Science.gov

Sample records for chemical absorption-biological reduction

  1. A Biophysicochemical Model for NO Removal by the Chemical Absorption-Biological Reduction Integrated Process.

    PubMed

    Zhao, Jingkai; Xia, Yinfeng; Li, Meifang; Li, Sujing; Li, Wei; Zhang, Shihan

    2016-08-16

    The chemical absorption-biological reduction (CABR) integrated process is regarded as a promising technology for NOx removal from flue gas. To advance the scale-up of the CABR process, a mathematic model based on mass transfer with reaction in the gas, liquid, and biofilm was developed to simulate and predict the NOx removal by the CABR system in a biotrickling filter. The developed model was validated by the experimental results and subsequently was used to predict the system performance under different operating conditions, such as NO and O2 concentration and gas and liquid flow rate. NO distribution in the gas phase along the biotrickling filter was also modeled and predicted. On the basis of the modeling results, the liquid flow rate and total iron concentration were optimized to achieve >90% NO removal efficiency. Furthermore, sensitivity analysis of the model revealed that the performance of the CABR process was controlled by the bioreduction activity of Fe(III)EDTA. This work will provide the guideline for the design and operation of the CABR process in the industrial application. PMID:27442232

  2. Evaluation of microbial reduction of Fe(III)EDTA in a chemical absorption-biological reduction integrated NOx removal system.

    PubMed

    Li, Wei; Wu, Cheng-Zhi; Zhang, Shi-Han; Shao, Ke; Shi, Yao

    2007-01-15

    A chemical absorption-biological reduction integrated process can be used to remove nitrogen oxides (NOx) from flue gas. In such a process, nitric oxide (NO) can be effectively absorbed by the ferrous chelate of ethylenediaminetetraacetate (Fe(II)EDTA) to form Fe(II)EDTA-NO, which can be biologically regenerated by denitrifying bacteria. However, in the course of these processes, part of the Fe(II)EDTA is also oxidized to Fe(III)EDTA. The reduction of Fe(III)EDTA to Fe(II)EDTA depends on the activity of iron-reducing bacteria in the system. Therefore, the effectiveness of the system relies on how to effectively bioreduce Fe(III)EDTA and Fe(II)EDTA-NO in the system. In this paper, a strain identified as Escherichia coli FR-2 (iron-reducing bacterium) was used to investigate the reduction rate of Fe(III)EDTA. The experimental results indicate that Fe(III)EDTA-NO and Fe(II)EDTA in the system can inhibit both the FR-2 cell growth and thus affect the Fe(III)EDTA reduction. The FR-2 cell growth rate and Fe(III)EDTA reduction rate decreased with increasing Fe(II)EDTA-NO and Fe(II)EDTA concentration in the solution. When the concentration of Fe(II)EDTA-NO reached 3.7 mM, the FR-2 cell growth almost stopped. A mathematical model was developed to explain the cell growth and inhibition kinetics. The predicted results are close to the experimental data and provide a preliminary evaluation of the kinetics of the biologically mediated reactions necessary to regenerate the spent scrubber solution. PMID:17310734

  3. NO(x) removal from simulated flue gas by chemical absorption-biological reduction integrated approach in a biofilter.

    PubMed

    Zhang, Shi-Han; Cai, Ling-Lin; Mi, Xu-Hong; Jiang, Jin-Lin; Li, Wei

    2008-05-15

    A chemical absorption-biological reduction integrated approach, which combines the advantages of both the chemical and biological technologies, is employed to achieve the removal of nitrogen monoxide (NO) from the simulated flue gas. The biological reduction of NO to nitrogen gas (N2) and regeneration of the absorbent Fe(II)EDTA (EDTA:ethylenediaminetetraacetate) take place under thermophilic conditions (50 +/- 0.5 degrees C). The performance of a laboratory-scale biofilter was investigated for treating NO(x) gas in this study. Shock loading studies were performed to ascertain the response of the biofilter to fluctuations of inlet loading rates (0.48 approximately 28.68 g NO m(-3) h(-1)). A maximum elimination capacity (18.78 g NO m(-3) h(-1)) was achieved at a loading rate of 28.68 g NO m(-3) h(-1) and maintained 5 h operation at the steady state. Additionally, the effect of certain gaseous compounds (e.g., O2 and SO2) on the NO removal was also investigated. A mathematical model was developed to describe the system performance. The model has been able to predict experimental results for different inlet NO concentrations. In summary, both theoretical prediction and experimental investigation confirm that biofilter can achieve high removal rate for NO in high inlet concentrations under both steady and transient states. PMID:18546728

  4. Biological and chemical interaction of oxygen on the reduction of Fe(III)EDTA in a chemical absorption-biological reduction integrated NOx removal system.

    PubMed

    Zhang, Shi-Han; Shi, Yao; Li, Wei

    2012-03-01

    A promising chemical absorption-biological reduction integrated process has been proposed. A major problem of the process is oxidation of the active absorbent, ferrous ethylenediaminetetraacetate (Fe(II)EDTA), to the ferric species, leading to a significant decrease in NO removal efficiency. Thus the biological reduction of Fe(III)EDTA is vitally important for the continuous NO removal. Oxygen, an oxidizing agent and biological inhibitor, is typically present in the flue gas. It can significantly retard the application of the integrated process. This study investigated the influence mechanism of oxygen on the regeneration of Fe(II)EDTA in order to provide insight on how to eliminate or decrease the oxygen influence. The experimental results revealed that the dissolved oxygen and Fe(III)EDTA simultaneously served as electron acceptor for the microorganism. The Fe(III)EDTA reduction activity were directly inhibited by the dissolved oxygen. When the bioreactor was supplied with 3% and 8% oxygen in the gas phase, the concentration of initial dissolved oxygen in the liquid phase was 0.28 and 0.68 mg l(-1). Correspondingly, the instinct Fe(III)EDTA reduction activity of the microorganism determined under anoxic condition in a rotation shaker decreased from 1.09 to 0.84 and 0.49 mM h(-1). The oxidation of Fe(II)EDTA with dissolved oxygen prevented more dissolved oxygen access to the microorganism and eased the inhibition of dissolved oxygen on the microorganisms. PMID:21931973

  5. Pathway of FeEDTA transformation and its impact on performance of NOx removal in a chemical absorption-biological reduction integrated process

    PubMed Central

    Li, Wei; Zhao, Jingkai; Zhang, Lei; Xia, Yinfeng; Liu, Nan; Li, Sujing; Zhang, Shihan

    2016-01-01

    A novel chemical absorption-biological reduction (CABR) integrated process, employing ferrous ethylenediaminetetraacetate (Fe(II)EDTA) as a solvent, is deemed as a potential option for NOx removal from the flue gas. Previous work showed that the Fe(II)EDTA concentration was critical for the NOx removal in the CABR process. In this work, the pathway of FeEDTA (Fe(III)/Fe(II)-EDTA) transformation was investigated to assess its impact on the NOx removal in a biofilter. Experimental results revealed that the FeEDTA transformation involved iron precipitation and EDTA degradation. X-ray photoelectron spectroscopy analysis confirmed the iron was precipitated in the form of Fe(OH)3. The iron mass balance analysis showed 44.2% of the added iron was precipitated. The EDTA degradation facilitated the iron precipitation. Besides chemical oxidation, EDTA biodegradation occurred in the biofilter. The addition of extra EDTA helped recover the iron from the precipitation. The transformation of FeEDTA did not retard the NO removal. In addition, EDTA rather than the iron concentration determined the NO removal efficiency. PMID:26743930

  6. Reduction of chemical reaction models

    NASA Technical Reports Server (NTRS)

    Frenklach, Michael

    1991-01-01

    An attempt is made to reconcile the different terminologies pertaining to reduction of chemical reaction models. The approaches considered include global modeling, response modeling, detailed reduction, chemical lumping, and statistical lumping. The advantages and drawbacks of each of these methods are pointed out.

  7. Current advances of integrated processes combining chemical absorption and biological reduction for NO x removal from flue gas.

    PubMed

    Zhang, Shihan; Chen, Han; Xia, Yinfeng; Liu, Nan; Lu, Bi-Hong; Li, Wei

    2014-10-01

    Anthropogenic nitrogen oxides (NO x ) emitted from the fossil-fuel-fired power plants cause adverse environmental issues such as acid rain, urban ozone smoke, and photochemical smog. A novel chemical absorption-biological reduction (CABR) integrated process under development is regarded as a promising alternative to the conventional selective catalytic reduction processes for NO x removal from the flue gas because it is economic and environmentally friendly. CABR process employs ferrous ethylenediaminetetraacetate [Fe(II)EDTA] as a solvent to absorb the NO x following microbial denitrification of NO x to harmless nitrogen gas. Meanwhile, the absorbent Fe(II)EDTA is biologically regenerated to sustain the adequate NO x removal. Compared with conventional denitrification process, CABR not only enhances the mass transfer of NO from gas to liquid phase but also minimize the impact of oxygen on the microorganisms. This review provides the current advances of the development of the CABR process for NO x removal from the flue gas. PMID:25149446

  8. Source reduction from chemical plants using on-line optimization

    SciTech Connect

    Zhang, Z.; Pike, R.W.; Hertwig, T.A.

    1995-12-01

    An effective approach for source reduction in chemical plants has been demonstrated using on-line optimization with flowsheeting (ASPEN PLUS) for process optimization and parameter estimation and the Tjao-Biegler algorithm implemented in a mathematical programming language (GAMS/MINOS) for data reconciliation and gross error detection. Results for a Monsanto sulfuric acid plant with a Bailey distributed control system showed a 25% reduction in the sulfur dioxide emissions and a 17% improvement in the profit over the current operating conditions. Details of the methods used are described.

  9. Chemical and Biological Mechanisms of Pathogen Reduction Technologies

    PubMed Central

    Mundt, Janna M; Rouse, Lindsay; Van den Bossche, Jeroen; Goodrich, Raymond P

    2014-01-01

    Within the last decade new technologies have been developed and implemented which employ light, often in the presence of a photosensitizer, to inactivate pathogens that reside in human blood products for the purpose of transfusion. These pathogen reduction technologies attempt to find the proper balance between pathogen kill and cell quality. Each system utilizes various chemistries that not only impact which pathogens they can inactivate and how, but also how the treatments affect the plasma and cellular proteins and to what degree. This paper aims to present the various chemical mechanisms for pathogen reduction in transfusion medicine that are currently practiced or in development. PMID:25041351

  10. Reduction of chemical reaction networks through delay distributions

    NASA Astrophysics Data System (ADS)

    Barrio, Manuel; Leier, André; Marquez-Lago, Tatiana T.

    2013-03-01

    Accurate modelling and simulation of dynamic cellular events require two main ingredients: an adequate description of key chemical reactions and simulation of such chemical events in reasonable time spans. Quite logically, posing the right model is a crucial step for any endeavour in Computational Biology. However, more often than not, it is the associated computational costs which actually limit our capabilities of representing complex cellular behaviour. In this paper, we propose a methodology aimed at representing chains of chemical reactions by much simpler, reduced models. The abridgement is achieved by generation of model-specific delay distribution functions, consecutively fed to a delay stochastic simulation algorithm. We show how such delay distributions can be analytically described whenever the system is solely composed of consecutive first-order reactions, with or without additional "backward" bypass reactions, yielding an exact reduction. For models including other types of monomolecular reactions (constitutive synthesis, degradation, or "forward" bypass reactions), we discuss why one must adopt a numerical approach for its accurate stochastic representation, and propose two alternatives for this. In these cases, the accuracy depends on the respective numerical sample size. Our model reduction methodology yields significantly lower computational costs while retaining accuracy. Quite naturally, computational costs increase alongside network size and separation of time scales. Thus, we expect our model reduction methodologies to significantly decrease computational costs in these instances. We anticipate the use of delays in model reduction will greatly alleviate some of the current restrictions in simulating large sets of chemical reactions, largely applicable in pharmaceutical and biological research.

  11. Fermentation, fractionation and purification of streptokinase by chemical reduction method

    PubMed Central

    Karimi, Z; Babashamsi, M; Asgarani, E; Niakan, M; Salimi, A

    2011-01-01

    Background and Objectives Streptokinase is used clinically as an intravenous thrombolytic agent for the treatment of acute myocardial infarction and is commonly prepared from cultures of Streptococcus equisimilis strain H46A. The objective of the present study was the production of streptokinase from strain H46A and purification by chemical reduction method. Materials and Methods The rate of streptokinase production evaluated under the effect of changes on some fermentation factors. Moreover, due to the specific structure of streptokinase, a chemical reduction method employed for the purification of streptokinase from the fermentation broth. The H46A strain of group C streptococcus, was grown in a fermentor. The proper pH adjusted with NaOH under glucose feeding in an optimum temperature. The supernatant of the fermentation product was sterilized by filtration and concentrated by ultrafiltration. The pH of the concentrate was adjusted, cooled, and precipitated by methanol. Protein solution was reduced with dithiothreitol (DTT). Impurities settled down by aldrithiol-2 and the biological activity of supernatant containing streptokinase was determined. Results In the fed –batch culture, the rate of streptokinase production increased over two times as compared with the batch culture and the impurities were effectively separated from streptokinase by reduction method. Conclusion Improvements in SK production are due to a decrease in lag phase period and increase in the growth rate of logarithmic phase. The methods of purification often result in unacceptable losses of streptokinase, but the chemical reduction method give high yield of streptokinase and is easy to perform it. PMID:22347582

  12. Copper removal from water by chemical reduction with sodium borohydride

    SciTech Connect

    Gomez-Lahoz, C.; Garcia-Herruzo, F.; Rodriguez-Maroto, J.M.; Rodriguez, J.J. )

    1992-09-01

    The use of NaBH{sub 4} as a chemical reductant to precipitate copper from water has been studied. Initial Cu{sup 2+} concentrations of 25 and 40 mg have been checked, and complete removal can be achieved. When solid NaBH{sub 4} is fed, BH{sub 4}{sup {minus}} to Cu{sup 2+} molar ratios higher than 2 were needed. This can be substantially improved by using NaBH{sub 4} as a stabilized alkaline solution. A kinetic model is proposed which gives information about the relative rates of the two competitive reactions involved (Cu{sup 2+} and water reduction with BH{sub 4}{sup {minus}}) and allows the operating conditions leading to minimum BH{sub 4}{sup {minus}} consumption to be established.

  13. Spontaneous Growth and Chemical Reduction Ability of Ge Nanoparticles

    PubMed Central

    Liu, Jun; Liang, Changhao; Tian, Zhenfei; Zhang, Shuyuan; Shao, Guosheng

    2013-01-01

    Forming colloidal solutions containing semiconductor quantum-sized nanoparticles (NPs) with clean surface has been a long-standing scientific challenge. In this contribution, we report a “top-down” method for the fabrication of Ge NPs by laser ablation of a Ge target in deionized water without adding any stabilizing reagents. The initial Ge NPs in amorphous structure showed spontaneous growth behavior by aging Ge colloids in deionized water under ambient temperature, which gradually evolved into a metastable tetragonal structure as an intermediate phase and then transformed into the stable cubic structure, being consistent with the Ostwald's rule of stages for the growth in a metastable system. The laser-induced initial Ge NPs demonstrate a unique and prominent size-dependent chemical reductive ability, which is evidenced by the rapid degradation of organic molecules such as chlorinated aromatic compounds, organic dyes, and reduction of heavy metal Cr(VI) ions.

  14. The enzymatic and chemical reduction of extended biliverdins.

    PubMed

    Frydman, R B; Bari, S; Tomaro, M L; Frydman, B

    1990-08-31

    The substrate specificity of rat liver biliverdin reductase was probed using helical and extended biliverdins. The former were the ZZZ-all-syn biliverdins IX alpha and IX gamma, and the latter were the 5Z-syn, 10Z-syn, 15Z-anti; 5Z-anti, 10E-anti, 15E-anti biliverdins. It was found that the reduction rates of the biliverdins increased with the progressive stretching of their conformations. The most extended biliverdin was reduced at a higher rate than biliverdin IX alpha. The chemical reduction rates to bilirubins followed a similar pattern. Nucleophilic addition of 2-mercaptoethanol to the C10 methine was also favored in the extended biliverdins. PMID:2393401

  15. Model reduction for chemical kinetics: An optimization approach

    SciTech Connect

    Petzold, L.; Zhu, W.

    1999-04-01

    The kinetics of a detailed chemically reacting system can potentially be very complex. Although the chemist may be interested in only a few species, the reaction model almost always involves a much larger number of species. Some of those species are radicals, which are very reactive species and can be important intermediaries in the reaction scheme. A large number of elementary reactions can occur among the species; some of these reactions are fast and some are slow. The aim of simplified kinetics modeling is to derive the simplest reaction system which retains the essential features of the full system. An optimization-based method for reduction of the number of species and reactions in chemical kinetics model is described. Numerical results for several reaction mechanisms illustrate the potential of this approach.

  16. Chemical oxygen demand reduction in coffee wastewater through chemical flocculation and advanced oxidation processes.

    PubMed

    Zayas Pérez, Teresa; Geissler, Gunther; Hernandez, Fernando

    2007-01-01

    The removal of the natural organic matter present in coffee processing wastewater through chemical coagulation-flocculation and advanced oxidation processes (AOP) had been studied. The effectiveness of the removal of natural organic matter using commercial flocculants and UV/H2O2, UV/O3 and UV/H2O2/O3 processes was determined under acidic conditions. For each of these processes, different operational conditions were explored to optimize the treatment efficiency of the coffee wastewater. Coffee wastewater is characterized by a high chemical oxygen demand (COD) and low total suspended solids. The outcomes of coffee wastewater treatment using coagulation-flocculation and photodegradation processes were assessed in terms of reduction of COD, color, and turbidity. It was found that a reduction in COD of 67% could be realized when the coffee wastewater was treated by chemical coagulation-flocculation with lime and coagulant T-1. When coffee wastewater was treated by coagulation-flocculation in combination with UV/H2O2, a COD reduction of 86% was achieved, although only after prolonged UV irradiation. Of the three advanced oxidation processes considered, UV/H2O2, UV/O3 and UV/H2O2/O3, we found that the treatment with UV/H2O2/O3 was the most effective, with an efficiency of color, turbidity and further COD removal of 87%, when applied to the flocculated coffee wastewater. PMID:17918591

  17. Comparison of four chemical uncouplers for excess sludge reduction.

    PubMed

    Aragón, C; Quiroga, J M; Coello, M D

    2009-06-01

    A substantial part of the operating costs of wastewater treatment plants (WWTP) is associated with the management and treatment of the excess sludge generated during the treatment process. Different strategies have been applied for excess sludge reduction, such as the oxic-settling-anaerobic process, the high dissolved oxygen process, the uncoupler-containing activated sludge process, the ozonation-combined activated sludge process, control of sludge retention time and biodegradation of sludge in a membrane-assisted reactor. Chemical uncouplers have been shown to reduce excess sludge production, disassociating the energy coupling between catabolism and anabolism. These metabolic uncouplers may be organic compounds, such as 2,4-dinitrophenol (2,4-DNP) or 3,3',4',5-tetrachlorosalicylanilide (TCS), or heavy metals. In this paper, four different chemicals (2,4-DNP, TCS, copper (Cu) and zinc (Zn)) were chosen for short-term tests for studying their ability to reduce sludge yield (Y(x/s)) and, consequently, their potential for reducing excess sludge production. According to the results obtained, only TCS seems to be very effective in reducing sludge production from the activated sludge process. Compared with the control test, Y(x/s) can be reduced by over 30% at 0.8 mg/l TCS. It was also found that the substrate removal capability was not adversely affected by the presence of TCS. Furthermore, an increase in the microbial activity of the system was observed. PMID:19705608

  18. The Use of Chemical Probes for the Characterization of the Predominant Abiotic Reductants in Anaerobic Sediments

    EPA Science Inventory

    Identifying the predominant chemical reductants and pathways for electron transfer in anaerobic systems is paramount to the development of environmental fate models that incorporate pathways for abiotic reductive transformations. Currently, such models do not exist. In this chapt...

  19. Antibacterial activity of silver bionanocomposites synthesized by chemical reduction route

    PubMed Central

    2012-01-01

    Background The aim of this study is to investigate the functions of polymers and size of nanoparticles on the antibacterial activity of silver bionanocomposites (Ag BNCs). In this research, silver nanoparticles (Ag NPs) were incorporated into biodegradable polymers that are chitosan, gelatin and both polymers via chemical reduction method in solvent in order to produce Ag BNCs. Silver nitrate and sodium borohydride were employed as a metal precursor and reducing agent respectively. On the other hand, chitosan and gelatin were added as a polymeric matrix and stabilizer. The antibacterial activity of different sizes of silver nanoparticles was investigated against Gram-positive and Gram-negative bacteria by the disk diffusion method using Mueller-Hinton Agar. Results The properties of Ag BNCs were studied as a function of the polymer weight ratio in relation to the use of chitosan and gelatin. The morphology of the Ag BNCs films and the distribution of the Ag NPs were also characterized. The diameters of the Ag NPs were measured and their size is less than 20 nm. The antibacterial trait of silver/chitosan/gelatin bionanocomposites was investigated. The silver ions released from the Ag BNCs and their antibacterial activities were scrutinized. The antibacterial activities of the Ag BNC films were examined against Gram-negative bacteria (E. coli and P. aeruginosa) and Gram-positive (S. aureus and M. luteus) by diffusion method using Muller-Hinton agar. Conclusions The antibacterial activity of Ag NPs with size less than 20 nm was demonstrated and showed positive results against Gram-negative and Gram-positive bacteria. The Ag NPs stabilized well in the polymers matrix. PMID:22967920

  20. Chemical reactions occurring during direct solar reduction of CO2.

    PubMed

    Lyma, J L; Jensen, R J

    2001-09-28

    At high temperatures carbon dioxide may absorb solar radiation and react to form carbon monoxide and molecular oxygen. The CO, so produced, may be converted by well-established means to a combustible fuel, such as methanol. We intend to make a future demonstration of the solar reduction of CO2 based on these processes. This paper, however, addresses only the problem of preserving, or even enhancing, the initial photolytic CO by quenching the hot gas with colder H2O or CO2. We present model calculations with a reaction mechanism used extensively in other calculations. If a CO2 gas stream is heated and photolyzed by intense solar radiation and then allowed to cool slowly, it will react back to the initial CO2 by a series of elementary chemical reactions. The back reaction to CO2 can be terminated with the rapid addition of CO2, water, or a mixture. Calculations show that a three-fold quench with pure CO2 will stop the reactions and preserve over 90% of the initial photolytic CO. We find that water has one of two effects. It can either increase the CO level, or it can catalyze the recombination of O and CO to CO2. The gas temperature is the determining factor. If the quench gas is not sufficient to keep the temperature below approximately 1100 K, a chain-branching reaction dominates and the reaction to CO2 occurs. If the temperature stays below that level a chain terminating reaction dominates and the CO is increased. The former case occurs below approximately a fourfold quench with a water/CO2 mixture. The later case occurs when the quench is greater than fourfold. We conclude that CO2, H2O, or a mixture may quench the hot gas stream photolyzed by solar radiation and preserve the photolytic CO. PMID:11589409

  1. Less is Better. Laboratory Chemical Management for Waste Reduction.

    ERIC Educational Resources Information Center

    American Chemical Society, Washington, DC.

    An objective of the American Chemical Society is to promote alternatives to landfilling for the disposal of laboratory chemical wastes. One method is to reduce the amount of chemicals that become wastes. This is the basis for the "less is better" philosophy. This bulletin discusses various techniques involved in purchasing control, inventory…

  2. Model reduction for stochastic chemical systems with abundant species

    NASA Astrophysics Data System (ADS)

    Smith, Stephen; Cianci, Claudia; Grima, Ramon

    2015-12-01

    Biochemical processes typically involve many chemical species, some in abundance and some in low molecule numbers. We first identify the rate constant limits under which the concentrations of a given set of species will tend to infinity (the abundant species) while the concentrations of all other species remains constant (the non-abundant species). Subsequently, we prove that, in this limit, the fluctuations in the molecule numbers of non-abundant species are accurately described by a hybrid stochastic description consisting of a chemical master equation coupled to deterministic rate equations. This is a reduced description when compared to the conventional chemical master equation which describes the fluctuations in both abundant and non-abundant species. We show that the reduced master equation can be solved exactly for a number of biochemical networks involving gene expression and enzyme catalysis, whose conventional chemical master equation description is analytically impenetrable. We use the linear noise approximation to obtain approximate expressions for the difference between the variance of fluctuations in the non-abundant species as predicted by the hybrid approach and by the conventional chemical master equation. Furthermore, we show that surprisingly, irrespective of any separation in the mean molecule numbers of various species, the conventional and hybrid master equations exactly agree for a class of chemical systems.

  3. Model reduction for stochastic chemical systems with abundant species.

    PubMed

    Smith, Stephen; Cianci, Claudia; Grima, Ramon

    2015-12-01

    Biochemical processes typically involve many chemical species, some in abundance and some in low molecule numbers. We first identify the rate constant limits under which the concentrations of a given set of species will tend to infinity (the abundant species) while the concentrations of all other species remains constant (the non-abundant species). Subsequently, we prove that, in this limit, the fluctuations in the molecule numbers of non-abundant species are accurately described by a hybrid stochastic description consisting of a chemical master equation coupled to deterministic rate equations. This is a reduced description when compared to the conventional chemical master equation which describes the fluctuations in both abundant and non-abundant species. We show that the reduced master equation can be solved exactly for a number of biochemical networks involving gene expression and enzyme catalysis, whose conventional chemical master equation description is analytically impenetrable. We use the linear noise approximation to obtain approximate expressions for the difference between the variance of fluctuations in the non-abundant species as predicted by the hybrid approach and by the conventional chemical master equation. Furthermore, we show that surprisingly, irrespective of any separation in the mean molecule numbers of various species, the conventional and hybrid master equations exactly agree for a class of chemical systems. PMID:26646867

  4. Model reduction for stochastic chemical systems with abundant species

    SciTech Connect

    Smith, Stephen; Cianci, Claudia; Grima, Ramon

    2015-12-07

    Biochemical processes typically involve many chemical species, some in abundance and some in low molecule numbers. We first identify the rate constant limits under which the concentrations of a given set of species will tend to infinity (the abundant species) while the concentrations of all other species remains constant (the non-abundant species). Subsequently, we prove that, in this limit, the fluctuations in the molecule numbers of non-abundant species are accurately described by a hybrid stochastic description consisting of a chemical master equation coupled to deterministic rate equations. This is a reduced description when compared to the conventional chemical master equation which describes the fluctuations in both abundant and non-abundant species. We show that the reduced master equation can be solved exactly for a number of biochemical networks involving gene expression and enzyme catalysis, whose conventional chemical master equation description is analytically impenetrable. We use the linear noise approximation to obtain approximate expressions for the difference between the variance of fluctuations in the non-abundant species as predicted by the hybrid approach and by the conventional chemical master equation. Furthermore, we show that surprisingly, irrespective of any separation in the mean molecule numbers of various species, the conventional and hybrid master equations exactly agree for a class of chemical systems.

  5. Fe-57 Moessbauer Spectroscopy of Fulgurites: Implications for Chemical Reduction

    NASA Technical Reports Server (NTRS)

    Sheffer, A. A.; Dyar, M. D.

    2004-01-01

    The high temperature (superliquidus) processing of silicates often results in very reduced products, such as Si-bearing Fe metal in type-1 chondrules and in lunar regolith agglutinates. Previous work on fulgurites (the glassy products of the lightning strike fusion of sand, soil, or rock) found silicon metal and iron-silicon alloys inside the silicate glass. The mechanism for this extreme reduction is not yet understood. In this work, we begin a Fe-57 Moessbauer spectroscopy study as well as continuing a microprobe study of several fulgurites in order to better constrain the extent and process of Fe reduction.

  6. A POLLUTION REDUCTION METHODOLOGY FOR CHEMICAL PROCESS SIMULATORS

    EPA Science Inventory

    A pollution minimization methodology was developed for chemical process design using computer simulation. It is based on a pollution balance that at steady state is used to define a pollution index with units of mass of pollution per mass of products. The pollution balance has be...

  7. GREENER CHEMICAL PROCESS DESIGN ALTERNATIVES ARE REVEALED USING THE WASTE REDUCTION DECISION SUPPORT SYSTEM (WAR DSS)

    EPA Science Inventory

    The Waste Reduction Decision Support System (WAR DSS) is a Java-based software product providing comprehensive modeling of potential adverse environmental impacts (PEI) predicted to result from newly designed or redesigned chemical manufacturing processes. The purpose of this so...

  8. Tool for the Reduction and Assessment of Chemical and other Environmental Impacts

    EPA Science Inventory

    TRACI, the Tool for the Reduction and Assessment of Chemical and other environmental Impacts, has been developed by the US Environmental Protection Agency’s National Risk Management Research Laboratory to facilitate the characterization of stressors that have potential effects, ...

  9. TRACI - THE TOOL FOR THE REDUCTION AND ASSESSMENT OF CHEMICAL AND OTHER ENVIRONMENTAL IMPACTS

    EPA Science Inventory

    TRACI, The Tool for the Reduction and Assessment of Chemical and other environmental Impacts, is described along with its history, the underlying research, methodologies, and insights within individual impact categories. TRACI facilitates the characterization of stressors that ma...

  10. Analysis and reduction of chemical models under uncertainty.

    SciTech Connect

    Oxberry, Geoff; Debusschere, Bert J.; Najm, Habib N.

    2008-08-01

    While models of combustion processes have been successful in developing engines with improved fuel economy, more costly simulations are required to accurately model pollution chemistry. These simulations will also involve significant parametric uncertainties. Computational singular perturbation (CSP) and polynomial chaos-uncertainty quantification (PC-UQ) can be used to mitigate the additional computational cost of modeling combustion with uncertain parameters. PC-UQ was used to interrogate and analyze the Davis-Skodje model, where the deterministic parameter in the model was replaced with an uncertain parameter. In addition, PC-UQ was combined with CSP to explore how model reduction could be combined with uncertainty quantification to understand how reduced models are affected by parametric uncertainty.

  11. Reduction of Microbial and Chemical Contaminants in Water Using POU/POE & Mobile Treatment Technologies

    EPA Science Inventory

    POU/POE may be a cost-effective option for reductions of a particular chemical to achieve water quality compliance under certain situations and given restrictions. Proactive consumers seeking to reduce exposure to potential pathogens, trace chemicals, and nanoparticles not curre...

  12. In-Situ Chemical Reduction and Oxidation of VOCs in Groundwater: Groundwater Treatability Studies

    NASA Technical Reports Server (NTRS)

    Keith, Amy; Glasgow, Jason; McCaleh, Rececca C. (Technical Monitor)

    2001-01-01

    This paper presents NASA Marshall Space Flight Center's treatability studies for volatile organic compounds in groundwater. In-Situ groundwater treatment technologies include: 1) Chemical Reduction(Ferox); 2) Chemical Oxidation (Fenton Reagents, Permanganate, and Persulfate); and 3) Thermal (Dynamic Underground Stripping, Six-Phase Heating). This paper is presented in viewgraph form.

  13. Reduction of percutaneous absorption of toxic chemicals by dendrimers.

    PubMed

    Moghimi, Hamid R; Varshochian, Reyhaneh; Kobarfard, Farzad; Erfan, Mohammad

    2010-03-01

    Polyamidoamine (PAMAM) dendrimer, a reactive nanoparticle, was investigated as a potential protectant against percutaneous absorption of chemicals. Permeation of furfural (model toxicant) through rat skin from a 1-mg/mL solution was studied in the absence and presence of PAMAM dendrimer, which was applied either as 1, 4, and 6 mg/mL in furfural solution (cotreatment) or 2.2 mg/cm(2) deposited on skin surface before furfural application (pretreatment). Furfural flux, about 70 microg/cm(2)/h in untreated samples, was decreased by PAMAM dendrimer in a concentration-dependent manner up to 12 times with the cotreatment methods and 2.3 times with the pretreatment method, indicating PAMAM's protective ability against cutaneous toxicants. PMID:19995245

  14. In Situ Chemical Reduction of Aquifer Sediments: Enhancement of Reactive Iron Phases and TCE Dechlorination

    SciTech Connect

    Szecsody, Jim E.; Fruchter, Jonathan S.; Williams, Mark D.; Vermeul, Vince R.; Sklarew, Debbie S.

    2004-07-29

    In situ chemical reduction of aquifer sediments is currently being used for chromate and TCE remediation by forming a permeable reactive barrier. The chemical and physical processes that occur during abiotic reduction of natural sediments by sodium dithionite were investigated. In different aquifer sediments, 15 to 25% of Fe{sup III} -oxides were dissolved/reduced, which produces primarily adsorbed Fe{sup II}, and some siderite. The sediment reduction rate ({approx} 5h) was the chemically controlled (58 kJ/mole) reduction of a minor phase (<20%). It was necessary to maintain neutral to high pH to maintain reduction efficiency and prevent iron mobilization, as reduction generated H{sup +}. Sequential extractions on reduced sediment showed that adsorbed ferrous iron and iron oxides on the clay size fraction controlled TCE reactivity, and not structural ferrous iron in clay. The mass and rate of field-scale reduction of aquifer sediments were generally predicted with laboratory data using a single reduction reaction.

