorbance changes centred around 430 nm and carotenoid red shifts coincides with that for continuous light-induced absorbance changes, bleaching at 865 nm and blue shift at 800 nm, of the photosynthetic reaction centre bacteriochlorophyll. In Ectothiorhodospira shaposhnikovii the photosynthetic reaction centre bacteriochlorophyll, its photooxidation can be seen as light-induced absorbance changes, bleaching at 890 nm, blue shift at 800 nm and broad band appearance near 440 nm, has a midpoint oxidation-reduction potential of +390 mV at pH 7.4. The analysis of the oxidation-reduction titration curves for the high-potential c-type cytochrome absorbance changes induced both by pulsed laser and continuous light allowed to show that at least two haems of this cytochrome with a midpoint potential of +290 mV (pH 7.4), associated with each reaction centre bacteriochlorophyll, can donate electrons to the oxidized pigment directly

Isothermal Oxidation of Magnetite to Hematite in Air and Cyclic Reduction/Oxidation Under Carbon Looping Combustion Conditions

Science.gov (United States)

Simmonds, Tegan; Hayes, Peter C.

2017-12-01

In the carbon looping combustion process the oxygen carrier is regenerated through oxidation in air; this process has been simulated by the oxidation of dense synthetic magnetite for selected temperatures and times. The oxidation of magnetite in air is shown to occur through the formation of dense hematite layers on the particle surface. This dense hematite forms through lath type shear transformations or solid-state diffusion through the product layer. Cyclic reduction in CO-CO2/oxidation in air of hematite single crystals has been carried out under controlled laboratory conditions at 1173 K (900 °C). It has been shown that the initial reduction step is critical to determining the product microstructure, which consists of gas pore dendrites in the magnetite matrix with blocky hematite formed on the pore surfaces. The progressive growth of the magnetite layer with the application of subsequent cycles appears to continue until no original hematite remains, after which physical disintegration of the particles takes place.

Effects of manganese oxide on arsenic reduction and leaching from contaminated floodplain soil

DEFF Research Database (Denmark)

Ehlert, Katrin; Mikutta, Christian; Kretzschmar, Ruben

2016-01-01

Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As.......7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. The reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating...

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li{sub 2}O Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon [Chungbook National University, Chungju (Korea, Republic of); Sohn, Jung Min [Chonbuk National University, Jeonju (Korea, Republic of)

2016-05-15

In this study, the electrochemical reduction of RE{sub 2}O{sub 3} (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li{sub 2}O. The electrochemical reduction behavior of the mixed RE{sub 2}O{sub 3}-NiO oxide has been investigated and the reduction path of RE{sub 2}O{sub 3} has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl{sub 3} in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li{sub 2}O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE{sub 2}O{sub 3} on the produced Ni to form intermetallic RENi{sub 5}. The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd{sub 2}O{sub 3} was successfully converted to the metal in the presence of NiO.

Direct electrocatalytic reduction of coenzyme NAD{sup +} to enzymatically-active 1,4-NADH employing an iridium/ruthenium-oxide electrode

Energy Technology Data Exchange (ETDEWEB)

Ullah, Nehar, E-mail: nehar.ullah@mail.mcgill.ca; Ali, Irshad; Omanovic, Sasha

2015-01-15

A thermally prepared iridium/ruthenium-oxide coating (Ir{sub 0.8}Ru{sub 0.2}-oxide) formed on a titanium substrate was investigated as a possible electrode for direct electrochemical regeneration of enzymatically-active 1,4-NADH from its oxidized form NAD{sup +}, at various electrode potentials, in a batch electrochemical reactor. The coating surface was characterized by ‘cracked mud’ morphology, yielding a high surface roughness. The NADH regeneration results showed that the percentage of enzymatically-active 1,4-NADH present in the product mixture (i.e. recovery) is strongly dependent on the electrode potential, reaching a maximum (88%) at −1.70 V vs. MSE. The relatively high recovery was explained on the basis of availability of adsorbed ‘active’ hydrogen (H{sub ads}) on the Ir/Ru-oxide surface, i.e. on the basis of electrochemical hydrogenation. - Highlights: • Ir{sub 0.8}Ru{sub 0.2}-oxide coating was formed thermally on a Ti substrate. • Electrochemical regeneration of enzymatically-active 1,4-NADH was investigated. • The 1,4-NADH recovery percentage is strongly dependent on the electrode potential. • A highest recovery, 88%, was obtained at −1.70 V vs. MSE. • The NADH regeneration process involved electrochemical hydrogenation.

Tin-oxide-coated single-walled carbon nanotube bundles supporting platinum electrocatalysts for direct ethanol fuel cells

International Nuclear Information System (INIS)

Hsu, Ryan S; Higgins, Drew; Chen Zhongwei

2010-01-01

Novel tin-oxide (SnO 2 )-coated single-walled carbon nanotube (SWNT) bundles supporting platinum (Pt) electrocatalysts for ethanol oxidation were developed for direct ethanol fuel cells. SnO 2 -coated SWNT (SnO 2 -SWNT) bundles were synthesized by a simple chemical-solution route. SnO 2 -SWNT bundles supporting Pt (Pt/SnO 2 -SWNTs) electrocatalysts and SWNT-supported Pt (Pt/SWNT) electrocatalysts were prepared by an ethylene glycol reduction method. The catalysts were physically characterized using TGA, XRD and TEM and electrochemically evaluated through cyclic voltammetry experiments. The Pt/SnO 2 -SWNTs showed greatly enhanced electrocatalytic activity for ethanol oxidation in acid medium, compared to the Pt/SWNT. The optimal SnO 2 loading of Pt/SnO 2 -SWNT catalysts with respect to specific catalytic activity for ethanol oxidation was also investigated.

Tin-oxide-coated single-walled carbon nanotube bundles supporting platinum electrocatalysts for direct ethanol fuel cells.

Science.gov (United States)

Hsu, Ryan S; Higgins, Drew; Chen, Zhongwei

2010-04-23

Novel tin-oxide (SnO(2))-coated single-walled carbon nanotube (SWNT) bundles supporting platinum (Pt) electrocatalysts for ethanol oxidation were developed for direct ethanol fuel cells. SnO(2)-coated SWNT (SnO(2)-SWNT) bundles were synthesized by a simple chemical-solution route. SnO(2)-SWNT bundles supporting Pt (Pt/SnO(2)-SWNTs) electrocatalysts and SWNT-supported Pt (Pt/SWNT) electrocatalysts were prepared by an ethylene glycol reduction method. The catalysts were physically characterized using TGA, XRD and TEM and electrochemically evaluated through cyclic voltammetry experiments. The Pt/SnO(2)-SWNTs showed greatly enhanced electrocatalytic activity for ethanol oxidation in acid medium, compared to the Pt/SWNT. The optimal SnO(2) loading of Pt/SnO(2)-SWNT catalysts with respect to specific catalytic activity for ethanol oxidation was also investigated.

Unusual nonlinear absorption response of graphene oxide in the presence of a reduction process

International Nuclear Information System (INIS)

Karimzadeh, Rouhollah; Arandian, Alireza

2015-01-01

The nonlinear absorption responses of graphene, graphene oxide and reduced graphene oxide are investigated using the Z-scan technique and laser beams at 405, 532 and 635 nm in a continuous wave regime. Results show that graphene, graphene oxide and reduced graphene oxide do not show any open Z-scan signals at wavelengths of 532 and 635 nm. At the same time, fresh graphene oxide suspension is found to exhibit a nonlinear absorption process in the case of a laser light at 405 nm. Moreover, it can be observed that the reduction of graphene oxide by 405 nm laser irradiation decreases its nonlinear absorption value significantly. These findings highlight the important role of the reduction process on the nonlinear absorption performance of graphene oxide. (letter)

Evidence for Single Metal Two Electron Oxidative Addition and Reductive Elimination at Uranium

OpenAIRE

Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; Mcinnes, Eric; Tuna, Floriana; Wooles, Ashley; Maron, Laurent; Liddle, Stephen

2017-01-01

Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here, we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido compl...

Effect of hydrogen peroxide and camellia sinensis extract on reduction of oxygen level in graphene oxide

Science.gov (United States)

Celina Selvakumari, J.; Dhanalakshmi, J.; Pathinettam Padiyan, D.

2016-10-01

The intention of this work is to reduce the oxygen level in graphene oxide. The reduction process was initiated while preparing graphene oxide using modified Hummer’s method. In this new method, increase in hydrogen peroxide concentration during the preparation process results in the oxygen content reduction. Adding green tea (camellia sinensis) extract with increased hydrogen peroxide results in further reduction of oxygen content and changed the graphene oxide to reduced graphene oxide. The structural and optical properties of the new found reduced graphene oxide was analysed using XRD, FTIR, TEM, Raman and UV-vis spectra. The overall observation reflects that the sp3 carbon network of graphene oxide changed into sp2 carbon lattice of graphene which is very handful in supercapacitor and biosensor fields.

Comparison of direct and indirect plasma oxidation of NO combined with oxidation by catalyst

DEFF Research Database (Denmark)

Jogi, Indrek; Stamate, Eugen; Irimiea, Cornelia

2015-01-01

of the DBD reactor decreased the long-term efficiency of direct plasma oxidation. At the same time, the efficiency of indirect oxidation increased at elevated reactor temperatures. Additional experiments were carried out to investigate the improvement of indirect oxidation by the introduction of catalyst...

Cell oxidation-reduction imbalance after modulated radiofrequency radiation.

Science.gov (United States)

Marjanovic, Ana Marija; Pavicic, Ivan; Trosic, Ivancica

2015-01-01

Aim of this study was to evaluate an influence of modulated radiofrequency field (RF) of 1800 MHz, strength of 30 V/m on oxidation-reduction processes within the cell. The assigned RF field was generated within Gigahertz Transversal Electromagnetic Mode cell equipped by signal generator, modulator, and amplifier. Cell line V79, was irradiated for 10, 30, and 60 min, specific absorption rate was calculated to be 1.6 W/kg. Cell metabolic activity and viability was determined by MTT assay. In order to define total protein content, colorimetric method was used. Concentration of oxidised proteins was evaluated by enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) marked with fluorescent probe 2',7'-dichlorofluorescin diacetate were measured by means of plate reader device. In comparison with control cell samples, metabolic activity and total protein content in exposed cells did not differ significantly. Concentrations of carbonyl derivates, a product of protein oxidation, insignificantly but continuously increase with duration of exposure. In exposed samples, ROS level significantly (p < 0.05) increased after 10 min of exposure. Decrease in ROS level was observed after 30-min treatment indicating antioxidant defence mechanism activation. In conclusion, under the given laboratory conditions, modulated RF radiation might cause impairment in cell oxidation-reduction equilibrium within the growing cells.

Evidence against a direct role for oxidative stress in cadmium-induced axial malformation in the chick embryo

International Nuclear Information System (INIS)

Thompson, Jennifer; Doi, Takashi; Power, Eoin; Balasubramanian, Ishwarya; Puri, Prem; Bannigan, John

2010-01-01

Cadmium (Cd) is a powerful inducer of oxidative stress. It also causes ventral body wall defects in chick embryos treated at Hamburger-Hamilton stages 16-17. By measuring malondialdehyde levels (TBARS method) and cotreating with antioxidants (tempol, ascorbate, and N-acetylcysteine), we sought to determine if oxidative stress were directly related to teratogenesis. We also investigated the expression of mRNAs for antioxidant enzymes superoxide dismutase (SOD) -1 and -2, catalase (CAT), and glutathione peroxidase (GPx). RT-PCR showed reductions in SOD-1, SOD-2, and CAT 1 hour after treatment with Cd. MDA levels increased 4 hours after Cd, and remained elevated 24 hours after treatment. Of the antioxidants, only N-acetylcysteine reduced MDA levels to control values. Nonetheless, no antioxidant could reduce embryo lethality or malformation rates. Furthermore, MDA levels 24 hours after treatment were identical in malformed and normal embryos exposed to Cd. Hence, we conclude that oxidative stress may not have a direct role in Cd teratogenesis.

Adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface: A spectroscopic study

Science.gov (United States)

Lucilha, Adriana Campano; Bonancêa, Carlos Eduardo; Barreto, Wagner José; Takashima, Keiko

2010-01-01

The adsorption of the diazo dye Direct Red 23 onto a zinc oxide surface at 30 °C in the dark was investigated. The color reduction was monitored by spectrophotometry at 503 nm. The FTIR and Raman spectra of the Direct Red 23 adsorption as a function of ZnO concentration were registered. From the PM3 semi-empirical calculations of the atomic charge density and dipole moment of the Direct Red 23 molecule, it was demonstrated that the azo dye molecule may be adsorbed onto the ZnO surface through molecule geometry modifications, enhancing the interfacial area causing a variation in the bonding frequencies.

Nanoscale reduction of graphene oxide thin films and its characterization.

Science.gov (United States)

Lorenzoni, M; Giugni, A; Di Fabrizio, E; Pérez-Murano, Francesc; Mescola, A; Torre, B

2015-07-17

In this paper, we report on a method to reduce thin films of graphene oxide (GO) to a spatial resolution better than 100 nm over several tens of micrometers by means of an electrochemical scanning probe based lithography. In situ tip-current measurements show that an edged drop in electrical resistance characterizes the reduced areas, and that the reduction process is, to a good approximation, proportional to the applied bias between the onset voltage and the saturation thresholds. An atomic force microscope (AFM) quantifies the drop of the surface height for the reduced profile due to the loss of oxygen. Complementarily, lateral force microscopy reveals a homogeneous friction coefficient of the reduced regions that is remarkably lower than that of native graphene oxide, confirming a chemical change in the patterned region. Micro Raman spectroscopy, which provides access to insights into the chemical process, allows one to quantify the restoration and de-oxidation of the graphitic network driven by the electrochemical reduction and to determine characteristic length scales. It also confirms the homogeneity of the process over wide areas. The results shown were obtained from accurate analysis of the shift, intensity and width of Raman peaks for the main vibrational bands of GO and reduced graphene oxide (rGO) mapped over large areas. Concerning multilayered GO thin films obtained by drop-casting we have demonstrated an unprecedented lateral resolution in ambient conditions as well as an improved control, characterization and understanding of the reduction process occurring in GO randomly folded multilayers, useful for large-scale processing of graphene-based material.

Oxidation-reduction conditions of the plants with reference to their gas resistance

Energy Technology Data Exchange (ETDEWEB)

Krasinskii, N P

1944-01-01

The object of this work was to see if there is any relation between the oxidation-reduction conditions existing in a plant, and its ability to grow successfully in the cities where air contains H/sub 2/S. Oxidation-reduction potential, capacity for its water-soluble and insoluble matter to be oxidized with KMnO/sub 4/ before and after treatment with H/sub 2/S, and finally the effect of the age of the plant were determined for different spp. of several common families of plants. In the majority of the families it was found that in various spp. of the same family these characteristics vary within a narrow and different range. Oxidation with KMnO/sub 4/ of the water-insoluble matter was found to be the best criterion of the sensitivity of a plant to H/sub 2/S.

High-rate reduction of copper oxide using atmospheric-pressure inductively coupled plasma microjets

International Nuclear Information System (INIS)

Tajima, Satomi; Tsuchiya, Shouichi; Matsumori, Masashi; Nakatsuka, Shigeki; Ichiki, Takanori

2011-01-01

Reduction of copper oxide was performed using an atmospheric-pressure inductively coupled plasma (AP-ICP) microjet while varying the input power P between 15 and 50 W. Cuprous oxide (Cu 2 O) and cupric oxide (CuO) were formed on the sputtered Cu surface by thermal annealing. Dynamic behavior of the microplasma jet, optical emission from H atoms, the substrate temperature, chemical bonding states of the treated surface, and the thickness of the reduced Cu layer were measured to study the fundamental reduction process. Surface composition and the thickness of the reduced Cu layer changed significantly with P. Rapid reduction of CuO and Cu 2 O was achieved at a rate of 493 nm/min at P = 50 W since high-density H atoms were produced by the AP-ICP microjet.

High-rate reduction of copper oxide using atmospheric-pressure inductively coupled plasma microjets

Energy Technology Data Exchange (ETDEWEB)

Tajima, Satomi; Tsuchiya, Shouichi [Department of Bioengineering, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-8656 (Japan); Matsumori, Masashi; Nakatsuka, Shigeki [Panasonic Factory Solutions Co., Ltd., 2-7 Matsuba-cho, Kadoma-city, Osaka, 571-8502 (Japan); Ichiki, Takanori, E-mail: ichiki@sogo.t.u-tokyo.ac.jp [Department of Bioengineering, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-8656 (Japan); Institute of Engineering Innovation, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 (Japan)

2011-08-01

Reduction of copper oxide was performed using an atmospheric-pressure inductively coupled plasma (AP-ICP) microjet while varying the input power P between 15 and 50 W. Cuprous oxide (Cu{sub 2}O) and cupric oxide (CuO) were formed on the sputtered Cu surface by thermal annealing. Dynamic behavior of the microplasma jet, optical emission from H atoms, the substrate temperature, chemical bonding states of the treated surface, and the thickness of the reduced Cu layer were measured to study the fundamental reduction process. Surface composition and the thickness of the reduced Cu layer changed significantly with P. Rapid reduction of CuO and Cu{sub 2}O was achieved at a rate of 493 nm/min at P = 50 W since high-density H atoms were produced by the AP-ICP microjet.

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy.

Science.gov (United States)

Maher, Robert C; Shearing, Paul R; Brightman, Edward; Brett, Dan J L; Brandon, Nigel P; Cohen, Lesley F

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

Reduction of nitric oxide catalyzed by hydroxylamine oxidoreductase from an anammox bacterium.

Science.gov (United States)

Irisa, Tatsuya; Hira, Daisuke; Furukawa, Kenji; Fujii, Takao

2014-12-01

The hydroxylamine oxidoreductase (HAO) from the anammox bacterium, Candidatus Kuenenia stuttgartiensis has been reported to catalyze the oxidation of hydroxylamine (NH2OH) to nitric oxide (NO) by using bovine cytochrome c as an oxidant. In contrast, we investigated whether the HAO from anammox bacterium strain KSU-1 could catalyze the reduction of NO with reduced benzyl viologen (BVred) and the NO-releasing reagent, NOC 7. The reduction proceeded, resulting in the formation of NH2OH as a product. The oxidation rate of BVred was proportional to the concentration of BVred itself for a short period in each experiment, a situation that was termed quasi-steady state. The analyses of the states at various concentrations of HAO allowed us to determine the rate constant for the catalytic reaction, (2.85 ± 0.19) × 10(5) M(-1) s(-1), governing NO reduction by BVred and HAO, which was comparable to that reported for the HAO from the ammonium oxidizer, Nitrosomonas with reduced methyl viologen. These results suggest that the anammox HAO functions to adjust anammox by inter-conversion of NO and NH2OH depending on the redox potential of the physiological electron transfer protein in anammox bacteria. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Descriptors and Thermodynamic Limitations of Electrocatalytic Carbon Dioxide Reduction on Rutile Oxide Surfaces

DEFF Research Database (Denmark)

Bhowmik, Arghya; Vegge, Tejs; Hansen, Heine Anton

2016-01-01

A detailed understanding of the electrochemical reduction of CO2 into liquid fuels on rutile metal oxide surfaces is developed by using DFT calculations. We consider oxide overlayer structures on RuO2(1 1 0) surfaces as model catalysts to elucidate the trends and limitations in the CO2 reduction...... and it defines the left leg of the activity volcano for CO2RR. HCOOH* is a key intermediate for products formed through further reduction, for example, methanediol, methanol, and methane. The surfaces that do not bind HCOOH* are selective towards formic acid (HCOOH) production, but hydrogen evolution limits...

Reduction of titanium dioxide and other metal oxides by electro-deoxidation

International Nuclear Information System (INIS)

Fray, Derek J.

2003-01-01

Titanium dioxide and other reactive metal compounds are reduced by more reactive metals to form pure metals. These, are expensive and time consuming processes which makes these metals very expensive. Many of these metals and alloys have excellent properties, high strength, low density and very good corrosion resistance, but their use is restricted by its high cost. Electro-deoxidation is a very simple technique where an oxide is made cathodic in a fused salt of an alkaline earth chloride. By applying a voltage, below the decomposition potential of the salt, it has been found that the cathodic reaction is the ionization of oxygen from the oxide to leave a pure metal, rather than the reduction of the ion alkaline earth ion element. Laboratory experiments have shown that this approach can be applied to the reduction of a large number of metal oxides. Another important observation is that when a mixture of oxides is used as the cathode, the product is an alloy of uniform composition. This is a considerable advantage for many alloys that are difficult to prepare using conventional technology. (Original)

Revisiting the effects of organic solvents on the thermal reduction of graphite oxide

International Nuclear Information System (INIS)

Barroso-Bujans, Fabienne; Fierro, José Luis G.; Alegría, Angel; Colmenero, Juan

2011-01-01

Highlights: ► Retention of organic solvent on graphite oxide interlayer space. ► Decreasing exfoliation temperature. ► Close link between structure and thermal behavior of solvent treated graphite oxide. ► Restacking inhibition of thermally reduced graphite oxide sheets. ► Changes in kinetic mechanisms of thermal reduction. - Abstract: Treatment of graphite oxide (GO) with organic solvents via sorption from either liquid or gas phase, and subsequent desorption, induces profound changes in the layered GO structure: loss of stacking order, retention of trace amounts of solvents and decreasing decomposition temperature. This study presents new evidences of the effect of organic solvents on the thermal reduction of GO by means of thermogravimetric analysis, X-ray diffraction and X-ray photoelectron spectroscopy. The results reveal a relative higher decrease of the oxygen amounts in solvent-treated GO as compared to untreated GO and the restacking inhibition of the thermally reduced GO sheets upon slow heating. The kinetic experiments evidence changes occurring in the reduction mechanisms of the solvent-treated GO, which support the close link between GO structure and thermal properties.

Use of ion conductors in the pyrochemical reduction of oxides

International Nuclear Information System (INIS)

Miller, W.E.; Tomczuk, Z.

1994-01-01

An electrochemical process and electrochemical cell for reducing a metal oxide are provided. First the oxide is separated as oxygen gas using, for example, a ZrO 2 oxygen ion conductor anode and the metal ions from the reduction salt are reduced and deposited on an ion conductor cathode, for example, sodium ion reduced on a β-alumina sodium ion conductor cathode. The generation of and separation of oxygen gas avoids the problem with chemical back reaction of oxygen with active metals in the cell. The method also is characterized by a sequence of two steps where an inert cathode electrode is inserted into the electrochemical cell in the second step and the metallic component in the ion conductor is then used as the anode to cause electrochemical reduction of the metal ions formed in the first step from the metal oxide where oxygen gas formed at the anode. The use of ion conductors serves to isolate the active components from chemically reacting with certain chemicals in the cell. While applicable to a variety of metal oxides, the invention has special importance for reducing CaO to Ca o used for reducing UO 2 and PuO 2 to U and Pu. 2 figures

Pathogenesis of Chronic Hyperglycemia: From Reductive Stress to Oxidative Stress

Directory of Open Access Journals (Sweden)

Liang-Jun Yan

2014-01-01

Full Text Available Chronic overnutrition creates chronic hyperglycemia that can gradually induce insulin resistance and insulin secretion impairment. These disorders, if not intervened, will eventually be followed by appearance of frank diabetes. The mechanisms of this chronic pathogenic process are complex but have been suggested to involve production of reactive oxygen species (ROS and oxidative stress. In this review, I highlight evidence that reductive stress imposed by overflux of NADH through the mitochondrial electron transport chain is the source of oxidative stress, which is based on establishments that more NADH recycling by mitochondrial complex I leads to more electron leakage and thus more ROS production. The elevated levels of both NADH and ROS can inhibit and inactivate glyceraldehyde 3-phosphate dehydrogenase (GAPDH, respectively, resulting in blockage of the glycolytic pathway and accumulation of glycerol 3-phospate and its prior metabolites along the pathway. This accumulation then initiates all those alternative glucose metabolic pathways such as the polyol pathway and the advanced glycation pathways that otherwise are minor and insignificant under euglycemic conditions. Importantly, all these alternative pathways lead to ROS production, thus aggravating cellular oxidative stress. Therefore, reductive stress followed by oxidative stress comprises a major mechanism of hyperglycemia-induced metabolic syndrome.

Nanoscale reduction of graphene oxide thin films and its characterization

KAUST Repository

Lorenzoni, M.

2015-06-29

In this paper, we report on a method to reduce thin films of graphene oxide (GO) to a spatial resolution better than 100 nm over several tens of micrometers by means of an electrochemical scanning probe based lithography. In situ tip-current measurements show that an edged drop in electrical resistance characterizes the reduced areas, and that the reduction process is, to a good approximation, proportional to the applied bias between the onset voltage and the saturation thresholds. An atomic force microscope (AFM) quantifies the drop of the surface height for the reduced profile due to the loss of oxygen. Complementarily, lateral force microscopy reveals a homogeneous friction coefficient of the reduced regions that is remarkably lower than that of native graphene oxide, confirming a chemical change in the patterned region. Micro Raman spectroscopy, which provides access to insights into the chemical process, allows one to quantify the restoration and de-oxidation of the graphitic network driven by the electrochemical reduction and to determine characteristic length scales. It also confirms the homogeneity of the process over wide areas. The results shown were obtained from accurate analysis of the shift, intensity and width of Raman peaks for the main vibrational bands of GO and reduced graphene oxide (rGO) mapped over large areas. Concerning multilayered GO thin films obtained by drop-casting we have demonstrated an unprecedented lateral resolution in ambient conditions as well as an improved control, characterization and understanding of the reduction process occurring in GO randomly folded multilayers, useful for large-scale processing of graphene-based material. © 2015 IOP Publishing Ltd.

High Efficient Reduction of Graphene Oxide via Nascent Hydrogen at Room Temperature

Directory of Open Access Journals (Sweden)

Qiqi Zhuo

2018-02-01

Full Text Available To develop a green and efficient method to synthesize graphene in relative milder conditions is prerequisite for graphene applications. A chemical reducing method has been developed to high efficiently reduce graphene oxide (GO using Fe2O3 and NH3BH3 as catalyst and reductants, respectively. During the process, environmental and strong reductive nascent hydrogen were generated surrounding the surface of GO sheets by catalyst hydrolysis reaction of NH3BH3 and were used for reduction of GO. The reduction process was studied by ultraviolet absorption spectroscopy, Raman spectroscopy, and Fourier transform infrared spectrum. The structure and morphology of the reduced GO were characterized with scanning electron microscopy and transmission electron microscopy. Compared to metal (Mg/Fe/Zn/Al particles and acid system which also use nascent hydrogen to reduce GO, this method exhibited higher reduction efficiency (43.6%. Also the reduction was carried out at room temperature condition, which is environmentally friendly. As a supercapacitor electrode, the reversible capacity of reduced graphene oxide was 113.8 F g−1 at 1 A g−1 and the capacitance retention still remained at 90% after 200 cycles. This approach provides a new method to reduce GO with high reduction efficiency by green reductant.

Thioredoxin-1 Negatively Modulates ADAM17 Activity Through Direct Binding and Indirect Reductive Activity.

Science.gov (United States)

Granato, Daniela C; E Costa, Rute A P; Kawahara, Rebeca; Yokoo, Sami; Aragão, Annelize Z; Domingues, Romênia R; Pauletti, Bianca A; Honorato, Rodrigo V; Fattori, Juliana; Figueira, Ana Carolina M; Oliveira, Paulo S L; Consonni, Silvio R; Fernandes, Denise; Laurindo, Francisco; Hansen, Hinrich P; Paes Leme, Adriana F

2018-02-27

A disintegrin and metalloprotease 17 (ADAM17) modulates signaling events by releasing surface protein ectodomains such as TNFa and the EGFR-ligands. We have previously characterized cytoplasmic thioredoxin-1 (Trx-1) as a partner of ADAM17 cytoplasmic domain. Still, the mechanism of ADAM17 regulation by Trx-1 is unknown, and it has become of paramount importance to assess the degree of influence that Trx-1 has on metalloproteinase ADAM17. Combining discovery and targeted proteomic approaches, we uncovered that Trx-1 negatively regulates ADAM17 by direct and indirect effect. We performed cell-based assays with synthetic peptides and site-directed mutagenesis, and we demonstrated that the interaction interface of Trx-1 and ADAM17 is important for the negative regulation of ADAM17 activity. However, both Trx-1 K72A and catalytic site mutant Trx-1 C32/35S rescued ADAM17 activity, although the interaction with Trx-1 C32/35S was unaffected, suggesting an indirect effect of Trx-1. We confirmed that the Trx-1 C32/35S mutant showed diminished reductive capacity, explaining this indirect effect on increasing ADAM17 activity through oxidant levels. Interestingly, Trx-1 K72A mutant showed similar oxidant levels to Trx-1 C32/35S , even though its catalytic site was preserved. We further demonstrated that the general reactive oxygen species inhibitor, Nacetylcysteine (NAC), maintained the regulation of ADAM17 dependent of Trx-1 reductase activity levels; whereas the electron transport chain modulator, rotenone, abolished Trx-1 effect on ADAM17 activity. We show for the first time that the mechanism of ADAM17 regulation, Trx-1 dependent, can be by direct interaction and indirect effect, bringing new insights into the cross-talk between isomerases and mammalian metalloproteinases. This unexpected Trx-1 K72A behavior was due to more dimer formation and, consequently, the reduction of its Trx-1 reductase activity, evaluated through dimer verification, by gel filtration and mass

Reduced graphene oxide supported gold nanoparticles for electrocatalytic reduction of carbon dioxide

Science.gov (United States)

Saquib, Mohammad; Halder, Aditi

2018-02-01

Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst "reduced graphene oxide supported gold nanoparticles" for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.

Lithium-Vanadium bronzes as model catalysts for the selective reduction of nitric oxide

NARCIS (Netherlands)

Bosch, H.; Bongers, Annemie; Enoch, Gert; Snel, Ruud; Ross, Julian R.H.

1989-01-01

The effect of alkali metals on the selective reduction of nitric oxide with ammonia has been studied on bulk iron oxide and bulk vanadium oxide. The influence of additions of LiOH, NaOH and KOH on the activity was screened by pulse experiments carried out in the absence of gaseous oxygen; FTIR

Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

Science.gov (United States)

Herbell, T. P.

1976-01-01

Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

Synthesis of reduced graphene oxide (rGO) via chemical reduction

International Nuclear Information System (INIS)

Thakur, Alpana; Rangra, V. S.; Kumar, Sunil

2015-01-01

Natural flake Graphite was used as the starting material for the graphene synthesis. In the first step flake graphite was treated with oxidizing agents under vigorous conditions to obtain graphite oxide. Layered graphite oxide decorated with oxygen has large inter-layer distance leading easy exfoliation into single sheets by ultrasonication giving graphene oxide. In the last step exfoliated graphene oxide sheets were reduced slowly with the help of reducing agent to obtain fine powder which is labeled as reduced graphene oxide (rGO). This rGO was further characterized by X-Ray Diffraction (XRD), Scanning Tunneling Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy techniques. XRD pattern shows peaks corresponding to (002) graphitic lattice planes indicating the formation of network of sp 2 like carbon structure. SEM images show the ultrathin, wrinkled, paper-like morphology of graphene sheets. IR study shows that the graphite has been oxidized to graphite oxide with the presence of various absorption bands confirming the presence of oxidizing groups. The FTIR spectrum of rGO shows no sharp peaks confirming the efficient reduction of rGO. The Raman spectrum shows disorder in the graphene sheets

Reduction of uranium and plutonium oxides by aluminum. Application to the recycling of plutonium

International Nuclear Information System (INIS)

Gallay, J.

1968-01-01

A process for treating plutonium oxide calcined at high temperatures (1000 to 2000 deg. C) with a view to recovering the metal consists in the reduction of this oxide dissolved in a mixture of aluminium, sodium and calcium fluorides by aluminium at about 1180 deg. C. The first part of the report presents the results of reduction tests carried out on the uranium oxides UO 2 and U 3 O 8 ; these are in agreement with the thermodynamic calculations of the exchange reaction at equilibrium. The second part describes the application of this method to plutonium oxides. The Pu-Al alloy obtained (60 per cent Pu) is then recycled in an aqueous medium. (author) [fr

Electrochemical processing of spent nuclear fuels: An overview of oxide reduction in pyroprocessing technology

Directory of Open Access Journals (Sweden)

Eun-Young Choi

2015-12-01

Full Text Available The electrochemical reduction process has been used to reduce spent oxide fuel to a metallic form using pyroprocessing technology for a closed fuel cycle in combination with a metal-fuel fast reactor. In the electrochemical reduction process, oxides fuels are loaded at the cathode basket in molten Li2O–LiCl salt and electrochemically reduced to the metal form. Various approaches based on thermodynamic calculations and experimental studies have been used to understand the electrode reaction and efficiently treat spent fuels. The factors that affect the speed of the electrochemical reduction have been determined to optimize the process and scale-up the electrolysis cell. In addition, demonstrations of the integrated series of processes (electrorefining and salt distillation with the electrochemical reduction have been conducted to realize the oxide fuel cycle. This overview provides insight into the current status of and issues related to the electrochemical processing of spent nuclear fuels.

The effect of ammonia upon the electrocatalysis of hydrogen oxidation and oxygen reduction on polycrystalline platinum

DEFF Research Database (Denmark)

Verdaguer Casadevall, Arnau; Hernandez-Fernandez, Patricia; Stephens, Ifan E.L.

2012-01-01

The influence of ammonium ions on the catalysis of hydrogen oxidation and oxygen reduction is studied by means of rotating ring-disk electrode experiments on polycrystalline platinum in perchloric acid. While ammonium does not affect the hydrogen oxidation reaction, the oxygen reduction reaction...

Evidence for single metal two electron oxidative addition and reductive elimination at uranium.

