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Sample records for thermochemical nitrate reduction

  1. Thermochemical nitrate reduction

    International Nuclear Information System (INIS)

    Cox, J.L.; Lilga, M.A.; Hallen, R.T.

    1992-09-01

    A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with ∼3 wt% NO 3 - solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200 degrees C to 350 degrees C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia ∼ methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics

  2. Differential nitrate accumulation, nitrate reduction, nitrate reductase ...

    African Journals Online (AJOL)

    However, the effects of potassium nitrate were higher than sodium nitrate, which was due to the positive effects of potassium on the enzyme activity, sugars transport, water and nutrient transport, protein synthesis and carbohydrate metabolism. In conclusion, potassium nitrate has better effect on the nitrate assimilatory ...

  3. 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.

  4. Catalyzed reduction of nitrate in aqueous solutions

    International Nuclear Information System (INIS)

    Haas, P.A.

    1994-08-01

    Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH 3 , hydrazine, or organic compounds containing oxygen would be advantageous for reduction of nitrate in sodium nitrate solutions. Objective of this seed money study was to determine minimum conditions for reduction. Proposed procedure was batchwise heating of aqueous solutions in closed vessels with monitoring of temperatures and pressures. A simple, convenient apparatus and procedure were demonstrated for observing formation of gaseous products and collecting samples for analyses. The test conditions were 250 degree C and 1000 psi max. Any useful reduction of sodium nitrate to sodium hydroxide as the primary product was not found. The nitrate present at pHs 3 or NH 4 NO 3 is easily decomposed, and the effect of nitromethane at these low pHs was confirmed. When acetic acid or formic acid was added, 21 to 56% of the nitrate in sodium nitrate solutions was reduced by methanol or formaldehyde. With hydrazine and acetic acid, 73 % of the nitrate was decomposed to convert NaNO 3 to sodium acetate. With hydrazine and formic acid, 36% of the nitrate was decomposed. If these products are more acceptable for final disposal than sodium nitrate, the reagents are cheap and the conversion conditions would be practical for easy use. Ammonium acetate or formate salts did not significantly reduce nitrate in sodium nitrate solutions

  5. Nitrate storage and dissimilatory nitrate reduction by eukaryotic microbes

    DEFF Research Database (Denmark)

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly......, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations....... and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate...

  6. Automated analysis for nitrate by hydrazine reduction

    Energy Technology Data Exchange (ETDEWEB)

    Kamphake, L J; Hannah, S A; Cohen, J M

    1967-01-01

    An automated procedure for the simultaneous determinations of nitrate and nitrite in water is presented. Nitrite initially present in the sample is determined by a conventional diazotization-coupling reaction. Nitrate in another portion of sample is quantitatively reduced with hydrazine sulfate to nitrite which is then determined by the same diazotization-coupling reaction. Subtracting the nitrite initially present in the sample from that after reduction yields nitrite equivalent to nitrate initially in the sample. The rate of analysis is 20 samples/hr. Applicable range of the described method is 0.05-10 mg/l nitrite or nitrate nitrogen; however, increased sensitivity can be obtained by suitable modifications.

  7. Nitrate reduction in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten; Kristiansen, Henning

    1991-01-01

    of total dissolved ions in the NO3- free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place. Nitrate is apparently reduced to N2 because both nitrite and ammonia are absent or found at very low concentrations. Possible electron donors......Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate...... processes of O2 and NO3- occur at rates that are fast compared to the rate of downward water transport. Nitrate-contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area. The persistence of the high content...

  8. Thermochemical sulphate reduction can improve carbonate petroleum reservoir quality

    Science.gov (United States)

    Jiang, Lei; Worden, Richard H.; Yang, Changbing

    2018-02-01

    Interest in the creation of secondary pore spaces in petroleum reservoirs has increased because of a need to understand deeper and more complex reservoirs. The creation of new secondary porosity that enhances overall reservoir quality in deeply buried carbonate reservoirs is controversial and some recent studies have concluded it is not an important phenomenon. Here we present petrography, geochemistry, fluid inclusion data, and fluid-rock interaction reaction modeling results from Triassic Feixianguan Formation, Sichuan Basin, China, core samples and explore the relative importance of secondary porosity due to thermochemical sulphate reduction (TSR) during deep burial diagenesis. We find that new secondary pores result from the dissolution of anhydrite and possibly from dissolution of the matrix dolomite. Assuming porosity before TSR was 16% and the percentage of anhydrite was 6%, modelling shows that, due to TSR, 1.6% additional porosity was created that led to permeability increasing from 110 mD (range 72-168 mD within a 95% confidence interval) to 264 mD (range 162-432 mD within a 95% confidence interval). Secondary porosity results from the density differences between reactant anhydrite and product calcite, the addition of new water during TSR, and the generation of acidity during the reaction of new H2S with the siderite component in pre-existing dolomite in the reservoir. Fluid pressure was high during TSR, and approached lithostatic pressure in some samples; this transient overpressure may have led to the maintenance of porosity due to the inhibition of compactional processes. An additional 1.6% porosity is significant for reserve calculations, especially considering that it occurs in conjunction with elevated permeability that results in faster flow rates to the production wells.

  9. Nitrate reduction in geologically heterogeneous catchments

    DEFF Research Database (Denmark)

    Refsgaard, Jens Christian; Auken, Esben; Bamberg, Charlotte A.

    2014-01-01

    In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface...... conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root...... the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface...

  10. The influence of nitrate concentrations and acidity on the electrocatalytic reduction of nitrate on platinum

    NARCIS (Netherlands)

    Groot, de M.T.; Koper, M.T.M.

    2004-01-01

    A study was performed to determine the influence of nitrate concentration and acidity on the reaction rate and selectivity of the electrocatalytic nitrate reduction on platinum. There are two different nitrate reduction mechanisms on platinum: a direct mechanism (0.4–0.1 V vs. SHE) and an indirect

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

    OpenAIRE

    Samuelsson, M O

    1985-01-01

    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 sod...

  12. CU(II): catalyzed hydrazine reduction of ferric nitrate

    International Nuclear Information System (INIS)

    Karraker, D.G.

    1981-11-01

    A method is described for producing ferrous nitrate solutions by the cupric ion-catalyzed reduction of ferric nitrate with hydrazine. The reaction is complete in about 1.5 hours at 40 0 C. Hydrazoic acid is also produced in substantial quantities as a reaction byproduct

  13. Inorganic nitrogen and nitrate reduction in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Qasim, S.Z.

    the secondary nitrite maximum seem to be associated with Persian Gulf water. It is suggested that these originate as a result of biological reduction of nitrate (denitrification) due to the prevailing reducing conditions associated with a pronounced depletion...

  14. Denitration of High Nitrate Salts Using Reductants

    Energy Technology Data Exchange (ETDEWEB)

    HD Smith; EO Jones; AJ Schmidt; AH Zacher; MD Brown; MR Elmore; SR Gano

    1999-05-03

    This report describes work conducted by Pacific Northwest National Laboratory (PNNL), in conjunction with Idaho National Engineering and Environmental Laboratory (INEEL), to remove nitrates in simulated low-activity waste (LAW). The major objective of this work was to provide data for identifying and demonstrating a technically viable and cost-effective approach to condition LAW for immobilization (grout).

  15. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes

    Science.gov (United States)

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-01-01

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes. PMID:26883983

  16. Lewis Acid Assisted Nitrate Reduction with Biomimetic Molybdenum Oxotransferase Complex.

    Science.gov (United States)

    Elrod, Lee Taylor; Kim, Eunsuk

    2018-03-05

    The reduction of nitrate (NO 3 - ) to nitrite (NO 2 - ) is of significant biological and environmental importance. While Mo IV (O) and Mo VI (O) 2 complexes that mimic the active site structure of nitrate reducing enzymes are prevalent, few of these model complexes can reduce nitrate to nitrite through oxygen atom transfer (OAT) chemistry. We present a novel strategy to induce nitrate reduction chemistry of a previously known catalyst Mo IV (O)(SN) 2 (2), where SN = bis(4- tert-butylphenyl)-2-pyridylmethanethiolate, that is otherwise incapable of achieving OAT with nitrate. Addition of nitrate with the Lewis acid Sc(OTf) 3 (OTf = trifluoromethanesulfonate) to 2 results in an immediate and clean conversion of 2 to Mo VI (O) 2 (SN) 2 (1). The Lewis acid additive further reacts with the OAT product, nitrite, to form N 2 O and O 2 . This work highlights the ability of Sc 3+ additives to expand the reactivity scope of an existing Mo IV (O) complex together with which Sc 3+ can convert nitrate to stable gaseous molecules.

  17. Electrochemical reduction of nitrate in the presence of an amide

    Science.gov (United States)

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2002-01-01

    The electrochemical reduction of nitrates in aqueous solutions thereof in the presence of amides to gaseous nitrogen (N.sub.2) is described. Generally, electrochemical reduction of NO.sub.3 proceeds stepwise, from NO.sub.3 to N.sub.2, and subsequently in several consecutive steps to ammonia (NH.sub.3) as a final product. Addition of at least one amide to the solution being electrolyzed suppresses ammonia generation, since suitable amides react with NO.sub.2 to generate N.sub.2. This permits nitrate reduction to gaseous nitrogen to proceed by electrolysis. Suitable amides include urea, sulfamic acid, formamide, and acetamide.

  18. NITRATE REDUCTION PROGRAM AT THE LINE CREEK OPERATION

    OpenAIRE

    Jeff W Hawley

    2015-01-01

    Blasting activities at the Line Creek operation are releasing oxides of nitrogen and arecontributing to chemical changes in the surrounding watersheds. Through analysis of themechanisms of nitrogen release, history of explosive usage, historical nitrate release, changingregulatory requirements, strategy analysis and social impacts associated with the release ofnitrates a nitrate reduction plan will be established.The paper develops the framework for engineering groups, operations groups andma...

  19. 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.

  20. Reduction of nitrate and nitrite salts under hydrothermal conditions

    International Nuclear Information System (INIS)

    Foy, B.R.; Dell'Orco, P.C.; Wilmanns, E.; McInroy, R.; Ely, J.; Robinson, J.M.; Buelow, S.J.

    1994-01-01

    The feasibility of reducing nitrate/nitrite salts under hydrothermal conditions for the treatment of aqueous mixed wastes stored in the underground tanks at the Department of Energy site at Hanford, Washington was studied. The reduction of nitrate and nitrite salts by reaction with EDTA using a tank waste simulant was examined at temperatures between 623K and 800K and pressures between 0.6 and 1.2 kbar. Continuous flow reactors were used to determine kinetics and products of reactions. All reactions were studied under pressures high enough to produce single phase conditions. The reactions are rapid, go to completion in less than a minute, and produce simple products, such as carbonate, nitrogen, and nitrous oxide gases. The experimental results demonstrate the ability of chemical reactions under hydrothermal conditions to reduce the nitrate and nitrite salts and destroy organic compounds in the waste mixtures

  1. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    Energy Technology Data Exchange (ETDEWEB)

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  2. Kinetics of uncatalyzed thermochemical sulfate reduction by sulfur-free paraffin

    Science.gov (United States)

    Zhang, Tongwei; Ellis, Geoffrey S.; Ma, Qisheng; Amrani, Alon; Tang, Yongchun

    2012-01-01

    To determine kinetic parameters of sulfate reduction by hydrocarbons (HC) without the initial presence of low valence sulfur, we carried out a series of isothermal gold-tube hydrous-pyrolysis experiments at 320, 340, and 360 °C under a constant confined pressure of 24.1 MPa. The reactants used consisted of saturated HC (sulfur-free) and CaSO4 in an aqueous solution buffered to three different pH conditions without the addition of elemental sulfur (S8) or H2S as initiators. H2S produced in the course of reaction was proportional to the extent of the reduction of CaSO4 that was initially the only sulfur-containing reactant. Our results show that the in situ pH of the aqueous solution (herein, in situ pH refers to the calculated pH value of the aqueous solution at certain experimental conditions) can significantly affect the rate of the thermochemical sulfate reduction (TSR) reaction. A substantial increase in the TSR reaction rate was observed with a decrease in the in situ pH. Our experimental results show that uncatalyzed TSR is a first-order reaction. The temperature dependence of experimentally measured H2S yields from sulfate reduction was fit with the Arrhenius equation. The determined activation energy for HC (sulfur-free) reacting with View the MathML sourceHSO4− in our experiments is 246.6 kJ/mol at pH values ranging from 3.0 to 3.5, which is slightly higher than the theoretical value of 227.0 kJ/mol using ab initio quantum chemical calculations on a similar reaction. Although the availability of reactive sulfate significantly affects the rate of reaction, a consistent rate constant was determined by accounting for the HSO4− ion concentration. Our experimental and theoretical approach to the determination of the kinetics of TSR is further validated by a reevaluation of several published experimental TSR datasets without the initial presence of native sulfur or H2S. When the effect of reactive sulfate concentration is appropriately accounted for, the

  3. Development of a chronocoulometric method for uranium traces determination with basis on nitrate catalytic reduction

    International Nuclear Information System (INIS)

    Cantagallo, M.I.C.; Gutz, I.G.R.

    1990-01-01

    The application of chronocoulometric technique with catalytic reduction of uranium/nitrate with catalytic reduction of uranium/nitrate system is described to give a detection limits on the sub-nanomolar region of uranium. (author)

  4. Effect of temperature and benzalkonium chloride on nitrate reduction.

    Science.gov (United States)

    Hajaya, Malek G; Tezel, Ulas; Pavlostathis, Spyros G

    2011-04-01

    The effect of temperature and benzalkonium chloride (BAC) on nitrate reduction was investigated in batch assays using a mixed nitrate reducing culture. Nitrate was transformed completely, mainly through denitrification, to dinitrogen at 5, 10, 15 and 22 °C. In the absence of BAC, reduction of individual nitrogen oxides had different susceptibility to temperature and transient nitrite accumulation was observed at low temperatures. When the effect of BAC was tested up to 100 mg/L from 5 to 22 °C, denitrification was inhibited at and above 50mg BAC/L with transient nitrite accumulation at all temperatures. The effect of BAC was described by a competitive inhibition model. Nitrite reduction was the denitrification step most susceptible to BAC, especially at low temperatures. BAC was not degraded during the batch incubation and was mostly biomass-adsorbed. Overall, this study shows that low temperatures exacerbate the BAC inhibitory effect, which in turn is controlled by adsorption to biomass. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. 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.

  6. Anaerobic BTEX biodegradation linked to nitrate and sulfate reduction

    International Nuclear Information System (INIS)

    Dou Junfeng; Liu Xiang; Hu Zhifeng; Deng Dong

    2008-01-01

    Effective anaerobic BTEX biodegradation was obtained under nitrate and sulfate reducing conditions by the mixed bacterial consortium that were enriched from gasoline contaminated soil. Under the conditions of using nitrate or sulfate as reducing acceptor, the degradation rates of the six tested substrates decreased with toluene > ethylbenzene > m-xylene > o-xylene > benzene > p-xylene. The higher concentrations of BTEX were toxic to the mixed cultures and led to reduce the degradation rates of BTEX. Benzene and p-xylene were more toxic than toluene and ethylbenzene. Nitrate was a more favorable electron acceptor compared to sulfate. The measured ratios between the amount of nitrate consumed and the amount of benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene degraded were 9.47, 9.26, 11.14, 12.46, 13.36 and 13.02, respectively. The measured ratios between sulfate reduction and BTEX degradation were 3.51, 4.33, 4.89, 4.81, 4.86 and 4.76, respectively, which were nearly the same to theoretical ones, and the relative error between the measured and calculated ratios was less than 10%

  7. Applicability of hydroxylamine nitrate reductant in pulse-column contactors

    International Nuclear Information System (INIS)

    Reif, D.J.

    1983-05-01

    Uranium and plutonium separations were made from simulated breeder reactor spent fuel dissolver solution with laboratory-sized pulse column contactors. Hydroxylamine nitrate (HAN) was used for reduction of plutonium (1V). An integrated extraction-partition system, simulating a breeder fuel reprocessing flowsheet, carried out a partial partition of uranium and plutonium in the second contactor. Tests have shown that acceptable coprocessing can be ontained using HAN as a plutonium reductant. Pulse column performance was stable even though gaseous HAN oxidation products were present in the column. Gas evolution rates up to 0.27 cfm/ft 2 of column cross section were tested and found acceptable

  8. Subsurface nitrate reduction under wetlands takes place in narrow superficial zones

    DEFF Research Database (Denmark)

    dos Santos Ribas, Osmar; Calderer, M.; Marti, Vicens

    2017-01-01

    This study aims to investigate the depth distribution of the Nitrate Reduction Potential (NRP) on a natural and a re-established wetland. The obtained NRP provides a valuable data of the driving factors affecting denitrification, the Dissimilatory Nitrate Reduction to Ammonium (DNRA) process and ...... that wetlands can be restored satisfactorily.......This study aims to investigate the depth distribution of the Nitrate Reduction Potential (NRP) on a natural and a re-established wetland. The obtained NRP provides a valuable data of the driving factors affecting denitrification, the Dissimilatory Nitrate Reduction to Ammonium (DNRA) process...... and the performance of a re-established wetland. Intact soil cores were collected and divided in slices for the determination of Organic Matter (OM) through Loss of Ignition (LOI) as well as Dissolved Organic Carbon (DOC) and NRP spiking nitrate in batch tests. The Nitrate Reduction (NR) was fitted as a pseudo...

  9. The effect of spatial heterogeneity on nitrate reduction in soil systems

    DEFF Research Database (Denmark)

    Pedersen, Lasse Lu

    the initial inoculum size, nitrate reduction was barely affected, but DNRA increased substantially by 71%. Additionally, nitrite-, ammonium-, and nitrous oxide were sequentially produced during nitrate reduction: an initial burst of nitrite production led to DNRA, and for the microcosms which became mass...... was chemically or biochemically fixed from inert nitrogen, back into the atmosphere as inert nitrogen. Over the last century, the excess of anthropogenically fixed nitrogen has put increasing pressures on the nitrogen cycle. Nitrate is a central molecule in the nitrogen cycle. Its concentration is, on the one...... hand governed by formation by oxidation of ammonia-N, and on the other hand by removal a removal by two dissimilatory nitrate reduction processes:denitrification, in which nitrate is converted to the gaseous compounds dinitrogen and nitrous oxide, and dissimilatory nitrate reduction to ammonium, DNRA...

  10. Modeling nitrate-nitrogen load reduction strategies for the des moines river, iowa using SWAT

    Science.gov (United States)

    Schilling, K.E.; Wolter, C.F.

    2009-01-01

    The Des Moines River that drains a watershed of 16,175 km2 in portions of Iowa and Minnesota is impaired for nitrate-nitrogen (nitrate) due to concentrations that exceed regulatory limits for public water supplies. The Soil Water Assessment Tool (SWAT) model was used to model streamflow and nitrate loads and evaluate a suite of basin-wide changes and targeting configurations to potentially reduce nitrate loads in the river. The SWAT model comprised 173 subbasins and 2,516 hydrologic response units and included point and nonpoint nitrogen sources. The model was calibrated for an 11-year period and three basin-wide and four targeting strategies were evaluated. Results indicated that nonpoint sources accounted for 95% of the total nitrate export. Reduction in fertilizer applications from 170 to 50 kg/ha achieved the 38% reduction in nitrate loads, exceeding the 34% reduction required. In terms of targeting, the most efficient load reductions occurred when fertilizer applications were reduced in subbasins nearest the watershed outlet. The greatest load reduction for the area of land treated was associated with reducing loads from 55 subbasins with the highest nitrate loads, achieving a 14% reduction in nitrate loads achieved by reducing applications on 30% of the land area. SWAT model results provide much needed guidance on how to begin implementing load reduction strategies most efficiently in the Des Moines River watershed. ?? 2009 Springer Science+Business Media, LLC.

  11. Modeling nitrate-nitrogen load reduction strategies for the Des Moines River, Iowa using SWAT.

    Science.gov (United States)

    Schilling, Keith E; Wolter, Calvin F

    2009-10-01

    The Des Moines River that drains a watershed of 16,175 km(2) in portions of Iowa and Minnesota is impaired for nitrate-nitrogen (nitrate) due to concentrations that exceed regulatory limits for public water supplies. The Soil Water Assessment Tool (SWAT) model was used to model streamflow and nitrate loads and evaluate a suite of basin-wide changes and targeting configurations to potentially reduce nitrate loads in the river. The SWAT model comprised 173 subbasins and 2,516 hydrologic response units and included point and nonpoint nitrogen sources. The model was calibrated for an 11-year period and three basin-wide and four targeting strategies were evaluated. Results indicated that nonpoint sources accounted for 95% of the total nitrate export. Reduction in fertilizer applications from 170 to 50 kg/ha achieved the 38% reduction in nitrate loads, exceeding the 34% reduction required. In terms of targeting, the most efficient load reductions occurred when fertilizer applications were reduced in subbasins nearest the watershed outlet. The greatest load reduction for the area of land treated was associated with reducing loads from 55 subbasins with the highest nitrate loads, achieving a 14% reduction in nitrate loads achieved by reducing applications on 30% of the land area. SWAT model results provide much needed guidance on how to begin implementing load reduction strategies most efficiently in the Des Moines River watershed.

  12. Competitive microbial reduction of perchlorate and nitrate with a cathode directly serving as the electron donor

    International Nuclear Information System (INIS)

    Xie, Daohai; Yu, Hui; Li, Chenchen; Ren, Yuan; Wei, Chaohai; Feng, Chunhua

    2014-01-01

    Microbial reduction of perchlorate with an electrode as the electron donor represents an emerging technology for remediation of perchlorate contamination; it is important to know how perchlorate reduction behaves when nitrate, a co-contaminant of perchlorate is present. We reported that electrons derived from the electrode can be directly transferred to the bacteria with perchlorate or nitrate as the sole electron acceptor. The presence of nitrate, even at the 0.07 mM level, can slow reduction of perchlorate (0.70 mM) as a poised potential of -0.50 V (vs. SCE) was applied to the inoculated cathode. Increasing the concentration of nitrate resulted in a noticeable inhibitory effect on perchlorate reduction. When the nitrate concentration was 2.10 mM, reduction of 0.70 mM perchlorate was totally inhibited. Bacterial community analyses based on 16S rDNA gene analysis with denaturing gradient gel electrophoresis (DGGE) revealed that most of the bacteria newly enriched on the nitrate and/or perchlorate biocathodes were the known electrochemically active denitrifiers, which possibly prefer to reduce nitrate over perchlorate. These results show that nitrate is a more favorable electron acceptor than perchlorate in the bioelectrochemical system where the cathode directly serves as the electron donor

  13. Thermochemical sulfate reduction in deep petroleum reservoirs: a molecular approach; Thermoreduction des sulfates dans les reservoirs petroliers: approche moleculaire

    Energy Technology Data Exchange (ETDEWEB)

    Hanin, S.

    2002-11-01

    The thermochemical sulfate reduction (TSR) is a set of chemical reactions leading to hydrocarbon oxidation and production of carbon dioxide and sour gas (H{sub 2}S) which is observed in deep petroleum reservoirs enriched in anhydrites (calcium sulfate). Molecular and isotopic studies have been conducted on several crude oil samples to determine which types of compounds could have been produced during TSR. Actually, we have shown that the main molecules formed by TSR were organo-sulfur compounds. Indeed, sulfur isotopic measurements. of alkyl-di-benzothiophenes, di-aryl-disulfides and thia-diamondoids (identified by NMR or synthesis of standards) shows that they are formed during TSR as their value approach that of the sulfur of the anhydrite. Moreover, thia-diamondoids are apparently exclusively formed during this phenomenon and can thus be considered as true molecular markers of TSR. In a second part, we have investigated with laboratory experiments the formation mechanism of the molecules produced during TSR. A first model has shown that sulfur incorporation into the organic matter occurred with mineral sulfur species of low oxidation degree. The use of {sup 34}S allowed to show that the sulfates reduction occurred during these simulations. At least, some experiments on polycyclic hydrocarbons, sulfurized or not, allowed to establish that thia-diamondoids could be formed by acid-catalysed rearrangements at high temperatures in a similar way as the diamondoids. (author)

  14. 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

  15. 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

  16. Photocatalytic reduction of nitrate using titanium dioxide for regeneration of ion exchange brine.

    Science.gov (United States)

    Yang, Ting; Doudrick, Kyle; Westerhoff, Paul

    2013-03-01

    Nitrate is often removed from groundwater by ion exchange (IX) before its use as drinking water. Accumulation of nitrate in IX brine reduces the efficiency of IX regeneration and the useful life of the regeneration brine. For the first time, we present a strategy to photocatalytically reduce nitrate in IX brine, thereby extending the use of the brine. Titanium dioxide (Evonik P90), acting as photocatalyst, reduced nitrate effectively in both synthetic brines and sulfate-removed IX brine when formic acid (FA) was used as the hole scavenger (i.e., electron donor) and the initial FA to nitrate molar ratio (IFNR) was 5.6. Increasing the NaCl level in the synthetic brine slowed the nitrate reduction rate without affecting by-product selectivity of ammonium and gaseous N species (e.g., N(2), N(2)O). In a non-modified IX brine, nitrate removal was greatly inhibited owing to the presence of sulfate, which competed with nitrate for active surface sites on P90 and induced aggregation of P90 nanoparticles. After removing sulfate through barium sulfate precipitation, nitrate was effectively reduced; approximately 3.6 × 10(24) photons were required to reduce each mole of nitrate to 83% N Gases and 17% NH(4)(+). To make optimum use of FA and control the residual FA level in treated brine, the IFNR was varied. High IFNRs (e.g., 4, 5.6) were found to be more efficient for nitrate reduction but left higher residual FA in brine. IX column tests were performed to investigate the impact of residual FA for brine reuse. The residual FA in the brine did not significantly affect the nitrate removal capacity of IX resins, and formate contamination of treated water could be eliminated by rinsing with one bed volume of fresh brine. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Rhodobacter capsulatus gains a competitive advantage from respiratory nitrate reduction during light-dark transitions.

    Science.gov (United States)

    Ellington, M J K; Richardson, D J; Ferguson, S J

    2003-04-01

    Rhodobacter capsulatus N22DNAR(+) possesses a periplasmic nitrate reductase and is capable of reducing nitrate to nitrite under anaerobic conditions. In the absence of light this ability cannot support chemoheterotrophic growth in batch cultures. This study investigated the effect of nitrate reduction on the growth of R. capsulatus N22DNAR(+) during multiple light-dark cycles of anaerobic photoheterotrophic/dark chemoheterotrophic growth conditions in carbon-limited continuous cultures. The reduction of nitrate did not affect the photoheterotrophic growth yield of R. capsulatus N22DNAR(+). After a transition from photoheterotrophic to dark chemoheterotrophic growth conditions, the reduction of nitrate slowed the initial washout of a R. capsulatus N22DNAR(+) culture. Towards the end of a period of darkness nitrate-reducing cultures maintained higher viable cell counts than non-nitrate-reducing cultures. During light-dark cycling of a mixed culture, the strain able to reduce nitrate (N22DNAR(+)) outcompeted the strain which was unable to reduce nitrate (N22). The evidence indicates that the periplasmic nitrate reductase activity supports slow growth that retards the washout of a culture during anaerobic chemoheterotrophic conditions, and provides a protonmotive force for cell maintenance during the dark period before reillumination. This translates into a selective advantage during repeated light-dark cycles, such that in mixed culture N22DNAR(+) outcompetes N22. Exposure to light-dark cycles will be a common feature for R. capsulatus in its natural habitats, and this study shows that nitrate respiration may provide a selective advantage under such conditions.

  18. Tuning the Thermochemical Properties of Oxonol Dyes for Digital Versatile Disc Recordable: Reduction of Thermal Interference in High-Speed Recording

    Science.gov (United States)

    Morishima, Shin-Ichi; Wariishi, Koji; Mikoshiba, Hisashi; Inagaki, Yoshio; Shibata, Michihiro; Hashimoto, Hirokazu; Kubo, Hiroshi

    To reduce thermal interference between adjacent recording marks on a recordable digital versatile disc, we examined the thermochemical behavior of oxonol dyes for digital versatile disc recordable (DVD-R). We found that oxonol dyes with Meldrum's acid skeleton exhibited an abrupt reduction in weight with increasing temperature without generating excessive heat that is the fundamental cause of thermal interference. DVD-R with the oxonol dyes suppressed fluctuation in the shapes of recorded marks, thereby attaining compatibility with high-speed recording.

  19. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea

    DEFF Research Database (Denmark)

    Stief, Peter; Fuchs-Ocklenburg, Silvia; Kamp, Anja

    2014-01-01

    Background: A wealth of microbial eukaryotes is adapted to life in oxygen-deficient marine environments. Evidence is accumulating that some of these eukaryotes survive anoxia by employing dissimilatory nitrate reduction, a strategy that otherwise is widespread in prokaryotes. Here, we report...... the dissimilatory nature of nitrate reduction. Interestingly, An-4 used intracellular nitrate stores (up to 6-8 μmol NO3 - g-1 protein) for dissimilatory nitrate reduction. Conclusions: Our findings expand the short list of microbial eukaryotes that store nitrate intracellularly and carry out dissimilatory nitrate...

  20. Identifying Efficient Nitrate Reduction Strategies in the Upper Danube

    Directory of Open Access Journals (Sweden)

    Angel Udias

    2016-08-01

    Full Text Available Nitrogen losses in the form of Nitrate (N-NO3 from point and diffuse sources of pollution are recognized to be the leading cause of water body impairment throughout Europe. Implementation of conservation programs is perceived as being crucial for restoring and protecting the good ecological status of freshwater bodies. The success of conservation programs depends on the efficient identification of management solutions with respect to the envisaged environmental and economic objectives. This is a complex task, especially considering that costs and effectiveness of conservation strategies depend on their locations. We applied a multi-objective, spatially explicit analysis tool, the R-SWAT-DM framework, to search for efficient, spatially-targeted solution of Nitrate abatement in the Upper Danube Basin. The Soil Water Assessment Tool (SWAT model served as the nonpoint source pollution estimator for current conditions as well as for scenarios with modified agricultural practices and waste water treatment upgrading. A spatially explicit optimization analysis that considered point and diffuse sources of Nitrate was performed to search for strategies that could achieve largest pollution abatement at minimum cost. The set of optimal spatial conservation strategies identified in the Basin indicated that it could be possible to reduce Nitrate loads by more than 50% while simultaneously provide a higher income.

  1. Influence of exchange reactions in salt melts on cathodic reduction of nitrate ion

    International Nuclear Information System (INIS)

    Prisyazhnyj, V.D.; Chernukhin, S.I.; Kirillov, S.A.; Safronova, I.M.; Zayats, A.D.

    1981-01-01

    Potentiodynamical method has been used to investigate the process of cathodic reduction of nitrate ion in the melts of ternary mutual systems K + , Li + /NO 3- , Dsup(n-) and K + , B 2 + /NO 3 , Dsup(n-) (where B 2 + -Ba 2 + , Sr 2 + , Ca 2 + , and Dsup(n-)-Fsup(-), Cl - , Br - , SO 4- ). The investigations show, that the anion reduction depends on nitrate ion centration of two-charge metals. Influence of the composition of the first and second spheres of the nitrate ion ionic environment on electrode process parameters according to the value of free exchange energy is shown

  2. Effect of high electron donor supply on dissimilatory nitrate reduction pathways in a bioreactor for nitrate removal

    DEFF Research Database (Denmark)

    Behrendt, Anna; Tarre, Sheldon; Beliavski, Michael

    2014-01-01

    The possible shift of a bioreactor for NO3- removal from predominantly denitrification (DEN) to dissimilatory nitrate reduction to ammonium (DNRA) by elevated electron donor supply was investigated. By increasing the C/NO3- ratio in one of two initially identical reactors, the production of high...... sulfide concentrations was induced. The response of the dissimilatory NO3- reduction processes to the increased availability of organic carbon and sulfide was monitored in a batch incubation system. The expected shift from a DEN- towards a DNRA-dominated bioreactor was not observed, also not under...

  3. Thermochemical Sulfate Reduction Simulation Experiments on the Formation and Distribution of Organic Sulfur Compounds in the Tuha Crude Oil

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Changtao; Li, Shuyuan [China Univ. of Petroleum, Beijing (China); Song, He [Research Institute of Petroleum Engineering of CNPC, Tianjin (China)

    2014-07-15

    Thermochemical sulfate reduction (TSR) was conducted in autoclave on the system of crude oil and MgSO{sub 4} at different temperatures. Gas chromatography pulsed flame photometric detector (GC-PFPD) was used to detected the composition of organic sulfur compounds in oil phase products. The results of the analysis indicate that with increased temperature, the contents of organic sulfur compounds with high molecular weight and thermal stability, such as benzothiophenes and dibenzothiophenes, gradually became dominated. In order to gain greater insight into the formation and distribution of organic sulphur compounds from TSR, positive ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used in detecting the detailed elemental composition and distribution of them. The mass spectra showed that the mass range of sulfur compounds was 200-550 Da. Four sulfur class species, S{sub 1}, N{sub 1}S{sub 1}, O{sub 1}S{sub 1} and O{sub 2}S{sub 1}, were assigned in the positive-ion spectrum. Among the identified sulfur compounds, the S{sub 1} class species was dominant. The most abundant S{sub 1} class species increase associated with the DBE value and carbon number increasing which also indicates the evolution of organic sulfur compounds in TSR is from the labile series to the stable one. In pure blank pyrolysis experiments with crude oil cracking without TSR, different composition and distribution of organic sulfur compounds in oil phase products were seen from mass spectra in order to evaluate their pyrolysis behaviors without MgSO{sub 4}. FT-IR and XRD were used in analyzing the products of solid phases. Two distinct crystallographic phases MgO and MgSO{sub 4} are found to coexist in the products which demonstrated the transformation of inorganic sulfur compounds into organosulfur compounds exist in TSR.

  4. Biological reduction of nitrate wastewater using fluidized-bed bioreactors

    International Nuclear Information System (INIS)

    Walker, J.F. Jr.; Hancher, C.W.; Patton, B.D.; Kowalchuk, M.

    1981-01-01

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt % NO 3 - and as large as 2000 m 3 /d, in the nuclear fuel cycle as well as in many commercial processes such as fertilizer production, paper manufacturing, and metal finishing. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO 3 - )/m 3 by the use of a fluidized-bed bioreactor. The major strain of denitrification bacteria is Pseudomonas which was derived from garden soil. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25 to 0.50-mm-diam coal particles, which are fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m 3 . A description is given of the results of two biodenitrification R and D pilot plant programs based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m 3 and achieving denitrification rates as high as 80 gN(NO 3 - )/d per liter of empty bioreactor volume. The first of these pilot plant programs consisted of two 0.2-m-diam bioreactors, each with a height of 6.3 m and a volume of 208 liters, operating in series. The second pilot plant was used to determine the diameter dependence of the reactors by using a 0.5-m-diam reactor with a height of 6.3 m and a volume of 1200 liters. These pilot plants operated for a period of six months and two months respectively, while using both a synthetic waste and the actual waste from a gaseous diffusion plant operated by Goodyear Atomic Corporation

  5. Comparison of the Efficiencies of Zero-Valent Iron Nanoparticles and Stabilized Iron Nanoparticles for Nitrate Reduction from Polluted Waters

    Directory of Open Access Journals (Sweden)

    Fatemeh Nooralivand

    2015-12-01

    Full Text Available The present study was conducted to evaluate the feasibility of zero-valent iron nanoparticles (ZVIN for the removal of nitrate from aqueous solutions. For this purpose, bare zero-valent iron nanoparticles (bare-ZVIN and CMC-ZVIN were synthesized using the borohydride reduction method and their morphological characteristics were examined via scanning electron microscopy (SEM, X-ray diffraction (XRD, and Fourier Transmission Infrared Spectroscopy (FTIR. The effects of pH of the aqueous solution, initial nitrate concentration, ZVIN concentration, and contact time on nitrate reduction were investigated as operational parameters and the kinetics of nitrate reduction was studied in batch experiments. The results showed that 93.65% of nitrate was removed by stabilized nanoparticles at pH=6 while non-stabilized nanoparticles at pH=2 were able to remove 85.55% of the nitrate.Furthermore, nitrate reduction was enhanced by increasing ZVIN concentration and contact time while it was decreased as a result of increasing initial nitrate concentration. The major product of nitrate reduction at an acidic pH was found to be ammonium; at an alkaline pH, however, nitrate was converted to nitrogen and nitrite production dropped to less than 2%. Kinetic analysis demonstrated that denitrification of nitrate by the nanoparticles fitted well with first-order and second-order reaction models. The results also demonstrated that the stabilized ZVI nanoparticles were more effective than bare-ZVIN for nitrate reduction in aqueous solutions.

  6. Thermophilic nitrate-reducing microorganisms prevent sulfate reduction in cold marine sediments incubated at high temperature

    Science.gov (United States)

    Nepomnyashchaya, Yana; Rezende, Julia; Hubert, Casey

    2014-05-01

    Hydrogen sulphide produced during metabolism of sulphate-reducing microorganisms (SRM) is toxic, corrosive and causes detrimental oil reservoir souring. During secondary oil recovery, injecting oil reservoirs with seawater that is rich in sulphate and that also cools high temperature formations provides favourable growth conditions for SRM. Nitrate addition can prevent metabolism of SRM by stimulating nitrate-reducing microorganisms (NRM). The investigations of thermophilic NRM are needed to develop mechanisms to control the metabolism of SRM in high temperature oil field ecosystems. We therefore established a model system consisting of enrichment cultures of cold surface marine sediments from the Baltic Sea (Aarhus Bay) that were incubated at 60°C. Enrichments contained 25 mM nitrate and 40 mM sulphate as potential electron acceptors, and a mixture of the organic substrates acetate, lactate, propionate, butyrate (5 mM each) and yeast extract (0.01%) as potential carbon sources and electron donors. Slurries were incubated at 60°C both with and without initial pasteurization at 80°C for 2 hours. In the enrichments containing both nitrate and sulphate, the concentration of nitrate decreased indicating metabolic activity of NRM. After a four-hour lag phase the rate of nitrate reduction increased and the concentration of nitrate dropped to zero after 10 hours of incubation. The concentration of nitrite increased as the reduction of nitrate progressed and reached 16.3 mM after 12 hours, before being consumed and falling to 4.4 mM after 19-day of incubation. No evidence for sulphate reduction was observed in these cultures during the 19-day incubation period. In contrast, the concentration of sulphate decreased up to 50% after one week incubation in controls containing only sulphate but no nitrate. Similar sulfate reduction rates were seen in the pasteurized controls suggesting the presence of heat resistant SRM, whereas nitrate reduction rates were lower in the

  7. Contributions of nonextracting Pu reductants (ferrous sulphamate and hydroxylamine nitrate) and holding reductant (hydrazine nitrate) to the aqueous density in U-Pu partitioning system

    International Nuclear Information System (INIS)

    Shekhar Kumar; Rajnish Kumar; Koganti, S.B.

    2005-08-01

    As nonextracting Pu reductants and holding reductants contribute to the density of aqueous phase sub-system considerably, to account their contributions in aqueous phase in solvent extraction simulation code is essential. In this regard, in-house generated precise density data on aqueous ferrous sulphamate solutions as well as aqueous density data, reported in the literature, for HAN, hydrazine nitrate and HAN-HNO 3 systems were analyzed and density equation earlier proposed by authors was extended to it. It was observed that the equation earlier proposed by the authors were simple and were easy to extend for multicomponent system. The contributions of ferrous sulphamate, HAN and hydrazine nitrate to the aqueous density were quantified. It was also observed that the classical value of contribution for nonextractible solute to the aqueous density was quite different from the results reported in this work. (author)

  8. Highly active Pd-In/mesoporous alumina catalyst for nitrate reduction.

    Science.gov (United States)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi; Werth, Charles J; Zhang, Yalei; Zhou, Xuefei

    2015-04-09

    The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd-In/Al2O3 with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO2-buffered water and under continuous H2 as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd-In ratio of 4, with a first-order rate constant (k(obs) = 0.241 L min(-1) g(cata)(-1)) that was 1.3× higher than that of conventional Pd-In/Al2O3 (5 wt% Pd; 0.19 L min(-1) g(cata)(-1)). The Pd-In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Colorimetric determination of nitrate plus nitrite in water by enzymatic reduction, automated discrete analyzer methods

    Science.gov (United States)

    Patton, Charles J.; Kryskalla, Jennifer R.

    2011-01-01

    This report documents work at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) to validate enzymatic reduction, colorimetric determinative methods for nitrate + nitrite in filtered water by automated discrete analysis. In these standard- and low-level methods (USGS I-2547-11 and I-2548-11), nitrate is reduced to nitrite with nontoxic, soluble nitrate reductase rather than toxic, granular, copperized cadmium used in the longstanding USGS automated continuous-flow analyzer methods I-2545-90 (NWQL laboratory code 1975) and I-2546-91 (NWQL laboratory code 1979). Colorimetric reagents used to determine resulting nitrite in aforementioned enzymatic- and cadmium-reduction methods are identical. The enzyme used in these discrete analyzer methods, designated AtNaR2 by its manufacturer, is produced by recombinant expression of the nitrate reductase gene from wall cress (Arabidopsis thaliana) in the yeast Pichia pastoris. Unlike other commercially available nitrate reductases we evaluated, AtNaR2 maintains high activity at 37°C and is not inhibited by high-phenolic-content humic acids at reaction temperatures in the range of 20°C to 37°C. These previously unrecognized AtNaR2 characteristics are essential for successful performance of discrete analyzer nitrate + nitrite assays (henceforth, DA-AtNaR2) described here.

  10. Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium.

    Science.gov (United States)

    Fernandes, Sheryl Oliveira; Bonin, Patricia C; Michotey, Valérie D; Garcia, Nicole; LokaBharathi, P A

    2012-01-01

    Earlier observations in mangrove sediments of Goa, India have shown denitrification to be a major pathway for N loss. However, percentage of total nitrate transformed through complete denitrification accounted for nitrate reduced. Here, we show that up to 99% of nitrate removal in mangrove sediments is routed through dissimilatory nitrate reduction to ammonium (DNRA). The DNRA process was 2x higher at the relatively pristine site Tuvem compared to the anthropogenically-influenced Divar mangrove ecosystem. In systems receiving low extraneous nutrient inputs, this mechanism effectively conserves and re-circulates N minimizing nutrient loss that would otherwise occur through denitrification. In a global context, the occurrence of DNRA in mangroves has important implications for maintaining N levels and sustaining ecosystem productivity. For the first time, this study also highlights the significance of DNRA in buffering the climate by modulating the production of the greenhouse gas nitrous oxide.

  11. Highly active Pd–In/mesoporous alumina catalyst for nitrate reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Werth, Charles J. [Civil, Architectural and Environmental Engineering, University of Texas at Austin, 301 East Dean Keeton St., Stop C1786, Austin, TX 78712 (United States); Zhang, Yalei, E-mail: zhangyalei2003@163.com [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhou, Xuefei, E-mail: zhouxuefei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China)

    2015-04-09

    Highlights: • Pd–In nanoparticles (6–7 nm) uniformly form in the mesopores of alumina (4 nm). • Pd–In nanoparticles aggregation is prevented during the synthesis process. • The reduction rate of nitrate is efficient by using the obtained catalyst. • The selectivity toward N{sub 2} is ideal by using the obtained catalyst. - Abstract: The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd–In/Al{sub 2}O{sub 3} with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO{sub 2}-buffered water and under continuous H{sub 2} as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd–In ratio of 4, with a first-order rate constant (k{sub obs} = 0.241 L min{sup −1} g{sub cata}{sup −1}) that was 1.3× higher than that of conventional Pd–In/Al{sub 2}O{sub 3} (5 wt% Pd; 0.19 L min{sup −1} g{sub cata}{sup −1}). The Pd–In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate.

  12. Control strategies for the reduction of airborne particulate nitrate in California's San Joaquin Valley

    Science.gov (United States)

    Kleeman, Michael J.; Ying, Qi; Kaduwela, Ajith

    this upwind material was small. A 50% reduction in NO x emissions applied to sources within the SJV reduced the predicted concentration of total nitrate by approximately 25% during the study episode. VOC emissions controls were less effective, while reasonable NH 3 emissions controls had the smallest effect on the amount of ammonium nitrate produced. A 50% reduction in VOC emissions lowered predicted concentrations of total nitrate by 17.5%, while a 50% reduction in NH 3 emissions lowered predicted concentrations of total nitrate by only 10%. This latter result is expected since the formation of ammonium nitrate aerosol is limited by the availability of gas-phase nitric acid, with large amounts of excess NH 3 available. NO x emissions controls appear to be the most efficient method to reduce the concentration of locally generated particulate nitrate in the SJV under the conditions experienced on 4-6 January, 1996.

  13. Abiotic nitrate reduction in the presence of steel material and hydrogen in cementitious environments

    International Nuclear Information System (INIS)

    Truche, L.; Berger, G.; Albrecht, A.

    2012-01-01

    Document available in extended abstract form only. Abiotic nitrate reduction induced by different electron donors represents a major reaction of interest in the context of disposal of nuclear waste containing such oxyanions (Honda et al., 2006; Katsounaros et al., 2009). These wastes are characterized, amongst others by the coexistence of oxyanions (nitrate, phosphate, sulfate...) and potentially reducing agents such as organic matter, native metals and hydrogen gas formed or from package material via radiolysis or anaerobic corrosion. In addition to the large number of reactants present in the waste itself, the medium-level long-lived (MAVL) waste concept is based on large masses of concrete and steel in part used for primary waste containers as well as armored cement over pack and engineered barrier; a concept that guarantees the mechanical stability of both the waste container and the waste cell. In this experimental study we evaluate the consequences of steel material (carbon steel and 316L stainless steel) from waste canisters and construction material (concrete and Callovo- Oxfordian argillite), as well as magnetite as their possible corrosion by-products, on the reduction of aqueous nitrate in the presence of hydrogen. A parametric study (0 2 ) - ] 2+ , Fe 2+ ) that can act as electron donors. This experimental study demonstrates that abiotic nitrate reduction induced by the combination of steel materials and hydrogen is a likely process under waste cell conditions, thus applicable to cases where nitrate-bearing waste (i.e. nuclear) is disposed in near-surface or in deep geological settings. Depending on the nature of the steel, the reaction may exhibit different kinetic features that would require dedicated assessment. An increase in nitrate concentrat ions above the steel saturation level of 10 mM (Fig. 1; beyond the range of the current study) may also have an influence on reaction processes and kinetics and thus influence nitrate reactivity. (authors)

  14. Evaluation of Nitrate and Nitrite Reduction Kinetics Related to Liquid-Air-Interface Corrosion

    International Nuclear Information System (INIS)

    Li, Xiaoji; Gui, F.; Cong, Hongbo; Brossia, C.S.; Frankel, G.S.

    2014-01-01

    Liquid-air interface (LAI) corrosion has been a concern for causing leaks in the carbon steel tanks used for holding high-level radioactive liquid waste. To assist in understanding the mechanism of LAI corrosion, the kinetics of nitrate and nitrite reduction reactions were investigated electrochemically. Cyclic voltammetry and cathodic polarization measurements indicated that the nitrite reduction reaction exhibited faster kinetics than the nitrate reduction reaction at higher cathodic overpotential. However, the primary reduction reaction at the open circuit potential under aerated conditions was the oxygen reduction reaction. The reduction of residual oxygen was also the dominant cathodic reaction at open circuit potential in deaerated conditions. Moreover, the kinetics of oxygen reduction on steel electrodes were significantly influenced by the sample immersion conditions (partial vs. full) for aerated liquid nuclear waste simulants, but not for deaerated conditions. Lastly, the gaseous products formed during LAI corrosion were analyzed using the gas detector tube method and gas chromatography-mass spectrometry and found to contain NH 3 , NO 2 and NO. However, the results suggested that these products were caused by the local acidification generated by the hydrolysis of cations after LAI corrosion underwent extensive propagation, instead of being directly reduced in alkaline conditions. Thus, the results in this work showed that the kinetics of nitrate and nitrite reduction could not generate a salt concentration cell in the meniscus region to cause LAI corrosion

  15. The importance of dissimilatory nitrate reduction to ammonium (DNRA) in the nitrogen cycle of coastal ecosystems

    DEFF Research Database (Denmark)

    Giblin, Anne E.; Tobias, Craig R.; Song, Bongkeun

    2013-01-01

    Until recently, it was believed that biological assimilation and gaseous nitrogen (N) loss through denitrification were the two major fates of nitrate entering or produced within most coastal ecosystems. Denitrification is often viewed as an important ecosystem service that removes reactive N from...... the ecosystem. However, there is a competing nitrate reduction process, dissimilatory nitrate reduction to ammonium (DNRA), that conserves N within the ecosystem. The recent application of nitrogen stable isotopes as tracers has generated growing evidence that DNRA is a major nitrogen pathway that cannot...... of denitrification and DNRA, and how the balance changes with increased nitrogen loading, is of critical importance for predicting eutrophication trajectories. Recent improvements in methods for assessing rates of DNRA have helped refine our understanding of the rates and controls of this process, but accurate...

  16. Effects of thiamphenicol on nitrate reduction and N2O release in estuarine and coastal sediments

    International Nuclear Information System (INIS)

    Yin, Guoyu; Hou, Lijun; Liu, Min; Zheng, Yanling; Li, Xiaofei; Lin, Xianbiao; Gao, Juan; Jiang, Xiaofen

    2016-01-01

    Nitrate overload is an important driver of water pollution in most estuarine and coastal ecosystems, and thus nitrate reduction processes have attracted considerable attention. Antibiotics contamination is also an emerging environmental problem in estuarine and coastal regions as a result of growing production and usage of antibiotics. However, the effects of antibiotics on nitrate reduction remain unclear in these aquatic ecosystems. In this study, continuous-flow experiments were conducted to examine the effects of thiamphenicol (TAP, a common chloramphenicol antibiotic) on nitrate reduction and greenhouse gas N 2 O release. Functional genes involved in nitrogen transformation were also quantified to explore the microbial mechanisms of the TAP influence. Production of N 2 were observed to be inhibited by TAP treatment, which implied the inhibition effect of TAP on nitrate reduction processes. As intermediate products of nitrogen transformation processes, nitrite and N 2 O were observed to accumulate during the incubation. Different TAP inhibition effects on related functional genes may be the microbial mechanism for the changes of nutrient fluxes, N 2 fluxes and N 2 O release rates. These results indicate that the antibiotics residues in estuarine and coastal ecosystems may contribute to nitrate retention and N 2 O release, which could be a major factor responsible for eutrophication and greenhouse effects. - Highlights: • Production of N 2 are inhibited by the TAP treatment. • Accumulation of nitrite and N 2 O is stimulated by TAP treatment. • Different TAP effects on functional genes may be the microbial mechanism. - TAP inhibits the production of N 2 and stimulates the accumulation of nitrite and N 2 O due to its different inhibition effects on functional genes.

  17. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea.

    Science.gov (United States)

    Stief, Peter; Fuchs-Ocklenburg, Silvia; Kamp, Anja; Manohar, Cathrine-Sumathi; Houbraken, Jos; Boekhout, Teun; de Beer, Dirk; Stoeck, Thorsten

    2014-02-11

    A wealth of microbial eukaryotes is adapted to life in oxygen-deficient marine environments. Evidence is accumulating that some of these eukaryotes survive anoxia by employing dissimilatory nitrate reduction, a strategy that otherwise is widespread in prokaryotes. Here, we report on the anaerobic nitrate metabolism of the fungus Aspergillus terreus (isolate An-4) that was obtained from sediment in the seasonal oxygen minimum zone in the Arabian Sea, a globally important site of oceanic nitrogen loss and nitrous oxide emission. Axenic incubations of An-4 in the presence and absence of oxygen and nitrate revealed that this fungal isolate is capable of dissimilatory nitrate reduction to ammonium under anoxic conditions. A ¹⁵N-labeling experiment proved that An-4 produced and excreted ammonium through nitrate reduction at a rate of up to 175 nmol ¹⁵NH₄⁺ g⁻¹ protein h⁻¹. The products of dissimilatory nitrate reduction were ammonium (83%), nitrous oxide (15.5%), and nitrite (1.5%), while dinitrogen production was not observed. The process led to substantial cellular ATP production and biomass growth and also occurred when ammonium was added to suppress nitrate assimilation, stressing the dissimilatory nature of nitrate reduction. Interestingly, An-4 used intracellular nitrate stores (up to 6-8 μmol NO₃⁻ g⁻¹ protein) for dissimilatory nitrate reduction. Our findings expand the short list of microbial eukaryotes that store nitrate intracellularly and carry out dissimilatory nitrate reduction when oxygen is absent. In the currently spreading oxygen-deficient zones in the ocean, an as yet unexplored diversity of fungi may recycle nitrate to ammonium and nitrite, the substrates of the major nitrogen loss process anaerobic ammonium oxidation, and the potent greenhouse gas nitrous oxide.

  18. Catalytic membrane in reduction of aqueous nitrates: operational principles and catalytic performance

    NARCIS (Netherlands)

    Ilinitch, O.M.; Cuperus, F.P.; Nosova, L.V.; Gribov, E.N.

    2000-01-01

    The catalytic membrane with palladium-copper active component supported over the macroporous ceramic membrane, and a series of γ-Al 2O 3 supported Pd-Cu catalysts were prepared and investigated. In reduction of nitrate ions by hydrogen in water at ambient temperature, pronounced internal diffusion

  19. Study of electrolytic reduction of uranium VI to uranium IV in nitrate systems

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, B.F. de; Almeida, S.G. de; Forbicini, S; Matsuda, H T; Araujo, J.A. de [Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo (Brazil). Centro de Engenharia Quimica

    1980-01-01

    Experimental parameters are optimized in order to obtain uranium (IV) nitrate solutions at maximum yield, using hydrazine as stabilizer. Uranium (VI) electrolytic reduction was chosen because: there is no increase in the volume of radioactive effluents; there are no secondary reactions; there is no need for further separations; all reagents used are not inflammable. The method is, therefore, efficient and of low cost.

  20. Economic Analysis of Nitrate Source Reductions in California Agriculture

    Science.gov (United States)

    Medellin-Azuara, J.; Howitt, R.; Rosenstock, T.; Harter, T.; Pettygrove, S. G.; Dzurella, K.; Lund, J. R.

    2011-12-01

    We present an analytical approach to assess the economic impact of improving nitrogen management practices in California agriculture. We employ positive mathematical programming to calibrate crop production to base input information. The production function representation is a nested constant elasticity of substitution with two nests: one for applied water and one for applied nitrogen. The first nest accounts for the tradeoffs between irrigation efficiency and capital investments in irrigation technology. The second nest represents the tradeoffs between nitrogen application efficiency and the marginal costs of improving nitrogen efficiency. In the production function nest, low elasticities of substitution and water and nitrogen stress constraints keep agricultural crop yields constant despite changes in nitrogen management practices. We use the Tulare Basin, and the Salinas Valley in California's Central Valley and Central Coast respectively as our case studies. Preliminary results show that initial reductions of 25% in nitrogen loads to groundwater may not impose large costs to agricultural crop production as substitution of management inputs results in only small declines in net revenue from farming and total land use. Larger reductions in the nitrogen load to groundwater of 50% imposes larger marginal costs for better nitrogen management inputs and reductions in the area of lower valued crops grown in the study areas. Despite the shortage of data on quantitative effects of improved nitrogen efficiency; our results demonstrate the potential of combining economic and agronomic data into a model that can reflect differences in cost and substitutabilty in nitrogen application methods, that can be used to reduce the quantity of nitrogen leaching into groundwater.

  1. The electrocatalytic reduction of nitrate in water on Pd/Sn-modified activated carbon fiber electrode.

    Science.gov (United States)

    Wang, Ying; Qu, Jiuhui; Wu, Rongcheng; Lei, Pengju

    2006-03-01

    The Pd/Sn-modified activated carbon fiber (ACF) electrodes were successfully prepared by the impregnation of Pd2+ and Sn2+ ions onto ACF, and their electrocatalytic reduction capacity for nitrate ions in water was evaluated in a batch experiment. The electrode was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) and temperature programmed reduction (TPR). The capacity for nitrate reduction depending on Sn content on the electrode and the pH of electrolyte was discussed at length. The results showed that at an applied current density of 1.11 mA cm(-2), nitrate ions in water (solution volume: 400 mL) were reduced from 110 to 3.4 mg L(-1) after 240 min with consecutive change of intermediate nitrite. Ammonium ions and nitrogen were formed as the main final products. The amount of other possible gaseous products (including NO and N2O) was trace. With the increase of Sn content on the Pd/Sn-modified ACF electrode, the activity for nitrate reduction went up to reach a maximum (at Pd/Sn = 4) and then decreased, while the selectivity to N2 was depressed. Higher pH value of electrolyte exhibited more suppression effect on the reduction of nitrite than that of nitrate. However, no significant influence on the final ammonia formation was observed. Additionally, Cu ion in water was found to cover the active sites of the electrode to make the electrode deactivated.

  2. Abiotic nitrate and sulphate reduction by hydrogen: a comparative experimental study

    International Nuclear Information System (INIS)

    Truche, L.; Berger, G.; Albrecht, A.; Giffaut, E.

    2010-01-01

    Document available in extended abstract form only. The bituminous waste which is part of the intermediate level, long-lived waste (MAVL) is characterised, amongst others, by the coexistence of nitrates, sulphates, organic matter, native metals and hydrogen gas in the waste mixture and package. It can be considered as the most complex example that will be used to discuss redox reactions occurring in such waste mixtures. The evaluation of the redox conditions requires quantification of the amount of electron acceptors and donors and definition of the kinetics of redox reaction. The objectives of an experimental study to unravel some of these reaction complexities are: - to investigate nature and rate of sulphate and nitrate reduction by hydrogen in the presence of different catalysts (stainless steel, hastelloy, magnetite and argillite); - to compare sulphate and nitrate as electron acceptors; - to provide a mechanistic model of these reactions. It is well known that reduction of sulphate and nitrate requires high activation energies, usually supplied either by thermal processes or via bacterial and surface catalysis, of which the latter has been investigated in this study. Preliminary experiments performed at 150 deg. C and under H 2 pressure show that sulphate reduction is enhanced in the presence of magnetite, but essentially under the restricted condition of low sulphate concentration and at a pH below the Point of Zero Charge of magnetite. This suggests that sorption of sulphate contributes to the catalysed reaction (at low pH) but provided that the magnetite surface sites are not saturated with respect to aqueous sulphate (low concentration). On the contrary, nitrate reduction is observed whatever the pH and the nitrate concentration in the presence of both magnetite and hastelloy C276 (Ni, Cr, Mo, W, Fe alloy). The effect of temperature on the rate of nitrate reduction (500 ppm KNO 3 solution) is shown by comparing three different experiments conducted in

  3. Determination of inorganic nitrate in serum and urine by a kinetic cadmium-reduction method.

    Science.gov (United States)

    Cortas, N K; Wakid, N W

    1990-08-01

    Nitrate in serum and urine was assayed by a modification of the cadmium-reduction method; the nitrite produced was determined by diazotization of sulfanilamide and coupling to naphthylethylene diamine. After samples were deproteinized with Somogyi reagent, the nitrate was reduced by Cu-coated Cd in glycine buffer at pH 9.7 (2.5 to 3 g of Cd granules for a 4-mL reaction mixture). The reduction followed pseudo-first-order reaction kinetics, a convenient time interval for assay being 75 to 90 min. Maximum reduction (85%) occurred at about 2 h. Detection limits in urine or serum were 2 to 250 mumol/L. This method does not require the reaction to go to completion, does not require expensive reagents or equipment, and can assay several samples simultaneously. Repeated assays of two serum pools gave CVs of 9.0% and 4.7% for nitrate concentrations of 31.4 and 80.2 mumol/L, respectively (n = 20 each). The mean concentration of nitrate was 1704.0 +/- 1294 (SD) mumol/L (n = 21) in untimed normal urine, 81.8 +/- 50.1 mumol/L in serum of 38 renal dialysis patients, and 51.2 +/- 26.4 mumol/L in serum of 38 controls.

  4. Microbial Oxidation of Pyrite Coupled to Nitrate Reduction in Anoxic Groundwater Sediment

    DEFF Research Database (Denmark)

    Jørgensen, Christian Juncher; Elberling, Bo; Jacobsen, Ole Stig

    2009-01-01

    denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can...... be ascribed to pyrite oxidation. The apparent zero-order denitrification rate in anoxic pyrite containing sediment at groundwater temperature has been determined to be 2-3 µmol NO3- kg-1 day-1. The in situ groundwater chemistry at the boundary between the redoxcline and the anoxic zone reveals that between 65......-anoxic boundary in sandy aquifers thus determining the position and downward progression of the redox boundary between nitrate-containing and nitrate-free groundwater....

  5. Vertical activity distribution of dissimilatory nitrate reduction in coastal marine sediments

    DEFF Research Database (Denmark)

    Behrendt, A.; de Beer, D.; Stief, P.

    2013-01-01

    The relative importance of two dissimilatory nitrate reduction pathways, denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA), was investigated in intact sediment cores from five different coastal marine field sites (Dorum, Aarhus Bight, Mississippi Delta, Limfjord...... reduction was clearly dominated by DEN (59-131% of the total NO3- reduced) rather than by DNRA, irrespective of the sedimentary inventories of electron donors such as organic carbon, sulfide, and iron. Highest ammonium production via DNRA, accounting for up to 8.9% of the total NO3- reduced, was found...... was detected accounting for 37-77% of the total NO3- reduced. These contradictory results might be explained by enhanced NO3- availability for DNRA bacteria in the sediment slurries compared to the core-incubated sediments in which diffusion of NO3- from the water column may only reach DEN bacteria...

  6. Biological reduction of nitrates in wastewaters from nuclear processing using a fluidized-bed bioreactor

    International Nuclear Information System (INIS)

    Pitt, W.W.; Hancher, C.W.; Patton, B.D.

    1981-01-01

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt.% NO 3 - and as large as 2000 m 3 /day, in the nuclear fuel cycle. The biological reduction of nitrate in wastewater to gaseous nitrogen, accompanied by the oxidation of a nutrient carbon source to gaseous carbon dioxide, is an ecologically sound and cost-effective method of treating wastewaters containing nitrates. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO 3 - )/m 3 by the use of a fluidized-bed bioreactor. The denitrification bacteria are a mixed culture derived from garden soil; the major strain is Pseudomonas. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25- to 0.50-mm-diam coal fluidization particles, which are then fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m 3 . This paper describes the results of a biodenitrification R and D program based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m 3 and achieving denitrification rates as high as 80 g N(NO 3 - ) per day per liter of empty bioreactor volume. 4 figures, 7 tables

  7. In situ analysis of microbial reduction of a nitrate plume in Opalinus clay

    International Nuclear Information System (INIS)

    Bleyen, N.; Smets, S.; Valcke, E.; Albrecht, A.; De Canniere, P.; Schwyn, B.; Wittebroodt, C.

