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Sample records for solution kinetics database

  1. Numeric databases on the kinetics of transient species in solution

    International Nuclear Information System (INIS)

    Helman, W.P.; Hug, G.L.; Carmichael, Ian; Ross, A.B.

    1988-01-01

    A description is given of data compilations on the kinetics of transient species in solution. In particular information is available for the reactions of radicals in aqueous solution and for excited states such as singlet molecular oxygen and those of metal complexes in solution. Methods for compilation and use of the information in computer-readable form are also described. Emphasis is placed on making the database available for online searching. (author)

  2. NLTE4 Plasma Population Kinetics Database

    Science.gov (United States)

    SRD 159 NLTE4 Plasma Population Kinetics Database (Web database for purchase)   This database contains benchmark results for simulation of plasma population kinetics and emission spectra. The data were contributed by the participants of the 4th Non-LTE Code Comparison Workshop who have unrestricted access to the database. The only limitation for other users is in hidden labeling of the output results. Guest users can proceed to the database entry page without entering userid and password.

  3. A kinetics database and scripts for PHREEQC

    Science.gov (United States)

    Hu, B.; Zhang, Y.; Teng, Y.; Zhu, C.

    2017-12-01

    Kinetics of geochemical reactions has been increasingly used in numerical models to simulate coupled flow, mass transport, and chemical reactions. However, the kinetic data are scattered in the literature. To assemble a kinetic dataset for a modeling project is an intimidating task for most. In order to facilitate the application of kinetics in geochemical modeling, we assembled kinetics parameters into a database for the geochemical simulation program, PHREEQC (version 3.0). Kinetics data were collected from the literature. Our database includes kinetic data for over 70 minerals. The rate equations are also programmed into scripts with the Basic language. Using the new kinetic database, we simulated reaction path during the albite dissolution process using various rate equations in the literature. The simulation results with three different rate equations gave difference reaction paths at different time scale. Another application involves a coupled reactive transport model simulating the advancement of an acid plume in an acid mine drainage site associated with Bear Creek Uranium tailings pond. Geochemical reactions including calcite, gypsum, and illite were simulated with PHREEQC using the new kinetic database. The simulation results successfully demonstrated the utility of new kinetic database.

  4. A KINETIC DATABASE FOR ASTROCHEMISTRY (KIDA)

    International Nuclear Information System (INIS)

    Wakelam, V.; Pavone, B.; Hébrard, E.; Hersant, F.; Herbst, E.; Loison, J.-C.; Chandrasekaran, V.; Bergeat, A.; Smith, I. W. M.; Adams, N. G.; Bacchus-Montabonel, M.-C.; Béroff, K.; Bierbaum, V. M.; Chabot, M.; Dalgarno, A.; Van Dishoeck, E. F.; Faure, A.; Geppert, W. D.; Gerlich, D.; Galli, D.

    2012-01-01

    We present a novel chemical database for gas-phase astrochemistry. Named the KInetic Database for Astrochemistry (KIDA), this database consists of gas-phase reactions with rate coefficients and uncertainties that will be vetted to the greatest extent possible. Submissions of measured and calculated rate coefficients are welcome, and will be studied by experts before inclusion into the database. Besides providing kinetic information for the interstellar medium, KIDA is planned to contain such data for planetary atmospheres and for circumstellar envelopes. Each year, a subset of the reactions in the database (kida.uva) will be provided as a network for the simulation of the chemistry of dense interstellar clouds with temperatures between 10 K and 300 K. We also provide a code, named Nahoon, to study the time-dependent gas-phase chemistry of zero-dimensional and one-dimensional interstellar sources.

  5. Kinetic equation solution by inverse kinetic method

    International Nuclear Information System (INIS)

    Salas, G.

    1983-01-01

    We propose a computer program (CAMU) which permits to solve the inverse kinetic equation. The CAMU code is written in HPL language for a HP 982 A microcomputer with a peripheral interface HP 9876 A ''thermal graphic printer''. The CAMU code solves the inverse kinetic equation by taking as data entry the output of the ionization chambers and integrating the equation with the help of the Simpson method. With this program we calculate the evolution of the reactivity in time for a given disturbance

  6. Bayesian Calibration of Thermodynamic Databases and the Role of Kinetics

    Science.gov (United States)

    Wolf, A. S.; Ghiorso, M. S.

    2017-12-01

    Self-consistent thermodynamic databases of geologically relevant materials (like Berman, 1988; Holland and Powell, 1998, Stixrude & Lithgow-Bertelloni 2011) are crucial for simulating geological processes as well as interpreting rock samples from the field. These databases form the backbone of our understanding of how fluids and rocks interact at extreme planetary conditions. Considerable work is involved in their construction from experimental phase reaction data, as they must self-consistently describe the free energy surfaces (including relative offsets) of potentially hundreds of interacting phases. Standard database calibration methods typically utilize either linear programming or least squares regression. While both produce a viable model, they suffer from strong limitations on the training data (which must be filtered by hand), along with general ignorance of many of the sources of experimental uncertainty. We develop a new method for calibrating high P-T thermodynamic databases for use in geologic applications. The model is designed to handle pure solid endmember and free fluid phases and can be extended to include mixed solid solutions and melt phases. This new calibration effort utilizes Bayesian techniques to obtain optimal parameter values together with a full family of statistically acceptable models, summarized by the posterior. Unlike previous efforts, the Bayesian Logistic Uncertain Reaction (BLUR) model directly accounts for both measurement uncertainties and disequilibrium effects, by employing a kinetic reaction model whose parameters are empirically determined from the experiments themselves. Thus, along with the equilibrium free energy surfaces, we also provide rough estimates of the activation energies, entropies, and volumes for each reaction. As a first application, we demonstrate this new method on the three-phase aluminosilicate system, illustrating how it can produce superior estimates of the phase boundaries by incorporating constraints

  7. Decomposition kinetics of aminoborane in aqueous solutions

    International Nuclear Information System (INIS)

    Shvets, I.B.; Erusalimchik, I.G.

    1984-01-01

    Kinetics of aminoborane hydrolysis has been studied using the method of polarization galvanostatical curves on a platinum electrode in buffer solutions at pH 3; 5; 7. The supposition that the reaction of aminoborane hydrolysis is the reaction of the first order by aminoborane is proved. The rate constant of aminoborane decomposition in the solution with pH 5 is equal to: K=2.5x10 -5 s -1 and with pH 3 it equals K=1.12x10 -4 s -1

  8. Analytical Solution of Multicompartment Solute Kinetics for Hemodialysis

    Directory of Open Access Journals (Sweden)

    Przemysław Korohoda

    2013-01-01

    Full Text Available Objective. To provide an exact solution for variable-volume multicompartment kinetic models with linear volume change, and to apply this solution to a 4-compartment diffusion-adjusted regional blood flow model for both urea and creatinine kinetics in hemodialysis. Methods. A matrix-based approach applicable to linear models encompassing any number of compartments is presented. The procedure requires the inversion of a square matrix and the computation of its eigenvalues λ, assuming they are all distinct. This novel approach bypasses the evaluation of the definite integral to solve the inhomogeneous ordinary differential equation. Results. For urea two out of four eigenvalues describing the changes of concentrations in time are about 105 times larger than the other eigenvalues indicating that the 4-compartment model essentially reduces to the 2-compartment regional blood flow model. In case of creatinine, however, the distribution of eigenvalues is more balanced (a factor of 102 between the largest and the smallest eigenvalue indicating that all four compartments contribute to creatinine kinetics in hemodialysis. Interpretation. Apart from providing an exact analytic solution for practical applications such as the identification of relevant model and treatment parameters, the matrix-based approach reveals characteristic details on model symmetry and complexity for different solutes.

  9. Reshaping Smart Businesses with Cloud Database Solutions

    Directory of Open Access Journals (Sweden)

    Bogdan NEDELCU

    2015-03-01

    Full Text Available The aim of this article is to show the importance of Big Data and its growing influence on companies. We can also see how much are the companies willing to invest in big data and how much are they currently gaining from their big data. In this big data era, there is a fiercely competition between the companies and the technologies they use when building their strategies. There are almost no boundaries when it comes to the possibilities and facilities some databases can offer. However, the most challenging part lays in the development of efficient solutions - where and when to take the right decision, which cloud service is the most accurate being given a certain scenario, what database is suitable for the business taking in consideration the data types. These are just a few aspects which will be dealt with in the following chapters as well as exemplifications of the most accurate cloud services (e.g. NoSQL databases used by business leaders nowadays.

  10. Recent results in muonium solution kinetics

    International Nuclear Information System (INIS)

    Jean, Y.C.; Ito, Y.; Stadlbauer, J.M.; Ng, B.W.; Walker, D.C.

    1983-06-01

    Using muonium spin rotation (MSR) techniques the aqueous solution kinetics of several muonium addition reactions and spin conversion interactions have been studied. The addition reactions show both diffusion and activation-controlled reaction rates with isotope effects between 1 and 3 for diffusion-control and between 7 and 31 for activation-control reactions. Barrier energies are typically approximately 15 kJ/mole and approximately 30 kJ/mole, respectively, for these processes in water. Spin-conversion interactions involving Ni +2 (aq) and Ni(cyclam) +2 complexes showed that spin-conversion of 'triplet' Mu by a paramagnetic solute occurs at or near the diffusion-controlled limit while the chemical reaction with the diamagnetic configuration of Ni(cyclam) +2 occurred some 100 times slower at ksub(M) 18 M -1 s -1

  11. Database Search Engines: Paradigms, Challenges and Solutions.

    Science.gov (United States)

    Verheggen, Kenneth; Martens, Lennart; Berven, Frode S; Barsnes, Harald; Vaudel, Marc

    2016-01-01

    The first step in identifying proteins from mass spectrometry based shotgun proteomics data is to infer peptides from tandem mass spectra, a task generally achieved using database search engines. In this chapter, the basic principles of database search engines are introduced with a focus on open source software, and the use of database search engines is demonstrated using the freely available SearchGUI interface. This chapter also discusses how to tackle general issues related to sequence database searching and shows how to minimize their impact.

  12. Solutions for medical databases optimal exploitation.

    Science.gov (United States)

    Branescu, I; Purcarea, V L; Dobrescu, R

    2014-03-15

    The paper discusses the methods to apply OLAP techniques for multidimensional databases that leverage the existing, performance-enhancing technique, known as practical pre-aggregation, by making this technique relevant to a much wider range of medical applications, as a logistic support to the data warehousing techniques. The transformations have practically low computational complexity and they may be implemented using standard relational database technology. The paper also describes how to integrate the transformed hierarchies in current OLAP systems, transparently to the user and proposes a flexible, "multimodel" federated system for extending OLAP querying to external object databases.

  13. Kinetics of Surfactant Desorption at an Air–Solution Interface

    KAUST Repository

    Morgan, C. E.; Breward, C. J. W.; Griffiths, I. M.; Howell, P. D.; Penfold, J.; Thomas, R. K.; Tucker, I.; Petkov, J. T.; Webster, J. R. P.

    2012-01-01

    The kinetics of re-equilibration of the anionic surfactant sodium dodecylbenzene sulfonate at the air-solution interface have been studied using neutron reflectivity. The experimental arrangement incorporates a novel flow cell in which the subphase

  14. Uniqueness of solution to a stationary boundary kinetic problem

    International Nuclear Information System (INIS)

    Zhykharsky, A.V.

    1992-01-01

    The paper treats the question of uniqueness of solution to the boundary kinetic problem. This analysis is based on the accurate solutions to the stationary one-dimensional boundary kinetic problem for the limited plasma system. In the paper a simplified problem statement is used (no account is taken of the external magnetic field, a simplest form of boundary conditions is accepted) which, however, covers all features of the problem considered. Omitting the details of the conclusion we will write a set of Vlasov stationary kinetic equations for the cases of plane, cylindrical and spherical geometry of the problem. (author) 1 ref

  15. Kinetics of catalytic reactions solutions manual

    CERN Document Server

    Vannice, M Albert

    2005-01-01

    Including countless exercises and worked examples, this advanced reference work and textbook will be extremely useful for the work of many industrial scientists. It teaches readers to design kinetic experiments involving heterogeneous catalysts, to characterize these catalysts, to acquire rate data, to find heat and mass transfer limitations in these data, to select reaction models, to derive rate expressions based on these models, and to assess the consistency of these rate equations.

  16. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NARCIS (Netherlands)

    Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth

  17. High-throughput ab-initio dilute solute diffusion database.

    Science.gov (United States)

    Wu, Henry; Mayeshiba, Tam; Morgan, Dane

    2016-07-19

    We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world.

  18. Databases in Cloud - Solutions for Developing Renewable Energy Informatics Systems

    Directory of Open Access Journals (Sweden)

    Adela BARA

    2017-08-01

    Full Text Available The paper presents the data model of a decision support prototype developed for generation monitoring, forecasting and advanced analysis in the renewable energy filed. The solutions considered for developing this system include databases in cloud, XML integration, spatial data representation and multidimensional modeling. This material shows the advantages of Cloud databases and spatial data representation and their implementation in Oracle Database 12 c. Also, it contains a data integration part and a multidimensional analysis. The presentation of output data is made using dashboards.

  19. Kinetic Uptake Studies of Powdered Materials in Solution

    Directory of Open Access Journals (Sweden)

    Mohamed H. Mohamed

    2015-06-01

    Full Text Available Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution systems: (i conventional batch method; (ii one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing for in situ sampling; and (iii one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii or ex situ (Method iii sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

  20. Subdiffusion kinetics of nanoprecipitate growth and destruction in solid solutions

    Science.gov (United States)

    Sibatov, R. T.; Svetukhin, V. V.

    2015-06-01

    Based on fractional differential generalizations of the Ham and Aaron-Kotler precipitation models, we study the kinetics of subdiffusion-limited growth and dissolution of new-phase precipitates. We obtain the time dependence of the number of impurities and dimensions of new-phase precipitates. The solutions agree with the Monte Carlo simulation results.

  1. Review of Kaganove's solution for the reactor point kinetics equations

    International Nuclear Information System (INIS)

    Couto, R.T.; Santo, A.C.F. de.

    1993-09-01

    A review of Kaganove's method for the reactor point kinetics equations solution is performed. This was method chosen to calculate the power in ATR, a computer program for the analysis of reactivity transients. The reasons for this choice and the adaptation of the method to the purposes of ATR are presented. (author)

  2. A database for extract solutions in general relativity

    International Nuclear Information System (INIS)

    Horvath, I.; Horvath, Zs.; Lukacs, B.

    1993-07-01

    The field of equations of General Relativity are coupled second order partial differential equations. Therefore no general method is known to generate solutions for prescribed initial and boundary conditions. In addition, the meaning of the particular coordinates cannot be known until the metric is not found. Therefore the result must permit arbitrary coordinate transformations, i.e. most kinds of approximating methods are improper. So exact solutions are necessary and each one is an individual product. For storage, retrieval and comparison database handling techniques are needed. A database of 1359 articles is shown (cross-referred at least once) published in 156 more important journals. It can be handled by dBase III plus on IBM PC's. (author) 5 refs.; 5 tabs

  3. Transparent Data Encryption -- Solution for Security of Database Contents

    OpenAIRE

    Deshmukh, Dr. Anwar Pasha; Qureshi, Dr. Riyazuddin

    2013-01-01

    The present study deals with Transparent Data Encryption which is a technology used to solve the problems of security of data. Transparent Data Encryption means encrypting databases on hard disk and on any backup media. Present day global business environment presents numerous security threats and compliance challenges. To protect against data thefts and frauds we require security solutions that are transparent by design. Transparent Data Encryption provides transparent, standards-based secur...

  4. Solution of the reactor point kinetics equations by MATLAB computing

    Directory of Open Access Journals (Sweden)

    Singh Sudhansu S.

    2015-01-01

    Full Text Available The numerical solution of the point kinetics equations in the presence of Newtonian temperature feedback has been a challenging issue for analyzing the reactor transients. Reactor point kinetics equations are a system of stiff ordinary differential equations which need special numerical treatments. Although a plethora of numerical intricacies have been introduced to solve the point kinetics equations over the years, some of the simple and straightforward methods still work very efficiently with extraordinary accuracy. As an example, it has been shown recently that the fundamental backward Euler finite difference algorithm with its simplicity has proven to be one of the most effective legacy methods. Complementing the back-ward Euler finite difference scheme, the present work demonstrates the application of ordinary differential equation suite available in the MATLAB software package to solve the stiff reactor point kinetics equations with Newtonian temperature feedback effects very effectively by analyzing various classic benchmark cases. Fair accuracy of the results implies the efficient application of MATLAB ordinary differential equation suite for solving the reactor point kinetics equations as an alternate method for future applications.

  5. Kinetic determination of As(III in solution

    Directory of Open Access Journals (Sweden)

    TODOR G. PECEV

    2003-10-01

    Full Text Available A new reaction is suggested and a new kinetic method is elaborated for the As(III traces determination in solution, on the basis of their catalyzing effect on komplexon III (EDTA oxidation by KMnO4 in a strong acid solution (H2SO4. Using a spectrophotometric technique, a sensitivity of 72 ng/cm3 As(III was achieved. The relative error of method varies from 5.5 to 13.9 % for As(III concentration range from 83 to 140 ng/cm3. Appropriate kinetic equations are formulated and the influence of some other ions, including the As(V, upon the reaction rate is tested.

  6. Development of AGNES, a kinetics code for fissile solutions, 1

    International Nuclear Information System (INIS)

    Nakajima, Ken; Ohnishi, Nobuaki

    1986-01-01

    A kinetics code for fissile solutions, AGNES (Accidentally Generated Nuclear Excursion Simulation code), has been developed. This code calculates the radiolytic gas void effect as a reactivity feedback. Physical and calculative models of the radiolytic gas void are summarized and the usage of AGNES is described. In addition, some benchmark calculations were performed and results of calculations show good agreement with those of experiments. (author)

  7. Comparative analysis of solution methods of the punctual kinetic equations

    International Nuclear Information System (INIS)

    Hernandez S, A.

    2003-01-01

    The following one written it presents a comparative analysis among different analytical solutions for the punctual kinetics equation, which present two variables of interest: a) the temporary behavior of the neutronic population, and b) The temporary behavior of the different groups of precursors of delayed neutrons. The first solution is based on a method that solves the transfer function of the differential equation for the neutronic population, in which intends to obtain the different poles that give the stability of this transfer function. In this section it is demonstrated that the temporary variation of the reactivity of the system can be managed as it is required, since the integration time for this method doesn't affect the result. However, the second solution is based on an iterative method like that of Runge-Kutta or the Euler method where the algorithm was only used to solve first order differential equations giving this way solution to each differential equation that conforms the equations of punctual kinetics. In this section it is demonstrated that only it can obtain a correct temporary behavior of the neutronic population when it is integrated on an interval of very short time, forcing to the temporary variation of the reactivity to change very quick way without one has some control about the time. In both methods the same change is used so much in the reactivity of the system like in the integration times, giving validity to the results graph the one the temporary behavior of the neutronic population vs. time. (Author)

  8. Numerical benchmarking of SPEEDUP trademark against point kinetics solutions

    International Nuclear Information System (INIS)

    Gregory, M.V.

    1993-02-01

    SPEEDUP trademark is a state-of-the-art, dynamic, chemical process modeling package offered by Aspen Technology. In anticipation of new customers' needs for new analytical tools to support the site's waste management activities, SRTC has secured a multiple-user license to SPEEDUP trademark. In order to verify both the installation and mathematical correctness of the algorithms in SPEEDUP trademark, we have performed several numerical benchmarking calculations. These calculations are the first steps in establishing an on-site quality assurance pedigree for SPEEDUP trademark. The benchmark calculations consisted of SPEEDUP trademark Version 5.3L representations of five neutron kinetics benchmarks (each a mathematically stiff system of seven coupled ordinary differential equations), whose exact solutions are documented in the open literature. In all cases, SPEEDUP trademark solutions to be in excellent agreement with the reference solutions. A minor peculiarity in dealing with a non-existent discontinuity in the OPERATION section of the model made itself evident

  9. Kinetics of radiocesium released from contaminated soil by fertilizer solutions

    International Nuclear Information System (INIS)

    Chiang, P.N.; Wang, M.K.; Huang, P.M.; Wang, J.J.

    2008-01-01

    137 Cs is one of the major artificial radionuclides found in environments; but the mechanisms behind fertilizer-induced 137 Cs desorption from soil remain unknown. This study aimed to investigate the kinetics and mechanisms underlying the various cations and anions that cause Cs release from soil under acidic conditions. NH 4 H 2 PO 4 (1 M), 0.5 M (NH 4 ) 2 SO 4 , 1 M NH 4 Cl, 1 M KCl or 1 M NaCl solutions were added to 137 Cs-contaminated soil. The power function model well described the short term 137 Cs desorption with the solutions. The rate coefficients for 137 Cs release from soil in NH 4 H 2 PO 4 , (NH 4 ) 2 SO 4 , NH 4 Cl, and KCl solutions were 7.7, 7.3, 6.8, and 6.1 times higher than the rate observed in a NaCl solution, respectively. The NH 4 H 2 PO 4 and (NH 4 ) 2 SO 4 solutions induced significantly greater 137 Cs release from the contaminated soil than the NH 4 Cl, KCl and NaCl solutions. After four times repeated extractions with the fertilizer solutions, the total amount of 137 Cs extracted by (NH 4 ) 2 SO 4 and NH 4 Cl solutions reached equilibrium, while that extracted using an NH 4 H 2 PO 4 solution continued to increase. The combined effect of phosphate and protons was the major mechanism behind 137 Cs release from contaminated soils, when an NH 4 H 2 PO 4 solution was used

  10. Sonochemical Degradation Kinetics of Methyl Violet in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Wei Lin Guo

    2003-01-01

    Full Text Available The sonochemical degradation in aqueous solution of methyl violet, chosen as a model of a basic dye, was studied. The ultrasonic degradation kinetics in water were found to be first-order and the degradation rate coefficient is 1.35×10-2 min-1 (R= 0.9934, n=8 at 20±1°C. The influence of the initial concentrations, reaction temperature and the pH of medium on the ultrasonic decomposition of methyl violet were also investigated.

  11. Fibrillization kinetics of insulin solution in an interfacial shearing flow

    Science.gov (United States)

    Balaraj, Vignesh; McBride, Samantha; Hirsa, Amir; Lopez, Juan

    2015-11-01

    Although the association of fibril plaques with neurodegenerative diseases like Alzheimer's and Parkinson's is well established, in-depth understanding of the roles played by various physical factors in seeding and growth of fibrils is far from well known. Of the numerous factors affecting this complex phenomenon, the effect of fluid flow and shear at interfaces is paramount as it is ubiquitous and the most varying factor in vivo. Many amyloidogenic proteins have been found to denature upon contact at hydrophobic interfaces due to the self-assembling nature of protein in its monomeric state. Here, fibrillization kinetics of insulin solution is studied in an interfacial shearing flow. The transient surface rheological response of the insulin solution to the flow and its effect on the bulk fibrillization process has been quantified. Minute differences in hydrophobic characteristics between two variants of insulin- Human recombinant and Bovine insulin are found to result in very different responses. Results presented will be in the form of fibrillization assays, images of fibril plaques formed, and changes in surface rheological properties of the insulin solution. The interfacial velocity field, measured from images (via Brewster Angle Microscopy), is compared with computations. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  12. Degradation kinetics of ptaquiloside in soil and soil solution

    DEFF Research Database (Denmark)

    Ovesen, Rikke Gleerup; Rasmussen, Lars Holm; Hansen, Hans Christian Bruun

    2008-01-01

    and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction...... was similar in all horizons, with the rate constant k1F ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k1S ranging between 0.00067 and 0.029/h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils....... Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA...

  13. Kinetics of neptunium (5) disproprotionation in nitric acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Koltunov, V S; Tikhonov, M F

    1975-01-01

    The kinetics of Np(5) disproportionation in HNO/sub 3/+NaNO/sub 3/ solutions at the ionic strength ..mu..=4 is studied by spectrophotometric method in the region of (HNO/sub 3/) = 2.1-4 M at 61-96 deg C. To shift an equilibrium of reaction and to exclude the reverse reaction of Np(6) and Np(4), 0.02 M of hydrazine was added to the solution which rapidly reduced Np(6) to Np(5). Under these conditions no further reduction of Np(5) into Np(4) occurs directly with hydrazine. The disproportionation rate of NpO/sub 2//sup +/ ions obeys the equation: -d(Np(5))dt = 2k(Np(5))/sup 2/H/sup +2/, where k = 0.113 + 0.005M/sup -3/min/sup -1/ at 90 deg C and ..mu.. = 4. Temperature dependence of k enabled to compute the energy (E=16.4 kcal/mole), enthalpy (..delta..Hsup(*) = 15.8 kcal/mole) free energy (..delta..Fsup(*) = 24.0 kcal/mole) and entropy (..delta..S=-27 eu) of the reaction activation. The reaction mechanism includes a slow step of charge transfer between two protonated NpO/sub 2/H/sup 2 +/ ions. The data obtaned are compared to the results of Np(5) diproportionation in HClO/sub 4/ medium.

  14. Kinetics of Surfactant Desorption at an Air–Solution Interface

    KAUST Repository

    Morgan, C. E.

    2012-12-18

    The kinetics of re-equilibration of the anionic surfactant sodium dodecylbenzene sulfonate at the air-solution interface have been studied using neutron reflectivity. The experimental arrangement incorporates a novel flow cell in which the subphase can be exchanged (diluted) using a laminar flow while the surface region remains unaltered. The rate of the re-equilibration is relatively slow and occurs over many tens of minutes, which is comparable with the dilution time scale of approximately 10-30 min. A detailed mathematical model, in which the rate of the desorption is determined by transport through a near-surface diffusion layer into a diluted bulk solution below, is developed and provides a good description of the time-dependent adsorption data. A key parameter of the model is the ratio of the depth of the diffusion layer, H c, to the depth of the fluid, Hf, and we find that this is related to the reduced Péclet number, Pe*, for the system, via Hc/Hf = C/Pe*1/2. Although from a highly idealized experimental arrangement, the results provide an important insight into the "rinse mechanism", which is applicable to a wide variety of domestic and industrial circumstances. © 2012 American Chemical Society.

  15. Degradation kinetics of ptaquiloside in soil and soil solution.

    Science.gov (United States)

    Ovesen, Rikke Gleerup; Rasmussen, Lars Holm; Hansen, Hans Christian Bruun

    2008-02-01

    Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glycoside produced in bracken (Pteridium aquilinum (L.) Kuhn), a widespread, aggressive weed. Transfer of PTA to soil and soil solution eventually may contaminate groundwater and surface water. Degradation rates of PTA were quantified in soil and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction was similar in all horizons, with the rate constant k(1F) ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k(1S) ranging between 0.00067 and 0.029/ h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils. Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA by clay silicates. Ptaquiloside appeared to be stable in all soil solutions, in which no degradation was observed within a period of 28 d, in strong contrast to previous studies of hydrolysis rates in artificial aqueous electrolytes. The present study predicts that the risk of PTA leaching is controlled mainly by the residence time of pore water in soil, soil microbial activity, and content of organic matter and clay silicates.

  16. Ionic solubility and solutal advection governed augmented evaporation kinetics of salt solution pendant droplets

    Science.gov (United States)

    Jaiswal, Vivek; Harikrishnan, A. R.; Khurana, Gargi; Dhar, Purbarun

    2018-01-01

    The presence of dispersed inclusions is known to modify the interfacial characteristics in liquids by adsorption-desorption of the ions at interfaces. The present article reports the influencing role of dissolved ions in a polar fluid on its evaporation dynamics. The evaporation dynamics of pendant droplets of aqueous solutions of variant simple salts and concentrations have been experimentally studied. The presence of salts is observed to enhance the evaporation rate (obeying the classical D2 law), and the enhancement has been found to hold a direct proportionality to the concentration of the dissolved salt. Furthermore, it is observed that the degree of enhancement in the evaporation rate is also directly proportional to the solubility of the salt in question. The phenomenon is explained based on the chemical kinetics and thermodynamics of hydration of the ionic species in the polar fluid. The classical evaporation rate constant formulation is found to be inadequate in modeling the enhanced species transport. Additional probing via particle image velocimetry reveals augmented internal circulation within the evaporating salt based drops compared to pure water. Mapping the dynamic surface tension reveals that a salt concentration gradient is generated between the bulk and periphery of the droplet and it could be responsible for the internal advection cells visualized. A thermo-solutal Marangoni and Rayleigh convection based mathematical formulation has been put forward, and it is shown that the enhanced solute-thermal convection could play a major role in enhanced evaporation. The internal circulation mapped from experiments is found to be in good quantitative agreement with the model predictions. Scaling analysis further reveals that the stability of the solutal Marangoni convection surpasses the thermal counterpart with higher salt concentration and solubility. The present article sheds insight into the possible domineering role of conjugate thermohydraulic and

  17. A Sustainable Spacecraft Component Database Solution, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Numerous spacecraft component databases have been developed to support NASA, DoD, and contractor design centers and design tools. Despite the clear utility of...

  18. an improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    DELL

    Accuracies of these methods were evaluated using relative error, Akaike ... Keywords: Wastewater, Environmental Engineering, Biochemical Oxygen Demand Kinetic Parameters,. Statistical ... evaluating organic pollution level and quality of wastewaters. ... compounds ...... method can be applied on electronic devices, and.

  19. Kinetics of reactions of aquacobalamin with aspartic and glutamic acids and their amides in water solutions

    Science.gov (United States)

    Bui, T. T. T.; Sal'nikov, D. S.; Dereven'kov, I. A.; Makarov, S. V.

    2017-04-01

    The kinetics of aquacobalamin reaction with aspartic and glutamic acids, and with their amides in water solutions, is studied via spectrophotometry. The kinetic and activation parameters of the process are determined. It is shown that the reaction product is cobalamin-amino acid complex. The data are compared to results on the reaction between aquacobalamin and primary amines.

  20. An improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    This paper evaluated selected Biochemical Oxygen Demand first order kinetics methods. Domesticinstitutional wastewaters were collected twice in a month for three months from the Obafemi Awolowo University, Ile-Ife waste stabilization ponds. Biochemical Oxygen Demand concentrations at different days were determined ...

  1. Numerical solution of the kinetic equation in reactor shielding

    International Nuclear Information System (INIS)

    Germogenova, T.A.

    1975-01-01

    A review is made of methods of solving marginal problems of multi-group systems of equations of neutron and γ radiation transfer. The first stage of the solution - the quantification of the basic task, is determined by the qualitative behaviour of the solution - is the nature of its performance and asymptotics. In the second stage - solution of the approximating system, various modifications of the iterative method are as a rule used. A description is given of the features of the major Soviet complexes of programmes (ROZ and RADUGA) for the solution of multi-group systems of transfer equations and some methodological research findings are presented. (author)

  2. Kinetics of transuranium element oxidation-reduction reactions in solution

    International Nuclear Information System (INIS)

    Gourisse, D.

    1966-09-01

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

  3. The thermodynamics and kinetics of interstitial solid solutions

    International Nuclear Information System (INIS)

    Silva, J.R.G. da.

    1976-04-01

    Studies of hydrogen metal systems where the hidrogen is disolved in a solid solution are presented. Particular items of interest are: the thermodynamics of the hydrogen-iron system; the solubility of hidrogen in super pure iron single crytals; the thermodinamic functions of hydrogen in solid solutions of Nb, Ta and V; and the solubility of hydrogen in α-manganese. The diffusion of carbon and nitrogen in BCC iron is also studied

  4. KINETICS OF THE HYDROXYPROPYLATION OF POTATO STARCH IN AQUEOUS-SOLUTION

    NARCIS (Netherlands)

    LAMMERS, G; STAMHUIS, EJ; BEENACKERS, AACM

    Kinetic results are presented for the hydroxypropylation of Potato starch with methyloxirane in aqueous solution. Reaction temperatures were varied from 303 to 362 K. Sodium hydroxide was used as a catalyst. The overall conversion rate of methyloxirane in alkaline starch solution is determined by

  5. Homotopy analysis solutions of point kinetics equations with one delayed precursor group

    International Nuclear Information System (INIS)

    Zhu Qian; Luo Lei; Chen Zhiyun; Li Haofeng

    2010-01-01

    Homotopy analysis method is proposed to obtain series solutions of nonlinear differential equations. Homotopy analysis method was applied for the point kinetics equations with one delayed precursor group. Analytic solutions were obtained using homotopy analysis method, and the algorithm was analysed. The results show that the algorithm computation time and precision agree with the engineering requirements. (authors)

  6. Zebrafish Database: Customizable, Free, and Open-Source Solution for Facility Management.

    Science.gov (United States)

    Yakulov, Toma Antonov; Walz, Gerd

    2015-12-01

    Zebrafish Database is a web-based customizable database solution, which can be easily adapted to serve both single laboratories and facilities housing thousands of zebrafish lines. The database allows the users to keep track of details regarding the various genomic features, zebrafish lines, zebrafish batches, and their respective locations. Advanced search and reporting options are available. Unique features are the ability to upload files and images that are associated with the respective records and an integrated calendar component that supports multiple calendars and categories. Built on the basis of the Joomla content management system, the Zebrafish Database is easily extendable without the need for advanced programming skills.

  7. The soliton solution of BBGKY quantum kinetic equations chain for different type particles system

    International Nuclear Information System (INIS)

    Rasulova, M.Yu.; Avazov, U.; Hassan, T.

    2006-12-01

    In the present paper on the basis of BBGKY chain of quantum kinetic equations the chain of equations for correlation matrices is derived, describing the evolution of a system of different types particles, which interact by pair potential. The series, which is the solution of this chain of equations for correlation matrices, is suggested. Using this series the solution of the last chain of equations is reduced to a solution of a set of homogeneous and nonhomogeneous von-Neumann's kinetic equations (analogue of Vlasov equations for quantum case). The first and second equations of this set of equations coincide with the first and second kinetic equations of the set, which is used in plasma physics. For an potential in the form of Dirac delta function, the solution of von-Neumann equation is defined through soliton solution of nonlinear Schrodinger equations. Based on von-Neumann equation one can define all terms of series, which is a solution of a chain of equations for correlation matrices. On the basis of these correlation matrices for a system of different types of particles we can define exact solution of BBGKY chain of quantum kinetic equations

  8. Low temperature kinetics of In-Cd solid solution decomposition

    Czech Academy of Sciences Publication Activity Database

    Pal-Val, P.P.; Pal-Val, L.N.; Ostapovets, A.A.; Vaněk, Přemysl

    2008-01-01

    Roč. 137, - (2008), s. 35-42 ISSN 1012-0394 Institutional research plan: CEZ:AV0Z10100520 Keywords : low temperatures * In-based alloys * solid solutions * isothermal structure instability * Young's modulus * electrical resistivity * phase diagrams Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.scientific.net/3-908451-53-1/35/

  9. Kinetics of absorption of carbon dioxide in aqueous ammonia solutions

    NARCIS (Netherlands)

    Derks, P. W. J.; Versteeg, G. F.

    2009-01-01

    In the present work the absorption of carbon dioxide into aqueous ammonia solutions has been studied in a stirred cell reactor, at low temperatures and ammonia concentrations ranging from 0.1 to about 7 kmol m-3. The absorption experiments were carried out at conditions where the so-called pseudo

  10. Kinetics and mechanism of nitrobenzene hydrogenation to phenylhydroxylamine in rhenium thiocomplexes solutions

    International Nuclear Information System (INIS)

    Korenyako, G.I.; Belousov, V.M.

    1985-01-01

    A study was made on kinetics of nitrobenzene hydrogenation to phenylhydroxylamine in dimethylformamide solutions of rhenium thiocomplexes. The mechanism of hydrogenation was suggested. Formation of hydride catalyst complex represents the first stage of the process. Kinetic equation derived on the basis of suggested mechanism corresponds satisfactorily with experimental results. Thermodynamic parameters of separate process stages calculated on the basis of equilibrium constant values testify as well to the benefit of suggested mechanism

  11. Biosorption kinetics of Cd (II), Cr (III) and Pb (II) in aqueous solutions by olive stone

    OpenAIRE

    M. Calero; F. Hernáinz; G. Blázquez; M. A. Martín-Lara; G. Tenorio

    2009-01-01

    A by-product from olive oil production, olive stone, was investigated for the removal of Cd (II), Cr (III) and Pb (II) from aqueous solutions. The kinetics of biosorption are studied, analyzing the effect of the initial concentration of metal and temperature. Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models have been used to represent the kinetics of the process and obtain the main kinetic parameters. The results show that the pseudo-second order model is th...

  12. Analytic solutions of the multigroup space-time reactor kinetics equations

    International Nuclear Information System (INIS)

    Lee, C.E.; Rottler, S.

    1986-01-01

    The development of analytical and numerical solutions to the reactor kinetics equations is reviewed. Analytic solutions of the multigroup space-time reactor kinetics equations are developed for bare and reflected slabs and spherical reactors for zero flux, zero current and extrapolated endpoint boundary conditions. The material properties of the reactors are assumed constant in space and time, but spatially-dependent source terms and initial conditions are investigated. The system of partial differential equations is reduced to a set of linear ordinary differential equations by the Laplace transform method. These equations are solved by matrix Green's functions yielding a general matrix solution for the neutron flux and precursor concentration in the Laplace transform space. The detailed pole structure of the Laplace transform matrix solutions is investigated. The temporally- and spatially-dependent solutions are determined from the inverse Laplace transform using the Cauchy residue theorem, the theorem of Frobenius, a knowledge of the detailed pole structure and matrix operators. (author)

  13. NMR studies of proton exchange kinetics in aqueous formaldehyde solutions.

    Science.gov (United States)

    Rivlin, Michal; Eliav, Uzi; Navon, Gil

    2014-05-01

    Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0±1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼10(4)s(-1) at pH 7.4 and 37°C, the activation energy, 50.2kJ/mol and its pH dependence at 1.1°C was fitted to: k (s(-1))=520+6.5×10(7)[H(+)]+3.0×10(9)[OH(-)]. Copyright © 2014. Published by Elsevier Inc.

  14. An analytical solution for the two-group kinetic neutron diffusion equation in cylindrical geometry

    International Nuclear Information System (INIS)

    Fernandes, Julio Cesar L.; Vilhena, Marco Tullio; Bodmann, Bardo Ernst

    2011-01-01

    Recently the two-group Kinetic Neutron Diffusion Equation with six groups of delay neutron precursor in a rectangle was solved by the Laplace Transform Technique. In this work, we report on an analytical solution for this sort of problem but in cylindrical geometry, assuming a homogeneous and infinite height cylinder. The solution is obtained applying the Hankel Transform to the Kinetic Diffusion equation and solving the transformed problem by the same procedure used in the rectangle. We also present numerical simulations and comparisons against results available in literature. (author)

  15. Databases

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.

    Information on bibliographic as well as numeric/textual databases relevant to coastal geomorphology has been included in a tabular form. Databases cover a broad spectrum of related subjects like coastal environment and population aspects, coastline...

  16. Kinetics of diuron and amitrole adsorption from aqueous solution on activated carbons.

    Science.gov (United States)

    Fontecha-Cámara, M A; López-Ramón, M V; Pastrana-Martínez, L M; Moreno-Castilla, C

    2008-08-15

    A study was conducted on the adsorption kinetics of diuron and amitrole from aqueous solutions on activated carbons of different particle sizes and on an activated carbon fiber. Different kinetic models were applied to the experimental results obtained. A pseudo-second-order rate equation fitted the adsorption kinetics data better than a pseudo-first-order rate equation. Amitrole showed faster adsorption kinetics compared with diuron because of the smaller size of the former herbicide, despite its lower driving force for adsorption. Both reaction rate constants increased when the particle size decreased. The activated carbon fiber and the activated carbon of smallest particle size (0.03 mm) showed similar adsorption kinetics. The intraparticle diffusion rate constant increased with higher initial concentration of herbicides in solution and with lower particle size of the adsorbent. This is because the rise in initial concentration increased the amount adsorbed at equilibrium, and the reduction in particle size increased the number of collisions between adsorbate and adsorbent particles. Demineralization of the activated carbon with particle size of 0.5mm had practically no effect on the adsorption kinetics.

  17. An Explicit Finite Difference scheme for numerical solution of fractional neutron point kinetic equation

    International Nuclear Information System (INIS)

    Saha Ray, S.; Patra, A.

    2012-01-01

    Highlights: ► In this paper fractional neutron point kinetic equation has been analyzed. ► The numerical solution for fractional neutron point kinetic equation is obtained. ► Explicit Finite Difference Method has been applied. ► Supercritical reactivity, critical reactivity and subcritical reactivity analyzed. ► Comparison between fractional and classical neutron density is presented. - Abstract: In the present article, a numerical procedure to efficiently calculate the solution for fractional point kinetics equation in nuclear reactor dynamics is investigated. The Explicit Finite Difference Method is applied to solve the fractional neutron point kinetic equation with the Grunwald–Letnikov (GL) definition (). Fractional Neutron Point Kinetic Model has been analyzed for the dynamic behavior of the neutron motion in which the relaxation time associated with a variation in the neutron flux involves a fractional order acting as exponent of the relaxation time, to obtain the best operation of a nuclear reactor dynamics. Results for neutron dynamic behavior for subcritical reactivity, supercritical reactivity and critical reactivity and also for different values of fractional order have been presented and compared with the classical neutron point kinetic (NPK) equation as well as the results obtained by the learned researchers .

  18. Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide

    International Nuclear Information System (INIS)

    Danilova, M.G.; Sveshnikova, L.L.; Stavitskaya, T.A.; Repinskij, S.M.

    1991-01-01

    Dissolution kinetics of lead telluride in alkali solutions of hydrogen peroxide was investigated. Dependences of change of PbTe dissolution rate on concentration of hydrogen peroxide and alkali in the solution were obtained. It is shown that dissolution rate of lead telluride is affected by dissolution rate of lead oxide, representing the product of ReTe dissolution. The obtained regularities can be explained by change of solution structure with increase of KOH concentration and by the state of hydrogen peroxide in the solution

  19. Machine learning-based kinetic modeling: a robust and reproducible solution for quantitative analysis of dynamic PET data.

    Science.gov (United States)

    Pan, Leyun; Cheng, Caixia; Haberkorn, Uwe; Dimitrakopoulou-Strauss, Antonia

    2017-05-07

    A variety of compartment models are used for the quantitative analysis of dynamic positron emission tomography (PET) data. Traditionally, these models use an iterative fitting (IF) method to find the least squares between the measured and calculated values over time, which may encounter some problems such as the overfitting of model parameters and a lack of reproducibility, especially when handling noisy data or error data. In this paper, a machine learning (ML) based kinetic modeling method is introduced, which can fully utilize a historical reference database to build a moderate kinetic model directly dealing with noisy data but not trying to smooth the noise in the image. Also, due to the database, the presented method is capable of automatically adjusting the models using a multi-thread grid parameter searching technique. Furthermore, a candidate competition concept is proposed to combine the advantages of the ML and IF modeling methods, which could find a balance between fitting to historical data and to the unseen target curve. The machine learning based method provides a robust and reproducible solution that is user-independent for VOI-based and pixel-wise quantitative analysis of dynamic PET data.

  20. Machine learning-based kinetic modeling: a robust and reproducible solution for quantitative analysis of dynamic PET data

    Science.gov (United States)

    Pan, Leyun; Cheng, Caixia; Haberkorn, Uwe; Dimitrakopoulou-Strauss, Antonia

    2017-05-01

    A variety of compartment models are used for the quantitative analysis of dynamic positron emission tomography (PET) data. Traditionally, these models use an iterative fitting (IF) method to find the least squares between the measured and calculated values over time, which may encounter some problems such as the overfitting of model parameters and a lack of reproducibility, especially when handling noisy data or error data. In this paper, a machine learning (ML) based kinetic modeling method is introduced, which can fully utilize a historical reference database to build a moderate kinetic model directly dealing with noisy data but not trying to smooth the noise in the image. Also, due to the database, the presented method is capable of automatically adjusting the models using a multi-thread grid parameter searching technique. Furthermore, a candidate competition concept is proposed to combine the advantages of the ML and IF modeling methods, which could find a balance between fitting to historical data and to the unseen target curve. The machine learning based method provides a robust and reproducible solution that is user-independent for VOI-based and pixel-wise quantitative analysis of dynamic PET data.

  1. On a closed form solution of the point kinetics equations with reactivity feedback of temperature

    International Nuclear Information System (INIS)

    Silva, Jeronimo J.A.; Vilhena, Marco T.M.B.; Petersen, Claudio Z.; Bodmann, Bardo E.J.; Alvim, Antonio C.M.

    2011-01-01

    An analytical solution of the point kinetics equations to calculate reactivity as a function of time by the Decomposition method has recently appeared in the literature. In this paper, we go one step forward, by considering the neutron point kinetics equations together with temperature feedback effects. To accomplish that, we extended the point kinetics by a temperature perturbation, obtaining a second order nonlinear ordinary differential equation. This equation is then solved by the Decomposition Method, that is, by expanding the neutron density in a series and the nonlinear terms into Adomian Polynomials. Substituting these expansions into the nonlinear ordinary equation, we construct a recursive set of linear problems that can be solved by the methodology previously mentioned for the point kinetics equation. We also report on numerical simulations and comparisons against literature results. (author)

  2. Investigation of cadmium(2) electrolytic reduction kinetics from α-aminoacetic solutions

    International Nuclear Information System (INIS)

    Nikitenko, V.N.; Litovchenko, K.I.; Kublanovskij, V.S.

    1980-01-01

    Kinetics and reduction mechanism of cadmium(2) reduction from α-amino acetic solutions is studied. It is shown that glycine and hydrogen ions take part directly in the electrode reaction of cadmium (2) reduction from α-amino acetic solutions. It is established that complex ion of the composition CdCl + is electroactive forM of the substance, which takes part in the transfer reaction. The rate of electrode process is limited with reduced ion supply to the electrode surface

  3. Analytical solution of point kinetic equations for sub-critical systems

    International Nuclear Information System (INIS)

    Henrice Junior, Edson; Goncalves, Alessandro C.

    2013-01-01

    This article presents an analytical solution for the set of point kinetic equations for sub-critical reactors. This solution stems from the ordinary, non-homogeneous differential equation that rules the neutron density and that presents the incomplete Gamma function in its functional form. The method used proved advantageous and allowed practical applications such as the linear insertion of reactivity, considering an external constant source or with both varying linearly. (author)

  4. Kinetics of a new phase formation in supersaturated solid solutions. 1. Dilute one-component systems

    International Nuclear Information System (INIS)

    Dubinko, V.I.

    1991-07-01

    A complete set of kinetic equations describing the diffusion decay of supersaturated solutions, as well as the formation of new-phase fluctuations in equilibrium systems, is derived. A novel method of determining forward and backward reaction rates entering the master equation is proposed which does not require the use of any reference cluster size distribution, either the constrained or the true equilibrium one, employed in all modifications of the classical nucleation theory. Instead, this reference distribution can be obtained as an equilibrium solution of the present master equation. The main advantage of this method is the possibility to take into account various factors affecting the diffusion decay, such as the reaction kinetics at the precipitate surfaces and the diffusion kinetics in the mother phase with account of elastic interaction between nucleating species and their clusters. The latter is of a key importance in the irradiation environment considered in the forthcoming second part of the article. (author). 3 refs

  5. An analytical solution of the one-dimensional neutron diffusion kinetic equation in cartesian geometry

    International Nuclear Information System (INIS)

    Ceolin, Celina; Vilhena, Marco T.; Petersen, Claudio Z.

    2009-01-01

    In this work we report an analytical solution for the monoenergetic neutron diffusion kinetic equation in cartesian geometry. Bearing in mind that the equation for the delayed neutron precursor concentration is a first order linear differential equation in the time variable, to make possible the application of the GITT approach to the kinetic equation, we introduce a fictitious diffusion term multiplied by a positive small value ε. By this procedure, we are able to solve this set of equations. Indeed, applying the GITT technique to the modified diffusion kinetic equation, we come out with a matrix differential equation which has a well known analytical solution when ε goes to zero. We report numerical simulations as well study of numerical convergence of the results attained. (author)

  6. STEREOCHEMICAL ASPECTS OF HYDRATION OF CARBOHYDRATES IN AQUEOUS-SOLUTIONS .2. KINETIC MEDIUM EFFECTS

    NARCIS (Netherlands)

    GALEMA, SA; BLANDAMER, MJ; ENGBERTS, JBFN

    1992-01-01

    Rate constants for the hydrolysis of 1-benzoyl-3-phenyl-1,2,4-triazole in aqueous solutions of carbohydrates have been measured as a function of molality and nature of added mono- and disaccharides. The kinetic medium effects induced by the carbohydrates originate from hydration sphere overlap

  7. A calorimetric study of solute effects on the kinetic stability of a-amylase

    DEFF Research Database (Denmark)

    Olsen, Søren Nymand; Andersen, Kim Bruno; Øgendal, Lars Holm

    2009-01-01

    In this study we evaluated the applications of isothermal titration calorimetry (ITC) to Study solute effects on the kinetics of irreversible protein denaturation. More specifically, denaturation of Bacillus Halmapalus alpha-amylase (BHA) was initiated by addition of EDTA to the calorimetric cell...

  8. Databases

    Directory of Open Access Journals (Sweden)

    Nick Ryan

    2004-01-01

    Full Text Available Databases are deeply embedded in archaeology, underpinning and supporting many aspects of the subject. However, as well as providing a means for storing, retrieving and modifying data, databases themselves must be a result of a detailed analysis and design process. This article looks at this process, and shows how the characteristics of data models affect the process of database design and implementation. The impact of the Internet on the development of databases is examined, and the article concludes with a discussion of a range of issues associated with the recording and management of archaeological data.

  9. Analytical solution of Luedeking-Piret equation for a batch fermentation obeying Monod growth kinetics.

    Science.gov (United States)

    Garnier, Alain; Gaillet, Bruno

    2015-12-01

    Not so many fermentation mathematical models allow analytical solutions of batch process dynamics. The most widely used is the combination of the logistic microbial growth kinetics with Luedeking-Piret bioproduct synthesis relation. However, the logistic equation is principally based on formalistic similarities and only fits a limited range of fermentation types. In this article, we have developed an analytical solution for the combination of Monod growth kinetics with Luedeking-Piret relation, which can be identified by linear regression and used to simulate batch fermentation evolution. Two classical examples are used to show the quality of fit and the simplicity of the method proposed. A solution for the combination of Haldane substrate-limited growth model combined with Luedeking-Piret relation is also provided. These models could prove useful for the analysis of fermentation data in industry as well as academia. © 2015 Wiley Periodicals, Inc.

  10. Kinetics of boron ions sorption from solution by inorganic anion exchanger of MNH type

    International Nuclear Information System (INIS)

    Leont'eva, G.V.

    1990-01-01

    By the method of restricted volume in case of boron excess in solution kinetics of boron sorption by inorganic anion-exchanger of the composition (Mg 0.55 Ni 0.45 )(OH) 2 has been studied. The sorption was carried out from solution containing Na + , K + , Ca 2+ , Mg 2+ , Cl - , SO 4 2- , CO 3 2- , HCO 3 at 283, 293, 303 and 313 K and pH 8.1, while the density of solution was 1225 kg/m 3 . The sorption mechanism was considered. It is shown that heterogeneity of the character of kinetic curves is caused by the change in the mechanism of limiting stages of the sorption

  11. A radiochemical study of gold electrodeposition kinetics in alkaline cyanide solutions

    International Nuclear Information System (INIS)

    Poshkus, D.; Agafonovas, G.; Zhebrauskas, A.

    1995-01-01

    Kinetics of gold electrodeposition from alkaline cyanide solutions was investigated by the use of labelled gold 195 atoms. The absorption of cyanide containing species from alkaline cyanide and dicyanoaurate solutions on a gold electrode by the use of labelled carbon atoms was investigated. Polarization curves of anodic dissolution and cathodic deposition of gold in alkaline cyanide solutions were obtained. The values of standard potential, exchange current density, transfer coefficient and standard polarization rate were determined from polarization curves. The errors in current density caused by the nuclear disintegration statistics were evaluated. 28 refs., 1 tab., 4 figs

  12. MyMolDB: a micromolecular database solution with open source and free components.

    Science.gov (United States)

    Xia, Bing; Tai, Zheng-Fu; Gu, Yu-Cheng; Li, Bang-Jing; Ding, Li-Sheng; Zhou, Yan

    2011-10-01

    To manage chemical structures in small laboratories is one of the important daily tasks. Few solutions are available on the internet, and most of them are closed source applications. The open-source applications typically have limited capability and basic cheminformatics functionalities. In this article, we describe an open-source solution to manage chemicals in research groups based on open source and free components. It has a user-friendly interface with the functions of chemical handling and intensive searching. MyMolDB is a micromolecular database solution that supports exact, substructure, similarity, and combined searching. This solution is mainly implemented using scripting language Python with a web-based interface for compound management and searching. Almost all the searches are in essence done with pure SQL on the database by using the high performance of the database engine. Thus, impressive searching speed has been archived in large data sets for no external Central Processing Unit (CPU) consuming languages were involved in the key procedure of the searching. MyMolDB is an open-source software and can be modified and/or redistributed under GNU General Public License version 3 published by the Free Software Foundation (Free Software Foundation Inc. The GNU General Public License, Version 3, 2007. Available at: http://www.gnu.org/licenses/gpl.html). The software itself can be found at http://code.google.com/p/mymoldb/. Copyright © 2011 Wiley Periodicals, Inc.

  13. The kinetics of dye formation by pulse radiolysis of pararosaniline cyanide in aqueous or organic solution

    International Nuclear Information System (INIS)

    McLaughlin, W.L.; Holcman, J.; Sehested, K.; Kosanic, M.M.

    1979-11-01

    The radiation-induced conversion of the leucocyanide of pararosaniline dye to the highly colored salt-isomer of the dye in acidic aqueous solution (wavelength of maximum absorption lambda sub(max)=540 nm) or polar organic solution (lambda sub(max)=550 nm), takes place in two separate processes. The first is very fast (within 3 s -1 to 10 6 s -1 , as the acidity or concentration of an oxidizing agent increases. In oxygen-free acidic aqueous or organic solutions (argon saturated) there is an unstable transient species (lambdasub(max)=380 nm). When using O 2 or N 2 O-saturated aqueous or organic solution, there is no intermediate absorption band at 380 nm, but the slow process of dye formation at 540 or 550 nm is still sequential to the initial fast process having somewhat faster kinetics than in Ar-saturated solution. (author)

  14. An accurate solution of point reactor neutron kinetics equations of multi-group of delayed neutrons

    International Nuclear Information System (INIS)

    Yamoah, S.; Akaho, E.H.K.; Nyarko, B.J.B.

    2013-01-01

    Highlights: ► Analytical solution is proposed to solve the point reactor kinetics equations (PRKE). ► The method is based on formulating a coefficient matrix of the PRKE. ► The method was applied to solve the PRKE for six groups of delayed neutrons. ► Results shows good agreement with other traditional methods in literature. ► The method is accurate and efficient for solving the point reactor kinetics equations. - Abstract: The understanding of the time-dependent behaviour of the neutron population in a nuclear reactor in response to either a planned or unplanned change in the reactor conditions is of great importance to the safe and reliable operation of the reactor. In this study, an accurate analytical solution of point reactor kinetics equations with multi-group of delayed neutrons for specified reactivity changes is proposed to calculate the change in neutron density. The method is based on formulating a coefficient matrix of the homogenous differential equations of the point reactor kinetics equations and calculating the eigenvalues and the corresponding eigenvectors of the coefficient matrix. A small time interval is chosen within which reactivity relatively stays constant. The analytical method was applied to solve the point reactor kinetics equations with six-groups delayed neutrons for a representative thermal reactor. The problems of step, ramp and temperature feedback reactivities are computed and the results compared with other traditional methods. The comparison shows that the method presented in this study is accurate and efficient for solving the point reactor kinetics equations of multi-group of delayed neutrons

  15. Kinetics of adsorption of dyes from aqueous solution using activated carbon prepared from waste apricot

    International Nuclear Information System (INIS)

    Onal, Yunus

    2006-01-01

    Adsorbent (WA11Zn5) has been prepared from waste apricot by chemical activation with ZnCl 2 . Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N 2 adsorption and DFT plus software. Adsorption of three dyes, namely, Methylene Blue (MB), Malachite Green (MG), Crystal Violet (CV), onto activated carbon in aqueous solution was studied in a batch system with respect to contact time, temperature. The kinetics of adsorption of MB, MG and CV have been discussed using six kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the Elovich equation, the intraparticle diffusion model, the Bangham equation, the modified Freundlich equation. Kinetic parameters and correlation coefficients were determined. It was shown that the second-order kinetic equation could describe the adsorption kinetics for three dyes. The dyes uptake process was found to be controlled by external mass transfer at earlier stages (before 5 min) and by intraparticle diffusion at later stages (after 5 min). Thermodynamic parameters, such as ΔG, ΔH and ΔS, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures and concentrations. The thermodynamics of dyes-WA11Zn5 system indicates endothermic process

  16. Kinetics of Ni3S2 sulfide dissolution in solutions of sulfuric and hydrochloric acids

    Science.gov (United States)

    Palant, A. A.; Bryukvin, V. A.; Vinetskaya, T. N.; Makarenkova, T. A.

    2008-02-01

    The kinetics of Ni3S2 sulfide (heazlewoodite) dissolution in solutions of hydrochloric and sulfuric acids is studied. The process under study in the temperature range of 30 90°C is found to occur in a kinetic regime and is controlled by the corresponding chemical reactions of the Ni3S2 decomposition by solutions of inorganic acids ( E a = 67 92 kJ/mol, or 16 22 kcal/mol). The only exception is the Ni3S2-HCl system at elevated temperatures (60 90°C). In this case, the apparent activation energy decreases sharply to 8.8 kJ/mol (2.1 kcal/mol), which is explained by the catalytic effect of gaseous chlorine formed under these conditions. The studies performed are related to the physicochemical substantiation of the hydrometallurgical processing of the copper-nickel converter mattes produced in the industrial cycle of the Norilsk Mining Company.

  17. Kinetic characteristics of crystallization from model solutions of the oral cavity

    Science.gov (United States)

    Golovanova, O. A.; Chikanova, E. S.

    2015-11-01

    The kinetic regularities of crystallization from model solutions of the oral cavity are investigated and the growth order and constants are determined for two systems: saliva and dental plaque fluid (DPF). It is found that the stage in which the number of particles increases occurs in the range of mixed kinetics and their growth occurs in the diffusion range. The enhancing effect of additives HCO- 3 > C6H12O6 > F- and the retarding effect of Mg2+ are demonstrated. The HCO- 3 and Mg2+ additives, taken in high concentrations, affect the corresponding rate constants. It is revealed the crystallization in DPF is favorable for the growth of small crystallites, while the model solution of saliva is, vice versa, favorable for the growth of larger crystals.

  18. On the exact solution for the multi-group kinetic neutron diffusion equation in a rectangle

    International Nuclear Information System (INIS)

    Petersen, C.Z.; Vilhena, M.T.M.B. de; Bodmann, B.E.J.

    2011-01-01

    In this work we consider the two-group bi-dimensional kinetic neutron diffusion equation. The solution procedure formalism is general with respect to the number of energy groups, neutron precursor families and regions with different chemical compositions. The fast and thermal flux and the delayed neutron precursor yields are expanded in a truncated double series in terms of eigenfunctions that, upon insertion into the kinetic equation and upon taking moments, results in a first order linear differential matrix equation with source terms. We split the matrix appearing in the transformed problem into a sum of a diagonal matrix plus the matrix containing the remaining terms and recast the transformed problem into a form that can be solved in the spirit of Adomian's recursive decomposition formalism. Convergence of the solution is guaranteed by the Cardinal Interpolation Theorem. We give numerical simulations and comparisons with available results in the literature. (author)

  19. The kinetics of anodic dissolution of rhenium in aqueous electrolyte solutions

    International Nuclear Information System (INIS)

    Atanasyants, A.G.; Kornienko, V.A.

    1986-01-01

    The kinetics of anodic rhenium dissolution was investigated by means of potentiodynamic and potentiostatic polarization curves recorded at temperature from 293 to 333 K in different media (NaOH, KOH, NaCl, NaBr, HCl, H 2 SO 4 ) using the rotating disc technique. It is shown that the kinetics of anodic rhenium dissolution and effective activation energy depend not only on the composition and pH value of the solutions but also on the structure of the dissolving rhenium surface. The investigation of the anodic behaviour of the rhenium monocrystal revealed the existence of anisotropy of the monocrystal electrochemical properties. The experimental results point to an important role of adsorption processes in anodic rhenium dissolution. Rhenium dissolution proceeds with formation of intermediate surface adsorption complexes between the metal and the components of the solution

  20. Kinetics of γ-rays induced decoloration of textile dye aqueous solutions

    International Nuclear Information System (INIS)

    Perkowski, J.; Ledakowicz, S.; Nowicki, L.

    1987-01-01

    The γ-rays induced decoloration of aqueous solutions of commercial dyes has been studied. Four chemical classes of dyes were applied. The initial dye concentration and the irradiation dose rate ranged from 0.025 to 0.250 g/dm 3 and 0.014 to 2.0 Gy/s respectively. On the base of obtained experimental data the kinetic paramaters in the proposed rate equation were calculated. 8 refs., 8 figs., 2 tabs. (author)

  1. KID - an algorithm for fast and efficient text mining used to automatically generate a database containing kinetic information of enzymes

    Directory of Open Access Journals (Sweden)

    Schomburg Dietmar

    2010-07-01

    Full Text Available Abstract Background The amount of available biological information is rapidly increasing and the focus of biological research has moved from single components to networks and even larger projects aiming at the analysis, modelling and simulation of biological networks as well as large scale comparison of cellular properties. It is therefore essential that biological knowledge is easily accessible. However, most information is contained in the written literature in an unstructured way, so that methods for the systematic extraction of knowledge directly from the primary literature have to be deployed. Description Here we present a text mining algorithm for the extraction of kinetic information such as KM, Ki, kcat etc. as well as associated information such as enzyme names, EC numbers, ligands, organisms, localisations, pH and temperatures. Using this rule- and dictionary-based approach, it was possible to extract 514,394 kinetic parameters of 13 categories (KM, Ki, kcat, kcat/KM, Vmax, IC50, S0.5, Kd, Ka, t1/2, pI, nH, specific activity, Vmax/KM from about 17 million PubMed abstracts and combine them with other data in the abstract. A manual verification of approx. 1,000 randomly chosen results yielded a recall between 51% and 84% and a precision ranging from 55% to 96%, depending of the category searched. The results were stored in a database and are available as "KID the KInetic Database" via the internet. Conclusions The presented algorithm delivers a considerable amount of information and therefore may aid to accelerate the research and the automated analysis required for today's systems biology approaches. The database obtained by analysing PubMed abstracts may be a valuable help in the field of chemical and biological kinetics. It is completely based upon text mining and therefore complements manually curated databases. The database is available at http://kid.tu-bs.de. The source code of the algorithm is provided under the GNU General Public

  2. Analytic solution of vector model kinetic equations with constant kernel and their applications

    International Nuclear Information System (INIS)

    Latyshev, A.V.

    1993-01-01

    For the first time exact solutions the heif-space boundary value problems for model kinetic equations is obtained. Here x > 0, μ is an element of (-∞, 0) union (0, +∞), Σ = diag {σ 1 , σ 2 }, C = [c ij ] - 2 x 2-matrix, Ψ (x, μ) is vector-column with elements ψ 1 and ψ 2 . Exact solution of the diffusion slip flow of the binary gas mixture as a application for the model Boltzmann equation with collision operator in the McCormack's form is found. 18 refs

  3. Analytic solution of boundary-value problems for nonstationary model kinetic equations

    International Nuclear Information System (INIS)

    Latyshev, A.V.; Yushkanov, A.A.

    1993-01-01

    A theory for constructing the solutions of boundary-value problems for non-stationary model kinetic equations is constructed. This theory was incorrectly presented equation, separation of the variables is used, this leading to a characteristic equation. Eigenfunctions are found in the space of generalized functions, and the eigenvalue spectrum is investigated. An existence and uniqueness theorem for the expansion of the Laplace transform of the solution with respect to the eigenfunctions is proved. The proof is constructive and gives explicit expressions for the expansion coefficients. An application to the Rayleigh problem is obtained, and the corresponding result of Cercignani is corrected

  4. Specific features of kinetics of He3-He4 solid solution transformations at superlow temperatures

    International Nuclear Information System (INIS)

    Mikheev, V.A.; Majdanov, V.A.; Mikhin, N.P.