Science.gov (United States)

Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; McInnes, Eric J L; Tuna, Floriana; Wooles, Ashley J; Maron, Laurent; Liddle, Stephen T

2017-12-01

Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition. Thermolysis of this complex promotes extrusion of azobenzene, where H-/D-isotopic labelling finds no isotopomer cross-over and the non-reactivity of a nitrene-trap suggests that nitrenes are not generated and thus a reductive elimination has occurred. Though not optimally balanced in this case, this work presents evidence that classical d-block redox chemistry can be performed reversibly by f-block metals, and that uranium can thus mimic elementary transition metal reactivity, which may lead to the discovery of new f-block catalysis.

Reduction and re-oxidation of Cu/Al{sub 2}O{sub 3} catalysts investigated with quick-scanning XANES and EXAFS

Energy Technology Data Exchange (ETDEWEB)

Stoetzel, J; Luetzenkirchen-Hecht, D; Frahm, R [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany); Kimmerle, B; Baiker, A [Department of Chemistry and Applied Biosciences, ETH Zuerich, CH-8093 Zuerich (Switzerland); Nachtegaal, M [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Beier, M J; Grunwaldt, J-D, E-mail: j.stoetzel@uni-wuppertal.d, E-mail: jdg@kt.dtu.d [Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby (Denmark)

2009-11-15

In the present study the structure of copper catalysts on alumina support were investigated in situ and time resolved during reduction and re-oxidation at different temperatures with the quick-scanning EXAFS (QEXAFS) technique. Different impregnation times (2 min and 90 min) were chosen for the preparation which resulted in different copper species that show a strong variation in the reduction/re-oxidation behaviour. These dynamic changes as well as possible intermediate phases during the gas atmospheres changes were followed with up to 20 EXAFS spectra per second at the copper K-edge covering an energy range of 450 eV. The high time resolution provided new insights into the dynamics of the catalysts e.g. revealing Cu(I) as intermediate state during re-oxidation. Latest advances in the data acquisition hardware are leading to an improved data quality of spectra collected at the SuperXAS beamline. Thus, not only accurate analysis of the catalysts via XANES but also by EXAFS was possible. This is also due to the recent upgrade to monitor the Bragg angle directly with an encoder during the experiments.

In Situ Spectroscopic Analysis of the Carbothermal Reduction Process of Iron Oxides during Microwave Irradiation

Directory of Open Access Journals (Sweden)

Jun Fukushima

2018-01-01

Full Text Available The effects of microwave plasma induction and reduction on the promotion of the carbothermal reduction of iron oxides (α-Fe2O3, γ-Fe2O3, and Fe3O4 are investigated using in situ emission spectroscopy measurements during 2.45 GHz microwave processing, and the plasma discharge (such as CN and N2 is measured during microwave E-field irradiation. It is shown that CN gas or excited CN molecules contribute to the iron oxide reduction reactions, as well as to the thermal reduction. On the other hand, no plasma is generated during microwave H-field irradiation, resulting in thermal reduction. Magnetite strongly interacts with the microwave H-field, and the reduction reaction is clearly promoted by microwave H-field irradiation, as well as thermal reduction reaction.

Are high rates of sulphate reduction associated with anaerobic oxidation of methane

Energy Technology Data Exchange (ETDEWEB)

Devol, A H; Ahmed, S I

1981-01-01

Classical models of sulphur diagenesis in marine sediments are based on the assumption that the rate of sulphate reduction is first order with respect to oxidizable particulate organic carbon (POC). This assumption requires that oxidizable POC, sulphate concentration and the sulphate reduction rate be highest at the top of the sulphate reduction zone and decrease exponentially with increasing sediment depth. However, to explain recent observations of concave upwards methane distributions, the anaerobic consumption of methane has been proposed. Furthermore, it has been proposed that this consumption takes place near the bottom of the sulphate reducing zone where sulphate concentrations are low. Thus, if sulphate reducing bacteria are associated with the anaerobic oxidation of methane, a peak in sulphate reduction rate might be expected in this deep consumption zone. The importance of the process in sedimentary sulphur diagenesis is indicated by calculations estimating that 30 to 75% of the downward sulphate flux at depth may be consumed by methane oxidation within this zone. We present here profiles of sulphate reduction rate in anoxic sediments that show distinct local maxima at the depth where the anaerobic oxidation of methane would be expected. Our measurements were made during July and August 1978 in Saanich Inlet, an anoxic fjord located on the south-east of Vancouver Island, British Columbia. The inlet has a shallow sill (approx 70 m) which restricts circulation of the deeper water (maximum depth 225 m) inside the basin to the extent that for about 8 months of the year the bottom waters contain hydrogen sulphide, the inlet is an ideal location for studying sedimentary sulphate reduction because reactions with oxygen and the effects of burrowing organisms can be neglected.

Dissimilatory oxidation and reduction of elemental sulfur in thermophilic archaea.

Science.gov (United States)

Kletzin, Arnulf; Urich, Tim; Müller, Fabian; Bandeiras, Tiago M; Gomes, Cláudio M

2004-02-01

The oxidation and reduction of elemental sulfur and reduced inorganic sulfur species are some of the most important energy-yielding reactions for microorganisms living in volcanic hot springs, solfataras, and submarine hydrothermal vents, including both heterotrophic, mixotrophic, and chemolithoautotrophic, carbon dioxide-fixing species. Elemental sulfur is the electron donor in aerobic archaea like Acidianus and Sulfolobus. It is oxidized via sulfite and thiosulfate in a pathway involving both soluble and membrane-bound enzymes. This pathway was recently found to be coupled to the aerobic respiratory chain, eliciting a link between sulfur oxidation and oxygen reduction at the level of the respiratory heme copper oxidase. In contrast, elemental sulfur is the electron acceptor in a short electron transport chain consisting of a membrane-bound hydrogenase and a sulfur reductase in (facultatively) anaerobic chemolithotrophic archaea Acidianus and Pyrodictium species. It is also the electron acceptor in organoheterotrophic anaerobic species like Pyrococcus and Thermococcus, however, an electron transport chain has not been described as yet. The current knowledge on the composition and properties of the aerobic and anaerobic pathways of dissimilatory elemental sulfur metabolism in thermophilic archaea is summarized in this contribution.

Generalized kinetic model of reduction of molecular oxidant by metal containing redox

International Nuclear Information System (INIS)

Kravchenko, T.A.

1986-01-01

Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.

Effects of Muscle-Specific Oxidative Stress on Cytochrome c Release and Oxidation-Reduction Potential Properties.

Science.gov (United States)

Ke, Yiling; Mitacek, Rachel M; Abraham, Anupam; Mafi, Gretchen G; VanOverbeke, Deborah L; DeSilva, Udaya; Ramanathan, Ranjith

2017-09-06

Mitochondria play a significant role in beef color. However, the role of oxidative stress in cytochrome c release and mitochondrial degradation is not clear. The objective was to determine the effects of display time on cytochrome c content and oxidation-reduction potential (ORP) of beef longissimus lumborum (LL) and psoas major (PM) muscles. PM discolored by day 3 compared with LL. On day 0, mitochondrial content and mitochondrial oxygen consumption were greater in PM than LL. However, mitochondrial content and oxygen consumption were lower (P stress can affect cytochrome c release and ORP changes.

EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

Directory of Open Access Journals (Sweden)

B. JOTHI THIRUMAL

2015-11-01

Full Text Available This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performance, and emissions are studied, and the dosing level of the additive is optimized. Cerium oxide acts as an oxygen-donating catalyst and provides oxygen for the oxidation of CO during combustion. The active energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall which results in reduction in HC emission by 56.5%. Furthermore, a low-cost metal oxide coated SCR (selective catalyst reduction, using urea as a reducing agent, along with different types of CC (catalytic converter, has been implemented in the exhaust pipe to reduce NOx. It was observed that a reduction in NOx emission is 50–60%. The tests revealed that cerium oxide nanoparticles can be used as an additive in diesel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

Study on emission characteristics and reduction strategy of nitrous oxide during wastewater treatment by different processes.

Science.gov (United States)

Sun, Shichang; Bao, Zhiyuan; Sun, Dezhi

2015-03-01

Given the inexorable increase in global wastewater treatment, increasing amounts of nitrous oxide are expected to be emitted from wastewater treatment plants and released to the atmosphere. It has become imperative to study the emission and control of nitrous oxide in the various wastewater treatment processes currently in use. In the present investigation, the emission characteristics and the factors affecting the release of nitrous oxide were studied via full- and pilot-scale experiments in anoxic-oxic, sequencing batch reactor and oxidation ditch processes. We propose an optimal treatment process and relative strategy for nitrous oxide reduction. Our results show that both the bio-nitrifying and bio-denitrifying treatment units in wastewater treatment plants are the predominant sites for nitrous oxide production in each process, while the aerated treatment units are the critical sources for nitrous oxide emission. Compared with the emission of nitrous oxide from the anoxic-oxic (1.37% of N-influent) and sequencing batch reactor (2.69% of N-influent) processes, much less nitrous oxide (0.25% of N-influent) is emitted from the oxidation ditch process, which we determined as the optimal wastewater treatment process for nitrous oxide reduction, given the current technologies. Nitrous oxide emissions differed with various operating parameters. Controlling the dissolved oxygen concentration at a proper level during nitrification and denitrification and enhancing the utilization rate of organic carbon in the influent for denitrification are the two critical methods for nitrous oxide reduction in the various processes considered.

A new green approach for the reduction of graphene oxide ...

Indian Academy of Sciences (India)

2.2 Preparation of GO. GO was prepared by oxidizing the graphite powder in a mix- ... measured using a Diamond TG/DTA analyzer (Perkin Elmer. Instruments). ... domains during the reduction of GO.23 This change of ID/IG value is in good ...

Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents

NARCIS (Netherlands)

Mutti, Francesco G.; Orthaber, Andreas; Schrittwieser, Joerg H.; Vries, Johannes G. de; Pietschnig, Rudolf; Kroutil, Wolfgang

2010-01-01

An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to

Oxidation of a Dimethoxyhydroquinone by Ferrihydrite and Goethite Nanoparticles: Iron Reduction versus Surface Catalysis.

Science.gov (United States)

Krumina, Lelde; Lyngsie, Gry; Tunlid, Anders; Persson, Per

2017-08-15

Hydroquinones are important mediators of electron transfer reactions in soils with a capability to reduce Fe(III) minerals and molecular oxygen, and thereby generating Fenton chemistry reagents. This study focused on 2,6-dimethoxy hydroquinone (2,6-DMHQ), an analogue to a common fungal metabolite, and its reaction with ferrihydrite and goethite under variable pH and oxygen concentrations. Combined wet-chemical and spectroscopic analyses showed that both minerals effectively oxidized 2,6-DMHQ in the presence of oxygen. Under anaerobic conditions the first-order oxidation rate constants decreased by one to several orders of magnitude depending on pH and mineral. Comparison between aerobic and anaerobic results showed that ferrihydrite promoted 2,6-DMHQ oxidation both via reductive dissolution and heterogeneous catalysis while goethite mainly caused catalytic oxidation. These results were in agreement with changes in the reduction potential (E H ) of the Fe(III) oxide/Fe(II) aq redox couple as a function of dissolved Fe(II) where E H of goethite was lower than ferrihydrite at any given Fe(II) concentration, which makes ferrihydrite more prone to reductive dissolution by the 2,6-DMBQ/2,6-DMHQ redox couple. This study showed that reactions between hydroquinones and iron oxides could produce favorable conditions for formation of reactive oxygen species, which are required for nonenzymatic Fenton-based decomposition of soil organic matter.

Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

Science.gov (United States)

Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Böhlke, J.K.

2017-01-01

weeks. Additionally, Fe(II)-oxidizing, nitrate-reducing microbial enrichment cultures were obtained from aquifer sediments. Growth experiments with the cultures sequentially produced nitrite and nitrous oxide from nitrate while simultaneously oxidizing Fe(II). Field and culture results suggest that nitrogen oxide reduction and Fe(II) oxidation in the aquifer are a complex interaction of coupled biotic and abiotic reactions. Overall, the results of this study demonstrate that anoxic nitrate-dependent iron oxidation can occur in groundwater; that it could control iron speciation; and that the process can impact the mobility of other chemical species (e.g., phosphate and arsenic) not directly involved in the oxidation–reduction reaction.

Direct versus indirect electrochemical oxidation of pesticide polluted drainage water containing sodium chloride

DEFF Research Database (Denmark)

Muff, Jens; Erichsen, Rasmus; Damgaard, Christian

2008-01-01

Drainage water from a depot of chemical waste, polluted with a mixture of organophosphates and degradation products was treated by a direct as well as an indirect electrochemical method using a Ti/Pt-Ir anode and Stainless Steel 304 cathode. With a concentration of 0.7%, sodium chloride...... the treatment. Indirect electrochemical treatment, where a highly oxidized brine solution was added to the drainage water, revealed immediately reduction in COD, and similar to the direct treatment, degradation of all of the pesticide pollutants was obtained except for the O,O,O-triethyl-phosphoric acid...... concentrations. Analyses of the actual pollutants, Me-Parathion, parathion, malathion and degradation products, confirmed that the concentrations of all initial pollutants were eliminated during the treatment. The only exception was O,O,O-triethyl-phosphoric acid, a degradation product which was formed during...

Direct versus indirect electrochemical oxidation of pesticide polluted drainage water containing sodium chloride

DEFF Research Database (Denmark)

Muff, Jens; Erichsen, Rasmus; Damgaard, Christian

2008-01-01

the treatment. Indirect electrochemical treatment, where a highly oxidized brine solution was added to the drainage water, revealed immediately reduction in COD, and similar to the direct treatment, degradation of all of the pesticide pollutants was obtained except for the O,O,O-triethyl-phosphoric acid......Drainage water from a depot of chemical waste, polluted with a mixture of organophosphates and degradation products was treated by a direct as well as an indirect electrochemical method using a Ti/Pt-Ir anode and Stainless Steel 304 cathode. With a concentration of 0.7%, sodium chloride...... concentrations. Analyses of the actual pollutants, Me-Parathion, parathion, malathion and degradation products, confirmed that the concentrations of all initial pollutants were eliminated during the treatment. The only exception was O,O,O-triethyl-phosphoric acid, a degradation product which was formed during...

Effects of Low-temperature Pre-oxidation on the Titanomagnetite Ore Structure and Reduction Behaviors in a Fluidized Bed

Science.gov (United States)

Adetoro, Ajala Adewole; Sun, Haoyan; He, Shengyi; Zhu, Qingshan; Li, Hongzhong

2018-04-01

With respect to high efficient utilization of low-grade iron ore resource, the behavior of low-temperature "973 K to 1123 K (700 °C to 850 °C)" oxidation, on the phase transition of SA TTM ore (South African titanomagnetite), and its effect on subsequent reduction was investigated. The results showed that hematite and rutile are the oxidation product below 1048 K (775 °C), while pseudobrookite is the stable phase above 1073 K (800 °C). With the increase in temperature and oxidation time, there is a competitive relationship between the amount of hematite and pseudobrookite generated. The reduction efficiency of SA TTM was significantly improved by oxidation pretreatment, primarily due to the dissociation of titania-ferrous oxides to more easily reducible hematite. But the generation of pseudobrookite phase decreases the amount of free hematite available for reduction, which weakens the improvement effect of pre-oxidation. The equilibrium relationship between the metallization degree and the gas reduction potential for TTM ore with pre-oxidation treatment has been built. Finally, the reduction metallization degree for the first and second step can be improved averagely by 16.67 and 3.45 pct, respectively, for sample pre-oxidized at 1098 K (825 °C) for 15 and 90 minutes, while 26.96 and 7.4 pct, improvement is achieved for sample pre-oxidized at a lower temperature of 1048 K (775 °C) for 120 minutes.

Effect of Ca-Fe oxides additives on NOx reduction in iron ore sintering

Institute of Scientific and Technical Information of China (English)

Zhi-yuan Yu; Xiao-hui Fan; Min Gan; Xu-ling Chen

2017-01-01

As the emission control regulations get stricter, the NOx reduction in the sintering process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. The NOx emissions from the sintering machine account for 48% of total amount from the iron and steel industry.Thus, it is essential to reduce NOx emissions from the sintering machine, for the achievement of clean production of sinter.Ca-Fe oxides, serving as the main binding phase in the sinter, are therefore used as additives into the sintering mixture to reduce NOx emissions.The results show that the NOx re-duction ratio achieves 27.76% with 8% Ca-Fe oxides additives since the Ca-Fe oxides can advance the ig-nition and inhibit the nitrogen oxidation compared with the conventional condition.Meanwhile, the exist-ence of Ca-Fe oxides was beneficial to the sinter quality since they were typical low melting point com-pounds.The optimal mass fraction of Ca-Fe oxides additives should be less than 8% since the permeability of sintering bed was significantly decreased with a further increase of the Ca-Fe oxides fines, inhibiting the mineralization reaction of sintering mixture.Additionally, the appropriate particle size can be obtained when mixing an equal amount of Ca-Fe oxides additives of -0.5 mm and 0.5-3.0 mm in size.

Coupled Metal/Oxide Catalysts with Tunable Product Selectivity for Electrocatalytic CO2 Reduction.

Science.gov (United States)

Huo, Shengjuan; Weng, Zhe; Wu, Zishan; Zhong, Yiren; Wu, Yueshen; Fang, Jianhui; Wang, Hailiang

2017-08-30

One major challenge to the electrochemical conversion of CO 2 to useful fuels and chemical products is the lack of efficient catalysts that can selectively direct the reaction to one desirable product and avoid the other possible side products. Making use of strong metal/oxide interactions has recently been demonstrated to be effective in enhancing electrocatalysis in the liquid phase. Here, we report one of the first systematic studies on composition-dependent influences of metal/oxide interactions on electrocatalytic CO 2 reduction, utilizing Cu/SnO x heterostructured nanoparticles supported on carbon nanotubes (CNTs) as a model catalyst system. By adjusting the Cu/Sn ratio in the catalyst material structure, we can tune the products of the CO 2 electrocatalytic reduction reaction from hydrocarbon-favorable to CO-selective to formic acid-dominant. In the Cu-rich regime, SnO x dramatically alters the catalytic behavior of Cu. The Cu/SnO x -CNT catalyst containing 6.2% of SnO x converts CO 2 to CO with a high faradaic efficiency (FE) of 89% and a j CO of 11.3 mA·cm -2 at -0.99 V versus reversible hydrogen electrode, in stark contrast to the Cu-CNT catalyst on which ethylene and methane are the main products for CO 2 reduction. In the Sn-rich regime, Cu modifies the catalytic properties of SnO x . The Cu/SnO x -CNT catalyst containing 30.2% of SnO x reduces CO 2 to formic acid with an FE of 77% and a j HCOOH of 4.0 mA·cm -2 at -0.99 V, outperforming the SnO x -CNT catalyst which only converts CO 2 to formic acid in an FE of 48%.

Electrochemical treatment of wastewater: A case study of reduction of DNT and oxidation of chlorinated phenols

Energy Technology Data Exchange (ETDEWEB)

Rodgers, J.D.; Bunce, N.J.; Jedral, W.

1999-07-01

Electrochemical treatment is under consideration as a treatment option for several recalcitrant compounds. In this work the authors investigate the oxidation of chlorophenols and the reduction of nitroaromatics. In the case of chlorinated phenols, they explore the problem of anode fouling which has hampered electrolytic treatment of phenolic compounds by examining phenols differing in the extent of chlorination, according to the mechanism of oxidation at different electrode types. Linear sweep voltammograms at a Pt anode were interpreted in terms of deposition of oligomers on the anode surface. Passivation increased in parallel with the uncompensated resistance of the solution and occurred only at potentials at which water is oxidized, suggesting that the formation of the oligomer film involves attack of hydroxyl radicals on electrochemically oxidized substrate. Relative reactivities of congeners were anode-dependent, due to different mechanisms of oxidation: direct electron transfer oxidation at PbO{sub 2} and hydroxyl radical attack at SnO{sub 2} and IrO{sub 2}. Voltammetry of 2,6-dinitrotoluene (DNT) was consistent with literature values. DNT was reduced at several cathodes with the most promising result at Ni-plated Ni wire. At current densities {lt} 0.1 mA cm{sup {minus}2}, current efficiencies {gt} 50% could be achieved with 4-chlorophenol at all three anodes and for 2,6-DNT at Ni-plated Ni wire.

The effect of preparation conditions and the ionizing radiation on the kinetics of cupric oxide reduction by hydrogen

International Nuclear Information System (INIS)

Pospisil, M.; Taras, P.

1977-01-01

Cupric oxide reduction in the temperature interval 170 to 350 degC was studied by thermogravimetry. The reduction kinetics can be quantitatively described by the modified Prout-Tompkinson equation, with the apparent activation energy varying within the limits (4.94 to 5.82)x10 4 J/mol. Irregularities observed during the reduction of the oxide of the oxalate origin are due to the high content of the metallic phase. The p-semiconducting nature of these oxides was proved for all samples. The effect of the pre-irradiation of samples with γ-rays (with an absorbed dose of (1.4 to 4.75)x10 6 J/kg) on the reduction kinetics depends on the origin of the cupric oxide. In contrast to NiO no correlation between the content of super-stoichiometric oxygen and the reduction kinetics was found. After irradiation with γ-rays or with fast neutrons at a dose of 79.8 J/kg the reduction rate increases and the activation energy decreases regardless of the oxide origin. At the same time the concentration of the ionic form of super-stoichiometric oxygen increases. (author)

Electrochemical characterization of Pt-Ru-Pd catalysts for methanol oxidation reaction in direct methanol fuel cells.

Science.gov (United States)

Choi, M; Han, C; Kim, I T; An, J C; Lee, J J; Lee, H K; Shim, J

2011-01-01

PtRuPd nanoparticles on carbon black were prepared and characterized as electrocatalysts for methanol oxidation reaction in direct methanol fuel cells. Nano-sized Pd (2-4 nm) particles were deposited on Pt/C and PtRu/C (commercial products) by a simple chemical reduction process. The structural and physical information of the PtRuPd/C were confirmed by TEM and XRD, and their electrocatalytic activities were measured by cyclic voltammetry and linear sweep voltammetry. The catalysts containing Pd showed higher electrocatalytic activity for methanol oxidation reaction than the other catalysts. This might be attributed to an increase in the electrochemical surface area of Pt, which is caused by the addition of Pd; this results in increased catalyst utilization.

Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.

Science.gov (United States)

Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

2007-09-12

Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab.

Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene.

Science.gov (United States)

Kaspar, H F; Tiedje, J M

1981-03-01

15N tracer methods and gas chromatography coupled to an electron capture detector were used to investigate dissimilatory reduction of nitrate and nitrite by the rumen microbiota of a fistulated cow. Ammonium was the only 15N-labeled end product of quantitative significance. Only traces of nitrous oxide were detected as a product of nitrate reduction; but in experiments with nitrite, up to 0.3% of the added nitrogen accumulated as nitrous oxide, but it was not further reduced. Furthermore, when 13NO3- was incubated with rumen microbiota virtually no [13N]N2 was produced. Acetylene partially inhibited the reduction of nitrite to ammonium as well as the formation of nitrous oxide. It is suggested that in the rumen ecosystem nitrous oxide is a byproduct of dissimilatory nitrite reduction to ammonium rather than a product of denitrification and that the latter process is absent from the rumen habitat.

Reduction of mixed Mn-Zr oxides: in situ XPS and XRD studies.

Science.gov (United States)

Bulavchenko, O A; Vinokurov, Z S; Afonasenko, T N; Tsyrul'nikov, P G; Tsybulya, S V; Saraev, A A; Kaichev, V V

2015-09-21

A series of mixed Mn-Zr oxides with different molar ratios Mn/Zr (0.1-9) have been prepared by coprecipitation of manganese and zirconium nitrates and characterized by X-ray diffraction (XRD) and BET methods. It has been found that at concentrations of Mn below 30 at%, the samples are single-phase solid solutions (MnxZr1-xO2-δ) based on a ZrO2 structure. X-ray photoelectron spectroscopy (XPS) measurements showed that manganese in these solutions exists mainly in the Mn(4+) state on the surface. An increase in Mn content mostly leads to an increase in the number of Mn cations in the structure of solid solutions; however, a part of the manganese cations form Mn2O3 and Mn3O4 in the crystalline and amorphous states. The reduction of these oxides with hydrogen was studied by a temperature-programmed reduction technique, in situ XRD, and near ambient pressure XPS in the temperature range from 100 to 650 °C. It was shown that the reduction of the solid solutions MnxZr1-xO2-δ proceeds via two stages. During the first stage, at temperatures between 100 and 500 °C, the Mn cations incorporated into the solid solutions MnxZr1-xO2-δ undergo partial reduction. During the second stage, at temperatures between 500 and 700 °C, Mn cations segregate on the surface of the solid solution. In the samples with more than 30 at% Mn, the reduction of manganese oxides was observed: Mn2O3 → Mn3O4 → MnO.

Efficient reduction of graphene oxide film by low temperature heat treatment and its effect on electrical conductivity

Energy Technology Data Exchange (ETDEWEB)

Hu, Xuebing; Chen, Zheng [Jingdezhen Ceramic Institute, Jingdezhen (China). Key Lab. of Inorganic Membrane; Yu, Yun [Shanghai Institute of Ceramics, Shanghai (China). Key Lab. of Inorganic Coating Materials; Zhang, Xiaozhen; Wang, Yongqing; Zhou, Jianer [Jingdezhen Ceramic Institute, Jingdezhen (China). Dept. of Materials Engineering

2018-03-01

Graphene-based conductive films have already attracted great attention due to their unique and outstanding physical properties. In this work, in order to develop a novel, effective method to produce these films with good electrical conductivity, a simple and green method is reported to rapidly and effectively reduce graphene oxide film using a low temperature heat treatment. The reduction of graphene oxide film is verified by XRD, FT-IR and Raman spectroscopy. Compared with graphene oxide film, the obtained reduced graphene oxide film has better electrical conductivity and its sheet resistance decreases from 25.3 kΩ x sq{sup -1} to 3.3 kΩ x sq{sup -1} after the heat treatment from 160 to 230 C. The mechanism of thermal reduction of the graphene oxide film mainly results from the removal of the oxygen-containing functional groups and the structural changes. All these results indicate that the low temperature heat treatment is a suitable and effective method for the reduction of graphene oxide film.

Microbial Reduction of Fe(III) in Acidic Sediments: Isolation of Acidiphilium cryptum JF-5 Capable of Coupling the Reduction of Fe(III) to the Oxidation of Glucose

Science.gov (United States)

Küsel, Kirsten; Dorsch, Tanja; Acker, Georg; Stackebrandt, Erko

1999-01-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4′,6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2.3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H2. Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium

Microbial reduction of Fe(III) in acidic sediments: isolation of Acidiphilium cryptum JF-5 capable of coupling the reduction of Fe(III) to the oxidation of glucose.

Science.gov (United States)

Küsel, K; Dorsch, T; Acker, G; Stackebrandt, E

1999-08-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12 degrees C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H(2) was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4', 6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2. 3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H(2). Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic

Evaluation of Biofuel Cells with Hemoglobin as Cathodic Electrocatalysts for Hydrogen Peroxide Reduction on Bare Indium-Tin-Oxide Electrodes

Directory of Open Access Journals (Sweden)

Yusuke Ayato

2013-12-01

Full Text Available A biofuel cell (BFC cathode has been developed based on direct electron transfer (DET of hemoglobin (Hb molecules with an indium-tin-oxide (ITO electrode and their electrocatalysis for reduction of hydrogen peroxide (H2O2. In this study, the ITO-coated glass plates or porous glasses were prepared by using a chemical vapor deposition (CVD method and examined the electrochemical characteristics of the formed ITO in pH 7.4 of phosphate buffered saline (PBS solutions containing and not containing Hb. In half-cell measurements, the reduction current of H2O2 due to the electrocatalytic activity of Hb increased with decreasing electrode potential from around 0.1 V versus Ag|AgCl|KCl(satd. in the PBS solution. The practical open-circuit voltage (OCV on BFCs utilizing H2O2 reduction at the Hb-ITO cathode with a hydrogen (H2 oxidation anode at a platinum (Pt electrode was expected to be at least 0.74 V from the theoretical H2 oxidation potential of −0.64 V versus Ag|AgCl|KCl(satd. in pH 7.4. The assembled single cell using the ITO-coated glass plate showed the OCV of 0.72 V and the maximum power density of 3.1 µW cm−2. The maximum power per single cell was recorded at 21.5 µW by using the ITO-coated porous glass.

Oxidative Addition and Reductive Elimination at Main-Group Element Centers.

Science.gov (United States)

Chu, Terry; Nikonov, Georgii I

2018-04-11

Oxidative addition and reductive elimination are key steps in a wide variety of catalytic reactions mediated by transition-metal complexes. Historically, this reactivity has been considered to be the exclusive domain of d-block elements. However, this paradigm has changed in recent years with the demonstration of transition-metal-like reactivity by main-group compounds. This Review highlights the substantial progress achieved in the past decade for the activation of robust single bonds by main-group compounds and the more recently realized activation of multiple bonds by these elements. We also discuss the significant discovery of reversible activation of single bonds and distinct examples of reductive elimination at main-group element centers. The review consists of three major parts, starting with oxidative addition of single bonds, proceeding to cleavage of multiple bonds, and culminated by the discussion of reversible bond activation and reductive elimination. Within each subsection, the discussion is arranged according to the type of bond being cleaved or formed and considers elements from the left to the right of each period and down each group of the periodic table. The majority of results discussed in this Review come from the past decade; however, earlier reports are also included to ensure completeness.

Investigations involving oxidation-reduction (REDOX) pretreatment in conjunction with biological remediation of contaminated soils

International Nuclear Information System (INIS)

Montemagno, C.D.; Peters, R.W.; Tyree, A.

1991-01-01

Oxidation-reduction (REDOX) reactions are among the most important reactions involved in the environmental engineering field. Oxidation is a reaction in which the oxidation state of the treated compound is increased, i.e., the material loses electrons. Reduction involves the addition of a chemical (reducing) agent which lowers the oxidation state of a substance, i.e., the material gains electrons. Both processes of oxidation and reduction occur together. All REDOX reactions are thermodynamically based. There are a number of oxidizing agents which have been reported in the technical literature for treatment of refractory organic compounds. Common oxidizing agents include: hydrogen peroxide, ozone, ultraviolet (UV) irradiation, and combinations thereof, such as UV/ozone and UV/peroxide. A gradient of REDOX reactions is possible, depending on such factors as the oxidation-reduction reaction conditions, the availability of electron donors and acceptors, and the nature of the organic compounds involved. A review of the technical literature revealed that the majority of the oxidation-reduction applications have been in the areas of wastewater treatment and groundwater remediation, with very little attention devoted to the potential of using REDOX technologies for remediation of hydrocarbon contaminated soils. In this particular study, feasibility studies were performed on gasoline- contaminated soil. These studies focused on three major phases: 1) containment of the contamination by addition of tailoring agents to the soil, 2) biological remediation either performed in situ or on-site (using a slurry reactor system), and 3) pretreatment of the contaminated soils using REDOX systems, prior to biological remediation. This particular paper focuses on the third phase of the project, aimed at ''softening'' the refractory organics resulting in the formation of organic compounds which are more amenable to biological degradation. This paper focuses its attention on the use of

Investigations involving oxidation-reduction (REDOX) pretreatment in conjunction with biological remediation of contaminated soils

Energy Technology Data Exchange (ETDEWEB)

Montemagno, C. D. [Argonne National Laboratory, Argonne, IL (United States); Peters, R. W.; Tyree, A.

1991-07-01

Oxidation-reduction (REDOX) reactions are among the most important reactions involved in the environmental engineering field. Oxidation is a reaction in which the oxidation state of the treated compound is increased, i.e., the material loses electrons. Reduction involves the addition of a chemical (reducing) agent which lowers the oxidation state of a substance, i.e., the material gains electrons. Both processes of oxidation and reduction occur together. All REDOX reactions are thermodynamically based. There are a number of oxidizing agents which have been reported in the technical literature for treatment of refractory organic compounds. Common oxidizing agents include: hydrogen peroxide, ozone, ultraviolet (UV) irradiation, and combinations thereof, such as UV/ozone and UV/peroxide. A gradient of REDOX reactions is possible, depending on such factors as the oxidation-reduction reaction conditions, the availability of electron donors and acceptors, and the nature of the organic compounds involved. A review of the technical literature revealed that the majority of the oxidation-reduction applications have been in the areas of wastewater treatment and groundwater remediation, with very little attention devoted to the potential of using REDOX technologies for remediation of hydrocarbon contaminated soils. In this particular study, feasibility studies were performed on gasoline- contaminated soil. These studies focused on three major phases: 1) containment of the contamination by addition of tailoring agents to the soil, 2) biological remediation either performed in situ or on-site (using a slurry reactor system), and 3) pretreatment of the contaminated soils using REDOX systems, prior to biological remediation. This particular paper focuses on the third phase of the project, aimed at ''softening'' the refractory organics resulting in the formation of organic compounds which are more amenable to biological degradation. This paper focuses its attention on the use of

Discrete Event System Based Pyroprocessing Modeling and Simulation: Oxide Reduction

International Nuclear Information System (INIS)

Lee, H. J.; Ko, W. I.; Choi, S. Y.; Kim, S. K.; Hur, J. M.; Choi, E. Y.; Im, H. S.; Park, K. I.; Kim, I. T.

