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Sample records for pseudo-first order kinetic

  1. Type-I pseudo-first-order phase transition induced electrocaloric effect in lead-free Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics

    Science.gov (United States)

    Li, Feng; Chen, Guorui; Liu, Xing; Zhai, Jiwei; Shen, Bo; Li, Shandong; Li, Peng; Yang, Ke; Zeng, Huarong; Yan, Haixue

    2017-05-01

    In this study, the electrocaloric effect (ECE) of Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-0.06BT) ceramic has been directly measured using a home-made adiabatic calorimeter. The maximum adiabatic temperature change (ΔT) approaches 0.86 K under an electric field of 5 kV/mm at 110 °C, which provides experimental evidence for optimizing the ECE near the type-I pseudo-first-order phase transition (PFOPT). Most importantly, a considerable ΔT value can be maintained over a wide temperature range well above the temperature of the PFOPT under a high electric field. In addition, ΔT is closely related to the structural transition and electric field strength. This work provides a guideline to investigate the high ECE in BNT-based ferroelectric ceramics for applications in cooling technologies.

  2. Kinetics and Mechanism of the Oxidation of Coomassie Brilliant Blue ...

    African Journals Online (AJOL)

    , in aqueous solution by hypochlorite as a function of pH was investigated. While the degradation of dye obeyed pseudo-first-order kinetics, the oxidation of the dye occurred through two competitive reactions facilitated by [OCl–] and [HOCl].

  3. Adsorption kinetics for the removal of chromium (VI) from aqueous ...

    African Journals Online (AJOL)

    A comparison of kinetic models applied to the adsorption of Cr(VI) ions on the adsorbents was evaluated for the pseudo first-order, the pseudo second-order, Elovich and intraparticle diffusion kinetic models, respectively. Results show that the pseudo second-order kinetic model was found to correlate the experimental data ...

  4. Chemical Dosing and First-Order Kinetics

    Science.gov (United States)

    Hladky, Paul W.

    2011-01-01

    College students encounter a variety of first-order phenomena in their mathematics and science courses. Introductory chemistry textbooks that discuss first-order processes, usually in conjunction with chemical kinetics or radioactive decay, stop at single, discrete dose events. Although single-dose situations are important, multiple-dose events,…

  5. Modelling and experimental checking of the influence of substrate concentration on the first order kinetic constant in photo-processes.

    Science.gov (United States)

    Gómez, M; Murcia, M D; Gómez, E; Ortega, S; Sánchez, A; Thaikovskaya, O; Briantceva, N

    2016-12-01

    Most photoprocesses follow a pseudo first order kinetic law and, commonly, the kinetic parameter depends on the initial concentration of the substrate. In this work, a kinetic model, which explains this dependence on the substrate concentration and on the other operational variables, has been developed. In the model, mass transfer of substrate from the bulk solution to the wall of the photoreactor was assumed as the step determining the rate of the process. To check the model, methylene blue (MB) has been used as model substrate and photodegradation experiments have been carried out in an exciplex KrCl flow-through photoreactor, It was observed that the methylene blue conversion improved with a decrease in its initial concentration, in good agreement with the model. Also, by fitting the experimental data to the model, high correlation coefficients and a high degree of agreement between experimental and calculated conversion was obtained, which validates the model. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Thermodynamic, kinetic and mechanistic investigations of ...

    Indian Academy of Sciences (India)

    standardized by iodometric titration and gravimetrically by the thiocyanate23 method. 2.3 Kinetic Measurements. Kinetics was followed under pseudo first order con- ditions where [PPZ] > [DPC] at 25 ± 0.1◦C, unless otherwise specified. The reaction was initiated by mix- ing the DPC to PPZ solution, which also contained.

  7. Adsorption kinetics of NO on ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC)

    Science.gov (United States)

    Chen, Jinghuan; Cao, Feifei; Chen, Songze; Ni, Mingjiang; Gao, Xiang; Cen, Kefa

    2014-10-01

    Ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC) were prepared using evaporation-induced self-assembly (EISA) method and used to adsorb NO. N2 sorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm their structures. The results showed that the ordered and uniform structures were successfully synthesized and with the introduction of cerium pore properties were not significantly changed. The NO adsorption capacity of OMC was two times larger than that of activated carbon (AC). With the introduction of cerium both the adsorption capacity and the adsorption rate were improved. The effects of residence time and oxygen concentration on NO adsorption were also investigated. Oxygen played an important role in the NO adsorption (especially in the form of chemisorption) and residence time had small influence on the NO adsorption capacity. The NO adsorption kinetics was analyzed using pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion models. The results indicated that the NO adsorption process can be divided into rapid adsorption period, slow adsorption period, and equilibrium adsorption period. The pseudo-second-order model was the most suitable model for NO adsorption on OMC and Ce-OMC. The rate controlling step was the intraparticle diffusion together with the adsorption reaction.

  8. Kinetics of first order phase transitions

    CERN Document Server

    Slezov, Vitaly V

    2009-01-01

    Filling a gap in the literature, this crucial publication on the renowned Lifshitz-Slezov-Wagner Theory of first-order phase transitions is authored by one of the scientists who gave it its name. Prof Slezov spent decades analyzing this topic and obtained a number of results that form the cornerstone of this rapidly developing branch of science.Following an analysis of unresolved problems together with proposed solutions, the book develops a theoretical description of the overall course of first-order phase transformations, starting from the nucleation state right up to the late stages of coarsening. In so doing, the author illustrates the results by way of numerical computations and experimental applications. The outline of the general results is performed for segregation processes in solutions and the results used in the analysis of a variety of different topics, such as phase formation in multi-component solutions, boiling in one- and multi-component liquids, vacancy cluster evolution in solids with and wi...

  9. Contact time optimization of two-stage batch adsorber design using second-order kinetic model for the adsorption of phosphate onto alunite.

    Science.gov (United States)

    Ozacar, Mahmut

    2006-09-01

    The adsorption of phosphate onto alunite in a batch adsorber has been studied. Four kinetic models including pseudo first- and second-order equation, intraparticle diffusion equation and the Elovich equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phosphate onto alunite could be described by the pseudo second-order equation. Adsorption of phosphate onto alunite followed the Langmuir isotherm. A model has been used for the design of a two-stage batch adsorber based on pseudo second-order adsorption kinetics. The model has been optimized with respect to operating time in order to minimize total operating time to achieve a specified amount of phosphate removal using a fixed mass of adsorbent. The results of two-stage batch adsorber design studies showed that the required times for specified amounts of phosphate removal significantly decreased. It is particularly suitable for low-cost adsorbents/adsorption systems when minimising operating time is a major operational and design criterion, such as, for highly congested industrial sites in which significant volume of effluent need to be treated in the minimum amount of time.

  10. Out-of-order event processing in kinetic data structures

    DEFF Research Database (Denmark)

    Abam, Mohammad; de Berg, Mark; Agrawal, Pankaj

    2011-01-01

    We study the problem of designing kinetic data structures (KDS’s for short) when event times cannot be computed exactly and events may be processed in a wrong order. In traditional KDS’s this can lead to major inconsistencies from which the KDS cannot recover. We present more robust KDS......’s for the maintenance of several fundamental structures such as kinetic sorting and kinetic tournament trees, which overcome the difficulty by employing a refined event scheduling and processing technique. We prove that the new event scheduling mechanism leads to a KDS that is correct except for finitely many short...

  11. Kinetics of the Adsorption of Bovine Serum Albumin of White Wine ...

    African Journals Online (AJOL)

    This study investigates the kinetics of adsorption of bovine serum albumin, BSA, in white wine model solutions onto activated carbon, AC, and alumina, AL. Pseudo-first order and pseudo-second order models were applied to determine the rate and mechanism of adsorption of the white wine protein during the haze removal ...

  12. Kinetics of the Adsorption of Bovine Serum Albumin of White Wine ...

    African Journals Online (AJOL)

    NJD

    2008-11-07

    Nov 7, 2008 ... This study investigates the kinetics of adsorption of bovine serum albumin, BSA, in white wine model solutions onto activated carbon, AC, and alumina, AL. Pseudo-first order and pseudo-second order models were applied to determine the rate and mechanism of adsorption of the white wine protein during ...

  13. Tebuconazole photocatalytic degradation kinetics

    OpenAIRE

    Prestes, Thiago de Hermann; Gibbon, Danielle de Oliveira; Lansarin, Marla Azário; Moro, Celso Camilo

    2010-01-01

    The tebuconazole photocatalytic degradation kinetics was studied in a batch reactor using TiO2 (P25-Degussa) as catalyst and a high pressure mercury lamp. The photolysis, adsorption and irradiation effects in the reaction rate were evaluated. Afterward, the suspension catalyst concentration and initial pH to the maximum reaction rate was determined. It was observed that the reaction rate can be approached by a pseudo-first order, with a maximum kinetics constant at 260 mg L-1catalyst concentr...

  14. Pseudo first ordered adsorption of noxious textile dyes by low-temperature synthesized amorphous carbon nanotubes

    Science.gov (United States)

    Banerjee, D.; Bhowmick, P.; Pahari, D.; Santra, S.; Sarkar, S.; Das, B.; Chattopadhyay, K. K.

    2017-03-01

    Amorphous carbon nanotubes (a-CNTs) were synthesized by solid state reaction. The as prepared a-CNTs were characterized by X-ray diffraction, field emission scanning and high resolution transmission electron microscope and Raman spectroscopy. As-synthesized a-CNTs were used for, the first time, for removing different organic dyes from water. The dyes mainly include Rhodamine B and Methyl Orange and systematic batch mode studies of a-CNTs assisted adsorption have been executed in detail. The removing efficiency of a-CNTs has also been investigated for various sorption parameters like contact time, dosage, pH, initial dye concentration, contact time etc. It is seen that a-CNTs can be material of potential for removal of dyes. In case of Rhodamine B, the maximum time for removal was 45 min whereas for Methyl orange rapid removal was plausible in about 30 min even in ambient condition. The experimental data have been well correlated with classical Langmuir-Freundlich and Temkin adsorption models.

  15. Adsorption kinetics of NO on ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jinghuan; Cao, Feifei; Chen, Songze; Ni, Mingjiang; Gao, Xiang, E-mail: xgao1@zju.edu.cn; Cen, Kefa

    2014-10-30

    Graphical abstract: - Highlights: • Ordered mesoporous carbon (OMC) and Ce-OMC were used for NO adsorption. • The NO adsorption capacity of OMC was two times larger than that of activated carbon. • With the addition of cerium both adsorption capacity and adsorption rate increased. • The pseudo-second-order model was the most suitable model for NO adsorption on OMC. • Intraparticle diffusion was the rate controlling step for NO adsorption. - Abstract: Ordered mesoporous carbon (OMC) and cerium-containing OMC (Ce-OMC) were prepared using evaporation-induced self-assembly (EISA) method and used to adsorb NO. N{sub 2} sorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm their structures. The results showed that the ordered and uniform structures were successfully synthesized and with the introduction of cerium pore properties were not significantly changed. The NO adsorption capacity of OMC was two times larger than that of activated carbon (AC). With the introduction of cerium both the adsorption capacity and the adsorption rate were improved. The effects of residence time and oxygen concentration on NO adsorption were also investigated. Oxygen played an important role in the NO adsorption (especially in the form of chemisorption) and residence time had small influence on the NO adsorption capacity. The NO adsorption kinetics was analyzed using pseudo-first-order, pseudo-second-order, Elovich equation and intraparticle diffusion models. The results indicated that the NO adsorption process can be divided into rapid adsorption period, slow adsorption period, and equilibrium adsorption period. The pseudo-second-order model was the most suitable model for NO adsorption on OMC and Ce-OMC. The rate controlling step was the intraparticle diffusion together with the adsorption reaction.

  16. Belousov-Zhabotinsky oscillatory reaction. Kinetics of malonic acid decomposition

    Directory of Open Access Journals (Sweden)

    LJILJANA KOLAR-ANIC

    2000-10-01

    Full Text Available The kinetics of the Belousov-Zhabotinsky (BZ oscillatory reaction was analyzed. With this aim, the time evolution of a reaction mixture composed of malonic acid, bromate, sulfuric acid and cerium(III was studied at 298 K. Pseudo-first order kinetics with respect to malonic acid as the species undergoing decomposition with a corresponding rate constant, k = 7.5×10-3 min-1, was found.

  17. 1 H NMR-Based Kinetic-Mechanistic Study of the Intramolecular ...

    African Journals Online (AJOL)

    A 1H NMR study of the acid-catalyzed, intramolecular trans-esterification between isomeric 2-exo-3-exo-dihydroxybornane monoacrylate esters has afforded insights into the reaction mechanism and permitted the determination of kinetic and thermodynamic parameters for the pseudo-first-order processes. KEYWORDS ...

  18. An Analogy Using Pennies and Dimes to Explain Chemical Kinetics Concepts

    Science.gov (United States)

    Cortes-Figueroa, Jose E.; Perez, Wanda I.; Lopez, Jose R.; Moore-Russo, Deborah A.

    2011-01-01

    In this article, the authors present an analogy that uses coins and graphical analysis to teach kinetics concepts and resolve pseudo-first-order rate constants related to transition-metal complexes ligand-solvent exchange reactions. They describe an activity that is directed to upper-division undergraduate and graduate students. The activity…

  19. Fundamental Studies of Novel Zwitterionic Hybrid Membranes: Kinetic Model and Mechanism Insights into Strontium Removal

    OpenAIRE

    Wen Zhu; Junsheng Liu; Meng Li

    2014-01-01

    A series of zwitterionic hybrid membranes were prepared via the ring opening of 1,3-propanesultone with the amine groups in the chains of TMSPEDA and a subsequent sol-gel process. Their kinetic models for strontium removal were investigated using three two-parameter kinetic equations (i.e., Lagergren pseudo-first order, pseudo-second order, and Elovich models). Adsorption mechanism was evaluated using intraparticle diffusion model, diffusion-chemisorption model, and Boyd equation. It was foun...

  20. A novel method for classifying starch digestion by modelling the amylolysis of plant foods using first-order enzyme kinetic principles.

    Science.gov (United States)

    Edwards, Cathrina H; Warren, Frederick J; Milligan, Peter J; Butterworth, Peter J; Ellis, Peter R

    2014-11-01

    Studying starch amylolysis kinetics in vitro is valuable for predicting the postprandial glycaemic response to starch intake. Prediction of starch amylolysis behaviour is challenging however, because of the many physico-chemical factors which influence amylolysis. The Logarithm of Slope (LOS) method for analysis of digestibility curves using first-order enzyme kinetics can identify and quantify nutritionally important starch fractions. The early stages of in vitro amylolysis of hydrothermally processed chickpea and durum wheat with variable degrees of structural integrity were studied. The end-point product concentration (C∞) and the pseudo first-order digestibility rate constant k, obtained from LOS analysis, were then used to compute predictive digestibility curves for evaluation of the model performance. LOS analysis enabled rapid identification of nutritionally important starch-fractions. It was clear that purified starches and flours were digested by a single-phase process, but starch amylolysis in macroparticles occurred by a two-phase system that reflected differences in substrate accessibility. The model gave an excellent fit to data obtained from a range of heterogeneous materials. It provides a rigorous means of studying the mechanisms of starch amylolysis in samples of varying complexity, and we strongly recommend its use for the rapid and accurate predictions of amylolysis. Such predictions have implications for prevention and management of type 2 diabetes mellitus and obesity.

  1. Two-dimensional topological order of kinetically constrained quantum particles

    Science.gov (United States)

    Kourtis, Stefanos

    2015-03-01

    Motivated by recent experimental and theoretical work on driven optical lattices, we investigate how imposing kinetic restrictions on quantum particles that would otherwise hop freely on a two-dimensional lattice can lead to topologically ordered states. The kinetically constrained models introduced here are derived as an approximate generalization of strongly interacting particles hopping on Haldane and equivalent lattices and are pertinent to systems irradiated by circularly polarized light. After introducing a broad class of models, we focus on particular realizations and show numerically that they exhibit topological order, by observing topological ground-state degeneracies and the quantization of corresponding invariants. Apart from potentially being crucial for the interpretation of forthcoming cold-atom experiments, our results also hint at unexplored possibilities for the realization of topologically ordered matter. A further implication, relevant to fractional quantum Hall (FQH) physics, is that the correlations responsible for FQH-like states can arise from processes other than density-density interactions. Financial support from EPSRC (Grant No. EP/K028960/1) and ICAM Branch Contributions.

  2. Kinetically driven ordered phase formation in binary colloidal crystals

    Science.gov (United States)

    Bochicchio, D.; Videcoq, A.; Ferrando, R.

    2013-02-01

    The aggregation of binary colloids of the same size and balanced charges is studied by Brownian dynamics simulations for dilute suspensions. It is shown that, under appropriate conditions, the formation of colloidal crystals is dominated by kinetic effects leading to the growth of well-ordered crystallites of the sodium-chloride (NaCl) bulk phase. These crystallites form with very high probability even when the cesium-chloride (CsCl) phase is more stable thermodynamically. Global optimization searches show that this result is not related to the most favorable structures of small clusters, which are either amorphous or of the CsCl structure. The formation of the NaCl phase is related to the specific kinetics of the crystallization process, which takes place by a two-step mechanism. In this mechanism, dense fluid aggregates form at first and then crystallization follows. It is shown that the type of short-range order in these dense fluid aggregates determines which phase is finally formed in the crystallites. The role of hydrodynamic effects in the aggregation process is analyzed by stochastic rotation dynamics - molecular dynamics simulations, and we find that these effects do not play a major role in the formation of the crystallites.

  3. Kinetically Inhibited Order in a Diamond-Lattice Antiferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    MacDougall, Gregory J [ORNL; Gout, Delphine J [ORNL; Zarestky, Jerel L [ORNL; Ehlers, Georg [ORNL; Podlesnyak, Andrey A [ORNL; McGuire, Michael A [ORNL; Mandrus, David [ORNL; Nagler, Stephen E [ORNL

    2011-01-01

    Frustrated magnetic systems exhibit highly degenerate ground states and strong fluctuations, often leading to new physics. An intriguing example of current interest is the antiferromagnet on a diamond lattice, realized physically in the A-site spinel materials. This is a prototypical system in three dimensions where frustration arises from competing interactions rather than purely geometric constraints, and theory suggests the possibility of novel order at low temperature. Here we present a comprehensive single crystal neutron scattering study CoAl2O4, a highly frustrated A-site spinel. We observe strong diffuse scattering that peaks at wavevectors associated with Neel ordering. Below the temperature T*=6.5K, there is a dramatic change in elastic scattering lineshape accompanied by the emergence of well-defined spin-wave excitations. T* had previously been associated with the onset of glassy behavior. Our new results suggest instead that in fact T* signifies a first-order phase transition, but with true long-range order inhibited by the kinetic freezing of domain walls. This scenario might be expected to occur widely in frustrated systems containing first-order phase transitions and is a natural explanation for existing reports of anomalous glassy behavior in other materials.

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

    OpenAIRE

    Senthilkumaar, S.; Krishna, S. K.; Kalaamanic, P.; Subburamaan, C. V.; N. Ganapathy Subramaniam; Kang, T W

    2010-01-01

    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 we...

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    Kinetic models for pollutants reduction by Nano-scale Zero Valent Iron (NZVI) were tested in this study to gain a better understanding and description of the reaction. Adsorption kinetic models and a heterogeneous catalytic reaction kinetic equation were proposed for nitrate removal and for ammonia...... generation, respectively. A widely used pseudo-first-order reaction model was a poor fit for nitrate removal in an iron-limiting condition and for ammonia generation in an excess iron condition. However, in this study, pseudo-first-order and pseudo-second-order adsorption kinetic equations were a good fit...... for nitrate removal; in addition, a Langmuir-Hinshelwood kinetic equation was able to successfully describe ammonia generation, regardless of the NZVI dose, the ionic strength, and the initial pH. These results strongly indicate that nitrate reduction by NZVI is a heterogeneous catalytic reaction...

  6. Distributions of Autocorrelated First-Order Kinetic Outcomes: Illness Severity.

    Directory of Open Access Journals (Sweden)

    James D Englehardt

    Full Text Available Many complex systems produce outcomes having recurring, power law-like distributions over wide ranges. However, the form necessarily breaks down at extremes, whereas the Weibull distribution has been demonstrated over the full observed range. Here the Weibull distribution is derived as the asymptotic distribution of generalized first-order kinetic processes, with convergence driven by autocorrelation, and entropy maximization subject to finite positive mean, of the incremental compounding rates. Process increments represent multiplicative causes. In particular, illness severities are modeled as such, occurring in proportion to products of, e.g., chronic toxicant fractions passed by organs along a pathway, or rates of interacting oncogenic mutations. The Weibull form is also argued theoretically and by simulation to be robust to the onset of saturation kinetics. The Weibull exponential parameter is shown to indicate the number and widths of the first-order compounding increments, the extent of rate autocorrelation, and the degree to which process increments are distributed exponential. In contrast with the Gaussian result in linear independent systems, the form is driven not by independence and multiplicity of process increments, but by increment autocorrelation and entropy. In some physical systems the form may be attracting, due to multiplicative evolution of outcome magnitudes towards extreme values potentially much larger and smaller than control mechanisms can contain. The Weibull distribution is demonstrated in preference to the lognormal and Pareto I for illness severities versus (a toxicokinetic models, (b biologically-based network models, (c scholastic and psychological test score data for children with prenatal mercury exposure, and (d time-to-tumor data of the ED01 study.

  7. Adsorption of methyl orange from aqueous solution onto PMMA nanofiber: Kinetics study

    Science.gov (United States)

    Zulfikar, Muhammad Ali; Bahri, Afdal; Setiyanto, Henry; Nasir, Muhammad

    2017-07-01

    The potential of polymethyl methacrylate (PMMA) nanofiber prepared by the electrospinning technique for the methyl orange (MO) adsorption from aqueous solution was investigated. In this study, the adsorption experiments were carried out to investigate the effect of temperatures in a batch system. From experiment it can be seen that the MO adsorption using PMMA nanofiber increased with increasing temperature. The kinetic data of MO were analyzed by pseudo-first-order and pseudo-second-order kinetic models. It was found that the amount of MO adsorbed increase with increasing temperature. Kinetics parameters data indicated that the MO adsorption onto PMMA nanofiber was found to follow both pseudo first and second-order rate equations.

  8. Kinetics of the reduction of Rasaniline hydrochloride with sulphite ...

    African Journals Online (AJOL)

    The kinetics of the reduction of rosaniline hydrochloride (RH) in perchloric acid has been investigated under pseudo-first order condition of an excess [SO32-] at ionic strength of 1.0 mol dm-3 (CH3COONa), T = 30 0.1 oC and λmax = 540nm. The stoichiometry of the reaction was observed to be 1:1in terms of mole ratio of ...

  9. Fourth-Order Vibrational Transition State Theory and Chemical Kinetics

    Science.gov (United States)

    Stanton, John F.; Matthews, Devin A.; Gong, Justin Z.

    2015-06-01

    Second-order vibrational perturbation theory (VPT2) is an enormously successful and well-established theory for treating anharmonic effects on the vibrational levels of semi-rigid molecules. Partially as a consequence of the fact that the theory is exact for the Morse potential (which provides an appropriate qualitative model for stretching anharmonicity), VPT2 calculations for such systems with appropriate ab initio potential functions tend to give fundamental and overtone levels that fall within a handful of wavenumbers of experimentally measured positions. As a consequence, the next non-vanishing level of perturbation theory -- VPT4 -- offers only slight improvements over VPT2 and is not practical for most calculations since it requires information about force constants up through sextic. However, VPT4 (as well as VPT2) can be used for other applications such as the next vibrational correction to rotational constants (the ``gammas'') and other spectroscopic parameters. In addition, the marriage of VPT with the semi-classical transition state theory of Miller (SCTST) has recently proven to be a powerful and accurate treatment for chemical kinetics. In this talk, VPT4-based SCTST tunneling probabilities and cumulative reaction probabilities are give for the first time for selected low-dimensional model systems. The prospects for VPT4, both practical and intrinsic, will also be discussed.

  10. 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.

  11. Nonlinear regression analysis of kinetics of the photocatalytic decolorization of an azo dye in aqueous TiO2 slurry.

    Science.gov (United States)

    Behnajady, Mohammad A; Modirshahla, Nasser

    2006-11-01

    The kinetics of decolorization of an anionic monoazo dye of acid class named C.I. Acid Red 27 (AR27) was investigated in the UV/TiO2 process with nonlinear regression analysis. The experimental results indicated that the kinetics of decolorization of AR27 in this process fit well by pseudo-first order kinetics. With nonlinear regression analysis a model was developed for pseudo-first order rate constant (k(ap,UV/TiO2)) as a function of operational parameters such as TiO2 dosage, initial concentration of AR27, concentration of O2 and UV-light intensity (I0) as following: k(ap,UV/TiO2) = 0.0025 [TiO2](0.65) [AR27]0(-0.96) [O2](0.16)I0. This rate expression can be used for predicting k(ap,UV/TiO2) at different conditions.

  12. 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.

  13. Kinetic Study of Free Radicals Scavenging by Saffron Petal Extracts

    Directory of Open Access Journals (Sweden)

    T. Ardalan

    2013-01-01

    Full Text Available Saffron petal is the main by-product of saffron processing which is produced in large amounts, annually. The objectives of this study were to study the antioxidant activity and free radical-scavenging effects of saffron petal extracts. The ability of saffron petal to act as an antioxidant using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH free-radical method was investigated by applying the Uv–Vis spectrometry. The Uv–Vis spectra of reaction mixtures in acetonitrile revealed that saffron petal has a considerable effect on scavenging free radical. Kinetic studies were conducted by measuring the disappearance of DPPH in acetonitrile over the wavelength range of 515-522 nm under pseudo-first-order conditions at 37oC. Furthermore, the pseudo first order rate constants were determined

  14. Kinetic lattice Monte-Carlo simulations on the ordering kinetics of free and supported FePt L10-nanoparticles

    Directory of Open Access Journals (Sweden)

    Michael Müller

    2011-01-01

    Full Text Available The ordering kinetics in free and supported L10 nanoparticles was studied by means of lattice-based kinetic Monte-Carlo simulations. Starting from a fully disordered particle of Wulff shape, the simulations show that the nucleation of ordered domains is starting quickly on various (100 facets but is retarded in the particle volume due to the lack of vacancies compared with a thin film geometry. If a substrate is present, we do not find significant differences in the ordering behavior. This holds true, even if we impose a massively increased thermodynamic driving force for interface segregation, because the nucleation of ordered domains on free facets is significantly faster than the bulk diffusion of the segregating species to the interface. In cases where wetting of the substrate or surface facetting occurs, we find that diffusional atomic motion on the surface goes along with an enhanced long-range order.

  15. Second order dissipative fluid dynamics from kinetic theory

    Directory of Open Access Journals (Sweden)

    Koide T.

    2011-04-01

    Full Text Available We derive the equations of second order dissipative fluid dynamics from the relativistic Boltzmann equation following the method of W. Israel and J. M. Stewart [1]. We present a frame independent calculation of all first- and second-order terms and their coefficients using a linearised collision integral. Therefore, we restore all terms that were previously neglected in the original papers of W. Israel and J. M. Stewart.

  16. Improved antimicrobial property and controlled drug release kinetics of silver sulfadiazine loaded ordered mesoporous silica

    National Research Council Canada - National Science Library

    Jangra, Suman; Devi, Sunita; Tomer, Vijay K; Chhokar, Vinod; Duhan, Surender

    2016-01-01

    The present study deals with the loading of silver sulfadiazine into ordered mesoporous silica material by post-impregnation method and its effect on the in vitro release kinetics and antimicrobial property of the drug...

  17. Kinetic characteristics of gas-liquid ozone reactions

    Science.gov (United States)

    Levanov, A. V.; Isaikina, O. Ya.; Lunin, V. V.

    2017-10-01

    An experimental chemical method for determining the kinetic characteristics (volumetric mass transfer coefficient and rate constant of a second-order reaction) of gas-liquid ozone reactions in a bubble column reactor is described. The calculation formulas are substantiated, and the ranges of values of the experimental factors that determine the method's limits of applicability are found. The conditions under which the boundary-value problem of a gas-liquid ozone reaction of the second order can be reduced to a problem of a pseudo-first order reaction allowing an analytical solution are revealed.

  18. Leading-order nonlocal kinetic energy in peridynamics for consistent energetics and wave dispersion

    Science.gov (United States)

    Dayal, Kaushik

    2017-08-01

    This work considers the approximation of peridynamics by strain-gradient models in the linear, one-dimensional setting. Strain-gradient expansions that approximate the peridynamic dispersion relation using Taylor series are compared to strain-gradient models that approximate the peridynamic elastic energy. The dynamic and energetic expansions differ from each other, and neither captures an important feature of peridynamics that mimics atomic-scale dynamics, namely that the frequency of short waves is bounded and non-zero. The paper next examines peridynamics as the limit model along a sequence of strain-gradient models that consistently approximate both the energetics and the dispersion properties of peridynamics. Formally examining the limit suggests that the inertial term in the dynamical equation of peridynamics - or equivalently, the peridynamic kinetic energy - is necessarily nonlocal in space to balance the spatial nonlocality in the elastic energy. The nonlocality in the kinetic energy is of leading-order in the following sense: classical elasticity is the zeroth-order theory in both the kinetically nonlocal peridynamics and the classical peridynamics, but once nonlocality in the elastic energy is introduced, it must be balanced by nonlocality in the kinetic energy at the same order. In that sense, the kinetic nonlocality is not a higher-order correction; rather, the kinetic nonlocality is essential for consistent energetics and dynamics even in the simplest setting. The paper then examines the implications of kinetically nonlocal peridynamics in the context of stationary and propagating discontinuities of the kinematic fields.

  19. Ordering kinetics in model systems with inhibited interfacial adsorption

    DEFF Research Database (Denmark)

    Willart, J.-F.; Mouritsen, Ole G.; Naudts, J.

    1992-01-01

    neighboring domains. This condition can be either hard, as modeled by a singularity in the domain-boundary potential, or soft, as modeled by a version of the Blume-Capel model. The results show that the effect of the steric hindrance, be it hard or soft, is only manifested in the amplitude, A......, of the algebraic growth law, R(t)∼Atn, whereas the growth exponent, n, remains close to the value n=1/2 predicted by the classical Lifshitz-Allen-Cahn growth law for systems with nonconserved order parameter. At very low temperatures there is, however, an effective crossover to a much slower algebraic growth...

  20. Equilibrium, kinetics and thermodynamics studies of textile dyes adsorption on modified Tunisian clay

    Directory of Open Access Journals (Sweden)

    naghmouchi nahed

    2016-04-01

    Full Text Available The adsorption capacity of two anionic textile dyes (RR120 and BB150 on DMSO intercalated Tunisian raw clay was investigated with respect to contact time, initial dye concentration, pH and Temperature. The equilibrium data were fitted into Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. The kinetic parameters were calculated using pseudo-first order, pseudo second-order, intra-particle diffusion and Elovich kinetic models. The thermodynamic parameters (DH°, DS° and DG° of the adsorption process were also evaluated.

  1. Fundamental Studies of Novel Zwitterionic Hybrid Membranes: Kinetic Model and Mechanism Insights into Strontium Removal

    National Research Council Canada - National Science Library

    Zhu, Wen; Liu, Junsheng; Li, Meng

    2014-01-01

    ...., Lagergren pseudo-first order, pseudo-second order, and Elovich models). Adsorption mechanism was evaluated using intraparticle diffusion model, diffusion-chemisorption model, and Boyd equation...

  2. Modelling of an EGSB treating sugarcane vinasse using first-order variable kinetics.

    Science.gov (United States)

    López, Iván; Borzacconi, Liliana

    2011-01-01

    An expanded granular sludge bed (EGSB) anaerobic reactor treating sugar cane vinasse was modelled using a simple model with two steps (acidogenesis and methanogenesis), two populations, two substrates and completely mixed conditions. A first-order kinetic equation for both steps with time-variant kinetic coefficients was used. An observer system was used to estimate the evolution of kinetic constants over time. The model was validated by comparing methane flow predictions with experimental values. An estimation of evolution of populations of microorganisms was also performed. This approach allows calculation of specific kinetic constants that reflect biological activity of microorganisms. Variation of specific kinetic constants reflects the influence of the fraction of raw vinasse in the feed. High salt concentrations in the reactor may have inhibited the process.

  3. Adsorption kinetic and desorption studies of Cd2+ on Multi-Carboxylic-Functionalized Silica Gel

    Science.gov (United States)

    Li, Min; Wei, Jian; Meng, Xiaojing; Wu, Zhuqiang; Liang, Xiuke

    2018-01-01

    In the present study, the adsorption behavior of cadmium (II) ion from aqueous solution onto multi-carboxylic-functionalized silica gel (SG-MCF) has been investigated in detail by means of batch and column experiments. Batch experiments were performed to evaluate the effects of contact time on adsorption capacity of cadmium (II) ion. The kinetic data were analyzed on the basis of the pseudo-first-order kinetic and the pseudo-second-order kinetic models and consequently, the pseudo-second-order kinetic can better describe the adsorption process than the pseudo-first-order kinetic model. And the adsorption mechanism of the process was studied by intra-particle and film diffusion, it was found out that the adsorption rate was governed primarily by film diffusion to the adsorption onto the SG-MCF. In addition, column experiments were conducted to assess the effects initial inlet concentration and the flow rate on breakthrough time and adsorption capacity ascertaining the practical applicability of the adsorbent. The results suggest that the total amount of adsorbed cadmium (II) ion increased with declined flow rate and increased the inlet concentration. The adsorption-desorption experiment confirmed that adsorption capacity of cadmium (II) ion didn’t present an obvious decrease after five cycles.

  4. Adsorption kinetic and desorption studies of Cu2+ on Multi-Carboxylic-Functionalized Silica Gel

    Science.gov (United States)

    Li, Min; Meng, Xiaojing; Liu, Yushuang; Hu, Xinju; Liang, Xiuke

    2018-01-01

    In the present study, the adsorption behavior of copper (II) ion from aqueous solution onto multi-carboxylic-functionalized silica gel (SG-MCF) has been investigated in detail by means of batch and column experiments. Batch experiments were performed to evaluate the effects of contact time on adsorption capacity of copper (II) ion. The kinetic data were analyzed on the basis of the pseudo-first-order kinetic and the pseudo-second-order kinetic models and consequently, the pseudo-second-order kinetic can better describe the adsorption process than the pseudo-first-order kinetic model. And the adsorption mechanism of the process was studied by intra-particle and film diffusion, it was found out that the adsorption rate was governed primarily by film diffusion to the adsorption onto the SG-MCF. In addition, column experiments were conducted to assess the effects initial inlet concentration and the flow rate on breakthrough time and adsorption capacity ascertaining the practical applicability of the adsorbent. The results suggest that the total amount of adsorbed copper (II) ion increased with declined flow rate and increased the inlet concentration. The adsorption-desorption experiment confirmed that adsorption capacity of copper (II) ion didn’t present an obvious decrease after five cycles.

  5. kinetics

    Directory of Open Access Journals (Sweden)

    D. E. Panayotounakos

    2002-01-01

    Full Text Available We present the construction of the general solutions concerning the one-dimensional (1D fully dynamic nonlinear partial differential equations (PDEs, for the erosion kinetics. After an uncoupling procedure of the above mentioned equations a second–order nonlinear PDE of the Monge type governing the porosity is derived, the general solution of which is constructed in the sense that a full complement of arbitrary functions (as many as the order is introduced. Afterwards, we specify the above solution according to convenient initial conditions.

  6. Evaluation of the kinetic oxidation of aqueous volatile organic compounds by permanganate.

    Science.gov (United States)

    Mahmoodlu, Mojtaba G; Hassanizadeh, S Majid; Hartog, Niels

    2014-07-01

    The use of permanganate solutions for in-situ chemical oxidation (ISCO) is a well-established groundwater remediation technology, particularly for targeting chlorinated ethenes. The kinetics of oxidation reactions is an important ISCO remediation design aspect that affects the efficiency and oxidant persistence. The overall rate of the ISCO reaction between oxidant and contaminant is typically described using a second-order kinetic model while the second-order rate constant is determined experimentally by means of a pseudo first order approach. However, earlier studies of chlorinated hydrocarbons have yielded a wide range of values for the second-order rate constants. Also, there is limited insight in the kinetics of permanganate reactions with fuel-derived groundwater contaminants such as toluene and ethanol. In this study, batch experiments were carried out to investigate and compare the oxidation kinetics of aqueous trichloroethylene (TCE), ethanol, and toluene in an aqueous potassium permanganate solution. The overall second-order rate constants were determined directly by fitting a second-order model to the data, instead of typically using the pseudo-first-order approach. The second-order reaction rate constants (M(-1) s(-1)) for TCE, toluene, and ethanol were 8.0×10(-1), 2.5×10(-4), and 6.5×10(-4), respectively. Results showed that the inappropriate use of the pseudo-first-order approach in several previous studies produced biased estimates of the second-order rate constants. In our study, this error was expressed as a function of the extent (P/N) in which the reactant concentrations deviated from the stoichiometric ratio of each oxidation reaction. The error associated with the inappropriate use of the pseudo-first-order approach is negatively correlated with the P/N ratio and reached up to 25% of the estimated second-order rate constant in some previous studies of TCE oxidation. Based on our results, a similar relation is valid for the other volatile

  7. Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

    Science.gov (United States)

    Oboh, I.; Aluyor, E.; Audu, T.

    2015-03-01

    The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R2), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.

  8. Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

    Energy Technology Data Exchange (ETDEWEB)

    Oboh, I., E-mail: innocentoboh@uniuyo.edu.ng [Department of Chemical and Petroleum Engineering, University of Uyo, Uyo (Nigeria); Aluyor, E.; Audu, T. [Department of Chemical Engineering, University of Uyo, BeninCity, BeninCity (Nigeria)

    2015-03-30

    The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R{sup 2}), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem.

  9. Kinetics and isotherm studies of Cd(II) adsorption from aqueous solution utilizing seeds of bottlebrush plant ( Callistemon chisholmii)

    Science.gov (United States)

    Rao, Rifaqat Ali Khan; Kashifuddin, Mohammad

    2014-12-01

    Seeds of bottlebrush, a novel plant material, were found to exhibit excellent adsorption capacity over a wide range of Cd(II) concentration. It was characterized by Fourier transform infrared spectroscopy and Scanning Electron Microscopy to support the adsorption of Cd(II) ions. Effect of various parameters like pH, contact time, initial concentration and different electrolytes was investigated using batch process to optimize conditions for maximum adsorption. The adsorbent data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Redushkeuich isotherm equations at 30°, 40° and 50 °C. Thermodynamic parameters such as standard enthalpy change (Δ H°), free energy change (Δ G°) and entropy change (Δ S°) were also evaluated and the results indicated that adsorption of Cd(II) are spontaneous and endothermic. Various kinetics models including the Pseudo-first-order kinetics, Pseudo-second-order kinetics and Intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Cd(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order equation supporting that chemisorption process was involved.

  10. Quality by Design (QbD approach to develop HPLC method for eberconazole nitrate: Application oxidative and photolytic degradation kinetics

    Directory of Open Access Journals (Sweden)

    M. Vamsi Krishna

    2016-09-01

    Full Text Available Stability of eberconazole nitrate (EBZ was investigated using a stability indicating HPLC method. Quality by Design (QbD approach was used to facilitate method development. EBZ was exposed to different stress conditions, including hydrolytic (acid, base, neutral, oxidative, thermal and photolytic. Relevant degradation was found to take place in all the conditions. The degradation of EBZ followed (pseudo first-order kinetics under experimental conditions. The kinetic parameters (rate constant, t1/2, and t90 of the degradation of EBZ were calculated.

  11. Automatic blocking of nucleation and the universality of kinetic phenomena in first-order phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Zel`tser, A.S.; Soboleva, T.K.; Filippov, A.E. [Donetsk Physicotechnical Inst. (Ukraine)

    1995-07-01

    The kinetics of a first-order phase transformation are investigated using a unified mathematical approach based on he generalized Ginaburg-Landau model with a nonlocal thermodynamic potential. It is shown that since the formation of nuclei includes processes that prevent their appearance and growth in other regions in space, it should result in autostabilization of an intermediate mixed state. Various mechanisms for the formation of an effective long-range interaction in such systems are analyzed. The universality of the kinetic phenomena in first-order phase transition, which is due to the self-consistent character of the blocking of the phase-separation process and is manifested by the establishment of universal relations between the effective parameters of the system, is point out for the first time. 29 refs., 6 figs.

  12. Simplification of the Flux Function for a Higher-order Gas-kinetic Evolution Model

    CERN Document Server

    Zhou, Guangzhao; Liu, Feng

    2016-01-01

    The higher-order gas-kinetic scheme for solving the Navier-Stokes equations has been studied in recent years. In addition to the use of higher-order reconstruction techniques, many terms are used in the Taylor expansion of the gas distribution functions. Therefore, a large number of coefficients need to be determined in the calculation of the time evolution of the gas distribution function at cell interfaces. As a consequence, the higher-order flux function takes much more computational time than that of a second-order gas-kinetic scheme. This paper aims to simplify the evolution model by two steps. Firstly, the coefficients related to the higher-order spatial and temporal derivatives of a distribution function are redefined to reduce the computational cost. Secondly, based on the physical analysis, some terms can be removed without loss of accuracy. Through the simplifications, the computational efficiency of the higher-order scheme is increased significantly. In addition, a self-adaptive numerical viscosity...

  13. Chemistry and kinetics of I2 loss in urine distillate and humidity condensate

    Science.gov (United States)

    Atwater, James E.; Wheeler, Richard R., Jr.; Olivadoti, J. T.; Sauer, Richard L.

    1992-01-01

    Time-resolved molecular absorption spectrophotometry of iodinated ersatz humidity condensates and iodinated ersatz urine distillates across the UV and visible spectral regions are used to investigate the chemistry and kinetics of I2 loss in urine distillate and humidity condensate. Single contaminant systems at equivalent concentrations are also employed to study rates of iodine. Pseudo-first order rate constants are identified for ersatz contaminant model mixtures and for individual reactive constituents. The second order bimolecular reaction of elemental iodine with formic acid, producing carbon dioxide and iodine anion, is identified as the primary mechanism underlying the decay of residual I2 in ersatz humidity concentrate.

  14. Kinetic order-disorder transitions in a pause-and-go swarming model with memory.

    Science.gov (United States)

    Rimer, Oren; Ariel, Gil

    2017-04-21

    A two dimensional model of self-propelled particles combining both a pause-and-go movement pattern and memory is studied in simulations. It is shown, that in contrast to previously studied agent based models in two-dimensions, order and disorder are metastable states that can co-exist at some parameter range. In particular, this implies that the formation and decay of global order in swarms may be kinetic rather than a phase transition. Our results explain metastability recently observed in swarming locust and fish. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Surface Runoff Contamination by Soil Chemicals: Simulations for Equilibrium and First-Order Kinetics

    Science.gov (United States)

    Wallach, Rony; Shabtai, Rina

    1992-01-01

    A model was developed to predict the potential contamination of overland flow by chemicals removed from soil water by rainfall on sloping soil. The model accounts for transient water infiltration and convective-dispersive solute transport in the soil and also considers rate-limited mass transfer through a laminar boundary layer at the soil surface/runoff water interface. Sorption-desorption interactions between soil and chemicals are assumed to be subject to linear and nonlinear isotherms or to first-order kinetics. The dissolved-chemical concentrations at the soil surface and in the surface runoff were determined for different antecedent soil moistures and rainfall intensities. These concentrations are lower when the antecedent moisture is low because the time of ponding for drier soil is longer and because during that period soil solutes are displaced by greater volumes of infiltrating water. For a specified initial soil water content, higher rainfall rates cause higher dissolved-chemical concentrations at the soil surface. The degree of nonlinearity of the equilibrium isotherm greatly affects the transient dissolved-chemical concentrations and the linear isotherm cannot always be used as an alternative. These concentrations are also greatly affected by the value of the kinetics rate coefficient. In the first-order kinetics model there is a recovery of the dissolved-chemical concentration at the soil surface during the period between rainstorms. As a result, the initial concentration at the soil surface for the subsequent rainstorm is higher than that expected when equilibrium is assumed.

  16. Kinetics and Isotherm of Sunset Yellow Dye Adsorption on Cadmium Sulfide Nanoparticle Loaded on Activated Carbon

    Directory of Open Access Journals (Sweden)

    N. Mosallanejad, A. Arami

    2012-03-01

    Full Text Available The objective of this study was to assess the potential of cadmium sulfide nanoparticles loaded onto activated carbon (CdSN-AC for the removal of sunset yellow (SY dye from aqueous solution. Adsorption studies were conducted in a batch mode varying solution pH, contact time, initial dye concentration, CdSN-AC dose. In order to investigate the efficiency of SY adsorption on CdSN-AC, pseudo-first-order, pseudo-second-order kinetic models were studied. It was observed that the pseudo-second-order kinetic model fits better than other kinetic models with good correlation coefficient. Equilibrium data were fitted to the Langmuir model. It was found that the sorption of SY onto CdSN-AC is followed by these results. 

  17. Sorption Kinetics for the Removal of Cadmium and Zinc onto Palm Kernel Shell Based Activated Carbon

    Directory of Open Access Journals (Sweden)

    Muhammad Muhammad

    2010-12-01

    Full Text Available The kinetics and mechanism of cadmium and zinc adsorption on palm kernel shell based activated carbons (PKSAC have been studied. A series of batch laboratory studies were conducted in order to investigate the suitability of palm kernel shell based activated carbon (PKSAC for the removal of cadmium (cadmium ions and zinc (zinc ions from their aqueous solutions. All batch experiments were carried out at pH 7.0 and a constant temperature of 30+-1°C using an incubator shaker that operated at 150 rpm. The kinetics investigated includes the pseudo first order, the pseudo-second order and the intraparticle diffusion models. The pseudo-second order model correlate excellently the experimental data, suggesting that chemisorption processes could be the rate-limiting step. Keywords: adsorption, cadmium, kinetics, palm kernel shell, zinc

  18. Communication: Kinetics of chemical ordering in Ag-Au and Ag-Ni nanoalloys

    Science.gov (United States)

    Calvo, F.; Fortunelli, A.; Negreiros, F.; Wales, D. J.

    2013-09-01

    The energy landscape and kinetics of medium-sized Ag-Au and Ag-Ni nanoalloy particles are explored via a discrete path sampling approach, focusing on rearrangements connecting regions differing in chemical order. The highly miscible Ag27Au28 supports a large number of nearly degenerate icosahedral homotops. The transformation from reverse core-shell to core-shell involves large displacements away from the icosahedron through elementary steps corresponding to surface diffusion and vacancy formation. The immiscible Ag42Ni13 naturally forms an asymmetric core-shell structure, and about 10 eV is required to extrude the nickel core to the surface. The corresponding transformation occurs via a long and smooth sequence of surface displacements. For both systems the rearrangement kinetics exhibit Arrhenius behavior. These results are discussed in the light of experimental observations.

  19. Degradação fotocatalítica do fungicida tebuconazole em solução aquosa Tebuconazole photocatalytic degradation kinetics

    Directory of Open Access Journals (Sweden)

    Thiago de Hermann Prestes

    2010-01-01

    Full Text Available The tebuconazole photocatalytic degradation kinetics was studied in a batch reactor using TiO2 (P25-Degussa as catalyst and a high pressure mercury lamp. The photolysis, adsorption and irradiation effects in the reaction rate were evaluated. Afterward, the suspension catalyst concentration and initial pH to the maximum reaction rate was determined. It was observed that the reaction rate can be approached by a pseudo-first order, with a maximum kinetics constant at 260 mg L-1catalyst concentration and pH 7.7.

  20. Adsorption equilibrium and kinetics of dibenzothiophene from n-octane on bamboo charcoal

    Science.gov (United States)

    Zhao, Dishun; Zhang, Juan; Duan, Erhong; Wang, Jinlong

    2008-03-01

    The adsorption of the model sulfur compound dibenzothiophene (DBT) from n-octane solution on to bamboo charcoal (BC) was investigated. The equilibrium and kinetics of DBT adsorption on BC were examined. Adsorption isotherm of DBT on BC was determined and correlated with two well-known isotherm equations (Langmuir and Freundlich). The equilibrium data for DBT adsorption fitted the Freundlich model well. Two simplified kinetic models including pseudo first-order and pseudo second-order equations were selected to follow the adsorption processes. The adsorption of DBT on BC can be best described by a pseudo second-order equation. The parameters of this best-fit kinetic model were calculated and discussed.

  1. Kinetics adsorption study of the ethidium bromide by graphene oxide as adsorbent from aqueous matrices

    Science.gov (United States)

    Rajabi, M.; Moradi, O.; Zare, K.

    2017-01-01

    In this study of ethidium bromide, adsorption from aqueous matrices by graphene oxide as adsorbent was investigated. Influencing parameters in the adsorption study included contact time, temperature, and pH. The optimum time was selected 17 min, and the best value of pH was determined at 8. All adsorption experiments were performed at 298 K temperature. The maximum wavelength of ethidium bromide was 475 nm. The Elovich, four types of the pseudo-second-order, the pseudo-first-order, and intra-particle diffusion kinetic adsorption models were used for kinetic study, and the results show that adsorption of ethidium bromide on graphene oxide surface best complied with type (I) of the pseudo-second-order kinetic model.

  2. Improved antimicrobial property and controlled drug release kinetics of silver sulfadiazine loaded ordered mesoporous silica

    Directory of Open Access Journals (Sweden)

    Suman Jangra

    2016-09-01

    Full Text Available The present study deals with the loading of silver sulfadiazine into ordered mesoporous silica material by post-impregnation method and its effect on the in vitro release kinetics and antimicrobial property of the drug. The formulated SBA-15 silica material with rope-like morphology and SBA-15-silver sulfadiazine (SBA-AgSD were characterized by UV–visible spectrophotometer, small and wide-angle powder X-ray diffraction (PXRD, field emission scanning electron microscope (FESEM and high resolution transmission electron microscope (HRTEM. Thermo-gravimetric analysis of SBA-AgSD revealed a high loading amount of 52.87%. Nitrogen adsorption–desorption analysis confirmed the drug entrapment into host material by revealing a reduced surface area (214 m2/g and pore diameter (6.7 nm of the SBA-AgSD. The controlled release of silver sulfadiazine drug from the mesoporous silica to simulated gastric, intestinal and body fluids was evaluated. The Korsmeyer–Peppas model fits the drug release data with the non-Fickian diffusion model and zero order kinetics of SBA-AgSD. The antibacterial performance of the SBA-AgSD was evaluated with respect to Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. The controlled drug delivery of the SBA-AgSD revealed improved antibacterial activity, thus endorsing its applicability in effective wound dressing.

  3. The Photocatalytic Kinetics of the Methyl Orange Degradation in the Aqueous Suspension of Irradiated TiO2

    OpenAIRE

    Mazyar Peyda; Nahid Nabavi; Gholam Reza Sadeghi

    2017-01-01

    Background: In the present study, the photocatalytic (TiO2/UV) batch process has been used for the methyl orange (MO) degradation. Methods: In the catalyst range from 0.25 to 1.5 g/L, the optimum concentration of TiO2 was found to be 0.5 g/L. The kinetic behavior of MO degradation has been evaluated using the non-linear form of pseudo-first order and pseudo-second order models. Results: The goodness of the fit was evaluated using the correlation coefficient R2 value and the mean square ...

  4. Application of first order kinetics to characterize MTBE natural attenuation in groundwater

    Science.gov (United States)

    Metcalf, Meredith J.; Stevens, Graham J.; Robbins, Gary A.

    2016-04-01

    Methyl tertiary butyl ether (MTBE) was a gasoline oxygenate that became widely used in reformulated gasoline as a means to reduce air pollution in the 1990s. Unfortunately, many of the underground storage tanks containing reformulated gasoline experienced subsurface releases which soon became a health concern given the increase in public and private water supplies containing MTBE. Many states responded to this by banning the use of MTBE as an additive, including Connecticut. Although MTBE dissipates by natural attenuation, it continues to be prevalent in groundwater long after the Connecticut ban in 2004. This study estimated the rate of the natural attenuation in groundwater following the Connecticut ban by evaluating the MTBE concentration two years prior to and two years after the MTBE ban at eighty-three monitoring wells from twenty-two retail gasoline stations where MTBE contamination was observed. Sites chosen for this study had not undergone active remediation ensuring no artificial influence to the natural attenuation processes that controls the migration and dissipation of MTBE. Results indicate that MTBE has dissipated in the natural environment, at more than 80% of the sites and at approximately 82% of the individual monitoring wells. In general, dissipation approximated first order kinetics. Dissipation half-lives, calculated using concentration data from the two year period after the ban, ranged from approximately three weeks to just over seven years with an average half-life of 7.3 months with little variability in estimates for different site characteristics. The accuracy of first order estimates to predict further MTBE dissipation were tested by comparing predicted concentrations with those observed after the two year post-ban period; the predicted concentrations closely match the observed concentrations which supports the use of first order kinetics for predictions of this nature.

  5. Investigating parasitic current formation in MITLs through high-order continuum kinetic simulations

    Science.gov (United States)

    Vogman, G. V.; Hammer, J. H.; Farmer, W. A.; Shumlak, U.

    2017-10-01

    The Z pulsed power facility is designed to deliver more than 20 MA of current to a load through magnetically insulated transmission lines (MITLs), which prevent high voltage arcs. Experimental results show that as much as 10% of the current can be lost due to the unintended formation of low-density plasmas in the MITLs. The configuration of the electric and magnetic fields within the MITL, where the plasma is born, creates conditions in which drift and kinetic instabilities can lead to the formation of parasitic currents. To understand the plasma dynamics that lead to current loss, the MITL configuration is investigated using a high-order continuum kinetic Vlasov-Poisson solver in two spatial and two velocity dimensions. The simulations capture the effects of varying magnetization and yield insights into plasma behavior over the course of current rise and corresponding magnetic field generation. The effects of plasma formation at the cathode versus at the anode are explored in detail. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  6. Enzyme kinetics of the human norovirus protease control virus polyprotein processing order.

    Science.gov (United States)

    May, Jared; Korba, Brent; Medvedev, Alexei; Viswanathan, Prasanth

    2013-09-01

    The human norovirus (NoV) polyprotein is cleaved into mature non-structural proteins by both mature NoV protease (Pro, NS6) and its un-cleaved precursor (ProPol, NS6-7). Processing order is well-established with 'early' and 'late' cleavages, but the governing enzymatic mechanisms are unknown. Enzyme kinetics of a GII Pro and ProPol were analyzed using synthetic peptides representing the five natural polyprotein cleavage sites. The relative efficiency of cleavage of the individual peptides was consistent with established polyprotein processing order, and primarily correlated with enzyme turnover (kcat). Enzymatic efficiencies (kcat/Km) of ProPol at all five sites were equivalent to, or greater than, that of Pro. Binding affinities (Km) for the two least efficiently cleaved sites (p20/VPg, VPg/Pro) were 2-4-fold higher than the other sites. This work further defines the role of ProPol in NoV polyprotein cleavage, and demonstrates that human norovirus polyprotein processing order is primarily an inherent property of enzymatic activity. © 2013 Published by Elsevier Inc.

  7. Heat-induced denaturation and aggregation of ovalbumin at neutral pH described by irreversible first-order kinetics.

    Science.gov (United States)

    Weijers, Mireille; Barneveld, Peter A; Cohen Stuart, Martien A; Visschers, Ronald W

    2003-12-01

    The heat-induced denaturation kinetics of two different sources of ovalbumin at pH 7 was studied by chromatography and differential scanning calorimetry. The kinetics was found to be independent of protein concentration and salt concentration, but was strongly dependent on temperature. For highly pure ovalbumin, the decrease in nondenatured native protein showed first-order dependence. The activation energy obtained with different techniques varied between 430 and 490 kJ*mole(-1). First-order behavior was studied in detail using differential scanning calorimetry. The calorimetric traces were irreversible and highly scan rate-dependent. The shape of the thermograms as well as the scan rate dependence can be explained by assuming that the thermal denaturation takes place according to a simplified kinetic process where N is the native state, D is denatured (or another final state) and k a first-order kinetic constant that changes with temperature, according to the Arrhenius equation. A kinetic model for the temperature-induced denaturation and aggregation of ovalbumin is presented. Commercially obtained ovalbumin was found to contain an intermediate-stable fraction (IS) of about 20% that was unable to form aggregates. The denaturation of this fraction did not satisfy first-order kinetics.

  8. Promoting Higher-Order Thinking Skills: Uses of Mathcad and Classical Chemical Kinetics To Foster Student Development.

    Science.gov (United States)

    Zielinski, Theresa Julia

    1995-01-01

    Explains how the Mathcad computer program can promote the development of higher-order chemical thinking skills of students taking junior-level physical chemistry courses. The kinetics of first-order series and reversible reactions is used as an example of how this can be implemented within an interactive laboratory or lecture format. (PVD)

  9. Effects of temperature on domain-growth kinetics of fourfold-degenerate (2×1) ordering in Ising models

    DEFF Research Database (Denmark)

    Høst-Madsen, Anders; Shah, Peter Jivan; Hansen, Torben

    1987-01-01

    Computer-simulation techniques are used to study the domain-growth kinetics of (2×1) ordering in a two-dimensional Ising model with nonconserved order parameter and with variable ratio α of next-nearest- and nearest-neighbor interactions. At zero temperature, persistent growth characterized...

  10. The kinetics of the ordering of 13C-18O bonds in calcite and apatite

    Science.gov (United States)

    Stolper, D. A.; Halevy, I.; Eiler, J. M.

    2011-12-01

    Eiler and Schauble (2004) showed that the isotopes of C and O are not randomly distributed within single phases such as CO2 gas and carbonates, and in particular, that heavy isotopes of C and O tend to bond preferentially (clump) at lower temperatures. Consequently, the measurement of the deviation from a random distribution of C and O isotope distributions in a single phase can be used as a thermometer. As with other geothermometers based on homogeneous or heterogeneous equilibria, the clumped-isotope thermometer is susceptible to resetting (e.g., if the phase is reheated or experiences slow cooling). Thus, clumped-isotope "temperatures" of phases that have experienced complex thermal histories may, in fact, be closure temperatures, the interpretation of which requires quantification of the kinetics of redistribution of C and O isotopes as a function of temperature. These kinetics have received increasing attention (Dennis and Schrag, 2010; Passey 2010), and are likely to be critical for understanding clumped-isotope temperatures of samples that have been buried for long periods of time. To better constrain these kinetics we performed experiments on natural optical calcite from Mexico and carbonate-bearing apatite from the Siilinjarvi carbonatite (Finland). For each experiment, multiple single crystal grains (~2 mm in diameter) of calcite or apatite were loaded in open Pt capsules, pressurized with Ar gas, and held at 400-700 °C, 550 bars using a rapid quench TZM apparatus for 5 min to 520 hrs. After quenching, 13C-18O clumping was measured in the samples; the change from the initial Δ47 with time for each phase at each temperature was fit to simple mechanistic models of isotope exchange between sites in these phases. One conclusion of the experimental study is that resetting the internal ordering of carbonate groups proceeds more rapidly in calcites than in apatites. For example, heating apatite at 400 °C results in no change in clumping over a 24 hr period

  11. Equilibrium and kinetic study for the adsorption of p-nitrophenol from wastewater using olive cake based activated carbon

    OpenAIRE

    N.T. Abdel-Ghani; E.S.A. Rawash; G.A. El-Chaghaby

    2016-01-01

    The present work was carried out to evaluate the removal of p-nitrophenol by adsorption onto olive cake based activated carbon having a BET surface area of 672 m²/g. The batch adsorption experimental results indicated that the equilibrium time for nitrophenol adsorption by olive cake-based activated carbon was 120min. The adsorption data was modeled by equilibrium and kinetic models. The pseudo- first and second order as well as the Elovichkinetic models were applied to fit the experimental d...

  12. Lead removal from aqueous solution by natural and pretreated clinoptilolite: Adsorption equilibrium and kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Guenay, Ahmet [Chairmenship of Environmental Protection Department, Antalya Great Municipality, Antalya (Turkey); Arslankaya, Ertan [Department of Environmental Engineering, Yildiz Technical University, 34349 Yildiz, Istanbul (Turkey); Tosun, Ismail [Department of Environmental Engineering, Suleyman Demirel University, 32260 Isparta (Turkey)]. E-mail: ismailt@mmf.sdu.edu.tr

    2007-07-19

    Adsorption of Pb(II) ions from aqueous solution onto clinoptilolite has been investigated to evaluate the effects of contact time, initial concentration and pretreatment of clinoptilolite on the removal of Pb(II). Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Temkin and Dubinin-Radushkevich), four three-parameter (Redlich-Peterson, Sips, Toth and Khan) isotherm models, and kinetic models including the pseudo-first order, the pseudo-second order and Elovich equations using nonlinear regression technique. Of the two-parameter isotherms, Temkin isotherm was the best to describe the experimental data. Three-parameter isotherms have higher regression coefficients (>0.99) and lower relative errors (<5%) than two-parameter isotherms. The best fitting isotherm was the Sips followed by Toth and Redlich-Peterson isotherm equations. Maximum experimental adsorption capacity was found to be 80.933 and 122.400 mg/g for raw and pretreated clinoptilolite, respectively, for the initial concentration of 400 mg/L. Kinetic parameters; rate constants, equilibrium adsorption capacities and related coefficients for each kinetic model were evaluated according to relative errors and correlation coefficients. Results of the kinetic studies show that best fitted kinetic models are obtained to be in the order: the pseudo-first order, the pseudo-second order and Elovich equations. Using the thermodynamic equilibrium coefficients, Gibbs free energy of the Pb(II)-clinoptilolite system was evaluated. The negative value of change in Gibbs free energy ({delta}G{sup o}) indicates that adsorption of Pb(II) on clinoptilolite is spontaneous.

  13. Silica coating and photocatalytic activities of ZnO nanoparticles: Effect of operational parameters and kinetic study

    Science.gov (United States)

    Ismail, L. F. M.; Emara, M. M.; El-Moselhy, M. M.; Maziad, N. A.; Hussein, O. K.

    2014-10-01

    Silica-coating ZnO nanoparticles were prepared using the hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray Spectroscopy (EDX). It was found that ultrafine core/shell structured silica-coating ZnO nanoparticles were successfully obtained. TEM analysis revealed a continuous and uniform silica coating layer of about 8 nm in thickness on the surface of ZnO nanoparticles. The photocatalytic performance of silica-coating ZnO core/shell nanoparticles in methylene blue aqueous solution was investigated. The effects of some operational parameters such as pH value, nanocatalyst loading and initial MB concentration on the degradation efficiency were discussed. Kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Thus, the main advantage of the coating is the stability of the photocatalysts and the better performance in acidic or alkaline solutions. Compared to ZnO the maximum apparent rate constant is obtained at pH 8.5 (pH 11.5 in case of bare ZnO). Moreover, the Langmuir adsorption model was applied to describe the equilibrium isotherm at different MB concentration. The applicability of the Langmuir isotherm suggests monolayer coverage of the MB onto surface of silica-coating ZnO nanoparticles. The kinetics of the adsorption with respect to the initial dye concentration, were also investigated. The pseudo-first-order and second-order kinetic models were used and the rate constants were evaluated. The kinetic studies revealed that the pseudo-second-order kinetic model better represented the adsorption kinetics, suggesting that the adsorption process may be chemisorption.

  14. Silica coating and photocatalytic activities of ZnO nanoparticles: effect of operational parameters and kinetic study.

    Science.gov (United States)

    Ismail, L F M; Emara, M M; El-Moselhy, M M; Maziad, N A; Hussein, O K

    2014-10-15

    Silica-coating ZnO nanoparticles were prepared using the hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray Spectroscopy (EDX). It was found that ultrafine core/shell structured silica-coating ZnO nanoparticles were successfully obtained. TEM analysis revealed a continuous and uniform silica coating layer of about 8nm in thickness on the surface of ZnO nanoparticles. The photocatalytic performance of silica-coating ZnO core/shell nanoparticles in methylene blue aqueous solution was investigated. The effects of some operational parameters such as pH value, nanocatalyst loading and initial MB concentration on the degradation efficiency were discussed. Kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Thus, the main advantage of the coating is the stability of the photocatalysts and the better performance in acidic or alkaline solutions. Compared to ZnO the maximum apparent rate constant is obtained at pH 8.5 (pH 11.5 in case of bare ZnO). Moreover, the Langmuir adsorption model was applied to describe the equilibrium isotherm at different MB concentration. The applicability of the Langmuir isotherm suggests monolayer coverage of the MB onto surface of silica-coating ZnO nanoparticles. The kinetics of the adsorption with respect to the initial dye concentration, were also investigated. The pseudo-first-order and second-order kinetic models were used and the rate constants were evaluated. The kinetic studies revealed that the pseudo-second-order kinetic model better represented the adsorption kinetics, suggesting that the adsorption process may be chemisorption. Copyright © 2014. Published by Elsevier B.V.

  15. Sorption of basic dyes onto granulated pillared clays: thermodynamic and kinetic studies.

    Science.gov (United States)

    Cheknane, B; Zermane, F; Baudu, M; Bouras, O; Basly, J P

    2012-09-01

    Effect of the granulation process onto the thermodynamic and kinetic sorption parameters of two basic dyes (Basic Yellow 28-BY 28 and Basic Green 4-BG 4) was evaluated in the present work. The charge surface properties of the surfactant-modified aluminium-pillared clay (CTAB-Al-Mont-PILC) particles were not modified, and the isoelectric point remains constant after high shear wet granulation. The Gibbs free energy of both BY 28 and BG 4 sorption was negative and decreased with the granulation; the endothermic nature of the sorption process was confirmed by the positive values of ΔH°. Adsorption kinetics of the two dyes, studied at pH 6 and 150 mg L(-1), follow the pseudo-first order kinetic model with observed rate constants of 2.5-4.2×10(-2) min(-1). The intraparticle diffusion model, proposed by Weber and Morris, was applied, and the intraparticle plots revealed three distinct sections representing external mass transfer, intraparticle diffusion and adsorption/desorption equilibrium. Diffusion coefficients, calculated from the Boyd kinetic equation, increased with the granulation and the particle size. Pseudo-first order kinetic constants, intraparticle diffusion rate constants and diffusion coefficients were determined for two other initial concentrations (50 and 100 mg L(-1)) and include in a statistical study to evaluate the impact of granulation and initial concentration on the kinetic parameters. Kruskal-Wallis tests, Spearman's rank order correlation and factor analysis revealed a correlation between (i) the diffusion coefficients and granulation, and between (ii) the intraparticle diffusion rate constants and initial concentration. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Adsorption Kinetics for the Removal of Fluoride from Aqueous Solution by Activated Carbon Adsorbents Derived from the Peels of Selected Citrus Fruits

    Directory of Open Access Journals (Sweden)

    C. Chakrapani

    2010-01-01

    Full Text Available Activated carbons (ACs were prepared from the peels of Citrus documana, Citrus medica and Citrus aurantifolia fruits. Adsorption of fluoride onto these activated carbons was investigated. Effect of contact time in the removal of fluoride from aqueous solution at neutral pH was studied. Five kinetic models; the pseudo first- and second-order equations, intraparticle diffusion, pore diffusion and the Elovich equation, were selected to follow adsorption process. Adsorption of fluoride onto adsorbents could be described by pseudo second-order equation. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. The good fitting of kinetic data to pore diffusion and Elovich equations indicate that pore diffusion plays a vital role in controlling the rate of the reaction.

  17. Fundamental studies of novel zwitterionic hybrid membranes: kinetic model and mechanism insights into strontium removal.

    Science.gov (United States)

    Zhu, Wen; Liu, Junsheng; Li, Meng

    2014-01-01

    A series of zwitterionic hybrid membranes were prepared via the ring opening of 1,3-propanesultone with the amine groups in the chains of TMSPEDA and a subsequent sol-gel process. Their kinetic models for strontium removal were investigated using three two-parameter kinetic equations (i.e., Lagergren pseudo-first order, pseudo-second order, and Elovich models). Adsorption mechanism was evaluated using intraparticle diffusion model, diffusion-chemisorption model, and Boyd equation. It was found that the adsorption of strontium ions on these zwitterionic hybrid membranes fitted well with the Lagergren pseudo-second order model. Mechanism insights suggested that diffusion-chemisorption was one of the main adsorption mechanisms. Boyd equation exhibited that film-diffusion mechanism might be the control process during the starting period. These findings are very useful in strontium removal from the stimulated radioactive wastewater.