    2012-01-01

    nitrate and nitrite concentrations and pH, an on-line UV spectrophotometer and pH electrode are installed in the water circuit of one of the intervals. In a first series of tests, the biogeochemical evolution of the artificial Opalinus Clay pore water in the intervals was investigated after injection of low concentrations of nitrate or nitrate and acetate, simulating the BDP. The results of these tests indicate that microbial reduction of nitrate and nitrite can occur in the Opalinus Clay artificial water in the borehole, using acetate and/or clay components as electron donors. In these tests, nitrate was reduced to nitrite, ammonium and/or nitrogenous gases. Comparing the evolution in nitrate and nitrite concentrations in the absence or presence of acetate, clearly indicates faster reaction rates of microbial nitrate reduction when the system is fueled with acetate. When easily degradable organic compounds like acetate were added to the nitrate containing artificial pore water, these compounds were preferentially used as electron donors for nitrate reduction by heterotrophic microorganisms. Afterwards, alternative electron donors have been used originating either from the clay rock, e.g. pyrite, siderite, clay minerals, and/or dissolved natural organic matter, or from the stainless steel equipment, i.e. Fe 0 and/or Fe 2+ . Furthermore, high concentrations of nitrate reducing prokaryotes were detected after injection of the intervals with nitrate, indicating that the nitrate and nitrite reduction, observed during all tests, was microbially mediated. Based on the results of the microbiological analyses, these nitrate reducers have most likely been introduced during the first injection or installation of the downhole equipment. The nature of the nitrate reduction reaction prevailing in the system appears to be depending on the microbial populations active in the borehole and on the electron donors and carbon sources present in the interval. Furthermore, the history of the

  8. 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

    Nitrate has become an increasingly abundant potential electron acceptor for Fe(II) oxidation in groundwater, but this redox couple has not been well characterized within aquifer settings. To investigate this reaction and some of its implications for redox-sensitive groundwater contaminants, we conducted an in situ field study in a wastewater-contaminated aquifer on Cape Cod. Long-term (15 year) geochemical monitoring within the contaminant plume indicated interacting zones with variable nitrate-, Fe(II)-, phosphate-, As(V)-, and As(III)-containing groundwater. Nitrate and phosphate were derived predominantly from wastewater disposal, whereas Fe(II), As(III), and As(V) were mobilized from the aquifer sediments. Multiple natural gradient, anoxic tracer tests were conducted in which nitrate and bromide were injected into nitrate-free, Fe(II)-containing groundwater. Prior to injection, aqueous Fe(II) concentrations were approximately 175 μM, but sorbed Fe(II) accounted for greater than 90% of the total reactive Fe(II) in the aquifer. Nitrate reduction was stimulated within 1 m of transport for 100 μM and 1000 μM nitrate additions, initially producing stoichiometric quantities of nitrous oxide (>300 μM N). In subsequent injections at the same site, nitrate was reduced even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and were accompanied by Fe(III) oxyhydroxide precipitation and decreases in dissolved phosphate, As(III), and As(V) concentrations. Nitrate N and O isotope fractionation effects during nitrate reduction were approximately equal (ε15N/ε18O = 1.11) and were similar to those reported for laboratory studies of biological nitrate reduction, including denitrification, but unlike some reported effects on nitrate by denitrification in aquifers. All constituents affected by the in situ tracer experiments returned to pre-injection levels after several

  9. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Stief, P.; Fuchs-Ocklenburg, S.; Kamp, A.; Manohar, C.S.; Houbraken, J.; Boekhout, T.; deBeer, D.; Stoeck, T.

    and nitrous oxide emission. Axenic incubations of An-4 in the presence and absence of oxygen and nitrate revealed that this fungal isolate is capable of dissimilatory nitrate reduction to ammonium under anoxic conditions. A 15N-labeling experiment proved...

  10. Nitrate effects on chromate reduction in a methane-based biofilm.

    Science.gov (United States)

    Zhong, Liang; Lai, Chun-Yu; Shi, Ling-Dong; Wang, Kai-Di; Dai, Yu-Jie; Liu, Yao-Wei; Ma, Fang; Rittmann, Bruce E; Zheng, Ping; Zhao, He-Ping

    2017-05-15

    The effects of nitrate (NO 3 - ) on chromate (Cr(VI)) reduction in a membrane biofilm reactor (MBfR) were studied when CH 4 was the sole electron donor supplied with a non-limiting delivery capacity. A high surface loading of NO 3 - gave significant and irreversible inhibition of Cr(VI) reduction. At a surface loading of 500 mg Cr/m 2 -d, the Cr(VI)-removal percentage was 100% when NO 3 - was absent (Stage 1), but was dramatically lowered to PCoA and UniFrac analyses proved that the introduction of NO 3 - had a strong impact on the microbial community in the biofilms, and the changes possibly were linked to the irreversible inhibition of Cr(VI) reduction. For example, Meiothermus, the main genus involved in Cr(VI) reduction at first, declined with introduction of NO 3 - . The denitrifier Chitinophagaceae was enriched after the addition of NO 3 - , while Pelomonas became important when nitrate was removed, suggesting its potential role as a Cr(VI) reducer. Moreover, introducing NO 3 - led to a decrease in the number of genes predicted (by PICRUSt) to be related to chromate reduction, but genes predicted to be related to denitrification, methane oxidation, and fermentation increased. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Effect of didecyl dimethyl ammonium chloride on nitrate reduction in a mixed methanogenic culture.

    Science.gov (United States)

    Tezel, U; Pierson, J A; Pavlostathis, S G

    2008-01-01

    The effect of the quaternary ammonium compound, didecyl dimethyl ammonium chloride (DDAC), on nitrate reduction was investigated at concentrations up to 100 mg/L in a batch assay using a mixed, mesophilic (35 degrees C) methanogenic culture. Glucose was used as the carbon and energy source and the initial nitrate concentration was 70 mg N/L. Dissimilatory nitrate reduction to ammonia (DNRA) and to dinitrogen (denitrification) were observed at DDAC concentrations up to 25 mg/L. At and above 50 mg DDAC/L, DNRA was inhibited and denitrification was incomplete resulting in accumulation of nitrous oxide. At DDAC concentrations above 10 mg/L, production of nitrous oxide, even transiently, resulted in complete, long-term inhibition of methanogenesis and accumulation of volatile fatty acids. Fermentation was inhibited at and above 75 mg DDAC/L. DDAC suppressed microbial growth and caused cell lysis at a concentration 50 mg/L or higher. Most of the added DDAC was adsorbed on the biomass. Over 96% of the added DDAC was recovered from all cultures at the end of the 100-days incubation period, indicating that DDAC did not degrade in the mixed methanogenic culture under the conditions of this study.

  12. Evaluating the potential for dissimilatory nitrate reduction by anammox bacteria for municipal wastewater treatment.

    Science.gov (United States)

    Castro-Barros, Celia M; Jia, Mingsheng; van Loosdrecht, Mark C M; Volcke, Eveline I P; Winkler, Mari K H

    2017-06-01

    Anammox bacteria can perform dissimilatory nitrate reduction to ammonium (DNRA) with nitrite as intermediate coupled to the oxidation of volatile fatty acids (VFA). Batch tests with enriched anammox and a co-culture of anammox and heterotrophic bacteria showed the capacity of Candidatus 'Brocadia fulgida' to perform the DNRA coupled to the anammox reaction (DNRA-anammox) at a high rate although the culture was not previously adapted to VFA. From thermodynamic calculations it could be stated that low COD/N influent ratios favour the DNRA-anammox transformation over heterotrophic conversions since more free energy is gained. A process scheme is proposed for an innovative nitrogen removal system in which the nitrate produced by nitrite oxidizing bacteria and/or anammox bacteria is converted during DNRA-anammox pathway, resulting in a sustainable nitrogen removal from municipal wastewater while circumventing the troublesome out-selection of nitrite oxidizing bacteria encountered in mainstream applications. Copyright © 2017. Published by Elsevier Ltd.

  13. Flow-injection analysis of nitrate by reduction to nitrite and gas-phase molecular absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, B.; Tavassoli, A. [Dept. of Chemistry, Inst. for Advanced Studies in Basic Sciences, Zanjan (Iran)

    2001-12-01

    Two flow-injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 {mu}L) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd-Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O{sub 2}carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV-visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd-Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd-Cu reduction method, up to 330 {mu}g of nitrate was determined. The limit of detection was 2.97 {mu}g nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 {mu}g nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd-Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample. (orig.)

  14. 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...

  15. H2-assisted CO2 thermochemical reduction on La0.9Ca0.1FeO3-δ membranes: a kinetics study

    KAUST Repository

    Wu, Xiao-Yu; Ghoniem, Ahmed F.

    2017-01-01

    Kinetics data for CO2 thermochemical reduction in an isothermal membrane reactor is required to identify the rate-limiting steps. Here, we report a detailed reaction kinetics study on this process supported by an La0.9Ca0.1FeO3-δ (LCF-91) membrane. The dependence of CO2 reduction rate on various operating conditions is examined such as CO2 concentration on the feed side, fuel concentrations on the sweep side and temperatures. CO2 reduction rate is proportional to the oxygen flux across the membrane, and the measured maximum fluxes are 0.191 and 0.164 μmol cm-2 s-1 with 9.5% H2 and 11.6% CO on the sweep side at 990oC, respectively. Fuel is used to maintain the chemical potential gradient across the membrane and CO is used by construction to derive the surface reaction kinetics. This membrane also exhibits stable performances for 106 hours. A resistance-network model is developed to describe the oxygen transport process and the kinetics data are parameterized using the experimental values. The model shows a transition of the rate limiting step between the surface reactions on the feed side and the sweep side depending on the operating conditions.

  16. H2-assisted CO2 thermochemical reduction on La0.9Ca0.1FeO3-δ membranes: a kinetics study

    KAUST Repository

    Wu, Xiao-Yu

    2017-11-04

    Kinetics data for CO2 thermochemical reduction in an isothermal membrane reactor is required to identify the rate-limiting steps. Here, we report a detailed reaction kinetics study on this process supported by an La0.9Ca0.1FeO3-δ (LCF-91) membrane. The dependence of CO2 reduction rate on various operating conditions is examined such as CO2 concentration on the feed side, fuel concentrations on the sweep side and temperatures. CO2 reduction rate is proportional to the oxygen flux across the membrane, and the measured maximum fluxes are 0.191 and 0.164 μmol cm-2 s-1 with 9.5% H2 and 11.6% CO on the sweep side at 990oC, respectively. Fuel is used to maintain the chemical potential gradient across the membrane and CO is used by construction to derive the surface reaction kinetics. This membrane also exhibits stable performances for 106 hours. A resistance-network model is developed to describe the oxygen transport process and the kinetics data are parameterized using the experimental values. The model shows a transition of the rate limiting step between the surface reactions on the feed side and the sweep side depending on the operating conditions.

  17. Influence of organic carbon and nitrate loading on partitioning between dissimilatory nitrate reduction to ammonium (DNRA) and N2 production

    Science.gov (United States)

    Hardison, Amber K.; Algar, Christopher K.; Giblin, Anne E.; Rich, Jeremy J.

    2015-09-01

    Biologically available nitrogen is removed from ecosystems through the microbial processes of anaerobic ammonium oxidation (anammox) or denitrification, while dissimilatory nitrate reduction to ammonium (DNRA) retains it. A mechanistic understanding of controls on partitioning among these pathways is currently lacking. The objective of this study was to conduct a manipulative experiment to determine the influence of organic C and NO3- loading on partitioning. Sediment was collected from a location on the southern New England shelf (78 m water depth) and sieved. Half of the sediment was mixed with freeze-dried phytoplankton and the other half was not. Sediment was then spread into 1.5 mm, "thin discs" closed at the bottom and placed in large aquarium tanks with filtered, N2/CO2 sparged seawater to maintain O2 limited conditions. Half of the discs received high NO3- loading, while the other half received low NO3- loading, resulting in a multifactorial design with four treatments: no C addition, low NO3- (-C-N); C addition, low NO3- (+C-N); no C addition, high NO3- (-C+N); and C addition, high NO3- (+C+N). Sediment discs were incubated in the tanks for 7 weeks, during which time inorganic N (NH4+, NO3-, and NO2-) was monitored, and sediment discs were periodically removed from the tanks to conduct 15N isotope labeling experiments in vials to measure potential rates of anammox, denitrification, and DNRA. Temporal dynamics of inorganic N concentrations in the tanks were indicative of anoxic N metabolism, with strong response of the build up or consumption of the intermediate NO2-, depending on treatments. Vial incubation experiments with added 15NO2- + 14NH4+ indicated significant denitrification and DNRA activity in sediment thin discs, but incubations with added 15NH4+ + 14NO2- indicated anammox was not at all significant. Inorganic N concentrations in the tanks were fit to a reactive transport model assuming different N transformations. Organic C decomposition rates

  18. X-ray induced inactivation of the capacity for photosynthetic oxygen evolution and nitrate reduction in blue-green algae

    International Nuclear Information System (INIS)

    Stevens, S.E. Jr.; Simic, M.G.; Rao, V.S.K.

    1975-01-01

    The level of inactivation of oxygen evolving photosynthesis in the green alga, Chlorella pyrenoidosa was 12 percent in N 2 at a dose of 100 krad of x irradiation. Under similar conditions, as well as under O 2 , there resulted a 20 percent inactivation of the same function in the blue-green algae, Agmenellum quadruplicatum, strains PR-6 and AQ-6. Nitrate reduction capacity in the mutant AQ-6 was inactivated to 40 percent in N 2 and to 7 percent in O 2 . Catalase and formate provided some protection from irradiation in O 2 , suggesting some inactivation by H 2 O 2 . Most of the damage to the nitrate reduction system resulted from the direct action of x irradiation on a constitutive subunit of the nitrate reductase complex. Moreover, the slight inactivation of the O 2 evolving system, a function which is associated with photosystem II, cannot account for the inactivation of nitrate reduction

  19. Silver modified platinum surface/H{sup +} conducting Nafion membrane for cathodic reduction of nitrate ions

    Energy Technology Data Exchange (ETDEWEB)

    Hasnat, M.A., E-mail: mahtazim@yahoo.com [Department of Chemistry, Graduate School of Physical Sciences, Shahajalal University of Science and Technology, Sylhet 3114 (Bangladesh); School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Ahamad, N.; Nizam Uddin, S.M. [Department of Chemistry, Graduate School of Physical Sciences, Shahajalal University of Science and Technology, Sylhet 3114 (Bangladesh); Mohamed, Norita [School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia)

    2012-01-15

    Electrocatalytic reduction of NO{sub 3}{sup -} was performed at an Ag modified Pt electrodes supported on a H{sup +} conducting Nafion-117 polymer electrolyte. The cyclic voltammetric and electrolysis experiments showed that the reduction process was a two-electron transfer reaction. The conversion of nitrate to nitrite follows first order kinetics. Controlled potential electrolysis experiments revealed that the highest reduction rate (k{sub 1}; 95.1 Multiplication-Sign 10{sup -3} min{sup -1}) could be obtained at -1.3 V versus Ag/AgCl (std. KCl) reference electrode. Meanwhile, substantial nitrate removal (ca. 89%) could be attained by a flow system when the flow rate is as low as 0.1 ml min{sup -1}. The Ag particles on the Pt film were a in polycrystalline state having roughness value of 0.45 {mu}m, which was reduced to 0.30 {mu}m after 270 min of undergoing electrolysis.

  20. Reaction pathways for reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes

    International Nuclear Information System (INIS)

    Cunha, M.C.P.M. da; De Souza, J.P.I.; Nart, F.C.

    2000-01-01

    The reduction of nitrate ions on platinum, rhodium, and platinum-rhodium alloy electrodes has been investigated using differential electrochemical mass spectrometry and in situ FTIR measurements. For 3 M HNO 3 concentration it has been found that nitrate starts the reduction with partial N-O bond dissociation and N-N bond formation generating NO and N 2 O. At potentials lower than 0.2 V the reaction proceeds forming dissolved NH 4 + . For potentials lower than 0 V the reduction continues via a multiple pathway reaction leading to the nonselective production of N 2 , NH 2 OH, and N 2 H 2 . On the alloyed electrodes, the production of NO and N 2 O has been observed in both cathodic and anodic scans, while on pure platinum and rhodium electrodes the reaction has been observed only during the cathodic scan. Contrasting with the pure platinum and rhodium alloys, where the N-O bond break starts forming NO and N 2 O, on the alloys HNO 2 has been observed as the first reaction step. For alloys with higher rhodium composition, like Pt 75 Rh 25 , no N 2 has been detected for potentials lower than 0 V

  1. Development of a choronocoulometric method for determining traces of uranium using the catalytic nitrate reduction

    International Nuclear Information System (INIS)

    Cantagallo, M.I.C.; Gutz, I.G.R.

    1990-01-01

    With the aim of improving the sensitivity of the electroanalytical determination of uranium at trace levels. The uranium catalyzed reduction of nitrate on mercury electrode and the technique of chronocoulometry were used. Several experimental parameters were investigated (electrolyte composition, potential program, integration time, blank correction, temperature, previous separation) and adequate conditions were selected for the analytical determination. Under these conditions it was possible to exceed the best reported sensitivity for the catalytic determination, extending the detection limit to 3.10 -10 M. Exploratory study of the combination of this procedure with pre-concentration of uranium ions on the electrode revealed a detection limit ten limes lower. (author) [pt

  2. Using rates of oxygen and nitrate reduction to map the subsurface distribution of groundwater denitrification

    Science.gov (United States)

    Kolbe, T.; De Dreuzy, J. R.; Abbott, B. W.; Aquilina, L.; Babey, T.; Green, C. T.; Fleckenstein, J. H.; Labasque, T.; Laverman, A.; Marçais, J.; Peiffer, S.; Thomas, Z.; Pinay, G.

    2017-12-01

    Widespread fertilizer application over the last 70 years has caused serious ecological and socioeconomic problems in aquatic and estuarine ecosystems. When surplus nitrogen leaches as nitrate (a major groundwater pollutant) to the aquifer, complex flow dynamics and naturally occurring degradation processes control its transport. Under the conditions of depleted oxygen and abundant electron donors, microorganisms reduce NO3- to N2 (denitrification). Denitrification rates vary over orders of magnitude among sites within the same aquifer, complicating estimation of denitrification capacity at the catchment scale. Because it is impractical or impossible to access the subsurface to directly quantify denitrification rates, reactivity is often assumed to occur continuous along flowlines, potentially resulting in substantial over- or underestimation of denitrification. Here we investigated denitrification in an unconfined crystalline aquifer in western France using a combination of common tracers (chlorofluorocarbons, O2, NO3-, and N2) measured in 16 wells to inform a time-based modeling approach. We found that spatially variable denitrification rates arise from the intersection of nitrate rich water with reactive zones defined by the abundance of electron donors (primarily pyrite). Furthermore, based on observed reaction rates of the sequential reduction of oxygen and nitrate, we present a general framework to estimate the location and intensity of the reactive zone in aquifers. Accounting for the vertical distribution of reaction rates results in large differences in estimations of net denitrification rates that assume homogeneous reactivity. This new framework provides a tractable approach for quantifying catchment and regional groundwater denitrification rates that could be used to improve estimation of groundwater resilience to nitrate pollution and develop more realistic management strategies.

  3. 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.

  4. 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.

  5. Efficient electrochemical reduction of nitrate to nitrogen using Ti/IrO2-Pt anode and different cathodes

    International Nuclear Information System (INIS)

    Li Miao; Feng Chuanping; Zhang Zhenya; Sugiura, Norio

    2009-01-01

    Electrochemical reduction of nitrate using Fe, Cu, and Ti as cathodes and Ti/IrO 2 -Pt as anode in an undivided and unbuffered cell was studied. In the presence of appropriate amount of NaCl, both cathodic reduction of nitrate and anodic oxidation of the by-products of ammonia and nitrite were achieved by all cathodes under a proper condition. Both in the absence and presence of NaCl, the order of nitrate removal rate was Fe > Cu > Ti. The nitrate removal was 87% and selectivity to nitrogen was 100% in 3 h with Fe cathode in the presence of NaCl. Ti/IrO 2 -Pt anode played an important role during nitrate reduction, especially in the presence of NaCl, at which by-products could efficiently be oxidized. Moreover, atomic force microscopy (AFM) investigation shown Ti/IrO 2 -Pt anode was suitable for nitration reduction and the surface roughness of all cathodes increased. The concentrations of Fe, Cu, and Ti in the electrolyte were less than 0.15, 0.12 and 0.09 mg/L after 3 h electrolysis, respectively.

  6. Application of chronocoulomentry for trace levels uranium determination using catalytic nitrate reduction on mercury electrode

    International Nuclear Information System (INIS)

    Cantagallo, M.I.C.

    1988-01-01

    With the aim of improving the sensitivity of the electro-analytical determination of uranium at trace levels, the uranium catalyzed reduction of nitrate on mercury electrodes was used and the technique of chronocoulometry was compared with other voltammetric techniques. The catalytic process offers high sensitivity in comparison with uranyl reduction in absence of nitrate. The chronocoulometry, virtually unexplored for analytical applications, was found to be specially well suited for determinations based on this kind of electrode process, when using current integration times in the range of several seconds. Under these conditions the interference from diffusion controlled faradaic processes is reduced to a minimum. Several experimental parameters were investigated (eletrolyte composition, potential program, integration time, blank correction, temperature, previous separation) and adequate conditions were selected for the analytical determination of pure and real samples. The proposed method was applied and evaluated with real and, when necessary, an adapted liquid-liquid extraction procedure was used. Reference materials with complex matrices like rocks were first solubilized by hot digestion under pressure. The obtained results are in good agreement with the values obtained with other techniques such as X-ray fluorescence, mass spectrometry-isotope dilution and epithermal netron activation analysis. (author) [pt

  7. 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.

  8. Reduction stripping of plutonium (IV) with hydroxylamine nitrate in the centrifugal contactor

    International Nuclear Information System (INIS)

    Zhang Zefu; Ding Dachun; Fei Hongcheng

    1989-01-01

    Reduction stripping of Pu(IV) with hydroxylamine nitrate under conditions of Purex 3B contactor is carried out with 16-stage mixer-centrifugal settler in laboratory scale. Results show that the apparent recovery of Pu is more than 99.9%. But there is a great difference in the concentration of plutonium of every stage in extraction equipment at different temperature. For example, plutonium concentrations in organic phase of several stages near the organic effluent at 45-50 deg C are lower than that at 20-24 deg C. Thus, recovery efficiency of plutonium can be assured only for the former. However, plutonium will probably be lost, if operating conditions are fluctuated. In addition, plutonium accumulated in the extraction equipment increased appreciably for the case of 20-24 deg C. Therefore, in order to ensure recovery efficiency of Pu, reduction stripping of Pu should be made at higher temperature

  9. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea

    OpenAIRE

    Stief, Peter; Fuchs-Ocklenburg, Silvia; Kamp, Anja; Manohar, Cathrine-Sumathi; Houbraken, Jos; Boekhout, Teun; de Beer, Dirk; Stoeck, Thorsten

    2014-01-01

    Background A wealth of microbial eukaryotes is adapted to life in oxygen-deficient marine environments. Evidence is accumulating that some of these eukaryotes survive anoxia by employing dissimilatory nitrate reduction, a strategy that otherwise is widespread in prokaryotes. Here, we report on the anaerobic nitrate metabolism of the fungus Aspergillus terreus (isolate An-4) that was obtained from sediment in the seasonal oxygen minimum zone in the Arabian Sea, a globally important site of oce...

  10. Physiology and interaction of nitrate and nitrite reduction in Staphylococcus carnosus.

    OpenAIRE

    Neubauer, H; Götz, F

    1996-01-01

    Staphylococcus carnosus reduces nitrate to ammonia in two steps. (i) Nitrate was taken up and reduced to nitrite, and nitrite was subsequently excreted. (ii) After depletion of nitrate, the accumulated nitrite was imported and reduced to ammonia, which again accumulated in the medium. The localization, energy gain, and induction of the nitrate and nitrite reductases in S. carnosus were characterized. Nitrate reductase seems to be a membrane-bound enzyme involved in respiratory energy conserva...

  11. A GIS-based groundwater travel time model to evaluate stream nitrate concentration reductions from land use change

    Science.gov (United States)

    Schilling, K.E.; Wolter, C.F.

    2007-01-01

    Excessive nitrate-nitrogen (nitrate) loss from agricultural watersheds is an environmental concern. A common conservation practice to improve stream water quality is to retire vulnerable row croplands to grass. In this paper, a groundwater travel time model based on a geographic information system (GIS) analysis of readily available soil and topographic variables was used to evaluate the time needed to observe stream nitrate concentration reductions from conversion of row crop land to native prairie in Walnut Creek watershed, Iowa. Average linear groundwater velocity in 5-m cells was estimated by overlaying GIS layers of soil permeability, land slope (surrogates for hydraulic conductivity and gradient, respectively) and porosity. Cells were summed backwards from the stream network to watershed divide to develop a travel time distribution map. Results suggested that groundwater from half of the land planted in prairie has reached the stream network during the 10 years of ongoing water quality monitoring. The mean travel time for the watershed was estimated to be 10.1 years, consistent with results from a simple analytical model. The proportion of land in the watershed and subbasins with prairie groundwater reaching the stream (10-22%) was similar to the measured reduction of stream nitrate (11-36%). Results provide encouragement that additional nitrate reductions in Walnut Creek are probable in the future as reduced nitrate groundwater from distal locations discharges to the stream network in the coming years. The high spatial resolution of the model (5-m cells) and its simplicity may make it potentially applicable for land managers interested in communicating lag time issues to the public, particularly related to nitrate concentration reductions over time. ?? 2007 Springer-Verlag.

  12. Concurrent nitrate and Fe(III) reduction during anaerobic biodegradation of phenols in a sandstone aquifer

    DEFF Research Database (Denmark)

    Broholm, Mette; Crouzet, C.; Arvin, Erik

    2000-01-01

    The biodegradation of phenols (similar to 5, 60, 600 mg 1(-1)) under anaerobic conditions (nitrate enriched and unamended) was studied in laboratory microcosms with sandstone material and groundwater from within an anaerobic ammonium plume in an aquifer, The aqueous phase was sampled and analyzed...... for phenols and selected redox sensitive parameters on a regular basis. An experiment with sandstone material from specific depth intervals from a vertical profile across the ammonium plume was also conducted. The miniature microcosms used in this experiment were sacrificed for sampling for phenols...... and selected redox sensitive parameters at the end of the experiment. The sandstone material was characterized with respect to oxidation and reduction potential and Fe(II) and Fe(III) speciation prior to use for all microcosms and at the end of the experiments for selected microcosms. The redox conditions...

  13. Modification of activated carbon using nitration followed by reduction for carbon dioxide capture

    Energy Technology Data Exchange (ETDEWEB)

    Shafeeyan, Mohammad Saleh; Houshmand, Amirhossein; Arami-Niya, Arash; Daud, Wan Mohd AshiWan [Dept. of Chemical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur (Malaysia); Razaghizadeh, Hosain [Dept. of Faculty of Environment and Energy, Research and Science Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2015-02-15

    Activated carbon (AC) samples were modified using nitration followed by reduction to enhance their CO{sub 2} adsorption capacities. Besides characterization of the samples, investigation of CO{sub 2} capture performance was conducted by CO{sub 2} isothermal adsorption, temperature-programmed (TP) CO{sub 2} adsorption, cyclic CO{sub 2} adsorption–desorption, and dynamic CO{sub 2} adsorption tests. Almost all modified samples showed a rise in the amount of CO{sub 2} adsorbed when the comparison is made in unit surface area. On the other hand, some of the samples displayed a capacity superior to that of the parent material when compared in mass unit, especially at elevated temperatures. Despite ⁓65% decrease in the surface area, TP-CO{sub 2} adsorption of the best samples exhibited increases of ⁓10 and 70% in CO{sub 2} capture capacity at 30 and 100 °C, respectively.

  14. Evidence for dissimilatory reduction of nitrate to ammonium in irradiated soil

    International Nuclear Information System (INIS)

    Castet, R.; Guiraud, G.

    1987-01-01

    The influence of gamma irradiation (1 kGy) on nitrogen transformation in a brown soil, labelled with 15 N(Ca(NO 3 ) 2 ) and glucose amended was studied. The fractions of the added nitrique-N in the ammoniacal-N, organic-N and N-gas forms were determined. In the unirradiated soil, after 3 days incubation, 54% of the N transformations from N-nitrique was accounted for by organization and 45% was lost by denitrification. In the irradiated soil, these transformations were less intense, but the production of ammonium by the dissimilatory nitrate reduction was noticeable (25% of the N-NO 3 - transformation). Two hypothesis are discussed: one on microbial dynamic population and the other, on the factors affecting this process [fr

  15. Dietary nitrate attenuates renal ischemia-reperfusion injuries by modulation of immune responses and reduction of oxidative stress.

    Science.gov (United States)

    Yang, Ting; Zhang, Xing-Mei; Tarnawski, Laura; Peleli, Maria; Zhuge, Zhengbing; Terrando, Niccolo; Harris, Robert A; Olofsson, Peder S; Larsson, Erik; Persson, A Erik G; Lundberg, Jon O; Weitzberg, Eddie; Carlstrom, Mattias

    2017-10-01

    Ischemia-reperfusion (IR) injury involves complex pathological processes in which reduction of nitric oxide (NO) bioavailability is suggested as a key factor. Inorganic nitrate can form NO in vivo via NO synthase-independent pathways and may thus provide beneficial effects during IR. Herein we evaluated the effects of dietary nitrate supplementation in a renal IR model. Male mice (C57BL/6J) were fed nitrate-supplemented chow (1.0mmol/kg/day) or standard chow for two weeks prior to 30min ischemia and during the reperfusion period. Unilateral renal IR caused profound tubular and glomerular damage in the ischemic kidney. Renal function, assessed by plasma creatinine levels, glomerular filtration rate and renal plasma flow, was also impaired after IR. All these pathologies were significantly improved by nitrate. Mechanistically, nitrate treatment reduced renal superoxide generation, pro-inflammatory cytokines (IL-1β, IL-6 and IL-12 p70) and macrophage infiltration in the kidney. Moreover, nitrate reduced mRNA expression of pro-inflammatory cytokines and chemo attractors, while increasing anti-inflammatory cytokines in the injured kidney. In another cohort of mice, two weeks of nitrate supplementation lowered superoxide generation and IL-6 expression in bone marrow-derived macrophages. Our study demonstrates protective effect of dietary nitrate in renal IR injury that may be mediated via modulation of oxidative stress and inflammatory responses. These novel findings suggest that nitrate supplementation deserve further exploration as a potential treatment in patients at high risk of renal IR injury. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers.

    Directory of Open Access Journals (Sweden)

    Helen eDecleyre

    2015-10-01

    Full Text Available The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate. In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary. We observed high variability in dominant nitrogen removing processes over a short distance (1.6 m, with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celeribacter and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms.

  17. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers.

    Science.gov (United States)

    Decleyre, Helen; Heylen, Kim; Van Colen, Carl; Willems, Anne

    2015-01-01

    The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary). We observed high variability in dominant nitrogen removing processes over a short distance (1.6 m), with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites) or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celeribacter, and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms.

  18. Mechanisms of direct inhibition of the respiratory sulfate-reduction pathway by (per)chlorate and nitrate.

    Science.gov (United States)

    Carlson, Hans K; Kuehl, Jennifer V; Hazra, Amrita B; Justice, Nicholas B; Stoeva, Magdalena K; Sczesnak, Andrew; Mullan, Mark R; Iavarone, Anthony T; Engelbrektson, Anna; Price, Morgan N; Deutschbauer, Adam M; Arkin, Adam P; Coates, John D

    2015-06-01

    We investigated perchlorate (ClO(4)(-)) and chlorate (ClO(3)(-)) (collectively (per)chlorate) in comparison with nitrate as potential inhibitors of sulfide (H(2)S) production by mesophilic sulfate-reducing microorganisms (SRMs). We demonstrate the specificity and potency of (per)chlorate as direct SRM inhibitors in both pure cultures and undefined sulfidogenic communities. We demonstrate that (per)chlorate and nitrate are antagonistic inhibitors and resistance is cross-inducible implying that these compounds share at least one common mechanism of resistance. Using tagged-transposon pools we identified genes responsible for sensitivity and resistance in Desulfovibrio alaskensis G20. We found that mutants in Dde_2702 (Rex), a repressor of the central sulfate-reduction pathway were resistant to both (per)chlorate and nitrate. In general, Rex derepresses its regulon in response to increasing intracellular NADH:NAD(+) ratios. In cells in which respiratory sulfate reduction is inhibited, NADH:NAD(+) ratios should increase leading to derepression of the sulfate-reduction pathway. In support of this, in (per)chlorate or nitrate-stressed wild-type G20 we observed higher NADH:NAD(+) ratios, increased transcripts and increased peptide counts for genes in the core Rex regulon. We conclude that one mode of (per)chlorate and nitrate toxicity is as direct inhibitors of the central sulfate-reduction pathway. Our results demonstrate that (per)chlorate are more potent inhibitors than nitrate in both pure cultures and communities, implying that they represent an attractive alternative for controlling sulfidogenesis in industrial ecosystems. Of these, perchlorate offers better application logistics because of its inhibitory potency, solubility, relative chemical stability, low affinity for mineral cations and high mobility in environmental systems.

  19. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea

    NARCIS (Netherlands)

    Stief, Peter; Fuchs-Ocklenburg, Silvia; Kamp, Anja; Manohar, Cathrine-Sumathi; Houbraken, Jos; Boekhout, Teun; de Beer, Dirk; Stoeck, Thorsten

    2014-01-01

    BACKGROUND: A wealth of microbial eukaryotes is adapted to life in oxygen-deficient marine environments. Evidence is accumulating that some of these eukaryotes survive anoxia by employing dissimilatory nitrate reduction, a strategy that otherwise is widespread in prokaryotes. Here, we report on the

  20. 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.

  1. Complete bromate and nitrate reduction using hydrogen as the sole electron donor in a rotating biofilm-electrode reactor

    International Nuclear Information System (INIS)

    Zhong, Yu; Li, Xin; Yang, Qi; Wang, Dongbo; Yao, Fubing; Li, Xiaoming; Zhao, Jianwei; Xu, Qiuxiang; Zhang, Chang; Zeng, Guangming

    2016-01-01

    Graphical abstract: Main mechanism of simultaneous bromate and nitrate removal in the RBER. - Highlights: • Cathode of RBER was designed to automatically rotate. • Simultaneous bromate and nitrate removal was achieved by auto-hydrogenotrophic reduction. • The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h. • An electron transfer process and main reaction mechanism in RBER was explored. - Abstract: Simultaneous reduction of bromate and nitrate was investigated using a rotating biofilm-electrode reactor (RBER) with graphite carbon (GC) rods as anode and activated carbon fiber (ACF) bonded with steel ring as cathode. In RBER, the community of denitrifying bacteria immobilized on the cathode surface could completely utilize hydrogen (H 2 ) as the electron donor, which was internally produced by the electrolysis of water. The short-term test confirmed that the RBER system could reduce 150–800 μg/L bromate to below 10 μg/L under autotrophic conditions. The reduced bromate was considered to be roughly equivalent to the amount of bromide in effluent, indicating that bromate was completely reduced to bromide without accumulation of by-products. The long-term test (over 120 days) showed that the removal fluxes of bromate and nitrate could be improved by increasing the electric current and decreasing the hydraulic retention time (HRT). But nitrite in effluent was significantly accumulated when the electric current was beyond 10 mA and the HRT was less than 6 h. The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h when the electric current was 10 mA and HRT was 12 h. It was proposed that the electron transfer process in RBER produced H 2 on the surface of the ACF cathode, and the microbial cultures attached closely on the cathode which could completely utilize H 2 as electron donors for reduction of bromate and nitrate.

  2. Reduction of the nitro group during sample preparation may cause underestimation of the nitration level in 3-nitrotyrosine immunoblotting

    DEFF Research Database (Denmark)

    Söderling, Ann-Sofi; Hultman, Lena; Delbro, Dick

    2007-01-01

    We noted differences in the antibody response to 3-nitrotyrosine (NO(2)Tyr) in fixed and non-fixed tissues, and studied therefore potential problems associated with non-fixed tissues in Western blot analyses. Three different monoclonal anti-nitrotyrosine antibodies in Western blot analysis of inf...... is not detected by anti-NO(2)Tyr antibodies. Western blot analysis may therefore underestimate the level of tissue nitration, and factors causing a reduction of NO(2)Tyr during sample preparation might conceal the actual nitration of proteins....

  3. Nonlinear-Optical and Fluorescent Properties of Ag Aqueous Colloid Prepared by Silver Nitrate Reduction

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Zhang

    2010-01-01

    Full Text Available The nonlinear-optical properties of metal Ag colloidal solutions, which were prepared by the reduction of silver nitrate, were investigated using Z-scan method. Under picosecond 532 nm excitation, the Ag colloidal solution exhibited negative nonlinear refractive index (n2=−5.17×10−4 cm2/W and reverse saturable absorption coefficient (β=4.32 cm/GW. The data fitting result of optical limiting (OL response of metal Ag colloidal solution indicated that the nonlinear absorption was attributed to two-photon absorption effect at 532 nm. Moreover, the fluorescence emission spectra of Ag colloidal solution were recorded under excitations at both 280 nm and 350 nm. Two fluorescence peaks, 336 nm and 543 nm for 280 nm excitation, while 544 nm and 694 nm for 350 nm excitation, were observed.

  4. Growth and nitrate reduction of Beggiatoa filaments studied in enrichment cultures

    DEFF Research Database (Denmark)

    Kamp, Anja

    In this thesis, several aspects of the gliding, filamentous, colourless sulphur bacteria Beggiatoa were investigated. The first part of this thesis addressed the growth mode, breakage of filaments for multiplication, and movement directions of filaments of Beggiatoa. Marine Beggiatoa were enriche...... to ammonium), whereas denitrification was not detected. This study revealed for the first time that a freshwater Beggiatoa strain was capable of intracellular accumulation of nitrate, and that the nitrate was used to perform DNRA....

  5. Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink

    Directory of Open Access Journals (Sweden)

    Alexander Klotz

    2015-03-01

    Full Text Available Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS by a precise dosage of l-methionine-sulfoximine (MSX mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction.

  6. Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink

    Science.gov (United States)

    Klotz, Alexander; Reinhold, Edgar; Doello, Sofía; Forchhammer, Karl

    2015-01-01

    Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS) by a precise dosage of l-methionine-sulfoximine (MSX) mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction. PMID:25780959

  7. Comparative study involving the uranium determination through catalytic reduction of nitrates and nitrides by using decoupled plasma nitridation (DPN)

    International Nuclear Information System (INIS)

    Aguiar, Marco Antonio Souza; Gutz, Ivano G. Rolf

    1999-01-01

    This paper reports a comparative study on the determination of uranium through the catalytic reduction of nitrate and nitride using the decoupled plasma nitridation. The uranyl ions are a good catalyst for the reduction of NO - 3 and NO - 2 ions on the surface of a hanging drop mercury electrode (HDME). The presence of NO - in a solution with p H = 3 presented a catalytic signal more intense than the signal obtained with NO - 3 (concentration ten times higher). A detection limit of 1x10 9 M was obtained using the technique of decoupled plasma nitridation (DPN), suggesting the development of a sensitive way for the determination of uranium in different matrixes

  8. Complete bromate and nitrate reduction using hydrogen as the sole electron donor in a rotating biofilm-electrode reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yu; Li, Xin [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yang, Qi, E-mail: yangqi@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wang, Dongbo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Advanced Water Management Centre, The University of Queensland, QLD 4072 (Australia); Yao, Fubing [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Li, Xiaoming, E-mail: xmli@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Zhao, Jianwei; Xu, Qiuxiang; Zhang, Chang; Zeng, Guangming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

    2016-04-15

    Graphical abstract: Main mechanism of simultaneous bromate and nitrate removal in the RBER. - Highlights: • Cathode of RBER was designed to automatically rotate. • Simultaneous bromate and nitrate removal was achieved by auto-hydrogenotrophic reduction. • The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h. • An electron transfer process and main reaction mechanism in RBER was explored. - Abstract: Simultaneous reduction of bromate and nitrate was investigated using a rotating biofilm-electrode reactor (RBER) with graphite carbon (GC) rods as anode and activated carbon fiber (ACF) bonded with steel ring as cathode. In RBER, the community of denitrifying bacteria immobilized on the cathode surface could completely utilize hydrogen (H{sub 2}) as the electron donor, which was internally produced by the electrolysis of water. The short-term test confirmed that the RBER system could reduce 150–800 μg/L bromate to below 10 μg/L under autotrophic conditions. The reduced bromate was considered to be roughly equivalent to the amount of bromide in effluent, indicating that bromate was completely reduced to bromide without accumulation of by-products. The long-term test (over 120 days) showed that the removal fluxes of bromate and nitrate could be improved by increasing the electric current and decreasing the hydraulic retention time (HRT). But nitrite in effluent was significantly accumulated when the electric current was beyond 10 mA and the HRT was less than 6 h. The maximum bromate reduction rate estimated by the Monod equation was 109.12 μg/L h when the electric current was 10 mA and HRT was 12 h. It was proposed that the electron transfer process in RBER produced H{sub 2} on the surface of the ACF cathode, and the microbial cultures attached closely on the cathode which could completely utilize H{sub 2} as electron donors for reduction of bromate and nitrate.

  9. The nitrate-reduction gene cluster components exert lineage-dependent contributions to optimization of Sinorhizobium symbiosis with soybeans.

    Science.gov (United States)

    Liu, Li Xue; Li, Qin Qin; Zhang, Yun Zeng; Hu, Yue; Jiao, Jian; Guo, Hui Juan; Zhang, Xing Xing; Zhang, Biliang; Chen, Wen Xin; Tian, Chang Fu

    2017-12-01

    Receiving nodulation and nitrogen fixation genes does not guarantee rhizobia an effective symbiosis with legumes. Here, variations in gene content were determined for three Sinorhizobium species showing contrasting symbiotic efficiency on soybeans. A nitrate-reduction gene cluster absent in S. sojae was found to be essential for symbiotic adaptations of S. fredii and S. sp. III. In S. fredii, the deletion mutation of the nap (nitrate reductase), instead of nir (nitrite reductase) and nor (nitric oxide reductase), led to defects in nitrogen-fixation (Fix - ). By contrast, none of these core nitrate-reduction genes were required for the symbiosis of S. sp. III. However, within the same gene cluster, the deletion of hemN1 (encoding oxygen-independent coproporphyrinogen III oxidase) in both S. fredii and S. sp. III led to the formation of nitrogen-fixing (Fix + ) but ineffective (Eff - ) nodules. These Fix + /Eff - nodules were characterized by significantly lower enzyme activity of glutamine synthetase indicating rhizobial modulation of nitrogen-assimilation by plants. A distant homologue of HemN1 from S. sojae can complement this defect in S. fredii and S. sp. III, but exhibited a more pleotropic role in symbiosis establishment. These findings highlighted the lineage-dependent optimization of symbiotic functions in different rhizobial species associated with the same host. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. Thermochemical surface engineering of steels

    DEFF Research Database (Denmark)

    Thermochemical Surface Engineering of Steels provides a comprehensive scientific overview of the principles and different techniques involved in thermochemical surface engineering, including thermodynamics, kinetics principles, process technologies and techniques for enhanced performance of steels...

  11. Nitrate and Perchlorate Destruction and Potable Water Production Using Membrane Biofilm Reduction

    Science.gov (United States)

    2014-01-01

    NDMA N-nitrosodimethylamine NDPA N-nitroso-di-n-propylamine ng/L nanograms per liter NO2- nitrite NO3- nitrate NTU nephelometric turbidity units...Nitrosamines including N-nitrosodiethylamine (NDEA), N- nitrosodimethylamine ( NDMA ), and N-nitroso-di-n-propylamine (NDPA) were below their

  12. NITRATE REDUCTION AND TRANSFORMATION IN ORGANIC COMPOST MEDIA: LABORATORY BATCH STUDIES

    Science.gov (United States)

    We studied the effectiveness of three organic solid reactive media (cotton burr compost, mulch compost, and Canadian sphagnum peat) that may be potentially used in permeable reactive barriers (PRBs) for groundwater nitrate removal. We aimed at answering the question about the na...

  13. Potential rates of ammonium oxidation, nitrite oxidation, nitrate reduction and denitrification in the young barley rhizosphere

    DEFF Research Database (Denmark)

    Højberg, Ole; Binnerup, S. J.; Sørensen, Jan

    1996-01-01

    Potential activities (enzyme contents) of ammonium (NH4+) oxidizing, nitrite (NO2-) oxidizing, nitrate (NO3-) reducing and denitrifying bacteria were measured in bulk and rhizosphere soil obtained from young barley plants in the field. The activities as well as pools of inorganic N (NH4+, NO2...

  14. Toxicity of xenobiotics during sulfate, iron, and nitrate reduction in primary sewage sludge suspensions

    DEFF Research Database (Denmark)

    Elsgaard, Lars

    2010-01-01

    The effect and persistence of six organic xenobiotics was tested under sulfate-, iron-, and nitrate-reducing conditions in primary sewage sludge suspensions. The xenobiotics tested were acenaphthene, phenanthrene, di(2-ethylhexyl)phthalate (DEHP), 4-nonylphenol (4-NP), linear alkylbenzene sulfonate...

  15. Nitrate reduction in geologically heterogeneous catchments — A framework for assessing the scale of predictive capability of hydrological models

    International Nuclear Information System (INIS)

    Refsgaard, Jens Christian; Auken, Esben; Bamberg, Charlotte A.; Christensen, Britt S.B.; Clausen, Thomas; Dalgaard, Esben; Effersø, Flemming; Ernstsen, Vibeke; Gertz, Flemming; Hansen, Anne Lausten; He, Xin; Jacobsen, Brian H.; Jensen, Karsten Høgh; Jørgensen, Flemming; Jørgensen, Lisbeth Flindt; Koch, Julian; Nilsson, Bertel; Petersen, Christian; De Schepper, Guillaume; Schamper, Cyril

    2014-01-01

    In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root zone is reduced in the saturated zone before reaching the streams, and vulnerable areas, where no subsurface reduction takes place, and then only impose regulations/restrictions on the vulnerable areas. Distributed hydrological models can make predictions at grid scale, i.e. at much smaller scale than the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface and for assessing at which spatial scales modelling tools have predictive capabilities. A new instrument has been developed for airborne geophysical measurements, Mini-SkyTEM, dedicated to identifying geological structures and heterogeneities with horizontal and lateral resolutions of 30–50 m and 2 m, respectively, in the upper 30 m. The geological heterogeneity and uncertainty are further analysed by use of the geostatistical software TProGS by generating stochastic geological realisations that are soft conditioned against the geophysical data. Finally, the flow paths within the catchment are simulated by use of the MIKE SHE hydrological modelling system for each of the geological models generated by TProGS and the prediction uncertainty is characterised by the variance between the

  16. Nitrate reduction in geologically heterogeneous catchments — A framework for assessing the scale of predictive capability of hydrological models

    Energy Technology Data Exchange (ETDEWEB)

    Refsgaard, Jens Christian, E-mail: jcr@geus.dk [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Auken, Esben [Department of Earth Sciences, Aarhus University (Denmark); Bamberg, Charlotte A. [City of Aarhus (Denmark); Christensen, Britt S.B. [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Clausen, Thomas [DHI, Hørsholm (Denmark); Dalgaard, Esben [Department of Earth Sciences, Aarhus University (Denmark); Effersø, Flemming [SkyTEM Aps, Beder (Denmark); Ernstsen, Vibeke [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Gertz, Flemming [Knowledge Center for Agriculture, Skejby (Denmark); Hansen, Anne Lausten [Department of Geosciences and Natural Resource Management, University of Copenhagen (Denmark); He, Xin [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Jacobsen, Brian H. [Department of Food and Resource Economics, University of Copenhagen (Denmark); Jensen, Karsten Høgh [Department of Geosciences and Natural Resource Management, University of Copenhagen (Denmark); Jørgensen, Flemming; Jørgensen, Lisbeth Flindt [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Koch, Julian [Department of Geosciences and Natural Resource Management, University of Copenhagen (Denmark); Nilsson, Bertel [Geological Survey of Denmark and Greenland (GEUS) (Denmark); Petersen, Christian [City of Odder (Denmark); De Schepper, Guillaume [Université Laval, Québec (Canada); Schamper, Cyril [Department of Earth Sciences, Aarhus University (Denmark); and others

    2014-01-01

    In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root zone is reduced in the saturated zone before reaching the streams, and vulnerable areas, where no subsurface reduction takes place, and then only impose regulations/restrictions on the vulnerable areas. Distributed hydrological models can make predictions at grid scale, i.e. at much smaller scale than the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface and for assessing at which spatial scales modelling tools have predictive capabilities. A new instrument has been developed for airborne geophysical measurements, Mini-SkyTEM, dedicated to identifying geological structures and heterogeneities with horizontal and lateral resolutions of 30–50 m and 2 m, respectively, in the upper 30 m. The geological heterogeneity and uncertainty are further analysed by use of the geostatistical software TProGS by generating stochastic geological realisations that are soft conditioned against the geophysical data. Finally, the flow paths within the catchment are simulated by use of the MIKE SHE hydrological modelling system for each of the geological models generated by TProGS and the prediction uncertainty is characterised by the variance between the

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

    International Nuclear Information System (INIS)

    Araujo, B.F. de; Almeida, S.G. de; Forbicini, S.; Matsuda, H.T.; Araujo, J.A. de.

    1981-05-01

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

  18. Halomonas desiderata as a bacterial model to predict the possible biological nitrate reduction in concrete cells of nuclear waste disposals.

    Science.gov (United States)

    Alquier, Marjorie; Kassim, Caroline; Bertron, Alexandra; Sablayrolles, Caroline; Rafrafi, Yan; Albrecht, Achim; Erable, Benjamin

    2014-01-01

    After closure of a waste disposal cell in a repository for radioactive waste, resaturation is likely to cause the release of soluble species contained in cement and bituminous matrices, such as ionic species (nitrates, sulfates, calcium and alkaline ions, etc.), organic matter (mainly organic acids), or gases (from steel containers and reinforced concrete structures as well as from radiolysis within the waste packages). However, in the presence of nitrates in the near-field of waste, the waste cell can initiate oxidative conditions leading to enhanced mobility of redox-sensitive radionuclides (RN). In biotic conditions and in the presence of organic matter and/or hydrogen as electron donors, nitrates may be microbiologically reduced, allowing a return to reducing conditions that promote the safety of storage. Our work aims to analyze the possible microbial reactivity of nitrates at the bitumen - concrete interface in conditions as close as possible to radioactive waste storage conditions in order (i) to evaluate the nitrate reaction kinetics; (ii) to identify the by-products (NO2(-), NH4(+), N2, N2O, etc.); and (iii) to discriminate between the roles of planktonic bacteria and those adhering as a biofilm structure in the denitrifying activity. Leaching experiments on solid matrices (bitumen and cement pastes) were first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface, e.g. highly alkaline pH conditions (10 < pH < 11) imposed by the cement matrix. The screening of a range of anaerobic denitrifying bacterial strains led us to select Halomonas desiderata as a model bacterium capable of catalyzing the reaction of nitrate reduction in these particular conditions of pH. The denitrifying activity of H. desiderata was quantified in a batch bioreactor in the presence of solid matrices and/or leachate from bitumen and cement matrices. Denitrification was relatively fast in the presence of cement

  19. Enhanced nitrogen selectivity for nitrate reduction on Cu–nZVI by TiO{sub 2} photocatalysts under UV irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Krasae, Nalinee, E-mail: k_nalinee@kkumail.com [Department of Chemical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002 (Thailand); Chemical Kinetics and Applied Catalysis Laboratory (CKCL), Faculty of Engineering, Khon Kaen University, Khon Kaen 40002 (Thailand); Wantala, Kitirote, E-mail: kitirote@kku.ac.th [Department of Chemical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002 (Thailand); Chemical Kinetics and Applied Catalysis Laboratory (CKCL), Faculty of Engineering, Khon Kaen University, Khon Kaen 40002 (Thailand); Research Center for Environmental and Hazardous Substance Management (EHSM), Faculty of Engineering, Khon Kaen University, Khon Kaen 40002 (Thailand)

    2016-09-01

    Highlights: • Photocatalytic process has been enhancing the nitrate removal over Cu–nZVI/TiO{sub 2}. • Highly nitrogen selectivity more than 80% over Cu–nZVI/TiO{sub 2}. • Nitrate removal can be reacted in neutral pH of solutions. - Abstract: The aims of this work were to study the effect of Cu–nZVI with and without TiO{sub 2} on nitrate reduction and to study the pathway of nitrate reduction utilizing to nitrogen gas. The chemical and physical properties of Cu–nZVI and Cu–nZVI/TiO{sub 2} such as specific surface area, crystalline phase, oxidation state of Cu and Fe and morphology were determined by N{sub 2} adsorption–desorption Brunauer–Emmett–Teller (BET) analytical technique, X-ray diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) technique and Transmittance Electron Microscopy (TEM). The full factorial design (FFD) was used in this experiment for the effect of Cu–nZVI with and without TiO{sub 2}, where the initial solution pH was varied at 4, 5.5, and 7 and initial nitrate concentration was varied at 50, 75, and 100 ppm. Finally, the pathway of nitrate reduction was examined to calculate the nitrogen gas selectivity. The specific area of Cu–nZVI and Cu–nZVI/TiO{sub 2} was found to be about 4 and 36 m{sup 2}/g, respectively. The XRD pattern of Fe{sup 0} in Cu–nZVI was found at 45° (2θ), whereas Cu–nZVI/TiO{sub 2} cannot be observed. TEM images can confirm the position of the core and the shell of nZVI for Fe{sup 0} and ferric oxide. Cu–nZVI/TiO{sub 2} proved to have higher activity in nitrogen reduction performance than that without TiO{sub 2} and nitrate can be completely degraded in both of solution pH of 4 and 7 in 75 ppm of initial nitrate concentration. It can be highlighted that the nitrogen gas selectivity of Cu–nZVI/TiO{sub 2} greater than 82% was found at an initial solution pH of 4 and 7. The main effects of Cu–nZVI with and without TiO{sub 2} and the initial nitrate concentration on nitrate

  20. Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Bleyen, N.; Smets, S. [Belgian Nuclear Research Centre SCK-CEN, Mol (Belgium); Small, J. [National Nuclear Laboratory NLL, Warrington (United Kingdom); and others

    2017-04-15

    At the Mont Terri rock laboratory (Switzerland), an in situ experiment is being carried out to examine the fate of nitrate leaching from nitrate-containing bituminized radioactive waste, in a clay host rock for geological disposal. Such a release of nitrate may cause a geochemical perturbation of the clay, possibly affecting some of the favorable characteristics of the host rock. In this in situ experiment, combined transport and reactivity of nitrate is studied inside anoxic and water-saturated chambers in a borehole in the Opalinus Clay. Continuous circulation of the solution from the borehole to the surface equipment allows a regular sampling and online monitoring of its chemical composition. In this paper, in situ microbial nitrate reduction in the Opalinus Clay is discussed, in the presence or absence of additional electron donors relevant for the disposal concept and likely to be released from nitrate-containing bituminized radioactive waste: acetate (simulating bitumen degradation products) and H{sub 2} (originating from radiolysis and corrosion in the repository). The results of these tests indicate that - in case microorganisms would be active in the repository or the surrounding clay - microbial nitrate reduction can occur using electron donors naturally present in the clay (e.g. pyrite, dissolved organic matter). Nevertheless, non-reactive transport of nitrate in the clay is expected to be the main process. In contrast, when easily oxidizable electron donors would be available (e.g. acetate and H{sub 2}), the microbial activity will be strongly stimulated. Both in the presence of H{sub 2} and acetate, nitrite and nitrogenous gases are predominantly produced, although some ammonium can also be formed when H{sub 2} is present. The reduction of nitrate in the clay could have an impact on the redox conditions in the pore-water and might also lead to a gas-related perturbation of the host rock, depending on the electron donor used during denitrification

  1. Goethite promoted biodegradation of 2,4-dinitrophenol under nitrate reduction condition.

    Science.gov (United States)

    Tang, Ting; Yue, Zhengbo; Wang, Jin; Chen, Tianhu; Qing, Chengsong

    2018-02-05

    Iron oxide may interact with other pollutants in the aquatic environments and further influence their toxicity, transport and fate. The current study was conducted to investigate the biodegradation of 2,4-dinitrophenol (2,4-DNP) in the presence of iron oxide of goethite under anoxic condition using nitrate as the electron acceptor. Experiment results showed that the degradation rate of 2,4-DNP was improved by goethite. High performance liquid chromatography-mass spectra analysis results showed that goethite promoted degradation and transformation of 2,4-diaminophenol and 2-amino-4-nitrophenol (2-nitro-4-aminophenol). Microbial community analysis results showed that the abundance of Actinobacteria, which have the potential ability to degrade PAHs, was increased when goethite was available. This might partially explain the higher degradation of 2,4-DNP. Furthermore, another bacterium of Desulfotomaculum reducens which could reduce soluble Fe(III) and nitrate was also increased. Results further confirmed that nanomaterials in the aquatic environment will influence the microbial community and further change the transformation process of toxic pollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Competitive, microbially-mediated reduction of nitrate with sulfide and aromatic oil components in a low-temperature, western Canadian oil reservoir.

    Science.gov (United States)

    Lambo, Adewale J; Noke, Kim; Larter, Steve R; Voordouw, Gerrit

    2008-12-01

    Fields from which oil is produced by injection of sulfate-bearing water often exhibit an increase in sulfide concentration with time (souring). Nitrate added to the injection water lowers the sulfide concentration by the action of sulfide-oxidizing, nitrate-reducing bacteria (SO-NRB). However, the injected nitrate can also be reduced with oil organics by heterotrophic NRB (hNRB). Aqueous volatile fatty acids (VFAs; a mixture of acetate, propionate, and butyrate) are considered important electron donors in this regard. Injection and produced waters from a western Canadian oil field with a low in situ reservoir temperature (30 degrees C) had only 0.1-0.2 mM VFAs. Amendment of these waters with nitrate gave therefore only partial reduction. More nitrate was reduced when 2% (v/v) oil was added, with light oil giving more reduction than heavy oil. GC-MS analysis of in vitro degraded oils and electron balance considerations indicated that toluene served as the primary electron donor for nitrate reduction. The differences in the extent of nitrate reduction were thus related to the toluene content of the light and heavy oil (30 and 5 mM, respectively). Reduction of nitrate with sulfide by SO-NRB always preceded that with oil organics by hNRB, even though microbially catalyzed kinetics with either electron donor were similar. Inhibition of hNRB by sulfide is responsible for this phenomenon. Injected nitrate will thus initially be reduced with sulfide through the action of SO-NRB. However, once sulfide has been eliminated from the near-injection wellbore region, oil organics will be targeted by the action of hNRB. Hence, despite the kinetic advantage of SO-NRB, the nitrate dose required to eliminate sulfide from a reservoir depends on the concentration of hNRB-degradable oil organics, with toluene being the most important in the field under study. Because the toluene concentration is lower in heavy oilthan in light oil, nitrate injection into a heavy-oil-producing field of

  3. Performance of nanoscale zero-valent iron in nitrate reduction from water using a laboratory-scale continuous-flow system.

    Science.gov (United States)

    Khalil, Ahmed M E; Eljamal, Osama; Saha, Bidyut Baran; Matsunaga, Nobuhiro

    2018-04-01

    Nanoscale zero-valent iron (nZVI) is a versatile treatment reagent that should be utilized in an effective application for nitrate remediation in water. For this purpose, a laboratory-scale continuous-flow system (LSCFS) was developed to evaluate nZVI performance in removal of nitrate in different contaminated-water bodies. The equipment design (reactor, settler, and polisher) and operational parameters of the LSCFS were determined based on nZVI characterization and nitrate reduction kinetics. Ten experimental runs were conducted at different dosages (6, 10 and 20 g) of nZVI-based reagents (nZVI, bimetallic nZVI-Cu, CuCl 2 -added nZVI). Effluent concentrations of nitrogen and iron compounds were measured, and pH and ORP values were monitored. The major role exhibited by the recirculation process of unreacted nZVI from the settler to the reactor succeeded in achieving overall nitrate removal efficiency (RE) of >90%. The similar performance of both nZVI and copper-ions-modified nZVI in contaminated distilled water was an indication of LSCFS reliability in completely utilizing iron nanoparticles. In case of treating contaminated river water and simulated groundwater, the nitrate reduction process was sensitive towards the presence of interfering substances that dropped the overall RE drastically. However, the addition of copper ions during the treatment counteracted the retardation effect and greatly enhanced the nitrate RE. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Cloning and nitrate induction of nitrate reductase mRNA

    OpenAIRE

    Cheng, Chi-Lien; Dewdney, Julia; Kleinhofs, Andris; Goodman, Howard M.

    1986-01-01

    Nitrate is the major source of nitrogen taken from the soil by higher plants but requires reduction to ammonia prior to incorporation into amino acids. The first enzyme in the reducing pathway is a nitrate-inducible enzyme, nitrate reductase (EC 1.6.6.1). A specific polyclonal antiserum raised against purified barley nitrate reductase has been used to immunoprecipitate in vivo labeled protein and in vitro translation products, demonstrating that nitrate induction increases nitrate reductase p...

  5. Nitrate accumulation in spinach

    NARCIS (Netherlands)

    Steingröver, Eveliene Geertruda

    1986-01-01

    Leafy vegetables, like spinach, may contain high concentrations of nitrate. In the Netherlands, about 75% of mean daily intake of nitrate orginates from the consumption of vegatables. Hazards to human health are associated with the reduction of nitrate to nitrite. Acute nitrite poisoning causes

  6. Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes

    DEFF Research Database (Denmark)

    Uldahl, Anne; Banta, Gary Thomas; Boegh, Eva

    the ecosystem in the form of gaseous N2, while the last process transforms of NO3- to another biologically available form, NH4+, and thus merely recycles N. Salt marshes are important ecosystems for the cycling, retention and removal of biologically available N transported from land to the oceans. We used...... ongoing ecosystem level nutrient additions experiments in two New England salt marshes, Plum Island Sound (NO3- additions since 2003) and Great Sippewissett Marsh (fertilizer additions since the 1970's) to examine the relative importance of these NO3- reduction pathways in salt marshes. Sediments from...... several experimental (and unmanipulated) sites were collected during the late summer/fall of 2009 and summer 2010 to measure the potential rates of NO3- reduction in sediment slurries enriched with NO3- and 15NO3- added as a tracer. The resulting 15N-labeled products (30N2, 29N2 and 15NH4+) were analyzed...

  7. Nitrate conversion and supercritical fluid extraction of UO2-CeO2 solid solution prepared by an electrolytic reduction-coprecipitation method

    International Nuclear Information System (INIS)

    Zhu, L.Y.; Duan, W.H.; Wen, M.F.; Xu, J.M.; Zhu, Y.J.

    2014-01-01

    A low-waste technology for the reprocessing of spent nuclear fuel (SNF) has been developed recently, which involves the conversion of actinide and lanthanide oxides with liquid N 2 O 4 into their nitrates followed by supercritical fluid extraction of the nitrates. The possibility of the reprocessing of SNF from high-temperature gas-cooled reactors (HTGRs) with nitrate conversion and supercritical fluid extraction is a current area of research in China. Here, a UO 2 -CeO 2 solid solution was prepared as a surrogate for a UO 2 -PuO 2 solid solution, and the recovery of U and Ce from the UO 2 -CeO 2 solid solution with liquid N 2 O 4 and supercritical CO 2 containing tri-n-butyl phosphate (TBP) was investigated. The UO 2 -CeO 2 solid solution prepared by electrolytic reduction-coprecipitation method had square plate microstructures. The solid solution after heat treatment was completely converted into nitrates with liquid N 2 O 4 . The XRD pattern of the nitrates was similar to that of UO 2 (NO 3 ) 2 . 3H 2 O. After 120 min of online extraction at 25 MPa and 50 , 99.98% of the U and 98.74% of the Ce were recovered from the nitrates with supercritical CO 2 containing TBP. The results suggest a promising potential technology for the reprocessing of SNF from HTGRs. (orig.)

  8. Catalytic reduction of nitrate and nitrite ions by hydrogen : investigation of the reaction mechanism over Pd and Pd-Cu catalysts

    NARCIS (Netherlands)

    Ilinitch, OM; Nosova, LV; Gorodetskii, VV; Ivanov, VP; Trukhan, SN; Gribov, EN; Bogdanov, SV; Cuperus, FP

    2000-01-01

    The catalytic behavior of mono- and bimetallic catalysts with Pd and/or Cu supported over gamma-Al2O3 in the reduction of aqueous nitrate and nitrite ions by hydrogen was investigated. The composition of the supported metal catalysts was analysed using secondary ion mass spectroscopy (SIMS) and

  9. Kinetics of nitrate adsorption and reduction by nano-scale zero valent iron (NZVI): Effect of ionic strength and initial pH

    DEFF Research Database (Denmark)

    Kim, Do-Gun; Hwang, Yuhoon; Shin, Hang-Sik

    2016-01-01

    Kinetic models for pollutants reduction by Nano-scale Zero Valent Iron (NZVI) were tested in this study to gain a better understanding and description of the reaction. Adsorption kinetic models and a heterogeneous catalytic reaction kinetic equation were proposed for nitrate removal and for ammon...

  10. Biotic and abiotic catalysis of nitrate reduction in alkaline environment of repository storage cell for long-lived intermediate-level radioactive wastes

    International Nuclear Information System (INIS)

    Bertron, A.; Jacquemet, N.; Escadeillas, G.; Erable, B.; Alquier, M.; Kassim, C.; Albasi, C.; Basseguy, R.; Strehaiano, P.; Sablayrolles, C.; Vignoles, M.; Albrecht, A.