2014-01-01

Dynamic changes according to the batch operation cannot be predicted in an equilibrium material flow. This study began to build a dynamic material balance model based on the previously developed pyroprocessing flowsheet. As a mid- and long-term research, an integrated pyroprocessing simulator is being developed at the Korea Atomic Energy Research Institute (KAERI) to cope with a review on the technical feasibility, safeguards assessment, conceptual design of facility, and economic feasibility evaluation. The most fundamental thing in such a simulator development is to establish the dynamic material flow framework. This study focused on the operation modeling of pyroprocessing to implement a dynamic material flow. As a case study, oxide reduction was investigated in terms of a dynamic material flow. DES based modeling was applied to build a pyroprocessing operation model. A dynamic material flow as the basic framework for an integrated pyroprocessing was successfully implemented through ExtendSim's internal database and item blocks. Complex operation logic behavior was verified, for example, an oxide reduction process in terms of dynamic material flow. Compared to the equilibrium material flow, a model-based dynamic material flow provides such detailed information that a careful analysis of every batch is necessary to confirm the dynamic material balance results. With the default scenario of oxide reduction, the batch mass balance was verified in comparison with a one-year equilibrium mass balance. This study is still under progress with a mid-and long-term goal, the development of a multi-purpose pyroprocessing simulator that is able to cope with safeguards assessment, economic feasibility, technical evaluation, conceptual design, and support of licensing for a future pyroprocessing facility

Reduction of ferrate(VI) and oxidation of cyanate in a Fe(VI)-TiO2-UV-NCO- system.

Science.gov (United States)

Winkelmann, Kurt; Sharma, Virender K; Lin, Yekaterina; Shreve, Katherine A; Winkelmann, Catherine; Hoisington, Laura J; Yngard, Ria A

2008-08-01

The aqueous photocatalytic degradation of cyanate (NCO(-)), which is a long-lived neurotoxin formed during the remediation of cyanide in industrial waste streams, was studied in the ferrate(VI)-UV-TiO2-NCO(-) system. Kinetics measurements of the photocatalytic reduction of ferrate(VI) were carried out as a function of [NCO(-)], [ferrate(VI)], [O(2)], light intensity (I(o)), and amount of TiO2 in suspensions at pH 9.0. The photocatalytic reduction rate of ferrate(VI) in the studied system can be expressed as -d[Fe(VI)]/dt=kI(o)(0.5) [NCO(-)] [TiO2]. The rate of photocatalytic oxidation of cyanate with ferrate(VI) was greater than the rate in the analogous system without ferrate(VI). The possibility of involvement of reactive ferrate(V) species for this enhancement was determined by studying the reactivity of ferrate(V) with NCO(-) in a homogeneous solution using a premix pulse radiolysis technique. The rate constant for the reaction of ferrate(V) and NCO(-) in alkaline medium was estimated to be (9.60+/-0.07) x 10(2) M(-1) s(-1), which is much slower than the ferrate(VI) self-decomposition reaction (k approximately 10(7) M(-1) s(-1)). An analysis of the kinetic data in the Fe(VI)-UV-TiO2-NCO(-) system suggests that ferrate(V) is not directly participating in the oxidation of cyanate. Possible reactions in the system are presented to explain results of ferrate(VI) reduction and oxidation of cyanate.

Enhanced Cr(VI) reduction and As(III) oxidation in ice phase: Important role of dissolved organic matter from biochar

Energy Technology Data Exchange (ETDEWEB)

Dong, Xiaoling [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Ma, Lena Q., E-mail: lqma@ufl.edu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046 (China); Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Gress, Julia; Harris, Willie [Department of Soil and Water Science, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Soil and Water Science Department, Tropical Research and Education Center, University of Florida, Homestead, FL 33031-3314 (United States)

2014-02-01

Graphical abstract: - Highlights: • Biochar-derived dissolved organic matter (DOM) effectively reduced Cr(VI) and oxidized As(III). • Cr(VI) and As(III) could serve as a redox couple. • Cr(VI) and As(III) redox conversion was more effective in the ice phase than aqueous phase. • FTIR and ESR showed that biochar DOM served as both electron donor and acceptor. - Abstract: This study evaluated the impact of DOM from two biochars (sugar beet tailing and Brazilian pepper) on Cr(VI) reduction and As(III) oxidation in both ice and aqueous phases with a soil DOM as control. Increasing DOM concentration from 3 to 300 mg C L{sup −1} enhanced Cr(VI) reduction from 20% to 100% and As(III) oxidation from 6.2% to 25%; however, Cr(VI) reduction decreased from 80–86% to negligible while As(III) oxidation increased from negligible to 18–19% with increasing pH from 2 to 10. Electron spin resonance study suggested semiquinone radicals in DOM were involved in As(III) oxidation while Fourier transform infrared analysis suggested that carboxylic groups in DOM participated in both Cr(VI) reduction and As(III) oxidation. During Cr(VI) reduction, part of DOM (∼10%) was oxidized to CO{sub 2}. The enhanced conversion of Cr(VI) and As(III) in the ice phase was due to the freeze concentration effect with elevated concentrations of electron donors and electron acceptors in the grain boundary. Though DOM enhanced both Cr(VI) reduction and As(III)oxidation, Cr(VI) reduction coupled with As(III) oxidation occurred in absence of DOM. The role of DOM, Cr(VI) and/or As(III) in Cr and As transformation may provide new insights into their speciation and toxicity in cold regions.

Palladium-based electrocatalysts for ethanol oxidation reaction in alkaline direct ethanol fuel cell

Energy Technology Data Exchange (ETDEWEB)

Moraes, Leticia Poras Reis de; Amico, Sandro Campos; Malfatti, Celia de Fraga, E-mail: leticiamoraes@usp.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil); Matos, Bruno R.; Santiago, Elisabete Inacio; Fonseca, Fabio Coral [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2016-07-01

Full text: Direct ethanol fuel cells require adequate electrocatalysts to promote the carbon carbon cleavage of ethanol molecule. Typical electrocatalysts are based on platinum, which have shown improved activity in acidic media. However, Pt-based catalysts have high cost and are easily deactivated by CO poisoning. Therefore, novel catalysts have been developed, and among then, palladium-based materials have shown promising results for the oxidation of ethanol in alkaline media. The present study reports on the performance of alkaline direct ethanol fuel cell (ADEFC) by using carbon-supported Pd, PdSn, PdNi, and PdNiSn produced by impregnation-reduction of the metallic precursors. The effect of chemical functionalization by acid treatment of the carbon support (Vulcan) was investigated. The electrocatalysts were studied by thermogravimetric analysis (TGA), X-rays diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), and ADEFC tests. TGA measurements of functionalized Vulcan evidenced the characteristic weight losses attributed to the presence of surface functional groups due to the acid treatment. A high degree of alloying between Pd and Sn was inferred from XRD data, whereas in both PdNi and PdNiSn, Ni occurs mostly segregated in the oxide form. TEM analyses indicated agglomeration of Pd and PdSn particles, whereas a more uniform particle distribution was observed for PdNi and PdNiSn samples. CV curves showed that the peak potential for the oxidation of ethanol shifts towards negative values for all samples supported on functionalized Vulcan indicating that ethanol oxidation is facilitated. Microstructural and electrochemical features were confirmed by ADEFC tests, which revealed that the highest open circuit voltage and maximum power density were achieved for PdNiSn electrocatalysts supported on functionalized Vulcan with uniform particle distribution and improved triple phase boundaries. (author)

Palladium-based electrocatalysts for ethanol oxidation reaction in alkaline direct ethanol fuel cell

International Nuclear Information System (INIS)

Moraes, Leticia Poras Reis de; Amico, Sandro Campos; Malfatti, Celia de Fraga; Matos, Bruno R.; Santiago, Elisabete Inacio; Fonseca, Fabio Coral

2016-01-01

Full text: Direct ethanol fuel cells require adequate electrocatalysts to promote the carbon carbon cleavage of ethanol molecule. Typical electrocatalysts are based on platinum, which have shown improved activity in acidic media. However, Pt-based catalysts have high cost and are easily deactivated by CO poisoning. Therefore, novel catalysts have been developed, and among then, palladium-based materials have shown promising results for the oxidation of ethanol in alkaline media. The present study reports on the performance of alkaline direct ethanol fuel cell (ADEFC) by using carbon-supported Pd, PdSn, PdNi, and PdNiSn produced by impregnation-reduction of the metallic precursors. The effect of chemical functionalization by acid treatment of the carbon support (Vulcan) was investigated. The electrocatalysts were studied by thermogravimetric analysis (TGA), X-rays diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), and ADEFC tests. TGA measurements of functionalized Vulcan evidenced the characteristic weight losses attributed to the presence of surface functional groups due to the acid treatment. A high degree of alloying between Pd and Sn was inferred from XRD data, whereas in both PdNi and PdNiSn, Ni occurs mostly segregated in the oxide form. TEM analyses indicated agglomeration of Pd and PdSn particles, whereas a more uniform particle distribution was observed for PdNi and PdNiSn samples. CV curves showed that the peak potential for the oxidation of ethanol shifts towards negative values for all samples supported on functionalized Vulcan indicating that ethanol oxidation is facilitated. Microstructural and electrochemical features were confirmed by ADEFC tests, which revealed that the highest open circuit voltage and maximum power density were achieved for PdNiSn electrocatalysts supported on functionalized Vulcan with uniform particle distribution and improved triple phase boundaries. (author)

Ferricytochrome (c directly oxidizes aminoacetone to methylglyoxal, a catabolite accumulated in carbonyl stress.

Directory of Open Access Journals (Sweden)

Adriano Sartori

Full Text Available Age-related diseases are associated with increased production of reactive oxygen and carbonyl species such as methylglyoxal. Aminoacetone, a putative threonine catabolite, is reportedly known to undergo metal-catalyzed oxidation to methylglyoxal, NH4(+ ion, and H2O2 coupled with (i permeabilization of rat liver mitochondria, and (ii apoptosis of insulin-producing cells. Oxidation of aminoacetone to methylglyoxal is now shown to be accelerated by ferricytochrome c, a reaction initiated by one-electron reduction of ferricytochrome c by aminoacetone without amino acid modifications. The participation of O2(•- and HO (• radical intermediates is demonstrated by the inhibitory effect of added superoxide dismutase and Electron Paramagnetic Resonance spin-trapping experiments with 5,5'-dimethyl-1-pyrroline-N-oxide. We hypothesize that two consecutive one-electron transfers from aminoacetone (E0 values = -0.51 and -1.0 V to ferricytochrome c (E0 = 0.26 V may lead to aminoacetone enoyl radical and, subsequently, imine aminoacetone, whose hydrolysis yields methylglyoxal and NH4(+ ion. In the presence of oxygen, aminoacetone enoyl and O2(•- radicals propagate aminoacetone oxidation to methylglyoxal and H2O2. These data endorse the hypothesis that aminoacetone, putatively accumulated in diabetes, may directly reduce ferricyt c yielding methylglyoxal and free radicals, thereby triggering redox imbalance and adverse mitochondrial responses.

Changes in physical properties of graphene oxide with thermal reduction

Science.gov (United States)

Pandit, Bhishma; Jo, Chang Hee; Joo, Kwan Seon; Cho, Jaehee

2017-08-01

Reduced graphene oxide (rGO) has attracted significant attention as an easily fabricable twodimensional material. Depending on the oxygen-containing functional groups (OFGs) in an rGO specimen, the optical and electrical properties can vary significantly, directly affecting the performance of devices in which rGO is implemented. Here, we investigated the optical and electrical properties of GO treated with various annealing (reduction) temperatures from 350 to 950 °C in H2 ambient. Using diverse characteristic tools, we found that the transmittance, nanoscale domain size, OFGs in GO and rGO, and Schottky barrier height (SBH) measured on n-type GaN are significantly influenced by the annealing temperature. The relative intensity of the defect-induced band in Raman spectroscopy showed a minimum at the annealing temperature of approximately 350 °C, before the OFGs in rGO showed vigorous changes in relative content. When the domain size of rGO reached a minimum at the annealing temperature of 650 °C, the SBH of rGO/GaN showed the maximum value of 1.07 eV.

Changes in Physical Properties of Graphene Oxide with Thermal Reduction

Energy Technology Data Exchange (ETDEWEB)

Pandit, Bhishma; Jo, Chang Hee; Joo, Kwan Seon; Cho, Jaehee [Chonbuk National University, Jeonju (Korea, Republic of)

2017-08-15

Reduced graphene oxide (rGO) has attracted significant attention as an easily fabricable two dimensional material. Depending on the oxygen-containing functional groups (OFGs) in an rGO specimen, the optical and electrical properties can vary significantly, directly affecting the performance of devices in which rGO is implemented. Here, we investigated the optical and electrical properties of GO treated with various annealing (reduction) temperatures from 350 to 950 ℃ in H2 ambient. Using diverse characteristic tools, we found that the transmittance, nanoscale domain size, OFGs in GO and rGO, and Schottky barrier height (SBH) measured on n-type GaN are significantly influenced by the annealing temperature. The relative intensity of the defect-induced band in Raman spectroscopy showed a minimum at the annealing temperature of approximately 350 ℃, before the OFGs in rGO showed vigorous changes in relative content. When the domain size of rGO reached a minimum at the annealing temperature of 650 ℃, the SBH of rGO/GaN showed the maximum value of 1.07 eV.

Catalyst for reduction of nitrogen oxides

Science.gov (United States)

Ott, Kevin C.

2010-04-06

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

A novel differential electrochemical mass spectrometry method to determine the product distribution from parasitic Methanol oxidation reaction on oxygen reduction reaction catalysts

Science.gov (United States)

Jurzinsky, Tilman; Kurzhals, Philipp; Cremers, Carsten

2018-06-01

The oxygen reduction reaction is in research focus since several decades due to its importance for the overall fuel cell performance. In direct methanol fuel cells, the crossover of methanol and its subsequent parasitic oxidation are main issues when it comes to preventing fuel cell performance losses. In this work, we present a novel differential electrochemical mass spectrometry method to evaluate oxygen reduction reaction catalysts on their tolerance to methanol being present at the cathode. Besides this, the setup allows to measure under more realistic fuel cell conditions than typical rotating disc electrode measurements, because the oxygen reduction reaction is evaluated in gaseous phase and a gas diffusion electrode is used as working electrode. Due to the new method, it was possible to investigate the oxygen reduction reaction on two commonly used catalysts (Pt/C and Pt3Co/C) in absence and presence of methanol. It was found, that Pt3Co/C is less prone to parasitic current losses due to methanol oxidation reaction. By connecting a mass spectrometer to the electrochemical cell, the new method allows to determine the products formed on the catalysts due to parasitic methanol electrooxidation.

Nitrogen loss from anaerobic ammonium oxidation coupled to Iron(III) reduction in a riparian zone.

Science.gov (United States)

Ding, Bangjing; Li, Zhengkui; Qin, Yunbin

2017-12-01

Anaerobic ammonium oxidation coupled to iron(III) reduction (termed Feammox) is a recently discovered pathway of nitrogen cycling. However, little is known about the pathways of N transformation via Feammox process in riparian zones. In this study, evidence for Feammox in riparian zones with or without vegetation cover was demonstrated using isotope tracing technique and high-throughput sequencing technology. The results showed that Feammox could occur in riparian zones, and demonstrated that N 2 directly from Feammox was dominant Feammox pathway. The Feammox rates in vegetated soil samples was 0.32-0.37 mg N kg -1 d -1 , which is higher than that in un-vegetated soil samples (0.20 mg N kg -1 d -1 ). Moreover, the growth of vegetation led to a 4.99-6.41% increase in the abundance of iron reducing bacteria (Anaeromyxobacter, Pseudomonas and Geobacter) and iron reducing bacteria play an essential role in Feammox process. An estimated loss of 23.7-43.9 kg N ha -1 year -1 was associated with Feammox in the examined riparian zone. Overall, the co-occurrence of ammonium oxidation and iron reduction suggest that Feammox can play an essential role in the pathway of nitrogen removal in riparian zones. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of 3-substituted 4-piperidinones via a one-pot tandem oxidation-cyclization-oxidation process: stereodivergent reduction to 3,4-disubstituted piperidines.

Science.gov (United States)

Bahia, Perdip S; Snaith, John S

2004-04-30

A novel approach to 3-substituted 4-piperidinones is described. The one-pot tandem oxidation-cyclization-oxidation of unsaturated alcohols 1a-e by PCC or PCC and trifluoromethanesulfonic acid affords piperidinones 2a-e in good yield. Reduction of 2a-e by L-Selectride gives the corresponding cis 3,4-disubstituted piperidines with diastereomeric ratios of >99:1. By contrast, reduction of 2a-e by Al-isopropoxydiisobutylalane gives the trans products with diastereomeric ratios of up to 99:1.

Oxidation and reduction behaviors of a prototypic MgO-PuO{sub 2-x} inert matrix fuel

Energy Technology Data Exchange (ETDEWEB)

Miwa, Shuhei, E-mail: miwa.shuhei@jaea.go.jp; Osaka, Masahiko

2017-04-15

Oxidation and reduction behaviors of prototypic MgO-based inert matrix fuels (IMFs) containing PuO{sub 2-x} were experimentally investigated by means of thermogravimetry. The oxidation and reduction kinetics of the MgO-PuO{sub 2-x} specimen were determined. The oxidation and reduction rates of the MgO-PuO{sub 2-x} were found to be low compared with those of PuO{sub 2-x}. It is note that the changes in O/Pu ratios of MgO-PuO{sub 2-x} from stoichiometry were smaller than those of PuO{sub 2-x} at high oxygen partial pressure.

Directed C-H Bond Oxidation of (+)-Pleuromutilin.

Science.gov (United States)

Ma, Xiaoshen; Kucera, Roman; Goethe, Olivia F; Murphy, Stephen K; Herzon, Seth B

2018-05-01

Antibiotics derived from the diterpene fungal metabolite (+)-pleuromutilin (1) are useful agents for the treatment Gram-positive infections in humans and farm animals. Pleuromutilins elicit slow rates of resistance development and minimal cross-resistance with existing antibiotics. Despite efforts aimed at producing new derivatives by semisynthesis, modification of the tricyclic core is underexplored, in part due to a limited number of functional group handles. Herein, we report methods to selectively functionalize the methyl groups of (+)-pleuromutilin (1) by hydroxyl-directed iridium-catalyzed C-H silylation, followed by Tamao-Fleming oxidation. These reactions provided access to C16, C17, and C18 monooxidized products, as well as C15/C16 and C17/C18 dioxidized products. Four new functionalized derivatives were prepared from the protected C17 oxidation product. C6 carboxylic acid, aldehyde, and normethyl derivatives were prepared from the C16 oxidation product. Many of these sequences were executed on gram scales. The efficiency and practicality of these routes provides an easy method to rapidly interrogate structure-activity relationships that were previously beyond reach. This study will inform the design of fully synthetic approaches to novel pleuromutilins and underscores the power of the hydroxyl-directed iridium-catalyzed C-H silylation reaction.

Characterization of Cu/CeO2/Al2O3 catalysts by temperature programmed reduction and activity for CO oxidation

International Nuclear Information System (INIS)

Cataluna, Renato; Baibich, Ione M.; Dallago, R.M.; Picinini, C.; Martinez-Arias, A.; Soria, J.

2001-01-01

The kinetic parameters for the CO oxidation reaction using copper/alumina-modified ceria as catalysts were determined. The catalysts with different concentrations of the metals were prepared using impregnation methods. In addition, the reduction-oxidation behaviour of the catalysts were investigated by temperature-programmed reduction. The activity results show that the mechanism for CO oxidation is bifunctional: oxygen is activated on the anionic vacancies of ceria surface, while carbon monoxide is adsorbed preferentially on the higher oxidation copper site. Therefore, the reaction occurs on the interfacial active centers. Temperatures-programmed Reduction patterns show a higher dispersion when cerium oxide is present. (author)

Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

Science.gov (United States)

Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

2015-11-16

Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trace methane oxidation and the methane dependency of sulfate reduction in anaerobic granular sludge

KAUST Repository

Meulepas, Roel J.W.; Jagersma, Christian G.; Zhang, Yu; Petrillo, Michele; Cai, Hengzhe; Buisman, Cees J.N.; Stams, Alfons J.M.; Lens, Piet N.L.

2010-01-01

This study investigates the oxidation of labeled methane (CH4) and the CH4 dependence of sulfate reduction in three types of anaerobic granular sludge. In all samples, 13C-labeled CH4 was anaerobically oxidized to 13C-labeled CO2, while net

Effects of directional microphone and adaptive multichannel noise reduction algorithm on cochlear implant performance.

Science.gov (United States)

Chung, King; Zeng, Fan-Gang; Acker, Kyle N

2006-10-01

Although cochlear implant (CI) users have enjoyed good speech recognition in quiet, they still have difficulties understanding speech in noise. We conducted three experiments to determine whether a directional microphone and an adaptive multichannel noise reduction algorithm could enhance CI performance in noise and whether Speech Transmission Index (STI) can be used to predict CI performance in various acoustic and signal processing conditions. In Experiment I, CI users listened to speech in noise processed by 4 hearing aid settings: omni-directional microphone, omni-directional microphone plus noise reduction, directional microphone, and directional microphone plus noise reduction. The directional microphone significantly improved speech recognition in noise. Both directional microphone and noise reduction algorithm improved overall preference. In Experiment II, normal hearing individuals listened to the recorded speech produced by 4- or 8-channel CI simulations. The 8-channel simulation yielded similar speech recognition results as in Experiment I, whereas the 4-channel simulation produced no significant difference among the 4 settings. In Experiment III, we examined the relationship between STIs and speech recognition. The results suggested that STI could predict actual and simulated CI speech intelligibility with acoustic degradation and the directional microphone, but not the noise reduction algorithm. Implications for intelligibility enhancement are discussed.

Oxidation-reduction enzymes of myocardium under ionizing radiation effect

International Nuclear Information System (INIS)

Uteshev, A.B.

1988-01-01

Tissue respiration proceses under radiation effect were investigated which allowed one to reveal slight biochemical disturbances in a cell which make up the base of functional changes of different organs and tissues and to get to know the essence of tissue respiration processes. An attempt to explain significant value of oxidation enzyme system radiosensitivity in the course of cell respiration process altogether is made when studying the state of separate links of oxidation-reduction chain. It is shown that at early periods of radiation injury activity of catalase, dehydrogenases (isocitric, α-ketoglutaric, malic, succinic acids) is suppressed, concentration of a number of cytochromes is reduced and general ferrum content is increased which is connected with conformation changes of ultrastructure of mitochondrial membranes

Global Emissions of Nitrous Oxide: Key Source Sectors, their Future Activities and Technical Opportunities for Emission Reduction

Science.gov (United States)

Winiwarter, W.; Höglund-Isaksson, L.; Klimont, Z.; Schöpp, W.; Amann, M.

2017-12-01

Nitrous oxide originates primarily from natural biogeochemical processes, but its atmospheric concentrations have been strongly affected by human activities. According to IPCC, it is the third largest contributor to the anthropogenic greenhouse gas emissions (after carbon dioxide and methane). Deep decarbonization scenarios, which are able to constrain global temperature increase within 1.5°C, require strategies to cut methane and nitrous oxide emissions on top of phasing out carbon dioxide emissions. Employing the Greenhouse gas and Air pollution INteractions and Synergies (GAINS) model, we have estimated global emissions of nitrous oxide until 2050. Using explicitly defined emission reduction technologies we demonstrate that, by 2030, about 26% ± 9% of the emissions can be avoided assuming full implementation of currently existing reduction technologies. Nearly a quarter of this mitigation can be achieved at marginal costs lower than 10 Euro/t CO2-eq with the chemical industry sector offering important reductions. Overall, the largest emitter of nitrous oxide, agriculture, also provides the largest emission abatement potentials. Emission reduction may be achieved by precision farming methods (variable rate technology) as well as by agrochemistry (nitrification inhibitors). Regionally, the largest emission reductions are achievable where intensive agriculture and industry are prevalent (production and application of mineral fertilizers): Centrally Planned Asia including China, North and Latin America, and South Asia including India. Further deep cuts in nitrous oxide emissions will require extending reduction efforts beyond strictly technological solutions, i.e., considering behavioral changes, including widespread adoption of "healthy diets" minimizing excess protein consumption.

Primary oxidation and reduction products in x-irradiated aspartic acid

International Nuclear Information System (INIS)

Adams, S.M.; Budzinski, E.E.; Box, H.C.

1976-01-01

The primary reduction products identified by ESR--ENDOR spectroscopy in single crystals of DL-aspartic acid hydrochloride irradiated at 4.2degreeK are anions formed by addition of an electron to the carbonyl oxygen atoms of the carboxylic acid groups. The main consequence of the oxidation process is to produce a hole centered mainly on atomic chlorine

In situ reduction of as-prepared γ-Iron Oxide Nanoparticles

DEFF Research Database (Denmark)

Garbus, Pelle Gorm; Ahlburg, Jakob; Christensen, Mogens

-ray diffraction measurement. The as-prepared maghemite nanoparticles were synthesized by the continuous decomposition of solutes in supercritical hydrothermal flow synthesis [3, 4]. The reagent used was ferric ammonium citrate (C6H8O7•xFe(III)•yNH3) that under hydrothermal flow synthesis decomposes into the γ......-iron oxide Fe2O3. The reduction of maghemite to body centered cubic (BCC) iron does not go through a detectable intermediate state.1.Jensen, K.M., et al., Mechanisms for iron oxide formation under hydrothermal conditions: an in situ total scattering study. ACS nano, 2014. 8(10): p. 10704-10714.2.Andersen, H...

Determination of reduction yield of lithium metal reduction process

International Nuclear Information System (INIS)

Choi, In Kyu; Cho, Young Hwan; Kim, Taek Jin; Jee, Kwang Young

2004-01-01

Metal reduction of spent oxide fuel is the first step for the effective storage of spent fuel in Korea as well as transmutation purpose of long-lived radio-nuclides. During the reduction of uranium oxide by lithium metal to uranium metal, lithium oxide is stoichiometrically produced. By determining the concentration of lithium oxide in lithium chloride, we can estimate that how much uranium oxide is converted to uranium metal. Previous method to determine the lithium oxide concentration in lithium chloride is tedious and timing consuming. This paper describe the on-line monitoring method of lithium oxide during the reduction process

Reduction of antibiotic resistance genes in municipal wastewater effluent by advanced oxidation processes

International Nuclear Information System (INIS)

Zhang, Yingying; Zhuang, Yao; Geng, Jinju; Ren, Hongqiang; Xu, Ke; Ding, Lili

2016-01-01

This study investigated the reduction of antibiotic resistance genes (ARGs), intI1 and 16S rRNA genes, by advanced oxidation processes (AOPs), namely Fenton oxidation (Fe"2"+/H_2O_2) and UV/H_2O_2 process. The ARGs include sul1, tetX, and tetG from municipal wastewater effluent. The results indicated that the Fenton oxidation and UV/H_2O_2 process could reduce selected ARGs effectively. Oxidation by the Fenton process was slightly better than that of the UV/H_2O_2 method. Particularly, for the Fenton oxidation, under the optimal condition wherein Fe"2"+/H_2O_2 had a molar ratio of 0.1 and a H_2O_2 concentration of 0.01 mol L"−"1 with a pH of 3.0 and reaction time of 2 h, 2.58–3.79 logs of target genes were removed. Under the initial effluent pH condition (pH = 7.0), the removal was 2.26–3.35 logs. For the UV/H_2O_2 process, when the pH was 3.5 with a H_2O_2 concentration of 0.01 mol L"−"1 accompanied by 30 min of UV irradiation, all ARGs could achieve a reduction of 2.8–3.5 logs, and 1.55–2.32 logs at a pH of 7.0. The Fenton oxidation and UV/H_2O_2 process followed the first-order reaction kinetic model. The removal of target genes was affected by many parameters, including initial Fe"2"+/H_2O_2 molar ratios, H_2O_2 concentration, solution pH, and reaction time. Among these factors, reagent concentrations and pH values are the most important factors during AOPs. - Highlights: • AOPs including Fenton oxidation and UV/H_2O_2 process could reduce ARGs effectively. • Fenton oxidation is slightly more effective than UV/H_2O_2 process in ARG reduction. • Removal of ARGs by AOPs follows the first-order reaction kinetic model. • Selected ARGs and 16S rRNA genes exhibit similar change trends during AOPs.

A study on the electrolytic reduction of uranium oxide in a LiCl-Li2O molten salt

International Nuclear Information System (INIS)

Su, J. S.; Hu, J. M.; Hong, S. S.; Jang, D. S.; Park, S. W.

2003-01-01

New electrolytic reduction technology was proposed that is based on the integration of metallization of uranium oxide and Li 2 O electrowinning. In this electrolytic reduction reaction, electrolytically reduced Li deposits on cathode and simultaneously reacts with uranium oxides to produce uranium metal showing more than 99% conversion. For the verification of process feasibility, the experiments to obtain basic data on the metallization of uranium oxide, investigation of reaction mechanism, the characteristics of closed recycle of Li 2 O and mass transfer were carried out. This evolutionary electrolytic reduction technology would give benefits over the conventional Li-reduction process improving economic viability such as: avoidance of handling of chemically active Li-LiCl molten salt, increase of metallization yield, and simplification of process

Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

Science.gov (United States)

Basirun, Wan J.; Sookhakian, Mehran; Baradaran, Saeid; Mahmoudian, Mohammad R.; Ebadi, Mehdi

2013-09-01

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.

Thermogravimetric study of the reduction of oxides of nickel and chromium

Science.gov (United States)

Herbell, T. P.

1973-01-01

The effectiveness of hydrogen, carbon and hydrogen-carbon in reducing NiO, Cr2O3, mixed NiO-Cr2O3 and oxidized Ni-20Cr was evaluated by thermogravimetry. NiO was effectively reduced by all three atmospheres, Cr2O3 only by hydrogen-carbon, NiO-Cr2O3 by hydrogen and hydrogen-carbon and oxidized Ni-20Cr by hydrogen, hydrogen-carbon and partially by carbon alone. The results indicate that nickel and carbon promote the reduction of Cr2O3.

Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

Science.gov (United States)

Tsang, Floris Y.

1980-01-01

Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

Oxidation and Reduction of Liquid SnPb (60/40) under Ambient and Vacuum Conditions

DEFF Research Database (Denmark)

Kuhmann, Jochen Friedrich; Maly, K.; Preuss, A.

1998-01-01

One of the most straightforward approaches to fluxless solder bonding is using vacuum conditions to prevent further oxidation and, where needed, to reduce solder oxides by the use of molecular hydrogen (H-2).(1-3) This study On oxidation and reduction of solder oxides on SnPb (60/40) is aimed...... to provide a better understanding for fluxless solder bonding applications under controlled atmospheric conditions; By means of scanning Auger spectroscopy it is shown, that growth of oxide films on metallic SnPb above the eutectic temperature can be significantly reduced by decreasing the O-2 partial...

The Simulation of an Oxidation-Reduction Titration Curve with Computer Algebra

Science.gov (United States)

Whiteley, Richard V., Jr.

2015-01-01

Although the simulation of an oxidation/reduction titration curve is an important exercise in an undergraduate course in quantitative analysis, that exercise is frequently simplified to accommodate computational limitations. With the use of readily available computer algebra systems, however, such curves for complicated systems can be generated…

Oxidation-reduction induced roughening of platinum (111) surface

International Nuclear Information System (INIS)

You, H.; Nagy, Z.

1993-06-01

Platinum (111) single crystal surface was roughened by repeated cycles of oxidation and reduction to study dynamic evolution of surface roughening. The interface roughens progressively upon repeated cycles. The measured width of the interface was fit to an assumed pow law, W ∼t β , with β = 0.38(1). The results are compared with a simulation based on a random growth model. The fraction of the singly stepped surface apparently saturates to 0. 25 monolayer, which explains the apparent saturation to a steady roughness observed in previous studies

Electrochemical Reduction of solid UO2 in Molten Fluoride Salts

International Nuclear Information System (INIS)

Gibilaro, Mathieu; Cassayre, Laurent; Massot, Laurent; Chamelot, Pierre; Malmbeck, Rikard; Dugne, Olivier; Allegri, Patrick

2010-01-01

The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+ 2wt % Li 2 O) at 850 deg. C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, reduction of oxide ions yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets have been performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to its direct reduction have been observed at a potential 150 mV more positive in comparison with the solvent reduction. Then, galvano-static electrolyses runs have been realised and products were characterised by SEM-EDX, EPMA/WDS and XRD. In one of the runs, uranium oxide was partially reduced and three phases were observed: non reduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides. (authors)

Interim glycol flowsheet reduction/oxidation (redox) model for the Defense Waste Processing Facility (DWPF)

Energy Technology Data Exchange (ETDEWEB)

Jantzen, C. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Williams, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Zamecnik, J. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Missimer, D. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-03-08

Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe⁺²/ΣFe ratios of between 0.09 and 0.33, a range which is not overly oxidizing or overly reducing, helps retain radionuclides in the melt, i.e. long-lived radioactive ⁹⁹Tc species in the less volatile reduced Tc⁴⁺ state, ¹⁰⁴Ru in the melt as reduced Ru⁺⁴ state as insoluble RuO₂, and hazardous volatile Cr⁶⁺ in the less soluble and less volatile Cr⁺³ state in the glass. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam. Currently, the Defense Waste Processing Facility (DWPF) is running a formic acid-nitric acid (FN) flowsheet where formic acid is the main reductant and nitric acid is the main oxidant. During decomposition formate and formic acid releases H₂ gas which requires close control of the melter vapor space flammability. A switch to a nitric acid-glycolic acid (GN) flowsheet is desired as the glycolic acid flowsheet releases considerably less H₂ gas upon decomposition. This would greatly simplify DWPF processing. Development of an EE term for glycolic acid in the GN flowsheet is documented in this study.

Measurement and reduction of nitrous oxide in operating rooms

NARCIS (Netherlands)

Schuyt, H. C.; Verberk, M. M.