  18. Fundamental Studies of Novel Zwitterionic Hybrid Membranes: Kinetic Model and Mechanism Insights into Strontium Removal

    Directory of Open Access Journals (Sweden)

    Wen Zhu

    2014-01-01

    Full Text Available A series of zwitterionic hybrid membranes were prepared via the ring opening of 1,3-propanesultone with the amine groups in the chains of TMSPEDA and a subsequent sol-gel process. Their kinetic models for strontium removal were investigated using three two-parameter kinetic equations (i.e., Lagergren pseudo-first order, pseudo-second order, and Elovich models. Adsorption mechanism was evaluated using intraparticle diffusion model, diffusion-chemisorption model, and Boyd equation. It was found that the adsorption of strontium ions on these zwitterionic hybrid membranes fitted well with the Lagergren pseudo-second order model. Mechanism insights suggested that diffusion-chemisorption was one of the main adsorption mechanisms. Boyd equation exhibited that film-diffusion mechanism might be the control process during the starting period. These findings are very useful in strontium removal from the stimulated radioactive wastewater.

  19. Fundamental Studies of Novel Zwitterionic Hybrid Membranes: Kinetic Model and Mechanism Insights into Strontium Removal

    Science.gov (United States)

    Zhu, Wen; Li, Meng

    2014-01-01

    A series of zwitterionic hybrid membranes were prepared via the ring opening of 1,3-propanesultone with the amine groups in the chains of TMSPEDA and a subsequent sol-gel process. Their kinetic models for strontium removal were investigated using three two-parameter kinetic equations (i.e., Lagergren pseudo-first order, pseudo-second order, and Elovich models). Adsorption mechanism was evaluated using intraparticle diffusion model, diffusion-chemisorption model, and Boyd equation. It was found that the adsorption of strontium ions on these zwitterionic hybrid membranes fitted well with the Lagergren pseudo-second order model. Mechanism insights suggested that diffusion-chemisorption was one of the main adsorption mechanisms. Boyd equation exhibited that film-diffusion mechanism might be the control process during the starting period. These findings are very useful in strontium removal from the stimulated radioactive wastewater. PMID:25405224

  20. 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; Rehman, Aziz Ur

    2015-07-08

    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.

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

    Directory of Open Access Journals (Sweden)

    Muhammad Imran Khan

    2015-07-01

    Full Text Available 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.

  2. Modeling the kinetics of essential oil hydrodistillation from plant materials

    Directory of Open Access Journals (Sweden)

    Milojević Svetomir Ž.

    2013-01-01

    Full Text Available The present work deals with modeling the kinetics of essential oils extraction from plant materials by water and steam distillation. The experimental data were obtained by studying the hydrodistillation kinetics of essential oil from juniper berries. The literature data on the kinetics of essential oils hydrodistillation from different plant materials were also included into the modeling. A physical model based on simultaneous washing and diffusion of essential oil from plant materials were developed to describe the kinetics of essential oils hydrodistillation, and two other simpler models were derived from this physical model assuming either instantaneous washing followed by diffusion or diffusion with no washing (i.e. the first-order kinetics. The main goal was to compare these models and suggest the optimum ones for water and steam distillation and for different plant materials. All three models described well the experimental kinetic data on water distillation irrespective of the type of distillation equipment and its scale, the type of plant materials and the operational conditions. The most applicable one is the model involving simultaneous washing and diffusion of the essential oil. However, this model was generally inapplicable for steam distillation of essential oils, except for juniper berries. For this hydrodistillation technique, the pseudo first-order model was shown to be the best one. In a few cases, a variation of the essential oil yield with time was observed to be sigmoidal and was modeled by the Boltzmann sigmoid function.

  3. Kinetic and thermodynamic studies of Hg(II) adsorption onto MCM-41 modified by ZnCl{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Raji, Foad; Pakizeh, Majid, E-mail: pakizeh@um.ac.ir

    2014-05-01

    Highlights: • ZnCl{sub 2}-MCM-41 introduced itself as a high performance sorbent for Hg(II) removal. • Kinetics data were analyzed by pseudo-first and second order and diffusion models. • The adsorption kinetic data were described very well by pseudo-second-order model. • Sorption of Hg(II) by ZnCl{sub 2}-MCM-41 was an exothermic chemical process. • Hg(II) sorption was a spontaneous process since of minus free energy change. - Abstract: Kinetics and thermodynamics of mercury ions sorption onto ZnCl{sub 2}-MCM-41 sorbent were studied. Several rate models in the form of two main classes of mathematic kinetic models (adsorption reaction models and adsorption diffusion models) were investigated. Pseudo-first-order, pseudo-second-order, Elovich, film and intraparticle diffusion models were used to analyze the kinetic data. Results showed that the pseudo-second order model can well describe the adsorption kinetic data. The thermodynamic parameters, such as Gibb's free energy change (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were also evaluated. Negative value of free energy at temperature range of 20–55 °C, indicates the spontaneous nature of Hg(II) sorption by ZnCl{sub 2}-MCM-41 sorbent. The adsorption capacity which was found to decrease with temperature showed the exothermic nature of the mercury sorption process (ΔH° = −49.4 kJ mol{sup −1}). The negative ΔS° value (−148.9 J mol{sup −1} K{sup −1}) revealed a decrease in the randomness at the solid/solution interface and also indicated the fast adsorption of the Hg(II) onto active sites.

  4. Kinetic sorption of contaminants of emerging concern by a palygorskite-montmorillonite filter medium.

    Science.gov (United States)

    Berhane, Tedros M; Levy, Jonathan; Krekeler, Mark P S; Danielson, Neil D

    2017-06-01

    Kinetic sorption of bisphenol A (BPA), carbamazepine (CMZ) and ciprofloxacin (CIP) by three palygorskite-montmorillonite (Pal-Mt) granule sizes was studied. For BPA, CMZ and CIP, apparent sorption equilibrium was reached within about 3, 5 and 16 h, respectively. The highest and the lowest sorption capacities were by the small and the large granule sizes, respectively. Experimental results were compared to various sorption kinetics models to gain insights regarding the sorption processes and achieve a predictive capacity. The pseudo-second order (PSO) and the Elovich models performed the best while the pseudo-first order (PFO) model was only adequate for CMZ. The intraparticle-diffusion (IPD) model showed a two-step linear plot of BPA, CMZ and CIP sorption versus square root of time that was indicative of surface-sorption followed by IPD as a rate-limiting process before equilibrium was reached. Using the pseudo-first order (PFO) and the pseudo-second order (PSO) rate constants combined with previously-established Langmuir equilibrium sorption models, the kinetic sorption (ka) and desorption (kd) Langmuir kinetic rate constants were theoretically calculated for BPA and CIP. Kinetic sorption was then simulated using these theoretically calculated ka and kd values, and the simulations were compared to the observed behavior. The simulations fit the observed sorbed concentrations better during the early part of the experiments; the observed sorption during later times occurred more slowly than expected, supporting the hypothesis that IPD becomes a rate-limiting process during the course of the experiment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Roots of the second order equation of neutronic kinetics; Raices de la ecuacion de segundo orden de la cinetica neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Polo L, M. A.; Espinosa P, G. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Area de Ingenieria en Recursos Energeticos, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico)], e-mail: gepe@xanum.uam.mx

    2009-10-15

    In this work is presented the deduction and solution of punctual equation of neutronic kinetics of second order, which is obtained applying the fundamental principles of nuclear reactor physics. The work hypothesis consisted on considering that the temporary dependence of current vector is not worthless in the constitutive law for the approach of neutronic processes with the diffusion equation. As results of work eight roots of analytical solution of punctual equation of neutronic kinetics of second order are obtained for case of six groups of slowed neutrons, a root more respect the classic pattern of punctual equation of neutronic kinetics. This theory can be used when appear highly heterogeneous configurations in the nuclear reactor. (Author)

  6. 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.

  7. Kinetic Analysis of Parallel-Consecutive First-Order Reactions with a Reversible Step: Concentration-Time Integrals Method

    Science.gov (United States)

    Mucientes, A. E.; de la Pena, M. A.

    2009-01-01

    The concentration-time integrals method has been used to solve kinetic equations of parallel-consecutive first-order reactions with a reversible step. This method involves the determination of the area under the curve for the concentration of a given species against time. Computer techniques are used to integrate experimental curves and the method…

  8. Deconvolution of the thermoluminescent emission curve. Second order kinetics; Deconvolucion de la curva de emision termoluminiscente. Cinetica de segundo orden

    Energy Technology Data Exchange (ETDEWEB)

    Moreno y M, A. [Departamento de Apoyo en Ciencias Aplicadas, Benemerita Universidad Autonoma de Puebla, Sur 104 Col. Centro, 72000 Puebla (Mexico); Moreno B, A. [Facultad de Quimica, Ciudad Universitaria, UNAM, 04510 Mexico D.F. (Mexico)

    1999-07-01

    In this work it is described the Randall and Wilkins second order kinetics in Microsoft Excel language, which allows its expression as the sum of Gaussian and the correction factors corresponding. These factors are obtained of the differences between the real thermoluminescent curve and the Gaussian proposed. The results obtained justify the Gaussian expression added to the correction factor. (Author)

  9. 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.

  10. Kinetics of Copper Adsorption from Effluent Stream by ZeoliteNaX

    Science.gov (United States)

    Singh, Surinder; Sambi, S. S.; Sharma, S. K.; Pandey, Pankaj Kumar

    2010-06-01

    The batch experiments were conducted to study the copper (II) removal by ZeoliteNaX at temperature of 288+1 K, adsorbent dose of 2 g/L and contact time of 24 hour. Effects of pH, temperature, contact time and Cu (II) ion concentration by the adsorbent were investigated. The data were analyzed using the Langmuir, Freundlich and Temkin isotherms. Freundlich isotherm was found to correlate the adsorption of Cu (II) better and the mono-layer adsorption capacity for Cu (II) removal was 41.6 mg/g. The adsorbed amounts of Cu (II) reached equilibrium within 150 minutes. The four adsorption kinetic models namely, the first order equation, second order equations, pseudo-first order equation and pseudo second-order equations were also tested to fit the data. The pseudo-first-order equation was found to fit best for the experimental data. Thermodynamic analysis indicated the spontaneous and endothermic nature of the adsorption of Cu (II) by ZeoliteNaX.

  11. Structural and Kinetic Properties of Lumazine Synthase Isoenzymes in the Order Rhizobiales

    Energy Technology Data Exchange (ETDEWEB)

    Klinke,S.; Zylberman, V.; Bonomi, H.; Haase, I.; Guimaraes, B.; Braden, B.; Bacher, A.; Fischer, M.; Goldbaum, F.

    2007-01-01

    6, 7-Dimethyl-8-ribityllumazine synthase (lumazine synthase; LS) catalyzes the penultimate step in the biosynthesis of riboflavin in plants and microorganisms. This protein is known to exhibit different quaternary assemblies between species, existing as free pentamers, decamers (dimers of pentamers) and icosahedrally arranged dodecamers of pentamers. A phylogenetic analysis on eubacterial, fungal and plant LSs allowed us to classify them into two categories: Type I LSs (pentameric or icosahedral) and Type II LSs (decameric). The Rhizobiales represent an order of ?-proteobacteria that includes, among others, the genera Mesorhizobium, Agrobacterium and Brucella. Here, we present structural and kinetic studies on several LSs from Rhizobiales. Interestingly, Mesorhizobium and Brucella encode both a Type-I LS and a Type-II LS called RibH1 and RibH2, respectively. We show that Type II LSs appear to be almost inactive, whereas Type I LSs present a highly variable catalytic activity according to the genus. Additionally, we have solved four RibH1/RibH2 crystallographic structures from the genera Mesorhizobium and Brucella. The relationship between the active-site architecture and catalytic properties in these isoenzymes is discussed, and a model that describes the enzymatic behavior is proposed. Furthermore, sequence alignment studies allowed us to extend our results to the genus Agrobacterium. Our results suggest that the selective pressure controlling the riboflavin pathway favored the evolution of catalysts with low reaction rates, since the excess of flavins in the intracellular pool in Rhizobiales could act as a negative factor when these bacteria are exposed to oxidative or nitrosative stress.

  12. 8-Hydroxyqunoline adsorption from aqueous solution using powdered orange peel: kinetic and isotherm study

    Directory of Open Access Journals (Sweden)

    Siraj Khalid

    2015-12-01

    Full Text Available Adsorption of 8-hydroxyquinoline (8HQ on powdered orange peel (POP, a locally available adsorbent, has been studied. Experiment was performed on different 8HQ concentration, particle size, and adsorbent dosage. The Langmuir and Freundlich adsorption isotherm model has been tested. The obtained results best fitted the Langmuir model, suggesting monolayer adsorption of 8HQ on POP. The kinetic studies for the adsorption process were also carried out using pseudo-first- and pseudo-second-order models, and the data obtained is best fitted to the pseudo-second-order kinetic model. Thermodynamic parameters were calculated for the adsorption process and the result showed that the values of ΔGads, ΔHads, and ΔSads are −1171.4J/mol, −140J/mol and −40.5 J/K at 303 K. Thus, it can be summarized that the adsorption of 8HQ is spontaneous, chemisorbed, monolayer, and exothermic

  13. Kinetic and isotherm studies of Cu(II) biosorption onto valonia tannin resin

    Energy Technology Data Exchange (ETDEWEB)

    Sengil, I. Ayhan [Department of Environmental Engineering, Engineering Faculty, Sakarya University, 54100 Sakarya (Turkey)], E-mail: asengil@sakarya.edu.tr; Ozacar, Mahmut [Department of Chemistry, Science and Arts Faculty, Sakarya University, 54100 Sakarya (Turkey); Tuerkmenler, Harun [Institute of Sciences and Technology, Sakarya University, 54040 Sakarya (Turkey)

    2009-03-15

    The biosorption of Cu(II) from aqueous solutions by valonia tannin resin was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, the Elovich and the intraparticle diffusion model equation - to determine the best fit equation for the biosorption of copper ions onto valonia tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well.

  14. On–off asymmetries in oxygen consumption kinetics of single Xenopus laevis skeletal muscle fibres suggest higher-order control

    Science.gov (United States)

    Wüst, Rob CI; van der Laarse, Willem J; Rossiter, Harry B

    2013-01-01

    The mechanisms controlling skeletal muscle oxygen consumption () during exercise are not well understood. We determined whether first-order control could explain kinetics at contractions onset () and cessation () in single skeletal muscle fibres differing in oxidative capacity, and across stimulation intensities up to . Xenopus laevis fibres (n= 21) were suspended in a sealed chamber with a fast response electrode to measure every second before, during and after stimulated isometric contractions. A first-order model did not well characterise on-transient kinetics. Including a time delay (TD) in the model provided a significantly improved characterisation than a first-order fit without TD (F-ratio; P fibres contracting at (mean ± SD TD: 14 ± 3 s). On-transient kinetics () was weakly and linearly related to (R2= 0.271, P= 0.015). Off-transient kinetics, however, were first-order, and was greater in low-oxidative ( fibres ( > 0.10 nmol mm−3 s−1; 170 ± 70 vs. 29 ± 6 s, P < 0.001). was proportional to (R2= 0.727, P < 0.001), unlike in the on-transient. The calculated oxygen deficit was larger (P < 0.05) than the post-contraction volume of consumed oxygen at all intensities except . These data show a clear dissociation between the kinetic control of at the onset and cessation of contractions and across stimulation intensities. More complex models are therefore required to understand the activation of mitochondrial respiration in skeletal muscle at the start of exercise. PMID:23165768

  15. Kinetic study of brilliant green adsorption from aqueous solution onto white rice husk ash.

    Science.gov (United States)

    Tavlieva, Mariana P; Genieva, Svetlana D; Georgieva, Velyana G; Vlaev, Lyubomir T

    2013-11-01

    The present research was focused on the study of adsorption kinetics of brilliant green (BG) onto white rice husk ash from aqueous solutions. The research was performed in the temperature interval 290-320 K in 10° steps and in the concentration range of 3-100 mg L(-1). Batch studies were conducted in order to determine the optimal adsorbent dose, and the time required to reach the adsorption equilibrium at each temperature. The effect of the initial concentration of brilliant green was studied (pH not adjusted), as well as the effect of temperature. The maximum adsorption capacity of the WRHA for BG at 320 K was determined to be 85.56 mg g(-1). The adsorption kinetic data were analyzed employing several kinetic models: pseudo-first-order equation, pseudo-second-order equation, Elovichequation, Banghman's equation, Diffusion-chemisorption model, and Boyd kinetic expression. It was established that the adsorption process obeyed the pseudo-second-order kinetic model. Based on the rate constants obtained by this kinetic model using Arrhenius and Eyring equations, the activation parameters were determined, namely the activation energy (50.04 kJ mol(-1)), the change of entropy (-318.31 J mol(-1) K(-1)), enthalpy (-47.50 kJ mol(-1)), and Gibbs free energy (range 44.81-54.36 kJ mol(-1)) for the formation of activated complex from the reagents. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. First-order kinetics of landfill leachate treatment in a pilot-scale anaerobic sequence batch biofilm reactor.

    Science.gov (United States)

    Contrera, Ronan Cleber; da Cruz Silva, Katia Cristina; Morita, Dione Mari; Domingues Rodrigues, José Alberto; Zaiat, Marcelo; Schalch, Valdir

    2014-12-01

    This paper reports the kinetics evaluation of landfill leachate anaerobic treatment in a pilot-scale Anaerobic Sequence Batch Biofilm Reactor (AnSBBR). The experiment was carried out at room temperature (23.8 ± 2.1 °C) in the landfill area in São Carlos-SP, Brazil. Biomass from the bottom of a local landfill leachate stabilization pond was used as inoculum. After acclimated and utilizing leachate directly from the landfill, the AnSBBR presented efficiency over 70%, in terms of COD removal, with influent COD ranging from 4825 mg L(-1) to 12,330 mg L(-1). To evaluate the kinetics of landfill leachate treatment, temporal profiles of CODFilt. concentration were performed and a first-order kinetics model was adjusted for substrate consumption, obtaining an average k1 = 4.40 × 10(-5) L mgTVS(-1) d(-1), corrected to 25 °C. Considering the temperature variations, a temperature-activity coefficient θ = 1.07 was obtained. Statistical "Randomness" and "F" tests were used to successfully validate the model considered. Thus, the results demonstrate that the first-order kinetic model is adequate to model the anaerobic treatment of the landfill leachate in the AnSBBR. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Adsorption and kinetic studies of seven different organic dyes onto magnetite nanoparticles loaded tea waste and removal of them from wastewater samples

    Science.gov (United States)

    Madrakian, Tayyebeh; Afkhami, Abbas; Ahmadi, Mazaher

    2012-12-01

    Adsorption of seven different organic dyes from aqueous solutions onto magnetite nanoparticles loaded tea waste (MNLTW) was studied. MNLTW was prepared via a simple method and was fully characterized. The properties of this magnetic adsorbent were characterized by scanning electron microscopy and X-ray diffraction. Adsorption characteristics of the MNLTW adsorbent was examined using Janus green, methylene blue, thionine, crystal violet, Congo red, neutral red and reactive blue 19 as adsorbates. Dyes adsorption process was thoroughly studied from both kinetic and equilibrium points of view for all adsorbents. The experimental isotherm data were analyzed using Langmuir, Freundlich, Sips, Redlich-Peterson, Brouers-Sotolongo and Temkin isotherms. The results from Langmuir isotherm indicated that the capacity of MNLTW for the adsorption of cationic dyes was higher than that for anionic dyes. The adsorption kinetics was tested for the pseudo-first order and pseudo-second order kinetic models at different experimental conditions.

  18. Sorption kinetics of diuron on volcanic ash derived soils.

    Science.gov (United States)

    Cáceres-Jensen, Lizethly; Rodríguez-Becerra, Jorge; Parra-Rivero, Joselyn; Escudey, Mauricio; Barrientos, Lorena; Castro-Castillo, Vicente

    2013-10-15

    Diuron sorption kinetic was studied in Andisols, Inceptisol and Ultisols soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Two types of kinetic models were used to fit the experimental dates: those that allow to establish principal kinetic parameters and modeling of sorption process (pseudo-first-order, pseudo-second-order), and some ones frequently used to describe solute transport mechanisms of organic compounds on different sorbents intended for remediation purposes (Elovich equation, intraparticle diffusion, Boyd, and two-site nonequilibrium models). The best fit was obtained with the pseudo-second-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the behavior of Diuron in each soil, in Andisols were observed the highest values for both parameters. The application of the models to describe solute transport mechanisms allowed establishing that in all soils the mass transfer controls the sorption kinetic across the boundary layer and intraparticle diffusion into macropores and micropores. The slowest sorption rate was observed on Ultisols, behavior which must be taken into account when the leaching potential of Diuron is considered. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Kinetics, equilibrium and thermodynamic studies on biosorption of Ag(I) from aqueous solution by macrofungus Pleurotus platypus

    Energy Technology Data Exchange (ETDEWEB)

    Das, Devlina [School of Biosciences and Technology, VIT University, Vellore, Tamil Nadu (India); Das, Nilanjana, E-mail: nilanjana00@lycos.com [School of Biosciences and Technology, VIT University, Vellore, Tamil Nadu (India); Mathew, Lazar [School of Biosciences and Technology, VIT University, Vellore, Tamil Nadu (India)

    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{sup -1} of biomass at pH 6.0 in the presence of 200 mg L{sup -1} Ag(I) at 20 deg. 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 ({Delta}G, {Delta}H and {Delta}S) 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.

  20. Influence of operational parameters and kinetics analysis on the photocatalytic reduction of Cr(VI) by immobilized ZnO.

    Science.gov (United States)

    Behnajady, Mohammad A; Mansoriieh, Nafiseh; Modirshahla, Nasser; Shokri, Mohammad

    2012-01-01

    In the present work the performance of immobilized ZnO on a glass plate with the heat attachment method has been described for photoreduction of Cr(VI) to the less harmful Cr(III) at different operational parameters. The photoreduction of Cr(VI) on the surface of the immobilized ZnO catalyst was studied as a function of the pH of solution, initial Cr(VI) concentration and ultraviolet (UV) light intensity. Results indicated that the reduction rate decreases with increasing initial concentration of Cr(VI) and initial pH of solution, whereas it increases with increasing UV light intensity. The photoreduction rate of Cr(VI) on the surface of the immobilized ZnO in the presence of O2 as mobile gas is more than Ar and N2. The reduction process of Cr(VI) by immobilized ZnO also could be done under visible light irradiation. Pseudo first-order kinetics were observed for the photoreduction of Cr(VI) at different operational conditions. With non-linear regression analysis a mathematical kinetics model was developed for the pseudo first-order constant (k(ap)) as a function of operational parameters.

  1. Kinetic studies on the adsorption of methylene blue onto vegetal fiber activated carbons

    Science.gov (United States)

    Cherifi, Hakima; Fatiha, Bentahar; Salah, Hanini

    2013-10-01

    The vegetable sponge of cylindrical loofa (CL), a natural product which grows in the north of Algeria, was used to prepare activated carbons. Two activated carbons, AC1 and AC2, by two physiochemical activation methods to be used for methylene blue removal from wastewater. The surface structure of AC1, AC2 and CL were analyzed by scanning electron microscopy. Adsorption isotherm of methylene blue onto the prepared activated carbons was determined by batch tests. The effects of various parameters such as contact time, initial concentration, pH, temperature, adsorbent dose and granulometry were investigated, at agitation rate 150 rpm. The results showed that the equilibrium uptake increased with increasing initial MB concentration. The maximum % removal of MB obtained was 99% at 50 °C for AC1 and 82% at 30 °C for AC2. The increase in initial pH in the ranges of 2-10 increases the yields removal of MB on AC2. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The latter provided the best correlation of the experimental data compared to the pseudo-first-order model.

  2. Kinetics and Product Selectivity (Yield) of Second Order Competitive Consecutive Reactions in Fed-Batch Reactor and Plug Flow Reactor

    OpenAIRE

    Selvamony, Subash Chandra Bose

    2013-01-01

    This literature compares the performance of second order competitive consecutive reaction in Fed-Batch Reactor with that in continuous Plug Flow Reactor. In a kinetic sense, this simulation study aims to develop a case for continuous Plug Flow Reactor in pharmaceutical, fine chemical, and related other chemical industries. MATLAB is used to find solutions for the differential equations. The simulation results show that, for certain cases of nonelementary scenario, product selectivity is highe...

  3. Kinetics and equilibrium adsorption study of p-nitrophenol onto activated carbon derived from walnut peel.

    Science.gov (United States)

    Liu, Xiaohong; Wang, Fang; Bai, Song

    2015-01-01

    An original activated carbon prepared from walnut peel, which was activated by zinc chloride, was modified with ammonium hydroxide or sodium hydroxide in order to contrast the adsorption property of the three different activated carbons. The experiment used a static adsorption test for p-nitrophenol. The effects of parameters such as initial concentration, contact time and pH value on amount adsorbed and removal are discussed in depth. The thermodynamic data of adsorption were analyzed by Freundlich and Langmuir models. The kinetic data of adsorption were measured by the pseudo-first-order kinetics and the pseudo-second-order kinetics models. The results indicated that the alkalized carbon samples derived from walnut peel had a better performance than the original activated carbon treated with zinc chloride. It was found that adsorption equilibrium time was 6 h. The maximum removal rate of activated carbon treated with zinc chloride for p-nitrophenol was 87.3% at pH 3,whereas the maximum removal rate of the two modified activated carbon materials was found to be 90.8% (alkalized with ammonium hydroxide) and 92.0% (alkalized with sodium hydroxide) at the same pH. The adsorption data of the zinc chloride activated carbon were fitted to the Langmuir isotherm model. The two alkalized activated carbon samples were fitted well to the Freundlich model. The pseudo-second-order dynamics equation provided better explanation of the adsorption dynamics data of the three activated carbons than the pseudo-first-order dynamics equation.

  4. Adsorption and kinetic studies on the removal of chromium and copper onto Chitosan-g-maliec anhydride-g-ethylene dimethacrylate.

    Science.gov (United States)

    Gopal Reddi, M R; Gomathi, T; Saranya, M; Sudha, P N

    2017-11-01

    The present work was designed to remove toxic metals chromium and copper using the double grafted copolymer Chitosan-g-Maleic anhydride-g-ethylene dimethacrylate. The graft copolymer was synthesized through chain polymerization reaction using ceric ammonium nitrate as the initiator. Prepared Chitosan-g-Maleic anhydride-g-ethylene dimethacrylate was used in order to remove the heavy metals chromium and copper from aqueous solutions of 200ppm/L concentration proceeding batch adsorption process by varying the parameters such as adsorbent dose, contact time, pH and initial concentration of the metal solution. The experimental data were equipped with isotherm models such as Langmuir and Freundlich and pseudo-first order and pseudo-second order kinetics. The calculated results revealed that the adsorption favours Freundlich isotherm and follows pseudo-second order kinetics. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Second-order advantage from kinetic-spectroscopic data matrices in the presence of extreme spectral overlapping

    Energy Technology Data Exchange (ETDEWEB)

    Culzoni, Maria J. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina); Goicoechea, Hector C. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina)], E-mail: hgoico@fbcb.unl.edu.ar; Ibanez, Gabriela A.; Lozano, Valeria A. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina); Marsili, Nilda R. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina); Olivieri, Alejandro C. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina)], E-mail: aolivier@fbioyf.unr.edu.ar; Pagani, Ariana P. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina)

    2008-04-28

    Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples.

  6. A multi-dimensional high-order discontinuous Galerkin method based on gas kinetic theory for viscous flow computations

    Science.gov (United States)

    Ren, Xiaodong; Xu, Kun; Shyy, Wei; Gu, Chunwei

    2015-07-01

    This paper presents a high-order discontinuous Galerkin (DG) method based on a multi-dimensional gas kinetic evolution model for viscous flow computations. Generally, the DG methods for equations with higher order derivatives must transform the equations into a first order system in order to avoid the so-called "non-conforming problem". In the traditional DG framework, the inviscid and viscous fluxes are numerically treated differently. Differently from the traditional DG approaches, the current method adopts a kinetic evolution model for both inviscid and viscous flux evaluations uniformly. By using a multi-dimensional gas kinetic formulation, we can obtain a spatial and temporal dependent gas distribution function for the flux integration inside the cell and at the cell interface, which is distinguishable from the Gaussian Quadrature point flux evaluation in the traditional DG method. Besides the initial higher order non-equilibrium states inside each control volume, a Linear Least Square (LLS) method is used for the reconstruction of smooth distributions of macroscopic flow variables around each cell interface in order to construct the corresponding equilibrium state. Instead of separating the space and time integrations and using the multistage Runge-Kutta time stepping method for time accuracy, the current method integrates the flux function in space and time analytically, which subsequently saves the computational time. Many test cases in two and three dimensions, which include high Mach number compressible viscous and heat conducting flows and the low speed high Reynolds number laminar flows, are presented to demonstrate the performance of the current scheme.

  7. Using a Datalogger to Determine First-Order Kinetics and Calcium Carbonate in Eggshells

    Science.gov (United States)

    Choi, Martin M. F.; Pui Shan Wong

    2004-01-01

    The applications of a Pasco CI-6532 pressure sensor used in conjunction with a datalogger to monitor the liberation of carbon dioxide in the reaction CaCO3(s) + 2H(super +)(aq) --> Ca(super 2+)(aq) + CO2 (g) + H2O(I) are described. The method serves for the determination of the chemical kinetics of the reaction and also can be extended to…

  8. A kinetic energy fitting metric for resolution of the identity second-order Møller-Plesset perturbation theory.

    Science.gov (United States)

    Lambrecht, Daniel S; Brandhorst, Kai; Miller, William H; McCurdy, C William; Head-Gordon, Martin

    2011-04-07

    A kinetic-energy-based fitting metric for application in the context of resolution of the identity second-order Møller-Plesset perturbation theory is presented, which is derived from the Poisson equation. Preliminary tests of the applicability include the evaluation of the error in the correlation energy, compared to standard Møller-Plesset perturbation theory, with respect to the auxiliary basis set employed. We comment on the potential merits of this fitting metric, compared to standard resolution of the identity second-order Møller-Plesset perturbation theory, and discuss its scaling behavior in the limit of large molecules.

  9. Removal of COD from olive mill wastewater by Fenton's reagent: Kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, Marco S. [Centro de Quimica, Universidade de Tras-os-Montes e Alto Douro (UTAD), Apartado 1013, 5001-801 Vila Real (Portugal); Peres, Jose A., E-mail: jperes@utad.pt [Centro de Quimica, Universidade de Tras-os-Montes e Alto Douro (UTAD), Apartado 1013, 5001-801 Vila Real (Portugal)

    2009-09-15

    This work describes the application of Fenton's reagent (H{sub 2}O{sub 2}/Fe{sup 2+}) to the removal of chemical oxygen demand (COD) from olive mill wastewater (OMW) in a laboratory-scale batch reactor. The effect of different operational conditions, namely, hydrogen peroxide and ferrous ion concentrations, temperature and initial pH were evaluated. ORP, pH and dissolved oxygen were on-line monitored. Working with an initial pH equal to 3.5, a temperature of 30 deg. C, a molar ratio H{sub 2}O{sub 2}/Fe{sup 2+} = 15 and a weight ratio R = H{sub 2}O{sub 2}/COD = 1.75 makes possible a COD conversion of 70%. A kinetic study was carried out using a modified pseudo-first-order model. The experiments performed at different temperatures allowed the calculation of the Arrhenius equation parameters and the global activation energy for the pseudo-first-order reaction (28.2 kJ/mol).

  10. A Nonlinear Evolution Equation in an Ordered Space, Arising from Kinetic Theory

    CERN Document Server

    Grünfeld, C P

    2005-01-01

    We investigate the Cauchy problem for a nonlinear evolution equation, formulated in an abstract Lebesgue space, as a generalization of various Boltzmann kinetic models. Our main result provides sufficient conditions for the existence, uniqueness, and positivity of global in time solutions. The proof is based on ideas behind a well-known monotonicity method, originally developed within the existence theory of the classical Boltzmann equation in $L^1$. Our application examples concern Smoluchowski's coagulation equation, a Povzner-like equation with dissipative collisions, and a Boltzmann model with chemical reactions.

  11. Soft-wall domain-growth kinetics of twofold-degenerate ordering

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.

    1986-01-01

    The domain growth in a two-dimensional twofold-degenerate system with soft domain walls is shown to obey dynamical scaling. The value of the growth exponent is n≃0.25 which differs from the classical Lifshitz-Allen-Cahn prediction n=(1/2), but accords with recent findings for other growth models ...... with soft walls. The results suggest that domain-wall softness may be more important than the degeneracy of the ground state for a possible universal classification of domain-growth kinetics....

  12. Equilibrium, kinetic and thermodynamic studies of the biosorption of textile dye (Reactive Red 195) onto Pinus sylvestris L

    Energy Technology Data Exchange (ETDEWEB)

    Aksakal, Ozkan [Department of Biology, Faculty of Science, Ataturk University, Erzurum 25240 (Turkey); Ucun, Handan, E-mail: hanucun@yahoo.com [Department of Environmental Engineering, Faculty of Engineering, Bartin University, Bartin 74100 (Turkey)

    2010-09-15

    This study investigated the biosorption of Reactive Red 195 (RR 195), an azo dye, from aqueous solution by using cone biomass of Pinus sylvestris Linneo. To this end, pH, initial dye concentration, biomass dosage and contact time were studied in a batch biosorption system. Maximum pH for efficient RR 195 biosorption was found to be 1.0 and the initial RR 195 concentration increased with decreasing percentage removal. Biosorption capacity increased from 6.69 mg/g at 20 deg. C to 7.38 mg/g at 50 deg. C for 200 mg/L dye concentration. Kinetics of the interactions was tested by pseudo-first-order and pseudo-second-order kinetics, the Elovich equation and intraparticle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order kinetic model and intraparticle diffusion mechanism. Moreover, the Elovich equation also showed a good fit to the experimental data. Freundlich and Langmuir adsorption isotherms were used for the mathematical description of the biosorption equilibrium data. The activation energy of biosorption (Ea) was found to be 8.904 kJ/mol by using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the study also evaluated the thermodynamic constants of biosorption ({Delta}G{sup o}, {Delta}H{sup o} and {Delta}S). The results indicate that cone biomass can be used as an effective and low-cost biosorbent to remove reactive dyes from aqueous solution.

  13. Equilibrium, kinetic and thermodynamic studies of the biosorption of textile dye (Reactive Red 195) onto Pinus sylvestris L.

    Science.gov (United States)

    Aksakal, Ozkan; Ucun, Handan

    2010-09-15

    This study investigated the biosorption of Reactive Red 195 (RR 195), an azo dye, from aqueous solution by using cone biomass of Pinus sylvestris Linneo. To this end, pH, initial dye concentration, biomass dosage and contact time were studied in a batch biosorption system. Maximum pH for efficient RR 195 biosorption was found to be 1.0 and the initial RR 195 concentration increased with decreasing percentage removal. Biosorption capacity increased from 6.69 mg/g at 20 degrees C to 7.38 mg/g at 50 degrees C for 200mg/L dye concentration. Kinetics of the interactions was tested by pseudo-first-order and pseudo-second-order kinetics, the Elovich equation and intraparticle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order kinetic model and intraparticle diffusion mechanism. Moreover, the Elovich equation also showed a good fit to the experimental data. Freundlich and Langmuir adsorption isotherms were used for the mathematical description of the biosorption equilibrium data. The activation energy of biosorption (Ea) was found to be 8.904 kJ/mol by using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the study also evaluated the thermodynamic constants of biosorption (DeltaG(o), DeltaH(o) and DeltaS). The results indicate that cone biomass can be used as an effective and low-cost biosorbent to remove reactive dyes from aqueous solution. Copyright 2010 Elsevier B.V. All rights reserved.

  14. Equilibrium, hysteresis and kinetics of cadmium desorption from sodium-feldspar using rhamnolipid biosurfactant.

    Science.gov (United States)

    Aşçi, Yeliz; Açikel, Unsal; Açikel, Yeşim Sağ

    2012-09-01

    In this study, the sorption/desorption equilibruim and the desorption kinetics of Cd by rhamnolipid biosurfactant from Na-feldspar as a soil component were investigated. The linear, Langmuir and Freundlich isotherms adequately fitted the equilibrium sorption data with regression coefficients ranging from 0.9836 - 0.9879. However, both the sorption/desorption equilibria were well characterized by the Freundlich model. The extent of hysteresis was quantified based on the differences obtained from sorption and desorption isotherms regarding the quantity of Cd(II) sorbed, the Freundlich exponent, concentration-dependent metal distribution coefficients, and the irreversibility index based on the metal distribution coefficient. The kinetics of desorption of Cd from Na-feldspar was investigated using 77 mM rhamnolipid and at pH 6.8. The first-order, an empirical first-order desorption model (two-coefficient), Lagergren-pseudo-first-order, pseudo-second-order, Elovich and modified Freundlich models were used to describe the kinetic data to estimate the rate constants. To determine the rate-controlling step, the intra-particle diffusion model was also applied to the desorption process. The desorption kinetics of Cd(II) on Na-feldspar was represented better by the pseudo-second-order, Elovich and modified Freundlich equations with correlation coefficients ranging from 0.9941- 0.9982 than by first-order equations. The rate-controlling stage was suggested to be mainly the surface reaction mechanism.

  15. Kinetically controlled transition from disordered aggregates to ordered lattices of a computationally designed peptide sequence.

    Science.gov (United States)

    Tian, Yu; Zhang, Huixi; Kiick, Kristi; Saven, Jeffrey; Pochan, Darrin

    Peptides with well-defined secondary-structures have the ability to exhibit specific, local shapes, which enables the design of complex nanostructures through intermolecular assembly. Our computationally designed coiled-coil homotetrameric peptide building block can self-assemble into 2-D nanomaterial lattices with predetermined symmetries by control of the coiled-coil bundle exterior amino acid residues. And the assemblies can be controlled kinetically. Firstly, the solution pH influences the assembly by affecting the external charged state of peptide bundles which can lead the bundles to be either repulsive or attractive to each other. At room temperature when peptides are under the least charged pH conditions, disordered aggregates are formed that slowly transformed into the desired 2-D lattice structures over long periods of time (weeks). Around neutral pH, even subtle charge differences that come from small pH changes can have an influence on the thickness of afterwards formed plates. Secondly, the solution temperature can largely eliminate the formation of disordered aggregates and accelerate the assembling of matured, desired nanomaterial plates by providing extra energy for the organization process of assembly building blocks. The ability to control the assembly process kinetically makes our peptide plate assemblies very promising templates for further applications to develop inorganic-organic hybrid materials. Funding acknowledged from NSF DMREF program under awards DMR-1234161 and DMR-1235084.

  16. Hydrodechlorination of dichlorobenzenes and their derivatives over Ni-Mo/C catalyst: kinetic analysis and effect of molecular structure of reactant.

    Science.gov (United States)

    Gryglewicz, Stanisław; Piechocki, Wojciech

    2011-04-01

    The kinetics of the catalytic hydrodechlorination (HDC) process of selected dichlorobenzenes (DCBs), dichlorotoluenes (DCTs) and dichlorodiphenyls (DCDs) was studied in the presence of a sulphided carbon-supported Ni-Mo catalyst. The HDC runs were performed in a magnetic stirred batch reactor in the range of 210-230°C under the hydrogen pressure of 3MPa. The kinetic constants were evaluated and the reaction network was proposed assuming the pseudo-first order kinetics of dechlorination process. The HDC of aromatic dichloroderivatives proceeded via a network of sequential-parallel reactions. At 210°C DCBs, DCTs and DCDs followed mainly the pathway of direct transformation to respective aromatic hydrocarbon. At 230°C, the contribution of sequential dechlorination to monochloroderivative became more predominant. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. The effects of substituent position on kinetics of benzene vapour adsorption onto 3-phenylphenoxy substituted metal-free and metallo-phthalocyanines thin films.

    Science.gov (United States)

    Alamin Ali, Haytham Elzien; Can, Nursel; Altun, Selçuk; Odabaş, Zafer

    2016-11-14

    The preparation of metal-free, Zn(ii), In(iii), and Cu(ii)-phthalocyanines containing tetrakis-(3-phenylphenoxy) groups was achieved by employing 3-(3-phenylphenoxy)phthalonitrile (1) and 4-(3-phenylphenoxy)phthalonitrile (2) as starting materials. The phthalonitriles and phthalocyanines were characterized by elemental analysis, infrared, proton nuclear magnetic resonance, ultraviolet-visible, and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopic techniques. The effect of the substituent group on the kinetics of benzene vapour adsorption onto these novel compounds was examined using three kinetics models: the pseudo first-order model, the Elovich equation, and a simple adsorption-desorption model. Results show that the benzene adsorption kinetics strongly depend on the position of the substituent groups.

  18. Path-integral calculations of heavy atom kinetic isotope effects in condensed phase reactions using higher-order Trotter factorizations.

    Science.gov (United States)

    Vardi-Kilshtain, Alexandra; Azuri, Asaf; Major, Dan Thomas

    2012-02-05

    A convenient approach to compute kinetic isotope effects (KIEs) in condensed phase chemical reactions is via path integrals (PIs). Usually, the primitive approximation is used in PI simulations, although such quantum simulations are computationally demanding. The efficiency of PI simulations may be greatly improved, if higher-order Trotter factorizations of the density matrix operator are used. In this study, we use a higher-order PI method, in conjunction with mass-perturbation, to compute heavy-atom KIE in the decarboxylation of orotic acid in explicit sulfolane solvent. The results are in good agreement with experiment and show that the mass-perturbation higher-order Trotter factorization provides a practical approach for computing condensed phase heavy-atom KIE. Copyright © 2011 Wiley Periodicals, Inc.

  19. kinetics and mechanism of long-range pore ordering in anodic films on aluminium

    NARCIS (Netherlands)

    Napolskii, K.S.; Roslyakov, I. V.; Eliseev, A.A.; Byelov, D.|info:eu-repo/dai/nl/298392720; Petukhov, A.V.|info:eu-repo/dai/nl/304829196; Grigoryeva, N.A.; Bouwman, W.G.; Lukashin, A.V.; Chumakov, A. P.; Grigoriev, S.V.

    2011-01-01

    Anodic aluminum oxide has unique and highly attractive properties, including self-ordering of porous structure during anodization. Although anodization regimes leading to formation of highly ordered porous structures had been found experimentally, many aspects of the self-organization mechanism

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

    Energy Technology Data Exchange (ETDEWEB)

    Onal, Yunus [Inonu University, Faculty of Engineering, Department of Chemical Engineering, 44280 Malatya (Turkey)]. E-mail: yonal@inonu.edu.tr

    2006-10-11

    Adsorbent (WA11Zn5) has been prepared from waste apricot by chemical activation with ZnCl{sub 2}. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N{sub 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 {delta}G, {delta}H and {delta}S, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures and concentrations. The thermodynamics of dyes-WA11Zn5 system indicates endothermic process.

  1. Equilibrium and kinetic studies on free cyanide adsorption from aqueous solution by activated carbon.

    Science.gov (United States)

    Behnamfard, Ali; Salarirad, Mohammad Mehdi

    2009-10-15

    Adsorption equilibrium and kinetics of free cyanide onto activated carbon were investigated in the batch tests, and the effects of contact time (1-72 h) and initial cyanide concentrations in the range of 102-532 mg/L were studied. Linear regression was used to determine the best fit of equilibrium and kinetics expressions. The two-parameter models including Freundlich, Dubinin-Radushkevich, Temkin and four different linearized forms of Langmuir and three-parameter models including Redlich-Peterson and Koble-Corrigan were employed for fitting the equilibrium data and it was found that, three-parameter models fitted the data better than the two-parameter models and among the three-parameter models the equilibrium data are best represented by Koble-Corrigan model. A number of kinetic models including fractional power, zero order, first order, pseudo-first order, Elovich, second order, intraparticle diffusion and four different linearized forms of pseudo-second order models were tested to fit the kinetic data. The latter was found to be consistent with the data. Intraparticle diffusion plots show that the adsorption process of free cyanide is a two steps process. In the first step, the adsorption of cyanide is fast while in the second step, cyanide adsorption slows down.

  2. Chemistry of N,N'-dimethylformamidine. II. Hydrolysis: kinetically controlled formation of cis-N-methylformamide

    Energy Technology Data Exchange (ETDEWEB)

    Halliday, J.D.; Symons, E.A.

    1978-06-01

    The hydrolysis of N,N'-dimethylformamidine (DMFA) has been investigated in acid and alkaline aqueous media by /sup 1/H nmr; only a narrow basic pH range could be extensively studied kinetically. The pseudo-first-order k/sub obs/, rose steadily from pH 11.5 to 13.0 (reaction approximately first order in OH/sup -/), then became independent of pH above 13.5 (9.3 x 10/sup -4/ s/sup -1/ at 10/sup 0/C). In contrast to many amidines, DMFA is quite stable in acid solution (estimated value of the pseudo-first-order hydrolysis rate constant is 1.4 x 10/sup -11/ s/sup -1/ at 10/sup 0/C, pH 0.05, from measurements at 100 and 140/sup 0/C). This stability is ascribed to the difficulty of eliminating the fairly stron base methylamine from the tetrahedral intermediate in acid solution. N-Methylformamide (NMF), one of the products, is formed initially as the cis isomer. A somewhat slower conversion then occurs to the thermodynamically more stable trans isomer. This unusual result is explained in terms of Deslongchamps and co-workers' theory of stereo-electronic control for the orbital-assisted breakdown of tetrahedral intermediates. 4 figures, 1 table.

  3. 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.

  4. Kinetics of chemical ordering in a Ag-Pt nanoalloy particle via first-principles simulations

    Energy Technology Data Exchange (ETDEWEB)

    Negreiros, F. R.; Fortunelli, A. [CNR-IPCF, Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche, Molecular Modeling Laboratory, via G. Moruzzi 1, Pisa I56124 (Italy); Taherkhani, F. [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Parsafar, G. [Department of Chemistry and Nanotechnology Center, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Caro, A. [Los Alamos National Laboratories, Division of Materials Science and Technology, Los Alamos, New Mexico 87545 (United States)

    2012-11-21

    The energetics and kinetic energy barriers of vacancy/atom exchange in a 37-atom truncated octahedron Ag-Pt binary cluster in the Ag-rich range of compositions are investigated via a first-principles atomistic approach. The energy of the local minima obtained considering various distributions of a single vacancy and a few Pt atoms within the cluster and the energy barriers connecting them are evaluated using accurate density-functional calculations. The effects of the simultaneous presence of a vacancy and Pt atoms are found to be simply additive when their distances are larger than first-neighbors, whereas when they can be stabilizing at low Pt content due to the release of strain by the Pt/vacancy interaction or destabilizing close to a perfect Pt(core)/Ag(shell) arrangement. It is found that alloying with Pt appreciably increases the barriers for homotops transformations, thus rationalizing the issues encountered at the experimental level in producing Ag-Pt equilibrated nanoparticles and bulk phase diagram.

  5. Semi-aerobic stabilized landfill leachate treatment by ion exchange resin: isotherm and kinetic study

    Science.gov (United States)

    Zamri, Mohd Faiz Muaz Ahmad; Kamaruddin, Mohamad Anuar; Yusoff, Mohd Suffian; Aziz, Hamidi Abdul; Foo, Keng Yuen

    2017-05-01

    This study was carried out to investigate the treatability of ion exchange resin (Indion MB 6 SR) for the removal of chromium (VI), aluminium (III), zinc (II), copper (II), iron (II), and phosphate (PO4)3-, chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and colour from semi-aerobic stabilized leachate by batch test. A range of ion exchange resin dosage was tested towards the removal efficiency of leachate parameters. It was observed that equilibrium data were best represented by the Langmuir model for metal ions and Freundlich was ideally fit for COD, NH3-N and colour. Intra particle diffusion model, pseudo first-order and pseudo second-order isotherm models were found ideally fit with correlation of the experimental data. The findings revealed that the models could describe the ion exchange kinetic behaviour efficiently, which further suggests comprehensive outlook for the future research in this field.

  6. Kinetic Study of Nitrate Removal from Aqueous Solutions Using Copper-Coated Iron Nanoparticles.

    Science.gov (United States)

    Vilardi, Giorgio; Di Palma, Luca

    2017-03-01

    Nitrates are considered hazard compounds for human health due to their tendency to be reduced to nitrites, in particular in reducing environment. Nano zero valent iron (nZVI) represents an efficient and low-cost adsorbent/reductive agent for nitrate removal from groundwater and wastewaters and a little addition of a second metal species (Cu, Pd, Ni, Ag) has proven to increase process effectiveness, by enhancing stability and oxidation resistance of nanoparticles. In this work Cu/Fe nanoparticles were loaded in a NO3- solution (100 mg L-1) and the removal efficiency was tested by monitoring nitrate concentration at selected time intervals. Results showed that the nitrate removal process involves both reduction and adsorption processes: the removal mechanism has been investigated, and the pseudo-first-order and pseudo-second-order-adsorption kinetic models were successfully tested.

  7. Kinetics of Adsorption of Nickel Ion on Kankara Kaolinite

    Directory of Open Access Journals (Sweden)

    Lawrence C. EDOMWONYI-OTU

    2013-06-01

    Full Text Available In this work, the kinetics and dynamics of nickel ion adsorption on calcined kaolinite clay were studied. The Kinetic models (k1=0.025, k2=0.00065 and ki=2.089 g/(mg·min were evaluated in order to identify potential adsorption mechanisms. The kinetic data were best represented by the pseudo first order model (R2=0.959 and the adsorption process is favored by decrease in pH i.e. Acidic condition (below 5.0. The Langmuir model was found to best suit the adsorption isotherm of nickel ion on clay than the Freundlich model. The maximum adsorption capacity of Kankara kaolinite was found to be 97.68% at a temperature of 50°C and pH of 2. The intra-particle diffusion model suggests that the process was diffusion controlled. The thermodynamic data indicates that the adsorption reaction is spontaneous with an increase in Gibbs free energy (∆G>0 and purely physisorption and exothermal in nature (∆H = -19.837 kJ/mol.

  8. 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.

  9. Removal of Hexavalent Chromium from Aqueous Solution by Using Adsorption onto Commerical Iron Powder; Study of Equilibrium and Kinetics

    Directory of Open Access Journals (Sweden)

    A.R. Rahmani

    2011-10-01

    Full Text Available Introduction & Objective: Industrial wastewaters including heavy metals, are one of the important sources of environmental pollution. Heavy metals such as chromium is found in plating wastewater and is harmful for human health and environment. The purpose of the present study was to investigate adsorption of hexavalent chromium Cr (VI from aqueous solution onto commerical Iron powder as an effective, faster ,and cheaper adsorbent. Materials & Methods: This research was an experimental- lablatory study done in batch system. This study investigated the removal of hexavalent chromium by using commerical Iron powder with variation pH, contact time, Iron powder dose and initial hexavalent chromium concentration in batch system , and the result was analyzed by Excel software.Results: The results showed that the removal efficiency decreased with increasing pH and initial chromium concentration. Also the results showed that the removal efficiency increased with increasing Iron powder dose and contact time. With increasing adsorbent dose from 0.1g/100cc to 1.5 g/100cc, the removal efficiency increased from 47.5% to 92.5 % in constant conditions (pH=7, initial hexavalent chromium concentration = 20 mg/L . Also removal efficiency increased from 41.1% to 48.5% with increasing contact time from 2 min to 120 min in constant conditions (pH=7, Iron powder= 0.1g/100cc, initial hexavalent chromium concentration= 20 mg/L. Experimental isotherms and kinetics models were assessed by Langmuir and Freundlich isotherms and pseudo-first-order, pseudo-second-order kinetics and modifed pseudo-first-order models. The results showed that the data were acceptably explained by Langmuir isotherms and pseudo-second-order kinetics models, respectively. Conclusion: The results showed that the removal of hexavalent chromium from aqueous solution using sawdust can be done faster and cheaper. (Sci J Hamadan Univ Med Sci 2011;18(3:33-39

  10. Kinetic investigation of the immobilization of chromotropic acid derivatives onto anion exchange resin

    Directory of Open Access Journals (Sweden)

    Savić Jasmina

    2007-01-01

    Full Text Available The adsorption kinetics of pyrazol- (РАСА and imidazol-azo-chromo-tropic acid (IACA onto Dowex 1-X8 resin, as a function of the dye concentration and temperature were investigated at pH 4.5. The pseudo-first- and second-order kinetic models and intraparticle diffusion model were used to describe the obtained kinetic data. The adsorption rate constants were found to be in the order of magnitude 10-2 min-1 for all of the used kinetics models. The adsorption capacity increases with increasing initial dye concentration. The study of adsorption kinetics at different temperatures (in the range from 5 to 25 °C reveals an increase in the rate of adsorption and adsorption capacity with increasing temperature. The activation energy (in the case of РАСА 16.6 kJ/mol, and for IACA 11.3 kJ/mol was determined using the Arrhenius dependence. Electrostatic interactions between the dye and resin beads were shown to be the adsorption mechanism.

  11. Kinetics and isotherm analysis of Tropaeoline 000 adsorption onto unsaturated polyester resin (UPR): a non-carbon adsorbent.

    Science.gov (United States)

    Jain, Rajeev; Sharma, Pooja; Sikarwar, Shalini

    2013-03-01

    The presence of dyes in water is undesirable due to the toxicological impact of their entrance into the food chain. Owing to the recalcitrant nature of dyes to biological oxidation, a tertiary treatment like adsorption is required. In the present study, unsaturated polyester resin (UPR) has been used as a sorbent in the treatment of dye-contaminated water. Different concentrations of Tropaeoline 000 containing water were treated with UPR. The preliminary investigations were carried out by batch adsorption to examine the effects of pH, adsorbate concentration, adsorbent dosage, contact time, and temperature. A plausible mechanism for the ongoing adsorption process and thermodynamic parameters have also been obtained from Langmuir and Freundlich adsorption isotherm models. Thermodynamic parameter showed that the sorption process of Tropaeoline 000 onto activated carbon (AC) and UPR were feasible, spontaneous, and endothermic under studied conditions. The estimated values for (ΔG) are -10.48 × 10(3) and -6.098 × 10(3) kJ mol(-1) over AC and UPR at 303 K (30 °C), indicating towards a spontaneous process. The adsorption process followed pseudo-first-order model. The mass transfer property of the sorption process was studied using Lagergren pseudo-first-order kinetic models. The values of % removal and k (ad) for dye systems were calculated at different temperatures (303-323 K). The mechanism of the adsorption process was determined from the intraparticle diffusion model.

  12. Kinetics and Mechanism of Oxidation of Triethylene Glycol and Tetraethylene Glycol by Ditelluratoargentate (III in Alkaline Medium

    Directory of Open Access Journals (Sweden)

    Jinhuan Shan

    2013-01-01

    Full Text Available The kinetics of oxidation of triethylene glycol and tetraethylene glycol by ditelluratoargentate (III (DTA in alkaline liquids has been studied spectrophotometrically in the temperature range of 293.2 K–313.2 K. The reaction rate showed first-order dependence in DTA and fractional order with respect to triethylene glycol or tetraethylene glycol. It was found that the pseudo-first-order rate constant (kobs increased with an increase in concentration of OH− and a decrease in concentration of H4TeO6 2−. There was a negative salt effect and no free radicals were detected. A plausible mechanism involving a two-electron transfer was proposed, and the rate equations derived from the mechanism explained all the experimental results and observations. The activation parameters along with the rate constants of the rate-determining step were calculated.

  13. Dimensionality dependence of aging in kinetics of diffusive phase separation: Behavior of order-parameter autocorrelation.

    Science.gov (United States)

    Midya, Jiarul; Majumder, Suman; Das, Subir K

    2015-08-01

    Behavior of two-time autocorrelation during the phase separation in solid binary mixtures is studied via numerical solutions of the Cahn-Hilliard equation as well as Monte Carlo simulations of the Ising model. Results are analyzed via state-of-the-art methods, including the finite-size scaling technique. Full forms of the autocorrelation in space dimensions 2 and 3 are obtained empirically. The long-time behavior is found to be power law, with exponents unexpectedly higher than the ones for the ferromagnetic ordering. Both Cahn-Hilliard and Ising models provide consistent results.

  14. An arbitrary-order, fully implicit, hybrid kinetic solver for linear radiative transport using integral deferred correction

    Science.gov (United States)

    Crockatt, Michael M.; Christlieb, Andrew J.; Garrett, C. Kristopher; Hauck, Cory D.

    2017-10-01

    In this work, we describe the implementation of an arbitrarily high-order hybrid solver for linear, kinetic, radiative transport equations. The hybrid method is derived from a splitting of the radiative flux into free-streaming and collisional components to which high- and low-resolution discrete ordinates methods are applied, respectively. Arbitrarily high orders of accuracy with respect to time and space are attained by combining an integral deferred correction (IDC) time integration scheme constructed with implicit Euler substepping on Radau II (right biased) nodes with an upwind discontinuous Galerkin (DG) spatial discretization on uniform Cartesian meshes. Numerical experiments are used to demonstrate that the aforementioned IDC methods can be constructed such that they are unconditionally stable (L-stable) to within machine precision. Asymptotic analysis is used to show that such IDC methods also preserve the diffusion limit of the underlying transport equation on the semi-discrete level, in the sense that the semi-discrete transport system under an implicit IDC discretization recovers the same IDC discretization of the limiting diffusion equation. Convergence results in one spatial dimension are provided, and it is found that while the hybrid method exhibits convergence stagnation and order reduction in certain scenarios, the overall accuracy of the hybrid approximation is comparable to a standard discrete ordinates approximation in many cases. Numerical results for two test problems in two spatial dimensions are given to compare the computational efficiency of the hybrid method against a standard discrete ordinates method, and to compare the efficiency of space-time discretizations of different orders of accuracy. The results indicate that a properly chosen hybrid discrete ordinates method can be more efficient than a standard discrete ordinates method by a factor of between 2 and 8 when IDC timestepping methods are used. Further, among the first-, third

  15. Second Order Kinetic Modeling of Headspace Solid Phase Microextraction of Flavors Released from Selected Food Model Systems

    Directory of Open Access Journals (Sweden)

    Jiyuan Zhang

    2014-09-01

    Full Text Available The application of headspace-solid phase microextraction (HS-SPME has been widely used in various fields as a simple and versatile method, yet challenging in quantification. In order to improve the reproducibility in quantification, a mathematical model with its root in psychological modeling and chemical reactor modeling was developed, describing the kinetic behavior of aroma active compounds extracted by SPME from two different food model systems, i.e., a semi-solid food and a liquid food. The model accounted for both adsorption and release of the analytes from SPME fiber, which occurred simultaneously but were counter-directed. The model had four parameters and their estimated values were found to be more reproducible than the direct measurement of the compounds themselves by instrumental analysis. With the relative standard deviations (RSD of each parameter less than 5% and root mean square error (RMSE less than 0.15, the model was proved to be a robust one in estimating the release of a wide range of low molecular weight acetates at three environmental temperatures i.e., 30, 40 and 60 °C. More insights of SPME behavior regarding the small molecule analytes were also obtained through the kinetic parameters and the model itself.

  16. Amplification of enantiomeric excess, mirror-image symmetry breaking and kinetic proofreading in Soai reaction models with different oligomeric orders.

    Science.gov (United States)

    Micheau, Jean-Claude; Coudret, Christophe; Cruz, José-Manuel; Buhse, Thomas

    2012-10-14

    A comprehensive kinetic analysis of three prototypical autocatalytic cycle models based on the absolute asymmetric Soai reaction is presented. The three models, which can give rise to amplification of enantiomeric excess and mirror-image symmetry breaking, vary by their monomeric, dimeric or trimeric order of the assumed catalytic species. Our numerical approach considered the entire chiral combinatorics of the diastereomeric interactions in the models as well as the multiplicity of coupled reversible reactions without applying fast equilibration or quasi-steady state approximations. For the simplest monomeric model, an extensive range of parameters was explored employing a random grid parameter scanning method that revealed the influence of the parameter values on the product distribution, the reaction-time, the attenuation or amplification of enantiomeric excess as well as on the presence or absence of mirror-image symmetry breaking. A symmetry breaking test was imposed on the three models showing that an increase in the catalytic oligomer size from one to three leads to a higher tolerance to poorer chiral recognition between the diastereoisomers and identifies the greater impact of the diastereoisomeric energy difference over an imperfect stereoselectivity in the catalytic step. This robustness is understood as a particular case of so-called kinetic proofreading in asymmetric autocatalysis.

  17. Thermodynamic and kinetic studies of cadmium adsorption from aqueous solution onto rice husk

    Directory of Open Access Journals (Sweden)

    P. Senthil Kumar

    2010-06-01

    Full Text Available The adsorption behavior of rice husk for cadmium ions from aqueous solutions has been investigated as a function of appropriate equilibrium time, adsorbent dose, temperature, adsorbate concentrations and pH in a batch system. Studies showed that the pH of aqueous solutions affected cadmium removal with the result that removal efficiency increased with increasing solution pH. The maximum adsorption was 98.65% at solution pH 6, contact time 60 min and initial concentration of 25 mg/L. The experimental data were analysed by the Langmuir, Freundlich and Temkin models of adsorption. The characteristic parameters for each isotherm and related correlation coefficients have been determined.  Thermodynamic parameters such as,  and have also been evaluated and it has been found that the sorption process was feasible, spontaneous and exothermic in nature. The kinetics of the sorption were analysed using the pseudo-first order and pseudo-second order kinetic models. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients for each kinetic model were calculated and discussed. It was shown that the adsorption of cadmium could be described by the pseudo-second order equation, suggesting that the adsorption process is presumably a chemisorption. The rice husk investigated in this study showed good potential for the removal of cadmium from aqueous solutions. The goal for this work is to develop inexpensive, highly available, effective metal ion adsorbents from natural waste as alternative to existing commercial adsorbents.

  18. Development of adsorbent from Teflon waste by radiation induced grafting: equilibrium and kinetic adsorption of dyes.

    Science.gov (United States)

    Goel, N K; Kumar, Virendra; Pahan, S; Bhardwaj, Y K; Sabharwal, S

    2011-10-15

    Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid-g-Teflon (PAA-g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA-g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor (R(L)) was found to be in the range 0 0.99) and better agreement between the q(e,cal) and q(e,exp) values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ~95% of the adsorbed dye could be eluted in suitable eluent. Copyright © 2011. Published by Elsevier B.V.

  19. Kinetic and Thermodynamic Studies on the Phosphate Adsorption Removal by Dolomite Mineral

    Directory of Open Access Journals (Sweden)

    Xiaoli Yuan

    2015-01-01

    Full Text Available The efficiency of dolomite to remove phosphate from aqueous solutions was investigated. The experimental results showed that the removal of phosphate by dolomite was rapid (the removal rate over 95% in 60 min when the initial phosphate concentration is at the range of 10–50 mg/L. Several kinetic models including intraparticle diffusion model, pseudo-first-order model, Elovich model, and pseudo-second-order model were employed to evaluate the kinetics data of phosphate adsorption onto dolomite and pseudo-second-order model was recommended to describe the adsorption kinetics characteristics. Further analysis of the adsorption kinetics indicated that the phosphate removal process was mainly controlled by chemical bonding or chemisorption. Moreover, both Freundlich and Langmuir adsorption isotherms were used to evaluate the experimental data. The results indicated that Langmuir isotherm was more suitable to describe the adsorption characteristics of dolomite. Maximum adsorption capacity of phosphate by dolomite was found to be 4.76 mg phosphorous/g dolomite. Thermodynamic studies showed that phosphate adsorption was exothermic. The study implies that dolomite is an excellent low cost material for phosphate removal in wastewater treatment process.

  20. Biosorption of lead contaminated wastewater using cattails (Typha angustifolia leaves: kinetic studies

    Directory of Open Access Journals (Sweden)

    YEN LING SHARAIN-LIEW

    2011-07-01

    Full Text Available In this work, dried leaves of Typha angustifolia (TA, also known as the common cattail, were used as an adsorbent in kinetic studies of Pb(II adsorption from synthetic aqueous solutions. Batch adsorption studies with dried TA leaves were conducted and they were able to adsorb Pb(II from 100 mL of a 25 mg L-1 Pb(II solution effectively with the optimized dosage of 0.6 g. Adsorption equilibrium was achieved within 8 h with an effective removal of 86.04 %. Adsorption kinetics was further evaluated using four kinetic models, i.e., the pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich model. Fitting of the data was performed based on linear regression analysis. The sorption kinetic data fitted best to the pseudo-second order model with an R2 of 0.9979, followed closely by the Elovich model with an R2 of 0.9952. The obtained results showed the adsorption of Pb(II by TA leaves, which is an abundant biological material, is feasible, cheap and environmentally friendly.

  1. Removal of methylparaben from synthetic aqueous solutions using polyacrylonitrile beads: kinetic and equilibrium studies.

    Science.gov (United States)

    Forte, Maurizio; Mita, Luigi; Perrone, Rosa; Rossi, Sergio; Argirò, Mario; Mita, Damiano Gustavo; Guida, Marco; Portaccio, Marianna; Godievargova, Tzonka; Ivanov, Yavour; Tamer, Mahmoud T; Omer, Ahmed M; Mohy Eldin, Mohamed S

    2017-01-01

    The removal of methylparaben (MP), a well-known endocrine disruptor, from aqueous solutions using polyacrylonitrile (PAN) beads has been studied under batch conditions, at room temperature and at different initial MP concentrations. The kinetic and equilibrium results have been analyzed. Kinetic modeling analysis has been carried out with three different types of adsorption models: pseudo-first-order, pseudo-second-order, and Elovich model. Kinetic data analysis indicated that the adsorption was a second-order process. The MP adsorption by PAN was also quantitatively evaluated by using the equilibrium adsorption isotherm models of Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin and the applicability of the respective isotherm equations has been compared through the correlation coefficients. Adsorption data resulted well fitted by the Freundlich isotherm model. Data of MP adsorption have also been used to test different adsorption diffusion models. The diffusion rate equations inside particulate of Dumwald-Wagner and the intraparticle diffusion model have been used to calculate the diffusion rate. The actual rate-controlling step involved in the MB adsorption process was determined. The kinetic expression by Boyd gave the right indications. All together, our results indicate that PAN beads are a useful tool to remediate water bodies polluted by endocrine disruptors.

  2. High order magnetic optics for high dynamic range proton radiography at a kinetic energy of 800 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Sjue, S. K. L., E-mail: sjue@lanl.gov; Mariam, F. G.; Merrill, F. E.; Morris, C. L.; Saunders, A. [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-01-15

    Flash radiography with 800 MeV kinetic energy protons at Los Alamos National Laboratory is an important experimental tool for investigations of dynamic material behavior driven by high explosives or pulsed power. The extraction of quantitative information about density fields in a dynamic experiment from proton generated images requires a high fidelity model of the proton imaging process. It is shown that accurate calculations of the transmission through the magnetic lens system require terms beyond second order for protons far from the tune energy. The approach used integrates the correlated multiple Coulomb scattering distribution simultaneously over the collimator and the image plane. Comparison with a series of static calibration images demonstrates the model’s accurate reproduction of both the transmission and blur over a wide range of tune energies in an inverse identity lens that consists of four quadrupole electromagnets.

  3. Numerical investigation of the recrystallization kinetics by means of the KWC phase-field model with special order parameters

    Science.gov (United States)

    Kundin, Julia

    2017-06-01

    The present paper proposes an extension to the phase-field model of Kobayashi, Warren and Carter (KWC) as described in (Warren et al 2002 Acta Mater.) to incorporate the recrystallization process which occurs during heat treatments of alloy systems with predeformed defect structure. The standard KWC model is extended by an additional order parameter for recrystallized grains and describes the general results for the steady-state moving boundary. The simulation results of the initial grain growth and recrystallization process in various systems show that the extended phase-field model is able to describe the influence of the initial grain boundaries on the recrystallization kinetics and to incorporate the misorientation dependency of the low angle grain boundary mobility which strongly influences the orientation distribution in the resulting microstructure.

  4. Modeling the sorption kinetic of metsulfuron-methyl on Andisols and Ultisols volcanic ash-derived soils: kinetics parameters and solute transport mechanisms.

    Science.gov (United States)

    Cáceres, Lizethly; Escudey, Mauricio; Fuentes, Edwar; Báez, María E

    2010-07-15

    Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide. 2010 Elsevier B.V. All rights reserved.

  5. Equilibrium and kinetics studies for the adsorption of Ni2+ and Fe3+ ions from aqueous solution by graphene oxide

    Directory of Open Access Journals (Sweden)

    Konicki Wojciech

    2017-09-01

    Full Text Available In this study, the adsorption of Ni2+ and Fe3+ metal ions from aqueous solutions onto graphene oxide (GO have been explored. The effects of various experimental factors such as pH of the solution, initial metal ion concentration and temperature were evaluated. The kinetic, equilibrium and thermodynamic studies were also investigated. The adsorption rate data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. Kinetic studies indicate that the adsorption of both ions follows the pseudo-second-order kinetics. The isotherms of adsorption data were analyzed by adsorption isotherm models such as Langmuir and Freundlich. Equilibrium data fitted well with the Langmuir model. The maximum adsorption capacities of Ni2+ and Fe3+ onto GO were 35.6 and 27.3 mg g−1, respectively. In addition, various thermodynamic parameters, such as enthalpy (ΔHO, entropy (ΔSO and Gibbs free energy (ΔGO, were calculated.