    2013-01-01

    This study investigates the reactivity of nitrates at the bitumen-concrete interface with the aim of determining redox conditions inside a repository storage cell for long-lived intermediate-level radioactive wastes. The first part of the work aimed to identify, under abiotic conditions, the interactions between two components of the system: concrete (introduced as cement pastes in the system) and bitumen (represented by leachates composed of organic acids and nitrates). The second part of the study was conducted under biotic conditions with selected denitrifying heterotrophic bacteria (Pseudomonas stutzeri - Ps and Halomonas desiderata - Hd) and aimed to analyse the microbial reaction of nitrate reduction (kinetics, by-products, role of the organic matter) under neutral to alkaline pH conditions (i.e. imposed by a concrete environment). Results showed that strong interactions occurred between cementitious matrices and acetic and oxalic organic acids, likely reducing the bio-availability of this organic matter (oxalate in particular). Results also confirmed the stability of nitrates under these conditions. Under biotic conditions, nitrates were reduced by both Ps and Hd following an anaerobic denitrification metabolic pathway. Reduction kinetics was higher with Ps but the reaction was inhibited for pH ≥ 9. Hd was capable of denitrification at least up to pH 11. (authors)

  11. Reduction of Net Sulfide Production Rate by Nitrate in Wastewater Bioreactors. Kinetics and Changes in the Microbial Community

    DEFF Research Database (Denmark)

    Villahermosa, Desiree; Corzo, Alfonso; Gonzalez, J M

    2013-01-01

    Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of ...

  12. Effect of organic enrichment and thermal regime on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in hypolimnetic sediments of two lowland lakes.

    Science.gov (United States)

    Nizzoli, Daniele; Carraro, Elisa; Nigro, Valentina; Viaroli, Pierluigi

    2010-05-01

    We analyzed benthic fluxes of inorganic nitrogen, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in hypolimnetic sediments of lowland lakes. Two neighbouring mesotrophic (Ca' Stanga; CS) and hypertrophic (Lago Verde; LV) lakes, which originated from sand and gravel mining, were considered. Lakes are affected by high nitrate loads (0.2-0.7 mM) and different organic loads. Oxygen consumption, dissolved inorganic carbon, methane and nitrogen fluxes, denitrification and DNRA were measured under summer thermal stratification and late winter overturn. Hypolimnetic sediments of CS were a net sink of dissolved inorganic nitrogen (-3.5 to -4.7 mmol m(-2)d(-1)) in both seasons due to high nitrate consumption. On the contrary, LV sediments turned from being a net sink during winter overturn (-3.5 mmol m(-2)d(-1)) to a net source of dissolved inorganic nitrogen under summer conditions (8.1 mmol m(-2)d(-1)), when significant ammonium regeneration was measured at the water-sediment interface. Benthic denitrification (0.7-4.1 mmol m(-2)d(-1)) accounted for up to 84-97% of total NO(3)(-) reduction and from 2 to 30% of carbon mineralization. It was mainly fuelled by water column nitrate. In CS, denitrification rates were similar in winter and in summer, while in LV summer rates were 4 times lower. DNRA rates were generally low in both lakes (0.07-0.12 mmol m(-2)d(-1)). An appreciable contribution of DNRA was only detected in the more reducing sediments of LV in summer (15% of total NO(3)(-) reduction), while during the same period only 3% of reduced NO(3)(-) was recycled into ammonium in CS. Under summer stratification benthic denitrification was mainly nitrate-limited due to nitrate depletion in hypolimnetic waters and parallel oxygen depletion, hampering nitrification. Organic enrichment and reducing conditions in the hypolimnetic sediment shifted nitrate reduction towards more pronounced DNRA, which resulted in the inorganic nitrogen recycling and

  13. Disproportionation and thermochemical sulfate reduction reactions in S-H20-Ch4 and S-D2O-CH4 systems from 200 to 340 °C at elevated pressures

    Science.gov (United States)

    Yuan, Shunda; Chou, I-Ming; Burruss, Robert A.

    2013-01-01

    Elemental sulfur, as a transient intermediate compound, by-product, or catalyst, plays significant roles in thermochemical sulfate reduction (TSR) reactions. However, the mechanisms of the reactions in S-H2O-hydrocarbons systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules (FSCC). After a heating period ranging from 24 to 2160 hours (hrs), the quenched samples were analyzed by Raman spectroscopy. Combined with the in situ Raman spectra collected at high temperatures and pressures in the S-H2O and S-H2O-CH4 systems, our results showed that (1) the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and possibly trace amount of HSO4-; (2) sulfate (and bisulfate), in the presence of sulfur, can be reduced by methane between 250 and 340 °C to produce CO2 and H2S, and these TSR temperatures are much closer to those of the natural system (2O-CH4 system may take place simultaneously, with TSR being favored at higher temperatures; and (4) in the system S-D2O-CH4, both TSR and the competitive disproportionation reactions occurred simultaneously at temperatures above 300 °C, but these reactions were very slow at lower temperatures. Our observation of methane reaction at 250 °C in a laboratory time scale suggests that, in a geologic time scale, methane may be destroyed by TSR reactions at temperatures > 200 °C that can be reached by deep drilling for hydrocarbon resources.

  14. Cascading pressure reactor and method for solar-thermochemical reactions

    Science.gov (United States)

    Ermanoski, Ivan

    2017-11-14

    Reactors and methods for solar thermochemical reactions are disclosed. The reactors and methods include a cascade of reduction chambers at successively lower pressures that leads to over an order of magnitude pressure decrease compared to a single-chambered design. The resulting efficiency gains are substantial, and represent an important step toward practical and efficient solar fuel production on a large scale.

  15. The interplay between hydrogen evolution reaction and nitrate reduction on boron-doped diamond in aqueous solution: the effect of alkali cations

    International Nuclear Information System (INIS)

    Manzo-Robledo, A.; Lévy-Clément, C.; Alonso-Vante, N.

    2014-01-01

    The nitrate ion reduction was studied on boron-doped diamond (BDD) electrodes by real-time on-line differential electrochemical mass spectrometry (DEMS) coupled with chronoamperometry in K + , Na + cation-containing electrolyte solutions. It was found, via steady state voltammetry, that the hydrogen evolution reaction (HER) was affected by the presence of K + or Na + . A moderate HER occurs in K + -containing electrolyte solution favoring the reaction between NO 3 − and H 2 species, whereas in Na + -containing electrolyte solutions, the HER kinetics was more important leading to a suppression of molecular nitrogen generation. The use of isotope-labeled nitrogen and DEMS confirmed the influence of alkali cations toward the nitrate ion reduction

  16. Nitrate reduction, nitrous oxide formation, and anaerobic ammonia oxidation to nitrite in the gut of soil-feeding termites (Cubitermes and Ophiotermes spp.)

    KAUST Repository

    Ngugi, David

    2011-11-28

    Soil-feeding termites play important roles in the dynamics of carbon and nitrogen in tropical soils. Through the mineralization of nitrogenous humus components, their intestinal tracts accumulate enormous amounts of ammonia, and nitrate and nitrite concentrations are several orders of magnitude above those in the ingested soil. Here, we studied the metabolism of nitrate in the different gut compartments of two Cubitermes and one Ophiotermes species using 15N isotope tracer analysis. Living termites emitted N 2 at rates ranging from 3.8 to 6.8nmolh -1 (g fresh wt.) -1. However, in homogenates of individual gut sections, denitrification was restricted to the posterior hindgut, whereas nitrate ammonification occurred in all gut compartments and was the prevailing process in the anterior gut. Potential rates of nitrate ammonification for the entire intestinal tract were tenfold higher than those of denitrification, implying that ammonification is the major sink for ingested nitrate in the intestinal tract of soil-feeding termites. Because nitrate is efficiently reduced already in the anterior gut, reductive processes in the posterior gut compartments must be fuelled by an endogenous source of oxidized nitrogen species. Quite unexpectedly, we observed an anaerobic oxidation of 15N-labelled ammonia to nitrite, especially in the P4 section, which is presumably driven by ferric iron; nitrification and anammox activities were not detected. Two of the termite species also emitted substantial amounts of N 2O, ranging from 0.4 to 3.9nmolh -1 (g fresh wt.) -1, providing direct evidence that soil-feeding termites are a hitherto unrecognized source of this greenhouse gas in tropical soils. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  17. Nitrate conversion and supercritical fluid extraction of UO{sub 2}-CeO{sub 2} solid solution prepared by an electrolytic reduction-coprecipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, L.Y. [Tsinghua Univ., Beijing (China). Inst. of Nuclear and New Energy Technology; China Institute of Atomic Energy, Beijing (China); Duan, W.H.; Wen, M.F.; Xu, J.M.; Zhu, Y.J. [Tsinghua Univ., Beijing (China). Inst. of Nuclear and New Energy Technology

    2014-04-01

    A low-waste technology for the reprocessing of spent nuclear fuel (SNF) has been developed recently, which involves the conversion of actinide and lanthanide oxides with liquid N{sub 2}O{sub 4} into their nitrates followed by supercritical fluid extraction of the nitrates. The possibility of the reprocessing of SNF from high-temperature gas-cooled reactors (HTGRs) with nitrate conversion and supercritical fluid extraction is a current area of research in China. Here, a UO{sub 2}-CeO{sub 2} solid solution was prepared as a surrogate for a UO{sub 2}-PuO{sub 2} solid solution, and the recovery of U and Ce from the UO{sub 2}-CeO{sub 2} solid solution with liquid N{sub 2}O{sub 4} and supercritical CO{sub 2} containing tri-n-butyl phosphate (TBP) was investigated. The UO{sub 2}-CeO{sub 2} solid solution prepared by electrolytic reduction-coprecipitation method had square plate microstructures. The solid solution after heat treatment was completely converted into nitrates with liquid N{sub 2}O{sub 4}. The XRD pattern of the nitrates was similar to that of UO{sub 2}(NO{sub 3}){sub 2} . 3H{sub 2}O. After 120 min of online extraction at 25 MPa and 50 , 99.98% of the U and 98.74% of the Ce were recovered from the nitrates with supercritical CO{sub 2} containing TBP. The results suggest a promising potential technology for the reprocessing of SNF from HTGRs. (orig.)

  18. Mg-Cu-Al layered double hydroxides based catalysts for the reduction of nitrates in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Vulić Tatjana J.

    2010-01-01

    Full Text Available The secondary waste and bacterial contamination in physico-chemical and biological separation processes used today for nitrate removal from ground water make novel catalytic technologies that convert nitrates to unharmful gaseous nitrogen, very attractive for scientific research. The Mg-Cu-Al layered double hydroxide (LDH based catalysts with different Mg/Al ratio were investigated in water denitrification reaction in the presence of hydrogen and with solely copper as an active phase. Since LDHs have ion exchange properties and their derived mixed oxides possess memory effect (restoration of layered structure after thermal decomposition, their adsorption capacity for nitrates was also measured in the same model system. All studied samples showed nitrate removal from 23% to 62% following the decrease in Al content, as well as the substantial adsorption capacity ranging from 18% to 38%. These results underlie the necessity to take into account the effects of the adsorption in all future investigations.

  19. ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light

    Science.gov (United States)

    Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

    2016-08-01

    We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

  20. ZnCr2S4: Highly effective photocatalyst converting nitrate into N2 without over-reduction under both UV and pure visible light.

    Science.gov (United States)

    Yue, Mufei; Wang, Rong; Cheng, Nana; Cong, Rihong; Gao, Wenliang; Yang, Tao

    2016-08-03

    We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst, and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp, and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem, and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

  1. The effect of soot on ammonium nitrate species and NO2 selective catalytic reduction over Cu-zeolite catalyst-coated particulate filter.

    Science.gov (United States)

    Mihai, Oana; Tamm, Stefanie; Stenfeldt, Marie; Olsson, Louise

    2016-02-28

    A selective catalytic reduction (SCR)-coated particulate filter was evaluated by means of dynamic tests performed using NH3, NO2, O2 and H2O. The reactions were examined both prior to and after soot removal in order to study the effect of soot on ammonium nitrate formation and decomposition, ammonia storage and NO2 SCR. A slightly larger ammonia storage capacity was observed when soot was present in the sample, which indicated that small amounts of ammonia can adsorb on the soot. Feeding of NO2 and NH3 in the presence of O2 and H2O at low temperature (150, 175 and 200°C) leads to a large formation of ammonium nitrate species and during the subsequent temperature ramp using H2O and argon, a production of nitrous oxides was observed. The N2O formation is often related to ammonium nitrate decomposition, and our results showed that the N2O formation was clearly decreased by the presence of soot. We therefore propose that in the presence of soot, there are fewer ammonium nitrate species on the surface due to the interactions with the soot. Indeed, we do observe CO2 production during the reaction conditions also at 150°C, which shows that there is a reaction with these species and soot. In addition, the conversion of NOx due to NO2 SCR was significantly enhanced in the presence of soot; we attribute this to the smaller amount of ammonium nitrate species present in the experiments where soot is available since it is well known that ammonium nitrate formation is a major problem at low temperature due to the blocking of the catalytic sites. Further, a scanning electron microscopy analysis of the soot particles shows that they are about 30-40 nm and are therefore too large to enter the pores of the zeolites. There are likely CuxOy or other copper species available on the outside of the zeolite crystallites, which could have been enhanced due to the hydrothermal treatment at 850°C of the SCR-coated filter prior to the soot loading. We therefore propose that soot is

  2. Thermochemical investigations on uranyl phosphates and arsenates

    International Nuclear Information System (INIS)

    Barten, H.

    1986-11-01

    The results are described of a study of the thermochemical stability of anhydrous uranyl phosphates and arsenates. A number of aspects of chemical technological importance are indicated in detail. The synthesized anhydrous uranyl phosphates and arsenates were very hygroscopic, so that experiments on these compounds had to be carried out under moisture-free conditions. Further characterisation of these compounds are given, including a study of their thermal stabilities and phase relations. The uranyl phosphates reduced reversibly at temperatures of the order of 1100 to 1600 0 C. This makes it possible to express their relative stabilities quantitatively, in terms of the oxygen pressures of the reduction reactions. The thermal decomposition of uranyl arsenates did not occur by reduction, as for the phosphates, but by giving off arsenic oxide vapour. The results of measurements of enthalpies of solution led to the determination of the enthalpies of formation, heat capacity and the standard entropies of the uranyl arsenates. The thermochemical functions at high-temperatures could consequently be calculated. Attention is paid to the possible formation of uranium arsenates, whose uranium has a valency lower than six, hitherto not reported in literature. It was not possible to prepare arsenates of tetravalent uranium. However, three new compounds were observed, one of these, UAsO 5 , was studied in some detail. (Auth.)

  3. Experimental investigation on thermochemical sulfate reduction in the presence of 1-pentanethiol at 200 and 250 °C: Implications for in situ TSR processes occurring in some MVT deposits

    Science.gov (United States)

    Yuan, Shunda; Ellis, Geoffrey S.; Chou, I-Ming; Burruss, Robert

    2017-01-01

    Organic sulfur compounds are ubiquitous in natural oil and gas fields and moderate-low temperature sulfide ore deposits. Previous studies have shown that organic sulfur compounds are important in enhancing the rates of thermochemical sulfate reduction (TSR) reactions, but the details of these reaction mechanisms remain unclear. In order to assess the extent of sulfate reduction in the presence of labile sulfur species at temperature conditions near to those where TSR occurs in nature, we conducted a series of experiments using the fused silica capillary capsule (FCSS) method. The tested systems containing labile sulfur species are MgSO4 + 1-pentanethiol (C5H11SH) + 1-octene (C8H16), MgSO4 + 1-octene (C8H16), MgSO4 + 1-pentanethiol (C5H11SH), 1-pentanethiol (C5H11SH)+H2O, and MgSO4 + 1-pentanethiol (C5H11SH) + ZnBr2 systems. Our results show that: (1) intermediate oxidized carbon species (ethanol and acetic acid) are formed during TSR simulation experiments when 1-pentanethiol is present; (2) in the presence of ZnBr2, 1-pentanethiol can be oxidized by sulfate to CO2 at 200 °C, which is within the temperature range observed in natural TSR; and (3) the precipitation of sulfide minerals may significantly promote the rate of TSR, indicating that the rates of in situ TSR reactions in ore deposits could be much faster than previously thought. This may be important for understanding the possibility of in situ TSR as a mechanism for the precipitation of metal sulfides in some ore deposits. These findings provide important experimental evidence for understanding the role of organic sulfur compounds in TSR reactions and the pathway of TSR reactions initiated by organic sulfur compounds under natural conditions.

  4. Thermochemical transformations of anthracite fractions

    Energy Technology Data Exchange (ETDEWEB)

    Belkina, T.V.; Privalov, V.E.; Stepanenko, atM.A.

    1979-08-01

    Research on the nature of thermochemical transformations of anthracite fractions and the possibility of increasing their activity and identifying conditions for their use in the electrode pitch process is described. From research done on different anthracite fractions processed at varying temperatures it was concluded that accumulations of condensates from heating anthracite fractions occur significantly slower in comparison with pitch. As a result the electrode pitch process is prolonged. Thermal treatment of an anthracite fraction causes the formation and accumulation of condensates and promotes thermochemical transformations. Lastly, the use of thermally treated anthracite fractions apparently intensifies the electrode pitch process and improves its quality. (16 refs.) (In Russian)

  5. Electrochemical reduction of oxygen on gold and boron-doped diamond electrodes in ambient temperature, molten acetamide-urea-ammonium nitrate eutectic melt

    International Nuclear Information System (INIS)

    Dilimon, V.S.; Venkata Narayanan, N.S.; Sampath, S.

    2010-01-01

    The electrochemical reduction of oxygen has been studied on gold, boron-doped diamond (BDD) and glassy carbon (GC) electrodes in a ternary eutectic mixture of acetamide (CH 3 CONH 2 ), urea (NH 2 CONH 2 ) and ammonium nitrate (NH 4 NO 3 ). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and rotating disk electrode (RDE) voltammetry techniques have been employed to follow oxygen reduction reaction (ORR). The mechanism for the electrochemical reduction of oxygen on polycrystalline gold involves 2-step, 2-electron pathways of O 2 to H 2 O 2 and further reduction of H 2 O 2 to H 2 O. The first 2-electron reduction of O 2 to H 2 O 2 passes through superoxide intermediate by 1-electron reduction of oxygen. Kinetic results suggest that the initial 1-electron reduction of oxygen to HO 2 is the rate-determining step of ORR on gold surfaces. The chronoamperometric and RDE studies show a potential dependent change in the number of electrons on gold electrode. The oxygen reduction reaction on boron-doped diamond (BDD) seems to proceed via a direct 4-electron process. The reduction of oxygen on the glassy carbon (GC) electrode is a single step, irreversible, diffusion limited 2-electron reduction process to peroxide.

  6. Agricultural nitrate pollution

    DEFF Research Database (Denmark)

    Anker, Helle Tegner

    2015-01-01

    Despite the passing of almost 25 years since the adoption of the EU Nitrates Directive, agricultural nitrate pollution remains a major concern in most EU Member States. This is also the case in Denmark, although a fairly strict regulatory regime has resulted in almost a 50 per cent reduction...

  7. Thermochemical reduction of pelletized gypsum mixed with ...

    African Journals Online (AJOL)

    2015-04-03

    Apr 3, 2015 ... Other saleable products such as sulphur may also be produced ... in the absence of air, as air was observed to impact nega- tively on the conversion of ... able mechanical strength to minimize disintegration during handling ...

  8. Electrocatalytic reduction of nitrate at low concentration on coinage and transition-metal electrodes in acid solutions

    NARCIS (Netherlands)

    Dima, G.E.; Vooys, de A.C.A.; Koper, M.T.M.

    2003-01-01

    A comparative study was performed to determine the reactivity of nitrate ions at 0.1 M on eight different polycrystalline electrodes (platinum, palladium, rhodium, ruthenium, iridium, copper, silver and gold) in acidic solution using cyclic voltammetry (CV), chronoamperometry and differential

  9. The reduction of nitrate, nitrite and hydroxylamine to ammonia by enzymes from Cucurbita pepo L. in the presence of reduced benzyl viologen as electron donor

    Science.gov (United States)

    Cresswell, C. F.; Hageman, R. H.; Hewitt, E. J.; Hucklesby, D. P.

    1965-01-01

    1. Enzyme systems from Cucurbita pepo have been shown to catalyse the reduction of nitrite and hydroxylamine to ammonia in yields about 90–100%. 2. Reduced benzyl viologen serves as an efficient electron donor for both systems. Activity of the nitrite-reductase system is directly related to degree of dye reduction when expressed in terms of the function for oxidation–reduction potentials, but appears to decrease to negligible activity below about 9% dye reduction. 3. NADH and NADPH alone produce negligible nitrite loss, but NADPH can be linked to an endogenous diaphorase system to reduce nitrite to ammonia in the presence of catalytic amounts of benzyl viologen. 4. The NADH– or NADPH–nitrate-reductase system that is also present can accept electrons from reduced benzyl viologen, but shows relationships opposite to that for the nitrite-reductase system with regard to effect of degree of dye reduction on activity. The product of nitrate reduction may be nitrite alone, or nitrite and ammonia, or ammonia alone, according only to the degree of dye reduction. 5. The relative activities of nitrite-reductase and hydroxylamine-reductase systems show different relationships with degree of dye reduction and may become reversed in magnitude when effects of degree of dye reduction are tested over a suitable range. 6. Nitrite severely inhibits the rate of reduction of hydroxylamine without affecting the yield of ammonia as a percentage of total substrate loss, but hydroxylamine has a negligible effect on the activity of the nitrite-reductase system. 7. The apparent Km for nitrite (1 μm) is substantially less than that for hydroxylamine, for which variable values between 0·05 and 0·9mm (mean 0·51 mm) have been observed. 8. The apparent Km values for reduced benzyl viologen differ for the nitrite-reductase and hydroxylamine-reductase systems: 60 and 7·5 μm respectively. 9. It is concluded that free hydroxylamine may not be an intermediate in the reduction of nitrite

  10. Inhibition of nitrate reduction by NaCl adsorption on a nano-zero-valent iron surface during a concentrate treatment for water reuse.

    Science.gov (United States)

    Hwang, Yuhoon; Kim, Dogun; Shin, Hang-Sik

    2015-01-01

    Nanoscale zero-valent iron (NZVI) has been considered as a possible material to treat water and wastewater. However, it is necessary to verify the effect of the matrix components in different types of target water. In this study, different effects depending on the sodium chloride (NaCl) concentration on reductions of nitrates and on the characteristics of NZVI were investigated. Although NaCl is known as a promoter of iron corrosion, a high concentration of NaCl (>3 g/L) has a significant inhibition effect on the degree of NZVI reactivity towards nitrate. The experimental results were interpreted by a Langmuir-Hinshelwood-Hougen-Watson reaction in terms of inhibition, and the decreased NZVI reactivity could be explained by the increase in the inhibition constant. As a result of a chloride concentration analysis, it was verified that 7.7-26.5% of chloride was adsorbed onto the surface of NZVI. Moreover, the change of the iron corrosion product under different NaCl concentrations was investigated by a surface analysis of spent NZVI. Magnetite was the main product, with a low NaCl concentration (0.5 g/L), whereas amorphous iron hydroxide was observed at a high concentration (12 g/L). Though the surface was changed to permeable iron hydroxide, the Fe(0) in the core was not completely oxidized. Therefore, the inhibition effect of NaCl could be explained as the competitive adsorption of chloride and nitrate.

  11. Solar Thermochemical Hydrogen Production Research (STCH)

    Energy Technology Data Exchange (ETDEWEB)

    Perret, Robert [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2011-05-01

    Eight cycles in a coordinated set of projects for Solar Thermochemical Cycles for Hydrogen production (STCH) were self-evaluated for the DOE-EERE Fuel Cell Technologies Program at a Working Group Meeting on October 8 and 9, 2008. This document reports the initial selection process for development investment in STCH projects, the evaluation process meant to reduce the number of projects as a means to focus resources on development of a few most-likely-to-succeed efforts, the obstacles encountered in project inventory reduction and the outcomes of the evaluation process. Summary technical status of the projects under evaluation is reported and recommendations identified to improve future project planning and selection activities.

  12. Thermochemical data for reactor materials

    International Nuclear Information System (INIS)

    Ronchi, C.; Turrini, F.

    1990-01-01

    This report describes a computer database of thermochemical properties of nuclear reactor materials to be used for source term calculations in reactor accident codes. In the first part, the structure and the content of the computer file is described. In the second part a set of thermochemical data is presented pertaining to chemical reactions occurring during severe nuclear reactor accidents and involving fuel (uranium dioxide), fission products and structural materials. These data are complementary to those collected in the databook recently published by Cordfunke and Potter after a study supported by the Commission of the European Communities. The present data were collected from review articles and databanks and follow a discussion on the uncertainties and errors involved in the calculation of complex chemical equilibria in the extrapolated temperature range

  13. Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

    Science.gov (United States)

    Klueglein, Nicole; Zeitvogel, Fabian; Stierhof, York-Dieter; Floetenmeyer, Matthias; Konhauser, Kurt O.; Obst, Martin

    2014-01-01

    Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ∼8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record. PMID:24271182

  14. Hybrid Thermochemical/Biological Processing

    Science.gov (United States)

    Brown, Robert C.

    The conventional view of biorefineries is that lignocellulosic plant material will be fractionated into cellulose, hemicellulose, lignin, and terpenes before these components are biochemically converted into market products. Occasionally, these plants include a thermochemical step at the end of the process to convert recalcitrant plant components or mixed waste streams into heat to meet thermal energy demands elsewhere in the facility. However, another possibility for converting high-fiber plant materials is to start by thermochemically processing it into a uniform intermediate product that can be biologically converted into a bio-based product. This alternative route to bio-based products is known as hybrid thermochemical/biological processing. There are two distinct approaches to hybrid processing: (a) gasification followed by fermentation of the resulting gaseous mixture of carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2) and (b) fast pyrolysis followed by hydrolysis and/or fermentation of the anhydrosugars found in the resulting bio-oil. This article explores this "cart before the horse" approach to biorefineries.

  15. Utilization of Common Automotive Three-Way NOx Reduction Catalyst for Managing Off- Gas from Thermal Treatment of High-Nitrate Waste - 13094

    International Nuclear Information System (INIS)

    Foster, Adam L.; Ki Song, P.E.

    2013-01-01

    Studsvik's Thermal Organic Reduction (THOR) steam reforming process has been tested and proven to effectively treat radioactive and hazardous wastes streams with high nitrate contents to produce dry, stable mineral products, while providing high conversion (>98%) of nitrates and nitrites directly to nitrogen gas. However, increased NO x reduction may be desired for some waste streams under certain regulatory frameworks. In order to enhance the NO x reduction performance of the THOR process, a common Three-Way catalytic NO x reduction unit was installed in the process gas piping of a recently completed Engineering Scale Technology Demonstration (ESTD). The catalytic DeNO x unit was located downstream of the main THOR process vessel, and it was designed to catalyze the reduction of residual NO x to nitrogen gas via the oxidation of the hydrogen, carbon monoxide, and volatile organic compounds that are inherent to the THOR process gas. There was no need for auxiliary injection of a reducing gas, such as ammonia. The unit consisted of four monolith type catalyst sections positioned in series with a gas mixing section located between each catalyst section. The process gas was monitored for NO x concentration upstream and downstream of the catalytic DeNO x unit. Conversion efficiencies ranged from 91% to 97% across the catalytic unit, depending on the composition of the inlet gas. Higher concentrations of hydrogen and carbon monoxide in the THOR process gas increased the NO x reduction capability of the catalytic DeNO x unit. The NO x destruction performance of THOR process in combination with the Three-Way catalytic unit resulted in overall system NO x reduction efficiencies of greater than 99.9% with an average NO x reduction efficiency of 99.94% for the entire demonstration program. This allowed the NO x concentration in the ESTD exhaust gas to be maintained at less than 40 parts per million (ppm), dry basis with an average concentration of approximately 17 ppm, dry

  16. Use of potassium ferrocyanide as habit modifier in the size reduction and phase modification of ammonium nitrate crystals in slurries.

    Science.gov (United States)

    Vargeese, Anuj A; Joshi, Satyawati S; Krishnamurthy, V N

    2010-08-15

    Ammonium nitrate (AN) is an inorganic crystalline compound used as a solid propellant oxidizer and as a nitrogenous fertilizer. The practical use of AN as solid propellant oxidizer is restricted due to the near room temperature polymorphic phase transition and hygroscopicity. A good deal of effort has been expended for last many years to stabilize the polymorphic transitions of AN, so as to minimize the storage difficulties of AN based fertilizers and to achieve more environmentally benign propellant systems. Also, particles with aspect ratio nearer to one are a vital requirement in fertilizer and propellant industries. In the present study AN is crystallized in presence of trace amount of potassium ferrocyanide (K(4)Fe(CN)(6)) crystal habit modifier and kept for different time intervals. And the effect of K(4)Fe(CN)(6) on the habit and phase modification of AN was studied. Phase modified ammonium nitrate (PMAN) with a particle aspect ratio nearer to one was obtained by this method and the reasons for this modifications are discussed. The morphology changes were studied by SEM, the phase modifications were studied by DSC and the structural properties were studied by powder XRD. Copyright 2010 Elsevier B.V. All rights reserved.

  17. The reaction of hydrazine nitrate with nitric acid

    International Nuclear Information System (INIS)

    Kida, Takashi; Sugikawa, Susumu

    2004-03-01

    It is known that hydrazine nitrate used in nuclear fuel reprocessing plants is an unstable substance thermochemically like hydroxylamine nitrate. In order to take the basic data regarding the reaction of hydrazine nitrate with nitric acid, initiation temperatures and heats of this reaction, effect of impurity on initiation temperature and self-accelerating reaction when it holds at constant temperature for a long time were measured by the pressure vessel type reaction calorimeter etc. In this paper, the experimental data and evaluation of the safe handling of hydrazine nitrate in nuclear fuel reprocessing plants are described. (author)

  18. Development of a seasonal thermochemical storage system

    NARCIS (Netherlands)

    Cuypers, R.; Maraz, N.; Eversdijk, J.; Finck, C.J.; Henquet, E.M.P.; Oversloot, H.P.; Spijker, J.C. van 't; Geus, A.C. de

    2012-01-01

    In our laboratories, a seasonal thermochemical storage system for dwellings and offices is being designed and developed. Based on a thermochemical sorption reaction, space heating, cooling and generation of domestic hot water will be achieved with up to 100% renewable energy, by using solar energy

  19. OECD/NEA thermochemical database

    Energy Technology Data Exchange (ETDEWEB)

    Byeon, Kee Hoh; Song, Dae Yong; Shin, Hyun Kyoo; Park, Seong Won; Ro, Seung Gy

    1998-03-01

    This state of the art report is to introduce the contents of the Chemical Data-Service, OECD/NEA, and the results of survey by OECD/NEA for the thermodynamic and kinetic database currently in use. It is also to summarize the results of Thermochemical Database Projects of OECD/NEA. This report will be a guide book for the researchers easily to get the validate thermodynamic and kinetic data of all substances from the available OECD/NEA database. (author). 75 refs.

  20. Efeito da aplicação de nitrato na redução biogênica de sulfeto sob diferentes concentrações iniciais de bactérias redutoras de nitrato e sulfato Effect of nitrate application on reduction of biogenic sulphide under different initial concentrations of nitrate and sulphate-reducing bacteria

    Directory of Open Access Journals (Sweden)

    Kally Alves de Sousa

    2010-01-01

    Full Text Available The effect of sodium nitrate application in the reduction of biogenic sulphide was evaluated through a 2k complete factorial design, using as variable response the production of sulfide at intervals of incubation of 7, 14 and 28 days. The most effective condition for reducing the sulphide production (final concentrations from 0.4 to 1.6 mg S2- L-1 was obtained with an initial population of sulphate-reducing bacteria and nitrate-reducing bacteria of 10(4 MPN mL-1 and 427.5 mg L-1 nitrate. The results also suggested that the applications of nitrate to control the process of souring should follow a continuous scheme.

  1. Respiration of Nitrate and Nitrite.

    Science.gov (United States)

    Cole, Jeffrey A; Richardson, David J

    2008-09-01

    Nitrate reduction to ammonia via nitrite occurs widely as an anabolic process through which bacteria, archaea, and plants can assimilate nitrate into cellular biomass. Escherichia coli and related enteric bacteria can couple the eight-electron reduction of nitrate to ammonium to growth by coupling the nitrate and nitrite reductases involved to energy-conserving respiratory electron transport systems. In global terms, the respiratory reduction of nitrate to ammonium dominates nitrate and nitrite reduction in many electron-rich environments such as anoxic marine sediments and sulfide-rich thermal vents, the human gastrointestinal tract, and the bodies of warm-blooded animals. This review reviews the regulation and enzymology of this process in E. coli and, where relevant detail is available, also in Salmonella and draws comparisons with and implications for the process in other bacteria where it is pertinent to do so. Fatty acids may be present in high levels in many of the natural environments of E. coli and Salmonella in which oxygen is limited but nitrate is available to support respiration. In E. coli, nitrate reduction in the periplasm involves the products of two seven-gene operons, napFDAGHBC, encoding the periplasmic nitrate reductase, and nrfABCDEFG, encoding the periplasmic nitrite reductase. No bacterium has yet been shown to couple a periplasmic nitrate reductase solely to the cytoplasmic nitrite reductase NirB. The cytoplasmic pathway for nitrate reduction to ammonia is restricted almost exclusively to a few groups of facultative anaerobic bacteria that encounter high concentrations of environmental nitrate.

  2. CFD Studies on Biomass Thermochemical Conversion

    Directory of Open Access Journals (Sweden)

    Lifeng Yan

    2008-06-01

    Full Text Available Thermochemical conversion of biomass offers an efficient and economically process to provide gaseous, liquid and solid fuels and prepare chemicals derived from biomass. Computational fluid dynamic (CFD modeling applications on biomass thermochemical processes help to optimize the design and operation of thermochemical reactors. Recent progression in numerical techniques and computing efficacy has advanced CFD as a widely used approach to provide efficient design solutions in industry. This paper introduces the fundamentals involved in developing a CFD solution. Mathematical equations governing the fluid flow, heat and mass transfer and chemical reactions in thermochemical systems are described and sub-models for individual processes are presented. It provides a review of various applications of CFD in the biomass thermochemical process field.

  3. Biomass Thermochemical Conversion Program: 1986 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

    1987-01-01

    Wood and crop residues constitute a vast majority of the biomass feedstocks available for conversion, and thermochemical processes are well suited for conversion of these materials. Thermochemical conversion processes can generate a variety of products such as gasoline hydrocarbon fuels, natural gas substitutes, or heat energy for electric power generation. The US Department of Energy is sponsoring research on biomass conversion technologies through its Biomass Thermochemical Conversion Program. Pacific Northwest Laboratory has been designated the Technical Field Management Office for the Biomass Thermochemical Conversion Program with overall responsibility for the Program. This report briefly describes the Thermochemical Conversion Program structure and summarizes the activities and major accomplishments during fiscal year 1986. 88 refs., 31 figs., 5 tabs.

  4. Bio-reduction of free and laden perchlorate by the pure and mixed perchlorate reducing bacteria: Considering the pH and coexisting nitrate.

    Science.gov (United States)

    Shang, Yanan; Wang, Ziyang; Xu, Xing; Gao, Baoyu; Ren, Zhongfei

    2018-08-01

    Pure bacteria cell (Azospira sp. KJ) and mixed perchlorate reducing bacteria (MPRB) were employed for decomposing the free perchlorate in water as well as the laden perchlorate on surface of quaternary ammonium wheat residuals (QAWR). Results indicated that perchlorate was decomposed by the Azospira sp. KJ prior to nitrate while MPRB was just the reverse. Bio-reduction of laden perchlorate by Azospira sp. KJ was optimal at pH 8.0. In contrast, bio-reduction of laden perchlorate by MPRB was optimal at pH 7.0. Generally, the rate of perchlorate reduction was controlled by the enzyme activity of PRB. In addition, perchlorate recovery (26.0 mg/g) onto bio-regenerated QAWR by MPRB was observed with a small decrease as compared with that (31.1 mg/g) by Azospira sp. KJ at first 48 h. Basically, this study is expected to offer some different ideas on bio-regeneration of perchlorate-saturated adsorbents using biological process, which may provide the economically alternative to conventional methods. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Static Thermochemical Model of COREX Melter Gasifier

    Science.gov (United States)

    Srishilan, C.; Shukla, Ajay Kumar

    2018-02-01

    COREX is one of the commercial smelting reduction processes. It uses the finer size ore and semi-soft coal instead of metallurgical coke to produce hot metal from iron ore. The use of top gas with high calorific value as a by-product export gas makes the process economical and green. The predictive thermochemical model of the COREX process presented here enables rapid computation of process parameters such as (1) required amount of ore, coal, and flux; (2) amount of slag and gas generated; and (3) gas compositions (based on the raw material and desired hot metal quality). The model helps in predicting the variations in process parameters with respect to the (1) degree of metallization and (2) post-combustion ratio for given raw material conditions. In general reduction in coal, flux, and oxygen, the requirement is concomitant with an increase in the degree of metallization and post-combustion ratio. The model reported here has been benchmarked using industrial data obtained from the JSW Steel Plant, India.

  6. Synthesis of iron nanoparticles with poly(1-vinylpyrrolidone-co-vinyl acetate) and its application to nitrate reduction

    DEFF Research Database (Denmark)

    Lee, Nara; Choi, Kyunghoon; Uthuppu, Basil

    2014-01-01

    This study aimed to synthesize dispersed and reactive nanoscale zero-valent iron (nZVI) with poly(1-vinylpyrrolidone-co-vinyl acetate) (PVP/VA), nontoxic and biodegradable stabilizer. The nZVI used for the experiments was prepared by reduction of ferric solution in the presence of PVP/VA with spe...

  7. Economic gains fromtargeted measures related to non-point pollution in agriculture based on detailed nitrate reduction maps

    DEFF Research Database (Denmark)

    Jacobsen, Brian H.; Hansen, Anne Lausten

    2016-01-01

    From 1990 to 2003, Denmark reduced N-leaching from the root zone by 50%. However, more measures are required, and in recent years, the focus has been on how to differentiate measures in order to ensure that they are implemented where the effect on N-loss reductions per ha is the greatest. The pur...

  8. Experimental study of a thermochemical compressor for an absorption/compression hybrid cycle

    International Nuclear Information System (INIS)

    Ventas, R.; Vereda, C.; Lecuona, A.; Venegas, M.

    2012-01-01

    Highlights: ► Experimental study of a thermochemical compressor for absorption/compression cycle. ► Spray adiabatic absorber using NH 3 –LiNO 3 solution working fluid. ► It is able to operate between 57 and 110 °C varying concentration between 0.46 and 0.59. ► The increase of absorber pressure decreases the circulation ratio. ► The numerical model performed agrees with the experimental results. -- Abstract: An experimental study of a thermochemical compressor with ammonia–lithium nitrate solution as working fluid has been carried out. This compressor incorporates a single-pass adiabatic absorber and all the heat exchangers are of the plate type: absorber subcooler, generator and solution heat exchanger. The thermochemical compressor has been studied as part of a single-effect absorption chiller hybridized with an in-series low-pressure compression booster. The adiabatic absorber uses fog jet injectors. The generator hot water temperatures for the external driving flow are in the range of 57–110 °C and the absorber pressures range between 429 and 945 kPa. Experimental results are compared with a numerical model showing a high agreement. The performance of the thermochemical compressor, evaluated through the circulation ratio, improves for higher absorber pressures, indicating the potential of pressure boosting. For the same circulation ratio, the driving hot water inlet temperature decreases with the rise of the absorber pressure. The thermochemical compressor, based on an adiabatic absorber, can produce refrigerant with very low driving temperatures, between 57 and 70 °C, what is interesting for solar cooling applications and very low temperature residual heat recovery. Efficiencies and cooling power are offered when this hybrid thermochemical compressor is implemented in a chiller, showing the effect of different operating parameters.

  9. Utilization of Common Automotive Three-Way NO{sub x} Reduction Catalyst for Managing Off- Gas from Thermal Treatment of High-Nitrate Waste - 13094

    Energy Technology Data Exchange (ETDEWEB)

    Foster, Adam L.; Ki Song, P.E. [Studsvik, Inc. 5605 Glenridge Drive Suite 705, Atlanta, GA 30342 (United States)

    2013-07-01

    Studsvik's Thermal Organic Reduction (THOR) steam reforming process has been tested and proven to effectively treat radioactive and hazardous wastes streams with high nitrate contents to produce dry, stable mineral products, while providing high conversion (>98%) of nitrates and nitrites directly to nitrogen gas. However, increased NO{sub x} reduction may be desired for some waste streams under certain regulatory frameworks. In order to enhance the NO{sub x} reduction performance of the THOR process, a common Three-Way catalytic NO{sub x} reduction unit was installed in the process gas piping of a recently completed Engineering Scale Technology Demonstration (ESTD). The catalytic DeNO{sub x} unit was located downstream of the main THOR process vessel, and it was designed to catalyze the reduction of residual NO{sub x} to nitrogen gas via the oxidation of the hydrogen, carbon monoxide, and volatile organic compounds that are inherent to the THOR process gas. There was no need for auxiliary injection of a reducing gas, such as ammonia. The unit consisted of four monolith type catalyst sections positioned in series with a gas mixing section located between each catalyst section. The process gas was monitored for NO{sub x} concentration upstream and downstream of the catalytic DeNO{sub x} unit. Conversion efficiencies ranged from 91% to 97% across the catalytic unit, depending on the composition of the inlet gas. Higher concentrations of hydrogen and carbon monoxide in the THOR process gas increased the NO{sub x} reduction capability of the catalytic DeNO{sub x} unit. The NO{sub x} destruction performance of THOR process in combination with the Three-Way catalytic unit resulted in overall system NO{sub x} reduction efficiencies of greater than 99.9% with an average NO{sub x} reduction efficiency of 99.94% for the entire demonstration program. This allowed the NO{sub x} concentration in the ESTD exhaust gas to be maintained at less than 40 parts per million (ppm

  10. Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation and Recycle of Sodium Hydroxide and Sodium Nitrate

    International Nuclear Information System (INIS)

    Moyer, Bruce A.; Marchand, Alan P.; Bonnesen, Peter V.; Bryan, Jeffrey C.; Haverlock, Tamara J.

    2004-01-01

    This research was intended to provide the scientific foundation upon which the feasibility of liquid-liquid extraction chemistry for bulk reduction of the volume of high-activity tank waste can be evaluated. Primary focus has been on sodium hydroxide separation, with potential Hanford application. Value in sodium hydroxide separation can potentially be found in alternative flowsheets for treatment and disposal of low-activity salt waste. Additional value can be expected in recycle of sodium hydroxide for use in waste retrieval and sludge washing, whereupon additions of fresh sodium hydroxide to the waste can be avoided. Potential savings are large both because of the huge cost of vitrification of the low-activity waste stream and because volume reduction of high-activity wastes could obviate construction of costly new tanks. Toward these ends, the conceptual development begun in the original proposal was extended with the formulation of eight fundamental approaches that could be undertaken for extraction of sodium hydroxide

  11. Biomass thermochemical conversion program: 1987 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

    1988-01-01

    The objective of the Biomass Thermochemical Conversion Program is to generate a base of scientific data and conversion process information that will lead to establishment of cost-effective processes for conversion of biomass resources into clean fuels. To accomplish this objective, in fiscal year 1987 the Thermochemical Conversion Program sponsored research activities in the following four areas: Liquid Hydrocarbon Fuels Technology; Gasification Technology; Direct Combustion Technology; Program Support Activities. In this report an overview of the Thermochemical Conversion Program is presented. Specific research projects are then described. Major accomplishments for 1987 are summarized.

  12. Biomass thermochemical conversion program. 1985 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

    1986-01-01

    Wood and crop residues constitute a vast majority of the biomass feedstocks available for conversion, and thermochemical processes are well suited for conversion of these materials. The US Department of Energy (DOE) is sponsoring research on this conversion technology for renewable energy through its Biomass Thermochemical Conversion Program. The Program is part of DOE's Biofuels and Municipal Waste Technology Division, Office of Renewable Technologies. This report briefly describes the Thermochemical Conversion Program structure and summarizes the activities and major accomplishments during fiscal year 1985. 32 figs., 4 tabs.

  13. Thermochemical evaluation and preparation of cesium uranates

    International Nuclear Information System (INIS)

    Takano, Masahide; Minato, Kazuo; Fukuda, Kousaku; Sato, Seichi; Ohashi, Hiroshi.

    1997-03-01

    Two kinds of cesium uranates, Cs 2 UO 4 and Cs 2 U 2 O 7 , which are predicted by thermochemical estimation to be formed in irradiated oxide fuels, were prepared from U 3 O 8 and Cs 2 CO 3 for measurements of the thermal expansions and thermal conductivities. In advance of the preparation, thermochemical calculations for the formation and decomposition of these cesium uranates were performed by Gibbs free energy minimizer. The preparation temperatures for Cs 2 UO 4 and Cs 2 U 2 O 7 were determined from the results of the thermochemical calculations. The prepared samples were analyzed by X-ray diffraction, which showed that the single phases of Cs 2 UO 4 and Cs 2 U 2 O 7 were formed. Thermogravimetry and differential thermal analysis were also performed on these samples, and the decomposition temperatures were evaluated. The experimental results were in good agreement with those of the thermochemical calculations. (author)

  14. Simulation of nitrate reduction in groundwater - An upscaling approach from small catchments to the Baltic Sea basin

    Science.gov (United States)

    Hansen, A. L.; Donnelly, C.; Refsgaard, J. C.; Karlsson, I. B.

    2018-01-01

    This paper describes a modeling approach proposed to simulate the impact of local-scale, spatially targeted N-mitigation measures for the Baltic Sea Basin. Spatially targeted N-regulations aim at exploiting the considerable spatial differences in the natural N-reduction taking place in groundwater and surface water. While such measures can be simulated using local-scale physically-based catchment models, use of such detailed models for the 1.8 million km2 Baltic Sea basin is not feasible due to constraints on input data and computing power. Large-scale models that are able to simulate the Baltic Sea basin, on the other hand, do not have adequate spatial resolution to simulate some of the field-scale measures. Our methodology combines knowledge and results from two local-scale physically-based MIKE SHE catchment models, the large-scale and more conceptual E-HYPE model, and auxiliary data in order to enable E-HYPE to simulate how spatially targeted regulation of agricultural practices may affect N-loads to the Baltic Sea. We conclude that the use of E-HYPE with this upscaling methodology enables the simulation of the impact on N-loads of applying a spatially targeted regulation at the Baltic Sea basin scale to the correct order-of-magnitude. The E-HYPE model together with the upscaling methodology therefore provides a sound basis for large-scale policy analysis; however, we do not expect it to be sufficiently accurate to be useful for the detailed design of local-scale measures.

  15. Using environmental tracers to determine the relative importance of travel times in the unsaturated and saturated zones for the delay of nitrate reduction measures

    Science.gov (United States)

    Gerber, Christoph; Purtschert, Roland; Hunkeler, Daniel; Hug, Rainer; Sültenfuss, Jürgen

    2018-06-01

    Groundwater quality in many regions with intense agriculture has deteriorated due to the leaching of nitrate and other agricultural pollutants. Modified agricultural practices can reduce the input of nitrate to groundwater bodies, but it is crucial to determine the time span over which these measures become effective at reducing nitrate levels in pumping wells. Such estimates can be obtained from hydrogeological modeling or lumped-parameter models (LPM) in combination with environmental tracer data. Two challenges in such tracer-based estimates are (i) accounting for the different modes of transport in the unsaturated zone (USZ), and (ii) assessing uncertainties. Here we extend a recently published Bayesian inference scheme for simple LPMs to include an explicit USZ model and apply it to the Dünnerngäu aquifer, Switzerland. Compared to a previous estimate of travel times in the aquifer based on a 2D hydrogeological model, our approach provides a more accurate assessment of the dynamics of nitrate concentrations in the aquifer. We find that including tracer measurements (3H/3He, 85Kr, 39Ar, 4He) reduces uncertainty in nitrate predictions if nitrate time series at wells are not available or short, but does not necessarily lead to better predictions if long nitrate time series are available. Additionally, the combination of tracer data with nitrate time series allows for a separation of the travel times in the unsaturated and saturated zone.

  16. Communication: The electronic entropy of charged defect formation and its impact on thermochemical redox cycles

    Science.gov (United States)

    Lany, Stephan

    2018-02-01

    The ideal material for solar thermochemical water splitting, which has yet to be discovered, must satisfy stringent conditions for the free energy of reduction, including, in particular, a sufficiently large positive contribution from the solid-state entropy. By inverting the commonly used relationship between defect formation energy and defect concentration, it is shown here that charged defect formation causes a large electronic entropy contribution manifesting itself as the temperature dependence of the Fermi level. This result is a general feature of charged defect formation and motivates new materials design principles for solar thermochemical hydrogen production.

  17. Evaluation of nitrate destruction methods

    International Nuclear Information System (INIS)

    Taylor, P.A.; Kurath, D.E.; Guenther, R.

    1993-01-01

    A wide variety of high nitrate-concentration aqueous mixed [radioactive and Resource Conservation and Recovery Act (RCRA) hazardous] wastes are stored at various US Department of Energy (DOE) facilities. These wastes will ultimately be solidified for final disposal, although the waste acceptance criteria for the final waste form is still being determined. Because the nitrates in the wastes will normally increase the volume or reduce the integrity of all of the waste forms under consideration for final disposal, nitrate destruction before solidification of the waste will generally be beneficial. This report describes and evaluates various technologies that could be used to destroy the nitrates in the stored wastes. This work was funded by the Department of Energy's Office of Technology Development, through the Chemical/Physical Technology Support Group of the Mixed Waste Integrated Program. All the nitrate destruction technologies will require further development work before a facility could be designed and built to treat the majority of the stored wastes. Several of the technologies have particularly attractive features: the nitrate to ammonia and ceramic (NAC) process produces an insoluble waste form with a significant volume reduction, electrochemical reduction destroys nitrates without any chemical addition, and the hydrothermal process can simultaneously treat nitrates and organics in both acidic and alkaline wastes. These three technologies have been tested using lab-scale equipment and surrogate solutions. At their current state of development, it is not possible to predict which process will be the most beneficial for a particular waste stream

  18. Thermochemical transformations of anthracene oil

    Energy Technology Data Exchange (ETDEWEB)

    Belkina, T.V.; Privalov, V.E.; Stepanenko, M.A.

    1979-01-01

    The basic technological step in electrode pitch production is the thermal processing of the original pitch, combined in some cases with air treatment. The thermal process of electrode pitch production is outstandingly simple and economical, but offers little scope for regulating the product quality. When the coal tar regulating the product quality has been highly pyrolyzed, it becomes difficult to produce a medium electrode pitch in conformity with GOST 10200-73 as regards its content of substances insoluble in quinoline (..cap alpha../sub 1/-fraction). It is particularly difficult to make ptich with a softening point of 85 to 90/sup 0/C from highly pyrolyzed coal tar, since this involves a prolonged treatment which increases the ..cap alpha../sub 1/-fraction content. These difficulties, associated with persistent consumer demand for higher electrode pitch quality, have greatly activated the search for new methods of making electrode pitch. A survey of the Soviet and foreign literature shows that the investigations now in progress relate both to methods of developing new production techniques and to methods of adjusting the initial feedstock composition by the addition of high-boiling coal-tar fractions, pitch distillates, highly aromatized petroleum refinery products and so on. As a result of experiments it was found that: (1) When anthracene oil is heated, its contents of condensation products (..cap alpha../sub 1/- and ..cap alpha..-fractions) increase quite slowly compared with pitch; consequently the electrode pitch production process is prolonged by mixing the two feedstock materials. (2) When the anthracene oil is heat treated first, condensation products form and accumulate in it and its thermochemical transformation activity is enhanced. (3) The use of heat-treated anthracene oil will clearly intensify the electrode pitch production process and raise the product quality.

  19. Nitrate glass

    International Nuclear Information System (INIS)

    Kirilenko, I.A.; Vinogradov, E.E.

    1977-01-01

    Experimental evidence on behaviour of nitrate glasses is reviewed in terms of relationships between the presence of water in vitrescent nitrate systems and the properties of the systems. The glasses considered belong to systems of Mg(NO 3 ) 2 - Nd(NO 3 ) 3 ; Hg(NO 3 ) 2 -Nd(NO 3 ) 3 ; NaNO 3 -Mg(NO 3 ) 2 -Nd(NO 3 ) 3 ; M-Zn(NO 3 ) 3 , where M is a mixture of 20% mass NaNO 3 and 80% mass Mg(NO 3 ) 2 , and Zn is a rare earth ion. Nitrate glass is shown to be a product of dehydration. Vitrification may be regarded as a resusl of formation of molecular complexes in the chain due to hydrogen bonds of two types, i.e. water-water, or water-nicrate group. Chain formation, along with low melting points of the nitrates, hinder crystallization of nitrate melts. Provided there is enough water, this results in vitrification

  20. Preparation and thermochemical stability of uranium-zirconium-carbonitrides

    International Nuclear Information System (INIS)

    Kouhsen, C.

    1975-08-01

    This investigation deals with the preparation and the thermochemical stability of uranium-zirconium-carbonitrides as well as with the mechanism of (U,Zr) (C,N)-preparation by carbothermic reduction of uranium-zirconium-oxide. Single-phase (U,Zr) (C,N)-solid solutions with U:Zr-propertions of 3:1, 1:1, and 1:3 were prepared from oxide powder. The thermochemical stability of the (U,Zr) (C,N)-solid solutions against carbon was measured for varying Zr- and N-contents and for several temperatures; the results indicate an increase of the uranium carbide stability potential by the formation of (U,Zr) (C,N)-solid solutions. The thermodynamic properties ΔG 0 , ΔH 0 , and ΔS 0 were calculated and the correlation between the M(C,N)-lattice constant and the N-content was evaluated. Through an intensive investigation of the reaction mechanism, several different reaction paths were found; for each of them the characteristical diffusion of matter was explained by means of the microsections. It was shown that the Zr-concentration of the oxide reactant and the heating rate during the carbothermic reduction influence the species of the reaction product, especially the homogeneity of the (U,Zr) (C,N)-solid solution. (orig.) [de

  1. Nitrate reduction, nitrous oxide formation, and anaerobic ammonia oxidation to nitrite in the gut of soil-feeding termites (Cubitermes and Ophiotermes spp.)

    KAUST Repository

    Ngugi, David; Brune, Andreas

    2011-01-01

    Soil-feeding termites play important roles in the dynamics of carbon and nitrogen in tropical soils. Through the mineralization of nitrogenous humus components, their intestinal tracts accumulate enormous amounts of ammonia, and nitrate and nitrite

  2. The relative abundance of predicted genes associated with ammonia-oxidation, nitrate reduction, and biomass decomposition in mineral soil are altered by intensive timber harvest.

    Science.gov (United States)

    Mushinski, R. M.; Zhou, Y.; Gentry, T. J.; Boutton, T. W.

    2017-12-01

    Forest ecosystems in the southern United States are substantially altered by anthropogenic disturbances such as timber harvest and land conversion, with effects being observed in carbon and nutrient pools as well as biogeochemical processes. Furthermore, the desire to develop renewable energy sources in the form of biomass extraction from logging residues may result in alterations in soil community structure and function. While the impact of forest management on soil physicochemical properties of the region has been studied, its' long-term effect on soil bacterial community composition and metagenomic potential is relatively unknown, especially at deeper soil depths. This study investigates how intensive organic matter removal intensities associated with timber harvest influence decadal-scale alterations in bacterial community structure and functional potential in the upper 1-m of the soil profile, 18 years post-harvest in a Pinus taeda L. forest of eastern Texas. Amplicon sequencing of the 16S rRNA gene was used in conjunction with soil chemical analyses to evaluate treatment-induced differences in community composition and potential environmental drivers of associated change. Furthermore, functional potential was assessed by using amplicon data to make metagenomic predictions. Results indicate that increasing organic matter removal intensity leads to altered community composition and the relative abundance of dominant OTUs annotated to Burkholderia and Aciditerrimonas. The relative abundance of predicted genes associated with dissimilatory nitrate reduction and denitrification were highest in the most intensively harvested treatment while genes involved in nitrification were significantly lower in the most intensively harvested treatment. Furthermore, genes associated with glycosyltransferases were significantly reduced with increasing harvest intensity while polysaccharide lyases increased. These results imply that intensive organic matter removal may create

  3. Vadose zone processes delay groundwater nitrate reduction response to BMP implementation as observed in paired cultivated vs. uncultivated potato rotation fields

    Science.gov (United States)

    Jiang, Y.; Nyiraneza, J.; Murray, B. J.; Chapman, S.; Malenica, A.; Parker, B.

    2017-12-01

    Nitrate leaching from crop production contributes to groundwater contamination and subsequent eutrophication of the receiving surface water. A study was conducted in a 7-ha potato-grain-forages rotation field in Prince Edward Island (PEI), Canada during 2011-2016 to link potato rotation practices and groundwater quality. The field consists of fine sandy loam soil and is underlain by 7-9 m of glacial till, which overlies the regional fractured ;red-bed; sandstone aquifer. The water table is generally located in overburden close to the bedrock interface. Field treatments included one field zone taken out of production in 2011 with the remaining zones kept under a conventional potato rotation. Agronomy data including crop tissue, soil, and tile-drain water quality were collected. Hydrogeology data including multilevel monitoring of groundwater nitrate and hydraulic head and data from rock coring for nitrate distribution in overburden and bedrock matrix were also collected. A significant amount of nitrate leached below the soil profile after potato plant kill (referred to as topkill) in 2011, most of it from fertilizer N. A high level of nitrate was also detected in the till vadose zone through coring in December 2012 and through multilevel groundwater sampling from January to May 2014 in both cultivated and uncultivated field zones. Groundwater nitrate concentrations increased for about 2.5 years after the overlying potato field was removed from production. Pressure-driven uniform flow processes dominate water and nitrate transport in the vadose zone, producing an apparently instant water table response but a delayed groundwater quality response to nitrate leaching events. These data suggest that the uniform flow dominated vadose zone in agricultural landscapes can cause the accumulation of a significant amount of nitrate originated from previous farming activities, and the long travel time of this legacy nitrate in the vadose zone can result in substantially delayed

  4. Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles

    International Nuclear Information System (INIS)

    Fernandez Saavedra, R.

    2007-01-01

    This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs

  5. Thermochemical treatment of radioactive waste by using powder metal fuels

    International Nuclear Information System (INIS)

    Dmitriev, S.A.; Ojovan, M.I.; Karlina, O.K.

    2001-01-01

    waste with necessary amount of PMF, ignition of self-sustaining vitrification reaction followed by annealing-cooling procedure. This technology was studied for a number of materials such as ash residue produced by conventional incineration facilities, spent inorganic sorbents, contaminated soils, salt residues after liquid waste drying. The carry over of radionuclides during the wave-like vitrification process is low: even for most volatile species it is below 1%. This process was tested on bench scale unit for the vitrification of ash residues volume reduction factors up to 3 being achieved. Usually up to 60 wt.% of dusty waste can be incorporated into a glass like material, which has high durability and low leaching rate. (4). Irradiated graphite contains besides long-lived carbon isotope 14 C nuclear fuel impurities as well as irradiated corrosion and fission products. The thermochemical graphite processing is based on the self-sustaining exothermic reactions. Thermal and chemically stable carbides of some metals resulting from these reactions provide practically complete retention of carbon in the final matrix form. Simultaneously other radionuclides are incorporated into mineral-like components ensuring their long-term retention in the matrix. An experimental bench-scale verification of thermodynamic simulation was conducted using radioactive waste simulator (reactor graphite). The end monolithic product specimens were obtained in the form of a carbide-corundum material of volume 500 cm 3 each. This technique will be used to process the waste powder graphite from the decommissioning of graphite reactors. The thermochemical treatment of waste is an efficient and safe technology, which can be used at both large and small scales. It provides qualitative treatment and conditioning of waste with minimal impact to environment. (author)

  6. Thermochemical evaluation and preparation of cesium uranates

    Energy Technology Data Exchange (ETDEWEB)

    Takano, Masahide; Minato, Kazuo; Fukuda, Kousaku [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Sato, Seichi; Ohashi, Hiroshi

    1997-03-01

    Two kinds of cesium uranates, Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7}, which are predicted by thermochemical estimation to be formed in irradiated oxide fuels, were prepared from U{sub 3}O{sub 8} and Cs{sub 2}CO{sub 3} for measurements of the thermal expansions and thermal conductivities. In advance of the preparation, thermochemical calculations for the formation and decomposition of these cesium uranates were performed by Gibbs free energy minimizer. The preparation temperatures for Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7} were determined from the results of the thermochemical calculations. The prepared samples were analyzed by X-ray diffraction, which showed that the single phases of Cs{sub 2}UO{sub 4} and Cs{sub 2}U{sub 2}O{sub 7} were formed. Thermogravimetry and differential thermal analysis were also performed on these samples, and the decomposition temperatures were evaluated. The experimental results were in good agreement with those of the thermochemical calculations. (author)

  7. 2009 Thermochemical Conversion Platform Review Report

    Energy Technology Data Exchange (ETDEWEB)

    Ferrell, John [Office of Energy Efficiency and Renewable Energy (EERE), Washington, DC (United States)

    2009-12-01

    This document summarizes the recommendations and evaluations provided by an independent external panel of experts at the U.S. Department of Energy Biomass Program’s Thermochemical Conversion platform review meeting, held on April 14-16, 2009, at the Sheraton Denver Downtown, Denver, Colorado.

  8. Ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium in two US Great Basin hot springs with abundant ammonia-oxidizing archaea.

    Science.gov (United States)

    Dodsworth, Jeremy A; Hungate, Bruce A; Hedlund, Brian P

    2011-08-01

    Many thermophiles catalyse free energy-yielding redox reactions involving nitrogenous compounds; however, little is known about these processes in natural thermal environments. Rates of ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in source water and sediments of two ≈ 80°C springs in the US Great Basin. Ammonia oxidation and denitrification occurred mainly in sediments. Ammonia oxidation rates measured using (15)N-NO(3)(-) pool dilution ranged from 5.5 ± 0.8 to 8.6 ± 0.9 nmol N g(-1) h(-1) and were unaffected or only mildly stimulated by amendment with NH(4) Cl. Denitrification rates measured using acetylene block ranged from 15.8 ± 0.7 to 51 ± 12 nmol N g(-1) h(-1) and were stimulated by amendment with NO(3)(-) and complex organic compounds. The DNRA rate in one spring sediment measured using an (15)N-NO(3)(-) tracer was 315 ± 48 nmol N g(-1) h(-1). Both springs harboured distinct planktonic and sediment microbial communities. Close relatives of the autotrophic, ammonia-oxidizing archaeon 'Candidatus Nitrosocaldus yellowstonii' represented the most abundant OTU in both spring sediments by 16S rRNA gene pyrotag analysis. Quantitative PCR (qPCR) indicated that 'Ca. N. yellowstonii'amoA and 16S rRNA genes were present at 3.5-3.9 × 10(8) and 6.4-9.0 × 10(8) copies g(-1) sediment. Potential denitrifiers included members of the Aquificales and Thermales. Thermus spp. comprised <1% of 16S rRNA gene pyrotags in both sediments and qPCR for T. thermophilus narG revealed sediment populations of 1.3-1.7 × 10(6) copies g(-1) sediment. These data indicate a highly active nitrogen cycle (N-cycle) in these springs and suggest that ammonia oxidation may be a major source of energy fuelling primary production. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  9. Ammonium nitrate-potassium nitrate system

    Energy Technology Data Exchange (ETDEWEB)

    Cady, H.H.

    1981-01-01

    A portion of the binary phase diagram for the system ammonium nitrate-potassium nitrate has been determined from -55/sup 0/C to 185/sup 0/C. Results are presented for the ammonium-nitrate-rich end of the system up to 30 wt% potassium nitrate.

  10. Oxygen regulation of nitrate uptake in denitrifying Pseudomonas aeruginosa.

    OpenAIRE

    Hernandez, D; Rowe, J J

    1987-01-01

    Oxygen had an immediate and reversible inhibitory effect on nitrate respiration by denitrifying cultures of Pseudomonas aeruginosa. Inhibition of nitrate utilization by oxygen appeared to be at the level of nitrate uptake, since nitrate reduction to nitrite in cell extracts was not affected by oxygen. The degree of oxygen inhibition was dependent on the concentration of oxygen, and increasing nitrate concentrations could not overcome the inhibition. The inhibitory effect of oxygen was maximal...