1996-01-01

In a program designed to lower exposure to anesthetic gases, nitrous oxide in the breathing zone of anesthesiologists was continuously monitored by means of a direct reading apparatus and a specially designed collar. Initially, the average concentration during anesthesia in intubated patients,

Facile synthesis of reduced graphene oxide nanosheets by a sodium diphenylamine sulfonate reduction process and its electrochemical property

International Nuclear Information System (INIS)

Ji, Yunzhou; Liu, Qi; Cheng, Meiling; Lai, Lifang; Li, Zhanfeng; Peng, Yuxin; Yang, Yong

2013-01-01

We report a new method to convert graphene oxide (GO) to stable colloidal dispersion of reduced graphene oxide nanosheets (RGONS) using sodium diphenylamine sulfonate (SDAS) as a reductant, as well as itself and its redox product as the stabilizer. The as-prepared RGONS have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible spectroscopy, thermo-gravimetric analysis, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and Raman spectroscopy. The results indicate that the bulk of oxygen-containing functional groups from GO have been removed. Based on the cyclic voltammogram (CV) analyses, it is found that the RGONS-based material exhibits better electrochemical activity in sensing ascorbic acid than GO. The simple method provides a new efficient route for the synthesis of water-soluble RGONS on a large scale and novel composites. - Highlights: • We report a new environment-friendly reductant for the reduction of graphene oxide. • The reduction process needn't use other stabilizer except for using reductant. • The reduced graphene oxide nanosheet (RGONS) aqueous dispersion is stable. • The RGONS shows a high electrochemical activity in sensing ascorbic acid

Anaerobic oxidation of methane coupled to thiosulfate reduction in a biotrickling filter.

Science.gov (United States)

Cassarini, Chiara; Rene, Eldon R; Bhattarai, Susma; Esposito, Giovanni; Lens, Piet N L

2017-09-01

Microorganisms from an anaerobic methane oxidizing sediment were enriched with methane gas as the substrate in a biotrickling filter (BTF) using thiosulfate as electron acceptor for 213days. Thiosulfate disproportionation to sulfate and sulfide were the dominating sulfur conversion process in the BTF and the sulfide production rate was 0.5mmoll -1 day -1 . A specific group of sulfate reducing bacteria (SRB), belonging to the Desulforsarcina/Desulfococcus group, was enriched in the BTF. The BTF biomass showed maximum sulfate reduction rate (0.38mmoll -1 day -1 ) with methane as sole electron donor, measured in the absence of thiosulfate in the BTF. Therefore, a BTF fed with thiosulfate as electron acceptor can be used to enrich SRB of the DSS group and activate the inoculum for anaerobic oxidation of methane coupled to sulfate reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Promotion effect of H2 on ethanol oxidation and NOx reduction with ethanol over Ag/Al2O3 catalyst.

Science.gov (United States)

Yu, Yunbo; Li, Yi; Zhang, Xiuli; Deng, Hua; He, Hong; Li, Yuyang

2015-01-06

The catalytic partial oxidation of ethanol and selective catalytic reduction of NOx with ethanol (ethanol-SCR) over Ag/Al2O3 were studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The intermediates were identified by PIMS and their photoionization efficiency (PIE) spectra. The results indicate that H2 promotes the partial oxidation of ethanol to acetaldehyde over Ag/Al2O3, while the simultaneously occurring processes of dehydration and dehydrogenation were inhibited. H2 addition favors the formation of ammonia during ethanol-SCR over Ag/Al2O3, the occurrence of which creates an effective pathway for NOx reduction by direct reaction with NH3. Simultaneously, the enhancement of the formation of ammonia benefits its reaction with surface enolic species, resulting in producing -NCO species again, leading to enhancement of ethanol-SCR over Ag/Al2O3 by H2. Using VUV-PIMS, the reactive vinyloxy radical was observed in the gas phase during the NOx reduction by ethanol for the first time, particularly in the presence of H2. Identification of such a reaction occurring in the gas phase may be crucial for understanding the reaction pathway of HC-SCR over Ag/Al2O3.

Investigation of the direct and indirect electrochemical oxidation of hydrazine in nitric acid medium on platinum

International Nuclear Information System (INIS)

Cames, B.

1997-01-01

In nuclear fuel processing by the PUREX process, the purification of plutonium in nitric acid medium requires the oxidation of Pu(III) to Pu(IV), and of hydrazinium nitrate to nitrogen. The study helped to characterize the electrochemical behavior of the oxidation of hydrazinium nitrate and the reduction of nitric acid to nitrous acid, a compound which can chemically oxidize hydrazinium nitrate and Pu(III). Electro-analytical studies on polycrystalline platinum showed that hydrazine is oxidized in two potential zones, which depend on the surface texture of the platinum anode. Electrolysis in separate compartments, carried out in medium-acid media (2 and 4 mo/l) in the potential zone where these processes take place, showed that, at 0.9 V/ECS, the hydrazine oxidation reactions involved are: a four-electron process (75 %) with nitrogen formation and a one-electron process (25 %) with formation of nitrogen and ammonium ion. By contrast, electrolysis carried out at 0.65 V/ECS (with reactivation of the electrode at - 0.2 V/ECS to remove the poison from the platinum) allowed the selective oxidation of hydrazine to nitrogen by the four-electron reaction. Nitric acid can only be reduced to nitrous acid in the absence of hydrazine. For medium-acid media (≤ 6 mol/l), this reaction takes place at potentials below - 0.2 V/ECS. However, the production rate of nitrous acid (partial order 0 with respect to nitric acid) is very low compared with the values obtained for strongly-acid media (6 to 10 mol/l) at the potential of - 0.1 V/ECS. Note that, in concentrated nitric medium, the selectivity of the reduction reaction is 47 to 85 % for nitrous acid, depending on the nitric acid concentration (6 to 10 mol/l) and the potential imposed (- 0.1 ≤ E ≤ 0.6 V/ECS). A kinetic study helped to determine the hydrazine oxidation rates as a function of the operating conditions. In all cases, the reaction rate is of partial order 0 with respect to hydrazine. These studies accordingly

Opportunities and challenges in green house gases reduction using high pressure direct injection of natural gas

International Nuclear Information System (INIS)

Ouellette, P.

2001-01-01

In an effort to reduce Greenhouse Gases, Westport Innovations is developing a high pressure direct injection (HPDI) technology for gaseous fuels. This technology adapts the diesel cycle for gaseous fuels, since the diesel cycle provides high efficiency, high low-speed torque, fast transient capabilities and reliability. Because of their high efficiency, diesels are very favorable from a Greenhouse Gas (GHG) point of view, however they remain challenged by high nitrogen oxides (NOx) and particulate matter (PM) emissions. When directly injecting natural gas, NOx and PM emissions can be reduced by approximately 50% while maintaining the performance of the diesel engine. This allows the use of abundant and historically cheaper natural gas. Because of its lower carbon content per unit energy, natural gas also offers further GHG reduction over the diesel if the efficiency is preserved and if methane emissions are low. This paper discusses development efforts at Westport for several applications including on-highway trucks, light-duty delivery trucks and power generation

A catalytic wet oxidation process for mixed waste volume reduction/recycling

International Nuclear Information System (INIS)

Dhooge, Patrick M.

1992-01-01

Mixed wastes have presented a challenge to treatment and destruction technologies. A recently developed catalytic wet oxidation method has promising characteristics for volume reduction and recycling of mixed wastes. The process utilizes iron (III) as an oxidant in the presence of homogeneous cocatalysts which increase organics' oxidation rates and the rate of oxidation of iron (II) by oxygen. The reaction is conducted in an aqueous mineral acid solution at temperatures of 373 - 573 deg K. The mineral acid should solvate a number of heavy metals, including U and Pu. Studies of reaction rates show that the process can oxidize a wide range of organic compounds including aromatics and chlorinated hydrocarbons. Rate constants in the range of 10 -7 to 10 -4 sec -1 , depending on the cocatalyst, acidity, type of anions, type of organic, temperature, and time. Activation energies ranged from 25. to 32. KJ/mole. Preliminary measurements of the extent of oxidation which could be obtained ranged from 80% for trichloroethylene to 99.8% for 1,2,4-trimethylbenzene; evidence was obtained that absorption by the fluorocarbon liners of the reaction bombs allowed some of the organics to escape exposure to the catalyst solution. The results indicate that complete oxidation of the organics used here, and presumably many others, can be achieved. (author)

Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

Energy Technology Data Exchange (ETDEWEB)

Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA; Co-Principal Investigator: Jeff Terry, Illinois Institute of Technology, Chicago, IL

2008-05-12

There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of the most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H{sub 2}S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H{sub 2}S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H{sub 2}S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H{sub 2}S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The

Reduction of Mn-oxides by ferrous iron in a flow system: column experiment and reactive transport modeling

DEFF Research Database (Denmark)

Postma, Diederik Jan; Appelo, C. A. J.

2000-01-01

Cl2 solution into the column, an ion distribution pattern was observed in the effluent that suggests the formation of separate reaction fronts for Mn(III)-oxide and Mn(IV)-oxide travelling at different velocities through the column. At the proximal reaction front, Fe21 reacts with MnO2 producing Fe......The reduction of Mn-oxide by Fe21 was studied in column experiments, using a column filled with natural Mn-oxide coated sand. Analysis of the Mn-oxide indicated the presence of both Mn(III) and Mn(IV) in the Mn-oxide. The initial exchange capacity of the column was determined by displacement...... of adsorbed Ca21 with Mg21. Subsequently a FeCl2 solution was injected into the column causing the reduction of the Mn-oxide and the precipitation of Fe(OH)3. Finally the exchange capacity of the column containing newly formed Fe(OH)3 was determined by injection of a KBr solution. During injection of the Fe...

Photoactivity of N-doped ZnO nanoparticles in oxidative and reductive reactions

Science.gov (United States)

Oliveira, Jéssica A.; Nogueira, André E.; Gonçalves, Maria C. P.; Paris, Elaine C.; Ribeiro, Caue; Poirier, Gael Y.; Giraldi, Tania R.

2018-03-01

N-doped ZnO is a prospective material for photocatalytic reactions. However, only oxidative paths are well investigated in the literature. This paper describes a comparative study about ZnO and ZnO:N potential for oxidative and reductive reactions, probed by rhodamine B dye photodegradation and CO2 photoreduction. The materials were prepared by the polymeric precursor method, using urea as a nitrogen source, and different heat treatments were used to observe their effects on surface decontamination, crystallinity, particle sizes and shapes, and photocatalytic performance. ZnO and ZnO:N presented a wurtzite crystalline structure and nanometric-scale particles. Samples submitted to higher temperatures showed lower specific surface areas, but higher crystallinity and lower contents of species adsorbed on their surfaces. On the other hand, the photocatalysts annealed in shorter times presented smaller crystallite sizes and lower crystallinity. These factors influenced the photoactivity in both conditions, i.e., oxidation and reduction reactions, under the ultraviolet and visible light, indicating that structural factors influenced the adequate charge separation and consequent photocatalytic activity since the as-synthesized samples were versatile photocatalysts in both redox reactions.

Topotactic reduction yielding black titanium oxide nanostructures as metallic electronic conductors.

Science.gov (United States)

Tominaka, Satoshi

2012-10-01

Detailed analyses of reduced, single crystal, rutile-type TiO(2) via high-resolution transmission electron microscopy (TEM) are reported which reveal that the reduction proceeds topotactically via interstitial diffusion of Ti ions at low temperature, around 350 °C. This important finding encouraged the production of various nanostructured reduced titanium oxides from TiO(2) precursors with morphology retention, and in the process, the synthesis of black titanium oxide nanorods using TiO(2) nanorods was demonstrated. Interestingly, as opposed to the semiconductive behavior of Ti(2)O(3) synthesized at high temperature, topotactically synthesized Ti(2)O(3) exhibits metallic electrical resistance, and the value at room temperature is quite low (topotactically synthesized Ti(2)O(3). This work shows that topotactically reduced titanium oxides can have fascinating properties as well as nanostructures.

Preparation of Highly Dispersed Reduced Graphene Oxide Decorated with Chitosan Oligosaccharide as Electrode Material for Enhancing the Direct Electron Transfer of Escherichia coli.

Science.gov (United States)

Luo, Zhimin; Yang, Dongliang; Qi, Guangqin; Yuwen, Lihui; Zhang, Yuqian; Weng, Lixing; Wang, Lianhui; Huang, Wei

2015-04-29

Water-dispersed reduced graphene oxide/chitosan oligosaccharide (RGO-CTSO) was prepared by chemical reduction of graphene oxide and synchronous functionalization with biocompatible chitosan oligosaccharide (CTSO). ζ potential measurement indicated that RGO-CTSO was highly stable in the acidic aqueous solution. RGO-CTSO was used to modify glassy carbon electrode (GCE) as the growth template of Escherichia coli (E. coli). The enhanced direct electron transfer of E. coli on the RGO-CTSO-modified GCE was studied by cyclic voltammetry. Compared with GCE or RGO-modified GCE, RGO-CTSO-modified GCE was more suitable for the adhesion growth of E. coli to improve direct electron transfer. The biocompatibility and versatility of RGO-CTSO made it promising for use as an anode material in microbial fuel cells.

Heterogeneous reduction of nitric oxide on synthetic coal chars

Energy Technology Data Exchange (ETDEWEB)

C. Pevida; A. Arenillas; F. Rubiera; J.J. Pis [Instituto Nacional del Carbon (CSIC), Oviedo (Spain)

2005-12-01

Model compounds, with a controlled heteroatoms content and well-defined functionalities, were used to study the release of nitrogen compounds from char combustion. In the present work, the mechanisms involved in NO-char heterogeneous reduction were studied with a synthetic coal (SC) char as carbon source. Another synthetic char (SN) without any nitrogen in its composition was also employed in these studies. Temperature programmed reduction (TPR) tests with a gas mixture of 400 ppm NO in argon and with isotopically labelled nitric oxide, {sup 15}NO (500 ppm {sup 15}NO in argon), were carried out. The gases produced were quantitatively determined by means of MS and FTIR analysers. Under the conditions of this work the main products of the NO-C reaction were found to be N{sub 2} and CO{sub 2}. The main path of reaction involves the formation of surface nitrogen compounds that afterwards react with nitrogen from the reactive gas to form N{sub 2}. It was observed that fuel-N also participates in the overall heterogeneous reduction reaction, although to a lesser extent.

Simulation of uranium oxides reduction kinetics by hydrogen. Reactivities of germination and growth; Modelisation de la cinetique de reduction d`oxydes d`uranium par l`hydrogene. Reactivites de germination et de croissance

Energy Technology Data Exchange (ETDEWEB)

Brun, C

1997-12-04

The aim of this work is to simulate the reduction by hydrogen of the tri-uranium octo-oxide U{sub 3}O{sub 8} (obtained by uranium trioxide calcination) into uranium dioxide. The kinetics curves have been obtained by thermal gravimetric analysis, the hydrogen and steam pressures being defined. The geometrical modeling which has allowed to explain the trend of the kinetics curves and of the velocity curves is an anisotropic germination-growth modeling. The powder is supposed to be formed of spherical grains with the same radius. The germs of the new UO{sub 2} phase appear at the surface of the U{sub 3}O{sub 8} grains with a specific germination frequency. The growth reactivity is anisotropic and is very large in the tangential direction to the grains surface. Then, the uranium dioxide growths inside the grain and the limiting step is the grain surface. The variations of the growth reactivity and of the germination specific frequency in terms of the gases partial pressures and of the temperature have been explained by two different mechanisms. The limiting step of the growth mechanism is the desorption of water in the uranium dioxide surface. Concerning the germination mechanism the limiting step is a water desorption too but in the tri-uranium octo-oxide surface. The same geometrical modeling and the same germination and growth mechanisms have been applied to the reduction of a tri-uranium octo-oxide obtained by calcination of hydrated uranium trioxide. The values of the germination specific frequency of this solid are nevertheless weaker than those of the solid obtained by direct calcination of the uranium trioxide. (O.M.) 45 refs.

Reduction of antibiotic resistance genes in municipal wastewater effluent by advanced oxidation processes

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yingying; Zhuang, Yao; Geng, Jinju, E-mail: jjgeng@nju.edu.cn; Ren, Hongqiang; Xu, Ke; Ding, Lili

2016-04-15

This study investigated the reduction of antibiotic resistance genes (ARGs), intI1 and 16S rRNA genes, by advanced oxidation processes (AOPs), namely Fenton oxidation (Fe{sup 2+}/H{sub 2}O{sub 2}) and UV/H{sub 2}O{sub 2} process. The ARGs include sul1, tetX, and tetG from municipal wastewater effluent. The results indicated that the Fenton oxidation and UV/H{sub 2}O{sub 2} process could reduce selected ARGs effectively. Oxidation by the Fenton process was slightly better than that of the UV/H{sub 2}O{sub 2} method. Particularly, for the Fenton oxidation, under the optimal condition wherein Fe{sup 2+}/H{sub 2}O{sub 2} had a molar ratio of 0.1 and a H{sub 2}O{sub 2} concentration of 0.01 mol L{sup −1} with a pH of 3.0 and reaction time of 2 h, 2.58–3.79 logs of target genes were removed. Under the initial effluent pH condition (pH = 7.0), the removal was 2.26–3.35 logs. For the UV/H{sub 2}O{sub 2} process, when the pH was 3.5 with a H{sub 2}O{sub 2} concentration of 0.01 mol L{sup −1} accompanied by 30 min of UV irradiation, all ARGs could achieve a reduction of 2.8–3.5 logs, and 1.55–2.32 logs at a pH of 7.0. The Fenton oxidation and UV/H{sub 2}O{sub 2} process followed the first-order reaction kinetic model. The removal of target genes was affected by many parameters, including initial Fe{sup 2+}/H{sub 2}O{sub 2} molar ratios, H{sub 2}O{sub 2} concentration, solution pH, and reaction time. Among these factors, reagent concentrations and pH values are the most important factors during AOPs. - Highlights: • AOPs including Fenton oxidation and UV/H{sub 2}O{sub 2} process could reduce ARGs effectively. • Fenton oxidation is slightly more effective than UV/H{sub 2}O{sub 2} process in ARG reduction. • Removal of ARGs by AOPs follows the first-order reaction kinetic model. • Selected ARGs and 16S rRNA genes exhibit similar change trends during AOPs.

In situ oxidation and reduction of triangular nickel nanoplates via environmental transmission electron microscopy

KAUST Repository

LAGROW, A.P.

2017-08-29

Understanding the oxidation and reduction mechanisms of transition metals, such as nickel (Ni), is important for their use in industrial applications of catalysis. A powerful technique for investigating the redox reactive species is in situ environmental transmission electron microscopy (ETEM), where oxidation and reduction can be tracked in real time. One particular difficulty in understanding the underlying reactions is understanding the underlying morphology of the starting structure in a reaction, in particular the defects contained in the material, and the exposed surface facets. Here-in, we use a colloidal nanoparticle synthesis in a continuous flow reactor to form nanoplates of nickel coated with oleylamine as a capping agent. We utilise an in situ heating procedure at 300 °C in vacuum to remove the oleylamine ligands, and then oxidise the Ni nanoparticles at 25 °C with 2 Pa oxygen, and follow the nanoparticles initial oxidation. After that, the nanoparticles are oxidised at 200 and 300 °C, making the size of the oxide shell increase to ∼4 nm. The oxide shell could be reduced under 2 Pa hydrogen at 500 °C to its initial size of ∼1 nm. High temperature oxidation encouraged the nanoparticles to form pure NiO nanoparticles, which occurred via the Kirkendall effect leading to hollowing and void formation.

In situ oxidation and reduction of triangular nickel nanoplates via environmental transmission electron microscopy

KAUST Repository

LAGROW, A.P.; AlYami, Noktan; LLOYD, D.C.; Bakr, Osman; BOYES, E.D.; GAI, P.L.

2017-01-01

Understanding the oxidation and reduction mechanisms of transition metals, such as nickel (Ni), is important for their use in industrial applications of catalysis. A powerful technique for investigating the redox reactive species is in situ environmental transmission electron microscopy (ETEM), where oxidation and reduction can be tracked in real time. One particular difficulty in understanding the underlying reactions is understanding the underlying morphology of the starting structure in a reaction, in particular the defects contained in the material, and the exposed surface facets. Here-in, we use a colloidal nanoparticle synthesis in a continuous flow reactor to form nanoplates of nickel coated with oleylamine as a capping agent. We utilise an in situ heating procedure at 300 °C in vacuum to remove the oleylamine ligands, and then oxidise the Ni nanoparticles at 25 °C with 2 Pa oxygen, and follow the nanoparticles initial oxidation. After that, the nanoparticles are oxidised at 200 and 300 °C, making the size of the oxide shell increase to ∼4 nm. The oxide shell could be reduced under 2 Pa hydrogen at 500 °C to its initial size of ∼1 nm. High temperature oxidation encouraged the nanoparticles to form pure NiO nanoparticles, which occurred via the Kirkendall effect leading to hollowing and void formation.

Photochemical modelling of photo-oxidant levels over the Swiss plateau and emission reduction scenarios

International Nuclear Information System (INIS)

Rosselet, C.M.; Kerr, J.A.

1993-05-01

During summertime high pressure conditions, high photo-oxidant (O 3 , H 2 O 2 , PAN and others) levels are frequently observed in the planetary boundary layer in central Europe. It is well known that close to the earth's surface ozone is formed by complex reactions involving VOC, NO x , and sunlight. Substantial reductions of both precursors are needed to reduce photo-oxidant levels. In this context the reductions of the abundance of the precursors and the variation of their ratios is of great importance. Here we report model calculations from the Harwell Photochemical Trajectory Model of the levels of O 3 , H 2 O 2 and PAN along a trajectory over the Swiss Plateau from Lake Constance to Lake Geneva. These calculations are in satisfactory agreement with measurements made during the intensive observation period of the research program POLLUMET (Pollution and Meteorology in Switzerland). Sensitivity calculations of emission reduction scenarios indicate that on the Swiss Plateau the ozone production may be mainly NO x -limited; under conditions where the CO levels are closer to the upper limit within the range (120-600 ppbv). The calculated peak ozone level reduction caused by an exclusive NO x -emission reduction is about three times larger than that caused by an exclusive VOC reduction. The combined reduction of all precursor compounds is the most efficient strategy, although it is only marginally more efficient than the NO x -reduction scenario alone. (author) figs., tabs., 75 refs

Metal porphyrin intercalated reduced graphene oxide nanocomposite utilized for electrocatalytic oxygen reduction

Directory of Open Access Journals (Sweden)

Mingyan Wang

2017-07-01

Full Text Available In this paper, we report a simple and facile self-assembly method to successfully fabricate cationic metal porphyrin –MtTMPyP (Mt= Cobalt (II, Manganese (III, or Iron (III; TMPyP = 5, 10, 15, 20-tetrakis (N-methylpyridinium-4-yl porphyrin intercalated into the layer of graphene oxide (GO by the cooperative effects of electrostatic and π–π stacking interaction between positively charged metal porphyrin and negatively charged GO sheets. Followed by reduction with hydrazine vapor, a series of novel 2D MtTMPyP/rGOn were fabricated. The as-prepared 2D hybrids were fully characterized and tested as non-noble metal catalysts for oxygen reduction reaction (ORR in an alkaline medium. The MtTMPyP/rGOn hybrids, especially CoTMPyP/rGO5, demonstrated an improved electrocatalytic activity for ORR and a number of exchanged electrons close to 4-electron reaction, increased stability and excellent tolerance to methanol, showing a potential alternative catalyst for ORR in fuel cells and air batteries. Keywords: Metal porphyrin, Reduced graphene oxide, Intercalation, Oxygen reduction reaction, Catalyst

Metallization of uranium oxide powders by lithium reduction

International Nuclear Information System (INIS)

Kim, I. S.; Seo, J. S.; Oh, S. C.; Hong, S. S.; Lee, W. K.

2002-01-01

Laboratory scale experiments on the reduction of uranium oxide powders into metal by lithium were performed in order to determine the equipment setup and optimum operation conditions. The method of filtration using the porous magnesia filter was introduced to recover uranium metal powders produced. Based on the laboratory scale experimental results, mock-up scale (20 kg U/batch) metallizer was designed and made. The applicability to the metallization process was estimated with respect to the thermal stability of the porous magnesia filter in the high temperature molten salt, the filtration of the fine uranium metal powders, and the operability of the equipment

A Study on the Electrolytic Reduction Mechanism of Uranium Oxide in a LiCl-Li2O Molten Salt

International Nuclear Information System (INIS)

Oh, Seung Chul; Hur, Jin Mok; Seo, Chung Seok; Park, Seong Won

2003-01-01

This study proposed a new electrolytic reduction technology that is based on the integration of simultaneous uranium oxide metallization and Li 2 O electrowinning. In this electrolytic reduction reaction, electrolytically reduced Li deposits on cathode and simultaneously reacts with uranium oxides to produce uranium metal showing more than 99% conversion. For the verification of process feasibility, the experiments to obtain basic data on the metallization of uranium oxide, investigation of reaction mechanism, the characteristics of closed recycle of Li 2 O and mass transfer were carried out. This evolutionary electrolytic reduction technology would give benefits over the conventional Li-reduction process improving economic viability such as: avoidance of handling of chemically active Li-LiCl molten salt increase of metallization yield, and simplification of process.

Study on the oxidation and reduction of tungsten surface for sub-50 nm patterning process

Energy Technology Data Exchange (ETDEWEB)

Kim, Jong Kyu; Nam, Seok Woo; Cho, Sung Il; Jhon, Myung S.; Min, Kyung Suk; Kim, Chan Kyu; Jung, Ho Bum; Yeom, Geun Young [Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711, South Korea and Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711 (Korea, Republic of); Department of Chemical Engineering and Data Storage Systems Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)

2012-11-15

The oxidation characteristics of tungsten line pattern during the carbon-based mask-layer removal process using oxygen plasmas have been investigated for sub-50 nm patterning processes, in addition to the reduction characteristics of the WO{sub x} layer formed on the tungsten line surface using hydrogen plasmas. The surface oxidation of tungsten lines during the mask layer removal process could be minimized by using low-temperature (300 K) plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WO{sub x} on the tungsten line could be decreased to 25% compared to results from high-temperature processing. The WO{sub x} layer could also be completely removed at a low temperature of 300 K using a hydrogen plasma by supplying bias power to the tungsten substrate to provide a activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40-nm-CD device processing, the complete removal of WO{sub x} formed on the sidewall of tungsten line could be observed.

Pilot-scale equipment development for lithium-based reduction of spent oxide fuel

International Nuclear Information System (INIS)

Herrmann, S. D.

1998-01-01

An integral function of the electrometallurgical conditioning of DOE spent nuclear fuel is the standardization of waste forms. Argonne National Laboratory (ANL) has developed and is presently demonstrating the electrometallurgical conditioning of sodium-bonded metal fuel from Experimental Breeder Reactor II, resulting in uranium, ceramic waste, and metal waste forms. Engineering studies are underway at ANL in support of pilot-scale equipment development, which would precondition irradiated oxide fuel and likewise demonstrate the application of electrometallurgical conditioning to such non-metallic fuels. This paper highlights the integration of proposed spent oxide fuel conditioning with existing electrometallurgical processes. Additionally, technical bases for engineering activities to support a scale up of an oxide reduction process are described

Standard test method for measurement of oxidation-reduction potential (ORP) of soil

CERN Document Server

American Society for Testing and Materials. Philadelphia

2009-01-01

1.1 This test method covers a procedure and related test equipment for measuring oxidation-reduction potential (ORP) of soil samples removed from the ground. 1.2 The procedure in Section 9 is appropriate for field and laboratory measurements. 1.3 Accurate measurement of oxidation-reduction potential aids in the analysis of soil corrosivity and its impact on buried metallic structure corrosion rates. 1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

Science.gov (United States)

Zhu, Yimin; Zelenay, Piotr

2006-03-21

A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

Thermogravimetric, Calorimetric, and Structural Studies of the Co3 O4 /CoO Oxidation/Reduction Reaction

Science.gov (United States)

Unruh, Karl; Cichocki, Ronald; Kelly, Brian; Poirier, Gerald

2015-03-01

To better assess the potential of cobalt oxide for thermal energy storage (TES), the Co3O4/CoO oxidation/reduction reaction has been studied by thermogravimetric (TGA), calorimetric (DSC), and x-ray diffraction (XRD) measurements in N2 and atmospheric air environments. TGA measurements showed an abrupt mass loss of about 6.6% in both N2 and air, consistent with the stoichiometric reduction of Co3O4 to CoO and structural measurements. The onset temperature of the reduction of Co3O4 in air was only weakly dependent on the sample heating rate and occurred at about 910 °C. The onset temperature for the oxidation of CoO varied between about 850 and 875 °C for cooling rates between 1 and 20 °C/min, but complete re-conversion to Co3O4 could only be achieved at the slowest cooling rates. Due to the dependence of the rate constant on the oxygen partial pressure, the oxidation of Co3O4 in a N2 environment occurred at temperatures between about 775 and 825 °C for heating rates between 1 and 20 °C/min and no subsequent re-oxidation of the reduced Co3O4 was observed on cooling to room temperature. In conjunction with a measured transition heat of about 600 J/g of Co3O4, these measurements indicate that cobalt oxide is a viable TES material.

Gold Decorated Graphene for Rapid Dye Reduction and Efficient Electro Catalytic Oxidation of Ethanol

Science.gov (United States)

Siddhardha, R. S.; Kumar v, Lakshman; Kaniyoor, A.; Podila, R.; Kumar, V. S.; Venkataramaniah, K.; Ramaprabhu, S.; Rao, A.; Ramamurthy, S. S.; Clemson University Team; Sri Sathya Sai Institute of Higher Learning Team; IITMadras Team

2013-03-01

A well known disadvantage in fabrication of metal-graphene composite is the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. Here, we demonstrate a novel one pot synthesis of gold nanoparticles (AuNPs) by laser ablation of gold strip and simultaneous decoration of these on functionalized graphene derivatives. Not only the impregnation of AuNPs was linker free, but also the synthesis by itself was surfactant free. This resulted in in-situ decoration of pristine AuNPs on functionalized graphene derivatives. These materials were well characterized and tested for catalytic applications pertaining to dye reduction and electrooxidation. The catalytic reduction rates are 1.4 x 102 and 9.4x102 times faster for Rhodamine B and Methylene Blue dyes respectively, compared to earlier reports. The enhanced rate involves synergistic interplay of electronic relay between AuNPs and the dye, also charge transfer between the graphene system and dye. In addition, the onset potential for ethanol oxidation was found to be more negative ~ 100 mV, an indication of its promising application in direct ethanol fuel cells.

Reduction of metal oxides in metal carbide fusion superheated with plasma

Energy Technology Data Exchange (ETDEWEB)

Hedai, L

1981-01-01

A significant part of metals is capable of binding a high quantity of carbon in the form of carbide. The carbide fusion produced as a result of smelting and superheating, metal carbides with the use of plasma might be a medium to be utilized for the reduction of different metal oxides, whilst also the original carbide structure of the metal carbides will be reduced to metallic structure. The experiments conducted by making use of plasma equipment, of 20, 55 and 100 kW performances are described. On the basis of the results of the experiments performed, the following statements are to be made. The oxide reductions taking place in the metal carbide fusion might also be carried out in open-hearth furnaces, because reducing atmosphere is not necessitated during this procedure. The quantity of energy required is basically defined by the energy needed for smelting and superheating the metal carbide. The method for producing the metal described may be mainly applied for the allied production of high-purity steels as well as for that of ferro-alloys.

Reduction of excess sludge production in sequencing batch reactor through incorporation of chlorine dioxide oxidation

International Nuclear Information System (INIS)

Wang Guanghua; Sui Jun; Shen Huishan; Liang Shukun; He Xiangming; Zhang Minju; Xie Yizhong; Li Lingyun; Hu Yongyou

2011-01-01

In this study, chlorine dioxide (ClO 2 ) instead of chlorine (Cl 2 ) was proposed to minimize the formation of chlorine-based by-products and was incorporated into a sequencing batch reactor (SBR) for excess sludge reduction. The results showed that the sludge disintegrability of ClO 2 was excellent. The waste activated sludge at an initial concentration of 15 g MLSS/L was rapidly reduced by 36% using ClO 2 doses of 10 mg ClO 2 /g dry sludge which was much lower than that obtained using Cl 2 based on similar sludge reduction efficiency. Maximum sludge disintegration was achieved at 10 mg ClO 2 /g dry sludge for 40 min. ClO 2 oxidation can be successfully incorporated into a SBR for excess sludge reduction without significantly harming the bioreactor performance. The incorporation of ClO 2 oxidation resulted in a 58% reduction in excess sludge production, and the quality of the effluent was not significantly affected.

GAMMA RADIATION INTERACTS WITH MELANIN TO ALTER ITS OXIDATION-REDUCTION POTENTIAL AND RESULTS IN ELECTRIC CURRENT PRODUCTION

Energy Technology Data Exchange (ETDEWEB)

Turick, C.; Ekechukwu, A.; Milliken, C.

2011-05-17

The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.