    1986-01-01

    The NMR data on the phase transition kinetics of 3 He- 4 He solid solutions at T=100 mK are considered. Studied are solid helium samples of a molecular volume of 20.55 cm 2 /mol with a 3 He content of 0.54 %. An unusually long phase transition time is found which is dependent on the prehistory of sample. The spin diffusion of 3 He in the transformated solution concentrated phase is found to be of a quasi-one-dimensional nature with the diffusion coefficient value typical of liquid

  5. An online interactive geometric database including exact solutions of Einstein's field equations

    International Nuclear Information System (INIS)

    Ishak, Mustapha; Lake, Kayll

    2002-01-01

    We describe a new interactive database (GRDB) of geometric objects in the general area of differential geometry. Database objects include, but are not restricted to, exact solutions of Einstein's field equations. GRDB is designed for researchers (and teachers) in applied mathematics, physics and related fields. The flexible search environment allows the database to be useful over a wide spectrum of interests, for example, from practical considerations of neutron star models in astrophysics to abstract space-time classification schemes. The database is built using a modular and object-oriented design and uses several Java technologies (e.g. Applets, Servlets, JDBC). These are platform-independent and well adapted for applications developed for the World Wide Web. GRDB is accompanied by a virtual calculator (GRTensorJ), a graphical user interface to the computer algebra system GRTensorII, used to perform online coordinate, tetrad or basis calculations. The highly interactive nature of GRDB allows systematic internal self-checking and minimization of the required internal records. This new database is now available online at http://grdb.org

  6. DASTCOM5: A Portable and Current Database of Asteroid and Comet Orbit Solutions

    Science.gov (United States)

    Giorgini, Jon D.; Chamberlin, Alan B.

    2014-11-01

    A portable direct-access database containing all NASA/JPL asteroid and comet orbit solutions, with the software to access it, is available for download (ftp://ssd.jpl.nasa.gov/pub/xfr/dastcom5.zip; unzip -ao dastcom5.zip). DASTCOM5 contains the latest heliocentric IAU76/J2000 ecliptic osculating orbital elements for all known asteroids and comets as determined by a least-squares best-fit to ground-based optical, spacecraft, and radar astrometric measurements. Other physical, dynamical, and covariance parameters are included when known. A total of 142 parameters per object are supported within DASTCOM5. This information is suitable for initializing high-precision numerical integrations, assessing orbit geometry, computing trajectory uncertainties, visual magnitude, and summarizing physical characteristics of the body. The DASTCOM5 distribution is updated as often as hourly to include newly discovered objects or orbit solution updates. It includes an ASCII index of objects that supports look-ups based on name, current or past designation, SPK ID, MPC packed-designations, or record number. DASTCOM5 is the database used by the NASA/JPL Horizons ephemeris system. It is a subset exported from a larger MySQL-based relational Small-Body Database ("SBDB") maintained at JPL. The DASTCOM5 distribution is intended for programmers comfortable with UNIX/LINUX/MacOSX command-line usage who need to develop stand-alone applications. The goal of the implementation is to provide small, fast, portable, and flexibly programmatic access to JPL comet and asteroid orbit solutions. The supplied software library, examples, and application programs have been verified under gfortran, Lahey, Intel, and Sun 32/64-bit Linux/UNIX FORTRAN compilers. A command-line tool ("dxlook") is provided to enable database access from shell or script environments.

  7. Generic Schemes for Single-Molecule Kinetics. 3: Self-Consistent Pathway Solutions for Nonrenewal Processes.

    Science.gov (United States)

    Piephoff, D Evan; Cao, Jianshu

    2018-04-23

    We recently developed a pathway analysis framework (paper 1) for describing single-molecule kinetics for renewal (i.e., memoryless) processes based on the decomposition of a kinetic scheme into generic structures. In our approach, waiting time distribution functions corresponding to such structures are expressed in terms of self-consistent pathway solutions and concatenated to form measurable probability distribution functions (PDFs), affording a simple way to decompose and recombine a network. Here, we extend this framework to nonrenewal processes, which involve correlations between events, and employ it to formulate waiting time PDFs, including the first-passage time PDF, for a general kinetic network model. Our technique does not require the assumption of Poissonian kinetics, permitting a more general kinetic description than the usual rate approach, with minimal topological restrictiveness. To demonstrate the usefulness of this technique, we provide explicit calculations for our general model, which we adapt to two generic schemes for single-enzyme turnover with conformational interconversion. For each generic scheme, wherein the intermediate state(s) need not undergo Poissonian decay, the functional dependence of the mean first-passage time on the concentration of an external substrate is analyzed. When conformational detailed balance is satisfied, the enzyme turnover rate (related to the mean first-passage time) reduces to the celebrated Michaelis-Menten functional form, consistent with our previous work involving a similar scheme with all rate processes, thereby establishing further generality to this intriguing result. Our framework affords a general and intuitive approach for evaluating measurable waiting time PDFs and their moments, making it a potentially useful kinetic tool for a wide variety of single-molecule processes.

  8. Compactness and robustness: Applications in the solution of integral equations for chemical kinetics and electromagnetic scattering

    Science.gov (United States)

    Zhou, Yajun

    This thesis employs the topological concept of compactness to deduce robust solutions to two integral equations arising from chemistry and physics: the inverse Laplace problem in chemical kinetics and the vector wave scattering problem in dielectric optics. The inverse Laplace problem occurs in the quantitative understanding of biological processes that exhibit complex kinetic behavior: different subpopulations of transition events from the "reactant" state to the "product" state follow distinct reaction rate constants, which results in a weighted superposition of exponential decay modes. Reconstruction of the rate constant distribution from kinetic data is often critical for mechanistic understandings of chemical reactions related to biological macromolecules. We devise a "phase function approach" to recover the probability distribution of rate constants from decay data in the time domain. The robustness (numerical stability) of this reconstruction algorithm builds upon the continuity of the transformations connecting the relevant function spaces that are compact metric spaces. The robust "phase function approach" not only is useful for the analysis of heterogeneous subpopulations of exponential decays within a single transition step, but also is generalizable to the kinetic analysis of complex chemical reactions that involve multiple intermediate steps. A quantitative characterization of the light scattering is central to many meteoro-logical, optical, and medical applications. We give a rigorous treatment to electromagnetic scattering on arbitrarily shaped dielectric media via the Born equation: an integral equation with a strongly singular convolution kernel that corresponds to a non-compact Green operator. By constructing a quadratic polynomial of the Green operator that cancels out the kernel singularity and satisfies the compactness criterion, we reveal the universality of a real resonance mode in dielectric optics. Meanwhile, exploiting the properties of

  9. Effects of Temperature on Aggregation Kinetics of Graphene Oxide in Aqueous Solutions

    Science.gov (United States)

    Wang, M.; Gao, B.; Tang, D.; Sun, H.; Yin, X.; Yu, C.

    2017-12-01

    Temperature may play an important role in controlling graphene oxide (GO) stability in aqueous solutions, but it has been overlooked in the literature. In this work, laboratory experiments were conducted to determine the effects of temperature (6, 25, and 40 °C) on GO aggregation kinetics under different combinations of ionic strength, cation type, humic acid (HA) concentration by monitoring GO hydrodynamic radii and attachment efficiencies. The results showed that, without HA, temperature increase promoted GO aggregation in both monovalent (Na+ and K+) and divalent (Ca2+) solutions. This phenomenon might be caused by multiple processes including enhanced collision frequency, enhanced cation dehydration, and reduced electrostatic repulsion. The presence of HA introduced steric repulsion forces that enhanced GO stability and temperature showed different effects GO aggregation kinetics in monovalent and divalent electrolytes. In monovalent electrolytes, cold temperature diminished the steric repulsion of HA-coated GO. As a result, the fastest increasing rate of GO hydrodynamic radius and the smallest critical coagulation concentration value appeared at the lowest temperature (6 °C). Conversely, in divalent electrolyte solutions with HA, high temperate favored GO aggregation, probably because the interactions between Ca2+ and HA increased with temperature resulting in lower HA coating on GO. Findings of this work emphasized the importance of temperature as well as solution chemistry on the stability and fate of GO nanoparticles in aquatic environment.

  10. Estimation of the growth kinetics for the cooling crystallisation of paracetamol and ethanol solutions

    Science.gov (United States)

    Mitchell, Niall A.; Ó'Ciardhá, Clifford T.; Frawley, Patrick J.

    2011-08-01

    This work details the estimation of the growth kinetics of paracetamol in ethanol solutions for cooling crystallisation processes, by means of isothermal seeded batch experiments. The growth kinetics of paracetamol crystals were evaluated in isolation, with the growth rate assumed to be size independent. Prior knowledge of the Metastable Zone Width (MSZW) was required, so that supersaturation ratios of 1.7-1.1 could be induced in solution without the occurrence of nucleation. The technique involved the utilisation of two in-situ Process Analytical Techniques (PATs), with a Focused Beam Reflectance Measurement (FBRM ®) utilised to ensure that negligible nucleation occurred and an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) probe employed for online monitoring of solute concentration. Initial Particle Size Distributions (PSDs) were used in conjunction with desupersaturation profiles to determine the growth rate as a function of temperature and supersaturation. Furthermore, the effects of seed loading and size on the crystal growth rate were investigated. A numerical model, incorporating the population balance equation and the method of moments, was utilised to describe the crystal growth process. Experimental parameters were compared to the model simulation, with the accuracy of the model validated by means of the final product PSDs and solute concentration.

  11. Biosorption kinetics of Cd (II, Cr (III and Pb (II in aqueous solutions by olive stone

    Directory of Open Access Journals (Sweden)

    M. Calero

    2009-06-01

    Full Text Available A by-product from olive oil production, olive stone, was investigated for the removal of Cd (II, Cr (III and Pb (II from aqueous solutions. The kinetics of biosorption are studied, analyzing the effect of the initial concentration of metal and temperature. Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models have been used to represent the kinetics of the process and obtain the main kinetic parameters. The results show that the pseudo-second order model is the one that best describes the biosorption of the three metal ions for all the range of experimental conditions investigated. For the three metal ions, the maximum biosoption capacity and the initial biosorption rate increase when the initial metal concentration rises. However, the kinetic constant decreases when the initial metal concentration increases. The temperature effect on biosorption capacity for Cd (II and Cr (III is less significant; however, for Pb (II the effect of temperature is more important, especially when temperature rises from 25 to 40ºC. The biosorption capacity at mmol/g of olive stone changes in the following order: Cr>Cd>Pb. Thus, for an initial concentration of 220 mg/ℓ, a maximum sorption capacity of 0.079 mmol/g for Cr (III, 0.065 mmol/g for Cd (II and 0.028 mmol/g for Pb (II has been obtained.

  12. Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

    Science.gov (United States)

    Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

    2016-06-01

    In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

  13. OSMOTIC DEHYDRATION KINETICS OF GUAVAS IN MALTOSE SOLUTIONS WITH CALCIUM SALT*

    Directory of Open Access Journals (Sweden)

    S. DI S. MASTRANTONIO

    2009-03-01

    Full Text Available

    The osmotic dehydration kinetics of guavas in maltose solutions at 40 and 60ºBrix, with addition of 0, 0.6 and 1.2% of calcium lactate was studied in this paper and the final product quality was evaluated. The experiments were carried out up to 60 hours and samples were taken for analysis at different times to evaluate guavas weight reduction, water loss and sugar gain and to characterize the product according to its texture and color. After 24 hours of process the mass transfer of water and sugar between the osmotic solution and the fruit was negligible, showing that process equilibrium was reached. The increase of sugar concentration in the osmotic solution showed strong influence on the dehydration process, increasing the water loss and reducing sugar gain. The presence of calcium ions in the osmotic solution also influenced the kinetics of mass transfer and showed a strong influence on fruit texture. Higher values of stress and strain at failure were obtained when calcium lactate was employed. The effect of the different osmotic treatments on the color parameters was also investigated and significant changes were observed in the values of chroma C* and hue H* due to sugar concentration and calcium addition.

    KEYWORDS: Osmotic dehydration; kinetics; guava; maltose; calcium lactate.

  14. Uranium (VI) complexing by macrocyclic or chelating ligands in aqueous solutions stability, formation kinetics, polarographic properties

    International Nuclear Information System (INIS)

    Brighli, M.

    1984-07-01

    Stability of chelates (with EDTA,N,N ethylenediamine diacetic acid EDDA nitrilotriacetic acid NTA and iminodiacetic acid) of UO 2 2+ and UO 4 species of uranium VI is studied in aqueous solution (NaClO 4 3M at 25 deg celcius). Structure in solution are proposed and discussed for mononuclear species. Only complexing kinetics (formation and acid hydrolysis) of UO 4 with EDDA and NTA are studied by spectrophotometry (other reactions are too fast). Besides UO 2 2+ complexes are formed with crown ethers I5C5 and I8C6 in aqueous solution (TEA ClO 4 M/10 at 25 deg celcius. Complexes are probably stabilized by solvation. Results are confirmed by voltametry and reduction mechanisms of UO 2 2+ and its complexes on mercury drop are proposed. 143 refs [fr

  15. Kinetics of the exchange of oxygen between carbon dioxide and carbonate in aqueous solution

    International Nuclear Information System (INIS)

    Tu, C.K.; Silverman, D.N.

    1975-01-01

    A kinetic analysis of the exchange of oxygen between carbon dioxide and carbonate ion in alkaline, aqueous solutions is presented. The exchange was observed by placing 18 O-labeled carbonate, not enriched in 13 C, into solution with 13 C-enriched carbonate, not enriched in 18 O. The rate of depletion of 18 O from the 12 C-containing species and the rate of appearance of 18 O in the 13 C-containing species was measured by mass spectrometry. From these data, the second-order rate constant for the reaction between carbon dioxide and carbonate which results in the exchange of oxygen at 25 0 is 114 +- 11 M -1 sec -1 . It is emphasized that this exchange of oxygen between species of CO 2 in solution must be recognized in studies using 18 O labels to determine the fate of CO 2 in biochemical and physiological processes. (auth)

  16. A Spatio-Temporal Building Exposure Database and Information Life-Cycle Management Solution

    Directory of Open Access Journals (Sweden)

    Marc Wieland

    2017-04-01

    Full Text Available With an ever-increasing volume and complexity of data collected from a variety of sources, the efficient management of geospatial information becomes a key topic in disaster risk management. For example, the representation of assets exposed to natural disasters is subjected to changes throughout the different phases of risk management reaching from pre-disaster mitigation to the response after an event and the long-term recovery of affected assets. Spatio-temporal changes need to be integrated into a sound conceptual and technological framework able to deal with data coming from different sources, at varying scales, and changing in space and time. Especially managing the information life-cycle, the integration of heterogeneous information and the distributed versioning and release of geospatial information are important topics that need to become essential parts of modern exposure modelling solutions. The main purpose of this study is to provide a conceptual and technological framework to tackle the requirements implied by disaster risk management for describing exposed assets in space and time. An information life-cycle management solution is proposed, based on a relational spatio-temporal database model coupled with Git and GeoGig repositories for distributed versioning. Two application scenarios focusing on the modelling of residential building stocks are presented to show the capabilities of the implemented solution. A prototype database model is shared on GitHub along with the necessary scenario data.

  17. An accurate technique for the solution of the nonlinear point kinetics equations

    International Nuclear Information System (INIS)

    Picca, Paolo; Ganapol, Barry D.; Furfaro, Roberto

    2011-01-01

    A novel methodology for the solution of non-linear point kinetic (PK) equations is proposed. The technique is based on a piecewise constant approximation of PK system of ODEs and explicitly accounts for reactivity feedback effects, through an iterative cycle. High accuracy is reached by introducing a sub-mesh for the numerical evaluation of integrals involved and by correcting the source term to include the non-linear effect on a finer time scale. The use of extrapolation techniques for convergence acceleration is also explored. Results for adiabatic feedback model are reported and compared with other benchmarks in literature. The convergence trend makes the algorithm particularly attractive for applications, including in multi-point kinetics and quasi-static frameworks. (author)

  18. Conductometric Studies Of Kinetics Of Ionic Reaction Between Ag And Cl- In Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Md. Rezwan Miah

    2017-01-01

    Full Text Available In the present report conductometric studies on the kinetic of formation of AgCl by ionic reaction between Ag and Clamp61485 in aqueous solution have been presented. The order of the mentioned reaction was determined by a new conductometric approach using half-life method. The obtained result showed that the reaction follows a second-order kinetics. The second-order rate constant of the reaction was obtained conductometrically using different initial concentrations of the reactants in the range of 2.5-5.0 mM. The average value of the rate constant was obtained as 20.648 L molamp614851 samp614851 at 25 amp61616C.

  19. Removal of Congo Red from Aqueous Solution by Anion Exchange Membrane (EBTAC): Adsorption Kinetics and Themodynamics

    Science.gov (United States)

    Khan, Muhammad Imran; Akhtar, Shahbaz; Zafar, Shagufta; Shaheen, Aqeela; Khan, Muhammad Ali; Luque, Rafael; ur Rehman, Aziz

    2015-01-01

    The adsorption behavior of anionic dye congo red (CR) from aqueous solutions using an anion exchange membrane (EBTAC) has been investigated at room temperature. The effect of several factors including contact time, membrane dosage, ionic strength and temperature were studied. Kinetic models, namely pseudo-first-order and pseudo-second-order, liquid film diffusion and Elovich models as well as Bangham and modified freundlich Equations, were employed to evaluate the experimental results. Parameters such as adsorption capacities, rate constant and related correlation coefficients for every model were calculated and discussed. The adsorption of CR on anion exchange membranes followed pseudo-second-order Kinetics. Thermodynamic parameters, namely changes in Gibbs free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) were calculated for the adsorption of congo red, indicating an exothermic process. PMID:28793430

  20. A kinetic study of the enhancement of solution chemiluminescence of glyoxylic acid oxidation by manganese species.

    Science.gov (United States)

    Otamonga, Jean-Paul; Abdel-Mageed, Amal; Agater, Irena B; Jewsbury, Roger A

    2015-08-01

    In order to study the mechanism of the enhancement of solution chemiluminescence, the kinetics of the decay of the oxidant and the chemiluminescence emission were followed for oxidations by permanganate, manganese dioxide sol and Mn(3+) (aq) of glyoxylic acid, using stopped-flow spectrophotometry. Results are reported for the glyoxylic acid oxidized under pseudo first-order conditions and in an acidic medium at 25 °C. For permanganate under these conditions, the decay is sigmoidal, consistent with autocatalysis, and for manganese dioxide sol and Mn(3+) it is pseudo first order. The effects of the presence of aqueous formaldehyde and Mn(2+) were observed and a fit to a simple mechanism is discussed. It is concluded that chemiluminescent enhancement in these systems is best explained by reaction kinetics. Copyright © 2014 John Wiley & Sons, Ltd.

  1. Kinetics of dodecanoic acid adsorption from caustic solution by activated carbon.

    Science.gov (United States)

    Pendleton, Phillip; Wu, Sophie Hua

    2003-10-15

    This study examines the influences of adsorbent porosity and surface chemistry and of carbon dosage on dodecanoic acid adsorption kinetics from aqueous and 2 M NaOH solutions as batch adsorption processes. Both adsorbents are steam-activated carbons prepared from either coconut or coal precursors. Prior to use the adsorbents were washed in deionized water or 2 M NaOH. Mass transfer coefficients and effective overall diffusion coefficients indicate a minor contribution from adsorbent porosity. In contrast, high surface oxygen content impedes transport to and into the adsorbent structure. Carbon dosage shows a proportional increase in transport coefficients with increasing mass; these coefficients are constant when normalized per unit mass. Neither water nor NaOH treatment of the adsorbents has a significant influence on dodecanoic acid adsorption kinetics. Molecular and Knudsen diffusion coefficients are defined to demonstrate that the overall effective diffusion coefficient values and the diffusion process are controlled by surface diffusion.

  2. PROXiMATE: a database of mutant protein-protein complex thermodynamics and kinetics.

    Science.gov (United States)

    Jemimah, Sherlyn; Yugandhar, K; Michael Gromiha, M

    2017-09-01

    We have developed PROXiMATE, a database of thermodynamic data for more than 6000 missense mutations in 174 heterodimeric protein-protein complexes, supplemented with interaction network data from STRING database, solvent accessibility, sequence, structural and functional information, experimental conditions and literature information. Additional features include complex structure visualization, search and display options, download options and a provision for users to upload their data. The database is freely available at http://www.iitm.ac.in/bioinfo/PROXiMATE/ . The website is implemented in Python, and supports recent versions of major browsers such as IE10, Firefox, Chrome and Opera. gromiha@iitm.ac.in. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  3. Preformulation study of methazolamide for topical ophthalmic delivery: physicochemical properties and degradation kinetics in aqueous solutions.

    Science.gov (United States)

    Jiang, Sunmin; Wang, Fengzhen; Zhu, Shuning; Zhang, Xiumei; Guo, Zhigang; Li, Rui; Xu, Qunwei

    2013-05-20

    Methazolamide (MTZ) is an anti-glaucoma drug. The present paper aims to characterize the physicochemical properties and degradation kinetics of MTZ to provide a basis for topical ophthalmic delivery. With the increase in pH (pH 5.5-8.0) of aqueous solution, the solubility of the compound increased while the partition coefficient (Ko/w) which was estimated in the system n-octanol/aqueous solution decreased. The degradation of MTZ in aqueous solution followed pseudo-first-order kinetic. The degradation rate kpH is the rate in the absence of buffer catalysis. Plotting the natural logarithm of kpH versus the corresponding pH value gave a V-shaped pH-rate profile with a maximum stability at pH 5.0. The degradation rate constants as a function of the temperature obeyed the Arrhenius equation (R(2)=0.9995 at pH 7.0 and R(2)=0.9955 at pH 9.0, respectively). A decrease in ionic strength and buffer concentration displayed a stabilizing effect on MTZ. Buffer species also influenced the MTZ hydrolysis. Phosphate buffer system was more catalytic than tris and borate buffer systems. In brief, it is important to consider the physicochemical properties and the stability of MTZ during formulation. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Closed-form kinetic parameter estimation solution to the truncated data problem

    International Nuclear Information System (INIS)

    Zeng, Gengsheng L; Kadrmas, Dan J; Gullberg, Grant T

    2010-01-01

    In a dedicated cardiac single photon emission computed tomography (SPECT) system, the detectors are focused on the heart and the background is truncated in the projections. Reconstruction using truncated data results in biased images, leading to inaccurate kinetic parameter estimates. This paper has developed a closed-form kinetic parameter estimation solution to the dynamic emission imaging problem. This solution is insensitive to the bias in the reconstructed images that is caused by the projection data truncation. This paper introduces two new ideas: (1) it includes background bias as an additional parameter to estimate, and (2) it presents a closed-form solution for compartment models. The method is based on the following two assumptions: (i) the amount of the bias is directly proportional to the truncated activities in the projection data, and (ii) the background concentration is directly proportional to the concentration in the myocardium. In other words, the method assumes that the image slice contains only the heart and the background, without other organs, that the heart is not truncated, and that the background radioactivity is directly proportional to the radioactivity in the blood pool. As long as the background activity can be modeled, the proposed method is applicable regardless of the number of compartments in the model. For simplicity, the proposed method is presented and verified using a single compartment model with computer simulations using both noiseless and noisy projections.

  5. Kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain from aqueous solutions

    International Nuclear Information System (INIS)

    Li Qingzhu; Chai Liyuan; Yang Zhihui; Wang Qingwei

    2009-01-01

    Spent grain, a main by-product of the brewing industry, is available in large quantities, but its main application has been limited to animal feeding. Nevertheless, in this study, spent grain modified with 1 M NaCl solution as a novel adsorbent has been used for the adsorption of Pb(II) in aqueous solutions. Isotherms, kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain were studied. The equilibrium data were well fitted with Langmuir, Freundlich and Dubinin-Radushkevick (D-R) isotherm models. The kinetics of Pb(II) adsorption followed pseudo-second-order model, using the rate constants of pseudo-second-order model, the activation energy (E a ) of Pb(II) adsorption was determined as 12.33 kJ mol -1 according to the Arrhenius equation. Various thermodynamic parameters such as ΔG ads , ΔH ads and ΔS ads were also calculated. Thermodynamic results indicate that Pb(II) adsorption onto modified spent grain is a spontaneous and endothermic process. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) removal from aqueous solutions.

  6. Effect of ionic strength on the kinetics of ionic and micellar reactions in aqueous solution

    International Nuclear Information System (INIS)

    Dung, M.H.; Kozak, J.J.

    1982-01-01

    The effect of electrostatic forces on the rate of reaction between ions in aqueous solutions of intermediate ionic strength is studied in this paper. We consider the kinetics of reactions involving simple ionic species (1--1 and 2--2 electrolyte systems) as well as kinetic processes mediated by the presence of micellar ions (or other charged organizates). In the regime of ionic strength considered, dielectric saturation of the solvent in the vicinity of the reacting ions must be taken into account and this is done by introducing several models to describe the recovery of the solvent from saturation to its continuum dielectric behavior. To explore the effects of ion size, charge number, and ionic strength on the overall rate constant for the process considered, we couple the traditional theory of ionic reactions in aqueous solution with calculations of the electrostatic potential obtained via solution of the nonlinear Poisson--Boltzmann equation. The great flexibility of the nonlinear Poisson--Boltzmann theory allows us to explore quantitatively the influence of each of these effects, and our simulations show that the short-range properties of the electrostatic potential affect primarily kinetically controlled processes (to varying degrees, depending on the ionic system considered) whereas the down-range properties of the potential play a (somewhat) greater role in influencing diffusion-controlled processes. A detailed examination is made of ionic strength effects over a broad range of ionic concentrations. In the regime of low ionic strength, the limiting slope and intercept of the curve describing the dependence of log k/sub D/ on I/sup 1/2//(1+I/sup 1/2/) may differ considerably from the usual Debye--Hueckel limiting relations, depending on the particular model chosen to describe local saturation effects

  7. Kinetic studies of adsorption of Cu (II) from aqueous solution by coriander seeds (Coriandrum Sativum)

    Science.gov (United States)

    Kadiri, L.; Lebkiri, A.; Rifi, E. H.; Ouass, A.; Essaadaoui, Y.; Lebkiri, I.; Hamad, H.

    2018-05-01

    The adsorption of copper ions Cu2+ by Coriandrum Sativum seeds (CSS) from aqueous solution was studied in order to highlight the importance of coriander seeds as a potential tool in the treatment of wastewaters containing heavy metals. The kinetic studies of adsorption of Cu (II) were discussed using the spectroscopic technique "Inducting Coupled Plasma" (ICP). The effects of initial copper ion concentration and contact time were determined. All results show that coriander seeds have, over their culinary and medicinal benefits, a significant adsorbent power of copper ions.

  8. The influence of temperature on the decomposition kinetics of peracetic acid in solutions

    OpenAIRE

    Kunigk, L.; Gomes, D.R.; Forte, F.; Vidal, K.P.; Gomes, L.F.; Sousa, P.F.

    2001-01-01

    Peracetic acid is a powerful sanitizer that has only recently been introduced in the Brazilian food industry. The main disadvantage of this sanitizer is its decomposition rate. The main purpose of this paper is to present results obtained in experiments carried out to study the decomposition kinetics of peracetic acid in aqueous solutions at 25, 35, 40 and 45 °C. The decompositon of peracetic acid is a first-order reaction. The decomposition rate constants are between 1.71x10-3 h -1 for 25 °C...

  9. Numerical Solution of Fractional Neutron Point Kinetics Model in Nuclear Reactor

    Directory of Open Access Journals (Sweden)

    Nowak Tomasz Karol

    2014-06-01

    Full Text Available This paper presents results concerning solutions of the fractional neutron point kinetics model for a nuclear reactor. Proposed model consists of a bilinear system of fractional and ordinary differential equations. Three methods to solve the model are presented and compared. The first one entails application of discrete Grünwald-Letnikov definition of the fractional derivative in the model. Second involves building an analog scheme in the FOMCON Toolbox in MATLAB environment. Third is the method proposed by Edwards. The impact of selected parameters on the model’s response was examined. The results for typical input were discussed and compared.

  10. THE KINETICS OF NH(4)+ AND NO3(-) UPTAKE BY DOUGLAS-FIR FROM SINGLE N-SOLUTIONS AND FROM SOLUTIONS CONTAINING BOTH NH(4)+ AND NO3(-)

    NARCIS (Netherlands)

    KAMMINGAVANWIJK, C; PRINS, HBA

    The kinetics of NH4+ and NO3- uptake in young Douglas fir trees (Pseudotsuga menziesii [Mirb.] Franco) were studied in solutions, containing either one or both N species. Using solutions containing a single N species, the V(max) of NH4+ uptake was higher than that of NO3- uptake. The K(m) of NH4+

  11. Compiling Holocene RSL databases from near- to far-field regions: proxies, difficulties and possible solutions

    Science.gov (United States)

    Vacchi, M.; Horton, B.; Mann, T.; Engelhart, S. E.; Rovere, A.; Nikitina, D.; Bender, M.; Roy, K.; Peltier, W. R.

    2017-12-01

    Reconstructions of relative sea level (RSL) have implications for investigation of crustal movements, calibration of earth rheology models and the reconstruction of ice sheets. In recent years, efforts were made to create RSL databases following a standardized methodology. These regional databases provide a framework for developing our understanding of the primary mechanisms of RSL change since the Last Glacial Maximum and a long-term baseline against which to gauge changes in sea level during the 20th century and forecasts for the 21st. We report here the results of recently compiled databases in very different climatic and geographic contexts that are the northeastern Canadian coast, the Mediterranean Sea as well as the southeastern Asiatic region. Our re-evaluation of sea-level indicators from geological and archaeological investigations have yielded more than 3000 RSL data-points mainly from salt and freshwater wetlands or adjacent estuarine sediment, isolation basins, beach ridges, fixed biological indicators, beachrocks as well as coastal archaeological structures. We outline some of the inherent difficulties, and potential solutions to analyse sea-level data in such different depositional environments. In particular, we discuss problems related with the definition of standardized indicative meaning, and with the re-evaluation of old radiocarbon samples. We further address complex tectonics influences and the framework to compare such large variability of RSL data-points. Finally we discuss the implications of our results for the patterns of glacio-isostatic adjustment in these regions.

  12. Technetium electrodeposition from aqueous formate solutions: electrolysis kinetics and material balance study

    International Nuclear Information System (INIS)

    Maslennikov, A.; Peretroukhine, V.

    1998-01-01

    The kinetics of the Tc electrodeposition and the material balance of potentiostatic electrolysis of formate buffer solutions (pH = 1.79-8.5) containing 5*10 -4 - 1*10 -2 M Tc(VII) at graphite cathode has been studied. The deposition of Tc from the solution was found to become possible at E x *y H 2 O (x ≤ 2, 1.5 cath. ) towards more negative values and the augmentation of the electrolyte surface/volume ratio (S/V) were found to increase the yield of the electrolysis and the rate of the electrodeposition process. A maximum technetium recovery of 92-95% has been observed in the electrolysis of neutral HCOONa solutions (pH = 6.0-7.5, μ = 1.0) containing up to 5*10 -1 M Tc(VII) at potentials of the graphite cathode E 2 . A starting Tc concentration in the solution of [Tc(VII)] > 5 *10 -1 M and the presence of more than 0.05 M NO 3 - in the electrolyte were found to suppress the recovery of technetium from the solution. (orig.)

  13. Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution

    Directory of Open Access Journals (Sweden)

    Sokić M.

    2012-01-01

    Full Text Available Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism.

  14. Precipitation kinetics and mechanical behavior in a solution treated and aged dual phase stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Badji, R., E-mail: riadbadji1@yahoo.fr [Welding and NDT Research Centre (CSC), B.P. 64, Cheraga (Algeria); Kherrouba, N.; Mehdi, B.; Cheniti, B. [Welding and NDT Research Centre (CSC), B.P. 64, Cheraga (Algeria); Bouabdallah, M. [LGSDS – ENP, 10, Avenue Hassan Badi, 16200 El Harrah, Alger (Algeria); Kahloun, C.; Bacroix, B. [LSPM – CNRS, Université Paris 13, 93430 Villetaneuse (France)

    2014-12-15

    The precipitation kinetics and the mechanical behavior in a solution treated and aged dual phase stainless steel (DSS) are investigated. X-ray diffraction, transmission and scanning electron microscopy techniques are used to characterize the microstructure and to identify its constituents. The precipitation kinetics analysis shows that the ferrite to σ phase transformation follows the modified Johnson Mehl Avrami (JMA) model containing an impingement parameter c that is adjusted to 0.3. Activation energies calculation leads to conclude that interface reaction is the main mechanism that controls the σ phase formation. Detailed analysis of the extent of the different tensile deformation domains reveals the significant contribution of both σ phase particles and dislocation accumulation to the strain hardening of the material. - Highlights: • The precipitation kinetics of the σ phase is affected by both soft and hard impingement phenomena. • Interface reaction is found to be the main mechanism that controls the ferrite to σ phase transformation. • Both σ phase particles and dislocation accumulation contribute to the strain hardening of the dual phase steel studied.

  15. The solution of the neutron point kinetics equation with stochastic extension: an analysis of two moments

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Milena Wollmann da; Vilhena, Marco Tullio M.B.; Bodmann, Bardo Ernst J.; Vasques, Richard, E-mail: milena.wollmann@ufrgs.br, E-mail: vilhena@mat.ufrgs.br, E-mail: bardobodmann@ufrgs.br, E-mail: richard.vasques@fulbrightmail.org [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica

    2015-07-01

    The neutron point kinetics equation, which models the time-dependent behavior of nuclear reactors, is often used to understand the dynamics of nuclear reactor operations. It consists of a system of coupled differential equations that models the interaction between (i) the neutron population; and (II) the concentration of the delayed neutron precursors, which are radioactive isotopes formed in the fission process that decay through neutron emission. These equations are deterministic in nature, and therefore can provide only average values of the modeled populations. However, the actual dynamical process is stochastic: the neutron density and the delayed neutron precursor concentrations vary randomly with time. To address this stochastic behavior, Hayes and Allen have generalized the standard deterministic point kinetics equation. They derived a system of stochastic differential equations that can accurately model the random behavior of the neutron density and the precursor concentrations in a point reactor. Due to the stiffness of these equations, this system was numerically implemented using a stochastic piecewise constant approximation method (Stochastic PCA). Here, we present a study of the influence of stochastic fluctuations on the results of the neutron point kinetics equation. We reproduce the stochastic formulation introduced by Hayes and Allen and compute Monte Carlo numerical results for examples with constant and time-dependent reactivity, comparing these results with stochastic and deterministic methods found in the literature. Moreover, we introduce a modified version of the stochastic method to obtain a non-stiff solution, analogue to a previously derived deterministic approach. (author)

  16. The solution of the neutron point kinetics equation with stochastic extension: an analysis of two moments

    International Nuclear Information System (INIS)

    Silva, Milena Wollmann da; Vilhena, Marco Tullio M.B.; Bodmann, Bardo Ernst J.; Vasques, Richard

    2015-01-01

    The neutron point kinetics equation, which models the time-dependent behavior of nuclear reactors, is often used to understand the dynamics of nuclear reactor operations. It consists of a system of coupled differential equations that models the interaction between (i) the neutron population; and (II) the concentration of the delayed neutron precursors, which are radioactive isotopes formed in the fission process that decay through neutron emission. These equations are deterministic in nature, and therefore can provide only average values of the modeled populations. However, the actual dynamical process is stochastic: the neutron density and the delayed neutron precursor concentrations vary randomly with time. To address this stochastic behavior, Hayes and Allen have generalized the standard deterministic point kinetics equation. They derived a system of stochastic differential equations that can accurately model the random behavior of the neutron density and the precursor concentrations in a point reactor. Due to the stiffness of these equations, this system was numerically implemented using a stochastic piecewise constant approximation method (Stochastic PCA). Here, we present a study of the influence of stochastic fluctuations on the results of the neutron point kinetics equation. We reproduce the stochastic formulation introduced by Hayes and Allen and compute Monte Carlo numerical results for examples with constant and time-dependent reactivity, comparing these results with stochastic and deterministic methods found in the literature. Moreover, we introduce a modified version of the stochastic method to obtain a non-stiff solution, analogue to a previously derived deterministic approach. (author)

  17. Solution for the multigroup neutron space kinetics equations by the modified Picard algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Tavares, Matheus G.; Petersen, Claudio Z., E-mail: matheus.gulartetavares@gmail.com [Universidade Federal de Pelotas (UFPEL), Capao do Leao, RS (Brazil). Departamento de Matematica e Estatistica; Schramm, Marcelo, E-mail: schrammmarcelo@gmail.com [Universidade Federal de Pelotas (UFPEL), RS (Brazil). Centro de Engenharias; Zanette, Rodrigo, E-mail: rodrigozanette@hotmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Instituto de Matematica e Estatistica

    2017-07-01

    In this work, we used a modified Picards method to solve the Multigroup Neutron Space Kinetics Equations (MNSKE) in Cartesian geometry. The method consists in assuming an initial guess for the neutron flux and using it to calculate a fictitious source term in the MNSKE. A new source term is calculated applying its solution, and so on, iteratively, until a stop criterion is satisfied. For the solution of the fast and thermal neutron fluxes equations, the Laplace Transform technique is used in time variable resulting in a rst order linear differential matrix equation, which are solved by classical methods in the literature. After each iteration, the scalar neutron flux and the delayed neutron precursors are reconstructed by polynomial interpolation. We obtain the fluxes and precursors through Numerical Inverse Laplace Transform using the Stehfest method. We present numerical simulations and comparisons with available results in literature. (author)

  18. The influence of temperature on the decomposition kinetics of peracetic acid in solutions

    Directory of Open Access Journals (Sweden)

    Kunigk L.

    2001-01-01

    Full Text Available Peracetic acid is a powerful sanitizer that has only recently been introduced in the Brazilian food industry. The main disadvantage of this sanitizer is its decomposition rate. The main purpose of this paper is to present results obtained in experiments carried out to study the decomposition kinetics of peracetic acid in aqueous solutions at 25, 35, 40 and 45 °C. The decompositon of peracetic acid is a first-order reaction. The decomposition rate constants are between 1.71x10-3 h -1 for 25 °C and 9.64x10-3 h-1 for 45 °C. The decomposition rate constant is affected by temperature according to the Arrhenius equation, and the activation energy for the decomposition of peracetic acid in aqueous solutions prepared from the commercial formulation used in this work is 66.20 kJ/mol.

  19. Solution for the multigroup neutron space kinetics equations by the modified Picard algorithm

    International Nuclear Information System (INIS)

    Tavares, Matheus G.; Petersen, Claudio Z.; Schramm, Marcelo; Zanette, Rodrigo

    2017-01-01

    In this work, we used a modified Picards method to solve the Multigroup Neutron Space Kinetics Equations (MNSKE) in Cartesian geometry. The method consists in assuming an initial guess for the neutron flux and using it to calculate a fictitious source term in the MNSKE. A new source term is calculated applying its solution, and so on, iteratively, until a stop criterion is satisfied. For the solution of the fast and thermal neutron fluxes equations, the Laplace Transform technique is used in time variable resulting in a rst order linear differential matrix equation, which are solved by classical methods in the literature. After each iteration, the scalar neutron flux and the delayed neutron precursors are reconstructed by polynomial interpolation. We obtain the fluxes and precursors through Numerical Inverse Laplace Transform using the Stehfest method. We present numerical simulations and comparisons with available results in literature. (author)

  20. Kinetic competitivity between ordering and solute segregation to dislocations in Cu-20% at. Mn

    International Nuclear Information System (INIS)

    Donoso, E.; Varschavsky, A.

    1997-01-01

    By using differential scanning calorimetry (DSC) energetic measurements associated with the different peaks displayed during linear heating of Cu-20% at. Mn were made, employing quenched and cold-worked materials. Unique to the situation observed in the quenched alloy in which disperse order is developed, in the deformed alloy such process is inhibited by the segregation of solute atoms to partial dislocations. An appropriate model for calculation the energy evolved during the pinning process was applied in order to determine the dislocation density from the exothermic peak designated as stage 4. The computed value, which is in excellent agreement with the one obtained from expressions governing the energy release accompanying recrystallization allows to verify together with microhardness measurements and kinetic analysis that the first observed thermal effect in the deformed materials effectively corresponds a solute segregation process. (Author) 35 refs

  1. Struvite Precipitation and Phosphorous Removal from Urine Synthetic Solution: Reaction Kinetic Study

    Directory of Open Access Journals (Sweden)

    Marwa Saied Shalaby

    2015-03-01

    Full Text Available Phosphorus, like oil, is a non-renewable resource that must be harvested from finite resources in the earth’s crust. An essential element for life, phosphorus is becoming increasingly scarce, contaminated, and difficult to extract. Struvite or magnesium ammonium phosphate (MgNH4PO4.6H2O is a white, crystalline phosphate mineral that can be used as a bio-available fertilizer. The main objective of this research is to indicate the most important operating parameters affecting struvite precipitation by means of chemical reaction kinetics. The present study explores struvite precipitation by chemical method under different starting molar ratios, pH and SSR. It is shown that an increase of starting Mg: PO4: NH4 with respect to magnesium (1.6:1:1 strongly influences the growth rate of struvite and so the efficiency of the phosphate removal. This was attributed to the effect of magnesium on the struvite solubility product and on the reached supersaturation Super Saturation Ratio at optimum starting molar ratio and pH. It was also shown, by using chemical precipitation method that the determined Super Saturation Ratio (SSR values of struvite, at 8, 8.5, 9, 9.5 and 10 are 1.314, 4.29, 8.89, 9.87 and 14.89 respectively are close to those presented in the literature for different origins of wastewater streams. The results show that SSR , pH, and starting molar ratio strongly influences the kinetics of precipitation and so phosphorous removal to reach 93% removal percent , 5.95 mg/lit as a minimum PO4 remained in solution, and 7.9 gm precipitated struvite from feed synthetic solution of 750 ml . The product was subjected to chemical analysis by means of EDIX-FTIR, SEM and XRD showing conformity with published literature. First-order kinetics was found to be sufficient to describe the rate data. The rates increased with increasing pH and so SSR and the apparent rate constants for the reaction were determined. © 2015 BCREC UNDIP. All rights reserved

  2. Equilibrium and kinetic models for colloid release under transient solution chemistry conditions.

    Science.gov (United States)

    Bradford, Scott A; Torkzaban, Saeed; Leij, Feike; Simunek, Jiri

    2015-10-01

    We present continuum models to describe colloid release in the subsurface during transient physicochemical conditions. Our modeling approach relates the amount of colloid release to changes in the fraction of the solid surface area that contributes to retention. Equilibrium, kinetic, equilibrium and kinetic, and two-site kinetic models were developed to describe various rates of colloid release. These models were subsequently applied to experimental colloid release datasets to investigate the influence of variations in ionic strength (IS), pH, cation exchange, colloid size, and water velocity on release. Various combinations of equilibrium and/or kinetic release models were needed to describe the experimental data depending on the transient conditions and colloid type. Release of Escherichia coli D21g was promoted by a decrease in solution IS and an increase in pH, similar to expected trends for a reduction in the secondary minimum and nanoscale chemical heterogeneity. The retention and release of 20nm carboxyl modified latex nanoparticles (NPs) were demonstrated to be more sensitive to the presence of Ca(2+) than D21g. Specifically, retention of NPs was greater than D21g in the presence of 2mM CaCl2 solution, and release of NPs only occurred after exchange of Ca(2+) by Na(+) and then a reduction in the solution IS. These findings highlight the limitations of conventional interaction energy calculations to describe colloid retention and release, and point to the need to consider other interactions (e.g., Born, steric, and/or hydration forces) and/or nanoscale heterogeneity. Temporal changes in the water velocity did not have a large influence on the release of D21g for the examined conditions. This insensitivity was likely due to factors that reduce the applied hydrodynamic torque and/or increase the resisting adhesive torque; e.g., macroscopic roughness and grain-grain contacts. Our analysis and models improve our understanding and ability to describe the amounts

  3. Kinetic and Thermodynamic Studies on Biosorption of Direct Red 81 from Aqueous Solutions by Chamomilla Plant

    Directory of Open Access Journals (Sweden)

    M. Momen Heravi

    2013-01-01

    Full Text Available In this study, Chamomilla plant biomass used as a sorbent for biosorption of a textile dye, direct red 81, from an aqueous solution. The batch sorption was studied with respect to dye concentration, adsorbent dose and temperature. Also, kinetic and isotherm parameters were determined for biosorption of Direct red 81 by Chamomilla plant. The maximum biosorption capacity (qm of Direct red 81 10 mg g-1 was obtained at 25oC. The kinetic and isotherm studies indicated that the biosorption process obeys a pseudo-second order and Langmuir isotherm models. In addition, various thermodynamic parameters, such as changes in Gibbs free energy (ΔG, enthalpy (ΔH and entropy (ΔS have been calculated. The biosorption process of Direct Red 81 dye onto activated carbon prepared from Chamomilla plant was found to be spontaneous and exothermic. The findings of this investigation suggest that this procces is a physical biosorption. The experimental studies indicated that Chamomilla plant had the potential to act as an alternative biosorbent to remove the Direct Red 81 dye from an aqueous solution.

  4. Kinetic and equilibrium studies of cesium adsorption on ceiling tiles from aqueous solutions.

    Science.gov (United States)

    Miah, Muhammed Yusuf; Volchek, Konstantin; Kuang, Wenxing; Tezel, F Handan

    2010-11-15

    A series of experiments were performed to quantify the adsorption of cesium on ceiling tiles as a representative of urban construction materials. Adsorption was carried out from solutions to mimic wet environmental conditions. Non-radioactive cesium chloride was used as a surrogate of the radioactive (137)Cs. The experiments were performed in the range of initial cesium concentrations of 0.114-23.9 mg L(-1) at room temperature (21°C) around three weeks. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The quantity of adsorbed Cs was calculated by mass balance as a function of time. Two kinetic and three equilibrium models were employed to interpret the test results. Determination of kinetic parameters for adsorption was carried out using the first-order reaction model and the intra-particle diffusion model. Adsorption equilibrium was studied using Langmuir, Freundlich and three-parameter Langmuir-Freundlich adsorption isotherm models. A satisfactory correlation between the experimental and the predicted values was observed. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

  5. Kinetic and equilibrium studies of cesium adsorption on ceiling tiles from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Miah, Muhammed Yusuf [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, K1A 0H3 (Canada); Department of Applied Chemistry and Chemical Technology, Noakhali Science and Technology University (Bangladesh); Volchek, Konstantin, E-mail: Konstantin.Volchek@ec.gc.ca [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, K1A 0H3 (Canada); Kuang, Wenxing [SAIC Canada, 335 River Road, Ottawa, Ontario, K1A 0H3 (Canada); Tezel, F. Handan [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, Ontario, K1N 6N5 (Canada)

    2010-11-15

    A series of experiments were performed to quantify the adsorption of cesium on ceiling tiles as a representative of urban construction materials. Adsorption was carried out from solutions to mimic wet environmental conditions. Non-radioactive cesium chloride was used as a surrogate of the radioactive {sup 137}Cs. The experiments were performed in the range of initial cesium concentrations of 0.114-23.9 mg L{sup -1} at room temperature (21 deg. C) around three weeks. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The quantity of adsorbed Cs was calculated by mass balance as a function of time. Two kinetic and three equilibrium models were employed to interpret the test results. Determination of kinetic parameters for adsorption was carried out using the first-order reaction model and the intra-particle diffusion model. Adsorption equilibrium was studied using Langmuir, Freundlich and three-parameter Langmuir-Freundlich adsorption isotherm models. A satisfactory correlation between the experimental and the predicted values was observed.

  6. Multiscale solutions of radiative heat transfer by the discrete unified gas kinetic scheme

    Science.gov (United States)

    Luo, Xiao-Ping; Wang, Cun-Hai; Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

    2018-06-01

    The radiative transfer equation (RTE) has two asymptotic regimes characterized by the optical thickness, namely, optically thin and optically thick regimes. In the optically thin regime, a ballistic or kinetic transport is dominant. In the optically thick regime, energy transport is totally dominated by multiple collisions between photons; that is, the photons propagate by means of diffusion. To obtain convergent solutions to the RTE, conventional numerical schemes have a strong dependence on the number of spatial grids, which leads to a serious computational inefficiency in the regime where the diffusion is predominant. In this work, a discrete unified gas kinetic scheme (DUGKS) is developed to predict radiative heat transfer in participating media. Numerical performances of the DUGKS are compared in detail with conventional methods through three cases including one-dimensional transient radiative heat transfer, two-dimensional steady radiative heat transfer, and three-dimensional multiscale radiative heat transfer. Due to the asymptotic preserving property, the present method with relatively coarse grids gives accurate and reliable numerical solutions for large, small, and in-between values of optical thickness, and, especially in the optically thick regime, the DUGKS demonstrates a pronounced computational efficiency advantage over the conventional numerical models. In addition, the DUGKS has a promising potential in the study of multiscale radiative heat transfer inside the participating medium with a transition from optically thin to optically thick regimes.

  7. Deviation from the kinetic law of mass action for reactions induced by binary encounters in liquid solutions

    International Nuclear Information System (INIS)

    Doktorov, Alexander B; Kipriyanov, Alexey A

    2007-01-01

    In considering the irreversible chemical reaction A+B→ C+B in liquid solutions two many-particle approaches to the derivation of binary non-Markovian kinetic equations are compared: simple superposition decoupling and a method of extracting 'pair' channels from three-particle correlation evolution. It is shown that both methods provide an almost identical description of this reaction. However, in studies of reversible reactions in liquid solutions only the channel extraction method gives a correct physically clear description of the reaction though it consists of a sequence of steps: the development of integral encounter theory (IET), effective pairs approximation (EPA), modified encounter theory (MET), and the final regular form (RF) of kinetic equations. It is shown that the rate equations often encountered in the literature correspond to the independence of transient channels of 'scattering' in the bimolecular reversible reaction (A+B -B), while the independent transient channel of 'decay' in the reversible reactionA+B -C is defined solely by time integral convolution. In the general case transient channels in non-Markovian theory are not independent, and their interference manifests itself as a non-Markovian inhomogeneous source in binary non-Markovian kinetic equations in regular form. Based on the derived equations new universal kinetics (independent of models) of chemical equilibrium attainment have been obtained. It is shown that these kinetics can differ essentially from the kinetics corresponding to the kinetic law of mass action of formal chemical kinetics

  8. Kinetics Modeling and Isotherms for Adsorption of Phosphate from Aqueous Solution by Modified Clinoptilolit

    Directory of Open Access Journals (Sweden)

    Mohammad Malakootian

    2012-01-01

    Full Text Available The Phosphorous discharge into the surface water led to excessive growth of algae and eutrophication in lakes and rivers. Therefore the phosphorus removal is important due to negative effect on water resources. The aim of this study was to investigat the modification of clinoptilolite and application of modified clinoptilolite for phosphorous adsorption from aqueous solution and isotherms and kinetics modeling. Hexadecyl Trimethyl Ammonium bromide (HDTMA-Br, Hexadecyl trimethyl Ammonium Chloride (HDTMA-Cl, Sodium Decyl Sulphate (SDS and Cetrimide-C were used for modification of clinoptilolite. Experiments were conducted using jar apparatus and batch system. The effect of pH, adsorbent doses, contact time, phosphate initial concentration and particle size were studied surveyed on phosphate adsorption by modified clinoptilolite. The most common isotherms and the kinetics adsorption equations were used for determination of adsorption rate and dynamic reaction. The results showed that maximum phosphate adsorption was obtained in the pH of 7 and contact time 90min. Also it was found with the increasing of phosphate initial concentration, phosphate removal efficiency decreased significantly. Langmuir No 2 showed a good correlation compared to other isotherms (R2=0.997. Maximum adsorption capacity was obtained in 20g/L adsorbent dose (22.73mg/g. Also Interaparticle diffusion kinetics well fits with experimental data (R2=0.999 with constant rate of 3.84mg/g min0.5. The result showed that modified clinoptilolite can be used successfully as low cost and effective absorbent for phosphate removal.

  9. Structural insights into the cubic-hexagonal phase transition kinetics of monoolein modulated by sucrose solutions.

    Science.gov (United States)

    Reese, Caleb W; Strango, Zachariah I; Dell, Zachary R; Tristram-Nagle, Stephanie; Harper, Paul E

    2015-04-14

    Using DSC (differential scanning calorimetry), we measure the kinetics of the cubic-HII phase transition of monoolein in bulk sucrose solutions. We find that the transition temperature is dramatically lowered, with each 1 mol kg(-1) of sucrose concentration dropping the transition by 20 °C. The kinetics of this transition also slow greatly with increasing sucrose concentration. For low sucrose concentrations, the kinetics are asymmetric, with the cooling (HII-cubic) transition taking twice as long as the heating (cubic-HII) transition. This asymmetry in transition times is reduced for higher sucrose concentrations. The cooling transition exhibits Avrami exponents in the range of 2 to 2.5 and the heating transition shows Avrami exponents ranging from 1 to 3. A classical Avrami interpretation would be that these processes occur via a one or two dimensional pathway with variable nucleation rates. A non-classical perspective would suggest that these exponents reflect the time dependence of pore formation (cooling) and destruction (heating). New density measurements of monoolein show that the currently accepted value is about 5% too low; this has substantial implications for electron density modeling. Structural calculations indicate that the head group area and lipid length in the cubic-HII transition shrink by about 12% and 4% respectively; this reduction is practically the same as that seen in a lipid with a very different molecular structure (rac-di-12:0 β-GlcDAG) that makes the same transition. Thermodynamic considerations suggest there is a hydration shell about one water molecule thick in front of the lipid head groups in both the cubic and HII phases.

  10. Kinetics of electrophilic substitution of neodymium(3) by ytterbium(3) in aqueous solution of ethylenediaminetetraacetate solution of ethylenediaminetetraacetate and cyclohexanediaminetetraacetate

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1981-01-01

    The process of electrophilic substitution is studied spectrophotometrically taking as an example neodymium (3) substitution for ytterbium (3) in solutions, containing NdL/sup -/ and Yb/sup 3 +/, where L/sup 4 -/ = A/sup 4 -/ and D/sup 4 -/ (ethylenediaminetetraacetate- and cyclohexanediaminetetraacetate). The study of the exchange kinetics is carried out in pH range of 4-6. For the system with L=A in pH range 4.0-4.8 the exchange is realized by the way of acidic dissociation, at pH 5.5-6.0 - by the way of the direct attack. In the system with L=D in pH range 3.5-4.0 the way of acid dissociation prevails, at the same time, the rate constant of acidic dissociation for NdD/sup -/ is two order lower the constant for NdA/sup -/. However, at pH 4.7 the machanism of spontaneous dissociation prevails in the system. Thus, the structure of the complex has considerable effect on the mechanism of electrophilic substitution in rare earth complexes.

  11. Kinetics of electrophilic substitution of neodymium(3) by ytterbium(3) in aqueous solution of ethylenediaminetetraacetate solution of ethylenediaminetetraacetate and cyclohexanediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1981-01-01

    The process of electrophilic substitution is studied spectrophotometrically taking as an example neodymium (3) substitution for ytterbium (3) in solutions, containing NdL - and Yb 3+ , where L 4- = A 4- and D 4- (ethylenediaminetetraacetate- and cyclohexanediaminetetraacetate). The study of the exchange kinetics is carried out in pH range of 4-6. For the system with L=A in pH range 4.0-4.8 the exchange is realized by the way of acidic dissociation, at pH 5.5-6.0 - by the way of the direct attack. In the system with L=D in pH range 3.5-4.0 the way of acid dissociation prevails, at the same time, the rate constant of acidic dissociation for NdD - is two order lower the constant for NdA - . However, at pH 4.7 the machanism of spontaneous dissociation prevails in the system. Thus, the structure of the complex has considerable effect on the mechanism of electrophilic substitution in rare earth complexes [ru

  12. Solution of the neutron point kinetics equations with temperature feedback effects applying the polynomial approach method

    Energy Technology Data Exchange (ETDEWEB)

    Tumelero, Fernanda, E-mail: fernanda.tumelero@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica; Petersen, Claudio Z.; Goncalves, Glenio A.; Lazzari, Luana, E-mail: claudiopeteren@yahoo.com.br, E-mail: gleniogoncalves@yahoo.com.br, E-mail: luana-lazzari@hotmail.com [Universidade Federal de Pelotas (DME/UFPEL), Capao do Leao, RS (Brazil). Instituto de Fisica e Matematica

    2015-07-01

    In this work, we present a solution of the Neutron Point Kinetics Equations with temperature feedback effects applying the Polynomial Approach Method. For the solution, we consider one and six groups of delayed neutrons precursors with temperature feedback effects and constant reactivity. The main idea is to expand the neutron density, delayed neutron precursors and temperature as a power series considering the reactivity as an arbitrary function of the time in a relatively short time interval around an ordinary point. In the first interval one applies the initial conditions of the problem and the analytical continuation is used to determine the solutions of the next intervals. With the application of the Polynomial Approximation Method it is possible to overcome the stiffness problem of the equations. In such a way, one varies the time step size of the Polynomial Approach Method and performs an analysis about the precision and computational time. Moreover, we compare the method with different types of approaches (linear, quadratic and cubic) of the power series. The answer of neutron density and temperature obtained by numerical simulations with linear approximation are compared with results in the literature. (author)

  13. Solution of the neutron point kinetics equations with temperature feedback effects applying the polynomial approach method

    International Nuclear Information System (INIS)

    Tumelero, Fernanda; Petersen, Claudio Z.; Goncalves, Glenio A.; Lazzari, Luana

    2015-01-01

    In this work, we present a solution of the Neutron Point Kinetics Equations with temperature feedback effects applying the Polynomial Approach Method. For the solution, we consider one and six groups of delayed neutrons precursors with temperature feedback effects and constant reactivity. The main idea is to expand the neutron density, delayed neutron precursors and temperature as a power series considering the reactivity as an arbitrary function of the time in a relatively short time interval around an ordinary point. In the first interval one applies the initial conditions of the problem and the analytical continuation is used to determine the solutions of the next intervals. With the application of the Polynomial Approximation Method it is possible to overcome the stiffness problem of the equations. In such a way, one varies the time step size of the Polynomial Approach Method and performs an analysis about the precision and computational time. Moreover, we compare the method with different types of approaches (linear, quadratic and cubic) of the power series. The answer of neutron density and temperature obtained by numerical simulations with linear approximation are compared with results in the literature. (author)

  14. Kinetics of Phenol Degradation in Aqueous Solution Oxidized under Low Frequency Ultrasonic Irradiation

    Directory of Open Access Journals (Sweden)

    Marwan Marwan

    2014-06-01

    Full Text Available Phenol is categorized as a refractory pollutant and its presence in water stream is strictly limited according to the government regulation. The present study investigated the degra-dation of phenol in aqueous solution by the effect of ultrasound. The process took place in a 500 ml glass reactor equipped with magnetic stirring and irradiated by low frequency (28 kHz ultrasound from a horn type probe. Ultrasonic irradiation was found to enhance oxidation rates at ambient conditions, compared to other approaches. Optimum conditions were observed at a stirring speed of 400 rpm and temperature of 30 C in acidic solution. It was revealed that the phenol degradation was the first order kinetics with respect to phenol. A low value of the activation energy 6.04 kcal/mol suggested that diffusional steps were rate determining during the phenol decomposition. It also confirmed that phenol was mostly degraded in the film region and less occurred in the bulk solution.

  15. The kinetics of free radical metathetical and addition reactions in silane solutions

    International Nuclear Information System (INIS)

    Aloni, R.

    1976-12-01

    In this work radiolytic technique was employed for the initiation of free radical chainreactions in silane solution. The kinetic analysis of the chain mechanism in various solutions enabled the determination of the Arrhenius parameters for metathesis, addition and unimolecular decomposition reactions which make up the chainpropagation sequence in the systems studied. The following radical reactions were investigated: chlorine atom abstraction from chloromethanes by SiCl 3 and Et 3 Si radicals, and chlorine atom abstraction from chloroethanes by Et 3 Si radicals; unimolecular decomposition reactions and hydrogen atom abstraction, *from the solvent, of chloroethyl radicals in triethylsilane solutions; addition and abstraction reactions of Et 3 Si radicals with chloroolefins. Arrhenius parameters were determined for abstraction of chlorine atom from CH 3 Cl, CH 2 Cl 2 , CHCl 3 and CCl 4 , by SiCl 3 radicals and from CCl 4 , CHCl 3 , CH 2 Cl 2 , CCl 3 CN, C 2 Cl 5 H, sym-C 2 Cl 4 H 2 , asym-C 2 Cl 4 H 2 , 1.1.1-C 2 Cl 3 H 3 , 1.1.1-C 2 Dl 3 F 3 and 1.1-C 2 Cl 2 H 4 by Et 3 Si radicals. (author)

  16. Kinetic assembly of block copolymers in solution helical cylindrical micelles and patchy nanoparticles

    Science.gov (United States)

    Zhong, Sheng

    There is always an interest to understand how molecules behave under different conditions. One application of this knowledge is to self-assemble molecules into increasingly complex structures in a simple fashion. Self-assembly of amphiphilic block copolymer in solution has produced a large variety of nanostructures through the manipulation in polymer chemistry, assembly environment, and additives. Moreover, some reports suggest the formation of many polymeric assemblies is driven by kinetic process. The goal of this dissertation is to study the influence of kinetics on the assembly of block copolymer. The study shows kinetic control can be a very effective way to make novel polymeric nanostructures. Two examples discussed here are helical cylindrical micelles and patchy nanoparticles. Helical cylindrical micelles are made from the co-assembly of amphiphilic triblock copolymer poly(acrylic acid)-block-poly(methyl acrylate)- block-polystyrene and organoamine molecules in a mixture of tetrahydrofuran (THF) and water (H2O). This system has already shown promise of achieving many assembled structures. The unique aspects about this system are the use of amine molecules to complex with acid groups and the existence of cosolvent system. Application of amine molecules offers a convenient control over assembled morphology and the introduction of PMA-PS selective solvent, THF, promotes the mobility of the polymer chains. In this study, multivalent organoamine molecules, such as diethylenetriamine and triethylenetetramine, are used to interact with block copolymer in THF/water mixture. As expected, the assembled morphologies are dependent on the polymer architecture, selection and quantity of the organoamine molecules, and solution composition. Under the right conditions, unprecedented, multimicrometer-long, supramolecular helical cylindrical micelles are formed. Both single-stranded and double-stranded helices are found in the same system. These helical structures share

  17. Adsorption of cationic dye from aqueous solution by clay as an adsorbent: thermodynamic and kinetic studies

    International Nuclear Information System (INIS)

    Fil, B.A.; Ozmetn, C.

    2012-01-01

    In the study, montmorillonite was used as an adsorbent for the removal of methylene blue (MB) from aqueous solutions. Batch studies were performed to address various experimental parameters like contact time, pH, temperature, stirring speed, ionic strength, adsorbent dosage and initial concentration for the removal of this dye. Adsorption rate increased with the increase in initial dye concentration, ionic strength, stirring speed, pH and temperature. Kinetic study showed that the adsorption of dye on montmorillonite was a gradual process. Quasi-equilibrium reached in 3 h. Pseudo-first-order, pseudo-second-order, Elovich, Bangham, mass transfer and intra-particle particle diffusion models were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. Intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The diffusion coefficient, D, was found to increase when the stirring speed, ionic strength and temperature were raised. Thermodynamic activation parameters such as delt G, delt S and del H were also calculated. (author)

  18. The solution of the point kinetics equations via converged accelerated Taylor series (CATS)

    Energy Technology Data Exchange (ETDEWEB)

    Ganapol, B.; Picca, P. [Dept. of Aerospace and Mechanical Engineering, Univ. of Arizona (United States); Previti, A.; Mostacci, D. [Laboratorio di Montecuccolino, Alma Mater Studiorum - Universita di Bologna (Italy)

    2012-07-01

    This paper deals with finding accurate solutions of the point kinetics equations including non-linear feedback, in a fast, efficient and straightforward way. A truncated Taylor series is coupled to continuous analytical continuation to provide the recurrence relations to solve the ordinary differential equations of point kinetics. Non-linear (Wynn-epsilon) and linear (Romberg) convergence accelerations are employed to provide highly accurate results for the evaluation of Taylor series expansions and extrapolated values of neutron and precursor densities at desired edits. The proposed Converged Accelerated Taylor Series, or CATS, algorithm automatically performs successive mesh refinements until the desired accuracy is obtained, making use of the intermediate results for converged initial values at each interval. Numerical performance is evaluated using case studies available from the literature. Nearly perfect agreement is found with the literature results generally considered most accurate. Benchmark quality results are reported for several cases of interest including step, ramp, zigzag and sinusoidal prescribed insertions and insertions with adiabatic Doppler feedback. A larger than usual (9) number of digits is included to encourage honest benchmarking. The benchmark is then applied to the enhanced piecewise constant algorithm (EPCA) currently being developed by the second author. (authors)

  19. Adsorption isotherm, kinetic and mechanism of expanded graphite for sulfadiazine antibiotics removal from aqueous solutions.