  15. Recovery of Cu(II) by chemical reduction using sodium dithionite.

    PubMed

    Chou, Yi-Hsuan; Yu, Jui-Hsuan; Liang, Yang-Min; Wang, Pin-Jan; Li, Chi-Wang; Chen, Shiao-Shing

    2015-12-01

    Wastewaters containing Cu(II) along with ligands are ubiquitous in various industrial sectors. Efficacy of treatment processes for copper removal, especially precipitation, is greatly debilitated by ligands. Chemical reduction being commonly employed for production of metal nanoparticles has also been used for removing copper. Addition of ammonia was reported to be essential for improving copper reduction efficiency by increasing copper solubility at alkaline pH values. In this study, chemical reduction was employed to treat ligand-containing wastewater, exploiting the fact that ligands and metals are coexisted in many wastewaters. Result shows that copper ions were removed by either reduction or precipitation mechanisms depending on pH, type of ligands, and mixing condition. Complete copper reduction/removal was achieved under optimal condition. The lowest removal efficiency observed at pH 9.0 for ammonia system is due to formation of nano-sized particles, which are readily to pass through 0.45μm filter used for sample pretreatment before copper analysis. Instead of producing metallic copper, cuprous and copper oxide are identified in the samples collected from ammonia system and EDTA system, respectively. Re-oxidation of metallic copper particles by atmospheric oxygen during sample handling or incomplete reduction of Cu(II) ions during reduction process might be the cause. Finally, reduction process was applied to treat real wastewater, achieving complete removal of copper but only 10% of nickel. PMID:26210323

  16. Photochemical reduction of CO{sub 2} to fuels and chemicals

    SciTech Connect

    DuBois, D.; Eisenberg, R.; Fujita, E.

    1996-09-01

    Photochemical reduction of CO{sub 2} represents a potentially useful approach to developing a sustainable source of carbon-based chemicals, fuels, and materials. In this report the present status of photochemical CO{sub 2} reduction is assessed, areas that need to be better understood for advancement are identified, and approaches to overcoming barriers are suggested. Because of the interdisciplinary nature of this field, assessments of three closely interrelated areas are given including integrated photochemical systems for catalytic CO{sub 2} reduction, thermal catalytic CO{sub 2} reactions, and electrochemical CO{sub 2} reduction. The report concludes with a summary and assessment of potential impacts of this area on chemical and energy technologies.

  17. Chemical Reduction of SIM MOX in Molten Lithium Chloride Using Lithium Metal Reductant

    NASA Astrophysics Data System (ADS)

    Kato, Tetsuya; Usami, Tsuyoshi; Kurata, Masaki; Inoue, Tadashi; Sims, Howard E.; Jenkins, Jan A.

    2007-09-01

    A simulated spent oxide fuel in a sintered pellet form, which contained the twelve elements U, Pu, Am, Np, Cm, Ce, Nd, Sm, Ba, Zr,Mo, and Pd, was reduced with Li metal in a molten LiCl bath at 923 K. More than 90% of U and Pu were reduced to metal to form a porous alloy without significant change in the Pu/U ratio. Small fractions of Pu were also combined with Pd to form stable alloys. In the gap of the porous U-Pu alloy, the aggregation of the rare-earth (RE) oxide was observed. Some amount of the RE elements and the actinoides leached from the pellet. The leaching ratio of Am to the initially loaded amount was only several percent, which was far from about 80% obtained in the previous ones on simple MOX including U, Pu, and Am. The difference suggests that a large part of Am existed in the RE oxide rather than in the U-Pu alloy. The detection of the RE elements and actinoides in the molten LiCl bath seemed to indicate that they dissolved into the molten LiCl bath containing the oxide ion, which is the by-product of the reduction, as solubility of RE elements was measured in the molten LiCl-Li2O previously.

  18. Reduction study of oxidized two-dimensional graphene-based materials by chemical and thermal reduction methods

    NASA Astrophysics Data System (ADS)

    Douglas, Amber M.

    Graphene is a two-dimensional (2D) sp2-hybridized carbon-based material possessing properties which include high electrical conductivity, ballistic thermal conductivity, tensile strength exceeding that of steel, high flexural strength, optical transparency, and the ability to adsorb and desorb atoms and molecules. Due to the characteristics of said material, graphene is a candidate for applications in integrated circuits, electrochromic devices, transparent conducting electrodes, desalination, solar cells, thermal management materials, polymer nanocomposites, and biosensors. Despite the above mentioned properties and possible applications, very few technologies have been commercialized utilizing graphene due to the high cost associated with the production of graphene. Therefore, a great deal of effort and research has been performed to produce a material that provides similar properties, reduced graphene oxide due (RGO) to the ease of commercial scaling of the production processes. This material is typically prepared through the oxidation of graphite in an aqueous media to graphene oxide (GO) followed by reduction to yield RGO. Although this material has been extensively studied, there is a lack of consistency in the scientific community regarding the analysis of the resulting RGO material. In this dissertation, a study of the reduction methods for GO and an alternate 2D carbon-based material, humic acid (HA), followed by analysis of the materials using Raman spectroscopy and Energy Dispersive X-ray Spectroscopy (EDS). Means of reduction will include chemical and thermal methods. Characterization of the material has been carried out on both before and after reduction.

  19. APPLICATIONS ANALYSIS REPORT: ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE REACTOR SYSTEM

    EPA Science Inventory

    This report details the Superfund Innovative Technology Evaluation of Eco Logic International's gas-phase chemical reduction process, with an emphasis on their Reactor System. he Eco Logic process employees a high temperature reactor filled with hydrogen gas as the means to destr...

  20. ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE THERMAL DESORPTION UNIT - APPLICATIONS ANALYSIS REPORT

    EPA Science Inventory

    ELI ECO Logic International, Inc.'s Thermal Desorption Unit (TDU) is specifically designed for use with Eco Logic's Gas Phase Chemical Reduction Process. The technology uses an externally heated bath of molten tin in a hydrogen atmosphere to desorb hazardous organic compounds fro...

  1. A MIXED CHEMICAL REDUCTANT FOR TREATING HEXAVALENT CHROMIUM IN A CHROMITE ORE PROCESSING SOLID WASTE

    EPA Science Inventory

    We evaluated a method for delivering ferrous iron into the subsurface to enhance chemical reduction of Cr(VI) in a chromite ore processing solid waste (COPSW). The COPSW is characterized by high pH (8.5 -11.5), high Cr(VI) concentrations in the solid phase (up to 550 mg kg-1) and...

  2. Reduction of risk to the marine environment from oilfield chemicals - balancing environmental and technical needs

    SciTech Connect

    O`Neill, J.E.; Hill, D.G.

    1996-12-31

    The study argues that the regulation of offshore use of hazardous chemicals for oilfield stimulation and Completion applications is an important but not a total solution to reduce marine pollution from offshore sources. The aim of the study is to demonstrate that for a complete solution, chemical reformulation must be considered hand-in-band with improved operational practices to provide a maximum effect on overall risk reduction. The study is directed at one major service company`s approach to the whole issue of chemical management in the 1990s, based mainly on North Sea experience in cementing, drilling fluid and stimulation activities. Oilfield chemicals are incorporated into a fluid design to solve a specific technical problem in a well, such as well completion, stimulation and damage removal. While it is desirable to replace all the harmful chemicals, the practicalities of doing so are limited if the industry is to continue to produce efficiently. Other alternatives need consideration. By their very chemistry, some chemicals have primary active ingredients which may be harmful if discharged into the environment. Improving the characteristics of chemicals to marine life requires the change of previously acceptable products, such as the elimination of banned materials as well as incorporating components with reduced toxicity and greater biodegradability. The idealistic goal is the immediate replacement of all chemicals by nontoxic, biodegrade alternatives; the practical solution is replacement reformulation where possible and the improved isolation the oilwell and marine environments through improvements in continuous-mix technology along with reduction of the chemicals by better job design.

  3. Development Of Chemical Reduction And Air Stripping Processes To Remove Mercury From Wastewater

    SciTech Connect

    Jackson, Dennis G.; Looney, Brian B.; Craig, Robert R.; Thompson, Martha C.; Kmetz, Thomas F.

    2013-07-10

    This study evaluates the removal of mercury from wastewater using chemical reduction and air stripping using a full-scale treatment system at the Savannah River Site. The existing water treatment system utilizes air stripping as the unit operation to remove organic compounds from groundwater that also contains mercury (C ~ 250 ng/L). The baseline air stripping process was ineffective in removing mercury and the water exceeded a proposed limit of 51 ng/L. To test an enhancement to the existing treatment modality a continuous dose of reducing agent was injected for 6-hours at the inlet of the air stripper. This action resulted in the chemical reduction of mercury to Hg(0), a species that is removable with the existing unit operation. During the injection period a 94% decrease in concentration was observed and the effluent satisfied proposed limits. The process was optimized over a 2-day period by sequentially evaluating dose rates ranging from 0.64X to 297X stoichiometry. A minimum dose of 16X stoichiometry was necessary to initiate the reduction reaction that facilitated the mercury removal. Competing electron acceptors likely inhibited the reaction at the lower 1 doses, which prevented removal by air stripping. These results indicate that chemical reduction coupled with air stripping can effectively treat large-volumes of water to emerging part per trillion regulatory standards for mercury.

  4. Chemical and enzymatic reductive activation of acylfulvene to isomeric cytotoxic reactive intermediates

    PubMed Central

    Pietsch, Kathryn E.; Neels, James F.; Yu, Xiang; Gong, Jiachang; Sturla, Shana J.

    2011-01-01

    Acylfulvenes, a class of semisynthetic analogues of the sesquiterpene natural product illudin S, are cytotoxic towards cancer cells. The minor structural changes between illudin S and AFs translate to an improved therapeutic window in preclinical cell-based assays and xenograft models. AFs are, therefore, unique tools for addressing the chemical and biochemical basis of cytotoxic selectivity. AFs elicit cytotoxic responses by alkylation of biological targets, including DNA. While AFs are capable of direct alkylation, cytosolic reductive bioactivation to an electrophilic intermediate is correlated with enhanced cytotoxicity. Data obtained in this study illustrates chemical aspects of the process of AF activation. By tracking reaction mechanisms with stable isotope-labeled reagents, enzymatic versus chemical activation pathways for AF were compared for reactions involving the NADPH-dependent enzyme prostaglandin reductase 1 (PTGR1) or sodium borohydride, respectively. These two processes resulted in isomeric products that appear to give rise to similar patterns of DNA modification. The chemically activated isomer has been newly isolated and chemically characterized in this study, including an assessment of its relative stereochemistry, and stability at varying pH and under bioassay conditions. In mammalian cancer cells, this chemically activated analog was shown to not rely on further cellular activation to significantly enhance cytotoxic potency, in contrast to the requirements of AF. On the basis of this study, we anticipate that the chemically activated form of AF will serve as a useful chemical probe for evaluating biomolecular interactions independent of enzyme-mediated activation. PMID:21939268

  5. Fundamental limits on gas-phase chemical reduction of NOx in a plasma

    SciTech Connect

    Penetrante, B.M.; Hsiao, M.C.; Merritt, B.T.; Vogtlin, G.E.

    1997-12-31

    In the plasma, the electrons do not react directly with the NOx molecules. The electrons collide mainly with the background gas molecules like N{sub 2}, O{sub 2} and H{sub 2}O. Electron impact on these molecules result partly in dissociation reactions that produce reactive species like N, O and OH. The NOx in the engine exhaust gas initially consist mostly of NO. The ground state nitrogen atom, N, is the only species that could lead to the chemical reduction of NO to N{sub 2}. The O radical oxidizes NO to NO{sub 2} leaving the same amount of NOx. The OH radical converts NO{sub 2} to nitric acid. Acid products in the plasma can easily get adsorbed on surfaces in the plasma reactor and in the pipes. When undetected, the absence of these oxidation products can often be mistaken for chemical reduction of NOx. In this paper the authors will examine the gas-phase chemical reduction of NOx. They will show that under the best conditions, the plasma can chemically reduce 1.6 grams of NOx per brake-horsepower-hour [g(NOx)/bhp-hr] when 5% of the engine output energy is delivered to the plasma.

  6. Synthesis of cuprous oxide nanocomposite electrodes by room-temperature chemical partial reduction.

    PubMed

    Park, Kyung-Soo; Seo, Seung-Deok; Jin, Yun-Ho; Lee, Seung-Hun; Shim, Hyun-Woo; Lee, Du-Hee; Kim, Dong-Wan

    2011-10-01

    We demonstrate a template-free synthetic approach for the preparation of a highly conductive Cu/Cu(2)O nanocomposite electrode by a chemical reduction process. Cu(2)O octahedra were prepared through chemical dehydrogenation of as-synthesized Cu(OH)(2) nanowire precursors. To provide a sufficiently electron-conducting network, the Cu(2)O particles were transformed into Cu/Cu(2)O nanocomposites by an intentional reduction process. The Cu/Cu(2)O nanocomposite electrodes showed enhanced cycling performance compared to Cu(2)O particles. Furthermore, their rate capabilities were superior to those of their mechanically mixed Cu/Cu(2)O counterparts. This enhanced electrochemical performance of the hybrid Cu/Cu(2)O nanocomposites was ascribed to the formation of homogeneous nanostructures, offering an efficient electron-transport path provided by the presence of highly dispersed Cu nanoparticles. PMID:21850303

  7. Sulfa Drugs Inhibit Sepiapterin Reduction and Chemical Redox Cycling by Sepiapterin Reductase

    PubMed Central

    Yang, Shaojun; Jan, Yi-Hua; Mishin, Vladimir; Richardson, Jason R.; Hossain, Muhammad M.; Heindel, Ned D.; Heck, Diane E.; Laskin, Debra L.

    2015-01-01

    Sepiapterin reductase (SPR) catalyzes the reduction of sepiapterin to dihydrobiopterin (BH2), the precursor for tetrahydrobiopterin (BH4), a cofactor critical for nitric oxide biosynthesis and alkylglycerol and aromatic amino acid metabolism. SPR also mediates chemical redox cycling, catalyzing one-electron reduction of redox-active chemicals, including quinones and bipyridinium herbicides (e.g., menadione, 9,10-phenanthrenequinone, and diquat); rapid reaction of the reduced radicals with molecular oxygen generates reactive oxygen species (ROS). Using recombinant human SPR, sulfonamide- and sulfonylurea-based sulfa drugs were found to be potent noncompetitive inhibitors of both sepiapterin reduction and redox cycling. The most potent inhibitors of sepiapterin reduction (IC50s = 31–180 nM) were sulfasalazine, sulfathiazole, sulfapyridine, sulfamethoxazole, and chlorpropamide. Higher concentrations of the sulfa drugs (IC50s = 0.37–19.4 μM) were required to inhibit redox cycling, presumably because of distinct mechanisms of sepiapterin reduction and redox cycling. In PC12 cells, which generate catecholamine and monoamine neurotransmitters via BH4-dependent amino acid hydroxylases, sulfa drugs inhibited both BH2/BH4 biosynthesis and redox cycling mediated by SPR. Inhibition of BH2/BH4 resulted in decreased production of dopamine and dopamine metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, and 5-hydroxytryptamine. Sulfathiazole (200 μM) markedly suppressed neurotransmitter production, an effect reversed by BH4. These data suggest that SPR and BH4-dependent enzymes, are “off-targets” of sulfa drugs, which may underlie their untoward effects. The ability of the sulfa drugs to inhibit redox cycling may ameliorate ROS-mediated toxicity generated by redox active drugs and chemicals, contributing to their anti-inflammatory activity. PMID:25550200

  8. Sulfa drugs inhibit sepiapterin reduction and chemical redox cycling by sepiapterin reductase.

    PubMed

    Yang, Shaojun; Jan, Yi-Hua; Mishin, Vladimir; Richardson, Jason R; Hossain, Muhammad M; Heindel, Ned D; Heck, Diane E; Laskin, Debra L; Laskin, Jeffrey D

    2015-03-01

    Sepiapterin reductase (SPR) catalyzes the reduction of sepiapterin to dihydrobiopterin (BH2), the precursor for tetrahydrobiopterin (BH4), a cofactor critical for nitric oxide biosynthesis and alkylglycerol and aromatic amino acid metabolism. SPR also mediates chemical redox cycling, catalyzing one-electron reduction of redox-active chemicals, including quinones and bipyridinium herbicides (e.g., menadione, 9,10-phenanthrenequinone, and diquat); rapid reaction of the reduced radicals with molecular oxygen generates reactive oxygen species (ROS). Using recombinant human SPR, sulfonamide- and sulfonylurea-based sulfa drugs were found to be potent noncompetitive inhibitors of both sepiapterin reduction and redox cycling. The most potent inhibitors of sepiapterin reduction (IC50s = 31-180 nM) were sulfasalazine, sulfathiazole, sulfapyridine, sulfamethoxazole, and chlorpropamide. Higher concentrations of the sulfa drugs (IC50s = 0.37-19.4 μM) were required to inhibit redox cycling, presumably because of distinct mechanisms of sepiapterin reduction and redox cycling. In PC12 cells, which generate catecholamine and monoamine neurotransmitters via BH4-dependent amino acid hydroxylases, sulfa drugs inhibited both BH2/BH4 biosynthesis and redox cycling mediated by SPR. Inhibition of BH2/BH4 resulted in decreased production of dopamine and dopamine metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, and 5-hydroxytryptamine. Sulfathiazole (200 μM) markedly suppressed neurotransmitter production, an effect reversed by BH4. These data suggest that SPR and BH4-dependent enzymes, are "off-targets" of sulfa drugs, which may underlie their untoward effects. The ability of the sulfa drugs to inhibit redox cycling may ameliorate ROS-mediated toxicity generated by redox active drugs and chemicals, contributing to their anti-inflammatory activity. PMID:25550200

  9. Are sulfur isotope ratios sufficient to determine the antiquity of sulfate reduction. [implications for chemical evolution

    NASA Technical Reports Server (NTRS)

    Ashendorf, D.

    1980-01-01

    Possible limitations on the use of sulfur isotope ratios in sedimentary sulfides to infer the evolution of microbial sulfate reduction are discussed. Current knowledge of the ways in which stable sulfur isotope ratios are altered by chemical and biological processes is examined, with attention given to the marine sulfur cycle involving various microbial populations, and sulfur reduction processes, and it is noted that satisfactory explanations of sulfur isotope ratios observed in live organisms and in sediments are not yet available. It is furthermore pointed out that all members of the same genus of sulfate reducing bacteria do not always fractionate sulfur to the same extent, that the extent of sulfur fractionation by many sulfate-reducing organisms has not yet been determined, and that inorganic processes can also affect sulfur isotope fractionation values. The information currently available is thus concluded to be insufficient to determine the time of initial appearance of biological sulfate reduction.

  10. Chemical and Biological Interactions during Nitrate and Goethite Reduction by Shewanella putrefaciens 200

    PubMed Central

    Cooper, D. Craig; Picardal, Flynn W.; Schimmelmann, Arndt; Coby, Aaron J.

    2003-01-01

    Although previous research has demonstrated that NO3− inhibits microbial Fe(III) reduction in laboratory cultures and natural sediments, the mechanisms of this inhibition have not been fully studied in an environmentally relevant medium that utilizes solid-phase, iron oxide minerals as a Fe(III) source. To study the dynamics of Fe and NO3− biogeochemistry when ferric (hydr)oxides are used as the Fe(III) source, Shewanella putrefaciens 200 was incubated under anoxic conditions in a low-ionic-strength, artificial groundwater medium with various amounts of NO3− and synthetic, high-surface-area goethite. Results showed that the presence of NO3− inhibited microbial goethite reduction more severely than it inhibited microbial reduction of the aqueous or microcrystalline sources of Fe(III) used in other studies. More interestingly, the presence of goethite also resulted in a twofold decrease in the rate of NO3− reduction, a 10-fold decrease in the rate of NO2− reduction, and a 20-fold increase in the amounts of N2O produced. Nitrogen stable isotope experiments that utilized δ15N values of N2O to distinguish between chemical and biological reduction of NO2− revealed that the N2O produced during NO2− or NO3− reduction in the presence of goethite was primarily of abiotic origin. These results indicate that concomitant microbial Fe(III) and NO3− reduction produces NO2− and Fe(II), which then abiotically react to reduce NO2− to N2O with the subsequent oxidation of Fe(II) to Fe(III). PMID:12788758

  11. Influence of physical and chemical aquifer heterogeneity on nitrate reduction processes by numerical simulations

    NASA Astrophysics Data System (ADS)

    Kalbacher, T.; Jang, E.; He, W.; Savoy, H.; Schueth, C.; Kolditz, O.

    2015-12-01

    Nitrate reduction reactions, as one of the most important redox reactions in a subsurface system, are strongly influenced by various heterogeneity factors which influence transport of chemical species and spatial distribution of redox substances and consequently have an effect on overall nitrate reduction capacity. In this presented work, the influence of two heterogeneity factors, spatially heterogeneity of hydrological parameters versus spatial heterogeneity of geochemical reactive substances distribution, are discussed with a focus on nitrate transport and redox transformation processes. For this purpose, a coupling interface OGS#IPhreeqc is employed. This code combines Finite-Element groundwater flow and multi-species transport code of OpenGeoSys (OGS) with the IPhreeqc module of open source geochemical solver PHREEQC. The resulting coupled model is applied for simulation of nitrate reduction processes with a series of hypothetical aquifer systems, built using exponentially-correlated log-normal distributed hydraulic conductivity and reactive substances. The spatially heterogeneous aquifer system is realized by a RandomFields package using a statistical program R. Results show that the heterogeneous hydraulics conductivity field has larger impact on nitrate reduction capacity than heterogeneous reactive substances distribution. Moreover, nitrate reduction capacity can be increased by enhanced mixing in heterogeneous hydraulic conductivity field however its overall reduction capacity has gradually decreased as a degree of heterogeneity has increased since accessibility of the chemical species by the reactive substances may be limited. These results support that appropriate characterization of the variance of hydraulic conductivity within the aquifer is important to predict contaminant fate and transport and quantify the impact of uncertainty on numerical groundwater simulation.

  12. Applying the Philosophical Concept of Reduction to the Chemistry of Water: Implications for Chemical Education

    NASA Astrophysics Data System (ADS)

    Erduran, Sibel

    Even though philosophical themes in science education have been advocated for several decades, little attention has been paid to how these themes can be contextualized in the teaching of a particular domain of science. The purpose of this paper is to provide an example theoretical framework for applying a philosophical theme, reduction, in chemistry education. The inclusion of the concept reduction in chemistry education not only elaborates on this important philosophical thesis in the specific context of chemistry but also it might offer some insight into how students interest in philosophical aspects of chemistry might be stimulated. The consideration of concepts such as chemical composition, molecular structure and bonding in chemistry of water provides an example for the application of reduction in chemistry education. The water example also promotes the reflection on the microscopic, macroscopic and symbolic features of substances, themes which are repeatedly covered in secondary as well as tertiary chemical education. Some implications include the need for restructuring the curriculum in higher education to be more inclusive of the controversial nature of quantum mechanical applications in chemistry.

  13. Synthesis of Hierarchical Nanoporous Microstructures via the Kirkendall Effect in Chemical Reduction Process

    PubMed Central

    Gao, Ling; Pang, Chao; He, Dafang; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2015-01-01

    A series of novel hierarchical nanoporous microstructures have been synthesized through one-step chemical reduction of micron size Cu2O and Co3O4 particles. By controlling the reduction time, non-porous Cu2O microcubes sequentially transform to nanoporous Cu/Cu2O/Cu dented cubic composites and hollow eightling-like Cu microparticles. The mechanism involved in the complex structural evolution is explained based on oxygen diffusion and Kirkendall effect. The nanoporous Cu/Cu2O/Cu dented cubic composites exhibit superior electrochemical performance as compared to solid Cu2O microcubes. The reduction of nonporous Co3O4 also exhibits a uniform sequential reduction process from nonporous Co3O4 to porous Co3O4/CoO composites, porous CoO, porous CoO/Co composites, and porous foam-like Co particles. Nanoscale channels originate from the particle surface and eventually develop inside the entire product, resulting in porous foam-like Co microparticles. The Kirkendall effect is believed to facilitate the formation of porous structures in both processes. PMID:26552845

  14. Synthesis of Hierarchical Nanoporous Microstructures via the Kirkendall Effect in Chemical Reduction Process

    NASA Astrophysics Data System (ADS)

    Gao, Ling; Pang, Chao; He, Dafang; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2015-11-01

    A series of novel hierarchical nanoporous microstructures have been synthesized through one-step chemical reduction of micron size Cu2O and Co3O4 particles. By controlling the reduction time, non-porous Cu2O microcubes sequentially transform to nanoporous Cu/Cu2O/Cu dented cubic composites and hollow eightling-like Cu microparticles. The mechanism involved in the complex structural evolution is explained based on oxygen diffusion and Kirkendall effect. The nanoporous Cu/Cu2O/Cu dented cubic composites exhibit superior electrochemical performance as compared to solid Cu2O microcubes. The reduction of nonporous Co3O4 also exhibits a uniform sequential reduction process from nonporous Co3O4 to porous Co3O4/CoO composites, porous CoO, porous CoO/Co composites, and porous foam-like Co particles. Nanoscale channels originate from the particle surface and eventually develop inside the entire product, resulting in porous foam-like Co microparticles. The Kirkendall effect is believed to facilitate the formation of porous structures in both processes.

  15. Synthesis and spectroscopic characterization of gold nanobipyramids prepared by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Thanh Ngo, Vo Ke; Phat Huynh, Trong; Giang Nguyen, Dang; Phuong Uyen Nguyen, Hoang; Lam, Quang Vinh; Dat Huynh, Thanh

    2015-12-01

    Gold nanobipyramids (NBPs) have attracted much attention because they have potential for applications in smart sensing devices, such as medical diagnostic equippments. This is due to the fact that they show more advantageous plasmonic properties than other gold nanostructures. We describe a chemical reduction method for synthesizing NBPs using conventional heating with ascorbic acid reduction and cetyltrimethylamonium bromide (CTAB) + AgNO3 as capping agents. The product was characterized by ultraviolet-visible spectroscopy (UV-vis), Fourier transmission infrared spectroscopy (FTIR), transmission electron microscopy (TEM), x-ray powder diffraction (XRD). The results showed that gold nanoparticles were formed with bipyramid shape (tip-to-tip distance of 88.4 ± 9.4 nm and base length of 29.9 ± 3.2 nm) and face-centered-cubic crystalline structure. Optimum parameters for preparation of NBPs are also found.

  16. Raman Chemical Imaging of Chromate Reduction Sites in a Single Bacterium Using Intracellularly Grown Gold Nanoislands

    PubMed Central

    Ravindranath, Sandeep P.; Henne, Kristene L.; Thompson, Dorothea K.; Irudayaraj, Joseph

    2011-01-01

    Imagingon act live molecular events within micro-organisms at single cell resolution would deliver valuable mechanistic information much needed in understanding key biological processes. We present a surface-enhanced Raman (SERS) chemical imaging strategy as a first step towards exploring the intracellular bioreduction pockets of toxic chromate in Shewanella. In order to achieve this, we take advantage of an innate reductive mechanism in bacteria of reducing gold ions into intracellular gold nanoislands which provide the necessary enhancement for SERS imaging. We show that SERS has the sensitivity and selectivity not only to identify, but also to differentiate between the two stable valence forms of chromate in cells. The imaging platform was used to understand intracellular metal reductiivities in a ubiquitous metal-reducing organism Shewanella oneidensis MR-1, by mapping Chromate reduction. PMID:21634405

  17. Heavy metal removal by chemical reduction with sodium borohydride. A pilot-plant study

    SciTech Connect

    Gomez-Lahoz, C.; Garcia-Herruzo, F.; Rodriguez-Maroto, J.M.; Rodriguez, J.J. )

    1992-10-01

    A 1,000/h continuous pilot-plant study dealing with Cu{sup 2+} and Co{sup 2+} removal from simulated industrial wastewater by means of chemical reduction with sodium borohydride is presented. Initial metal concentrations in the 25 to 40 mg range have been tested. Residual concentrations lower than 0.1 mg have been achieved when operating under optimal conditions. Prior addition of sodium dithionite was required to avoid reoxidation problems arising from dissolved oxygen. Flocculation-sedimentation and sand filtration have been studied for sludge separation.

  18. Synthesis of high magnetization Fe and FeCo nanoparticles by high temperature chemical reduction

    SciTech Connect

    Kandapallil, B; Colborn, RE; Bonitatibus, PJ; Johnson, F

    2015-03-15

    Fe and FeCo ferromagnetic nanoparticles in the 5-10 nm size regimes featuring high magnetization were synthesized using a modified chemical reduction method. The structure and morphology of these nanoparticles were confirmed by XRD and TOM analysis. These small, monodisperse and phase pure nanoparticles exhibited magnetic saturation of 210 emu/g (Fe) and 220 emu/g (Fe+Co) for Fe and FeCo nanoparticles respectively. The magnetization was found to be dependent on the temperature at which the reducing agent was introduced. (C) 2014 Elsevier B.V. All rights reserved,

  19. IF-WS{sub 2} nanoparticles size design and synthesis via chemical reduction

    SciTech Connect

    Ghoreishi, S.M.; Meshkat, S.S.; Dadkhah, A.A.

    2010-05-15

    An innovative synthesis of inorganic fullerene-like disulfide tungsten (IF-WS{sub 2}) nanoparticles was developed using a chemical reduction reaction in a horizontal quartz reactor. In this process, first tungsten trisulfide (WS{sub 3}) was formed via a chemical reaction of tetra thiotungstate ammonium ((NH{sub 4}){sub 2}WS{sub 4}), polyethylene glycol (PEG), and hydrochloric acid (HCl) at ambient temperature and pressure. Subsequently, WS{sub 3} was reacted with hydrogen (H{sub 2}) at high temperature (1173-1373 K) in a quartz tube. The produced WS{sub 2} nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX), and transmission electron microscopy (TEM). The characterization results indicated that the high-purity (100%) IF-WS{sub 2} nanoparticles were produced. Moreover, addition of surfactant (PEG) and higher operating temperature (1173-1373 K) decreased the particles agglomeration, and consequently led to the reduction of average diameter of WS{sub 2} particles in the range of 50-78 nm. The developed method is simple, environmentally compatible, and cost-effective in contrast to the conventional techniques.

  20. Reduction of chemical oxygen demand of industrial wastes using subcritical water oxidation

    SciTech Connect

    Lin, J.C.; Chang, C.J. )

    1992-10-01

    If wastes have strong toxicity, high organic content, and a deep hue, they are difficult to handle in the waste disposal. It is very practical that waste of this kind is treated by Subcritical Water Oxidation (SWO). In our work, caprolactum (CPL) waste, purged from a petrochemical plant, and dyeing waste, purged from a textile plant, were individually treated by a semi-batch SWO process. Within a one-hour treatment, Chemical Oxygen Demand (COD) reduction reached 89% for CPL waste (6.90 MPa, 260[degree]C) and 95% for dyeing waste (6.90 MPa, 240[degree]C). There is also a great improvement in hue, especially for the dyeing waste. When CPL wastewater was treated by the SWO process using a chromium metal powder as a catalyst, COD reduction improved further under the same operating conditions. A kinetic model was used to illustrate the oxidation mechanism and the effectiveness of the catalyst. The oxygen concentration in the effluent showed that oxygen consumption corresponded to COD reduction. With the monitoring of concentrations of total soluble chromium in the effluent, a suitable reaction period could be found in order to meet the standard of the Environmental Protection Agency (EPA). 12 refs., 11 figs., 2 tabs.

  1. Reduction kinetics of iron-based oxygen carriers using methane for chemical-looping combustion

    NASA Astrophysics Data System (ADS)

    Luo, Ming; Wang, Shuzhong; Wang, Longfei; Lv, Mingming

    2014-12-01

    The performance of three iron-based oxygen carriers (pure Fe2O3, synthetic Fe2O3/MgAl2O4 and iron ore) in reduction process using methane as fuel is investigated in thermo-gravimetric analyzer (TGA). The reaction rate and mechanism between three oxygen carriers and methane are investigated. On the basis of reactivity in reduction process, it may be concluded that Fe2O3/MgAl2O4 has the best reactivity with methane. The reaction rate constant is found to be in the following order: Fe2O3/MgAl2O4 > pure Fe2O3 > iron ore and the activation energy varies between 49 and 184 kJ mol-1. Reduction reactions for the pure Fe2O3 and synthetic Fe2O3/MgAl2O4 are well represented by the reaction controlling mechanism, and for the iron ore the phase-boundary controlled (contracting cylinder) model dominates. The particles of iron ore and synthetic Fe2O3/MgAl2O4 have better stability than that of pure Fe2O3 when the reaction temperature is limited to lower than 1223 K. These preliminary results suggest that iron-based mixed oxygen carrier particles are potential to be used in methane chemical looping process, but the reactivity of the iron ore needs to be increased.