  6. Adsorption of anionic azo-dyes from aqueous solutions onto graphene oxide: Equilibrium, kinetic and thermodynamic studies.

    Science.gov (United States)

    Konicki, Wojciech; Aleksandrzak, Małgorzata; Moszyński, Dariusz; Mijowska, Ewa

    2017-06-15

    In the present study, graphene oxide (GO) was used for the adsorption of anionic azo-dyes such as Acid Orange 8 (AO8) and Direct Red 23 (DR23) from aqueous solutions. GO was characterized by Fourier Transform-Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and zeta potential measurements. The influence of dye initial concentration, temperature and pH on AO8 and DR23 adsorption onto GO was investigated. Equilibrium data were analyzed by model equations such as Langmuir Freundlich, Temkin, Dubinin-Radushkevich and Redlich-Peterson isotherms and were best represented by Langmuir and Redlich-Peterson isotherm model. Kinetic adsorption data were analyzed using the pseudo-first-order kinetic model, the pseudo-second-order kinetic model and the intraparticle diffusion model. The adsorption kinetics well fitted using a pseudo-second-order kinetic model. Thermodynamics parameters, ΔG°, ΔH° and ΔS°, were calculated, indicating that the adsorption of AO8 and DR23 onto GO was spontaneous process. The adsorption process of AO8 onto GO was exothermic, while the adsorption of DR23 onto GO was endothermic in nature. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. 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.

  8. Elucidation of the naproxen sodium adsorption onto activated carbon prepared from waste apricot: Kinetic, equilibrium and thermodynamic characterization

    Energy Technology Data Exchange (ETDEWEB)

    Onal, Y. [Inonu University, Faculty of Engineering, Department of Chemical Engineering, 44280 Malatya (Turkey)], E-mail: yonal@inonu.edu.tr; Akmil-Basar, C.; Sarici-Ozdemir, C. [Inonu University, Faculty of Engineering, Department of Chemical Engineering, 44280 Malatya (Turkey)

    2007-09-30

    In this study, activated carbon (WA11Zn5) was prepared from waste apricot, which is waste in apricot plants in Malatya, by chemical activation with ZnCl{sub 2}. BET surface area of activated carbon is determined as 1060 m{sup 2}/g. The ability of WA11Zn5, to remove naproxen sodium from effluent solutions by adsorption has been studied. Equilibrium isotherms for the adsorption of naproxen sodium on activated carbon were measured experimentally. Results were analyzed by the Langmiur, Freundlich equation using linearized correlation coefficient at 298 K. The characteristic parameters for each isotherm have been determined. Langmiur equation is found to best represent the equilibrium data for naproxen sodium-WA11Zn5 systems. The monolayer adsorption capacity of WA11Zn5 for naproxen sodium was found to be 106.38 mg/g at 298 K. The process was favorable and spontaneous. The kinetics of adsorption of naproxen sodium have been discussed using three kinetic models, i.e., the pseudo first-order model, the pseudo second-order model, the intraparticle diffusion model. Kinetic parameters and correlation coefficients were determined. It was shown that the pseudo second-order kinetic equation could describe the adsorption kinetics for naproxen sodium onto WA11Zn5. The thermodynamic parameters, such as {delta}G{sup o}, {delta}S{sup o} and {delta}H{sup o}, were calculated. The thermodynamics of naproxen sodium-WA11Zn5 system indicates endothermic process.

  9. Kinetic study of ozonation of molasses fermentation wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Coca, M. [Departamento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Prado de la Magdalena s/n, 47011 Valladolid (Spain)], E-mail: monica@iq.uva.es; Pena, M.; Gonzalez, G. [Departamento de Ingenieria Quimica y Tecnologia del Medio Ambiente, Universidad de Valladolid, Prado de la Magdalena s/n, 47011 Valladolid (Spain)

    2007-10-22

    A kinetic study of molasses wastewater ozonation was carried out in a stirred tank reactor to obtain the rate constants for the decolorization reaction and the regime through which ozone is absorbed. First, fundamental mass transfer parameters such as ozone solubility, volumetric mass transfer coefficients and ozone decomposition kinetics were determined from semi-batch experiments in organic-free solutions with an ionic composition similar that of industrial wastewater. The influence of operating variables such as the stirring rate and gas flow rate on the kinetic and mass transfer parameters was also studied. The application of film theory allows to establish that the reactions between ozone and colored compounds in wastewater take place in the fast and pseudo-first-order regime, within the liquid film. The decolorization rate constants were evaluated at pH 8.7 and 25 deg. C, varying from 0.6 x 10{sup 7} to 3.8 x 10{sup 7} L mol{sup -1} s{sup -1}, depending on the stirring rate and the inlet gas flow.

  10. Adsorption Kinetics of Malachite Green and Methylene Blue from Aqueous Solutions Using Surfactant-modified Organoclays.

    Science.gov (United States)

    Ullah, Haseeb; Nafees, Muhammad; Iqbal, Farhat; Awan, Muhammad; Shah, Afzal; Waseem, Amir

    2017-06-01

    The main objective of this research is to study the adsorption behaviour of malachite green and methylene blue dyes onto the surfactant modified natural clays. The results of SEM, XRD, IR, and thermal analysis confirms the intercalation of organic moiety in to the clay. The adsorption results show that pseudo-first order kinetics best fitted for both the dyes adsorbed on organo-clay. The data also reveals that both dyes are in a good agreement with Langmuir isotherm in both types of modified clays. The value of separation factor, RL, from Langmuir equation and Freundlich constant, n, give an indication of favourable adsorption. The maximum adsorption capacity qm based on Langmuir model was found to be 294-303 mg/g at 25 °C, is in good agreement with the experimental values.

  11. Kinetic study of microwave-assisted alkaline hydrolysis of Jatropha curcas oil

    Science.gov (United States)

    Yusuf, Nur'aini Raman; Kamil, Ruzaimah Nik Mohamad; Yusup, Suzana

    2016-11-01

    The kinetics of hydrolysis of Jatropha curcas oil under microwave irradation in the presence of alkaline solution was studied. The temperature of 50°C, 65°C and 80°C were studied in the range of optimum condition of 1.75 M catalyst, solvent/oil ratio of (1: 68) and 15 minutes reaction time. The rate constants of oil hydrolysis are corresponding to triglyceride disappearance concentration. The rates of reaction for fatty acids production was determined by pseudo first order. The activation energy (Ea) achieved at 30.61 kJ/mol is lower using conventional method. This conclude that the rate of reaction via microwave heating is less temperature sensitive therefore reaction can be obtained at lower temperature.

  12. Heavy and toxic metal uptake by mesoporous hypercrosslinked SMA beads: Isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Renuka Gonte

    2016-09-01

    Full Text Available Hypercrosslinked styrene-maleic acid copolymer beads were used for the removal of metal ions from mimicked industrial effluents. The polymer was characterized by SEM which revealed the presence of a porous network. Carboxyl acid groups of the polymer were identified as active sites for metal uptake. Highly porous surface enhanced metal ion uptake was achieved through a physicochemical process. Equilibrium sorption of metal ions was best described by the Freundlich and Temkin model with R2 > 0.99. Adsorption followed pseudo first and pseudo second order reaction kinetics. Intraparticle diffusion model suggested a three step equilibrium. Desorption was a fast process with ∼90% in 60 min.

  13. Equilibrium and kinetic modelling of Cd(II) biosorption by algae Gelidium and agar extraction algal waste.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2006-01-01

    In this study an industrial algal waste from agar extraction has been used as an inexpensive and effective biosorbent for cadmium (II) removal from aqueous solutions. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction. Equilibrium data follow both Langmuir and Redlich-Peterson models. The parameters of Langmuir equilibrium model are q(max)=18.0 mgg(-1), b=0.19 mgl(-1) and q(max)=9.7 mgg(-1), b=0.16 mgl(-1), respectively for Gelidium and the algal waste. Kinetic experiments were conducted at initial Cd(II) concentrations in the range 6-91 mgl(-1). Data were fitted to pseudo-first- and second-order Lagergren models. For an initial Cd(II) concentration of 91 mgl(-1) the parameters of the pseudo-first-order Lagergren model are k(1,ads)=0.17 and 0.87 min(-1); q(eq)=16.3 and 8.7 mgg(-1), respectively, for Gelidium and algal waste. Kinetic constants vary with the initial metal concentration. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model. The model successfully predicts Cd(II) concentration profiles and provides significant insights on the biosorbents performance. The homogeneous diffusivity, D(h), is in the range 0.5-2.2 x10(-8) and 2.1-10.4 x10(-8)cm(2)s(-1), respectively, for Gelidium and algal waste.

  14. Modelling Escherichia coli concentration in a wastewater reservoir using an operational parameter MRT%FE and first order kinetics.

    Science.gov (United States)

    Cirelli, Giuseppe Luigi; Consoli, Simona; Juanicó, Marcelo

    2009-01-01

    The operational parameter MRT%FE, representing the mean residence time of different ages fractions of effluent within a completely mixed reactor, was evaluated and integrated with first order kinetics. The parameter was used to model Escherichia coli concentrations in a municipal wastewater reservoir managed under different operating conditions (continuous and discontinuous). The study was conducted during 2004-2005 in a reservoir receiving effluents from the activated sludge treatment plant of Caltagirone (Eastern Sicily - Italy). The analytical approach is applied to the hydraulic state variables of the system (daily stored volumes, inlet and outlet flows), and the physical-chemical (pH, temperature, EC, TSS, BOD(5), COD) and bacteriological wastewater parameters (E. coli, FC, FS). In order to evaluate the reliability of the proposed approach, predicted E. coli concentrations within the reservoir were compared with measured ones by the correlation coefficient, F-test and Sperman's index. The study included the evaluation of die-off coefficient K(T) (d(-1)), light extinction coefficient K (m(-1)) and their relationships with climatic factors. Results of the study confirm that E. coli removal is related to the fractions of fresh effluent remaining each day within the reservoir with MRT%FE of about 5-8d, significantly lower than the nominal detention time (about 27d). The E. coli die-off coefficient (K(T)) was higher during system discontinuous operations and correlated with incident solar radiation and water temperature.

  15. Sorption of Ammonium Ions onto Natural and Modified Egyptian Kaolinites: Kinetic and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    Ola I. El-Shafey

    2014-01-01

    Full Text Available Thermally activated, acid-activated, and acid-leached of thermally activated kaolinites were prepared from the Egyptian ore. The physical and chemical properties were studied using N2 sorption at −196°C, FTIR, SEM, and the total surface acidity. The sorption of NH4+ ions on the investigated sorbents was controlled with the solution pH, sorbent dosage, and initial concentration of NH4+ solution. Kinetic and equilibrium NH4+ sorption at 30°C were employed. Four kinetic models were applied to the kinetic sorption data; pseudo-second-order, Elovich, and intraparticle diffusion models fitted well the kinetic data whereas pseudo-first-order model was less applicable. Elovich parameters refer to physical sorption type of NH4+ on nonuniform sites and the intraparticle diffusion controls the sorption of NH4+ by kaolinites to a small extent. The equilibrium sorption data followed Langmuir and D-R models; the negative value of ΔG indicates a spontaneous sorption and the mean sorption energy obtained shows also physical sorption. The sorption capacities of nonactivated and activated Egyptian kaolinites towards NH4+ sorption (10.87–45.45 mg·g−1 were good sorbents as compared with those uptaken by other clays reported in the literature and proved to be more active besides being less expensive and highly available.

  16. The Oxidation of 2-(2-Methoxyethoxyethanol and 2-(2-Ethoxyethoxyethanol by Ditelluratocuprate(III: A Kinetic and Mechanistic Study

    Directory of Open Access Journals (Sweden)

    Jin-huan Shan

    2013-01-01

    Full Text Available The oxidation of 2-(2-methoxyethoxyethanol (MEE and 2-(2-ethoxyethoxyethanol (EEE by ditelluratocuprate(III (DTC had been studied spectrophotometrically in alkaline medium. The reaction between and showed first-order dependence in DTC and fractional order in MEE and EEE. The rate constant of the pseudo-first-order reaction decreased with an increase of [TeO4  2−], whereas adding [OH−] enhanced the constant. In addition, the reaction had a negative salt effect. The rate of EEE was higher than that of MEE. A suitable assumption involving preequilibriums before the rate-controlling step and a free radical mechanism was proposed, based on the kinetic data. Activation parameters and the rate constant of the rate-determining step were calculated.

  17. Claisen rearrangement of allyl phenyl ether: heavy-atom kinetic isotope effects and bond orders in the transition structure

    Energy Technology Data Exchange (ETDEWEB)

    Kupczyk-Subotkowska, L.; Saunders, W.H. Jr.; Shine, H.J.

    1988-10-12

    Kinetic isotope effects (KIE) were measured for the rearrangement at 220/degree/C of allyl ether (1) which was labeled successively at its oxygen atom ((/sup 18/O)-1), /alpha/-carbon atom ((/alpha/-/sup 14/C)-1), /gamma/-carbon atom ((/gamma/-/sup 14/C)-1), and ortho-carbon atom ((2-/sup 14/C)-1). The KIE were 1.0297 (/sup 18/O), 1.0306 (/alpha/-/sup 14/C), 1.0362 (/gamma/-/sup 14/C), and 1.0375 (2-/sup 14/C). KIE were determined from isotopic abundances in the product, o-allylphenol (2), which were measured by multiscan mass spectrometry (/sup 18/O) and scintillation counting (/sup 14/C). A model of the transition structure was then developed, whose bond orders gave calculated KIE in reasonably good agreement not only with the experimentally determined heavy-atom KIE but also with the deuterium KIE reported earlier by McMichael and Korver. A loose transition structure was thus found for the rearrangement of 1 into 2. In this transition structure the C/sub /alpha//-O bond is 50-60% broken while the C/sub /gamma//-C/sub ortho/ bond is only 10-20% complete. The results thus define this concerted, nonsynchronous rearrangement more explicitly than hitherto possible. 40 references, 8 tables.

  18. Synthesis and kinetics studies of poly(styrene-b-vinylmethylsiloxane) and its thin film ordering by thermal and solvent annealing

    Science.gov (United States)

    Chatterjee, Sourav; Uddin, Md Fakar; Lwoya, Baraka; Albert, Julie N. L.

    Nano-structured thin film materials are important materials that find uses in templating and membrane applications. Block copolymers (BCP) have gained considerable attention for next-generation lithographic masks due to their self-assemble into morphologies with periodic sub 20 nm feature sizes with high regularity and reproducibility. A novel synthetic block copolymer of poly(styrene-b-vinylmethylsiloxane) (PS-b-PVMS) was synthesized. Like poly(styrene-b-dimethylsiloxane), this polymer has a high Flory Huggins interaction parameter between blocks to minimize feature size. Furthermore, incorporation of the vinyl side group provides an opportunity for post-polymerization chemical modification to manipulate the interaction parameter or impart functionality for various applications. Synthesis and kinetic studies of PS-b-PVMS as well as PS and PVMS homopolymers will be presented. All polymers are well characterized by proton NMR and GPC. As proof of concept, we show that block copolymers having different block fractions self-assemble into the expected nanostructures (lamellae, cylinders, spheres). Thin film studies also will be presented showing how the ordering of PS-b-PVMS is affected by different solvent and thermal annealing conditions.

  19. Heat-induced denaturation and aggregation of ovalbumin at neutral pH described by irreversible first-order kinetics

    NARCIS (Netherlands)

    Weijers, M.; Barneveld, P.A.; Cohen Stuart, M.A.; Visschers, R.W.

    2003-01-01

    The heat-induced denaturation kinetics of two different sources of ovalbumin at pH 7 was studied by chromatography and differential scanning calorimetry. The kinetics was found to be independent of protein concentration and salt concentration, but was strongly dependent on temperature. For highly

  20. Comparison of three combined sequencing batch reactor followed by enhanced Fenton process for an azo dye degradation: Bio-decolorization kinetics study

    Energy Technology Data Exchange (ETDEWEB)

    Azizi, A., E-mail: armina_84@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Alavi Moghaddam, M.R., E-mail: alavim@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Maknoon, R., E-mail: rmaknoon@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Kowsari, E., E-mail: kowsarie@aut.ac.ir [Department of Chemistry, Amirkabir University of Technology, Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)

    2015-12-15

    Highlights: • Three combined advanced SBR and enhanced Fenton process as post treatment was compared. • Higher biomass concentration, dye, COD and metabolites removal was presented together. • Pseudo zero and pseudo first-order bio-decolorization kinetics were observed in all SBRs. • High reduction of AR18 to intermediate metabolites was monitored by HPLC. - Abstract: The purpose of this research was to compare three combined sequencing batch reactor (SBR) – Fenton processes as post-treatment for the treatment of azo dye Acid Red 18 (AR18). Three combined treatment systems (CTS1, CTS2 and CTS3) were operated to investigate the biomass concentration, COD removal, AR18 dye decolorization and kinetics study. The MLSS concentration of CTS2 reached 7200 mg/L due to the use of external feeding in the SBR reactor of CTS2. The COD concentration remained 273 mg/L and 95 mg/L (initial COD = 3270 mg/L) at the end of alternating anaerobic–aerobic SBR with external feeding (An-A MSBR) and CTS2, respectively, resulting in almost 65% of Fenton process efficiency. The dye concentration of 500 mg/L was finally reduced to less than 10 mg/L in all systems indicating almost complete AR18 decolorization, which was also confirmed by UV–vis analysis. The dye was removed following two successive parts as parts 1 and 2 with pseudo zero-order and pseudo first-order kinetics, respectively, in all CTSs. Higher intermediate metabolites degradation was obtained using HPLC analysis in CTS2. Accordingly, a combined treatment system can be proposed as an appropriate and environmentally-friendly system for the treatment of the azo dye AR18 in wastewater.

  1. Kinetics of ozone-initiated oxidation of textile dye, Amaranth in aqueous systems.

    Science.gov (United States)

    Dachipally, Purnachandar; Jonnalagadda, Sreekanth B

    2011-01-01

    The ozone facilitated oxidation mechanism of water soluble azo anionic dye, amaranth (Am) was investigated monitoring the depletion kinetics of the dye spectrometrically at 521 nm. The oxidation kinetics of the dye by ozone was studied under semi-batch conditions, by bubbling ozone enriched oxygen through the aqueous reaction mixture of dye, as function of flow rate, ionic strength, [O(3)] and pH variations. With excess concentration of ozone and other reagents and low [amaranth], reaction followed pseudo-first-order kinetics with respect to the dye. Added neutral salts had marginal effect on the reaction rate and the variation of pH from 7 to 2 and 7 to 12 exerted only small increases in the reaction rate suggesting molecular ozone possibly is the principle reactive species in oxidation of dye. The reaction order with respect ozone was near unity and it varied slightly with pH and flow rate variations. The overall second-order rate constant for the reaction was (105 ± 4) M(-1) min(-1). The main oxidation products immediately after amaranth decolorization were identified. The reaction mechanism and overall rate law were proposed. After spiking the seawater, river water and wastewaters with Amaranth dye, the reaction rates and trends in BOD and COD under control and natural conditions were investigated. The rate of depletion of the dye in natural waters was relatively lower, but the ozonation process significantly decreased both the BOD and COD levels.

  2. Equilibrium and Kinetic Studies on the Adsorption of Acid Yellow 36 Dye by Pinecone

    Directory of Open Access Journals (Sweden)

    Amir Sheikh Mohammadi

    2013-11-01

    Full Text Available Background & Aims of the Study: Dyes have significant role in environmental problems, due to their toxic effects on the food chain and sources of water. The purpose of this research was to study the adsorption of acid yellow 36 dye onto pinecone using batch system. Materials & Methods: This research was performed at laboratory scale and batch system. Equilibrium isotherms were modeled using Langmuir, Freundlich, and D-R models. Also kinetic studies were done by three models of pseudo first order, pseudo second order, and intra-particle diffusion. Results: The maximum adsorption was achieved at pH 5.0, adsorbent dose 0.7 g/l and contact time 20 min. The equilibrium adsorption capacity (mg/g increased with increasing initial dye concentration. The Langmuir model (R2=0.99 provided the best fit for the experimental data. The adsorption kinetics were studied and best fit was achieved by pseudo- second order model (R2= 0.96. Conclusions: According to the results obtained of equilibrium and kinetic studies on the adsorption of acid yellow 36, pinecone can be a suitable and efficient adsorbent in the removal of yellow acid 36 dye from industrial wastewater.

  3. Interaction of silver nanoparticles (SNPs) with bacterial extracellular proteins (ECPs) and its adsorption isotherms and kinetics.

    Science.gov (United States)

    Khan, S Sudheer; Srivatsan, P; Vaishnavi, N; Mukherjee, Amitava; Chandrasekaran, N

    2011-08-15

    Indiscriminate and increased use of silver nanoparticles (SNPs) in consumer products leads to the release of it into the environment. The fate and transport of SNPs in environment remains unknown. We have studied the interaction of SNPs with extracellular protein (ECP) produced by two environmental bacterial species and the adsorption behavior in aqueous solutions. The effect of pH and salt concentrations on the adsorption was also investigated. The adsorption process was found to be dependent on surface charge (zeta potential). The capping of SNPs by ECP was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction. The adsorption of ECP on SNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fitted well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicated that pseudo-second-order kinetic equation would better describe the adsorption kinetics. The capping was stable at environmental pH and salt concentration. The destabilization of nanoparticles was observed at alkaline pH. The study suggests that the stabilization of nanoparticles in the environment might lead to the accumulation and transport of nanomaterials in the environment, and ultimately destabilizes the functioning of the ecosystem. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Kinetics of adsorption of bovine serum albumin on magnetic carboxymethyl chitosan nanoparticles.

    Science.gov (United States)

    Wang, Zhouli; Yue, Tianli; Yuan, Yahong; Cai, Rui; Niu, Chen; Guo, Caixia

    2013-07-01

    The magnetic carboxymethyl chitosan nanoparticles (MNPs-CMC) were developed as effective magnetic affinity adsorbent for Bovine serum albumin and the adsorption reactions were investigated. The obtained experimental data were compared with the adsorption kinetics models and equilibrium isotherms. The experimental kinetic data were modeled using Pseudo-first order, Pseudo-second order, Bangham's equation, Intra-particle diffusion model and Elovich equations. It was found that the adsorption reactions followed the Pseudo-second order kinetics equation. The experimental isotherm data were analyzed using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin equations. By comparing the correlation coefficients determined for each linear transformation of isotherm analysis, it was found that the Langmuir equation was the best fit equilibrium model for the adsorption of BSA. Error functions have been used to determine the alternative single component parameters by nonlinear regression due to the inherent bias in using the correlation coefficient resulting from linearization. It showed that the Langmuir equation resulted in the lowest values for the error function and thus fitted the data better than the other isotherm. Various thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were evaluated. MNPs-CMC nanoaprticles were shown to be a promising material for adsorption of BSA from aqueous solutions. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  5. Adsorption of methyl tert-butyl ether using granular activated carbon : equilibrium and kinetic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D.Z.; Chen, J.M. [Zhejiang Univ. of Technology, Hangzhou (China). College of Biological and Environmental Engineering; Zhang, J.X. [Yuhuan County Environmental Protection Bureau, Yuhuan (China)

    2010-04-01

    Methyl tert-butyl ether (MTBE) is used in gasoline as a replacement for lead in order to promote combustion efficiency. However, MTBE is one of the most frequently detected underground water pollutants caused by leaks in underground fuel storage tanks, and has been classified as a potential human carcinogen. This study investigated that adsorption of MTBE through a granular activated carbon filter. Pseudo-first order, pseudo-second order equation and intraparticle diffusion equation kinetic models were used to predict the constant rate of adsorption. The study showed that the pseudo-second order model accurately described the adsorption kinetics for the removal of MTBE from an aqueous solution onto granular activated carbon. The Lagergren first-order rate constant k{sub 1} and the pseudo-second order rate constant k{sub 2} decreased with initial increases of MTBE. A Boyd plot was used to demonstrate that external mass transfer is the principal rate-limiting step during the initial stages of adsorption. Results of the study indicated that granular activated carbon is an effective adsorbent for MTBE. 34 refs., 2 tabs., 7 figs.

  6. Kinetic and thermodynamic studies of Hg(II) adsorption onto MCM-41 modified by ZnCl2

    Science.gov (United States)

    Raji, Foad; Pakizeh, Majid

    2014-05-01

    Kinetics and thermodynamics of mercury ions sorption onto ZnCl2-MCM-41 sorbent were studied. Several rate models in the form of two main classes of mathematic kinetic models (adsorption reaction models and adsorption diffusion models) were investigated. Pseudo-first-order, pseudo-second-order, Elovich, film and intraparticle diffusion models were used to analyze the kinetic data. Results showed that the pseudo-second order model can well describe the adsorption kinetic data. The thermodynamic parameters, such as Gibb's free energy change (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were also evaluated. Negative value of free energy at temperature range of 20-55 °C, indicates the spontaneous nature of Hg(II) sorption by ZnCl2-MCM-41 sorbent. The adsorption capacity which was found to decrease with temperature showed the exothermic nature of the mercury sorption process (ΔH° = -49.4 kJ mol-1). The negative ΔS° value (-148.9 J mol-1 K-1) revealed a decrease in the randomness at the solid/solution interface and also indicated the fast adsorption of the Hg(II) onto active sites.

  7. Evaluation of Lagergren Kinetics Equation by Using Novel Kinetics Expression of Sorption of Zn2+ onto Horse Dung Humic Acid (HD-HA

    Directory of Open Access Journals (Sweden)

    Bambang Rusdiarso

    2016-12-01

    Full Text Available Extraction and purification of humic acid from dry horse dung powder (HD-HA was performed successfully and the purified HD-HA was then applied as sorbent to adsorb Zn2+. Extraction and purification were performed based on procedure of Stevenson (1994 under atmospheric air. Parameters investigated in this work consist of effect of medium sorption acidity, sorption rate (ka and desorption rate constant (kd, Langmuir (monolayer and Freundlich (multilayer sorption capacities, and energy (E of sorption. The ka and kd were determined according to the kinetic model of second order sorption reaching equilibrium, monolayer sorption capacity (b and energy (E were determined according to Langmuir isotherm model, and multilayer sorption capacity (B was determined based on Freundlich isotherm model. Sorption of Zn2+ on purified HD-HA was maximum at pH 5.0. The novel kinetic expression resulted from proposed kinetic model has been shown to be more applicable than the commonly known Lagergren equation obtained from the pseudo-first order sorption model. The application of the equation revealed that the intercept of Lagergren equation, ln qe was more complex function of initial concentration of Zn2+ (a, Langmuir sorption capacity (b, and sorbed Zn2+ at equilibrium (xe.

  8. Thermodynamics and Kinetics of Cadmium Ion Adsorption onto Lignite-derived Amendments

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    BAO Xiu-li

    2017-06-01

    Full Text Available Adsorption kinetics and thermodynamics of cadmium onto lignite-derived humic acid and lignite-derived active carbon were investigated by batch experiments under different temperatures. The adsorption thermodynamic isotherms were fitted using Langmuir, Freundlich and Temkin models, the adsorption kinetics were fitted to pseudo-first-order, pseudo-second-order, Elovich, fractional power and intraparticle diffusion models. Thermodynamic studies showed that Temkin model displayed the most suitable model to describe adsorption of cadmium onto raw lignite, extracted humic acid and active carbon. Thermodynamic parameters indicated the adsorption process were spontaneous, favourable, and endothermic physical adsorption in nature. The equilibrium adsorption capacity of cadmium obtained from the Langmiur model for humic acid, lignite and active carbon was 36.14~44.09, 29.63~38.20 mg·g-1 and 21.04~30.34 mg·g-1 respectively in the temperature range of 294.55~313.15 K, adsorption capacity magnitudes increased with a rise of temperature, indicating more feasible adsorption at high temperature. Adsorption kinetics parameters showed that the pseudo-second-order model was better than the pseudo-first-order, Elovich, fractional power and the intraparticle diffusion models, this indicated that cadmium adsorption might be a physisorption associated with chemisorption process. According to the adsorption characteristics of kinetics, thermodynamics parameters such as change in free energy(△G, change in enthalpy(△H, and change in entropy(△S, it was concluded that the adsorption process of cadmium onto these different adsorbents were spontaneous, endothermic, simultaneous physisorption and accompanied by chemisorption or alternatively physicochemical process. Adsorbents of humic acid had the great adsorption capacity and adsorption intensity. Temkin isotherm model and pseudo-second-order model could be the suitable models with good fitting for describing the

  9. A kinetic modeling study of phosphate adsorption onto Phoenix dactylifera L. date palm fibers in batch mode

    Directory of Open Access Journals (Sweden)

    Khalifa Riahi

    2017-01-01

    Full Text Available The removal of phosphates from aqueous solutions by adsorption onto date palm fibers (DPF has been studied in batch mode. The aim of this study was to understand the mechanisms that govern phosphate sorption and find an appropriate model for the kinetics of removal. In order to investigate the mechanism of sorption and potential rate controlling steps, pseudo first-order, pseudo second-order, intra-particle diffusion and the Elovich equations have been used to test experimental data. Kinetic analysis of the four models has been carried out for initial phosphate concentration in the range of 30–110 mg/L. The rate constants for the four models have been determined and the correlation coefficients have been calculated in order to assess which model provides the best fit predicted data with experimental results. Seven statistical functions were used to estimate the error deviations between experimental and theoretically predicted kinetic adsorption values, including the average relative error deviation (ARED, Marquardt’s percent standard error deviation (MPSED, the hybrid fractional error function (HYBRID, the sum of the squares of the errors (SSE and three alternative statistical functions, including the Chi-square test, the F-test and Student’s T-test. The results showed that, both Elovich equation and pseudo second-order equation provide the best fit to experimental data for different initial phosphate concentrations.

  10. Preparation of Zirconia Supported Basic Nanocatalyst: A Physicochemical and Kinetic Study of Biodiesel Production from Soybean Oil.

    Science.gov (United States)

    Patil, Pramod; Pratap, Amit

    2016-01-01

    Zirconia supported cadmium oxide basic nanocatalyst was prepared by simple co-precipitation method using aq. ammonia as precipitating reagent. The catalyst was characterised by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy technique (TEM), Brunauer-Emmet-Teller surface area measurement (BET), temperature program desorption (TPD-CO2) etc. The transesterificaton of soybean oil with methanol into biodiesel was catalysed by employing zirconia supported nanocatalyst. Kinetics of transesterificaton of oil was studied and obeyed the pseudo first order equation. While, the activation energy (Ea) for the transesterification of oil was found to be 41.18 kJ mol(-1). The 97% yield of biodiesel was observed using 7% catalyst loading (with respect of oil), 1:40 molar ratio of oil to methanol at 135°C.

  11. Kinetic study of DPPH scavenging in the presence of mixture of Zinc and Vitamin C as an antioxidant

    Directory of Open Access Journals (Sweden)

    M. Momen Heravi

    2012-08-01

    Full Text Available Reactions of free radicals and reactive oxygen species (ROS with biological molecules in vivo play an important physiological role in many diseases. 2,2-diphenyl-1-picrylhydrazyl (DPPH is a stable free radical and often used as a routine reagent to evaluate the antioxidant capacity of an antioxidant. This study was undertaken to investigate the free radical-scavenging and antioxidant activities of Zinc, Vitamin C and mixture of them. UV-Vis spectrophotometry method was used to evaluate the ability of Zinc, Vitamin C and mixture of them to scavenge DPPH radical. The kinetic parameters such as rate constant and activation energy in experimental conditions were calculated. The rate constants of the H atom abstraction by DPPH (, in the presence of Zinc, Vitamin C and mixture of them were obtained (0.4209, 2.092 and 1.82 min-1 respectively, under pseudo-first-order conditions at 25 oC.

  12. Nitrogen Removal in a Horizontal Subsurface Flow Constructed Wetland Estimated Using the First-Order Kinetic Model

    Directory of Open Access Journals (Sweden)

    Lijuan Cui

    2016-11-01

    Full Text Available We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N removal rate, N load, seasonal variations in the N removal rate, and environmental factors—such as the area-based constant, temperature, and dissolved oxygen (DO. The effluent ammonia (NH4+-N and nitrate (NO3−-N concentrations were significantly lower than the influent concentrations (p < 0.01, n = 38. The NO3−-N load was significantly correlated with the removal rate (R2 = 0.96, p < 0.01, but the NH4+-N load was not correlated with the removal rate (R2 = 0.02, p > 0.01. The area-based constants of NO3−-N and NH4+-N at 20 °C were 27 ± 26 (mean ± SD and 14 ± 10 m∙year−1, respectively. The temperature coefficients for NO3−-N and NH4+-N were estimated at 1.004 and 0.960, respectively. The area-based constants for NO3−-N and NH4+-N were not correlated with temperature (p > 0.01. The NO3−-N area-based constant was correlated with the corresponding load (R2 = 0.96, p < 0.01. The NH4+-N area rate was correlated with DO (R2 = 0.69, p < 0.01, suggesting that the factors that influenced the N removal rate in this wetland met Liebig’s law of the minimum.

  13. Phototransformation of amlodipine: degradation kinetics and identification of its photoproducts.

    Directory of Open Access Journals (Sweden)

    Anna Jakimska

    Full Text Available Nowadays, monitoring focuses on the primary compounds and does not include degradation products formed during various biological and chemical processes. Transformation products may have the same effects to human health and the environment or sometimes they can be more toxic than the parent compound. Unfortunately, knowledge about the formation of degradation products is still limited, however, can be very important for the environmental risk assessment. Firstly, the photodegradation kinetic of amlodipine was investigated in two experimental conditions: during the exposure to solar radiation and during the exposure to the light emitted by the xenon lamp. In all cases degradation of amlodipine followed a pseudo-first-order kinetics. In the next step, identification of transformation products of amlodipine formed during the exposure to xenon lamp irradiation was performed using ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS. As a result sixteen photoproducts were identified, their structures were elucidated and ultimately the transformation pathway was proposed. Fifteen compounds (out of 16 photoproducts were newly identified and reported here for the first time; some of those compounds were formed from the first photoproduct, amlodipine pyridine derivative. Several analytes were formed only in acidic or basic conditions. Furthermore, the occurrence of amlodipine and its identified degradation products was investigated in environmental waters. Only one out of 16 compounds was found in wastewater effluent. The possibility of the sorption of examined analytes to sewage sludge particles was discussed based on QSAR.

  14. Kinetic of Th ions adsorption process in the magnetic chitosan; Cinetica do processo de adsorcao de ions de Th na quitosana magnetica

    Energy Technology Data Exchange (ETDEWEB)

    Oda, Hugo Takao Yamaura; Horita, Andreia Sayuri; Yamaura, Mitiko, E-mail: htyoda@hotmail.co, E-mail: ash.horita@gmail.co, E-mail: myamaura@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    A magnetic bio absorbent called chitosan was prepared and it potentiality for removal Th ions in nitric medium was verified. The chitosan is a derivative processed from crustacean shells which is a fishing residue. The adsorption studies were accomplished by essays in batch. The equilibrium time was determined for the concentration of Th 101,4 mg L{sup -1} and the kinetic of equilibrium was analysed according to the pseudo-first order, pseudo-second order and intra particle diffusion models. A removal of 35 % by adsorption was observed to confirm that the magnetic chitosan posses a considerable potential as Th absorbent. The magnetic use of chitosan can contribute in the economic and environmental aspects, viewing the low cost of chitosan and the strategies application of control of fishing activity residues and radionuclides with development of a sustainable technology

  15. Kinetic studies of elemental mercury adsorption in activated carbon fixed bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Skodras, G. [Chemical Process Engineering Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki (Greece); Laboratory of Energy and Environmental Processes, Chemical Process Engineering Research Institute, Thessaloniki (Greece); Institute for Solid Fuels Technology and Applications, Ptolemais (Greece); Diamantopoulou, Ir. [Chemical Process Engineering Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki (Greece)], E-mail: ediamant@vergina.eng.auth.gr; Pantoleontos, G. [Institute for Solid Fuels Technology and Applications, Ptolemais (Greece); Sakellaropoulos, G.P. [Chemical Process Engineering Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki (Greece); Laboratory of Energy and Environmental Processes, Chemical Process Engineering Research Institute, Thessaloniki (Greece)

    2008-10-01

    Activated carbons are suitable materials for Hg{sup 0} adsorption in fixed bed operation or in injection process. The fixed bed tests provide good indication of activated carbons effectiveness and service lives, which depend on the rates of Hg{sup 0} adsorption. In order to correlate fixed bed properties and operation conditions, with their adsorptive capacity and saturation time, Hg{sup 0} adsorption tests were realized in a bench-scale unit, consisted of F400 activated carbon fixed bed reactor. Hg{sup 0} adsorption tests were conducted at 50 deg. C, under 0.1 and 0.35 ng/cm{sup 3} Hg{sup 0} initial concentrations and with carbon particle sizes ranging between 75-106 and 150-250 {mu}m. Based on the experimental breakthrough data, kinetic studies were performed to investigate the mechanism of adsorption and the rate controlling steps. Kinetic models evaluated include the Fick's intraparticle diffusion equation, the pseudo-first order model, the pseudo-second order model and Elovich kinetic equation. The obtained experimental results revealed that the increase in particle size resulted in significant decrease of breakthrough time and mercury adsorptive capacity, due to the enhanced internal diffusion limitations and smaller external mass transfer coefficients. Additionally, higher initial mercury concentrations resulted in increased breakthrough time and mercury uptake. From the kinetic studies results it was observed that all the examined models describes efficiently Hg{sup 0} breakthrough curves, from breakpoint up to equilibrium time. The most accurate prediction of the experimental data was achieved by second order model, indicating that the chemisorption rate seems to be the controlling step in the procedure. However, the successful attempt to describe mercury uptake with Fick's diffusion model and the first order kinetic model, reveals that the adsorption mechanism studied was complex and followed both surface adsorption and particle diffusion.

  16. Kinetic study for copper adsorption onto soil minerals in the absence and presence of humic acid.

    Science.gov (United States)

    Komy, Zanaty R; Shaker, Ali M; Heggy, Said E M; El-Sayed, Mohamed E A

    2014-03-01

    Equilibrium and kinetics of Cu(2+) adsorption onto soil minerals (kaolinite and hematite) in the absence and presence of humic acid have been investigated under various conditions. The influences of ionic strength, pH and solution cations on the rate of the adsorption have been studied. The rate and the amount of adsorbed Cu(2+) onto soil minerals in the absence or the presence of humic acid increased with decreasing ionic strength, increasing pH and in the presence of the background electrolyte K(+) rather than Ca(2+). Humic acid enhanced the rate and the amount of adsorbed Cu(2+) onto soil minerals. The adsorption equilibrium data showed that adsorption behavior of Cu(2+) could be described more reasonably by Langmiur adsorption isotherm than Freundlich isotherm in the absence or presence of humic acid. Pseudo first and pseudo second order models were used to evaluate the kinetic data and the rate constants. The results indicated that the adsorption of Cu(2+) onto hematite and kaolinite in the absence and presence of humic acid is more conforming to pseudo second order kinetics. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Equilibrium and kinetic studies of phosphate removal from solution onto a hydrothermally modified oyster shell material.

    Science.gov (United States)

    Chen, Jie; Cai, Yun; Clark, Malcolm; Yu, Yan

    2013-01-01

    Phosphate removal to a hydrothermally modified fumed silica and pulverized oyster shell material for use in wastewater treatments were made. Sorption data modeling (pH's 3-11, P concentrations of 3, 5, 10, 15, 20, & 25 mg/L, and at an ambient temperature of 23°C) indicate that an optimal removal of P occurs at pH 11. Three kinetic models were also applied (a pseudo-first-order Lagergren kinetic model, a pseudo-second-order (PSO) kinetic and Elovich) and indicate that a PSO model best describes P-removal. In addition, an application of the Weber and Morris intra-particle diffusion model indicates that external mass transfer and intra-particle diffusion were both involved in the rate-determining step. Langmuir, Freundlich modeling of the sorption data also indicate that the heterogeneous Freundlich sorption site model best describes the data although Langmuir data also fit with data tailing suggesting data are not linear. The data collected indicates that the hydrothermally modified fumed silica and pulverized oyster shell material is suitable for use in wastewater treatment, with P-removal to the solids being preferential and spontaneous.

  18. Equilibrium and kinetic studies of phosphate removal from solution onto a hydrothermally modified oyster shell material.

    Directory of Open Access Journals (Sweden)

    Jie Chen

    Full Text Available Phosphate removal to a hydrothermally modified fumed silica and pulverized oyster shell material for use in wastewater treatments were made. Sorption data modeling (pH's 3-11, P concentrations of 3, 5, 10, 15, 20, & 25 mg/L, and at an ambient temperature of 23°C indicate that an optimal removal of P occurs at pH 11. Three kinetic models were also applied (a pseudo-first-order Lagergren kinetic model, a pseudo-second-order (PSO kinetic and Elovich and indicate that a PSO model best describes P-removal. In addition, an application of the Weber and Morris intra-particle diffusion model indicates that external mass transfer and intra-particle diffusion were both involved in the rate-determining step. Langmuir, Freundlich modeling of the sorption data also indicate that the heterogeneous Freundlich sorption site model best describes the data although Langmuir data also fit with data tailing suggesting data are not linear. The data collected indicates that the hydrothermally modified fumed silica and pulverized oyster shell material is suitable for use in wastewater treatment, with P-removal to the solids being preferential and spontaneous.

  19. Adsorption characteristics of graphene oxide as a solid adsorbent for aniline removal from aqueous solutions: Kinetics, thermodynamics and mechanism studies

    Directory of Open Access Journals (Sweden)

    Ali Fakhri

    2017-01-01

    Full Text Available The aim of this study is to investigate the possibility of graphene oxide (GO as an alternative adsorbent for aniline removal from aqueous solution. Adsorption properties of GO for aniline removal were regularly investigated, including pH effect, adsorbent dose, temperature, contact time and initial concentration. The adsorption amount of aniline decreased with increasing pH. The experimental data were evaluated by Langmuir, Freundlich, Temkin and Harkins–Jura models in order to describe the equilibrium isotherms. Equilibrium data fitted well to the Langmuir model. The kinetic parameters achieved at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intra-particle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Thermodynamic parameters (free energy change, enthalpy change, and entropy change announced that the removal of aniline from GO was endothermic and spontaneous. The study showed that GO could be used as an efficient adsorbent material for the adsorption of aniline from aqueous solution.

  20. KINETICS OF SUBSTITUTION OF CIS-BIS(MALONATO ...

    African Journals Online (AJOL)

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    Effect of concentration of amino acids. The pseudo-first order rate constants were evaluated from the straight line plot of log (A∞-At) vs. time by using KINTOB software procedure. The rate of the reaction increases with increase in the concentration of amino acids (Table 1). In the amino acid variation studies the pH was kept.

  1. Kinetics of Oxidation of Aliphatic Alcohols by Potassium Dichromate ...

    African Journals Online (AJOL)

    The pseudo-first-order rate constants were found to be independent of concentration of the oxidant. The presence of TX-100 enhanced the rate of the reaction for all alcohols. Negative salt effects were observed with addition of KCl to the reaction mixture. A suitable mechanism for the reaction was suggested which agrees ...

  2. Kinetic arrest induced antiferromagnetic order in hexagonal FeMnP{sub 0.75}Si{sub 0.25} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guijiang, E-mail: guijiangli@gmail.com; Li, Wei; Schönecker, Stephan; Li, Xiaoqing [Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Delczeg-Czirjak, Erna K.; Kvashnin, Yaroslav O.; Eriksson, Olle [Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Johansson, Börje [Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Vitos, Levente [Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest H-1525 (Hungary)

    2014-12-29

    The magnetic state of the FeMnP{sub 0.75}Si{sub 0.25} alloy was investigated by first principles calculations. The coexistence of ferromagnetic and antiferromagnetic phases in FeMnP{sub 0.75}Si{sub 0.25} with the same hexagonal crystal structure was revealed. It was found that kinetic arrest during the transition from the high temperature disordered paramagnetic phase to the low temperature ordered ferromagnetic phase results in the intermediate metastable and partially disordered antiferromagnetic phase. We propose that the ratio of the ferromagnetic and antiferromagnetic phases in the FeMnP{sub 0.75}Si{sub 0.25} sample can be tuned by adjusting the kinetic process of atomic diffusion. The investigations suggest that careful control of the kinetic diffusion process provides another tuning parameter to design candidate magnetocaloric materials.

  3. Development and analysis of some versions of the fractional-order point reactor kinetics model for a nuclear reactor with slab geometry

    Science.gov (United States)

    Vyawahare, Vishwesh A.; Nataraj, P. S. V.

    2013-07-01

    In this paper, we report the development and analysis of some novel versions and approximations of the fractional-order (FO) point reactor kinetics model for a nuclear reactor with slab geometry. A systematic development of the FO Inhour equation, Inverse FO point reactor kinetics model, and fractional-order versions of the constant delayed neutron rate approximation model and prompt jump approximation model is presented for the first time (for both one delayed group and six delayed groups). These models evolve from the FO point reactor kinetics model, which has been derived from the FO Neutron Telegraph Equation for the neutron transport considering the subdiffusive neutron transport. Various observations and the analysis results are reported and the corresponding justifications are addressed using the subdiffusive framework for the neutron transport. The FO Inhour equation is found out to be a pseudo-polynomial with its degree depending on the order of the fractional derivative in the FO model. The inverse FO point reactor kinetics model is derived and used to find the reactivity variation required to achieve exponential and sinusoidal power variation in the core. The situation of sudden insertion of negative reactivity is analyzed using the FO constant delayed neutron rate approximation. Use of FO model for representing the prompt jump in reactor power is advocated on the basis of subdiffusion. Comparison with the respective integer-order models is carried out for the practical data. Also, it has been shown analytically that integer-order models are a special case of FO models when the order of time-derivative is one. Development of these FO models plays a crucial role in reactor theory and operation as it is the first step towards achieving the FO control-oriented model for a nuclear reactor. The results presented here form an important step in the efforts to establish a step-by-step and systematic theory for the FO modeling of a nuclear reactor.

  4. Metal accumulation kinetics by the estuarine macroalga, Fucus ceranoides

    Science.gov (United States)

    Varma, Ranjit; Turner, Andrew; Brown, Murray T.; Millward, Geoff E.

    2013-08-01

    The kinetics of Cu, Cd and Pb accumulation by the macroalga, Fucus ceranoides, was studied under simulated estuarine conditions. Accumulation of Cu and Pb proceeded via a pseudo-first-order reaction that was reversible, suggesting desorption or efflux of accumulated metal, with forward rate constants on the order of 0.1 h-1. For both metals, reaction reversibility increased and the equilibrium constant decreased with increasing salinity (from 1 to 33.5) and system response times were <10 h throughout. Accumulation of Cd proceeded via a first-order reaction that was irreversible, suggesting little desorption or efflux of metal, with rate constants that decreased with increasing salinity (from 0.023 to 0.015 h-1) and reaction half-lives ranging from approximately 30-50 h. Inorganic equilibrium speciation calculations suggest that interactions of Cu, Cd and Pb principally involve the respective free ions, but that additional ions (e.g. CdCl+) and biotic processes may also be significant.

  5. REMOVAL OF METHYLENE BLUE BY ADSORPTION ONTO RETAMA RAETAM PLANT: KINETICS AND EQUILIBRIUM STUDY

    Directory of Open Access Journals (Sweden)

    Dalila Badis

    2016-12-01

    Full Text Available The feasibility of using medicinal plants species Retama raetam as a low cost and an eco-friendly adsorbent for the adsorption of cationic dye methylene blue from simulated aqueous solution has been investigated. Adsorption kinetics of methylene blue onto Retama raetam plants was studied in a batch system. The effects of pH and contact time were examined. The methylene blue maximum adsorption occurred at pH 8 and the lowest adsorption occurred at pH 2. The apparent equilibrium was reached after 120 min. Optimal experimental conditions were determined. Adsorption modelling parameters for Freundlich and Langmuir isotherms were determined and, based on R2, various error distribution functions were evaluated as well. Adsorption isotherm was best described by non linear Freundlich isotherm model. Thermodynamic studies show that adsorption was spontaneous and exothermic. For determining the best-fit-kinetic adsorption model, the experimental data were analyzed by using pseudo-first-order, pseudo-second-order, pseudo-third-order, Esquivel, and Elovich models. Linear regressive and non-linear regressive method was used to obtain the relative parameters. The statistical functions were estimated to find the suitable method that fit better the experimental data. Both methods were appropriate for obtaining the parameters. The linear pseudo-second-order (type 9 and type 10 models were the best to fit the equilibrium data. The present work showed that plant Retama raetam can be used as a low cost adsorbent for the removal of methylene blue from water.

  6. Electrochemical degradation of sulfonamides at BDD electrode: Kinetics, reaction pathway and eco-toxicity evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Fabiańska, Aleksandra; Białk-Bielińska, Anna; Stepnowski, Piotr [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland); Stolte, Stefan [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland); UFT-Centre of Environmental Research and Sustainable Technology, University of Bremen, Leobener Straße UFT, D-28359 Bremen (Germany); Siedlecka, Ewa Maria, E-mail: ewa.siedlecka@ug.edu.pl [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland)

    2014-09-15

    Highlights: • SNs were electrochemically oxidized at BDD in one compartment reactor. • The efficiency of SN degradation was the highest in effluents from municipal WWTP. • The electro-degradation SNs based on oxidation but reduction was also possible. • Electrochemical oxidation of SNs led in some cases to mixtures toxic to L. minor. - Abstract: The investigation dealt with electrochemical oxidation of five sulfonamides (SNs): sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMN) and sulfadimethoxine (SDM) in aqueous solution at boron-doped diamond (BDD) electrode. All studied sulfonamides were degraded according to a pseudo first order kinetics. The structure of SNs had no significant effect on the values of pseudo first order rate constants. Increased degradation efficiency was observed in higher temperature and in acidic pH. Due to the presence of chlorine and nitrate SNs were more effectively oxidized from municipal wastewater treatment plant (WWTP) effluents than from pure supporting electrolyte Na{sub 2}SO{sub 4}. The intermediates identified by LC–MS and GC–MS analysis suggested that the hydroxyl radicals attack mainly the S-N bond, but also the aromatic ring systems (aniline, pyrimidine or triazole) of SNs. Finally, the toxicity of the SNs solutions and effluents after electrochemical treatment was assessed through the measurement of growth inhibition of green algae (Scenedesmus vacualatus) and duckweed (Lemna minor). Toxicity of SMR, STZ, SMN solutions before and after electrochemical oxidation and SDM solution after the process in L. minor test was observed. No significant toxicity of studied SNs was observed in algae test.

  7. Kinetics and mechanism of the oxidation of amaranth with hypochlorite.

    Science.gov (United States)

    Nadupalli, S; Koorbanally, N; Jonnalagadda, S B

    2011-07-14

    The reaction mechanism of the oxidation of Amaranth dye (2-hydroxy-1-(4-sulfonato-1-naphthylazo) naphthalene-3,6-disulfonate) with hypochlorite under varied pH conditions was elucidated by a kinetic approach. Under excess concentration of oxidant, the reaction followed pseudo-first-order kinetics with respect to Amaranth, and the oxidation was found to occur through two competitive reactions, initiated by hypochlorite and hypochlorous acid. The reaction order with respect to both OCl(-) ion and HOCl was unity. While the latter reaction was fast, the significance of the oxidation paths depended on the relative concentration of the two oxidizing species, which was dictated by the reaction pH. The role of the H(+) ion in the reaction was established. For the hypochlorite ion and hypochlorous acid facilitated reactions, the second-order rate coefficients were 1.9 and 23.2 M(-1) s(-1), respectively. The energy parameters were E(a) = 33.7 kJ mol(-1), ΔH(‡) = 31.2 kJ mol(-1) and ΔS(‡) = -190.6 J K(-1) mol(-1) for the OCl(-) ion-driven oxidation, and E(a) = 26.9 kJ mol(-1), ΔH(‡) = 24.3 kJ mol(-1) and ΔS(‡) = -222.8 J K(-1) mol(-1) for the reaction with HOCl-initiated oxidation. The major oxidation products for both the pathways were 3,4-dihydroxy naphthalene-2,7-disulfonic sodium salt (P(1)), dichloro-1,4-naphthoquione (P(2)) and naphtha(2,3)oxirene-2, 3-dione (P(3)). On the basis of the primary salt effect and other kinetic data, the rate law for the overall reaction and probable reaction mechanism was elucidated. The proposed mechanism was validated by simulations using Simkine-2.

  8. Neutron diffraction study of the formation kinetics of ordered antiphase domains in titanium carbohydride TiC{sub x}H{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Khidirov, I., E-mail: khidirov@inp.uz [Uzbekistan Academy of Sciences, Institute of Nuclear Physics (Uzbekistan)

    2015-09-15

    The kinetics of formation and growth of ordered antiphase domains (APDs) in titanium carbohydride TiC{sub 0.50}H{sub 0.21} has been investigated by neutron diffraction. A model of ordered APDs is proposed. It is established that the pronounced ordering of interstitial atoms and APDs begin at 450°C. It is shown that the period of ordered APDs (P ≈ 10–12) is independent of the exposure time at a constant temperature. It is found that the temperature of ordered APDs, T{sub OAPD}, increases nonlinearly with an increase in the carbon concentration in the range 0.50 ≤ C/Ti ≤ 0.70. The formation temperature of ordered APDs is found to correlate with the concentration dependence of the order–disorder transition temperature and be 0.60 of the order–disorder transition temperature: T{sub APD} = 0.60Τ{sub C}.

  9. ASPECTS OF KINETICS AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION OF SEWAGE SLUDGE - THE USE OF EQUATIONS OF VARIOUS ORDERS

    Directory of Open Access Journals (Sweden)

    Magdalena Filkiewicz

    2016-12-01

    Work to identify the kinetics of the process are aimed at, among others, creating a model describing the speed of the process, including obtaining an answer whether the above equations can be the basis for further work on identifying the factors influencing the stabilization process.

  10. ADSORPTION OF Pb2+ IONS FROM AQUEOUS SOLUTIONS ONTO BAEL TREE LEAF POWDER: ISOTHERMS, KINETICS AND THERMODYNAMICS STUDY

    Directory of Open Access Journals (Sweden)

    P. SENTHIL KUMAR

    2009-12-01

    Full Text Available In this study, bael tree (BT leaf powder was used as an adsorbent for removal of Pb2+ ions from aqueous solutions through batch equilibrium technique. The influence of pH, equilibrium time, temperature, adsorbent dosage and initial concentration of metal ions on adsorbed amount of metals ions were investigated. Studies showed that the pH of aqueous solutions affected Pb2+ ions removal as a result of removal efficiency increased with increasing solution pH. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich equations. The monolayer adsorption capacity is 4.065 mg/g with the correlation coefficient of 0.993. The experiments showed that highest removal rate was 84.93% at solution pH 5, contact time 60 min and initial concentration of 50 mg/L. Thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy have also been evaluated and it has been found that the sorption process was feasible, spontaneous and exothermic in nature. Three simplified kinetic models including a pseudo-first-order equation, pseudo-second-order equation and intraparticle diffusion equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of Pb2+ ions could be described by the pseudo-second order equation, suggesting that the adsorption process is presumable a chemisorption.

  11. Carrageenan-based semi-IPN nanocomposite hydrogels: Swelling kinetic and slow release of sequestrene Fe 138 fertilizer

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    Mohammad Kazem Bahrami

    2016-09-01

    Full Text Available Nanocomposite hydrogels based on kappa-carrageenan were synthesized by incorporating natural sodium montmorillonite (Cloisite nanoclay. Acrylamide (AAm and methylenebisacrylamide (MBA were used as a monomer and a crosslinker, respectively. Effects of reaction variables on the swelling kinetics were studied. The results revealed that the rate of swelling for nanocomposites with high content of MBA was higher than those of nanocomposites consisting of low content of MBA. Similar to the effect of MBA, the rate of swelling enhanced as the carrageenan content was decreased. The influence of clay content on swelling rate was not remarkable. The experimental swelling data were evaluated by pseudo-first-order and pseudo-second-order kinetic models. The swelling data described well by pseudo-second-order kinetic model. Sequestrene Fe 138 (Sq as an agrochemical was loaded into nanocomposites and releasing of this active agent from nanocomposites was studied. The clay-free hydrogel released the whole loaded Sq; whereas the presence of clay restricted the release of Sq.

  12. Study of Fluoride Affinity by Zirconium Impregnated Walnut Shell Carbon in Aqueous Phase: Kinetic and Isotherm Evaluation

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    M. Rajan

    2013-01-01

    Full Text Available This paper examines the kinetics of fluoride removal from water by the adsorbent zirconium-impregnated walnut-shell carbon (ZIWSC, exploring the mechanisms involved. The dependence of the adsorption of fluoride on the pH of the solution has been studied to achieve the optimum pH value and a better understanding of the adsorption mechanism. The presence of bicarbonate ions in aqueous solution was found to affect the fluoride removal indicating that these anions compete with the sorption of fluoride on adsorbents. The kinetic profile has been modeled using pseudo-first-order model, pseudo-second-order model, and intraparticle diffusion model. The kinetic sorption profiles offered excellent fit with pseudo-second-order model. Adsorption isotherms have been modeled by Langmuir, Freundlich, and Temkin equations, and their constants were determined. The equilibrium adsorption data were fitted reasonably well for Freundlich isotherm model. XRD and SEM patterns of the ZIWSC were recorded to get better insight into the mechanism of adsorption process.

  13. Adsorptive Removal of Formaldehyde by Chemically Bamboo Activated Carbon with addition of Ag nanoparticle: Equilibrium and Kinetic

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    Pita Rengga Wara Dyah

    2016-01-01

    Full Text Available Carbon was prepared from dried waste bamboo (Dendrocalamus asper using chemical activation with KOH. The carbon was prepared with the activating agent in a mass ratio of KOH and dried bamboo (3:1 at 800oC. Using impregnation technique, the bamboo-based activated carbon has developed with modified Ag nanoparticle (Ag-AC to capture formaldehyde. The Ag-AC has characteristics of moderate surface area of 685 m2/g and average pore size of 2.7 nm. The adsorption equilibriums and kinetics of formaldehyde on Ag-AC measured. The influences of initial formaldehyde on adsorption performance have measured in a batch system. The equilibrium data were evaluated by isotherm models of Langmuir, Freundlich, and Temkin. The Langmuir model well describes the adsorptive removal of formaldehyde on Ag-AC in this study. Pseudo-first-order and pseudo-second-order kinetic equations were applied to test the experimental data. The pseudo-second-order exhibited the best fit for kinetic study.

  14. Kinetic and equilibrium profile of the adsorptive removal of Acid Red 17 dye by surfactant-modified fuller's earth.

    Science.gov (United States)

    Shah, Jasmin; Jan, Muhammad Rasul; Muhammad, Mian; Ara, Behisht; Fahmeeda, Fahmeeda

    2017-03-01

    In the present study, fuller's earth (FE) was modified with sodium dodecyl sulfate for removal of Acid Red 17 (AR 17) dye from aqueous solutions. The surfactant-modified FE and FE were characterized by a Fourier transform infrared spectrometer, thermogravimetric analyzer and scanning electron microscope. Batch adsorption experiments were carried out as a function of contact time, pH, initial concentration of AR 17 and adsorbent dosage. About 99.1% adsorption efficiency was achieved within 60 min at adsorbent dose of 0.1 g for initial dye concentration of 1,000 mg L-1 at pH 10. The adsorption data were well fitted with the Dubinin-Radushkevich isotherm model implying physisorption as the major phenomenon for adsorption. The kinetic data were analyzed using four kinetic equations: pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich equations. The rates of adsorption confirmed the pseudo-second-order kinetics with good correlation value (R2 = 0.999). The results indicate that the modified adsorbent can effectively be used for the removal of AR 17 from wastewater with high absorption capacity of 2164.61 mg g-1.

  15. Equilibrium, thermodynamic and kinetic studies for the biosorption of aqueous lead(II) ions onto the seed husk of Calophyllum inophyllum.

    Science.gov (United States)

    Lawal, O S; Sanni, A R; Ajayi, I A; Rabiu, O O

    2010-05-15

    Biosorption of lead(II) ions from aqueous solution onto the seed husk of Calophyllum inophyllum was investigated in a batch system. Equilibrium, thermodynamics and kinetic studies were conducted by considering the effects of pH, initial metal ion concentration, contact time, and temperature. The results showed that the uptake of the metal ions increased with increase in initial metal ion concentration. The pH for optimum adsorption was 4 for the Pb(II) ions (q=4.86 mg/g and 97.2% adsorption). Langmuir isotherm described the biosorption of Pb(II) ions onto the biomass (R(2)=0.9531) better than the Freundlich model (R(2)=0.7984), and the Temkin model (R(2)=0.8761). Biosorption kinetics data obtained for the metal ions sorption were fitted using pseudo-first-order and pseudo-second-order. It was found that the kinetics data fitted well into the pseudo-second-order kinetics. Thermodynamic parameters such as Gibbs free energy (DeltaG), standard enthalpy (DeltaH) and standard entropy (DeltaS) were evaluated. The result showed that biosorption of the metal ion onto C. inophyllum biomass was spontaneous and endothermic in nature. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the adsorption of Pb(II) ions. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  16. Equilibrium, thermodynamic and kinetic studies for the biosorption of aqueous lead(II) ions onto the seed husk of Calophyllum inophyllum

    Energy Technology Data Exchange (ETDEWEB)

    Lawal, O.S., E-mail: laidelawal2@yahoo.com [Department of Chemical Sciences, Faculty of Science, Olabisi Onabanjo University, P.M.B 2002, Ago Iwoye, Ogun State (Nigeria); Sanni, A.R. [Department of Chemical Sciences, Faculty of Science, Olabisi Onabanjo University, P.M.B 2002, Ago Iwoye, Ogun State (Nigeria); Ajayi, I.A. [Department of Chemistry, Faculty of Science, University of Ibadan (Nigeria); Rabiu, O.O. [Department of Chemical Sciences, Faculty of Science, Olabisi Onabanjo University, P.M.B 2002, Ago Iwoye, Ogun State (Nigeria)

    2010-05-15

    Biosorption of lead(II) ions from aqueous solution onto the seed husk of Calophyllum inophyllum was investigated in a batch system. Equilibrium, thermodynamics and kinetic studies were conducted by considering the effects of pH, initial metal ion concentration, contact time, and temperature. The results showed that the uptake of the metal ions increased with increase in initial metal ion concentration. The pH for optimum adsorption was 4 for the Pb(II) ions (q = 4.86 mg/g and 97.2% adsorption). Langmuir isotherm described the biosorption of Pb(II) ions onto the biomass (R{sup 2} = 0.9531) better than the Freundlich model (R{sup 2} = 0.7984), and the Temkin model (R{sup 2} = 0.8761). Biosorption kinetics data obtained for the metal ions sorption were fitted using pseudo-first-order and pseudo-second-order. It was found that the kinetics data fitted well into the pseudo-second-order kinetics. Thermodynamic parameters such as Gibbs free energy ({Delta}G), standard enthalpy ({Delta}H) and standard entropy ({Delta}S) were evaluated. The result showed that biosorption of the metal ion onto C. inophyllum biomass was spontaneous and endothermic in nature. The results of FTIR (Fourier-transform infrared spectroscopy) revealed that carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the adsorption of Pb(II) ions.

  17. Kinetic, equilibrium and thermodynamic studies for the removal of lead (II) and copper (II) ions from aqueous solutions by nanocrystalline TiO

    Science.gov (United States)

    Rashidi, Fatemeh; Sarabi, Reza Sadeghi; Ghasemi, Zinab; Seif, Ahmad

    2010-12-01

    Titanium dioxide nanocrystallites were synthesized as adsorbents through the hydrolysis of titanium tetrachloride as the precursor in hydrochloric acid. The product was analyzed by XRD, BET and SEM-EDX; analysis indicated that the particles were a mixture of 86.8% rutile and 13.2% anatase TiO 2 with spherical shapes. The adsorption of Pb (II) and Cu (II) metal ions from aqueous solution onto nano- TiO 2 were investigated with variations in pH, contact time, initial metal ion concentration and temperature. The kinetics, adsorption isotherm and adsorption thermodynamics of the heavy metals were studied. The kinetics data were analyzed by the pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models; the best correlation coefficients were obtained for the pseudo-second order kinetic model. The adsorption results obtained from equilibrium experiments were analyzed by Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms with the Freundlich isotherm giving the best fitting isotherm to the equilibrium data. The thermodynamic parameters ( ΔG°, ΔH° and ΔS°) were calculated and it was found that the adsorption process is spontaneous and endothermic and is favored at higher temperature.

  18. Adsorption of Direct of Yellow ARLE Dye by Activated Carbon of Shell of Coconut Palm: Diffusional Effects on Kinetics and Equilibrium States

    Directory of Open Access Journals (Sweden)

    Aparecido Nivaldo Módenes

    2015-06-01

    Full Text Available In this paper, the characteristics and potential removal of direct yellow ARLE (DYA dye by using coconut palm shell-based activated carbon (CPS-AC were assessed. Both kinetic and equilibrium experimental data were obtained from a series of DYA dye sorption experiments. All the sorption experiments were performed in closed batch system under constant temperature and stirring speed, at the predetermined pH of initial solution. The kinetic mathematical models of pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion model were used in order to better interpret the adsorption kinetics phenomenon. Equilibrium data were described by applying the isotherm models of Langmuir, Freundlich, Tóth, Sips and Khan. The best description of DYA sorption equilibrium data was achieved for the Langmuir isotherm model, reaching a maximum adsorption capacity of 100 mg·g-1. Finally, the DYA dye adsorption functional groups characterizations were successfully accomplished and the results elucidated the most important groups linked with CPS-AC surface where molecular interactions could occur. Hence, the quantitative evaluation of equilibrium and kinetic experiments of adsorption process have demonstrated that the CPS-AC adsorbent was a promising high effective adsorbent and its potential can be successfully used for DYA dye removal.

  19. Adsorption Kinetics for the Removal of Hazardous Dye Congo Red by Biowaste Materials as Adsorbents

    Directory of Open Access Journals (Sweden)

    Sumanjit Kaur

    2013-01-01

    Full Text Available The present work aims to investigate the removal of dye congo red from aqueous solutions by two low-cost biowaste adsorbents such as ground nut shells charcoal (GNC and eichhornia charcoal (EC under various experimental conditions. The effect of contact time, ionic strength, temperature, pH, dye concentration, and adsorbent dose on the removal of dye was studied. The kinetic experimental data were fitted to pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich model, and Bangham’s model. Results imply that adsorption of congo red on these adsorbents nicely followed the second order kinetic model and maximum adsorption capacity was found to be 117.6 and 56.8 mg g−1 for GNC and EC at 318 K, however it increases with increase in temperature for both adsorbents. Equilibrium isotherms were analyzed by Langmuir, Freundlich, Temkin, Dubinin and Radushkevich, and Generalized Isotherms. Freundlich isotherm described the isotherm data with high-correlation coefficients. The results of the present study substantiate that biowaste material GNC and EC are promising adsorbents for the removal of the dye congo red.

  20. Ni (II) adsorption onto Chrysanthemum indicum: Influencing factors, isotherms, kinetics, and thermodynamics.

    Science.gov (United States)

    Vilvanathan, Sowmya; Shanthakumar, S

    2016-10-02

    The study explores the adsorption potential of Chrysanthemum indicum biomass for nickel ion removal from aqueous solution. C. indicum flowers in raw (CIF-I) and biochar (CIF-II) forms were used as adsorbents in this study. Batch experiments were conducted to ascertain the optimum conditions of solution pH, adsorbent dosage, contact time, and temperature for varying initial Ni(II) ion concentrations. Surface area, surface morphology, and functionality of the adsorbents were characterized by Brunauer, Emmett, and Teller (BET) surface analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). Adsorption kinetics were modeled using pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, Bangham's, and Boyd's plot. The equilibrium data were modeled using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. Experimental data provided the best fit to pseudo-second-order kinetic model and Langmuir isotherm model for the adsorption of Ni(II) ion on both CIF-I and CIF-II with maximum adsorption capacities of 23.97 and 44.02 mg g(-1), respectively. Thermodynamic analysis of the data proved the process to be spontaneous and endothermic in nature. Desorption studies were conducted to evaluate the possibility of reusing the adsorbents. Findings of the present study provide substantial evidence for the use of C. indicum flower as an eco-friendly and potential adsorbent for the removal of Ni(II) ions from aqueous solution.