High aspect ratio silicon nanomoulds for UV embossing fabricated by directional thermal oxidation using an oxidation mask

International Nuclear Information System (INIS)

Chen, L Q; Chan-Park, Mary B; Yan, Y H; Zhang Qing; Li, C M; Zhang Jun

2007-01-01

Nanomoulding is simple and economical but moulds with nanoscale features are usually prohibitively expensive to fabricate because nanolithographic techniques are mostly serial and time-consuming for large-area patterning. This paper describes a novel, simple and inexpensive parallel technique for fabricating nanoscale pattern moulds by silicon etching followed by thermal oxidation. The mask pattern can be made by direct photolithography or photolithography followed by metal overetching for submicron- and nanoscale features, respectively. To successfully make nanoscale channels having a post-oxidation cross-sectional shape similar to that of the original channel, an oxidation mask to promote unidirectional (specifically horizontal) oxide growth is found to be essential. A silicon nitride or metal mask layer prevents vertical oxidation of the Si directly beneath it. Without this mask, rectangular channels become smaller but are V-shaped after oxidation. By controlling the silicon etch depth and oxidation time, moulds with high aspect ratio channels having widths ranging from 500 to 50 nm and smaller can be obtained. The nanomould, when passivated with a Teflon-like layer, can be used for first-generation replication using ultraviolet (UV) nanoembossing and second-generation replication in other materials, such as polydimethylsiloxane (PDMS). The PDMS stamp, which was subsequently coated with Au, was used for transfer printing of Au electrodes with a 600 nm gap which will find applications in plastics nanoelectronics

Self-Driven Bioelectrochemical Mineralization of Azobenzene by Coupling Cathodic Reduction with Anodic Intermediate Oxidation

International Nuclear Information System (INIS)

Liu, Rong-Hua; Li, Wen-Wei; Sheng, Guo-Ping; Tong, Zhong-Hua; Lam, Michael Hon-Wah; Yu, Han-Qing

2015-01-01

Highlights: • Azobenzene was reduced to aniline at the cathode of an acetate-fueled MFC. • Aniline was degraded at the bioanode of a single-chamber MFC. • Cathodic reduction of azobenzene was coupled with anodic oxidation of aniline. • Self-driven, complete mineralization of azobenzene in an MFC was accomplished. - Abstract: Bioelectrochemical systems have been intensively studied as a promising technology for wastewater treatment and environment remediation. Coupling of the anodic and cathodic electrochemical reactions allows an enhanced degradation of recalcitrant organics, but external power supply is usually needed to overcome the thermodynamic barrier. In this work, we report a self-driven degradation of azobenzene in a microbial fuel cell (MFC), where the cathodic reduction of azobenzene was effectively coupled with the anodic oxidation of its reduction degradation intermediate (i.e., aniline). The anodic degradation rate of aniline, as the sole carbon source, was significantly higher than that under open-circuit conditions, suggesting a considerable bioelectrochemical oxidation of aniline. Output voltages up to 8 mV were obtained in the MFC. However, a shift of cathodic electron acceptor from oxygen to azobenzene resulted in a decreased aniline degradation rate and output voltage. The present work may provide valuable implications for development of sustainable bioelectrochemical technologies for environmental remediation

Periplasmic Cytochrome c(3) of Desulfovibrio vulgaris Is Directly Involved in H2-Mediated Metal but Not Sulfate Reduction

International Nuclear Information System (INIS)

Elias, Dwayne A.; Suflita, Joseph M.; McInerney, Michael J.; Krumholz, Lee R.

2004-01-01

Kinetic parameters and the role of cytochrome c3 in sulfate, Fe(III), and U(VI) reduction were investigated in Desulfovibrio vulgaris Hildenborough. While sulfate reduction followed Michaelis-Menten kinetics (Km 220 uM), loss of Fe(III) and U(VI) was first-order at all concentrations tested. Initial reduction rates of all electron acceptors were similar for cells grown with H2 and sulfate, while cultures grown using lactate and sulfate had similar rates of metal loss but lower sulfate reduction activities. The similarities in metal, but not sulfate, reduction with H2 and lactate suggest divergent pathways. Respiration assays and reduced minus oxidized spectra were carried out to determine c-type cytochrome involvement in electron acceptor reduction. c-type cytochrome oxidation was immediate with Fe(III) and U(VI) in the presence of H2, lactate, or pyruvate. Sulfidogenesis occurred with all three electron donors and effectively oxidized the c-type cytochrome in lactate or pyruvate-reduced, but not H2-reduced cells. Correspondingly, electron acceptor competition assays with lactate or pyruvate as electron donors showed that Fe(III) inhibited U(VI) reduction, and U(VI) inhibited sulfate loss. However, sulfate reduction was slowed but not halted when H2 was the electron donor in the presence of Fe(III) or U(VI). U(VI) loss was still impeded by Fe(III) when H2 was used. Hence, we propose a modified pathway for the reduction of sulfate, Fe(III), and U(VI) which helps explain why these bacteria cannot grow using these metals. We further propose that cytochrome c3 is an electron carrier involved in lactate and pyruvate oxidation and is the reductase for alternate electron acceptors with higher redox potentials than sulfate

Reduction of nickel oxide particles by hydrogen studied in an environmental TEM

DEFF Research Database (Denmark)

Jeangros, Q.; Hansen, Thomas Willum; Wagner, Jakob Birkedal

2013-01-01

In situ reduction of nickel oxide (NiO) particles is performed under 1.3 mbar of hydrogen gas (H2) in an environmental transmission electron microscope (ETEM). Images, diffraction patterns and electron energy-loss spectra (EELS) are acquired to monitor the structural and chemical evolution of the...

Influence of Short-time Oxidation on Corrosion Properties of Directionally Solidified Superalloys with Different Orientations

Directory of Open Access Journals (Sweden)

MA Luo-ning

2016-07-01

Full Text Available In order to investigate the corrosion performance on intersecting and longitudinal surfaces of unoxidized and oxidized directionally solidified superalloys, Ni-base directionally solidified superalloy DZ125 and Co-base directionally solidified superalloy DZ40M were selected. Oxidation behavior on both alloys with different orientations was investigated at 1050℃ at different times, simulating the oxidation process of vanes or blades in service; subsequent electrochemical performance in 3.5%NaCl aqueous solution was studied on two orientations of unoxidized and oxidized alloys, simulating the corrosion process of superalloy during downtime. The results show that grain boundaries and sub-boundaries of directionally solidified superalloys are susceptible to corrosion and thus longitudinal surface with lower area fraction of grain boundaries has higher corrosion resistance. Compared to intersecting surface of alloys, the structure of grain boundaries of longitudinal surface is less conducive to diffusion and thus the oxidation rate on longitudinal surface is lower. Formation of oxide layers on alloys after short-time oxidation provides protective effect and enhances the corrosion resistance.

Novel mode of microbial energy metabolism: organic carbon oxidation coupled to dissimilatory reduction of iron or manganese.

Science.gov (United States)

Lovley, D R; Phillips, E J

1988-06-01

A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments.

Selective catalytic reduction of nitric oxide with acetaldehyde over NaY zeolite catalyst in lean exhaust feed

International Nuclear Information System (INIS)

Schmieg, Steven J.; Cho, Byong K.; Oh, Se H.

2004-01-01

Steady-state selective catalytic reduction (SCR) of nitric oxide (NO) was investigated under simulated lean-burn conditions using acetaldehyde (CH 3 CHO) as the reductant. This work describes the influence of catalyst space velocity and the impact of nitric oxide, acetaldehyde, oxygen, sulfur dioxide, and water on NO x reduction activity over NaY zeolite catalyst. Results indicate that with sufficient catalyst volume 90% NO x conversion can be achieved at temperatures relevant to light-duty diesel exhaust (150-350C). Nitric oxide and acetaldehyde react to form N 2 , HCN, and CO 2 . Oxygen is necessary in the exhaust feed stream to oxidize NO to NO 2 over the catalyst prior to reduction, and water is required to prevent catalyst deactivation. Under conditions of excess acetaldehyde (C 1 :N>6:1) and low temperature ( x conversion is apparently very high; however, the NO x conversion steadily declines with time due to catalytic oxidation of some of the stored (adsorbed) NO to NO 2 , which can have a significant impact on steady-state NO x conversion. With 250ppm NO in the exhaust feed stream, maximum NO x conversion at 200C can be achieved with =400ppm of acetaldehyde, with higher acetaldehyde concentrations resulting in production of acetic acid and breakthrough of NO 2 causing lower NO x conversion levels. Less acetaldehyde is necessary at lower NO concentrations, while more acetaldehyde is required at higher temperatures. Sulfur in the exhaust feed stream as SO 2 can cause slow deactivation of the catalyst by poisoning the adsorption and subsequent reaction of nitric oxide and acetaldehyde, particularly at low temperature

Oxidation of mercury across selective catalytic reduction catalysts in coal-fired power plants

Energy Technology Data Exchange (ETDEWEB)

Constance L. Senior [Reaction Engineering International, Salt Lake City, UT (United States)

2006-01-15

A kinetic model for predicting the amount of mercury (Hg) oxidation across selective catalytic reduction (SCR) systems in coal-fired power plants was developed and tested. The model incorporated the effects of diffusion within the porous SCR catalyst and the competition between ammonia and Hg for active sites on the catalyst. Laboratory data on Hg oxidation in simulated flue gas and slipstream data on Hg oxidation in flue gas from power plants were modeled. The model provided good fits to the data for eight different catalysts, both plate and monolith, across a temperature range of 280-420{sup o}C, with space velocities varying from 1900 to 5000 hr{sup -1}. Space velocity, temperature, hydrochloric acid content of the flue gas, ratio of ammonia to nitric oxide, and catalyst design all affected Hg oxidation across the SCR catalyst. The model can be used to predict the impact of coal properties, catalyst design, and operating conditions on Hg oxidation across SCRs. 20 refs., 9 figs., 2 tabs.

Rare earth metal oxides as BH4-tolerance cathode electrocatalysts for direct borohydride fuel cells

Institute of Scientific and Technical Information of China (English)

NI Xuemin; WANG Yadong; GUO Feng; YAO Pei; PAN Mu

2012-01-01

Rare earth metal oxides (REMO) as cathode electrocatalysts in direct borohydride fuel cell (DBFC) were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH4- in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm2.The DBFC using Sm2O3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm2 was obtained at the cell voltage of 0.52 V.

Methanol electro-oxidation and direct methanol fuel cell using Pt/Rh and Pt/Ru/Rh alloy catalysts

International Nuclear Information System (INIS)

Choi, Jong-Ho; Park, Kyung-Won; Park, In-Su; Nam, Woo-Hyun; Sung, Yung-Eun

2004-01-01

Pt-based binary or ternary catalysts containing Rh for use as anodes in direct methanol fuel cells (DMFC) were synthesized by borohydride reduction method combined with freeze-drying. The resulting catalysts had a specific surface area of approximately 65-75 m 2 /g. X-ray diffraction (XRD) patterns indicated that the catalysts were well alloyed and the average size of alloy catalysts was confirmed by transmission electron microscopy (TEM). The Pt/Rh (2:1) and Pt/Ru/Rh (5:4:1) alloy catalysts showed better catalytic activities for methanol electro-oxidation than Pt or Pt/Ru (1:1), respectively

Kinetics of sodium borohydride direct oxidation and oxygen reduction in sodium hydroxide electrolyte - Part II. O-2 reduction

Czech Academy of Sciences Publication Activity Database

Chatenet, M.; Micoud, F.; Roche, I.; Chainet, E.; Vondrák, Jiří

2006-01-01

Roč. 51, č. 25 (2006), s. 5452-5458 ISSN 0013-4686 Institutional research plan: CEZ:AV0Z40320502 Keywords : oxygen reduction reaction selectivity * platinum * silver Subject RIV: CA - Inorganic Chemistry Impact factor: 2.955, year: 2006

Simultaneous Fe(III) reduction and ammonia oxidation process in Anammox sludge.

Science.gov (United States)

Li, Xiang; Huang, Yong; Liu, Heng-Wei; Wu, Chuan; Bi, Wei; Yuan, Yi; Liu, Xin

2018-02-01

In recent years, there have been a number of reports on the phenomenon in which ferric iron (Fe(III)) is reduced to ferrous iron [Fe(II)] in anaerobic environments, accompanied by simultaneous oxidation of ammonia to NO 2 - , NO 3 - , or N 2. However, studies on the relevant reaction characteristics and mechanisms are rare. Recently, in research on the effect of Fe(III) on the activity of Anammox sludge, excess ammonia oxidization has also been found. Hence, in the present study, Fe(III) was used to serve as the electron acceptor instead of NO 2 - , and the feasibility and characteristics of Anammox coupled to Fe(III) reduction (termed Feammox) were investigated. After 160days of cultivation, the conversion rate of ammonia in the reactor was above 80%, accompanied by the production of a large amount of NO 3 - and a small amount of NO 2 - . The total nitrogen removal rate was up to 71.8%. Furthermore, quantities of Fe(II) were detected in the sludge fluorescence in situ hybridization (FISH) and denaturated gradient gel electrophoresis (DGGE) analyses further revealed that in the sludge, some Anammox bacteria were retained, and some microbes were enriched during the acclimatization process. We thus deduced that in Anammox sludge, Fe(III) reduction takes place together with ammonia oxidation to NO 2 - and NO 3 - along with the Anammox process. Copyright © 2017. Published by Elsevier B.V.

Microbial reduction of graphene oxide by Escherichia coli: a green chemistry approach.

Science.gov (United States)

Gurunathan, Sangiliyandi; Han, Jae Woong; Eppakayala, Vasuki; Kim, Jin-Hoi

2013-02-01

Graphene and graphene related materials are an important area of research in recent years due to their unique properties. The extensive industrial application of graphene and related compounds has led researchers to devise novel and simple methods for the synthesis of high quality graphene. In this paper, we developed an environment friendly, cost effective, simple method and green approaches for the reduction of graphene oxide (GO) using Escherichia coli biomass. In biological method, we can avoid use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The biomass of E. coli reduces exfoliated GO to graphene at 37°C in an aqueous medium. The E. coli reduced graphene oxide (ERGO) was characterized with UV-visible absorption spectroscopy, particle analyzer, high resolution X-ray diffractometer, scanning electron microscopy and Raman spectroscopy. Besides the reduction potential, the biomass could also play an important role as stabilizing agent, in which synthesized graphene exhibited good stability in water. This method can open up the new avenue for preparing graphene in cost effective and large scale production. Our findings suggest that GO can be reduced by simple eco-friendly method by using E. coli biomass to produce water dispersible graphene. Copyright © 2012 Elsevier B.V. All rights reserved.

Photochemical reduction of uranyl nitrate

Energy Technology Data Exchange (ETDEWEB)

Duerksen, W.K.

1993-10-20

The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

Effect of plasma power on reduction of printable graphene oxide thin films on flexible substrates

Science.gov (United States)

Banerjee, Indrani; Mahapatra, Santosh K.; Pal, Chandana; Sharma, Ashwani K.; Ray, Asim K.

2018-05-01

Room temperature hydrogen plasma treatment on solution processed 300 nm graphene oxide (GO) films on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates has been performed by varying the plasma power between 20 W and 60 W at a constant exposure time of 30 min with a view to examining the effect of plasma power on reduction of GO. X-ray powder diffraction (XRD) and Raman spectroscopic studies show that high energy hydrogen species generated in the plasma assist fast exfoliation of the oxygenated functional groups present in the GO samples. Significant decrease in the optical band gap is observed from 4.1 eV for untreated samples to 0.5 eV for 60 W plasma treated samples. The conductivity of the films treated with 60 W plasma power is estimated to be six orders of magnitude greater than untreated GO films and this enhancement of conductivity on plasma reduction has been interpreted in terms of UV-visible absorption spectra and density functional based first principle computational calculations. Plasma reduction of GO/ITO/PET structures can be used for efficiently tuning the electrical and optical properties of reduced graphene oxide (rGO) for flexible electronics applications.

Kinetics of transuranium element oxidation-reduction reactions in solution

International Nuclear Information System (INIS)

Gourisse, D.

1966-09-01

A review of the kinetics of U, Np, Pu, Am oxidation-reduction reactions is proposed. The relations between the different activation thermodynamic functions (compensatory effect, formal entropy of the activated complex, magnitude of reactions velocities) are considered. The effects of acidity, ionic strength deuterium and mixed solvents polarity on reactions rates are described. The effect of different anions on reactions rates are explained by variations of the reaction standard free energy and variations of the activation free energy (coulombic interactions) resulting from the complexation of dissolved species by these anions. (author) [fr

Highly Selective TiN-Supported Highly Dispersed Pt Catalyst: Ultra Active toward Hydrogen Oxidation and Inactive toward Oxygen Reduction.

Science.gov (United States)

Luo, Junming; Tang, Haibo; Tian, Xinlong; Hou, Sanying; Li, Xiuhua; Du, Li; Liao, Shijun

2018-01-31

The severe dissolution of the cathode catalyst, caused by an undesired oxygen reduction reaction at the anode during startup and shutdown, is a fatal challenge to practical applications of polymer electrolyte membrane fuel cells. To address this important issue, according to the distinct structure-sensitivity between the σ-type bond in H 2 and the π-type bond in O 2 , we design a HD-Pt/TiN material by highly dispersing Pt on the TiN surface to inhibit the unwanted oxygen reduction reaction. The highly dispersed Pt/TiN catalyst exhibits excellent selectivity toward hydrogen oxidation and oxygen reduction reactions. With a Pt loading of 0.88 wt %, our catalyst shows excellent hydrogen oxidation reaction activity, close to that of commercial 20 wt % Pt/C catalyst, and much lower oxygen reduction reaction activity than the commercial 20 wt % Pt/C catalyst. The lack of well-ordered Pt facets is responsible for the excellent selectivity of the HD-Pt/TiN materials toward hydrogen oxidation and oxygen reduction reactions. Our work provides a new and cost-effective solution to design selective catalysts toward hydrogen oxidation and oxygen reduction reactions, making the strategy of using oxygen-tolerant anode catalyst to improve the stability of polymer electrolyte membrane fuel cells during startup and shutdown more affordable and practical.

ANAEROBIC DDT BIOTRANSFORMATION: ENHANCEMENT BY APPLICATION OF SURFACTANTS AND LOW OXIDATION REDUCTION POTENTIAL

Science.gov (United States)

Enhancement of anaerobic DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane) biotransformation by mixed cultures was studied with application of surfactants and oxidation reduction potential reducing agents. Without amendments, DDT transformation resulted mainly in the pr...

Accelerated creep in solid oxide fuel cell anode supports during reduction

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Makowska, Malgorzata Grazyna; Greco, Fabio

2016-01-01

To evaluate the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. The creep of reduced Ni-YSZ anode support at operating conditions has been...... studied previously. In this work a newly discovered creep phenomenon taking place during the reduction is reported. This relaxes stresses at a much higher rate (∼ x104) than creep during operation. The phenomenon was studied both in three-point bending and uniaxial tension. Differences between the two...... measurements could be explained by newly observed stress promoted reduction. Finally, samples exposed to a small tensile stress (∼ 0.004 MPa) were observed to expand during reduction, which is in contradiction to previous literature. These observations suggest that release of internal residual stresses between...

Highly controllable and green reduction of graphene oxide to flexible graphene film with high strength

International Nuclear Information System (INIS)

Wan, Wubo; Zhao, Zongbin; Hu, Han; Gogotsi, Yury; Qiu, Jieshan

2013-01-01

Graphical abstract: Highly controllable and green reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant. Self-assembly of the as-made CCG sheets results in a flexible CCG film, of which the tensile strength strongly depends on the deoxygenation degree of graphene sheets. - Highlights: • Graphene was synthesized by an effective and environmentally friendly approach. • We introduced a facile X-ray diffraction analysis method to investigate the reduction process from graphene oxide to graphene. • Flexible graphene films were prepared by self-assembly of the graphene sheets. • The strength of the graphene films depends on the reduction degree of graphene. - Abstract: Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach. Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV–vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film. This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded

Selective reduction of nitric oxide over Cu/ZSM-5: The role of oxygen in suppressing catalyst deactivation by carbonaceous deposits

Energy Technology Data Exchange (ETDEWEB)

d' Itri, Julie L; Sachtler, Wolfgang M.H. [V.N. Ipatieff Laboratory, Center for Catalysis and Surface Science, Departments of Chemical Engineering and Chemistry, Northwestern University, Evanston, IL (United States)

1993-06-15

The role of oxygen in the selective reduction of nitrogen monoxide by either propane or propene over 'excessively' ion-exchanged Cu/ZSM-5 has been studied. In a wide temperature region and in the absence of additives such as steam, propane is a more effective reductant than propene; with propane and in the presence of oxygen reduction of nitric oxide to nitrogen approaches 100% above 600 K. The difference in effectiveness is due to the different degree of catalyst deactivation by carbonaceous deposits: more carbonaceous material is deposited from propene than from propane. Temperature-programmed oxidation shows that above 600 K the rate of oxidation of carbonaceous deposits by oxygen is significant. The amount of such carbonaceous deposits is, therefore, lower when catalytic tests above 600 K are done in the presence of oxygen. At very high temperatures, the in situ volatilization of the deposits by reaction with oxygen keeps the catalyst surface clean in the steady state of nitric oxide reduction.

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis

DEFF Research Database (Denmark)

Su, Hai-Yan; Gorlin, Yelena; Man, Isabela Costinela

2012-01-01

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen...... reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn2O3 and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V...

Simple and cost-effective fabrication of size-tunable zinc oxide architectures by multiple size reduction technique

Directory of Open Access Journals (Sweden)

Hyeong-Ho Park, Xin Zhang, Seon-Yong Hwang, Sang Hyun Jung, Semin Kang, Hyun-Beom Shin, Ho Kwan Kang, Hyung-Ho Park, Ross H Hill and Chul Ki Ko

2012-01-01

Full Text Available We present a simple size reduction technique for fabricating 400 nm zinc oxide (ZnO architectures using a silicon master containing only microscale architectures. In this approach, the overall fabrication, from the master to the molds and the final ZnO architectures, features cost-effective UV photolithography, instead of electron beam lithography or deep-UV photolithography. A photosensitive Zn-containing sol–gel precursor was used to imprint architectures by direct UV-assisted nanoimprint lithography (UV-NIL. The resulting Zn-containing architectures were then converted to ZnO architectures with reduced feature sizes by thermal annealing at 400 °C for 1 h. The imprinted and annealed ZnO architectures were also used as new masters for the size reduction technique. ZnO pillars of 400 nm diameter were obtained from a silicon master with pillars of 1000 nm diameter by simply repeating the size reduction technique. The photosensitivity and contrast of the Zn-containing precursor were measured as 6.5 J cm−2 and 16.5, respectively. Interesting complex ZnO patterns, with both microscale pillars and nanoscale holes, were demonstrated by the combination of dose-controlled UV exposure and a two-step UV-NIL.

Simple and cost-effective fabrication of size-tunable zinc oxide architectures by multiple size reduction technique

International Nuclear Information System (INIS)

Park, Hyeong-Ho; Hwang, Seon-Yong; Jung, Sang Hyun; Kang, Semin; Shin, Hyun-Beom; Kang, Ho Kwan; Ko, Chul Ki; Zhang Xin; Hill, Ross H; Park, Hyung-Ho

2012-01-01

We present a simple size reduction technique for fabricating 400 nm zinc oxide (ZnO) architectures using a silicon master containing only microscale architectures. In this approach, the overall fabrication, from the master to the molds and the final ZnO architectures, features cost-effective UV photolithography, instead of electron beam lithography or deep-UV photolithography. A photosensitive Zn-containing sol–gel precursor was used to imprint architectures by direct UV-assisted nanoimprint lithography (UV-NIL). The resulting Zn-containing architectures were then converted to ZnO architectures with reduced feature sizes by thermal annealing at 400 °C for 1 h. The imprinted and annealed ZnO architectures were also used as new masters for the size reduction technique. ZnO pillars of 400 nm diameter were obtained from a silicon master with pillars of 1000 nm diameter by simply repeating the size reduction technique. The photosensitivity and contrast of the Zn-containing precursor were measured as 6.5 J cm −2 and 16.5, respectively. Interesting complex ZnO patterns, with both microscale pillars and nanoscale holes, were demonstrated by the combination of dose-controlled UV exposure and a two-step UV-NIL.

Bacteria-mediated arsenic oxidation and reduction in the growth media of arsenic hyperaccumulator Pteris vittata.

Science.gov (United States)

Wang, Xin; Rathinasabapathi, Bala; de Oliveira, Letuzia Maria; Guilherme, Luiz R G; Ma, Lena Q

2012-10-16

Microbes play an important role in arsenic transformation and cycling in the environment. Microbial arsenic oxidation and reduction were demonstrated in the growth media of arsenic hyperaccumulator Pteris vittata L. All arsenite (AsIII) at 0.1 mM in the media was oxidized after 48 h incubation. Oxidation was largely inhibited by antibiotics, indicating that bacteria played a dominant role. To identify AsIII oxidizing bacteria, degenerate primers were used to amplify ∼500 bp of the AsIII oxidase gene aioA (aroA) using DNA extracted from the media. One aioA (aroA)-like sequence (MG-1, tentatively identified as Acinetobacter sp.) was amplified, exhibiting 82% and 91% identity in terms of gene and deduced protein sequence to those from Acinetobacter sp. 33. In addition, four bacterial strains with different arsenic tolerance were isolated and identified as Comamonas sp.C-1, Flavobacterium sp. C-2, Staphylococcus sp. C-3, and Pseudomonas sp. C-4 using carbon utilization, fatty acid profiles, and/or sequencing 16s rRNA gene. These isolates exhibited dual capacity for both AsV reduction and AsIII oxidation under ambient conditions. Arsenic-resistant bacteria with strong AsIII oxidizing ability may have potential to improve bioremediation of AsIII-contaminated water using P. vittata and/or other biochemical strategies.

Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene.

OpenAIRE

Kaspar, H F; Tiedje, J M

1981-01-01

15N tracer methods and gas chromatography coupled to an electron capture detector were used to investigate dissimilatory reduction of nitrate and nitrite by the rumen microbiota of a fistulated cow. Ammonium was the only 15N-labeled end product of quantitative significance. Only traces of nitrous oxide were detected as a product of nitrate reduction; but in experiments with nitrite, up to 0.3% of the added nitrogen accumulated as nitrous oxide, but it was not further reduced. Furthermore, whe...

Dissimilatory nitrate reduction to nitrate, nitrous oxide, and ammonium by Pseudomonas putrefaciens.

Science.gov (United States)

Samuelsson, M O

1985-10-01

The influence of redox potential on dissimilatory nitrate reduction to ammonium was investigated on a marine bacterium, Pseudomonas putrefaciens. Nitrate was consumed (3.1 mmol liter-1), and ammonium was produced in cultures with glucose and without sodium thioglycolate. When sodium thioglycolate was added, nitrate was consumed at a lower rate (1.1 mmol liter-1), and no significant amounts of nitrite or ammonium were produced. No growth was detected in glucose media either with or without sodium thioglycolate. When grown on tryptic soy broth, the production of nitrous oxide paralleled growth. In the same medium, but with sodium thioglycolate, nitrous oxide was first produced during growth and then consumed. Acetylene caused the nitrous oxide to accumulate. These results and the mass balance calculations for different nitrogen components indicate that P. putrefaciens has the capacity to dissimilate nitrate to ammonium as well as to dinitrogen gas and nitrous oxide (denitrification). The dissimilatory pathway to ammonium dominates except when sodium thioglycolate is added to the medium.

Antioxidant (A-tocopherol acetate) effect on oxidation stability and NOx emission reduction in methyl ester of Annona oil operated diesel engine

Science.gov (United States)

Senthil, R.; Silambarasan, R.; Pranesh, G.

2017-05-01

There is a major drawback while using biodiesel as a alternate fuel for compression ignition diesel engine due to lower heating value, higher viscosity, higher density and higher oxides of nitrogen emission. To minimize these drawbacks, fuel additives can contribute towards engine performance and exhaust emission reduction either directly or indirectly. In this current work, the test was conducted to investigate the effect of antioxidant additive (A-tocopherol acetate) on oxidation stability and NOx emission in a of Annona methyl ester oil (MEAO) fueled diesel engine. The A-tocopherol acetate is mixed in different concentrations such as 0.01, 0.02, 0.03 and 0.04% with 100% by vol MEAO. It is concluded that the antioxidant additive very effective in increasing the oxidation stability and in controlling the NOx emission. Further, the addition of antioxidant additive is slight increase the HC, CO and smoke emissions. Hence, A-tocopherol acetate is very effective in controlling the NOx emission with MEAO operated diesel engine without any major modification.

Reduction of excess sludge production in sequencing batch reactor through incorporation of chlorine dioxide oxidation

Energy Technology Data Exchange (ETDEWEB)

Wang Guanghua [Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration area, College of Environmental Science and Engineering, South China University of Technology, Guangzhou, 510006 (China); Guangzhou municipal engineering design and research institute, Guangzhou, 510060 (China); Sui Jun [Guangzhou municipal engineering design and research institute, Guangzhou, 510060 (China); Shen Huishan; Liang Shukun [Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration area, College of Environmental Science and Engineering, South China University of Technology, Guangzhou, 510006 (China); He Xiangming; Zhang Minju; Xie Yizhong; Li Lingyun [Nanhai Limited Liability Development Company, Foshan, 528200 (China); Hu Yongyou, E-mail: ppyyhu@scut.edu.cn [Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration area, College of Environmental Science and Engineering, South China University of Technology, Guangzhou, 510006 (China) and State Key Lab of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology; Guangzhou, 510640 (China)

2011-08-15

In this study, chlorine dioxide (ClO{sub 2}) instead of chlorine (Cl{sub 2}) was proposed to minimize the formation of chlorine-based by-products and was incorporated into a sequencing batch reactor (SBR) for excess sludge reduction. The results showed that the sludge disintegrability of ClO{sub 2} was excellent. The waste activated sludge at an initial concentration of 15 g MLSS/L was rapidly reduced by 36% using ClO{sub 2} doses of 10 mg ClO{sub 2}/g dry sludge which was much lower than that obtained using Cl{sub 2} based on similar sludge reduction efficiency. Maximum sludge disintegration was achieved at 10 mg ClO{sub 2}/g dry sludge for 40 min. ClO{sub 2} oxidation can be successfully incorporated into a SBR for excess sludge reduction without significantly harming the bioreactor performance. The incorporation of ClO{sub 2} oxidation resulted in a 58% reduction in excess sludge production, and the quality of the effluent was not significantly affected.

Oxidation-reduction reactions. Overview and implications for repository studies

International Nuclear Information System (INIS)

Apted, Michael J.; Arthur, Randolph C.; Sasamoto, Hiroshi; Yui, Mikazu; Iwatsuki, Teruki

2001-02-01

The purpose of this report is to provide a survey and review on oxidation-reduction ('redox') reactions, with particular emphasis on implications for disposal of high-level waste (HLW) in deep geological formations. As an overview, the focus is on basic principles, problems, and proposed research related specifically to the assessment of redox for a HLW repository in Japan. For a more comprehensive treatment of redox and the myriad associated issues, the reader is directed to the cited textbooks used as primary references in this report. Low redox conditions in deep geological formations is a key assumption in the 'Second Progress Report on Research and Development for the Geological Disposal of HLW in Japan' (hereafter called H12'). The release behavior of multi-valent radioelements (e.g., Tc, Se, U, Pu, Np), as well as daughter radioelements of these radioelements, from a deep geological repository are sensitively related to redox conditions. Furthermore, the performance of certain barrier materials, such as overpack and buffer, may be impacted by redox conditions. Given this importance, this report summarizes some key topics for future technical studies supporting site characterization and repository performance as follows: To fully test the conceptual models for system Eh, it will be necessary to measure and evaluate trace element and isotopic information of both coexisting groundwater and reactive minerals of candidate rocks. Because of importance of volatile species (e.g., O 2 , H 2 etc.) in redox reactions, and given the high total pressure of a repository located 500 to 1000 meter deep, laboratory investigations of redox will necessarily require use of pressurized test devices that can fully simulate repository conditions. The stability (redox capacity) of the repository system with respect to potential changes in redox boundary condition induced by oxidizing waters intrusion should be established experimentally. An overall conceptual model that unifies

Selective and efficient reduction of carbon dioxide to carbon monoxide on oxide-derived nanostructured silver electrocatalysts

NARCIS (Netherlands)

Ma, Ming; Trześniewski, Bartek J.; Xie, Jie; Smith, Wilson A.

2016-01-01

In this work, the selective electrocatalytic reduction of carbon dioxide to carbon monoxide on oxide-derived silver electrocatalysts is presented. By a simple synthesis technique, the overall high faradaic efficiency for CO production on the oxide-derived Ag was shifted by more than 400 mV towards a

Mitochondrial isocitrate dehydrogenase is inactivated upon oxidation and reactivated by thioredoxin-dependent reduction in Arabidopsis

Directory of Open Access Journals (Sweden)

Keisuke eYoshida

2014-09-01

Full Text Available Regulation of mitochondrial metabolism is essential for ensuring cellular growth and maintenance in plants. Based on redox-proteomics analysis, several proteins involved in diverse mitochondrial reactions have been identified as potential redox-regulated proteins. NAD+-dependent isocitrate dehydrogenase (IDH, a key enzyme in the tricarboxylic acid cycle, is one such candidate. In this study, we investigated the redox regulation mechanisms of IDH by biochemical procedures. In contrast to mammalian and yeast counterparts reported to date, recombinant IDH in Arabidopsis mitochondria did not show adenylate-dependent changes in enzymatic activity. Instead, IDH was inactivated by oxidation treatment and partially reactivated by subsequent reduction. Functional IDH forms a heterodimer comprising regulatory (IDH-r and catalytic (IDH-c subunits. IDH-r was determined to be the target of oxidative modifications forming an oligomer via intermolecular disulfide bonds. Mass spectrometric analysis combined with tryptic digestion of IDH-r indicated that Cys128 and Cys216 are involved in intermolecular disulfide bond formation. Furthermore, we showed that mitochondria-localized o-type thioredoxin (Trx-o promotes the reduction of oxidized IDH-r. These results suggest that IDH-r is susceptible to oxidative stress, and Trx-o serves to convert oxidized IDH-r to the reduced form that is necessary for active IDH complex.

Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

International Nuclear Information System (INIS)

Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

2015-01-01

Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields

Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

Energy Technology Data Exchange (ETDEWEB)

Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, Dong Rip, E-mail: dongrip@hanyang.ac.kr [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-791 (Korea, Republic of)

2015-06-15

Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions

Energy Technology Data Exchange (ETDEWEB)

Arenillas, A.; Rubiera, F.; Pis, J.J. [Instituto Nacional del Carbon, CSIC, Oviedo (Spain)

2002-12-15

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with on-line battery of analyzers. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behaviour in other combustion equipments, i.e. fluidized bed combustors. It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range NO heterogeneous reduction seems to be controlled by the evolution of surface complexes. In the high-temperature range a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor. 27 refs., 6 figs., 1 tab.