  2. Visible light Cr(VI) reduction and organic chemical oxidation by TiO2 photocatalysis.

    PubMed

    Sun, Bo; Reddy, Ettireddy P; Smirniotis, Panagiotis G

    2005-08-15

    Here we report the simultaneous Cr(VI) reduction and 4-chlorophenol (4-CP) oxidation in water under visible light (wavelength > 400 nm) using commercial Degussa P25 TiO2. This remarkable observation was attributed to a synergistic effect among TiO2, Cr(VI), and 4-CP. It is well known that TiO2 alone cannot remove either 4-CP or Cr(VI) efficiently under visible light. Moreover, the interaction between Cr(VI) and 4-CP is minimal if not negligible. However, we found that the combination of TiO2, Cr(VI), and 4-CP together can enable efficient Cr(VI) reduction and 4-CP oxidation under visible light. The specific roles of the three ingredients in the synergistic system were studied parametrically. It was found that optimal concentrations of Cr(VI) and TiO2 exist for the Cr(VI) reduction and 4-CP oxidation. Cr(VI) was compared experimentally with other metals such as Cu(ll), Fe(lll), Mn(IV), Ce(IV), and V(V). Among all these metal ions, only Cr(VI) promotes the photocatalytic oxidation of 4-CP. The amount of 4-CP removed was directly related to the initial concentration of Cr(VI). The system was also tested with four other chemicals (aniline, salicylic acid, formic acid, and diethyl phosphoramidate). We found that the same phenomenon occurred for organics containing acid and/or phenolic groups. Cr(VI) was reduced at the same time as the organic chemicals being oxidized during photoreaction under visible light. The synergistic effect was also found with pure anatase TiO2 and rutile TiO2. This study demonstrates a possible economical way for environmental cleanup under visible light. PMID:16173589

  3. In situ observation of reduction kinetics and 2D mapping of chemical state for heterogeneous reduction in iron-ore sinters

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Murao, R.; Ohta, N.; Noami, K.; Uemura, Y.; Niwa, Y.; Kimijima, K.; Takeichi, Y.; Nitani, H.

    2016-05-01

    Iron-ore sinters constitute the major component of the iron-bearing burden in blast furnaces, and the mechanism of their reduction is one of the key processes in iron making. The heterogeneous reduction of sintered oxides was investigated by the combination of X-ray fluorescence and absorption fine structure, X-ray diffraction, and computed tomography. Two - dimensional mapping of the chemical states (CSs) was performed. The iron CSs FeIII, FeII, and Fe0 exhibited a heterogeneous distribution in a reduced sinter. The reduction started near micro pores, at iron-oxide grains rather than calcium-ferrite ones. The heterogeneous reduction among grains in a sinter may cause the formation of micro cracks. These results provide fundamental insights into heterogeneous reduction schemes for iron-ore sinters.

  4. Reduction of VOCs during pressing of OSB with the use of chemical additives

    SciTech Connect

    Williams, L.S.; McGinnis, G.D.; Kleinheinz, G.T.; Niemi, B.A.; Flicker, T.M.

    1999-07-01

    As air pollution regulations continue to become increasingly stringent, it is critical for the wood composite industry to develop more efficient and economical methods for handling air pollutant emissions. Technologies currently being used for end of pipeline control are often expensive to install and operate; therefore, more cost-effective methods of reduction are necessary. This project was undertaken to determine the feasibility of using various chemical compounds during pressing or drying of wood particles to minimize/reduce volatile organic compound (VOC) emissions from wood composite plants. This study was designed specifically to develop chemical treatment systems, which would reduce VOCs in air emitted from presses and dryers during the oriented strandboard (OSB) manufacturing process. A series of acids, bases, oxidizing agents and nucleophiles were evaluated in this study. The initial model waste stream consisted of furfural and a series of mono-terpenes. The first year results indicated that several of the chemicals did destroy the VOCs; in some cases destruction was observed as high as 75%. The first year of this study was conducted in the laboratory, while the second and third years will combine laboratory studies and OSB plant studies.

  5. Reduction, partial evaporation, and spattering - Possible chemical and physical processes in fluid drop chondrule formation

    NASA Technical Reports Server (NTRS)

    King, E. A.

    1983-01-01

    The major chemical differences between fluid drop chondrules and their probable parent materials may have resulted from the loss of volatiles such as S, H2O, Fe, and volatile siderophile elements by partial evaporation during the chondrule-forming process. Vertical access solar furnace experiments in vacuum and hydrogen have demonstrated such chemical fractionation trends using standard rock samples. The formation of immiscible iron droplets and spherules by in situ reduction of iron from silicate melt and the subsequent evaporation of the iron have been observed directly. During the time that the main sample bead is molten, many small spatter spherules are thrown off the main bead, thereby producing many additional chondrule-like melt spherules that cool rapidly and generate a population of spherules with size frequency distribution characteristics that closely approximate some populations of fluid drop chondrules in chondrites. It is possible that spatter-produced fluid drop chondrules dominate the meteoritic fluid drop chondrule populations. Such meteoritic chondrule populations should be chemically related by various relative amounts of iron and other volatile loss by vapor fractionation.

  6. Chemical and biological reduction of the radical SAM enzyme CPH4 synthase

    PubMed Central

    Bruender, Nathan A.; Young, Anthony P.; Bandarian, Vahe

    2016-01-01

    The radical S-adenosyl-l-methionine (SAM) superfamily is a large and growing group of enzymes that carry out complex radical-mediated transformations. A one-electron reduction of SAM via the +1 state of the cubane [4Fe-4S] cluster generates a 5′-deoxyadenosyl radical, which initiates turnover. The [4Fe-4S] cluster must be reduced from its resting +2 to the catalytically active +1 oxidation state by an electron. In practice, dithionite or the Escherichia coli flavodoxin (EcFldA)/ferredoxin (flavodoxin):NADP+ oxidoreductase (Fpr)/NADPH system is used. Herein, we present a systematic investigation of the reductive activation of the radical SAM enzyme CDG synthase (BsQueE) from Bacillus subtilis comparing biological and chemical reductants. These data show that either of the flavodoxin homologs encoded by the B. subtilis genome, BsYkuN or BsYkuP, as well as a series of small molecule redox mediators, support BsQueE activity. With dithionite as a reductant, activity of BsQueE is ~75-fold greater in the presence of BsYkuN and BsYkuP compared to dithionite alone. By contrast, EcFldA supports turnover to ~10-fold greater levels than dithionite alone under the same conditions. Comparing the ratio of the rate of turnover to the apparent binding constant for the flavodoxin homologs reveals 10- and 240-fold preference for BsYkuN over BsYkuP and EcFldA respectively. The differential activation of the enzyme cannot be explained by the abortive cleavage of SAM. We conclude from these observations that the differential activation of BsQueE by Fld homologs may reside in the details of the interaction between the flavodoxin and the radical SAM enzyme. PMID:25933252

  7. Chemical and Biological Reduction of the Radical SAM Enzyme CPH4 Synthase.

    PubMed

    Bruender, Nathan A; Young, Anthony P; Bandarian, Vahe

    2015-05-12

    The radical S-adenosyl-L-methionine (SAM) superfamily is a large and growing group of enzymes that conduct complex radical-mediated transformations. A one-electron reduction of SAM via the +1 state of the cubane [4Fe-4S] cluster generates a 5'-deoxyadenosyl radical, which initiates turnover. The [4Fe-4S] cluster must be reduced from its resting +2 state to the catalytically active +1 oxidation state by an electron. In practice, dithionite or the Escherichia coli flavodoxin (EcFldA)/ferredoxin (flavodoxin):NADP(+) oxidoreductase (Fpr)/NADPH system is used. Herein, we present a systematic investigation of the reductive activation of the radical SAM enzyme CDG synthase (BsQueE) from Bacillus subtilis comparing biological and chemical reductants. These data show that either of the flavodoxin homologues encoded by the B. subtilis genome, BsYkuN or BsYkuP, as well as a series of small molecule redox mediators, supports BsQueE activity. With dithionite as a reductant, the activity of BsQueE is ~75-fold greater in the presence of BsYkuN and BsYkuP compared to that in the presence of dithionite alone. By contrast, EcFldA supports turnover to ~10-fold greater levels than dithionite alone under the same conditions. Comparing the ratio of the rate of turnover to the apparent binding constant for the flavodoxin homologues reveals 10- and 240-fold preferences for BsYkuN over BsYkuP and EcFldA, respectively. The differential activation of the enzyme cannot be explained by the abortive cleavage of SAM. We conclude from these observations that the differential activation of BsQueE by Fld homologues may reside in the details of the interaction between the flavodoxin and the radical SAM enzyme. PMID:25933252

  8. Distinguishing solid bitumens formed by thermochemical sulfate reduction and thermal chemical alteration

    USGS Publications Warehouse

    Kelemen, S.R.; Walters, C.C.; Kwiatek, P.J.; Afeworki, M.; Sansone, M.; Freund, H.; Pottorf, R.J.; Machel, H.G.; Zhang, T.; Ellis, G.S.; Tang, Y.; Peters, K.E.

    2008-01-01

    Insoluble solid bitumens are organic residues that can form by the thermal chemical alteration (TCA) or thermochemical sulfate reduction (TSR) of migrated petroleum. TCA may actually encompass several low temperature processes, such as biodegradation and asphaltene precipitation, followed by thermal alteration. TSR is an abiotic redox reaction where petroleum is oxidized by sulfate. It is difficult to distinguish solid bitumens associated with TCA of petroleum from those associated with TSR when both processes occur at relatively high temperature. The focus of the present work was to characterize solid bitumen samples associated with TCA or TSR using X-ray photoelectron spectroscopy (XPS). XPS is a surface analysis conducted on either isolated or in situ (>25 ??m diameter) solid bitumen that can provide the relative abundance and chemical speciation of carbon, organic and inorganic heteroatoms (NSO). In this study, naturally occurring solid bitumens from three locations, Nisku Fm. Brazeau River area (TSR-related), LaBarge Field Madison Fm. (TSR-related), and the Alaskan Brooks range (TCA-related), are compared to organic solids generated during laboratory simulation of the TSR and TCA processes. The abundance and chemical nature of organic nitrogen and sulfur in solid bitumens can be understood in terms of the nature of (1) petroleum precursor molecules, (2) the concentration of nitrogen by way of thermal stress and (3) the mode of sulfur incorporation. TCA solid bitumens originate from polar materials that are initially rich in sulfur and nitrogen. Aromaticity and nitrogen increase as thermal stress cleaves aliphatic moieties and condensation reactions take place. Organic sulfur in TCA organic solids remains fairly constant with increasing maturation (3.5 to ???17 sulfur per 100 carbons) into aromatic structures and to the low levels of nitrogen in their hydrocarbon precursors. Hence, XPS results provide organic chemical composition information that helps to

  9. Synthesis of Cu core Ag shell nanoparticles using chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chinh Trinh, Dung; Dung Dang, Thi My; Khanh Huynh, Kim; Fribourg-Blanc, Eric; Chien Dang, Mau

    2015-01-01

    A simple chemical reduction method is used to prepare colloidal bimetallic Cu-Ag core-shell (Cu@Ag) nanoparticles. Polyvinyl pyrrolidone (PVP) was used as capping agent, and ascorbic acid (C6H8O6) and sodium borohydride (NaBH4) were used as reducing agents. The obtained Cu@Ag nanoparticles were characterized by powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectrophotometry. The influence of [Ag]/[Cu] molar ratios on the formation of Ag coatings on the Cu particles was investigated. From the TEM results we found that the ratio [Ag+]/[Cu2+] = 0.2 is the best for the stability of Cu@Ag nanoparticles with an average size of 22 nm. It is also found out that adding ammonium hydroxide (NH4OH) makes the obtained Cu@Ag nanoparticles more stable over time when pure deionized water is used as solvent.

  10. Reduction and Uncertainty Analysis of Chemical Mechanisms Based on Local and Global Sensitivities

    NASA Astrophysics Data System (ADS)

    Esposito, Gaetano

    Numerical simulations of critical reacting flow phenomena in hypersonic propulsion devices require accurate representation of finite-rate chemical kinetics. The chemical kinetic models available for hydrocarbon fuel combustion are rather large, involving hundreds of species and thousands of reactions. As a consequence, they cannot be used in multi-dimensional computational fluid dynamic calculations in the foreseeable future due to the prohibitive computational cost. In addition to the computational difficulties, it is also known that some fundamental chemical kinetic parameters of detailed models have significant level of uncertainty due to limited experimental data available and to poor understanding of interactions among kinetic parameters. In the present investigation, local and global sensitivity analysis techniques are employed to develop a systematic approach of reducing and analyzing detailed chemical kinetic models. Unlike previous studies in which skeletal model reduction was based on the separate analysis of simple cases, in this work a novel strategy based on Principal Component Analysis of local sensitivity values is presented. This new approach is capable of simultaneously taking into account all the relevant canonical combustion configurations over different composition, temperature and pressure conditions. Moreover, the procedure developed in this work represents the first documented inclusion of non-premixed extinction phenomena, which is of great relevance in hypersonic combustors, in an automated reduction algorithm. The application of the skeletal reduction to a detailed kinetic model consisting of 111 species in 784 reactions is demonstrated. The resulting reduced skeletal model of 37--38 species showed that the global ignition/propagation/extinction phenomena of ethylene-air mixtures can be predicted within an accuracy of 2% of the full detailed model. The problems of both understanding non-linear interactions between kinetic parameters and

  11. Chemical degradation and toxicity reduction of 4-chlorophenol in different matrices by gamma-ray treatment

    NASA Astrophysics Data System (ADS)

    Kang, Sung-Wook; Shim, Seung-Bo; Park, Young-Kwon; Jung, Jinho

    2011-03-01

    Gamma-ray treatment of 4-chlorophenol (4-CP) in different matrices was studied in terms of both chemical degradation and toxicity reduction. Degradation of 4-CP in a complex effluent matrix was less efficient than that in ultrapure water. This is most likely due to the consumption of reactive radicals by matrix components, such as dissolved organic matter in effluents. The matrix effect caused much more profound changes in toxicity. Gamma-ray treatment of 4-CP in ultrapure water abruptly increased acute toxicity toward Daphnia magna while slightly decreased toxicity of 4-CP in effluent. In the presence of ZrO 2 catalyst, degradation of 4-CP as well as toxicity reduction was substantially improved mostly by adsorption of 4-CP onto the nanoparticles. It was found that benzoquinone, hydroquinone and 4-chlorocatechol were generated for ultrapure water sample while only 4-chlorocatechol was formed for effluent samples by gamma-ray treatment. As determined in this work, EC 50 values of benzoquinone (0.46 μM), hydroquinone (0.61 μM) and chlorocatechol (8.87 μM) were much lower than those of 4-CP (31.50 μM), explaining different toxicity changes of 4-CP in different matrices by gamma-ray treatment. The observed toxicity of gamma-ray treated 4-CP was well correlated with the one calculated from individual toxicity based on EC 50 value.

  12. Assembly of FePt nanoparticles by chemical reduction within nanochannels

    NASA Astrophysics Data System (ADS)

    Sui, Yucheng; Sellmyer, David J.

    2003-03-01

    A novel way of assembling FePt nanoparticles into long nanochannels of porous alumina templates is reported. The templates consist of closely packed parallel nanochannels with diameter of about 20 nm and length of 50 um. An aqueous solution of hexachloroplatinate acid and iron acetate with 1:1 molar ratio was inserted into the pores. After drying and surface cleaning, the impregnated templates were heated in flowing hydrogen at different temperatures. Through this hydrogen reduction process, FePt L10 nanoparticles with average particle size of about 15 nm were grown in the nanochannels when treated at 900oC. As the chemical reduction of Pt and Co takes place within the one-dimension nanochannels and the final products of the FePt nanoparticles were also confined in the channels, the largest particle sizes should be less than 20 nm, which is consist with the x-ray results. Coercivity as high as 29.6 kOe was obtained when the samples were treated in flowing hydrogen at 900oC. This work is supported by DOE, NSF-MRSEC, NRI and CMRA.

  13. In situ self-assembly of mild chemical reduction graphene for three-dimensional architectures

    NASA Astrophysics Data System (ADS)

    Chen, Wufeng; Yan, Lifeng

    2011-08-01

    Three-dimensional (3D) architectures of graphene are of interest in applications in electronics, catalysis devices, and sensors. However, it is still a challenge to fabricate macroscopic all-graphene 3D architectures under mild conditions. Here, a simple method for the preparation of 3D architectures of graphene is developed via the in situ self-assembly of graphene prepared by mild chemical reduction at 95 °C under atmospheric pressure without stirring. No chemical or physical cross-linkers or high pressures are required. The reducing agents include NaHSO3, Na2S, Vitamin C, HI, and hydroquinone. Both graphene hydrogels and aerogels can be prepared by this method, and the shapes of the 3D architectures can be controlled by changing the type of reactor. The 3D architectures of graphene have low densities, high mechanical properties, thermal stability, high electrical conductivity, and high specific capacitance, which make them candidates for potential applications in supercapacitors, hydrogen storage and as supports for catalysts.

  14. Sequential repetitive chemical reduction technique to study size-property relationships of graphene attached Ag nanoparticle

    NASA Astrophysics Data System (ADS)

    Haider, M. Salman; Badejo, Abimbola Comfort; Shao, Godlisten N.; Imran, S. M.; Abbas, Nadir; Chai, Young Gyu; Hussain, Manwar; Kim, Hee Taik

    2015-06-01

    The present study demonstrates a novel, systematic and application route synthesis approach to develop size-property relationship and control the growth of silver nanoparticles (AgNPs) embedded on reduced graphene oxide (rGO). A sequential repetitive chemical reduction technique to observe the growth of silver nanoparticles (AgNPs) attached to rGO, was performed on a single solution of graphene oxide (GO) and silver nitrate solution (7 runs, R1-R7) in order to manipulate the growth and size of the AgNPs. The physical-chemical properties of the samples were examined by RAMAN, XPS, XRD, SEM-EDAX, and HRTEM analyses. It was confirmed that AgNPs with diameter varying from 4 nm in first run (R1) to 50 nm in seventh run (R7) can be obtained using this technique. A major correlation between particle size and activities was also observed. Antibacterial activities of the samples were carried out to investigate the disinfection performance of the samples on the Gram negative bacteria (Escherichia coli). It was suggested that the sample obtained in the third run (R3) exhibited the highest antibacterial activity as compared to other samples, toward disinfection of bacteria due to its superior properties. This study provides a unique and novel application route to synthesize and control size of AgNPs embedded on graphene for various applications.

  15. Chemical noise reduction via mass spectrometry and ion/ion charge inversion: amino acids.

    PubMed

    Hassell, Kerry M; LeBlanc, Yves C; McLuckey, Scott A

    2011-05-01

    Charge inversion ion/ion reactions can provide a significant reduction in chemical noise associated with mass spectra derived from complex mixtures for species composed of both acidic and basic sites, provided the ions derived from the matrix largely undergo neutralization. Amino acids constitute an important class of amphoteric compounds that undergo relatively efficient charge inversion. Precipitated plasma constitutes a relatively complex biological matrix that yields detectable signals at essentially every mass-to-charge value over a wide range. This chemical noise can be dramatically reduced using multiply charged reagent ions that can invert the charge of species amenable to the transfer of multiple charges upon a single interaction and by detecting product ions of opposite polarity. The principle is illustrated here with amino acids present in precipitated plasma subjected to ionization in the positive mode, reaction with anions derived from negative nanoelectrospray ionization of poly (amido amine) dendrimer generation 3.5, and mass analysis in the negative ion mode. PMID:21456599

  16. Implications of Arctic Sea Ice Reduction on Arctic Tropospheric Chemical Change (Invited)

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.

    2009-12-01

    We examine the drastic reduction of Arctic sea ice in this decade and discuss the potential implications on bromine, ozone, and mercury change in the Arctic troposphere. We are witnessing extraordinary change in the Arctic sea ice cover. In the context of a half century change, perennial sea ice, the class of thicker and older ice important to the stability of Arctic sea ice, has been declining precipitously in this decade. Perennial ice extent declines at rate of 0.5 million km2 per decade in the 1970s-1990s while there is no discernable trend in the 1950s-1960s. Abruptly, the rate of decrease has tripled to 1.5 million km2 per decade in the 2000s. A record was set in the reduction of Arctic perennial ice extent in winter 2008. By 1 March 2008, perennial ice extent was reduced by one million km2 compared to that at the same time in 2007, which continued the precipitous declining trend observed in this decade. While the record low of total ice extent in summer 2007 is a historical mark of sea ice loss, the distribution and extent of different sea ice classes in spring (March-May) are critical information to understand the implications of sea ice reduction on photochemical processes, such as bromine explosions, ozone depletion episodes (ODEs), gaseous elementary mercury depletion episodes (MDEs), which occur at the time of polar sunrise. In this regard, the drastic reduction of perennial ice means that the Arctic becomes dominated by seasonal ice consisting of thinner ice, more leads, polynyas, frost flowers, and salty snow (due to seawater spray from open water), representing the overall saltier condition of the Arctic sea ice cover conducive to ice-mediated chemical processes leading to Arctic tropospheric ODEs and MDEs. To date (2009), the extent of perennial sea ice remains low and the extent of the thinner and saltier seasonal ice continues to dominate the Arctic sea ice cover. The shift of the state of Arctic sea ice cover to the dominance domain of seasonal

  17. Reduction of hexavalent chromium by fasted and fed human gastric fluid. I. Chemical reduction and mitigation of mutagenicity.

    PubMed

    De Flora, Silvio; Camoirano, Anna; Micale, Rosanna T; La Maestra, Sebastiano; Savarino, Vincenzo; Zentilin, Patrizia; Marabotto, Elisa; Suh, Mina; Proctor, Deborah M

    2016-09-01

    Evaluation of the reducing capacity of human gastric fluid from healthy individuals, under fasted and fed conditions, is critical for assessing the cancer hazard posed by ingested hexavalent chromium [Cr(VI)] and for developing quantitative physiologically-based pharmacokinetic models used in risk assessment. In the present study, the patterns of Cr(VI) reduction were evaluated in 16 paired pre- and post-meal gastric fluid samples collected from 8 healthy volunteers. Human gastric fluid was effective both in reducing Cr(VI), as measured by using the s-diphenylcarbazide colorimetric method, and in attenuating mutagenicity in the Ames test. The mean (±SE) Cr(VI)-reducing ability of post-meal samples (20.4±2.6μgCr(VI)/mL gastric fluid) was significantly higher than that of pre-meal samples (10.2±2.3μgCr(VI)/mL gastric fluid). When using the mutagenicity assay, the decrease of mutagenicity produced by pre-meal and post-meal samples corresponded to reduction of 13.3±1.9 and 25.6±2.8μgCr(VI)/mL gastric fluid, respectively. These data are comparable to parallel results conducted by using speciated isotope dilution mass spectrometry. Cr(VI) reduction was rapid, with >70% of total reduction occurring within 1min and 98% of reduction is achieved within 30min with post-meal gastric fluid at pH2.0. pH dependence was observed with decreasing Cr(VI) reducing capacity at higher pH. Attenuation of the mutagenic response is consistent with the lack of DNA damage observed in the gastrointestinal tract of rodents following administration of ≤180ppm Cr(VI) for up to 90days in drinking water. Quantifying Cr(VI) reduction kinetics in the human gastrointestinal tract is necessary for assessing the potential hazards posed by Cr(VI) in drinking water. PMID:27404458

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

    PubMed

    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. PMID:27434736

  19. Synthesis and optical properties of copper nanoparticles prepared by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Dung Dang, Thi My; Tuyet Thu Le, Thi; Fribourg-Blanc, Eric; Chien Dang, Mau

    2011-03-01

    Copper nanoparticles, due to their interesting properties, low cost preparation and many potential applications in catalysis, cooling fluid or conductive inks, have attracted a lot of interest in recent years. In this study, copper nanoparticles were synthesized through the chemical reduction of copper sulfate with sodium borohydride in water without inert gas protection. In our synthesis route, ascorbic acid (natural vitamin C) was employed as a protective agent to prevent the nascent Cu nanoparticles from oxidation during the synthesis process and in storage. Polyethylene glycol (PEG) was added and worked both as a size controller and as a capping agent. Cu nanoparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy to investigate the coordination between Cu nanoparticles and PEG. Transmission electron microscopy (TEM) and UV–vis spectrometry contributed to the analysis of size and optical properties of the nanoparticles, respectively. The average crystal sizes of the particles at room temperature were less than 10 nm. It was observed that the surface plasmon resonance phenomenon can be controlled during synthesis by varying the reaction time, pH, and relative ratio of copper sulfate to the surfactant. The surface plasmon resonance peak shifts from 561 to 572 nm, while the apparent color changes from red to black, which is partly related to the change in particle size. Upon oxidation, the color of the solution changes from red to violet and ultimately a blue solution appears.

  20. Chemical evaluation of odor reduction by soil injection of animal manure.

    PubMed

    Feilberg Tavs Nyord, Anders; Hansen, Martin Nørregaard; Lindholst, Sabine

    2011-01-01

    Field application of animal manure is a major cause of odor nuisance in the local environment. Therefore, there is a need for methods for measuring the effect of technologies for reducing odor after manure application. In this work, chemical methods were used to identify key odorants from field application of pig manure based on experiments with surface application by trailing hoses and soil injection. Results from three consecutive years of field trials with full-scale equipment are reported. Methods applied were: membrane inlet mass spectrometry (MIMS), proton-transfer-reaction mass spectrometry (PTR-MS), gold-film hydrogen sulfide (H₂S) detection, all performed on site, and thermal desorption gas chromatography with mass spectrometry (TD-GC/MS) based on laboratory analyses of field samples. Samples were collected from a static flux chamber often used for obtaining samples for dynamic olfactometry. While all methods were capable of detecting relevant odorants, PTR-MS gave the most comprehensive results. Based on odor threshold values, 4-methylphenol, H₂S, and methanethiol are suggested as key odorants. Significant odorant reductions by soil injection were consistently observed in all trials. The flux chamber technique was demonstrated to be associated with critical errors due to compound instabilities in the chamber. This was most apparent for H₂S, on a time scale of a few minutes, and on a longer time scale for methanethiol. PMID:21869529

  1. Occurrence of two-photon absorption saturation in Ag nanocolloids, prepared by chemical reduction method

    NASA Astrophysics Data System (ADS)

    Rahulan, K. Mani; Ganesan, S.; Aruna, P.

    2012-09-01

    Silver nanocolloids stabilized with polyvinyl pyrrolidone (PVP) have been prepared from (AgNO3) by a chemical reduction method, involving the intermediate preparation of (Ag2O) colloidal dispersions in the presence of sodium dodecycle sulfate as a surfactant and formaldehyde as reducing agent. The molecules of PVP play an important role in growth and agglomeration of silver nanocolloids. The formation of Ag nanocolloids was studied from the UV-vis absorption characteristics. An energy dispersive X-ray (EDX) spectrum and X-ray diffraction peak of the nanoparticles showed the highly crystalline nature of silver structure. The particle size was found to be 40 nm as analyzed from Field emission scanning electron microscopy (FESEM). The nonlinear optical and optical limiting properties of these nanoparticle dispersions were studied by using the Z-scan technique at 532 nm. Experimental results show that the Ag nanocolloids possess strong optical limiting effect, originated from absorption saturation followed by two-photon mechanism. The data show that Ag nanocolloids have great potential for nonlinear optical devices.

  2. Magnetite Fe3O4 nanoparticles synthesis by wet chemical reduction and their characterization

    NASA Astrophysics Data System (ADS)

    Chaki, S. H.; Malek, Tasmira J.; Chaudhary, M. D.; Tailor, J. P.; Deshpande, M. P.

    2015-09-01

    The authors report the synthesis of Fe3O4 nanoparticles by wet chemical reduction technique at ambient temperature and its characterization. Ferric chloride hexa-hydrate (FeCl3 · 6H2O) and sodium boro-hydrate (NaBH4) were used for synthesis of Fe3O4 nanoparticles at ambient temperature. The elemental composition of the synthesized Fe3O4 nanoparticles was determined by energy dispersive analysis of x-rays technique. The x-ray diffraction (XRD) technique was used for structural characterization of the nanoparticles. The crystallite size of the nanoparticles was determined using XRD data employing Scherrer’s formula and Hall-Williamson’s plot. Surface morphology of as-synthesized Fe3O4 nanoparticles was studied by scanning electron microscopy. High resolution transmission electron microscopy analysis of the as-synthesized Fe3O4 nanoparticles showed narrow range of particles size distribution. The optical absorption of the synthesized Fe3O4 nanoparticles was studied by UV-vis-NIR spectroscopy. The as-synthesized nanoparticles were analyzed by Fourier transform infrared spectroscopy technique for absorption band study in the infrared region. The magnetic properties of the as-synthesized Fe3O4 nanoparticles were evaluated by vibrating sample magnetometer technique. The thermal stability of the as-synthesized Fe3O4 nanoparticles was studied by thermogravimetric technique. The obtained results are elaborated and discussed in details in this paper.

  3. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals

    SciTech Connect

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. ); Jacobsen, P.S. )

    1991-09-01

    This report summarizes the washability and comprehensive characterization of 975 raw coal channel samples collected from the Eastern, Central, and Western Regions (including Alaska) of the United States. All of this information is sorted in the Pittsburgh Energy Technology Center (PETC) Coal Technology Data Base. Individual reports for each region were completed previously as Volumes 1, 2, and 3 and included the detailed data for each of the 975 samples. This report is a summation of the results of those three reports on a state- and region-wide basis only, and does not include the data for individual samples, but only includes the composite data for each state and region. Graphical summations are presented by state, section or rank, and region showing the effects of crushing on impurity reductions and showing the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. The statistical evaluations in the Appendices present the composited washability data of 1.30, 1.40, and 1.60 specific gravities of separation, the selected chemical and physical properties, and the composited washability data interpolated at various levels of Btu recovery. 13 refs., 93 figs., 9 tabs.

  4. Deposition of silver nanoparticles on multiwalled carbon nanotubes by chemical reduction process and their antimicrobial effects

    NASA Astrophysics Data System (ADS)

    Haider, Adawiya J.; Thamir, Amin D.; Ahmed, Duha S.; Mohammad, M. R.

    2016-07-01

    In this paper, the functionalization of raw-MWCNTs involves oxidation reaction using concentrated acid mixture of HNO3:H2SO4 (1:3), via ultrasonic bath (170 W, 50 kHz) to obtain functional groups. Then Ag nanoparticles are decorated the outside over the surface of functionalized MWCNTs using a chemical reduction process resulting in the formation of(Ag/ MWCNTs) hybrid material. The results showed that outer diameter functionalized F-MWCNTs andAg nanoparticles size was about (11-80) nm and (10 to 25) nm, respectively using TEM and HRTEM. The crystallographic structure of MWCNTs using X-ray diffraction (XRD) analysis proved diffraction peaks at 38.1°, 44.3°, 64.7° and 77.4° degrees namely, Ag (111), Ag (200), Ag (220), and Ag (311) of the face-centered cubic lattice of Ag, respectively, excepting the peak at 2θ =25.6°, which correspond to the (0 0 2) reflection of the MWNTs are corresponding to Ag/MWNTs. The antimicrobial activities of Ag/MWCNTs hybrid using plate count method showed that decreasing a large number of bacteria colonies of E. coli and S. aureu with increasing the hybrid concentrations after incubation for 24h in shaker incubator with percentage of inhibition approaching 100%.

  5. SITE PROGRAM DEMONSTRATION ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS, BAY CITY, MICHIGAN TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    The SITE Program funded a field demonstration to evaluate the Eco Logic Gas-Phase Chemical Reduction Process developed by ELI Eco Logic International Inc. (ELI), Ontario, Canada. The Demonstration took place at the Middleground Landfill in Bay City, Michigan using landfill wa...

  6. TRACI THE TOOL FOR THE REDUCTION AND ASSESSMENT OF CHEMICAL AND OTHER ENVIRONMENTAL IMPACTS - VERSION 2 CHANGES

    EPA Science Inventory

    The Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) was developed to allow the quantification of environmental impacts for a variety of impact categories which are necessary for a comprehensive impact assessment. See Figure 1. TRACI is c...

  7. TRACI 2.0 - The Tool for the Reduction and Assessment of Chemical and other environmental Impacts

    EPA Science Inventory

    TRACI 2.0, the Tool for the Reduction and Assessment of Chemical and other environmental Impacts 2.0, has been expanded and developed for sustainability metrics, life cycle impact assessment, industrial ecology, and process design impact assessment for developing increasingly sus...