  1. EQUILIBRIUM AND KINETIC STUDY OF ADSORPTION OF NICKEL FROM AQUEOUS SOLUTION ONTO BAEL TREE LEAF POWDER

    Directory of Open Access Journals (Sweden)

    P. SENTHIL KUMAR

    2009-12-01

    Full Text Available The ability of bael tree (BT leaf powder to adsorb nickel, Ni2+, from aqueous solutions has been investigated through batch experiments. The Ni2+ adsorption was found to be dependent on adsorbent dosage, initial concentration and contact time. All batch experiments were carried out at natural solution pH and at a constant temperature of 30°C using wrist-action shaker that operated at 120 rpm. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. The monolayer adsorption capacity is 1.527 mg Ni per g BT leaf powder. The experiments showed that highest removal rate was 60.21% for Ni2+ under optimal conditions. The kinetic processes of Ni2+ adsorption on BT leaf powder were described by applying pseudo-first-order and pseudo-second-order rate equations. The kinetic data for the adsorption process obeyed pseudo-second-order rate equations. The BT leaf powder investigated in this study exhibited a high potential for the removal of Ni2+ from aqueous solution.

  2. Efficient removal of cadmium using magnetic multiwalled carbon nanotube nanoadsorbents: equilibrium, kinetic, and thermodynamic study

    Science.gov (United States)

    Pashai Gatabi, Maliheh; Milani Moghaddam, Hossain; Ghorbani, Mohsen

    2016-07-01

    Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pHPZC determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber-Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir's adsorption capacity was found to be 78.81 mg g-1 at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.

  3. 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.

  4. Kinetics, equilibrium data and modeling studies for the sorption of chromium by Prosopis juliflora bark carbon

    Directory of Open Access Journals (Sweden)

    M. Kumar

    2017-05-01

    Full Text Available In this study, the activated carbon was prepared from Prosopis juliflora bark as a novel adsorbent. Removal of chromium (Cr was assessed by varying the parameters like metal concentration, temperature, pH, adsorbent dose and contact time. The feasibility of the sorption was studied using Freundlich and Langmuir isotherms including linear and non-linear regression methods. In Langmuir, various forms of linearized equations were evaluated. The isotherm parameter of dimensionless separation factor (RL was also studied. The kinetics of adsorption was studied by using Lagergren’s pseudo-first order and pseudo-second order equations and the results have shown that the adsorption process follows pseudo-second order kinetics and the adsorption process depends on both time and concentration. The mechanistic pathway of the adsorption process was evaluated with intraparticle diffusion model. The effect of heat of adsorption of the adsorbate onto the adsorbent material was determined using the thermodynamic parameters and the reusability of the adsorbent materials was ascertained with desorption studies. The adsorbent material characterization was done by using Fourier Transform Infrared Spectroscopy (FTIR, X-ray Diffraction (XRD method and morphology of the surface of adsorbent was identified with Scanning Electron Microscope (SEM.

  5. KINETICS OF PALM OIL TRANSESTERIFICATION IN METHANOL WITH POTASSIUM HYDROXIDE AS A CATALYST

    Directory of Open Access Journals (Sweden)

    Yoeswono Yoeswono

    2010-06-01

    Full Text Available A study on palm oil transesterification to evaluate the effect of some parameters in the reaction on the reaction kinetics has been carried out. Transesterification was started by preparing potassium methoxide from potassium hydroxide and methanol and then mixed it with the palm oil. An aliquot was taken at certain time interval during transesterification and poured into test tube filled with distilled water to stop the reaction immediately. The oil phase that separated from the glycerol phase by centrifugation was analyzed by 1H-NMR spectrometer to determine the percentage of methyl ester conversion. Temperature and catalyst concentration were varied in order to determine the reaction rate constants, activation energies, pre-exponential factors, and effective collisions. The results showed that palm oil transesterification in methanol with 0.5 and 1 % w/w KOH/palm oil catalyst concentration appeared to follow pseudo-first order reaction. The rate constants increase with temperature. After 13 min of reaction, More methyl esters were formed using KOH 1 % than using 0.5 % w/w KOH/palm oil catalyst concentration. The activation energy (Ea and pre-exponential factor (A for reaction using 1 % w/w KOH was lower than those using 0.5 % w/w KOH.   Keywords: palm oil, transesterification, catalyst, first order kinetics, activation energy, pre-exponential factor

  6. Probing cluster surface morphology by cryo kinetics of N2 on cationic nickel clusters

    Science.gov (United States)

    Mohrbach, Jennifer; Dillinger, Sebastian; Niedner-Schatteburg, Gereon

    2017-11-01

    We present the stepwise N2 adsorption kinetics of size selected Nin + (n = 5-20) clusters at 26 K as obtained by a hybrid tandem ion trap instrument. Pseudo-first-order kinetic fits confirm consecutive adsorption steps without evidence of cluster isomers and up to adsorption limits, which scale with the cluster size. The reaction rates for the initial N2 adsorption increase smoothly with the cluster size and similar to hard sphere cluster modeling. The isothermal kinetics allow for the tentative elucidation of cluster surface morphologies and for their classification into highly symmetrical clusters with all smooth surfaces, small clusters with rough surfaces, and large clusters with partially rough and smooth surface areas. The parallel characterization of the vibrational spectroscopy of some cluster adsorbate complexes supports and refines the achieved conclusions and is published back to back with this contribution [S. Dillinger, J. Mohrbach, and G. Niedner-Schatteburg, J. Chem. Phys. 147, 184305 (2017)]. These two studies elucidate the adsorbate to cluster interaction, and they confirm and specify the sometimes considerable structural fluxionality of finite and curved metal surfaces in high detail. This work precedes further studies along the present lines of thought.

  7. Adsorption laboratory experiment for undergraduate chemical engineering: Introducing kinetic, equilibrium and thermodynamic concepts

    Science.gov (United States)

    Muryanto, S.; Djatmiko Hadi, S.

    2016-11-01

    Adsorption laboratory experiment for undergraduate chemical engineering program is discussed. The experiment demonstrated adsorption of copper ions commonly found in wastewater using bio-sorbent, i.e. agricultural wastes. The adsorption was performed in a batch mode under various parameters: adsorption time (up to 120 min), initial pH (2 to 6), adsorbent dose (2.0 to 12.0 g L-1), adsorbent size (50 to 170 mesh), initial Cu2+ concentration (25 to 100 ppm) and temperatures (room temp to 40°C). The equilibrium and kinetic data of the experiments were calculated using the two commonly used isotherms: Langmuir and Lagergren pseudo-first-order kinetics. The maximum adsorption capacity for Cu2+ was found as 94.34 mg g-1. Thermodynamically, the adsorption process was spontaneous and endothermic. The calculated activation energy for the adsorption was observed as high as 127.94 kJ mol-1. Pedagogically, the experiment was assumed to be important in increasing student understanding of kinetic, equilibrium and thermodynamic concepts.

  8. Visible light photocatalytic water disinfection and its kinetics using Ag-doped titania nanoparticles.

    Science.gov (United States)

    Younas, Hassan; Qazi, Ishtiaq A; Hashmi, Imran; Awan, M Ali; Mahmood, Asif; Qayyum, Hafiz Adil

    2014-01-01

    The UN estimated about five million deaths every year due to water-borne diseases, accounting from four billion patients. Keeping in view, the ever increasing health issues and to undermine this statistics, a reliable and sustainable water-treatment method has been developed using visible light for water treatment. titania nanoparticles (NPs) have been synthesized successfully by a more applicable method Viz: liquid impregnation (LI) method. The bacterial death rate by photocatalysis under visible light was studied by employing a typical fluorescent source and was found to follow pseudo first-order reaction kinetics. The nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy, and energy-dispersive X-ray spectroscopy to deduce their size range, surface morphology, and elemental compositions, respectively. Among all the prepared grades, 1% Ag-TiO2 was found to be a very effective photocatalytic agent against Escherichia coli. The resulted photoinactivated data were also evaluated by different empirical kinetic models for bacterial inactivation. Hom, Hom-power, Rational, and Selleck models were not able to explain the disinfection kinetics but modified-Hom model fitted best with the experimentally obtained data by producing a shoulder, log-linear, and a tail region.

  9. Effect of Humic Acid on As Redox Transformation and Kinetic Adsorption onto Iron Oxide Based Adsorbent (IBA

    Directory of Open Access Journals (Sweden)

    Hoda Fakour

    2014-10-01

    Full Text Available Due to the importance of adsorption kinetics and redox transformation of arsenic (As during the adsorption process, the present study elucidated natural organic matter (NOM effects on As adsorption-desorption kinetics and speciation transformation. The experimental procedures were conducted by examining interactions of arsenate and arsenite with different concentrations of humic acid (HA as a model representative of NOM, in the presence of iron oxide based adsorbent (IBA, as a model solid surface in three environmentally relevant conditions, including the simultaneous adsorption of both As and HA onto IBA, HA adsorption onto As-presorbed IBA, and As adsorption onto HA-presorbed IBA. Experimental adsorption-desorption data were all fitted by original and modified Lagergren pseudo-first and -second order adsorption kinetic models, respectively. Weber’s intraparticle diffusion was also used to gain insight into the mechanisms and rate controlling steps, which the results suggested that intraparticle diffusion of As species onto IBA is the main rate-controlling step. Different concentrations of HA mediated the redox transformation of As species, with a higher oxidation ability than reduction. The overall results indicated the significant effect of organic matter on the adsorption kinetics and redox transformation of As species, and consequently, the fate, transport and mobility of As in different environmentally relevant conditions.

  10. Four types of attenuation of phenol and cresols in microcosms under simulated marine conditions: A kinetic study.

    Science.gov (United States)

    Wang, Yuejie; Meng, Fanping; Lin, Yufei; Duan, Weiyan; Liu, Qunqun

    2017-10-01

    Phenol, o-cresol, m-cresol, and p-cresol were selected to conduct microcosm experiments to examine their attenuation under simulated marine conditions, aiming at estimating natural attenuation and the contribution of oxidation, photolysis, biodegradation, and volatilisation to total attenuation of phenol and three cresols in the marine environment. The development of attenuation in microcosms showed the relevance of the pseudo-first-order kinetic for all phenols. The half-lives of phenol, o-cresol, m-cresol, and p-cresol attenuation under optimal conditions were 7.9, 4.3, 5.3, and 4.4 d, respectively. Attenuation kinetics was proposed to analyse the natural attenuation of phenol and cresols. The leading attenuation type of phenol, o-cresol, and p-cresol was volatilisation, and the attenuation rate constants (Kv) were 0.0356, 0.0687, and 0.0710 d-1. Photolysis (Kp: 0.0584 d-1) was the major attenuation type for m-cresol. Biodegradation of phenol (Kb: 0.0021 d-1) and m-cresol (Kb: 0.0049 d-1) were extremely inhibited. The rank between the contributions of the four types of attenuation to total attenuation differed between phenol and the three cresols. The attenuation kinetics proposed in this study possibly demonstrated the attenuation of the phenol and cresols in microcosm. This new reaction kinetics can be used in the analysis of natural attenuation of chemical substances. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Effect of Human and Bovine Serum Albumin on kinetic Chemiluminescence of Mn (III-Tetrakis (4-Sulfonatophenyl Porphyrin-Luminol-Hydrogen Peroxide System

    Directory of Open Access Journals (Sweden)

    Sayed Yahya Kazemi

    2012-01-01

    Full Text Available The present work deals with an attempt to study the effect of human and bovine serum albumin on kinetic parameters of chemiluminescence of luminol-hydrogen peroxide system catalyzed by manganese tetrasulfonatophenyl porphyrin (MnTSPP. The investigated parameters involved pseudo-first-order rise and fall rate constant for the chemiluminescence burst, maximum level intensity, time to reach maximum intensity, total light yield, and values of the intensity at maximum CL which were evaluated by nonlinear least square program KINFIT. Because of interaction of metalloporphyrin with proteins, the CL parameters are drastically affected. The systems resulted in Stern-Volmer plots with values of 3.17×105 and 3.7×105M−1 in the quencher concentration range of 1.5×10−6 to 1.5×10−5 M for human serum albumin (HSA and bovine serum albumin (BSA, respectively.

  12. Photoactive Hybrid Film Photocatalyst of Polyethersulfone-ZnO for the Degradation of Methyl Orange Dye: Kinetic Study and Operational Parameters

    Directory of Open Access Journals (Sweden)

    Zul Adlan Mohd Hir

    2017-10-01

    Full Text Available A facile and effective technique to immobilize photocatalyst nanoparticles by incorporating zinc oxide (ZnO into polyethersulfone polymeric films by means of a phase inversion technique is reported. The degradation study of methyl orange (MO dye was performed using a series of ZnO-embedded polymer hybrid systems. The photoactivity of the films increased in parallel with increased ZnO loading up to 17 wt%. The photodegradation process followed a pseudo first-order kinetics with an achievement of almost 100% MO removal in original conditions. The PZ-17 film demonstrated an excellent and comparable degradation performance up to five cycles, signifying the reliability of the film photocatalyst against ultraviolet irradiation and degradation.

  13. Fast and calibration free determination of first order reaction kinetics in API synthesis using in-situ ATR-FTIR.

    Science.gov (United States)

    Rehbein, Moritz C; Husmann, Sascha; Lechner, Christian; Kunick, Conrad; Scholl, Stephan

    2017-09-28

    In early stages of drug development only sparse amounts of the key substances are available, which is problematic for the determination of important process data like reaction kinetics. Therefore, it is important to perform experiments as economically as possible, especially in regards to limiting compounds. Here we demonstrate the use of a temperature step experiment enabling the determination of complete reaction kinetics in a single non-isothermal experiment. In contrast to the traditionally used HPLC, the method takes advantage of the high measuring rate and the low amount of labor involved in using in-situ ATR-FTIR to determine time-dependent concentration-equivalent data. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan: stirring rate effect in kinetics and mechanism.

    Science.gov (United States)

    Dotto, G L; Pinto, L A A

    2011-03-15

    Adsorption of food dyes acid blue 9 and food yellow 3 onto chitosan was studied. Stirring rate influence on kinetics and mechanism was verified. Infra-red analysis was carried out before and after adsorption in order to verify the adsorption nature. Adsorption experiments were carried out in batch systems with different stirring rates (15-400 rpm). Kinetic behavior was analyzed through the pseudo-first-order, pseudo-second-order and Elovich models. Adsorption mechanism was verified according to the film diffusion model and HSDM model. Pseudo-second-order and Elovich models were satisfactory in order to represent experimental data in all stirring rates. For both dyes, adsorption occurred by film and intraparticle diffusion, and the stirring rate increase caused a decrease in film diffusion resistance. Therefore, the film diffusivity increased the adsorption capacity and, consequently, intraparticle diffusivity increased. In all stirring rates, the rate-limiting step was film diffusion. Adsorption of acid blue 9 and food yellow 3 onto chitosan occurred by chemiosorption. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Potential Use of Molecular Sieves for the Removal of Ni2+ Metal Ion: Kinetics, Isotherms and Thermodynamic Studies

    Science.gov (United States)

    Gaddala, Babu Rao; Monditoka, Krishna Prasad; Challa, Venkata Ramachandra Murthy; Kadimpati, Kishore Kumar

    2016-10-01

    The potential of using molecular sieves as adsorbent for the removal of nickel from aqueous solution was investigated. The isotherms and kinetics of nickel adsorption using 3 Å molecular sieves were evaluated. The results indicated that equilibrium was established in about 5 h. The effect of the pH was examined in the range of 2-6. The maximum removal of nickel obtained is at pH value of 5. The effect of dosage also evaluated to get optimum adsorption of nickel. The maximum adsorption capacity at 25 °C is 18.25 mg/g. The effect of temperature has been carried out at 15, 25, 30, and 40 °C. The data obtained from adsorption isotherms of nickel at different temperatures fit to linear form of Freundlich adsorption equation followed by Langmuir equations. Adsorption kinetic data were modelled using the pseudo-first and pseudo-second-order equation models. The results indicated that the pseudo-second-order model was best described adsorption kinetic data. The thermodynamic parameters such as enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) were calculated. They show that adsorption of nickel onto molecular sieves is an exothermic process. These results show that molecular sieves are a good adsorbent for the removal of nickel from aqueous solutions and could be used as a purifier for water and wastewater.

  16. Immobilization of phenanthrene onto gemini surfactant modified sepiolite at solid/aqueous interface: Equilibrium, thermodynamic and kinetic studies.

    Science.gov (United States)

    Zhao, Shan; Huang, Guohe; Mu, Sen; An, Chunjiang; Chen, Xiujuan

    2017-11-15

    The immobilization of phenanthrene from aqueous phase onto natural and gemini surfactant modified sepiolite was investigated with respect to contact time, pH, ionic strength and temperature. The surface modification was examined through FT-IR characterization, SEM technique, and the thermogravimetric analysis. The maximum sorption capacity of phenanthrene on modified sepiolite was 95.15μgg-1 with initial PHE concentration 1.0mgL-1, temperature 293K, pH7, and ionic strength 1M. The corresponding PHE removal efficiency was higher than 95%. The Langmuir, Freundlich and Temkin isotherm models were applied to describe the phenanthrene sorption behavior and the Freundlich equation agreed well with the experimental data. The evaluation of the thermodynamic parameters indicated that the immobilization of phenanthrene onto gemini surfactant modified sepiolite was a spontaneous and exothermic process from 283 to 313K. The pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to evaluate the kinetic data. According to the calculated kinetic parameters, the immobilization process of phenanthrene followed the Elovich kinetic model with the highest correlation coefficients. The obtained results show that gemini surfactant modified sepiolite could be effectively utilized as one type of low-cost clay material to remove polycyclic aromatic hydrocarbons from water effluents. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. One-step synthesized calcium phosphate-based material for the removal of alizarin S dye from aqueous solutions: isothermal, kinetics, and thermodynamics studies

    Science.gov (United States)

    Adeogun, Abideen Idowu; Babu, Ramesh Balakrishnan

    2015-07-01

    Calcium phosphate hydroxyapatite (Ca-Hap) synthesized from CaCO3 and H3PO5, it was characterized by scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The Ca-Hap was used for the removal of Alizarin Red S dye from its aqueous solution. The kinetics, equilibrium, and thermodynamic of the adsorption of the dye onto the Ca-Hap were investigated. The effects of contact time, initial dye concentration, pH as well as temperature on adsorption capacity of Ca-Hap were studied. Experimental data were analyzed 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 and Dubinin-Radushkevich isotherm models. Pseudo-first-order, pseudo-second-order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process and it was found that pseudo-second-order model best fit the data. The calculated thermodynamics parameters (∆G°, ∆H° and ∆S°) indicated that the process is spontaneous and endothermic in nature.

  18. ZnS:Cu nanoparticles loaded on activated carbon as novel adsorbent for kinetic, thermodynamic and isotherm studies of Reactive Orange 12 and Direct yellow 12 adsorption

    Science.gov (United States)

    Ghaedi, Mehrorang; Ansari, Amin; Sahraei, Reza

    2013-10-01

    The objective of this work is the study of adsorption of Reactive Orange 12 (RO-12) and Direct yellow 12 (DY 12) by zinc sulfide:copper (ZnS-Cu-NP-AC) nanoparticles loaded on activated carbon. This new material with high efficiency in a routine manner was synthesized in our laboratory and its surface properties viz surface area, pore volume and functional groups was characterized with different techniques such FT-IR, SEM, and BET analysis. Generally, in batch adsorption procedure variables including amount of adsorbent, initial dyes concentration, contact time, temperature on dyes removal percentage has great effect on removal percentage that their influence was optimized. The kinetic of proposed adsorption processes efficiently followed, pseudo-second-order, and intra-particle diffusion kinetic models. The equilibrium data the removal strongly follow Langmuir monolayer adsorption with high adsorption capacity in short time. This novel adsorbent by small amount (0.08 g) really is applicable for removal of high amount of both dyes (RO 12 and DY 12) in short time (model such as pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion was assessed and it was found that the removal processes follow pseudo second order kinetics and interparticle diffusion mechanism.

  19. Equilibrium, kinetics, mechanism, and process design for the sorption of methylene blue onto rice husk.

    Science.gov (United States)

    Vadivelan, V; Kumar, K Vasanth

    2005-06-01

    Batch experiments were carried out for the sorption of methylene blue onto rice husk particles. The operating variables studied were initial solution pH, initial dye concentration, adsorbent concentration, and contact time. Equilibrium data were fitted to the Freundlich and Langmuir isotherm equations and the equilibrium data were found to be well represented by the Langmuir isotherm equation. The monolayer sorption capacity of rice husks for methylene blue sorption was found to be 40.5833 mg/g at room temperature (32 degrees C). The sorption was analyzed using pseudo-first-order and pseudo-second-order kinetic models and the sorption kinetics was found to follow a pseudo-second-order kinetic model. Also the applicability of pseudo second order in modeling the kinetic data was also discussed. The sorption process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at the later stages. The average external mass transfer coefficient and intraparticle diffusion coefficient was found to be 0.01133 min(-1) and 0.695358 mg/g min0.5. Analysis of sorption data using a Boyd plot confirms that external mass transfer is the rate limiting step in the sorption process. The effective diffusion coefficient, Di was calculated using the Boyd constant and was found to be 5.05 x 10(-04) cm2/s for an initial dye concentration of 50 mg/L. A single-stage batch-adsorber design of the adsorption of methylene blue onto rice husk has been studied based on the Langmuir isotherm equation.

  20. The kinetics of YOYO-1 intercalation into single molecules of double-stranded DNA.

    Science.gov (United States)

    Reuter, Marcel; Dryden, David T F

    2010-12-10

    The cyanine dye, YOYO-1, has frequently been used in single DNA molecule imaging work to stain double-stranded DNA as it fluoresces strongly when bound. The binding of YOYO-1 lengthens the DNA due to bis-intercalation. We have investigated the kinetics of binding, via this increase in DNA length, for single, hydrodynamically-stretched molecules of lambda DNA observed via Total Internal Reflection Fluorescence (TIRF) microscopy. The rate and degree of lengthening in 40mM NaHCO(3) (pH 8.0) buffer depend upon the free dye concentration with the reaction taking several minutes to reach completion even in relatively high, 40nM, concentrations of YOYO-1. In the absence of overstretching of the DNA molecule, we determine the second order rate constant to be 3.8±0.7×10(5)s(-1)M(-1), the dissociation constant to be 12.1±3.4nM and the maximum DNA molecule extension to be 36±4%. The intercalation time constant (inverse of the pseudo-first order rate constant), τ, decreased from 309 to 62s as YOYO-1 levels increased from 10 to 40nM. The kinetics of binding help with interpretation of the behavior of DNA-YOYO-1 complexes when overstretched and establish defined conditions for the preparation of DNA-YOYO-1 complexes. Copyright © 2010 Elsevier Inc. All rights reserved.

  1. Application potential of grapefruit peel as dye sorbent: Kinetics, equilibrium and mechanism of crystal violet adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Saeed, Asma, E-mail: asmadr@wol.net.pk [Environmental Biotechnology Group, Biotechnology and Food Research Centre, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan); Sharif, Mehwish [School of Biological Sciences, University of the Punjab, Lahore 54590 (Pakistan); Iqbal, Muhammad [Environmental Biotechnology Group, Biotechnology and Food Research Centre, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan)

    2010-07-15

    This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation {>=}0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g{sup -1}. The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions.

  2. Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics.

    Science.gov (United States)

    Prakash Kumar, B G; Shivakamy, K; Miranda, Lima Rose; Velan, M

    2006-08-25

    Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1h and 750 degrees C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g(-1) for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

  3. Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Prakash Kumar, B.G. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Shivakamy, K. [Centralised Waste Management Facility, Bhabha Atomic Research Centre, Kalpakkam 603 102 (India); Miranda, Lima Rose [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Velan, M. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India)]. E-mail: velan@annauniv.edu

    2006-08-25

    Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1 h and 750 deg. C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g{sup -1} for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

  4. Kinetics and mechanism of arsenate removal by nanosized iron oxide-coated perlite.

    Science.gov (United States)

    Mostafa, M G; Chen, Yen-Hua; Jean, Jiin-Shuh; Liu, Chia-Chuan; Lee, Yao-Chang

    2011-03-15

    This study discussed the adsorption kinetics of As(V) onto nanosized iron oxide-coated perlite. The effects of pH, initial concentration of As(V) and common anions on the adsorption efficiency were also investigated. It was observed that a 100% As(V) adsorption was achieved at pH value of 4-8 from the initial concentration containing 1.0 mg-As(V)L(-1) and the adsorption percentage depended on the initial concentration; the phosphate and silicate ions would not interfere with the adsorption efficiency. Furthermore, nanosized iron oxide-coated perlite (IOCP) has been shown to be an effective adsorbent for the removal of arsenate from water. The adsorption kinetics were studied using pseudo-first- and pseudo-second-order models, and the experimental data fitted well with the pseudo-second-order model. Moreover, it suggests that the Langmuir isotherm is more adequate than the Freundlich isotherm in simulating the adsorption isotherm of As(V). The adsorption rate constant is 44.84 L mg(-1) and the maximum adsorption capacity is 0.39 mg g(-1). These findings indicate that the adsorption property of IOCP gives the compound a great potential for applications in environmental remediation. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Eriobotrya japonica seed biocomposite efficiency for copper adsorption: Isotherms, kinetics, thermodynamic and desorption studies.

    Science.gov (United States)

    Mushtaq, Mehwish; Bhatti, Haq Nawaz; Iqbal, Munawar; Noreen, Saima

    2016-07-01

    Adsorption techniques are widely used to remove pollutants from wastewater; however, composites are gaining more importance due to their excellent adsorption properties. Bentonite composite with Eriobotrya japonica seed was prepared and used for the adsorption of copper (Cu) metal from aqueous media. The process variables such as pH, Cu(II) ions initial concentration, adsorbent dose, contact time and temperature were optimized for maximum Cu(II) adsorption. At pH 5, adsorbent dose 0.1 g, contact time 45 min, Cu(II) ions initial concentration 75 mg/L and temperature 45 °C, maximum Cu(II) adsorption was achieved. Desorption studies revealed that biocomposite is recyclable. Langmuir, Freundlich and Harkins-Jura isotherms as well as pseudo-first and pseudo-second-order kinetics models were applied to understand the adsorption mechanism. Thermodynamic parameters (ΔG(0), ΔH(0) and ΔS(0)) suggest that the adsorption process was spontaneous and endothermic in nature. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the adsorption data. Results showed that biocomposite was more efficient for Cu(II) adsorption in comparison to individuals native Eriobotrya japonica seed biomass and Na-bentonite. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Kinetics and Mechanism of Micellar Catalyzed Oxidation of Dextrose by N-Bromosuccinimide in H2SO4 Medium

    Directory of Open Access Journals (Sweden)

    Minu Singh

    2014-01-01

    Full Text Available Kinetics and mechanism of micellar catalyzed N-bromosuccinimide oxidation of dextrose in H2SO4 medium was investigated under pseudo-first-order condition temperature of 40°C. The results of the reactions studied over a wide range of experimental conditions show that NBS shows a first order dependence, fractional order, on dextrose and negative fractional order dependence on sulfuric acid. The determined stoichiometric ratio was 1 : 1 (dextrose : N-bromosuccinimide. The variation of Hg(OAC2 and succinimide (reaction product has insignificant effect on reaction rate. Effects of surfactants, added acrylonitrile, added salts, and solvent composition variation have been studied. The Arrhenius activation energy and other thermodynamic activation parameters are evaluated. The rate law has been derived on the basis of obtained data. A plausible mechanism has been proposed from the results of kinetic studies, reaction stoichiometry, and product analysis. The role of anionic and nonionic micelle was best explained by the Berezin’s model.

  7. Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.

    Science.gov (United States)

    Cataldo, Salvatore; Gianguzza, Antonio; Milea, Demetrio; Muratore, Nicola; Pettignano, Alberto

    2016-11-01

    The adsorption capacity of an activated carbon - calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH=5, in NaCl medium and in the ionic strength range 0.1-0.75molL-1. Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate (AA-Ca) improves the adsorption capacity (qm) of active carbon (AC) in the ACAA-Ca adsorbent material (e.g., qm=15.7 and 10.5mgg-1 at I=0.25molL-1, for ACAA-Ca and AC, respectively). SEM-EDX and thermogravimetric (TGA) measurements were carried out in order to characterize the composite material. The results of the speciation study on the Pb(II) solution and of the characterization of the ACAA-Ca and of the pristine AA-Ca and AC were evaluated in order to explain the specific contribution of AC and AA-Ca to the adsorption of the metal ion. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Quantitative fluorescence kinetic analysis of NADH and FAD in human plasma using three- and four-way calibration methods capable of providing the second-order advantage

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Chao [School of Chemistry and Chemical Engineering, Guizhou University, Guiyang 550025 (China); Wu, Hai-Long, E-mail: hlwu@hnu.edu.cn [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Zhou, Chang; Xiang, Shou-Xia; Zhang, Xiao-Hua; Yu, Yong-Jie; Yu, Ru-Qin [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

    2016-03-03

    The metabolic coenzymes reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are the primary electron donor and acceptor respectively, participate in almost all biological metabolic pathways. This study develops a novel method for the quantitative kinetic analysis of the degradation reaction of NADH and the formation reaction of FAD in human plasma containing an uncalibrated interferent, by using three-way calibration based on multi-way fluorescence technique. In the three-way analysis, by using the calibration set in a static manner, we directly predicted the concentrations of both analytes in the mixture at any time after the start of their reactions, even in the presence of an uncalibrated spectral interferent and a varying background interferent. The satisfactory quantitative results indicate that the proposed method allows one to directly monitor the concentration of each analyte in the mixture as the function of time in real-time and nondestructively, instead of determining the concentration after the analytical separation. Thereafter, we fitted the first-order rate law to their concentration data throughout their reactions. Additionally, a four-way calibration procedure is developed as an alternative for highly collinear systems. The results of the four-way analysis confirmed the results of the three-way analysis and revealed that both the degradation reaction of NADH and the formation reaction of FAD in human plasma fit the first-order rate law. The proposed methods could be expected to provide promising tools for simultaneous kinetic analysis of multiple reactions in complex systems in real-time and nondestructively. - Highlights: • A novel three-way calibration method for the quantitative kinetic analysis of NADH and FAD in human plasma is proposed. • The method can directly monitor the concentration of each analyte in the reaction in real-time and nondestructively. • The method has the second-order advantage. • A

  9. Clinical evaluation of iterative reconstruction (ordered-subset expectation maximization) in dynamic positron emission tomography: quantitative effects on kinetic modeling with N-13 ammonia in healthy subjects

    DEFF Research Database (Denmark)

    Hove, Jens D; Rasmussen, Rune; Freiberg, Jacob

    2008-01-01

    BACKGROUND: The purpose of this study was to investigate the quantitative properties of ordered-subset expectation maximization (OSEM) on kinetic modeling with nitrogen 13 ammonia compared with filtered backprojection (FBP) in healthy subjects. METHODS AND RESULTS: Cardiac N-13 ammonia positron...... and OSEM flow values were observed with a flow underestimation of 45% (rest/dipyridamole) in the septum and of 5% (rest) and 15% (dipyridamole) in the lateral myocardial wall. CONCLUSIONS: OSEM reconstruction of myocardial perfusion images with N-13 ammonia and PET produces high-quality images for visual...

  10. Equilibrium and kinetic studies of C.I. Basic Blue 41 adsorption onto N, F-codoped flower-like TiO{sub 2} microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yinhua, E-mail: jyinhua@126.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Luo, Yingying; Zhang, Fumei; Guo, Leiqun; Ni, Liang [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2013-05-15

    Three-dimensional (3D) N, F-codoped flower-like TiO{sub 2} microspheres were successfully synthesized by a hydrothermal method combined with calcination process. The as-prepared samples were characterized by XRD, FE-SEM and EDS. The adsorption abilities of prepared samples were investigated for the removal of C.I. Basic Blue 41(CB41) from aqueous solution. The FE-SEM and adsorption results showed that doping amount of NH{sub 4}F affected the morphologies of samples and sample NFT-1 with the structure of 3D flower-like microsphere had the highest adsorption amount of CB41. The effects of varying parameters such as pH, contact time, initial dye concentration and temperature on the CB41 adsorption onto NFT-1 were further examined. Equilibrium data correlated with Langmuir, Freundlich and Temkin isotherms. The Langmuir isotherm showed the best fit to the equilibrium data. The kinetic experimental data were analyzed by three kinetic models including the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model to access the adsorption mechanism and the potential rate-controlling step. The pseudo-second-order kinetic model described best for the adsorption of CB41 on NFT-1 and the intraparticle diffusion was not the only rate-controlling step. The thermodynamics parameters as positive values of ΔH° and negative values of ΔG° showed that the adsorption process was endothermic and spontaneous in nature.

  11. Equilibrium and kinetic studies of C.I. Basic Blue 41 adsorption onto N, F-codoped flower-like TiO2 microspheres

    Science.gov (United States)

    Jiang, Yinhua; Luo, Yingying; Zhang, Fumei; Guo, Leiqun; Ni, Liang

    2013-05-01

    Three-dimensional (3D) N, F-codoped flower-like TiO2 microspheres were successfully synthesized by a hydrothermal method combined with calcination process. The as-prepared samples were characterized by XRD, FE-SEM and EDS. The adsorption abilities of prepared samples were investigated for the removal of C.I. Basic Blue 41(CB41) from aqueous solution. The FE-SEM and adsorption results showed that doping amount of NH4F affected the morphologies of samples and sample NFT-1 with the structure of 3D flower-like microsphere had the highest adsorption amount of CB41. The effects of varying parameters such as pH, contact time, initial dye concentration and temperature on the CB41 adsorption onto NFT-1 were further examined. Equilibrium data correlated with Langmuir, Freundlich and Temkin isotherms. The Langmuir isotherm showed the best fit to the equilibrium data. The kinetic experimental data were analyzed by three kinetic models including the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model to access the adsorption mechanism and the potential rate-controlling step. The pseudo-second-order kinetic model described best for the adsorption of CB41 on NFT-1 and the intraparticle diffusion was not the only rate-controlling step. The thermodynamics parameters as positive values of ΔH° and negative values of ΔG° showed that the adsorption process was endothermic and spontaneous in nature.

  12. Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite.

    Science.gov (United States)

    Arancibia-Miranda, Nicolás; Silva-Yumi, Jorge; Escudey, Mauricio

    2015-12-15

    Modification of surface charge and changes in the isoelectric point (IEP) of synthetic imogolite were studied for various cations in the background electrolyte (K(+), NH4(+), Mg(2+), and Ca(2+)). From the electrophoretic mobility data, it was established that the K(+) (KCl) concentration does not affect the IEP of imogolite; therefore, KCl is a suitable background electrolyte. In terms of the magnitude of changes in the IEP and surface charge, the cations may be ranked in the following order: Mg(2+)≈Ca(2+)>NH4(+)>K(+). Four different kinetic models were used to evaluate the influence of Mg(2+), Ca(2+), NH4(+), and K(+) on the adsorption of Cd and Cu on synthetic imogolite. When adsorption occurs in the presence of cations with the exception of K(+), the kinetics of the process is well described by the pseudo-first order model. On the other hand, when adsorption is conducted in the presence of K(+), the adsorption kinetics is well described by the pseudo-second order, Elovich, and Weber-Morris models. From the surface charge measurements, the affinity between imogolite and the cations and their effect on the adsorption of trace elements, namely Cu and Cd, were established. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: a kinetic and equilibrium study.

    Science.gov (United States)

    Caliskan, Necla; Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan

    2011-10-15

    The removal of Zn(II) ions from aqueous solution was studied using natural and MnO(2) modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH(0)), Gibbs' free energy (ΔG(0)) and entropy (ΔS(0)) were calculated for natural and MnO(2) modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Equilibrium, kinetics and thermodynamic parameters for adsorptive removal of dye Basic Blue 9 by ground nut shells and Eichhornia

    Directory of Open Access Journals (Sweden)

    Sumanjit

    2016-11-01

    Full Text Available Adsorption of dye Basic Blue 9 (BB9 was studied using ground nut shells charcoal (GNC, and Eichhornia charcoal (EC as adsorbents. The characterization was done with FTIR spectroscopy, scanning electron microscopy and X-ray diffraction. Batch adsorption studies have been investigated by measuring the effect of pH, adsorbent dose, adsorbate concentration, contact time, temperature, and ionic strength. Adsorption of the dye increased with increase in contact time, temperature, amount of adsorbent and initial concentration. The kinetic experimental data were fitted to pseudo-first order, pseudo-second order, intra-particle diffusion, Elovich model and Bangham’s model and corresponding constants were calculated and discussed. Pseudo-second order kinetics was found to describe the adsorption of dye BB9 on both the adsorbents and rate is mainly controlled by intra particle diffusion. A study of five isotherm models; Langmuir, Freundlich, Temkin, Dubinin and Radushkevich and generalized isotherms have been made and important thermodynamic parameters have been obtained. The adsorption of BB9 onto GNC and EC was spontaneous and endothermic as concluded from thermodynamic assays. Experimental results confirmed that dye BB9 can be successfully removed from the aqueous solutions economically and efficiently.

  15. One-step fabricated Fe3O4@C core-shell composites for dye removal: Kinetics, equilibrium and thermodynamics

    Science.gov (United States)

    Qu, Lingling; Han, Tingting; Luo, Zhijun; Liu, Cancan; Mei, Yan; Zhu, Ting

    2015-03-01

    B-Fe3O4@C core-shell composites were synthesized via one-pot hydrothermal carbonization (HTC) process and used as an adsorbent for the removal of methylene blue (MB) from aqueous solution. By using sodium borate as the catalyst, the hydrothermal carbonization process of B-Fe3O4@C core-shell composites was optimized and a higher surface area was obtained. The adsorbent was characterized by XRD, Raman spectra, SEM, TEM and N2 adsorption/desorption isotherms. We studied the dye adsorption process at different conditions and analyzed the data by employing the Langmuir and Freundlich models, and the equilibrium data fitted well with both models. Kinetic analyses were conducted by using the Lagergren pseudo-first-order and pseudo-second-order model and the results showed that the adsorption process was more consistent with the pseudo-second-order kinetics. To better understand the dye adsorption process from the thermodynamics perspective, we also calculated ΔHο, ΔSο, ΔGο and Ea, the results suggesting that the MB adsorption process was physisorption endothermic process, and spontaneous at room temperature. The as-synthesized B-Fe3O4@C showing high magnetic sensitivity provides a facile and efficient way to recycle from aqueous solution.

  16. Removal of reactive blue 19 dyes from textile wastewater by pomegranate seed powder: Isotherm and kinetic studies

    Directory of Open Access Journals (Sweden)

    Mahboobeh Dehvari

    2016-01-01

    Full Text Available Aims: The aim of this study was the evaluation of adsorption kinetics and equilibrium of reactive blue 19 dyes from textile synthetic wastewater by pomegranate seed powder. Materials and Methods: This study is an experimental research, which was performed in laboratory scale. In this study, the parameters such as adsorbent dose, pH and retention time, initial concentration of dye and agitation rate have been investigated. After washing and boiling of pomegranate seeds for 2 h, they dried, milled and finally pulverized by standard ASTM sieves (40-100 mesh. Maximum adsorption wave length (λmax by spectrophotometer ultra violet/visible (model SP-3000 Plus 592 nm was determined. The Langmuir, Freundlich and Temkin isotherm models and the pseudo-first-order and pseudo-second-order kinetic models were analyzed. Results: According to results, the removal efficiency with adsorbent dose, retention time and agitation rate has a direct relation. Maximum adsorption occurred in the first 60 min. The removal efficiency with initial concentration of dye and pH of solution has indirect relation. The Freundlich isotherm fits the experimental data better than the other isotherms. It was recognized that the adsorption followed by pseudo-second-order model (R2 > 0.99. Conclusion: Based on the results, pomegranate seeds as a new natural sorbent can be used in removal of dye and other environmental pollutants with desirable absorption capacity.

  17. Equilibrium, kinetic and thermodynamic studies for sorption of Ni (II from aqueous solution using formaldehyde treated waste tea leaves

    Directory of Open Access Journals (Sweden)

    Jasmin Shah

    2015-05-01

    Full Text Available The sorption characteristic of Ni (II from aqueous solution using formaldehyde treated waste tea leaves as a low cost sorbent has been studied. The effect of pH, contact time, sorbent dose, initial metal ion concentration and temperature were investigated in batch experiments. The equilibrium data were fitted into four most common isotherm models; Freundlich, Langmuir, Tempkin and Dubinin–Radushkevich (D–R. The Langmuir model described the sorption isotherm best with maximum monolayer sorption capacity of 120.50 mg g−1. Four kinetic models, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich were employed to explain the sorption mechanism. The kinetics of sorption data showed that the pseudo-second-order model is the best with correlation coefficient of 0.9946. The spontaneous and exothermic nature of the sorption process was revealed from thermodynamic investigations. The effect of some common alkali and alkaline earth metal ions were also studied which showed that the presence of these ions have no effect on the sorption of Ni (II. The results showed that waste tea leaves have the potential to be used as a low cost sorbent for the removal of Ni (II from aqueous solutions.

  18. Application of a heterogeneous adsorbent (HA for the removal of hexavalent chromium from aqueous solutions: Kinetic and equilibrium modeling

    Directory of Open Access Journals (Sweden)

    Varsha Srivastava

    2017-05-01

    Full Text Available In the present study, a heterogeneous adsorbent material (HA was used as an adsorbent for the removal of Cr(VI from aqueous solutions at laboratory scale. Cr(VI containing water was treated with heterogeneous adsorbent(HA.Chromium solutions of various initial concentrations were treated with adsorbent in batch mode experiments to investigate the adsorption characteristics of heterogeneous adsorbent (HA. Kinetics of adsorption of Cr(VI ions on adsorbent was investigated by using pseudo first order and second order kinetic models. Removal processes were found to be governed by pseudo second order model. Intraparticle diffusion model was also analyzed for this system. Removal was found to be increased by increasing the temperature from 298 to 318 K which indicates the endothermic nature of the process. Various two parameter isotherm models viz. Langmuir, Freundlich, Elovich, Tempkin, Dubnin–Raduskevich (D–R, Harkin–Jura and BET isotherm were applied on resultant data for equilibrium modeling. It was observed that heterogeneous adsorbent (HA particles were highly efficient for the removal of Cr(VI.

  19. Factors impacting biotransformation kinetics of trace organic compounds in lab-scale activated sludge systems performing nitrification and denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Su, Lijuan; Aga, Diana [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260 (United States); Chandran, Kartik [Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027 (United States); Khunjar, Wendell O., E-mail: wkhunjar@hazenandsawyer.com [Hazen and Sawyer P.C., Fairfax, VA 22030 (United States)

    2015-01-23

    Highlights: • We examined TOrC biotransformation kinetics in nitrifying and denitrifying reators. • TOrC biotransformation was linked to heterotrophic and autotrophic activity. • TOrC biotransformation rates were not sensitive to the initial TOrC concentration. • Readily biodegradable organic matter suppressed TOrC biotransformation rates. - Abstract: To predict TOrC fate in biological activated sludge systems, there is a need to accurately determine TOrC biodegradation kinetics in mixed microbial cultures. Short-term batch tests with salicylic acid, 17α-ethinylestradiol, nonylphenol, trimethoprim and carbamazepine were conducted with lab-scale activated sludge cultures in which the initial TOrC concentration (1 mg/L and 0.0005 mg/L) and readily biodegradable substrate concentrations were varied. The results indicate that pseudo-first order kinetic estimates of TOrC are not sensitive (p > 0.05) to the initial TOrC concentration as long as the initial TOrC concentration (S{sub 0}) to biomass (X{sub 0}) ratio (on COD basis) is below 2 × 10{sup −3}. The presence of readily biodegradable organic matter suppresses TOrC biotransformation rates under nitrifying and denitrifying conditions, and this impact can be adequately described using a reversible non-competitive inhibition equation. These results demonstrate the importance of closely mimicking parent reactor conditions in batch testing because biotransformation parameters are impacted by in-situ carbon loading and redox conditions.

  20. The removal of COD and NH3-N from atrazine production wastewater treatment using UV/O3: experimental investigation and kinetic modeling.

    Science.gov (United States)

    Jing, Liang; Chen, Bing; Wen, Diya; Zheng, Jisi; Zhang, Baiyu

    2018-01-01

    In this study, a UV/O 3 hybrid advanced oxidation system was used to remove chemical oxygen demand (COD), ammonia nitrogen (NH 3 -N), and atrazine (ATZ) from ATZ production wastewater. The removal of COD and NH 3 -N, under different UV and O 3 conditions, was found to follow pseudo-first-order kinetics with rate constants ranging from 0.0001-0.0048 and 0.0015-0.0056 min -1 , respectively. The removal efficiency of ATZ was over 95% after 180 min treatment, regardless the level of UV power. A kinetic model was further proposed to simulate the removal processes and to quantify the individual roles and contributions of photolysis, direct O 3 oxidation, and hydroxyl radical (OH·) induced oxidation. The experimental and kinetic modeling results agreed reasonably well with deviations of 12.2 and 13.1% for the removal of COD and NH 3 -N, respectively. Photolysis contributed appreciably to the degradation of ATZ, while OH· played a dominant role for the removal of both COD and NH 3 -N, especially in alkaline environments. This study provides insights into the treatment of ATZ containing wastewater using UV/O 3 and broadens the knowledge of kinetics of ozone-based advanced oxidation processes.

  1. Estimating changes of isotopic fractionation based on chemical kinetics and microbial dynamics during anaerobic methane oxidation: apparent zero- and first-order kinetics at high and low initial methane concentrations.

    Science.gov (United States)

    Vavilin, V A

    2013-02-01

    Changes in natural isotopic composition may be used to reveal metabolic pathways of substrate transformation by microbial communities (Vavilin in Ecol Model 240:84-92, 2012b). Anaerobic oxidation of methane (AOM) by sulfate has been described using a mathematical model based on chemical kinetics, microbial dynamics and equations for (13)C isotope accumulation in products as well as their redistribution between substrate and products. Experimental data for two batch cultures that originated from microbial mats covering methane seep chimneys in the Black Sea, previously obtained by Seifert et al. (Org Geochem 37:1411-1419, 2006) and Holler et al. (Env Microbiol Reports 1(5):370-376, 2009), were used to model AOM. During long-time incubation, changes of isotope signatures in CH(4) showed that in the Seifert et al. batch tests (low methane concentration), in contrast to the Holler et al. batch tests (high methane concentration), methane production occurred along with methane oxidation. In accordance with the model, apparent zero and first-order kinetics of methane oxidation were valid for the Holler et al. and Seifert et al. batch tests, respectively. The observed change of [Formula: see text] was explained by microbial kinetics reflecting that the rate is lower for heavy substrate microbial utilization when compared to light substrate microbial utilization. The model showed that small amounts of methanogenesis will change the carbon isotopic composition of methane because biogenic methane has a distinct isotopic composition and due to the large difference between the maximum specific rates of methane oxidation and production. The estimated biomass doubling time of methane-oxidizers for high and low methane concentration was 408/126 days and 4640/1160 days, respectively, depending on the value of the half-saturation constant K ( S ) (5 and 20 mM).

  2. Photo-kinetics of photoinduced transformation reaction of methylene green with titanium trichloride in different solvents

    Science.gov (United States)

    Nadeem, Syed Muhammad Saqib; Saeed, Rehana

    2017-08-01

    The photo-kinetics of photoinduced transformation reaction of methylene green and titanium trichloride was investigated in water and different aqueous-alcoholic solvents. The reaction is pseudo-first order, dependent only on the concentration of titanium trichloride at fixed concentration of methylene green. The effect of water and aqueous-alcoholic solvents was studied in the acidic range from 4 to 7. It was observed that the quantum yield (φ) of reaction increased with increase in polarity of the solvent. The quantum yield (φ) was high in acidic condition and decreased with further increase in acidity. The quantum yield (φ) increased sharply with increase in concentration of titanium trichloride while it almost remained unaffected by change in concentration of methylene green. The addition of ions increased the quantum yield (φ) of reaction. The increase in temperature decreased the rate and quantum yield (φ) of reaction. An electron transfer mechanism for the reaction has been proposed in accordance with the kinetics of reaction. The absence of any reaction intermediate was confirmed by spectroscopic investigations. Activation energy ( E a) was calculated by Arrhenius relation. Thermodynamic parameters such as activation energy ( E a), enthalpy change (Δ H), free energy change (Δ G) and entropy change (Δ S) were also evaluated.

  3. Kinetics and equilibrium properties of the biosorption of Cu2+ by algae.

    Science.gov (United States)

    Wang, Qiong; Peckenham, John; Pinto, Jamie; Patterson, Howard

    2012-11-01

    The purpose of this study was to examine the kinetics and equilibrium properties of freshwater algae with Cu(2+). This was a model system to explore using algae as biosensors for water quality. Methods included making luminescence measurements (fluorescence) and copper ion-selective electrode (CuISE) measurements vs. time to obtain kinetic data. Results were analyzed using a pseudo-first-order model to calculate the rate constants of Cu(2+) uptake by algae: k (p(Cu-algae)) = 0.0025 ± 0.0006 s(-1) by CuISE and k (p(Cu-algae)) = 0.0034 ± 0.0011 s(-1) by luminescence. The binding constant of Cu-algae, K (Cu-algae), was 1.62 ± 0.07 × 10(7) M(-1). Fluorescence results analyzed using the Stern-Volmer relationship indicate that algae have two types of binding sites of which only one appears to affect quenching. The fluorescence-based method was found to be able to detect the reaction of algae with Cu(2+) quickly and at a detection limit of 0.1 mg L(-1).

  4. Kinetic characteristics of Cu (II) adsorption on nano(poly)-cumulene

    Science.gov (United States)

    Babkin, Alexander; Neskoromnaya, Elena; Burakova, Irina; Kucherova, Ananstasia; Burakov, Alexander; Mkrtchyan, Elina

    2017-11-01

    The present paper considers the possibility of using a new type of nanocarbon materials for sorption - polycumulene modified with "Taunit-M" carbon nanotubes or graphene nanoplatelets. To evaluate the efficiency of these novel nanomodified materials as sorbents, the following studies were carried out: 1) determination of the optimum pH value to perform static batch sorption experiments, 2) identification of the onset of equilibrium for the adsorption of heavy metal ions (on the example of Cu(II) ions), and 3) elucidation of kinetic adsorption mechanisms. As a result of implementation of kinetic models such as external and internal diffusion, as well as pseudo-first- and pseudo-second-order and Elovich (to determine the contribution of chemisorption), rate constants for the Cu(II) adsorption were estimated. It was noted that the absorption process occurs in a mixed-diffusion mode with the influence of the limiting factor - "sorbate-sorbate" chemical interaction. The equilibrium time was found to be 45 min at the sorption capacity values of about 30.71 mg g-1 (in the case of the material containing carbon nanotubes) and about 24.7 mg g-1 (in the case of the material containing graphene nanoplatelets).

  5. Cadmium-109 Radioisotope Adsorption onto Polypyrrole Coated Sawdust of Dryobalanops aromatic: Kinetics and Adsorption Isotherms Modelling

    Science.gov (United States)

    Olatunji, Michael Adekunle; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Mahmud, Habibun Nabi Muhammad Ekramul

    2016-01-01

    A radiotracer study was conducted to investigate the removal characteristics of cadmium (109Cd) from aqueous solution by polypyrrole/ sawdust composite. Several factors such as solution pH, sorbent dosage, initial concentration, contact time, temperature and interfering metal ions were found to have influence on the adsorption process. The kinetics of adsorption was relatively fast, reaching equilibrium within 3 hours. A lowering of the solution pH reduced the removal efficiency from 99.3 to ~ 46.7% and an ambient temperature of 25°C was found to be optimum for maximum adsorption. The presence of sodium and potassium ions inhibited 109Cd removal from its aqueous solution. The experimental data for 109Cd adsorption showed a very good agreement with the Langmuir isotherm and a pseudo-first order kinetic model. The surface condition of the adsorbent before and after cadmium loading was investigated using BET, FESEM and FTIR. Considering the low cost of the precursor’s materials and the toxicity of 109Cd radioactive metal, polypyrrole synthesized on the sawdust of Dryobalanops aromatic could be used as an efficient adsorbent for the removal of 109Cd radioisotope from radionuclide-containing effluents. PMID:27706232

  6. KINETICS OF THE PHOTOCATALYTIC DEGRADATION OF SELECTED ORGANIC MICROPOLLUTANTS IN THE WATER ENVIROMENT

    Directory of Open Access Journals (Sweden)

    Edyta Anna Kudlek

    2017-04-01

    Full Text Available The paper presents an assessment of the removal degree of selected polycyclic aromatic hydrocarbons (anthracene, benzo(apyrene, xenoestrogens (octylphenol, pentachlorophenol and pharmaceutical compounds (diclofenac in the process of heterogeneous photocatalysis of their water solutions, which were prepared on the base of deionized water. Titanium dioxide at a dose of 100 mg/dm3 was used as a photocatalyst of the process. The kinetics of the process was determined based on the Langmuir-Hinsherlwood equation, assuming the pseudo-first-order reaction of micropollutants decomposition. Furthermore a toxicological analysis of water samples of test compounds was performed by the use of the Microtox® test. It has been found that the micropollutant concentrations decreased with the increase of process time and their removal degree after 60 minutes exceeds 90%. The analysis of the proces kinetic showed that the oxidation of the compounds occurred with the greatest intensity in the first stage of the process up to 10 min. The preformed toxicological assessment confirmed the incomplete decomposition of pollutants and the generation of by-products, which contribute to the increase of the toxicity of treated water solutions.

  7. A Novel Biosorbent, Water-Hyacinth, Uptaking Methylene Blue from Aqueous Solution: Kinetics and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    Md. Nasir Uddin

    2014-01-01

    Full Text Available The adsorption of MB dye from aqueous solution onto HCl acid treated water-hyacinth (H-WH was investigated by carried out batch sorption experiments. The effect of process parameters such as pH, adsorbent dosage, concentrations and contact time, and ionic strength were studied. Adsorption of MB onto H-WH was found highly pH dependent and ionic strength shows negative impact on MB removal. To predict the biosorption isotherms and to determine the characteristic parameters for process design, Langmuir, Freundlich, Temkin, and Halsey isotherms models were utilized to equilibrium data. The adsorption kinetics was tested for pseudo-first-order (PFO, pseudo-second-order (PSO, intraparticle diffusion (IPD, and Bangham’s kinetic models. The Langmuir isotherm model showed the goodness-of-fit among the tested models for equilibrium adsorption of MB over H-WH and indicated the maximum adsorption capacity as 63.30 mg/g. Higher coefficient of determination (R2>0.99 and better agreement between the qe (experimental and qe (calculated values predicted that PSO kinetic model showed the goodness-of-fit for kinetic data along with rate constant 1.66×10-3, 4.42×10-3, and 3.57×10-3 mg·g-1min⁡-1/2⁡, respectively, for the studied concentration range. At the initial stage of adsorption, the overall rate of dye uptake was found to be dominated by external mass transfer, and afterwards, it is controlled by IPD mechanism.

  8. Investigation of kinetics and absorption isotherm models for hydroponic phytoremediation of waters contaminated with sulfate.

    Science.gov (United States)

    Saber, Ali; Tafazzoli, Milad; Mortazavian, Soroosh; James, David E

    2017-11-24

    Two common wetland plants, Pampas Grass (Cortaderia selloana) and Lucky Bamboo (Dracaena sanderiana), were used in hydroponic cultivation systems for the treatment of simulated high-sulfate wastewaters. Plants in initial experiments at pH 7.0 removed sulfate more efficiently compared to the same experimental conditions at pH 6.0. Results at sulfate concentrations of 50, 200, 300, 600, 900, 1200, 1500 and 3000 mg/L during three consecutive 7-day treatment periods with 1-day rest intervals, showed decreasing trends of both removal efficiencies and uptake rates with increasing sulfate concentrations from the first to the second to the third 7-day treatment periods. Removed sulfate masses per unit dry plant mass, calculated after 23 days, showed highest removal capacity at 600 mg/L sulfate for both plants. A Langmuir-type isotherm best described sulfate uptake capacity of both plants. Kinetic studies showed that compared to pseudo first-order kinetics, pseudo-second order kinetic models slightly better described sulfate uptake rates by both plants. The Elovich kinetic model showed faster rates of attaining equilibrium at low sulfate concentrations for both plants. The dimensionless Elovich model showed that about 80% of sulfate uptake occurred during the first four days' contact time. Application of three 4-day contact times with 2-day rest intervals at high sulfate concentrations resulted in slightly higher uptakes compared to three 7-day contact times with 1-day rest intervals, indicating that pilot-plant scale treatment systems could be sized with shorter contact times and longer rest-intervals. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Degradation of diclofenac by TiO(2) photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays.

    Science.gov (United States)

    Rizzo, L; Meric, S; Kassinos, D; Guida, M; Russo, F; Belgiorno, V

    2009-03-01

    In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO(2) photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5-80mgL(-1)) and photocatalyst loadings (0.2-1.6gTiO(2)L(-1)) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80mgL(-1)) and at 1.6gTiO(2)L(-1) photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate.

  10. Establishment of a finite element model for extracting chemical reaction kinetics in a micro-flow injection system with high throughput sampling.

    Science.gov (United States)

    Wu, Zeng-Qiang; Du, Wen-Bin; Li, Jin-Yi; Xia, Xing-Hua; Fang, Qun

    2015-08-01

    Numerical simulation can provide valuable insights for complex microfluidic phenomena coupling mixing and diffusion processes. Herein, a novel finite element model (FEM) has been established to extract chemical reaction kinetics in a microfluidic flow injection analysis (micro-FIA) system using high throughput sample introduction. To reduce the computation burden, the finite element mesh generation is performed with different scales based on the different geometric sizes of micro-FIA. In order to study the contribution of chemical reaction kinetics under non-equilibrium condition, a pseudo-first-order chemical kinetics equation is adopted in the numerical simulations. The effect of reactants diffusion on reaction products is evaluated, and the results demonstrate that the Taylor dispersion plays a determining role in the micro-FIA system. In addition, the effects of flow velocity and injection volume on the reaction product are also simulated. The simulated results agree well with the ones from experiments. Although gravity driven flow is used to the numerical model in the present study, the FEM model also can be applied into the systems with other driving forces such as pressure. Therefore, the established FEM model will facilitate the understanding of reaction mechanism in micro-FIA systems and help us to optimize the manifold of micro-FIA systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Adsorption and kinetic studies of seven different organic dyes onto magnetite nanoparticles loaded tea waste and removal of them from wastewater samples.

    Science.gov (United States)

    Madrakian, Tayyebeh; Afkhami, Abbas; Ahmadi, Mazaher

    2012-12-01

    Adsorption of seven different organic dyes from aqueous solutions onto magnetite nanoparticles loaded tea waste (MNLTW) was studied. MNLTW was prepared via a simple method and was fully characterized. The properties of this magnetic adsorbent were characterized by scanning electron microscopy and X-ray diffraction. Adsorption characteristics of the MNLTW adsorbent was examined using Janus green, methylene blue, thionine, crystal violet, Congo red, neutral red and reactive blue 19 as adsorbates. Dyes adsorption process was thoroughly studied from both kinetic and equilibrium points of view for all adsorbents. The experimental isotherm data were analyzed using Langmuir, Freundlich, Sips, Redlich-Peterson, Brouers-Sotolongo and Temkin isotherms. The results from Langmuir isotherm indicated that the capacity of MNLTW for the adsorption of cationic dyes was higher than that for anionic dyes. The adsorption kinetics was tested for the pseudo-first order and pseudo-second order kinetic models at different experimental conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. A comparative examination of the adsorption mechanism of an anionic textile dye (RBY 3GL) onto the powdered activated carbon (PAC) using various the isotherm models and kinetics equations with linear and non-linear methods

    Science.gov (United States)

    Açıkyıldız, Metin; Gürses, Ahmet; Güneş, Kübra; Yalvaç, Duygu

    2015-11-01

    The present study was designed to compare the linear and non-linear methods used to check the compliance of the experimental data corresponding to the isotherm models (Langmuir, Freundlich, and Redlich-Peterson) and kinetics equations (pseudo-first order and pseudo-second order). In this context, adsorption experiments were carried out to remove an anionic dye, Remazol Brillant Yellow 3GL (RBY), from its aqueous solutions using a commercial activated carbon as a sorbent. The effects of contact time, initial RBY concentration, and temperature onto adsorbed amount were investigated. The amount of dye adsorbed increased with increased adsorption time and the adsorption equilibrium was attained after 240 min. The amount of dye adsorbed enhanced with increased temperature, suggesting that the adsorption process is endothermic. The experimental data was analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm equations in order to predict adsorption isotherm. It was determined that the isotherm data were fitted to the Langmuir and Redlich-Peterson isotherms. The adsorption process was also found to follow a pseudo second-order kinetic model. According to the kinetic and isotherm data, it was found that the determination coefficients obtained from linear method were higher than those obtained from non-linear method.

  13. 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.

  14. Kinetic and isotherm error optimization studies for adsorption of atrazine and imidacloprid on bark of Eucalyptus tereticornis L.

    Science.gov (United States)

    Mandal, Abhishek; Singh, Neera

    2016-01-01

    The aim of this study was to establish the bark of Eucalyptus tereticornis L. (EB) as a low cost bio-adsorbent for the removal of imidacloprid and atrazine from aqueous medium. The pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD) models were used to describe the kinetic data and rate constants were evaluated. Adsorption data was analysed using ten 2-, 3- and 4-parameter models viz. Freundlich, Jovanovic, Langmuir, Temkin, Koble-Corrigan, Redlich-Peterson, Sips, Toth, Radke-Prausnitz, and Fritz-Schluender isotherms. Six error functions were used to compute the best fit single component isotherm parameters by nonlinear regression analysis. The results showed that the sorption of atrazine was better explained by PSO model, whereas the sorption of imidacloprid followed the PFO kinetic model. Isotherm model optimization analysis suggested that the Freundlich along with Koble-Corrigan, Toth and Fritz-Schluender were the best models to predict atrazine and imidacloprid adsorption onto EB. Error analysis suggested that minimization of chi-square (χ(2)) error function provided the best determination of optimum parameter sets for all the isotherms.

  15. Removal of cobalt from lubricant oil by the use of bentonite: equilibrium, kinetic and adsorption preliminary studies

    Energy Technology Data Exchange (ETDEWEB)

    Cuccia, Valeria; Seles, Sandro R.N.; Ladeira, Ana Cláudia Queiroz, E-mail: vc@cdtn.br, E-mail: seless@cdtn.br, E-mail: acql@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-11-01

    Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator's facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Bentonite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system's kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assumption that the adsorption is due to chemisorption. Batch sorption tests were conducted and the results fitted to Langmuir and Freundlich sorption models. Both isotherm models chosen for this work did not fit to the experimental data. Thus, these are preliminary results and the studies must be repeated to evaluate data variability and better statistical inference. Other isotherm models must be evaluated to choose the best fitted one and describe the sorption of cobalt on bentonite in oil matrix. Even though, bentonite has considerable potential as sorbent for the removal of cobalt from lubricant oil. Finally, the results might be extended to other kinds of radioactive oils and radioactive organic wastes. (author)

  16. Adsorptive features of acid-treated olive stones for drin pesticides: equilibrium, kinetic and thermodynamic modeling studies.

    Science.gov (United States)

    El Bakouri, Hicham; Usero, José; Morillo, José; Ouassini, Abdelhamid

    2009-09-01

    The adsorption behavior of drin pesticides from aqueous solution onto acid treated olive stones (ATOS) was investigated using stir bar sorptive extraction and gas chromatography coupled with mass spectroscopy. The effects of sorbent particle size, adsorbent dose, contact time, concentration of pesticide solution and temperature on the adsorption processes were systematically studied in batch shaking sorption experiments. Maximum removal efficiency (94.8%) was reached for aldrin (0.5 mg L(-1)) using the fraction 63-100 microm of ATOS (solid/liquid ratio: 1 g L(-1)). Experimental data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The Freundlich isotherm model (R(2)=0.98-0.99) fitted the equilibrium data better than the Langmuir and D-R isotherm models, with low sum of error values (SE=1.4-9.2%). The mean adsorption free energy derived from the D-R isotherm model (R(2)=0.95-0.99) showed that the adsorption of drin pesticides was taken place by weak physical forces, such as van der Waals forces and hydrogen bonding. The calculated thermodynamic parameters, DeltaH, DeltaS and DeltaG prove that drin pesticides adsorption on ATOS was feasible, spontaneous and exothermic under examined conditions. The pseudo first order, pseudo second order kinetic and the intra-particle diffusion models were used to describe the kinetic data and rate constants were evaluated.

  17. Comparing adsorption activity of raw Sepiolite and CTAB modified Sepiolite: kinetic and adsorption study for removal of Hg+

    Directory of Open Access Journals (Sweden)

    Ali Ġmran Vaġzoğullar

    2015-12-01

    Full Text Available In our study adsorption of Hg+2 ions from water solutions on Sepiolite (Sep and Modified Sepiolite (MSep with cationic surfactants namely cetyl trimethyl ammonium bromide CTAB was investigated. Different parameters were used to investigate such as contact time, pH and adsorbent dosage. The adsorption capacity of MSep and Sep was examined. Both particles were characterized with FTIR spectrum. According to the our results the equilibrium adsorption data corresponded to the Langmuir isotherm and qmax was 54,7 mg/g and 104,1 mg/g for Sep and MSep respectively. Kinetic parameters showed that pseudo-second-order adsorption kinetic model was the best model than the pseudo-first-order. MSep is more active adsorbent than Sep and it can be the best alternative adsorbent for removing of heavy metal from industrial waste water. In addition MSep can be used as adsorbent for removal of nonpolar toxic organic molecules, because sepiolite surface can be converted from hydrophilic form to hydrophobic form by CTAB resulting in increased the adsorption capacity.International Journal of Environment Vol.4(4 2015: 19-31

  18. Isotherm, Kinetic and Thermodynamic Characteristics for Adsorption of Congo Red by Activated Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Jib [Kongju National University, Cheonan (Korea, Republic of)

    2015-02-15

    Batch experiment studies were carried out for adsorption of congo red using granular activated carbon with various parameters such as activated carbon dose, pH, initial dye concentration, temperature and contact time. Equilibrium experimental data are fitted to the Langmuir, Freundlich, Temkin and Dubin-Radushkevich isotherm equations. From Freundlich's separation factor (1/n) estimated, adsorption could be employed as effective treatment method for adsorption of congo red from aqueous solution. Base on Temkin constant (B) and Dubinin-Radushkevich constant (E), this adsorption process is physical adsorption. Adsorption kinetics has been tested using pseudo-first order and pseudo second order models. The results followed pseudo second order model with good correlation. Adsorption process of congo red on granular activated carbon was endothermic (ΔH=42.036 kJ/mol) and was accompanied by decrease in Gibbs free energy (ΔG=-2.414 to -4.596 kJ/mol) with increasing adsorption temperature.

  19. Assessment of TiO2 photoactivity on the lead removal: kinetic and mechanistic processing.

    Science.gov (United States)

    Peter, Anca; Mihaly-Cozmuta, Anca; Nicula, Camelia; Mihaly-Cozmuta, Leonard

    2017-06-01

    Removal of lead ions from aqueous solutions, in the presence and in absence of commercial TiO2, under UV-light was studied. The influence of catalyst mass, concentration of Pb(II) ions and of citric acid in the starting solution as well as the impact of illumination conditions on the removal rate were also investigated. The results were fitted on the pseudo-first order, pseudo-second order and Elovich kinetic models, Weber-Morris intraparticle and liquid film diffusion models, in order to establish the photoreduction mechanism. The Pb removal rate increased in time by a combined linear-exponential mechanism. The catalyst had a positive influence on the removal rate at the start of the photoreduction. At a low concentration of Pb(II) ions (20 mg/L), the amount of photoreduced Pb(II) ions was proportional to the concentration of the citric acid solution, but at high concentrations (240 mg/L), the correlation was inversely proportional. The rate limiting steps in the removal of lead were both the photoreduction on the TiO2 surface and the diffusion through the film surrounding the catalyst particle. The lead removal was significantly influenced by the mobility and by the concentration of the species in solution.

  20. Adsorption kinetic parameters of Fe3+ and Ni2+ ions by gyrolite

    Directory of Open Access Journals (Sweden)

    Kestutis Baltakys

    2015-03-01

    Full Text Available In this work the adsorption kinetic parameters for Fe3+ and Ni2+ ions by gyrolite are presented. Additionally, the adsoption mechanism was described by using pseudo first order and pseudo second order  equations. It was determined that the adsorption capacity of gyrolite and intrusion of heavy metals ions in its structure depends on reaction time and the pH value of adsorptive. It was observed that the incorporation of Fe3+ ions occurs more intensive than Ni2+ ions. It was found that in the acidic solution the intrusion of Fe3+ ions into gyrolite structure proceeds by two types of chemical reaction mechanisms: substitution and addition. Meanwhile, nickel ions were participated only in substitution reaction: gyrolite-Ca0 + Mex+ ↔ gyrolite-Me0 + Ca2+. It was observed that the pseudo second order model fit well for iron and nickel ions adsorption mechanism. It was estimated that the adsorption reactions are not reversible process and the crystal structure of gyrolite is stable. Moreover, synthetic adsorbent and the products of sorption were characterized by XRD, STA and FT-IR methods.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5735

  1. Extractive efficacy of microwave synthesized zeolitic material for acephate: Equilibrium and kinetics

    Directory of Open Access Journals (Sweden)

    Shah Bhavna A.