    Science.gov (United States)

    Zhang, Ling; Wang, Yong; Jin, SuWan; Lu, QunZan; Ji, Jiang

    2017-10-01

    The adsorption of sulfadiazine from water by expanded graphite (EG), a low cost and environmental-friendly adsorbent, was investigated. Several adsorption parameters (including the initial sulfadiazine concentration, contact time, pH of solution, ionic strength and temperature) were studied. Results of equilibrium experiments indicated that adsorption of sulfadiazine onto EG were better described by the Langmuir and Tempkin models than by the Freundlich model. The maximum adsorption capacity is calculated to be 16.586 mg/g at 298 K. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle models. The results indicated that the adsorption process followed pseudo-second-order kinetics and may be controlled by two steps. Moreover, the pH significantly influenced the adsorption process, with the relatively high adsorption capacity at pH 2-10. The electrostatic and hydrophobic interactions are manifested to be two main mechanisms for sulfadiazine adsorption of EG. Meanwhile, the ionic concentration of Cl - slightly impacted the removal of sulfadiazine. Results of thermodynamics analysis showed spontaneous and exothermic nature of sulfadiazine adsorption on EG. In addition, regeneration experiments imply that the saturated EG could be reused for sulfadiazine removal by immersing sodium hydroxide.

  20. The removal of fluoride from aqueous solution by a lateritic soil adsorption: Kinetic and equilibrium studies.

    Science.gov (United States)

    Iriel, Analia; Bruneel, Stijn P; Schenone, Nahuel; Cirelli, Alicia Fernández

    2018-03-01

    The use of natural sorbents to remove fluoride from drinking water is a promising alternative because of its low-cost and easy implementation. In this article, fluoride adsorption on a latosol soil from Misiones province (Argentina) was studied regarding kinetic and equilibrium aspects. Experiments were conducted in batch at room temperature under controlled conditions of pH 4-8) and ionic strength (1-10mM KNO 3 ). Experimental data indicated that adsorption processes followed a PSO kinetic where initial rates have showed to be influenced by pH solution. The necessary time to reach an equilibrium state had resulted approximately 30min. Equilibrium adsorption studies were performed at pH 8 which is similar to the natural groundwater. For that, fluoride adsorption data were successfully adjusted to Dubinin-Ataskhov model determining that the fluoride adsorption onto soil particles mainly followed a physical mechanism with a removal capacity of 0.48mgg -1 . Finally, a natural groundwater was tested with laterite obtaining a reduction close to 30% from initial concentration and without changing significantly the physicochemical properties of the natural water. Therefore, it was concluded that the use of lateritic soils for fluoride removal is very promising on a domestic scale. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Kinetics of solute leachate from imbibing Caesalpinia echinata Lam. (Brazilwood seeds

    Directory of Open Access Journals (Sweden)

    Nestor Martini Neto

    2014-02-01

    Full Text Available The electrical conductivity of leachates from imbibing seeds has been used as a vigor test for several species. The adaptation of this methodology to different species requires knowledge on the leaching kinetics of electrolytes. For Brazilwood seeds, the classic method was not satisfactory and rapid tests are essential because they have low storage capacity at room temperature. Leaching kinetics during seed imbibition is a function of physiological quality, presence or absence of seed coat, imbibing temperature and the initial moisture content of seed. In this study, the electrolyte leaching rate of six different categories of seeds, from two regions, was evaluated in seeds with and without seed coat and incubated with different moisture contents and at different temperatures. The results showed that the electrolyte leaching rate in Brazilwood seeds is independent of the physiological quality, the presence or absence of seed coat and imbibition temperature, but these factors changed the total amount of electrolytes leached. The leaching rate increased in the first few minutes of imbibition, suggesting that the adjustment of the methodology must consider the reduction in imbibition time, reduction in temperature, use of a controlled and slower pre-imbibition, and replacement of the imbibition solution after the first few minutes.

  2. Adsorption of Ag (I) from aqueous solution by waste yeast: kinetic, equilibrium and mechanism studies.

    Science.gov (United States)

    Zhao, Yufeng; Wang, Dongfang; Xie, Hezhen; Won, Sung Wook; Cui, Longzhe; Wu, Guiping

    2015-01-01

    One type of biosorbents, brewer fermentation industry waste yeast, was developed to adsorb the Ag (I) in aqueous solution. The result of FTIR analysis of waste yeast indicated that the ion exchange, chelating and reduction were the main binding mechanisms between the silver ions and the binding sites on the surface of the biomass. Furthermore, TEM, XRD and XPS results suggested that Ag(0) nanoparticles were deposited on the surface of yeast. The kinetic experiments revealed that sorption equilibrium could reach within 60 min, and the removal efficiency of Ag (I) could be still over 93 % when the initial concentration of Ag (I) was below 100 mg/L. Thermodynamic parameters of the adsorption process (ΔG, ΔH and ΔS) identified that the adsorption was a spontaneous and exothermic process. The waste yeast, playing a significant role in the adsorption of the silver ions, is useful to fast adsorb Ag (I) from low concentration.

  3. Kinetic of the COLUMBO-TANTALITE dissolution in aqueous solutions of hydrofluoric acid

    International Nuclear Information System (INIS)

    Rodriguez, Mario; Quiroga, Oscar; Ruiz, Maria del Carmen

    2003-01-01

    The dissolution rate of a columbo-tantalite of the San Luis Province in aqueous solutions of hydrofluoric acid has been studied.Experiments at different temperatures were carried out in a pressure reactor.The experimental results show that the mineral dissolution increases with the reaction time.This effect is greater when the temperature increases from 348 up to 396 K, but it is little 493 K. The experimental data were treated with different models, which have been deduced for the kinetic study of solid-fluid non-catalytic heterogeneous reactions. As a result, the better model that fit the experimental data is a model based on the nucleation and growth theory.This model is physically according to the attack observed by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDXS) on the mineral residues.These residues show an irregular located-type attack

  4. Kinetics of isotopic exchange between calcium molybdate and molybdate ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Atun, G.; Ayar, N.; Bilgin, B. [Istanbul Univ. (Turkey). Dept. of Chemistry, Fac. of Engineering; Bodur, N.; Ayyildiz, H. [Cekmece Nuclear Research and Training Center, Istanbul (Turkey)

    2007-07-01

    The heterogeneous isotopic anion exchange kinetics and equilibria between calcium molybdate and sodium molybdate solutions have been studied by using {sup 99}Mo as tracer in batch experiments. The values of exchange ratio lower than unity suggest that rate-limiting step is particle diffusion process and the effect of re-crystallization can be neglected. The self-diffusion coefficients calculated using both Paterson's and Nernst-Plank approximations are increased by the temperature. The observed values for isotope exchange characteristics such as exchange fractions, exchanging amounts and fractional attainment of equilibrium are consistent with those of their calculated values. Activation energy and thermodynamic parameters calculated based on transition state theory indicate the existence of both energy and entropy barrier in the system. (orig.)

  5. Kinetics of isotopic exchange between calcium molybdate and molybdate ions in aqueous solution

    International Nuclear Information System (INIS)

    Atun, G.; Ayar, N.; Bilgin, B.

    2007-01-01

    The heterogeneous isotopic anion exchange kinetics and equilibria between calcium molybdate and sodium molybdate solutions have been studied by using 99 Mo as tracer in batch experiments. The values of exchange ratio lower than unity suggest that rate-limiting step is particle diffusion process and the effect of re-crystallization can be neglected. The self-diffusion coefficients calculated using both Paterson's and Nernst-Plank approximations are increased by the temperature. The observed values for isotope exchange characteristics such as exchange fractions, exchanging amounts and fractional attainment of equilibrium are consistent with those of their calculated values. Activation energy and thermodynamic parameters calculated based on transition state theory indicate the existence of both energy and entropy barrier in the system. (orig.)

  6. Adsorption of reactive dyes from aqueous solutions by fly ash: Kinetic and equilibrium studies

    International Nuclear Information System (INIS)

    Dizge, N.; Aydiner, C.; Demirbas, E.; Kobya, M.; Kara, S.

    2008-01-01

    Adsorption kinetic and equilibrium studies of three reactive dyes namely, Remazol Brillant Blue (RB), Remazol Red 133 (RR) and Rifacion Yellow HED (RY) from aqueous solutions at various initial dye concentration (100-500 mg/l), pH (2-8), particle size (45-112.5 μm) and temperature (293-323 K) on fly ash (FA) were studied in a batch mode operation. The adsorbent was characterized with using several methods such as SEM, XRD and FTIR. Adsorption of RB reactive dye was found to be pH dependent but both RR and RY reactive dyes were not. The result showed that the amount adsorbed of the reactive dyes increased with increasing initial dye concentration and contact time. Batch kinetic data from experimental investigations on the removal of reactive dyes from aqueous solutions using FA have been well described by external mass transfer and intraparticle diffusion models. It was found that external mass transfer and intraparticle diffusion had rate limiting affects on the removal process. This was attributed to the relatively simple macropore structure of FA particles. The adsorption data fitted well with Langmuir and Freundlich isotherm models. The optimum conditions for removal of the reactive dyes were 100 mg/l initial dye concentration, 0.6 g/100 ml adsorbent dose, temperature of 293 K, 45 μm particle size, pH 6 and agitation speed of 250 rpm, respectively. The values of Langmuir and Freundlich constants were found to increase with increasing temperature in the range 135-180 and 15-34 mg/g for RB, 47-86 and 1.9-3.7 mg/g for RR and 37-61 and 3.0-3.6 mg/g for RY reactive dyes, respectively. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy were evaluated and it was found that the reaction was spontaneous and endothermic in nature

  7. Kinetics and thermodynamics of textile dye adsorption from aqueous solutions using babassu coconut mesocarp

    International Nuclear Information System (INIS)

    Vieira, Adriana P.; Santana, Sirlane A.A.; Bezerra, Cicero W.B.; Silva, Hildo A.S.; Chaves, Jose A.P.; Melo, Julio C.P. de; Silva Filho, Edson C. da; Airoldi, Claudio

    2009-01-01

    Extracted babassu coconut (Orbignya speciosa) mesocarp (BCM) was applied as a biosorbent for aqueous Blue Remazol R160 (BR 160), Rubi S2G (R S2G), Red Remazol 5R (RR 5), Violet Remazol 5R (VR 5) and Indanthrene Olive Green (IOG) dye solutions. The natural sorbent was processed batchwise while varying several system parameters such as stirring time, pH and temperature. The interactions were assayed with respect to both pseudo-first-order and second-order reaction kinetics, with the latter the more suitable kinetic model. The maximum adsorption was obtained at pH 1.0 for all dyes due to available anionic groups attached to the structures, which can be justified by pH pzc 6.7 for the biosorbent BCM. The ability of babassu coconut mesocarp to adsorb dyes gave the order R S2G > VR 5 > BR 160 > IOG > RR 5, which data were best fit to Freundlich model, but did not well-adjusted for all dyes. The dye/biopolymer interactions at the solid/liquid interface are all spontaneous as given by free Gibbs energy, with exothermic enthalpic values of -26.1, -15.8, -17.8, -15.8 and -23.7 kJ mol -1 for BR 160, R S2G, RR 5, IOG and VR 5, respectively. In spite of the negative entropic values contribution, the set of thermodynamic data is favorable for all dyes removal. However, the results pointed to the effectiveness of the mesocarp of babassu coconut as a biosorbent for removing textile dyes from aqueous solutions.

  8. Parametric and kinetic study of adsorptive removal of dyes from aqueous solutions using an agriculture waste

    Science.gov (United States)

    Bencheikh, imane; el hajjaji, souad; abourouh, imane; Kitane, Said; Dahchour, Abdelmalek; El M'Rabet, Mohammadine

    2017-04-01

    -first- order kinetic model the pseudo-second-order kinetic model , and the Intraparticule diffusion model . It was observed that the pseudo -second -order model was the best model describing the adsorption behavior of MB and MO onto holocellulose. This suggested that the adsorption mechanism might be a chemisorptions process. In general, the results indicated that holocellulose is suitable as sorbent material for adsorption of MO and MB from aqueous solutions for its high effectiveness and low cost.

  9. Soil solution phosphorus turnover: derivation, interpretation, and insights from a global compilation of isotope exchange kinetic studies

    Science.gov (United States)

    Helfenstein, Julian; Jegminat, Jannes; McLaren, Timothy I.; Frossard, Emmanuel

    2018-01-01

    The exchange rate of inorganic phosphorus (P) between the soil solution and solid phase, also known as soil solution P turnover, is essential for describing the kinetics of bioavailable P. While soil solution P turnover (Km) can be determined by tracing radioisotopes in a soil-solution system, few studies have done so. We believe that this is due to a lack of understanding on how to derive Km from isotopic exchange kinetic (IEK) experiments, a common form of radioisotope dilution study. Here, we provide a derivation of calculating Km using parameters obtained from IEK experiments. We then calculated Km for 217 soils from published IEK experiments in terrestrial ecosystems, and also that of 18 long-term P fertilizer field experiments. Analysis of the global compilation data set revealed a negative relationship between concentrations of soil solution P and Km. Furthermore, Km buffered isotopically exchangeable P in soils with low concentrations of soil solution P. This finding was supported by an analysis of long-term P fertilizer field experiments, which revealed a negative relationship between Km and phosphate-buffering capacity. Our study highlights the importance of calculating Km for understanding the kinetics of P between the soil solid and solution phases where it is bioavailable. We argue that our derivation can also be used to calculate soil solution turnover of other environmentally relevant and strongly sorbing elements that can be traced with radioisotopes, such as zinc, cadmium, nickel, arsenic, and uranium.

  10. Kinetics of reaction between O 2 and Mn(II) species in aqueous solutions

    Science.gov (United States)

    Morgan, James J.

    2005-01-01

    The objective of this research is to assess critically the experimental rate data for O 2 oxidation of dissolved Mn(II) species at 25°C and to interpret the rates in terms of the solution species of Mn(II) in natural waters. A species kinetic rate expression for parallel paths expresses the total rate of Mn(II) oxidation as Σk i a ij, where k i is the rate constant of species i and a ij is the species concentration fraction in solution j. Among the species considered in the rate expression are Mn(II) hydrolysis products, carbonate complexes, ammonia complexes, and halide and sulfate complexes, in addition to the free aqueous ion. Experiments in three different laboratory buffers and in seawater yield an apparent rate constant for Mn(II) disappearance, k app,j ranging from 8.6 × 10 -5 to 2.5 × 10 -2 (M -1s -1), between pH 8.03 and 9.30, respectively. Observed values of k app exceed predictions based on Marcus outer-sphere electron transfer theory by more than four orders of magnitude, lending strong support to the proposal that Mn(II) + O 2 electron transfer follows an inner-sphere path. A multiple linear regression analysis fit of the observed rates to the species kinetic rate expression yields the following oxidation rate constants (M -1s -1) for the most reactive species: MnOH +, 1.66 × 10 -2; Mn(OH) 2, 2.09 × 10 1; and Mn(CO 3) 22-, 8.13 × 10 -2. The species kinetic rate expression accounts for the influence of pH and carbonate on oxidation rates of Mn(II), through complex formation and acid-base equilibria of both reactive and unreactive species. At pH ˜8, the greater fraction of the total rate is carried by MnOH +. At pH greater than ˜8.4, the species Mn(OH) 2 and Mn(CO 3) 22- make the greater contributions to the total rate.

  11. Expert Oracle database architecture Oracle database programming 9i, 10g, and 11g : Techniques and solution

    CERN Document Server

    Kyte, Thomas

    2010-01-01

    Now in its second edition, this best-selling book by Tom Kyte of Ask Tom fame continues to bring you some of the best thinking on how to apply Oracle Database to produce scalable applications that perform well and deliver correct results. Tom has a simple philosophy: you can treat Oracle as a black box and just stick data into it or you can understand how it works and exploit it as a powerful computing environment. If you choose the latter, then you'll find that there are few information management problems that you cannot solve quickly and elegantly. This fully revised second edition covers t

  12. Kinetics of the exchange between fibrous manganese dioxide and Mn2+ ions in solution

    International Nuclear Information System (INIS)

    Rophael, M.W.

    1983-01-01

    The rate of exchange between fibrous manganese dioxide epsilon-MnO 2 and a 0.1 M MnSO 4 solution at 25 0 C and pH 2.0 was higher than the corresponding rate at pH 5.4. When the solid was washed with dilute acid (pH 2.0) before the exchange at pH 2.0, the results of the exchange at the two pH values were similar. When epsilon-MnO 2 was partially reduced with N 2 H 4 .H 2 O solution before the exchange, the rate of exchange was appreciably higher than that obtained for the unreduced solid. The exchange, at nearly pH 2.0, between epsilon-MnO 2 and various concentrations of Mn(NO 3 ) 2 solutions was increased to a small extent as the concentration increased tenfold. The exchange was followed by using 56 Mn-labelled MnO 2 and by measuring the β activity acquired by the Mn 2+ ion solution. The activity induced in the solid MnO 2 was produced by irradiation with thermal neutrons from a 241 Am- 9 Be laboratory neutron source. The neutron activation of manganese oxides has the following advantages: (i) a relatively high level of activity can be induced in the 55 Mn of the irradiated oxide because of its 100% abundance and its high neutron activation cross section, whereas the oxygen is unaffected; (ii) the half-life of the product 56 Mn is 9274 s which is convenient for kinetic studies; (iii) the activity produced almost decays in 24 h. (Auth.)

  13. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    Science.gov (United States)

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

    2016-01-01

    KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 ÿ 1017 cm⿿3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  14. Kinetics of oxidation of bilirubin and its protein complex by hydrogen peroxide in aqueous solutions

    Science.gov (United States)

    Solomonov, A. V.; Rumyantsev, E. V.; Antina, E. V.

    2010-12-01

    A comparative study of oxidation reactions of bilirubin and its complex with albumin was carried out in aqueous solutions under the action of hydrogen peroxide and molecular oxygen at different pH values. Free radical oxidation of the pigment in both free and bound forms at pH 7.4 was shown not to lead to the formation of biliverdin, but to be associated with the decomposition of the tetrapyrrole chromophore into monopyrrolic products. The effective and true rate constants of the reactions under study were determined. It was assumed that one possible mechanism of the oxidation reaction is associated with the interaction of peroxyl radicals and protons of the NH groups of bilirubin molecules at the limiting stage with the formation of a highly reactive radical intermediate. The binding of bilirubin with albumin was found to result in a considerable reduction in the rate of the oxidation reaction associated with the kinetic manifestation of the protein protection effect. It was found that the autoxidation of bilirubin by molecular oxygen with the formation of biliverdin at the intermediate stage can be observed with an increase in the pH of solutions.

  15. Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis

    International Nuclear Information System (INIS)

    Annadurai, Gurusamy; Ling, L.Y.; Lee, J.-F.

    2008-01-01

    The adsorption of Remazol black 13 (Reactive) dye onto chitosan in aqueous solutions was investigated. Experiments were carried out as function of contact time, initial dye concentration (100-300 mg/L), particle size (0.177, 0.384, 1.651 mm), pH (6.7-9.0), and temperature (30-60 deg. C). The equilibrium adsorption data of reactive dye on chitosan were analyzed by Langmuir and Freundlich models. The maximum adsorption capacity (q m ) has been found to be 91.47-130.0 mg/g. The amino group nature of the chitosan provided reasonable dye removal capability. The kinetics of reactive dye adsorption nicely followed the pseudo-first and second-order rate expression which demonstrates that intraparticle diffusion plays a significant role in the adsorption mechanism. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (0.212 kJ/mol) indicated that the adsorption is endothermic process. The results indicate that chitosan is suitable as adsorbent material for adsorption of reactive dye form aqueous solutions

  16. Numerical solutions of the semiclassical Boltzmann ellipsoidal-statistical kinetic model equation

    Science.gov (United States)

    Yang, Jaw-Yen; Yan, Chin-Yuan; Huang, Juan-Chen; Li, Zhihui

    2014-01-01

    Computations of rarefied gas dynamical flows governed by the semiclassical Boltzmann ellipsoidal-statistical (ES) kinetic model equation using an accurate numerical method are presented. The semiclassical ES model was derived through the maximum entropy principle and conserves not only the mass, momentum and energy, but also contains additional higher order moments that differ from the standard quantum distributions. A different decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. The numerical method in phase space combines the discrete-ordinate method in momentum space and the high-resolution shock capturing method in physical space. Numerical solutions of two-dimensional Riemann problems for two configurations covering various degrees of rarefaction are presented and various contours of the quantities unique to this new model are illustrated. When the relaxation time becomes very small, the main flow features a display similar to that of ideal quantum gas dynamics, and the present solutions are found to be consistent with existing calculations for classical gas. The effect of a parameter that permits an adjustable Prandtl number in the flow is also studied. PMID:25104904

  17. Mechanism and Kinetics for the Dissolution of Apatitic Materials in Acid Solutions

    Directory of Open Access Journals (Sweden)

    Calmanovici C.E.

    1997-01-01

    Full Text Available Abstract - This work concerns the study of the digestion step in the production process of phosphoric acid. Some qualitative experiments indicate that the difference between the pH at the surface of the phosphate and that in the bulk of the solution is negligible and that the dissolution is controlled by diffusion of products away from the phosphate particle. In further experiments, to isolate the dissolution phenomenon from the formation of calcium sulfate, the sulfuric acid normally used industrially is replaced by hydrochloric acid. The phosphate material used in our experiments is a model apatitic material: synthetic hydroxyapatite (HAP. The dissolution of calcium hydroxyapatite was studied with increasing amounts of calcium and phosphate at different temperatures. A simple method was developed for this observation based on the time required for complete dissolution of the HAP powder. The results confirm that the dissolution is controlled by a diffusional process through an interface of calcium and phosphate ions released from the solid surface. A kinetic model for the dissolution of apatitic materials is proposed which assumes a shrinking particle behaviour controlled by diffusion of calcium ions. The experimental results are fitted to this model to determine the mass transfer constant for HAP dissolution in acid solutions. The activation energy of the reaction is about 14kJ/mol. This study was carried on in conditions similar to the industrial ones for the production of phosphoric acid by the dihydrate-process

  18. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    International Nuclear Information System (INIS)

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

    2016-01-01

    Graphical abstract: - Highlights: • Effects of Mg doping on wet etching of N-polar GaN are illustrated and analysed. • Etching process model of Mg-doped N-polar GaN in KOH solution is purposed. • It is found that Mg doping can induce tensile strain in N-polar GaN film. • N-polar p-GaN film with a hole concentration of 2.4 × 10"1"7 cm"−"3 is obtained. - Abstract: KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 10"1"7 cm"−"3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  19. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Zhao, Degang [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Science, PO Box 912, Beijing 100083 (China); Zhang, Baolin; Du, Guotong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

    2016-01-01

    Graphical abstract: - Highlights: • Effects of Mg doping on wet etching of N-polar GaN are illustrated and analysed. • Etching process model of Mg-doped N-polar GaN in KOH solution is purposed. • It is found that Mg doping can induce tensile strain in N-polar GaN film. • N-polar p-GaN film with a hole concentration of 2.4 × 10{sup 17} cm{sup −3} is obtained. - Abstract: KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 10{sup 17} cm{sup −3} was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  20. Analytical solution of point kinetics equations for linear reactivity variation during the start-up of a nuclear reactor

    Energy Technology Data Exchange (ETDEWEB)

    Palma, Daniel A.P. [CEFET QUIMICA de Nilopolis/RJ, 21941-914 Rio de Janeiro (Brazil)], E-mail: agoncalves@con.ufrj.br; Martinez, Aquilino S.; Goncalves, Alessandro C. [COPPE/UFRJ - Programa de Engenharia Nuclear, Rio de Janeiro (Brazil)

    2009-09-15

    The analytical solution of point kinetics equations with a group of delayed neutrons is useful in predicting the variation of neutron density during the start-up of a nuclear reactor. In the practical case of an increase of nuclear reactor power resulting from the linear insertion of reactivity, the exact analytical solution cannot be obtained. Approximate solutions have been obtained in previous articles, based on considerations that need to be verifiable in practice. In the present article, an alternative analytic solution is presented for point kinetics equations in which the only approximation consists of disregarding the term of the second derivative for neutron density in relation to time. The results proved satisfactory when applied to practical situations in the start-up of a nuclear reactor through the control rods withdraw.

  1. Analytical solution of point kinetics equations for linear reactivity variation during the start-up of a nuclear reactor

    International Nuclear Information System (INIS)

    Palma, Daniel A.P.; Martinez, Aquilino S.; Goncalves, Alessandro C.

    2009-01-01

    The analytical solution of point kinetics equations with a group of delayed neutrons is useful in predicting the variation of neutron density during the start-up of a nuclear reactor. In the practical case of an increase of nuclear reactor power resulting from the linear insertion of reactivity, the exact analytical solution cannot be obtained. Approximate solutions have been obtained in previous articles, based on considerations that need to be verifiable in practice. In the present article, an alternative analytic solution is presented for point kinetics equations in which the only approximation consists of disregarding the term of the second derivative for neutron density in relation to time. The results proved satisfactory when applied to practical situations in the start-up of a nuclear reactor through the control rods withdraw.

  2. A middle layer solution to support ACID properties for NoSQL databases

    Directory of Open Access Journals (Sweden)

    Ayman E. Lotfy

    2016-01-01

    Full Text Available The main objective of this paper is to keep the strengths of RDBMSs as consistency and ACID properties and at the same time providing the benefits that inspired the NoSQL movement through a middle layer. The proposed middle layer uses a four phase commit protocol to ensure: the use of recent data, the use of the Pessimistic technique to forbid others dealing with data while it is used and the data updates residing in many locations to avoid the loss of data and disappointment. This mechanism is required, especially in distributed database application NoSQL based environment, because allowing conflicting transactions to continue not only wastes constrained computing power and decreases bandwidth, but also exacerbates conflicts. The middle layer keeps tracking all running transactions and manages with other layers the execution of concurrent transactions. This solution will help increase both of the scalability, and throughput. Finally, the experimental results show that the throughput of the system improves on increasing the number of middle layers in scenarios and the amount of updates to read in a transaction increases. Also the data are consistent with executing many transactions related to each other through updating the same data. The scalability and availability of the system is not affected while ensuring strict consistency.

  3. Equilibrium and Kinetic Sorption of Some Heavy Metals from Aqueous Waste Solutions Using p (AAc-HEMA)

    International Nuclear Information System (INIS)

    El-Sayed, A.H.; Khalil, F.H.; Elnesr, E.; Mansour, T.; El-Gammal, B.; El -Sabbah, M.M.B.

    2013-01-01

    Removal of heavy metals from aqueous waste solution using poly acrylic acid / 2-hydroxy ethyle methacrylate ( p-AAc/ HEMA) was investigated. Experiments were carried out as function of contact time, initial concentration, ph, particle size and temperature. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. The results indicated that poly acrylic acid / 2-hydroxy ethyle methacrylate (p-AAc/ HEMA) is suitable as adsorbent material for adsorption of Sr 2+ , Co 2+ , Cd 2+ , Zn 2+ , Nd 3+ and Eu 3+ radio active nuclei from aqueous solutions.

  4. Kinetic Study of COS with Tertiary Alkanolamine Solutions. 2. Modeling and Experiments in a Stirred Cell Reactor

    NARCIS (Netherlands)

    Littel, Rob J.; Versteeg, Geert F.; Swaaij, Wim P.M. van

    1992-01-01

    Absorption experiments of COS into aqueous solutions of MDEA and DEMEA at 303 K have been carried out in a stirred cell reactor. An absorption model, based on Higbie’s penetration theory, has been developed and applied to interpret the absorption experiments, using the kinetic data obtained in part

  5. A unified approach to model uptake kinetics of trace elements in complex aqueous – solid solution systems

    International Nuclear Information System (INIS)

    Thien, Bruno M.J.; Kulik, Dmitrii A.; Curti, Enzo

    2014-01-01

    Highlights: • There are several models able to describe trace element partitioning in growing minerals. • To describe complex systems, those models must be embedded in a geochemical code. • We merged two models into a unified one suitable for implementation in a geochemical code. • This unified model was tested against coprecipitation experimental data. • We explored how our model reacts to solution depletion effects. - Abstract: Thermodynamics alone is usually not sufficient to predict growth-rate dependencies of trace element partitioning into host mineral solid solutions. In this contribution, two uptake kinetic models were analyzed that are promising in terms of mechanistic understanding and potential for implementation in geochemical modelling codes. The growth Surface Entrapment Model (Watson, 2004) and the Surface Reaction Kinetic Model (DePaolo, 2011) were shown to be complementary, and under certain assumptions merged into a single analytical expression. This Unified Uptake Kinetics Model was implemented in GEMS3K and GEM-Selektor codes ( (http://gems.web.psi.ch)), a Gibbs energy minimization package for geochemical modelling. This implementation extends the applicability of the unified uptake kinetics model to accounting for non-trivial factors influencing the trace element partitioning into solid solutions, such as the changes in aqueous solution composition and speciation, or the depletion effects in closed geochemical systems

  6. A thermodynamic and kinetic study of trace iron removal from aqueous cobalt sulfate solutions using Monophos resin.

    Science.gov (United States)

    Wang, Guangxin; Zhao, Yunchao; Yang, Bin; Song, Yongfa

    2018-01-01

    High purity cobalt has many important applications, such as magnetic recording media, magnetic recording heads, optoelectronic devices, magnetic sensors, and integrated circuits, etc. To produce 5N or higher purity cobalt in an electro-refining process, one of the challenges is to effectively reduce the Fe content of aqueous cobalt salt solution before electrolysis. This paper describes thermodynamic and kinetic investigations of the Fe adsorption process of a new sulfonated monophosphonic resin with the trade mark Monophos. Five cobalt sulfate solutions of different Co concentrations were prepared. Fe ions were removed from the solutions by ion exchange method using Monophos resin. Chemical analysis was carried out using a Perkin Elmer ICP-OES. The initial Fe concentrations of about 0.9-2.0 mg/L can be reduced to about 0.3-0.8 mg/L, which is equivalent to an Fe removal rate of 60-67%. The Langmuir isothermal adsorption model applies well to the Fe removal process. A second-order type based on McKay equation fits better with experimental data than other kinetic models. The kinetic curve can be divided into two sections. For t 30 min. Monophos resin is effective for the removal of trace Fe from cobalt sulfate solution. This ion exchange process obeys the Langmuir isothermal adsorption model and the McKay equation of second-order kinetics.

  7. Different nonideality relationships, different databases and their effects on modeling precipitation from concentrated solutions using numerical speciation codes

    Energy Technology Data Exchange (ETDEWEB)

    Brown, L.F.; Ebinger, M.H.

    1996-08-01

    Four simple precipitation problems are solved to examine the use of numerical equilibrium codes. The study emphasizes concentrated solutions, assumes both ideal and nonideal solutions, and employs different databases and different activity-coefficient relationships. The study uses the EQ3/6 numerical speciation codes. The results show satisfactory material balances and agreement between solubility products calculated from free-energy relationships and those calculated from concentrations and activity coefficients. Precipitates show slightly higher solubilities when the solutions are regarded as nonideal than when considered ideal, agreeing with theory. When a substance may precipitate from a solution dilute in the precipitating substance, a code may or may not predict precipitation, depending on the database or activity-coefficient relationship used. In a problem involving a two-component precipitation, there are only small differences in the precipitate mass and composition between the ideal and nonideal solution calculations. Analysis of this result indicates that this may be a frequent occurrence. An analytical approach is derived for judging whether this phenomenon will occur in any real or postulated precipitation situation. The discussion looks at applications of this approach. In the solutes remaining after the precipitations, there seems to be little consistency in the calculated concentrations and activity coefficients. They do not appear to depend in any coherent manner on the database or activity-coefficient relationship used. These results reinforce warnings in the literature about perfunctory or mechanical use of numerical speciation codes.

  8. Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

    Science.gov (United States)

    Tosun, Ismail

    2012-03-01

    The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

  9. Ammonium Removal from Aqueous Solutions by Clinoptilolite: Determination of Isotherm and Thermodynamic Parameters and Comparison of Kinetics by the Double Exponential Model and Conventional Kinetic Models

    Directory of Open Access Journals (Sweden)

    İsmail Tosun

    2012-03-01

    Full Text Available The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R and four three-parameter (Redlich-Peterson (R-P, Sips, Toth and Khan isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R2 of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°, enthalpy (∆H° and entropy (∆S° of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

  10. Kinetics of the reaction between plutonium (4) and neptunium (4) in nitric acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Koltunov, V S; Zhuravleva, G I; Marchenko, V I

    1976-01-01

    The kinetics of the oxidation of neptunium(IV) to neptunium(V) by tetravalent plutonium ions in solutions of HNO/sub 3/ + NaNO/sub 3/ at constant (..mu.. = 2) and variable (..mu.. = 0.7-2.0) ionic strengths of the solution was investigated by a spectrophotometric method. It was established that in the range of concentrations (Np(IV)) = (4.25-10.6) x 10/sup 13/; (Pu(IV)) = (2.6-3.9)x10/sup -3/ M; (H/sup +/) 0.37-1.91 M, a first order is observed with respect to the reagents, while the order of the reaction with respect to H/sup +/ ions is equal to -3. The average value of the true rate constant of the reaction is k = 27.9+-1.3 M/sup 2/xmin/sup -1/ at ..mu..=2 and 39/sup 0/C. It was shown that with increasing analytical concentration of HNO/sub 3/ and NO/sub 3//sup -/ ions (in a mixture of HNO/sub 3/ +HClO/sub 4/), the value of K decreases. On the basis of an invetigation of the dependence of the reaction rate on the temperature in the interval 31-44.8/sup 0/, we calculated the values of the energy (E = 34.6 kcal/mole), enthalpy (..delta..H* = 34 kcal/mole), free energy (..delta..F* = 19.6 kcal/mole, entropy (..delta..S* = 49 entropy units) of activation of the reaction and the formal ionic entropy of the activated complex (PuOOHNp/sup 5 +/)*, S* = -87 entropy units. A reaction mechanism including an interaction of hydrolyzed neptunium and plutonium ions as the rate-determining step was proposed and discusses. The results obtained are compared with data for this reaction in perchloric acid wolution and for other similar redox reactions.

  11. Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes

    Science.gov (United States)

    Zhu, Yajun; Zhong, Chengwen; Xu, Kun

    2016-06-01

    This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.

  12. Removal of three nitrophenols from aqueous solutions by adsorption onto char ash: equilibrium and kinetic modeling

    Science.gov (United States)

    Magdy, Yehia M.; Altaher, Hossam; ElQada, E.

    2018-03-01

    In this research, the removal of 2,4 dinitrophenol, 2 nitrophenol and 4 nitrophenol from aqueous solution using char ash from animal bones was investigated using batch technique. Three 2-parameter isotherms (Freundlich, Langmuir, and Temkin) were applied to analyze the experimental data. Both linear and nonlinear regression analyses were performed for these models to estimate the isotherm parameters. Three 3-parameter isotherms (Redlich-Peterson, Sips, Toth) were also tested. Moreover, the kinetic data were tested using pseudo-first order, pseudo-second order, Elovich, Intraparticle diffusion and Boyd methods. Langmuir adsorption isotherm provided the best fit for the experimental data indicating monolayer adsorption. The maximum adsorption capacity was 8.624, 7.55, 7.384 mg/g for 2 nitrophenol, 2,4 dinitrophenol, and 4 nitrophenol, respectively. The experimental data fitted well to pseudo-second order model suggested a chemical nature of the adsorption process. The R 2 values for this model were 0.973 up to 0.999. This result with supported by the Temkin model indicating heat of adsorption to be greater than 10 kJ/mol. The rate controlling step was intraparticle diffusion for 2 nitrophenol, and a combination of intraparticle diffusion and film diffusion for the other two phenols. The pH and temperature of solution were found to have a considerable effect, and the temperature indicated the exothermic nature of the adsorption process. The highest adsorption capacity was obtained at pH 9 and 25 °C.

  13. Adsorption of 4-chlorophenol from aqueous solutions by xad-4 resin: Isotherm, kinetic, and thermodynamic analysis

    International Nuclear Information System (INIS)

    Bilgili, M. Sinan

    2006-01-01

    Removal of 4-chlorophenol (4-CP) from synthetic aqueous solutions through adsorption on Amberlite XAD-4 resin, a non-ionic macroreticular resins, under batch equilibrium experimental conditions at 298, 308 and 318 K was investigated. It is necessary to propose a suitable model to a better understanding on the mechanism of 4-CP adsorption. For this purpose, Langmiur, Freundlich, Toth, and Redlich-Peterson (RP) isotherm models were compared. The two and three parameters in the adopted adsorption isotherm models were determined by the help of MATLAB package program. It was determined that best fitted adsorption isotherm models were obtained to be in the order: Redlich-Peterson > Langmuir > Toth > Freundlich isotherms. The pseudo-second-order kinetic model provided the best correlation to the experimental results. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate limiting step. The lower correlation of the data to the Bangham's equation also represents that the diffusion of the adsorbate into pores of the sorbent is not the only rate-controlling step. The thermodynamic constants of adsorption phenomena; ΔG o , ΔH o , and ΔS o were found as -4.17 (at 298 K) kJ/mol, -42.01 kJ/mol, and -0.127 kJ/(mol K), respectively. The results showed that adsorption of 4-CP on Amberlite XAD-4, a nonionic polymeric resin was exothermic and spontaneous

  14. DISPL-1, 2. Order Nonlinear Partial Differential Equation System Solution for Kinetics Diffusion Problems

    International Nuclear Information System (INIS)

    Leaf, G.K.; Minkoff, M.

    1982-01-01

    1 - Description of problem or function: DISPL1 is a software package for solving second-order nonlinear systems of partial differential equations including parabolic, elliptic, hyperbolic, and some mixed types. The package is designed primarily for chemical kinetics- diffusion problems, although not limited to these problems. Fairly general nonlinear boundary conditions are allowed as well as inter- face conditions for problems in an inhomogeneous medium. The spatial domain is one- or two-dimensional with rectangular Cartesian, cylindrical, or spherical (in one dimension only) geometry. 2 - Method of solution: The numerical method is based on the use of Galerkin's procedure combined with the use of B-Splines (C.W.R. de-Boor's B-spline package) to generate a system of ordinary differential equations. These equations are solved by a sophisticated ODE software package which is a modified version of Hindmarsh's GEAR package, NESC Abstract 592. 3 - Restrictions on the complexity of the problem: The spatial domain must be rectangular with sides parallel to the coordinate geometry. Cross derivative terms are not permitted in the PDE. The order of the B-Splines is at most 12. Other parameters such as the number of mesh points in each coordinate direction, the number of PDE's etc. are set in a macro table used by the MORTRAn2 preprocessor in generating the object code

  15. Adsorptive removal of malachite green from aqueous solutions by almond gum: Kinetic study and equilibrium isotherms.

    Science.gov (United States)

    Bouaziz, Fatma; Koubaa, Mohamed; Kallel, Fatma; Ghorbel, Rhoudha Ellouz; Chaabouni, Semia Ellouz

    2017-12-01

    This work aimed at investigating the potential of almond gum as low cost adsorbent for the removal of the cationic dye; malachite green from aqueous solutions. Almond gum was first analyzed by scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR), and then the adsorption behavior was studied in batch system. The effects of the adsorption parameters (adsorbent dose, pH, contact time, particle size, initial dye concentration, temperature and agitation) on the dye removal have been studied. Adsorption equilibrium and isotherms were evaluated depending on temperature using the isotherms of Freundlich, Langmuir, and Tempkin. The obtained result showed that both Langmuir and Freundlich models were adapted to study the dye sorption. The maximum adsorption capacities were equal to 172.41mg/g, 181.81mg/g, and 196.07mg/g at 303.16K, 313.16K, and 323.16K, respectively. The kinetics of sorption were following the pseudo-second order model. The thermodynamic changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) indicated that the adsorption of malachite green at the surface of almond gum is endothermic and occurs spontaneously. Desorption experiments were conducted to regenerate almond gum, showing great desorption capacity when using HCl at pH 2. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Fenton-Like Oxidation of Malachite Green Solutions: Kinetic and Thermodynamic Study

    Directory of Open Access Journals (Sweden)

    Saeedeh Hashemian

    2013-01-01

    Full Text Available Oxidation by Fenton-like (Fe3+/H2O2 reactions is proven to be an economically feasible process for destruction of a variety of hazardous pollutants in wastewater. In this study, the degradation and mineralization of malachite green dye are reported using Fenton-like reaction. The effects of different parameters like pH of the solution, the initial concentrations of Fe3+, H2O2, and dye, temperature, and added electrolytes (Cl− and on the oxidation of the dye were investigated. Optimized condition was determined. The efficiency of 95.5% degradation of MAG after 15 minutes of reaction at pH 3 was obtained. TOC removal indicates partial and insignificant mineralization of malachite green dye. The results of experiments showed that degradation of malachite green dye in Fenton-like oxidation process can be described with a pseudo-second-order kinetic model. The thermodynamic constants of the Fenton oxidation process were evaluated. The results implied that the oxidation process was feasible, spontaneous, and endothermic. The results will be useful for designing the treatment systems of various dye-containing wastewaters.

  17. Solution of fractional kinetic equation by a class of integral transform of pathway type

    Science.gov (United States)

    Kumar, Dilip

    2013-04-01

    Solutions of fractional kinetic equations are obtained through an integral transform named Pα-transform introduced in this paper. The Pα-transform is a binomial type transform containing many class of transforms including the well known Laplace transform. The paper is motivated by the idea of pathway model introduced by Mathai [Linear Algebra Appl. 396, 317-328 (2005), 10.1016/j.laa.2004.09.022]. The composition of the transform with differential and integral operators are proved along with convolution theorem. As an illustration of applications to the general theory of differential equations, a simple differential equation is solved by the new transform. Being a new transform, the Pα-transform of some elementary functions as well as some generalized special functions such as H-function, G-function, Wright generalized hypergeometric function, generalized hypergeometric function, and Mittag-Leffler function are also obtained. The results for the classical Laplace transform is retrieved by letting α → 1.

  18. Evaporation kinetics of surfactant solution droplets on rice (Oryza sativa) leaves

    Science.gov (United States)

    Cao, Li-Dong; Zheng, Li; Xu, Jun; Li, Feng-Min; Huang, Qi-Liang

    2017-01-01

    The dynamics of evaporating sessile droplets on hydrophilic or hydrophobic surfaces is widely studied, and many models for these processes have been developed based on experimental evidence. However, few research has been explored on the evaporation of sessile droplets of surfactant or pesticide solutions on target crop leaves. Thus, in this paper the impact of surfactant concentrations on contact angle, contact diameter, droplet height, and evolution of the droplets’ evaporative volume on rice leaf surfaces have been investigated. The results indicate that the evaporation kinetics of surfactant droplets on rice leaves were influenced by both the surfactant concentrations and the hydrophobicity of rice leaf surfaces. When the surfactant concentration is lower than the surfactant CMC (critical micelle concentration), the droplet evaporation time is much longer than that of the high surfactant concentration. This is due to the longer existence time of a narrow wedge region under the lower surfactant concentration, and such narrow wedge region further restricts the droplet evaporation. Besides, our experimental data are shown to roughly collapse onto theoretical curves based on the model presented by Popov. This study could supply theoretical data on the evaporation of the adjuvant or pesticide droplets for practical applications in agriculture. PMID:28472108

  19. Solution of non-steady-state substrate concentration in the action of biosensor response at mixed enzyme kinetics

    Science.gov (United States)

    Senthamarai, R.; Jana Ranjani, R.

    2018-04-01

    In this paper, a mathematical model of an amperometric biosensor at mixed enzyme kinetics and diffusion limitation in the case of substrate inhibition has been developed. The model is based on time dependent reaction diffusion equation containing a non -linear term related to non -Michaelis - Menten kinetics of the enzymatic reaction. Solution for the concentration of the substrate has been derived for all values of parameters using the homotopy perturbation method. All the approximate analytic expressions of substrate concentration are compared with simulation results using Scilab/Matlab program. Finally, we have given a satisfactory agreement between them.

  20. HF effect on dissociation kinetics of plutonium and neptunium complexes with 1,2-diaminocyclohexanetetraacetic acid in nitric acid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nikitina, S.A.; Stepanov, A.V.

    1982-01-01

    Dissociation kinetics of Pusup((4)) and Np sup((4)) complexes with DCTA were investigated in HNO/sub 3/ solutions in the presence of HF and arsenazo 3. It was found that HF or NaF produced a differentiating effect on the reactivity of the complexes at (HNO/sub 3/)=1-6 mol/l as well as inhibiting effect at (HNO/sub 3/)=0.01 mol/l. Conditions of the differential kinetic analysis of plutonium and neptunium in the mixture and differential spectrophotometric analysis of uranium (6) during the camouflage of neptunium (4) and plutonium (4) were determined.

  1. HF effect on dissociation kinetics of plutonium and neptunium complexes with 1,2-diaminocyclohexanetetraacetic acid in nitric acid solutions

    International Nuclear Information System (INIS)

    Nikitina, S.A.; Stepanov, A.V.

    1982-01-01

    Dissociation kinetics of Pusup((4)) and Np sup((4)) complexes with DCTA were investigated in HNO 3 solutions in the presence of HF and arsenazo 3. It was found that HF or NaF produced a differentiating effect on the reactivity of the complexes at [HNO 3 ]=1-6 mol/l as well as inhibiting effect at [HNO 3 ]=0.01 mol/l. Conditions of the differential kinetic analysis of plutonium and neptunium in the mixture and differential spectrophotometric analysis of uranium (6) during the camouflage of neptunium (4) and plutonium (4) were determined

  2. The relational clinical database: a possible solution to the star wars in registry systems.

    Science.gov (United States)

    Michels, D K; Zamieroski, M

    1990-12-01

    In summary, having data from other service areas available in a relational clinical database could resolve many of the problems existing in today's registry systems. Uniting sophisticated information systems into a centralized database system could definitely be a corporate asset in managing the bottom line.

  3. Theory of First Order Chemical Kinetics at the Critical Point of Solution.

    Science.gov (United States)

    Baird, James K; Lang, Joshua R

    2017-10-26

    Liquid mixtures, which have a phase diagram exhibiting a miscibility gap ending in a critical point of solution, have been used as solvents for chemical reactions. The reaction rate in the forward direction has often been observed to slow down as a function of temperature in the critical region. Theories based upon the Gibbs free energy of reaction as the driving force for chemical change have been invoked to explain this behavior. With the assumption that the reaction is proceeding under relaxation conditions, these theories expand the free energy in a Taylor series about the position of equilibrium. Since the free energy is zero at equilibrium, the leading term in the Taylor series is proportional to the first derivative of the free energy with respect to the extent of reaction. To analyze the critical behavior of this derivative, the theories exploit the principle of critical point isomorphism, which is thought to govern all critical phenomena. They find that the derivative goes to zero in the critical region, which accounts for the slowing down observed in the reaction rate. As has been pointed out, however, most experimental rate investigations have been carried out under irreversible conditions as opposed to relaxation conditions [Shen et al. J. Phys. Chem. A 2015, 119, 8784-8791]. Below, we consider a reaction governed by first order kinetics and invoke transition state theory to take into account the irreversible conditions. We express the apparent activation energy in terms of thermodynamic derivatives evaluated under standard conditions as well as the pseudoequilibrium conditions associated with the reactant and the activated complex. We show that these derivatives approach infinity in the critical region. The apparent activation energy follows this behavior, and its divergence accounts for the slowing down of the reaction rate.

  4. Estimation of glucose kinetics in fetal-maternal studies: Potential errors, solutions, and limitations

    International Nuclear Information System (INIS)

    Menon, R.K.; Bloch, C.A.; Sperling, M.A.

    1990-01-01

    We investigated whether errors occur in the estimation of ovine maternal-fetal glucose (Glc) kinetics using the isotope dilution technique when the Glc pool is rapidly expanded by exogenous (protocol A) or endogenous (protocol C) Glc entry and sought possible solutions (protocol B). In protocol A (n = 8), after attaining steady-state Glc specific activity (SA) by [U-14C]glucose (period 1), infusion of Glc (period 2) predictably decreased Glc SA, whereas. [U-14C]glucose concentration unexpectedly rose from 7,208 +/- 367 (means +/- SE) in period 1 to 8,558 +/- 308 disintegrations/min (dpm) per ml in period 2 (P less than 0.01). Fetal endogenous Glc production (EGP) was negligible during period 1 (0.44 +/- 1.0), but yielded a physiologically impossible negative value of -2.1 +/- 0.72 mg.kg-1.min-1 during period 2. When the fall in Glc SA during Glc infusion was prevented by addition of [U-14C]glucose admixed with the exogenous Glc (protocol B; n = 7), EGP was no longer negative. In protocol C (n = 6), sequential infusions of four increasing doses of epinephrine serially decreased SA, whereas tracer Glc increased from 7,483 +/- 608 to 11,525 +/- 992 dpm/ml plasma (P less than 0.05), imposing an obligatory underestimation of EGP. Thus a tracer mixing problem leads to erroneous estimations of fetal Glc utilization and Glc production via the three-compartment model in sheep when the Glc pool is expanded exogenously or endogenously. These errors can be minimized by maintaining the Glc SA relatively constant

  5. A kinetic study of the mechanism of radiation induced agglomeration of ovalbumin in aqueous solution

    International Nuclear Information System (INIS)

    Tuce, Zorana; Janata, Eberhard; Radojcic, Marija; Milosavljevic, B.H.

    2001-01-01

    The effect of concentration on the protein radiolytic damage resulting in a change in molecular mass was measured in the concentration range from 0.2 to 2 mmolxdm -3 ovalbumin in phosphate buffered solutions saturated with N 2 O. The electrophoretic analysis of samples on discontinuous SDS-polyacrylamide gels in the presence or absence of 5% β-mercaptoethanol showed an expected result, i.e. that the protein scission did not take place in the absence of oxygen. Only ovalbumin agglomerates, bonded by covalent bonds other than S-S bridges, were observed. The G-value for the formation of ovalbumin agglomerates increased linearly from 1.1 to 2.4 by increasing the ovalbumin concentration from 0.2 to 2 mmolxdm -3 . The result is interpreted as to be owing to the competition between ovalbumin agglomeration and some intramolecular reactions which did not lead to the change in the molecular mass. It was also found that the G-value is independent of irradiation dose rate. The result was rationalized as a kinetic evidence that the agglomeration is not a cross-linking process, i.e. it does not occur via recombination of the protein radicals produced in the interaction of ovalbumin and · OH radical. The result suggested that the agglomeration takes place via the process of grafting, i.e. it occurs in the reaction of ovalbumin radical and an intact ovalbumin molecule. The time-resolved light scattering experiments provided an additional proof, supporting the reaction scheme of radiation-induced protein agglomeration. The biological consequences of the proposed mechanism of protein agglomeration are also discussed

  6. Photodegradation of gemfibrozil in aqueous solution under UV irradiation: kinetics, mechanism, toxicity, and degradation pathways.

    Science.gov (United States)

    Ma, Jingshuai; Lv, Wenying; Chen, Ping; Lu, Yida; Wang, Fengliang; Li, Fuhua; Yao, Kun; Liu, Guoguang

    2016-07-01

    The lipid regulator gemfibrozil (GEM) has been reported to be persistent in conventional wastewater treatment plants. This study investigated the photolytic behavior, toxicity of intermediate products, and degradation pathways of GEM in aqueous solutions under UV irradiation. The results demonstrated that the photodegradation of GEM followed pseudo-first-order kinetics, and the pseudo-first-order rate constant was decreased markedly with increasing initial concentrations of GEM and initial pH. The photodegradation of GEM included direct photolysis via (3)GEM(*) and self-sensitization via ROS, where the contribution rates of degradation were 0.52, 90.05, and 8.38 % for ·OH, (1)O2, and (3)GEM(*), respectively. Singlet oxygen ((1)O2) was evidenced by the molecular probe compound, furfuryl alcohol (FFA), and was identified as the primary reactive species in the photolytic process. The steady-state concentrations of (1)O2 increased from (0.324 ± 0.014) × 10(-12) to (1.021 ± 0.040) × 10(-12) mol L(-1), as the initial concentrations of GEM were increased from 5 to 20 mg L(-1). The second-order rate constant for the reaction of GEM with (1)O2 was calculated to be 2.55 × 10(6) M(-1) s(-1). The primary transformation products were identified using HPLC-MS/MS, and possible photodegradation pathways were proposed by hydroxylation, aldehydes reactions, as well as the cleavage of ether side chains. The toxicity of phototransformation product evaluation revealed that photolysis potentially provides a critical pathway for GEM toxicity reduction in potable water and wastewater treatment facilities.

  7. Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads

    Directory of Open Access Journals (Sweden)

    Ruth Alfaro-Cuevas-Villanueva

    2014-01-01

    Full Text Available The sorption of cadmium (Cd and lead (Pb by calcium alginate beads (CAB from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2 for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F and Dubinin-Radushkevich (D-R models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

  8. Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan polysaccharides as sulfated carbohydrates in acid perchlorate solutions.

    Science.gov (United States)

    Hassan, Refat M; Fawzy, Ahmed; Ahmed, Gamal A; Zaafarany, Ishaq A; Asghar, Basim H; Takagi, Hideo D; Ikeda, Yasuhisa

    2011-10-18

    The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm(-3) have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that Mn(III) is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Specific features of kinetics of He/sup 3/-He/sup 4/ solid solution transformations at superlow temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mikheev, V A; Majdanov, V A; Mikhin, N P

    1986-06-01

    The NMR data on the phase transition kinetics of /sup 3/He-/sup 4/He solid solutions at T=100 mK are considered. Studied are solid helium samples of a molecular volume of 20.55 cm/sup 2//mol with a /sup 3/He content of 0.54%. An unusually long phase transition time is found which is dependent on the prehistory of sample. The spin diffusion of /sup 3/He in the transformated solution concentrated phase is found to be of a quasi-one-dimensional nature with the diffusion coefficient value typical of liquid.

  10. Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

    Directory of Open Access Journals (Sweden)

    Zun Maria

    2014-12-01

    Full Text Available In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w of urea had the best constancy.

  11. Analytical solution of spatial kinetics of the diffusion model for subcritical homogeneous systems driven by external source

    International Nuclear Information System (INIS)

    Oliveira, Fernando Luiz de

    2008-01-01

    This work describes an analytical solution obtained by the expansion method for the spatial kinetics using the diffusion model with delayed emission for source transients in homogeneous media. In particular, starting from simple models, and increasing the complexity, numerical results were obtained for different types of source transients. An analytical solution of the one group without precursors was solved, followed by considering one precursors family. The general case of G-groups with R families of precursor although having a closed form solution, cannot be solved analytically, since there are no explicit formulae for the eigenvalues, and numerical methods must be used to solve such problem. To illustrate the general solution, the multi-group (three groups) time-dependent problem without precursors was solved and the numerical results of a finite difference code were compared with the exact results for different transients. (author)

  12. Adsorption of cadmium from aqueous solution onto untreated coffee grounds: Equilibrium, kinetics and thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Azouaou, N., E-mail: azouaou20@yahoo.fr [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria); Sadaoui, Z. [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria); Djaafri, A. [Central laboratory, SEAAL, 97 Parc ben omar, Kouba, Algiers (Algeria); Mokaddem, H. [Laboratory of Reaction Genius, Faculty of Mechanical and Processes Genius, University of Sciences and Technology Houari - Boumediene, USTHB, BP no 32 El Alia bab ezzouar, 16111 Algiers (Algeria)

    2010-12-15

    Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin-Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd{sup 2+} adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65 mg g{sup -1}. Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120 min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd{sup 2+} removal.

  13. Adsorption of cadmium from aqueous solution onto untreated coffee grounds: Equilibrium, kinetics and thermodynamics

    International Nuclear Information System (INIS)

    Azouaou, N.; Sadaoui, Z.; Djaafri, A.; Mokaddem, H.

    2010-01-01

    Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin-Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd 2+ adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65 mg g -1 . Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120 min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd 2+ removal.

  14. Kinetics, isotherms, and thermodynamic studies of lead, chromium, and cadmium bio-adsorption from aqueous solution onto Picea smithiana sawdust.

    Science.gov (United States)

    Mahmood-Ul-Hassan, Muhammad; Yasin, Muhammad; Yousra, Munazza; Ahmad, Rizwan; Sarwar, Sair

    2018-05-01

    Lead (Pb), chromium (Cr), and cadmium (Cd) removal capacity of sawdust (Picea smithiana) from aqueous solution was investigated by conducting batch experiments. Thermodynamic parameters, like change in standard free energy (ΔG Θ ), enthalpy (ΔH Θ ) and entropy (ΔS Θ ) during bio-adsorption process were estimated using the Van't Hoff equation. The maximum metals adsorption was observed at pH 8, 20 g L -1 bio-adsorbent and at 60 min of contact time. The metal adsorption kinetics was examined by fitting the pseudo-first-order as well as four forms of pseudo-second-order kinetic models. Type 1 pseudo-second-order equation described adsorption kinetics better than others. Langmuir model and Freundlich equations were used for calculation of sorption parameters. The Langmuir maximum adsorption capacity of Pb, Cr, and Cd was 6.35, 3.37, and 2.87 mg g -1 at room temperature, respectively. The values of the separation factor (RL) were in between 0 and 1, indicating that bio-adsorption was favorable. Thermodynamics study revealed that the Pb, Cr, and Cd uptake reactions were endothermic and spontaneous. Results of the study asserted that the removal of heavy metal ions from aqueous solution is viable and the sawdust could be used in the treatment of effluents from industries, thereby reducing the level of water pollution.

  15. Sorption of malachite green from aqueous solution by potato peel: Kinetics and equilibrium modeling using non-linear analysis method

    Directory of Open Access Journals (Sweden)

    El-Khamsa Guechi

    2016-09-01

    Full Text Available Potato peel (PP was used as a biosorbent to remove malachite green (MG from aqueous solution under various operating conditions. The effect of the experimental parameters such as initial dye concentration, biosorbent dose, initial pH, stirring speed, temperature, ionic strength and biosorbent particle size was investigated through a number of batch sorption experiments. The sorption kinetic uptake for MG by PP at various initial dye concentrations was analyzed by non-linear method using pseudo-first, pseudo-second and pseudo-nth order models. It was found that the pseudo-nth order kinetic model was the best applicable model to describe the sorption kinetic data and the order n of sorption reaction was calculated in the range from 0.71 to 2.71. Three sorption isotherms namely the Langmuir, Freundlich and Redlich–Peterson isotherms in their non-linear forms were applied to the biosorption equilibrium data. Both the Langmuir and Redlich–Peterson models were found to fit the sorption isotherm data well, but the Redlich–Peterson model was better. Thermodynamic parameters show that the sorption process of MG is endothermic and more effective process at high temperatures. The results revealed that PP is very effective for the biosorption of MG from aqueous solutions.

  16. Database Security for an Integrated Solution to Automate Sales Processes in Banking

    OpenAIRE

    Alexandra Maria Ioana FLOREA

    2013-01-01

    In order to maintain a competitive edge in a very active banking market the implementation of a web-based solution to standardize, optimize and manage the flow of sales / pre-sales and generating new leads is requested by a company. This article presents the realization of a development framework for software interoperability in the banking financial institutions and an integrated solution for achieving sales process automation in banking. The paper focuses on presenting the requirements for ...

  17. Kinetics of bromide catalysed oxidation of dextrose by cerium (IV) in aqueous sulphuric acid solution

    International Nuclear Information System (INIS)

    Sharma, J.; Sah, M.P.

    1994-01-01

    Kinetics of bromide catalysed oxidation of dextrose by Ce IV in aqueous sulphuric acid medium show first order dependence each in dextrose and cerium(IV). The reaction rate decreases on increasing the concentration of hydrogen ion. The increase in [HSO 4 - ] or [SO 4 2- ] decreases the rate. The bromide ion shows positive catalytic effect on the reaction rate. The value of activation energy has been calculated and a suitable mechanism confirming to the kinetic data is proposed. (author). 3 refs., 3 tabs

  18. Numerical solution of the point reactor kinetics equations with fuel burn-up and temperature feedback

    International Nuclear Information System (INIS)

    Tashakor, S.; Jahanfarnia, G.; Hashemi-Tilehnoee, M.

    2010-01-01

    Point reactor kinetics equations are solved numerically using one group of delayed neutrons and with fuel burn-up and temperature feedback included. To calculate the fraction of one-group delayed neutrons, a group of differential equations are solved by an implicit time method. Using point reactor kinetics equations, changes in mean neutrons density, temperature, and reactivity are calculated in different times during the reactor operation. The variation of reactivity, temperature, and maximum power with time are compared with the predictions by other methods.

  19. Reaction kinetics of hydrazine neutralization in steam generator wet lay-up solution: Identifying optimal degradation conditions

    International Nuclear Information System (INIS)

    Schildermans, Kim; Lecocq, Raphael; Girasa, Emmanuel

    2012-09-01

    During a nuclear power plant outage, hydrazine is used as an oxygen scavenger in the steam generator lay-up solution. However, due to the carcinogenic effects of hydrazine, more stringent discharge limits are or will be imposed in the environmental permits. Hydrazine discharge could even be prohibited. Consequently, hydrazine alternatives or hydrazine degradation before discharge is needed. This paper presents the laboratory tests performed to characterize the reaction kinetics of hydrazine neutralization using bleach or hydrogen peroxide, catalyzed with either copper sulfate (CuSO 4 ) or potassium permanganate (KMnO 4 ). The tests are performed on two standard steam generator lay-up solutions based on different pH control agents: ammonia or ethanolamine. Different neutralization conditions are tested by varying temperature, oxidant addition, and catalyst concentration, among others, in order to identify the optimal parameters for hydrazine neutralization in a steam generator wet lay-up solution. (authors)

  20. Kinetic Approach for the Adsorption of Organophosphorous Pesticides from Aqueous Solution Using “Waste” Jute Fiber Carbon

    Directory of Open Access Journals (Sweden)

    S. Senthilkumaar

    2010-01-01

    Full Text Available Chemically activated “Waste” Jute Fiber carbon has been effectively used for the removal of five organophosphorous pesticides (malathion, monocrotophos, methylparathion, phosphamidon and dimethoate from aqueous solutions. The prepared activated jute fiber carbon was characterized by using Elemental analyzer and proximate analysis methods. The adsorption equilibrium was examined at 28 ºC. Three different kinetic models, the pseudo first order, pseudo second order and Elovich kinetic models were selected to analyses the adsorption process. To compare the fitness of pseudo first order and pseudo second order, sum of the squares of the errors and correlation coefficient, r2 values were calculated. The Elovich model was used to confirm the chemisorptions.

  1. Kinetics of electrophilic substitution of neodymium(III) by ytterbium(III) in aqueous solutions of ethylenediamintetraacetate and cyclohexanediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1982-01-01

    The kinetics of electrophilic substitution in systems containing rare earth element ions (REE) and Komplexon [tetrasodium ethylenediaminetetraacetate] have been studied little. At the same time, information about the mechanism of exchange is not only of theoretical interest but is important for the optimization of processes for separating and purifying REE. Least studied of all has been the mutual exchange in Komplexonate ions of light and heavy REE, although it is precisely the kinetics of exchange of different kinds of REE ions that primarily determines the effectiveness of the separation of their mixtures. We have studied electrophilic substitution in the case of the replacement of neodymium(III) by ytterbium(III) in solutions containing NdL - and Yb 3 + , where L 4 - and D 4 -

  2. Comparisons of kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide adsorption in aqueous solution with graphene oxide, zeolite and activated carbon

    Science.gov (United States)

    Chang, Shenteng; Lu, Chungsying; Lin, Kun-Yi Andrew

    2015-01-01

    Graphene oxide (GO), sodium Y-type zeolite (NaY) and granular activated carbon (GAC) are selected as adsorbents to study their kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide (TMAH) adsorption from water. The adsorption kinetics follows the pseudo-second-order rate law while the adsorption thermodynamics shows an exothermic reaction with GO and GAC but displays an endothermic reaction with NaY. The adsorbed TMAH can be readily desorbed from the surface of GO and NaY by 0.05 M NaCl solution. A comparative study on the cyclic TMAH adsorption with GO, NaY and GAC is also conducted and the results reveal that GO exhibits the greatest TMAH adsorption capacity as well as superior reversibility of TMAH adsorption over 10 cycles of adsorption and desorption process. These features indicate that GO is a promising and efficient adsorbent for TMAH removal in wastewater treatment.

  3. Solution of the two-dimensional space-time reactor kinetics equation by a locally one-dimensional method

    International Nuclear Information System (INIS)

    Chen, G.S.; Christenson, J.M.

    1985-01-01

    In this paper, the authors present some initial results from an investigation of the application of a locally one-dimensional (LOD) finite difference method to the solution of the two-dimensional, two-group reactor kinetics equations. Although the LOD method is relatively well known, it apparently has not been previously applied to the space-time kinetics equations. In this investigation, the LOD results were benchmarked against similar computational results (using the same computing environment, the same programming structure, and the same sample problems) obtained by the TWIGL program. For all of the problems considered, the LOD method provided accurate results in one-half to one-eight of the time required by the TWIGL program

  4. Structural and silver/vanadium ratio effects on silver vanadium phosphorous oxide solution formation kinetics: impact on battery electrochemistry.