  8. Estimating the One-Electron Reduction Potential for Vanadium (V) by Chemical Techniques: An Experiment for General Chemistry.

    ERIC Educational Resources Information Center

    Wentworth, R. A. D.

    1985-01-01

    Describes an experiment which requires only qualitative observations, is suitable for general chemistry students, prompts an understanding of thermodynamic spontaneity, gives chemical meaning to electrode potentials, requires non-electrochemical equipment, and allows estimates of the standard potential for the reduction of Vanadium (V) to V (IV).…

  9. The effect of chemical treatment on reduction of aflatoxins and ochratoxin A in black and white pepper during washing.

    PubMed

    Jalili, M; Jinap, S; Son, R

    2011-04-01

    The effect of 18 different chemicals, which included acidic compounds (sulfuric acid, chloridric acid, phosphoric acid, benzoic acid, citric acid, acetic acid), alkaline compounds (ammonia, sodium bicarbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide), salts (acetate ammonium, sodium bisulfite, sodium hydrosulfite, sodium chloride, sodium sulfate) and oxidising agents (hydrogen peroxide, sodium hypochlorite), on the reduction of aflatoxins B(1), B(2), G(1) and G(2) and ochratoxin A (OTA) was investigated in black and white pepper. OTA and aflatoxins were determined using HPLC after immunoaffinity column clean-up. Almost all of the applied chemicals showed a significant degree of reduction on mycotoxins (p < 0.05). The lowest and highest reduction of aflatoxin B(1), which is the most dangerous aflatoxin, was 20.5% ± 2.7% using benzoic acid and 54.5% ± 2.7% using sodium hydroxide. There was no significant difference between black and white peppers (p < 0.05). PMID:21416415

  10. Photochemical modeling in California with two chemical mechanisms: model intercomparison and response to emission reductions.

    PubMed

    Cai, Chenxia; Kelly, James T; Avise, Jeremy C; Kaduwela, Ajith P; Stockwell, William R

    2011-05-01

    An updated version of the Statewide Air Pollution Research Center (SAPRC) chemical mechanism (SAPRC07C) was implemented into the Community Multiscale Air Quality (CMAQ) version 4.6. CMAQ simulations using SAPRC07C and the previously released version, SAPRC99, were performed and compared for an episode during July-August, 2000. Ozone (O3) predictions of the SAPRC07C simulation are generally lower than those of the SAPRC99 simulation in the key areas of central and southern California, especially in areas where modeled concentrations are greater than the federal 8-hr O3 standard of 75 parts per billion (ppb) and/or when the volatile organic compound (VOC)/nitrogen oxides (NOx) ratio is less than 13. The relative changes of ozone production efficiency (OPE) against the VOC/NOx ratio at 46 sites indicate that the OPE is reduced in SAPRC07C compared with SAPRC99 at most sites by as much as approximately 22%. The SAPRC99 and SAPRC07C mechanisms respond similarly to 20% reductions in anthropogenic VOC emissions. The response of the mechanisms to 20% NOx emissions reductions can be grouped into three cases. In case 1, in which both mechanisms show a decrease in daily maximum 8-hr O3 concentration with decreasing NOx emissions, the O3 decrease in SAPRC07C is smaller. In case 2, in which both mechanisms show an increase in O3 with decreasing NOx emissions, the O3 increase is larger in SAPRC07C. In case 3, SAPRC07C simulates an increase in O3 in response to reduced NOx emissions whereas SAPRC99 simulates a decrease in O3 for the same region. As a result, the areas where NOx controls would be disbeneficial are spatially expanded in SAPRC07C. Although the results presented here are valuable for understanding differences in predictions and model response for SAPRC99 and SAPRC07C, the study did not evaluate the impact of mechanism differences in the context of the U.S. Environmental Protection Agency's guidance for using numerical models in demonstrating air quality attainment

  11. Direct chemical reduction of neptunium oxide to neptunium metal using calcium and calcium chloride

    NASA Astrophysics Data System (ADS)

    Squires, Leah N.; Lessing, Paul

    2016-04-01

    A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can be easily removed upon cooling. The direct reduction technique consistently produces high purity (98%-99% pure) neptunium metal.

  12. Bacterial Disproportionation of Elemental Sulfur Coupled to Chemical Reduction of Iron or Manganese

    PubMed Central

    Thamdrup, Bo; Finster, Kai; Hansen, Jens Würgler; Bak, Friedhelm

    1993-01-01

    A new chemolithotrophic bacterial metabolism was discovered in anaerobic marine enrichment cultures. Cultures in defined medium with elemental sulfur (S0) and amorphous ferric hydroxide (FeOOH) as sole substrates showed intense formation of sulfate. Furthermore, precipitation of ferrous sulfide and pyrite was observed. The transformations were accompanied by growth of slightly curved, rod-shaped bacteria. The quantification of the products revealed that S0 was microbially disproportionated to sulfate and sulfide, as follows: 4S0 + 4H2O → SO42- + 3H2S + 2H+. Subsequent chemical reactions between the formed sulfide and the added FeOOH led to the observed precipitation of iron sulfides. Sulfate and iron sulfides were also produced when FeOOH was replaced by FeCO3. Further enrichment with manganese oxide, MnO2, instead of FeOOH yielded stable cultures which formed sulfate during concomitant reduction of MnO2 to Mn2+. Growth of small rod-shaped bacteria was observed. When incubated without MnO2, the culture did not grow but produced small amounts of SO42- and H2S at a ratio of 1:3, indicating again a disproportionation of S0. The observed microbial disproportionation of S0 only proceeds significantly in the presence of sulfide-scavenging agents such as iron and manganese compounds. The population density of bacteria capable of S0 disproportionation in the presence of FeOOH or MnO2 was high, > 104 cm-3 in coastal sediments. The metabolism offers an explanation for recent observations of anaerobic sulfide oxidation to sulfate in anoxic sediments. PMID:16348835

  13. Plasma chemical reduction of model corrosion brass layers prepared in soil

    NASA Astrophysics Data System (ADS)

    Radkova, Lucie; Mikova, Petra; Prikryl, Radek; Krcma, Frantisek

    2016-08-01

    The brass plates of (50 × 10 × 1) mm3 were prepared with model corrosion layer because the real archaeological artifacts could be damaged during the method optimization. Samples corroded naturally more than 2 years in the soil. Excavated samples were treated in the low pressure (150 Pa) quartz glass plasma reactor (90 cm long and 9.5 cm in diameter) which was surrounded by two external copper electrodes supplied by radio-frequency generator (13.56 MHz). The experiments were carried out in a hydrogen-argon gas mixture at mass flows of 30 sccm for hydrogen and 20 sccm for argon for 90 min. The plasma power was 100, 200, 300 and 400 W in continuous and pulsed mode. Maximum sample temperature was set at 120 °C. The whole process was monitored by optical emission spectroscopy and the obtained data were used to calculate the relative intensity of OH radicals and rotational temperature. The results showed that the higher power had the greater maximum intensity of the OH radicals and rapidly degraded the corrosion layer. Corrosion layer was not completely removed during the reduction, but due to the reactions which occur in the plasma corrosion layer became brittle and after plasma chemical treatment can be removed easily. Finally, the SEM-EDX analysis of the surface composition confirmed removal of chlorine and oxygen from the corrosion products layers. Contribution to the topical issue "6th Central European Symposium on Plasma Chemistry (CESPC-6)", edited by Nicolas Gherardi, Ester Marotta and Cristina Paradisi

  14. Effect of five cycle rapid freeze-thaw treatment in conjunction with various chemicals for the reduction of Salmonella typhimurium.

    PubMed

    Olson, V M; Swaminathan, B; Pratt, D E; Stadelman, W J

    1981-08-01

    A five cycle rapid freeze-rapid thaw process was used in conjunction with chemicals to reduce numbers of Salmonella typhimurium cells on poultry meat. The second portion of chicken wings consisting of ulna and radius with attached skin and muscle was inoculated with 400 to 900 colony forming units (CFU/g) of a nalidixic acid resistant strain of S. typhimurium. Chemicals used were 20 ppm chlorine, 5% potassium sorbate, 5% lactic acid, and 5% calcium propionate. The wings were either sprayed with or dipped into all chemicals before the freeze-thaw process. Wings were also chemically treated and not subjected to the freeze-thaw process. Numbers of S. typhimurium were determined by the most probable number procedure. The relative effectiveness of combinations of chemicals and the freeze-thaw process was compared to a control with the following percentage reductions of numbers of S. typhimurium cells: lactic acid, 98%; calcium propionate, 96%; potassium sorbate, 96%; chlorine, 95%; and freeze-thaw process without chemicals, 95%. There were no statistically significant differences among the treatments. In pilot plant study simulating commercial conditions, a carbon dioxide freezer was used for the rapid freeze and a microwave oven was used for the rapid thaw. Treatment of wings with 5% lactic acid plus freeze-thaw process resulted in statistically significant fewer numbers of S. typhimurium cells when compared to the freeze-thaw process without chemical treatment or to wings chemically treated without the freeze-thaw process. PMID:7322982

  15. Recovery of Cu(II) by chemical reduction using sodium dithionite: effect of pH and ligands.

    PubMed

    Chou, Yi-Hsuan; Yu, Jui-Hsuan; Liang, Yang-Min; Wang, Pin-Jan; Li, Chi-Wang; Chen, Shiao-Shing

    2015-01-01

    Wastewaters containing Cu(II) and ligands are ubiquitous in various industrial sectors, and efficacy of copper removal processes, especially precipitation, is greatly compromised by ligands. Chemical reduction, being commonly employed for production of metal nanoparticles, is also effective for metal removal. Adjustment of pH and addition of ligands are important to control the particle size in metallic nanoparticle production. Exploiting the fact that ligands and metals coexist in many wastewaters, chemical reduction was employed to treat ligand-containing wastewater in this study. The experimental result shows that depending on pH, type of ligands, and copper:ligand molar ratio, copper could be removed by either the reduction or precipitation mechanism. Almost complete copper removal could be achieved by the reduction mechanism under optimal condition for solutions containing either EDTA (ethylenediaminetetraacetic acid) or citrate ligands. For solutions containing ammonia, depending on pH and Cu:ammonia molar ratio, copper was removed by both precipitation and reduction mechanisms. At pH of 9.0, formation of nano-sized particles, which readily pass through a 0.45 μm filter used for sample pretreatment before residual copper analysis, results in the lowest copper removal efficiency. Both cuprous oxide and metallic copper are identified in the solids produced, and the possible explanations are provided. PMID:26606104

  16. Synthesis of silver nanoparticles by chemical reduction at various fraction of MSA and their structure characterization

    NASA Astrophysics Data System (ADS)

    Diantoro, Markus; Fitrianingsih, Rina; Mufti, Nandang; Fuad, Abdulloh

    2014-03-01

    Nanosilver is currently one of the most common engineered nanomaterials and is used in many applications that lead to the release of silver nanoparticles and silver ions into aqueous systems. Nanosilver also possesses enhanced antimicrobial activity and bioavailability that may less environmental risk compared with other manufactured nanomaterials. Described in this research are the synthesis of silver nanoparticle produced by chemical reduction from silver nitrate (AgNO3) solution. As a reducing agent, Sodium Borohydride (NaBH4) was used and mercaptosuccinic Acid (MSA) as stabilizer to prevent the nanoparticle from aglomerating. It was also used two kinds of solvent, they are water and methanol. In typical experiment MSA was dissolve in methanol with a number of variation of molarity i.e. 0,03 M, 0,06 M, 0,12 M, 0,15 M, and the mixture was kept under vigorous stirring in an ice bath. A solution of silver nitrate of 340 mg in 6,792 ml water was added. A freshly prepared aqueous solution of sodium borohydride (756,6 mL in 100 mL of water) was added drop wisely. The solution was kept for half an hour for stirring and were allowed to settle down in methanol. The obtained samples then characterized by means of x-ray diffractometer, and scanning electron microscopy, as well as transmission electron microscopy to obtain their structures of silver nanoparticles, morphology, and sizes. It is shown that diameter of silver nanoparticle sized about 24.3 nm (Ag@MSA 0.03 M), 20.4 nm (Ag@MSA 0.06 M), 16.8 nm (Ag@MSA 0.12 M), 16.9 nm (Ag@MSA 0.15 M) which was calculated by Scherrer formula by taking the FWHM from fitting to Gaussian. The phases and lattice parameter showed that there is no significant change in its volume by increasing molarity of stabilizer. In contrast, the size of particles is decreasing.

  17. Synthesis of silver nanoparticles by chemical reduction at various fraction of MSA and their structure characterization

    SciTech Connect

    Diantoro, Markus Fitrianingsih, Rina Mufti, Nandang Fuad, Abdulloh

    2014-03-24

    Nanosilver is currently one of the most common engineered nanomaterials and is used in many applications that lead to the release of silver nanoparticles and silver ions into aqueous systems. Nanosilver also possesses enhanced antimicrobial activity and bioavailability that may less environmental risk compared with other manufactured nanomaterials. Described in this research are the synthesis of silver nanoparticle produced by chemical reduction from silver nitrate (AgNO{sub 3}) solution. As a reducing agent, Sodium Borohydride (NaBH{sub 4}) was used and mercaptosuccinic Acid (MSA) as stabilizer to prevent the nanoparticle from aglomerating. It was also used two kinds of solvent, they are water and methanol. In typical experiment MSA was dissolve in methanol with a number of variation of molarity i.e. 0,03 M, 0,06 M, 0,12 M, 0,15 M, and the mixture was kept under vigorous stirring in an ice bath. A solution of silver nitrate of 340 mg in 6,792 ml water was added. A freshly prepared aqueous solution of sodium borohydride (756,6 mL in 100 mL of water) was added drop wisely. The solution was kept for half an hour for stirring and were allowed to settle down in methanol. The obtained samples then characterized by means of x-ray diffractometer, and scanning electron microscopy, as well as transmission electron microscopy to obtain their structures of silver nanoparticles, morphology, and sizes. It is shown that diameter of silver nanoparticle sized about 24.3 nm (Ag@MSA 0.03 M), 20.4 nm (Ag@MSA 0.06 M), 16.8 nm (Ag@MSA 0.12 M), 16.9 nm (Ag@MSA 0.15 M) which was calculated by Scherrer formula by taking the FWHM from fitting to Gaussian. The phases and lattice parameter showed that there is no significant change in its volume by increasing molarity of stabilizer. In contrast, the size of particles is decreasing.

  18. Fast variance reduction for steady-state simulation and sensitivity analysis of stochastic chemical systems using shadow function estimators

    SciTech Connect

    Milias-Argeitis, Andreas Khammash, Mustafa; Lygeros, John

    2014-07-14

    We address the problem of estimating steady-state quantities associated to systems of stochastic chemical kinetics. In most cases of interest, these systems are analytically intractable, and one has to resort to computational methods to estimate stationary values of cost functions. In this work, we introduce a novel variance reduction algorithm for stochastic chemical kinetics, inspired by related methods in queueing theory, in particular the use of shadow functions. Using two numerical examples, we demonstrate the efficiency of the method for the calculation of steady-state parametric sensitivities and evaluate its performance in comparison to other estimation methods.

  19. Fast variance reduction for steady-state simulation and sensitivity analysis of stochastic chemical systems using shadow function estimators

    NASA Astrophysics Data System (ADS)

    Milias-Argeitis, Andreas; Lygeros, John; Khammash, Mustafa

    2014-07-01

    We address the problem of estimating steady-state quantities associated to systems of stochastic chemical kinetics. In most cases of interest, these systems are analytically intractable, and one has to resort to computational methods to estimate stationary values of cost functions. In this work, we introduce a novel variance reduction algorithm for stochastic chemical kinetics, inspired by related methods in queueing theory, in particular the use of shadow functions. Using two numerical examples, we demonstrate the efficiency of the method for the calculation of steady-state parametric sensitivities and evaluate its performance in comparison to other estimation methods.

  20. Continuum and Quantum-Chemical Modeling of Oxygen Reduction on the Cathode in a Solid Oxide Fuel Cell

    SciTech Connect

    Choi, Yongman; Mebane, David S.; Wang, Jeng-Han; Liu, Meilin

    2009-10-08

    Solid oxide fuel cells (SOFCs) have several advantages over other types of fuels cells such as high-energy efficiency and excellent fuel flexibility. To be economically competitive, however, new materials with extraordinary transport and catalytic properties must be developed to dramatically improve the performance while reducing the cost. This article reviews recent advancements in understanding oxygen reduction on various cathode materials using phenomenological and quantum chemical approaches in order to develop novel cathode materials with high catalytic activity toward oxygen reduction. We summarize a variety of results relevant to understanding the interactions between O2 and cathode materials at the molecular level as predicted using quantum-chemical cal-culations and probed using in situ surface vibrational spectroscopy. It is hoped that this in-depth understanding may provide useful insights into the design of novel cath-ode materials for a new generation of SOFCs.

  1. Function of a landscape lake in the reduction of biotoxicity related to trace organic chemicals from reclaimed water.

    PubMed

    Ma, Xiaoyan Y; Wang, Xiaochang C; Wang, Donghong; Ngo, Huu Hao; Zhang, Qiuya; Wang, Yongkun; Dai, Dinan

    2016-11-15

    The storage of water in a landscape lake can act as a buffer zone between reclaimed water production and reuse, but there is still uncertainty about the variation of water quality and toxic effects during the open-storage process. In this study, long-term sample collection, chemical analyses and biotoxicity assessments were conducted on reclaimed water before and after open storage in a landscape lake. The organic contents, in terms of chemical oxygen demand and total organic carbon, were found to be slightly higher in the lake water than that in the reclaimed water, but substantial reduction of the total concentration of 52 trace organic chemicals was obtained and microorganism toxicity, phytotoxicity, aquatic vertebrate toxicity and genotoxicity, were significantly weakened after open storage. Furthermore, the total risk quotient (RQTotal) decreased from 5.12 (potential ecological risk level) in the reclaimed water to 0.18 (negligible ecological risk level) in the lake water. The removal of chlorpyrifos, dichlorphos and tetracycline was identified as the main reason for biotoxicity reduction after open storage. The seminatural environment of the landscape lake would have provided a favorable condition for the decay of toxic trace organic chemicals so that the stored water turned to be safer for further reuse. PMID:27475464

  2. Reduction of Salmonella on chicken meat and chicken skin by combined or sequential application of lytic bacteriophage with chemical antimicrobials.

    PubMed

    Sukumaran, Anuraj T; Nannapaneni, Rama; Kiess, Aaron; Sharma, Chander Shekhar

    2015-08-17

    The effectiveness of recently approved Salmonella lytic bacteriophage preparation (SalmoFresh™) in reducing Salmonella in vitro and on chicken breast fillets was examined in combination with lauric arginate (LAE) or cetylpyridinium chloride (CPC). In another experiment, a sequential spray application of this bacteriophage (phage) solution on Salmonella inoculated chicken skin after a 20s dip in chemical antimicrobials (LAE, CPC, peracetic acid, or chlorine) was also examined in reducing Salmonella counts on chicken skin. The application of phage in combination with CPC or LAE reduced S. Typhimurium, S. Heidelberg, and S. Enteritidis up to 5 log units in vitro at 4 °C. On chicken breast fillets, phage in combination with CPC or LAE resulted in significant (p<0.05) reductions of Salmonella ranging from 0.5 to 1.3 log CFU/g as compared to control up to 7 days of refrigerated storage. When phage was applied sequentially with chemical antimicrobials, all the treatments resulted in significant reductions of Salmonella. The application of chlorine (30 ppm) and PAA (400 ppm) followed by phage spray (10(9)PFU/ml) resulted in highest Salmonella reductions of 1.6-1.7 and 2.2-2.5l og CFU/cm(2), respectively. In conclusion, the surface applications of phage in combination with LAE or CPC significantly reduced Salmonella counts on chicken breast fillets. However, higher reductions in Salmonella counts were achieved on chicken skin by the sequential application of chemical antimicrobials followed by phage spray. The sequential application of chlorine, PAA, and phage can provide additional hurdles to reduce Salmonella on fresh poultry carcasses or cut up parts. PMID:25950852

  3. DNAPL mass transfer and permeability reduction during in situ chemical oxidation with permanganate

    NASA Astrophysics Data System (ADS)

    Li, X. David; Schwartz, Franklin W.

    2004-03-01

    This study utilized a series of laboratory experiments to examine the DNAPL mass removal rate and permeability reduction during ISCO using permanganate (MnO4-). Results show that MnO4- oxidation is effective in removing residual DNAPL from a porous medium. The DNAPL mass removal rate correlated positively with both the hydraulic stress and the oxidant load. A power relationship model of DNAPL mass removal under ISCO was proposed. Results also show that oxidation by-products CO2(g) and Mn oxide can cause pore plugging and flow by-passing. The reduction in hydraulic conductivity due to the Mn oxide precipitates was quantified. Hydraulic conductivity reduction as high as 80% was observed for oxidizing a small quantity of TCE.

  4. Integration of polyelectrolyte enhanced ultrafiltration and chemical reduction for metal-containing wastewater treatment and metal recovery.

    PubMed

    Yu, Jui-Hsuan; Chou, Yi-Hsuan; Liang, Yang-Min; Li, Chi-Wang

    2015-01-01

    Chemical reduction was firstly employed to treat synthetic wastewaters of various compositions prepared to simulate the retentate stream of polyelectrolyte enhanced ultrafiltration (PEUF). With fixed Cu:polyethylenimine (PEI) monomer:dithionite molar ratio, increasing copper concentration increases copper removal efficiency. Under fixed Cu:dithionite molar ratio and fixed Cu concentration, increasing PEI monomer:copper molar ratio decreases copper removal efficiency. The formation of nano-sized copper particles, which readily pass through 0.45 μm filter used for sample pretreatment before residual copper analysis, might be the reason behind the decreasing copper removal efficiency observed. Particle size analysis shows that the size of copper particles, which are formed through reduction reaction, increases with decreasing pH value and increasing reaction time. As ultrafiltration is capable of removing these nano-sized particles, integration of chemical reduction and PEUF is proposed to simultaneously achieve regeneration of polyelectrolyte and recovery of copper in one process. Results show that the proposed process could achieve almost complete copper removal without being affected by reaction pH. PMID:26398024

  5. DEMONSTRATION BULLETIN: GAS-PHASE CHEMICAL REDUCTION - ECO LOGIC INTERNATIONAL, INC.

    EPA Science Inventory

    The patented Eco Logic Process employs a gas-phase reduction reaction of hydrogen with organic and chlorinated organic compounds at elevated temperatures to convert aqueous and oily hazardous contaminants into a hydrocarbon-rich gas product. After passing through a scrubber, the ...

  6. Chemical reduction of actinides probed by resonant inelastic X-ray scattering.

    PubMed

    Butorin, Sergei M; Shuh, David K; Kvashnina, Kristina O; Guo, Jinghua; Werme, Lars; Nordgren, Joseph

    2013-12-01

    The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister. PMID:24187957

  7. Applying the Philosophical Concept of Reduction to the Chemistry of Water: Implications for Chemical Education

    ERIC Educational Resources Information Center

    Erduran, Sibel

    2005-01-01

    Even though philosophical themes in science education have been advocated for several decades, little attention has been paid to how these themes can be contextualized in the teaching of a particular domain of science. The purpose of this paper is to provide an example theoretical framework for applying a philosophical theme, reduction, in…

  8. QUANTITATIVE STRUCTURE-ACTIVITY RELATIONSHIPS FOR CHEMICAL REDUCTIONS OF ORGANIC CONTAMINANTS

    EPA Science Inventory

    Sufficient kinetic data on abiotic reduction reactions involving organic contaminants are now available that quantitative structure-activity relationships (QSARs) for these reactions can be developed. Over 50 QSARs have been reported, most in just the last few years, and they ar...

  9. Highly Stable and Tunable Chemical Doping of Multilayer WS2 Field Effect Transistor: Reduction in Contact Resistance.

    PubMed

    Khalil, Hafiz M W; Khan, Muhammad Farooq; Eom, Jonghwa; Noh, Hwayong

    2015-10-28

    The development of low resistance contacts to 2D transition-metal dichalcogenides (TMDs) is still a big challenge for the future generation field effect transistors (FETs) and optoelectronic devices. Here, we report a chemical doping technique to achieve low contact resistance by keeping the intrinsic properties of few layers WS2. The transfer length method has been used to investigate the effect of chemical doping on contact resistance. After doping, the contact resistance (Rc) of multilayer (ML) WS2 has been reduced to 0.9 kΩ·μm. The significant reduction of the Rc is mainly due to the high electron doping density, thus a reduction in Schottky barrier height, which limits the device performance. The threshold voltage of ML-WS2 FETs confirms a negative shift upon the chemical doping, as further confirmed from the positions of E(1)2g and A1g peaks in Raman spectra. The n-doped samples possess a high drain current of 65 μA/μm, with an on/off ratio of 1.05 × 10(6) and a field effect mobility of 34.7 cm(2)/(V·s) at room temperature. Furthermore, the photoelectric properties of doped WS2 flakes were also measured under deep ultraviolet light. The potential of using LiF doping in contact engineering of TMDs opens new ways to improve the device performance. PMID:26434774

  10. Chemical methods for reduction of the transfer of radionuclides to farm animals in semi-natural environments.

    PubMed

    Hove, K

    1993-09-24

    The same chemicals can be used for reduction of radionuclide transfer to animals whether kept on farms or grazing in semi-natural and natural habitats. However, different techniques are required for administration of the active compounds. Dairy ruminants may be treated effectively by inclusion of chemicals in supplemental concentrates. Practical experience gained after the Chernobyl accident has shown that both clay minerals and hexacyanoferrates are effective in preventing high radiocaesium levels in animal products. Chemicals such as bentonite clays and CaCO3, used for reduction of 137Cs and 90Sr transfer respectively, must be fed in hectogram quantities and are only practical for dairy animals in semi-natural ecosystems. Salt licks and sustained release boli with hexacyanoferrates as caesium binders have been developed and used successfully after the Chernobyl accident for meat producing cattle, sheep and reindeer which graze freely for extended periods. Daily doses of 25-300 mg in sheep and 250-2000 mg in cows reduces 137Cs accumulation 2-10-fold. Binders for 90Sr have not been tested in grazing animals. Stable iodine could be provided in salt licks and indwelling rumen boli at rates required to block radioiodine uptake by the thyroid gland. Boli and salt licks are highly cost effective in reducing doses to man when compared to interdiction of food from farm animals. PMID:8248770

  11. Asymptotic expansions of slow invariant manifolds and reduction of chemical kinetics models

    NASA Astrophysics Data System (ADS)

    Sobolev, V. A.; Tropkina, E. A.

    2012-01-01

    Methods of the geometric theory of singular perturbations are used to reduce the dimensions of problems in chemical kinetics. The methods are based on using slow invariant manifolds. As a result, the original system is replaced by one on an invariant manifold, whose dimension coincides with that of the slow subsystem. Explicit and implicit representations of slow invariant manifolds are applied. The mathematical apparatus described is used to develop N.N. Semenov's fundamental ideas related to the method of quasi-stationary concentrations and is used to study particular problems in chemical kinetics.

  12. Reduction of Cr(VI) to Cr(III) in Artificially-Contaminated Soil using Chemical Reagents

    NASA Astrophysics Data System (ADS)

    Kostarelos, Konstantinos; Rao, Ennio; Reale, Daniela

    2010-05-01

    The presence of hexavalent chromium (CrVI) in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. A remediation approach that has been studied in the literature is that of reducing the hexavalent chromium to its trivalent form using a chemical reagent, namely ferrous sulfate heptahydrate (FeSO4.7H20). In this study, we compared performance of ferrous sulfate heptahydrate to sodium thiosulfate (Na2S2O3), a less costly reductant. The means of measuring the performance of the reductants is the US EPA's Toxicity Characteristic Leaching Procedure (TCLP), which states that the total chromium release from the soil must be less than 5 ppm. Because this treatment approach is pH sensitive and thus, susceptible to acid rain effects, it was studied with the intention that it be coupled with a stabilization/fixation approach so as to provide a second level of treatment; i.e., it is not intended to be the stand-alone treatment approach. In this study, the reductants were initially used to treat a contaminated, artificial soil and allowed to cure for varying time periods to determine the minimum curing time. Contaminated artificial soil were then prepared using the same percentage of white sand, kaolinite clay and potassium chromate and varying amount of water as a function of the humidity of the specimens in order to illucidate the effect of moisture on the reductant performance. Finally, the reductant (either ferrous sulfate heptahydrate or sodium thiosulfate) was added in varying doses to determine the best ratio Cr/reagent dose. Chromium release from the soil was evaluated with a modified Toxicity Characteristic Leaching Procedure (TCLP) test after allowing the samples to cure. Results indicated that chromium(VI) released from the specimens was less than 5 ppm for the samples treated with either ferrous sulfate heptahydrate (99.9% of reduction) and sodium thiosulfate (98

  13. The Reduction of Microbial and Chemical Contaminants with Selected POU/POE Systems

    EPA Science Inventory

    Centralized drinking water treatment and distribution alone may not always be the most practical or cost-effective option. Also, some consumers seeking a proactive measure to reduce exposure to pathogens and chemicals not currently monitored or regulated might consider employing...

  14. Reduction of Allowed Inventory When Chemicals are Located in Close Proximity with Explosives

    SciTech Connect

    Chong, Y P; Nguyen, S N

    2006-09-27

    The objective of this report is to determine the allowed inventory of chemicals stored in the same bay, building or magazine, i.e., in close proximity, with high explosives (HE) that would, in the event of an accident, result in acceptable risks to colocated workers and the public.

  15. ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE REACTOR SYSTEM - APPLICATIONS ANALYSIS REPORT

    EPA Science Inventory

    The ELI Eco Logic International Inc. (Eco Logic) process thermally separates organics, then chemically reduces them in a hydrogen atmosphere, converting them to a reformed gas that consists of light hydrocarbons and water. A scrubber treats the reformed gas to remove hydrogen chl...

  16. Features in chemical kinetics. I. Signatures of self-emerging dimensional reduction from a general format of the evolution law

    NASA Astrophysics Data System (ADS)

    Nicolini, Paolo; Frezzato, Diego

    2013-06-01

    Simplification of chemical kinetics description through dimensional reduction is particularly important to achieve an accurate numerical treatment of complex reacting systems, especially when stiff kinetics are considered and a comprehensive picture of the evolving system is required. To this aim several tools have been proposed in the past decades, such as sensitivity analysis, lumping approaches, and exploitation of time scales separation. In addition, there are methods based on the existence of the so-called slow manifolds, which are hyper-surfaces of lower dimension than the one of the whole phase-space and in whose neighborhood the slow evolution occurs after an initial fast transient. On the other hand, all tools contain to some extent a degree of subjectivity which seems to be irremovable. With reference to macroscopic and spatially homogeneous reacting systems under isothermal conditions, in this work we shall adopt a phenomenological approach to let self-emerge the dimensional reduction from the mathematical structure of the evolution law. By transforming the original system of polynomial differential equations, which describes the chemical evolution, into a universal quadratic format, and making a direct inspection of the high-order time-derivatives of the new dynamic variables, we then formulate a conjecture which leads to the concept of an "attractiveness" region in the phase-space where a well-defined state-dependent rate function ω has the simple evolution dot{ω }= - ω ^2 along any trajectory up to the stationary state. This constitutes, by itself, a drastic dimensional reduction from a system of N-dimensional equations (being N the number of chemical species) to a one-dimensional and universal evolution law for such a characteristic rate. Step-by-step numerical inspections on model kinetic schemes are presented. In the companion paper [P. Nicolini and D. Frezzato, J. Chem. Phys. 138, 234102 (2013)], 10.1063/1.4809593 this outcome will be naturally

  17. Permanent reduction of dissipation in nanomechanical Si resonators by chemical surface protection.

    PubMed

    Tao, Y; Navaretti, P; Hauert, R; Grob, U; Poggio, M; C L Degen

    2015-11-20

    We report on mechanical dissipation measurements carried out on thin (∼100 nm), single-crystal silicon cantilevers with varying chemical surface termination. We find that the 1-2 nm-thick native oxide layer of silicon contributes about 85% to the friction of the mechanical resonance. We show that the mechanical friction is proportional to the thickness of the oxide layer and that it crucially depends on oxide formation conditions. We further demonstrate that chemical surface protection by nitridation, liquid-phase hydrosilylation, or gas-phase hydrosilylation can inhibit rapid oxide formation in air and results in a permanent improvement of the mechanical quality factor between three- and five-fold. This improvement extends to cryogenic temperatures. Presented recipes can be directly integrated with standard cleanroom processes and may be especially beneficial for ultrasensitive nanomechanical force- and mass sensors, including silicon cantilevers, membranes, or nanowires. PMID:26501931

  18. Permanent reduction of dissipation in nanomechanical Si resonators by chemical surface protection

    NASA Astrophysics Data System (ADS)

    Tao, Y.; Navaretti, P.; Hauert, R.; Grob, U.; Poggio, M.; Degen, C. L.