    2013-01-01

    Full Text Available Present investigation deals with the utilization of Bagasse fly ash (BFA a sugar industry waste and Zeolitic material (MZBFA, synthesized from BFA by combined conventional and microwave reflux method as adsorbents for the extraction of Acephate (ACP, an organophosphorus pesticide from aqueous solution. The synthesized adsorbents were characterized using various techniques such as FTIR, PXRD and SEM. The effect of various experimental parameters has been investigated using a batch adsorption technique for the extraction of ACP. The extent of removal is increased with decrease in initial ACP concentration and particle size of the adsorbent. Adsorption was fast and the equilibrium was established within 90 min. Pseudo-first-order, Pseudo-second-order, Bangham 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. Equilibrium isotherms were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich and Tempkin isotherm equations. Langmuir equation was found to best represent the equilibrium data. The thermodynamic study showed that adsorption of ACP on MZBFA is higher than that on BFA. The results indicate that such Zeolitic material could be employed as low cost alternatives to Bagasse fly ash in wastewater treatment for the removal of pesticides.

  2. Chlorination of oxybenzone: Kinetics, transformation, disinfection byproducts formation, and genotoxicity changes.

    Science.gov (United States)

    Zhang, Shujuan; Wang, Xiaomao; Yang, Hongwei; Xie, Yuefeng F

    2016-07-01

    UV filters are a kind of emerging contaminant, and their transformation behavior in water treatment processes has aroused great concern. In particular, toxic products might be produced during reaction with disinfectants during the disinfection process. As one of the most widely used UV filters, oxybenzone has received significant attention, because its transformation and toxicity changes during chlorine oxidation are a concern. In our study, the reaction between oxybenzone and chlorine followed pseudo-first-order and second-order kinetics. Three transformation products were detected by LC-MS/MS, and the stability of products followed the order of tri-chloro-methoxyphenoyl > di-chlorinated oxybenzone > mono-chlorinated oxybenzone. Disinfection byproducts (DBPs) including chloroform, trichloroacetic acid, dichloroacetic acid and chloral hydrate were quickly formed, and increased at a slower rate until their concentrations remained constant. The maximum DBP/oxybenzone molar yields for the four compounds were 12.02%, 6.28%, 0.90% and 0.23%, respectively. SOS/umu genotoxicity test indicated that genotoxicity was highly elevated after chlorination, and genotoxicity showed a significantly positive correlation with the response of tri-chloro-methoxyphenoyl. Our results indicated that more genotoxic transformation products were produced in spite of the elimination of oxybenzone, posing potential threats to drinking water safety. This study shed light on the formation of DBPs and toxicity changes during the chlorination process of oxybenzone. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Kinetics of the adsorption of strontium ions by a crosslinked copolymer containing methacrylic acid functional groups

    Energy Technology Data Exchange (ETDEWEB)

    Oezeroglu, C.; Keceli, G. [Istanbul Univ. (Turkey). Dept. of Chemistry

    2007-07-01

    The crosslinked copolymers of ethylene glycol dimethacrylate (EGDM) and methacrylic acid (MA) containing different amounts of MA as weight percentage (MA content = 10.00%, 25.00% and 50.00%) were synthesized by using BPO-DMA initiator system at room temperature. Infrared (FTIR) and thermal gravimetric analysis (TGA) were used to characterize the crosslinked copolymers. The crosslinked copolymer containing 25.00% of MA as weight percentage (w/w) was used as adsorbent for the removal of strontium ions from aqueous solution. The effects of parameters including strontium concentration, agitation time, temperature and pH were examined. Kinetics of the adsorption of strontium ions on the copolymer bearing methacrylic acid functional groups from aqueous solution at various initial strontium concentrations was studied. Goodness of experimental results to the Elovich, fractional powder, pseudo-first order and pseudo-second order models have been examined. The pseudo-second order model provided a high degree of correlation with the experimental data for the adsorption process of strontium ion on the crosslinked copolymer bearing methacrylic acid functional groups from aqueous solutions. (orig.)

  4. Removal of Cr(VI from Aqueous Solution Using Modified Pomegranate Peel : Equilibrium and Kinetic Studies

    Directory of Open Access Journals (Sweden)

    Tariq S. Najim

    2009-01-01

    Full Text Available The present investigation deals with the utilization of modified pomegrenate peel (MPGP and formaldehyde modified pomegrenate peel (FMPGP as adsorbents for the removal of chromium Cr(VI from aqueous solution. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The effect of pH, initial Cr(VI concentration, contact time, adsorbent dosage and temperature were considered. The optimal pH values of Cr(VI removal by MPGP and FMPGP were 2.0 and 3.0 respectively. The time required for equilibrium was found to be about 100 minutes. The initial Cr(VI concentration and adsorbent dosage was found to have large effect on the adsorption of Cr(VI. The maximum uptake capacities were 13.01 and 22.28 mg of Cr(VI per gram of MPGP and FMPGP respectively. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Kinetic studies showed that the adsorption followed a pseudo second order reaction due to the high correlation coefficient and the agreement between the experimental and calculated values of qe.The adsorption may follow intraparticle diffusion as well, due to the highest values of rate constants for the surface adsorption and intraparticle diffusion kinetic models, the higher values of rate constants are related to an improved bonding between Cr(VI ions and adsorbent particle.The Dubinin-radushkevich, Freundlich and Tempkin models were the closest fit for the equilibrium data of MPGP and FMPGP.

  5. Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica

    Directory of Open Access Journals (Sweden)

    Atyaf Khalid Hameed

    2016-08-01

    Full Text Available Zero valent iron supported on mesoporous silicanano particles (NZVI/MSNs was prepared by the aqueous phase borohydride reduction methods. Prior to the reduction, mesoporous silica nanoparticles (MSNs were prepared through the activation of fumed silica with concentrated HCl by refluxing at 90 °C. FTIR, XRD, FESEM, EDX and BET were used to characterize theadsorbents prepared. BET surface areas of MSNs, NZVI, and NZVI/MSNs were 126, 41, and 72 m2/g for, respectively. The performance of NZVI/MSNs as adsorbent was examined by adsorption of methylene blue (MB, performed in series of batch experiments. In the kinetic studies, pseudo first order and pseudo second order kinetic models were examined. The pseudo second order equation provided the best fit with the experimental data. Thermodynamic studies indicated that the adsorption process is endothermic with ΔH° was 90.53 kJ/mol. Positive ΔS° (300 J/mol and negative ΔG° (-6.42 kJ/mol was recorded, indicating the spontaneous of the adsorption process and naturally favorable. Copyright © 2016 BCREC GROUP. All rights reserved Received: 5th March 2016; Revised: 18th March 2016; Accepted: 18th March 2016 How to Cite: Hameed, A.K., Dewayanto, N., Dongyun, D., Nordin, M.R., Mohd Hasbi Ab. Rahim, M.H.A. (2016. Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 250-261 (doi:10.9767/bcrec.11.2.443.250-261 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.443.250-261

  6. Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers.

    Science.gov (United States)

    Maksin, Danijela D; Nastasović, Aleksandra B; Milutinović-Nikolić, Aleksandra D; Suručić, Ljiljana T; Sandić, Zvjezdana P; Hercigonja, Radmila V; Onjia, Antonije E

    2012-03-30

    Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70°C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q(max), at pH 1.8 and 25°C was 143 mg g(-1) for PGME2-deta (sample with the highest amino group concentration) while at 70°C Q(max) reached the high value of 198 mg g(-1). Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Clinical evaluation of iterative reconstruction (ordered-subset expectation maximization) in dynamic positron emission tomography: quantitative effects on kinetic modeling with N-13 ammonia in healthy subjects

    DEFF Research Database (Denmark)

    Hove, Jens Dahlgaard; Rasmussen, R.; Freiberg, J.

    2008-01-01

    BACKGROUND: The purpose of this study was to investigate the quantitative properties of ordered-subset expectation maximization (OSEM) on kinetic modeling with nitrogen 13 ammonia compared with filtered backprojection (FBP) in healthy subjects. METHODS AND RESULTS: Cardiac N-13 ammonia positron...... emission tomography (PET) studies from 20 normal volunteers at rest and during dipyridamole stimulation were analyzed. Image data were reconstructed with either FBP or OSEM. FBP- and OSEM-derived input functions and tissue curves were compared together with the myocardial blood flow and spillover values...... and OSEM flow values were observed with a flow underestimation of 45% (rest/dipyridamole) in the septum and of 5% (rest) and 15% (dipyridamole) in the lateral myocardial wall. CONCLUSIONS: OSEM reconstruction of myocardial perfusion images with N-13 ammonia and PET produces high-quality images for visual...

  8. Sulfidation kinetics of silver nanoparticles reacted with metal sulfides.

    Science.gov (United States)

    Thalmann, Basilius; Voegelin, Andreas; Sinnet, Brian; Morgenroth, Eberhard; Kaegi, Ralf

    2014-05-06

    Recent studies have documented that the sulfidation of silver nanoparticles (Ag-NP), possibly released to the environment from consumer products, occurs in anoxic zones of urban wastewater systems and that sulfidized Ag-NP exhibit dramatically reduced toxic effects. However, whether Ag-NP sulfidation also occurs under oxic conditions in the absence of bisulfide has not been addressed, yet. In this study we, therefore, investigated whether metal sulfides that are more resistant toward oxidation than free sulfide, could enable the sulfidation of Ag-NP under oxic conditions. We reacted citrate-stabilized Ag-NP of different sizes (10-100 nm) with freshly precipitated and crystalline CuS and ZnS in oxygenated aqueous suspensions at pH 7.5. The extent of Ag-NP sulfidation was derived from the increase in dissolved Cu(2+) or Zn(2+) over time and linked with results from X-ray absorption spectroscopy (XAS) analysis of selected samples. The sulfidation of Ag-NP followed pseudo first-order kinetics, with rate coefficients increasing with decreasing Ag-NP diameter and increasing metal sulfide concentration and depending on the type (CuS and ZnS) and crystallinity of the reacting metal sulfide. Results from analytical electron microscopy revealed the formation of complex sulfidation patterns that seemed to follow preexisting subgrain boundaries in the pristine Ag-NP. The kinetics of Ag-NP sulfidation observed in this study in combination with reported ZnS and CuS concentrations and predicted Ag-NP concentrations in wastewater and urban surface waters indicate that even under oxic conditions and in the absence of free sulfide, Ag-NP can be transformed into Ag2S within a few hours to days by reaction with metal sulfides.

  9. Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: kinetic, equilibrium and thermodynamic study.

    Science.gov (United States)

    Kul, Ali Riza; Koyuncu, Hülya

    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(-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(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 (DeltaG), the enthalpy (DeltaH) and the entropy change of sorption (DeltaS) were determined as about -5.06, 10.29 and 0.017 kJ mol(-1) K(-1), respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. 2010 Elsevier B.V. All rights reserved.

  10. Electrochemical oxidation of COD from real textile wastewaters: Kinetic study and energy consumption.

    Science.gov (United States)

    Zou, Jiaxiu; Peng, Xiaolan; Li, Miao; Xiong, Ying; Wang, Bing; Dong, Faqin; Wang, Bin

    2017-03-01

    In the present study, the electrochemical oxidation of real wastewaters discharged by textile industry was carried out using a boron-doped diamond (BDD) anode. The effect of operational variables, such as applied current density (20-100 mA·cm-2), NaCl concentration added to the real wastewaters (0-3 g·L-1), and pH value (2.0-10.0), on the kinetics of COD oxidation and on the energy consumption was carefully investigated. The obtained experimental results could be well matched with a proposed kinetic model, in which the indirect oxidation mediated by electrogenerated strong oxidants would be described through a pseudo-first-order kinetic constant k. Values of k exhibited a linear increase with increasing applied current density and decreasing pH value, and an exponential increase with NaCl concentration. Furthermore, high oxidation kinetics resulted in low specific energy consumption, but this conclusion was not suitable to the results obtained under different applied current density. Under the optimum operational conditions, it only took 3 h to complete remove the COD in the real textile wastewaters and the specific energy consumption could be as low as 11.12 kWh·kg-1 COD. The obtained results, low energy consumption and short electrolysis time, allowed to conclude that the electrochemical oxidation based on BDD anodes would have practical industrial application for the treatment of real textile wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Reaction kinetics of resveratrol with tert-butoxyl radicals

    Science.gov (United States)

    Džeba, Iva; Pedzinski, Tomasz; Mihaljević, Branka

    2012-09-01

    The rate constant for the reaction of t-butoxyl radicals with resveratrol was studied under pseudo-first order conditions. The rate constant was determined by measuring the phenoxyl radical formation rate at 390 nm as function of resveratrol concentration in acetonitrile. The rate constant was determined to be 6.5×108 M-1s-1. This high value indicates the high reactivity consistent with the strong antioxidant activity of resveratrol.

  12. Kinetic, equilibrium isotherm and thermodynamic studies of Cr(VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid.

    Science.gov (United States)

    ALOthman, Zeid A; Naushad, Mu; Ali, Rahmat

    2013-05-01

    A particular agricultural waste, peanut shell, has been used as precursor for activated carbon production by chemical activation with H₃PO₄. Unoxidized activated carbon was prepared in nitrogen atmosphere which was then heated in air at a desired temperature to get oxidized activated carbon. The prepared carbons were characterized for surface area, surface morphology, and pore volume and utilized for the removal of Cr(VI) from aqueous solution. Batch mode experiments were conducted to study the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature on the adsorption of Cr(VI). Cr(VI) adsorption was significantly dependent on solution pH, and the optimum adsorption was observed at pH 2. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial Cr(VI) concentrations. The adsorption kinetic data were described very well by the pseudo-second-order model. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich, and Temkin models. The results showed that the Langmuir adsorption isotherm model fitted the data better in the temperature range studied. The adsorption capacity which was found to increase with temperature showed the endothermic nature of Cr(VI) adsorption. The thermodynamic parameters, such as Gibb's Free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were evaluated.

  13. Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Limin [Key Laboratory of Nuclear Resources and Environment, East China Institute of Technology, Ministry of Education, Xuefu Road No. 56, Fuzhou, Jiangxi 344000 (China); School of Chemistry and Chemical Engineering, Tianjin University, Weijin Road No. 92, Tianjin 300072 (China)], E-mail: minglzh@sohu.com; Wang Yiping [School of Chemistry and Chemical Engineering, Tianjin University, Weijin Road No. 92, Tianjin 300072 (China); Liu Zhirong [Key Laboratory of Nuclear Resources and Environment, East China Institute of Technology, Ministry of Education, Xuefu Road No. 56, Fuzhou, Jiangxi 344000 (China); Huang Qunwu [School of Chemistry and Chemical Engineering, Tianjin University, Weijin Road No. 92, Tianjin 300072 (China)

    2009-01-30

    Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg{sup 2+}, Cu{sup 2+}, and Ni{sup 2+} ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3 mg/g for Hg{sup 2+}, Cu{sup 2+}, and Ni{sup 2+} ions, respectively. TMCS displayed higher adsorption capacity for Hg{sup 2+} in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88% using 0.01-0.1 M ethylendiamine tetraacetic acid (EDTA)

  14. Reactions of enolisable ketones with dichloroisocyanuric acid in absence and presence of added chloride ions – a kinetic study

    Directory of Open Access Journals (Sweden)

    Y. L. Kumar

    2015-01-01

    Full Text Available Kinetics of reactions of enolisable ketones (S = acetone/2-butanone with dichloroisocyanuric acid (DCICA were studied in aqueous acetic acid and perchloric acid media in absence and presence of added chloride ions. The reactions were found to be pseudo zero order and pseudo first order on [DCICA] in absence and presence of chloride ions respectively. Both in presence and absence of chloride ions, first order and fractional order in substrate and perchloric acid were observed respectively. An increase in the rate of reaction was observed with an increase in chloride ion concentration as well as acetic acid composition. The results were interpreted in terms of probable mechanisms involving (i rate-determining enol formation from the conjugate acid of the ketone (SH+ in the absence of added chloride ions and (ii rate-determining interaction of SH+ with the most effective molecular chlorine species produced by the hydrolysis of DCICA (rather than a rate-determining interaction of enol with chlorine in the presence of added chloride ions, prior to the rapid steps of product formation. DOI: http://dx.doi.org/10.4314/bcse.v29i1.12

  15. Photocatalytic degradation of methyl orange by TiO2-coated activated carbon and kinetic study.

    Science.gov (United States)

    Li, Youji; Li, Xiaodong; Li, Junwen; Yin, Jing

    2006-03-01

    TiO2-coated activated carbon (AC) grain (TiO2/AC) was prepared through hydrolytic precipitation of TiO2 from Tetrabutylorthotitanate and following heat treatment. The TiO2/AC was characterized by BET, SEM, XRD and optical absorption spectroscopy. The samples were employed as catalysts for methyl orange photocatalytic oxidation degradation in aqueous suspension, used as probe reaction. The kinetics of methyl orange photodegradation was analyzed. The results indicate that BET surface area of TiO2-coated ACs decreased drastically in comparison with the original AC with increasing TiO2 coatings by more than 1 doped cycle. Nano-TiO2 particles were dispersed on the AC with the size of 20-40 nm. Crystalline TiO2 doped onto AC was from anatase to rutile with increase of heat-treatment temperature. The TiO2/AC was shown high photoactivity for the photodegradation of methyl orange (MO) dyestuff in aqueous solution under UV irradiation. The kinetics of photocatalytic MO dyestuff degradation was found to follow a pseudo-first-order rate law. It was observed that the presence of the AC enhanced the photoefficiency of the titanium dioxide catalyst. Different amount of TiO2 coatings induced different increases in the apparent first-order rate constant of the process. The kinetic behavior could be described in terms of a modified Langmuir-Hinshelwood model. The values of the adsorption equilibrium constants for the organic molecules, KC, and for the rate constants, kc, were certainly dependent on TiO2 content. At 47wt% TiO2 coatings with the highest rate constant, the KC and kc was 0.1116l mmol(-1) and 0.1872 mmol l(-1) min(-1), respectively. The mechanism of methyl orange degradation was discussed in terms of the titanium dioxide photosensitization by the AC.

  16. Equilibrium and kinetics of phosphorous adsorption onto bone charcoal from aqueous solution.

    Science.gov (United States)

    Ghaneian, Mohammad Taghi; Ghanizadeh, Ghader; Alizadeh, Mohammad Tahghighi Haji; Ehrampoush, Mohammad Hasan; Said, Farhan Mohd

    2014-01-01

    Pyrolysis of fresh sheep bone led to the formation of bone charcoal (BC). The structural characteristics of BC and surface area were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). N2 gas adsorption-desorption was analysed by Brunauer-Emmett-Teller isotherm model. The prepared BC was used as an effective sorbent for the removal of phosphate from aqueous solutions. The effect of major parameters, including initial phosphorous concentration, sorbent dosage, pH and temperature, was investigated in this study. Furthermore, adsorption isotherms and kinetics were evaluated. BC was an effective sorbent in phosphate removal from aqueous solution especially in phosphate concentration between 2 and 100 mg/L. The maximum amount of sorption capacity was 30.21 mg/g, which was obtained with 100 mg/L as the initial phosphate concentration and 0.2 g as the sorbent dosage. Best reported pH in this study is 4; in higher pH, adsorption rate decreased dramatically. By increasing the temperature from 20 to 40 degrees C sorption capacity increased; this phenomenon described that adsorption is endothermic. Equilibrium data were analysed by Langmuir, Freundlich and Temkin isotherms. Pseudo first- and second-order and Elovich models were used to determine the kinetics of adsorption in this study. Collected data highly fitted with Freundlich isotherms and pseudo second-order kinetics. Achieved results have shown well the potentiality for the BC to be utilized as a natural sorbent to remove phosphorous from water and wastewater.

  17. Kinetics and

    Directory of Open Access Journals (Sweden)

    Mojtaba Ahmadi

    2016-11-01

    Full Text Available The aqueous degradation of Reactive Yellow 84 (RY84 by potassium peroxydisulfate (K2S2O8 has been studied in laboratory scale experiments. The effect of the initial concentrations of potassium peroxydisulfate and RY84, pH and temperature on RY84 degradation were also examined. Experimental data were analyzed using first and second-order kinetics. The degradation kinetics of RY84 of the potassium peroxydisulfate process followed the second-order reaction kinetics. These rate constants have an extreme values similar to of 9.493 mM−1min−1 at a peroxydisulfate dose of 4 mmol/L. Thermodynamic parameters such as activation (Ea and Gibbs free energy (ΔG° were also evaluated. The negative value of ΔGo and Ea shows the spontaneous reaction natural conditions and exothermic nature.

  18. Monod kinetics rather than a first-order degradation model explains atrazine fate in soil mini-columns: Implications for pesticide fate modelling

    Energy Technology Data Exchange (ETDEWEB)

    Cheyns, K., E-mail: Karlien.Cheyns@ees.kuleuven.b [Division soil and water management, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee (Belgium); Mertens, J.; Diels, J.; Smolders, E.; Springael, D. [Division soil and water management, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee (Belgium)

    2010-05-15

    Pesticide transport models commonly assume first-order pesticide degradation kinetics for describing reactive transport in soil. This assumption was assessed in mini-column studies with associated batch degradation tests. Soil mini-columns were irrigated with atrazine in two intermittent steps of about 30 days separated by 161 days application of artificial rain water. Atrazine concentration in the effluent peaked to that of the influent concentration after initial break-through but sharply decreased while influx was sustained, suggesting a degradation lag phase. The same pattern was displayed in the second step but peak height and percentage of atrazine recovered in the effluent were lower. A Monod model with biomass decay was successfully calibrated to this data. The model was successfully evaluated against batch degradation data and mini-column experiments at lower flow rate. The study suggested that first-order degradation models may underestimate risk of pesticide leaching if the pesticide degradation potential needs amplification during degradation. - Population dynamics of pesticide degrading population should be taken into account when predictions of pesticide fate are made to avoid underestimation of pesticide break-through towards groundwater.

  19. Monod kinetics rather than a first-order degradation model explains atrazine fate in soil mini-columns: implications for pesticide fate modelling.

    Science.gov (United States)

    Cheyns, K; Mertens, J; Diels, J; Smolders, E; Springael, D

    2010-05-01

    Pesticide transport models commonly assume first-order pesticide degradation kinetics for describing reactive transport in soil. This assumption was assessed in mini-column studies with associated batch degradation tests. Soil mini-columns were irrigated with atrazine in two intermittent steps of about 30 days separated by 161 days application of artificial rain water. Atrazine concentration in the effluent peaked to that of the influent concentration after initial break-through but sharply decreased while influx was sustained, suggesting a degradation lag phase. The same pattern was displayed in the second step but peak height and percentage of atrazine recovered in the effluent were lower. A Monod model with biomass decay was successfully calibrated to this data. The model was successfully evaluated against batch degradation data and mini-column experiments at lower flow rate. The study suggested that first-order degradation models may underestimate risk of pesticide leaching if the pesticide degradation potential needs amplification during degradation. Copyright 2010 Elsevier Ltd. All rights reserved.

  20. Higher adsorption capacity of Spirulina platensis alga for Cr(VI) ions removal: parameter optimisation, equilibrium, kinetic and thermodynamic predictions.

    Science.gov (United States)

    Gunasundari, Elumalai; Senthil Kumar, Ponnusamy

    2017-04-01

    This study discusses about the biosorption of Cr(VI) ion from aqueous solution using ultrasonic assisted Spirulina platensis (UASP). The prepared UASP biosorbent was characterised by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmet-Teller, scanning electron spectroscopy and energy dispersive X-ray and thermogravimetric analyses. The optimum condition for the maximum removal of Cr(VI) ions for an initial concentration of 50 mg/l by UASP was measured as: adsorbent dose of 1 g/l, pH of 3.0, contact time of 30 min and temperature of 303 K. Adsorption isotherm, kinetics and thermodynamic parameters were calculated. Freundlich model provided the best results for the removal of Cr(VI) ions by UASP. The adsorption kinetics of Cr(VI) ions onto UASP showed that the pseudo-first-order model was well in line with the experimental data. In the thermodynamic study, the parameters like Gibb's free energy, enthalpy and entropy changes were evaluated. This result explains that the adsorption of Cr(VI) ions onto the UASP was exothermic and spontaneous in nature. Desorption of the biosorbent was done using different desorbing agents in which NaOH gave the best result. The prepared material showed higher affinity for the removal of Cr(VI) ions and this may be an alternative material to the existing commercial adsorbents.

  1. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry

    Energy Technology Data Exchange (ETDEWEB)

    Vilar, Vitor J.P. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Botelho, Cidalia M.S. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Boaventura, Rui A.R. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal)]. E-mail: bventura@fe.up.pt

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mg l{sup -1} and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D {sub h}, are 3.6 x 10{sup -8}; 6.1 x 10{sup -8} and 2.4 x 10{sup -8} cm{sup 2} s{sup -1}, respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  2. Effects of pH and particle size on kinetics of nitrobenzene reduction by zero-valent iron.

    Science.gov (United States)

    Dong, Jun; Zhao, Yongsheng; Zhao, Ran; Zhou, Rui

    2010-01-01

    Nitrobenzene has been considered as a significant groundwater contaminant due to its wide usage in explosives, insecticides, herbicides, pharmaceuticals and dyes. Nitrobenzene is of environmental concern because of its toxicity. In the presence of zero-valent iron (ZVI), reduction of the nitro group is the dominant transformation process for nitrobenzene. A series of experiments were carried out to investigate the kinetics of nitrobenzene reduction by ZVI and the effects of pH and ZVI particle size on nitrobenzene removal in groundwater. The results indicated that nitrobenzene could be reduced to aniline by ZVI; the reduction of nitrobenzene by ZVI followed a pseudo first-order kinetics; the observed nitrobenzene reduction rate constant (k(obs)) was 0.0006 min(-1) and the half-life of nitrobenzene (t1/2) was 115.5 min; the mass balance achieved 87.5% for nitrobenzene reduction by the 1 mm ZVI particle and the final removal efficiency was 80.98%. In addition, the pH and ZVI particle size were found to exhibit significant influences on the nitrobenzene reduction. The observed nitrobenzene reduction rate constant linearly decreased with increase pH and the data fitted on polynomial regression equation for the observed nitrobenzene reduction rate constant and ZVI particle size. Therefore, use of ZVI based permeable reactive barrier technology to remedy nitrobenzene contaminated groundwater was feasible.

  3. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mgl(-1) and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D(h), are 3.6 x 10(-8); 6.1 x 10(-8) and 2.4 x 10(-8)cm(2)s(-1), respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  4. Removal of mixed pesticides from aqueous solutions using organoclays: evaluation of equilibrium and kinetic model.

    Science.gov (United States)

    Saha, Ajoy; Ahammed Shabeer Tp; Gajbhiye, V T; Gupta, Suman; Kumar, Rajesh

    2013-07-01

    Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p'-DDT and two metabolites p,p'-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951-0.992). High values (0.17-0.52 mg g⁻¹) of Freundlich constant (K(f)) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol-water partition coefficient (K(ow)) and low water solubility showed faster adsorption with higher K(f) values as compared to the pesticides with low K(ow) and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.

  5. Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite

    Energy Technology Data Exchange (ETDEWEB)

    Arancibia-Miranda, Nicolás, E-mail: nicolas.arancibia@usach.cl [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Facultad de Química y Biología, Universidad de Santiago de Chile, Av. B. O' Higgins, 3363, Santiago (Chile); Silva-Yumi, Jorge [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Escudey, Mauricio [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Facultad de Química y Biología, Universidad de Santiago de Chile, Av. B. O' Higgins, 3363, Santiago (Chile)

    2015-12-15

    Highlights: • Effect of various cations on the IEP of imogolite was studied. • Studied adsorption kinetics of Cd and Cu on imogolite in the presence of cations. • K{sup +} acted as an indifferent electrolyte and did not affect the IEP of imogolite. • Adsorption in the presence of K{sup +} is described well by three of the four models. • These include pseudo-second order, Elovich equation, and Weber–Morris model. - Abstract: Modification of surface charge and changes in the isoelectric point (IEP) of synthetic imogolite were studied for various cations in the background electrolyte (K{sup +}, NH{sub 4}{sup +}, Mg{sup 2+}, and Ca{sup 2+}). From the electrophoretic mobility data, it was established that the K{sup +} (KCl) concentration does not affect the IEP of imogolite; therefore, KCl is a suitable background electrolyte. In terms of the magnitude of changes in the IEP and surface charge, the cations may be ranked in the following order: Mg{sup 2+} ≈ Ca{sup 2+} >> NH{sub 4}{sup +} >> K{sup +}. Four different kinetic models were used to evaluate the influence of Mg{sup 2+}, Ca{sup 2+}, NH{sub 4}{sup +}, and K{sup +} on the adsorption of Cd and Cu on synthetic imogolite. When adsorption occurs in the presence of cations with the exception of K{sup +}, the kinetics of the process is well described by the pseudo-first order model. On the other hand, when adsorption is conducted in the presence of K{sup +}, the adsorption kinetics is well described by the pseudo-second order, Elovich, and Weber–Morris models. From the surface charge measurements, the affinity between imogolite and the cations and their effect on the adsorption of trace elements, namely Cu and Cd, were established.

  6. Kinetics of biosorption of hazardous metals by green soil supplement

    Science.gov (United States)

    Bagla, Hemlata; Khilnani, Roshan

    2016-04-01

    of the biosorption in terms of the order of the rate constant were studied applying different kinetic models such as First order, Second order, Pseudo-first order, Pseudo-second order and the intra particle diffusion model. But among these models best fitting model was Lagergren pseudo second order model. The correlation coefficients of all the elements have R2 values close to 1 indicating the applicability of pseudo second order model to the present system. The applicability of this model suggested that biosorption of elements under study, on DCP was based on chemical interactions between metals and active sites of biosorbent. References 1. E. Tipping, Cation Binding by Humic Substances. Cambridge University Press, 2002. 2. S. Lagergren, Zur theorie der sogenannten adsorption geloster stoffe. Kungliga Svenska Vetenskapsakademiens, Handlingar vol. 24, no.4, pp. 1-39, 1898. 3. Y. S. Ho and G. McKay, "Pseudo-second order model for sorption processes," Process Biochem., vol. 34, no. 5, pp. 451-465, Jul. 1999. 4. N. S. Barot and H. K. Bagla, "Extraction of humic acid from biological matrix - dry cow dung powder," Green Chem. Lett. Rev., vol. 2, no. 4, pp. 217-221, 2009.

  7. Photocatalytic degradation of a widely used insecticide Thiamethoxam in aqueous suspension of TiO2: adsorption, kinetics, product analysis and toxicity assessment.

    Science.gov (United States)

    Mir, Niyaz A; Khan, A; Muneer, M; Vijayalakhsmi, S

    2013-08-01

    This paper deals with the study of photocatalyzed degradation of an insecticide, Thiamethoxam in aqueous suspension of TiO2. The adsorption of Thiamethoxam on TiO2 surface under dark conditions was also investigated in order to find out equilibrium adsorption constant. The degradation kinetics was studied using spectrophotometric method under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and in the presence of electron acceptors such as hydrogen peroxide, potassium bromate, and ammonium persulphate under continuous purging of atmospheric oxygen, and the degradation rates were found to be strongly influenced by these parameters. The results manifested that the photocatalysis of Thiamethoxam follows pseudo-first-order kinetics. The toxicity assessments of the irradiated samples were carried out using human erythrocytes as a model system under in vitro conditions. GC-MS study showed the formation of several intermediate products which were characterised based on their molecular mass and mass fragmentation pattern. A probable mechanism for the formation of various products formed during the photocatalytic process of Thiamethoxam was also proposed. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models

    Directory of Open Access Journals (Sweden)

    Md. Sayedur Rahman

    2015-01-01

    Full Text Available 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 Pb2+, Cu2+, Fe2+, and Zn2+ 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.

  9. 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 Pb2+, Cu2+, Fe2+, and Zn2+ 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. PMID:26295032

  10. Photocatalytic degradation of a widely used insecticide Thiamethoxam in aqueous suspension of TiO{sub 2}: Adsorption, kinetics, product analysis and toxicity assessment

    Energy Technology Data Exchange (ETDEWEB)

    Mir, Niyaz A.; Khan, A. [Department of Chemistry, Aligarh Muslim University, Aligarh-202002, UP (India); Muneer, M., E-mail: readermuneer@gmail.com [Department of Chemistry, Aligarh Muslim University, Aligarh-202002, UP (India); Vijayalakhsmi, S. [SAIF, CRNTS, IIT Bombay, Powai, 400076, Mumbai (India)

    2013-08-01

    This paper deals with the study of photocatalyzed degradation of an insecticide, Thiamethoxam in aqueous suspension of TiO{sub 2}. The adsorption of Thiamethoxam on TiO{sub 2} surface under dark conditions was also investigated in order to find out equilibrium adsorption constant. The degradation kinetics was studied using spectrophotometric method under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and in the presence of electron acceptors such as hydrogen peroxide, potassium bromate, and ammonium persulphate under continuous purging of atmospheric oxygen, and the degradation rates were found to be strongly influenced by these parameters. The results manifested that the photocatalysis of Thiamethoxam follows pseudo-first-order kinetics. The toxicity assessments of the irradiated samples were carried out using human erythrocytes as a model system under in vitro conditions. GC–MS study showed the formation of several intermediate products which were characterised based on their molecular mass and mass fragmentation pattern. A probable mechanism for the formation of various products formed during the photocatalytic process of Thiamethoxam was also proposed. Highlights: • TiO{sub 2} P25 is a more efficient photocatalyst than UV100 and PC500 for degradation of Thiamethoxam. • Low H{sub 2}O{sub 2} dosages enhance degradation whereas overdose retards it. • Toxicity of Thiamethoxam decreases with the increase in irradiation time. • Eight intermediate products have been identified using GC–MS analysis technique.

  11. Isotherms, kinetics and thermodynamic studies of adsorption of Cu{sup 2+} from aqueous solutions by Mg{sup 2+}/K{sup +} type orange peel adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Liang Sha [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Guo Xueyi, E-mail: xyguo@mail.csu.edu.cn [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Feng Ningchuan; Tian Qinghua [School of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China)

    2010-02-15

    Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg{sup 2+} type orange peel adsorbent) and KOP (K{sup +} type orange peel adsorbent). FTIR and SEM were used to characterize the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu{sup 2+} adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu{sup 2+} by both MgOP and KOP, and the mono-layer adsorption capacity for Cu{sup 2+} removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu{sup 2+} increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu{sup 2+} by MgOP and KOP.

  12. 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.

  13. Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

    Science.gov (United States)

    Öztürk, A.; Malkoc, E.

    2014-04-01

    In this work, natural untreated clay (NUC) was studied for the removal of Basic Yellow 2 (BY2) from aqueous solution in batch system. The effects of initial BY2 concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

  14. Isotherms, kinetics and thermodynamic studies of adsorption of Cu2+ from aqueous solutions by Mg2+/K+ type orange peel adsorbents.

    Science.gov (United States)

    Liang, Sha; Guo, Xueyi; Feng, Ningchuan; Tian, Qinghua

    2010-02-15

    Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg(2+) type orange peel adsorbent) and KOP (K(+) type orange peel adsorbent). FTIR and SEM were used to characterize the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu(2+) adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu(2+) by both MgOP and KOP, and the mono-layer adsorption capacity for Cu(2+) removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu(2+) increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu(2+) by MgOP and KOP.

  15. Cr(VI) sorption by free and immobilised chromate-reducing bacterial cells in PVA-alginate matrix: equilibrium isotherms and kinetic studies.

    Science.gov (United States)

    Rawat, Monica; Rawat, A P; Giri, Krishna; Rai, J P N

    2013-08-01

    Chromate-resistant bacterial strain isolated from the soil of tannery was studied for Cr(VI) bioaccumulation in free and immobilised cells to evaluate its applicability in chromium removal from aqueous solution. Based on the comparative analysis of the 16S rRNA gene, and phenotypic and biochemical characterization, this strain was identified as Paenibacillus xylanilyticus MR12. Mechanism of Cr adsorption was also ascertained by chemical modifications of the bacterial biomass followed by Fourier transform infrared spectroscopy analysis of the cell wall constituents. The equilibrium biosorption analysed using isotherms (Langmuir, Freundlich and Dubinin-Redushkevich) and kinetics models (pseudo-first-order, second-order and Weber-Morris) revealed that the Langmuir model best correlated to experimental data, and Weber-Morris equation well described Cr(VI) biosorption kinetics. Polyvinyl alcohol alginate immobilised cells had the highest Cr(VI) removal efficiency than that of free cells and could also be reused four times for Cr(VI) removal. Complete reduction of chromate in simulated effluent containing Cu(2+), Mg(2+), Mn(2+) and Zn(2+) by immobilised cells, demonstrated potential applications of a novel immobilised bacterial strain MR12, as a vital bioresource in Cr(VI) bioremediation technology.

  16. Structure regulation of silica nanotubes and their adsorption behaviors for heavy metal ions: pH effect, kinetics, isotherms and mechanism.

    Science.gov (United States)

    Wang, Pan; Du, Mingliang; Zhu, Han; Bao, Shiyong; Yang, Tingting; Zou, Meiling

    2015-04-09

    Silica nanotubes (SNTs) with controlled nanotubular structure were synthesized via an electrospinning and calcination process. In this regard, SNTs were found to be ideal adsorbents for Pb(II) removal with a higher adsorption capacity, and surface modification of the SNTs by sym-diphenylcarbazide (SD-SNTs) markedly enhanced the adsorption ability due to the chelating interaction between imino groups and Pb(II). The pH effect, kinetics, isotherms and adsorption mechanism of SNTs and SD-SNTs on Pb(II) adsorption were investigated and discussed detailedly. The adsorption capacity for Pb(II) removal was found to be significantly improved with the decrease of pH value. The Langmuir adsorption model agreed well with the experimental data. As for kinetic study, the adsorption onto SNTs and SD-SNTs could be fitted to pseudo-first-order and pseudo-second-order model, respectively. In addition, the as-prepared SNTs and SD-SNTs also exhibit high adsorption ability for Cd(II) and Co(II). The experimental results demonstrate that the SNTs and SD-SNTs are potential adsorbents and can be used effectively for the treatment of heavy-metal-ions-containing wastewater. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. 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.

  18. Preparation of activated carbon from doum stone and its application on adsorption of 60Co and 152+154Eu: Equilibrium, kinetic and thermodynamic studies.

    Science.gov (United States)

    Hamed, Mostafa M; Ali, M M S; Holiel, M

    2016-11-01

    Removal of radionuclides from wastewater before discharging to environment is necessary for the safety of living beings. Activated carbon prepared from doum stone (DS), an agricultural waste by-product, has been used for the sorption of 60Co and 152+154Eu radionuclides from aqueous solutions. DS has been characterized by different analytical tools. The efficiency of the adsorbent was investigated using batch sorption technique under different experimental conditions. The equilibrium sorption data were analyzed using Freundlich and Langmuir isotherm models. The kinetic experimental data were analyzed using four kinetic models including pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion model to examine the mechanism of sorption and potential rate-controlling step. The maximum capacity of DS was found to be 121 mg/g and 166 mg/g for cobalt and europium, respectively. Sorption efficiency of DS to remove 60Co, 152+154Eu and 134Cs from real radioactive wastewater and environmental (river water and sea water) samples was also investigated. The results revealed that the prepared DS as low cost could be used as a promising material for the simultaneous removal of different radionuclides such as 60Co, 152+154Eu and 134Cs, or trivalent actinides such as 241, 242m,243Am from real radioactive waste and environmental water samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Adsorption of colour, TSS and COD from palm oil mill effluent (POME using acid-washed coconut shell activated carbon: Kinetic and mechanism studies

    Directory of Open Access Journals (Sweden)

    Sia Yong Yin

    2017-01-01

    Full Text Available The disposal of palm oil mill effluent (POME without proper treatment before being discharged into natural water sources has become undesirable because of high concentration of suspended solid (SS, oil and grease (O&G, chemical oxygen demand (COD and biological oxygen demand (BOD. This study investigated the feasibility of removing colour, total suspended solid (TSS and COD using acid-washed coconut shell based activated carbon (CSAC through the evaluation of the adsorption uptake as well as the adsorption kinetics and mechanism. The percentage removal of colour, TSS and COD from POME onto CSAC were 61%, 39%, 66%, respectively achieved within 48 hours of contact time. The kinetic models studied were pseudo-first-order (PFO, pseudo-second-order (PSO, and Elovich models. The intra-particle diffusion (IPD model was studied to interpret the adsorption diffusion mechanism. The adsorption of colour, TSS and COD onto CSAC were best interpreted by the PSO model, and well fitted by the Elovich model. The IPD and Boyd plots indicated that IPD and film diffusion controlled the adsorption of colour, TSS and COD onto the CSAC.

  20. Comparison of three combined sequencing batch reactor followed by enhanced Fenton process for an azo dye degradation: Bio-decolorization kinetics study.

    Science.gov (United States)

    Azizi, A; Alavi Moghaddam, M R; Maknoon, R; Kowsari, E

    2015-12-15

    The purpose of this research was to compare three combined sequencing batch reactor (SBR) - Fenton processes as post-treatment for the treatment of azo dye Acid Red 18 (AR18). Three combined treatment systems (CTS1, CTS2 and CTS3) were operated to investigate the biomass concentration, COD removal, AR18 dye decolorization and kinetics study. The MLSS concentration of CTS2 reached 7200 mg/L due to the use of external feeding in the SBR reactor of CTS2. The COD concentration remained 273 mg/L and 95 mg/L (initial COD=3270 mg/L) at the end of alternating anaerobic-aerobic SBR with external feeding (An-A MSBR) and CTS2, respectively, resulting in almost 65% of Fenton process efficiency. The dye concentration of 500 mg/L was finally reduced to less than 10mg/L in all systems indicating almost complete AR18 decolorization, which was also confirmed by UV-vis analysis. The dye was removed following two successive parts as parts 1 and 2 with pseudo zero-order and pseudo first-order kinetics, respectively, in all CTSs. Higher intermediate metabolites degradation was obtained using HPLC analysis in CTS2. Accordingly, a combined treatment system can be proposed as an appropriate and environmentally-friendly system for the treatment of the azo dye AR18 in wastewater. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Kinetic modeling of liquid-phase adsorption of Congo red dye using guava leaf-based activated carbon

    Science.gov (United States)

    Ojedokun, Adedamola Titi; Bello, Olugbenga Solomon

    2017-07-01

    Guava leaf, a waste material, was treated and activated to prepare adsorbent. The adsorbent was characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infra Red (FTIR) and Energy-Dispersive X-ray (EDX) techniques. The carbonaceous adsorbent prepared from guava leaf had appreciable carbon content (86.84 %). The adsorption of Congo red dye onto guava leaf-based activated carbon (GLAC) was studied in this research. Experimental data were analyzed by four different model equations: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms and it was found to fit Freundlich equation most. Adsorption rate constants were determined using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion model equations. The results clearly showed that the adsorption of CR dye onto GLAC followed pseudo-second-order kinetic model. Intraparticle diffusion was involved in the adsorption process. The mean energy of adsorption calculated from D-R isotherm confirmed the involvement of physical adsorption. Thermodynamic parameters were obtained and it was found that the adsorption of CR dye onto GLAC was an exothermic and spontaneous process at the temperatures under investigation. The maximum adsorption of CR dye by GLAC was found to be 47.62 mg/g. The study shows that GLAC is an effective adsorbent for the adsorption of CR dye from aqueous solution.

  2. Sorption of uranium(VI) using oxime-grafted ordered mesoporous carbon CMK-5

    Energy Technology Data Exchange (ETDEWEB)

    Tian Gan; Geng Junxia; Jin Yongdong; Wang Chunli; Li Shuqiong; Chen Zhen; Wang Hang; Zhao Yongsheng [College of Chemistry, Sichuan University, Chengdu 610064 (China); Li Shoujian, E-mail: sjli000616@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu 610064 (China)

    2011-06-15

    A new sorbent for uranium(VI) has been developed by functionalizing ordered mesoporous carbon CMK-5 with 4-acetophenone oxime via thermally initiated diazotization. The sorption of U(VI) ions onto the functionalized CMK-5 (Oxime-CMK-5) was investigated as a function of sorbent dosage, pH value, contact time, ionic strength and temperature using batch sorption techniques. The results showed that U(VI) sorption onto Oxime-CMK-5 was strongly dependent on pH, but to a lesser extent, on ionic strength. Kinetic studies revealed that the sorption process achieved equilibrium within 30 min and followed a pseudo-first-order rate equation. The isothermal data correlated with the Langmuir model better than the Freundlich model. Thermodynamic data indicated the spontaneous and endothermic nature of the process. Under current experimental conditions, a maximum U(VI) sorption capacity was found to be 65.18 mg/g. Quantitative recovery of uranium was achieved by desorbing the U(VI)-loaded Oxime-CMK-5 with 1.0 mol/L HCl and no significant decrease in U(VI) sorption capability of Oxime-CMK-5 was observed after five consecutive sorption-desorption cycles. The sorption study performed in a simulated nuclear industry effluent demonstrated that the new sorbent showed a desirable selectivity for U(VI) ions over a range of competing metal ions.

  3. Kinetics of heterogeneous reaction of ozone with linoleic acid and its dependence on temperature, physical state, RH, and ozone concentration.

    Science.gov (United States)

    Zeng, Guang; Holladay, Sara; Langlois, Danielle; Zhang, Yunhong; Liu, Yong

    2013-03-07

    Heterogeneous reaction between ozone and linoleic acid (LA) thin film was investigated by a flow reactor coupled to attenuated total reflection infrared spectroscopy (FR-ATR-IR) over wide ranges of temperature, relative humidity (RH), and ozone concentration under atmospheric pressure condition. Pseudo-first-order rate constants kapp and overall reactive uptake coefficients γ were acquired on the basis of changes in absorbance from peaks located near 1743, 1710, 1172, and 1110 cm(-1), which can be assigned to C═O in ester, C═O in acid, and C-C and C-O stretching modes, respectively. Results showed that the kapp and γ increased nearly by a factor of 6 with increasing temperatures from 258 to 314 K. It was noted the temperature effect on the reaction kinetics was much more pronounced at lower temperatures. Such behavior can be explained by a change in the physical state of LA at lower temperatures. In addition, kapp and γ were enhanced by 2-fold as the RH increased from 0 to 80%. Moreover, the effect of ozone concentration on the reaction kinetics was reported for the first time. kapp was found to display a Langmuir-Hinshelwood dependence on ozone concentration with KO3 = (1.146 ± 0.017) × 10(-15) molecules cm(-3) and k[S] = 0.0522 ± 0.0004 s(-1), where KO3 is a parameter that describes the partitioning of ozone to the thin film surface, and k[S] is the maximum pseudo-first-order coefficient at high ozone concentration. Furthermore, yields and hygroscopic properties of reaction products were also investigated by FTIR spectroscopy. The intensity ratio of two C═O stretching bands, A1743/A1710, which was utilized as an indicator of the product yields, increased sharply with increasing temperatures in the lower temperature region (258-284 K), and then remained nearly constant in the higher temperature region (284-314 K). The product yields showed no significant variation with RH, for the intensity ratio of A1743/A1710 barely changed in the wide RH range 0

  4. Phototransformation of iodate by UV irradiation: Kinetics and iodinated trihalomethane formation during subsequent chlor(am)ination

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Fu-Xiang [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Hu, Xiao-Jun, E-mail: hu-xj@mail.tsinghua.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Xu, Bin; Zhang, Tian-Yang; Gao, Yu-Qiong [State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

    2017-03-15

    Highlights: • IO{sub 3}{sup −} can be photodegraded by UV irradiation with pseudo-first order kinetics. • Solution pH has no remarkable influence on the photodegradation rate of IO{sub 3}{sup −}. • The I{sup −} and HOI derived from the photoreduction of IO{sub 3}{sup −} were determined. • The presence of NOM greatly enhanced the photolysis rate of IO{sub 3}{sup −}. • NOM sources can affect the formation of I-THMs in UV-chlor(am)ination of IO{sub 3}{sup −}. - Abstract: The photodegradation of IO{sub 3}{sup −} at 254 nm and the formation of iodinated trihalomethanes (I-THMs) during subsequent chlorination or chloramination in the presence of natural organic matter (NOM) were investigated in this study. The thermodynamically stable IO{sub 3}{sup −} can be degraded by UV irradiation with pseudo-first order kinetics and the quantum yield was calculated as 0.0591 mol einstein{sup −1}. Solution pH posed no remarkable influence on the photolysis rate of IO{sub 3}{sup −}. The UV phototransformation of IO{sub 3}{sup −} was evidenced by the determination of iodide (I{sup −}) and hypoiodous acid (HOI) in solution. NOM sources not only enhanced the photodegradation rate of IO{sub 3}{sup −} by photoejecting solvated electrons, but also greatly influenced the production I-THMs in subsequent chlor(am)ination processes. In UV irradiation and sequential oxidation processes by chlorine or chloramine, the I-THMs formation was susceptible to NOM sources, especially the two major fractions of aqueous humic substances (humic acid and fulvic acid). The toxicity of disinfected waters greatly increased in chloramination over chlorination of the UV photodecomposed IO{sub 3}{sup −}, as far more I-THMs especially CHI{sub 3}, were formed. As “the fourth iodine source” of iodinated disinfection by-products, the occurrence, transportation and fate of IO{sub 3}{sup −} in aquatic environment should be of concern instead of being considered a desired

  5. Kinetics, Reaction Orders, Rate Laws, and Their Relation to Mechanisms: A Hands-On Introduction for High School Students Using Portable Spectrophotometry

    Science.gov (United States)

    Carraher, Jack M.; Curry, Sarah M.; Tessonnier, Jean-Philippe

    2016-01-01

    Teaching complex chemistry concepts such as kinetics using inquiry-based learning techniques can be challenging in a high school classroom setting. Access to expensive laboratory equipment such as spectrometers is typically limited and most reaction kinetics experiments have been designed for advanced placement (AP) or first-year undergraduate…

  6. Adsorption of Lead Ion from Aqueous Solution by Modified Walnut Shell: Kinetics and Thermodynamics.

    Science.gov (United States)

    Li, Shenmaishang; Zeng, Zuoxiang; Xue, Weilan

    2018-01-18

    The novel modified walnut shell (WNS-MAH) with higher adsorption capacity for lead ion (carboxyl value, 2.77 mmol/g) was prepared by reacting walnut shell (WNS) with maleic anhydride. Both WNS and WNS-MAH were analysed by scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The adsorption capacity of WNS-MAH for lead ion was evaluated at different adsorbent doses, pHs, time and temperatures. The adsorption kinetics and adsorption isotherms were investigated in the temperature range of 298-318K. The adsorption kinetics of lead ion onto WNS-MAH were fitted using pseudo-first-order, pseudo-second-order and Elovich model. It was found that pseudo-second-order model gives the best correlation results. The diffusion mechanism was determined according to the intraparticle diffusion equation and Boyd equation. Results suggested the adsorption process was governed by film diffusion. The equilibrium adsorption data of lead ion onto WNS-MAH were fitted with Freundlich model and Langmuir model. The maximum adsorption capacity of WNS-MAH for lead ion removal was 221.24 mg/g at 318 K. The equilibrium adsorption data were analyzed using D-R model, and the feature concentration (Ce') was determined at different temperatures to distinguish chemisorption and physisorption. The thermodynamic parameters (ΔG, ΔH and ΔS) were calculated and revealed the adsorption of lead ion onto WNS-MAH was spontaneous and endothermic. Additionally, the regeneration property was studied and the adsorption process was confirmed by Energy Disperse Spectroscopy (EDS).

  7. Efficient removal of cadmium using magnetic multiwalled carbon nanotube nanoadsorbents: equilibrium, kinetic, and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Pashai Gatabi, Maliheh; Milani Moghaddam, Hossain, E-mail: Milani@umz.ac.ir [University of Mazandaran, Soid State Physics Department (Iran, Islamic Republic of); Ghorbani, Mohsen [Babol Noshirvani University of Technology, Chemical Engineering Department (Iran, Islamic Republic of)

    2016-07-15

    Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pH{sub PZC} determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber–Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir’s adsorption capacity was found to be 78.81 mg g{sup −1} at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.Graphical Abstract.

  8. Enzymatic kinetics of the quinol peroxidase of an aggressive periodontopathic bacterium.

    Science.gov (United States)

    Abe, Tasuku; Kawarai, Taketo; Takahashi, Yukihiro; Konishi, Kiyoshi

    2017-06-01

    Aggregatibacter actinomycetemcomitans is an oral pathogen for aggressive periodontitis, and encodes a triheme c-containing membrane-bound enzyme, quinol peroxidase (QPO) that catalyzes peroxidase activity using quinol in the respiratory chain. In the previous work, we have characterized recombinant QPO purified from the membrane fraction of Escherichia coli harboring a plasmid containing QPO gene. Irreversible inactivation of QPO by high concentration of H2O2 exhibited pseudo-first order kinetics. Analysis of initial-rate kinetics of QPO may suggest that enzyme catalytic mechanism is explained by a Ping Pong Bi Bi system rather than sequential systems. In addition, the redox reactions of cytochrome c in the presence of several values of [Q1H2]/[Q1] were at equilibrium, and only about 2/3 of the cytochrome c of QPO is reduced at high ratios of [Q1H2]/[Q1]. These results indicated that one of the three heme c moieties of QPO is maintained in an oxidized form even at increased ratios of [Q1H2]/[Q1], suggesting that QPO is reduced in the absence of H2O2 and only two of the three heme c moieties are reduced in the presence of high concentration of the Q1H2. Product inhibition of QPO accorded with our theoretical model for the reaction mechanism. Considered together, the enzymatic kinetics data for QPO confirm the Ping Pong Bi Bi system. © The Authors 2017. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

  9. Dissipation kinetics of fluquinconazole and pyrimethanil residues in apples intended for baby food production.

    Science.gov (United States)

    Szpyrka, Ewa; Walorczyk, Stanisław

    2013-12-15

    Dissipation behaviour of simultaneously applied fungicides fluquinconazole and pyrimethanil was studied in/on apples intended for baby food production (cultivars Jonagold Decosta, Golden and Champion). The apples were sprayed at two dosages to control the pathogen Venturia inaedequalis (Cooke) Aderh. A validated gas chromatographic method (GC-ECD and GC-NPD) was used to determine the fungicides residues, the analytical performance of which was highly satisfactory with expanded uncertainties not higher than 15% (coverage factor k=2, confidence level 95%) The dissipation of the fungicide residues was fitted to the experimental data assuming pseudo first-order decay kinetics (R(2) between 0.897 and 0.992). To obtain the fungicide residues below 0.01 mg/kg, which is the default maximum residue level for food intended for infants and young children, the application of the fungicides under study should be carried out 2 or 3 months before harvest at the lower (1.0 L/ha) and the higher (1.5 L/ha) recommended dose, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: a kinetic study.

    Science.gov (United States)

    Akimoto, Ryo; Tokugawa, Takehiro; Yamamoto, Yutaro; Yamataka, Hiroshi

    2012-04-20

    The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N(2) liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a ρ value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions. © 2012 American Chemical Society

  11. Kinetics of the reduction of 4-amino and 4-cyanopyridinechlorocobaloximes by iron(II

    Directory of Open Access Journals (Sweden)

    A. DAYALAN

    2006-12-01

    Full Text Available Cobaloximes such as trans[Co(dmgH2(Py–NH2Cl] and trans-[Co(dmgH2(Py–CNCl], where, dmgH = dimethylglyoximato anion, Py–NH2 =4-aminopyiridne and Py–CN = 4-cyanopyridine, were prepared and characterized by elemental analysis, UV-VIS, IR and NMR spectroscopy. The kinetics of iron(II reduction of the complexes were studied spectrophotometrically at 300 nm in 2 % (v/v DMSO–H2O medium at 27±0.1 °C and I = 0.25 M (LiClO4 at various hydrogen ion concentrations in the range 2.5 x 10-4 to 5.0 × 10-2 M under pseudo-first-order conditions using an excess of the reductant. The inverse dependence of rate on [H+] suggests an equilibrium between the protonated and unportonated forms of the complexes, the protonated form reacting slower than the unprotonated form. Computation of the data enabled the evaluation of the rate constants for the protonated and unprotonated from of the complexes, leading to an evaluation of the protonation constant for the complexes.

  12. Degradation kinetics and mechanism of aniline by heat-assisted persulfate oxidation.

    Science.gov (United States)

    Xie, Xiaofang; Zhang, Yongqing; Huang, Weilin; Huang, Shaobing

    2012-01-01

    Oxidation of aniline by persulfate in aqueous solutions was investigated and the reaction kinetic rates under different temperature, persulfate concentration and pH conditions were examined in batch experiments. The results showed that, the aniline degradation followed pseudo first-order reaction model. Aniline degradation rate increased with increasing temperature or persulfate concentration. In the pH range of 3 to 11, a low aniline degradation rate was obtained at strong acid system (pH 3), while a high degradation rate was achieved at strong alkalinity (pH 11). Maximum aniline degradation occurred at pH 7 when the solution was in a weak level of acid and alkalinity (pH 5, 7 and 9). Produced intermediates during the oxidation process were identified using liquid chromatography-mass spectrometry technology. And nitrobenzene, 4-4'-diaminodiphenyl and 1-hydroxy-1,2-diphenylhydrazine have been identified as the major intermediates of aniline oxidation by persulfate and the degradation mechanism of aniline was also tentatively proposed.

  13. Kinetic and thermodynamic studies of the Co(II) and Ni(II) ions removal from aqueous solutions by Ca-Mg phosphates.

    Science.gov (United States)

    Ivanets, A I; Srivastava, V; Kitikova, N V; Shashkova, I L; Sillanpää, M

    2017-03-01

    The aim of this work was to study the sorption kinetics and thermodynamics of Co(II) and Ni(II) from aqueous solutions by sorbents on the basis of hydrogen (PD-1) and tertiary (PD-2) Ca-Mg phosphates depending on the solution temperature and sorbents chemical composition. Kinetic studies of adsorption of Co(II) and Ni(II) ions onto samples of phosphate sorbents were performed in batch experiment at the temperatures 288, 303, 318 and 333 K. The sorbent dose was fixed at 10 g L-1, initial pH value 2.6, and contact time varied from 5 to 600 min. The kinetics of Co(II) and Ni(II) adsorption were analyzed by using pseudo-first order, pseudo-second order and intraparticle diffusion models. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for the sorption of Co(II) and Ni(II) were determined using the Gibbs-Helmholtz equation. The calculated kinetic parameters and corresponding correlation coefficients revealed that Co(II) and Ni(II) uptake process followed the pseudo-second order rate expression. Thermodynamic studies confirmed the spontaneous and endothermic nature of removal process which indicate that sorption of Co(II) and Ni(II) ions onto both phosphate sorbents is favoured at higher temperatures and has the chemisorptive mechanism. The data thus obtained would be useful for practical application of the low cost and highly effective Ca-Mg phosphate sorbents. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

    Science.gov (United States)

    Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

    2017-03-01

    Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

  15. A new semi-empirical kinetic method for the determination of ion exchange constants for the counterions of cationic micelles.

    Science.gov (United States)

    Khan, M Niyaz

    2010-09-15

    A new method, based upon semi-empirical kinetic approach, for the determination of ion exchange constant for ion exchange processes occurring between counterions at the cationic micellar surface is described in this review article. Basically, the method involves a reaction kinetic probe which gives observed pseudo-first-order rate constants (k(obs)) for a nucleophilic substitution reaction between the nonionic and anionic reactants (R and S) in the presence of a constant concentration of both reactants as well as cationic micelles and varying concentrations of an inert inorganic or organic salt (MX). The observed data (k(obs), versus [MX]) fit satisfactorily (in terms of residual errors) to an empirical equation which could be derived from an equation explaining the mechanism of the reaction of the kinetic probe in terms of pseudophase micellar (PM) model coupled with another empirical equation. This (another) empirical equation explains the effect of [MX] on cationic micellar binding constant (K(S)) of the anionic reactant (say S) and gives an empirical constant, K(X/S). The magnitude of K(X/S) is the measure of the ability of X(-) to expel S(-) from a cationic micellar pseudophase to the bulk aqueous phase through ion exchange X(-)/S(-). The values of K(X/S) and K(Y/S) (where Y(-) is another inert counterion) give the ion exchange constant, K(X)(Y) (=K(X)/K(Y) where K(X) and K(Y) represent cationic micellar binding constants of X(-) and Y(-), respectively). The suitability of this method is demonstrated by the use of three different reaction kinetic probes and various MX. Copyright 2010 Elsevier B.V. All rights reserved.

  16. Kinetic modelling of cytochrome c adsorption on SBA-15.

    Science.gov (United States)

    Yokogawa, Yoshiyuki; Yamauchi, Rie; Saito, Akira; Yamato, Yuta; Toma, Takeshi

    2017-01-01

    The adsorption capacity of mesoporous silicate (MPS) materials as an adsorbent for protein adsorption from the aqueous phase and the mechanism of the adsorption processes by comparative analyses of the applicability of five kinetic transfer models, pseudo-first-order model, pseudo-second-order model, Elovich kinetic model, Bangham's equation model, and intraparticle diffusion model, were investigated. A mixture of tetraethyl orthosilicate (TEOS) and triblock copolymer as a template was stirred, hydrothermally treated to form the mesoporous SBA-15 structure, and heat-treated at 550°C to form the MPS material, SBA-15. The synthesized SBA-15 was immersed in a phosphate buffered saline (PBS) solution containing cytochrome c for 2, 48, and 120 hours at 4°C. The TEM observations of proteins on/in mesoporous SBA-15 revealed the protein behaviors. The holes of the MPS materials were observed to overlap those of the stained proteins for the first 2 hours of immersion. The stained proteins were observed between primary particles and partly inside the mesoporous channels in the MPS material when it had been immersed for 48 hours. For MPS when it had been immersed for 120 hours, stained proteins were observed in almost all meso-scale channels of MPS. The time profiles for adsorption of proteins can be described well by Bangham's equation model and the intraparticle diffusion model. The Bangham's equation model is based on the assumption that pore diffusion was the only rate controlling step during adsorption, whose contribution to the overall mechanism of cytochrome c adsorption on SBA-15 should not be neglected. The kinetic curves obtained from the experiment for cytochrome c adsorption on SBA-15 could show the three steps: the initial rapid increase of the adsorbed amount of cytochrome c, the second gradual increase, and the final equilibrium stage. These three adsorption steps can be interpreted well by the multi-linearity of the intraparticle diffusion model

  17. A novel fourth-order calibration method based on alternating quinquelinear decomposition algorithm for processing high performance liquid chromatography-diode array detection- kinetic-pH data of naptalam hydrolysis.

    Science.gov (United States)

    Qing, Xiang-Dong; Wu, Hai-Long; Zhang, Xi-Hua; Li, Yong; Gu, Hui-Wen; Yu, Ru-Qin

    2015-02-25

    Five-way high performance liquid chromatography-diode array detection (HPLC-DAD)-kinetic-pH data were obtained by recording the kinetic evolution of HPLC-DAD signals of samples at different pH values and a new fourth-order calibration method, alternating quinquelinear decomposition (AQQLD) based on pseudo-fully stretched matrix forms of the quinquelinear model, was developed. Simulated data were analyzed to investigate the performance of AQQLD in comparison with five-way parallel factor analysis (PARAFAC). The tested results demonstrated that AQQLD has the advantage of faster convergence rate and being insensitive to the excess component number adopted in the model. Then, they have been successfully applied to investigate quantitatively the kinetics of naptalam (NAP) hydrolysis in two practical systems. Additionally, the serious chromatographic peak shifts were accurately corrected by means of chromatographic peak alignment method based on abstract subspace difference. The good recoveries of NAP were obtained in these samples by selecting the time region of chromatogram. The elution time, spectral, kinetic time and pH profiles resolved by the chemometric techniques were in good agreement with experimental observations. It demonstrates the potential for the utilization of fourth-order data for some complex systems, opening up a new approach to fourth-order data generation and subsequent fourth-order calibration. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Assessment of adsorption kinetics for removal potential of Crystal Violet dye from aqueous solutions using Moroccan pyrophyllite

    Directory of Open Access Journals (Sweden)

    Youssef Miyah

    2017-06-01

    Full Text Available This study involves the adsorption of Crystal Violet (CV dye adsorbed from solution on the pyrophyllite’s surface. The batch technique was used under a variety of conditions to produce quantitative adsorption, namely amount of adsorbent, dye concentration, contact time, pH solution and temperature. The maximum adsorption capacity of Crystal Violet on pyrophyllite was 9.58 mg/g for 10 mg/L of CV concentration, pH = 6.8 at a temperature 20 °C and 1 g/L of adsorbent. This study of adsorption kinetics was carried out within framework of three models: intraparticle diffusion, pseudo-first order and pseudo-second order. The experimental isotherm data were analyzed using Langmuir and Freundlich models. Different thermodynamic parameters have shown spontaneous reaction with endothermic nature (The estimated value for ΔG was −7.64 kJ/mol at 293 K. Various techniques for characterizing the adsorbent were applied including X-ray diffraction (XRD, X-ray fluorescence spectroscopy (XRF, scanning electron microscopy (SEM and transmission electron microscopy (TEM coupled by energy dispersive X-ray spectroscopy (EDX. In addition, the regenerated adsorbents technique was reused several times; this demonstrated an economical aspect of using pyrophyllite which underlines the re-use importance considering the material capacity to regenerate.

  19. 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.

  20. Equilibrium and kinetic study for the adsorption of p-nitrophenol from wastewater using olive cake based activated carbon

    Directory of Open Access Journals (Sweden)

    N.T. Abdel-Ghani

    2016-01-01

    Full Text Available The present work was carried out to evaluate the removal of p-nitrophenol by adsorption onto olive cake based activated carbon having a BET surface area of 672 m²/g. The batch adsorption experimental results indicated that the equilibrium time for nitrophenol adsorption by olive cake-based activated carbon was 120min. The adsorption data was modeled by equilibrium and kinetic models. The pseudo- first and second order as well as the Elovichkinetic models were applied to fit the experimental data and the intraparticle diffusion model was assessed for describing the mechanism of adsorption. The data were found to be best fitted to the pseudo-second order model with a correlation coefficient (R2=0.986. The intraparticle diffusion mechanism also showed a good fit to the experimental data, showing two distinct linear parts assuming that more than one step could be involved in the adsorption of nitrophenol by the activated carbon. The equilibrium study was performed using three models including Langmuir, Freundlich and Temkin. The results revealed that the Temkin equilibrium model is the best model fitting the experimental data (R2=0.944. The results of the present study proved the efficiency of using olive cake based activated carbon as a novel adsorbent for the removal of nitrophenol from aqueous solution.

  1. Evaluating the potential of a Nigerian soil as an adsorbent for tartrazine dye: Isotherm, kinetic and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    M.O. Dawodu

    2016-12-01

    Full Text Available The release of toxic tartrazine dye from industrial effluent into the environment is of public health concern. This study therefore aimed at the removal of tartrazine from solution using Nigerian soil as a low cost potential sorbent. The sorbent was characterized by the Fourier transform infrared spectrophotometer and Scanning electron microscope. Batch sorption methodology was used to investigate the effect of pH, adsorbent dose, dye concentration, contact time and temperature. The sorbent recorded a Brunauer, Emmett and Teller surface area of 9.8 m2/g and pH point of zero charge of 5.8. Optimum sorption was achieved at pH 2.0, contact time of 120 min, adsorbent dose of 0.05 g and tartrazine concentration of 50 mg/L. Equilibrium isotherms were analyzed by the Langmuir, Freundlich, Scatchard and Flory-Huggins isotherm models. The pseudo-first-order, pseudo-second-order, Elovich and Bangham models were used for kinetic analysis. Thermodynamics revealed a spontaneous, feasible and endothermic sorption process. The soil was found to be suitable as a low cost sorbent for tartrazine from contaminated solution.