Direct plasma NO_x reduction using single surface dielectric barrier discharge

DEFF Research Database (Denmark)

Kroushawi, Feisal; Stamate, Eugen

2014-01-01

NOx reduction using direct atmospheric barrier discharge in air-NO mixture at different voltages and flow rates is inversigated. Reduction rate of 80% is achieved at 3.18 W/cm2 power density and gas mixture of 20 slm air and 0.006 slm NO. The ozone for NO reduction is produced by a honeycomb stru...

Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

International Nuclear Information System (INIS)

Jeong, Sang Mun; Shin, Ho-Sup; Hong, Sun-Seok; Hur, Jin-Mok; Do, Jae Bum; Lee, Han Soo

2010-01-01

The reduction path of the U 3 O 8 powder vol-oxidized at 1200 deg. C has been determined by a series of electrochemical experiments in a 1 wt.% Li 2 O/LiCl molten salt. Various reaction intermediates are observed by during electrolysis of U 3 O 8 . The formation of the metallic uranium is caused from two different reduction paths, a direct reduction of uranium oxide and an electro-lithiothermic reduction. As the uranium oxide is converted to the metallic uranium, the lithium metal is more actively formed in the cathode basket. The reducibility of the rare earth oxides with the U 3 O 8 powder has been tested by constant voltage electrolysis. The results suggest the advanced vol-oxidation could lead to the enhancement in the reducibility of the rare earth fission products.

Complete relaxation of residual stresses during reduction of solid oxide fuel cells

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Chatzichristodoulou, Christodoulos; Hendriksen, Peter Vang

2015-01-01

reduce significantly over minutes. In this work the stresses are measured in-situ before and after the reduction by use of XRD. The phenomenon of accelerated creep has to be considered both in the production of stacks and in the analysis of the stress field in a stack based on anode supported SOFCs.......To asses the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. This work reports further details on a newly discovered creep phenomenon......, accelerated creep, taking place during the reduction of the anode. This relaxes stresses at a much higher rate (~×104) than creep during operation. The phenomenon has previously been studied by simultaneous loading and reduction. With the recorded high creep rates, the stresses at the time of reduction should...

Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

Energy Technology Data Exchange (ETDEWEB)

Gopalan, Srikanth [Boston Univ., MA (United States)

2013-03-31

In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

New Catalysts for Direct Methanol Oxidation Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Adzic, Radoslav

1998-08-01

A new class of efficient electrocatalytic materials based on platinum - metal oxide systems has been synthetized and characterized by several techniques. Best activity was found with NiWO{sub 4}-, CoWO{sub 4}-, and RuO{sub 2}- sr¡pported platinum catalysts. A very similar activity at room temperature was observed with the electrodes prepared with the catalyst obtained from International Fuel Cells Inc. for the same Pt loading. Surprisingly, the two tungstates per se show a small activity for methanol oxidation without any Pt loading. Synthesis of NiWO{sub 4} and CoWO{sub 4} were carried out by solid-state reactions. FTIR spectroscopy shows that the tungstates contain a certain amount of physically adsorbed water even after heating samples at 200{degrees}C. A direct relationship between the activity for methanol oxidation and the amount of adsorbed water on those oxides has been found. The Ru(0001) single crystal shows a very small activity for CO adsorption and oxidation, in contrast to the behavior of polycrystalline Ru. In situ extended x-ray absorption fine structure spectroscopy (EXAFS) and x-ray absorption near edge spectroscopy (XANES) showed that the OH adsorption on Ru in the Pt-Ru alloy appears to be the limiting step in methanol oxidation. This does not occur for Pt-RuO{SUB 2} electrocatalyst, which explains its advantages over the Pt-Ru alloys. The IFCC electrocatalyst has the properties of the Pt-Ru alloy.

Natural printed silk substrate circuit fabricated via surface modification using one step thermal transfer and reduction graphene oxide

Science.gov (United States)

Cao, Jiliang; Huang, Zhan; Wang, Chaoxia

2018-05-01

Graphene conductive silk substrate is a preferred material because of its biocompatibility, flexibility and comfort. A flexible natural printed silk substrate circuit was fabricated by one step transfer of graphene oxide (GO) paste from transfer paper to the surface of silk fabric and reduction of the GO to reduced graphene oxide (RGO) using a simple hot press treatment. The GO paste was obtained through ultrasonic stirring exfoliation under low temperature, and presented excellent printing rheological properties at high concentration. The silk fabric was obtained a surface electric resistance as low as 12.15 KΩ cm-1, in the concentration of GO 50 g L-1 and hot press at 220 °C for 120 s. Though the whiteness and strength decreased with the increasing of hot press temperature and time slowly, the electric conductivity of RGO surface modification silk substrate improved obviously. The surface electric resistance of RGO/silk fabrics increased from 12.15 KΩ cm-1 to 18.05 KΩ cm-1, 28.54 KΩ cm-1 and 32.53 KΩ cm-1 after 10, 20 and 30 washing cycles, respectively. The results showed that the printed silk substrate circuit has excellent washability. This process requires no chemical reductant, and the reduction efficiency and reduction degree of GO is high. This time-effective and environmentally-friendly one step thermal transfer and reduction graphene oxide onto natural silk substrate method can be easily used to production of reduced graphene oxide (RGO) based flexible printed circuit.

Development of Head-end Pyrochemical Reduction Process for Advanced Oxide Fuels

International Nuclear Information System (INIS)

Park, B. H.; Seo, C. S.; Hur, J. M.; Jeong, S. M.; Hong, S. S.; Choi, I. K.; Choung, W. M.; Kwon, K. C.; Lee, I. W.

2008-12-01

The development of an electrolytic reduction technology for spent fuels in the form of oxide is of essence to introduce LWR SFs to a pyroprocessing. In this research, the technology was investigated to scale a reactor up, the electrochemical behaviors of FPs were studied to understand the process and a reaction rate data by using U 3 O 8 was obtained with a bench scale reactor. In a scale of 20 kgHM/batch reactor, U 3 O 8 and Simfuel were successfully reduced into metals. Electrochemical characteristics of LiBr, LiI and Li 2 Se were measured in a bench scale reactor and an electrolytic reduction cell was modeled by a computational tool

Characteristics of an integrated cathode assembly for the electrolytic reduction of uranium oxide in a LiCl-Li2O molten salt

International Nuclear Information System (INIS)

Sung Bin Park; Byung Heung Park; Sang Mun Jeong; Jin Mok Hur; Chung Seok Seo; Seong Won Park; Seung-Hoon Choi

2006-01-01

Electrochemical behavior of the reduction of uranium oxide was studied in a LiCl-Li 2 O molten salt system with an integrated cathode assembly. The mechanism for the electrolytic reduction of uranium oxide was studied through cyclic voltammetry. By means of a chronopotentiometry, the effects of the thickness of the uranium oxide, the thickness of the MgO membrane and the material of the conductor of an integrated cathode assembly on the overpotential of the cathode were investigated. From the voltamograms, the reduction potential of the uranium oxide and Li 2 O was obtained and the two mechanisms of the electrolytic reduction were considered with regard to the applied cathode potential. From the chronopotentiograms, the exchange current, the transfer coefficient and the maximum allowable current based on the Tafel behavior were obtained with regard to the thickness of the uranium oxide, and of the MgO membrane and the material of the conductor of an integrated cathode assembly. (author)

From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources.

Science.gov (United States)

Ishii, Takumi; Kawaichi, Satoshi; Nakagawa, Hirotaka; Hashimoto, Kazuhito; Nakamura, Ryuhei

2015-01-01

At deep-sea vent systems, hydrothermal emissions rich in reductive chemicals replace solar energy as fuels to support microbial carbon assimilation. Until recently, all the microbial components at vent systems have been assumed to be fostered by the primary production of chemolithoautotrophs; however, both the laboratory and on-site studies demonstrated electrical current generation at vent systems and have suggested that a portion of microbial carbon assimilation is stimulated by the direct uptake of electrons from electrically conductive minerals. Here we show that chemolithoautotrophic Fe(II)-oxidizing bacterium, Acidithiobacillus ferrooxidans, switches the electron source for carbon assimilation from diffusible Fe(2+) ions to an electrode under the condition that electrical current is the only source of energy and electrons. Site-specific marking of a cytochrome aa3 complex (aa3 complex) and a cytochrome bc1 complex (bc1 complex) in viable cells demonstrated that the electrons taken directly from an electrode are used for O2 reduction via a down-hill pathway, which generates proton motive force that is used for pushing the electrons to NAD(+) through a bc1 complex. Activation of carbon dioxide fixation by a direct electron uptake was also confirmed by the clear potential dependency of cell growth. These results reveal a previously unknown bioenergetic versatility of Fe(II)-oxidizing bacteria to use solid electron sources and will help with understanding carbon assimilation of microbial components living in electronically conductive chimney habitats.

Nitric-glycolic flowsheet reduction/oxidation (redox) model for the defense waste processing facility (DWPF)

Energy Technology Data Exchange (ETDEWEB)

Jantzen, C. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Williams, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Edwards, T. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Trivelpiece, C. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Ramsey, W. G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-06-14

Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe⁺²/ΣFe ratios of between 0.09 and 0.33, retains radionuclides in the melt and thus the final glass. Specifically, long-lived radioactive ⁹⁹Tc species are less volatile in the reduced Tc⁴⁺ state as TcO₂ than as NaTcO₄ or Tc₂O₇, and ruthenium radionuclides in the reduced Ru⁴⁺ state are insoluble RuO₂ in the melt which are not as volatile as NaRuO₄ where the Ru is in the +7 oxidation state. Similarly, hazardous volatile Cr⁶⁺ occurs in oxidized melt pools as Na₂CrO₄ or Na₂Cr₂O₇, while the Cr⁺³ state is less volatile and remains in the melt as NaCrO₂ or precipitates as chrome rich spinels. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam.

Ce-Fe-O mixed oxide as oxygen carrier for the direct partial oxidation of methane to syngas

Institute of Scientific and Technical Information of China (English)

魏永刚; 王华; 李孔斋

2010-01-01

The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...

A rapid room temperature chemical route for the synthesis of graphene: metal-mediated reduction of graphene oxide.

Science.gov (United States)

Dey, Ramendra Sundar; Hajra, Saumen; Sahu, Ranjan K; Raj, C Retna; Panigrahi, M K

2012-02-07

A rapid and facile route for the synthesis of reduced graphene oxide sheets (rGOs) at room temperature by the chemical reduction of graphene oxide using Zn/acid in aqueous solution is demonstrated. This journal is © The Royal Society of Chemistry 2012

Nitrous oxide emission reduction in temperate biochar-amended soils

Science.gov (United States)

Felber, R.; Hüppi, R.; Leifeld, J.; Neftel, A.

2012-01-01

Biochar, a pyrolysis product of organic residues, is an amendment for agricultural soils to improve soil fertility, sequester CO2 and reduce greenhouse gas (GHG) emissions. In highly weathered tropical soils laboratory incubations of soil-biochar mixtures revealed substantial reductions for nitrous oxide (N2O) and carbon dioxide (CO2). In contrast, evidence is scarce for temperate soils. In a three-factorial laboratory incubation experiment two different temperate agricultural soils were amended with green waste and coffee grounds biochar. N2O and CO2 emissions were measured at the beginning and end of a three month incubation. The experiments were conducted under three different conditions (no additional nutrients, glucose addition, and nitrate and glucose addition) representing different field conditions. We found mean N2O emission reductions of 60 % compared to soils without addition of biochar. The reduction depended on biochar type and soil type as well as on the age of the samples. CO2 emissions were slightly reduced, too. NO3- but not NH4+ concentrations were significantly reduced shortly after biochar incorporation. Despite the highly significant suppression of N2O emissions biochar effects should not be transferred one-to-one to field conditions but need to be tested accordingly.

Surface oxidization-reduction reactions in Columbia Plateau basalts

International Nuclear Information System (INIS)

White, A.F.; Yee, A.

1984-01-01

Results are presented which define principal oxidation-reduction reactions expected between ground water and iron in the Umtanum and Cohassett basalt flows of south central Washington. Data include kinetics of aqueous iron speciation, rates of O 2 uptake and nature of oxyhydroxide precipitates. Such data are important in predicting behavior of radionuclides in basalt aquifers including determination of valence states, speciation, solubility, sorption, and coprecipitation on iron oxyhydroxide substrates and colloids. Analyses of the basalt by XPS indicates that ferrous iron is oxidized to ferric iron on the surface and that the total iron decreases as a function of pH during experimental weathering. Iron oxyhydroxide phases did not form surface coating on basalt surfaces but rather nucleated as separate plases in solution. No significant increases in Cs or Sr sorption were observed with increased weathering of the basalt. Concurrent increases in Fe(II) and decreases in Fe(III) in slightly to moderately acid solutions indicated continued oxidization of ferrous iron in the basalt. At neutral to basic pH, Fe(II) was strongly sorbed onto the basalt surface (Kd = 6.5 x 10 -3 1 x m 2 ) resulting in low dissolved concentrations even under anoxic conditions. The rate of O 2 uptake increased with decreasing pH. Diffusion rates (-- 10 -14 cm 2 x s -1 ), calculated using a one-dimensional analytical model, indicate grain boundary diffusion. Comparisons of Eh values calculated by Pt electrode, dissolved O 2 and Fe(II)/Fe(III) measurements showed considerable divergence, with the ferric-ferrous couple being the preferred method of estimating Eh

Modeling of oxide reduction in repeated-batch pyroprocessing

International Nuclear Information System (INIS)

Lee, Hyo Jik; Im, Hun Suk; Park, Geun Il

2016-01-01

Highlights: • Pyroprocessing is a complicated batch-type operation. • Discrete event system modeling was used to create an integrated operation model. • Simulation showed that could be accomplished. • The dynamic material flow helps us understand the process operation. • We showed that complex material flow could be simulated in terms of mass balance. - Abstract: Pyroprocessing is a complicated batch-type operation, involving a highly complex material flow logic with a huge number of unit processes. Discrete event system modeling was used to create an integrated operation model for which simulation showed that dynamic material flow could be accomplished to provide considerable insight into the process operation. In the model simulation, the amount of material transported upstream and downstream in the process satisfies a mass balance equation while considering the hold-up incurred by every batch operation. This study also simulated, in detail, an oxide reduction group process embracing electrolytic reduction, cathode processing, and salt purification. Based on the default operation scenario, it showed that complex material flows could be precisely simulated in terms of the mass balance. Specifically, the amount of high-heat elements remaining in the molten salt bath is analyzed to evaluate the operation scenario.

Direct laser writing of micro-supercapacitors on hydrated graphite oxide films

Science.gov (United States)

Gao, Wei; Singh, Neelam; Song, Li; Liu, Zheng; Reddy, Arava Leela Mohana; Ci, Lijie; Vajtai, Robert; Zhang, Qing; Wei, Bingqing; Ajayan, Pulickel M.

2011-08-01

Microscale supercapacitors provide an important complement to batteries in a variety of applications, including portable electronics. Although they can be manufactured using a number of printing and lithography techniques, continued improvements in cost, scalability and form factor are required to realize their full potential. Here, we demonstrate the scalable fabrication of a new type of all-carbon, monolithic supercapacitor by laser reduction and patterning of graphite oxide films. We pattern both in-plane and conventional electrodes consisting of reduced graphite oxide with micrometre resolution, between which graphite oxide serves as a solid electrolyte. The substantial amounts of trapped water in the graphite oxide makes it simultaneously a good ionic conductor and an electrical insulator, allowing it to serve as both an electrolyte and an electrode separator with ion transport characteristics similar to that observed for Nafion membranes. The resulting micro-supercapacitor devices show good cyclic stability, and energy storage capacities comparable to existing thin-film supercapacitors.

Influence of V2O5 Content on the Gas-Based Direct Reduction of Hongge Vanadium Titanomagnetite Pellets with Simulated Shaft Furnace Gases

Science.gov (United States)

Li, Wei; Fu, Guiqin; Chu, Mansheng; Zhu, Miaoyong

2018-01-01

The influence of V2O5 content on the gas-based direct reduction of Hongge vanadium titanomagnetite pellets (HVTMP) was investigated with simulated shaft furnace gases, and the content levels were selected as 0 wt.%, 2 wt.%, 4 wt.%, and 6 wt.%, respectively. The results indicated that, with the increase of V2O5 content, the reduction was accelerated at an early stage due to the increase of the original porosity of the HVTMP. However, as the reduction proceeded, a slowing down in the reduction rate was observed, which was attributed to the formation of hardly reducible Fe2VO4. Major phases of reduced HVTMP were Fe2VO4, FeTiO3, and metallic iron. The morphology showed that the size of metallic iron particles of reduced HVTMP decreased with the increase of V2O5 content, V-bearing oxides embedded into the Ti-rich phases, and further reduction was restricted. This study not only established a relationship between the V2O5 content of HVTMP and its reduction behavior but could also contribute greatly to the effective utilization of Hongge vanadium titanomagnetite in shaft furnace.

Reversible conversion of valence-tautomeric copper metal-organic frameworks dependent single-crystal-to-single-crystal oxidation/reduction: a redox-switchable catalyst for C-H bonds activation reaction.

Science.gov (United States)

Huang, Chao; Wu, Jie; Song, Chuanjun; Ding, Ran; Qiao, Yan; Hou, Hongwei; Chang, Junbiao; Fan, Yaoting

2015-06-28

Upon single-crystal-to-single-crystal (SCSC) oxidation/reduction, reversible structural transformations take place between the anionic porous zeolite-like Cu(I) framework and a topologically equivalent neutral Cu(I)Cu(II) mixed-valent framework. The unique conversion behavior of the Cu(I) framework endowed it as a redox-switchable catalyst for the direct arylation of heterocycle C-H bonds.

Reduction and Immobilization of Potassium Permanganate on Iron Oxide Catalyst by Fluidized-Bed Crystallization Technology

Directory of Open Access Journals (Sweden)

Guang-Xia Li

2012-03-01

Full Text Available A manganese immobilization technology in a fluidized-bed reactor (FBR was developed by using a waste iron oxide (i.e., BT-3 as catalyst which is a by-product from the fluidized-bed Fenton reaction (FBR-Fenton. It was found that BT-3 could easily reduce potassium permanganate (KMnO4 to MnO2. Furthermore, MnO2 could accumulate on the surface of BT-3 catalyst to form a new Fe-Mn oxide. Laboratory experiments were carried out to investigate the KMnO4-reduction mechanism, including the effect of KMnO4 concentration, BT-3 dosage, and operational solution pH. The results showed that the pH solution was a significant factor in the reduction of KMnO4. At the optimum level, pHf 6, KMnO4 was virtually reduced in 10 min. A pseudo-first order reaction was employed to describe the reduction rate of KMnO4.

Self-assembled manganese oxide structures through direct oxidation

KAUST Repository

Zhao, Chao; Wang, Qingxiao; Yang, Yang; Zhang, Bei; Zhang, Xixiang

2012-01-01

The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

Self-assembled manganese oxide structures through direct oxidation

KAUST Repository

Zhao, Chao

2012-12-01

The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

Reductive Deprotection of Monolayer Protected Nanoclusters: An Efficient Route to Supported Ultrasmall Au Nanocatalysts for Selective Oxidation

Czech Academy of Sciences Publication Activity Database

Das, S.; Goswami, A.; Hesari, M.; Al-Sharab, J. F.; Mikmeková, Eliška; Maran, F.; Asefa, T.

2014-01-01

Roč. 10, č. 8 (2014), s. 1473-1478 ISSN 1613-6810 R&D Projects: GA MŠk(CZ) LO1212 Keywords : gold nanoclusters * selective oxidation * heterogeneous nanocatalysis * styrene oxidation * borohydride reduction Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 8.368, year: 2014

Efficient and simple approaches towards direct oxidative esterification of alcohols.

Science.gov (United States)

Ray, Ritwika; Jana, Rahul Dev; Bhadra, Mayukh; Maiti, Debabrata; Lahiri, Goutam Kumar

2014-11-17

The present article describes novel oxidative protocols for direct esterification of alcohols. The protocols involve successful demonstrations of both "cross" and "self" esterification of a wide variety of alcohols. The cross-esterification proceeds under a simple transition-metal-free condition, containing catalytic amounts of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)/TBAB (tetra-n-butylammonium bromide) in combination with oxone (potassium peroxo monosulfate) as the oxidant, whereas the self-esterification is achieved through simple induction of Fe(OAc)2 /dipic (dipic=2,6-pyridinedicarboxylic acid) as the active catalyst under an identical oxidizing environment. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of natural gas to the direct reduction of iron ore

Energy Technology Data Exchange (ETDEWEB)

1975-05-01

The Gas Committee of the U.N. Economic Commission for Europe evaluated the potentials of natural gas for direct reduction of iron ore. The report, based essentially on that by the Italian representative E. Pasero with comments and observations from experts of the other member countries, indicated the general tendency of the iron and steel industry to use natural gas to reduce production costs by reducing coke consumption. By the end of 1972, gas consumption by these industries was reported at 38.8 billion Btu/ton (10.79 Gcal/m ton) by the Steel Committee of the U.N. Economic Commission at the symposium on the economic and technical aspects of the direct reduction of iron ore, held in September 1972 in Bucharest. In comparison, coke consumption was 9.5 billion Btu/ton (2.64 Gcal/m ton) steel, liquid hydrocarbons 3.1 billion Btu (0.85 Gcal), and electricity 16.1 billion Btu (4.46 Gcal). Natural gas was used mainly for ore reduction and generation of the reducing gas in-shaft furnaces with backdraft heating circulation, fixed-bed furances (Hyl type), and fluidized-bed reactors. Processes include the Midrex (shaft furnace), H.I.B. (fluidized bed), and Novalfer (fluidized bed). These processes are used to obtain 4.5 million tons/yr of iron sponge for the production of steel in electric furnaces. The natural gas outlook for direct reduction of iron will depend on local conditions and fuel availability. Its industrial application has been most successful in mini-steel installations, especially in the U.S., Japan, and Western Europe, and it is recommended for developing countries with no steel-industry basis.

Synthesis of high intrinsic loss power aqueous ferrofluids of iron oxide nanoparticles by citric acid-assisted hydrothermal-reduction route

International Nuclear Information System (INIS)

Behdadfar, Behshid; Kermanpur, Ahmad; Sadeghi-Aliabadi, Hojjat; Morales, Maria del Puerto; Mozaffari, Morteza

2012-01-01

Monodispersed aqueous ferrofluids of iron oxide nanoparticle were synthesized by hydrothermal-reduction route. They were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy and dynamic light scattering. The results showed that certain concentrations of citric acid (CA) are required to obtain only magnetic iron oxides with mean particle sizes around 8 nm. CA acts as a modulator and reducing agent in iron oxide formation which controls nanoparticle size. The XRD, magnetic and heating measurements showed that the temperature and time of hydrothermal reaction can affect the magnetic properties of obtained ferrofluids. The synthesized ferrofluids were stable at pH 7. Their mean hydrodynamic size was around 80 nm with polydispersity index (PDI) of 0.158. The calculated intrinsic loss power (ILP) was 9.4 nHm 2 /kg. So this clean and cheap route is an efficient way to synthesize high ILP aqueous ferrofluids applicable in magnetic hyperthermia. - Graphical abstract: Monodispersed aqueous ferrofluids of iron oxide nanoparticles were synthesized by hydrothermal-reduction method with citric acid as reductant which is an efficient way to synthesize aqueous ferrofluids applicable in magnetic hyperthermia. Highlights: ► Aqueous iron oxide ferrofluids were synthesized by hydrothermal-reduction route. ► Citric acid acted as reducing agent and surfactant in the route. ► This is a facile, low energy and environmental friendly route. ► The aqueous iron oxide ferrofluids were monodispersed and stable at pH of 7. ► The calculated intrinsic loss power of the synthesized ferrofluids was very high.

Production and reduction of nitrous oxide in agricultural and forest soils.

Science.gov (United States)

Yu, K; Chen, G; Struwe, S; Kjøller, A

2000-06-01

A soil-water slurry experiment was conducted to study the potentials of N2O production and reduction in denitrification of agricultural and beech forest soils in Denmark. The effects of nitrate and ammonium additions on denitrification were also investigated. The forest soil showed a higher denitrification potential than the agricultural soil. However, N2O reduction potential of the agricultural soil was higher than the beech forest soil, shown by the ratio of N2O/N2 approximately 0.11 and 3.65 in the agricultural and the beech forest soils, respectively. Both nitrate and ammonium additions stimulated the N2O production in the two soils, but reduced the N2O reduction rates in the agricultural soil slurries. In contrast to the effect on the agricultural soil, nitrate reduced the N2O reduction rate in the beech forest soil, while ammonium showed a stimulating effect on the N2O reduction activity. After one week incubation, all of the N2O produced was reduced to N2 in the agricultural soil when nitrate was still present. Nitrous oxide reduction in the beech forest soil occurred only when nitrate almost disappeared. The different nitrate inhibitory effect on the N2O reduction activity in the two soils was due to the difference in soil pH. Inhibition of nitrate on N2O reduction was significant under acidic condition. Consequently, soil could serve as a sink of atmospheric N2O under the conditions of anaerobic, pH near neutral and low nitrate content.

Anaerobic Oxidation of Methane Coupled to Nitrite Reduction by Halophilic Marine NC10 Bacteria.

Science.gov (United States)

He, Zhanfei; Geng, Sha; Cai, Chaoyang; Liu, Shuai; Liu, Yan; Pan, Yawei; Lou, Liping; Zheng, Ping; Xu, Xinhua; Hu, Baolan

2015-08-15

Anaerobic oxidation of methane (AOM) coupled to nitrite reduction is a novel AOM process that is mediated by denitrifying methanotrophs. To date, enrichments of these denitrifying methanotrophs have been confined to freshwater systems; however, the recent findings of 16S rRNA and pmoA gene sequences in marine sediments suggest a possible occurrence of AOM coupled to nitrite reduction in marine systems. In this research, a marine denitrifying methanotrophic culture was obtained after 20 months of enrichment. Activity testing and quantitative PCR (qPCR) analysis were then conducted and showed that the methane oxidation activity and the number of NC10 bacteria increased correlatively during the enrichment period. 16S rRNA gene sequencing indicated that only bacteria in group A of the NC10 phylum were enriched and responsible for the resulting methane oxidation activity, although a diverse community of NC10 bacteria was harbored in the inoculum. Fluorescence in situ hybridization showed that NC10 bacteria were dominant in the enrichment culture after 20 months. The effect of salinity on the marine denitrifying methanotrophic culture was investigated, and the apparent optimal salinity was 20.5‰, which suggested that halophilic bacterial AOM coupled to nitrite reduction was obtained. Moreover, the apparent substrate affinity coefficients of the halophilic denitrifying methanotrophs were determined to be 9.8 ± 2.2 μM for methane and 8.7 ± 1.5 μM for nitrite. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Electrochemical behavior for a reduction of uranium oxide in a LiCl-Li2O molten salt with an integrated cathode assembly

International Nuclear Information System (INIS)

Park, Sung Bin; Park, Byung Heung; Seo, Chung Seok; Jung, Ki Jung; Park, Seong Won

2005-01-01

Electrolytic reduction of uranium oxide to uranium metal was studied in a LiCl-Li 2 O molten salt system. The reduction mechanism of the uranium oxide to a uranium metal has been studied by means of a cyclic voltammetry. Effects of the layer thickness of the uranium oxide and the thickness of the MgO on the overpotential of the cathode and the anode were investigated by means of a chronopotentiometry. From the cyclic voltamograms, the decomposition potentials of the metal oxides are the determining factors for the mechanism of the reduction of the uranium oxide in a Li Cl-3 wt% Li 2 O molten salt and the two mechanisms of the electrolytic reduction were considered with regards to the applied cathode potential. In the chronopotentiograms, the exchange current and the transfer coefficient based on the Tafel behavior were obtained with regard to the layer thickness of the uranium oxide which is loaded into the porous MgO membrane and the thickness of the porous MgO membrane. The maximum allowable currents for the changes of the layer thickness of the uranium oxide and the thickness of the MgO membrane were also obtained from the limiting potential which is the decomposition potential of LiCl

Nitric oxide reduction in coal combustion: role of char surface complexes in heterogeneous reactions.

Science.gov (United States)

Arenillas, Ana; Rubiera, Fernando; Pis, José J

2002-12-15

Nitrogen oxides are one of the major environmental problems arising from fossil fuel combustion. Coal char is relatively rich in nitrogen, and so this is an important source of nitrogen oxides during coal combustion. However, due to its carbonaceous nature, char can also reduce NO through heterogeneous reduction. The objectives of this work were on one hand to compare NO emissions from coal combustion in two different types of equipment and on the other hand to study the influence of char surface chemistry on NO reduction. A series of combustion tests were carried out in two different scale devices: a thermogravimetric analyzer coupled to a mass spectrometer and an FTIR (TG-MS-FTIR) and a fluidized bed reactor with an on line battery of analyzers. The TG-MS-FTIR system was also used to perform a specific study on NO heterogeneous reduction reactions using chars with different surface chemistry. According to the results obtained, it can be said that the TG-MS-FTIR system provides valuable information about NO heterogeneous reduction and it can give good trends of the behavior in other combustion equipments (i.e., fluidized bed combustors). It has been also pointed out that NO-char interaction depends to a large extent on temperature. In the low-temperature range (800 degrees C), a different mechanism is involved in NO heterogeneous reduction, the nature of the carbon matrix being a key factor.

The impact of electrochemical reduction potentials on the electrocatalytic activity of graphene oxide toward the oxygen reduction reaction in an alkaline medium

International Nuclear Information System (INIS)

Toh, Shaw Yong; Loh, Kee Shyuan; Kamarudin, Siti Kartom; Daud, Wan Ramli Wan

2016-01-01

We report the synthesis of graphene via the electrochemical reduction of graphene oxide (GO). In this study, GO nanosheets from aqueous dispersion were pre-assembled on a glassy carbon (GC) electrode and then electrochemically reduced in 1 M KOH under various constant reduction potentials in the range of −0.6 V to −1.5 V (vs. Ag/AgCl). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses revealed that the graphitic structure was substantially restored in the resulting electrochemically reduced graphene oxide (ERGO). The ERGO electrodes exhibited significantly enhanced catalytic activity toward the oxygen reduction reaction (ORR) in an alkaline medium compared with the initial GO electrode. Of the ERGO electrodes produced at various cathodic potentials, the ERGO-1.2 V electrode, which was produced at a reduction potential of −1.2 V, demonstrated the best catalytic activity toward the ORR in an alkaline medium. The ORR on GO and ERGO electrodes was shown to proceed via a two-electron mechanism at low overpotentials. The agreement between the spectroscopy results and electrochemical measurements provide strong evidence that the enhanced ORR catalytic activity is mainly attributed to the restoration of GO’s graphitic structure. Furthermore, the ERGO-1.2 V electrode showed excellent tolerance to the methanol poisoning effect compared with a Pt/C catalyst electrode.

Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

Energy Technology Data Exchange (ETDEWEB)

Taette, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Maendar, Hugo; Pohako, Kaija; Reivelt, Kaido; Lohmus, Ants [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Pehk, Tonis [National Institute of Chemical and Biological Physics, Akadeemia tee 23, Tallinn 12618 (Estonia); Natali, Marco [ICIS-CNR, Corso Stati Uniti 4, Padova 35127 (Italy); Gurauskis, Jonas [Instituto de Ciencia de Materiales de Aragon C.S.I.C., University of Zaragoza Fac. De Ciencias, c/Pedro Cerbuna 12, Zaragoza 50009 (Spain); Maeeorg, Uno, E-mail: tanelt@fi.tartu.ee [Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411 (Estonia)

2011-06-15

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO{sub 2}, TiO{sub 2}, ZrO{sub 2}, HfO{sub 2} and CeO{sub 2}) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

Catalyst and method for reduction of nitrogen oxides

Science.gov (United States)

Ott, Kevin C [Los Alamos, NM

2008-05-27

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

Probing the Active Surface Sites for CO Reduction on Oxide-Derived Copper Electrocatalysts

DEFF Research Database (Denmark)

Verdaguer Casadevall, Arnau; Li, Christina W.; Johansson, Tobias Peter

2015-01-01

CO electroreduction activity on oxide-derived Cu (OD-Cu) was found to correlate with metastable surface features that bind CO strongly. OD-Cu electrodes prepared by H-2 reduction of Cu2O precursors reduce CO to acetate and ethanol with nearly 50% Faradaic efficiency at moderate overpotential. Tem...

Nitrate Reduction to Nitrite, Nitric Oxide and Ammonia by Gut Bacteria under Physiological Conditions

Science.gov (United States)

Tiso, Mauro; Schechter, Alan N.

2015-01-01

The biological nitrogen cycle involves step-wise reduction of nitrogen oxides to ammonium salts and oxidation of ammonia back to nitrites and nitrates by plants and bacteria. Neither process has been thought to have relevance to mammalian physiology; however in recent years the salivary bacterial reduction of nitrate to nitrite has been recognized as an important metabolic conversion in humans. Several enteric bacteria have also shown the ability of catalytic reduction of nitrate to ammonia via nitrite during dissimilatory respiration; however, the importance of this pathway in bacterial species colonizing the human intestine has been little studied. We measured nitrite, nitric oxide (NO) and ammonia formation in cultures of Escherichia coli, Lactobacillus and Bifidobacterium species grown at different sodium nitrate concentrations and oxygen levels. We found that the presence of 5 mM nitrate provided a growth benefit and induced both nitrite and ammonia generation in E.coli and L.plantarum bacteria grown at oxygen concentrations compatible with the content in the gastrointestinal tract. Nitrite and ammonia accumulated in the growth medium when at least 2.5 mM nitrate was present. Time-course curves suggest that nitrate is first converted to nitrite and subsequently to ammonia. Strains of L.rhamnosus, L.acidophilus and B.longum infantis grown with nitrate produced minor changes in nitrite or ammonia levels in the cultures. However, when supplied with exogenous nitrite, NO gas was readily produced independently of added nitrate. Bacterial production of lactic acid causes medium acidification that in turn generates NO by non-enzymatic nitrite reduction. In contrast, nitrite was converted to NO by E.coli cultures even at neutral pH. We suggest that the bacterial nitrate reduction to ammonia, as well as the related NO formation in the gut, could be an important aspect of the overall mammalian nitrate/nitrite/NO metabolism and is yet another way in which the microbiome

Nitrate reduction to nitrite, nitric oxide and ammonia by gut bacteria under physiological conditions.