    2015-11-01

    We report on mechanical dissipation measurements carried out on thin (˜100 nm), single-crystal silicon cantilevers with varying chemical surface termination. We find that the 1-2 nm-thick native oxide layer of silicon contributes about 85% to the friction of the mechanical resonance. We show that the mechanical friction is proportional to the thickness of the oxide layer and that it crucially depends on oxide formation conditions. We further demonstrate that chemical surface protection by nitridation, liquid-phase hydrosilylation, or gas-phase hydrosilylation can inhibit rapid oxide formation in air and results in a permanent improvement of the mechanical quality factor between three- and five-fold. This improvement extends to cryogenic temperatures. Presented recipes can be directly integrated with standard cleanroom processes and may be especially beneficial for ultrasensitive nanomechanical force- and mass sensors, including silicon cantilevers, membranes, or nanowires.

  19. Chemical Fouling Reduction of a Submersible Steel Spectrophotometer in Estuarine Environments Using a Sacrificial Zinc Anode.

    PubMed

    Tait, Zachary S; Thompson, Megan; Stubbins, Aron

    2015-07-01

    The availability of in situ spectrophotometers, such as the S::CAN spectro::lyser, has expanded the possibilities for high-frequency water quality data collection. However, biological and chemical fouling can degrade the performance of in situ spectrophotometers, especially in saline environments with rapid flow rates. A complex freshwater washing system has been previously designed to reduce chemical fouling for the S::CAN spectro::lyser spectrophotometer. In the current study, we present a simpler, cheaper alternative: the attachment of a sacrificial zinc anode. Results are presented detailing the S::CAN spectro::lyser performance with and without the addition of the sacrificial anode. Attachment of the zinc anode provided efficient corrosion protection during 2-wk deployments in a highly dynamic (average tidal range, 2.5 m) saline tidal saltmarsh creek at Groves Creek, Skidaway Institute of Oceanography, Savannah, GA. PMID:26437114

  20. Removal efficiency and toxicity reduction of 4-chlorophenol with physical, chemical and biochemical methods.

    PubMed

    Gómez, M; Murcia, M D; Dams, R; Christofi, N; Gómez, E; Gómez, J L

    2012-01-01

    Chlorophenols are well-known priority pollutants and many different treatments have been assessed to facilitate their removal from industrial wastewater. However, an absolute and optimum solution still has to be practically implemented in an industrial setting. In this work, a series ofphysical, chemical and biochemical treatments have been systematically tested for the removal of 4-chlorophenol, and their results have been compared in order to determine the most effective treatment based on removal efficiency and residual by-product formation. Chemical treatments based on advanced oxidation processes (AOP) produced the best results on rate and extent of pollutant removal. The non-chemical technologies showed advantages in terms of complete (in the case of adsorption) or easy (enzymatic treatments) removal of toxic treatment by-products. The AOP methods led to the production of different photoproducts depending on the chosen treatment. Toxic products remained in most cases following treatment, though the toxicity level is significantly reduced with combination treatments. Among the treatments, a photochemical method combining UV, produced with a KrCl excilamp, and hydrogen peroxide achieved total removal of chlorophenol and all by-products and is considered the best treatment for chlorophenol removal. PMID:22720434

  1. Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) TRACI version 2.1 User’s Guide

    EPA Science Inventory

    TRACI 2.1 (the Tool for the Reduction and Assessment of Chemical and other environmental Impacts) has been developed for sustainability metrics, life cycle impact assessment, industrial ecology, and process design impact assessment for developing increasingly sustainable products...

  2. Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst.

    PubMed

    Dutta, Indrajit; Carpenter, Michael K; Balogh, Michael P; Ziegelbauer, Joseph M; Moylan, Thomas E; Atwan, Mohammed H; Irish, Nicholas P

    2010-10-01

    A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multi-step synthetic procedure. Material produced at each step was characterized using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS) mapping, x-ray absorption spectroscopy (XAS), x-ray diffraction (XRD), and cyclic voltammetry (CV), and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode (TF-RDE) technique. The initial synthetic step, a co-reduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. TEM shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12-25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete coreshell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a "Swiss cheese" type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report. PMID:23807900

  3. Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst

    PubMed Central

    Dutta, Indrajit; Carpenter, Michael K; Balogh, Michael P; Ziegelbauer, Joseph M; Moylan, Thomas E; Atwan, Mohammed H; Irish, Nicholas P

    2013-01-01

    A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multi-step synthetic procedure. Material produced at each step was characterized using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS) mapping, x-ray absorption spectroscopy (XAS), x-ray diffraction (XRD), and cyclic voltammetry (CV), and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode (TF-RDE) technique. The initial synthetic step, a co-reduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. TEM shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12–25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete coreshell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a “Swiss cheese” type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report. PMID:23807900

  4. Factors affecting chemical and biological reduction of hexavalent chromium in soil

    SciTech Connect

    Losi, M.E.; Amrhein, C.; Frankenberger, W.T. Jr. . Dept. of Soil and Environmental Sciences)

    1994-11-01

    Hexavalent chromium [Cr(VI)] is a common environmental pollutant that is mobile in soils and is a known mutagen. The trivalent form [Cr(III)] has not known mutagenic properties and is highly insoluble and immobile above pH 5.5. Reduction to the trivalent state thus represents an effective mechanism for detoxification and immobilization of Cr(VI) in soil/water systems. In this study, the authors conducted experiments to examine various parameters involving aerobic reduction of Cr(VI) in a field soil. They found that organic matter content, bioactivity, and oxygen status were important factors. Under optimum conditions, the soil reduced 96% of added Cr(VI) under aerobic, field-moist conditions. The pH of the system was shown to have little effect. Both biological and nonbiological processes were influential, and, of 20 chromate-resistant bacterial cultures isolated from soils, 9 were found to actively reduce Cr(VI) to Cr(III) in liquid media. Their study suggests that organic-amended soils can readily reduce Cr(VI) and could promote excellent removal efficiency either as a primary treatment technique, or in conjunction with bioreactor-type wastewater treatment systems.

  5. Development of oxide dispersion strengthened ferritic steel prepared by chemical reduction and mechanical milling

    NASA Astrophysics Data System (ADS)

    Sun, Q. X.; Fang, Q. F.; Zhou, Y.; Xia, Y. P.; Zhang, T.; Wang, X. P.; Liu, C. S.

    2013-08-01

    The oxide dispersion strengthened ferritic steel with a nominal composition of Fe-14Cr-2W-0.5Ti-0.06Si-0.2V-0.1Mn-0.05Ta-0.03C-0.3Y2O3 (14Cr-ODS) was fabricated by sol-gel method in combination with hydrogen reduction, mechanical alloying (MA) and hot isostatic pressing (HIP) techniques. Pure Fe-1.5Y2O3 precursor was obtained by a sol-gel process and a reduction process at 650 °C for 3 h and pure 14Cr-ODS alloy powders were obtained from this precursor and the alloying metallic powders by mechanical alloying. The microstructure analysis investigated by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS) reveal that Y-Ti-O complexes and V-Ti-O complexes with a main particle size of 8 nm are formed in the 14Cr-ODS steel matrix. After HIP sintering the weight and the relative density of the compacted ingots are about 0.8 kg and 99.7%. The uniform elongation and ultimate tensile strength of the ODS steel obtained by HIP after annealing at 1100 °C for 5 h are about 13% and 840 MPa, respectively.

  6. Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst

    SciTech Connect

    Dutta, Indrajit; Carpenter, Michael K.; Balogh, Michael P.; Ziegelbauer, Joseph M.; Moylan, Thomas E.; Atwan, Mohammed H.; Irish, Nicholas P.

    2010-10-22

    A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multistep synthetic procedure. Material produced at each step was characterized using high-angle annular dark-field scanning transmission electron microscopy, electron energy loss spectroscopy mapping, X-ray absorption spectroscopy, X-ray diffraction, and cyclic voltammetry, and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode technique. The initial synthetic step, a coreduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. Transmission electron microscopy shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12-25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete core-shell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a 'Swiss cheese' type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report.

  7. A review of chemical, electrochemical and biological methods for aqueous Cr(VI) reduction.

    PubMed

    Barrera-Díaz, Carlos E; Lugo-Lugo, Violeta; Bilyeu, Bryan

    2012-07-15

    Hexavalent chromium is of particular environmental concern due to its toxicity and mobility and is challenging to remove from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. It does not form insoluble compounds in aqueous solutions, so separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, Cr(III) cations are not. Like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI) to Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. In this review, we describe the environmental implications of Cr(VI) presence in aqueous solutions, the chemical species that could be present and then we describe the technologies available to efficiently reduce hexavalent chromium. PMID:22608208

  8. IN-SITU CHEMICAL STABILIZATION OF METALS AND RADIONUCLIDES THROUGH ENHANCED ANAEROBIC REDUCTIVE PRECIPITATION

    SciTech Connect

    Christopher C. Lutes; Angela Frizzell, PG; Todd A. Thornton; James M. Harrington

    2003-08-01

    The objective of this NETL sponsored bench-scale study was to demonstrate the efficacy of enhanced anaerobic reductive precipitation (EARP) technology for precipitating uranium using samples from contaminated groundwater at the Fernald Closure Project (FCP) in Cincinnati, Ohio. EARP enhances the natural biological reactions in the groundwater through addition of food grade substrates (typically molasses) to drive the oxidative-reductive potential of the groundwater to a lower, more reduced state, thereby precipitating uranium from solution. In order for this in-situ technology to be successful in the long term, the precipitated uranium must not be re-dissolved at an unacceptable rate once groundwater geochemical conditions return to their pretreatment, aerobic state. The approach for this study is based on the premise that redissolution of precipitated uranium will be slowed by several mechanisms including the presence of iron sulfide precipitates and coatings, and sorption onto fresh iron oxides. A bench-scale study of the technology was performed using columns packed with site soil and subjected to a continuous flow of uranium-contaminated site groundwater (476 {micro}g/L). The ''treated'' column received a steady stream of dilute food grade molasses injected into the contaminated influent. Upon attainment of a consistently reducing environment and demonstrated removal of uranium, an iron sulfate amendment was added along with the molasses in the influent solution. After a month long period of iron addition, the treatments were halted, and uncontaminated, aerobic, unamended water was introduced to the treated column to assess rebound of uranium concentrations. In the first two months of treatment, the uranium concentration in the treated column decreased to the clean-up level (30 {micro}g/L) or below, and remained there for the remainder of the treatment period. A brief period of resolubilization of uranium was observed as the treated column returned to aerobic

  9. Synthesis of reduced graphene oxide (rGO) via chemical reduction

    SciTech Connect

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

    2015-05-15

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

  10. Reduction of Contaminants (Physical, Chemical, and Microbial) in Domestic Wastewater through Hybrid Constructed Wetland

    PubMed Central

    Sehar, Shama; Aamir, Rabia; Naz, Iffat; Ali, Naeem; Ahmed, Safia

    2013-01-01

    The current research was focused mainly on the designing and construction of efficient laboratory scale hybrid constructed wetland (HCW) for the treatment of domestic wastewater. Parameters like COD, BOD5, PO4, SO4, NO3, NO2, and pathogenic indicator microbes were monitored after hydraulic retention time (HRT) of 4, 8, 12, 16, and 20 days. Treatment efficiency of HCW kept on increasing with the increase in hydraulic retention time. Maximum efficiency of HCW was observed with a 20-day HRT, that is, 97.55, 97.5, 89.35, 80.75, 96.04, 91.52, and 98.6% reduction from the zero time value for COD, BOD5, PO4, SO4, NO3, NO2, and fecal coliforms, respectively. After 20 days' time, the treated water was free of almost all nutrients and microbial pollutants. Hence, increasing hydraulic retention time was found to ameliorate the operational competence of HCW. Thus HCW can serve as a promising technology for wastewater treatment and can be scaled up for small communities in the developing countries. PMID:23724336

  11. Photomask defect tracing, analysis, and reduction with chemically amplified resist process

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-ming; Lai, Rick; Huang, W. H.; Wang, B. C.; Chen, C. Y.; Kung, C. H.; Yoo, Chue-San; Chen, Jieh-Jang; Lee, Sheng-Cha

    2003-08-01

    The features of optical proximity correction are becoming very aggressive as production technology migrates into 90nm/130 nm regime. The complicated optical proximity correction (OPC) patterns often result in un-repairable defects, a major yield loss mechanisms in a mask production line. Defect control is increasingly important. A methodology for identifying defect sources and reduction is demonstrated in this paper. The mechanisms and causes of defect formation could be determined with corresponding process step on the strength of sequence inspections. The cause of half-etched opaque defect on negative CAR process was found from PR fragment contamination of e-beam exposure step. After clean-up of e-beam chamber, yield was increased over 20%. Big pinhole defect and contact of AttPSM positive process was found on ADI step. The possible cause was poor CAR adhesion. These two type defects were decreased by modification of developing recipe, special on rinse step. Design experiment with Taguchi method was used to optimize the interactive recipe of plasma descum and rinse step on developing step of implanted layer. Average defect density was decreased from 0.99 to 0.27, and percentage of zero defect rate has been increased from 29.5 to 63.3%.

  12. Synthesis of reduced graphene oxide (rGO) via chemical reduction

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Natural flake Graphite was used as the starting material for the graphene synthesis. In the first step flake graphite was treated with oxidizing agents under vigorous conditions to obtain graphite oxide. Layered graphite oxide decorated with oxygen has large inter-layer distance leading easy exfoliation into single sheets by ultrasonication giving graphene oxide. In the last step exfoliated graphene oxide sheets were reduced slowly with the help of reducing agent to obtain fine powder which is labeled as reduced graphene oxide (rGO). This rGO was further characterized by X-Ray Diffraction (XRD), Scanning Tunneling Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy techniques. XRD pattern shows peaks corresponding to (002) graphitic lattice planes indicating the formation of network of sp2 like carbon structure. SEM images show the ultrathin, wrinkled, paper-like morphology of graphene sheets. IR study shows that the graphite has been oxidized to graphite oxide with the presence of various absorption bands confirming the presence of oxidizing groups. The FTIR spectrum of rGO shows no sharp peaks confirming the efficient reduction of rGO. The Raman spectrum shows disorder in the graphene sheets.

  13. Quantifying the value of information for uncertainty reduction in chemical EOR modeling

    NASA Astrophysics Data System (ADS)

    Leray, Sarah; Yeates, Christopher; Douarche, Frédéric; Roggero, Frédéric

    2016-04-01

    Reservoir modeling is a powerful tool to assess the technical and economic feasibility of chemical Enhanced Oil Recovery methods such as the joint injection of surfactant and polymer. Laboratory recovery experiments are usually undertaken on cores to understand recovery mechanisms and to estimate properties, that will be further used to build large scale models. To capture the different processes involved in chemical EOR, models are described by a large number of parameters which are basically only partially constrained by recovery experiments and additional characterizations, mainly because of cost and time restrictions or limited representativeness. Among the most uncertain properties, features the surfactant adsorption which cannot be straightforwardly derived from bulk or simplified dynamic measurements (e.g. single phase dynamic adsorption experiments). It is unfortunately critical for the economics of the process. Identifying the most informative observations (e.g. saturation scans, pressure differential, surfactant production, oil recovery) is of primary interest to compensate deficiency of some characterizations and improve models robustness and their predictive capability. Building a consistent set of recovery experiments that will allow to seize recovery mechanisms is critical as well. To address these inverse methodology issues, we create a synthetic numerical model with a well-defined set of parameter values, considered to be our reference case. This choice of model is based on a similar real data set and a broad literature review. It consists of a water-wet sandstone subject to typical surfactant-polymer injections. We first study the effect of a salinity gradient injected after a surfactant-polymer slug, as it is known to significantly improve oil recovery. We show that reaching optimal conditions of salinity gradient is a fragile balance between surfactant desorption and interfacial tension increase. This high dependence on surfactant adsorption

  14. Software algorithms for false alarm reduction in LWIR hyperspectral chemical agent detection

    NASA Astrophysics Data System (ADS)

    Manolakis, D.; Model, J.; Rossacci, M.; Zhang, D.; Ontiveros, E.; Pieper, M.; Seeley, J.; Weitz, D.

    2008-04-01

    The long-wave infrared (LWIR) hyperpectral sensing modality is one that is often used for the problem of detection and identification of chemical warfare agents (CWA) which apply to both military and civilian situations. The inherent nature and complexity of background clutter dictates a need for sophisticated and robust statistical models which are then used in the design of optimum signal processing algorithms that then provide the best exploitation of hyperspectral data to ultimately make decisions on the absence or presence of potentially harmful CWAs. This paper describes the basic elements of an automated signal processing pipeline developed at MIT Lincoln Laboratory. In addition to describing this signal processing architecture in detail, we briefly describe the key signal models that form the foundation of these algorithms as well as some spatial processing techniques used for false alarm mitigation. Finally, we apply this processing pipeline to real data measured by the Telops FIRST hyperspectral (FIRST) sensor to demonstrate its practical utility for the user community.

  15. Fractal aggregation and optical absorption of copper nanoparticles prepared by in situ chemical reduction within a Cu2+-polymer complex

    NASA Astrophysics Data System (ADS)

    Huang, C.; Yang, C. Z.

    1999-03-01

    A polymer-matrix nanocomposite containing copper particles has been prepared by in situ chemical reduction within a Cu2+-poly(itaconic acid-co-acrylic acid) complex solid film. The copper particle size in the order of 10 nm is controlled by the initial content of the metal ions in the complex. Their fractal pattern and the value of the fractal dimension indicate that there exists a cluster-cluster aggregation process in the present system. Optical absorption spectra of copper-polymer nanocomposites show distinct plasma absorption bands and quantum size effect in the samples. The calculated blueshift of the resonance peak based on a quantum-sphere model gives remarkable agreement with the experimental data as the size of copper particles embedded in the polymer becomes smaller.

  16. Response Behaviour of a Hydrogen Sensor Based on Ionic Conducting Polymer-metal Interfaces Prepared by the Chemical Reduction Method

    PubMed Central

    Sakthivel, Mariappan; Weppner, Werner

    2006-01-01

    A solid-state amperometric hydrogen sensor based on a protonated Nafion membrane and catalytic active electrode operating at room temperature was fabricated and tested. Ionic conducting polymer-metal electrode interfaces were prepared chemically by using the impregnation-reduction method. The polymer membrane was impregnated with tetra-ammine platinum chloride hydrate and the metal ions were subsequently reduced by using either sodium tetrahydroborate or potassium tetrahydroborate. The hydrogen sensing characteristics with air as reference gas is reported. The sensors were capable of detecting hydrogen concentrations from 10 ppm to 10% in nitrogen. The response time was in the range of 10-30 s and a stable linear current output was observed. The thin Pt films were characterized by XRD, Infrared Spectroscopy, Optical Microscopy, Atomic Force Microscopy, Scanning Electron Microscopy and EDAX.

  17. Three Dimensional P-doped Graphene Synthesized by Eco-Friendly Chemical Vapor Deposition for Oxygen Reduction Reactions.

    PubMed

    Li, Xiaoguang; Qiu, Yunfeng; Hu, Ping An

    2016-06-01

    Heteroatom doping provides possibilities for changing the electronic properties of graphene. Three Dimensional P-doped graphene (3DPG) was fabricated via chemical vapor deposition (CVD) using nickel foam as template and triphenylphosphine (TPP) as C and P sources simultaneously without using toxic organic solvent as carrier liquid. The invasion of P atoms into graphene networks make them non-electroneutral and consequently favor the adsorption of oxygen and O-O bond cleavage due to the charge polarization increase of the P-C bond. Thus, the as-prepared 3DPG served as an efficient electrocatalyst for oxygen reduction reaction (ORR). Additionally, the 3D porous structure is favorable for the mass transfer of electrolytes ions, hence 3DPG exhibit better electrocatalytic activity, long-term stability, and tolerance to crossover effect of methanol than pristine 3D graphene and Pt/C for ORR. PMID:27427693

  18. Efficiency of some soil bacteria for chemical oxygen demand reduction of synthetic chlorsulfuron solutions under agiated culture conditions.

    PubMed

    Erguven, G O; Yildirim, N

    2016-01-01

    This study searches the efficiency of certain soil bacteria on chemical oxygen demand (COD) reduction of synthetic chlorsulfuron solutions under agitated culture conditions. It also aims to determine the turbidity of liquid culture medium with chlorsulfuron during bacterial incubation for 120 hours. As a result the highest and lowest COD removal efficiency of bacteria was determined for Bacillus simplex as 94% and for Micrococcus luteus as 70%, respectively at the end of the 96th hour. It was found that COD removal efficiency showed certain differences depend on the bacterial species. It was also observed that B. simplex had the highest COD removal efficiency and it was a suitable bacterium species for bioremediation of a chlorsulfuron contaminated soils. PMID:27262810

  19. Determination of decimal reduction time (D value) of chemical agents used in hospitals for disinfection purposes

    PubMed Central

    Mazzola, Priscila Gava; Penna, Thereza Christina Vessoni; da S Martins, Alzira M

    2003-01-01

    Background Prior to the selection of disinfectants for low, intermediate and high (sterilizing) levels, the decimal reduction time, D-value, for the most common and persistent bacteria identified at a health care facility should be determined. Methods The D-value was determined by inoculating 100 mL of disinfecting solution with 1 mL of a bacterial suspension (104 – 105 CFU/mL for vegetative and spore forms). At regular intervals, 1 mL aliquots of this mixture were transferred to 8 mL of growth media containing a neutralizing agent, and incubated at optimal conditions for the microorganism. Results The highest D-values for various bacteria were determined for the following solutions: (i) 0.1% sodium dichloroisocyanurate (pH 7.0) – E. coli and A. calcoaceticus (D = 5.9 min); (ii) sodium hypochlorite (pH 7.0) at 0.025% for B. stearothermophilus (D = 24 min), E. coli and E. cloacae (D = 7.5 min); at 0.05% for B. stearothermophilus (D = 9.4 min) and E. coli (D = 6.1 min) and 0.1% for B. stearothermophilus (D = 3.5 min) and B. subtilis (D = 3.2 min); (iii) 2.0% glutaraldehyde (pH 7.4) – B. stearothermophilus, B. subtilis (D = 25 min) and E. coli (D = 7.1 min); (iv) 0.5% formaldehyde (pH 6.5) – B. subtilis (D = 11.8 min), B. stearothermophilus (D = 10.9 min) and A. calcoaceticus (D = 5.2 min); (v) 2.0% chlorhexidine (pH 6.2) – B. stearothermophilus (D = 9.1 min), and at 0.4% for E. cloacae (D = 8.3 min); (vi) 1.0% Minncare® (peracetic acid and hydrogen peroxide, pH 2.3) – B. stearothermophilus (D = 9.1 min) and E. coli (D = 6.7 min). Conclusions The suspension studies were an indication of the disinfectant efficacy on a surface. The data in this study reflect the formulations used and may vary from product to product. The expected effectiveness from the studied formulations showed that the tested agents can be recommended for surface disinfection as stated in present guidelines and emphasizes the importance and need to develop routine and novel programs to

  20. Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

    2011-01-01

    Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24–1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28–9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles. PMID:21499424

  1. Chemical and Microbial Characterization of North Slope Viscous Oils to Assess Viscosity Reduction and Enhanced Recovery

    SciTech Connect

    Shirish Patil; Abhijit Dandekar; Mary Beth Leigh

    2008-12-31

    A large proportion of Alaska North Slope (ANS) oil exists in the form of viscous deposits, which cannot be produced entirely using conventional methods. Microbially enhanced oil recovery (MEOR) is a promising approach for improving oil recovery for viscous deposits. MEOR can be achieved using either ex situ approaches such as flooding with microbial biosurfactants or injection of exogenous surfactant-producing microbes into the reservoir, or by in situ approaches such as biostimulation of indigenous surfactant-producing microbes in the oil. Experimental work was performed to analyze the potential application of MEOR to the ANS oil fields through both ex situ and in situ approaches. A microbial formulation containing a known biosurfactant-producing strain of Bacillus licheniformis was developed in order to simulate MEOR. Coreflooding experiments were performed to simulate MEOR and quantify the incremental oil recovery. Properties like viscosity, density, and chemical composition of oil were monitored to propose a mechanism for oil recovery. The microbial formulation significantly increased incremental oil recovery, and molecular biological analyses indicated that the strain survived during the shut-in period. The indigenous microflora of ANS heavy oils was investigated to characterize the microbial communities and test for surfactant producers that are potentially useful for biostimulation. Bacteria that reduce the surface tension of aqueous media were isolated from one of the five ANS oils (Milne Point) and from rock oiled by the Exxon Valdez oil spill (EVOS), and may prove valuable for ex situ MEOR strategies. The total bacterial community composition of the six different oils was evaluated using molecular genetic tools, which revealed that each oil tested possessed a unique fingerprint indicating a diverse bacterial community and varied assemblages. Collectively we have demonstrated that there is potential for in situ and ex situ MEOR of ANS oils. Future work

  2. Size Control and Characterization of Sn-Ag-Cu Lead-Free Nanosolders by a Chemical Reduction Process

    NASA Astrophysics Data System (ADS)

    Yung, K. C.; Law, C. M. T.; Lee, C. P.; Cheung, B.; Yue, T. M.

    2012-02-01

    Sn-3.0Ag-0.5Cu nanosolders were synthesized via a chemical reduction method. Polyvinyl pyrrolidone (PVP) and sodium borohydride (NaBH4) were employed as surfactant and reducing agent, respectively. Ultraviolet-visible (UV-visible) absorption and x-ray diffraction patterns revealed that alloying had successfully taken place during the reduction process. Different amounts of PVP and NaBH4 additions influenced the nanosolder particle size. Under varying reaction temperatures and pH values, various ranges of nanosolder size were obtained. Optimized nanosolders were studied by differential scanning calorimetry to investigate the depression of the melting temperature, and were analyzed by transmission electron microscopy to measure actual particle sizes. The dependence of the particle size on the melting temperature was observed. The melting point was depressed to 204.4°C when the average diameter of the nanosolders was 20 nm. Although SnO2 was formed on the nanosolders, it could be cleaned by citric acid. These low-melting-temperature Sn-Ag-Cu nanosolders are candidates for use in lead-free interconnect applications.

  3. One-Step Synthesis and Magnetic Phase Transformation of Ln-TM-B Alloy by Chemical Reduction.

    PubMed

    Kim, Chang Woo; Kim, Young Hwan; Cha, Hyun Gil; Lee, Don Keun; Kang, Young Soo

    2007-04-11

    Binary and ternary intermetallic alloy systems are of interest for a variety of academic and technological applications. Despite recent advances in synthesizing binary alloy, there are very few reports of ternary alloy related to lanthanide series. The purpose of this work is to contribute to ternary alloy systems such as lanthanide-transition metal-boron with a simple chemical method and analysis of its magnetic behavior. Ternary Nd-Fe-B amorphous alloy was successfully synthesized with borohydride. The magnetic behavior in the process of formation of ternary Nd-Fe-B alloy and Nd2Fe14B from amorphous phase alloy is reported. Compared with the synthesis of a transition metal, the existence of a lanthanide ion makes aggregates-like particles with a diameter of 2 nm possible in the formation of a nanosphere, which is a significantly important result in terms of acceleration of the reduction-diffusion reaction for the formation of ternary alloy. In the process of reduction and diffusion, the Nd phase is diffused into the Fe-based phase, and then the ternary Nd2Fe14B intermetallic compound is fabricated. PMID:17425319

  4. Direct growth of tellurium nanorod arrays on Pt/FTO/glass through a surfactant-assisted chemical reduction.

    PubMed

    Liu, Hongmei; Zeng, Boming; Jia, Falong

    2011-07-29

    Uniform tellurium nanorod arrays (TNA) have been successfully deposited directly on Pt/FTO (F-doped SnO(2))/glass substrate through a facile surfactant-assisted approach, which involved chemical reduction of TeO(3)(2-) ions by hydrazine hydrate. The whole synthesis process is highly repeatable and performed simply by immersing the Pt/FTO/glass in the solution for a certain time. During the growth of TNA, Pt catalyzed the reduction of TeO(3)(2-) ions by hydrazine hydrate and Te nanoparticles were deposited firmly on the substrate at first. Then, under the regulation of the surfactant (cetyltrimethylammonium bromide, CTAB), the deposited Te grew into nanorod arrays and adhered firmly to the substrate. Similar Te nanorod arrays could also grow on a Pd substrate which has the same catalytic performance as that of Pt. The as-synthesized TNA could be used as a good template to synthesize platinum-and gold-coated nanorods through convenient galvanic replacement. As a demonstration of potential application, the gold/tellurium nanorods showed uniform surface-enhanced Raman scattering (SERS) using rhodamine 6G (Rh6G) as the analyte. This approach provides a simple route for the growth of standing Te nanorods on a substrate, which may be used for the synthesis of other standing one-dimensional materials through a similar mechanism. PMID:21719969

  5. Direct growth of tellurium nanorod arrays on Pt/FTO/glass through a surfactant-assisted chemical reduction

    NASA Astrophysics Data System (ADS)

    Liu, Hongmei; Zeng, Boming; Jia, Falong

    2011-07-01

    Uniform tellurium nanorod arrays (TNA) have been successfully deposited directly on Pt/FTO (F-doped SnO2)/glass substrate through a facile surfactant-assisted approach, which involved chemical reduction of TeO32 - ions by hydrazine hydrate. The whole synthesis process is highly repeatable and performed simply by immersing the Pt/FTO/glass in the solution for a certain time. During the growth of TNA, Pt catalyzed the reduction of TeO32 - ions by hydrazine hydrate and Te nanoparticles were deposited firmly on the substrate at first. Then, under the regulation of the surfactant (cetyltrimethylammonium bromide, CTAB), the deposited Te grew into nanorod arrays and adhered firmly to the substrate. Similar Te nanorod arrays could also grow on a Pd substrate which has the same catalytic performance as that of Pt. The as-synthesized TNA could be used as a good template to synthesize platinum-and gold-coated nanorods through convenient galvanic replacement. As a demonstration of potential application, the gold/tellurium nanorods showed uniform surface-enhanced Raman scattering (SERS) using rhodamine 6G (Rh6G) as the analyte. This approach provides a simple route for the growth of standing Te nanorods on a substrate, which may be used for the synthesis of other standing one-dimensional materials through a similar mechanism.

  6. Characterization and optimization of Fe(II)Cit-No reduction by Pseudomonas sp.

    PubMed

    Liu, Nan; Jiang, Jin-Lin; Cai, Ling-Lin; Li, Wei

    2011-12-01

    Biological reduction of nitric oxide (NO), chelated by ferrous L (L: chelate reagent), to N2 is one of the core processes in a chemical absorption-biological reduction integrated technique for nitrogen oxide (NOx) removal from flue gases. In this study, a newly isolated strain, Pseudomonas sp., was used to reduce NO chelated by Fe(II)Cit (Cit: citrate) as Fe(II)Cit-NO, and some factors were investigated. The results showed that, at the NO concentration of 670 mg/m3, 65.9% of NO was totally reduced within 25 h under anaerobic conditions, and the optimal conditions for the bioreduction of NO were found. The strain of Pseudomonas sp. could efficiently use glucose as the carbon source for Fe(II)Cit-NO reduction. Though each complex could be reduced by its own dedicated bacterial strain, Fe(III)Cit could also be reduced by the strain of Pseudomonas sp. The nitrite ion, NO2-, could inhibit cell growth and thus affect the Fe(III) reduction process. These findings provide some useful data for Fe(II)Cit-NO reduction, scrubber solution regeneration and NOx removal process design. PMID:22439583

  7. Study of Impacts of Arctic Sea Ice Reduction on Atmospheric Chemical Processes - The BROMEX 2012 Field Campaign

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.