  11. Temporal and spatial variations in groundwater quality resulting from policy-induced reductions in nitrate leaching to the Rabis Creek aquifer, Denmark

    Science.gov (United States)

    Jessen, Søren; Engesgaard, Peter; Thorling, Lærke; Müller, Sascha; Leskelä, Jari; Postma, Dieke

    2016-04-01

    Twenty-five years of annual groundwater quality monitoring data from the sandy unconfined Rabis Creek aquifer were used to assess the effects of political actions aimed to reduce nitrate leaching to the aquifer. Data were collected from eight multilevel samplers along a ˜3 km transect, which follows the general direction of groundwater flow. Each multilevel sampler comprises 20 screens placed with a 1 m vertical distance from near the water table downwards. The transect covers areas of livestock, plantation & heath, and agriculture. The history of nitrate leaching to the aquifer was assessed using data from screens close to the water table of multilevel samplers placed within agricultural areas. According to these data, nitrate concentrations of infiltrating 'agricultural' water peaked at 2-3 mM (120-180 mg/L) in the year 1989, and then gradually decreased and stabilized at 0.25-1.0 mM (15-60 mg/L) from year 2000. Local farmers declare having used the maximum fertilization rate allowed during the period. The timing of the observed decrease therefore suggests a direct link to the political action plans implemented in the same period. Parallel to the development in nitrate leaching, although with a transport time lag, the average concentration of nitrate in the oxic zone of the aquifer was roughly halved between 2000 and 2013. As a response to political initiatives of the late 1980'ies, part of the area covering the aquifer was changed from agriculture to non-fertilized grass for livestock; the data shows that this effectively remediated the aquifer underneath in less than 20 years, to become nitrate-free and attain background sulfate levels. The oxidized and pyritic reduced zone of the aquifer is separated by a <1 m redoxcline. Denitrification by the pyrite releases sulfate that is retained down-gradient as a tracer for historical nitrate loading to the aquifer. Thus sulfate concentrations currently increase in the multilevel samplers positioned furthest down

  12. Positronium hydride defects in thermochemically reduced alkaline-Earth oxides

    International Nuclear Information System (INIS)

    Monge, M.A.; Pareja, R.; Gonzalez, R.; Chen, Y.

    1997-01-01

    Thermochemical reduction of both hydrogen-doped MgO and CaO single crystals results in large concentrations of hydride (H - ) ions. In MgO crystals, positron lifetime and Doppler broadening experiments show that positrons are trapped at H - centers forming positronium hydride molecules [e + - H - ]. A value of 640 ps is obtained for the lifetime of the PsH states located in an anion vacancy In MgO positrons are also trapped at H 2- sites at low temperatures. The H 2- ions were induced in the crystals by blue light illumination. The formation of PsH states in CaO could not be conclusively established. (orig.)

  13. Aminoethyl nitrate – the novel super nitrate?

    Science.gov (United States)

    Bauersachs, Johann

    2009-01-01

    Long-term use of most organic nitrates is limited by development of tolerance, induction of oxidative stress and endothelial dysfunction. In this issue of the BJP, Schuhmacher et al. characterized a novel class of organic nitrates with amino moieties (aminoalkyl nitrates). Aminoethyl nitrate was identified as a novel organic mononitrate with high potency but devoid of induction of mitochondrial oxidative stress. Cross-tolerance to nitroglycerin or the endothelium-dependent agonist acetylcholine after in vivo treatment was not observed. Like all nitrates, aminoethyl nitrate induced vasorelaxation by activation of soluble guanylate cyclase. Thus, in contrast to the prevailing view, high potency in an organic nitrate is not necessarily accompanied by induction of oxidative stress or endothelial dysfunction. This work from Daiber's group is an important step forward in the understanding of nitrate bioactivation, tolerance phenomena and towards the development of better organic nitrates for clinical use. PMID:19732062

  14. Thermochemical Surface Engineering: A Playground for Science and Innovation

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Jellesen, Morten Stendahl

    2017-01-01

    Surface engineering by thermochemical processing is the intentional change of the composition of a material at elevated temperature with the purpose to improve materials performance. In thermochemical processing components from the starting material are essential in the development of the phases...... at the surface. Current research and innovation activities are used to exemplify thermochemical surface engineering and the interplay of science and innovation. The examples given encompass aspects of the synthesis of extremely porous materials, low temperature surface hardening of stainless steel, surface...

  15. Impact of Sulfide on Nitrate Conversion in Eutrophic Nitrate-Rich Marine Sludge

    DEFF Research Database (Denmark)

    Schwermer, Carsten U.; Krieger, Bärbel; Lavik, Gaute

    2006-01-01

    IMPACT OF SULFIDE ON NITRATE CONVERSION IN EUTROPHIC NITRATE-RICH MARINE SLUDGE C.U. Schwermer 1, B.U. Krieger 2, G. Lavik 1, A. Schramm 3, J. van Rijn 4, D. de Beer 1, D. Minz 5, E. Cytryn 4, M. Kuypers 1, A. Gieseke 1 1 Max Planck Institute for Marine Microbiology, Bremen, Germany; 2 Dept...... nitrate conversion from denitrification to dissimilatory nitrate-reduction to ammonium (DNRA). In situ microsensor profiling in stagnant sludge revealed the typical stratification of nitrate reduction on top of sulfate reduction. Increasing the bulk nitrate concentration lead to a downward shift....... Our results show that the presence of sulfide generally decreased growth rates but increased N2O production. We conclude that sulfide plays a key role in causing incomplete denitrification, presumably by inhibiting the N2O reductase, and enhancing DNRA compared to denitrification.  ...

  16. Nitrate removal from alkaline high nitrate effluent by in situ generation of hydrogen using zinc dust

    International Nuclear Information System (INIS)

    Rajagopal, S.; Chitra, S.; Paul, Biplob

    2016-01-01

    Alkaline radioactive low level waste generated in Nuclear Fuel Cycle contains substantial amount of nitrate and needs to be treated to meet Central Pollution Control Board discharge limits of 90 mg/L in marine coastal area. Several denitrification methods like chemical treatment, electrochemical reduction, biological denitrification, ion exchange, reverse osmosis, photochemical reduction etc are followed for removal of nitrate. In effluent treatment plants where chemical treatment is carried out, chemical denitrification can be easily adapted without any additional set up. Reducing agents like zinc and aluminum are suitable for reducing nitrate in alkaline solution. Study on denitrification with zinc dust was taken up in this work. Not much work has been done with zinc dust on reduction of nitrate to nitrogen in alkaline waste with high nitrate content. In the present work, nitrate is reduced by nascent hydrogen generated in situ, caused by reaction between zinc dust and sodium hydroxide

  17. Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage.

    Science.gov (United States)

    Carrillo, A J; Sastre, D; Serrano, D P; Pizarro, P; Coronado, J M

    2016-03-21

    The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

  18. Solar Thermochemical Hydrogen Production via Terbium Oxide Based Redox Reactions

    Directory of Open Access Journals (Sweden)

    Rahul Bhosale

    2016-01-01

    Full Text Available The computational thermodynamic modeling of the terbium oxide based two-step solar thermochemical water splitting (Tb-WS cycle is reported. The 1st step of the Tb-WS cycle involves thermal reduction of TbO2 into Tb and O2, whereas the 2nd step corresponds to the production of H2 through Tb oxidation by water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined via HSC simulations. Influence of oxygen partial pressure in the inert gas on thermal reduction of TbO2 and effect of water splitting temperature (TL on Gibbs free energy related to the H2 production step were examined in detail. The cycle (ηcycle and solar-to-fuel energy conversion (ηsolar-to-fuel efficiency of the Tb-WS cycle were determined by performing the second-law thermodynamic analysis. Results obtained indicate that ηcycle and ηsolar-to-fuel increase with the decrease in oxygen partial pressure in the inert flushing gas and thermal reduction temperature (TH. It was also realized that the recuperation of the heat released by the water splitting reactor and quench unit further enhances the solar reactor efficiency. At TH=2280 K, by applying 60% heat recuperation, maximum ηcycle of 39.0% and ηsolar-to-fuel of 47.1% for the Tb-WS cycle can be attained.

  19. Vasodilator Therapy: Nitrates and Nicorandil.

    Science.gov (United States)

    Tarkin, Jason M; Kaski, Juan Carlos

    2016-08-01

    Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

  20. Microencapsulation of salts for enhanced thermochemical storage materials

    NARCIS (Netherlands)

    Cuypers, R.; Jong, A.J. de; Eversdijk, J.; Spijker, J.C. van 't; Oversloot, H.P.; Ingenhut, B.L.J.; Cremers, R.K.H.; Papen-Botterhuis, N.E.

    2013-01-01

    Thermochemical storage is a new and emerging long-term thermal storage for residential use (cooling, heating & domestic hot water generation), offering high thermal storage density without the need for thermal insulation during storage (Fig. 1). However, existing materials for thermochemical storage

  1. Thermochemical investigation of lithium-vanadium bronzes

    International Nuclear Information System (INIS)

    Filippova, S.E.; Kesler, Ya.A.; Tret'yakov, Yu.D.; Gordeev, I.V.

    1979-01-01

    A thermochemical investigation was carried out of lithium-vanadium bronzes. The enthalpies of solution and the standard enthalpies of formation of the bronzes β-Lisub(x)Vsub(2)Osub(5) were determined. Investigated was the dependence of the enthalpy of mixing bronzes on the composition; a linear character of the dependence evidences of negligibly small, as compared to the experimental error, energy variations of the matrix V 2 O 5 on introduction of lithium. The variation was calculated of the partial molar enthalpy of lithium in the formation of β-Lisub(x)Vsub(2)Osub(5)

  2. Solar thermochemical processing system and method

    Science.gov (United States)

    Wegeng, Robert S.; Humble, Paul H.; Krishnan, Shankar; Leith, Steven D.; Palo, Daniel R.; Dagle, Robert A.

    2018-04-24

    A solar thermochemical processing system is disclosed. The system includes a first unit operation for receiving concentrated solar energy. Heat from the solar energy is used to drive the first unit operation. The first unit operation also receives a first set of reactants and produces a first set of products. A second unit operation receives the first set of products from the first unit operation and produces a second set of products. A third unit operation receives heat from the second unit operation to produce a portion of the first set of reactants.

  3. Screening analysis of solar thermochemical hydrogen concepts.

    Energy Technology Data Exchange (ETDEWEB)

    Diver, Richard B., Jr.; Kolb, Gregory J.

    2008-03-01

    A screening analysis was performed to identify concentrating solar power (CSP) concepts that produce hydrogen with the highest efficiency. Several CSP concepts were identified that have the potential to be much more efficient than today's low-temperature electrolysis technology. They combine a central receiver or dish with either a thermochemical cycle or high-temperature electrolyzer that operate at temperatures >600 C. The solar-to-hydrogen efficiencies of the best central receiver concepts exceed 20%, significantly better than the 14% value predicted for low-temperature electrolysis.

  4. Solar hydrogen project - Thermochemical process design

    Energy Technology Data Exchange (ETDEWEB)

    Allen, D.J.; Ng, L.F.; Rao, M.S.M.; Wu, S.F.; Zoschak, R.J.

    1984-08-01

    The thermochemical decomposition of water using solar energy offers an elegant way of combining solar and chemical technologies to produce a high quality fuel. The DOE has sponsored Foster Wheeler to develop a process design for a solar water-splitting process based on the sulfuric acid/iodine cycle. The study has centered around the design of a sulfuric acid decomposition reactor and the central receiver. Materials' properties impose severe constraints upon the design of decomposition reactor. In this paper, the constraints imposed on the design are specified and a reactor and receiver design is presented together with a preliminary design of the balance of plant.

  5. Haemolytic activity of uranium compounds haemolysis by thermochemical derivatives of ammonium uranate

    International Nuclear Information System (INIS)

    Stuart, W.I.; Tucker, A.D.; Adams, R.B.

    1975-01-01

    A study has been made of the haemolytic action on human erythrocytes by ammonium uranate (AU) and various thermochemical products of AU. These products were obtained by heating AU in hydrogen at 5 0 C min -1 to various temperatures. Haemolysis has been interpreted in terms of a diffusion model which for each product yields a single parameter Ksub(N), the haemolytic activity factor. The magnitude of Ksub(N) is a convenient measure of the ability of a powder to damage erythrocytes. The haemolytic activity of certain thermochemical derivatives indicates an exceptionally high potential for damage to erythrocytes. Infrared and thermoanalytical measurements have shown that the high activity of these products derives principally from a self-reduction reaction, induced by heating AU to 400-420 0 C in hydrogen. (author)

  6. The outer membrane protein Omp35 affects the reduction of Fe(III, nitrate, and fumarate by Shewanella oneidensis MR-1

    Directory of Open Access Journals (Sweden)

    Myers Charles R

    2004-06-01

    Full Text Available Abstract Background Shewanella oneidensis MR-1 uses several electron acceptors to support anaerobic respiration including insoluble species such as iron(III and manganese(IV oxides, and soluble species such as nitrate, fumarate, dimethylsulfoxide and many others. MR-1 has complex branched electron transport chains that include components in the cytoplasmic membrane, periplasm, and outer membrane (OM. Previous studies have implicated a role for anaerobically upregulated OM electron transport components in the use of insoluble electron acceptors, and have suggested that other OM components may also contribute to insoluble electron acceptor use. In this study, the role for an anaerobically upregulated 35-kDa OM protein (Omp35 in the use of anaerobic electron acceptors was explored. Results Omp35 was purified from the OM of anaerobically grown cells, the gene encoding Omp35 was identified, and an omp35 null mutant (OMP35-1 was isolated and characterized. Although OMP35-1 grew on all electron acceptors tested, a significant lag was seen when grown on fumarate, nitrate, and Fe(III. Complementation studies confirmed that the phenotype of OMP35-1 was due to the loss of Omp35. Despite its requirement for wild-type rates of electron acceptor use, analysis of Omp35 protein and predicted sequence did not identify any electron transport moieties or predicted motifs. OMP35-1 had normal levels and distribution of known electron transport components including quinones, cytochromes, and fumarate reductase. Omp35 is related to putative porins from MR-1 and S. frigidimarina as well as to the PorA porin from Neisseria meningitidis. Subcellular fraction analysis confirmed that Omp35 is an OM protein. The seven-fold anaerobic upregulation of Omp35 is mediated post-transcriptionally. Conclusion Omp35 is a putative porin in the OM of MR-1 that is markedly upregulated anaerobically by a post-transcriptional mechanism. Omp35 is required for normal rates of growth on Fe

  7. Nitrate ammonification in mangrove soils: A hidden source of nitrite?

    NARCIS (Netherlands)

    Balk, M.; Laverman, A.M.; Keuskamp, J.A.; Laanbroek, H.J.

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought

  8. Nitrates of rare earths

    International Nuclear Information System (INIS)

    Komissarova, L.N.; Pushkina, L.Ya.

    1984-01-01

    The systematization of experimental data with account of the last achievements in the field of studying the RE nitrate properties is realized. The methods of production, solubility in aqueous solutions structure, thermodynamic characteristics and thermal stability of nitrate hydrates, RE anhydrous and basic nitrates are considered. The data on RE nirtrate complexing in aqueous solutions are given. Binary nitrates, nitrate solvates and RE nitrate adducts with organic compounds are described. The use of RE nitrates in the course of RE production, in the processes of separation and fine cleaning of RE preparations is considered

  9. TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

    Energy Technology Data Exchange (ETDEWEB)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver, E-mail: jasmina@physics.ucf.edu [Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States)

    2016-07-01

    We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

  10. TEA: A CODE CALCULATING THERMOCHEMICAL EQUILIBRIUM ABUNDANCES

    International Nuclear Information System (INIS)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

    2016-01-01

    We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows and Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows and Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

  11. Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes 15N/14N and 18O/16O in dissolved nitrate during microbial dentrification in groundwater

    International Nuclear Information System (INIS)

    Wunderlich, Anja A.L.

    2012-01-01

    Stable isotopes of nitrate are commonly used to determine sources and degradation of nitrate. In this study, nitrite oxidizing bacteria were found to promote an oxygen isotope exchange between water and nitrate under anoxic conditions. Also, different carbon sources were found to influence the enrichment of stable isotopes in nitrate during microbial denitrification. Both results refine the stable isotope model of nitrate in respect to nitrate source determination and microbial nitrate reduction.

  12. Holistic analysis of thermochemical processes by using solid biomass for fuel production in Germany

    International Nuclear Information System (INIS)

    Henssler, Martin

    2015-01-01

    According to the German act ''Biokraftstoff-Nachhaltigkeitsverordnung'', biofuels must show a CO 2eq -reduction compared to the fossil reference fuel (83.8 g CO 2eq /MJ fuel /Richtlinie 98/70/EG/) of 35 % beginning with 2011. In new plants, which go into operation after the 31.12.2016 the CO 2eq -savings must be higher than 50 % in 2017 and higher than 60 % in 2018 /Biokraft-NachV/. The biofuels (methyl ester of rapeseed, bioethanol and biomethane) considered in this study do not meet these requirements for new plants. To comply with these rules new processes must be deployed. Alternative thermochemical generated fuels could be an option. The aim of this work is to evaluate through a technical, ecological and economic analysis (Well-to-Wheel) whether and under what conditions the thermochemical production of Fischer-Tropsch-diesel or -gasoline, hydrogen (H 2 ) and Substitute Natural Gas (SNG) complies with the targets. Four different processes are considered (fast pyrolysis and torrefaction with entrained flow gasifier, CHOREN Carbo-V registered -gasifier, Absorption Enhanced Reforming (AER-) gasifier). Beside residues such as winter wheat straw and residual forest wood, wood from short-rotation plantations is taken into account. The technical analysis showed that at present status (2010) two and in 2050 six plants can be operated energy-self-sufficient. The overall efficiency of the processes is in the range of 41.5 (Fischer-Tropsch-diesel or -gasoline) and 59.4 % (H 2 ). Furthermore, it was found that for 2010, all thermochemical produced fuels except the H 2 -production from wood from short-rotation plantations in decentralised or central fast pyrolysis and in decentralised torrefactions with entrained flow gasifier keep the required CO 2eq -saving of 60 %. In 2050, all thermochemical produced fuels will reach these limits. The CO 2eq -saving is between 72 (H 2 ) and 95 % (Fischer-Tropsch-diesel or -gasoline). When the production costs of the

  13. Maximizing Efficiency in Two-step Solar-thermochemical Fuel Production

    Energy Technology Data Exchange (ETDEWEB)

    Ermanoski, I. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    Widespread solar fuel production depends on its economic viability, largely driven by the solar-to-fuel conversion efficiency. In this paper, the material and energy requirements in two-step solar-thermochemical cycles are considered.The need for advanced redox active materials is demonstrated, by considering the oxide mass flow requirements at a large scale. Two approaches are also identified for maximizing the efficiency: optimizing reaction temperatures, and minimizing the pressure in the thermal reduction step by staged thermal reduction. The results show that each approach individually, and especially the two in conjunction, result in significant efficiency gains.

  14. Uranous nitrate production using PtO2 catalyst and H2/H2 gas mixtures

    International Nuclear Information System (INIS)

    Rao, K.S.; Shyamlal, R.; Narayanan, C.V.; Patil, A.R.; Ramanujam, A.; Kansra, V.P.; Balu, K.; Vaidya, V.N.

    2001-01-01

    The feasibility of producing near 100% uranous nitrate, the partitioning agent used in the spent fuel reprocessing by Purex process, by catalytically reducing uranyl nitrate with H 2 and H 2 gas mixtures was extensively studied. As near quantitative reduction of uranyl nitrate could be easily achieved in laboratory scale studies, pilot plant scale reduction of uranyl nitrate was also carried out and five litres of uranyl nitrate of 100 g/1 could be quantitatively reduced in one hour. (author)

  15. Advances in hydrogen production by thermochemical water decomposition: A review

    International Nuclear Information System (INIS)

    Rosen, Marc A.

    2010-01-01

    Hydrogen demand as an energy currency is anticipated to rise significantly in the future, with the emergence of a hydrogen economy. Hydrogen production is a key component of a hydrogen economy. Several production processes are commercially available, while others are under development including thermochemical water decomposition, which has numerous advantages over other hydrogen production processes. Recent advances in hydrogen production by thermochemical water decomposition are reviewed here. Hydrogen production from non-fossil energy sources such as nuclear and solar is emphasized, as are efforts to lower the temperatures required in thermochemical cycles so as to expand the range of potential heat supplies. Limiting efficiencies are explained and the need to apply exergy analysis is illustrated. The copper-chlorine thermochemical cycle is considered as a case study. It is concluded that developments of improved processes for hydrogen production via thermochemical water decomposition are likely to continue, thermochemical hydrogen production using such non-fossil energy will likely become commercial, and improved efficiencies are expected to be obtained with advanced methodologies like exergy analysis. Although numerous advances have been made on sulphur-iodine cycles, the copper-chlorine cycle has significant potential due to its requirement for process heat at lower temperatures than most other thermochemical processes.

  16. Biomass thermochemical gasification: Experimental studies and modeling

    Science.gov (United States)

    Kumar, Ajay

    The overall goals of this research were to study the biomass thermochemical gasification using experimental and modeling techniques, and to evaluate the cost of industrial gas production and combined heat and power generation. This dissertation includes an extensive review of progresses in biomass thermochemical gasification. Product gases from biomass gasification can be converted to biopower, biofuels and chemicals. However, for its viable commercial applications, the study summarizes the technical challenges in the gasification and downstream processing of product gas. Corn stover and dried distillers grains with solubles (DDGS), a non-fermentable byproduct of ethanol production, were used as the biomass feedstocks. One of the objectives was to determine selected physical and chemical properties of corn stover related to thermochemical conversion. The parameters of the reaction kinetics for weight loss were obtained. The next objective was to investigate the effects of temperature, steam to biomass ratio and equivalence ratio on gas composition and efficiencies. DDGS gasification was performed on a lab-scale fluidized-bed gasifier with steam and air as fluidizing and oxidizing agents. Increasing the temperature resulted in increases in hydrogen and methane contents and efficiencies. A model was developed to simulate the performance of a lab-scale gasifier using Aspen Plus(TM) software. Mass balance, energy balance and minimization of Gibbs free energy were applied for the gasification to determine the product gas composition. The final objective was to optimize the process by maximizing the net energy efficiency, and to estimate the cost of industrial gas, and combined heat and power (CHP) at a biomass feedrate of 2000 kg/h. The selling price of gas was estimated to be 11.49/GJ for corn stover, and 13.08/GJ for DDGS. For CHP generation, the electrical and net efficiencies were 37 and 86%, respectively for corn stover, and 34 and 78%, respectively for DDGS. For

  17. Thermochemical equilibrium modelling of a gasifying process

    International Nuclear Information System (INIS)

    Melgar, Andres; Perez, Juan F.; Laget, Hannes; Horillo, Alfonso

    2007-01-01

    This article discusses a mathematical model for the thermochemical processes in a downdraft biomass gasifier. The model combines the chemical equilibrium and the thermodynamic equilibrium of the global reaction, predicting the final composition of the producer gas as well as its reaction temperature. Once the composition of the producer gas is obtained, a range of parameters can be derived, such as the cold gas efficiency of the gasifier, the amount of dissociated water in the process and the heating value and engine fuel quality of the gas. The model has been validated experimentally. This work includes a parametric study of the influence of the gasifying relative fuel/air ratio and the moisture content of the biomass on the characteristics of the process and the producer gas composition. The model helps to predict the behaviour of different biomass types and is a useful tool for optimizing the design and operation of downdraft biomass gasifiers

  18. IS process for thermochemical hydrogen production

    International Nuclear Information System (INIS)

    Onuki, Kaoru; Nakajima, Hayato; Ioka, Ikuo; Futakawa, Masatoshi; Shimizu, Saburo

    1994-11-01

    The state-of-the-art of thermochemical hydrogen production by IS process is reviewed including experimental data obtained at JAERI on the chemistry of the Bunsen reaction step and on the corrosion resistance of the structural materials. The present status of laboratory scale demonstration at JAERI is also included. The study on the chemistry of the chemical reactions and the products separations has identified feasible methods to function the process. The flowsheeting studies revealed a process thermal efficiency higher than 40% is achievable under efficient process conditions. The corrosion resistance of commercially available structural materials have been clarified under various process conditions. The basic scheme of the process has been realized in a laboratory scale apparatus. R and D requirements to proceed to the engineering demonstration coupled with HTTR are briefly discussed. (author)

  19. Method for thermochemical decomposition of water

    Science.gov (United States)

    Abraham, Bernard M.; Schreiner, Felix

    1977-01-11

    Water is thermochemically decomposed to produce hydrogen by the following sequence of reactions: KI, NH.sub.3, CO.sub. 2 and water in an organic solvent such as ethyl or propyl alcohol are reacted to produce KHCO 3 and NH.sub.4 I. The KHCO.sub.3 is thermally decomposed to K.sub.2 CO.sub.3, H.sub.2 O and CO.sub.2, while the NH.sub.4 I is reacted with Hg to produce HgI.sub.2, NH.sub.3 and H.sub.2. The K.sub.2 CO.sub.3 obtained by calcining KHCO.sub.3 is then reacted with HgI.sub.2 to produce Hg, KI, CO and O.sub.2. All products of the reaction are recycled except hydrogen and oxygen.

  20. Construction apparatus for thermochemical hydrogen production process

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, S.; Nakajima, H.; Higashi, S.; Onuki, K.; Akino, S.S.N. [Japan Atomic Energy Research Inst., Ibaraki-ken (Japan). Nuclear Heat Utilization Engineering Lab

    2001-06-01

    Studies have been carried out at the Japan Atomic Energy Research Institute (JAERI) on hydrogen production through thermochemical processes such as water-splitting. These studies are classified with iodine-sulphur cycle studies using heat from high temperature gas-cooled reactors. An experimental apparatus was constructed with fluorine resin, glass and quartz. It can produce hydrogen at a rate of 50 litres per hour. Electricity provides the heat required for the operation. The closed chemical process requires special control techniques. The process flow diagram for the apparatus was designed based on the results of previous studies including one where hydrogen production was successfully achieved at a rate of one liter per hour for 48 hours. Experimental operations under atmospheric pressure will be carried out for the next four years to develop the process. The data will be used in the next research and development programs aimed at designing a bench-scale apparatus. 7 refs., 1 tab., 8 figs.

  1. Thermochemical production of hydrogen from water

    International Nuclear Information System (INIS)

    Funk, J.E.; Conger, W.L.; Carty, R.H.; Barker, R.E.

    1975-01-01

    A review of recent developments in the selection and evaluation of multi-step thermochemical water-splitting cycles is presented. A computerized and thermodynamic and chemical engineering analysis procedure is discussed with calculates, among other things, the thermal efficiency of the process which is defined to be the ratio of the enthalpy change for water decomposition to the total thermal energy required by the process. Changes in the thermodynamic state in each step of the process are also determined. Engineering considerations such as the effect of approach to equilibrium in the chemical reaction steps on the work of separation, and the magnitude of the recycle streams are included. Important practical matters such as thermal regeneration in the product and reactant streams are dealt with in some detail. The effect of reaction temperature on thermal efficiency is described and the use of the analysis procedure is demonstrated by applying it to several processes. (author)

  2. THERMOCHEMICAL HEAT STORAGE FOR CONCENTRATED SOLAR POWER

    Energy Technology Data Exchange (ETDEWEB)

    PROJECT STAFF

    2011-10-31

    Thermal energy storage (TES) is an integral part of a concentrated solar power (CSP) system. It enables plant operators to generate electricity beyond on sun hours and supply power to the grid to meet peak demand. Current CSP sensible heat storage systems employ molten salts as both the heat transfer fluid and the heat storage media. These systems have an upper operating temperature limit of around 400 C. Future TES systems are expected to operate at temperatures between 600 C to 1000 C for higher thermal efficiencies which should result in lower electricity cost. To meet future operating temperature and electricity cost requirements, a TES concept utilizing thermochemical cycles (TCs) based on multivalent solid oxides was proposed. The system employs a pair of reduction and oxidation (REDOX) reactions to store and release heat. In the storage step, hot air from the solar receiver is used to reduce the oxidation state of an oxide cation, e.g. Fe3+ to Fe2+. Heat energy is thus stored as chemical bonds and the oxide is charged. To discharge the stored energy, the reduced oxide is re-oxidized in air and heat is released. Air is used as both the heat transfer fluid and reactant and no storage of fluid is needed. This project investigated the engineering and economic feasibility of this proposed TES concept. The DOE storage cost and LCOE targets are $15/kWh and $0.09/kWh respectively. Sixteen pure oxide cycles were identified through thermodynamic calculations and literature information. Data showed the kinetics of re-oxidation of the various oxides to be a key barrier to implementing the proposed concept. A down selection was carried out based on operating temperature, materials costs and preliminary laboratory measurements. Cobalt oxide, manganese oxide and barium oxide were selected for developmental studies to improve their REDOX reaction kinetics. A novel approach utilizing mixed oxides to improve the REDOX kinetics of the selected oxides was proposed. It partially

  3. Nitrate removal by electro-bioremediation technology in Korean soil

    International Nuclear Information System (INIS)

    Choi, Jeong-Hee; Maruthamuthu, Sundaram; Lee, Hyun-Goo; Ha, Tae-Hyun; Bae, Jeong-Hyo

    2009-01-01

    The nitrate concentration of surface has become a serious concern in agricultural industry through out the world. In the present study, nitrate was removed in the soil by employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics. The abundance of Bacillus spp. as nitrate reducing bacteria were isolated and identified from the soil sample collected from a greenhouse at Jinju City of Gyengsangnamdo, South Korea. The nitrate reducing bacterial species were identified by 16 s RNA sequencing technique. The efficiency of bacterial isolates on nitrate removal in broth was tested. The experiment was conducted in an electrokinetic (EK) cell by applying 20 V across the electrodes. The nitrate reducing bacteria (Bacillus spp.) were inoculated in the soil for nitrate removal process by the addition of necessary nutrient. The influence of nitrate reducers on electrokinetic process was also studied. The concentration of nitrate at anodic area of soil was higher when compared to cathode in electrokinetic system, while adding bacteria in EK (EK + bio) system, the nitrate concentration was almost nil in all the area of soil. The bacteria supplies electron from organic degradation (humic substances) and enhances NO 3 - reduction (denitrification). Experimental results showed that the electro-bio kinetic process viz. electroosmosis and physiological activity of bacteria reduced nitrate in soil environment effectively. Involvement of Bacillus spp. on nitrification was controlled by electrokinetics at cathode area by reduction of ammonium ions to nitrogen gas. The excellence of the combined electro-bio kinetics technology on nitrate removal is discussed.

  4. Modeled Wet Nitrate Deposition

    Data.gov (United States)

    U.S. Environmental Protection Agency — Modeled data on nitrate wet deposition was obtained from Dr. Jeff Grimm at Penn State Univ. Nitrate wet depostion causes acidification and eutrophication of surface...

  5. 2011 Biomass Program Platform Peer Review. Thermochemical Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Grabowski, Paul E. [Office of Energy Efficiency and Renewable Energy (EERE), Washington, DC (United States)

    2012-02-01

    This document summarizes the recommendations and evaluations provided by an independent external panel of experts at the 2011 U.S. Department of Energy Biomass Program’s Thermochemical Conversion Platform Review meeting.

  6. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources of...

  7. Diatoms respire nitrate to survive dark and anoxic conditions

    DEFF Research Database (Denmark)

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L.

    2011-01-01

    +, indicating dissimilatory nitrate reduction to ammo- nium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dis- similatory nitrate reduction pathway used by a eukaryotic photo- troph. Similar to large sulfur bacteria and benthic foraminifera...

  8. Forensic methodology for the thermochemical characterization of ANNM and ANFO homemade explosives

    Energy Technology Data Exchange (ETDEWEB)

    Nazarian, Ashot; Presser, Cary, E-mail: cpresser@nist.gov

    2015-05-20

    Highlights: • The LDTR is a useful diagnostic for characterizing HME thermochemical behavior. • ANNM thermograms indicated sensitivity to varying HME composition. • ANFO measurements demonstrated sensitivity to fuel hydrocarbon volatility. • Mixture preparation time can be defined by studying vaporization effects on mass. - Abstract: Measurements were carried out to obtain thermal signatures of the most commonly used homemade explosive (HME) materials, i.e., ammonium nitrate/nitromethane and ammonium nitrate/No. 2 diesel fuel oil, using a novel laser-heating technique referred to as the laser-driven thermal reactor (LDTR). Experiments were performed for different compositions, initial masses, and steady-state temperatures, along with the effects associated with HME aging. For ammonium nitrate/nitromethane (ANNM), the NM/ANNM mass fractions investigated were 29% (stoichiometric value) and 14%; these experiments were with fresh mixtures. The 29% NM/ANNM mass fraction mixture was also aged to 3%. For ammonium nitrate/fuel oil (ANFO), a fresh stoichiometric FO/ANFO mass fraction of 6% was used initially, and aged mixtures were then investigated for mass fractions of 5.4%, 4.7%, 4.4%, and 3.7%. The results indicated that the LDTR thermograms (i.e., sample temperature change with time) for the mixed ANNM were different than the individual isolated components, and that the technique was sensitive to varying HME composition. In addition, changes in the thermograms as ANFO aged were attributed to the varying volatility of the fuel hydrocarbon fractions, and thus provide important information for forensics analysis as to the HME reactivity.

  9. Forensic methodology for the thermochemical characterization of ANNM and ANFO homemade explosives

    International Nuclear Information System (INIS)

    Nazarian, Ashot; Presser, Cary

    2015-01-01

    Highlights: • The LDTR is a useful diagnostic for characterizing HME thermochemical behavior. • ANNM thermograms indicated sensitivity to varying HME composition. • ANFO measurements demonstrated sensitivity to fuel hydrocarbon volatility. • Mixture preparation time can be defined by studying vaporization effects on mass. - Abstract: Measurements were carried out to obtain thermal signatures of the most commonly used homemade explosive (HME) materials, i.e., ammonium nitrate/nitromethane and ammonium nitrate/No. 2 diesel fuel oil, using a novel laser-heating technique referred to as the laser-driven thermal reactor (LDTR). Experiments were performed for different compositions, initial masses, and steady-state temperatures, along with the effects associated with HME aging. For ammonium nitrate/nitromethane (ANNM), the NM/ANNM mass fractions investigated were 29% (stoichiometric value) and 14%; these experiments were with fresh mixtures. The 29% NM/ANNM mass fraction mixture was also aged to 3%. For ammonium nitrate/fuel oil (ANFO), a fresh stoichiometric FO/ANFO mass fraction of 6% was used initially, and aged mixtures were then investigated for mass fractions of 5.4%, 4.7%, 4.4%, and 3.7%. The results indicated that the LDTR thermograms (i.e., sample temperature change with time) for the mixed ANNM were different than the individual isolated components, and that the technique was sensitive to varying HME composition. In addition, changes in the thermograms as ANFO aged were attributed to the varying volatility of the fuel hydrocarbon fractions, and thus provide important information for forensics analysis as to the HME reactivity

  10. Electrolytic production of uranous nitrate

    International Nuclear Information System (INIS)

    Orebaugh, E.G.; Propst, R.C.

    1980-04-01

    Efficient production of uranous nitrate is important in nuclear fuel reprocessing because U(IV) acts as a plutonium reductant in solvent extraction and can be coprecipitated with plutonium and/or throium as oxalates during fuel reprocessing. Experimental conditions are described for the efficient electrolytic production of uranous nitrate for use as a reductant in the SRP Purex process. The bench-scale, continuous-flow, electrolysis cell exhibits a current efficiency approaching 100% in combination with high conversion rates of U(VI) to U(IV) in simulated and actual SRP Purex solutions. High current efficiency is achieved with a voltage-controlled mercury-plated platinum electrode and the use of hydrazine as a nitrite scavenger. Conversion of U(VI) to U(IV) proceeds at 100% efficiency. Cathodic gas generation is minimal. The low rate of gas generation permits a long residence time within the cathode, a necessary condition for high conversions on a continuous basis. Design proposals are given for a plant-scale, continuous-flow unit to meet SRP production requirements. Results from the bench-scale tests indicate that an 8-kW unit can supply sufficient uranous nitrate reductant to meet the needs of the Purex process at SRP

  11. Do nitrates differ?

    Science.gov (United States)

    Fung, H.-L.

    1992-01-01

    1 The organic nitrates all share a common biochemical and physiological mechanism of action. 2 The organic nitrates differ substantially in their pharmacologic potency and pharmacokinetics. In vitro potency differences appear larger than the corresponding in vivo activities. 3 The duration of action of organic nitrates, after a single immediate-release dose, is governed by the pharmacokinetics of the drug. However, the duration of action of available sustained-release preparations, whatever the nitrate or formulation, is limited to about 12 h, due to the development of pharmacologic tolerance. 4 Nitrates do not appear to differ in their production of undesirable effects. PMID:1633079

  12. Nitrate pollution of groundwater

    International Nuclear Information System (INIS)

    Heaton, T.H.E.

    1986-01-01

    Concern about the possible health risks associated with the consumption of nitrate has led many countries, including South Africa, to propose that 10mg of nitrogen (as nitrate or nitrite) per liter should be the maximum allowable limit for domestic water supplies. Groundwater in certain parts of South Africa and Namibia contains nitrate in concentrations which exceed this limit. The CSIR's Natural Isotope Division has been studying the nitrogen isotope composition of the nitrate as an aid to investigation into the sources of this nitrate contamination

  13. An overview of renewable hydrogen production from thermochemical process of oil palm solid waste in Malaysia

    International Nuclear Information System (INIS)

    Hosseini, Seyed Ehsan; Wahid, Mazlan Abdul; Ganjehkaviri, A.

    2015-01-01

    Highlights: • 40% of energy demand of Malaysia could be supplied by thermochemical process of PSR. • SCWG of PSR is preferable thermochemical process due to char and tar elimination. • Potential of H 2 production from SCWG of PSR is 1.05 × 10 10 kgH 2 per year in Malaysia. • Highly moisturized PSR could be used in hydrogen production by SCWG process. - Abstract: Hydrogen is one of the most promising energy carriers for the future of the world due to its tremendous capability of pollution reduction. Hydrogen utilization is free of toxic gases formation as well as carbon dioxide (CO 2 ) emission. Hydrogen production can be implemented using a wide variety of resources including fossil fuels, nuclear energy and renewable and sustainable energy (RSE). Amongst various RSE resources, biomass has great capacity to be employed for renewable hydrogen production. Hydrogen production from palm solid residue (PSR) via thermochemical process is a perfect candidate for waste-to-well strategy in palm oil mills in Malaysia. In this paper, various characteristics of hydrogen production from thermochemical process of PSR includes pyrolysis and gasification are reviewed. The annual oil palm fruits production in Malaysia is approximately 100 million tonnes which the solid waste of the fruits is capable to generate around 1.05 × 10 10 kgH 2 (1.26 EJ) via supercritical water gasification (SCWG) process. The ratio of energy output to energy input of SCWG process of PSR is about 6.56 which demonstrates the priority of SCWG to transform the energy of PSR into a high energy end product. The high moisture of PSR which is the most important barrier for its direct combustion, emerges as an advantage in thermochemical reactions and highly moisturized PSR (even more than 50%) is utilized directly in SCWG without application of any high cost drying process. Implementation of appropriate strategies could lead Malaysia to supply about 40% of its annual energy demand by hydrogen yield from

  14. Ammonium nitrate explosion hazards

    Directory of Open Access Journals (Sweden)

    Negovanović Milanka

    2015-01-01

    Full Text Available Ammonium nitrate (AN primarily is used as a fertilizer but it is also very important compound in the production of industrial explosives. The application of ammonium nitrate in the production of industrial explosives was related with the early era of Nobel dynamite and widely increased with the appearance of blasting agents such as ANFO and Slurry, in the middle of the last Century. Throughout the world millions of tons of ammonium nitrate are produced annually and handled without incident. Although ammonium nitrate generally is used safely, accidental explosions involving AN have high impact resulting in loss of lives and destruction of property. The paper presents the basic properties of ammonium nitrate as well as hazards in handling of ammonium nitrate in order to prevent accidents. Several accidents with explosions of ammonium nitrate resulted in catastrophic consequences are listed in the paper as examples of non-compliance with prescribed procedures.

  15. Nicotinamides: Evaluation of thermochemical experimental properties

    International Nuclear Information System (INIS)

    Zhabina, Aleksandra A.; Nagrimanov, Ruslan N.; Emel’yanenko, Vladimir N.; Solomonov, Boris N.; Verevkin, Sergey P.

    2016-01-01

    Highlights: • Vapor pressures measured by transpiration method. • Enthalpies of solution measured using high-precision solution calorimetry. • Enthalpies of fusion measured by DSC. • Sublimation enthalpies derived from transpiration and solution calorimetry in agreement. • Experimental results evaluated and compared with G4 calculations. - Abstract: Vapor pressures of the isomeric 2-, 3-, and 4-pyridinecarboxamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298.15 K were derived from vapor pressure temperature dependences. The enthalpies of solution of the isomeric pyridinecarboxamides were measured with the high-precision solution calorimetry. The enthalpies of sublimation of 3- and 4-pyridinecarboxamides were independently derived with help of the solution calorimetry based procedure. The enthalpies of fusion of the pyridinecarboxamides were measured by the DSC. Thermochemical data isomeric pyridinecarboxamides were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation successfully.

  16. Thermochemical parameters of caffeine, theophylline, and xanthine

    Energy Technology Data Exchange (ETDEWEB)

    Ngo Tuan Cuong; Truong Ba Tai [Department of Chemistry, and Mathematical Modeling and Computational Science Center (LMCC), Katholieke Universiteit Leuven, B-3001 Leuven (Belgium); Vu Thi Thu Ha [Institute of Chemistry, Vietnam Academy of Science and Technology, Hanoi (Viet Nam); Minh Tho Nguyen, E-mail: minh.nguyen@chem.kuleuven.b [Department of Chemistry, and Mathematical Modeling and Computational Science Center (LMCC), Katholieke Universiteit Leuven, B-3001 Leuven (Belgium)

    2010-04-15

    Thermochemical parameters of caffeine 1, theophylline 2, xanthine 3, uracil, and imidazole derivatives are determined by quantum chemical calculations. Using the composite G3B3 method, the standard heat of formation of caffeine in the gaseous phase amounts to DELTA{sub f}H{sub g}{sup 0}(1)=-243+-8kJ.mol{sup -1}, which lends a support for the recent experimental value of -237.0 +- 2.5 kcal . mol{sup -1}. We also obtain DELTA{sub f}H{sub g}{sup 0}(2)=-232+-8kJ.mol{sup -1}andDELTA{sub f}H{sub g}{sup 0}(3)=-209+-8kJ.mol{sup -1}. The adiabatic ionization energies are IE{sub a}(1) = 7.9 eV, IE{sub a}(2) = 8.1 eV, and IE{sub a}(3) = 8.5 eV using B3LYP calculations. The enhanced ability of caffeine to eject electron, as compared to the parent compounds and cyclic components, is of interest with regard to its potential use as a corrosion inhibitor.

  17. Thermochemical investigations on uranyl phosphates and arsenates

    International Nuclear Information System (INIS)

    Barten, H.

    1986-01-01

    Results are described of a study of the thermochemical stability of anhydrous phosphates and arsenates. The results of phase studies deal with compound formation and characterization, coexisting phases and limiting physical or chemical properties. The uranyl phosphates evolve oxygen at higher temperatures and the arsenates lose arsenic oxide vapour. These phenomena give the possibility to describe their thermodynamic stabilities. Thus oxygen pressures of uranyl phosphates have been measured using a static, non-isothermal method. Having made available the pure anhydrous compounds in the course of this investigation, molar thermodynamic quantities have been measured as well. These include standard enthalpies of formation from solution calorimetry and high-temperature heat-capacity functions derived from enthalpy increments measured. Some attention is given to compounds with uranium in valencies lower than six which have been met during the investigation. An evaluation is made of the thermodynamics of the compounds studied, to result in tabulized high-temperature thermodynamic functions. Relative stabilities within the systems are discussed and comparisons of the uranyl phosphates and the arsenates are made. (Auth.)

  18. Effect of nitrate on activity and community structure of a sulfidogenic wastewater biofilm

    DEFF Research Database (Denmark)

    Kofoed, Michael Vedel Wegener; Mohanakrishnan, Janani; Schramm, Andreas

    (dsrB), and periplasmic nitrate reductase(napA). Addition of nitrate did not inhibit sulfide production although sulfate reduction and dsrB expression were suppressed, suggesting that sulfide production occurred from the reduction of other sulfur compounds. Nitrate induced a community-shift of SRB from Desulfobacter...

  19. Thermochemical performance analysis of solar driven CO_2 methane reforming

    International Nuclear Information System (INIS)

    Fuqiang, Wang; Jianyu, Tan; Huijian, Jin; Yu, Leng

    2015-01-01

    Increasing CO_2 emission problems create urgent challenges for alleviating global warming, and the capture of CO_2 has become an essential field of scientific research. In this study, a finite volume method (FVM) coupled with thermochemical kinetics was developed to analyze the solar driven CO_2 methane reforming process in a metallic foam reactor. The local thermal non-equilibrium (LTNE) model coupled with radiative heat transfer was developed to provide more temperature information. A joint inversion method based on chemical process software and the FVM coupled with thermochemical kinetics was developed to obtain the thermochemical reaction parameters and guarantee the calculation accuracy. The detailed thermal and thermochemical performance in the metal foam reactor was analyzed. In addition, the effects of heat flux distribution and porosity on the solar driven CO_2 methane reforming process were analyzed. The numerical results can serve as theoretical guidance for the solar driven CO_2 methane reforming application. - Highlights: • Solar driven CO_2 methane reforming process in metal foam reactor is analyzed. • FVM with chemical reactions was developed to analyze solar CO_2 methane reforming. • A joint inversion method was developed to obtain thermochemical reaction parameters. • Results can be a guidance for the solar driven CO_2 methane reforming application.

  20. Thermal integration of SCWR nuclear and thermochemical hydrogen plants

    International Nuclear Information System (INIS)

    Wang, Z.; Naterer, G.F.; Gabriel, K.S.

    2010-01-01

    In this paper, the intermediate heat exchange between a Generation IV supercritical water-cooled nuclear reactor (SCWR) and a thermochemical hydrogen production cycle is discussed. It is found that the maximum and range of temperatures of a thermochemical cycle are the dominant parameters that affect the design of its coupling with SCWR. The copper-chlorine (Cu-Cl) thermochemical cycle is a promising cycle that can link with SCWRs. The location of extracting heat from a SCWR to a thermochemical cycle is investigated in this paper. Steam bypass lines downstream of the SCWR core are suggested for supplying heat to the Cu-Cl hydrogen production cycle. The stream extraction location is strongly dependent on the temperature requirements of the chemical steps of the thermochemical cycle. The available quantity of heat exchange at different hours of a day is also studied. It is found that the available heat at most hours of power demand in a day can support an industrial scale steam methane reforming plant if the SCWR power station is operating at full design capacity. (author)

  1. Biomass Thermochemical Conversion Program. 1983 Annual report

    Energy Technology Data Exchange (ETDEWEB)

    Schiefelbein, G.F.; Stevens, D.J.; Gerber, M.A.

    1984-08-01

    Highlights of progress achieved in the program of thermochemical conversion of biomass into clean fuels during 1983 are summarized. Gasification research projects include: production of a medium-Btu gas without using purified oxygen at Battelle-Columbus Laboratories; high pressure (up to 500 psia) steam-oxygen gasification of biomass in a fluidized bed reactor at IGT; producing synthesis gas via catalytic gasification at PNL; indirect reactor heating methods at the Univ. of Missouri-Rolla and Texas Tech Univ.; improving the reliability, performance, and acceptability of small air-blown gasifiers at Univ. of Florida-Gainesville, Rocky Creek Farm Gasogens, and Cal Recovery Systems. Liquefaction projects include: determination of individual sequential pyrolysis mechanisms at SERI; research at SERI on a unique entrained, ablative fast pyrolysis reactor for supplying the heat fluxes required for fast pyrolysis; work at BNL on rapid pyrolysis of biomass in an atmosphere of methane to increase the yields of olefin and BTX products; research at the Georgia Inst. of Tech. on an entrained rapid pyrolysis reactor to produce higher yields of pyrolysis oil; research on an advanced concept to liquefy very concentrated biomass slurries in an integrated extruder/static mixer reactor at the Univ. of Arizona; and research at PNL on the characterization and upgrading of direct liquefaction oils including research to lower oxygen content and viscosity of the product. Combustion projects include: research on a directly fired wood combustor/gas turbine system at Aerospace Research Corp.; adaptation of Stirling engine external combustion systems to biomass fuels at United Stirling, Inc.; and theoretical modeling and experimental verification of biomass combustion behavior at JPL to increase biomass combustion efficiency and examine the effects of additives on combustion rates. 26 figures, 1 table.

  2. High dose potassium-nitrate chemical dosimeter

    International Nuclear Information System (INIS)

    Dorda de Cancio, E.M.; Munoz, S.S.

    1982-01-01

    This dosimeter is used to control 10 kGY-order doses (1 Mrad). Nitrate suffers a radiolitic reduction phenomena, which is related to the given dose. The method to use potassium nitrate as dosimeter is described, as well as effects of the temperature of irradiation, pH, nitrate concentration and post-irradiation stability. Nitrate powder was irradiated at a Semi-Industrial Plant, at Centro Atomico Ezeiza, and also in a Gammacell-220 irradiator. The dose rates used were 2,60 and 1,80 KGY/hour, and the given doses varied between 1,0 and 150 KGY. The uncertainty was +-3% in all the range. (author) [es

  3. Capabilities to Support Thermochemical Hydrogen Production Technology Development

    Energy Technology Data Exchange (ETDEWEB)

    Daniel M. Ginosar

    2009-05-01

    This report presents the results of a study to determine if Idaho National Laboratory (INL) has the skilled staff, instrumentation, specialized equipment, and facilities required to take on work in thermochemical research, development, and demonstration currently being performed by the Nuclear Hydrogen Initiative (NHI). This study outlines the beneficial collaborations between INL and other national laboratories, universities, and industries to strengthen INL's thermochemical efforts, which should be developed to achieve the goals of the NHI in the most expeditious, cost effective manner. Taking on this work supports INL's long-term strategy to maintain leadership in thermochemical cycle development. This report suggests a logical path forward to accomplish this transition.

  4. Overview of recent advances in thermo-chemical conversion of biomass

    International Nuclear Information System (INIS)

    Zhang Linghong; Xu Chunbao; Champagne, Pascale

    2010-01-01

    Energy from biomass, bioenergy, is a perspective source to replace fossil fuels in the future, as it is abundant, clean, and carbon dioxide neutral. Biomass can be combusted directly to generate heat and electricity, and by means of thermo-chemical and bio-chemical processes it can be converted into bio-fuels in the forms of solid (e.g., charcoal), liquid (e.g., bio-oils, methanol and ethanol), and gas (e.g., methane and hydrogen), which can be used further for heat and power generation. This paper provides an overview of the principles, reactions, and applications of four fundamental thermo-chemical processes (combustion, pyrolysis, gasification, and liquefaction) for bioenergy production, as well as recent developments in these technologies. Some advanced thermo-chemical processes, including co-firing/co-combustion of biomass with coal or natural gas, fast pyrolysis, plasma gasification and supercritical water gasification, are introduced. The advantages and disadvantages, potential for future applications and challenges of these processes are discussed. The co-firing of biomass and coal is the easiest and most economical approach for the generation of bioenergy on a large-sale. Fast pyrolysis has attracted attention as it is to date the only industrially available technology for the production of bio-oils. Plasma techniques, due to their high destruction and reduction efficiencies for any form of waste, have great application potential for hazardous waste treatment. Supercritical water gasification is a promising approach for hydrogen generation from biomass feedstocks, especially those with high moisture contents.

  5. Open-Source Photometric System for Enzymatic Nitrate Quantification.

    Science.gov (United States)

    Wittbrodt, B T; Squires, D A; Walbeck, J; Campbell, E; Campbell, W H; Pearce, J M

    2015-01-01

    Nitrate, the most oxidized form of nitrogen, is regulated to protect people and animals from harmful levels as there is a large over abundance due to anthropogenic factors. Widespread field testing for nitrate could begin to address the nitrate pollution problem, however, the Cadmium Reduction Method, the leading certified method to detect and quantify nitrate, demands the use of a toxic heavy metal. An alternative, the recently proposed Environmental Protection Agency Nitrate Reductase Nitrate-Nitrogen Analysis Method, eliminates this problem but requires an expensive proprietary spectrophotometer. The development of an inexpensive portable, handheld photometer will greatly expedite field nitrate analysis to combat pollution. To accomplish this goal, a methodology for the design, development, and technical validation of an improved open-source water testing platform capable of performing Nitrate Reductase Nitrate-Nitrogen Analysis Method. This approach is evaluated for its potential to i) eliminate the need for toxic chemicals in water testing for nitrate and nitrite, ii) reduce the cost of equipment to perform this method for measurement for water quality, and iii) make the method easier to carryout in the field. The device is able to perform as well as commercial proprietary systems for less than 15% of the cost for materials. This allows for greater access to the technology and the new, safer nitrate testing technique.

  6. Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes {sup 15}N/{sup 14}N and {sup 18}O/{sup 16}O in dissolved nitrate during microbial dentrification in groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, Anja A.L.

    2012-11-02

    Stable isotopes of nitrate are commonly used to determine sources and degradation of nitrate. In this study, nitrite oxidizing bacteria were found to promote an oxygen isotope exchange between water and nitrate under anoxic conditions. Also, different carbon sources were found to influence the enrichment of stable isotopes in nitrate during microbial denitrification. Both results refine the stable isotope model of nitrate in respect to nitrate source determination and microbial nitrate reduction.

  7. Nitrate leaching index

    Science.gov (United States)

    The Nitrate Leaching Index is a rapid assessment tool that evaluates nitrate (NO3) leaching potential based on basic soil and climate information. It is the basis for many nutrient management planning efforts, but it has considerable limitations because of : 1) an oversimplification of the processes...

  8. SUNgas: Thermochemical Approaches to Solar Fuels

    Science.gov (United States)

    Davidson, Jane

    2013-04-01

    Solar energy offers an intelligent solution to reduce anthropogenic emissions of greenhouse gases and to meet an expanding global demand for energy. A transformative change from fossil to solar energy requires collection, storage, and transport of the earth's most abundant but diffuse and intermittent source of energy. One intriguing approach for harvest and storage of solar energy is production of clean fuels via high temperature thermochemical processes. Concentrated solar energy is the heat source and biomass or water and carbon dioxide are the feedstocks. Two routes to produce fuels using concentrated solar energy and a renewable feed stock will be discussed: gasification of biomass or other carbonaceous materials and metal oxide cycles to produce synthesis gas. The first and most near term route to solar fuels is to gasify biomass. With conventional gasification, air or oxygen is supplied at fuel-rich levels to combust some of the feedstock and in this manner generate the energy required for conversion to H2 and CO. The partial-combustion consumes up to 40% of the energetic value of the feedstock. With air combustion, the product gas is diluted by high levels of CO2 and N2. Using oxygen reduces the product dilution, but at the expense of adding an oxygen plant. Supplying the required heat with concentrated solar radiation eliminates the need for partial combustion of the biomass feedstock. As a result, the product gas has an energetic value greater than that of the feedstock and it is not contaminated by the byproducts of combustion. The second promising route to solar fuels splits water and carbon dioxide. Two-step metal-oxide redox cycles hold out great potential because they the temperature required to achieve a reasonable degree of dissociation is lower than direct thermal dissociation and O2 and the fuel are produced in separate steps. The 1^st step is the endothermic thermal dissociation of the metal oxide to the metal or lower-valence metal oxide. The 2

  9. Thermal characterization of nitrates and nitrates/expanded graphite mixture phase change materials for solar energy storage

    International Nuclear Information System (INIS)

    Xiao, X.; Zhang, P.; Li, M.

    2013-01-01

    Highlights: • The addition of expanded graphite improved apparent thermal conductivity significantly. • The quadratic parallel model was used to predict the effective thermal conductivity. • The melting/freezing temperatures of mixture PCMs shifted slightly with adding of EG. - Abstract: Solar energy storage has become more attractive in recent years. In particular, latent thermal energy storage (LTES) with large energy storage density and isothermal heat storage/retrieval characteristics is a hot research topic. In the present study, sodium nitrate, potassium nitrate and their mixture were used as the base materials, and expanded graphite (EG) with high thermal conductivity and thermo-chemical stability was used as an additive to enhance the thermal conductivity. EG with various mass fractions was added to the base materials to form mixture phase change materials (PCMs), and the thermal characteristics of the mixtures were studied extensively. The transient hot-wire tests showed that the addition of EG enhanced the apparent thermal conductivity significantly, e.g. the apparent thermal conductivity of the nitrates/10 wt.% EG mixture PCM was increased by about 30–40%. The test results showed good agreement with theoretical calculations of the quadratic parallel model. Tests with differential scanning calorimeter (DSC) revealed that the melting/freezing temperatures of the mixture PCMs shifted slightly, compared with those of pure nitrates

  10. Nitrate ammonification in mangrove soils: A hidden source of nitrite?

    Directory of Open Access Journals (Sweden)

    Melike eBalk

    2015-03-01

    Full Text Available Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests.The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden under the nitrate-limited conditions of most mangrove forest soils.

  11. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    KAUST Repository

    Balk, Melike; Laverman, Anniet M; Keuskamp, Joost A; Laanbroek, Hendrikus J

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils.

  12. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    KAUST Repository

    Balk, Melike

    2015-03-02

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils.

  13. Nitrate Adsorption on Clay Kaolin: Batch Tests

    Directory of Open Access Journals (Sweden)

    Morteza Mohsenipour

    2015-01-01

    Full Text Available Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 mgNO3-/L, with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

  14. Fuels production by the thermochemical transformation of the biomass

    International Nuclear Information System (INIS)

    Claudet, G.

    2005-01-01

    The biomass is a local and renewable energy source, presenting many advantages. This paper proposes to examine the biomass potential in France, the energy valorization channels (thermochemical chains of thermolysis and gasification) with a special interest for the hydrogen production and the research programs oriented towards the agriculture and the forest. (A.L.B.)

  15. Prototype thermochemical heat storage with open reactor system

    NARCIS (Netherlands)

    Zondag, H.A.; Kikkert, B.; Smeding, S.F.; Boer, de R.; Bakker, M.

    2013-01-01

    Thermochemical (TC) heat storage is an interesting technology for future seasonal storage of solar heat in the built environment. This technology enables high thermal energy storage densities and low energy storage losses. A small-scale laboratory prototype TC storage system has been realized at

  16. Thermochemical biorefinery based on dimethyl ether as intermediate: Technoeconomic assessment

    International Nuclear Information System (INIS)

    Haro, P.; Ollero, P.; Villanueva Perales, A.L.; Gómez-Barea, A.

    2013-01-01

    Highlights: ► A thermochemical biorefinery based on bio-DME as intermediate is studied. ► The assessed concepts (12) lead to multi-product generation (polygeneration). ► In all concepts DME is converted by carbonylation or hydrocarbonylation. ► Rates of return are similar to or higher than plants producing a single product. -- Abstract: Thermochemical biorefinery based on dimethyl ether (DME) as an intermediate is studied. DME is converted into methyl acetate, which can either be hydrogenated to ethanol or sold as a co-product. Considering this option together with a variety of technologies for syngas upgrading, 12 different process concepts are analyzed. The considered products are ethanol, methyl acetate, H 2 , DME and electricity. The assessment of each alternative includes biomass pretreatment, gasification, syngas clean-up and conditioning, DME synthesis and conversion, product separation, and heat and power integration. A plant size of 500 MW th processing poplar chips is taken as a basis. The resulting energy efficiency to products ranges from 34.9% to 50.2%. The largest internal rate of return (28.74%) corresponds to a concept which produces methyl acetate, DME and electricity (exported to grid). A sensitivity analysis with respect to total plant investment (TPI), total operation costs (TOC) and market price of products was carried out. The overall conclusion is that, despite its greater complexity, this kind of thermochemical biorefinery is more profitable than thermochemical bioprocesses oriented to a single product.

  17. A process for the thermochemical poduction of H2

    International Nuclear Information System (INIS)

    Norman, J.H.; Russell, J.L. Jr.; Porter, J.T. II; McCorkl, K.H.; Roemer, T.S.; Sharp, Robert.

    1976-01-01

    A process is described for the thermochemical production of H 2 from water. HI 3 and H 2 SO 4 are prepared by chemical reaction between I 2 , SO 2 and H 2 O. Then HI 3 is heated and decomposed into H 2 and I 2 . The heat is produced by a nuclear reactor [fr

  18. The NAGRA/PSI thermochemical database: new developments

    Energy Technology Data Exchange (ETDEWEB)

    Hummel, W.; Berner, U.; Thoenen, T. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Pearson, F.J.Jr. [Ground-Water Geochemistry, New Bern, NC (United States)

    2000-07-01

    The development of a high quality thermochemical database for performance assessment is a scientifically fascinating and demanding task, and is not simply collecting and recording numbers. The final product can by visualised as a complex building with different storeys representing different levels of complexity. The present status report illustrates the various building blocks which we believe are integral to such a database structure. (authors)

  19. Renewable hydrogen production via thermochemical/electrochemical coupling

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosini, Andrea [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Babiniec, Sean Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Miller, James E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    A coupled electrochemical/thermochemical cycle was investigated to produce hydrogen from renewable resources. Like a conventional thermochemical cycle, this cycle leverages chemical energy stored in a thermochemical working material that is reduced thermally by solar energy. However, in this concept, the stored chemical energy only needs to be partially, but not fully, capable of splitting steam to produce hydrogen. To complete the process, a proton-conducting membrane is driven to separate hydrogen as it is produced, thus shifting the thermodynamics toward further hydrogen production. This novel coupled-cycle concept provides several benefits. First, the required oxidation enthalpy of the reversible thermochemical material is reduced, enabling the process to occur at lower temperatures. Second, removing the requirement for spontaneous steam-splitting widens the scope of materials compositions, allowing for less expensive/more abundant elements to be used. Lastly, thermodynamics calculations suggest that this concept can potentially reach higher efficiencies than photovoltaic-to-electrolysis hydrogen production methods. This Exploratory Express LDRD involved assessing the practical feasibility of the proposed coupled cycle. A test stand was designed and constructed and proton-conducting membranes were synthesized. While the full proof of concept was not achieved, the individual components of the experiment were validated and new capabilities that can be leveraged by a variety of programs were developed.

  20. The NAGRA/PSI thermochemical database: new developments

    International Nuclear Information System (INIS)

    Hummel, W.; Berner, U.; Thoenen, T.; Pearson, F.J.Jr.

    2000-01-01

    The development of a high quality thermochemical database for performance assessment is a scientifically fascinating and demanding task, and is not simply collecting and recording numbers. The final product can by visualised as a complex building with different storeys representing different levels of complexity. The present status report illustrates the various building blocks which we believe are integral to such a database structure. (authors)

  1. Biomass Program 2007 Program Peer Review - Thermochemical Conversion Platform Summary

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2009-10-27

    This document discloses the comments provided by a review panel at the U.S. Department of Energy Office of the Biomass Program Peer Review held on November 15-16, 2007 in Baltimore, MD and the Biomass Program Peer Review for the Thermochemical Platform, held on July 9th and 10th in Golden, Colorado.

  2. Thermochemical properties of the alkali hydroxides: A review

    International Nuclear Information System (INIS)

    Konings, R.J.M.; Cordfunke, E.H.P.

    1989-01-01

    The formation of volatile alkali hydroxides as a result of high-temperature steam corrosion plays an important role in nuclear technology. For the modeling of the volatilization processes, reliable thermodynamic data are required. In the present paper recent physico-chemical experiments by the authors will be discussed and the thermochemical properties of the alkali hydroxide series will be evaluated. (orig.)

  3. Probabilistic thermo-chemical analysis of a pultruded composite rod

    DEFF Research Database (Denmark)

    Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

    2012-01-01

    In the present study the deterministic thermo-chemical pultrusion simulation of a composite rod taken from the literature [7] is used as a validation case. The predicted centerline temperature and cure degree profiles of the rod match well with those in the literature [7]. Following the validation...

  4. Thermochemical structure of the Earth's mantle and continental crust

    DEFF Research Database (Denmark)

    Guerri, Mattia

    A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging...

  5. Redução de nitrato em plantas jovens de café cultivadas em diferentes níveis de luz e de nitrogênio Nitrate reduction in young coffee trees grown under different levels of light and nitrogen

    Directory of Open Access Journals (Sweden)

    Maria Luiza Carvalho Carelli

    1990-01-01

    . These results indicate that the lower nitrate reductase activity of plants grown under full sunlight was apparently not due to limitations of available nitrate and sugars to supply the energy necessary for nitrate reduction.