Directory of Open Access Journals (Sweden)

Mauro Tiso

Full Text Available The biological nitrogen cycle involves step-wise reduction of nitrogen oxides to ammonium salts and oxidation of ammonia back to nitrites and nitrates by plants and bacteria. Neither process has been thought to have relevance to mammalian physiology; however in recent years the salivary bacterial reduction of nitrate to nitrite has been recognized as an important metabolic conversion in humans. Several enteric bacteria have also shown the ability of catalytic reduction of nitrate to ammonia via nitrite during dissimilatory respiration; however, the importance of this pathway in bacterial species colonizing the human intestine has been little studied. We measured nitrite, nitric oxide (NO and ammonia formation in cultures of Escherichia coli, Lactobacillus and Bifidobacterium species grown at different sodium nitrate concentrations and oxygen levels. We found that the presence of 5 mM nitrate provided a growth benefit and induced both nitrite and ammonia generation in E.coli and L.plantarum bacteria grown at oxygen concentrations compatible with the content in the gastrointestinal tract. Nitrite and ammonia accumulated in the growth medium when at least 2.5 mM nitrate was present. Time-course curves suggest that nitrate is first converted to nitrite and subsequently to ammonia. Strains of L.rhamnosus, L.acidophilus and B.longum infantis grown with nitrate produced minor changes in nitrite or ammonia levels in the cultures. However, when supplied with exogenous nitrite, NO gas was readily produced independently of added nitrate. Bacterial production of lactic acid causes medium acidification that in turn generates NO by non-enzymatic nitrite reduction. In contrast, nitrite was converted to NO by E.coli cultures even at neutral pH. We suggest that the bacterial nitrate reduction to ammonia, as well as the related NO formation in the gut, could be an important aspect of the overall mammalian nitrate/nitrite/NO metabolism and is yet another way in

Development of Head-end Pyrochemical Reduction Process for Advanced Oxide Fuels

Energy Technology Data Exchange (ETDEWEB)

Park, B. H.; Seo, C. S.; Hur, J. M.; Jeong, S. M.; Hong, S. S.; Choi, I. K.; Choung, W. M.; Kwon, K. C.; Lee, I. W. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2008-12-15

The development of an electrolytic reduction technology for spent fuels in the form of oxide is of essence to introduce LWR SFs to a pyroprocessing. In this research, the technology was investigated to scale a reactor up, the electrochemical behaviors of FPs were studied to understand the process and a reaction rate data by using U{sub 3}O{sub 8} was obtained with a bench scale reactor. In a scale of 20 kgHM/batch reactor, U{sub 3}O{sub 8} and Simfuel were successfully reduced into metals. Electrochemical characteristics of LiBr, LiI and Li{sub 2}Se were measured in a bench scale reactor and an electrolytic reduction cell was modeled by a computational tool.

Effect of high-temperature treatment on Fe/ZSM-5 prepared by chemical vapor deposition of FeCl3. II. Nitrous oxide decomposition, selective oxidation of benzene to phenol, and selective reduction of nitric oxide by isobutane

NARCIS (Netherlands)

Zhu, Q.; Teeffelen, van R.M.; Santen, van R.A.; Hensen, E.J.M.

2004-01-01

The catalytic performance (nitrous oxide decomposition, hydroxylation of benzene to phenol with nitrous oxide, and selective reduction of nitric oxide by i-butane) was evaluated for a set of HZSM-5 and sublimed Fe/ZSM-5 catalysts, which have been extensively characterized in an earlier contribution

Reduction and shaping of graphene-oxide by laser-printing for controlled bone tissue regeneration and bacterial killing

Science.gov (United States)

Palmieri, Valentina; Barba, Marta; Di Pietro, Lorena; Gentilini, Silvia; Chiara Braidotti, Maria; Ciancico, Carlotta; Bugli, Francesca; Ciasca, Gabriele; Larciprete, Rosanna; Lattanzi, Wanda; Sanguinetti, Maurizio; De Spirito, Marco; Conti, Claudio; Papi, Massimiliano

2018-01-01

Graphene and graphene oxide (GO) are capable of inducing stem cells differentiation into bone tissue with variable efficacy depending on reductive state of the material. Thus, modulation of osteogenic process and of bone mineral density distribution is theoretically possible by controlling the GO oxidative state. In this study, we laser-printed GO surfaces in order to obtain both a local photo-thermal GO reduction and the formation of nano-wrinkles along precise geometric pattern. Initially, after cells adhered on the surface, stem cells migrated and accumulated on the reduced and wrinkled surface. When the local density of the stem cells on the reduced stripes was high, cells started to proliferate and occupy the oxidized/flat area. The designed surfaces morphology guided stem cell orientation and the reduction accelerated differentiation. Furthermore the reduced sharp nano-wrinkles were able to enhance the GO antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), a common cause of prosthetic joints infections. This strategy can offer a revolution in present and future trends of scaffolds design for regenerative medicine.

IMPACTS OF ANTIFOAM ADDITIONS AND ARGON BUBBLING ON DEFENSE WASTE PROCESSING FACILITY REDUCTION/OXIDATION

Energy Technology Data Exchange (ETDEWEB)

Jantzen, C.; Johnson, F.

2012-06-05

During melting of HLW glass, the REDOX of the melt pool cannot be measured. Therefore, the Fe{sup +2}/{Sigma}Fe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., foaming) or melter life (e.g., metal formation and accumulation). A production facility such as the Defense Waste Processing Facility (DWPF) cannot wait until the melt or waste glass has been made to assess its acceptability, since by then no further changes to the glass composition and acceptability are possible. therefore, the acceptability decision is made on the upstream process, rather than on the downstream melt or glass product. That is, it is based on 'feed foward' statistical process control (SPC) rather than statistical quality control (SQC). In SPC, the feed composition to the melter is controlled prior to vitrification. Use of the DWPF REDOX model has controlled the balanjce of feed reductants and oxidants in the Sludge Receipt and Adjustment Tank (SRAT). Once the alkali/alkaline earth salts (both reduced and oxidized) are formed during reflux in the SRAT, the REDOX can only change if (1) additional reductants or oxidants are added to the SRAT, the Slurry Mix Evaporator (SME), or the Melter Feed Tank (MFT) or (2) if the melt pool is bubble dwith an oxidizing gas or sparging gas that imposes a different REDOX target than the chemical balance set during reflux in the SRAT.

Direct electrodeposition of a biocomposite consisting of reduced graphene oxide, chitosan and glucose oxidase on a glassy carbon electrode for direct sensing of glucose

International Nuclear Information System (INIS)

Yang, S.; Lu, Z.; Luo, S.; Liu, C.; Tang, Y.

2013-01-01

We have electrodeposited a composite film consisting of graphene oxide, chitosan and glucose oxidase directly on a glassy carbon electrode (GCE) through electrochemical reduction of a solution of the 3 components under controlled direct electrical potential. The procedure takes only several minutes, and the thickness of the resulting film is uniform and controllable. The GOx has uncompromised bioactivity and exhibits reversible 2-proton and 2-electron transfer in presence of glucose. It therefore can be used amperometric sensing of glucose. The biosensor has a fast response (<3 s), a detection limit of 0.4 μM (which is 50-fold lower compared to the biosensor prepared by drop-casting solutions of the same materials onto an GCE), and a linear response in the 0.4 μM to 2 mM concentration range (which again is much better than that of the biosensor prepared by the drop-casting method). Other features include high reproducibility, long-time storage stability, and satisfactory selectivity. We presume that the direct single-step electrodeposition of this nanocomposite offers a promising approach towards novel types of highly sensitive and stable electrochemical biosensors. (author)

A study on the reduction of uranium oxide to uranium metal in LiCl molten salt

International Nuclear Information System (INIS)

Seo, J. S.; Hur, J. M.; Lee, W. K.; Hong, S. S.; Kang, D. S.; Park, S. W.

2002-01-01

Research for the analysis on a metallization process of uranium oxide in LiCl-Li molten salt was carried out. Effect of a concentration of Li 2 O on the metallization process was also studied. The new concept, electrochemical reduction of uranium oxide in LiCl-Li 2 O molten salt was proposed. The concept is based on the integrated process of metallization of UO 2 with simultaneous electrochemical reduction of Li 2 O which is recycled in a closed system. In a LiCl-Li molten salt system, U 3 O 8 whose conversion ratio to U turns out to be 97.1%, showed a better metallization characteristic than UO 2 . It is verified that electrochemically reduced Li is well deposited on the UO 2 powder cathode through a porous magnesia filter in LiCl-Li 2 O molten salt. In that process Li 2 O was from by the reduction process of UO 2 to U. This electrochemical reduction process showed good results to covert UO 2 to U

Electrocatalytic Reduction-oxidation of Chlorinated Phenols using a Nanostructured Pd-Fe Modified Graphene Catalyst

International Nuclear Information System (INIS)

Shi, Qin; Wang, Hui; Liu, Shaolei; Pang, Lei; Bian, Zhaoyong

2015-01-01

A Pd-Fe modified graphene (Pd-Fe/G) catalyst was prepared by the Hummers oxidation method and bimetallic co-deposition method. The catalyst was then characterized by various characterization techniques and its electrochemical property toward the electrocatalytic reduction-oxidation of chlorinated phenols was investigated by using cyclic voltammetry and differential pulse voltammetry. The results of the characterization show that the Pd-Fe/G catalyst in which the weight proportion of Pd and Fe is 1:1 has an optimal surface performance. The diameter of the Pd-Fe particles is approximately 5.2 ± 0.3 nm, with a uniform distribution on the supporting graphene. This is smaller than the Pd particles of a Pd-modified graphene (Pd/G) catalyst. The Pd-Fe/G catalyst shows a higher electrocatalytic activity than the Pd/G catalyst for reductive dechlorination when feeding with hydrogen gas. The reductive peak potentials of −0.188 V, −0.836 V and −0.956 V in the DPV curves are attributed to the dechlorination of ortho-Cl, meta-Cl, and para-Cl in 2-chlorophenol, 3-chlorophenol and 4-chlorophenol, respectively. In accordance with an analysis of the frontier orbital theory, the order of ease of dechlorination with Pd-Fe/G catalyst is 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. The Pd-Fe/G catalyst has a greater activity than the Pd/G catalyst in accelerating the two-electron reduction of O_2 to H_2O_2, which is attributed to the higher current of the reduction peak at approximately −0.40 V when feeding with oxygen gas. Therefore, the Pd-Fe/G catalyst exhibits a higher electrocatalytic activity than the Pd/G catalyst for the reductive dechlorination and acceleration of the two-electron reduction of O_2 to H_2O_2.

RP-UHPLC-UV-ESI-MS/MS analysis of LPMO generated C4-oxidized gluco-oligosaccharides after non-reductive labeling with 2-aminobenzamide.

Science.gov (United States)

Frommhagen, Matthias; van Erven, Gijs; Sanders, Mark; van Berkel, Willem J H; Kabel, Mirjam A; Gruppen, Harry

2017-08-07

Lytic polysaccharide monooxygenases (LPMOs) are able to cleave recalcitrant polysaccharides, such as cellulose, by oxidizing the C1 and/or C4 atoms. The analysis of the resulting products requires a variety of analytical techniques. Up to now, these techniques mainly focused on the identification of non-oxidized and C1-oxidized oligosaccharides. The analysis of C4-oxidized gluco-oligosaccharides is mostly performed by using high pressure anion exchange chromatography (HPAEC). However, the alkaline conditions used during HPAEC analysis lead to tautomerization of C4-oxidized gluco-oligosaccharides, which limits the use of this technique. Here, we describe the use of reverse phase-ultra high performance liquid chromatography (RP-UHPLC) in combination with non-reductive 2-aminobenzamide (2-AB) labeling. Non-reductive 2-AB labeling enabled separation of C4-oxidized gluco-oligosaccharides from their non-oxidized counterparts. Moreover, RP-UHPLC does not require buffered mobile phases, which reduce mass spectrometry (MS) sensitivity. The latter is seen as an advantage over other techniques such as hydrophilic interaction liquid chromatography and porous graphitized carbon coupled to MS. RP-UHPLC coupled to UV detection and mass spectrometry allowed the identification of both labeled non-oxidized and C4-oxidized oligosaccharides. Non-reductive labeling kept the ketone at the C4-position of LPMO oxidized oligosaccharides intact, while selective reducing agents such as sodium triacetoxyborohydride (STAB) reduced this ketone group. Our results show that RP-UHPLC-UV-ESI-MS in combination with non-reductively 2-AB labeling is a suitable technique for the separation and identification of LPMO-generated C4-oxidized gluco-oligosaccharides. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Direct measurement of the Cu oxidation number of cuprate superconductor ceramics

International Nuclear Information System (INIS)

Dankhazi, Z.; Szasz, A.; Kojnok, J.; Gal, M.; Torkos, K.; Solymos, K.; Kirchmayr, H.; Mueller, H.; Watson, L.M.

1991-01-01

The Cu oxidation number of YBa 2 Cu 3 O 7 was measured directly by soft X-ray fluorescent spectroscopy both at room temperature and at liquid N 2 temperature. The measurements are based on a calibration curve from different Ba-O compounds. The effects of changes in oxidation number above and below the transition temperature and its role in high-T c superconductivity are discussed

Particle-particle interactions in aluminum reduction of boron oxide

International Nuclear Information System (INIS)

Logan, K.V.; McLemore, W.J.S.; Sparrow, J.T.

1988-01-01

The Georgia Tech Research Institute has been studying the use of thermite reactions for the production of specialized compounds since the mid-1950's. One of the goals of the research at GTRI is to define the reaction mechanism in order to be ble to predict the resultant reaction behaviour and thus prevent hazardous conditions. Thermite processing advantages are discussed in this paper. A typical thermite type of reaction to produce a composite titanium diboride/alumina is shown. The reactions typically use three starting materials for the production of a specific compound. A preliminary experimental mechanistic model of the extremely exothermic oxidation-reduction reaction is being developed

Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides

Science.gov (United States)

Lehninger, Albert L.; Vercesi, Anibal; Bababunmi, Enitan A.

1978-01-01

Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca2+ and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca2+ is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as β-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca2+. Successive cycles of Ca2+ release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca2+-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca2+, mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport. Images PMID:25436

Synthesis of full-density nanocrystalline tungsten carbide by reduction of tungstic oxide at room temperature

International Nuclear Information System (INIS)

El-Eskandarany, M.S.; Omori, M.; Ishikuro, M.; Konno, T.J.; Takada, K.; Sumiyama, K.; Hirai, T.; Suzuki, K.

1996-01-01

Among the hard alloys, WC alloys find wide industrial applications as tips for cutting tools and wear-resistant parts. Their intrinsic resistance to oxidation and corrosion at high temperatures also makes them desirable as a protective coating for devices at elevated temperatures. In the industrial scale of production, WC is prepared by a direct union of the elements at a temperature of 3,273 to 3,473 K. Accordingly, the high cost of preparation is a disadvantage of this process. Here, the authors report a novel technique for preparing a large amount of WC powder using a simple method. This process is based on mechanical solid-state reduction (MSSR) followed y solid-state reaction (SSR) during room-temperature ball milling (a high energy ball mill, Fritsch P6, was used at a rotation speed of 4.2 s -1 ) of a mixture of WO 3 , Mg, and C powders

A Graphite Oxide Paper Polymer Electrolyte for Direct Methanol Fuel Cells

Directory of Open Access Journals (Sweden)

Ravi Kumar

2011-01-01

Full Text Available A flow directed assembly of graphite oxide solution was used in the formation of free-standing graphene oxide paper of approximate thickness of 100 μm. The GO papers were characterised by XRD and SEM. Electrochemical characterization of the GO paper membrane electrode assembly revealed proton conductivities of 4.1 × 10−2 S cm−1 to 8.2 × 10−2 S cm−1 at temperatures of 25–90°C. A direct methanol fuel cell, at 60°C, gave a peak power density of 8 mW cm−2 at a current density of 35 mA cm−2.

Biogeochemistry of Fe and Tc Reduction and Oxidation in FRC Sediment

International Nuclear Information System (INIS)

John M, Zachara; James K, Fredrickson; Ravi K, Kukkadapu; Steven C, Smith; David W, Kennedy

2004-01-01

The objectives are: (1) To rigorously characterize the distribution of Fe(II) and Fe(III) in FRC sediment. (2) To identify changes to Fe(II)/Fe(III) distribution and concentration resulting from DIRB activity. (3) To determine the dependence of Tc(VII) reduction rate on biogenic Fe(II) and it's forms. (4) To establish tendency of Tc(IV) and biogenic Fe(II) to oxidize and their effects on Tc immobilization. The mineralogic and chemical properties of the pristine, bioreduced, and chemically extracted FRC sediments were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), X-ray microscopy (XRM, at the PNC-CAT beamline at APS), Moessbauer spectroscopy, and scanning and transmission electron microscopy with lattice fringe imaging. Chemical extraction included dithionite-citrate-bicarbonate (DCB), acid ammonium oxalate (AAO), and hydroxylamine hydrochloride (HAH). The FRC sediment was incubated under anoxic conditions with the facultative dissimilatory metal-reducing bacterium Shewanella putrefaciens, strain CN32 in defined aqueous solutions/media with bicarbonate and PIPES buffers for time periods exceeding 75 d. Lactate was used as the electron donor. Aqueous and sorbed Fe(II) (ferrozine assay and 0.5 N HCl extraction) and Mn(II) (ICP-MS and 10 mM CuSO 4 extraction), and pH were monitored to define the reduction progress and extent. The bioreduced materials were characterized using the abovementioned techniques. Bioreduced (pasteurized) sediment or chemically extracted/reduced sediment spiked with Fe(II) was washed with a PIPES buffer/electrolyte solution, and spiked with NaTc(VII)O 4 to yield a concentration of 20 (micro)M. The Tc(VII)-spiked samples were agitated and equilibrated at 25 C and sampled over time to assess the Tc(VII) reduction rate. Selected sediment samples containing 20 (micro)M of reduced Tc [Tc(IV)] were subjected to oxidation by: (1) successive headspace replacements of air, and (2) open system equilibration with air. Removed aqueous

Inhibition of Direct Electrolytic Ammonia Oxidation Due to a Change in Local pH

International Nuclear Information System (INIS)

Zöllig, Hanspeter; Morgenroth, Eberhard; Udert, Kai M.

2015-01-01

Electrochemical ammonia oxidation has gained a lot of attention recently as an efficient method for ammonia removal from wastewater, for the use in ammonia-based fuel cells and the production of high purity hydrogen. Thermally decomposed iridium oxide films (TDIROF) have been shown to be catalytically active for direct ammonia oxidation in aqueous solutions if NH 3 is present. However, the process was reported to be rapidly inhibited on TDIROF. Herein, we show that this fast inhibition of direct ammonia oxidation does not result from surface poisoning by adsorbed elemental nitrogen (N ads ). Instead, we propose that direct ammonia oxidation and oxygen evolution can lead to a drop of the local pH at the electrode resulting in a low availability of the actual reactant, NH 3 . The hypothesis was tested with cyclic voltammetry (CV) experiments on stagnant and rotating disk electrodes (RDE). The CV experiments on the stagnant electrode revealed that the decrease of the ammonia oxidation peaks was considerably reduced by introducing an idle phase at open circuit potential between subsequent scans. Furthermore, the polarization of the TDIROF electrode into the hydrogen evolution region (HER) resulted in increased ammonia oxidation peaks in the following anodic scans which can be explained with an increased local pH after the consumption of protons in the HER. On the RDE, the ammonia oxidation peaks did not decrease in immediately consecutive scans. These findings would not be expected if surface poisoning was responsible for the fast inhibition but they are in good agreement with the proposed mechanism of pH induced limitation by the reactant, NH 3 . The plausibility of the mechanism was also supported by our numerical simulations of the processes in the Nernstian diffusion layer. The knowledge about this inhibition mechanism of direct ammonia oxidation is especially important for the design of electrochemical cells for wastewater treatment. The mechanism is not only

Oxygen Reduction Kinetics Enhancement on a Heterostructured Oxide Surface for Solid Oxide Fuel Cells

KAUST Repository

Crumlin, Ethan J.

2010-11-04

Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of ∼85 nm thick La0.8Sr0.2CoO3-δ (LSC113) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced (∼3-4 orders of magnitude above bulk LSC113) by surface decorations of (La 0.5Sr0.5)2CoO4±δ (LSC214) with coverage in the range from ∼0.1 to ∼15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC113/LSC214 regions, which were shown to be atomically sharp. © 2010 American Chemical Society.

Oxygen Reduction Kinetics Enhancement on a Heterostructured Oxide Surface for Solid Oxide Fuel Cells

KAUST Repository

Crumlin, Ethan J.; Mutoro, Eva; Ahn, Sung-Jin; la O’ , Gerardo Jose; Leonard, Donovan N.; Borisevich, Albina; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

2010-01-01

Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of ∼85 nm thick La0.8Sr0.2CoO3-δ (LSC113) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced (∼3-4 orders of magnitude above bulk LSC113) by surface decorations of (La 0.5Sr0.5)2CoO4±δ (LSC214) with coverage in the range from ∼0.1 to ∼15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC113/LSC214 regions, which were shown to be atomically sharp. © 2010 American Chemical Society.

The cathodic reduction of dioxygen on uranium oxide in dilute alkaline aqueous solution

International Nuclear Information System (INIS)

Hocking, W.H.; Betteridge, J.S.; Shoesmith, D.W.

1991-09-01

The cathodic reduction of dioxygen on uranium oxide in dilute alkaline aqueous solutions has been investigated within the context of a program to develop a comprehensive model to predict the behaviour of used CANDU (Canada Deuterium Uranium) nuclear fuel under disposal-vault conditions. Two different kinds of ceramic UO 2 were studied: reactor-grade CANDU fuel with normal p-type electrical conductivity and low-resistance material that exhibits n-type photoelectrochemical behaviour. The transport of electroactive species in solution was controlled by varying the rotation rate of rotating disc electrodes (RDE) and rotating ring-disc electrodes (RRDE). Steady-state polarization measurements were made using the current-interrupt method to compensate for the potential drop caused by ohmic resistance. Any release of peroxide to solution from the UO 2 (disc) surface could be monitored by oxidizing it at the Au ring of an RRDE. The existing theory for the cathodic 0 2 -reduction process as applied to RDE and RRDE experiments has been reviewed as a starting point for the interpretation of the results obtained in our work. (37 figs., 2 tabs., 170 refs.)

Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing

International Nuclear Information System (INIS)

Shamsipur, Mojtaba; Amouzadeh Tabrizi, Mahmoud

2014-01-01

In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28 mV in 0.1 M phosphate buffer solution (pH 7.0) with a scan rate of 50 mV/s. The average surface coverage is 2.62 × 10 −10 mol cm −2 . The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8 mM (R 2 = 0.9878), good reproducibility and detection limit of 40.8 μM. The results from the biosensor were similar (± 5%) to those obtained from the clinical analyzer. - Highlights: • A direct electron transfer reaction of glucose oxidase was observed on GCE/ERGO/SDS. • This composite film was successfully applied in preparation of glucose biosensor. • The detection limit of the biosensor was estimated to be 40.8 μM. • The results from the sensor were similar to those obtained from the clinical analyzer

Determination of the extent of reduction of dense UO{sub 2} cathodes from direct electrochemical reduction studies in molten chloride medium

Energy Technology Data Exchange (ETDEWEB)

Sri Maha Vishnu, D.; Sanil, N. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Murugesan, N. [Materials Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Shakila, L. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Ramesh, C. [Materials Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Mohandas, K.S., E-mail: ksmd@igcar.gov.in [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Nagarajan, K. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2012-08-15

Electro-reduction of solid UO{sub 2} to U has been studied with molten CaCl{sub 2} or LiCl as the electrolyte medium. Electro-reduction of thick (>3 mm), powder compacted and sintered pellets of UO{sub 2} showed incomplete reduction resulting in a mixture of uranium metal and UO{sub 2}. The extent of reduction of UO{sub 2} to U was determined by employing a novel method called 'metal estimation by hydrogen sensor (MEHS)', in which the hydrogen evolved during the reaction of U metal in the reduced product with con. HBr was measured using an in-house developed polymer electrolyte based amperometric hydrogen sensor. The results of our investigations on incompletely reduced UO{sub 2} pellets in both CaCl{sub 2} and LiCl melts showed that the extent of reduction of different regions of the oxide pellet was different. It varied from 88.3% on the surface of the pellet as against 3.7% towards the centre bulk during electro-reduction in CaCl{sub 2} (at 1173 K). The metallisation was found restricted to the surface of the pellets reduced in LiCl melt (at 923 K). Electro-reduction of small chunks of UO{sub 2} pellet in CaCl{sub 2} melt resulted in products with lower extent of reduction. Based on the measurements, a probable mechanism on the propagation of reduction through the solid UO{sub 2} matrix during the electrochemical reduction process has been proposed.

Enhanced reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide

International Nuclear Information System (INIS)

Li, F.B.; Li, X.M.; Zhou, S.G.; Zhuang, L.; Cao, F.; Huang, D.Y.; Xu, W.; Liu, T.X.; Feng, C.H.

2010-01-01

The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (α-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of α-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe 2+ + α-FeOOH and the system of DIRB + α-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of α-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments. - This is the first case reporting the reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide.

Enhanced reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide

Energy Technology Data Exchange (ETDEWEB)

Li, F.B., E-mail: cefbli@soil.gd.c [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Li, X.M. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhou, S.G.; Zhuang, L. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Cao, F. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Huang, D.Y.; Xu, W.; Liu, T.X. [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650 (China); Feng, C.H. [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China)

2010-05-15

The transformation of DDT was studied in an anaerobic system of dissimilatory iron-reducing bacteria (Shewanella decolorationis S12) and iron oxide (alpha-FeOOH). The results showed that S. decolorationis could reduce DDT into DDD, and DDT transformation rate was accelerated by the presence of alpha-FeOOH. DDD was observed as the primary transformation product, which was demonstrated to be transformed in the abiotic system of Fe{sup 2+} + alpha-FeOOH and the system of DIRB + alpha-FeOOH. The intermediates of DDMS and DBP were detected after 9 months, likely suggesting that reductive dechlorination was the main dechlorination pathway of DDT in the iron-reducing system. The enhanced reductive dechlorination of DDT was mainly due to biogenic Fe(II) sorbed on the surface of alpha-FeOOH, which can serve as a mediator for the transformation of DDT. This study demonstrated the important role of DIRB and iron oxide on DDT and DDD transformation under anaerobic iron-reducing environments. - This is the first case reporting the reductive dechlorination of DDT in an anaerobic system of dissimilatory iron-reducing bacteria and iron oxide.

A Study on N{sub 2}O Direct Oxidation Process with Re-oxidation Annealing for the Improvement of Interface Properties in 4H-SiC MOS Capacitor

Energy Technology Data Exchange (ETDEWEB)

Cho, Doohyung; Park, Kunsik; Yoo, Seongwook; Kim, Sanggi; Lee, Jinhwan; Kim, Kwangsoo [Electronics and Telecommunications Research Institute (ETRI), Daejeon (Korea, Republic of)

2017-08-15

The effect of N{sub 2}O direct oxidation processes with re-oxidation on SiC/SiO{sub 2} interface characteristics has been investigated. With different oxidation and post oxidation annealing (POA) processes, the flat-band voltage, effective dielectric charge density, and interface trap density are obtained from the capacitance-voltage curves. For the proposed N{sub 2}O direct oxidation processes with re-oxidation, oxides were grown in N{sub 2}O ambient, diluted in high-purity N{sub 2} to 10% concentration, for 5 h at 1230 ℃. After the growth, some samples were annealed additionally at 1200 ℃ in O{sub 2} or H{sub 2}O for 20 min. N{sub 2}O direct oxidation with re-oxidation processes was confirmed that SiC/SiO{sub 2} interface properties and dielectric stability have better performance than with other conventional oxidation processes. This oxidation technique is expected to improve gate dielectric stability for application to SiC MOS devices; in particular, it can be used to obtain high-quality SiC/SiO{sub 2} interface properties.

Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

Science.gov (United States)

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

Energy Technology Data Exchange (ETDEWEB)

Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Marry K.; Tyliszczak, T.; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

2015-09-01

Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells.

Effect of stress on NiO reduction in solid oxide fuel cells: A new application of energy-resolved neutron imaging

DEFF Research Database (Denmark)

Makowska, Malgorzata; Strobl, Markus; Lauridsen, Erik Mejdal

2015-01-01

Recently, two new phenomena linking stress field and reduction rates in anode-supported solid oxide fuel cells (SOFCs) have been demonstrated, so-called accelerated creep during reduction and reduction rate enhancement and nucleation due to stress (Frandsen et al., 2014). These complex phenomena...

Surface Selective Oxide Reduction During the Intercritical Annealing of Medium Mn Steel

Science.gov (United States)

Jo, Kyoung Rae; Cho, Lawrence; Oh, Jong Han; Kim, Myoung Soo; Kang, Ki Cheol; De Cooman, Bruno C.

2017-08-01

Third generation advanced high-strength steels achieve an excellent strength-ductility balance using a cost-effective alloy composition. During the continuous annealing of medium Mn steel, the formation of an external selective oxide layer of MnO has a negative impact on the coating quality after galvanizing. A procedure to reduce the selective oxide was therefore developed. It involves annealing in the temperature range of 1073 K to 1323 K (800 °C to 1050 °C) in a HNx gas atmosphere. Annealing at higher temperatures and the use of larger H2 volume fractions are shown to make the gas atmosphere reducing with respect to MnO. The reduction of the surface MnO layer was observed by SEM, GDOES, and cross-sectional TEM analysis.

Low-temperature aluminum reduction of graphene oxide, electrical properties, surface wettability, and energy storage applications.

Science.gov (United States)

Wan, Dongyun; Yang, Chongyin; Lin, Tianquan; Tang, Yufeng; Zhou, Mi; Zhong, Yajuan; Huang, Fuqiang; Lin, Jianhua

2012-10-23

Low-temperature aluminum (Al) reduction is first introduced to reduce graphene oxide (GO) at 100-200 °C in a two-zone furnace. The melted Al metal exhibits an excellent deoxygen ability to produce well-crystallized reduced graphene oxide (RGO) papers with a low O/C ratio of 0.058 (Al-RGO), compared with 0.201 in the thermally reduced one (T-RGO). The Al-RGO papers possess outstanding mechanical flexibility and extremely high electrical conductivities (sheet resistance R(s) ~ 1.75 Ω/sq), compared with 20.12 Ω/sq of T-RGO. More interestingly, very nice hydrophobic nature (90.5°) was observed, significantly superior to the reported chemically or thermally reduced papers. These enhanced properties are attributed to the low oxygen content in the RGO papers. During the aluminum reduction, highly active H atoms from H(2)O reacted with melted Al promise an efficient oxygen removal. This method was also applicable to reduce graphene oxide foams, which were used in the GO/SA (stearic acid) composite as a highly thermally conductive reservoir to hold the phase change material for thermal energy storage. The Al-reduced RGO/SnS(2) composites were further used in an anode material of lithium ion batteries possessing a higher specific capacity. Overall, low-temperature Al reduction is an effective method to prepare highly conductive RGO papers and related composites for flexible energy conversion and storage device applications.

Direct reduction process using fines and with reduced CO2 emission

CSIR Research Space (South Africa)

Morrison, A

2004-08-01

Full Text Available , of which there is an abundant supply in South Africa. The rotary hearth process is one and two such units are currently in operation in Japan: one at Nippon Steel and another at Kobe Steel.3 Direct reduction for ferroalloy production offers...

Calibration of redox potential in sperm wash media and evaluation of oxidation-reduction potential values in various assisted reproductive technology culture media using MiOXSYS system.

Science.gov (United States)

Panner Selvam, M K; Henkel, R; Sharma, R; Agarwal, A

2018-03-01

Oxidation-reduction potential describes the balance between the oxidants and antioxidants in fluids including semen. Various artificial culture media are used in andrology and IVF laboratories for sperm preparation and to support the development of fertilized oocytes under in vitro conditions. The composition and conditions of these media are vital for optimal functioning of the gametes. Currently, there are no data on the status of redox potential of sperm processing and assisted reproduction media. The purpose of this study was to compare the oxidation-reduction potential values of the different media and to calibrate the oxidation-reduction potential values of the sperm wash medium using oxidative stress inducer cumene hydroperoxide and antioxidant ascorbic acid. Redox potential was measured in 10 different media ranging from sperm wash media, freezing media and assisted reproductive technology one-step medium to sequential media. Oxidation-reduction potential values of the sequential culture medium and one-step culture medium were lower and significantly different (p value to identify the physiological range of oxidation-reduction potential that does not have any adverse effect on normal physiological sperm function. © 2017 American Society of Andrology and European Academy of Andrology.

The Fundamental Role of Nano-Scale Oxide Films in the Oxidation of Hydrogen and the Reduction of Oxygen on Noble Metal Electrocatalysts

Energy Technology Data Exchange (ETDEWEB)

Digby Macdonald

2005-04-15

The derivation of successful fuel cell technologies requires the development of more effective, cheaper, and poison-resistant electrocatalysts for both the anode (H{sub 2} oxidation in the presence of small amounts of CO from the reforming of carbonaceous fuels) and the cathode (reduction of oxygen in the presence of carried-over fuel). The proposed work is tightly focused on one specific aspect of electrocatalysis; the fundamental role(s) played by nanoscale (1-2 nm thick) oxide (''passive'') films that form on the electrocatalyst surfaces above substrate-dependent, critical potentials, on charge transfer reactions, particularly at elevated temperatures (25 C < T < 200 C). Once the role(s) of these films is (are) adequately understood, we will then use this information to specify, at the molecular level, optimal properties of the passive layer for the efficient electrocatalysis of the oxygen reduction reaction.