  2. Decarboxylation of Δ 9-tetrahydrocannabinol: Kinetics and molecular modeling

    Science.gov (United States)

    Perrotin-Brunel, Helene; Buijs, Wim; van Spronsen, Jaap; van Roosmalen, Maaike J. E.; Peters, Cor J.; Verpoorte, Rob; Witkamp, Geert-Jan

    2011-02-01

    Efficient tetrahydrocannabinol (Δ 9-THC) production from cannabis is important for its medical application and as basis for the development of production routes of other drugs from plants. This work presents one of the steps of Δ 9-THC production from cannabis plant material, the decarboxylation reaction, transforming the Δ 9-THC-acid naturally present in the plant into the psychoactive Δ 9-THC. Results of experiments showed pseudo-first order reaction kinetics, with an activation barrier of 85 kJ mol -1 and a pre-exponential factor of 3.7 × 10 8 s -1. Using molecular modeling, two options were identified for an acid catalyzed β-keto acid type mechanism for the decarboxylation of Δ 9-THC-acid. Each of these mechanisms might play a role, depending on the actual process conditions. Formic acid proved to be a good model for a catalyst of such a reaction. Also, the computational idea of catalysis by water to catalysis by an acid, put forward by Li and Brill, and Churchev and Belbruno was extended, and a new direct keto-enol route was found. A direct keto-enol mechanism catalyzed by formic acid seems to be the best explanation for the observed activation barrier and the pre-exponential factor of the decarboxylation of Δ 9-THC-acid. Evidence for this was found by performing an extraction experiment with Cannabis Flos. It revealed the presence of short chain carboxylic acids supporting this hypothesis. The presented approach is important for the development of a sustainable production of Δ 9-THC from the plant.

  3. Kinetics, mechanistic and thermodynamics of Zn(II) ion sorption: a modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Vishal; Balomajumder, Chandrajit; Agarwal, Vijay Kumar [Department of Chemical Engineering, Indian Institute of Technology, Roorkee (India)

    2012-07-15

    Biosorption potential of Cedrus deodara sawdust (CDS) in terms of sorption of Zn(II) ion across liquid phase has been evaluated in the present investigation. The surface of the CDS biomass before the sorption of Zn(II) ions seemed to be more porous, non-crystalline and heterogeneous. The maximum uptake capacity of CDS was 97.39 mg g{sup -1}. Sorption of Zn(II) ion on the surface of CDS sawdust was maximum at pH 5, temperature 45 C, initial concentration of Zn(II) ion 100 mg L{sup -1}, biomass dose 1 g L{sup -1}, contact time 150 min, and agitation rate 160 rpm. Pseudo second-order kinetics with the highest linear regression coefficient (R{sup 2} = 0.99), and lowest values of error functions, i.e., chi ({chi}{sup 2}) and sum of square errors (SSE) against pseudo first-order rate kinetics showed that the sorption of Zn(II) ion on the surface of CDS was mediated by chemosorptive forces of attraction rather than physical adsorption. Mechanistically, relatively higher proportion of sorption of Zn(II) ion in early phase of contact time was profoundly explained by Bangham's equation and film diffusivity (D{sup f}). Intraparticle or pore diffusion (D{sub p}) of Zn(II) ion inside the pores of CDS was rate limiting step at the later stage of contact time. Furthermore, the thermodynamic study on sorption of metal ion delineated the fact that the Zn(II) sorption on the surface of CDS was spontaneous, endothermic together with increased entropy at solid liquid interface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Kinetics of the Autoreduction of Hexavalent Americium in Aqueous Nitric Acid.

    Science.gov (United States)

    Grimes, Travis S; Horne, Gregory P; Dares, Christopher J; Pimblott, Simon M; Mezyk, Stephen P; Mincher, Bruce J

    2017-07-17

    The rate of reduction of hexavalent 243 Am due to self-radiolysis was measured across a range of total americium and nitric acid concentrations. These so-called autoreduction rates exhibited zero-order kinetics with respect to the concentration of hexavalent americium, and pseudo-first-order kinetics with respect to the total concentration of americium. However, the rate constants did vary with nitric acid concentration, resulting in values of 0.0048 ± 0.0003, 0.0075 ± 0.0005, and 0.0054 ± 0.0003 h -1 for 1.0, 3.0, and 6.5 M HNO 3 , respectively. This indicates that reduction is due to reaction of hexavalent americium with the radiolysis products of total americium decay. The concentration changes of Am(III), Am(V), and Am(VI) were determined by UV-vis spectroscopy. The Am(III) molar extinction coefficients are known; however, the unknown values for the Am(V) and Am(VI) absorbances across the studied range of nitric acid concentrations were determined by sensitivity analysis in which a mass balance with the known total americium concentration was obtained. The new extinction coefficients and reduction rate constants have been tabulated here. Multiscale radiation chemical modeling using a reaction set with both known and optimized rate coefficients was employed to achieve excellent agreement with the experimental results, and indicates that radiolytically produced nitrous acid from nitric acid radiolysis and hydrogen peroxide from water radiolysis are the important reducing agents. Since these species also react with each other, modeling indicated that the highest concentrations of these species available for Am(VI) reduction occurred at 3.0 M HNO 3 . This is in agreement with the empirical finding that the highest rate constant for autoreduction occurred at the intermediate acid concentration.

  5. Defluoridation using biomimetically synthesized nano zirconium chitosan composite: Kinetic and equilibrium studies

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Kumar Suranjit, E-mail: suranjit@gmail.com [Department of Environmental Biotechnology, Ashok and Rita Patel Institute of Integrated Study and Research in Biotechnology and Allied Sciences (ARIBAS), New Vallabh Vidyanagar, Anand, 388121 Gujarat (India); Amin, Yesha, E-mail: yesha_2879@yahoo.co.in [Department of Environmental Biotechnology, Ashok and Rita Patel Institute of Integrated Study and Research in Biotechnology and Allied Sciences (ARIBAS), New Vallabh Vidyanagar, Anand, 388121 Gujarat (India); Selvaraj, Kaliaperumal, E-mail: k.selvaraj@ncl.res.in [Nano and Computational Materials Lab, Catalysis Division, National Chemical Laboratory, Council of Scientific and Industrial Research, Pune 411008 (India)

    2014-07-15

    Highlights: • Colloidal Zr nanoparticles, synthesized using Aloe vera extract were entrapped in chitosan beads. • Zr loaded beads were employed for removal of F{sup −} ion and showed excellent removal efficiency. • Zr and chitosan are cost effective materials hence can be a good adsorbent for removal of fluoride. - Abstract: The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV–vis absorption peak at 420 nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18 nm to 42 nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like -NH, -C=O, -C=N and -C=C were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R{sup 2} value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F{sup −} onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water.

  6. Copper removal by algae Gelidium, agar extraction algal waste and granulated algal waste: kinetics and equilibrium.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2008-03-01

    Biosorption of copper ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). The effects of contact time, pH, ionic strength (IS) and temperature on the biosorption process have been studied. Equilibrium data follow both Langmuir and Langmuir-Freundlich models. The parameters of Langmuir equilibrium model were: q(max)=33.0mgg(-1), K(L)=0.015mgl(-1); q(max)=16.7mgg(-1), K(L)=0.028mgl(-1) and q(max)=10.3mgg(-1), K(L)=0.160mgl(-1) respectively for Gelidium, algal waste and composite material at pH=5.3, T=20 degrees C and IS=0.001M. Increasing the pH, the number of deprotonated active sites increases and so the uptake capacity of copper ions. In the case of high ionic strengths, the contribution of the electrostatic component to the overall binding decreases, and so the uptake capacity. The temperature has little influence on the uptake capacity principally for low equilibrium copper concentrations. Changes in standard enthalpy, Gibbs energy and entropy during biosorption were determined. Kinetic data at different solution pH (3, 4 and 5.3) were fitted to pseudo-first-order and pseudo-second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model, which successfully predicts Cu(II) concentration profiles.

  7. Photocatalytic degradation kinetics and mechanism of environmental pharmaceuticals in aqueous suspension of TiO{sub 2}: A case of {beta}-blockers

    Energy Technology Data Exchange (ETDEWEB)

    Yang Hai [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); An Taicheng, E-mail: antc99@gig.ac.cn [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Li Guiying [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Song Weihua; Cooper, William J. [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175 (United States); Luo Haiying [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Guangzhou Product Quality Supervision and Testing Institute, National Centre for Quality Supervision and Testing of Processed Food (Guangzhou), Guangzhou 510110 (China); Guo Xindong [Guangzhou Product Quality Supervision and Testing Institute, National Centre for Quality Supervision and Testing of Processed Food (Guangzhou), Guangzhou 510110 (China)

    2010-07-15

    This study investigated the photocatalytic degradation of three {beta}-blockers in TiO{sub 2} suspensions. The disappearance of the compounds followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model and the rate constants were 0.075, 0.072 and 0.182 min{sup -1} for atenolol, metoprolol and propranolol, respectively. After 240 min irradiation, the reaction intermediates were completely mineralized to CO{sub 2} and the nitrogen was predominantly as NH{sub 4}{sup +}. The influence of initial pH and {beta}-blocker concentration on the kinetics was also studied. From adsorption studies it appears that the photocatalytic degradation occurred mainly on the surface of TiO{sub 2}. Further studies indicated that surface reaction with {center_dot}OH radical was principally responsible for the degradation of these three {beta}-blockers. The major degradation intermediates were identified by HPLC/MS analysis. Cleavage of the side chain and the addition of the hydroxyl group to the parent compounds were found to be the two main degradation pathways for all three {beta}-blockers.

  8. Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO2 Thin Films with Porphyrin Dyes for DSSC Applications

    Directory of Open Access Journals (Sweden)

    Rita Giovannetti

    2014-01-01

    Full Text Available Free base, Cu(II and Zn(II complexes of the 2,7,12,17-tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (CPI in solution and bounded to transparent monolayer TiO2 nanoparticle films were studied to determine their adsorption on TiO2 surface, to measure the adsorption kinetics and isotherms, and to use the results obtained to optimize the preparation of DSSC photovoltaic cells. Adsorption studies were carried out on monolayer transparent TiO2 films of a known thickness. Langmuir and Frendlich adsorption constants of CPI-dyes on TiO2 monolayer surface have been calculated as a function of the equilibrium concentrations in the solutions. The amount of these adsorbed dyes showed the accordance with Langmuir isotherm. Kinetic data on the adsorption of dyes showed significantly better fits to pseudo-first-order model and the evaluated rate constants linearly increased with the grow of initial dye concentrations. The stoichiometry of the adsorption of CPI-dyes into TiO2 and the influence of presence of coadsorbent (chenodeoxycholic acid have been established. The DSSC obtained in the similar conditions showed that the best efficiency can be obtained in the absence of coadsorbent with short and established immersion times.

  9. The kinetic study of the inhibition of human cholinesterases by demeton-S-methyl shows that cholinesterase-based titration methods are not suitable for this organophosphate.

    Science.gov (United States)

    Bazire, Alexandre; Gillon, Emilie; Lockridge, Oksana; Vallet, Virginie; Nachon, Florian

    2011-04-01

    The organophosphorus insecticide, demeton-S-methyl (DSM), is considered as a good surrogate of the highly toxic nerve agent VX for skin absorption studies due to similar physico-chemical properties and in vitro percutaneous penetration profile. But, when skin distribution was estimated by measuring inhibition of cholinesterase activity, the results were poorly reproducible. The various grades of commercial DSM solutions were suspected to be the origin of the discrepancies. This hypothesis was tested by measuring inhibition of human acetyl- and butyrylcholinesterase by two commercial DSM solutions. The inhibition rate was independent on the enzyme concentration confirming pseudo-first order conditions. But complete inhibition of butyrylcholinesterase activity was achieved only when the DSM concentration was at least 1500-fold higher than the enzyme concentration. Besides, complete inhibition of acetylcholinesterase was never achieved. Mass spectrometry analysis of the inhibited butyrylcholinesterase adducts identified monomethoxyphosphorylated-serine, the aged product of inhibition by DSM or a derivative with a modified leaving group. Neither spontaneous reactivation nor aging of the dimethoxyphosphorylated-serine could account for the inhibition kinetics observed, suggesting an overly complicated kinetic scheme not compatible with the requirement of a titration experiment. In conclusion, cholinesterase-based analytical methods should be avoided for DSM titration in skin penetration studies. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. The effect of microwave pretreatment of seeds on the stability and degradation kinetics of phenolic compounds in rapeseed oil during long-term storage.

    Science.gov (United States)

    Rękas, Agnieszka; Ścibisz, Iwona; Siger, Aleksander; Wroniak, Małgorzata

    2017-05-01

    Storage stability and degradation kinetics of phenolic compounds in rapeseed oil pressed from microwave treated seeds (0, 2, 4, 6, 8, 10min, 800W) during long-term storage (12months) at a temperature of 20°C was discussed in the current study. The dominant phenolic compound detected in rapeseed oil was canolol, followed by minor amounts of free phenolic acids and sinapine. The most pronounced effect of seeds microwaving was noted for canolol formation - after 10-min exposure the quantity of this compound was approximately 63-fold higher than in control oil. The degradation of phenolics during storage displayed pseudo first-order kinetics. Differences in the initial degradation rate (r0) demonstrated significant impact of the period of seeds microwave exposure on the degradation rates of phenolic compounds. Results of the half-life calculation (t1/2) showed that the storage stability of phenolic compounds was higher in oils produced from microwave treated rapeseeds than in control oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Adsorption kinetics, isotherm, and thermodynamics studies of acetyl-11-keto-β-boswellic acids (AKBA) from Boswellia serrata extract using macroporous resin.

    Science.gov (United States)

    Niphadkar, Sonali S; Rathod, Virendra K

    2017-09-14

    An acetyl-11-keto-β-boswellic acid (AKBA) is potent anti-inflammatory agent found in Boswellia serrata oleogum resin. Adsorption characteristics of AKBA from B. serrata were studied using macroporous adsorbent resin to understand separation and adsorption mechanism of targeted molecules. Different macroporous resins were screened for adsorption and desorption of AKBA and Indion 830 was screened as it showed higher adsorption capacity. The kinetic equations were studied and results showed that the adsorption of AKBA on Indion 830 was well fitted to the pseudo first-order kinetic model. The influence of two parameters such as temperature (298, 303, and 308 K) and pH (5-8) on the adsorption process was also studied. The experimental data was further investigated using Langmuir, Freundlich, and Temkin isotherm models. It was observed that Langmuir isotherm model was found to be the best fit for AKBA adsorption by Indion 830 and highest adsorption capacity (50.34 mg/g) was obtained at temperature of 303 K. The values of thermodynamic parameters such as the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), indicated that the process of adsorption was spontaneous, favourable, and exothermic.

  12. Advanced oxidation kinetics and mechanism of preservative propylparaben degradation in aqueous suspension of TiO2 and risk assessment of its degradation products.

    Science.gov (United States)

    Fang, Hansun; Gao, Yanpeng; Li, Guiying; An, Jibin; Wong, Po-Keung; Fu, Haiying; Yao, Side; Nie, Xiangping; An, Taicheng

    2013-03-19

    The absolute kinetic rate constants of propylparaben (PPB) in water with different free radicals were investigated, and it was found that both hydroxyl radicals (HO(•)) and hydrated electrons could rapidly react with PPB. The advanced oxidation kinetics and mechanisms of PPB were investigated using photocatalytic process as a model technology, and the degradation was found to be a pseudo-first-order model. Oxidative species, particularly HO(•), were the most important reactive oxygen species mediating photocatalytic degradation of PPB, and PPB degradation was found to be significantly affected by pH because it was controlled by the radical reaction mechanism and was postulated to occur primarily via HO(•)-addition or H-abstraction reactions on the basis of pulse radiolysis measurements and observed reaction products. To investigate potential risk of PPB to humans and aqueous organisms, the estrogenic assays and bioassays were performed using 100 μM PPB solution degraded by photocatalysis at specific intervals. The estrogenic activity decreased as PPB was degraded, while the acute toxicity at three trophic levels first increased slowly and then decreased rapidly as the total organic carbon decreased during photocatalytic degradation.

  13. [Effects of particle size of zero-valent iron on the reactivity of activating persulfate and kinetics for the degradation of acid orange 7].

    Science.gov (United States)

    Li, Huan-xuan; Wan, Jin-quan; Ma, Yong-wen; Huang, Ming-zhiz; Wang, Yan; Chen Yang, Mei

    2014-09-01

    This research described the heterogeneous reactions of persulfate with different particle sizes of zero-valent iron (including 1 mm-ZVI,150 μm-ZVI,50 nm-ZVI) for degradation of acid orange 7(AO7) , and studied the kinetics and intermediate products of AO7 under these systems. The results demonstrated that these three types of ZVI were efficient in promoting the degradation of AO7, the degradation efficiencies of AO7 were 43% , 97% , and 100% within 90 min respectively, in the 1 mm-ZVI,150 μm-ZVI and 50 nm- ZVI systems, respectively. With the results of kinetic fitting models, the pseudo first-order kinetics exhibited better fitting results in the 1 mm-ZVI,150 μm-ZVI systems, while the second-order kinetics exhibited better fitting results in the 50 nm-ZVI system. And the different ZVI types exhibited difference on the AO7 degradation rate constant, which ranged as 50 nm-ZVI > 150 μm-ZVI > 1 mm-ZVI. The iron corrosion products coating on the ZVI after reaction were composed of α-Fe2 O3 and some Fe3O4 in the 1 mm-ZVI system while that consisted of Fe3O4 and α-Fe2O3, FeOOH respectively, in thel50 μm-ZVI and 50 nm-ZVI systems,. Which were identified by scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and Raman spectroscopy. Some intermediate products, including 2-naphthalenol, 2-methylphenol, 4-ethyl- 3-methyl-phenol, isoindole- 1,3-dione and phthalic acid et al. were identified by GC/MS measurement. Both UV-vis absorbance spectra and GC/MS determination indicated that there was difference in degradation paths of AO7 between the three systems.

  14. Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: A kinetic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Caliskan, Necla, E-mail: ncaliskan7@hotmail.com [Department of Physical Chemistry, Faculty of Science, Yuezuencue Yil University, Van 65080 (Turkey); Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan [Department of Physical Chemistry, Faculty of Science, Yuezuencue Yil University, Van 65080 (Turkey)

    2011-10-15

    Highlights: {center_dot}The removal of Zn(II) ions from aqueous solution was studied using natural and MnO{sub 2} modified diatomite samples at different temperatures. {center_dot} The sorption of Zn(II) on the natural and modified diatomite was an endothermic processes, controlled by physical mechanisms and spontaneously. {center_dot} Adsorption of zinc metal ion on diatomite samples is more or less a two step process. {center_dot} Adsorption of Zn(II) on natural and modified diatomite could be explained by the mechanism of pseudo-second-order. - Abstract: The removal of Zn(II) ions from aqueous solution was studied using natural and MnO{sub 2} modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol{sup -1}, indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy ({Delta}H{sup 0}), Gibbs' free energy ({Delta}G{sup 0}) and entropy ({Delta}S{sup 0}) were calculated for natural and MnO{sub 2} modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously.

  15. Influence of soil copper content on the kinetics of thiram adsorption and on thiram leachability from soils.

    Science.gov (United States)

    Filipe, Olga M S; Costa, Carina A E; Vidal, Maria M; Santos, Eduarda B H

    2013-01-01

    This work aimed to assess the influence of soil copper content on the sorption processes of thiram, a fungicide widely used in agriculture, most of the times together with copper. Two different types of studies were performed: (1) desorption studies of thiram with acetonitrile after batch adsorption equilibration, and ageing of the wet soil for a variable period of time; (2) kinetic studies of thiram adsorption performed using the soil in its original form and after fortification with copper ions. In the desorption studies, with the increase of the ageing time, a decrease of the thiram peak and a simultaneous increase of a new peak, assigned to a copper complex, were observed in the chromatograms. This new peak increases sharply until an ageing period of about 4d and then this area is maintained approximately constant until 18 d, the maximum ageing period studied. These results indicate that thiram reacts with copper ions along time giving rise to the formation of relatively persistent copper complexes in soil. Desorption studies with CaCl(2) 0.01 M solution showed that this complex is not extracted. Thus, it is not easily leached to ground and surface waters and copper may contribute to thiram immobilization in soil. The kinetic studies of thiram adsorption were performed in both soils and for two initial thiram concentrations (~7 and 20 mg L(-1)). For the soil fortified with copper the percentage of adsorbed thiram is higher than observed for the original soil at the same initial concentrations and equilibration times and 100% of adsorption is attained in 15 h or 48 h, depending on the thiram initial concentration. Four kinetic equations, the pseudo first- and second-order equations, the Elovich and the intraparticle diffusion equations were selected to fit the kinetic data of the adsorption process of thiram onto both original and fortified soil. The best model to describe the kinetics of thiram adsorption onto the original soil is the intraparticle diffusion

  16. 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

    Wastewater treatment is the subject of several studies through decades. Interest is continuously oriented to provide cheaper and efficient methods of treatment. Several methods of treatment exit including coagulation flocculation, filtration, precipitation, ozonation, ion exchange, reverse osmosis, advanced oxidation process. The use of these methods proved limited because of their high investment and operational cost. Adsorption can be an efficient low-cost process to remove pollutants from wastewater. This method of treatment calls for an solid adsorbent which constitutes the purification tool. Agricultural wastes have been widely exploited in this case .As we know the agricultural wastes are an important source of water pollution once discharged into the aquatic environment (river, sea ...). The valorization of such wastes and their use allows the prevention of this problem with an economic and environment benefits. In this context our study aimed testing the wastewater treatment capacity by adsorption onto holocellulose resulting from the valorization of an agriculture waste. In this study, methylene blue (MB) and methyl orange (MO) are selected as models pollutants for evaluating the holocellulose adsorbent capacity. The kinetics of adsorption is performed using UV-visible spectroscopy. In order to study the effect of the main parameters for the adsorption process and their mutual interaction, a full factorial design (type nk) has been used.23 full factorial design analysis was performed to screen the parameters affecting dye removal efficiency. Using the experimental results, a linear mathematical model representing the influence of the different parameters and their interactions was obtained. The parametric study showed that efficiency of the adsorption system (Dyes/ Holocellulose) is mainly linked to pH variation. The best yields were observed for MB at pH=10 and for MO at pH=2.The kinetic data was analyzed using different models , namely , the pseudo-first

  17. Cauliflower Leave, an Agricultural Waste Biomass Adsorbent, and Its Application for the Removal of MB Dye from Aqueous Solution: Equilibrium, Kinetics, and Thermodynamic Studies

    Science.gov (United States)

    Ansari, Seraj Anwar; Khan, Fauzia

    2016-01-01

    Cauliflower leaf powder (CLP), a biosorbent prepared from seasonal agricultural crop waste material, has been employed as a prospective adsorbent for the removal of a basic dye, methylene blue (MB) from aqueous solution by the batch adsorption method under varying conditions, namely, initial dye concentration, adsorbent dose, solution pH, and temperature. Characterization of the material by FTIR and SEM indicates the presence of functional groups and rough coarse surface suitable for the adsorption of methylene blue over it. Efforts were made to fit the isotherm data using Langmuir, Freundlich, and Temkin equation. The experimental data were best described by Freundlich isotherm model, with an adsorption capacity of 149.22 mg/g at room temperature. To evaluate the rate of methylene blue adsorption onto CLP, pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were employed. The experimental data were best described by the pseudo-second-order kinetic model. Evaluation of thermodynamic parameters such as changes in enthalpy, entropy, and Gibbs' free energy showed the feasible, spontaneous, and exothermic nature of the adsorption process. On the basis of experimental results obtained, it may be concluded that the CLP prepared from agricultural waste has considerable potential as low-cost adsorbent in wastewater treatment for the removal of basic dye, MB. PMID:27974892

  18. Synthesis and Properties of Fe3O4-Activated Carbon Magnetic Nanoparticles for Removal of Aniline from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies

    Directory of Open Access Journals (Sweden)

    Babak Kakavandi

    2013-02-01

    Full Text Available In this study, powder activated carbon (PAC and magnetic nanoparticles of iron (III oxide were used for synthesis of Fe3O4-activated carbon magnetic nanoparticles (AC-Fe3O4 MNPs as an adsorbent for the removal of aniline. The characteristics of adsorbent were evaluated by SEM, TEM, XRD and BET. Also, the impact of different parameters such as pH, contact time, adsorbent dosage, aniline initials concentration and solution temperature were studied. The experimental data investigated by Langmuir and Freundlich adsorption isotherms and two models kinetically of pseudo first-order and pseudo second-order. The results indicated that the adsorption followed Langmuir and pseudo second-order models with correlation r2 > 0.98 and r2 > 0.99, respectively. The equilibrium time was obtained after 5 h. According to Langmuir model, the maximum adsorption capacity was 90.91 mg/g at pH = 6, and 20°C. The thermodynamic parameters indicated that adsorption of aniline on magnetic activated carbon was exothermic and spontaneous. This synthesized AC-Fe3O4 MNPs due to have advantages such as easy and rapid separation from solution could be applied as an adsorbent effective for removal of pollutants such as aniline from water and wastewater

  19. Batch sorption dynamics, kinetics and equilibrium studies of Cr(VI), Ni(II) and Cu(II) from aqueous phase using agricultural residues

    Science.gov (United States)

    Kaur, Rajvinder; Singh, Joginder; Khare, Rajshree; Cameotra, Swaranjit Singh; Ali, Amjad

    2013-03-01

    In the present study, the agricultural residues viz., Syzygium cumini and Populus deltoides leaves powder have been used for the biosorption of Cu(II), Ni(II), and Cr(VI) from aqueous solutions. FTIR and SEM analysis of the biosorbents were performed to explore the type of functional groups available for metal binding and to study the surface morphology. Various physico-chemical parameters such as pH, adsorbent dosage, initial metal ion concentration, and equilibrium contact time were studied. Thermodynamic studies were carried out and the results demonstrated the spontaneous and endothermic nature of the biosorption process. The equilibrium data were tested using four isotherm models—Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the maximum biosorption capacities were evaluated. The Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were applied to study the reaction kinetics with pseudo-second order model giving the best fit ( R 2 = 0.99) to the experimental data.

  20. UV and solar photo-degradation of naproxen: TiO{sub 2} catalyst effect, reaction kinetics, products identification and toxicity assessment

    Energy Technology Data Exchange (ETDEWEB)

    Jallouli, Nabil [University of Sfax, Laboratory of Water, Energy and Environment, National School of Engineers of Sfax (ENIS), Route de Soukra Km 3.5, PO Box 1173, 3038 Sfax (Tunisia); Elghniji, Kais [University of Gafsa, Research Unit of Materials, Environment and Energy, Campus Universitaire Sidi Ahmed Zarroug, 2112 Gafsa (Tunisia); Hentati, Olfa [University of Sfax, Laboratory of Water, Energy and Environment, National School of Engineers of Sfax (ENIS), Route de Soukra Km 3.5, PO Box 1173, 3038 Sfax (Tunisia); Higher Institute of Biotechnology of Sfax (ISBS), Route de Soukra Km 3, 5 PO Box 1175, 3038 Sfax (Tunisia); Ribeiro, Ana R.; Silva, Adrián M.T. [LCM – Laboratory of Catalysis and Materials – Associate Laboratory LSRE-LCM, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Ksibi, Mohamed, E-mail: mohamed.ksibi@isbs.rnu.tn [University of Sfax, Laboratory of Water, Energy and Environment, National School of Engineers of Sfax (ENIS), Route de Soukra Km 3.5, PO Box 1173, 3038 Sfax (Tunisia); Higher Institute of Biotechnology of Sfax (ISBS), Route de Soukra Km 3, 5 PO Box 1175, 3038 Sfax (Tunisia)

    2016-03-05

    Highlights: • Degradation kinetics and mineralization rate of naproxen (NPX) were studied. • Direct photolysis and TiO{sub 2}/UV approaches were evaluated. • The formation of by-products was followed by UHPLC-DAD-MS. • Ecological risk assessment of NPX-treated solutions was assessed using E. andrei. - Abstract: Direct photolysis and TiO{sub 2}-photocatalytic degradation of naproxen (NPX) in aqueous solution were studied using a UV lamp and solar irradiation. The degradation of NPX was found to be in accordance with pseudo-first order kinetics, the photocatalytic process being more efficient than photolysis. The NPX removal by photolysis (pH{sub initial} 6.5) was 83% after 3 h, with 11% of chemical oxygen demand (COD) reduction, whereas the TiO{sub 2}-UV process led to higher removals of both NPX (98%) and COD (25%). The apparent pseudo-first-order rate constant (k{sub app}) for NPX degradation by photolysis ranged from 0.0050 min{sup −1} at pH 3.5 to 0.0095 min{sup −1} at pH 6.5, while it was estimated to be 0.0063 min{sup −1} under acidic conditions in photocatalysis, increasing by 4-fold at pH 6.5. Ultra High Performance Liquid chromatography (UHPLC) coupled with a triple quadrupole detector and also a hybrid mass spectrometer which combines the linear ion trap triple quadrupole (LTQ) and OrbiTrap mass analyser, were used to identify NPX degradation products. The main intermediates detected were 1-(6-methoxynaphtalene-2-yl) ethylhydroperoxide, 2-ethyl-6-methoxynaphthalene, 1-(6-methoxynaphtalen-2-yl) ethanol, 1-(6-methoxynaphtalen-2-yl) ethanone and malic acid. Solar photocatalysis of NPX showed COD removals of 33% and 65% after 3 and 4 h of treatment, respectively, and some reduction of acute toxicity, evaluated by the exposure of Eisenia andrei to OECD soils spiked with NPX-treated solutions.

  1. Peroxone mineralization of chemical oxygen demand for direct potable water reuse: Kinetics and process control.

    Science.gov (United States)

    Wu, Tingting; Englehardt, James D

    2015-04-15

    Mineralization of organics in secondary effluent by the peroxone process was studied at a direct potable water reuse research treatment system serving an occupied four-bedroom, four bath university residence hall apartment. Organic concentrations were measured as chemical oxygen demand (COD) and kinetic runs were monitored at varying O3/H2O2 dosages and ratios. COD degradation could be accurately described as the parallel pseudo-1st order decay of rapidly and slowly-oxidizable fractions, and effluent COD was reduced to below the detection limit (<0.7 mg/L). At dosages ≥4.6 mg L(-1) h(-1), an O3/H2O2 mass ratio of 3.4-3.8, and initial COD <20 mg/L, a simple first order decay was indicated for both single-passed treated wastewater and recycled mineral water, and a relationship is proposed and demonstrated to estimate the pseudo-first order rate constant for design purposes. At this O3/H2O2 mass ratio, ORP and dissolved ozone were found to be useful process control indicators for monitoring COD mineralization in secondary effluent. Moreover, an average second order rate constant for OH oxidation of secondary effluent organics (measured as MCOD) was found to be 1.24 × 10(7) ± 0.64 × 10(7) M(-1) S(-1). The electric energy demand of the peroxone process is estimated at 1.73-2.49 kW h electric energy for removal of one log COD in 1 m(3) secondary effluent, comparable to the energy required for desalination of medium strength seawater. Advantages/disadvantages of the two processes for municipal wastewater reuse are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Kinetic and isotherm studies for nickel (II) removal using novel mesoparticle graphene sand composite synthesised from sand and arenga palm sugar

    Science.gov (United States)

    Zularisam, A. W.; Wahida, Norul

    2017-07-01

    Nickel (II) is one of the most toxic contaminants recognised as a carcinogenic and mutagenic agent which needs complete removal from wastewater before disposal. In the present study, a novel adsorbent called mesoparticle graphene sand composite (MGSCaps) was synthesised from arenga palm sugar and sand by using a green, simple, low cost and efficient methodology. Subsequently, this composite was characterised and identified using field emission scanning electron microscope (FESEM), x-ray diffraction (XRD) and elemental mapping (EM). The adsorption process was investigated and optimised under the experimental parameters such as pH, contact time and bed depth. The results showed that the interaction between nickel (II) and MGSCaps was not ion to ion interaction hence removal of Ni (II) can be applied at any pH. The results were also exhibited the higher contact time and bed depth, the higher removal percentage of nickel (II) occurred. Adsorption kinetic data were modelled using Pseudo-first-order and Pseudo-second-order equation models. The experimental results indicated pseudo-second-order kinetic equation was most suitable to describe the experimental adsorption kinetics data with maximum capacity of 40% nickel (II) removal for the first hour. The equilibrium adsorption data was fitted with Langmuir, and Freundlich isotherms equations. The data suggested that the most fitted equation model is the Freundlich with correlation R2=0.9974. Based on the obtained results, it can be stated that the adsorption method using MGSCaps is an efficient, facile and reliable method for the removal of nickel (II) from waste water.

  3. Removal of P-chloro Phenol from Aqueous Solutions Using Chestnut Shell Modified by Sulfuric Acid: Study of Adsorption Kinetic and Isotherm

    Directory of Open Access Journals (Sweden)

    Hatam Godini

    2015-06-01

    Full Text Available Background: Present of p-chloro phenol in the environment due to high toxicity, mutagenic and carcinogenic effects, powerful odor production and stability in the environment caused to be categorized as priority pollutants. The aim of this study was to investigate the removal of p-chloro phenol from aqueous solution using chestnut shell modified by sulfuric acid. Methods: This study was an experimental study and chestnut shell (Quercus brantii Var. persica was used as an adsorbent. The effects of pH, contact time, adsorbent dosage, and initial concentration on the adsorption process were evaluated, in a batch scale. The characterizations of the raw and modified adsorbent were investigated by Fourier transform infrared (FTIR spectroscopy, scanning electron microscopy (SEM and X-ray diffractometer (XRD. Langmuir and Fruindlich isotherm models and pseudo-first order kinetic, pseudo-second order kinetic were evaluated by experimental data. Results: The results showed that the removal efficiency of p-chloro phenol increased with increasing of the contact time and adsorbent dosage, and had a reverse effect with increasing of pH and p-chloro phenol initial concentration. The maximum adsorption capacity of p-chloro phenol by modified chestnut shell adsorbent was achieved of 3.33 mg/g and the maximum removal efficiency of p-chloro phenol was 87 percent at pH=4. The experimental data were well descripted by Freundlich isotherm (R2>0.92 and pseudo-second order kinetic (R2>0.94. Conclusion: This study showed that the chestnut shell could be effectively used at removal of p-chloro phenol from aqueous solutions. As the chestnut shell is a waste, so it can be applied as an adsorbent for removal of pollutants such as p-chloro phenol.

  4. The adsorption and Fenton behavior of iron rich Terra Rosa soil for removal of aqueous anthraquinone dye solutions: kinetic and thermodynamic studies.

    Science.gov (United States)

    Aktas, Doga; Dizge, Nadir; Cengiz Yatmaz, H; Caliskan, Yasemin; Ozay, Yasin; Caputcu, Ayten

    2017-12-01

    Adsorption and advanced oxidation processes are being extensively used for treatment of wastewater containing dye chemicals. In this study, the adsorption and Fenton behavior of iron rich Terra Rosa soil was investigated for the treatment of aqueous anthraquinone dye (Reactive Blue 19 (RB19)) solutions. The impact of pH, initial dye concentration, soil loading rate, contact time and temperature was systematically investigated for adsorption process. A maximum removal efficiency of dye (86.6%) was obtained at pH 2, soil loading of 10 g/L, initial dye concentration of 25 mg/L, and contact time of 120 min. Pseudo-first-order, pseudo-second-order, Elovich, and Weber-Morris kinetic models were applied to describe the adsorption mechanism and sorption kinetic followed a pseudo-second-order kinetic model. Moreover, Langmuir, Freundlich and Temkin isotherm models were used to investigate the isothermal mechanism and equilibrium data were well represented by the Langmuir equation. The maximum adsorption capacity of soil was found as 4.11 mg/g using Langmuir adsorption isotherm. The effect of soil loading and hydrogen peroxide (H2O2) dosage was solely tested for Fenton oxidation process. The highest removal efficiency of dye (89.4%) was obtained at pH 2, H2O2 dosage of 10 mM, soil loading of 5 g/L, initial dye concentration of 50 mg/L, and contact time of 60 min. Thermodynamic studies showed that when the adsorption dosage of dye was 25 mg/L at 293-313 K, adsorption enthalpy (ΔH) and entropy (ΔS) were negative and adsorption free energy (ΔG) was positive. This result indicated that the adsorption was exothermic. Morphological characteristics of the soil were evaluated by X-ray fluorescence (XRF), scanning electron microscopy (SEM), and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy before and after the adsorption and oxidation process.

  5. Valorization of two waste streams into activated carbon and studying its adsorption kinetics, equilibrium isotherms and thermodynamics for methylene blue removal

    Directory of Open Access Journals (Sweden)

    Zeid Abdullah AlOthman

    2014-12-01

    Full Text Available Wastes must be managed properly to avoid negative impacts that may result. Open burning of waste causes air pollution which is particularly hazardous. Flies, mosquitoes and rats are major problems in poorly managed surroundings. Uncollected wastes often cause unsanitary conditions and hinder the efforts to keep streets and open spaces in a clean and attractive condition. During final disposal methane is generated, it is much more effective than carbon dioxide as a greenhouse gas, leading to climate change. Therefore, this study describes the possible valorization of two waste streams into activated carbon (AC with added value due to copyrolysis. High efficiency activated carbon was prepared by the copyrolysis of palm stem waste and lubricating oil waste. The effects of the lubricating oil waste to palm stem ratio and the carbonization temperature on the yield and adsorption capacity of the activated carbon were investigated. The results indicated that the carbon yield depended strongly on both the carbonization temperature and the lubricating oil to palm stem ratio. The efficiency of the adsorption of methylene blue (MB onto the prepared carbons increased when the lubricating oil to palm stem ratio increased due to synergistic effect. The effects of pH, contact time, and the initial adsorbate concentration on the adsorption of methylene blue were investigated. The maximum adsorption capacity (128.89 mg/g of MB occurred at pH 8.0. The MB adsorption kinetics were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The results indicated that the adsorption of MB onto activated carbon is best described using a second order kinetic model. Adsorption data are well fitted with Langmuir and Freundlich isotherms. The thermodynamic parameters; ΔG°, ΔH° and ΔS° indicate that the adsorption is spontaneous and endothermic.

  6. Extraction and optimization of chitosan from shrimp shell: preparation, characterization and application in fluoride removal (isotherm, kinetic and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    Ali Azari

    2016-09-01

    Full Text Available Background: Fluoride in low concentrations is useful for human health. However, high concentrations of this substance is associated with problems such as fluorosis and Alzheimer's. Adsorption is efficient technique in removal of this pollutant. The aim of this study was to extraction and optimization of Chitosan as a natural biosorbent in fluoride removal. Materials and Methods: In present study, magnetized chitosan-iron oxide nano particles was prepared by co-precipitation method and its characteristics were determined by SEM, XRD, TEM and FTIR analyzes. Subsequently, the effect of magnetized chitosan was assessed as an adsorbent in fluoride removal from water solution in the batch system with considering various parameters included pH, contact time, adsorbent dosage, initial Fluoride concentration and solution temperature. The Langmuir and Freundlich isotherm models and pseudo first-order and pseudo second-order kinetics were used to examine experimental data. Results: The results showed that the Fluoride adsorption have followed Langmuir (R2>0.982 and kinetic model of pseudo second-order (R2>0.931. The maximum adsorption capacity of Fluoride was 22.756 mg/g at optimized condition, pH 50 adsorbent dose of 1g/L at 500C. Investigation of thermodynamically parameters and positive value of ΔH0 indicatethat this process was endothermic. Conclusion: Generally, we can report that t he magnetic chitosan was used as a useful sorbent for the removal of pollutants from water and wastewater due to advantages such as easy and rapid separation from solution and high removal efficiency.

  7. Improved adsorption performance of nanostructured composite by ultrasonic wave: Optimization through response surface methodology, isotherm and kinetic studies.

    Science.gov (United States)

    Dastkhoon, Mehdi; Ghaedi, Mehrorang; Asfaram, Arash; Goudarzi, Alireza; Mohammadi, Seyyedeh Maryam; Wang, Shaobin

    2017-07-01

    In this work, ultrasound-assisted adsorption of an anionic dye, sunset yellow (SY) and cationic dyes, malachite green (MG), methylene blue (MB) and their ternary dye solutions onto Cu@ Mn-ZnS-NPs-AC from water aqueous was optimized by response surface methodology (RSM) using the central composite design (CCD). The adsorbent was characterized using Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and EDX mapping images. The effects of various parameters such as pH, sonication time, adsorbent mass and initial concentrations of SY, MG and MB were examined. A total 33 experiments were conducted to establish a quadratic model. Cu@ Mn-ZnS-NPs-AC has the maximum adsorption efficiency (>99.5%) when the pH, sonication time, adsorbent mass and initial concentrations of SY, MG and MB were optimally set as 6.0, 5min, 0.02g, 9, 12 and 12mgL-1, respectively. Sonication time has a statistically significant effect on the selected responses. Langmuir isotherm model was found to be best fitted to adsorption and adsorption capacities were 67.5mgg-1 for SY, 74.6mgg-1 for MG and 72.9mgg-1 for MB. Four kinetic models (pseudo-first order, pseudo-second order, Weber-Morris intraparticle diffusion rate and Elovich) were tested to correlate the experimental data and the sorption was fitted well with the pseudo-second order kinetic model. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Adsorption of methyl orange from aqueous solution by aminated pumpkin seed powder: Kinetics, isotherms, and thermodynamic studies.

    Science.gov (United States)

    Subbaiah, Munagapati Venkata; Kim, Dong-Su

    2016-06-01

    Present research discussed the utilization of aminated pumpkin seed powder (APSP) as an adsorbent for methyl orange (MO) removal from aqueous solution. Batch sorption experiments were carried to evaluate the influence of pH, initial dye concentration, contact time, and temperature. The APSP was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The experimental equilibrium adsorption data were fitted using two two-parameter models (Langmuir and Freundlich) and two three-parameter models (Sips and Toth). Langmuir and Sips isotherms provided the best model for MO adsorption data. The maximum monolayer sorption capacity was found to be 200.3mg/g based on the Langmuir isotherm model. The pseudo-first-order and pseudo-second-order model equations were used to analyze the kinetic data of the adsorption process and the data was fitted well with the pseudo-second-order kinetic model (R(2)>0.97). The calculated thermodynamic parameters such as ΔG(0), ΔH(0) and ΔS(0) from experimental data showed that the sorption of MO onto APSP was feasible, spontaneous and endothermic in the temperature range 298-318 K. The FTIR results revealed that amine and carboxyl functional groups present on the surface of APSP. The SEM results show that APSP has an irregular and porous surface which is adequate morphology for dye adsorption. Desorption experiments were carried to explore the feasibility of adsorbent regeneration and the adsorbed MO from APSP was desorbed using 0.1M NaOH with an efficiency of 93.5%. Findings of the present study indicated that APSP can be successfully used for removal of MO from aqueous solution. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Kinetics study of metaxalone degradation under hydrolytic, oxidative and thermal stress conditions using stability-indicating HPLC method

    Directory of Open Access Journals (Sweden)

    Vamsi Krishna Marothu

    2012-12-01

    Full Text Available An isocratic stability indicating RP-HPLC–UV method is presented for the determination of metaxalone (MET in the presence of its degradation products. The method uses Dr. Maisch C18 column (250 mm×4.6 mm, 5 μm with mobile phase consisting of acetonitrile–potassium dihydrogen orthophosphate buffer with 4 mL of 0.4% triethyl amine (pH 3.0; 10 mM (58:42, v/v at a flow rate of 1.0 mL/min. pH of the buffer was adjusted with o-phosphoric acid. UV detection was performed at 225 nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The calibration plot was linear over the concentration range of 1–100 μg/mL having a correlation coefficient (r2 of 0.999. Limits of detection and quantification were 0.3 and 1 μg/mL, respectively. Intra-day and inter-day precision (% RSD was 0.65 and 0.79 respectively. The proposed method was used to investigate the degradation kinetics of MET under different stress conditions employed. Degradation of MET followed a pseudo-first-order kinetics, and rate constant (K, time left for 50% potency (t1/2, and time left for 90% potency (t90 were calculated. Keywords: Metaxalone, Degradation kinetics, RP-HPLC–UV

  10. Kinetic degradation of guar gum in oilfield wastewater by photo-Fenton process.

    Science.gov (United States)

    Wang, Shunwu; Li, Ziwang; Yu, Qinglong

    2017-01-01

    Guar gum is considered as a main component of oilfield wastewater. This work is intended to optimize the experimental conditions (H2O2 dosage, Fe2+ dosage, initial concentration of organics, initial pH and temperature) for the maximum oxidative degradation of guar gum by Fenton's reagent. The kinetics of guar gum removal were evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements. The batch experiment results showed that the optimum conditions were: H2O2 dosage, 10,000 mg/L; Fe2+dosage, 2,000 mg/L; initial concentration of organics, 413 mg/L; pH, 3 and temperature, 35 °C, under which the COD removal could reach 61.07% and fairly good stability could be obtained. Under the optimum experimental conditions, using UV irradiation to treat the wastewater, the photo-Fenton systems can successfully eliminate COD from guar gum solution. The COD removal always obeyed a pseudo-first-order kinetics and the degradation rate (kapp) was increased by 25.7% in the photo-Fenton process compared to the Fenton process. The photo-Fenton system needed less time and consequently less quantity of H2O2 to obtain the same results as the Fenton process. The photo-Fenton process needs a dose of H2O2 20.46% lower than that used in the Fenton process to remove 79.54% of COD. The cost of the photo/Fenton process amounted to RMB9.43/m3, which was lower than that of the classic Fenton process alone (RMB10.58/m3) and the overall water quality of the final effluent could meet the class Ι national wastewater discharge standard for the petrochemical industry of China.

  11. Kinetics of transesterification of palm oil and dimethyl carbonate for biodiesel production at the catalysis of heterogeneous base catalyst.

    Science.gov (United States)

    Zhang, Liping; Sheng, Boyang; Xin, Zhong; Liu, Qun; Sun, Shuzhen

    2010-11-01

    The transesterification of palm oil with dimethyl carbonate (DMC) for preparing biodiesel has been studied in solvent-free system at the catalysis of potassium hydroxide (KOH) as heterogeneous catalyst. Fatty acid methyl esters (FAMEs) were analyzed by GC with internal standard method. The effects of reaction conditions (molar ratio of DMC and palm oil, catalyst amount and time) on FAMEs yield were investigated. The highest FAMEs yield could reach 96.2% at refluxing temperature for 8h with molar ratio of DMC and oil 9:1 and 8.5% KOH (based on oil weight). Kinetics of the KOH-catalyzed transesterification of palm oil and DMC was researched over a temperature range of 65-75 degrees C. A pseudo first-order model was proposed. The activation energy (E(a)) was 79.1 kJ mo1(-1) and the pre-exponential factor (k(o)) was 1.26 x 10(9) min(-1) from Arrhenius equation. Further, a plausible reaction mechanism for the catalytic process with DMC as acyl acceptor was proposed. Copyright 2010 Elsevier Ltd. All rights reserved.

  12. Visible-light-mediated Sr-Bi2O3 photocatalysis of tetracycline: kinetics, mechanisms and toxicity assessment.

    Science.gov (United States)

    Niu, Junfeng; Ding, Shiyuan; Zhang, Liwen; Zhao, Jinbo; Feng, Chenghong

    2013-09-01

    Photodegradation of tetracycline (TC) was investigated in aqueous solution by visible-light-driven photocatalyst Sr-doped β-Bi2O3 (Sr-Bi2O3) prepared via solvothermal synthesis. The decomposition of TC by Sr-Bi2O3 under visible light (λ>420nm) irradiation followed pseudo-first-order kinetics, and the removal ratio reached 91.2% after 120min of irradiation. Sr-Bi2O3 photocatalysis is able to break the naphthol ring of TC which decomposes to m-cresol via dislodging hydroxyl group step by step by photogenerated electron. This mechanism was verified by electron spin resonance measurement, the addition of radical scavengers and the intermediate product analysis, indicating that the photogenerated electron acts as a reductant and can be the key to the degradation process. In contrast, in TiO2 photocatalysis the naphthol ring is broken via oxidation by hydroxyl radical, while in direct photolysis the ring remains intact. In addition, the toxicity of photodegradation products was analyzed by bioluminescence inhibition. After 120min of irradiation by Sr-Bi2O3, the toxicity decreases by 90.6%, which is more substantial than direct photolysis (70%) and TiO2 photocatalysis (80%), indicating that the Sr-Bi2O3 photocatalysis is more eco-friendly than the other two methods. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Photocatalytic degradation of bisphenol A in the presence of Ce–ZnO: Evolution of kinetics, toxicity and photodegradation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Bechambi, Olfa [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Jlaiel, Lobna [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia); Najjar, Wahiba, E-mail: najjarwahiba2014@gmail.com [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Sayadi, Sami [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia)

    2016-04-15

    Ce–ZnO (2 mol %) and undoped ZnO catalysts have been synthesized through hydrothermal method and characterized by X-ray diffraction (XRD), Nitrogen physisorption at 77 K; Fourier transformed infrared spectroscopy (FTIR), UV–Visible spectroscopy, Photoluminescence spectra (PL), and Raman spectroscopy. Ce-doping reduces the average crystallite size, increases the BET surface area, shifts the absorption edge, reduces the electron–hole recombination and consequently improves photodegradation efficiency of Bisphenol A (BPA) in the presence of UV irradiation and hydrogen peroxide. The photocatalytic optimum conditions were established by studying the influence of various operational parameters including catalyst concentration, initial BPA concentration, H{sub 2}O{sub 2} concentration and initial pH. Under optimum conditions, Ce–ZnO (2%) achieved 100% BPA degradation and 61% BPA mineralization after 24 h of UV irradiation. BPA degradation reaction followed pseudo first-order kinetics according to the Langmuir–Hinshelwood model. Based on the identified intermediate products, the possible mechanism for BPA photodegradation is proposed. Toxicity under the optimum condition was also evaluated. - Graphical abstract: Proposed photocatalytic degradation pathway of BPA in the presence of Ce– ZnO (2%)/UV/H{sub 2}O{sub 2} system. - Highlights: • Influence of different parameters on the degradation and mineralization of BPA. • Identification of possible degradation products. • Toxicity tests conducted with Vibrio fischeri. • Simple and direct photodegradation mechanism of BPA is proposed.

  14. Kinetics and mechanism of 17β-estradiol chlorination in a pilot-scale water distribution systems.

    Science.gov (United States)

    Li, Cong; Dong, Feilong; Crittenden, John C; Luo, Feng; Chen, Xinbo; Zhao, Taotao

    2017-07-01

    The kinetics and mechanisms of 17β-estradiol (E2) chlorination in water distribution systems (WDS) were studied. We examined the impacts of different factors, including pH, temperature, humic acid concentration and type, and flow velocity. The experimental results showed that the rate constants in beaker tests and WDS were described by a pseudo-first-order model. pH had the greatest impact on E2 chlorination in the beaker tests. However, temperature had the greatest impact on E2 chlorination in WDS. Mechanistic analysis of E2 chlorination showed that chlorine attacked E2 in three stages: 1) halogenation of the aromatic ring, 2) cleavage of the benzene moiety and chlorine or bromine substitution formation, and 3) formation of trihalomethanes (THMs) and halogenated acetic acids (HAAs) from phenolic intermediates through benzene ring opening with chlorine and/or bromine substitution of hydrogen on the carbon atoms. In the third stage, the concentrations of THMs and HAAs increased rapidly. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Statistics of fermions in the Randall-Wilkins model for kinetics of general order; Estadistica de fermiones en el modelo de Randall-Wilkins para cinetica de orden general

    Energy Technology Data Exchange (ETDEWEB)

    Nieto H, B.; Azorin N, J.; Vazquez C, G.A. [UAM-I, 09340 Mexico D.F. (Mexico)

    2004-07-01

    As a theoretical planning of the thermoluminescence phenomena (Tl), we study the behavior of the systems formed by fermions, which are related with this phenomenon establishing a generalization of the Randall-Wilkins model, as for first order kinetics as for general order (equation of May and Partridge) in which we consider a of Fermi-Dirac statistics. As consequence of this study a new variable is manifested: the chemical potential, also we establish its relationship with some of the other magnitudes already known in Tl. (Author)

  16. Transformation of acesulfame in chlorination: Kinetics study, identification of byproducts, and toxicity assessment.

    Science.gov (United States)

    Li, Adela Jing; Wu, Pengran; Law, Japhet Cheuk-Fung; Chow, Chi-Hang; Postigo, Cristina; Guo, Ying; Leung, Kelvin Sze-Yin

    2017-06-15

    Acesulfame (ACE) is one of the most commonly used artificial sweeteners. Because it is not metabolized in the human gut, it reaches the aquatic environment unchanged. In the present study, the reactivity of ACE in free chlorine-containing water was investigated for the first time. The degradation of ACE was found to follow pseudo-first-order kinetics. The first-order rate increased with decreasing pH from 9.4 to 4.8 with estimated half-lives from 693 min to 2 min. Structural elucidation of the detected transformation products (TPs) was performed by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Integration of MS/MS fragments, isotopic pattern and exact mass allowed the characterization of up to 5 different TPs in the ultrapure water extracts analyzed, including two proposed new chlorinated compounds reported for the first time. Unexpectedly, several known and regulated disinfection by-products (DBPs) were present in the ACE chlorinated solution. In addition, two of the six DBPs are proposed as N-DBPs. Time-course profiles of ACE and the identified by-products in tap water and wastewater samples were followed in order to simulate the actual disinfection process. Tap water did not significantly affect degradation, but wastewater did; it reacted with the ACE to produce several brominated-DBPs. A preliminary assessment of chlorinated mixtures by luminescence inhibition of Vibrio fischeri showed that these by-products were up to 1.8-fold more toxic than the parent compound. The generation of these DBPs, both regulated and not, representing enhanced toxicity, make chlorine disinfection a controversial treatment for ACE. Further efforts are urgently needed to both assess the consequences of current water treatment processes on ACE and to develop new processes that will safely treat ACE. Human health and the health of our aquatic ecosystems are at stake. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Kinetic, isotherm and thermodynamics investigation on adsorption of divalent copper using agro-waste biomaterials, Musa acuminata, Casuarina equisetifolia L. and Sorghum bicolor

    Directory of Open Access Journals (Sweden)

    Mokkapati Ramya Prasanthi

    2016-06-01

    Full Text Available Three novel and distinct agricultural waste materials, viz., Casuarinas fruit powder (CFP, sorghum stem powder (SSP and banana stem powder (BSP were used as low cost adsorbents for the removal of toxic copper(II from aqueous solutions. Acid treated adsorbents were characterized by SEM, EDX and FTIR. Different factors effecting adsorption capacity were analyzed and the efficiency order was BSP>SSP>CFP. Based on the extent of compatibility to Freundlich/Langmuir/D-R/Temkin adsorption isotherm and different models (pseudo-first and second order, Boyd, Weber’s and Elovich, chemisorption primarily involved in the case of CFP and SSP, whereas, simultaneous occurrence of chemisorption and physisorption was proposed in the case of BSP. Based on the observations, it was proposed that three kinetic stages involve in adsorption process viz., diffusion of sorbate to sorbent, intra particle diffusion and then establishment of equilibrium. These adsorbents have promising role towards removal of Cu(II from industrial wastewater to contribute environmental protection.

  18. Cu(II immobilization onto a one-step synthesized poly(4-vinylpyridine-co-ethylene glycol dimethacrylate resin: Kinetics and XPS analysis

    Directory of Open Access Journals (Sweden)

    Maksin Danijela D.

    2016-01-01

    Full Text Available Synthesis of an unconventional resin based on 4-vinylpyridine (4-VP and its Cu(II sorption behavior were studied. Three samples of macroporous crosslinked poly(4-vinylpyridine-co-ethylene glycol dimethacrylate [P4VPE] with different porosity parameters were prepared by suspension copolymerization by varying the n-heptane amount in the inert component. The samples were characterized by mercury porosimetry, elemental analysis and x-ray photoelectron spectroscopy (XPS. The sorption of P4VPE for Cu(II ions, determined under non-competitive conditions, was relatively rapid, i.e. the maximum capacity was reached within 30 min. The maximum experimental sorption capacity for the sample with the highest values of pore diameter and specific pore volume (Sample 3, Qeq = 89 mg g-1 was 17.5 times higher than for the sample with the lowest values of pore diameter and specific pore volume (Sample 1, Qeq = 5.1 mg g-1. Since the values for pyridine content in all P4VPE samples were almost the same, it was concluded that the porosity parameters have predominant influence on Cu(II sorption rates on P4VPE. The sorption behavior and the rate-controlling mechanisms were analyzed using six kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, Bangham and Boyd models. XPS study clarified the nature of the formed P4VPE-Cu(II species. [Projekat Ministarstva nauke Republike Srbije, br. TR 37021 i br. III 43009

  19. Performance, kinetics, and equilibrium of methylene blue adsorption on biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids.

    Science.gov (United States)

    Sun, Lei; Chen, Dongmei; Wan, Shungang; Yu, Zebin

    2015-12-01

    Biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids at low temperatures was utilized as adsorbent to remove methylene blue (MB) from aqueous solutions. Fourier transform infrared spectroscopy analysis showed that the carboxyl group was introduced on the biochar surface. Adsorption experiment data indicated that eucalyptus saw dust modified with citric acid showed higher MB adsorption efficiency than that modified with tartaric and acetic acids. Pseudo-second-order kinetics was the most suitable model for describing MB adsorption on biochar compared with pseudo-first-order, Elovich, and intraparticle diffusion models. The calculated values of ΔG(0) and ΔH(0) indicated the spontaneous and endothermic nature of the adsorption process. MB adsorption on biochar followed the Langmuir isotherm. The maximum adsorption capacities for eucalyptus saw dust modified with citric, tartaric, and acetic acids were 178.57, 99.01, and 29.94 mg g(-1), respectively, at 35°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Reactions of sulfur-nitrosyl iron complexes of "g=2.03" family with hemoglobin (Hb): kinetics of Hb-NO formation in aqueous solutions.

    Science.gov (United States)

    Sanina, N A; Syrtsova, L A; Shkondina, N I; Rudneva, T N; Malkova, E S; Bazanov, T A; Kotel'nikov, A I; Aldoshin, S M

    2007-03-01

    NO-donating ability of nitrosyl [Fe-S] complexes, namely, mononuclear dinitrosyl complexes of anionic type [Fe(S2O3)2(NO)2]-(I) and neutral [Fe2(SL1)2(NO)2] with L1=1H-1,2,4-triazole-3-yl (II); tetranitrosyl binuclear neutral complexes [Fe2(SL2)2(NO)4] with L2=5-amino-1,2,4-triazole-3-yl (III); 1-methyl-1H-tetrazole-5-yl (IV); imidazole-2-yl (V) and 1-methyl-imidazole-2-yl (VI) has been studied. In addition, Roussin's "red salt" Na2[Fe2S2(NO)4] x 8H2O (VII) and Na2[Fe(CN)5NO] x H2O (VIII) have been investigated. The method for research has been based on the formation of Hb-NO adduct upon the interaction of hemoglobin with NO generated by complexes I-VIII in aqueous solutions. Kinetics of NO formation was studied by registration of absorption spectra of the reaction systems containing Hb and the complex under study. For determination of HbNO concentration, the experimental absorption spectra were processed during the reaction using standard program MATHCAD to determine the contribution of individual Hb and HbNO spectra in each spectrum. The reaction rate constants were obtained by analyzing kinetic dependence of Hb interaction with NO donors under study. All kinetic dependences for complexes I-VI were shown to be described well in the frame of formalism of pseudo first-order reactions. The effective first-order rate constants for the studied reactions have been determined. As follows from the values of rate constants, the rate of interaction of sulfur-nitrosyl iron complexes (I-VI) with Hb is limited by the stage of NO release in the solution.

  1. [Determination of trace amounts of nitrite and its chemical reaction kinetics].

    Science.gov (United States)

    Luo, Zhi-yong; Zheng, Huai-li

    2014-06-01

    A catalytic kinetic spectrophotometric method for the determination of nitrite, NO2(-)-S2O8(2-)-MR, was developed. It is based on the fading reaction of methyl red (MR) oxidized by potassium persulfate which can be catalyzed by NO2- in the medium of dilute HCl. The optimum experimental conditions were gained by combining single factor experiments with orthogonal experiments. Calibration curve, detection limit, precision, and anti-interference under the optimum experimental conditions were researched. Its kinetics principles and parameters were discussed. Its quantitative principle was investigated. The results show that the optimum experimental conditions of this method should be as follows: 1.0 mL 0.3 mol x L(-1) HCl, 1.0 mL 0.01 mol x L(-1) K2S2O8, 0.6 mL 0.2 g x L(-1) MR, reaction temperature 80 degrees C and reaction time 9 min. The principles for the quantitative determination of trace nitrite is that variation of MR concentration at the maximum absorption wavelength of 518 nm, ln(A0/A), shows a good linear relationship with the concentration of NO2- under the optimum experimental conditions. Its determination range is 0.01-0.80 mg x L(-1) and its detection limit is 0.007 mg x L(-1). The kinetic characteristics are that the reaction order in NO2- is 1 and the fading reaction is a pseudo first order reaction. Its apparent activation energy is 85.04 kJ x mol(-1). Its apparent rate constant is 0.021 4 min(-1), and the half-life is 32.39 min at 80 degrees C. The kinetic principle is that the variation of MR concentration is directly proportional to the concentration of NO2-, ln(A0/A) = kc(NO2-). This new method for the determination of trace nitrite has never previously been reported in the published literature so far. It is highly sensitive and selective. Most of the common ions don't interfere with the determination of nitrite. This method has the advantages of convenient operation and the regents used are cheap and nontoxic. It was applied to the determination

  2. Biosorptive uptake of arsenic(V) by steam activated carbon from mung bean husk: equilibrium, kinetics, thermodynamics and modeling

    Science.gov (United States)

    Mondal, Sandip; Aikat, Kaustav; Halder, Gopinath

    2017-07-01

    The present investigation emphasizes on the biosorptive removal of toxic pentavalent arsenic from water using steam activated carbon prepared from mung bean husk (SAC-MBH). Characterization of the synthesized sorbent was done using different instrumental techniques, i.e., SEM, BET and point of zero charge. Sorptive uptake of As(V) over steam activated MBH as a function of pH (3-9), agitation speed (40-200 rpm), dosage (50-1000 mg) and temperature (298-313 K) was studied by batch process at arsenic concentration of 2 mg L-1. Lower pH increases the arsenic removal over the pH range of 3-9. Among three adsorption isotherm models examined, Langmuir model was observed to show superior results over Freundlich model. The mean sorption energy (E) estimated by Dubinin-Radushkevich model suggested that the process of adsorption was chemisorption. Thermodynamic parameters confer that the sorption process was spontaneous, exothermic and feasible in nature. The pseudo-second-order rate kinetics of arsenic gave better correlation coefficients as compared to pseudo-first-order kinetics equation. Three process parameters, viz. adsorbent dosage, agitation speed and pH were opted for optimizing As(V) elimination using central composite design matrix of response surface methodology (RSM). The identical design setup was used for artificial neural network (ANN) for comparing its prediction capability with RSM towards As(V) removal. Maximum arsenic removal was observed to be 98.75% at sorbent dosage 0.75 gm L-1, pH 3.0, agitation speed 160 rpm and temperature 308 K. The study concluded that SAC-MBH could be a competent adsorbent for As(V) removal and ANN model was better in arsenic removal predictability results than RSM model.

  3. Equilibrium and kinetic studies of Pb(II, Cd(II and Zn(II sorption by Lagenaria vulgaris shell

    Directory of Open Access Journals (Sweden)

    Mitić-Stojanović Dragana-Linda

    2012-01-01

    Full Text Available The sorption of lead, cadmium and zinc ions from aqueous solution by Lagenaria vulgaris shell biosorbent (LVB in batch system was investigated. The effect of relevant parameters such as contact time, biosorbent dosage and initial metal ions concentration was evaluated. The Pb(II, Cd(II and Zn(II sorption equilibrium (when 98% of initial metal ions were sorbed was attained within 15, 20 and 25 min, respectively. The pseudo first, pseudo-second order, Chrastil’s and intra-particle diffusion models were used to describe the kinetic data. The experimental data fitted the pseudo-second order kinetic model and intra-particle diffusion model. Removal efficiency of lead(II, cadmium(II and zinc(II ions rapidly increased with increasing biosorbent dose from 0.5 to 8.0 g dm-3. Optimal biosorbent dose was set to 4.0 g dm-3. An increase in the initial metal concentration increases the sorption capacity. The sorption data of investigated metal ions are fitted to Langmuir, Freundlich and Temkin isotherm models. Langmuir model best fitted the equilibrium data (r2 > 0.99. Maximal sorption capacities of LVB for Pb(II, Cd(II and Zn(II at 25.0±0.5°C were 0.130, 0.103 and 0.098 mM g-1, respectively. The desorption experiments showed that the LVB could be reused for six cycles with a minimum loss of the initial sorption capacity.

  4. Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Maksin, Danijela D., E-mail: dmaksin@vinca.rs [University of Belgrade, Vinca Institute of Nuclear Sciences, P.O. Box 522, Belgrade (Serbia); Nastasovic, Aleksandra B., E-mail: anastaso@chem.bg.ac.rs [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Njegoseva 12, Belgrade (Serbia); Milutinovic-Nikolic, Aleksandra D., E-mail: snikolic@nanosys.ihtm.bg.ac.rs [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Njegoseva 12, Belgrade (Serbia); Surucic, Ljiljana T., E-mail: ljilja_m@yahoo.com [University of Belgrade, Faculty of Forestry, Kneza Viseslava 1, Belgrade (Serbia); Sandic, Zvjezdana P., E-mail: zvjezdana.sandic@gmail.com [Faculty of Science, Mladena Stojanovica 2, Banja Luka, Bosnia and Herzegovina (Bosnia and Herzegowina); Hercigonja, Radmila V., E-mail: radah@ffh.bg.ac.rs [University of Belgrade, Faculty of Physical Chemistry, Studentski trg 12-16, 11001 Belgrade (Serbia); Onjia, Antonije E., E-mail: onjia@vinca.rs [University of Belgrade, Vinca Institute of Nuclear Sciences, P.O. Box 522, Belgrade (Serbia)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer Methacrylate based copolymers grafted with diethylene triamine as Cr(VI) sorbents. Black-Right-Pointing-Pointer Chemisorption and pore diffusion are characteristics of this sorption system. Black-Right-Pointing-Pointer Langmuir isotherm provided best fit and maximum adsorption capacity was 143 mg g{sup -1}. Black-Right-Pointing-Pointer Cr(VI) sorption onto amino-functionalized copolymer was endothermic and spontaneous. Black-Right-Pointing-Pointer A simple, efficient and cost-effective hexavalent chromium removal method. - Abstract: Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70 Degree-Sign C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q{sub max}, at pH 1.8 and 25 Degree-Sign C was 143 mg g{sup -1} for PGME2-deta (sample with the highest amino group concentration) while at 70 Degree-Sign C Q{sub max} reached the high value of 198

  5. Mechanism and kinetics of uranium adsorption onto soil around coal-fired power plant

    Science.gov (United States)

    Yasim, Nurzulaifa Shaheera Erne Mohd; Ariffin, Nik Azlin Nik; Mohammed, Noradila; Ayob, Syafina

    2017-11-01

    Coal is the largest source of energy in Malaysia providing approximately 80 % of all entire power needs. The combustion of coal concentrates a high content of heavy metals and radioactive elements in the ashes and sludge. Hazardous emissions from coal combustion were deposited into the soil and most likely transported into the groundwater system. The presence of radioactive materials in the ground water system can cause a wide range of environmental impacts and adverse health effects like cancer, impairment of neurological function and cardiovascular disease. However, the soil has a natural capability in adsorption of radioactive materials. Thus, this study was evaluated the adsorption capacity of Uranium onto the soil samples collected nearby the coal-fired power plants. In the batch experiment, parameters that were set constant include pH, the amount of soil and contact time. Various initial concentrations of radionuclides elements in the range of 2 mg/L - 10 mg/L were used. The equilibrium adsorption data was analyzed by the Freundlich isotherm and Langmuir isotherms. Then, the influences of solution pH, contact time and temperature on the adsorption process were investigated. The kinetics of radioactive materials was discussed by pseudo-first-order and pseudo-second-order rate equation. Thus, the data from this study could provide information about the potentiality of soil in sorption of radioactive materials that can be leached into groundwater. Besides that, this study could also be used as baseline data for future reference in the development of adsorption modeling in the calculation of distribution coefficient.