  6. Growing patterns to produce 'nitrate-free' lettuce (Lactuca sativa).

    Science.gov (United States)

    Croitoru, Mircea Dumitru; Muntean, Daniela-Lucia; Fülöp, Ibolya; Modroiu, Adriana

    2015-01-01

    Vegetables can contain significant amounts of nitrate and, therefore, may pose health hazards to consumers by exceeding the accepted daily intake for nitrate. Different hydroponic growing patterns were examined in this work in order to obtain 'nitrate-free lettuces'. Growing lettuces on low nitrate content nutrient solution resulted in a significant decrease in lettuces' nitrate concentrations (1741 versus 39 mg kg(-1)), however the beneficial effect was cancelled out by an increase in the ambient temperature. Nitrate replacement with ammonium was associated with an important decrease of the lettuces' nitrate concentration (from 1896 to 14 mg kg(-1)) and survival rate. An economically feasible method to reduce nitrate concentrations was the removal of all inorganic nitrogen from the nutrient solution before the exponential growth phase. This method led to lettuces almost devoid of nitrate (10 mg kg(-1)). The dried mass and calcinated mass of lettuces, used as markers of lettuces' quality, were not influenced by this treatment, but a small reduction (18%, p < 0.05) in the fresh mass was recorded. The concentrations of nitrite in the lettuces and their modifications are also discussed in the paper. It is possible to obtain 'nitrate-free' lettuces in an economically feasible way.

  7. Mutation of the Arabidopsis NRT1.5 nitrate transporter causes defective root-to-shoot nitrate transport.

    Science.gov (United States)

    Lin, Shan-Hua; Kuo, Hui-Fen; Canivenc, Geneviève; Lin, Choun-Sea; Lepetit, Marc; Hsu, Po-Kai; Tillard, Pascal; Lin, Huey-Ling; Wang, Ya-Yun; Tsai, Chyn-Bey; Gojon, Alain; Tsay, Yi-Fang

    2008-09-01

    Little is known about the molecular and regulatory mechanisms of long-distance nitrate transport in higher plants. NRT1.5 is one of the 53 Arabidopsis thaliana nitrate transporter NRT1 (Peptide Transporter PTR) genes, of which two members, NRT1.1 (CHL1 for Chlorate resistant 1) and NRT1.2, have been shown to be involved in nitrate uptake. Functional analysis of cRNA-injected Xenopus laevis oocytes showed that NRT1.5 is a low-affinity, pH-dependent bidirectional nitrate transporter. Subcellular localization in plant protoplasts and in planta promoter-beta-glucuronidase analysis, as well as in situ hybridization, showed that NRT1.5 is located in the plasma membrane and is expressed in root pericycle cells close to the xylem. Knockdown or knockout mutations of NRT1.5 reduced the amount of nitrate transported from the root to the shoot, suggesting that NRT1.5 participates in root xylem loading of nitrate. However, root-to-shoot nitrate transport was not completely eliminated in the NRT1.5 knockout mutant, and reduction of NRT1.5 in the nrt1.1 background did not affect root-to-shoot nitrate transport. These data suggest that, in addition to that involving NRT1.5, another mechanism is responsible for xylem loading of nitrate. Further analyses of the nrt1.5 mutants revealed a regulatory loop between nitrate and potassium at the xylem transport step.

  8. MITIGASI PELINDIAN NITRAT PADA TANAH INCEPTISOL MELALUI PEMANFAATAN BAHAN NITRAT INHIBITOR ALAMI

    Directory of Open Access Journals (Sweden)

    Joko Pramono

    2012-05-01

    Full Text Available Mitigation of Nitrate Leaching in Inceptisol Soil Through the Use of Natural Nitrate Inhibitor ABSTRAK Pelindian NO3- merupakan salah satu mekanisme kehilangan N dalam aktivitas pertanian, yang dapat berdampak terhadap pencemaran lingkungan. Tujuan dari penelitian adalah untuk mengetahui penggunaan bahan alami sebagai nitrat inhibitor terhadap pelindian nitrat pada tanah Inceptisol. Pada penelitian ini diuji tiga jenis bahan nitrat inhibitor (NI alami yang berasal dari; serbuk biji Mimba (SBM, serbuk kulit kayu bakau (SKKB, dan serbuk daun kopi (SDK,yang dikombinasikan dengan tiga taraf dosis NI, yaitu: 20 %, 30 % dan 40 % dari urea yang diberikan, dan ditambah satu perlakuan kontrol tanpa NI. Bahan nitrat inhibitor diberikan bersama urea pada permukaan tanah dalam pot percobaan yang telah dibasahi dengan air suling. Hasil penelitian menunjukkan bahwa bahan NI yang berbeda memberikan respon terhadap penghambatan nitrifi kasi yang berbeda. Bahan NI yang berasal dari serbuk biji mimba memberikan tingkat penghambatan tertinggi sebesar (25,6 %, serbuk kulit kayu bakau sebesar (19,1 %, dan serbuk daun kopi sebesar 11,8 %. Bahan NI alami mampu menghambat nitrifi kasi melalui penghambatan pertumbuhan bakteri nitrifi kasi (pengoksida ammonium yang bersifat sementara pada kisaran 7-14 hari setelah aplikasi. Perlakuan berbagai bahan dan dosis NI mampu menekan pelindian nitrat rata-rata pada kisaran antara 56,6 sampai 62,8 % dan berbeda sangat nyata terhadap perlakuan kontrol tanpa NI. Bahan NI yang mampu menurunkan rata-rata pelindian nitrat pada pengamatan 14 hari setelah aplikasi tertinggi adalah SBM sebesar 74,15 %. Dosis optimal dua bahan NI terpilih yang menunjukkan kinerja penghambatan nitrifi kasi terbaik (SBM dan SKKB pada 7 hsa, masing-masing 18,30 % (R2 = 0,694 dan 21,67 % (R2=0.691 dari dosis urea yang diberikan. Kata kunci: Nitrifi kasi, nitrat inhibitor, pelindian nitrat ABSTRACT NO3 - leaching is one mechanism of N reduction in agricultural

  9. Radiation chemistry of the aqueous aluminium nitrate solution (Preprint no. RC-26)

    International Nuclear Information System (INIS)

    Kalkar, C.D.; Date, D.B.

    1991-01-01

    Radiolysis of aqueous aluminium nitrate solution is studied as a function of concentration in the range 10 -4 M to 10 -1 M. The stable radiolytic product of nitrate radiolysis is nitrite. The yield of nitrite linearly increases with absorbed dose. The G(NO 2 ) values are determined at various concentrations of aluminium nitrate. A suitable mechanism is proposed to explain the observed G-value for the reduction of nitrate to nitrite. (author). 6 refs., 1 tab

  10. Plutonium purification cycle in centrifugal extractors: comparative study of flowsheets using uranous nitrate and hydroxylamine nitrate

    International Nuclear Information System (INIS)

    Baron, P.; Dinh, B.; Mauborgne, B.; Drain, F.; Gillet, B.

    1998-01-01

    The extension of the UP2 plant at La Hague includes a new plutonium purification cycle using multi-stage centrifugal extractors, to replace the present cycle which uses mixer/settler banks. The advantage of this type of extractor is basically the compactness of the equipment and the short residence time, which limits solvent degradation, particularly when reprocessing fuel containing a high proportion of plutonium 238. Two types of reducing agents have been considered for the plutonium stripping operation, uranous nitrate and hydroxylamine nitrate. Uranous nitrate displays a very fast reduction kinetics, ideal for the very short residence time of the phases in the centrifugal extractors. However, its extractability in the organic phase exacerbates the undesirable re-oxidation of plutonium, which is present in high concentration in this stage of the process. The short residence time of the centrifugal extractors is an advantage in as much as it could conceivably be adequate to obtain a sufficient reduction efficiency, while minimizing undesirable re-oxidation mechanisms. Hydroxylamine nitrate helps to minimize undesirable re-oxidation and is the normal choice for this type of operation. However, the plutonium (IV) reduction kinetics obtained is slower than with uranous nitrate, making it necessary to check whether its use is compatible with the very short residence times of centrifugal extractors.This article discusses the feasibility studies employing these two reducing agents. (author)

  11. Effect of high oral doses of nitrate on salivary recirculation of nitrates and nitrites and on bacterial diversity in the saliva of young pigs.

    Science.gov (United States)

    Trevisi, P; Casini, L; Nisi, I; Messori, S; Bosi, P

    2011-04-01

    Ingested nitrate is absorbed in the small intestine, recirculated into the saliva and reduced to nitrite by oral bacteria. In pigs receiving a moderate dietary addition of nitrate, the recirculation into the saliva is modest, so we aimed to assess the effect of higher nitrate doses to find out how the animal reacts to this new situation and to evaluate if a higher nitrate level could enhance the nitrate reduction process, improving the nitrite production Trial 1. Six piglets received 100 g of a commercial diet with 2.45% KNO(3) . In relation to baseline values, nitrate in blood serum and saliva increased 15 times, and declined after 6 h vs. 2 h. Salivary nitrite increased seven times after the addition and declined after 6 h vs. 2 h. Trial 2. Six piglets were fed a diet with or without 1.22% KNO(3) for 2 weeks. Salivary nitrate and nitrite increased with the addition of KNO3: nitrate increased from d0 to the end of the trial, nitrite increased 15 times after 1 week, but decreased after 2 weeks to 4.5-fold the control. After 2 weeks, nitrate reduced Shan diversity index of salivary microbiota. The present results indicate that the long exposure to high quantities of nitrates impairs the oral reduction of nitrate to nitrite and engenders a reduction of the mouth's microbiota diversity. © 2010 Blackwell Verlag GmbH.

  12. Thermochemically active iron titanium oxide materials

    Energy Technology Data Exchange (ETDEWEB)

    Coker, Eric Nicholas; Miller, James E.

    2018-01-16

    A thermal oxidation-reduction cycle is disclosed that uses iron titanium oxide as the reactive material. The cycle may be used for the thermal splitting of water and/or carbon dioxide to form hydrogen and/or carbon monoxide. The formed compounds may be used as syngas precursors to form fuels.

  13. [Can nitrates lead to indirect toxicity?].

    Science.gov (United States)

    Hamon, M

    2007-09-01

    For many years, nitrates have been used, at low dosages, as an additive in salted food. New laws have been promulgated to limit their concentration in water due to increased levels found in soils, rivers and even the aquifer. Although nitrate ions themselves have not toxic properties, bacterial reduction into nitrite ions (occurring even in aqueous medium) can lead to nitrous anhydride, which in turn generates nitrosonium ions. Nitrosium ions react with secondary amine to give nitrosamines, many of which are cancer-inducing agents at very low doses. Opinions on this toxicity are clear-cut and difficult to reconcile. In fact, increased levels are due, in a large part, to the use of nitrates as fertiliéers but also to bacterial transformation of human and animal nitrogenous wastes such as urea.

  14. Thermochemical stability of Soviet macroporous sulfonated cation-exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Rukhlyada, N.N.; Plotnikova, V.P.; Roginskaya, B.S.; Znamenskii, Yu.P.; Zavodovskaya, A.S.; Dobrova, E.I.

    1988-10-20

    The purpose of this work was to study the influence of macroporosity on the thermochemical stability of sulfonated cation-exchangers. The investigations were carried out on commercial macroporous sulfonated cation-exchangers based on styrene-divinylbenzene copolymers. Study of the thermochemical stability of macroporous sulfonated cation-exchangers in dilute hydrogen peroxide solutions showed that the type of macroporosity has virtually no influence on their stability. The determining factor in thermal stability of macroporous cation-exchangers, as of the gel type, is the degree of cross-linking of the polymer matrix. The capacity loss of macroporous cation-exchangers during oxidative thermolysis is caused by destruction of the macromolecular skeleton and elution of fragments of polar chains containing sulfo groups into the solution.

  15. Quantitative Thermochemical Measurements in High-Pressure Gaseous Combustion

    Science.gov (United States)

    Kojima, Jun J.; Fischer, David G.

    2012-01-01

    We present our strategic experiment and thermochemical analyses on combustion flow using a subframe burst gating (SBG) Raman spectroscopy. This unconventional laser diagnostic technique has promising ability to enhance accuracy of the quantitative scalar measurements in a point-wise single-shot fashion. In the presentation, we briefly describe an experimental methodology that generates transferable calibration standard for the routine implementation of the diagnostics in hydrocarbon flames. The diagnostic technology was applied to simultaneous measurements of temperature and chemical species in a swirl-stabilized turbulent flame with gaseous methane fuel at elevated pressure (17 atm). Statistical analyses of the space-/time-resolved thermochemical data provide insights into the nature of the mixing process and it impact on the subsequent combustion process in the model combustor.

  16. Thermochemical study of MoS2 oxidation

    International Nuclear Information System (INIS)

    Filimonov, D.S.; Topor, N.D.; Kesler, Ya.A.

    1990-01-01

    Thermochemical studies of oxidation processes of metallic molybdenum, sulfur, molybdenum disulfide under different conditions in microcalorimeter are conducted. Values of thermal effects which are used to calculate standard formation enthalpy of MoS 2 and which correlate well are obtained. Δ f H 0 (MoS 2 ,298.15 K) recommended value constitutes (-223.0±16.7) kJ/mol

  17. Observations of Circumstellar Thermochemical Equilibrium: The Case of Phosphorus

    Science.gov (United States)

    Milam, Stefanie N.; Charnley, Steven B.

    2011-01-01

    We will present observations of phosphorus-bearing species in circumstellar envelopes, including carbon- and oxygen-rich shells 1. New models of thermochemical equilibrium chemistry have been developed to interpret, and constrained by these data. These calculations will also be presented and compared to the numerous P-bearing species already observed in evolved stars. Predictions for other viable species will be made for observations with Herschel and ALMA.

  18. The Effect of Nitrate Levels and Harvest Times on Fe, Zn, Cu, and K, Concentrations and Nitrate Reductase Activity in Lettuce and Spinach

    Directory of Open Access Journals (Sweden)

    Z. Gheshlaghi

    2015-09-01

    Full Text Available Leafy vegetables are considered as the main sources of nitrate in the human diet. In order to investigate the effect of nitrate levels and harvest times on nitrate accumulation, nitrate reductase activity, concentrations of Fe, Zn, Cu and K in Lettuce and Spinach and their relation to nitrate accumulation in these leafy vegetables, two harvest times (29 and 46 days after transplanting, two vegetable species of lettuce and spinach and two concentrations of nitrate (10 and 20 mM were used in a hydroponics greenhouse experiment with a completely randomized design and 3 replications. Modified Hoagland and Arnon nutrient solutions were used for the experiment. The results indicated that by increasing nitrate concentration of solution, nitrate accumulation in roots and shoots of lettuce and spinach increased significantly (P ≤ 0.05, and the same trend was observed for the nitrate reductase activity in the shoots of the two species. Increasing the nitrate concentrations of solution, reduced the shoot dry weight and the concentration of Fe and Cu in both species, where as it increased the K and Zn concentrations in the shoots of the two species in each both harvest times, the nitrate accumulation increased, but the nitrate reductase activity decreased in the shoots of the two species over the course of the growth. The Concentration of Fe, Cu and K decreased in the shoots of lettuce and the spinach with the time, despite the increase in Zn concentration in the shoots. The results also indicated that increasing nitrate concentrations of solution to the levels greater than the plant capacity for reduction and net uptake of nitrate, leads to the nitrate accumulation in the plants. Nitrate accumulation in plant tissue led to decreases in fresh shoot yield and Fe and Cu concentrations and nitrate reductase activities in both lettuce and spinach.

  19. Performance analysis of a photovoltaic-thermochemical hybrid system prototype

    International Nuclear Information System (INIS)

    Li, Wenjia; Ling, Yunyi; Liu, Xiangxin; Hao, Yong

    2017-01-01

    Highlights: •A modular photovoltaic-thermochemical hybrid system prototype is proposed. •Net solar-electric efficiency up to 41% is achievable. •Stable solar power supply is achievable via convenient energy storage. •The modular design facilitates the scalability of the hybrid system. -- Abstract: A solar photovoltaic (PV) thermochemical hybrid system consisting of a point-focus Fresnel concentrator, a PV cell and a methanol thermochemical reactor is proposed. In particular, a reactor capable of operating under high solar concentration is designed, manufactured and tested. Studies on both kinetic and thermodynamic characteristics of the reactor and the system are performed. Analysis of numerical and experimental results shows that with cascaded solar energy utilization and synergy among different forms of energy, the hybrid system has the advantages of high net solar-electric efficiency (up to 41%), stable solar energy power supply, solar energy storage (via syngas) and flexibility in application scale. The hybrid system proposed in this work provides a potential solution to some key challenges of current solar energy utilization technologies.

  20. OPTIMIZED WTE CONVERSION OF MUNICIPAL SOLID WASTE IN SHANGHAI APPLYING THERMOCHEMICAL TECHNOLOGIES

    OpenAIRE

    Dai, Siyang

    2016-01-01

    Thermochemical technologies have been proven effective in treating municipal solid waste (MSW) for many years. China, with a rapid increase of MSW, plans to implement more environmental friendly ways to treat MSW than landfill, which treats about 79 % of total MSW currently. The aim of this master thesis was to find out a suitable thermochemical technology to treat MSW in Shanghai, China. Several different thermochemical technologies are compared in this thesis and plasma gasification was sel...

  1. Assessment of a closed thermochemical energy storage using energy and exergy methods

    International Nuclear Information System (INIS)

    Abedin, Ali Haji; Rosen, Marc A.

    2012-01-01

    Highlights: ► Thermodynamics assessments are reported for a general closed thermochemical thermal energy storage system. ► Energy and exergy efficiencies of various processes in a closed thermochemical TES are evaluated and compared. ► Understanding is enhanced of thermochemical TES technologies and their potential implementations. ► Exergy analysis is observed to be useful when applied to thermochemical TES, with or in place of energy analysis. - Abstract: Thermal energy storage (TES) is an important technology for achieving more efficient and environmentally benign energy systems. Thermochemical TES is a type of TES with the potential for high energy density and is only recently being considered intensively. To improve understanding of thermochemical TES systems and their implementation, energy and exergy analyses are beneficial. Here, thermodynamics assessments are presented for a general closed thermochemical TES system, including assessments and comparisons of the efficiencies of the overall thermochemical TES cycle and its charging, storing and discharging processes. Locations and causes of thermodynamic losses in thermochemical TES systems are being specified using exergy analysis. The analytical methodology applied in this study identifies that energy and exergy efficiencies differ for thermochemical TESs, e.g. the energy efficiency for a case study is approximately 50% while the exergy efficiency is about 10%. Although the focus is to evaluate thermodynamic efficiencies, other design parameters such as cost, and environmental impact also need to be examined in assessing thermochemical storage. The efficiencies for thermochemical TES provided here should be helpful for designing these energy systems and enhancing their future prospects.

  2. Electrochemical processing of nitrate waste solutions

    International Nuclear Information System (INIS)

    Genders, D.; Weinberg, N.; Hartsough, D.

    1992-01-01

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F - ions from the synthetic mix migrating across the cation exchange membrane and forming HF in the acid anolyte. Other possibilities for anode materials were explored. A membrane separation process was investigated which employs an anion and cation exchange membrane to remove nitrite and nitrate, recovering caustic and nitric acid. Present research has shown poor current efficiencies for nitrite and nitrate transport across the anion exchange membrane due to co-migration of hydroxide anions. Precipitates form within the anion exchange membranes which would eventually result in the failure of the membranes. Electrochemical processing offers a highly promising and viable method for the treatment of nitrate waste solutions

  3. Reactivity of Metal Nitrates.

    Science.gov (United States)

    1982-07-20

    02NOCuOH Any mechanism suggested for the nitration of aromatic systems by titanium(IV) nitrate must take into account the observed similarity, in...occurs. -26- References 1. For recent reviews see (a) R. B. Moodie and K. Schofield, Accounts Chem. Res., 1976, 9, 287; (b) G. A. Olah and S. J. Kuhn...Ithaca, N.Y., 1969, Chapter VI; L. M. Stock, Prog. Phys. Org. Chem., 1976, 12, 21; J. G. Hoggett , R. B. Moodie, J. R. Penton, and K. Schofield

  4. System and process for producing fuel with a methane thermochemical cycle

    Science.gov (United States)

    Diver, Richard B.

    2015-12-15

    A thermochemical process and system for producing fuel are provided. The thermochemical process includes reducing an oxygenated-hydrocarbon to form an alkane and using the alkane in a reforming reaction as a reducing agent for water, a reducing agent for carbon dioxide, or a combination thereof. Another thermochemical process includes reducing a metal oxide to form a reduced metal oxide, reducing an oxygenated-hydrocarbon with the reduced metal oxide to form an alkane, and using the alkane in a reforming reaction as a reducing agent for water, a reducing agent for carbon dioxide, or a combination thereof. The system includes a reformer configured to perform a thermochemical process.

  5. Influence of Nitrate on the Hanford 100D Area In Situ Redox Manipulation Barrier Longevity

    International Nuclear Information System (INIS)

    Szecsody, Jim E.; Phillips, Jerry L.; Vermeul, Vince R.; Fruchter, Jonathan S.; Williams, Mark D.

    2005-01-01

    The purpose of this laboratory study is to determine the influence of nitrate on the Hanford 100D Area in situ redox manipulation (ISRM) barrier longevity. There is a wide spread groundwater plume of 60 mg/L nitrate upgradient of the ISRM barrier with lower nitrate concentrations downgradient, suggestive of nitrate reduction occurring. Batch and 1-D column experiments showed that nitrate is being slowly reduced to nitrite and ammonia. These nitrate reduction reactions are predominantly abiotic, as experiments with and without bactericides present showed no difference in nitrate degradation rates. Nitrogen species transformation rates determined in experiments covered a range of ferrous iron/nitrate ratios such that the data can be used to predict rates in field scale conditions. Field scale reaction rate estimates for 100% reduced sediment (16 C) are: (a) nitrate degradation = 202 ± 50 h (half-life), (b) nitrite production = 850 ± 300 h, and (c) ammonia production = 650 ± 300 h. Calculation of the influence of nitrate reduction on the 100D Area reductive capacity requires consideration of mass balance and reaction rate effects. While dissolved oxygen and chromate reduction rates are rapid and essentially at equilibrium in the aquifer, nitrate transformation reactions are slow (100s of hours). In the limited (20-40 day) residence time in the ISRM barrier, only a portion of the nitrate will be reduced, whereas dissolved oxygen and chromate are reduced to completion. Assuming a groundwater flow rate of 1 ft/day, it is estimated that the ISRM barrier reductive capacity is 160 pore volumes (with no nitrate), and 85 pore volumes if 60 mg/L nitrate is present (i.e., a 47% decrease in the ISRM barrier longevity). Zones with more rapid groundwater flow will be less influenced by nitrate reduction. For example, a zone with a groundwater flow rate of 3 ft/day and 60 mg/L nitrate will have a reductive capacity of 130 pore volumes. Finally, long-term column experiments

  6. Solar Hydrogen Production via a Samarium Oxide-Based Thermochemical Water Splitting Cycle

    Directory of Open Access Journals (Sweden)

    Rahul Bhosale

    2016-04-01

    Full Text Available The computational thermodynamic analysis of a samarium oxide-based two-step solar thermochemical water splitting cycle is reported. The analysis is performed using HSC chemistry software and databases. The first (solar-based step drives the thermal reduction of Sm2O3 into Sm and O2. The second (non-solar step corresponds to the production of H2 via a water splitting reaction and the oxidation of Sm to Sm2O3. The equilibrium thermodynamic compositions related to the thermal reduction and water splitting steps are determined. The effect of oxygen partial pressure in the inert flushing gas on the thermal reduction temperature (TH is examined. An analysis based on the second law of thermodynamics is performed to determine the cycle efficiency (ηcycle and solar-to-fuel energy conversion efficiency (ηsolar−to−fuel attainable with and without heat recuperation. The results indicate that ηcycle and ηsolar−to−fuel both increase with decreasing TH, due to the reduction in oxygen partial pressure in the inert flushing gas. Furthermore, the recuperation of heat for the operation of the cycle significantly improves the solar reactor efficiency. For instance, in the case where TH = 2280 K, ηcycle = 24.4% and ηsolar−to−fuel = 29.5% (without heat recuperation, while ηcycle = 31.3% and ηsolar−to−fuel = 37.8% (with 40% heat recuperation.

  7. Nitrous oxide emission by the non-denitrifying, nitrate ammonifier Bacillus licheniformis

    OpenAIRE

    Sun, Yihua; De Vos, Paul; Heylen, Kim

    2016-01-01

    Background Firmicutes have the capacity to remove excess nitrate from the environment via either denitrification, dissimilatory nitrate reduction to ammonium or both. The recent renewed interest in their nitrogen metabolism has revealed many interesting features, the most striking being their wide variety of dissimilatory nitrate reduction pathways. In the present study, nitrous oxide production from Bacillus licheniformis, a ubiquitous Gram-positive, spore-forming species with many industria...

  8. Phase extraction equilibria in systems rare earth (3) nitrates-ammonium nitrate-water-trialkylmethylammonium nitrate

    International Nuclear Information System (INIS)

    Pyartman, A.K.; Kopyrin, A.A.; Puzikov, E.A.

    1995-01-01

    The distribution of rare earth metals (3) between aqueous and organic phases in the systems rare earth metal (3) (praseodymium-lutetium (3), yttrium (3)) nitrate-ammonium nitrate-water-trialkylmethylammonium (kerosene diluent nitrate has been studied. It is shown that in organic phase di- and trisolvates of metals (3) with tralkylmethylammonium nitrate are formed. The influence of concentration of rare earth metal (3) nitrate and ammonium nitrate on the values of extraction concentrational constants has been ascertained: they decrease with increase in the ordinal number of lanthanide (3). 11 refs., 4 figs. 1 tab

  9. Identification of nitrate sources and discharge-depending nitrate dynamics in a mesoscale catchment

    Science.gov (United States)

    Mueller, Christin; Strachauer, Ulrike; Brauns, Mario; Musolff, Andreas; Kunz, Julia Vanessa; Brase, Lisa; Tarasova, Larisa; Merz, Ralf; Knöller, Kay

    2017-04-01

    discharge resulting in a higher impact of evaporation on water isotopes and a higher/different level of biological activity (esp. in the WWTP). Enriched isotope values for nitrogen and oxygen are not indicative of a significant impact of bacterial denitrification, because they are accompanied by increased nitrate concentrations (1 to 16 mg L-1). Based on the presented study, 50 % of the nitrate export from the Holtemme river catchment can be attributed to WWTP effluent. The remaining amount is related to agricultural land use. Consequently, nitrate load reduction in the river system cannot rely on internal processing but needs to be regulated by preventive measures especially by an improved wastewater treatment and land use management.

  10. Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription

    DEFF Research Database (Denmark)

    Cheng, Chi-Lien; Acedo, Gregoria N; Kristensen, Michael

    1992-01-01

    can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants. We show further that sucrose alone is sufficient for the full expression of nitrate reductase genes in etiolated Arabidopsis plants. Finally, using a reporter gene, we show......Nitrate reductase, the first enzyme in nitrate assimilation, is located at the crossroad of two energy-consuming pathways: nitrate assimilation and carbon fixation. Light, which regulates the expression of many higher-plant carbon fixation genes, also regulates nitrate reductase gene expression....... Located in the cytosol, nitrate reductase obtains its reductant not from photosynthesis but from carbohydrate catabolism. This relationship prompted us to investigate the indirect role that light might play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose...

  11. Nitrate Leaching Management

    Science.gov (United States)

    Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site’s hydrologic cycle, avoiding excess ...

  12. Waterproofing Materials for Ammonium Nitrate

    OpenAIRE

    R.S. Damse

    2004-01-01

    This study explores the possibility of overcoming the problem of hygroscopicity of ammonium nitrate by coating the particles with selected waterproofing materials. Gravimetric analysis ofthe samples of ammonium nitrate coated with eight different waterproofing materials, vis-a-vis, uncoated ammonium nitrate, were conducted at different relative humidity and exposuretime. The results indicate that mineral jelly is the promising waterproofing material for ammonium nitrate among the materials te...

  13. Thermodynamic comparison of two processes of hydrogen production: steam methane reforming-A solar thermochemical process

    International Nuclear Information System (INIS)

    Gomri, Rabah; Boumaza, Mourad

    2006-01-01

    Hydrogen is mainly employed like primary product, for the synthesis of ammonia. The ammonia is synthesized by chemically combining hydrogen and nitrogen under pressure, in the presence of a catalyst. This ammonia is used, for the production of the nitrate fertilizers. Nowadays hydrogen gains more attention mainly because, it is regarded as a future significant fuel by much of experts. The widespread use of hydrogen as source of energy could help to reduce the concern concerning the safety of energy, the total change of climate and the quality of air. Hydrogen is presented then as an excellent alternate initially and as substitute thereafter. It can play a role even more significant than conventional energies. Indeed, it has the advantage of being nonpolluting and it can use the same means of transport as conventional energies. For Algeria, it proves of importance capital. It not only makes it possible to increase and diversify its energy reserves and its exports but also to provide for its energy needs which become increasingly significant. Although hydrogen can be produced starting from a large variety of resources using a range of various technologies, the natural gas is generally preferred and will remain in the near future the principal primary product for the manufacture of hydrogen. Currently the most effective means of production of hydrogen is the Steam Reforming of Natural Gas (SMR). This process is seen as a one of principal technologies for the production of hydrogen. The disadvantages of this process it's that it consumes a great quantity of primary energy and that it releases in the atmosphere the gases that contribute to the warming of the plane. Among the alternatives processes of hydrogen production one can quote solar thermochemical processes. In this study, an exergetic analysis of the process of hydrogen production based on Zn/ZnO redox reactions is presented. In the first part of this study, an exergetic analysis is made for a temperature of the

  14. Chemical and electrochemical behaviour of halides in nitrate melts

    International Nuclear Information System (INIS)

    Tkalenko, D.A.; Kudrya, S.A.; Delimarskij, Yu.K.; Antropov, L.I.

    1978-01-01

    The possibility of improving the positive electrode characteristics of medium temperature lithium-nitrate element by means of adding alkali metal halogenides into nitrate melt is considered. The experiments have been made at the temperature of 150 deg C in (K, Na, Li) NO 3 melts of eutectic composition. It has been found that only at temperatures higher than 250 deg C in nitrate melts containing Li + and Na + cations, an interaction of nitrate ions with the added iodides is possible. The interaction does not take place in case of chloride, bromide, and fluoride additions. The waves of halogenide oxidation and reduction of the corresponding halogens have been identified. The analysis of the obtained experimental data shows that halogenide addition into nitrate melt does not result in speed increase of cathodic reduction of nitrate ions or in formation of a new cathode process at more positive potentials. A conclusion is made that halogenide addition into electrolyte of lithium-nitrate current source is inexpedient

  15. Perspectives of advanced thermal management in solar thermochemical syngas production using a counter-flow solid-solid heat exchanger

    Science.gov (United States)

    Falter, Christoph; Sizmann, Andreas; Pitz-Paal, Robert

    2017-06-01

    A modular reactor model is presented for the description of solar thermochemical syngas production involving counter-flow heat exchangers that recuperate heat from the solid phase. The development of the model is described including heat diffusion within the reactive material as it travels through the heat exchanger, which was previously identified to be a possibly limiting factor in heat exchanger design. Heat transfer within the reactive medium is described by conduction and radiation, where the former is modeled with the three-resistor model and the latter with the Rosseland diffusion approximation. The applicability of the model is shown by the analysis of heat exchanger efficiency for different material thicknesses and porosities in a system with 8 chambers and oxidation and reduction temperatures of 1000 K and 1800 K, respectively. Heat exchanger efficiency is found to rise strongly for a reduction of material thickness, as the element mass is reduced and a larger part of the elements takes part in the heat exchange process. An increase of porosity enhances radiation heat exchange but deteriorates conduction. The overall heat exchange in the material is improved for high temperatures in the heat exchanger, as radiation dominates the energy transfer. The model is shown to be a valuable tool for the development and analysis of solar thermochemical reactor concepts involving heat exchange from the solid phase.

  16. Advanced Electrochemical Technologies for Hydrogen Production by Alternative Thermochemical Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Lvov, Serguei; Chung, Mike; Fedkin, Mark; Lewis, Michele; Balashov, Victor; Chalkova, Elena; Akinfiev, Nikolay; Stork, Carol; Davis, Thomas; Gadala-Maria, Francis; Stanford, Thomas; Weidner, John; Law, Victor; Prindle, John

    2011-01-06

    Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted of Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and

  17. New applications with time-dependent thermochemical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Koukkari, P. [VTT Chemical Technology, Espoo (Finland); Laukkanen, L. [VTT Automation, Espoo (Finland); Penttilae, K. [Kemira Engineering Oy, Helsinki (Finland)

    1996-12-31

    A new method (RATEMIX) to calculate multicomponent chemical reaction mixtures as a series of sequential thermochemical states was recently introduced. The procedure combines multicomponent thermodynamics with chemical kinetics and may be used to simulate the multicomponent reactors as a thermochemical natural process. The method combines the desired reaction rates sequentially with constrained Gibbs energy minimization. The reactant concentrations are determined by the experimental (Arrhenius) rate laws. During the course of the given reaction the subsequent side reactions are supposed to occur reversibly. At every sequential stage of the given reaction the temperature and composition of the reaction mixture are calculated by a thermodynamic subroutine, which minimizes the Gibbs energy of the system and takes into account the heat transfer between the system and its surroundings. The extents of reaction are included as algorithmic constraints in the Gibbs energy minimization procedure. Initially, the reactants are introduced to the system as inert copies to match both the mass and energy balance of the reactive system. During the calculation the copies are sequentially interchanged to the actual reactants which allows one to simulate the time-dependent reaction route by using the thermochemical procedure. For each intermediate stage, the temperature and composition are calculated and as well numerical estimates of the thermodynamic functions are obtained. The method is applicable in processes where the core thermodynamic and kinetic data of the system are known and the time-dependent heat transfer data can either be measured or estimated by calculation. The method has been used to simulate e.g. high temperature flame reactions, zinc vapour oxidation and a counter-current rotary drum with chemical reactions. The procedure has today been tested with SOLGASMIX, CHEMSAGE and HSC programs. (author)

  18. New applications with time-dependent thermochemical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Koukkari, P [VTT Chemical Technology, Espoo (Finland); Laukkanen, L [VTT Automation, Espoo (Finland); Penttilae, K [Kemira Engineering Oy, Helsinki (Finland)

    1997-12-31

    A new method (RATEMIX) to calculate multicomponent chemical reaction mixtures as a series of sequential thermochemical states was recently introduced. The procedure combines multicomponent thermodynamics with chemical kinetics and may be used to simulate the multicomponent reactors as a thermochemical natural process. The method combines the desired reaction rates sequentially with constrained Gibbs energy minimization. The reactant concentrations are determined by the experimental (Arrhenius) rate laws. During the course of the given reaction the subsequent side reactions are supposed to occur reversibly. At every sequential stage of the given reaction the temperature and composition of the reaction mixture are calculated by a thermodynamic subroutine, which minimizes the Gibbs energy of the system and takes into account the heat transfer between the system and its surroundings. The extents of reaction are included as algorithmic constraints in the Gibbs energy minimization procedure. Initially, the reactants are introduced to the system as inert copies to match both the mass and energy balance of the reactive system. During the calculation the copies are sequentially interchanged to the actual reactants which allows one to simulate the time-dependent reaction route by using the thermochemical procedure. For each intermediate stage, the temperature and composition are calculated and as well numerical estimates of the thermodynamic functions are obtained. The method is applicable in processes where the core thermodynamic and kinetic data of the system are known and the time-dependent heat transfer data can either be measured or estimated by calculation. The method has been used to simulate e.g. high temperature flame reactions, zinc vapour oxidation and a counter-current rotary drum with chemical reactions. The procedure has today been tested with SOLGASMIX, CHEMSAGE and HSC programs. (author)

  19. Absorção e redução de nitrato em duas cultivares de arroz na presença de alumínio Uptake and reduction of nitrate in two rice cultivars in the presence of aluminum

    Directory of Open Access Journals (Sweden)

    Gilberto Costa Justino

    2006-08-01

    Full Text Available O objetivo deste trabalho foi estudar os efeitos do alumínio (Al sobre a absorção e a redução de nitrato, em duas cultivares de arroz: Fernandes (tolerante e Maravilha (sensível, expostas a 0 e 500 µM de Al. Depois de 21 dias de crescimento, foram determinados o comprimento, a produção de matéria seca, os teores de Al e de nitrato e a atividade in vitro da redutase do nitrato (RN, nas raízes e na parte aérea, bem como as constantes cinéticas de absorção de nitrato pelas raízes. O Al reduziu o crescimento em comprimento e a produção de matéria seca, nas duas partes das plantas, apenas da cultivar Maravilha. Os teores de Al aumentaram nas raízes e parte aérea das plantas nas duas cultivares, enquanto o teor de nitrato sofreu redução apenas nas raízes da cultivar Maravilha. A Vmax não se modificou, enquanto o Km da absorção de nitrato diminuiu cerca de 11% na cultivar Fernandes e aumentou 310% na Maravilha. Em presença de Al, houve redução na atividade da RN nas raízes das duas cultivares, e na parte aérea apenas da cultivar Maravilha. A cultivar tolerante foi mais eficiente na absorção e na redução de nitrato, o que indica que esses processos são importantes componentes da tolerância ao Al em arroz.The objective of this work was to evaluate the effects of Al on the nitrate uptake and reduction in two rice cultivars, Fernandes (Al tolerant and Maravilha (Al sensitive, exposed to 0 and 500 µM Al. After 21 days of Al treatment, growth in size and dry matter yield, Al and nitrate contents and in vitro nitrate reductase activity (NR in the tops and roots, and the kinetic constants of root nitrate uptake were determined. Aluminum reduced the growth and dry matter yield of both plant parts only in the Maravilha cultivar. Aluminum content increased in the tops and roots of both cultivars, while nitrate content decreased only in the roots of Maravilha cultivar. Vmax did not change, while Km of the nitrate uptake

  20. Thermochemical treatment of spent ion exchange resins

    International Nuclear Information System (INIS)

    Ojovan, M.I.; Petrov, G.A.; Dmitriev, S.A.; Trusov, B.G.; Semenov, K.N.; Klimov, V.L.

    2001-01-01

    Spent ion exchange resins (IER) is a principal type of radioactive waste constantly generated by nuclear plants of various functions. The reduction of volume of this waste and its treatment to the forms suitable for long-term disposal is an urgent problem facing the present-day atomic energetics. Nowadays the technological process THOR (Studsvik, Sweden) based on the thermodestruction of IER is the best developed and realized on the industrial scale. Unfortunately, this process requires expensive equipment and great energy consumption for the moisture to be evaporated and thereafter IER to be destroyed by heat. Meanwhile the capability of some elements (Mg, Al, Si, Ti etc.) has long been known and practical use found for active interaction with water in combustion regime. This property of the metals has been used in the development of new technology of treatment of IERs in SIA ''Radon''. Wet IER is mixed with powder metal fuel (PMF) which represents a mixture of metal powder, a quantity of burning activator and some technological additives. On initiation, the mixture of IER with PMF burns without extra energy supply to generate enough heat for the moisture to be evaporated and products of IER decomposition to be destroyed and evaporated. To burn out the products of IER evaporation the air is used. The thermodynamic simulation data and the results of experiments using a pilot plant show that radionuclides contained in IER are chemically bound in ash residue consisting of metal oxides, spinel, silicates, etc. According to the experimental data, radionuclides in amounts of 90% or more of Cs-137 and up to 95% of Sr-90 and Co-60 are fixed in the ash residue. The residue volume is several times less than the initial volume of IER. Concentrations of hazard gases in off-gases do not exceed maximum permissible ones accepted in different countries. The technological process is easy to perform, it does not require sophisticated equipment and great energy consumption which

  1. Thermochemical data for reactor materials and fission products: The ECN database

    International Nuclear Information System (INIS)

    Cordfunke, E.H.P.; Konings, R.J.M.

    1993-02-01

    The activities of the authors regarding the compilation of a database of thermochemical properties for reactor materials and fission products is reviewed. The evaluation procedures and techniques are outlined and examples are given. In addition, examples of the use of thermochemical data for the application in the field of Nuclear Technology are given. (orig.)

  2. Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass

    NARCIS (Netherlands)

    Fernandes, T.; Klaasse Bos, G.J.; Zeeman, G.; Sanders, J.P.M.; Lier, van J.B.

    2009-01-01

    The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After

  3. Thermochemical Heat Storage: from Reaction Storage Density to System Storage Density

    NARCIS (Netherlands)

    Jong, A.J. de; Vliet, L.D. van; Hoegaerts, C.L.G.; Roelands, C.P.M.; Cuypers, R.

    2016-01-01

    Long-term and compact storage of solar energy is crucial for the eventual transition to a 100% renewable energy economy. For this, thermochemical materials provide a promising solution. The compactness of a long-term storage system is determined by the thermochemical reaction, operating conditions,

  4. Sustainable energy with thermochemical storage; Duurzame energie met thermochemische opslag

    Energy Technology Data Exchange (ETDEWEB)

    Bakker, M. [ECN Efficiency and Infrastructure, Petten (Netherlands)

    2010-03-15

    The Energy research Centre of the Netherlands ECN) foresees an important role for heat in sustainable construction of buildings. Using salt hydrates the surplus of heat can be stored in the summer which then can be used in the winter. By means of thermochemical storage natural gas for heating tap water or houses is no longer necessary. [Dutch] Energieonderzoek Centrum Nederland (ECN) ziet voor warmteopslag een belangrijke rol weggelegd in het duurzaam bouwen. Met behulp van zouthydraten kan de overtollige warmte in de zomer opgeslagen worden om deze in de winter weer vrij te maken. Met deze thermochemische opslag is in de nabije toekomst aardgas overbodig voor de verwarming van kraanwater of woonhuis.

  5. Revisiting dibenzothiophene thermochemical data: Experimental and computational studies

    International Nuclear Information System (INIS)

    Freitas, Vera L.S.; Gomes, Jose R.B.; Ribeiro da Silva, Maria D.M.C.

    2009-01-01

    Thermochemical data of dibenzothiophene were studied in the present work by experimental techniques and computational calculations. The standard (p 0 =0.1MPa) molar enthalpy of formation, at T = 298.15 K, in the gaseous phase, was determined from the enthalpy of combustion and sublimation, obtained by rotating bomb calorimetry in oxygen, and by Calvet microcalorimetry, respectively. This value was compared with estimated data from G3(MP2)//B3LYP computations and also with the other results available in the literature.

  6. High Efficiency Solar Thermochemical Reactor for Hydrogen Production.

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Anthony H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2017-09-30

    This research and development project is focused on the advancement of a technology that produces hydrogen at a cost that is competitive with fossil-based fuels for transportation. A twostep, solar-driven WS thermochemical cycle is theoretically capable of achieving an STH conversion ratio that exceeds the DOE target of 26% at a scale large enough to support an industrialized economy [1]. The challenge is to transition this technology from the laboratory to the marketplace and produce hydrogen at a cost that meets or exceeds DOE targets.

  7. Thermochemical hydrogen production studies at LLNL: a status report

    International Nuclear Information System (INIS)

    Krikorian, O.H.

    1982-01-01

    Currently, studies are underway at the Lawrence Livermore National Laboratory (LLNL) on thermochemical hydrogen production based on magnetic fusion energy (MFE) and solar central receivers as heat sources. These areas of study were described earlier at the previous IEA Annex I Hydrogen Workshop (Juelich, West Germany, September 23-25, 1981), and a brief update will be given here. Some basic research has also been underway at LLNL on the electrolysis of water from fused phosphate salts, but there are no current results in that area, and the work is being terminated

  8. Purification of alkali metal nitrates

    Science.gov (United States)

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  9. Nitrate in drinking water

    DEFF Research Database (Denmark)

    Schullehner, Jörg

    is highly decentralized and fully relying on simple treated groundwater. At the same time, Denmark has an intensive agriculture, making groundwater resources prone to nitrate pollution. Drinking water quality data covering the entire country for over 35 years are registered in the public database Jupiter......Annual nationwide exposure maps for nitrate in drinking water in Denmark from the 1970s until today will be presented based on the findings in Schullehner & Hansen (2014) and additional work on addressing the issue of private well users and estimating missing data. Drinking water supply in Denmark....... In order to create annual maps of drinking water quality, these data had to be linked to 2,852 water supply areas, which were for the first time digitized, collected in one dataset and connected to the Jupiter database. Analyses of the drinking water quality maps showed that public water supplies...

  10. Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles; Revision Bibliografica sobre la Produccion de Hidrogeno Solar Mediante Ciclos Termoquimicos

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Saavedra, R.

    2008-08-06

    This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly y described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs.

  11. Bibliographic Review about Solar Hydrogen Production Through Thermochemical Cycles; Revision Bibliografica sobre la Produccion de Hidrogeno Solar Mediante Ciclos Termoquimicos

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Saavedra, R.

    2007-12-28

    This report presents a summary of the different thermical processes used to obtain hydrogen through solar energy, paying more attention to the production of hydrogen from water through thermochemical cycles. In this aspect, it is briefly described the most interesting thermochemical cycles, focusing on thermochemical cycles based on oxides. (Author) 25 refs.

  12. Modeling of Thermochemical Behavior in an Industrial-Scale Rotary Hearth Furnace for Metallurgical Dust Recycling

    Science.gov (United States)

    Wu, Yu-Liang; Jiang, Ze-Yi; Zhang, Xin-Xin; Xue, Qing-Guo; Yu, Ai-Bing; Shen, Yan-Song

    2017-10-01

    Metallurgical dusts can be recycled through direct reduction in rotary hearth furnaces (RHFs) via addition into carbon-based composite pellets. While iron in the dust is recycled, several heavy and alkali metal elements harmful for blast furnace operation, including Zn, Pb, K, and Na, can also be separated and then recycled. However, there is a lack of understanding on thermochemical behavior related to direct reduction in an industrial-scale RHF, especially removal behavior of Zn, Pb, K, and Na, leading to technical issues in industrial practice. In this work, an integrated model of the direct reduction process in an industrial-scale RHF is described. The integrated model includes three mathematical submodels and one physical model, specifically, a three-dimensional (3-D) CFD model of gas flow and heat transfer in an RHF chamber, a one-dimensional (1-D) CFD model of direct reduction inside a pellet, an energy/mass equilibrium model, and a reduction physical experiment using a Si-Mo furnace. The model is validated by comparing the simulation results with measurements in terms of furnace temperature, furnace pressure, and pellet indexes. The model is then used for describing in-furnace phenomena and pellet behavior in terms of heat transfer, direct reduction, and removal of a range of heavy and alkali metal elements under industrial-scale RHF conditions. The results show that the furnace temperature in the preheating section should be kept at a higher level in an industrial-scale RHF compared with that in a pilot-scale RHF. The removal rates of heavy and alkali metal elements inside the composite pellet are all faster than iron metallization, specifically in the order of Pb, Zn, K, and Na.

  13. Impact of ammonium nitrate and sodium nitrate on tadpoles of Alytes obstetricans.

    Science.gov (United States)

    Garriga, Núria; Montori, A; Llorente, G A

    2017-07-01

    The presence of pesticides, herbicides and fertilisers negatively affect aquatic communities in general, and particularly amphibians in their larval phase, even though sensitivity to pollutants is highly variable among species. The Llobregat Delta (Barcelona, Spain) has experienced a decline of amphibian populations, possibly related to the reduction in water quality due to the high levels of farming activity, but also to habitat loss and alteration. We studied the effects of increasing ammonium nitrate and sodium nitrate levels on the survival and growth rate of Alytes obstetricans tadpoles under experimental conditions. We exposed larvae to increasing concentrations of nitrate and ammonium for 14 days and then exposed them to water without pollutants for a further 14 days. Only the higher concentrations of ammonium (>33.75 mg/L) caused larval mortality. The growth rate of larvae was reduced at ≥22.5 mg/L NH 4 + , although individuals recovered and even increased their growth rate once exposure to the pollutant ended. The effect of nitrate on growth rate was detected at ≥80 mg/L concentrations, and the growth rate reduction in tadpoles was even observed during the post-exposure phase. The concentrations of ammonium with adverse effects on larvae are within the range levels found in the study area, while the nitrate concentrations with some adverse effect are close to the upper range limit of current concentrations in the study area. Therefore, only the presence of ammonium in the study area is likely to be considered of concern for the population of this species, even though the presence of nitrate could cause some sublethal effects. These negative effects could have an impact on population dynamics, which in this species is highly sensitive to larval mortality due to its small clutch size and prolonged larval period compared to other anuran amphibians.

  14. Nitrates and nitrites intoxications’ management

    Directory of Open Access Journals (Sweden)

    Alexandra Trif

    2007-12-01

    Full Text Available The study pointed out the major sources for clinical and subclinical intoxications with nitrates/nitrites (drinking water and nitrates containing fertilizers, circumstances that determine fertilizers to became sources of intoxication (excessive fertilization/consecutive high level of nitrates in fodders, free access of animals to the fertilizers, administration into the diet instead of natrium chloride, factors that determine high nitrates accumulation in fodders despite optimal fertilization (factors related to the plants, soil, clime, harvest methods, storage, agrotechnical measures, nitrates/nitrites toxicity (over 45 ppm nitrates in drinking water, over 0.5 g nitrate/100 g D.M fodder/diet, the factors that influence nitrates/nitrites toxicity ( species, age, rate of feeding, diet balance especially energetically, pathological effects and symptoms (irritation and congestions on digestive tract, resulting diarrhoea, transformation of hemoglobin into methemoglobin determining severe respiratory insufficiency, vascular collapse, low blood pressure inthe acute nitrates intoxication; hypotiroidism, hypovitaminosis A, reproductive disturbances(abortion, low rate of fertility, dead born offspring, diarrhoea and/or respiratory insufficiency in new born e.g. calves, immunosuppression, decrease of milk production in chronic intoxication. There were presented some suggestions concerning management practices to limit nitrate intoxication (analyze of nitrates/nitrites in water and fodders, good management of the situation of risk ,e .g. dilution of the diet with low nitrate content fodders, feeding with balanced diet in energy, protein, minerals and vitamins, accommodation to high nitrate level diet, avoid grazing one week after a frost period, avoid feeding chop green fodders stored a couple of days, monitoring of health status of animals fed with fodders containing nitrates at risk level, a.o..

  15. Electrochemical determination of nitrate with nitrate reductase-immobilized electrodes under ambient air.

    Science.gov (United States)

    Quan, De; Shim, Jun Ho; Kim, Jong Dae; Park, Hyung Soo; Cha, Geun Sig; Nam, Hakhyun

    2005-07-15

    Nitrate monitoring biosensors were prepared by immobilizing nitrate reductase derived from yeast on a glassy carbon electrode (GCE, d = 3 mm) or screen-printed carbon paste electrode (SPCE, d = 3 mm) using a polymer (poly(vinyl alcohol)) entrapment method. The sensor could directly determine the nitrate in an unpurged aqueous solution with the aid of an appropriate oxygen scavenger: the nitrate reduction reaction driven by the enzyme and an electron-transfer mediator, methyl viologen, at -0.85 V (GCE vs Ag/AgCl) or at -0.90 V (SPCE vs Ag/AgCl) exhibited no oxygen interference in a sulfite-added solution. The electroanalytical properties of optimized biosensors were measured: the sensitivity, linear response range, and detection limit of the sensors based on GCE were 7.3 nA/microM, 15-300 microM (r2 = 0.995), and 4.1 microM (S/N = 3), respectively, and those of SPCE were 5.5 nA/microM, 15-250 microM (r2 = 0.996), and 5.5 microM (S/N = 3), respectively. The disposable SPCE-based biosensor with a built-in well- or capillary-type sample cell provided high sensor-to-sensor reproducibility (RSD sensor system was demonstrated by determining nitrate in real samples.

  16. Effects of continuous addition of nitrate to a thermophilic anaerobic digestion system

    International Nuclear Information System (INIS)

    Rivard, C.J.

    1983-01-01

    The biodegradation of complex organic matter is regulated partially by the ability to dump electrons which build up in the form of reduced nicotinamide adenine dinucleotide (NAD). The effects of the continuous addition of the oxidant, nitrate, were investigated on a single-stage, thermophilic, anaerobic digester. The digester acclimated rapidly to nitrate addition. The continuous addition of nitrate resulted in a constant inhibition of total gas (30%) and methane production (36%). Reduction in total gas and methane production was accompanied by increases in sludge pH and acetate, propionate, and ammonium ion pools. Effluent particle size distribution revealed a shift to smaller particle sizes in the nitrate-pumped sludge. The continuous addition of nitrate resulted in lower numbers of methanogens and sulfate reducers in the sludge, with increases in nitrate-reducing and cellulose-degrading microorganisms. These findings indicate that added nitrate underwent dissimilatory reduction to ammonium ion, as determined from gas analysis, ammonium pools, and 15 N-nitrate-label experiments. Continuous nitrate addition to a single-phase digestion system was determined to inhibit methane production from biomass and wastes. Thus for the single-stage digestion system in which maximum methane production is desired, the addition of nitrate is not recommended. However, in a multistage digestion system, the continuous addition of nitrate in the primary stage to increase the rate and extent of degradation of organic matter to volatile fatty acids, which then would serve as feed to a second stage, may be advantageous

  17. Post-anthesis nitrate uptake is critical to yield and grain protein content in Sorghum bicolor.

    Science.gov (United States)

    Worland, Belinda; Robinson, Nicole; Jordan, David; Schmidt, Susanne; Godwin, Ian

    2017-09-01

    Crops only use ∼50% of applied nitrogen (N) fertilizer creating N losses and pollution. Plants need to efficiently uptake and utilize N to meet growing global food demands. Here we investigate how the supply and timing of nitrate affects N status and yield in Sorghum bicolor (sorghum). Sorghum was grown in pots with either 10mM (High) or 1mM (Low) nitrate supply. Shortly before anthesis the nitrate supply was either maintained, increased 10-fold or eliminated. Leaf sheaths of sorghum grown with High nitrate accumulated nitrate in concentrations >3-times higher than leaves. Removal of nitrate supply pre-anthesis resulted in the rapid reduction of stored nitrate in all organs. Plants receiving a 10-fold increase in nitrate supply pre-anthesis achieved similar grain yield and protein content and 29% larger grains than those maintained on High nitrate, despite receiving 24% less nitrate over the whole growth period. In sorghum, plant available N is important throughout development, particularly anthesis and grain filling, for grain yield and grain protein content. Nitrate accumulation in leaf sheaths presents opportunities for the genetic analysis of mechanisms behind nitrate storage and remobilization in sorghum to improve N use efficiency. Copyright © 2017 Elsevier GmbH. All rights reserved.

  18. Thermochemical conversion of microalgal biomass into biofuels: a review.

    Science.gov (United States)

    Chen, Wei-Hsin; Lin, Bo-Jhih; Huang, Ming-Yueh; Chang, Jo-Shu

    2015-05-01

    Following first-generation and second-generation biofuels produced from food and non-food crops, respectively, algal biomass has become an important feedstock for the production of third-generation biofuels. Microalgal biomass is characterized by rapid growth and high carbon fixing efficiency when they grow. On account of potential of mass production and greenhouse gas uptake, microalgae are promising feedstocks for biofuels development. Thermochemical conversion is an effective process for biofuel production from biomass. The technology mainly includes torrefaction, liquefaction, pyrolysis, and gasification. Through these conversion technologies, solid, liquid, and gaseous biofuels are produced from microalgae for heat and power generation. The liquid bio-oils can further be upgraded for chemicals, while the synthesis gas can be synthesized into liquid fuels. This paper aims to provide a state-of-the-art review of the thermochemical conversion technologies of microalgal biomass into fuels. Detailed conversion processes and their outcome are also addressed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Energy balance calculations and assessment of two thermochemical sulfur cycles

    International Nuclear Information System (INIS)

    Leger, D.; Lessart, P.; Manaud, J.P.; Benizri, R.; Courvoisier, P.

    1978-01-01

    Thermochemical cyclic processes which include the highly endothermal decomposition of sulphuric acid are promising for hydrogen production by water-splitting. Our study is directed toward two cycles of this family, each involving the formation and decomposition of sulphuric acid and including other reactions using iron sulphide for the first and oxides and bromides of copper and magnesium for the second. Thermochemical analyses of the two cycles are undertaken. Thermodynamic studies of the reactions are carried out, taking into account possible side-reactions. The concentration of reactants, products and by-products resulting from simultaneous equilibria are calculated, the problems of separation thoroughly studied and the flow-diagrams of the processes drawn up. Using as heat source the helium leaving a 3000 MWth high temperature nuclear reactor and organizing internal heat exchange the enthalpy diagrams are drawn up and the net energy balances evaluated. The overall thermal efficiencies are about 28%, a value corresponding to non-optimized process schemes. Possible improvements aiming at energy-saving and increased efficiency are indicated

  20. Thermo-Chemical Conversion of Microwave Activated Biomass Mixtures

    Science.gov (United States)

    Barmina, I.; Kolmickovs, A.; Valdmanis, R.; Vostrikovs, S.; Zake, M.

    2018-05-01

    Thermo-chemical conversion of microwave activated wheat straw mixtures with wood or peat pellets is studied experimentally with the aim to provide more effective application of wheat straw for heat energy production. Microwave pre-processing of straw pellets is used to provide a partial decomposition of the main constituents of straw and to activate the thermo-chemical conversion of wheat straw mixtures with wood or peat pellets. The experimental study includes complex measurements of the elemental composition of biomass pellets (wheat straw, wood, peat), DTG analysis of their thermal degradation, FTIR analysis of the composition of combustible volatiles entering the combustor, the flame temperature, the heat output of the device and composition of the products by comparing these characteristics for mixtures with unprocessed and mw pre-treated straw pellets. The results of experimental study confirm that mw pre-processing of straw activates the thermal decomposition of mixtures providing enhanced formation of combustible volatiles. This leads to improvement of the combustion conditions in the flame reaction zone, completing thus the combustion of volatiles, increasing the flame temperature, the heat output from the device, the produced heat energy per mass of burned mixture and decreasing at the same time the mass fraction of unburned volatiles in the products.

  1. Effect of nitrate, acetate and hydrogen on native perchlorate-reducing microbial communities and their activity in vadose soil

    Science.gov (United States)

    Nozawa-Inoue, Mamie; Jien, Mercy; Yang, Kun; Rolston, Dennis E.; Hristova, Krassimira R.; Scow, Kate M.

    2011-01-01

    Effect of nitrate, acetate and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared to unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the acetate concentration which was inhibitory to the native PRB. In hydrogen-amended and unamended soils, perchlorate reductase gene (pcrA) copies, representing PRB densities, increased with either perchlorate or nitrate reduction, suggesting either perchlorate or nitrate stimulates growth of the PRB. In contrast, in acetate-amended soil pcrA increased only when perchlorate was depleted: a large portion of the PRB may have not utilized nitrate in this amendment. Nitrate addition did not alter the distribution of the dominant pcrA clones in hydrogen-amended soil, likely because of the functional redundancy of PRB as nitrate-reducers/denitrifiers, whereas acetate selected different pcrA clones from those with hydrogen amendment. PMID:21284679

  2. Towards the renewal of the NEA Thermochemical Database

    International Nuclear Information System (INIS)

    Ragoussi, Maria-Eleni; Costa, Davide; Bossant, Manuel

    2015-01-01

    The Thermochemical Database (TDB) Project was created three decades ago as a joint undertaking of the NEA Radioactive Waste Management Committee and the NEA Data Bank. The project involves the collection of high-quality and traceable thermochemical data for a set of elements (mainly minor actinides and fission products) relevant to geophysical modelling of deep geological repositories. Funding comes from 15 participating organisations, primarily national nuclear waste authorities and research institutions. The quantities that are stored in the TDB database are: the standard molar Gibbs energy and enthalpy of formation, the standard molar entropy and, when available, the heat capacity at constant pressure, together with their uncertainty intervals. Reaction data are also provided: equilibrium constant of reaction, molar Gibbs energy of reaction, molar enthalpy of reaction and molar entropy of reaction. Data assessment is carried out by teams of expert reviewers through an in-depth analysis of the available scientific literature, following strict guidelines defined by the NEA to ensure the accuracy and self-consistency of the adopted datasets. Thermochemical data that has been evaluated and selected over the years have been published in the 13 volumes of the Chemical Thermodynamics series. They are also stored in a database that is updated each time the study of a new element is completed. The TDB selected data are made available to external third parties through the NEA web site where data extracted from the database can be displayed and downloaded as plain text files. Following recent recommendations of the Task Force on the Future Programme of the NEA Data Bank to enhance scientific expertise and user services, a renewal of the software managing the TDB database is being undertaken. The software currently used was designed 20 years ago and is becoming obsolete. Redesigning the application will provide an opportunity to correct current shortcomings and to develop

  3. Laboratory investigation of microbiologically influenced corrosion of C1018 carbon steel by nitrate reducing bacterium Bacillus licheniformis

    International Nuclear Information System (INIS)

    Xu, Dake; Li, Yingchao; Song, Fengmei; Gu, Tingyue

    2013-01-01

    Nitrate injection is used to suppress reservoir souring in oil and gas fields caused by Sulfate Reducing Bacteria (SRB) through promotion of nitrate respiration by Nitrate Reducing Bacteria (NRB). However, it is not well publicized that nitrate reduction by NRB can cause Microbiologically Influenced Corrosion (MIC) because nitrate reduction coupled with iron oxidation is thermodynamically favorable. NRB benefits bioenergetically from this redox reaction under biocatalysis. This work showed that the Bacillus licheniformis biofilm, when grown as an NRB biofilm, caused a 14.5 μm maximum pit depth and 0.89 mg/cm 2 normalized weight loss against C1018 carbon steel in one-week lab tests

  4. Disguised as a sulfate reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate

    DEFF Research Database (Denmark)

    Thorup, Casper; Schramm, Andreas; Findlay, Alyssa Jean Lehsau

    2017-01-01

    This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D...... of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane......-anchored nitrite reductase....

  5. Holistic analysis of thermochemical processes by using solid biomass for fuel production in Germany; Ganzheitliche Analyse thermochemischer Verfahren bei der Nutzung fester Biomasse zur Kraftstoffproduktion in Deutschland

    Energy Technology Data Exchange (ETDEWEB)

    Henssler, Martin

    2015-04-28

    According to the German act ''Biokraftstoff-Nachhaltigkeitsverordnung'', biofuels must show a CO{sub 2eq}-reduction compared to the fossil reference fuel (83.8 g CO{sub 2eq}/MJ{sub fuel} /Richtlinie 98/70/EG/) of 35 % beginning with 2011. In new plants, which go into operation after the 31.12.2016 the CO{sub 2eq}-savings must be higher than 50 % in 2017 and higher than 60 % in 2018 /Biokraft-NachV/. The biofuels (methyl ester of rapeseed, bioethanol and biomethane) considered in this study do not meet these requirements for new plants. To comply with these rules new processes must be deployed. Alternative thermochemical generated fuels could be an option. The aim of this work is to evaluate through a technical, ecological and economic analysis (Well-to-Wheel) whether and under what conditions the thermochemical production of Fischer-Tropsch-diesel or -gasoline, hydrogen (H{sub 2}) and Substitute Natural Gas (SNG) complies with the targets. Four different processes are considered (fast pyrolysis and torrefaction with entrained flow gasifier, CHOREN Carbo-V {sup registered} -gasifier, Absorption Enhanced Reforming (AER-) gasifier). Beside residues such as winter wheat straw and residual forest wood, wood from short-rotation plantations is taken into account. The technical analysis showed that at present status (2010) two and in 2050 six plants can be operated energy-self-sufficient. The overall efficiency of the processes is in the range of 41.5 (Fischer-Tropsch-diesel or -gasoline) and 59.4 % (H{sub 2}). Furthermore, it was found that for 2010, all thermochemical produced fuels except the H{sub 2}-production from wood from short-rotation plantations in decentralised or central fast pyrolysis and in decentralised torrefactions with entrained flow gasifier keep the required CO{sub 2eq}-saving of 60 %. In 2050, all thermochemical produced fuels will reach these limits. The CO{sub 2eq}-saving is between 72 (H{sub 2}) and 95 % (Fischer

  6. Generation of H2 and CO by solar thermochemical splitting of H2O and CO2 by employing metal oxides

    International Nuclear Information System (INIS)

    Rao, C.N.R.; Dey, Sunita

    2016-01-01

    Generation of H 2 and CO by splitting H 2 O and CO 2 respectively constitutes an important aspect of the present-day concerns with energy and environment. The solar thermochemical route making use of metal oxides is a viable means of accomplishing these reduction reactions. The method essentially involves reducing a metal oxide by heating and passing H 2 O or CO 2 over the nonstoichiometric oxide to cause reverse oxidation by abstracting oxygen from H 2 O or CO 2 . While ceria, perovskites and other oxides have been investigated for this purpose, recent studies have demonstrated the superior performance of perovskites of the type Ln 1−x A x Mn 1−y M y O 3 (Ln=rare earth, A=alkaline earth, M=various +2 and +3 metal ions), in the thermochemical generation of H 2 and CO. We present the important results obtained hitherto to point out how the alkaine earth and the Ln ions, specially the radius of the latter, determine the performance of the perovskites. The encouraging results obtained are exemplefied by Y 0.5 Sr 0.5 MnO 3 which releases 483 µmol/g of O 2 at 1673 K and produces 757 µmol/g of CO from CO 2 at 1173 K. The production of H 2 from H 2 O is also quite appreciable. Modification of the B site ion of the perovskite also affects the performance. In addition to perovskites, we present the generation of H 2 based on the Mn 3 O 4 /NaMnO 2 cycle briefly. - Graphical abstract: Ln 0.5 A 0.5 Mn 1−x M x O 3 (Ln=lanthanide; A=Ca, Sr; M=Al, Ga, Sc, Mg, Cr, Fe, Co) perovskites are employed for the two step thermochemical splitting of CO 2 and H 2 O for the generation of CO and H 2 . - Highlights: • Perovskite oxides based on Mn are ideal for the two-step thermochemical splitting of CO 2 and H 2 O. • In Ln 1−x A x MnO 3 perovskite (Ln=rare earth, A=alkaline earth) both Ln and A ions play major roles in the thermochemical process. • H 2 O splitting is also achieved by the use of the Mn 3 O 4 -sodium carbonate system. • Thermochemical splitting of CO 2 and H

  7. Lanthanum (samarium) nitrate-4-aminoantipyrine nitrate-water systems

    International Nuclear Information System (INIS)

    Starikova, L.I.; Zhuravlev, E.F.