    Science.gov (United States)

    Bock, David C; Takeuchi, Kenneth J; Marschilok, Amy C; Takeuchi, Esther S

    2015-01-21

    The detailed understanding of non-faradaic parasitic reactions which diminish battery calendar life is essential to the development of effective batteries for use in long life applications. The dissolution of cathode materials including manganese, cobalt and vanadium oxides in battery systems has been identified as a battery failure mechanism, yet detailed dissolution studies including kinetic analysis are absent from the literature. The results presented here provide a framework for the quantitative and kinetic analyses of the dissolution of cathode materials which will aid the broader community in more fully understanding this battery failure mechanism. In this study, the dissolution of silver vanadium oxide, representing the primary battery powering implantable cardioverter defibrillators (ICD), is compared with the dissolution of silver vanadium phosphorous oxide (Ag(w)VxPyOz) materials which were targeted as alternatives to minimize solubility. This study contains the first kinetic analyses of silver and vanadium solution formation from Ag0.48VOPO4·1.9H2O and Ag2VP2O8, in a non-aqueous battery electrolyte. The kinetic results are compared with those of Ag2VO2PO4 and Ag2V4O11 to probe the relationships among crystal structure, stoichiometry, and solubility. For vanadium, significant dissolution was observed for Ag2V4O11 as well as for the phosphate oxide Ag0.49VOPO4·1.9H2O, which may involve structural water or the existence of multiple vanadium oxidation states. Notably, the materials from the SVPO family with the lowest vanadium solubility are Ag2VO2PO4 and Ag2VP2O8. The low concentrations and solution rates coupled with their electrochemical performance make these materials interesting alternatives to Ag2V4O11 for the ICD application.

  5. KINETICS OF THE OXIDATION OF FERROUS CHELATES OF EDTA AND HEDTA IN AQUEOUS-SOLUTION

    NARCIS (Netherlands)

    WUBS, HJ; BEENACKERS, AACM

    1993-01-01

    The kinetics of the reaction of oxygen with ferrous chelates of EDTA and HEDTA was studied in a stirred cell reactor under industrial conditions. The temperature was varied from 20 to 60-degrees-C and the concentration of the ferrous chelate ranged from 0 to 100 mol/m3. The initial pH was 7.5. Under

  6. Equilibrium and kinetic models for colloid release under transient solution chemistry conditions

    Science.gov (United States)

    We present continuum models to describe colloid release in the subsurface during transient physicochemical conditions. Our modeling approach relates the amount of colloid release to changes in the fraction of the solid surface area that contributes to retention. Equilibrium, kinetic, equilibrium and...

  7. Enzyme allocation problems in kinetic metabolic networks: Optimal solutions are elementary flux modes

    Czech Academy of Sciences Publication Activity Database

    Müller, Stefan; Regensburger, G.; Steuer, Ralf

    2014-01-01

    Roč. 347, APR 2014 (2014), s. 182-190 ISSN 0022-5193 R&D Projects: GA MŠk(CZ) EE2.3.20.0256 Institutional support: RVO:67179843 Keywords : metabolic optimization * enzyme kinetics * oriented matroid * elementary vector * conformal sum Subject RIV: EI - Biotechnology ; Bionics Impact factor: 2.116, year: 2014

  8. Microsoft Access Small Business Solutions State-of-the-Art Database Models for Sales, Marketing, Customer Management, and More Key Business Activities

    CERN Document Server

    Hennig, Teresa; Linson, Larry; Purvis, Leigh; Spaulding, Brent

    2010-01-01

    Database models developed by a team of leading Microsoft Access MVPs that provide ready-to-use solutions for sales, marketing, customer management and other key business activities for most small businesses. As the most popular relational database in the world, Microsoft Access is widely used by small business owners. This book responds to the growing need for resources that help business managers and end users design and build effective Access database solutions for specific business functions. Coverage includes::; Elements of a Microsoft Access Database; Relational Data Model; Dealing with C

  9. Database Security for an Integrated Solution to Automate Sales Processes in Banking

    Directory of Open Access Journals (Sweden)

    Alexandra Maria Ioana FLOREA

    2013-05-01

    Full Text Available In order to maintain a competitive edge in a very active banking market the implementation of a web-based solution to standardize, optimize and manage the flow of sales / pre-sales and generating new leads is requested by a company. This article presents the realization of a development framework for software interoperability in the banking financial institutions and an integrated solution for achieving sales process automation in banking. The paper focuses on presenting the requirements for security and confidentiality of stored data and also on presenting the identified techniques and procedures to implement these requirements.

  10. Removal of Cadmium and Lead from Aqueous Solution by Hydroxyapatite/Chitosan Hybrid Fibrous Sorbent: Kinetics and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    Soyeon Park

    2015-01-01

    Full Text Available Hydroxyapatite (HAp/chitosan composites were prepared by a coprecipitation method, dropping a mixture of chitosan solution and phosphoric acid solution into a calcium hydroxide solution. Using the HAp/chitosan composites prepared, HAp/chitosan hybrid fibers with various HAp contents were prepared by a wet spinning method. X-ray diffraction and scanning electron microscopy analyses revealed that HAp particles were coated onto the surface of the fiber, and the surface roughness increased with increasing the HAp contents in the fiber. In order to evaluate the heavy metal removal characteristics of the HAp/chitosan hybrid fiber, adsorption tests were conducted and the results were compared with those of bare chitosan fibers. The results showed better performance in heavy metal ion removal for the HAp/chitosan hybrid fiber than the chitosan fiber. As the HAp content in the hybrid fiber increased, the removal efficiency of heavy metal ions also increased due to the increase of the specific surface area of the HAp/chitosan hybrid fiber. Adsorption kinetic and isotherm tests revealed that Pb2+ and Cd2+ adsorption to the hybrid fiber follows pseudo-second-order kinetic and Langmuir-type adsorption, respectively.

  11. Adsorptive removal of phenol from aqueous solutions on activated carbon prepared from tobacco residues: Equilibrium, kinetics and thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, Murat; Apaydin-Varol, Esin [Department of Chemical Engineering, Anadolu University, Eskisehir 26470 (Turkey); Puetuen, Ayse E., E-mail: aeputun@anadolu.edu.tr [Department of Chemical Engineering, Anadolu University, Eskisehir 26470 (Turkey)

    2011-05-15

    This study consists of producing high surface area activated carbon from tobacco residues by chemical activation and its behavior of phenol removal from aqueous solutions. K{sub 2}CO{sub 3} and KOH were used as chemical activation agents and three impregnation ratios (50, 75 and 100 wt.%) were applied on biomass. Maximum BET surface areas of activated carbons were obtained from impregnation with 75 wt.% of K{sub 2}CO{sub 3} and 75 wt.% of KOH as 1635 and 1474 m{sup 2}/g, respectively. Optimum adsorption conditions were determined as a function of pH, adsorbent dosage, initial phenol concentration, contact time and temperature of solution for phenol removal. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as {Delta}G{sup o}, {Delta}H{sup o} and {Delta}S{sup o} were calculated for predicting the nature of adsorption. According to the experimental results, activated carbon prepared from tobacco residue seems to be an effective, low-cost and alternative adsorbent precursor for the removal of phenol from aqueous solutions.

  12. Removal of methylene blue from aqueous solution with magnetite loaded multi-wall carbon nanotube: Kinetic, isotherm and mechanism analysis

    International Nuclear Information System (INIS)

    Ai, Lunhong; Zhang, Chunying; Liao, Fang; Wang, Yao; Li, Ming; Meng, Lanying; Jiang, Jing

    2011-01-01

    Highlights: ► M-MWCNTs were synthesized by a facile one-pot solvothermal method and used as an efficient adsorbent for removing toxic dye from aqueous solution. ► The adsorption process was characterized by kinetics and isotherm analysis. ► FTIR analysis was employed to investigate the interactions between M-MWCNTs and dye. - Abstract: In this study, we have demonstrated the efficient removal of cationic dye, methylene blue (MB), from aqueous solution with the one-pot solvothermal synthesized magnetite-loaded multi-walled carbon nanotubes (M-MWCNTs). The as-prepared M-MWCNTs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The effects of contact time, initial dye concentration, and solution pH on the adsorption of MB onto M-MWCNTs were systematically studied. It was shown that the MB adsorption was pH-dependent. Adsorption kinetics was best described by the pseudo-second-order model. Equilibrium data were well fitted to the Langmuir isotherm model, yielding maximum monolayer adsorption capacity of 48.06 mg g −1 . FTIR analysis suggested that the adsorption mechanism was possibly attributed to the electrostatic attraction and π–π stacking interactions between MWCNTs and MB.

  13. Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: Equilibrium, kinetic and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Senturk, Hasan Basri; Ozdes, Duygu; Gundogdu, Ali; Duran, Celal [Department of Chemistry, Karadeniz Technical University, Faculty of Arts and Sciences, 61080 Trabzon (Turkey); Soylak, Mustafa, E-mail: soylak@erciyes.edu.tr [Department of Chemistry, Erciyes University, Faculty of Arts and Sciences, 38039 Kayseri (Turkey)

    2009-12-15

    A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1 h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g{sup -1}. Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R{sup 2} > 0.99). Thermodynamic parameters including the Gibbs free energy ({Delta}G{sup o}), enthalpy ({Delta}H{sup o}), and entropy ({Delta}S{sup o}) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 {sup o}C.

  14. Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: Equilibrium, kinetic and thermodynamic study

    International Nuclear Information System (INIS)

    Senturk, Hasan Basri; Ozdes, Duygu; Gundogdu, Ali; Duran, Celal; Soylak, Mustafa

    2009-01-01

    A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1 h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g -1 . Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R 2 > 0.99). Thermodynamic parameters including the Gibbs free energy (ΔG o ), enthalpy (ΔH o ), and entropy (ΔS o ) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 o C.

  15. AKA-TPG: a program for kinetic and epidemiological analysis of data from labeled glucose investigations using the two-pool model and database technology

    DEFF Research Database (Denmark)

    Boston, Raymond C; Stefanovski, Darko; Henriksen, Jan E

    2007-01-01

    of technical reasons have deterred researchers from performing TPG analysis. METHODS AND RESULTS: In this paper, we describe AKA-TPG, a new program that combines automatic kinetic analysis of the TPG model data with database technologies. AKA-TPG enables researchers who have no expertise in modeling to quickly...... fit the TPG model to individual FSHGT data sets consisting of plasma concentrations of unlabeled glucose, labeled glucose, and insulin. Most importantly, because the entire process is automated, parameters are almost always identified, and parameter estimates are accurate and reproducible. AKA...

  16. A Database for Climatic Conditions around Europe for Promoting GSHP Solutions

    Directory of Open Access Journals (Sweden)

    Michele De Carli

    2018-02-01

    Full Text Available Weather plays an important role for energy uses in buildings. For this reason, it is required to define the proper boundary conditions in terms of the different parameters affecting energy and comfort in buildings. They are also the basis for determining the ground temperature in different locations, as well as for determining the potential for using geothermal energy. This paper presents a database for climates in Europe that has been used in a freeware tool developed as part of the H2020 research project named “Cheap-GSHPs”. The standard Köppen-Geiger climate classification has been matched with the weather data provided by the ENERGYPLUS and METEONORM software database. The Test Reference Years of more than 300 locations have been considered. These locations have been labelled according to the degree-days for heating and cooling, as well as by the Köppen-Geiger scale. A comprehensive data set of weather conditions in Europe has been created and used as input for a GSHP sizing software, helping the user in selecting the weather conditions closest to the location of interest. The proposed method is based on lapse rates and has been tested at two locations in Switzerland and Ireland. It has been demonstrated as quite valid for the project purposes, considering the spatial distribution and density of available data and the lower computing load, in particular for locations where altitude is the main factor controlling on the temperature variations.

  17. Kinetics and thermodynamics of the dissolution of Th1-xMxO2 solid solutions (M = U, Pu)

    International Nuclear Information System (INIS)

    Hubert, S.; Heisbourg, G.; Dacheux, N.; Moisy, Ph.; Purans, J.

    2004-01-01

    Kinetics of the dissolution of Th 1-x M x O 2 (M = U, Pu) solid solutions was investigated as a function of several chemical parameters such as pH, substitution ratio, temperature, ionic strength, and electrolyte. Several compositions of Th 1-x U x O 2 and Th 1-x Pu x O 2 were synthesized and characterized before and after leaching by using several methods such as XRD, EXAFS, BET, PIXE, SEM, and XPS. Leaching tests were performed in nitric, hydrochloric or sulfuric media and groundwater. The normalized dissolution rates were evaluated for Th 1-x U x O 2 , and Th 0.88 Pu 0.12 O 2 leading to the determination of the partial order related to the proton concentration, n, and to the corresponding normalized dissolution rate constant at pH = 0, k'T. While for Th enriched solids, the solid solutions Th 1-x U x O 2 have the same dissolution behaviour than ThO 2 with a partial order n ∼ 0.3, in the case of uranium enriched solids, Th 1-x U x O 2 has the same dissolution behaviour than UO 2 with a partial order of n = 1, indicating that uranium oxidation rate becomes the limiting step of the dissolution process. The stoichiometry of the release of both actinides (U or Pu, Th) was verified until the precipitation of thorium occurred in the leachate for pH > 2, while uranium was released in the solution as an uranyl form. For uranium enriched solid solutions, thermodynamic equilibrium was reached after 100 days, and solubility constant of secondary phase was determined. In the case of Th 1-x Pu x O 2 , the dissolution behaviour is similar to that of ThO 2 , but only kinetic aspect of the dissolution can be studied. From the analysis of XPS and EXAFS data on leached and un-leached Th 1-x U x O 2 samples, the dissolution mechanism of solid solutions was explained and will be discussed. The role of the electrolytes on the dissolution of the solid solutions is discussed. Kinetics parameters of dissolution are also given in groundwater and in neutral media

  18. Kinetics of electrophilic substitution of erbium (3) for ytterbium (3) in aqueous solution of ethylenediaminetetraacetate

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1983-08-01

    The results obtained while studing the exchange kinetics in the ErA/sup -/ - Yb/sup 3 +/ system are compared with the kinetic regularities found for the NdA/sup -/ - Yb/sup 3 +/ system. Electrophilic substitution in ethylenediamine tetraacetates of rare earths (3) independently of the nature of a departing cation is realized through two competitive mechanisms: acid dissociation and associative mechanisms. Exchange through the acid dissociation mechanisms is catalized by protons while, depending on the medium acidity, mono- and biprotonated intermediate complexes are formed. The associative mechanism predominates in less acid media and is realized through the formation of intermediate binuclear complexes. The limiting exchange stage is a break in the metal-nitrogen bond formed by the departing cation and ligand in the intermediate binuclear complex.

  19. Kinetics of electrophilic substitution of erbium (3) for ytterbium (3) in aqueous solution of ethylenediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1983-01-01

    The results obtained while stUdying the exchange kinetics in the ErA - - Yb 3+ system are compared with the kinetic regularities found for the NdA - - Yb 3+ system. Electrophilic substitution in ethylenediamine tetraacetates of rare earths (3) independently of the nature of a departing cation is realized through two competitive mechanisms: acid dissociation and associatiVe mechanisms. Exchange through the acid dissociation mechanisms is catalized by protons while, depending on the medium acidity, mono- and biprotonated intermediate complexes are formed. The associative mechanism predominates in less acid media and is realized through the formation of intermediate binOclear compleXes. The limiting exchange stage is a break in the metal-nitrogen bond formed by the departing cation and ligand in the intermediate binUclear complex

  20. Kinetics of some rare earth ions substitution for neodymium(3) ion in aqueous solutions of ethylenediaminetetraacetate

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Afonin, E.G.; Pechurova, N.I.

    1984-01-01

    Kinetics of electrophilic interaction in the systems NdA - -Ln 3+ (where Ln 3+ - Tu 3+ , Er 3+ , Gd 3+ , Eu 3+ , Pr 3+ ) has been studied. It is found that the following kinetic equation: W=W 1 +W 2 = (Ksub(1)csub(Hsup(+))+Ksub(2)csub(Lnsup(3+) 3+))csub(NdAsup(-)), where csub(Lnsup(3+)) and csub(NdA - ) - initial concentrations of Ln 3+ and NdA - , corresponds to the exchange rate. It is shown that W 1 - component of exchange rate according to the mechanism of acid dissociation, and W 2 - according to associative mechanism. The values of K 1 and K 2 at t=20 deg C, μ=0.1 are calculated. The dependence of K 2 on the nature of the ligand included is studied. It is shown that K 2 depends linearly on stability constant of Ln 3+ iminodiacetate

  1. Kinetic determination of ultramicro amounts of As(III in solution

    Directory of Open Access Journals (Sweden)

    RANGEL P. IGOV

    2003-02-01

    Full Text Available A new catalytic reaction is proposed and a kinetic method developed for the determination of ultramicro amounts of As(III on the basis of its catalytic activity in the oxidation of ethylenediamine-N,N’-diacetic-N,N’ dipropionic acid (EAP by KMnO4 in the presence of hydrochloric acid. Under optimal conditions, the sensivity of the method is 20 ng/cm3. The probable relative error is 7.6 – 14.5 % for the concentration range 50 – 200 ng/cm3 As(III. The effect of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The method has relatively good selectivity. Kinetic equations were proposed for the investigated process.

  2. Kinetics of neptunim(6) reduction by hydroxylamine in chloric acid solutions

    International Nuclear Information System (INIS)

    Shilov, V.P.; Stepanova, E.S.; Krot, N.N.

    1975-01-01

    Stoichiometry and kinetics of neptunium (6) reaction with hydroxylamine is studied by spectrophotometric method at the ionic strength equal to unity and at 20-30 deg C. The reaction obeys the equation: -d[Np(6)]/dt = k 0 [Np(6)][NH 3 OH + ]/[H + ]sup(0.74), where k 0 = 2.6 M -1 min -1 at 25 deg C. Possible mechanism of the process includes two steps

  3. Numerical solution of multi groups point kinetic equations by simulink toolbox of Matlab software

    International Nuclear Information System (INIS)

    Hadad, K.; Mohamadi, A.; Sabet, H.; Ayobian, N.; Khani, M.

    2004-01-01

    The simulink toolbox of Matlab Software was employed to solve the point kinetics equation with six group delayed neutrons. The method of Adams-Bash ford showed a good convergence in solving the system of simultaneous equations and the obtained results showed good agreements with other numerical schemes. The flexibility of the package in changing the system parameters and the user friendly interface makes this approach a reliable educational package in revealing the affects of reactivity changes on power incursions

  4. Kinetics of photochromic processes in substituted dihydropyridines in the solid state and in solution

    Czech Academy of Sciences Publication Activity Database

    Sworakowski, J.; Nešpůrek, Stanislav; Lipinski, J.; Lewanowicz, A.; Sliwinska, E.

    2001-01-01

    Roč. 356, - (2001), s. 163-173 ISSN 1058-725X. [International Conference on the Chemistry of the Organic Solid State /14./. Cambridge, 25.07.1999-30.07.1999] R&D Projects: GA AV ČR IAA1050901; GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : dihydropyridine * photochromism * reaction kinetics Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.457, year: 2001

  5. Solution of the kinetic equation in the P3-approximation in a plane geometry

    International Nuclear Information System (INIS)

    Vlasov, Yu.A.

    1975-01-01

    A method and a program are described for solving single-velocity kinetic equations of neutron transfer for the plane geometry in the finite-difference approximation. A difference high-accuracy scheme and a matrix factorization method are used for the differential-difference equation systems. The program is written in the ALGOL-60 language and is adapted for M-20, M-220, M-222 and BESM-4 computers

  6. Equilibrium, kinetic and thermodynamic studies of adsorption of Th(IV) from aqueous solution onto kaolin

    International Nuclear Information System (INIS)

    Hongxia Zhang; Zhiwei Niu; Zhi Liu; Zhaodong Wen; Weiping Li; Xiaoyun Wang; Wangsuo Wu

    2015-01-01

    The kinetics and thermodynamics of the adsorption of Th(IV) on the kaolin were studied by using batch method. In addition, the experimental data were studied by dynamic and thermodynamic models. The results showed that the adsorption capacity of the adsorbent increased with increasing temperature and solid liquid ratio, but decreased with increasing initial Th(IV) ion concentration, and the best fit was obtained for the pseudo-second-order kinetics model. The calculated activation energy for adsorption was about 45 kJ/mol, which indicated the adsorption process to be chemisorption. The adsorption isotherm data could be well described by the Langmuir as well as Dubinin-Radushkevich model. The mean free energy (E) of adsorption was calculated to be about 15 kJ/mol. The thermodynamic data calculated showed that the adsorption was spontaneous and enhanced at higher temperature. Considering kinetics and equilibrium studies, the adsorption on the sites was the rate-limiting step and that adsorption was mainly a chemisorption process through cation exchange. (author)

  7. Addition and elimination kinetics in OH radical induced oxidation of phenol and cresols in acidic and alkaline solutions

    International Nuclear Information System (INIS)

    Roder, M.; Wojnarovits, L.; Foeldiak, G.; Emmi, S.S.; Beggiato, G.; D'Angelantonio, M.

    1999-01-01

    The rates of the two consecutive reactions, OH radical addition and H 2 O/OH - elimination, were studied by pulse radiolysis in highly acidic (pH=1.3-1.9) and alkaline (pH∼11) solutions, respectively, for phenol and for the three cresol isomers. The rate coefficient of the addition as measured by the build-up of phenoxyl radical absorbance and by a competitive method is the same (1.4±0.1)x10 10 mol -1 dm 3 s -1 both in acidic and alkaline solution. The rate coefficient of the H 2 O elimination in acidic solution is (1.6±0.2)x10 6 s -1 , whereas the coefficient of the OH - elimination in alkaline solutions is 6-8 times higher. The kinetics of the phenoxyl radical formation was described by the two-exponential equation of the consecutive reactions: the first exponential is related to the pseudo-first-order addition, while the second to the elimination reaction. No considerable structure dependence was found in the rate coefficients, indicating that the methyl substitutent in these highly acidic or alkaline solutions influences neither the addition nor the elimination rate

  8. Kinetics of the oxidation of hydrogen sulfite by hydrogen peroxide in aqueous solution:. ionic strength effects and temperature dependence

    Science.gov (United States)

    Maaß, Frank; Elias, Horst; Wannowius, Klaus J.

    Conductometry was used to study the kinetics of the oxidation of hydrogen sulfite, HSO -3, by hydrogen peroxide in aqueous non-buffered solution at the low concentration level of 10 -5-10 -6 M, typically found in cloud water. The kinetic data confirm that the rate law reported for the pH range 3-6 at higher concentration levels, rate= kH·[H +]·[HSO -3]·[H 2O 2], is valid at the low concentration level and at low ionic strength Ic. At 298 K and Ic=1.5×10 -4 M, third-order rate constant kH was found to be kH=(9.1±0.5)×10 7 M -2 s -1. The temperature dependence of kH led to an activation energy of Ea=29.7±0.9 kJ mol -1. The effect of the ionic strength (adjusted with NaCl) on rate constant kH was studied in the range Ic=2×10 -4-5.0 M at pH=4.5-5.2 by conductometry and stopped-flow spectrophotometry. The dependence of kH on Ic can be described with a semi-empirical relationship, which is useful for the purpose of comparison and extrapolation. The kinetic data obtained are critically compared with those reported earlier.

  9. Recovery of nickel and cobalt as MHP from limonitic ore leaching solution: Kinetics analysis and precipitate characterization

    Science.gov (United States)

    Safitri, Nina; Mubarok, M. Zaki; Winarko, Ronny; Tanlega, Zela

    2018-05-01

    In the present study, precipitation of nickel and cobalt as mixed hydroxide precipitate (MHP) from pregnant leach solution of nickel limonite ore from Soroako after iron removal stage was carried out. A series of MHP precipitation experiments was conducted by using MgO slurry as neutralizing agent and the effects of pH, temperature, duration of precipitation and the addition of MHP seed on the precipitation behavior of nickel, cobalt, as well as iron and manganese was studied. Characterization of MHP product was performed by particle size analyzer (PSA) as well as X-Ray Fluorescence (XRF), X-Ray Diffractometer (XRD) and Scanning Electron Microscope (SEM) analyses. Kinetics analysis was made by using differential-integral method for the rate of homogenous reaction. Precipitation at pH 7, temperature 50°C for 30 minute, without seed addition resulted in nickel and cobalt recoveries of 82.8% and 92%, respectively with co-precipitated iron and manganese of 70% and 24.2%, respectively. The seed addition increases nickel and cobalt precipitations significantly to 99.9% and 99.1%, respectively. However, the addition of seed into led to a significant increase of manganese co-precipitation from 24.2% without seed addition to 39.5% at the addition of 1 g seed per 200 mL of PLS. Kinetics analysis revealed that Ni precipitation to form MHP follows the second-order reaction kinetics with activation energy of 94.6 kJ/mol.

  10. Estimation of the nucleation kinetics for the anti-solvent crystallisation of paracetamol in methanol/water solutions

    Science.gov (United States)

    Ó'Ciardhá, Clifford T.; Frawley, Patrick J.; Mitchell, Niall A.

    2011-08-01

    In this work the primary nucleation kinetics have been estimated for the anti-solvent crystallisation of paracetamol in methanol-water solutions from metastable zone widths (MSZW) and induction times at 25 °C. Laser back-scattering via a focused beam reflectance Measurement (FBRM ®) is utilised to detect the onset of nucleation. The theoretical approach of Kubota was employed to estimate the nucleation kinetics, which accounts for the sensitivity of the nucleation detection technique. This approach is expanded in this work to analyse the induction time for an anti-solvent crystallisation process. Solvent composition is known to have a significant impact on the measured induction times and MSZW. The induction time in this paper was measured from 40% to 70% mass water and the MSZW is measured from 40% to 60% mass water. The primary focus of the paper was to gauge the extent of how solvent composition affects nucleation kinetics so that this effect may be incorporated into a population balance model. Furthermore, the effects of solvent composition on the estimated nucleation rates are investigated. The primary nucleation rates were found to decrease with dynamic solvent composition, with the extent of their reduction linked to the gradient of the solubility curve. Finally, both MSZW and induction time methods have been found to produce similar estimates for the nucleation parameters.

  11. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  12. Kinetic and Thermodynamic Studies for the Removal of Europium Ions from Waste Solution Using Some Local Clay Minerals

    International Nuclear Information System (INIS)

    El-Kamash, A.M.; El-Masry, E.H.; El-Dessouky, M.I.

    2008-01-01

    Thermodynamic and kinetic investigations on the removal of Eu 3+ ions from aqueous waste solution using bentonite and sandstone, as local clay minerals, has been done using batch technique. The influences of ph, contact time between liquid and solid phases, initial metal ion concentration, and temperature have been evaluated. Pseudo first-order and pseudo second-order kinetic models were used to analyze the sorption rate data and the results showed that the pseudo second-order model is best correlate the kinetic data. Equilibrium isotherms were determined to assess the maximum sorption capacity of bentonite and sandstone and the equilibrium sorption data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models. All tested models fit the data reasonably well in terms of regression coefficients. The maximum sorption capacity of bentonite was found to be greater than that of sandstone and the mean free energy is in all cases in the range corresponding to the ion exchange type of sorption. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The numerical value of δG degree decreases with an increase in temperature, indicating that the sorption reaction is more favorable at higher temperature. The positive values of δH degree correspond to the endothermic nature of the sorption process

  13. Aqueous solutions that model the cytosol : studies on polarity, chemical reactivity and enzyme kinetics

    NARCIS (Netherlands)

    Asaad, N.; den Otter, M.J.; Engberts, J.B.F.N.

    2004-01-01

    Concentrated solutions of a series of organic compounds have been prepared and the effects of these solutes on the properties of the solvent system assessed as a function of their concentration and nature. Polarity, as measured by Reichardt's E-T(30) probe, exhibits a linear variation with both

  14. Adsorption kinetics of diblock copolymers from a micellar solution on silica and titania.

    NARCIS (Netherlands)

    Bijsterbosch, H.D.; Cohen Stuart, M.A.; Fleer, G.J.

    1998-01-01

    The solution and adsorption behavior of a series of diblock copolymers of hydrophobic poly(dimethyl siloxane) and hydrophilic poly(2-ethyl-2-oxazoline) was studied. These block copolymers formed large polydisperse micelles in an aqueous solution. The critical micelle concentration was lower than 2

  15. Modeling the chemical kinetics of atmospheric plasma for cell treatment in a liquid solution

    International Nuclear Information System (INIS)

    Kim, H. Y.; Kang, S. K.; Lee, H. Wk.; Lee, H. W.; Kim, G. C.; Lee, J. K.

    2012-01-01

    Low temperature atmospheric pressure plasmas have been known to be effective for living cell inactivation in a liquid solution but it is not clear yet which species are key factors for the cell treatment. Using a global model, we elucidate the processes through which pH level in the solution is changed from neutral to acidic after plasma exposure and key components with pH and air variation. First, pH level in a liquid solution is changed by He + and He(2 1 S) radicals. Second, O 3 density decreases as pH level in the solution decreases and air concentration decreases. It can be a method of removing O 3 that causes chest pain and damages lung tissue when the density is very high. H 2 O 2 , HO 2 , and NO radicals are found to be key factors for cell inactivation in the solution with pH and air variation.

  16. Mechanism and kinetic considerations of TOC removal from the powdered activated carbon ozonation of diclofenac aqueous solutions.

    Science.gov (United States)

    Beltrán, Fernando J; Pocostales, J Pablo; Alvarez, Pedro M; Jaramillo, Josefa

    2009-09-30

    Ozonation of DCF in aqueous solution in the presence of powdered activated carbon (PAC) has been studied for mechanistic and kinetic purposes. The effects of gas flow rate, ozone gas concentration and initial TOC on the TOC elimination rate were then investigated. The use of PAC allows liquid-solid and internal diffusion mass transfer resistances being eliminated. Gas-liquid mass transfer resistance is also eliminated when ozonation is applied to DCF preozonated solutions. In the absence of mass transfer resistances a mechanism of reactions involving homogeneous and heterogeneous steps for TOC removal was proposed. From this mechanism a mathematical model constituted by mass balances of main species in water was established. Considerations about the changing nature of ozonation intermediates, as being promoters or inhibitors of ozone decomposition, is a key point to better predict the experimental concentrations of species present in this system.

  17. Crevice-corrosion kinetics on titanium and a Ti-Ni-Mo alloy in chloride solutions at elevated temperature

    International Nuclear Information System (INIS)

    McKay, P.

    1987-01-01

    The results of an electrochemical investigation of the crevice-corrosion kinetics on titanium and a dilute Ti-Ni-Mo alloy (0.8% Ni, 0.3% Mo), in concentrated chloride solutions at 150 0 C, are presented. The current-time transients, obtained on creviced electrodes under both potentiostatic and galvanic (coupling to a large area of uncreviced titanium) conditions, are interpreted in terms of crevice acidification leading to the formation of an active-passive cell, maintained by iR gradient in the electrolyte. The passivating effect of the Ni and Mo additions on the crevice corrosion of titanium are described, together with the results of an electrochemical study, carried out in bulk acid chloride solutions, that were used to substantiate a proposed mechanism of crevice passivation. (author)

  18. Non-dissipative kinetic simulation and analytical solution of three-mode equations of ion temperature gradient instability

    International Nuclear Information System (INIS)

    Watanabe, T.-H.; Sugama, H.; Sato, T.

    1999-12-01

    A non-dissipative drift kinetic simulation scheme, which rigorously satisfies the time-reversibility, is applied to the three-mode coupling problem of the ion temperature gradient (ITG) instability. It is found from the simulation that the three-mode ITG system repeats growth and decay with a period which shows a logarithmic divergence for infinitesimal initial perturbations. Accordingly, time average of the mode amplitude vanishes, as the initial amplitude approaches to zero. An exact solution is analytically given for a class of initial conditions. An excellent agreement is confirmed between the analytical solution and numerical results. The results obtained here provide a useful reference for basic benchmarking of theories and simulation of the ITG modes. (author)

  19. Correction of MHS Viscosimetric Constants upon Numerical Simulation of Temperature Induced Degradation Kinetic of Chitosan Solutions

    Directory of Open Access Journals (Sweden)

    Vincenzo Maria De Benedictis

    2016-05-01

    Full Text Available The Mark–Houwink–Sakurada (MHS equation allows for estimation of rheological properties, if the molecular weight is known along with good understanding of the polymer conformation. The intrinsic viscosity of a polymer solution is related to the polymer molecular weight according to the MHS equation, where the value of the constants is related to the specific solvent and its concentration. However, MHS constants do not account for other characteristics of the polymeric solutions, i.e., Deacetilation Degree (DD when the solute is chitosan. In this paper, the degradation of chitosan in different acidic environments by thermal treatment is addressed. In particular, two different solutions are investigated (used as solvent acetic or hydrochloric acid with different concentrations used for the preparation of chitosan solutions. The samples were treated at different temperatures (4, 30, and 80 °C and time points (3, 6 and 24 h. Rheological, Gel Permeation Chromatography (GPC, Fourier Transform Infrared Spectroscopy (FT-IR, Differential Scanning Calorimetry (DSC and Thermal Gravimetric Analyses (TGA were performed in order to assess the degradation rate of the polymer backbones. Measured values of molecular weight have been integrated in the simulation of the batch degradation of chitosan solutions for evaluating MHS coefficients to be compared with their corresponding experimental values. Evaluating the relationship between the different parameters used in the preparation of chitosan solutions (e.g., temperature, time, acid type and concentration, and their contribution to the degradation of chitosan backbone, it is important to have a mathematical frame that could account for phenomena involved in polymer degradation that go beyond the solvent-solute combination. Therefore, the goal of the present work is to propose an integration of MHS coefficients for chitosan solutions that contemplate a deacetylation degree for chitosan systems or a more

  20. Kinetic modeling and simulation of PCE and TCE removal in aqueous solutions by electron-beam irradiation

    International Nuclear Information System (INIS)

    Nickelsen, Michael G.; Cooper, William J.; Secker, David A.; Rosocha, Louis A.; Kurucz, Charles N.; Waite, Thomas D.

    2002-01-01

    The irradiation of aqueous solutions of TCE and PCE using a high-energy electron-beam results in the rapid decomposition of both chemicals. It is known that both TCE and PCE react with the aqueous electron and the hydroxyl radical with bimolecular rate constants greater than 10 9 M -1 s -1 for each reaction. The fact that high-energy electrons produce significant concentrations of both e aq - and ·OH radicals in water makes it an effective process for the removal of TCE and PCE from aqueous solution. We have employed steady state and computer-based chemical kinetic models to simulate and better understand the chemistry and kinetics of e-beam irradiation when applied to natural water systems. Model results were benchmarked to experimental data, allowing for the optimization of the reaction of DOC with the ·OH radical. Values for the associated second-order reaction rate constant were found to be 2.5x10 8 and 4.0x10 8 M -1 s -1 , consistent with reported values for k OH,DOC . The models were also used to investigate the possibility of incomplete irradiation during treatment and the presence of proposed chemical reactions of by-products. The reactions involve radicals and radical-adduct species formed by the reaction of TCE and PCE with the hydroxyl radical

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

    International Nuclear Information System (INIS)

    Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

    2015-01-01

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

  2. Equilibrium, Kinetic and Thermodynamic Study of Removal of Eosin Yellow from Aqueous Solution Using Teak Leaf Litter Powder.

    Science.gov (United States)

    Oyelude, Emmanuel O; Awudza, Johannes A M; Twumasi, Sylvester K

    2017-09-22

    Low-cost teak leaf litter powder (TLLP) was prepared as possible substitute for activated carbon. The feasibility of using the adsorbent to remove eosin yellow (EY) dye from aqueous solution was investigated through equilibrium adsorption, kinetic and thermodynamic studies. The removal of dye from aqueous solution was feasible but influenced by temperature, pH, adsorbent dosage and contact time. Variation in the initial concentration of dye did not influence the equilibrium contact time. Optimum adsorption of dye occurred at low adsorbent dosages, alkaline pH and high temperatures. Langmuir isotherm model best fit the equilibrium adsorption data and the maximum monolayer capacity of the adsorbent was 31.64 mg g -1 at 303 K. The adsorption process was best described by pseudo-second order kinetic model at 303 K. Boundary layer diffusion played a key role in the adsorption process. The mechanism of uptake of EY by TLLP was controlled by both liquid film diffusion and intraparticle diffusion. The values of mean adsorption free energy, E (7.91 kJ mol -1 ), and standard enthalpy, ΔH° (+13.34 kJ mol -1 ), suggest physical adsorption. The adsorption process was endothermic and spontaneous. Teak leaf litter powder is a promising low-cost adsorbent for treating wastewaters containing eosin yellow.

  3. Raman database of amino acids solutions: A critical study of Extended Multiplicative Signal Correction

    KAUST Repository

    Candeloro, Patrizio

    2013-01-01

    The Raman spectra of biological materials always exhibit complex profiles, constituting several peaks and/or bands which arise due to the large variety of biomolecules. The extraction of quantitative information from these spectra is not a trivial task. While qualitative information can be retrieved from the changes in peaks frequencies or from the appearance/disappearance of some peaks, quantitative analysis requires an examination of peak intensities. Unfortunately in biological samples it is not easy to identify a reference peak for normalizing intensities, and this makes it very difficult to study the peak intensities. In the last decades a more refined mathematical tool, the extended multiplicative signal correction (EMSC), has been proposed for treating infrared spectra, which is also capable of providing quantitative information. From the mathematical and physical point of view, EMSC can also be applied to Raman spectra, as recently proposed. In this work the reliability of the EMSC procedure is tested by application to a well defined biological system: the 20 standard amino acids and their combination in peptides. The first step is the collection of a Raman database of these 20 amino acids, and subsequently EMSC processing is applied to retrieve quantitative information from amino acids mixtures and peptides. A critical review of the results is presented, showing that EMSC has to be carefully handled for complex biological systems. © 2013 The Royal Society of Chemistry.

  4. Integral solution of equiaxed solidification with an interface kinetics model for nuclear waste management

    International Nuclear Information System (INIS)

    Naterer, G.F.

    1996-01-01

    In this paper, a one-dimensional analysis of energy and species transport during binary dendritic solidification is presented and compared to experimental results. The paper's objective is a continuation of previous studies of solidification control for the waste management of nuclear materials in the underground disposal concept. In the present analysis, interface kinetics at the solid - liquid interface accounts for recalescent thermal behaviour during solidification. The theoretical results were compared to available experimental results and the agreement appears fair although some discrepancies have been attributed to uncertainties with thermophysical properties. (author)

  5. General kinetic solution for the Biermann battery with an associated pressure anisotropy generation

    Science.gov (United States)

    Schoeffler, K. M.; Silva, L. O.

    2018-01-01

    Fully kinetic analytic calculations of an initially Maxwellian distribution with arbitrary density and temperature gradients exhibit the development of temperature anisotropies and magnetic field growth associated with the Biermann battery. The calculation, performed by taking a small order expansion of the ratio of the Debye length to the gradient scale, predicts anisotropies and magnetic fields as a function of space given an arbitrary temperature and density profile. These predictions are shown to qualitatively match the values measured from particle-in-cell simulations, where the development of the Weibel instability occurs at the same location and with a wavenumber aligned with the predicted temperature anisotropy.

  6. Charge-transfer complexes between p-toluidine and iodine in solution: a kinetic study

    International Nuclear Information System (INIS)

    Beggiato, G.; Casalbore, G.; Marconi, G.; Baraldi, C.

    1985-01-01

    The kinetics of charge-transfer interaction between p-toluidine and iodine in methylene chloride was investigated in depth. The thermal process of formation of the 'inner' complex was found to proceed to an equilibrium. The photochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excited 'outer' complex and the amine ground state. In both cases the same ionic complex (Am 2 I + I - 3 , where Am stands for p-toluidine) was detected as the final product. (Author)

  7. Simulation of light generation in cholesteric liquid crystals using kinetic equations: Time-independent solution

    Energy Technology Data Exchange (ETDEWEB)

    Shtykov, N. M., E-mail: nshtykov@mail.ru; Palto, S. P.; Umanskii, B. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-08-15

    We report on the results of calculating the conditions for light generation in cholesteric liquid crystals doped with fluorescent dyes using kinetic equations. Specific features of spectral properties of the chiral cholesteric medium as a photonic structure and spatially distributed type of the feedback in the active medium are taken into account. The expression is derived for the threshold pump radiation intensity as a function of the dye concentration and sample thickness. The importance of taking into account the distributed loss level in the active medium for calculating the optimal parameters of the medium and for matching the calculated values with the results of experiments is demonstrated.

  8. Diffusion kinetics and spinodal decay of quasi-equilibrium solid solutions

    International Nuclear Information System (INIS)

    Zakharov, M.A.

    2000-01-01

    Phenomenological theory for rearrangement of solid solutions with the hierarchy of the component atomic mobilities is elaborated in the approximation of the local equilibrium. The hydrodynamic stage of the evolution of these solutions is studied as a sequence of quasi-equilibrium states characterized by implementation of some conditions of the total equilibrium. On the basis of separation of fast and slow constituents of diffusion and on the basis of the method of reduced description one derived equation for evolution of separations of fast components in quasi-equilibrium solid solutions at the arbitrary stages of rearrangement in terms of the generalized lattice model taking account of the proper volumes of the components. The conditions of the stability of quasi-equilibrium solutions to the spinodal decomposition are determined and the equations of metastability boundaries of such systems are derived [ru

  9. Phynx: an open source software solution supporting data management and web-based patient-level data review for drug safety studies in the general practice research database and other health care databases.

    Science.gov (United States)

    Egbring, Marco; Kullak-Ublick, Gerd A; Russmann, Stefan

    2010-01-01

    To develop a software solution that supports management and clinical review of patient data from electronic medical records databases or claims databases for pharmacoepidemiological drug safety studies. We used open source software to build a data management system and an internet application with a Flex client on a Java application server with a MySQL database backend. The application is hosted on Amazon Elastic Compute Cloud. This solution named Phynx supports data management, Web-based display of electronic patient information, and interactive review of patient-level information in the individual clinical context. This system was applied to a dataset from the UK General Practice Research Database (GPRD). Our solution can be setup and customized with limited programming resources, and there is almost no extra cost for software. Access times are short, the displayed information is structured in chronological order and visually attractive, and selected information such as drug exposure can be blinded. External experts can review patient profiles and save evaluations and comments via a common Web browser. Phynx provides a flexible and economical solution for patient-level review of electronic medical information from databases considering the individual clinical context. It can therefore make an important contribution to an efficient validation of outcome assessment in drug safety database studies.

  10. Determination of H-atom reaction rate constants by the competition kinetic technique using riboflavin as a standard solute [Paper No. RD-7

    International Nuclear Information System (INIS)

    Kishore, Kamal; Moorthy, P.N.; Rao, K.N.

    1982-01-01

    Riboflavin has been used as a standard solute to evaluate H-atom rate constants of other solutes by steady state radiolytic competition kinetic method. The bleaching of absorbance of riboflavin at 445 nm as a result of its reaction with H-atoms is made use of in estimating its decomposition. The merits and demerits of this method are discussed. (author)

  11. Efficient removal of cobalt from aqueous solution by zinc oxide nanoparticles. Kinetic and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Khezami, L.; Modwi, A. [Al Imam Mohammad Ibn Saud Islamic Univ. (IMSIU), Riyadh (Saudi Arabia). Dept. of Chemistry; Taha, Kamal K. [Al Imam Mohammad Ibn Saud Islamic Univ. (IMSIU), Riyadh (Saudi Arabia). Dept. of Chemistry; Univ. of Bahri, Khartoum (Sudan). College of Applied and Industrial Sciences

    2017-08-01

    This article deals with the removal of cobalt ions using zinc oxide nanopowder. The nanomaterial was prepared via the sol-gel method under supercritical drying. The nanomaterial was characterised via XRD, SEM, EDX, FTIR, and BET surface area techniques. The kinetics, equilibrium, and thermodynamic studies of the metal ions adsorption on the nanomaterial were conducted in batch mode experiments by varying some parameters such as pH, contact time, initial ion concentrations, nanoparticles dose, and temperature. The data revealed significant dependence of the adsorption process on concentration, and the temperature was found to enhance the adsorption rate indicating an endothermic nature of the adsorption. The adsorption complied well with the pseudo-second-order kinetics model. The adsorption process was found to match the Langmuir adsorption isotherm. The ZnO nanoparticles could successfully remove up to 125 mg.g{sup -1} of Co(II) ions at elevated temperature. The metal ions adsorption could be described as an endothermic, spontaneous physisorption process. A mechanism for the metal ions adsorption was proposed.

  12. A highly accurate algorithm for the solution of the point kinetics equations

    International Nuclear Information System (INIS)

    Ganapol, B.D.

    2013-01-01

    Highlights: • Point kinetics equations for nuclear reactor transient analysis are numerically solved to extreme accuracy. • Results for classic benchmarks found in the literature are given to 9-digit accuracy. • Recent results of claimed accuracy are shown to be less accurate than claimed. • Arguably brings a chapter of numerical evaluation of the PKEs to a close. - Abstract: Attempts to resolve the point kinetics equations (PKEs) describing nuclear reactor transients have been the subject of numerous articles and texts over the past 50 years. Some very innovative methods, such as the RTS (Reactor Transient Simulation) and CAC (Continuous Analytical Continuation) methods of G.R. Keepin and J. Vigil respectively, have been shown to be exceptionally useful. Recently however, several authors have developed methods they consider accurate without a clear basis for their assertion. In response, this presentation will establish a definitive set of benchmarks to enable those developing PKE methods to truthfully assess the degree of accuracy of their methods. Then, with these benchmarks, two recently published methods, found in this journal will be shown to be less accurate than claimed and a legacy method from 1984 will be confirmed

  13. Ozone direct oxidation kinetics of Cationic Red X-GRL in aqueous solution

    International Nuclear Information System (INIS)

    Zhao Weirong; Wu Zhongbiao; Wang Dahui

    2006-01-01

    This study characterizes the ozonation of the azo dye Cationic Red X-GRL in the presence of TBA (tert-butyl alcohol), a scavenger of hydroxyl radical, in a bubble column reactor. Effects of oxygen flow rate, temperature, initial dye concentration, and pH were investigated through a series of batch tests. Generally, enhancing oxygen flow rate enhanced the removal of dye. However, there was a minimum removal of dye at temperature 298 K. Increasing or decreasing temperature enhanced the degradation of dye. Increasing the initial dye concentration decreased the removal of dye while the ozonation rate increased. The rate constants and the kinetic regime of the reaction between ozone and dye were obtained by fitting the experimental data to a kinetics model based on a second order overall reaction, first order with respect to both ozone and dye. The Hatta numbers of the reactions were between 0.039 and 0.083, which indicated that the reaction occurred in the liquid bulk. The direct oxidation rate constant k D was correlated with temperature by a modified Arrhenius Equation with an activation energy E a of 15.538 kJ mol -1

  14. Kinetics of some rare earth ions substitution for neodymium(3) ion in aqueous solutions of ethylenediaminetetraacetate

    Energy Technology Data Exchange (ETDEWEB)

    Nikitenko, S.I.; Martynenko, L.I.; Afonin, E.G.; Pechurova, N.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1984-04-01

    Kinetics of electrophilic interaction in the systems NdA/sup -/-Ln/sup 3 +/ (where Ln/sup 3 +/ - Tm/sup 3 +/, Er/sup 3 +/, Gd/sup 3 +/, Eu/sup 3 +/, Pr/sup 3 +/) has been studied. It is found that the following kinetic equation: W=W/sub 1/+W/sub 2/ = (Ksub(1)csub(Hsup(+))+Ksub(2)csub(Lnsup(3+) 3+))csub(NdAsup(-)), where csub(Lnsup(3+)) and csub(NdA/sup -/) - initial concentrations of Ln/sup 3 +/ and NdA/sup -/, corresponds to the exchange rate. It is shown that W/sub 1/ - component of exchange rate according to the mechanism of acid dissociation, and W/sub 2/ - according to associative mechanism. The values of K/sub 1/ and K/sub 2/ at t=20 deg C, ..mu..=0.1 are calculated. The dependence of K/sub 2/ on the nature of the ligand included is studied. It is shown that K/sub 2/ depends linearly on stability constant of Ln/sup 3 +/ iminodiacetate.

  15. Efficient removal of cobalt from aqueous solution by zinc oxide nanoparticles. Kinetic and thermodynamic studies

    International Nuclear Information System (INIS)

    Khezami, L.; Modwi, A.; Taha, Kamal K.; Univ. of Bahri, Khartoum

    2017-01-01

    This article deals with the removal of cobalt ions using zinc oxide nanopowder. The nanomaterial was prepared via the sol-gel method under supercritical drying. The nanomaterial was characterised via XRD, SEM, EDX, FTIR, and BET surface area techniques. The kinetics, equilibrium, and thermodynamic studies of the metal ions adsorption on the nanomaterial were conducted in batch mode experiments by varying some parameters such as pH, contact time, initial ion concentrations, nanoparticles dose, and temperature. The data revealed significant dependence of the adsorption process on concentration, and the temperature was found to enhance the adsorption rate indicating an endothermic nature of the adsorption. The adsorption complied well with the pseudo-second-order kinetics model. The adsorption process was found to match the Langmuir adsorption isotherm. The ZnO nanoparticles could successfully remove up to 125 mg.g -1 of Co(II) ions at elevated temperature. The metal ions adsorption could be described as an endothermic, spontaneous physisorption process. A mechanism for the metal ions adsorption was proposed.

  16. Kinetics of the electropolymerization of aminoanthraquinone from aqueous solutions and analytical applications of the polymer film

    Directory of Open Access Journals (Sweden)

    Shymaa S. Medany

    2012-07-01

    Full Text Available Poly 1-amino-9, 10-anthraquinone (PAAQ films were prepared by the electropolymerization of 1-amino-9,10-anthraquinone (AAQ on platinum substrate from aqueous media, where 5.0 × 10−3 mol L−1 AAQ and 6.0 mol L−1 H2SO4 were used. The kinetics of the electropolymerization process was investigated by determining the change of the charge consumed during the polymerization process with time at different concentrations of both monomer and electrolyte. The results have shown that the process follows first order kinetics with respect to the monomer concentration. The order of the reaction with respect to the aqueous solvent i.e. H2SO4 was found to be negative. The polymer films were successfully used as sensors for the electroanalytical determination of many hazardous compounds, e.g. phenols, and biologically important materials like dopamine. The electroanalytical determination was based on the measurements of the oxidation current peak of the material in the cyclic voltammetric measurements. The cyclic voltammograms were recorded at a scan rate of 100 mV s−1 and different analyte concentrations. A calibration curve was constructed for each analyte, from which the determination of low concentrations of catechol and hydroquinone (HQ as examples of hazardous compounds present in waste water and also for ascorbic acid and dopamine as examples of valuable biological materials can be achieved.

  17. Analytical representation of the solution of the space kinetic diffusion equation in a one-dimensional and homogeneous domain

    Energy Technology Data Exchange (ETDEWEB)

    Tumelero, Fernanda; Bodmann, Bardo E. J.; Vilhena, Marco T. [Universidade Federal do Rio Grande do Sul (PROMEC/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos Graduacao em Engenharia Mecanica; Lapa, Celso M.F., E-mail: fernanda.tumelero@yahoo.com.br, E-mail: bardo.bodmann@ufrgs.br, E-mail: mtmbvilhena@gmail.com, E-mail: lapa@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2017-07-01

    In this work we solve the space kinetic diffusion equation in a one-dimensional geometry considering a homogeneous domain, for two energy groups and six groups of delayed neutron precursors. The proposed methodology makes use of a Taylor expansion in the space variable of the scalar neutron flux (fast and thermal) and the concentration of delayed neutron precursors, allocating the time dependence to the coefficients. Upon truncating the Taylor series at quadratic order, one obtains a set of recursive systems of ordinary differential equations, where a modified decomposition method is applied. The coefficient matrix is split into two, one constant diagonal matrix and the second one with the remaining time dependent and off-diagonal terms. Moreover, the equation system is reorganized such that the terms containing the latter matrix are treated as source terms. Note, that the homogeneous equation system has a well known solution, since the matrix is diagonal and constant. This solution plays the role of the recursion initialization of the decomposition method. The recursion scheme is set up in a fashion where the solutions of the previous recursion steps determine the source terms of the subsequent steps. A second feature of the method is the choice of the initial and boundary conditions, which are satisfied by the recursion initialization, while from the rst recursion step onward the initial and boundary conditions are homogeneous. The recursion depth is then governed by a prescribed accuracy for the solution. (author)

  18. Green Synthesis of Zinc Oxide Nanoparticles for Enhanced Adsorption of Lead Ions from Aqueous Solutions: Equilibrium, Kinetic and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    Susan Azizi

    2017-06-01

    Full Text Available In the present study, ZnO nanoparticles (NPs were synthesized in zerumbone solution by a green approach and appraised for their ability to absorb Pb(II ions from aqueous solution. The formation of as-synthesized NPs was established by X-ray diffraction (XRD, Transmission Electron Microscopy (TEM, and UV–visible studies. The XRD and TEM analyses revealed high purity and wurtzite hexagonal structure of ZnO NPs with a mean size of 10.01 ± 2.6 nm. Batch experiments were performed to investigate the impact of process parameters viz. Pb(II concentration, pH of solution, adsorbent mass, solution temperature, and contact time variations on the removal efficiency of Pb(II. The adsorption isotherm data provided that the adsorption process was mainly monolayer on ZnO NPs. The adsorption process follows pseudo-second-order reaction kinetic. The maximum removal efficiencies were 93% at pH 5. Thermodynamic parameters such as enthalpy change (ΔH0, free energy change (ΔG0, and entropy change (ΔS0 were calculated; the adsorption process was spontaneous and endothermic. The good efficiency of the as-synthesized NPs makes them attractive for applications in water treatment, for removal of heavy metals from aqueous system.

  19. Kinetics and thermodynamics of β-carotene and chlorophyll adsorption onto acid-activated bentonite from Xinjiang in xylene solution

    International Nuclear Information System (INIS)

    Wu Zhansheng; Li Chun

    2009-01-01

    The kinetics and thermodynamics of β-carotene and chlorophyll adsorption from xylene solution onto acid-activated bentonite (AAB) within the temperature range 65-95 deg. C were investigated. Adsorption of β-carotene was described well with the Langmuir isotherm, whereas chlorophyll adsorption was determined well with the Freundlich isotherm, and the experimental data on chlorophyll adsorption were also fitted by the Langmuir isotherm to a certain extent, as reflected by correlation coefficients (R 2 ) over 0.9865. In addition, the adsorption of β-carotene and chlorophyll onto AAB are favorable. The pseudo-second-order model was found to explain the kinetics of adsorption of both pigments more effectively. Increase of temperature enhanced the adsorption rate and equilibrium adsorption capacity of β-carotene and chlorophyll on AAB. The activation energy for the sorption of β-carotene and chlorophyll on AAB was 19.808 kJ/mol and 16.475 kJ/mol, respectively. The thermodynamic parameters ΔH θ , ΔS θ and ΔG θ , computed from K F of the adsorption isotherm constant, were 21.766 kJ/mol, 92.244 J/K mol and -9.554 kJ/mol respectively for the adsorption of β-carotene on AAB at 65 deg. C, and for adsorption of chlorophyll on AAB at 65 deg. C were 31.051 kJ/mol, 93.549 J/K mol and -0.729 kJ/mol, respectively. The adsorption of β-carotene and chlorophyll in xylene solution on AAB was a spontaneous and endothermic process with increasing in the randomness at the solid-solution interface.

  20. Elastic-Plastic J-Integral Solutions or Surface Cracks in Tension Using an Interpolation Methodology. Appendix C -- Finite Element Models Solution Database File, Appendix D -- Benchmark Finite Element Models Solution Database File

    Science.gov (United States)

    Allen, Phillip A.; Wells, Douglas N.

    2013-01-01

    No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.

  1. THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS.

    Science.gov (United States)

    Brdicka, R

    1936-07-20

    1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions.

  2. Effective Microporosity for Enhanced Adsorption Capacity of Cr (VI) from Dilute Aqueous Solution: Isotherm and Kinetics

    OpenAIRE

    Lloyd Mukosha; Maurice S. Onyango; Aoyi Ochieng; John Siame

    2017-01-01

    The adsorbent pore structure significant to enhanced adsorption capacity of Cr (VI) from dilute aqueous solution is evaluated. As reference, low-cost micro-mesoporous activated carbon (AC) of high basicity, mesoporosity centred about 2.4 nm, and effective microporosity centred about 0.9 nm was tested for removal of Cr (VI) from dilute aqueous solution in batch mode. At pH 2 the low-cost AC exhibited highly improved Langmuir Cr (VI) capacity of 115 mg/g which was competitive to high performanc...

  3. Kinetics of ethylenediaminetetraacetate exchange of americium (3) with copper (2) in aqueous solution

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.

    1985-01-01

    By the method of spectrophotometry exchange kinetics in the AmA - -Cu 2+ , where A 4- -ethylenediaminetetraacetate, is studied. The values of exchange rate constants and thermodynamic activation parameters have been found. It is shown that exchange of central ions is rialized according to the dissociative mechanism with formation of intermediate protonated complexes and according to the associative mechanism with formation of binuclear intermediates. The exchange mechanisms identity for AmA - and LnA - , where Ln 3+ -RE cations of cerium subgroup is proved. It is assumed that values of activation entropy in exchange processes are determined by the radius of the leaving cation and of activation enthalpy - by the peculiarities of the electronic structure

  4. Kinetics of imidazolium-based ionic liquids degradation in aqueous solution by Fenton oxidation.

    Science.gov (United States)

    Domínguez, Carmen M; Munoz, Macarena; Quintanilla, Asunción; de Pedro, Zahara M; Casas, Jose A

    2017-10-15

    In the last few years, several works dealing with Fenton oxidation of ionic liquids (ILs) have proved the capability of this technology for their degradation, achieving complete ILs removal and non-toxic effluents. Nevertheless, very little is known about the kinetics of this process, crucial for its potential application. In this work, the effect of several operating conditions, including reaction temperature (50-90 °C), catalyst load (10-50 mg L -1 Fe 3+ ), initial IL concentration (100-2000 mg L -1 ), and hydrogen peroxide dose (10-200% of the stoichiometric amount for the complete IL mineralization) on 1-butyl-3-methylimidazolium chloride ([C 4 mim]Cl) oxidation has been investigated. Under the optimum operating conditions (T = 90 °C; [Fe 3+ ] 0  = 50 mg L -1 ; [H 2 O 2 ] 0  = 100% of the stoichiometric amount), the complete removal of [C 4 mim]Cl (1000 mg L -1 ) was achieved at 1.5-min reaction time. From the experimental results, a potential kinetic model capable to describe the removal of imidazolium-based ILs by Fenton oxidation has been developed. By fitting the proposed model to the experimental data, the orders of the reaction with respect to IL initial concentration, Fe 3+ amount and H 2 O 2 dose were found to be close to 1, with an apparent activation energy of 43.3 kJ mol -1 . The model resulted in a reasonable fit within the wide range of operating conditions tested in this work.

  5. Kinetics and equilibrium modeling of uranium(VI) sorption by bituminous shale from aqueous solution

    International Nuclear Information System (INIS)

    Ortaboy, Sinem; Atun, Gülten

    2014-01-01

    Highlights: • Oil shales are sedimentary rocks containing a polymeric matter in a mineral matrix. • Sorption potential of bituminous shale (BS) for uranium recovery was investigated. • U(VI) sorption increased with decreasing pH and increasing temperature. • Kinetic data were analyzed based on single and two resistance diffusion models. • The results fit well to the McKay equation assuming film and intraparticle diffusion. - Abstract: Sorption of U(VI) onto a bituminous shale (BS) from a nuclear power plant project site in Black Sea region was investigated for potential risk assessment when it releases into the environment with contaminated ground and surface water. The sorption characteristics of the BS for U(VI) recovery were evaluated as a function of contact time, adsorbent dosage, initial concentration, pH and temperature. Kinetic results fit better with pseudo-second-order model rather than pseudo-first-order. The possibility of diffusion process was analyzed based on Weber–Morris intra-particle diffusion model. The McKay equation assuming film- and intraparticle diffusion better predicted the data than the Vermeulen approximation presuming surface diffusion. Equilibrium sorption data were modeled according to the Langmuir, Dubinin–Radushkevich (D–R) and Freundlich isotherm equations. Sorption capacity increased from 0.10 to 0.15 mmol g −1 in 298–318 K temperature range. FT-IR analysis and pH dependent sorption studies conducted in hydroxide and carbonate media revealed that U(VI) species were sorbed in uranyl and its hydroxo forms on the BS. Desorption studies showed that U(VI) leaching with Black Sea water was negligible from the loaded BS. The activation parameters (E a , ΔH ∗ and ΔG ∗ ) estimated from diffusion coefficients indicated the presence of an energy barrier in the sorption system. However, thermodynamic functions derived from sorption equilibrium constants showed that overall sorption process was spontaneous in nature

  6. Sustainable Energy Solutions Task 3.0:Life-Cycle Database for Wind Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Twomey, Janet M. [Wichita State Univ., KS (United States)

    2010-03-01

    The benefits of wind energy had previously been captured in the literature at an overview level with relatively low transparency or ability to understand the basis for that information. This has limited improvement and decision-making to larger questions such as wind versus other electrical sources (such as coal-fired plants). This research project has established a substantially different approach which is to add modular, high granularity life cycle inventory (lci) information that can be used by a wide range of decision-makers, seeking environmental improvement. Results from this project have expanded the understanding and evaluation of the underlying factors that can improve both manufacturing processes and specifically wind generators. The use of life cycle inventory techniques has provided a uniform framework to understand and compare the full range of environmental improvement in manufacturing, hence the concept of green manufacturing. In this project, the focus is on 1. the manufacturing steps that transform materials and chemicals into functioning products 2. the supply chain and end-of-life influences of materials and chemicals used in industry Results have been applied to wind generators, but also impact the larger U.S. product manufacturing base. For chemicals and materials, this project has provided a standard format for each lci that contains an overview and description, a process flow diagram, detailed mass balances, detailed energy of unit processes, and an executive summary. This is suitable for integration into other life cycle databases (such as that at NREL), so that broad use can be achieved. The use of representative processes allows unrestricted use of project results. With the framework refined in this project, information gathering was initiated for chemicals and materials in wind generation. Since manufacturing is one of the most significant parts of the environmental domain for wind generation improvement, this project research has

  7. The analytical benchmark solution of spatial diffusion kinetics in source driven systems for homogeneous media

    International Nuclear Information System (INIS)

    Oliveira, F.L. de; Maiorino, J.R.; Santos, R.S.

    2007-01-01

    This paper describes a closed form solution obtained by the expansion method for the general time dependent diffusion model with delayed emission for source transients in homogeneous media. In particular, starting from simple models, and increasing the complexity, numerical results were obtained for different types of source transients. Thus, first an analytical solution of the one group without precursors was solved, followed by considering one precursors family. The general case of G-groups with R families of precursor although having a closed form solution, cannot be solved analytically, since there are no explicit formulae for the eigenvalues, and numerical methods must be used to solve such problem. To illustrate the general solution, the multi-group (three groups) time-dependent without precursors was also solved and the results inter compared with results obtained by the previous one group models for a given fast homogeneous media, and different types of source transients. The results are being compared with the obtained by numerical methods. (author)

  8. Study of the mechanism and kinetics of the reduction of uranyl ions in phosphoric acid solutions

    International Nuclear Information System (INIS)

    El Kacemi, K.; Tyburce, B.; Belcadi, S.

    1982-01-01

    The electrochemical reduction of uranyl ions in 0.1 to 9 M phosphoric acid has been investigated by polarography, cyclic voltammetry, chronopotentiometry and potentiostatic coulometry. In concentrated phosphoric acid solutions (H 3 PO 4 3 PO 4 concentrations. So, when the concentration of U(VI) increases and/or that of H 3 PO 4 reduces, the system becomes reversible. (author)

  9. Kinetics of phenol degradation in water solutions under gamma-irradiation

    International Nuclear Information System (INIS)

    Guliyeva, U.A.; Gurbanov, M.A.; Abdullayev, E.T.

    2014-01-01

    Full text : In this work the chemical oxygen demand and change of phenol concentration at the radiolysis of aqueous solutions of phenol was studied. Irradiation conducted under gamma-irradiation of 60Co at static conditions and at room temperature. The main component is water, therefore the radiolysis process of water plays an important role in radiolytic degradation of phenol

  10. Bifurcating Solutions to the Monodomain Model Equipped with FitzHugh-Nagumo Kinetics

    Directory of Open Access Journals (Sweden)

    Robert Artebrant

    2009-01-01

    cells surrounded by collections of normal cells. Thus, the cell model features a discontinuous coefficient. Analytical techniques are applied to approximate the time-periodic solution that arises at the Hopf bifurcation point. Accurate numerical experiments are employed to complement our findings.