  6. A thermodynamic and kinetic study of hydride transfer of a caffeine derivative.

    Science.gov (United States)

    Han, Xiaozhen; Hao, Weifang; Zhu, Xiao-Qing; Parker, Vernon D

    2012-08-03

    One representative type of heterocyclic compound that can release a hydride ion is 7,8-dihydro-9-methylcaffeine (CAFH). The one-electron oxidation potential of CAFH [-0.294 (V vs Fc(+/0))] and the one-electron reduction potential of CAF(+) [-2.120 (V vs Fc(+/0))] were obtained using two different methods, CV and OSWV. Applying titration calorimetry data in thermodynamic cycles, the enthalpies of CAFH releasing a hydride ion [57.6 kcal/mol] and releasing a hydrogen atom [80.3 kcal/mol] and of its radical cation CAFH(•+) releasing a proton [33.0 kcal/mol] and releasing a hydrogen atom [38.4 kcal/mol] have been determined. Several conclusions can be drawn from the thermodynamic results: (1) CAFH is a very good single-electron donor whose single-electron oxidation potential is much less positive than that of NAD(P)H model compound BNAH [E(ox) = 0.219 V vs Fc(+/0)]. (2) The single-electron reduction potential of CAF(+) is much more negative than that of BNA(+) [E(red) = -1.419 V], which means that CAF(+) is not a good electron acceptor. Furthermore, CAFH is a very good hydride donor compared to BNAH. The results of non-steady-state kinetic studies, for the reaction of CAFH and AcrH(+)ClO(4)(-), show that the ratio of t(0.50)/t(0.05) is larger than 13.5 and the ratio of k(init)/k(pfo) is larger than 1. The pseudo-first-order rate constants obtained at different reaction stages decrease with the time, and the kinetic isotope was observed to be small at a short reaction time and slowly increases to 3.72 with the progress of the reaction. These kinetic results clearly display that the hydride transfer of CAFH to AcrH(+) in acetonitrile is not a one-step mechanism, while the thermodynamic results show that CAFH is a very good electron donor. The combination of the kinetic results with the thermodynamics analysis shows that the hydride transfer of the caffeine derivative CAFH takes place by a two-step reversible mechanism and there is an intermediate in the reaction.

  7. Kinetic and Equilibrium Studies of Sorption of Ammonium in the Soil-Water Environment in Agricultural Areas of Central Poland

    Directory of Open Access Journals (Sweden)

    Anna Sieczka

    2016-09-01

    Full Text Available Sorption characteristics of nitrogen compounds is necessary in ascertaining their fate in the soil-water environment. This paper presents a laboratory “batch” experiment for determining the sorption parameters of ammonium in the soil-water environment. Three agricultural soils (silt loam, loam, and sand with different contents of the clay fraction, significantly affecting the range of the adsorption of contaminants on the surface of solid particles, were chosen as research material. Considering the composition of ammonium nitrate (a commonly used fertilizer in Poland, ammonium solutions with a concentration of 0–52 mg NH4+/L were used as markers. Pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models were used to describe the mechanisms of ammonium adsorption. Experimental data obtained from the equilibrium tests have been analysed using two-parameter (Freundlich, Langmuir, Temkin and three-parameter (Redlich-Peterson, Hill, Sips models. In order to adjust the parameters of the considered isotherms to the experimental data, the method of minimization of the sum of squared errors was used. Additionally, the maximum sorption capacities and reduction ratios of ammonium versus time were assessed. It was observed that the presence of silt loam and loam in the soil profile can increase the possibility of ammonium adsorption up to almost 20%. Taking into consideration the results of the batch tests, it was concluded that ammonium adsorption attains equilibrium within 48 h. Experimental data was best followed by the pseudo-second order equation and the adsorption isotherm conformed to the Redlich-Peterson model for loam and sand.

  8. Optimization, equilibrium, kinetic, thermodynamic and desorption studies on the sorption of Cu(II) from an aqueous solution using marine green algae: Halimeda gracilis.

    Science.gov (United States)

    Jayakumar, R; Rajasimman, M; Karthikeyan, C

    2015-11-01

    The aptitude of marine green algae Helimeda gracilis for sorption of Cu(II) ions from an aqueous solution was studied in batch experiments. The effect of relevant parameters such as function of pH, sorbent dosage, agitation speed and contact time was evaluated by using Response surface methodology (RSM). A maximum percentage removal of Cu (II) by Halimeda gracilis occurs at pH-4.49, sorbent dosage-1.98g/L, agitation speed-119.43rpm and contact time-60.21min. Further, the sorbent was characterized by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron microscope (SEM) analysis. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order, intraparticle diffusion, power function and elovich kinetic models. The results showed that the sorption process of Cu(II) ions followed well pseudo-second order kinetics. The sorption data of Cu(II) ions at 308.15K are fitted to Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Sips and Toth isotherms. Sorption of Cu(II) onto marine green algae Helimeda gracilis followed the Langmuir and Toth isotherm models (R(2)=0.998 and R(2)=0.999) with the maximum sorption capacity of 38.46 and 38.07mg/g. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the sorption of Cu(II) ions onto Helimeda gracilis biomass was feasible, spontaneous and endothermic. Desorption study shows that the sorbent could be regenerated using 0.2M HCl solution, with up to 89% recovery. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Chitosan modification persimmon tannin bioadsorbent for highly efficient removal of Pb(II) from aqueous environment: the adsorption equilibrium, kinetics and thermodynamics.

    Science.gov (United States)

    Li, Xiaojuan; Wang, Zhongmin; Liang, Haijun; Ning, Jingliang; Li, Guiyin; Zhou, Zhide

    2017-10-04

    Lead (Pb) pollution has triggered a great threat to ecological system as well as public health due to its highly toxic and mutagenic properties. In this study, chitosan surface modified persimmon tannin (PT-CS) biomass composite as an environmental-friendly bioadsorbent for highly efficient removal of Pb(II) from aqueous solutions was investigated. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy and Zeta potential were used to elucidate the adsorption mechanism. Combining oxidation reaction, electrostatic interaction and chelation reaction, PT-CS exhibited fine adsorption to Pb(II). The maximum adsorption capacity was 179.3 mg/g. Equilibrium isotherm for the adsorption of Pb(II) was analyzed by the Langmuir, Freundlich and Temkin models, and the Langmuir isotherm (R2 > 0.99) was the best. The pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were used to analyze the kinetic data of the adsorption process and the pseudo-second-order kinetic (Rs2 > 0.98) model was fitted well. Moreover, thermodynamic parameters including ΔG0  0 and ΔS0 (456.13 J/mol K) > 0 showed that the process of Pb(II) adsorption by PT-CS was spontaneous and endothermic. All these results illustrated that PT-CS would be a promising and low-cost alternative bioadsorbent of Pb(II) in wastewater treatment.

  10. Adsorptive, thermodynamic and kinetic performances of Al/Ti and Al/Zr-pillared clays from the Brazilian Amazon region for zinc cation removal

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, Denis L. [Instituto de Quimica, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, Sao Paulo (Brazil); Airoldi, Claudio [Instituto de Quimica, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, Sao Paulo (Brazil)], E-mail: airoldi@iqm.unicamp.br; Lemos, Vanda P.; Angelica, Romulo S. [Universidade Federal do Para, Centro de Geociencia, Caixa Postal 1611, 66075-110 Belem, Para (Brazil)

    2008-06-30

    Smectite clay samples from the Amazon region, Brazil, were pillarized by intercalating the species obtained from the chemical reactions: (i) AlCl{sub 3}.6H{sub 2}O/NaOH, (ii) titanium ethoxide in hydrochloric acid and (iii) direct use of ZrOCl{sub 2}.8H{sub 2}O solution. The natural matrices and the pillaring solutions were maintained under vigorous stirring at 298 K for 3 h and then subjected to calcination at temperatures of 723 and 873 K. Natural and pillared matrices were characterized by XRD, FTIR, TG-DTG and nitrogen adsorption-desorption isotherms. The resulting materials were used for zinc adsorption from aqueous solution at room temperature. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data and the Freundlich model is limited for higher concentrations. The pillaring process increases the thermal stability, the basal spacing of the natural clay sample (A{sub 1}) from 1.55 to 2.06 nm and the surface area from 44.30 to 223.73 m{sup 2} g{sup -1}. Kinetic studies demonstrated an equilibrium time of 180 min for zinc adsorption on the pillared matrices. Pseudo-first-order, Lagergren pseudo-second-order and Elovich equations demonstrated a better agreement with second-order kinetics was obtained with K{sub 2} = 4.17-10.43 x 10{sup -3} g mg{sup -1} min{sup -1} for the A{sub 1} sample.

  11. Investigation of the profile and kinetics of degradation of rivaroxaban using HPLC, TLC-densitometry and LC/MS/MS: Application to pre-formulation studies

    Directory of Open Access Journals (Sweden)

    Mohamed A. Abdallah

    2015-06-01

    Full Text Available Rivaroxaban (RIVA, an amide group-containing oral anticoagulant was subjected to stress conditions commonly required for the registration of pharmaceuticals: base and acid-catalyzed hydrolysis (0.1 M, 60 °C, 3–6 h, oxidation (10% H2O2, 24 h, photodegradation (300–800 nm, 24 h and thermal decomposition (50 °C, 6 h. Two major degradation products were separated and identified using TLC and LC/MS/MS, respectively. An orthogonal stability-indicating testing protocol (RP-HPLC and NP-TLC-densitometry was developed and validated according to ICH guidelines. Both assays enabled the determination of RIVA in the presence of its degradation products as well as the kinetics of degradation. Determination was carried out over a concentration range of (5.00–50.00 μg/mL and (0.40–12.00 μg/band with an accuracy of (100.81% ± 1.03 and (100.29% ± 1.08 for HPLC and TLC-densitometry, respectively. Results indicated that RIVA was stable towards oxidation, photodegradation and thermal decomposition but extremely sensitive to hydrolysis. Two major degradation products were detected in the case of base-catalyzed hydrolysis while only one degradation product was detected upon acid-catalyzed hydrolysis. This could be attributed to the presence of amide groups in RIVA structure of different stability profiles. The kinetics of hydrolysis was investigated in more detail and the reaction was found to follow the pseudo first order kinetics, as confirmed by the results of both HPLC and TLC-densitometric assays. The applicability of the assay for the determination of RIVA content and dissolution pattern of the innovator product as well as three generic formulations was demonstrated.

  12. Synthesis of CdSe quantum dots decorated SnO2 nanotubes as anode for photo-assisted electrochemical degradation of hydrochlorothiazide: Kinetic process.

    Science.gov (United States)

    Gupta, Vinod Kumar; Fakhri, Ali; Azad, Mona; Agarwal, Shilpi

    2017-12-15

    Pharmaceutical residues have been increasingly detected in the aquatic environment and are considered important contaminants of emerging concern. This study examines the photo assisted electrochemical degradation of the Hydrochlorothiazide by using CdSe quantum dots decorated SnO2 nanotubes. The characteristic devices such as Scanning electron microscopy, X-ray diffraction, UV-vis diffuse reflectance Transmission electron Microscopy were used to analyze information structure of CdSe QDs/SnO2 nanotubes. All the experiments were perform with influence of the current density (10-60mAcm(-2)) and sodium chloride (0.02-0.10molL(-1)) in the supporting electrolyte composition was analyzed. The results showed that the Hydrochlorothiazide and TOC removal was achieved in the current density range used. As expected, the degradation kinetics presented a pseudo first order behavior. Comparison of the efficiencies of the photocatalytic, electrochemical (EC) and photo-assisted electrochemical (PAEC) techniques verified that the combined process showed a synergism for HCT and TOC removal. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Enhancement of activated sludge dewatering performance by combined composite enzymatic lysis and chemical re-flocculation with inorganic coagulants: Kinetics of enzymatic reaction and re-flocculation morphology.

    Science.gov (United States)

    Chen, Zhan; Zhang, Weijun; Wang, Dongsheng; Ma, Teng; Bai, Runying

    2015-10-15

    The feasibility of combined process of composite enzymatic treatment and chemical flocculation with inorganic salt coagulants was investigated in this study. The evolution of extracellular polymeric substances (EPS) distribution, composition and morphological properties were analyzed to unravel the sludge conditioning mechanism. It was found that sludge filtration performance was deteriorated due to release of a large amount of biopolymers after enzymatic treatment. The change in EPS followed the pseudo-first-order kinetic equation well under enzymatic treatment. The feeding modes of enzymes had a significant influence on sludge lysis efficiency under compound enzymes treatment. Alpha amylase + protease was more effective in solubilization than other two addition modes (protease + α-amylase or simultaneous addition). The sludge floc re-formed and macromolecule biopolymers were effectively removed through coagulation process. At the same time, both of filtration rate and cake solid content of sludge treated with enzymes were improved with increasing dosage of coagulants, and ferric iron (FeCl3) had better performance in sludge dewaterability enhancement than polyaluminium chloride (PACl). In addition, sludge filtration property was slightly deteriorated, while the cake moisture reduction was favored at the optimal dosage of inorganic coagulants. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Kinetic Studies of Inhibition of the Aβ(1–42) Aggregation Using a Ferrocene-tagged β-Sheet Breaker Peptide

    Science.gov (United States)

    Zhang, Lin; Yagnik, Gargey; Peng, Yong; Wang, Jianxiu; Xu, H. Howard; Hao, Yuanqiang; Liu, You-Nian; Zhou, Feimeng

    2013-01-01

    The aggregation of amyloidogenic proteins/peptides has been closely linked to the neuropathology of several important neurological disorders. In Alzheimer's disease (AD), amyloid beta (Aβ) peptides and their aggregation are believed to be at least partially responsible for the etiology of AD. The aggregate-inflicted cellular toxicity can be inhibited by short peptides whose sequence are homologous to segments of the Aβ(1–42) peptide responsible for β-sheet stacking (referred to as the β-sheet breaker peptides). Herein a water-soluble ferrocene (Fc)-tagged β-sheet breaker peptide (Fc-KLVFFK6) is used as an electrochemical probe for kinetic studies of the inhibition of the Aβ(1–42) fibrillation process and for determination of the optimal concentration of β-sheet breaker peptide for efficient inhibition. Our results demonstrated that Fc-KLVFFK6 interacts with the Aβ aggregates instantaneously in solution, and sub-stoichiometric amount of Fc-KLVFFK6 is sufficient to inhibit the formation of the Aβ oligomers and fibrils and to reduce the toxicity of Aβ(1–42). The interaction between Fc-KLVFFK6 and Aβ(1–42) follows a pseudo-first-order reaction, with a rate constant of 1.89 ± 0.05 × 10−4 s−1. Tagging β-sheet breaker peptides with a redox label facilitates design, screening, and rational use of peptidic inhibitors for impeding/altering Aβ aggregation. PMID:23232068

  15. Kinetic study on aminolysis of 4-pyridyl benzoate and o-4-pyridyl thionobenzoate in acetonitrile: Factors influencing reactivity and reaction mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Um, Ik Hwan; Kim, Min Young [Dept. of Chemistry, and Nano Science, Ewha Womans University, Seoul (Korea, Republic of); Lee, Jae In [Dept. of Chemistry, and Plant Resources Research Institute, Duksung Women' s University, Seoul (Korea, Republic of)

    2016-10-15

    A kinetic study on nucleophilic substitution reactions of 4-pyridyl benzoate (2a) and O-4-pyridyl thionobenzoate (2b) with a series of cyclic secondary amines in acetonitrile at 25.0°C is reported. Plots of pseudo-first-order rate constant (k{sub obsd}) vs. [amine] are linear and pass through the origin for the reactions of 2a but curve upward for those of 2b. The upward curvature observed for the reactions of 2b is typical for reactions that proceed through a stepwise mechanism with a zwitterionic intermediate T{sup ±}, which decomposes to the products via uncatalyzed and catalyzed routes competitively. The reaction of 2a has been suggested to proceed through a stepwise mechanism with T±, in which expulsion of the leaving group occurs in the rate-determining step on the basis of a linear Broensted-type plot with β{sub nuc} = 0.77. The catalyzed reaction of 2b from T{sup ±} has been proposed to proceed through a concerted mechanism with a six-membered cyclic transition state rather than via a stepwise pathway with an anionic intermediate T{sup −}. Factors influencing reactivity and reaction mechanism are discussed in detail.

  16. Discharge flow kinetic study of NO/sub 3/ reactions with free radicals: the reaction of NO/sub 3/ with Cl

    Energy Technology Data Exchange (ETDEWEB)

    Mellouki, A.; Le Bras, G.; Poulet, G.

    1987-10-22

    The discharge flow technique was used to perform a direct measurement of the rate constant for the reaction NO/sub 3/ + Cl ..-->.. ClO + NO/sub 2/ (1) under pseudo-first-order conditions with NO/sub 3/ in excess. NO/sub 3/ was produced via the reaction F + HNO/sub 3/ ..-->.. HF + NO/sub 3/ (2) for which the rate constant was also determined: k/sub 2/ = (2.7 +/- 0.5) x 10/sup -11/ cm/sup 3/ molecule/sup -1/ s/sup -1/ at 298 K. Absolute titration of NO/sub 3/ was done using NO and 2,3-dimethyl-2-butene as the titrants. The titration experiments with NO were simulated, and the analysis of potential errors resulting from the secondary chemistry indicated that NO is a precise titrant of NO/sub 3/ in discharge flow studies. In the kinetic investigation of reaction 1, the obtained value of k/sub 1/ at 298 K was k/sub 1/ = (2.6 +/- 0.5) x 10/sup -11/ cm/sup 3/ molecule/sup -1/ s/sup -1/.

  17. Decolorization of malachite green, decolorization kinetics and stoichiometry of ozone-malachite green and removal of antibacterial activity with ozonation processes

    Energy Technology Data Exchange (ETDEWEB)

    Kusvuran, Erdal, E-mail: erdalkusvuran@yahoo.com [Chemistry Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey); Gulnaz, Osman [Biology Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey); Samil, Ali [Chemistry Department, Arts and Sciences Faculty, Sutcu Imam University, 46100 Kahramanmaras (Turkey); Yildirim, Ozlem [Chemistry Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey)

    2011-02-15

    This study aimed to identify degradation intermediates and to investigate the stoichiometry of decolorization and degradation, decolorization kinetics, and removal of antibacterial activity of malachite green (MG) using ozonization processes. The decolorization of MG was optimal at an acidic pH value of 3 based on molecular ozone attack on MG molecules. The stoichiometric ratio of decolorization between ozone and MG was calculated to be 7.0 with a regression coefficient of 0.995, whereas the ratio for degradation was calculated as 13.1 with a regression coefficient of 0.998. With MG concentrations in the range of 0.30-1.82 mM, the concentration of decolorized MG increased with higher initial concentrations of MG, whereas the ozonolytic decolorization rates of MG, decreased with increasing initial concentration. The pseudo-first-order degradation rate constants (k') decreased with the initial concentration and ranged from 0.769 to 0.223 min{sup -1}. Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5 min and 30 min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10 min, the decrease of antibacterial activity was very low (10%) for Bacillus subtilis and Staphylococcus epidermidis because the degradation intermediates, phenol and benzoic acid, also have antibacterial activity. The antibacterial activity of both MG and its intermediates were removed successfully with ozonation times above 26 min.

  18. Behavior and kinetic of hydrolysis of amine boranes in acid media employed in chemical vapor generation.

    Science.gov (United States)

    D'Ulivo, Lucia; Spiniello, Roberto; Onor, Massimo; Campanella, Beatrice; Mester, Zoltan; D'Ulivo, Alessandro

    2018-01-15

    The behavior of NaBH4 (THB) and the amine boranes, NH3BH3 (AB), tertbutylNH2BH3 (TBAB), Me2NHBH3 (DMAB) was investigated in continuous flow chemical vapor generation of H2Se from aqueous Se(IV) coupled with atomic absorption spectrometry. Unexpected higher efficiency of H2Se generation was obtained with amine boranes compared to THB (TBAB > AB > THB) using millimolar concentration of reductant (0.001-0.1 mol L(-1)) under strongly acidic conditions (HCl, HClO4, H2SO4, HNO3, 0.5-5 mol L(-1) H(+)). Analytical applicability of the CVG system was tested by the determination of Se(IV) in natural water samples certified reference materials, using 0.01 mol L(-1) TBAB in 0.5 M H2SO4. In order to explain this unexpected higher efficiency of amine boranes with respect of THB, the kinetic of hydrolysis of AB, TBAB and DMAB was investigated in acid media typically employed in chemical vapor generation for trace element determination. The kinetic was investigated by monitoring the rate the hydrogen gas evolved during hydrolysis, using a laboratory made thermostated reaction cell. Kinetics were measured for AB, TBAB and DMAB in 0.1, 0.5, 5 mol L(-1) HCl or HClO4 reaction media and in 0.1 mol L(-1) cysteine +0.1 mol L(-1) HCl or HClO4 buffer, for reaction times from 0 to 30 min. Under strongly acidic conditions, the rates of hydrogen evolution produced by amine boranes hydrolysis appear to be much slower than those predicted by a pseudo-first order reaction and using the rate constants reported in the literature. This suggests that, at elevated acidities (5 mol L(-1) HCl or HClO4), the hydrolysis of amine boranes takes place in two steps, generating a first amount of H2 (0.67-1.15 mol) much faster than the remaining about 2 mol. This evidence indicates a different mechanism of hydrolysis to the one accepted in the literature for amine boranes. The relatively high efficiencies of H2Se observed with amine borane reduction of inorganic Se(IV) at elevated

  19. Polyoxometalate oxidation of non-phenolic lignin subunits in water : effect of substrate structure on reaction kinetics

    Science.gov (United States)

    Tomoya Yokoyama; Hou-min Chang; Richard S. Reiner; Raja H. Atalla; Ira A. Weinstock; John F. Kadla

    2004-01-01

    The effect of lignin-biopolymer structure on the mechanism of its oxidative depolymerization by polyoxometalates (POMs) was investigated by reacting an equilibrated POM ensemble with a series of ring-substituted benzyl alcohols. Under anaerobic conditions in mixed water/methanol, observed pseudo-first order reaction rates (150°C) of 8.96 x 10–3 and 4.89 x 10–3 sec–1...

  20. 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....

  1. Stability of an anti-stroke peptide: driving forces and kinetics in chemical degradation.

    Science.gov (United States)

    Li, Rui; Wang, Fengzhen; Chen, Li; Zhu, Shuning; Wu, Lin; Jiang, Sunmin; Xu, Qunwei; Zhu, Dongya

    2014-09-10

    NR2B9c (Lys-Leu-Ser-Ser-Ile-Glu-Ser-Asp-Val) is a 9-amino acid peptide that has been illustrated to be a potential anti-stroke drug. For more effective treatment, suitable drug delivery systems should be developed. However, little is known about the stability of NR2B9c which is essential to its formulation. In this study, a reversed-phase high-performance liquid chromatography (HPLC) was applied to study the forced degradation behavior and stability of NR2B9c. HPLC studies were performed with an C8 column using a mobile phase consisting of acetonitrile (14.5:85.5, v/v) and aqueous solution (0.1% trifluoroacetic acid (TFA) and 0.05 M KH2PO4). The flow rate and the wavelength set during HPLC detection were 1.0 mL/min and 205 nm, respectively. The degradation pattern of NR2B9c aqueous solution followed pseudo first-order kinetics. The degradation rate at pH 7.5 was the slowest according to the plotting V-shaped pH-rate profile. The influence of temperature on the rate of reactions was interpreted in terms of Arrhenius equation (r(2)>0.98). Thermodynamic parameters were calculated based on Eyring equation (r(2)>0.98). The concentrations of drug, buffer species, buffer concentrations, oxidation and organic solvents have noticeable effects on the degradation of NR2B9c while ultrasound shows little impact under the experimental conditions. In a word, this study may give a detailed description of stability of NR2B9c. Copyright © 2014. Published by Elsevier B.V.

  2. Thermal stability and degradation kinetics of polyphenols and polyphenylenediamines enzymatically synthesized by horseradish peroxidase

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hansol; Ryu, Keungarp [University of Ulsan, Ulsan (Korea, Republic of); Kwon, Oyul [Seoul National University of Science and Technology, Seoul (Korea, Republic of)

    2015-09-15

    Various substituted phenols and phenylenediamines were enzymatically polymerized by horseradish peroxidase in 80% (v/v) organic solvents-aqueous buffer (100 mM sodium acetate, pH 5) mixtures with H{sub 2}O{sub 2} as the oxidant. The thermal stability of the polymers was investigated by thermogravimetric analysis (TGA) and represented by the char yield (wt% of the initial polymer mass) after being heated at 800 .deg. C. Poly(p-phenylphenol) had the highest thermal stability among the synthesized polymers with a char yield of 47 wt%. The polymers containing amino groups such as poly(p-aminophenol) and polyphenylenediamines were also shown to possess high thermal stabilities. The activation energies for the thermal degradation of the polymers determined by derivative thermogravimetric analysis (DTG) using Horowitz-Metzger's pseudo-first-order kinetics were in the range between 23-65 kJ/mol and comparable to those of the chemically synthesized polymers. Dynamic structural changes of the enzymatically synthesized polymers upon heating were studied by differential scanning calorimetry (DSC). The DSC curves of poly(p-phenylphenol) showed a broad exothermic peaks between 150-250 .deg. C, indicating that the polymer undergoes complex structural transitions in the temperature range. On the other hand, the DSC curves of the poly(p-aminophenol) and the poly(p-phenylenediamine) which contain amino groups showed strong sharp endothermic peaks near 150 .deg. C, implying that these polymers possess homogeneous oriented structures which undergo a concerted structural disintegration upon heating.

  3. Using a CBL Unit, a Temperature Sensor, and a Graphing Calculator to Model the Kinetics of Consecutive First-Order Reactions as Safe In-Class Demonstrations

    Science.gov (United States)

    Moore-Russo, Deborah A.; Cortes-Figueroa, Jose E.; Schuman, Michael J.

    2006-01-01

    The use of Calculator-Based Laboratory (CBL) technology, the graphing calculator, and the cooling and heating of water to model the behavior of consecutive first-order reactions is presented, where B is the reactant, I is the intermediate, and P is the product for an in-class demonstration. The activity demonstrates the spontaneous and consecutive…

  4. Kinetic removal of haloacetonitrile precursors by photo-based advanced oxidation processes (UV/H2O2, UV/O3, and UV/H2O2/O3).

    Science.gov (United States)

    Srithep, Sirinthip; Phattarapattamawong, Songkeart

    2017-06-01

    The objective of the study is to evaluate the performance of conventional treatment process (i.e., coagulation, flocculation, sedimentation and sand filtration) on the removals of haloacetonitrile (HAN) precursors. In addition, the removals of HAN precursors by photo-based advanced oxidation processes (Photo-AOPs) (i.e., UV/H2O2, UV/O3, and UV/H2O2/O3) are investigated. The conventional treatment process was ineffective to remove HAN precursors. Among Photo-AOPs, the UV/H2O2/O3 was the most effective process for removing HAN precursors, followed by UV/H2O2, and UV/O3, respectively. For 20min contact time, the UV/H2O2/O3, UV/H2O2, and UV/O3 suppressed the HAN formations by 54, 42, and 27% reduction. Increasing ozone doses from 1 to 5 mgL-1 in UV/O3 systems slightly improved the removals of HAN precursors. Changes in pH (6-8) were unaffected most of processes (i.e., UV, UV/H2O2, and UV/H2O2/O3), except for the UV/O3 system that its efficiency was low in the weak acid condition. The pseudo first-order kinetic constant for removals of dichloroacetonitrile precursors (k'DCANFP) by the UV/H2O2/O3, UV/H2O2 and standalone UV systems were 1.4-2.8 orders magnitude higher than the UV/O3 process. The kinetic degradation of dissolved organic nitrogen (DON) tended to be higher than the k'DCANFP value. This study firstly differentiates the kinetic degradation between DON and HAN precursors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. A kinetic study of the oxidation by molecular oxygen of the cytochrome chain of intact yeast cells, Acetobacter suboxydans cells, and of particulate suspensions of heart muscle.

    Science.gov (United States)

    Ludwig, G D; Kuby, S A; Edelman, G M; Chance, B

    1983-01-01

    The pre-steady state kinetics of the cytochrome c oxidase reaction with oxygen were studied by a variation in the reaction time between approximately 6 and 25 ms at oxygen concentrations less than 6 mumol/l. For baker's yeast, a pseudo-first-order velocity constant of approximately 150 s-1 at 1.3 mumol/l O2 was obtained corresponding to a second-order reaction between O2 and a3 at a forward velocity constant (k+1) of approximately 3 X 10(7) liter equiv.-1s-1. Thus, the membrane-bound oxidase in the intact cell exhibits one of the most rapid enzyme-substrate reactions to be reported. The value is identical with that of Greenwood and Gibson on an isolated, solubilized cytochrome c oxidase. Similar values of k+1 are calculated from the turnover numbers [k+2 (a+2)] divided by the Km values (formula; see text) measured for these yeast preparations, which points to an almost negligible reverse reaction (k-1) compared to k+2(a+2). Similar calculations for the membrane-bound cytochrome c oxidase of heart muscle give a value of k+1 approximately equal to 10(7) liter equiv.-1s-1. The concordance of the different values of k+1 supports the view that the yeast cell wall does not impart a significant diffusion barrier to the transport of molecular oxygen. In contrast, Acetobacter suboxydans exhibits a much larger value for Km, and has a terminal oxidase of different kinetic parameters.

  6. Influence of organic acids on kinetic release of chromium in soil contaminated with leather factory waste in the presence of some adsorbents.

    Science.gov (United States)

    Taghipour, Marzieh; Jalali, Mohsen

    2016-07-01

    In this study, batch experiments were conducted to investigate the effects of nanoparticles (NPs) (MgO, ZnO, TiO2) and clay minerals (bentonite, zeolite) on the release of chromium (Cr) from leather factory waste (LFW) and LFW treated soil using organic acids. Chromium release from all treatments was studied in the presence of citric acid, oxalic acid and CaCl2 solutions. The results showed that, in all treatments, organic acids released more Cr than inorganic salt (CaCl2). The release of Cr by citric acid was higher than that by oxalic acid. In LFW treated soil and LFW, the release of Cr from the all treatments with NPs was less than that from the clay mineral treatments. On the other hand, in the presence of organic acids, Cr release by NPs and clay minerals decreased. Two kinetic models including pseudo-first- and pseudo-second-order model were tested to describe the time dependent Cr release data. Among the kinetic models used, the pseudo-second-order model generally gave the best fits to experimental data. Before and after release experiments, Cr in LFW, treated LFW, control soil and LFW treated soils were fractionated. In all treatments, the greatest amounts of Cr were found in the residual fraction (RES). The organic acids were effective in reducing the exchangeable (EXC), bound to organic matter (OM) and bound to carbonate (CAR) fractions of Cr in all treatments, whereas, after release of Cr from treated soils, Cr remained mainly in the RES fraction. The application of NPs and clay minerals in soil led to a significant transformation of Cr from mobile fractions to the RES fraction. Therefore, organic ligands played a dominant role in mobility and bioavailability of Cr and the removal of Cr by adsorbents. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Changes in the Kinetics of Uranium(VI) Sorption Reactions to Mineral Surfaces in the Presence of Fulvic Acid

    Science.gov (United States)

    Honeyman, B. D.; Tinnacher, R. M.

    2010-12-01

    In this study, we investigate changes in the kinetics of uranium(VI) sorption reactions to silica sand due to the presence of fulvic acid, a recalcitrant natural organic matter fraction. On the field scale, local contact times between metal contaminants and bulk mineral phases may often be too short to attain full sorption equilibria. Hence, kinetic limitations for surface reactions need to be included in predictive transport models. Natural organic matter is ubiquitous in the environment and can substantially influence metal sorption and transport behavior in saturated porous media. However, at this point little is known about potential effects of organic matter on metal sorption kinetics. Therefore, we investigated the kinetics of uranium(VI) (U(VI)) sorption onto a pretreated silica sand in the absence and presence of fulvic acid in lab-scale experiments. Furthermore, experimental data were simulated in pseudo-first order kinetic models in order to determine the characteristic times for U(VI) sorption reactions under various chemical conditions. Last, speciation modeling allowed for a qualitative assessment of dominant U(VI) solution species as a function of organic ligand concentrations and pH. Results indicate that U(VI) surface reactions are slowed down in the presence of low concentrations of fulvic acid (0.4 and 4.3 mg/l TOC), at conditions where U(VI)-fulvic acid solution complexes can be neglected. This kinetic behavior can be attributed to the competition of U(VI) and fulvic acid for a limited number of fast-sorbing surface sites. In contrast, metal sorption reactions seem to be faster relative to the binary metal-mineral system at a high FA concentration (26 mg/l TOC) and pH conditions where a substantial fraction of U(VI)-FA solution complexes is expected. In this case, U(VI) and fulvic acid sorption kinetics appear to be very similar, which suggests the formation of ternary U(VI)-FA-surface complexes. Hence, kinetic sorption data indicate a change in

  8. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Science.gov (United States)

    Al-Rubaiey, Najem A.; Walsh, Robin

    2017-03-01

    Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann

  9. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Directory of Open Access Journals (Sweden)

    Al-Rubaiey Najem A.

    2017-01-01

    Full Text Available Silylenes (silanediyls have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2 are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using

  10. Aqueous photochemical degradation of hydroxylated PAHs: Kinetics, pathways, and multivariate effects of main water constituents

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Linke; Na, Guangshui [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Chen, Chang-Er [Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ (United Kingdom); Li, Jun [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); College of Marine Science, Shanghai Ocean University, Shanghai 201306 (China); Ju, Maowei; Wang, Ying; Li, Kai [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Zhang, Peng, E-mail: pzhang@nmemc.org.cn [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China); Yao, Ziwei [Key Laboratory for Ecological Environment in Coastal Areas (SOA), National Marine Environmental Monitoring Center, Dalian 116023 (China)

    2016-03-15

    Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are contaminants of emerging concern in the aquatic environment, so it is of great significance to understand their environmental transformation and toxicity. This study investigated the aqueous photochemical behavior of four OH-PAHs, 9-Hydroxyfluorene (9-OHFL), 2-Hydroxyfluorene, 9-Hydroxyphenanthrene and 1-Hydroxypyrene, under simulated sunlight irradiation (λ > 290 nm). It was observed that their photodegradation followed the pseudo-first-order kinetics. Based on the determined quantum yields, their calculated solar apparent photodegradation half-lives in surface waters at 45° N latitude ranged from 0.4 min for 9-Hydroxyphenanthrene to 7.5 × 10{sup 3} min for 9-OHFL, indicating that the OH-PAHs would intrinsically photodegrade fast in sunlit surface waters. Furthermore, 9-OHFL as an example was found to undergo direct photolysis, and self-sensitized photooxidation via ·OH rather than {sup 1}O{sub 2} in pure water. The potential photoreactions involved photoinduced hydroxylation, dehydrogenation and isomerization based on product identification by GC–MS/MS. 9-OHFL photodegraded slower in natural waters than in pure water, which was attributed to the integrative effects of the most photoreactive species, such as Fe(III), NO{sub 3}{sup −}, Cl{sup −} and humic acid. The photomodified toxicity was further examined using Vibrio fischeri, and it was found that the toxicity of photolyzed 9-OHFL did not decrease significantly (p > 0.05) either in pure water or in seawater, implying the comparable or higher toxicity of some intermediates. These results are important for assessing the fate and risks of OH-PAHs in surface waters. - Graphical abstract: Aqueous photochemical behavior of 4 hydroxylated PAHs is first reported on revealing the kinetics, mechanisms, toxicity, and multivariate effects of water constituents. - Highlights: • It is first reported on aqueous photochemical behavior of 4 hydroxylated

  11. Time-dependent kinetic complexities in cholinesterase-catalyzed reactions.

    Science.gov (United States)

    Masson, P

    2012-10-01

    Cholinesterases (ChEs) display a hysteretic behavior with certain substrates and inhibitors. Kinetic cooperativity in hysteresis of ChE-catalyzed reactions is characterized by a lag or burst phase in the approach to steady state. With some substrates damped oscillations are shown to superimpose on hysteretic lags. These time dependent peculiarities are observed for both butyrylcholinesterase and acetylcholinesterase from different sources. Hysteresis in ChE-catalyzed reactions can be interpreted in terms of slow transitions between two enzyme conformers E and E'. Substrate can bind to E and/or E', both Michaelian complexes ES and Ε'S can be catalytically competent, or only one of them can make products. The formal reaction pathway depends on both the chemical structure of the substrate and the type of enzyme. In particular, damped oscillations develop when substrate exists in different, slowly interconvertible, conformational, and/or micellar forms, of which only the minor form is capable of binding and reacting with the enzyme. Biphasic pseudo-first-order progressive inhibition of ChEs by certain carbamates and organophosphates also fits with a slow equilibrium between two reactive enzyme forms. Hysteresis can be modulated by medium parameters (pH, chaotropic and kosmotropic salts, organic solvents, temperature, osmotic pressure, and hydrostatic pressure). These studies showed that water structure plays a role in hysteretic behavior of ChEs. Attempts to provide a molecular mechanism for ChE hysteresis from mutagenesis studies or crystallographic studies failed so far. In fact, several lines of evidence suggest that hysteresis is controlled by the conformation of His438, a key residue in the catalytic triad of cholinesterases. Induction time may depend on the probability of His438 to adopt the operative conformation in the catalytic triad. The functional significance of ChE hysteresis is puzzling. However, the accepted view that proteins are in equilibrium between

  12. An application of second-order UV-derivative spectrophotometry for study of solvolysis of a novel fluocinolone acetonide ester.

    Science.gov (United States)

    Markovic, Bojan; Vladimirov, Sote; Cudina, Olivera; Savic, Vladimir; Karljikovic-Rajic, Katarina

    2010-02-01

    A novel topical corticosteroid FA-21-PhP, 2-phenoxypropionate ester of fluocinolone acetonide, has been synthesized in order to investigate the possibility of decreasing systemic side effects. In this study model system for in vitro solvolytic reaction of FA-21-PhP has been analyzed in ethanol/water (90:10, v/v) with excess of sodium hydrogen carbonate. The selected conditions have been used as in vitro model for activation of corticosteroid C-21 ester prodrug. The second-order derivative spectrophotometric method (DS) using zero-crossing technique was developed for monitoring ternary mixture of solvolysis. Fluocinolone acetonide (FA) as a solvolyte was determined in the mixture in the concentration range 0.062-0.312 mM using amplitude (2)D(274.96). Experimentally determined LOD value was 0.0295 mM. The accuracy of proposed DS method was confirmed with HPLC referent method. Peak area of parent ester FA-21-PhP was used for solvolysis monitoring to ensure the initial stage of changes. Linear relationship in HPLC assay for parent ester was obtained in the concentration range 0.054-0.54 mM, with experimentally determined LOD value of 0.0041 mM. Investigated solvolytic reaction in the presence of excess of NaHCO(3) proceeded via a pseudo-first-order kinetic with significant correlation coefficients 0.9891 and 0.9997 for DS and HPLC, respectively. The values of solvolysis rate constant calculated according to DS and HPLC methods are in good accordance 0.038 and 0.043 h(-1), respectively. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  13. 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

  14. Enhanced debromination of decabrominated diphenyl ether in aqueous solution by attapulgite supported Fe/Ni bimetallic nanoparticles: kinetics and pathways

    Science.gov (United States)

    Liu, Zongtang; Gu, Chenggang; Bian, Yongrong; Jiang, Xin; Sun, Yufeng; Fei, Zhenghao; Dai, Jingtao

    2017-08-01

    In this study, Fe/Ni bimetallic nanoparticles were supported on the attapulgite (A-Fe/Ni) to enhance the degradation reactivity of decabrominated diphenyl ether (BDE209) in aqueous solution. The Fe/Ni nanoparticles were well distributed on the attapulgite surface with an average diameter of 20-40 nm. The removal percentage of BDE209 by A-Fe/Ni was 1.59 times higher than Fe/Ni nanoparticles alone because attapulgite could act as supporting material to disperse Fe/Ni nanoparticles and prevent Fe/Ni nanoparticles from aggregation. The degradation kinetics for BDE209 debromination by A-Fe/Ni could be well described by a pseudo-first-order model, and the debromination rate constant of BDE209 increased with increasing the dosage of A-Fe/Ni, water/THF ratio, and decreasing the initial BDE209 concentration and solution pH. The degradation products were identified using a third-order polynomial regression equation between the experimental and reference gas chromatography relative retention times. Stepwise debromination from n-bromo-DE to (n  -  1)-bromo-DE was a possible pathway with bromines being substituted sequentially by hydrogen. The preferred elimination of bromines of BDE209 by A-Fe/Ni followed the debromination preference of para-Br  >  meta-Br  >  ortho-Br. The results provide evidences for understanding the debromination mechanism of polybrominated diphenyl ether by clay-supported Fe/Ni nanoparticles.

  15. Insights of ibuprofen electro-oxidation on metal-oxide-coated Ti anodes: Kinetics, energy consumption and reaction mechanisms.

    Science.gov (United States)

    Wang, Chong; Yu, Yanxin; Yin, Lifeng; Niu, Junfeng; Hou, Li-An

    2016-11-01

    Electrochemical degradation of ibuprofen (IBP) was performed on three types of Ti-based metal oxide electrodes. The degradation of IBP followed pseudo-first-order kinetics and the electrochemical degradation rate constant (k) over Ti/SnO2-Sb/Ce-PbO2 (9.4 × 10(-2) min(-1)) was 2.0 and 1.7 times of the values over Ti/Ce-PbO2 (4.7 × 10(-2) min(-1)) and Ti/SnO2-Sb (5.6 × 10(-2) min(-1)), respectively. The removal of total organic carbon and the energy consumption per order for IBP degradation were 93.2% and 13.1 Wh L(-1), respectively, under the optimal conditions using Ti/SnO2-Sb/Ce-PbO2 anode. Six aromatic intermediate products of IBP were identified by ultra-high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. The electrochemical mineralization mechanism of IBP was proposed. It was supposed that OH radicals produced on the surface of anode attacked IBP to form hydroxylated IBP derivatives that were then followed by a series of hydroxylation, loss of isopropanol and isopropyl, decarboxylation and benzene ring cleavage processes to form simple linear carboxylic acids. By successive hydroxylation, these carboxylic acids were then oxidized to CO2 and H2O, achieving the complete mineralization of IBP. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Biosorption of chromium(III) by two Brown algae macrocystis pyrifera and undaria pinnatifida: equilibrium and kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Cazon, Josefina Plaza H.; Benitez, Leonardo; Donati, Edgardo; Viera, Marisa [Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115 (1900) La Plata (Argentina)

    2012-02-15

    Two brown algae, Macrocystis pyrifera and Undaria pinnatifida, were employed to remove Cr(III) from aqueous solutions. Both seaweeds were characterized in terms of alginate yields. The alginate contents were 20 and 30% of the dry weight for M. pyrifera and U. pinnatifida, respectively. Kinetics experiments were carried out at different initial pH values. Cr(III) biosorption was affected by the solution pH. The highest metal uptake was found at pH 4 for both biosorbents. Different models were applied to elucidate the rate-controlling mechanism: pseudo-first-order, pseudo-second-order, external mass transfer and intra-particle diffusion. The application of Langmuir, Freundlich and Dubinin-Radushkevich models to the equilibrium data showed a better fitting to the first model. The maximum Cr(III) sorption capacity (q{sub m}) and the affinity coefficient (b) were very similar for both biosorbents: 0.77 mmol/g and 1.20 L/mmol for M. pyrifera and 0.74 mmol/g and 1.06 L/mmol for U. pinnatifida. The free energy of the sorption process was estimated using the Dubinin-Radushkevich isotherm. The values indicate that the processes are chemical sorptions. To evaluate the significance of the ion-exchange mechanism, the light metals (Ca{sup 2+}, Na{sup +}, Mg{sup 2+} and K{sup +}) and pH were measured during the experiments. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Novel modulation of drug delivery using binary zinc-alginate-pectinate polyspheres for zero-order kinetics over several days: experimental design strategy to elucidate the crosslinking mechanism.

    Science.gov (United States)

    Pillay, Viness; Danckwerts, Michael P; Muhidinov, Zayniddin; Fassihi, Reza

    2005-01-01

    A Box-Behnken design was applied to mathematically establish whether different degrees of crosslinking were induced by Zn2+ and Ca2+ ions in polyspheres composed of alginate and/or pectin, and the model drug ibuprofen. Based on their different crystal structures and coordination numbers, a theoretical model was proposed demonstrating that Zn2+ ions preferentially crosslink alginate and pectin. In addition, the lower coordination number of Zn2+ (4-6) would significantly retard hydration of both polymers, as opposed to Ca2+ (7-9). The responses studied for 28 statistically derived polyspheres included drug encapsulation efficiency, physicomechanical behavior, and in vitro drug release potential. Single-tailed Student's t-tests on data generated for the encapsulation efficiencies, primary facture values, and rupture energies indicated that Zn2+ was statistically superior (pDurbin-Watson statistic and correlation coefficient revealed that the quadratic regression function was highly accurate in predicting the responses. Using a generalized reduced gradient algorithm on dissolution values obtained after 2 hours (t2h) provided optimized solutions for achieving zero-order release extending from 2 hours to 7 days. Mathematical simulations projected drug release from 25 to 50 days.

  18. Electrocatalytic mechanism and kinetics of SOMs oxidation on ordered PtPb and PtBi intermetallic compounds: DEMS and FTIRS study.

    Science.gov (United States)

    Wang, Hongsen; Alden, Laif; Disalvo, F J; Abruña, Héctor D

    2008-07-07

    The electrocatalytic activities and mechanisms of PtPb and PtBi ordered intermetallic phases towards formic acid, formaldehyde and methanol oxidation have been studied by DEMS and FTIRS, and the results compared to those for a pure polycrystalline platinum electrode. While PtPb exhibits an enhanced electrocatalytic activity for the oxidation of all three organic molecules when compared to a Pt electrode, PtBi exhibits an enhanced catalytic activity towards formic acid and formaldehyde oxidation, but not methanol. FTIRS data indicate that adsorbed CO does not form on PtPb or PtBi intermetallic compounds during the oxidation of formic acid, formaldehyde and methanol, and therefore their oxidation on both PtPb and PtBi intermetallic compounds proceeds via a non-CO(ads) pathway. Quantitative DEMS measurements indicate that only CO(2) was detected as a final product during formic acid oxidation on Pt, PtPb and PtBi electrodes. At a smooth polycrystalline platinum electrode, the oxidation of formaldehyde and methanol produces mainly intermediates (formaldehyde and formic acid), while CO(2) is a minor product. In contrast, CO(2) is the major product for formaldehyde and methanol oxidation at a PtPb electrode. The high current efficiency of CO(2) formation for methanol and formaldehyde oxidation at a PtPb electrode can be ascribed to the complete dehydrogenation of formaldehyde and formic acid due to electronic effects. The low onset potential, high current density and high CO(2) yield make PtPb one of the most promising electrocatalysts for fuel cell applications using small organic molecules as fuels.

  19. Application of activated carbon derived from 'waste' bamboo culms for the adsorption of azo disperse dye: kinetic, equilibrium and thermodynamic studies.

    Science.gov (United States)

    Wang, Lianggui

    2012-07-15

    The utilization of activated carbon derived from 'waste' bamboo culms (BAC) for the removal of Disperse Red 167 (DR167), an azo disperse dye, was investigated. Studies of the properties of the adsorbent, the effect of contact time, the initial pH of the solution, the initial concentration of the dye solution and temperature indicated that a low initial pH or concentration of dye solution favors the adsorption process; temperature exerts a greater effect on the removal of azo disperse red 167 dye from aqueous solution. Kinetic and isotherm data were fitted to five non-linear kinetic and nine non-linear isotherm equations. In addition, the fits were evaluated in terms of the non-linear coefficient, Chi-square test, Marquardt's percent standard deviation error function and small-sample-corrected Akaike Information Criterion (AICc) methodology. The results showed that the AICc analysis was the best statistical tool for analyzing the data, the intra-particle diffusion and the pseudo-first-order models played important roles in the controlling rate step, and the Temkin equation best described the BAC isotherm data. Furthermore, the thermodynamic analysis indicated that the adsorption was a spontaneous, endothermic, entropy-increasing and physical process. Two types of commercial activated carbon, Filtrasorb 400 and Filtrasorb (F400 and F300), were used as contrast adsorbents. The contrast experiments revealed that BAC exhibits similar properties to F400 and F300. The utilization of bamboo wastes as carbon precursors is feasible. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. New Dihydro OO′Bis(Salicylidene) 2,2′ Aminobenzothiazolyl Borate Complexes: Kinetic and Voltammetric Studies of Dimethyltin Copper Complex with Guanine, Adenine, and Calf Thymus DNA

    Science.gov (United States)

    Arjmand, Farukh; Mohani, Bhawana; Parveen, Shamima

    2006-01-01

    The newly synthesized ligand, dihydro OO′bis(salicylidene) 2,2′ aminobenzothiazolyl borate (2), was derived from the reaction of Schiff base of 2-aminobenzothiazole and salicylaldehyde with KBH4. CuII (3) and ZnII (4) complexes of (2) were synthesized and further metallated with dimethyltindichloride to yield heterobimetallic complexes (5) and (6). All complexes have been thoroughly characterized by elemental analysis, and IR, NMR, EPR, and UV-Vis spectroscopy and conductance measurements. The spectroscopic data support square planar environment around the CuII atom, while the SnIV atom acquires pentacoordinate geometry. The interaction of complex (5) with guanine, adenine, and calf thymus DNA was studied by spectrophotometric, electrochemical, and kinetic methods. The absorption spectra of complex (5) exhibit a remarkable “hyperchromic effect” in the presence of guanine and calf thymus DNA. Indicative of strong binding of the complex to calf thymus DNA preferentially binds through N7 position of guanine base, while the adenine shows binding to a lesser extent. The kinetic data were obtained from the rate constants, kobs, values under pseudo-first-order conditions. Cyclic voltammetry was employed to study the interaction of complex (5) with guanine, adenine, and calf thymus DNA. The CV of complex (5) in the absence and in the presence of guanine and calf thymus DNA altered drastically, with a positive shift in formal peak potential Epa and Epc values and a significant increase in peak current. The positive shift in formal potentials with increase in peak current favours strong interaction of complex (5) with calf thymus DNA. The net shift in E 1/2 has been used to estimate the ratio of equilibrium constants for the binding of Cu(II) and Cu(I) complexes to calf thymus DNA. PMID:17497007

  1. New Dihydro OO'Bis(Salicylidene) 2,2' Aminobenzothiazolyl Borate Complexes: Kinetic and Voltammetric Studies of Dimethyltin Copper Complex with Guanine, Adenine, and Calf Thymus DNA.

    Science.gov (United States)

    Arjmand, Farukh; Mohani, Bhawana; Parveen, Shamima

    2006-01-01

    The newly synthesized ligand, dihydro OO'bis(salicylidene) 2,2' aminobenzothiazolyl borate (2), was derived from the reaction of Schiff base of 2-aminobenzothiazole and salicylaldehyde with KBH(4). Cu(II) (3) and Zn(II) (4) complexes of (2) were synthesized and further metallated with dimethyltindichloride to yield heterobimetallic complexes (5) and (6). All complexes have been thoroughly characterized by elemental analysis, and IR, NMR, EPR, and UV-Vis spectroscopy and conductance measurements. The spectroscopic data support square planar environment around the Cu(II) atom, while the Sn(IV) atom acquires pentacoordinate geometry. The interaction of complex (5) with guanine, adenine, and calf thymus DNA was studied by spectrophotometric, electrochemical, and kinetic methods. The absorption spectra of complex (5) exhibit a remarkable "hyperchromic effect" in the presence of guanine and calf thymus DNA. Indicative of strong binding of the complex to calf thymus DNA preferentially binds through N(7) position of guanine base, while the adenine shows binding to a lesser extent. The kinetic data were obtained from the rate constants, k(obs), values under pseudo-first-order conditions. Cyclic voltammetry was employed to study the interaction of complex (5) with guanine, adenine, and calf thymus DNA. The CV of complex (5) in the absence and in the presence of guanine and calf thymus DNA altered drastically, with a positive shift in formal peak potential E(pa) and E(pc) values and a significant increase in peak current. The positive shift in formal potentials with increase in peak current favours strong interaction of complex (5) with calf thymus DNA. The net shift in E(1/2) has been used to estimate the ratio of equilibrium constants for the binding of Cu(II) and Cu(I) complexes to calf thymus DNA.

  2. 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.

  3. Sorption of Th(IV) onto ZnO nanoparticles and diatomite-supported ZnO nanocomposite. Kinetics, mechanism and activation parameters

    Energy Technology Data Exchange (ETDEWEB)

    Yusan, Sabriye; Aslani, Mahmut A.A.; Aytas, Sule [Ege Univ., Izmir (Turkey). Inst. of Nuclear Sciences; Bampaiti, Anastasia; Noli, Fotini [Aristotle University of Thessaloniki (Greece). Dept. of Chemistry; Erenturk, Sema [Istanbul Technical Univ., Ayazaga Campus, Maslak-Istanbul (Turkey). Energy Inst.

    2016-11-01

    In this study, for the first time ZnO nanoparticles and diatomite-supported ZnO nanocomposite have been utilized as adsorbent for the removal of Th(IV) ions from aqueous solutions under different experimental conditions. The Langmuir, Freundlich, Temkin and Dubinin- Radushkevich (D-R) isotherms were used to analyze the equilibrium data. The sorption equilibrium data were fitted well to the Langmuir isotherm with maximum sorption capacities values was found to be 1.105 mmol/g and 0.320 mmol/g for ZnO nanoparticles and diatomite supported ZnO nanocomposite, respectively. Pseudo-first and pseudo-second order equations, Intraparticle diffusion and Bangham's models were considered to evaluate the rate parameters and sorption mechanism. Sorption kinetics were better reproduced by the pseudo-second order model (R{sup 2} > 0.999), with an activation energy (E{sub a}) of +99.74 kJ/mol and +62.95 kJ/mol for ZnO nanoparticles and diatomite-supported ZnO nanocomposite, respectively. In order to specify the type of sorption reaction, thermodynamic parameters were also determined. The evaluated ΔG* and ΔH* indicate the non-spontaneous and endothermic nature of the reactions. The results of this work suggest that both of the used materials are fast and effective adsorbents for removing Th(IV) from aqueous solutions and chemical sorption plays a role in controlling the sorption rate.

  4. Selective reduction of Cr(VI) in chromium, copper and arsenic (CCA) mixed waste streams using UV/TiO2 photocatalysis

    National Research Council Canada - National Science Library

    Zheng, Shan; Jiang, Wenjun; Rashid, Mamun; Cai, Yong; Dionysiou, Dionysios D; O'Shea, Kevin E

    2015-01-01

    .... The reduction follows pseudo-first order kinetics and increases with decreasing solution pH. Saturation of the reaction solution with argon during UV/TiO2 photocatalysis had no significant effect on the Cr(VI...

  5. Determination of Rate Constants for Ouabain Inhibition of Adenosine Triphosphatase: An Undergraduate Biological Chemistry Laboratory Experiment

    Science.gov (United States)

    Sall, Eri; And Others

    1978-01-01

    Describes an undergraduate biological chemistry laboratory experiment which provides students with an example of pseudo-first-order kinetics with the cardiac glycoside inhibition of mammalism sodium and potassium transport. (SL)

  6. Kinetics of decolorization of azo dye by bipolar pulsed barrier discharge in a three-phase discharge plasma reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ruobing [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)]. E-mail: zrbingdut@163.com; Zhang Chi [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Cheng Xingxin [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Wang Liming [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Wu Yan [Institute of Electrostatics and Special Power, Dalian University of Technology, Dalian 116024 (China); Guan Zhicheng [Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2007-04-02

    Removal of amaranth, a commercial synthetic azo dye widely used in the dye and food industry, was examined as a possible remediation technology for treating dye-contaminated water. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetition frequency, etc., on decolorization kinetics were investigated. Experimental results show that an aqueous solution of 24 mg/l dye is 81.24% decolorized following 30 min plasma treatment for a 50 kV voltage and 0.75 m{sup 3}/h gas flow rate. Decolorization reaction of amaranth in the plasma reactor is a pseudo first order reaction. Rate constant (k) of decolorization increases quickly with increasing the applied voltage, pulse repetition frequency and the gas flow rate. However, when the applied voltage is beyond 50 kV and increases further, increase rate of k decreases. In addition, k decreases quickly when the solution conductivity increases from 200 to 1481 {mu}S/cm. The decolorization reaction has a high rate constant (k = 0.0269 min{sup -1}) when the solution pH is beyond 10. Rate constant k decreases with the decrease of pH and reaches minimum at a pH of about 5 (k {sub min} = 0.01603 min{sup -1}), then increases to 0.02105 min{sup -1} when pH decreases to 3.07. About 15% of the initial TOC can be degraded only in about 120 min non-thermal plasma treatment.

  7. Kinetic comparison of two basic heterogenous catalysts obtained from sustainable resources for transesterification of waste cooking oil

    Directory of Open Access Journals (Sweden)

    G.R. Moradi

    2015-06-01

    Full Text Available Alkaline earth metal oxides are appropriate catalysts for biodiesel production and among them, CaO and MgO are known for possessing the best efficiency. In this study, catalysts synthesized from economical and sustainable resources were used for biodiesel production. More specifically, waste mussel shells and demineralized (DM water treatment precipitates as calcium and magnesium carbonate sources, were converted into calcium and magnesium oxides at temperatures above 900 oC. Methanol and waste cooking oil were reacted in a 250 mL two-necked flask at 24:1 and 22.5:1 ratios in presence of 12 and 9.08 wt% of mussel shell-based and DM water treatment precipitates-based catalysts, respectively. The effects of temperature (328, 333, 338, 343 and 348 K and time (1, 3, 5, 7 and 8 h at a stirrer speed of 350 rpm on the conversion of the oil into biodiesel were investigated. The results obtained indicated a pseudo-first order kinetics for the transesterification reaction using both catalysts. The activation energies in the presence of the DM water treatment precipitates and mussel shell catalysts were measured at 77.09 and 79.83 kJ.mol-1, respectively. Accordingly, the DM water treatment precipitates catalyst resulted in a faster reaction due to its lower activation energy value. Moreover, the catalysts were reused five times and the results obtained showed that the methanol-driven extraction of CaO contained in the DM water treatment precipitates catalyst was lower than the waste mussel shell catalyst proving the higher stability of the new heterogeneous catalyst i.e. the calcinated DM water treatment precipitates.

  8. A breakthrough biosorbent in removing heavy metals: Equilibrium, kinetic, thermodynamic and mechanism analyses in a lab-scale study

    Energy Technology Data Exchange (ETDEWEB)

    Abdolali, Atefeh [Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Broadway, NSW 2007 (Australia); Ngo, Huu Hao, E-mail: h.ngo@uts.edu.au [Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Broadway, NSW 2007 (Australia); Guo, Wenshan [Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Broadway, NSW 2007 (Australia); Lu, Shaoyong [Chinese Research Academy of Environmental Science, Beijing 100012 (China); Chen, Shiao-Shing; Nguyen, Nguyen Cong [Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd, Taipei 106, Taiwan (China); Zhang, Xinbo [Department of Environmental and Municipal Engineering, Tianjin Key Laboratory of Aquatic Science and Technology, Tianjin Chengjian University, Jinjing Road 26, Tianjin 300384 (China); Wang, Jie; Wu, Yun [School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387 (China)

    2016-01-15

    A breakthrough biosorbent namely multi-metal binding biosorbent (MMBB) made from a combination of tea wastes, maple leaves and mandarin peels, was prepared to evaluate their biosorptive potential for removal of Cd(II), Cu(II), Pb(II) and Zn(II) from multi-metal aqueous solutions. FTIR and SEM were conducted, before and after biosorption, to explore the intensity and position of the available functional groups and changes in adsorbent surface morphology. Carboxylic, hydroxyl and amine groups were found to be the principal functional groups for the sorption of metals. MMBB exhibited best performance at pH 5.5 with maximum sorption capacities of 31.73, 41.06, 76.25 and 26.63 mg/g for Cd(II), Cu(II), Pb(II) and Zn(II), respectively. Pseudo-first and pseudo-second-order models represented the kinetic experimental data in different initial metal concentrations very well. Among two-parameter adsorption isotherm models, the Langmuir equation gave a better fit of the equilibrium data. For Cu(II) and Zn(II), the Khan isotherm describes better biosorption conditions while for Cd(II) and Pb(II), the Sips model was found to provide the best correlation of the biosorption equilibrium data. The calculated thermodynamic parameters indicated feasible, spontaneous and exothermic biosorption process. Overall, this novel MMBB can effectively be utilized as an adsorbent to remove heavy metal ions from aqueous solutions. - Highlights: • A novel multi-metal binding biosorbent (MMBB) was studied. • The biosorption of Cd{sup 2+}, Cu{sup 2+}, Pb{sup 2+} and Zn{sup 2+} on MMBB was evaluated. • Hydroxyl, carbonyl and amine groups are involved in metal binding of MMBB. • Equilibrium data were presented and the best fitting models were identified. • The obtained results recommend this MMBB as potentially low-cost biosorbent.

  9. Photodegradation of the azole fungicide climbazole by ultraviolet irradiation under different conditions: Kinetics, mechanism and toxicity evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wang-Rong; Ying, Guang-Guo, E-mail: guang-guo.ying@gig.ac.cn; Zhao, Jian-Liang; Liu, You-Sheng; Hu, Li-Xin; Yao, Li; Liang, Yan-Qiu; Tian, Fei

    2016-11-15

    Highlights: • Climbazole (CZ) could be effectively degraded under UV-254 irradiation. • CZ underwent direct and self-sensitized photolysis involving ROS. • The main photodegradation by-products of CZ were identified and semi-quantitated. • Pathway includes hydroxylative dechlorination, dechlorination, and de-pinacolone. • The toxicity of the photodegradation system reduced after UV-254 irradiation. - Abstract: Climbazole (CZ) has been known to persist in various environmental media, and may cause potential risks to aquatic organisms. This study investigated the photodegradation of CZ by ultraviolet (UV, 254 nm) under different conditions. The results revealed that CZ could be effectively degraded in aqueous solutions under UV-254 irradiation with a half-life of 9.78 min (pH = 7.5), and the photodegradation followed pseudo-first-order kinetics. pH had almost no effect on its rate constants and quantum yields; but the water quality of natural waters could affect the photolysis of CZ, and the coexisting constituents such as Fe{sup 3+}, NO{sub 3}{sup −}, and HA obviously inhibited its photolysis. The addition of different radical scavengers also inhibited the photodegradation of CZ due to the reduction of reactive oxygen species (ROS). CZ underwent direct and self-sensitized photolysis involving ROS. Based on the identified photodegradation by-products, the proposed pathways included hydroxylative dechlorination, dechlorination and de-pinacolone. Moreover, toxicity evaluation using duckweed found significant toxicity reduction in the photodegradation system of CZ after the irradiation of UV-254, and the remaining by-products did not pose extra toxicity compared with CZ itself. These findings from present study suggest that CZ in effluent could be further reduced by applying UV photolysis treatment.

  10. Adsorption studies of molasse's wastewaters on activated carbon: modelling with a new fractal kinetic equation and evaluation of kinetic models.

    Science.gov (United States)

    Figaro, S; Avril, J P; Brouers, F; Ouensanga, A; Gaspard, S

    2009-01-30

    Adsorption kinetic of molasses wastewaters after anaerobic digestion (MSWD) and melanoidin respectively on activated carbon was studied at different pH. The kinetic parameters could be determined using classical kinetic equations and a recently published fractal kinetic equation. A linear form of this equation can also be used to fit adsorption data. Even with lower correlation coefficients the fractal kinetic equation gives lower normalized standard deviation values than the pseudo-second order model generally used to fit adsorption kinetic data, indicating that the fractal kinetic model is much more accurate for describing the kinetic adsorption data than the pseudo-second order kinetic model.

  11. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Kara, Ali, E-mail: akara@uludag.edu.tr [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey); Demirbel, Emel [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey); Tekin, Nalan [Kocaeli University, Faculty of Arts and Science, Department of Chemistry, 41380 Kocaeli (Turkey); Osman, Bilgen; Beşirli, Necati [Uludag University, Faculty of Arts and Science, Department of Chemistry, 16059 Bursa (Turkey)

    2015-04-09

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N{sub 2} adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  12. Kinetic energy budget details

    Indian Academy of Sciences (India)

    Abstract. This paper presents the detailed turbulent kinetic energy budget and higher order statistics of flow behind a surface-mounted rib with and without superimposed acoustic excitation. Pattern recognition technique is used to determine the large-scale structure magnitude. It is observed that most of the turbulence ...

  13. Kinetic Interface

    DEFF Research Database (Denmark)

    2009-01-01

    A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises.......A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises....

  14. Roles of reactive chlorine species in trimethoprim degradation in the UV/chlorine process: Kinetics and transformation pathways.

    Science.gov (United States)

    Wu, Zihao; Fang, Jingyun; Xiang, Yingying; Shang, Chii; Li, Xuchun; Meng, Fangang; Yang, Xin

    2016-11-01

    The UV/chlorine process, which forms several reactive species including hydroxyl radicals (HO) and reactive chlorine species (RCS) to degrade contaminants, is being considered to be an advanced oxidation process. This study investigated the kinetics and mechanism of the degradation of trimethoprim (TMP) by the UV/chlorine process. The degradation of TMP was much faster by UV/chlorine compared to UV/H2O2. The degradation followed pseudo first-order kinetics, and the rate constant (k') increased linearly as the chlorine dosage increased from 20 μM to 200 μM and decreased as pH rose from 6.1 to 8.8. k' was not affected by chloride and bicarbonate but decreased by 50% in the presence of 1-mg/L NOM. The contribution of RCS, including Cl, Cl2- and ClO, to the degradation removal rate was much higher than that of HO and increased from 67% to 87% with increasing pH from 6.1 to 8.8 under the experimental condition. The increasing contribution of RCS to the degradation with increasing pH was attributable to the increase in the ClO concentration. Kinetic modeling and radical scavenging tests verified that ClO mainly attacked the trimethoxybenzyl moiety of TMP. RCS reacted with TMP much faster than HOCl/OCl- to form chlorinated products (i.e., m/z 325) and chlorinated disinfection byproducts such as chloroform, chloral hydrate, dichloroacetonitrile and trichloronitromethane. The hydroxylation and demethylation of m/z 325 driven by HO generated m/z 327 and m/z 341. Meanwhile, reactions of m/z 325 with HO and RCS/HOCl/OCl- generated dichlorinated and hydroxylated products (i.e., m/z 377). All the chlorinated products could be further depleted to produce products with less degree of halogenation in the UV/chlorine process, compared to dark chlorination. The acute toxicity to Vibrio fischeri by UV/chlorine was lower than chlorination at the same removal rate of TMP. This study demonstrated the importance of RCS, in particular, ClO, in the degradation of micropollutants in the

  15. Kinetics and Mechanism of Mn(II Catalyzed Periodate Oxidation of p-anisidine: Effect of pH

    Directory of Open Access Journals (Sweden)

    Rajneesh Dutt Kaushik

    2014-10-01

    Full Text Available The stoichiometry for the initial part of the reaction, Mn(II catalysed periodate oxidation of p-anisidine (PMA, has been found to be 1 mol of PMA consuming 2 mol of periodate ion. The kinetic-mechanistic study of reaction in acetone-water medium was made spectrophotometrically by noting the increase in the absorbance of reaction intermediate. Reaction is first order in reactants and catalyst each. A decrease in dielectric constant of the medium results in decrease in the rate of reaction suggesting an ion-dipole type interaction. Free radical scavengers do not affect the reaction rate. A special type of rate-pH profile shows a maximum at pH = 7.0. This pH effect also suggests the involvement of at least three differently reactive reactant species in the reaction and this fact has been considered by us while deriv-ing the rate law. Under pseudo first order conditions [IO4-] >> [PMA] and in agreement with the derived rate law, the 1/kcat versus [H+] plot passes through the minimum and the results can be fitted to the equation: 1/kcat = (K2 / k K3 K4 [H+] + {(Kw + Kb K2 / k K3 K4 Kw} + Kb [H+] / k K3 K4 Kw, where kK3K4 is the empirical composite rate constant, Kw is ionic product of water, K2 is acid dissociation constant of H4IO6- and Kb is base dissociation constant of PMA. The experimental value of [H+]min is in good agreement with the value calculated by using the derived rate law equation and is character-istic of the substrate involved relating to the base dissociation constant of PMA. The value of thermo-dynamic parameters have been evaluated. © 2014 BCREC UNDIP. All rights reservedReceived: 2nd May 2014; Revised: 2nd July 2014; Accepted: 5th July 2014How to Cite: Kaushik, R.D., Singh, J., Manila, M., Kaur, M., Singh, P. (2014. Kinetics and Mechanism of MnII Catalyzed Periodate Oxidation of p-anisidine: Effect of pH. Bulletin of Chemical Reaction En-gineering & Catalysis, 9(3: 182-191. (doi: 10.9767/bcrec.9.3.6823.182-191Permalink

  16. Modeling the kinetics of vulcanization polydienes

    Directory of Open Access Journals (Sweden)

    V. I. Molchanov

    2013-01-01

    Full Text Available A model of vulcanization kinetics, which allows describing the kinetic curves of any form and on the basis of economical laboratory experiment analytically evaluate the kinetics of isothermal curing was proposed. In studying the kinetics of vulcanization, we assumed that the individual stages of the vulcanization process differ significantly speed and to determine the parameters on reometric curve isolated several areas. It allows to describe the process of a set of simple coupled first and second order vulcanization reactions.