    1985-01-01

    Using the isothermal method of cross-sections at 50 deg C systems lanthanum nitrate-4-aminoantipyrine nitrate-water (1), samarium nitrate-4-aminoantipyrine nitrate-water (2), are studied. Isotherms of system 1 consist of two crystallization branches of initial salt components. In system 2 formation of congruently soluble compounds of the composition Sm(No) 3 ) 3 xC 11 H 13 ON 3 xHNO 3 is established. Analytical, X-ray phase and thermogravimetric analysis of the isolated binary salt are carried out

  8. Nitrate biosensors and biological methods for nitrate determination.

    Science.gov (United States)

    Sohail, Manzar; Adeloju, Samuel B

    2016-06-01

    The inorganic nitrate (NO3‾) anion is present under a variety of both natural and artificial environmental conditions. Nitrate is ubiquitous within the environment, food, industrial and physiological systems and is mostly present as hydrated anion of a corresponding dissolved salt. Due to the significant environmental and toxicological effects of nitrate, its determination and monitoring in environmental and industrial waters are often necessary. A wide range of analytical techniques are available for nitrate determination in various sample matrices. This review discusses biosensors available for nitrate determination using the enzyme nitrate reductase (NaR). We conclude that nitrate determination using biosensors is an excellent non-toxic alternative to all other available analytical methods. Over the last fifteen years biosensing technology for nitrate analysis has progressed very well, however, there is a need to expedite the development of nitrate biosensors as a suitable alternative to non-enzymatic techniques through the use of different polymers, nanostructures, mediators and strategies to overcome oxygen interference. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Determination of Nitrate Reductase Assay Depending on the Microbial Growth

    International Nuclear Information System (INIS)

    El-Kabbany, H.M.

    2012-01-01

    A rapid micro-dilution assay for determination of the antimicrobial susceptibility of different bacterial isolates was developed. This assay is based on the ability of the most of viable organisms to reduce nitrates. The MIC or MBC could be determined by nitrate reductase (NR) only after 30 to 90 min of incubation depending on the behaviour of microbial growth. Bacterial viability is detected by a positive nitrite reduction rather than visible turbidity. The nitrate reduction assay was compared with standard micro-assay using 250 isolates of different taxa against 10 antibiotics belonging to different classes. An excellent agreement of 82.5 % was found between the two methods and only 17.5 % of 1794 trials showed difference in the determined MIC by tow-dilution interval above or below the MIC determined by the turbidimetric method under the same test conditions. However, the nitrate reduction assay was more rapid and sensitive in detecting viable bacteria and so, established an accurate estimate of the minimal inhibitory concentration (MIC) or the minimal bacterial concentration (MBC). The nitrate reduction assay offers the additional advantage that it could be used to determine the MBC without having to subculture the broth. 232 cases of resistance were detected by NR and 4 different media were tested for susceptibility test. The bacterial isolates were exposed to ultra violet (UV) light for different period

  10. Electrolytic treatment of liquid waste containing ammonium nitrate

    International Nuclear Information System (INIS)

    Komori, R.; Ogawa, N.; Ohtsuka, K.; Ohuchi, J.

    1981-01-01

    A study was made on the safe decomposition of ammonium nitrate, which is the main component of α-liquid waste from plutonium fuel facilities, by means of electrolytic reduction and thermal decomposition. In the first stage, ammonium nitrate is reduced to ammonium nitrite by electrolytic reduction using an electrolyser with a cation exchange membrane as a diaphragm. In the second stage, ammonium nitrite is decomposed to N 2 and H 2 O. The alkaline region and a low temperature are preferable for electrolytic reduction and the acidic region and high temperature for thermal decomposition. A basis was established for an ammonium nitrate treatment system in aqueous solution through the operation of a bench-scale unit, and the operating data obtained was applied to the basic design of a 10-m 3 /a facility. (author)

  11. Nitrate in groundwater of the United States, 1991-2003

    Science.gov (United States)

    Burow, Karen R.; Nolan, Bernard T.; Rupert, Michael G.; Dubrovsky, Neil M.

    2010-01-01

    An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program. The well networks reflect the existing used resource represented by domestic wells in major aquifers (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations were highest in shallow groundwater beneath agricultural land use in areas with well-drained soils and oxic geochemical conditions. Nitrate concentrations were lowest in deep groundwater where groundwater is reduced, or where groundwater is older and hence concentrations reflect historically low N application rates. Classification and regression tree analysis was used to identify the relative importance of N inputs, biogeochemical processes, and physical aquifer properties in explaining nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm N fertilizer inputs, percent well-drained soils, and dissolved oxygen. Overall, nitrate concentrations in groundwater are most significantly affected by redox conditions, followed by nonpoint-source N inputs. Other water-quality indicators and physical variables had a secondary influence on nitrate concentrations.

  12. Metallothermic reduction of molybdate

    International Nuclear Information System (INIS)

    Mukherjee, T.K.; Bose, D.K.

    1987-01-01

    This paper gives a brief account of the investigations conducted so far on metallothermic reduction of high grade molybdenite with particular emphasis on the work carried out in Bhabha Atomic Research Centre. Based on thermochemical considerations, the paper first introduces a number of metallic reductants suitable for use in metallothermic reduction of molybdenite. Aluminium, sodium and tin are found to be suitable reducing agents and very rightly they have found most applications in the research and development efforts on metallothermic reduction of molybdenite. The reduction with tin was conducted on fairly large scale both in vacuum and hydrogen atmosphere. The reaction was reported to be invariant depending mainly on the reduction temperature and a temperature of the order of 1250deg to 1300degC was required for good metal recovery. In comparison to tin, aluminothermic reduction of molybdenite was studied more extensively and it was conducted in closed bomb, vacuum and also in open atmosphere. In aluminothermic reduction, the influence of amount of reducing agent, amount of heat booster, preheating temperature and charging procedure on these metal yield was studied in detail. The reduction generally yielded massive molybdenum metal contaminated with aluminium as the major impurity element. Efforts were made to purify the reduced metal by arc melting, electron beam melting and molten salt electrorefining. 9 refs. (author)

  13. Effect of the method to prepare platinum-based nanoparticles versus electro-reduction of nitrates and proton adsorption; Efecto de la ruta de preparacion de nanoparticulas basadas en platino versus la electro-reduccion de nitratos y la adsorcion de protones

    Energy Technology Data Exchange (ETDEWEB)

    Estudillo-Wong, L.A.; Torres-Santillan, E.; Arce-Estrada, E.M.; J.R. Vargas-Garcia [Escuela Superior de Ingenieria Quimica e Industrias Extractivas (ESIQIE), IPN, Mexico D.F. (Mexico)]. E-mail: amanzor@ipn.mx; Alonso-Vante, N. [Universite de Poitiers, Poitiers (France); Manzo-Robledo, A. [Escuela Superior de Ingenieria Quimica e Industrias Extractivas (ESIQIE), IPN, Mexico D.F. (Mexico)

    2009-09-15

    The electro-reduction of nitrate ions (ERN) was carried out in an alkaline medium on platinum-tin nanoparticles, synthesized with metal organic chemical vapor deposition (MOCVD) and carbonyl complex route (CCR) and supported on carbon nanotubes (CNT) and Vulcan carbon. These catalysts were deposited on 4.0 mm diameter vitreous carbon. Cyclic voltametry was used to evaluate this reduction reaction. Different current magnitudes for hydrogen evolution reaction (HER) and ERN were found. Nevertheless, the proton and ion nitrate adsorption processes on the surface of the catalysts evaluated presented a potential range of -0.7 to -1.0V/SCE, indicating that the reaction mechanism is similar. Studies of nitrate concentrations indicate that the magnitude of the reduction current decreases and, in addition, different magnitudes are presented according to the catalyst/substrate used. These variations are explained by local disorder, due to the nature of the substrate, and the size of the nanoparticles resulting from the preparation method. Indirectly, the kinetic parameters calculated enable clarifying these suppositions. [Spanish] La electro-reduccion de iones nitrato (NER) sobre nano-particulas de platino-(estano) sintetizadas via MOCVD (metal organic chemical vapor deposition) y via carbonilo (carbonyl complex route, CCR) soportadas sobre nano-tubos de carbon (NTC) y carbon Vulcan (C), fue llevada a cabo en medio alcalino. Estos catalizadores fueron depositados sobre carbon vitreo de 4.0mm de diametro. La tecnica de voltametria ciclica fue utilizada para evaluar dicha reaccion de reduccion. Diferentes magnitudes de corriente versus la reaccion de evolucion de hidrogeno (HER) y la NER fueron encontradas. Sin embargo, los procesos de adsorcion de protones e iones nitrato en la superficie de los catalizadores evaluados se presentan en un intervalo de potencial de -0.7 a -1.0V/SCE, indicando que el mecanismo de reaccion es similar. Estudios en funcion de la concentracion de

  14. Balance and saving of GHG emissions in thermochemical biorefineries

    International Nuclear Information System (INIS)

    Haro, Pedro; Aracil, Cristina; Vidal-Barrero, Fernando; Ollero, Pedro

    2015-01-01

    Highlights: • A simplified methodology for the balance and saving of GHG emissions is provided. • The GHG balance has a physical meaning and does not depend on the fossil reference. • The GHG saving depends on regulation of energy carriers. • The impact of Bio-CCS incorporation and multiproduction is analyzed. • The co-production of chemicals needs to be included in future regulation. - Abstract: In this study, a simplified methodology for the calculation of the balance of greenhouse gas (GHG) emissions and corresponding saving compared with the fossil reference is presented. The proposed methodology allows the estimation of the anthropogenic GHG emissions of thermochemical biorefineries (net emitted to the atmosphere). In the calculation of the GHG balance, all relevant factors have been identified and analyzed including multiproduction, emissions from biogenic carbon capture and storage (Bio-CCS), co-feeding of fossil fuels (secondary feedstock) and possible carbon storage in biomass-derived products (chemicals). Therefore, it is possible to calculate the balance of GHG emissions of a hypothetical thermochemical biorefinery considering different alternatives of land-use, biomass feedstock, co-feeding of fossil fuels, Bio-CCS incorporation and final use of the products. The comparison of the estimated GHG balance with the corresponding fossil reference for each product is of special relevance in the methodology since it is the parameter used in European regulation for the fulfillment of sustainability criteria in biomass-derived fuels and liquids. The proposed methodology is tested using a previously assessed set of different process concepts of thermochemical biorefineries (techno-economic analysis). The resulting GHG balance and saving are analyzed to identify uncertainties and provide recommendations for future regulation. In all process concepts, the GHG savings are above the minimum requirement of GHG emissions for 2018. In the case of incorporating

  15. Transformation of Nitrate and Toluene in Groundwater by Sulfur Modified Iron(SMI-III)

    Science.gov (United States)

    Lee, W.; Park, S.; Lim, J.; Hong, U.; Kwon, S.; Kim, Y.

    2009-12-01

    In Korea, nitrate and benzene, toluene, ethylbenzene, and xylene isomers (BTEX) are frequently detected together as ground water contaminants. Therefore, a system simultaneously treating both nitrate (inorganic compound) and BTEX (organic compounds) is required to utilize groundwater as a water resource. In this study, we investigated the efficiency of Sulfur Modified Iron (SMI-III) in treating both nitrate and BTEX contaminated groundwater. Based on XRD (X-Ray Diffraction) analysis, the SMI-III is mainly composed of Fe3O4, S, and Fe. A series of column tests were conducted at three different empty bed contact times (EBCTs) for each compound. During the experiments, removal efficiency for both nitrate and toluene were linearly correlated with EBCT, suggesting that SMI-III have an ability to transform both nitrate and toluene. The concentration of SO42- and oxidation/reduction potential (ORP) were also measured. After exposed to nitrate contaminated groundwater, the composition of SMI-III was changed to Fe2O3, Fe3O4, Fe, and Fe0.95S1.05. The trends of effluent sulfate concentrations were inversely correlated with effluent nitrate concentrations, while the trends of ORP values, having the minimum values of -480 mV, were highly correlated with effluent nitrate concentrations. XRD analysis before and after exposed to nitrate contaminated groundwater, sulfate production, and nitrite detection as a reductive transformation by-product of nitrate suggest that nitrate is reductively transformed by SMI-III. Interestingly, in the toluene experiments, the trends of ORP values were inversely correlated with effluent toluene concentrations, suggesting that probably degrade through oxidation reaction. Consequently, nitrate and toluene probably degrade through reduction and oxidation reaction, respectively and SMI-III could serve as both electron donor and acceptor.

  16. dl-Asparaginium nitrate

    Science.gov (United States)

    Moussa Slimane, Nabila; Cherouana, Aouatef; Bendjeddou, Lamia; Dahaoui, Slimane; Lecomte, Claude

    2009-01-01

    In the title compound, C4H9N2O3 +·NO3 −, alternatively called (1RS)-2-carbamoyl-1-carboxy­ethanaminium nitrate, the asymmetric unit comprises one asparaginium cation and one nitrate anion. The strongest cation–cation O—H⋯O hydrogen bond in the structure, together with other strong cation–cation N—H⋯O hydrogen bonds, generates a succession of infinite chains of R 2 2(8) rings along the b axis. Additional cation–cation C—H⋯O hydrogen bonds link these chains into two-dimensional layers formed by alternating R 4 4(24) and R 4 2(12) rings. Connections between these layers are provided by the strong cation–anion N—H⋯O hydrogen bonds, as well as by one weak C—H⋯O inter­action, thus forming a three-dimensional network. Some of the cation–anion N—H⋯O hydrogen bonds are bifurcated of the type D—H⋯(A 1,A 2). PMID:21577586

  17. Food sources of nitrates and nitrites: the physiologic context for potential health benefits.

    Science.gov (United States)

    Hord, Norman G; Tang, Yaoping; Bryan, Nathan S

    2009-07-01

    The presence of nitrates and nitrites in food is associated with an increased risk of gastrointestinal cancer and, in infants, methemoglobinemia. Despite the physiologic roles for nitrate and nitrite in vascular and immune function, consideration of food sources of nitrates and nitrites as healthful dietary components has received little attention. Approximately 80% of dietary nitrates are derived from vegetable consumption; sources of nitrites include vegetables, fruit, and processed meats. Nitrites are produced endogenously through the oxidation of nitric oxide and through a reduction of nitrate by commensal bacteria in the mouth and gastrointestinal tract. As such, the dietary provision of nitrates and nitrites from vegetables and fruit may contribute to the blood pressure-lowering effects of the Dietary Approaches to Stop Hypertension (DASH) diet. We quantified nitrate and nitrite concentrations by HPLC in a convenience sample of foods. Incorporating these values into 2 hypothetical dietary patterns that emphasize high-nitrate or low-nitrate vegetable and fruit choices based on the DASH diet, we found that nitrate concentrations in these 2 patterns vary from 174 to 1222 mg. The hypothetical high-nitrate DASH diet pattern exceeds the World Health Organization's Acceptable Daily Intake for nitrate by 550% for a 60-kg adult. These data call into question the rationale for recommendations to limit nitrate and nitrite consumption from plant foods; a comprehensive reevaluation of the health effects of food sources of nitrates and nitrites is appropriate. The strength of the evidence linking the consumption of nitrate- and nitrite-containing plant foods to beneficial health effects supports the consideration of these compounds as nutrients.

  18. The ytterbium nitrate-quinoline (piperidine) nitrate-water system

    International Nuclear Information System (INIS)

    Khisaeva, D.A.; Boeva, M.K.; Zhuravlev, E.F.

    1985-01-01

    Using the method of cross sections the solubility of solid phases in the ytterbium nitrate-quinoline nitrate - water (1) and ytterbium nitrate-piperidine nitrate-water (2) systems is studied at 25 and 50 deg C. It is established, that in system 1 congruently melting compound of the composition Yb(NO 3 ) 3 x2C 9 H 7 NxHNO 3 x3H 2 O is formed. The new solid phase has been isolated as a preparation and subjected to chemical X-ray diffraction, differential thermal and IR spectroscopic analyses. Isotherms of system 2 in the studied range of concentrations and temperatures consist of two branches, corresponding to crystallization of tetruaqueous ytterbi um nitrate and nitric acid piperidine

  19. NITRATE DESTRUCTION LITERATURE SURVEY AND EVALUATION CRITERIA

    Energy Technology Data Exchange (ETDEWEB)

    Steimke, J.

    2011-02-01

    literature survey of technologies to perform the nitrate to hydroxide conversion, selection of the most promising technologies, preparation of a flowsheet and design of a system. The most promising technologies are electrochemical reduction of nitrates and chemical reduction with hydrogen or ammonia. The primary reviewed technologies are listed and they aredescribed in more detail later in the report: (1) Electrochemical destruction; (2) Chemical reduction with agents such as ammonia, hydrazine or hydrogen; (3) Hydrothermal reduction process; and (4) Calcination. Only three of the technologies on the list have been demonstrated to generate usable amounts of caustic; electrochemical reduction and chemical reduction with ammonia, hydrazine or hydrogen and hydrothermal reduction. Chemical reduction with an organic reactant such as formic acid generates carbon dioxide which reacts with caustic and is thus counterproductive. Treatment of nitrate with aluminum or other active metals generates a solid product. High temperature calcination has the potential to generate sodium oxide which may be hydrated to sodium hydroxide, but this is unproven. The following criteria were developed to evaluate the most suitable option. The numbers in brackets after the criteria are relative weighting factors to account for importance: (1) Personnel exposure to radiation for installation, routine operation and maintenance; (2) Non-radioactive safety issues; (3) Whether the technology generates caustic and how many moles of caustic are generated per mole of nitrate plus nitrite decomposed; (4) Whether the technology can handle nitrate and nitrite at the concentrations encountered in waste; (5) Maturity of technology; (6) Estimated annual cost of operation (labor, depreciation, materials, utilities); (7) Capital cost; (8) Selectivity to nitrogen as decomposition product (other products are flammable and/or toxic); (9) Impact of introduced species; (10) Selectivity for destruction of nitrate vs

  20. Thermochemical and thermophysical properties of alkaline-earth perovskites

    International Nuclear Information System (INIS)

    Yamanaka, Shinsuke; Kurosaki, Ken; Maekawa, Takuji; Matsuda, Tetsushi; Kobayashi, Shin-ichi; Uno, Masayoshi

    2005-01-01

    In order to contribute to safety evaluation of high burnup oxide fuels, we studied the thermochemical and thermophysical properties of alkaline-earth perovskites known as oxide inclusions. Polycrystalline samples of alkaline-earth perovskites, BaUO 3 , BaZrO 3 , BaCeO 3 , BaMoO 3 , SrTiO 3 , SrZrO 3 , SrCeO 3 , SrMoO 3 , SrHfO 3 and SrRuO 3 , were prepared and the thermal expansion coefficient, melting temperature, elastic moduli, Debye temperature, microhardness, heat capacity, and thermal conductivity were measured. The relationship between some physical properties was studied

  1. The NEA thermochemical database project. 30 years of accomplishments

    International Nuclear Information System (INIS)

    Ragoussi, Maria-Eleni; Brassinnes, Stephane

    2015-01-01

    The NEA Thermochemical Database (TDB) Project (www.oecd-nea.org/dbtdb/) provides a database of chemical thermodynamic values treating the most significant elements related to nuclear waste management. The work carried out since the initiation of TDB in 1984 has resulted in the publication of thirteen major reviews and a large set of selected values that have become an international reference in the field, as they are characterized for their accuracy, consistency and high quality. Herein, we describe the basis, scientific principles and organization of the TDB project, together with its evolution from its inception to the present organization as a joint undertaking under Article 5(b) of the Statute of the OECD Nuclear Energy Agency (NEA).

  2. Hydrogen production from biomass by thermochemical recuperative energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Fushimi, C.; Araki, K.; Yamaguchi, Y.; Tsutsumi, A. [Tokyo Univ. (Japan). Dept. of Chemical System Engineering

    2002-07-01

    The authors conducted, using a thermogravimetric reactor, a kinetic study of production of thermochemical recuperative hydrogen from biomass. The four different biomass materials used were: cellulose, lignin, metroxylon stem, and coconut husk. Under both rapid heating and slow heating conditions, the weight changes of the biomass samples during the steam gasification or pyrolysis were measured at 973 Kelvin. Simultaneously, measurements of the evolution rates of low-molecular-weight gas products such as hydrogen, methane, carbon monoxide, and carbon dioxide were taken with the help of a mass spectrometer and a micro gas chromatograph (GC). The steam gasification of char significantly increased the amount of hydrogen and carbon dioxide production. The results also indicated that at higher heating rate, the cold gas efficiency of steam gasification was increased. This can be explained by the suppression of the tar production at lower temperature. 25 refs., 2 tabs., 10 figs.

  3. Thermochemical heat storage for high temperature applications. A review

    Energy Technology Data Exchange (ETDEWEB)

    Felderhoff, Michael [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany); Urbanczyk, Robert; Peil, Stefan [Institut fuer Energie- und Umwelttechnik e.V. (IUTA), Duisburg (Germany)

    2013-07-01

    Heat storage for high temperature applications can be performed by several heat storage techniques. Very promising heat storage methods are based on thermochemical gas solid reactions. Most known systems are metal oxide/steam (metal hydroxides), carbon dioxide (metal carbonates), and metal/hydrogen (metal hydrides) systems. These heat storage materials posses high gravimetric and volumetric heat storage densities and because of separation of the reaction products and their storage in different locations heat losses can be avoided. The reported volumetric heat storage densities are 615, 1340 and 1513 [ kWh m{sup -3}] for calcium hydroxide Ca(OH){sub 2}, calcium carbonate CaCO{sub 3} and magnesium iron hydride Mg{sub 2}FeH{sub 6} respectively. Additional demands for gas storage decrease the heat storage density, but metal hydride systems can use available hydrogen storage possibilities for example caverns, pipelines and chemical plants. (orig.)

  4. Environmental requirements in thermochemical and biochemical conversion of biomass

    International Nuclear Information System (INIS)

    Frings, R.M.; Mackie, K.L.; Hunter, I.R.

    1992-01-01

    Many biological and thermochemical processing options exist for the conversion of biomass to fuels. Commercially, these options are assessed in terms of fuel product yield and quality. However, attention must also be paid to the environmental aspects of each technology so that any commercial plant can meet the increasingly stringent environmental legislation in the world today. The environmental aspects of biological conversion (biogasification and bioliquefaction) and thermal conversion (high pressure liquefaction, flash pyrolysis, and gasification) are reviewed. Biological conversion processes are likely to generate waste streams which are more treatable than those from thermal conversion processes but the available data for thermal liquefaction are very limited. Close attention to waste minimisation is recommended and processing options that greatly reduce or eliminate waste streams have been identified. Product upgrading and its effect on wastewater quality also requires attention. Emphasis in further research studies needs to be placed on providing authentic waste streams for environmental assessment. (author)

  5. Blanket materials for fusion reactors: comparisons of thermochemical performance

    International Nuclear Information System (INIS)

    Johnson, C.E.; Fischer, A.K.; Tetenbaum, M.

    1984-01-01

    Thermodynamic calculations have been made to predict the thermochemical performance of the fusion reactor breeder materials, Li 2 O, LiAlO 2 , and Li 4 SiO 4 in the temperature range 900 to 1300 0 K and in the oxygen activity range 10 -25 to 10 -5 . Except for a portion of these ranges, the performance of LiAlO 2 is predicted to be better than that of Li 2 O and Li 4 SiO 4 . The protium purge technique for enhancing tritium release is explored for the Li 2 O system; it appears advantageous at higher temperatures but should be used cautiously at lower temperatures. Oxygen activity is an important variable in these systems and must be considered in executing and interpreting measurements on rates of tritium release, the form of released tritium, diffusion of tritiated species and their identities, retention of tritium in the condensed phase, and solubility of hydrogen isotope gases

  6. Thermochemical and thermophysical properties of minor actinide compounds

    International Nuclear Information System (INIS)

    Minato, Kazuo; Takano, Masahide; Otobe, Haruyoshi; Nishi, Tsuyoshi; Akabori, Mitsuo; Arai, Yasuo

    2009-01-01

    Burning or transmutation of minor actinides (MA: Np, Am, Cm) that are classified as the high-level radioactive waste in the current nuclear fuel cycle is an option for the advanced nuclear fuel cycle. Although the thermochemical and thermophysical properties of minor actinide compounds are essential for the design of MA-bearing fuels and analysis of their behavior, the experimental data on minor actinide compounds are limited. To support the research and development of the MA-bearing fuels, the property measurements were carried out on minor actinide nitrides and oxides. The lattice parameters and their thermal expansions were measured by high-temperature X-ray diffractometry. The specific heat capacities were measured by drop calorimetry and the thermal diffusivities by laser-flash method. The thermal conductivities were determined by the specific heat capacities, thermal diffusivities and densities. The oxygen potentials were measured by electromotive force method.

  7. An approach to thermochemical modeling of nuclear waste glass

    International Nuclear Information System (INIS)

    Besmann, T.M.; Beahm, E.C.; Spear, K.E.

    1998-01-01

    This initial work is aimed at developing a basic understanding of the phase equilibria and solid solution behavior of the constituents of waste glass. Current, experimentally determined values are less than desirable since they depend on measurement of the leach rate under non-realistic conditions designed to accelerate processes that occur on a geologic time scale. The often-used assumption that the activity of a species is either unity or equal to the overall concentration of the metal can also yield misleading results. The associate species model, a recent development in thermochemical modeling, will be applied to these systems to more accurately predict chemical activities in such complex systems as waste glasses

  8. Characteristics of thermochemical treated EN10090 X50 steel

    International Nuclear Information System (INIS)

    Schmitz, S.; Graf, K.; Scheid, A.; Moreno, A.

    2014-01-01

    EN10090 X50 steel is commonly used for engine valves to withstand severe operation conditions involving high temperature and corrosion from fuel and combustion gas. Usually, to enhance wear performance, valves undergo nitriding thermochemical treatment by salt baths. The aim of this work is to produce diffusion layers at least 20μm thick with hardness higher than 700HV by plasma surface treatment with no continuous compounds layer using nitrogen and methane based atmospheres. Samples were characterized by laser Confocal and scanning electron microscopy, X-ray diffraction and Vickers hardness. Salt bath treatment induced formation of undesirable compounds layer at the surface and a diffusion layer thicker than 40μm, with hardness arising 1280HV_0_,_0_1_0. Plasma surface treatment produced diffusion layer thicker than 40μm with no continuous compounds layer and mean hardness varying from 750 to 960HV_0_,_0_1_0. (author)

  9. Nagra thermochemical data base. II. Supplement data 05/92

    International Nuclear Information System (INIS)

    Pearson, F.J.; Berner, U.; Hummel, W.

    1992-05-01

    Chemical thermodynamic data for aqueous species, minerals, and gases are required by Nagra for geochemical modelling. The Nagra thermochemical data base contains core and supplemental data. Core data for well-characterised entities were individually carefully selected and given by Pearson and Berner (1991). Supplemental data are for less common entities and for elements principally of safety assessment concern. They were selected in groups from other data bases for geochemical modelling and did not receive individual scrutiny. This report gives tables with the Nagra thermochemical data as of 5/92. It includes the core data described in the earlier report with supplemental data for the elements aluminium, silicon, iron, and manganese, the actinides thorium, uranium, neptunium, plutonium, and americium, and elements found as fission or activation products in nuclear waste, including nickel, zirconium, niobium, molybdenum, technetium, palladium, tin, selenium and iodine. Aqueous complexes of four representative organic anions are also included. The sources of these supplemental data are described in the text. Other compilations of data were examined during the selection on the supplemental data. These included the data bases used at the Paul Scherrer Institut with the geochemical programs MINEQL as of 3/91, PHREEQE as of 4/91, and the HATCHES 3.0 data base. This report also gives tables comparing selected data in these three data bases with values from the Nagra data base. This data base has not yet been tested for a full range of nuclear waste management applications, although such work is in progress. It should thus be regarded as a reference fixed point for quality assurance purpose and not critically reviewed standard. (author) tabs., refs

  10. Estimation of thermochemical behavior of spallation products in mercury target

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Kaoru; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Teshigawara, Makoto; Hino, Ryutaro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2002-02-01

    In order to examine the radiation safety of a spallation mercury target system, especially source term evaluation, it is necessary to clarify the chemical forms of spallation products generated by spallation reaction with proton beam. As for the chemical forms of spallation products in mercury that involves large amounts of spallation products, these forms were estimated by using the binary phase diagrams and the thermochemical equilibrium calculation based on the amounts of spallation product. Calculation results showed that the mercury would dissolve Al, As, B, Be, Bi, C, Co, Cr, Fe, Ga, Ge, Ir, Mo, Nb, Os, Re, Ru, Sb, Si, Ta, Tc, V and W in the element state, and Ag, Au, Ba, Br, Ca, Cd, Ce, Cl, Cs, Cu, Dy, Er, Eu, F, Gd, Hf, Ho, I, In, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, O, Pb, Pd, Pr, Pt, Rb, Rh, S, Sc, Se, Sm, Sn, Sr, Tb, Te, Ti, Tl, Tm, Y, Yb, Zn and Zr in the form of inorganic mercury compounds. As for As, Be, Co, Cr, Fe, Ge, Ir, Mo, Nb, Os, Pt, Re, Ru, Se, Ta, V, W and Zr, precipitation could be occurred when increasing the amounts of spallation products with operation time of the spallation target system. On the other hand, beryllium-7 (Be-7), which is produced by spallation reaction of oxygen in the cooling water of a safety hull, becomes the main factor of the external exposure to maintain the cooling loop. Based on the thermochemical equilibrium calculation to Be-H{sub 2}O binary system, the chemical forms of Be in the cooling water were estimated. Then the Be could exist in the form of cations such as BeOH{sup +}, BeO{sup +} and Be{sup 2+} under the condition of less than 10{sup -8} of the Be mole fraction in the cooling water. (author)

  11. Estimation of thermochemical behavior of spallation products in mercury target

    International Nuclear Information System (INIS)

    Kobayashi, Kaoru; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Aso, Tomokazu; Teshigawara, Makoto; Hino, Ryutaro

    2002-02-01

    In order to examine the radiation safety of a spallation mercury target system, especially source term evaluation, it is necessary to clarify the chemical forms of spallation products generated by spallation reaction with proton beam. As for the chemical forms of spallation products in mercury that involves large amounts of spallation products, these forms were estimated by using the binary phase diagrams and the thermochemical equilibrium calculation based on the amounts of spallation product. Calculation results showed that the mercury would dissolve Al, As, B, Be, Bi, C, Co, Cr, Fe, Ga, Ge, Ir, Mo, Nb, Os, Re, Ru, Sb, Si, Ta, Tc, V and W in the element state, and Ag, Au, Ba, Br, Ca, Cd, Ce, Cl, Cs, Cu, Dy, Er, Eu, F, Gd, Hf, Ho, I, In, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, O, Pb, Pd, Pr, Pt, Rb, Rh, S, Sc, Se, Sm, Sn, Sr, Tb, Te, Ti, Tl, Tm, Y, Yb, Zn and Zr in the form of inorganic mercury compounds. As for As, Be, Co, Cr, Fe, Ge, Ir, Mo, Nb, Os, Pt, Re, Ru, Se, Ta, V, W and Zr, precipitation could be occurred when increasing the amounts of spallation products with operation time of the spallation target system. On the other hand, beryllium-7 (Be-7), which is produced by spallation reaction of oxygen in the cooling water of a safety hull, becomes the main factor of the external exposure to maintain the cooling loop. Based on the thermochemical equilibrium calculation to Be-H 2 O binary system, the chemical forms of Be in the cooling water were estimated. Then the Be could exist in the form of cations such as BeOH + , BeO + and Be 2+ under the condition of less than 10 -8 of the Be mole fraction in the cooling water. (author)

  12. Membranes for H2 generation from nuclear powered thermochemical cycles

    International Nuclear Information System (INIS)

    Nenoff, Tina Maria; Ambrosini, Andrea; Garino, Terry J.; Gelbard, Fred; Leung, Kevin; Navrotsky, Alexandra; Iyer, Ratnasabapathy G.; Axness, Marlene

    2006-01-01

    In an effort to produce hydrogen without the unwanted greenhouse gas byproducts, high-temperature thermochemical cycles driven by heat from solar energy or next-generation nuclear power plants are being explored. The process being developed is the thermochemical production of Hydrogen. The Sulfur-Iodide (SI) cycle was deemed to be one of the most promising cycles to explore. The first step of the SI cycle involves the decomposition of H 2 SO 4 into O 2 , SO 2 , and H 2 O at temperatures around 850 C. In-situ removal of O 2 from this reaction pushes the equilibrium towards dissociation, thus increasing the overall efficiency of the decomposition reaction. A membrane is required for this oxygen separation step that is capable of withstanding the high temperatures and corrosive conditions inherent in this process. Mixed ionic-electronic perovskites and perovskite-related structures are potential materials for oxygen separation membranes owing to their robustness, ability to form dense ceramics, capacity to stabilize oxygen nonstoichiometry, and mixed ionic/electronic conductivity. Two oxide families with promising results were studied: the double-substituted perovskite A x Sr 1-x Co 1-y B y O 3-δ (A=La, Y; B=Cr-Ni), in particular the family La x Sr 1-x Co 1-y Mn y O 3-δ (LSCM), and doped La 2 Ni 1-x M x O 4 (M = Cu, Zn). Materials and membranes were synthesized by solid state methods and characterized by X-ray and neutron diffraction, SEM, thermal analyses, calorimetry and conductivity. Furthermore, we were able to leverage our program with a DOE/NE sponsored H 2 SO 4 decomposition reactor study (at Sandia), in which our membranes were tested in the actual H 2 SO 4 decomposition step

  13. Nuclear Production of Hydrogen Using Thermochemical Water-Splitting Cycles

    International Nuclear Information System (INIS)

    Brown, L.C.; Besenbruch, G.E.; Schultz, K.R.; Marshall, A.C.; Showalter, S.K.; Pickard, P.S.; Funk, J.F.

    2002-01-01

    The purpose of this work is to determine the potential for efficient, cost-effective, large-scale production of hydrogen utilizing high-temperature heat from an advanced nuclear power station in a thermochemical water-splitting cycle. We carried out a detailed literature search to create a searchable database with 115 cycles and 822 references. We developed screening criteria to reduce the list to 25 cycles. We used detailed evaluation to select two cycles that appear most promising, the Adiabatic UT-3 cycle and the Sulfur-Iodine cycle. We have selected the Sulfur-Iodine thermochemical water-splitting cycle for further development. We then assessed the suitability of various nuclear reactor types to the production of hydrogen from water using the Sulfur-Iodine cycle. A basic requirement is to deliver heat to the process interface heat exchanger at temperatures up to 900 deg. C. We considered nine categories of reactors: pressurized water-cooled, boiling water-cooled, organic-cooled, alkali metal-cooled, heavy metal-cooled, gas-cooled, molten salt-cooled, liquid-core and gas-core reactors. We developed requirements and criteria to carry out the assessment, considering design, safety, operational, economic and development issues. This assessment process led to our choice of the helium gas-cooled reactor for coupling to the Sulfur-Iodine cycle. In continuing work, we are investigating the improvements that have been proposed to the Sulfur-Iodine cycle and will generate an integrated flowsheet describing a hydrogen production plant powered by a high-temperature helium gas-cooled nuclear reactor. This will allow us to size process equipment and calculate hydrogen production efficiency and capital cost, and to estimate the cost of the hydrogen produced as a function of nuclear reactor cost. (authors)

  14. A solar receiver-storage modular cascade based on porous ceramic structures for hybrid sensible/thermochemical solar energy storage

    Science.gov (United States)

    Agrafiotis, Christos; de Oliveira, Lamark; Roeb, Martin; Sattler, Christian

    2016-05-01

    The current state-of-the-art solar heat storage concept in air-operated Solar Tower Power Plants is to store the solar energy provided during on-sun operation as sensible heat in porous solid materials that operate as recuperators during off-sun operation. The technology is operationally simple; however its storage capacity is limited to 1.5 hours. An idea for extending this capacity is to render this storage concept from "purely" sensible to "hybrid" sensible/ thermochemical one, via coating the porous heat exchange modules with oxides of multivalent metals for which their reduction/oxidation reactions are accompanied by significant heat effects, or by manufacturing them entirely of such oxides. In this way solar heat produced during on-sun operation can be used (in addition to sensibly heating the porous solid) to power the endothermic reduction of the oxide from its state with the higher metal valence to that of the lower; the thermal energy can be entirely recovered by the reverse exothermic oxidation reaction (in addition to sensible heat) during off-sun operation. Such sensible and thermochemical storage concepts were tested on a solar-irradiated receiver- heat storage module cascade for the first time. Parametric studies performed so far involved the comparison of three different SiC-based receivers with respect to their capability of supplying solar-heated air at temperatures sufficient for the reduction of the oxides, the effect of air flow rate on the temperatures achieved within the storage module, as well as the comparison of different porous storage media made of cordierite with respect to their sensible storage capacity.

  15. Decomposition of metal nitrate solutions

    International Nuclear Information System (INIS)

    Haas, P.A.; Stines, W.B.

    1982-01-01

    Oxides in powder form are obtained from aqueous solutions of one or more heavy metal nitrates (e.g. U, Pu, Th, Ce) by thermal decomposition at 300 to 800 deg C in the presence of about 50 to 500% molar concentration of ammonium nitrate to total metal. (author)

  16. Direct transcriptional activation of BT genes by NLP transcription factors is a key component of the nitrate response in Arabidopsis.

    Science.gov (United States)

    Sato, Takeo; Maekawa, Shugo; Konishi, Mineko; Yoshioka, Nozomi; Sasaki, Yuki; Maeda, Haruna; Ishida, Tetsuya; Kato, Yuki; Yamaguchi, Junji; Yanagisawa, Shuichi

    2017-01-29

    Nitrate modulates growth and development, functioning as a nutrient signal in plants. Although many changes in physiological processes in response to nitrate have been well characterized as nitrate responses, the molecular mechanisms underlying the nitrate response are not yet fully understood. Here, we show that NLP transcription factors, which are key regulators of the nitrate response, directly activate the nitrate-inducible expression of BT1 and BT2 encoding putative scaffold proteins with a plant-specific domain structure in Arabidopsis. Interestingly, the 35S promoter-driven expression of BT2 partially rescued growth inhibition caused by reductions in NLP activity in Arabidopsis. Furthermore, simultaneous disruption of BT1 and BT2 affected nitrate-dependent lateral root development. These results suggest that direct activation of BT1 and BT2 by NLP transcriptional activators is a key component of the molecular mechanism underlying the nitrate response in Arabidopsis. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Thermochemical Erosion Modeling of the 25-MM M242/M791 Gun System

    National Research Council Canada - National Science Library

    Sopok, Samuel

    1997-01-01

    The MACE gun barrel thermochemical erosion modeling code addresses wall degradations due to transformations, chemical reactions, and cracking coupled with pure mechanical erosion for the 25-mm M242/M791 gun system...

  18. Synfuels from fusion: producing hydrogen with the Tandem Mirror Reactor and thermochemical cycles

    Energy Technology Data Exchange (ETDEWEB)

    Werner, R.W.; Ribe, F.L.

    1981-01-21

    This volume contains the following sections: (1) the Tandem Mirror fusion driver, (2) the Cauldron blanket module, (3) the flowing microsphere, (4) coupling the reactor to the process, (5) the thermochemical cycles, and (6) chemical reactors and process units. (MOW)

  19. Study of the hydrolysis reaction of the copper-chloride hybrid thermochemical cycle using optical spectrometries

    International Nuclear Information System (INIS)

    Doizi, D.; Borgard, J.M.; Dauvois, V.; Roujou, J.L.; Zanella, Y.; Croize, L.; Cartes, Ph.; Hartmann, J.M.

    2010-01-01

    The copper-chloride hybrid thermochemical cycle is one of the best potential low temperature thermochemical cycles for the massive production of hydrogen. It could be used with nuclear reactors such as the sodium fast reactor or the supercritical water reactor. Nevertheless, this thermochemical cycle is composed of an electrochemical reaction and two thermal reactions. Its efficiency has to be compared with other hydrogen production processes like alkaline electrolysis for example. The purpose of this article is to study the viability of the copper chloride thermochemical cycle by studying the hydrolysis reaction of CuCl 2 which is not favoured thermodynamically. To better understand the occurrence of possible side reactions, together with a good control of the kinetics of the hydrolysis reaction, the use of optical absorption spectrometries, UV visible spectrometry to detect molecular chlorine which may be formed in side reactions, FTIR spectrometry to follow the concentrations of H 2 O and HCl is proposed. (authors)

  20. Synfuels from fusion: producing hydrogen with the Tandem Mirror Reactor and thermochemical cycles

    International Nuclear Information System (INIS)

    Werner, R.W.; Ribe, F.L.

    1981-01-01

    This volume contains the following sections: (1) the Tandem Mirror fusion driver, (2) the Cauldron blanket module, (3) the flowing microsphere, (4) coupling the reactor to the process, (5) the thermochemical cycles, and (6) chemical reactors and process units

  1. Mortality of nitrate fertiliser workers.

    Science.gov (United States)

    Al-Dabbagh, S; Forman, D; Bryson, D; Stratton, I; Doll, R

    1986-01-01

    An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been employed in the production of fertilisers between 1946 and 1981 and who had been occupationally exposed to nitrates for at least one year were followed up until 1 March 1981. In total, 304 deaths were observed in this group and these were compared with expected numbers calculated from mortality rates in the northern region of England, where the factory was located. Analysis was also carried out separately for a subgroup of the cohort who had been heavily exposed to nitrates--that is, working in an environment likely to contain more than 10 mg nitrate/m3 for a year or longer. In neither the entire cohort nor the subgroup was any significant excess observed for all causes of mortality or for mortality from any of five broad categories of cause or from four specific types of cancer. A small excess of lung cancer was noted more than 20 years after first exposure in men heavily exposed for more than 10 years. That men were exposed to high concentrations of nitrate was confirmed by comparing concentrations of nitrates in the saliva of a sample of currently employed men with control men, employed at the same factory but not in fertiliser production. The men exposed to nitrate had substantially raised concentrations of nitrate in their saliva compared with both controls within the industry and with men in the general population and resident nearby. The results of this study therefore weight against the idea that exposure to nitrates in the environment leads to the formation in vivo of material amounts of carcinogens. PMID:3015194

  2. Electrochemical processing of nitrate waste solutions

    Energy Technology Data Exchange (ETDEWEB)

    Genders, D.; Weinberg, N.; Hartsough, D. (Electrosynthesis Co., Inc., Cheektowaga, NY (United States))

    1992-10-07

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F[sup [minus

  3. Efficient uranous nitrate production using membrane electrolysis

    International Nuclear Information System (INIS)

    Zhongwei Yuan; Taihong Yan; Weifang Zheng; Hongying Shuang; Liang Xian; Xiaoyan Bian; Chen Zuo; Chuanbo Li; Zhi Cao

    2013-01-01

    Electrochemical reduction of uranyl nitrate is a green, simple way to make uranous ion. In order to improve the ratio of uranous ion to the total uranium and maintain high current efficiency, an electrolyser with very thin cathodic and anodic compartment, which were separated by a cation exchange membrane, was setup, and its performance was tested. The effects of various parameters on the reduction were also evaluated. The results show that the apparatus is quite positive. It runs well with 120 mA/cm 2 current density (72 cm 2 cathode, constant current batch operation). U(IV) yield can achieve 93.1 % (500 mL feed, total uranium 199 g/L) after 180 min electrolysis. It was also shown that when U(IV) yield was below 80 %, very high current efficiency was maintained, and there was almost a linear relationship between uranous ion yield and electrolysis time; under the range of experimental conditions, the concentration of uranyl nitrate, hydrazine, and nitric acid had little effect on the reduction. (author)

  4. Third millenium ideal gas and condensed phase thermochemical database for combustion (with update from active thermochemical tables).

    Energy Technology Data Exchange (ETDEWEB)

    Burcat, A.; Ruscic, B.; Chemistry; Technion - Israel Inst. of Tech.

    2005-07-29

    The thermochemical database of species involved in combustion processes is and has been available for free use for over 25 years. It was first published in print in 1984, approximately 8 years after it was first assembled, and contained 215 species at the time. This is the 7th printed edition and most likely will be the last one in print in the present format, which involves substantial manual labor. The database currently contains more than 1300 species, specifically organic molecules and radicals, but also inorganic species connected to combustion and air pollution. Since 1991 this database is freely available on the internet, at the Technion-IIT ftp server, and it is continuously expanded and corrected. The database is mirrored daily at an official mirror site, and at random at about a dozen unofficial mirror and 'finger' sites. The present edition contains numerous corrections and many recalculations of data of provisory type by the G3//B3LYP method, a high-accuracy composite ab initio calculation. About 300 species are newly calculated and are not yet published elsewhere. In anticipation of the full coupling, which is under development, the database started incorporating the available (as yet unpublished) values from Active Thermochemical Tables. The electronic version now also contains an XML file of the main database to allow transfer to other formats and ease finding specific information of interest. The database is used by scientists, educators, engineers and students at all levels, dealing primarily with combustion and air pollution, jet engines, rocket propulsion, fireworks, but also by researchers involved in upper atmosphere kinetics, astrophysics, abrasion metallurgy, etc. This introductory article contains explanations of the database and the means to use it, its sources, ways of calculation, and assessments of the accuracy of data.

  5. Nitrate in leafy green vegetables and estimated intake | Brkić ...

    African Journals Online (AJOL)

    Background: Vegetarian diets are rich in vegetables. Green leafy vegetables are foods that contain considerable amounts of nitrate, which can have both positive and negative effects on the human body. Their potential carcinogenicity and toxicity have been proven, particularly after the reduction of nitrate to nitrite itself or ...

  6. Isolation of a nitrate-reducing bacteria strain from oil field brine and ...

    African Journals Online (AJOL)

    A nitrate-reducing bacteria (NRB) strain with vigorous growth, strong nitrate reduction ability, strain B9 2-1, was isolated from Suizhong36-1 oilfield, its routine identification and analysis of 16S rRNA and also the competitive inhibition experiments with the enrichment of sulfate-reducing bacteria (SRB) were carried out.

  7. Bioelectrode-based approach for enhancing nitrate and nitrite removal and electricity generation from eutrophic lakes

    DEFF Research Database (Denmark)

    Zhang, Yifeng; Angelidaki, Irini

    2012-01-01

    Nitrate and nitrite contamination of surface waters (e.g. lakes) has become a severe environmental and health problem, especially in developing countries. The recent demonstration of nitrate reduction at the cathode of microbial fuel cell (MFC) provides an opportunity to develop a new technology ...

  8. Land cover changes as a result of environmental restrictions on nitrate leaching in diary farming

    NARCIS (Netherlands)

    Groeneveld, R.; Bouwman, L.; Kruitwagen, S.; Ierland, van E.

    2001-01-01

    Nitrate leaching forms an important environmental problem because it causes pollution of groundwater and surface water, and adds to already problematic eutrophication. This study analyses the impact of reductions in nitrate leaching on land cover decisions of dairy farms, of which the activities

  9. Thermochemical Stability and Friction Properties of Soft Organosilica Networks for Solid Lubrication

    Directory of Open Access Journals (Sweden)

    Pablo Gonzalez Rodriguez

    2018-01-01

    Full Text Available In view of their possible application as high temperature solid lubricants, the tribological and thermochemical properties of several organosilica networks were investigated over a range of temperatures between 25 and 580 °C. Organosilica networks, obtained from monomers with terminal and bridging organic groups, were synthesized by a sol-gel process. The influence of carbon content, crosslink density, rotational freedom of incorporated hydrocarbon groups, and network connectivity on the high temperature friction properties of the polymer was studied for condensed materials from silicon alkoxide precursors with terminating organic groups, i.e., methyltrimethoxysilane, propyltrimethoxysilane, diisopropyldimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane and 4-biphenylyltriethoxysilane networks, as well as precursors with organic bridging groups between Si centers, i.e., 1,4-bis(triethoxysilylbenzene and 4,4′-bis(triethoxysilyl-1,1′-biphenyl. Pin-on-disc measurements were performed using all selected solid lubricants. It was found that materials obtained from phenyltrimethoxysilane and cyclohexyltrimethoxysilane precursors showed softening above 120 °C and performed best in terms of friction reduction, reaching friction coefficients as low as 0.01. This value is lower than that of graphite films (0.050 ± 0.005, a common bench mark for solid lubricants.

  10. Development of hydraulic analysis code for optimizing thermo-chemical is process reactors

    International Nuclear Information System (INIS)

    Terada, Atsuhiko; Hino, Ryutaro; Hirayama, Toshio; Nakajima, Norihiro; Sugiyama, Hitoshi

    2007-01-01

    The Japan Atomic Energy Agency has been conducting study on thermochemical IS process for water splitting hydrogen production. Based on the test results and know-how obtained through the bench-scale test, a pilot test plant, which has a hydrogen production performance of 30 Nm 3 /h, is being designed conceptually as the next step of the IS process development. In design of the IS pilot plant, it is important to make chemical reactors compact with high performance from the viewpoint of plant cost reduction. A new hydraulic analytical code has been developed for optimizing mixing performance of multi-phase flow involving chemical reactions especially in the Bunsen reactor. Complex flow pattern with gas-liquid chemical interaction involving flow instability will be characterized in the Bunsen reactor. Preliminary analytical results obtained with above mentioned code, especially flow patterns induced by swirling flow agreed well with that measured by water experiments, which showed vortex breakdown pattern in a simplified Bunsen reactor. (author)

  11. Positronium hydride in hydrogen-laden thermochemically reduced MgO single crystals

    International Nuclear Information System (INIS)

    Pareja, R.; la Cruz, R.M. de; Pedrosa, M.A.; Gonzalez, R.; Chen, Y.

    1990-01-01

    Thermochemical reduction of hydrogen-laden MgO single crystals at T∼2400 K results in a large concentration of both hydride (H - ) ions and anion vacancies (>10 24 m -3 ). Positron-lifetime experiments of these crystals provide evidence for bound positronium hydride states also referred to as [e + -H - ] or PsH states. The presence of the anion vacancies was found to inhibit the formation of these states. After thermally annealing out these vacancies, such that H - concentration remains intact, two long-lived components appear in the lifetime spectrum. Furthermore, these two components correlate with the presence of the H - ions. These results suggest the existence of bound [e + -H - ] states when positrons are trapped by the H - ions, and the subsequent formation of positronium (Ps) states by the dissociation of the [e + -H - ] states. From the values of the intermediate lifetime component, a value of (570±50) ps is obtained for the lifetime of the PsH state located in an anion vacancy in MgO. The longest lifetime component ∼(1--3) ns is attributed to pick-off annihilation of ortho-Ps states

  12. Positronium hydride in hydrogen-laden thermochemically reduced MgO single crystals

    Science.gov (United States)

    Pareja, R.; de La Cruz, R. M.; Pedrosa, M. A.; González, R.; Chen, Y.

    1990-04-01

    Thermochemical reduction of hydrogen-laden MgO single crystals at T~2400 K results in a large concentration of both hydride (H-) ions and anion vacancies (>1024 m-3). Positron-lifetime experiments of these crystals provide evidence for bound positronium hydride states also referred to as [e+-H-] or PsH states. The presence of the anion vacancies was found to inhibit the formation of these states. After thermally annealing out these vacancies, such that H- concentration remains intact, two long-lived components appear in the lifetime spectrum. Furthermore, these two components correlate with the presence of the H-ions. These results suggest the existence of bound [e+-H-] states when positrons are trapped by the H- ions, and the subsequent formation of positronium (Ps) states by the dissociation of the [e+-H-] states. From the values of the intermediate lifetime component, a value of (570+/-50) ps is obtained for the lifetime of the PsH state located in an anion vacancy in MgO. The longest lifetime component ~(1-3) ns is attributed to pick-off annihilation of ortho-Ps states.

  13. Economics and synergies of electrolytic and thermochemical methods of environmentally benign hydrogen production

    International Nuclear Information System (INIS)

    Naterer, G.F.

    2010-01-01

    Most of the world's hydrogen (about 97%) is currently derived from fossil fuels. For reduction of greenhouse gases, improvement of urban air quality, and energy security, among other reasons, carbon-free sources of hydrogen production are crucial to hydrogen becoming a significant energy carrier. Nuclear hydrogen production is a promising carbon-free alternative for large-scale, low-cost production of hydrogen in the future. Two nuclear technologies, applied in tandem, have a promising potential to generate hydrogen economically without leading to greenhouse gas emissions: 1) electrolysis and 2) thermochemical decomposition of water. This paper will investigate their unique complementary roles and economics of producing hydrogen, from a Canadian perspective. Together they can serve a unique potential for both de-centralized hydrogen needs in periods of low-demand electricity, and centralized base-load production from a nuclear station. Hydrogen production has a significantly higher thermal efficiency, but electrolysis can take advantage of low electricity prices during off-peak hours. By effectively linking these systems, water-based production of hydrogen can become more competitive against the predominant existing technology, SMR (steam-methane reforming). (orig.)

  14. Materials considerations for the coupling of thermochemical hydrogen cycles to tandem mirror reactors

    International Nuclear Information System (INIS)

    Krikorian, O.H.

    1980-01-01

    Candidate materials are discussed and initial choices made for the critical elements in a liquid Li-Na Cauldron Tandem Mirror blanket and the General Atomic Sulfur-Iodine Cycle for thermochemical hydrogen production. V and Ti alloys provide low neutron activation, good radiation damage resistance, and good chemical compatibility for the Cauldron design. Aluminide coated In-800H and siliconized SiC are materials choices for heat exchanger components in the thermochemical cycle interface

  15. Neodymium nitrate-tetraethylammonium nitrate-water system

    International Nuclear Information System (INIS)

    Khisaeva, D.A.; Boeva, M.K.

    1987-01-01

    Method of isothermal cross sections at 25 and 50 deg C is used to study solid phase solubility in the neodymium nitrate-tetraethylammonium nitrate-water system. Crystallization fields of congruently soluble compounds, the salt component ratio being 1:1:4H 2 O and 1:3:2H 2 O are detected. New solid phases are preparatively obtained and subjected to chemical, differential thermal, IR spectroscopic and X-ray diffraction analyses. The obtained compounds are acido-complexes in which nitrate groups enter into the first coordination sphere

  16. Influence of Reactive Transport on the Reduction of U(VI) in the Presence of Fe(III) and Nitrate: Implications for U(VI) Immobilization by Bioremediation/Biobarriers - Final Report

    International Nuclear Information System (INIS)

    B.D. Wood

    2007-01-01

    Subsurface contamination by metals and radionuclides represent some of the most challenging remediation problems confronting the Department of Energy (DOE) complex. In situ remediation of these contaminants by dissimilatory metal reducing bacteria (DMRB) has been proposed as a potential cost effective remediation strategy. The primary focus of this research is to determine the mechanisms by which the fluxes of electron acceptors, electron donors, and other species can be controlled to maximize the transfer of reductive equivalents to the aqueous and solid phases. The proposed research is unique in the NABIR portfolio in that it focuses on (i) the role of flow and transport in the initiation of biostimulation and the successful sequestration of metals and radionuclides [specifically U(VI)], (ii) the subsequent reductive capacity and stability of the reduced sediments produced by the biostimulation process, and (iii) the potential for altering the growth of biomass in the subsurface by the addition of specific metabolic uncoupling compounds. A scientifically-based understanding of these phenomena are critical to the ability to design successful bioremediation schemes. The laboratory research will employ Shewanella putrefaciens (CN32), a facultative DMRB that can use Fe(III) oxides as a terminal electron acceptor. Sediment-packed columns will be inoculated with this organism, and the reduction of U(VI) by the DMRB will be stimulated by the addition of a carbon and energy source in the presence of Fe(III). Separate column experiments will be conducted to independently examine: (1) the importance of the abiotic reduction of U(VI) by biogenic Fe(II); (2) the influence of the transport process on Fe(III) reduction and U(VI) immobilization, with emphasis on methods for controlling the fluxes of aqueous species to maximize uranium reduction; (3) the reductive capacity of biologically-reduced sediments (with respect to re-oxidation by convective fluxes of O2 and NO3-) and

  17. Metagenomic analysis of nitrate-reducing bacteria in the oral cavity: implications for nitric oxide homeostasis.

    Science.gov (United States)

    Hyde, Embriette R; Andrade, Fernando; Vaksman, Zalman; Parthasarathy, Kavitha; Jiang, Hong; Parthasarathy, Deepa K; Torregrossa, Ashley C; Tribble, Gena; Kaplan, Heidi B; Petrosino, Joseph F; Bryan, Nathan S

    2014-01-01

    The microbiota of the human lower intestinal tract helps maintain healthy host physiology, for example through nutrient acquisition and bile acid recycling, but specific positive contributions of the oral microbiota to host health are not well established. Nitric oxide (NO) homeostasis is crucial to mammalian physiology. The recently described entero-salivary nitrate-nitrite-nitric oxide pathway has been shown to provide bioactive NO from dietary nitrate sources. Interestingly, this pathway is dependent upon oral nitrate-reducing bacteria, since humans lack this enzyme activity. This pathway appears to represent a newly recognized symbiosis between oral nitrate-reducing bacteria and their human hosts in which the bacteria provide nitrite and nitric oxide from nitrate reduction. Here we measure the nitrate-reducing capacity of tongue-scraping samples from six healthy human volunteers, and analyze metagenomes of the bacterial communities to identify bacteria contributing to nitrate reduction. We identified 14 candidate species, seven of which were not previously believed to contribute to nitrate reduction. We cultivated isolates of four candidate species in single- and mixed-species biofilms, revealing that they have substantial nitrate- and nitrite-reduction capabilities. Colonization by specific oral bacteria may thus contribute to host NO homeostasis by providing nitrite and nitric oxide. Conversely, the lack of specific nitrate-reducing communities may disrupt the nitrate-nitrite-nitric oxide pathway and lead to a state of NO insufficiency. These findings may also provide mechanistic evidence for the oral systemic link. Our results provide a possible new therapeutic target and paradigm for NO restoration in humans by specific oral bacteria.

  18. Metagenomic analysis of nitrate-reducing bacteria in the oral cavity: implications for nitric oxide homeostasis.

    Directory of Open Access Journals (Sweden)

    Embriette R Hyde

    Full Text Available The microbiota of the human lower intestinal tract helps maintain healthy host physiology, for example through nutrient acquisition and bile acid recycling, but specific positive contributions of the oral microbiota to host health are not well established. Nitric oxide (NO homeostasis is crucial to mammalian physiology. The recently described entero-salivary nitrate-nitrite-nitric oxide pathway has been shown to provide bioactive NO from dietary nitrate sources. Interestingly, this pathway is dependent upon oral nitrate-reducing bacteria, since humans lack this enzyme activity. This pathway appears to represent a newly recognized symbiosis between oral nitrate-reducing bacteria and their human hosts in which the bacteria provide nitrite and nitric oxide from nitrate reduction. Here we measure the nitrate-reducing capacity of tongue-scraping samples from six healthy human volunteers, and analyze metagenomes of the bacterial communities to identify bacteria contributing to nitrate reduction. We identified 14 candidate species, seven of which were not previously believed to contribute to nitrate reduction. We cultivated isolates of four candidate species in single- and mixed-species biofilms, revealing that they have substantial nitrate- and nitrite-reduction capabilities. Colonization by specific oral bacteria may thus contribute to host NO homeostasis by providing nitrite and nitric oxide. Conversely, the lack of specific nitrate-reducing communities may disrupt the nitrate-nitrite-nitric oxide pathway and lead to a state of NO insufficiency. These findings may also provide mechanistic evidence for the oral systemic link. Our results provide a possible new therapeutic target and paradigm for NO restoration in humans by specific oral bacteria.

  19. The Abundance and Activity of Nitrate-Reducing Microbial Populations in Estuarine Sediments

    Science.gov (United States)

    Cardarelli, E.; Francis, C. A.

    2014-12-01

    Estuaries are productive ecosystems that ameliorate nutrient and metal contaminants from surficial water supplies. At the intersection of terrestrial and aquatic environments, estuarine sediments host major microbially-mediated geochemical transformations. These include denitrification (the conversion of nitrate to nitrous oxide and/or dinitrogen) and dissimilatory nitrate reduction to ammonium (DNRA). Denitrification has historically been seen as the predominant nitrate attenuation process and functions as an effective sink for nitrate. DNRA has previously been believed to be a minor nitrate reduction process and transforms nitrate within the ecosystem to ammonium, a more biologically available N species. Recent studies have compared the two processes in coastal environments and determined fluctuating environmental conditions may suppress denitrification, supporting an increased role for DNRA in the N cycle. Nitrate availability and salinity are factors thought to influence the membership of the microbial communities present, and the nitrate reduction process that predominates. The aim of this study is to investigate how nitrate concentration and salinity alter the transcript abundances of N cycling functional gene markers for denitrification (nirK, nirS) and DNRA (nrfA) in estuarine sediments at the mouth of the hypernutrified Old Salinas River, CA. Short-term whole core incubations amended with artificial freshwater/artificial seawater (2 psu, 35 psu) and with varying NO3- concentrations (200mM, 2000mM) were conducted to assess the activity as well as the abundance of the nitrate-reducing microbial populations present. Gene expression of nirK, nirS, and nrfA at the conclusion of the incubations was quantified using reverse transcription quantitative polymerase chain reaction (RT-qPCR). High abundances of nirK, nirS, and nrfA under particular conditions coupled with the resulting geochemical data ultimately provides insight onto how the aforementioned factors

  20. Investigation of ammonium nitrate effect on kinetics and mechanism of thermal decomposition of ammonium polyuranates

    International Nuclear Information System (INIS)

    Karelin, A.I.; Lobas, O.P.; Zhiganov, A.N.; Vasil'ev, K.F.; Zhiganova, A.A.

    1987-01-01

    A study was made on ammonium nitrate effect on the mechanism and kinetics of dehydration and thermal decomposition of ammonium polyuranates. Sufficient effect of nitrate ion content in ammonium polyuranate samples on their thermal stability was noted. Kinetic parameters of thermal decomposition of ammonium polyuranates were evaluated. Mechanism of dehydration and thermal decomposition of ammonium polyuranates in the presence of ammonium nitrate was suggested. It was shown that increase of ammonium nitrate content in ammonium polyuranate precipitate resulted to reduction of the specific surface of prepared uranium mixed oxide

  1. Soil nitrate reducing processes drivers, mechanisms for spatial variation, and significance for nitrous oxide production

    OpenAIRE

    Giles, M.; Morley, N.; Baggs, E.M.; Daniell, T.J.

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium\\ud (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for\\ud the loss of nitrate (NO−\\ud 3 ) and production of the potent greenhouse gas, nitrous oxide (N2O).\\ud A number of factors are known to control these processes, including O2 concentrations and\\ud moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms\\ud responsible for the ...