  11. A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets.

    Science.gov (United States)

    Knopf, Daniel A; Alpert, Peter A

    2013-01-01

    Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, a(w), which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, J(het), to be uniquely expressed by T and a(w), a result we term the a(w) based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, J(het), frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(J(het)) values for the various IN types derived exclusively by Tand a(w), provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Lastly, we demonstrate that ABIFM can

  12. Comparisons of kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide adsorption in aqueous solution with graphene oxide, zeolite and activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Shenteng; Lu, Chungsying, E-mail: clu@nchu.edu.tw; Lin, Kun-Yi Andrew

    2015-01-30

    Graphical abstract: A comparison of TMAH adsorption capacity with GO, NaY and GAC is conducted and the result reveals that the magnitude of qe follows the order of GO > NaY > GAC. The adsorption capacity of GO is significantly higher than those of zeolite and activated carbon in this and reported studies, showing its encouraging potential. GO also exhibits good reversibility of TMAH adsorption through 10 cycles of adsorption and desorption process. This reflects that GO is a promising and efficient adsorbent for TMAH removal in wastewater treatment. - Highlights: • Adsorption kinetics and isotherms of TMAH to GO, NaY and GAC are compared. • Thermodynamics of TMAH adsorption to GO, NaY and GAC is determined. • GO exhibits the highest TMAH adsorption capacity, followed by NaY and GAC. • Recyclabilities of NaY and GO remain above 95% but that of GAC dropped to 70%. - Abstract: Graphene oxide (GO), sodium Y-type zeolite (NaY) and granular activated carbon (GAC) are selected as adsorbents to study their kinetics, thermodynamics and regeneration of tetramethylammonium hydroxide (TMAH) adsorption from water. The adsorption kinetics follows the pseudo-second-order rate law while the adsorption thermodynamics shows an exothermic reaction with GO and GAC but displays an endothermic reaction with NaY. The adsorbed TMAH can be readily desorbed from the surface of GO and NaY by 0.05 M NaCl solution. A comparative study on the cyclic TMAH adsorption with GO, NaY and GAC is also conducted and the results reveal that GO exhibits the greatest TMAH adsorption capacity as well as superior reversibility of TMAH adsorption over 10 cycles of adsorption and desorption process. These features indicate that GO is a promising and efficient adsorbent for TMAH removal in wastewater treatment.

  13. Chloride Anions Regulate Kinetics but Not Voltage-Sensor Qmax of the Solute Carrier SLC26a5.

    Science.gov (United States)

    Santos-Sacchi, Joseph; Song, Lei

    2016-06-07

    In general, SLC26 solute carriers serve to transport a variety of anions across biological membranes. However, prestin (SLC26a5) has evolved, now serving as a motor protein in outer hair cells (OHCs) of the mammalian inner ear and is required for cochlear amplification, a mechanical feedback mechanism to boost auditory performance. The mechanical activity of the OHC imparted by prestin is driven by voltage and controlled by anions, chiefly intracellular chloride. Current opinion is that chloride anions control the Boltzmann characteristics of the voltage sensor responsible for prestin activity, including Qmax, the total sensor charge moved within the membrane, and Vh, a measure of prestin's operating voltage range. Here, we show that standard narrow-band, high-frequency admittance measures of nonlinear capacitance (NLC), an alternate representation of the sensor's charge-voltage (Q-V) relationship, is inadequate for assessment of Qmax, an estimate of the sum of unitary charges contributed by all voltage sensors within the membrane. Prestin's slow transition rates and chloride-binding kinetics adversely influence these estimates, contributing to the prevalent concept that intracellular chloride level controls the quantity of sensor charge moved. By monitoring charge movement across frequency, using measures of multifrequency admittance, expanded displacement current integration, and OHC electromotility, we find that chloride influences prestin kinetics, thereby controlling charge magnitude at any particular frequency of interrogation. Importantly, however, this chloride dependence vanishes as frequency decreases, with Qmax asymptoting at a level irrespective of the chloride level. These data indicate that prestin activity is significantly low-pass in the frequency domain, with important implications for cochlear amplification. We also note that the occurrence of voltage-dependent charge movements in other SLC26 family members may be hidden by inadequate

  14. CAMPHORQUINONE AS A PHOTOINITIATOR IN THE POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE IN AQUEOUS SOLUTION: A KINETIC STUDY

    Directory of Open Access Journals (Sweden)

    Iqbal Ahmad

    2017-06-01

    Full Text Available The photoinitiated polymerization of 2-hydroxyethyl methacrylate (HEMA (1-3 M using camphorquinone (CQ \\ triethanolamine (TEOHA system has been studied in the pH range 6.0-9.0. The kinetics of the reaction has been evaluated during the initial stages causing about 5% HEMA conversion to avoid the effects of any variation in the volume of the solution. The change in the concentration of HEMA during polymerization has been determined by a UV spectrometric method at 208 nm with a precision of 3%. The apparent first-order rate constants (kobs for the polymerization of HEMA by CQ in the presence of 0.01 M TEOHA, carried out up to 100 s, range from 3.35-7.78 (1 M, 2.72-6.78 (2 M and 2.33`5.89x104 s-1(3 M. The second-order rate constants for the interaction of TEOHA radicals with HEMA (1-3 M range from 2.33-7.78x10-2 M 1 s-lat pH 6.0-9.0 indicating an increase in the reactivity of TEOHA radicals with an increase in the pH of the solution. There is a linear relation between kobs (1-3 M HEMA and inverse of solution viscosity suggesting the quenching of CQ excited state with an increase in the viscosity of the medium.

  15. Equilibrium, kinetic and thermodynamic studies of adsorption of Pb(II) from aqueous solution onto Turkish kaolinite clay

    International Nuclear Information System (INIS)

    Sari, Ahmet; Tuzen, Mustafa; Citak, Demirhan; Soylak, Mustafa

    2007-01-01

    The adsorption of Pb(II) onto Turkish (Bandirma region) kaolinite clay was examined in aqueous solution with respect to the pH, adsorbent dosage, contact time, and temperature. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms and both models fitted well. The monolayer adsorption capacity was found as 31.75 mg/g at pH 5 and 20 deg. C. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (13.78 kJ/mol) indicated that the adsorption of Pb(II) onto kaolinite clay may be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, free energy (ΔG o ), enthalpy (ΔH o ) and entropy (ΔS o ) of adsorption were also calculated. These parameters showed that the adsorption of Pb(II) onto kaolinite clay was feasible, spontaneous and exothermic process in nature. Furthermore, the Lagergren-first-order, pseudo-second-order and the intraparticle diffusion models were used to describe the kinetic data. The experimental data fitted well the pseudo-second-order kinetics

  16. Ion Exchange Kinetics of some Heavy Metals from Aqueous Solutions onto Poly(Acrylic Acid-Acrylo nitrle) Potassium Titanate

    International Nuclear Information System (INIS)

    El-Shorbagy, M.M.; El-Sadek, A.A.

    2012-01-01

    Composite inorganic-organic absorbers represent a group of inorganic ion exchangers modified using binding organic materials for preparation of larger size particles heaving higher granular strength. Such modification of originally powdered or microcrystalline inorganic ion exchangers makes their application in peaked beds possible-modified polyacrylonitrile (PAN) has been used as a universal binding polymer for a number of inorganic ion exchangers. The kinetic of ion exchange and sorption capacity of such composite absorbers is not influenced by the binding polymer mentioned above. These composites have been tested for separation and concentration of various contaminants from aqueous solutions. Their high selectivity and sorption efficiency are advantageous for treatment of various industrial waste waters. Removal of natural or artificial and the heavy metals, Pb, Cd and Zn ions. the influence of initial metal ion concentration and ph on metal ion removal has been studied. The process was found to follow a first order rate kinetics. The intra-particle diffusion of ions through pores in the adsorbent was to be the main rate limiting step. The selectivity order towards the ions was Pb(II) > Cd(II) > Zn(II)

  17. Kinetics, isothermal and thermodynamics studies of electrocoagulation removal of basic dye rhodamine B from aqueous solution using steel electrodes

    Science.gov (United States)

    Adeogun, Abideen Idowu; Balakrishnan, Ramesh Babu

    2017-07-01

    Electrocoagulation was used for the removal of basic dye rhodamine B from aqueous solution, and the process was carried out in a batch electrochemical cell with steel electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process, were investigated. Equilibrium was attained after 10 min at 30 °C. Pseudo-first-order, pseudo-second-order, Elovich and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analysed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich and Sips isotherms and it was found that the data fitted well with Sips isotherm model. The study showed that the process depends on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (Δ G°, Δ H° and Δ S°) indicated that the process is spontaneous and endothermic in nature.

  18. Kinetics and mechanism of photoaccelerated isotope exchange between U(VI) and U(IV) in oxalate solutions

    International Nuclear Information System (INIS)

    Shaban, I.S.; Owreit, M.F.; Nikitenko, S.I.

    1992-01-01

    A kinetic study of thermal and photoaccelerated U(IV)-U(VI) isotope exchange has been carried out in oxalate solutions at 11-40 deg C. The rate and quantum yield were determined as a function of U(IV), U(VI) and oxalate concentration, wavelength of incident light, temperature and absorbed dose of γ-radiation. The kinetic equations for thermal and photoaccelerated exchange have been obtained. It was assumed that the mechanism of exchange involves formation of U(V) as an intermediate, followed by slow exchange between U(V) and U(IV). The isokinetic dependence confirms the identity of limiting stages for thermal and photostimulated exchange. The upper component of photoexcited T 1 level of uranyl is supposed to be the most reactive in the process of U(V) generation. It was observed that the small doses of γ-radiation evoke the acceleration of isotope exchange, however, at D>100 krad the rate of exchange is reduced to the level of thermal exchange. (author) 8 refs.; 4 figs.; 2 tabs

  19. Removal of Cr(VI Ions from Aqueous Solutions Using Nickel Ferrite Nanoparticles: Kinetic and Equilibrium Study

    Directory of Open Access Journals (Sweden)

    Raziyeh Zandi Pak

    2017-01-01

    Full Text Available Background & Aims of the Study: Heavy metals are the most important and main pollutants because of their accumulation and high toxicity even at very low dose and cause serious hazards to ecological system as well as human health. Thus, their removal has been challenged from drinking water and industrial waters with different technologies. The purpose of this work is to investigate the removal of Cr(VI from aqueous solutions. Materials & Methods: NiFe2O4 nanoparticles was prepared by the co-precipitation method and then applied for adsorption of Cr(VI ions from water. Characterization of nanoparticles was carried out via TEM, EDX, XRD and BET analysis. Various physico-chemical parameters like the effect of contact time, pH and adsorbent dose were studied, using batch process to optimize conditions for maximum adsorption. Results: The results demonstrated that the size of the NiFe2O4 nanoparticles was about 12 nm and had selectivity for Cr(VI adsorption. Also, adsorption process was found to be fast with equilibrium time of 55 min. Optimum pH was found to be 3. Maximum adsorption capacity (qm as calculated from Langmuir isotherm was found to be 294.1 mg g-1. Analysis of adsorption kinetics indicated better applicability of pseudo-second-order kinetic model. Conclusions: The results of this study represented that the synthesized NiFe2O4 nanoparticles could be useful for the simultaneous removal of anionic ions from wastewaters.

  20. Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers

    International Nuclear Information System (INIS)

    Mittal, Alok; Kurup, Lisha; Mittal, Jyoti

    2007-01-01

    Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (ΔG o ), change in enthalpy (ΔH o ) and change in entropy (ΔS o ) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures

  1. Kinetic Studies For the Removal of UO22+ and Pb2+ Ions From Aqueous Solution Using Zirconia Composite Material

    International Nuclear Information System (INIS)

    Sharaf El-Deen, G.E.

    2008-01-01

    Zirconia composite material was chemically synthesized previously and prepared by applying the sol-gel polymeric route using MgO as a stabilizer. The prepared composite material was characterized using various techniques: x-ray fluorescence (XRF), scanning electron microscope (SEM), differential thermal analysis and thermogravimetric analysis (DTA-TG), x-ray diffraction (XRD) and surface area using the BET-method. The sorption removal of UO 2 2+ and Pb 2+ ions from aqueous waste solution by zirconia composite material using batch technique was investigated. The sorption was carried out as a function of ph, particle size, shaking time and temperature. In this work, a comparison of kinetic models applied to the sorption process of each ion was evaluated for the pseudo first-order, the pseudo second-order, intra particle diffusion and homogeneous particle diffusion kinetic models, respectively. The results showed that the homogeneous particle diffusion model (HPDM) best correlate the experimental rate data and the numerical values of the rate constants and particle diffusion coefficients were determined from the graphical representation of the proposed models. Activation energy (Ε a ) and thermodynamic parameters of free energy (δ G * ), enthalpy (δ H * ) and entropy (δ S * ) of activation were also computed from the linearized form of Arrhenius equation

  2. Investigation of Acorn fruit Ash Efficiency in Cadmium Removal from Aqueous Solutions: Adsorption Isotherm and Kinetic Studies

    Directory of Open Access Journals (Sweden)

    Salman Zarei

    2014-12-01

    Full Text Available Background: Heavy metals are known as significant pollutants because of toxicity and nonbiodegradable characteristics. Cadmium is one of the heavy metals that have carcinogen potential. So, this study carried out in order to investigate the acorn fruit ash efficiency in cadmium removal from aqueous solutions. Methods: This study was done in the batch laboratory conditions. In this study, the effect of different parameters including pH, contact time, adsorbent dose, and initial cadmium concentration were evaluated. The Langmuir, Freundlich and Temkin isotherm models were used for analysis of the equilibrium isotherm. Adsorption kinetics of cadmium by different models were also investigated. The measurement of residual cadmium in the samples was determined by atomic absorption spectrophotometry at 228.8 nm. The SPSS-16 software was used for analysis of data. Results: According to the results, the maximum adsorption capacity of cadmium was 9.29 mg/g at pH=7 and 8 g/L adsorbent dose. The removal efficiency was increased with increasing contact time and decreased with increasing of cadmium initial concentration. Investigation of achieving data showed that the adsorption process followed better by Freundlich isotherm and the pseudo-second order kinetic. Conclusions: According to the results of this study, it could be concluded that the acorn fruit ash had high ability in cadmium adsorption and could be used as a cheap adsorbent in the removal of cadmium.

  3. Sorption performance of activated nkaliki clay in removing chromium (vi) ion from aqueous solution: kinetics, isotherm, and thermodynamic studies

    International Nuclear Information System (INIS)

    Ajemba, R.O.; Ugonabo, V.I.; Okafor, V.N.

    2017-01-01

    Bentonite from Nkaliki was modified by acid activation using different concentrations of sulphuric acid. The physicochemical properties of the raw and modified samples were analyzed. The sorption performance of the modified and raw bentonite was studied in the removal of chromium (VI) ion from aqueous solution. Effect of key process parameters on the adsorption process was studied. Results of the physicochemical analyses showed that the acid activation altered the structural arrangements of the bentonite. The surface area and adsorption capacity increased from 37.6m/sup 2//g to 74m/sup 2//g and 45 to 98%, respectively, after activating with 6mol/l of H/sub 2/SO/sub 4/. The chromium (VI) ion adsorption increased with increase in process parameters studied. The kinetics analysis of the adsorption data follows the pseudo second-order kinetics, while equilibrium analysis conformed to the Langmuir isotherm. The thermodynamic parameters revealed that adsorption process is spontaneous and endothermic. This study shows that modified Nkaliki bentonite could be used for wastewater treatment. (author)

  4. Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Alok [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India)]. E-mail: aljymittal@yahoo.co.in; Kurup, Lisha [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India); Mittal, Jyoti [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India)

    2007-07-19

    Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy ({delta}G{sup o}), change in enthalpy ({delta}H{sup o}) and change in entropy ({delta}S{sup o}) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

  5. Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers.

    Science.gov (United States)

    Mittal, Alok; Kurup, Lisha; Mittal, Jyoti

    2007-07-19

    Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (DeltaG degrees), change in enthalpy (DeltaH degrees) and change in entropy (DeltaS degrees) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

  6. Kinetics of transuranium element oxidation-reduction reactions in solution; Cinetique des reactions d'oxydo-reduction des elements transuraniens en solution

    Energy Technology Data Exchange (ETDEWEB)

    Gourisse, D. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-09-01

    A review of the kinetics of U, Np, Pu, Am oxidation-reduction reactions is proposed. The relations between the different activation thermodynamic functions (compensatory effect, formal entropy of the activated complex, magnitude of reactions velocities) are considered. The effects of acidity, ionic strength deuterium and mixed solvents polarity on reactions rates are described. The effect of different anions on reactions rates are explained by variations of the reaction standard free energy and variations of the activation free energy (coulombic interactions) resulting from the complexation of dissolved species by these anions. (author) [French] Une revue systematique de la cinetique des reactions d'oxydo-reduction des elements U, Np, Pu, Am, en solution perchlorique est proposee. Des considerations relatives aux grandeurs thermodynamiques d'activation associees aux actes elementaires (effet de compensation, entropie standard des complexes actives, rapidite des reactions) sont developpees. L'influence de l'acidite, de la force ionique, de l'eau lourde et de la polarite des solvants mixtes sur la vitesse des reactions est decrite. Enfin l'influence des differents anions sur la vitesse des reactions est expliquee par les variations de l'enthalpie libre standard de la reaction et de l'enthalpie libre d'activation (travail des forces electrostatiques) resultant de la complexation des especes dissoutes dans la solution. (auteur)

  7. Kinetics of transuranium element oxidation-reduction reactions in solution; Cinetique des reactions d'oxydo-reduction des elements transuraniens en solution

    Energy Technology Data Exchange (ETDEWEB)

    Gourisse, D [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-09-01

    A review of the kinetics of U, Np, Pu, Am oxidation-reduction reactions is proposed. The relations between the different activation thermodynamic functions (compensatory effect, formal entropy of the activated complex, magnitude of reactions velocities) are considered. The effects of acidity, ionic strength deuterium and mixed solvents polarity on reactions rates are described. The effect of different anions on reactions rates are explained by variations of the reaction standard free energy and variations of the activation free energy (coulombic interactions) resulting from the complexation of dissolved species by these anions. (author) [French] Une revue systematique de la cinetique des reactions d'oxydo-reduction des elements U, Np, Pu, Am, en solution perchlorique est proposee. Des considerations relatives aux grandeurs thermodynamiques d'activation associees aux actes elementaires (effet de compensation, entropie standard des complexes actives, rapidite des reactions) sont developpees. L'influence de l'acidite, de la force ionique, de l'eau lourde et de la polarite des solvants mixtes sur la vitesse des reactions est decrite. Enfin l'influence des differents anions sur la vitesse des reactions est expliquee par les variations de l'enthalpie libre standard de la reaction et de l'enthalpie libre d'activation (travail des forces electrostatiques) resultant de la complexation des especes dissoutes dans la solution. (auteur)

  8. Solution of Point Reactor Neutron Kinetics Equations with Temperature Feedback by Singularly Perturbed Method

    Directory of Open Access Journals (Sweden)

    Wenzhen Chen

    2013-01-01

    Full Text Available The singularly perturbed method (SPM is proposed to obtain the analytical solution for the delayed supercritical process of nuclear reactor with temperature feedback and small step reactivity inserted. The relation between the reactivity and time is derived. Also, the neutron density (or power and the average density of delayed neutron precursors as the function of reactivity are presented. The variations of neutron density (or power and temperature with time are calculated and plotted and compared with those by accurate solution and other analytical methods. It is shown that the results by the SPM are valid and accurate in the large range and the SPM is simpler than those in the previous literature.

  9. Optimization and analysis of large chemical kinetic mechanisms using the solution mapping method - Combustion of methane

    Science.gov (United States)

    Frenklach, Michael; Wang, Hai; Rabinowitz, Martin J.

    1992-01-01

    A method of systematic optimization, solution mapping, as applied to a large-scale dynamic model is presented. The basis of the technique is parameterization of model responses in terms of model parameters by simple algebraic expressions. These expressions are obtained by computer experiments arranged in a factorial design. The developed parameterized responses are then used in a joint multiparameter multidata-set optimization. A brief review of the mathematical background of the technique is given. The concept of active parameters is discussed. The technique is applied to determine an optimum set of parameters for a methane combustion mechanism. Five independent responses - comprising ignition delay times, pre-ignition methyl radical concentration profiles, and laminar premixed flame velocities - were optimized with respect to thirteen reaction rate parameters. The numerical predictions of the optimized model are compared to those computed with several recent literature mechanisms. The utility of the solution mapping technique in situations where the optimum is not unique is also demonstrated.

  10. Numerical solution of kinetics equation for point defects accumulation in metals under irradiation

    International Nuclear Information System (INIS)

    Aldzhambekova, G.T.; Iskakov, B.M.

    1999-01-01

    In the report the mathematical model, describing processes of generation and accumulation of defects in solids under irradiation is considered. The equations of this model take into account the velocity of Frenkel pairs generation, the mutual recombination of vacancies and the interstitials, as well as velocity of defects absorption by discharge channeling of vacancies and interstitials. By Runge-Kutta method the numerical solution of the model was carried out

  11. Master equation for a kinetic model of a trading market and its analytic solution.

    Science.gov (United States)

    Chatterjee, Arnab; Chakrabarti, Bikas K; Stinchcombe, Robin B

    2005-08-01

    We analyze an ideal-gas-like model of a trading market with quenched random saving factors for its agents and show that the steady state income (m) distribution P(m) in the model has a power law tail with Pareto index nu exactly equal to unity, confirming the earlier numerical studies on this model. The analysis starts with the development of a master equation for the time development of P(m) . Precise solutions are then obtained in some special cases.

  12. On solution to the problem of reactor kinetics with delayed neutrons by Monte Carlo method

    International Nuclear Information System (INIS)

    Kyncl, Jan

    2013-07-01

    The initial value problem is addressed for the neutron transport equation and for the system of equations that describe the behaviour of emitters of delayed neutrons. Examination of the solution to this problem is based on several main assumptions concerning the behaviour of macroscopic effective cross-sections describing the reaction of the neutron with the medium, the temperature of medium and the remaining parameters of the equations. Formulation of these assumptions is adequately general and is in agreement with the properties of all known models of the physical quantities involved. Among others, the assumptions admit dependence of the macroscopic effective cross-sections and temperature on spatial coordinates and time that can be arbitrary to a great extent. The problem starts from a set of integro-differential equations. This problem is first transposed into the equivalent problem of solving a linear integral equation for neutron flux. This integral equation is solved by the method of successive iterations and its uniqueness is demonstrated. Numeric solution to the integral equation by Monte Carlo method consists in finding a functional of the exact solution. For this, a random process is set up and some random variables are proposed. Then it is demonstrated that each of these variables is an unbiased estimator of that functional. (author)

  13. Photodegradation kinetics, transformation, and toxicity prediction of ketoprofen, carprofen, and diclofenac acid in aqueous solutions.

    Science.gov (United States)

    Li, Jian; Ma, Li-Yun; Li, Lu-Shuang; Xu, Li

    2017-12-01

    Photodegradation of 3 commonly used nonsteroidal anti-inflammatory drugs, ketoprofen, carprofen, and diclofenac acid, was conducted under ultraviolet (UV) irradiation. The kinetic results showed that the 3 pharmaceuticals obeyed the first-order reaction with decreasing rate constants of 1.54 × 10 -4 , 5.91 × 10 -5 , and 7.78 × 10 -6  s -1 for carprofen, ketoprofen, and diclofenac acid, respectively. Moreover, the main transformation products were identified by ion-pair liquid-liquid extraction combined with injection port derivatization-gas chromatography-mass spectrometry and high-performance liquid chromatography-quadrupole-time of flight mass spectrometric analysis. There were 8, 3, and 6 transformation products identified for ketoprofen, carprofen, and diclofenac acid, respectively. Decarboxylation, dechlorination, oxidation, demethylation, esterification, and cyclization were proposed to be associated with the transformation of the 3 pharmaceuticals. Toxicity prediction of the transformation products was conducted on the EPI Suite software based on ECOSAR model, and the results indicate that some of the transformation products were more toxic than the parent compounds. The present study provides the foundation to understand the transformation behavior of the studied pharmaceuticals under UV irradiation. Environ Toxicol Chem 2017;36:3232-3239. © 2017 SETAC. © 2017 SETAC.

  14. Radical Copolymerization Kinetics of Bio-Renewable Butyrolactone Monomer in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Sharmaine B. Luk

    2017-10-01

    Full Text Available The radical copolymerization kinetics of acrylamide (AM and the water-soluble monomer sodium 4-hydroxy-4-methyl-2-methylene butanoate (SHMeMB, formed by saponification of the bio-sourced monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL, are investigated to explain the previously reported slow rates of reaction during synthesis of superabsorbent hydrogels. Limiting conversions were observed to decrease with increased temperature during SHMeMB homopolymerization, suggesting that polymerization rate is limited by depropagation. Comonomer composition drift also increased with temperature, with more AM incorporated into the copolymer due to SHMeMB depropagation. Using previous estimates for the SHMeMB propagation rate coefficient, the conversion profiles were used to estimate rate coefficients for depropagation and termination (kt. The estimate for kt,SHMeMB was found to be of the same order of magnitude as that recently reported for sodium methacrylate, with the averaged copolymerization termination rate coefficient dominated by the presence of SHMeMB in the system. In addition, it was found that depropagation still controlled the SHMeMB polymerization rate at elevated temperatures in the presence of added salt.

  15. Numerical solution of the 1D kinetics equations using a cubic reduced nodal scheme

    International Nuclear Information System (INIS)

    Gomez T, A.M.; Valle G, E. del; Delfin L, A.; Alonso V, G.

    2003-01-01

    In this work a finite differences technique centered in mesh based on a cubic reduced nodal scheme type finite element to solve the equations of the kinetics 1 D that include the equations corresponding to the concentrations of precursors of delayed neutrons is described. The technique of finite elements used is that of Galerkin where so much the neutron flux as the concentrations of precursors its are spatially approached by means of a three grade polynomial. The matrices of rigidity and of mass that arise during this discretization process are numerically evaluated using the open quadrature non standard of Newton-Cotes and that of Radau respectively. The purpose of the application of these quadratures is the one of to eliminate in the global matrices the couplings among the values of the flow in points of the discretization with the consequent advantages as for the reduction of the order of the matrix associated to the discreet problem that is to solve. As for the time dependent part the classical integration scheme known as Θ scheme is applied. After carrying out the one reordering of unknown and equations it arrives to a reduced system that it can be solved but quickly. With the McKin compute program developed its were solved three benchmark problems and those results are shown for the relative powers. (Author)

  16. Phosphorus removal from aqueous solution in parent and aluminum-modified eggshells: thermodynamics and kinetics, adsorption mechanism, and diffusion process.

    Science.gov (United States)

    Guo, Ziyan; Li, Jiuhai; Guo, Zhaobing; Guo, Qingjun; Zhu, Bin

    2017-06-01

    Parent and aluminum-modified eggshells were prepared and characterized with X-ray diffraction, specific surface area measurements, infrared spectroscopy, zeta potential, and scanning electron microscope, respectively. Besides, phosphorus adsorptions in these two eggshells at different temperatures and solution pH were carried out to study adsorption thermodynamics and kinetics as well as the mechanisms of phosphorus adsorption and diffusion. The results indicated that high temperature was favorable for phosphorus adsorption in parent and aluminum-modified eggshells. Alkaline solution prompted phosphorus adsorption in parent eggshell, while the maximum adsorption amount was achievable at pH 4 in aluminum-modified eggshell. Adsorption isotherms of phosphorus in these eggshells could be well described by Langmuir and Freundlich models. Phosphorus adsorption amounts in aluminum-modified eggshell were markedly higher compared to those in parent eggshell. Adsorption heat indicated that phosphorus adsorption in parent eggshell was a typically physical adsorption process, while chemical adsorption mechanism of ion exchange between phosphorus and hydroxyl groups on the surface of eggshells was dominated in aluminum-modified eggshell. The time-resolved uptake curves showed phosphorus adsorption in aluminum-modified eggshell was significantly faster than that in parent eggshell. Moreover, there existed two clear steps in time-resolved uptake curves of phosphorus in parent eggshell. Based on pseudo-second order kinetic model and intraparticle diffusion model, we inferred more than one process affected phosphorus adsorption. The first process was the diffusion of phosphorus through water to external surface and the opening of pore channel in the eggshells, and the second process was mainly related to intraparticle diffusion.

  17. SPAN: A Network Providing Integrated, End-to-End, Sensor-to-Database Solutions for Environmental Sciences

    Science.gov (United States)

    Benzel, T.; Cho, Y. H.; Deschon, A.; Gullapalli, S.; Silva, F.

    2009-12-01

    In recent years, advances in sensor network technology have shown great promise to revolutionize environmental data collection. Still, wide spread adoption of these systems by domain experts has been lacking, and these have remained the purview of the engineers who design them. While there are many data logging options for basic data collection in the field currently, scientists are often required to visit the deployment sites to retrieve their data and manually import it into spreadsheets. Some advanced commercial software systems do allow scientists to collect data remotely, but most of these systems only allow point-to-point access, and require proprietary hardware. Furthermore, these commercial solutions preclude the use of sensors from other manufacturers or integration with internet based database repositories and compute engines. Therefore, scientists often must download and manually reformat their data before uploading it to the repositories if they wish to share their data. We present an open-source, low-cost, extensible, turnkey solution called Sensor Processing and Acquisition Network (SPAN) which provides a robust and flexible sensor network service. At the deployment site, SPAN leverages low-power generic embedded processors to integrate variety of commercially available sensor hardware to the network of environmental observation systems. By bringing intelligence close to the sensed phenomena, we can remotely control configuration and re-use, establish rules to trigger sensor activity, manage power requirements, and control the two-way flow of sensed data as well as control information to the sensors. Key features of our design include (1) adoption of a hardware agnostic architecture: our solutions are compatible with several programmable platforms, sensor systems, communication devices and protocols. (2) information standardization: our system supports several popular communication protocols and data formats, and (3) extensible data support: our

  18. PET kinetic analysis --pitfalls and a solution for the Logan plot.

    Science.gov (United States)

    Kimura, Yuichi; Naganawa, Mika; Shidahara, Miho; Ikoma, Yoko; Watabe, Hiroshi

    2007-01-01

    The Logan plot is a widely used algorithm for the quantitative analysis of neuroreceptors using PET because it is easy to use and simple to implement. The Logan plot is also suitable for receptor imaging because its algorithm is fast. However, use of the Logan plot, and interpretation of the formed receptor images should be regarded with caution, because noise in PET data causes bias in the Logan plot estimates. In this paper, we describe the basic concept of the Logan plot in detail and introduce three algorithms for the Logan plot. By comparing these algorithms, we demonstrate the pitfalls of the Logan plot and discuss the solution.

  19. Kinetic speciation of mercury–humate complexes in aqueous solutions by using competing ligand exchange method

    Digital Repository Service at National Institute of Oceanography (India)

    Vudamala, K.; Chakraborty, P.

    with ultrapure water (of resistivity 18.2 MΩ cm-1) acidified to contain 1 % (v/v) ultrapure HNO3 (Merck, Germany). Stock solutions of humic acid (HA) was prepared using HA from Fluka (commercialized by Sigma-Aldrich, cat. No. 53680, Sigma-Aldrich, Inc... river emptying into Cochin backwaters, Indian J. Mar. Sci. 15 (1986) 253–259. http://cat.inist.fr/?aModele=afficheN&cpsidt=8219806 (accessed September 4, 2015). [25] P.K. Krishnakumar, V.K. Pillai, Mercury Near a Caustic Soda plant at karwar,India, Mar...

  20. The kinetics of oxidation of bilirubin and ascorbic acid in solution

    Science.gov (United States)

    Solomonov, A. V.; Rumyantsev, E. V.; Kochergin, B. A.; Antina, E. V.

    2012-07-01

    The results of a comparative study of the oxidation of bilirubin, ascorbic acid, and their mixture in aqueous solutions under the action of air oxygen and hydrogen peroxide are presented. The observed and true rate constants for the oxidation reactions were determined. It was shown that the oxidation of tetrapyrrole pigment occurred under these conditions bypassing the stage of biliverdin formation to monopyrrole products. Simultaneous oxidation of bilirubin and ascorbic acid was shown to be accompanied by the inhibition of ascorbic acid oxidation by bilirubin, whereas ascorbic acid itself activated the oxidation of bilirubin.

  1. Kinetics of Solute Partitioning During Intercritical Annealing of a Medium-Mn Steel

    Science.gov (United States)

    Kamoutsi, H.; Gioti, E.; Haidemenopoulos, Gregory N.; Cai, Z.; Ding, H.

    2015-11-01

    The evolution of austenite fraction and solute partitioning (Mn, Al, and C) during intercritical annealing was calculated for a medium-Mn steel containing 11 pct Mn. Austenite growth takes place in three stages. The first stage is growth under non-partitioning local equilibrium (NPLE) controlled by carbon diffusion in ferrite. The second stage is growth under partitioning local equilibrium (PLE) controlled by diffusion of Mn in ferrite. The third stage is shrinkage of austenite under PLE controlled by diffusion of Mn in austenite. During PLE growth, the austenite is progressively enriched in Mn. Compositional spikes evolve early during NPLE growth and broaden with annealing temperature and time.

  2. Cu(II)-catalyzed oxidation of dopamine in aqueous solutions: mechanism and kinetics.

    Science.gov (United States)

    Pham, A Ninh; Waite, T David

    2014-08-01

    Spontaneous oxidation of dopamine (DA) and the resultant formation of free radical species within dopamine neurons of the substantia nigra (SN) is thought to bestow a considerable oxidative load upon these neurons and may contribute to their vulnerability to degeneration in Parkinson's disease (PD). An understanding of DA oxidation under physiological conditions is thus critical to understanding the relatively selective vulnerability of these dopaminergic neurons in PD and may support the development of novel neuro-protective approaches for this disorder. In this study, the oxidation of dopamine (0.2-10μM) was investigated both in the absence and the presence of copper (0.01-0.4μM), a redox active metal that is present at considerable concentrations in the SN, over a range of background chloride concentrations (0.01-0.7M), different oxygen concentrations and at physiological pH7.4. DA was observed to oxidize extremely slowly in the absence of copper and at moderate rates only in the presence of copper but without chloride. The oxidation of DA however was significantly enhanced in the presence of both copper and chloride with the rate of DA oxidation greatest at intermediate chloride concentrations (0.05-0.2M). The variability of the catalytic effect of Cu(II) on DA oxidation at different chloride concentrations can be explained and successfully modeled by appropriate consideration of the reaction of Cu(II) species with DA and the conversion of Cu(I) to Cu(II) through oxygenation. This model suggests that the speciation of Cu(II) and Cu(I) is critically important to the kinetics of DA oxidation and thus the vulnerability to degradation of dopaminergic neuron in the brain milieu. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Kinetics of patulin degradation in model solution, apple cider and apple juice by ultraviolet radiation.

    Science.gov (United States)

    Zhu, Yan; Koutchma, Tatiana; Warriner, Keith; Shao, Suqin; Zhou, Ting

    2013-08-01

    Patulin is a mycotoxin produced by a wide range of molds involved in fruit spoilage, most commonly by Penicillium expansum and is a health concern for both consumers and manufacturers. The current study evaluated feasibility of monochromatic ultraviolet (UV) radiation at 253.7 nm as a possible commercial application for the reduction of patulin in fresh apple cider and juice. The R-52G MINERALIGHT® UV bench top lamp was used for patulin destruction. It was shown that 56.5%, 87.5%, 94.8% and 98.6% reduction of patulin can be achieved, respectively, in the model solution, apple cider, apple juice without ascorbic acid addition and apple juice with ascorbic acid addition in 2-mm thickness sample initially spiked by 1 mg·L(-1) of patulin after UV exposure for 40 min at UV irradiance of 3.00 mW·cm(-2). A mathematic model to compare the degradation rate and effective UV dose was developed. The effective UV doses that were directly absorbed by patulin for photochemical reaction were 430, 674, 724 and 763 mJ·cm(-3), respectively. The fluence-based decimal reduction time was estimated to 309.3, 31.3, 28.9 and 5.1 mW·cm(-2)·min, respectively, in four media mentioned above. The degradation of patulin followed the first-order reaction model. The time-based and fluence-based reaction rate constants were determined to predict patulin degradation. The time-based reaction rate constant of samples treated in dynamic regime with constant stirring (model solution: 2.95E-4 s(-1), juice: 4.31E-4 s(-1)) were significantly higher than samples treated in static regime (model solution: 2.79E-4 s(-1), juice: 3.49E-4 s(-1), p radiation may be an effective method for treating patulin-containing apple cider and juice.

  4. Surface controlled dissolution rates of gypsum in aqueous solutions exhibit nonlinear dissolution kinetics

    Science.gov (United States)

    Jeschke, Alexander A.; Vosbeck, Katrin; Dreybrodt, Wolfgang

    2001-01-01

    The effective dissolution rates of gypsum are determined by mixed kinetics, where the rate constants of dissolution at the surface and the transport constant of molecular diffusion of dissolved material are similar. To obtain the surface reaction rate law it is necessary to know the transport constant. We have determined the surface rate law for monocrystalline selenite by using a rotating disc set-up, where the transport coefficients are well known. As a result, up to a calcium concentration of 0.6 · ceq, we find a nearly linear rate law Rs = ksl (1- cs/ ceq) n1, where cs is the total calcium concentration at the surface and ceq the equilibrium concentration with respect to gypsum, n1 = 1.2 ± 0.2, and ksl = 1.1 · 10 -4 mmol cm -2 s -1 ± 15%. We also employed batch-experiments for selenite, alabaster and gypsum rock samples. The result of these experiments were interpreted by using a transport constant determined by NaCl dissolution experiments under similar physical conditions. The batch experiments reveal a dissolution rate law Rs = ksl (1- cs/ ceq) n1, ksl = 1.3 · 10 -4 mmol · cm -2 s -1, n1 = 1.2 ± 0.2 for c ≤ 0.94 · ceq. Close to equilibrium a nonlinear rate law, Rs = ks2 (1- cs/ ceq) n2, is observed, where ks2 is in the order of 10 mmol · cm -2 s -1 and n2 ≈ 4.5. The experimentally observed gypsum dissolution rates from the batch experiments could be accurately fitted, with only minor variations of the surface reaction constant obtained from the rotating disk experiment and the transport coefficient from the NaCl dissolution batch experiment. Batch experiments on pure synthetic gypsum, reveal a linear rate law up to equilibrium. This indicates inhibition of dissolution in natural samples close to equilibrium, as is known also for calcite minerals.

  5. Reaction Kinetics of Monomethylhydrazine With Nitrous Acid in Perchloric Acid Solution

    International Nuclear Information System (INIS)

    Wei Yan; Wang Hui; Pan Yongjun; Cong Haifeng; Jiao Haiyang; Jia Yongfen; Zheng Weifang

    2009-01-01

    The oxidation of monomethylhydrazine (MMH) by nitrous acid was researched in perchloric acid solution with spectrophotometry. The rate equation has been determined as follows: -dc (HNO 2 ) /dt= kc (H + ) 0.9 c (MMH) 1.1 c (HNO 2 ), k is (46.0 ± 2.7) L 2 / (mol 2 · s) with the initial perchlorate concentration of 0.50 mol/L at the temperature of 4.5 degree C. The corresponding activation energy of the reaction is (42.4 ± 0.1) kJ/mol. The results indicate that oxidation of mono-methylhydrazine (MMH) by nitrous acid is fast. The higher concentration of MMH can accelerate the reduction process of nitrous acid. Higher acidity can also speed up the reduction of nitrous acid. (authors)

  6. Uptake of phosphorus from surfactant solutions by wheat leaves: spreading kinetics, wetted area, and drying time.

    Science.gov (United States)

    Peirce, Courtney A E; Priest, Craig; McBeath, Therese M; McLaughlin, Mike J

    2016-01-07

    The delivery and uptake of nutrients at the surface of plant leaves is an important physicochemical phenomenon that depends on leaf surface morphology and chemistry, fertilizer formulation chemistry (including adjuvant and associated surfactants), wetting dynamics, and many other physical, chemical and biological factors. In this study, the role of spreading dynamics in determining uptake of the macronutrient phosphorus from phosphoric acid fertilizer solution in combination with three different adjuvants was measured in the absence of droplet run-off and splashing. When run-off and splashing losses were zero, spreading and drying rates had a small to negligible effect on the uptake efficiency. The results suggest that uptake may be much less sensitive to the specific choice of adjuvant and long time-scale spreading behaviour than one might intuitively expect.

  7. Abstract of programs for nuclear reactor calculation and kinetic equations solution

    International Nuclear Information System (INIS)

    Marakazov, A.A.

    1977-01-01

    The collection includes about 50 annotations of programmes,developed in the Kurchatov Atomic Energy Institute in 1971-1976. The programmes are intended for calculating the neutron flux, for solving systems of multigroup equations in P 3 approximation, for calculating the reactor cell, for analysing the system stability, breeding ratio etc. The programme annotations are compiled according to the following diagram: 1.Programme title. 2.Computer type. 3.Physical problem. 4.Solution method. 5.Calculation limitations. 6.Characteristic computer time. 7.Programme characteristic features. 8.Bound programmes. 9.Programme state. 10.Literature allusions in the programme. 11.Required memory resourses. 12.Programming language. 13.Operation system. 14.Names of authors and place of programme adjusting

  8. Kinetic Aspects of Leaching Zinc from Waste Galvanizing Zinc by Using Hydrochloric Acid Solutions

    Science.gov (United States)

    Sminčáková, Emília; Trpčevská, Jarmila; Pirošková, Jana

    2017-10-01

    In this work, the results of acid leaching of flux skimmings coming from two plants are presented. Sample A contained two phases, Zn(OH)Cl and NH4Cl. In sample B, the presence of three phases, Zn5(OH)8Cl2·H2O, (NH4)2(ZnCl4) and ZnCl2(NH3)2, was proved. The aqueous solution of hydrochloric acid and distilled water was used as the leaching medium. The effects of the leaching time, temperature and concentration of the leaching medium on the zinc extraction were investigated. The apparent activation energy, E a = 4.61 kJ mol-1, and apparent reaction order n = 0.18 for sample A, and the values E a = 6.28 kJ mol-1 and n = 0.33 for sample B were experimentally determined. Zinc leaching in acid medium is a diffusion-controlled process.

  9. Kinetics of isotopic exchange between strontium polymolybdate and strontium ions in aqueous solution

    International Nuclear Information System (INIS)

    Atun, Gulten; Bilgin, Binay; Kilislioglu, Ayben

    2002-01-01

    A heterogeneous isotopic exchange reaction of strontium polymolybdate in strontium chloride solution was studied using 90 Sr as a tracer. The effects of low and high strontium chloride concentration on the rate and mechanism of the isotopic exchange reaction were investigated. It was found that, at high concentrations, the rate is independent of strontium concentration, but, at low concentrations, the rate is proportional to the strontium concentration. These results support a hypothesis that, at low concentrations, the rate is controlled by film diffusion, whereas at high concentrations it is controlled by particle diffusion. Experiments were performed at 293, 303 and 313 K. Activation energy of isotopic exchange reaction and thermodynamic parameters ΔH*, ΔS*, and ΔG* were calculated using the Arrhenius and Eyring equations. The results also indicated that recrystallization is a predominant factor in the present exchange reaction

  10. Kinetics of isotopic exchange between strontium polymolybdate and strontium ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Atun, Gulten E-mail: gultena@istanbul.edu.tr; Bilgin, Binay; Kilislioglu, Ayben

    2002-06-01

    A heterogeneous isotopic exchange reaction of strontium polymolybdate in strontium chloride solution was studied using {sup 90}Sr as a tracer. The effects of low and high strontium chloride concentration on the rate and mechanism of the isotopic exchange reaction were investigated. It was found that, at high concentrations, the rate is independent of strontium concentration, but, at low concentrations, the rate is proportional to the strontium concentration. These results support a hypothesis that, at low concentrations, the rate is controlled by film diffusion, whereas at high concentrations it is controlled by particle diffusion. Experiments were performed at 293, 303 and 313 K. Activation energy of isotopic exchange reaction and thermodynamic parameters {delta}H*, {delta}S*, and {delta}G* were calculated using the Arrhenius and Eyring equations. The results also indicated that recrystallization is a predominant factor in the present exchange reaction.

  11. Electron kinetics with attachment and ionization from higher order solutions of Boltzmann's equation

    International Nuclear Information System (INIS)

    Winkler, R.; Wilhelm, J.; Braglia, G.L.

    1989-01-01

    An appropriate approach is presented for solving the Boltzmann equation for electron swarms and nonstationary weakly ionized plasmas in the hydrodynamic stage, including ionization and attachment processes. Using a Legendre-polynomial expansion of the electron velocity distribution function the resulting eigenvalue problem has been solved at any even truncation-order. The technique has been used to study velocity distribution, mean collision frequencies, energy transfer rates, nonstationary behaviour and power balance in hydrodynamic stage, of electrons in a model plasma and a plasma of pure SF 6 . The calculations have been performed for increasing approximation-orders, up to the converged solution of the problem. In particular, the transition from dominant attachment to prevailing ionization when increasing the field strength has been studied. Finally the establishment of the hydrodynamic stage for a selected case in the model plasma has been investigated by solving the nonstationary, spatially homogeneous Boltzmann equation in twoterm approximation. (author)

  12. Solute kinetics with short-daily home hemodialysis using slow dialysate flow rate.

    Science.gov (United States)

    Kohn, Orly F; Coe, Fredric L; Ing, Todd S

    2010-01-01

    "NxStage System One()" is increasingly used for daily home hemodialysis. The ultrapure dialysate volumes are typically between 15 L and 30 L per dialysis, substantially smaller than the volumes used in conventional dialysis. In this study, the impact of the use of low dialysate volumes on the removal rates of solutes of different molecular weights and volumes of distribution was evaluated. Serum measurements before and after dialysis and total dialysate collection were performed over 30 times in 5 functionally anephric patients undergoing short-daily home hemodialysis (6 d/wk) over the course of 8 to 16 months. Measured solutes included beta(2) microglobulin (beta(2)M), phosphorus, urea nitrogen, and potassium. The average spent dialysate volume (dialysate plus ultrafiltrate) was 25.4+/-4.7 L and the dialysis duration was 175+/-15 min. beta(2) microglobulin clearance of the polyethersulfone dialyzer averaged 53+/-14 mL/min. Total beta(2)M recovered in the dialysate was 106+/-42 mg per treatment (n=38). Predialysis serum beta(2)M levels remained stable over the observation period. Phosphorus removal averaged 694+/-343 mg per treatment with a mean predialysis serum phosphorus of 5.2+/-1.8 mg/dL (n=34). Standard Kt/V averaged 2.5+/-0.3 per week and correlated with the dialysate-based weekly Kt/V. Weekly beta(2)M, phosphorus, and urea nitrogen removal in patients dialyzing 6 d/wk with these relatively low dialysate volumes compared favorably with values published for thrice weekly conventional and with short-daily hemodialysis performed with machines using much higher dialysate flow rates. Results of the present study were achieved, however, with an average of 17.5 hours of dialysis per week.

  13. Eggshell Powder as an Adsorbent for Removal of Fluoride from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    R. Bhaumik

    2012-01-01

    Full Text Available A new medium, eggshell powder has been developed for fluoride removal from aqueous solution. Fluoride adsorption was studied in a batch system where adsorption was found to be pH dependent with maximum removal efficiency at 6.0. The experimental data was more satisfactorily fitted with Langmuir isotherm model. The kinetics and the factor controlling adsorption process fully accepted by pseudo-second-order model were also discussed. Ea was found to be 45.98 kJmol-1 by using Arrhenius equation, indicating chemisorption nature of fluoride onto eggshell powder. Thermodynamic study showed spontaneous nature and feasibility of the adsorption process with negative enthalpy (∆H0 value also supported the exothermic nature. Batch experiments were performed to study the applicability of the adsorbent by using fluoride contaminated water collected from affected areas. These results indicate that eggshell powder can be used as an effective, low-cost adsorbent to remove fluoride from aqueous solution as well as groundwater.

  14. Thermodynamics and kinetics of adsorption of Cu(II from aqueous solutions onto multi-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Iman Mobasherpour

    2014-12-01

    Full Text Available Release of heavy metals into water as a result of industrial activities may pose a serious threat to the environment. The objective of this study is to assess the uptake of Cu2+ from aqueous solutions onto multi-walled carbon nanotubes (MWCNT. The potential of the t-MWCNT to remove Cu2+ cations from aqueous solutions was investigated in batch reactor under different experimental conditions. The processing parameters such as initial concentration of Cu2+ ions, temperature, and adsorbent mass were also investigated. Copper uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR models. In addition, the adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 12.34 mg/g of Cu2+ cations on t-MWCNT. Various thermodynamic parameters, such as ΔG0, ΔH0 and ΔS0 were calculated. The thermodynamics of Cu2+ cations adsorption onto t-MWCNT system pointed at spontaneous and endothermic nature of the process. Using the second-order kinetic constants, the activation energy of adsorption (Ea was determined as 27.187 kJ/mol according to the Arrhenius equation.

  15. Analytical solution of the multigroup neutron diffusion kinetic equation in one-dimensional cartesian geometry by the integral transform technique

    International Nuclear Information System (INIS)

    Ceolin, Celina

    2010-01-01

    The objective of this work is to obtain an analytical solution of the neutron diffusion kinetic equation in one-dimensional cartesian geometry, to monoenergetic and multigroup problems. These equations are of the type stiff, due to large differences in the orders of magnitude of the time scales of the physical phenomena involved, which make them difficult to solve. The basic idea of the proposed method is applying the spectral expansion in the scalar flux and in the precursor concentration, taking moments and solving the resulting matrix problem by the Laplace transform technique. Bearing in mind that the equation for the precursor concentration is a first order linear differential equation in the time variable, to enable the application of the spectral method we introduce a fictitious diffusion term multiplied by a positive value which tends to zero. This procedure opened the possibility to find an analytical solution to the problem studied. We report numerical simulations and analysis of the results obtained with the precision controlled by the truncation order of the series. (author)

  16. Cadmium and chromium removal kinetics from solution by two aquatic macrophytes

    International Nuclear Information System (INIS)

    Sune, N.; Sanchez, G.; Caffaratti, S.; Maine, M.A.

    2007-01-01

    The aim of this work was to determine chromium and cadmium bioaccumulation processes of two free-floating macrophytes commonly used in wetlands for water treatment: Salvinia herzogii and Pistia stratiotes. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The most important processes of Cd uptake are biological ones in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes. The main processes of Cr uptake in both macrophytes are adsorption, chelation and ion exchange. The slow stage is different for each species and metal. Cr precipitation induced by roots occurs in P. stratiotes. Cr uptake through leaves is probably the main cause of the increase of Cr in the aerial parts of S. herzogii. - Cd uptake processes are biological processes in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes, whereas Cr uptake processes in both macrophytes are adsorption, chelation and ion exchange

  17. Plasma Creatine Kinetics After Ingestion of Microencapsulated Creatine Monohydrate with Enhanced Stability in Aqueous Solutions.

    Science.gov (United States)

    Hone, Michelle; Kent, Robert M; Scotto di Palumbo, Alessandro; Bleiel, Sinead B; De Vito, Giuseppe; Egan, Brendan

    2017-07-04

    Creatine monohydrate represents one of the largest sports supplement markets. Enhancing creatine (CRE) stability in aqueous solutions, such as with microencapsulation, represents innovation potential. Ten physically active male volunteers were randomly assigned in a double-blind design to either placebo (PLA) (3-g maltodextrin; n = 5) or microencapsulated CRE (3-g creatine monohydrate; n = 5) conditions. Experimental conditions involved ingestion of the samples in a 70-mL ready-to-drink format. CRE was delivered in a novel microencapsulation matrix material consisting entirely of hydrolyzed milk protein. Three hours after ingestion, plasma creatine concentrations were unchanged during PLA, and averaged ∼45 μM. During CRE, plasma creatine concentration peaked after 30 min at 101.6 ± 14.9 μM (p creatine concentration gradually trended downwards but remained significantly elevated (∼50% above resting levels) 3 hr after ingestion. These results demonstrate that the microencapsulated form of creatine monohydrate reported herein remains bioavailable when delivered in aqueous conditions, and has potential utility in ready-to-drink formulations for creatine supplementation.

  18. Photocatalytic degradation kinetics and mechanism of phenobarbital in TiO(2) aqueous solution.

    Science.gov (United States)

    Cao, Hua; Lin, Xiulian; Zhan, Haiying; Zhang, Hong; Lin, Jingxin

    2013-01-01

    5-Ethyl-5-phenylpyrimidine-2,4,6(1H, 3H, 5H)-trione is an anti-convulsant used to treat disorders of movement, e.g. tremors. This work deals with the transformation of phenobarbital by UV/TiO(2) heterogeneous photocatalysis, to assess the decomposition of the pharmaceutical compound, to identify intermediates, as well as to elucidate some mechanistic details of the degradation. The photocatalytic removal efficiency of 100 μm phenobarbital is about 80% within 60 min, while the degradation efficiency of phenobarbital was better in alkaline solution. The study on contribution of reactive oxidative species (ROSs) has shown that ()OH is responsible for the major degradation of phenobarbital, while the photohole, photoelectrons and the other ROSs have the minor contribution to the degradation. Finally, based on the identification of degradation intermediates, two main photocatalytic degradation pathways have been tentatively proposed, including the hydroxylation and cleavage of pyrimidine ring in the phenobarbital molecule respectively. Certainly, the phenobarbital can be mineralized when the photocatalytic reaction time prolongs. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Kinetics of Np(4) oxidation reaction by persulphate in nitric acid solution in the presence of ferric ions as catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Koltunov, V S; Marchenko, V I

    1976-01-01

    The kinetics of the reaction Np(IV) + Fe(III) = Np(V) + Fe(II)was investigated by a spectrophotometric method according to observation of the consumption of Np(IV) at 720 nm in a solution of HNO/sub 3/ + NaNO/sub 3/ in the concentration range; (F(III))equal (5.12-102.4).10/sup -3/ M, (H+) equal 0.14-1 M, (NO/sub 3//sup -/) = 0.5-2 M at an ionic strength of the solution ..mu.. = 0.2-2 and temperatures of 25-46/sup 0/C. To exclude the reverse reaction, (3-6).10/sup -2/ M (NH/sub 4/)/sub 2/S/sub 2/O/sub 8/, which rapidly oxidizes Fe(II), was added to the solution. The possible oxidation of Np(V) to Np(VI) was prevented by the addition of small quantities of N/sub 2/H/sub 4/. It was shown that the reaction rate is described by the equation -d(Np(IV))/dt=k(Np(IV))(Fe(III))/(H/sup +/)/sup 3/. where k = 0.490 +- 0.026 M/sup 2/.min/sup -1/ at 25/sup 0/ and ..mu.. = 1. The No/sub 3//sup -/ ions inhibit the reaction in the interval (NO/sub 3//sup -/) = 0-1 M and do not influence it at (NO/sub 3//sup -/) > 1 M. On the basis of an investigation of the dependence of k on the temperature, the energy (E = 32.5 kcal/mole), free energy (..delta..F* = 20.3 kcal/mole), and entropy (..delta..S* = 39 entropy units) of activation of the reaction were calculated. The reaction mechanism is discussed.

  20. Mass and heat transfer between evaporation and condensation surfaces: Atomistic simulation and solution of Boltzmann kinetic equation.

    Science.gov (United States)

    Zhakhovsky, Vasily V; Kryukov, Alexei P; Levashov, Vladimir Yu; Shishkova, Irina N; Anisimov, Sergey I

    2018-04-16

    Boundary conditions required for numerical solution of the Boltzmann kinetic equation (BKE) for mass/heat transfer between evaporation and condensation surfaces are analyzed by comparison of BKE results with molecular dynamics (MD) simulations. Lennard-Jones potential with parameters corresponding to solid argon is used to simulate evaporation from the hot side, nonequilibrium vapor flow with a Knudsen number of about 0.02, and condensation on the cold side of the condensed phase. The equilibrium density of vapor obtained in MD simulation of phase coexistence is used in BKE calculations for consistency of BKE results with MD data. The collision cross-section is also adjusted to provide a thermal flux in vapor identical to that in MD. Our MD simulations of evaporation toward a nonreflective absorbing boundary show that the velocity distribution function (VDF) of evaporated atoms has the nearly semi-Maxwellian shape because the binding energy of atoms evaporated from the interphase layer between bulk phase and vapor is much smaller than the cohesive energy in the condensed phase. Indeed, the calculated temperature and density profiles within the interphase layer indicate that the averaged kinetic energy of atoms remains near-constant with decreasing density almost until the interphase edge. Using consistent BKE and MD methods, the profiles of gas density, mass velocity, and temperatures together with VDFs in a gap of many mean free paths between the evaporation and condensation surfaces are obtained and compared. We demonstrate that the best fit of BKE results with MD simulations can be achieved with the evaporation and condensation coefficients both close to unity.

  1. Removal of Hexavalent Chromium from Aqueous Solution by Modified Holly Sawdust: A Study of Equilibrium and Kinetics

    Directory of Open Access Journals (Sweden)

    S. Azizian

    2010-01-01

    Full Text Available Introduction & Objective: Industrial wastewaters including heavy metals, are among the important sources of environmental pollution. Heavy metals such as chromium are found in plating wastewater and is harmful for human health and environment. The purpose of the present study was to investigate the absorption of heavy metals such as chromium onto modified holly sawdust as an cheaper absorbent. Materials & Methods: This study was a fundamental- application study done in Hamadan University of Medical Sciences, hygiene faculty water and wastewater chemistry laboratory. This study investigated the removal of hexavalent chromium by using modified holly sawdust with pH changes ,contact time ,absorbent dose and Cr(VI concentrations in batch system. Then the result was analyzed by Excel software.Results: The results showed that the removal efficiency decrease is accompanied by the increase of pH and initial chromium concentration. pH increase from 2 to 12(equilibrium time= 180 min, adsorbent dose= 0.6g/100CC, Cr(VI concentrations= 60 mg/L,leaded to the removal efficiency decrease from 99.67 % to 29.78 %. Also removal efficiency decreased from 99.37 % to 40.24 % after increasing the initial chromium concentrations from 20 mg/L to 100 mg/L. Moreover the results showed the removal efficiency increased after increasing the adsorbent dose and contact time. By increasing adsorbent dose from 0.2 g/100CC to 1 g/100CC, the removal efficiency increased from 34.65 % to 99.76 %.Additionally, the removal efficiency increased from 48.53%to 99.76% by increasing contact time from 5 mins to 180 mins. Experimental isotherms and kinetics models were assessed by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetics models. The results showed that the data were acceptably explained acceptably by Langmuir isotherms and pseudo-second-order kinetics models respectively.Conclusion: The results showed that the removal of hexavalent chromium

  2. Effects of Convective Transport of Solute and Impurities on Defect-Causing Kinetics Instabilities

    Science.gov (United States)

    Vekilov, Peter G.; Higginbotham, Henry Keith (Technical Monitor)

    2001-01-01

    For in-situ studies of the formation and evolution of step patterns during the growth of protein crystals, we have designed and assembled an experimental setup based on Michelson interferometry with the surface of the growing protein crystal as one of the reflective surfaces. The crystallization part of the device allows optical monitoring of a face of a crystal growing at temperature stable within 0.05 C in a developed solution flow of controlled direction and speed. The reference arm of the interferometer contains a liquid-crystal element that allows controlled shifts of the phase of the interferograms. We employ an image processing algorithm which combines five images with a pi/2 phase difference between each pair of images. The images are transferred to a computer by a camera capable of capturing 6-8 frames per second. The device allows data collection data regarding growth over a relatively large area (approximately .3 sq. mm) in-situ and in real time during growth. The estimated dept resolution of the phase shifting interferometry is about 100 A. The lateral resolution, depending on the zoom ratio, varies between 0.3 and 0.6 micrometers. We have now collected quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, position on the facet, crystal size and temperature with the proteins ferritin, apoferritin and thaumatin. Comparisons with theory, especially with the AFM results on the molecular level processes, see below, allow tests of the rational for the effects of convective flows and, as a particular case, the lack thereof, on step bunching.

  3. Removal kinetics for gaseous NO and SO2by an aqueous NaClO2solution mist in a wet electrostatic precipitator

    KAUST Repository

    Park, Hyun-Woo; Park, Dong-Wha

    2016-01-01

    Removal kinetics for NO and SO2 by NaClO2 solution mist were investigated in a wet electrostatic precipitator. By varying the molar concentrations of NO, SO2, and NaClO2, the removal rates of NO and SO2 confirmed to range from 34.8 to 72.9 mmol/m3

  4. Oxidation of D-glucose and D-fructose with oxygen in aqueous, alkaline solutions. III. Kinetic approach to the product distribution

    NARCIS (Netherlands)

    de Wilt, H.G.J.; Kuster, Ben

    1972-01-01

    Based on a previously reported, integral reaction-scheme for the homogeneous oxidation of -glucose and -fructose with oxygen in aqueous, alkaline solutions, a kinetic model covering the product distribution has been developed. The model consists of a repeated set of reactions with constant rate

  5. Corrosion kinetics and topography analysis of Ti–6Al–4V alloy subjected to different mouthwash solutions

    Energy Technology Data Exchange (ETDEWEB)

    Faverani, Leonardo Perez [Department of Surgery and Integrated Clinic, Aracatuba Dental School, Univ Estadual Paulista (UNESP), Jose Bonifacio, 1193, Aracatuba, São Paulo 16015-050 (Brazil); Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ Estadual Paulista (UNESP), Jose Bonifacio, 1193, Aracatuba, São Paulo 16015-050 (Brazil); Barao, Valentim Adelino Ricardo, E-mail: barao@fop.unicamp.br [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av. Limeira 901, Piracicaba, São Paulo 13414-903 (Brazil); Pires, Maria Flávia Araújo [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ Estadual Paulista (UNESP), Jose Bonifacio, 1193, Aracatuba, São Paulo 16015-050 (Brazil); Yuan, Judy Chia-Chun; Sukotjo, Cortino [Department of Restorative Dentistry, University of Illinois at Chicago-College of Dentistry, 801 S Paulina, Chicago, IL 60612-7211 (United States); Mathew, Mathew T. [Department of Orthopedic Surgery, Rush University Medical Center, 1611 West Harrison, Chicago, IL 60612-7211 (United States); Assunção, Wirley Gonçalves [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ Estadual Paulista (UNESP), Jose Bonifacio, 1193, Aracatuba, São Paulo 16015-050 (Brazil)

    2014-10-01

    This study evaluated the corrosion kinetics and surface topography of Ti–6Al–4V alloy exposed to mouthwash solutions (0.12% chlorhexidine digluconate, 0.053% cetylpyridinium chloride and 3% hydrogen peroxide) compared to artificial saliva (pH 6.5) (control). Twenty Ti–6Al–4V alloy disks were used and divided into 4 groups (n = 5). For the electrochemical assay, standard tests as open circuit potential and electrochemical impedance spectroscopy (EIS) were applied at baseline, 7 and 14 days after immersion in the solutions. Scanning electron microscopy, atomic force microscopy and profilometry (average roughness — R{sub a}) were used for surface characterization. Total weight loss of disks was calculated. Data were analyzed by ANOVA and Bonferroni's test (α = 0.05). Hydrogen peroxide generated the lowest polarization resistance (R{sub p}) values for all periods (P < 0.05). For the capacitance (C{sub dl}), similar results were observed among groups at baseline (P = 0.098). For the 7 and 14-day periods, hydrogen peroxide promoted the highest C{sub dl} values (P < 0.0001). Hydrogen peroxide promoted expressive superficial changes and greater Ra values than the others (P < 0.0001). It could be concluded that solutions containing cetylpyridinium chloride and chlorhexidine digluconate might be the mouthwashes of choice during the post-operatory period of dental implants. However, hydrogen peroxide is counter-indicated in these situations. Further studies evaluating the dynamics of these solutions (tribocorrosion) and immersing the disks in daily cycles (two or three times a day) to mimic a clinical situation closest to the application of mouthwashes in the oral cavity are warranted to prove our results. - Highlights: • Long-term electrochemical stability of Ti–6Al–4V in mouthwashes was investigated. • 3% percent hydrogen peroxide reduced the corrosion resistance of the Ti–6Al–4V. • Ti is stable in 0.12% chlorhexidine digluconate and 0

  6. Valorization of aquaculture waste in removal of cadmium from aqueous solution: optimization by kinetics and ANN analysis

    Science.gov (United States)

    Aditya, Gautam; Hossain, Asif

    2018-05-01

    Cadmium is one of the most hazardous heavy metal concerning human health and aquatic pollution. The removal of cadmium through biosorption is a feasible option for restoration of the ecosystem health of the contaminated freshwater ecosystems. In compliance with this proposition and considering the efficiency of calcium carbonate as biosorbent, the shell dust of the economically important snail Bellamya bengalensis was tested for the removal of cadmium from aqueous medium. Following use of the flesh as a cheap source of protein, the shells of B. bengalensis made up of CaCO3 are discarded as aquaculture waste. The biosorption was assessed through batch sorption studies along with studies to characterize the morphology and surface structures of waste shell dust. The data on the biosorption were subjected to the artificial neural network (ANN) model for optimization of the process. The biosorption process changed as functions of pH of the solution, concentration of heavy metal, biomass of the adsorbent and time of exposure. The kinetic process was well represented by pseudo second order ( R 2 = 0.998), and Langmuir equilibrium ( R 2 = 0.995) had better fits in the equilibrium process with 30.33 mg g-1 of maximum sorption capacity. The regression equation ( R 2 = 0.948) in the ANN model supports predicted values of Cd removal satisfactorily. The normalized importance analysis in ANN predicts Cd2+ concentration, and pH has the most influence in removal than biomass dose and time. The SEM and EDX studies show clear peaks for Cd confirming the biosorption process while the FTIR study depicts the main functional groups (-OH, C-H, C=O, C=C) responsible for the biosorption process. The study indicated that the waste shell dust can be used as an efficient, low cost, environment friendly, sustainable adsorbent for the removal of cadmium from aqueous solution.