    2012-12-01

    Arctic perennial sea ice has decreased drastically in the last decade and still remained low in spring 2012 as observed from scatterometer datasets acquired by QuikSCAT and Oceansat-2 satellites. In particular, the thinner, weaker, and saltier seasonal sea ice has dominated over the perennial ice in the Chukchi Sea and Beaufort Sea. To investigate impacts of sea ice reduction on atmospheric chemical processes, we conducted the BRomine, Ozone, and Mercury EXperiment in (BROMEX) in March-April 2012 around Barrow, extending out to a large region offshore and inland. Here we present overview results from BROMEX, which was successfully carried out by about 30 scientists, researchers, and field workers from multiple international institutions. For BROMEX, we coordinated and collected satellite data, including a number of near-real-time products, from multiple satellite instruments including MODIS, AMSR-E, GOME-2, SCIAMACHY, OMI, RADARSAT-2, Envisat ASAR, TanDEM-X, SMOS, CryoSat-2, and Oceansat-2. Over the BROMEX field region, we made measurements and collected sea ice, snow, ocean, and air samples for physical, meteorological, chemical, biological, and acoustic studies. A helicopter was used to deploy chemical and meteorological buoys in the Chukchi Sea and the Beaufort Sea. Measurements were also made with airborne sensors across sea ice, leads, lagoon, and tundra along various flight patterns of the ALAR aircraft. Furthermore, we coordinated with the NASA IceBridge P3 aircraft to collect surface temperature, surface height, snow depth, and ice thickness measurements. We set up and maintained field sites on sea ice and in the tundra to measure bromine, ozone, mercury, and other chemical species. Moreover, we obtained temperature data from many different types of temperature sensors for temperature accuracy assessment to identify potential issues that might cause errors or biases in temperature measurements. An enormous amount of in-situ snow and ice data was collected

  8. NITRO-HYDROLYSIS: AN ENERGY EFFICIENT SOURCE REDUCTION AND CHEMICAL PRODUCTION PROCESS FOR WASTEWATER TREATMENT PLANT BIOSOLIDS

    SciTech Connect

    Klasson, KT

    2003-03-10

    The nitro-hydrolysis process has been demonstrated in the laboratory in batch tests on one municipal waste stream. This project was designed to take the next step toward commercialization for both industrial and municipal wastewater treatment facility (WWTF) by demonstrating the feasibility of the process on a small scale. In addition, a 1-lb/hr continuous treatment system was constructed at University of Tennessee to treat the Kuwahee WWTF (Knoxville, TN) sludge in future work. The nitro-hydrolysis work was conducted at University of Tennessee in the Chemical Engineering Department and the gas and liquid analysis were performed at Oak Ridge National Laboratory. Nitro-hydrolysis of sludge proved a very efficient way of reducing sludge volume, producing a treated solution which contained unreacted solids (probably inorganics such as sand and silt) that settled quickly. Formic acid was one of the main organic acid products of reaction when larger quantities of nitric acid were used in the nitrolysis. When less nitric acid was used formic acid was initially produced but was later consumed in the reactions. The other major organic acid produced was acetic acid which doubled in concentration during the reaction when larger quantities of nitric acid were used. Propionic acid and butyric acid were not produced or consumed in these experiments. It is projected that the commercial use of nitro-hydrolysis at municipal wastewater treatment plants alone would result in a total estimated energy savings of greater than 20 trillion Btu/yr. A net reduction of 415,000 metric tons of biosolids per year would be realized and an estimated annual cost reduction of $122M/yr.

  9. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals. [Contains glossary

    SciTech Connect

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. . Coal Preparation Div.); Jacobsen, P.S. )

    1991-02-01

    This report presents the washability and comprehensive characterization results of 184 raw coal channel samples, including anthracite, bituminous and lignite coals, collected from the Central Region of the United States. This is the second of a three volume report on the coals of the United States. All the data are presented in six appendices. Statistical techniques and definitions are presented in Appendix A, and a glossary of terms is presented in Appendix B. The complete washability data and an in-depth characterization of each sample are presented alphabetically by state in Appendix C. In Appendix D, a statistical evaluation is given for the composited washability data, selected chemical and physical properties and washability data interpolated at various levels of Btu recovery. This presentation is shown by state, section, and region where four or more samples were collected. Appendix E presents coalbed codes and names for the Central Region coals. Graphical summations are presented by state, section and region showing the effects of crushing on impurity reductions, and the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. 35 figs., 5 tabs.

  10. Application of integrated ozone and granular activated carbon for decolorization and chemical oxygen demand reduction of vinasse from alcohol distilleries.

    PubMed

    Hadavifar, Mojtaba; Younesi, Habibollah; Zinatizadeh, Ali Akbar; Mahdad, Faezeh; Li, Qin; Ghasemi, Zahra

    2016-04-01

    This study investigates the treatment of the distilleries vinasse using a hybrid process integrating ozone oxidation and granular activated carbons (GAC) in both batch and continuous operation mode. The batch-process studies have been carried out to optimize initial influent pH, GAC doses, the effect of the ozone (O3) and hydrogen peroxide (H2O2) concentrations on chemical oxygen demand (COD) and color removal of the distilleries vinasse. The continuous process was carried out on GAC and ozone treatment alone as well as the hybrid process comb both methods to investigate the synergism effectiveness of the two methods for distilleries vinasse COD reduction and color removal. In a continuous process, the Yan model described the experimental data better than the Thomas model. The efficiency of ozonation of the distilleries vinasse was more effective for color removal (74.4%) than COD removal (25%). O3/H2O2 process was not considerably more effective on COD and color removal. Moreover, O3/GAC process affected negatively on the removal efficiency by reducing COD and color from distilleries vinasse. The negative effect decreased by increasing pH value of the influent. PMID:26789200

  11. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals. [Contains glossary

    SciTech Connect

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. ); Jacobsen, P.S. )

    1990-01-01

    This report presents the washability and comprehensive characterization results of 543 raw coal samples collected from the Eastern Region of the United States. This is the first volume of a three-volume report on the coals of the United States. All the data are presented in six appendices. Statistical techniques and definitions are presented in Appendix A, and a glossary of terms is presented in Appendix B. The complete washability data and an in- depth characterization of each sample are presented alphbetically by state in Appendix C. In Appendix D, a statistical evaluation is given for the composited washability data, selected chemical and physical properties, and washability data interpolated at various levels of Btu recovery. This presentation is shown by state, section, and region where four or more samples were collected. Appendix E presents coalbed codes and names for the Eastern Region coals. Graphical summations are presented by state, section, and region showing the effects of crushing on impurity reductions, and the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. 14 refs., 27 figs., 3 tabs.

  12. Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

    2016-05-01

    Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

  13. Influence of Sn on the magnetic ordering of Ni-Sn alloy synthesized using chemical reduction method

    NASA Astrophysics Data System (ADS)

    Dhanapal, K.; Narayanan, V.; Stephen, A.

    2016-05-01

    The Ni-Sn alloy was synthesized using borohydride assisted chemical reduction method. The composition of the synthesized alloy was determined using atomic absorption spectroscopy which revealed that the observed composition of Sn is high when compared to the initial composition. The ultrafine particles are clearly observed from field emission scanning electron microscope for all the sample. The X-ray diffraction measurement confirmed that the as-synthesized samples are of amorphous like nature while the samples annealed at 773 K showed crystalline nature. The Fourier transform infrared spectroscopy confirmed metallic bond stretching in the alloy samples. The crystallization and phase transition temperature was observed from differential scanning calorimetry. The shift in the crystallization temperature of Ni with increasing percentage of Sn was observed. The vibrating sample magnetometer was employed to understand the magnetic behavior of the Ni-Sn alloy. As-synthesized alloy samples showed paramagnetic nature while the annealed ones exhibit the soft ferromagnetic, antiferromagnetic and paramagnetic nature. The saturation magnetization value and magnetic ordering in the Ni-Sn alloys depend on the percentage of Sn present in the alloy.

  14. Synthesis and characterization of novel bactericidal Cu/HPMC BNCs using chemical reduction method for food packaging.

    PubMed

    Ebrahimiasl, Saeideh; Rajabpour, Ataollah

    2015-09-01

    In this research copper nanoparticles (Cu NPs) were incorporated in the biodegradable hydroxypropyl methylcellulose (HPMC) matrix using the simple and low cost chemical reduction method for application as food packaging material. The properties of Cu/HPMC bionanocomposites (BNCs) were studied as a function of the CuSO4 concentration. Surface morphology of the film was investigated by scanning electron microscopy. Mechanical analysis and water vapor barrier properties of HPMC/Cu nanocomposites were analyzed. It was observed that mechanical and water vapor barrier properties of the films were improved by the concentration of CuSO4. The antibacterial activity of HPMC/Cu thin films were evaluated based on the diameter of inhibition zone in a disk diffusion test against Gram positive bacteria, ie, Streptococus A., S. epidermidis, S.aureus , B.cereus and Gram negative bacteria, ie, E. coli, E. faecalis, Salmonella, P. aeruginosa using Mueller Hinton agar at different concentration of CuSO4. The results revealed a greater bactericidal effectiveness for nanocomposite films containing 5 % of CuSO4. Packages prepared from HPMC/Cu nanocomposite films were used for meat packaging. The films were filled with meat and then stored at 4 °C. Microbial stability of the meat was evaluated after 3, 7, 10 and 15 days of storage. The results showed that microbial growth rate significantly reduced as a result of using this nanocomposite packaging material. PMID:26345017

  15. Carbon emissions reduction potential in the US chemicals and pulp and paper industries by applying CHP technologies

    SciTech Connect

    Khrushch, M.; Worrell, E.; Price, L.; Martin, N.; Einstein, D.

    1999-07-01

    The chemical and the pulp/paper industries combined provide 55% of CHP generation in the US industry. Yet, significant potential for new CHP capacities exists in both industries. From the present steam consumption data, the authors estimate about 50 GW of additional technical potential for CHP in both industries. The reduced carbon emissions will be equivalent to 44% of the present carbon emissions in these industries. They find that most of the carbon emissions reductions can be achieved at negative costs. Depending on the assumptions used in calculations, the economic potential of CHP in these industries can be significantly lower, and carbon emissions mitigation costs can be much higher. Using sensitivity analyses, they determine that the largest effect on the CHP estimate have the assumptions in the costs of CHP technology, in the assumed discount rates, in improvements in efficiency of CHP technologies, and in the CHP equipment depreciation periods. Changes in fuel and electricity prices and the growth in the industries' steam demand have less of an effect. They conclude that the lowest carbon mitigation costs are achieved with the CHP facility is operated by the utility and when industrial company that owns the CHP unit can sell extra electricity and steam to the open wholesale market. Based on the results of the analyses they discuss policy implications.

  16. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals. [Contains glossary

    SciTech Connect

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. . Coal Preparation Div.); Jacobsen, P.S. )

    1991-06-01

    This report presents the washability and comprehensive characterization results of 247 raw coal channel samples, including anthracite, bituminous and lignite coals, collected from the Western Region of the United States. Although the Western Region includes Alaska, coal data from this state will often be cited apart from the Western Region data from the lower United States. This is the third of a three volume report on the coals of the United States. All the data are presented in six appendices. Statistical techniques and definitions are presented in Appendix A, and a glossary of terms is presented in Appendix B. The complete washability data and an in-depth characterization of each sample are presented alphabetically by state in Appendix C. In Appendix D, a statistical evaluation is given for the composited washability data, selected chemical and physical properties, and washability data interpolated at various levels of Btu recovery. This presentation is shown by state, section, and region where four or more samples were collected. Appendix E presents coalbed codes and names for the Western Region coals. Graphical summations are presented by state, rank, and region showing the effects of crushing on impurity reductions, and the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. 35 figs., 3 tabs.

  17. Reduction of Fe(II)EDTA-NO by a newly isolated Pseudomonas sp. strain DN-2 in NOx scrubber solution.

    PubMed

    Zhang, Shi-Han; Li, Wei; Wu, Cheng-Zhi; Chen, Han; Shi, Yao

    2007-10-01

    Biological reduction of nitric oxide (NO) chelated by ferrous ethylenediaminetetraacetate (Fe(II)EDTA) to N2 is one of the core processes in a chemical absorption-biological reduction integrated technique for nitrogen oxide (NOx) removal from flue gases. A new isolate, identified as Pseudomonas sp. DN-2 by 16S rRNA sequence analysis, was able to reduce Fe(II)EDTA-NO. The specific reduction capacity as measured by NO was up to 4.17 mmol g DCW(-1) h(-1). Strain DN-2 can simultaneously use glucose and Fe(II)EDTA as electron donors for Fe(II)EDTA-NO reduction. Fe(III)EDTA, the oxidation of Fe(II)EDTA by oxygen, can also serve as electron acceptor by strain DN-2. The interdependency between various chemical species, e.g., Fe(II)EDTA-NO, Fe(II)EDTA, or Fe (III)EDTA, was investigated. Though each complex, e.g., Fe(II)EDTA-NO or Fe(III)EDTA, can be reduced by its own dedicated bacterial strain, strain DN-2 capable of reducing Fe(III)EDTA can enhance the regeneration of Fe(II)EDTA, hence can enlarge NO elimination capacity. Additionally, the inhibition of Fe(II)EDTA-NO on the Fe(III)EDTA reduction has been explored previously. Strain DN-2 is probably one of the major contributors for the continual removal of NOx due to the high Fe(II)EDTA-NO reduction rate and the ability of Fe(III)EDTA reduction. PMID:17598105

  18. THE SECOND GENERATION OF THE WASTE REDUCTION (WAR) ALGORITHM: A DECISION SUPPORT SYSTEM FOR GREENER CHEMICAL PROCESSES

    EPA Science Inventory

    chemical process designers using simulation software generate alternative designs for one process. One criterion for evaluating these designs is their potential for adverse environmental impacts due to waste generated, energy consumed, and possibilities for fugitive emissions. Co...

  19. Selective recovery of pure copper nanopowder from indium-tin-oxide etching wastewater by various wet chemical reduction process: Understanding their chemistry and comparisons of sustainable valorization processes.

    PubMed

    Swain, Basudev; Mishra, Chinmayee; Hong, Hyun Seon; Cho, Sung-Soo

    2016-05-01

    Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11kg/m(3) of copper and 1.35kg/m(3) of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered using various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100-500nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process. PMID:26918838

  20. Sulfidation of Nano Zerovalent Iron (nZVI) for Improved Selectivity During In-Situ Chemical Reduction (ISCR).

    PubMed

    Fan, Dimin; O'Brien Johnson, Graham; Tratnyek, Paul G; Johnson, Richard L

    2016-09-01

    The high reactivity of nano zerovalent iron (nZVI) leads to inefficient treatment due to competition with various natural reductant demand (NRD) processes, especially the reduction of water to hydrogen. Here we show that this limitation can be alleviated by sulfidation (i.e., modification by reducing sulfur compounds). nZVI synthesized on carboxylmethylcelluose (CMC-nZVI) was sulfidated with either sulfide or dithionite. The reactivity of the resulting materials was examined with three complementary assays: (i) direct measurement of hydrogen production, (ii) reduction of a colorimetric redox probe (indigo disulfonate, I2S), and (iii) dechlorination of trichloroethylene (TCE). The results indicate that sulfidation at S/Fe molar ratios of ≥0.3, effectively eliminates reaction with water, but retains significant reactivity with TCE. However, sulfidation with sulfide leaves most of the nZVI as Fe(0), whereas dithionite converts a majority of the nZVI to FeS (thus consuming much of the reducing capacity originally provided by the Fe(0)). Simplified numerical models show that the reduction kinetics of I2S and TCE are mainly dependent on the initial reducing equivalents and that the TCE reduction rate is affected by the aging of FeS. Overall, the results suggest that pretreatment of nZVI with reducing sulfur compounds could result in substantial improvement in nZVI selectivity. PMID:27454131

  1. Functional Fixedness and Functional Reduction as Common Sense Reasonings in Chemical Equilibrium and in Geometry and Polarity of Molecules.

    ERIC Educational Resources Information Center

    Furio, C.; Calatayud, M. L.; Barcenas, S. L.; Padilla, O. M.

    2000-01-01

    Focuses on learning difficulties in procedural knowledge, and assesses the procedural difficulties of grade 12 and first- and third-year university students based on common sense reasoning in two areas of chemistry--chemical equilibrium and geometry, and polarity of molecules. (Contains 55 references.) (Author/YDS)

  2. COMPUTER AIDED CHEMICAL PROCESS DESIGN METHODOLOGIES FOR POLLUTION REDUCTION(SYSTEMS ANALYSIS BRANCH, SUSTAINABLE TECHNOLOGY DIVISION, NRMRL)

    EPA Science Inventory

    The objective of the project is to develop computer optimization and simulation methodologies for the design of economical chemical manufacturing processes with a minimum of impact on the environment. The computer simulation and optimization tools developed in this project can be...

  3. On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. V. Comparison and Properties of Electrochemical and Chemical Rate Constants

    DOE R&D Accomplishments Database

    Marcus, R. A.

    1962-01-01

    Using a theory of electron transfers which takes cognizance of reorganization of the medium outside the inner coordination shell and of changes of bond lengths inside it, relations between electrochemical and related chemical rate constants are deduced and compared with the experimental data. A correlation is found, without the use of arbitrary parameters. Effects of weak complexes with added electrolytes are included under specified conditions. The deductions offer a way of coordinating a variety of data in the two fields, internally as well as with each those in another. For example, the rate of oxidation or reduction of a series of related reactants by one reagent is correlated with that of another and with that of the corresponding electrochemical oxidation-reduction reaction, under certain specified conditions. These correlations may also provide a test for distinguishing an electron from an atom transfer mechanism. (auth)

  4. Reduction of Large Detailed Chemical Kinetic Mechanisms for Autoignition Using Joint Analyses of Reaction Rates and Sensitivities

    SciTech Connect

    Saylam, A; Ribaucour, M; Pitz, W J; Minetti, R

    2006-11-29

    A new technique of reduction of detailed mechanisms for autoignition, which is based on two analysis methods is described. An analysis of reaction rates is coupled to an analysis of reaction sensitivity for the detection of redundant reactions. Thresholds associated with the two analyses have a great influence on the size and efficiency of the reduced mechanism. Rules of selection of the thresholds are defined. The reduction technique has been successfully applied to detailed autoignition mechanisms of two reference hydrocarbons: n-heptane and iso-octane. The efficiency of the technique and the ability of the reduced mechanisms to reproduce well the results generated by the full mechanism are discussed. A speedup of calculations by a factor of 5.9 for n-heptane mechanism and by a factor of 16.7 for iso-octane mechanism is obtained without losing accuracy of the prediction of autoignition delay times and concentrations of intermediate species.

  5. Single-step treatment of 2,4-dinitrotoluene via zero-valent metal reduction and chemical oxidation.

    PubMed

    Thomas, J Mathew; Hernandez, Rafael; Kuo, Chiang-Hai

    2008-06-30

    Many nitroaromatic compounds (NACs) are considered toxic and potential carcinogens. The purpose of this study was to develop an integrated reductive/oxidative process for treating NACs contaminated waters. The process consists of the combination of zero-valent iron and an ozonation based treatment technique. Corrosion promoters are added to the contaminated water to minimize passivation of the metallic species. Water contaminated with 2,4-dinitrotoluene (DNT) was treated with the integrated process using a recirculated batch reactor. It was demonstrated that addition of corrosion promoters to the contaminated water enhances the reduction of 2,4-DNT with zero-valent iron. The addition of corrosion promoters resulted in 62% decrease in 2,4-DNT concentration to 2,4-diaminotoluene. The data shows that iron reduced the 2,4-DNT and ozone oxidized these products resulting in a 73% removal of TOC and a 96% decrease in 2,4-DNT concentration. PMID:18166266

  6. Interplay between grain size reduction, chemical reaction, and shear localization in lower crustal rocks: a case study from Archaean Bundelkhand Craton, North-Central India

    NASA Astrophysics Data System (ADS)

    Bhandari, Ankit; Nasipuri, Pritam; Saha, Lopamudra; Pati, Jayanta Kumar; Sarkar, Saheli; Purohit, Rohan

    2016-04-01

    Weakening of the rocks is pronounced during the formation of shear zone. Crustal scale shear zones at the plate boundary develop due to grain size reduction, either by mechanical breakdown of minerals or by the development of new minerals due to change in pressure (P) - temperature (T) conditions. In either of the mechanisms for grain size reduction, the Gibb's free energy of the system should be minimum in value to stabilize the mineral.In this contribution, we have studied the deformation mechanism and P-T conditions from acrustal scale shear zone, in the North Central Part of Archaean Bundelkhand Craton. In the Archaean Buldelkhand craton, tens of kilometre wide E-W trending shear zone developed in the sodic-potassic granite. The undeformed rock (protolith) is characterized by euhedral to subhedral sodic feldspar (XAb =0.80) and subordinate quartz, whereas the deformed rock is characterized by the development of extremely deformed feldspar and quartz associated with chlorite. The onset of the strain localization and shear zone formation in the proto-mylonite has been accompanied by developing brittle fractures in the euhedral feldspar grains. In contrast to the brittle deformation in feldspar, quartz grains are characterized by development of small bulges around the grain boundary. Chlorite develops at the fractures in the feldspar that are indicative of fluid infiltration in the proto-mylonite.In the extremely deformed samples (ultramylonite) grain size reduction occurs by bulging recrystallization in quartz. Flow stress obtained from grain size analysis of quartz indicates that the palaeo-stress varies from ~44-46 MPa in proto-mylonite to ~ 61-63 MPa in Ultra-mylonite. Mineral chemical analysis of undeformed feldspar grains in the protolith and mylonite indicate significant changes in the chemical composition that leads to minimum Gibbs energy. Also the presence of chlorite indicates hydration reaction, which has reduced the chemical energy of the system

  7. One-pot wet-chemical co-reduction synthesis of bimetallic gold-platinum nanochains supported on reduced graphene oxide with enhanced electrocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, De-Jun; Zhang, Qian-Li; Feng, Jin-Xia; Ju, Ke-Jian; Wang, Ai-Jun; Wei, Jie; Feng, Jiu-Ju

    2015-08-01

    In this work, a simple, rapid and facile one-pot wet-chemical co-reduction method is developed for synthesis of bimetallic Au-Pt alloyed nanochains supported on reduced graphene oxide (Au-Pt NCs/RGO), in which caffeine is acted as a capping agent and a structure-directing agent, while no any seed, template, surfactant or polymer involved. The as-prepared nanocomposites display enlarged electrochemical active surface area, significantly enhanced catalytic activity and better stability for methanol and ethylene glycol oxidation, compared with commercial Pt-C (Pt 50 wt%), PtRu-C (Pt 30 wt% and Ru 15 wt%) and Pt black.

  8. Enhanced reduction of Fe(II)EDTA-NO/Fe(III)EDTA in NO(x) scrubber solution using a three-dimensional biofilm-electrode reactor.

    PubMed

    Zhou, Ya; Gao, Lin; Xia, Yin-Feng; Li, Wei

    2012-11-20

    A promising technique called chemical absorption-biological reduction (CABR) integrated approach has been developed recently for the nitrogen oxides (NO(x)) removal from flue gases. The major challenge for this approach is how to enhance the rate of the biological reduction step. To tackle the challenge, a three-dimensional biofilm-electrode reactor (3D-BER) was utilized. This reactor provides not only considerable amount of sites for biofilm, but also many electron donors for bioreduction. Factors affecting the performance of 3D-BER were optimized, including material of the third electrode (graphite), glucose concentration (1000 mg·L(-1)), and volume current density (30.53 A·m(-3) NCC). Experimental results clearly demonstrated that this method significantly promotes the bioreduction rate of Fe(II)EDTA-NO (0.313 mmol·L(-1)·h(-1)) and Fe(III)EDTA (0.564 mmol·L(-1)·h(-1)) simultaneously. Experiments on the mechanism showed that Fe(II)EDTA serves as the primary electron donor in the reduction of Fe(II)EDTA-NO, whereas the reduction of Fe(III)EDTA took advantage of both glucose and electrolysis-generated H(2) as electron donors. High concentration of Fe(II)EDTA-NO or Fe(III)EDTA interferes the bioreduction of the other one. The proposed methodology shows a promising prospect for NO(x) removal from flue gas. PMID:23113866

  9. Reduction on the anaerobic biological activity inhibition caused by heavy metals and sulphates in effluents through chemical precipitation with soda and lime.

    PubMed

    Alves, L de Carvalho; Cammarota, M C; De França, F P

    2006-12-01

    The School of Chemistry Environmental Technology Laboratory generates 43.4 1 of effluent with low pH (0.7) and high contents of COD (1908 mgO2 l(-1)), phenol (132.1 mg l(-1)), sulfate (36700 mg l(-1)) and heavy metals (28.2 mg Hg l(-1); 82.1 mg Cr(total) l(-1); 30.8 mg Cu l(-1); 57.4 mg Fe(total) l(-1); 16.2 mg Al l(-1)) weekly. These data show that this effluent presents high toxicity for biological treatment, with a physical-chemical step being necessary before a biological step. Preliminary studies showed that the most toxic constituents of the effluent were sulfate, phenol and total chromium. In this work, a chemical precipitation step with sodium hydroxide or lime was evaluated for the toxicity reduction on anaerobic microbial consortium. These experiments were carried out with increasing concentrations of alkalis in the effluent in order to obtain pH initial values of 8-12. Similar results were obtained for COD (15-28%), turbidity (95-98%), phenol (13-24%) and total chromium (99.8-99.9%) removals in each condition studied with soda or lime. Sulfate was only removed by precipitation with lime, obtaining reductions from 84 to 88%. The toxicity on the anaerobic sludge was studied employing specific methanogenic activity (SMA) analysis of raw and treated effluent (after chemical precipitation step). The SMA experiments showed that chemical precipitation at pH 8 reduces the toxic effect of the effluent on anaerobic microbial consortium three times (with soda) and thirteen times (with lime). These results indicate that precipitation with lime is more efficient at toxicity removal, however the produced sludge volume is around two times higher than that produced with soda. PMID:17285944

  10. Solutia: Massachusetts Chemical Manufacturer Uses SECURE Methodology to Identify Potential Reductions in Utility and Process Energy Consumption

    SciTech Connect

    2005-07-01

    This case study prepared for the U.S. Department of Energy's Industrial Technologies Program describes a plant-wide energy assessment conducted at the Solutia Inc. chemical production facility in Springfield, Massachusetts. Solutia manufactures polymers, intermediates, and chemicals for a variety of products. The assessment focused on finding ways to reduce the plant's use of steam, electricity, compressed air, and water. If the company were to implement all the recommendations that came out of the assessment, its total annual energy savings could be about 9.6 million kWh for electricity and more than 338,000 MBtu for natural gas. Annual cost savings could amount to nearly $3.3 million.

  11. Sorption and toxicity reduction of pharmaceutically active compounds and endocrine disrupting chemicals in the presence of colloidal humic acid.

    PubMed

    Kim, Injeong; Kim, Hyo-Dong; Jeong, Tae-Yong; Kim, Sang Don

    2016-01-01

    This study investigated the toxicity changes and sorption of pharmaceuticals and endocrine disrupters in the presence of humic acid (HA). For the sorption experiment, a dead end filtration (DEF) system was used to separate bound and free-form target compounds. An algae growth inhibition test and E-screen assay were conducted to estimate the toxic effect of pharmaceutically active compounds (PhACs) and endocrine disrupting chemicals (EDCs), respectively. The permeate concentration was confirmed using liquid chromatography-mass spectrometry. In the sorption test, we observed significant sorption of PhACs and EDCs on colloidal HA, except for sulfamethoxazole (SMX). The values of log KCOC derived from DEF determinations ranged from 4.40 to 5.03. The removal efficiency varied with the HA concentration and the target chemical properties. Tetracycline and 4-octylphenol showed the highest sorption or removal efficiency (≈50%), even at 5 mg C/L HA. The algal growth inhibition of PhACs and the estrogenic effects of EDCs were significantly decreased in proportion to HA concentrations, except for SMX. In addition, the chemical analysis results showed a positive relationship with the bioassay results. Consequently, the sorption of PhACs and EDCs onto colloidal HA should be emphasized in natural environments because it significantly reduces bioavailable concentrations and toxicity to aquatic organisms. PMID:27533865

  12. Flow processes in overexpanded chemical rocket nozzles. Part 3: Methods for the aimed flow separation and side load reduction

    NASA Technical Reports Server (NTRS)

    Schmucker, R. H.

    1983-01-01

    Methods aimed at reduction of overexpansion and side load resulting from asymmetric flow separation for rocket nozzles with a high opening ratio are described. The methods employ additional measures for nozzles with a fixed opening ratio. The flow separation can be controlled by several types of nozzle inserts, the properties of which are discussed. Side loads and overexpansion can be reduced by adapting the shape of the nozzle and taking other additional measures for controlled separation of the boundary layer, such as trip wires.

  13. Chemical oxygen demand, total organic carbon and colour reduction in slaughterhouse wastewater by unmodified and iron-modified clinoptilolite-rich tuff.

    PubMed

    Torres-Pérez, J; Solache-Ríos, M; Martínez-Miranda, V

    2014-01-01

    In this study, reduction of chemical oxygen demand (COD), colour, and total organic carbon in effluents from a slaughterhouse in central Mexico was performed using clinoptilolite-rich tuff. The experimental parameters considered were initial concentration of the adsorbate, pH, adsorbent dosage, and contact time. Surface morphology of the materials was tested by using scanning electron microscopy. Specific surface area was analysed by using Brunauer-Emmett-Teller (BET) and phase composition was analysed by using X-ray diffraction. The experimental adsorption data were fitted to the first- and pseudo-second-order kinetic models. The highest COD removal was observed in slightly acidic pH conditions. The maximum reduction efficiency of COD was accomplished with unmodified clinoptilolite-rich tuff at a contact time of 1440 min. In these conditions, the adsorbent was efficient for treating wastewater from a slaughterhouse. Moreover, after several regeneration cycles with Fenton reagent or hydrogen peroxide, the regenerated zeolite with H2O2 (3%) showed the best reduction efficiencies. PMID:24701954

  14. Three-dimensional assemblies of graphene prepared by a novel chemical reduction-induced self-assembly method

    NASA Astrophysics Data System (ADS)

    Zhang, Lianbin; Chen, Guoying; Hedhili, Mohamed Nejib; Zhang, Hongnan; Wang, Peng

    2012-10-01

    In this study, three-dimensional (3D) graphene assemblies are prepared from graphene oxide (GO) by a facile in situ reduction-assembly method, using a novel, low-cost, and environment-friendly reducing medium which is a combination of oxalic acid (OA) and sodium iodide (NaI). It is demonstrated that the combination of a reducing acid, OA, and NaI is indispensable for effective reduction of GO in the current study and this unique combination (1) allows for tunable control over the volume of the thus-prepared graphene assemblies and (2) enables 3D graphene assemblies to be prepared from the GO suspension with a wide range of concentrations (0.1 to 4.5 mg mL-1). To the best of our knowledge, the GO concentration of 0.1 mg mL-1 is the lowest GO concentration ever reported for preparation of 3D graphene assemblies. The thus-prepared 3D graphene assemblies exhibit low density, highly porous structures, and electrically conducting properties. As a proof of concept, we show that by infiltrating a responsive polymer of polydimethylsiloxane (PDMS) into the as-resulted 3D conducting network of graphene, a conducting composite is obtained, which can be used as a sensing device for differentiating organic solvents with different polarity.In this study, three-dimensional (3D) graphene assemblies are prepared from graphene oxide (GO) by a facile in situ reduction-assembly method, using a novel, low-cost, and environment-friendly reducing medium which is a combination of oxalic acid (OA) and sodium iodide (NaI). It is demonstrated that the combination of a reducing acid, OA, and NaI is indispensable for effective reduction of GO in the current study and this unique combination (1) allows for tunable control over the volume of the thus-prepared graphene assemblies and (2) enables 3D graphene assemblies to be prepared from the GO suspension with a wide range of concentrations (0.1 to 4.5 mg mL-1). To the best of our knowledge, the GO concentration of 0.1 mg mL-1 is the lowest GO

  15. Chemical exposure reduction: Factors impacting on South African herbicide sprayers' personal protective equipment compliance and high risk work practices.

    PubMed

    Andrade-Rivas, Federico; Rother, Hanna-Andrea

    2015-10-01

    The high exposure risks of workers to herbicides in low- and middle-income countries is an important public health concern because of the potential resulting negative impacts on workers' health. This study investigated workers' personal protective equipment (PPE) compliance as a risk mitigation measure; particularly workers who apply herbicides for Working for Water (WfW) - a South African invasive alien vegetation control programme. The study aim was to understand workers' low PPE compliance by analysing their risk perceptions of herbicide use, working conditions and socio-cultural context. Research methods included ethnographic observations, informal interviews, visual media, questionnaires and a focus group. Study results indicated that low PPE compliance persists despite workers' awareness of herbicide exposure risks and as a result of the influence from workers' socio-cultural context (i.e. gender dynamics and social status), herbicide risk perceptions and working conditions (i.e. environmental and logistical). Interestingly, teams comprised of mostly women had the highest compliance rate. These findings highlighted that given the complexity of PPE compliance, especially in countries with several economic and social constraints, exposure reduction interventions should not rely solely on PPE use promotion. Instead, other control strategies requiring less worker input for effectiveness should be implemented, such as elimination and substitution of highly hazardous pesticides, and altering application methods. PMID:26093240

  16. Reduction of carbon dioxide gas formation at the anode of a direct methanol fuel cell using chemically enhanced solubility

    NASA Astrophysics Data System (ADS)

    Lundin, Michael D.; McCready, Mark J.