  17. Understanding the role of clay minerals in the chromium(VI) bioremoval by Pseudomonas aeruginosa CCTCC AB93066 under growth condition: microscopic, spectroscopic and kinetic analysis.

    Science.gov (United States)

    Kang, Chunxi; Wu, Pingxiao; Li, Yuewu; Ruan, Bo; Li, Liping; Tran, Lytuong; Zhu, Nengwu; Dang, Zhi

    2015-11-01

    Laboratory batch experiments were conducted to investigate the role of clay minerals, e.g., kaolinite and vermiculite, in microbial Cr(VI) reduction by Pseudomonas aeruginosa under growth condition in glucose-amended mediums as a method for treating Cr(VI)-contaminated subsurface environment such as soil. Our results indicated that glucose could acted as an essential electron donor, and clay minerals significantly enhanced microbial Cr(VI) reduction rates by improving the consumption rate of glucose and stimulating the growth and propagation of P. aeruginosa. Cr(VI) bioreduction by both free cells and clay minerals-amended cells followed the pseudo-first-order kinetic model, with the latter one fitting better. The mass balance analyses and X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to Cr(III) and the adsorption of total chromium on clay minerals-bacteria complex was small, implying that Cr(VI) bioremoval was not mainly due to the adsorption of Cr(VI) onto cells or clay minerals or clay minerals-cells complex but mainly due to the Cr(VI) reduction capacity of P. aeruginosa under the experimental conditions studied (e.g., pH 7). Atomic force microscopy revealed that the addition of clay minerals (e.g. vermiculite) decreased the surface roughness of Cr(VI)-laden cells and changed the cell morphology and dimension. Fourier transform infrared spectroscopy revealed that organic matters such as aliphatic species and/or proteins played an important role in the combination of cells and clay minerals. Scanning electron microscopy confirmed the attachment of cells on the surface of clay minerals, indicating that clay minerals could provide a microenvironment to protect cells from Cr(VI) toxicity and serve as growth-supporting materials. These findings manifested the underlying influence of clay minerals on microbial reduction of Cr(VI) and gave an understanding of the interaction between pollutants, the environment and the biota.

  18. Adsorption of Pb(II) on mesoporous activated carbons fabricated from water hyacinth using H3PO4 activation: Adsorption capacity, kinetic and isotherm studies

    Science.gov (United States)

    Huang, Yang; Li, Shunxing; Chen, Jianhua; Zhang, Xueliang; Chen, Yiping

    2014-02-01

    Activated carbons with high mesoporosity and abundant oxygen-containing functional groups were prepared from water hyacinth using H3PO4 activation (WHAC) to eliminate Pb(II) in water. Characterizations of the WHAC were performed using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET analysis showed that WHAC possesses a high mesoporosity (93.9%) with a BET surface area of 423.6 m2/g. The presence of oxygen-containing functional groups including hydroxyl, carbonyl, carboxyl and phosphate groups renders the WHAC a favorable adsorbent for Pb(II) with the maximum monolayer capacity (qm) 118.8 mg/g. The adsorption behavior follows pseudo-first order kinetic and Langmuir isotherm. The desorption study demonstrated that the WHAC could be readily regenerated using 0.1 M HCl (pH = 1.0). The desorbed WHAC could be reused at least six times without significant adsorption capacity reduction. The adsorption process was spontaneous and endothermic with ΔG (-0.27, -1.13, -3.02, -3.62, -5.54, and -9.31 kJ/mol) and ΔH (38.72 kJ/mol). Under the optimized conditions, a small amount of the adsorbent (1.0 g/L) could remove as much as 90.1% of Pb(II) (50 mg/L) in 20 min at pH 6.0 and temperature of 298 K. Therefore, the WHAC has a great potential to be an economical and efficient adsorbent in the treatment of lead-contaminated water.

  19. Spectrophotometric evaluation of surface morphology dependent catalytic activity of biosynthesized silver and gold nanoparticles using UV–vis spectra: A comparative kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Ankamwar, Balaprasad, E-mail: bankamwar@yahoo.com [Bio-inspired Materials Research Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkhind, Pune 411007 (India); Kamble, Vaishali; Sur, Ujjal Kumar [Bio-inspired Materials Research Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkhind, Pune 411007 (India); Santra, Chittaranjan [Department of Chemistry, Netaji Nagar Day College, Regent Park, Kolkata 700092 (India)

    2016-03-15

    Graphical abstract: - Highlights: • The biosynthesized silver nanoparticles were stable for 6 months and used as effective SERS active substrate. • They are effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. • Comparative catalytic efficiency of both silver and gold nanoparticles was studied spectrophotometrically. • Our results demonstrate surface morphology dependent catalytic activity of both nanoparticles. - Abstract: The development of eco-friendly and cost-effective synthetic protocol for the preparation of nanomaterials, especially metal nanoparticles is an emerging area of research in nanotechnology. These metal nanoparticles, especially silver can play a crucial role in various catalytic reactions. The biosynthesized silver nanoparticles described here was very stable up to 6 months and can be further exploited as an effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. The silver nanoparticles were utilized as an efficient surface-enhanced Raman scattering (SERS) active substrate using Rhodamine 6G as Raman probe molecule. We have also carried out systematic comparative studies on the catalytic efficiency of both silver and gold nanoparticles using UV–vis spectra to monitor the above reaction spectrophotometrically. We find that the reaction follows pseudo-first order kinetics and the catalytic activity can be explained by a simple model based on Langmuir–Hinshelwood mechanism for heterogeneous catalysis. We also find that silver nanoparticles are more efficient as a catalyst compare to gold nanoparticles in the reduction of 4-nitrophenol to 4-aminophenol, which can be explained by the morphology of the nanoparticles as determined by transmission electron microscopy.

  20. Experimental studies of the kinetics of small polyatomic free radicals in combustion reactions; Moniatomisten radikaalien kinetiikka palamisreaktioissa, kokeellinen tutkimus

    Energy Technology Data Exchange (ETDEWEB)

    Seetula, J. [Helsinki Univ. (Finland). Lab. of Physical Chemistry

    1996-12-01

    The kinetics of the reactions of CH{sub 2}Cl, CHClBr, CH{sub 3}CCl{sub 2} and CCl{sub 3}, with Cl{sub 2} has been investigated in a tubular reactor coupled to a photoionization mass spectrometer. The radicals of interest, R, were generated homogeneously in the reactor by pulse 248 nm exciplex laser photolysis. The decay of R was monitored as a function of Cl{sub 2} concentration under pseudo-first-order condition to determine the rate constant as a function of temperature pressure. The reactions were studied separately over a temperature range up to a temperature of 873 K. The rate constants of CH{sub 2}Cl, CHClBr and CH{sub 3}CCl{sub 2} radicals determined were fitted to three-parameter Arrhenius-type expression (with units of cm{sup 3} molecule{sup -1} s{sup -1}): k(CH{sub 2}Cl) = 1.05x10{sup -16} x (T){sup 1.4} x exp(-357 J mol{sup -1} / RT), k(CHClBr) = 5.83x10{sup -20} x (T){sup 2.3} x exp(-300 J mol{sup -1}/ RT) and k(CH{sub 3}CCl{sub 2}) 1.10x10{sup -}2{sup 6} x (T){sup 4.3} x exp(15000 J mol{sup -1}/ RT). The rate constants CCl{sub 3} radical were fitted to a two-parameter Arrhenius expression (units in cm{sup 3} molecule{sup -1} s{sup -1}): k(CCl{sub 3}) = (8.1 +- 6.7)10{sup -l3} exp[-(25.0 +- 8.7) kJ mol{sup -1}/ RT]. An Arrhenius expression for the reaction of Cl+CCl{sub 4} -> <- CCl{sub 3}+Cl{sub 2} is also obtained from the kinetics of the reaction of CCl{sub 3} radical with Cl{sub 2} combined with the known heat of formation and entropy values of CCl{sub 3} free radical to be as follows (in units cm{sup 3} molecule{sup -1-}5 s{sup -1}): k(Cl+CCl{sub 4}) = (3.9 + 3.2)10{sup -10} exp[-(71 + 9) kJ mol{sup -1}/ RT]. The error limits stated are l{sigma}+Student`s t and base on statistical uncertainties only. (author)

  1. Kinetic Biochemistry

    OpenAIRE

    Jäntschi, Lorentz

    2003-01-01

    Mathematics and computer programming have a major contribution to chemistry. Two directions can be identified: one that searches and tries (rich) to explain the structural binding and shape of the chemical compounds [1] with major applications in QSPR/QSAR studies [2], and applied sciences such as engineering of materials or agriculture [3]; the second direction is to models the kinetic processes that are involved in chemical reactions [4]. Many such models are available here. The present pap...

  2. Kinetic Biochemistry

    Directory of Open Access Journals (Sweden)

    Lorentz JÄNTSCHI

    2003-03-01

    Full Text Available Mathematics and computer programming have a major contribution to chemistry. Two directions can be identified: one that searches and tries (rich to explain the structural binding and shape of the chemical compounds [1] with major applications in QSPR/QSAR studies [2], and applied sciences such as engineering of materials or agriculture [3]; the second direction is to models the kinetic processes that are involved in chemical reactions [4]. Many such models are available here. The present paper describes three variants of well the known kinetic models and presents the mathematical equations associated with them. The differential equations are numerically solved and fitted with MathCad program. [1] Diudea M., Gutman I., Jäntschi L., Molecular Topology, Nova Science, Huntington, New York, 332 p., 2001, 2002. [2] Diudea M. V., Ed., QSPR / QSAR Studies by Molecular Descriptors, Nova Science, Huntington, New York, 438 p., 2001. [3] Jäntschi L., Microbiology and Toxicology. Phytochemistry Studies (in Romanian, Amici, Cluj-Napoca, 184 p., 2003. [4] Jäntschi L., Unguresan M., Physical Chemistry. Molecular Kinetic and Dynamic (in Romanian, Mediamira, Cluj-Napoca, 159 p., 2001.

  3. Physisorption kinetics

    CERN Document Server

    Kreuzer, Hans Jürgen

    1986-01-01

    This monograph deals with the kinetics of adsorption and desorption of molecules physisorbed on solid surfaces. Although frequent and detailed reference is made to experiment, it is mainly concerned with the theory of the subject. In this, we have attempted to present a unified picture based on the master equation approach. Physisorption kinetics is by no means a closed and mature subject; rather, in writing this monograph we intended to survey a field very much in flux, to assess its achievements so far, and to give a reasonable basis from which further developments can take off. For this reason we have included many papers in the bibliography that are not referred to in the text but are of relevance to physisorption. To keep this monograph to a reasonable size, and also to allow for some unity in the presentation of the material, we had to omit a number of topics related to physisorption kinetics. We have not covered to any extent the equilibrium properties of physisorbed layers such as structures, phase tr...

  4. Chromium and zinc uptake by algae Gelidium and agar extraction algal waste: kinetics and equilibrium.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-11-19

    Biosorption of chromium and zinc ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). Langmuir and Langmuir-Freundlich equilibrium models describe well the equilibrium data. The parameters of Langmuir equilibrium model at pH 5.3 and 20 degrees C were for the algae, q(L)=18 mg Cr(III)g(-1) and 13 mgZn(II)g(-1), K(L) = 0.021l mg(-1)Cr(III) and 0.026l mg(-1) Zn(II); for the algal waste, q(L)=12 mgCr(III)g(-1) and 7mgZn(II)g(-1), K(L)=0.033lmg(-1) Cr(III) and 0.042l mg(-1) Zn(II); for the composite material, q(L) = 9 mgCr(III)g(-1) and 6 mgZn(II)g(-1), K(L)=0.032l mg(-1)Cr(III) and 0.034l mg(-1)Zn(II). The biosorbents exhibited a higher preference for Cr(III) ions and algae Gelidium is the best one. The pseudo-first-order Lagergren and pseudo-second-order models fitted well the kinetic data for the two metal ions. Kinetic constants and equilibrium uptake concentrations given by the pseudo-second-order model for an initial Cr(III) and Zn(II) concentration of approximately 100 mgl(-1), at pH 5.3 and 20 degrees C were k(2,ads)=0.04 g mg(-1)Cr(III)min(-1) and 0.07 g mg(-1)Zn(II)min(-1), q(eq)=11.9 mgCr(III)g(-1) and 9.5 mgZn(II)g(-1) for algae; k(2,ads)=0.17 g mg(-1)Cr(III)min(-1) and 0.19 g mg(-1)Zn(II)min(-1), q(eq)=8.3 mgCr(III)g(-1) and 5.6 mgZn(II)g(-1) for algal waste; k(2,ads)=0.01 g mg(-1)Cr(III)min(-1) and 0.18 g mg(-1)Zn(II)min(-1), q(eq)=8.0 mgCr(III)g(-1) and 4.4 mgZn(II)g(-1) for composite material. Biosorption was modelled using a batch adsorber mass transfer kinetic model, which successfully predicts Cr(III) and Zn(II) concentration profiles. The calculated average homogeneous diffusivities, D(h), were 4.2 x 10(-8), 8.3 x 10(-8) and 1.4 x 10(-8)cm(2)s(-1) for Cr(III) and 4.8 x 10(-8), 9.7 x 10(-8) and 6.2 x 10(-8)cm(2)s(-1

  5. Study on the kinetics and transformation products of salicylic acid in water via ozonation.

    Science.gov (United States)

    Hu, Ruikang; Zhang, Lifeng; Hu, Jiangyong

    2016-06-01

    As salicylic acid is one of widely used pharmaceuticals, its residue has been found in various environmental water systems e.g. wastewater, surface water, treated water and drinking water. It has been reported that salicylic acid can be efficiently removed by advanced oxidation processes, but there are few studies on its transformation products and ozonation mechanisms during ozonation process. The objective of this study is to characterize the transformation products, investigate the degradation mechanisms at different pH, and propose the ozonation pathways of salicylic acid. The results showed that the rate of degradation was about 10 times higher at acidic condition than that at alkaline condition in the first 1 min when 1 mg L(-1) of ozone solution was added into 1 mg L(-1) of salicylic acid solution. It was proposed that ozone direct oxidation mechanism dominates at acidic condition, while indirect OH radical mechanism dominates at alkaline condition. A two stages pseudo-first order reaction was proposed at different pH conditions. Various hydroxylation products, carbonyl compounds and carboxylic acids, such as 2,5-dihydroxylbenzoic acid, 2,3-dihydroxylbenzoic acid, catechol, formaldehyde, glyoxal, acetaldehyde, maleic acid, acetic acid and oxalic acid etc. were identified as ozonation transformation products. In addition, acrylic acid was identified, for the first time, as ozonation transformation products through high resolution liquid chromatography-time of flight mass spectrometer. The information demonstrated in this study will help us to better understand the possible effects of ozonation products on the water quality. The degradation pathways of salicylic acid by ozonation in water sample were proposed. As both O3 and OH radical were important in the reactions, the degradation pathways of salicylic acid by ozonation in water sample were proposed at acidic and basic conditions. To our knowledge, there was no integrated study reported on the ozonation of

  6. Download this PDF file

    African Journals Online (AJOL)

    of four acids of different acid strengths, pseudo-first-order rate constants were obtained, and the reaction was found to be follow third order kinetics, first order in triazine, and second order in acid. The kinetic ... constant (36.7 at 25°), and its aprotic nature make it particularly useful for acid-base studies, and a good solvent for ...

  7. Effects of pH on the Kinetics of Methyl Tertiary Butyl Ether Degradation by Oxidation Process (H2O2/Nano Zero-Valent Iron/Ultrasonic

    Directory of Open Access Journals (Sweden)

    Samaei

    2015-07-01

    Full Text Available Background In advanced oxidation processes, pH has a significant effect on the removal efficiency of organic compounds. This study examined the effect of pH changes on the removal efficiency and kinetics of methyl tertiary butyl ether (MTBE concentration in aquatic environment. Objectives The primary objective of this study was to evaluate the effect of pH changes on removal kinetics of the mentioned compound, using H2O2/nZVI (nano zero-valent iron/ultrasonic process, and its impact on the reaction rate. Materials and Methods In order to create the right conditions for oxidation, first of all iron nanoparticles combined with H2O2 oxidizer were synthesized, and then they were subjected to ultrasound waves and used in MTBE oxidation. In MTBE removal via H2O2/nZVI/Ultrasonic process, the effects of some parameters such as contact time (2 to 60 minutes, concentration of hydrogen peroxide (5 to 20 mL/L, concentrations of nZVI (0.15 to 0.45 g/L, MTBE concentrations (50 to 750 mg/L, and pH (2 to 9 were investigated. MTBE concentration analysis was performed using gas chromatography (GC. Results According to this study, the best removal efficiency of 50 mg/L MTBE concentration in 89.56% under oxidation condition occurred when H2O2 level equals to 10 mL/L, nZVI is 0.25 g/L at pH 3.5. The results showed that the increase or decrease of pH from 3.5 results in a loss of oxidation efficiency as well as reduction in the amount of kap. In addition, the logarithmic changes curve of MTBE concentration showed that MTBE oxidation in H2O2/nZVI/ultrasonic method follows pseudo first order reactions. Conclusions Changes of pH could remarkably affect the efficiency and oxidation rate of MTBE. In particular, the amount of kap in terms of oxidation declines substantially by moving away from the optimum pH range. In this study, pH 3.5 was considered as the optimal pH in H2O2/nZVI/ultrasonic oxidation process, with the elimination of about 89.56% of the high MTBE

  8. Kinetic buffers.

    Science.gov (United States)

    Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio

    2015-01-12

    This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Review of reactive kinetic models describing reductive dechlorination of chlorinated ethenes in soil and groundwater

    DEFF Research Database (Denmark)

    Chambon, Julie Claire Claudia; Bjerg, Poul Løgstrup; Scheutz, Charlotte

    2013-01-01

    include first order kinetics, Monod kinetics to describe sequential reductive dechlorination and bacterial growth, and metabolic models which simulate fermentation and redox processes interacting with reductive dechlorination processes. The review shows that the estimated kinetic parameters reported vary...

  10. Preventing Corrosion by Controlling Cathodic Reaction Kinetics

    Science.gov (United States)

    2016-03-25

    Preventing corrosion by controlling cathodic reaction kinetics Progress Report for Period: 1 SEP 2015-31 MAR 2016 John Keith Department of...25 March 2016 Preventing corrosion by controlling cathodic reaction kinetics Annual Summary Report: FY16 PI: John Keith, 412-624-7016,jakeith...elements on the kinetics of oxygen reduction reaction catalyzed on titanium oxide in order to develop new approaches for controlling galvanic corrosion

  11. Adsorption of Pb(II) on mesoporous activated carbons fabricated from water hyacinth using H{sub 3}PO{sub 4} activation: Adsorption capacity, kinetic and isotherm studies

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yang, E-mail: zzsfxyhy@163.com [Department of Chemistry and Environmental Science, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Li, Shunxing; Chen, Jianhua; Zhang, Xueliang; Chen, Yiping [Department of Chemistry and Environmental Science, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China)

    2014-02-28

    Activated carbons with high mesoporosity and abundant oxygen-containing functional groups were prepared from water hyacinth using H{sub 3}PO{sub 4} activation (WHAC) to eliminate Pb(II) in water. Characterizations of the WHAC were performed using Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The BET analysis showed that WHAC possesses a high mesoporosity (93.9%) with a BET surface area of 423.6 m{sup 2}/g. The presence of oxygen-containing functional groups including hydroxyl, carbonyl, carboxyl and phosphate groups renders the WHAC a favorable adsorbent for Pb(II) with the maximum monolayer capacity (q{sub m}) 118.8 mg/g. The adsorption behavior follows pseudo-first order kinetic and Langmuir isotherm. The desorption study demonstrated that the WHAC could be readily regenerated using 0.1 M HCl (pH = 1.0). The desorbed WHAC could be reused at least six times without significant adsorption capacity reduction. The adsorption process was spontaneous and endothermic with ΔG (−0.27, −1.13, −3.02, −3.62, −5.54, and −9.31 kJ/mol) and ΔH (38.72 kJ/mol). Under the optimized conditions, a small amount of the adsorbent (1.0 g/L) could remove as much as 90.1% of Pb(II) (50 mg/L) in 20 min at pH 6.0 and temperature of 298 K. Therefore, the WHAC has a great potential to be an economical and efficient adsorbent in the treatment of lead-contaminated water.

  12. Efficient photocatalytic degradation of tetrabromodiphenyl ethers and simultaneous hydrogen production by TiO2-Cu2O composite films in N2 atmosphere: Influencing factors, kinetics and mechanism.

    Science.gov (United States)

    Hu, Zhe; Wang, Xi; Dong, Haitai; Li, Shangyi; Li, Xukai; Li, Laisheng

    2017-10-15

    TiO2-Cu2O photocatalyst composite film with a heterostructure was synthesized on a copper substrate for 2,2',4,4'-tetrabromodiphenyl ether (BDE47) reduction. First, Cu2O film was synthesized by the electrochemical deposition method, and then TiO2 was coated on the surface of the Cu2O film. The morphology, surface chemical composition and optical characteristics of TiO2-Cu2O film were characterized. The degradation efficiency of BDE47 and hydrogen production by TiO2-Cu2O films was higher than those by pure TiO2 or Cu2O films. The highest BDE47 degradation efficiency of 90% and hydrogen production of 12.7mmolLliq(-1) after 150min were achieved by 67%TiO2-Cu2O films. The influencing factors were investigated in terms of film component, solvent condition, and initial pH. A kinetics study demonstrated that BDE47 degradation followed a pseudo-first-order model. Photocatalytic apparent reaction rate constant of BDE47 by TiO2-Cu2O films was 0.0070min(-1), which was 3.3 times of that by directly photolysis process. During photocatalytic debrmination process, the photogenerated holes were reserved in the valance band of Cu2O to oxidize methanol. Meanwhile, the partial photogenerated electrons transferred to the conduction band of TiO2 and directly eliminated the ortho-Br of BDE47 and yielded BDE28 and BDE15. The other partial photogenerated electrons reduced protons (H(+)) to form atomic hydrogen (H°), which could substitute the para-Br of BDE47 and generated BDE17 and produce hydrogen. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Calcite Dissolution Kinetics

    Science.gov (United States)

    Berelson, W.; Subhas, A.; Dong, S.; Naviaux, J.; Adkins, J. F.

    2016-12-01

    A geological buffer for high atmospheric CO2 concentrations is neutralization via reaction with CaCO3. We have been studying the dissolution kinetics of carbonate minerals using labeled 13C calcite and Picarro-based measurements of 13C enrichments in solution DIC. This methodology has greatly facilitated our investigation of dissolution kinetics as a function of water carbonate chemistry, temperature and pressure. One can adjust the saturation state Omega by changing the ion activity product (e.g. adjusting carbonate ion concentration), or by changing the solubility product (e.g. adjusting temperature or pressure). The canonical formulation of dissolution rate vs. omega has been refined (Subhas et al. 2015) and shows distinct non-linear behavior near equilibrium and rates in sea water of 1-3 e-6 g/cm2day at omega = 0.8. Carbonic anhydrase (CA), an enzyme that catalyzes the hydration of dissolved CO2 to carbonic acid, was shown (in concentrations rate at low degrees of undersaturation by >500x. This result points to the importance of carbonic acid in enhancing dissolution at low degrees of undersaturation. CA activity and abundance in nature must be considered regarding the role it plays in catalyzing dissolution. We also have been investigating the role of temperature on dissolution kinetics. An increase of 16C yields an order of magnitude increase in dissolution rate. Temperature (and P) also change Omega critical, the saturation state where dissolution rates change substantially. Increasing pressure (achieved in a pressure reaction chamber we built) also shifts Omega critical closer to equilibrium and small pressure increases have large impact on dissolution kinetics. Dissolution rates are enhanced by an order of magnitude for a change in pressure of 1500 psi relative to the dissolution rate achieved by water chemistry effects alone for an omega of 0.8. We've shown that the thermodynamic determination of saturation state does not adequately describe the kinetics

  14. Non-kinetic capabilities: complementing the kinetic prevalence to targeting

    NARCIS (Netherlands)

    Ducheine, P.A.L.; Ducheine, P.A.L.; Schmitt, M.N.; Osinga, F.P.B.

    2016-01-01

    Targeting is used in military doctrine to describe a military operational way, using (military) means to influence a target (or addressee) in order to achieve designated political and/or military goals. The four factors italicized are used to analyse non-kinetic targeting, thereby complementing our

  15. Non-kinetic capabilities: complementing the kinetic prevalence to targeting

    NARCIS (Netherlands)

    Ducheine, P.

    2014-01-01

    Targeting is used in military doctrine to describe a military operational way, using (military) means to influence a target (or addressee) in order to achieve designated political and/or military goals. The four factors italicized are used to analyse non-kinetic targeting, complementing our

  16. Inflation Rates, Car Devaluation, and Chemical Kinetics.

    Science.gov (United States)

    Pogliani, Lionello; Berberan-Santos, Mario N.

    1996-01-01

    Describes the inflation rate problem and offers an interesting analogy with chemical kinetics. Presents and solves the car devaluation problem as a normal chemical kinetic problem where the order of the rate law and the value of the rate constant are derived. (JRH)

  17. COMPARATIVE ANALYSIS OF SOME EXISTING KINETIC MODELS ...

    African Journals Online (AJOL)

    In terms of highest values of R2, first proposed model accounted for 46.7%, Pseudo second-order kinetics model 40% while Elovich, Webber-Morris and second proposed kinetic models accounted for 6.7% respectively of the total results for biosorption of the three heavy metals by five selected microorganisms. But based ...

  18. An equilibrium and kinetic modeling

    African Journals Online (AJOL)

    SERVER

    2007-06-18

    Jun 18, 2007 ... The Langmuir and Freundlich adsorption models fitted well with the equilibrium data of the process studied. ... followed the first order rate expression. Key words: Penicillin-G wastewater, Phanerochate chrysosporium, equilibrium, kinetic study. ... Ammonia-nitrogen (mg/l). 300 - 500. Total phosphate (mg/l).

  19. Kinetics and Mechanistic Studies on the Reaction between Cytochrome c and Tea Catechins

    Directory of Open Access Journals (Sweden)

    Lihua Wang

    2014-08-01

    Full Text Available Green tea is characterized by the presence of an abundance of polyphenolic compounds, also known as catechins, including epicatechin (EC, epigallocatechin (EGC, epicatechin gallate (EGC and epigallocatechin gallate (EGCG. In addition to being a popular beverage, tea consumption has been suggested as a mean of chemoprevention. However, its mode of action is unclear. It was discovered that tea catechins can react with cytochrome c. When oxidized cytochrome c was mixed with catechins commonly found in green tea under non-steady-state conditions, a reduction of cytochrome c was observed. The reaction rate of the catechins was dependent on the pH and the nature of the catechin. The pseudo-first order rate constant obtained increased in the order of EC < ECG < EGC < EGCG, which is consistent with previously reported superoxide reduction activities and Cu2+ reduction activities of tea catechins.

  20. Kinetics of coal pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Seery, D.J.; Freihaut, J.D.; Proscia, W.M. (United Technologies Research Center, East Hartford, CT (USA)); Howard, J.B.; Peters, W.; Hsu, J.; Hajaligol, M.; Sarofim, A. (Massachusetts Inst. of Tech., Cambridge, MA (USA)); Jenkins, R.; Mallin, J.; Espindola-Merin, B. (Pennsylvania State Univ., University Park, PA (USA)); Essenhigh, R.; Misra, M.K. (Ohio State Univ., Columbus, OH (USA))

    1989-07-01

    This report contains results of a coordinated, multi-laboratory investigation of coal devolatilization. Data is reported pertaining to the devolatilization for bituminous coals over three orders of magnitude in apparent heating rate (100 to 100,000 + {degree}C/sec), over two orders of magnitude in particle size (20 to 700 microns), final particle temperatures from 400 to 1600{degree}C, heat transfer modes ranging from convection to radiative, ambient pressure ranging from near vacuum to one atmosphere pressure. The heat transfer characteristics of the reactors are reported in detail. It is assumed the experimental results are to form the basis of a devolatilization data base. Empirical rate expressions are developed for each phase of devolatilization which, when coupled to an awareness of the heat transfer rate potential of a particular devolatilization reactor, indicate the kinetics emphasized by a particular system reactor plus coal sample. The analysis indicates the particular phase of devolatilization that will be emphasized by a particular reactor type and, thereby, the kinetic expressions appropriate to that devolatilization system. Engineering rate expressions are developed from the empirical rate expressions in the context of a fundamental understanding of coal devolatilization developed in the course of the investigation. 164 refs., 223 figs., 44 tabs.

  1. Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

    Science.gov (United States)

    van der Grift, B.; Behrends, T.; Osté, L. A.; Schot, P. P.; Wassen, M. J.; Griffioen, J.

    2016-08-01

    Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition, reaction kinetics, and the characteristics of the produced Fe hydroxyphosphate precipitates in a series of aeration experiments with anoxic synthetic water and natural groundwater. A pH stat device was used to maintain constant pH and to record the H+ production during Fe(II) oxidation in the aeration experiments in which the initial aqueous P/Fe ratios ((P/Fe)ini), oxygen concentration and pH were varied. In general, Fe(II) oxidation proceeded slower in the presence of PO4 but the decrease of the PO4 concentration during Fe(II) oxidation due to the formation of Fe hydroxyphosphates caused additional deceleration of the reaction rate. The progress of the reaction could be described using a pseudo-second-order rate law with first-order dependencies on PO4 and Fe(II) concentrations. After PO4 depletion, the Fe(II) oxidation rates increased again and the kinetics followed a pseudo-first-order rate law. The first-order rate constants after PO4 depletion, however, were lower compared to the Fe(II) oxidation in a PO4-free solution. Hence, the initially formed Fe hydroxyphosphates also affect the kinetics of continuing Fe(II) oxidation after PO4 depletion. Presence of aqueous PO4 during oxidation of Fe(II) led to the formation of Fe hydroxyphosphates. The P/Fe ratios of the precipitates ((P/Fe)ppt) and the recorded ratio of H+ production over decrease in dissolved Fe(II) did not change detectably throughout the reaction despite a changing P/Fe ratio in the solution. When (P/Fe)ini was 0.9, precipitates with a (P/Fe)ppt ratio of about 0.6 were formed. In experiments with (P/Fe)ini ratios below 0.6, the (P/Fe)ppt decreased with decreasing (P/Fe)ini and pH value. Aeration experiments with

  2. Biosorption of Hexavalent Chromium Using Bark of Cassia spectabilis

    African Journals Online (AJOL)

    The dimensionless equilibrium parameter, RL, signifies a favorable adsorption of Cr(VI) on the adsorbent and is found to be 0.441 (0 < RL<1). Pseudo first-order and second order kinetic models were used to evaluate the mechanism of adsorption. Kinetic evaluation of the experimental data showed that the biosorption ...

  3. Adsorption of methyl orange and salicylic acid on a nano-transition metal composite: Kinetics, thermodynamic and electrochemical studies.

    Science.gov (United States)

    Arshadi, M; Mousavinia, F; Amiri, M J; Faraji, A R

    2016-12-01

    In this work synthesis of Mn-nanoparticles (MnNPs) supported on the Schiff base modified nano-sized SiO2Al2O3 mixed-oxides (Si/Al) and its implementation as an adsorbent for the removal of organic pollutions such as methyl orange (MO) and salicylic acid (SA) was investigated. Si/Al were functionalized by grafting Schiff base ligand and in the next step, MnNPs were prepared over the modified nano sol-gel Si/Al. Structures and adsorption characteristics of the obtained organometallic-modified SiO2/Al2O3 mixed oxide were studied by several methods such as elemental analysis, diffuse reflectance UV-vis spectroscopy, FT-IR spectroscopy, nitrogen adsorption/desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX), inductively coupled plasma (ICP-AES), Electron Paramagnetic Resonance (EPR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EPR data of the immobilized manganese ions resulted that the transition state of active sites in the nano-adsorbent are in the form of Mn(II) ions at the surface. The adsorption properties of heterogeneous Mn(II) ions showed that this nano-adsorbent has very good potential to remove MO and SA ions from aqueous solution. The removal efficiency of the SAPAS@MnNPs towards MO reached out to 89.3 and 29.1% and for SA approached to 54.6 and 18.9% at 150 and 500mg/dm(3) initial organic pollution concentrations, respectively. To investigate the adsorption kinetic of Mn(II) ions onto the nano-sized support, pseudo first and pseudo second order kinetics, and the Freundlich, Langmuir and Langmuir-Freundlich isotherm models have also been applied to the equilibrium adsorption data. The contact time to obtain equilibrium for maximum adsorption capacity was 45min. The adsorption process was spontaneous and endothermic in nature and it was well explained with pseudo-second-order kinetic model. No remarkable loss of removal capacity even after 8th times regeneration

  4. comparative analysis of some existing kinetic models with proposed ...

    African Journals Online (AJOL)

    IGNATIUS NWIDI

    But based on values of ARE%, first proposed kinetic model accounted for 93.3% while pseudo second-order kinetic model accounted for 6.7% of the results for biosorption of the three heavy metals by the five microbes. Keynotes: Heavy metals, Biosorption, Kinetics Models, Comparative analysis, Average Relative Error. 1.

  5. Kinetics of tetrataenite disordering

    Energy Technology Data Exchange (ETDEWEB)

    Dos Santos, E., E-mail: edisanfi@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil); Gattacceca, J.; Rochette, P. [Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement, UM34, CNRS/Aix-Marseille University, Aix-en-Provence (France); Fillion, G. [Laboratoire National des Champs Magnétiques Intenses (LNCMI), CNRS, UJF, 38042 Grenoble (France); Scorzelli, R.B. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil)

    2015-02-01

    Tetrataenite is a chemically ordered L1{sub 0}-type Fe{sub 50}Ni{sub 50} alloy detected for the first time in 1977 by {sup 57}Fe Mössbauer spectroscopy studies in iron meteorites. The thermal history of meteorites, in particular short thermal events like those associated to hypervelocity impacts, can be constrained by tracing the presence of tetrataenite or its disordering into taenite. The knowledge of the disordering kinetics of tetrataenite, that is associated with changes in its magnetic properties, is still very fragmentary so that the time–temperature history of these meteorites cannot be constrained in details. Furthermore, knowledge of disordering kinetics is important due to potential technological application of tetrataenite as a rare-earth free strong magnet. Thus, this work provides the first time–temperature data for disordering reaction of tetrataenite. We have shown that disordering is not an instantaneous process but is a kinetic limited reaction. It was shown that disordering may take place at any temperature above the order–disorder transition for L{sub 10} superstructure phase (∼320 °C) when the appropriate time-scale is considered. This result means that the apparent Curie point for tetrataenite is not an absolute property in the sense that any estimate of this parameter should be referred to a given time-scale. - Highlights: • The first time–temperature data for tetrataenite disordering reaction is provided. • Previous works does not give a complete picture of tetrataenite disordering. • Apparent Curie temperature of tetrataenite should be referred to a time-scale. • Tetrataenite can be used as a probe to detect thermal/shock events recorded in meteorites.

  6. Kinetics of stress fibers

    Energy Technology Data Exchange (ETDEWEB)

    Stachowiak, Matthew R; O' Shaughnessy, Ben [Department of Chemical Engineering, Columbia University, New York, NY 10027 (United States)], E-mail: bo8@columbia.edu

    2008-02-15

    Stress fibers are contractile cytoskeletal structures, tensile actomyosin bundles which allow sensing and production of force, provide cells with adjustable rigidity and participate in various processes such as wound healing. The stress fiber is possibly the best characterized and most accessible multiprotein cellular contractile machine. Here we develop a quantitative model of the structure and relaxation kinetics of stress fibers. The principal experimentally known features are incorporated. The fiber has a periodic sarcomeric structure similar to muscle fibers with myosin motor proteins exerting contractile force by pulling on actin filaments. In addition the fiber contains the giant spring-like protein titin. Actin is continuously renewed by exchange with the cytosol leading to a turnover time of several minutes. In order that steady state be possible, turnover must be regulated. Our model invokes simple turnover and regulation mechanisms: actin association and dissociation occur at filament ends, while actin filament overlap above a certain threshold in the myosin-containing regions augments depolymerization rates. We use the model to study stress fiber relaxation kinetics after stimulation, as observed in a recent experimental study where some fiber regions were contractile and others expansive. We find that two distinct episodes ensue after stimulation: the turnover-overlap system relaxes rapidly in seconds, followed by the slow relaxation of sarcomere lengths in minutes. For parameter values as they have been characterized experimentally, we find the long time relaxation of sarcomere length is set by the rate at which actin filaments can grow or shrink in response to the forces exerted by the elastic and contractile elements. Consequently, the stress fiber relaxation time scales inversely with both titin spring constant and the intrinsic actin turnover rate. The model's predicted sarcomere velocities and contraction-expansion kinetics are in good

  7. Kinetics of cisplatin binding to short r(GG) containing miRNA mimics - influence of Na(+)versus K(+), temperature and hydrophobicity on reactivity.

    Science.gov (United States)

    Alshiekh, Alak; Clausén, Maria; Elmroth, Sofi K C

    2015-07-28

    Nucleic acids are well recognized targets for platinum-based anticancer drugs, with RNA and DNA being kinetically comparable. In the case of RNA, previous studies have shown that the reaction between small duplex RNAs (dsRNAs) and monoaquated cisplatin (cis-Pt(NH3)2Cl(OH2)(+), ) can be followed by the metal induced hyperchromicity occurring directly after addition of to e.g. microRNA mimics. In the present study, we have used this approach to compare thermal stability and reactivity between intracellularly- and extracellularly relevant salt concentration (CNa(+) and CK(+)ca. 0.1 M), and also as a function of increased hydrophobicity (10% v/v EtOH). In addition, reactivity was studied as a function of temperature in the interval ca. 5-20 °C below the respective dsRNA melting temperatures (Tms). Four different 13- to 20-mer dsRNAs with two different central sequence motifs were used as targets containing either a central r(GG)·r(CC)- or r(GG)·r(UAU)-sequence. The reactions exhibited half-lives in the minute- to hour range at 38 °C in the presence of excess in the μM range. Further, a linear dependence was found between C and the observed pseudo-first-order rate constants. The resulting apparent second-order rate constants were significantly larger for the lower melting r(GG)·r(UAU)-containing sequences compared with that of the fully complementary ones; the higher and lower reactivities represented by RNA-1-3 and RNA-1-1 with k2,appca. 30 and 8 M(-1) s(-1) respectively at CNa(+) = 122 mM. For all RNAs a common small, but significant, trend was observed with increased reactivity in the presence of K(+) compared with Na(+), and decreased reactivity in the presence of EtOH. Finally, the temperature dependence of k2,app was evaluated using the Eyring equation. The retrieved activation parameters reveal positive values for both ΔH(≠) and ΔS(≠) for all dsRNAs, in the range ca. 23-34 kcal mol(-1) and 22-57 cal K(-1) mol(-1) respectively. These values indicate

  8. Kinetics of tetrabromobisphenol A (TBBPA) reactions with H{sub 2}SO{sub 4}, HNO{sub 3} and HCl: Implication for hydrometallurgy of electronic wastes

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yin [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640 (China); Li, Dan; Mao, Zhe [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Huang, Weilin [Department of Environmental Sciences, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick 08901, NJ (United States); Peng, Ping’an, E-mail: pinganp@gig.ac.cn [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640 (China); Chen, Pei [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Mei, Jun [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640 (China); Department of Chemistry, Guangdong Medical College, Dongguan 523808 (China)

    2014-04-01

    Highlights: • Effect of hydrometallurgical processes on the fate of TBBPA was evaluated. • TBBPA could react rapidly with HNO{sub 3} and concentrated H{sub 2}SO{sub 4}. • TBBPA did not show measurable reactivity in HCl and the dilute H{sub 2}SO{sub 4} (≤24 wt%). • The reaction kinetics of TBBPA with HNO{sub 3} differed from that with concentrated H{sub 2}SO{sub 4}. • The transformation pathways of TBBPA in different acids were different. - Abstract: Hydrometallurgy is an acid leaching based process widely used for recovering precious metals from electronic wastes (e-wastes). The effects of acid leaching on the fate of brominated flame retardants (BFRs) in typical hydrometallurgical processes remain largely unknown. This study was aimed at evaluating the fate of tetrabromobisphenol A (TBBPA), a commonly used BFR, in three acid leaching reagents (i.e. H{sub 2}SO{sub 4}, HNO{sub 3}, and HCl) commonly used in hydrometallurgy. It was found that the reactions of TBBPA with concentrated H{sub 2}SO{sub 4} followed a pseudo-zero-order rate and the reaction rates declined rapidly as the concentrations of H{sub 2}SO{sub 4} decreased. In contrast, TBBPA could be easily transformed in less concentrated HNO{sub 3} solutions (<21.7 wt%) and the reactions followed a pseudo-first-order rate. The reaction products identified by GC–MS indicated different transformation pathways of TBBPA in H{sub 2}SO{sub 4} and HNO{sub 3}. HCl or HCl/H{sub 2}SO{sub 4} mixtures (3:1, v/v) did not appear to react with TBBPA, while aqua regia (3:1 HCl/HNO{sub 3}, v/v) reacted violently with TBBPA and led to almost complete disappearance of TBBPA within a minute. It suggested that HNO{sub 3} significantly affected the fate of TBBPA and the use of HNO{sub 3} as leaching reagents in hydrometallurgy of e-wastes should be carefully evaluated. Collectively, our findings of distinct fate of TBBPA in different acid leaching reagents provided fundamental information for design of hydrometallurgical

  9. Kinetics of the reaction of iodine atoms with HO sub 2 radicals

    Energy Technology Data Exchange (ETDEWEB)

    Jenkin, M.E.; Cox, R.A. (Harwell Laboratory, Oxfordshire (England)); Mellouki, A.; Le Bras, G.; Poulet, G. (CNRS, Orleans (France))

    1990-04-05

    The rate coefficient (k{sub 7}) for the reaction of iodine atoms with HO{sub 2} radicals, I + HO{sub 2} {yields} HI + O{sub 2}, has been measured directly with use of the discharge-flow/EPR technique, and the molecular-modulation/UV-absorption spectroscopy technique. Discharge-flow measurements were made under pseudo-first-order conditions with iodine atoms in large excess over HO{sub 2}. Molecular-modulation measurements were made with iodine atoms in excess over HO{sub 2}, but the I + HO{sub 2} reaction was occurring in competition with the self-reaction of HO{sub 2}. The potential significance of this reaction as a sink for iodine in the troposphere and other aspects of tropospheric iodine chemistry are considered with a simple model of the atmospheric boundary layer.

  10. Word Order

    DEFF Research Database (Denmark)

    Rijkhoff, Jan

    2015-01-01

    The way constituents are ordered in a linguistic expression is determined by general principles and language specific rules. This article is mostly concerned with general ordering principles and the three main linguistic categories that are relevant for constituent order research: formal......, functional and semantic categories. The general principles appear to be motivated by cognitive considerations, which are deemed to facilitate language processing and which can all be regarded as manifestations of iconicity: non-arbitrary relations between the form and the content of a linguistic expression....... Three major iconic ordering principles are the principles of Domain Integrity, Scope, and Head Proximity....

  11. Assessment of Orbital-Optimized Third-Order Møller-Plesset Perturbation Theory and Its Spin-Component and Spin-Opposite Scaled Variants for Thermochemistry and Kinetics.

    Science.gov (United States)

    Soydaş, Emine; Bozkaya, Uğur

    2013-03-12

    An assessment of the OMP3 method and its spin-component and spin-scaled variants for thermochemistry and kinetics is presented. For reaction energies of closed-shell systems, the CCSD, SCS-MP3, and SCS-OMP3 methods show better performances than other considered methods, and no significant improvement is observed due to orbital optimization. For barrier heights, OMP3 and SCS-OMP3 provide the lowest mean absolute deviations. The MP3 method yields considerably higher errors, and the spin scaling approaches do not help to improve upon MP3, but worsen it. For radical stabilization energies, the CCSD, OMP3, and SCS-OMP3 methods exhibit noticeably better performances than MP3 and its variants. Our results demonstrate that if the reference wave function suffers from a spin-contamination, then the MP3 methods dramatically fail. On the other hand, the OMP3 method and its variants can tolerate the spin-contamination in the reference wave function. For overall evaluation, we conclude that OMP3 is quite helpful, especially in electronically challenged systems, such as free radicals or transition states where spin contamination dramatically deteriorates the quality of the canonical MP3 and SCS-MP3 methods. Both OMP3 and CCSD methods scale as n(6), where n is the number of basis functions. However, the OMP3 method generally converges in much fewer iterations than CCSD. In practice, OMP3 is several times faster than CCSD in energy computations. Further, the stationary properties of OMP3 make it much more favorable than CCSD in the evaluation of analytic derivatives. For OMP3, the analytic gradient computations are much less expensive than CCSD. For the frequency computation, both methods require the evaluation of the perturbed amplitudes and orbitals. However, in the OMP3 case there is still a significant computational time savings due to simplifications in the analytic Hessian expression owing to the stationary property of OMP3. Hence, the OMP3 method emerges as a very useful

  12. Picolinic acid promoted oxidative decarboxylation of ...

    African Journals Online (AJOL)

    The kinetics and mechanism of picolinic acid promoted reaction of phenylsulfinylacetic acid (PSAA) with Cr(VI) was carried out in aqueous acetonitrile medium under pseudo first order conditions. The reaction follows Michaelis-Menten type of kinetics with respect to PSAA. The catalytic activity by picolinic acid can be ...

  13. Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

    Energy Technology Data Exchange (ETDEWEB)

    Öztürk, A.; Malkoc, E., E-mail: emalkoc@atauni.edu.tr

    2014-04-01

    concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

  14. Modified mean generation time parameter in the neutron point kinetics equations

    Energy Technology Data Exchange (ETDEWEB)

    Diniz, Rodrigo C.; Gonçalves, Alessandro C.; Rosa, Felipe S.S., E-mail: alessandro@nuclear.ufrj.br, E-mail: frosa@if.ufrj.br [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

    2017-07-01

    This paper proposes an approximation for the modified point kinetics equations proposed by NUNES et. al, 2015, through the adjustment of a kinetic parameter. This approximation consists of analyzing the terms of the modified point kinetics equations in order to identify the least important ones for the solution, resulting in a modification of the mean generation time parameter that incorporates all influences of the additional terms of the modified kinetics. This approximation is applied on the inverse kinetics, to compare the results with the inverse kinetics from the modified kinetics in order to validate the proposed model. (author)

  15. Modeling of Reactor Kinetics and Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Matthew Johnson; Scott Lucas; Pavel Tsvetkov

    2010-09-01

    In order to model a full fuel cycle in a nuclear reactor, it is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by coupling fuel burnup equations with the kinetics equations. When the equations are solved simultaneously with a nonlinear equation solver, the end result is a code with the unique capability of modeling transients at any time during a fuel cycle.

  16. The evolution of enzyme kinetic power.

    OpenAIRE

    Keleti, T.; Welch, G. R.

    1984-01-01

    Evolution of the kinetic potential of enzyme reactions is discussed. Quantitative assessment of the evolution of enzyme action has usually focused on optimization of the parametric ratio kcat./Km, which is the apparent second-order rate constant for the reaction of free substrate with free enzyme to give product. We propose that the general form kcat.[E]T/Km (where [E]T is total enzyme concentration), which is designated the 'kinetic power', is the real measure of kinetic/catalytic potential ...

  17. The kinetics of the hydrogen chloride oxidation

    Directory of Open Access Journals (Sweden)

    Gonzalez Martinez Isai

    2013-01-01

    Full Text Available Hydrogen chloride (HCl oxidation has been investigated on technical membrane electrode assemblies in a cyclone flow cell. Influence of Nafion loading, temperature and hydrogen chloride mole fraction in the gas phase has been studied. The apparent kinetic parameters like reaction order with respect to HCl, Tafel slope and activation energy have been determined from polarization data. The apparent kinetic parameters suggest that the recombination of adsorbed Cl intermediate is the rate determining step.

  18. The biosorption capacity of biochar for 4-bromodiphengl ether: study of its kinetics, mechanism, and use as a carrier for immobilized bacteria.

    Science.gov (United States)

    Du, Jingting; Sun, Pengfei; Feng, Zhuo; Zhang, Xin; Zhao, Yuhua

    2016-02-01

    Polybrominated diphenyl ethers (PBDEs) are known as ubiquitous pollutants in ecological systems and thus pose a great threat to the health of humans and other organisms due to their bioamplification and bioaccumulation along the food chain. The present study was designed to investigate the biosorption capacity of biochar for the removal of 4-monobromodiphengl ether and its synergistic effect when used as a carrier to immobilize the 4-monobromodiphengl ether-degrading strain Sphingomonas sp. DZ3. The raw biochar material was prepared by pyrolyzing maize straw at 350 °C under oxygen-limited conditions. The maximum biosorption capacity of biochar for 4-bromodiphengl ether was determined to be 50.23 mg/L under an initial concentration of 800 mg/L at pH 7.0 and 40 °C. The data obtained from the biosorption studies were fitted successfully with the pseudo-first-order kinetic and Freundlich isotherm models. The Weber-Morris model analysis indicated that intraparticle diffusion was the limiting step in the biosorption of 4-bromodiphengl ether onto the biosorbent. The values of thermodynamic parameters △G0 were calculated as -24.61 kJ/mol (20 °C), -24.35 kJ/mol (30 °C), and -23.98 kJ/mol (40 °C), △S(0) was -8.45 kJ/mol/K, and △H(0) was 21.36 kJ/mol. The artificial neural network analysis indicated that the initial concentration appeared to be the most influential parameter on the biosorption processes. The removal rate of 4-bromodiphengl ether achieved using the biochar-microorganism system was increased by 63 and 83% compared with the rates obtained with biochar and the strain individually, respectively. The morphology of the biochar and immobilized strain was determined using a scanning electron microscope, and information of the surface functional groups of biochar was obtained through an infrared spectra study.

  19. Kinetic Studies of Iron Deposition Catalyzed by Recombinant Human Liver Heavy, and Light Ferritins and Azotobacter Vinelandii Bacterioferritin Using O2 and H2O2 as Oxidants

    Science.gov (United States)

    Bunker, Jared; Lowry, Thomas; Davis, Garrett; Zhang, Bo; Brosnahan, David; Lindsay, Stuart; Costen, Robert; Choi, Sang; Arosio, Paolo; Watt, Gerald D.

    2005-01-01

    The discrepancy between predicted and measured H2O2 formation during iron deposition with recombinant heavy human liver ferritin (rHF) was attributed to reaction with the iron protein complex [Biochemistry 40 (2001) 10832-10838]. This proposal was examined by stopped-flow kinetic studies and analysis for H2O2 production using (1) rHF, and Azotobacter vinelandii bacterial ferritin (AvBF), each containing 24 identical subunits with ferroxidase centers; (2) site-altered rHF mutants with functional and dysfunctional ferroxidase centers; and (3) rccombinant human liver light ferritin (rLF), containing 110 ferroxidase center. For rHF, nearly identical pseudo-first-order rate constants of 0.18 per second at pH 7.5 were measured for Fe(2+) oxidation by both O2 and H2O2, but for rLF, the rate with O2 was 200-fold slower than that for H2O2 (k-0.22 per second). A Fe(2+)/O2 stoichiometry near 2.4 was measured for rHF and its site altered forms, suggesting formation of H2O2. Direct measurements revealed no H2O2 free in solution 0.5-10 min after all Fe(2+) was oxidized at pH 6.5 or 7.5. These results are consistent with initial H2O2 formation, which rapidly reacts in a secondary reaction with unidentified solution components. Using measured rate constants for rHF, simulations showed that steady-state H2O2 concentrations peaked at 14 pM at approx. 600 ms and decreased to zero at 10-30 s. rLF did not produce measurable H2O2 but apparently conducted the secondary reaction with H2O2. Fe(2+)/O2 values of 4.0 were measured for AvBF. Stopped-flow measurements with AvBF showed that both H2O2 and O2 react at the same rate (k=0.34 per second), that is faster than the reactions with rHF. Simulations suggest that AvBF reduces O2 directly to H2O without intermediate H2O2 formation.

  20. Degradation of 2,4-dihydroxibenzoic acid by vacuum UV process in aqueous solution: Kinetic, identification of intermediates and reaction pathway

    Energy Technology Data Exchange (ETDEWEB)

    Azrague, Kamal [Laboratoire IMRCP, CNRS UMR 5623, University of Toulouse, 118 route de Narbonne, 31062 Toulouse (France); Department for Water and Environment, SINTEF, Klaebuveien 153, Trondheim 7465 (Norway); Pradines, Vincent; Bonnefille, Eric [Laboratoire IMRCP, CNRS UMR 5623, University of Toulouse, 118 route de Narbonne, 31062 Toulouse (France); Laboratoire LCC, CNRS, 205 route de Narbonne, F31077 Toulouse Cedex 4 (France); Claparols, Catherine [Laboratoire LCC, CNRS, 205 route de Narbonne, F31077 Toulouse Cedex 4 (France); Universite de Toulouse, UPS, Service Commun de Spectrometrie de Masse, 118 route de Narbonne, F31062 Toulouse Cedex 9 (France); Maurette, Marie-Therese [Laboratoire IMRCP, CNRS UMR 5623, University of Toulouse, 118 route de Narbonne, 31062 Toulouse (France); Benoit-Marquie, Florence, E-mail: florence@chimie.ups-tlse.fr [Laboratoire IMRCP, CNRS UMR 5623, University of Toulouse, 118 route de Narbonne, 31062 Toulouse (France)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer Degradation of 2,4-dihydroxybenzoic acid (DHBA) by vacuum UV photolysis of water. Black-Right-Pointing-Pointer V-UV Xe-excimer lamps produced essentially hydroxyl radicals (HO Degree-Sign ). Black-Right-Pointing-Pointer Identification of all intermediates formed allowed us to propose a reaction pathway. Black-Right-Pointing-Pointer This reaction pathway showed that DHBA reacts differently with HO Degree-Sign and h+. Black-Right-Pointing-Pointer DHBA would be used as a probe to determine which of these entities were involved. - Abstract: 2,4-Dihydroxybenzoic acid (2,4-DHBA) is found frequently as a pollutant in natural waters and represents a threat to water quality because it is a precursor to the formation of quinones which are highly toxic. The degradation of 2,4-DHBA using the vacuum UV photolysis of water has been investigated. Irradiation was carried out in an annular photoreactor equipped with a Xe-excimer lamp situated in the centre and emitting at 172 nm. The degradation kinetic followed a pseudo first order and the reaction has been found to be very heterogeneous, especially at low concentration. Impacts of oxygen or temperature have also been investigated but no effect has been shown. LC-MS and HPLC-UV combined with other analytical techniques allowed the identification of the formation of trihydroxybenzoiec acids and trihydroxybenzenes which underwent a ring opening, conducting to the formation of aliphatic products named {alpha}, {beta}, {delta} and {gamma}. These products were in turn degraded successively into maleiec acid, malic and succinic acid, malonic acid, glyoxalic acid and oxalic acid before reaching the complete mineralization in about 180 min. The proposed reaction pathway has shown to be very different from the one observed for the TiO{sub 2} photocatalysis which involves only holes (h{sup +}) without any formation of aromatic intermediates. The different behaviours of 2,4-DHBA towards the h

  1. Kinetic investigation of wood pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Thurner, F.; Mann, U.; Beck, S. R.

    1980-06-01

    The objective of this investigation was to determine the kinetics of the primary reactions of wood pyrolysis. A new experimental method was developed which enabled us to measure the rate of gas, tar, and char production while taking into account the temperature variations during the wood heating up. The experimental method developed did not require any sophisticated instruments. It facilitated the collection of gas, tar and residue (unreacted wood and char) as well as accurate measurement of the temperature inside the wood sample. Expressions relating the kinetic parameters to the measured variables were derived. The pyrolysis kinetics was investigated in the range of 300 to 400/sup 0/C at atmospheric pressure and under nitrogen atmosphere. Reaction temperature and mass fractions of gas, tar, and residue were measured as a function of time. Assuming first-order reactions, the kinetic parameters were determined using differential method. The measured activation energies of wood pyrolysis to gas, tar, and char were 88.6, 112.7, and 106.5 kJ/mole, respectively. These kinetic data were then used to predict the yield of the various pyrolysis products. It was found that the best prediction was obtained when an integral-mean temperature obtained from the temperature-time curve was used as reaction temperature. The pyrolysis products were analyzed to investigate the influence of the pyrolysis conditions on the composition. The gas consisted mainly of carbon dioxide, carbon monoxide, oxygen, and C/sub 3//sup +/-compounds. The gas composition depended on reaction time as well as reactor temperature. The tar analysis indicated that the tar consisted of about seven compounds. Its major compound was believed to be levoglucosan. Elemental analysis for the char showed that the carbon content increased with increasing temperature.

  2. Adsorptive removal of congo red dye from aqueous solution using bael shell carbon

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Rais, E-mail: olifiaraju@gmail.com [Environmental Research Laboratory, Department of Applied Chemistry, Aligarh Muslim University, Aligarh, U.P. 202002 (India); Kumar, Rajeev [Environmental Research Laboratory, Department of Applied Chemistry, Aligarh Muslim University, Aligarh, U.P. 202002 (India)

    2010-12-15

    This study investigates the potential use of bael shell carbon (BSC) as an adsorbent for the removal of congo red (CR) dye from aqueous solution. The effect of various operational parameters such as contact time, temperature, pH, and dye concentration were studied. The adsorption kinetics was modeled by first-order reversible kinetics, pseudo-first-order kinetics, and pseudo-second-order kinetics. The dye uptake process obeyed the pseudo-second-order kinetic expression at pH 5.7, 7 and 8 whereas the pseudo-first-order kinetic model was fitted well at pH 9. Langmuir, Freundlich and Temkin adsorption models were applied to fit adsorption equilibrium data. The best-fitted data was obtained with the Freundlich model. Thermodynamic study showed that adsorption of CR onto BSC was endothermic in nature and favorable with the positive {Delta}H{sup o} value of 13.613 kJ/mol.

  3. Adsorptive removal of congo red dye from aqueous solution using bael shell carbon

    Science.gov (United States)

    Ahmad, Rais; Kumar, Rajeev

    2010-12-01

    This study investigates the potential use of bael shell carbon (BSC) as an adsorbent for the removal of congo red (CR) dye from aqueous solution. The effect of various operational parameters such as contact time, temperature, pH, and dye concentration were studied. The adsorption kinetics was modeled by first-order reversible kinetics, pseudo-first-order kinetics, and pseudo-second-order kinetics. The dye uptake process obeyed the pseudo-second-order kinetic expression at pH 5.7, 7 and 8 whereas the pseudo-first-order kinetic model was fitted well at pH 9. Langmuir, Freundlich and Temkin adsorption models were applied to fit adsorption equilibrium data. The best-fitted data was obtained with the Freundlich model. Thermodynamic study showed that adsorption of CR onto BSC was endothermic in nature and favorable with the positive Δ H° value of 13.613 kJ/mol.

  4. Aperiodic order

    CERN Document Server

    Grimm, Uwe

    2017-01-01

    Quasicrystals are non-periodic solids that were discovered in 1982 by Dan Shechtman, Nobel Prize Laureate in Chemistry 2011. The mathematics that underlies this discovery or that proceeded from it, known as the theory of Aperiodic Order, is the subject of this comprehensive multi-volume series. This second volume begins to develop the theory in more depth. A collection of leading experts, among them Robert V. Moody, cover various aspects of crystallography, generalising appropriately from the classical case to the setting of aperiodically ordered structures. A strong focus is placed upon almost periodicity, a central concept of crystallography that captures the coherent repetition of local motifs or patterns, and its close links to Fourier analysis. The book opens with a foreword by Jeffrey C. Lagarias on the wider mathematical perspective and closes with an epilogue on the emergence of quasicrystals, written by Peter Kramer, one of the founders of the field.

  5. 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

  6. Introduction to chemical kinetics

    CERN Document Server

    Soustelle, Michel

    2013-01-01

    This book is a progressive presentation of kinetics of the chemical reactions. It provides complete coverage of the domain of chemical kinetics, which is necessary for the various future users in the fields of Chemistry, Physical Chemistry, Materials Science, Chemical Engineering, Macromolecular Chemistry and Combustion. It will help them to understand the most sophisticated knowledge of their future job area. Over 15 chapters, this book present the fundamentals of chemical kinetics, its relations with reaction mechanisms and kinetic properties. Two chapters are then devoted to experimental re

  7. Model-order reduction of biochemical reaction networks

    NARCIS (Netherlands)

    Rao, Shodhan; Schaft, Arjan van der; Eunen, Karen van; Bakker, Barbara M.; Jayawardhana, Bayu

    2013-01-01

    In this paper we propose a model-order reduction method for chemical reaction networks governed by general enzyme kinetics, including the mass-action and Michaelis-Menten kinetics. The model-order reduction method is based on the Kron reduction of the weighted Laplacian matrix which describes the

  8. SABIO-RK: Curated Kinetic Data of Biochemical Reactions

    OpenAIRE

    Ulrike Wittig

    2009-01-01

    SABIO-RK ("http://sabio.villa-bosch.de/SABIORK/":http://sabio.villa-bosch.de/SABIORK/) is a curated, web-accessible database for modellers and wet-lab scientists to get comprehensive information about biochemical reactions and their kinetic properties. It integrates data from different origin in order to facilitate the access to reaction kinetics data and corresponding information. Since most of the kinetic data is exclusively found in the literature SABIO-RK offers data manually ex...

  9. Application of Detailed Chemical Kinetics to Combustion Instability Modeling

    Science.gov (United States)

    2016-01-04

    chemical kinetics of the methane oxidation. Two-dimensional results with global chemistry have shown significantly lower amplitudes than the ex...Conference Paper 3. DATES COVERED (From - To) 12 November 2015 – 04 January 2016 4. TITLE AND SUBTITLE Application of Detailed Chemical Kinetics to...under two different conditions corresponding to marginally stable and unstable operation in order to evaluate the performance of the chemical kinetics

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

    African Journals Online (AJOL)

    The results revealed that Microsoft Excel Solver provided an improved description of Biochemical Oxygen Demand removal patterns based on relative error, MSC and AIC. The study concluded that Microsoft Excel Solver, non-linear regression, least squares and Thomas' methods were valuable methods at higher ...

  11. A variable order kinetic model to predict defluoridation of drinking ...

    African Journals Online (AJOL)

    In this study two EC cells with the same capacity (V=20 L) were used to carry out fluoride removal with aluminum electrodes, the first is a stirred tank reactor (STR) the second is an airlift reactor (ALR). The comparison of energy consumption demonstrates that the (ALR) is advantageous for carrying out the defluoridation ...

  12. Kinetic Algorithms for Harbour Management

    Science.gov (United States)

    Gold, C. M.; Goralski, R. I.

    2012-07-01

    Modern harbour management for a busy port needs to resolve a variety of simultaneous problems. Harbour traffic may be busy and the waterways congested, both by the major shipping and by the attendant harbour tugs. The harbour channel may be narrow and tortuous, and rapidly changing tides may require frequent course adjustments. Navigation aids must be clearly specified and immediately identifiable, in order to permit safe passage for the vessels. This requires a GIS with attributes not easily available with traditional products. The GeoVS system is a kinetic GIS with full three-dimensional visualisation, so that ships, bathymetry and landscape may be viewed in a form that is immediately understandable to both harbour pilots and the harbour authority. The system is kinetic because the data structures used to preserve the topological relationships between ships, seafloor and coastline are able to be maintained on a real-time basis, taking account of ship movement recorded on the compulsory AIS (Automatic Information System) beacons. Maintenance of this real-time topology allows for easy detection of potential collisions, as well as real-time bathymetric estimations, necessary to prevent ship grounding in highly tidal environments. The system, based on previous research into kinetic Voronoi diagrams, as well as development of a completely new graphical engine, is now in commercial production, where its advantages over simpler twodimensional models without automatic collision and grounding detection are becoming evident. Other applications are readily envisaged, and will be addressed in the near future.

  13. KINETIC ALGORITHMS FOR HARBOUR MANAGEMENT

    Directory of Open Access Journals (Sweden)

    C. M. Gold

    2012-07-01

    Full Text Available Modern harbour management for a busy port needs to resolve a variety of simultaneous problems. Harbour traffic may be busy and the waterways congested, both by the major shipping and by the attendant harbour tugs. The harbour channel may be narrow and tortuous, and rapidly changing tides may require frequent course adjustments. Navigation aids must be clearly specified and immediately identifiable, in order to permit safe passage for the vessels. This requires a GIS with attributes not easily available with traditional products. The GeoVS system is a kinetic GIS with full three-dimensional visualisation, so that ships, bathymetry and landscape may be viewed in a form that is immediately understandable to both harbour pilots and the harbour authority. The system is kinetic because the data structures used to preserve the topological relationships between ships, seafloor and coastline are able to be maintained on a real-time basis, taking account of ship movement recorded on the compulsory AIS (Automatic Information System beacons. Maintenance of this real-time topology allows for easy detection of potential collisions, as well as real-time bathymetric estimations, necessary to prevent ship grounding in highly tidal environments. The system, based on previous research into kinetic Voronoi diagrams, as well as development of a completely new graphical engine, is now in commercial production, where its advantages over simpler twodimensional models without automatic collision and grounding detection are becoming evident. Other applications are readily envisaged, and will be addressed in the near future.

  14. reactions of enolisable ketones with dichloroisocyanuric acid

    African Journals Online (AJOL)

    B. S. Chandravanshi

    ABSTRACT. Kinetics of reactions of enolisable ketones (S = acetone/2-butanone) with dichloroisocyanuric acid (DCICA) were studied in aqueous acetic acid and perchloric acid media in absence and presence of added chloride ions. The reactions were found to be pseudo zero order and pseudo first order on [DCICA] in ...

  15. Removal of chromium and nickel ions from aqueous solution by ...

    African Journals Online (AJOL)

    The Freundlich isotherm was found to be more suitable for Cr(VI) adsorption, while the Langmuir isotherm was observed to better for. Ni adsorption on coconut husk. To evaluate the mechanism of adsorption, pseudo-first order and second order kinetic models were used. The adsorption mechanism was found fit the second ...

  16. Reaction Order Ambiguity in Integrated Rate Plots

    Science.gov (United States)

    Lee, Joe

    2008-01-01

    Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for these plots to yield unambiguous orders. The present article gives a theoretical and statistical…

  17. Kinetic ELISA in Microfluidic Channels

    Directory of Open Access Journals (Sweden)

    Debashis Dutta

    2011-06-01

    Full Text Available In this article, we describe the kinetic ELISA of Blue Tongue and Epizootic Hemorrhagic Disease viral antibodies in microfluidic channels by monitoring the rate of generation of the enzyme reaction product under static conditions. It has been shown that this format of the immunoassay allows very reliable quantitation of the target species using inexpensive glass microchips and a standard epifluorescence microscope system coupled to a CCD camera. For the viral antibodies assayed here, the limit of detection (LOD for the analyte concentration in our microchips was established to be 3–5 times lower than that obtained on commercial microwell plates using a fiftieth of the sample volume and less than a third of the incubation time. Our analyses further show that when compared to the end-point ELISA format, the kinetic mode of this assay yields an improvement in the LOD by over an order of magnitude in microfluidic devices. This benefit is primarily realized as the observed variation in the background fluorescence (signal at the start of the enzyme reaction period was significantly larger than that in the rate of signal generation upon repeating these assays in different microchannels/microchips. Because the kinetic ELISA results depend only on the latter quantity, the noise level in them was substantially lower compared to that in its end-point counterpart in which the absolute fluorescence measurements are of greater significance. While a similar benefit was also recorded through implementation of kinetic ELISAs on the microwell platform, the improvement in LOD registered in that system was not as significant as was observed in the case of microfluidic assays.

  18. Irreversible processes kinetic theory

    CERN Document Server

    Brush, Stephen G

    2013-01-01

    Kinetic Theory, Volume 2: Irreversible Processes deals with the kinetic theory of gases and the irreversible processes they undergo. It includes the two papers by James Clerk Maxwell and Ludwig Boltzmann in which the basic equations for transport processes in gases are formulated, together with the first derivation of Boltzmann's ""H-theorem"" and a discussion of this theorem, along with the problem of irreversibility.Comprised of 10 chapters, this volume begins with an introduction to the fundamental nature of heat and of gases, along with Boltzmann's work on the kinetic theory of gases and s

  19. Kinetics of Ascorbic acid degradation in asceptically packaged ...

    African Journals Online (AJOL)

    The recent ban on importation of fruit juices into Nigeria led to increase in production of locally - made orange juice. Degradation kinetics of ascorbic acid at refrigeration (70C ± 20C) and ambient temperature (280C