  7. Adsorption of ammonium ion by coconut shell-activated carbon from aqueous solution: kinetic, isotherm, and thermodynamic studies.

    Science.gov (United States)

    Boopathy, Ramasamy; Karthikeyan, Sekar; Mandal, Asit Baran; Sekaran, Ganesan

    2013-01-01

    Ammonium ions are one of the most encountered nitrogen species in polluted water bodies. High level of ammonium ion in aqueous solution imparts unpleasant taste and odor problems, which can interfere with the life of aquatics and human population when discharged. Many chemical methods are developed and being used for removal of ammonium ion from aqueous solution. Among various techniques, adsorption was found to be the most feasible and environmentally friendly with the use of natural-activated adsorbents. Hence, in this study, coconut shell-activated carbon (CSAC) was prepared and used for the removal of ammonium ion by adsorption techniques. Ammonium chloride (analytical grade) was purchased from Merck Chemicals for adsorption studies. The CSAC was used to adsorb ammonium ions under stirring at 100 rpm, using orbital shaker in batch experiments. The concentration of ammonium ion was estimated by ammonia distillate, using a Buchi distillation unit. The influence of process parameters such as pH, temperature, and contact time was studied for adsorption of ammonium ion, and kinetic, isotherm models were validated to understand the mechanism of adsorption of ammonium ion by CSAC. Thermodynamic properties such as ∆G, ∆H, and ∆S were determined for the ammonium adsorption, using van't Hoff equation. Further, the adsorption of ammonium ion was confirmed through instrumental analyses such as SEM, XRD, and FTIR. The optimum conditions for the effective adsorption of ammonium ion onto CSAC were found to be pH 9.0, temperature 283 K, and contact time 120 min. The experimental data was best followed by pseudosecond order equation, and the adsorption isotherm model obeyed the Freundlich isotherm. This explains the ammonium ion adsorption onto CSAC which was a multilayer adsorption with intraparticle diffusion. Negative enthalpy confirmed that this adsorption process was exothermic. The instrumental analyses confirmed the adsorption of ammonium ion onto CSAC.

  8. Clean production of corn stover pulp using KOH+NH4OH solution and its kinetic during delignification

    Directory of Open Access Journals (Sweden)

    Sun Yong

    2012-01-01

    Full Text Available The self-made KOH together with NH4OH pulping of corn stover was investigated. The combined alkaline system could effectively remove lignin during pulping. There are three stages of lignin removal during delginification. Approximately 90% of lignin could be removed after temperature reached 150ºC for over 30 minutes. The p-hydroxyl phenol groups in lignin could be completely removed during the delignification reaction. The tendency of the increase of the crystalline degree of cellulose is observed with increase of reaction temperature. The kinetics of delignification is found to be the first order with respect to the remained lignin and the 0.4 order with respect to the remained hydroxide concentration. The activation energy of delignification is 23 kJ/mol. The solution obtained from precipitation of lignin is rich in nitrogen, phosphorous, potassium elements and organic matters. Various techniques including FT-IR, GPC, DSC, were applied to characterize the acid precipitated lignin. The result shows that the lignin with the polydispersity of 1.4 still maintains the p-coumaryl, coniferyl, and sinapyl units in its matrix.

  9. Effective Remediation of Lead Ions from Aqueous Solution by Chemically Carbonized Rubber Wood Sawdust: Equilibrium, Kinetics, and Thermodynamic Study

    Directory of Open Access Journals (Sweden)

    Swarup Biswas

    2015-01-01

    Full Text Available Rubber wood sawdust was carbonized into charcoal by chemical treatment which was used for removal of lead ion from aqueous solution. The work involves batch experiments to investigate the pH effect, initial concentration of adsorbate, contact time, and adsorbent dose. Experimental data confirmed that the adsorption capacities increased with increasing inlet concentration and bed height and decreased with increasing flow rate. Adsorption results showed a maximum adsorption capacity of 37 mg/g at 308 K. Langmuir, Freundlich, and Temkin model adsorption isotherm models were applied to analyze the process where Temkin was found as a best fitted model for present study. Simultaneously kinetics of adsorption like pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were investigated. Thermodynamic parameters were used to analyze the adsorption experiment. Fourier transform infrared spectroscopy, scanning electron microscope, and energy dispersive X-ray spectroscopy confirmed the batch adsorption of lead ion onto chemically carbonized rubber wood sawdust.

  10. Kinetics and Thermodynamics of Sorption of 4-Nitrophenol on Activated Kaolinitic Clay and Jatropha Curcas Activated Carbon from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Samsudeen Olanrewaju Azeez

    2016-06-01

    Full Text Available Adsorption behaviour of 4-nitrophenol (4-NP on activated kaolinitic clay and Jatropha curcas activated carbon was investigated. The kaolinitic clay and Jatropha curcas were activated with 1 M HNO3 and 0.5 M NaOH respectively and were characterized by XRF, XRD, BET, SEM and FTIR techniques. The effects of processing parameters, such as initial 4-NP concentration, temperature, pH, contact time and adsorbent dosage on the adsorption process were investigated. The results obtained showed that Jatropha curcas activated carbon exhibited higher performance than activated kaolinitic clay for the removal of 4-nitrophenol from aqueous solution. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models were used to describe the adsorption isotherms. The adsorption data were best fitted with Freundlich model. The experimental data of the two adsorbate-adsorbent systems fitted very well with the pseudo-second order kinetic model with r2 values of 0.999 respectively. Adsorption thermodynamic parameters were also estimated. The results revealed that the adsorption of 4-nitrophenol onto both adsorbents were exothermic processes and spontaneous for Jatropha curcas activated carbon but non spontaneous for activated kaolinitic clay.

  11. Kinetics and thermodynamics of sorption of 4-nitrophenol on activated kaolinitic clay and jatropha curcas activated carbon from aqueous solution

    International Nuclear Information System (INIS)

    Azeez, S.O.; Adekola, F.A.

    2016-01-01

    Adsorption behaviour of 4-nitrophenol (4-NP) on activated kaolinitic clay and Jatropha curcas activated carbon was investigated. The kaolinitic clay and Jatropha curcas were activated with 1 M HNO/sub 3/ and 0.5 M NaOH respectively and were characterized by XRF, XRD, BET, SEM and FTIR techniques. The effects of processing parameters, such as initial 4-NP concentration, temperature, pH, contact time and adsorbent dosage on the adsorption process were investigated. The results obtained showed that Jatropha curcas activated carbon exhibited higher performance than activated kaolinitic clay for the removal of 4-nitrophenol from aqueous solution. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models were used to describe the adsorption isotherms. The adsorption data were best fitted with Freundlich model. The experimental data of the two adsorbate-adsorbent systems fitted very well with the pseudosecond order kinetic model with r2 values of 0.999 respectively. Adsorption thermodynamic parameters were also estimated. The results revealed that the adsorption of 4-nitrophenol onto both adsorbents were exothermic processes and spontaneous for Jatropha curcas activated carbon but non spontaneous for activated kaolinitic clay. (author)

  12. Kinetics, equilibrium and thermodynamic studies on biosorption of Ag(I) from aqueous solution by macrofungus Pleurotus platypus.

    Science.gov (United States)

    Das, Devlina; Das, Nilanjana; Mathew, Lazar

    2010-12-15

    Reports are available on silver binding capacity of some microorganisms. However, reports on the equilibrium studies on biosorption of silver by macrofungi are seldom known. The present study was carried out in a batch system using dead biomass of macrofungus Pleurotus platypus for the sorption of Ag(I). P. platypus exhibited the highest silver uptake of 46.7 mg g(-1) of biomass at pH 6.0 in the presence of 200 mg L(-1) Ag(I) at 20°C. Kinetic studies based on fractional power, zero order, first order, pseudo-first order, Elovich, second order and pseudo-second order rate expressions have been carried out. The results showed a very good compliance with the pseudo-first order model. The experimental data were analyzed using two parameter isotherms (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Halsey), three parameter isotherms (Redlich-Peterson, Sips, Khan, Koble-Corrigan, Hill, Toth, Radke-Prausmitz, Jossens, Langmuir-Freundlich), four parameter isotherms (Weber-van Vliet, Fritz-Schlunder, Baudu) and five parameter isotherm (Fritz-Schlunder). Thermodynamic parameters of the biosorption (ΔG, ΔH and ΔS) were also determined. The present study confirmed that macrofungus P. platypus may be used as a cost effective efficient biosorbent for the removal of Ag(I) ions from aqueous solution. Copyright © 2010 Elsevier B.V. All rights reserved.

  13. Periodic protein adsorption at the gold/biotin aqueous solution interface: evidence of kinetics with time delay

    Science.gov (United States)

    Neff, H.; Laborde, H. M.; Lima, A. M. N.

    2016-11-01

    An oscillatory molecular adsorption pattern of the protein neutravidin from aqueous solution onto gold, in presence of a pre-deposited self assembled mono-molecular biotin film, is reported. Real time surface Plasmon resonance sensing was utilized for evaluation of the adsorption kinetics. Two different fractions were identified: in the initial phase, protein molecules attach irreversibly onto the Biotin ligands beneath towards the jamming limit, forming a neutravidin-biotin fraction. Afterwards, the growth rate exhibits distinct, albeit damped adsorption-desorption oscillations over an extended time span, assigned to a quasi reversibly bound fraction. These findings agree with, and firstly confirm a previously published model, proposing macro-molecular adsorption with time delay. The non-linear dynamic model is applicable to and also resembles non-damped oscillatory binding features of the hetero-catalytic oxidation of carbon monoxide molecules on platinum in the gas phase. An associated surface residence time can be linked to the dynamics and time scale required for self-organization.

  14. The removal of Cr(VI from aqueous solution by almond green hull waste material: kinetic and equilibrium studies

    Directory of Open Access Journals (Sweden)

    Negin Nasseh

    2017-12-01

    Full Text Available The discharge of industrial effluents containing hexavalent chromium into the environment can be very harmful to living things. Therefore, prior to effluent discharge into the environment, hexavalent chromium should be removed from contaminated water and especially from wastewaters. In the present work, almond green hull powder (AGHP was investigated for the removal of hexavalent chromium from wastewater. The effects of pH (2–10, adsorbent dose (2–24 g L−1, Cr(VI concentration (10–100 mg L−1, contact time (1–60 min, and temperature (5–50 °C were studied. All the experiments were performed in triplicate and average results were reported. The surface morphology, pore volume and size, pH of zero point charge (pHZPC and surface functional groups of AGHP were characterized. Isotherm and kinetic evaluations were also conducted in the present study. The results revealed that the adsorption of Cr(VI by AGHP was an adsorbate, adsorbent, and temperature dependent process that was favorable under acidic conditions. Furthermore, AGHP absorbed over 99% of chromium from the solutions containing 10–100 mg L−1 of Cr(VI based on the Freundlich model. In summary, hexavalent chromium was not found in almond kernel. Biosorption onto AGHP is an affordable and economical adsorption process for treating Cr(VI-laden industrial wastewater.

  15. Kinetics of CO2 with primary and secondary amines in aqueous solutions I. Zwitterion deprotonation kinetics for DEA and DIPA in aqueous blends of alkanolamines

    NARCIS (Netherlands)

    Littel, R.J.; Littel, R.J.; Versteeg, Geert; van Swaaij, Willibrordus Petrus Maria

    1992-01-01

    The deprotonation kinetics of the DEA—CO2 and the DIPA—CO2 zwitterions have been studied in aqueous blends of amines at 298 K. Amine mixtures investigated were: DEA—TEA, DEA—MDEA, DEA—DMMEA, DEA—DEMEA, DIPA—TEA. DIPA—MDEA, DIPA—DMMEA, DIPA—DEMEA. For each blend the zwitterion deprotonation constant

  16. Kinetics and selectivity of the oxidation of methylbenzenes in Co(III)-CH3COOH-CF3COOH solutions. Comparison with nitration and hydroxylation reactions

    International Nuclear Information System (INIS)

    Rudakov, E.S.; Lobachev, V.L.

    1989-01-01

    Data have been obtained concerning the kinetics, substrate selectivity, and kinetic isotope effect for the first stage in the oxidation of a series of arenes, from benzene to hexamethylbenzene, by Co(III) acetate in CH 3 COOH-CF 3 COOH (1.9 M) solutions at 25 degree C. A similarity was noted between substrate selectivity for reactions of alkylbenzenes with Co(III) and electrophilic nitration reactions, which occur via an electron transfer step. It was also found that substrate selectivity for these reactions differs significantly from that found for electrophilic hydroxylation reactions, which occur via an intermediate slow step involving σ-complex formation

  17. Kinetics of the Reduction of Cadmium Sulfate by Thiourea Dioxide in an Aqueous Ammonia Solution upon the Metallization of Carbon Fiber

    Science.gov (United States)

    Polenov, Yu. V.; Egorova, E. V.; Shestakov, G. A.

    2018-01-01

    The kinetics of the decomposition of thiourea dioxide and the reduction of cadmium cations by thiourea dioxide in an aqueous ammonia solution are studied. The kinetic parameters of these reactions are calculated using experimental data, allowing us to adjust conditions for the synthesis of cadmium coatings on carbon fiber of grade UKN-M-12K. The presence of the metal crystalline phase on the fiber is confirmed by means of X-ray diffraction, and its amount is measured via atomic absorption spectroscopy.

  18. Kinetics and mechanisms of the oxidation of iodide and bromide in aqueous solutions by a trans-dioxoruthenium(VI) complex.

    Science.gov (United States)

    Lam, William W Y; Man, Wai-Lun; Wang, Yi-Ning; Lau, Tai-Chu

    2008-08-04

    The kinetics and mechanisms of the oxidation of I (-) and Br (-) by trans-[Ru (VI)(N 2O 2)(O) 2] (2+) have been investigated in aqueous solutions. The reactions have the following stoichiometry: trans-[Ru (VI)(N 2O 2)(O) 2] (2+) + 3X (-) + 2H (+) --> trans-[Ru (IV)(N 2O 2)(O)(OH 2)] (2+) + X 3 (-) (X = Br, I). In the oxidation of I (-) the I 3 (-)is produced in two distinct phases. The first phase produces 45% of I 3 (-) with the rate law d[I 3 (-)]/dt = ( k a + k b[H (+)])[Ru (VI)][I (-)]. The remaining I 3 (-) is produced in the second phase which is much slower, and it follows first-order kinetics but the rate constant is independent of [I (-)], [H (+)], and ionic strength. In the proposed mechanism the first phase involves formation of a charge-transfer complex between Ru (VI) and I (-), which then undergoes a parallel acid-catalyzed oxygen atom transfer to produce [Ru (IV)(N 2O 2)(O)(OHI)] (2+), and a one electron transfer to give [Ru (V)(N 2O 2)(O)(OH)] (2+) and I (*). [Ru (V)(N 2O 2)(O)(OH)] (2+) is a stronger oxidant than [Ru (VI)(N 2O 2)(O) 2] (2+) and will rapidly oxidize another I (-) to I (*). In the second phase the [Ru (IV)(N 2O 2)(O)(OHI)] (2+) undergoes rate-limiting aquation to produce HOI which reacts rapidly with I (-) to produce I 2. In the oxidation of Br (-) the rate law is -d[Ru (VI)]/d t = {( k a2 + k b2[H (+)]) + ( k a3 + k b3[H (+)]) [Br (-)]}[Ru (VI)][Br (-)]. At 298.0 K and I = 0.1 M, k a2 = (2.03 +/- 0.03) x 10 (-2) M (-1) s (-1), k b2 = (1.50 +/- 0.07) x 10 (-1) M (-2) s (-1), k a3 = (7.22 +/- 2.19) x 10 (-1) M (-2) s (-1) and k b3 = (4.85 +/- 0.04) x 10 (2) M (-3) s (-1). The proposed mechanism involves initial oxygen atom transfer from trans-[Ru (VI)(N 2O 2)(O) 2] (2+) to Br (-) to give trans-[Ru (IV)(N 2O 2)(O)(OBr)] (+), which then undergoes parallel aquation and oxidation of Br (-), and both reactions are acid-catalyzed.

  19. Adsorption Kinetics of Cd(ll and Pb(ll Ions from Aqueous Solutions by Bamboo-Based Activated Charcoal and Bamboo Dust

    Directory of Open Access Journals (Sweden)

    Stevens Azubuike Odoemelam

    2015-01-01

    Full Text Available The use of bamboo dust (BD and bamboo-based activated charcoal for adsorption of Pb(ll and Cd(ll ions from aqueous solutions were assessed in this work. The effect of contact time on the uptake of these metal ions was studied in batch process. The adsorption data were correlated with pseudo first-order, pseudo second-order and diffusivity kinetic models. Results show that pseudo second-order kinetic model gave the best description for the adsorption process. Kinetic studies further showed that the adsorption transport mechanism was particle-diffusion controlled for the adsorption process. Results obtained generally showed that lead(ll ions were better adsorbed onto both adsorbents as compared to cadmium(ll. Comparison of sorption capacity for the two adsorbents shows that bamboo-based activated charcoal exhibited better removal for the metal ions than the bamboo dust.

  20. Kinetic and thermodynamic aspects of Cu(II) and Cr(III) removal from aqueous solutions using rose waste biomass

    International Nuclear Information System (INIS)

    Iftikhar, Abdur Rauf; Bhatti, Haq Nawaz; Hanif, Muhammad Asif; Nadeem, Razyia

    2009-01-01

    Distillation waste of rose petals was used to remove Cu(II) and Cr(III) from aqueous solutions. The results demonstrated the dependency of metal sorption on pH, sorbent dose, sorbent size, initial bulk concentration, time and temperature. A dosage of 1 g/L of rose waste biomass was found to be effective for maximum uptake of Cu(II) and Cr(III). Optimum sorption temperature and pH for Cu(II) and Cr(III) were 303 ± 1 K and 5, respectively. The Freundlich regression model and pseudo-second-order kinetic model were resulted in high correlation coefficients and described well the sorption of Cu(II) and Cr(III) on rose waste biomass. At equilibrium q max (mg/g) of Cu(II) and Cr(III) was 55.79 and 67.34, respectively. The free energy change (ΔG o ) for Cu(II) and Cr(III) sorption process was found to be -0.829 kJ/mol and -1.85 kJ/mol, respectively, which indicates the spontaneous nature of sorption process. Other thermodynamic parameters such as entropy change (ΔS o ), enthalpy (ΔH o )and activation energy (ΔE) were found to be 0.604 J mol -1 K -1 , -186.95 kJ/mol and 68.53 kJ/mol, respectively for Cu(II) and 0.397 J mol -1 K -1 , -119.79 kJ/mol and 114.45 kJ/mol, respectively for Cr(III). The main novelty of this work was the determination of shortest possible sorption time for Cu(II) and Cr(III) in comparison to earlier studies. Almost over 98% of Cu(II) and Cr(III) were removed in only first 20 min at an initial concentration of 100 mg/L

  1. Effect of medium acidity on the thermodynamics and kinetics of the reaction of pyridoxal 5'-phosphate with isoniazid in an aqueous solution

    Science.gov (United States)

    Gamov, G. A.; Zavalishin, M. N.; Usacheva, T. R.; Sharnin, V. A.

    2017-05-01

    Thermodynamic characteristics of the formation of the Schiff base between isoniazid and pyridoxal 5'-phosphate in an aqueous solution at different pH values of a medium are determined by means of spectrophotometry and calorimetric titration. The process kinetics is studied spectrophotometrically, and the reaction rate constants for the formation of the imine at different acidities of a medium are determined. Biochemical aspects of the binding of pyridoxal 5'-phosphate into stable compounds are discussed.

  2. Kinetics of the rapid reaction Br/sub 2/ + 2 I/sup -/. -->. I/sub 2/ + 2 Br/sup -/ in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Rao, T S; Mali, S I; Dangat, V T [Presidency Coll., Calcutta (India). Dept. of Chemistry

    1979-01-01

    The displacement of iodine from aqueous iodide ion solutions by bromine is a rapid reaction whose kinetics has been studied by the competition technique. The reaction is of second order, having a specific rate of 6.85 x 10/sup 5/ M/sup -1/ s/sup -1/ at 25.0 /sup 0/C and energy of activation of 30.8 kJ mol/sup -1/. A mechanism for the reaction is proposed.

  3. Removal of ibuprofen, naproxen and carbamazepine in aqueous solution onto natural clay: equilibrium, kinetics, and thermodynamic study

    Science.gov (United States)

    Khazri, Hassen; Ghorbel-Abid, Ibtissem; Kalfat, Rafik; Trabelsi-Ayadi, Malika

    2017-10-01

    This study aimed to describe the adsorption of three pharmaceuticals compounds (ibuprofen, naproxen and carbamazepine) onto natural clay on the basis of equilibrium parameters such as a function of time, effect of pH, varying of the concentration and the temperature. Adsorption kinetic data were modeled using the Lagergren's first-order and the pseudo-second-order kinetic equations. The kinetic results of adsorption are described better using the pseudo-second order model. The isotherm results were tested in the Langmuir, Freundlich and Dubinin-Radushkevich models. The thermodynamic parameters obtained indicate that the adsorption of pharmaceuticals on the clay is a spontaneous and endothermic process.

  4. Competition between organics and bromide at the aqueous solution-air interface as seen from ozone uptake kinetics and X-ray photoelectron spectroscopy.

    Science.gov (United States)

    Lee, Ming-Tao; Brown, Matthew A; Kato, Shunsuke; Kleibert, Armin; Türler, Andreas; Ammann, Markus

    2015-05-14

    A more detailed understanding of the heterogeneous chemistry of halogenated species in the marine boundary layer is required. Here, we studied the reaction of ozone (O3) with NaBr solutions in the presence and absence of citric acid (C6H8O7) under ambient conditions. Citric acid is used as a proxy for oxidized organic material present at the ocean surface or in sea spray aerosol. On neat NaBr solutions, the observed kinetics is consistent with bulk reaction-limited uptake, and a second-order rate constant for the reaction of O3 + Br(-) is 57 ± 10 M(-1) s(-1). On mixed NaBr-citric acid aqueous solutions, the uptake kinetics was faster than that predicted by bulk reaction-limited uptake and also faster than expected based on an acid-catalyzed mechanism. X-ray photoelectron spectroscopy (XPS) on a liquid microjet of the same solutions at 1.0 × 10(-3)-1.0 × 10(-4) mbar was used to obtain quantitative insight into the interfacial composition relative to that of the bulk solutions. It revealed that the bromide anion becomes depleted by 30 ± 10% while the sodium cation gets enhanced by 40 ± 20% at the aqueous solution-air interface of a 0.12 M NaBr solution mixed with 2.5 M citric acid in the bulk, attributed to the role of citric acid as a weak surfactant. Therefore, the enhanced reactivity of bromide solutions observed in the presence of citric acid is not necessarily attributable to a surface reaction but could also result from an increased solubility of ozone at higher citric acid concentrations. Whether the acid-catalyzed chemistry may have a larger effect on the surface than in the bulk to offset the effect of bromide depletion also remains open.

  5. RADARS, a bioinformatics solution that automates proteome mass spectral analysis, optimises protein identification, and archives data in a relational database.

    Science.gov (United States)

    Field, Helen I; Fenyö, David; Beavis, Ronald C

    2002-01-01

    RADARS, a rapid, automated, data archiving and retrieval software system for high-throughput proteomic mass spectral data processing and storage, is described. The majority of mass spectrometer data files are compatible with RADARS, for consistent processing. The system automatically takes unprocessed data files, identifies proteins via in silico database searching, then stores the processed data and search results in a relational database suitable for customized reporting. The system is robust, used in 24/7 operation, accessible to multiple users of an intranet through a web browser, may be monitored by Virtual Private Network, and is secure. RADARS is scalable for use on one or many computers, and is suited to multiple processor systems. It can incorporate any local database in FASTA format, and can search protein and DNA databases online. A key feature is a suite of visualisation tools (many available gratis), allowing facile manipulation of spectra, by hand annotation, reanalysis, and access to all procedures. We also described the use of Sonar MS/MS, a novel, rapid search engine requiring 40 MB RAM per process for searches against a genomic or EST database translated in all six reading frames. RADARS reduces the cost of analysis by its efficient algorithms: Sonar MS/MS can identifiy proteins without accurate knowledge of the parent ion mass and without protein tags. Statistical scoring methods provide close-to-expert accuracy and brings robust data analysis to the non-expert user.

  6. The effect of cation:anion ratio in solution on the mechanism of barite growth at constant supersaturation: Role of the desolvation process on the growth kinetics

    Science.gov (United States)

    Kowacz, M.; Putnis, C. V.; Putnis, A.

    2007-11-01

    The mechanism of barite growth has been investigated in a fluid cell of an Atomic Force Microscope by passing solutions of constant supersaturation ( Ω) but variable ion activity ratio ( r=a/a) over a barite substrate.The observed dependence of step-spreading velocity on solution stoichiometry can be explained by considering non-equivalent attachment frequency factors for the cation and anion. We show that the potential for two-dimensional nucleation changes under a constant thermodynamic driving force due to the kinetics of barium integration into the surface, and that the growth mode changes from preexisting step advancement to island spreading as the cation/anion activity ratio increases. Scanning electron microscopy studies of crystals grown in bulk solutions support our findings that matching the ion ratio in the fluid to that of the crystal lattice does not result in maximum growth and nucleation rates. Significantly more rapid rates correspond to solution stoichiometries where [Ba 2+] is in excess with respect to [ SO42-]. Experiments performed in dilute aqueous solutions of methanol show that even 0.02 molar fraction of organic cosolvent in the growth solution significantly accelerates step growth velocity and nucleation rates (while keeping Ω the same as in the reference solution in water). Our observations suggest that the effect of methanol on barite growth results first of all from reduction of the barrier that prevents the Ba 2+ from reaching the surface and corroborate the hypothesis that desolvation of the cation and of the surface is the rate limiting kinetic process for two-dimensional nucleation and for crystal growth.

  7. Kinetic studies for the use of fermented agricultural byproduct by fungi in removal of some toxic metals from their waste solutions

    International Nuclear Information System (INIS)

    Moloukhia, H.; Ouda, S.

    2010-01-01

    A new sorbent material has been developed that sesame stalks as agricultural byproduct which are available at very little or no cost was fermented by fungi to produce high quality sorbent material. Microbial biomass offers an economical option for removing heavy metals by the phenomenon of bio sorption. Fermented sesame stalks by the fungal biomass Aspergillus terreus (Thom), was tested for its ability to remove chromium and cadmium ions from waste solutions. Some significant parameters i.e., contact time, solution ph, mass of sorbent material and the effect of metal concentrations were investigated. Desorption studies were also performed. The kinetic of sorption was evaluated by applying the Lagergren equation. Results showed that the ph of the solution strongly affected the degree of bio sorption of metal ions by biomass. The metal ion sorption obeyed Freundlich isotherm. It was found that the exponent 1/n is in the range of 1> 1/n > 0, which signify that strong adsorptive forces are operative on the surface of the fermented sesame stalks by fungal biomass. The kinetics of sorption indicated that the removal of both chromium and cadmium ions from solution follows a first-order reaction with fast rate. It could be concluded that fermented sesame stalks by the fungal biomass Aspergillus terreus (Thom), can be considered as an economical alternative sorbent material for the removal of heavy metals from wastewater by the phenomenon of bio sorption

  8. Experimental Database with Baseline CFD Solutions: 2-D and Axisymmetric Hypersonic Shock-Wave/Turbulent-Boundary-Layer Interactions

    Science.gov (United States)

    Marvin, Joseph G.; Brown, James L.; Gnoffo, Peter A.

    2013-01-01

    A database compilation of hypersonic shock-wave/turbulent boundary layer experiments is provided. The experiments selected for the database are either 2D or axisymmetric, and include both compression corner and impinging type SWTBL interactions. The strength of the interactions range from attached to incipient separation to fully separated flows. The experiments were chosen based on criterion to ensure quality of the datasets, to be relevant to NASA's missions and to be useful for validation and uncertainty assessment of CFD Navier-Stokes predictive methods, both now and in the future. An emphasis on datasets selected was on surface pressures and surface heating throughout the interaction, but include some wall shear stress distributions and flowfield profiles. Included, for selected cases, are example CFD grids and setup information, along with surface pressure and wall heating results from simulations using current NASA real-gas Navier-Stokes codes by which future CFD investigators can compare and evaluate physics modeling improvements and validation and uncertainty assessments of future CFD code developments. The experimental database is presented tabulated in the Appendices describing each experiment. The database is also provided in computer-readable ASCII files located on a companion DVD.

  9. Kinetics and mechanism of oxidation of 1-hydroxymethyl-eta/sup 3/-allypalladium chloride by p-benzoquinone in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Belov, A.P.; Kalabin, S.M.; Statsenko, O.N.

    1988-03-01

    /sup 1/H NMR spectroscopy was used to show that the primary product of the oxidation of the eta/sup 3/-allyl complex of palladium, (based on 1,3-butadiene-1-hydroxymethyl-eta/sup 3/-allylpalladium chloride), by the action of p-benzoquinone in acid aqueous solutions is 4-chloro-2-buten-1-o1. The reaction kinetics were studied colorimetrically. It was found that the rate of reaction is described by a kinetic equation of the second order (first with respect to each of the reagents). It was shown that the second order rate constant increases nonlinearly with increase in the concentration of the chloride ions and hydrogen ions, and tends to a constant value in the region of high concentrations of these ions. The values of the activation parameters and the isotopic kinetic effect were determined. The kinetic equation and the mechanism of the reaction studied were compared with those of the oxidation processes of unsubstituted eta/sup 3/-allyl complexes of palladium.

  10. A look at the density functional theory zoo with the advanced GMTKN55 database for general main group thermochemistry, kinetics and noncovalent interactions.

    Science.gov (United States)

    Goerigk, Lars; Hansen, Andreas; Bauer, Christoph; Ehrlich, Stephan; Najibi, Asim; Grimme, Stefan

    2017-12-13

    We present the GMTKN55 benchmark database for general main group thermochemistry, kinetics and noncovalent interactions. Compared to its popular predecessor GMTKN30 [Goerigk and Grimme J. Chem. Theory Comput., 2011, 7, 291], it allows assessment across a larger variety of chemical problems-with 13 new benchmark sets being presented for the first time-and it also provides reference values of significantly higher quality for most sets. GMTKN55 comprises 1505 relative energies based on 2462 single-point calculations and it is accessible to the user community via a dedicated website. Herein, we demonstrate the importance of better reference values, and we re-emphasise the need for London-dispersion corrections in density functional theory (DFT) treatments of thermochemical problems, including Minnesota methods. We assessed 217 variations of dispersion-corrected and -uncorrected density functional approximations, and carried out a detailed analysis of 83 of them to identify robust and reliable approaches. Double-hybrid functionals are the most reliable approaches for thermochemistry and noncovalent interactions, and they should be used whenever technically feasible. These are, in particular, DSD-BLYP-D3(BJ), DSD-PBEP86-D3(BJ), and B2GPPLYP-D3(BJ). The best hybrids are ωB97X-V, M052X-D3(0), and ωB97X-D3, but we also recommend PW6B95-D3(BJ) as the best conventional global hybrid. At the meta-generalised-gradient (meta-GGA) level, the SCAN-D3(BJ) method can be recommended. Other meta-GGAs are outperformed by the GGA functionals revPBE-D3(BJ), B97-D3(BJ), and OLYP-D3(BJ). We note that many popular methods, such as B3LYP, are not part of our recommendations. In fact, with our results we hope to inspire a change in the user community's perception of common DFT methods. We also encourage method developers to use GMTKN55 for cross-validation studies of new methodologies.

  11. Kinetic Rate Law Parameter Measurements on a Borosilicate Waste Glass: Effect of Temperature, pH, and Solution Composition on Alkali Ion Exchange

    International Nuclear Information System (INIS)

    Pierce, Eric M.; McGrail, B PETER.; Icenhower, J P.; Rodriguez, Elsa A.; Steele, Jackie L.; Baum, Steven R.

    2004-01-01

    The reaction kinetics of glass is controlled by matrix dissolution and ion exchange (IEX). Dissolution of an alkali-rich simulated borosilicate waste glass was investigated using single-pass flow-through (SPFT) experiments. Experiments were conducted as a function of temperature, pH, and solution composition by varying the SiO 2 (aq) activity in the influent solution. Results showed that under dilute conditions matrix dissolution increased with increasing pH and temperature, and decreased with increasing SiO 2 (aq) activity. IEX rates decreased with increasing pH and temperature, and increased with increasing SiO 2 (aq) activity. Over the solution composition range interrogated in this study the dominant dissolution mechanism changed from matrix dissolution to IEX. These results suggest that ''secondary'' reactions may become dominant under certain environmental conditions and emphasize the need to incorporate these reactions into dissolution rate models

  12. Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO3 (-) and SO3 (2-) in Aqueous Solution.

    Science.gov (United States)

    Wang, Qian; Zhao, Hong Yan; Man, Wai-Lun; Lam, William W Y; Lau, Kai-Chung; Lau, Tai-Chu

    2016-07-25

    The kinetics and mechanism of the reaction of S(IV) (SO3 (2-) +HSO3 (-) ) with a ruthenium(VI) nitrido complex, [(L)Ru(VI) (N)(OH2 )](+) (Ru(VI) N, L=N,N'-bis(salicylidene)-o-cyclohexyldiamine dianion), in aqueous acidic solutions are reported. The kinetic results are consistent with parallel pathways involving oxidation of HSO3 (-) and SO3 (2-) by Ru(VI) N. A deuterium isotope effect of 4.7 is observed in the HSO3 (-) pathway. Based on experimental results and DFT calculations the proposed mechanism involves concerted N-S bond formation (partial N-atom transfer) between Ru(VI) N and HSO3 (-) and H(+) transfer from HSO3 (-) to a H2 O molecule. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Coupled electron and atomic kinetics through the solution of the Boltzmann equation for generating time-dependent X-ray spectra

    International Nuclear Information System (INIS)

    Sherrill, M.E.; Abdallah, J. Jr.; Csanak, G.; Kilcrease, D.P.; Dodd, E.S.; Fukuda, Y.; Akahane, Y.; Aoyama, M.; Inoue, N.; Ueda, H.; Yamakawa, K.; Faenov, A.Ya.; Magunov, A.I.; Pikuz, T.A.; Skobelev, I.Yu.

    2006-01-01

    In this work, we present a model that solves self-consistently the electron and atomic kinetics to characterize highly non-equilibrium plasmas, in particular for those systems where both the electron distribution function is far from Maxwellian and the evolution of the ion level populations are dominated by time-dependent atomic kinetics. In this model, level populations are obtained from a detailed collisional-radiative model where collision rates are computed from a time varying electron distribution function obtained from the solution of the zero-dimensional Boltzmann equation. The Boltzmann collision term includes the effects of electron-electron collisions, electron collisional ionization, excitation and de-excitation. An application for He α spectra from a short pulse laser irradiated argon cluster target will be shown to illustrate the results of our model

  14. Solution of the point kinetics equations in the presence of Newtonian temperature feedback by Pade approximations via the analytical inversion method

    International Nuclear Information System (INIS)

    Aboanber, A E; Nahla, A A

    2002-01-01

    A method based on the Pade approximations is applied to the solution of the point kinetics equations with a time varying reactivity. The technique consists of treating explicitly the roots of the inhour formula. A significant improvement has been observed by treating explicitly the most dominant roots of the inhour equation, which usually would make the Pade approximation inaccurate. Also the analytical inversion method which permits a fast inversion of polynomials of the point kinetics matrix is applied to the Pade approximations. Results are presented for several cases of Pade approximations using various options of the method with different types of reactivity. The formalism is applicable equally well to non-linear problems, where the reactivity depends on the neutron density through temperature feedback. It was evident that the presented method is particularly good for cases in which the reactivity can be represented by a series of steps and performed quite well for more general cases

  15. Coupled electron and atomic kinetics through the solution of the Boltzmann equation for generating time-dependent X-ray spectra

    Energy Technology Data Exchange (ETDEWEB)

    Sherrill, M.E. [Los Alamos National Laboratory, T-4, Los Alamos, NM 87545 (United States)]. E-mail: manolo@t4.lanl.gov; Abdallah, J. Jr. [Los Alamos National Laboratory, T-4, Los Alamos, NM 87545 (United States); Csanak, G. [Los Alamos National Laboratory, T-4, Los Alamos, NM 87545 (United States); Kilcrease, D.P. [Los Alamos National Laboratory, T-4, Los Alamos, NM 87545 (United States); Dodd, E.S. [Los Alamos National Laboratory, X-1, Los Alamos, NM 87545 (United States); Fukuda, Y. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Akahane, Y. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Aoyama, M. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Inoue, N. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Ueda, H. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Yamakawa, K. [Advanced Photon Research Center, JAERI, Kyoto 619-0215 (Japan); Faenov, A.Ya. [Multicharged Ions Spectra Data Center of VNIIFTRI, Mendeleevo, Moscow Region 141570 (Russian Federation); Magunov, A.I. [Multicharged Ions Spectra Data Center of VNIIFTRI, Mendeleevo, Moscow Region 141570 (Russian Federation); Pikuz, T.A. [Multicharged Ions Spectra Data Center of VNIIFTRI, Mendeleevo, Moscow Region 141570 (Russian Federation); Skobelev, I.Yu. [Multicharged Ions Spectra Data Center of VNIIFTRI, Mendeleevo, Moscow Region 141570 (Russian Federation)

    2006-05-15

    In this work, we present a model that solves self-consistently the electron and atomic kinetics to characterize highly non-equilibrium plasmas, in particular for those systems where both the electron distribution function is far from Maxwellian and the evolution of the ion level populations are dominated by time-dependent atomic kinetics. In this model, level populations are obtained from a detailed collisional-radiative model where collision rates are computed from a time varying electron distribution function obtained from the solution of the zero-dimensional Boltzmann equation. The Boltzmann collision term includes the effects of electron-electron collisions, electron collisional ionization, excitation and de-excitation. An application for He{sub {alpha}} spectra from a short pulse laser irradiated argon cluster target will be shown to illustrate the results of our model.

  16. Passivation kinetics of Mg-Nd-Gd-Zn-Zr (EV31A and Mg-Y-Nd-Gd-Zr (WE43C in NaOH solutions

    Directory of Open Access Journals (Sweden)

    Jakraphan Ninlachart

    2017-09-01

    Full Text Available Passivation kinetics of two Mg-RE alloys, such as Mg-Nd-Gd-Zn-Zr (EV31A, and Mg-Y-Nd-Gd-Zr (WE43C were investigated in two different heat treated conditions (solution treated and overaged in 0.01 - 1.0 M NaOH solutions under potentiostatic conditions. Negative reaction order was observed in dilute NaOH which transitioned to positive values as the passivation time increased and in the 1 M NaOH as well. The passive layers showed platelet morphology and the size of the platelets decreased with increase in the NaOH concentration. The hydrogen evolution reaction (HER kinetics was not improved on the passive layer covered surface of the Mg-RE alloys in contrast to the improvements reported on the hydroxide covered pure magnesium. The electrochemical impedance increased with increase in the NaOH concentration in the solution treated condition of both Mg-RE alloys, whereas the overaged EV31A alloy showed a reverse trend. The passive layer of EV31A showed almost 100% higher charge carrier density than the film formed on the WE43C in the overaged condition. A better passivation behavior was observed in the solution treated condition than that in the overaged condition which could be attributed to the uniform distribution of the RE elements in the solution treated specimens. The WE43C alloy revealed better corrosion resistance in the alkaline solution than the EV31A alloy.

  17. Reactant-solute encounters in aqueous solutions studied by kinetic methods: hydration cosphere overlap and camouflage effects : hydration cosphere overlap and camouflage effects

    NARCIS (Netherlands)

    Engberts, Jan B.F.N.; Blandamer, Michael J.

    1998-01-01

    Rates of chemical reactions in aqueous solutions are often sensitive to low concentrations of added solutes such as ureas, alcohols, α-amino acids and carbohydrates. In this work, several simple chemical reactions were used to probe this sensitivity, which arises from interactions between added

  18. Structure, Dynamics, and Kinetics of Weak Protein-Protein Complexes from NMR Spin Relaxation Measurements of Titrated Solutions

    International Nuclear Information System (INIS)

    Salmon, L.; Licinio, A.; Jensen, M.R.; Blackledge, M.; Ortega Roldan, J.L.; Van Nuland, N.; Lescop, E.

    2011-01-01

    We have recently presented a titration approach for the determination of residual dipolar couplings (RDCs) from experimentally inaccessible complexes. Here, we extend this approach to the measurement of 15 N spin relaxation rates and demonstrate that this can provide long-range structural, dynamic, and kinetic information about these elusive systems. (authors)

  19. Radionuclide transport in fractured porous media -- Analytical solutions for a system of parallel fractures with a kinetic solubility-limited dissolution model

    International Nuclear Information System (INIS)

    Li, S.H.; Chen, C.T.

    1997-01-01

    Analytical solutions are developed for the problem of radionuclide transport in a system of parallel fractures situated in a porous rock matrix. A kinetic solubility-limited dissolution model is used as the inlet boundary condition. The solutions consider the following processes: (a) advective transport in the fractures, (b) mechanical dispersion and molecular diffusion along the fractures, (c) molecular diffusion from a fracture to the porous matrix, (d) molecular diffusion within the porous matrix in the direction perpendicular to the fracture axis, (e) adsorption onto the fracture wall, (f) adsorption within the porous matrix, and (g) radioactive decay. The solutions are based on the Laplace transform method. The general transient solution is in the form of a double integral that is evaluated using composite Gauss-Legendre quadrature. A simpler transient solution that is in the form of a single integral is also presented for the case that assumes negligible longitudinal dispersion along the fractures. The steady-state solutions are also provided. A number of examples are given to illustrate the effects of the following important parameters: (a) fracture spacings, (b) dissolution-rate constants, (c) fracture dispersion coefficient, (d) matrix retardation factor, and (e) fracture retardation factor

  20. A Kinetic Model for β-Amyloid Adsorption at the Air/Solution Interface and Its Implication to the β-Amyloid Aggregation Process

    Science.gov (United States)

    Jiang, Dianlu; Dinh, Kim Lien; Ruthenburg, Travis; Zhang, Yi; Su, Lei; Land, Donald; Zhou, Feimeng

    2011-01-01

    The kinetics of adsorption at the air/buffer solution interface of amyloid beta peptide, Aβ(1–42), whose bulk concentration (submicromolar) is more than two orders of magnitude lower than that typically used in other in vitro aggregation studies, has been studied using a Langmuir-Blodgett trough. The pressure–time curves exhibit a lag phase, wherein the surface pressure essentially remains at zero, and a rising phase, corresponding to the Aβ adsorption at the interface. The duration of the lag phase was found to be highly dependent on both the Aβ bulk concentration and the solution temperature. A large activation energy (62.2 ± 4.1 KJ/mol) was determined and the apparent adsorption rate constant was found to be linearly dependent on the Aβ bulk concentration. Attenuated total reflection-IR spectra of the adsorbed Aβ transferred to a solid substrate and circular dichroism measurements of Aβ in the solution layer near the interface reveal that the natively unstructured Aβ in the bulk undergo a conformation change (folding) to mainly the α-helical structure. The results suggest that, prior to the adsorption step, an equilibrium between Aβ conformations is established within the subsurface. The kinetic equation derived from this model confirms that the overall Aβ adsorption is kinetically controlled and the apparent rate constant is proportional to the Aβ bulk concentration. This model also indicates that interfaces such as cell membranes and lipid bilayers may facilitate Aβ aggregation/fibrillation by providing a thin hydrophobic layer adjacent to the interface for the initial Aβ conformation change (misfolding) and accumulation. Such a preconcentration effect offers a plausible explanation of the fact that Aβ fibrillation occurs in vivo at nanomolar concentrations. Another important biological implication from our work is that Aβ misfolding may occur before its adsorption onto a cell membrane. This general kinetic model should also find

  1. A kinetic model for beta-amyloid adsorption at the air/solution interface and its implication to the beta-amyloid aggregation process.

    Science.gov (United States)

    Jiang, Dianlu; Dinh, Kim Lien; Ruthenburg, Travis C; Zhang, Yi; Su, Lei; Land, Donald P; Zhou, Feimeng

    2009-03-12

    At the air/buffer solution interface the kinetics of adsorption of amyloid beta peptide, Abeta(1-42), whose bulk concentration (submicromolar) is more than 2 orders of magnitude lower than that typically used in other in vitro aggregation studies, has been studied using a Langmuir-Blodgett trough. The pressure-time curves exhibit a lag phase, wherein the surface pressure essentially remains at zero, and a rising phase, corresponding to the Abeta adsorption at the interface. The duration of the lag phase was found to be highly dependent on both the Abeta bulk concentration and the solution temperature. A large activation energy (62.2 +/- 4.1 KJ/mol) was determined and the apparent adsorption rate constant was found to be linearly dependent on the Abeta bulk concentration. Attenuated total reflection-IR spectra of the adsorbed Abeta transferred to a solid substrate and circular dichroism measurements of Abeta in the solution layer near the interface reveal that the natively unstructured Abeta in the bulk undergo a conformation change (folding) to mainly the alpha-helical structure. The results suggest that, prior to the adsorption step, an equilibrium between Abeta conformations is established within the subsurface. The kinetic equation derived from this model confirms that the overall Abeta adsorption is kinetically controlled and the apparent rate constant is proportional to the Abeta bulk concentration. This model also indicates that interfaces such as cell membranes and lipid bilayers may facilitate Abeta aggregation/ fibrillation by providing a thin hydrophobic layer adjacent to the interface for the initial A/beta conformation change (misfolding) and accumulation. Such a preconcentration effect offers a plausible explanation of the fact that Abeta fibrillation occurs in vivo at nanomolar concentrations. Another important biological implication from our work is that Abeta misfolding may occur before its adsorption onto a cell membrane. This general kinetic model

  2. Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: equilibrium, kinetic and thermodynamic study.

    Science.gov (United States)

    Ozdes, Duygu; Gundogdu, Ali; Kemer, Baris; Duran, Celal; Senturk, Hasan Basri; Soylak, Mustafa

    2009-07-30

    The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud (a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4 mg g(-1) for 10 g L(-1) of a-WM concentration. Thermodynamic parameters including the Gibbs free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (DeltaS degrees) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0-40 degrees C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions.

  3. Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: Equilibrium, kinetic and thermodynamic study

    International Nuclear Information System (INIS)

    Ozdes, Duygu; Gundogdu, Ali; Kemer, Baris; Duran, Celal; Senturk, Hasan Basri; Soylak, Mustafa

    2009-01-01

    The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud (a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4 mg g -1 for 10 g L -1 of a-WM concentration. Thermodynamic parameters including the Gibbs free energy (ΔG o ), enthalpy (ΔH o ), and entropy (ΔS o ) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0-40 o C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions.

  4. Removal of Pb(II) ions from aqueous solution by a waste mud from copper mine industry: Equilibrium, kinetic and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Ozdes, Duygu; Gundogdu, Ali; Kemer, Baris; Duran, Celal; Senturk, Hasan Basri [Department of Chemistry, Karadeniz Technical University, Faculty of Arts and Sciences, 61080 Trabzon (Turkey); Soylak, Mustafa, E-mail: soylak@erciyes.edu.tr [Department of Chemistry, Erciyes University, Faculty of Arts and Sciences, 38039 Kayseri (Turkey)

    2009-07-30

    The objective of this study was to assess the adsorption potential of a waste mud (WM) for the removal of lead (Pb(II)) ions from aqueous solutions. The WM was activated with NaOH in order to increase its adsorption capacity. Adsorption studies were conducted in a batch system as a function of solution pH, contact time, initial Pb(II) concentration, activated-waste mud (a-WM) concentration, temperature, etc. Optimum pH was specified as 4.0. The adsorption kinetic studies indicated that the overall adsorption process was best described by pseudo-second-order kinetics. The equilibrium adsorption capacity of a-WM was obtained by using Langmuir and Freundlich isotherm models and both models fitted well. Adsorption capacity for Pb(II) was found to be 24.4 mg g{sup -1} for 10 g L{sup -1} of a-WM concentration. Thermodynamic parameters including the Gibbs free energy ({Delta}G{sup o}), enthalpy ({Delta}H{sup o}), and entropy ({Delta}S{sup o}) indicated that the adsorption of Pb(II) ions on the a-WM was feasible, spontaneous and endothermic, at temperature range of 0-40 {sup o}C. Desorption studies were carried out successfully with diluted HCl solutions. The results indicate that a-WM can be used as an effective and no-cost adsorbent for the treatment of industrial wastewaters contaminated with Pb(II) ions.

  5. Analytical representation for solution of the neutron point kinetics equation with time-dependent reactivity and free of the stiffness character

    International Nuclear Information System (INIS)

    Silva, Milena Wollmann da

    2013-01-01

    In this work, we report a genuine analytical representation for the solution of the neutron point kinetics equation free of the stiffness character, assuming that the reactivity is a continuous and sectionally continuous function of time. To this end, we initially cast the point kinetics equation in a first order linear differential equation. Next, we split the corresponding matrix as a sum of a diagonal matrix with a matrix, whose components contain the off-diagonal elements. Next, expanding the neutron density and the delayed neutron precursors concentrations in a truncated series, and replacing these expansions in the matrix equation, we come out with an equation, which allows to construct a recursive system, a first order matrix differential equation with source. The fundamental characteristic of this system relies on the fact that the corresponding matrix is diagonal, meanwhile the source term is written in terms of the matrix with the off-diagonal components. Further, the first equation of the recursive system has no source and satisfies the initial conditions. On the other hand, the remaining equations satisfy the null initial condition. Due to the diagonal feature of the matrix, we attain analytical solutions for these recursive equations. We also mention that we evaluate the results for any time value, without the analytical continuity because the purposed solution is free on the stiffness character. Finally, we present numerical simulations and comparisons against literature results, considering specific the applications for the following reactivity functions: constant, step, ramp, and sine. (author)

  6. Batch kinetics, isotherm and thermodynamic studies of adsorption of strontium from aqueous solutions onto low cost rice-straw based carbons.

    Directory of Open Access Journals (Sweden)

    S. M. Yakout

    2010-09-01

    Full Text Available Present study explored the feasibility of using waste rice-straw based carbons as adsorbent for the removal of strontium under different experimental conditions. The batch sorption is studied with respect to solute concentration (2.8 - 110 mg/L, contact time, adsorbent dose (2.5 - 20 g/L and solution temperature (25 - 55oC. The Langmuir and Dubinin-Radushkevich adsorption models were applied to experimental equilibrium data and isotherm constants were calculated using linear regression analysis. A comparison of kinetic models applied to the adsorption of strontium on rice-straw carbon was evaluated for the pseudo-second-order, Elovich, intraparticle diffusion and Bangham’s kinetics models. The experimental data fitted very well the pseudosecond-order kinetic model and also followed by intra-particle diffusion model, whereas diffusion is not only the rate-controlling step. The results show that the sorption capacity increases with an increase in solution temperature from 25 to 55 oC. The thermodynamics parameters were evaluated. The positive value of ΔH (40.93 kJ indicated that the adsorption of strontium onto RS1 carbon was endothermic, which result was supported by the increasing adsorption of strontium with temperature. The positive value of ΔS (121.8 kJ/mol reflects good affinity of strontium ions towards the rice-straw based carbons. The results have establishedgood potentiality for the carbons particles to be used as a sorbent for the removal of strontium from wastewater.

  7. Synthesis, characterization, kinetic and thermodynamic studies of the dissolution of ThO2 and of solid solutions Th1-xMxO2 (M = U, Pu)

    International Nuclear Information System (INIS)

    Heisbourg, G.

    2003-12-01

    The aim of this work was to understand the mechanisms of dissolution of ThO 2 and of thorium mixed oxides such as Th 1-x U x O 2 and Th 1-x Pu x O 2 in aqueous, oxygenated or inert media. Several solids have been synthesized by precipitation in oxalic medium: Th 1-x U x O 2 (x= 0.11; 0.24; 0.37; 0.53; 0.67; 0.81 and 0.91) and Th 1-x Pu x O 2 (x= 0.13; 0.32 and 0.66). They have been characterized by XRD, SEM, TEM, XPS, XAS, PIXE and EPMA. The sintering conditions of these materials have been studied and optimized in order to obtain sintered samples with a measured density very near the theoretical densities. A kinetic study of the dissolution of ThO 2 and of solid solutions Th 1-x U x O 2 has been carried out in several aqueous media (HNO 3 , HCl, H 2 SO 4 ) in terms of several parameters: protons concentration, temperature, pH, ionic strength, nature of the electrolyte solution and uranium molar ratio for the solid solutions Th 1-x U x O 2 in order to determine the kinetic laws of dissolution of the solid solutions having different compositions comparatively to ThO 2 . The leaching tests carried out in natural waters of compositions near those of the deep geologic sites considered for the storage of nuclear wastes have shown that the dissolution of the solids was bound to the complexing effect of the constitutional ions of the water considered. The leaching tests carried out on sintered samples of the same composition have led to the same normalized dissolution velocities. The thermodynamic aspect of the dissolution of the solid solutions Th 1-x U x O 2 in nitric medium has been studied at last. (O.M.)

  8. Kinetic modeling of the biosorption of Cd2+ ions from aqueous solutions onto Eichhornia crassipes roots using potentiometry: low-cost alternative to conventional methods

    Directory of Open Access Journals (Sweden)

    Carolina Martínez-Sánchez

    2013-01-01

    Full Text Available This work presents the use of potentiometric measurements for kinetic studies of biosorption of Cd2+ ions from aqueous solutions on Eichhornia crassipes roots. The open circuit potential of the Cd/Cd2+ electrode of the first kind was measured during the bioadsorption process. The amount of Cd2+ ions accumulated was determined in real time. The data were fit to different models, with the pseudo-second-order model proving to be the best in describing the data. The advantages and limitations of the methodology proposed relative to the traditional method are discussed.

  9. NUMERICAL SOLUTION OF STEADY STATE DISPERSION FLOW MODEL FOR LACTOSE-LACTASE HYDROLYSIS WITH DIFFERENT KINETICS IN FIXED BED

    Directory of Open Access Journals (Sweden)

    OLAOSEBIKAN ABIDOYE OLAFADEHAN

    2010-06-01

    Full Text Available A detailed computational procedure for evaluating lactose hydrolysis with immobilized enzyme in a packed bed tubular reactor under dispersion flow conditions is presented. The dispersion flow model for lactose hydrolysis using different kinetics, taking cognizance of external mass transfer resistances, was solved by the method of orthogonal collocation. The reliability of model simulations was tested using experimental data from a laboratory packed bed column, where the -galactosidase of Kluyveromyces fragilis was immobilized on spherical chitosan beads. Comparison of the simulated results with experimental exit conversion shows that the dispersion flow model and using Michaelis-Menten kinetics with competitive product (galactose inhibition are appropriate to interpret the experimental results and simulate the process of lactose hydrolysis in a fixed bed.

  10. Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: Kinetic, equilibrium and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Kul, Ali Riza [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey); Koyuncu, Huelya, E-mail: hkoyuncu@yyu.edu.tr [Forensic Medicine Foundation, Felek Street No. 45, 06300 Kecioren, Ankara (Turkey)

    2010-07-15

    In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore-size distributions of the samples were fully characterized. The adsorption efficiency of Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol{sup -1} for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R{sub L} separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy ({Delta}G), the enthalpy ({Delta}H) and the entropy change of sorption ({Delta}S) were determined as about -5.06, 10.29 and 0.017 kJ mol{sup -1} K{sup -1}, respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously.

  11. Modelling the effect of acoustic waves on the thermodynamics and kinetics of phase transformation in a solution: Including mass transportation.

    Science.gov (United States)

    Haqshenas, S R; Ford, I J; Saffari, N

    2018-01-14

    Effects of acoustic waves on a phase transformation in a metastable phase were investigated in our previous work [S. R. Haqshenas, I. J. Ford, and N. Saffari, "Modelling the effect of acoustic waves on nucleation," J. Chem. Phys. 145, 024315 (2016)]. We developed a non-equimolar dividing surface cluster model and employed it to determine the thermodynamics and kinetics of crystallisation induced by an acoustic field in a mass-conserved system. In the present work, we developed a master equation based on a hybrid Szilard-Fokker-Planck model, which accounts for mass transportation due to acoustic waves. This model can determine the kinetics of nucleation and the early stage of growth of clusters including the Ostwald ripening phenomenon. It was solved numerically to calculate the kinetics of an isothermal sonocrystallisation process in a system with mass transportation. The simulation results show that the effect of mass transportation for different excitations depends on the waveform as well as the imposed boundary conditions and tends to be noticeable in the case of shock waves. The derivations are generic and can be used with any acoustic source and waveform.

  12. REMOVAL OF AN ACID DYE FROM AQUEOUS SOLUTIONS BY ADSORPTION ON A COMMERCIAL GRANULAR ACTIVATED CARBON: EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDY

    Directory of Open Access Journals (Sweden)

    Marius Sebastian Secula

    2011-12-01

    Full Text Available The present paper approaches the study of the adsorption of an acid dye on a commercial granular activated carbon (GAC. Batch experiments were conducted to study the equilibrium isotherms and kinetics of Indigo Carmine on GAC. The kinetic data were analyzed using the Lagargren, Ho, Elovich, Weber-Morris and Bangham models in order to establish the most adequate model that describes this process, and to investigate the rate of IC adsorption. Equilibrium data were fitted to Langmuir and Freundlich isotherms. Langmuir isotherm equilibrium model and Ho kinetic model fitted best the experimental data.The effects of temperature (25 – 45 °C, initial concentration of dye (7.5 – 150 mg•L−1, GAC dose (0.02 – 1 g•L-1, particle size (2 – 7 mm in diameter, solution pH (3 – 11 on GAC adsorption capacity were established. The adsorption process is found to be favored by a neutral pH, high values of temperature and small particle sizes. The highest adsorption capacity (133.8 mg•g-1 of the GAC is obtained at 45 °C. The removal efficiency increases with GAC dose at relatively low initial concentrations of dye. Thermodynamic parameters such as standard enthalpy (H, standard entropy (S and standard free energy (G were evaluated. The adsorption of Indigo Carmine onto GAC is an endothermic process.

  13. Kinetics of polymer degradation in solution. 6. Laser flash photolysis and pulse radiolysis studies of polymethylvinylketone in solution using the light scattering detection method

    Energy Technology Data Exchange (ETDEWEB)

    Lindenau, D; Beavan, S W; Beck, G; Schnabel, W [Hahn-Meitner-Institut fuer Kernforschung Berlin G.m.b.H. (Germany, F.R.)

    1977-01-01

    Polymethylvinylketone (PMVK) was irradiated in solution with 2 ..mu..s pulses of 15 MeV electrons or with 15 ns flashes of 262 nm light. The change of the intensity of the light scattered by the solution (LSI) after the irradiation was measured. For the radiolysis experiments, a main chain scission process tausub(1/2) (decr) approximately 20 ..mu..s) and a subsequent crosslinking process (tausub(1/2) (incr) approximately 0.4 sec) could be discriminated. The LSI change pertaining to the main chain degradation was found to be due to disentanglement diffusion, whereas the LSI change pertaining to the crosslinking process could be correlated to a chemical reaction. The rate constant for combination of lateral macroradicals in acetone solution was estimated as 2 k/sub 2/ - (4.5 +- 1.5)10/sup 6/ M/sup -1/ sec/sup -1/. Stationary irradiation with /sup 60/Co-..gamma..-rays showed that PMVK is predominantly crosslinked to form a macrogel when irradiated in the solid state or in solution at concentrations greater than 100 g/l. At lower concentrations, microgel formation occurred. Photolysis of PMVK in solution yielded only main chain degradation. The LSI change was found to be due to disentanglement diffusion as during radiolysis. It was concluded that the same mechanism for main chain rupture is operative as in radiolysis. Stationary irradiations with uv light (lambda > 260 nm ) resulted in main chain degradation; no indication of crosslinking was obtained.

  14. Comparative analysis of solution methods of the punctual kinetic equations; Analisis comparativo de metodos de solucion de las ecuaciones de cinetica puntual

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez S, A. [UNAM-LAIRN, Jiutepec, Morelos (Mexico)] e-mail: augusto_vib@yahoo.com.mx

    2003-07-01

    The following one written it presents a comparative analysis among different analytical solutions for the punctual kinetics equation, which present two variables of interest: a) the temporary behavior of the neutronic population, and b) The temporary behavior of the different groups of precursors of delayed neutrons. The first solution is based on a method that solves the transfer function of the differential equation for the neutronic population, in which intends to obtain the different poles that give the stability of this transfer function. In this section it is demonstrated that the temporary variation of the reactivity of the system can be managed as it is required, since the integration time for this method doesn't affect the result. However, the second solution is based on an iterative method like that of Runge-Kutta or the Euler method where the algorithm was only used to solve first order differential equations giving this way solution to each differential equation that conforms the equations of punctual kinetics. In this section it is demonstrated that only it can obtain a correct temporary behavior of the neutronic population when it is integrated on an interval of very short time, forcing to the temporary variation of the reactivity to change very quick way without one has some control about the time. In both methods the same change is used so much in the reactivity of the system like in the integration times, giving validity to the results graph the one the temporary behavior of the neutronic population vs. time. (Author)

  15. Salt effects on the air/solution interfacial properties of PEO-containing copolymers: equilibrium, adsorption kinetics and surface rheological behavior.

    Science.gov (United States)

    Llamas, Sara; Mendoza, Alma J; Guzmán, Eduardo; Ortega, Francisco; Rubio, Ramón G

    2013-06-15

    Lithium cations are known to form complexes with the oxygen atoms of poly(oxyethylene) chains. The effect of Li(+) on the surface properties of three block-copolymers containing poly(oxyethylene) (PEO) have been studied. Two types of copolymers have been studied, a water soluble one of the pluronic family, PEO-b-PPO-b-PEO, PPO being poly(propyleneoxyde), and two water insoluble ones: PEO-b-PS and PEO-b-PS-b-PEO, PS being polystyrene. In the case of the pluronic the adsorption kinetics, the equilibrium surface tension isotherm and the aqueous/air surface rheology have been measured, while for the two insoluble copolymers only the surface pressure and the surface rheology have been studied. In all the cases two different Li(+) concentrations have been used. As in the absence of lithium ions, the adsorption kinetics of pluronic solutions shows two processes, and becomes faster as [Li(+)] increases. The kinetics is not diffusion controlled. For a given pluronic concentration the equilibrium surface pressure increases with [Li(+)], and the isotherms show two surface phase transitions, though less marked than for [Li(+)]=0. A similar behavior was found for the equilibrium isotherms of PEO-b-PS and PEO-b-PS-b-PEO. The surface elasticity of these two copolymers was found to increase with [Li(+)] over the whole surface concentration and frequency ranges studied. A smaller effect was found in the case of the pluronic solutions. The results of the pluronic solutions were modeled using a recent theory that takes into account that the molecules can be adsorbed at the surface in two different states. The theory gives a good fit for the adsorption kinetics and a reasonably good prediction of the equilibrium isotherms for low and intermediate concentrations of pluronic. However, the theory is not able to reproduce the isotherm for [Li(+)]=0. Only a semi-quantitative prediction of the surface elasticity is obtained for [pluronic]≤1×10(-3) mM. Copyright © 2013 Elsevier Inc. All

  16. Equilibrium, kinetics and thermodynamics studies of chitosan-based solid phase nanoparticles as sorbent for lead (II) cations from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Shaker, Medhat A., E-mail: drmashaker@yahoo.com [Current address: Chemistry Department, Faculty of Science, University of Jeddah, Jeddah (Saudi Arabia); Permanent address: Chemistry Department, Faculty of Science, Damanhour University, Damanhour (Egypt)

    2015-07-15

    Ternary nanoparticles of chitosan, non-viable biomass (Pseudomonas sp.) and gelatin, CPG were synthesized by chemical crosslinking method and applied as a novel and cost-effective solid phase to adsorb Pb(II) cations from aqueous solution. Characterization of the fabricated CPG nanoparticles and their complexation behavior were extensively interrogated by dynamic light scattering (DLS), FTIR, TGA, XRD and SEM techniques. The extent of adsorption was found to be a function of medium pH, contact time, initial Pb(II) concentration and temperature. The Langmuir, Freundlich, Dubinin–Radushkevich and Redlich–Peterson models were used to illustrate the isotherms of the adsorption system. The adsorption of Pb(II) cations onto CPG best-fits the Langmuir isotherm model which predicts two stoichiometric temperature-independent adsorption sites, A and B with variable capacities, 35.4 and 91.1 mg g{sup −1}, respectively and removal capacity above 90%. Thermodynamic studies revealed that the adsorption process was physical, spontaneous, and endothermic. The adsorption rate is influenced by temperature and the adsorption kinetic is well confirmed with pseudo-second-order equation compared with three other investigated kinetic models. Present study indicated potential applications of CPG nanoparticles as excellent natural and promising solid phase for Pb(II) extraction in wastewater treatment. - Graphical abstract: Display Omitted - Highlights: • Kinetics and thermodynamics of Pb{sup 2+} biosorption onto CPG nanoparticles are studied. • Adsorption kinetic data are best modeled using second-order rate equations. • The Pb{sup 2}adsorption onto CPG was physical diffusion controlled reaction. • The experimental equilibrium results well fit the Langmuir model. • The thermodynamics show endothermic, favorable and spontaneous adsorption processes.