    The production of CO 2 gas at the DMFC anode leads to dramatic increases in pumping power requirements and reduced power output because of mass transfer limitations as bubble trains form in the channels of larger stacks. Experimental observations taken in a 5 cm 2 DMFC test cell operated at 60 °C, 1 atm, and with a methanol/water fuel flow rates of 5-10 cm 3 min -1 indicate that the rate of bubble formation can be reduced by increasing the fuel flow because more liquid is available for the CO 2 to dissolve in. Further observations indicate that KOH and LiOH added to the fuel eliminates CO 2 gas formation in situ at low concentrations because of the greatly increased solubility that results. A mathematical model for the volumetric rate of CO 2 gas production that includes effects of temperature and solubility is developed and extended to include the effects of hydroxide ions in solution. The model is used to predict the onset location of gas formation in the flow field as well as the void fraction at any point in the flow field. Predictions from the model agree very well with our experiments. Model predictions explain differences in the initial location of bubble formation for fuel solutions pre-saturated with CO 2 as opposed to CO 2-free solutions. Experiments with KOH and LiOH added to fuel solutions confirm the validity of the model extension that includes solubility that is enhanced by chemical reaction. Experiments with LiOH, KOH, and ammonium hydroxide show that the long-term durability of standard Pt-Ru/Nafion ®/Pt membrane electrode assemblies is compromised because of the presence of lithium, potassium, and ammonium cations that interact with the Nafion ® membrane and result in increasing the ohmic limitations of the polymer electrolyte membrane. Experiments with Ca(OH) 2, while reducing gas formation, precipitate the product CaCO 3 out of solution too rapidly for downstream filtering, blocking channels in the flow field.

  17. Using chemical reactivity to provide insights into environmental transformations of priority organic substances: the Fe⁰-mediated reduction of Acid Blue 129.

    PubMed

    Shirin, Salma; Balakrishnan, Vimal K

    2011-12-15

    Sulfonated anthracenedione dyes are medium priority organic compounds targeted for environmental assessment under the Government of Canada's Chemical Management Plan (CMP). Since organic compounds undergo transformations in environmental matrices, understanding these transformations is critical for a proper assessment of their environmental fate. In the current study, we used zero-valent iron (ZVI) to provide insight into reductive transformation processes available to the anthracenedione dye, Acid Blue 129 (AB 129), a dye which is used in the textile industry. At high temperatures, we found that AB 129 was rapidly reduced (within 3 h) after being adsorbed onto the ZVI-surface, whereupon decomposition took place via multiple competitive and consecutive reaction pathways. Reaction products were identified using state-of-the-art accurate mass Liquid Chromatography-Quadrupole Time of Flight-Mass Spectroscopy (LC-QToF-MS). Five transformation products were identified, including a genotoxic (and thus, potentially carcinogenic) end-product, 2,4,6-trimethylaniline. The same products were found at room temperature, demonstrating that the transformation pathways revealed here could plausibly arise from biological and/or environmental reductions of AB 129. Our results demonstrate the importance of identifying reaction product arising from priority substances as part of the environmental risk assessment process. PMID:22050543

  18. Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Mohammadi Ziarani, Ghodsi

    2015-01-01

    In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol-gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV-light-assisted photo and NaBH4 -assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles. PMID:25809844

  19. Kinetics of the reduction of hematite (Fe{sub 2}O{sub 3}) by methane (CH{sub 4}) during chemical looping combustion: A global mechanism

    SciTech Connect

    Monazam, Esmail R; Breault, Ronald W; Siriwardane, Ranjani; Richards, George; Carpenter, Stephen

    2013-10-01

    Chemical-looping combustion (CLC) has emerged as a promising technology for fossil fuel combustion which produces a sequestration ready concentrated CO{sub 2} stream in power production. A CLC system is composed with two reactors, an air and a fuel reactor. An oxygen carrier such as hematite (94%Fe{sub 2}O{sub 3}) circulates between the reactors, which transfers the oxygen necessary for the fuel combustion from the air to the fuel. An important issue for the CLC process is the selection of metal oxide as oxygen carrier, since it must retain its reactivity through many cycles. The primary objective of this work is to develop a global mechanism with respective kinetics rate parameters such that CFD simulations can be performed for large systems. In this study, thermogravimetric analysis (TGA) of the reduction of hematite (Fe{sub 2}O{sub 3}) in a continuous stream of CH{sub 4} (15, 20, and 35%) was conducted at temperatures ranging from 700 to 825{degrees}C over ten reduction cycles. The mass spectroscopy analysis of product gas indicated the presence of CO{sub 2} and H{sub 2}O at the early stage of reaction and H{sub 2} and CO at the final stage of reactions. A kinetic model based on two parallel reactions, 1) first-order irreversible rate kinetics and 2) Avrami equation describing nucleation and growth processes, was applied to the reduction data. It was found, that the reaction rates for both reactions increase with, both, temperature and the methane concentration in inlet gas.

  20. Reduction of Surrogates for Escherichia coli O157:H7 and Salmonella during the Production of Nonintact Beef Products by Chemical Antimicrobial Interventions.

    PubMed

    Ulbrich, Carson J; Lucia, Lisa M; Arnold, Ashley N; Taylor, T Matthew; Savell, Jeffrey W; Gehring, Kerri B

    2015-05-01

    The efficacy of chemical antimicrobials for controlling Escherichia coli O157:H7 and Salmonella during production of marinated nonintact beef products was evaluated using nonpathogenic surrogates. Boneless beef strip loins were inoculated with either approximately 5.8 or 1.9 log CFU/cm(2) (high and low inoculation levels, respectively) of nonpathogenic rifampin-resistant E. coli. Inoculated strip loins were chilled at 2°C for 24 h, vacuum packaged, and aged for 7 to 24 days at 2°C. After aging, strip loins received no treatment (control) or one of five antimicrobial spray treatments: 2.5% L-lactic acid (pH 2.6), 5.0% L-lactic acid (pH 2.4), 1,050 ppm of acidified sodium chlorite (pH 2.8), 205 ppm of peroxyacetic acid (pH 5.2), or tap water (pH 8.6). Mean application temperatures were 53, 26, 20, and 18°C for lactic acid, water, peroxyacetic acid, and acidified sodium chlorite treatments, respectively. Treated and control strip loins were vacuum tumbled in a commercial marinade. Samples were collected throughout the experiment to track the effects of antimicrobial treatment and processing on inoculated surrogates. For high-inoculation strip loins, the 5.0% L-lactic acid treatment was most effective for reducing surrogates on meat surfaces before marination, producing a 2.6-log mean reduction. Peroxyacetic acid treatment resulted in the greatest reduction of surface-located surrogate microorganisms in marinated product. Water treatment resulted in greater internalization of surrogate microorganisms compared with the control, as determined by enumeration of surrogates from cored samples. Producers of nonintact beef products should focus on use of validated antimicrobial sprays that maximize microbial reduction and minimize internalization of surface bacteria into the finished product. PMID:25951381

  1. Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: insights from dual element isotope analysis (13C/12C, 37Cl/35Cl).

    PubMed

    Cretnik, Stefan; Thoreson, Kristen A; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

    2013-07-01

    Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors ε(carbon) and ε(chlorine) (i.e., molecular-average isotope effects) were -12.2‰ ± 0.5‰ and -3.6‰ ± 0.1‰ with Geobacter lovleyi strain SZ; -9.1‰ ± 0.6‰ and -2.7‰ ± 0.6‰ with Desulfitobacterium hafniense Y51; -16.1‰ ± 0.9‰ and -4.0‰ ± 0.2‰ with the enzymatic cofactor cobalamin; -21.3‰ ± 0.5‰ and -3.5‰ ± 0.1‰ with cobaloxime. Dual element isotope slopes m = Δδ(13)C/ Δδ(37)Cl ≈ ε(carbon)/ε(chlorine) of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems. PMID:23627862

  2. Reduction kinetics of Cu-, Ni-, and Fe-based oxygen carriers using syngas (CO + H{sub 2}) for chemical-looping combustion

    SciTech Connect

    Alberto Abad; Francisco Garcia-Labiano; Luis F. de Diego; Pilar Gayn; Juan Adnez

    2007-08-15

    The reactivity of three Cu-, Fe-, and Ni-based oxygen carriers to be used in a chemical-looping combustion (CLC) system using syngas as fuel has been analyzed. The oxygen carriers exhibited high reactivity during reduction with fuel gases present in syngas (H{sub 2} and CO), with average values in the range 8-30% min{sup -1}. No effect of the gas products (H{sub 2}O, CO{sub 2}) on the reduction reaction rate was detected. The kinetic parameters of reaction with H{sub 2} and CO have been determined by thermogravimetric analysis. The grain model with spherical or platelike geometry in the grain was used for the kinetic determination, in which the chemical reaction controlled the global reaction rate. The activation energies determined for these reactions were low, with values ranging from 14 to 33 kJ mol{sup -1}. The reaction order depended on the reacting gas, and values from 0.5 to 1 were found. Moreover, the reactivity of the oxygen carriers when both H{sub 2} and CO are simultaneously present in the reacting gases has been analyzed, both at atmospheric and pressurized conditions. For the Cu- and Fe-based oxygen carriers, the reaction rate of the oxygen carrier with syngas corresponded to the addition of the reaction rates for the individual fuel gases, H{sub 2} and CO. For the Ni-based oxygen carrier, the reaction rate was that corresponding to the fuel gas that reacted faster with the oxygen carrier at the reacting conditions (fuel concentration, temperature, and pressure). The consequences of the behavior of the reaction of syngas and the water-gas shift (WGS) equilibrium on the design of the fuel reactor of a CLC system have been analyzed. A preliminary estimation of the solids inventory for the use of syngas in the fuel reactor of a CLC system gave values in the range of 19-34 kg MW{sup -1} when the WGS equilibrium was considered to be instantaneous. 8 figs., 4 tabs.

  3. Photo-chemical reduction of iodate (IO3-) in sea-water leading to the emission of iodine (I2) in the atmosphere

    NASA Astrophysics Data System (ADS)

    Kumar, R.

    2013-12-01

    Iodine exists in open seawaters mainly in the inorganic forms iodate (IO3-) and iodide (I-). While the concentration of IO3- predominates in deep water, I- concentrations increase toward the surface. The primary precursor for iodine oxide particle (IOP) formation in the coastal marine boundary layer (MBL) is iodine (I2) originating from exposed macroalgae. In contrast, recent field measurements of IO above the open ocean suggest that biogenic organic-iodine emissions cannot account for the observed levels. Thus, the alternative mechanisms include the reduction of IO3- to I- in seawater which in turn is converted to, and emitted as I2 to the atmosphere which may contribute to observed levels of I2 in the MBL. In this study a series of laboratory investigations of the photo-chemical reduction of iodate (IO3-) to both aqueous iodide (I-) and a bound, soluble iodinated organic form have been conducted to investigate three potentially important processes likely to participate in the recycling of I2 from seawater in the presence of sunlight: (i) the role of dissolved organic materials (i.e. humic acid), (ii) the effect of salinity (Cl- concentration) and (iii) deposition and uptake of O3. The experiments involved the initial photolysis of IO3- solutions with either humic acid or Cl- added. The formation of I- in solution (due to IO3- reduction) was detected using time-resolved UV-Vis spectroscopy. Oxidation of iodide ions to I2 formation in the solutions and release to the gas-phase was confirmed indirectly by the detection of iodine oxide particles (IOPs) generated by the photo-oxidation of the gas-phase I2 released from solution using a coupled differential mobility analyser (DMA) and Faraday cup electrometer (FCE) system. The results indicate a constant fraction of ~ 20% of reduced iodate is in the form free iodide (I-) and by difference, ~ 80% of reduced iodate is most likely in an iodinated humic acid. Iodine (I2) is emitted by the uptake of ozone on iodide (I

  4. Chemical speciation of PM emissions from heavy-duty diesel vehicles equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) retrofits

    NASA Astrophysics Data System (ADS)

    Biswas, Subhasis; Verma, Vishal; Schauer, James J.; Sioutas, Constantinos

    Four heavy-duty diesel vehicles (HDDVs) in six retrofitted configurations (CRT ®, V-SCRT ®, Z-SCRT ®, Horizon, DPX and CCRT ®) and a baseline vehicle operating without after--treatment were tested under cruise (50 mph), transient UDDS and idle driving modes. As a continuation of the work by Biswas et al. [Biswas, S., Hu, S., Verma, V., Herner, J., Robertson, W.J., Ayala, A., Sioutas, C., 2008. Physical properties of particulate matter (PM) from late model heavy-duty diesel vehicles operating with advanced emission control technologies. Atmospheric Environment 42, 5622-5634.] on particle physical parameters, this paper focuses on PM chemical characteristics (Total carbon [TC], Elemental carbon [EC], Organic Carbon [OC], ions and water-soluble organic carbon [WSOC]) for cruise and UDDS cycles only. Size-resolved PM collected by MOUDI-Nano-MOUDI was analyzed for TC, EC and OC and ions (such as sulfate, nitrate, ammonium, potassium, sodium and phosphate), while Teflon coated glass fiber filters from a high volume sampler were extracted to determine WSOC. The introduction of retrofits reduced PM mass emissions over 90% in cruise and 95% in UDDS. Similarly, significant reductions in the emission of major chemical constituents (TC, OC and EC) were achieved. Sulfate dominated PM composition in vehicle configurations (V-SCRT ®-UDDS, Z-SCRT ®-Cruise, CRT ® and DPX) with considerable nucleation mode and TC was predominant for configurations with less (Z-SCRT ®-UDDS) or insignificant (CCRT ®, Horizon) nucleation. The transient operation increases EC emissions, consistent with its higher accumulation PM mode content. In general, solubility of organic carbon is higher (average ˜5 times) for retrofitted vehicles than the baseline vehicle. The retrofitted vehicles with catalyzed filters (DPX, CCRT ®) had decreased OC solubility (WSOC/OC: 8-25%) unlike those with uncatalyzed filters (SCRT ®s, Horizon; WSOC/OC ˜ 60-100%). Ammonium was present predominantly in the

  5. IN SITU CHEMICAL REDUCTION OF CR(VI) IN GROUNDWATER USING A COMBINATION OF FERROUS SULFATE AND SODIUM DITHIONITE: A FIELD INVESTIGATION

    EPA Science Inventory

    A field pilot test was conducted to evaluate the effectiveness of a FeSO4 + Na2S2O4 reductant solution blend for in situ saturated zone treatment of dissolved-phase Cr(VI) at the former Macalloy Corporation site in Charleston, SC. The reductant blend was injected into the path o...

  6. Impact of reaction parameters on the chemical profile of 3,4-methylenedioxymethamphetamine synthesized via reductive amination: target analysis based on GC-qMS compared to non-targeted analysis based on GC×GC-TOF-MS.

    PubMed

    Schäffer, M; Dieckmann, S; Pütz, M; Kohles, T; Pyell, U; Zimmermann, R

    2013-12-10

    The most common clandestine manufacturing procedure for the ecstasy derivative 3,4-methylenedioxymethamphetamine (MDMA), is the reductive amination of piperonylmethylketone (PMK) via platinum(IV) oxide/hydrogen. Deviations of the reaction conditions during the synthesis may result in different chemical profiles of the products. The chemical analysis of these profiles is an important objective for forensic drug intelligence. In this work we studied the impact of a systematic variation of the hydrogenation time, the reaction temperature and the precursor batch on the resulting organic chemical profiles of the MDMA bases and MDMA hydrochlorides. Target analysis was based on a gas chromatography mass spectrometry (GC-MS) method which was harmonized during the European project CHAMP.(2) In addition, samples were analyzed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) and subjected to non-targeted data analysis for a comprehensive analysis of the complete profiles. The reaction temperature, followed by the used precursor batch, revealed the highest impact on the chemical profile. The effect on individual impurity compounds is discussed in detail. With respect to the interpretation of the data, the profiles were compared to the profiles of MDMA samples obtained by reductive amination using sodium borohydride ("cold method") and aluminium/mercury amalgam as alternative reducing agents. Non-targeted analysis revealed that the discrimination according to the synthetic route and the batch of precursor used for the synthesis strongly depends on the selected target compounds. PMID:24314521

  7. Use of HPLC/UPLC-spectrophotometry for detection of formazan in in vitro Reconstructed human Tissue (RhT)-based test methods employing the MTT-reduction assay to expand their applicability to strongly coloured test chemicals.

    PubMed

    Alépée, N; Barroso, J; De Smedt, A; De Wever, B; Hibatallah, J; Klaric, M; Mewes, K R; Millet, M; Pfannenbecker, U; Tailhardat, M; Templier, M; McNamee, P

    2015-06-01

    A number of in vitro test methods using Reconstructed human Tissues (RhT) are regulatory accepted for evaluation of skin corrosion/irritation. In such methods, test chemical corrosion/irritation potential is determined by measuring tissue viability using the photometric MTT-reduction assay. A known limitation of this assay is possible interference of strongly coloured test chemicals with measurement of formazan by absorbance (OD). To address this, Cosmetics Europe evaluated use of HPLC/UPLC-spectrophotometry as an alternative formazan measurement system. Using the approach recommended by the FDA guidance for validation of bio-analytical methods, three independent laboratories established and qualified their HPLC/UPLC-spectrophotometry systems to reproducibly measure formazan from tissue extracts. Up to 26 chemicals were then tested in RhT test systems for eye/skin irritation and skin corrosion. Results support that: (1) HPLC/UPLC-spectrophotometry formazan measurement is highly reproducible; (2) formazan measurement by HPLC/UPLC-spectrophotometry and OD gave almost identical tissue viabilities for test chemicals not exhibiting colour interference nor direct MTT reduction; (3) independent of the test system used, HPLC/UPLC-spectrophotometry can measure formazan for strongly coloured test chemicals when this is not possible by absorbance only. It is therefore recommended that HPLC/UPLC-spectrophotometry to measure formazan be included in the procedures of in vitro RhT-based test methods, irrespective of the test system used and the toxicity endpoint evaluated to extend the applicability of these test methods to strongly coloured chemicals. PMID:25701760

  8. N2O production in the Fe(II)(EDTA)-NO reduction process: the effects of carbon source and pH.

    PubMed

    Chen, Jun; Wang, Lei; Zheng, Ji; Chen, Jianmeng

    2015-07-01

    Chemical absorption-biological reduction (BioDeNOx), which uses Fe(II)(EDTA) as a complexing agent for promoting the mass transfer efficiency of NO from gas to water, is a promising technology for removing nitric oxide (NO) from flue gases. The carbon source and pH are important parameters for Fe(II)(EDTA)-NO (the production of absorption) reduction and N2O emissions from BioDeNOx systems. Batch tests were performed to evaluate the effects of four different carbon sources (i.e., methanol, ethanol, sodium acetate, and glucose) on Fe(II)(EDTA)-NO reduction and N2O emissions at an initial pH of 7.2 ± 0.2. The removal efficiency of Fe(II)(EDTA)-NO was 93.9%, with a theoretical rate of 0.77 mmol L(-1) h(-1) after 24 h of operation. The highest N2O production was 0.025 mmol L(-1) after 3 h when glucose was used as the carbon source. The capacities of the carbon sources to enhance the activity of the Fe(II)(EDTA)-NO reductase enzyme decreased in the following order based on the C/N ratio: glucose > ethanol > sodium acetate > methanol. Over the investigated pH range of 5.5-8.5, the Fe(II)(EDTA)-NO removal efficiency was highest at a pH of 7.5, with a theoretical rate of 0.88 mmol L(-1) h(-1). However, the N2O production was lowest at a pH of 8.5. The primary effect of pH on denitrification resulted from the inhibition of nosZ in acidic conditions. PMID:25698260

  9. A COMPARATIVE RISK REDUCTION ANALYSIS OF THE OFFICE OF SOLID WASTE'S WASTE MINIMIZATION PRIORITY CHEMICALS INITIATIVE USING THE 3MRA MULTIMEDIA MODELING SYSTEM

    EPA Science Inventory

    A study was initiated by the EPA/ORD National Exposure Research Lab (NERL) in FY05 to quantify risk reduction resulting from this national EPA initiative to reduce WMPC disposal. Using the 3MRA modeling system, which was recommended for use by the EPA Science Advisory Board for ...

  10. Effect of natural Bayah zeolite particle size reduction to physico-chemical properties and absortion against potassium permanganate (KMnO4)

    NASA Astrophysics Data System (ADS)

    Widayanti, Siti Mariana; Syamsu, Khaswar; Warsiki, Endang; Yuliani, Sri

    2016-02-01

    Recently, researches on nanotechnology have been developed very rapid, as well as the utilization of nano-zeolites. Nano-sized material has several advantages which are expanding absorptive surfaces so it will enhance the material absorption and shorten the absorption time. Zeolite as a KMnO4 binder, has been widely recognized for its ability to extend the shelf life of vegetables and fruits. This study was conducted to determine zeolites physico-chemical characters from different particle size and the effect on KMnO4 absorption. Potassium permanganate (KMnO4) is a strong oxidizer for reducing the quantity of ethylene in storage process of fresh horticultural products. The treatment consisted of (1) different length of milling time (10, 20, 30, 40, and 60 minutes) and (2) the duration of chemical activation with 1 N KOH solution. Physical and chemical characters of zeolite were analyzed using BET, PSA, XRD and SEM. The research design was randomized design. The result implied that milling time was significantly affecting the zeolite particle size, material surface area, and the size of pore diameter and volume. Milling treatment for 40 minutes produced higher zeolite surface area and pore volume than other treatments. While the duration of chemical activation using 1 N KOH solution gives different effect on zeolite absorption to KMnO4 solution. Milling time for 60 minutes and activated for 48 hours has higher initial adsorption than other treatments.

  11. Studies of chemical reduction of Fe(III)*EDTA in an SO{sub 2}/NO{sub x} aqueous scrubber system

    SciTech Connect

    Li, W.; Keener, T.C.; Mendelsohn, M.; Harkness, J.B.L.; Livengood, C.D.

    1996-03-01

    Ferrous*EDTA has been found to be an effective scrubbing agent for nitric oxide gas. A major process problem is oxidation of the iron to the ferric species, leading to a significant decrease in NO{sub x}-removal capability. Argonne National Laboratory discovered a class of organic compounds that, when used with ferrous*EDTA in a sodium carbonate chemistry, could maintain high levels of NO{sub x} removal. However, those antioxidant/reducing agents (A/R) are not effective in a lime-based chemistry. In recent reports, it has been found that ascorbic acid and related compounds are capable of maintaining stable NO{sub x} removals of about 50% (compared with about 15% without the agent) in a lime-based FGD chemistry with Fe(II)*EDTA. It is believed that the improved performance of Fe(II)*EDTA is due to the catalytic action of ascorbate in the Fe(III)*EDTA reduction system, where Fe(III)*EDTA is reduced by ascorbate and oxidized ascorbate is then reduced back to the ascorbate by sulfite/bisulfite anions, which come from the dissolution of SO{sub 2} in the flue gas. In the present work, the kinetics of the reduction of ferric chelate by ascorbate and reduction of oxidized ascorbate by sulfite/bisulfite anions at a typical flue-gas scrubber-system operating temperature ({approximately}55 C) have been determined.

  12. Chemical Reduction of Nd 1.85 Ce 0.15 CuO 4− δ Powders in Supercritical Sodium Ammonia Solutions

    DOE PAGESBeta

    Dias, Yasmin; Wang, Hui; Zhou, Haiqing; Lin, Feng; Lan, Yucheng

    2015-01-01

    Nd 1.85 Ce 0.15 CuO 4− δ powders are chemically reduced in supercritical sodium ammonia solutions from room temperature to 350°C. The crystallographic structure of the reduced powders is investigated from Rietveld refinement of X-ray powder diffraction. The atomic positions are maintained constant within experimental errors while temperature factors of all atoms increase significantly after the chemical treatments, especially of Nd/Ce atoms. The ammonothermally reduced Nd 1.85 Ce 0.15 CuO 4− δ powders show diamagnetic below 24 K which is contributed to the lower oxygen content and higher temperature factors of atoms in the treated compound.more » The ammonothermal method paves a new way to reduce oxides in supercritical solutions near room temperature.« less

  13. Quantitative Determination of Paraquat in Meconium by Sodium Borohydride-Nickel Chloride Chemical Reduction and Gas Chromatography/Mass Spectrometry (GC/MS)

    PubMed Central

    Posecion, Norberto C.; Ostrea, Enrique M.; Bielawski, Dawn M.

    2008-01-01

    The objective of this study was to develop a procedure for the GC/MS assay of paraquat in meconium as a biomarker of fetal exposure to paraquat. The method involved a sodium borohydride-nickel chloride reduction procedure, liquid-liquid extraction of the perhydrogenated product, concentration, and GC/MS assay. The method demonstrated good overall recovery (102.56 %) with %CV (inter-assay) of less than 13%, and a limit of detection of 0.0156 μg/g. Analysis of meconium samples from a study population in the Philippines (n = 70) showed a 2.8% prevalence of fetal exposure to paraquat. PMID:18037033

  14. Hydrogen production from the steam-iron process with direct reduction of iron oxide by chemical looping combustion of coal char

    SciTech Connect

    Jing-biao Yang; Ning-sheng Cai; Zhen-shan Li

    2008-07-15

    Experimental results performed with a fluidized-bed reactor supported the feasibility of the three processes including direct reduction of iron oxide by char, H{sub 2} production by the steam-iron process, and the oxidation of Fe{sub 3}O{sub 4} resulting from the steam-iron process to the original Fe{sub 2}O{sub 3} by air. Chars resulting from a Chinese lignite loaded with K{sub 2}CO{sub 3} were used successfully as a reducing material, leading to the reduction of Fe{sub 2}O{sub 3} to FeO and Fe for the steam-iron process, which was confirmed by both the off-gases concentrations and X-ray diffractometer analysis. The reduction of Fe{sub 2}O{sub 3} by K-10-char at 1073 K is desirable from the perspective of the carbon conversion rate and high concentration of CO{sub 2}. The carbon in char was completely converted to CO{sub 2} when the mass ratio of Fe{sub 2}O{sub 3}/K-10-char was increased to 10/0.3. The oxidation rate of K-10-char by Fe{sub 2}O{sub 3} without a gasifying agent was comparable to the K-10-char steam gasification rate. The fractions of FeO and Fe in the reduced residue were 43 and 57%, respectively, in the case of 3 g of Fe{sub 2}O{sub 3} and 0.5 g of K-10-char, which was verified by the total H{sub 2} yield equaling 1000 mL/g K-10-char from the steam-iron process. The time that it took to achieve complete oxidation of Fe{sub 3}O{sub 4} to Fe{sub 2}O{sub 3} by air with an 8.7% O{sub 2} concentration at 1073 K was about 15 min. 53 refs., 19 figs., 5 tabs.

  15. Development and Application of Computational/In Vitro Toxicological Methods for Chemical Hazard Risk Reduction of New Materials for Advanced Weapon Systems

    NASA Technical Reports Server (NTRS)

    Frazier, John M.; Mattie, D. R.; Hussain, Saber; Pachter, Ruth; Boatz, Jerry; Hawkins, T. W.

    2000-01-01

    The development of quantitative structure-activity relationship (QSAR) is essential for reducing the chemical hazards of new weapon systems. The current collaboration between HEST (toxicology research and testing), MLPJ (computational chemistry) and PRS (computational chemistry, new propellant synthesis) is focusing R&D efforts on basic research goals that will rapidly transition to useful products for propellant development. Computational methods are being investigated that will assist in forecasting cellular toxicological end-points. Models developed from these chemical structure-toxicity relationships are useful for the prediction of the toxicological endpoints of new related compounds. Research is focusing on the evaluation tools to be used for the discovery of such relationships and the development of models of the mechanisms of action. Combinations of computational chemistry techniques, in vitro toxicity methods, and statistical correlations, will be employed to develop and explore potential predictive relationships; results for series of molecular systems that demonstrate the viability of this approach are reported. A number of hydrazine salts have been synthesized for evaluation. Computational chemistry methods are being used to elucidate the mechanism of action of these salts. Toxicity endpoints such as viability (LDH) and changes in enzyme activity (glutahoione peroxidase and catalase) are being experimentally measured as indicators of cellular damage. Extrapolation from computational/in vitro studies to human toxicity, is the ultimate goal. The product of this program will be a predictive tool to assist in the development of new, less toxic propellants.

  16. A novel approach for enhancing the catalytic efficiency of a protease at low temperature: reduction in substrate inhibition by chemical modification.

    PubMed

    Siddiqui, Khawar Sohail; Parkin, Don M; Curmi, Paul M G; De Francisci, Davide; Poljak, Anne; Barrow, Kevin; Noble, Malcolm H; Trewhella, Jill; Cavicchioli, Ricardo

    2009-07-01

    The alkaline protease, savinase was chemically modified to enhance the productivity of the enzyme at low temperatures on a complex polymeric protein (azocasein) substrate. At 5 and 15 degrees C, savinase modified with ficol or dextran hydrolyzed fivefold more azocasein than the unmodified savinase. Kinetic studies showed that the catalytic improvements are associated with changes in uncompetitive substrate inhibition with K(i) values of modified savinases sixfold higher than the unmodified savinase. Modeling of small-angle scattering data indicates that two substrate molecules bind on opposing sides of the enzyme. The combined kinetic and structural data indicate that the polysaccharide modifier sterically blocks the allosteric site and reduces substrate inhibition. In contrast to the properties of cold-active enzymes that generally manifest as low activation enthalpy and high flexibility, this study shows that increased activity and productivity at low temperature can be achieved by reducing uncompetitive substrate inhibition, and that this can be achieved using chemical modification with an enzyme in a commercial enzyme-formulation. PMID:19288442

  17. Termination of light-water reactor core-melt accidents with a chemical core catcher: the core-melt source reduction system (COMSORS)

    SciTech Connect

    Forsberg, C.W.; Parker, G.W.; Rudolph, J.C.; Osborne-Lee, I.W.; Kenton, M.A.

    1996-09-01

    The Core-Melt Source Reduction System (COMSORS) is a new approach to terminate light-water reactor core melt accidents and ensure containment integrity. A special dissolution glass is placed under the reactor vessel. If core debris is released onto the glass, the glass melts and the debris dissolves into the molten glass, thus creating a homogeneous molten glass. The molten glass, with dissolved core debris, spreads into a wide pool, distributing the heat for removal by radiation to the reactor cavity above or by transfer to water on top of the molten glass. Expected equilibrium glass temperatures are approximately 600 degrees C. The creation of a low-temperature, homogeneous molten glass with known geometry permits cooling of the glass without threatening containment integrity. This report describes the technology, initial experiments to measure key glass properties, and modeling of COMSORS operations.

  18. In situ chemical reduction of Cr(VI) in groundwater using a combination of ferrous sulfate and sodium dithionite: a field investigation.

    PubMed

    Ludwig, Ralph D; Su, Chunming; Lee, Tony R; Wilkin, Richard T; Acree, Steven D; Ross, Randall R; Keeley, Ann

    2007-08-01

    A field study was conducted to evaluate the performance of a ferrous iron based in situ redox zone for the treatment of a dissolved phase Cr(VI) plume at a former industrial site. The ferrous iron based in situ redox zone was created by injecting a blend of 0.2 M ferrous sulfate and 0.2 M sodium dithionite into the path of a dissolved Cr(VI) plume within a shallow medium to fine sand unconfined aquifer formation. Monitoring data collected over a period of 1020 days after more than 100 m of linear groundwater flow through the treatment zone indicated sustained treatment of dissolved phase Cr(VI) from initial concentrations between 4 and 8 mg/L to less than 0.015 mg/L. Sustained treatment is assumed to be primarily due to the reduction of Cr(VI) to Cr(III) by ferrous iron adsorbed to, precipitated on, and/or incorporated into aquifer iron (hydr)oxide solid surfaces within the treatment zone. Precipitated phases likely include FeCO3 and FeS based on saturation index considerations and SEM/EDS analysis. The detection of solid phase sulfites and thiosulfates in aquifer sediments collected from the treatment zone more than 2 years following injection suggests dithionite decomposition products may also play a significant role in the long-term treatment of the dissolved phase Cr(VI). PMID:17822094

  19. Direct determination of arsenic in soil samples by fast pyrolysis-chemical vapor generation using sodium formate as a reductant followed by nondispersive atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Duan, Xuchuan; Zhang, Jingya; Bu, Fanlong

    2015-09-01

    This new study shows for the first time that sodium formate can react with trace arsenic to form volatile species via fast pyrolysis - chemical vapor generation. We found that the presence of thiourea greatly enhanced the generation efficiency and eliminated the interference of copper. We studied the reaction temperature, the volume of sodium formate, the reaction acidity, and the carried argon rate using nondispersive atomic fluorescence spectrometry. Under optimal conditions of T = 500 °C, the volumes of 30% sodium formate and 10% thiourea were 0.2 ml and 0.05 ml, respectively. The carrier argon rate was 300 ml min- 1 and the detection limit and precision of arsenic were 0.39 ng and 3.25%, respectively. The amount of arsenic in soil can be directly determined by adding trace amount of hydrochloric acid as a decomposition reagent without any sample pretreatment. The method was successfully applied to determine trace amount of arsenic in two soil-certified reference materials (GBW07453 and GBW07450), and the results were found to be in agreement with certified reference values.