  2. Research factors of the electrochemical remediation clay soils from the nitrates

    Energy Technology Data Exchange (ETDEWEB)

    Korolev, V.A.; Babakina, O.A. [Moscow State Univ. (Russian Federation)

    2001-07-01

    The electrokinetic's methods are prevalent [1, 2], but abilities of the method for remediation nitrates contaminated soils are studied insufficiently. The investigations of effectiveness electrochemical remediation are complicated by processes of reduction nitrates to nitrites (that are more toxic) and then to nitrogen in soil under the constant electric current. Therefore, the objectives of the research was following: - Evaluate mechanism of electrokinetic's removing nitrates from soil; - Evaluate basic value of moisture and alkalinity influence for electrochemical remediation of soil from nitrates; - Determine flow-through regime effect on electrokinetic's treating. (orig.)

  3. Nitrate photolysis in salty snow

    Science.gov (United States)

    Donaldson, D. J.; Morenz, K.; Shi, Q.; Murphy, J. G.

    2016-12-01

    Nitrate photolysis from snow can have a significant impact on the oxidative capacity of the local atmosphere, but the factors affecting the release of gas phase products are not well understood. Here, we report the first systematic study of the amounts of NO, NO2, and total nitrogen oxides (NOy) emitted from illuminated snow samples as a function of both nitrate and total salt (NaCl and Instant Ocean) concentration. We show that the release of nitrogen oxides to the gas phase is directly related to the expected nitrate concentration in the brine at the surface of the snow crystals, increasing to a plateau value with increasing nitrate, and generally decreasing with increasing NaCl or Instant Ocean (I.O.). In frozen mixed nitrate (25 mM) - salt (0-500 mM) solutions, there is an increase in gas phase NO2 seen at low added salt amounts: NO2 production is enhanced by 35% at low prefreezing [NaCl] and by 70% at similar prefreezing [I.O.]. Raman microscopy of frozen nitrate-salt solutions shows evidence of stronger nitrate exclusion to the air interface in the presence of I.O. than with added NaCl. The enhancement in nitrogen oxides emission in the presence of salts may prove to be important to the atmospheric oxidative capacity in polar regions.

  4. Intermittent Nitrate Use and Risk of Hip Fracture

    Science.gov (United States)

    Misra, Devyani; Peloquin, Christine; Kiel, Douglas P.; Neogi, Tuhina; Lu, Na; Zhang, Yuqing

    2016-01-01

    Purpose Nitrates, commonly used anti-anginal medications, also have beneficial effect on bone remodeling and bone density, particularly with intermittent use. However, their effect on fracture risk is not clear. We examined the relation of short-acting nitrate use (proxy for intermittent use) to the risk of hip fracture in a large cohort of older adults with ischemic heart disease. Materials and Methods Participants ≥ 60 years old with ischemic heart disease and without history of hip fracture from The Health Improvement Network (THIN), an electronic medical records database in the UK, were included. The association of incident (new) use of short-acting nitrate formulations (nitroglycerin sublingual/spray/ointment or ISDN injection/sprays) with incident (new-onset) hip fracture risk was examined by plotting Kaplan-Maier curves and calculating Hazard ratios (HR) using Cox proportional hazards regression models. Competing risk by death was analyzed in separate analyses. Results Among 14, 451 pairs of matched nitrate users and non-users (mean age 72±7.6, 41% women for each cohort), 573 fractures occurred during follow up (257 nitrate users; 316 non-users). Hip fracture risk was 33% lower among short-acting nitrate users compared with non-users (HR=0.67, 95% CI 0.53–0.85, p=0.0008). Competing risk analysis by death did not change effect estimates. Conclusion In this large population-based cohort of older adults with ischemic heart disease, we found significant reduction in hip fracture risk with use of short-acting nitrates (intermittent use). Future studies are warranted given the potential for nitrates to be potent, inexpensive and readily available anti-osteoporotic agents. PMID:27720852

  5. A hydrogen production experiment by the thermo-chemical and electrolytic hybrid hydrogen production in lower temperature range. System viability and preliminary thermal efficiency estimation

    International Nuclear Information System (INIS)

    Takai, Toshihide; Nakagiri, Toshio; Inagaki, Yoshiyuki

    2008-10-01

    A new experimental apparatus by the thermo-chemical and electrolytic Hybrid-Hydrogen production in Lower Temperature range (HHLT) was developed and hydrogen production experiment was performed to confirm the system operability. Hydrogen production efficiency was estimated and technical problems were clarified through the experimental results. Stable operation of the SO 3 electrolysis cell and the sulfur dioxide solution electrolysis cell were confirmed during experimental operation and any damage which would be affected solid operation was not detected under post operation inspection. To improve hydrogen production efficiency, it was found that the reduction of sulfuric acid circulation and the decrease in the cell voltage were key issues. (author)

  6. A new method to produce nanoscale iron for nitrate removal

    International Nuclear Information System (INIS)

    Chen, S.-S.; Hsu, H.-D.; Li, C.-W.

    2004-01-01

    This article proposes a novel technology combining electrochemical and ultrasonic methods to produce nanoscale zero valent iron (NZVI). With platinum placed in the cathode and the presence of the dispersion agent, 0.2g/l cetylpyridinium chloride (CPC), a cation surfactant, in the solution, the nanoscale iron particle was successfully produced with diameter of 1-20 nm and specific surface area of 25.4m 2 /g. The produced NZVI was tested in batch experiments for nitrate removal. The results showed that the nitrate reduction was affected by pH. Al low pH, nitrate was shown faster decline and more reduction in term of g NO 3 - -N/g NZVI. The reaction was first order and kinetic coefficients for the four pHs were directly related to pH with R 2 >0.95. Comparing with microscale zero-valent iron (45μm, 0.183m 2 /g), microscale zero-valent iron converted nitrate to ammonia completely, but NZVI converted nitrate to ammonia partially from 36.2 to 45.3% dependent on pH. For mass balance of iron species, since the dissolved iron in the solution was very low ( 2 O 3 was recognized. Thus the reaction mechanisms can be determined

  7. [Removal of nitrate from groundwater using permeable reactive barrier].

    Science.gov (United States)

    Li, Xiu-Li; Yang, Jun-Jun; Lu, Xiao-Xia; Zhang, Shu; Hou, Zhen

    2013-03-01

    To provide a cost-effective method for the remediation of nitrate-polluted groundwater, column experiments were performed to study the removal of nitrate by permeable reactive barrier filled with fermented mulch and sand (biowall), and the mechanisms and influence factors were explored. The experimental results showed that the environmental condition in the simulated biowall became highly reduced after three days of operation (oxidation-reduction potential was below - 100 mV), which was favorable for the reduction of nitrate. During the 15 days of operation, the removal rate of nitrate nitrogen (NO3(-) -N) by the simulated biowall was 80%-90% (NO3(-)-N was reduced from 20 mg x L(-1) in the inlet water to 1.6 mg x L(-1) in the outlet water); the concentration of nitrite nitrogen (NO2(-) -N) in the outlet water was below 2.5 mg x L(-1); the concentration of ammonium nitrogen (NH4(+) -N) was low in the first two days but increased to about 12 mg x L(-1) since day three. The major mechanisms involved in the removal of nitrate nitrogen were adsorption and biodegradation. When increasing the water flow velocity in the simulated biowall, the removal rate of NO3(-) -N was reduced and the concentration of NH4(+) -N in the outlet water was significantly reduced. A simulated zeolite wall was set up following the simulated biowall and 98% of the NH4(+) -N could be removed from the water.

  8. Nitrate reductase gene involvement in hexachlorobiphenyl dechlorination by Phanerochaete chrysosporium

    International Nuclear Information System (INIS)

    De, Supriyo; Perkins, Michael; Dutta, Sisir K.

    2006-01-01

    Polychlorobiphenyl (PCB) degradation usually occurs through reductive dechlorination under anaerobic conditions and phenolic ring cleavage under aerobic conditions. In this paper, we provide evidence of nitrate reductase (NaR) mediated dechlorination of hexachlorobiphenyl (PCB-153) in Phanerochaete chrysosporium under non-ligninolytic condition and the gene involved. The NaR enzyme and its cofactor, molybdenum (Mo), were found to mediate reductive dechlorination of PCBs even in aerobic condition. Tungsten (W), a competitive inhibitor of this enzyme, was found to suppress this dechlorination. Chlorine release assay provided further evidence of this nitrate reductase mediated dechlorination. Commercially available pure NaR enzyme from Aspergillus was used to confirm these results. Through homology search using TBLASTN program, NaR gene was identified, primers were designed and the RT-PCR product was sequenced. The NaR gene was then annotated in the P. chrysosporium genome (GenBank accession no. AY700576). This is the first report regarding the presence of nitrate reductase gene in this fungus with the explanation why this fungus can dechlorinate PCBs even in aerobic condition. These fungal inoculums are used commercially as pellets in sawdust for enhanced bioremediation of PCBs at the risk of depleting soil nitrates. Hence, the addition of nitrates to the pellets will reduce this risk as well as enhance its activity

  9. Yttrium Nitrate mediated Nitration of Phenols at room temperature in ...

    Indian Academy of Sciences (India)

    The described method is selective for phenols. ... the significant cause of post translational modification that can ... decades, significant attention was paid on nitration of phenols to .... Progress of the reaction can be noted visually. Yttrium.

  10. Removal of nitrate by zero-valent iron and pillared bentonite

    International Nuclear Information System (INIS)

    Li Jianfa; Li Yimin; Meng Qingling

    2010-01-01

    The pillared bentonite prepared by intercalating poly(hydroxo Al(III)) cations into bentonite interlayers was used together with Fe(0) for removing nitrate in column experiments. The obvious synergetic effect on nitrate removal was exhibited through uniformly mixing the pillared bentonite with Fe(0). In such a mixing manner, the nitrate was 100% removed, and the removal efficiency was much higher than the simple summation of adsorption by the pillared bentonite and reduction by Fe(0). The influencing factors such as bentonite type, amount of the pillared bentonite and initial pH of nitrate solutions were investigated. In this uniform mixture, the pillared bentonite could adsorb nitrate ions, and facilitated the mass transfer of nitrate onto Fe(0) surface, then accelerated the nitrate reduction. The pillared bentonite could also act as the proton-donor, and helped to keep the complete nitrate removal for at least 10 h even when the nitrate solution was fed at nearly neutral pH.

  11. Øget indhold af nitrat i foderet til malkekøer reducerer udledningen af metan betydeligt

    DEFF Research Database (Denmark)

    Lund, Peter; Olijhoek, Dana; Dahl, Regina

    2015-01-01

    would be a substrate for the formation of methane, is being consumed during the energy-favorable reduction of nitrate to ammonia in the rumen. Nitrite is formed during the reduction of nitrate to ammonium and is a potentially toxic intermediate. Neither acute nor long-term negative effect...... metabolism, and energy loss from the process amounts to 5-7 % of the total feed gross energy. Recent Danish research shows that the addition of nitrate to feed can reduce methane emissions by up to 23 % without feed digestibility being negatively affected. This reduction is due to hydrogen, which otherwise...... of the addition of nitrate on the animal's health could be detected. Surprisingly, addition of nitrate resulted in significant emission of nitrous oxide (N2O), which is a very potent greenhouse gas. This underlines that there is a significant change in the rumen nitrogen metabolism when nitrate is added...

  12. 15N studies on the in-vivo assay of nitrate reductase in leaves

    International Nuclear Information System (INIS)

    Yoneyama, Tadakatsu

    1981-01-01

    The reduction of nitrate and nitrite in the leaf disks of seven di- and two mono-cotyledonous species under the in-vivo assay conditions of nitrate reductase was studied using N-15 labeled substrates. The significant reduction of both nitrate and nitrite into ammonia and amino acids was detected in the atmosphere of air. In the atmosphere of N 2 gas, anaerobic incubation enhanced the accumulation of nitrite, but the subsequent reduction to the basic nitrogen compounds was from 40 to 180 % of the aerobic rate. The present examination indicated that the in-vivo assay of nitrate reductase under aerobic condition may give greatly underestimated results due to nitrite reduction, and that the exclusion of oxygen from the in-vivo assay mixture is desirable. The addition of n- propanol may be desirable for the assay under aerobic condition. Significant difference was not observed in the reduction of nitrate supplied as sodium and potassium salts on the nitrite formation and on the incorporation of nitrate-N into basic fractions. The N-15 experiment on the dark assimilation of nitrate, nitrite and ammonia into amino acids in wheat leaves showed that these three nitrogen sources were assimilated through the same route, and that the glutamine synthetase/glutamate synthetase pathway was the main route. By anaerobic treatment, the incorporation of nitrogen into alanine and serine was relatively high. (Kako, I.)

  13. Vascular effects of dietary nitrate (as found in green leafy vegetables and beetroot) via the nitrate-nitrite-nitric oxide pathway.

    Science.gov (United States)

    Lidder, Satnam; Webb, Andrew J

    2013-03-01

    The discovery that dietary (inorganic) nitrate has important vascular effects came from the relatively recent realization of the 'nitrate-nitrite-nitric oxide (NO) pathway'. Dietary nitrate has been demonstrated to have a range of beneficial vascular effects, including reducing blood pressure, inhibiting platelet aggregation, preserving or improving endothelial dysfunction, enhancing exercise performance in healthy individuals and patients with peripheral arterial disease. Pre-clinical studies with nitrate or nitrite also show the potential to protect against ischaemia-reperfusion injury and reduce arterial stiffness, inflammation and intimal thickness. However, there is a need for good evidence for hard endpoints beyond epidemiological studies. Whilst these suggest reduction in cardiovascular risk with diets high in nitrate-rich vegetables (such as a Mediterranean diet), others have suggested possible small positive and negative associations with dietary nitrate and cancer, but these remain unproven. Interactions with other nutrients, such as vitamin C, polyphenols and fatty acids may enhance or inhibit these effects. In order to provide simple guidance on nitrate intake from different vegetables, we have developed the Nitrate 'Veg-Table' with 'Nitrate Units' [each unit being 1 mmol of nitrate (62 mg)] to achieve a nitrate intake that is likely to be sufficient to derive benefit, but also to minimize the risk of potential side effects from excessive ingestion, given the current available evidence. The lack of data concerning the long term effects of dietary nitrate is a limitation, and this will need to be addressed in future trials. © 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.

  14. Total salivary nitrates and nitrites in oral health and periodontal disease.

    Science.gov (United States)

    Sánchez, Gabriel A; Miozza, Valeria A; Delgado, Alejandra; Busch, Lucila

    2014-01-30

    It is well known that nitrites are increased in saliva from patients with periodontal disease. In the oral cavity, nitrites may derive partly from the reduction of nitrates by oral bacteria. Nitrates have been reported as a defence-related mechanism. Thus, the aim of the present study was to determine the salivary levels of total nitrate and nitrite and their relationship, in unstimulated and stimulated saliva from periodontal healthy subjects, and from patients with chronic periodontal disease. Nitrates and nitrites were determined in saliva from thirty healthy subjects and forty-four patients with periodontal disease. A significant increase in salivary nitrates and nitrites was observed. Nitrates and nitrites concentration was related to clinical attachment level (CAL). A positive and significant Pearson's correlation was found between salivary total nitrates and nitrites. Periodontal treatment induced clinical improvement and decreased nitrates and nitrites. It is concluded that salivary nitrates and nitrites increase, in patients with periodontal disease, could be related to defence mechanisms. The possibility that the salivary glands respond to oral infectious diseases by increasing nitrate secretion should be explored further. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Membranes for H2 generation from nuclear powered thermochemical cycles.

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina Maria; Ambrosini, Andrea; Garino, Terry J.; Gelbard, Fred; Leung, Kevin; Navrotsky, Alexandra (University of California, Davis, CA); Iyer, Ratnasabapathy G. (University of California, Davis, CA); Axness, Marlene

    2006-11-01

    In an effort to produce hydrogen without the unwanted greenhouse gas byproducts, high-temperature thermochemical cycles driven by heat from solar energy or next-generation nuclear power plants are being explored. The process being developed is the thermochemical production of Hydrogen. The Sulfur-Iodide (SI) cycle was deemed to be one of the most promising cycles to explore. The first step of the SI cycle involves the decomposition of H{sub 2}SO{sub 4} into O{sub 2}, SO{sub 2}, and H{sub 2}O at temperatures around 850 C. In-situ removal of O{sub 2} from this reaction pushes the equilibrium towards dissociation, thus increasing the overall efficiency of the decomposition reaction. A membrane is required for this oxygen separation step that is capable of withstanding the high temperatures and corrosive conditions inherent in this process. Mixed ionic-electronic perovskites and perovskite-related structures are potential materials for oxygen separation membranes owing to their robustness, ability to form dense ceramics, capacity to stabilize oxygen nonstoichiometry, and mixed ionic/electronic conductivity. Two oxide families with promising results were studied: the double-substituted perovskite A{sub x}Sr{sub 1-x}Co{sub 1-y}B{sub y}O{sub 3-{delta}} (A=La, Y; B=Cr-Ni), in particular the family La{sub x}Sr{sub 1-x}Co{sub 1-y}Mn{sub y}O{sub 3-{delta}} (LSCM), and doped La{sub 2}Ni{sub 1-x}M{sub x}O{sub 4} (M = Cu, Zn). Materials and membranes were synthesized by solid state methods and characterized by X-ray and neutron diffraction, SEM, thermal analyses, calorimetry and conductivity. Furthermore, we were able to leverage our program with a DOE/NE sponsored H{sub 2}SO{sub 4} decomposition reactor study (at Sandia), in which our membranes were tested in the actual H{sub 2}SO{sub 4} decomposition step.

  16. Differential responses of nitrate reducer community size, structure, and activity to tillage systems.

    Science.gov (United States)

    Chèneby, D; Brauman, A; Rabary, B; Philippot, L

    2009-05-01

    The main objective of this study was to determine how the size, structure, and activity of the nitrate reducer community were affected by adoption of a conservative tillage system as an alternative to conventional tillage. The experimental field, established in Madagascar in 1991, consists of plots subjected to conventional tillage or direct-seeding mulch-based cropping systems (DM), both amended with three different fertilization regimes. Comparisons of size, structure, and activity of the nitrate reducer community in samples collected from the top layer in 2005 and 2006 revealed that all characteristics of this functional community were affected by the tillage system, with increased nitrate reduction activity and numbers of nitrate reducers under DM. Nitrate reduction activity was also stimulated by combined organic and mineral fertilization but not by organic fertilization alone. In contrast, both negative and positive effects of combined organic and mineral fertilization on the size of the nitrate reducer community were observed. The size of the nitrate reducer community was a significant predictor of the nitrate reduction rates except in one treatment, which highlighted the inherent complexities in understanding the relationships the between size, diversity, and structure of functional microbial communities along environmental gradients.

  17. Effects of nitrate addition to a diet on fermentation and microbial populations in the rumen of goats, with special reference to Selenomonas ruminantium having the ability to reduce nitrate and nitrite.

    Science.gov (United States)

    Asanuma, Narito; Yokoyama, Shota; Hino, Tsuneo

    2015-04-01

    This study investigated the effects of dietary nitrate addition on ruminal fermentation characteristics and microbial populations in goats. The involvement of Selenomonas ruminantium in nitrate and nitrite reduction in the rumen was also examined. As the result of nitrate feeding, the total concentration of ruminal volatile fatty acids decreased, whereas the acetate : propionate ratio and the concentrations of ammonia and lactate increased. Populations of methanogens, protozoa and fungi, as estimated by real-time PCR, were greatly decreased as a result of nitrate inclusion in the diet. There was modest or little impact of nitrate on the populations of prevailing species or genus of bacteria in the rumen, whereas Streptococcus bovis and S. ruminantium significantly increased. Both the activities of nitrate reductase (NaR) and nitrite reductase (NiR) per total mass of ruminal bacteria were increased by nitrate feeding. Quantification of the genes encoding NaR and NiR by real-time PCR with primers specific for S. ruminantium showed that these genes were increased by feeding nitrate, suggesting that the growth of nitrate- and nitrite-reducing S. ruminantium is stimulated by nitrate addition. Thus, S. ruminantium is likely to play a major role in nitrate and nitrite reduction in the rumen. © 2014 Japanese Society of Animal Science.

  18. Impact of elevated nitrate on sulfate-reducing bacteria: A comparative study of Desulfovibrio vulgaris

    Energy Technology Data Exchange (ETDEWEB)

    He, Q.; He, Z.; Joyner, D.C.; Joachimiak, M.; Price, M.N.; Yang, Z.K.; Yen, H.-C. B.; Hemme, C. L.; Chen, W.; Fields, M.; Stahl, D. A.; Keasling, J. D.; Keller, M.; Arkin, A. P.; Hazen, T. C.; Wall, J. D.; Zhou, J.

    2010-07-15

    Sulfate-reducing bacteria have been extensively studied for their potential in heavy-metal bioremediation. However, the occurrence of elevated nitrate in contaminated environments has been shown to inhibit sulfate reduction activity. Although the inhibition has been suggested to result from the competition with nitrate-reducing bacteria, the possibility of direct inhibition of sulfate reducers by elevated nitrate needs to be explored. Using Desulfovibrio vulgaris as a model sulfate-reducing bacterium, functional genomics analysis reveals that osmotic stress contributed to growth inhibition by nitrate as shown by the upregulation of the glycine/betaine transporter genes and the relief of nitrate inhibition by osmoprotectants. The observation that significant growth inhibition was effected by 70 mM NaNO{sub 3} but not by 70 mM NaCl suggests the presence of inhibitory mechanisms in addition to osmotic stress. The differential expression of genes characteristic of nitrite stress responses, such as the hybrid cluster protein gene, under nitrate stress condition further indicates that nitrate stress response by D. vulgaris was linked to components of both osmotic and nitrite stress responses. The involvement of the oxidative stress response pathway, however, might be the result of a more general stress response. Given the low similarities between the response profiles to nitrate and other stresses, less-defined stress response pathways could also be important in nitrate stress, which might involve the shift in energy metabolism. The involvement of nitrite stress response upon exposure to nitrate may provide detoxification mechanisms for nitrite, which is inhibitory to sulfate-reducing bacteria, produced by microbial nitrate reduction as a metabolic intermediate and may enhance the survival of sulfate-reducing bacteria in environments with elevated nitrate level.

  19. 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.

  20. Thermodynamics of coproportionation reactions of homogeneous samarium (3) and yttrium (3) nitrates solvates with neutral organic phosphorus compounds

    International Nuclear Information System (INIS)

    Pyartman, A.K.

    1995-01-01

    Reaction heats of homogeneous samarium (3) and yttrium (3) nitrate solvates coproportionation with neutral organophosphoric compounds (tri-n.-butylphosphate, diisooctylmethylphosphonate, diisoamylmethylphosphonate) at T=298.15 K in hexane have been measured by thermochemical method. It has been ascertained that enthalpies of coproportionation reactions practically do not depend on the nature, concentration of rare earth metal (3) nitrate solvates in hexane, nature of neutral organophosphoric compound and constitute 1.1±-.2 kJ/mol. The Gibbs free energy of coproportionation reactions is -5.43 kJ/mol, while entropy of the reactions in 14.5±0.7 J/mol·K. 8 refs., 1 tab

  1. Variability of nitrate and phosphate

    Digital Repository Service at National Institute of Oceanography (India)

    Sardessai, S.; Sundar, D.

    Nitrate and phosphate are important elements of the biogeochemical system of an estuary. Observations carried out during the dry season April-May 2002, and March 2003 and wet season September 2002, show temporal and spatial variability of these two...

  2. Nitrate removal by Fe0/Pd/Cu nano-composite in groundwater.

    Science.gov (United States)

    Liu, Hongyuan; Guo, Min; Zhang, Yan

    2014-01-01

    Nitrate pollution in groundwater shows a great threat to the safety of drinking water. Chemical reduction by zero-valent iron is being considered as a promising technique for nitrate removal from contaminated groundwater. In this paper, Fe0/Pd/Cu nano-composites were prepared by the liquid-phase reduction method, and batch experiments of nitrate reduction by the prepared Fe0/Pd/Cu nano-composites under various operating conditions were carried out. It has been found that nano-Fe0/Pd/Cu composites processed dual functions: catalytic reduction and chemical reduction. The introduction of Pd and Cu not only improved nitrate removal rate, but also reduced the generation of ammonia. Nitrate removal rate was affected by the amount of Fe0/Pd/Cu, initial nitrate concentration, solution pH, dissolved oxygen (DO), reaction temperature, the presence of anions, and organic pollutant. Moreover, nitrate reduction by Fe0/Pd/Cu composites followed the pseudo-first-order reaction kinetics. The removal rate of nitrate and total nitrogen were about 85% and 40.8%, respectively, under the reaction condition of Fe-6.0%Pd-3.0%Cu amount of 0.25 g/L, pH value of 7.1, DO of 0.42 mg/L, and initial nitrate concentration of 100 mg/L. Compared with the previous studies with Fe0 alone or Fe-Cu, nano-Fe-6%Pd-3%Cu composites showed a better selectivity to N2.

  3. Headspace Analysis of Ammonium Nitrate

    Science.gov (United States)

    2017-01-25

    explosive ammonium nitrate produces ammonia and nitric acid in the gaseous headspace above bulk solids, but the concentrations of the products have been...and NO2-, a product of nitrate fragmentation (Figure 7). Brief spikes in the background and dips in oxalic acid signal were observed at the time of...either filtered air or experimental nitric acid vapor sources so that analyte signal could be measured directly opposite background. With oxalic

  4. Thermochemical hydrogen generation of indium oxide thin films

    Directory of Open Access Journals (Sweden)

    Taekyung Lim

    2017-03-01

    Full Text Available Development of alternative energy resources is an urgent requirement to alleviate current energy constraints. As such, hydrogen gas is gaining attention as a future alternative energy source to address existing issues related to limited energy resources and air pollution. In this study, hydrogen generation by a thermochemical water-splitting process using two types of In2O3 thin films was investigated. The two In2O3 thin films prepared by chemical vapor deposition (CVD and sputtering deposition systems contained different numbers of oxygen vacancies, which were directly related to hydrogen generation. The as-grown In2O3 thin film prepared by CVD generated a large amount of hydrogen because of its abundant oxygen vacancies, while that prepared by sputtering had few oxygen vacancies, resulting in low hydrogen generation. Increasing the temperature of the In2O3 thin film in the reaction chamber caused an increase in hydrogen generation. The oxygen-vacancy-rich In2O3 thin film is expected to provide a highly effective production of hydrogen as a sustainable and efficient energy source.

  5. Thermochemical data acquisition - Reactor safety programme 1988-1991

    International Nuclear Information System (INIS)

    Ball, R.G.J.; Rand, M.H.; Cordfunke, E.H.P.; Konings, R.J.M.

    1991-10-01

    Thermochemical data are required for specific fission product and reactor materials compounds in order to quantify the consequences of a severe accident within a light water reactor. Approximately 40 important compounds/systems have been identified for study for which thermodynamic data did not exist or were inadequate. Work is described on the analysis of approximately half of these systems. Experimental studies have been undertaken to determine the thermodynamic quantities of the following compounds : Cs 2 MoO 4 , CsBO 2 , Cs 2 RuO 4 , Cs 2 RuO 4 , Cs 2 Mno 4 , Cs 2 CrO 4 , Cs 2 TeO 3 ,Cs 2 Te, InI, InI 3 , In 2 I 6 , In 2 Te, Cd(OH) 2 , Cd(OH) 2 , TeO(OH) 2 ,CdI 2 , Cd 2 I 4 , Cs 2 CdI 4 , CsCdI 3 , Cs 2 CdI 4 , Cs 3 PO 4 and Cd-In-Ag. Critical assessments have been made on the following systems : In-I, In-Te, Cd-I, Sr-B-O and Ba-B-O. The thermodynamic quantities of these compounds have been calculated over the temperature range from 298 to 3000 K. The adoption of these data within appropriate modelling codes will allow the fission product species and transport to be predicted with greater confidence, thus providing more accurate assessments of the consequences of severe reactor accidents

  6. Environmental impacts of thermochemical biomass conversion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; McKinney, M.D.; Norton, M.V.; Abrams, C.W. [Pacific Northwest Lab., Richland, WA (United States)

    1995-06-01

    Thermochemical conversion in this study is limited to fast pyrolysis, upgrading of fast pyrolysis oils, and gasification. Environmental impacts of all types were considered within the project, but primary emphasis was on discharges to the land, air, and water during and after the conversion processes. The project discussed here is divided into five task areas: (1) pyrolysis oil analysis; (2) hydrotreating of pyrolysis oil; (3) gas treatment systems for effluent minimization; (4) strategic analysis of regulatory requirements; and (5) support of the IEA Environmental Systems Activity. The pyrolysis oil task was aimed at understanding the oil contaminants and potential means for their removal. The hydrotreating task was undertaken to better define one potential means for both improving the quality of the oil but also removing contaminants from the oil. Within Task 3, analyses were done to evaluate the results of gasification product treatment systems. Task 4 was a review and collection of regulatory requirements which would be applicable to the subject processes. The IEA support task included input to and participation in the IEA Bioenergy activity which directly relates to the project subject. Each of these tasks is described along with the results. Conclusions and recommendations from the overall project are given.

  7. Environmental impacts of thermochemical biomass conversion. Final report

    International Nuclear Information System (INIS)

    Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; McKinney, M.D.; Norton, M.V.; Abrams, C.W.

    1995-06-01

    Thermochemical conversion in this study is limited to fast pyrolysis, upgrading of fast pyrolysis oils, and gasification. Environmental impacts of all types were considered within the project, but primary emphasis was on discharges to the land, air, and water during and after the conversion processes. The project discussed here is divided into five task areas: (1) pyrolysis oil analysis; (2) hydrotreating of pyrolysis oil; (3) gas treatment systems for effluent minimization; (4) strategic analysis of regulatory requirements; and (5) support of the IEA Environmental Systems Activity. The pyrolysis oil task was aimed at understanding the oil contaminants and potential means for their removal. The hydrotreating task was undertaken to better define one potential means for both improving the quality of the oil but also removing contaminants from the oil. Within Task 3, analyses were done to evaluate the results of gasification product treatment systems. Task 4 was a review and collection of regulatory requirements which would be applicable to the subject processes. The IEA support task included input to and participation in the IEA Bioenergy activity which directly relates to the project subject. Each of these tasks is described along with the results. Conclusions and recommendations from the overall project are given

  8. Thermal energy storage using thermo-chemical heat pump

    International Nuclear Information System (INIS)

    Hamdan, M.A.; Rossides, S.D.; Haj Khalil, R.

    2013-01-01

    Highlights: ► Understanding of the performance of thermo chemical heat pump. ► Tool for storing thermal energy. ► Parameters that affect the amount of thermal stored energy. ► Lithium chloride has better effect on storing thermal energy. - Abstract: A theoretical study was performed to investigate the potential of storing thermal energy using a heat pump which is a thermo-chemical storage system consisting of water as sorbet, and sodium chloride as the sorbent. The effect of different parameters namely; the amount of vaporized water from the evaporator, the system initial temperature and the type of salt on the increase in temperature of the salt was investigated and hence on the performance of the thermo chemical heat pump. It was found that the performance of the heat pump improves with the initial system temperature, with the amount of water vaporized and with the water remaining in the system. Finally it was also found that lithium chloride salt has higher effect on the performance of the heat pump that of sodium chloride.

  9. Thermochemical study of cyanopyrazines: Experimental and theoretical approaches

    International Nuclear Information System (INIS)

    Miranda, Margarida S.; Morais, Victor M.F.; Matos, M. Agostinha R.

    2006-01-01

    The standard (p - bar =0.1MPa) molar energy of combustion, at T=298.15K, of crystalline 2,3-dicyanopyrazine was measured by static bomb calorimetry, in oxygen atmosphere. The standard molar enthalpy of sublimation, at T=298.15K, was obtained by Calvet Microcalorimetry, allowing the calculation of the standard molar enthalpy of formation of the compound, in the gas phase, at T=298.15K: Δ f H m - bar (g)=(518.7+/-3.4)kJ.mol -1 . In addition, the geometries of all cyanopyrazines were obtained using density functional theory with the B3LYP functional and two basis sets: 6-31G* and 6-311G**. These calculations were then used for a better understanding of the relation between structure and energetics of the cyanopyrazine systems. These calculations also reproduce measured standard molar enthalpies of formation with some accuracy and do provide estimates of this thermochemical parameter for those compounds that could not be studied experimentally, namely the tri- and tetracyanopyrazines: the strong electron withdrawing cyano group on the pyrazine ring makes cyanopyrazines highly destabilized compounds

  10. SWINE MANURE SOLIDS SEPARATION AND THERMOCHEMICAL CONVERSION TO HEAVY OIL

    Directory of Open Access Journals (Sweden)

    Shuangning Xiu

    2009-05-01

    Full Text Available Separation of solids from liquid swine manure and subsequent thermo-chemical conversion (TCC of the solids fraction into oil is one way of reducing the waste strength and odor emission. Such processing also provides a potential means of producing renewable energy from animal wastes. Gravity settling and mechanical separation techniques, by means of a centrifuge and belt press, were used to remove the solids from liquid swine manure. The solid fractions from the above separation processes were used as the feedstock for the TCC process for oil production. Experiments were conducted in a batch reactor with a steady temperature 305 oC, and the corresponding pressure was 10.34 Mpa. Gravity settling was demonstrated to be capable of increasing the total solids content of manure from 1% to 9%. Both of the mechanical separation systems were able to produce solids with dry matter around 18% for manure, with 1% to 2% initial total solids. A significant amount of volatile solid (75.7% was also obtained from the liquid fraction using the belt press process. The oil yields of shallow pit manure solids and deep pit manure solids with belt press separation were 28.72% and 29.8% of the total volatile solids, respectively. There was no visible oil product obtained from the deep pit manure solids with centrifuge separation. It is believed that it is the volatile solid content and the other components in the manure chemical composition which mainly deter-mine the oil production.

  11. Thermochemical properties of media for pyrometallurgical nuclear fuel reprocessing

    International Nuclear Information System (INIS)

    Hosoya, Yuji; Terai, Takayuki

    1998-01-01

    Molten chloride/cadmium system is considered to be applied to a solvent in pyrochemical reprocessing of spent nuclear fuel. In this work, phase diagrams for molten chloride systems were constructed, using NdCl 3 as an imitative substance in place of UCl 3 or PuCl 3 . Hastelloy-X (Ni/Cr21/Fe18/Mo9/W) was examined as a structural material for the corrosion-resistance against molten chloride baths containing NdCl 3 . The process of corrosion was thermochemically discussed and the form of the corrosion was illustrated. Rutherford backscattering spectroscopy was successfully applied to determine the elemental distribution profile of specimens tested on the compatibility with molten chloride mixture at elevated temperature. Ferritic steel was also examined as another candidate material for the compatibility with molten cadmium covered with LiCl-KCl eutectic salt. Variation of near-surface composition was observed by comparing the results of Rutherford backscattering spectroscopy obtained before and after the dipping. (author)

  12. R and D thermochemical I-S process at JAERI

    International Nuclear Information System (INIS)

    Onuki, K.; Kubo, S.; Nakajima, H.; Higashi, S.; Kasahara, S.; Ishiyama, S.; Okuda, H.

    2004-01-01

    The Japan Atomic Energy Research Institute (JAERI) has conducted a study on the thermochemical water-splitting process of the iodine-sulfur family (IS process). In the IS process, water will react with iodine and sulfur dioxide to produce hydrogen iodide and sulfuric acid, which are then decomposed thermally to produce hydrogen and oxygen. High temperature nuclear heat, mainly supplied by a High Temperature Gas-cooled Reactor (HTGR), is used to drive the endothermic decomposition of sulfuric acid. JAERI has demonstrated the feasibility of the water-splitting hydrogen production process by carrying out laboratory-scale experiments in which combined operation of fundamental reactions and separations using the IS process was performed continuously. At present, the hydrogen production test is continuing, using a scaled-up glass apparatus. Corrosion-resistant materials for constructing a large-scale plant and process improvements by introducing advanced separation techniques, such as membrane separation, are under study. Future R and D items are discussed based on the present activities. (author)

  13. Thermochemical liquefaction characteristics of microalgae in sub- and supercritical ethanol

    Energy Technology Data Exchange (ETDEWEB)

    You, Qiao; Chen, Liang [College of Environmental Science and Engineering, Hunan University, Changsha (China); Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Changsha (China)

    2011-01-15

    Thermochemical liquefaction characteristics of Spirulina, a kind of high-protein microalgae, were investigated with the sub- and supercritical ethanol as solvent in a 1000 mL autoclave. The influences of various liquefaction parameters on the yields of products (bio-oil and residue) from the liquefaction of Spirulina were studied, such as the reaction temperature (T), the S/L ratio (R{sub 1}, solid: Spirulina, liquid: ethanol), the solvent filling ratio (R{sub 2}) and the type and dosage of catalyst. Without catalyst, the bio-oil yields were in the range of 35.4 wt.% and 45.3 wt.% depending on the changes of T, R{sub 1} and R{sub 2}. And the bio-oil yields increased generally with increasing T and R{sub 2}, while the bio-oil yields reduced with increasing R{sub 1}. The FeS catalyst was certified to be an ideal catalyst for the liquefaction of Spirulina microalgae for its advantages on promoting bio-oil production and suppressing the formation of residue. The optimal dosage of catalyst (FeS) was ranging from 5-7 wt.%. The elemental analyses and FT-IR and GC-MS measurements for the bio-oils revealed that the liquid products have much higher heating values than the crude Spirulina sample and fatty acid ethyl ester compounds were dominant in the bio-oils, irrespective of whether catalyst was used. (author)

  14. Thermochemical conversion of biomass storage covers to reduce ammonia emissions from dairy manure Thermochemical conversion of biomass storage covers to reduce ammonia emissions from dairy manure

    Science.gov (United States)

    Manure storages, and in particular those storing digested manure, are a source of ammonia (NH3) emissions. Permeable manure storage covers can reduce NH3 emissions, however performance can decline as they degrade. Thermochemical conversion of biomass through pyrolysis and steam treatment could incre...

  15. Use of carbon dioxide as a reaction medium in the thermo-chemical process for the enhanced generation of syngas and tuning adsorption ability of biochar

    International Nuclear Information System (INIS)

    Cho, Dong-Wan; Kwon, Eilhann E.; Song, Hocheol

    2016-01-01

    Highlights: • Utilizing CO_2 as a reaction medium in thermo-chemical conversion of aquatic biomass. • Enhanced generation of syngas in the presence of CO_2. • Considerable reduction of pyrolytic oil in CO_2-assisted pyrolysis. • Generation of biochar with high surface area and more porous structure by CO_2. - Abstract: This study mechanistically investigated the influences of CO_2 on syngas (H_2 and CO) production during thermo-chemical conversion of red seaweed, and further explored the possible utility of the produced biochar as a medium for adsorption of inorganic/organic contaminants in aqueous phase. In order to elucidate the key roles of CO_2 in the thermo-chemical process, the composition analysis of syngas and the qualitative analysis of pyrolytic oil were conducted and compared with those in pyrolysis in N_2 condition. Pyrolysis of red seaweed in the presence of CO_2 led to the enhanced generation of syngas at the entire experimental temperatures. For example, the ratio of CO to H_2 in the presence of CO_2 at 620 °C was enhanced by ∼400%, as compared to the case in N_2. This enhanced generation of syngas resulted in significant pyrolytic oil reduction by ∼70% at 620 °C via the unknown reactions between VOCs and CO_2. In addition, biochar generated in the CO_2 environment exhibited comparatively higher surface area (61 m"2 g"−"1) and more porous structure. The morphological modification induced by CO_2 provided the favorable condition for removal of methylene blue from the aqueous phase. Thus, this study experimentally demonstrated that exploiting CO_2 as a reaction medium would provide an attractive option for the enhanced generation of syngas and the tuned adsorption capability of biochar.

  16. Lead nitrate induced changes in the thyroid physiology of the catfish Clarias batrachus (L)

    International Nuclear Information System (INIS)

    Katti, S.R.; Sathyanesan, A.G.

    1987-01-01

    Chronic exposure of Clarias batrachus to sublethal dose of 5 ppm lead nitrate for a period of 150 days impaired thyroid function. Histological observations revealed hypertrophy, increased cell height, vacuolation, and reduction of colloid. The thyrotrophs of the pituitary also exhibited hypertrophy. Radioiodine ( 131 I) uptake was significantly lowered. Fish exposed to 5, 10, and 25 ppm of lead nitrate for 7 days also exhibited significant reduction in 131 I uptake which was dose dependent. These findings suggest that lead nitrate impairs thyroid function involving the hypothalamohypophysiothyroid axis

  17. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    Science.gov (United States)

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  18. Development of biological treatment of high concentration sodium nitrate waste liquid

    International Nuclear Information System (INIS)

    Ogawa, Naoki; Kuroda, Kazuhiko; Shibata, Katsushi; Kawato, Yoshimi; Meguro, Yoshihiro; Takahashi, Kuniaki

    2009-01-01

    An electrolytic reduction, chemical reduction, and biological reduction have been picked up as a method of nitrate liquid waste treatment system exhausted from the reprocessing process. As a result of comparing them, it was shown that the biological treatment was the most excellent method in safety and the economy. (author)

  19. Effects of Dietary Neutral Detergent Fiber to Non-Fiber Carbohydrates Ratio on Ruminal Nitrate Reduction of Hu Sheep%饲粮中性洗涤纤维与非纤维性碳水化合物比例对湖羊瘤胃还原硝态氮的影响

    Institute of Scientific and Technical Information of China (English)

    林淼; 张建刚; 陈志远; 赵国琦

    2014-01-01

    experiment period. In conclusion, the optimum NDF/NFC in the diet of Hu sheep is 0.71 for nitrate nitrogen reduction and fermentation in the rumen under this experimental condition.

  20. Sintering of Cu–Al2O3 nano-composite powders produced by a thermochemical route

    Directory of Open Access Journals (Sweden)

    MARIJA KORAC

    2007-11-01

    Full Text Available This paper presents the synthesis of nano-composite Cu–Al2O3 powder by a thermochemical method and sintering, with a comparative analysis of the mechanical and electrical properties of the obtained solid samples. Nano-crystalline Cu–Al2O3 powders were produced by a thermochemical method through the following stages: spray-drying, oxidation of the precursor powder, reduction by hydrogen and homogenization. Characterization of powders included analytical electron microscopy (AEM coupled with energy dispersive spectroscopy (EDS, differenttial thermal and thermogravimetric (DTA–TGA analysis and X-ray diffraction (XRD analysis. The size of the produced powders was 20–50 nm, with a noticeable presence of agglomerates. The composite powders were characterized by a homogenous distribution of Al2O3 in a copper matrix. The powders were cold pressed at a pressure of 500 MPa and sintered in a hydrogen atmosphere under isothermal conditions in the temperature range from 800 to 900 °C for up to 120 min. Characterization of the Cu–Al2O3 sintered system included determination of the density, relative volume change, electrical and mechanical properties, examination of the microstructure by SEM and focused ion beam (FIB analysis, as well as by EDS. The obtained nano-composite, the structure of which was, with certain changes, presserved in the final structure, provided a sintered material with a homogenеous distribution of dispersoid in a copper matrix, with exceptional effects of reinforcement and an excellent combination of mechanical and electrical properties.

  1. Review of the direct thermochemical conversion of lignocellulosic biomass for liquid fuels

    Directory of Open Access Journals (Sweden)

    Jianchun JIANG,Junming XU,Zhanqian SONG

    2015-03-01

    Full Text Available Increased demand for liquid transportation fuels, environmental concerns and depletion of petroleum resources requires the development of efficient conversion technologies for production of second-generation biofuels from non-food resources. Thermochemical approaches hold great potential for conversion of lignocellulosic biomass into liquid fuels. Direct thermochemical processes convert biomass into liquid fuels in one step using heat and catalysts and have many advantages over indirect and biological processes, such as greater feedstock flexibility, integrated conversion of whole biomass, and lower operation costs. Several direct thermochemical processes are employed in the production of liquid biofuels depending on the nature of the feedstock properties: such as fast pyrolysis/liquefaction of lignocellulosic biomass for bio-oil, including upgrading methods, such as catalytic cracking and hydrogenation. Owing to the substantial amount of liquid fuels consumed by vehicular transport, converting biomass into drop-in liquid fuels may reduce the dependence of the fuel market on petroleum-based fuel products. In this review, we also summarize recent progress in technologies for large-scale equipment for direct thermochemical conversion. We focus on the technical aspects critical to commercialization of the technologies for production of liquid fuels from biomass, including feedstock type, cracking catalysts, catalytic cracking mechanisms, catalytic reactors, and biofuel properties. We also discuss future prospects for direct thermochemical conversion in biorefineries for the production of high grade biofuels.

  2. Effects of key factors on solar aided methane steam reforming in porous medium thermochemical reactor

    International Nuclear Information System (INIS)

    Wang, Fuqiang; Tan, Jianyu; Ma, Lanxin; Leng, Yu

    2015-01-01

    Highlights: • Effects of key factors on chemical reaction for solar methane reforming are studied. • MCRT and FVM method coupled with UDFs is used to establish numerical model. • Heat and mass transfer model coupled with thermochemical reaction is established. • LTNE model coupled with P1 approximation is used for porous matrix solar reactor. • A formula between H 2 production and conductivity of porous matrix is put forward. - Abstract: With the aid of solar energy, methane reforming process can save up to 20% of the total methane consumption. Monte Carlo Ray Tracing (MCRT) method and Finite Volume Method (FVM) combined method are developed to establish the heat and mass transfer model coupled with thermochemical reaction kinetics for porous medium solar thermochemical reactor. In order to provide more temperature information, local thermal non-equilibrium (LTNE) model coupled with P1 approximation is established to investigate the thermal performance of porous medium solar thermochemical reaction. Effects of radiative heat loss and thermal conductivity of porous matrix on temperature distribution and thermochemical reaction for solar driven steam methane reforming process are numerically studied. Besides, the relationship between hydrogen production and thermal conductivity of porous matrix are analyzed. The results illustrate that hydrogen production shows a 3 order polynomial relation with thermal conductivity of porous matrix

  3. The nitrate to ammonia and ceramic (NAC) process

    International Nuclear Information System (INIS)

    Mattus, A.J.; Lee, D.D.

    1993-01-01

    A new low-temperature (50--60 degrees C) process for the reduction of nitrate or nitrite to ammonia gas in a stirred, ethylene glycol led reactor has been developed. The process has nearly completed 2 years of bench-top testing in preparation for a pilot-scale demonstration in the fall of 1994. The nitrate to ammonia and ceramic (NAC) process utilizes the active metal Al (in powder or shot form) in alkaline solution to convert nitrate to ammonia gas with the liberation of heat. Between 0.8 and 1.6 kg of Al per kilogram of sodium nitrate is required to convert solutions of between 3.1 and 6.2 M nitrate to near zero concentration. Prior to feeding Al to the reactor, 40 μm quartz is added based upon the total sodium content of the waste. Upon adding the Al, a by-product of gibbsite precipitates in the reactor as the ammonia leaves the solution. At the end of the reaction, the alumina-silica-based solids are dewatered, calcined, pressed, and sintered into a hard ceramic. Comparing the volume of the final ceramic product with the volume of the starting waste solution, we obtain an ∼70% volume reduction. This compares with an expected 50% volume increase if the waste were immobilized in cement-based grout. The process is being developed for use at Hanford, where as much as 125,000 tonnes of nitrate salts is stored in 4 million liter tanks. DOE may be able to shred radioactively contaminated scrap aluminum, and use this metal to feed the NAC reactor

  4. Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States.

    Science.gov (United States)

    Pye, Havala O T; Luecken, Deborah J; Xu, Lu; Boyd, Christopher M; Ng, Nga L; Baker, Kirk R; Ayres, Benjamin R; Bash, Jesse O; Baumann, Karsten; Carter, William P L; Edgerton, Eric; Fry, Juliane L; Hutzell, William T; Schwede, Donna B; Shepson, Paul B

    2015-12-15

    Organic nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chemical transport models may include a representation of organic aerosol from monoterpene reactions with nitrate radicals (the primary source of particle-phase organic nitrates in the Southeast United States), secondary organic aerosol (SOA) models can underestimate yields. Furthermore, SOA parametrizations do not explicitly take into account organic nitrate compounds produced in the gas phase. In this work, we developed a coupled gas and aerosol system to describe the formation and subsequent aerosol-phase partitioning of organic nitrates from isoprene and monoterpenes with a focus on the Southeast United States. The concentrations of organic aerosol and gas-phase organic nitrates were improved when particulate organic nitrates were assumed to undergo rapid (τ = 3 h) pseudohydrolysis resulting in nitric acid and nonvolatile secondary organic aerosol. In addition, up to 60% of less oxidized-oxygenated organic aerosol (LO-OOA) could be accounted for via organic nitrate mediated chemistry during the Southern Oxidants and Aerosol Study (SOAS). A 25% reduction in nitrogen oxide (NO + NO2) emissions was predicted to cause a 9% reduction in organic aerosol for June 2013 SOAS conditions at Centreville, Alabama.

  5. Removal of Nitrate by Zero Valent Iron in the Presence of H2O2

    Directory of Open Access Journals (Sweden)

    M.R. Samarghandi

    2014-01-01

    Full Text Available Background & Aims: Nitrate is the oxidation state of nitrogen compounds, which is founded in water resources that contaminated by municipal, industrial and agricultural waste water. If nitrate leek in to ground water resources, it can cause health problems. Material and Methods: Removal of nitrate from ground water by iron powder in the presence of H2O2 was investigated. Experiments have been done by use of 250 ml of water samples containing 100 mg/L nitrate in various condition. Various parameters such as pH (3, 5, 7, 9, iron dosage (10, 15, 20, 30 g/L, initial H2O2 concentration (5, 10, 15, 20 ml/L and contact time (10-120 min. Results: Obtained results shows the removal of nitrate was increased by pH reduction, increment of iron mass and contact time. In addition, nitrate reduction was increased by increment of initial H2O2 concentration up to 15 ml/L. High removal was observed at pH=3, iron mass=30 g/L, contact time equal 120 min and H2O2 concentration=15 ml/L. At above condition, upon 98% of nitrate was removed. Conclusion: In summary, this method is simple, low cost and effective for removal of nitrate from ground water and industrial activity.

  6. Nitrate removal through combination of nanofiltration and electrocatalysis; Nitratentfernung durch Kombination von Nanofiltration und Elektrokatalyse

    Energy Technology Data Exchange (ETDEWEB)

    Roehricht, M.; Stadlbauer, E.A.; Happel, H. [Fachhochschule Giessen (Germany). Zentrum fuer Umwelttechnik

    1999-07-01

    In a new process combination, nitrate-containing ground water is first of all separated by nanofiltration into a concentrate stream (some 25 %) and a largely nitrate-free permeate (75 %). Then the enriched nitrate in the concentrate is converted into nitrogen by means of electrocatalytic nitrate reduction. Whereas, in nanofiltration, a concentration takes place, electrocatalytic nitrate reduction is a process by which nitrate is converted into elemental nitrogen and, thus, removed. Nanofiltration is a membrane separating process making use of 'open' reverse osmosis membranes, which are characterized by high flow but also reduced retention. (orig.) [German] In einer neuen Verfahrenskombination wird das nitrathaltige Grundwasser zuerst durch Nanofiltration in einen Konzentratstrom (ca. 25%) und ein weitgehend nitratfreies Permeat (75%) aufgeteilt. Im Konzentrat wird dann mittels Elektrokatalytischer Nitratreduktion (EKN) das angereicherte Nitrat zu Stickstoff umgewandelt. Waehrend bei der Nanofiltration eine Aufkonzentrierung erfolgt, wird durch die Elektrokatalytische Nitratreduktion das Nitrat in elementaren Stickstoff umgewandelt und so entfernt. Die Nanofiltration ist ein Membrantrennverfahren, bei dem 'offene' Umkehrosmosemembranen eingesetzt werden, die einen hohen Fluss aber auch eine verminderte Rueckhaltung aufweisen. (orig.)

  7. Transformation of benzalkonium chloride under nitrate reducing conditions.

    Science.gov (United States)

    Tezel, Ulas; Pavlostathis, Spyros G

    2009-03-01

    The effect and transformation potential of benzalkonium chlorides (BAC) under nitrate reducing conditions were investigated at concentrations up to 100 mg/L in batch assays using a mixed, mesophilic (35 degrees C) methanogenic culture. Glucose was used as the carbon and energy source and the initial nitrate concentration was 70 mg N/L Dissimilatory nitrate reduction to ammonia (DNRA) and to dinitrogen (DNRN) were observed at BAC concentrations up to 25 mg/L At and above 50 mg BAC/L, DNRA was inhibited and DNRN was incomplete resulting in accumulation of nitrous oxide. Long-term inhibition of methanogenesis and accumulation of volatile fatty acids were observed at and above 50 mg BAC/L Over 99% of the added BAC was recovered from all cultures except the one amended with 100 mg BAC/L where 37% of the initially added BAC was transformed during the 100 day incubation period. Abiotic and biotic assays performed with 100 mg/L of BAC and 5 mM (in the liquid phase) of either nitrate, nitrite, or nitric oxide demonstrated that BAC transformation was abiotic and followed the modified Hofmann degradation pathway, i.e., bimolecular nucleophilic substitution with nitrite. Alkyl dimethyl amines (tertiary amines) were produced at equamolar levels to BAC transformed, but were not further degraded. This is the first report demonstrating the transformation of BAC under nitrate reducing conditions and elucidating the BAC transformation pathway.

  8. Biomass thermochemical conversion - overview of results; Biomassan jalostus - tutkimusalueen katsaus

    Energy Technology Data Exchange (ETDEWEB)

    Sipilae, K [VTT Energy, Espoo (Finland). Energy Production Technologies

    1996-12-31

    In this Bioenergy research program the thermochemical conversion activities are mainly concentrated in three fields (1) flash pyrolysis and the use of wood oil in boilers and engines (2) biomass gasification for gas engine power plants and finally (3) conversion of black liquor and extractives in a pulp mill to various liquid fuels. Parallel to activities in Finland also significant work has been done in EU-Joule and Apas projects and in the IEA Bioenergy Agreement. In the area of flash pyrolysis technology, three new laboratory and PDU-units have been installed to VTT in order to produce various qualities of bio oils from wood and straw. The quality of pyrolysis oils have been characterized by physical and chemical methods supported by EU and IEA networks. Several companies are carrying out pyrolysis activities as well: Neste Oy is testing the wood oil in a 200 kW boiler, Waertsilae Diesel Oy is testing Canadian wood oil in a 1.5 MWe diesel power plant engine and Vapo Oy is carrying out investigations to produce pyrolysis oils in Finland. The biomass gasification coupled to a gas engine is an interesting alternative for small scale power production parallel to existing fluid bed boiler technology. VTT has installed a circulating fluid bed gasifier with advanced gas cleaning system to test various technologies in order to feed the gas to an engine. In order to produce liquid fuels at a pulp mill, the laboratory work has continued using crude soap as a raw material for high pressure liquid phase treatment and atmospheric pyrolysis process. The quality of the oil is like light fuel oil or diesel fuel, possibilities to use it as a lubricant will be investigated

  9. Biomass thermochemical conversion - overview of results; Biomassan jalostus - tutkimusalueen katsaus

    Energy Technology Data Exchange (ETDEWEB)

    Sipilae, K. [VTT Energy, Espoo (Finland). Energy Production Technologies

    1995-12-31

    In this Bioenergy research program the thermochemical conversion activities are mainly concentrated in three fields (1) flash pyrolysis and the use of wood oil in boilers and engines (2) biomass gasification for gas engine power plants and finally (3) conversion of black liquor and extractives in a pulp mill to various liquid fuels. Parallel to activities in Finland also significant work has been done in EU-Joule and Apas projects and in the IEA Bioenergy Agreement. In the area of flash pyrolysis technology, three new laboratory and PDU-units have been installed to VTT in order to produce various qualities of bio oils from wood and straw. The quality of pyrolysis oils have been characterized by physical and chemical methods supported by EU and IEA networks. Several companies are carrying out pyrolysis activities as well: Neste Oy is testing the wood oil in a 200 kW boiler, Waertsilae Diesel Oy is testing Canadian wood oil in a 1.5 MWe diesel power plant engine and Vapo Oy is carrying out investigations to produce pyrolysis oils in Finland. The biomass gasification coupled to a gas engine is an interesting alternative for small scale power production parallel to existing fluid bed boiler technology. VTT has installed a circulating fluid bed gasifier with advanced gas cleaning system to test various technologies in order to feed the gas to an engine. In order to produce liquid fuels at a pulp mill, the laboratory work has continued using crude soap as a raw material for high pressure liquid phase treatment and atmospheric pyrolysis process. The quality of the oil is like light fuel oil or diesel fuel, possibilities to use it as a lubricant will be investigated

  10. Thermochemical Wastewater Valorization via Enhanced Microbial Toxicity Tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Beckham, Gregg T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Thelhawadigedara, Lahiru Niroshan Jayakody [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Johnson, Christopher W [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Pleitner, Brenna P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Cleveland, Nicholas S [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Michener, William E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Olstad-Thompson, Jessica L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Vardon, Derek R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Whitham, Jason M. [Oak Ridge National Laboratory; Giannone, Richard J. [Oak Ridge National Laboratory; Klingeman, Dawn M. [Oak Ridge National Laboratory; Brown, Robert C. [Iowa State University; Brown, Steven D. [Oak Ridge National Laboratory; LanzaTech, Inc.; Hettich, Robert L. [Oak Ridge National Laboratory; Guss, Adam M. [Oak Ridge National Laboratory

    2018-04-17

    Thermochemical (TC) biomass conversion processes such as pyrolysis and liquefaction generate considerable amounts of wastewater, which often contains highly toxic compounds that are incredibly challenging to convert via standard wastewater treatment approaches such as anaerobic digestion. These streams represent a cost for TC biorefineries, and a potential valorization opportunity, if effective conversion methods are developed. The primary challenge hindering microbial conversion of TC wastewater is toxicity. In this study, we employ a robust bacterium, Pseudomonas putida, with TC wastewater streams to demonstrate that aldehydes are the most inhibitory compounds in these streams. Proteomics, transcriptomics, and fluorescence-based immunoassays of P. putida grown in a representative wastewater stream indicate that stress results from protein damage, which we hypothesize is a primary toxicity mechanism. Constitutive overexpression of the chaperone genes, groEL, groES, and clpB, in a genome-reduced P. putida strain improves the tolerance towards multiple TC wastewater samples up to 200-fold. Moreover, the concentration ranges of TC wastewater are industrially relevant for further bioprocess development for all wastewater streams examined here, representing different TC process configurations. Furthermore, we demonstrate proof-of-concept polyhydroxyalkanoate production from the usable carbon in an exemplary TC wastewater stream. Overall, this study demonstrates that protein quality control machinery and repair mechanisms can enable substantial gains in microbial tolerance to highly toxic substrates, including heterogeneous waste streams. When coupled to other metabolic engineering advances such as expanded substrate utilization and enhanced product accumulation, this study generally enables new strategies for biological conversion of highly-toxic, organic-rich wastewater via engineered aerobic monocultures or designer consortia.

  11. Nitrate decreases ruminal methane production with slight changes to ruminal methanogen composition of nitrate-adapted steers.

    Science.gov (United States)

    Zhao, Liping; Meng, Qingxiang; Li, Yan; Wu, Hao; Huo, Yunlong; Zhang, Xinzhuang; Zhou, Zhenming

    2018-03-20

    This study was conducted to examine effects of nitrate on ruminal methane production, methanogen abundance, and composition. Six rumen-fistulated Limousin×Jinnan steers were fed diets supplemented with either 0% (0NR), 1% (1NR), or 2% (2NR) nitrate (dry matter basis) regimens in succession. Rumen fluid was taken after two-week adaptation for evaluation of in vitro methane production, methanogen abundance, and composition measurements. Results showed that nitrate significantly decreased in vitro ruminal methane production at 6 h, 12 h, and 24 h (P methane reduction was significantly related to Methanobrevibacter and Methanoplanus abundance, and negatively correlated with Methanosphaera and Methanimicrococcus abundance.

  12. Dietary nitrate improves vascular function in patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled study123

    Science.gov (United States)

    Velmurugan, Shanti; Gan, Jasmine Ming; Rathod, Krishnaraj S; Khambata, Rayomand S; Ghosh, Suborno M; Hartley, Amy; Van Eijl, Sven; Sagi-Kiss, Virag; Chowdhury, Tahseen A; Curtis, Mike; Kuhnle, Gunter GC; Wade, William G; Ahluwalia, Amrita

    2016-01-01

    Background: The beneficial cardiovascular effects of vegetables may be underpinned by their high inorganic nitrate content. Objective: We sought to examine the effects of a 6-wk once-daily intake of dietary nitrate (nitrate-rich beetroot juice) compared with placebo intake (nitrate-depleted beetroot juice) on vascular and platelet function in untreated hypercholesterolemics. Design: A total of 69 subjects were recruited in this randomized, double-blind, placebo-controlled parallel study. The primary endpoint was the change in vascular function determined with the use of ultrasound flow-mediated dilatation (FMD). Results: Baseline characteristics were similar between the groups, with primary outcome data available for 67 patients. Dietary nitrate resulted in an absolute increase in the FMD response of 1.1% (an ∼24% improvement from baseline) with a worsening of 0.3% in the placebo group (P nitrate group, showing a trend (P = 0.06) to improvement in comparison with the placebo group. Dietary nitrate also caused a small but significant reduction (7.6%) in platelet-monocyte aggregates compared with an increase of 10.1% in the placebo group (P = 0.004), with statistically significant reductions in stimulated (ex vivo) P-selectin expression compared with the placebo group (P nitrate were detected. The composition of the salivary microbiome was altered after the nitrate treatment but not after the placebo treatment (P nitrate treatment; of those taxa present, 2 taxa were responsible for >1% of this change, with the proportions of Rothia mucilaginosa trending to increase and Neisseria flavescens (P nitrate treatment relative to after placebo treatment. Conclusions: Sustained dietary nitrate ingestion improves vascular function in hypercholesterolemic patients. These changes are associated with alterations in the oral microbiome and, in particular, nitrate-reducing genera. Our findings provide additional support for the assessment of the potential of dietary nitrate as a

  13. Solubility isotherms in ternary systems of samarium nitrate, water and nitrates of amidopyrine, benzotriazole

    International Nuclear Information System (INIS)

    Starikova, L.I.

    1991-01-01

    Solubility in the system of samarium nitrate-amidopyrine nitrate-water at 25 and 50 deg C was studied. Solubility isotherms consist of three branches, corresponding to crystallization of samarium nitrate tetrahydrate, amidopyrine nitrate and congruently soluble compounds of Sm(NO 3 ) 3 · 2C 13 H 17 ON 3 ·HNO 3 composition. Its thermal behaviour was studied. The system of samarium nitrate-benzotriazole nitrate-water is referred to eutonic type

  14. JAEA’s R&D on the Thermochemical Hydrogen Production IS Process

    International Nuclear Information System (INIS)

    Kasahara, Seiji; Tanaka, Nobuyuki; Noguchi, Hiroki; Iwatsuki, Jin; Takegami, Hiroaki; Yan, Xing L.; Kubo, Shinji

    2014-01-01

    Japan Atomic Energy Agency (JAEA) has studied iodine-sulfur (IS) process, a thermochemical cycle to produce hydrogen by water splitting. This process is a candidate application of high temperature heat from high temperature gas-cooled reactors. This paper outlines the IS process study in JAEA, in particular recent situation of the R&D. Reactor components and a total process facility are tested to evaluate their integrity. A Bunsen reactor, a H_2SO_4 decomposer and a HI decomposer made of industrial materials such as SiC ceramic, fluoroplastic and lining materials have been examined separately as reactor components. A semibatch test and a thermal cycle test were operated in the Bunsen reactor. H_2SO_4 decomposition test is in a bayonet type reactor and HI decomposition test in an adiabatic radial flow type reactor are now under way. On the basis of a demonstration of continuous hydrogen production of 31 NL/h by a glass apparatus, an experimental apparatus of the total IS process has just been constructed to verify integrity of process components of industrial materials, H_2 production scale of which is 200 NL/h. Electro-electrodialysis (EED) cells to concentrate HI before distillation and a SiC-made bayonet type H_2SO_4 decomposer are applied in the facility. Process data of EED cells has been collected aiming to improve H_2 production thermal efficiency. Influence of temperature, composition in solution and existence of impurities on the cell properties has been investigated. Reduction of heat input to a HI separation step by applying the results of the study was shown. (author)

  15. Physicochemical and thermal characteristics of the sludge produced after thermochemical treatment of petrochemical wastewater.