  17. A direct method for numerical solution of a class of nonlinear Volterra integro-differential equations and its application to the nonlinear fission and fusion reactor kinetics

    International Nuclear Information System (INIS)

    Nakahara, Yasuaki; Ise, Takeharu; Kobayashi, Kensuke; Itoh, Yasuyuki

    1975-12-01

    A new method has been developed for numerical solution of a class of nonlinear Volterra integro-differential equations with quadratic nonlinearity. After dividing the domain of the variable into subintervals, piecewise approximations are applied in the subintervals. The equation is first integrated over a subinterval to obtain the piecewise equation, to which six approximate treatments are applied, i.e. fully explicit, fully implicit, Crank-Nicolson, linear interpolation, quadratic and cubic spline. The numerical solution at each time step is obtained directly as a positive root of the resulting algebraic quadratic equation. The point reactor kinetics with a ramp reactivity insertion, linear temperature feedback and delayed neutrons can be described by one of this type of nonlinear Volterra integro-differential equations. The algorithm is applied to the Argonne benchmark problem and a model problem for a fast reactor without delayed neutrons. The fully implicit method has been found to be unconditionally stable in the sense that it always gives the positive real roots. The cubic spline method is divergent, and the other four methods are intermediate in between. From the estimation of the stability, convergency, accuracy and CPU time, it is concluded that the Crank-Nicolson method is best, then the linear interpolation method comes closely next to it. Discussions are also made on the possibility of applying the algorithm to the fusion reactor kinetics in the form of a nonlinear partial differential equation. (auth.)

  18. Deposition and release kinetics of nano-TiO2 in saturated porous media: Effects of solution ionic strength and surfactants

    International Nuclear Information System (INIS)

    Godinez, Itzel G.; Darnault, Christophe J.G.; Khodadoust, Amid P.; Bogdan, Dorin

    2013-01-01

    The aggregation, transport and deposition kinetics (i.e. attachment and release) of TiO 2 nanoparticles (nano-TiO 2 ) were investigated as a function of ionic strength and the presence of anionic (sodium dodecylbenzene sulfonate, SDBS) and non-ionic (Triton X-100) surfactants in 100% critical micelle concentration (CMC). The electrolyte concentration of the suspensions dictated the kinetic stability of nano-TiO 2 thus influencing the transport and retention of the nanoaggregates in the saturated porous medium. With increasing ionic strength, the interaction between approaching nano-TiO 2 and nano-TiO 2 already deposited onto collectors surfaces seemed to be more favorable than the interaction between approaching nano-TiO 2 and bare collectors surfaces. The abrupt and gradual reduction in electrolyte concentration during the flushing cycles of the column experiments induced the release of previously deposited nano-TiO 2 suggesting attachment of nano-TiO 2 through secondary energy minimum. Highlights: ► This study focuses on aggregation, transport and deposition kinetics of nano-TiO 2 . ► Ionic strength and surfactants impact nano-TiO 2 transport in saturated porous media. ► Previously deposited nano-TiO 2 serve as preferential sites for subsequent deposition. ► Changes in solution chemistry cause nanodeposits to release a portion of nano-TiO 2 . -- Previously deposited nano-TiO 2 serve as preferential sites for subsequent deposition and changes in solution chemistry cause nanodeposits to release a portion of nano-TiO 2

  19. Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions

    NARCIS (Netherlands)

    Rispens, T; Cabaleiro-Lago, C; Engberts, JBFN

    2005-01-01

    Rate constants are reported for the pH-independent hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in aqueous solution as a function of the concentration of added cyanomethane ( acetonitrile), polyethylene glycol ( PEG 400) and tetrahydrofuran ( THF). The concentration of water was varied

  20. Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions

    NARCIS (Netherlands)

    Rispens, Theo; Cabaleiro-Lago, Celia; Engberts, Jan B. F. N.

    2005-01-01

    Rate constants are reported for the pH-independent hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in aqueous solution as a function of the concentration of added cyanomethane (acetonitrile), polyethylene glycol (PEG 400) and tetrahydrofuran (THF). The concentration of water was varied between

  1. DEVELOPMENT OF A KINETIC MODEL OF BOEHMITE DISSOLUTION IN CAUSTIC SOLUTIONS APPLIED TO OPTIMIZE HANFORD WASTE PROCESSING

    International Nuclear Information System (INIS)

    Disselkamp, R.S.

    2011-01-01

    Boehmite (e.g., aluminum oxyhydroxide) is a major non-radioactive component in Hanford and Savannah River nuclear tank waste sludge. Boehmite dissolution from sludge using caustic at elevated temperatures is being planned at Hanford to minimize the mass of material disposed of as high-level waste (HLW) during operation of the Waste Treatment Plant (WTP). To more thoroughly understand the chemistry of this dissolution process, we have developed an empirical kinetic model for aluminate production due to boehmite dissolution. Application of this model to Hanford tank wastes would allow predictability and optimization of the caustic leaching of aluminum solids, potentially yielding significant improvements to overall processing time, disposal cost, and schedule. This report presents an empirical kinetic model that can be used to estimate the aluminate production from the leaching of boehmite in Hanford waste as a function of the following parameters: (1) hydroxide concentration; (2) temperature; (3) specific surface area of boehmite; (4) initial soluble aluminate plus gibbsite present in waste; (5) concentration of boehmite in the waste; and (6) (pre-fit) Arrhenius kinetic parameters. The model was fit to laboratory, non-radioactive (e.g. 'simulant boehmite') leaching results, providing best-fit values of the Arrhenius A-factor, A, and apparent activation energy, E A , of A = 5.0 x 10 12 hour -1 and E A = 90 kJ/mole. These parameters were then used to predict boehmite leaching behavior observed in previously reported actual waste leaching studies. Acceptable aluminate versus leaching time profiles were predicted for waste leaching data from both Hanford and Savannah River site studies.

  2. Super-thermal particles in hot plasmas—Kinetic models, numerical solution strategies, and comparison to tokamak experiments

    International Nuclear Information System (INIS)

    Lauber, Philipp

    2013-01-01

    The excitation of collective instabilities by super-thermal particles in hot plasmas and the related transport processes attract increasing interest due to their fundamental challenges for theoretical models and their practical importance for burning fusion plasmas. In fact, the physics of a self-heated thermonuclear plasma due to fusion-born 3.5 MeV α-particles is one of the most important outstanding fundamental research topics on the way to a fusion power plant with magnetic confinement. Within the last 10 years significant advances on both the theoretical and the experimental sides have been made leading to a more detailed and quantitative understanding of fast-particle-driven instabilities. On the theoretical side, the crucial step was to move from fluid models for the plasma background with a hybrid kinetic expression for the energetic particles to a fully kinetic model for all the plasma species, i.e. background ions, background electrons, and fast ions. This improvement allows one to describe consistently the resonant interaction between global plasma waves such as shear Alfvén and Alfvén–acoustic waves, and the particles via Landau damping, i.e. the dynamics parallel to the magnetic background field. Also, mode conversion mechanisms require the inclusion of background ion scales in a kinetic, non-perturbative way. This accurate treatment of the plasma background leads not only to changes in the linear mode properties such as frequency, growth/damping rate, and mode structure but also influences the non-linear dynamics. Due to major advances, innovations and installation of diagnostics in present day experiments, this comparison can be carried out in a more detailed and comprehensive way than a few years ago. For example, the measurement of damping rates via active external antennas, the imaging of 2D mode structures via electron–cyclotron-emission spectroscopy, and the direct detection of escaping fast ions allow to diagnose various kinetic features

  3. Degradation of the fungicide carbendazim in aqueous solutions with UV/TiO2 process: Optimization, kinetics and toxicity studies

    International Nuclear Information System (INIS)

    Saien, J.; Khezrianjoo, S.

    2008-01-01

    An attempt was made to investigate the potential of UV-photocatalytic process in the presence of TiO 2 particles for the degradation of carbendazim (C 9 H 9 N 3 O 2 ), a fungicide with a high worldwide consumption but considered as a 'priority hazard substance' by the Water Framework Directive of the European Commission (WFDEC). A circulating upflow photo-reactor was employed and the influence of catalyst concentration, pH and temperature were investigated. The results showed that degradation of this fungicide can be conducted in the both processes of only UV-irradiation and UV/TiO 2 ; however, the later provides much better results. Accordingly, a degradation of more than 90% of fungicide was achieved by applying the optimal operational conditions of 70 mg L -1 of catalyst, natural pH of 6.73 and ambient temperature of 25 deg. C after 75 min irradiation. Under these mild conditions, the initial rate of degradation can be described well by the Langmuir-Hinshelwood kinetic model. Toxicological assessments on the obtained samples were also performed by measurement of the mycelium growth inhibition of Fusarium oxysporum fungus on PDA medium. The results indicate that the kinetics of degradation and toxicity are in reasonably good agreement mainly after 45 min of irradiation; confirming the effectiveness of photocatalytic process

  4. Equilibrium and Kinetics Study of Adsorption of Crystal Violet onto the Peel of Cucumis sativa Fruit from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    T. Smitha

    2012-01-01

    Full Text Available The use of low-cost, locally available, high efficiency and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This study investigates the potential use of the peel of Cucumis sativa fruit for the removal of crystal violet (CV dye from simulated wastewater. The effects of different system variables, adsorbent dosage, initial dye concentration, pH and contact time were investigated and optimal experimental conditions were ascertained. The results showed that as the amount of the adsorbent increased, the percentage of dye removal increased accordingly. Optimum pH value for dye adsorption was determined as 7.0. The adsorption of crystal violet followed pseudo-second order rate equation and fit well Langmuir and Freundlich equations. The maximum removal of CV was obtained at pH 7 as 92.15% for adsorbent dose of 0.2 g/50 mL and 25 mg L-1 initial dye concentration at room temperature. The maximum adsorption capacity obtained from Langmuir equation was 34.24 mg g-1. Furthermore, adsorption kinetics of (CV was studied and the rate of adsorption was found to conform to pseudo-second order kinetics with a good correlation (R2 > 0.9739. The peel of Cucumis sativa fruit can be attractive options for dye removal from diluted industrial effluents since test reaction made on simulated dyeing wastewater show better removal percentage of (CV.

  5. Evaluation of kinetic parameters of 1, 1'-dibenzoylferrocene in non aqueous methanol solution by cyclic voltammetry (abstract)

    International Nuclear Information System (INIS)

    Parveen, R.; Kirmani, M.Z.; Naqvi, I.I.

    2011-01-01

    The electrochemical Kinetic study of 1, 1/sup '/- Dibenzoylferrocene (DBF) at a platinum working electrode in 0.1 mol dm/sup -3/ NaClO/sub 4/ non aqueous medium has been studied by Cyclic voltammetry. The heterogeneous electron transfer rate constants (ks) and the diffusion coefficients (Do) of DBF were estimated at various temperatures (283 - 323 K) and at different scan rates (0.05 - 0.5 V s/sup -1/). A calibration curve, linear over the range of 1 X 10/sup -3/ - 9 X 10/sup -3/ mol dm/sup -3/ ,was plotted at the scan rate of 0.25 Vs/sup -1/. This plot can be used to analyze an unknown sample of the compound. The kinetic data was also used to evaluate the Activation energy (Ea). The thermodynamic parameters such as enthalpy change of activation (delta H/sup */), Entropy change (delta S/sup */) and Gibbs free energy change (delta GH/sup */) were also investigated during the study. (author)

  6. Characteristics, kinetics and thermodynamics of Congo Red bio sorption by activated sulfidogenic sludge from an aqueous solution

    International Nuclear Information System (INIS)

    Rasool, K.; Lee, D. S.

    2015-01-01

    The kinetics and thermodynamics of the bio sorption of textile dye Congo Red on anaerobic activated sulfidogenic sludge were examined. The influence of different adsorption parameters such as p H, temperature, contact time and initial dye concentrations on the bio sorption capacity was also investigated. The sulfidogenic sludge showed a maximum bio sorption density of 238.90 mg dye/g cell for Congo Red at an initial dye concentration of 1,000 mg/L, p H 3.5 and 22 C, which is higher than that of many other adsorbents reported in the literature. The bio sorption processes obeyed the Langmuir isotherm and exhibited pseudo-second-order rate kinetics. The thermodynamic parameters indicated the spontaneous and exothermic nature of Congo Red bio sorption. The Fourier transform infrared spectra revealed the dye interaction with the biomass. Scanning electron microscopy showed significant changes in the surface morphology of the sludge after dye bio sorption. These results showed that sulfidogenic sludge biomass is an attractive alternative low-cost bio sorbent for the removal of the dye from aqueous media.

  7. Sorption of Lead (Pb from Aqueous Solutions by Sepiolite and Bentonite Modified with Chitosan Biopolymers: Isotherms and Kinetics

    Directory of Open Access Journals (Sweden)

    Hamid Reza Rafiei

    2016-07-01

    Full Text Available In this study, sepiolite and bentonite clay minerals were modified with a natural chitosan biopolymer and the modified-clays were characterized using XRF, XRD, FTIR, SEM, and TOC analyses. The isothermal and kinetic parameters of lead (Pb sorption by both the minerals and the modified-minerals were determined in a batch mode under various conditions such as different contact times and initial concentrations of Pb. It was found that the Freundlich model described well the isotherm experimental data of Pb sorption by the sorbents. Modification with chitosan, however, decreased the Pb adsorption capacity of sepiolite from 83 to 27 mg g-1 and that of bentonite from 56 to 29 mg g-1. Kinetic results showed that more than 24 hours was required for Pb sorption by the natural clays to reach equilibrium, while the equilibrium time reduced to 16 and 4 hours for Pb sorption on chitosan-sepiolite and chitosan–bentonite, respectively. The pseudo-second-order model well described the time-dependent Pb sorption data by sepiolite, chitosan-sepiolite, and chitosan-bentonite, suggesting that chemical sorption is the rate-limiting step of Pb adsorption mechanism. The Pb sorption data by bentonite showed the best fit with Elovich model.

  8. Redox potentials and kinetics of the Ce 3+/Ce 4+ redox reaction and solubility of cerium sulfates in sulfuric acid solutions

    Science.gov (United States)

    Paulenova, A.; Creager, S. E.; Navratil, J. D.; Wei, Y.

    Experimental work was performed with the aim of evaluating the Ce 4+/Ce 3+ redox couple in sulfuric acid electrolyte for use in redox flow battery (RFB) technology. The solubility of cerium sulfates in 0.1-4.0 M sulfuric acid at 20-60 °C was studied. A synergistic effect of both sulfuric acid concentration and temperature on the solubility of cerous sulfate was observed. The solubility of cerous sulfate significantly decreased with rising concentration of sulfuric acid and rising temperature, while the solubility of ceric sulfate goes through a significant maximum at 40 °C. Redox potentials and the kinetics of the cerous/ceric redox reaction were also studied under the same temperature-concentration conditions. The redox potentials were measured using the combined redox electrode (Pt-Ag/AgCl) in equimolar Ce 4+/Ce 3+ solutions (i.e.[Ce 3+]=[Ce 4+]) in sulfuric acid electrolyte. The Ce 3+/Ce 4+ redox potentials significantly decrease (i.e. shift to more negative values) with rising sulfuric acid concentration; a small maximum is observed at 40 °C. Cyclic voltammetric experiments confirmed slow electrochemical kinetics of the Ce 3+/Ce 4+ redox reaction on carbon glassy electrodes (CGEs) in sulfuric acid solutions. The observed dependencies of solubilities, the redox potentials and the kinetics of Ce 3+/Ce 4+ redox reaction on sulfuric acid concentration are thought to be the result of inequivalent complexation of the two redox species by sulfate anions: the ceric ion is much more strongly bound to sulfate than is the cerous ion. The best temperature-concentration conditions for the RFB electrolytes appear to be 40 °C and 1 M sulfuric acid, where the relatively good solubility of both cerium species, the maximum of redox potentials, and the more or less satisfying stability of CGE s were found. Even so, the relatively low solubility of cerium salts in sulfuric acid media and slow redox kinetics of the Ce 3+/Ce 4+ redox reaction at carbon indicate that the Ce 3+/Ce

  9. Influence of Irradiance, Flow Rate, Reactor Geometry, and Photopromoter Concentration in Mineralization Kinetics of Methane in Air and in Aqueous Solutions by Photocatalytic Membranes Immobilizing Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    Ignazio Renato Bellobono

    2008-01-01

    Full Text Available Photomineralization of methane in air (10.0–1000 ppm (mass/volume of C at 100% relative humidity (dioxygen as oxygen donor was systematically studied at 318±3 K in an annular laboratory-scale reactor by photocatalytic membranes immobilizing titanium dioxide as a function of substrate concentration, absorbed power per unit length of membrane, reactor geometry, and concentration of a proprietary vanadium alkoxide as photopromoter. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC disappearance, to yield carbon dioxide, were followed. At a fixed value of irradiance (0.30 W⋅cm-1, the mineralization experiments in gaseous phase were repeated as a function of flow rate (4–400 m3⋅h−1. Moreover, at a standard flow rate of 300 m3⋅h−1, the ratio between the overall reaction volume and the length of the membrane was varied, substantially by varying the volume of reservoir, from and to which circulation of gaseous stream took place. Photomineralization of methane in aqueous solutions was also studied, in the same annular reactor and in the same conditions, but in a concentration range of 0.8–2.0 ppm of C, and by using stoichiometric hydrogen peroxide as an oxygen donor. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters, k1 and K1, k2 and K2, were calculated, which is able to fit the whole kinetic profile adequately. The influence of irradiance on k1 and k2, as well as of flow rate on K1 and K2, is rationalized. The influence of reactor geometry on k values is discussed in view of standardization procedures of photocatalytic experiments. Modeling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photopromoter, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or

  10. On the predictions and limitations of the Becker–Döring model for reaction kinetics in micellar surfactant solutions

    KAUST Repository

    Griffiths, I.M.

    2011-08-01

    We investigate the breakdown of a system of micellar aggregates in a surfactant solution following an order-one dilution. We derive a mathematical model based on the Becker-Döring system of equations, using realistic expressions for the reaction constants fit to results from Molecular Dynamics simulations. We exploit the largeness of typical aggregation numbers to derive a continuum model, substituting a large system of ordinary differential equations for a partial differential equation in two independent variables: time and aggregate size. Numerical solutions demonstrate that re-equilibration occurs in two distinct stages over well-separated timescales, in agreement with experiment and with previous theories. We conclude by exposing a limitation in the Becker-Döring theory for re-equilibration of surfactant solutions. © 2011 Elsevier Inc.

  11. Tomato root growth and phosphorus absorption kinetics by tomato plants as affected by phosphorus concentration in nutrient solution

    International Nuclear Information System (INIS)

    Fontes, P.C.R.; Barber, S.A.

    1984-01-01

    To evaluate the effects P concentrations in nutrient solution on root growth and on root physiological characteristics involved in P uptake by tomato Lycopersicon esculentum Mill plants, six seedlings were grown in nutrient solution at initial concentrations of 48.5, 97, 194 and 388 μMP until one day before harvest. They were then transferred to solutions with P at 20 μM and 30 μM, and the depletion curves and Michaelis-Menten parameters were determined. The conclusions were that as P supply increased and as the plant P contents are sufficient for maximum growth, the rate of P uptake tends to be lower. The results also indicate that total P uptake by tomato seedlings depends on the amount of root surface area exposed to P. (M.A.C.) [pt

  12. Electrochemical oxidation of zirconium alloys in pre-transition and post-transition kinetic regimes at corrosion in electrolyte solutions

    International Nuclear Information System (INIS)

    Barkov, A.A.; Shavshin, V.M.

    1986-01-01

    With the aim of investigation on oxidation of zirconium alloys (Zr+2.5% Nb) the critical thickness of beginning of spalling of froming oxide films in HCl and NHO 3 aqueous solutions was evaluated by coulometry with accelerated procedure. Some variants of predeposition of modificated oxide coatings are proposed increase pre-transition regime time and to decrease corrosion during post-transition regime. Increase in agressivity of solutions (addition of 1 vol.% HF) and UV irradiation are found to increase 3-4 times pre-transition period

  13. Removal of Dye (Blue 56 From Aqueous Solution via Adsorption onto Pistachio Shell: kinetic and isotherm study of removal process

    Directory of Open Access Journals (Sweden)

    A. Ravanpaykar

    2012-03-01

    Full Text Available In the present investigation, shells of pistachio are used as adsorbents and they have been successfully used for the removal of Blue 56, from water samples. The effect of various parameters such as: pH, amounts of adsorbents, size of adsorbent particles and contact time on removal processing were investigated. Inthisstudy Freundlichabsorptionisotherms and Langmuir were investigated. The experimental data were correlated reasonably well by the Freundlich adsorption isotherm and isotherm parameters were calculated. In order to investigate the efficiency of Blue 56 adsorption on the pistachio shell, pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models were studied. Themodel that hadgoodcorrelationtoattractFreundlichwas chosenasthemodel. Its kineticsfollowsthepseudosecond order reaction.

  14. Swelling and hydrolysis kinetics of Kraft pulp fibers in aqueous 1-butyl-3-methylimidazolium hydrogen sulfate solutions.

    Science.gov (United States)

    Mao, Jia; Abushammala, Hatem; Pereira, Laura Barcellos; Laborie, Marie-Pierre

    2016-11-20

    1Butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) is efficient at extracting cellulose nanocrystals from pulp fibers. To shed some light on the respective contributions of swelling and hydrolysis of pulp fibers by [Bmim]HSO4, the physical, structural and morphological characteristics of hardwood Kraft pulp fibers were monitored under various conditions of temperature, water content and time. Swelling was largely compounded by hydrolysis at the highest temperatures (120°C) as evidenced by mass loss and reduced degree of polymerization (DPn) at this temperature. At 120°C only, water content appeared to play a significant role on the extent of hydrolysis. At this temperature, a heterogeneous kinetic model involving weak links and amorphous regions best described the experimental data. Hydrolysis rates were maximum at 25% water content in the aqueous ionic liquid. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Removal of thorium (IV) ions from aqueous solution by a novel nanoporous ZnO: Isotherms, kinetic and thermodynamic studies.

    Science.gov (United States)

    Kaynar, Ümit H; Ayvacıklı, Mehmet; Hiçsönmez, Ümran; Kaynar, Sermin Çam

    2015-12-01

    The adsorption of thorium (IV) from aqueous solutions onto a novel nanoporous ZnO particles prepared by microwave assisted combustion was studied using batch methods under different experimental conditions. The effect of contact time, solution pH, initial concentration and temperature on adsorption process was studied. The ability of this material to remove Th (IV) from aqueous solution was characterises by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption percent and distribution coefficient for nanoporous ZnO powders in optimum conditions were 97% ± 1.02; 8080 L kg(-1)for Th (IV), respectively. Based on the Langmuir model, the maximum adsorption capacity of nanoporous ZnO for Th (IV) was found to be 1500 g kg(-1). Thermodynamic parameters were determined and discussed. The results indicated that nanoporous ZnO was suitable as sorbent material for recovery and adsorption of Th (IV) ions from aqueous solutions. The radioactive Th (VI) in surface water, sea water and waste waters from technologies producing nuclear fuels, mining (uranium and thorium) and laboratories working with radioactive materials (uranium and thorium) can be removed with this nanoporous ZnO. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics

    International Nuclear Information System (INIS)

    Dove, Patricia M.

    1999-01-01

    Our goal is to develop a quantitative and mechanistic understanding of amorphous silica, SiO2(am), dissolution kinetics in aqueous solutions. A knowledge of fundamental controls on the reactivity of simple Si-O bonded phases is the baseline of behavior for understanding highly complex silica phases. In the Earth, silicate minerals comprise >70% of the crust and dominate virtually every subsurface system. More importantly for the objectives of this EMSP project, the silicates are important because compositionally complex glasses will become the front line of defense in containing radioactive wastes in the nation's long term and interim storage strategies. To date, the behavior of SiO2(am) is largely inferred from studies of the better known crystalline polymorphs (e.g. alpha-quartz). In the first step towards constructing a general model for amorphous silica reactivity in the complex fluid compositions of natural waters, we are determining the dissolution behavior as a function of temperature, solution pH and cation concentration. With these data we are determining relationships between SiO2 glass structure and dissolution rates in aqueous solutions, as described below

  17. Kinetics and thermodynamics of adsorption of azinphosmethyl from aqueous solution onto pyrolyzed (at 600 deg. C) ocean peat moss (Sphagnum sp.)

    International Nuclear Information System (INIS)

    Aroguz, A.Z.

    2006-01-01

    The removal of azinphosmethyl from aqueous solution onto pyrolyzed ocean peat moss (Sphagnum sp.), as a residue, from the Rhode Island coast (USA), has been investigated at different temperatures and initial concentrations. The ocean peat moss had been pyrolyzed at 600 deg. C in nitrogen atmosphere before the adsorption process. The kinetic data obtained from batch studies have been analyzed using pseudo-first order kinetic model. The rate constants were evaluated at different temperatures. The thermodynamic parameters (ΔG o , ΔH o , ΔS o ) for the adsorption process were calculated and the results suggest that the nature of adsorption is endothermic and the process is spontaneous and favorable. The activation energy for adsorption process was estimated, about 18.3 kJ mol -1 . According to this value the adsorption of azinphosmethyl onto pyrolyzed ocean peat moss is in the range of physical adsorption. The experimental data have been modeled using Langmuir, Freundlich and Temkin isotherms. It was found that Langmuir and Freundlich isotherms give the best correlation with the experimental data

  18. LSENS: A General Chemical Kinetics and Sensitivity Analysis Code for homogeneous gas-phase reactions. Part 1: Theory and numerical solution procedures

    Science.gov (United States)

    Radhakrishnan, Krishnan

    1994-01-01

    LSENS, the Lewis General Chemical Kinetics and Sensitivity Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part 1 of a series of three reference publications that describe LENS, provide a detailed guide to its usage, and present many example problems. Part 1 derives the governing equations and describes the numerical solution procedures for the types of problems that can be solved. The accuracy and efficiency of LSENS are examined by means of various test problems, and comparisons with other methods and codes are presented. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions.

  19. Kinetics, Thermodynamics and Isotherm studies on Adsorption of Eriochrome Black-T from aqueous solution using Rutile TiO2

    Science.gov (United States)

    Priyadarshini, B.; Rath, P. P.; Behera, S. S.; Panda, S. R.; Sahoo, T. R.; Parhi, P. K.

    2018-02-01

    In this study, rutile phase of TiO2 particles have been synthesized by co-precipitation method and is used as an adsorbent for removal of toxic azo dye Eriochrome black-T (EBT) from aqueous solution. The rutile phase of TiO2 was confirmed by the X-ray powder diffraction pattern. Effect of initial dye concentration, adsorbent dose, pH, agitation speed and temperature on the adsorption process of EBT was examined. Removal of EBT was increased by increasing in adsorbent dose and decrease in initial dye concentration and pH. The optimum conditions resulted were: 25 ppm initial dye concentration, 20 mg adsorbent dose and pH of 2. Using Langmuir, Freundlich and Temkin isotherm models, equilibrium data was determined. The Freundlich model showed the best fit for uptake of the EBT dye, which evident that the process of adsorption of EBT dye onto TiO2 particles was heterogeneous. The kinetic data were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion equation. The pseudo-second order showed the best fit for the kinetic studies (R2 = 0.999), which ascertains that the adsorption process was of chemisorptions type. The intraparticle diffusion model indicated a linear relationship (R2= 0.99) suggesting the pore diffusion to be a limiting step in the overall adsorption process.

  20. Kinetic and equilibrium studies of the removal of ammonium ions from aqueous solution by rice husk ash-synthesized zeolite Y and powdered and granulated forms of mordenite

    International Nuclear Information System (INIS)

    Yusof, Alias Mohd; Keat, Lee Kian; Ibrahim, Zaharah; Majid, Zaiton Abdul; Nizam, Nik Ahmad

    2010-01-01

    The removal of ammonium from aqueous solutions using zeolite NaY prepared from a local agricultural waste, rice husk ash waste was investigated and a naturally occurring zeolite mordenite in powdered and granulated forms was used as comparison. Zeolite NaY and mordenite were well characterized by powder X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and the total cation exchange capacity (CEC). CEC of the zeolites were measured as 3.15, 1.46 and 1.34 meq g -1 for zeolite Y, powdered mordenite and granular mordenite, respectively. Adsorption kinetics and equilibrium data for the removal of NH 4 + ions were examined by fitting the experimental data to various models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The equilibrium pattern fits well with the Langmuir isotherm compared to the other isotherms. The monolayer adsorption capacity for zeolite Y (42.37 mg/g) was found to be higher than that powdered mordenite (15.13 mg/g) and granular mordenite (14.56 mg/g). Thus, it can be concluded that the low cost and economical rice husk ash-synthesized zeolite NaY could be a better sorbent for ammonium removal due to its rapid adsorption rate and higher adsorption capacity compared to natural mordenite.

  1. Murmanite and lomonosovite as Ag-selective ionites: kinetics and products of ion exchange in aqueous AgNO3 solutions

    Science.gov (United States)

    Lykova, Inna S.; Chukanov, Nikita V.; Kazakov, Anatoliy I.; Tarasov, Viktor P.; Pekov, Igor V.; Yapaskurt, Vasiliy O.; Chervonnaya, Nadezhda A.

    2013-09-01

    Products and kinetics of ion exchange of heterophyllosilicate minerals lomonosovite and murmanite with aqueous AgNO3 solutions under low-temperature conditions have been studied using scanning electron microscopy, electron microprobe analysis, single-crystal X-ray diffraction, infrared spectroscopy, 23Na nuclear magnetic resonance spectroscopy and dynamic calorimetry. Both minerals show strong affinity for silver in cation exchange. Simplified formulae of Ag-exchanged forms of murmanite and lomonosovite are (Ag3.0Ca0.5Na0.5) (Ti,Nb,Mn,Fe)3.7-4 (Si2O7)2O4·4(H2O,OH) and (Ag8.2Na1.2Ca0.3) (Ti,Nb,Mn,Fe)3.9-4 (Si2O7)2 (PO4)1.9O4· xH2O, respectively. The reaction of ion exchange for murmanite follows the first-order kinetic model up to ca. 70-80 % conversion. The rate of the process is described by the equation k(h-1) = 107.64±0.60 exp[-(12.2 ± 0.9)·103/RT]. The average heat release value in the temperature range 39.4-72 °C is 230 J g-1. The cation exchange is limited by processes in solid state, most probably binding of silver.

  2. Equilibrium, kinetics and mechanism of Au3+, Pd2+ and Ag+ ions adsorption from aqueous solutions by graphene oxide functionalized persimmon tannin.

    Science.gov (United States)

    Wang, Zhongmin; Li, Xiaojuan; Liang, Haijun; Ning, Jingliang; Zhou, Zhide; Li, Guiyin

    2017-10-01

    In this study, a novel bio-adsorbent (PT-GO) was prepared by functionalization persimmon tannin (PT) with graphene oxide (GO) and the effective adsorption behaviors of Au 3+ , Pd 2+ and Ag + ions from aqueous solution was investigated. The PT-GO was characterized by Fourier transform infrared spectrometer (FTIR), scanning electronic microscope (SEM), thermogravimetric analysis (TGA) and Zeta potential. Many influence factors such as pH value, bio-adsorbent dosage, initial concentration of metal ions and contact time were optimized. The maximum adsorption capacity for Au 3+ , Pd 2+ and Ag + was 1325.09mg/g, 797.66mg/g and 421.01mg/g, respectively. The equilibrium isotherm for the adsorption of Au 3+ and Ag + on PT-GO were found to obey the Langmuir model, while the Freundlich model fitted better for Pd 2+ . The adsorption process of Au 3+ , Pd 2+ presented relatively fast adsorption kinetics with pseudo-second-order equation as the best fitting model, while the pseudo-first-order kinetic model was suitable for describing the adsorption of Ag + . Combination of ion exchange, electrostatic interaction and physical adsorption was the mechanism for adsorption of Au 3+ , Pd 2+ and Ag + onto PT-GO bio-adsorbent. Therefore, the PT-GO bio-adsorbent would be an ideal adsorbent for removal of precious metal ions and broaden the potential applications of persimmon tannin in environmental research. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models.

    Science.gov (United States)

    Rahman, Md Sayedur; Sathasivam, Kathiresan V

    2015-01-01

    Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.

  4. Ionic Diffusion and Kinetic Homogeneous Chemical Reactions in the Pore Solution of Porous Materials with Moisture Transport

    DEFF Research Database (Denmark)

    Johannesson, Björn

    2009-01-01

    Results from a systematic continuum mixture theory will be used to establish the governing equations for ionic diffusion and chemical reactions in the pore solution of a porous material subjected to moisture transport. The theory in use is the hybrid mixture theory (HMT), which in its general form......’s law of diffusion and the generalized Darcy’s law will be used together with derived constitutive equations for chemical reactions within phases. The mass balance equations for the constituents and the phases together with the constitutive equations gives the coupled set of non-linear differential...... general description of chemical reactions among constituents is described. The Petrov – Galerkin approach are used in favour of the standard Galerkin weighting in order to improve the solution when the convective part of the problem is dominant. A modified type of Newton – Raphson scheme is derived...

  5. THE TREATED EGGSHELLS AS A NEW BIOSORBENT FOR ELIMINATION OF CARBARYL PESTICIDE FROM AQUEOUS SOLUTIONS: KINETICS, THERMODYNAMICS AND ISOTHERMS

    Directory of Open Access Journals (Sweden)

    ABDELHAMID BAKKA

    2016-10-01

    Full Text Available The efficiency of treated eggshells (TES for removing the carbaryl pesticide from aqueous solutions was examined by biosorption process. Batch mode experiments were conducted using various parameters such as contact time, temperature, biosorbent amount, carbaryl concentration and pH. Removal efficiency of carbaryl by the TES attained 87.35 % after 60 min of contact time, using 10 mg·L-1 of pesticide and 1.5 g·L-1 of biosorbent. The results indicate that Freundlich equation is well described with the carbaryl adsorption, with correlation coefficient R2 value of 0.99. They showed that the biosorption processes were spontaneous and exothermic. The Gibbs energy ∆G increased with increase in temperature indicating an increase in feasibility of biosorption at low temperature. These results show that treated eggshells can be employed as an alternative to commercial adsorbents in the removal of pesticides from aqueous solutions.

  6. Growth kinetics and long-term stability of CdS nanoparticles in aqueous solution under ambient conditions

    International Nuclear Information System (INIS)

    Mullaugh, Katherine M.; Luther, George W.

    2011-01-01

    The ubiquity of naturally occurring nanoparticles in the aquatic environment is now widely accepted, but a better understanding of the conditions that promote their formation and persistence is needed. Using cadmium sulfide (CdS) as a model metal sulfide species, thiolate-capped CdS nanoparticles were prepared in the laboratory to evaluate how aquatic conditions influence metal sulfide nanoparticle growth and stability. This work examines CdS nanoparticle growth directly in aqueous solution at room temperature by utilizing the size-dependent spectroscopic properties of semiconductors detectable by UV/vis. CdS nanoparticle growth was governed by oriented attachment, a non-classical mechanism of crystallization in which small precursor nanoparticles coalesce to form larger nanoparticle products. Nanoparticle growth was slowed with increasing capping agent and decreasing ionic strength. In addition to examining the short-term (hours) growth of the nanoparticles, a long-term study was conducted in which cysteine-capped CdS nanoparticles were monitored over 3 weeks in solutions of various ionic strengths. The long-term study revealed an apparent shift from small nanoparticles to nanoparticles twice their original size, suggesting nanoparticle growth may continue through oriented attachment over longer time scales. High-ionic strength solutions resulted in salt-induced aggregation and eventual settling of nanoparticles within days, whereas low-ionic strength solutions were stable against settling over the course of the experiment. Sulfide recovery from cysteine-capped CdS nanoparticles as acid volatile sulfide was nearly quantitative after 2 weeks in fully oxygenated water, demonstrating significantly slowed oxidation of sulfide when complexed to Cd(II) within CdS nanoparticles. The nanoparticles were also shown to be resistant to oxidation by Fe(III) (hydr)oxide. This study illustrates that aggregation, rather than chemical oxidation, is likely more important to the

  7. Kinetics and mechanism of superoxide radical reactions with some biologically important compounds in aqueous solutions. Pulse radiolysis

    Science.gov (United States)

    Revina, A. A.; Amiragova, M. I.; Volod'ko, V. V.; Vannikov, A. V.

    Microsecond pulse radiolysis of oxygenated aqueous solutions containing 0.02 mol dm -3 sodium formate and 2 mmol dm -3 phosphate buffer at pH 7 was used to generate superoxide anion radicals. The influence of some biologically important compounds upon the rate of O ⨪2 decay was monitored spectrophotometrically in the range of 245-300 nm. Hematoporphyrin (HP), hemin C (HC), catalase (Cat), cobalt sulfophthalocyanine (CoTSPc) were studied. Among the investigated compounds only Cat was found to show a high catalytic efficiency towards the self-decay of O ⨪2. A red shift of O ⨪2 absorption band and slowing down of its decay were observed to take place by adding HP or CoTSPc to the solutions containing formate ions in excess. This effect is associated with the formation of a transient superoxo-complex. An appearance of an intermediate species with absorption maxima at 350 nm and half-life of about 2s was observed to accompany the superoxo-complex of CoTSPc decay. In the aerated solution of HP the intensity of absorbance at 260 nm was found to be independent of the presence of formate ions.

  8. Kinetics and mechanism of superoxide radical reactions with some biologically important compounds in aqueous solutions. Pulse radiolysis

    International Nuclear Information System (INIS)

    Revina, A.A.; Volod'ko, V.V.; Vannikov, A.V.

    1989-01-01

    Microsecond pulse radiolysis of oxygenated aqueous solutions containing 0.02 mol dm -3 sodium formate and 2 mmol dm -3 phosphate buffer at pH 7 was used to generate superoxide anion radicals. The influence of some biologically important compounds upon the rate of O 2 .-bar decay as monitored spectrophotometrically in the range of 245-300 nm. Hematoporphyrin (HP), hemin C (HC), catalase (Cat), cobalt sulfophthalocyanine (CoTSPc) were studied. Among the investigated compounds only Cat was found to show a high catalytic efficiency towards the self-decay of O 2 .-bar . A red shift of 0 2 .-bar absorption band and slowing down of its decay were observed to take place by adding HP or CoTSPc to the solutions containing formate ions in excess. This effect is associated with the formation of a transient superoxo-complex. An appearance of an intermediate species with absorption maxima at 350 nm and half-life of about 2 s was observed to accompany the superoxo-complex of CoTSPc decay. In the aerated solution of HP the intensity of absorbance at 260 nm was found to be independent of the presence of formate ions. (author)

  9. Transport and reaction kinetics at the glass:solution interface region: results of repository-oriented leaching experiments

    International Nuclear Information System (INIS)

    Abrajano, T.A. Jr.; Bates, J.K.

    1987-01-01

    Repository-oriented leaching experiments involving Savannah River Laboratory (SRL) 165 type glass under a γ-radiation field (1 +/- 0.2 x 10 4 R/h) have been performed by the Nevada Nuclear Waste Storage Investigations (NNWSI) project. In this communication, they discuss glass surface analyses obtained by SEM, nuclear resonance profiling, and SIMS together with leachate solution data in relation to a mechanism that couples diffusion, hydrolysis (etching and gelation), and precipitation to qualitatively describe the release of different glass components to the leachant solutions. The release of mobile (e.g., Li) and partly mobile (e.g., B) species is controlled primarily by interdiffusion with water species across the interdiffusion zone. Glass components that are immobile in the interdiffusion zone are released to the solution by etching. For prediction of long-term steady-state concentrations of glass components with low solubility, the relative rates of release from the glass and secondary mineral precipitation must be taken into account. 20 references, 5 figures, 1 table

  10. Feasibility of creating a specialized reactimeter based on the inverse solution to kinetics equation with a current-mode neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Koshelev, A. S., E-mail: alexsander.coshelev@yandex.ru; Arapov, A. V.; Ovchinnikov, M. A. [Russian Federal Nuclear Center–All-Russian Research Institute of Experimental Physics (Russian Federation)

    2016-12-15

    The file-evaluation results of a reactimeter based on the inverse solution to the kinetics equation (ISKE) are presented, which were obtained using an operating hardware-measuring complex with a KNK-4 neutron detector working in the current mode. The processing of power-recording files of the BR-1M, BR-K1, and VIR-2M reactors of the Russian Federal Nuclear Center—All-Russian Research Institute of Experimental Physics, which was performed with the use of Excel simulation of the ISKE formalism, demonstrated the feasibility of implementation of the reactivity monitoring (during the operation of these reactors at stationary power) beginning from the level of ~5 × 10{sup –4}β{sub eff}.

  11. Recursive solutions for multi-group neutron kinetics diffusion equations in homogeneous three-dimensional rectangular domains with time dependent perturbations

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, Claudio Z. [Universidade Federal de Pelotas, Capao do Leao (Brazil). Programa de Pos Graduacao em Modelagem Matematica; Bodmann, Bardo E.J.; Vilhena, Marco T. [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Programa de Pos-graduacao em Engenharia Mecanica; Barros, Ricardo C. [Universidade do Estado do Rio de Janeiro, Nova Friburgo, RJ (Brazil). Inst. Politecnico

    2014-12-15

    In the present work we solve in analytical representation the three dimensional neutron kinetic diffusion problem in rectangular Cartesian geometry for homogeneous and bounded domains for any number of energy groups and precursor concentrations. The solution in analytical representation is constructed using a hierarchical procedure, i.e. the original problem is reduced to a problem previously solved by the authors making use of a combination of the spectral method and a recursive decomposition approach. Time dependent absorption cross sections of the thermal energy group are considered with step, ramp and Chebyshev polynomial variations. For these three cases, we present numerical results and discuss convergence properties and compare our results to those available in the literature.

  12. Determination of moxifloxacin and its oxidation products with kinetic evaluation under potassium permanganate treatment in acidic solution by ultra-performance liquid chromatography/tandem mass spectrometry.

    Science.gov (United States)

    Hubicka, Urszula; Zmudzki, Paweł; Zajdel, Paweł; Krzek, Jan

    2013-01-01

    A simple, sensitive, and reproducible ultra-performance LC method for the determination of moxifloxacin (MOXI) oxidation stability under permanganate treatment in acidic conditions (pH 3.0-6.0) was developed. Besides the MOXI peak [retention time (RT) = 2.58], four additional products (RT = 0.86, 0.91, 1.42, and 1.89) were observed in all conditions tested. The oxidation process followed second-order reaction kinetics and depended upon solution acidity. The highest reaction rate constant was observed at pH 3.0, and this value decreased as the pH was increased to 6.0. The oxidation products were characterized, and their fragmentation pathways, derived from MS/MS data, were proposed. Two of these products were identified as hydroxyl derivatives of MOXI and two others as their oxidation product analogs with molecular ions of 418.4 and 416.4 m/z, respectively.

  13. Oxidation of alginate and pectate biopolymers by cerium(IV) in perchloric and sulfuric acid solutions: A comparative kinetic and mechanistic study.

    Science.gov (United States)

    Fawzy, Ahmed

    2016-03-15

    The kinetics of oxidation of alginate (Alg) and pectate (Pec) carbohydrate biopolymers was studied by spectrophotometry in aqueous perchloric and sulfuric acid solutions at fixed ionic strengths and temperature. In both acids, the reactions showed a first order dependence on [Ce(IV)], whereas the orders with respect to biopolymer concentrations are less than unity. In perchloric acid, the reactions exhibited less than unit orders with respect to [H(+)] whereas those proceeded in sulfuric acid showed negative fractional-first order dependences on [H(+)]. The effect of ionic strength and dielectric constant was studied. Probable mechanistic schemes for oxidation reactions were proposed. In both acids, the final oxidation products were characterized as mono-keto derivatives of both biopolymers. The activation parameters with respect to the slow step of the mechanisms were computed and discussed. The rate laws were derived and the reaction constants involved in the different steps of the mechanisms were calculated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. A sensitive kinetic spectrophotometric determination of traces of tungsten in solution based on its inhibitory effect on the decolorization reaction of potassium permanganate

    Directory of Open Access Journals (Sweden)

    Petković Branka

    2016-01-01

    Full Text Available The present work describes a rapid and sensitive method for the determination of ultra micro amounts of tungsten (VI based on its inhibitory effect on the oxidation of 4-hidroxycoumarine by potassium permanganate in the presence of hydrochloric acid. The sensitivity of the method is 20 ng/cm3. The probable relative error is -4.8-13 % for the W(VI concentration range 250 to 20 ng/cm3, respectively. Kinetic equations for the investigated process which determine the order of the reactions regarding to each reaction parameter under certain experimental conditions were proposed, and they allowed quantification of the unknown concentrations W(VI in solution. The detection and quantification limit of the method are 4.5 and 15.1 ng/cm3. The effects of certain foreign ions upon the reaction rate were determined for the assessing the selectivity of the method.

  15. Kinetics of Coil-to-Globule Transition of Dansyl-Labeled Poly(N-sopropylacrylamide) Chains in Aqueous Solution

    Science.gov (United States)

    Li, Chun-liang; Ye, Xiao-dong; Ding, Yan-wei; Liu, Shi-lin

    2012-08-01

    The coil-to-globule transition of thermally sensitive linear poly(N-isopropylacrylamide) (PNIPAM) labeled with dansyl group is induced by 1.54 μm laser pulses (width≈10 ns). The dansyl group is used to follow the transition kinetics because its fluorescence intensity is very sensitive to its micro-environment. As the molar ratio of NIPAM monomer to dansyl group increases from 110 to 300, the effect of covalently attached dansyl fluorophores on the transition decreases. In agreement with our previous study in which we used 8-anilino-1-naphthalensulfonic acid ammonium salt free in water as a fluorescent probe, the current study reveals that the transition has two distinct stages with two characteristic times, namely, τfast≈0.1 ms, which can be attributed to the nucleation and formation of some “pearls" (locally contracting segments) on the chain, and τslow≈0.5 ms, which is related to the merging and coarsening of the “pearls". τfast is independent of the PNIPAM chain length over a wide range (Mw=2.8×106-4.2×107 g/mol). On the other hand, τslow only slightly increases with the chain length.

  16. Effect of local environment on crossluminescence kinetics in SrF{sub 2}:Ba and CaF{sub 2}:Ba solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Terekhin, M.A. [P.N. Lebedev Physical Institute, Leninskij Prospekt 53, 119991 Moscow (Russian Federation); Makhov, V.N., E-mail: makhov@sci.lebedev.ru [P.N. Lebedev Physical Institute, Leninskij Prospekt 53, 119991 Moscow (Russian Federation); Lebedev, A.I.; Sluchinskaya, I.A. [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2015-10-15

    Spectral and kinetic properties of extrinsic crossluminescence (CL) in SrF{sub 2}:Ba (1%) and CaF{sub 2}:Ba (1%) are compared with those of intrinsic CL in BaF{sub 2} and are analyzed taking into account EXAFS data obtained at the Ba L{sub III} edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF{sub 2}:Ba and CaF{sub 2}:Ba compared to BaF{sub 2}. This fact contradicts the expected acceleration of luminescence decay which could result from an increased overlap of wave functions in solid solutions due to shortening of the Ba-F distance obtained in both EXAFS measurements and first-principles calculations. This discrepancy is explained by the effect of migration and subsequent non-radiative decay of the Ba (5p) core holes in BaF{sub 2} and by decreasing of the probability of optical transitions between Ba (5p) states and the valence band in SrF{sub 2}:Ba and CaF{sub 2}:Ba predicted by first-principles calculations. - Highlights: • The crossluminescence kinetics in SrF{sub 2}:Ba and CaF{sub 2}:Ba is slower than in BaF{sub 2}. • Ba{sup 2+} ions substitute for host Ca{sup 2+}(Sr{sup 2+}) ions in the on-center positions. • The nearest Ba-F distances in SrF{sub 2}:Ba and CaF{sub 2}:Ba are shorter than in BaF{sub 2}. • EXAFS data and first-principles calculations of the local structure agree well. • First-principles calculations explain slower luminescence decay in solid solutions.

  17. Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Mohammad, E-mail: m.karimi407@alumni.ut.ac.ir [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of); Milani, Saeid Alamdar [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 14893-836, Tehran (Iran, Islamic Republic of); Abolgashemi, Hossein [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of)

    2016-10-15

    In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe{sub 3}O{sub 4}/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1–5), Th (IV) initial concentration (50–300 mg L{sup −1}) and adsorbent concentration (1–5 g L{sup −1}) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g{sup −1} with respect to pH = 4.5, initial concentration of 250 mg L{sup −1} and adsorbent concentration of 1 g L{sup −1} for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin–Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R{sup 2} = 0.9739. Also thermodynamic parameters (ΔG{sup o}, ΔH{sup o}, ΔS{sup o}) declared that the Th (IV) adsorption was endothermic and spontaneous. - Highlights: • Thorium ions were removed from aqueous solutions by modified magnetite nanoparticle. • The effects of process variables on adsorption capacity were investigated by RSM. • Thermodynamic parameters showed that the adsorption was endothermic and spontaneous. • The equilibrium data for the adsorption of Thorium followed the Langmuir isotherm. • The experimental kinetic data were described by the pseudo-second-order equation.

  18. Effect of Process Variables, Adsorption Kinetics and Equilibrium Studies of Hexavalent Chromium Removal from Aqueous Solution by Date Seeds and its Activated Carbon by ZnCl2

    Directory of Open Access Journals (Sweden)

    Samar K. Theydan

    2018-03-01

    Full Text Available The adsorption of hexavalent chromium by preparing activated carbon from date seeds with zinc chloride as chemical activator and granular date seeds was studied in a batch system. The characteristics of date seeds and prepared activated carbon (ZAC were determined and found to have a surface area 500.01 m2/g and 1050.01 m2/g , respectively and iodine number of 485.78 mg/g and 1012.91 mg/g, respectively. The effects of PH value (2-12, initial sorbate concentration(50-450mg/L, adsorbent weight (0.004-0.036g and contact time (30-150 min on the adsorption process were studied . For Cr(VI adsorption on ZAC, at 120 min time contact, pH solution 2 and 0.02 adsorbent weight will achieve an amount of 35.6 mg/g adsorbed . While when use date seeds as adsorbent , conditions of 3 solution pH, 0.02 absorbent weight , and 120 contact time gave 26.49 mg/g adsorbed amount. Using both Langmuir, Freundlich and Sips models were explain the dsorption isotherms. It declare that the Sips model fits well with the experimental data with a maximum Cr( VI adsorption capacity for (ZAC and granular date stone 233.493 and 208.055 mg/g, respectively . The kinetics data which obtained at different initial Cr(VI concentrations were examined by using pseudo-first-order, pseudo-second-order, and intra-particle diffusion models . The result gained showed that the second-order model was only describing well the empirical kinetics data of both (ZAC and granular date seeds. It was noticed that the granular date seeds has adsorption performance lower than the (ZAC.

  19. Removal of direct blue-106 dye from aqueous solution using new activated carbons developed from pomegranate peel: Adsorption equilibrium and kinetics

    International Nuclear Information System (INIS)

    Amin, Nevine Kamal

    2009-01-01

    The use of cheap, high efficiency and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study investigates the use of activated carbons prepared from pomegranate peel for the removal of direct blue dye from aqueous solution. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e. initial pH, temperature, initial dye concentration adsorbent dosage and contact time. The results showed that the adsorption of direct blue dye was maximal at pH 2, as the amount of adsorbent increased, the percentage of dye removal increased accordingly but it decreased with the increase in initial dye concentration and solution temperature. The adsorption kinetics was found to follow pseudo-second-order rate kinetic model, with a good correlation (R 2 > 0.99) and intra-particle diffusion as one of the rate determining steps. Langmuir, Freundlich, Temkin, Dubinin-RadushKevich (D-R) and Harkins-Jura isotherms were used to analyze the equilibrium data at different temperatures. In addition, various thermodynamic parameters, such as standard Gibbs free energy (ΔG o ), standard enthalpy (ΔH o ), standard entropy (ΔS o ), and the activation energy (E a ) have been calculated. The adsorption process of direct blue dye onto different activated carbons prepared from pomegranate peel was found to be spontaneous and exothermic process. The findings of this investigation suggest that the physical sorption plays a role in controlling the sorption rate.

  20. Removal of direct blue-106 dye from aqueous solution using new activated carbons developed from pomegranate peel: Adsorption equilibrium and kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Amin, Nevine Kamal, E-mail: nkamalamin@yahoo.com [Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria (Egypt)

    2009-06-15

    The use of cheap, high efficiency and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study investigates the use of activated carbons prepared from pomegranate peel for the removal of direct blue dye from aqueous solution. A series of experiments were conducted in a batch system to assess the effect of the system variables, i.e. initial pH, temperature, initial dye concentration adsorbent dosage and contact time. The results showed that the adsorption of direct blue dye was maximal at pH 2, as the amount of adsorbent increased, the percentage of dye removal increased accordingly but it decreased with the increase in initial dye concentration and solution temperature. The adsorption kinetics was found to follow pseudo-second-order rate kinetic model, with a good correlation (R{sup 2} > 0.99) and intra-particle diffusion as one of the rate determining steps. Langmuir, Freundlich, Temkin, Dubinin-RadushKevich (D-R) and Harkins-Jura isotherms were used to analyze the equilibrium data at different temperatures. In addition, various thermodynamic parameters, such as standard Gibbs free energy ({Delta}G{sup o}), standard enthalpy ({Delta}H{sup o}), standard entropy ({Delta}S{sup o}), and the activation energy (E{sub a}) have been calculated. The adsorption process of direct blue dye onto different activated carbons prepared from pomegranate peel was found to be spontaneous and exothermic process. The findings of this investigation suggest that the physical sorption plays a role in controlling the sorption rate.

  1. Uncertainty in geochemical modelling of CO2 and calcite dissolution in NaCl solutions due to different modelling codes and thermodynamic databases

    International Nuclear Information System (INIS)

    Haase, Christoph; Dethlefsen, Frank; Ebert, Markus; Dahmke, Andreas

    2013-01-01

    Highlights: • CO 2 and calcite dissolution is calculated. • The codes PHREEQC, Geochemist’s Workbench, EQ3/6, and FactSage are used. • Comparison with Duan and Li (2008) shows lowest deviation using phreeqc.dat and wateq4f.dat. • Using Pitzer databases does not improve accurate calculations. • Uncertainty in dissolved CO 2 is largest using the geochemical models. - Abstract: A prognosis of the geochemical effects of CO 2 storage induced by the injection of CO 2 into geologic reservoirs or by CO 2 leakage into the overlaying formations can be performed by numerical modelling (non-invasive) and field experiments. Until now the research has been focused on the geochemical processes of the CO 2 reacting with the minerals of the storage formation, which mostly consists of quartzitic sandstones. Regarding the safety assessment the reactions between the CO 2 and the overlaying formations in the case of a CO 2 leakage are of equal importance as the reactions in the storage formation. In particular, limestone formations can react very sensitively to CO 2 intrusion. The thermodynamic parameters necessary to model these reactions are not determined explicitly through experiments at the total range of temperature and pressure conditions and are thus extrapolated by the simulation code. The differences in the calculated results lead to different calcite and CO 2 solubilities and can influence the safety issues. This uncertainty study is performed by comparing the computed results, applying the geochemical modelling software codes The Geochemist’s Workbench, EQ3/6, PHREEQC and FactSage/ChemApp and their thermodynamic databases. The input parameters (1) total concentration of the solution, (2) temperature and (3) fugacity are varied within typical values for CO 2 reservoirs, overlaying formations and close-to-surface aquifers. The most sensitive input parameter in the system H 2 O–CO 2 –NaCl–CaCO 3 for the calculated range of dissolved calcite and CO 2 is the

  2. Removal kinetics for gaseous NO and SO2by an aqueous NaClO2solution mist in a wet electrostatic precipitator

    KAUST Repository

    Park, Hyun-Woo

    2016-07-26

    Removal kinetics for NO and SO2 by NaClO2 solution mist were investigated in a wet electrostatic precipitator. By varying the molar concentrations of NO, SO2, and NaClO2, the removal rates of NO and SO2 confirmed to range from 34.8 to 72.9 mmol/m3 s and 36.6 to 84.7 mmol/m3 s, respectively, at a fixed gas residence time of 0.25 s. The rate coefficients of NO and SO2 were calculated to be 0.679 (mmol/m3)−0.33 s−1 and 1.401 (mmol/m3)−0.1 s−1 based on the rates of the individual removal of NO and SO2. Simultaneous removal of NO and SO2 investigated after the evaluation of removal rates for their individual treatment was performed. At a short gas residence time, SO2 gas removed more quickly by a mist of NaClO2 solution than NO gas in simultaneous removal experiments. This is because SO2 gas, which has a relatively high solubility in solution, was absorbed more rapidly at the gas–liquid interface than NO gas. NO and SO2 gases were absorbed as nitrite (Formula presented.) and sulfite (Formula presented.) ions, respectively, by the NaClO2 solution mist at the gas–liquid interface. Then, (Formula presented.) and (Formula presented.) were oxidized to nitrate (Formula presented.) and sulfate (Formula presented.), respectively, by reactions with (Formula presented.), ClO2, HClO, and ClO in the liquid phase. © 2016 Informa UK Limited, trading as Taylor & Francis Group

  3. Effect of temperature on hydration kinetics and polymerization of tricalcium silicate in stirred suspensions of CaO-saturated solutions

    International Nuclear Information System (INIS)

    Grant, Steven A.; Boitnott, Ginger E.; Korhonen, Charles J.; Sletten, Ronald S.

    2006-01-01

    Tricalcium silicate was hydrated at 274, 278, 283, 298, and 313 K in stirred suspensions of saturated CaO solutions under a nitrogen-gas atmosphere until the end of deceleratory period. The suspension conductivities and energy flows were measured continuously. The individual reaction rates for tricalcium silicate dissolution, calcium silicate hydrate precipitation, and calcium hydroxide precipitation were calculated from these measurements. The results suggest that the proportion of tricalcium silicate dissolved was determined by the rate of tricalcium silicate dissolution and the time to very rapid calcium hydroxide precipitation. The time to very rapid calcium hydroxide precipitation was more sensitive to changes in temperature than was the rate of tricalcium silicate dissolution, so that the proportion of tricalcium silicate hydration dissolved by the deceleratory period increased with decreasing temperature. The average chain length of the calcium silicate hydrate ascertained by magic-angle spinning nuclear magnetic resonance spectroscopy increased with increasing temperature

  4. Numerical solution of the kinetic equation for photoelectrons in the plasmasphere with account for free and trapped zones

    International Nuclear Information System (INIS)

    Khazanov, G.V.; Koen, M.A.; Burenkov, S.I.

    1979-01-01

    Considered is the dinamics of photoelectron fluxes formation in the Earth plasmasphere with account of zone interaction of free and trapped photoelectrons. An algorithm and the results of numerical solution of the equation are presented. The problem of boundary condition choice is discussed. The angular distribution of 10 eV energy photoelectrons at different altitudes of plasmasphere is presented as an example. It is shown that the changes of photoelectron distribution function from bottom of plasmasphere to the top of a force line of the geomagnetic field are within the 1.6 limits. Presented is the estimate of plasmasphere transmittance value and its comparison with the experiment for Mc Ilwain parameter L=2

  5. The kinetics of colour change in textiles and fibres treated with detergent solutions Part II - Spectrophotometric measurements.

    Science.gov (United States)

    Was-Gubala, Jolanta; Grzesiak, Edyta

    2010-06-01

    The aim of this study was to assess colour variations that occur in several types of textiles and their constituent fibres, resulting from the long-term influence of various laundry detergents. A 14-day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. The spectrophotometric measurement of colour changes in fabric samples and test solutions, as well as the microspectrophotometric analysis of colour changes in single fibres were described. An evaluation of the observed colour changes from a forensic fibre analysis expert's point of view, as well as that of an average user/consumer of the textiles and laundry detergents is also provided. Copyright 2009 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

  6. Kinetics and mechanism of the oxidation of uranium(III) by aqueous acidic solutions of iodine and bromine

    International Nuclear Information System (INIS)

    Adegite, A.; Egboh, H.; Ojo, J.F.; Olieh, R.

    1977-01-01

    The rates of oxidation of U 3+ by I 2 and Br 2 in aqueous acidic solutions have been investigated. The rate equations for iodine and bromine are shown, together with the corresponding activation parameters. An excellent correlation has been obtained between the rates of uranium(III) reduction of some oxidants, including iodine and bromine, and the free energies of these reactions. Since these other non-halogen reactions go via the outer-sphere mechanism, it is concluded that at least the first step in the two-step oxidation of U 3+ by Br 2 , I 2 , or [I 3 ] - is outer sphere. The homonuclear exchange rate constant ksub(ex) for U 3+ + U 4+ is deduced to be 1.66 +- 0.16 dm 3 mol -1 s -1 . (author)

  7. Equilibrium, thermodynamic and kinetic studies on biosorption of Mn(II) from aqueous solution by Pseudomonas sp., Staphylococcus xylosus and Blakeslea trispora cells

    International Nuclear Information System (INIS)

    Gialamouidis, D.; Mitrakas, M.; Liakopoulou-Kyriakides, M.

    2010-01-01

    Biosorption of Mn(II) from aqueous solutions using Pseudomonas sp., Staphylococcus xylosus and Blakeslea trispora cells was investigated under various experimental conditions of pH, biomass concentration, contact time and temperature. The optimum pH value was determined to 6.0 and the optimum biomass concentration to 1.0 g L -1 for all types of cells. Mn(II) biosorption was found to fit better to the Langmuir model for Pseudomonas sp. and B. trispora and to Freundlich model for S. xylosus. Langmuir model gave maximum Mn(II) uptake capacity 109 mg g -1 for Pseudomonas sp. and much lower, 59 mg g -1 and 40 mg g -1 for S. xylosus and B. trispora, respectively. Pseudo-second-order kinetic model was also found to be in good agreement with the experimental results. Thermodynamic parameters of the adsorption confirmed the endothermic nature of sorption process with positive heat of enthalpy, accompanied by a positive value of entropy change. Interestingly, desorption experiments by treating biomass with 0.1 M HNO 3 solution resulted to more than 88% recovery of the adsorbed Mn(II) from Pseudomonas sp. and almost 95% and 99% from S. xylosus and B. trispora cells respectively, thus indicating that Mn(II) can be easily and quantitatively recovered from biomass.

  8. Effect of the synthesis temperature of sodium nona-titanate on batch kinetics of strontium-ion adsorption from aqueous solution

    International Nuclear Information System (INIS)

    Merceille, A.; Weinzaepfel, E.; Grandjean, A.; Merceille, A.; Weinzaepfel, E.; Barre, Y.

    2011-01-01

    Sodium titanate materials are promising inorganic ion exchangers for the adsorption of strontium from aqueous solutions. Sodium nona-titanate exhibits a layered structure consisting of titanate layers and exchangeable sodium ions between the layers. The materials used in this study include samples synthesized by a hydrothermal method at temperatures between 60 degrees C and 200 degrees C. Their structure, composition, and morphology were investigated with X-Ray diffraction measurements; thermogravimetric, compositional and surface area analyses, and scanning electron microscopy. The structure, composition, and morphology depended on the synthesis temperature. Batch kinetics experiments for the removal of strontium from aqueous solutions were performed, and the data were fitted by a pseudo-second-order reaction model and a diffusive model. The strontium extraction capacity also depended on the synthesis temperature and exhibited a maximum for samples synthesized at 100 degrees C. The sorption process occurs in one or two diffusion-controlled steps that also depend on the synthesis temperature. These diffusion-limited steps are the boundary-layer diffusion and intra-particle diffusion in the case of pure nona-titanate synthesized at temperatures lower than 170 degrees C, and only intra-particle diffusion in the case of nona-titanate synthesized at 200 degrees C. (authors)

  9. Pulse radiolysis of porphyrin and ferriporphyrin solutions in 2-propanol-carbon tetrachloride systems. Protonation and ligand exchange kinetics

    International Nuclear Information System (INIS)

    Brault, D.; Neta, P.