A comprehensive skeletal mechanism for the oxidation of n-heptane generated by chemistry-guided reduction

Energy Technology Data Exchange (ETDEWEB)

Zeuch, Thomas [Institut fuer Physikalische Chemie, Tammannstrasse 6, 37077 Goettingen (Germany); Moreac, Gladys [Renault, 1, avenue du Golf, 78288 Guyancourt cedex (France); Ahmed, Syed Sayeed; Mauss, Fabian [Lehrstuhl fuer Thermodynamik und Thermische Verfahrenstechnik, Sielower Strasse 12, 03044 Cottbus (Germany)

2008-12-15

Applied to the primary reference fuel n-heptane, we present the chemistry-guided reduction (CGR) formalism for generating kinetic hydrocarbon oxidation models. The approach is based on chemical lumping and species removal with the necessity analysis method, a combined reaction flow and sensitivity analysis. Independent of the fuel size, the CGR formalism generates very compact submodels for the alkane low-temperature oxidation and provides a general concept for the development of compact oxidation models for large model fuel components such as n-decane and n-tetradecane. A defined sequence of simplification steps, consisting of the compilation of a compact detailed chemical model, the application of linear chemical lumping, and finally species removal based on species necessity values, allows a significantly increased degree of reduction compared to the simple application of the necessity analysis, previously published species, or reaction removal methods. The skeletal model derived by this procedure consists of 110 species and 1170 forward and backward reactions and is validated against the full range of combustion conditions including low and high temperatures, fuel-lean and fuel-rich mixtures, pressures between 1 and 40 bar, and local (species concentration profiles in flames, plug flow and jet-stirred reactors, and reaction sensitivity coefficients) and global parameters (ignition delay times in shock tube experiments, ignition timing in a HCCI engine, and flame speeds). The species removal is based on calculations using a minimum number of parameter configurations, but complemented by a very broad parameter variation in the process of compiling the kinetic input data. We further demonstrate that the inclusion of sensitivity coefficients in the validation process allows efficient control of the reduction process. Additionally, a compact high-temperature n-heptane oxidation model of 47 species and 468 reactions was generated by the application of necessity

Synthesis of carboxylate-functionalized graphene nanosheets for high dispersion of platinum nanoparticles based on the reduction of graphene oxide via 1-pyrenecarboxaldehyde

International Nuclear Information System (INIS)

Kuang, Yinjie; Zheng, Xingliang; Zhou, Qionghua; Lu, Cuihong; Chen, Jinhua; Zhang, Xiaohua

2013-01-01

A one-step reduction/functionalization strategy for the synthesis of carboxylate-functionalized graphene nanosheets is reported in this paper. 1-pyrenecarboxaldehyde (PCA) is introduced as a new reductant for the chemical reduction of graphene oxide (GO), serving three roles: reducing GO to graphene nanosheets (GNs), stabilizing the as-prepared GNs due to the electrostatic repulsion of the oxidation products of PCA (1-pyrenecarboxylate, PC − ) on the surface of the GNs and anchoring Pt nanoparticles (Pt NPs) with high dispersion and small particle size. Transmission electron microscopy shows that Pt NPs with an average diameter of 1.3 ± 0.2 nm are uniformly dispersed on the surface of the PC − -functionalized GNs (PC − -GNs). The obtained Pt NPs/PC − -GNs nanohybrids have higher electrocatalytic activity and stability towards methanol oxidation in comparison with Pt NPs supported on GNs obtained by the chemical reduction of GO with the typical reductant, hydrazine. (paper)

Electrochemical Reduction of Oxygen and Nitric Oxide at Low Temperature on La1−xSrxFeO3−δ Cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2014-01-01

A series of six strontium-substituted lanthanum ferrites (La1-xSrxFeO3-delta, x = 0.00, 0.05, 0.15, 0.25, 0.35, and 0.50) were synthesized using the glycine-nitrate process and evaluated as cathodes for the electrochemical reduction of oxygen and nitric oxide in the temperature range 200 to 400...... degrees C, using cone-shaped electrodes and cyclic voltammetry. It was shown that the ferrites had a higher activity towards the electrochemical reduction of nitric oxide than towards the electrochemical reduction of oxygen, in the investigated temperature range. The highest activity towards...... the electrochemical reduction of nitric oxide was found for La0.95Sr0.05FeO3-delta at 400 degrees C. This compound also showed the highest activity towards the electrochemical reduction of oxygen at 400 degrees C. The highest apparent selectivity was found for the compound LaFeO3 at 200 degrees C. The materials...

The anaerobic degradation of organic matter in Danish coastal sediments: iron reduction, manganese reduction, and sulfate reduction

DEFF Research Database (Denmark)

Canfield, Donald Eugene; Thamdrup, B; Hansen, Jens Würgler

1993-01-01

). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic carbon oxidation process in the upper 10 cm of the sediment. In the less Mn-rich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far more...... speculate that in shallow sediments of the Skagerrak, surface Mn oxides are present in a somewhat reduced oxidation level (deep basin....

Triplet-State Dissolved Organic Matter Quantum Yields and Lifetimes from Direct Observation of Aromatic Amine Oxidation.

Science.gov (United States)

Schmitt, Markus; Erickson, Paul R; McNeill, Kristopher

2017-11-21

Excited triplet state chromophoric dissolved organic matter ( 3 CDOM*) is a short-lived mixture of excited-state species that plays important roles in aquatic photochemical processes. Unlike the study of the triplet states of well-defined molecules, which are amenable to transient absorbance spectroscopy, the study of 3 CDOM* is hampered by it being a complex mixture and its low average intersystem crossing quantum yield (Φ ISC ). This study is an alternative approach to investigating 3 CDOM* using transient absorption laser spectroscopy. The radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formed through oxidation by 3 CDOM*, was directly observable by transient absorption spectroscopy and was used to probe basic photophysical properties of 3 CDOM*. Quenching and control experiments verified that TMPD •+ was formed from 3 CDOM* under anoxic conditions. Model triplet sensitizers with a wide range of excited triplet state reduction potentials and CDOM oxidized TMPD at near diffusion-controlled rates. This gives support to the idea that a large cross-section of 3 CDOM* moieties are able to oxidize TMPD and that the complex mixture of 3 CDOM* can be simplified to a single signal. Using the TMPD •+ transient, the natural triplet lifetime and Φ ISC for different DOM isolates and natural waters were quantified; values ranged from 12 to 26 μs and 4.1-7.8%, respectively.

General Solvent-dependent Strategy toward Enhanced Oxygen Reduction Reaction in Graphene/Metal Oxide Nanohybrids: Effects of Nitrogen-containing Solvent

Science.gov (United States)

Kao, Wei-Yao; Chen, Wei-Quan; Chiu, Yu-Hsiang; Ho, Yu-Hsuan; Chen, Chun-Hu

2016-11-01

A general solvent-dependent protocol directly influencing the oxygen reduction reaction (ORR) in metal oxide/graphene nanohybrids has been demonstrated. We conducted the two-step synthesis of cobalt oxide/N-doped graphene nanohybrids (CNG) with solvents of water, ethanol, and dimethylformamide (DMF), representing tree typical categories of aqueous, polar organic, and organic N-containing solvents commonly adopted for graphene nanocomposites preparation. The superior ORR performance of the DMF-hybrids can be attributed to the high nitrogen-doping, aggregation-free hybridization, and unique graphene porous structures. As DMF is the more effective N-source, the spectroscopic results support a catalytic nitrogenation potentially mediated by cobalt-DMF coordination complexes. The wide-distribution of porosity (covering micro-, meso-, to macro-pore) and micron-void assembly of graphene may further enhance the diffusion kinetics for ORR. As the results, CNG by DMF-synthesis exhibits the high ORR activities close to Pt/C (i.e. only 8 mV difference of half-wave potential with electron transfer number of 3.96) with the better durability in the alkaline condition. Additional graphene hybrids comprised of iron and manganese oxides also show the superior ORR activities by DMF-synthesis, confirming the general solvent-dependent protocol to achieve enhanced ORR activities.

Electrochemical oxidation of ethanol using PtRh/C electrocatalysts in alkaline medium and synthesized by sodium borohydride and alcohol reduction

International Nuclear Information System (INIS)

Fontes, Eric Hossein

2017-01-01

PtRh/C were prepared by the following atomic proportions: (100,0), (0,100), (90,10), (70,30) and (50,50). The methods employed in the synthesis of these materials were reduction by sodium borohydride and reduction by alcohol. The metal salts used were H 2 PtCl 6 3•6H 2 0 and (RhNO 3 ) 3 , the support used was Carbon black XC72 and the bulk metal composition was 20% and 80% of support. The electrocatalysts were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction and Transmission electron microscopy. The ethanol electrochemical oxidation mechanism was investigated by in situ Fourier Transform Infrared Spectroscopy couple to an Attenuated Total Reflection technique. The electrocatalytic activity were evaluated by Cyclic Voltammetry, Linear Sweep Voltammetry and Chronoamperometry techniques. The Fuel Cells tests were made in a single direct alcohol fuel cell with alkaline membrane. The working electrodes were prepared by a thin porous coating technique. X-ray diffraction allowed to verify metallic alloys, segregate phases and to calculate the percentage of metallic alloys. It was else possible to identify crystallographic phases. Infrared Spectroscopy allowed to verify that the electrochemical oxidation of ethanol was carried out by an incomplete mechanism. PtRh(70:30)/C prepared by sodium borohydride produced large amounts of carbon dioxide and acetaldehyde. Rh/C showed electrocatalytic activity when compared with other materials studied.

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

Radiation-induced destruction of organic compounds in aqueous solutions by dual oxidation/reduction mechanism

Energy Technology Data Exchange (ETDEWEB)

Chaychiana, M.; Silverman, J.; Al-Sheikhly, M. [Department of Materials Science and Engineering, University of Maryland (United States); Poster, D.; Neta, P.; Huie, R. [Chemical Science and Technology Laboratory, National Institute of Standard and Technology (United States)

2011-07-01

This research presents the feasibility and mechanisms of using high energy electrons for the dechlorination of polychlorinated biphenyls (PCBs) in marine sediment, and hazardous organic compounds in waste water. The remediation of the organic contaminants by ionizing radiation is achieved by means of both reduction and oxidation processes. PCBs in marine sediment can be effectively dechlorinated by reduction, while toxic organic compounds in water are removed mainly by oxidation. Radiolytic degradation of aqueous suspensions of PCBs in marine sediments in the presence of isopropanol was also studied. Addition of isopropanol was necessary to enhance the radiolytic yield and the dechlorination of PCBs. Also presented are results from an examination of the oxidative and reductive effects of electron-beam irradiation on the concentrations of six organic solvents in water. The organic solvents in water were prepared to mimic a pharmaceutical waste stream. Radiation-induced destruction of benzene was also investigated using pulse radiolysis technique. Pulse radiolysis with spectrophotometric and conductometric detection was utilized to study the formation and reactions of radicals from benzene and dienes in aqueous solutions. The benzene OH adduct, {sup ●}C{sub 6}H{sub 6}OH, reacts with O{sub 2} (k = 3x10{sup 8} L mol{sup -1} s{sup -1}) in a reversible reaction. The peroxyl radical, HOC{sub 6}H{sub 6}O{sub 2}{sup ●}, undergoes O{sub 2}●- elimination, bimolecular decay, and reaction with benzene to initiate a chain reaction, depending on the dose rate, benzene concentration, and pH. The occurrence of the chain reaction is demonstrated in low-dose-rate gamma radiolysis experiments where the consumption of O{sub 2} was monitored. (author)

Reduction of U3O8 to U by a metallic reductant, Li

International Nuclear Information System (INIS)

Jin-Mok Hur; Sun-Seok Hong; Hansoo Lee

2010-01-01

Reduction of U 3 O 8 was investigated for the recycling of spent oxide fuel from a commercial nuclear power plant. The possible reduction methods were proposed and compared. Based on the thermodynamic analysis, Li metal was selected as a reductant. The optimum reaction temperature for the reduction of U 3 O 8 was investigated at the wider reaction temperature range. The adverse oxidation of U metal by Li 2 O at 1,000 deg C was experimentally verified. Ellingham diagram was constructed to investigate the extent of the uranium oxides reduction when the reaction was carried out above melting point of U metal. (author)

Palladium catalyzed direct oxidation of benzene with molecular oxygen to phenol

International Nuclear Information System (INIS)

Jintoku, Tetsuro; Takaki, Ken; Fujiwara, Yuzo; Fuchita, Yoshio; Hiraki, Katsuma.

1990-01-01

Direct phenol synthesis from benzene is currently one of the most important problems in modern chemistry. We have reported new phenol synthesis from benzene and O 2 via direct activation of a C-H aromatic bond by the Pd(OAc) 2 /phenanthroline catalyst system. The evidence for direct oxidation of benzene by O 2 was obtained using 18 O and 2 H isotopes. The mechanism was proposed on the basis of these results and the reactions of Ph-Pd σ complex intermediates. (author)

Reduction of blood nitric oxide levels is associated with clinical improvement of the chronic pelvic pain related to endometriosis

Directory of Open Access Journals (Sweden)

M.G. Rocha

2015-04-01

Full Text Available The objective of this prospective study was to determine the plasma levels of nitric oxide (NO in women with chronic pelvic pain secondary to endometriosis (n=24 and abdominal myofascial pain syndrome (n=16. NO levels were measured in plasma collected before and 1 month after treatment. Pretreatment NO levels (μM were lower in healthy volunteers (47.0±12.7 than in women with myofascial pain (64.2±5.0, P=0.01 or endometriosis (99.5±12.9, P<0.0001. After treatment, plasma NO levels were reduced only in the endometriosis group (99.5±12.9 vs 61.6±5.9, P=0.002. A correlation between reduction of pain intensity and reduction of NO level was observed in the endometriosis group [correlation = 0.67 (95%CI = 0.35 to 0.85, P<0.0001]. Reduction of NO levels was associated with an increase of pain threshold in this group [correlation = -0.53 (-0.78 to -0.14, P<0.0001]. NO levels appeared elevated in women with chronic pelvic pain diagnosed as secondary to endometriosis, and were directly associated with reduction in pain intensity and increase in pain threshold after treatment. Further studies are needed to investigate the role of NO in the pathophysiology of pain in women with endometriosis and its eventual association with central sensitization.

Hydrogen permeation rate reduction by post-oxidation of aluminide coatings on DIN 1.4914 martensitic steel (MANET)

International Nuclear Information System (INIS)

Perujo, A.; Sample, T.

1996-01-01

In a previous work, it has been shown that lower aluminium content aluminide, having the same permeation rate reduction as the higher aluminium content, exhibited a lower hardness and greater ductility and therefore greater crack resistance than the higher aluminium content. In this work we combine this characteristic with a post-oxidation to obtain a further deuterium permeation reduction. The post-oxidation was performed in air at 1023 K for 15 h and at 1223 K for 10 h and 1 h. The maximum deuterium permeation rate reduction obtained is very moderate (maximum of a factor 500 for 1 h at 1223 K) as compared to that of the non-oxidised aluminide specimen (two orders of magnitude) and is constant in the temperature range studied (573-800 K). This method has the technological appeal of using air rather than the controlled environment used by other authors. (orig.)

A study for an electrolytic reduction of tantalum oxide in a LiCl-Li2O molten salt

International Nuclear Information System (INIS)

Park, Sung Bin; Park, Byung Heung; Seo, Chung Seok; Kang, Dae Seung; Kwon, Seon Gil; Park, Seong Won

2005-01-01

Korea Atomic Energy Research Institute (KAERI) has developed the Advanced Spent Fuel Conditioning Process (ACP) to be an innovative technology for handling the PWR spent fuel. As part of ACP, the electrolytic reduction process (ER process) is the electrochemical reduction process of uranium oxide to uranium metal in a molten salt. The ER process has advantages in a technical stability, an economic potential and a good proliferation resistance. KAERI has reported on the good experimental results of an electrochemical reduction of the uranium oxide in a 20 kg HM/batch lab-scale. The ER process can be applicable to the reduction of other metal oxides. Metal tantalum powder has attracted attention for a variety of applications. A tantalum capacitor made from superfine and pliable tantalum powders is very small in size and it has a higher-capacitance part, therefore it is useful for microelectronic devices. By the ER process the metal tantalum can be obtained from tantalum pentoxide. In this work, a 40 g Ta 2 O 5 /batch electrochemical reactor was used for the synthesis of the metal tantalum. From the results of the cyclic voltammograms for the Ta 2 O 5 -LiCl-Li 2 O system, the mechanism of the tantalum reduction in a molten LiCl-Li 2 O salt system was investigated. Tantalum pentoxide is chemically reduced to tantalum metal by the lithium metal which is electrochemically deposited into an integrated cathode assembly in the LiCl-Li 2 O molten salt. The experiments for the tantalum reduction were performed with a chronopotentiometry in the reactor cell, the reduced products were analyzed from an analysis of the X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray (SEM-EDX). From the results, the electrolytic reduction process is applicable to the synthesis of metal tantalum

Effects of Oxygen Partial Pressure on Oxidation Behavior of CMnSi TRIP Steel in an Oxidation-Reduction Scheme

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong-Hwan; Huh, Joo-Youl [Korea University, Seoul (Korea, Republic of); Kim, Myung-Soo; Kim, Jong-Sang [POSCO Technical Research Laboratories, Gwangyang (Korea, Republic of)

2017-02-15

An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure (Po{sub 2}) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at 700 ℃ under atmospheres with various Po{sub 2} values. Irrespective of Po{sub 2}, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe oxide scale (a Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4} bilayer) in the heating stage. In contrast to Si, Mn tended to segregate at the scale surface as (Fe,Mn){sub 2}O{sub 3}. The multilayered structure of (Fe,Mn){sub 2}O{sub 3}/Fe{sub 2}O{sub 3}/Fe{sub 3}O{sub 4}/amorphous Si-Mn-O remained even after extended oxidizing at 700 ℃ for 60 s. Fe{sub 2}O{sub 3} was the dominantly growing oxide phase in the scale. The enhanced growth rate of Fe{sub 2}O{sub 3} with increasing Po{sub 2} resulted in the formation of more Kirkendall voids in the amorphous Si-rich layer and a less Mn segregation at the scale surface. The mechanisms underlying the absence of FeO and the formation of Kirkendall voids are discussed.

Improving Technology And Setting-Up A Production Line For High Quality Zinc Oxide (99.5%) With A Capacity Of 150 Ton/Year By Reduction-Oxidation Process

International Nuclear Information System (INIS)

Pham Minh Tuan; Tran The Dinh; Tran Ngoc Vuong; Tuong Duy Nhan; Tran Trung Son; Le Huu Thiep; Nguyen Trung Dung; Le Thi Hong; Luong Manh Hung; Bui Huy Cuong

2014-01-01

Zinc oxide is used not only for the rubber industry, but also in many other industries such as pigments, ceramics, cosmetics etc. On the basis of references on international scientific researches and practical activities for the production of zinc oxide in our country, we have carried out additional research and testing to establish a zinc oxide production line for preparation of high quality (99.5%) product by treating the industrial zinc containing waste to obtain required composition materials [Zn] >50%; [Pb] < 0.3%; [Cl]/[PbO] < 0.2 for reduction-oxidation processes using reverberatory furnace. (author)

In situ spectroscopic monitoring of CO2 reduction at copper oxide electrode.

Science.gov (United States)

Wang, Liying; Gupta, Kalyani; Goodall, Josephine B M; Darr, Jawwad A; Holt, Katherine B

2017-04-28

Copper oxide modified electrodes were investigated as a function of applied electrode potential using in situ infrared spectroscopy and ex situ Raman and X-ray photoelectron spectroscopy. In deoxygenated KHCO 3 electrolyte bicarbonate and carbonate species were found to adsorb to the electrode during reduction and the CuO was reduced to Cu(i) or Cu(0) species. Carbonate was incorporated into the structure and the CuO starting material was not regenerated on cycling to positive potentials. In contrast, in CO 2 saturated KHCO 3 solution, surface adsorption of bicarbonate and carbonate was not observed and adsorption of a carbonato-species was observed with in situ infrared spectroscopy. This species is believed to be activated, bent CO 2 . On cycling to negative potentials, larger reduction currents were observed in the presence of CO 2 ; however, less of the charge could be attributed to the reduction of CuO. In the presence of CO 2 CuO underwent reduction to Cu 2 O and potentially Cu, with no incorporation of carbonate. Under these conditions the CuO starting material could be regenerated by cycling to positive potentials.

Reduced-graphene-oxide supported tantalum-based electrocatalysts: Controlled nitrogen doping and oxygen reduction reaction

Science.gov (United States)

Yang, Xiaoyun; Mo, Qijie; Guo, Yulin; Chen, Nana; Gao, Qingsheng

2018-03-01

Controlled N-doping is feasible to engineer the surface stoichiometry and the electronic configuration of metal-oxide electrocatalysts toward efficient oxygen reduction reactions (ORR). Taking reduced graphene oxide supported tantalum-oxides (TaOx/RGO) for example, this work illustrated the controlled N-doping in both metal-oxides and carbon supports, and the contribution to the improved ORR activity. The active N-doped TaOx/RGO electrocatalysts were fabricated via SiO2-assisted pyrolysis, in which the amount and kind of N-doping were tailored toward efficient electrocatalysis. The optimal nanocomposites showed a quite positive half-wave potential (0.80 V vs. RHE), the excellent long-term stability, and the outstanding tolerance to methanol crossing. The improvement in ORR was reasonably attributed to the synergy between N-doped TaOx and N-doped RGO. Elucidating the importance of controlled N-doping for electrocatalysis, this work will open up new opportunities to explore noble-metal-free materials for renewable energy applications.

Achieving direct electrochemistry of glucose oxidase by one step electrochemical reduction of graphene oxide and its use in glucose sensing

Energy Technology Data Exchange (ETDEWEB)

Shamsipur, Mojtaba; Amouzadeh Tabrizi, Mahmoud, E-mail: mahmoud.tabrizi@gmail.com

2014-12-01

In this paper, the direct electrochemistry of glucose oxidase (GOD) was accomplished at a glassy carbon electrode modified with electrochemically reduced graphene oxide/sodium dodecyl sulfate (GCE/ERGO/SDS). A pair of reversible peaks is exhibited on GCE/ERGO/SDS/GOD by cyclic voltammetry. The peak-to-peak potential separation of immobilized GOD is 28 mV in 0.1 M phosphate buffer solution (pH 7.0) with a scan rate of 50 mV/s. The average surface coverage is 2.62 × 10{sup −10} mol cm{sup −2}. The resulting biosensor exhibited a good response to glucose with linear range from 1 to 8 mM (R{sup 2} = 0.9878), good reproducibility and detection limit of 40.8 μM. The results from the biosensor were similar (± 5%) to those obtained from the clinical analyzer. - Highlights: • A direct electron transfer reaction of glucose oxidase was observed on GCE/ERGO/SDS. • This composite film was successfully applied in preparation of glucose biosensor. • The detection limit of the biosensor was estimated to be 40.8 μM. • The results from the sensor were similar to those obtained from the clinical analyzer.

Bacterial Oxidation and Reduction of Iron in the Processes of Creation and Treatment of Acid Mining Waters

Directory of Open Access Journals (Sweden)

Daniel Kupka

2004-12-01

Full Text Available Acid mine drainages (AMDs arise at the weathering of sulphidic minerals. The occurrence of acidic streams is commonly associated with the human mining activities. Due to the disruption and excavation of sulphide deposits, the oxidation processes have initiated. Acidic products of sulphide oxidation accelerate the degradation of accompanying minerals. AMDs typically contain high concentrations of sulfuric acid and soluble metals and cause serious ecological problems due to the water pollution and the devastation of adjacent country. Microbial life in these extremely acidic environments may be considerably diverse. AMDs are abundant in bacteria capable to oxidize and/or to reduce iron. The rate of bacterial oxidation of ferrous iron released from pyrite surfaces is up to one million times faster than the chemical oxidation rate at low pH. Bacterial regeneration of ferric iron maintains the continuity of pyrite oxidation and the production of AMDs. Another group of microorganisms living in these environments are acidophilic ferric iron reducing bacteria. This group of microorganisms has been discovered only relatively recently. Acidophilic heterotrophic bacteria reduce ferric iron in either soluble or solid forms to ferrous iron. The reductive dissolution of ferric iron minerals brings about a mobilization of iron as well as associated heavy metals. The Bacterial oxidation and reduction of iron play an important role in the transformation of either crystalline or amorphous iron-containing minerals, including sulphides, oxides, hydroxysulfates, carbonates and silicates. This work discusses the role of acidophilic bacteria in the natural iron cycling and the genesis of acidic effluents. The possibilities of application of iron bacteria in the remediation of AMDs are also considered.

A novel direct carbon fuel cell by approach of tubular solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Liu, Renzhu; Zhao, Chunhua; Li, Junliang; Zeng, Fanrong; Wang, Shaorong; Wen, Tinglian; Wen, Zhaoyin [CAS Key Laboratory of Materials for Energy Conversion, Shanghai Inorganic Energy Materials and Power Source Engineering Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS), 1295 Dingxi Road, Shanghai 200050 (China)

2010-01-15

A direct carbon fuel cell based on a conventional anode-supported tubular solid oxide fuel cell, which consisted of a NiO-YSZ anode support tube, a NiO-ScSZ anode functional layer, a ScSZ electrolyte film, and a LSM-ScSZ cathode, has been successfully achieved. It used the carbon black as fuel and oxygen as the oxidant, and a preliminary examination of the DCFC has been carried out. The cell generated an acceptable performance with the maximum power densities of 104, 75, and 47 mW cm{sup -2} at 850, 800, and 750 C, respectively. These results demonstrate the feasibility for carbon directly converting to electricity in tubular solid oxide fuel cells. (author)

Dimension reduction of frequency-based direct Granger causality measures on short time series.

Science.gov (United States)

Siggiridou, Elsa; Kimiskidis, Vasilios K; Kugiumtzis, Dimitris

2017-09-01

The mainstream in the estimation of effective brain connectivity relies on Granger causality measures in the frequency domain. If the measure is meant to capture direct causal effects accounting for the presence of other observed variables, as in multi-channel electroencephalograms (EEG), typically the fit of a vector autoregressive (VAR) model on the multivariate time series is required. For short time series of many variables, the estimation of VAR may not be stable requiring dimension reduction resulting in restricted or sparse VAR models. The restricted VAR obtained by the modified backward-in-time selection method (mBTS) is adapted to the generalized partial directed coherence (GPDC), termed restricted GPDC (RGPDC). Dimension reduction on other frequency based measures, such the direct directed transfer function (dDTF), is straightforward. First, a simulation study using linear stochastic multivariate systems is conducted and RGPDC is favorably compared to GPDC on short time series in terms of sensitivity and specificity. Then the two measures are tested for their ability to detect changes in brain connectivity during an epileptiform discharge (ED) from multi-channel scalp EEG. It is shown that RGPDC identifies better than GPDC the connectivity structure of the simulated systems, as well as changes in the brain connectivity, and is less dependent on the free parameter of VAR order. The proposed dimension reduction in frequency measures based on VAR constitutes an appropriate strategy to estimate reliably brain networks within short-time windows. Copyright © 2017 Elsevier B.V. All rights reserved.

The Effect of Thickness and Chemical Reduction of Graphene Oxide on Nanoscale Friction.

Science.gov (United States)

Kwon, Sangku; Lee, Kyung Eun; Lee, Hyunsoo; Koh, Sang Joon; Ko, Jae-Hyeon; Kim, Yong-Hyun; Kim, Sang Ouk; Park, Jeong Young

2018-01-18

The tribological properties of two-dimensional (2D) atomic layers are quite different from three-dimensional continuum materials because of the unique mechanical responses of 2D layers. It is known that friction on graphene shows a remarkable decreasing behavior as the number of layers increases, which is caused by the puckering effect. On other graphene derivatives, such as graphene oxide (GO) or reduced graphene oxide (rGO), the thickness dependence of friction is important because of the possibilities for technical applications. In this report, we demonstrate unexpected layer-dependent friction behavior on GO and rGO layers. Friction force microscopy measurements show that nanoscale friction on GO does not depend on the number of layers; however, after reduction, friction on rGO shows an inverse thickness dependence compared with pristine graphene. We show that the friction on rGO is higher than that on SiO 2 at low load, and that an interesting crossover behavior at higher load occurs because of the lower friction coefficient and higher adhesion of the rGO. We provide a relevant interpretation that explains the effect of thickness and chemical reduction on nanoscale friction.

Sequential reductive and oxidative biodegradation of chloroethenes stimulated in a coupled bioelectro-process.

Science.gov (United States)

Lohner, Svenja T; Becker, Dirk; Mangold, Klaus-Michael; Tiehm, Andreas

2011-08-01

This article for the first time demonstrates successful application of electrochemical processes to stimulate sequential reductive/oxidative microbial degradation of perchloroethene (PCE) in mineral medium and in contaminated groundwater. In a flow-through column system, hydrogen generation at the cathode supported reductive dechlorination of PCE to cis-dichloroethene (cDCE), vinyl chloride (VC), and ethene (ETH). Electrolytically generated oxygen at the anode allowed subsequent oxidative degradation of the lower chlorinated metabolites. Aerobic cometabolic degradation of cDCE proved to be the bottleneck for complete metabolite elimination. Total removal of chloroethenes was demonstrated for a PCE load of approximately 1.5 μmol/d. In mineral medium, long-term operation with stainless steel electrodes was demonstrated for more than 300 days. In contaminated groundwater, corrosion of the stainless steel anode occurred, whereas DSA (dimensionally stable anodes) proved to be stable. Precipitation of calcareous deposits was observed at the cathode, resulting in a higher voltage demand and reduced dechlorination activity. With DSA and groundwater from a contaminated site, complete degradation of chloroethenes in groundwater was obtained for two months thus demonstrating the feasibility of the sequential bioelectro-approach for field application.

Accelerated creep in solid oxide fuel cell anode supports during reduction

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Makowska, Malgorzata Grazyna; Greco, Fabio

2016-01-01

To evaluate the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. The creep of reduced Ni-YSZ anode support at operating conditions has been...... studied previously. In this work a newly discovered creep phenomenon taking place during the reduction is reported. This relaxes stresses at a much higher rate (∼ x104) than creep during operation. The phenomenon was studied both in three-point bending and uniaxial tension. Differences between the two...... the NiO and the YSZ phases occurs during reduction. The accelerated creep should practically eliminate any residual stress in the anode support in an SOFC stack, as has previously been indirectly observed. This phenomenon has to be taken into account both in the production of stacks and in the simulation...

KINETICS OF DIRECT OXIDATION OF H2S IN COAL GAS TO ELEMENTAL SULFUR; F

International Nuclear Information System (INIS)

K.C. Kwon

2002-01-01

Removal of hydrogen sulfide (H(sub 2)S) from coal gasifier gas and sulfur recovery are key steps in the development of Department of Energy's (DOE's) advanced Vision 21 plants that employ coal and natural gas and produce electric power and clean transportation fuels. These Vision 21 plants will require highly clean coal gas with H(sub 2)S below 1 ppm and negligible amounts of trace contaminants such as hydrogen chloride, ammonia, alkali, heavy metals, and particulate. The conventional method of sulfur removal and recovery employing amine, Claus, and tail-gas treatment is very expensive. A second generation approach developed under DOE's sponsorship employs hot-gas desulfurization (HGD) using regenerable metal oxide sorbents followed by Direct Sulfur Recovery Process (DSRP). However, this process sequence does not remove trace contaminants and is targeted primarily towards the development of advanced integrated gasification combined cycle (IGCC) plants that produce electricity (not both electricity and transportation fuels). There is an immediate as well as long-term need for the development of cleanup processes that produce highly clean coal gas for next generation Vision 21 plants. To this end, a novel process is now under development at Research Triangle Institute (RTI) in which the H(sub 2)S in coal gas is directly oxidized to elemental sulfur over a selective catalyst. Such a process is ideally suited for coal gas from commercial gasifiers with a quench system to remove essentially all the trace contaminants except H(sub 2)S. This direct oxidation process has the potential to produce a super clean coal gas more economically than both conventional amine-based processes and HGD/DSRP. The objective of this research is to support the near- and long-term DOE efforts to commercialize this direct oxidation technology. Specifically, we aim to: Measure the kinetics of direct oxidation of H(sub 2)S to elemental sulfur over selective catalysts in the presence of major

Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

KAUST Repository

Li, Hailong

2016-07-19

Synergy for low temperature Hg0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO2/TiO2 (CuCeTi) catalyst. Hg0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO2 (CuTi), CeO2/TiO2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O2 to surface oxygen, which are favorable for Hg0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg0 oxidation in the absence of gas-phase O2. Cerium oxides in the combination promoted Hg0 oxidation through enhancing the transformations of NO to NO2. In the absence of NO, NH3 exhibited no inhibitive effect on Hg0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH3 and Hg0. In the presence of NO, although NH3 lowered Hg0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH3. This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg0 oxidation co-benefit from SCR units in coal-fired power plants.

Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

Energy Technology Data Exchange (ETDEWEB)

Hareesh, K., E-mail: appi.2907@gmail.com [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Joshi, R.P. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Sunitha, D.V. [School of Physics, Reva University, Bangalore 560064 (India); Bhoraskar, V.N. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

2016-12-15

Highlights: • Ag-Au-rGO nanocomposite was synthesized by gamma radiation assisted method. • Ag-Au nanoparticles of size (5–19) nm were decorated on rGO. • Ag-Au-rGO showed enhanced catalytic activity for reduction of 4-Nitrophenol. - Abstract: One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV–vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5–19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp{sup 2} domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

Study for electrochemical behavior of uranium oxide in a molten LiCl-Li2O system