    Science.gov (United States)

    Verma, Shilpi; Prasad, Basheshwar; Mishra, I M

    2012-01-01

    The present work describes the physicochemical and thermal characteristics of the sludge generated after thermochemical treatment of wastewater from a petrochemical plant manufacturing purified terephthalic acid (PTA). Although FeCl3 was found to be more effective than CuSO4 in removing COD from wastewater, the settling and filtration characteristics of FeCl3 sludge were poorer. Addition of cationic polyacrylamide (CPAA; 0.050kg/m3) to the FeCl3 wastewater system greatly improved the values of the filter characteristics of specific cake resistance (1.2 x 10(8) m/kg) and resistance of filter medium (9.9 x 10(8) m(-1)) from the earlier values of 1.9 x 10(9) m/kg and 1.7 x 10(8) m(-1), respectively. SEM-EDAX and FTIR studies were undertaken, to understand the sludge structure and composition, respectively. The moisture distribution in the CuSO4 sludge, FeCl3 sludge and FeCl3 + CPAA sludge showed that the amount of bound water content in the CuSO4 and FeCl3 + CPAA sludges is less than that of the FeCl3 sludge and there was a significant reduction in the solid-water bond strength of FeCl3 + CPAA sludge, which was responsible for better settling and filtration characteristics. Due to the hazardous nature of the sludge, land application is not a possible route of disposal. The thermal degradation behaviour of the sludge was studied for its possible use as a co-fuel. The studies showed that degradation behaviour of the sludge was exothermic in nature. Because of the exothermic nature of the sludge, it can be used in making fuel briquettes or it can be disposed of via wet air oxidation.

  16. Comprehensive characterisation of sewage sludge for thermochemical conversion processes - Based on Singapore survey.

    Science.gov (United States)

    Chan, Wei Ping; Wang, Jing-Yuan

    2016-08-01

    Recently, sludge attracted great interest as a potential feedstock in thermochemical conversion processes. However, compositions and thermal degradation behaviours of sludge were highly complex and distinctive compared to other traditional feedstock led to a need of fundamental research on sludge. Comprehensive characterisation of sludge specifically for thermochemical conversion was carried out for all existing Water Reclamation Plants in Singapore. In total, 14 sludge samples collected based on the type, plant, and batch categorisation. Existing characterisation methods for physical and chemical properties were analysed and reviewed using the collected samples. Qualitative similarities and quantitative variations of different sludge samples were identified and discussed. Oxidation of inorganic in sludge during ash forming analysis found to be causing significant deviations on proximate and ultimate analysis. Therefore, alternative parameters and comparison basis including Fixed Residues (FR), Inorganic Matters (IM) and Total Inorganics (TI) were proposed for better understanding on the thermochemical characteristics of sludge. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Hydrogen production at <550 C using a low temperature thermochemical cycle

    International Nuclear Information System (INIS)

    Lewis, M.A.; Serban, M.; Basco, J.K.

    2004-01-01

    A Department of Energy goal is to identify new technologies for producing hydrogen cost effectively without greenhouse gas emissions. Thermochemical cycles are one of the potential options under investigation. Thermochemical cycles consist of a series of reactions in which water is thermally decomposed and all other chemicals are recycled. Only heat and water are consumed. However, most thermochemical cycles require process heat at temperatures of 850-900 deg C. Argonne National Laboratory is developing low temperature cycles designed for lower temperature heat, 500-550 deg C, which is more readily available. For this temperature region, copper-chlorine (Cu-Cl) cycles are the most promising cycle. Several Cu-Cl cycles have been examined in the laboratory and the most promising cycle has been identified. Proof-of-principle experiments are nearly complete. A preliminary assessment of cycle efficiency is promising. Details of the experiments and efficiency calculations are discussed. (author)

  18. Research, Development, and Field Testing of Thermochemical Recuperation for High Temperature Furnace

    Energy Technology Data Exchange (ETDEWEB)

    Kurek, Harry; Kozlov, Aleksandr

    2014-03-31

    Gas Technology Institute (GTI) evaluated the technical and economic feasibility of utilizing a non-catalytic ThermoChemical Recuperation System (TCRS) to recover a significant amount of energy from the waste gases of natural gas fired steel reheat furnaces. The project was related to DOE-AMO’s (formerly known as ITP) one of the technical areas of interest: Technologies to improve energy efficiency and reduce the carbon footprint of equipment currently used in energy-intensive industries such as iron and steel, and reduce by at least 30% energy consumption and carbon dioxide emission compared to the conventional technologies. ThermoChemical Recuperation (TCR) is a technique that recovers sensible heat in the exhaust gas from an industrial process, furnace, engine etc., when a hydrocarbon fuel is used for combustion. TCR enables waste heat recovery by both combustion air preheat and hydrocarbon fuel (natural gas, for example) reforming into a higher calorific fuel. The reforming process uses hot flue gas components (H2O and CO2) or steam to convert the fuel into a combustible mixture of hydrogen (H2), carbon monoxide (CO), and some unreformed hydrocarbons (CnHm). Reforming of natural gas with recycled exhaust gas or steam can significantly reduce fuel consumption, CO2 emissions and cost as well as increase process thermal efficiency. The calorific content of the fuel can be increased by up to ~28% with the TCR process if the original source fuel is natural gas. In addition, the fuel is preheated during the TCR process adding sensible heat to the fuel. The Research and Development work by GTI was proposed to be carried out in three Phases (Project Objectives). • Phase I: Develop a feasibility study consisting of a benefits-derived economic evaluation of a ThermoChemical Recuperation (TCR) concept with respect to high temperature reheat furnace applications within the steel industry (and cross-cutting industries). This will establish the design parameters and

  19. Crystallization of sodium nitrate from radioactive waste

    International Nuclear Information System (INIS)

    Krapukhin, V.B.; Krasavina, E.P.; Pikaev, A.K.

    1997-07-01

    From the 1940s to the 1980s, the Institute of Physical Chemistry of the Russian Academy of Sciences (IPC/RAS) conducted research and development on processes to separate acetate and nitrate salts and acetic acid from radioactive wastes by crystallization. The research objective was to decrease waste volumes and produce the separated decontaminated materials for recycle. This report presents an account of the IPC/RAS experience in this field. Details on operating conditions, waste and product compositions, decontamination factors, and process equipment are described. The research and development was generally related to the management of intermediate-level radioactive wastes. The waste solutions resulted from recovery and processing of uranium, plutonium, and other products from irradiated nuclear fuel, neutralization of nuclear process solutions after extractant recovery, regeneration of process nitric acid, equipment decontamination, and other radiochemical processes. Waste components include nitric acid, metal nitrate and acetate salts, organic impurities, and surfactants. Waste management operations generally consist of two stages: volume reduction and processing of the concentrates for storage, solidification, and disposal. Filtration, coprecipitation, coagulation, evaporation, and sorption were used to reduce waste volume. 28 figs., 40 tabs

  20. Thermochemical reactivity of 5–15 mol% Fe, Co, Ni, Mn-doped cerium oxides in two-step water-splitting cycle for solar hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Gokon, Nobuyuki, E-mail: ngokon@eng.niigata-u.ac.jp [Center for Transdisciplinary Research, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181 (Japan); Suda, Toshinori [Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan); Kodama, Tatsuya [Department of Chemistry & Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan)

    2015-10-10

    Highlights: • 5–15 mol% M-doped ceria are examined for thermochemical two-step water-splitting. • 5 mol% Fe- and Co-doped ceria have stoichiometric production of oxygen and hydrogen. • 10–15 mol% Fe- and Mn-doped ceria showed near-stoichiometric production. - Abstract: The thermochemical two-step water-splitting cycle using transition element-doped cerium oxide (M–CeO{sub 2−δ}; M = Fe, Co, Ni, Mn) powders was studied for hydrogen production from water. The oxygen/hydrogen productivity and repeatability of M–CeO{sub 2−δ} materials with M doping contents in the 5–15 mol% range were examined using a thermal reduction (TR) temperature of 1500 °C and water decomposition (WD) temperatures in the 800–1150 °C range. The temperature, steam partial pressure, and steam flow rate in the WD step had an impact on the hydrogen productivity and production rate. 5 mol% Fe- and Co-doped CeO{sub 2−δ} enhances hydrogen productivity by up to 25% on average compared to undoped CeO{sub 2}, and shows stable repeatability of stoichiometric oxygen and hydrogen production for the cyclic thermochemical two-step water-splitting reaction. In addition, 5 mol% Mn-doped CeO{sub 2−δ}, 10 and 15 mol% Fe- and Mn-doped CeO{sub 2−δ} show near stoichiometric reactivities.

  1. Electrochemical processing of nitrate waste solutions. Phase 2, Final report

    Energy Technology Data Exchange (ETDEWEB)

    Genders, D.; Weinberg, N.; Hartsough, D. [Electrosynthesis Co., Inc., Cheektowaga, NY (US)

    1992-10-07

    The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F{sup {minus}} ions from the synthetic mix migrating across the cation exchange membrane and forming HF in the acid anolyte. Other possibilities for anode materials were explored. A membrane separation process was investigated which employs an anion and cation exchange membrane to remove nitrite and nitrate, recovering caustic and nitric acid. Present research has shown poor current efficiencies for nitrite and nitrate transport across the anion exchange membrane due to co-migration of hydroxide anions. Precipitates form within the anion exchange membranes which would eventually result in the failure of the membranes. Electrochemical processing offers a highly promising and viable method for the treatment of nitrate waste solutions.

  2. A systematic multi-step screening of numerous salt hydrates for low temperature thermochemical energy storage

    International Nuclear Information System (INIS)

    N’Tsoukpoe, Kokouvi Edem; Schmidt, Thomas; Rammelberg, Holger Urs; Watts, Beatriz Amanda; Ruck, Wolfgang K.L.

    2014-01-01

    Highlights: • We report an evaluation of the potential of salt hydrates for thermochemical storage. • Both theoretical calculations and experimental measurements using TGA/DSC are used. • Salt hydrates offer very low potential for thermochemical heat storage. • The efficiency of classical processes using salt hydrates is very low: typically 25%. • New processes are needed for the use of salt hydrates in thermochemical heat storage. - Abstract: In this paper, the potential energy storage density and the storage efficiency of salt hydrates as thermochemical storage materials for the storage of heat generated by a micro-combined heat and power (micro-CHP) have been assessed. Because salt hydrates used in various thermochemical heat storage processes fail to meet the expectations, a systematic evaluation of the suitability of 125 salt hydrates has been performed in a three-step approach. In the first step general issues such as toxicity and risk of explosion have been considered. In the second and third steps, the authors implement a combined approach consisting of theoretical calculations and experimental measurements using Thermogravimetric Analysis (TGA). Thus, application-oriented comparison criteria, among which the net energy storage density of the material and the thermal efficiency, have been used to evaluate the potential of 45 preselected salt hydrates for a low temperature thermochemical heat storage application. For an application that requires a discharging temperature above 60 °C, SrBr 2 ·6H 2 O and LaCl 3 ·7H 2 O appear to be the most promising, only from thermodynamic point of view. However, the maximum net energy storage density including the water in the water storage tank that they offer (respectively 133 kW h m −3 and 89 kW h m −3 ) for a classical thermochemical heat storage process are not attractive for the intended application. Furthermore, the thermal efficiency that would result from the storage process based on salt hydrates

  3. Thermochemical treatment of the pay zone in the well RK-3

    Energy Technology Data Exchange (ETDEWEB)

    Labudovic, V

    1970-02-01

    The elements are given for the calculation of the thermochemical treatment of the Well RK-3. From the diagram, the Mg and HCl reaction velocity vs. pressure and the temperature vs. the quantity of the reacted CaCO/sub 3/ can be read out. These are important elements for the calculation of a thermochemical treatment. A comparison of calculated and measured temperatures and the factors influencing the heat conductivity of the formation rock is given. The heating range at formation depths is calculated. The relation quantity of warm acid vs. injection pressure also is given.

  4. REITP3-Hazard evaluation program for heat release based on thermochemical calculation

    Energy Technology Data Exchange (ETDEWEB)

    Akutsu, Yoshiaki.; Tamura, Masamitsu. [The University of Tokyo, Tokyo (Japan). School of Engineering; Kawakatsu, Yuichi. [Oji Paper Corp., Tokyo (Japan); Wada, Yuji. [National Institute for Resources and Environment, Tsukuba (Japan); Yoshida, Tadao. [Hosei University, Tokyo (Japan). College of Engineering

    1999-06-30

    REITP3-A hazard evaluation program for heat release besed on thermochemical calculation has been developed by modifying REITP2 (Revised Estimation of Incompatibility from Thermochemical Properties{sup 2)}. The main modifications are as follows. (1) Reactants are retrieved from the database by chemical formula. (2) As products are listed in an external file, the addition of products and change in order of production can be easily conducted. (3) Part of the program has been changed by considering its use on a personal computer or workstation. These modifications will promote the usefulness of the program for energy hazard evaluation. (author)

  5. Thermodynamic limits on the performance of a solar thermochemical energy storage system

    Energy Technology Data Exchange (ETDEWEB)

    Lovegrove, K [Australian National Univ., Canberra (Australia). Energy Research Centre

    1993-12-01

    General expressions for the exergetic and work recovery efficiencies of thermochemical storage systems have been developed by assuming that the reaction process is the only source irreversibility within the closed-loop system. These have been used to plot contours of constant efficiency for the ammonia-based thermochemical system. The effect of spontaneous separation of mixtures due to the preferential condensation of ammonia has been examined analytically and graphically. The analysis presented represents a necessary prerequisite for the optimization of system efficiencies by reactor design. (author)

  6. Thermochemical equilibrium in a kernel of a UN TRISO coated fuel particle

    International Nuclear Information System (INIS)

    Kim, Young Min; Jo, C. K.; Lim, H. S.; Cho, M. S.; Lee, W. J.

    2012-01-01

    A coated fuel particle (CFP) with a uranium mononitride (UN) kernel has been recently considered as an advanced fuel option, such as in fully ceramic micro encapsulated (FCM) replacement fuel for light water reactors (LWRs). In FCM fuel, a large number of tri isotropic coated fuel particles (TRISOs) are embedded in a silicon carbide (SiC) matrix. Thermochemical equilibrium calculations can predict the chemical behaviors of a kernel in a TRISO of FCM fuel during irradiation. They give information on the kind and quantity of gases generated in a kernel during irradiation. This study treats the quantitative analysis of thermochemical equilibrium in a UN TRISO of FCM LWR fuel using HSC software

  7. Process simulation of nuclear-based thermochemical hydrogen production with a copper-chlorine cycle

    International Nuclear Information System (INIS)

    Chukwu, C.C.; Naterer, G.F.; Rosen, M.A.

    2008-01-01

    Thermochemical processes for hydrogen production driven by nuclear energy are promising alternatives to existing technologies for large-scale commercial production of hydrogen without fossil fuels. The copper-chlorine (Cu-Cl) cycle, in which water is decomposed into hydrogen and oxygen, is promising for thermochemical hydrogen production in conjunction with a Supercritical Water Cooled Reactor. Here, the cycle efficiency is examined using the Aspen Plus process simulation code. Possible efficiency improvements are discussed. The results are expected to assist the development of a lab-scale cycle demonstration, which is currently being undertaken at University of Ontario Institute of Technology in collaboration with numerous partners. (author)

  8. Bioelectrode-based approach for enhancing nitrate and nitrite removal and electricity generation from eutrophic lakes

    DEFF Research Database (Denmark)

    Zhang, Yifeng; Angelidaki, Irini

    Nitrate and nitrite contamination of surface waters (e.g. lakes) has become a severe environmental and health problem, especially in developing countries. The recent demonstration of nitrate reduction at the cathode of microbial fuel cell (MFC) provides an opportunity to develop a new technology...... from nitrate- and nitrite-rich synthetic lake waters at initial concentration of 10 mg-N/L. Along with the electricity production a total nitrogen removal of 62% and 77% was accomplished, for nitrate and nitrite, respectively. The nitrogen removal was almost 4 times higher under close-circuit condition...... with biocathode, compared to either the open-circuit operation or with abiotic cathode. The mass balance on nitrogen indicates that most of the removed nitrate and nitrite (84.7±0.1% and 81.8±0.1%, respectively) was reduced to nitrogen gas. The nitrogen removal and power generation was limited by the dissolved...

  9. Dietary nitrate protects submandibular gland from hyposalivation in ovariectomized rats via suppressing cell apoptosis.

    Science.gov (United States)

    Xu, Yipu; Pang, Baoxing; Hu, Liang; Feng, Xiaoyu; Hu, Lei; Wang, Jingsong; Zhang, Chunmei; Wang, Songlin

    2018-02-26

    Xerostomia, a major oral symptom of menopause, is a subjective feeling of dry mouth associated with oral pain and difficulties in deglutition and speech, which significantly reduces patient's quality of life. Dietary nitrate, which can be converted to nitric oxide, has multiple physiological functions in the body, including antioxidant activity and vasodilatation; however, its protective effect against xerostomia remains poorly understood. The present study aimed to evaluate the effects of dietary nitrate on estrogen deficiency-induced xerostomia. We established an ovariectomized (OVX) rat model, which included five groups: sham-operated, OVX, OVX + 0.4 mM nitrate, OVX + 2 mM nitrate, and OVX + 4 mM nitrate (n = 6). After ovariectomy, animals in the nitrate treatment groups received appropriate amounts of sodium nitrate dissolved in distilled water for 3 months. The results showed that nitrate treatment reduced body weight and water intake, and increased serum nitrate and nitrite levels. Furthermore, nitrate uptake increased saliva secretion as evidenced by saliva flow rates and aquaporin 5 expression, and alleviated histological lesions as evidenced by reduction of the fibrotic area and cell atrophy in the salivary glands. Although protective effects of nitrate against estrogen deficiency-induced xerostomia were observed at all doses, treatment with 2 mM nitrate was more effective than that with 0.4 mM and 4 mM nitrate. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase-3 expression analyses showed that nitrate also protected cells from apoptosis, possibly through upregulation of Cu-Zn superoxide dismutase (Cu-Zn SOD) known to inhibit oxidative stress-related apoptosis. Our findings indicate that nitrate could improve functional activity of the salivary glands in OVX rats by suppressing apoptosis and upregulating Cu-Zn SOD expression, suggesting that dietary nitrate may potentially prevent hyposalivation in menopausal

  10. Thermo-chemical Ice Penetrator for Icy Moons

    Science.gov (United States)

    Arenberg, J. W.; Lee, G.; Harpole, G.; Zamel, J.; Sen, B.; Ross, F.; Retherford, K. D.

    2016-12-01

    The ability to place sensors or to take samples below the ice surface enables a wide variety of potential scientific investigations. Penetrating an ice cap can be accomplished via a mechanical drill, laser drill, kinetic impactor, or heated penetrator. This poster reports on the development of technology for the latter most option, namely a self-heated probe driven by an exothermic chemical reaction: a Thermo-chemical ice penetrator (TChIP). Our penetrator design employs a eutectic mix of alkali metals that produce an exothermic reaction upon contact with an icy surface. This reaction increases once the ice starts melting, so no external power is required. This technology is inspired by a classified Cold-War era program developed at Northrop Grumman for the US Navy. Terrestrial demonstration of this technology took place in the Arctic; however, this device cannot be considered high TRL for application at the icy moons of the solar system due to the environmental differences between Earth's Arctic and the icy moons. These differences demand a TChIP design specific to these cold, low mass, airless worlds. It is expected that this model of TChIP performance will be complex, incorporating all of the forces on the penetrator, gravity, the thermo-chemistry at the interface between penetrator and ice, and multi-phase heat and mass transport, and hydrodynamics. Our initial efforts are aimed at the development of a validated set of tools and simulations to predict the performance of the penetrator for both the environment found on these icy moons and for a terrestrial environment. The purpose of the inclusion of the terrestrial environment is to aid in model validation. Once developed and validated, our models will allow us to design penetrators for a specific scientific application on a specific body. This poster discusses the range of scientific investigations that are enabled by TChIP. We also introduce the development plan to advance TChIP to the point where it can be

  11. Renewable energy from corn residues by thermochemical conversion

    Science.gov (United States)

    Yu, Fei

    Declining fossil oil reserve, skyrocket price, unsecured supplies, and environment pollution are among the many energy problems we are facing today. It is our conviction that renewable energy is a solution to these problems. The long term goal of the proposed research is to develop commercially practical technologies to produce energy from renewable resources. The overall objective of my research is to study and develop thermochemical processes for converting bulky and low-energy-density biomass materials into bio-fuels and value-added bio-products. The rationale for the proposed research is that, once such processes are developed, processing facility can be set up on or near biomass product sites, reducing the costs associated with transport of bulky biomass which is a key technical barrier to biomass conversion. In my preliminary research, several conversion technologies including atmospheric pressure liquefaction, high pressure liquefaction, and microwave pyrolysis have been evaluated. Our data indicated that microwave pyrolysis had the potential to become a simple and economically viable biomass conversion technology. Microwave pyrolysis is an innovative process that provides efficient and uniform heating, and are robust to type, size and uniformity of feedstock and therefore suitable for almost any waste materials without needing to reduce the particle size. The proposed thesis focused on in-depth investigations of microwave pyrolysis of corn residues. My first specific aim was to examine the effects of processing parameters on product yields. The second specific research aim was to characterize the products (gases, bio-oils, and solid residues), which was critical to process optimization and product developments. Other research tasks included conducting kinetic modeling and preliminary mass and energy balance. This study demonstrated that microwave pyrolysis could be optimized to produce high value syngas, liquid fuels and pyrolytic carbons, and had a great

  12. Thermochemical properties for isooctane and carbon radicals: computational study.

    Science.gov (United States)

    Snitsiriwat, Suarwee; Bozzelli, Joseph W

    2013-01-17

    Thermochemical properties for isooctane, its internal rotation conformers, and radicals with corresponding bond energies are determined by use of computational chemistry. Enthalpies of formation are determined using isodesmic reactions with B3LYP density function theory and composite CBS-QB3 methods. Application of group additivity with comparison to calculated values is illustrated. Entropy and heat capacities are determined using geometric parameters, internal rotor potentials, and frequencies from B3LYP/6-31G(d,p) calculations for the lowest energy conformer. Internal rotor potentials are determined for the isooctane parent and for the primary, secondary, and tertiary radicals in order to identify isomer energies. Intramolecular interactions are shown to have a significant effect on the enthalpy of formation of the isooctane parent and its radicals. The computed standard enthalpy of formation for the lowest energy conformers of isooctane from this study is -54.40 ± 1.60 kcal mol(-1), which is 0.8 kcal mol(-1) lower than the evaluated experimental value -53.54 ± 0.36 kcal mol(-1). The standard enthalpy of formation for the primary radical for a methyl on the quaternary carbon is -5.00 ± 1.69 kcal mol(-1), for the primary radical on the tertiary carbon is -5.18 ± 1.69 kcal mol(-1), for the secondary isooctane radical is -9.03 ± 1.84 kcal mol(-1), and for the tertiary isooctane radical is -12.30 ± 2.02 kcal mol(-1). Bond energy values for the isooctane radicals are 100.64 ± 1.73, 100.46 ± 1.73, 96.41 ± 1.88 and 93.14 ± 2.05 kcal mol(-1) for C3•CCCC2, C3CCCC2•, C3CC•CC2, and C3CCC•C2, respectively. Entropy and heat capacity values are reported for the lowest energy homologues.

  13. Oxygen permeation and thermo-chemical stability of oxygen separation membrane materials for the oxyfuel process

    Energy Technology Data Exchange (ETDEWEB)

    Ellett, Anna Judith

    2009-07-01

    The reduction of CO{sub 2} emissions, generally held to be one of the most significant contributors to global warming, is a major technological issue. CO{sub 2} Capture and Storage (CCS) techniques applied to large stationary sources such as coal-fired power plants could efficiently contribute to the global carbon mitigation effort. The oxyfuel process, which consists in the burning of coal in an oxygen-rich atmosphere to produce a flue gas highly concentrated in CO{sub 2}, is a technology considered for zero CO{sub 2} emission coal-fired power plants. The production of this O{sub 2}-rich combustion gas from air can be carried out using high purity oxygen separation membranes. Some of the most promising materials for this application are mixed ionic-electronic conducting (MIEC) materials with perovskite and K{sub 2}NiF{sub 4} perovskite-related structures. The present work examines the selection of La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF58), La{sub 2}NiO{sub 4+{delta}}, Pr{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (PSCF58) and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF50) as membrane materials for the separation of O{sub 2} and N{sub 2} in the framework of the oxyfuel process with flue gas recycling. Annealing experiments were carried out on pellets exposed to CO{sub 2}, water vapour, O{sub 2} and Cr{sub 2}O{sub 3} in order to determine the thermo-chemical resistance to the atmospheres and the high temperature conditions present during membrane operation in a coal-fired power plant. The degradation of their microstructure was investigated using Scanning Electron Microscopy (SEM) in combination with electron dispersive spectroscopy (EDS) as well as X-Ray Diffraction (XRD). Also, the oxygen permeation fluxes of selected membranes were investigated as a function of temperature. The membrane materials selected were characterised using thermo-analytical techniques such as precision thermogravimetric

  14. Efficiency of nitrate uptake in spinach : impact of external nitrate concentration and relative growth rate on nitrate influx and efflux

    NARCIS (Netherlands)

    Ter Steege, MW; Stulen, [No Value; Wiersema, PK; Posthumus, F; Vaalburg, W

    1999-01-01

    Regulation of nitrate influx and efflux in spinach (Spinacia oleracea L., cv. Subito), was studied in short-term label experiments with N-13- and N-15-nitrate. Nitrate fluxes were examined in relation to the N demand for growth, defined as relative growth rate (RGR) times plant N concentration.

  15. Removal of gadolinium nitrate from heavy water

    Energy Technology Data Exchange (ETDEWEB)

    Wilde, E.W.

    2000-03-22

    Work was conducted to develop a cost-effective process to purify 181 55-gallon drums containing spent heavy water moderator (D2O) contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS). These drums also contain low level radioactive contamination, including tritium, which complicates treatment options. Presently, the drums of degraded moderator are being stored on site. It was suggested that a process utilizing biological mechanisms could potentially lower the total cost of heavy water purification by allowing the use of smaller equipment with less product loss and a reduction in the quantity of secondary waste materials produced by the current baseline process (ion exchange).

  16. Thermal Decomposition Of Hydroxylamine Nitrate

    Science.gov (United States)

    Oxley, Jimmie C.; Brower, Kay R.

    1988-05-01

    used hydroxylamine nitrate decomposes within a few minutes in the temperature range 130-140°C. Added ammonium ion is converted to N2, while hydrazinium ion is converted to HN3. Nitrous acid is an intermediate and its formation is rate-determining. A hygride transfer process is postulated. The reaction pathways have been elucidated by use of N tracers.

  17. Nitrate and bicarbonate selective CHEMFETs

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Engbersen, Johannes F.J.; Reinhoudt, David

    1995-01-01

    The development of durable anion selective CHEMFET micro sensors is described. Selectivity in these sensors is either obtained from differences in hydration energy of the anions (the Hlofmeister series, giving nitrate selectivity) or by introduction of a new class of uranyl salophene ionophores

  18. Model-Based Integration and Analysis of Biogeochemical and Isotopic Dynamics in a Nitrate-Polluted Pyritic Aquifer

    NARCIS (Netherlands)

    Zhang, Y.C.; Prommer, H.; Slomp, C.P.; Broers, H.P.; van der Grift, B.; Passier, H.F.; Greskowiak, J.; Boettcher, M.E.; van Capellen, P.

    2013-01-01

    Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as

  19. Model-based integration and analysis of biogeochemical and isotopic dynamics in a nitrate-polluted pyritic aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Prommer, H.; Broers, H.P.; Slomp, C.P.; Greskowiak, J.; Van Der Grift, B.; Van Cappellen, P.

    2013-01-01

    Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as

  20. Uranous nitrate production for purex process applications using PtO2 catalyst and H2/H2-gas mixtures

    International Nuclear Information System (INIS)

    Sreenivasa Rao, K.; Shyamali, R.; Narayan, C.V.; Patil, A.R.; Jambunathan, U.; Ramanujam, A.; Kansara, V.P.

    2003-04-01

    In the Purex process of spent fuel reprocessing. the twin objectives- decontamination and partitioning are achieved by extracting uranium (VI) and plutonium (IV) together in the solvent 30% TBP-dodecane and then selectively reducing Pu (IV) to Pu (III) in which valency it is least extractable in the solvent. Uranous nitrate stabilized with hydrazine nitrate is the widely employed partitioning agent. The conventional method of producing U(IV) is by the electrolytic reduction of uranyl nitrate with hydrazine nitrate as uranous ion stabilizer. Tre percentage conversion of U(VI) to U(IV) obtained in this method is 50 -60 %. The use of this solution as partitioning agent leads not only to the dilution of the plutonium product but also to increase in uranium processing load by each externally fed uranous nitrate batch. Also the oxide coating of the anode, TSIA (Titanium Substrate Insoluble Anode) wears out after a certain period of operation. This necessitates recoating which is quite cumbersome considering the amount of the decontamination involved. An alternative to the conventional electrolytic method of reduction of uranyl nitrate to uranous nitrate was explored at FRD laboratory .The studies have revealed that near 100% uranous nitrate can be produced by reducing uranyl nitrate with H 2 gas or H 2 (8%)- Ar/N 2 gas mixture in presence of PtO 2 catalyst. This report describes the laboratory scale studies carried out to optimize the various parameters. Based on these studies reduction of uranyl nitrate on a pilot plant scale was carried out. The design and operation of the reductor column and also the various studies carried out in the pilot plant studies are discussed. Near 100% conversion of uranyl nitrate to uranous nitrate and also the redundancy of supply of electrical energy make this process a viable alternative to the existing electrolytic method. (author)

  1. Generation of H{sub 2} and CO by solar thermochemical splitting of H{sub 2}O and CO{sub 2} by employing metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Rao, C.N.R., E-mail: cnrrao@jncasr.ac.in; Dey, Sunita

    2016-10-15

    Generation of H{sub 2} and CO by splitting H{sub 2}O and CO{sub 2} respectively constitutes an important aspect of the present-day concerns with energy and environment. The solar thermochemical route making use of metal oxides is a viable means of accomplishing these reduction reactions. The method essentially involves reducing a metal oxide by heating and passing H{sub 2}O or CO{sub 2} over the nonstoichiometric oxide to cause reverse oxidation by abstracting oxygen from H{sub 2}O or CO{sub 2}. While ceria, perovskites and other oxides have been investigated for this purpose, recent studies have demonstrated the superior performance of perovskites of the type Ln{sub 1−x}A{sub x}Mn{sub 1−y}M{sub y}O{sub 3} (Ln=rare earth, A=alkaline earth, M=various +2 and +3 metal ions), in the thermochemical generation of H{sub 2} and CO. We present the important results obtained hitherto to point out how the alkaine earth and the Ln ions, specially the radius of the latter, determine the performance of the perovskites. The encouraging results obtained are exemplefied by Y{sub 0.5}Sr{sub 0.5}MnO{sub 3} which releases 483 µmol/g of O{sub 2} at 1673 K and produces 757 µmol/g of CO from CO{sub 2} at 1173 K. The production of H{sub 2} from H{sub 2}O is also quite appreciable. Modification of the B site ion of the perovskite also affects the performance. In addition to perovskites, we present the generation of H{sub 2} based on the Mn{sub 3}O{sub 4}/NaMnO{sub 2} cycle briefly. - Graphical abstract: Ln{sub 0.5}A{sub 0.5}Mn{sub 1−x}M{sub x}O{sub 3} (Ln=lanthanide; A=Ca, Sr; M=Al, Ga, Sc, Mg, Cr, Fe, Co) perovskites are employed for the two step thermochemical splitting of CO{sub 2} and H{sub 2}O for the generation of CO and H{sub 2}. - Highlights: • Perovskite oxides based on Mn are ideal for the two-step thermochemical splitting of CO{sub 2} and H{sub 2}O. • In Ln{sub 1−x}A{sub x}MnO{sub 3} perovskite (Ln=rare earth, A=alkaline earth) both Ln and A ions play major roles

  2. Engineering Database of Liquid Salt Thermophysical and Thermochemical Properties

    Energy Technology Data Exchange (ETDEWEB)

    Manohar S. Sohal; Matthias A. Ebner; Piyush Sabharwall; Phil Sharpe

    2010-03-01

    The purpose of this report is to provide a review of thermodynamic and thermophysical properties of candidate molten salt coolants, which may be used as a primary coolant within a nuclear reactor or heat transport medium from the Next Generation Nuclear Plant (NGNP) to a processing plant, for example, a hydrogen-production plant. Thermodynamic properties of four types of molten salts, including LiF-BeF2 (67 and 33 mol%, respectively; also known as FLiBe), LiF-NaF-KF (46.5, 11.5, and 52 mol%, also known as FLiNaK), and KCl-MgCl2 (67 and 33 mol%), and sodium nitrate-sodium nitrite-potassium nitrate (NaNO3–NaNO2–KNO3, (7-49-44 or 7-40-53 mol%) have been investigated. Limitations of existing correlations to predict density, viscosity, specific heat capacity, surface tension, and thermal conductivity, were identified. The impact of thermodynamic properties on the heat transfer, especially Nusselt number was also discussed. Stability of the molten salts with structural alloys and their compatibility with the structural alloys was studied. Nickel and alloys with dense Ni coatings are effectively inert to corrosion in fluorides but not so in chlorides. Of the chromium containing alloys, Hastelloy N appears to have the best corrosion resistance in fluorides, while Haynes 230 was most resistant in chloride. In general, alloys with increasing carbon and chromium content are increasingly subject to corrosion by the fluoride salts FLiBe and FLiNaK, due to attack and dissolution of the intergranular chromium carbide. Future research to obtain needed information was identified.

  3. Nitrate Removal from Ground Water: A Review

    OpenAIRE

    Archna; Sharma, Surinder K.; Sobti, Ranbir Chander

    2012-01-01

    Nitrate contamination of ground water resources has increased in Asia, Europe, United States, and various other parts of the world. This trend has raised concern as nitrates cause methemoglobinemia and cancer. Several treatment processes can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that biological denitrification is more acceptable for nitrate removal than reverse osmosis and ion ex...

  4. Final Report UCLA-Thermochemical Storage with Anhydrous Ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Lavine, Adrienne [Univ. of California, Los Angeles, CA (United States)

    2018-02-05

    In ammonia-based thermochemical energy storage (TCES), ammonia is dissociated endothermically as it absorbs solar energy during the daytime. When energy is required, the reverse reaction releases energy to heat a working fluid such as steam, to produce electricity. Ammonia-based TCES has great advantages of simplicity, low cost reactants, and a strong industrial base in the conventional ammonia industry. The concept has been demonstrated over three decades of research at Australian National University, achieving a 24-hour demonstration of a complete system. At the start of this project, three challenges were identified that would have to be addressed to show that the system is technically and economically viable for incorporation into a CSP plant with an advanced, high temperature power block. All three of these challenges have now been addressed: 1. The ammonia synthesis reaction had not, to our knowledge, been carried out at temperatures consistent with modern power blocks (i.e., ~650°C). The technical feasibility of operating a reactor under high-temperature, near-equilibrium conditions was an unknown, and was therefore a technical risk. The project has successfully demonstrated steam heating to 650°C and energy recovery to steam at the 5 kWt level. 2. The ammonia system has a relatively low enthalpy of reaction combined with gas phase reactants. This is not a direct disadvantage since the reactants themselves are low cost. The challenge lies in storing the required volume of reactants cost effectively. Therefore, a second key goal was to show, through techno-economic analysis, that underground storage technologies can be used to store the energy-rich gas at a cost that is consistent with the SunShot cost goal. We have identified two promising technologies for gas storage: storage in salt caverns has an estimated cost of 1(USD)/kWht and storage in drilled shafts could be on the order of 7(USD)/kWht. Together these two options answer the technical challenge

  5. Effect of Stabilized Zero-Valent Iron Nanoparticles on Nitrate Removal from Sandy Soil

    Directory of Open Access Journals (Sweden)

    F. Nooralivand

    2016-02-01

    Full Text Available Introduction: During the recent decades, the use of N fertilizers has undeniable development regardless of their effects on the soil and environment. Increasing nitrate ion concentration in soil solution and then, leaching it into groundwater causes increase nitrate concentration in the water and raise the risk suffering from the people to some diseases. World health organization recommended maximum concentration level for nitrate and nitrite in the drinking water 50 and 3 mg/l, respectively. There are different technologies for the removal of nitrate ions from aqueous solution. The conventional methods are ion exchange, biological denitrification, reverse osmosis and chemical reduction. Using nanoscale Fe0 particles compared to other methods of nitrate omission was preferred because of; its high surface area, more reactive, lower cost and higher efficiency. More studies on the reduction of nitrate by zero-valent iron nanoparticles have been in aqueous solutions or in the soil in batch scale. Nanoparticles surface modified with poly-electrolytes, surfactants and polymers cause colloidal stability of the particles against the forces of attraction between particles and increases nanoparticle transport in porous media. The objectives of this study were to synthesize carboxymethyl cellulose stabilized zero-valent iron nanoparticles and consideration of their application for nitrate removal from sandy soil. Materials and Methods: The nanoparticles were synthesized in a lab using borohydride reduction method and their morphological characteristics were examined via scanning electron microscopy (SEM, X-ray diffraction (XRD and Fourier Transmission Infrared Spectroscopy (FTIR. Experiments were conducted on packed sand column (40 cm length and 2.5 cm inner diameter under conditions of different nanoparticle concentration (1, 2, and 3 g1-1and high initial NO3- concentration (150, 250, and 350 mgl-1. Homogeneous soil column was filled with the wet packed

  6. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed with...

  7. Interaction in triple systems of neodymium nitrate, water and nitrates of trimethylammonium and tetramethylammonium

    International Nuclear Information System (INIS)

    Boeva, M.K.; Zhuravlev, E.F.

    1977-01-01

    At 20 and 40 deg C the mutual solubility is studied in systems neodymium nitrate-water-trimethylamine nitrate and neodymium nitrate-water-tetramethylammonium nitrate. It has been established that the above systems belong to those with chemical interaction of the components. The compounds have been isolated preparatively, their composition has been confirmed analytically, and their thermal behaviour studied

  8. Method of producing thin cellulose nitrate film

    International Nuclear Information System (INIS)

    Lupica, S.B.

    1975-01-01

    An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent

  9. 21 CFR 172.160 - Potassium nitrate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing...

  10. Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN above a Ponderosa pine forest

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2009-01-01

    Full Text Available During the Biosphere Effects on AeRosols and Photochemistry EXperiment 2007 (BEARPEX-2007, we observed eddy covariance (EC fluxes of speciated acyl peroxy nitrates (APNs, including peroxyacetyl nitrate (PAN, peroxypropionyl nitrate (PPN and peroxymethacryloyl nitrate (MPAN, above a Ponderosa pine forest in the western Sierra Nevada. All APN fluxes are net downward during the day, with a median midday PAN exchange velocity of −0.3 cm s−1; nighttime storage-corrected APN EC fluxes are smaller than daytime fluxes but still downward. Analysis with a standard resistance model shows that loss of PAN to the canopy is not controlled by turbulent or molecular diffusion. Stomatal uptake can account for 25 to 50% of the observed downward PAN flux. Vertical gradients in the PAN thermal decomposition (TD rate explain a similar fraction of the flux, suggesting that a significant portion of the PAN flux into the forest results from chemical processes in the canopy. The remaining "unidentified" portion of the net PAN flux (~15% is ascribed to deposition or reactive uptake on non-stomatal surfaces (e.g. leaf cuticles or soil. Shifts in temperature, moisture and ecosystem activity during the summer – fall transition alter the relative contribution of stomatal uptake, non-stomatal uptake and thermochemical gradients to the net PAN flux. Daytime PAN and MPAN exchange velocities are a factor of 3 smaller than those of PPN during the first two weeks of the measurement period, consistent with strong intra-canopy chemical production of PAN and MPAN during this period. Depositional loss of APNs can be 3–21% of the gross gas-phase TD loss depending on temperature. As a source of nitrogen to the biosphere, PAN deposition represents approximately 4–19% of that due to dry deposition of nitric acid at this site.

  11. Comparative modelling and molecular docking of nitrate reductase from Bacillus weihenstephanensis (DS45

    Directory of Open Access Journals (Sweden)

    R. Seenivasagan

    2016-07-01

    Full Text Available Nitrate reductase catalyses the oxidation of NAD(PH and the reduction of nitrate to nitrite. NR serves as a central point for the integration of metabolic pathways by governing the flux of reduced nitrogen through several regulatory mechanisms in plants, algae and fungi. Bacteria express nitrate reductases that convert nitrate to nitrite, but mammals lack these specific enzymes. The microbial nitrate reductase reduces toxic compounds to nontoxic compounds with the help of NAD(PH. In the present study, our results revealed that Bacillus weihenstephanensis expresses a nitrate reductase enzyme, which was made to generate the 3D structure of the enzyme. Six different modelling servers, namely Phyre2, RaptorX, M4T Server, HHpred, SWISS MODEL and Mod Web, were used for comparative modelling of the structure. The model was validated with standard parameters (PROCHECK and Verify 3D. This study will be useful in the functional characterization of the nitrate reductase enzyme and its docking with nitrate molecules, as well as for use with autodocking.

  12. Nitrate removal from drinking water with a focus on biological methods: a review.

    Science.gov (United States)

    Rezvani, Fariba; Sarrafzadeh, Mohammad-Hossein; Ebrahimi, Sirous; Oh, Hee-Mock

    2017-05-31

    This article summarizes several developed and industrial technologies for nitrate removal from drinking water, including physicochemical and biological techniques, with a focus on autotrophic nitrate removal. Approaches are primarily classified into separation-based and elimination-based methods according to the fate of the nitrate in water treatment. Biological denitrification as a cost-effective and promising method of biological nitrate elimination is reviewed in terms of its removal process, applicability, efficiency, and associated disadvantages. The various pathways during biological nitrate removal, including assimilatory and dissimilatory nitrate reduction, are also explained. A comparative study was carried out to provide a better understanding of the advantages and disadvantages of autotrophic and heterotrophic denitrification. Sulfur-based and hydrogen-based denitrifications, which are the most common autotrophic processes of nitrate removal, are reviewed with the aim of presenting the salient features of hydrogenotrophic denitrification along with some drawbacks of the technology and research areas in which it could be used but currently is not. The application of algae-based water treatment is also introduced as a nature-inspired approach that may broaden future horizons of nitrate removal technology.

  13. Contextualizing Wetlands Within a River Network to Assess Nitrate Removal and Inform Watershed Management

    Science.gov (United States)

    Czuba, Jonathan A.; Hansen, Amy T.; Foufoula-Georgiou, Efi; Finlay, Jacques C.

    2018-02-01

    Aquatic nitrate removal depends on interactions throughout an interconnected network of lakes, wetlands, and river channels. Herein, we present a network-based model that quantifies nitrate-nitrogen and organic carbon concentrations through a wetland-river network and estimates nitrate export from the watershed. This model dynamically accounts for multiple competing limitations on nitrate removal, explicitly incorporates wetlands in the network, and captures hierarchical network effects and spatial interactions. We apply the model to the Le Sueur Basin, a data-rich 2,880 km2 agricultural landscape in southern Minnesota and validate the model using synoptic field measurements during June for years 2013-2015. Using the model, we show that the overall limits to nitrate removal rate via denitrification shift between nitrate concentration, organic carbon availability, and residence time depending on discharge, characteristics of the waterbody, and location in the network. Our model results show that the spatial context of wetland restorations is an important but often overlooked factor because nonlinearities in the system, e.g., deriving from switching of resource limitation on denitrification rate, can lead to unexpected changes in downstream biogeochemistry. Our results demonstrate that reduction of watershed-scale nitrate concentrations and downstream loads in the Le Sueur Basin can be most effectively achieved by increasing water residence time (by slowing the flow) rather than by increasing organic carbon concentrations (which may limit denitrification). This framework can be used toward assessing where and how to restore wetlands for reducing nitrate concentrations and loads from agricultural watersheds.

  14. Relationship Between Urinary Nitrate Excretion and Blood Pressure in the InChianti Cohort.

    Science.gov (United States)

    Smallwood, Miranda J; Ble, Alessandro; Melzer, David; Winyard, Paul G; Benjamin, Nigel; Shore, Angela C; Gilchrist, Mark

    2017-07-01

    Inorganic nitrate from the oxidation of endogenously synthesized nitric oxide (NO) or consumed in the diet can be reduced to NO via a complex enterosalivary circulation pathway. The relationship between total nitrate exposure by measured urinary nitrate excretion and blood pressure in a large population sample has not been assessed previously. For this cross-sectional study, 24-hour urinary nitrate excretion was measured by spectrophotometry in the 919 participants from the InChianti cohort at baseline and blood pressure measured with a mercury sphygmomanometer. After adjusting for age and sex only, diastolic blood pressure was 1.9 mm Hg lower in subjects with ≥2 mmol urinary nitrate excretion compared with those excreting nitrate in 24 hours: systolic blood pressure was 3.4 mm Hg (95% confidence interval (CI): -3.5 to -0.4) lower in subjects for the same comparison. Effect sizes in fully adjusted models (for age, sex, potassium intake, use of antihypertensive medications, diabetes, HS-CRP, or current smoking status) were marginally larger: systolic blood pressure in the ≥2 mmol urinary nitrate excretion group was 3.9 (CI: -7.1 to -0.7) mm Hg lower than in the comparison nitrate exposure are associated with lower blood pressure. These differences are at least equivalent to those seen from substantial (100 mmol) reductions in sodium intake. © American Journal of Hypertension, Ltd 2017. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  15. Experimental results of a 3 k Wh thermochemical heat storage module for space heating application

    NARCIS (Netherlands)

    Finck, C.J.; Henquet, E.M.R.; Soest, C.F.L. van; Oversloot, H.P.; Jong, A.J. de; Cuypers, R.; Spijker, J.C. van 't

    2014-01-01

    A 3 kWh thermochemical heat storage (TCS) module was built as part of an all-in house system implementation focusing on space heating application at a temperature level of 40 ºC and a temperature lift of 20 K. It has been tested and measurements showed a maximum water circuit temperature span

  16. A review on the properties of salt hydrates for thermochemical storage

    NARCIS (Netherlands)

    Trausel, F.; Jong, A.J. de; Cuypers, R.

    2014-01-01

    Solar energy is capable of supplying enough energy to answer the total demand of energy in dwellings. However, because of the discrepancy between energy supply and energy demand, an efficient way of storing thermal energy is crucial. Thermochemical storage of heat in salt hydrates provides an

  17. Thermo-chemical simulation of a composite offshore vertical axis wind turbine blade

    DEFF Research Database (Denmark)

    Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

    2012-01-01

    In the present study three dimensional steady state thermo-chemical simulation of a pultrusion process is investigated by using the finite element/nodal control volume (FE/NCV) technique. Pultrusion simulation of a composite having a C-shaped cross section is performed as a validation case. The o...

  18. Thermo-chemical simultion of a composite offshore vertical axis wind turbine blade

    NARCIS (Netherlands)

    Baran, Ismet; Tutum, Cem Celal; Hattel, Jesper Henri

    2012-01-01

    In the present study three dimensional steady state thermo-chemical simulation of a pultrusion process is investigated by using the finite element/nodal control volume (FE/NCV) technique. Pultrusion simulation of a composite having a C-shaped cross section is performed as a validation case. The

  19. Recommended Ideal-Gas Thermochemical Functions for Heavy Water and its Substituent Isotopologues

    Czech Academy of Sciences Publication Activity Database

    Simkó, I.; Furtenbacher, T.; Hrubý, Jan; Zobov, N. F.; Polyansky, O. L.; Tennyson, J.; Gamache, R. R.; Szidarovszky, T.; Dénes, N.; Császár, A. G.

    2017-01-01

    Roč. 46, č. 2 (2017), č. článku 023104. ISSN 0047-2689 R&D Projects: GA ČR GA16-02647S Institutional support: RVO:61388998 Keywords : heavy water * ideal-gas thermochemical functions * partition function Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 4.204, year: 2016

  20. Design of GA thermochemical water-splitting process for the Mirror Advanced Reactor System

    International Nuclear Information System (INIS)

    Brown, L.C.

    1983-04-01

    GA interfaced the sulfur-iodine thermochemical water-splitting cycle to the Mirror Advanced Reactor System (MARS). The results of this effort follow as one section and part of a second section to be included in the MARS final report. This section describes the process and its interface to the reactor. The capital and operating costs for the hydrogen plant are described

  1. Exergy analysis of thermochemical ethanol production via biomass gasification and catalytic synthesis

    NARCIS (Netherlands)

    van der Heijden, H.H.J.L.; Ptasinski, K.J.

    2012-01-01

    In this paper an exergy analysis of thermochemical ethanol production from biomass is presented. This process combines a steam-blown indirect biomass gasification of woody feedstock, with a subsequent conversion of produced syngas into ethanol. The production process involves several process

  2. Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

    Science.gov (United States)

    Bamberger, C.E.

    A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

  3. Improvement in Performance of a Thermochemical Heat Storage System by Implementing an Internal Heat Recovery System

    NARCIS (Netherlands)

    Gaeini, M.; Saris, L.; Zondag, H.A.; Rindt, C.C.M.

    A lab-scale prototype of a thermochemical heat storage system, employing a water-zeolite 13X as the working pair, is designed and optimized for providing hot tap water. During the hydration process, humid air is introduced to the packed bed reactor filled with dehydrated zeolite 13X, and the

  4. Neutralization and Acid Dissociation of Hydrogen Carbonate Ion: A Thermochemical Approach

    Science.gov (United States)

    Koga, Nobuyoshi; Shigedomi, Kana; Kimura, Tomoyasu; Tatsuoka, Tomoyuki; Mishima, Saki

    2013-01-01

    A laboratory inquiry into the thermochemical relationships in the reaction between aqueous solutions of NaHCO[subscript 3] and NaOH is described. The enthalpy change for this reaction, delta[subscript r]H, and that for neutralization of strong acid and NaOH(aq), delta[subscript n]H, are determined calorimetrically; the explanation for the…

  5. The NREL Biochemical and Thermochemical Ethanol Conversion Processes: Financial and Environmental Analysis Comparison

    Directory of Open Access Journals (Sweden)

    Jesse Sky Daystar

    2015-07-01

    Full Text Available The financial and environmental performance of the National Renewable Energy Lab’s (NREL thermochemical and biochemical biofuel conversion processes are examined herein with pine, eucalyptus, unmanaged hardwood, switchgrass, and sweet sorghum. The environmental impacts of the process scenarios were determined by quantifying greenhouse gas (GHG emissions and TRACI impacts. Integrated financial and environmental performance metrics were introduced and used to examine the biofuel production scenarios. The thermochemical and biochemical conversion processes produced the highest financial performance and lowest environmental impacts when paired with pine and sweet sorghum, respectively. The high ash content of switchgrass and high lignin content of loblolly pine lowered conversion yields, resulting in the highest environmental impacts and lowest financial performance for the thermochemical and biochemical conversion processes, respectively. Biofuel produced using the thermochemical conversion process resulted in lower TRACI single score impacts and somewhat lower GHG emissions per megajoule (MJ of fuel than using the biochemical conversion pathway. The cost of carbon mitigation resulting from biofuel production and corresponding government subsidies was determined to be higher than the expected market carbon price. In some scenarios, the cost of carbon mitigation was several times higher than the market carbon price, indicating that there may be other more cost-effective methods of reducing carbon emissions.

  6. Evaluation energy efficiency of bioconversion knot rejects to ethanol in comparison to other thermochemically pretreated biomass

    Science.gov (United States)

    Zhaojiang Wang; Menghua Qin; J.Y. Zhu; Guoyu Tian; Zongquan. Li

    2013-01-01

    Rejects from sulfite pulp mill that otherwise would be disposed of by incineration were converted to ethanol by a combined physical–biological process that was comprised of physical refining and simultaneous saccharification and fermentation (SSF). The energy efficiency was evaluated with comparison to thermochemically pretreated biomass, such as those pretreated by...

  7. To Error Problem Concerning Measuring Concentration of Carbon Oxide by Thermo-Chemical Sen

    Directory of Open Access Journals (Sweden)

    V. I. Nazarov

    2007-01-01

    Full Text Available The paper gives additional errors in respect of measuring concentration of carbon oxide by thermo-chemical sensors. A number of analytical expressions for calculation of error data and corrections for environmental factor deviations from admissible ones have been obtained in the paper

  8. Remarks on the thermochemical production of hydrogen from water using heat from the high temperature reactor

    International Nuclear Information System (INIS)

    Barnert, H.

    1980-06-01

    In this report, some aspects of the production of hydrogen from water using heat from the High Temperature Reactor has been studied. These aspects are: the theoretical potential for economic competitivness, the application of hydrogen in the Heat Market, the size of the market potential in the Federal Republic of Germany and the extent of research and development work. In addition another novel proposal for a thermochemical cycle has been studied. For the description of the theoretical potential for economic competitivness, a definition of the 'coupling', has been introduced, which is thermodynamicaly developed; the thermochemical cycle is compared with the thermochemical cycle. Using the coupling, it becomes possible to describe a relation between thermodynamical parameters and the ecomomical basic data of capital costs. Reasons are given from the theoretical point of view for the application of hydrogen as an energy carrier of high exergetic value in the heat market. The discussion of energy problems as 'questions of global survival' leads here to a proposal for the introduction of the term 'extropy'. The market potential in the Federal Republic of Germany is estimated. A further novel proposal for a thermochemical cycle is the 'hydrocarbon-hybrid-process'. The extent of research and development work is explained. (orig.) [de

  9. Improving Students' Chemical Literacy Levels on Thermochemical and Thermodynamics Concepts through a Context-Based Approach

    Science.gov (United States)

    Cigdemoglu, Ceyhan; Geban, Omer

    2015-01-01

    The aim of this study was to delve into the effect of context-based approach (CBA) over traditional instruction (TI) on students' chemical literacy level related to thermochemical and thermodynamics concepts. Four eleventh-grade classes with 118 students in total taught by two teachers from a public high school in 2012 fall semester were enrolled…

  10. Soil nitrate reducing processes – drivers, mechanisms for spatial variation, and significance for nitrous oxide production

    Science.gov (United States)

    Giles, Madeline; Morley, Nicholas; Baggs, Elizabeth M.; Daniell, Tim J.

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3−) and production of the potent greenhouse gas, nitrous oxide (N2O). A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub centimeter areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location, and potential for N2O production from soils. PMID:23264770

  11. Soil nitrate reducing processes – drivers, mechanisms for spatial variation and significance for nitrous oxide production

    Directory of Open Access Journals (Sweden)

    Madeline Eleanore Giles

    2012-12-01

    Full Text Available The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3-¬ and production of the potent greenhouse gas, nitrous oxide (N2O. A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub cm areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location and potential for N2O production from soils.

  12. Soil nitrate reducing processes - drivers, mechanisms for spatial variation, and significance for nitrous oxide production.

    Science.gov (United States)

    Giles, Madeline; Morley, Nicholas; Baggs, Elizabeth M; Daniell, Tim J

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate ([Formula: see text]) and production of the potent greenhouse gas, nitrous oxide (N(2)O). A number of factors are known to control these processes, including O(2) concentrations and moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub centimeter areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location, and potential for N(2)O production from soils.

  13. Effects of over-winter green cover on soil solution nitrate concentrations beneath tillage land.

    Science.gov (United States)

    Premrov, Alina; Coxon, Catherine E; Hackett, Richard; Kirwan, Laura; Richards, Karl G

    2014-02-01

    There is a growing need to reduce nitrogen losses from agricultural systems to increase food production while reducing negative environmental impacts. The efficacy of vegetation cover for reducing nitrate leaching in tillage systems during fallow periods has been widely investigated. Nitrate leaching reductions by natural regeneration (i.e. growth of weeds and crop volunteers) have been investigated to a lesser extent than reductions by planted cover crops. This study compares the efficacy of natural regeneration and a sown cover crop (mustard) relative to no vegetative cover under both a reduced tillage system and conventional plough-based system as potential mitigation measures for reducing over-winter soil solution nitrate concentrations. The study was conducted over three winter fallow seasons on well drained soil, highly susceptible to leaching, under temperate maritime climatic conditions. Mustard cover crop under both reduced tillage and conventional ploughing was observed to be an effective measure for significantly reducing nitrate concentrations. Natural regeneration under reduced tillage was found to significantly reduce the soil solution nitrate concentrations. This was not the case for the natural regeneration under conventional ploughing. The improved efficacy of natural regeneration under reduced tillage could be a consequence of potential stimulation of seedling germination by the autumn reduced tillage practices and improved over-winter plant growth. There was no significant effect of tillage practices on nitrate concentrations. This study shows that over winter covers of mustard and natural regeneration, under reduced tillage, are effective measures for reducing nitrate concentrations in free draining temperate soils. © 2013.

  14. Preparation of acid deficient solutions of uranyl nitrate and thorium nitrate by steam denitration

    International Nuclear Information System (INIS)

    Yamagishi, Shigeru; Takahashi, Yoshihisa

    1996-01-01

    Acid deficient heavy metal (HM) nitrate solutions are often required in the internal gelation processes for nuclear fuel fabrication. The stoichiometric HM-nitrate solutions are needed in a sol-gel process for fuel fabrication. A method for preparing such nitrate solutions with a controlled molar ratio of nitrate/metal by denitration of acid-excess nitrate solutions was developed. The denitration was conducted by bubbling a nitrate solution with a mixture of steam+Ar. It was found that steam was more effective for the denitration than Ar. The acid deficient uranyl nitrate solution with nitrate/U=1.55 was yielded by steam bubbling, while not by only Ar bubbling. As for thorium nitrate, acid deficient solutions of nitrate/Th≥3.1 were obtained by steam bubbling. (author)

  15. High temperature interaction studies on equimolar nitrate mixture of uranyl nitrate hexahydrate and gadolinium nitrate hexahydrate

    International Nuclear Information System (INIS)

    Kalekar, Bhupesh B.; Raje, Naina; Reddy, A.V.R.

    2015-01-01

    Rare earths including gadolinium form a sizeable fraction of the fission products in the nuclear fission of fissile material in the reactor. These fission products can interact with uranium dioxide fuel and can form various compounds which can alter the thermal behavior of the fuel. The mixed oxide formed due to the high temperature interactions of mixture of uranyl nitrate hexahydrate (UNH) and gadolinium nitrate hexahydrate (GdNH) has been studied using thermal and X- ray diffraction techniques. The equimolar mixture of UNH and GdNH was prepared by mixing the weighed amount of individual nitrates and grinding gently with mortar and pestle. Thermogravimetry (TG) measurements were carried out by separately heating 100 mg of mixture and individual nitrates at heating rate of 10°C min -1 using Netzsch thermal analyzer (Model No.: STA 409 PC Luxx) in high purity nitrogen atmosphere with a flow rate of 120 mL min -1 . The XRD measurement was carried out on a Philips X-ray diffractometer (Model PW1710) using nickel-filtered Cu-Kα radiation

  16. The Effect of Gallium Nitrate on Arresting Blood Flow from a Wound

    Directory of Open Access Journals (Sweden)

    Paul H. Goodley

    2011-01-01

    Full Text Available A novel application of gallium nitrate, hitherto unreported, in reducing bleeding time from an open wound is presented. Experiments performed using simple punctures in the forearm demonstrated a very substantial reduction in bleeding time when a solution of gallium nitrate was applied relative to a control. This outcome was shown to be unaffected by the anticoagulant properties of warfarin. The mechanism for such action of gallium nitrate is unknown and merits further investigation, as do the possibilities for such an application to improve both civilian and defense trauma treatment modalities.

  17. SolarSyngas: Results from a virtual institute developing materials and key components for solar thermochemical fuel production

    Science.gov (United States)

    Roeb, Martin; Steinfeld, Aldo; Borchardt, Günter; Feldmann, Claus; Schmücker, Martin; Sattler, Christian; Pitz-Paal, Robert

    2016-05-01

    The Helmholtz Virtual Institute (VI) SolarSynGas brings together expertise from solar energy research and materials science to develop metal oxide based redox materials and to integrate them in a suitable way into related process technologies for two-step thermochemical production of hydrogen and carbon monoxide from water and CO2. One of the foci of experimental investigation was exploring the impact of doping on the feasibility of ceria-based materials - mainly by Zr-doping. The results indicate that a certain Zr-content enhances the reducibility and therefore the splitting performance. Increasing the Zr-content to x = 0.15 improved the specific CO2-splitting performance by 50% compared to pure ceria. This finding agrees with theoretical studies attributing the improvements to lattice modification caused by the introduction of Zr4+. Thermogravimetric relaxation experiments and equilibrium oxygen isotope exchange experiments with subsequent depth profiling analysis were carried out on ceria. As a result the reduction reaction of even dense samples of pure ceria with a grain size of about 20 µm is surface reaction controlled. The structure of the derived expression for the apparent activation energy suggests that the chemical surface exchange coefficient should show only a very weak dependence on temperature for ceria doped with lower valence cations. A solar receiver reactor exhibiting a foam-type reticulated porous ceramics made of ceria was tested. It could be shown that applying dual-scale porosity to those foams with mm-size pores for effective radiative heat transfer during reduction and μm-size pores within its struts for enhanced kinetics during oxidation allows enhancing the performance of the reactor significantly. Also a particle process concept applying solid-solid heat recovery from redox particles in a high temperature solar thermochemical process was analysed that uses ceramic spheres as solid heat transfer medium. This concept can be implemented

  18. The chemistry, waste form development, and properties of the Nitrate to Ammonia and Ceramic (NAC) process

    International Nuclear Information System (INIS)

    Mattus, A.J.; Lee, D.D.; Youngblood, E.L.; Walker, J.F. Jr.; Tiegs, T.N.

    1994-01-01

    A process for the conversion of alkaline, aqueous nitrate wastes to ammonia gas at low temperature, based upon the use of the active metal reductant aluminum, has been developed at the Oak Ridge National Laboratory (ORNL). The process is also well suited for the removal of low-level waste (LLW) radioelements and hazardous metals which report to the solid, alumina-based by-product. ne chemistry of the interaction of aluminum powders with nitrate, and other waste stream metals is presented

  19. Plasma nitrate and nitrite are increased by a high nitrate supplement, but not by high nitrate foods in older adults

    Science.gov (United States)

    Miller, Gary D.; Marsh, Anthony P.; Dove, Robin W.; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S. Bruce; Kim-Shapiro, Daniel

    2012-01-01

    Little is known about the effect of dietary nitrate on the nitrate/nitrite/NO (nitric oxide) cycle in older adults. We examined the effect of a 3-day control diet vs. high nitrate diet, with and without a high nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics, and blood pressure using a randomized four period cross-over controlled design. We hypothesized that the high nitrate diet would show higher levels of plasma nitrate/nitrite and blood pressure compared to the control diet, which would be potentiated by the supplement. Participants were eight normotensive older men and women (5 female, 3 male, 72.5±4.7 yrs) with no overt disease or medications that affect NO metabolism. Plasma nitrate and nitrite levels and blood pressure were measured prior to and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet+supplement (pnitrate and nitrite, respectively) and high nitrate diet+supplement (p=0.001 and 0.002), but not for control diet (p=0.713 and 0.741) or high nitrate diet (p=0.852 and 0.500). Blood pressure decreased from the morning baseline measure to the three 2 hr post-meal follow-up time-points for all treatments, but there was no main effect for treatment. In healthy older adults, a high nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction. PMID:22464802

  20. Reactivity of Surface Nitrates in H2-Assisted SCR of NOx Over Ag/Al2O3 Catalyst

    DEFF Research Database (Denmark)

    Sadokhina, N. A.; Doronkin, Dmitry E.; Baeva, G. N.

    2013-01-01

    The role of nitrate ad-species in H2-assisted SCR over Ag/Al2O3 was compared in NH3-SCR and n-C6H14-SCR processes. It was found that nitrates could be reduced by NH3 or n-C6H14 at similar rates with H2 co-feeding which indicates a common rate-limiting step. However, contributions of surface nitrate...... reduction to the overall NH3-SCR or n-C6H14-SCR are different as revealed by comparing the rates of nitrate reduction with the rates of steady-state processes. The rate of the steady-state n-C6H14-SCR is virtually identical to the rate of surface nitrate reduction suggesting a significant contribution...... of the surface nitrates reduction to the overall n-C6H14-SCR process. On the other hand, the steady-state rate of NH3-SCR is by ~15 times higher, which indicates that the reduction of surface nitrates plays a marginal role in the overall NH3-SCR....