    1983-01-01

    Pulse radiolysis of aqueous and nonaqueous 2-propanol-acetone-carbon tetrachloride mixtures has been investigated by means of conductivity measurements and spectrophotometry. In these solvent mixtures, a pulse of hydrochloric acid originating from either primary events of solvent radiolysis or from further reactions of carbon tetrachloride with radicals derived from 2-propanol and acetone, is produced within ca 100 nanoseconds. Further production of hydrochloric acid occurs as a result of chain reactions involving hydrogen abstraction by CCl 3 or CCl 3 O 2 radicals. These latter radicals appear to be much more reactive and are likely to be involved in the reaction unless the solutions have been thoroughly deoxygenated. Protonation Reactions of porphyrins and ferriporphyrins, which do not react rapidly with the above radicals, were followed by means of spectrophotometric measurements. In turn, these reactions may be used to monitor hydrochloric acid formation. Spectrophotometric measurements on porphyrins corroborate conductivity results, although a quantitative comparison is not feasible because of differences in solvent properties. 6 figures

  10. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid

    International Nuclear Information System (INIS)

    Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

    2015-01-01

    Highlights: • The objective of the study is to investigate the potential application of a selective EIR for sorption of U(VI) and Th(IV) ions. • The effects of several physiochemical parameters were investigated. • The sorption kinetics and sorption isotherms were used to explain the sorption mechanism. • The thermodynamic studies showed the feasibility of sorption process. • The EIR beads showed a great potential for effective removal of U(VI) and Th(IV) ions. - Abstract: In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid–liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions

  11. Kinetic and analytical study on precipitation reactions with 110AgNO3 of some di(β-chloroethyl)amine derivatives and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers from dimethylformamide - water solution

    International Nuclear Information System (INIS)

    Cecal, Al.; Sunel, V.; Ghimiciu, L.

    1983-01-01

    The kinetics of precipitation reactions with 110 AgNO 3 of some di(β-chloroethyl) amine derivates and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers in dimethylformamide-water mixture, were studied. The rate constants of these reactions were of the order of 10 -4 lxmol -1 xmin -1 . The concentrations of the corresponding hydrochloride solutions were measured by radiometric titration with 110 AgNO 3 solution of given concentration. (author)

  12. Stochastic kinetics

    International Nuclear Information System (INIS)

    Colombino, A.; Mosiello, R.; Norelli, F.; Jorio, V.M.; Pacilio, N.

    1975-01-01

    A nuclear system kinetics is formulated according to a stochastic approach. The detailed probability balance equations are written for the probability of finding the mixed population of neutrons and detected neutrons, i.e. detectrons, at a given level for a given instant of time. Equations are integrated in search of a probability profile: a series of cases is analyzed through a progressive criterium. It tends to take into account an increasing number of physical processes within the chosen model. The most important contribution is that solutions interpret analytically experimental conditions of equilibrium (moise analysis) and non equilibrium (pulsed neutron measurements, source drop technique, start up procedures)

  13. Building a comprehensive mill-level database for the Industrial Sectors Integrated Solutions (ISIS) model of the U.S. pulp and paper sector.

    Science.gov (United States)

    Modak, Nabanita; Spence, Kelley; Sood, Saloni; Rosati, Jacky Ann

    2015-01-01

    Air emissions from the U.S. pulp and paper sector have been federally regulated since 1978; however, regulations are periodically reviewed and revised to improve efficiency and effectiveness of existing emission standards. The Industrial Sectors Integrated Solutions (ISIS) model for the pulp and paper sector is currently under development at the U.S. Environmental Protection Agency (EPA), and can be utilized to facilitate multi-pollutant, sector-based analyses that are performed in conjunction with regulatory development. The model utilizes a multi-sector, multi-product dynamic linear modeling framework that evaluates the economic impact of emission reduction strategies for multiple air pollutants. The ISIS model considers facility-level economic, environmental, and technical parameters, as well as sector-level market data, to estimate the impacts of environmental regulations on the pulp and paper industry. Specifically, the model can be used to estimate U.S. and global market impacts of new or more stringent air regulations, such as impacts on product price, exports and imports, market demands, capital investment, and mill closures. One major challenge to developing a representative model is the need for an extensive amount of data. This article discusses the collection and processing of data for use in the model, as well as the methods used for building the ISIS pulp and paper database that facilitates the required analyses to support the air quality management of the pulp and paper sector.

  14. Building a Comprehensive Mill-Level Database for the Industrial Sectors Integrated Solutions (ISIS) Model of the U.S. Pulp and Paper Sector

    Science.gov (United States)

    Modak, Nabanita; Spence, Kelley; Sood, Saloni; Rosati, Jacky Ann

    2015-01-01

    Air emissions from the U.S. pulp and paper sector have been federally regulated since 1978; however, regulations are periodically reviewed and revised to improve efficiency and effectiveness of existing emission standards. The Industrial Sectors Integrated Solutions (ISIS) model for the pulp and paper sector is currently under development at the U.S. Environmental Protection Agency (EPA), and can be utilized to facilitate multi-pollutant, sector-based analyses that are performed in conjunction with regulatory development. The model utilizes a multi-sector, multi-product dynamic linear modeling framework that evaluates the economic impact of emission reduction strategies for multiple air pollutants. The ISIS model considers facility-level economic, environmental, and technical parameters, as well as sector-level market data, to estimate the impacts of environmental regulations on the pulp and paper industry. Specifically, the model can be used to estimate U.S. and global market impacts of new or more stringent air regulations, such as impacts on product price, exports and imports, market demands, capital investment, and mill closures. One major challenge to developing a representative model is the need for an extensive amount of data. This article discusses the collection and processing of data for use in the model, as well as the methods used for building the ISIS pulp and paper database that facilitates the required analyses to support the air quality management of the pulp and paper sector. PMID:25806516

  15. Probing into the effects of a magnetic field on the electrode processes of iron in sulphuric acid solutions with dichromate based on the fundamental electrochemistry kinetics

    International Nuclear Information System (INIS)

    Lu Zhanpeng; Huang Delun; Yang Wu

    2005-01-01

    The effects of an applied magnetic field on the electrode processes of iron in sulphuric acid solutions with dichromate have been investigated by electrochemical measurements. Open circuit potentials, cathodic and anodic polarisation curves, values of polarisation resistance were measured in the presence or absence of a 0.4 T horizontal magnetic field (HMF). A potentiostatic polarisation plus magnetic field perturbation technique was used to study the effect of the magnetic field on open circuit corrosion. Cathodic reaction rates at open circuit potentials for iron in sulphuric acid solutions containing dichromate ions are controlled by both the electron-transfer process and the diffusion process. A magnetic field made the open circuit potential move in the positive direction, and changes of the open circuit potentials due to the magnetic field increase with increasing dichromate concentration. When iron was potentiostatically polarised at open circuit potentials in the absence of a magnetic field, a cathodic current was observed after a magnetic field was imposed. Such cathodic currents induced by the magnetic field increases with increasing dichromate concentration. The positive shifts of open circuit potential, the decrease of polarisation resistance, and the occurrence of cathodic currents induced by the magnetic field are caused by the accelerating effect of magnetic field on the cathodic diffusion process. Measured current densities showed lower, equal, or higher values in the presence of the magnetic field than those in the absence of a magnetic field at certain anodic potentials. This effect of the magnetic field is related to the contribution of the cathodic and anodic reactions to the measured current and the types of rate-determining steps for each reaction at certain potentials. The applied magnetic field significantly decreased the polarisation resistance. The experimental results in this paper are formulated based on the fundamental electrochemistry

  16. Application of soft- and hard-modelling approaches to resolution of kinetics of electron donor-acceptor complex formation of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with imipramine in different solutions

    International Nuclear Information System (INIS)

    Hasani, Masoumeh; Shariati-Rad, Masoud; Abdollahi, Hamid

    2009-01-01

    Kinetics of electron donor-acceptor (EDA) complex formation of imipramine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was investigated spectrophotometrically in acetonitrile, 1,2-dichloroethane, and chloroform solutions using soft- and hard-modelling approaches. From the results of exploratory analysis of kinetic data and the spectral changes by soft-modelling approaches, evolving factor analysis (EFA) and orthogonal projection approach (OPA), a consecutive two-steps reaction with two intermediates was proposed for the process in acetonitrile and 1,2-dichloroethane media and one with a single intermediate in chloroform solution. Secondly, by applying, multivariate nonlinear least squares hard-modelling approach on the collected experimental kinetic data matrix, the nonlinear parameters (rate constants) as well as the linear parameters (spectral profiles) were obtained by fitting the collected experimental kinetic data matrix to the proposed model. Small values of standard deviation in the resulting parameters and sum of squares of the residuals (ssq) obtained showed the proper selection of the model. Furthermore, the values of lack of fit and percent of explained variance confirmed the correct identified models. Identification of the model with the aid of soft-modelling approaches followed by application of the hard-modelling approaches decreases significantly the rotational ambiguity associated with the obtained concentration and spectral profiles. Variations in the kinetic constants were in complete agreement with the model proposed and the solvent polarities

  17. Application of soft- and hard-modelling approaches to resolution of kinetics of electron donor-acceptor complex formation of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with imipramine in different solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hasani, Masoumeh [Faculty of Chemistry, Bu-Ali Sina University, Mahdieh, Hamedan, 65174 (Iran, Islamic Republic of)], E-mail: hasani@basu.ac.ir; Shariati-Rad, Masoud [Faculty of Chemistry, Bu-Ali Sina University, Mahdieh, Hamedan, 65174 (Iran, Islamic Republic of); Abdollahi, Hamid [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)

    2009-03-23

    Kinetics of electron donor-acceptor (EDA) complex formation of imipramine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was investigated spectrophotometrically in acetonitrile, 1,2-dichloroethane, and chloroform solutions using soft- and hard-modelling approaches. From the results of exploratory analysis of kinetic data and the spectral changes by soft-modelling approaches, evolving factor analysis (EFA) and orthogonal projection approach (OPA), a consecutive two-steps reaction with two intermediates was proposed for the process in acetonitrile and 1,2-dichloroethane media and one with a single intermediate in chloroform solution. Secondly, by applying, multivariate nonlinear least squares hard-modelling approach on the collected experimental kinetic data matrix, the nonlinear parameters (rate constants) as well as the linear parameters (spectral profiles) were obtained by fitting the collected experimental kinetic data matrix to the proposed model. Small values of standard deviation in the resulting parameters and sum of squares of the residuals (ssq) obtained showed the proper selection of the model. Furthermore, the values of lack of fit and percent of explained variance confirmed the correct identified models. Identification of the model with the aid of soft-modelling approaches followed by application of the hard-modelling approaches decreases significantly the rotational ambiguity associated with the obtained concentration and spectral profiles. Variations in the kinetic constants were in complete agreement with the model proposed and the solvent polarities.

  18. Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    Samarghandi Mohammad

    2012-11-01

    Full Text Available Abstract Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99 and Langmuir (r2>0.99 isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99 and intra-particle diffusion (r2>0.98 models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.

  19. Effect of Graphene Oxide on the Reaction Kinetics of Methyl Methacrylate In Situ Radical Polymerization via the Bulk or Solution Technique

    Directory of Open Access Journals (Sweden)

    Ioannis S. Tsagkalias

    2017-09-01

    Full Text Available The synthesis of nanocomposite materials based on poly(methyl methacrylate and graphene oxide (GO is presented using the in situ polymerization technique, starting from methyl methacrylate, graphite oxide, and an initiator, and carried out either with (solution or without (bulk in the presence of a suitable solvent. Reaction kinetics was followed gravimetrically and the appropriate characterization of the products took place using several experimental techniques. X-ray diffraction (XRD data showed that graphite oxide had been transformed to graphene oxide during polymerization, whereas FTIR spectra revealed no significant interactions between the polymer matrix and GO. It appears that during polymerization, the initiator efficiency was reduced by the presence of GO, resulting in a reduction of the reaction rate and a slight increase in the average molecular weight of the polymer formed, measured by gel permeation chromatography (GPC, along with an increase in the glass transition temperature obtained from differential scanning calorimetry (DSC. The presence of the solvent results in the suppression of the gel-effect in the reaction rate curves, the synthesis of polymers with lower average molecular weights and polydispersities of the Molecular Weight Distribution, and lower glass transition temperatures. Finally, from thermogravimetric analysis (TG, it was verified that the presence of GO slightly enhances the thermal stability of the nano-hybrids formed.

  20. Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: kinetics and equilibrium isotherms study.

    Science.gov (United States)

    Ma, Wei; Lv, Tengfei; Song, Xiaoyan; Cheng, Zihong; Duan, Shibo; Xin, Gang; Liu, Fujun; Pan, Decong

    2014-03-15

    In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir-Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Kinetics of Cd2+ and Cr3+ Sorption from Aqueous Solutions Using Mercaptoacetic Acid Modified and Unmodified Oil Palm Fruit Fibre(Elaeis guineensis) Adsorbents

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The kinetics of the sorption of Cd2+ and Cr3+ from aqueous solutions by mercaptoacetic acid modified and unmodified oil palm fruit fibre adsorbents were investigated. The results indicate that sorption equilibrium was reached within 60 min for both metals. Also, the removal efficiency of the three adsorbents was observed to increase for both metals with stronger treatments with mercaptoacetic acid. This may be attributed to the influence of the thiolation of the adsorbents. Furthermore, Cr3+ had higher removal percentages than Cd2+ for all the adsorbents. The sorption mechanism based on the intraparticle diffusion model shows that Cd2+ sorption is better described than Cr3+. The intraparticle diffusion rate constants, K1d, for Cd2+are 62.04 min-1 (untreated), 67.01 min-1 (treated with 0.5 mol/L mercaptoacetic acid), and 71.43 min-1(treated with 1.0 mol/L mercaptocacetic acid) while those for Cr3+ are 63.41 min-1 (untreated), 65.79 min-1(0.5 mol/L acid treated), and 66.25 min-1 (1.0 mol/L acid treated).

  2. Application of Acidic Treated Pumice as an Adsorbent for the Removal of Azo Dye from Aqueous Solutions:kinetic, Equilibrium and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    Saied Bashiri

    2012-11-01

    Full Text Available Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as anefficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal ofAR14 and AR18 followed Freundlich (r2>0.99 and Langmuir (r2>0.99 isotherm models.Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99 and intra-particle diffusion (r2>0.98 models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer.Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89 % regeneration for AR14 and AR18,respectively.

  3. Adsorption Behaviour of La(III and Eu(III Ions from Aqueous Solutions by Hydroxyapatite: Kinetic, Isotherm, and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    F. Granados-Correa

    2013-01-01

    Full Text Available The hydroxyapatite was successfully synthesized, characterized, and used as an alternative low-cost adsorbent material to study the adsorption behavior of La(III and Eu(III ions from nitrate aqueous solutions as a function of contact time, initial metal ion concentration, pH, and temperature by using a bath technique. The kinetic data correspond very well to the pseudo-second-order equation, and in both cases the uptake was affected by intraparticle diffusion. Isotherm adsorption data were well fitted by the Freundlich model equation with 1/n>1, indicating a multilayer and cooperative-type adsorption. Thermodynamic parameters for the adsorption systems were determinated at 293, 303, 313, and 323 K. These parameters show that adsorptions of La(III and Eu(III ions on hydroxyapatite are endothermic and spontaneous processes. The adsorption was found to follow the order Eu(III > La(III and is dependent on ion concentration, pH, and temperature.

  4. Pyridine sorption from aqueous solution by rice husk ash (RHA) and granular activated carbon (GAC): Parametric, kinetic, equilibrium and thermodynamic aspects

    International Nuclear Information System (INIS)

    Lataye, D.H.; Mishra, I.M.; Mall, I.D.

    2008-01-01

    The present study deals with the adsorption of pyridine (Py) from synthetic aqueous solutions by rice husk ash (RHA) and commercial grade granular activated carbon (GAC) and reports on the kinetic, equilibrium and thermodynamic aspects of Py sorption. Batch sorption studies were carried out to evaluate the effect of various parameters, such as adsorbent dose (m), initial pH (pH 0 ), contact time (t), initial concentration (C 0 ) and temperature (T) on the removal of Py. The maximum removal of Py is found to be ∼96% and ∼97% at lower concentrations ( -3 ) and ∼79.5% and ∼84% at higher concentrations (600 mg dm -3 ) using 50 kg m -3 and 30 kg m -3 of RHA and GAC dosage, respectively, at 30 ± 1 o C. Adsorption of Py is found to be endothermic in nature and the equilibrium data can be adequately represented by Toth and Redlich-Peterson isotherm equations. Py can be recovered from the spent adsorbents by using acidic water and 0.1 N H 2 SO 4 . The overall adsorption of Py on RHA and GAC is found to be in the order of GAC > RHA. Comparative assessment of adsorbents used by various investigators available in literature showed the effectiveness of BFA and RHA over other adsorbents. Spent RHA can simply be filtered, dried and used in the boiler furnaces/incinerators. Thus, its heating value can be recovered

  5. Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

    International Nuclear Information System (INIS)

    Guerra, Denis L.; Leidens, Victor L.; Viana, Rubia R.; Airoldi, Claudio

    2010-01-01

    The compound N 1 -[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of 29 Si and 13 C. The well-defined peaks obtained in the 13 C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k 2 values 16.0 and 25.1 mmol g -1 min -1 ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations. - Graphical abstract: This investigation reports the use of original and modified kaolinites as alternative absorbents. The compound N-[3-trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route.

  6. Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

    Science.gov (United States)

    Guerra, Denis L.; Leidens, Victor L.; Viana, Rúbia R.; Airoldi, Claudio

    2010-05-01

    The compound N 1-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of 29Si and 13C. The well-defined peaks obtained in the 13C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k2 values 16.0 and 25.1 mmol g -1 min -1 ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations.

  7. Growth kinetics for the precipitation of zirconium hydroxide from aqueous zirconium and tin bearing solutions by the addition of ammonium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Carleson, T.E. [Idaho Univ., Moscow, ID (United States). Dept. of Chemical Engineering; Chipman, N.A. [Westinghouse Idaho Nuclear Co., Inc., Idaho Falls, ID (United States)

    1989-09-11

    The precipitation of zirconium hydroxide from an aqueous solution of ammonium hexafluorozirconate occurs rapidly upon addition of ammonium hydroxide. Experimental data indicate growth and nucleation rates between 0.06 and 0.28 microns/minute and around 10 {times} 107 number/L-min, respectively. Experiments with a mixed suspension mixed product removal crystallizer for concentrations of reactants of about 0.05 M ammonium hexafluorozirconate precipitating with 0.002 M ammonium hydroxide showed apparent nonlinear growth rates in some cases but not others. Batch studies indicated that growth rate dispersion is probably not present. When the AFL nonlinear model was used to fit the data, the power coefficient obtained was greater than 1, in disagreement with theory. In addition, for some of the data ``S`` shaped curves of the logarithm of the cumulative number greater than versus size were obtained. These curves can not be fit by the AFL model. A program developed at the University of Arizona was used to simulate the crystallization runs. The program results indicated that some of the nonlinear behavior may be attributed to transient conditions. Experimental data also illustrated this behavior. The effect of trace amounts of tin fluoride (0.008 M) on the nucleation and growth kinetics was also evaluated. For some residence times, the presence of tin resulted in reduced median particle diameters, higher growth rates, and lower number counts.

  8. Synthesis of a new low-cost activated carbon from activated sludge for the removal of Cr (Ⅵ) from aqueous solution: Equilibrium, kinetics, thermodynamics and desorption studies

    Energy Technology Data Exchange (ETDEWEB)

    Gorzin, Fatemeh; Ghoreyshi, Ali Asghar [Babol University of Technology, Babol (Iran, Islamic Republic of)

    2013-08-15

    Elimination of Cr (Ⅵ) from aqueous solution was investigated by a new low cost activated carbon developed from aerobically digested activated sludge (ADAS). The adsorbent demonstrated remarkable characteristics such as high surface area of 760m{sup 2}·g{sup −1} and large total pore volume of 0.8383 cm{sup 3}·g{sup −1}. The maximum equilibrium uptake of Cr (Ⅵ) was 70.15 mg·g{sup −1} at optimum pH 2.0. Interpretation of equilibrium data revealed that the best description was provided by the Freundlich isotherm. The kinetics of Cr (Ⅵ) adsorption was well described by the pseudo-second order equation. Calculation of thermodynamic parameters revealed that the adsorption process was endothermic, spontaneous and feasible.. The adsorbent was regenerated using NaOH and it was found to be suitable for reuse in successive adsorption-desorption cycles. The desorption efficiency of Cr (Ⅵ) ion was up to 78%. Finally, comparison of Cr (Ⅵ) adsorption capacity of the developed adsorbent with commercial activated carbon demonstrated its higher performance.

  9. Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri.

    Science.gov (United States)

    Manirethan, Vishnu; Raval, Keyur; Rajan, Reju; Thaira, Harsha; Balakrishnan, Raj Mohan

    2018-05-15

    The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. Copyright © 2018 Elsevier Ltd. All rights reserved.

  10. Principles of chemical kinetics

    CERN Document Server

    House, James E

    2007-01-01

    James House's revised Principles of Chemical Kinetics provides a clear and logical description of chemical kinetics in a manner unlike any other book of its kind. Clearly written with detailed derivations, the text allows students to move rapidly from theoretical concepts of rates of reaction to concrete applications. Unlike other texts, House presents a balanced treatment of kinetic reactions in gas, solution, and solid states. The entire text has been revised and includes many new sections and an additional chapter on applications of kinetics. The topics covered include quantitative rela

  11. The study of kinetics of uranyl nitrate extraction and reextraction, di-n-butylphosphoric acid reextraction in the flow mixer in the system aqueous solutions - tri-n-butyl phosphate in diluent

    International Nuclear Information System (INIS)

    Shchepetil'nikov, N.N.; Timofeev, A.N.; Kharitonov, V.V.

    1992-01-01

    Kinetics of uranyl nitrate and HNO 3 extraction and reextraction in a flow-type mixer for the system 30 vol.% TBP in extractant dearomatized diluent (EDD) was studied. Kinetics of dibutylphosphate acid reextraction was considered and the influence of uranium and zirconium presence on the process was investigated. It is shown that in laboratory mixer of continuous action in case of phase contact duration of 1 min. in system 30 % solution of TBP in EDD extraction sufficiently similar to equilibrium extraction of uranyl nitrate and nitric acid during their extraction and reextraction is achieved

  12. Spectrophotometric Analysis of the Kinetic of Pd(II Chloride Complex Ions Sorption Process from Diluted Aqua Solutions Using Commercially Available Activated Carbon

    Directory of Open Access Journals (Sweden)

    Wojnicki M.

    2017-12-01

    Full Text Available In this paper, results of adsorption kinetic studies of Pd(II chloride complex ions on activated carbon Organosrob 10 CO are presented. Spectorphotometrical method was applied to investigate the process. Kinetic model was proposed, and fundamental thermodynamic parameters were determined. Proposed kinetic model describes well observed phenomenon in the studied range of concentration of Pd(II chloride complex ions as well, as concentration of activated carbon.

  13. Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

    NARCIS (Netherlands)

    Sabil, K.M.; Duarte, A.R.C.; Zevenbergen, J.F.; Ahmad, M.M.; Yusup, S.; Omar, A.A.; Peters, C.J.

    2010-01-01

    A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time

  14. Adsorption Removal of Glycidyl Esters from Palm Oil and Oil Model Solution by Using Acid-Washed Oil Palm Wood-Based Activated Carbon: Kinetic and Mechanism Study.

    Science.gov (United States)

    Cheng, Weiwei; Liu, Guoqin; Wang, Xuede; Han, Lipeng

    2017-11-08

    Acid-washed oil palm wood-based activated carbon (OPAC) has been investigated for its potential application as a promising adsorbent in the removal of glycidyl esters (GEs) from both palm oil and oil model (hexadecane) solution. It was observed that the removal rate of GEs in palm oil was up to >95%, which was significantly higher than other adsorbents used in this study. In batch adsorption system, the adsorption efficiency and performance of acid-washed OPAC were evaluated as a function of several experimental parameters such as contact time, initial glycidyl palmitate (PGE) concentration, adsorbent dose, and temperature. The Langmuir, Freundlich, and Dubinin-Radushkevich models were used to describe the adsorption equilibrium isotherm, and the equilibrium data were fitted best by the Langmuir model. The maximum adsorption capacity of acid-washed OPAC was found to be 36.23 mg/g by using the Langmuir model. The thermodynamic analysis indicated that the adsorption of PGE on acid-washed OPAC was an endothermic and physical process in nature. The experimental data were fitted by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was found that the kinetic of PGE adsorption onto acid-washed OPAC followed well the pseudo-second-order model for various initial PGE concentrations and the adsorption process was controlled by both film diffusion and intraparticle diffusion. The desorption test indicated the removal of GEs from palm oil was attributed to not only the adsorption of GEs on acid-washed OPAC, but also the degradation of GEs adsorbed at activated sites with acidic character. Furthermore, no significant difference between before and after PGE adsorption in oil quality was observed.

  15. Removal of malathion from aqueous solution using De-Acidite FF-IP resin and determination by UPLC-MS/MS: equilibrium, kinetics and thermodynamics studies.

    Science.gov (United States)

    Naushad, Mu; Alothman, Z A; Khan, M R

    2013-10-15

    In the present study, De-Acidite FF-IP resin was used to remove a highly toxic and persistent organophosphorus pesticide (malathion) from the aqueous solution. Batch experiments were performed as a function of various experimental parameters such as effect of pH (2-10), contact time (10-120 min), resin dose (0.05-0.5 g), initial malathion concentration (0.5-2.5 µg mL(-1)) and temperature (25-65°C). The concentration of malathion was determined using a sensitive, selective and rapid ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. The uptake rate of malathion on De-Acidite FF-IP resin was rapid and equilibrium established within 40 min. Kinetics studies showed better applicability for pseudo-second-order model. The equilibrium data was fitted to Langmuir and Freundlich isotherm models and the isotherm constants were calculated for malathion. The values of thermodynamic parameters (ΔG(0), ΔH(0) and ΔS(0)) were computed from the Van't Hoff plot of lnKC vs. 1/T which showed that the adsorption of malathion was feasible, endothermic and spontaneous. The regeneration studies were carried out which demonstrated a decrease in the recovery of malathion from 95% to 68% after five consecutive cycles. Breakthrough and exhaustive capacities of malathion were found to be 1.25 mg g(-1) and 3.5 mg g(-1), respectively. © 2013 Elsevier B.V. All rights reserved.

  16. OECD/NEA thermochemical database

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  17. Coordinating Mobile Databases: A System Demonstration

    OpenAIRE

    Zaihrayeu, Ilya; Giunchiglia, Fausto

    2004-01-01

    In this paper we present the Peer Database Management System (PDBMS). This system runs on top of the standard database management system, and it allows it to connect its database with other (peer) databases on the network. A particularity of our solution is that PDBMS allows for conventional database technology to be effectively operational in mobile settings. We think of database mobility as a database network, where databases appear and disappear spontaneously and their network access point...

  18. Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics

    International Nuclear Information System (INIS)

    Dove, Patricia M.

    2000-01-01

    During the three years of this project, Professor Dove's laboratory made tremendous progress in understanding controls on amorphous silica dissolution kinetics in aqueous solutions. Our findings have already received considerable attention. In hydrothermal and low temperature studies, the work focused on determining quantitative and mechanistic controls on the most abundant silica polymorphs in Earth environments--quartz and amorphous silica. Our studies achieved goals set forth in the original proposal to establish a new quantitative understanding of amorphous silica dissolution. This support has resulted in 10 journal, 12 abstracts and 2 thesis publications. The PI and students were also recognized with 6 awards during this period. The 1998 EMSP conference in Chicago was an important meeting for our project. The symposium, enabled P.I. Dove to establish valuable contacts with ''users'' having specific needs for the findings of our EMSP project related to the urgency of problems in the Tanks Focus Area (TFA). Since that time, our working relations developed as Dove interacted with TFA scientists and engineers on the problems of waste glass properties. These interactions refined our experimental objectives to better meet their needs. Dove presented the results of EMSP research findings to a TFA subgroup at a Product Acceptance Workshop held in Salt Lake City during December 1998. The travel costs to attend this unanticipated opportunity were paid from EMSP project funds. In January 2000, Dove also attended a similar meeting in Atlanta with PNNL, SRL and BNF scientists/engineers to discuss new issues and make another level of decisions on the Product Acceptance goals. Our EMSP-funded research interfaced very well with the ongoing studies of Dr. Pete McGrail and colleagues in the Applied Geochemistry Group at PNNL. The value of our work to ''users'' was further demonstrated when Dove's EMSP-funded Postdoc, Dr. Jonathan Icenhower was hired by the same PNNL group. With

  19. Relational databases

    CERN Document Server

    Bell, D A

    1986-01-01

    Relational Databases explores the major advances in relational databases and provides a balanced analysis of the state of the art in relational databases. Topics covered include capture and analysis of data placement requirements; distributed relational database systems; data dependency manipulation in database schemata; and relational database support for computer graphics and computer aided design. This book is divided into three sections and begins with an overview of the theory and practice of distributed systems, using the example of INGRES from Relational Technology as illustration. The

  20. Biofuel Database

    Science.gov (United States)

    Biofuel Database (Web, free access)   This database brings together structural, biological, and thermodynamic data for enzymes that are either in current use or are being considered for use in the production of biofuels.

  1. Community Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This excel spreadsheet is the result of merging at the port level of several of the in-house fisheries databases in combination with other demographic databases such...

  2. Database Administrator

    Science.gov (United States)

    Moore, Pam

    2010-01-01

    The Internet and electronic commerce (e-commerce) generate lots of data. Data must be stored, organized, and managed. Database administrators, or DBAs, work with database software to find ways to do this. They identify user needs, set up computer databases, and test systems. They ensure that systems perform as they should and add people to the…

  3. Kinetic Typography

    DEFF Research Database (Denmark)

    van Leeuwen, Theo; Djonov, Emilia

    2014-01-01

    After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images.......After discussing broad cultural drivers behind the development of kinetic typography, the chapter outlines an approach to analysing kinetic typography which is based on Halliday's theory of transitivity, as applied by Kress and Van Leeuwen to visual images....

  4. Ion transfer kinetics at the interface between two immiscible electrolyte solutions supported on a thick-wall micro-capillary. A mini review

    Czech Academy of Sciences Publication Activity Database

    Mareček, Vladimír; Samec, Zdeněk

    2017-01-01

    Roč. 1, č. 1 (2017), s. 133-139 ISSN 2451-9103 R&D Projects: GA ČR GA13-04630S Institutional support: RVO:61388955 Keywords : Experimental ion transfer kinetics * ITIES * Theoretical aspects Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis)

  5. Studies of Double-Layer Effects at Single-Crystal Gold Electrodes. 3. Reduction Kinetics of Fluoropentaamminecobalt(III) Cation in Aqueous Solutions

    Czech Academy of Sciences Publication Activity Database

    Hromadová, Magdaléna; Fawcett, W. R.

    2004-01-01

    Roč. 108, - (2004), s. 3277-3282 ISSN 1089-5647 R&D Projects: GA ČR GP203/02/P082 Institutional research plan: CEZ:AV0Z4040901 Keywords : double - layer * single crystal * reduction kinetics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.679, year: 2003

  6. Cold Incineration of Chlorophenols in Aqueous Solution by Advanced Electrochemical Process Electro-Fenton. Effect of Number and Position of Chlorine Atoms on the Degradation Kinetics

    Science.gov (United States)

    Oturan, Nihal; Panizza, Marco; Oturan, Mehmet A.

    2009-09-01

    This study reports the kinetics of the degradation of several chlorophenols (CPs), such as monochlorophenols (2-chlorophenol and 4-chlorophenol), dichlorophenols (2,4-dichlorophenol and 2,6- dichlorophenol), trichlorophenols (2,3,5- trichlorophenol and 2,4,5-trichlorophenol), 2,3,5,6-tetrachlorophenol, and pentachlorophenol, by the electro-Fenton process using a carbon felt cathode and a Pt anode. The effect of number and the position of the chlorine atoms in the aromatic ring on the oxidative degradation rate was evaluated and discussed. The oxidation reaction of all the CPs with hydroxyl radicals evidenced a pseudo-first-order kinetics and the rate constant decreased with increasing the number of chlorine atoms. The absolute rate constant of second-order reaction kinetics between CPs and •OH was determined by the competition kinetics method in the range of (3.56-7.75) × 109 M-1 s-1 and follows the same sequence of the apparent rate constants. The mineralization of several CPs and of a mixture of all CPs under study was monitored by the total organic carbon (TOC) removal and the chlorine release during mineralization was followed by ion chromatography. Our results demonstrated that more chlorinated phenols are more difficult to mineralize; however for all the tested CPs, almost quantitative release of chloride ions was obtained after 6 h of treatment.

  7. Analytical representation for solution of the neutron point kinetics equation with time-dependent reactivity and free of the stiffness character; Representacao analitica da solucao da equacao de cinetica pontual para a reatividade variavel no tempo livre de rigidez

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Milena Wollmann da

    2013-08-01

    In this work, we report a genuine analytical representation for the solution of the neutron point kinetics equation free of the stiffness character, assuming that the reactivity is a continuous and sectionally continuous function of time. To this end, we initially cast the point kinetics equation in a first order linear differential equation. Next, we split the corresponding matrix as a sum of a diagonal matrix with a matrix, whose components contain the off-diagonal elements. Next, expanding the neutron density and the delayed neutron precursors concentrations in a truncated series, and replacing these expansions in the matrix equation, we come out with an equation, which allows to construct a recursive system, a first order matrix differential equation with source. The fundamental characteristic of this system relies on the fact that the corresponding matrix is diagonal, meanwhile the source term is written in terms of the matrix with the off-diagonal components. Further, the first equation of the recursive system has no source and satisfies the initial conditions. On the other hand, the remaining equations satisfy the null initial condition. Due to the diagonal feature of the matrix, we attain analytical solutions for these recursive equations. We also mention that we evaluate the results for any time value, without the analytical continuity because the purposed solution is free on the stiffness character. Finally, we present numerical simulations and comparisons against literature results, considering specific the applications for the following reactivity functions: constant, step, ramp, and sine. (author)

  8. Chemical kinetics and reaction mechanism

    International Nuclear Information System (INIS)

    Jung, Ou Sik; Park, Youn Yeol

    1996-12-01

    This book is about chemical kinetics and reaction mechanism. It consists of eleven chapters, which deal with reaction and reaction speed on reaction mechanism, simple reaction by rate expression, reversible reaction and simultaneous reaction, successive reaction, complicated reaction mechanism, assumption for reaction mechanism, transition state theory, successive reaction and oscillating reaction, reaction by solution, research method high except kinetics on reaction mechanism, high reaction of kinetics like pulsed radiolysis.

  9. Solving Simple Kinetics without Integrals

    Science.gov (United States)

    de la Pen~a, Lisandro Herna´ndez

    2016-01-01

    The solution of simple kinetic equations is analyzed without referencing any topic from differential equations or integral calculus. Guided by the physical meaning of the rate equation, a systematic procedure is used to generate an approximate solution that converges uniformly to the exact solution in the case of zero, first, and second order…

  10. Kinetics of uranium (4) oxidation with nitrous acid in the presence of oxalate-ions in nitric and perchloric acid solutions

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Astafurova, L.N.

    1991-01-01

    Kinetics of uranium (4) oxidation with nitrous acid in the presence of oxalate-ions are studied spectrometrically. It is shown that even at small oxalate concentrations a notable effect of tetravalent uranium stabilization is observed relatively to the oxidation with nitrous acid. In case of a significant excess of oxalate-ions the oxidation rate will be considerably slower as a result of the formation of U(4) bisoxalate complex

  11. Kinetics on Demand Is a Simple Mathematical Solution that Fits Recorded Caffeine-Induced Luminal SR Ca2+ Changes in Smooth Muscle Cells.

    Directory of Open Access Journals (Sweden)

    Norma C Perez-Rosas

    Full Text Available The process of Ca2+ release from sarcoplasmic reticulum (SR comprises 4 phases in smooth muscle cells. Phase 1 is characterized by a large increase of the intracellular Ca2+ concentration ([Ca2+]i with a minimal reduction of the free luminal SR [Ca2+] ([Ca2+]FSR. Importantly, active SR Ca2+ ATPases (SERCA pumps are necessary for phase 1 to occur. This situation cannot be explained by the standard kinetics that involves a fixed amount of luminal Ca2+ binding sites. A new mathematical model was developed that assumes an increasing SR Ca2+ buffering capacity in response to an increase of the luminal SR [Ca2+] that is called Kinetics-on-Demand (KonD model. This approach can explain both phase 1 and the refractory period associated with a recovered [Ca2+]FSR. Additionally, our data suggest that active SERCA pumps are a requisite for KonD to be functional; otherwise luminal SR Ca2+ binding proteins switch to standard kinetics. The importance of KonD Ca2+ binding properties is twofold: a more efficient Ca2+ release process and that [Ca2+]FSR and Ca2+-bound to SR proteins ([Ca2+]BSR can be regulated separately allowing for Ca2+ release to occur (provided by Ca2+-bound to luminal Ca2+ binding proteins without an initial reduction of the [Ca2+]FSR.

  12. Federal databases

    International Nuclear Information System (INIS)

    Welch, M.J.; Welles, B.W.

    1988-01-01

    Accident statistics on all modes of transportation are available as risk assessment analytical tools through several federal agencies. This paper reports on the examination of the accident databases by personal contact with the federal staff responsible for administration of the database programs. This activity, sponsored by the Department of Energy through Sandia National Laboratories, is an overview of the national accident data on highway, rail, air, and marine shipping. For each mode, the definition or reporting requirements of an accident are determined and the method of entering the accident data into the database is established. Availability of the database to others, ease of access, costs, and who to contact were prime questions to each of the database program managers. Additionally, how the agency uses the accident data was of major interest

  13. Point kinetics modeling

    International Nuclear Information System (INIS)

    Kimpland, R.H.

    1996-01-01

    A normalized form of the point kinetics equations, a prompt jump approximation, and the Nordheim-Fuchs model are used to model nuclear systems. Reactivity feedback mechanisms considered include volumetric expansion, thermal neutron temperature effect, Doppler effect and void formation. A sample problem of an excursion occurring in a plutonium solution accidentally formed in a glovebox is presented

  14. On the Future of Thermochemical Databases, the Development of Solution Models and the Practical Use of Computational Thermodynamics in Volcanology, Geochemistry and Petrology: Can Innovations of Modern Data Science Democratize an Oligarchy?

    Science.gov (United States)

    Ghiorso, M. S.

    2014-12-01

    Computational thermodynamics (CT) has now become an essential tool of petrologic and geochemical research. CT is the basis for the construction of phase diagrams, the application of geothermometers and geobarometers, the equilibrium speciation of solutions, the construction of pseudosections, calculations of mass transfer between minerals, melts and fluids, and, it provides a means of estimating materials properties for the evaluation of constitutive relations in fluid dynamical simulations. The practical application of CT to Earth science problems requires data. Data on the thermochemical properties and the equation of state of relevant materials, and data on the relative stability and partitioning of chemical elements between phases as a function of temperature and pressure. These data must be evaluated and synthesized into a self consistent collection of theoretical models and model parameters that is colloquially known as a thermodynamic database. Quantitative outcomes derived from CT reply on the existence, maintenance and integrity of thermodynamic databases. Unfortunately, the community is reliant on too few such databases, developed by a small number of research groups, and mostly under circumstances where refinement and updates to the database lag behind or are unresponsive to need. Given the increasing level of reliance on CT calculations, what is required is a paradigm shift in the way thermodynamic databases are developed, maintained and disseminated. They must become community resources, with flexible and assessable software interfaces that permit easy modification, while at the same time maintaining theoretical integrity and fidelity to the underlying experimental observations. Advances in computational and data science give us the tools and resources to address this problem, allowing CT results to be obtained at the speed of thought, and permitting geochemical and petrological intuition to play a key role in model development and calibration.

  15. MARC and Relational Databases.

    Science.gov (United States)

    Llorens, Jose; Trenor, Asuncion

    1993-01-01

    Discusses the use of MARC format in relational databases and addresses problems of incompatibilities. A solution is presented that is in accordance with Open Systems Interconnection (OSI) standards and is based on experiences at the library of the Universidad Politecnica de Valencia (Spain). (four references) (EA)

  16. Database Vs Data Warehouse

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available Data warehouse technology includes a set of concepts and methods that offer the users useful information for decision making. The necessity to build a data warehouse arises from the necessity to improve the quality of information in the organization. The date proceeding from different sources, having a variety of forms - both structured and unstructured, are filtered according to business rules and are integrated in a single large data collection. Using informatics solutions, managers have understood that data stored in operational systems - including databases, are an informational gold mine that must be exploited. Data warehouses have been developed to answer the increasing demands for complex analysis, which could not be properly achieved with operational databases. The present paper emphasizes some of the criteria that information application developers can use in order to choose between a database solution or a data warehouse one.

  17. Database Replication

    CERN Document Server

    Kemme, Bettina

    2010-01-01

    Database replication is widely used for fault-tolerance, scalability and performance. The failure of one database replica does not stop the system from working as available replicas can take over the tasks of the failed replica. Scalability can be achieved by distributing the load across all replicas, and adding new replicas should the load increase. Finally, database replication can provide fast local access, even if clients are geographically distributed clients, if data copies are located close to clients. Despite its advantages, replication is not a straightforward technique to apply, and

  18. Refactoring databases evolutionary database design

    CERN Document Server

    Ambler, Scott W

    2006-01-01

    Refactoring has proven its value in a wide range of development projects–helping software professionals improve system designs, maintainability, extensibility, and performance. Now, for the first time, leading agile methodologist Scott Ambler and renowned consultant Pramodkumar Sadalage introduce powerful refactoring techniques specifically designed for database systems. Ambler and Sadalage demonstrate how small changes to table structures, data, stored procedures, and triggers can significantly enhance virtually any database design–without changing semantics. You’ll learn how to evolve database schemas in step with source code–and become far more effective in projects relying on iterative, agile methodologies. This comprehensive guide and reference helps you overcome the practical obstacles to refactoring real-world databases by covering every fundamental concept underlying database refactoring. Using start-to-finish examples, the authors walk you through refactoring simple standalone databas...

  19. Adsorption isotherms, kinetics and column operations for the removal of hazardous dye, Tartrazine from aqueous solutions using waste materials-Bottom Ash and De-Oiled Soya, as adsorbents

    International Nuclear Information System (INIS)

    Mittal, Alok; Mittal, Jyoti; Kurup, Lisha

    2006-01-01

    Adsorbents, Bottom Ash (a power plant waste) and De-Oiled Soya (an agricultural waste) exhibit good efficacy to adsorb a highly toxic dye, Tartrazine. Through the batch technique equilibrium uptake of the dye is observed at different concentrations, pH of the solution, dosage of adsorbents and sieve size of adsorbents. Langmuir and Freundlich adsorption isotherms are successfully employed on both the adsorbents and on the basis of these models the thermodynamic parameters are evaluated. Kinetic investigations reveal that more than 50% adsorption of dye is achieved in about 1 h in both the cases, whereas, equilibrium establishment takes about 3-4 h. The linear plots obtained in rate constant and mass transfer studies further confirm the applicability of first order rate expression and mass transfer model, respectively. The kinetic data treated to identify rate controlling step of the ongoing adsorption processes indicate that for both the systems, particle diffusion process is predominant at higher concentrations, while film diffusion takes place at lower concentrations. The column studies reveal that about 96% saturation of both the columns is attained during their exhaustion, while about 88 and 84% of the dye material is recovered by eluting dilute NaOH solution through exhausted Bottom Ash and De-Oiled Soya columns, respectively

  20. Adsorption isotherms, kinetics and column operations for the removal of hazardous dye, Tartrazine from aqueous solutions using waste materials-Bottom Ash and De-Oiled Soya, as adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Alok [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal 462 007 (India)]. E-mail: aljymittal@yahoo.co.in; Mittal, Jyoti [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal 462 007 (India); Kurup, Lisha [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal 462 007 (India)

    2006-08-25

    Adsorbents, Bottom Ash (a power plant waste) and De-Oiled Soya (an agricultural waste) exhibit good efficacy to adsorb a highly toxic dye, Tartrazine. Through the batch technique equilibrium uptake of the dye is observed at different concentrations, pH of the solution, dosage of adsorbents and sieve size of adsorbents. Langmuir and Freundlich adsorption isotherms are successfully employed on both the adsorbents and on the basis of these models the thermodynamic parameters are evaluated. Kinetic investigations reveal that more than 50% adsorption of dye is achieved in about 1 h in both the cases, whereas, equilibrium establishment takes about 3-4 h. The linear plots obtained in rate constant and mass transfer studies further confirm the applicability of first order rate expression and mass transfer model, respectively. The kinetic data treated to identify rate controlling step of the ongoing adsorption processes indicate that for both the systems, particle diffusion process is predominant at higher concentrations, while film diffusion takes place at lower concentrations. The column studies reveal that about 96% saturation of both the columns is attained during their exhaustion, while about 88 and 84% of the dye material is recovered by eluting dilute NaOH solution through exhausted Bottom Ash and De-Oiled Soya columns, respectively.

  1. Adsorption isotherms, kinetics and column operations for the removal of hazardous dye, Tartrazine from aqueous solutions using waste materials--Bottom Ash and De-Oiled Soya, as adsorbents.

    Science.gov (United States)

    Mittal, Alok; Mittal, Jyoti; Kurup, Lisha

    2006-08-25

    Adsorbents, Bottom Ash (a power plant waste) and De-Oiled Soya (an agricultural waste) exhibit good efficacy to adsorb a highly toxic dye, Tartrazine. Through the batch technique equilibrium uptake of the dye is observed at different concentrations, pH of the solution, dosage of adsorbents and sieve size of adsorbents. Langmuir and Freundlich adsorption isotherms are successfully employed on both the adsorbents and on the basis of these models the thermodynamic parameters are evaluated. Kinetic investigations reveal that more than 50% adsorption of dye is achieved in about 1h in both the cases, whereas, equilibrium establishment takes about 3-4h. The linear plots obtained in rate constant and mass transfer studies further confirm the applicability of first order rate expression and mass transfer model, respectively. The kinetic data treated to identify rate controlling step of the ongoing adsorption processes indicate that for both the systems, particle diffusion process is predominant at higher concentrations, while film diffusion takes place at lower concentrations. The column studies reveal that about 96% saturation of both the columns is attained during their exhaustion, while about 88 and 84% of the dye material is recovered by eluting dilute NaOH solution through exhausted Bottom Ash and De-Oiled Soya columns, respectively.

  2. Kinetics of exchange reaction between neodymium(3) transcyclohexanediaminetetraacetate and europium(3)- and holmium(3) aquo-ions in the H2O and D2O solutions

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1983-01-01

    The exchange reaction between central ions in the NdD - Ln' 3+ systems, where Ln' 3+ is a substituting cation (Eu 3+ and Ho 3+ , D 4 =cyclohexanediaminetetraacetate) is studied and the electrophilic suhstitution mechanism is considered. To study the kinetic isotope effects, the reagents have been solVed in heavy water containing 99.9% D 2 O. The electrophilic substitution in the indicated systems proceeds through the dissociative mechanism catalyzed by protons and via the spontaneous dissociation mechanism. The exchange via the acid-catalyzed mechanism is limited by the intermediate protonated complex decay. The associative mechanism of the electrophilic exchange in the studied systems is not realized

  3. RDD Databases

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This database was established to oversee documents issued in support of fishery research activities including experimental fishing permits (EFP), letters of...

  4. Snowstorm Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Snowstorm Database is a collection of over 500 snowstorms dating back to 1900 and updated operationally. Only storms having large areas of heavy snowfall (10-20...

  5. Dealer Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dealer reporting databases contain the primary data reported by federally permitted seafood dealers in the northeast. Electronic reporting was implemented May 1,...

  6. National database

    DEFF Research Database (Denmark)

    Kristensen, Helen Grundtvig; Stjernø, Henrik

    1995-01-01

    Artikel om national database for sygeplejeforskning oprettet på Dansk Institut for Sundheds- og Sygeplejeforskning. Det er målet med databasen at samle viden om forsknings- og udviklingsaktiviteter inden for sygeplejen.......Artikel om national database for sygeplejeforskning oprettet på Dansk Institut for Sundheds- og Sygeplejeforskning. Det er målet med databasen at samle viden om forsknings- og udviklingsaktiviteter inden for sygeplejen....

  7. Physical kinetics

    International Nuclear Information System (INIS)

    Lifschitz, E.M.; Pitajewski, L.P.

    1983-01-01

    The textbook covers the subject under the following headings: kinetic gas theory, diffusion approximation, collisionless plasma, collisions within the plasma, plasma in the magnetic field, theory of instabilities, dielectrics, quantum fluids, metals, diagram technique for nonequilibrium systems, superconductors, and kinetics of phase transformations

  8. Experimental Characterization and Modelization of Ion Exchange Kinetics for a Carboxylic Resin in Infinite Solution Volume Conditions. Application to Monovalent-Trivalent Cations Exchange

    Energy Technology Data Exchange (ETDEWEB)

    Picart, S.; Mokhtari, H.; Jobelin, I. [CEA Marcoule, Nucl Energy Div, RadioChem and Proc Dept, Actinides Chem and Convers Lab, F-30207 Bagnols Sur Ceze (France); Ramiere, I. [Fuel Simulat Lab, Fuel Study Dept, F-13108 St Paul Les Durance (France)

    2010-07-01

    This study is devoted to the characterization of ion exchange inside a microsphere of carboxylic resin. It aims at describing the kinetics of this exchange reaction which is known to be controlled by interdiffusion in the particle. The fractional attainment of equilibrium function of time depends on the concentration of the cations in the resin which can be modelled by the Nernst-Planck equation. A powerful approach for the numerical resolution of this equation is introduced in this paper. This modeling is based on the work of Helfferich but involves an implicit numerical scheme which reduces the computational cost. Knowing the diffusion coefficients of the cations in the resin and the radius of the spherical exchanger, the kinetics can be hence completely determined. When those diffusion parameters are missing, they can be deduced by fitting experimental data of fractional attainment of equilibrium. An efficient optimization tool coupled with the implicit resolution has been developed for this purpose. A monovalent/trivalent cation exchange had been experimentally characterized for a carboxylic resin. Diffusion coefficients and concentration profiles in the resin were then deduced through this new model. (authors)

  9. Removal of phenol from aqueous solution by Mahua seed activated carbon: Kinetic, isotherm, mass transfer and isosteric heat of adsorption studies

    Directory of Open Access Journals (Sweden)

    Singh Yadav Lallan

    2016-01-01

    Full Text Available Mahua (Madhuca longifolia seed activated carbon (MSAC has been developed as an effective adsorbent for the removal of phenol from contaminated wastewaters. Prepared MSAC was characterized for various physico-chemical properties, Fourier transform infra- red (FTIR and scanning electron microscopy (SEM analysis. Laboratory batch experiments were performed to investigate the effect of MSAC dosage (w, pH, contact time (t, and initial phenol concentrations (Co on sorption efficiency at optimal conditions. The maximum adsorption capacity of phenol was obtained at pH=6, t=5 h and MSAC dosage=1.2 g/l. The kinetics data of phenol adsorption was very well described by the pseudo-second-order kinetic model. The equilibrium adsorption data were best fitted to the Langmuir isotherm. The average effective diffusion coefficient 6.4×10-13 m2/s was calculated from the experimental data. Thermodynamic studies confirmed the sorption process to be spontaneous and exothermic. The isosteric heat of adsorption of phenol was found to increase with an increase in the surface loading indicating that MSAC have more homogeneous surface.

  10. The Adsorption of Pb, Zn, Cu, Ni, and Cd by Modified Ligand in a Single Component Aqueous Solution: Equilibrium, Kinetic, Thermodynamic, and Desorption Studies

    Directory of Open Access Journals (Sweden)

    E. Igberase

    2017-01-01

    Full Text Available In this investigation, an amino functionalized adsorbent was developed by grafting 4-aminobenzoic acid onto the backbone of cross-linked chitosan beads. The 3 sets of beads including chitosan (CX, glutaraldehyde cross-linked chitosan (CCX, and 4-aminobenzoic acid grafted cross-linked chitosan (FGCX were characterized by FTIR, XRD, SEM, and TGA. The water content and amine concentration of FGCX were determined. The effect of adsorption parameters was studied and the optimum was used for further studies. Equilibrium data was obtained from the adsorption experiment carried out at different initial concentration; the data were applied in isotherm, thermodynamics, and kinetic studies. The Langmuir and Dubinin-Kaganer-Radushkevich (DKR models were successful in describing the isotherm data for the considered metal ions while the Freundlich and Temkin model fit some of the considered metal ions. Pseudo-second-order and intraparticle model described the kinetic data quite well. Thermodynamic parameters such as Gibb’s free energy change (ΔGo, enthalpy change (ΔHo, and entropy change (ΔSo were calculated and the results showed that the adsorption of Pb, Cu, Ni, Zn, and Cd ions onto FGCX is spontaneous and endothermic in nature. Regeneration of the spent adsorbent was efficient for the considered metal ions.

  11. Degradation of the fungicide carbendazim in aqueous solutions with UV/TiO{sub 2} process: Optimization, kinetics and toxicity studies

    Energy Technology Data Exchange (ETDEWEB)

    Saien, J. [Department of Applied Chemistry, Bu-Ali Sina University, Hamedan 65174 (Iran, Islamic Republic of)], E-mail: saien@basu.ac.ir; Khezrianjoo, S. [Department of Applied Chemistry, Bu-Ali Sina University, Hamedan 65174 (Iran, Islamic Republic of)

    2008-09-15

    An attempt was made to investigate the potential of UV-photocatalytic process in the presence of TiO{sub 2} particles for the degradation of carbendazim (C{sub 9}H{sub 9}N{sub 3}O{sub 2}), a fungicide with a high worldwide consumption but considered as a 'priority hazard substance' by the Water Framework Directive of the European Commission (WFDEC). A circulating upflow photo-reactor was employed and the influence of catalyst concentration, pH and temperature were investigated. The results showed that degradation of this fungicide can be conducted in the both processes of only UV-irradiation and UV/TiO{sub 2}; however, the later provides much better results. Accordingly, a degradation of more than 90% of fungicide was achieved by applying the optimal operational conditions of 70 mg L{sup -1} of catalyst, natural pH of 6.73 and ambient temperature of 25 deg. C after 75 min irradiation. Under these mild conditions, the initial rate of degradation can be described well by the Langmuir-Hinshelwood kinetic model. Toxicological assessments on the obtained samples were also performed by measurement of the mycelium growth inhibition of Fusarium oxysporum fungus on PDA medium. The results indicate that the kinetics of degradation and toxicity are in reasonably good agreement mainly after 45 min of irradiation; confirming the effectiveness of photocatalytic process.

  12. Experimental Characterization and Modelization of Ion Exchange Kinetics for a Carboxylic Resin in Infinite Solution Volume Conditions. Application to Monovalent-Trivalent Cations Exchange

    International Nuclear Information System (INIS)

    Picart, S.; Mokhtari, H.; Jobelin, I.; Ramiere, I.

    2010-01-01

    This study is devoted to the characterization of ion exchange inside a microsphere of carboxylic resin. It aims at describing the kinetics of this exchange reaction which is known to be controlled by interdiffusion in the particle. The fractional attainment of equilibrium function of time depends on the concentration of the cations in the resin which can be modelled by the Nernst-Planck equation. A powerful approach for the numerical resolution of this equation is introduced in this paper. This modeling is based on the work of Helfferich but involves an implicit numerical scheme which reduces the computational cost. Knowing the diffusion coefficients of the cations in the resin and the radius of the spherical exchanger, the kinetics can be hence completely determined. When those diffusion parameters are missing, they can be deduced by fitting experimental data of fractional attainment of equilibrium. An efficient optimization tool coupled with the implicit resolution has been developed for this purpose. A monovalent/trivalent cation exchange had been experimentally characterized for a carboxylic resin. Diffusion coefficients and concentration profiles in the resin were then deduced through this new model. (authors)

  13. The kinetic and thermodynamic sorption and stabilization of multiwalled carbon nanotubes in natural organic matter surrogate solutions: The effect of surrogate molecular weight

    International Nuclear Information System (INIS)

    Li, Tingting; Lin, Daohui; Li, Lu; Wang, Zhengyu; Wu, Fengchang

    2014-01-01

    Styrene sulfonate (SS) and polystyrene sulfonates (PSSs) were used as surrogates of natural organic matter to study the effect of molecular weight (from 206.2 to 70,000 Da) on their sorption by a multiwalled carbon nanotube (MWCNT) and an activated carbon (AC) and on their stabilization of MWCNT suspension. Results indicate that surface-diffusion through the liquid-sorbent boundary was the rate-controlling step of the kinetic sorption of both MWCNTs and AC, and surface-occupying and pore-filling mechanisms respectively dominated the thermodynamic sorption of MWCNTs and AC. Sorption rates and capacities of MWCNTs and AC in molecular concentration of SS and PSS decreased with increasing molecular weight. The PSSs but not SS facilitated the stabilization of MWCNT suspension because of the increased electrosteric repulsion. The PSSs with more monomers had greater capabilities to stabilize the MWCNT suspension, but the capabilities were comparable after being normalized by the total monomer number. -- Highlights: • Surface-diffusion controlled the kinetic sorption of NOM surrogates to MWCNTs and AC. • Surface-occupying mechanism dominates the thermodynamic sorption of MWCNTs. • The sorption in molecular concentration decreased with increasing M w of the PSSs. • PSS but not SS stabilized MWCNT suspension through electrosteric repulsion. • Stabilization capabilities normalized by monomer number of the PSSs were comparable. -- Molecular weight of NOM influences its sorption on and stabilizing MWCNTs

  14. Heparin kinetics

    International Nuclear Information System (INIS)

    Swart, C.A.M. de.

    1983-01-01

    The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interactions with proteins resulting in anticoagulant and lipolytic effects are discussed in a review (chapter II), which also comprises some clinical aspects of heparin therapy. In chapter III the kinetics of the anticoagulant effect are described after intravenous administration of five commercial heparin preparations. A mathematical model is presented that fits best to these kinetics. The kinetics of the anticoagulant and lipolytic effects after intravenous injection of various 35 S-radiolabelled heparin fractions and their relationship with the disappearance of the radiolabel are described in chapter IV. Chapter V gives a description of the kinetics of two radiolabels after injection of in vitro formed complexes consisting of purified, 125 I-radiolabelled antithrombin III and various 35 S-radiolabelled heparin fractions. (Auth.)

  15. Developments in diffraction databases

    International Nuclear Information System (INIS)

    Jenkins, R.

    1999-01-01

    Full text: There are a number of databases available to the diffraction community. Two of the more important of these are the Powder Diffraction File (PDF) maintained by the International Centre for Diffraction Data (ICDD), and the Inorganic Crystal Structure Database (ICSD) maintained by Fachsinformationzentrum (FIZ, Karlsruhe). In application, the PDF has been used as an indispensable tool in phase identification and identification of unknowns. The ICSD database has extensive and explicit reference to the structures of compounds: atomic coordinates, space group and even thermal vibration parameters. A similar database, but for organic compounds, is maintained by the Cambridge Crystallographic Data Centre. These databases are often used as independent sources of information. However, little thought has been given on how to exploit the combined properties of structural database tools. A recently completed agreement between ICDD and FIZ, plus ICDD and Cambridge, provides a first step in complementary use of the PDF and the ICSD databases. The focus of this paper (as indicated below) is to examine ways of exploiting the combined properties of both databases. In 1996, there were approximately 76,000 entries in the PDF and approximately 43,000 entries in the ICSD database. The ICSD database has now been used to calculate entries in the PDF. Thus, to derive d-spacing and peak intensity data requires the synthesis of full diffraction patterns, i.e., we use the structural data in the ICSD database and then add instrumental resolution information. The combined data from PDF and ICSD can be effectively used in many ways. For example, we can calculate PDF data for an ideally random crystal distribution and also in the absence of preferred orientation. Again, we can use systematic studies of intermediate members in solid solutions series to help produce reliable quantitative phase analyses. In some cases, we can study how solid solution properties vary with composition and

  16. The effect of the cooling rate during quenching, electron bombardment and plastic deformation on the kinetics of a solid solution disintegration in iron-copper alloys

    International Nuclear Information System (INIS)

    Fedorov, G.B.; Zhukov, V.P.; Braun, A.G.; Smirnov, E.A.

    1974-01-01

    From the electroresistivity variation at 77 0 K, the influence of nonequilibrium point defect density and of complexes and dislocations on the decay process of the iron-copper solid solution is determined. Owing to high quenching rate of thin foils, isochrones of their electroconductivity curves appear shifted by about 200 0 C to lower temperatures. For quenched and irradiated specimens at 200-250 0 C a sharp retardation of electroconductivity decline is observed due to a zone stage. The plastic deformation (15%) leads to a partial suppression of that stage. Both irradiation and deformation initiate the process of copper separation from the solid solution, the latter being the stronger, the more copper is in the solid solution

  17. Experiment Databases

    Science.gov (United States)

    Vanschoren, Joaquin; Blockeel, Hendrik

    Next to running machine learning algorithms based on inductive queries, much can be learned by immediately querying the combined results of many prior studies. Indeed, all around the globe, thousands of machine learning experiments are being executed on a daily basis, generating a constant stream of empirical information on machine learning techniques. While the information contained in these experiments might have many uses beyond their original intent, results are typically described very concisely in papers and discarded afterwards. If we properly store and organize these results in central databases, they can be immediately reused for further analysis, thus boosting future research. In this chapter, we propose the use of experiment databases: databases designed to collect all the necessary details of these experiments, and to intelligently organize them in online repositories to enable fast and thorough analysis of a myriad of collected results. They constitute an additional, queriable source of empirical meta-data based on principled descriptions of algorithm executions, without reimplementing the algorithms in an inductive database. As such, they engender a very dynamic, collaborative approach to experimentation, in which experiments can be freely shared, linked together, and immediately reused by researchers all over the world. They can be set up for personal use, to share results within a lab or to create open, community-wide repositories. Here, we provide a high-level overview of their design, and use an existing experiment database to answer various interesting research questions about machine learning algorithms and to verify a number of recent studies.

  18. Properties of solvated electrons, alkali anions and other species in metal solutions and kinetics of cation and electron exchange reactions. Final report

    International Nuclear Information System (INIS)

    Dye, J.L.

    1979-01-01

    The properties of solutions of alkali metals in amine solvents were studied by optical, ETR, NMR and electrochemical methods. Complexation of the alkali cations by crown ethers and cryptands permitted the preparation of concentrated solutions of alkali metals in amine and ether solvents. Extensive alkali metal NMR studies of the exchange of M + with crown-ethers and cryptands and of the alkali metal anion, M - , were made. The first crystalline salt of an alkali metal anion, Na + Cryptand [2.2.2]Na - was synthesized and characterized and led to the preparation of other alkali metal anion salts. This research provided the foundation for continuing studies of crystalline alkalide salts

  19. The kinetics of colour change in textiles and fibres treated with detergent solutions. Part I-Colour perception and fluorescence microscopy analysis.

    Science.gov (United States)

    Was-Gubala, Jolanta

    2009-09-01

    The aim of this study was to assess colour changes that occur in several types of commonly available textiles as a result of the long-term effects of various popularly used laundry detergents. A 14 day experiment was conducted using blue, red and grey/black cotton, wool, acrylic and polyester textiles. Colour changes were evaluated through the visual comparison of the colour of the textile samples against that of the untreated (control) material. The kinetics of the changes in the colour of the fibres were monitored using fluorescence microscopy (UV excitation filter). The conclusions include an assessment of the observed changes from a fibre analysis expert's point of view, as well as that of an average user/consumer of the products involved.

  20. Measuring dynamic and kinetic information in the previously inaccessible supra-τ(c) window of nanoseconds to microseconds by solution NMR spectroscopy.

    Science.gov (United States)

    Ban, David; Sabo, T Michael; Griesinger, Christian; Lee, Donghan

    2013-09-26

    Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool that has enabled experimentalists to characterize molecular dynamics and kinetics spanning a wide range of time-scales from picoseconds to days. This review focuses on addressing the previously inaccessible supra-tc window (defined as τ(c) supra-τ(c) supra-τ(c) window. In the second section, the current state of the art for RD is analyzed, as well as the considerable progress toward pushing the sensitivity of RD further into the supra-τ(c) scale by up to a factor of two (motion up to 25 μs). From the data obtained with these techniques and methodology, the importance of the supra-τ(c) scale for protein function and molecular recognition is becoming increasingly clearer as the connection between motion on the supra-τ(c) scale and protein functionality from the experimental side is further strengthened with results from molecular dynamics simulations.