  20. Chemical Domino Demonstration

    NASA Astrophysics Data System (ADS)

    Alexander, M. Dale

    1998-04-01

    The Chemical Domino Demonstration is both educational and entertaining. It provides an excellent means for a review of chemical concepts at the conclusion of a general chemistry course. This demonstration consists of a number of different chemical reactions occurring in sequence in a Rube Goldberg-type apparatus. These reactions include the reduction of water by an active metal, the oxidation of a moderately active metal by an acid, reduction of metallic ions by a metal of greater activity, acid-base neutralization reactions in solution monitored with indicators, a gas-phase acid-base neutralization reaction, decomposition of a compound, precipitation of an insoluble salt, substitution reactions of coordination complexes, and pyrotechnic oxidation-reduction reactions including a hypergolic oxidation-reduction reaction, an intramolecular oxidation-reduction reaction, and the combustion of a flammable gas.

  1. Industrial Waste Reduction Program

    SciTech Connect

    Not Available

    1991-10-24

    US industry generates over 12 billion tons of wastes each year. These wastes consist of undesirable by-products of industrial production that are discarded into our environment. Energy is an integral part of these wastes; it is found in the embodied energy of industrial feedstocks not optimally used, in the energy content of the wastes themselves, and in the energy needed to transport, treat, and dispose of wastes. Estimates of the potential energy savings from reducing industrial wastes range from three to four quadrillion Btu per year -- enough to meet the annual energy needs of 30 million American homes. This document presents a plan for the Industrial Waste Reduction Program, which has been designed to help achieve national goals for energy efficiency and waste minimization. The objective of the program is to improve the energy efficiency of industrial processes through cost-effective waste reduction. The initial program focus is on waste reduction opportunities in the production and use of chemicals, due to the significant amount of energy used in these activities and the large amounts of hazardous and toxic wastes they generate. The chemical industry will be the initial subject of a series of waste reduction opportunity assessments conducted as part of the program. Assessments of other industries and waste problems will follow.

  2. Examination of surface phenomena of V₂O₅ loaded on new nanostructured TiO₂ prepared by chemical vapor condensation for enhanced NH₃-based selective catalytic reduction (SCR) at low temperatures.

    PubMed

    Cha, Woojoon; Yun, Seong-Taek; Jurng, Jongsoo

    2014-09-01

    In this article, we describe the investigation and surface characterization of a chemical vapor condensation (CVC)-TiO2 support material used in a V2O5/TiO2 catalyst for enhanced selective catalytic reduction (SCR) activity and confirm the mechanism of surface reactions. On the basis of previous studies and comparison with a commercial TiO2 catalyst, we examine four fundamental questions: first, the reason for increased surface V(4+) ion concentrations; second, the origin of the increase in surface acid sites; third, a basis for synergistic influences on improvements in SCR activity; and fourth, a reason for improved catalytic activity at low reaction temperatures. In this study, we have cited the result of SCR with NH3 activity for removing NOx and analyzed data using the reported result and data from previous studies on V2O5/CVC-TiO2 for the SCR catalyst. In order to determine the properties of suitable CVC-TiO2 surfaces for efficient SCR catalysis at low temperatures, CVC-TiO2 specimens were prepared and characterized using techniques such as XRD, BET, HR-TEM, XPS, FT-IR, NH3-TPD, photoluminescence (PL) spectroscopy, H2-TPR, and cyclic voltammetry. The results obtained for the CVC-TiO2 materials were also compared with those of commercial TiO2. PMID:25045767

  3. Nitrate reduction

    DOEpatents

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2000-01-01

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

  4. Modern Chemical Technology, Volume 5.

    ERIC Educational Resources Information Center

    Pecsok, Robert L., Ed.; Chapman, Kenneth, Ed.

    This volume contains chapters 26-31 for the American Chemical Society (ACS) "Modern Chemical Technology" (ChemTeC) instructional material intended to prepare chemical technologists. Chapter 26 reviews oxidation and reduction, including applications in titrations with potassium permanganate and iodometry. Coordination compounds are described in the…

  5. Radon reduction

    SciTech Connect

    Hamilton, M.A. )

    1990-11-01

    During a radon gas screening program, elevated levels of radon gas were detected in homes on Mackinac Island, Mich. Six homes on foundations with crawl spaces were selected for a research project aimed at reducing radon gas concentrations, which ranged from 12.9 to 82.3 pCi/l. Using isolation and ventilation techniques, and variations thereof, radon concentrations were reduced to less than 1 pCi/l. This paper reports that these reductions were achieved using 3.5 mil cross laminated or 10 mil high density polyethylene plastic as a barrier without sealing to the foundation or support piers, solid and/or perforated plastic pipe and mechanical fans. Wind turbines were found to be ineffective at reducing concentrations to acceptable levels. Homeowners themselves installed all materials.

  6. Chemical Emergencies

    MedlinePlus

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  7. Substructure Search by Set Reduction

    ERIC Educational Resources Information Center

    Figueras, John

    1972-01-01

    The set reduction algorithm is based on set theory and Boolean algebra rather than the graph-theoretic approach. Time trials with a small file of organic chemical structures indicate that the algorithm can be economically used for substructure (or complete structure) sequential searches on a file containing 30,000-50,000 computer-coded structures.…

  8. Some Early Usages of Chemical Terms

    ERIC Educational Resources Information Center

    Oldroyd, D. R.

    1973-01-01

    Discusses the origins of such chemical terms as substance, element, analysis, synthesis, compounds, mixture, organic,'' affinity, oxidation, reduction, acid, base, and salt for the purpose of providing a background to facilitate student's understanding of chemical terminology. (CC)

  9. REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

    EPA Science Inventory

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

  10. Interactions between Biological and Abiotic Pathways in the Reduction of Chlorinated Solvents

    EPA Science Inventory

    While biologically mediated reductive dechlorination continues to be a significant focus of chlorinated solvent remediation, there has been an increased interest in abiotic reductive processes for the remediation of chlorinated solvents. In situ chemical reduction (ISCR) uses zer...

  11. Chemical repair activity of free radical scavenger edaravone: reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA

    PubMed Central

    Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Lin, Mingzhang; Muroya, Yusa; Shikazono, Naoya; Yokoya, Akinari; Fu, Haiying; Katsumura, Yosuke

    2015-01-01

    Reactions of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) with deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts were investigated by pulse radiolysis technique. Edaravone was found to reduce the dGMP hydroxyl radical adducts through electron transfer reactions. The rate constants of the reactions were greater than 4 × 108 dm3 mol−1 s−1 and similar to those of the reactions of ascorbic acid, which is a representative antioxidant. Yields of single-strand breaks, base lesions, and abasic sites produced in pUC18 plasmid DNA by gamma ray irradiation in the presence of low concentrations (10–1000 μmol dm−3) of edaravone were also quantified, and the chemical repair activity of edaravone was estimated by a method recently developed by the authors. By comparing suppression efficiencies to the induction of each DNA lesion, it was found that base lesions and abasic sites were suppressed by the chemical repair activity of edaravone, although the suppression of single-strand breaks was not very effective. This phenomenon was attributed to the chemical repair activity of edaravone toward base lesions and abasic sites. However, the chemical repair activity of edaravone for base lesions was lower than that of ascorbic acid. PMID:25212600

  12. Chemically rechargeable battery

    NASA Technical Reports Server (NTRS)

    Graf, James E. (Inventor); Rowlette, John J. (Inventor)

    1984-01-01

    Batteries (50) containing oxidized, discharged metal electrodes such as an iron-air battery are charged by removing and storing electrolyte in a reservoir (98), pumping fluid reductant such as formalin (aqueous formaldehyde) from a storage tank (106) into the battery in contact with the surfaces of the electrodes. After sufficient iron hydroxide has been reduced to iron, the spent reductant is drained, the electrodes rinsed with water from rinse tank (102) and then the electrolyte in the reservoir (106) is returned to the battery. The battery can be slowly electrically charged when in overnight storage but can be quickly charged in about 10 minutes by the chemical procedure of the invention.

  13. Lithium Ethylene Dicarbonate Identified as the Primary Product ofChemical and Electrochemical Reduction of EC in EC:EMC/1.2M LiPF6Electrolyte

    SciTech Connect

    Zhuang, Guorong V.; Xu, Kang; Yang, Hui; Jow, T. Richard; RossJr., Philip N.

    2005-05-11

    Lithium ethylene dicarbonate (CH2OCO2Li)2 was chemically synthesized and its Fourier Transform Infrared (FTIR) spectrum was obtained and compared with that of surface films formed on Ni after cyclic voltammetry (CV) in 1.2M lithium hexafluorophosphate(LiPF6)/ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7, w/w) electrolyte and on metallic lithium cleaved in-situ in the same electrolyte. By comparison of IR experimental spectra with that of the synthesized compound, we established that the title compound is the predominant surface species in both instances. Detailed analysis of the IR spectrum utilizing quantum chemical (Hartree-Fock) calculations indicates that intermolecular association through O...Li...O interactions is very important in this compound. It is likely that the title compound in passivation layer has a highly associated structure, but the exact intermolecular conformation could not be established based on analysis of the IR spectrum.

  14. Dissolution and reduction of magnetite by bacteria.

    PubMed

    Kostka, J E; Nealson, K H

    1995-10-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis. PMID:11539843

  15. Dissolution and reduction of magnetite by bacteria

    NASA Technical Reports Server (NTRS)

    Kostka, J. E.; Nealson, K. H.

    1995-01-01

    Magnetite (Fe3O4) is an iron oxide of mixed oxidation state [Fe(II), Fe(III)] that contributes largely to geomagnetism and plays a significant role in diagenesis in marine and freshwater sediments. Magnetic data are the primary evidence for ocean floor spreading and accurate interpretation of the sedimentary magnetic record depends on an understanding of the conditions under which magnetite is stable. Though chemical reduction of magnetite by dissolved sulfide is well known, biological reduction has not been considered likely based upon thermodynamic considerations. This study shows that marine and freshwater strains of the bacterium Shewanella putrefaciens are capable of the rapid dissolution and reduction of magnetite, converting millimolar amounts to soluble Fe(II)in a few days at room temperature. Conditions under which magnetite reduction is optimal (pH 5-6, 22-37 degrees C) are consistent with an enzymatic process and not with simple chemical reduction. Magnetite reduction requires viable cells and cell contact, and it appears to be coupled to electron transport and growth. In a minimal medium with formate or lactate as the electron donor, more than 10 times the amount of magnetite was reduced over no carbon controls. These data suggest that magnetite reduction is coupled to carbon metabolism in S. putrefaciens. Bacterial reduction rates of magnetite are of the same order of magnitude as those estimated for reduction by sulfide. If such remobilization of magnetite occurs in nature, it could have a major impact on sediment magnetism and diagenesis.

  16. Biomass - chemicals

    SciTech Connect

    Kovaly, K.A.

    1982-08-01

    A host of industrial chemicals, specialty items, solvents, plastics, elastomers, fibers and films can be produced from agricultural crops, wood, paper mill wastes, food processing wastes, municipal waste and sewage. Existing chemical processes based on readily renewable plant materials are reviewed. These include ethanol and acetone-butanol fermentations, oilseed chemicals, furfural and cellulosics. (Refs. 16).

  17. Chemical sensor

    NASA Technical Reports Server (NTRS)

    Rauh, R. David (Inventor)

    1990-01-01

    A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

  18. Crystallographic Control in Ilmenite Reduction

    NASA Astrophysics Data System (ADS)

    de Vries, M. L.; Grey, I. E.; Fitz Gerald, J. D.

    2007-04-01

    Scanning electron microscopy and transmission electron microscopy techniques were used to characterize the products from hydrogen reduction of polygranular synthetic ilmenite discs at temperatures in the range 823 to 1173 K and pressures in the range 1 to 13 atm. Reduction commences at grain boundaries and cracks and advances progressively to grain interiors. Within individual grains, the morphology of the reduction products was found to be crystallographically controlled. Near parallel bands of metallic iron (Fe m ) form within each grain, aligned with the basal plane of ilmenite (il) (0001) il . The separation between bands is of the order of 1 μm and is relatively constant with change of pressure and temperature. In the interband region, conversion of ilmenite to rutile occurs preferentially parallel to \\{ 11ifmmodeexpandafterbarelseexpandafter\\=fi{2}0\\} _{{il}} ilmenite planes, generating platelets of rutile that grow normal to the Fe m bands. The intergrain duplex morphology of the reduction products closely resembles cellular precipitation in alloys. At reduction temperatures above ˜1000 K, the interband region comprises dense, nonporous oriented intergrowths of rutile platelets and residual ilmenite, whereas below ˜900 K, the interband region contains a fine, filamentary network of pores. In the intermediate temperature regime, a change from dense to porous interband region occurs with increasing pressure. The observations have been interpreted in terms of the relative rates of interfacial chemical reaction and solid-state diffusion, with the latter having a controlling influence at lower temperatures or higher pressures.

  19. Chemical Leukoderma.

    PubMed

    Bonamonte, Domenico; Vestita, Michelangelo; Romita, Paolo; Filoni, Angela; Foti, Caterina; Angelini, Gianni

    2016-01-01

    Chemical leukoderma, often clinically mimicking idiopathic vitiligo and other congenital and acquired hypopigmentation, is an acquired form of cutaneous pigment loss caused by exposure to a variety of chemicals that act through selective melanocytotoxicity. Most of these chemicals are phenols and aromatic or aliphatic catechols derivatives. These chemicals, however, are harmful for melanocytes in individuals with an individual susceptibility. Nowadays, chemical leukoderma is fairly common, caused by common domestic products. The presence of numerous acquired confetti- or pea-sized macules is clinically characteristic of chemical leukoderma, albeit not diagnostic. Other relevant diagnostic elements are a history of repeated exposure to a known or suspected depigmenting agent at the sites of onset and a macules distribution corresponding to sites of chemical exposure. Spontaneous repigmentation has been reported when the causative agent is avoided; the repigmentation process is perifollicular and gradual, taking place for a variable period of weeks to months. PMID:27172302

  20. [Chemical weapons and chemical terrorism].

    PubMed

    Nakamura, Katsumi

    2005-10-01

    Chemical Weapons are kind of Weapons of Mass Destruction (WMD). They were used large quantities in WWI. Historically, large quantities usage like WWI was not recorded, but small usage has appeared now and then. Chemical weapons are so called "Nuclear weapon for poor countrys" because it's very easy to produce/possession being possible. They are categorized (1) Nerve Agents, (2) Blister Agents, (3) Cyanide (blood) Agents, (4) Pulmonary Agents, (5) Incapacitating Agents (6) Tear Agents from the viewpoint of human body interaction. In 1997 the Chemical Weapons Convention has taken effect. It prohibits chemical weapons development/production, and Organization for the Prohibition of Chemical Weapons (OPCW) verification regime contributes to the chemical weapons disposal. But possibility of possession/use of weapons of mass destruction by terrorist group represented in one by Matsumoto and Tokyo Subway Sarin Attack, So new chemical terrorism countermeasures are necessary. PMID:16296384

  1. Evolution was chemically constrained.

    PubMed

    Williams, R J P; Fraústo Da Silva, J J R

    2003-02-01

    The objective of this paper is to present a systems view of the major features of biological evolution based upon changes in internal chemistry and uses of cellular space, both of which it will be stated were dependent on the changing chemical environment. The account concerns the major developments from prokaryotes to eukaryotes, to multi-cellular organisms, to animals with nervous systems and a brain, and finally to human beings and their uses of chemical elements in space outside themselves. It will be stated that the changes were in an inevitable progression, and were not just due to blind chance, so that "random searching" by a coded system to give species had a fixed overall route. The chemical sequence is from a reducing to an ever-increasingly oxidizing environment, while organisms retained reduced chemicals. The process was furthered recently by human beings who have also increased the range of reduced products trapped on Earth in novel forms. All the developments are brought about from the nature of the chemicals which organisms accumulate using the environment and its changes. The relationship to the manner in which particular species (gene sequences) were coincidentally changed, the molecular view of evolution, is left for additional examination. There is a further issue in that the changes of the chemistry of the environment developed largely at equilibrium due to the relatively fast reactions there of the available inorganic chemicals. Inside cells, some of these same chemicals also came to equilibrium within compounds. All such equilibria reduced the variance (degrees of freedom) of the total environmental/biological system and its possible development. However, the more sophisticated organic chemistry, almost totally inside cells until humans evolved, is kinetically controlled and limited by the demands of cellular reduction necessary to produce essential chemicals and by the availability of certain elements and energy. Hence the variability of

  2. Chemical microsensors

    DOEpatents

    Li, DeQuan; Swanson, Basil I.

    1995-01-01

    An article of manufacture is provided including a substrate having an oxide surface layer and a selective thin film of a cyclodextrin derivative chemically bound upon said substrate, said film is adapted for the inclusion of a selected organic compound therewith. Such an article can be either a chemical sensor capable of detecting a resultant mass change from inclusion of the selected organic compound or a chemical separator capable of reversibly selectively separating a selected organic compound.

  3. Reductive dissolution of goethite by phenolic reductants

    NASA Astrophysics Data System (ADS)

    LaKind, Judy S.; Stone, Alan T.

    1989-05-01

    The reductive dissolution of goethite (α-FeOOH) and hematite (α-Fe 2O 3) by phenolic reductants has been examined in order to improve the understanding of iron transformations in soils, sediments and aquifers. Rates of goethite reductive dissolution by hydroquinone increased as the pH was increased from pH 1.8 to 4.65, arid the following reaction stoichiometry was obeyed: 2 α- FeOOH + QH2 = 2 Fe2+ + Q + 4 OH-. As the pH was increased from pH 4.5 to 6.0, the reductive dissolution rate decreased to below the detection limit. At pH 3.4, the reductive dissolution of hematite was two orders of magnitude slower than goethite. The relationship between structure and reactivity was examined for a series of mono-, di-, and tri-hydroxybenzene reductants. Rates of reductive dissolution decreased in the following order: catechol ˜- hydroquinone > 3,4-dihydroxybenzoic acid > resorcinol-phenol-4-hydroxybenzoic acid.

  4. Drastic reduction in the surface recombination velocity of crystalline silicon passivated with catalytic chemical vapor deposited SiN{sub x} films by introducing phosphorous catalytic-doped layer

    SciTech Connect

    Thi, Trinh Cham Koyama, Koichi; Ohdaira, Keisuke; Matsumura, Hideki

    2014-07-28

    We improve the passivation property of n-type crystalline silicon (c-Si) surface passivated with a catalytic chemical vapor deposited (Cat-CVD) Si nitride (SiN{sub x}) film by inserting a phosphorous (P)-doped layer formed by exposing c-Si surface to P radicals generated by the catalytic cracking of PH{sub 3} molecules (Cat-doping). An extremely low surface recombination velocity (SRV) of 2 cm/s can be achieved for 2.5 Ω cm n-type (100) floating-zone Si wafers passivated with SiN{sub x}/P Cat-doped layers, both prepared in Cat-CVD systems. Compared with the case of only SiN{sub x} passivated layers, SRV decreases from 5 cm/s to 2 cm/s. The decrease in SRV is the result of field effect created by activated P atoms (donors) in a shallow P Cat-doped layer. Annealing process plays an important role in improving the passivation quality of SiN{sub x} films. The outstanding results obtained imply that SiN{sub x}/P Cat-doped layers can be used as promising passivation layers in high-efficiency n-type c-Si solar cells.

  5. Chemical Peels

    MedlinePlus

    ... the complications or potential side effects of a chemical peel? Temporary or permanent change in skin color, particularly for women on birth control pills, who subsequently become pregnant or have a history of brownish facial ... after having a chemical peel? All peels require some follow-up care: ...

  6. Chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Frye-Mason, Gregory C.

    2001-01-01

    A chemical preconcentrator is disclosed with applications to chemical sensing and analysis. The preconcentrator can be formed by depositing a resistive heating element (e.g. platinum) over a membrane (e.g. silicon nitride) suspended above a substrate. A coating of a sorptive material (e.g. a microporous hydrophobic sol-gel coating or a polymer coating) is formed on the suspended membrane proximate to the heating element to selective sorb one or more chemical species of interest over a time period, thereby concentrating the chemical species in the sorptive material. Upon heating the sorptive material with the resistive heating element, the sorbed chemical species are released for detection and analysis in a relatively high concentration and over a relatively short time period. The sorptive material can be made to selectively sorb particular chemical species of interest while not substantially sorbing other chemical species not of interest. The present invention has applications for use in forming high-sensitivity, rapid-response miniaturized chemical analysis systems (e.g. a "chem lab on a chip").

  7. Chemical sensors

    DOEpatents

    Lowell, Jr., James R.; Edlund, David J.; Friesen, Dwayne T.; Rayfield, George W.

    1991-01-01

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising (a) a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, operatively coupled to (b) a transducer capable of directly converting said expansion or contraction to a measurable electrical response.

  8. Chemical sensors

    DOEpatents

    Lowell, J.R. Jr.; Edlund, D.J.; Friesen, D.T.; Rayfield, G.W.

    1991-07-02

    Sensors responsive to small changes in the concentration of chemical species are disclosed. The sensors comprise a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment. They are operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical response. 9 figures.

  9. Chemical Emergencies

    MedlinePlus

    ... agents such as sarin and VX. Many hazardous chemicals are used in industry - for example, chlorine, ammonia, and benzene. Some can be made from everyday items such as household cleaners. Although there are no guarantees of safety during a chemical emergency, you can take actions to protect yourself. ...

  10. Chemical simulation of greywater.

    PubMed

    Abed, Suhail Najem; Scholz, Miklas

    2016-01-01

    Sustainable water resources management attracts considerable attention in today's world. Recycling and reuse of both wastewater and greywater are becoming more attractive. The strategy is to protect ecosystem services by balancing the withdrawal of water and the disposal of wastewater. In the present study, a timely and novel synthetic greywater composition has been proposed with respect to the composition of heavy metals, nutrients and organic matter. The change in water quality of the synthetic greywater due to increasing storage time was monitored to evaluate the stability of the proposed chemical formula. The new greywater is prepared artificially using analytical-grade chemicals to simulate either low (LC) or high (HC) pollutant concentrations. The characteristics of the synthetic greywater were tested (just before starting the experiment, after two days and a week of storage under real weather conditions) and compared to those reported for real greywater. Test results for both synthetic greywater types showed great similarities with the physiochemical properties of published findings concerning real greywater. Furthermore, the synthetic greywater is relatively stable in terms of its characteristics for different storage periods. However, there was a significant (p < .05) reduction in 5-day biochemical oxygen demand (BOD5) for both low (LC) and high (HC) concentrations of greywater after two days of storage with reductions of 62% and 55%, respectively. A significant (p < .05) change was also noted for the reduction (70%) of nitrate-nitrogen (NO3-N) concerning HC greywater after seven days of storage. PMID:26745659

  11. Hazardous waste reduction in the metal finishing industry

    SciTech Connect

    Not Available

    1989-01-01

    This study identifies opportunities for waste reduction available to the metal finishing industry and develops a generic audit protocol that can be used by metal finishers to assess their own waste reduction opportunities. The study emphasizes technologies available to metal finishing plants of various sizes. Typically, these shops operate a variety of physical, chemical and electrochemical processes. Chemical processes include degreasing, cleaning, pickling, etching, coating, and electroless plating. Electrochemical processes include plating and anodizing. The study identifies three categories of waste reduction technologies that are available to metal finishers: source reduction, recycling and resource recovery, and alternative treatment.

  12. Regeneration of anion exchange resins by catalyzed electrochemical reduction

    DOEpatents

    Gu, Baohua; Brown, Gilbert M.

    2002-01-01

    Anion exchange resins sorbed with perchlorate may be regenerated by a combination of chemical reduction of perchlorate to chloride using a reducing agent and an electrochemical reduction of the oxidized reducing agent. Transitional metals including Ti, Re, and V are preferred chemical reagents for the reduction of perchlorate to chloride. Complexing agents such as oxalate are used to prevent the precipitation of the oxidized Ti(IV) species, and ethyl alcohol may be added to accelerate the reduction kinetics of perchlorate. The regeneration may be performed by continuously recycling the regenerating solution through the resin bed and an electrochemical cell so that the secondary waste generation is minimized.

  13. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Four new drift control adjuvants were sele...

  14. Cost Reduction Incentive Awards. 1981 Winners.

    ERIC Educational Resources Information Center

    National Association of College and University Business Officers, Washington, DC.

    Brief descriptions of 47 college programs recognized for awards in the National Association of College and University Officers/U. S. Steel Foundation Cost Reduction Incentive Awards Program are given. They include awards for: shower stall repair; chemical waste exchange; vibrating alarms for hearing-imparied; self-funding insurance consortium;…

  15. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Five new drift control adjuvants were sele...

  16. Chemical geodynamics

    NASA Astrophysics Data System (ADS)

    Zindler, A.; Hart, S.

    Consideration is given to the following three principal boundary conditions relating to the nature and development of chemical structure in the earth's mantle: (1) inferred scale lengths for mantle chemical heterogeneities, (2) interrelationships of the various isotopic tracers, and (3) the bulk composition of the earth. These boundary conditions are integrated with geophysical constraints in order to evaluate models for the development of the physical and chemical structure of the mantle. Data indicate that: (1) km-size heterogeneities can survive diffusive equilibrium for billions of years; (2) the mantle is chemically heterogeneous on both very small and very large scales; (3) isotopic heterogeneities in the mantle require the existence of four 'end-member' components (DMM, HIMU, EM I, and EM II) and are consistent with the existence of at least two additional components (BSE, PREMA); and (4) primitive undepleted mantle can made up no more than about 55 percent of the total mantle.

  17. Unnecessary Chemicals

    ERIC Educational Resources Information Center

    Johnson, Anita

    1978-01-01

    Discusses the health hazards resulting from chemical additions of many common products such as cough syrups, food dyes, and cosmetics. Steps being taken to protect consumers from these health hazards are included. (MDR)

  18. Chemical sensors

    DOEpatents

    Lowell, Jr., James R.; Edlund, David J.; Friesen, Dwayne T.; Rayfield, George W.

    1992-01-01

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising a mechanicochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, either operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical or optical response, or adhered to a second inert polymeric strip, or doped with a conductive material.

  19. Chemical sensors

    DOEpatents

    Lowell, J.R. Jr.; Edlund, D.J.; Friesen, D.T.; Rayfield, G.W.

    1992-06-09

    Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising a mechanicochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, either operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical or optical response, or adhered to a second inert polymeric strip, or doped with a conductive material. 12 figs.

  20. Chemical processing of lunar materials

    NASA Technical Reports Server (NTRS)

    Criswell, D. R.; Waldron, R. D.

    1979-01-01

    The paper highlights recent work on the general problem of processing lunar materials. The discussion covers lunar source materials, refined products, motivations for using lunar materials, and general considerations for a lunar or space processing plant. Attention is given to chemical processing through various techniques, including electrolysis of molten silicates, carbothermic/silicothermic reduction, carbo-chlorination process, NaOH basic-leach process, and HF acid-leach process. Several options for chemical processing of lunar materials are well within the state of the art of applied chemistry and chemical engineering to begin development based on the extensive knowledge of lunar materials.

  1. Collaborating for Multi-Scale Chemical Science

    SciTech Connect

    William H. Green

    2006-07-14

    Advanced model reduction methods were developed and integrated into the CMCS multiscale chemical science simulation software. The new technologies were used to simulate HCCI engines and burner flames with exceptional fidelity.

  2. Reduction by monovalent zinc, cadmium, and nickel cations

    NASA Technical Reports Server (NTRS)

    Meyerstein, D.; Mulac, W. A.

    1969-01-01

    Understanding of chemical properties of monovalent transition metal cations in aqueous solutions was obtained by a study of kinetics of reduction of different inorganic substrates by zinc, cadmium, and nickel.

  3. 75 FR 60430 - Federal Advisory Committee; Threat Reduction Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-30

    ... technology security, combating weapons of mass destruction (WMD), chemical and biological defense, the future... level briefings on WMD threats, the Defense Threat Reduction Agency, and the status of the...

  4. Chemical sensors

    SciTech Connect

    Hubbard, C.W.; Gordon, R.L.

    1987-05-01

    The revolution in analytical chemistry promised by recent developments in the field of chemical sensors has potential for significant positive impact on both research and production activities conducted by and for the Department of Energy. Analyses which were, in the past, performed only with a roomful of expensive equipment can now be performed with miniature solid-state electronic devices or small optical probes. Progress in the development of chemical sensors has been rapid, and the field is currently growing at a great rate. In accordance, Pacific Northwest Laboratory initiated a survey of recent literature so that contributors to active programs in research on analytical methods could be made aware of principles and applications of this new technology. This report presents the results of that survey. The sensors discussed here are divided into three types: micro solid-state devices, optical sensors, and piezoelectric crystal devices. The report is divided into three corresponding sections. The first section, ''Micro Solid-State Devices,'' discusses the design, operation, and application of electronic sensors that are produced in much the same way as standard solid-state electronic devices. The second section, ''Optrodes,'' covers the design and operation of chemical sensors that use fiber optics to detect chemically induced changes in optical properties. The final section, ''Piezoelectric Crystal Detectors,'' discusses two types of chemical sensors that depend on the changes in the properties of an oscillating piezoelectric crystal to detect the presence of certain materials. Advantages and disadvantages of each type of sensor are summarized in each section.

  5. Drag reduction in nature

    NASA Technical Reports Server (NTRS)

    Bushnell, D. M.; Moore, K. J.

    1991-01-01

    Recent studies on the drag-reducing shapes, structures, and behaviors of swimming and flying animals are reviewed, with an emphasis on potential analogs in vehicle design. Consideration is given to form drag reduction (turbulent flow, vortex generation, mass transfer, and adaptations for body-intersection regions), skin-friction drag reduction (polymers, surfactants, and bubbles as surface 'additives'), reduction of the drag due to lift, drag-reduction studies on porpoises, and drag-reducing animal behavior (e.g., leaping out of the water by porpoises). The need for further research is stressed.

  6. Drag reduction in nature

    NASA Astrophysics Data System (ADS)

    Bushnell, D. M.; Moore, K. J.

    Recent studies on the drag-reducing shapes, structures, and behaviors of swimming and flying animals are reviewed, with an emphasis on potential analogs in vehicle design. Consideration is given to form drag reduction (turbulent flow, vortex generation, mass transfer, and adaptations for body-intersection regions), skin-friction drag reduction (polymers, surfactants, and bubbles as surface 'additives'), reduction of the drag due to lift, drag-reduction studies on porpoises, and drag-reducing animal behavior (e.g., leaping out of the water by porpoises). The need for further research is stressed.

  7. Chemical networks

    NASA Astrophysics Data System (ADS)

    Thi, Wing-Fai

    2015-09-01

    This chapter discusses the fundamental ideas of how chemical networks are build, their strengths and limitations. The chemical reactions that occur in disks combine the cold phase reactions used to model cold molecular clouds with the hot chemistry applied to planetary atmosphere models. With a general understanding of the different types of reactions that can occur, one can proceed in building a network of chemical reactions and use it to explain the abundance of species seen in disks. One on-going research subject is finding new paths to synthesize species either in the gas-phase or on grain surfaces. Specific formation routes for water or carbon monoxide are discussed in more details. 13th Lecture of the Summer School "Protoplanetary Disks: Theory and Modelling Meet Observations"

  8. Lithium metal reduction of plutonium oxide to produce plutonium metal

    DOEpatents

    Coops, Melvin S.

    1992-01-01

    A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used as a solvent metal to improve thermodynamics of the reduction reaction at lower temperatures. Lithium metal reduction enables plutonium oxide reduction without the production of huge quantities of CaO--CaCl.sub.2 residues normally produced in conventional direct oxide reduction processes.

  9. Does Source Reduction Work?

    ERIC Educational Resources Information Center

    Allaway, David

    1992-01-01

    Suggests that quantification is essential to establish the cost-effectiveness of source reduction (SR). Presents case studies of monitoring methods for seven different kinds of SR efforts: (1) packaging changes, (2) SR businesses, (3) waste exchanges, (4) individual nonresidential efforts, (5) variable garbage rates, (6) yard waste reduction, and…

  10. Intelligent Data Reduction (IDARE)

    NASA Technical Reports Server (NTRS)

    Brady, D. Michael; Ford, Donnie R.

    1990-01-01

    A description of the Intelligent Data Reduction (IDARE) expert system and an IDARE user's manual are given. IDARE is a data reduction system with the addition of a user profile infrastructure. The system was tested on a nickel-cadmium battery testbed. Information is given on installing, loading, maintaining the IDARE system.